Battery

Abstract

The invention relates to the technical field of batteries, in particular to a battery which comprises a positive plate, a negative plate, a diaphragm and electrolyte, and the positive plate, the diaphragm and the negative plate are stacked or wound to form an electrode assembly; the positive plate comprises a first surface and a second surface which are arranged back to back in the thickness direction of the positive plate, the first surface is provided with a plurality of convex parts, the convex direction of the convex parts faces the outer side of the electrode assembly, and the height h1 [mu] m of the convex parts is 1-35 [mu] m; the electrolyte contains 1, 2, 4-butane tricarbonitrile, and the mass content b% of the 1, 2, 4-butane tricarbonitrile in the electrolyte is 0.1%-5.1%. According to the battery, the problem of partial purple spots appearing at the position, corresponding to the positive electrode convex part, of the negative electrode plate in the later period of high-temperature circulation can be solved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more particularly to a battery. Background Technology

[0002] As the energy density requirements for lithium batteries increase, the compaction density of the positive electrode sheet becomes increasingly larger. In the later stages of cycling, the positive electrode sheet is prone to wrinkling and deformation, which becomes more severe. To address this issue, protrusions are typically added to the positive electrode to restrict its freedom of movement and improve its resistance to wrinkling and deformation. However, in the later stages of high-temperature cycling, purple spots appear in some areas of the negative electrode sheet corresponding to the positive electrode protrusions, severely affecting the battery's float charging and high-temperature storage performance. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a battery. The battery of this invention can improve the problem of partial purple spots appearing at the locations corresponding to the convex portions of the negative electrode and the positive electrode during the later stages of high-temperature cycling.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode, the separator, and the negative electrode are stacked or wound to form an electrode assembly. The positive electrode includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active layer contains a positive active material, which includes lithium cobalt oxide. The negative electrode includes a negative current collector and a negative active layer located on at least one surface of the negative current collector. The negative active layer contains a negative active material, which includes a silicon-based material. The positive electrode sheet includes a first surface and a second surface that are arranged back to back along its thickness direction. The first surface has a plurality of protrusions, the protrusions of which face outwards from the electrode assembly, and the height of the protrusions is 1μm-35μm. The electrolyte contains 1,2,4-butanetrionitrile, and the mass content of 1,2,4-butanetrionitrile in the electrolyte is 0.1%-5.1%.

[0005] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: The convex portion of the positive electrode sheet is prone to microcracks due to stress concentration during cycling, which accelerates electrolyte decomposition and the dissolution of transition metal Co, leading to the failure of the positive electrode active material. The dissolved Co ions deposit on the negative electrode surface, further damaging the SEI film and causing purple spots to appear at the locations corresponding to the convex portions of the negative and positive electrodes. This problem is particularly severe in the later stages of high-temperature cycling, significantly impacting battery float charging and high-temperature storage performance. Therefore, the positive electrode sheet of this invention, by aligning the convex portion of its protrusion towards the outside of the electrode assembly, avoids relative compression between positive electrode protrusions in different directions at the center of the electrode assembly, effectively reducing stress between the protrusions and minimizing cracking in the positive electrode active layer and lithium cobalt oxide. The opposite orientation of the positive electrode protrusions on both sides of the center of the electrode assembly can increase the electrolyte retention capacity inside the battery, thereby improving the wettability of the active material. Combined with the addition of 1,2,4-butanetrionitrile in the electrolyte, it can further suppress the dissolution of metal ions, better offsetting the risk of stress concentration at the positive electrode protrusions leading to cracks in the positive electrode active layer and lithium cobalt oxide. Furthermore, controlling the height of the protrusions to a lower range can further reduce the risk of cracking at the positive electrode protrusions, while ensuring that the 1,2,4-butanetrionitrile fully protects the positive electrode active material at the positive electrode protrusions. This suppresses the problem of purple spots appearing at the corresponding positions of the negative electrode and the positive electrode protrusions, improving the battery's float charging and high-temperature storage performance.

[0006] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the 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. Attached Figure Description

[0007] Figure 1 The figure shown is a schematic diagram of the cross-sectional structure of the positive electrode sheet provided in an example of the present invention.

[0008] Figure 2 The diagram shown is a schematic diagram of lithium deposition on the negative electrode sheet provided in an example of the present invention.

[0009] Figure 3 The image shown is a physical representation of a positive electrode sheet with a protrusion provided in an example of the present invention.

[0010] Explanation of reference numerals in the attached figures: Positive current collector 10, positive active layer 20, first surface 21, second surface 22, protrusion 211, and concave portion 221. Detailed Implementation

[0011] 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 invention. Unless otherwise specified herein, data ranges include endpoints.

