Positive plate and battery comprising same

Abstract

The invention relates to the technical field of batteries, and particularly provides a positive plate and a battery comprising the same. The positive plate comprises a positive current collector, a first positive active layer, a second positive active layer, a first positive tab and a second positive tab; the positive current collector comprises a first part and a second part, one surface of the first part is provided with a first positive active layer, and two surfaces of the second part are provided with second positive active layers; the first positive tab is connected with the first part, and the second positive tab is connected with the second part; the width of the first positive tab is smaller than that of the second positive tab. According to the invention, the tab is welded in the positive electrode single-sided area, so that even if the junction of the single-sided area and the double-sided area is broken, the positive electrode single-sided area is still communicated with an external circuit, and the problem of capacity diving of the battery can be effectively avoided; and the width of the first tab arranged in the positive single-sided area is smaller than that of the second tab arranged in the double-sided area, so that the overcurrent coefficient of the tabs is consistent with the mass of the active material in the charging area where the tabs are located.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and specifically proposes a positive electrode sheet and a battery comprising the same. Background Art

[0002] In the related art, the outermost side of the positive electrode sheet of a conventional wound battery has a single-sided and double-sided interface area, and there is a certain stress in the interface area. If the negative electrode sheet uses a high-expansion material (such as silicon-carbon material), then the expansion of the negative electrode sheet during the charging process will squeeze the diaphragm and the positive electrode sheet, causing the single-sided and double-sided interface area of ​​the positive electrode sheet to easily break, thereby causing the single-sided area of ​​the positive electrode sheet to be electrically disconnected from the external circuit, causing part of the battery capacity to be unable to function, and the battery capacity will rapidly decay.

[0003] In addition, conventional batteries are generally equipped with multiple pole ears, but the widths of the multiple pole ears are consistent, making it difficult to ensure that the current coefficient of the pole ears is consistent with the mass of the active material in the charging area where they are located. If the current coefficient is relatively too large, it will cause lithium deposition in the pole ears; if the current coefficient is relatively too small, it will reduce the overall charging and discharging capacity of the battery. Summary of the invention

[0004] The purpose of this application is to solve at least part of the technical problems mentioned above, and this purpose is achieved through the following technical solutions:

[0005] In the first aspect, the present application proposes a positive electrode sheet, which includes a positive electrode collector, a first positive electrode active layer, a second positive electrode active layer, a first positive electrode ear and a second positive electrode ear; the positive electrode collector includes a first part and a second part connected along its length direction, the first part is provided with the first positive electrode active layer on one side along its thickness direction, and the second part is provided with the second positive electrode active layer on two opposite sides along its thickness direction; the first positive electrode ear is connected to the first part of the positive electrode collector, and the second positive electrode ear is connected to the second part of the positive electrode collector; the size of the first positive electrode ear along the length direction of the positive electrode collector is d1, and the size of the second positive electrode ear along the length direction of the positive electrode collector is d2, 0.5:1.0≤d1:d2≤0.8:1.0.

[0006] In some embodiments, the mass of the first positive electrode active layer on the first portion is m1, the total mass of the second positive electrode active layers on both sides of the second portion is m2, and 0.1:1.0≤m1:m2≤0.4:1.0.

[0007] In some embodiments, 5 mm ≤ d1 ≤ 8 mm, 8 mm ≤ d2 ≤ 10 mm.

[0008] In some embodiments, the surface density of the first positive electrode active layer on the first portion is CW1, the surface density of the second positive electrode active layer on the second portion is CW2, and 0.8:1.2≤CW1:CW2≤1.0:1.5.

[0009] In some embodiments, 1.0:5.0≤d1:CW1≤3.0:5.0, in mm:mg / cm 2 .

[0010] In some embodiments, the first positive electrode tab is located on one side of the first portion centered close to the second portion, and the areas of the first portion along its length on two opposite sides of the first positive electrode tab are S1 and S2, respectively, 0.6:1.0≤S1:S2≤0.9:1.0.

