Battery cell, battery device, and electric device

Abstract

The application provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises a shell, an electrolyte and an electrode assembly, the electrolyte is contained in the shell, and the electrode assembly is contained in the shell. The electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet, and the positive electrode sheet, the separator and the negative electrode sheet are arranged in layers. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, and along the thickness direction of the positive electrode current collector, the positive electrode active material layer is arranged on at least one surface of the positive electrode current collector. At least one positive electrode active material layer is provided with a groove on the surface away from the positive electrode current collector, and a liquid storage layer is arranged in the groove. The porosity of the liquid storage layer is greater than that of the positive electrode active material layer, and the liquid storage layer stores part of the electrolyte. By storing the electrolyte in the liquid storage layer, the travel path of lithium ions in the charging and discharging process can be shortened, the lithium precipitation problem caused by the difficulty of electrolyte backflow in the later stage of the battery monomer cycle can be alleviated, and the cycle life of the battery monomer is prolonged.

Description

Technical Field

[0001] This application relates to the field of batteries, and more specifically, to a battery cell, a battery device, and an electrical device. Background Technology

[0002] Batteries are widely used in the new energy field, such as in electric vehicles and new energy vehicles, which have become a new trend in the automotive industry. The development of battery technology must consider multiple design factors simultaneously, such as energy density, discharge capacity, and charge / discharge rate. Additionally, battery cycle life must be considered. However, currently, the cycle life of batteries is relatively short. Utility Model Content

[0003] The purpose of this application is to provide a battery cell, a battery device, and an electrical device, which aims to improve the problem of short cycle life of batteries in related technologies.

[0004] In a first aspect, embodiments of this application provide a battery cell, the battery cell including a casing, an electrolyte, and an electrode assembly, wherein the electrolyte is contained within the casing; the electrode assembly is contained within the casing, the electrode assembly including a positive electrode, a separator, and a negative electrode, the positive electrode, the separator, and the negative electrode being stacked; wherein the positive electrode includes a positive current collector and a positive active material layer, the positive active material layer being disposed on at least one surface of the positive current collector along the thickness direction of the positive current collector, at least one surface of the positive active material layer having a groove opposite to the surface of the positive current collector, a liquid storage layer being disposed within the groove, the porosity of the liquid storage layer being greater than the porosity of the positive active material layer, and the liquid storage layer storing a portion of the electrolyte.

[0005] In the above technical solution, by setting grooves on the surface of the positive electrode active material layer away from the positive electrode current collector, on the one hand, the electrolyte can penetrate into the positive electrode active material layer from the groove wall, increasing the contact area between the positive electrode active material layer and the electrolyte, which is beneficial to improving the wetting effect of the positive electrode active material layer. On the other hand, by setting grooves on the surface of the positive electrode active material layer away from the positive electrode current collector, the lithium-ion abundance of the positive electrode active material layer is also reduced, which is beneficial to reduce side reactions, delay the electrode thicknessing process, and extend the life of the battery cell. By setting a storage layer in the groove, the porosity of the storage layer is greater than that of the positive electrode active material layer, making it easier to store electrolyte than the positive electrode active material layer. By storing electrolyte in the storage layer, the travel path of lithium ions during the charge and discharge process can be shortened, which is beneficial to alleviating the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of battery cell cycle, and is beneficial to extending the cycle life of battery cells.

[0006] As an optional technical solution in this application embodiment, the liquid storage layer and the isolation membrane are separately disposed, and the liquid storage layer is in contact with the isolation membrane.

[0007] In the above technical solution, the liquid storage layer and the separator are two independent structures. Both the liquid storage layer and the separator store electrolyte. By making the liquid storage layer and the separator in contact, the travel path of lithium ions during the charging and discharging process can be further shortened. This helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of battery cell cycle and helps to extend the cycle life of battery cells.

[0008] As an optional technical solution in this application embodiment, the surface of the positive electrode active material layer with the groove is the first surface, and the surface of the liquid storage layer away from the positive electrode current collector is flush with the first surface.

[0009] In the above technical solution, by making the surface of the liquid storage layer away from the positive electrode current collector flush with the first surface, on the one hand, it facilitates contact between the first surface and the separator, and on the other hand, it facilitates contact between the surface of the liquid storage layer away from the positive electrode current collector and the separator, thus shortening the ion path. On the other hand, when flush, the stress on the separator, the positive electrode active material layer, and / or the liquid storage layer is smaller when the electrode assembly is pressed, which helps to reduce the risk of damage to the separator, the positive electrode active material layer, and / or the liquid storage layer.

[0010] As an optional technical solution in this application embodiment, the material of the liquid storage layer is a conductive material, including at least one of carbon nanotubes, graphite, carbon black, carbon fiber, and graphene; or the material of the liquid storage layer is an insulating material, including at least one of inorganic powder, ceramic fiber, and polymer gel.

[0011] Among the aforementioned technical solutions, carbon nanotubes, graphite, carbon black, carbon fiber, graphene, inorganic powder, ceramic fiber, and polymer gel have relatively high porosity, enabling them to store a large amount of electrolyte, while maintaining relatively low cost. Furthermore, carbon nanotubes, graphite, carbon black, carbon fiber, graphene, inorganic powder, ceramic fiber, and polymer gel do not provide lithium ions, which helps reduce the lithium-ion abundance of the positive electrode, thus reducing side reactions, slowing down the electrode thickness increase process, and extending the lifespan of the battery cell.

[0012] As an optional technical solution in this application embodiment, at least a portion of the liquid storage layer and the isolation membrane are integrally formed.

[0013] In the above technical solution, at least a portion of the liquid storage layer and the separator are integrally formed, so that the liquid storage layer can be regarded as part of the separator. In this way, the liquid storage layer and the separator are always connected, and there is no gap between the liquid storage layer and the separator. This is beneficial to shorten the travel path of lithium ions during the charging and discharging process, alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of battery cell cycle, and extend the cycle life of battery cells.

[0014] As an optional technical solution in this application embodiment, the isolation membrane includes a substrate, and the liquid storage layer and the substrate are integrally formed.

[0015] In the above technical solution, the separator membrane includes a substrate, a liquid storage layer and the substrate integrally formed, the liquid storage layer can be regarded as part of the substrate, and the separator membrane can be a single-layer film.

[0016] As an optional technical solution in this application embodiment, the separator includes a substrate and a first insulating layer. The first insulating layer is disposed on the surface of the substrate facing the positive electrode sheet, and the first insulating layer and the liquid storage layer are integrally formed.

[0017] In the above technical solution, the separator includes a substrate and a first insulating layer. The separator is a composite film. The first insulating layer and the liquid storage layer are integrally formed. The liquid storage layer can be regarded as a part of the first insulating layer. When coating the first insulating layer, more coating can be applied to the position of the first insulating layer corresponding to the groove to locally thicken the first insulating layer. The thickened part can form the liquid storage layer, which is easier to manufacture.

[0018] As an optional technical solution in this application embodiment, each part of the groove wall surface is in contact with the surface of the liquid storage layer.

[0019] In the above technical solution, by ensuring that all parts of the groove wall are in contact with the surface of the liquid storage layer, on the one hand, the electrolyte can easily penetrate into the positive electrode active material layer through the liquid storage layer from the groove wall, which is beneficial to improving the wetting effect of the positive electrode active material layer. On the other hand, it can shorten the travel path of lithium ions during the charging and discharging process, which helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stages of battery cell cycle, and helps to extend the cycle life of battery cells.

[0020] As an optional technical solution in this application embodiment, the positive electrode sheet is provided with a positive electrode tab at at least one end along the first direction. Along the first direction, the minimum distance between the groove and one end of the positive electrode active material layer is A1, and the minimum distance between the groove and the other end of the positive electrode active material layer is A2, satisfying: 0.9≤A1 / A2≤1.1.

[0021] In the above technical solution, when 0.9≤A1 / A2≤1.1, the groove is approximately located in the middle of the positive electrode active material layer along the first direction. Since the middle of the positive electrode active material layer along the first direction is relatively more difficult to wet, the electrolyte reflux is more difficult in the later stage of battery cell cycle. Therefore, by making the groove approximately located in the middle of the positive electrode active material layer along the first direction, it can achieve better results and help extend the cycle life of the battery cell.

[0022] As an optional technical solution in this application embodiment, the groove forms an opening on the side of the positive electrode active material layer away from the positive electrode current collector. Along the first direction, the maximum size of the opening of the groove is A3, and the size of the positive electrode active material layer is A, satisfying: 0.05≤A3 / A≤0.9, optionally, 0.2≤A3 / A≤0.4.

