Pole piece and battery

Abstract

The utility model relates to the technical field of batteries, in particular to a pole piece and a battery. The pole piece active substance layer comprises n sub active substance layers, and each sub active substance layer comprises a main body region and a thinned region; the main body region comprises a first surface far away from the current collector, and the thinned region comprises a second surface far away from the current collector; each sub active material layer comprises a third surface close to the current collector; the current collector comprises a fourth surface close to the active material layer; in every two adjacent sub active material layers, the projection of the first surface of the sub active material layer close to the current collector on the current collector coincides with the projection of the third surface of the sub active material layer far away from the current collector on the current collector; the included angles between the second surfaces and the fourth surfaces of the first sub-active material layer,..., and the nth sub-active material layer are sequentially recorded as theta 1,..., theta n; [theta] 1, [theta] 2,... [theta] n are each independently 0.3-3 degrees, and [theta] 1, [theta] 2,... [theta] n are equal. The design of the electrode plate can effectively improve the edge bulging problem of the multi-layer coated electrode.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, specifically to electrode sheets and batteries. Background Art

[0002] Lithium-ion batteries have received extensive attention in social life and have been increasingly widely used in many fields due to their advantages such as high voltage, large capacity, long life cycle, low self-discharge rate, and wide operating temperature range.

[0003] Improving energy and power density is an important improvement direction for the performance of lithium-ion batteries. However, with the increase in coating weight, it will inevitably lead to an increase in internal resistance, resulting in a series of problems such as capacity attenuation, increased heat generation, decreased output voltage, decreased power output, reduced charging efficiency, and battery thermal runaway. The multi-layer coating process can well solve this problem. However, during the production process of the multi-layer coating process, problems such as edge bulging are likely to occur in the thinned area at the edge of the electrode sheet. Edge bulging will cause the following problems:

[0004] 1. During coating winding, it is easy to cause the empty foil area to bend and wrinkle, resulting in uneven winding and a high risk of tab folding;

[0005] 2. During rolling, the local stress is too large, and the local deformation is serious, resulting in the bending deformation of the film surface;

[0006] 3. During charge and discharge, the relative distance between the positive and negative electrodes varies greatly, which is likely to cause local polarization, resulting in the risk of lithium deposition, reducing the cycle life and safety performance, etc.

[0007] Currently, the relevant design points of multi-layer coated electrode sheets in the industry are not perfect. Most rely solely on experience accumulation, resulting in a huge trial-and-error cost. Utility Model Content

[0008] In view of this, the present utility model provides an electrode sheet and a battery. The design of this electrode sheet can effectively improve the edge bulging problem of multi-layer coated electrodes.

[0009] In order to achieve the above utility model purpose, the present utility model provides the following technical solutions:

[0010] In a first aspect, the present utility model provides an electrode sheet, which includes a current collector 100, and an active material layer 200 disposed on at least one surface in the thickness direction of the current collector;

[0011] The active material layer includes n sub-active material layers stacked, where n is a natural number greater than or equal to 2. Along the direction gradually away from the thickness of the current collector, they are sequentially denoted as the first sub-active material layer 210, the second sub-active material layer 220,... the nth sub-active material layer;

[0012] In the width direction of the current collector, each sub-active material layer includes a main body region and thinning regions provided on both sides of the main body region; the main body region includes a first surface away from the thickness direction of the current collector, and the thinning region includes a second surface away from the thickness direction of the current collector; each sub-active material layer includes a third surface close to the thickness direction of the current collector; the current collector includes a fourth surface 100c close to the active material layer;

[0013] Among two adjacent sub-active material layers, the projection of the first surface of the sub-active material layer close to the thickness direction of the current collector on the current collector coincides with the projection of the third surface of the sub-active material layer away from the thickness direction of the current collector on the current collector;

[0014] The included angle between the second surface 212b of the thinning region 212 of the first-layer sub-active material layer and the fourth surface 100c of the current collector is denoted as θ1, the included angle between the second surface 222b of the thinning region 222 of the second-layer sub-active material layer and the fourth surface 100c of the current collector is denoted as θ2, …… the included angle between the second surface of the thinning region of the nth-layer sub-active material layer and the fourth surface 100c of the current collector is denoted as θ n ;

[0015] θ1, θ2, …… θ n are independently 0.3° to 3°, and θ1, θ2, …… θ n are equal.

[0016] Preferably, n is any natural number from 2 to 5.