[0011] In some embodiments, the first positive electrode active layer and / or the second positive electrode active layer include a positive electrode active material, a conductive agent and a binder; preferably, the positive electrode active material includes one or more of lithium nickel oxide, lithium titanate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide.

[0012] In a second aspect, the present application proposes a battery, which includes the positive electrode sheet of the first aspect, and also includes a negative electrode sheet, an electrolyte, and a separator located between the positive electrode sheet and the negative electrode sheet.

[0013] In some embodiments, the negative electrode sheet includes a negative electrode collector, a negative electrode active layer and a negative electrode tab. The negative electrode collector is provided with a negative electrode active layer on at least one side along the thickness direction thereof, and the negative electrode tab is connected to the negative electrode collector.

[0014] In some embodiments, a dimension of the negative electrode ear along the length direction of the negative electrode current collector is d3, and 6 mm ≤ d3 ≤ 10 mm.

[0015] In some embodiments, the negative electrode active layer includes silicon material, and the content of the silicon material in the negative electrode active layer is W, 5%≤W≤100%; preferably, the silicon material includes at least one of elemental silicon, silicon oxide, silicon carbon composite, silicon nitrogen composite and silicon alloy.

[0016] In some embodiments, the median particle size of silicon in the silicon-carbon material is D50, and 4 μm≤D50≤10 μm.

[0017] In some embodiments, the silicon content in the region corresponding to the negative electrode active layer and the first positive electrode active layer is W1, the silicon content in the region corresponding to the negative electrode active layer and the second positive electrode active layer is W2, 0.6:1.0≤W1:W2≤1.0:1.0.

[0018] In some embodiments, 0.06≤d1 / W1≤1.5, unit is mm / %.

[0019] The technical solution proposed in this application has at least the following technical effects:

[0020] In the present application, an external pole ear is welded to the single-sided area of ​​the positive electrode. Even if there is a break at the junction of the single-sided and double-sided areas, the single-sided area of ​​the positive electrode is still connected to the external circuit, which can effectively avoid the problem of the single-sided area of ​​the positive electrode losing contact with the external circuit due to the break at the junction of the single-sided and double-sided areas, causing the battery capacity to drop.

[0021] Moreover, the width of the first positive electrode ear arranged in the single-sided area of ​​the positive electrode is smaller than the width of the second positive electrode ear arranged in the double-sided area, so that the flow coefficient of the positive electrode ear is consistent with the mass of the active material in the charging area where it is located. At the same time, the ratio of the width of the first positive electrode ear to the second positive electrode ear is moderate, which can avoid overcharging of the single-sided area and causing lithium deposition, and also avoid insufficient charging of the single-sided area, which reduces the charging and discharging capacity of the overall battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to better combine the contents shown in the drawings of the specification with the contents described in the specific implementation methods, the drawings of the specification are briefly introduced below. It can be understood that the drawings of the specification mentioned below only schematically show some embodiments of the relevant technical solutions and the technical solutions of this application. Without paying creative labor, those skilled in the art can also make drawings showing other embodiments.

[0023] Specifically, the annotations of the drawings in the specification are as follows:

[0024] Figure 1 A cross-sectional view of a positive electrode sheet described in some embodiments of the present application;

[0025] Figure 2 This is a top view of the positive electrode sheet described in some embodiments of the present application.

[0026] Specifically, the annotations of the accompanying drawings in the specification are as follows:

[0027] 100, positive electrode sheet; 110, positive electrode current collector; 120, first positive electrode active layer; 130, second positive electrode active layer; 140, first positive electrode ear; 150, second positive electrode ear; X, length direction; Z, thickness direction. DETAILED DESCRIPTION

[0028] In order to make the contents of the embodiments of the present application clearer, the following description will be made in conjunction with the accompanying drawings. It can be understood that the contents mentioned below are only some embodiments of the present application, and all embodiments are listed in detail. Therefore, without paying creative work, other embodiments obtained based on the following embodiments fall within the protection scope of the present application.

[0029] It should be understood that the terms used herein are only for the purpose of describing specific embodiments and are not intended to strictly limit the technical solutions unless the context clearly indicates otherwise. For example, the use of "a", "an" and "the" to modify a feature does not exclude that the feature may also be plural in other embodiments.

