Battery

Abstract

The invention relates to the technical field of batteries, and discloses a battery. A battery cell; the negative plate comprises a silicon-based negative electrode active material, the positive plate comprises an outermost positive plate on the outermost side and an inner positive plate, the inner positive plate is provided with a first region and a second region, the second region is arranged close to the edge of the positive plate, the inner positive plate comprises a texture region arranged in the first region, and the surface of one side, facing the center of the battery cell, of the texture region is provided with a concave part; the surface of one side, deviating from the center of the battery cell, of the texture region is provided with a convex part, and the second region of the positive plate on the inner side and the positive plate on the outermost side are not provided with convex parts and concave parts; the first adhesive layer is arranged on the surface of one side, deviating from the center of the battery cell, of the outermost positive plate, and the orthographic projection of the first adhesive layer is at least partially overlapped with the orthographic projection of the second area of the inner positive plate; the overlapping size D1 of the two parts in the first direction is larger than 0 and smaller than or equal to 7 mm. According to the invention, the cycle performance and safety of the battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to batteries. Background Technology

[0002] Currently, batteries are widely used in electronic devices, electric vehicles, energy storage, and other fields. This places higher demands on both the range and safety of batteries.

[0003] High-energy-density batteries can improve battery life, but during charge-discharge cycles, repeated volume changes and drop tests can cause the outermost electrode edge to fold and repeatedly rub against or even puncture the casing, leading to abnormal voltage changes, reduced battery cycle life, and even the risk of battery failure. This can also deteriorate battery electrical performance and increase safety hazards. Summary of the Invention

[0004] In view of this, the present invention provides a battery to solve the problems of low electrical performance and high safety risks in battery use.

[0005] In a first aspect, the present invention provides a battery comprising: a casing; and a battery cell disposed within the casing, the battery cell comprising a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, the negative electrode comprising a silicon-based negative electrode active material along the thickness direction of the battery cell, the positive electrode comprising an outermost positive electrode located away from the center of the battery cell and on the outermost side of the battery cell, and an inner positive electrode located near the center of the battery cell, the inner positive electrode having a first region and a second region, the second region being located on at least one side of the first region along a first direction, and the second region being disposed near the edge of the positive electrode along the first direction, the inner positive electrode including a textured region disposed in the first region. The surface of the textured area facing the center of the cell has a recess, and the surface of the textured area away from the center of the cell has a protrusion corresponding to the recess. Neither the protrusion nor the recess is provided on the second region of the inner positive electrode sheet nor on the outermost positive electrode sheet. A first adhesive layer is provided on the surface of the outermost positive electrode sheet away from the center of the cell. On the same projection plane perpendicular to the thickness direction of the cell, the orthographic projection of the first adhesive layer at least partially overlaps with the orthographic projection of the second region of the inner positive electrode sheet. The overlap dimension D1 of the orthographic projection of the first adhesive layer and the orthographic projection of the second region of the inner positive electrode sheet along the first direction is greater than 0 and less than or equal to 7 mm.

[0006] In some embodiments, on the same projection plane perpendicular to the thickness direction of the cell, the overlap dimension of the orthographic projection of the first adhesive layer and the orthographic projection of the protrusion in the textured area of ​​the inner positive electrode sheet along the first direction is D4, 0mm≤D4≤5mm; and / or, along the first direction, the overlap dimension of the first adhesive layer and the outermost positive electrode sheet is D2, 3mm≤D2≤12mm.

[0007] In some embodiments, along the same side of the first direction, the edge of the negative electrode extends beyond the edge of the positive electrode, and the edge of the separator extends beyond the edge of the negative electrode; wherein, along the same side of the first direction, one end of the first adhesive layer is flush with the edge of the outermost positive electrode; or, along the same side of the first direction, one end of the first adhesive layer extends beyond the edge of the outermost positive electrode but does not extend beyond the edge of the separator.

[0008] In some embodiments, the overlap dimension of the portion of the first adhesive layer extending beyond the edge of the outermost positive electrode sheet with the separator along the first direction is D3, where 0 < D3 ≤ 1.5 mm; and / or, on the same side along the first direction, one end of the first adhesive layer extends beyond the edge of the outermost positive electrode sheet and is located between the edge of the outermost positive electrode sheet and the edge of the negative electrode sheet; or, on the same side along the first direction, one end of the first adhesive layer extends beyond the edge of the outermost positive electrode sheet and is located between the edge of the negative electrode sheet and the edge of the separator.

[0009] In some embodiments, the portion of the first adhesive layer extending beyond the edge of the outermost positive electrode overlaps with the separator, and a functional layer is disposed on the surface of the separator. The functional layer is at least partially located within the overlapping region, and the portion of the first adhesive layer extending beyond the edge of the outermost positive electrode is bonded to the functional layer. The functional layer includes Al2O3, SiO2, ZrO2, barium titanate, boehmite, melamine cyanurate, melamine polyphosphate, melamine trithiocyanate, melamine, 2,4- At least one of the following: 6-tris(aminohexanoic acid)-1,3,5-triazine, 2-(4-bromophenyl)-4,6-dimethyl-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazine-2-yl)guanidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, cyanuric chloride, 2,4,6-tris(2-pyridyl)triazine, 2,4,6-triphenyl-1,3,5-triazine, tris(tribromophenoxy)triazine, and 2-amino-4,6-methoxy-1,3,5-triazine.

[0010] In some embodiments, the thickness of the first adhesive layer is greater than the thickness of the functional layer, and the ratio A / B of the thickness A of the first adhesive layer and the thickness B of the functional layer ranges from 1.2 to 28; and / or, the thickness B of the functional layer ranges from 0.5 μm to 6 μm.

[0011] In some embodiments, at 120°C to 160°C, the viscosity of the first adhesive layer is 2000 mPa·s to 4000 mPa·s; and / or, the peel strength between the first adhesive layer and the outermost positive electrode sheet is 0.2 N / mm. 2 ~0.6N / mm 2 ; and / or, the material of the first adhesive layer includes at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer, polyamide, and polyester elastomer; and / or, along the thickness direction, the maximum depth of the recess ranges from 3 μm to 40 μm.

[0012] In some embodiments, the battery further includes insulating tape, which is at least partially adhered to the outer surface of the outermost positive electrode of the cell. The insulating tape does not overlap with the first adhesive layer, and the thickness of the first adhesive layer is less than or equal to the thickness of the insulating tape.

[0013] In some embodiments, the thickness of the first adhesive layer ranges from 6 μm to 14 μm; and / or, the thickness of the insulating tape ranges from 10 μm to 16 μm; and / or, the battery cell is a wound core, the battery cell includes two flat regions opposite each other along the thickness direction of the battery cell; the insulating tape includes a first insulating tape adhered to the flat regions, and along the winding direction of the battery cell, the outermost positive electrode sheet, at its positive electrode termination point away from the battery cell, is fixed to one of the flat regions by the first insulating tape, the first insulating tape not overlapping the first adhesive layer. The thickness direction of the battery cell is perpendicular to the first direction, and the first direction is parallel to the axial direction of the battery cell; and / or, one side of the first insulating tape is adhered to the flat area, and the other side is adhered to the inner wall of the outer casing; and / or, the first insulating tape is double-sided adhesive; and / or, the insulating tape further includes a second insulating tape, the two ends of which are respectively adhered to both sides of the flat area along the thickness direction of the battery cell, and bypass the end of the battery cell along the first direction, and the second insulating tape does not overlap with the first adhesive layer.

