An electrode assembly and a battery

Abstract

The application discloses an electrode assembly and a battery. The electrode assembly comprises a plurality of pole pieces and a separator arranged between two pole pieces with opposite polarities, wherein at least one pole piece has a plurality of first protrusions; the pole piece comprises a current collector and an active material layer arranged on the surface of the current collector, the first protrusions are formed by bending a part of the current collector and a part of the active material layer towards the same side of the pole piece, the height of the first protrusions is H1, and 20 microns ≤ H1 ≤ 80 microns; the active material layer comprises a softener, the softener is selected from at least one of organic silicon, a fatty acid salt and a quaternary amine salt, the weight percentage of the softener in the total weight of the active material layer is A, and 0.01% ≤ A ≤ 0.4%. In the application, the overall flexibility of the pole piece 300 is improved by adding the softener to the active material layer, the height of the first protrusions is higher, the active material layer at the first protrusions does not produce micro-cracks, and then the electrode assembly meeting the use requirements is easily processed, and the electrolyte infiltration effect is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrode assembly and a battery. Background Art

[0002] Currently, the electrode assemblies within secondary batteries utilize a wound structure. After winding, the electrode assemblies must be hot-pressed and secured to prevent movement or puncture of the outer packaging after being placed in it. However, wound electrode assemblies make it difficult for electrolyte to enter the electrode assembly, which can easily lead to problems such as electrolyte insufficiency and poor wetting. Ultimately, this can deteriorate the electrode interface, impacting battery charge and discharge cycle performance and even causing lithium deposition, compromising battery safety. Summary of the Invention

[0003] The inventors discovered that there would be extrusion between the layers of the electrode assembly, especially during the battery charging and discharging process, the expansion and extrusion of the electrode assembly would be further aggravated, resulting in insufficient electrolyte between the layers of the electrode assembly, poor infiltration, and easy interface deterioration, and even abnormal conditions such as poor infiltration and cycle failure.

[0004] The embodiments of the present application provide an electrode assembly and a battery, which can improve the problem of poor electrolyte infiltration in the battery.

[0005] In a first aspect, an embodiment of the present application provides an electrode assembly, comprising a plurality of pole pieces and an isolation membrane disposed between two pole pieces with opposite polarities, wherein at least one pole piece has a plurality of first protrusions.

[0006] The pole piece includes a current collector and an active material layer provided on the surface of the current collector. The first protrusion is formed by a portion of the current collector and a portion of the active material layer protruding toward the same side of the pole piece. The height of the first protrusion is H1, and H1 satisfies: 20μm≤H1≤80μm; the active material layer includes a softener, and the softener is selected from at least one of silicone, fatty acid salt, and quaternary ammonium salt. Based on the total weight of the active material layer, the weight percentage of the softener is A, and A satisfies: 0.01%≤A≤0.4%.

[0007] Based on the electrode assembly of the embodiment of the present application, the height H1 of the first protrusion is in the range of 20μm≤H1≤80μm, and the first protrusion can provide good support to improve the wetting effect of the electrolyte. The weight percentage A of the softener is in the range of 0.01%≤A≤0.40%. The softener can increase the flexibility of the active material layer, prevent the active material layer from being easily broken, and make it easy to bend the electrode sheet to form the first protrusion.

[0008] In some embodiments, the electrode assembly satisfies at least one of the following conditions:

[0009] (1) A satisfies: 0.01% ≤ A ≤ 0.10%, then H1 satisfies: 20 μm ≤ H1 ≤ 40 μm;

[0010] (2) A meets: 0.10% <A≤0.20%,则H1满足:40μm

[0011] (3) A meets: 0.20% <A≤0.40%,则H1满足:60μm

[0012] Based on the above embodiments, the softener can improve the overall flexibility of the electrode, achieve a higher height of the first protrusion, and reduce damage to the electrode, so that no microcracks are generated in the active material layer at the first protrusion, and have no side effects on the processing process, thereby facilitating the processing of electrode assemblies that can meet usage requirements and improving the electrolyte infiltration effect.

[0013] In some embodiments, the silicone is selected from at least one of methyl silicone resin, phenyl silicone resin, vinyl silicone resin, and silicone rubber; the fatty acid salt is selected from at least one of aluminum stearate, magnesium stearate, aluminum isooctanoate, and magnesium isooctanoate; and the quaternary ammonium salt is selected from at least one of long-chain quaternary ammonium salt, short-chain quaternary ammonium salt, aliphatic quaternary ammonium salt, and aromatic quaternary ammonium salt.

[0014] In some embodiments, the active material layer includes a first binder, and the weight percentage of the first binder is B based on the total weight of the active material layer; and the electrode assembly satisfies at least one of the following conditions:

[0015] (1) B satisfies: 0.8% ≤ B ≤ 1.6%, then H1 satisfies: 20 μm ≤ H1 ≤ 40 μm;

[0016] (2) B meets: 1.6% <B≤2.4%,则H1满足:40μm

[0017] Based on the above embodiment, during the process of bending the active material layer of the corner section together with the current collector to form the first convex portion, the active material layer has good ductility and is not prone to cracks, thereby improving the efficiency during the winding process of the electrode and improving the safety of the battery. In addition, the content of the first adhesive is appropriate to prevent the excessive content of the first adhesive from reducing the energy density of the battery.

[0018] In some embodiments, the first adhesive is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride, polyvinyl alcohol, polystyrene, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, and polytetrafluoroethylene.

[0019] In some embodiments, the compacted density of the active material layer is p,3.6 g / cm 3 ​​​≤ρ≤4.35g / cm 3 .

[0020] Based on the above embodiments, the active material layer can have good toughness and is not prone to brittle fracture, while the battery has a suitable energy density.

[0021] In some embodiments, the electrode further includes a primer layer, which is disposed between the active material layer and the current collector. The primer layer includes a primer material, which is selected from at least one of an inorganic oxide and a carbon-containing material.

[0022] In some embodiments, the unit primer weight of the primer layer is n, and the electrode assembly satisfies at least one of the following conditions:

[0023] (1) η satisfies: 0.5 mg / 1540.25 mm 2 ≤η≤2.0mg / 1540.25mm 2 , then H1 satisfies: 20μm≤H1≤40μm;

[0024] (2) η satisfies: 2.0 mg / 1540.25 mm 2 ≤η≤4.0mg / 1540.25mm 2 , then H1 satisfies: 40μm≤H1≤80μm.

[0025] Based on the above embodiment, the adhesion between the current collector and the active material layer can be improved, and thus when processing the first protrusion, the adhesion between the active material layer of the first protrusion and the current collector is stronger, reducing the generation of microcracks and powder loss.

[0026] In some embodiments, the straight portion has a second convex portion, which is formed by bending another portion of the current collector and another portion of the active material layer toward the same side of the electrode sheet. The height of the second convex portion is H2, and 5μm≤H2≤40μm.

[0027] Based on the above embodiment, the second convex portion provided on the straight portion can also provide good support for the isolation membrane, allowing the electrolyte to smoothly enter the gap between the straight sections of the straight portion, thereby improving the electrolyte infiltration effect and improving the liquid retention.

[0028] In some embodiments, the radius of the inner surface of the first protrusion is R1, the radius of the inner surface of the second protrusion is R2, R1=R2, 0.3mm≤R2≤10.0mm.

[0029] Based on the above embodiment, the heights of the first and second protrusions formed by processing are within a suitable range, and the first and second protrusions can have a suitable elongation, so that the first protrusion can provide good support for the isolation membrane and is not easily deformed.

[0030] In some embodiments, the flat portion has a first thickness L1 in a first direction; the two corner portions are respectively arranged at opposite ends of the flat portion in a second direction perpendicular to the first direction, and the corner portions have a second thickness L2 in the second direction; each coil of the pole piece includes two flat segments arranged opposite to each other in the first direction and two corner segments arranged at opposite ends of the flat segments in the second direction; the pole piece has a tail end arranged corresponding to the flat segment of the outermost coil of the pole piece, and all the flat segments and the tail end arranged in the first direction form the flat portion; the first thickness L1 is the thickness of the flat portion passing through the tail end in the first direction; all the corner segments located on the same side of the flat segment in the second direction form the corner portion, and the second thickness L2 is the thickness of the corner portion passing through the midpoint of the line connecting the two ends of the innermost one of the corner segments in the second direction. The electrode assembly satisfies at least one of the following conditions:

[0031] (1) the number of the winding turns of the pole piece of the electrode body is even, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.2; or,

[0032] (2) the number of the winding turns of the pole piece of the electrode body is odd, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.4.