[0017] In the present utility model, the perpendicular distance from the first surface 211a of the main body region 211 of the first-layer sub-active material layer to the fourth surface 100c of the current collector is denoted as H1, the perpendicular distance from the first surface 221a of the main body region 221 of the second-layer sub-active material layer to the fourth surface 100c of the current collector is denoted as H2, …… the perpendicular distance from the first surface of the main body region of the nth-layer sub-active material layer to the fourth surface 100c of the current collector is denoted as H n ;

[0018] H1 < H2 …… < H n .

[0019] In the embodiment of the present utility model, the pole piece is a positive pole piece or a negative pole piece.

[0020] Preferably, the positive active material of the positive pole piece includes one of ternary materials, lithium iron phosphate, and lithium manganese iron phosphate.

[0021] Preferably, the negative active material of the negative pole piece includes one of graphite, hard carbon, silicon oxide, and silicon carbon.

[0022] In some embodiments, the pole piece is a positive pole piece, and the H n of the positive pole piece is 20 to 300 μm.

[0023] In some other embodiments, the electrode tab is a negative electrode tab, and the H of the negative electrode tab n is 10 - 200 μm.

[0024] Preferably, θ1, θ2,... θ n are independently 0.6° - 1.0° respectively.

[0025] Preferably, the projection of the active material layer on the plane formed by the thickness direction and the width direction of the current collector is a trapezoid.

[0026] In some embodiments, the electrode tab is a positive electrode tab, and the tap density of the positive electrode tab is 2.0 - 4.0 g / cm 3 .

[0027] In some other embodiments, the electrode tab is a negative electrode tab, and the tap density of the negative electrode tab is 0.5 - 2.0 g / cm 3 .

[0028] In a second aspect, the present invention further provides a battery, which includes the above-mentioned electrode tab.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The present application adopts a structure with edge dislocation of multiple sub-active material layers, which can effectively improve the problem of edge bulging of the multi-layer coated electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic cross-sectional view of the thinned area where the protrusions of two layers are not staggered;

[0032] Figure 2A It is a schematic structural view of the double-layer coated electrode tab of Example 1-1;

[0033] Figure 2B It is a schematic structural view of the double-layer coated electrode tab of Example 1-1;

[0034] Figure 3A It is a schematic structural view of the double-layer coated electrode tab of Comparative Example 1-1;

[0035] Figure 3B It is a schematic structural view of the double-layer coated electrode tab of Comparative Example 1-1;

[0036] Figure 4A It is a schematic structural view of the triple-layer coated electrode tab of Example 2-1;

[0037] Figure 4B It is a schematic structural view of the triple-layer coated electrode tab of Example 2-1;

[0038] Figure 5ASchematic diagram of the three-layer coated electrode sheet for Comparative Example 2-1;

[0039] Figure 5B Schematic diagram of the three-layer coated electrode sheet for Comparative Example 2-1.

[0040] Reference numerals are as follows:

[0041] 100: Current collector;

[0042] 100c: Fourth surface of the current collector;

[0043] 200: Active material layer;

[0044] 210: First sub-active material layer;

[0045] 211: Main body region of the first sub-active material layer;

[0046] 211a: First surface of the main body region of the first sub-active material layer;

[0047] 212: Thinned region of the first sub-active material layer;

[0048] 212b: Second surface of the thinned region of the first sub-active material layer;

[0049] 220: Second sub-active material layer;

[0050] 221: Main body region of the second sub-active material layer;

[0051] 221a: First surface of the main body region of the second sub-active material layer;

[0052] 222: Thinned region of the second sub-active material layer;

[0053] 222b: Second surface of the thinned region of the second sub-active material layer;

[0054] 230: Third sub-active material layer;

[0055] 231: Main body region of the third sub-active material layer;

[0056] 231a: First surface of the main body region of the third sub-active material layer;

[0057] 232: Thinned region of the third sub-active material layer;

[0058] 232b: Second surface of the thinned region of the third sub-active material layer. Detailed implementation mode

[0059] The present utility model discloses a pole piece and a battery. Those skilled in the art can draw on the content of this article and appropriately improve process parameters to achieve it. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present utility model. The methods and applications of the present utility model have been described through preferred embodiments. Relevant personnel can obviously make changes or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of the present utility model to implement and apply the technology of the present utility model.

[0060] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values or individual point values of each range, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0061] If there is no special instruction, all implementation manners and optional implementation manners of the present application can be combined with each other to form a new technical solution.

[0062] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0063] If there is no special instruction, the "including" and "comprising" mentioned in the present application mean open-ended or can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or it can only include or comprise the listed components.

