Lithium ion secondary battery

Abstract

The application relates to the technical field of batteries, in particular to a battery. The battery comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector, the negative electrode active layer comprises silicon-carbon material, the silicon-carbon material comprises first silicon-carbon material and second silicon-carbon material; at least two included angles are included in the cross-sectional profile of the first silicon-carbon material, the average angle of the included angles is alpha, alpha is 60 DEG to 150 DEG; the second silicon-carbon material has a plurality of edges and a plurality of surfaces formed by the edges, the number of edges constituting a surface is N, N is greater than or equal to 6, the included angle between any two intersecting edges is greater than or equal to 90 DEG, the number of surfaces is greater than or equal to 4; alpha and N satisfy 7.5 <= alpha / N <= 25; the average particle size of the first silicon-carbon material is greater than that of the second silicon-carbon material. The battery of the application simultaneously realizes the improvement of cycle stability and rate performance and improves self-discharge.

Description

Technical Field

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

[0002] With continuous technological advancements, the actual capacity of graphite materials in practical applications is gradually approaching its theoretical capacity (372 mAh / g), which is no longer sufficient to meet the demand for higher energy density lithium-ion batteries. Silicon, with a theoretical capacity reaching up to 4200 mAh / g, is considered the most promising next-generation lithium-ion battery anode material. Current technologies commonly use spherical silicon-carbon materials with near-spherical shapes, as well as bulk silicon-carbon materials with poor shape regularity. While spherical silicon-carbon materials possess high strength and isotropy, their poor adhesion and small contact area with other components in the active layer make them prone to detachment during battery cycling and under expansion stress, damaging the conductive network in the active layer and thus degrading the battery's rate performance. Bulk silicon-carbon materials, on the other hand, have many sharp edges and corners, making them prone to cracking and shattering under pressure, posing a risk of puncturing the separator and causing self-discharge. Therefore, providing a lithium-ion battery that effectively improves self-discharge, rate performance, and cycle stability is crucial. Summary of the Invention

[0003] The purpose of this invention is to provide a battery that not only effectively improves self-discharge, but also enhances rate performance and cycle stability.

[0004] In related technologies, bulk silicon-carbon materials and spherical silicon-carbon materials are commonly used negative electrode active materials, which can significantly improve the negative electrode capacity and battery energy density. However, silicon-carbon materials undergo drastic volume expansion and contraction during lithium insertion and extraction, which increases the instability of the negative electrode structure. Spherical silicon-carbon materials have strong compressive strength, but their regular shape and smooth surface mean that when used in the negative electrode, they mostly make point contact with other components in the negative electrode active layer (such as graphite and binders). This results in a small contact area and low contact strength. During negative electrode rolling or battery cycling, these fragile point-to-point contacts are damaged, and the spherical silicon-carbon material is prone to detachment. This leads to an incomplete conductive network in the negative electrode active layer, which not only hinders the improvement of the battery's rate performance but also affects the negative electrode's capacity. Blocky silicon-carbon materials have many sharp edges. Although these edges can achieve good adhesion in the negative electrode active layer, they are prone to becoming stress concentration points after negative electrode rolling or during battery cycling, causing the silicon-carbon material to crack and pulverize. This results in the negative electrode active material losing electrical connection with the negative electrode current collector, leading to rapid capacity decay. At the same time, the edges of blocky silicon-carbon materials are prone to piercing the separator when expanding, leading to increased battery self-discharge. When spherical silicon-carbon materials and bulk silicon-carbon materials are used in combination, not only do the above-mentioned defects exist, but due to the large difference in morphology, it is difficult for the two silicon-carbon materials to achieve close stacking in the negative electrode active layer, resulting in a decrease in the overall strength of the negative electrode sheet and an increase in impedance, which leads to the deterioration of battery cycle stability and rate performance.

[0005] To address the aforementioned issues, this invention improves the morphology of silicon-carbon materials by employing a first silicon-carbon material with an included angle in its cross-sectional profile and a second silicon-carbon material with several edges and a surface formed by those edges. Simultaneously, the average particle size of the first silicon-carbon material is adjusted to be larger than that of the second silicon-carbon material, thereby improving the rate performance and cycle stability of the resulting battery while also improving self-discharge.