[0033] Based on the above embodiments, the tension and the interlayer extrusion force borne by the flat segments and the corner segments are suitable, so that the first protrusion and the second protrusion can play a good supporting role and are not easy to deform, and the electrolyte infiltration effect is improved.

[0034] In some embodiments, 1mm≤L1≤20mm, and 0.5mm≤L2≤10mm.

[0035] Based on the above embodiments, it is convenient to select the first thickness L1 of the flat portion and the second thickness L2 of the corner portion to be suitable relative to the height H1 of the first protrusion respectively, so as to prevent the flat segments of the flat portion from pulling the corner segments of the corner portion, and further prevent the first protrusion from being excessively extruded, so as to maintain the good supporting stability of the first protrusion, and make the gap between the corner portion and the corner segment of the isolation film suitable, which can meet the electrolyte infiltration requirement and prevent the overall size of the corner portion from being too large due to the excessively large gap.

[0036] In a second aspect, the application provides a battery, which includes a shell and an electrode assembly as above, and the electrode assembly is arranged in the internal space of the shell.

[0037] Based on the electrode assembly and battery of the embodiments of the present application, by adding a softener to the active material layer and selecting the height H1 of the first protrusion and the weight percentage A of the softener to satisfy 0.01%≤A≤0.40% and 20μm≤H1≤80μm, the softener can improve the overall flexibility of the electrode 300. For the structure at the first protrusion, the height of the first protrusion can be higher while reducing the damage to the electrode sheet, so that no microcracks are generated in the active material layer at the first protrusion, and there is no side effect on the processing process, thereby facilitating the processing of an electrode assembly that can meet the use requirements, improving the electrolyte infiltration effect, and improving the battery's charge and discharge cycle performance when the electrode assembly is used in the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 This is a schematic diagram of the main structure of the pole piece in an embodiment of the present application in an unfolded state;

[0040] Figure 2 This is a schematic cross-sectional view of an electrode assembly according to an embodiment of the present application;

[0041] Figure 3 This is a schematic diagram of a partial cross-sectional structure of a pole piece with a convex portion according to an embodiment of the present application;

[0042] Figure 4 This is a schematic diagram of the main structure of a pole piece having an end free space in one embodiment of the present application;

[0043] Figure 5 This is a schematic diagram of the main structure of a pole piece having a pole ear area according to an embodiment of the present application;

[0044] Figure 6 This is a schematic diagram of the main structure of a pole piece in which the pole ear area penetrates the pole piece in one embodiment of the present application.

[0045] Reference numerals:

[0046] 20. Electrode body; 21. Straight section; 22. Corner section; 40. Tab assembly; 50. Separator; 201. Straight section; 202. Corner section;

[0047] 300. pole piece; 311. convex part; 3111. inner surface; 3112. outer surface; 301. first convex part; 302. second convex part;

[0048] 410, positive electrode; 420, negative electrode;

[0049] 310, bump area; 320, tab area; 321, tab mounting area; 322, protective adhesive mounting area; 330, end avoidance area; 3201, first side boundary; 3202, second side boundary; 3203, bottom boundary; 3204, third side boundary; 3205, fourth side boundary; 331, head avoidance area; 332, tail avoidance area;

[0050] 3411, first edge; 3421, second edge; 3431, third edge; 3441, fourth edge;

[0051] 3101, first boundary; 3102, second boundary; 3103, third boundary; 3104, fourth boundary;

[0052] 341, first area; 342, second area;

[0053] X, length direction; Y, width direction; Z, thickness direction. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0055] The inventors discovered that the electrode assembly inside the secondary battery adopts a winding structure, and the electrode assembly needs to be hot-pressed after the electrode sheets and isolation membranes are alternately stacked and wound. There is internal stress inside the electrode assembly, resulting in poor electrolyte wettability. In addition, the electrode assembly will expand during the charging and discharging process, and the interlayer extrusion of the electrode assembly will be further aggravated, resulting in insufficient electrolyte, poor wettability, and ultimately deterioration of the interface at the weak position, and even lithium plating. To solve the above problems, it is necessary to create gaps between battery layers. Currently, there are the following methods for creating gaps: (1) sticking adhesive tape at specific positions on the electrode to support the formation of gaps. This method currently improves the wetting ability, but the presence of the adhesive tape occupies the thickness, which increases the thickness of the electrode assembly and has a certain loss on the energy density of the battery; (2) applying soluble chemical substances to form gaps by evenly applying some electrolyte-soluble glue on the electrode, but the improvement effect is limited and has other side effects on battery performance; (3) thickening the isolation membrane. The isolation membrane's ability to store electrolyte is enhanced, and the electrolyte wetting effect is improved, but this method will make the battery thicker and greatly lose energy density.

[0056] The inventors also discovered that by machining protrusions on the electrode sheets, the protrusions provide support during the winding process, creating gaps between the electrode sheets of the electrode assembly, thereby improving the electrolyte transport within the electrode assembly and the battery's cycling performance. Based on this, the present invention provides an electrode assembly and battery that utilizes a designed protrusion on the electrode sheet to effectively improve electrolyte wetting and electrode sheet interface issues.

[0057] The battery provided in the embodiment of the present application includes an outer package and an electrode assembly disposed in the inner space of the outer package, and an electrolyte filled in the inner space of the outer package. The electrode assembly includes two pole pieces with opposite polarities and a separator, such as Figure 1 , which is a schematic diagram of the front structure of an electrode sheet 300 in an expanded state according to an embodiment of the present application. The electrode sheets 300 have a length direction X, a width direction Y, and a thickness direction Z that are perpendicular to each other. The length directions X, width directions Y, and thickness directions Z of the two electrode sheets 300 of opposite polarity in the electrode assembly are consistent. The separator 50 is provided between the two electrode sheets 300 of opposite polarity in the thickness direction Z. One of the two electrode sheets 300 of opposite polarity is a positive electrode sheet 410, and the other is a negative electrode sheet 420. The separator 50 has insulating properties and is used to separate the positive electrode sheet 410 from the negative electrode sheet 420 to prevent the positive electrode sheet 410 and the negative electrode sheet 420 from shorting.

[0058] At least one of the positive electrode sheet 410 and the negative electrode sheet 420 has a protrusion 311. Specifically, the electrode sheet includes a current collector and an active material layer. The active material layer and the current collector are stacked along the thickness direction Z of the electrode sheet 300, and the active material layer is disposed on the surface of the current collector. The protrusion 311 is formed by portions of the current collector and the active material layer protruding toward the same side of the electrode sheet 300 along the thickness direction Z. The protrusion 311 provides support for the separator 50, creating a gap between the separator 50 and the electrode sheet 300, thereby improving electrolyte wetting.

[0059] The pole piece 300 includes a first surface perpendicular to the thickness direction Z of the pole piece 300. Figure 1 The first surface includes a convex region 310, and a plurality of convex portions 311 are provided in the convex region 310. There is a gap between the convex region 310 and the edge of the first surface. After the two pole pieces 300 and the separator 50 are wound multiple times to form the electrode body 20, the convex portions 311 contact the separator 50, providing support for the separator 50. When the electrode body 20 expands, the convex portions 311 can still support the separator 50. The contact area between the convex portions 311 and the separator 50 is small, leaving space between the portion of the pole piece 300 corresponding to the convex region 310 and the separator 50 for accommodating electrolyte, thereby preventing abnormal conditions such as insufficient electrolyte and poor wetting between the pole piece 300 and the separator 50 due to expansion and squeezing.

[0060] like Figure 2 As shown, the separator 50 and two electrode pieces 300 are wound multiple times along the length direction X of the electrode pieces 300 to form the electrode body 20. The length direction X of the electrode pieces 300 is the direction in which the electrode pieces 300 are wound. The electrode body 20 is flat and includes a straight portion 201 and two corner portions 202. The two corner portions 202 are located at opposite ends of the straight portion 201. Specifically, each turn of the electrode pieces 300 of the electrode body 20 includes two straight sections 21 and two corner sections 22. The two straight sections 21 are arranged side by side in a direction perpendicular to the plate surface of the straight sections 21. The two straight sections 21 are arranged opposite each other in a direction perpendicular to the plate surface of the straight sections 21. That is, the two straight sections 21 and the two corner sections 22 are connected end to end in sequence. The electrode body 20 has a tail end, which is formed by a portion of the straight section 21 of the outermost turn of the electrode pieces 300. All the straight sections 21 stacked in the first direction, the tail ends, and the isolation membrane 50 sandwiched between two adjacent straight sections 21 together form a straight portion 201; all the corner sections 22 located on the same side of the straight section 21 in the second direction and the isolation membrane 50 sandwiched between two adjacent corner sections 22 together form a corner portion 202.