[0064] The design principle of the present utility model is as follows:

[0065] For a multi-layer coated pole piece, the surface of each layer of thinning area away from the current collector is taken as the outer surface of each layer of thinning area, and θ is the angle between the outer surface of the thinning area of each layer of sub-active material layer and the plane of the current collector; the surface of the main body area away from the current collector is taken as the outer surface of the main body area, H is the vertical distance from the outer surface of the main body area of each layer of sub-active material layer to the plane of the current collector, and d is the projection width of the outer surface of the thinning area on the current collector. When the θ angle is less than or equal to 3°, H = d * tanθ ≈ d * θ. When H1 / H2 = θ1 / θ2, the intersection position of the outer surface of the main body area (the first surface) and the outer surface of the thinning area (the second surface) in the first layer of sub-active material layer (i.e., the raised position of the first coating layer) coincides with the intersection position of the outer surface of the main body area (the first surface) and the outer surface of the thinning area (the second surface) in the second layer of sub-active material layer (i.e., the raised position of the second coating layer) in the projection on the current collector, that is, d1 = d2, and the protrusions of the two layers are not staggered, which will exacerbate the edge bulging phenomenon ( Figure 1)。The utility model adopts a structure with edge dislocation of multiple sub-active material layers, so that the thinning areas of each sub-active material layer are dislocated and independent, avoiding the accumulation of protrusions, and can effectively improve the problem of edge bulging of the multi-layer coated electrode.

[0066] Specifically, the utility model adopts the following technical solutions:

[0067] In the first aspect, the utility model provides a pole piece, which includes a current collector 100 and an active material layer 200 disposed on at least one surface in the thickness direction of the current collector;

[0068] The active material layer includes n sub-active material layers stacked, where n is a natural number greater than or equal to 2. Along the direction gradually away from the thickness of the current collector, they are sequentially denoted as the first sub-active material layer 210, the second sub-active material layer 220,... the nth sub-active material layer;

[0069] Along the width direction of the current collector, each sub-active material layer includes a main body area and thinning areas disposed on both sides of the main body area; the main body area includes a first surface away from the thickness direction of the current collector, and the thinning area includes a second surface away from the thickness direction of the current collector; each sub-active material layer includes a third surface close to the thickness direction of the current collector; the current collector includes a fourth surface 100c close to the active material layer;

[0070] In adjacent two sub-active material layers, the projection of the first surface of the sub-active material layer close to the thickness direction of the current collector on the current collector coincides with the projection of the third surface of the sub-active material layer away from the thickness direction of the current collector on the current collector;

[0071] The included angle between the second surface 212b of the thinning area 212 of the first sub-active material layer and the fourth surface 100c of the current collector is denoted as θ1, the included angle between the second surface 222b of the thinning area 222 of the second sub-active material layer and the fourth surface 100c of the current collector is denoted as θ2,... the included angle between the second surface of the thinning area of the nth sub-active material layer and the fourth surface 100c of the current collector is denoted as θ n ;

[0072] θ1, θ2,... θ n are independently 0.3° to 3°, and θ1, θ2,... θ n are equal.

[0073] Exemplarily, θ1, θ2,... or θ nis any value among 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, 1.0°, 1.1°, 1.2°, 1.3°, 1.4°, 1.5°, 1.6°, 1.7°, 1.8°, 1.9°, 2.0°, 2.1°, 2.2°, 2.3°, 2.4°, 2.5°, 2.6°, 2.7°, 2.8°, 2.9°, 3° or any value within the range formed by any two of the above values. θ1, θ2, … or θ n If the value is too small, it will increase the size of the thinning area, resulting in N / P ratio < 1, with risks of lithium plating and thermal runaway, and it is likely to cause uneven edge coating; θ1, θ2, … or θ n If the value is too large, the slurry will be affected by molecular force, forming dewdrop-like protrusions, causing serious edge swelling. On the one hand, it increases the process difficulty, and on the other hand, it will increase the gap between the electrode sheets, increase the internal resistance, and reduce the margin of the battery cell group, thereby reducing the energy density of the battery cell.

[0074] Preferably, n is any natural number from 2 to 5. Exemplarily, n is 2, 3, 4 or 5.

[0075] In the present utility model, the vertical distance from the first surface 211a of the first-layer sub-active material layer main body region 211 to the fourth surface 100c of the current collector is denoted as H1, the vertical distance from the first surface 221a of the second-layer sub-active material layer main body region 221 to the fourth surface 100c of the current collector is denoted as H2, … the vertical distance from the first surface of the nth-layer sub-active material layer main body region to the fourth surface 100c of the current collector is denoted as H n ;

[0076] H1 < H2 … < H n 。

[0077] In the embodiments of the present utility model, the electrode sheet is a positive electrode sheet or a negative electrode sheet.

