Battery cells, battery packs and electrical devices

Abstract

A battery cell, a battery device, and an electrical device are provided. The battery cell includes a casing, an electrode assembly, and an electrolyte, with the electrode assembly and electrolyte housed within the casing. The electrode assembly includes a first electrode, which comprises a current collector, an active material layer, and an insulating layer. The active material layer and the insulating layer are both disposed on at least one surface of the current collector along its thickness direction. The active material layer includes a main region and a thinned region arranged along the width direction of the first electrode, with the thickness of the main region being greater than the thickness of the thinned region. Along the width direction, at least one end of the main region is connected to the thinned region, and the insulating layer is in contact with the thinned region. Both the insulating layer and the main region store electrolyte, with the insulating layer having a higher electrolyte retention rate than the main region. The insulating layer comprises, by weight percentage: 30-75% inorganic filler, 10-30% binder, and 5-30% electrolyte-retaining material. The insulating layer improves the wetting effect on the thinned region and reduces the risk of lithium plating.

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. Furthermore, battery reliability also needs to be considered. However, current battery reliability is relatively poor. Summary of the Invention

[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 poor battery reliability in related technologies.

[0004] In a first aspect, embodiments of this application provide a battery cell, the battery cell including a casing, an electrode assembly, and an electrolyte. The electrode assembly and the electrolyte are housed within the casing. The electrode assembly includes a first electrode, the first electrode including a current collector, an active material layer, and an insulating layer. The active material layer and the insulating layer are both disposed on at least one surface of the current collector along its thickness direction. The active material layer includes a main body region and a thinned region arranged along the width direction of the first electrode. The thickness of the main body region is greater than the thickness of the thinned region. Along the width direction, at least one end of the main body region is connected to the thinned region. The insulating layer is in contact with the thinned region. The electrolyte is stored in both the insulating layer and the main body region. The electrolyte retention rate of the insulating layer is greater than that of the main body region. The insulating layer includes, by mass percentage: 30-75% inorganic filler, 10-30% binder, and 5-30% electrolyte-retaining material.

[0005] In the above technical solution, by providing an insulating layer on at least one surface of the current collector along its thickness direction, the insulating layer can insulate and isolate the positive and negative electrode sheets, reducing the risk of short circuits caused by contact between the positive and negative electrode sheets, which is beneficial to improving the reliability of the battery cell. The insulating layer includes a liquid-retaining material, which can improve the liquid retention rate of the electrolyte, thereby improving the liquid retention rate of the insulating layer for the electrolyte. By making the liquid retention rate of the insulating layer for the electrolyte greater than that of the main body region for the electrolyte, on the one hand, the insulating layer can act as a "water channel" for the electrolyte. Under capillary action, the electrolyte preferentially and rapidly penetrates along the insulating layer, and then actively diffuses into the thinned area through capillary force, which is beneficial to improving the wetting effect on the thinned area, reducing the risk of lithium plating, and improving the reliability of the battery cell. On the other hand, the insulating layer can act as a "reservoir" for the electrolyte. The insulating layer can actively and continuously supply electrolyte to the thinned area, reducing the risk of interface failure caused by electrolyte depletion in the thinned area during charging and discharging, reducing the risk of lithium plating, and thus improving the reliability of the battery cell. Furthermore, during high-speed charging and discharging, the thinned area is prone to excessively rapid local electrolyte consumption due to concentrated ion flux. The insulating layer can replenish the electrolyte in the thinned area through capillary action, maintaining the wettability continuity of the electrode / electrolyte interface, which helps reduce the risk of lithium plating and improves the reliability of the battery cell.

[0006] As an optional technical solution in this application embodiment, the liquid-retaining material includes at least one of cross-linked polyvinylidene fluoride, polychlorotrifluoroethylene, fluororubber, fluorinated polyimide, polyimide, and perfluoroalkoxy vinyl ether copolymer.

[0007] In the above technical solutions, cross-linked polyvinylidene fluoride, polychlorotrifluoroethylene, fluororubber, fluorinated polyimide, polyimide, and perfluoroalkoxy vinyl ether copolymer can not only resist electrolyte corrosion, but also have good electrolyte retention capacity, which can effectively improve the electrolyte retention capacity of the insulation layer.

[0008] As an optional technical solution in this application embodiment, the liquid retention rate of the insulating layer is 22%~25%.

[0009] In the above technical solutions, when the liquid retention rate of the insulating layer is greater than or equal to 22%, the liquid retention rate is relatively high. On the one hand, this is beneficial for improving the electrolyte drainage effect of the insulating layer, improving the wetting effect on the thinned area, reducing the risk of lithium plating, and improving the reliability of the battery cell. On the other hand, the insulating layer can store more electrolyte, which is beneficial for improving the liquid replenishment effect of the insulating layer, reducing the risk of lithium plating, and improving the reliability of the battery cell. When the liquid retention rate of the insulating layer is less than or equal to 25%, the liquid retention rate of the insulating layer is not too large, so that the volume occupied by the insulating layer is not too large, which is beneficial for improving the energy density of the battery cell. Therefore, when the liquid retention rate of the insulating layer is 22%~25%, the reliability and energy density of the battery cell can be balanced.

[0010] As an optional technical solution in this application embodiment, the thinning area includes a first surface, the first surface having a first end and a second end, the first end being farther away from the main body area than the second end along the width direction, the first end being located at the position of the thinning area furthest from the main body area, the second end being farther away from the current collector than the first end along the thickness direction, and the insulating layer covering at least a portion of the first surface.

[0011] In the above technical solution, by covering at least a portion of the first surface with an insulating layer, lithium ions can be transported through the insulating layer, which helps to shorten the ion path and reduce the risk of lithium plating.

[0012] As an optional technical solution in this application embodiment, a portion of the insulating layer is located between the thinned area and the current collector.

[0013] In the above technical solution, since the side of the thinned area facing the current collector is relatively more difficult to wet, by placing a part of the insulating layer between the thinned area and the current collector, the electrolyte can actively diffuse from the part of the insulating layer between the thinned area and the current collector to the thinned area through capillary force, thereby further improving the wetting effect on the thinned area, reducing the risk of lithium plating, and improving the reliability of the battery cell.

[0014] As an optional technical solution in this application embodiment, the insulating layer includes a first part and a second part connected together. The first part and the second part are arranged along the width direction. The first part is located on the side of the second part away from the main body area. Along the thickness direction, the first part has a second surface away from the current collector. A portion of the second part protrudes from the second surface. The second part covers at least a portion of the first surface, and a portion of the second part is located between the thinned area and the current collector.

[0015] In the above technical solution, the second part can cover at least a portion of the first surface, and a portion of the second part is located between the thinned region and the current collector, which is beneficial to improving the wetting effect of the thinned region, shortening the ion path, and reducing the risk of lithium plating. The presence of the first part, on the one hand, can insulate and isolate the positive and negative electrode sheets, reducing the risk of short circuits due to contact between the positive and negative electrode sheets, and thus improving the reliability of the battery cell. On the other hand, the connection between the first part and the current collector is relatively more robust, and the connection between the first and second parts helps maintain the relative position of the second part and the thinned region.

[0016] As an optional technical solution in this application embodiment, the electrode assembly includes a first electrode tab, which is disposed at one end of the current collector along the width direction, and the first portion covers a portion of the first electrode tab.

[0017] In the above technical solution, by covering a portion of the first tab with the first part, it is beneficial to reduce the risk of short circuit caused by the burrs on the first tab piercing the separator when the first tab is folded, which would result in the positive and negative electrodes coming into contact. This is beneficial to improving the reliability of the battery cell.

[0018] As an optional technical solution in this application embodiment, along the thickness direction, the thickness of the first part is H1, and the thickness of the main body area is H, satisfying: 0.01≤H1 / H≤0.15.

[0019] In the above technical solution, when H1 / H≥0.01, the thickness of the first part is relatively large, which is beneficial for covering the burrs on the first electrode tab and reducing the risk of short circuit caused by the burrs on the first electrode tab piercing the insulating component and causing the positive and negative electrode plates to come into contact when the first electrode tab is folded. When H1 / H≤0.15, the thickness of the first part is not too large, which facilitates the cutting of the electrode tab.

[0020] As an optional technical solution in this application embodiment, the thickness of the first part along the thickness direction is H1, which satisfies: 0.5μm≤H1≤70μm.