[0030] It should be understood that the terms "include", "comprises", and "have" are open ended, indicating the presence of the stated features, but not excluding the possibility that the embodiment may have other features. Similarly, the use of the terms first, second, etc. in the text to describe multiple features only means to distinguish one feature from another, and unless the context clearly indicates otherwise, such terms do not imply an order or sequence.

[0031] It should be understood that, unless the context clearly indicates otherwise, the terms "dispose", "connect", and "install" should be understood in a broad sense, for example, they can be fixedly connected, detachably connected, or integrally connected; they can be directly connected or indirectly connected through a medium. For those skilled in the art, the specific meanings of the above terms in the text can be understood according to the specific circumstances.

[0032] In addition, for the convenience of description, the text will use terms of spatial relative relationships to illustrate the position of one feature relative to another feature, for example, "inside", "outside", "end", "side", "top", "middle", "bottom", "high", "low", "axial", "circumferential", "radial", "horizontal", "vertical", "first direction", "second direction", etc. It can be understood that the spatial relative relationship between two features should include other specific situations in addition to those shown in the drawings of the specification.

[0033] The embodiments of the present application are described below in conjunction with the accompanying drawings.

[0034] First, refer to Figure 1 and Figure 2 The present application proposes a positive electrode sheet 100, which includes a positive electrode collector 110, a first positive electrode active layer 120, a second positive electrode active layer 130, a first positive electrode ear 140 and a second positive electrode ear 150; the positive electrode collector 110 includes a first part and a second part connected along its length direction X, the first part is provided with the first positive electrode active layer 120 on one side along its thickness direction Z, and the second part is provided with the second positive electrode active layer 130 on two opposite sides along its thickness direction Z; the first positive electrode ear 140 is connected to the first part of the positive electrode collector 110, and the second positive electrode ear 150 is connected to the second part of the positive electrode collector 110; the size of the first positive electrode ear 140 along the length direction X of the positive electrode collector 110 is d1, and the size of the second positive electrode ear 150 along the length direction X of the positive electrode collector 110 is d2, 0.5:1.0≤d1:d2≤0.8:1.0.

[0035] It can be understood that the first part of the positive current collector 110 in the positive electrode sheet 100 and the first positive active layer 120 thereon constitute a positive single-sided region, and the second part of the positive current collector 110 and the second positive active layer 130 thereon constitute a positive double-sided region.

[0036] In the present application, an external pole ear is welded to the single-sided area of ​​the positive electrode. Even if there is a break at the junction of the single-sided and double-sided areas, the single-sided area of ​​the positive electrode is still connected to the external circuit, which can effectively avoid the problem of the single-sided area of ​​the positive electrode losing contact with the external circuit due to the break at the junction of the single-sided and double-sided areas, causing the battery capacity to drop.

[0037] Moreover, the width of the first positive electrode ear 140 disposed in the single-sided area of ​​the positive electrode is smaller than the width of the second positive electrode ear 150 disposed in the double-sided area, so that the flow coefficient of the positive electrode ear is consistent with the mass of the active material in the charging area where it is located, and at the same time, the width ratio of the first positive electrode ear 140 to the second positive electrode ear 150 is moderate, which not only avoids the single-sided area from being overcharged and causing negative electrode lithium deposition, but also avoids the single-sided area from being insufficiently charged, thereby reducing the overall charge and discharge capacity of the battery. For example, the width ratio d1:d2 of the first positive electrode ear 140 to the second positive electrode ear 150 can be 0.5:1.0, 0.6:1.0, or 0.8:1.0.

[0038] In summary, the present application can at least improve the capacity attenuation problem of batteries containing high-expansion negative electrodes due to the breakage of the positive electrode sheet 100, specifically including: improving the energy density of the battery; improving the capacity retention rate of the battery; and improving the cycle stability of the battery.

[0039] In some embodiments, the mass of the first positive electrode active layer 120 on the first portion is m1, the total mass of the second positive electrode active layers 130 on both sides of the second portion is m2, and 0.1:1.0≤m1:m2≤0.4:1.0.