[0014] In some embodiments, the battery cell is a wound core, the positive electrode sheet includes a positive electrode start end and a positive electrode end, the end of the inner positive electrode sheet away from the outermost positive electrode sheet is the positive electrode start end, the outermost positive electrode sheet includes a single-sided active layer segment, the end of the single-sided active layer segment away from the positive electrode start end is the positive electrode end, the side of the single-sided active layer segment facing near the center of the battery cell has a positive electrode active layer, and the side of the single-sided active layer segment away from the center of the battery cell does not have the positive electrode active layer; wherein, the first adhesive layer is disposed on at least a portion of the side of the single-sided active layer segment of the outermost positive electrode sheet away from the center of the battery cell; or, the battery cell is a wound core, the positive electrode sheet includes a positive electrode start end and a positive electrode end. The end of the inner positive electrode sheet away from the outermost positive electrode sheet is the positive electrode starting end. The outermost positive electrode sheet includes a connected single-sided active layer segment and an empty foil segment. Along the winding direction of the battery cell, the single-sided active layer segment is located between the inner positive electrode sheet and the empty foil segment. The end of the empty foil segment away from the single-sided active layer segment is the positive electrode ending end. The side of the single-sided active layer segment facing closer to the center of the battery cell has a positive electrode active layer, and the side of the single-sided active layer segment facing the center of the battery cell does not have the positive electrode active layer. The first adhesive layer is provided on at least a portion of the side of the single-sided active layer segment of the outermost positive electrode sheet facing away from the center of the battery cell and on at least a portion of the side of the empty foil segment facing away from the center of the battery cell.

[0015] Beneficial effects: While silicon-based anode active materials in the negative electrode can improve the energy density of the battery, they expand significantly during battery cycling. This expansion acts on the adjacent positive electrode, easily leading to deformation, powder shedding (active material loss), and breakage. Adding a textured area with protrusions and concave sections to the inner positive electrode can alleviate the pressure exerted by the negative electrode on the positive electrode during cycling and release interlayer stress. However, to avoid the protrusions and concave sections affecting the battery's surface flatness and heat dissipation consistency, the outermost positive electrode does not have a textured area. Typically, when a textured area is added, a certain amount of clearance (secondary area) needs to be reserved near the edge of the inner positive electrode to prevent the protrusions and concave sections from being too close to the edge, which could cause edge shedding, warping, or breakage, leading to short circuits and other safety issues.

[0016] However, due to the presence of the protrusion and its location on the inner positive electrode sheet facing away from the center of the cell, during battery cycling, the expansion of the negative electrode acts on the inner positive electrode sheet. The protrusion of the inner positive electrode sheet will squeeze the outermost positive electrode sheet, causing the outermost positive electrode sheet to experience different stresses in the textured area with protrusions and concave parts on the inner positive electrode sheet compared to the unsupported area near the edge. This results in deformation of the outermost positive electrode sheet at the position corresponding to the second area on the inner positive electrode sheet without protrusions and near the edge, causing it to fold into a flange. This flange will repeatedly scrape against the inner wall of the casing during battery cycling, eventually leading to casing damage, reduced strength, and problems such as water vapor ingress and leakage, affecting the battery's cycle life and safety.

[0017] This invention provides a first adhesive layer on the surface of the outermost positive electrode sheet facing away from the center of the battery cell. The orthographic projection of the first adhesive layer along the thickness direction of the battery cell at least partially overlaps with the orthographic projection of the second region of the inner positive electrode sheet near the edge along the thickness direction of the battery cell. This enhances the resistance of the outermost positive electrode sheet and the corresponding position of the second region of the inner positive electrode sheet that does not have protrusions and is near the edge to bending and buckling. This effectively suppresses the deformation of the outermost positive electrode sheet caused by the protrusions on the inner positive electrode sheet when the battery expands. It also improves the problems of reduced shell strength, damage, water vapor ingress, and leakage caused by the bending and warping of the outermost positive electrode sheet, which lead to abnormal changes in the internal voltage of the battery, reduced cycle life, and battery failure. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a battery according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of the battery cell according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the positive electrode sheet according to an embodiment of the present invention; Figure 4 This is a partially enlarged schematic diagram of the positive electrode sheet according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the front structure of the battery cell according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the back side of the battery cell according to an embodiment of the present invention; Figure 7A schematic diagram of the structure of the outermost positive electrode sheet of this invention having a first adhesive layer; Figure 8 A schematic diagram of the structure of the outermost positive electrode sheet of another embodiment of the present invention with a first adhesive layer; Figure 9 A schematic diagram of a structure in which a first adhesive layer is provided on the outermost positive electrode sheet according to another embodiment of the present invention; Figure 10 This is an enlarged schematic diagram of the cross-section of the positive electrode sheet of the present invention.

[0020] Explanation of reference numerals in the attached figures: 100-Battery; 10-Casing; 20-Cell; 21-Positive electrode sheet; 21a-First region; 21b-Second region; 21c-Positive electrode termination; 21d-Positive electrode start-up; 213-Positive electrode current collector; 214-Positive electrode active layer; 22-Negative electrode sheet; 23-Separator; 30-First adhesive layer; 41-First insulating tape; 42-Second insulating tape; 50-Second adhesive layer; 201-Protrusion; 202-Concave; 203-Straight region; 211-Outermost positive electrode sheet; 212-Inner positive electrode sheet; 2111-Single-sided active layer segment; 2112-Empty foil segment. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The following is combined Figures 1 to 10 The embodiments of the present invention will be described below.

[0023] According to an embodiment of the present invention, in a first aspect, a battery 100 is provided, including a casing 10, a cell 20, and a first adhesive layer 30.

[0024] Battery 100 can be a pouch battery. Casing 10 can be an aluminum-plastic film.

[0025] The battery cell 20 can be a single cell or a stacked cell. The battery cell 20 is disposed inside the housing 10 and includes a positive electrode 21, a negative electrode 22 and a separator 23 located between the positive electrode 21 and the negative electrode 22.

[0026] The positive electrode 21 may include a positive current collector 213 and a positive active layer 214 disposed on at least one side surface of the positive current collector 213.

[0027] In some embodiments, the positive current collector may comprise aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector). The composite current collector can be formed by depositing a metallic material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) onto a polymer substrate.

[0028] The positive electrode active material of the positive electrode active layer can include lithium nickel cobalt manganese oxide (LiNi). 0.90 Co 0.05 Mn 0.05 At least one of the following: O2 (NCM955), NCM811, NCM622, NCM523, NCM111, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganese oxide, spinel-type lithium nickel manganese oxide, and lithium titanate.

[0029] In some embodiments, the negative electrode 22 includes a negative electrode current collector and a negative electrode active layer disposed on at least one side surface of the negative electrode current collector.

[0030] The negative electrode current collector can be, for example, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a composite current collector.

[0031] The negative electrode active material in the negative electrode active layer includes a silicon-based material, which may be at least one of silicon, silicon-carbon composite material, and silicon-oxygen composite material, including at least one of spherical silicon-carbon composite material and blocky silicon-carbon composite material.

[0032] In some embodiments, the battery 100 further includes an electrolyte comprising a lithium salt and a solvent, wherein the solvent comprises at least one selected from ethylene carbonate, diethyl carbonate, or fluoroethylene carbonate. In other embodiments, the electrolyte further includes a nitrile additive, wherein the content of the nitrile additive is 0.5%-8% based on the total mass of the electrolyte, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%. In some embodiments, the nitrile additive includes, for example, at least one selected from butadionitrile, adiponitrile, and 1,3,6-hexanetrionitrile.

