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; the current collector comprises a third surface close to the active material layer; the vertical distances from the first surface to the third surface of the first sub-active material layer to the nth sub-active material layer are sequentially marked as H1,... Hn; the included angles between the second surfaces and the third surfaces of the first sub-active material layer,..., and the nth sub-active material layer are sequentially recorded as theta 1,..., theta n; h1 / H2 is in the range of 1.1 to 3.0,... Hn-1 / Hn is in the range of 1.1 to 3.0; theta1 is 0.3 to 3 degrees; [theta] 1 / [theta] 2 is 1.1 to 3.0,... [theta] n-1 / [theta] n is 1.1 to 3.0; and H1 / H2 is less than theta1 / theta2. The design can improve the edge bulging problem of the multi-layer coated electrode.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to pole pieces and batteries. Background Art

[0002] Lithium-ion batteries have received widespread attention in social life and have been increasingly 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 a key area for improving lithium-ion battery performance. However, as coating weight increases, internal resistance inevitably increases, leading to a series of problems such as capacity decay, increased heat generation, decreased output voltage, decreased power output, reduced charging efficiency, and thermal runaway. Multi-layer coating processes can effectively address this issue. However, during the production process, multi-layer coating processes are prone to bulging in the thinned areas of the electrode edges. This bulging can cause the following problems:

[0004] 1. During coating and rewinding, the empty foil area is prone to bending and wrinkling, resulting in uneven rewinding and a high risk of tab folding;

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

[0006] 3. The large difference in the relative distance between the positive and negative electrodes during charging and discharging can easily lead to local polarization, resulting in the risk of lithium plating, reducing cycle life and safety performance, etc.

[0007] Currently, the industry's design of multi-layer coated electrodes is not perfect, and most of them rely purely on accumulated experience, resulting in huge trial and error costs. Utility Model Content

[0008] In view of this, the present invention provides a pole piece and a battery. The pole piece design can effectively improve the edge bulging problem of multi-layer coated electrodes.

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

[0010] In a first aspect, the present invention provides a pole piece, which includes a current collector 100 and an active material layer 200 provided on at least one surface in a thickness direction of the current collector;

[0011] The active material layer includes n stacked sub-active material layers, where n is a natural number greater than or equal to 2. The layers are sequentially designated as the first sub-active material layer 210, the second sub-active material layer 220, and so on, along a direction gradually approaching the thickness of the current collector. The widths of the n sub-active material layers are equal, and the projections of the n sub-active material layers in the thickness direction of the current collector overlap.

[0012] Along the width direction of the current collector, each sub-active material layer includes a main region and thinned regions disposed on both sides of the main region; the main region includes a first surface away from the thickness direction of the current collector, and the thinned regions include a second surface away from the thickness direction of the current collector; the current collector includes a third surface 100c adjacent to the active material layer;

[0013] The vertical distance from the first surface 211a of the main body region 211 of the first sub-active material layer to the third surface 100c of the current collector is recorded 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 third surface 100c of the current collector is recorded as H2, ... The vertical distance from the first surface of the main body region of the nth sub-active material layer to the third surface 100c of the current collector is recorded as H n ;

[0014] The angle between the second surface 212b of the first sub-active material layer thinned area 212 and the third surface 100c of the current collector is recorded as θ1, the angle between the second surface 222b of the second sub-active material layer thinned area 222 and the third surface 100c of the current collector is recorded as θ2, ... The angle between the second surface of the nth sub-active material layer thinned area and the third surface 100c of the current collector is recorded as θ n ;

[0015] H1 / H2 is 1.1~3.0, H2 / H3 is 1.1~3.0, ...H n-1 / H n 1.1~3.0;

[0016] θ1 is 0.3° to 3°;

[0017] θ1 / θ2 is 1.1~3.0, θ2 / θ3 is 1.1~3.0,...θ n-1 / θ n 1.1~3.0;

[0018] And H1 / H2<θ1 / θ2.

[0019] Preferably, n is any natural number from 2 to 5.