[0021] In the above technical solution, when H1 ≥ 0.5 μm, the thickness of the first part is relatively large, which is beneficial for covering the burrs on the first electrode tab and reducing the risk of short circuit caused by the burrs on the first electrode tab piercing the insulating component and causing the positive and negative electrode plates to come into contact when the first electrode tab is folded. When H1 ≤ 70 μm, the thickness of the first part is not too large, which facilitates the cutting of the electrode tab.

[0022] As an optional technical solution in this application embodiment, the second part includes a first region located between the thinning region and the current collector. Along the thickness direction, the maximum size of the first region is H2, and the thickness of the main body region is H, satisfying: 0.05≤H2 / H≤0.3.

[0023] In the above technical solution, when H2 / H ≥ 0.05, the maximum size of the first region along the thickness direction is relatively large, which facilitates the active diffusion of electrolyte from the portion of the insulating layer located between the thinned region and the current collector to the thinned region via capillary force. This further enhances the wetting effect on the thinned region, reduces the risk of lithium plating, and improves the reliability of the battery cell. When H2 / H ≤ 0.3, the maximum size of the first region along the thickness direction is not too large, ensuring that the volume occupied by the first region is not too large, which is beneficial to improving the energy density of the battery cell. Therefore, when 0.05 ≤ H2 / H ≤ 0.3, both the reliability and energy density of the battery cell can be balanced.

[0024] As an optional technical solution in this application embodiment, 2μm≤H2≤40μm.

[0025] In the above technical solution, when H2 ≥ 2μm, the maximum size of the first region along the thickness direction is relatively large, which facilitates the active diffusion of electrolyte from the portion of the insulating layer located between the thinned region and the current collector to the thinned region via capillary force. This further enhances the wetting effect on the thinned region, reduces the risk of lithium plating, and improves the reliability of the battery cell. When H2 ≤ 40μm, the maximum size of the first region along the thickness direction is not too large, ensuring that the volume occupied by the first region is not too large, which is beneficial to improving the energy density of the battery cell. Therefore, when 2μm ≤ H2 ≤ 40μm, both the reliability and energy density of the battery cell can be balanced.

[0026] As an optional technical solution in this application embodiment, the second part includes a first region located between the thinning region and the current collector. Along the width direction, the maximum size of the first region is W1, and the maximum size of the active material layer is W, satisfying: 0.05≤W1 / W≤0.25.

[0027] In the above technical solution, when W1 / W ≥ 0.05, the maximum dimension of the first region along the width direction is relatively large, which helps to increase the contact area between the first region and the thinned region. This facilitates the active diffusion of electrolyte from the portion of the insulating layer located between the thinned region and the current collector to the thinned region via capillary force, thereby further improving the wetting effect on the thinned region, reducing the risk of lithium plating, and improving the reliability of the battery cell. When W1 / W ≤ 0.25, the maximum dimension of the first region along the width direction is not too large, ensuring that the volume occupied by the first region is not too large, which helps to improve the energy density of the battery cell. Therefore, when 0.05 ≤ W1 / W ≤ 0.25, both the reliability and energy density of the battery cell can be balanced.

[0028] As an optional technical solution in this application embodiment, 0.1mm≤W1≤15mm.

[0029] In the above technical solution, when W1 ≥ 0.1 mm, the maximum dimension of the first region along the width direction is relatively large, which helps to increase the contact area between the first region and the thinned region. This facilitates the active diffusion of electrolyte from the portion of the insulating layer located between the thinned region and the current collector to the thinned region via capillary force, thereby further improving the wetting effect on the thinned region, reducing the risk of lithium plating, and improving the reliability of the battery cell. When W1 / W ≤ 0.25, the maximum dimension of the first region along the width direction is not too large, ensuring that the volume occupied by the first region is not too large, which helps to improve the energy density of the battery cell. Therefore, when 0.1 mm ≤ W1 ≤ 15 mm, both the reliability and energy density of the battery cell can be balanced.

[0030] As an optional technical solution in this application embodiment, the second part includes a third surface, the second surface transitions to the first surface through the third surface, the maximum distance between the third surface and the surface of the current collector facing the second part along the thickness direction is H3, and the thickness of the main body area is H, satisfying: 0.4≤H3 / H≤1.

[0031] In the above technical solution, when H3 / H ≥ 0.4, the maximum distance between the third surface along the thickness direction and the surface of the current collector facing the second part is relatively large, which is beneficial for lithium ions to be transported through the insulating layer, shortening the ion path and reducing the risk of lithium plating. When H3 / H ≤ 1, the maximum distance between the third surface along the thickness direction and the surface of the current collector facing the second part is not too large, ensuring that the insulating layer along the direction from the current collector to the active material layer does not extend beyond the surface of the main area away from the current collector. This is beneficial for reducing the distance between the main area and the other electrode (when the first electrode is a positive electrode, the other electrode is a negative electrode; when the first electrode is a negative electrode, the other electrode is a positive electrode), thereby shortening the ion path and reducing the risk of lithium plating.

[0032] As an optional technical solution in this application embodiment, the thinning area includes a fourth surface, one end of the fourth surface is connected to the first end, the other end of the fourth surface extends to the surface of the current collector facing the active material layer, and the insulating layer covers the fourth surface.

[0033] In the above technical solution, by covering the fourth surface with an insulating layer, the contact area between the insulating layer and the thinned area is increased. On the one hand, this facilitates the diffusion of electrolyte from the insulating layer to the thinned area, thereby further improving the wetting effect on the thinned area, reducing the risk of lithium plating, and improving the reliability of the battery cell. On the other hand, the insulating layer can better and continuously supply electrolyte to the thinned area, reducing the risk of interface failure caused by electrolyte depletion during charging and discharging, thus reducing the risk of lithium plating and improving the reliability of the battery cell.

[0034] As an optional technical solution in this application embodiment, along the direction from the current collector to the active material layer, the insulating layer does not extend beyond the surface of the main body area away from the current collector.

[0035] In the above technical solution, by ensuring that the insulating layer does not extend beyond the surface of the main body region away from the current collector in the direction from the current collector along the current collector to the active material layer, it is beneficial to reduce the distance between the main body region and the other electrode (when the first electrode is a positive electrode, the other electrode is a negative electrode, and when the first electrode is a negative electrode, the other electrode is a positive electrode), thereby shortening the ion path and reducing the risk of lithium plating.

[0036] As an optional technical solution in this application embodiment, the active material layer includes a transition region, at least a portion of which is located in the thinned region, and the material of the transition region includes the material of the insulating layer and the material of the active material layer.

[0037] In the above technical solution, a transition zone is provided. The materials of the transition zone include the materials of the insulating layer and the active material layer. The insulating layer material has a high electrolyte retention rate, which helps to improve the electrolyte retention rate of the transition zone. On the one hand, this is beneficial to further improve the wetting effect on the thinned area.

[0038] As an optional technical solution in this application embodiment, the transition zone includes a second zone and a third zone connected together, the second zone being located in the thinning zone and the third zone being located in the main body zone.

[0039] In the above technical solution, by placing a portion of the transition region within the thinning region and another portion within the main body region, the wetting effect on both the thinning and main body regions is improved. This helps reduce the risk of lithium plating and improves the reliability of the battery cell. Furthermore, the electrolyte stored in the transition region can also supply electrolyte to the main and thinning regions, reducing the risk of interface failure due to electrolyte depletion during charging and discharging, thus further reducing the risk of lithium plating and improving the reliability of the battery cell.

[0040] As an optional technical solution in this application embodiment, the first electrode is a positive electrode.

[0041] In the above technical solution, when the first electrode is a positive electrode, the insulating layer can protect the thinned area. When lithium plating occurs on the negative electrode, it prevents lithium dendrites from contacting the thinned area and causing a short circuit, thus improving the reliability of the battery cell. Furthermore, in embodiments where a portion of the insulating layer is located between the thinned area and the current collector, this portion replaces a portion of the active material layer, thereby reducing the capacity of the thinned area, increasing the CB value, reducing the risk of lithium plating, and improving the reliability of the battery cell.

[0042] Secondly, embodiments of this application also provide a battery device, which includes the aforementioned battery cell.

[0043] 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

[0044] 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.

