Battery cell, battery apparatus and electrical apparatus

Abstract

Disclosed in the present application are a battery cell, a battery apparatus and an electrical apparatus. The battery cell comprises a casing and an electrode assembly, an electrolyte being accommodated in the casing; at least part of the electrode assembly is located in the casing, and the electrode assembly comprises a separator, and a first electrode sheet and a second electrode sheet having opposite polarities, at least part of the separator being located between the first electrode sheet and the second electrode sheet; the first electrode sheet comprises a first current collector and a first active material layer, at least partial area of at least one surface of the first current collector in the thickness direction thereof being connected to the first active material layer, and at least part of the first active material layer being located between the first current collector and the separator; the first active material layer has a first surface arranged facing away from the first current collector, and the first surface is provided with a first recess extending in a first direction, the first direction being parallel to the direction of gravity.

Description

Battery cells, battery packs and electrical devices Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to a battery cell, a battery device, and an electrical device. Background Technology

[0002] Battery devices are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools, etc.

[0003] Battery devices typically consist of one or more individual cells, which are used to store and provide electrical energy through charging and discharging. During the charging and discharging process of a battery cell, the electrolyte plays a role in transporting ions, which mainly move back and forth between the electrodes through the electrolyte. However, due to its own gravity, the electrolyte tends to deposit at the bottom of the electrodes. The limited ability of the electrolyte to rise from the bottom restricts the wetting effect of the electrolyte. Therefore, improving the ability of the electrolyte to rise is an important research direction for battery cells.

[0004] The above statements are for the purpose of providing background information in relation to this application only and do not necessarily constitute prior art.

[0005] Application content

[0006] The purpose of this application is to provide a battery cell, a battery device, and an electrical device that can improve the cycle performance of the battery cell.

[0007] The technical solution adopted in the embodiments of this application is:

[0008] In a first aspect, a battery cell is provided, the battery cell including a casing and an electrode assembly, the casing containing an electrolyte; at least a portion of the electrode assembly is located within the casing, the electrode assembly including a separator and a first electrode and a second electrode with opposite polarities, at least a portion of the separator being located between the first electrode and the second electrode; the first electrode includes a first current collector and a first active material layer, at least a portion of at least one surface of the first current collector along its own thickness direction is connected to the first active material layer, at least a portion of the first active material layer being located between the first current collector and the separator; the first active material layer has a first surface disposed away from the first current collector, the first surface having a first groove extending along a first direction; the first direction is parallel to the direction of gravity.

[0009] By adopting the technical solution of this embodiment, since the first surface of the first active material layer is provided with a first groove extending along a first direction, and the first direction is parallel to the direction of gravity, the first groove extends along the direction of gravity, and the electrolyte can climb upward along the first groove, thereby improving the climbing ability of the electrolyte, improving the wetting effect of the electrolyte, and improving the cycle performance of the battery cell.

[0010] In some embodiments, along the first direction, the size of the first groove is l, and the size of the first active material layer is L, wherein 0.65≤l / L≤1; optionally, 0.8≤l / L≤0.98.

[0011] By adopting the technical solution of this embodiment, in the first direction, the first groove can occupy most of the area of ​​the first active material layer, and the first groove can extend from the lower part to the upper part of the first active material layer. The electrolyte can flow from the lower part of the first active material layer to the upper part of the first active material layer along the first groove, which is beneficial to improve the climbing ability of the electrolyte, improve the wetting effect of the upper part of the first active material layer, reduce the ion transport resistance, and improve the cycle performance of the battery cell.

[0012] In some embodiments, the battery cell is a cylindrical battery cell with a diameter of 60mm ≤ L ≤ 350mm; optionally, it has a diameter of 80mm ≤ L ≤ 210mm; or, the battery cell is a prismatic battery cell with a diameter of 120mm ≤ L ≤ 330mm; optionally, it has a diameter of 160mm ≤ L ≤ 250mm.

[0013] By adopting the technical solution of this embodiment, the size of the first active material layer is larger along the first direction, and the first active material layer contains more active material, thereby increasing the capacity of the battery cell. However, in the first direction, the distance for the extruded electrolyte to flow back to the middle of the first active material layer is long, which increases the difficulty of the extruded electrolyte flowing back to the middle of the first active material layer. However, combined with the design of 0.65≤l / L≤1, the extruded electrolyte can quickly flow back to the middle of the first active material layer through the first groove, which is beneficial to improving the wetting effect of the first electrode and improving the cycle performance of the battery cell. Therefore, the capacity and cycle performance of the battery cell can be balanced.

[0014] In some embodiments, along the first direction, the distance between the lower end of the first groove and the lower end surface of the first active material layer is S, where 0mm≤S≤20mm, optionally 2mm≤S≤10mm, and optionally 4mm≤S≤8mm.

[0015] By adopting the technical solution of this embodiment, the distance between the lower end of the first groove and the lower end surface of the first active material layer is relatively small, which is conducive to the electrolyte accumulated at the bottom of the first electrode entering the first groove and entering the electrode assembly through the first groove for ion transport. This reduces the ion transport resistance, improves the wetting effect of the electrode assembly, and improves the cycle performance of the battery cell. Furthermore, since the first groove is formed along the first direction and the first direction is parallel to the direction of gravity, the electrolyte accumulated at the bottom of the first electrode can also move along the first groove toward the upper side of the first active material layer, improving the uniformity of electrolyte distribution and further improving the cycle performance of the battery cell.

[0016] In some embodiments, along the first direction, the distance between the upper end of the first groove and the upper surface of the first active material layer is s, where 0mm≤s≤20mm, optionally 0.1mm≤s≤8mm, and optionally 0.5mm≤s≤3mm.

[0017] By adopting the technical solution of this embodiment, the distance between the upper end of the first groove and the upper surface of the first active material layer is relatively small, which is conducive to the electrolyte on the upper part of the first electrode entering the first groove and entering the electrode assembly through the first groove for ion transport. This reduces the ion transport resistance, improves the wetting effect of the first electrode, and improves the cycle performance of the battery cell.

[0018] In some embodiments, the first active material layer includes a first active material portion and a second active material portion arranged along a first direction, wherein at least one end of the first active material portion is connected to the second active material portion along the first direction, and the thickness of the second active material portion is less than the thickness of the first active material portion.

[0019] By adopting the technical solution of this embodiment, the thickness of the second active material portion is less than that of the first active material portion, making the surface of the second active material portion facing away from the first current collector closer to the first current collector than the surface of the first active material portion facing away from the first current collector. On the one hand, this can reduce the rolling pressure on the edge of the first active material layer during the rolling process of the first electrode, reducing the risk of edge cracking of the first active material layer; on the other hand, the side of the second active material portion facing away from the first current collector can accommodate more electrolyte, thereby facilitating the flow of electrolyte to the first active material portion. Furthermore, the thickness difference between the second and first active material portions can be used to form a siphon effect, which can increase the speed at which electrolyte flows into the first and second electrodes, improve the wetting effect of the electrode assembly, and improve the cycle performance of the battery cell.

[0020] In some embodiments, the thickness of the second active material portion decreases along the direction from the first active material portion to the second active material portion.

[0021] By adopting the technical solution of this embodiment, a flared structure can be formed on the side of the second active material portion facing away from the first current collector. The large end of the flared structure is positioned facing away from the first active material portion. The flared structure makes it easier for the electrolyte to be drawn into the space between the first active material portion and the second electrode, which is more conducive to improving the wetting effect of the electrode assembly and improving the cycle performance of the battery cell.

[0022] In some embodiments, the first active material portion has a first side facing away from the first current collector, and the second active material portion has a second side facing away from the first current collector, the second side being closer to the first current collector than the first side.

[0023] By adopting the technical solution of this embodiment, the side of the second surface facing away from the first current collector has more space to accommodate the electrolyte. Furthermore, the distance difference between the second surface and the first surface and the first current collector can be used to form a siphon effect, thereby increasing the speed of electrolyte reflux, improving the wetting effect of the electrode assembly, and improving the cycle performance of the battery cell.

[0024] In some embodiments, the first active material portion is provided with a first groove, and the second active material portion is disposed at a distance from the first groove along a first direction.

[0025] By adopting the technical solution of this embodiment, the first active material part is provided with a first groove, which can improve the wetting effect of the first active material part and improve the cycle performance of the battery cell. The second active material part is spaced apart from the first groove, which is beneficial to improve the structural strength of the second active material part and reduce the risk of powder shedding or even collapse of the second active material part. This is beneficial to improve the capacity and reliability of the battery cell. Therefore, the cycle performance, capacity and reliability of the battery cell can be taken into account.

[0026] In some embodiments, the distance between the second active material portion and the first groove along the first direction is S1, wherein 0mm < S1 ≤ 18mm, and optionally, 2mm ≤ S1 ≤ 8mm.

[0027] By adopting the technical solution of this embodiment, the first groove will not extend into the second active material portion, which is beneficial to improving the structural strength of the second active material portion and reducing the risk of powder shedding or even collapse of the second active material portion. This is beneficial to improving the capacity and reliability of the battery cell. It also allows the electrolyte located on the side of the second active material portion away from the first current collector to be closer to the first groove, so that the electrolyte can flow into the first groove better, improving the wetting effect of the first electrode and improving the cycle performance of the battery cell. Therefore, the cycle performance, capacity and reliability of the battery cell can be balanced.

[0028] In some embodiments, the first electrode is a negative electrode.

[0029] By adopting the technical solution of this embodiment, the first electrode is a negative electrode, the first active material part and the second active material part include negative electrode active material, the first groove and the second active material part are spaced apart, the first groove does not extend to the second active material part, the negative electrode active material of the second active material part is not grooved, and the second active material part has more negative electrode active material, which reduces the risk of lithium plating in the battery cell and is conducive to improving the performance of the battery cell.

[0030] In some embodiments, along the first direction, one end of the first active material portion is connected to the second active material portion, and the other end of the first active material portion is not connected to the second active material portion. The surface of the first active material portion facing away from the first current collector is provided with a first groove. Along the first direction, the first groove penetrates the end face of the first active material portion facing away from the second active material portion; or, along the first direction, the end face of the first active material portion facing away from the second active material portion is spaced apart from the first groove.

[0031] By adopting the technical solution of this embodiment, the first groove can be flexibly set on the first active material part to meet different usage requirements.

[0032] In some embodiments, the first current collector includes a first current collector body and a first electrode tab arranged and connected along a first direction, wherein at least a portion of the first current collector body is covered with a first active material layer, and the first electrode tab is not covered with the first active material layer.

[0033] By adopting the technical solution of this embodiment, the first electrode tab is led out from the end of the first electrode plate along the first direction, which facilitates the electrical connection of the first electrode tab with other components.

[0034] In some embodiments, there are two first active material layers, which respectively cover two surfaces of the first current collector along its thickness direction, and at least one first active material layer is provided with a first groove.

[0035] By adopting the technical solution of this embodiment, the setting of two first active material layers can increase the amount of active material in the first electrode, which is beneficial to increasing the capacity of the battery cell; in addition, the setting of the first groove is also more flexible to meet different usage requirements.

[0036] In some embodiments, there are multiple first grooves, each including a first groove and a second groove. In two first active material layers, one layer is provided with multiple first grooves and the other layer is provided with multiple second grooves. The first grooves and the second grooves are staggered along the thickness direction of the first current collector.

[0037] By adopting the technical solution of this embodiment, the two first active material layers are respectively provided with multiple first grooves and multiple second grooves to improve the wetting effect of the two first active material layers and improve the cycle performance of the battery cell; in addition, the first grooves and second grooves are staggered along the thickness direction of the first current collector, which is beneficial to improve the structural strength of the first electrode and improve the reliability of the battery cell.

[0038] In some embodiments, a plurality of first grooves and a plurality of second grooves are alternately arranged along a second direction, the second direction being perpendicular to the first direction and the thickness direction of the first current collector.

[0039] By adopting the technical solution of this embodiment, multiple first tanks and multiple second tanks can be evenly distributed on two first active material layers, which can improve the uniformity of electrolyte distribution in the battery cell and is beneficial to improving the cycle performance of the battery cell.

[0040] In some embodiments, along the second direction, the distance between adjacent first and second slots is C, wherein C ≥ 1.5 mm, optionally 1.8 mm ≤ C ≤ 5 mm, and optionally 2 mm ≤ C ≤ 3 mm.

[0041] By adopting the technical solution of this embodiment, the density of the first and second tanks is set reasonably, which can reduce the loss of active material in the first active material layer and also help improve the structural strength of the first electrode. Therefore, the reliability and energy density of the battery cell can be taken into account.

[0042] In some embodiments, the electrode assembly is a wound structure, the first electrode is wound to form a plurality of first electrode windings, the first current collector includes a first current collector winding located in the first electrode winding, the first active material layer includes a first active winding located in the first electrode winding, and the first surface includes a first winding surface located in the first electrode winding; wherein, at least one first winding surface of the first electrode winding is provided with a first groove.

[0043] By adopting the technical solution of this embodiment, at least one first groove is provided on the first winding surface of at least one first electrode winding. On the one hand, electrolyte can flow into the first groove for storage. The stored electrolyte can wet the first electrode and provide a transport path for ions, reducing the transport resistance of ions and improving the cycle performance of the battery cell. On the other hand, the electrolyte at the bottom can also move to the upper side of the electrode assembly through the first groove, improving the uniformity of electrolyte distribution. In addition, the first groove can also provide a channel for the return of the electrolyte at the bottom, reducing the difficulty of electrolyte return, reducing the transport resistance of ions, improving the wetting effect of the first electrode, and also helping to improve the cycle performance of the battery cell.

[0044] In some embodiments, the first direction is parallel to the winding axis of the electrode assembly.

[0045] By adopting the technical solution of this embodiment, the winding axis of the electrode assembly is parallel to the first direction, and the winding gap formed by the first electrode and the second electrode has openings at the upper and lower ends of the electrode assembly. On this basis, the lower end of the first groove is close to the lower end surface of the first active material layer, and the lower end of the first groove is close to the lower end opening of the winding gap. The electrolyte accumulated at the bottom can smoothly enter the winding gap through the opening at the lower end of the winding gap to wet the electrode assembly, which is beneficial to improving the utilization rate of the electrolyte accumulated at the bottom. In addition, after the electrode assembly expands, the electrolyte is squeezed out from the upper and lower ends of the electrode assembly, which is also beneficial to the return flow of the electrolyte and improves the wetting effect of the electrode assembly, which can effectively improve the wetting effect of the battery cell.

[0046] In some embodiments, there are multiple first grooves, and the multiple first grooves are spaced apart along a second direction, with the distance between two adjacent first grooves increasing progressively. The second direction is the winding direction of the electrode assembly.

[0047] By adopting the technical solution of this embodiment, after the first electrode is wound along the winding direction V of the electrode assembly, the number of first grooves near the inner side of the electrode assembly is large, and the number of first grooves near the outer side of the electrode assembly is small. This is beneficial to improve the entry of electrolyte near the inner side of the electrode assembly into the inner side of the electrode assembly, which is beneficial to improve the wetting effect of the inner side of the electrode assembly, thereby improving the cycle performance of the battery cell.

[0048] In some embodiments, the number of first electrode windings is n, n≥30, where n is a natural number, the innermost first electrode winding is the first first electrode winding, and at least one of the first 10 first electrode windings is provided with a first groove.

[0049] By adopting the technical solution of this embodiment, at least one of the first 10 first electrode windings is provided with a first groove, which can improve the wetting effect on the inner side of the electrode assembly and improve the cycle performance of the battery cell.

[0050] In some embodiments, the number of first electrode windings is n, n≥30, where n is a natural number, the innermost first electrode winding is the first first electrode winding, and at least the first first electrode winding does not have a first groove.

[0051] By adopting the technical solution of this embodiment, at least the first first electrode winding ring does not have a first groove, which is beneficial to improving the structural strength of the first first electrode winding ring and reducing the risk of powder shedding, damage or even breakage of the first first electrode winding ring caused by grooving, which is beneficial to improving the reliability of the battery cell. In addition, the absence of a first groove in the first first electrode winding ring can also reduce the number of grooves, which is beneficial to improving the production efficiency of the first electrode.

[0052] In some embodiments, at least the first three first electrode windings do not have a first groove.

[0053] By adopting the technical solution of this embodiment, at least the first to third first electrode windings do not have a first groove, which is beneficial to improving the structural strength of the first to third first electrode windings and reducing the risk of powder shedding, damage, or even breakage of the first to third first electrode windings caused by grooving, which is beneficial to improving the reliability of the battery cell. In addition, the absence of a first groove in the first to third first electrode windings can also reduce the number of grooves, which is beneficial to improving the production efficiency of the first electrode.

[0054] In some embodiments, the electrode assembly has a central hole, and the first first electrode winding is closest to the central hole compared to the other first electrode windings.

[0055] By adopting the technical solution of this embodiment, the central hole can be used to contain electrolyte and allow electrolyte flow, thereby wetting the first electrode winding ring located on the inner side, improving the wetting effect on the inner side of the electrode assembly, and improving the cycle performance of the battery cell. In addition, the first electrode winding ring located on the inner side can be wetted by the electrolyte in the central hole, which can also reduce the need for the first groove to be set on the first electrode winding ring located on the inner side, thereby improving the structural strength of the first electrode winding ring located on the inner side and reducing the problem of powder shedding from the first electrode winding ring located on the inner side, thus effectively balancing the cycle performance and reliability of the battery cell.

[0056] In some embodiments, the number of first electrode windings is n, n≥30, where n is a natural number; the innermost first electrode winding is the first first electrode winding; at least the last two first electrode windings do not have a first groove.

[0057] By adopting the technical solution of this embodiment, at least the last two first electrode windings do not have a first groove, which helps to improve the structural strength of the last two first electrode windings and reduce the risk of breakage of the last two first electrode windings, thereby effectively improving the reliability of the battery cell. In addition, the absence of a first groove in the last two first electrode windings reduces the number of grooves and improves the production efficiency of the first electrode.

[0058] In some embodiments, at least the last 10 first electrode windings do not have a first groove.

[0059] By adopting the technical solution of this embodiment, at least the last 10 first electrode windings do not have a first groove, which helps to improve the structural strength of the last 10 first electrode windings and reduce the risk of breakage of the last 10 first electrode windings, thereby improving the reliability of the battery cell. In addition, the absence of a first groove in the last 10 first electrode windings reduces the number of grooves and improves the production efficiency of the first electrode.

[0060] In some embodiments, the number of first electrode windings is n, n≥30, where n is a natural number; the innermost first electrode winding is the first first electrode winding; the first f first electrode windings do not have a first groove, and the last q first electrode windings do not have a first groove; all first electrode windings between the f-th first electrode winding and the last q first electrode windings have a first groove, where f+q<n, and f and q are positive integers.

[0061] By adopting the technical solution of this embodiment, the first electrode winding ring located on the inner and outer sides can be free of the first groove, which is beneficial to improving the structural strength of the first electrode winding ring on the inner and outer sides and improving the reliability of the battery cell. In addition, it can also reduce the number of grooves and improve the production and processing efficiency of the first electrode. Furthermore, the groove in the middle area of ​​the electrode assembly on the inner and outer sides is beneficial to improving the wetting effect of the electrode assembly in the middle area of ​​the inner and outer sides and improving the cycle performance of the battery cell.

[0062] In some embodiments, 30 ≤ n ≤ 80, and optionally, 60 ≤ n ≤ 75.

[0063] By adopting the technical solution of this embodiment, the first electrode has a large number of winding turns, the battery cell has a large capacity, and the electrode assembly is difficult to wet. In this embodiment, the first groove can be selectively provided on the inner or outer side of the electrode assembly, thereby improving the wettability of the electrode assembly and also improving the structural strength of the inner or outer side of the electrode assembly, thus taking into account the reliability, capacity and cycle performance of the electrode assembly.

[0064] In some embodiments, the number of windings of the first electrode with the first groove is v, 0.23≤v / n≤1, where v and n are positive integers, and optionally, 0.3≤v / n≤0.7.

[0065] By adopting the technical solution of this embodiment, selective grooves can be made on the first electrode winding ring, which is beneficial to simultaneously take into account the manufacturing of the first electrode, the reliability of the battery cell, and the cycle performance of the battery cell.

[0066] In some embodiments, the first electrode has a first winding end, the second electrode has a second winding end, the innermost first electrode winding is the first first electrode winding, and the second winding end is located between the last two first electrode windings; the last two first electrode windings are not provided with a first groove at the position corresponding to the end face of the first winding end; and / or, the last two first electrode windings are not provided with a first groove at the position corresponding to the end face of the second winding end.

[0067] By adopting the technical solution of this embodiment, the risk of the last two first electrode windings being cut off by the end face of the first winding end and / or the end face of the second winding end can be reduced, thereby improving the reliability of the battery cell.

[0068] In some embodiments, the last two first electrode windings are provided with a first groove, which is offset from at least one of the end faces of the first winding end and the second winding end; or, the last two first electrode windings are not provided with a first groove.

[0069] By adopting the technical solution of this embodiment, the risk of the last two first electrode windings being cut off by the end face of the first winding end and / or the end face of the second winding end can be reduced, thereby improving the reliability of the battery cell.

[0070] In some embodiments, the first electrode has a first winding start end, the second electrode has a second winding start end, the innermost first electrode winding ring is the first first electrode winding ring, and the second winding start end is located between the first two first electrode winding rings; the first groove is not provided at the position corresponding to the end face of the first two first electrode winding rings and the first winding start end; and / or, the first groove is not provided at the position corresponding to the end face of the second winding start end of the first two first electrode winding rings.

[0071] By adopting the technical solution of this embodiment, the risk of the first two first electrode windings being sheared by the end face of the first winding start end and / or the end face of the second winding start end can be reduced, thereby improving the reliability of the battery cell.

[0072] In some embodiments, the first two first electrode windings are provided with a first groove, which is offset from at least one of the end face of the first winding start end and the end face of the second winding start end; or, the first two first electrode windings are not provided with a first groove.

[0073] By adopting the technical solution of this embodiment, the risk of the first two first electrode windings being sheared by the end face of the first winding start end and / or the end face of the second winding start end can be reduced, thereby improving the reliability of the battery cell.

[0074] In some embodiments, the first electrode is a negative electrode and the second electrode is a positive electrode; or, the second electrode is a negative electrode and the first electrode is a positive electrode.

[0075] By adopting the technical solution of this embodiment, the polarity of the first electrode and the second electrode can be flexibly set to meet different usage requirements.

[0076] In some embodiments, the electrode assembly includes a flat region and two bent regions located at both ends of the flat region; the first active winding includes a first active bent portion located in the bent region and a first active flat portion located in the flat region; at least one first active winding has a first active flat portion having a first groove; and / or, at least one first active winding has a first active bent portion having a first groove.

[0077] By adopting the technical solution of this embodiment, the wetting effect in the straight area and / or the bending area can be improved, thereby improving the cycle performance of the battery cell.

[0078] In some embodiments, the first active straight portion of all first active windings is provided with a first groove, while the first active bent portion of all first active windings is not provided with a first groove.

[0079] By adopting the technical solution of this embodiment, the bending of the first active bending portion in the bending area increases the risk of powder shedding from the first active bending portion. However, since the first active bending portions of all the first active windings do not have first grooves, it is beneficial to improve the structural strength of the first active bending portion, reduce the risk of powder shedding from the bending area, and improve the capacity and reliability of the battery cell. At the same time, all the first active straight portions are provided with first grooves, which can effectively improve the wetting effect of the straight area and improve the cycle performance of the battery cell. Therefore, the cycle performance, capacity and reliability of the battery cell can be taken into account at the same time.

[0080] In some embodiments, the battery cell is a cylindrical battery cell, and the central axis of the cylindrical battery cell is parallel to the first direction.

[0081] By adopting the technical solution of this embodiment, the central axis of the cylindrical battery cell is parallel to the first direction, the cylindrical battery cell is vertically arranged, and the first groove extends from bottom to top, which is conducive to the electrolyte accumulated at the bottom climbing upward and improving the wetting effect of the cylindrical battery cell. In addition, the electrode assembly inside the cylindrical battery cell is tightly wound, which is not conducive to the return of electrolyte. However, the first electrode is provided with a first groove, which is conducive to the return of electrolyte and improves the wetting effect of the electrode assembly. This can effectively improve the wetting effect of the cylindrical battery cell.

[0082] In some embodiments, the electrode assembly is a stacked structure, and the stacking direction of the electrode assembly is perpendicular to the first direction.

[0083] By adopting the technical solution of this embodiment, the stacking direction of the electrode assembly is perpendicular to the first direction, so that the first electrode and the second electrode are vertically arranged. The gap formed by the first electrode and the second electrode has an opening at the upper and lower ends of the electrode assembly. On this basis, the lower end of the first groove is close to the lower end surface of the first active material layer, and the lower end of the first groove is close to the lower end opening of the gap. The electrolyte accumulated at the bottom can enter the space between the first electrode and the second electrode more smoothly through the opening at the lower end of the gap to wet the electrode assembly, which is beneficial to improving the utilization rate of the electrolyte accumulated at the bottom. In addition, after the electrode assembly expands, the electrolyte is squeezed out from the upper and lower ends of the electrode assembly, which is also beneficial to the return flow of the electrolyte and improves the wetting effect of the electrode assembly, which can effectively improve the wetting effect of the battery cell.

[0084] In some embodiments, the thickness of the first active material layer is t, and the groove depth of the first groove is h, wherein 0.05≤h / t≤0.84, optionally 0.08≤h / t≤0.8; optionally, 0.1≤h / t≤0.5.

[0085] By adopting the technical solution of this embodiment, the first groove can guide the electrolyte accumulated at the bottom to flow to the electrode assembly, improving the effective utilization rate of the electrolyte, enhancing the wetting effect of the electrode assembly, and improving the cycle performance of the battery cell. Furthermore, since the first groove does not penetrate the first active material layer and the first current collector is not exposed, the risk of direct reaction between the first current collector and ions is reduced. Additionally, compared to the first groove penetrating the first active material layer, the grooved first active material layer removes less active material, which is beneficial for increasing the active material capacity of the first electrode and reducing the risk of decreased battery cell performance due to insufficient active material capacity of the first electrode. Therefore, both the cycle performance and overall performance of the battery cell can be considered.

[0086] In some embodiments, the groove depth of the first groove is h, where 0 μm < h ≤ 50 μm, and optionally, 6 μm ≤ h ≤ 30 μm.

[0087] By adopting the technical solution of this embodiment, the depth of the first groove is reasonable, enabling it to guide the electrolyte accumulated at the bottom to flow to the electrode assembly, thereby improving the effective utilization rate of the electrolyte, enhancing the wetting effect of the electrode assembly, and improving the cycle performance of the battery cell. Furthermore, reducing the amount of active material removed by the groove in the first active material layer helps increase the active material capacity of the first electrode and reduces the risk of performance degradation in the battery cell due to insufficient active material capacity in the first electrode. Therefore, both the cycle performance and overall performance of the battery cell can be balanced.

[0088] In some embodiments, the groove width of the first groove is w, wherein 30μm≤w≤1000μm; optionally, 50μm≤w≤500μm; optionally, 80μm≤w≤120μm.

[0089] By adopting the technical solution of this embodiment, the first groove can guide the electrolyte accumulated at the bottom to flow to the electrode assembly, improving the effective utilization rate of the electrolyte, enhancing the wetting effect of the electrode assembly, and improving the cycle performance of the battery cell. It also facilitates the processing and fabrication of the first groove. Furthermore, it reduces the amount of active material removed from the first active material layer, which is beneficial for increasing the active material capacity of the first electrode and reducing the risk of decreased battery cell performance due to insufficient active material capacity in the first electrode. In addition, during the hot pressing process of the first electrode, the first groove is not easily flattened, and its shape can be stably maintained. Therefore, both the cycle performance and overall performance of the battery cell can be considered.