[0020] Preferably, H1 / H2 is 2.06 to 2.10;

[0021] Preferably, H2 / H3 is 2.06 to 2.10;

[0022] …

[0023] As a preference, H n-1 / H n It is 2.06~2.10.

[0024] Preferably, θ1 / θ2 is 2.12 to 2.16;

[0025] Preferably, θ2 / θ3 is 2.12 to 2.16;

[0026] …

[0027] As a preference, θ n-1 / θ n It is 2.12 to 2.16.

[0028] In an embodiment of the present invention, the electrode is a positive electrode or a negative electrode.

[0029] In some embodiments, the electrode sheet is a positive electrode sheet, and H1 of the positive electrode sheet is 20 to 300 μm.

[0030] In other embodiments, the electrode sheet is a negative electrode sheet, and H1 of the negative electrode sheet is 10 to 200 μm.

[0031] Preferably, θ1 is 0.6° to 1.0°.

[0032] 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.

[0033] In some embodiments, the electrode is a positive electrode, and the compaction density of the positive electrode is 2.0 to 4.0 g / cm 3 .

[0034] In other embodiments, the electrode is a negative electrode, and the compaction density of the negative electrode is 0.5 to 2.0 g / cm 3 .

[0035] In a second aspect, the present invention further provides a battery comprising the above-mentioned electrode.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This application adopts a stepped structure at the edge of the thinned area, which can effectively improve the bulging problem of the edge of the multi-layer coated electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1A Schematic diagram of the cross section of the thinning area where the protrusions of the two layers are not staggered;

[0039] Figure 1B It is a schematic diagram of the cross section of the thinning area with staggered protrusions of the two layers;

[0040] Figure 2A Schematic diagram of the double-layer coated electrode structure of Example 1-1;

[0041] Figure 2BSchematic diagram of the double-layer coated electrode structure of Example 1-1;

[0042] Figure 3A Schematic diagram of the three-layer coated electrode structure of Example 2-1;

[0043] Figure 3B Schematic diagram of the three-layer coated electrode structure of Example 2-1.

[0044] The reference numerals are as follows:

[0045] 100: current collector;

[0046] 100c: third surface of the current collector;

[0047] 200: active material layer;

[0048] 210: 1st sub-active material layer;

[0049] 211: main area of ​​the first sub-active material layer;

[0050] 211a: first surface of the main body region of the first sub-active material layer;

[0051] 212: thinning area of ​​the first sub-active material layer;

[0052] 212b: the second surface of the thinned region of the first sub-active material layer;

[0053] 220: second sub-active material layer;

[0054] 221: main area of ​​the second sub-active material layer;

[0055] 221a: first surface of the main body region of the second sub-active material layer;

[0056] 222: thinning area of ​​the second sub-active material layer;

[0057] 222b: the second surface of the thinned region of the second sub-active material layer;

[0058] 230: third sub-active material layer;

[0059] 231: main area of ​​the third sub-active material layer;

[0060] 231a: first surface of the main body region of the third sub-active material layer;

[0061] 232: thinning area of ​​the third sub-active material layer;

[0062] 232b: the second surface of the thinned region of the third sub-active material layer. DETAILED DESCRIPTION

[0063] The present invention discloses a pole piece and a battery. Those skilled in the art can refer to the contents of this article and appropriately improve the process parameters to achieve the desired effect. It should be noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments. It is obvious that relevant personnel can modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0064] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0065] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0066] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0067] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0068] The design principle of this utility model is as follows:

[0069] For multi-layer coated electrodes, the surface of the thinned area of ​​each layer away from the current collector is the outer surface of the thinned area of ​​each layer, θ is the angle between the outer surface of the thinned area of ​​each layer of sub-active material layer and the plane of the current collector; the surface of the main area away from the current collector is the outer surface of the main area, H is the vertical distance from the outer surface of the main 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 thinned area on the current collector. When the angle θ is less than or equal to 3°, H = d*tanθ≈d*θ. When H1 / H2 = θ1 / θ2, the intersection of the outer surface of the main area (first surface) and the outer surface of the thinned area (second surface) in the first sub-active material layer (i.e., the protruding position of the first coating layer) and the intersection of the outer surface of the main area (first surface) and the outer surface of the thinned area (second surface) in the second sub-active material layer (i.e., the protruding position of the second coating layer) on the current collector coincide, that is, d1 = d2. If the protrusions of the two layers are not staggered, the bulging phenomenon will be aggravated ( Figure 1AWhen H1 / H2<θ1 / θ2, the projections of the first coating layer and the second coating layer on the current collector do not overlap, d1<d2, and the protrusions of the two layers are staggered, which can reduce the occurrence of bulging ( Figure 1B The staggered design of the protrusions can not only gradually stagger the corners of the coating thinning area from the outside to the inside, but also make the transition of each coating thinning area smoother, improving the bulging of the thinning area. Therefore, the application adopts a stepped structure of the thinning area edge, which can effectively improve the bulging problem of the edge of the multi-layer coated electrode.

[0070] Specifically, the present invention adopts the following technical solutions:

[0071] In a first aspect, the present invention provides a pole piece, which includes a current collector 100 and an active material layer 200 provided on at least one surface in a thickness direction of the current collector;

[0072] The active material layer includes n stacked sub-active material layers, where n is a natural number greater than or equal to 2. The layers are sequentially designated as the first sub-active material layer 210, the second sub-active material layer 220, and so on, along a direction gradually approaching the thickness of the current collector. The widths of the n sub-active material layers are equal, and the projections of the n sub-active material layers in the thickness direction of the current collector overlap.

[0073] Along the width direction of the current collector, each sub-active material layer includes a main region and thinned regions disposed on both sides of the main region; the main region includes a first surface away from the thickness direction of the current collector, and the thinned regions include a second surface away from the thickness direction of the current collector; the current collector includes a third surface 100c adjacent to the active material layer;

[0074] The vertical distance from the first surface 211a of the main body region 211 of the first sub-active material layer to the third surface 100c of the current collector is recorded 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 third surface 100c of the current collector is recorded as H2, ... The vertical distance from the first surface of the main body region of the nth sub-active material layer to the third surface 100c of the current collector is recorded as H n ;

[0075] The angle between the second surface 212b of the first sub-active material layer thinned area 212 and the third surface 100c of the current collector is recorded as θ1, the angle between the second surface 222b of the second sub-active material layer thinned area 222 and the third surface 100c of the current collector is recorded as θ2, ... The angle between the second surface of the nth sub-active material layer thinned area and the third surface 100c of the current collector is recorded as θ n ;

[0076] H1 / H2 is 1.1~3.0, H2 / H3 is 1.1~3.0, ...Hn-1 / H n 1.1~3.0;

[0077] θ1 is 0.3° to 3°;

[0078] θ1 / θ2 is 1.1~3.0, θ2 / θ3 is 1.1~3.0,...θ n-1 / θ n 1.1~3.0;

[0079] And H1 / H2<θ1 / θ2.

[0080] In this utility model, it is necessary to meet the requirements of H1 / H2 being 1.1 to 3.0, H2 / H3 being 1.1 to 3.0, ...H n-1 / H n is 1.1 to 3.0. For example, H1 / H2, H2 / H3, ... or H n-1 / H n Any value among 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, 3.0 or any value within the range of any two of the above values. H1 / H2, H2 / H3, ... or H n-1 / H n If the height ratio is too small, it will easily cause uneven edge coating, and there will be risks of lithium plating and thermal runaway; if the height ratio is too large, it will reduce the benefits of multi-layer coating.

[0081] In the present invention, θ1 is 0.3° to 3°. Exemplarily, θ1 is 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 a range consisting of any two of the above values. If the value of θ1 is too small, the size of the thinned area will be increased, resulting in an N / P ratio of less than 1, which will pose a risk of lithium plating and thermal runaway, and easily cause uneven edge coating. If the value of θ1 is too large, the slurry will be affected by molecular forces, forming dewdrop-shaped protrusions and causing serious bulging edges. On the one hand, it will increase the difficulty of the process, and on the other hand, it will increase the gap between the electrodes, increase the internal resistance, reduce the margin of the battery cell group, and thus reduce the battery cell capacity density.

