Cathode sheet, battery cell, and battery

Abstract

The utility model discloses a kind of cathode sheet, battery cell and battery, comprising: cathode current collector, cathode active material and first adhesive layer.Cathode current collector includes first surface and second surface opposite along cathode sheet thickness direction;Cathode active material includes first active material layer and second active material layer, first active material layer is set to first surface, and second active material layer is set to second surface;First adhesive layer is connected to first active material layer, and first active material layer is fully covered along the width direction of pole piece, and the cavity of avoidance is formed between first adhesive layer and cathode current collector;When cathode sheet is used to be wound to form battery cell with anode sheet and separator, at least part of the cavity of avoidance is located in the inside of the corner of the innermost layer of cathode sheet.Reduce the corner of the innermost layer of cathode current collector, thereby reduce the risk of deformation of cathode current collector towards second surface, and then reduce the risk of fracture of second active material layer located in the back side of corner, to improve the performance of battery.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a cathode sheet, a battery cell, and a battery. Background Technology

[0002] In some technologies, to reduce the risk of lithium plating on the anode surface, adhesive is typically applied to the inner side of the innermost corner of the cathode sheet to prevent lithium ions from migrating towards the anode. However, because the adhesive layer adheres to the cathode active material, the active material at the corner cannot move along the length or width of the cathode sheet when compressed during cell winding. Therefore, during winding, the cathode active material compresses the cathode current collector towards the thickness direction of the cathode sheet, causing the cathode current collector to deform away from the corner. This can easily lead to breakage of the active material on the back side of the corner, resulting in reduced battery performance. Utility Model Content

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a cathode sheet that can reduce the risk of breakage of the cathode active material on the back side of the innermost corner, thereby improving battery performance.

[0004] This invention also provides a battery cell comprising the aforementioned cathode sheet.

[0005] This utility model also provides a battery including the above-mentioned battery cell.

[0006] A cathode sheet according to a first aspect of the present invention includes: a cathode current collector, a cathode active material, and a first adhesive layer. The cathode current collector includes a first surface and a second surface facing away from each other along the thickness direction of the cathode sheet; the cathode active material includes a first active material layer and a second active material layer, the first active material layer being disposed on the first surface and the second active material layer being disposed on the second surface; the first adhesive layer is connected to the first active material layer and completely covers the first active material layer along the width direction of the cathode sheet, and a cavity is defined between the first active material layer and the cathode current collector, the first adhesive layer being capable of preventing lithium ion movement; wherein, when the cathode sheet is used to be wound together with an anode sheet and a separator to form a battery cell, at least a portion of the cavity is located inside the innermost curved section of the cathode sheet.

[0007] The cathode sheet according to the embodiments of this utility model has at least the following beneficial effects:

[0008] In this embodiment, a cavity is defined between the first adhesive layer and the cathode current collector. When the cathode sheet, anode sheet, and separator of this embodiment are wound together to form a battery cell, the cavity is set inside the corner of the innermost layer of the cathode sheet to reduce the compressive force at the corner of the innermost layer of the cathode current collector, thereby reducing the risk of deformation of the current collector toward the second surface, and further reducing the risk of breakage of the second active material layer located on the back side of the corner, so as to improve the performance of the battery.

[0009] According to some embodiments of the present invention, the first adhesive layer has a first cavitation groove on the side facing the cathode current collector, and the inner wall of the first cavitation groove and the first active material layer together define the cavitation cavity.

[0010] According to some embodiments of the present invention, the first active material layer has a second void groove, the first adhesive layer is connected to the first active material layer and covers the second void groove, and the first adhesive layer and the inner wall of the second void groove together define the void cavity.

[0011] According to some embodiments of the present invention, along the direction from the first adhesive layer to the cathode current collector, the second void groove includes a first groove portion and a second groove portion that are interconnected. Along the length direction of the cathode sheet, the size of the first groove portion is larger than the size of the second groove portion. The first groove portion includes a first sub-groove portion and two second sub-groove portions located on both sides of the first sub-groove portion. In the thickness direction of the cathode sheet, the first sub-groove portion and the second groove portion are aligned, and the second sub-groove portion and the second groove portion are offset. The first adhesive layer includes two connecting portions on both sides of the length direction of the cathode sheet. The connecting portions are connected to the inner wall of the first sub-groove portion. In the thickness direction of the electrode sheet, the distance between the surface of the connecting portion away from the cathode current collector and the surface of the first active material around the second void groove away from the cathode current collector is less than or equal to 8 μm.

[0012] According to some embodiments of the present invention, along the thickness direction of the cathode sheet, the size of the second void groove is H1, the size of the first active material layer is H2, and the value of H1 / H2 ranges from 30% to 90%.

[0013] According to some embodiments of the present invention, the cathode sheet further includes a second adhesive layer, the second adhesive layer having pores through which lithium ions can pass, the second adhesive layer being connected to the second active material layer and disposed opposite to the first adhesive layer.

[0014] According to some embodiments of the present invention, along the width direction of the cathode sheet, the size of the cavity is a, the size of the cathode sheet is b, and 0.7≤a / b≤1.

[0015] A battery cell according to a second aspect of the present invention includes an anode sheet, a separator, and a cathode sheet as described in the first aspect embodiment. The separator is stacked between the cathode sheet and the anode sheet and is wound together with the cathode sheet and the anode sheet to form the battery cell. The battery cell includes a flat region and bent regions located on both sides of the flat region. The cathode sheet includes multiple bent sections located in the bent regions, with the innermost bent section being a first bent section. At least a portion of the cavity is located in the first bent section.

[0016] The battery cell according to the embodiments of this utility model has at least the following beneficial effects:

[0017] In the cathode sheet of the first aspect embodiment, the cavity on the cathode sheet is located inside the innermost corner to reduce the compressive force on the innermost corner of the cathode current collector, thereby reducing the risk of deformation of the cathode current collector toward the second surface, and further reducing the risk of fracture of the second active material layer located on the back side of the corner, so as to improve the performance of the battery.