[0012] This invention provides a battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode, the separator, and the negative electrode are stacked or wound to form an electrode assembly (when the positive electrode, the separator, and the negative electrode are stacked, they form a stacked battery cell; when the positive electrode, the separator, and the negative electrode are wound sequentially, they form a wound battery cell). Figure 1 As shown, the positive electrode includes a positive current collector 10 and a positive active layer 20 located on at least one side of the positive current collector 10. The positive active layer 20 contains a positive active material, which includes lithium cobalt oxide. The negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector. The negative active layer contains a negative active material, which includes a silicon-based material. The positive electrode includes a first surface 21 and a second surface 22 arranged opposite to each other along its thickness direction. The first surface 21 has a plurality of protrusions 211. The protrusion direction of the protrusions 211 faces outward of the electrode assembly (facing outward of the electrode assembly means facing the opposite direction to the stacking center of the stacked cell or the opposite direction to the winding center of the wound cell). The distance between the apex of the protrusion 211 and the first surface 21 along the height h1 μm of the protrusion is 1μm-35μm (e.g., ...). Figure 1 As shown, 30 protrusions are randomly selected on the electrode sheet, and the height difference between the apex of the protrusion and the first surface along the protrusion direction is measured, with the average value taken as h1, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, and 35μm. In one specific embodiment, the height difference h1 μm of the protrusions is 1μm-30μm. The height difference between the vertex of the protrusion and the first surface along the protrusion direction of the protrusion can be simply understood as the height of the protrusion.

[0013] The electrolyte of the present invention contains 1,2,4-butanetrionitrile (BTCN), wherein the mass percentage (b%) of the 1,2,4-butanetrionitrile in the electrolyte is 0.1%-5.1%, for example, 0.1%, 0.2%, 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%, or 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%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, or 5.1%. In one specific embodiment, the 1,2,4-butanetrionitrile has a mass content of 0.2%-3.8% in the electrolyte.

[0014] In this invention, the specific structure of the 1,2,4-butanetrionitrile is as follows: .

[0015] With the increasing demand for higher energy density in lithium batteries, the compaction density of the cathode sheet is also increasing. In the later stages of cycling, the cathode sheet is prone to severe wrinkling and deformation. Therefore, incorporating protrusions in the cathode has become a common industry practice to address this problem. Figure 3 The image shown is a physical illustration of a positive electrode with a protrusion. When a protrusion is placed on the positive electrode in conjunction with a silicon-based negative electrode, the silicon-based material undergoes significant volume expansion during cycling, compressing the protrusion on the positive electrode. This causes cracking in both the positive and negative electrodes at the protrusion location, exacerbating crack formation and metal ion dissolution in lithium cobalt oxide. It also causes the SEI film on the negative electrode to rupture, exposing the internal active material and leading to side reactions with the electrolyte. These problems worsen, especially during the later stages of high-temperature cycling at 45°C. The deposition of metal and lithium ions at the locations corresponding to the protrusions on the negative and positive electrodes results in purple spots, which also affects the battery's float charging performance.

[0016] This invention effectively solves the above-mentioned problems through targeted positive electrode structure design and the addition of appropriate electrolyte additives: On the one hand, the protrusion direction of the positive electrode protrusion is oriented towards the outside of the electrode assembly. This design avoids relative compression between the positive electrode protrusions on both sides of the core center, significantly reducing the stress between the protrusions and reducing the risk of cracking in the positive electrode active layer and lithium cobalt oxide. At the same time, this design can also increase the electrolyte retention capacity inside the cell, thereby improving the wetting effect of the active material. On the other hand, the addition of 0.1%-5.1% by mass of BTCN to the electrolyte has a lower viscosity than 1,3,6-hexanetrionitrile (HTCN) and a more compact cyano spatial structure, which provides better protection for metal ions in lithium cobalt oxide and can effectively inhibit the dissolution of metal ions, offsetting the negative impact of lithium cobalt oxide cracking caused by the protrusions. In addition, the height of the protrusion is controlled within a relatively low range of 1μm-35μm, which not only further reduces the probability of protrusion cracking, but also ensures that BTCN can fully act on the lithium cobalt oxide of the positive electrode protrusion, thereby effectively suppressing the appearance of purple spots at the corresponding positions of the negative electrode sheet and the positive electrode protrusion, and improving the battery float charging problem and high temperature storage performance.

[0017] In summary, this invention, through the synergistic effect of positive electrode structure design and electrolyte formulation, addresses stress relief, metal ion dissolution inhibition, and wettability improvement, significantly suppressing the generation of negative electrode purple spots and lithium plating in the later stages of high-temperature cycling. At the same time, it improves battery float charging performance and ensures battery reliability and cycle stability under high energy density requirements.

[0018] In this invention, the battery can further satisfy the following: the range of b / h1 is 0.01-4.5, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, or 4.5. The mass content b of 1,2,4-butanetrionitrile in the electrolyte can determine the metal ion dissolution suppression effect. The height h1 of the protrusion affects the protrusion stress and electrolyte wettability. By further controlling the two to satisfy the above relationship, it is possible to avoid the problem that insufficient b cannot offset the dissolution caused by protrusion cracks, or excessive b leads to increased interfacial impedance and aggravated side reactions. This can further suppress the generation of negative electrode purple spots in the later stage of high-temperature cycling, and optimize the battery's float charging stability, high-temperature storage performance, and cycle life.

[0019] In this invention, such as Figure 1 As shown, the convex portions of the positive electrode can be formed on the first surface by an embossing process (embossing roller pressing the positive electrode sheet), forming multiple convex portions on the second surface corresponding to the convex portions, such as... Figure 1As shown, the positive electrode includes a first surface 21 and a second surface 22 disposed opposite to each other along its thickness direction. The first surface 21 has a plurality of protrusions 211, and the second surface 22 has a plurality of recesses 221 corresponding to the protrusions 211. The projection of the protrusions on the electrode can be at least one of a circle, an ellipse, a rectangle, a triangle, a trapezoid, or an irregular shape. "A plurality of protrusions" can be interpreted as two or more, for example, 20, 40, 80, 150, 300, 500, 1000, 2000, 3000, 5000, 10000, or more protrusions.