[0023] In the above technical solution, when A3 / A ≥ 0.05, the maximum size of the groove opening along the first direction is relatively large, resulting in a larger groove. On the one hand, the electrolyte can penetrate the positive electrode active material layer from the groove wall, increasing the contact area between the positive electrode active material layer and the electrolyte, which is beneficial to improving the wetting effect of the positive electrode active material layer. On the other hand, it reduces the lithium-ion abundance of the positive electrode active material layer, which helps to reduce side reactions, delay the electrode thicknessing process, and extend the life of the battery cell. Furthermore, more liquid storage layer can be filled in the groove, which can shorten the lithium-ion travel path during the charging and discharging process, which helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of battery cell cycle, and helps to extend the cycle life of the battery cell. When A3 / A ≤ 0.9, the maximum size of the groove along the first direction is not too large, so that the lithium-ion abundance of the positive electrode active material layer is not too low, allowing the battery cell to still have a high energy density. Therefore, when 0.05 ≤ A3 / A ≤ 0.9, both the cycle life and energy density of the battery cell can be balanced.

[0024] When A3 / A ≥ 0.2, the maximum size of the groove opening along the first direction is larger, resulting in a larger groove. On one hand, the electrolyte can penetrate the positive electrode active material layer from the groove wall, further increasing the contact area between the positive electrode active material layer and the electrolyte, which is more conducive to improving the wetting effect of the positive electrode active material layer. On the other hand, it further reduces the lithium-ion abundance of the positive electrode active material layer, which helps to reduce side reactions, delay the electrode thicknessing process, and extend the life of the battery cell. Furthermore, more electrolyte can be filled in the groove, which can shorten the lithium-ion travel path during charging and discharging, helping to alleviate the lithium plating problem caused by electrolyte reflux difficulties in the later stages of battery cell cycling, and further extending the cycle life of the battery cell. When A3 / A ≤ 0.4, the maximum size of the groove along the first direction is not too large, ensuring that the lithium-ion abundance of the positive electrode active material layer is not too low, allowing the battery cell to still have a high energy density. Therefore, when 0.2 ≤ A3 / A ≤ 0.4, both the cycle life and energy density of the battery cell can be balanced.

[0025] As an optional technical solution in this application embodiment, the positive electrode sheet is provided with a positive electrode tab at at least one end along the first direction, and the groove extends to both ends of the positive active material layer along the second direction. The first direction, the second direction and the thickness direction of the positive current collector are perpendicular to each other.

[0026] In the above technical solution, by extending the groove along the second direction to both ends of the positive electrode active material layer, the contact area between the positive electrode active material layer and the electrolyte is further increased, which is more conducive to improving the wetting effect of the positive electrode active material layer, further reducing the lithium-ion abundance of the positive electrode active material layer, which helps to reduce side reactions, delay the electrode thicknessing process, and extend the life of the battery cell. Furthermore, the groove can be filled with more electrolyte layer, which can shorten the lithium-ion travel path during charging and discharging, helping to alleviate the lithium plating problem caused by electrolyte reflux difficulties in the later stages of battery cell cycling, and further extending the cycle life of the battery cell.

[0027] As an optional technical solution in this application embodiment, the positive electrode active material layer includes a main region and a thinning region. The thickness of the main region is greater than the thickness of the thinning region. The main region and the thinning region are connected. The positive electrode active material layer forms the thinning region in the area where the groove is provided. The minimum thickness of the thinning region is H1, and the minimum thickness of the main region is H2, satisfying: 0≤H1 / H2≤0.9. Optionally, 0.85≤H1 / H2≤0.9.

[0028] In the above technical solution, when 0 ≤ H1 / H2 ≤ 0.9, the minimum thickness of the thinned area is smaller, and the depth of the groove is larger, which further increases the contact area between the positive electrode active material layer and the electrolyte, which is more conducive to improving the wetting effect of the positive electrode active material layer, further reducing the lithium-ion abundance of the positive electrode active material layer, which helps to reduce side reactions, delay the electrode thicknessing process, and extend the life of the battery cell. Furthermore, more electrolyte layer can be filled in the groove, which can shorten the lithium-ion travel path during charging and discharging, which helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stages of battery cell cycling, and further extends the cycle life of the battery cell.

[0029] When H1 / H2 ≤ 0.9, the minimum thickness of the thinned region is smaller, and the depth of the groove is larger, further increasing the contact area between the positive electrode active material layer and the electrolyte. This is more conducive to improving the wetting effect of the positive electrode active material layer and further reducing the lithium-ion abundance of the positive electrode active material layer. This helps to reduce side reactions, slow down the electrode thicknessing process, and extend the life of the battery cell. Furthermore, more electrolyte can be filled in the groove, which can shorten the lithium-ion travel path during charging and discharging, helping to alleviate the lithium plating problem caused by electrolyte reflux difficulties in the later stages of battery cell cycling, and further extending the cycle life of the battery cell. When H1 / H2 ≥ 0.85, the minimum thickness of the thinned region is not too small, and the depth of the groove is not too deep, ensuring that the lithium-ion abundance of the positive electrode active material layer is not too low, allowing the battery cell to still have a high energy density. Therefore, when 0.85 ≤ H1 / H2 ≤ 0.9, both the cycle life and energy density of the battery cell can be balanced.

[0030] As an optional technical solution in this application embodiment, the volume of the groove is V1, and the volume of the positive electrode active material layer with the groove is V2, satisfying: 0.95≤V2 / (V1+V2)<1.

[0031] In the above technical solution, when 0.95≤V2 / (V1+V2)<1, the abundance of lithium ions reduced due to the opening of the groove is small, so that the battery cell still has a high energy density.

[0032] As an optional technical solution in this application embodiment, the positive electrode sheet is provided with a positive electrode tab at at least one end along the first direction, and the size of the outer shell along the first direction is D, which satisfies: 120mm≤D≤350mm.

[0033] In the above technical solution, when 120mm≤D≤350mm, the size of the outer shell along the first direction is large, the height of the battery cell is high, the electrode assembly is more difficult to wet, and the electrolyte reflux is more difficult. Therefore, it is necessary to set grooves and liquid storage layers to extend the life of the battery cell.

[0034] As an optional technical solution in this application embodiment, the volume of the groove is V1, and the volume of the positive electrode active material layer with the groove is V2; when 120mm≤D≤160mm, 0.97≤V2 / (V1+V2)≤0.99; when 160mm<D≤350mm, 0.95≤V2 / (V1+V2)<0.97.

[0035] In the above technical solutions, when 120mm≤D≤160mm, the outer casing has a larger dimension along the first direction, and the battery cell is taller. By ensuring V2 / (V1+V2)≤0.99, the volume of the groove is larger, which is beneficial for extending the life of the battery cell. By ensuring V2 / (V1+V2)≥0.97, the battery cell still has a high energy density. When 160mm<D≤350mm, the outer casing has an even larger dimension along the first direction, and the battery cell is even taller. The electrode assembly is more difficult to wet, and electrolyte reflux is more difficult. By ensuring V2 / (V1+V2)<0.97, the volume of the groove is larger, which is beneficial for extending the life of the battery cell. By ensuring V2 / (V1+V2)≥0.95, the battery cell still has a high energy density.

[0036] Secondly, embodiments of this application also provide a battery device, which includes the aforementioned battery cell.

[0037] Thirdly, embodiments of this application also provide an electrical device, which includes the aforementioned battery cell, and the battery cell is used to provide electrical energy to the electrical device. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0040] Figure 2 Exploded views of battery devices provided in some embodiments of this application;

[0041] Figure 3 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0042] Figure 4 Exploded views of a single battery cell provided in some embodiments of this application;

[0043] Figure 5 This is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application;

[0044] Figure 6 A cross-sectional view showing the stacked arrangement of a positive electrode, a separator, and a negative electrode according to some embodiments of this application;

[0045] Figure 7 This is a cross-sectional view of a positive electrode sheet (without a liquid storage layer in the groove) provided in some embodiments of this application;

[0046] Figure 8 This is a cross-sectional view of a positive electrode sheet (with a liquid storage layer disposed in the groove) provided in some embodiments of this application;

[0047] Figure 9 A cross-sectional view showing the stacked arrangement of a positive electrode, a separator, and a negative electrode according to other embodiments of this application;

[0048] Figure 10 Cross-sectional views of the isolation membrane provided in some embodiments of this application;

[0049] Figure 11 Cross-sectional view of the isolation membrane provided in other embodiments of this application;

[0050] Figure 12 This is a schematic diagram of the structure of the positive electrode sheet provided in some embodiments of this application;

[0051] Figure 13 Schematic diagrams of the structure of the positive electrode sheet provided in other embodiments of this application;

[0052] Figure 14 This is a side view schematic diagram of a battery cell provided in some embodiments of this application.