[0078] Preferably, the positive active material of the positive electrode sheet includes one of ternary materials, lithium iron phosphate, and lithium manganese iron phosphate.

[0079] Preferably, the negative active material of the negative electrode sheet includes one of graphite, hard carbon, silicon oxide, and silicon carbon.

[0080] In some embodiments, the electrode sheet is a positive electrode sheet, and the H of the positive electrode sheet n is 20 - 300 μm. Exemplarily, H1 of the positive electrode sheet is any value among 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm or any value within the range formed by any two of the above values.

[0081] In the embodiments of the present invention, for different cathode active materials, the range of H1 is slightly different. For example, H1 in the cathode sheet including lithium iron phosphate is 20 to 250 μm, and H1 in the cathode sheet including NCM or NCA ternary materials is 20 to 200 μm.

[0082] In some other embodiments, the electrode sheet is an anode sheet, and H of the anode sheet n is 10 to 200 μm. Exemplarily, H1 of the anode sheet is any value among 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm or any value within the range value composed of any two of the above values.

[0083] In the embodiments of the present invention, for different anode active materials, the range of H1 is slightly different. For example, H1 in the anode sheet including graphite is 10 to 150 μm, and H1 in the anode sheet including hard carbon is 20 to 140 μm.

[0084] To meet the electrode sheet design of negative wrapping positive, preferably, θ1, θ2,... θ n are independently 0.6° to 1.0° respectively.

[0085] Preferably, the projection of the active material layer on the plane formed by the thickness direction and the width direction of the current collector is a trapezoid.

[0086] In some embodiments, the electrode sheet is a cathode sheet, and the tap density of the cathode sheet is 2.0 to 4.0 g / cm 3 . Exemplarily, the tap density of the cathode sheet is 2.0 g / cm 3 , 2.2 g / cm 3 , 2.4 g / cm 3 , 2.6 g / cm 3 , 2.8 g / cm 3 , 3.0 g / cm 3 , 3.2 g / cm 3 , 3.4 g / cm 3 , 3.6 g / cm 3 , 3.8 g / cm 3 , 4.0 g / cm 3 or any value within the range value composed of any two of the above values.

[0087] In the embodiments of the present invention, for different cathode active materials, the range of the tap density of the cathode sheet is slightly different. For example, the tap density of the cathode sheet including NCM ternary materials is 3.2 to 3.7 g / cm 3; The tap density of the positive electrode sheet including lithium iron phosphate material is 2.3 to 2.6 g / cm 3 ; The tap density of the positive electrode sheet including lithium manganese iron phosphate is 2.1 to 2.4 g / cm 3 .

[0088] In some other embodiments, the electrode sheet is a negative electrode sheet, and the tap density of the negative electrode sheet is 0.5 to 2.0 g / cm 3 . Exemplarily, the tap density of the negative electrode sheet is 0.5 g / cm 3 , 0.6 g / cm 3 , 0.8 g / cm 3 , 1.0 g / cm 3 , 1.2 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.8 g / cm 3 , 2.0 g / cm 3 or any value within the range formed by any two of the above values.

[0089] In the embodiments of the present invention, for different negative active materials, the range of the tap density of the negative electrode sheet is slightly different. For example, the tap density of the negative electrode sheet including graphite material is 1.5 to 1.7 g / cm 3 ; The tap density of the negative electrode sheet including hard carbon is 0.75 to 1.05 g / cm 3 ; The tap density of the negative electrode sheet including silicon oxide is 1.2 to 1.6 g / cm 3 ; The tap density of the negative electrode sheet including silicon carbon is 1.2 to 1.6 g / cm 3 .

[0090] Second, the present invention also provides a battery, and the battery includes the above electrode sheet.

[0091] In the embodiments of the present invention, the battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet and / or the negative electrode sheet has the above electrode sheet structure.

[0092] In the embodiments of the present invention, the battery structure includes but is not limited to button cells, soft-pack batteries, cylindrical batteries, etc.

[0093] The present application has no special restrictions on the separator and electrolyte in the battery, and those skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved.

[0094] The instruments or materials used in the present invention can all be obtained through commercial channels.