[0020] In one specific embodiment, the projection of the protrusion in the direction perpendicular to the thickness of the positive electrode sheet is circular.

[0021] In one specific embodiment, the diameter of the projection of the protrusion in the direction perpendicular to the thickness of the positive electrode sheet is 0.1mm-10mm, for example, 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm or 10mm.

[0022] In one specific embodiment, the spacing between the projections of the protrusions perpendicular to the thickness direction of the positive electrode sheet is 0.1mm-10mm, for example, 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm or 10mm.

[0023] In one specific embodiment, the electrolyte further contains dinitrile additives. Based on the total mass of the electrolyte, the sum of the mass content of the 1,2,4-butanetrionitrile and the dinitrile additives is 1.1%-6.2%, for example, 1.1%, 1.2%, 1.3%, 1.5%, 1.7%, 1.9%, 2.1%, 2.3%, 2.5%, 2.7%, 2.9%, 3.1%, 3.3%, 3.5%, 3.7%, 3.9%, 4.1%, 4.3%, 4.5%, 4.7%, 4.9%, 5.1%, 5.3%, 5.5%, 5.7%, 5.9%, 6.1%, or 6.2%. In a preferred embodiment, the sum of the mass content of the BTCN and the dinitrile additives is 2%-5%. Under high voltage (>4.3 V), lithium cobalt oxide (LiCoO2) is prone to oxygen release and electrolyte oxidation. Dinitrile additives and BTCN can be adsorbed on the surface of the positive electrode and complex with Co ions in lithium cobalt oxide to form a complex, thereby forming a protective passivation layer on the surface of the positive electrode. This passivation layer helps to reduce the dissolution of transition metals, thereby further improving the battery's purple spot suppression effect, high temperature storage performance, float charge stability and cycle life. Furthermore, the protective passivation layer formed by dinitrile additives has better flexibility and can compensate for sites not protected by BTCN. The combination of the two can better isolate the electrolyte from the active material and suppress electrolyte side reactions, thereby improving the battery's float charge and high-temperature storage performance. However, when the sum of the mass content of BTCN and dinitrile additives is less than 1.1%, the further optimization and improvement of the positive electrode protective passivation layer will not be significant. When the sum of the mass content of BTCN and dinitrile additives is greater than 6.2%, it indicates that there is an excess of cyano-containing organic matter in the electrolyte. Excessive additives will form an excessively thick passivation layer on the positive electrode surface, resulting in a significant increase in the positive electrode interface impedance (Rct). In addition, excessive cyano-containing organic matter can also easily react with lithium salts at high temperatures to generate impurities such as cyanide and fluoride. At the same time, it may decompose and generate gas. In severe cases, it may cause cell bulging and sealing failure, resulting in a serious deterioration of the battery's high-temperature storage performance.

[0024] In one specific embodiment, the dinitrile additive includes at least one of succinic anhydride and adiponitrile.

[0025] In one specific embodiment, the electrolyte further contains ethyl propionate (EP), and the mass content of ethyl propionate in the electrolyte is 12.5%-60%, for example, 12.5%, 13%, 14%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, and 60%. In a preferred embodiment, the mass content of ethyl propionate in the electrolyte is 15%-40%. EP solvent has low viscosity, which can improve wetting performance and kinetics, thereby improving the purple spot lithium deposition phenomenon at the corresponding positions of the negative electrode and the positive electrode protrusion. However, excessive content will lead to deterioration of high-temperature storage performance; therefore, its content needs to be controlled within a suitable range. Furthermore, since BTCN and dinitrile additives can improve the high-temperature storage performance of the battery, but excessive mass content of BTCN and dinitrile additives will lead to excessive impedance, the sum of the mass contents of EP and BTCN, and dinitrile additives needs to be within a certain ratio range to achieve both improvement and deterioration. This method addresses the issue of purple spots in batteries while ensuring their high-temperature storage performance. Furthermore, in one specific embodiment, based on the total mass of the electrolyte, the ratio of the mass content of ethyl propionate to the sum of the mass contents of BTCN and the dinitrile additives is 3-30, for example, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30. In a preferred embodiment, the ratio of the mass content of ethyl propionate to the sum of the mass contents of BTCN and the dinitrile additives is 5-25.

[0026] In one specific embodiment, the electrolyte further contains a sulfur-containing additive, which includes at least one selected from mannitol sulfate carbonate, 1,3-propanesulfonyl lactone (PS), 1,3-propenesulfonyl lactone (PST), and vinyl sulfate. The sulfur-containing additive accounts for 0.5%-6% of the mass content of the electrolyte, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, and 6%. In a preferred embodiment, the sulfur-containing additive accounts for 2%-4% of the mass content of the electrolyte. Sulfur-containing additives such as mannitol sulfate and 1,3-propanesulfonate lactone have higher reduction potentials than the main electrolyte solvent. During the initial charge formation, they undergo a reduction reaction on the negative electrode surface before the solvent, preventing excessive decomposition and consumption of solvent molecules. This reduces side reactions in the electrolyte and improves the battery's high-temperature performance. Furthermore, these sulfur-containing additives can form a denser and more stable SEI film on the negative electrode. This SEI film can mitigate the volume expansion of silicon-based materials during cycling. The SEI film rupture caused by this, in synergy with BTCN, inhibits the dissolution of Co ions at the positive electrode, while the stable SEI film constructed by sulfur-containing additives such as mannitol carbonate sulfate and 1,3-propanesulfonate lactone can block the deposition of dissolved Co ions on the negative electrode surface. This can cut off the path of purple spot generation in both the positive and negative electrodes, inhibit the generation of purple spots, and ultimately reduce cell gas production and thickness expansion rate during high-temperature cycling, significantly improving the battery's capacity retention rate and long-term cycle stability, and enhancing the battery's high-temperature performance.