[0053] Icons: 10-Box body; 11-First box body; 12-Second box body; 20-Battery cell; 21-Outer shell; 211-Shell; 212-End cap; 22-Electrode assembly; 221-Main body; 2211-Straight section; 2212-Bent section; 222-Taper; 2221-Negative electrode tab; 2222-Positive electrode tab; 223-Negative electrode sheet; 2231-Negative current collector; 2232-Negative active material layer; 224-Positive electrode sheet ; 2241-Positive current collector; 2242-Positive active material layer; 22421-Groove; 22422-Main area; 22423-Thinned area; 22424-First surface; 2243-Second insulating layer; 225-Separator; 2251-Substrate; 2252-First insulating layer; 226-Reservoir layer; 25-Electrode terminal; 27-Insulating component; 100-Battery device; 200-Controller; 300-Motor; 1000-Vehicle. Detailed Implementation

[0054] 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 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.

[0055] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0056] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0057] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0058] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0059] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0060] In this application, "multiple" means two or more (including two).

[0061] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0062] Battery cells include, but are not limited to, lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0063] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, placed between the positive and negative electrodes, reduces the risk of short circuits while allowing active ions to pass through.

[0064] In some embodiments, the positive electrode can be a positive electrode sheet, which may include a positive current collector and a positive active material disposed on at least one surface of the positive current collector.

[0065] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0066] As an example, the positive electrode current collector can be a foil or a composite current collector. For example, as a foil, it can be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, or titanium, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors 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.).

[0067] As an example, the positive electrode active material 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 positive electrode active materials in battery cells 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 oxide 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 / 3Mn 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) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds.

[0068] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloys, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, lithium source material, potassium metal, or sodium metal can also be filled and / or deposited within the foamed metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0069] In some embodiments, the negative electrode can be a negative electrode sheet, and the negative electrode sheet can include a negative current collector.

[0070] As an example, the negative electrode current collector can be a foil, a foamed metal, or a composite current collector. For example, as a foil, it can be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, carbon electrodes, carbon, nickel, or titanium, etc. The foamed metal can be nickel foam, copper foam, aluminum foam, foam alloy, etc. The composite current collector can include a polymer material base layer 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.).

[0071] As an example, the negative electrode sheet may include a negative current collector and a negative active material disposed on at least one surface of the negative current collector.

[0072] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0073] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. 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 in battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0074] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0075] In some embodiments, the separator can be any known porous separator with good chemical and mechanical stability.

[0076] As an example, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes.

[0077] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte includes an electrolyte salt and a solvent.

[0078] In some embodiments, the electrolyte salt may include 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.

[0079] In some embodiments, the solvent may include at least one selected from 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 selected from 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.

[0080] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0081] In some implementations, the electrode assembly is a stacked structure.

[0082] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0083] As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0084] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0085] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0086] As an example, the separator can be continuously installed between any adjacent positive or negative electrode plates by folding or rolling.

[0087] In some implementations, the electrode assembly may be flat or polygonal in shape.

[0088] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0089] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes. The housing may be made of steel, aluminum, or a composite metal (such as a copper-aluminum composite housing).

[0090] In some embodiments, the housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a sealed structure, it can protect the electrode assembly and prevent, to some extent, electrolyte leakage. When the housing is a non-sealed structure, it can still protect the electrode assembly, and a sealing bag may be included between the housing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag can be a bag-shaped insulating component or an aluminum-plastic film.

[0091] As an example, a battery cell can be a prismatic battery cell or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic battery cells, such as hexagonal prismatic battery cells.

[0092] The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0093] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells; as an example, a battery cell assembly can be a battery module, which is formed by arranging multiple battery cells and fixing them together to form an independent module.

[0094] As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0095] In some embodiments, the battery device may be a battery pack, which may include a housing and one or more individual battery cell assemblies housed within the housing.

[0096] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0097] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0098] As an example, the enclosure may include a first enclosure body and a second enclosure body. The first enclosure body and the second enclosure body are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, which can be either sealed or unsealed. The first enclosure body may be a top cover or a bottom plate.

[0099] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0100] As an example, the housing can be part of the vehicle's chassis structure. For instance, the housing's roof can be at least part of the vehicle's floor, or the housing's frame can be at least part of the vehicle's crossbeams and longitudinal beams.

[0101] In some embodiments, the battery device refers to an energy storage device, which includes a housing with a door on at least one side. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0102] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing.

[0103] The development of battery technology must consider multiple design factors simultaneously, such as energy density, discharge capacity, and charge / discharge rate. Additionally, cycle life must be considered. However, current battery cycle life is relatively short.

[0104] Electrode components are the parts in a battery cell where electrochemical reactions occur. During battery cell cycling, electrode components gradually expand, the thickness of the electrode plates gradually increases, and the space left for electrolyte decreases, making it difficult for electrolyte to flow back, thus making lithium plating more likely and resulting in a shorter cycle life of the battery cell.

[0105] Therefore, this application provides a battery cell, which includes a casing, an electrolyte, and an electrode assembly. The electrolyte is contained within the casing, and the electrode assembly is contained within the casing. The electrode assembly includes a positive electrode, a separator, and a negative electrode, which are stacked together. The positive electrode includes a positive current collector and a positive active material layer. Along the thickness direction of the positive current collector, the positive active material layer is disposed on at least one surface of the positive current collector. At least one surface of the positive active material layer facing away from the positive current collector has a groove, and a liquid storage layer is disposed within the groove. The porosity of the liquid storage layer is greater than that of the positive active material layer, and the liquid storage layer stores a portion of the electrolyte.

[0106] By creating grooves on the surface of the positive electrode active material layer facing away from the positive electrode current collector, the electrolyte can penetrate into the positive electrode active material layer from the groove walls, increasing the contact area between the positive electrode active material layer and the electrolyte, which is beneficial to improving the wetting effect of the positive electrode active material layer. On the other hand, creating grooves on the surface of the positive electrode active material layer facing away from the positive electrode current collector also reduces the lithium-ion abundance of the positive electrode active material layer, which helps to reduce side reactions, slow down the electrode thicknessing process, and extend the life of the battery cell. By setting a reservoir layer in the groove, the porosity of the reservoir layer is greater than that of the positive electrode active material layer, making it easier to store electrolyte. Storing electrolyte in the reservoir layer can shorten the travel path of lithium ions during charge and discharge, which helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stages of battery cell cycle, and further extends the cycle life of the battery cell.

[0107] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery cells and battery devices, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships and spacecraft, etc. For example, spacecraft include airplanes, rockets, space shuttles and spacecraft.

[0108] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0109] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of this application. A battery device 100 is disposed inside the vehicle 1000, and the battery device 100 may be located at the bottom, front, or rear of the vehicle 1000. The battery device 100 can be used to power the vehicle 1000; for example, the battery device 100 can serve as the operating power source for the vehicle 1000.

[0110] The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery device 100 to supply power to the motor 300, for example, for the power needs of the vehicle 1000 during startup, navigation and driving.

[0111] In some embodiments of this application, the battery device 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0112] Please refer to Figure 2 , Figure 2This is an exploded view of a battery device 100 provided in some embodiments of this application. The battery device 100 may include a housing 10 and battery cells 20, the housing 10 being used to house the battery cells 20.

[0113] The housing 10 has an enclosed space inside for accommodating the battery cells 20. The housing 10 can have various structures. In some embodiments, the housing 10 may include a first housing body 11 and a second housing body 12, which are interlocked. The first housing body 11 and the second housing body 12 can have various shapes, such as cuboids or cylinders. The first housing body 11 can be a hollow structure open on one side, and the second housing body 12 can also be a hollow structure open on one side. The open side of the second housing body 12 interlocks with the open side of the first housing body 11, thus forming a housing 10 with an enclosed space. Alternatively, the first housing body 11 can be a hollow structure open on one side, and the second housing body 12 can be a plate-like structure, with the second housing body 12 interlocked with the open side of the first housing body 11, thus forming a housing 10 with an accommodating chamber.

[0114] In the battery device 100, there can be one or more battery cells 20. If there are multiple battery cells 20, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel. Alternatively, multiple battery cells 20 can be first connected in series, parallel, or in a mixed configuration to form a battery module, and then multiple battery modules can be connected in series, parallel, or in a mixed configuration to form a whole, which is then housed within the housing 10. Another option is that all battery cells 20 can be directly connected in series, parallel, or in a mixed configuration, and then the whole consisting of all battery cells 20 is housed within the housing 10.

[0115] In some embodiments, the battery device 100 may further include a busbar component, through which multiple battery cells 20 can be electrically connected to each other to achieve series, parallel, or mixed connection of the multiple battery cells 20. The busbar component may be a metallic conductor, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc.