[0040] In some embodiments, 5 mm ≤ d1 ≤ 8 mm, 8 mm ≤ d2 ≤ 10 mm.

[0041] In some embodiments, the surface density of the first positive electrode active layer 120 on the first portion is CW1, the surface density of the second positive electrode active layer 130 on the second portion is CW2, and 0.8:1.2≤CW1:CW2≤1.0:1.5.

[0042] In some embodiments, 1.0:5.0≤d1:CW1≤3.0:5.0, in mm:mg / cm 2 .

[0043] In the above embodiment, the ratio d1:CW1 of the width of the first positive electrode ear 140 to the surface density of the first positive electrode active layer 120 in the positive electrode single-sided area should be moderate, for example, d1:CW1 can be 1.0:5.0, 2.0:5.0, 3.0:5.0, in units of mm:mg / cm 2 If the ratio is too large, the charge and discharge capacity of the single-sided area will increase, and local overcharging may cause lithium plating at the negative electrode. If the ratio is too small, there is a risk of not being able to fully charge the double-sided area, resulting in the charge and discharge level of the single-sided area being lower than that of the double-sided area, affecting the overall charge and discharge efficiency of the battery.

[0044] In some embodiments, the first positive electrode tab 140 is located on one side of the first portion, centered on the first portion and close to the second portion. The areas of the first portion along its length direction X on opposite sides of the first positive electrode tab 140 are S1 and S2, respectively, and 0.6:1.0≤S1:S2≤0.9:1.0.

[0045] In the above embodiment, if the area ratio of the two sides of the first positive electrode ear 140 on the first part is too large or too small, it will cause the charges and ions in the two areas of the positive electrode single-sided area to be relatively unevenly distributed, thereby causing the charge and discharge levels of the two areas to be inconsistent, and lowering the overall charge and discharge efficiency of the battery. Therefore, the area ratio S1:S2 of the two sides of the first positive electrode ear 140 should be moderate, for example, S1:S2 can be 0.6:1.0, 0.8:1.0, 0.9:1.0.

[0046] In some embodiments, the first positive electrode active layer 120 and / or the second positive electrode active layer 130 include a positive electrode active material, a conductive agent, and a binder;

[0047] In some embodiments, the positive electrode active material includes one or more of lithium nickel oxide, lithium titanate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide.

[0048] In some embodiments, the conductive agent includes one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene; the adhesive includes one or more of polyvinylidene fluoride, acrylic modified polyvinylidene fluoride, polyacrylate polymers, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0049] In a second aspect, the present application proposes a battery, which includes the positive electrode sheet 100 of the first aspect, and also includes a negative electrode sheet, an electrolyte, and a separator located between the positive electrode sheet 100 and the negative electrode sheet.

[0050] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0051] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorophosphate, lithium difluorobis(oxalatophosphate) and lithium tetrafluorooxalatophosphate;

[0052] In some embodiments, the solvent includes one or more of fluoroethylene carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0053] In some embodiments, the electrolyte further includes additives, and the additives include one or more of negative electrode surface film-forming additives, positive electrode surface film-forming additives, and positive and negative electrode current collector surface film-forming additives.

[0054] In some embodiments, the negative electrode sheet includes a negative electrode collector, a negative electrode active layer and a negative electrode tab. The negative electrode collector is provided with a negative electrode active layer on at least one side along the thickness direction Z thereof, and the negative electrode tab is connected to the negative electrode collector.

[0055] In some embodiments, the dimension of the negative electrode ear along the length direction X of the negative electrode current collector is d3, and 6 mm≤d3≤10 mm.

[0056] In some embodiments, the negative electrode active layer includes silicon material, and the content of the silicon material in the negative electrode active layer is W, 5%≤W≤100%; the silicon material includes at least one of elemental silicon, silicon oxide, silicon carbon composite, silicon nitrogen composite and silicon alloy.

[0057] In some embodiments, the median particle size of the silicon particles in the silicon material is D50, and 4 μm≤D50≤10 μm.

