Positive plate and battery

Abstract

The invention relates to the field of lithium ion batteries, and provides a positive plate and a battery. The positive plate comprises a positive current collector and a positive active material layer, wherein the positive active material layer comprises a positive active material; the Dv50 of the positive electrode active material is 2 [mu] m-20 [mu] m; the positive electrode active material comprises a ternary material; gummed paper is arranged at one end of the positive plate in the length direction and comprises a base material and a glue layer; the surface of the substrate is provided with a first area and a second area, and the adhesive layer is arranged in the second area; the first region covers the positive active material layer, and the second region covers the positive current collector; the thickness of the adhesive layer in the first area is d1, and the thickness of the adhesive layer in the second area is d2; and d1 and d2 satisfy 0 < = d1 < d2. According to the battery disclosed by the invention, the positive plate near the gummed paper is not easy to fall powder, the problem of lithium precipitation is not easy to occur, and the battery also has relatively good energy density.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a positive electrode and a battery. Background Technology

[0002] With the ever-expanding demand for electronic products such as mobile phones, electric vehicles, tablets, and wearable devices, lithium-ion batteries, as an energy conversion carrier, have a wide market application and great potential, and their safety performance has attracted much attention. In lithium-ion batteries, adhesive tape is often applied to the end of the positive electrode to prevent burrs from piercing the separator and causing a short circuit, thus improving safety performance; at the same time, it ensures that the negative electrode is higher than the positive electrode to prevent lithium plating. When adhesive tape is applied to the surface of the positive electrode, the adhesive layer of the tape, the electrolyte, and the positive electrode binder in the positive electrode are all organic materials. According to the principle of like compatibility, under conditions such as high temperature (30-60℃) and high voltage (4.43-4.53V), these three substances are prone to interaction and side reactions, leading to the failure of the positive electrode binder and the loss of adhesiveness of the adhesive layer on the tape. This results in powder shedding from the positive electrode near the tape. Powder shedding at the edges of the positive electrode can then lead to uneven local lithium intercalation and deintercalation, causing lithium plating near the tape.

[0003] The positive electrode active particles of ternary materials are relatively small, and the problem of powder shedding is easy to occur after the positive electrode binder fails. Moreover, the nickel content of ternary materials is relatively high, and the positive electrode active material is prone to absorbing water, which aggravates the side reactions of the interaction between the adhesive layer, electrolyte and positive electrode binder, making the powder shedding problem more serious. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a positive electrode sheet and a battery containing the positive electrode sheet. This invention involves applying adhesive tape to the end of the positive electrode sheet, dividing the tape into a first region covering the positive electrode active material layer and a second region covering the positive electrode current collector. The thickness of the adhesive layer in the first region is adjusted to be less than that in the second region. This reduces the contact between the adhesive tape and the positive electrode active material layer, reduces the interaction between the adhesive tape, the electrolyte, and the organic matter in the positive electrode binder, thereby reducing the problem of positive electrode binder failure and the problem of powder shedding from the positive electrode sheet.

[0005] Furthermore, by attaching adhesive tape at the end of the positive electrode sheet and adjusting the thickness of the adhesive layer in the first region of the adhesive tape to be less than that in the second region, the present invention can reduce the problem of lithium plating near the adhesive tape and improve the cycle capacity retention rate of the battery.

[0006] To achieve the above objectives, a first aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer comprising a positive active material; the Dv50 of the positive active material is 2μm-20μm; the positive active material comprises a ternary material Li.a Ni x Co y Mn z A k O2, wherein 0.9≤a≤1.1, 0.3≤x≤0.98, 0<y≤0.2, 0<z≤0.3, 0≤k≤0.05, and A includes at least one of Al, Mg, Ti, Y, B, P, Zr, W, and Nb;

[0007] The positive electrode sheet has an adhesive paper at one end along its length. The adhesive paper includes a substrate and an adhesive layer. The surface of the substrate has a first region and a second region, and the adhesive layer is disposed in the second region. The first region covers the positive electrode active material layer, and the second region covers the positive electrode current collector. In the adhesive paper, the thickness of the adhesive layer in the first region is d1, and the thickness of the adhesive layer in the second region is d2. d1 and d2 satisfy: 0 ≤ d1 < d2.

[0008] A second aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, and a separator as described in the first aspect of the present invention, wherein the positive electrode, the separator, and the negative electrode are stacked sequentially and wound from one end along the length direction to form a core; the core includes an arcuate region and a straight region extending between the arcuate regions, the arcuate region including a first arcuate region and a second arcuate region, the first arcuate region having a first outer end, the first outer end being located on the side of the first arcuate region opposite to the straight region in the width direction of the core, and the first arcuate region being closer to the beginning end of the adhesive tape in the width direction of the core than the second arcuate region;

[0009] Adhesive tape is disposed at the tail end of the positive electrode in the winding direction, and the adhesive tape has a beginning end and a tail end extending along the winding direction; the tail end of the negative electrode in the winding direction extends beyond the beginning end of the adhesive tape along the winding direction.

[0010] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0011] (1) The positive electrode sheet provided by the present invention has adhesive paper at one end in the length direction. The thickness of the adhesive layer in the first region of the adhesive paper is adjusted to be less than that in the second region, thereby reducing the contact between the adhesive layer of the adhesive paper and the positive electrode active material layer, reducing the interaction between the adhesive layer of the adhesive paper, the electrolyte, and the organic matter in the positive electrode binder, thus reducing the problem of positive electrode binder failure, reducing the problem of powder shedding at the end of the positive electrode sheet of the ternary material system, and reducing the problem of lithium plating near the adhesive paper. Furthermore, by controlling the particle size of the ternary material, the problem of powder shedding caused by positive electrode bonding failure can be reduced.

[0012] (2) The positive electrode sheet provided by the present invention is conducive to the positive electrode binder and adhesive paper still having a good bonding effect after multiple cycles, making the positive electrode sheet near the adhesive paper less prone to powder shedding and less prone to lithium plating problems, thereby improving the energy density of the battery.

[0013] (3) In the positive electrode sheet provided by the present invention, when the Dv50 of the positive electrode active material and the thickness of the first and second regions in the adhesive layer meet certain conditions, it is beneficial to improve the energy density of the battery.

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to those ranges or values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In this document, unless otherwise specified, data ranges include endpoints. Attached Figure Description

[0015] Figure 1 The diagram shown is a schematic diagram of an embodiment of adhesive tape.

[0016] Figure 2 The diagram shown is a schematic of a roll core containing adhesive tape in one embodiment.

[0017] Figure 3 The diagram shown is a top view of an embodiment in which adhesive tape is disposed on the positive electrode sheet.

[0018] Figure 4 The image shown is a frontal view of the first region of the adhesive paper on the positive electrode sheet in one embodiment.

[0019] Figure 5 The diagram shown is a front view of a positive electrode sheet containing adhesive paper when a thinning region is provided on the positive electrode sheet in one embodiment.