[0006] The first silicon-carbon material has an angled cross-sectional profile, and its morphological characteristics are manifested in the presence of uneven regions on its surface. These uneven regions provide more anchoring points for the conductive agent and binder in the negative electrode active layer, enabling close contact between particles and alleviating the problems of particle detachment and partial interruption of the conductive network, thus improving the mechanical integrity of the negative electrode active layer. At the same time, the uneven regions on the surface of the first silicon-carbon material can provide more reactive sites for the diffusion of lithium ions in the electrolyte, allowing the electrolyte to quickly diffuse from the surface of the silicon-carbon particles into the particle interior, improving the rate performance of the battery. The surface of the first silicon-carbon material particles has no sharp protrusions and has high strength characteristics similar to spherical silicon-carbon materials. During the rolling of the negative electrode sheet and battery cycling, the first silicon-carbon material can withstand the stress of external rolling and internal expansion, maintaining the integrity of the particles without breakage, thus improving the cycle stability and capacity performance of the battery.

[0007] The second silicon-carbon material contains several edges, forming surfaces, and there is a certain degree of included angle between two intersecting edges. Its morphology is characterized by a relatively regular polyhedral shape, which can be highly ordered and tightly packed in the negative electrode active layer to achieve high packing density and improve the space utilization of the negative electrode sheet. In addition, there are still protruding areas at the intersection of the edges of the second silicon-carbon material, but these protruding areas are not as sharp as those of block silicon-carbon. They can not only form good contact and adhesion with other components in the negative electrode active layer, but also avoid the stress concentration points formed by sharp edges, maintaining particle strength and electrode integrity. During battery cycling, the volume expansion of the second silicon-carbon material causes less extrusion pressure on the separator, making it less likely to puncture the separator and improving the long-cycle stability of the battery.

[0008] To improve the matching degree between the first silicon carbide material and the second silicon carbide material, the ratio of the average angle α of the included angle on the interface contour of the first silicon carbide material and the number of edges N of the constituent surfaces in the second silicon carbide material is also adjusted to a suitable range. When α / N is too large (e.g., >25), the first silicon carbide material is nearly spherical or has no uneven surface, while the protruding area on the surface of the second silicon carbide material is reduced. The two lack the basis for forming an interlocking structure, lose the gain brought by the shape matching, and are no different from ordinary mixing. When α / N is too small (e.g., <7.5), the first silicon carbide material has a sharp included angle on the cross section, close to a sharp angle, while the second silicon carbide material has too many edges, making its protruding area too smooth. The second silicon carbide material cannot be embedded in the depression of the first silicon carbide material, making it difficult to form a stable interlocking structure.

[0009] Further limiting the average particle size of the first silicon-carbon material to be larger than that of the second silicon-carbon material allows for a more substantial stacking of the negative electrode active materials, forming a compact and dense spatial structure. The first silicon-carbon material has a relatively smooth particle surface, no stress concentration at the tip, and high particle strength. Selecting the first silicon-carbon material with a larger average particle size to form a rigid skeleton in the negative electrode active material layer effectively improves the pressure resistance and resistance to expansion stress of the negative electrode sheet. The second silicon-carbon material has good particle flowability, making it easier to distribute and rearrange evenly during the preparation of the negative electrode sheet, forming a uniform skeleton and avoiding excessively large voids caused by local bridging. The second silicon-carbon material has a smooth particle surface and a large contact area between particles and between particles and other components. Choosing the second silicon-carbon material with a smaller average particle size to fill the skeleton of the first silicon-carbon material can effectively connect the two silicon-carbon material particles indirectly together. In addition, the second silicon-carbon material has edges and planes, and its rolling properties are worse than those of the first silicon-carbon material. Once it enters the pores, its irregular shape and edges can create an interlocking effect, trapping itself between large particles and forming a more stable interlocking structure. At the same particle size, the packing density of the second silicon-carbon material is higher than that of the first silicon-carbon material. As a filler phase, it can improve the space utilization rate between the skeletons of the first silicon-carbon material. Its surface protrusions can fill the depressions on the surface of the first silicon-carbon material, further improving the overall density and compaction density of the negative electrode sheet, enhancing the overall mechanical strength and structural integrity of the negative electrode sheet, and improving the cycle stability of the battery.