[0082] In the present invention, it is necessary to satisfy the following conditions: θ1 / θ2 is 1.1 to 3.0, θ2 / θ3 is 1.1 to 3.0, ...θ n-1 / θn is 1.1 to 3.0. For example, θ1 / θ2, θ2 / θ3, ... or θ n-1 / θ n Any value among 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, 3.0, or any value within the range consisting of any two of the above values. θ1 / θ2, θ2 / θ3, ... θ n-1 / θ n If the angle ratio is too small, it will easily cause uneven edge coating, and there will be risks of lithium plating and thermal runaway; if the angle ratio is too large, it will reduce the actual benefits of multi-layer coating.

[0083] In the present invention, H1 / H2 < θ1 / θ2 must be satisfied. The θ1 / θ2 angle ratio must be higher than the H1 / H2 height ratio. This is to ensure that the outer coating protrusion is within the inner thinning area, minimizing the protrusion and its impact on the manufacturing process and electrical performance.

[0084] In the present invention, when θ1 is fixed within the range of 0.3° to 3°, θ2, θ3, ..., θ n According to θ1 / θ2, θ2 / θ3,...θ n-1 / θ n The values ​​are taken within a given range. For example, if θ1 is 0.8°, θ1 / θ2 is 2.14, and θ2 is 0.37°; if θ2 / θ3 is 2.14, θ3 is 0.17°; and so on.

[0085] In this utility model, when H1 is fixed, H2, H3, ... H n According to H1 / H2, H2 / H3, ...H n-1 / H n For example, for lithium iron phosphate cathode material, H1 is 150 μm, H1 / H2 is 2.08, and H2 is 72.1 μm; H2 / H3 is 2.08, and H3 is 34.7 μm; and so on.

[0086] Preferably, n is any natural number from 2 to 5. Exemplarily, n is 2, 3, 4 or 5.

[0087] Preferably, H1 / H2 is 2.06 to 2.10;

[0088] Preferably, H2 / H3 is 2.06 to 2.10;

[0089] …

[0090] As a preference, H n-1 / H n It is 2.06~2.10.

[0091] For example, H1 / H2, H2 / H3, ... or H n-1 / H n It is any value among 2.06, 2.07, 2.08, 2.09, 2.10 or any value within the range formed by any two of the above values.

[0092] Preferably, θ1 / θ2 is 2.12 to 2.16;

[0093] Preferably, θ2 / θ3 is 2.12 to 2.16;

[0094] …

[0095] As a preference, θ n-1 / θ n It is 2.12 to 2.16.

[0096] For example, θ1 / θ2, θ2 / θ3, ... or θ n-1 / θ n It is any value among 2.12, 2.13, 2.14, 2.15, 2.16 or any value within the range formed by any two of the above values.

[0097] In an embodiment of the present invention, the electrode is a positive electrode or a negative electrode.

[0098] Preferably, the positive electrode active material of the positive electrode sheet includes one of ternary materials, lithium iron phosphate, and lithium iron manganese.

[0099] Preferably, the negative electrode active material of the negative electrode sheet includes one of graphite, hard carbon, silicon oxide, and silicon carbon.

[0100] In some embodiments, the electrode sheet is a positive electrode sheet, and H1 of the positive electrode sheet 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, and 300 μm, or any value within a range consisting of any two of the above values.

[0101] In the embodiment of the present invention, the range of H1 varies slightly for different positive electrode active materials. For example, H1 in a positive electrode sheet comprising lithium iron phosphate is 20-250 μm, and H1 in a positive electrode sheet comprising NCM or NCA ternary materials is 20-200 μm.

[0102] In other embodiments, the electrode sheet is a negative electrode sheet, and H1 of the negative electrode sheet is 10 to 200 μm. Exemplarily, H1 of the negative electrode 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, and 200 μm, or any value within a range consisting of any two of the above values.