[0116] Please refer to Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 , Figure 3 This is a schematic diagram of the structure of a battery cell 20 provided in some embodiments of this application. Figure 4 An exploded view of a battery cell 20 provided in some embodiments of this application. Figure 5 This is a schematic diagram of the structure of the electrode assembly 22 provided in some embodiments of this application. Figure 6 This is a cross-sectional view showing the stacked arrangement of a positive electrode 224, a separator 225, and a negative electrode 223 according to some embodiments of this application. Figure 7This is a cross-sectional view of a positive electrode 224 (without a liquid storage layer 226 in the groove 22421) provided in some embodiments of this application. Embodiments of this application provide a battery cell 20, which includes a casing 21, an electrolyte, and an electrode assembly 22. The electrolyte and the electrode assembly 22 are housed within the casing 21. The electrode assembly 22 includes a positive electrode 224, a separator 225, and a negative electrode 223, which are stacked together. The positive electrode 224 includes a positive current collector 2241 and a positive active material layer 2242. Along the thickness direction of the positive current collector 2241, the positive active material layer 2242 is disposed on at least one surface of the positive current collector 2241. At least one positive electrode active material layer 2242 has a groove 22421 on its surface away from the positive electrode current collector 2241. A liquid storage layer 226 is disposed in the groove 22421. The porosity of the liquid storage layer 226 is greater than that of the positive electrode active material layer 2242. The liquid storage layer 226 stores a portion of the electrolyte.

[0117] Battery cell 20 refers to the smallest unit that makes up battery device 100.

[0118] The housing 21 includes a housing 211 and an end cap 212. The housing 211 has a receiving space with an opening at one end for accommodating the electrode assembly 22. The end cap 212 is connected to the housing 211 and closes the opening.

[0119] End cap 212 refers to a component that covers the opening of housing 211 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 212 can be adapted to the shape of housing 211 to fit it. Optionally, end cap 212 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that end cap 212 is not easily deformed under pressure and impact, giving battery cell 20 higher structural strength and improved reliability. The material of end cap 212 can include, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. Battery cell 20 also includes an insulating member 27, which is disposed inside end cap 212. The insulating member 27 can be used to isolate the electrical connection components inside housing 211 from end cap 212 to reduce the risk of short circuit. For example, insulating member 27 can be plastic, rubber, etc.

[0120] The housing 211 is a component used to cooperate with the end cap 212 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 22, electrolyte, and other components. The housing 211 and the end cap 212 can be independent components. An opening can be provided on the housing 211, and the end cap 212 can be used to close the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 212 and the housing 211 can be integrated. Specifically, the end cap 212 and the housing 211 can form a common mating surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 211, the end cap 212 closes the housing 211. The housing 211 can have various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 211 can be determined according to the specific shape and size of the electrode assembly 22. The material of the housing 211 can include, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.

[0121] In some embodiments, the housing 211 may have an opening at only one end, with one end cap 212 correspondingly provided. In other embodiments, the housing 211 may have openings at both ends, with two end caps 212 correspondingly provided, the two end caps 212 respectively closing the two opposite openings of the housing 211. Figure 3 and Figure 4 In the embodiment shown, the housing 211 has an opening at only one end, and an end cap 212 is provided accordingly.

[0122] Electrode terminals 25 may also be provided on the end cap 212 or the housing 211. These terminals are used for electrical connection to the tabs 222 of the electrode assembly 22 to input or output electrical energy from the battery cell 20. The electrode terminals 25 and tabs 222 can be directly connected, for example, by direct welding. Alternatively, they can be indirectly connected, for example, through a current collector. The current collector can be a metallic conductor, such as copper, iron, aluminum, steel, or aluminum alloy.

[0123] Electrode assembly 22 is the component in the battery cell 20 where electrochemical reactions occur. The casing 211 may contain one or more electrode assemblies 22. The electrode assembly 22 is mainly formed by winding or stacking positive electrode 224 and negative electrode 223, and typically a separator 225 is provided between the positive electrode 224 and the negative electrode 223. The portions of the positive electrode 224 and the negative electrode 223 containing active material constitute the main body 221 of the electrode assembly 22, while the portions of the positive electrode 224 and the negative electrode 223 without active material each constitute a tab 222. The positive tab 2222 and the negative tab 2221 may be located together at one end of the main body 221 or respectively at both ends of the main body 221. During the charging and discharging process of the battery cell 20, the positive and negative active materials react with the electrolyte.

[0124] The electrode assembly 22 includes a positive electrode 224, a separator 225, and a negative electrode 223, which are stacked together. The electrode assembly 22 can be a wound electrode assembly or a stacked electrode assembly. When the electrode assembly 22 is a wound electrode assembly, in some embodiments, the electrode assembly 22 includes a straight portion 2211 and a bent portion 2212. The straight portion 2211 is the part of the electrode assembly 22 that extends along a straight trajectory, and the bent portion 2212 is connected to one end of the straight portion 2211. The bent portion 2212 can extend along an arc trajectory. The electrode assembly 22 includes two bent portions 2212, which are respectively connected to both ends of the straight portion 2211. The positive electrode 224, separator 225, and negative electrode 223 located in the straight portion 2211 are stacked along the thickness direction of the straight portion 2211, while the positive electrode 224, separator 225, and negative electrode 223 located in the bent portion 2212 are stacked along the radial direction of the bent portion 2212. In other embodiments, the electrode assembly 22 is generally cylindrical, and the positive electrode 224, separator 225, and negative electrode 223 are stacked along the radial direction of the electrode assembly 22. When the electrode assembly 22 is a stacked electrode assembly, the positive electrode 224, separator 225, and negative electrode 223 are stacked along the thickness direction of the positive current collector 2241.

[0125] Please refer to Figure 6 and Figure 7 The thickness direction of the positive current collector 2241 is the Z direction shown in the figure.

[0126] The positive electrode 224 includes a positive current collector 2241 and a positive active material layer 2242, the positive active material layer 2242 including the aforementioned positive active material. The positive active material layer 2242 is disposed on at least one side of the positive current collector 2241 along its thickness direction. For example, in some embodiments, the positive active material layer 2242 is disposed on one surface of the positive current collector 2241 along its thickness direction. In other embodiments, the positive active material layer 2242 is disposed on both opposite surfaces of the positive current collector 2241 along its thickness direction. Please refer to... Figure 6 and Figure 7 In the embodiment shown in the figure, positive electrode active material layers 2242 are provided on both opposite surfaces of the positive electrode current collector 2241 along the thickness direction of the positive electrode current collector 2241.

[0127] The negative electrode sheet 223 includes a negative electrode current collector 2231 and a negative electrode active material layer 2232, the negative electrode active material layer 2232 including the aforementioned negative electrode active material. Along the thickness direction of the negative electrode current collector 2231, the negative electrode active material layer 2232 is disposed on at least one side of the negative electrode current collector 2231. For example, in some embodiments, the negative electrode active material layer 2232 is disposed on one surface of the negative electrode current collector 2231 along its thickness direction. In other embodiments, the negative electrode active material layer 2232 is disposed on both opposite surfaces of the negative electrode current collector 2231 along its thickness direction. Please refer to... Figure 6 and Figure 7 In the embodiment shown in the figure, the negative electrode current collector 2231 has a negative electrode active material layer 2232 on both of its opposite surfaces along the thickness direction of the negative electrode current collector 2231.

[0128] In an embodiment where positive electrode active material layers 2242 are provided on both opposite surfaces of the positive electrode current collector 2241 along the thickness direction of the positive electrode current collector 2241, a groove 22421 may be provided on the surface of the positive electrode active material layer 2242 facing away from the positive electrode current collector 2241, or grooves 22421 may be provided on the surfaces of both positive electrode active material layers 2242 facing away from the positive electrode current collector 2241.

[0129] In some embodiments, during the process of coating the positive electrode active material onto the positive electrode current collector 2241 to form the positive electrode active material layer 2242, the coating is reduced in a predetermined area so that a groove 22421 is formed in the predetermined area on the positive electrode active material layer 2242. In other embodiments, normal coating is performed when coating the positive electrode active material onto the positive electrode current collector 2241. After the positive electrode active material dries and forms the positive electrode active material layer 2242, the groove 22421 can be processed on the positive electrode active material layer 2242 by means of laser cleaning, milling, or other methods.

[0130] The cross-section of the groove 22421 can be rectangular, trapezoidal, semi-elliptical, semi-circular, etc., and the cross-section of the groove 22421 is perpendicular to the extension direction of the groove 22421.

[0131] A storage layer 226 is disposed within the groove 22421. The storage layer 226 does not provide lithium ions and has a large number of micropores, allowing electrolyte ions to pass freely while maintaining good permeability to metal ions. The storage layer 226 can store electrolyte, so even in the later stages of battery cell 20 cycling, electrolyte will still be retained in the storage layer 226. The electrolyte stored in the storage layer 226 can still provide a path for lithium ions, thereby alleviating the lithium plating problem caused by difficulties in electrolyte reflux.

[0132] Porosity refers to the proportion of pore volume to the total volume in a porous material. The porosity of the liquid storage layer 226 is greater than that of the positive electrode active material layer. Optionally, the porosity of the liquid storage layer 226 is 1.2 to 3 times that of the positive electrode active material layer. The porosity of the liquid storage layer 226 can be 25% to 80%.

[0133] To obtain the porosity of the liquid storage layer 226 and the positive electrode active material layer 2242, the battery cell 20 can be disassembled first, and the positive electrode 224 in the outer casing 21 can be removed. Then, the porosity can be determined by SEM analysis (Scanning Electron Microscope) or BET detection method (Brunauer-Emmett-Teller).