[0061] The pole piece 300 has a plurality of protrusions 311, and at least one of the straight section 21 and the corner section 22 has a protrusion 311. Optionally, all the protrusions 311 provided on a single pole piece 300 protrude toward the same side of the pole piece 300 in the thickness direction Z of the pole piece 300. For example, when both the straight section 21 and the corner section 22 have protrusions 311, the protrusions 311 provided on the straight section 21 protrude toward the side of the winding center of the electrode body 20, and the protrusions 311 provided on the corner section 22 protrude toward the side where the winding center of the electrode body 20 is located; alternatively, the protrusions 311 provided on the straight section 21 protrude toward the side away from the winding center of the electrode body 20, and the protrusions 311 provided on the corner section 22 protrude toward the side away from the winding center of the electrode body 20. Optionally, a portion of the protrusions 311 provided on a single pole piece 300 protrudes toward one side of the pole piece 300 in the thickness direction Z of the pole piece 300, and another portion of the protrusions 311 protrudes toward the other side of the pole piece 300 in the thickness direction Z of the pole piece 300. For example, the protrusion 311 provided on the straight section 21 protrudes toward one side of the winding center of the electrode body 20, and the protrusion 311 provided on the corner section 22 protrudes toward the side away from the winding center of the electrode body 20; or, the protrusion 311 provided on the straight section 21 protrudes toward the side away from the winding center of the electrode body 20, and the protrusion 311 provided on the corner section 22 protrudes toward the side of the winding center of the electrode body 20.

[0062] The above is merely an exemplary introduction. This application does not limit the orientation of the protrusion 311 of each pole piece 300 , and the orientation can be selected according to actual needs.

[0063] Due to the internal stress inside the electrode body 20 and the expansion of the electrode body 20 during the charging and discharging process of the battery, the two adjacent circles of electrode sheets 300 are easily squeezed, especially the corner sections 22 of the two adjacent circles of electrode sheets 300 are squeezed more strongly, which can easily lead to insufficient gaps and poor electrolyte infiltration. Under the action of squeezing force and internal stress, when the corner section 22 has a convex portion 311, the convex portion 311 in the corner section 22 is prone to deformation and cracks in the active material layer, thereby affecting the cycle performance of the battery.

[0064] The pole piece 300 has a plurality of protrusions 311, some of which are first protrusions 301. The corner portion 202 has a first protrusion 301 (specifically, each corner segment 22 has a first protrusion 301). In the thickness direction Z of the pole piece 300, the height of the first protrusion 301 is H1. Within this height range of 20 μm ≤ H1 ≤ 80 μm, the first protrusion 301 can provide good support to improve the electrolyte infiltration effect.

[0065] The material of the active material layer includes a softener, which is selected from at least one of silicone, fatty acid salt, and quaternary ammonium salt. Based on the total weight of the active material layer, the weight percentage of the softener is A, 0.01%≤A≤0.40%. Within this content range, the softener can increase the flexibility of the active material layer, prevent the active material layer from being easily broken, and make the electrode 300 easy to bend to form the protrusion 311.

[0066] Since the corner section 22 is a high-incidence area for bending and deformation, the greater the height H1 of the first protrusion 301 of the corner section 22, the larger the gap between the isolation diaphragm 50 and the pole piece 300 supported by the first protrusion 301, and the better the effect of improving the infiltration of the electrolyte. However, the higher the height of the first protrusion 301, the greater the elongation of the pole piece 300 at the first protrusion 301 or the area covered by the first protrusion 301, and the more likely it is to cause the pole piece 300 at the first protrusion 301 to deform, or cause cracks to appear in the active material layer. Based on this, in the implementation of this application, the height H1 of the first protrusion 301 of the corner section 22 and the weight percentage A of the softener are selected to meet the following conditional formula:

[0067] (1) When A satisfies: 0.01% ≤ A ≤ 0.10%, then H1 satisfies: 20 μm ≤ H1 ≤ 40 μm.

[0068] (2) When A satisfies: 0.10% <A≤0.20%时,则H1满足:40μm

[0069] (3) When A satisfies: 0.20% <A≤0.40%时,则H1满足:60μm

[0070] ​​By selecting H1 and A to meet the above range, the softener can improve the overall flexibility of the electrode 300. For the structure at the first protrusion 301, the height of the first protrusion 301 can be made higher while reducing the damage to the electrode 300, so that the active material layer at the first protrusion 301 does not produce microcracks, and has no side effects on the processing process, thereby facilitating the processing of an electrode assembly that can meet the use requirements, improving the electrolyte infiltration effect, and improving the battery's charge and discharge cycle performance when the electrode assembly is used in the battery. Among them, when H1 is lower than the lower limit of 20μm, the height of the first protrusion 301 is too low, and the first protrusion 301 has insufficient support capacity for the isolation membrane 50. When H1 is higher than the upper limit of 80μm, the height of the first protrusion 301 is too high, and the first protrusion 301 is easily deformed by external forces. In addition, when A satisfies 0.01%≤A≤0.10%, H1 exceeds the upper limit of 40μm, or when A satisfies 0.10% <A≤0.20%,H1超出上限60μm时,容易由于柔顺剂的含量不足,导致第一凸部301处的活性材料层出现裂纹;当A满足0.10%<A≤0.20%,H1低于下限40μm,或者,当A满足0.20%<A≤0.40%,H1低于下限60μm时,由于第一凸部301高度可选择范围窄,无法造出足够的第一凸部301的高度,导致对浸润改善效果不足,容易导致电池充放电循环性能变差。

[0071] In some embodiments, the organosilicon is selected from at least one of methyl silicone resin, phenyl silicone resin, vinyl silicone resin, and silicone rubber.

[0072] In some embodiments, the fatty acid salt is selected from at least one of aluminum stearate, magnesium stearate, aluminum ethyl octanoate, and magnesium ethyl octanoate.

[0073] In some embodiments, the quaternary ammonium salt is selected from at least one of a long-chain quaternary ammonium salt, a short-chain quaternary ammonium salt, an aliphatic quaternary ammonium salt, and an aromatic quaternary ammonium salt. For example, the long-chain quaternary ammonium salt is selected from at least one of hexadecyldimethylammonium bromide, octadecyldimethylammonium bromide, dimethyldidecylammonium bromide, hexadecyldimethylbenzylammonium chloride, and octadecyldimethylbenzylammonium chloride; the short-chain quaternary ammonium salt is selected from at least one of sodium octoate, dodecyltrimethylammonium bromide, benzalkonium chloride, and benzalkonium bromide; the aliphatic quaternary ammonium salt is selected from at least one of dodecylamine, hexadecylamine, dodecylpropylamine, and hexadecylpropylamine; and the aromatic quaternary ammonium salt is selected from at least one of aniline, aromatic amine, benzidine, and naphthylamine.

[0074] In some embodiments, the active material layer further includes a first adhesive. Based on the total weight of the active material layer, the weight percentage of the first adhesive is B. The height H1 of the first protrusion 301 of the corner segment 22 and the weight percentage B of the first adhesive satisfy the following conditional formula:

[0075] (1) If B satisfies: 0.8% ≤ B ≤ 1.6%, then H1 satisfies: 20 μm ≤ H1 ≤ 40 μm.

[0076] (2) B meets: 1.6% <B≤2.4%,则H1满足:40μm

[0077] By selecting H1 and B within the above ranges, the active material layer exhibits excellent toughness and ductility, making it less susceptible to microcracks. During the process of bending the active material layer in the corner section 22 together with the current collector to form the first protrusion 301, the active material layer maintains excellent ductility and is less susceptible to cracking, thereby improving the winding efficiency of the pole piece 300 and enhancing battery safety. Furthermore, the weight percentage of the first binder, B, within the above range, is appropriate in the active material layer, preventing an excessive amount of the first binder from reducing the battery's energy density.

[0078] In some embodiments, the first adhesive is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride, polyvinyl alcohol, polystyrene, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, and polytetrafluoroethylene.