[0033] Along the thickness direction of the battery cell, the positive electrode 21 includes an outermost positive electrode 211 located away from the center O of the battery cell and on the outermost side of the battery cell, and an inner positive electrode 212 located close to the center O of the battery cell. It can be understood that the inner positive electrode 212 is located on the inner side of the outermost positive electrode 211, close to the center O of the battery cell.

[0034] In some embodiments, the battery cell is a wound core, and the thickness direction of the battery cell is the same as the layer thickness direction after the battery cell is wound and stacked. The battery cell includes a flat region and an arc region. In the flat region, the thickness direction Z of the battery cell is perpendicular to the large surface of the battery cell; in the arc region, the thickness direction of the battery cell is the radial direction of the arc segment of the electrode sheet, and also the stacking direction of the arc segment of the electrode sheet.

[0035] In some other embodiments, the battery cell can be a stacked cell, and the outermost positive electrode 211 refers to the two outermost positive electrode 211 located in the thickness direction of the battery cell, and the positive electrode 211 located between the two outermost positive electrode 211 is the inner positive electrode 211.

[0036] In this embodiment of the invention, the first direction X can be the length direction of the battery, and the second direction Y can be the width direction of the battery.

[0037] The outermost positive electrode 211 is a section of positive electrode 21 exposed on the outside along the thickness direction of the cell 20, and the cell 20 ends at the outermost positive electrode 211. The inner positive electrode 212 is another section of positive electrode 21 located on the inside of the outermost positive electrode 211 near the center O of the cell, along the thickness direction of the cell 20.

[0038] Specifically, refer to Figure 2 The positive electrode 21 has a positive electrode start end 21d and a positive electrode end 21c. Along the winding direction of the cell 20, the end of the inner positive electrode 212 that is away from the outer positive electrode 21 is the positive electrode start end 21d, and the end of the outermost positive electrode 211 that is away from the inner positive electrode 212 is the positive electrode end 21c.

[0039] Reference Figure 3 and Figure 4 The inner positive electrode 212 has a first region 21a and a second region 21b. The second region 21b is located on at least one side of the first region 21a along the first direction X, and is disposed near the edge of the positive electrode along the first direction X. When the cell is a wound core, the first direction X is parallel to the winding direction of the cell 20. The inner positive electrode 212 includes a textured region disposed in the first region 21a. The surface of the textured region facing the center O of the cell has a recess, and the surface of the textured region away from the center O of the cell has a protrusion 201 corresponding to the recess. No protrusions or recesses are provided on the second region 21b of the inner positive electrode 212 and the outermost positive electrode 211. This arrangement reserves a certain clearance area near the edge of the inner positive electrode 212 along the first direction X. This prevents the protrusions and recesses on the textured area from being too close to the edge of the inner positive electrode 21, which could cause edge material loss, warping, or breakage and lead to battery short circuits and other safety issues. It also improves the problem that the protrusions and recesses in the textured area affect the flatness of the battery appearance and cause poor heat dissipation consistency of the battery.

[0040] Reference Figure 4Take the tangent line passing through the edge of the protrusion 201 that is parallel to the edge of the positive electrode 21 along the first direction X and is closest to the edge of the positive electrode 21 as the first straight line L1. Along the first direction X, the part of the positive electrode 21 located between the edge and the first straight line L1 is the second region 21b. Along the first direction X, the other part of the positive electrode 21 other than the second region 21b is the first region 21a. Figure 4 Two second regions 21b are shown near the two edges of the positive electrode 21 along the first direction X, and a first region 21a is shown between the two second regions 21b.

[0041] The first adhesive layer 30 is disposed on the surface of the outermost positive electrode 211 facing away from the center O of the cell. On the same projection plane perpendicular to the thickness direction of the cell, the orthographic projection of the first adhesive layer 30 at least partially overlaps with the orthographic projection of the second region 21b of the inner positive electrode 212. That is, there is an overlapping area between the orthographic projection of the first adhesive layer 30 and the orthographic projection of the second region 21b of the inner positive electrode 212. With this configuration, the ability of the portion of the outermost positive electrode 211 corresponding to the second region 21b of the inner positive electrode 212 to resist bending and buckling is enhanced. This effectively suppresses the deformation of the outermost positive electrode 211 caused by the extrusion of the inner positive electrode 212 due to battery expansion, and improves the problem of reduced battery cycle life and battery failure caused by the outermost positive electrode 211 bending and warping, resulting in a rolled edge.

[0042] The first adhesive layer 30 can be a colloid formed by extruding and bonding the outermost positive electrode sheet 211 in a viscous state at high temperature (e.g., 120℃~160℃) and then curing it. The material of the first adhesive layer 30 includes at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer, polyamide, and polyester elastomer.

[0043] The overlap dimension D1 between the orthographic projection of the first adhesive layer 30 and the orthographic projection of the second region 21b of the inner positive electrode 212 along the first direction X is greater than 0 and less than or equal to 7 mm. D1 can be, for example, any one of 0.1 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, or any value between two of them.

[0044] A larger D1 increases the resistance of the outermost positive electrode 211 to bending and buckling in the second region 21b of the inner positive electrode 212, thus reducing the risk of deformation of the outermost positive electrode 211 and minimizing damage to the battery casing after deformation and folding. This prevents voltage differential issues after drop tests and cycles, affecting battery performance. However, if D1 is too large, for example, greater than 7mm, it requires increasing the area of ​​the inner positive electrode 212 without texture to increase the size of D1. This fails to effectively mitigate the compression of the positive electrode by the negative electrode during battery cycling and release interlayer stress. This can lead to localized breakage of the positive electrode during battery cycling. On the other hand, if the first adhesive layer is a viscous flow state formed by extrusion and bonding to the outermost positive electrode 211 after curing at high temperature (e.g., 120℃~160℃), and D1 is too large, then the extrusion amount of the first adhesive layer 30 at high temperature (e.g., 120℃~160℃) needs to be increased. This will cause the first adhesive layer 30 to flow from the edge of the cell into the positive electrode 21, negative electrode 22, and separator 23, which may lead to the deactivation of the positive active material on the positive electrode 21 and the negative active material on the negative electrode 22, as well as the shrinkage of the separator 23, increasing the probability of problems such as reduced battery capacity, lithium plating, and short circuits. If D1 is too small, it will not be able to improve the ability of the outermost positive electrode 211 to resist bending and buckling of the second region 21b corresponding to the inner positive electrode 212, and increase the risk of voltage difference failure after the battery is dropped and cycled. Therefore, D1 needs to be controlled within a suitable range, that is, D1 is greater than 0 and less than or equal to 7 mm.

[0045] In some embodiments. See reference. Figure 4 Along the first direction X, the overlap dimension between the first adhesive layer 30 and the outermost positive electrode 211 is D2, where 3mm ≤ D2 ≤ 12mm. D2 can be any one of 3mm, 4mm, 5mm, 6mm, 10mm, 11mm, and 12mm, or any value between two of them.

[0046] The first adhesive layer 30 may extend beyond the edge of the outermost positive electrode 211 along the first direction X, or it may not extend beyond the edge of the outermost positive electrode 211.