[0018] According to some embodiments of this utility model

[0019] The first active material layer has a second void groove, the first adhesive layer is connected to the first active material layer and covers the second void groove, and the first adhesive layer and the inner wall of the second void groove together define the void cavity.

[0020] Along the winding direction of the battery cell, the first curved section has a first end and a second end opposite to each other, and the second clearance groove has a first sidewall and a second sidewall opposite to each other. The first end is closer to the winding start end of the cathode sheet than the second end, and the first sidewall is closer to the winding start end of the cathode sheet than the second sidewall.

[0021] Along the winding direction of the battery cell, the length of the first bent section is S1, the length between the first sidewall and the first end is S2, the length between the second sidewall and the second end is S3, 0≤S2 / S1≤10%, and / or, 0≤S3 / S1≤10%.

[0022] According to some embodiments of the present invention, the first active material layer has a second void groove, the first adhesive layer is connected to the first active material layer and covers the second void groove, and the first adhesive layer and the inner wall of the second void groove together define the void cavity.

[0023] The cathode sheet includes multiple cathode straight sections located in the straight region. The cathode straight sections include a first cathode straight section and a second cathode straight section. Along the winding direction of the battery cell, the first cathode straight section and the second cathode straight section are respectively connected to both sides of the first curved section. The second clearance slot includes a third slot, a fourth slot, and a fifth slot that are sequentially distributed and connected along the winding direction of the battery cell. The first cathode straight section has the third slot, the first curved section has the fourth slot, and the second cathode straight section has the fifth slot.

[0024] According to some embodiments of the present invention, along the winding direction of the battery cell, the first adhesive layer includes a third end and a fourth end opposite to each other;

[0025] The starting end of the winding of the anode sheet is the first winding starting end. The first winding starting end is located in the flat area. The plane in which the flat area is located is the first plane. Along the thickness direction of the battery cell, the projection of the first adhesive layer on the first plane covers the first winding starting end.

[0026] According to some embodiments of the present invention, the cathode sheet includes multiple layers of cathode straight sections located in the straight region. The cathode straight sections include a first cathode straight section and a second cathode straight section. Along the winding direction of the battery cell, the first cathode straight section and the second cathode straight section are respectively connected to both sides of the first curved section. The first cathode straight section includes the winding start end of the cathode sheet, and the winding start end of the cathode sheet is a second winding start end. The anode sheet includes multiple layers of anode straight sections located in the straight region. The anode straight sections include a first anode straight section. The first anode straight section includes the first winding start end. The first winding start end and the second winding start end have opposite orientations, and the first anode straight section is located between the first cathode straight section and the second cathode straight section.

[0027] According to some embodiments of the present invention, the first adhesive layer includes a second curved section located in the bending area, and in the width direction of the battery cell, the second curved section has a curved top that is furthest from the first winding start end;

[0028] In the width direction of the battery cell, the distance between the third end and the inner side of the bend top is L1, the distance between the fourth end and the inner side of the bend top is L2, and the distance between the first winding start end and the inner side of the bend top is L3, wherein 2mm≤L1≤5mm, 2mm≤L2≤5mm, 1mm≤L3≤4mm, and 0.3≤L3 / L1≤0.6, 0.3≤L3 / L2≤0.6.

[0029] According to some embodiments of the present invention, the cathode active material is covered on both sides of the first cathode straight section along its own thickness direction;

[0030] The anode sheet includes an anode active material, and the anode active material is covered on both sides of the first straight section of the anode along its own thickness direction.

[0031] The battery according to a third aspect embodiment of the present invention includes the battery cell described in the second aspect embodiment.

[0032] The battery according to the embodiments of the present invention has at least the following beneficial effects:

[0033] In the battery cell of the second aspect embodiment, the inner side of the corner of the innermost layer of the cathode sheet has a cavity to reduce the compressive force on the first surface at the corner of the innermost layer of the cathode current collector, thereby reducing the risk of deformation of the cathode current collector toward the second surface, and further reducing the risk of fracture of the second active material layer located on the back side of the corner, so as to improve the performance of the battery.

[0034] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0036] Figure 1 This is a schematic diagram of the structure of the first cathode sheet according to the first aspect of the present invention;

[0037] Figure 2 This is a schematic diagram of the structure of a second type of cathode sheet according to the first aspect of the present invention;

[0038] Figure 3 This is a schematic diagram of the structure of a third type of cathode sheet according to the first aspect of the present invention;

[0039] Figure 4 This is a schematic diagram of the structure of a fourth type of cathode sheet according to the first aspect of the present invention;

[0040] Figure 5 for Figure 4 A schematic diagram of the structure of the first active material layer;

[0041] Figure 6 This is a schematic diagram of the structure of the fifth type of cathode sheet according to the first aspect of the present invention;

[0042] Figure 7 This is a schematic diagram of the structure of the first type of battery cell according to the second aspect of the present invention;

[0043] Figure 8 for Figure 7 A magnified view of area A in the middle;

[0044] Figure 9 This is a partial cross-sectional view of the structure of the second type of battery cell according to the second aspect of the present invention;

[0045] Figure 10 This is a partial cross-sectional view of the structure of a third type of battery cell according to a second aspect embodiment of the present invention.

[0046] Figure label:

[0047] Cathode plate 1000;

[0048] The cathode current collector is 100, with a first surface 110 and a second surface 120.