[0079] In some embodiments, the compacted density of the active material layer is p,3.6 g / cm 3 ≤ρ≤4.35g / cm 3 , for example, ρ can be 3.6 g / cm 3 、3.8g / cm 3 , 4.00g / cm 3 , 4.05g / cm 3 , 4.08g / cm 3 , 4.10g / cm 3 , 4.18g / cm 3 , 4.28g / cm 3 , 4.35g / cm 3 Or any range of the above two. Within the above range, the active material layer can have good toughness and is not easy to be brittle, while making the battery have a suitable energy density.

[0080] In some embodiments, the active material layer has a thickness of h1, and h1 satisfies: 10 μm≤h1≤500 μm.

[0081] ​In some embodiments, the electrode further comprises a primer layer, which is disposed between the active material layer and the current collector. The primer layer comprises a primer material, which is selected from at least one of an inorganic oxide and a carbonaceous material. The primer layer further comprises an adhesive material, the adhesive material in the primer layer is mixed with the primer material, and the primer layer is bonded to the active material layer and the current collector via the adhesive material. The provision of the primer layer can improve the connection stability of the active material layer and prevent the active material layer from peeling off and shedding. The inorganic oxide is selected from at least one of aluminum oxide, titanium oxide, and magnesium oxide, and the carbonaceous material is selected from at least one of graphene, carbon nanotubes, and fluorocarbon. The adhesive material can be the same material as the first adhesive.

[0082] In some embodiments, the unit weight of the primer layer is η, and the height H1 of the first protrusion 301 of the corner section 22 and the unit weight η of the primer layer satisfy the following conditional formula:

[0083] (1) η satisfies: 0.5 mg / 1540.25 mm 2 ≤η≤2.0mg / 1540.25mm 2 , then H1 satisfies: 20μm≤H1≤40μm.

[0084] (2) η satisfies: 2.0 mg / 1540.25 mm 2 ≤η≤4.0mg / 1540.25mm 2 , then H1 satisfies: 40μm≤H1≤80μm.

[0085] By selecting H1 and η to meet the above range, the adhesion between the current collector and the active material layer can be improved. Therefore, when processing the first protrusion 301, the adhesion between the active material layer of the first protrusion 301 and the current collector is stronger, reducing the generation of microcracks and powder loss.

[0086] In some embodiments, the primer layer has a thickness h2, and h2 satisfies: 0.5 μm≤h2≤4.0 μm.

[0087] In some embodiments, a portion of the protrusion 311 is a second protrusion 302, and the straight portion 201 has the second protrusion 302. Specifically, the straight segment 21 has the second protrusion 302. Along the thickness direction Z of the electrode 300, the height of the second protrusion is H2, 5μm≤H2≤40μm. For example, H2 can be 5μm, 10μm, 20μm, 30μm, 5μm, 35μm, 40μm, or any range thereof. By selecting the height H2 of the second protrusion 302 to meet the above range, the second protrusion 302 can provide good support for the isolation membrane 50, allowing the electrolyte to smoothly enter the gaps between the straight segments 21 of the straight portion 201, thereby improving the electrolyte infiltration effect and improving the electrolyte retention.

[0088] It should be noted that in the embodiments of the present application, the material composition, thickness and compaction density of the active material layers corresponding to the straight section 21 and the corner section 22 are the same, and the material composition, thickness and unit primer weight of the primer layers corresponding to the straight section 21 and the corner section 22 are the same.

[0089] In some embodiments, the inner surface radius of the first protrusion 301 is R1, which is the diameter of the inscribed sphere D1 on the inner surface of the first protrusion 301. The inner surface radius of the second protrusion 302 is R2, which is the diameter of the inscribed sphere D2 on the inner surface of the second protrusion 302. Here, R1 = R2, and 0.3 mm ≤ R2 ≤ 10.0 mm. For example, R2 can be 0.3 mm, 2.3 mm, 5.5 mm, 7.3 mm, 8.5 mm, or 10.0 mm. By selecting the radii of the first and second protrusions 301, 302 within the above range, the heights of the first and second protrusions 301, 302 formed during processing are within an appropriate range, and the first and second protrusions 301, 302 can have appropriate elongation, so that the first protrusion 301 can provide good support for the isolation membrane 50 and is not easily deformed.

[0090] In some embodiments, please refer to Figure 2 The straight portion 201 has a first thickness L1 in the first direction, which is the thickness of the straight portion 201 passing the end in the first direction. The corner portion 202 has a second thickness L2 in the second direction, which is the thickness of the corner portion 202 passing the midpoint of the line connecting the two ends of the innermost corner segment 22 in the second direction. L1 and L2 satisfy the following conditional formula:

[0091] (1) The number of winding turns of the electrode sheet of the electrode body is an even number, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.2.

[0092] (2) The number of winding turns of the electrode sheet of the electrode body is an odd number, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.4.

[0093] By selecting the first thickness L1 of the straight portion 201 and the second thickness L2 of the corner portion 202 to satisfy the above-mentioned conditional range, the tension and interlayer extrusion force on the straight section 21 and the corner section 22 are appropriate, so that the first protrusion 301 and the second protrusion 302 can play a good supporting role, are not easily deformed, and improve the electrolyte infiltration effect.

[0094] In some embodiments, the straight portion 201 has a first thickness L1 in the first direction that satisfies the following: 1 mm ≤ L1 ≤ 20 mm. For example, L1 can be 1 mm, 2 mm, 5 mm, 8 mm, 10 mm, 15 mm, 20 mm, or any range thereof. Within the above range, it is convenient to select both the first thickness L1 of the straight portion 201 and the height H1 of the first protrusion 301 within an appropriate range, thereby preventing the straight section 22 of the straight portion 201 from pulling on the corner section 21 of the corner portion 202, thereby preventing excessive compression of the first protrusion 301, and maintaining good support stability for the first protrusion 301.

[0095] In some embodiments, the corner portion 202 has a second thickness L2 in the second direction that satisfies the following: 0.5 mm ≤ L2 ≤ 10 mm. For example, L2 can be 0.5 mm, 1 mm, 2 mm, 5 mm, 6 mm, 8 mm, 10 mm, or any range thereof. Within the above range, the second thickness L2 of the corner portion 202 and the height H1 of the first protrusion 301 are both within an appropriate range, thereby ensuring an appropriate gap between the isolation membrane 50 of the corner portion 202 and the corner segment 21. This not only meets the electrolyte infiltration requirements but also prevents an excessively large gap from causing the overall size of the corner portion 202 to be excessive.

[0096] In some embodiments, the surface of the active material layer facing away from the current collector forms a first surface, the first surface including a bump region 310, a protrusion 311 provided in the bump region 310, the bump region 310 being defined by a bump boundary line, the protrusion 311 of the bump region 310 being located within the inner region defined by the bump boundary line, or being inscribed within the bump boundary line. The first surface also includes an end clearance region 330 and an edge clearance region. The end clearance region 330 is connected to the end of the bump region 310 in the length direction X of the electrode 300 and extends to the edge of the electrode 300. The edge clearance region is provided on one side of the bump region 310 in the width direction Y of the electrode 300 and extends to the edge of the electrode 300. Neither the edge clearance region nor the end clearance region 330 is provided with a protrusion 311. After the two electrode sheets 300 and the isolation film 50 are wound, the surfaces of the electrode 300 corresponding to the edge clearance region and the end clearance region 330 can be spaced apart from the isolation film 50.

[0097] The end avoidance region 330 is provided at the end of the convex region 310 in the length direction X of the pole piece 300 and extends to the edge of the pole piece 300, and the end avoidance region 330 also extends to the edge of the pole piece 300 in the width direction Y of the pole piece 300. Figure 4As shown, the end space avoidance area 330 includes at least one of a head space avoidance area 331 and a tail space avoidance area 332. Preferably, the end space avoidance area 330 includes both a head space avoidance area 331 and a tail space avoidance area 332. In the length direction X of the pole piece 300, the head space avoidance area 331 is arranged at one end of the convex point area 310, and the tail space avoidance area 332 is arranged at the other end of the convex point area 310.