[0103] In the embodiment of the present invention, the range of H1 is slightly different for different negative electrode active materials. For example, H1 in a negative electrode sheet comprising graphite is 10-150 μm, and H1 in a negative electrode sheet comprising hard carbon is 20-140 μm.

[0104] In order to meet the negative-wrapped-positive electrode design, preferably, θ1 is 0.6° to 1.0°.

[0105] 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.

[0106] In some embodiments, the electrode is a positive electrode, and the compaction density of the positive electrode is 2.0 to 4.0 g / cm 3 For example, the compaction density of the positive electrode is 2.0 g / cm 3 , 2.2g / cm 3 , 2.4g / cm 3 , 2.6g / cm 3 , 2.8g / cm 3 , 3.0g / cm 3 、3.2g / cm 3 、3.4g / cm 3 、3.6g / cm 3 、3.8g / cm 3 , 4.0g / cm 3 Any value in or any value within the range consisting of any two of the above values.

[0107] In the embodiment of the present invention, the compaction density range of the positive electrode sheet is slightly different for different positive electrode active materials. For example, the compaction density of the positive electrode sheet including NCM ternary material is 3.2-3.7 g / cm 3 The compaction density of the positive electrode sheet including lithium iron phosphate material is 2.3 to 2.6 g / cm 3 The compaction density of the positive electrode sheet including manganese iron lithium is 2.1~2.4g / cm 3 .

[0108] In other embodiments, the electrode is a negative electrode, and the compaction density of the negative electrode is 0.5 to 2.0 g / cm 3 For example, the compaction density of the negative electrode is 0.5 g / cm3 , 0.6g / cm 3 , 0.8g / cm 3 , 1.0g / cm 3 , 1.2g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.8g / cm 3 , 2.0g / cm 3 Any value in or any value within the range consisting of any two of the above values.

[0109] In the embodiment of the present invention, the compaction density range of the negative electrode sheet is slightly different for different negative electrode active materials. For example, the compaction density of the negative electrode sheet including graphite material is 1.5 to 1.7 g / cm 3 The compaction density of the negative electrode sheet including hard carbon is 0.75 to 1.05 g / cm 3 The compaction density of the negative electrode sheet including silicon oxide is 1.2 to 1.6 g / cm 3 The compaction density of the negative electrode sheet including silicon carbon is 1.2 to 1.6 g / cm 3 .

[0110] In a second aspect, the present invention further provides a battery comprising the above-mentioned electrode.

[0111] In an embodiment 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-mentioned electrode sheet structure.

[0112] In the embodiment of the present invention, the battery structure includes but is not limited to button batteries, soft-pack batteries, cylindrical batteries, etc.

[0113] The present application has no particular restrictions on the separator and electrolyte in the battery, and those skilled in the art can select them according to actual needs, as long as the purpose of the present application can be achieved.

[0114] The instruments and materials used in this invention can be obtained through commercial channels.

[0115] The present invention will be further described below in conjunction with the embodiments:

[0116] Example 1-1 Double-layer coating

[0117] 1. Negative or positive electrode

[0118] Structural reference for negative or positive electrode sheets Figure 2A and Figure 2B As shown, it includes a current collector 100 and an active material layer 200 ( Figure 2A and Figure 2B Only the active material layer on one surface is shown); the cross section of the active material layer 200 is a trapezoid;

[0119] The active material layer 200 includes two stacked sub-active material layers, which are sequentially designated as a first sub-active material layer 210 and a second sub-active material layer 220 as they gradually approach the thickness of the current collector. The widths of the two sub-active material layers are equal, and their projections in the thickness direction of the current collector overlap.