[0020] Explanation of icon symbols:

[0021] 1. Adhesive tape; 11. Substrate; 12. Adhesive layer; 13. First zone; 14. Second zone;

[0022] 21. Positive current collector; 22. Positive active material layer; 23. Positive electrode tab;

[0023] 31. Negative electrode current collector; 32. Negative electrode active material layer; 33. Negative electrode tab; 41. Non-thinning region; 42. Thinning region. Detailed Implementation

[0024] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0025] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0026] A first aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer comprising a positive active material; the Dv50 of the positive active material is 2μm-20μm; the positive active material comprises a ternary material Li. a Ni x Co y Mn z A k O2, wherein 0.9≤a≤1.1, 0.3≤x≤0.98, 0<y≤0.2, 0<z≤0.3, 0≤k≤0.05, and A includes at least one of Al, Mg, Ti, Y, B, P, Zr, W, and Nb;

[0027] The positive electrode sheet has an adhesive film at one end along its length. The adhesive film includes a substrate and an adhesive layer. The substrate surface has a first region and a second region, and the adhesive layer is disposed in the second region. The first region covers the positive electrode active material layer, and the second region covers the positive electrode current collector. In the adhesive film, the adhesive layer thickness in the first region is d1, and the adhesive layer thickness in the second region is d2. d1 and d2 satisfy: 0 ≤ d1 < d2. In this invention, the adhesive film with different adhesive layer thicknesses in the first and second regions is called zebra adhesive film.

[0028] In some implementations, such as Figure 3 As shown, the positive electrode sheet includes a positive current collector 21 and a positive active material layer 22 disposed on at least one surface of the positive current collector 21. The positive active material layer includes a positive active material and also includes a positive binder.

[0029] In some embodiments, the positive electrode binder includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber (SBR), polytetrafluoroethylene, and polyethylene oxide.

[0030] In some embodiments, the Dv50 of the positive electrode active material is 2μm-20μm, for example, it can be 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, and 20μm. The Dv50 of the positive electrode active material is tested using a laser particle size analyzer. An ultrasonic generator is activated to fully disperse the sample, and laser parameters are selected for measurement to obtain the corresponding Dv50 of the material.

[0031] In some embodiments, the positive electrode active material includes the ternary material Li. a Ni x Co y Mn z Ak O2, wherein 0.9≤a≤1.1, 0.3≤x≤0.98, 0<y≤0.2, 0<z≤0.3, 0≤k≤0.05, and A includes at least one of Al, Mg, Ti, Y, B, P, Zr, W, and Nb. The positive electrode active material Dv50 is 2μm-20μm. When the positive electrode active material Dv50 is within the above range, it can increase the compaction density of the electrode, thereby increasing the battery energy density.

[0032] In this invention, by dividing the adhesive tape attached to the end of the positive electrode sheet into a first region covering the positive electrode active material layer and a second region covering the empty foil region of the positive electrode current collector, and by adjusting the thickness of the first region to be smaller than the thickness of the second region, and by adjusting the particle size of the ternary material to be within the aforementioned range, the interaction between the adhesive layer of the adhesive tape, the electrolyte, and the organic matter in the positive electrode binder is reduced. This reduces the problem of positive electrode binder failure, reduces the problem of powder shedding caused by positive electrode binder failure, reduces the problem of lithium plating near the adhesive tape, and improves the cycle performance of the battery.

[0033] In some implementations, such as Figure 1 and Figure 3 As shown, the positive electrode sheet has an adhesive tape at one end along its length. The adhesive tape includes a substrate 11 and an adhesive layer 12 disposed on at least one surface of the substrate 11. The surface of the substrate 11 facing the positive electrode current collector 21 has a first region 13 and a second region 14. The first region 13 covers the positive electrode active material layer, and the second region 14 covers the positive electrode current collector 21 (i.e., the empty foil area of ​​the positive electrode current collector that is not coated with positive electrode paste).

[0034] In some embodiments, the substrate includes one or more of polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, and polyimide. The adhesive layer includes one or more of natural rubber, synthetic rubber, polyacrylate, polypropylene, polyisobutylene, and styrene-isoprene copolymer. The substrate in the adhesive paper serves to support the adhesive layer, and the adhesive layer serves to bond the electrode sheet.

[0035] In some embodiments, the adhesive layer thickness in the first region of the adhesive tape is d1, and the adhesive layer thickness in the second region is d2; d1 and d2 satisfy: 0 ≤ d1 < d2. The adhesive layer thickness d1 in the first region is less than the adhesive layer thickness d2 in the second region, thereby reducing the contact between the adhesive layer of the adhesive tape and the positive electrode active material, reducing the interaction between the adhesive layer of the adhesive tape, the electrolyte, and the organic matter in the positive electrode binder, thus reducing the problem of positive electrode binder failure, reducing powder shedding at the end of the positive electrode sheet, and reducing lithium plating near the adhesive tape.

[0036] In one embodiment, the adhesive layer thickness of the first region is d1, and the adhesive layer thickness of the second region is d2; d1 and d2 satisfy: 0 < d1 < d2, the thickness of the first region is not 0, the adhesive paper covers part of the positive electrode active material layer (positive electrode paste area, that is, the area in the positive electrode active material layer coated with positive electrode active slurry), ensuring that the size of the negative electrode paste area (the area in the negative electrode active material layer coated with negative electrode active slurry) exceeds the size of the positive electrode paste area, reducing lithium intercalation at the tail of the negative electrode sheet, and thus reducing lithium plating in the tail area of ​​the negative electrode.

[0037] In one embodiment, the adhesive layer thickness in the first region is d1, and the adhesive layer thickness in the second region is d2; d1 and d2 satisfy: 0 = d1 < d2. The adhesive layer thickness in the first region is 0, meaning there is no adhesive layer on the positive electrode active material layer, and the positive electrode active material does not directly contact the adhesive layer. At this time, the adhesive layer, electrolyte, and positive electrode binder will not react at all. Therefore, after multiple battery cycles, the adhesion of the positive electrode binder will not be affected, effectively solving the problem of positive electrode powder shedding.

[0038] In some implementations, d1 and d2 satisfy the condition: 0 ≤ d1 < d2 ≤ 100 μm. For example, it can be 0 ≤ d1 < d2 ≤ 80 μm, 0 ≤ d1 < d2 ≤ 60 μm, 0 ≤ d1 < d2 ≤ 40 μm, 0 ≤ d1 < d2 ≤ 20 μm, 0 ≤ d1 < d2 ≤ 10 μm, 5 μm ≤ d1 < d2 ≤ 100 μm, 10 μm ≤ d1 < d2 ≤ 100 μm, 20 μm ≤ d1 < d2 ≤ 100 μm, and 30 μm ≤ d1 < d2 ≤ 100 μm, etc.