[0098] After the two pole pieces 300 and the isolation film 50 are wound, the head air avoidance area 331 can be located in the innermost turns of the electrode body 20, which is convenient for the winding and forming of the electrode body 20 and helps to improve the structural stability of the central area of ​​the electrode body 20. The tail air avoidance area 332 can be located in the outermost turns of the electrode body 20. The tail air avoidance area 332 can serve as a buffer area between the protrusion 311 and the tail end of the electrode body 20, so that the part of the pole piece 300 corresponding to the end air avoidance area 330 can more smoothly form a constraint on the inner layer structure of the electrode body 20, which helps to improve the packaging stability of the electrode body 20. Especially when the electrode body 20 has a tendency to expand, the tail air avoidance area 332 without the protrusion 311 is used for tailing, which can prevent the tail of the electrode body 20 from slipping due to expansion stress and improve the structural stability of the electrode body 20.

[0099] Specifically, the first surface of the pole piece 300 includes a first edge 3411 and a second edge 3421 that are oppositely arranged in the length direction X of the pole piece 300, and the convex point boundary line of the convex point area 310 includes a first boundary 3101 and a second boundary 3102 that are oppositely arranged in the length direction X of the pole piece 300, the first boundary 3101 corresponds to the first edge 3411, and the second boundary 3102 corresponds to the second edge 3421. The head space avoidance area 331 is formed between the first edge 3411 and the first boundary 3101, and the tail space avoidance area 332 is formed between the second edge 3421 and the second boundary 3102. One end of the isolation membrane 50 is flush with the head space avoidance area 331 or extends out of the head space avoidance area 331 to be clamped between two pole pieces 300 with opposite polarity. The pole piece 300 is wound along the length direction X of the pole piece 300 from the head space avoidance area 331 and the isolation membrane 50 to form a flat electrode body 20, that is, the head space avoidance area 331 is in the inner circle of the electrode body 20, and the tail space avoidance area 332 is in the outer circle of the electrode body 20. The other end of the isolation membrane 50 extends out of the tail space avoidance area 332 in the winding direction of the pole piece 300 to prevent the isolation membrane 50 from shrinking and causing the two pole pieces 300 with opposite polarity to short-circuit.

[0100] The first surface of the pole piece 300 has an edge avoidance area, which includes a first area 341 and a second area 342. In the width direction Y of the pole piece 300, the first area 341 is connected to one side of the convex area 310, and the second area 342 is connected to the other side of the convex area 310. The first area 341 extends to the edge of the pole piece 300 in a direction away from the second area 342, and the second area 342 extends to the edge of the pole piece 300 in a direction away from the first area 341. That is, the two opposite boundaries of the convex area 310 in the width direction Y of the pole piece 300 are respectively spaced from the corresponding edges of the pole piece 300 to prevent the deformation stress when the convex portion 311 is processed in the convex area 310 from causing abnormal deformation such as wavy edges or wrinkles on the edge of the pole piece 300.

[0101] Specifically, the pole piece 300 includes a third edge 3431 and a fourth edge 3441 that are relatively arranged in the width direction Y of the pole piece 300, and the convex boundary line of the convex area 310 includes a third boundary 3103 and a fourth boundary 3104 that are relatively arranged in the width direction Y of the pole piece 300, the third boundary 3103 corresponds to the third edge 3431, and the fourth boundary 3104 corresponds to the fourth edge 3441. The first area 341 is formed between the third boundary 3103 and the third edge 3431, and the second area 342 is formed between the fourth boundary 3104 and the fourth edge 3441, and the first area 341 and the second area 342 extend in the length direction X of the pole piece 300 to connect to the end avoidance area 330, that is, the extension line of the first boundary 3101, the extension line of the second boundary 3102, the third boundary 3103 and the first boundary 3104. The three edges 3431 define a first area 341, the extension line of the first boundary 3101, the extension line of the second boundary 3102, the fourth boundary 3104 and the fourth edge 3441 define a second area 342, the extension line of the first boundary 3101, the first edge 3411, the third edge 3431 and the fourth edge 3441 define a head avoidance area 331, the extension line of the second boundary 3102, the second edge 3421, the third edge 3431 and the fourth edge 3441 define a tail avoidance area 332, the convex point area 310 is located within the area defined by the first boundary 3101, the second boundary 3102, the third boundary 3103 and the fourth boundary 3104, and the convex portion 311 can be inscribed in at least one of the first boundary 3101, the second boundary 3102, the third boundary 3103 and the fourth boundary 3104.

[0102] Optionally, the first boundary 3101 and the second boundary 3102 are parallel to the width direction Y of the pole piece 300, the third boundary 3103 and the fourth boundary 3104 are parallel to the length direction X of the pole piece 300, and the head clearance 331 and the tail clearance 332 are each independently rectangular or square, and the first region 341 and the second region 342 are rectangular.

[0103] Optionally, one of the first region 341 and the second region 342 is used to mount the tab assembly 40 of the electrode assembly, for example, as shown in Figure 4 Optionally, the second region 342 is used to mount the tab assembly 40 of the electrode assembly, and the bump area 310 is spaced apart from the tab assembly 40, as shown in

[0104] Optionally, as shown in Figure 5 Optionally, the first surface further comprises a tab area 320 extending from the third boundary 3103 to the side where the fourth boundary 3104 is located, and the tab area 320 is used to mount the tab assembly 40 of the electrode assembly, and the tab assembly 40 is spaced apart from the bump area 310. When the tab assembly 40 is mounted on the tab area 320, the processing method will affect the mounting stability of the tab assembly 40, and the stability of the structure around the tab assembly 40, and then affect the stability of the interface of the pole piece 300. For example, when the tab assembly 40 is press-fit mounted on the pole piece 300 by rolling, the tab assembly 40 is press-fit together with the area provided with the convex part 311, or the distance between the tab assembly 40 and the convex part 311 is too close, which may cause the deformation of the convex part 311, indentation, etc. By planning the tab area 320 to mount the tab assembly 40, the mounting of the tab assembly 40 is facilitated, the process difficulty is reduced, the mounting stability of the tab assembly 40 is improved, the interface stability near the tab assembly 40 is improved, the tab assembly 40 and the convex part 311 are dislocated in the thickness direction Z of the pole piece 300, and the energy density of the battery is improved when the electrode assembly is applied to the battery.

[0105] Each tab area 320 is used to mount at least one tab assembly 40. For example, the tab assembly 40 comprises a tab and a protective glue, and the tab and the protective glue can be mounted on the same tab area 320; or the tab is mounted on one of the tab areas 320, and the protective glue is mounted on another tab area 320. The tab extends beyond the edge of the pole piece 300 in the width direction Y of the pole piece, and the protective glue is flush with the edge of the pole piece 300. The protective glue is used to space the corresponding tab away from the pole piece 300 to prevent lithium precipitation at the tab.

[0106] Optionally, as shown inFigure 5 As shown, the tab region 320 extends from the fourth boundary 3104 along the width direction Y of the pole piece 300 to the side where the third boundary 3103 is located, and is spaced apart from the third boundary 3103; or, as shown in Figure 6, the tab region 320 extends from the fourth boundary 3104 along the width direction Y of the pole piece 300 through the convex region 310.

[0107] The electrode sheet 300 of the embodiment of the present application can form at least one of a positive electrode sheet 410 and a negative electrode sheet 420. The current collector of the negative electrode sheet 420 is a negative electrode current collector and the active material layer is a negative electrode active material layer. The current collector of the positive electrode sheet 410 is a positive electrode current collector and the active material layer is a positive electrode active material layer. The negative electrode active material layer includes, in addition to the softener and first binder described above, a negative electrode active material. The positive electrode active material layer includes, in addition to the softener and first binder described above, a positive electrode active material.

[0108] The embodiments of the present application have no particular restrictions on the materials of the positive electrode active material, positive electrode current collector, negative electrode active material and negative electrode current collector. Various materials that can be used as positive electrode active materials, positive electrode current collector, negative electrode active materials and negative electrode current collectors that are well known in the art are applicable to the present application.

[0109] Illustratively, the negative electrode current collector can be made of at least one of copper foil, aluminum foil, nickel foil, or a carbon-based current collector; the thickness of the negative electrode current collector can range from 1 μm to 200 μm. The negative electrode active material layer can be disposed on one surface or two opposing surfaces of the negative electrode current collector. Furthermore, in the thickness direction Z of the negative electrode electrode sheet 420, the negative electrode active material layer can be coated only on a portion of the negative electrode current collector. Illustratively, the thickness of the negative electrode active material layer can range from 10 μm to 500 μm.