[0090] In some embodiments, the width of the first groove is w, the depth of the first groove is h, and 0.05≤h / w≤1; optionally, 0.1≤h / w≤0.5.

[0091] By adopting the technical solution of this embodiment, under a certain h, the width of the first groove is not too large, so that the first groove is not easily flattened during the hot pressing of the first electrode sheet, and the shape of the first groove can be stably maintained; it also provides a wider channel for the electrolyte accumulated at the bottom to flow to the upper part of the electrode assembly, which is conducive to the flow of the electrolyte accumulated at the bottom, improves the wetting effect of the electrode assembly, and improves the cycle performance of the battery cell; therefore, the processing and manufacturing of the first groove and the cycle performance of the battery cell can be taken into account.

[0092] In some embodiments, along the first direction, the size of the first active material layer is L, and the groove depth of the first groove is h, 5*10. -5 ≤h / L≤5*10 -4 The first direction is perpendicular to the thickness direction of the first current collector.

[0093] By adopting the technical solution of this embodiment, when L is constant, h / L≥5*10 -5 The design allows the depth of the first groove to enable the electrolyte at the bottom to flow upwards more quickly, improving the wetting effect of the first electrode; additionally, h / L ≤ 5*10 -4 The design reduces the risk of the first current collector being exposed due to excessive groove depth and the loss of active material of the first electrode, thus balancing the capacity, cycle performance and reliability of the battery cell.

[0094] In some embodiments, along the first direction, the size of the first active material layer is L, and the groove depth of the first groove is h, wherein L≥60mm and h≥6μm.

[0095] By adopting the technical solution of this embodiment, for battery cells with L≥60mm and h≥6μm, the first groove can store more electrolyte and can also better guide the electrolyte at the bottom to flow upward, which can effectively improve the wetting effect of the first electrode and improve the cycle performance of the battery cell.

[0096] In some embodiments, the first groove includes a first groove segment and a second groove segment arranged along a first direction, at least one end of the first groove segment along the first direction is connected to the second groove segment, the groove depth of the first groove segment is greater than the groove depth of the second groove segment, and / or the groove width of the first groove segment is greater than the groove width of the second groove segment.

[0097] By adopting the technical solution of this embodiment, the smaller size of the second tank section compared to the first tank section allows the electrolyte to easily generate a siphon effect in the second tank section, which facilitates the rapid flow of the electrolyte into the first tank section, improves the wetting effect of the first electrode, and enhances the cycle performance of the battery cell.

[0098] In some embodiments, the depth of the second groove segment is progressively reduced from that of the first groove segment in the direction from the first groove segment to the second groove segment; and / or, the width of the second groove segment is progressively reduced from that of the first groove segment in the direction from the first groove segment to the second groove segment.

[0099] By adopting the technical solution of this embodiment, in the direction away from the first tank section, the size of the second tank section gradually decreases compared to the size of the first tank section, which can form a pressure difference for electrolyte flow. The second tank section can produce a better siphon effect, which can draw the electrolyte into the second tank section more quickly and flow into the first tank section through the second tank section, thereby improving the first wetting effect and improving the cycle performance of the battery cell.

[0100] In some embodiments, the first groove includes a plurality of sub-segments, which are spaced apart along a first direction.

[0101] By adopting the technical solution of this embodiment, the first groove includes multiple sub-segments, which can reduce the removal of active material by grooving the first active material layer and reduce the amount of active material loss of the first electrode, which is beneficial to improving the capacity and performance of the battery cell. In addition, the multiple sub-segments are spaced apart, which is beneficial to improving the structural strength and rigidity of the first electrode compared with the use of a whole-section first groove, and is beneficial to the reliability of the battery cell.

[0102] In some embodiments, the spacing between two adjacent segments is d, where 0.1mm ≤ d ≤ 1mm; alternatively, 0.3mm ≤ d ≤ 0.6mm.

[0103] By adopting the technical solution of this embodiment, the interval between two adjacent sub-segments is set, which reduces the loss of active material of the first electrode and improves the performance of the battery cell; it also allows the electrolyte between two adjacent sub-segments to flow to each other, making the electrolyte distribution more uniform and improving the cycle performance of the battery cell.

[0104] In some embodiments, there are multiple first grooves, and the multiple first grooves are arranged at intervals along a second direction; along the second direction, in two adjacent first grooves, a sub-segment of one first groove is at least partially offset from a sub-segment of the other first groove, and the second direction is perpendicular to the first direction and the thickness direction of the first current collector.

[0105] By adopting the technical solution of this embodiment, the multiple sub-segments of two adjacent first grooves are staggered, which is beneficial to improving the uniformity of electrolyte distribution, improving the wetting effect of the first electrode, and improving the cycle performance of the battery cell.

[0106] In some embodiments, there are multiple first grooves, and the multiple first grooves form multiple sets of first grooves. Each set of first grooves includes multiple intersecting first grooves. The multiple sets of first grooves are arranged at intervals along a second direction, which is perpendicular to the first direction and the thickness direction of the first current collector.

[0107] By adopting the technical solution of this embodiment, the multiple first grooves are divided into multiple groups, and each group of first grooves includes multiple intersecting first grooves. The electrolyte can flow within the multiple first grooves, which helps to improve the uniformity of electrolyte distribution, improve the wetting effect of the first electrode, and improve the cycle performance of the battery cell. In addition, the multiple groups of first grooves are spaced apart along the second direction, which can reduce the loss of active material of the first electrode, which helps to improve the performance and capacity of the battery cell. At the same time, it can also improve the structural strength and rigidity of the first electrode, which helps to improve the reliability of the battery cell.

[0108] In some embodiments, the second electrode includes a second current collector and a second active material layer, at least a portion of at least one surface of the second current collector along its thickness direction is connected to the second active material layer, and at least a portion of the second active material layer is located between the second current collector and the separator.

[0109] In some embodiments, the electrode assembly is a wound structure, with m gap windings formed between the first active material layer and the second active material layer, where m ≥ 30 and m is a natural number; the innermost gap winding is the first gap winding; the average radial dimension of the (m-13)th to (m-5)th gap windings is greater than the average radial dimension of the 5th to 13th gap windings.

[0110] By adopting the technical solution of this embodiment, during the cycling process of a battery cell, the expansion of the electrode assembly gradually accumulates radially from the inside to the outside, with a large cumulative expansion force on the outer side of the electrode assembly. Meanwhile, the average radial dimension of the (m-13)th to (m-5)th gap winding turns is large, providing more expansion space for the outer side of the electrode assembly, absorbing the accumulated expansion, thereby reducing the interaction force between the electrode assembly and the casing, reducing casing deformation, lowering the risk of casing cracking, and improving reliability. Furthermore, the average radial dimension of the 5th to 13th gap winding turns is small, increasing the structural compactness of the inner side of the electrode assembly, which is beneficial for improving the energy density of the battery cell.

[0111] In some embodiments, the gap winding includes a first gap sub-ring and a second gap sub-ring, the first gap sub-ring being located between the first active material layer and the spacer, and the second gap sub-ring being located between the second active material layer and the spacer.

[0112] By adopting the technical solution of this embodiment, both the first gap sub-ring and the second gap sub-ring can provide space for the expansion of the electrode assembly, thereby reducing the squeezing effect on the shell, reducing the risk of shell deformation and cracking, and improving the reliability of the battery cell.

[0113] In some embodiments, the radial dimension of the first gap winding is smaller than the radial dimension of the m-th gap winding.

[0114] By adopting the technical solution of this embodiment, the radial dimension of the m-th gap winding ring is large, which can provide more expansion space for the electrode assembly, absorb the accumulated expansion of the electrode assembly, thereby reducing the interaction force between the electrode assembly and the shell, reducing the deformation of the shell, reducing the risk of shell cracking, and improving reliability.

[0115] In some embodiments, the m gap windings are divided into j groups of gap windings in order from the inner side to the outer side of the electrode assembly; the innermost group of gap windings is the first group of gap windings. In the first group to the (j-1)th group, each group of gap windings includes 9 gap windings, 1≤m-9*(j-1)≤9, and j is a natural number; the average radial dimension of the gap windings in the first group to the (j-1)th group is set to increase incrementally.

[0116] By adopting the technical solution of this embodiment, the average radial dimension of the gap windings from the first group to the (j-1)th group increases progressively. From the inner to the outer side of the electrode assembly, the radial dimension of the gap windings also increases. The larger radial dimension of the gap windings on the outer side of the electrode assembly provides more expansion space, absorbing the accumulated expansion of the electrode assembly, thereby reducing the force between the electrode assembly and the casing, reducing the deformation of the casing, lowering the risk of casing cracking, and improving reliability. Furthermore, the smaller radial dimension of the gap windings on the outer side of the electrode assembly effectively increases the structural compactness of the inner side of the electrode assembly, which is beneficial for improving the energy density of the battery cell.

[0117] In some embodiments, the first current collector includes a first current collector body and a first electrode tab connected together, at least a portion of the first current collector body is covered with a first active material layer, and the first electrode tab is not covered with the first active material layer; the second current collector includes a second current collector body and a second electrode tab connected together, at least a portion of the second current collector body is covered with a second active material layer, and the second electrode tab is not covered with the second active material layer.

[0118] In some embodiments, the housing includes a casing and an end cap. The casing includes connected sidewalls and end walls. The sidewalls surround the electrode assembly. The end walls and end caps are distributed opposite each other along the axial direction of the battery cell. The end caps are sealed to the sidewalls. The end caps are insulatedly provided with electrode terminals. A second electrode tab is electrically connected to the electrode terminals. At least one of the sidewalls and end walls is electrically connected to a first electrode tab. Alternatively, the end walls are insulatedly provided with electrode terminals. The second electrode tab is electrically connected to the electrode terminals. At least one of the end caps and sidewalls is electrically connected to the first electrode tab.

[0119] By adopting the technical solution of this embodiment, the output electrodes of the battery cell can be flexibly set to meet different needs.

[0120] In some embodiments, the battery cell further includes a first current collector and a second current collector; the first tab and the second tab are respectively located at both ends of the electrode assembly along the axial direction of the battery cell, and the second tab is located on the side of the electrode assembly near the electrode terminal; the second current collector is electrically connected between the second tab and the electrode terminal.

[0121] The electrode terminals are insulated on the end cap, the first current collector is located between the first electrode tab and the end wall, the first current collector is electrically connected to the first electrode tab, and at least one of the side wall and the end wall is electrically connected to the first current collector.

[0122] Alternatively, the electrode terminals are insulated on the end wall, the first current collector is located between the first electrode tab and the end cap, the first current collector is electrically connected to the first electrode tab, and at least one of the side wall and the end cap is electrically connected to the first current collector.

[0123] By adopting the technical solution of this embodiment, the assembly operation of the battery cell is made simpler by utilizing the switching function of the first current collector and the second current collector.

[0124] In some embodiments, the electrode terminals are insulated from the end wall;

[0125] The side wall is provided with an inwardly protruding protrusion, which is located on the side of the first tab facing the end cover along the axial direction of the battery cell.

[0126] The second current collector includes a first connecting part, a second connecting part, and a third connecting part. The second connecting part is connected between the first connecting part and the third connecting part. The first connecting part is connected to the first electrode tab. At least a portion of the third connecting part is located between the protrusion and the end cap. The third connecting part is connected to the side of the protrusion facing away from the first electrode tab.

[0127] By adopting the technical solution of this embodiment, at least part of the third connecting part is disposed between the protrusion and the end cap. The third connecting part is connected to the side of the protrusion facing the end cap, so that the first current collector can be assembled through the opening of the housing, which facilitates the installation of the first current collector. In addition, the protrusion also plays a limiting role for the third connecting part, improving the installation stability of the first current collector, improving the connection reliability between the first current collector and the first tab and between the first current collector and the protrusion, and improving the reliability of the battery cell.

[0128] Secondly, a battery device is provided, comprising a plurality of the aforementioned battery cells.

[0129] By adopting the technical solution of this embodiment, the cycle performance of the battery cell is good, which is beneficial to improving the performance and service life of the battery device.

[0130] Thirdly, an electrical device is provided, including the aforementioned battery cell or battery device, wherein the battery cell or battery device is used to store or provide electrical energy.

[0131] By adopting the technical solution of this embodiment, the battery cell has good cycle performance, the battery device has good performance and long service life, which is conducive to improving the performance and service life of the electrical device.

[0132] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0133] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0134] Figure 1 is a schematic diagram of the vehicle structure provided in some embodiments of this application;

[0135] Figure 2 is a schematic diagram of a battery device provided in some embodiments of this application;

[0136] Figure 3 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0137] Figure 4 is a schematic diagram of the explosion of the battery cell shown in Figure 3;

[0138] Figure 5 is a cross-sectional schematic diagram of a battery cell provided in some embodiments of this application;

[0139] Figure 6 is a partial cross-sectional schematic diagram of the electrode assembly of a battery cell provided in some embodiments of this application;

[0140] Figure 7 is a cross-sectional view of section AA in Figure 6;

[0141] Figure 8 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0142] Figure 9 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0143] Figure 10 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0144] Figure 11 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0145] Figure 12 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0146] Figure 13 is a cross-sectional view of CC in Figure 8;

[0147] Figure 14 is a cross-sectional view of DD in Figure 8;

[0148] Figure 15 is a magnified view of part B in Figure 6;

[0149] Figure 16 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0150] Figure 17 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0151] Figure 18 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0152] Figure 19 is a cross-sectional view of an electrode assembly provided in some embodiments of this application;

[0153] Figure 20 is a magnified view of a portion of point E in Figure 19;

[0154] Figure 21 is a cross-sectional view of the bending area in Figure 19;

[0155] Figure 22 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0156] Figure 23 is a cross-sectional view of FF in Figure 22;

[0157] Figure 24 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0158] Figure 25 is a cross-sectional view of section HH in Figure 24;

[0159] Figure 26 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0160] Figure 27 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0161] Figure 28 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0162] Figure 29 is a schematic diagram of the first electrode sheet in an unfolded state according to some embodiments of this application;

[0163] Figure 30 is a cross-sectional schematic diagram of a battery cell provided in some other embodiments of this application;

[0164] Figure 31 is a magnified view of part I in Figure 30;

[0165] Figure 32 is a partial cross-sectional schematic diagram of a battery cell provided in some embodiments of this application.

[0166] In the figures, the following labels are used: 1. Vehicle; 2. Battery unit; 3. Controller; 4. Motor; 5. Housing; 51. First housing; 52. Second housing; 6. Battery cell; 10. Electrode assembly; 101. Center hole; 11. Positive electrode; 111. Positive current collector; 112. Positive active material layer; 12. Negative electrode; 121. Negative current collector; 122. Negative active material layer; 13. Separator; 14. First electrode; 141. First current collector; 1411. First current collector body; 1412. First... 142. Electrode tab; 1421. First active material layer; 1421. First surface; 1421c. Measurement area; 1421d. Outer edge; 1422. First active material portion; 1423. Second active material portion; 1424. First surface; 1425. Second surface; 143. First electrode winding coil; 1431. First current collector winding coil; 1432. First active winding coil; 1433. First winding surface; 1434. First active bending portion; 1435. First active straight portion; 144b 1441. Groove opening; 1442. First groove segment; 1443. Second groove segment; 1444. Second groove; 1445. Sub-segment; 1446. First groove; 1447. Second groove; 15. Second electrode; 151. Second current collector; 1511. Second current collector body; 1512. Second electrode tab; 152. Second active material layer; 1521. Second surface; 153. Second electrode winding coil; 1531. Second current collector winding coil; 1532. Second active winding coil ; 1533, Second winding surface; 1534, Second active bending part; 1535, Second active straight part; 20, Outer shell; 21, Housing; 211, End wall; 212, Side wall; 2121, Protrusion; 2122, Recess; 2123, Press-fit part; 22, End cap; 30, Electrode terminal; 31, Through hole; 40, Cover plate; 60, First current collector; 61, First connecting part; 62, Second connecting part; 63, Third connecting part; 70, Second current collector; 80, Insulating component. Detailed Implementation

[0167] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0168] In the description of the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include at least one of that feature.

[0169] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0170] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0171] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0172] In the description of this application, it should be understood that the terms "inner", "outer", "side", "upper", "bottom", "front", "rear", etc., indicating the orientation or positional relationship are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0173] In the description of this application, it should be noted that the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0174] It should also be noted that in the embodiments of this application, the same reference numerals are used to represent the same component or part. For the same part in the embodiments of this application, the reference numerals may only be used to mark one part or component as an example. It should be understood that the reference numerals are also applicable to other identical parts or components.

[0175] A single battery cell can be a rechargeable battery, which refers to a battery cell that can be recharged after being discharged to activate the active materials and continue to be used.

[0176] A battery device can refer to a single physical module that includes one or more battery cells to provide higher voltage and capacity.

[0177] A single battery cell typically includes an electrode assembly and a housing for containing the electrode assembly. The electrode assembly typically includes a separator and two electrodes of opposite polarity, with the separator separating the two electrodes.

[0178] Battery cells are used in electrical devices to store and provide electrical energy through charging and discharging. During the charging and discharging process, the electrolyte plays a role in transporting ions, which mainly move back and forth between the electrodes through the electrolyte. However, due to its own gravity, the electrolyte will deposit at the bottom of the electrodes. The upward mobility of the electrolyte at the bottom is limited, which restricts the wetting effect of the electrolyte. Therefore, how to improve the upward mobility of the electrolyte is an important research direction for battery cells.

[0179] The difficulty in getting the electrolyte to wet the upper part of the electrode increases the ion transport resistance at the top of the battery cell, increases the internal resistance of the battery cell, and affects the cycle performance of the battery cell.

[0180] In view of this, the present application provides a technical solution that improves the electrolyte climbing ability, enhances the electrode wetting effect, reduces ion transport resistance, and improves the cycle performance of the battery cell by rationally designing the structure of the electrode.

[0181] The battery cells described in this application are applicable to battery devices and electrical devices that use battery devices. Electrical devices can be equipment that uses battery devices as a power source or various energy storage systems that use battery devices as energy storage elements. Electrical devices can be, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0182] For ease of explanation, the following embodiments will be described using vehicle 1 as an example of an electrical device.

[0183] As shown in Figure 1, a battery device 2 is installed inside the vehicle 1. The battery device 2 can be located at the bottom, front, or rear of the vehicle 1. The battery device 2 can be used to power the vehicle 1; for example, the battery device 2 can serve as the operating power source for the vehicle 1.

[0184] The vehicle 1 may also include a controller 3 and a motor 4. The controller 3 is used to control the battery device 2 to supply power to the motor 4, for example, for the power needs of the vehicle 1 during starting, navigation and driving.

[0185] In some embodiments of this application, the battery device 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0186] Referring to Figure 2, in some embodiments, the battery device 2 may include one or more battery cell assemblies for providing voltage and capacity.

[0187] A battery cell assembly may include multiple battery cells 6, which are connected in series, parallel, or mixed connection via a busbar. Mixed connection means that multiple battery cells 6 are connected in both series and parallel.

[0188] Battery cell 6 can be a secondary battery cell. A secondary battery cell refers to a battery cell that can be recharged after being discharged, allowing the active materials to be activated and continue to be used.

[0189] As an example, the battery cell 6 can be a lithium-ion battery cell, a sodium-ion battery cell, a sodium-lithium-ion battery cell, a lithium metal battery cell, a sodium metal battery cell, a lithium-sulfur battery cell, a magnesium-ion battery cell, a nickel-metal hydride battery cell, a nickel-cadmium battery cell, a lead-acid battery cell, etc.

[0190] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells 6; as an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells 6 into a single module. As an example, a battery module can be formed by bundling multiple battery cells 6 together with cable ties.

[0191] In some embodiments, the battery device 2 may be a battery pack, which includes a housing 5 and one or more battery cell assemblies housed within the housing 5. As an example, the battery cell assembly may be a battery module, which can be housed within the housing 5 by securing the battery module to the housing 5. Alternatively, as an example, the battery cell assembly may be housed within the housing 5 by directly securing multiple battery cells 6 to the housing 5.

[0192] In some embodiments, the housing 5 is used to house the battery cell 6, and the housing 5 can have various structures.

[0193] In some embodiments, the housing 5 may include a first housing 51 and a second housing 52. The first housing 51 and the second housing 52 are fastened together to form a closed space inside the housing 5 to house the battery cell assembly. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first housing 51 may be a top cover or a bottom plate.

[0194] In some embodiments, the housing 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that the interior of the housing 5 forms an enclosed space to accommodate the battery cell assembly. As an example, the frame may include multiple side beams.

[0195] In some embodiments, the housing 5 may be part of the chassis structure of the vehicle 1. For example, a portion of the housing 5 may be at least a portion of the floor of the vehicle 1, or a portion of the housing 5 may be at least a portion of the crossbeams and longitudinal beams of the vehicle 1.

[0196] In some embodiments, the battery device 2 may be an energy storage device.

[0197] Energy storage devices can be used in energy storage power stations, wind power generation systems, solar power generation systems, mobile power systems, or temporary power supply systems. Energy storage devices can store electrical energy as needed and output it when appropriate. For example, energy storage devices can store electrical energy during off-peak hours and provide power to relevant users or electrical equipment during peak hours.

[0198] In some embodiments, the energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0199] Referring to Figures 3 to 7, an embodiment of this application provides a battery cell 6, which includes a housing 20 and an electrode assembly 10, with at least a portion of the electrode assembly 10 housed within the housing 20.

[0200] The housing 20 may be a hollow structure, with an internal space for accommodating the electrode assembly 10 and the electrolyte. Exemplarily, the housing 20 of the battery cell 6 is a housing 20.

[0201] In some embodiments, the housing 20 may be a metal housing 20, such as a steel housing, an aluminum housing, a composite metal housing (e.g., a copper-aluminum composite housing), or other metal housings. Alternatively, the housing 20 may also be a non-metallic housing, such as a plastic housing (e.g., polypropylene).

[0202] In some embodiments, the housing 20 can be a sealed structure or a non-sealed structure. As an example, when the housing 20 is a non-sealed structure, it serves to protect the electrode assembly, and a sealing bag is included between the housing 20 and the electrode assembly 10 to encapsulate the electrode assembly 10 and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating component or an aluminum-plastic film. When the housing is a sealed structure, it is used to encapsulate the electrode assembly 10 and components such as the electrolyte.

[0203] As an example, the battery cell 10 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries.

[0204] In some embodiments, the housing 20 includes a housing 21 and an end cap 22, the housing 21 having an opening, and the end cap 22 being connected to the housing 21 and covering the opening.

[0205] The housing 21 is a component used to fit the end cap 22 to form the internal cavity of the battery cell 6. The formed internal cavity can be used to accommodate the electrode assembly 10, electrolyte, and other components.

[0206] The housing 21 and the end cap 22 can be separate components. For example, an opening can be provided on the housing 21, and the end cap 22 can be used to close the opening to form an internal cavity for the battery cell.

[0207] The shell 21 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc.

[0208] The shape of the end cap 22 can be adapted to the shape of the housing 21 to fit the housing 21. The material of the end cap 22 can be the same as or different from the material of the housing 21. Optionally, the end cap 22 can be made of a material with a certain hardness and strength (such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.), so that the end cap 22 is not easily deformed when subjected to compression and impact, so that the battery cell can have higher structural strength and improve reliability.

[0209] The end cap 22 is connected to the housing 21 by welding, bonding, snap-fitting or other means.

[0210] The housing 21 may be open at one end or open at both ends. In some examples, the housing 21 may be a structure with an opening on one side, and one end cap 22 is provided to cover the housing 21. In other examples, the housing 21 may also be a structure with openings on both sides, and two end caps 22 are provided, with the two end caps 22 respectively covering the two openings of the housing 21.

[0211] In some embodiments, the housing 21 includes an integrally formed sidewall 212 and an endwall 211, the endwall 211 and the end cap 22 being opposite each other along the axial direction of the battery cell 6, and the end cap 22 being sealed to the sidewall 212.

[0212] Electrode assembly 10 is the component in the battery cell 6 where the electrochemical reaction takes place. Electrode assembly 10 can be entirely housed within housing 20 or partially housed within housing 20. For example, a portion of the tabs of electrode assembly 10 can extend outside housing 20.

[0213] Optionally, the electrode assembly 10 is entirely housed within the housing 20.

[0214] In some embodiments, the electrode assembly 10 includes a positive electrode 11 and a negative electrode 12. During the charging and discharging of the battery cell 6, active ions (e.g., lithium ions) are inserted and extracted back and forth between the positive electrode 11 and the negative electrode 12.

[0215] In some embodiments, the positive electrode 11 may include a positive current collector 111 and a positive active material layer 112 disposed on at least one surface of the positive current collector 111.

[0216] As an example, the positive current collector 111 has two surfaces opposite each other in its own thickness direction, and the positive active material layer 112 is disposed on either or both of the two opposite surfaces of the positive current collector 111.

[0217] As an example, the positive current collector 111 can be made of metal foil, conductive polymer material, carbon material, or composite current collector. For example, as a metal foil, pure metal, alloy, or surface-treated metal can be used, including but not limited to stainless steel, copper, aluminum, nickel, nickel alloy, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0218] As an example, the positive electrode active material layer 112 includes a positive electrode active material, which may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 (O2) and at least one of its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0219] In some embodiments, the negative electrode sheet 12 may include a negative electrode current collector 121 and a negative electrode active material layer 122 disposed on at least one surface of the negative electrode current collector 121.

[0220] As an example, the negative electrode current collector 121 has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer 122 is disposed on either or both of the two opposite surfaces of the negative electrode current collector 121.

[0221] As an example, the negative electrode current collector 121 can be made of metal foil, conductive polymer material, carbon material, or composite current collector. For example, as a metal foil, pure metal, alloy, or surface-treated metal can be used, including but not limited to stainless steel, copper, aluminum, nickel, nickel alloy, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0222] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cell 6. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for battery cell 6 may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0223] In some embodiments, the positive current collector 111 may be made of aluminum, and the negative current collector 121 may be made of copper.

[0224] In some embodiments, the electrode assembly 10 further includes a separator 13 disposed between the positive electrode 11 and the negative electrode 12. The separator 13 serves to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0225] The separator 13 may be partially located between the positive electrode 11 and the negative electrode 12. For example, the separator 13 protrudes from both ends of the positive electrode 11 and the negative electrode 12 along the axial direction of the battery cell 6; or the entire separator 13 may be located between the positive electrode 11 and the negative electrode 12.

[0226] In some embodiments, the separator 13 is a separator membrane. The separator membrane of this application can be any known porous structure separator membrane with good chemical and mechanical stability.

[0227] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different. The separator 13 can be a single component located between the positive electrode 11 and the negative electrode 12, or it can be attached to the surface of the positive electrode 11 or the surface of the negative electrode 12. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0228] In some embodiments, the battery cell 6 further includes an electrolyte that serves to conduct ions between the positive electrode 11 and the negative electrode 12. The electrolyte used in this application can be selected according to requirements.

[0229] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0230] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0231] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0232] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell 6, such as additives that improve the overcharge / fast charge performance of the battery cell 6, additives that improve the high-temperature performance of the battery cell 6, additives that improve the low-temperature performance of the battery cell 6, etc.

[0233] The electrode assembly 10 can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0234] In some embodiments, the positive electrode 11, the negative electrode 12, and the separator 13 are wound together.

[0235] The electrode assembly 10 has a wound structure. For example, the positive electrode 11, the separator 13, and the negative electrode 12 are wound into a cylindrical wound structure.