[0039] In some implementations, 0 < d1 ≤ 30 μm, for example, d1 can be 1 μm, 5 μm, 10 μm, 20 μm, or 30 μm. The larger d1 is, the greater the side reactions between the adhesive layer in the first region and the electrolyte and positive electrode binder, resulting in poorer adhesion between the positive electrode binder and the adhesive layer, and making the positive electrode sheet more prone to powder shedding. However, a larger thickness in the first region improves the adhesion of the adhesive paper, making it less prone to peeling and preventing the adhesive paper from failing to effectively cover the tail of the positive electrode sheet, thus avoiding lithium plating at the battery's tail. Conversely, the smaller d1 is, the smaller the side reactions between the adhesive layer in the first region and the electrolyte and positive electrode binder, making the positive electrode sheet less prone to powder shedding. However, in this case, due to the smaller thickness of the binder in the first region, the adhesion between the adhesive paper and the positive electrode active material layer is poor, making the adhesive paper prone to peeling and easily causing lithium plating at the negative electrode edge. When zebra tape is applied to the tail of the positive electrode, adjusting d1 to the range described above can help reduce powder shedding from the positive electrode, effectively prevent lithium plating caused by adhesive resurfacing, and improve the cycle performance of the battery.

[0040] In some implementations, 1μm ≤ d2 ≤ 70μm, for example, d2 can be 1μm, 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, and 70μm. When zebra tape is applied to the tail of the positive electrode, adjusting d2 to the above range ensures good adhesion between the tape and the empty foil area of ​​the positive electrode current collector, improves the adhesion of the tape, reduces tape rollover, and also helps reduce the thickness difference between the tape and the electrode surface, reduces the gap between the electrodes due to the tape thickness, shortens the ion migration channel, reduces lithium plating at the winding tail, and improves the battery's cycle performance.

[0041] In some embodiments, the peel force of the adhesive tape in the first zone is f1, and the peel force of the second zone is f2, wherein the relationship between f1 and f2 satisfies: 0 ≤ f1 < f2. The peel force is tested by fixing the adhesive tape to a stainless steel plate in one clamp of a tensile testing machine, with another clamp of the machine holding the free end of the adhesive tape at a 180° angle to the stainless steel plate. The adhesive tape is pulled apart at 300 mm / min, and the peel force is measured by the force required to continuously peel the adhesive tape from the stainless steel plate. The peel force of the first zone is f1, which tests the peel force between the first zone of the adhesive tape and the steel plate. The peel force of the second zone is f2, which tests the peel force between the second zone and the steel plate. The first zone is in contact with the positive electrode active material layer. The adhesive layer in the first zone reacts with the electrolyte and the positive electrode active material layer, causing the adhesion between the positive electrode binder in the positive electrode active material layer and the adhesive layer material in the first zone to fail, resulting in poor adhesion. The second zone is not in direct contact with the positive electrode active material layer, therefore the adhesion performance of the adhesive layer in the second zone is not worse, and the adhesion of the positive electrode adhesive layer in contact with it is also not worse. Therefore, the peel force of the first zone is less than that of the second zone. With zebra tape applied to the tail of the positive electrode sheet, adjusting the peel force of the first zone to be less than that of the second zone can reduce the contact between the first zone and the positive electrode active material layer, thereby reducing the contact between the adhesive layer of the tape and the positive electrode active material. This reduces the interaction between the adhesive layer of the tape, the electrolyte, and the organic matter in the positive electrode binder, reduces pore blockage at the tape edge, reduces powder shedding at the tail of the positive electrode sheet, and reduces lithium plating on the corresponding negative electrode at the tape edge.

[0042] In some implementations, 0 ≤ f1 < f2 ≤ 0.2 kgf / mm, for example, it can be 0 ≤ f1 < f2 ≤ 0.15 kgf / mm, 0 ≤ f1 < f2 ≤ 0.1 kgf / mm, 0 ≤ f1 < f2 ≤ 0.05 kgf / mm, 0 ≤ f1 < f2 ≤ 0.02 kgf / mm, 0.05 ≤ f1 < f2 ≤ 0.2 kgf / mm, 0.1 ≤ f1 < f2 ≤ 0.02 kgf / mm, and 0.15 ≤ f1 < f2 ≤ 0.02 kgf / mm.

[0043] In some embodiments, 0 ≤ f1 ≤ 0.1 kgf / mm, for example, f1 can be 0 kgf / mm, 0.02 kgf / mm, 0.04 kgf / mm, 0.06 kgf / mm, 0.08 kgf / mm, and 0.1 kgf / mm. When f1 is 0 kgf / mm, the adhesive layer thickness in the first region of the adhesive tape is 0 μm.

[0044] In some implementations, 0.01 kgf / mm ≤ f2 < 0.2 kgf / mm, for example, f2 can be 0.01 kgf / mm, 0.05 kgf / mm, 0.1 kgf / mm, 0.15 kgf / mm and 0.2 kgf / mm.

[0045] In some embodiments, the adhesive tape extends beyond both sides of the positive electrode sheet in the width direction, such as... Figure 3 As shown, the length of the adhesive tape 1 in the Y direction is greater than the length of the positive electrode sheet in the Y direction.

[0046] In some implementations, such as Figure 4 As shown, in the adhesive tape, the first region also covers a portion of the positive electrode current collector. The total width of the first region is w1 mm, and the width of the positive electrode active material layer covering the first region is w2 mm. w1 and w2 satisfy: w2≤w1≤w2+a mm, where a=3~10, such as a can be 3, 4, 5, 6, 7, 8, 9, and 10. That is, the total width w1 of the first region is equal to the sum of the width of the empty foil region covering the portion of the positive electrode current collector in the first region and the width w2 of the positive electrode active material layer covering the first region. In this invention, the width of the first region is... Figure 3 The length in the X direction. When w1 and w2 satisfy w2≤w1≤w2+a mm, it can avoid the first area of ​​the adhesive tape covering too much of the current collector empty foil area, thereby avoiding the problem of poor adhesive strength and easy tape flipping.

[0047] In some embodiments, the area of ​​the first region of the adhesive tape is S1, and the area of ​​the first region covering the positive electrode active material layer is S2. The ratio of S2 / S1 is 0.2 to 1, for example, the ratio can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1, preferably 0.5 to 1. The ratio of S2 / S1 is the proportion of the area of ​​the first region of the adhesive tape that covers the positive electrode active material layer. When zebra adhesive tape is provided at the tail of the positive electrode sheet, adjusting the ratio of S2 / S1 within the above range can reduce positive electrode powder shedding, avoid local uneven lithium insertion / extraction, and further reduce lithium plating on the negative electrode. When S1 remains unchanged, the larger the ratio of S2 / S1, the larger the area of ​​the adhesive tape in contact with the positive electrode active material layer, the more positive electrode active material is covered, which can reduce the extraction of active lithium ions and improve lithium plating on the negative electrode. The smaller the S2 / S1 ratio, the smaller the contact area between the adhesive tape and the positive electrode active material layer, resulting in fewer side reactions between the adhesive tape, the positive electrode active material layer, and the electrolyte, thus reducing powder shedding. However, if the S2 / S1 ratio is too small (e.g., less than 0.2), the adhesive tape is prone to peeling and cannot guarantee that the negative electrode exceeds the positive electrode, easily causing lithium plating at the edge of the negative electrode. Therefore, when the S2 / S1 ratio is within the above range, it can ensure that the negative electrode exceeds the positive electrode and reduce lithium plating.