[0045] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0046] Figure 2 Exploded views of battery devices provided in some embodiments of this application;

[0047] Figure 3 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0048] Figure 4 Exploded views of a single battery cell provided in some embodiments of this application;

[0049] Figure 5 This is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application;

[0050] Figure 6 A cross-sectional view of a first electrode provided for some embodiments of this application;

[0051] Figure 7 Cross-sectional view of the first electrode provided for other embodiments of this application;

[0052] Figure 8 A cross-sectional view of a first electrode provided for 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; 222-Taper; 2221-First tab; 223-Negative electrode; 224-Positive electrode; 225-Separator; 23-First electrode; 231-Current collector; 232-Active material layer; 2321-Main body area; 2322-Thinned area; 23221-First surface; 23222 - Fourth surface; 232211 - First end; 232212 - Second end; 2323 - Transition region; 23231 - Second region; 23232 - Third region; 233 - Insulating layer; 2331 - First part; 23311 - Second surface; 2332 - Second part; 23321 - Third surface; 23322 - First region; 25 - Electrode terminal; 27 - Insulator; 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, positioned 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 0.05At 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, nickel, carbon electrodes, carbon, 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 is a separator membrane. The separator membrane can be any known porous structure separator membrane 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 separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0078] 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 can be liquid, gel-like, or solid. Liquid electrolytes include electrolyte salts and solvents.

[0079] 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.

[0080] 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.

[0081] Among them, the gel electrolyte includes a polymer as the electrolyte backbone network, combined with an ionic liquid - lithium salt.

[0082] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0083] As an example, polymer solid electrolytes can be polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids-lithium salts, cellulose, etc.

[0084] As an example, inorganic solid electrolytes may include one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium germanium phosphate sulfide, silver sulfide germanium ore), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0085] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0086] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0087] In some implementations, the electrode assembly is a stacked structure.

[0088] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0089] 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.

[0090] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0091] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0092] As an example, the separator can be set continuously, either by folding or rolling between any adjacent positive or negative electrode plates.

[0093] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0094] In some embodiments, the electrode assembly has tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0095] 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).

[0096] 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.

[0097] As an example, a battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic battery cells, such as hexagonal prismatic battery cells.

[0098] 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.

[0099] 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.

[0100] As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0101] In some embodiments, the battery device may be a battery pack, which may include a housing and one or more battery cell assemblies housed within the housing.

[0102] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be housed in the housing by fixing the battery module in the housing.

[0103] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] The development of battery technology must consider multiple design factors simultaneously, such as energy density, discharge capacity, and charge / discharge rate. Additionally, battery reliability must also be considered. However, current battery reliability is relatively poor.

[0110] The production process of a battery cell involves a coating step, in which a slurry containing active materials is coated onto the current collector by a certain weight to form an active material layer. However, due to the natural fluidity of the slurry, thinning zones will form at the edges of the active material layer. During the cycling process of the battery cell, lithium plating is prone to occur in the thinned zones of the negative electrode, and lithium dendrites can easily pierce the separator and come into contact with the positive electrode, resulting in a short circuit and poor battery reliability.

[0111] Therefore, this application provides a battery cell comprising a casing, an electrode assembly, and an electrolyte, wherein the electrode assembly and the electrolyte are housed within the casing. The electrode assembly includes a first electrode, which comprises a current collector, an active material layer, and an insulating layer. Both the active material layer and the insulating layer are disposed on at least one surface of the current collector along its thickness direction. The active material layer includes a main region and a thinned region arranged along the width direction of the first electrode, wherein the thickness of the main region is greater than the thickness of the thinned region. Along the width direction, at least one end of the main region is connected to the thinned region, and the insulating layer is in contact with the thinned region. Electrolyte is stored in both the insulating layer and the main region, with the insulating layer having a higher electrolyte retention rate than the main region.

[0112] By providing an insulating layer on at least one surface of the current collector along its thickness direction, the insulating layer can insulate and isolate the positive and negative electrode plates, reducing the risk of short circuits caused by contact between the positive and negative electrode plates, thus improving the reliability of the battery cell. By ensuring that the electrolyte retention rate of the insulating layer is greater than that of the main body region, on the one hand, the insulating layer can act as a "water channel" for the electrolyte, allowing it to preferentially and rapidly penetrate along the insulating layer under capillary action, and then actively diffuse into the thinned area through capillary force. This improves the wetting effect on the thinned area, reduces the risk of lithium plating, and enhances the reliability of the battery cell. On the other hand, the insulating layer can act as a "reservoir" for the electrolyte, actively and continuously supplying electrolyte to the thinned area, reducing the risk of interface failure due to electrolyte depletion during charging and discharging, thus reducing the risk of lithium plating and improving the reliability of the battery cell. Furthermore, during high-speed charging and discharging, the thinned area is prone to excessively rapid local electrolyte consumption due to concentrated ion flux. The insulating layer can replenish the electrolyte in the thinned area through capillary action, maintaining the wettability of the electrode / electrolyte interface, which helps reduce the risk of lithium plating and improves the reliability of the battery cell.

[0113] 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.

[0114] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] Please refer to Figure 2 , Figure 2 This 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] Please refer to Figure 3 , Figure 4 , Figure 5 and Figure 6 , 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 6This is a cross-sectional view of a first electrode 23 provided in some embodiments of this application. Embodiments of this application provide a battery cell 20, which includes a housing 21, an electrode assembly 22, and an electrolyte. The electrode assembly 22 and the electrolyte are housed within the housing 21. The electrode assembly 22 includes a first electrode 23, which includes a current collector 231, an active material layer 232, and an insulating layer 233. The active material layer 232 and the insulating layer 233 are both disposed on at least one surface of the current collector 231 along its thickness direction. The active material layer 232 includes a main region 2321 and a thinned region 2322 arranged along the width direction of the first electrode 23. The thickness of the main region 2321 is greater than the thickness of the thinned region 2322. Along the width direction, at least one end of the main region 2321 is connected to the thinned region 2322, and the insulating layer 233 is in contact with the thinned region 2322. Both the insulating layer 233 and the main body region 2321 contain electrolyte, and the electrolyte retention rate of the insulating layer 233 is greater than that of the main body region 2321.

[0123] Battery cell 20 refers to the smallest unit that makes up battery device 100.

[0124] 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.

[0125] 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 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] Electrode assembly 22 is the component in the battery cell 20 where electrochemical reactions occur. The housing 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 and negative tabs may be located together at one end of the main body 221 or separately 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.

[0130] The electrode assembly 22 includes a positive electrode 224, a separator 225, and a negative electrode 223, which are wound or stacked. In other words, the electrode assembly 22 can be a wound electrode assembly or a stacked electrode assembly.

[0131] The electrolyte comprises an electrolyte salt and a solvent. 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. The solvent may include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. Ether solvents may also be selected. Ether solvents may include one or more of the following: ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, and crown ether.

[0132] The positive electrode 224 mentioned above can be the first electrode 23, or the negative electrode 223 mentioned above can be the first electrode 23, or both the positive electrode 224 and the negative electrode 223 mentioned above can be the first electrode 23.

[0133] When the aforementioned positive electrode 224 is the first electrode 23, the current collector 231 is the positive electrode current collector, and the active material layer 232 is the positive electrode active material layer. The positive electrode active material layer includes a positive electrode active material, which may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for battery cells 20 may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0134] When the aforementioned negative electrode 223 is the first electrode 23, the current collector 231 is the negative electrode current collector, and the active material layer 232 is the negative electrode active material layer. The negative electrode active material layer includes a negative electrode active material, which can be a negative electrode active material known in the art for use in battery cells 20. As an example, the negative electrode active material can 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. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for battery cells 20 can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0135] Insulating layer 233 is an insulating coating. The material of insulating layer 233 can be a polymer or a ceramic.

[0136] Please refer to Figure 6 The thickness direction of the current collector 231 is the X direction shown in the figure.

[0137] The current collector 231 may have an active material layer 232 and an insulating layer 233 disposed on one surface along its thickness direction, or the current collector 231 may have an active material layer 232 and an insulating layer 233 disposed on both surfaces along its thickness direction.

[0138] For wound electrode assemblies, the width direction of the first electrode 23 is generally parallel to the winding axis of the electrode assembly 22. For stacked electrode assemblies, both the width and length directions of the first electrode 23 are perpendicular to the thickness direction of the current collector 231. The width of the first electrode 23 is smaller than its length. Generally, the tab 222 is located at one end of the width direction of the first electrode 23, and the width direction of the first electrode 23 can be determined based on the position of the tab 222. Please refer to... Figure 6 The width direction of the first electrode 23 is the Y direction shown in the figure.