[0047] D2 is greater than or equal to 3mm, ensuring sufficient overlap between the first adhesive layer 30 and the outermost positive electrode 211. This guarantees that the portion of the outermost positive electrode 211 corresponding to the second region 21b of the inner positive electrode 212 has sufficient resistance to bending and buckling deformation, reducing the risk of edge folding, friction, and puncture of the outermost positive electrode during battery cycling and drop tests. This also reduces the risk of voltage differential problems after drop tests and cycling, thereby improving battery cycle life and safety. D2 is less than or equal to 12mm, ensuring sufficient overlap between the first adhesive layer 30 and the outermost positive electrode 211. The overlap size with the outermost positive electrode 211 should not be too large. Excessive overlap increases surface roughness and reduces volumetric energy density. Furthermore, if the first adhesive layer is a viscous flow state extruded and bonded to the outermost positive electrode 211 at high temperatures (e.g., 120℃~160℃) and cured, a large D2 will hinder the rapid dissipation of heat from the extruded (e.g., 120℃~160℃) viscous flow first adhesive layer 30. This increases the risk of deactivation of the positive electrode active layer on the positive electrode 21 due to heat conduction from the positive electrode current collector, leading to a decrease in volumetric energy density. Therefore, it is necessary to control 3mm ≤ D2 ≤ 12mm.

[0048] In some embodiments. See reference. Figure 4 On the same projection plane perpendicular to the thickness direction of the battery cell, the overlap dimension D4 of the orthographic projection of the first adhesive layer 30 and the orthographic projection of the protrusion 201 in the textured area of ​​the inner positive electrode 212 along the first direction X satisfies 0mm≤D4≤5mm. D3 can be any one of 0, 1mm, 2mm, 3mm, 4mm, 5mm or any value between two of them.

[0049] When D4 equals 0, the orthographic projection of the first adhesive layer 30 does not cover the orthographic projection of the protrusion 201, that is, the projections of the two in the thickness direction of the cell do not overlap.

[0050] When D4 is greater than 0, the orthographic projection of the first adhesive layer 30 covers the orthographic projection of the protrusion 201, further increasing the resistance of the outermost positive electrode sheet 211 to bending and buckling deformation in the second region 21b corresponding to the inner positive electrode sheet 212. This reduces the risk of folding of the two edges of the outermost positive electrode sheet 211 along the X direction after the textured area is set on the inner positive electrode sheet, which may occur after drop testing and cycling. This reduces the risk of voltage differential problems in the battery, thereby improving battery cycle life and safety. When D4 is less than or equal to 5mm, the size of the orthographic projection of the first adhesive layer 30 covering the orthographic projection of the protrusion 201 is not too large. If it is too large, the first adhesive layer 30 in a high-temperature viscous state will be difficult to dissipate quickly, and the positive electrode active layer on the positive electrode sheet 21 will be at high risk of deactivation due to heat conduction from the positive electrode current collector, resulting in a decrease in battery energy density. Therefore, it is necessary to control 0mm≤D4≤5mm.

[0051] In some embodiments, along the same side of the first direction X, the edge of the negative electrode 22 extends beyond the edge of the positive electrode 21, and the edge of the separator 23 extends beyond the edge of the negative electrode 22. Along the same side of the first direction X, one end of the first adhesive layer 30 is flush with the edge of the outermost positive electrode 211. Figure 7 (As shown).

[0052] With this configuration, if the outermost positive electrode 211 is folded inward, the contact area between it and the negative electrode can be reduced. At the same time, it can also prevent the first adhesive layer 30 from extending beyond the edge of the outermost positive electrode 211, which could lead to safety issues such as lithium plating at the edge of the battery caused by the negative electrode active layer covering the negative electrode 22.

[0053] In some embodiments, along the same side of the first direction X, one end of the first adhesive layer 30 extends beyond the edge of the outermost positive electrode 211 but does not extend beyond the edge of the separator 23.

[0054] With this design, the edge position of the outermost positive electrode 211, which is most prone to deformation and forming a folded edge, is further enhanced to resist bending and buckling. This reduces the risk of the outermost positive electrode 211 scraping or damaging the outer casing when it folds outward, and reduces problems such as casing damage and leakage, which could cause abnormal voltage changes in the battery.

[0055] As an example, refer to Figure 8 Along the same side of the first direction X, one end of the first adhesive layer 30 extends beyond the edge of the outermost positive electrode 211 and is located between the edge of the outermost positive electrode 211 and the edge of the negative electrode 22.

[0056] With this configuration, the edge position of the outermost positive electrode 211, which is most prone to deformation and forming a fold, is further enhanced to resist bending and buckling. This reduces the risk of short circuit when the outermost positive electrode 211 folds over and comes into contact with the negative electrode active layer on the negative electrode 22, thereby improving battery safety.

[0057] As another example, along the same side of the first direction X, one end of the first adhesive layer 30 extends beyond the edge of the outermost positive electrode 211 and is located between the edge of the negative electrode 22 and the edge of the separator 23.

[0058] With this configuration, one end of the first adhesive layer 30 is bonded to the separator 23. Compared to bonding it to the relatively smooth current collector surface of the positive or negative electrode, the risk of peeling off during battery cycling is greatly reduced. The bonding is more reliable and can also prevent the separator from shrinking rapidly during furnace temperature testing, which could lead to direct contact and short circuit between the positive and negative electrodes, and the risk of battery explosion.

[0059] In some embodiments, the overlap dimension of the portion of the first adhesive layer 30 extending beyond the edge of the outermost positive electrode 211 with the separator 23 along the first direction X is D3, where 0 < D3 ≤ 1.5 mm. D3 can be any one of 0.1 mm, 0.5 mm, 0.7 mm, 1 mm, 1.3 mm, 1.5 mm, or any value between two of them.

[0060] If D3 is too large, exceeding 1.5mm, it may affect the smooth insertion and extraction of lithium ions near the overlapping area, reducing the battery's cycle performance. Furthermore, the separator 23 may experience pre-deformation and shrinkage of the first adhesive layer 30 under high-temperature viscous flow conditions, leading to separator 23 isolation failure during subsequent furnace temperature testing and reducing the battery's furnace temperature test pass rate. Therefore, it is necessary to control 0 < D3 ≤ 1.5mm.

[0061] In some embodiments, the portion of the first adhesive layer 30 extending beyond the edge of the outermost positive electrode 211 overlaps with the separator 23. A functional layer is disposed on the surface of the separator 23, and the functional layer is at least partially located in the overlapping region. The portion of the first adhesive layer 30 extending beyond the edge of the outermost positive electrode 211 is bonded to the functional layer. The functional layer may include at least one of Al2O3, SiO2, ZrO2, barium titanate, boehmite, melamine cyanurate, melamine polyphosphate, melamine trithiocyanate, melamine, 2,4,6-tris(aminohexanoic acid)-1,3,5-triazine, 2-(4-bromophenyl)-4,6-dimethyl-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazin-2-yl)guanidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, cyanuric chloride, 2,4,6-tris(2-pyridyl)triazine, 2,4,6-triphenyl-1,3,5-triazine, tris(tribromophenoxy)triazine, and 2-amino-4,6-methoxy-1,3,5-triazine.

[0062] The first adhesive layer 30 is bonded to the functional layer by extending beyond the edge of the outermost positive electrode 211. The functional layer includes ceramic material, which can prevent the separator 23 from shrinking and shifting due to the high temperature viscous flow of the first adhesive layer 30, thus avoiding safety issues such as isolation failure leading to battery short circuits during battery cycling and subsequent furnace temperature testing.