[0027] In one specific embodiment, the electrolyte further contains fluoroethylene carbonate.

[0028] In one specific embodiment, the surface of the negative electrode active layer has multiple negative electrode recesses (multiple can be two or more, for example, any value within the range of 2, 10, 20, 30, 40, 50, 100, 150, 200, etc.), and the negative electrode recesses are linear or porous. The linear or porous negative electrode recesses are formed by laser drilling. A high-power-density laser beam irradiates the negative electrode surface, rapidly heating the negative electrode active layer material to its vaporization temperature. Through evaporation, porous or linear negative electrode recesses are formed. The core function is to construct efficient electrolyte diffusion channels and stable electrolyte storage space, thereby optimizing battery performance from multiple dimensions. The electrolyte can rapidly diffuse from the negative electrode recesses on the negative electrode surface and penetrate deep into the negative electrode active layer. With the progress of formation, sorting, and other charge-discharge processes, the electrolyte retention of the cell further increases and the electrolyte retention state becomes more stable. Increased electrolyte retention means that the pores of the positive electrode, negative electrode, separator, and overhang within the cell are more fully filled with electrolyte. This directly reduces the interfacial impedance between the positive and negative electrodes and the separator, accelerating the conduction efficiency of lithium ions within the electrode assembly. This shortens the lithium ion diffusion path in the silicon-based negative electrode, improves its kinetic performance, and avoids the risk of lithium plating caused by ion conduction lag during fast charging cycles. It effectively avoids interface problems such as lithium plating and interfacial polarization that are prone to occur during fast charging cycles. At the same time, ensuring sufficient electrolyte inside the negative electrode reduces the probability of SEI film rupture when the silicon-based material expands in volume. Combined with components such as BTCN in the electrolyte, it suppresses the formation of purple spots, ultimately improving the high-temperature cycle stability of the battery.

[0029] In addition, compared with graphite anode materials, silicon-based materials have poor conductivity and poor kinetic performance as anode active materials. The setting of the anode recess can directly shorten the diffusion path of lithium ions in the anode active layer, which can specifically improve the kinetic performance of silicon-based anode materials.

[0030] In one specific embodiment, the negative electrode recess is a linear recess.

[0031] In one specific embodiment, the depth of the linear recess is 3μm-40μm, for example, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm or 40μm.

[0032] In one specific embodiment, the width of the linear recess is 20μm-500μm, for example, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 120μm, 140μm, 160μm, 180μm, 200μm, 220μm, 240μm, 260μm, 280μm, 300μm, 320μm, 340μm, 360μm, 380μm, 400μm, 420μm, 440μm, 460μm, 480μm or 500μm.

[0033] In one specific embodiment, the spacing between the linear recesses is 0.1mm-10mm, for example, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm.

[0034] In one specific embodiment, the silicon-based material includes a silicon-carbon composite material, which comprises a porous carbon matrix and silicon material deposited in the porous carbon matrix. The silicon content in the silicon-carbon composite material is 30%-80% by mass, for example, 30%, 35%, 40%, 45%, 47%, 48%, 50%, 52%, 55%, 60%, 65%, 72%, 75%, or 80%. If the silicon content in the silicon-carbon composite material is too low, the energy density improvement is limited; if the silicon content is too high, the electrode may crack due to silicon volume expansion. Therefore, to balance high capacity and volume expansion, the silicon content in the silicon-carbon composite material can be controlled within a suitable range.

[0035] In one specific embodiment, the sphericity of the silicon-carbon composite material is 0.8-0.99, for example, 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99.

[0036] In one specific embodiment, the particle size Dv50 of the silicon-carbon composite material is 1μm-15μm (e.g., 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, or 15μm). Particle size Dv refers to the volumetric particle size distribution, a particle size parameter defined by the volume percentage of the silicon-carbon composite material particles. For example, Dv50 represents the median particle size range of 1μm-15μm for 50% of the particles by volume. By further controlling the particle size Dv50 of the silicon-carbon composite material within a suitable range, this invention can effectively improve the poor kinetic performance of spherical silicon particles, thereby shortening the lithium-ion diffusion path, reducing agglomeration, and improving electrode compaction and ion conduction efficiency.

[0037] In one specific embodiment, the specific surface area of ​​the silicon-carbon composite material is 0.5 m². 2 / g-10m 2 / g, for example, 0.5m 2 / g、1m 2 / g, 1.5m 2 / g、2m 2 / g, 2.5m 2 / g、3m 2 / g, 3.5m 2 / g、4m 2 / g, 4.5m 2 / g、5m 2 / g, 5.5m 2 / g、6m 2 / g, 6.5m 2 / g、7m 2 / g, 7.5m 2 / g、8m 2 / g, 8.5m 2 / g、9m 2 / g, 9.5m 2 / g, 10m 2 / g. Specific surface area refers to the total surface area per unit mass of silicon-carbon composite material, including the outer surface of the particles and the inner surface of the internal pores. Specific surface area is controlled at 0.5m². 2 / g-10m 2 / g can reduce the contact area with the electrolyte, reduce side reactions, and further improve the cycle stability of the battery.