[0134] By providing grooves 22421 on the surface of the positive electrode active material layer 2242 facing away from the positive electrode current collector 2241, on the one hand, the electrolyte can penetrate into the positive electrode active material layer 2242 from the groove wall surface of the groove 22421, increasing the contact area between the positive electrode active material layer 2242 and the electrolyte, which is beneficial to improving the wetting effect of the positive electrode active material layer 2242. On the other hand, by providing grooves 22421 on the surface of the positive electrode active material layer 2242 facing away from the positive electrode current collector 2241, the lithium-ion abundance of the positive electrode active material layer 2242 is also reduced, which is beneficial to reduce side reactions, delay the electrode thicknessing process, and extend the life of the battery cell 20. By setting a liquid storage layer 226 in the groove 22421, the porosity of the liquid storage layer 226 is greater than that of the positive electrode active material layer 2242, making it easier for the liquid storage layer 226 to store electrolyte compared to the positive electrode active material layer 2242. By storing electrolyte in the liquid storage layer 226, the travel path of lithium ions during the charging and discharging process can be shortened, which helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of the battery cell 20 cycle, and helps to extend the cycle life of the battery cell 20.

[0135] Please refer to Figure 7 and Figure 8 , Figure 8 This is a cross-sectional view of a positive electrode 224 (with a liquid storage layer 226 disposed in a groove 22421) provided in some embodiments of this application. In some embodiments, the liquid storage layer 226 and the separator 225 are separately disposed, and the liquid storage layer 226 is in contact with the separator 225.

[0136] "Separate arrangement of liquid reservoir 226 and isolation membrane 225" means that during manufacturing, liquid reservoir 226 and isolation membrane 225 are provided separately, and liquid reservoir 226 and isolation membrane 225 can be connected together or not connected to each other.

[0137] In some embodiments, a liquid reservoir 226 is formed by filling the groove 22421 with a porous material. The liquid reservoir 226 is provided together with the positive electrode 224.

[0138] The reservoir layer 226 and the separator 225 can be made of the same material or different materials. The reservoir layer 226 can be made of a conductive material, such as carbon nanotubes or graphite. The reservoir layer 226 can also be made of an insulating material, such as ceramic fibers or polymer gels.

[0139] The liquid storage layer 226 is in contact with the isolation membrane 225. This contact can occur either with a portion of the surface of the liquid storage layer 226 facing away from the current collector, or with the entire surface of the liquid storage layer 226 facing away from the current collector in contact with the isolation membrane 225. The contact between the liquid storage layer 226 and the isolation membrane 225 may or may not involve a force interaction.

[0140] The electrolyte storage layer 226 and the separator 225 are two independent structures. Both the electrolyte storage layer 226 and the separator 225 store electrolyte. By making the electrolyte storage layer 226 and the separator 225 in contact, the travel path of lithium ions during the charging and discharging process can be further shortened. This helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of the battery cell 20 cycle and helps to extend the cycle life of the battery cell 20.

[0141] Please refer to Figure 7 and Figure 8 In some embodiments, the surface of the positive electrode active material layer 2242 with the groove 22421 is the first surface 22424, and the surface of the liquid storage layer 226 away from the positive electrode current collector 2241 is flush with the first surface 22424.

[0142] Along the thickness direction of the positive electrode current collector 2241, the positive electrode active material layer 2242 has a first surface 22424 facing away from the positive electrode current collector 2241, and a groove 22421 is disposed on the first surface 22424 (the groove 22421 is recessed from the first surface 22424 into the positive electrode active material layer 2242).

[0143] If the surface of the liquid storage layer 226 away from the positive electrode current collector 2241 is flush with the first surface 22424, the liquid storage layer 226 can fill the groove 22421, so that the distance from the surface of the liquid storage layer 226 away from the positive electrode current collector 2241 to the positive electrode current collector 2241 is equal to the distance from the first surface 22424 to the positive electrode current collector 2241, thereby making the surface of the positive electrode sheet 224 relatively flat.

[0144] By aligning the surface of the reservoir layer 226 away from the positive electrode current collector 2241 with the first surface 22424, it facilitates contact between the first surface 22424 and the separator 225, and also facilitates contact between the surface of the reservoir layer 226 away from the positive electrode current collector 2241 and the separator 225, thus shortening the ion path. Furthermore, when aligned, the stress on the separator 225, the positive electrode active material layer 2242, and / or the reservoir layer 226 is reduced when the electrode assembly 22 is compressed, which helps to decrease the risk of damage to the separator 225, the positive electrode active material layer 2242, and / or the reservoir layer 226.

[0145] In some embodiments, the material of the reservoir layer 226 is a conductive material, including at least one of carbon nanotubes, graphite, carbon black, carbon fiber, and graphene; or the material of the reservoir layer 226 is an insulating material, including at least one of inorganic powder, ceramic fiber, and polymer gel.

[0146] Since the separator 225 can separate the positive electrode 224 and the negative electrode 223, the material of the liquid storage layer 226 can be a conductive material. The material of the liquid storage layer 226 can include one of carbon nanotubes, graphite, carbon black, carbon fiber, and graphene, or multiple of these materials.

[0147] The inorganic material may include at least one of alumina, silicon dioxide, boehmite, barium sulfate, zirconium oxide, silicon dioxide, magnesium oxide, zinc oxide, and tin oxide. The material of the reservoir layer 226 may also include an adhesive, which may include at least one of polyvinylidene fluoride, polyvinylidene fluoride, styrene, acrylate, vinyl acetate, vinyl fatty acid ester, epoxy resin, linear polyester, polyacrylic acid, polyacrylate, polyvinyl alcohol, polyimide, polyacrylonitrile, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, styrene-butadiene rubber, gelatin, and sorbitol.

[0148] Ceramic fibers have a capillary effect and can store a large amount of electrolyte. Ceramic fibers include alumina ceramic fibers, zirconia ceramic fibers, silicon nitride ceramic fibers, barium titanate ceramic fibers, zirconia ceramic fibers, magnesium oxide ceramic fibers, etc.

[0149] Polymer gels include polyimide, polyethylene terephthalate, polypropylene, polyacrylonitrile, polymethyl acrylate, sorbitol, etc.

[0150] Carbon nanotubes, graphite, carbon black, carbon fiber, graphene, inorganic powders, ceramic fibers, and polymer gels have relatively high porosity, enabling them to store a large amount of electrolyte, and their cost is relatively low. Furthermore, carbon nanotubes, graphite, carbon black, carbon fiber, graphene, inorganic powders, ceramic fibers, and polymer gels do not provide lithium ions, which helps reduce the lithium-ion abundance of the positive electrode 224, reduces side reactions, slows down the electrode thickening process, and extends the lifespan of the battery cell 20.

[0151] Please refer to Figure 9 and Figure 10 , Figure 9 A cross-sectional view showing the stacked arrangement of positive electrode 224, separator 225 and negative electrode 223 provided in other embodiments of this application. Figure 10 This is a cross-sectional view of the isolation membrane 225 provided in some embodiments of this application. In some embodiments, at least a portion of the liquid reservoir 226 and the isolation membrane 225 are integrally formed.

[0152] "At least a portion of the reservoir layer 226 and the separator 225 are integrally formed" means that at least a portion of the reservoir layer 226 and the separator 225 are provided as a single structure. In this case, the reservoir layer 226 can be considered as part of the separator 225. For example, the reservoir layer 226 is a protrusion on the separator 225.

[0153] When the separator 225 is a single-layer film, the liquid storage layer 226 and the separator 225 are integrally formed. When the separator 225 is a multi-layer composite film, the liquid storage layer 226 and the layer of the separator 225 closest to the positive electrode 224 are integrally formed.

[0154] At least a portion of the liquid storage layer 226 and the separator 225 are integrally formed, so that the liquid storage layer 226 can be regarded as part of the separator 225. In this way, the liquid storage layer 226 and the separator 225 are always connected, and there is no gap between the liquid storage layer 226 and the separator 225. This is beneficial to shorten the travel path of lithium ions during the charging and discharging process, to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of the battery cell 20 cycle, and to extend the cycle life of the battery cell 20.

[0155] Please refer to Figure 9 and Figure 10 In some embodiments, the isolation membrane 225 includes a substrate 2251, a liquid storage layer 226, and the substrate 2251 integrally formed.

[0156] The material of the substrate 2251 may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0157] The separator 225 may consist only of the substrate 2251, in which case the separator 225 is a single-layer film. In addition to the substrate 2251, the separator 225 may also include other coatings applied to the substrate 2251, in which case the separator 225 is a multilayer composite film.

[0158] The separator 225 includes a substrate 2251, a liquid storage layer 226, and the substrate 2251 are integrally formed. The liquid storage layer 226 can be regarded as a part of the substrate 2251.