[0063] In some embodiments, the thickness of the first adhesive layer 30 is greater than the thickness of the functional layer, and the ratio A / B of the thickness A of the first adhesive layer 30 and the thickness B of the functional layer ranges from 1.2 to 28. The thickness B of the functional layer ranges from 0.5 μm to 6 μm. A / B can be any one of 1.2, 5, 10, 15, 20, 25, 28, or any value between any two. B can be any one of 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or any value between any two.

[0064] If A / B is less than 1.2, the thickness of the first adhesive layer 30 is too thin, and it cannot effectively bind the outermost positive electrode 211. After the battery is dropped or cycled, the outermost positive electrode 211 of the cell still has a large risk of folding, which will cause damage to the casing, increase the voltage difference of the battery, and reduce the battery's service life and safety. If A / B is greater than 28, the thickness of the functional layer on the separator is too thin. During the furnace temperature test, the separator 23 is more likely to shrink and fail, increasing the probability of the battery exploding and reducing the battery's safety.

[0065] During the process of setting the first adhesive layer 30 on the outermost positive electrode 211, the first adhesive layer 30 is in a viscous flow state and has a certain temperature during extrusion. The greater the thickness of the first adhesive layer 30, the more difficult it is to dissipate the temperature during extrusion. The positive electrode current collector metal has strong thermal conductivity, which can easily affect the activity of the positive electrode active layer on the side of the positive electrode current collector close to the center of the cell, or conduct the heat in the first adhesive layer 30 to the adjacent separator 23 and negative electrode 22, causing the separator 23 to shrink or the positive electrode active material or negative electrode active material in the battery to deactivate, thereby causing problems such as reduced battery capacity, lithium plating, and short circuit.

[0066] In some embodiments, at 120°C to 160°C, the viscosity of the first adhesive layer 30 is 2000 mPa·s to 4000 mPa·s. For example, it can be any one of 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 3500 mPa·s, 4000 mPa·s, or a value between any two of them.

[0067] Viscosity measurement method: The rotational viscometer method is used. The equipment used is Brookfield RVDV-II+ (rotary rotor type). Start the equipment, turn on the power, and enter the test interface; set the temperature, enter the target temperature (e.g., 120℃, 100℃, 160℃); set the rotation speed, select the initial rotation speed (e.g., 10rpm); start the test, press the "Start" button to start the rotation; wait for stabilization, and record the reading after it stabilizes (usually 1–3 minutes).

[0068] If the viscosity of the first adhesive layer 30 is too low (less than 2000 mPa·s), during the application of the first adhesive layer 30 to the outermost positive electrode 211, the viscous flow of the first adhesive layer 30 can easily flow to the negative electrode 22 or the separator 23, causing the separator 23 to shrink under high temperature or localized deactivation of the positive or negative electrode active materials in the battery, resulting in reduced battery capacity, lithium plating, short circuits, or other problems. If the viscosity of the first adhesive layer 30 is too high (greater than 4000 mPa·s), during the application of the first adhesive layer 30 to the outermost positive electrode 211, the flow rate of the first adhesive layer 30 is low, the dispensing accuracy is poor, and the manufacturing efficiency is low. Therefore, it is necessary to control the viscosity of the first adhesive layer 30 to be between 2000 mPa·s and 4000 mPa·s.

[0069] In some embodiments, the peel strength between the first adhesive layer 30 and the outermost positive electrode 211 is 0.2 N / mm. 2 ~0.6N / mm 2 It can be 0.2 N / mm. 2 0.3N / mm 2 0.4N / mm 2 0.5N / mm 2 0.6N / mm 2 The value is any one of the values ​​or any two of them. It should be noted that the first adhesive layer 30 is bonded to the empty foil surface of the outermost positive electrode 211 where no positive active layer is provided. Therefore, the peel strength between the first adhesive layer 30 and the outermost positive electrode 211 refers to the peel strength between the first adhesive layer 30 and the empty foil surface of the outermost positive electrode 211 where no positive active layer is provided.

[0070] The peel strength between the first adhesive layer 30 and the outermost positive electrode plate 211 should not be too low, less than 0.2 N / mm. 2 The first adhesive layer 30 is easily soaked in electrolyte and may fall off during battery cycling, leading to bonding failure. Ultimately, the outermost positive electrode 211 may flip up and puncture the outer casing, causing abnormal battery voltage changes or even safety issues.

[0071] The test method for peel strength is as follows: GB / T 2792-2014 "Test Method for Peel Strength of Pressure Sensitive Adhesive Tape", with a test angle of 180°, a peel speed of 300 mm / min, and ≥3 tests, and the average value is taken.

[0072] In some embodiments, the maximum depth of the recess along the thickness direction of the battery cell ranges from 3 μm to 40 μm. It can be any one of 3 μm, 10 μm, 20 μm, 30 μm, and 40 μm, or a value between any two of them.

[0073] The maximum depth of the recess is the vertical distance between the lowest point of the recess and the part of the surface of the positive electrode 21 near the center of the cell (the surface on the same side as the recess) where the recess is not provided.

[0074] Reference Figure 10 The positive electrode 21 is cut to obtain a cross-section. The cross-section is perpendicular to the length direction of the positive electrode 21 and passes through the recess 202. Under a scanning electron microscope magnified to 500x, the cross-section has an arc Q1 corresponding to the recess 202 on the surface of the positive electrode active layer 214 and a straight line Q2 corresponding to the part of the surface of the positive electrode active layer 214 on the same side as the recess 202 where the recess 202 is not provided (e.g., the part of the surface located between two recesses 202). The vertical distance between the tangent Q3 at the lowest point of the arc Q1 and the straight line Q2 is the maximum depth of the recess 202.

[0075] If the maximum depth of the recess is too small, less than 3μm, it cannot effectively alleviate and release the interlayer stress caused by the negative electrode pressing against the positive electrode during battery cycling. This can easily lead to deformation, powder shedding (active material loss), and breakage of the positive electrode. Therefore, the maximum depth of the recess needs to be greater than 3μm. However, the maximum depth of the recess should not be too large, greater than 40μm. The area of ​​the outermost positive electrode 211 corresponding to the second region 21b of the inner positive electrode 212 is prone to deformation and edge flipping. This can cause repeated friction with the outer casing during battery cycling, leading to casing cracking, reduced strength, leakage, and other issues, resulting in abnormal battery voltage changes and safety problems. Therefore, the maximum depth of the recess needs to be controlled within the range of 3μm to 40μm.

[0076] In some embodiments, the maximum width of the recess along the first direction X ranges from 1 mm to 8 mm. For example, it can be any one of 1 mm, 1.2 mm, 2 mm, 2.5 mm, 4 mm, 5 mm, 5.6 mm, 7 mm, 8 mm, or any combination thereof.

[0077] If the maximum width of the recess is too small, less than 1 mm, the corresponding convex part 201 is too sharp, which can easily cause the outermost positive electrode 211 to deform at the second region 21b of the inner positive electrode 212, forming a flange. This can cause repeated friction with the outer casing during battery cycling, leading to safety issues such as casing cracking, reduced strength, and leakage. Therefore, the maximum width of the recess needs to be greater than or equal to 1 mm. If the maximum width of the recess is too large, greater than 8 mm, the corresponding convex part 201 is too flat, close to a plane, which cannot effectively alleviate and release the interlayer stress when the negative electrode extrudes the positive electrode during battery cycling. This can easily lead to deformation, powder shedding (active material shedding), and breakage of the positive electrode. Therefore, the maximum width of the recess needs to be controlled within the range of 1 mm to 8 mm.