[0048] In some embodiments, the width of the adhesive tape is 5–50 mm, for example, it can be 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, and 50 mm. In this invention, the width of the adhesive tape is the sum of the total width of the first region and the width of the second region, such as… Figure 3 As shown, W2 is the width of the positive electrode active material layer 22 in the first region, W1 is the width of the positive electrode active material layer 22 and the width of the empty foil area covering the positive electrode current collector 21 in the first region, W3 is the width of the empty foil area covering the positive electrode current collector in the second region, and the width of the adhesive tape is the sum of W1 and W3.

[0049] In some embodiments, the width of the first region in the adhesive tape is 2–20 mm, for example, it can be 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 12 mm, 15 mm, 18 mm, or 20 mm, preferably 2–6 mm. When zebra adhesive tape is provided at the tail of the positive electrode, adjusting the width of the adhesive tape to the above range helps prevent burrs from piercing the separator, improving battery safety performance, and also ensures that the negative electrode exceeds the positive electrode, reducing lithium plating. A larger width of the first region will affect the energy density of the battery, while a smaller width of the first region is not conducive to preventing burrs from piercing the separator.

[0050] In some embodiments, the width of the positive electrode sheet is L1 mm, and the length of the adhesive tape is L2 mm; L1 and L2 satisfy: L1≤L2≤L1+b mm; b=10~20. With zebra-striped adhesive tape at the tail of the positive electrode sheet, adjusting the length L2 of the adhesive tape to be greater than or equal to the width L1 mm of the positive electrode sheet helps to better cover the positive electrode sheet, preventing burrs from piercing the separator and causing a short circuit. This improves safety performance and avoids the impact of process fluctuations, ensuring that in each batch of positive electrode sheets, the adhesive tape completely covers the edge of the positive electrode sheet slices, preventing burrs from piercing the separator, thereby avoiding short circuits between the positive and negative electrodes and improving battery safety performance.

[0051] In one embodiment, the width of the positive electrode is L1 mm, and the length of the adhesive tape is L2 mm; L1 and L2 satisfy: L1 = L2.

[0052] In some embodiments, the width of the positive electrode sheet is L1 mm, and the length of the adhesive tape is L2 mm; L1 and L2 satisfy: L1 < L2 ≤ L1 + b mm; b = 10~20. Figure 3 As shown, with zebra tape placed at the tail of the positive electrode, adjusting the tape can better cover the positive electrode, prevent burrs from piercing the separator, avoid short circuits between the positive and negative electrodes, improve the safety performance of the battery, and the tape also has good adhesion to the positive electrode active material layer, forming a better film protection for the positive electrode and making it less prone to powder shedding.

[0053] In some embodiments, the ternary material comprises polycrystalline particles and / or monocrystalline particles, wherein the polycrystalline particles are formed by the aggregation of monocrystalline particles. Preferably, the cathode ternary material uses monocrystalline particles mixed with polycrystalline particles, with polycrystalline particles being the predominant component. Monocrystalline particles have strong material orientation, low energy density, and poor ion conduction performance, but their lower particle specific surface area results in a smaller contact area with the electrolyte, reducing side reactions and improving cycle retention. Polycrystalline particles have weak material orientation, high specific capacity, and superior ion conduction and power performance, but their larger particle specific surface area leads to a larger contact area with the electrolyte, resulting in more side reactions and poorer capacity retention. Using monocrystalline particles mixed with polycrystalline particles can give the cathode good cycle and rate performance.

[0054] In some embodiments, the ternary polycrystalline particles have the following particle sizes: Dv10 = 1 μm to 5 μm, Dv50 = 2 μm to 10 μm, Dv90 = 5 μm to 15 μm, and Dv99 = 10 μm to 20 μm. When the particle size of the ternary polycrystalline particles meets the above conditions, stress concentration caused by lithium ion migration within the particles can be reduced, thereby reducing particle breakage and pulverization, and reducing the problem of cathode powder shedding.

[0055] In some embodiments, the positive electrode active material includes a ternary material and lithium cobalt oxide. Preferably, the mass ratio of the ternary material to lithium cobalt oxide is 1:(1-10), for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, and 1:10. When the mass ratio of the ternary material to lithium cobalt oxide is within the above range, it is more conducive to leveraging the advantages of the ternary material, improving the battery energy density, and also giving the battery better stability. Ternary materials have high energy density, while lithium cobalt oxide has high cycle stability and low cost. Using them together can improve the battery's energy density and cycle stability while also reducing production costs. However, anodes made from silicon materials are prone to expansion, have insufficient kinetics, and are susceptible to powder shedding and lithium plating problems. This invention reduces the contact between the adhesive layer of the adhesive paper and the positive electrode active material by adjusting the thickness of the first region of the adhesive paper to be less than the thickness of the second region. This reduces the interaction between the adhesive layer of the adhesive paper, the electrolyte, and the organic matter in the positive electrode binder, and can effectively avoid the problems of powder shedding and lithium plating at the edges of the adhesive paper caused by the combination of ternary materials and silicon materials.

[0056] In some embodiments, the mass ratio of the ternary material to lithium cobalt oxide is 1:(2-6).

[0057] A second aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, and a separator as described in the first aspect of the present invention, wherein the positive electrode, the separator, and the negative electrode are sequentially stacked and wound from one end along the length direction to form a core (e.g., ...). Figure 2 (The Y-axis direction shown is the winding direction); the core includes an arc region and a straight region extending within the arc region. The arc region includes a first arc region and a second arc region. The first arc region has a first outer end, which is located on the side of the first arc region facing away from the straight region in the width direction of the core. The first arc region is closer to the beginning of the adhesive tape than the second arc region in the width direction of the core. The adhesive tape is disposed at the tail end of the positive electrode in the winding direction. The adhesive tape has a beginning end and a tail end extending along the winding direction. The tail end of the negative electrode in the winding direction extends beyond the beginning end of the adhesive tape along the winding direction.

[0058] In this invention, adhesive tape is applied to the surface of the positive electrode sheet at the winding tail and to the adjacent positive electrode current collector. The adhesive tape at the winding tail prevents burrs from piercing the separator, avoids contact between the positive electrode sheet and the positive electrode, reduces the risk of short circuits, and improves safety performance. Simultaneously, the adhesive tape covers part of the positive electrode active material layer (i.e., the positive electrode active paste), ensuring that the size of the negative electrode active paste exceeds that of the positive electrode, reducing lithium intercalation at the winding tail of the negative electrode sheet, and thus reducing lithium plating in the negative electrode tail region.