[0010] Based on this, the present invention proposes the following technical solution: This invention provides a battery comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material, the negative electrode active material comprising a silicon-carbon material, the silicon-carbon material comprising a first silicon-carbon material and a second silicon-carbon material; the cross-sectional profile of the first silicon-carbon material includes at least two included angles, the average angle of the included angles being α, α being 60°~150°; the second silicon-carbon material has a plurality of edges and faces formed by the edges, the number of edges constituting the faces being N, N≥6 and N being an integer, the included angle between any two intersecting edges being greater than or equal to 90°, the number of faces being greater than or equal to 4; α and N satisfy: 7.5≤α / N≤25; the average particle size of the first silicon-carbon material is greater than the average particle size of the second silicon-carbon material.

[0011] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: The battery of the present invention improves the rate performance and cycle stability of the battery while improving the self-discharge of the battery.

[0012] 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

[0013] Figure 1 The image shown is a scanning electron microscope image of the first silicon-carbon material in one embodiment of the present invention.

[0014] Figure 2 The image shown is a scanning electron microscope image of the second silicon-carbon material in one embodiment of the present invention. Detailed Implementation

[0015] 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.

[0016] The present invention provides a battery comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material, the negative electrode active material comprising a silicon-carbon material, the silicon-carbon material comprising a first silicon-carbon material and a second silicon-carbon material.

[0017] In this invention, the cross-sectional profile of the first silicon-carbon material includes at least two included angles, the average angle of which is α, and α is 60°~150°, for example, 60°, 65°, 70°, 75°, 80°, 85°, 90°, 100°, 110°, 120°, 130°, 140° or 150°.

[0018] It is understood that the included angle located in the cross-sectional profile of the first silicon carbide material refers to: taking a single point on the cross-sectional profile of the first silicon carbide material, whose vertical distance from its convex hull segment exceeds 0.25 μm as the vertex, and drawing a straight line tangent to the cross-sectional profile of the first silicon carbide material, there are two different tangent lines. The angle formed by the two tangent lines outside the cross-section of the first silicon carbide material is the included angle.

[0019] like Figure 1 The image shown is a scanning electron microscope image of the first silicon-carbon material in one embodiment of the present invention.

[0020] In this invention, the second silicon-carbon material has a plurality of edges and faces formed by the edges, the number of edges constituting the faces being N, N≥6 and N is an integer (e.g., 6, 10, 15, 20, 25, 30, 40, 50, 60, 80, 100, 120, 140, 160, 180 or 200), the included angle between any two intersecting edges is greater than or equal to 90° (e.g., 90°, 95°, 100°, 110°, 120°, 130°, 140°, 150° or 160°), and the number of faces is greater than or equal to 4 (e.g., 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16 or 18).

[0021] It is understood that "the number N of edges constituting the face" refers to the number of edges required to form a face in each of the second silicon carbide material particles; and "the number of faces" refers to the number of faces on each of the second silicon carbide material particles. Figure 2 The image shown is a scanning electron microscope image of the second silicon-carbon material in one embodiment of the present invention.

[0022] In this invention, α and N satisfy: 7.5≤α / N≤25, for example, 7.5, 8, 8.5, 9, 10, 11, 12, 14, 16, 18, 20, 22, 24 or 25.

[0023] In one embodiment, α and N satisfy: 18 ≤ α / N ≤ 23.

[0024] In this invention, the average particle size of the first silicon-carbon material is greater than the average particle size of the second silicon-carbon material.

[0025] In this invention, N can be obtained by conventional testing methods in the art, such as by scanning electron microscopy, specifically as follows: discharge the battery to 0% SOC, disassemble and remove the negative electrode sheet, or directly remove the negative electrode sheet, and use backscatter imaging mode to image a local area of ​​the obtained negative electrode sheet in scanning electron microscopy (SEM); the silicon-carbon material particles appear white in the image, select particles with a particle size comparable to the average particle size of the second silicon-carbon material, count the number of edges required to form a complete surface on the second silicon-carbon material in the test area, count at least 10 different second silicon-carbon materials and take the average value (integer) as the number of edges of the second silicon-carbon material.

[0026] In this invention, α can be obtained by conventional testing methods in the art, such as by SEM measurement, specifically as follows: Discharge the battery to 0% SOC, disassemble and remove the negative electrode, or directly remove the negative electrode. Polish the cross-section of the negative electrode with an argon ion mill, and image the obtained cross-section using backscatter imaging mode in an SEM device. Find the point on the contour of the first silicon-carbon material particle that is more than 0.25 μm away from its convex hull line segment as the vertex. Draw two tangent lines through the vertex to the cross-sectional contour of the first silicon-carbon material. Use image processing software to measure the angle between the two tangent lines outside the cross-section. Measure a total of 10 different first silicon-carbon material particles and take the average value, which is α.