[0078] In some embodiments, the distance between two adjacent recesses along the first direction X ranges from 1 mm to 10 mm. For example, it can be any one of 1 mm, 2 mm, 3 mm, 5 mm, 5.5 mm, 6 mm, 7 mm, 8 mm, 10 mm, or any value between two of them.

[0079] The spacing between two adjacent recesses should not be too large, greater than 10mm. Without a support structure, the portion between two adjacent protrusions 201 corresponding to the recesses on the positive electrode sheet is prone to local bending and wrinkling when squeezed by the negative electrode sheet during battery cycling. This can lead to material loss from the positive electrode active layer and fatigue fracture of the positive electrode current collector during battery cycling. Conversely, the spacing between two adjacent recesses should not be too small, less than 1mm. If the protrusions 201 corresponding to the recesses are too dense, there is no buffer space, which cannot effectively alleviate and release the interlayer stress caused by the negative electrode sheet squeezing the positive electrode sheet during battery cycling. This can easily lead to deformation, powder loss (active material shedding), and breakage of the positive electrode sheet. It can also easily cause deformation and edge curling of the outermost positive electrode sheet 211 corresponding to the second region 21b of the inner positive electrode sheet 212, resulting in abnormal changes in battery voltage. Therefore, the spacing between two adjacent protrusions 201 needs to be controlled within the range of 1mm to 10mm. It should be noted that the spacing between two adjacent recesses refers to the straight-line distance between the two edges of the two recesses that are close to each other.

[0080] In some embodiments, the battery further includes insulating tape, which is at least partially adhered to the outer side of the outermost positive electrode 211 of the cell 20. The insulating tape does not overlap with the first adhesive layer 30, and the thickness of the first adhesive layer 30 is less than or equal to the thickness of the insulating tape.

[0081] With this configuration, the first adhesive layer 30 effectively prevents the outermost positive electrode sheet 211 from flipping over, while not taking up extra space inside the battery, which helps to improve the volumetric energy density of the battery.

[0082] In some embodiments, the thickness of the first adhesive layer 30 ranges from 6 μm to 14 μm. For example, it can be any one of 6 μm, 7 μm, 10 μm, 11.5 μm, 12 μm, 13 μm, 14 μm, or a value between any two of them.

[0083] The thickness of the first adhesive layer 30 is between 6μm and 14μm. The first adhesive layer 30 has a suitable thickness, which can both ensure the strength of the outermost positive electrode 211 near the edge and prevent space occupation, thus helping to improve the volumetric energy density of the battery.

[0084] The thickness of the insulating tape ranges from 10μm to 16μm. For example, it can be any value or a combination of 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, and 16μm.

[0085] The appropriate thickness of the insulating tape ensures that it effectively binds the battery cells while preventing space occupation, thus helping to improve the volumetric energy density of the battery.

[0086] As a concrete example, refer to Figure 5 The battery cell 20 is a battery cell, comprising two flat regions 203 opposite each other along the thickness direction Z of the battery cell. The insulating tape includes a first insulating tape 41 adhered to the flat regions 203. Along the winding direction of the battery cell, the outermost positive electrode plate 211, at its positive electrode termination end 21c away from the battery cell, is fixed to one of the flat regions 203 by the first insulating tape 41. The first insulating tape 41 does not overlap with the first adhesive layer 30. The thickness direction Z of the battery cell is perpendicular to the first direction X, and the first direction X is parallel to the axial direction of the battery cell. And / or, one side of the first insulating tape 41 is adhered to the flat region 203, and the other side is adhered to the inner wall of the outer casing 10. And / or, the first insulating tape 41 is double-sided adhesive. And / or, the insulating tape also includes a second insulating tape 42, the two ends of which are respectively bonded to both sides of the straight area 203 along the thickness direction Z of the battery core, and pass around the end of the battery core along the first direction X. The second insulating tape 42 does not overlap with the first adhesive layer 30.

[0087] In some embodiments, the battery cell 20 is a battery cell, and the positive electrode 21 includes a positive electrode start end 21d and a positive electrode end 21c. The end of the inner positive electrode 212 away from the outermost positive electrode 211 is the positive electrode start end 21d. The outermost positive electrode 211 includes a single-sided active layer segment 2111, and the end of the single-sided active layer segment 2111 away from the positive electrode start end 21d is the positive electrode end 21c. The side of the single-sided active layer segment 2111 facing the center O of the battery cell has a positive electrode active layer, and the side of the single-sided active layer segment 2111 facing away from the center O of the battery cell does not have a positive electrode active layer. The first adhesive layer 30 is disposed on at least a portion of the area of ​​the single-sided active layer segment 2111 of the outermost positive electrode 211 facing away from the center of the battery cell.

[0088] Alternatively, the battery cell is a wound core, with the positive electrode 21 including a positive electrode starting end 21d and a positive electrode ending end 21c. The end of the inner positive electrode 212 furthest from the outermost positive electrode 211 is the positive electrode starting end 21d. The outermost positive electrode 211 includes a connected single-sided active layer segment 2111 and a blank foil segment 2112. Along the winding direction of the battery cell, the single-sided active layer segment 2111 is located between the inner positive electrode 212 and the blank foil segment 2112, and the blank foil segment 2112 is furthest from the single-sided active layer. One end of segment 2111 is the positive electrode termination end 21c. The side of the single-sided active layer segment 2111 facing the center O of the cell has a positive electrode active layer, and the side of the single-sided active layer segment 2111 facing away from the center O of the cell does not have a positive electrode active layer. The first adhesive layer 30 is disposed on at least a portion of the side of the single-sided active layer segment 2111 of the outermost positive electrode sheet 211 facing away from the center of the cell and on at least a portion of the side of the empty foil segment 2112 facing away from the center of the cell.

[0089] In some embodiments, the housing 10 includes an inner sidewall, and a second adhesive layer 50 is disposed on the inner sidewall at a position corresponding to the edge of the outermost positive electrode 211 along the first direction X. This further reduces the risk of deformation of the outermost positive electrode 211 during battery cycling and the resulting damage, leakage, and decreased strength of the housing due to friction with the inner sidewall, which could lead to reduced battery cycle life and safety issues.

[0090] Example 1: Battery preparation steps: (1) Preparation of positive electrode Positive electrode active material: Lithium cobalt oxide (doped with Mg and Al, median particle size of 17 μm) 97.2 parts by weight; Positive electrode conductive agent: Super P and carbon nanotubes (where Super P: carbon nanotube mass ratio = 1:1) total 1.5 parts by weight; Positive electrode binder: polyvinylidene fluoride (PVDF520) 1.3 parts by weight; The positive electrode active material, positive electrode binder, and positive electrode conductive agent are mixed in N In methylpyrrolidone (NMP) solvent, the mixture is continuously stirred under the action of a stirrer to form a uniform positive electrode slurry. Subsequently, the positive electrode slurry is coated on both sides of a positive electrode current collector (aluminum foil) with a thickness of 10 μm, and then dried in a vacuum oven at 120°C for 5 hours. After rolling and slitting, the desired positive electrode sheet is obtained.

[0091] The electrode is obtained by molding. On the surface of the first region of the inner positive electrode near the center of the cell, a concave part and a corresponding convex part are formed to form a textured area. The depth of the concave part is 10 μm, the distance between two adjacent concave parts is 1.2 mm, and the maximum width of the concave part is 2 mm. No concave or convex parts are provided on the surface of the second region of the inner positive electrode that is connected to the first region. A first adhesive layer is provided on the surface of the outermost positive electrode in the thickness direction of the cell on the side away from the center of the cell. The overlap dimension D1 between the orthographic projection of the first adhesive layer and the orthographic projection of the second region of the inner positive electrode along the first direction X is 4 mm, the width D2 of the first adhesive layer is 8 mm, and the thickness A of the first adhesive layer is 12 μm.