[0095] The present utility model will be further described below in conjunction with embodiments:

[0096] Example 1-1 Double coating

[0097] 1. Negative electrode sheet or positive electrode sheet

[0098] The structure of the negative electrode sheet or positive electrode sheet refers to Figure 2A and Figure 2B as shown, including a current collector 100, and active material layers 200 disposed on two surfaces of the current collector ( Figure 2A and Figure 2B only show the active material layer on one surface); the cross-section of the active material layer 200 is trapezoidal;

[0099] The active material layer 200 includes 2 sub-active material layers stacked, and are sequentially denoted as the first sub-active material layer 210 and the second sub-active material layer 220 along the direction gradually away from the thickness of the current collector;

[0100] Along the width direction of the current collector, each sub-active material layer includes a main body area, and thinning areas disposed on both sides of the main body area; the main body area includes a first surface away from the thickness direction of the current collector, and the thinning area includes a second surface away from the thickness direction of the current collector; each sub-active material layer includes a third surface close to the thickness direction of the current collector; the current collector includes a fourth surface 100c close to the active material layer;

[0101] Among adjacent two sub-active material layers, the projection of the first surface of the sub-active material layer close to the thickness direction of the current collector on the current collector coincides with the projection of the third surface of the sub-active material layer away from the thickness direction of the current collector on the current collector;

[0102] The vertical distance from the first surface 211a of the main body area 211 of the first sub-active material layer to the fourth surface 100c of the current collector is denoted as H1, and the vertical distance from the first surface 221a of the main body area 221 of the second sub-active material layer to the fourth surface 100c of the current collector is denoted as H2;

[0103] The included angle between the second surface 212b of the thinning area 212 of the first sub-active material layer and the fourth surface 100c of the current collector is denoted as θ1, and the included angle between the second surface 222b of the thinning area 222 of the second sub-active material layer and the fourth surface 100c of the current collector is denoted as θ2;

[0104] The values of H1, H2, θ1, and θ2 are shown in Table 1. And H1 < H2, θ1 = θ2.

[0105] The active material in the negative electrode sheet is graphite. The first sub-active material layer of the negative electrode sheet includes the following components by mass percentage: 96.9% of graphite as the negative active material, 1.1% of styrene-butadiene rubber (SBR) as the binder, 0.5% of super P (SP) as the conductive agent, and 1.5% of carboxymethyl cellulose (CMC) as the binder; the second sub-active material layer of the negative electrode sheet includes the following components by mass percentage: 95.1% of graphite, 1.9% of SBR, 1.5% of SP, and 1.5% of CMC; the tap density of the negative electrode sheet is 1.5 g / cm 3 ;

[0106] The active material in the positive electrode sheet is NCM622. Each sub-active material layer of the positive electrode sheet includes the following components by mass percentage: 96.5% of nickel-cobalt-manganese ternary material (NCM622) as the positive active material, 1.5% of polyvinylidene fluoride (PVDF) as the binder, 1.5% of SP as the conductive agent, and 0.5% of carbon nanotubes (CNT) as the conductive agent; the tap density of the positive electrode sheet is 3.4 g / cm 3 。

[0107] The preparation method of the negative electrode sheet or the positive electrode sheet uses the existing technology. After uniformly mixing materials such as the active material, the conductive agent, and the binder, as well as the solvent, it is coated on the current collector. Subsequently, after processes such as drying and cold pressing, the electrode sheet is obtained.

[0108] 2. Separator

[0109] The separator can be made of materials such as polyethylene film, polypropylene film, polyvinylidene fluoride film, and non-woven fabric. For example, the separator is selected from polyethylene film.

[0110] 3. Electrolyte

[0111] The electrolyte includes a lithium salt and a solvent. Among them, the types of the lithium salt and the solvent are not specifically limited and can be selected according to actual needs. For example, the lithium salt can be selected from LiPF6, LiTFSI, LiBF4, etc. For example, the electrolyte is prepared by dissolving LiPF6 in a solvent with a ratio of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate of 1:1:1, and the concentration is 1.2 mol / L.

[0112] 4. Battery

[0113] In the process of assembling the battery cell, the positive electrode sheet, the separator, and the negative electrode sheet are arranged in sequence. The assembly methods are winding and stacking. The electrolyte is injected into the dry battery cell, and the battery is obtained after formation and aging.

[0114] Example 1-2 Double-layer Coating

[0115] The difference between this example and Example 1-1 is only that the value of H1 is different. The values of each parameter are shown in Table 1.

[0116] Example 1-3 Double-layer Coating

[0117] The difference between this embodiment and Embodiment 1-1 is only that: the value of H1 is different. The values of each parameter are shown in Table 1.