[0058] In some embodiments, the silicon content in the region corresponding to the negative electrode active layer and the first positive electrode active layer 120 is W1, and the silicon content in the region corresponding to the negative electrode active layer and the second positive electrode active layer 130 is W2, 0.6:1.0≤W1:W2≤1.0:1.0.

[0059] In some embodiments, 0.06≤d1 / W1≤1.5, unit is mm / %.

[0060] In the above embodiment, the ratio d1 / W1 of the width of the first positive electrode ear 140 to the silicon content of the area on the negative electrode sheet corresponding to the positive electrode single-sided area should be moderate. For example, d1 / W1 can be 0.06, 1, 0.1, 0.8, 1.2, 1.5, and the unit is mm:%. If the ratio is too high, the flow coefficient of the positive electrode single-sided area is large, resulting in a high charge and discharge level in the single-sided area, and the electrical conductivity of silicon materials is generally low, which will make the charge and discharge level of graphite too high and cause serious crosstalk, resulting in local lithium deposition at the negative electrode. If the ratio is too low, it will lead to the failure to meet the charge and discharge efficiency in the single-sided area.

[0061] It should be noted that the battery of the second aspect includes the positive electrode sheet 100 of the first aspect. Therefore, the battery of the second aspect has at least all the technical effects of the positive electrode sheet 100 of the first aspect, and its specific technical effects will not be repeated here.

[0062] The embodiments of the present application only illustrate the structure of the battery of the second aspect related to the improvement points of the present application, but it does not mean that it does not have other structures. For example, the battery also includes a shell, a cover, etc. Other structures will not be described one by one here.

[0063] Specifically, some detailed embodiments and comparative examples are listed below to illustrate the present application:

[0064] 1. Preparation method of lithium-ion battery

[0065] (1) Preparation of positive electrode

[0066] The positive electrode active material lithium cobalt oxide LiCoO2, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride PVDF are dissolved in N-methylpyrrolidone NMP solution at an appropriate weight ratio to form a positive electrode slurry. A 9μm aluminum foil is used as the positive electrode current collector, and the positive electrode slurry is coated on the positive electrode current collector. After drying, cold pressing, and cutting, the positive electrode sheet is obtained.

[0067] In the following embodiments and comparative examples, the performance parameters of the positive electrode sheets are shown in the table.

[0068] (2) Preparation of negative electrode

[0069] The negative electrode active materials silicon carbon, graphite, binder styrene butadiene rubber SBR, and thickener sodium carboxymethyl cellulose CMC are dissolved in deionized water at an appropriate weight ratio to form a negative electrode slurry. A 10 μm thick copper foil is used as a negative electrode current collector, and the negative electrode slurry is coated on the negative electrode current collector, and the negative electrode sheet is obtained after drying, cold pressing, and cutting.

[0070] (3) Preparation of isolation membrane

[0071] The diaphragm substrate is 5 μm thick polyethylene PE, and a 2 μm thick alumina ceramic layer is coated on one side of the diaphragm substrate. Finally, a 0.5 μm thick binder polyvinylidene fluoride PVDF is coated on both sides of the diaphragm substrate coated with a single ceramic layer, and dried to form a porous layer.

[0072] (4) Preparation of electrolyte

[0073] In an environment with a water content of less than 10ppm, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP) and propyl propionate (PP) are mixed in a mass ratio of 1:1:1:1:1, and then the electrolyte salt LiPF6 is dissolved in the above-mentioned non-aqueous solvent. After mixing, an electrolyte is formed, in which the mass percentage of LiPF6 is 12.5% ​​based on the mass of the electrolyte.

[0074] (5) Assembly of lithium-ion electronics

[0075] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain the electrode body. The electrode assembly is placed in an outer packaging aluminum plastic film, and after dehydration at 80°C, the above electrolyte is injected and packaged, and a lithium-ion battery is obtained through a process of formation, degassing, and trimming.