[0236] In some embodiments, the electrode assembly 10 has a stacked structure.

[0237] As an example, multiple positive electrode plates 11 and multiple negative electrode plates 12 can be set, and multiple positive electrode plates 11 and multiple negative electrode plates 12 can be stacked alternately.

[0238] As an example, multiple positive electrode plates 11 can be provided, and negative electrode plates 12 can be folded to form multiple stacked folded segments, with a positive electrode plate 11 sandwiched between adjacent folded segments.

[0239] As an example, both the positive electrode 11 and the negative electrode 12 are folded to form multiple stacked folded segments.

[0240] As an example, multiple separators 13 can be provided, respectively disposed between any adjacent positive electrode 11 or negative electrode 12.

[0241] As an example, the separator 13 can be continuously arranged and disposed between any adjacent positive electrode 11 or negative electrode 12 by means of folding or rolling.

[0242] In some embodiments, the electrode assembly 10 may be cylindrical, flat, or polygonal, etc.

[0243] In some embodiments, the electrode assembly 10 is provided with tabs that can conduct current from the electrode assembly 10. The tabs include a positive tab and a negative tab.

[0244] In some embodiments, the battery cell 6 is used in an electrical device. The battery cell 6 includes a housing 20 and an electrode assembly 10. The housing 20 contains an electrolyte. At least a portion of the electrode assembly 10 is located within the housing 20. The electrode assembly 10 includes a separator 13 and a first electrode 14 and a second electrode 15 with opposite polarities. At least a portion of the separator 13 is located between the first electrode 14 and the second electrode 15. The first electrode 14 includes a first current collector 141 and a first active material layer 142. At least a portion of at least one surface of the first current collector 141 along its thickness direction Y is connected to the first active material layer 142. At least a portion of the first active material layer 142 is located between the first current collector 141 and the separator 13. The first active material layer 142 has a first surface 1421 disposed away from the first current collector 141. The first surface 1421 is provided with a first groove 1441 extending along a first direction Z. The first direction Z is parallel to the direction of gravity.

[0245] The battery cell 6 is installed inside the electrical device and is used to provide or store electrical energy.

[0246] In some examples, when the electrical device is operating normally, the first direction Z is parallel to the direction of gravity.

[0247] For example, the electrical device is vehicle 1. When vehicle 1 is driving on a flat road or parked on a flat ground, the first direction Z is parallel to the direction of gravity.

[0248] For example, the first direction Z can be the vertical direction, i.e., the up-down direction. The first direction Z can also refer to the height direction of the battery cell 6.

[0249] In some examples, the first direction Z can be the axial direction of the battery cell 6.

[0250] Referring to Figure 8, in some examples, the first electrode 14 is in an unfolded state, and the first direction Z can refer to the width direction of the first electrode 14; referring to Figure 5, the first electrode 14 is in a wound state, and the first direction Z can refer to the direction parallel to the winding axis X2 of the electrode assembly 10.

[0251] One of the first electrode 14 and the second electrode 15 is the aforementioned positive electrode 11, and the other is the aforementioned negative electrode 12.

[0252] A portion of the spacer 13 is located between the first electrode 14 and the second electrode 15. Alternatively, the entire spacer 13 is located between the first electrode 14 and the second electrode 15.

[0253] For example, the first electrode 14 is a negative electrode 12, and the first electrode 14 includes a first current collector 141 and a first active material layer 142. The first current collector 141 is the aforementioned negative current collector 121, and the first active material layer 142 is the aforementioned negative active material layer 122. Alternatively, the first electrode 14 is a positive electrode 11, the first current collector 141 is the aforementioned positive current collector 111, and the first active material layer 142 is the aforementioned positive active material layer 112.

[0254] The first current collector 141 has one surface covered with a first active material layer 142 along its thickness direction Y, or both surfaces of the first current collector 141 along its thickness direction Y are covered with the first active material layer 142.

[0255] The first active material layer 142 may cover a portion of the surface of the first current collector 141, or it may cover the entire surface of the first current collector 141.

[0256] The first active material layer 142 can be directly applied to the first current collector 141. Alternatively, other layer structures, such as a conductive protective layer, can be provided between the first active material layer 142 and the first current collector 141. The conductive protective layer can be made by mixing a conductive agent and an adhesive. The adhesive bonds the first active material layer 142 and the first current collector 141, while the conductive agent is responsible for conducting electrons. The conductive agent can be carbon black, graphite, etc., and the adhesive can be polyvinylidene fluoride, etc.

[0257] The surface of the first active material layer 142 facing away from the first current collector 141 is the first surface 1421. The first surface 1421 has a first groove 1441 formed along the first direction Z. The first groove 1441 can be processed on the surface of the first active material layer 142 by means of laser or mechanical cutting.

[0258] The first surface 1421 has a first groove 1441 extending along the first direction Z. It can be understood that the first groove 1441 is a straight groove or similar to a straight groove. The extension direction of the first groove 1441 (e.g., the length direction of the first groove 1441) is parallel or nearly parallel to the first direction Z. Especially when there is an installation error or manufacturing error in the battery cell 6, the extension direction of the first groove 1441 can form an angle of 0° to 10° with the first direction Z.

[0259] By adopting the technical solution of this embodiment, since the first surface 1421 of the first active material layer 142 is provided with a first groove 1441 extending along a first direction, and the first direction is parallel to the direction of gravity, the first groove 1441 extends along the direction of gravity, and the electrolyte can climb upward along the first groove 1441, thereby improving the climbing ability of the electrolyte, improving the wetting effect of the electrolyte, and improving the cycle performance of the battery cell 6.

[0260] In some embodiments, the size of the first groove 1441 along the first direction is l, and the size of the first active material layer 142 is L, wherein 0.65≤l / L≤1.

[0261] It is understood that the first groove 1441 extends from the lower side of the first surface 1421 toward the upper side, or the first groove 1441 extends from the upper side of the first surface 1421 toward the lower side, but it is not required that the first groove 1441 extend completely in the first direction Z.

[0262] In some examples, the first groove 1441 may extend in a straight line along the first direction Z, or extend obliquely relative to the first direction Z, or extend in an arc or bend from the lower side of the first surface 1421 toward the upper side. Of course, other extension shapes are also possible.

[0263] In some examples, the value of l / L can be 0.65, 1, or any value between 0.65 and 1. For example, the value of l / L can be, but is not limited to, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.98, 0.99, and 1.

[0264] In the battery cell 6 of this application embodiment, along the first direction, the size of the first groove 1441 is l, and the size of the first active material layer 142 is L, wherein 0.65≤l / L≤1. In the first direction, the first groove 1441 can occupy most of the area of ​​the first active material layer 142. The first groove 1441 can extend from the lower part to the upper part of the first active material layer 142. The electrolyte can flow from the lower part to the upper part of the first active material layer 142 along the first groove 1441, which is beneficial to improve the climbing ability of the electrolyte, improve the wetting effect of the upper part of the first active material layer 142, reduce the ion transport resistance, and improve the cycle performance of the battery cell 6.

[0265] In the battery cell 6 of this application embodiment, during the charging and discharging process, the electrode assembly 10 expands, and the electrolyte is squeezed out from between the first electrode 14 and the second electrode 15. The first groove 1441 can also be used to store the electrolyte, reducing the amount of electrolyte squeezed out, which is also beneficial to improving the cycle performance of the battery cell 6. In addition, the first groove 1441 can also be used to guide the electrolyte back to between the first electrode 14 and the second electrode 15, which is also beneficial to improving the reliability of the battery cell 6.

[0266] In some embodiments, 0.8 ≤ l / L ≤ 1.

[0267] In this embodiment of the battery cell, the design of 0.8≤l / L≤1 ensures that the size l of the first groove 1441 and the size L of the first active material layer 142 are not much different or the same along the first direction Z. The two ends of the first groove 1441 are relatively close to the two ends of the first active material layer 142, so that the electrolyte squeezed out from the two ends of the electrode assembly 10 can quickly flow back through the first groove 1441, which can effectively improve the wetting effect of the first electrode 14 and improve the cycle performance of the battery cell 6.

[0268] In some embodiments, 0.8 ≤ l / L ≤ 0.98.

[0269] In some embodiments, 0.8≤l / L≤0.98, while improving the cycle performance of the battery cell 6, the first groove 1441 also has a larger size at the lower part of the first active material layer 142, which can better guide the electrolyte at the lower part of the first active material layer 142 to the upper part of the first active material layer 142, so that the upper part of the first active material layer 142 has a better wetting effect, effectively improving the cycle performance of the battery cell 6.

[0270] As the requirements for battery cell capacity gradually increase, the height of battery cells also gradually increases. However, the increased height of battery cells makes it more difficult for the electrolyte to penetrate upwards during the charging and discharging process, affecting the cycle performance of the battery cells. Therefore, how to improve the cycle performance of taller battery cells is an important research direction in the field of battery technology.

[0271] In some embodiments, the battery cell is a cylindrical battery cell with a diameter of 60mm ≤ L ≤ 350mm.

[0272] In some examples, the value of L can be 60mm, 330mm, or any value between 60mm and 350mm. For example, the value of L can be, but is not limited to, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 100mm, 150mm, 200mm, 250mm, 300mm, 330mm, and 350mm.

[0273] By adopting the technical solution of this embodiment, with a design of 60mm≤L≤350mm, the size of the first active material layer 142 is larger along the first direction Z, and the first active material layer 142 can accommodate more active material, thereby increasing the capacity of the cylindrical battery cell. However, in the first direction Z, the distance for the extruded electrolyte to flow back to the middle of the first active material layer 142 is long, increasing the difficulty of the extruded electrolyte flowing back to the middle of the first active material layer 142. Combined with the design of 0.65≤l / L≤1, on the one hand, in the first direction, the first groove 1441 can occupy most of the area of ​​the first active material layer 142. The first groove 1441 can extend from the lower part to the upper part of the first active material layer 142, and the electrolyte can flow from the lower part to the upper part of the first active material layer 142 along the first groove 1441, which is beneficial to improve the climbing ability of the electrolyte, improve the wetting effect of the upper part of the first active material layer 142, reduce the ion transport resistance, and improve the cycle performance of the battery cell 6. On the other hand, the extruded electrolyte can be quickly returned to the middle of the first active material layer 142 through the first groove 1441, which is beneficial to improve the wetting effect of the first electrode 14 and improve the cycle performance of the cylindrical battery cell. Therefore, the capacity and cycle performance of the cylindrical battery cell can be taken into account.

[0274] In some embodiments, 80mm≤L≤210mm can better balance the capacity and cycle performance of cylindrical battery cells.

[0275] Example

[0276] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosures in this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0277] Preparation of battery cells

[0278] 1. Preparation of positive electrode sheet

[0279] The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is located on both sides of the positive current collector. The positive current collector is an aluminum foil. The positive active material layer is a film layer formed by uniformly coating the positive current collector aluminum foil with a positive slurry (solvent is N-methylpyrrolidone NMP) and then drying and cold pressing it. The positive active material layer includes positive active material, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) in a weight ratio of 97:1:2.

[0280] Positive electrode active materials include those with the molecular formula LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 Layered transition metal oxides.

[0281] 2. Preparation of negative electrode sheet

[0282] The negative electrode sheet includes a negative current collector and a negative active material layer. The negative active material layer is located on both sides of the negative current collector. The negative current collector is a copper foil. The negative active material layer is a film layer formed by uniformly coating the surface of the copper foil with a negative electrode slurry (solvent is deionized water), and then drying and cold pressing. The negative active material layer includes silicon-based material (specifically silicon oxide compound), graphite, conductive carbon black, conductive carbon nanotubes, and binder polyacrylic acid in a weight ratio of 12.6:82.4:1.9:0.1:3. Laser grooving is performed on the surface of the negative active material layer to obtain the first groove.

[0283] The areal density of the negative electrode active material layer is 9.0 mg / cm³. 2 The porosity is 22.1%, and the compacted density is 1.7 g / cm³. 3 The surface of the negative electrode active material layer facing away from the negative electrode current collector has a first groove.

[0284] 3. Isolation components

[0285] We provide PE (polyethylene) based films.

[0286] 4. Preparation of electrolyte

[0287] The electrolyte consists of an organic solvent and a lithium salt. Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0288] 5. Preparation of cylindrical battery cells

[0289] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The positive electrode, separator, and negative electrode are then wound to form an electrode assembly. This assembly is placed in a cylindrical shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a cylindrical battery cell is obtained. The electrode assembly and the shell are both cylindrical, comprising a housing and end caps. The housing includes integrally formed sidewalls and end walls. The sidewalls surround the electrode assembly, while the end caps and end walls are axially aligned with the battery cell. The cylindrical battery cell has a diameter of 46 mm and a height of 95 mm.

[0290] Performance testing

[0291] Battery cycle performance test

[0292] At 45°C, the prepared cylindrical battery cells are fully charged at 1C and then fully discharged at 1C. This constitutes one charge-discharge cycle. The discharge capacity at this point is recorded as the first cycle discharge capacity. The cylindrical battery cells are then subjected to cyclic charge-discharge tests using the same method, and the discharge capacity after each cycle is recorded until the discharge capacity of the cylindrical battery cell decreases to 80% of its initial discharge capacity. The number of cycles at this point characterizes the cycle performance of the cylindrical battery cell. A higher number of cycles indicates better cycle performance.

[0293] Cylindrical battery cells were manufactured according to the numerical parameters recorded in Table 1 below, and the performance tests described above were performed. The results are shown in the table below.

[0294] Table 1

[0295] Referring to Table 1, 0.65≤l / L≤1, in the first direction, the first groove can occupy most of the area of ​​the first active material layer. The first groove can extend from the lower part to the upper part of the first active material layer. The electrolyte can flow from the lower part to the upper part of the first active material layer along the first groove, which is beneficial to improve the climbing ability of the electrolyte, improve the wetting effect of the upper part of the first active material layer, reduce the ion transport resistance, and improve the cycle performance of the battery cell.

[0296] In some embodiments, the battery cell is a prismatic battery cell with a diameter of 120mm ≤ L ≤ 330mm.

[0297] In some examples, the value of L can be 120mm, 330mm or any value between 120mm and 350mm. For example, the value of L can be, but is not limited to, 100mm, 110mm, 100mm, 150mm, 200mm, 250mm, 300mm, and 330mm.

[0298] By adopting the technical solution of this embodiment, with a design of 120mm≤L≤330mm, the size of the first active material layer 142 is larger along the first direction Z, and the first active material layer 142 can accommodate more active material, thereby increasing the capacity of the prismatic battery cell. However, in the first direction Z, the distance for the extruded electrolyte to flow back to the middle of the first active material layer 142 is long, increasing the difficulty of the extruded electrolyte flowing back to the middle of the first active material layer 142. Combined with the design of 0.65≤l / L≤1, on the one hand, in the first direction, the first groove 1441 can occupy most of the area of ​​the first active material layer 142. The first groove 1441 can extend from the lower part to the upper part of the first active material layer 142, and the electrolyte can flow from the lower part to the upper part of the first active material layer 142 along the first groove 1441, which is beneficial to improve the climbing ability of the electrolyte, improve the wetting effect of the upper part of the first active material layer 142, reduce the ion transport resistance, and improve the cycle performance of the battery cell 6. On the other hand, the extruded electrolyte can be quickly returned to the middle of the first active material layer 142 through the first groove 1441, which is beneficial to improve the wetting effect of the first electrode 14 and improve the cycle performance of the prismatic battery cell. Therefore, the capacity and cycle performance of the prismatic battery cell can be taken into account.

[0299] In some embodiments, 160mm≤L≤250mm can better balance the capacity and cycle performance of prismatic battery cells.

[0300] Example

[0301] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0302] Preparation of battery cells

[0303] 1. Preparation of positive electrode sheet

[0304] The positive electrode includes a positive current collector, a positive conductive layer on the positive current collector, and a positive film layer. The positive current collector is an aluminum foil with the same thickness as the positive electrode tab. The positive conductive layer on the positive current collector is a film layer formed by uniformly mixing the positive conductive agent superconducting carbon, the positive binder polyvinylidene fluoride (PVDF), and the solvent N-methylpyrrolidone (NMP) and then coating it on the surface of the current collector. The thickness is 1 μm. The positive conductive agent in the positive conductive layer has a mass content of 40%, and the positive binder has a mass content of 60%.

[0305] The positive electrode film layer comprises a film layer formed by uniformly coating a positive electrode slurry (solvent being N-methylpyrrolidone, NMP) onto the surface of a positive electrode conductive layer, followed by drying and cold pressing. The positive electrode film layer comprises positive electrode active material, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black in a weight ratio of 97:2:1.

[0306] The positive electrode active material includes lithium iron phosphate and a coating layer. The coating layer is coated on the surface of the lithium iron phosphate and includes lithium titanium iron phosphate (Li2FeTi(PO4)3) and amorphous carbon. The Dv50 of the positive electrode active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0307] The single-sided coating weight of the positive electrode film is 290 mg / 1540.25 mm. 2 .

[0308] 2. Preparation of negative electrode sheet

[0309] The negative electrode sheet includes a negative current collector, a negative conductive layer on the negative current collector, and a negative active material layer. The negative current collector is a copper foil with the same thickness as the negative electrode tab. The negative conductive layer on the negative current collector is a film layer with a thickness of 1 μm formed by uniformly mixing superconducting carbon as a negative conductive agent, styrene-butadiene rubber (SBR) as a negative binder, sodium carboxymethyl cellulose (CMC-Na) as a thickener, and water as a solvent, and then coating it onto the surface of the negative current collector. The negative conductive agent has a mass content of 35% in the negative conductive layer, the negative binder has a mass content of 60% in the negative conductive layer, and the thickener has a mass content of 5% in the negative conductive layer.

[0310] The negative electrode active material layer consists of a film layer formed by uniformly coating the negative electrode slurry (with deionized water as the solvent) onto the surface of the negative electrode conductive layer, followed by drying and cold pressing.

[0311] The single-sided coating weight of the negative electrode active material layer is 135 mg / 1540.25 mm. 2 .

[0312] The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer. The first negative electrode active material layer is located on the surface of the negative electrode conductive layer, and the second negative electrode active material layer is located on the surface of the first negative electrode active material layer.

[0313] The first negative electrode active material layer comprises graphite particles in a mass ratio of 96.5:0.5:0.5:1.5:1, conductive agent acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer), negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose; the lithium content in the first lithium-containing binder is 4.8% by mass; the Dv50 of the graphite particles is 11.3 μm, and the graphite particles include artificial graphite and an amorphous carbon layer, with the amorphous carbon layer coating the surface of the artificial graphite, and the amorphous carbon content is 3.5% by mass.

[0314] The second negative electrode active material layer comprises graphite particles in a mass ratio of 97.5:0.5:0.5:0.5:1, conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer), negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose; the lithium content in the second lithium-containing binder is 4.8% by mass; the graphite particles have a Dv50 of 11.3 μm and include artificial graphite and an amorphous carbon layer, with the amorphous carbon layer coating the surface of the artificial graphite, and the amorphous carbon content is 3.5% by mass. A first groove is provided on the surface of the second negative electrode active material layer facing away from the negative electrode current collector.

[0315] 3. Separating membrane

[0316] The separator includes a base membrane, which is a 7μm polyethylene film layer with a porosity of 42%.

[0317] 4. Preparation of electrolyte

[0318] The electrolyte comprises an organic solvent, a lithium salt, and additives. The organic solvent consists of 60% chain carboxylic acid esters (ethyl acetate) and 40% carbonates (30% ethylene carbonate EC and 10% dimethyl carbonate by mass). The additives comprise 6.5% by mass and include vinylene carbonate VC, fluoroethylene carbonate FEC, vinyl sulfite ES, and lithium difluorooxalate borate LiDFOB in a mass ratio of 5:0.5:0.5:0.5. The lithium salt comprises 1 mol / L lithium hexafluorophosphate LiPF6. The electrolyte has a conductivity of 16.4 mS / cm.

[0319] 5. Preparation of battery cells

[0320] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then obtained through a winding process. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a prismatic battery cell is obtained. The compaction density of the positive electrode film at 100% SOC is 2.60 g / cm³. 3 The compaction density of the negative electrode active material layer at 100% SOC is 1.25 g / cm³. 3 The electrode assembly has a flat structure, and the outer shell has a cuboid structure. The outer shell includes a housing and end caps. The housing includes integrally formed sidewalls and end walls. The sidewalls surround the electrode assembly, and the end caps and end walls are positioned opposite each other along the height direction of the battery cell. The cuboid battery cell has a length of 200mm, a width of 47.7mm, and a height of 215mm.

[0321] Performance testing

[0322] Battery cycle performance test

[0323] At 45°C, the prepared prismatic battery cells are fully charged at 1C and then fully discharged at 1C. This constitutes one charge-discharge cycle. The discharge capacity at this point is recorded as the first cycle discharge capacity. The prismatic battery cells are then subjected to cyclic charge-discharge tests using the same method, and the discharge capacity after each cycle is recorded until the discharge capacity of the prismatic battery cell decreases to 80% of its initial discharge capacity. The number of cycles at this point characterizes the cycle performance of the prismatic battery cell. The higher the number of cycles, the better the cycle performance.

[0324] The prismatic battery cells were manufactured according to the numerical parameters recorded in Table 2 below, and the performance tests described above were performed. The results are shown in the table below.

[0325] Table 2

[0326] Referring to Table 2, 0.65≤l / L≤1, in the first direction, the first groove can occupy most of the area of ​​the first active material layer. The first groove can extend from the lower part to the upper part of the first active material layer. The electrolyte can flow from the lower part to the upper part of the first active material layer along the first groove, which is beneficial to improve the climbing ability of the electrolyte, improve the wetting effect of the upper part of the first active material layer, reduce the ion transport resistance, and improve the cycle performance of the battery cell.

[0327] In some embodiments, along the first direction, the distance between the lower end of the first groove 1441 and the lower end face of the first active material layer 142 is S, where 0mm≤S≤20mm.

[0328] In some examples, the lower end face of the first active material layer 142 may be a plane. If the lower end of the first active material layer 142 has a small thickness, the lower end face of the first active material layer 142 has a small dimension in the thickness direction Y of the first current collector 141, and the lower end face of the first active material layer 142 may be approximated as a line.

[0329] In some examples, S can be 0mm, 20mm, or any value between 0mm and 20mm. For example, S can be 0mm, 0.2mm, 0.5mm, 1mm, 2mm, 2.5mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 15mm, or 20mm.

[0330] By adopting the technical solution of this embodiment, the design of 0mm≤S≤20mm makes the distance between the lower end of the first groove 1441 and the lower end face of the first active material layer 142 closer, so that the electrolyte accumulated at the bottom of the first electrode 14 can enter the first groove 1441 and wet the electrode assembly 10 through the first groove 1441, reducing the ion transport resistance, improving the wetting effect of the first electrode 14, and improving the cycle performance of the battery cell 6. Furthermore, since the first groove 1441 is formed along the first direction Z, which is parallel to the direction of gravity, the electrolyte accumulated at the bottom of the first electrode 14 can also move along the first groove 1441 toward the upper side of the first active material layer 142, which is beneficial to improving the distribution uniformity of the electrolyte and further improving the cycle performance of the battery cell 6.

[0331] The battery cell 6 in this embodiment can utilize the electrolyte accumulated at the bottom of the battery cell 6, which is beneficial to improve the effective utilization rate of the electrolyte and improve the overall performance of the battery cell 6.

[0332] In some embodiments, 2mm ≤ S ≤ 10mm.

[0333] With a depth S≥2mm, a distance exists between the lower end of the first groove 1441 and the lower end face of the first active material layer 142. The first groove 1441 does not penetrate the lower end face of the first active material layer 142, which helps improve the structural strength of the lower end of the first active material layer 142, reducing the risk of powder shedding or even collapse at the lower end of the first active material layer 142, and thus improving the capacity and reliability of the battery cell 6. With a depth S≤10mm, the electrolyte accumulated at the bottom of the first electrode 14 flows more easily into the first groove 1441 and moves upwards through it, more effectively improving the cycle performance of the battery cell 6. Therefore, the capacity, reliability, and cycle performance of the battery cell 6 can be balanced.

[0334] In some embodiments, 4mm≤S≤8mm can better balance the capacity, reliability and cycle performance of the battery cell 6.

[0335] In some embodiments, along the first direction Z, the distance between the upper end of the first groove 1441 and the upper end face of the first active material layer 142 is s, where 0mm≤s≤20mm.

[0336] In some examples, the upper surface of the first active material layer 142 may be a plane. If the upper end of the first active material layer 142 has a small thickness, the upper surface of the first active material layer 142 has a small dimension in the thickness direction Y of the first current collector 141, and the upper surface of the first active material layer 142 may be approximated as a line.

[0337] In some examples, s can be 0mm, 20mm, or any value between 0mm and 20mm. For example, s can be 0mm, 0.1mm, 0.2mm, 0.5mm, 1mm, 2mm, 2.5mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 15mm, or 20mm.

[0338] By adopting the technical solution of this embodiment, the design of 0mm≤s≤20mm makes the distance between the upper end of the first groove 1441 and the upper end surface of the first active material layer 142 closer, which is conducive to the electrolyte on the upper part of the first electrode 14 entering the first groove 1441 and entering the electrode assembly 10 through the first groove 1441 for ion transport, reducing the ion transport resistance, improving the wetting effect of the first electrode 14, and improving the cycle performance of the battery cell 6.

[0339] In some embodiments, 0.1mm ≤ s ≤ 8mm.

[0340] With a diameter s ≥ 0.1 mm, a distance exists between the upper end of the first groove 1441 and the upper surface of the first active material layer 142. The first groove 1441 does not penetrate the upper surface of the first active material layer 142, which is beneficial to the structural strength of the upper part of the first active material layer 142. This reduces the risk of powder shedding or even collapse at the upper part of the first active material layer 142, and is conducive to improving the capacity and reliability of the battery cell 6. With a diameter s ≤ 8 mm, the electrolyte on the upper part of the first electrode 14 flows more easily into the first groove 1441 and enters the electrode assembly 10 through the first groove 1441 for ion transport. This reduces ion transport resistance, improves the wetting effect of the first electrode 14, and improves the cycle performance of the battery cell 6. Therefore, it can better balance the cycle performance, capacity, and reliability of the battery cell 6.

[0341] In some embodiments, 0.5mm≤s≤3mm can better balance the cycle performance, capacity and reliability of the battery cell 6.

[0342] Referring to Figures 9 and 10, in the first direction Z, the first groove 1441 may be disposed at the lower end of the first active material layer 142 or located in the middle of the first active material layer 142.

[0343] In the battery cell 6, the electrode assembly 10 expands, and the electrolyte is squeezed out from both ends of the electrode assembly 10 along the first direction Z. The first groove 1441 is formed along the first direction Z, which can better guide the electrolyte squeezed out of the electrode assembly 10 to flow back, effectively improving the electrolyte flow rate, improving the wetting effect of the first electrode 14, and improving the cycle performance of the battery cell 6.

[0344] Referring to Figure 11, in some embodiments, the first surface 1421 is further provided with a plurality of second grooves 1444, which are intersected with the first grooves 1441, and the plurality of first grooves 1441 and the plurality of second grooves 1444 form a grid structure.

[0345] Referring to Figure 12, in some embodiments, the first groove 1441 may be a straight structure, or the first groove 1441 may be inclined relative to the first direction Z.

[0346] Referring to FIG7, in some embodiments, the second electrode 15 includes a second current collector 151 and a second active material layer 152. At least a portion of at least one surface of the second current collector 151 along its thickness direction is connected to the second active material layer 152. At least a portion of the second active material layer 152 is located between the second current collector 151 and the spacer 13.