[0139] The active material layer 232 includes a main region 2321 and a thinned region 2322, which are arranged along the width direction of the first electrode 23.

[0140] The main body region 2321 is the main part of the active material layer 232, and it performs the main functions of the active material layer 232. The thinned region 2322 is the thinned portion of the active material layer 232 located at one end of the main body region 2321 along the width direction of the first electrode 23. It should be noted that the thinned region 2322 can be formed by thinning from the side of the active material layer 232 away from the current collector 231, or by thinning from the side of the active material layer 232 facing the current collector 231, or by thinning from both the side of the active material layer 232 away from the current collector 231 and the side of the active material layer 232 facing the current collector 231. Please refer to... Figure 6 To facilitate the distinction between the main body region 2321 and the thinned region 2322, the boundary positions of the main body region 2321 and the thinned region 2322 are shown by dashed lines in the figure. It should be noted that the dashed lines are only for the purpose of distinguishing between the main body region 2321 and the thinned region 2322, and do not represent any other meaning.

[0141] "The thickness of the main body region 2321 is greater than the thickness of the thinned region 2322" means that the minimum thickness of the main body region 2321 is greater than the maximum thickness of the thinned region 2322, or in other words, the thickness of the main body region 2321 at any position is greater than the thickness of the thinned region 2322 at any position. In some embodiments, the thinned region 2322 is connected to only one end of the main body region 2321 along the width direction of the first electrode 23, that is, the thinned region 2322 is only disposed at one end of the main body region 2321 along the width direction of the first electrode 23. In other embodiments, the thinned region 2322 is connected to both ends of the main body region 2321 along the width direction of the first electrode 23, that is, the thinned region 2322 is disposed at both ends of the main body region 2321 along the width direction of the first electrode 23.

[0142] "Contact between insulating layer 233 and thinned area 2322" can mean that insulating layer 233 and thinned area 2322 are arranged side by side and in contact along the width direction, or that a part of insulating layer 233 covers a part of thinned area 2322, thereby making contact between insulating layer 233 and thinned area 2322, or that a part of thinned area 2322 covers a part of insulating layer 233, thereby making contact between insulating layer 233 and thinned area 2322.

[0143] The electrolyte retention rate of insulating layer 233 can be measured by the following methods:

[0144] 1. Disassemble the battery cell 20, remove the first electrode 23, and take a sample from the insulating layer 233 of the first electrode 23;

[0145] 2. Gently absorb the free electrolyte on the sample surface with lint-free paper, then transfer the sample to a 110℃ constant temperature oven to dry for 3 minutes, and then remove the sample.

[0146] 3. Immerse the sample in the electrolyte, which is the electrolyte from the disassembled battery cell 20. Seal and soak the sample in a 25°C room temperature environment for 24 hours to ensure that the sample is completely submerged and no air bubbles adhere to it.

[0147] 4. After soaking, gently absorb the free electrolyte on the surface with lint-free paper, and then place the sample on a clean workbench to air dry. When no liquid droplets seep out from the sample surface, immediately use the original analytical balance to measure the mass, and take the average of five measurements as the mass M1 after liquid absorption;

[0148] 5. Transfer the sample to a 110℃ constant temperature oven and dry for 3 minutes. Take out the sample and measure the mass M2 after drying. The liquid retention rate is (M1-M2) / M2, expressed as a percentage.

[0149] The electrolyte retention rate of the main body region 2321 can be measured by the following methods:

[0150] 1. Disassemble the battery cell 20, remove the first electrode 23, and take a sample from the main body area 2321 of the first electrode 23;

[0151] 2. Gently absorb the free electrolyte on the sample surface with lint-free paper, then transfer the sample to a 110℃ constant temperature oven to dry for 3 minutes, and then remove the sample.

[0152] 3. Immerse the sample in the electrolyte, which is the electrolyte from the disassembled battery cell 20. Seal and soak the sample in a 25°C room temperature environment for 24 hours to ensure that the sample is completely submerged and no air bubbles adhere to it.

[0153] 4. After soaking, gently absorb the free electrolyte on the surface with lint-free paper, and then place the sample on a clean workbench to air dry. When no liquid droplets seep out from the sample surface, immediately use the original analytical balance to measure the mass, and take the average of five measurements as the mass M3 after liquid absorption;

[0154] 5. Transfer the sample to a 110℃ constant temperature oven and dry for 3 minutes. Take out the sample and measure the mass M4 after drying. The liquid retention rate is (M3-M4) / M4, expressed as a percentage.

[0155] By providing an insulating layer 233 on at least one surface of the current collector 231 along its thickness direction, the insulating layer 233 can insulate and isolate the positive and negative electrode plates, reducing the risk of short circuits caused by contact between the positive and negative electrode plates, which is beneficial to improving the reliability of the battery cell 20. By making the electrolyte retention rate of the insulating layer 233 greater than that of the main body region 2321, on the one hand, the insulating layer 233 can act as a "water channel" for the electrolyte. Under capillary action, the electrolyte preferentially and rapidly penetrates along the insulating layer 233, and then actively diffuses into the thinned region 2322 through capillary force, which is beneficial to improving the wetting effect on the thinned region 2322, reducing the risk of lithium plating, and improving the reliability of the battery cell 20. On the other hand, the insulating layer 233 can act as a "reservoir" for the electrolyte. The insulating layer 233 can actively and continuously supply electrolyte to the thinned region 2322, reducing the risk of interface failure caused by electrolyte depletion in the thinned region 2322 during charging and discharging, reducing the risk of lithium plating, and improving the reliability of the battery cell 20. Furthermore, during high-speed charging and discharging, the thinned region 2322 is prone to excessive local electrolyte consumption due to concentrated ion flux. The insulating layer 233 can replenish the electrolyte in the thinned region 2322 through capillary action, maintaining the wettability continuity of the electrode / electrolyte interface, which helps reduce the risk of lithium plating and improves the reliability of the battery cell 20.

[0156] In some embodiments, the insulating layer 233 comprises, by weight percentage: 30-75% inorganic filler, 10-30% adhesive, and 5-30% liquid-retaining material.

[0157] Inorganic fillers include borosilicate, alumina, barium sulfate, silicon dioxide, titanium dioxide, etc.

[0158] Adhesives include polyvinylidene fluoride, styrene-butadiene rubber, polyacrylic acid, and polyvinylidene fluoride-hexafluoropropylene.

[0159] The electrolyte-retaining material can be selected from materials that form a three-dimensional network molecular structure through chemical cross-linking or radiation cross-linking. The material with the three-dimensional cross-linked network molecular structure can serve as a "storage carrier" for the electrolyte. The swelling effect of the network structure enables efficient absorption of the electrolyte, while the mechanical binding effect of the cross-linking points inhibits electrolyte loss. This reduces the problem of increased interfacial impedance caused by electrolyte drying during the cycle of the battery cell 20, and ultimately improves the cycle stability and rate discharge performance of the battery cell 20.

[0160] The insulating layer 233 includes a liquid-retaining material, which can improve the liquid retention rate of the electrolyte, thereby improving the liquid retention rate of the insulating layer 233 for the electrolyte.

[0161] In some embodiments, the liquid-retaining material includes at least one of cross-linked polyvinylidene fluoride, polychlorotrifluoroethylene, fluororubber, fluorinated polyimide, polyimide, and perfluoroalkoxy vinyl ether copolymer.

[0162] Crosslinked polyvinylidene fluoride, polychlorotrifluoroethylene, fluororubber, fluorinated polyimide, polyimide, and perfluoroalkoxy vinyl ether copolymer can resist electrolyte corrosion and have good electrolyte retention capacity, which can effectively improve the electrolyte retention capacity of insulation layer 233.

[0163] In some embodiments, the liquid retention rate of the insulating layer 233 is 22% to 25%.

[0164] The liquid retention rate of the insulating layer 233 can be: 22%, 22.2%, 22.5%, 22.8%, 23%, 23.2%, 23.5%, 23.8%, 24%, 24.2%, 24.5%, 24.8%, 25%, etc.