[0027] In this invention, the number of the first silicon-carbon material accounts for 30% to 50% of the total number of silicon-carbon materials, for example, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48% or 50%.

[0028] In this invention, the number of the second silicon-carbon material accounts for 50% to 70% of the total number of silicon-carbon materials, for example, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68% or 70%.

[0029] In this invention, the average particle size of the first silicon-carbon material is 7μm to 10μm, for example, 7μm, 7.2μm, 7.4μm, 7.6μm, 7.8μm, 8μm, 8.5μm, 9μm, 9.5μm or 10μm.

[0030] Preferably, the average particle size of the second silicon-carbon material is 2μm to 8μm, for example, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm, 3μm, 3.5μm, 4μm, 5μm, 6μm, 7μm or 8μm.

[0031] When the proportions of the first and second silicon-carbon materials in the total number of silicon-carbon materials meet the above-mentioned range, the negative electrode active materials can be stacked solidly to form a compact and dense spatial structure. When the proportion of the first silicon-carbon material is too low (e.g., <30%) / the proportion of the second silicon-carbon material is too high (e.g., >70%), the small-particle-size second silicon-carbon material dominates. Initially, increasing the small-particle-size second silicon-carbon material can effectively fill the pores, but after exceeding the optimal point, due to the difficulty in forming a robust framework, the porosity generated by the self-accumulation of the second silicon-carbon material becomes dominant, and the overall density cannot be further improved, and may even decrease due to particle agglomeration. The small-particle-size second silicon-carbon material has a higher specific surface area, requiring more binder and conductive agent to be consumed, exacerbating the side reactions with the electrolyte, accelerating SEI film growth, consuming lithium source and electrolyte, and the side reactions are often accompanied by gas generation, affecting the battery's safety performance, cycle stability, and rate performance. When the proportion of primary silicon-carbon material is too high (e.g., >50%) and the proportion of secondary silicon-carbon material is too low (e.g., <50%), the large-particle-size primary silicon-carbon material dominates. A large number of primary silicon-carbon material particles form many unfilled large pores. The amount of secondary silicon-carbon material is insufficient to fill these spaces, resulting in a loose overall structure. This is not conducive to maintaining or improving the volumetric energy density of the battery. The bonding between the primary silicon-carbon material particles mainly relies on binders. The lack of filling and mechanical interlocking by secondary silicon-carbon material leads to a decrease in the flexibility and strength of the negative electrode sheet. After volume expansion during rolling or charging and discharging, it is more likely to crack or shed powder, increasing self-discharge. In addition, when there is too much primary silicon-carbon material, it will also increase the contact points between them, which can easily form mechanical arches or voids in local areas. These voids may suddenly collapse during subsequent rolling, resulting in uneven density, which is not conducive to improving the cycle stability and rate performance of the battery.

[0032] In this invention, the average particle size of the first silicon-carbon material and the second silicon-carbon material can be obtained by conventional testing methods in the art, such as the following method: discharging the battery to 0% SOC, disassembling and removing the negative electrode sheet, or directly removing the negative electrode sheet, polishing its cross-section with an argon ion mill, and then imaging the obtained cross-section using backscatter imaging mode in an SEM device; the silicon-carbon particles in the image appear grayish-white, and then using electron microscopy image analysis software such as ImageJ to measure the particle size and perform distribution statistics, distinguishing the first silicon-carbon material and the second silicon-carbon material by morphological differences, and calculating the maximum distance between any two points on the contours of at least 15 first silicon-carbon materials and at least 15 second silicon-carbon materials respectively and taking the average value.

[0033] In this invention, the proportion of the number of the first silicon-carbon material and the second silicon-carbon material to the total number of silicon-carbon materials can be obtained by conventional testing methods in the art, such as the following method: discharge the battery to 0% SOC, disassemble and remove the negative electrode sheet, or directly remove the negative electrode sheet, polish its cross-section with an argon ion mill, and then image the obtained cross-section at a certain magnification (e.g., 1000x) using backscatter imaging mode in an SEM device; select a region of size 50μm×50μm to count the number of the first silicon-carbon material and the second silicon-carbon material in the region, and repeat the count with at least 5 different selected regions, and take the average value as the proportion of the number of the first silicon-carbon material and the second silicon-carbon material to the total number of silicon-carbon materials.