[0118] Comparative Example 1-1 Double coating

[0119] The difference between this comparative example and Embodiment 1-1 is only that: the structure of the negative electrode sheet or the positive electrode sheet is different, specifically as follows:

[0120] The structure of the negative electrode sheet or the positive electrode sheet refers to Figure 3A and Figure 3B as shown, including a current collector 100, and active material layers 200 provided on two surfaces of the current collector ( Figure 3A and Figure 3B only the active material layer on one surface is shown); the cross-section of the active material layer 200 is trapezoidal;

[0121] The active material layer 200 includes 2 sub-active material layers arranged in a stacked manner, and are sequentially denoted as the first sub-active material layer 210 and the second sub-active material layer 220 along the direction gradually away from the thickness of the current collector. The widths of the two sub-active material layers are equal, and the projections of the two sub-active material layers in the thickness direction of the current collector coincide;

[0122] Along the width direction of the current collector, each sub-active material layer includes a main body area, and thinning areas provided on both sides of the main body area; the main body area includes a first surface away from the thickness direction of the current collector, and the thinning area includes a second surface away from the thickness direction of the current collector; the current collector includes a fourth surface close to the active material layer;

[0123] The perpendicular distance from the first surface 211a of the main body area 211 of the first sub-active material layer to the fourth surface 100c of the current collector is denoted as H1, and the perpendicular distance from the first surface 221a of the main body area 221 of the second sub-active material layer to the fourth surface 100c of the current collector is denoted as H2;

[0124] The included angle between the second surface 212b of the thinning area 212 of the first sub-active material layer and the fourth surface 100c of the current collector is denoted as θ1, and the included angle between the second surface 222b of the thinning area 222 of the second sub-active material layer and the fourth surface 100c of the current collector is denoted as θ2;

[0125] The values of H1, H2, θ1, and θ2 are shown in Table 1.

[0126] Comparative Example 1-2 Double coating

[0127] The difference between this comparative example and Comparative Example 1-1 is only that: the values of H1 and θ1 are different. The values of each parameter are shown in Table 1.

[0128] Embodiment 2-1 Triple coating

[0129] The structure of the positive electrode sheet or the negative electrode sheet is referred to Figure 4A and Figure 4B as shown, including a current collector 100, and an active material layer 200 disposed on two surfaces of the current collector ( Figure 4A and Figure 4B only the active material layer on one surface is shown in ); the cross-section of the active material layer 200 is trapezoidal;

[0130] The active material layer 200 includes three sub-active material layers arranged in a stacked manner, which are sequentially denoted as the first sub-active material layer 210, the second sub-active material layer 220, and the third sub-active material layer 230 along the direction gradually away from the thickness of the current collector;

[0131] Along the width direction of the current collector, each sub-active material layer includes a main body region, and thinning regions disposed on both sides of the main body region; the main body region includes a first surface away from the thickness direction of the current collector, and the thinning region includes a second surface away from the thickness direction of the current collector; each sub-active material layer includes a third surface close to the thickness direction of the current collector; the current collector includes a fourth surface 100c close to the active material layer;

[0132] Among two adjacent sub-active material layers, the projection of the first surface of the sub-active material layer close to the thickness direction of the current collector on the current collector coincides with the projection of the third surface of the sub-active material layer away from the thickness direction of the current collector on the current collector;

[0133] The vertical distance from the first surface 211a of the main body region 211 of the first sub-active material layer to the fourth surface 100c of the current collector is denoted as H1, the vertical distance from the first surface 221a of the main body region 221 of the second sub-active material layer to the fourth surface 100c of the current collector is denoted as H2, and the vertical distance from the first surface 231a of the main body region 231 of the third sub-active material layer to the fourth surface 100c of the current collector is denoted as H3;

[0134] The included angle between the second surface 212b of the thinning region 212 of the first sub-active material layer and the fourth surface 100c of the current collector is denoted as θ1, the included angle between the second surface 222b of the thinning region 222 of the second sub-active material layer and the fourth surface 100c of the current collector is denoted as θ2, and the included angle between the second surface 232b of the thinning region 232 of the third sub-active material layer and the fourth surface 100c of the current collector is denoted as θ3;

[0135] The values of H1, H2, H3, θ1, θ2, and θ3 are shown in Table 2. And H1 < H2 < H3, θ1 = θ2 = θ3.