[0059] In some embodiments, the distance L3 between the end of the negative electrode sheet and the beginning of the adhesive tape is ≥ 2mm. For example... Figure 2 L3 in the figure can also be considered as the distance of the tape covering the negative electrode active material layer. With zebra tape set at the tail of the positive electrode, adjusting the length of the negative electrode active material layer to be greater than the length of the positive electrode active material layer helps to suppress lithium deposition at the edge of the negative electrode.

[0060] In some implementations, such as Figure 2 As shown, the distance between the first end of the adhesive tape and the first outer end of the first arc region is L4, and the maximum distance along the width direction of the first arc region is R. L4 and R satisfy: L4 ≤ R + c mm; c = 15~25. With zebra adhesive tape at the tail of the positive electrode sheet, adjusting L4 and R to meet the above conditions ensures that the tail of the adhesive tape is located in the arc region of the wound battery. The arc region is where the core thickness is relatively thin. The tail of the adhesive tape being located in the arc region reduces the impact of the adhesive tape thickness on the battery thickness. Positive and negative active materials are located in the non-arc region of the core. When L4 and R meet the above range, the adhesive tape's presence in the non-arc region can prevent it from affecting the capacity of the positive and negative active materials, thus improving the battery's energy density.

[0061] In some implementations, such as Figure 5 As shown, the positive electrode sheet has a thinning region 42 at the tail end in the winding direction. The thickness of the positive active material layer in the thinning region 42 is d3, and the thickness of the positive active material layer in the non-thinning region 41 of the positive electrode sheet is d4; d3 and d4 satisfy: d4-d3≥10μm. With zebra tape at the tail end of the positive electrode sheet, the thickness of the positive active material layer covered by the thinning tape is adjusted, that is, the positive electrode paste area in the positive active material layer is thinned, so that the thickness of the positive active material layer in the thinning region 42 is less than the thickness of the positive active material layer in the non-thinning region 41. At this time, tape is placed on the active material layer, with the first region of the tape layer located in the thinning region 42 of the active material layer, and the second region located in the empty foil area on the current collector. This helps to reduce the thickness difference between the tape and the electrode surface, shorten the ion migration channel, and reduce lithium plating at the tail end of the winding. When d4-d3≥10μm, it is more conducive to making the thickness of the electrode surface uniform, so that lithium can be uniformly inserted and extracted, and reducing lithium deposition on the adhesive paper negative electrode.

[0062] In some implementations, when zebra tape is provided at the tail of the positive electrode, adjusting the first region of the adhesive layer to be entirely located in the thinning region can reduce the length of the first region of the tape, thereby avoiding the large length of the first region from affecting the overall bonding performance of the tape and reducing the problem of tape rollover.

[0063] In some implementations, 10μm≤d3≤200μm, for example, can be 10μm, 20μm, 40μm, 60μm, 80μm, 100μm, 120μm, 140μm, 160μm, 180μm and 200μm.

[0064] In some embodiments, 30μm≤d4≤250μm, for example, can be 30μm, 60μm, 80μm, 100μm, 120μm, 140μm, 160μm, 180μm, 200μm, 220μm and 250μm, preferably 50μm to 120μm.

[0065] In some embodiments, the length of the thinning region is 2mm-35mm, for example, it can be 2mm, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, and 35mm, preferably 2-10mm. With zebra tape attached to the tail of the positive electrode sheet, adjusting the length of the thinning region within the above range can prevent the thinning region from being too short, allowing it to better fulfill its function. This helps shorten the ion migration channel at the battery tail and reduces lithium plating at the winding tail. Conversely, it can prevent the thinning region from being too long, which would result in excessive loss of positive electrode active material and affect the battery's energy density.

[0066] In some embodiments, the area of ​​the thinning region covered by the adhesive tape accounts for 20%-100% of the total area of ​​the thinning region, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%, preferably 20%-70%. When the area of ​​the thinning region covered by the adhesive tape accounts for less than 20% of the total area of ​​the thinning region, the contact area between the adhesive tape and the positive electrode active material layer is smaller, resulting in fewer side reactions between the adhesive tape, the positive electrode active material layer, and the electrolyte, and reducing the shedding of powder from the positive electrode sheet. However, the adhesion between the adhesive tape and the positive electrode active material layer is also poor, and the adhesive tape is prone to peeling, making it difficult to ensure that the negative electrode exceeds the positive electrode, which can easily cause lithium plating at the edge of the negative electrode. When zebra adhesive tape is provided at the tail of the positive electrode sheet, and the area of ​​the thinning region covered by the adhesive tape is within the above-mentioned range, the thickness difference between the adhesive tape and the electrode sheet is smaller, which is beneficial for uniform lithium ion insertion and extraction and avoids lithium plating problems.

[0067] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, the negative electrode active material including a silicon material.

[0068] In some implementations, such as Figure 2 As shown, the negative electrode sheet in the wound battery includes a negative electrode current collector 31 and a negative electrode active material layer 32. The wound battery also includes a positive electrode tab 23 and a negative electrode tab 33.

[0069] In some embodiments, the mass percentage of silicon material in the negative electrode active material is 2%-50%, for example, 2%, 5%, 10%, 20%, 30%, 40%, and 50%, preferably 4%-50%. Ternary materials have a large specific capacity, and silicon negative electrodes also have the advantage of high specific capacity. Using them together is beneficial for improving the energy density of the battery. However, negative electrodes made of silicon material are prone to expansion and have insufficient kinetics, easily leading to powder shedding and lithium plating problems. This invention reduces the contact between the adhesive layer of the adhesive paper and the positive electrode active material by adjusting the thickness of the first region of the adhesive paper to be less than the thickness of the second region. This reduces the interaction between the adhesive layer of the adhesive paper, the electrolyte, and the organic matter in the positive electrode binder, effectively avoiding the problems of powder shedding and lithium plating at the edges of the adhesive paper caused by the combination of ternary materials and silicon materials.

[0070] In some embodiments, the silicon material includes at least one of silicon-carbon, silicon-oxygen, elemental silicon, and silicon alloys; preferably, it is silicon-carbon. Silicon-carbon is a mixture of nano-silicon and carbon materials, with silicon located within the carbon framework structure.

[0071] In some embodiments, the particle size of the silicon material satisfies the following conditions: 2μm≤Dv10≤7μm, 3μm≤Dv50≤15μm, and 10μm≤Dv90≤20μm. Larger silicon particle sizes are more prone to expansion and breakage, resulting in poorer kinetics and a greater likelihood of lithium plating on the negative electrode. By adjusting the silicon particle size within the aforementioned range, while ensuring the thickness of the first region of the adhesive film is less than the thickness of the second region, excessive silicon expansion can reduce pressure on the separator, thus reducing separator pore blockage. It can also reduce negative electrode material breakage, improve battery kinetic performance, and decrease lithium plating on the negative electrode.