[0347] In some examples, the second electrode 15 is a negative electrode 12, and the second electrode 15 includes a second current collector 151 and a second active material layer 152. The second current collector 151 is the aforementioned negative current collector 121, and the second active material layer 152 is the aforementioned negative active material layer 122. Alternatively, the second electrode 15 is a positive electrode 11, the second current collector 151 is the aforementioned positive current collector 111, and the second active material layer 152 is the aforementioned positive active material layer 112.

[0348] The second current collector 151 has a second active material layer 152 covering one surface along its thickness direction, or both surfaces of the second current collector 151 along its thickness direction are covered with the second active material layer 152.

[0349] The second active material layer 152 may cover a portion of the surface of the second current collector 151, or it may cover the entire surface of the second current collector 151.

[0350] The second active material layer 152 can be directly covered on the second current collector 151, or other layer structures, such as a conductive protective layer, can be provided between the second active material layer 152 and the second current collector 151.

[0351] Referring to Figures 8 and 13, in some embodiments, the first active material layer 142 includes a first active material portion 1422 and a second active material portion 1423 arranged along a first direction Z. At least one end of the first active material portion 1422 along the first direction Z is connected to the second active material portion 1423, and the thickness of the second active material portion 1423 is less than the thickness of the first active material portion 1422.

[0352] The lower end of the first active material portion 1422 is connected to the second active material portion 1423, or the upper end of the first active material portion 1422 is connected to the second active material portion 1423; or both the lower end and the lower end of the first active material portion 1422 are connected to the second active material portion 1423.

[0353] The thickness of the second active material portion 1423 is less than the thickness of the first active material portion 1422. The boundary between the first active material portion 1422 and the second active material portion 1423 can be referred to the thickness transition position of the first active material layer 142. The second active material portion 1423 can become the thinning area of ​​the first active material layer 142.

[0354] In some examples, the second active material portion 1423 and the first active material portion 1422 may have a generally equal thickness structure, with the thickness of the second active material portion 1423 being less than the thickness of the first active material portion 1422, so that the second active material portion 1423 and the first active material portion 1422 form a stepped structure.

[0355] In some examples, the first active material portion 1422 may have a generally uniform thickness. Along the direction from the first active material portion 1422 to the second active material portion 1423, the thickness of the second active material portion 1423 decreases from that of the first active material portion 1422, such that the thickness of the second active material portion 1423 is less than the thickness of the first active material portion 1422. The direction from the first active material portion 1422 to the second active material portion 1423 can be seen in the direction indicated by arrow Z in Figure 13.

[0356] By adopting the technical solution of this embodiment, the thickness of the second active material portion 1423 is less than the thickness of the first active material portion 1422, making the surface of the second active material portion 1423 facing away from the first current collector 141 closer to the first current collector 141 than the surface of the first active material portion 1422 facing away from the first current collector 141. On the one hand, this can reduce the rolling pressure on the edge of the first active material layer 142 during the rolling process of the first electrode 14, reducing the risk of edge cracking of the first active material layer 142. On the other hand, the side of the second active material portion 1423 facing away from the first current collector 141 can accommodate more electrolyte, thereby facilitating the return of electrolyte. Furthermore, the thickness difference between the second active material portion 1423 and the first active material portion 1422 can be used to form a siphon effect, which can increase the speed at which electrolyte flows into the space between the first electrode 14 and the second electrode 15, improve the wetting effect of the electrode assembly 10, and improve the cycle performance of the battery cell 6.

[0357] In some embodiments, the thickness of the second active material portion 1423 decreases along the direction from the first active material portion 1422 to the second active material portion 1423.

[0358] For example, along the direction from the first active material portion 1422 to the second active material portion 1423, the thickness of the second active material portion 1423 decreases in a stepped manner, making the second active material portion 1423 a stepped structure; or, along the direction from the first active material portion 1422 to the second active material portion 1423, the thickness of the second active material portion 1423 decreases slowly, and the shape of the second active material portion 1423 is more rounded or smooth, which helps to reduce stress concentration and improve the structural strength of the positive electrode 11.

[0359] In some examples, along the direction from the first active material portion 1422 to the second active material portion 1423, the end face of the second active material layer 152 extends beyond the end face of the second active material portion 1423 and is close to the end face of the first active material portion 1422. The thickness of the second active material portion 1423 tends to decrease, so that a flared structure can be formed between the second active material portion 1423 and the second active material layer 152. The larger end of the flared structure is positioned away from the first active material portion 1422. The flared structure makes it easier for the electrolyte to be drawn into the space between the first active material portion 1422 and the second electrode 15, which is more conducive to improving the wetting effect of the electrode assembly 10 and improving the cycle performance of the battery cell 6.

[0360] In some examples, along the direction from the first active material portion 1422 to the second active material portion 1423, the end face of the second active material layer 152 does not exceed the end face of the second active material portion 1423 that is close to the first active material portion 1422. The second active material portions 1423 of two adjacent first electrode windings 143 are also arranged to form a flared structure. The larger end of the flared structure is set away from the first active material portion 1422. The flared structure makes it easier for the electrolyte to be drawn into the space between the first active material portion 1422 and the second electrode 15, which is more conducive to improving the wetting effect of the electrode assembly 10 and improving the cycle performance of the battery cell 6.

[0361] In some embodiments, the first active material portion 1422 has a first surface 1424 facing away from the first current collector 141, and the second active material portion 1423 has a second surface 1425 facing away from the first current collector 141, wherein the second surface 1425 is closer to the first current collector 141 than the first surface 1424.

[0362] The distance between the second surface 1425 and the first current collector 141 is less than the distance between the first surface 1424 and the first current collector 141.

[0363] By adopting the technical solution of this embodiment, the side of the second surface 1425 facing away from the first current collector 141 has more space to accommodate the electrolyte. Furthermore, the distance difference between the second surface 1425 and the first surface 1424 and the first current collector 141 can be used to form a siphon effect, thereby increasing the speed of electrolyte reflux, improving the wetting effect of the electrode assembly 10, and improving the cycle performance of the battery cell 6.

[0364] In some embodiments, the first active material portion 1422 is provided with a first groove 1441 along the first direction Z, and the second active material portion 1423 is disposed at a distance from the first groove 1441.

[0365] Along the first direction Z, there is a distance between the second active material portion 1423 and the first groove 1441, such that the first groove 1441 of the first active material portion 1422 does not extend to the second active material portion 1423.

[0366] By adopting the technical solution of this embodiment, the first active material part 1422 is provided with a first groove 1441, which can improve the wetting effect of the first active material part 1422 and improve the cycle performance of the battery cell 6. The second active material part 1423 is spaced apart from the first groove 1441, which is beneficial to improve the structural strength of the second active material part 1423 and reduce the risk of powder shedding or even collapse of the second active material part 1423. This is beneficial to improve the capacity and reliability of the battery cell 6. Therefore, the cycle performance, capacity and reliability of the battery cell 6 can be taken into account.

[0367] In some embodiments, along the first direction Z, the distance between the second active material portion 1423 and the first groove 1441 is S1, wherein 0mm < S1 ≤ 18mm.

[0368] In some examples, S1 can be 18mm or any value between 0mm and 18mm. For example, S1 can be 0.1mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 12mm, 14mm, 16mm, or 18mm.

[0369] S1 > 0 mm ensures that the first groove 1441 does not extend into the second active material portion 1423, which is beneficial to improving the structural strength of the second active material portion 1423 and reducing the risk of powder shedding or even collapse of the second active material portion 1423. This is beneficial to improving the capacity and reliability of the battery cell 6. The design of S1 ≤ 10 mm ensures that the electrolyte located on the side of the second active material portion 1423 away from the first current collector 141 is closer to the first groove 1441, allowing the electrolyte to flow better into the first groove 1441, improving the wetting effect of the first electrode 14, and improving the cycle performance of the battery cell 6. Therefore, the cycle performance, capacity, and reliability of the battery cell 6 can be balanced.

[0370] In some embodiments, 2mm≤S1≤8mm can better balance the reliability and cycle performance of the battery cell 6.

[0371] In some embodiments, the first electrode 14 is the negative electrode 12.

[0372] The first electrode 14 is the negative electrode 12. The first active material portion 1422 and the second active material portion 1423 include negative electrode active materials. The first groove 1441 and the second active material portion 1423 are spaced apart. The first groove 1441 does not extend to the second active material portion 1423. The negative electrode active material in the second active material portion 1423 is not grooved. The second active material portion 1423 has more negative electrode active material, which reduces the risk of lithium plating in the battery cell 6 and helps to improve the performance of the battery cell 6.

[0373] In some embodiments, the lower end of the first active material portion 1422 is connected to the second active material portion 1423.

[0374] By adopting the technical solution of this embodiment, the lower end of the first active material part 1422 is connected to the second active material part 1423, so that the lower part of the first electrode 14 can form a siphon effect, which can better draw the electrolyte accumulated at the bottom into the first groove 1441 and move upward through the first groove 1441, effectively improving the cycle performance of the battery cell 6.

[0375] In some embodiments, the upper end of the first active material portion 1422 is connected to the second active material portion 1423.

[0376] By adopting the technical solution of this embodiment, the upper end of the first active material part 1422 is connected to the second active material part 1423, so that the upper part of the first electrode 14 can form a siphon effect, which can better guide the electrolyte in the upper part to be drawn into the first groove 1441 and move upward through the first groove 1441, effectively improving the cycle performance of the battery cell 6.

[0377] In some embodiments, along the first direction, one end of the first active material portion 1422 is connected to the second active material portion 1423, and the other end of the first active material portion 1422 is not connected to the second active material portion 1423. The surface of the first active material portion 1422 facing away from the first current collector 141 is provided with a first groove 1441. Along the first direction, the first groove 1441 penetrates the end face of the first active material portion 1422 facing away from the second active material portion 1423.

[0378] The first groove 1441 penetrates the end face of the first active material portion 1422 facing away from the second active material portion 1423 and forms an opening. This opening can directly draw the electrolyte accumulated at the bottom of the first electrode 14 into the first groove 1441, effectively improving the wetting effect of the first electrode 14 and helping to improve the cycle performance of the battery cell 6.

[0379] In some embodiments, along the first direction, one end of the first active material portion 1422 is connected to the second active material portion 1423, and the other end of the first active material portion 1422 is not connected to the second active material portion 1423. The surface of the first active material portion 1422 facing away from the first current collector 141 is provided with a first groove 1441. Along the first direction, the end face of the first active material portion 1422 facing away from the second active material portion 1423 is spaced apart from the first groove 1441.

[0380] Along the first direction Z, there is a distance between the end face of the first active material portion 1422 facing away from the second active material portion 1423 and the first groove 1441, so that the first groove 1441 does not penetrate the end face of the first active material portion 1422 facing away from the second active material portion 1423.

[0381] By adopting the technical solution of this embodiment, the end face of the first active material part 1422 facing away from the second active material part 1423 is spaced apart from the first groove 1441, which is beneficial to improve the structural strength of the lower end of the first active material part 1422 and can reduce the risk of powder falling off or even collapsing at the lower end of the first active material part 1422.

[0382] In some embodiments, along the first direction Z, both ends of the first active material portion 1422 are connected to the second active material portion 1423, which is beneficial for the first electrode 14 to form a siphon effect at both ends along the first direction Z, thereby facilitating the return of electrolyte, improving the wetting effect of the electrode assembly 10, and improving the cycle performance of the battery cell 6.

[0383] Referring to Figure 7, in some embodiments, the first current collector 141 includes a first current collector body 1411 and a first tab 1412 arranged and connected along the first direction Z. At least a portion of the first current collector body 1411 is covered with a first active material layer 142, and the first tab 1412 is not covered with the first active material layer 142.

[0384] Along the first direction Z, the first current collector 141 is divided into two parts. The part covered by the first active material layer 142 is called the first current collector body 1411, and the other part not covered by the first active material layer 142 is called the first tab 1412. The interface between the first tab 1412 and the first current collector body 1411 can be the end face of the first active material layer 142. The first tab 1412 is used for electrical connection with the output electrode to facilitate the input and output of electrical energy.

[0385] In some examples, the first current collector 1411 may be completely covered by the first active material layer 142, or it may be partially covered by the first active material layer 142. For example, the side of the first current collector 1411 facing away from the first tab 1412 is not covered by the first active material layer 142.

[0386] By adopting the technical solution of this embodiment, the first electrode 1412 is led out from the end of the first electrode 14 along the first direction Z, which facilitates the electrical connection of the first electrode 1412 with other components.

[0387] Referring to Figures 8 and 14, in some embodiments, there are two first active material layers 142, which respectively cover two surfaces of the first current collector 141 along its own thickness direction Y, and at least one first active material layer 142 is provided with a first groove 1441.

[0388] The first current collector 141 has two surfaces covered with a first active material layer 142 along its thickness direction Y; one of the two first active material layers 142 is provided with a first groove 1441, and the other first active material layer 142 is not provided with a first groove 1441, or both first active material layers 142 are provided with a first groove 1441.

[0389] By adopting the technical solution of this embodiment, the arrangement of two first active material layers 142 can increase the amount of active material in the first electrode 14, which is beneficial to increasing the capacity of the battery cell 6; in addition, the arrangement of the first groove 1441 is also more flexible to meet different usage requirements.

[0390] In some embodiments, there are multiple first grooves 1441, including first grooves 1446 and second grooves 1447. In two first active material layers 142, one is provided with multiple first grooves 1446 and the other is provided with multiple second grooves 1447. Along the thickness direction Y of the first current collector 141, the first grooves 1446 and the second grooves 1447 are staggered.

[0391] Both first active material layers 142 are provided with first grooves 1441, one of which is a first groove 1446 and the other is a second groove 1447.

[0392] The number of first grooves 1446 is multiple, and the number of second grooves 1447 is multiple, in order to improve the wetting effect of the first electrode 14.

[0393] In some examples, along the thickness direction Y of the first current collector 141, in adjacent first grooves 1446 and second grooves 1447, the projection of the first groove 1446 does not coincide with the projection of the second groove 1447.

[0394] For example, there may be one or more second slots 1447 between two adjacent first slots 1446.

[0395] By adopting the technical solution of this embodiment, the two first active material layers 142 are respectively provided with a plurality of first grooves 1446 and a plurality of second grooves 1447, so as to improve the wetting effect of the two first active material layers 142 and improve the cycle performance of the battery cell 6; in addition, the first grooves 1446 and the second grooves 1447 are staggered along the thickness direction Y of the first current collector 141, which is beneficial to improve the structural strength of the first electrode 14 and improve the reliability of the battery cell 6.

[0396] In some embodiments, a plurality of first grooves 1446 and a plurality of second grooves 1447 are alternately arranged along a second direction X, the second direction X being perpendicular to the first direction Z and the thickness direction Y of the first current collector 141.

[0397] For example, a second slot 1447 may be provided between two adjacent first slots 1446.

[0398] By adopting the technical solution of this embodiment, multiple first grooves 1446 and multiple second grooves 1447 can be evenly distributed on the two first active material layers 142, which can improve the uniformity of electrolyte distribution in the battery cell 6 and is beneficial to improving the cycle performance of the battery cell 6.

[0399] In some embodiments, along the second direction X, the distance between adjacent first groove 1446 and second groove 1447 is C, where C ≥ 1.5 mm.

[0400] In some examples, the distance C between adjacent first slots 1446 and second slots 1447 along the second direction X can refer to the distance between the center plane of the first slot 1446 perpendicular to the second direction X and the center plane of the second slot 1447 perpendicular to the second direction X.

[0401] In some examples, C is 1.5mm or any value greater than 1.5mm. For example, C is 1.5mm, 1.8mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, and 10mm.

[0402] By adopting the technical solution of this embodiment, the design with C≥1.5mm and the reasonable density setting of the first groove 1446 and the second groove 1447 can reduce the loss of active material in the first active material layer 142 and also help improve the structural strength of the first electrode 14. Therefore, the reliability and energy density of the battery cell 6 can be taken into account.

[0403] In some embodiments, 1.8mm ≤ C ≤ 5mm, and optionally, 2mm ≤ C ≤ 3mm.

[0404] With a design of 1.8mm≤C≤5mm, the spacing between adjacent first grooves 1446 and second grooves 1447 is reasonably designed, and the first grooves 1441 of the two first active material layers 142 are reasonably distributed. This is beneficial to improving the wetting performance of the first electrode 14, reducing the loss of active material in the first active material layer 142, and improving the structural strength of the first electrode 14. Therefore, the cycle performance, reliability, and energy density of the battery cell 6 can be taken into account.

[0405] In some embodiments, 2mm≤C≤3mm can better balance the cycle performance, reliability and energy density of the battery cell 6.

[0406] Referring to Figures 5, 6, and 15, in some embodiments, the electrode assembly 10 is a wound structure, with the first electrode 14 wound to form a plurality of first electrode winding coils 143, the first current collector 141 including a first current collector winding coil 1431 located in the first electrode winding coils 143, the first active material layer 142 including a first active winding coil 1432 located in the first electrode winding coils 143, and the first surface 1421 including a first winding surface 1433 located in the first electrode winding coils 143; wherein, at least one first winding surface 1433 of the first electrode winding coil 143 is provided with a first groove 1441.

[0407] In some examples, the first electrode 14, the second electrode 15, and the separator 13 are stacked along the thickness direction Y of the first current collector 141, and then wound from one end of the first electrode 14 to the other end along the second direction X, thereby forming a wound structure. For example, the wound structure may be a cylindrical structure.

[0408] In some examples, the battery cell 6 is a cylindrical battery cell with a central axis X1, which is the geometric center line of the cylindrical battery cell. The axial direction of the cylindrical battery cell is parallel to or nearly parallel to the central axis X1, and the winding axis X2 of the electrode assembly 10 may coincide with the central axis X1.

[0409] In some examples, the battery cell 6 may also be a prismatic battery cell, and the winding axis X2 of the electrode assembly 10 may refer to the center line of the winding of the first electrode 14, the second electrode 15, or the separator 13.

[0410] In some examples, the winding direction V of the electrode assembly 10 can refer to the direction of rotation, either counterclockwise or clockwise, around the winding axis X2 of the electrode assembly 10.

[0411] In the battery cell 6, the side of the electrode assembly 10 close to the winding axis X2 of the electrode assembly 10 is called the inner side of the electrode assembly 10, and the side of the electrode assembly 10 away from the winding axis X2 of the electrode assembly 10 is called the outer side of the electrode assembly 10.

[0412] The electrode assembly 10 has a wound structure. The first electrode 14 is wound multiple times along the winding direction V of the electrode assembly 10, forming multiple first electrode winding coils 143. The first current collector 141 includes a first current collector winding coil 1431 located on the first electrode winding coils 143. The first active material layer 142 includes a first active winding coil 1432 located on the first electrode winding coils 143. The first active material layer 142 has a first surface 1421 facing away from the first electrode winding coils 143. The first electrode 14 has a first winding start end A1 and a first winding end end A2. The first winding start end A1 can refer to the end of the first electrode 14 closest to the winding axis X2 of the electrode assembly 10, and the first winding end end A2 can refer to the end of the first electrode 14 farthest from the winding axis X2 of the electrode assembly 10.

[0413] The first current collector 141 is also wound multiple times along the winding direction V of the electrode assembly 10. The starting end of the winding of the first current collector 141 can refer to the end of the first current collector 141 that is closest to the winding axis X2 of the electrode assembly 10, and the ending end of the winding of the first current collector 141 can refer to the end of the first current collector 141 that is farthest from the winding axis X2 of the electrode assembly 10.

[0414] The first active material layer 142 is also wound multiple times along the winding direction V of the electrode assembly 10. The starting end of the winding of the first active material layer 142 can refer to the end of the first active material layer 142 that is closest to the winding axis X2 of the electrode assembly 10, and the ending end of the winding of the first active material layer 142 can refer to the end of the first active material layer 142 that is farthest from the winding axis X2 of the electrode assembly 10.

[0415] The surface of the first active material layer 142 facing away from the first current collector 141 is the first surface 1421, and the first surface 1421 is wound multiple times along the winding direction V of the electrode assembly 10.

[0416] From the starting end of the first active material layer 142 to the ending end of the first active material layer 142, the first electrode 14 is wound into multiple first electrode winding loops 143. The first electrode winding loop 143 closest to the winding axis X2 of the electrode assembly 10 is the first first electrode winding loop 143. From the first to the second to last first electrode winding loop 143, they are all full loop structures. The last first electrode winding loop 143 can be a full loop structure or a structure of less than one loop, such as 1 / 4 loop, 1 / 2 loop or 3 / 4 loop.

[0417] For example, a plane M is drawn through the winding axis X2 of the electrode assembly 10 and the winding start end of the first active material layer 142. The plane M extends from the winding axis X2 of the electrode assembly 10 toward the winding start end of the first active material layer 142 until it reaches the outer side of the first electrode 14. The plane M intersects with the first electrode 14, and the first electrode 14 is divided into multiple first electrode winding loops 143 according to the intersection point of the plane M and the first electrode 14. The portion of the first electrode 14 located between two adjacent intersection points forms a whole. The first electrode winding loop 143 has a loop structure; if the winding end of the first active material layer 142 intersects the plane M exactly, the penultimate first electrode winding loop 143 is also a complete loop structure; if the winding end of the first active material layer 142 does not intersect the plane M, the portion between the outermost intersection point of the first electrode 14 and the winding end of the first active material layer 142 forms the penultimate first electrode winding loop 143, which is a structure of less than one loop.

[0418] The first electrode winding ring 143 is divided based on the winding start end and winding end end of the first active material layer 142, so that each first electrode winding ring 143 includes a first current collector winding ring 1431 and a first active winding ring 1432.

[0419] For example, in the opposite direction of the winding direction V of the electrode assembly 10, the winding start end of the first current collector 141 extends beyond the winding start end of the first active material layer 142, and the portion of the first current collector 141 that extends beyond the first active material layer 142 does not belong to the first first electrode winding loop 143. In this case, the winding start end of the first current collector 141 can be the first winding start end A1.

[0420] For example, along the winding direction V of the electrode assembly 10, the winding end of the first current collector 141 extends beyond the winding end of the first active material layer 142. The portion of the first current collector 141 that extends beyond the first active material layer 142 does not belong to the penultimate first electrode winding loop 143. In this case, the winding end of the first current collector 141 can be the first winding end A2.

[0421] For example, the starting end of the winding of the first current collector 141 is aligned with the starting end of the winding of the first active material layer 142, the ending end of the winding of the first current collector 141 is aligned with the ending end of the winding of the first active material layer 142, the starting end of the winding of the first current collector 141 and the starting end of the winding of the first active material layer 142 together form the first winding starting end A1, and the ending end of the winding of the first current collector 141 and the ending end of the winding of the first active material layer 142 together form the first winding ending end A2.

[0422] The portion of the first current collector 141 located on the first electrode winding 143 is the first current collector winding 1431, the portion of the first active material layer 142 located on the first electrode winding 143 is the first active winding 1432, and the portion of the first surface 1421 located on the first electrode winding 143 is the first winding surface 1433.

[0423] If the two surfaces of the first current collector 141 along its thickness direction Y are covered with a first active material layer 142, each first electrode winding coil 143 includes a first current collector winding coil 1431 and two first active winding coils 1432, with the two first active winding coils 1432 located on the inner and outer sides of the first current collector 141, respectively.

[0424] If a first current collector 141 has a first active material layer 142 covering one surface along its thickness direction Y, each first electrode winding 143 includes a first current collector winding 1431 and a first active winding 1432, with the first active winding 1432 located on one side of the first current collector winding 1431.

[0425] The first active winding 1432 is located between the first current collector winding 1431 and the separator 13, so that ions can pass through the separator 13 and be inserted or extracted from the first active winding 1432, thereby realizing the charging and discharging of the battery cell.

[0426] The first active winding 1432 has a first winding surface 1433 facing away from the corresponding first current collector winding 1431. Here, "the corresponding first current collector winding 1431" refers to the first current collector winding 1431 located in the same first electrode winding 143 as the first active winding 1432. The surface of the first active winding 1432 facing away from the first current collector winding 1431 connected to it is the first winding surface 1433. The separator 13 is located between the second electrode 15 and the first winding surface 1433. During the expansion of the electrode assembly 10, the distance between the second electrode 15 and the first winding surface 1433 decreases, thereby squeezing out the electrolyte between the second electrode 15 and the first winding surface 1433.

[0427] At least one first electrode winding coil 143 has at least one first groove 1441 on its first winding surface 1433. For example, the number of first electrode winding coils 143 with first grooves 1441 is one or more. The first winding surface 1433 may have one or more first grooves 1441. The cross-sectional shape of the first groove 1441 may be rectangular, trapezoidal, arc-shaped, or inverted triangular, etc.

[0428] For example, one or more first electrode windings 143 near the inner side of the electrode assembly 10 do not have the first groove 1441; or, one or more first electrode windings 143 near the outer side of the electrode assembly 10 do not have the first groove 1441; or, one or more first electrode windings 143 located in the middle of the electrode assembly 10 do not have the first groove 1441.

[0429] For example, all the first electrode windings 143 are provided with a first groove 1441.

[0430] By adopting the technical solution of this embodiment, at least one first winding surface 1433 of the first electrode winding ring 143 is provided with at least one first groove 1441. On the one hand, electrolyte can flow into the first groove 1441 for storage. The stored electrolyte can wet the first electrode 14 and provide a transport path for ions, reducing the transport resistance of ions and improving the cycle performance of the battery cell 6. On the other hand, the electrolyte at the bottom can also move to the upper side of the electrode assembly 10 through the first groove 1441, improving the uniformity of electrolyte distribution. In addition, the first groove 1441 can also provide a channel for the return of the electrolyte at the bottom, reducing the difficulty of electrolyte return, reducing the transport resistance of ions, improving the wetting effect of the first electrode 14, and also helping to improve the cycle performance of the battery cell 6.

[0431] The electrode assembly 10 has a wound structure. The second electrode 15 is wound multiple times along the winding direction V of the electrode assembly 10, forming multiple second electrode winding coils 153. The second current collector 151 includes a second current collector winding coil 1531 located at the second electrode winding coil 153. The second active material layer 152 includes a second active winding coil 1532 located at the second electrode winding coil 153. The second active material layer 152 has a second surface 1521 facing away from the second current collector winding coil 1531. The second electrode 15 has a second winding start end B1 and a second winding end B2. The second winding start end B1 can refer to the end of the second electrode 15 closest to the winding axis X2 of the electrode assembly 10, and the second winding end B2 can refer to the end of the second electrode 15 farthest from the winding axis X2 of the electrode assembly 10.

[0432] The second current collector 151 is also wound multiple times along the winding direction V of the electrode assembly 10. The starting end of the winding of the second current collector 151 can refer to the end of the second current collector 151 that is closest to the winding axis X2 of the electrode assembly 10, and the ending end of the winding of the second current collector 151 can refer to the end of the second current collector 151 that is farthest from the winding axis X2 of the electrode assembly 10.

[0433] The second active material layer 152 is also wound multiple times along the winding direction V of the electrode assembly 10. The starting end of the winding of the second active material layer 152 can refer to the end of the second active material layer 152 closest to the winding axis X2 of the electrode assembly 10, and the ending end of the winding of the second active material layer 152 can refer to the end of the second active material layer 152 farthest from the winding axis X2 of the electrode assembly 10.

[0434] The surface of the second active material layer 152 facing away from the second current collector 151 is the second surface 1521, and the second surface 1521 is wound multiple times along the winding direction V of the electrode assembly 10.