[0038] In one specific embodiment, the silicon content of the negative electrode active layer is 2%-50%, for example, 2%, 5%, 10%, 15%, 25%, 35%, 40%, 45%, 50%.

[0039] In one specific embodiment, the thickness of the positive electrode sheet is H, in μm; the height of the protrusion is h1, in μm; the percentage L of h1 to H satisfies: 1% ≤ L ≤ 30%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%. It should be noted that the thickness of the positive electrode sheet represents only the total thickness of the positive current collector and the positive active layer, excluding the height of the protrusion. The convex portion of the positive electrode should not be too high to avoid greater stress on the convex portion, reduce cracks in the positive electrode sheet, lower the possibility of cracks in lithium cobalt oxide, and avoid damage to the electrode sheet. The convex portion height h1μm and the positive electrode sheet thickness Hμm, by satisfying the above relationship, can ensure the above benefits while avoiding damage to the electrode sheet. The convex portion can improve the electrolyte retention and wettability, and avoid excessive stress on the convex portion that could lead to electrode sheet cracking. It can also work with components such as BTCN in the electrolyte to more effectively suppress the formation of purple spots and ensure the battery's high-temperature cycling and storage performance.

[0040] In one specific embodiment, the thickness H of the positive electrode sheet is 50μm-200μm, for example, 50μm, 60μm, 70μm, 80μm, 100μm, 1200μm, 150μm, or 200μm.

[0041] In one specific embodiment, the positive electrode active layer further comprises a solid electrolyte, which includes at least one of lithium aluminum titanium phosphate (LATP), lithium aluminum germanium phosphate, lithium lanthanum zirconate, and lithium lanthanum titanate. The mass fraction of the solid electrolyte in the positive electrode sheet is 0.1%-15%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, and 15%. In a preferred embodiment, the mass fraction of the solid electrolyte in the positive electrode sheet is 0.2%-10%. Solid electrolytes such as LATP are fast ion conductors, capable of rapidly conducting Li... + Therefore, introducing solid electrolytes such as LATP into the positive electrode active layer can construct a continuous Li + The conductive network significantly reduces interface impedance, which can further improve the high-rate performance and cycle life of the battery. It can also help enhance the stability of the positive electrode structure. Combined with electrolyte components such as BTCN, it can further optimize the purple spot suppression effect under high-temperature cycling.

[0042] In one specific embodiment, the particle size Dv50 of the solid electrolyte is 0.05μm-3μm, for example, 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm or 3μm.

[0043] In one specific embodiment, the lithium cobalt oxide has a particle size Dv50 of 5μm-25μm, for example, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm or 25μm.

[0044] In one specific embodiment, the lithium cobalt oxide includes aluminum as a dopant, and the mass content of aluminum in the lithium cobalt oxide is 4000ppm-13000ppm, for example, 4000ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm, 9000ppm, 10000ppm, 11000ppm, 12000ppm or 13000ppm.

[0045] In one specific embodiment, the charging cutoff voltage of the battery is greater than or equal to 4.53V.

[0046] In this invention, the electrolyte may also include at least one of the following solvents: ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), ethyl butyrate (EB), ethyl acetate (EA), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

[0047] In this invention, the electrolyte may further include lithium salts, which include at least one of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI), lithium difluorobis(oxalate)phosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(pentafluoroethyl)imide, and lithium tri(trifluoromethyl)sulfonyl)methyl.

[0048] In this invention, the electrolyte may also include other additives, which can be selected according to battery performance requirements and conventional industry technologies.

[0049] In this invention, the negative electrode active material further includes carbon-based materials, which include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, and hard carbon.

[0050] In this invention, the negative electrode active layer further includes a negative electrode conductive agent and a negative electrode binder.

[0051] In one specific embodiment, the negative electrode conductive agent includes at least one of conductive carbon black (Super P), furnace black, acetylene black, Ketjen black, and carbon nanotubes.

[0052] In one specific embodiment, the negative electrode binder includes at least one of polyurethane, acrylic-acrylonitrile copolymer, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR).

[0053] In this invention, the positive electrode active material may further include at least one of lithium nickel oxide, lithium titanate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide.

[0054] In this invention, the positive electrode active layer further includes a positive electrode conductive agent and a positive electrode binder.

[0055] In this invention, the compaction density of the positive electrode sheet is 3.8 g / cm³. 3 -4.6g / cm 3 (e.g., 3.8g / cm) 3 3.9g / cm 3 4.0g / cm 3 4.1g / cm 3 4.2g / cm 3 4.3g / cm 3 4.4 g / cm 3 4.5g / cm 3 4.6g / cm 3 4.7g / cm 3 Or 4.8g / cm 3 ), which here refers to the compaction density of the single-sided active material layer.

[0056] In one specific embodiment, the positive electrode conductive agent includes at least one of conductive carbon black (Super P), carbon nanotubes, conductive graphite, and graphene.

[0057] In one specific embodiment, the positive electrode binder includes at least one of polyvinylidene fluoride (PVDF), acrylic acid-modified PVDF, polyacrylate polymers, acrylic polymers, polytetrafluoroethylene, polyacrylonitrile, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0058] In one specific embodiment, the lithium-ion battery is a lithium-ion secondary battery.