[0049] Cathode active material 200, first active material layer 210, second vented groove 211, first groove section 2111, first sub-groove section 21112, second sub-groove section 21113, second groove section 2112, first sidewall 2113, second sidewall 2114, third groove section 2115, fourth groove section 2116, fifth groove section 2117, second active material layer 220;

[0050] First adhesive layer 300, first clearance groove 310, third end 320, fourth end 330, second bending section 340, bending top 341, connecting part 350;

[0051] Avoid cavity 400;

[0052] Bending section 500, first bending section 510, first end 511, second end 512;

[0053] The cathode straight section is 600, the first cathode straight section is 610, and the second cathode straight section is 620.

[0054] Second winding starting end 700, second adhesive layer 800, support member 900;

[0055] Anode sheet 2000, first winding start end 2100, anode straight section 2200, first anode straight section 2210, anode current collector 2300, anode active material 2400;

[0056] The separator is 3000mm thick, the straight section is 4000mm thick, and the bending section is 5000mm thick. Detailed Implementation

[0057] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0058] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0059] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0060] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0061] In some technologies, to reduce the risk of lithium plating on the anode surface, adhesive is typically applied to the inner side of the innermost corner of the cathode sheet to prevent lithium ions from migrating towards the anode. However, because the adhesive layer adheres to the cathode active material, the active material at the corner cannot move along the length or width direction of the cathode sheet when compressed during cell winding. Therefore, during winding, the cathode active material compresses the cathode current collector towards the thickness direction of the cathode sheet, causing the cathode current collector to deform away from the corner. This can easily lead to breakage of the active material on the back side of the corner, resulting in reduced battery performance, for example:

[0062] 1. Degradation of Battery Electrochemical Performance: The positive electrode active material is the main component of the battery's positive electrode, responsible for the insertion and extraction of lithium ions. When the active material breaks, the lithium ion transport path is affected, leading to a decrease in the battery's electrochemical performance. Breakage may cause poor contact between active material particles, altering the transport paths of electrons and ions, restricting diffusion, and further affecting the efficiency of the electrochemical reaction.

[0063] 2. Deterioration of battery cycle stability: The breakage of active materials may cause the accumulation of mechanical or thermal stress inside the particles, resulting in the destruction of the integrity between particles. As the battery is charged and discharged, this breakage phenomenon may be aggravated, leading to a deterioration of the battery's cycle stability.

[0064] 3. Reversible capacity decay of the battery; the breakage of active materials may lead to the loss of active materials, thereby reducing the reversible capacity of the battery. As the temperature rises, the capacity loss caused by the loss of active materials will accelerate.

[0065] In view of the above background, this utility model proposes a cathode sheet 1000 that can reduce the risk of breakage of the cathode active material 200 on the back side of the innermost curved section 500, thereby improving battery performance. (Refer to...) Figures 1 to 3 , Figure 1 This is a schematic diagram of the structure of the first cathode sheet according to the first aspect of the present invention. Figure 2 This is a schematic diagram of the structure of the second type of cathode sheet according to the first aspect of the present invention. Figure 3 This is a schematic diagram of the structure of a third type of cathode sheet according to the first aspect of the present invention. The cathode sheet 1000 of this embodiment includes: a cathode current collector 100, a cathode active material 200, and a first adhesive layer 300.

[0066] The cathode current collector 100 can be made of one or more materials selected from aluminum, nickel, and titanium. The cathode current collector 100 includes a first surface 110 and a second surface 120 facing away from each other along the thickness direction of the cathode sheet 1000. The cathode active material 200 is, for example, a lithium-ion compound such as lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO4), or lithium iron phosphate (LiFePO4). The cathode active material 200 includes a first active material layer 210 and a second active material layer 220, with the first active material layer 210 disposed on the first surface 110 and the second active material layer 220 disposed on the second surface 120. The first adhesive layer 300 is connected to the first active material layer 210 and fully covers the first active material layer 210 along the width direction of the cathode sheet 1000. A cavity 400 is defined between the first adhesive layer 300 and the cathode current collector 100. The first adhesive layer 300 is made of materials such as polyimide (PI), polyethylene terephthalate (PET), or polytetrafluoroethylene (PTFE). The first adhesive layer 300 can isolate lithium ion movement. When the cathode sheet 1000 is wound together with the anode sheet 2000 and the separator 3000 to form a battery cell, at least a portion of the cavity 400 is located inside the innermost curved section 500 (first curved section 510) of the cathode sheet 1000. Specifically, in this embodiment, a cavity 400 is defined between the first adhesive layer 300 and the cathode current collector 100. When the cathode sheet 1000, anode sheet 2000, and separator 3000 of this embodiment are wound together to form a battery cell, the cavity 400 is disposed inside the innermost curved section 500 of the cathode sheet 1000 to reduce the compressive force on the innermost curved section 500 of the cathode current collector 100, thereby reducing the risk of deformation of the cathode current collector toward the second surface 120, and further reducing the risk of breakage of the second active material layer 220 located on the back side of the innermost curved section 500, so as to improve the performance of the battery.

[0067] For example, in some embodiments, the side of the first adhesive layer 300 facing the cathode current collector 100 has a first vent groove 310 (e.g. Figure 1As shown, the inner wall of the first clearance groove 310 and the first active material layer 210 together define a clearance cavity 400. Specifically, the first adhesive layer 300 has the first clearance groove 310, thereby preventing the first adhesive layer 300 from binding the cathode active material 200 (i.e., the first active material layer 210 in this embodiment) at the bent section 500 of the cathode current collector 100. Therefore, during the winding process, when the first active material layer 210 at the bent section 500 is compressed, it can shift to a certain extent along the width and length directions of the cathode sheet 1000, thereby reducing the compressive force on the first surface 110 along the thickness direction of the cathode sheet 1000, thereby reducing the deformation of the cathode current collector 100 toward the second surface 120, and further reducing the risk of breakage of the second active material layer 220 disposed on the second surface 120, so as to improve the energy density of the battery.