[0110] Illustratively, the negative electrode active material includes at least one of lithium metal, natural graphite, artificial graphite, or a silicon-based material. The silicon-based material includes at least one of silicon, a silicon oxide, a silicon carbon compound, or a silicon alloy. The negative electrode active material layer may further include a conductive agent. Illustratively, the conductive agent in the negative electrode active material layer may include at least one of carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes, carbon fibers, or carbon nanowires. The negative electrode active material layer may further include a second binder. The second binder may include at least one of carboxymethyl cellulose (CMC), polyacrylate, polyacrylate, polyvinyl pyrrolidone, polyaniline, polyimide, polyamide-imide, polysiloxane, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.

[0111] The positive electrode current collector can be an aluminum foil, for example, and can be another positive electrode current collector commonly used in the art. The thickness of the positive electrode current collector can be 1 μm to 200 μm. The positive electrode active material layer can be provided on one surface or both opposite surfaces of the positive electrode current collector. Further, the positive electrode active material layer can be coated only on a partial region of the positive electrode current collector in the thickness direction Z of the positive electrode tab 410. The thickness of the positive electrode active material layer can be 10 μm to 500 μm.

[0112] The positive electrode active material can include LiCoO2, LiNiO2, LiMn2O4, LiCo 1-y M y O2, LiNi 1-y M y O2, LiMn 2-y M y O4, LiNi x Co y Mn z M 1-x-y-z O2, wherein M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1. The positive electrode active material can include at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or lithium nickel manganese oxide, for example. The positive electrode active material can be doped and / or coated. The positive electrode active material layer can further include a conductive agent. The conductive agent in the positive electrode active material layer can include at least one of conductive carbon black, acetylene black, ketjen black, flake graphite, graphene, carbon nanotube, or carbon fiber, for example. The positive electrode active material layer can further include a third binder. The third binder can include at least one of a copolymer of vinylidene fluoride-hexafluoropropylene, a styrene-acrylate copolymer, a styrene-butadiene copolymer, a polyamide, a polyacrylonitrile, a polyacrylate, a polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.

[0113] The embodiments of the present application do not particularly limit the isolation membrane 50, and various materials that can be used as the isolation membrane 50 that are well known in the art are applicable to the present application. Exemplarily, the isolation membrane 50 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene or ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene have a good effect on preventing short circuits and can improve the stability of the electrode assembly through the shutdown effect. The thickness of the isolation membrane 50 is in the range of about 3μm to 500μm. The positive and negative tabs are made of metal conductive materials.

[0114] The tabs in the embodiments of the present application include positive tabs and negative tabs. The positive tabs are arranged on the positive electrode sheet, and the negative tabs are arranged on the negative electrode sheet. The embodiments of the present application have no special restrictions on the positive tabs, negative tabs and protective glue. Various materials that can be used as positive tabs, negative tabs and protective glue that are well known in the art are applicable to this application.

[0115] The embodiments of the present application do not particularly limit the electrolyte. Various materials that can be used as electrolytes known in the art are applicable to the present application. The electrolyte includes lithium salts and non-aqueous organic solvents.

[0116] Illustratively, the lithium salt includes lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium nitrate, and lithium methylsulfite.

[0117] Exemplarily, the non-aqueous organic solvent may also include at least one of a carboxylate compound, an ether compound or other organic solvent. The above-mentioned carbonate compound may include but is not limited to at least one of a chain carbonate compound and a cyclic carbonate compound. The above-mentioned chain carbonate compound may include but is not limited to at least one of dipropyl carbonate (DPC) or ethyl methyl carbonate (EMC). The above-mentioned cyclic carbonate compound may include but is not limited to at least one of butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The above-mentioned carboxylate compound may include but is not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate or propyl propionate. The above-mentioned ether compound may include but is not limited to at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The above-mentioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or a phosphate ester. This application does not particularly limit the weight percentage of the non-aqueous organic solvent in the electrolyte, as long as the purpose of this application can be achieved. For example, based on the total weight of the electrolyte, the weight percentage of the non-aqueous organic solvent is 10% to 70%.

[0118] The present application has no particular limitation on the battery packaging bag, which can be any packaging bag known in the art, as long as it can achieve the purpose of the present application.

[0119] The present application does not particularly limit the type of battery, which may include any device that generates an electrochemical reaction. In the present application, the battery may include but is not limited to: lithium metal battery, lithium ion battery, lithium polymer battery or lithium ion polymer battery, etc.

[0120] The preparation process of the battery of the present application is well known to those skilled in the art and is not particularly limited in the present application. For example, it may include but is not limited to the following steps: after installing the positive electrode tab on the positive electrode sheet and the negative electrode tab on the negative electrode sheet, the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence, and they are wound, folded and other operations are performed as needed to obtain an electrode assembly with a wound structure, the electrode assembly is placed in a packaging bag, the electrolyte is injected into the packaging bag and the bag is sealed to obtain a battery; or, the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence, and the four corners of the entire laminated structure are fixed with tape to obtain an electrode assembly with a laminated structure, the electrode assembly is placed in a packaging bag, the electrolyte is injected into the packaging bag and the bag is sealed to obtain a battery.

[0121] The battery of the present application can be used in electrical devices. The present application does not particularly limit the type of electrical devices, and the battery can be used in any electrical device known in the prior art. In some embodiments, the electrical devices may include, but are not limited to, laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors.

[0122] The present application will be further described below using a lithium-ion battery as an example and in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0123] The following methods were used to test the performance of lithium-ion batteries in the various embodiments and comparative examples of the present application:

[0124] (1) 25℃ 1C charge / 0.7C discharge cycle capacity retention test method

[0125] In a 25°C environment, perform constant current charging of the lithium-ion battery at a charging current of 1C to the full charge voltage (the maximum design voltage of the lithium-ion battery is 4.5V), then perform constant voltage charging at the maximum voltage until the current reaches 0.02C, and then perform constant current discharge at a discharge current of 0.7C until the final voltage reaches 3.0V, and record the discharge capacity of the first cycle. Repeat the above steps for 1000 charge and discharge cycles, and record the discharge capacity of the lithium-ion battery after 1000 charge and discharge cycles.

[0126] 25° C. 1C charge / 0.7C discharge cycle capacity retention rate=(discharge capacity at the 1000th cycle / discharge capacity at the first cycle)×100%.

[0127] (2) 25℃ cyclic lithium deposition test method

[0128] In a 25°C environment, perform constant current charging of the lithium-ion battery at a charging current of 1C to the full charge voltage (the battery's maximum design voltage is 4.5V), then perform constant voltage charging at the maximum voltage until the current reaches 0.02C, and then perform constant current discharge at a discharge current of 0.7C until the final voltage reaches 3.0V. Record the discharge capacity of the first cycle. Repeat the above steps for 1000 charge and discharge cycles, and record the discharge capacity of the lithium-ion battery after 1000 charge and discharge cycles.

[0129] After testing at 25°C and 1000 charge-discharge cycles, the battery was disassembled when it was fully charged (the battery's maximum design voltage was 4.5V) to observe whether there was lithium deposition at the negative electrode interface / ear / protective glue.

[0130] (3) Testing method for processing quality of winding process

[0131] An electrode body 20 is formed by placing a separator between two electrode sheets 300 (a positive electrode sheet 410 and a negative electrode sheet 420) of opposite polarity on an integrated winding machine. An X-ray device is used to measure the distance M (a value greater than 0.1 mm) between the edge of the negative electrode sheet 420 of the electrode body 20 and the edge of the positive electrode sheet 410 in the width direction of the positive electrode sheet 410 (a value greater than 0.1 mm is acceptable). Samples are continuously prepared, and the total number of samples T (a total of 100) and the number of qualified products N are counted.

[0132] Winding ratio = N / T × 100%.

[0133] (4) Battery energy density test method

[0134] In an environment of 25°C, the lithium-ion battery is charged with constant current at a charging current of 0.5C to the full charge voltage (the battery design maximum voltage is 4.5V), and then charged with constant voltage at the maximum voltage until the current is 0.02C, and then discharged with constant current at a discharge current of 0.2C until the final voltage is 3.0V, and the discharge capacity of the first cycle is recorded.

[0135] Battery energy density = first 0.2C discharge capacity * first 0.2C discharge platform voltage / lithium-ion battery volume

[0136] (5) Testing method for softener

[0137] The softener content is obtained by measuring the content of specific elements in the sample using ICP (inductively coupled plasma emission spectrometry), and the specific elements include but are not limited to the content of silicon in silicone, metal elements in fatty acid salts, and nitrogen in quaternary ammonium salts.