[0076] 2. Performance test of lithium-ion batteries

[0077] Normal temperature cycle test: In an environment of 25°C, the electrode assembly is charged at a constant current of 1C to the full charge voltage (the battery design maximum voltage is 4.5V), and then constant voltage charging is performed at the maximum voltage until the current is 0.02C, and then constant current discharge is performed at a discharge current of 0.7C until the final voltage is 3.0V, and the discharge capacity of the first cycle is recorded. After that, the above steps are repeated for 1000 charge and discharge cycles, and the discharge capacity of the lithium-ion battery after 1000 charge and discharge cycles is recorded.

[0078] Lithium deposition test: At 25°C, after 1000 cycles, when the battery is fully charged, disassemble it and observe whether lithium deposition occurs at the negative electrode interface / protective glue. The degree of lithium deposition is divided into slight lithium deposition and severe lithium deposition. Slight lithium deposition refers to the occurrence of lithium deposition at the interface, and the color of the lithium deposition is gray or gray-black. In severe lithium deposition, the interface appears silvery white, indicating that the amount of lithium deposition is large and the lithium deposition is relatively dense.

[0079] The conditions of Examples 1-1 to 1-4, Comparative Examples 1-1 and 1-2 are shown in Table 1.

[0080] Table 1

[0081] project d1(mm) d2(mm) d1:d2 Lithium precipitation Cycle capacity retention rate (%) Example 1-1 5 10 0.5:1 No lithium precipitation 90.43 Example 1-2 6 10 0.6:1 No lithium precipitation 92.38 Examples 1-3 7 10 0.7:1 No lithium precipitation 93.42 Examples 1-4 8 10 0.8:1 Slight lithium deposition 91.67 Comparative Example 1-1 4 10 0.4:1 No lithium precipitation 87.48 Comparative Example 1-2 9 10 0.9:1 Severe lithium deposition 82.16 Comparative Examples 1-3 8 8.5 0.94：1 Severe lithium deposition 81.17

[0082] According to the experimental results in Table 1, it can be seen that when d1:d2 is in the range of 0.5:1 to 0.8:1, that is, the situation in Example 1-1 to Example 1-4, the experimental results show that no serious negative electrode lithium deposition occurs, and the battery cycle capacity retention rate is relatively good, generally above 90%; In addition, it can also be seen from Table 1 that the smaller the ratio of d1:d2, the less likely it is to cause negative electrode lithium deposition, and the larger the ratio, the easier it is to cause lithium deposition. For example, in Example 1-4, slight lithium deposition has occurred; However, if the ratio of d1:d2 is too small, for example, 0.4:1 in Comparative Example 1-1, although no lithium deposition occurs, it will cause a low battery cycle capacity retention rate; On the contrary, if the ratio of d1:d2 is too large, for example, 0.9:1 in Comparative Example 1-2, serious lithium deposition will occur, which will ultimately further affect the battery cycle capacity retention rate.

[0083] The conditions of Examples 2-1 to 2-4, Comparative Examples 2-1 and 2-2 are shown in Table 2.

[0084] Table 2 (where d1:CW1 is in mm:mg / cm 2 )

[0085] project d1(mm) <![CDATA[CW1(mg / cm 2 )]]> d1:CW1 Lithium precipitation Cycle capacity retention rate (%) Example 2-1 6 30 1:5 No lithium precipitation 90.53 Example 2-2 6 20 1.5:5 No lithium precipitation 92.25 Example 2-3 6 15 2:5 No lithium precipitation 93.72 Embodiment 2-4 6 10 3:5 Slight lithium deposition 91.47 Comparative Example 2-1 6 40 0.75:5 No lithium precipitation 85.42 Comparative Example 2-2 6 8 3.75:5 Severe lithium deposition 83.78 Comparative Examples 2-3 8 10 4：5 Severe lithium deposition 82.46