[0068] For example, in some embodiments, the first adhesive layer 300 is connected to the first active material layer 210, and a cavity 400 is formed inside the first active material layer 210 (e.g., Figure 2 (As shown). Exemplarily, during processing, a layer of cathode active material 200 (referred to as the inner active material) is first coated onto the first surface 110, forming a notch. A support member 900 is provided at the notch, and the support member 900 has a hollow or mesh structure. Then, another layer of cathode active material is coated onto the surface of the inner active material, covering the support member 900, thereby forming a cavity 400 inside the first active material layer 210. Therefore, even when the first active material layer 210 is constrained by the first adhesive layer 300 and moves towards the first surface 110, the cavity 400 can provide a certain amount of movement space, preventing the first surface 110 from being directly compressed, thereby reducing the risk of the second active material layer 220 breaking.

[0069] Furthermore, in some embodiments, the first active material layer 210 has a second void groove 211, and the first adhesive layer 300 is connected to the first active material layer 210 and covers the second void groove 211 (e.g., Figure 3 As shown, the first adhesive layer 300 and the inner wall of the second cavitation groove 211 together define a cavity 400. That is, the second cavitation groove 211 is located on the surface of the first active material layer 210 and can be easily formed by laser processing to reduce the processing cost of the cathode sheet 1000 in this embodiment.

[0070] It is understood that in this embodiment, since the cathode active material 200 inside the innermost curved section 500 does not participate in the redox reaction of the battery, in some embodiments, the first active material layer 210 corresponding to the cathode active material 200 at the curved section 500 is completely removed, that is, the depth of the second venting groove 211 is equal to the thickness of the first active material layer 210, thereby reducing the risk of lithium plating in the battery. However, since the cathode sheet 1000 is relatively thin in the battery, the first active material layer 210 is even thinner. Directly removing the entire first active material layer 210 requires high precision in laser processing and is prone to burning the cathode current collector 100. Based on this, in some embodiments, along the thickness direction of the cathode sheet 1000, the size of the second venting groove 211 is H1, and the size of the first active material layer 210 is H2, with H1 / H2 = 50% to 90%. That is, during the removal of the first active material layer 210, a certain amount is retained, which can effectively reduce the risk of burning the cathode current collector 100, thereby improving the performance of the battery.

[0071] Reference Figure 4 and Figure 5 , Figure 4 This is a schematic diagram of the structure of the fourth type of cathode sheet according to the first aspect of the present invention. Figure 5 for Figure 4A schematic diagram of the structure of the first active material layer. In some embodiments, along the direction from the first adhesive layer 300 to the cathode current collector 100, the second clearance groove 211 includes a first groove portion 2111 and a second groove portion 2112 that are interconnected. Along the length direction of the cathode sheet 1000, the size of the first groove portion 2111 is larger than that of the second groove portion 2112. The first groove portion 2111 includes a first sub-groove portion 21112 and two second sub-groove portions 21113 located on both sides of the first sub-groove portion 21112. In the thickness direction of the cathode sheet 1000, the first sub-groove portion 21112 is larger than that of the second groove portion 2112. The first sub-groove 21112 is aligned with the second sub-groove 21113, and the second sub-groove 21113 is offset from the second sub-groove 21112. The first adhesive layer 300 includes two connecting portions 350 on both sides of the cathode sheet 1000 along its length. The connecting portions 350 are connected to the inner wall of the first sub-groove 21112. The distance between the surface of the connecting portion 350 facing away from the cathode current collector 100 and the surface of the first active material layer 210 surrounding the second clearance groove 2112 facing away from the cathode current collector 1000 is less than or equal to 8 μm, thus reducing the space occupied. For example, the connecting portions 350 are all disposed within the first sub-groove 2111, that is, the connecting portions 350 do not protrude from the first active material layer 210 in the thickness direction of the cathode sheet 1000, and do not need to occupy the external space of the first active material layer 210. Therefore, when the cathode sheet 1000 of this embodiment is used in a battery, the energy density of the battery can be improved. Furthermore, the distance between the surface of the connecting portion 350 facing away from the cathode current collector 100 and the surface of the first active material layer 210 surrounding the second venting groove 211 facing away from the cathode current collector 100 is less than or equal to 8 μm. This includes both cases where the surface of the connecting portion 350 facing away from the cathode current collector 100 is located inside or outside the first sub-groove portion 21112. Even when the surface of the connecting portion 350 facing away from the cathode current collector 100 is located outside the first groove portion 2111, since the distance between it and the surface of the first active material layer 210 surrounding the second venting groove 211 is less than or equal to 8 μm, that is, the size of the first adhesive layer 300 protruding from the first active material layer 210 is less than or equal to 8 μm. The cathode sheet 1000 can still be guaranteed to have sufficient flatness. Therefore, when the cathode sheet 1000 of this embodiment is wound to form a battery cell, when a portion of the first adhesive layer 300 is located in the flat area of ​​the battery cell, the increase in battery cell thickness caused by reducing the first adhesive layer 300 can be reduced, thereby ensuring the energy density of the battery cell.

[0072] Reference Figure 6 , Figure 6This is a schematic diagram of the structure of a fifth type of cathode sheet according to the first aspect of the present invention. In some embodiments, the cathode sheet 1000 further includes a second adhesive layer 800. The second adhesive layer 800 has pores for lithium ions to pass through. For example, the second adhesive layer 800 is composed of a substrate and an adhesive layer. The substrate layer is polypropylene (PP) or polyethylene (PE), and the adhesive layer is polyacrylic acid, PVDF, polyimide (PI), or polyester (PET). The second adhesive layer 800 is connected to the second active material layer 220 and is disposed opposite to the first adhesive layer 300. That is, when the cathode sheet 1000 of this embodiment is used in a battery, the second adhesive layer 800 is located outside the innermost curved section 500 of the cathode sheet 1000, thereby forming a certain constraint on the second active material layer 220 disposed on the second surface 120 to reduce the risk of breakage of the second active material layer 220 and improve the performance of the battery.