[0136] The active material in the negative electrode sheet is graphite. The first sub-active material layer of the negative electrode sheet includes the following components by mass percentage: graphite 96.9%, styrene-butadiene rubber (SBR) 1.1%, conductive carbon black (SP) 0.5%, carboxymethyl cellulose (CMC) 1.5%; the second sub-active material layer of the negative electrode sheet includes the following components by mass percentage: graphite 96.0%, SBR 1.5%, SP 1.0%, CMC 1.5%; the third sub-active material layer of the negative electrode sheet includes the following components by mass percentage: graphite 95.1%, SBR 1.9%, SP 1.5%, CMC 1.5%; the compaction density of the negative electrode sheet is 1.5 g / cm 3 ;

[0137] The active material in the positive electrode sheet is NCM622. Each sub-active material layer of the positive electrode sheet includes the following components by mass percentage: nickel-cobalt-manganese ternary material (NCM622) 96.5%, polyvinylidene fluoride (PVDF) 1.5%, SP 1.5%, carbon nanotubes (CNT) 0.5%; the compaction density of the positive electrode sheet is 3.4 g / cm 3 。

[0138] The preparation method of the negative electrode sheet or the positive electrode sheet uses the existing technology. After uniformly mixing materials such as active material, conductive agent, binder, etc. and a solvent, it is coated on the current collector. Subsequently, after processes such as drying and cold pressing, the electrode sheet is obtained.

[0139] 2. Separator

[0140] The separator can be made of materials such as polyethylene film, polypropylene film, polyvinylidene fluoride film, and non-woven fabric. For example, the separator is selected from polyethylene film.

[0141] 3. Electrolyte

[0142] The electrolyte includes a lithium salt and a solvent. Among them, the types of the lithium salt and the solvent are not specifically limited and can be selected according to actual needs. For example, the lithium salt can be selected from LiPF6, LiTFSI, LiBF4, etc. For example, the electrolyte is prepared by dissolving LiPF6 in a solvent with a ratio of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate of 1:1:1, and the concentration is 1.2 mol / L.

[0143] 4. Battery

[0144] During the cell assembly process, the positive electrode sheet, the separator, and the negative electrode sheet are arranged in sequence. The assembly methods are winding and stacking. The electrolyte is injected into the dry cell, and the battery is obtained after formation and aging.

[0145] Example 2-2 Three-layer coating

[0146] The difference between this example and Example 2-1 is only that the values of H1 and H2 are different. The values of each parameter are shown in Table 2.

[0147] Example 2-3 Three-layer Coating

[0148] The difference between this example and Example 2-1 is only that the values of H1 and H2 are different. The values of each parameter are shown in Table 2.

[0149] Comparative Example 2-1 Three-layer Coating

[0150] The difference between this comparative example and Example 2-1 is only that the structure of the negative electrode or the positive electrode is different, specifically as follows:

[0151] The structure of the negative electrode or the positive electrode refers to Figure 5A and Figure 5B as shown, including a current collector 100, and an active material layer 200 provided on two surfaces of the current collector ( Figure 5A and Figure 5B only the active material layer on one surface is shown); the cross-section of the active material layer 200 is trapezoidal;

[0152] The active material layer 200 includes 2 sub-active material layers arranged in a stacked manner. Along the direction gradually away from the thickness of the current collector, they are sequentially denoted as the first sub-active material layer 210, the second sub-active material layer 220, and the third sub-active material layer 230. The widths of the three sub-active material layers are equal, and the projections of the three sub-active material layers in the thickness direction of the current collector coincide;

[0153] Along the width direction of the current collector, each sub-active material layer includes a main body area, and thinning areas provided on both sides of the main body area; the main body area includes a first surface away from the thickness direction of the current collector, and the thinning area includes a second surface away from the thickness direction of the current collector; the current collector includes a fourth surface close to the active material layer;

[0154] The perpendicular distance from the first surface 211a of the main body area 211 of the first sub-active material layer to the fourth surface 100c of the current collector is denoted as H1, the perpendicular distance from the first surface 221a of the main body area 221 of the second sub-active material layer to the fourth surface 100c of the current collector is denoted as H2, and the perpendicular distance from the first surface 231a of the main body area 231 of the third sub-active material layer to the fourth surface 100c of the current collector is denoted as H3;

[0155] The included angle between the second surface 212b of the thinning area 212 of the first sub-active material layer and the fourth surface 100c of the current collector is denoted as θ1, the included angle between the second surface 222b of the thinning area 222 of the second sub-active material layer and the fourth surface 100c of the current collector is denoted as θ2, and the included angle between the second surface 232b of the thinning area 232 of the third sub-active material layer and the fourth surface 100c of the current collector is denoted as θ3;

[0156] The values of H1, H2, H3, θ1, θ2, and θ3 are shown in Table 2.

[0157] Comparative Example 2-2 Three-layer coating

[0158] The difference between this comparative example and Comparative Example 2-1 is only that the values of H1, H2, θ1, and θ2 are different. The values of each parameter are shown in Table 2.