[0435] From the starting end of the winding of the second active material layer 152 to the ending end of the winding of the second active material layer 152, the second electrode 15 is wound into multiple second electrode winding loops 153. The second electrode winding loop 153 closest to the winding axis X2 of the electrode assembly 10 is the first second electrode winding loop 153. From the first to the second-to-last second electrode winding loop 153, all are full loop structures. The last second electrode winding loop 153 can be a full loop structure or a structure with less than one loop, such as 1 / 4 loop, 1 / 2 loop, or 3 / 4 loop. The winding axis X2 of the electrode assembly 10 can be parallel to or nearly parallel to the axial direction of the battery cell 6.

[0436] For example, a plane N is drawn through the winding axis X2 of the electrode assembly 10 and the winding start end of the second active material layer 152. The plane N extends from the winding axis X2 of the electrode assembly 10 toward the winding start end of the second active material layer 152 until it reaches the outer side of the second electrode 15. The plane N intersects with the second electrode 15 and divides the second electrode 15 into multiple second electrode winding loops 153 according to the intersection point of the plane N and the second electrode 15. The portion of the second electrode 15 located between two adjacent intersection points forms a whole. The second electrode winding coil 153 has a loop structure; if the winding end of the second active material layer 152 intersects the plane N exactly, the penultimate second electrode winding coil 153 is also a complete loop structure; if the winding end of the second active material layer 152 does not intersect the plane N, the portion between the outermost intersection point of the second electrode 15 and the winding end of the second active material layer 152 forms the penultimate second electrode winding coil 153, which is a structure of less than one loop.

[0437] The second electrode winding ring 153 is divided based on the winding start end and winding end end of the second active material layer 152, so that each second electrode winding ring 153 includes a second current collector winding ring 1531 and a second active winding ring 1532.

[0438] For example, in the opposite direction of the winding direction V of the electrode assembly 10, the winding start end of the second current collector 151 extends beyond the winding start end of the second active material layer 152, and the portion of the second current collector 151 that extends beyond the second active material layer 152 does not belong to the first second electrode winding loop 153. In this case, the winding start end of the second current collector 151 can be the second winding start end B1.

[0439] For example, along the winding direction V of the electrode assembly 10, the winding end of the second current collector 151 extends beyond the winding end of the second active material layer 152. The portion of the second current collector 151 that extends beyond the second active material layer 152 does not belong to the penultimate second electrode winding loop 153. In this case, the winding end of the second current collector 151 can be the second winding end B2.

[0440] For example, the starting end of the winding of the second current collector 151 is aligned with the starting end of the winding of the second active material layer 152, the ending end of the winding of the second current collector 151 is aligned with the ending end of the winding of the second active material layer 152, the starting end of the winding of the second current collector 151 and the starting end of the winding of the second active material layer 152 together form the second winding starting end B1, and the ending end of the winding of the second current collector 151 and the ending end of the winding of the second active material layer 152 together form the second winding ending end B2.

[0441] The portion of the second current collector 151 located on the second electrode winding 153 is the second current collector winding 1531, and the portion of the second active material layer 152 located on the second electrode winding 153 is the second active winding 1532. The portion of the second surface 1521 located on the second electrode winding 153 is the second winding surface 1533.

[0442] From the inside to the outside of the electrode assembly 10, the first active winding 1432 and the second active winding 1532 are arranged alternately in sequence, and the separator 13 is wound and separates the first active winding 1432 and the second active winding 1532.

[0443] The second active winding 1532 is located between the second current collector winding 1531 and the separator 13, allowing ions to pass through the separator 13 and be inserted or extracted from the second active winding 1532, thereby realizing the charging and discharging of the battery cell.

[0444] The second active winding 1532 has a second winding surface 1533 facing away from the corresponding second current collector winding 1531. Here, "the corresponding second current collector winding 1531" refers to the second current collector winding 1531 located in the same second electrode winding 153 as the second active winding 1532. The surface of the second active winding 1532 facing away from the second current collector winding 1531 connected to it is the second winding surface 1533. The separator 13 is located between the first winding surface 1433 and the second winding surface 1533. During the expansion of the electrode assembly 10, the distance between the first winding surface 1433 and the second winding surface 1533 decreases, thereby squeezing out the electrolyte between the first winding surface 1433 and the second winding surface 1533.

[0445] At least one second electrode winding 153 has at least one first groove 1441 on its second winding surface 153. For example, the number of second electrode windings 153 with first grooves 1441 is one or more. The second winding surface 153 may be provided with one or more first grooves 1441.

[0446] For example, one or more second electrode windings 153 near the inner side of the electrode assembly 10 do not have the first groove 1441; or, one or more second electrode windings 153 near the outer side of the electrode assembly 10 do not have the first groove 1441; or, one or more second electrode windings 153 located in the middle of the electrode assembly 10 do not have the first groove 1441.

[0447] For example, all the second electrode windings 153 are provided with a first groove 1441.

[0448] The first winding surface 1433 and the second winding surface 1533 are arranged opposite to each other. Both the first winding surface 1433 and the second winding surface 1533 are provided with a first groove 1441. The first groove 1441 of the first active winding ring 1432 and the first groove 1441 of the second active winding ring 1532 can store electrolyte and guide electrolyte reflux. The first active winding ring 1432 and the second active winding ring 1532 have good wetting effect, which is beneficial to improving the cycle performance of the battery cell 6.

[0449] The structure of the first groove 1441 of the second winding surface 1533 may be the same as or different from the structure of the first winding surface 1433. For ease of explanation, the following description will take the example of the first winding surface 1433 having a first groove 1441.

[0450] In some embodiments, the first direction Z is parallel to the winding axis X2 of the electrode assembly 10.

[0451] The winding axis of the electrode assembly 10 is parallel to the first direction Z. The winding gap formed by the first electrode 14 and the second electrode 15 has openings at the upper and lower ends of the electrode assembly 10. Based on this, the lower end of the first groove 1441 is close to the lower end face of the first active material layer 142, and the lower end of the first groove 1441 is close to the lower end opening of the winding gap. The electrolyte accumulated at the bottom can enter the winding gap smoothly through the lower end opening of the winding gap to wet the electrode assembly 10, which is beneficial to improving the utilization rate of the electrolyte accumulated at the bottom. In addition, after the electrode assembly 10 expands, the electrolyte is squeezed out from the upper and lower ends of the electrode assembly 10, which is also beneficial to the return of the electrolyte and improves the wetting effect of the electrode assembly 10, which can effectively improve the wetting effect of the battery cell 6.

[0452] Of course, in other examples, the first direction Z is perpendicular to the winding axis of the electrode assembly 10 or inclined relative to the winding axis of the electrode assembly 10.

[0453] Referring to Figures 5, 6 and 16, in some embodiments, there are multiple first grooves 1441. Along the second direction X, multiple first grooves 1441 are spaced apart, and the distance between two adjacent first grooves 1441 increases progressively. The second direction X is perpendicular to the first direction Z and the thickness direction Y of the first current collector 141.

[0454] In some examples, the electrode assembly 10 is a wound structure, and when the first electrode 14 is in a wound state, the second direction X can be the winding direction V of the electrode assembly 10.

[0455] In some examples, when the first electrode 14 is in the unfolded state, the second direction X can be the length direction of the first electrode 14.

[0456] Multiple first grooves 1441 are not equidistantly arranged. For example, along the winding direction V of the electrode assembly 10, the distance between two adjacent first grooves 1441 increases in a stepwise manner, such that two adjacent first grooves 1441 have the same distance in some sections of the first electrode 14.

[0457] For example, along the winding direction V of the electrode assembly 10, the distance between two adjacent first grooves 1441 increases sequentially, so that the distance between two adjacent first grooves 1441 is different throughout the entire first electrode 14.

[0458] Along the winding direction V of the electrode assembly 10, a plurality of first grooves 1441 are spaced apart, and the distance between two adjacent first grooves 1441 is increased, such that the distance between two adjacent first grooves 1441 near the inner side of the electrode assembly 10 is smaller than the distance between two adjacent first grooves 1441 near the outer side of the electrode assembly 10.

[0459] By adopting the technical solution of this embodiment, after the first electrode 14 is wound along the winding direction V of the electrode assembly 10, the number of first grooves 1441 near the inner side of the electrode assembly 10 is large, and the number of first grooves 1441 near the outer side of the electrode assembly 10 is small. This is beneficial to improve the entry of electrolyte near the inner side of the bottom of the electrode assembly 10 into the inner side of the electrode assembly 10, and to improve the wetting effect of the inner side of the electrode assembly 10, thereby improving the cycle performance of the battery cell 6.

[0460] In particular, when the gap between the first electrode 14 and the second electrode 15 near the inner side of the electrode assembly 10 is small, the number of first grooves 1441 near the inner side of the electrode assembly 10 is large, which can effectively improve the wetting effect on the inner side of the electrode assembly 10, thereby effectively improving the cycle performance of the battery cell 6.

[0461] Of course, in other examples, multiple first grooves 1441 can also be set at equal intervals.

[0462] Referring to Figures 5, 6 and 17, in some embodiments, the number of first electrode windings 143 is n, n≥30, where n is a natural number, the innermost first electrode winding 143 is the first first electrode winding 143, and at least one of the first 10 first electrode windings 143 is provided with a first groove 1441.

[0463] For example, n is 30, 40, 50, 60, 70, 80, 90, 100, 150, or 200.

[0464] From the inside to the outside, multiple first electrode windings 143 are arranged in sequence in the electrode assembly 10. The first electrode winding 143 located at the innermost side of the electrode assembly 10 is the first first electrode winding 143. Compared with the other first electrode windings 143, the first first electrode winding 143 is closest to the winding axis X2 of the electrode assembly 10.

[0465] At least one of the first 10 first electrode winding coils 143 is provided with a first groove 1441. From the 1st to the 10th first electrode winding coils 143, one first electrode winding coil 143 is provided with a first groove 1441; or, from the 1st to the 10th first electrode winding coils 143, multiple first electrode winding coils 143 are provided with first grooves 1441. The 11th to the nth first electrode winding coils 143 may be partially provided with first grooves 1441, may be all provided with first grooves 1441, or may not be provided with first grooves 1441 at all.

[0466] For example, the first and second first electrode windings 143 do not have the first groove 1441, while the third to tenth first electrode windings 143 all have the first groove 1441.

[0467] For example, the first to fifth first electrode windings 143 do not have the first groove 1441, while the sixth to tenth first electrode windings 143 all have the first groove 1441.

[0468] For example, the first to tenth first electrode windings 143 are all provided with a first groove 1441. Of course, in other examples, the first groove 1441 in the first to tenth first electrode windings 143 may also have other distributions.

[0469] By adopting the technical solution of this embodiment, the number of first electrode winding coils 143 is n, n≥30. The number of first electrode coils 14 is large, and the wetting requirement of the inner side of the electrode assembly 10 is large. At least one of the first 10 first electrode winding coils 143 is provided with a first groove 1441, which can improve the wetting effect of the inner side of the electrode assembly 10 and improve the cycle performance of the battery cell 6.

[0470] Referring to Figures 5, 6 and 17, in some embodiments, the number of first electrode winding coils 143 is n, n≥30, where n is a natural number, and the innermost first electrode winding coil 143 is the first first electrode winding coil 143. At least the first first electrode winding coil 143 is not provided with a first groove 1441.

[0471] The first first electrode winding 143 does not have a first groove 1441, while at least one of the second to nth first electrode windings 143 has a first groove 1441.

[0472] After the first electrode 14 is wound, the winding radius of the first electrode winding ring 143 closer to the inner side is smaller, and the winding stress of the first electrode winding ring 143 closer to the inner side is greater. Among them, the first first electrode winding ring 143 has the smallest winding radius and the largest winding stress. The first first electrode winding ring 143 does not have the first groove 1441, which is beneficial to improving the structural strength of the first first electrode winding ring 143 and reducing the risk of powder shedding, damage or even breakage of the first first electrode winding ring 143 caused by grooving. This is beneficial to improving the capacity and reliability of the battery cell 6. In addition, the absence of the first groove 1441 in the first first electrode winding ring 143 can also reduce the number of grooves, which is beneficial to improving the production efficiency of the first electrode 14.

[0473] In some embodiments, at least the first three first electrode windings 143 do not have a first groove 1441.

[0474] The first to third first electrode windings 143 do not have a first groove 1441. At least one of the fourth to nth first electrode windings 143 has a first groove 1441.

[0475] By adopting the technical solution of this embodiment, the winding radius of the first to third first electrode winding coils 143 is small, the winding stress of the first to third first electrode winding coils 143 is large, and the first to third first electrode winding coils 143 do not have the first groove 1441, which is beneficial to improving the structural strength of the first to third first electrode winding coils 143 and reducing the risk of powder shedding, damage or even breakage of the first to third first electrode winding coils 143 caused by grooving, which is beneficial to improving the reliability of the battery cell 6. In addition, the absence of the first groove 1441 in the first to third first electrode winding coils 143 can also reduce the number of grooves, which is beneficial to improving the production efficiency of the first electrode 14.

[0476] Referring to Figure 7, in some embodiments, the electrode assembly 10 is provided with a central hole 101, and the first first electrode winding 143 is closest to the central hole 101 compared to the other first electrode windings 143.

[0477] For example, the winding axis X2 of the electrode assembly 10 passes through the central hole 101.

[0478] The central hole 101 can be used to contain electrolyte and allow electrolyte flow, thereby wetting the inner first electrode winding 143, improving the wetting effect inside the electrode assembly 10, and improving the cycle performance of the battery cell 6. In addition, the inner first electrode winding 143 can be wetted by the electrolyte in the central hole 101, which can also reduce the need for the first groove 1441 in the inner first electrode winding 143, thereby improving the structural strength of the inner first electrode winding 143 and reducing the problem of powder shedding from the inner first electrode winding 143, thus effectively balancing the cycle performance and reliability of the battery cell 6.

[0479] The central hole 101 can also provide space for the expansion of the inner side of the electrode assembly 10, thereby reducing the squeezing effect on the housing 20, reducing the risk of deformation and cracking of the housing 20, and improving the reliability of the battery cell 6.

[0480] When thermal runaway occurs in battery cell 6, the central hole 101 can serve as a gas discharge channel to increase the gas discharge rate and reduce the risk of explosion.

[0481] Referring to Figures 5, 6 and 17, in some embodiments, the number of first electrode winding coils 143 is n, n≥30, where n is a natural number; the innermost first electrode winding coil 143 is the first first electrode winding coil 143; at least the last two first electrode winding coils 143 do not have a first groove 1441.

[0482] The (n-1)th to the nth first electrode winding coil 143 does not have a first groove 1441. At least one of the 1st to the (n-2)th first electrode winding coils 143 has a first groove 1441.

[0483] When the electrode assembly 10 expands, the expansion force accumulates on the outer side. The second to last first electrode winding 143 experiences the greatest accumulated expansion force. Since the second to last first electrode winding 143 does not have the first groove 1441, this improves the structural strength of the second to last first electrode winding 143, reducing the risk of breakage and effectively enhancing the reliability of the battery cell 6. Furthermore, the absence of the first groove 1441 in the second to last first electrode winding 143 reduces the number of grooves required, improving the manufacturing efficiency of the first electrode 14.

[0484] In some embodiments, at least the last 10 first electrode windings 143 are not provided with the first groove 1441.

[0485] The (n-9)th to (n-8)th first electrode windings 143 do not have a first groove 1441. At least one of the 1st to (n-8)th first electrode windings 143 has a first groove 1441.

[0486] The cumulative expansion force of the last 10 first electrode windings 143 is relatively large, and since the last 10 first electrode windings 143 do not have the first groove 1441, this helps to improve the structural strength of the last 10 first electrode windings 143, reduces the risk of breakage, and thus improves the reliability of the battery cell 6. In addition, the absence of the first groove 1441 in the last 10 first electrode windings 143 reduces the number of grooves and improves the production efficiency of the first electrode 14.

[0487] In particular, in some battery cells 6, where the gap between the outer first electrode 14 and the second electrode 15 is large, the wetting effect of the outer first electrode winding 143 is better. Since the outer first electrode winding 143 does not have a first groove 1441, the structural strength of the outer first electrode winding 143 can be improved. Therefore, the reliability and cycle performance of the battery cell 6 can be taken into account.

[0488] Referring to Figures 5, 6, and 18, in some embodiments, the number of first electrode windings 143 is n, n ≥ 30, where n is a natural number; the innermost first electrode winding 143 is the first first electrode winding 143; the first f first electrode windings 143 do not have a first groove 1441, and the last q first electrode windings 143 do not have a first groove 1441; all first electrode windings 143 located between the f-th first electrode winding 143 and the last q first electrode windings 143 have a first groove 1441, where f + q < n, and f and q are positive integers.

[0489] f and q are natural numbers greater than 1. For example, f is 1, 3, 5, 7, 10, 20, etc., and q is 1, 5, 10, 15, 20, 30, 40, etc.

[0490] For example, when f is 1 and q is 1, the first first electrode winding 143 does not have a first groove 1441, the second to the (n-1)th first electrode windings 143 all have a first groove 1441, and the nth first electrode winding 143 does not have a first groove 1441.

[0491] For example, when f > 1 and q > 1, the first to f first electrode windings 143 do not have the first groove 1441, the (f+1)th to nqth first electrode windings 143 have the first groove 1441, and the (n-q+1)th to nth first electrode windings 143 do not have the first groove 1441.

[0492] By adopting the technical solution of this embodiment, the first electrode winding ring 143 located on the inner and outer sides can be free of the first groove 1441, which is beneficial to improving the structural strength of the first electrode winding ring 143 on the inner and outer sides and improving the reliability of the battery cell 6. In addition, it can also reduce the number of grooves and improve the production efficiency of the first electrode 14. Furthermore, the groove in the middle region of the electrode assembly 10 on the inner and outer sides is beneficial to improving the wetting effect of the electrode assembly 10 in the middle region of the inner and outer sides and improving the cycle performance of the battery cell 6.

[0493] In some embodiments, 30 ≤ n ≤ 80.

[0494] For example, n can be 30, 40, 50, 60, 65, 70, 75, 80, 90, etc.

[0495] The design of 30≤n≤80 results in a large number of first electrode winding turns 143, a large capacity of battery cell 6, and a high difficulty in wetting the electrode assembly 10. In this embodiment, the first groove 1441 can be selectively provided on the inner or outer side of the electrode assembly 10, thereby improving the wetting effect of the electrode assembly 10 and also improving the structural strength of the inner or outer side of the electrode assembly 10, thus taking into account the reliability, capacity and cycle performance of the electrode assembly 10.

[0496] In some embodiments, 60≤n≤75 better balances the reliability, capacity and cycle performance of the electrode assembly 10.

[0497] In some embodiments, the number of first electrode windings 143 with the first groove 1441 is v, 0.23≤v / n≤1, where v and n are positive integers, and optionally, 0.3≤v / n≤0.7.

[0498] In some examples, the value of v / n can be 0.23, 1, or any value between 0.23 and 1; for example, the value of v / n can be, but is not limited to, 0.23, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.

[0499] The design with 0.23≤v / n≤1 can meet the wetting requirements of the electrode assembly 10 and improve the cycle performance of the battery cell 6.

[0500] In some embodiments, 0.3 ≤ v / n ≤ 0.7.

[0501] With a v / n ≥ 0.3 design, the number of first electrode winding coils 143 with the first groove 1441 can better meet the wetting requirements of the electrode assembly 10 and improve the cycle performance of the battery cell 6; with a v / n ≤ 0.7 setting, some of the first electrode winding coils 143 are not provided with the first groove 1441, which helps to reduce the number of grooves and improve the production and processing efficiency of the first electrode 14.

[0502] Referring to Figures 5, 6, and 18, in some embodiments, the first electrode 14 has a first winding end A2, the second electrode 15 has a second winding end B2, the innermost first electrode winding coil 143 is the first first electrode winding coil 143, and the second winding end B2 is located between the last two first electrode winding coils 143; the last two first electrode winding coils 143 do not have a first groove 1441 at the position corresponding to the end face of the first winding end A2; and / or, the last two first electrode winding coils 143 do not have a first groove 1441 at the position corresponding to the end face of the second winding end B2.

[0503] The first electrode 14 has a first winding end A2 and a first winding start end A1. Along the winding direction V of the electrode assembly 10, at the two oppositely distributed ends of the first electrode 14, the end closer to the winding axis X2 of the electrode assembly 10 is the first winding start end A1, and the end farther from the winding axis X2 of the electrode assembly 10 is the first winding end A2. Along the winding direction V of the electrode assembly 10, at the two oppositely distributed end faces of the first electrode 14, the end face closer to the winding axis X2 of the electrode assembly 10 is the end face of the first winding start end A1, and the end face farther from the winding axis X2 of the electrode assembly 10 is the end face of the first winding end A2.

[0504] For example, along the winding direction V of the electrode assembly 10, the first winding end A2 can refer to the end of the penultimate first electrode winding 143 that is away from the penultimate first electrode winding 143, and the first winding start end A1 can refer to the end of the first first electrode winding 143 that is away from the second first electrode winding 143.

[0505] The second electrode 15 has a second winding end B2 and a second winding start end B1. Along the winding direction V of the electrode assembly 10, of the two oppositely distributed ends of the second electrode 15, the end closer to the winding axis X2 of the electrode assembly 10 is the second winding start end B1, and the end farther from the winding axis X2 of the electrode assembly 10 is the second winding end B2. Along the winding direction V of the electrode assembly 10, of the two oppositely distributed end faces of the second electrode 15, the end face closer to the winding axis X2 of the electrode assembly 10 is the end face of the second winding start end B1, and the end face farther from the winding axis X2 of the electrode assembly 10 is the end face of the second winding end B2.

[0506] For example, along the winding direction V of the electrode assembly 10, the second winding end B2 can refer to the end of the penultimate second electrode winding 153 that is away from the penultimate second electrode winding 153, and the second winding start end B1 can refer to the end of the first second electrode winding 153 that is away from the second second electrode winding 153.

[0507] In some examples, along the winding direction V of the electrode assembly 10, after the second electrode 15 is wound, the first electrode 14 continues to be wound forward for a distance and for less than one turn, so that the last two first electrode winding turns 143 can completely cover the second winding end B2, and the second winding end B2 is located between the last two first electrode winding turns 143. There is no second electrode winding turn 153 between the first winding end A2 and the second to last first electrode winding turn 143.

[0508] The first groove 1441 is not provided at the position corresponding to the end face of the second to last first electrode winding coil 143 and the end face of the first winding end A2. It can be understood that the first groove 1441 is not provided at the position corresponding to the end face of the first winding end A2 and the second to last first electrode winding coil 143.

[0509] The first groove 1441 is not provided at the position corresponding to the end face of the second to last first electrode winding coil 143 and the end face of the second winding termination B2. It can be understood that the first groove 1441 is not provided at the position corresponding to the end face of the second to last first electrode winding coil 143 and the end face of the second winding termination B2 is not provided at the position corresponding to the end face of the first to last first electrode winding coil 143.

[0510] During the expansion of the electrode assembly 10, the second-to-last first electrode coil 143 presses against the last first electrode coil 143. During this process, the edge of the end face of the first winding termination A2 presses against the second-to-last first electrode coil 143, and the end face of the second winding termination B2 is sandwiched between the two last first electrode coils 143. The edge of the end face of the second winding termination B2 presses against both the last first electrode coil 143 and the second-to-last first electrode coil 143. If the two last first electrode coils 143 are provided with a first groove 1441 corresponding to the end face of the first winding termination A2, the first winding termination... The end face of the tail end A2 is opposite to and presses against the first groove 1441. The structural strength of the first groove 1441 is poor, and the end face of the first winding tail end A2 is at risk of cutting off the last two first electrode winding coils 143. Similarly, if the last two first electrode winding coils 143 are provided with the first groove 1441 at the position corresponding to the end face of the second winding tail end B2, the end face of the second winding tail end B2 is opposite to and presses against the first groove 1441. The structural strength of the first groove 1441 is poor, and the end face of the second winding tail end B2 is at risk of cutting off the last two first electrode winding coils 143.

[0511] In some examples, the first electrode 14 has a first winding end A2, the second electrode 15 has a second winding end B2, the innermost first electrode winding coil 143 is the first first electrode winding coil 143, and the second winding end B2 is located between the last two first electrode winding coils 143; the last two first electrode winding coils 143 do not have a first groove 1441 at the end face corresponding to the first winding end A2.

[0512] For example, the second to last first electrode winding loop 143 does not have a first groove 1441 at the position corresponding to the end face of the first winding end A2.

[0513] During the expansion of the electrode assembly 10, the positions corresponding to the end faces of the last two first electrode winding coils 143 and the first winding end A2 are not provided with the first groove 1441. The structural strength at the positions corresponding to the end faces of the last two first electrode winding coils 143 and the first winding end A2 is good, which reduces the risk of the last two first electrode winding coils 143 being sheared by the end face of the first winding end A2 and improves the reliability of the battery cell 6.

[0514] In some examples, the first electrode 14 has a first winding end A2, the second electrode 15 has a second winding end B2, the innermost first electrode winding coil 143 is the first first electrode winding coil 143, and the second winding end B2 is located between the last two first electrode winding coils 143; the position corresponding to the end face of the last two first electrode winding coils 143 and the second winding end B2 is not provided with a first groove 1441.

[0515] For example, the first groove 1441 is not provided at the position corresponding to the end face of the first electrode winding 143 to the second winding end B2; the first groove 1441 is not provided at the position corresponding to the end face of the second electrode winding 143 to the second winding end B2.

[0516] During the expansion of the electrode assembly 10, the first groove 1441 is not provided at the position corresponding to the end face of the second winding end B2 of the last two first electrode windings 143. The structural strength at the position corresponding to the end face of the second winding end B2 of the last two first electrode windings 143 is good, which reduces the risk of the last two first electrode windings 143 being sheared by the end face of the second winding end B2 and improves the reliability of the battery cell 6.

[0517] In some examples, the first electrode 14 has a first winding end A2, the second electrode 15 has a second winding end B2, the innermost first electrode winding coil 143 is the first first electrode winding coil 143, and the second winding end B2 is located between the last two first electrode winding coils 143; the last two first electrode winding coils 143 do not have a first groove 1441 at the position corresponding to the end face of the first winding end A2; the last two first electrode winding coils 143 do not have a first groove 1441 at the position corresponding to the end face of the second winding end B2.

[0518] For example, the first groove 1441 is not provided at the position corresponding to the end face of the first electrode winding 143 to the second winding end B2; the first groove 1441 is not provided at the position corresponding to the end face of the second electrode winding 143 to the second winding end B2; and the first groove 1441 is not provided at the position corresponding to the end face of the second electrode winding 143 to the first winding end A2.

[0519] During the expansion of the electrode assembly 10, the positions corresponding to the end faces of the second to last first electrode winding coils 143 and the end faces of the first winding end A2 and the second winding end B2 are not provided with the first groove 1441. The structural strength at the positions corresponding to the end faces of the second to last first electrode winding coils 143 and the end faces of the first winding end A2 and the second winding end B2 is good, which reduces the risk of the second to last first electrode winding coils 143 being sheared by the end faces of the first winding end A2 and the second winding end B2, and improves the reliability of the battery cell 6.

[0520] In some embodiments, the second to last first electrode winding coil 143 is provided with a first groove 1441, which is offset from at least one of the end face of the first winding end A2 and the end face of the second winding end B2.

[0521] The last two first electrode windings 143 are provided with a first groove 1441. It can be understood that at least one of the last first electrode winding 143 or the last second first electrode winding 143 is provided with the first groove 1441. The first groove 1441 on the last two first electrode windings 143 can improve the wetting effect of the last two first electrode windings 143 and improve the cycle performance of the battery cell 6.