[0086] According to the experimental results in Table 2, it can be seen that when d1:CW1 is in the range of 1:5 to 3:5, that is, the situation in Example 2-1 to Example 2-4, the experimental results show that no serious negative electrode lithium plating occurs, and the battery cycle capacity retention rate is relatively good, generally above 90%; In addition, it can also be seen from Table 2 that the smaller the ratio of d1:CW1, the less likely it is to cause negative electrode lithium plating, and the larger the ratio, the easier it is to cause lithium plating. For example, in Example 2-4, slight lithium plating has occurred; However, if the ratio of d1:CW1 is too small, for example, 0.75:5 in Comparative Example 2-1, although lithium plating does not occur, it will cause a low battery cycle capacity retention rate; On the contrary, if the ratio of d1:CW1 is too large, for example, 3.75:5 in Comparative Example 2-2, serious lithium plating will occur, which will ultimately further affect the battery cycle capacity retention rate.

[0087] The conditions of Example 3-1 to Example 3-4, Comparative Example 3-1 and Comparative Example 3-2 are shown in Table 3.

[0088] Table 3 (wherein the unit of d1 / W1 is mm:%)

[0089]

[0090]

[0091] According to the experimental results in Table 3, it can be seen that when d1 / W1 is in the range of 0.06 to 1.5, that is, the situation in Example 3-1 to Example 3-4, the experimental results show that no serious negative electrode lithium plating occurs, and the battery cycle capacity retention rate is relatively good, generally above 90%; in addition, it can also be seen from Table 3 that the smaller the ratio of d1 / W1, the less likely it is to cause negative electrode lithium plating, and the larger the ratio, the easier it is to cause lithium plating. For example, in Example 3-4, slight lithium plating has occurred; however, if the ratio of d1 / W1 is too small, for example, 0.04 in Comparative Example 3-1, although lithium plating does not occur, it will cause a low battery cycle capacity retention rate; on the contrary, if the ratio of d1 / W1 is too large, for example, 2 in Comparative Example 3-2, serious lithium plating will occur, and the battery cycle capacity retention rate will also be low.

[0092] The conditions of Example 4-1 to Example 4-4, Comparative Example 4-1 and Comparative Example 4-2 are shown in Table 4.

[0093] Table 4

[0094] project W1(％) W2(％) W1:W2 Lithium precipitation Cycle capacity retention rate (%) Example 4-1 18 30 0.6:1 No lithium precipitation 90.15 Example 4-2 40 60 0.67:1 No lithium precipitation 92.98 Example 4-3 16.6 20 0.83:1 No lithium precipitation 93.56 Example 4-4 18 20 0.9：1 No lithium precipitation 93.15 Embodiment 4-5 20 20 1:1 Slight lithium deposition 91.74 Comparative Example 4-1 30 60 0.5:1 No lithium precipitation 88.45 Comparative Example 4-2 70 60 1.17:1 Severe lithium deposition 82.43

[0095] According to the experimental results in Table 4, it can be seen that when W1:W2 is in the range of 0.6:1 to 1:1, that is, the situation in Example 4-1 to Example 4-5, the experimental results show that no serious negative electrode lithium plating occurs, and the battery cycle capacity retention rate is relatively good, generally above 90%; In addition, it can also be seen from Table 4 that the smaller the ratio of W1:W2, the less likely it is to cause negative electrode lithium plating, and the larger the ratio, the easier it is to cause lithium plating. For example, in Example 4-5, slight lithium plating has occurred; However, if the ratio of W1:W2 is too small, for example, 0.5:1 in Comparative Example 4-1, although lithium plating does not occur, it will cause a low battery cycle capacity retention rate; On the contrary, if the ratio of W1:W2 is too large, for example, 1.17:1 in Comparative Example 4-2, serious lithium plating will occur, which will ultimately further affect the battery cycle capacity retention rate.

[0096] In particular, the term "and / or" in this application should be understood as follows:

[0097] In the first case, the term "and / or" located between a first subject and a second subject includes any one of the following meanings: (1) only the first subject; (2) only the second subject; and (3) the first subject and the second subject.

[0098] In the second case, the term "and / or" between the last two subjects among three or more subjects means including at least any one of the multiple subjects. For example, "the first subject, the second subject and / or the third subject" has the same meaning as "the first subject and / or the second subject and / or the third subject", specifically including the following combinations: (1) only the first subject; (2) only the second subject; (3) only the third subject; (4) the first subject and the second subject but not the third subject; (5) the first subject and the third subject but not the second subject; (6) the second subject and the third subject but not the first subject; and (7) the first subject, the second subject and the third subject.