[0072] In some embodiments, the negative electrode active material further includes a carbon-based material, which includes at least one of artificial graphite, natural graphite, hard carbon, and soft carbon.

[0073] The battery of the present invention includes a positive electrode, a separator, and a negative electrode.

[0074] In some embodiments, the separator includes a base film, a polymer layer, and an inorganic particle layer; the inorganic particle layer is disposed on at least one side of the surface of the base film; the polymer layer is disposed on at least one side of the surface of the base film, or on the surface of the inorganic particle layer away from the base film, with the inorganic particle layer facing the positive electrode. Based on the combination of zebra tape with ternary materials and silicon anode, adjusting the separator structure, including the polymer layer and the inorganic particle layer, can control the gas permeability of the separator within the range of 20s to 500s, thereby improving the cycle performance of the battery and reducing problems such as powder shedding from the tape edges, separator pore blockage, and lithium plating.

[0075] In some embodiments, the thickness of the base film is 3 μm to 10 μm; and / or, the thickness of the polymer layer is 0.2 μm to 3 μm; and / or, the thickness of the inorganic particle layer is 0.2 to 3 μm. The base film comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide; the inorganic particles comprise at least one of alumina, boehmite, barium sulfate, titanium dioxide, and magnesium hydroxide; the polymer layer comprises at least one of polyvinylidene fluoride, polyacrylate, styrene-butadiene rubber, polyacrylamide, or polyolefin.

[0076] In some embodiments, the diaphragm has micropores; the air permeability of the diaphragm is 20s to 500s, preferably 20s to 300s. The air permeability test method includes taking a diaphragm sample of 100mm × 100mm size, placing the diaphragm in the test head of an air permeability meter with a suitable test range for air permeability testing, and taking the average of three test results as the air permeability value of the diaphragm.

[0077] Based on the combination of zebra tape, ternary materials, and silicon anode, adjusting the permeability value within the above range keeps the membrane porosity within a suitable range. This avoids problems such as insufficient electrolyte wettability due to excessively high membrane permeability (e.g., greater than 500s), which affects lithium ion transport and causes membrane clogging, leading to decreased battery cycle performance and lithium plating. It also avoids problems such as excessively low membrane permeability (e.g., less than 20s), which affects the battery's K value and makes the battery prone to self-discharge.

[0078] In some embodiments, the thickness of the separator is 4 μm to 30 μm. An appropriate separator thickness helps maintain the integrity of the battery structure while maximizing battery energy density, preventing structural damage due to compression, and thus contributing to improved battery energy density and cycle life.

[0079] Based on the combination of adhesive tape, ternary materials, and silicon anode, adjusting the separator structure to meet the aforementioned conditions in terms of permeability and thickness ensures sufficient mechanical strength. When used in combination with adhesive tape, it better prevents punctures and short circuits caused by burrs, improving battery safety. Furthermore, the polymer layer enhances the adhesion between the separator and the electrode, reducing positive electrode powder shedding, separator pore blockage, and negative electrode lithium plating when used with adhesive tape. The inorganic particle layer improves the separator's thermal stability, preventing thermal deformation or shrinkage and wrinkling after internal battery heating, and reducing adhesive tape peeling issues. Simultaneously, when used in combination with adhesive tape, the separator exhibits good interfacial adhesion between the positive electrode and adhesive tape, forming an integrated cell that facilitates lithium-ion transport, improving battery structural stability and cycle life.

[0080] In some embodiments, the battery is a lithium-ion secondary battery.

[0081] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0082] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0083] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the invention.

[0084] The positive electrode sheets of the examples and comparative examples were prepared according to the following preparation method, and the specific differences are shown in Tables 1-3.

[0085] Example 1-1 illustrates the preparation of a wound battery cell when a thinning region is provided on the positive electrode sheet, with the first region partially located on the active material layer and partially located in the empty foil region. The preparation method of Example 1-1 is as follows:

[0086] (1) Preparation of the positive electrode:

[0087] The ternary material NCM811 (chemical formula LiNi) 0.8 Co 0.1 Mn 0.1 O2 (Dv50 = 4.3 μm), polyvinylidene fluoride (positive electrode binder), and conductive carbon black (conductive agent) were dry-mixed at a mass ratio of 96:2:2. Then, under vacuum stirring, an appropriate amount of N-methylpyrrolidone (NMP) was gradually added and mixed to form a uniform slurry. Subsequently, the positive electrode active slurry was uniformly coated onto both surfaces of an aluminum foil using a coating machine. The coated aluminum foil was dried, and then rolled, slit, and die-cut to obtain the desired positive electrode sheet. The width of the positive electrode sheet, L1 = 94 mm.

[0088] (2) Preparation of negative electrode:

[0089] The negative electrode active materials graphite and silicon carbon (silicon carbon mass percentage of 5%, Dv10 = 5μm, Dv50 = 10μm, Dv90 = 15μm), styrene-butadiene rubber (SBR), and conductive carbon black (SP) were mixed evenly at a mass ratio of 96:2:2. Then, an appropriate amount of deionized water was added step by step, and a negative electrode slurry was obtained under the action of a vacuum stirrer. The negative electrode active slurry was evenly coated on both surfaces of copper foil using a coating machine. The coated copper foil was dried at room temperature until surface dry, and then transferred to an 80℃ oven for drying for 10 hours. Finally, it was rolled, slit, and die-cut to obtain a multi-tab negative electrode sheet.

[0090] (3) Preparation of the diaphragm

[0091] The diaphragm's base membrane is made of polyethylene. An inorganic particulate layer (comprising borosilicate and PVDF in a 7:1 mass ratio) is formed on one side of the polyethylene base membrane; a polyvinylidene fluoride (polymer layer) is formed on the other side. The base membrane thickness is 5 μm; the polymer layer thickness is 2 μm; and the inorganic particulate layer thickness is 1 μm. The total diaphragm thickness is 8 μm, and the diaphragm's permeability is 250 s.

[0092] (4) Preparation of adhesive tape

[0093] In the electrode fabrication process, adhesive tape is applied to the electrode. The adhesive tape substrate is PET with a thickness of 6μm; the adhesive layer is rubber. The adhesive layer thickness in the first zone is d1 = 0μm, and the adhesive layer thickness in the second zone is d2 = 4μm. The adhesive tape width is 20mm, and the adhesive tape length L2 is 96mm.