[0092] (2) Preparation of negative electrode sheet Negative electrode active material: 80.5 parts by weight of graphite, 16 parts by weight of silicon carbide, totaling 96.5 parts by weight; Negative electrode conductive agent: 1.5 parts by weight of carbon nanotubes; Negative electrode binder: 1 part by weight of sodium carboxymethyl cellulose (CMC) and 1 part by weight of styrene-butadiene rubber (SBR); The negative electrode active material and negative electrode binder are mixed in an aqueous solvent and continuously stirred under the action of a stirrer to form a fluid negative electrode slurry. Subsequently, the slurry is coated on both sides of a negative electrode current collector (copper foil) with a thickness of 8μm, and then dried in a vacuum oven at 120℃ for 5 hours. After rolling and slitting, the desired negative electrode sheet is obtained.

[0093] (3) Electrolyte preparation Lithium salts: LiPF6 18% by weight; propyl propionate (PP) 25% by weight, ethyl propionate 15% by weight, propylene carbonate 10% by weight; diethyl carbonate 17% by weight; 1,3 The following ingredients were selected: 4% propane sulfonate lactone, 3% adiponitrile, and 8% fluoroethylene carbonate (FEC). The above substances were mixed into a homogeneous solution in an argon-filled glove box (moisture content <1 ppm, oxygen content <1 ppm). After thorough stirring, the desired lithium-ion battery electrolyte was obtained.

[0094] (4) Preparation of diaphragm A functional layer is formed by coating one side of a 5μm polyethylene substrate with a mixture of Al2O3 and polyvinylidene fluoride, and coating the other side with an adhesive layer containing polyvinylidene fluoride. The functional layer is formed by coating the substrate with both the Al2O3 layer and the polyvinylidene fluoride adhesive layer. The functional layer is adjacent to the positive electrode and has a thickness B of 0.8μm.

[0095] (5) Preparation of lithium-ion batteries After the positive electrode sheet of step (1), the separator of step (4), and the negative electrode sheet of step (2) are prepared by winding, the battery cell is fixed by adhesive tape. Then the bare battery cell is placed in an aluminum-plastic film shell, and the electrolyte of step (3) is injected into the dried bare battery cell. After vacuum sealing, room temperature standing, high temperature formation and other processes, the required lithium-ion battery is obtained. In the first direction X, one end of the first adhesive layer extends beyond the edge of the outermost positive electrode sheet but does not extend beyond the edge of the separator. The overlap dimension D3 between the part of the first adhesive layer that extends beyond the edge of the outermost positive electrode sheet and the separator in the first direction is 0.5 mm.

[0096] The batteries of each embodiment are processed according to Table 1 for other parameters. The specific parameters are different, please refer to the table, and will not be described in detail here.

[0097] Table 1:

[0098] 1. Test method for battery voltage change after drop: The voltage of a fully charged battery is measured using a 6.5-digit voltmeter and recorded as V1. The fully charged battery is then fixed at a height of 10cm using a clamp, and a micro-drop test is performed, totaling 14,400 micro-drops. The battery is then left to stand at room temperature and pressure (25℃, 1 standard atmosphere) for 48 hours. The voltage V2 of the battery after the micro-drop and resting is measured again using a 6.5-digit voltmeter. The voltage difference B before and after the micro-drop is calculated as B = (V2 - V1) / 48. If the voltage difference B is within the range of -0.01 to 0.1 (unit: mV / h), the battery voltage change after the drop test is considered to meet the standard, i.e., the test is passed. A total of 5 batteries were tested, and 4 / 5 means that 4 out of the 5 batteries passed the above test.

[0099] 2. Test method for battery voltage change after 800T cycles: The battery was left to stand in a 45℃ constant temperature room for 2 hours. The voltage V1 of the fully charged battery was measured using a 6.5-digit voltmeter and recorded as V1. The battery was then charged with a constant current of 10A to 4.28V, then with a constant current of 8.8A to 4.5V, then with a constant current of 6.5A to 4.55V, and finally with a constant voltage of 2.15A. After standing for 5 minutes, the battery was charged with a constant current of 2A to 4.5V, and finally with a constant voltage of 0.05C. After standing for 10 minutes, the battery was discharged at 0.5C to 3V. This cycle was repeated 800 times (800T). The battery was left to stand in a constant temperature room at 45℃ for 48 hours. The voltage V3 of the battery was measured when it was fully charged after 800 cycles using a 6.5-digit voltmeter. The voltage difference C before and after 800 cycles was calculated as C = (V3 - V1) / 48. If the absolute value of the voltage difference C is between -0.01 and 0.1 (unit: mV / h), then the voltage change of the battery after the drop test is considered to meet the standard, which means it has passed the test. A total of 5 batteries were tested. 4 / 5 means that 4 out of the 5 batteries passed the above test.

[0100] 3. Battery VED Measurement Method: The battery is charged to its limiting voltage using a 0.2°C vapor source, then charged at a constant voltage until the current drops to 0.02C. It is then discharged at a 0.2C current until the limiting voltage is reached. The energy discharged is denoted as E. The battery's thickness, width, and length are measured, and their product is calculated to obtain the battery's volume, denoted as V. The formula for calculating volumetric energy density is VED = EV.

[0101] 4. Battery furnace temperature testing method: A fully charged battery is heated from room temperature (25°C) to 130°C at a rate of 5°C / min and held at that temperature for 60 minutes. After the time is up, the temperature chamber is opened to check the battery. If the battery does not catch fire or explode, it is considered to have passed the furnace temperature test.

[0102] As shown in Table 1, in Examples 1-15, when D1 is in the range of 0-7mm, the pass rates of voltage difference change after battery drop and voltage difference change after 800T cycles are higher than those in Comparative Example 1 when D1=0 and Comparative Example 2 when D1=7.5. These results in higher pass rates for voltage measurement after battery drop, voltage drop after 800T cycles, and furnace temperature. This indicates that when D1 is in the range of 0-7mm, it can improve the problem of abnormal battery voltage changes caused by the outermost positive electrode sheet bending and warping, resulting in decreased shell strength, damage, and leakage. This improves cycle life and safety performance, and reduces the likelihood of battery failure.

[0103] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the scope of the present invention.

Claims

1. A battery, characterized in that, include: Outer shell (10); A battery cell (20) is disposed within the casing. The battery cell includes a positive electrode (21), a negative electrode (22), and a separator (23) located between the positive electrode and the negative electrode. The negative electrode includes a silicon-based negative electrode active material. Along the thickness direction of the battery cell, the positive electrode (21) includes an outermost positive electrode (211) located away from the center (O) of the battery cell and on the outermost side of the battery cell, and an inner positive electrode (212) located near the center of the battery cell. The inner positive electrode (212) has a first region (21a) and a second region (21b). The second region (21b) is located within the casing. The first region (21a) is located on at least one side along the first direction (X), and the second region (21b) is located near the edge of the positive electrode sheet along the first direction (X). The inner positive electrode sheet (212) includes a textured region located in the first region (21a). The surface of the textured region facing the center of the cell has a recess (202), and the surface of the textured region away from the center of the cell has a protrusion (201) corresponding to the recess. Neither the protrusion nor the recess is provided on the second region (21b) of the inner positive electrode sheet (212) nor on the outermost positive electrode sheet (211). The first adhesive layer (30) is disposed on the surface of the outermost positive electrode (211) away from the center of the cell. On the same projection plane perpendicular to the thickness direction of the cell, the orthographic projection of the first adhesive layer (30) and the orthographic projection of the second region (21b) of the inner positive electrode (212) overlap at least partially. The overlap dimension D1 of the orthographic projection of the first adhesive layer (30) and the orthographic projection of the second region (21b) of the inner positive electrode (212) along the first direction (X) is greater than 0 and less than or equal to 7 mm.