[0034] In this invention, the silicon-carbon material comprises a porous carbon matrix and silicon particles located in the pores within the porous carbon matrix.

[0035] In this invention, at least a portion of the outer surface of the silicon-carbon material is provided with a coating layer; wherein, "at least a portion" can be understood as the proportion of the orthographic projection area of ​​the coating layer on the outer surface of the silicon-carbon material being greater than 0%, and may be less than 100% or equal to 100%.

[0036] In one embodiment, the coating layer comprises amorphous carbon.

[0037] In this invention, the average thickness of the coating layer is 10 nm to 50 nm, for example, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm. The average thickness of the coating layer can be measured by conventional testing methods in the art, such as using a transmission electron microscope (TEM). After preparing the silicon-carbon material sample, it is imaged under the TEM. After magnification to a certain magnification, the coating layer is determined according to the interface. Five different silicon-carbon material particles are randomly selected, and the thickness of the coating layer is measured at five different points, and the average value is taken.

[0038] When the coating thickness on the surface of the silicon-carbon material meets the above-mentioned range, the coating can achieve uniform and complete coverage, avoiding contact between the electrolyte and the silicon particles inside the silicon-carbon material and repeated growth of SEI film rupture. When the coating thickness is too small (e.g., <10nm), the surface coating is not completely covered, and direct contact between the electrolyte and the highly active silicon triggers local side reactions, leading to continuous gas production in the battery. At the same time, the thin coating is prone to rupture and failure during the initial expansion of silicon, resulting in repeated rupture and regeneration of the SEI film in subsequent cycles, causing severe gas production. When the coating thickness is too large (e.g., >50nm), ion transport within the coating is slow, and lithium intercalation may not be possible in time within the silicon-carbon material particles. Furthermore, the coating surface has an excessively low potential, leading to excessive reduction and decomposition of the electrolyte, generating gas.

[0039] In this invention, based on the total mass of the silicon-carbon material, the mass content of the porous carbon matrix is ​​38% to 55%, for example, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54% or 55%.

[0040] In this invention, based on the total mass of the silicon-carbon material, the mass content of silicon element is 40% to 60%, for example, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58% or 60%.

[0041] In this invention, based on the total mass of the silicon-carbon material, the mass content of the coating layer is 2% to 5%, for example, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.5%, 4%, 4.5% or 5%.

[0042] In this invention, based on the total mass of the negative electrode active layer, the mass content of silicon element is 1% to 50%, for example, 1%, 2%, 4%, 6%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%.

[0043] When the proportions of each component in a silicon-carbon material satisfy the above-mentioned relationship, the silicon-carbon material exhibits high specific capacity, high initial coulombic efficiency, and low expansion rate. Further limiting the mass content of silicon in the anode active layer within the above range ensures good cycle stability and a low expansion rate while maintaining anode capacity.

[0044] In this invention, the mass content of silicon in the negative electrode active layer can be obtained by conventional methods in the art. For example, after discharging the battery to 0% SOC, the negative electrode sheet is disassembled and soaked in dimethyl carbonate (DMC) solvent for 12 hours, then rinsed with DMC solvent to remove the lithium salt adhering to the negative electrode sheet. After drying, the negative electrode sheet is subjected to high-temperature treatment at 400°C in an inert atmosphere for 2 hours (e.g., in a tube furnace under nitrogen or argon atmosphere). The negative electrode active layer can then be peeled off from the negative electrode current collector, and the negative electrode active layer is collected as a test sample. Using a thermogravimetric analyzer (e.g., a TGA 550 thermogravimetric analyzer), the test sample amount is 5mg-15mg. Under an air or oxygen atmosphere, the temperature is increased from room temperature (25°C) to 900°C at a rate of 10°C / min, and held at 900°C for 40 minutes, so that the non-silicon components in the negative electrode active layer volatilize while the silicon is fully oxidized to silicon dioxide. The remaining substance is the ash of the negative electrode active layer. The mass content of silicon in the negative electrode active layer can be calculated based on the mass of ash. The calculation formula is as follows: Mass content of silicon in the negative electrode active layer = 7 × mass of ash / (15 × mass of test sample).