[0059] In this invention, the mass content of solvents or additives such as 1,2,4-butanetrionitrile, sulfur-containing additives, dinitrile additives, and ethyl propionate is determined by methods known in the art, such as GC (gas chromatography) or GC-MS (gas chromatography-mass spectrometry).

[0060] The Dv50 of lithium cobalt oxide material, Dv50 particle size of silicon-based material, and particle size Dv50 of solid electrolyte in this invention are obtained by methods known in the art, such as SEM or laser particle size analyzer.

[0061] In this invention, the sphericity of the silicon-based material is tested using methods known in the art. For example, an SEM image (backscattered mode) of the negative electrode active layer at 2500x magnification is analyzed using image processing software (ImageProPlus) to obtain the perimeter and area of ​​each silicon-based material particle in the image. The equivalent radius r1 of the perimeter and the equivalent radius r2 of the area of ​​each silicon-based material particle are calculated respectively, and the sphericity S = r2 / r1 is obtained. Then, the sphericity of each silicon-based material particle is weighted and averaged to obtain the sphericity of the silicon-based material.

[0062] In this invention, the specific surface area of ​​the silicon-based material can be obtained by methods conventional in the art, such as measuring it using a Tri Star II specific surface area analyzer.

[0063] In this invention, the method for testing the mass content of silicon in the silicon-based material is adopted using methods known in the art. For example, the determination method may include the following steps: after disassembling the lithium-ion battery, the negative electrode sheet is removed, soaked and rinsed with dimethyl carbonate, dried, and then at least 20 silicon-based particles are selected in SEM backscatter mode. The percentage of silicon content in each silicon-based particle is obtained by EDS spot scanning mode, and the average silicon content ratio in the silicon-based particles is calculated.

[0064] In this invention, the aluminum content in the lithium cobalt oxide is obtained by testing using methods known in the art. For example, the following method can be used: the battery can be completely discharged and disassembled to separate the positive electrode sheet. The positive electrode sheet is then soaked in DMC, and then placed in a muffle furnace to be heated to 400°C at a rate of 2°C / min and held at that temperature for 4 hours. After natural cooling, the positive electrode powder material is taken and tested using ICP-OES (Inductively Coupled Plasma Atomic Emission Spectrometry) or ICP-MS (Inductively Coupled Plasma Mass Spectrometry) to obtain the aluminum content of the lithium cobalt oxide material.

[0065] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0066] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0067] Example 1 (1) Preparation of electrolyte: In a glove box (H2O < 0.01 ppm, O2 < 0.01 ppm, Ar atmosphere), the solvents EC / PC / PP / ethyl propionate (EP) were mixed evenly, with an EC / PC / PP ratio of 12:10:38 and EP accounting for 40% of the electrolyte. Then, 15% of fully dried LiPF6 based on the total mass of the electrolyte was added and dissolved. After dissolving, 2% of 1,2,4-butanetrionitrile (BTCN), 2% mannitol carbonate sulfate (BDD), 1% 1,3-propenesulfonyl lactone (PST) (the total mass percentage of sulfur-containing additives is 3%), 2% succinic anionibacterium dinitrile additive, and 8% fluoroethylene carbonate were added based on the total mass of the electrolyte. After stirring evenly and passing the moisture and free acid tests, the desired electrolyte was obtained.

[0068] (2) Preparation of the positive electrode: The prepared positive electrode active material lithium cobalt oxide (particle size 15 μm, aluminum doping content 9000 ppm), solid electrolyte lithium aluminum titanium phosphate (particle size 100 nm), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were weighed and dispersed in an appropriate amount of N-methylpyrrolidone (NMP) at a weight ratio of 97:1:1.2:0.8. The mixture was thoroughly stirred to form a uniform positive electrode slurry. The positive electrode slurry was coated onto the positive electrode current collector aluminum foil, then dried, rolled, cut, cleaned, and fitted with tab adhesive to obtain the positive electrode sheet. The thickness H of the positive electrode sheet was 100 μm, and the compaction density was 4.25 g / cm³. 3 .

[0069] (3) Preparation of negative electrode: Weigh out the prepared negative electrode active material (artificial graphite and silicon carbon mixed at a mass ratio of 90:10, with silicon content of 50% in the silicon carbon composite material, particle size Dv10 of 2 μm, particle size Dv50 of 8 μm, particle size Dv90 of 20 μm, and specific surface area of ​​silicon carbon of 0.5 m²). 2The following components (g), conductive agent Super P, binder styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) are dispersed in an appropriate amount of deionized water at a weight ratio of 97:1:1.5:0.5. The mixture is thoroughly stirred to form a uniform negative electrode slurry. This slurry is then coated onto a copper foil current collector, followed by drying, rolling, cutting, cleaning, and attaching tab adhesive to obtain the negative electrode sheet. The rolled negative electrode sheet is then placed in a laser wire-forming device to obtain a negative electrode sheet with lines on its surface (the negative electrode recess is linear).

[0070] Preparing the diaphragm: A 5μm thick substrate is used. A ceramic layer is coated on one side of the substrate, and an adhesive layer is coated on the other side of both the ceramic layer and the substrate. The substrate is composed of polyethylene, and the ceramic layer includes alumina. The adhesive layer is polyvinylidene fluoride.