[0073] In some implementations, along the width direction of the cathode sheet 1000, the size of the cavity 400 is 'a', and the size of the cathode sheet 1000 is 'b', with 0.7 ≤ a / b ≤ 1. Specifically, it can be understood that if the size of the cavity 400 is too small, it means that the space for the active material to expand when compressed is smaller, resulting in greater compression of the cathode current collector 100 and increasing the risk of breakage of the second active material layer 220. Therefore, to reduce the risk of breakage of the second active material layer 220, in this embodiment, a / b ≥ 0.7, that is, the proportion of the cavity 400 in the width direction of the cathode sheet 1000 is greater than or equal to 70%. As in the above embodiment, the first active material layer 210 has a second cavity 211, and in the width direction of the cathode sheet 1000, the size of the second cavity 211 accounts for greater than or equal to 70% of the size of the first active material layer 210. For example, when a / b = 0.7, the second void-avoiding groove 211 is located within the first active material layer 210, such that both sides of the second void-avoiding groove 211 are spaced apart from both sides of the first active material layer 210. When a / b = 1, the second void-avoiding groove 211 penetrates the first active material layer 210 along the width direction of the cathode plate 1000.

[0074] Reference Figure 7 and Figure 8 , Figure 8 for Figure 6 A magnified view of area A in the middle. Figure 7This is a schematic diagram of the structure of a first type of battery cell according to a second aspect embodiment of the present invention. The battery cell according to the second aspect embodiment of the present invention includes: an anode sheet 2000, a separator 3000, and a cathode sheet 1000 as described in the first aspect embodiment. The separator 3000 is stacked between the cathode sheet 1000 and the anode sheet 2000, and is wound together with the cathode sheet 1000 and the anode sheet 2000 to form the battery cell. The battery cell includes a flat region 4000 and bending regions 5000 located on both sides of the flat region 4000. The cathode sheet 1000 includes multiple bending sections 500 located in the bending regions 5000. The innermost bending section 500 is the first bending section 510. At least a portion of the cavity 400 is located inside the first bending section 510 to reduce the compressive force on the first bending section 510 of the cathode current collector 100, thereby reducing the risk of deformation of the cathode current collector 100 toward the second surface 120, and further reducing the risk of breakage of the second active material layer 220 located on the back side of the first bending section 510, so as to improve the performance of the battery.

[0075] It should be noted that since the battery cell of this embodiment adopts all the technical features of the cathode sheet 1000 of the first aspect embodiment, the battery cell of this embodiment has all the beneficial effects brought by the first aspect embodiment, which will not be repeated here.

[0076] Reference Figure 8 In some embodiments, the first active material layer 210 has a second void 211, and the first adhesive layer 300 is connected to the first active material layer 210 and covers the second void 211 (e.g., Figure 3As shown, the first adhesive layer 300 and the inner wall of the second clearance groove 211 together define a clearance cavity 400. Along the winding direction of the battery cell, the first bent section 510 has opposing first end 511 and second end 512, and the second clearance groove 211 has opposing first sidewalls 2113 and second sidewalls 2114. The first end 511 is closer to the winding start end of the cathode sheet 1000 than the second end 512, and the first sidewall 2113 is closer to the winding start end of the cathode sheet 1000 than the second sidewall 2114. Along the winding direction of the battery cell, the length of the first bent section 510 is S1, the length between the first sidewall 2113 and the first end 511 is S2, and the length between the second sidewall 2114 and the second end 512 is S3, where 0 ≤ S2 / S1 ≤ 10%, and / or 0 ≤ S3 / S1 ≤ 10%. Specifically, it can be understood that during the winding process, the cathode active material 200 in the middle region of the first curved section 510 experiences the greatest compression, while the compression decreases with distance from the middle of the first curved section 510. Therefore, it is not necessary for the cavity 400 to cover the entire first curved section 510; that is, the first sidewall 2113 can be located at the first end 511, or it can be at a certain distance from the first end 511, i.e., 0≤S2 / S1≤10%, thereby reducing the processing requirements of the cavity 400 and reducing processing costs. Similarly, the second sidewall 2114 can be located at the second end 512, or it can be at a certain distance from the second end 512, i.e., 0≤S3 / S1≤10%.

[0077] Conversely, please refer to Figure 9 , Figure 9 This is a partial cross-sectional view of the structure of a second type of battery cell according to a second aspect embodiment of the present invention. In some embodiments, the second void 211 extends to the flat region 4000. Specifically, the first active material layer 210 has the second void 211, and the first adhesive layer 300 is connected to the first active material layer 210 and covers the second void 211 (e.g., ...). Figure 3As shown, the first adhesive layer 300 and the inner wall of the second clearance groove 211 together define a clearance cavity 400. The cathode sheet 1000 includes a multi-layer cathode straight section 600 located in the straight region 4000. The cathode straight section 600 includes a first cathode straight section 610 and a second cathode straight section 620. Along the winding direction of the battery cell, the first cathode straight section 610 and the second cathode straight section 620 are respectively connected to both sides of the first bent section 510, that is, the first cathode straight section 610 and the second cathode straight section 620 are respectively connected to the first end 511 and the second end 512. The second clearance groove 211 includes a third groove portion 2115, a fourth groove portion 2116 and a fifth groove portion 2117 that are sequentially distributed and connected along the winding of the battery cell. The first cathode straight section 610 has the third groove portion 2115, the first bent section 510 has the fourth groove portion 2116, and the second cathode straight section 620 has the fifth groove portion 2117. That is, in this embodiment, the two ends of the second clearance groove 211 extend to the first cathode straight section 610 and the second cathode straight section 620 of the cathode sheet 1000, thereby ensuring that the first bent section 510 has expansion space after winding, hot pressing, charging and other processes, so that the entire first bent section 510 is not easy to break.