[0522] In some examples, the last two first electrode windings 143 are provided with a first groove 1441, which is offset from the end face of the first winding end A2.

[0523] For example, the second-to-last first electrode winding 143 is provided with a first groove 1441, which is offset from the end face of the first winding end A2. The penultimate first electrode winding 143 may or may not have a first groove 1441.

[0524] The first groove 1441 of the last two first electrode winding coils 143 is not opposite to the end face of the first winding end A2, which reduces the risk that the last two first electrode winding coils 143 will be cut by the end face of the first winding end A2 and improves the reliability of the battery cell 6.

[0525] In some examples, the last two first electrode windings 143 are provided with a first groove 1441, which is offset from the end face of the second winding end B2.

[0526] For example, the penultimate first electrode winding 143 is provided with a first groove 1441, while the penultimate first electrode winding 143 is not provided with a first groove 1441. The first groove 1441 of the penultimate first electrode winding 143 is offset from the end face of the second winding end B2.

[0527] For example, the second to last first electrode winding 143 is provided with a first groove 1441, while the first to last first electrode winding 143 is not provided with a first groove 1441. The first groove 1441 of the second to last first electrode winding 143 is offset from the end face of the second winding end B2.

[0528] For example, the penultimate first electrode winding coil 143 and the penultimate first electrode winding coil 143 are provided with a first groove 1441. The first groove 1441 of the penultimate first electrode winding coil 143 and the first groove 1441 of the penultimate first electrode winding coil 143 are both offset from the end face of the second winding end B2.

[0529] The first groove 1441 of the last two first electrode windings 143 is not opposite to the end face of the second winding end B2, which reduces the risk that the last two first electrode windings 143 will be cut by the end face of the second winding end B2 and improves the reliability of the battery cell 6.

[0530] In some examples, the last two first electrode windings 143 are provided with a first groove 1441, which is offset from the end face of the first winding end A2 and the end face of the second winding end B2.

[0531] For example, the penultimate first electrode winding 143 is provided with a first groove 1441, while the penultimate first electrode winding 143 is not provided with a first groove 1441. The first groove 1441 of the penultimate first electrode winding 143 is offset from the end face of the second winding end B2.

[0532] For example, the second to last first electrode winding 143 is provided with a first groove 1441, while the first to last first electrode winding 143 is not provided with a first groove 1441. The first groove 1441 of the second to last first electrode winding 143 is offset from the end face of the first winding end A2 and the end face of the second winding end B2.

[0533] For example, the penultimate first electrode winding coil 143 and the penultimate first electrode winding coil 143 are provided with a first groove 1441. The first groove 1441 of the penultimate first electrode winding coil 143 and the first groove 1441 of the penultimate first electrode winding coil 143 are both offset from the end face of the second winding end B2, and the first groove 1441 of the penultimate first electrode winding coil 143 is offset from the end face of the first winding end A2.

[0534] The first groove 1441 of the last two first electrode windings 143 is not opposite to the end face of the second winding end B2, and the first groove 1441 of the last two first electrode windings 143 is not opposite to the end face of the first winding end A2. This reduces the risk that the last two first electrode windings 143 will be cut by the end face of the first winding end A2 and the end face of the second winding end B2, and improves the reliability of the battery cell 6.

[0535] In some embodiments, the last two first electrode windings 143 are not provided with the first groove 1441.

[0536] The penultimate first electrode winding coil 143 and the penultimate first electrode winding coil 143 do not have a first groove 1441.

[0537] By adopting the technical solution of this embodiment, the last two first electrode winding coils 143 are not provided with the first groove 1441. On the one hand, the structural strength of the last two first electrode winding coils 143 is improved. On the other hand, the risk of the last two first electrode winding coils 143 being cut by the end face of the first winding end A2 and the end face of the second winding end B2 is reduced, thereby improving the reliability of the battery cell 6.

[0538] In some embodiments, the first electrode 14 has a first winding start end A1, the second electrode 15 has a second winding start end B1, the innermost first electrode winding coil 143 is the first first electrode winding coil 143, and the second winding start end B1 is located between the first two first electrode winding coils 143; the first two first electrode winding coils 143 are not provided with a first groove 1441 at the end face corresponding to the end face of the first winding start end A1; and / or, the first two first electrode winding coils 143 are not provided with a first groove 1441 at the end face corresponding to the end face of the second winding start end B1.

[0539] In some examples, along the winding direction V of the electrode assembly 10, the second electrode 15 begins to be wound only after the first electrode 14 has started to be wound a certain distance. Before the second electrode 15 is wound, the first electrode 14 is wound less than one turn, so that the first two first electrode winding turns 143 can completely cover the second winding start end B1, and the second winding start end B1 is located between the first two first electrode winding turns 143. There is no second electrode winding turn 153 between the first winding start end A1 and the second first electrode winding turn 143.

[0540] The first two first electrode winding coils 143 do not have a first groove 1441 at the position corresponding to the end face of the first winding start end A1. It can be understood that the end face of the first winding start end A1 does not have a first groove 1441 at the position corresponding to the second first electrode winding coil 143.

[0541] The first two first electrode winding coils 143 do not have a first groove 1441 at the position corresponding to the end face of the second winding starting end B1. It can be understood that the end face of the second winding starting end B1 does not have a first groove 1441 at the position opposite to the second first electrode winding coil 143, and the end face of the second winding starting end B1 does not have a first groove 1441 at the position opposite to the first first electrode winding coil 143.

[0542] During the expansion of the electrode assembly 10, or under the self-restoring force of the first electrode 14, the first electrode winding 143 presses against the second electrode winding 143. The edge of the end face of the first winding starting end A1 presses against the second electrode winding 143. The end face of the second winding starting end B1 is sandwiched between the first two electrode windings 143. The edge of the end face of the second winding starting end B1 presses against the first and second electrode windings 143. If the first two electrode windings 143 are provided with a first groove 1441 corresponding to the end face of the first winding starting end A1, the first winding... If the end face of the starting end A1 is opposite to and presses against the first groove 1441, the structural strength of the first groove 1441 is poor, and the end face of the first winding starting end A1 is at risk of cutting off the first two first electrode winding coils 143. Similarly, if the first two first electrode winding coils 143 are provided with the first groove 1441 at the position corresponding to the end face of the second winding starting end B1, and the end face of the second winding starting end B1 is opposite to and presses against the first groove 1441, the structural strength of the first groove 1441 is poor, and the end face of the second winding starting end B1 is at risk of cutting off the first two first electrode winding coils 143.

[0543] In some examples, the first electrode 14 has a first winding start end A1, the second electrode 15 has a second winding start end B1, the innermost first electrode winding coil 143 is the first first electrode winding coil 143, and the second winding start end B1 is located between the first two first electrode winding coils 143; the first groove 1441 is not provided at the position corresponding to the end face of the first two first electrode winding coils 143 and the first winding start end A1.

[0544] For example, the second first electrode winding 143 does not have a first groove 1441 at the position corresponding to the end face of the first winding start end A1.

[0545] During the expansion of the electrode assembly 10 or under the self-restoring force of the first electrode 14, the first groove 1441 is not provided at the position corresponding to the end face of the first winding start end A1 of the first two first electrode windings 143. The structural strength at the position corresponding to the end face of the first winding start end A1 of the first two first electrode windings 143 is good, which reduces the risk that the first two first electrode windings 143 will be sheared by the end face of the first winding start end A1 and improves the reliability of the battery cell 6.

[0546] In some examples, the first electrode 14 has a first winding start end A1, the second electrode 15 has a second winding start end B1, the innermost first electrode winding coil 143 is the first first electrode winding coil 143, and the second winding start end B1 is located between the first two first electrode winding coils 143; the first groove 1441 is not provided at the position corresponding to the end face of the first two first electrode winding coils 143 and the second winding start end B1.

[0547] For example, the first groove 1441 is not provided at the position corresponding to the end face of the first first electrode winding 143 and the end face of the second winding starting end B1; the first groove 1441 is not provided at the position corresponding to the end face of the second first electrode winding 143 and the end face of the second winding starting end B1.

[0548] During the expansion of the electrode assembly 10 or under the self-restoring force of the first electrode 14, the first groove 1441 is not provided at the position corresponding to the end face of the first two first electrode windings 143 and the end face of the second winding start end B1. The structural strength at the position corresponding to the end face of the first two first electrode windings 143 and the end face of the second winding start end B1 is good, which reduces the risk that the first two first electrode windings 143 will be sheared by the end face of the second winding start end B1 and improves the reliability of the battery cell 6.

[0549] In some examples, the first electrode 14 has a first winding start end A1, the second electrode 15 has a second winding start end B1, the innermost first electrode winding coil 143 is the first first electrode winding coil 143, and the second winding start end B1 is located between the first two first electrode winding coils 143; the first two first electrode winding coils 143 do not have a first groove 1441 at the end face corresponding to the end face of the first winding start end A1; the first two first electrode winding coils 143 do not have a first groove 1441 at the end face corresponding to the end face of the second winding start end B1.

[0550] For example, the first electrode winding 143 does not have a first groove 1441 at the position corresponding to the end face of the second winding start end B1; the second electrode winding 143 does not have a first groove 1441 at the position corresponding to the end face of the second winding start end B1, and the second electrode winding 143 does not have a first groove 1441 at the position corresponding to the end face of the first winding start end A1.

[0551] During the expansion of the electrode assembly 10 or under the self-restoring force of the first electrode 14, the first groove 1441 is not provided at the position corresponding to the end face of the first winding start end A1 and the end face of the second winding start end B1 of the first two first electrode winding coils 143. The structural strength at the position corresponding to the end face of the first winding start end A1 and the end face of the second winding start end B1 of the first two first electrode winding coils 143 is good, which reduces the risk of the first two first electrode winding coils 143 being sheared by the end face of the first winding start end A1 and the end face of the second winding start end B1, and improves the reliability of the battery cell 6.

[0552] In some embodiments, the first two first electrode winding coils 143 are provided with a first groove 1441, which is offset from at least one of the end face of the first winding start end A1 and the end face of the second winding start end B1.

[0553] The first two first electrode windings 143 are provided with first grooves 1441. It can be understood that at least one of the first first electrode windings 143 or the second first electrode winding 143 is provided with the first groove 1441. The first groove 1441 on the first two first electrode windings 143 can improve the wetting effect of the first two first electrode windings 143 and improve the cycle performance of the battery cell 6.

[0554] In some examples, the first two first electrode windings 143 are provided with a first groove 1441, which is offset from the end face of the first winding start end A1.

[0555] For example, the second first electrode winding 143 is provided with a first groove 1441, which is offset from the end face of the first winding start end A1. The first first electrode winding 143 may or may not be provided with the first groove 1441.

[0556] The first groove 1441 of the first two first electrode winding coils 143 is not set opposite to the end face of the first winding start end A1, which reduces the risk that the first two first electrode winding coils 143 will be cut by the end face of the first winding start end A1 and improves the reliability of the battery cell 6.

[0557] In some examples, the first two first electrode windings 143 are provided with a first groove 1441, which is offset from the end face of the second winding start end B1.

[0558] For example, the first first electrode winding 143 is provided with a first groove 1441, and the second first electrode winding 143 is not provided with a first groove 1441. The first groove 1441 of the first first electrode winding 143 is offset from the end face of the second winding starting end B1.

[0559] For example, the second first electrode winding 143 is provided with a first groove 1441, the first first electrode winding 143 is not provided with a first groove 1441, and the first groove 1441 of the second first electrode winding 143 is offset from the end face of the second winding starting end B1.

[0560] For example, the first first electrode winding coil 143 and the second first electrode winding coil 143 are provided with a first groove 1441. The first groove 1441 of the first first electrode winding coil 143 and the first groove 1441 of the second first electrode winding coil 143 are both offset from the end face of the second winding starting end B1.

[0561] The first groove 1441 of the first two first electrode windings 143 is not set opposite to the end face of the second winding start end B1, which reduces the risk that the first two first electrode windings 143 will be cut by the end face of the second winding start end B1 and improves the reliability of the battery cell 6.

[0562] In some examples, the first two first electrode winding coils 143 are provided with a first groove 1441, which is offset from the end face of the first winding start end A1 and the end face of the second winding start end B1.

[0563] For example, the first first electrode winding 143 is provided with a first groove 1441, and the second first electrode winding 143 is not provided with a first groove 1441. The first groove 1441 of the first first electrode winding 143 is offset from the end face of the second winding starting end B1.

[0564] For example, the second first electrode winding 143 is provided with a first groove 1441, the first first electrode winding 143 is not provided with a first groove 1441, and the first groove 1441 of the second first electrode winding 143 is offset from the end face of the first winding start end A1 and the end face of the second winding start end B1.

[0565] For example, the first first electrode winding coil 143 and the second first electrode winding coil 143 are provided with a first groove 1441. The first groove 1441 of the first first electrode winding coil 143 and the first groove 1441 of the second first electrode winding coil 143 are both offset from the end face of the second winding starting end B1, and the first groove 1441 of the second first electrode winding coil 143 is offset from the end face of the first winding starting end A1.

[0566] The first grooves 1441 of the first two first electrode windings 143 are not opposite to the end face of the second winding start end B1, and the first grooves 1441 of the first two first electrode windings 143 are not opposite to the end face of the first winding start end A1. This reduces the risk that the first two first electrode windings 143 will be cut by the end face of the first winding start end A1 and the end face of the second winding start end B1, and improves the reliability of the battery cell 6.

[0567] In some embodiments, the first two first electrode windings 143 are not provided with the first groove 1441.

[0568] The first electrode winding 143 and the second electrode winding 143 do not have a first groove 1441.

[0569] By adopting the technical solution of this embodiment, the first two first electrode winding coils 143 are not provided with the first groove 1441. On the one hand, the structural strength of the first two first electrode winding coils 143 is improved. On the other hand, the risk of the first two first electrode winding coils 143 being sheared by the end face of the first winding start end A1 and the end face of the second winding start end B1 is reduced, thereby improving the reliability of the battery cell 6.

[0570] In some embodiments, the first electrode 14 is the negative electrode 12, and the second electrode 15 is the positive electrode 11.

[0571] With the second winding end B2 located at the second to last winding end of the first electrode 14, along the winding direction V of the electrode assembly 10, the winding end of the negative electrode 12 extends beyond the winding end of the positive electrode 11. The portion of the negative electrode 12 that extends beyond the positive electrode 11 provides more space for ions to intercalate, reducing the risk of lithium plating and improving the reliability of the battery cell 6.

[0572] Based on the second winding start end B1 being located at the winding ends of the first two first electrode sheets 14, along the winding direction V of the negative electrode sheet 12 of the electrode assembly 10, the negative electrode sheet 12 needs to be wound for a certain distance before the positive electrode sheet 11 begins to be wound. The part of the negative electrode sheet 12 wound first can provide more space for ions to be inserted, reduce the risk of lithium plating, and improve the reliability of the battery cell 6.

[0573] In other embodiments, the second electrode 15 is the negative electrode 12, and the first electrode 14 is the positive electrode 11.

[0574] Referring to Figures 19-21, in some embodiments, the electrode assembly 10 includes a flat region E2 and two bending regions E1, with the two bending regions E1 located at both ends of the flat region E2; the first active winding 1432 includes a first active bending portion 1434 located in the bending region E1 and a first active flat portion 1435 located in the flat region E2; at least one first active flat portion 1435 of the first active winding 1432 is provided with a first groove 1441.

[0575] The flat region E2 is the area in the electrode assembly 10 with a flat structure. The portions of the first electrode 14 and the second electrode 15 located in the flat region E2 are both arranged in a basically flat manner. The portions of the first electrode winding 143 and the second electrode winding 153 located in the flat region E2 are also arranged in a basically flat manner.

[0576] The bending region E1 is the area of ​​the electrode assembly 10 with a bending structure. The portion of the first electrode 14 located in the bending region E1 and the portion of the second electrode 15 located in the bending region E1 are both bent. The portion of the first electrode winding 143 located in the bending region E1 and the portion of the second electrode winding 153 located in the bending region E1 are both bent.

[0577] In some examples, the portion of the first electrode 14 located in the bending region E1 and the portion of the second electrode 15 located in the bending region E1 are both arc-shaped, and the portion of the first electrode winding 143 located in the bending region E1 and the portion of the second electrode winding 153 located in the bending region E1 are both arc-shaped.

[0578] The portion of the first active winding 1432 located in the bending region E1 is the first active bending portion 1434, and the portion of the first active winding 1432 located in the straight region E2 is the first active straight portion 1435.

[0579] In some examples, a first active flat portion 1435 of a first active winding 1432 is provided with a first groove 1441, or, multiple first active windings 1432 have active flat portions provided with first grooves 1441.

[0580] For example, the first active flat portion 1435 of all the first active windings 1432 is provided with a first groove 1441.

[0581] Compared to the bending region E1, the gap between the first electrode 14 and the second electrode 15 in the straight region E2 is small, making electrolyte reflux difficult. However, at least one first active straight portion 1435 of the first active winding 1432 is provided with a first groove 1441, which can be used to store electrolyte or provide a reflux channel for electrolyte, which is beneficial to improving the wetting effect of the straight region E2, thereby effectively improving the cycle performance of the battery cell 6.

[0582] In some embodiments, the electrode assembly 10 includes a flat region E2 and two bending regions E1, the two bending regions E1 being located at both ends of the flat region E2; the first active winding 1432 includes a first active bending portion 1434 located in the bending region E1 and a first active flat portion 1435 located in the flat region E2, and at least one of the first active bending portions 1434 of the first active winding 1432 is provided with a first groove 1441.

[0583] In some examples, the first active bend 1434 of a first active winding 1432 is provided with a first groove 1441, or the active bends of multiple first active windings 1432 are provided with the first groove 1441.

[0584] For example, all the first active bends 1434 of the first active windings 1432 are provided with first grooves 1441.

[0585] By adopting the technical solution of this embodiment, at least one first active bending portion 1434 of the first active winding 1432 is provided with a first groove 1441, which can be used to store electrolyte or provide a return channel for electrolyte, which is beneficial to improve the wetting effect of the bending area E1, thereby improving the cycle performance of the battery cell 6.

[0586] In some embodiments, the electrode assembly 10 includes a flat region E2 and two bending regions E1, with the two bending regions E1 located at both ends of the flat region E2; the first active winding 1432 includes a first active bending portion 1434 located in the bending region E1 and a first active flat portion 1435 located in the flat region E2, and at least one first active flat portion 1435 of the first active winding 1432 is provided with a first groove 1441, and at least one first active bending portion 1434 of the first active winding 1432 is provided with a first groove 1441, which can simultaneously improve the wetting effect of the flat region E2 and the bending region E1, thereby improving the cycle performance of the battery cell 6.

[0587] In some embodiments, the first active straight portion 1435 of all the first active windings 1432 is provided with a first groove 1441, and the first active bent portion 1434 of all the first active windings 1432 is not provided with a first groove 1441.

[0588] The bending of the first active bending portion 1434 within the bending zone E1 increases the risk of powder shedding from the first active bending portion 1434. However, the absence of a first groove 1441 in the first active bending portions 1434 of all the first active windings 1432 improves the structural strength of the first active bending portion 1434, reduces the risk of powder shedding from the bending zone E1, and helps improve the capacity and reliability of the battery cell 6. At the same time, the presence of a first groove 1441 in all the first active straight portions 1435 effectively improves the wetting effect of the straight zone E2 and enhances the cycle performance of the battery cell 6. Therefore, the cycle performance, capacity, and reliability of the battery cell 6 can be simultaneously considered.

[0589] In some embodiments, the portion of the second active winding 1532 located in the bending region E1 is the second active bending portion 1534, and the portion of the second active winding 1532 located in the straight region E2 is the second active straight portion 1535; at least one second active straight portion 1535 of the second active winding 1532 is provided with a first groove 1441; and / or, at least one second active bending portion 1534 of the second active winding 1532 is provided with a first groove 1441, so as to improve the wetting effect of the electrode assembly 10 and improve the cycle performance of the battery cell 6.

[0590] In some embodiments, the battery cell 6 is a cylindrical battery cell, and the central axis X1 of the cylindrical battery cell is parallel to the first direction Z.

[0591] The central axis X1 of the cylindrical battery cell is parallel to the first direction Z. The cylindrical battery cell is vertically arranged, and the first groove 1441 extends from bottom to top, which is conducive to the electrolyte accumulated at the bottom climbing upward and improving the wetting effect of the cylindrical battery cell. In addition, the electrode assembly 10 inside the cylindrical battery cell is tightly wound, which is not conducive to the return of electrolyte. However, the first electrode 14 is provided with the first groove 1441, which is conducive to the return of electrolyte and improves the wetting effect of the electrode assembly 10. This can effectively improve the wetting effect of the cylindrical battery cell.

[0592] In some embodiments, the electrode assembly 10 is a stacked structure, and the stacking direction of the electrode assembly 10 is perpendicular to the first direction Z.

[0593] The stacking direction of the electrode assembly 10 can refer to the stacking direction of the first electrode 14, the second electrode 15 and the spacer 13. In some examples, the stacking direction of the electrode assembly 10 can be the thickness direction Y of the first current collector.

[0594] The stacking direction of the electrode assembly 10 is perpendicular to the first direction Z, so that the first electrode 14 and the second electrode 15 are vertically arranged. The gap formed by the first electrode 14 and the second electrode 15 has openings at the upper and lower ends of the electrode assembly 10. Based on this, the lower end of the first groove 1441 is close to the lower end face of the first active material layer 142, and the lower end of the first groove 1441 is close to the lower end opening of the gap. The electrolyte accumulated at the bottom can enter the space between the first electrode 14 and the second electrode 15 more smoothly through the opening at the lower end of the gap to wet the electrode assembly 10, which is beneficial to improving the utilization rate of the electrolyte accumulated at the bottom. In addition, after the electrode assembly 10 expands, the electrolyte is squeezed out from the upper and lower ends of the electrode assembly 10, which is also beneficial to the return flow of the electrolyte and improves the wetting effect of the electrode assembly 10, which can effectively improve the wetting effect of the battery cell 6.

[0595] Of course, in other examples, the first direction Z is perpendicular to the stacking direction of the electrode assembly 10 or inclined relative to the stacking direction of the electrode assembly 10.

[0596] Referring to Figures 22-25, in some embodiments, the thickness of the first active material layer 142 is t, and the groove depth of the first groove 1441 is h, wherein 0.05≤h / t≤0.84.

[0597] In some examples, the first groove 1441 forms a slot 144b on the first surface 1421, and the area within a preset distance of the first surface 1421 from the slot 144b is the measurement area 1421c. The thickness of the first active material layer 142 at the measurement area 1421c is equal to the thickness t of the first active material layer 142, and the preset distance is 5mm.

[0598] The measurement area 1421c can refer to the area enclosed by the slot 144b and the outer edge 1421d of the measurement area 1421c. The outer edge 1421d is arranged around the slot 144b, and the outer edge 1421d has the same shape as the slot 144b. The distance between the outer edge 1421d and the slot 144b is 5mm.

[0599] In some examples, the groove depth of the first groove 1441 does not change along the first direction Z, and the groove depth of the first groove 1441 at any position is equal to the groove depth h of the first groove 1441.

[0600] In some examples, the groove depth of the first groove 1441 changes along the first direction Z, and the maximum groove depth of the first groove 1441 is equal to the groove depth h of the first groove 1441. For example, along the first direction Z, the groove depth at the end of the first groove 1441 is less than the groove depth at the middle of the first groove 1441, and the groove depth at the middle of the first groove 1441 is equal to the groove depth h of the first groove 1441.

[0601] In some examples, the value of h / t can be 0.05, 0.84, or any value between 0.05 and 0.84. For example, the value of h / t can be, but is not limited to, 0.05, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.81, and 0.84.

[0602] The design with h / t ≥ 0.05 allows the first groove 1441 to guide the electrolyte accumulated at the bottom to the electrode assembly 10, improving the effective utilization rate of the electrolyte, enhancing the wetting effect of the electrode assembly 10, and improving the cycle performance of the battery cell 6. The design with h / t ≤ 0.84 ensures that the first groove 1441 does not penetrate the first active material layer 142, and the first current collector winding coil 1431 is not exposed, reducing the risk of direct reaction between the first current collector winding coil 1431 and ions. Furthermore, compared to the first groove 1441 penetrating the first active material layer 142, the grooved first active material layer 142 removes less active material, which is beneficial for increasing the active material capacity of the first electrode 14 and reducing the risk of decreased battery cell performance due to insufficient active material capacity of the first electrode 14. Therefore, both the cycle performance and overall performance of the battery cell 6 can be balanced.

[0603] In particular, the first electrode 14 is the negative electrode 12, and the first groove 1441 does not penetrate the negative electrode active material layer 122, so that ions do not react directly with the first current collector 141, reducing the lithium plating problem of the battery cell 6. In addition, the negative electrode active material layer 122 removes less negative electrode active material, which helps to reduce the risk of lithium plating caused by insufficient negative electrode active material and improves the performance of the battery cell 6.

[0604] In some embodiments, 0.08 ≤ h / t ≤ 0.8 can better balance the cycle performance and usage performance of the battery cell 6.

[0605] In some embodiments, 0.1 ≤ h / t ≤ 0.5 can better balance the cycle performance and usage performance of the battery cell 6.

[0606] In some embodiments, the groove depth of the first groove 1441 is h, where 0 μm < h ≤ 50 μm.

[0607] In some examples, the value of h can be 50 μm or any value between 0 and 50 μm. For example, the value of h can be, but is not limited to, 0 μm, 2 μm, 4 μm, 6 μm, 10 μm, 20 μm, 30 μm, 40 μm, and 50 μm.

[0608] The design with 0μm < h ≤ 50μm ensures a reasonable groove depth h for the first groove 1441. This allows the groove 1441 to guide the electrolyte accumulated at the bottom to flow to the electrode assembly 10, improving the effective utilization rate of the electrolyte, enhancing the wetting effect of the electrode assembly 10, and improving the cycle performance of the battery cell 6. Furthermore, reducing the amount of active material removed by the groove in the first active material layer 142 helps increase the active material capacity of the first electrode 14 and reduces the risk of performance degradation in the battery cell 6 due to insufficient active material capacity in the first electrode 14. Therefore, both the cycle performance and overall performance of the battery cell 6 can be balanced.

[0609] In some embodiments, 6μm≤h≤30μm can better balance the cycle performance and usage performance of the battery cell 6.

[0610] In some embodiments, the groove width of the first groove 1441 is w, wherein 30μm≤w≤1000μm.

[0611] In some examples, the groove width of the first groove 1441 does not change along the first direction Z, and the groove width of the first groove 1441 at any position is equal to the groove width w of the first groove 1441.

[0612] In some examples, the width of the first groove 1441 changes along the first direction Z, and the maximum width of the first groove 1441 is equal to the width w of the first groove 1441. For example, along the first direction Z, the width of the end of the first groove 1441 is less than the width of the middle of the first groove 1441, and the width of the middle of the first groove 1441 is equal to the width w of the first groove 1441.

[0613] In some examples, the value of w can be 30 μm, 1000 μm, or any value between 30 μm and 1000 μm. For example, the value of w can be, but is not limited to, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 100 μm, 110 μm, 140 μm, 180 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 800 μm, and 1000 μm.

[0614] The design with a w≥30μm allows the first groove 1441 to guide the electrolyte accumulated at the bottom to flow to the electrode assembly 10, improving the effective utilization rate of the electrolyte, enhancing the wetting effect of the electrode assembly 10, and improving the cycle performance of the battery cell 6. It also facilitates the fabrication of the first groove 1441. The design with a w≤1000μm reduces the amount of active material removed from the first active material layer 142, which is beneficial for increasing the active material capacity of the first electrode 14 and reducing the risk of performance degradation in the battery cell 6 due to insufficient active material capacity of the first electrode 14. Furthermore, during the hot-pressing process of the first electrode 14, the first groove 1441 is not easily flattened, and its shape can be stably maintained. Therefore, both the cycle performance and overall performance of the battery cell 6 can be considered.