[0165] When the liquid retention rate of the insulating layer 233 is greater than or equal to 22%, the liquid retention rate of the insulating layer 233 is relatively high. On the one hand, this is beneficial to improving the electrolyte drainage effect of the insulating layer 233, improving the wetting effect of the thinned region 2322, reducing the risk of lithium plating, and improving the reliability of the battery cell 20. On the other hand, the insulating layer 233 can store more electrolyte, which is beneficial to improving the liquid replenishment effect of the insulating layer 233, reducing the risk of lithium plating, and improving the reliability of the battery cell 20. When the liquid retention rate of the insulating layer 233 is less than or equal to 25%, the liquid retention rate of the insulating layer 233 is not too high, so that the volume occupied by the insulating layer 233 is not too large, which is beneficial to improving the energy density of the battery cell 20. Therefore, when the liquid retention rate of the insulating layer 233 is 22%~25%, the reliability and energy density of the battery cell 20 can be balanced.

[0166] Please refer to Figure 6 and Figure 7 , Figure 7 This is a cross-sectional view of a first electrode 23 provided for other embodiments of this application. In some embodiments, the thinned region 2322 includes a first surface 23221 having a first end 232211 and a second end 232212. Along the width direction, the first end 232211 is further away from the body region 2321 than the second end 232212, and the first end 232211 is located at the position of the thinned region 2322 furthest from the body region 2321. Along the thickness direction, the second end 232212 is further away from the current collector 231 than the first end 232211. An insulating layer 233 covers at least a portion of the first surface 23221.

[0167] The first end 232211 and the second end 232212 are the two ends of the first surface 23221, respectively. The first end 232211 is the position of the thinned area 2322 furthest from the main body area 2321 along the width direction. The distance between the second end 232212 and the main body area 2321 along the width direction is less than the distance between the first end 232211 and the main body area 2321 along the width direction. In other words, the second end 232212 is closer to the main body area 2321 along the width direction than the first end 232211. The distance between the second end 232212 and the current collector 231 along the thickness direction is greater than the distance between the first end 232211 and the current collector 231 along the thickness direction. In other words, the second end 232212 is farther from the current collector 231 along the thickness direction than the first end 232211.

[0168] Please refer to Figure 6 ,exist Figure 6 In the embodiment shown, the first surface 23221 connects the surface of the current collector 231 and the surface of the main body region 2321 that is away from the current collector 231. At this time, the end of the first surface 23221 that is connected to the current collector 231 is the first end 232211, and the end of the first surface 23221 that is connected to the surface of the main body region 2321 that is away from the current collector 231 is the second end 232212.

[0169] Please refer to Figure 7 ,exist Figure 7 In the embodiment shown, the first surface 23221 is the surface of the thinned region 2322 that is away from the current collector 231. The position of the first surface 23221 that is furthest away from the main body region 2321 along the width direction is the first end 232211. The end of the first surface 23221 that is connected to the surface of the main body region 2321 that is away from the current collector 231 is the second end 232212.

[0170] The insulating layer 233 may cover only a portion of the first surface 23221, or the insulating layer 233 may completely cover the first surface 23221.

[0171] By covering at least a portion of the first surface 23221 with the insulating layer 233, lithium ions can be transported through the insulating layer 233, which helps to shorten the ion path and reduce the risk of lithium plating.

[0172] Please refer to Figure 7 In some embodiments, a portion of the insulating layer 233 is located between the thinned region 2322 and the current collector 231.

[0173] Along the thickness direction, a portion of the insulating layer 233 is disposed between the thinned region 2322 and the current collector 231 and is in contact with the thinned region 2322. The thinned region 2322 may be partially in contact with the current collector 231, or the thinned region 2322 may be completely separated by the insulating layer 233 and not in contact with the current collector 231.

[0174] Since the side of the thinned region 2322 facing the current collector 231 is relatively more difficult to wet, by placing a portion of the insulating layer 233 between the thinned region 2322 and the current collector 231, the electrolyte can actively diffuse from the portion of the insulating layer 233 between the thinned region 2322 and the current collector 231 to the thinned region 2322 through capillary force, thereby further improving the wetting effect on the thinned region 2322, reducing the risk of lithium plating, and improving the reliability of the battery cell 20.

[0175] Please refer to Figure 7 In some embodiments, the insulating layer 233 includes a first portion 2331 and a second portion 2332 connected together, the first portion 2331 and the second portion 2332 arranged along the width direction, the first portion 2331 located on the side of the second portion 2332 facing away from the body region 2321. Along the thickness direction, the first portion 2331 has a second surface 23311 facing away from the current collector 231, and a portion of the second portion 2332 protrudes from the second surface 23311. The second portion 2332 covers at least a portion of the first surface 23221, and a portion of the second portion 2332 is located between the thinned region 2322 and the current collector 231.

[0176] The first part 2331 and the second part 2332 are two portions of the insulating layer 233 arranged along its width. The second part 2332 is disposed between the first part 2331 and the main body region 2321 along the width direction from the current collector 231 to the active material layer 232. A portion of the second part 2332 protrudes from the surface of the first part 2331 away from the current collector 231, that is, along the direction from the current collector 231 to the active material layer 232, a portion of the second part 2332 protrudes from the second surface 23311. Please refer to... Figure 7 To facilitate the distinction between the first part 2331 and the second part 2332, a dashed line is used in the diagram to indicate the boundary between them. It should be noted that the dashed line is solely for distinguishing between the first part 2331 and the second part 2332 and does not represent any other meaning.

[0177] A portion of the second part 2332 covers at least a portion of the first surface 23221, and another portion of the second part 2332 is located between the thinned region 2322 and the current collector 231. It should be noted that the other portion of the second part 2332 refers to a portion of the second part 2332 that is different from the portion of the second part 2332 that covers the first surface 23221, and not the remaining portion of the second part 2332 other than the portion that covers the first surface 23221. Please refer to... Figure 7The second part 2332 includes a portion covering the first surface 23221, a portion located between the thinned area 2322 and the current collector 231, and a portion connecting the two parts and the first part 2331.

[0178] The second portion 2332 can cover at least a portion of the first surface 23221, and a part of the second portion 2332 is located between the thinned region 2322 and the current collector 231, which is beneficial to improving the wetting effect of the thinned region 2322, shortening the ion path, and reducing the risk of lithium plating. The presence of the first portion 2331 can, on the one hand, insulate and isolate the positive and negative electrode sheets, reducing the risk of short circuits caused by contact between the positive and negative electrode sheets, which is beneficial to improving the reliability of the battery cell 20. On the other hand, the connection between the first portion 2331 and the current collector 231 is relatively more robust, and the connection between the first portion 2331 and the second portion 2332 helps to maintain the relative position of the second portion 2332 and the thinned region 2322.

[0179] Please refer to Figure 7 In some embodiments, the electrode assembly 22 includes a first tab 2221 disposed at one end of the current collector 231 along the width direction, and a first portion 2331 covers a portion of the first tab 2221.

[0180] When the first electrode 23 is the positive electrode 224, the first electrode tab 2221 is the positive electrode tab. When the first electrode 23 is the negative electrode 223, the first electrode tab 2221 is the negative electrode tab. Please refer to... Figure 7 The portion of the current collector 231 not covered by the active material layer 232 constitutes the first tab 2221, which is disposed at one end of the current collector 231 along the width direction of the first electrode 23.

[0181] By covering a portion of the first tab 2221 with the first part 2331, it is beneficial to reduce the risk that when the first tab 2221 is folded, the burrs on the first tab 2221 will puncture the separator 225, causing the positive electrode 224 and the negative electrode 223 to come into contact and short circuit, which is beneficial to improving the reliability of the battery cell 20.

[0182] Please refer to Figure 7 In some embodiments, along the thickness direction, the thickness of the first part 2331 is H1, and the thickness of the main body region 2321 is H, satisfying: 0.01≤H1 / H≤0.15.

[0183] H1 represents the thickness of the first part 2331 along the thickness direction. During measurement, multiple measurements can be taken and the average value can be used as H1. Alternatively, a cross-sectional image can be captured using a scanning electron microscope, and H1 can be obtained by measuring it using software.

[0184] H represents the thickness of the main body region 2321 along the thickness direction. During measurement, multiple measurements can be taken and the average value can be used as H. Alternatively, a cross-sectional image can be captured using a scanning electron microscope, and H can be obtained by measuring it using software.

[0185] H1 / H represents the ratio of the thickness of the first part 2331 along the thickness direction to the thickness of the main body region 2321 along the thickness direction.

[0186] H1 / H can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, etc.