[0071] The positive electrode, negative electrode, and separator are wound into a core according to a predetermined process. A winding machine with embossing function is used for winding. Before winding, the positive electrode is embossed by an embossing roller so that the height h1μm of the protrusion is 10μm, the projection of the protrusion on the electrode is circular with a diameter of 1.5mm, the spacing between the protrusions is 4mm, and the protrusions face the outside of the electrode assembly. Then, the electrolyte is injected and the lithium-ion battery is prepared by vacuum sealing, settling, and formation processes.

[0072] Example 2 group This embodiment is based on Embodiment 1, except that the rolling process conditions of the positive electrode sheet are changed, resulting in a change in the height of the protrusion h1 μm. Furthermore, the positive electrode active material in Embodiment 2-1, lithium cobalt oxide (particle size 15 μm, aluminum doping content 9000 ppm), the solid electrolyte lithium aluminum titanium phosphate (particle size 700 nm), the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF), are in a weight ratio of 95:3:1.2:0.8. Other parameters are detailed in Table 1.

[0073] Example 3 Group This embodiment is based on Embodiment 1, except that the amount of BTCN added to the electrolyte is changed by b%. See Table 1-1 for details.

[0074] Example 4 group This embodiment is based on Embodiment 1, except that the rolling process conditions of the positive electrode are changed to change the height of the protrusion h1 μm, and / or the amount of BTCN added in the electrolyte b% is changed to change the ratio of b / h1, as detailed in Table 1-1.

[0075] Comparative Example 1 This comparative example is based on Example 1, except that the rolling process conditions of the positive electrode are changed, which changes the height of the protrusion h1μm, as detailed in Table 1-1.

[0076] Comparative Example 2 This comparative example is based on Example 1, except that the amount of BTCN added to the electrolyte is changed by b%. See Table 1-1 for details.

[0077] Comparative Example 3 This comparative example is based on Example 1, except that the rolling direction of the positive electrode sheet is changed, and the protrusion of the protrusion faces the inside of the electrode assembly (towards the center of the winding core).

[0078] Table 1-1 Example 5 group This embodiment is based on Embodiment 1, except that the mass content percentage b% of BTCN in the electrolyte and / or the mass content percentage of dinitrile additives are changed, as detailed in Tables 1-2.

[0079] Example 6 group This embodiment is based on Example 1, except that the mass content ratio of ethyl propionate in the electrolyte is changed. See Table 1-2 for details. It should be noted that when the mass content ratio of ethyl propionate in the electrolyte changes, in order to keep the total amount of solvent in the electrolyte constant, the mass ratios of EC, PC and PP are changed proportionally to ensure that the sum of the mass ratios of each solvent is 100.

[0080] Example 7 group This embodiment is based on Embodiment 1, except that the mass content ratio of sulfur-containing additives in the electrolyte is changed. See Table 1-2 for details. It should be noted that two sulfur-containing additives were added in Embodiment 1. When the mass content ratio of sulfur-containing additives is changed, the ratio of these two sulfur-containing additives remains unchanged, and they are increased or decreased proportionally.

[0081] Table 1-2 Example 8 group This embodiment is based on Embodiment 1, except that the thickness H of the positive electrode is changed, thereby changing the percentage L of h1 to H. Specifically: Example 8-1: The thickness H of the positive electrode is 50 μm, and the percentage L of h1 to H is 40%. In Example 8-2, the thickness of the positive electrode is H=150μm, and the percentage L of h1 to H is 13.3%.

[0082] Example 9 This embodiment is based on Embodiment 1, except that the negative electrode is not subjected to laser wire bonding.

[0083] Test case The batteries obtained in the above embodiments and comparative examples were subjected to the following tests.

[0084] (1) 60℃ high-temperature storage experiment: At 25°C, the thickness D0 of the fully charged battery cell was tested. The sorted batteries obtained from the above examples and comparative examples were charged to 4.55V at 0.7C, then charged at a constant voltage of 4.55V to the cutoff current of 0.05C, then discharged at a constant current of 0.5C to 3.0V, then charged to 4.55V at 0.7C, and then charged at a constant voltage of 4.55V to the cutoff current of 0.05C. After being placed in an environment of 60°C for 35 days, the thickness D1 of the fully charged battery was tested, and the thickness change rate (%) was calculated. The thickness change rate (%) of the battery stored at 60°C is (D1-D0) / D0×100%. The results are recorded in Table 2.

[0085] (2) Float filling test: At 45°C, the batteries obtained in the above examples and comparative examples were charged at 7C to 4.55V, and then charged at a constant voltage of 4.55V to the cutoff current of 0.05C. The thickness D0 of the fully charged cell was measured. The cells were charged at a constant voltage for 35 days. After 35 days, the thickness D2 was measured. The thickness change rate (%) was calculated. The thickness change rate (%) of the float charge test battery is calculated as (D2-D0) / D0×100%. The results are shown in Table 2.