[0615] In some embodiments, 50μm≤w≤500μm can better balance the cycle performance and performance of the battery cell 6.

[0616] In some embodiments, 80μm≤w≤120μm can better balance the cycle performance and usage performance of the battery cell 6.

[0617] In some embodiments, the groove width of the first groove 1441 is w, the groove depth of the first groove 1441 is h, and 0.05≤h / w≤1.

[0618] In some examples, the value of h / w can be 0.05, 1, or any value between 0.05 and 1. For example, the value of h / w can be, but is not limited to, 0.05, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.

[0619] With a fixed h, the design of h / w ≥ 0.05 ensures that the groove width w of the first groove 1441 is not too large, making it less likely to be flattened during the hot pressing process of the first electrode 14, and the shape of the first groove 1441 can be stably maintained. The design of h / w ≤ 1 provides a wider channel for the electrolyte accumulated at the bottom to flow to the upper part of the electrode assembly 10, which is beneficial to the flow of the electrolyte accumulated at the bottom, improves the wetting effect of the electrode assembly 10, and improves the cycle performance of the battery cell 6. Therefore, the processing and manufacturing of the first groove 1441 and the cycle performance of the battery cell 6 can be taken into account.

[0620] Based on 0μm<h≤50μm, the design of 0.05≤h / w≤1 ensures that the first groove 1441 has a suitable width and depth, which can form a capillary channel and guide the electrolyte accumulated at the bottom to flow to the electrode assembly 10 by using capillary action, thereby effectively improving the wetting effect of the electrode assembly 10 and improving the cycle performance of the battery cell 6.

[0621] In some embodiments, 0.1 ≤ h / w ≤ 0.5 can better balance the processing and fabrication of the first groove 1441 and the cycle performance of the battery cell 6.

[0622] In some embodiments, along the first direction Z, the size of the first active material layer 142 is L, and the groove depth of the first groove 1441 is h, 5*10. -5 ≤h / L≤5*10 -4 .

[0623] In some examples, the value of h / L can be 5*10. -5 5*10 -4 Or located at 5*10 -5 ~5*10 -4 Any value between 5 and 10; for example, the value of h / L can be, but is not limited to, 5*10. -5 7*10 -5 9*10 -5 1*10 -4 2*10 -4 3*10 -4 4*10 -4 5*10 -4 .

[0624] Given a constant L, h / L ≥ 5 * 10 -5 The design allows the electrolyte at the bottom of the first groove 1441 to flow upwards more quickly, improving the wetting effect of the first electrode 14; furthermore, h / L ≤ 5*10 -4 The design reduces the risk of the first current collector 141 being exposed due to excessive groove depth h of the first groove 1441 and excessive loss of active material of the first electrode 14. Therefore, it can balance the capacity, cycle performance and reliability of the battery cell 6.

[0625] In some embodiments, along the first direction Z, the size of the first active material layer 142 is L, and the groove depth of the first groove 1441 is h, wherein L≥60mm and h≥6μm.

[0626] In some examples, the value of L can be 60mm or any value greater than 60mm. For example, the value of L can be, but is not limited to, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 150mm, 200mm, 300mm, and 400mm.

[0627] In some examples, the value of h can be 6 μm or any value greater than 6 μm. For example, the value of h can be, but is not limited to, 6 μm, 10 μm, 20 μm, 30 μm, 40 μm, and 50 μm.

[0628] By adopting the technical solution of this embodiment, for battery cells 6 with L≥60mm and h≥6μm, the first groove 1441 can store more electrolyte and can also better guide the electrolyte at the bottom to flow upward, which can effectively improve the wetting effect of the first electrode 14 and improve the cycle performance of the battery cell 6.

[0629] Referring to Figures 24 and 25, in some embodiments, the first groove 1441 includes a first groove segment 1442 and a second groove segment 1443 arranged along a first direction Z. At least one end of the first groove segment 1442 along the first direction Z is connected to the second groove segment 1443. The groove depth of the first groove segment 1442 is greater than the groove depth of the second groove segment 1443, and / or the groove width of the first groove segment 1442 is greater than the groove width of the second groove segment 1443.

[0630] Along the first direction Z, one end of the first groove segment 1442 is connected to the second groove segment 1443, or both ends of the first groove segment 1442 are connected to the second groove segment 1443.

[0631] For example, the first groove 1441 is divided into three segments along the first direction Z. The middle segment is the first groove segment 1442, and the two ends are the second groove segments 1443. The first groove segment 1442 and the second groove 1444 are divided based on the groove depth change point of the first groove 1441 or the groove width change point of the first groove segment 1442.

[0632] The depth of the first groove segment 1442 is greater than the depth of the second groove segment 1443. For example, the first groove segment 1442 and the second groove segment 1443 are of equal depth, and the bottom surface of the first groove segment 1442 and the bottom surface of the second groove segment 1443 form a stepped structure.

[0633] The width of the first groove segment 1442 is greater than the width of the second groove segment 1443. For example, the first groove segment 1442 and the second groove segment 1443 are both of equal width, and the side of the first groove segment 1442 and the side of the second groove segment 1443 form a stepped structure.

[0634] In some examples, the first groove 1441 includes a first groove segment 1442 and a second groove segment 1443 arranged along the first direction Z. At least one end of the first groove segment 1442 along the first direction Z is connected to the second groove segment 1443. The groove depth of the first groove segment 1442 is greater than the groove depth of the second groove segment 1443, which makes it easier for the electrolyte to generate a siphon effect at the second groove segment 1443, which is more conducive to the rapid upward flow of the bottom electrolyte, improves the wetting effect of the first electrode 14, and improves the cycle performance of the battery cell 6.

[0635] In some examples, the first groove 1441 includes a first groove segment 1442 and a second groove segment 1443 arranged along the first direction Z. At least one end of the first groove segment 1442 along the first direction Z is connected to the second groove segment 1443. The groove width of the first groove segment 1442 is greater than the groove width of the second groove segment 1443, which makes it easier for the electrolyte to generate a siphon effect at the second groove segment 1443, which is more conducive to the rapid upward flow of the bottom electrolyte, improves the wetting effect of the first electrode 14, and improves the cycle performance of the battery cell 6.

[0636] In some examples, the first groove 1441 includes a first groove segment 1442 and a second groove segment 1443 arranged along the first direction Z. At least one end of the first groove segment 1442 is connected to the second groove segment 1443 along the first direction Z. The groove depth of the first groove segment 1442 is greater than the groove depth of the second groove segment 1443, and the groove width of the first groove segment 1442 is greater than the groove width of the second groove segment 1443. This makes it easier for the electrolyte to generate a siphon effect at the second groove segment 1443, which is more conducive to the rapid upward flow of the bottom electrolyte, improves the wetting effect of the first electrode 14, and improves the cycle performance of the battery cell 6.

[0637] In some embodiments, the depth of the second groove segment 1443 is progressively reduced from that of the first groove segment 1442 in the direction from the first groove segment 1442 to the second groove segment 1443; and / or, the width of the second groove segment 1443 is progressively reduced from that of the first groove segment 1442 in the direction from the first groove segment 1442 to the second groove segment 1443.

[0638] For example, the first groove segment 1442 has a uniform depth structure, and the second groove segment 1443 has a non-uniform depth structure. The groove depth of the second groove segment 1443 is set to decrease from that of the first groove segment 1442. The groove depth of the second groove segment 1443 can decrease stepwise or slowly from that of the first groove segment 1442 to form a smooth structure and reduce stress concentration at the second groove segment 1443.

[0639] For example, the first groove segment 1442 has a constant width structure, and the second groove segment 1443 has a non-constant width structure. The groove width of the second groove segment 1443 is set to decrease from that of the first groove segment 1442. The groove width of the second groove segment 1443 can decrease stepwise or slowly from that of the first groove segment 1442 to form a smooth structure and reduce stress concentration at the second groove segment 1443.

[0640] In some examples, the depth of the second segment 1443 is set to decrease from that of the first segment 1442 in the direction from the first segment 1442. The gradual decrease in depth of the second segment 1443 compared to the first segment 1442 can create a pressure difference for electrolyte flow. The second segment 1443 can produce a better siphon effect, allowing the electrolyte to be drawn into the second segment 1443 more quickly and then rapidly flow back into the first segment 1442. This can better improve the first wetting effect and improve the cycle performance of the battery cell 6.

[0641] In some examples, along the direction from the first segment 1442 to the second segment 1443, the width of the second segment 1443 is set to decrease from that of the first segment 1442. The gradual decrease in the width of the second segment 1443 compared to the width of the first segment 1442 can create a pressure difference for electrolyte flow. The second segment 1443 can produce a better siphon effect, allowing the electrolyte to be drawn into the second segment 1443 more quickly and flow rapidly into the first segment 1442 through the second segment 1443. This can better improve the first wetting effect and improve the cycle performance of the battery cell 6.

[0642] In some examples, the depth of the second segment 1443 is set to decrease from that of the first segment 1442 along the direction from the first segment 1442 to the second segment 1443; the width of the second segment 1443 is set to decrease from that of the first segment 1442 along the direction from the first segment 1442 to the second segment 1443. This can create a larger pressure difference for electrolyte flow, and the second segment 1443 can produce a better siphon effect, which can draw the electrolyte into the second segment 1443 more quickly and return it to the first segment 1442 through the second segment 1443. This can better improve the first wetting effect and improve the cycle performance of the battery cell 6.

[0643] Referring to Figures 26-28, in some embodiments, the first groove 1441 includes a plurality of sub-segments 1445, which are spaced apart along a first direction Z, which is perpendicular to the thickness direction Y of the first current collector 141.

[0644] The first groove 1441 has a segmented structure, and the first groove 1441 includes multiple sub-segments 1445. Adjacent sub-segments 1445 are not connected and there is a distance between them. The multiple sub-segments 1445 can be set at equal intervals or at non-equal intervals.

[0645] By adopting the technical solution of this embodiment, the first groove 1441 includes multiple segments 1445, which can reduce the removal of active material by grooving the first active material layer 142, reduce the amount of active material loss of the first electrode 14, and help improve the capacity and performance of the battery cell. In addition, the multiple segments 1445 are spaced apart, which is beneficial to improving the structural strength and rigidity of the first electrode 14 compared with the use of a whole segment first groove 1441, and is beneficial to the reliability of the battery cell 6.

[0646] In some embodiments, along the first direction Z, the spacing between two adjacent sub-segments 1445 is d, where 0.1mm≤d≤1mm.

[0647] In some examples, the value of d can be 0.1mm, 1mm, or any value between 0.1mm and 1mm. For example, the value of d can be, but is not limited to, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1mm.

[0648] The design with d≥0.1mm allows for spacing between adjacent sub-segments 1445, reducing the loss of active material in the first electrode 14 and improving the performance of the battery cell 6. The design with d≤1mm allows the electrolyte between adjacent sub-segments 1445 to flow between each other, resulting in a more uniform distribution of the electrolyte and improving the cycle performance of the battery cell 6.

[0649] In some embodiments, 0.3mm≤d≤0.6mm can better balance the cycle performance and usage performance of the battery cell 6.

[0650] Referring to Figures 27 and 28, in some embodiments, in the two first grooves 1441, the distance between two adjacent sub-segments 1445 of one first groove 1441 may be the same as or different from the distance between two adjacent sub-segments 1445 of the other first groove 1441.

[0651] Referring to Figure 29, in some embodiments, there are multiple first grooves 1441, and the multiple first grooves 1441 are arranged at intervals along the second direction X; along the second direction X, in two adjacent first grooves 1441, at least a portion of the sub-segment 1445 of one first groove 1441 is offset from the sub-segment 1445 of the other first groove 1441, and the second direction X is perpendicular to the first direction Z and the thickness direction Y of the first current collector 141.

[0652] For example, in two adjacent first grooves 1441, along the second direction X, the projection of a segment 1445 of one first groove 1441 does not coincide with or partially coincides with the projection of a segment 1445 of the other first groove 1441.

[0653] In some examples, in two adjacent first grooves 1441, the electrolyte in the two adjacent segments 1445 of the first first groove 1441 is not easily wetted to the middle position of the two segments 1445. However, the segment 1445 of the second first groove 1441 can be set opposite to the middle position between the two adjacent segments 1445 of the first first groove 1441. In this way, the segment 1445 of the second first groove 1441 can be used to wet the middle position between the two adjacent segments 1445 of the first first groove 1441, reducing the wettability dead zone of the first electrode 14, improving the uniformity of electrolyte distribution, which is beneficial to improving the wettability of the first electrode 14 and improving the cycle performance of the battery cell 6.

[0654] By adopting the technical solution of this embodiment, the multiple segments 1445 of two adjacent first grooves 1441 are staggered, which is beneficial to improving the uniformity of electrolyte distribution, improving the wetting effect of the first electrode 14, and improving the cycle performance of the battery cell 6.

[0655] Referring to Figure 29, in some embodiments, there are multiple first grooves 1441, and multiple first grooves 1441 form multiple sets of first grooves 1441. Each set of first grooves 1441 includes multiple intersecting first grooves 1441. The multiple sets of first grooves 1441 are arranged at intervals along the second direction X, and the second direction X is perpendicular to the first direction Z and the thickness direction Y of the first current collector 141.

[0656] The multiple first grooves 1441 are divided into multiple groups, and each group of first grooves 1441 includes multiple intersecting first grooves 1441. In some examples, each group of first grooves 1441 includes two intersecting first grooves 1441, and the two first grooves 1441 form an X-shaped structure. Of course, in other examples, each group of first grooves 1441 may also include three, four or more first grooves 1441.

[0657] By adopting the technical solution of this embodiment, the multiple first grooves 1441 are divided into multiple groups, and each group of first grooves 1441 includes multiple intersecting first grooves 1441. The electrolyte can flow within the multiple first grooves 1441, which is beneficial to improving the uniformity of electrolyte distribution, improving the wetting effect of the first electrode 14, and improving the cycle performance of the battery cell 6. In addition, the multiple groups of first grooves 1441 are spaced apart along the second direction X, which can reduce the loss of active material in the first electrode 14, which is beneficial to improving the performance and capacity of the battery cell 6. At the same time, it can also improve the structural strength and rigidity of the first electrode 14, which is beneficial to improving the reliability of the battery cell 6.

[0658] Referring to Figures 6 and 7, in some embodiments, the electrode assembly 10 is a wound structure, with m gap windings G formed between the first active material layer 142 and the second active material layer 152, where m ≥ 30 and m is a natural number; the innermost gap winding G is the first gap winding G; the average radial dimension of the (m-13)th to (m-5)th gap windings G is greater than the average radial dimension of the 5th to 13th gap windings G.

[0659] For example, m is 30, 40, 50, 60, 70, 80, 90, 100, 150 or 200.

[0660] For example, referring to Figure 7, after the first electrode 14 and the second electrode 15 are wound, two gaps are formed between the first active material layer 142 and the second active material layer 152. The gaps can be spaces located between the first electrode 14 and the second electrode 15 that are not filled by the separator 13.

[0661] The two gaps are divided into a first gap and a second gap. The first gap is wound to form a gap windings G, and the second gap is wound to form ma gap windings G. The gap windings G of the first gap and the gap windings G of the second gap are arranged alternately from the inside to the outside of the electrode assembly 10, that is, from the center to the outer periphery of the electrode assembly 10, the gap windings G of the first gap and the gap windings G of the second gap are arranged alternately.

[0662] As an example, the first gap and the second gap can be formed in a variety of ways.

[0663] For example, when winding the first electrode 14, the separator 13, and the second electrode 15, the tightness of the electrode assembly 10 after winding is adjusted by controlling the tension or other parameters of the three components, thereby forming a first gap and a second gap of predetermined size.

[0664] During the cycling process of the battery cell 6, the gap winding ring G can provide space for the expansion of the electrode assembly 10, reduce the pressure between the first active material layer 142 and the second active material layer 152, thereby reducing the amount of electrolyte squeezed out between the first electrode 14 and the second electrode 15. On this basis, in conjunction with the first groove 1441, the wetting effect of the first electrode 14 and the second electrode 15 can be effectively improved, thereby improving the cycle performance of the battery cell 6. In addition, the first gap and the second gap can reduce the expansion of the electrode assembly 10, thereby reducing the squeezing effect on the outer casing 20, reducing the risk of deformation and cracking of the outer casing 20, and improving the reliability of the battery cell 6.

[0665] From the inside to the outside of the electrode assembly 10, m gap windings G are arranged sequentially. The first gap winding G is closest to the central axis X1 of the battery cell 6 compared to the other gap windings G.

[0666] For example, a first gap winding G is formed between the first first electrode winding 143 and the first second electrode winding 153, a second gap winding G is formed between the first second electrode winding 153 and the second first electrode winding 143, a third gap winding G is formed between the second first electrode winding 143 and the second second electrode winding 153, and so on, until m gap windings are finally formed.

[0667] In some examples, the average radial dimension of the 5th to 13th gap windings G can be measured as follows:

[0668] Discharge cell 6 to the lower cutoff voltage (e.g., 2.5V);

[0669] Using CT (Computed Tomography) technology, an image of the cross-section of the battery cell 6 is obtained using X-rays. This cross-section is perpendicular to the central axis X1 of the battery cell 6 and intersects with the first active material layer 142 and the second active material layer 152. The cross-section shows the first electrode 14, the second electrode 15 and the separator 13.

[0670] Based on the image and the virtual line X3, along a direction away from the center of the cross section and parallel to the virtual line X3, the first intersection point of the outer surface of the third first electrode winding 143 and the virtual line X3 is obtained, and the second intersection point of the inner surface of the seventh second electrode winding 153 and the virtual line X3 is obtained. The distance D1 between the first intersection point and the second intersection point is measured.

[0671] Disassemble the battery cell 6 and unfold the first electrode 14, the second electrode 15 and the separator 13;

[0672] Fifty positions are randomly selected on the surface of the first active material layer 142, and the thickness values ​​of the 50 first electrode sheets 14 are measured. Then the average value of the 50 thickness values ​​is calculated, which can be the thickness T1 of the first electrode sheet 14.

[0673] Fifty positions are randomly selected on the surface of the second active material layer 152, and the thickness values ​​of the 50 second electrode sheets 15 are measured. Then the average value of the 50 thickness values ​​is calculated, which can be the thickness T2 of the second electrode sheet 15.

[0674] Fifty arbitrary locations are selected on the isolation member 13, and 50 thickness values ​​are measured. Then, the average value of the 50 thickness values ​​is calculated, which can be the thickness T3 of the isolation member 13.

[0675] Four first electrode windings 143, four second electrode windings 153, and nine layers of separators 13 are provided between the outer surface of the third first electrode winding 143 and the inner surface of the seventh second electrode winding 153. Nine gap windings G are formed between the outer surface of the third first electrode winding 143 and the inner surface of the seventh second electrode winding 153. The average radial dimension of the fifth to thirteenth gap windings G is W1 = (D1 - 4 × T1 - 4 × T2 - 9 × T3) / 9.

[0676] Similarly, based on the image and the virtual line X3, along the direction away from the center of the cross section and parallel to the virtual line X3, the third intersection point of the inner surface of the third-to-last second electrode winding 153 and the virtual line X3 is obtained, and the fourth intersection point of the outer surface of the eighth-to-last first electrode winding 143 and the virtual line X3 is obtained. The distance D2 between the third intersection point and the fourth intersection point is measured.

[0677] Four first electrode windings 143, four second electrode windings 153, and nine layers of separators 13 are provided between the inner surface of the third-to-last second electrode winding 153 and the outer surface of the eighth-to-last first electrode winding 143. The inner surface of the third-to-last second electrode winding 153 and the outer surface of the eighth-to-last first electrode winding 143 form nine gap windings G. The average radial dimension of the gap windings G from m-13 to m-5 is W2 = (D2 - 4 × T1 - 4 × T2 - 9 × T3) / 9.

[0678] Where W1 < W2.

[0679] During the cycling process of the battery cell 6, the expansion of the electrode assembly 10 gradually accumulates radially from the inside to the outside, with a larger cumulative expansion force on the outer side of the electrode assembly 10. The gap windings G from m-13 to m-5 are positioned further outward than the gap windings G from 5 to 13, and the average radial dimension of the gap windings G from m-13 to m-5 is greater than the average radial dimension of the gap windings G from 5 to 9. This larger average radial dimension of the gap windings G from m-13 to m-5 results in a larger radial dimension on the outer side of the electrode assembly 10, providing more expansion space for the outer side of the electrode assembly 10 and absorbing the expansion force of the electrode assembly 10. The cumulative expansion amount is zero, which effectively reduces the force between the electrode assembly 10 and the outer casing 20, reduces the deformation of the outer casing 20, reduces the risk of cracking of the outer casing 20, and improves the reliability of the battery cell 6. In addition, the gap winding ring G on the outside of the electrode assembly 10 has a large radial dimension, which also helps to reduce the amount of electrolyte extruded on the outside of the electrode assembly 10 and improves the cycle performance of the battery cell 6. The average radial dimension of the 5th to 9th gap winding rings G is small, which makes the gap winding ring G on the inside of the electrode assembly 10 have a large radial dimension, which can increase the structural compactness of the inside of the electrode assembly 10 and improve the energy density of the battery cell 6.

[0680] In some embodiments, the gap winding G includes a first gap sub-ring G1 and a second gap sub-ring G2, wherein the first gap sub-ring G1 is located between the first active material layer 142 and the spacer 13, and the second gap sub-ring G2 is located between the second active material layer 152 and the spacer 13.

[0681] As an example, the radial dimension of the first gap sub-ring G1 is W3, and the radial dimension of the second gap sub-ring G2 is W4. The radial dimension W of the gap winding G is W = W3 + W4.

[0682] Both the first gap sub-ring G1 and the second gap sub-ring G2 can provide space for the expansion of the electrode assembly 10, thereby reducing the squeezing effect on the outer casing 20, reducing the risk of deformation and cracking of the outer casing 20, and improving the reliability of the battery cell 6.

[0683] In some embodiments, the radial dimension of the first gap winding G is smaller than the radial dimension of the m-th gap winding G.

[0684] By adopting the technical solution of this embodiment, the large radial dimension of the m-th gap winding G results in a larger gap space between the first active material layer 142 and the second active material layer 152 on the outer side of the electrode assembly 10. This provides more expansion space for the outer side of the electrode assembly 10, absorbs the accumulated expansion of the electrode assembly 10, and effectively reduces the force between the electrode assembly 10 and the outer shell 20, reduces the deformation of the outer shell 20, reduces the risk of cracking of the outer shell 20, and improves reliability. In addition, the large gap between the first active material layer 142 and the second active material layer 152 on the outer side of the electrode assembly 10 also helps to reduce the amount of electrolyte extruded on the outer side of the electrode assembly 10, which is beneficial to improving the cycle performance of the battery cell 6. The small radial dimension of the first gap winding G results in a smaller gap between the first active material layer 142 and the second active material layer 152 on the inner side of the electrode assembly 10, which increases the structural compactness of the inner side of the electrode assembly 10 and is beneficial to improving the energy density of the battery cell 6.

[0685] In some embodiments, the m gap windings G are divided into j groups of gap windings G in the order from the inner side to the outer side of the electrode assembly 10; that is, from the center to the outer periphery, the m gap windings G of the electrode assembly 10 are divided into j groups of gap windings G.

[0686] The innermost set of gap winding rings G is the first set of gap winding rings G. In the first set to the (j-1)th set, each set of gap winding rings G includes 9 gap winding rings G, 1≤m-9*(j-1)≤9, where j is a natural number; the average radial dimension of the first set to the (j-1)th set of gap winding rings G is set to increase incrementally.

[0687] The electrode assembly 10 consists of m gap windings G divided into j groups from the inside to the outside. The group of gap windings G closest to the central axis X1 of the battery cell 6 is the first group of gap windings G. Each of the first to the (j-1)th group of gap windings G includes 9 gap windings G. The number of gap windings G in the jth group is 1, 2, 3, 4, 5, 6, 7, 8, or 9.

[0688] For example, the 1st to 9th gap windings G form the 1st group of gap windings G, the 10th to 18th gap windings G form the 2nd group of gap windings G, the 19th to 27th gap windings G form the 3rd group of gap windings G, and so on.

[0689] For example, the average radial dimension of the first group of gap windings G can be measured in the following manner, and the average radial dimension of the other groups of gap windings G can also be obtained in the following manner.

[0690] Discharge cell 6 to the lower cutoff voltage (e.g., 2.5V);

[0691] An image of the cross-section of battery cell 6 was obtained using the aforementioned X-rays;

[0692] Based on this image, a virtual straight line X3 is defined, which can pass through the center of the cross section (the virtual straight line X3 intersects the central axis X1);

[0693] Based on the image and the virtual line X3, along the direction away from the center of the cross section and parallel to the virtual line X3, the fifth intersection point of the outer surface of the first first electrode winding 143 and the virtual line X3 is obtained, the sixth intersection point of the inner surface of the fifth second electrode winding 153 and the virtual line X3 is obtained, and the distance D3 between the fifth intersection point and the sixth intersection point is measured.

[0694] Four first electrode windings 143, four second electrode windings 153, and nine spacers 13 are provided between the outer surface of the first first electrode winding 143 and the inner surface of the fifth second electrode winding 153. Nine gap windings G are formed between the outer surface of the first first electrode winding 143 and the inner surface of the fifth second electrode winding 153. The average radial dimension of the first group of gap windings G is W5 = (D3 - 4 × T1 - 4 × T2 - 9 × T3) / 9.

[0695] By adopting the technical solution of this embodiment, the average radial dimension of the gap winding rings G from the first group to the (j-1)th group is set to increase progressively. From the inside to the outside of the electrode assembly 10, the radial dimension of the gap winding rings G of the electrode assembly 10 is set to increase progressively. The larger radial dimension of the gap winding rings G on the outside of the electrode assembly 10 can provide more expansion space for the electrode assembly 10, absorb the accumulated expansion of the electrode assembly 10, thereby reducing the interaction force between the electrode assembly 10 and the outer casing 20, reducing the deformation of the outer casing 20, reducing the risk of cracking of the outer casing 20, and improving reliability. In addition, the smaller radial dimension of the gap winding rings G on the inside of the electrode assembly 10 can effectively increase the structural compactness of the inside of the electrode assembly 10, which is beneficial to improving the energy density of the battery cell 6.

[0696] Referring to Figure 8, in some embodiments, the first current collector 141 includes a first current collector body 1411 and a first tab 1412 connected together. At least a portion of the first current collector body 1411 is covered with a first active material layer 142, while the first tab 1412 is not covered with the first active material layer 142. The second current collector 151 includes a second current collector body 1511 and a second tab 1512 connected together. At least a portion of the second current collector body 1511 is covered with a second active material layer 152, while the second tab 1512 is not covered with the second active material layer 152.

[0697] Along the axial direction of the battery cell 6, the second current collector 151 is divided into two parts. The part covered by the second active material layer 152 is called the second current collector body 1511, and the other part not covered by the second active material layer 152 is called the second tab 1512. The interface between the second tab 1512 and the second current collector body 1511 is the end face of the second active material layer 152 near the second tab 1512. The second tab 1512 is used for electrical connection with the output electrode to facilitate the input and output of electrical energy.

[0698] In some examples, the second current collector 1511 may be completely covered by the second active material layer 152, or it may be partially covered by the second active material layer 152. For example, the side of the second current collector 1511 facing away from the second tab 1512 is not covered by the second active material layer 152.