[0045] In this invention, the specific surface area of ​​the silicon-carbon material is 0.1 m². 2 / g~10m 2 / g, for example, 0.1m 2 / g, 0.2m 2 / g, 0.5m 2 / g、1m 2 / g, 1.5m 2 / g、2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、8m 2 / g or 10m 2 / g. The pore volume of the silicon-carbon material is 0.0005 cm³. 3 / g~0.002cm 3 / g, for example, 0.0005cm 3 / g, 0.0006cm 3 / g, 0.0008cm 3 / g, 0.001cm 3 / g, 0.0012cm 3 / g, 0.0014cm 3 / g, 0.0016cm 3 / g, 0.0018cm 3 / g or 0.002cm 3 / g. The specific surface area and pore volume of the silicon-carbon material can be determined by conventional testing methods in the art, such as the Brunauer-Emmett-Teller (BET) test method, for example, by using a TriStar II specific surface area analyzer, with N2 as the adsorbed gas.

[0046] When the specific surface area and pore volume of silicon-carbon materials meet the above-mentioned range, the negative electrode active material can have a high specific capacity, while effectively reducing the contact between the negative electrode active material and the electrolyte, reducing the repeated regeneration of the SEI film, thereby improving the battery's initial coulombic efficiency and capacity retention.

[0047] In this invention, the true density of the silicon-carbon material can be 1.5 cm³. 3 / g-2.4cm 3 / g, for example, 1.5cm 3 / g, 1.6cm 3 / g, 1.7cm 3 / g, 1.8cm 3 / g, 1.9cm 3 / g、2cm 3 / g, 2.1cm3 / g, 2.2cm 3 / g, 2.3cm 3 / g or 2.4cm 3 / g. The true density of the silicon-carbon material can be obtained by conventional methods in the art, such as the gas volume displacement method, as follows: the test is performed using a JW-M100A fully automatic true density tester, the test gas is helium, and the test environment temperature is 25℃±2℃.

[0048] When the true density of silicon-carbon materials is within a specific range, it can ensure a high specific capacity of the negative electrode active material while providing sufficient buffer space for the volume expansion of silicon during charging, thereby avoiding failure of the negative electrode active material due to excessive volume expansion. When the true density of silicon-carbon materials is low (e.g., <1.5 cm⁻¹), it can cause problems. 3 The density ( / g) indicates that there are still many pores in the silicon-carbon material, and silicon has not been fully deposited inside the porous carbon material, resulting in a low specific capacity of the negative electrode active material; while when the true density of the silicon-carbon material is large (e.g., >2.4 cm⁻¹), the actual capacity is low. 3 The result ( / g) indicates that the silicon-carbon material has a relatively small number of pores. When the battery is charged, the silicon undergoes volume expansion due to lithium intercalation. If the pore structure in the silicon-carbon material is insufficient to support the volume expansion of silicon, it will lead to the destruction of the structure of the negative electrode active material.

[0049] In this invention, the negative electrode active layer includes a negative electrode binder, which includes a polyacrylonitrile-alkane acrylate copolymer.

[0050] In one embodiment, the polyacrylonitrile-alkane acrylate copolymer includes a polyacrylonitrile-butyl acrylate copolymer.

[0051] In this invention, the negative electrode active layer is formed by a negative electrode active slurry, which includes an oily solvent.

[0052] In one embodiment, the oily solvent includes N-methylpyrrolidone (NMP) and / or dimethylacetamide (DMAC).

[0053] It is understood that the term "oil-based solvent" generally refers to an organic solvent that is oleophilic and hydrophobic, has limited miscibility or is immiscible with water, and has excellent solubility for non-water-soluble polymers such as oils and fluorinated resins.