[0187] When H1 / H ≥ 0.01, the thickness of the first part 2331 is relatively large, which helps to cover the burrs on the first tab 2221 and reduces the risk of a short circuit caused by the burrs on the first tab 2221 piercing the separator 225 when the first tab 2221 is bent. When H1 / H ≤ 0.15, the thickness of the first part 2331 is not too large, which facilitates the cutting of the tab 222.

[0188] Please refer to Figure 7 In some embodiments, the thickness of the first portion 2331 along the thickness direction is H1, satisfying: 0.5μm≤H1≤70μm.

[0189] H1 can be 0.5μm, 1μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, etc.

[0190] When H1 ≥ 0.5 μm, the thickness of the first part 2331 is relatively large, which helps to cover the burrs on the first tab 2221 and reduces the risk of short circuit caused by the burrs on the first tab 2221 piercing the separator 225 when the first tab 2221 is folded. When H1 ≤ 70 μm, the thickness of the first part 2331 is not too large, which facilitates the cutting of the tab 222.

[0191] Please refer to Figure 7 In some embodiments, the second portion 2332 includes a first region 23322 located between the thinning region 2322 and the current collector 231. Along the thickness direction, the maximum dimension of the first region 23322 is H2, and the thickness of the main body region 2321 is H, satisfying: 0.05≤H2 / H≤0.3.

[0192] The first region 23322 is the portion of the second part 2332 located between the thinned region 2322 and the current collector 231. H2 represents the maximum dimension of the first region 23322 along the thickness direction. The thickness of the first region 23322 can be uniform; in this case, the thickness at any location of the first region 23322 can be measured as H2. The thickness of the first region 23322 can also vary; in this case, the thickness at the location with the maximum thickness of the first region 23322 can be measured as H2. A cross-sectional image can be captured using a scanning electron microscope, and H2 can be obtained by measuring it using software.

[0193] H2 / H represents the ratio of the maximum dimension of the first region 23322 along the thickness direction to the thickness of the main body region 2321 along the thickness direction.

[0194] H2 / H can be taken as: 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, etc.

[0195] When H2 / H ≥ 0.05, the maximum size of the first region 23322 along the thickness direction is larger, which facilitates the active diffusion of electrolyte from the portion of the insulating layer 233 located between the thinned region 2322 and the current collector 231 to the thinned region 2322 via capillary force. This further enhances the wetting effect on the thinned region 2322, reduces the risk of lithium plating, and improves the reliability of the battery cell 20. When H2 / H ≤ 0.3, the maximum size of the first region 23322 along the thickness direction is not too large, ensuring that the volume occupied by the first region 23322 is not too large, which is beneficial to improving the energy density of the battery cell 20. Therefore, when 0.05 ≤ H2 / H ≤ 0.3, both the reliability and energy density of the battery cell 20 can be balanced.

[0196] Please refer to Figure 7 In some embodiments, 2μm≤H2≤40μm.

[0197] H2 can be in the following sizes: 2μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 35μm, 38μm, 40μm, etc.

[0198] When H2 ≥ 2 μm, the maximum size of the first region 23322 along the thickness direction is relatively large, which facilitates the active diffusion of electrolyte from the portion of the insulating layer 233 located between the thinned region 2322 and the current collector 231 to the thinned region 2322 via capillary force. This further enhances the wetting effect on the thinned region 2322, reduces the risk of lithium plating, and improves the reliability of the battery cell 20. When H2 ≤ 40 μm, the maximum size of the first region 23322 along the thickness direction is not too large, ensuring that the volume occupied by the first region 23322 is not too large, which is beneficial to improving the energy density of the battery cell 20. Therefore, when 2 μm ≤ H2 ≤ 40 μm, both the reliability and energy density of the battery cell 20 can be balanced.

[0199] Please refer to Figure 7 In some embodiments, the second portion 2332 includes a first region 23322 located between the thinning region 2322 and the current collector 231. The maximum size of the first region 23322 is W1 along the width direction, and the maximum size of the active material layer 232 is W, satisfying: 0.05≤W1 / W≤0.25.

[0200] W1 represents the maximum dimension of the first region 23322 along the width direction. W1 can be obtained by taking a cross-sectional image using a scanning electron microscope and measuring it using software.

[0201] W represents the maximum dimension of the active material layer 232 along the width direction, which is the distance between the first end 232211 along the width direction and the position of the active material layer 232 furthest from the first end 232211. W can be obtained by taking a cross-sectional image with a scanning electron microscope and measuring it with software.

[0202] W1 / W represents the ratio of the maximum dimension of the first region 23322 along the width direction to the maximum dimension of the active material layer 232 along the width direction.

[0203] W1 / W can be: 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.013, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, etc.

[0204] When W1 / W ≥ 0.05, the maximum dimension of the first region 23322 along the width direction is relatively large, which helps to increase the contact area between the first region 23322 and the thinned region 2322. This facilitates the active diffusion of electrolyte from the portion of the insulating layer 233 located between the thinned region 2322 and the current collector 231 to the thinned region 2322 via capillary force, thereby further improving the wetting effect on the thinned region 2322, reducing the risk of lithium plating, and improving the reliability of the battery cell 20. When W1 / W ≤ 0.25, the maximum dimension of the first region 23322 along the width direction is not too large, ensuring that the volume occupied by the first region 23322 is not too large, which helps to improve the energy density of the battery cell 20. Therefore, when 0.05 ≤ W1 / W ≤ 0.25, both the reliability and energy density of the battery cell 20 can be balanced.

[0205] Please refer to Figure 7 In some embodiments, 0.1mm ≤ W1 ≤ 15mm.

[0206] W1 can be in the following sizes: 0.1mm, 0.5mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, etc.

[0207] When W1 ≥ 0.1 mm, the maximum dimension of the first region 23322 along the width direction is relatively large, which helps to increase the contact area between the first region 23322 and the thinned region 2322. This facilitates the active diffusion of electrolyte from the portion of the insulating layer 233 located between the thinned region 2322 and the current collector 231 to the thinned region 2322 via capillary force, thereby further improving the wetting effect on the thinned region 2322, reducing the risk of lithium plating, and improving the reliability of the battery cell 20. When W1 / W ≤ 0.25, the maximum dimension of the first region 23322 along the width direction is not too large, ensuring that the volume occupied by the first region 23322 is not too large, which helps to improve the energy density of the battery cell 20. Therefore, when 0.1 mm ≤ W1 ≤ 15 mm, both the reliability and energy density of the battery cell 20 can be balanced.

[0208] Please refer to Figure 7 In some embodiments, the second portion 2332 includes a third surface 23321, through which the second surface 23311 transitions to the first surface 23221. Along the thickness direction, the maximum distance between the third surface 23321 and the surface of the current collector 231 facing the second portion 2332 is H3, and the thickness of the main body region 2321 is H, satisfying: 0.4 ≤ H3 / H ≤ 1.

[0209] The third surface 23321 is the surface of the second part 2332 that connects the second surface 23311 and the first surface 23221, that is, the surface of the second part 2332 that faces away from the current collector 231. Specifically, please refer to... Figure 7 ,exist Figure 7 In the embodiment shown, when the second part 2332 completely covers the first surface 23221, the third surface 23321 connects the second surface 23311 and the second end 232212 of the first surface 23221. At this time, it can also be considered that the third surface 23321 connects the second surface 23311 and the surface of the main body area 2321 away from the current collector 231.

[0210] H3 represents the maximum distance along the thickness direction between the third surface 23321 and the surface of the current collector 231 facing the second part 2332. H3 can be obtained by taking a cross-sectional image with a scanning electron microscope and measuring it with software.

[0211] H3 / H represents the ratio of the maximum distance between the third surface 23321 along the thickness direction and the surface of the current collector 231 facing the second part 2332 to the thickness of the main body region 2321 along the thickness direction.

[0212] H3 / H can be taken as: 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, etc.

[0213] When H3 / H ≥ 0.4, the maximum distance between the third surface 23321 and the surface of the current collector 231 facing the second part 2332 along the thickness direction is relatively large, which is beneficial for lithium ions to be transported through the insulating layer 233, shortening the ion path and reducing the risk of lithium plating. When H3 / H ≤ 1, the maximum distance between the third surface 23321 and the surface of the current collector 231 facing the second part 2332 along the thickness direction is not too large, so that the insulating layer 233 does not extend beyond the surface of the main region 2321 away from the current collector 231 in the direction from the current collector 231 to the active material layer 232. This is beneficial for reducing the distance between the main region 2321 and the other electrode (when the first electrode 23 is the positive electrode 224, the other electrode is the negative electrode 223; when the first electrode 23 is the negative electrode 223, the other electrode is the positive electrode 224), thereby shortening the ion path and reducing the risk of lithium plating.