[0120] Along the width direction of the current collector, each sub-active material layer includes a main region and thinned regions arranged on both sides of the main region; the main region includes a first surface away from the thickness direction of the current collector, and the thinned region includes a second surface away from the thickness direction of the current collector; the current collector includes a third surface close to the active material layer;

[0121] The vertical distance from the first surface 211a of the main region 211 of the first sub-active material layer to the third surface 100c of the current collector is denoted as H1, and the vertical distance from the first surface 221a of the main region 221 of the second sub-active material layer to the third surface 100c of the current collector is denoted as H2;

[0122] The angle between the second surface 212b of the first sub-active material layer thinned area 212 and the third surface 100c of the current collector is denoted as θ1, and the angle between the second surface 222b of the second sub-active material layer thinned area 222 and the third surface 100c of the current collector is denoted as θ2;

[0123] The values ​​of H1, H2, H1 / H2, θ1, θ2, and θ1 / θ2 are shown in Table 1. And H1 / H2<θ1 / θ2.

[0124] 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 negative electrode active material graphite, 1.1% of binder styrene butadiene rubber (SBR), 0.5% of conductive agent conductive carbon black (SP), and 1.5% of binder carboxymethyl cellulose (CMC). 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 compacted density of the negative electrode sheet is 1.5g / cm 3 ;

[0125] The active material in the positive electrode sheet is NCM622. The active material layers of each positive electrode sheet include the following components by weight: 96.5% of the positive electrode active material nickel-cobalt-manganese ternary material (NCM622), 1.5% of the binder polyvinylidene fluoride (PVDF), 1.5% of the conductive agent SP, and 0.5% of the conductive agent carbon nanotube (CNT). The compacted density of the positive electrode sheet is 3.4g / cm3 .

[0126] The preparation method of the negative electrode sheet or the positive electrode sheet uses existing technology. After the active material, conductive agent, binder and other materials are uniformly mixed with a solvent, the mixture is applied to the current collector. After drying and cold pressing, the electrode sheet is obtained.

[0127] 2. Isolation film

[0128] The isolation film can be made of polyethylene film, polypropylene film, polyvinylidene fluoride film, non-woven fabric, etc. For example, the isolation film is selected from polyethylene film.

[0129] 3. Electrolyte

[0130] The electrolyte comprises a lithium salt and a solvent. The types of the lithium salt and solvent are not specifically limited and can be selected based on actual needs. For example, the lithium salt can be LiPF6, LiTFSI, LiBF4, etc. For example, the electrolyte is LiPF6 dissolved in a solvent of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a ratio of 1:1:1, with a concentration of 1.2 mol / L.

[0131] 4. Battery

[0132] During the cell assembly process, the positive electrode sheet, separator, and negative electrode sheet are arranged in sequence. There are two assembly methods: winding and lamination. Electrolyte is injected into the dry cell, and after formation and aging, the battery is obtained.

[0133] Example 1-2 Double-layer coating

[0134] The only difference between this embodiment and embodiment 1-1 is that the values ​​of θ2 and θ1 / θ2 are different. The values ​​of each parameter are shown in Table 1.

[0135] Examples 1-3 Double-layer coating

[0136] The only difference between this embodiment and embodiment 1-1 is that the values ​​of θ2 and θ1 / θ2 are different. The values ​​of each parameter are shown in Table 1.

[0137] Examples 1-4 Double-layer coating

[0138] The only difference between this embodiment and embodiment 1-1 is that the values ​​of θ2, θ1 / θ2, H2, and H1 / H2 are different. The values ​​of each parameter are shown in Table 1.

[0139] Examples 1-5 Double-layer coating

[0140] The only difference between this embodiment and embodiment 1-1 is that the values ​​of θ2, θ1 / θ2, H2, and H1 / H2 are different. The values ​​of each parameter are shown in Table 1.

[0141] Example 2-1 Three-layer coating

[0142] Structural reference for positive or negative electrode sheets Figure 3A and Figure 3B As shown, it includes a current collector 100 and an active material layer 200 ( 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 a trapezoid;

[0143] The active material layer 200 includes three stacked sub-active material layers, which are sequentially designated as the first sub-active material layer 210, the second sub-active material layer 220, and the third sub-active material layer 230 as they gradually approach the thickness of the current collector. The three sub-active material layers have equal widths, and their projections in the thickness direction of the current collector overlap.