[0094] (4) Battery assembly

[0095] The positive electrode sheet, negative electrode sheet, and separator sheet obtained in the above steps are wound to form a bare battery cell. After hot pressing, aluminum tabs and copper-plated nickel tabs are welded on. After punching indentations in the aluminum-plastic film, the cells are encapsulated and vacuum-baked at 95°C for 24 hours. The electrolyte used is a 1M lithium hexafluorophosphate electrolyte, with a solvent of PC, PP, EP, DEC, and EMC (volume ratio 5:3:1:1:1). After electrolyte injection, the battery undergoes formation, secondary sealing, sorting, and OCV testing to obtain a wound battery. The battery thickness is 3.8mm, the width is 62mm, and the height is 100mm. The arc width R of the wound battery is 3mm.

[0096] The positive electrode of the wound battery also has a thinning zone at the tail end. The length of the thinning zone is 8 mm. The first zone covers part of the thinned active material layer and also covers the empty foil area on the positive current collector. The area covered by the first zone accounts for 50% of the total thinning area. The total width of the first zone is 4 mm. The width of the active material layer covered by the first zone is 4 mm. The thickness d3 of the thinned active material layer covered by the first zone is 76 μm, and the thickness d4 of the active material layer not covered by the first zone is 86 μm. The thickness d1 of the first zone is 0 μm, and the peel force f1 is 0 kgf / mm. The second zone covers the empty foil area of ​​the positive current collector. The thickness d2 of the second zone is 4 μm, the width W3 of the second zone is 12 mm, and the peel force f2 is 0.05 kgf / mm. The distance L3 between the tail end of the negative electrode and the end of the adhesive tape away from the winding tail is 2 mm. The distance L4 between the end of the adhesive tape away from the winding tail and the edge of the arc area of ​​the core is 8 mm.

[0097] The batteries obtained in the examples and comparative examples were subjected to the following performance tests:

[0098] Cyclic test method: 1. Charge at 1.1C to 4.1V, then switch to 0.5C to fully charge (cut off at 0.05C), let stand for 24 hours, then discharge at 0.5C, cycle for 50T.

[0099] 1. Powder shedding test: After cycling, disassemble and observe the powder shedding at the edge of the positive electrode adhesive paper; after powder shedding, the current collector can be seen exposed in the active material area of ​​the positive electrode sheet.

[0100] 2. Condition of the diaphragm at the edge of the adhesive tape: After circulation, disassemble and observe whether there are black lines formed by by-products on the diaphragm corresponding to the adhesive tape.

[0101] 3. Lithium plating at the edge of the adhesive tape on the negative electrode: After cycling, disassemble the electrode and observe whether lithium plating has occurred on the negative electrode corresponding to the edge of the adhesive tape. Analyze the degree of lithium plating along the length of the electrode according to the range of lithium plating: severe lithium plating: lithium plating range ≥ 2mm; slight lithium plating: 0mm < lithium plating range < 2mm.

[0102] 4. Energy density test: Energy density = discharge capacity * platform voltage / battery width / battery height / battery thickness; the discharge capacity was obtained by charging to 4.25V at 0.2C constant current and then discharging to 3.0V at 0.7C. The platform voltage was 3.76V, the battery height was 100.5mm, the width was 62.5mm, and the thickness was measured by a 600PPG thickness gauge.

[0103] 5. Peel strength test method: The peel strength test method is to fix the adhesive tape to a stainless steel plate in one clamp of a tensile testing machine, and clamp the free end of the adhesive tape in another clamp of the testing machine at a 180° angle to the stainless steel plate. Pull the adhesive tape apart at 300 mm / min, and measure the peel strength by the force required to continuously peel the adhesive tape from the stainless steel plate.

[0104] 6. Cyclic capacity retention test:

[0105] Charge the battery at 1.1C to 4.1V, then reduce to 0.5C to fully charge (cut off at 0.05C), let it stand for 24 hours, and then discharge at 0.5C. Record the discharge capacity value C0 for the first cycle, the discharge capacity C for the fiftieth cycle, and the capacity retention rate C / C0*100% for the fiftieth cycle.

[0106] Referring to Examples 1-1, the specific differences between Examples 1-6 are shown in Table 1. In Example 1, the thickness of the adhesive layer in the first and second regions of the adhesive tape was changed. In Example 2, the peel strength of the first region was changed by altering the type of adhesive layer; in Example 2-1, the adhesive layer was polyacrylate, and in Example 2-2, it was polyisobutylene. In Example 3, the area ratio S2 / S1 covering the positive electrode active material layer in the first region was changed. In Example 4, the thickness d3 of the positive electrode active material layer in the thinning region was changed; d4 remained unchanged in Examples 4-1 and 4-3, while d4 was adjusted to 110 μm in Example 4-2. In Example 5, the length of the thinning region was changed. In Example 6, the area of ​​the first region of the adhesive tape covering the thinning region was changed as a percentage of the total area of ​​the thinning region.

[0107] Table 1

[0108]

[0109]

[0110] Note: "*" indicates that the corresponding parameters in this embodiment or comparative example are the same as those in Embodiment 1-1.

[0111] In Comparative Example 1, the adhesive tape is only applied to the first region and is only attached to the positive electrode active material layer. In Comparative Example 2, the thickness of the first region of the adhesive tape is not reduced.

[0112] The test results of Examples 1-6, and Comparative Examples 1 and 2 are shown in Table 2.

[0113] Table 2

[0114]

[0115]

[0116] As shown in Table 2, the present invention improves battery safety by applying adhesive tape to the end of the positive electrode sheet, making it less likely for metal dendrites to pierce the separator. The adhesive tape is divided into a first region and a second region. The first region covers the positive electrode active material layer, and the second region covers the empty foil area of ​​the positive electrode current collector. The thickness of the first region is less than that of the second region, ensuring good adhesion between the positive electrode adhesive and the adhesive tape after multiple cycles. This reduces the likelihood of powder shedding from the positive electrode sheet near the adhesive tape and prevents lithium plating. Batteries prepared with the adhesive tape of the present invention also exhibit better energy density. In contrast, in Comparative Document 1, because the adhesive tape is only applied to the positive electrode active material layer, adhesive peeling is prone to occur. In Comparative Examples 1 and 2, the adhesive layer thickness is not reduced, and the interaction between the adhesive layer, electrolyte, and positive electrode adhesive causes the positive electrode adhesive to fail, resulting in severe powder shedding from the positive electrode sheet near the adhesive tape and significant lithium plating.

[0117] Referring to Examples 1-1, the specific differences in Examples 7-9 are shown in Table 3. In Example 7, the mixing ratio of single-crystal and polycrystalline particles in the ternary material was changed. In Example 1-1, the mass ratio of single-crystal to polycrystalline particles was 1:1; in Example 7-1, the mass ratio was 1:5; in Example 7-2, only single-crystal particles were used; and in Example 7-3, only polycrystalline particles were used. In Example 8, the ternary material and lithium cobalt oxide were used in combination. In Example 9, the mass percentage of silicon material in the negative electrode active material was changed.