[0159] Comparative Example 2-3 Three-layer coating

[0160] The difference between this comparative example and Comparative Example 2-1 is only that the values of H1, H2, θ1, and θ2 are different. The values of each parameter are shown in Table 2.

[0161] Battery performance test:

[0162] After coating, the CCD of the electrode sheet was detected and the edge of the electrode roll was observed by human eyes to check if there was any edge bulging problem.

[0163] Table 1 Double-layer coating

[0164] Category <![CDATA[H1 thickness / μm]]> <![CDATA[H2 thickness / μm]]> <![CDATA[θ1 / °]]> <![CDATA[θ2 / °]]> Drum edge Comparative Example 1-1 60 120 0.47 0.8 Slight Comparative Example 1-2 80 120 0.5 0.8 Yes Example 1-1 40 120 0.8 0.8 No Example 1-2 60 120 0.8 0.8 No Example 1-3 80 120 0.8 0.8 No

[0165] Table 2 Three-layer coating

[0166]

[0167] It can be seen from the experimental data that compared with the electrode sheets of the comparative examples, the electrode sheets of the embodiments of the present invention have obvious advantages in terms of appearance edge bulging.

[0168] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A pole piece, characterized in that, The electrode includes a current collector (100) and an active material layer (200) disposed on at least one surface in the thickness direction of the current collector; The active material layer includes n sub-active material layers stacked on top of each other, where n is a natural number greater than or equal to 2. Along the direction gradually away from the thickness of the current collector, they are sequentially denoted as the first sub-active material layer (210), the second sub-active material layer (220),... the nth sub-active material layer; In the width direction of the current collector, each sub-active material layer includes a main body region and thinning regions disposed on both sides of the main body region; the main body region includes a first surface away from the thickness direction of the current collector, and the thinning region includes a second surface away from the thickness direction of the current collector; each sub-active material layer includes a third surface close to the thickness direction of the current collector; the current collector includes a fourth surface (100c) close to the active material layer; Among two adjacent sub-active material layers, the projection of the first surface of the sub-active material layer close to the thickness direction of the current collector on the current collector coincides with the projection of the third surface of the sub-active material layer away from the thickness direction of the current collector on the current collector; The included angle between the second surface (212b) of the first-layer sub-active material layer thinning region (212) and the fourth surface (100c) of the current collector is denoted as θ1, the included angle between the second surface (222b) of the second-layer sub-active material layer thinning region (222) and the fourth surface (100c) of the current collector is denoted as θ2, …… the included angle between the second surface of the nth-layer sub-active material layer thinning region and the fourth surface (100c) of the current collector is denoted as θ n ; The θ1, θ2, …… θ n are independently 0.3° to 3°, and θ1, θ2, …… θ n are equal.

2. The pole piece according to claim 1, characterized in that, The n is any natural number from 2 to 5.

3. The pole piece according to claim 1, wherein The vertical distance from the first surface (211a) of the first-layer sub-active material layer main region (211) to the fourth surface (100c) of the current collector is denoted as H1, the vertical distance from the first surface (221a) of the second-layer sub-active material layer main region (221) to the fourth surface (100c) of the current collector is denoted as H2, …… the vertical distance from the first surface of the nth-layer sub-active material layer main region to the fourth surface (100c) of the current collector is denoted as H n ; H1 < H2…… < H n .

4. The pole piece according to claim 1, characterized in that, The electrode is a positive electrode or a negative electrode.

5. The pole piece according to claim 4, wherein, The positive active material of the positive electrode includes one of ternary materials, lithium iron phosphate, and lithium manganese iron phosphate; The negative active material of the negative electrode includes one of graphite, hard carbon, silicon oxide, and silicon carbon.

6. The pole piece according to claim 4, characterized in that, The electrode is a positive electrode, and the H of the positive electrode n is 20 to 300 μm; The electrode is a negative electrode, and the H of the negative electrode n is 10 to 200 μm.

7. The pole piece according to claim 1, wherein The θ1, θ2, …… θ n are independently 0.6° to 1.0° respectively.

8. The pole piece according to claim 1, characterized in that, The projection of the active material layer on the plane formed by the thickness direction and the width direction of the current collector is trapezoidal.

9. The pole piece according to claim 4, wherein The electrode is a positive electrode, and the tap density of the positive electrode is 2.0 to 4.0 g / cm 3 ; The electrode is a negative electrode, and the tap density of the negative electrode is 0.5 to 2.0 g / cm 3 .

10. A battery, characterized in that, The battery includes the electrode according to any one of claims 1-9.

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