[0078] Reference Figure 9 In some embodiments, along the winding direction of the battery cell, the first adhesive layer 300 includes opposing third ends 320 and fourth ends 330. The winding start end of the anode sheet 2000 is a first winding start end 2100, located in a flat region 4000. The plane containing the flat region 4000 is a first plane. Along the thickness direction of the battery cell, the projection of the first adhesive layer 300 onto the first plane covers the first winding start end 2100. That is, the first winding start end 2100 is wrapped inside the bent structure formed by the first adhesive layer 300, thereby reducing the risk of battery short circuit. Specifically, the anode sheet 2000 includes an anode current collector 2300, which is, for example, a copper foil. The edge of the anode current collector 2300 protrudes from the first winding start end 2100, thus posing a risk of cutting the separator 3000. Once the separator 3000 is cut, there is a risk that the anode sheet 2000 and the cathode sheet 1000 will come into contact, leading to a battery short circuit. In this embodiment, the first winding start end 2100 is wrapped in the first adhesive layer 300. Even if the separator 3000 is cut, the first adhesive layer 300 can still isolate the anode plate 2000 and the cathode plate 1000, thereby reducing the risk of battery short circuit.

[0079] Reference Figure 9In some embodiments, the cathode sheet 1000 includes multiple cathode straight sections 600 located in the straight region 4000. The cathode straight sections 600 include a first cathode straight section 610 and a second cathode straight section 620. Along the winding direction of the battery cell, the first cathode straight section 610 and the second cathode straight section 620 are respectively connected to both sides of the first curved section 510. The first cathode straight section 610 includes the winding start end of the cathode sheet 1000. That is, the first cathode straight section 610 is the innermost cathode straight section 600, the second cathode straight section 620 is the next innermost cathode straight section 600, and the winding start end of the cathode sheet 1000 is the second winding start end 700. The anode sheet 2000 includes multiple anode straight sections 2200 located in the straight region 4000. The anode straight section 2200 includes a first anode straight section 2210, which includes a first winding start end 2100. That is, the first anode straight section 2210 is the innermost anode straight section 2200. The first winding start end 2100 and the second winding start end 700 have opposite orientations. The first anode straight section 2210 is located between the first cathode straight section 610 and the second cathode straight section 620. That is, the innermost anode straight section 2200 is located between the innermost cathode straight section 600 and the next innermost cathode straight section 600. This allows the heads of the anode sheet 2000 and the cathode sheet 1000 to be interlocked without having to go through the first bending section 510. This reduces the risk of the first winding start end 2100 and the second winding start end 700 cutting the separator 3000, thereby reducing the risk of battery short circuit. Specifically, if the first winding start end 2100 passes through the first bending section 510, that is, the anode sheet 2000 forms a bent structure at the first bending section 510, the anode sheet 2000 itself has a certain elasticity, which will cause the first winding start end 2100 to press tightly against the separator 3000, increasing the risk of the separator 3000 being cut. In this embodiment, the first winding start end 2100 is located at the first anode straight section 2210, thereby reducing the force between the first winding start end 2100 and the separator 3000, reducing the risk of the separator 3000 being cut, and thus reducing the risk of battery short circuit.

[0080] As can be seen from the above embodiments, the first winding start end 2100 is located between the first cathode straight section 610 and the second cathode straight section 620, and the first winding start end 2100 is located between the third end 320 and the fourth end 330 of the first adhesive layer 300, that is, part of the first adhesive layer 300 is located in the first cathode straight section 610, and part is located in the second cathode straight section 620. It is understood that, due to the shrinkage property of the anode sheet 2000 and the first adhesive layer 300 when cooled, the first winding start end 2100 will move away from the first adhesive layer 300 when the anode sheet 2000 and the first adhesive layer 300 shrink. If the distance between the first winding start end 2100 and the ends (third end 320 and fourth end 340) of the first adhesive layer 300 is too small, the first winding start end 2100 will easily move to the outside of the first adhesive layer 300. Therefore, referring to... Figure 10 , Figure 10 This is a partial cross-sectional view of the structure of a third type of battery cell according to a second aspect embodiment of the present invention. In this embodiment, the first adhesive layer 300 includes a second bent segment 340 located in the bending region 5000. In the width direction of the battery cell, the second bent segment 340 has a bent top 341 that is furthest from the first winding start end 2100. In the width direction of the battery cell, the distance between the third end 320 and the inner side of the bent top 341 is L1, the distance between the fourth end 330 and the inner side of the bent top 341 is L2, and the distance between the first winding start end 2100 and the inner side of the bent top 341 is L3, wherein 2mm≤L1≤5mm, 2mm≤L2≤5mm, and L3 / L1≤0.6, L3 / L2≤0.6. For example. Specifically, for the range 2mm≤L1≤5mm and 2mm≤L2≤5mm, L1 and L2 are sufficiently large to ensure that the first winding start end 2100 has enough moving distance. However, if L1 and L2 are too large, it also means that the first adhesive layer 300 needs to occupy more space, thus reducing the energy density of the battery. Moreover, limiting L1 and L2 alone cannot guarantee that the first winding start end 2100 has enough moving space. For example, if the first winding start end 2100 is aligned with the third end 320, i.e., L3 / L1=1, then even if L1 is larger, as long as the anode sheet 2000 or the first adhesive layer 300 contracts, the first winding start end 2100 will move to the outside of the first adhesive layer 300. Therefore, in this embodiment, not only are the sizes of L1 and L2 limited, but the setting position of the first winding start end 2100 is also limited, that is, 2mm≤L1≤5mm, 2mm≤L2≤5mm, while L3 / L1≤0.6, L3 / L2≤0.6, so that there is a certain distance between the first winding start end 2100 and the third end end 320 and the fourth end end 330. Even if the anode sheet 2000 and the first adhesive layer 300 shrink, the first winding start end 2100 can still be guaranteed to be located inside the first adhesive layer 300, thereby improving the safety of the battery.