[0144] Along the width direction of the current collector, each sub-active material layer includes a main region and thinned regions arranged on both sides of the main region; the main region includes a first surface away from the thickness direction of the current collector, and the thinned region includes a second surface away from the thickness direction of the current collector; the current collector includes a third surface close to the active material layer;

[0145] The vertical distance from the first surface 211a of the main region 211 of the first sub-active material layer to the third surface 100c of the current collector is recorded as H1, the vertical distance from the first surface 221a of the main region 221 of the second sub-active material layer to the third surface 100c of the current collector is recorded as H2, and the vertical distance from the first surface 231a of the main region 231 of the third sub-active material layer to the third surface 100c of the current collector is recorded as H3;

[0146] The angle between the second surface 212b of the first sub-active material layer thinned area 212 and the third surface 100c of the current collector is recorded as θ1, the angle between the second surface 222b of the second sub-active material layer thinned area 222 and the third surface 100c of the current collector is recorded as θ2, and the angle between the second surface 232b of the third sub-active material layer thinned area 232 and the third surface 100c of the current collector is recorded as θ3;

[0147] The values ​​of H1, H2, H3, H1 / H2, H2 / H3, θ1, θ2, θ3, θ1 / θ2, and θ2 / θ3 are shown in Table 1. And H1 / H2<θ1 / θ2.

[0148] The active material in the negative electrode sheet is graphite. The first 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 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 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 compacted density of the negative electrode sheet is 1.5g / cm 3 ;

[0149] The active material in the positive electrode sheet is NCM622. The active material layers of each positive electrode sheet include the following components by weight: nickel-cobalt-manganese ternary material (NCM622) 96.5%, polyvinylidene fluoride (PVDF) 1.5%, SP 1.5%, carbon nanotubes (CNT) 0.5%; the compacted density of the positive electrode sheet is 3.4g / cm 3 .

[0150] The preparation method of the negative electrode sheet or the positive electrode sheet uses existing technology. After the active material, conductive agent, binder and other materials are uniformly mixed with a solvent, the mixture is applied to the current collector. After drying and cold pressing, the electrode sheet is obtained.

[0151] 2. Isolation film

[0152] The isolation film can be made of polyethylene film, polypropylene film, polyvinylidene fluoride film, non-woven fabric, etc. For example, the isolation film is selected from polyethylene film.

[0153] 3. Electrolyte

[0154] The electrolyte comprises a lithium salt and a solvent. The types of the lithium salt and solvent are not specifically limited and can be selected based on actual needs. For example, the lithium salt can be LiPF6, LiTFSI, LiBF4, etc. For example, the electrolyte is LiPF6 dissolved in a solvent of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a ratio of 1:1:1, with a concentration of 1.2 mol / L.

[0155] 4. Battery

[0156] During the cell assembly process, the positive electrode sheet, separator, and negative electrode sheet are arranged in sequence. There are two assembly methods: winding and lamination. Electrolyte is injected into the dry cell, and after formation and aging, the battery is obtained.

[0157] Example 2-2 Three-layer coating

[0158] The only difference between this embodiment and embodiment 2-1 is that the values ​​of θ3 and θ2 / θ3 are different. The values ​​of each parameter are shown in Table 1.

[0159] Example 2-3 Three-layer coating

[0160] The only difference between this embodiment and embodiment 2-1 is that the values ​​of θ3 and θ2 / θ3 are different. The values ​​of each parameter are shown in Table 1.

[0161] Comparative Example 1 Double-layer coating

[0162] The only difference between this comparative example and Example 1-1 is that the values ​​of θ2, θ1 / θ2, H2, and H1 / H2 are different, and H1 / H2 = θ1 / θ2. The values ​​of each parameter are shown in Table 1.