[0159] Please refer to Figure 11 , Figure 11 This is a cross-sectional view of the separator 225 provided in some other embodiments of this application. In some embodiments, the separator 225 includes a substrate 2251 and a first insulating layer 2252. The first insulating layer 2252 is disposed on the surface of the substrate 2251 facing the positive electrode 224. The first insulating layer 2252 and the liquid storage layer 226 are integrally formed.

[0160] The first insulating layer 2252 is a coating disposed on at least one surface of the substrate 2251 in the thickness direction. In some embodiments, the first insulating layer 2252 is disposed only on the surface of the substrate 2251 facing the positive electrode 224. In other embodiments, the first insulating layer 2252 is disposed on both opposite surfaces of the substrate 2251 in the thickness direction.

[0161] The material of the first insulating layer 2252 includes at least one of aluminum oxide, silicon oxide, boehmite, barium sulfate, zirconium oxide, silicon oxide, magnesium oxide, zinc oxide, and tin oxide.

[0162] The first insulating layer 2252 and the liquid storage layer 226 are integrally formed. In the process of coating the substrate 2251 with insulating material to form the first insulating layer 2252, the coating is added in a predetermined area so that the predetermined area on the first insulating layer 2252 forms a protrusion that can be accommodated in the groove 22421. The protrusion serves as the liquid storage layer 226.

[0163] The separator 225 includes a substrate 2251 and a first insulating layer 2252. The separator 225 is a composite film. The first insulating layer 2252 and the liquid storage layer 226 are integrally formed. The liquid storage layer 226 can be regarded as a part of the first insulating layer 2252. When coating the first insulating layer 2252, more paint can be applied to the position of the first insulating layer 2252 corresponding to the groove 22421 to locally thicken the first insulating layer 2252. The thickened part can form the liquid storage layer 226, which is easier to manufacture.

[0164] In some embodiments, each portion of the groove wall of the groove 22421 is in contact with the surface of the liquid storage layer 226.

[0165] The liquid storage layer 226 can fill the groove 22421, so that all parts of the groove wall of the groove 22421 are in contact with the surface of the liquid storage layer 226.

[0166] By ensuring that all portions of the groove wall of the groove 22421 are in contact with the surface of the liquid storage layer 226, on the one hand, the electrolyte can easily penetrate from the groove wall of the groove 2242 through the liquid storage layer 226 into the positive electrode active material layer 2242, which is beneficial to improving the wetting effect of the positive electrode active material layer 2242. On the other hand, it can shorten the travel path of lithium ions during the charging and discharging process, which helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stages of the battery cell 20 cycle, and helps to extend the cycle life of the battery cell 20.

[0167] Please refer to Figure 12 , Figure 12 This is a schematic diagram of the structure of the positive electrode 224 provided in some embodiments of this application. In some embodiments, the positive electrode 224 has a positive electrode tab 2222 at at least one end along a first direction. Along the first direction, the minimum distance between the groove 22421 and one end of the positive active material layer 2242 is A1, and the minimum distance between the groove 22421 and the other end of the positive active material layer 2242 is A2, satisfying: 0.9≤A1 / A2≤1.1.

[0168] Along the first direction, at least one end of the positive electrode 224 is provided with a positive electrode tab 2222. In some embodiments, the portion of the positive current collector 2241 not covered by the positive active material layer 2242 includes the positive electrode tab 2222. Optionally, the positive electrode 224 includes a second insulating layer 2243, which is disposed on at least one surface of the positive current collector 2241 along the thickness direction of the positive current collector 2241. The second insulating layer 2243 and the positive active material layer 2242 are arranged along the first direction. The second insulating layer 2243 covers the root of the positive electrode tab 2222 to reduce the risk of short circuit due to contact between the positive electrode tab 2222 and the negative electrode 223.

[0169] Please refer to Figure 12 The first direction is the X direction shown in the figure.

[0170] A1 represents the minimum distance between the groove 22421 and one end of the positive electrode active material layer 2242 along the first direction. During measurement, the minimum distance between the groove 22421 at the opening of the first surface 22424 along the first direction and one end of the positive electrode active material layer 2242 can be measured.

[0171] A2 represents the minimum distance between the groove 22421 along the first direction and the other end of the positive electrode active material layer 2242. During measurement, the minimum distance between the groove 22421 at the opening of the first surface 22424 along the first direction and the other end of the positive electrode active material layer 2242 can be measured.

[0172] A1 / A2 represents the ratio of the minimum distance between the groove 22421 and one end of the positive electrode active material layer 2242 along the first direction to the minimum distance between the groove 22421 and the other end of the positive electrode active material layer 2242 along the first direction.

[0173] A1 / A2 can take values ​​of: 0.9, 0.92, 0.95, 0.98, 1, 1.02, 1.05, 1.08, 1.1, etc.

[0174] When 0.9≤A1 / A2≤1.1, the groove 22421 is approximately located in the middle of the positive electrode active material layer 2242 along the first direction. Since the middle of the positive electrode active material layer 2242 along the first direction is relatively more difficult to wet, the electrolyte reflux is more difficult in the later stage of the cycle of the battery cell 20. Therefore, by making the groove 22421 approximately located in the middle of the positive electrode active material layer 2242 along the first direction, it can achieve better results and help extend the cycle life of the battery cell 20.

[0175] Please refer to Figure 12In some embodiments, the groove 22421 has an opening on the side of the positive electrode active material layer 2242 opposite to the positive electrode current collector 2241. Along the first direction, the maximum size of the opening of the groove 22421 is A3, and the size of the positive electrode active material layer 2242 is A, satisfying: 0.05≤A3 / A≤0.9.

[0176] "The groove 22421 has an opening on the side of the positive electrode active material layer 2242 away from the positive electrode current collector 2241" means that the groove 22421 has an opening on the first surface 22424, and the opening is the groove of the groove 22421 on the first surface 22424.

[0177] A3 represents the maximum dimension of the opening of groove 22421 along the first direction.

[0178] A represents the dimension of the positive electrode active material layer 2242 along the first direction, that is, the distance between the two ends of the positive electrode active material layer 2242 along the first direction.

[0179] A3 / A represents the ratio of the maximum dimension of the opening of the groove 22421 along the first direction to the dimension of the positive electrode active material layer 2242 along the first direction.

[0180] A3 / A can take values ​​of 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, etc.

[0181] When A3 / A ≥ 0.05, the maximum size of the opening of the groove 22421 along the first direction is larger, making the groove 22421 larger. On the one hand, the electrolyte can penetrate into the positive electrode active material layer 2242 from the groove wall surface of the groove 22421, increasing the contact area between the positive electrode active material layer 2242 and the electrolyte, which is beneficial to improving the wetting effect of the positive electrode active material layer 2242. On the other hand, it reduces the lithium-ion abundance of the positive electrode active material layer 2242, which is beneficial to reduce side reactions, delay the electrode thicknessing process, and extend the life of the battery cell 20. Furthermore, more liquid storage layer 226 can be filled in the groove 22421, which can shorten the travel path of lithium ions during the charging and discharging process, which is beneficial to alleviating the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of the battery cell 20 cycle, and is beneficial to extending the cycle life of the battery cell 20. When A3 / A ≤ 0.9, the maximum size of the groove 22421 along the first direction will not be too large, ensuring that the lithium-ion abundance of the positive electrode active material layer 2242 is not too low, thus allowing the battery cell 20 to still have a high energy density. Therefore, when 0.05 ≤ A3 / A ≤ 0.9, both the cycle life and energy density of the battery cell 20 can be balanced.

[0182] Optionally, 0.2 ≤ A3 / A ≤ 0.4.

[0183] A3 / A can take values ​​of 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, etc.

[0184] When A3 / A ≥ 0.2, the maximum size of the opening of the groove 22421 along the first direction is larger, making the groove 22421 larger. On the one hand, the electrolyte can penetrate into the positive electrode active material layer 2242 from the groove wall surface of the groove 22421, further increasing the contact area between the positive electrode active material layer 2242 and the electrolyte, which is more conducive to improving the wetting effect of the positive electrode active material layer 2242. On the other hand, it further reduces the lithium-ion abundance of the positive electrode active material layer 2242, which is conducive to reducing side reactions, delaying the electrode thicknessing process, and extending the life of the battery cell 20. In addition, more liquid storage layer 226 can be filled in the groove 22421, which can shorten the travel path of lithium ions during the charging and discharging process, which is conducive to alleviating the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of the battery cell 20 cycle, and is conducive to extending the cycle life of the battery cell 20. When A3 / A ≤ 0.4, the maximum size of the groove 22421 along the first direction will not be too large, ensuring that the lithium-ion abundance of the positive electrode active material layer 2242 is not too low, thus allowing the battery cell 20 to still have a high energy density. Therefore, when 0.2 ≤ A3 / A ≤ 0.4, both the cycle life and energy density of the battery cell 20 can be balanced.