[0099] In addition, although the above content describes the embodiments of the present application in conjunction with the accompanying drawings, those skilled in the art can also make various modifications and variations without departing from the concept of the present application, and such modifications and variations shall fall within the scope of protection of the present application.

Claims

1. A positive electrode sheet, characterized in that: It includes a positive electrode current collector, a first positive electrode active layer, a second positive electrode active layer, a first positive electrode ear and a second positive electrode ear; The positive electrode current collector comprises a first part and a second part connected along its length direction, the first part is provided with the first positive electrode active layer on one side along its thickness direction, and the second part is provided with the second positive electrode active layer on two opposite sides along its thickness direction; The first positive electrode tab is connected to a first portion of the positive electrode current collector, and the second positive electrode tab is connected to a second portion of the positive electrode current collector; The dimension of the first positive electrode tab along the length direction of the positive electrode current collector is d1, the dimension of the second positive electrode tab along the length direction of the positive electrode current collector is d2, and 0.5:1.0≤d1:d2≤0.8:1.

0.

2. The positive electrode sheet according to claim 1, characterized in that: The mass of the first positive electrode active layer on the first part is m1, the total mass of the second positive electrode active layers on both sides of the second part is m2, and 0.1:1.0≤m1:m2≤0.4:1.

0.

3. The positive electrode sheet according to claim 1, characterized in that: 5mm≤d1≤8mm, 8mm≤d2≤10mm.

4. The positive electrode sheet according to claim 1, characterized in that: The surface density of the first positive electrode active layer on the first portion is CW1, the surface density of the second positive electrode active layer on the second portion is CW2, and 0.8:1.2≤CW1:CW2≤1.0:1.

5.

5. The positive electrode sheet according to claim 4, characterized in that: 1.0:5.0≤d1:CW1≤3.0:5.0, unit:mm:mg / cm 2 .

6. The positive electrode sheet according to claim 1, characterized in that: The first positive electrode ear is located on one side of the first part, centered on the first part and close to the second part. The areas of the first part on two opposite sides of the first positive electrode ear along its length direction are S1 and S2 respectively, and 0.6:1.0≤S1:S2≤0.9:1.

0.

7. The positive electrode sheet according to any one of claims 1 to 6, characterized in that: The first positive electrode active layer and / or the second positive electrode active layer comprises a positive electrode active material, a conductive agent and a binder; Preferably, the positive electrode active material includes one or more of lithium nickel oxide, lithium titanate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide.

8. A battery, characterized in that: It comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator located between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is the positive electrode sheet according to any one of claims 1 to 7.

9. The battery according to claim 8, characterized in that The negative electrode sheet comprises a negative electrode collector, a negative electrode active layer and a negative electrode tab. The negative electrode collector is provided with the negative electrode active layer on at least one side along the thickness direction thereof, and the negative electrode tab is connected to the negative electrode collector.

10. The battery according to claim 9, characterized in that The dimension of the negative electrode ear along the length direction of the negative electrode current collector is d3, 6mm≤d3≤10mm.

11. The battery according to claim 9, characterized in that The negative electrode active layer includes silicon material, and the content of the silicon material in the negative electrode active layer is W, 5%≤W≤100%; Preferably, the silicon material includes at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites and silicon alloys.

12. The battery according to claim 11, characterized in that The median particle size of the silicon material is D50, 4 μm≤D50≤10 μm.

13. The battery according to claim 11, characterized in that The content of silicon in the region corresponding to the negative electrode active layer and the first positive electrode active layer is W1, and the content of silicon in the region corresponding to the negative electrode active layer and the second positive electrode active layer is W2, 0.6:1.0≤W1:W2≤1.0:1.

0.

14. The battery according to claim 13, characterized in that 0.06≤d1 / W1≤1.5, unit: mm / %.

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