[0118] Table 3

[0119]

[0120] Note: In Table 3, " / " indicates that it does not contain lithium cobalt oxide.

[0121] As can be seen from Table 3, by adjusting the thickness of the adhesive layer in the first region of the adhesive paper to be less than that in the second region, the interaction between the adhesive layer of the adhesive paper, the electrolyte, and the organic matter in the positive electrode binder is reduced, thereby reducing the problem of positive electrode binder failure. This can reduce the problem of powder shedding at the end of the positive electrode sheet in the ternary material system and reduce the problem of lithium plating near the adhesive paper.

[0122] Referring to Examples 1-1, the specific differences in Example 10 are shown in Table 4. In Example 10, the air permeability of the diaphragm was altered by adjusting the diaphragm base membrane preparation process, coating areal density, or coating material type.

[0123] Table 4

[0124]

[0125] As can be seen from Table 4, in this invention, by combining a thinner adhesive film with ternary materials and a silicon anode, and adjusting the air permeability of the separator within the range of 20s to 500s, the cycle performance of the battery can be improved, and problems such as powder shedding at the edges of the adhesive film, separator pore blockage, and lithium plating can be reduced.

[0126] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0127] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications or equivalent substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A positive electrode sheet characterized by comprising: The positive electrode sheet includes a positive electrode current collector, and a positive electrode active material layer provided on at least one side surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material; the positive electrode active material has a Dv50 of 2 to 20 μm; and the positive electrode active material includes a ternary material Li a Ni x Co y Mn z A k O2, wherein 0.9≤a≤1.1, 0.3≤x≤0.98, 0 The positive electrode sheet is provided with adhesive paper at one end in the length direction, the adhesive paper comprising a substrate and an adhesive layer; the surface of the substrate has a first area and a second area, the adhesive layer being provided on the second area; the first area covers the positive electrode active material layer, and the second area covers the positive electrode current collector; in the adhesive paper, the thickness of the adhesive layer in the first area is d1, and the thickness of the adhesive layer in the second area is d2; d1 and d2 satisfy: 0≤d1 2. The positive electrode sheet according to claim 1, characterized by d1 and d2 satisfy: 0≤d1 Preferably, 0≤d1≤50μm; 1μm≤d2≤70μm.

3. The positive electrode sheet according to claim 1, characterized by In the adhesive paper, the peeling force of the first area is f1, and the peeling force of the second area is f2, the relationship between f1 and f2 satisfying: 0≤f1 Preferably, 0≤f1 Preferably, 0≤f1≤0.1kgf / mm; 0.01kgf / mm≤f2 4. The positive electrode sheet according to claim 1, characterized by The adhesive paper extends beyond both sides of the positive electrode sheet in the width direction; Preferably, in the adhesive paper, the first area also covers part of the positive electrode current collector, the total width of the first area being w1 mm, and the width of the first area covering the positive electrode active material layer being w2 mm; w1 and w2 satisfy: w2≤w1≤w2+a mm, a=3-10; Preferably, in the adhesive paper, the area of the first area is S1, and the area of the first area covering the positive electrode active material layer is S2; the ratio of S2 / S1 is 0.2-1; Preferably, the width of the adhesive paper is 5-50 mm, and the width of the first area in the adhesive paper is 2-20 mm.

5. The positive electrode sheet according to any one of claims 1 to 4, characterized by, The width of the positive electrode sheet is L1 mm, and the length of the adhesive paper is L2 mm; L1 and L2 satisfy: L1≤L2≤L1+b mm; b=10-20; Preferably, the substrate comprises one or more of polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, and polyimide; Preferably, the adhesive layer comprises one or more of natural rubber, synthetic rubber, polyacrylate, polypropylene, polyisobutylene, and styrene-isoprene copolymer.

6. The positive electrode sheet according to any one of claims 1 to 4, characterized by, The ternary material comprises polycrystalline particles and / or single-crystal particles; Preferably, the Dv10 of the polycrystalline particles of the ternary material is 1μm-5μm, the Dv50 is 2μm-10μm, the Dv90 is 5μm-15μm, and the Dv99 is 10μm-20μm; Preferably, the positive electrode active material comprises the ternary material and lithium cobaltate; Preferably, the mass ratio of the ternary material to lithium cobaltate is 1:(1-10), preferably 1:(2-6).

7. A battery, characterized by The positive electrode sheet, negative electrode sheet, and separator according to any one of claims 1-6 are sequentially stacked and wound in the length direction from one end to form a core; the core comprises a circular arc area and a flat area extending between the circular arc areas, the circular arc area comprises a first circular arc area and a second circular arc area, the first circular arc area has a first outer end, the first outer end is located on the side of the first circular arc area away from the flat area in the width direction of the core, and the first circular arc area is closer to the first end of the adhesive paper than the second circular arc area in the width direction of the core. The adhesive tape is arranged at the tail of the positive electrode sheet in the winding direction, the adhesive tape has a leading end and a trailing end extending along the winding direction; the tail end of the negative electrode sheet in the winding direction exceeds the leading end of the adhesive tape along the winding direction; Preferably, the distance L3 between the tail end of the negative electrode sheet and the leading end of the adhesive tape is greater than or equal to 2 mm; Preferably, the distance between the leading end of the adhesive tape and the first outer end in the first circular arc region is L4 mm, the maximum distance of the first circular arc region along the width direction of the core is R mm, and L4 and R satisfy: L4≤R+c mm; c=15-25.

8. The battery of claim 7, wherein, The positive electrode sheet is provided with a thinning region at the tail in the winding direction, and the thickness of the positive electrode active material layer in the thinning region is d3; Preferably, 10 μm≤d3≤200 μm; Preferably, the length of the thinning region is 2 mm-35 mm; Preferably, the first region in the adhesive tape covers at least part of the positive electrode active material layer in the thinning region; Preferably, the area of the first region in the adhesive tape covering the thinning region accounts for 20%-100% of the total area of the thinning region.

9. The battery of claim 7, wherein, The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side surface of the negative electrode current collector, the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises a silicon material; Preferably, the mass fraction of the silicon material in the negative electrode active material is 2-50%; Preferably, the silicon material comprises at least one of silicon carbon, silicon oxide, silicon element and silicon alloy; more preferably, the silicon material comprises silicon carbon; Preferably, the particle size of the silicon material satisfies: 2 μm≤Dv10≤7 μm, 3 μm≤Dv50≤15 μm, and 10 μm≤Dv90≤20 μm.

10. The battery of claim 7, wherein, The separator comprises a base film, a polymer layer and an inorganic particle layer; the inorganic particle layer is arranged on at least one side surface of the base film; the polymer layer is arranged on at least one side surface of the base film, or the polymer layer is arranged on the surface of the inorganic particle layer away from the base film, and the inorganic particle layer faces the positive electrode; Preferably, the separator has micropores; Preferably, the air permeability of the separator is 20 s-500 s.

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