[0185] Please refer to Figure 13 , Figure 13 This is a schematic diagram of the structure of the positive electrode 224 provided in other embodiments of this application. In other embodiments, the positive electrode 224 has a positive electrode tab 2222 at at least one end along a first direction. Along a second direction, a groove 22421 extends to both ends of the positive electrode active material layer 2242. The first direction, the second direction, and the thickness direction of the positive electrode current collector 2241 are perpendicular to each other.

[0186] Please refer to Figure 13 The second direction is the Y direction shown in the figure.

[0187] The groove 22421 extends along the second direction to both ends of the positive electrode active material layer 2242, that is, the groove 22421 penetrates both ends of the positive electrode active material layer 2242 along the second direction.

[0188] By extending the groove 22421 along the second direction to both ends of the positive electrode active material layer 2242, the contact area between the positive electrode active material layer 2242 and the electrolyte is further increased, which is more conducive to improving the wetting effect of the positive electrode active material layer 2242 and further reducing the lithium-ion abundance of the positive electrode active material layer 2242. This helps to reduce side reactions, slow down the electrode thicknessing process, and extend the life of the battery cell 20. Furthermore, more electrolyte storage layer 226 can be filled in the groove 22421, which can shorten the travel path of lithium ions during the charging and discharging process. This helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stages of battery cell 20 cycling and further extends the cycle life of battery cell 20.

[0189] Please refer to this again. Figure 7 In some embodiments, the positive electrode active material layer 2242 includes a main region 22422 and a thinned region 22423. The thickness of the main region 22422 is greater than the thickness of the thinned region 22423, and the main region 22422 and the thinned region 22423 are connected. The positive electrode active material layer 2242 forms the thinned region 22423 in the area where the groove 22421 is formed. The minimum thickness of the thinned region 22423 is H1, and the minimum thickness of the main region 22422 is H2, satisfying: 0≤H1 / H2≤0.9, optionally, 0.85≤H1 / H2≤0.9.

[0190] The main body region 22422 is the portion of the positive electrode active material layer 2242 without the groove 22421. The thinned region 22423 is the remaining portion of the positive electrode active material layer 2242 after the groove 22421 is formed. The minimum thickness of the main body region 22422 is greater than the maximum thickness of the thinned region 22423.

[0191] H1 represents the minimum thickness of the thinned region 22423. During measurement, the thickness of the thinned region 22423 at the location where the depth of the groove 22421 is the greatest can be measured.

[0192] H2 represents the minimum thickness of the main body region 22422. Generally, the thickness of the main body region 22422 is uniform, and the thickness at any position of the main body region 22422 can be measured as the minimum thickness of the main body region 22422.

[0193] H1 / H2 represents the ratio of the minimum thickness of the thinned region 22423 to the minimum thickness of the main body region 22422.

[0194] H1 / H2 can take values ​​of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc.

[0195] When 0 ≤ H1 / H2 ≤ 0.9, the minimum thickness of the thinning region 22423 is smaller, and the depth of the groove 22421 is larger, further increasing the contact area between the positive electrode active material layer 2242 and the electrolyte. This is more conducive to improving the wetting effect of the positive electrode active material layer 2242, further reducing the lithium-ion abundance of the positive electrode active material layer 2242, which helps to reduce side reactions, delay the electrode thicknessing process, and extend the life of the battery cell 20. Furthermore, more electrolyte storage layer 226 can be filled in the groove 22421, which can shorten the lithium-ion travel path during charging and discharging, helping to alleviate the lithium plating problem caused by electrolyte reflux difficulties in the later stages of battery cell 20 cycling, and further extending the cycle life of battery cell 20.

[0196] Optionally, 0.85 ≤ H1 / H2 ≤ 0.9.

[0197] H1 / H2 can take values ​​of 0.85, 0.855, 0.86, 0.865, 0.87, 0.875, 0.88, 0.885, 0.89, 0.895, 0.9, etc.

[0198] When H1 / H2 ≤ 0.9, the minimum thickness of the thinning region 22423 is small, and the depth of the groove 22421 is large, further increasing the contact area between the positive electrode active material layer 2242 and the electrolyte. This is more conducive to improving the wetting effect of the positive electrode active material layer 2242 and further reducing the lithium-ion abundance of the positive electrode active material layer 2242. This helps to reduce side reactions, slow down the electrode thicknessing process, and extend the life of the battery cell 20. Furthermore, the groove 22421 can be filled with more electrolyte layer 226, which can shorten the lithium-ion travel path during charging and discharging. This helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stages of battery cell 20 cycling, and further extends the cycle life of battery cell 20. When H1 / H2 ≥ 0.85, the minimum thickness of the thinning region 22423 is not too small, and the depth of the groove 22421 is not too deep, ensuring that the lithium-ion abundance of the positive electrode active material layer 2242 is not too low, so that the battery cell 20 still has a high energy density. Therefore, when 0.85≤H1 / H2≤0.9, the cycle life and energy density of the battery cell 20 can be balanced.

[0199] In some embodiments, the volume of the groove 22421 is V1, and the volume of the positive electrode active material layer 2242 with the groove 22421 is V2, satisfying: 0.95≤V2 / (V1+V2)<1.

[0200] V1 represents the volume of groove 22421.

[0201] V2 represents the volume of the positive electrode active material layer 2242 with grooves 22421.

[0202] (V1+V2) represents the sum of the volume of the groove 22421 and the volume of the positive electrode active material layer 2242 on which the groove 22421 is provided.

[0203] V2 / (V1+V2) represents the ratio of the volume of the positive electrode active material layer 2242 with groove 22421 to the sum of the volume of groove 22421 and the volume of the positive electrode active material layer 2242 with groove 22421.

[0204] V2 / (V1+V2) can take values ​​of 0.95, 0.955, 0.96, 0.965, 0.97, 0.975, 0.98, 0.985, 0.99, 0.995, etc.

[0205] When 0.95≤V2 / (V1+V2)<1, the volume of the remaining positive electrode active material layer 2242 after setting the groove 22421 is relatively large, and the abundance of lithium ions reduced due to the opening of the groove 22421 is relatively small, so that the battery cell 20 still has a high energy density.

[0206] Please refer to Figure 14 , Figure 14 This is a side view of a battery cell 20 provided in some embodiments of this application. In some embodiments, the positive electrode 224 has a positive electrode tab 2222 at at least one end along a first direction, and the size of the outer casing 21 along the first direction is D, which satisfies: 120mm≤D≤350mm.

[0207] D represents the dimension of the outer casing 21 along the first direction. D can be 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, 320mm, 330mm, 340mm, 350mm, etc.

[0208] When D≥120mm, the size of the outer casing 21 along the first direction is larger, the height of the battery cell 20 is higher, the electrode assembly 22 is more difficult to wet, and the electrolyte reflux is more difficult. Therefore, it is necessary to set the groove 22421 and the liquid storage layer 226 to extend the life of the battery cell 20.

[0209] In some embodiments, the volume of the groove 22421 is V1, and the volume of the positive electrode active material layer 2242 with the groove 22421 is V2. When 120mm≤D≤160mm, 0.97≤V2 / (V1+V2)≤0.99. When 160mm<D≤350mm, 0.95≤V2 / (V1+V2)<0.97.

[0210] When 120mm≤D≤160mm, V2 / (V1+V2) can take values ​​of 0.97, 0.971, 0.972, 0.973, 0.974, 0.975, 0.976, 0.977, 0.978, 0.979, 0.98, 0.981, 0.982, 0.983, 0.984, 0.985, 0.986, 0.987, 0.988, 0.989, 0.99, etc.

[0211] When 120mm≤D≤160mm, the size of the outer casing 21 along the first direction is larger, and the height of the battery cell 20 is higher. By making V2 / (V1+V2)≤0.99, the volume of the groove 22421 is larger, which is beneficial to extending the life of the battery cell 20. By making V2 / (V1+V2)≥0.97, it is beneficial to ensure that the battery cell 20 still has a high energy density.

[0212] When 160mm < D ≤ 350mm, V2 / (V1+V2) can be taken as 0.95, 0.951, 0.952, 0.953, 0.954, 0.955, 0.956, 0.957, 0.958, 0.959, 0.96, 0.961, 0.962, 0.963, 0.964, 0.965, 0.966, 0.967, 0.968, 0.969, etc.

[0213] When 160mm < D ≤ 350mm, the size of the outer casing 21 along the first direction is larger, the height of the battery cell 20 is higher, the electrode assembly 22 is more difficult to wet, and the electrolyte reflux is more difficult. By making V2 / (V1+V2) < 0.97, the volume of the groove 22421 is larger, which is beneficial to extending the life of the battery cell 20. By making V2 / (V1+V2) ≥ 0.95, it is beneficial to ensure that the battery cell 20 still has a high energy density.

[0214] This application embodiment also provides a battery device 100, which includes the aforementioned battery cell 20.