[0081] Furthermore, it can be understood that during battery use, there are instances where the first winding start end 2100 moves away from the first adhesive layer 300, and also instances where the first winding start end 2100 moves towards the first adhesive layer 300. For example, when the battery cell is dropped or subjected to external pressure, or when heat is released during charging and discharging, the internal temperature of the battery cell is higher than the temperature at the edge, meaning the internal temperature change is relatively greater than the external temperature change. This results in the inner electrode sheet expanding more than the outer electrode sheet. In other words, in this embodiment, the innermost anode straight section 2200 (first anode straight section 2210) expands more than the outer anode straight section 2200, causing the first winding start end 2100 to move towards the first adhesive layer 300. Taking thermal expansion as an example, if L3 / L2 = 0, meaning the first winding start end 2100 of the anode sheet 2000 is located at the top of the bend 341, after the cell expands due to heat, the first winding start end 2100 will press against the separator 3000 located in the bending area 5000 towards the top of the bend 341. This makes the separator 3000 susceptible to compression, wrinkling, or even being cut. Therefore, in some embodiments, 0.3 ≤ L3 / L1 and 0.3 ≤ L3 / L2 are used to ensure sufficient distance between the first winding start end 2100 and the top of the bend 341 for the first winding start end 2100 to move. Thus, even if the cell is compressed or expands due to heat, the first winding start end 2100 still has a certain amount of room to move, thereby reducing the risk of the separator 3000 being compressed, wrinkled, or even cut, and improving battery safety.

[0082] To verify the effects of the above parameters, this application conducted the following 8 sets of experiments. Each set of experiments used 20 batteries, including those with cells from this embodiment, for charge-discharge testing. For example, in an environment of 12℃~45℃, the initial charge and discharge were performed. Constant current charging was conducted at a charging current density of 1.5C until the full charge voltage of 4.5V, followed by constant voltage charging at the maximum voltage until the current was cut off at 0.02C. Then, constant current discharging was performed at a discharge current of 0.5C until the final voltage reached 3.0V. Finally, 500 charge-discharge cycles were performed to examine the number of batteries with short circuits and creases during the charge-discharge process. A crease was defined as one where the width of the separator 3000 was greater than or equal to 0.5mm. The experimental data are shown in the table below.

[0083]

[0084]

[0085] The experimental data above shows that when L3 / L1 and L3 / L2 are both 0.2, the wrinkle ratio is 7 / 20, which is relatively high. When L3 / L1 and L3 / L2 increase to 0.33, the wrinkle ratio is 3 / 20 and the short circuit ratio is 0 / 20, both relatively low. Furthermore, when L3 / L1 and L3 / L2 increase to 0.6, the wrinkle ratio and short circuit ratio are both 2 / 20, still relatively low. Only when L3 / L1 and L3 / L2 increase to 0.75 does the short circuit ratio reach 7 / 20, which is relatively high. Therefore, it can be concluded that when 0.3≤L3 / L1≤0.6 and 0.3≤L3 / L2≤0.6, the risk of 3000 wrinkles and puncture of the separator membrane can be reduced. When L3 / L1 and L3 / L2 are 0.4 and L3 / L2 are 0.5, the proportion of wrinkles and short circuits is smaller. When 0.4≤L3 / L1≤0.5 and 0.4≤L3 / L2≤0.5, the risk of wrinkles and punctures in the separator membrane can be further reduced, which is the optimal range.

[0086] In some embodiments, the innermost cathode straight section 600 (first cathode straight section 610) is covered with cathode active material 200 on both sides along its thickness direction, and the anode sheet 2000 includes anode active material 2400. The innermost anode straight section 2200 (first anode straight section 2210) is also covered with anode active material 2400 on both sides along its thickness direction. That is, in this embodiment, the heads of the anode sheet 2000 and the cathode sheet 1000 are in a paired insertion structure, and neither the head of the anode sheet 2000 nor the cathode sheet 1000 is provided with an empty foil area, making greater use of the anode current collector 2300 and the cathode current collector 100, thereby improving the energy density of the battery in this embodiment.

[0087] According to the third aspect embodiment of the present invention, the battery is, for example, a pouch battery, a steel-cased battery, or an aluminum-cased battery. The battery includes the cell of the second aspect embodiment. The innermost curved section 500 of the cathode sheet 1000 of the cell has a cavity 400 on its inner side to reduce the compressive force on the first surface 110 at the innermost curved section 500 of the cathode current collector 100, thereby reducing the risk of deformation of the cathode current collector 100 toward the second surface 120, and further reducing the risk of breakage of the second active material layer 220 located on the back side of the curved section 500, so as to improve the performance of the battery.

[0088] It should be noted that since the battery in this embodiment adopts all the technical features of the cell in the first aspect embodiment, this embodiment has all the beneficial effects brought by the first aspect embodiment, which will not be repeated here.

[0089] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, in the description of the present invention, the reference to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A cathode plate, characterized in that, include: The cathode current collector includes a first surface and a second surface that are opposite to each other along the thickness direction of the cathode sheet; The cathode active material includes a first active material layer and a second active material layer, wherein the first active material layer is disposed on the first surface and the second active material layer is disposed on the second surface; A first adhesive layer is attached to the first active material layer and fully covers the first active material layer along the width direction of the cathode sheet. A cavity is formed between the first active material layer and the cathode current collector. The first adhesive layer can prevent lithium ions from moving. When the cathode sheet is wound together with the anode sheet and the separator to form a battery cell, the cavity is at least partially located inside the innermost curved section of the cathode sheet.

2. The cathode sheet according to claim 1, characterized in that, The first adhesive layer has a first cavitation groove on the side facing the cathode current collector, and the inner wall of the first cavitation groove and the first active material layer together define the cavitation cavity.