2. The battery according to claim 1, characterized in that, On the same projection plane perpendicular to the thickness direction of the battery cell, the overlap dimension of the orthographic projection of the first adhesive layer (30) and the orthographic projection of the protrusion in the textured area of ​​the inner positive electrode sheet (212) along the first direction is D4, 0mm≤D4≤5mm; and / or, Along the first direction (X), the overlap dimension between the first adhesive layer (30) and the outermost positive electrode sheet (211) is D2, 3mm≤D2≤12mm.

3. The battery according to claim 1, characterized in that, Along the same side of the first direction (X), the edge of the negative electrode (22) extends beyond the edge of the positive electrode (21), and the edge of the separator (23) extends beyond the edge of the negative electrode (22); Wherein, along the same side of the first direction (X), one end of the first adhesive layer (30) is flush with the edge of the outermost positive electrode (211); or, along the same side of the first direction (X), one end of the first adhesive layer (30) extends beyond the edge of the outermost positive electrode (211) but does not extend beyond the edge of the separator (23).

4. The battery according to claim 3, characterized in that, The overlap dimension of the first adhesive layer extending beyond the edge of the outermost positive electrode sheet (211) with the separator along the first direction is D3, where 0 < D3 ≤ 1.5 mm; and / or, Along the same side of the first direction (X), one end of the first adhesive layer (30) extends beyond the edge of the outermost positive electrode (211) and is located between the edge of the outermost positive electrode (211) and the edge of the negative electrode (22); or, along the same side of the first direction (X), one end of the first adhesive layer (30) extends beyond the edge of the outermost positive electrode (211) and is located between the edge of the negative electrode (22) and the edge of the separator (23).

5. The battery according to claim 4, characterized in that, The portion of the first adhesive layer (30) extending beyond the edge of the outermost positive electrode (211) overlaps with the separator (23). A functional layer is disposed on the surface of the separator (23), and the functional layer is at least partially located in the overlapping region. The portion of the first adhesive layer (30) extending beyond the edge of the outermost positive electrode (211) is bonded to the functional layer. The functional layer includes Al2O3, SiO2, ZrO2, barium titanate, boehmite, melamine cyanurate, melamine polyphosphate, and melamine trithiocyanate. At least one of the following: melamine, 2,4,6-tris(aminohexanoic acid)-1,3,5-triazine, 2-(4-bromophenyl)-4,6-dimethyl-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazin-2-yl)guanidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, cyanuric chloride, 2,4,6-tris(2-pyridyl)triazine, 2,4,6-triphenyl-1,3,5-triazine, tris(tribromophenoxy)triazine, and 2-amino-4,6-methoxy-1,3,5-triazine.

6. The battery according to claim 5, characterized in that, The thickness of the first adhesive layer (30) is greater than the thickness of the functional layer, and the ratio A / B of the thickness A of the first adhesive layer and the thickness B of the functional layer ranges from 1.2 to 28; and / or, The thickness B of the functional layer ranges from 0.5μm to 6μm.

7. The battery according to claim 1, characterized in that, At 120℃~160℃, the viscosity of the first adhesive layer (30) is 2000 mPa·s~4000 mPa·s; and / or, The peel strength between the first adhesive layer (30) and the outermost positive electrode sheet is 0.2 N / mm. 2 ~0.6N / mm 2 ; and / or, The material of the first adhesive layer (30) includes at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer, polyamide, and polyester elastomer; and / or, Along the thickness direction, the maximum depth of the recess ranges from 3μm to 40μm.

8. The battery according to any one of claims 1-7, characterized in that, The battery also includes insulating tape, which is at least partially adhered to the outer side of the outermost positive electrode plate (211) of the cell (20). The insulating tape does not overlap with the first adhesive layer (30), and the thickness of the first adhesive layer (30) is less than or equal to the thickness of the insulating tape.

9. The battery according to claim 8, characterized in that, The thickness of the first adhesive layer (30) ranges from 6 μm to 14 μm; and / or, The thickness of the insulating tape ranges from 10 μm to 16 μm; and / or, The battery cell (20) is a battery cell, and the battery cell includes two flat regions (203) opposite each other along the thickness direction (Z) of the battery cell; the insulating tape includes a first insulating tape (41) bonded to the flat region (203). Along the winding direction of the battery cell, the outermost positive electrode plate (211) away from the positive electrode end (21c) of the battery cell is fixed to one of the flat regions (203) by the first insulating tape (41). The first insulating tape (41) does not overlap with the first adhesive layer (30). The thickness direction of the battery cell is perpendicular to the first direction, and the first direction is parallel to the axial direction of the battery cell. And / or, one side of the first insulating tape (41) is adhered to the flat area (203), and the other side is adhered to the inner wall of the outer casing (10); And / or, the first insulating tape (41) is double-sided adhesive; And / or, the insulating tape further includes a second insulating tape (42), the two ends of which are respectively bonded to both sides of the straight area along the thickness direction (Z) of the battery cell, and bypass the end of the battery cell along the first direction (X), and the second insulating tape (42) does not overlap with the first adhesive layer (30).

10. The battery according to any one of claims 1-7, characterized in that, The battery cell is a wound core. The positive electrode sheet (21) includes a positive electrode starting end (21d) and a positive electrode ending end (21c). The end of the inner positive electrode sheet (212) away from the outermost positive electrode sheet (211) is the positive electrode starting end (21d). The outermost positive electrode sheet (211) includes a single-sided active layer segment (2111). The end of the single-sided active layer segment (2111) away from the positive electrode starting end (21d) is the positive electrode ending end (21c). The side of the single-sided active layer segment (2111) facing closer to the center of the battery cell has a positive electrode active layer, and the side of the single-sided active layer segment (2111) away from the center of the battery cell does not have the positive electrode active layer. The first adhesive layer (30) is disposed on at least a portion of the area of ​​the single-sided active layer segment (2111) of the outermost positive electrode sheet (211) away from the center of the battery cell. Alternatively, the battery cell is a wound core, and the positive electrode sheet (21) includes a positive electrode starting end (21d) and a positive electrode ending end (21c). The end of the inner positive electrode sheet (212) away from the outermost positive electrode sheet (211) is the positive electrode starting end (21d). The outermost positive electrode sheet (211) includes a connected single-sided active layer segment (2111) and a blank foil segment (2112). Along the winding direction of the battery cell, the single-sided active layer segment (2111) is located between the inner positive electrode sheet (212) and the blank foil segment (2112). The blank foil segment (2112) The end away from the single-sided active layer segment (2111) is the positive electrode termination end (21c). The side of the single-sided active layer segment (2111) facing closer to the center of the cell has a positive electrode active layer, and the side of the single-sided active layer segment (2111) away from the center of the cell does not have the positive electrode active layer. The first adhesive layer (30) is provided on at least a portion of the side of the single-sided active layer segment (2111) of the outermost positive electrode sheet (211) away from the center of the cell and on at least a portion of the side of the empty foil segment (2112) away from the center of the cell.

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