[0138] (6) Test method for height H1 of convex part

[0139] Take the pole piece at the corner of the battery cell to test the height of the convex part.

[0140] Example 1-1

[0141] (1) Preparation of positive electrode sheet

[0142] The binder sodium carboxymethyl cellulose and the primer material aluminum oxide were mixed in a mass ratio of 3:97, water was added as a solvent, and the mixture was stirred evenly under the action of a vacuum mixer to obtain a primer slurry with a solid content of 40wt%. The primer slurry was evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 9μm, dried at 85℃, and cold pressed to obtain a primer layer with a single-side coating thickness of 1μm. The unit primer weight η of the primer layer was 2mg / 1540.25mm 2 .

[0143] The positive electrode active material, lithium cobalt oxide (LiCoO2), the conductive agent, conductive carbon black, the primary binder, polyvinylidene fluoride (PVDF), and the softener, methyl silicone resin, were mixed in a mass ratio of 97.5:1.69:0.8:0.01. N-methylpyrrolidone (NMP) was added as a solvent and stirred evenly in a vacuum mixer to produce a positive electrode slurry with a solid content of 75 wt%. The slurry was evenly coated on the surface of the primer layer, dried at 85°C, and cold pressed to produce a positive electrode sheet coated on one side with a 95 μm thick layer of positive electrode active material.

[0144] After that, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. After cutting, a positive electrode sheet with a size of 74mm×851mm was obtained for use. The compacted density of the positive electrode active material layer was 4.20g / cm 3 .

[0145] (2) Preparation of negative electrode sheet

[0146] The negative electrode active material artificial graphite, the binder styrene-butadiene rubber (SBR), and the second binder sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 97.4:1.4:1.2, and then deionized water was added as a solvent and stirred evenly under the action of a vacuum mixer to obtain a negative electrode plate slurry with a solid content of 50wt%. The negative electrode plate slurry was evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 10μm, dried at 85°C, and cold pressed to obtain a negative electrode plate with a negative electrode active material layer coated on one side with a thickness of 130μm. Thereafter, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode plate with a negative electrode active material layer coated on both sides. After cutting, a negative electrode plate with a specification of 76mm×867mm was obtained for standby use. The compaction density of the negative electrode active material layer was 1.80g / cm 3 .

[0147] (3) Preparation of isolation membrane

[0148] A polyethylene (PE) porous membrane with a thickness of 5 μm was used.

[0149] (4) Preparation of electrolyte

[0150] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed in a mass ratio of 1:1:2 to form a base solvent. Lithium hexafluorophosphate (LiPF6) was then dissolved in the base solvent to produce an electrolyte solution. The mass percentage of LiPF6 based on the total mass of the electrolyte was 12.5%.

[0151] (5) Assembly of lithium-ion batteries

[0152] The positive electrode aluminum tab is installed on the edge area of ​​the positive electrode sheet 410 by rolling, and the protective glue is attached to the edge area of ​​the positive electrode sheet 410. The negative electrode nickel tab is installed on the edge area of ​​the negative electrode sheet 420 by rolling.

[0153] The positive electrode sheet 410 with the positive tab, the separator 50, and the negative electrode sheet 420 with the negative tab are stacked in sequence, with the separator 50 positioned between the positive and negative electrode sheets 410 and 420 to provide isolation. The electrodes are then wound to form the electrode body 20. The electrode assembly is placed in an outer aluminum-plastic film package and dried in an 85°C vacuum oven for 12 hours to remove moisture. The electrolyte is then injected and the lithium-ion battery is produced through vacuum packaging, standing, formation, capacitance, degassing, and trimming.

[0154] In Example 1-1, the positive electrode sheet has a convex portion, and the convex portion is rolled out on the positive electrode sheet by rolling. Figure 4 The electrode sheet shown is used as a positive electrode sheet, and in the wound electrode body 20, the corner section 21 of each turn of the electrode sheet 300 has a first protrusion 301 and the straight section 22 has a second protrusion 302. The parameters of the lithium-ion battery are shown in Table I.

[0155] Table I

[0156] Parameter Value Parameter Value H1 20 mm A 0.01％ H2 10 mm B 0.8％ p <![CDATA[4.2g / cm 3 ]]> η 2 mg / 15 40.25 mm 2 ]] L1 4.5 mm L2 3 mm L1 / L2 1.5 R2 3 mm h1 95 μm h2 0 μm

[0157] Examples 1-2 to 1-25 and Comparative Examples 1-1 to 1-6 are the same as Example 1-1 except that the height H1 of the first protrusion 301 and the weight percentage A of the softener are adjusted as shown in Table 1 in the preparation of the positive electrode sheet.

[0158] Examples 1-26 to 1-35 are the same as Example 1-1 except that the type of softener is adjusted as shown in Table 1 during the preparation of the positive electrode sheet.

[0159] Examples 1-36 to 1-39 are the same as Example 1-1 except that the compaction density ρ of the active material layer is adjusted as shown in Table 1 during the preparation of the positive electrode sheet.

[0160] The parameters of the lithium-ion batteries of Examples 1-1 to 1-39 and Comparative Examples 1-1 to 1-6 and the performance test results of the lithium-ion batteries are shown in Table 1.

[0161] Table 1

[0162]

[0163]

[0164] As shown in Examples 1-1 to 1-39 and Comparative Examples 1-1 to 1-6 in Table 1, by adding a softener to the active material layer, selecting the height H1 of the first protrusion 301 of the corner section 22 to satisfy 20 μm ≤ H1 ≤ 80 μm, and the weight percentage A of the softener to satisfy 0.01% ≤ A ≤ 0.40%, the lithium-ion battery exhibits good charge-discharge cycle performance, exhibits no lithium deposition during the charge-discharge cycle, and exhibits a good winding process yield. When H1 is below the lower limit of 20 μm, the height of the first protrusion 301 is too low, the supporting capacity of the first protrusion 301 is insufficient, and the gap between the positive electrode sheet 410 and the separator 50 is insufficient, resulting in poor charge-discharge cycle performance of the lithium-ion battery. When H1 is above the upper limit of 50 μm, the height of the first protrusion 301 is too high, microcracks are easily formed in the active material layer, and the winding process yield is reduced.

[0165] According to Examples 1-1 to 1-25 and Comparative Examples 1-1 to 1-6 in Table 1, the height H1 of the first protrusion 301 of the corner section 22 and the weight percentage A of the softener satisfy (1) 0.01% ≤ A ≤ 0.10%, 20 μm ≤ H1 ≤ 40 μm, or satisfy (2) 0.10% <A≤0.20%,40μm

[0166] Examples 2-1 to 2-16 and Comparative Examples 2-1 to 2-4 are the same as Examples 1-4 except that the height H1 of the first protrusion 301 and the weight percentage B of the first adhesive are adjusted as shown in Table 1 during the preparation of the positive electrode sheet.

[0167] The parameters of the lithium-ion batteries of Examples 2-1 to 2-14 and Comparative Examples 2-1 to 2-6 and the performance test results of the lithium-ion batteries are shown in Table 2.

[0168] Table 2

[0169] ​

[0170] According to Examples 1-4, 2-1 to 2-16, and Comparative Examples 2-1 to 2-4 in Table 2, it can be seen that the height H1 of the first protrusion 301 of the corner section 22 and the weight percentage B of the first adhesive are selected to satisfy (1) 0.8% ≤ B ≤ 1.6%, 20 μm ≤ H1 ≤ 40 μm, or (2) 1.6% <B≤2.4%、40μm

[0171] Examples 3-1 to 3-16 and Comparative Examples 3-1 to 3-4 are the same as Examples 1-4 except that the height H1 of the first protrusion 301 and the unit primer weight η of the primer layer are adjusted as shown in Table 1 in the preparation of the positive electrode sheet.

[0172] The parameters of the lithium-ion batteries of Examples 3-1 to 3-16 and Comparative Examples 3-1 to 3-4 and the performance test results of the lithium-ion batteries are shown in Table 3.