[0215] This application embodiment also provides an electrical device, which includes the aforementioned battery cell 20, and the battery cell 20 is used to provide electrical energy to the electrical device.

[0216] According to some embodiments of this application, please refer to Figures 3 to 14 .

[0217] This application provides a battery cell 20, which includes a casing 21, an electrolyte, and an electrode assembly 22. The electrolyte and the electrode assembly 22 are housed within the casing 21. The electrode assembly 22 includes a positive electrode 224, a separator 225, and a negative electrode 223, which are stacked together. The positive electrode 224 includes a positive current collector 2241 and a positive active material layer 2242. Along the thickness direction of the positive current collector 2241, the positive active material layer 2242 is disposed on at least one surface of the positive current collector 2241. At least one surface of the positive active material layer 2242 facing away from the positive current collector 2241 has a groove 22421. A liquid storage layer 226 is disposed within the groove 22421. The porosity of the liquid storage layer 226 is greater than that of the positive active material layer, and the liquid storage layer 226 stores a portion of the electrolyte. By providing grooves 22421 on the surface of the positive electrode active material layer 2242 facing away from the positive electrode current collector 2241, on the one hand, the electrolyte can penetrate into the positive electrode active material layer 2242 from the groove wall surface of the groove 22421, increasing the contact area between the positive electrode active material layer 2242 and the electrolyte, which is beneficial to improving the wetting effect of the positive electrode active material layer 2242. On the other hand, by providing grooves 22421 on the surface of the positive electrode active material layer 2242 facing away from the positive electrode current collector 2241, the lithium-ion abundance of the positive electrode active material layer 2242 is also reduced, which is beneficial to reduce side reactions, delay the electrode thicknessing process, and extend the life of the battery cell 20. By setting a liquid storage layer 226 in the groove 22421, the porosity of the liquid storage layer 226 is greater than that of the positive electrode active material layer 2242, making it easier for the liquid storage layer 226 to store electrolyte compared to the positive electrode active material layer 2242. By storing electrolyte in the liquid storage layer 226, the travel path of lithium ions during the charging and discharging process can be shortened, which helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stage of the battery cell 20 cycle, and helps to extend the cycle life of the battery cell 20.

[0218] In some embodiments, the electrolyte storage layer 226 and the separator 225 are separately disposed, with the electrolyte storage layer 226 in contact with the separator 225. The electrolyte storage layer 226 and the separator 225 are two independent structures, both storing electrolyte. By bringing the electrolyte storage layer 226 and the separator 225 into contact, the travel path of lithium ions during charging and discharging can be further shortened, which helps alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stages of battery cell 20 cycling, and helps extend the cycle life of battery cell 20.

[0219] The surface of the positive electrode active material layer 2242 with the groove 22421 is the first surface 22424, and the surface of the liquid storage layer 226 facing away from the positive electrode current collector 2241 is flush with the first surface 22424. By making the surface of the liquid storage layer 226 facing away from the positive electrode current collector 2241 flush with the first surface 22424, on the one hand, it facilitates contact between the first surface 22424 and the separator 225, and facilitates contact between the surface of the liquid storage layer 226 facing away from the positive electrode current collector 2241 and the separator 225, thus shortening the ion path. On the other hand, when they are flush, the stress on the separator 225, the positive electrode active material layer 2242, and / or the liquid storage layer 226 is smaller when the electrode assembly 22 is pressed, which helps to reduce the risk of damage to the separator 225, the positive electrode active material layer 2242, and / or the liquid storage layer 226.

[0220] In other embodiments, at least a portion of the reservoir layer 226 and the separator 225 are integrally formed. This integral forming ensures that the reservoir layer 226 can be considered part of the separator 225, maintaining a constant connection between them without gaps. This shortens the lithium-ion path during charging and discharging, alleviates lithium plating problems caused by electrolyte reflux difficulties in the later stages of battery cell 20 cycling, and extends the cycle life of the battery cell 20.

[0221] All parts of the groove wall 22421 are in contact with the surface of the liquid storage layer 226. By ensuring that all parts of the groove wall 22421 are in contact with the surface of the liquid storage layer 226, on the one hand, the electrolyte can easily penetrate from the groove wall 2242 through the liquid storage layer 226 into the positive electrode active material layer 2242, which is beneficial to improving the wetting effect of the positive electrode active material layer 2242. On the other hand, it can shorten the travel path of lithium ions during the charging and discharging process, which helps to alleviate the lithium plating problem caused by the difficulty of electrolyte reflux in the later stages of battery cell 20 cycle, and helps to extend the cycle life of battery cell 20.

[0222] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery cell, characterized in that, include: shell; Electrolyte, contained within the outer casing; An electrode assembly is housed within the housing. The electrode assembly includes a positive electrode, a separator, and a negative electrode, which are stacked together. The positive electrode includes a positive current collector and a positive active material layer. Along the thickness direction of the positive current collector, the positive active material layer is disposed on at least one surface of the positive current collector. At least one surface of the positive active material layer opposite to the positive current collector is provided with a groove. A liquid storage layer is disposed in the groove. The porosity of the liquid storage layer is greater than that of the positive active material layer. The liquid storage layer stores a portion of the electrolyte.

2. The battery cell according to claim 1, characterized in that, The liquid storage layer and the isolation membrane are separately disposed, and the liquid storage layer is in contact with the isolation membrane.

3. The battery cell according to claim 2, characterized in that, The surface of the positive electrode active material layer with the groove is the first surface, and the surface of the liquid storage layer opposite to the positive electrode current collector is flush with the first surface.

4. The battery cell according to claim 2, characterized in that, The liquid storage layer is made of a conductive material, which includes one of the following: carbon nanotubes, graphite, carbon black, carbon fiber, and graphene; or The material of the liquid storage layer is an insulating material, which includes one of inorganic powder, ceramic fiber, and polymer gel.

5. The battery cell according to claim 1, characterized in that, At least a portion of the liquid storage layer and the isolation membrane are integrally formed.

6. The battery cell according to claim 5, characterized in that, The isolation membrane includes a substrate, and the liquid storage layer and the substrate are integrally formed.

7. The battery cell according to claim 5, characterized in that, The separator includes a substrate and a first insulating layer. The first insulating layer is disposed on the surface of the substrate facing the positive electrode sheet. The first insulating layer and the liquid storage layer are integrally formed.

8. The battery cell according to any one of claims 1-7, characterized in that, Each part of the groove wall is in contact with the surface of the liquid storage layer.

9. The battery cell according to any one of claims 1-7, characterized in that, The positive electrode sheet has a positive electrode tab at at least one end along the first direction. Along the first direction, the minimum distance between the groove and one end of the positive electrode active material layer is A1, and the minimum distance between the groove and the other end of the positive electrode active material layer is A2, satisfying: 0.9≤A1 / A2≤1.

1.

10. The battery cell according to claim 9, characterized in that, The groove has an opening on the side of the positive electrode active material layer away from the positive electrode current collector. Along the first direction, the maximum size of the opening of the groove is A3, and the size of the positive electrode active material layer is A, satisfying: 0.05≤A3 / A≤0.

9.

11. The battery cell according to claim 10, characterized in that, 0.2≤A3 / A≤0.

4.

12. The battery cell according to any one of claims 1-7, characterized in that, The positive electrode sheet has a positive electrode tab at at least one end along the first direction, and the groove extends to both ends of the positive active material layer along the second direction. The first direction, the second direction, and the thickness direction of the positive current collector are perpendicular to each other.

13. The battery cell according to any one of claims 1-7, characterized in that, The positive electrode active material layer includes a main region and a thinning region. The thickness of the main region is greater than the thickness of the thinning region. The main region and the thinning region are connected. The positive electrode active material layer forms the thinning region in the area where the groove is provided. The minimum thickness of the thinning region is H1, and the minimum thickness of the main region is H2, satisfying: 0≤H1 / H2≤0.

9.

14. The battery cell according to claim 13, characterized in that, 0.85≤H1 / H2≤0.

9.

15. The battery cell according to any one of claims 1-7, characterized in that, The volume of the groove is V1, and the volume of the positive electrode active material layer with the groove is V2, satisfying: 0.95≤V2 / (V1+V2)<1.

16. The battery cell according to any one of claims 1-7, characterized in that, The positive electrode sheet has a positive electrode tab at at least one end along the first direction. Along the first direction, the size of the outer shell is D, which satisfies: 120mm≤D≤350mm.

17. The battery cell according to claim 16, characterized in that, The volume of the groove is V1, and the volume of the positive electrode active material layer with the groove is V2. When 120mm≤D≤160mm, 0.97≤V2 / (V1+V2)≤0.99; When 160mm < D ≤ 350mm, 0.95 ≤ V2 / (V1+V2) < 0.

97.

18. A battery device, characterized in that, Includes the battery cell according to any one of claims 1-15.

19. An electrical appliance, characterized in that, Includes a battery cell according to any one of claims 1-15, the battery cell being used to provide electrical energy to the electrical device.

Images