[0214] Please refer to Figure 7 In some embodiments, the thinned region 2322 includes a fourth surface 23222, one end of which is connected to the first end 232211, and the other end of which extends to the surface of the current collector 231 facing the active material layer 232. An insulating layer 233 covers the fourth surface 23222.

[0215] One end of the fourth surface 23222 is connected to the first end 232211, and the other end of the fourth surface 23222 is connected to the surface of the current collector 231 facing the active material layer 232. In other words, the first surface 23221 transitions to the surface of the current collector 231 facing the active material layer 232 through the fourth surface 23222.

[0216] The insulating layer 233 may cover a portion of the fourth surface 23222, or it may completely cover the fourth surface 23222. Please refer to [reference needed]. Figure 7 ,exist Figure 7 In the embodiment shown, the insulating layer 233 completely covers the fourth surface 23222.

[0217] By covering the fourth surface 23222 with the insulating layer 233, the contact area between the insulating layer 233 and the thinned region 2322 is increased. On the one hand, this facilitates the diffusion of electrolyte from the insulating layer 233 to the thinned region 2322, thereby further improving the wetting effect on the thinned region 2322, reducing the risk of lithium plating, and improving the reliability of the battery cell 20. On the other hand, the insulating layer 233 can better and continuously supply electrolyte to the thinned region 2322, reducing the risk of interface failure in the thinned region 2322 due to electrolyte depletion during charging and discharging, reducing the risk of lithium plating, and thus improving the reliability of the battery cell 20.

[0218] Please refer to Figure 7 In some embodiments, along the direction from the current collector 231 to the active material layer 232, the insulating layer 233 does not extend beyond the surface of the main body region 2321 away from the current collector 231.

[0219] "In the direction from the current collector 231 to the active material layer 232, the insulating layer 233 does not extend beyond the main body region 2321 and away from the surface of the current collector 231." That is, the insulating layer 233 does not extend beyond the main body region 2321 and away from the surface of the current collector 231 in the direction from the current collector 231 to the active material layer 232.

[0220] By ensuring that the insulating layer 233 does not extend beyond the surface of the main region 2321 away from the current collector 231 in the direction from the current collector 231 toward the active material layer 232, it is beneficial to reduce the distance between the main region 2321 and the other electrode (when the first electrode 23 is the positive electrode 224, the other electrode is the negative electrode 223; when the first electrode 23 is the negative electrode 223, the other electrode is the positive electrode 224), thereby shortening the ion path and reducing the risk of lithium plating.

[0221] Please refer to Figure 8 , Figure 8This is a cross-sectional view of a first electrode 23 provided for some embodiments of this application. In some embodiments, the active material layer 232 includes a transition region 2323, at least a portion of which is located in the thinned region 2322. The material of the transition region 2323 includes the material of the insulating layer 233 and the material of the active material layer 232.

[0222] The material of the transition region 2323 includes the material of the insulating layer 233 and the material of the active material layer 232. The transition region 2323 can be entirely located in the thinned region 2322, or part of the transition region 2323 can be located in the thinned region 2322 and another part in the main body region 2321. The specific part belonging to the transition region 2323 can be determined based on the different materials used. For example, a scanning electron microscope can be used to observe and determine which part belongs to the transition region 2323.

[0223] By setting a transition region 2323, the materials of the transition region 2323 include the materials of the insulating layer 233 and the active material layer 232. Among them, the material of the insulating layer 233 has a high electrolyte retention rate, which is beneficial to improving the electrolyte retention rate of the transition region 2323. On the one hand, it is beneficial to further improve the wetting effect on the thinned region 2322.

[0224] Please refer to Figure 8 In some embodiments, the transition region 2323 includes a second region 23231 and a third region 23232 connected together, with the second region 23231 located in the thinning region 2322 and the third region 23232 located in the main body region 2321.

[0225] The second region 23231 is the part of the transition layer located in the thinning region 2322, and the third region 23232 is the part of the transition layer located in the main region 2321. The materials of the second region 23231 and the third region 23232 both include the material of the insulating layer 233 and the material of the active material layer 232.

[0226] By placing a portion of the transition region 2323 in the thinning region 2322 and another portion in the main region 2321, the wetting effect on both the thinning region 2322 and the main region 2321 is improved. This helps reduce the risk of lithium plating and improves the reliability of the battery cell 20. Furthermore, the electrolyte stored in the transition region 2323 can also supply electrolyte to the main region 2321 and the thinning region 2322, reducing the risk of interface failure due to electrolyte depletion during charging and discharging, thus reducing the risk of lithium plating and improving the reliability of the battery cell 20.

[0227] In some embodiments, the first electrode 23 is a positive electrode 224.

[0228] When the first electrode 23 is the positive electrode 224, the insulating layer 233 can protect the thinned region 2322. When lithium plating occurs on the negative electrode 223, it prevents lithium dendrites from contacting the thinned region 2322 and causing a short circuit, thus improving the reliability of the battery cell 20. Furthermore, in embodiments where a portion of the insulating layer 233 is located between the thinned region 2322 and the current collector 231, this portion replaces a portion of the active material layer 232, thereby reducing the capacity of the thinned region 2322, increasing the CB value, reducing the risk of lithium plating, and improving the reliability of the battery cell 20.

[0229] This application embodiment also provides a battery device 100, which includes the aforementioned battery cell 20.

[0230] 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.

[0231] According to some embodiments of this application, please refer to Figures 3-8 .

[0232] This application provides a battery cell 20, which includes a casing 21, an electrode assembly 22, and an electrolyte. The electrode assembly 22 and the electrolyte are housed within the casing 21. The electrode assembly 22 includes a first electrode 23, which includes a current collector 231, an active material layer 232, and an insulating layer 233. The active material layer 232 and the insulating layer 233 are both disposed on at least one surface of the current collector 231 along its thickness direction. The active material layer 232 includes a main region 2321 and a thinned region 2322 arranged along the width direction of the first electrode 23. The thickness of the main region 2321 is greater than the thickness of the thinned region 2322. Along the width direction, at least one end of the main region 2321 is connected to the thinned region 2322, and the insulating layer 233 is in contact with the thinned region 2322. Both the insulating layer 233 and the main body region 2321 store electrolyte. The electrolyte retention rate of the insulating layer 233 is greater than that of the main body region 2321. By providing the insulating layer 233 on at least one surface of the current collector 231 along its thickness direction, the insulating layer 233 can insulate and isolate the positive and negative electrode plates, reducing the risk of short circuits caused by contact between the positive and negative electrode plates, which is beneficial to improving the reliability of the battery cell 20. By making the electrolyte retention rate of the insulating layer 233 greater than that of the main body region 2321, on the one hand, the insulating layer 233 can act as a "water channel" for the electrolyte. Under capillary action, the electrolyte preferentially and rapidly penetrates along the insulating layer 233, and then actively diffuses into the thinned region 2322 through capillary force, which is beneficial to improving the wetting effect on the thinned region 2322, reducing the risk of lithium plating, and improving the reliability of the battery cell 20. On the other hand, the insulating layer 233 can act as a "reservoir" for the electrolyte. The insulating layer 233 can actively and continuously supply electrolyte to the thinned region 2322, reducing the risk of interface failure due to electrolyte depletion during charging and discharging, thus reducing the risk of lithium plating and improving the reliability of the battery cell 20. Furthermore, during high-speed charging and discharging, the thinned region 2322 is prone to excessively rapid local electrolyte consumption due to concentrated ion flux. The insulating layer 233 can replenish electrolyte in the thinned region 2322 through capillary action, maintaining the wettability continuity of the electrode / electrolyte interface, which helps reduce the risk of lithium plating and improves the reliability of the battery cell 20.

[0233] The insulating layer 233 comprises, by weight percentage: 30-75% inorganic filler, 10-30% binder, and 5-30% electrolyte retention material. The electrolyte retention material in the insulating layer 233 enhances the electrolyte retention rate, thereby improving the electrolyte retention rate of the insulating layer 233.