[0163] Battery performance test:

[0164] 1. Internal resistance: ACR (alternating current impedance), detection frequency is 1KHz, 50mA;

[0165] 2. 0.5C first effect: The first constant current and constant voltage full charge cutoff condition is 4.25V, and the charging capacity obtained at 0.05C is CAP1; then stand for 10 minutes, and discharge at 0.5C constant current to 2.8V, and the discharge capacity obtained is CAP2; first effect = CAP2 / CAP1;

[0166] 3. 2C capacity: At 25°C, the full charge cutoff condition of constant current and constant voltage is 4.25V, and the charging capacity obtained at 0.05C is C0; the discharge capacity obtained by discharging to 2.8V at a constant current of 2C0 is C1; 2C capacity = C1 / C0;

[0167] 4. Drum edge: After coating, the electrode is inspected by CCD and the electrode roll is observed by human eyes to see if there is any bulging problem at the edge.

[0168] Table 1

[0169]

[0170]

[0171] Table 2

[0172]

[0173] It can be seen from the experimental data in Table 2 that, compared with the pole piece of comparative example 1 having a conventional structure, the pole piece of the embodiment of the present utility model has an obvious advantage in terms of the bulging edge appearance.

[0174] Compared with Examples 1-4 and 1-5, the electrodes of Examples 1-1 to 1-3 of the present invention have obvious advantages in internal resistance / first effect / 2C rate capacity.

[0175] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A pole piece, characterized in that: The pole piece comprises a current collector (100), and an active material layer (200) arranged on at least one surface in a thickness direction of the current collector; The active material layer comprises n layers of stacked sub-active material layers, where n is a natural number greater than or equal to 2, and along a direction gradually approaching the thickness of the current collector, the layers are sequentially recorded as the first sub-active material layer (210), the second sub-active material layer (220), ... the nth sub-active material layer, the widths of the n sub-active material layers are equal, and the projections of the n sub-active material layers in the thickness direction of the current collector overlap; Along the width direction of the current collector, each sub-active material layer includes a main body region and thinned regions arranged 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 thinned region includes a second surface away from the thickness direction of the current collector; the current collector includes a third surface (100c) close to the active material layer; The vertical distance from the first surface (211a) of the main region (211) of the first sub-active material layer to the third surface (100c) of the current collector is recorded as H1, the vertical distance from the first surface (221a) of the main region (221) of the second sub-active material layer to the third surface (100c) of the current collector is recorded as H2, ... The vertical distance from the first surface of the main region of the nth sub-active material layer to the third surface (100c) of the current collector is recorded as H n ; The angle between the second surface (212b) of the first sub-active material layer thinning area (212) and the third surface (100c) of the current collector is recorded as θ1, the angle between the second surface (222b) of the second sub-active material layer thinning area (222) and the third surface (100c) of the current collector is recorded as θ2, ... The angle between the second surface of the nth sub-active material layer thinning area and the third surface (100c) of the current collector is recorded as θ n ; H1 / H2 is 1.1~3.0, H2 / H3 is 1.1~3.0, ...H n-1 / H n 1.1~3.0; The θ1 is 0.3° to 3°; θ1 / θ2 is 1.1 to 3.0, θ2 / θ3 is 1.1 to 3.0, …… θ n-1 / θ n is 1.1 to 3.0; And H1 / H2<θ1 / θ2.

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, characterized in that: The H1 / H2 is 2.06 to 2.10; H2 / H3 is 2.06-2.10; …… H n-1 / H n It is 2.06~2.

10.

4. The pole piece according to claim 1, characterized in that: The θ1 / θ2 is 2.12 to 2.16; θ2 / θ3 is 2.12 to 2.16; …… θ n-1 / θ n is 2.12 to 2.

16.

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

6. The pole piece according to claim 5, characterized in that: The electrode is a positive electrode, and H1 of the positive electrode is 20 to 300 μm; The electrode sheet is a negative electrode sheet, and H1 of the negative electrode sheet is 10 to 200 μm.

7. The pole piece according to claim 1, characterized in that: The θ1 is 0.6° to 1.0°.

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

9. The pole piece according to claim 5, characterized in that: The electrode is a positive electrode, and the compaction density of the positive electrode is 2.0 to 4.0 g / cm 3 ; The electrode is a negative electrode, and the compaction density of the negative electrode is 0.5 to 2.0 g / cm 3 .

10. A battery, characterized in that: The battery comprises the pole piece according to any one of claims 1 to 9.

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