[0173] Table 3

[0174]

[0175] According to Examples 1-4, 3-1 to 3-16, and 3-1 to 3-4 in Table 3, it can be seen that the height H1 of the first convex portion 301 of the corner section 22 and the unit primer weight η of the primer layer are selected to satisfy (1) 0.5 mg / 1540.25 mm 2 ≤η≤2.0mg / 1540.25mm 2 , 20μm≤H1≤40μm, or satisfy (2) 2.0mg / 1540.25mm 2 ≤η≤4.0mg / 1540.25mm 2 , 40μm≤H1≤80μm, the lithium-ion battery has better charge and discharge cycle performance, and there is no lithium deposition during the charge and discharge cycle, and the winding process has a good processing rate.

[0176] Examples 4-1 to 4-10 are the same as Example 1-1 except that the winding number of the electrode sheet is adjusted as shown in Table 1 and the first thickness L1 and the second thickness L2 of the electrode body 20 are adjusted during the assembly of the lithium-ion battery.

[0177] The parameters of the lithium-ion batteries of Examples 4-1 to 4-10 and the performance test results of the lithium-ion batteries are shown in Table 4.

[0178] Table 4

[0179] ​

[0180] According to Example 1-1, Example 4-1 to Example 4-3, and Example 4-9 to Example 4-10 in Table 4, it can be seen that when the number of winding turns of the electrode sheet 300 of the electrode body is an even number, L1 and L2 satisfy: 1.5≤L1 / L2≤2.2, the lithium-ion battery has good charge and discharge cycle performance, and there is no lithium deposition during the charge and discharge cycle.

[0181] It can be seen from Examples 4-4 to 4-6 and 4-7 to 4-8 in Table 4 that when the number of winding turns of the electrode sheet 300 of the electrode body is an odd number, L1 and L2 satisfy: 1.5≤L1 / L2≤2.4, the lithium-ion battery has good charge and discharge cycle performance, and there is no lithium deposition during the charge and discharge cycle.

[0182] Examples 5-1 to 5-7 are the same as Example 1-1 except that the height H1 of the first protrusion 301 and the height H2 of the second protrusion 302 are adjusted as shown in Table 1 during the preparation of the positive electrode sheet.

[0183] The parameters of the lithium-ion batteries of Examples 5-1 to 5-7 and the performance test results of the lithium-ion batteries are shown in Table 5.

[0184] Table 5

[0185]

[0186] According to Example 1-1 and Example 5-1 to Example 5-7 in Table 5, it can be seen that when the height H1 of the first protrusion 301 satisfies 20μm≤H1≤80μm, and the height H2 of the second protrusion 302 satisfies 5μm≤H2≤40μm, the heights of the first protrusion 301 and the second protrusion 302 are matched, so that there is a suitable gap between the layers of the straight part and the corner part for accommodating the electrolyte, and the first protrusion 301 and the second protrusion 302 are not easily deformed, thereby improving the charging cycle performance of the lithium-ion battery and having a good winding rate during the winding process of the electrode 300.

[0187] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. This is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0188] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An electrode assembly, characterized in that: The electrode assembly includes a plurality of electrode plates and a separator film disposed between two electrode plates with opposite polarities, wherein at least one of the electrode plates has a plurality of first protrusions; The electrode plate includes a current collector and an active material layer disposed on the surface of the current collector. The first protrusion is formed by the protrusion of a part of the current collector and a part of the active material layer toward the same side of the electrode plate. The height of the first protrusion is H1; The active material layer includes a softening agent, and the softening agent is selected from at least one of silicone, fatty acid salt, and quaternary ammonium salt. Based on the total weight of the active material layer, the weight percentage content of the softening agent is A; Wherein, A satisfies: 0.01% ≤ A ≤ 0.4%, and H1 satisfies: 20μm ≤ H1 ≤ 80μm.

2. The electrode assembly according to claim 1, wherein The electrode plate and the separator film are wound around multiple times to form a flat electrode body. The electrode body includes a straight part and two corner parts. The two corner parts are respectively disposed at opposite ends of the straight part. The first protrusion is provided on the corner part.

3. The electrode assembly according to claim 1, wherein The electrode assembly satisfies at least one of the following conditions: (1) A satisfies: 0.01% ≤ A ≤ 0.10%, and H1 satisfies: 20μm ≤ H1 ≤ 40μm; (2) A satisfies: 0.10% < A ≤ 0.20%, and H1 satisfies: 40μm < H1 ≤ 60μm; (3) A satisfies: 0.20% < A ≤ 0.40%, and H1 satisfies: 60μm < H1 ≤ 80μm.

4. The electrode assembly according to claim 1, wherein The silicone is selected from at least one of methyl silicone resin, phenyl silicone resin, vinyl silicone resin, and silicone rubber; The fatty acid salt is selected from at least one of aluminum stearate, magnesium stearate, aluminum isooctanoate, and magnesium isooctanoate; The quaternary ammonium salt is selected from at least one of aliphatic quaternary ammonium salts and aromatic quaternary ammonium salts.

5. The electrode assembly according to claim 4, characterized in that The aliphatic quaternary ammonium salt is selected from at least one of long-chain quaternary ammonium salts and short-chain quaternary ammonium salts.

6. The electrode assembly according to claim 1, wherein: The active material layer includes a first binder. Based on the total weight of the active material layer, the weight percentage content of the first binder is B; the electrode assembly satisfies at least one of the following conditions: (1) B satisfies: 0.8% ≤ B ≤ 1.6%, and H1 satisfies: 20μm ≤ H1 ≤ 40μm; (2) B satisfies: 1.6% < B ≤ 2.4%, and H1 satisfies: 40μm < H1 ≤ 80μm.

7. The electrode assembly according to claim 6, characterized in that The first binder is selected from at least one of polyvinylidene fluoride, polyvinyl fluoride, polyvinyl alcohol, polystyrene, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyvinyl ether, polymethyl methacrylate, and polytetrafluoroethylene; 8. The electrode assembly according to claim 1, wherein: The compacted density of the active material layer is ρ,3.6 g / cm 3 ≤ρ≤4.35 g / cm 3 .

9. The electrode assembly according to claim 1, wherein: The electrode plate further includes a primer layer, and the primer layer is disposed between the active material layer and the current collector. The primer layer includes a primer material, and the primer material is selected from at least one of inorganic oxides and carbon-containing materials; The unit primer weight of the primer layer is η; the electrode assembly satisfies at least one of the following conditions: (1) η satisfies: 0.5 mg / 1540.25 mm 2 ≤η≤2.0mg / 1540.25mm 2 , H1 satisfies: 20μm≤H1≤40μm; (2) η satisfies: 2.0 mg / 1540.25 mm 2 ≤η≤4.0mg / 1540.25mm 2 , H1 meets: 40μm <H1≤80μm。 10. The electrode assembly according to claim 2, wherein The straight portion has a second convex portion, wherein the second convex portion is formed by a portion of the current collector and a portion of the active material layer located on the straight portion protruding toward the same side of the electrode sheet; The height of the second convex portion is H2, 5 μm≤H2≤40 μm.

11. The electrode assembly according to claim 10, wherein: The radius of the inner surface of the first convex portion is R1, and the radius of the inner surface of the second convex portion is R2, R1=R2, 0.3mm≤R2≤10.0mm.

12. The electrode assembly according to claim 2, wherein: The straight portion has a first thickness L1 in the first direction; The two corner portions are provided at opposite ends of the straight portion in a second direction perpendicular to the first direction, and the corner portions have a second thickness L2 in the second direction; Each circle of the pole piece includes two straight sections arranged opposite to each other along the first direction, and two corner sections arranged at both ends of the straight section along the second direction; The electrode piece has a tail end provided corresponding to the straight segment of the outermost circle electrode piece, and all the straight segments and the tail end stacked in the first direction form the straight portion; the first thickness L1 is the thickness of the straight portion passing the tail end in the first direction; all the corner segments located on the same side of the straight segment in the second direction form a corner portion, and the second thickness L2 is the thickness of the corner portion passing the midpoint of the line connecting the two ends of one of the innermost corner segments in the second direction; the electrode assembly satisfies at least one of the following conditions: (1) The number of winding turns of the electrode sheet of the electrode assembly is an even number, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.2; or, (2) The number of winding turns of the electrode sheet of the electrode assembly is an odd number, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.

4.

13. The electrode assembly according to claim 12, wherein: 1mm≤L1≤20mm, 0.5mm≤L2≤10mm.

14. A battery, characterized in that: include: shell; and, The electrode assembly according to any one of claims 1 to 13, wherein the electrode assembly is disposed in the inner space of the housing.

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