[0234] The electrolyte-retaining material includes at least one of cross-linked polyvinylidene fluoride, polychlorotrifluoroethylene, fluororubber, fluorinated polyimide, polyimide, and perfluoroalkoxy vinyl ether copolymer. Cross-linked polyvinylidene fluoride, polychlorotrifluoroethylene, fluororubber, fluorinated polyimide, polyimide, and perfluoroalkoxy vinyl ether copolymer exhibit both resistance to electrolyte corrosion and good electrolyte retention capacity, effectively enhancing the electrolyte retention capacity of insulation layer 233.

[0235] The electrolyte retention rate of the insulating layer 233 is 22%~25%. When the electrolyte retention rate of the insulating layer 233 is greater than or equal to 22%, the higher retention rate is beneficial. On the one hand, it improves the electrolyte drainage effect of the insulating layer 233, enhances the wetting effect of the thinned region 2322, reduces the risk of lithium plating, and improves the reliability of the battery cell 20. On the other hand, the insulating layer 233 can store more electrolyte, which improves the electrolyte replenishment effect of the insulating layer 233, reduces the risk of lithium plating, and improves the reliability of the battery cell 20. When the electrolyte retention rate of the insulating layer 233 is less than or equal to 25%, the retention rate is not too high, so the volume occupied by the insulating layer 233 is not too large, which helps to improve the energy density of the battery cell 20. Therefore, when the electrolyte retention rate of the insulating layer 233 is 22%~25%, both the reliability and energy density of the battery cell 20 can be balanced.

[0236] The thinned region 2322 includes a first surface 23221, which has a first end 232211 and a second end 232212. Along the width direction, the first end 232211 is further away from the main region 2321 than the second end 232212, and is located at the position in the thinned region 2322 furthest from the main region 2321. Along the thickness direction, the second end 232212 is further away from the current collector 231 than the first end 232211. An insulating layer 233 covers at least a portion of the first surface 23221. A portion of the insulating layer 233 is located between the thinned region 2322 and the current collector 231. By covering at least a portion of the first surface 23221 with the insulating layer 233, lithium ions can be transported through the insulating layer 233, which helps to shorten the ion path and reduce the risk of lithium plating. Since the side of the thinned region 2322 facing the current collector 231 is relatively more difficult to wet, by placing a portion of the insulating layer 233 between the thinned region 2322 and the current collector 231, the electrolyte can actively diffuse from the portion of the insulating layer 233 between the thinned region 2322 and the current collector 231 to the thinned region 2322 through capillary force, thereby further improving the wetting effect on the thinned region 2322, reducing the risk of lithium plating, and improving the reliability of the battery cell 20.

[0237] The active material layer 232 includes a transition region 2323, at least a portion of which is located in the thinned region 2322. The material of the transition region 2323 includes the material of the insulating layer 233 and the material of the active material layer 232. By providing the transition region 2323, whose material includes both the insulating layer 233 and the active material layer 232, the insulating layer 233 exhibits a higher electrolyte retention rate, thereby improving the electrolyte retention rate of the transition region 2323. This also helps to further enhance the wetting effect on the thinned region 2322.

[0238] The first electrode 23 is the positive electrode 224. When the first electrode 23 is the positive electrode 224, the insulating layer 233 can protect the thinned region 2322. When lithium plating occurs on the negative electrode 223, it prevents lithium dendrites from contacting the thinned region 2322 and causing a short circuit, which is beneficial to improving the reliability of the battery cell 20. In addition, in the embodiment where a portion of the insulating layer 233 is located between the thinned region 2322 and the current collector 231, the portion of the insulating layer 233 located between the thinned region 2322 and the current collector 231 replaces a portion of the active material layer 232, thereby reducing the capacity of the thinned region 2322, increasing the CB value, which is beneficial to reducing the risk of lithium plating and improving the reliability of the battery cell 20.

[0239] 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; An electrode assembly is housed within the housing. The electrode assembly includes a first electrode sheet, which includes a current collector, an active material layer, and an insulating layer. The active material layer and the insulating layer are both disposed on at least one surface of the current collector along its thickness direction. The active material layer includes a main body region and a thinned region arranged along the width direction of the first electrode sheet. The thickness of the main body region is greater than the thickness of the thinned region. Along the width direction, at least one end of the main body region is connected to the thinned region. The insulating layer is in contact with the thinned region, and a portion of the insulating layer is located between the thinned region and the current collector. An electrolyte is contained within the outer casing, and both the insulating layer and the main body region store the electrolyte. The electrolyte retention rate of the insulating layer is greater than that of the main body region. The insulating layer comprises, by weight percentage: 30-75% inorganic filler, 10-30% adhesive, and 5-30% liquid-retaining material, wherein the liquid-retaining material is a material with a three-dimensional cross-linked network molecular structure.

2. The battery cell according to claim 1, characterized in that, The liquid-retaining material includes at least one of cross-linked polyvinylidene fluoride, polychlorotrifluoroethylene, fluororubber, polyimide, and perfluoroalkoxy vinyl ether copolymer.

3. The battery cell according to claim 1, characterized in that, The liquid retention rate of the insulating layer is 22%~25%.

4. The battery cell according to claim 1, characterized in that, The thinned region includes a first surface having a first end and a second end. Along the width direction, the first end is further away from the main body region than the second end. The first end is located at the position of the thinned region furthest from the main body region. Along the thickness direction, the second end is further away from the current collector than the first end. The insulating layer covers at least a portion of the first surface.

5. The battery cell according to claim 4, characterized in that, The insulating layer includes a first portion and a second portion connected together, the first portion and the second portion being arranged along the width direction, the first portion being located on the side of the second portion away from the main body region, the first portion having a second surface away from the current collector along the thickness direction, a portion of the second portion protruding from the second surface, the second portion covering at least a portion of the first surface, and a portion of the second portion being located between the thinned region and the current collector.

6. The battery cell according to claim 5, characterized in that, The electrode assembly includes a first tab, which is disposed at one end of the current collector along the width direction, and the first portion covers a portion of the first tab.

7. The battery cell according to claim 5, characterized in that, Along the thickness direction, the thickness of the first part is H1, and the thickness of the main body region is H, satisfying: 0.01≤H1 / H≤0.

15.

8. The battery cell according to claim 5, characterized in that, Along the thickness direction, the thickness of the first portion is H1, which satisfies: 0.5μm≤H1≤70μm.

9. The battery cell according to claim 5, characterized in that, The second part includes a first region located between the thinning region and the current collector. Along the thickness direction, the maximum dimension of the first region is H2, and the thickness of the main body region is H, satisfying: 0.05≤H2 / H≤0.

3.

10. The battery cell according to claim 9, characterized in that, 2μm≤H2≤40μm.

11. The battery cell according to claim 5, characterized in that, The second part includes a first region located between the thinned region and the current collector. Along the width direction, the maximum size of the first region is W1, and the maximum size of the active material layer is W, satisfying: 0.05≤W1 / W≤0.

25.

12. The battery cell according to claim 11, characterized in that, 0.1mm≤W1≤15mm.

13. The battery cell according to claim 5, characterized in that, The second part includes a third surface, through which the second surface transitions to the first surface. Along the thickness direction, the maximum distance between the third surface and the surface of the current collector facing the second part is H3, and the thickness of the main body region is H, satisfying: 0.4≤H3 / H≤1.

14. The battery cell according to claim 4, characterized in that, The thinned region includes a fourth surface, one end of which is connected to the first end, and the other end of which extends to the surface of the current collector facing the active material layer, and the insulating layer covers the fourth surface.

15. The battery cell according to any one of claims 1-14, characterized in that, Along the direction from the current collector to the active material layer, the insulating layer does not extend beyond the surface of the main body region away from the current collector.

16. The battery cell according to any one of claims 1-14, characterized in that, The active material layer includes a transition region, at least a portion of which is located in the thinned region, and the material of the transition region includes the material of the insulating layer and the material of the active material layer.

17. The battery cell according to claim 16, characterized in that, The transition zone includes a second zone and a third zone connected together, the second zone being located in the thinning zone and the third zone being located in the main body zone.

18. The battery cell according to any one of claims 1-14, characterized in that, The first electrode is a positive electrode.

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

20. An electrical appliance, characterized in that, Includes a battery cell according to any one of claims 1-18, the battery cell being used to provide electrical energy to the electrical device.

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