[0699] By adopting the technical solution of this embodiment, the first tab 1412 is led out from the end of the first electrode 14 along the axial direction of the battery cell 6, and the second tab 1512 is led out from the end of the second electrode 15 along the axial direction of the battery cell 6, which facilitates the input or output of the battery cell 6.

[0700] Referring to Figures 30-32, in some embodiments, the housing 20 includes a housing 21 and an end cap 22. The housing 21 includes a side wall 212 and an end wall 211 connected to each other. The side wall 212 surrounds the electrode assembly 10. The end wall 211 and the end cap 22 are distributed opposite to each other along the axial direction of the battery cell 6. The end cap 22 is sealed to the side wall 212. The end cap 22 is insulatedly provided with an electrode terminal 30. The second tab 1512 is electrically connected to the electrode terminal 30. At least one of the side wall 212 and the end wall 211 is electrically connected to the first tab 1412.

[0701] The end cover 22 is provided with electrode terminals 30, which are insulated from the end cover 22. The electrode terminals 30 serve as output electrodes for outputting or inputting electrical energy.

[0702] The second tab 1512 can be directly connected to the electrode terminal 30. For example, the second tab 1512 can be directly soldered to the electrode terminal 30, or the second tab 1512 can be soldered to the electrode terminal 30 through a conductive component.

[0703] The first tab 1412 can be directly connected to the end wall 211, or indirectly connected to the end wall 211 through the side wall 212 or other components.

[0704] The first tab 1412 can be directly connected to the side wall 212, or it can be connected to the side wall 212 at intervals through the end wall 211 or other components.

[0705] The electrode terminal 30 serves as one exposed electrode of the battery cell 6, and the side wall 212 or end wall 211 serves as another exposed electrode of the battery cell 6. The circuit connection between the battery cells 6 is simpler and more flexible, which is conducive to assembling multiple battery cells 6 into a group and simplifying the battery structure.

[0706] In some embodiments, the electrode terminal 30 is provided with a through hole 31, which can be used to inject electrolyte.

[0707] In some embodiments, the battery cell 6 further includes a cover plate 40, which is connected to the electrode terminal 30 and serves to separate the through hole 31 from the external space of the battery cell 6.

[0708] In some embodiments, the housing 20 includes a housing 21 and an end cap 22. The housing 21 includes a side wall 212 and an end wall 211 connected to each other. The side wall 212 surrounds the electrode assembly 10. The end wall 211 and the end cap 22 are distributed opposite to each other along the axial direction of the battery cell 6. The end cap 22 is sealed to the side wall 212. The end wall 211 is insulated with an electrode terminal 30. The second tab 1512 is electrically connected to the electrode terminal 30. At least one of the end cap 22 and the side wall 212 is electrically connected to the first tab 1412.

[0709] The end wall 211 is provided with an electrode terminal 30, which is insulated from the end wall 211. The electrode terminal 30 serves as an output electrode for outputting or inputting electrical energy.

[0710] The second tab 1512 can be directly connected to the electrode terminal 30. For example, the second tab 1512 can be directly soldered to the electrode terminal 30, or the second tab 1512 can be soldered to the electrode terminal 30 through a conductive component.

[0711] The first tab 1412 can be directly connected to the end cap 22, or indirectly connected to the end wall 211 through the side wall 212 or other components.

[0712] The first tab 1412 can be directly connected to the side wall 212, or it can be connected to the side wall 212 at intervals through the end cap 22 or other components.

[0713] The electrode terminal 30 serves as one exposed electrode of the battery cell 6, and the side wall 212 or end cap 22 serves as another exposed electrode of the battery cell 6. The circuit connection between the battery cells 6 is simpler and more flexible, which is conducive to assembling multiple battery cells 6 into a group and simplifying the battery structure.

[0714] In some embodiments, the battery cell 6 further includes a first current collector 60 and a second current collector 70; a first tab 1412 and a second tab 1512 are respectively located at both ends of the electrode assembly 10 along the axial direction of the battery cell 6, and the second tab 1512 is located on the side of the electrode assembly 10 near the electrode terminal 30; the second current collector 70 is electrically connected between the second tab 1512 and the electrode terminal 30; the electrode terminal 30 is insulated from the end cap 22, the first current collector 60 is located between the first tab 1412 and the end wall 211, the first current collector 60 is electrically connected to the first tab 1412, and at least one of the side wall 212 and the end wall 211 is electrically connected to the first current collector 60.

[0715] The second tab 1512 and the first tab 1412 are located at both ends of the electrode assembly 10, which can reduce the risk of short circuit in the battery cell 6.

[0716] The second current collector 70 can serve as a converter to facilitate the electrical connection between the second tab 1512 and the electrode terminal 30.

[0717] For example, the second current collector 70 is welded to the second tab 1512, and the second current collector 70 is welded to the electrode terminal 30.

[0718] In some examples, the second collector element 70 is annular.

[0719] The first current collector 60 can serve as a converter to facilitate electrical connection between the first electrode 1412 and at least one of the side wall 212 and the end wall 211.

[0720] For example, the first current collector 60 is welded to the first tab 1412, the second current collector 70 is welded to the side wall 212, or the first current collector 60 is welded to the end wall 211.

[0721] In some embodiments, the battery cell 6 further includes a first current collector 60 and a second current collector 70; a first tab 1412 and a second tab 1512 are respectively located at both ends of the electrode assembly 10 along the axial direction of the battery cell 6, and the second tab 1512 is located on the side of the electrode assembly 10 near the electrode terminal 30; the second current collector 70 is electrically connected between the second tab 1512 and the electrode terminal 30; the electrode terminal 30 is insulated on the end wall 211, the first current collector 60 is located between the first tab 1412 and the end cap 22, the first current collector 60 is electrically connected to the first tab 1412, and at least one of the side wall 212 and the end cap 22 is electrically connected to the first current collector 60.

[0722] The first current collector 60 can serve as a converter to facilitate electrical connection between the first electrode 1412 and at least one of the side wall 212 and the end cap 22.

[0723] For example, the first current collector 60 is welded to the first tab 1412, the second current collector 70 is welded to the side wall 212, or the first current collector 60 is welded to the end cap 22.

[0724] In some embodiments, the electrode terminal 30 is insulatedly disposed on the end wall 211; the side wall 212 is provided with an inwardly protruding protrusion 2121, which is located on the side of the first tab 1412 facing the end cap 22 along the axial direction of the battery cell 6; the second current collector 70 includes a first connecting portion 61, a second connecting portion 62 and a third connecting portion 63, the second connecting portion 62 being connected between the first connecting portion 61 and the third connecting portion 63; the first connecting portion 61 being connected to the first tab 1412, at least a portion of the third connecting portion 63 being located between the protrusion 2121 and the end cap 22, and the third connecting portion 63 being connected to the side of the protrusion 2121 facing away from the first tab 1412.

[0725] The side wall 212 is provided with an inwardly protruding protrusion 2121. For example, the protrusion 2121 can be a solid structure or a hollow structure.

[0726] In the axial direction of the battery cell 6, at least a portion of the protrusion 2121 is located between the end cap 22 and the first tab 1412.

[0727] The protrusion 2121 overlaps with the first tab 1412 in the axial direction of the battery cell 6. When the battery cell 6 is subjected to external impact, it can restrict the movement of the first tab 1412 along the axial direction of the battery cell 6, reducing the risk of failure of the connection between the first tab 1412 and the first current collector 60.

[0728] The first current collector 60 includes a first connecting portion 61, a second connecting portion 62, and a third connecting portion 63; the first connecting portion 61 is welded to the first electrode tab 1412; the third connecting portion 63 is connected to the protrusion 2121. As an example, the third connecting portion 63 may be welded to the protrusion 2121; alternatively, the third connecting portion 63 may also be press-fitted to the protrusion 2121. The first connecting portion 61 may be welded to the first electrode tab 1412.

[0729] At least a portion of the third connecting part 63 is disposed between the protrusion 2121 and the end cap 22. The third connecting part 63 is connected to the side of the protrusion 2121 facing the end cap 22, so that the first current collector 60 can be assembled through the end cap 22, which facilitates the installation of the first current collector 60. In addition, the protrusion 2121 also limits the third connecting part 63, improves the installation stability of the first current collector 60, improves the connection reliability between the first current collector 60 and the first tab 1412 and between the first current collector 60 and the protrusion 2121, and improves the reliability of the battery cell 6.

[0730] In some embodiments, the third connecting portion 63 is welded to the protrusion 2121.

[0731] In some embodiments, the outer side of the sidewall 212 is provided with a recess 2122, which corresponds to the position of the protrusion 2121. As an example, after the electrode assembly 10 is installed into the housing 21, the sidewall 212 is pressed from the outside to form an inwardly protruding protrusion 2121.

[0732] In some embodiments, the sidewall 212 further includes a crimping portion 2123, which extends from the end of the protrusion 2121 away from the endwall 211 and surrounds the end cap 22.

[0733] A portion of the pressing part 2123 is bent to form a flange structure. In the axial direction of the battery cell 6, a portion of the end cap 22 is located between the flange structure and the protrusion 2121. The protrusion 2121 and the flange structure can limit the end cap 22 to fix the end cap 22 in the axial direction of the battery cell 6.

[0734] In some embodiments, the battery cell 6 further includes an insulating member 80, which is disposed between the sidewall 212 and the end cap 22 and insulates the end cap 22 from the sidewall 212.

[0735] In some embodiments, a portion of the insulating member 80 is located between the third connection portion 63 and the end cap 22 to insulate the first current collector 60 from the end cap 22.

[0736] In some embodiments, a battery device 2 is provided, comprising a plurality of the aforementioned battery cells 6.

[0737] In some embodiments, an electrical device is provided, including the battery cell 6 or the battery device 2 described above, wherein the battery cell or the battery device 2 is used to store or provide electrical energy.

[0738] By adopting the technical solution of this embodiment, the battery cell 6 has good cycle performance, and the battery device 2 has good performance and long service life, which is conducive to improving the performance and service life of the electrical device.

[0739] Referring to Figures 3-8, this application embodiment provides a battery cell 6, which includes a housing 20, an electrode assembly 10, electrode terminals 30, a first current collector 60, and a second current collector 70. The battery cell 6 is used in an electrical device.

[0740] The outer casing 20 includes a housing 21 and an end cap 22. The housing 21 includes an integrally formed side wall 212 and an end wall 211. The end wall 211 and the end cap 22 are opposite each other along the axial direction of the battery cell 6. The end cap 22 is welded to the side wall 212.

[0741] Electrode terminals 30 are insulatedly disposed on end wall 211.

[0742] At least a portion of the electrode assembly 10 is housed within the housing 20. The electrode assembly 10 includes a first electrode 14, a second electrode 15, and a spacer 13, which are wound together. The spacer 13 is used to isolate the second electrode 15 and the first electrode 14.

[0743] The first electrode 14 includes a first current collector 141 and a first active material layer 142 covering the surface of the first current collector 141. The second electrode 15 includes a second current collector 151 and a second active material layer 152 covering the surface of the second current collector 151. The portion of the first current collector 141 not covered by the first active material layer 142 forms a first tab 1412, and the portion of the second current collector 151 not covered by the second active material layer 152 forms a second tab 1512. A first current collector member 60 connects the first tab 1412 and the sidewall 212, and a second current collector member 70 connects the electrode terminal 30 and the second tab 1512.

[0744] The first active material layer 142 has a first surface 1421 disposed opposite to the first current collector 141, and the first surface 1421 is provided with a first groove 1441 extending along the first direction Z; the first direction Z is parallel to the direction of gravity.

[0745] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0746] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, wherein, include: The outer casing contains the electrolyte; The electrode assembly is at least partially housed within the housing; The electrode assembly includes an isolator and a first electrode and a second electrode with opposite polarities, at least a portion of the isolator being located between the first electrode and the second electrode; The first electrode includes a first current collector and a first active material layer. At least a portion of at least one surface of the first current collector along its thickness direction is connected to the first active material layer. At least a portion of the first active material layer is located between the first current collector and the separator. The first active material layer has a first surface facing away from the first current collector, and the first surface has a first groove extending along a first direction; the first direction is parallel to the direction of gravity.

2. The battery cell according to claim 1, wherein: Along the first direction, the size of the first groove is l, and the size of the first active material layer is L, wherein 0.65≤l / L≤1; optionally, 0.8≤l / L≤0.

98.

3. The battery cell according to claim 2, wherein: The battery cell is a cylindrical battery cell with a diameter of 60mm ≤ L ≤ 350mm; optionally, it has a diameter of 80mm ≤ L ≤ 210mm. Alternatively, the battery cell may be a prismatic battery cell with a diameter of 120mm ≤ L ≤ 330mm; optionally, the diameter may be 160mm ≤ L ≤ 250mm.

4. The battery cell according to any one of claims 1 to 3, wherein: Along the first direction, the distance between the lower end of the first groove and the lower end surface of the first active material layer is S, where 0mm≤S≤20mm, optionally 2mm≤S≤10mm, and optionally 4mm≤S≤8mm.

5. The battery cell according to any one of claims 1 to 4, wherein: Along the first direction, the distance between the upper end of the first groove and the upper surface of the first active material layer is s, where 0mm≤s≤20mm, optionally 0.1mm≤s≤8mm, and optionally 0.5mm≤s≤3mm.

6. The battery cell according to any one of claims 1 to 5, wherein: The first active material layer includes a first active material portion and a second active material portion arranged along the first direction. At least one end of the first active material portion along the first direction is connected to the second active material portion, and the thickness of the second active material portion is less than the thickness of the first active material portion.

7. The battery cell according to claim 6, wherein: Along the direction from the first active material portion to the second active material portion, the thickness of the second active material portion decreases.

8. The battery cell according to claim 6 or 7, wherein: The first active material portion has a first side facing away from the first current collector, and the second active material portion has a second side facing away from the first current collector, the second side being closer to the first current collector than the first side.

9. The battery cell according to any one of claims 6 to 8, wherein: The first active material portion is provided with the first groove, and along the first direction, the second active material portion is spaced apart from the first groove.

10. The battery cell according to claim 9, wherein: Along the first direction, the distance between the second active material portion and the first groove is S1, where 0mm < S1 ≤ 18mm, and optionally, 2mm ≤ S1 ≤ 8mm.

11. The battery cell according to claim 9 or 10, wherein: The first electrode is the negative electrode.

12. The battery cell according to any one of claims 6 to 11, wherein: Along the first direction, one end of the first active material portion is connected to the second active material portion, and the other end of the first active material portion is not connected to the second active material portion. The surface of the first active material portion facing away from the first current collector is provided with the first groove. Along the first direction, the first groove penetrates the end face of the first active material portion facing away from the second active material portion; or, along the first direction, the end face of the first active material portion facing away from the second active material portion is spaced apart from the first groove.

13. The battery cell according to any one of claims 6 to 12, wherein: The first current collector includes a first current collector body and a first electrode tab arranged and connected along the first direction. At least a portion of the first current collector body is covered with the first active material layer, and the first electrode tab is not covered with the first active material layer.

14. The battery cell according to any one of claims 1 to 13, wherein: The number of the first active material layers is two, and the two first active material layers respectively cover the two surfaces of the first current collector along its own thickness direction, and at least one of the first active material layers is provided with the first groove.

15. The battery cell according to claim 14, wherein: The number of the first grooves is multiple, and the multiple first grooves include first grooves and second grooves. In the two first active material layers, one is provided with multiple first grooves and the other is provided with multiple second grooves. The first grooves and second grooves are staggered along the thickness direction of the first current collector.

16. The battery cell according to claim 15, wherein: Along a second direction, a plurality of first grooves and a plurality of second grooves are alternately arranged, the second direction being perpendicular to the first direction and the thickness direction of the first current collector.

17. The battery cell according to claim 16, wherein: Along the second direction, the distance between adjacent first and second slots is C, where C ≥ 1.5 mm, optionally 1.8 mm ≤ C ≤ 5 mm, and optionally 2 mm ≤ C ≤ 3 mm.

18. The battery cell according to any one of claims 1 to 17, wherein: The electrode assembly is a wound structure, the first electrode is wound to form a plurality of first electrode winding rings, the first current collector includes a first current collector winding ring located in the first electrode winding ring, the first active material layer includes a first active winding ring located in the first electrode winding ring, and the first surface includes a first winding surface located in the first electrode winding ring; wherein, at least one of the first winding surfaces of the first electrode winding ring is provided with the first groove.

19. The battery cell according to claim 18, wherein: The first direction is parallel to the winding axis of the electrode assembly.

20. The battery cell according to claim 19, wherein: The number of the first grooves is multiple, and the multiple first grooves are spaced apart along the second direction, with the distance between two adjacent first grooves increasing progressively. The second direction is the winding direction of the electrode assembly.

21. The battery cell according to any one of claims 18 to 20, wherein: The number of first electrode windings is n, n≥30, where n is a natural number. The innermost first electrode winding is the first first electrode winding. At least one of the first 10 first electrode windings is provided with the first groove.

22. The battery cell according to any one of claims 18 to 21, wherein: The number of first electrode windings is n, n≥30, where n is a natural number. The innermost first electrode winding is the first first electrode winding, and at least the first first electrode winding does not have the first groove.

23. The battery cell according to claim 22, wherein: At least the first three first electrode windings do not have the first groove.

24. The battery cell according to claim 22 or 23, wherein: The electrode assembly has a central hole, and the first first electrode winding is closest to the central hole compared to the other first electrode windings.

25. The battery cell according to any one of claims 18 to 24, wherein: The number of the first electrode windings is n, n≥30, where n is a natural number; the innermost first electrode winding is the first first electrode winding; at least the last two first electrode windings do not have the first groove.

26. The battery cell according to claim 25, wherein: At least the last 10 first electrode windings do not have the first groove.

27. The battery cell according to any one of claims 18 to 26, wherein: The number of first electrode windings is n, n≥30, where n is a natural number; the innermost first electrode winding is the first first electrode winding; the first f first electrode windings do not have the first groove, and the last q first electrode windings do not have the first groove; all first electrode windings between the f-th first electrode winding and the last q first electrode windings have the first groove, where f+q<n, and f and q are positive integers.

28. The battery cell according to any one of claims 21 to 27, wherein: 30≤n≤80, optionally, 60≤n≤75.

29. The battery cell according to any one of claims 21 to 28, wherein: The number of windings of the first electrode with the first groove is v, where 0.23≤v / n≤1, and v and n are positive integers. Optionally, 0.3≤v / n≤0.

7.

30. The battery cell according to any one of claims 18 to 29, wherein: The first electrode has a first winding end, the second electrode has a second winding end, the innermost first electrode winding is the first first electrode winding, and the second winding end is located between the last two first electrode windings. The first groove is not provided at the position corresponding to the end face of the last two first electrode winding loops and the first winding end; And / or, the first groove is not provided at the position corresponding to the end face of the last two first electrode winding loops and the second winding end.

31. The battery cell according to claim 30, wherein: The last two first electrode windings are provided with the first groove, and the first groove is offset from at least one of the end face of the first winding end and the end face of the second winding end. Alternatively, the first groove may not be provided in the last two first electrode winding loops.

32. The battery cell according to any one of claims 18 to 31, wherein: The first electrode has a first winding start end, the second electrode has a second winding start end, the innermost first electrode winding loop is the first first electrode winding loop, and the second winding start end is located between the first two first electrode winding loops. The first groove is not provided at the position corresponding to the end face of the first winding start end of the first two first electrode winding coils; And / or, the first groove is not provided at the position corresponding to the end face of the first two first electrode winding loops and the second winding start end.

33. The battery cell according to claim 32, wherein: The first two first electrode winding coils are provided with the first groove, and the first groove is offset from at least one of the end face of the first winding start end and the end face of the second winding start end. Alternatively, the first groove may not be provided in the first two windings of the first electrode sheet.

34. The battery cell of any one of claims 30-33, wherein: The first electrode is a negative electrode and the second electrode is a positive electrode; or, the second electrode is a negative electrode and the first electrode is a positive electrode.

35. The battery cell of any one of claims 18-34, wherein: The electrode assembly includes a straight region and two bent regions, with the two bent regions located at both ends of the straight region; The first active winding includes a first active bending portion located in the bending region and a first active straight portion located in the straight region; At least one of the first active straight portions of the first active winding is provided with the first groove; and / or, at least one of the first active bent portions of the first active winding is provided with the first groove.

36. The battery cell of claim 35, wherein: The first active straight portion of all the first active windings is provided with the first groove, while the first active bent portion of all the first active windings is not provided with the first groove.

37. The battery cell of any one of claims 18-36, wherein: The battery cell is a cylindrical battery cell, and the central axis of the cylindrical battery cell is parallel to the first direction.

38. The battery cell of any one of claims 1-37, wherein: The electrode assembly has a stacked structure, and the stacking direction of the electrode assembly is perpendicular to the first direction.

39. The battery cell of any one of claims 1-38, wherein: The thickness of the first active material layer is t, and the depth of the first groove is h, wherein 0.05≤h / t≤0.84, optionally 0.08≤h / t≤0.8; optionally, 0.1≤h / t≤0.

5.

40. The battery cell of any one of claims 1-39, wherein: The groove depth of the first groove is h, where 0μm < h ≤ 50μm, and optionally, 6μm ≤ h ≤ 30μm.

41. The battery cell of any one of claims 1-40, wherein: The width of the first groove is w, wherein 30μm≤w≤1000μm; optionally, 50μm≤w≤500μm; optionally, 80μm≤w≤120μm.

42. The battery cell of any one of claims 1-41, wherein: The width of the first groove is w, the depth of the first groove is h, and 0.05≤h / w≤1; Optionally, 0.1 ≤ h / w ≤ 0.

5.

43. The battery cell of any one of claims 1-42, wherein: Along the first direction, the size of the first active material layer is L, and the groove depth of the first groove is h, 5*10. -5 ≤h / L≤5*10 -4 The first direction is perpendicular to the thickness direction of the first current collector.

44. The battery cell of any one of claims 1-43, wherein: Along the first direction, the size of the first active material layer is L, and the depth of the first groove is h, wherein L≥60mm and h≥6μm.

45. The battery cell of any one of claims 1-44, wherein: The first groove includes a first groove segment and a second groove segment arranged along the first direction. At least one end of the first groove segment along the first direction is connected to the second groove segment. The groove depth of the first groove segment is greater than the groove depth of the second groove segment, and / or the groove width of the first groove segment is greater than the groove width of the second groove segment.

46. The battery cell of claim 45, wherein: Along the direction from the first groove segment to the second groove segment, the groove depth of the second groove segment is set to decrease from that of the first groove segment; and / or, along the direction from the first groove segment to the second groove segment, the groove width of the second groove segment is set to decrease from that of the first groove segment.

47. The battery cell of any one of claims 1-46, wherein: The first groove includes multiple sub-segments, which are spaced apart along the first direction.

48. The battery cell of claim 47, wherein: The spacing between two adjacent segments is d, where 0.1mm ≤ d ≤ 1mm; alternatively, 0.3mm ≤ d ≤ 0.6mm.

49. The battery cell of claim 47 or 48, wherein: The number of the first grooves is multiple, and the multiple first grooves are arranged at intervals along the second direction; Along the second direction, in two adjacent first grooves, a segment of one first groove is at least partially offset from a segment of the other first groove, the second direction being perpendicular to the first direction and the thickness direction of the first current collector.

50. The battery cell of any one of claims 1-49, wherein: The number of the first grooves is multiple, and the multiple first grooves form multiple groups of the first grooves. Each group of the first grooves includes multiple intersecting first grooves. The multiple groups of the first grooves are arranged at intervals along a second direction, which is perpendicular to the first direction and the thickness direction of the first current collector.

51. The battery cell of any one of claims 1-50, wherein: The second electrode includes a second current collector and a second active material layer. At least a portion of at least one surface of the second current collector along its thickness direction is connected to the second active material layer. At least a portion of the second active material layer is located between the second current collector and the separator.

52. The battery cell of claim 51, wherein: The electrode assembly is a wound structure, with m gap windings formed between the first active material layer and the second active material layer, where m ≥ 30 and m is a natural number; the innermost gap winding is the first gap winding; the average radial dimension of the (m-13)th to (m-5)th gap windings is greater than the average radial dimension of the 5th to 13th gap windings.

53. The battery cell of claim 52, wherein: The gap winding includes a first gap sub-ring and a second gap sub-ring, the first gap sub-ring being located between the first active material layer and the separator, and the second gap sub-ring being located between the second active material layer and the separator.

54. The battery cell of claim 52 or 53, wherein: The radial dimension of the first gap winding is smaller than the radial dimension of the m-th gap winding.

55. The battery cell of claim 54, wherein: The m gap windings are divided into j groups of gap windings in order from the inside to the outside of the electrode assembly; The innermost group of gap windings is the first group of gap windings. In the first group to the (j-1)th group, each group of gap windings includes 9 gap windings, 1≤m-9*(j-1)≤9, where j is a natural number; the average radial dimension of the gap windings in the first group to the (j-1)th group is set to increase incrementally.

56. The battery cell of any one of claims 51-55, wherein: The first current collector includes a first current collector body and a first electrode tab connected together. At least a portion of the first current collector body is covered with the first active material layer, while the first electrode tab is not covered with the first active material layer. The second current collector includes a second current collector body and a second electrode tab connected together. At least a portion of the second current collector body is covered with the second active material layer, while the second electrode tab is not covered with the second active material layer.

57. The battery cell of claim 56, wherein: The housing includes a shell and an end cap. The shell includes a connected sidewall and an end wall. The sidewall surrounds the electrode assembly. The end wall and the end cap are distributed opposite to each other along the axial direction of the battery cell. The end cap is sealed to the sidewall. The end cap is insulated with electrode terminals, the second electrode tab is electrically connected to the electrode terminals, and at least one of the side wall and the end wall is electrically connected to the first electrode tab. Alternatively, the end wall is insulated with electrode terminals, the second electrode tab is electrically connected to the electrode terminals, and at least one of the end cap and the side wall is electrically connected to the first electrode tab.

58. The battery cell according to claim 57, wherein: The battery cell further includes a first current collector and a second current collector; the first tab and the second tab are respectively located at both ends of the electrode assembly along the axial direction of the battery cell, and the second tab is located on the side of the electrode assembly near the electrode terminal; The second current collector is electrically connected between the second tab and the electrode terminal; The electrode terminal is insulated on the end cap, the first current collector is located between the first electrode tab and the end wall, the first current collector is electrically connected to the first electrode tab, and at least one of the side wall and the end wall is electrically connected to the first current collector. Alternatively, the electrode terminal is insulated from the end wall, the first current collector is located between the first tab and the end cap, the first current collector is electrically connected to the first tab, and at least one of the side wall and the end cap is electrically connected to the first current collector.

59. The battery cell according to claim 58, wherein: The electrode terminal is insulated from the end wall; The sidewall is provided with an inwardly protruding protrusion along the axial direction of the battery cell, and the protrusion is located on the side of the first tab facing the end cap. The second current collector includes a first connecting portion, a second connecting portion, and a third connecting portion. The second connecting portion is connected between the first connecting portion and the third connecting portion. The first connecting portion is connected to the first electrode tab. At least a portion of the third connecting portion is located between the protrusion and the end cap. The third connecting portion is connected to the side of the protrusion facing away from the first electrode tab.

60. A battery device, wherein: It includes multiple battery cells according to any one of claims 1 to 59.

61. An electrical device, wherein: Includes a battery cell according to any one of claims 1 to 59 or a battery device according to claim 60, wherein the battery cell or the battery device is used to store or provide electrical energy.

Images