[0086] (3) Lithium plating test: The batteries obtained in the above embodiments and comparative examples were placed in an environment of 45°C and left to stand for 0.5 hours. When the battery temperature was 45±2°C, they were charged at a constant current of 0.7C to the upper limit voltage (4.5V), then charged at a constant voltage of 4.5V to 0.05C, and left to stand for 5 minutes. Next, they were discharged at a constant current of 0.5C to 3.0V and left to stand for 5 minutes. This constitutes one charge-discharge cycle. 300 charge-discharge cycles were performed. Then, the batteries were charged at a constant current of 0.7C to the upper limit voltage (4.5V). The battery cells were then disassembled, and the purple spot lithium deposition phenomenon was observed at the positions corresponding to the convex parts of the negative electrode and the positive electrode (divided into four levels: no lithium deposition, slight lithium deposition, lithium deposition, and severe lithium deposition). Among them, no lithium deposition means that no purple spot lithium deposition appears at the top bottom or middle area of ​​the negative electrode; slight lithium deposition means that purple spot lithium deposition appears at the top bottom of the negative electrode; severe lithium deposition means that purple spot lithium deposition appears at the top bottom of the negative electrode and spreads to the middle area; severe lithium deposition means that purple spot lithium deposition appears on the entire surface of the negative electrode. Figure 2 As shown in the figure, a serious lithium plating problem occurred at the position corresponding to the convex part of the negative electrode and the positive electrode. The results are recorded in Table 2.

[0087] Table 2 As can be seen from the analysis in Table 2, the battery of the present invention, by setting a protrusion structure on the positive electrode sheet with the protrusion direction facing the outside of the electrode assembly, and simultaneously adding BTCN to the electrolyte, can improve the problem of partial purple spots appearing at the positions corresponding to the protrusions of the negative electrode sheet and the positive electrode sheet in the later stage of high temperature cycling, and improve the float charging and high temperature storage performance of the battery.

[0088] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A battery, characterized in that, The electrode assembly includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode, the separator, and the negative electrode are stacked or wound to form an electrode assembly. The positive electrode includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active layer contains a positive active material, which includes lithium cobalt oxide. The negative electrode includes a negative current collector and a negative active layer located on at least one surface of the negative current collector. The negative active layer contains a negative active material, which includes a silicon-based material. The positive electrode sheet includes a first surface and a second surface that are arranged back to back along its thickness direction. The first surface has a plurality of protrusions, the protrusions of which face outwards from the electrode assembly. The height h1 μm of the protrusions is 1 μm-35 μm. The electrolyte contains 1,2,4-butanetrionitrile, and the mass content (b%) of the 1,2,4-butanetrionitrile in the electrolyte is 0.1%-5.1%.

2. The battery according to claim 1, characterized in that, The electrolyte also contains dinitrile additives. Based on the total mass of the electrolyte, the sum of the mass content of the 1,2,4-butanetrionitrile and the dinitrile additives is 1.1%-6.2%. Preferably, the dinitrile additives include at least one of succinic anhydride and adiponitrile. And / or, the battery satisfies the following condition: b / h1 ranges from 0.01 to 4.5; And / or, the second surface has a plurality of recesses.

3. The battery according to claim 2, characterized in that, The electrolyte also contains ethyl propionate, and the mass content of ethyl propionate in the electrolyte is 12.5%-60%.

4. The battery according to claim 3, characterized in that, Based on the total mass of the electrolyte, the ratio of the mass content of ethyl propionate to the sum of the mass content of 1,2,4-butanetrionitrile and the dinitrile additives is 3-30.

5. The battery according to claim 1, characterized in that, The electrolyte also contains sulfur-containing additives, including at least one of mannitol sulfate, 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, and vinyl sulfate, wherein the sulfur-containing additives account for 0.5%-6% of the mass content of the electrolyte.

6. The battery according to claim 1, characterized in that, The surface of the negative electrode active layer is provided with a plurality of negative electrode recesses, which are linear or pore-shaped. Preferably, the depth of the negative electrode recess is 3μm-40μm; Preferably, the width of the negative electrode recess is 20μm-500μm; Preferably, the spacing between the negative electrode recesses is 0.1mm-10mm.

7. The battery according to claim 1, characterized in that, The silicon-based material includes a silicon-carbon composite material, wherein the silicon content of the silicon-carbon composite material is 30%-80% by mass. Preferably, the sphericity of the silicon-carbon composite material is 0.8-0.99; Preferably, the particle size Dv50 of the silicon-carbon composite material is 1μm-15μm; Preferably, the specific surface area of ​​the silicon-carbon composite material is 0.5 m². 2 / g-10m 2 / g; Preferably, the silicon content of the negative electrode active layer is 2%-50%.

8. The battery according to claim 1, characterized in that, The thickness of the positive electrode is H μm, and the ratio L of h1 to H satisfies: 1%≤L≤30%. Preferably, the H μm is 50 μm-200 μm. And / or, the diameter of the projection of the protrusion in the direction perpendicular to the thickness of the positive electrode sheet is 0.1mm-10mm; And / or, the spacing between the projections of the protrusions in the direction perpendicular to the thickness of the positive electrode is 0.1mm-10mm.

9. The battery according to claim 1, characterized in that, The positive electrode active layer also contains a solid electrolyte, which includes at least one of lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum zirconate, and lithium lanthanum titanate. Preferably, the particle size Dv50 of the solid electrolyte is 0.05 μm-3 μm; Preferably, the solid electrolyte has a mass fraction of 0.1%-15% in the positive electrode active material layer.

10. The battery according to claim 1, characterized in that, The lithium cobalt oxide has a particle size Dv50 of 5 μm-25 μm; and / or, the lithium cobalt oxide includes aluminum, and the aluminum content in the lithium cobalt oxide is 4000 ppm-13000 ppm by mass; and / or, the charging cut-off voltage of the battery is greater than or equal to 4.53V; and / or, the compaction density of the positive electrode sheet is 3.8 g / cm³. 3 -4.6g / cm 3 .

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