3. The cathode sheet according to claim 1, characterized in that, The first active material layer has a second void groove, the first adhesive layer is connected to the first active material layer and covers the second void groove, and the first adhesive layer and the inner wall of the second void groove together define the void cavity.

4. The cathode sheet according to claim 3, characterized in that, Along the direction from the first adhesive layer to the cathode current collector, the second void groove includes a first groove portion and a second groove portion that are interconnected. Along the length direction of the cathode sheet, the size of the first groove portion is larger than the size of the second groove portion. The first groove portion includes a first sub-groove portion and two second sub-groove portions located on both sides of the first sub-groove portion. In the thickness direction of the cathode sheet, the first sub-groove portion and the second groove portion are aligned, and the second sub-groove portion and the second groove portion are offset. The first adhesive layer includes two connecting portions on both sides of the length direction of the cathode sheet. The connecting portions are connected to the inner wall of the first sub-groove portion. In the thickness direction of the electrode sheet, the distance between the surface of the connecting portion away from the cathode current collector and the surface of the first active material around the second void groove away from the cathode current collector is less than or equal to 8 μm.

5. The cathode sheet according to claim 3, characterized in that, Along the thickness direction of the cathode sheet, the size of the second void groove is H1, the size of the first active material layer is H2, and the value of H1 / H2 ranges from 30% to 90%.

6. The cathode sheet according to claim 5, characterized in that, The cathode sheet further includes a second adhesive layer, which has pores through which lithium ions can pass. The second adhesive layer is connected to the second active material layer and is disposed opposite to the first adhesive layer.

7. The cathode plate according to any one of claims 1 to 6, characterized in that, Along the width direction of the cathode sheet, the size of the cavity is a, the size of the cathode sheet is b, and 0.7≤a / b≤1.

8. A battery cell, characterized in that, include: The cathode plate according to any one of claims 1 to 7; Anode plate; An isolation membrane is stacked between the cathode sheet and the anode sheet and wound together with the cathode sheet and the anode sheet to form the battery cell. The battery cell includes a flat region and a bent region located on both sides of the flat region. The cathode sheet includes multiple bent sections located in the bent regions, with the innermost bent section being the first bent section. At least a portion of the cavity is located in the first bent section.

9. The battery cell according to claim 8, characterized in that, The first active material layer has a second void groove, the first adhesive layer is connected to the first active material layer and covers the second void groove, and the first adhesive layer and the inner wall of the second void groove together define the void cavity. Along the winding direction of the battery cell, the first curved section has a first end and a second end opposite to each other, and the second clearance groove has a first sidewall and a second sidewall opposite to each other. The first end is closer to the winding start end of the cathode sheet than the second end, and the first sidewall is closer to the winding start end of the cathode sheet than the second sidewall. Along the winding direction of the battery cell, the length of the first bent section is S1, the length between the first sidewall and the first end is S2, the length between the second sidewall and the second end is S3, 0≤S2 / S1≤10%, and / or, 0≤S3 / S1≤10%.

10. The battery cell according to claim 8, characterized in that, The first active material layer has a second void groove, the first adhesive layer is connected to the first active material layer and covers the second void groove, and the first adhesive layer and the inner wall of the second void groove together define the void cavity. The cathode sheet includes multiple cathode straight sections located in the straight region. The cathode straight sections include a first cathode straight section and a second cathode straight section. Along the winding direction of the battery cell, the first cathode straight section and the second cathode straight section are respectively connected to both sides of the first curved section. The second clearance slot includes a third slot, a fourth slot, and a fifth slot that are sequentially distributed and connected along the winding direction of the battery cell. The first cathode straight section has the third slot, the first curved section has the fourth slot, and the second cathode straight section has the fifth slot.

11. The battery cell according to any one of claims 8 to 10, characterized in that, Along the winding direction of the battery cell, the first adhesive layer includes opposing third and fourth ends; The starting end of the winding of the anode sheet is the first winding starting end. The first winding starting end is located in the flat area. The plane in which the flat area is located is the first plane. Along the thickness direction of the battery cell, the projection of the first adhesive layer on the first plane covers the first winding starting end.

12. The battery cell according to claim 11, characterized in that, The cathode sheet includes multiple layers of cathode straight sections located in the straight region. The cathode straight sections include a first cathode straight section and a second cathode straight section. Along the winding direction of the battery cell, the first cathode straight section and the second cathode straight section are respectively connected to both sides of the first curved section. The first cathode straight section includes the winding start end of the cathode sheet, and the winding start end of the cathode sheet is the second winding start end. The anode sheet includes multiple layers of anode straight sections located in the straight region. The anode straight sections include a first anode straight section. The first anode straight section includes the first winding start end. The first winding start end and the second winding start end have opposite orientations, and the first anode straight section is located between the first cathode straight section and the second cathode straight section.

13. The battery cell according to claim 12, characterized in that, The first adhesive layer includes a second curved section located in the bending area, wherein the second curved section has a curved top that is furthest from the first winding start end in the width direction of the cell; In the width direction of the battery cell, the distance between the third end and the inner side of the bend is L1, the distance between the fourth end and the inner side of the bend is L2, and the distance between the first winding start end and the inner side of the bend is L3. Among them, 2mm≤L1≤5mm, 2mm≤L2≤5mm, 1mm≤L3≤4mm, and 0.3≤L3 / L1≤0.6, 0.3≤L3 / L2≤0.

6.

14. The battery cell according to claim 11, characterized in that, The first cathode straight section is covered with the cathode active material on both sides along its thickness direction; The anode sheet includes an anode active material, and the anode active material is covered on both sides of the first straight section of the anode along its own thickness direction.

15. A battery, characterized in that, Includes the battery cell according to any one of claims 8 to 14.

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