[0054] Traditional aqueous formulations use styrene-butadiene rubber (SBR) as a binder and deionized water as a solvent. The main chain consists of nonpolar carbon-hydrogen bonds, relying primarily on the physical entanglement of molecular chains and van der Waals forces to form a bonding network. While possessing strong elasticity, it is relatively weak and prone to interfacial slippage under long-term, high stress. Furthermore, SBR's point-contact bonding method reduces the number of contact sites between the conductive agent and silicon-carbon materials, making it difficult to adapt to the expansion and contraction of silicon-carbon materials. This leads to bonding failure during battery cycling, resulting in damage to the negative electrode structure, breakage of the conductive network, and decreased adhesion, which is detrimental to further improvements in battery cycle stability, rate performance, and self-discharge. In contrast, polyacrylonitrile-alkane acrylate copolymers contain both rigid acrylonitrile segments providing strong adhesion and flexible alkane acrylate segments (such as butyl acrylate segments) providing elasticity. The rigid portion anchors the negative electrode active material particles and the negative electrode current collector, while the flexible portion provides elastic deformation space to enhance the resistance to the volume expansion of silicon-carbon materials. When using oily solvents such as NMP / DMAC as solvents, the combination with polyacrylonitrile-alkane acrylate copolymers can form a film-like structure on the surface of silicon-carbon materials. This better adapts to the expansion and contraction of silicon-carbon materials, effectively buffering volume changes and avoiding the easy breakage problem caused by the point contact method of traditional SBR binders. This greatly improves the structural stability of silicon-carbon materials and negative electrode sheets, significantly improving the problem of easy expansion of silicon-carbon negative electrodes during charge and discharge, and further improving the cycle stability, rate performance, and self-discharge of the battery. In addition, the cyano groups in the polyacrylonitrile-alkane acrylate copolymer have a certain degree of electron-withdrawing effect, which is beneficial to improving charge transport inside the electrode and further enhancing the rate performance of the battery.

[0055] In this invention, the negative electrode active layer includes a first negative electrode active layer and a second negative electrode active layer, the first negative electrode active layer and the second negative electrode active layer are disposed opposite to each other along the thickness direction of the negative electrode sheet, and the length of the first negative electrode active layer is greater than the length of the second negative electrode active layer.

[0056] In this invention, the outer surface of the first negative electrode active layer has a plurality of recesses, and the outer surface of the second negative electrode active layer has a plurality of protrusions, wherein the recesses and protrusions correspond one-to-one. Here, "a plurality of" means that the number of recesses is ≥2 and the number of protrusions is ≥2.

[0057] In this invention, the depth of the recess is 3μm to 50μm (e.g., 3μm, 4μm, 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm), the width of the recess is 0.3mm to 8mm (e.g., 0.3mm, 0.5mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm or 8mm), and the spacing between the recesses is 0.5mm to 5mm (e.g., 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm or 5mm).

[0058] In this invention, the height of the protrusion is 3μm to 50μm (e.g., 3μm, 4μm, 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm), the width of the protrusion is 0.3mm to 8mm (e.g., 0.3mm, 0.5mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm or 8mm), and the spacing between the protrusions is 0.5mm to 5mm (e.g., 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm or 5mm).

[0059] In this invention, the recess and the protrusion can be obtained by conventional means in the art, for example, by using an embossing roller (with protrusions).

[0060] In this invention, the shape of the recess projected onto the first negative electrode active layer is not limited; it can be circular or rectangular. The width of the recess refers to the maximum distance between any two points on the outline of the recess; the spacing between the recesses refers to the distance between the lowest points of two adjacent recesses; and the height of the protrusion refers to the vertical distance from the lowest point within the recess to the surface of the first negative electrode active layer.

[0061] In this invention, the shape of the protrusion projected onto the second negative electrode active layer is not limited; it can be circular or rectangular. The width of the protrusion refers to the maximum distance between any two points on the outline of the protrusion; the spacing between the protrusions refers to the distance between the highest points of two adjacent protrusions; and the height of the protrusion refers to the vertical distance from the highest point within the protrusion to the surface of the second negative electrode active layer.

[0062] During high-rate charging and discharging, lithium ions rapidly surge from the positive electrode to the negative electrode. On the smooth surface of the negative electrode, ions can only embed themselves perpendicular to the current collector, easily leading to localized supersaturation near the surface. This causes lithium metal to deposit on the surface, further deteriorating the battery's cycle retention and thickness expansion rate. Adding concave and convex sections to the surface of the negative electrode increases its specific surface area and provides additional lateral diffusion channels for lithium ions. This allows lithium ions to be more evenly distributed across a larger surface area and rapidly diffuse into the interior of the negative electrode along the concave structure, reducing local current density and ion concentration gradient. This significantly improves the fast-charging limit (e.g., supporting charging at higher rates) and effectively suppresses the risk of lithium plating. Furthermore, on a high-load, high-compact smooth negative electrode, electrolyte cannot quickly and evenly penetrate the interior. The concave and convex sections in the negative electrode can store electrolyte, providing penetration channels, shortening the wetting time, and reducing ion transport resistance. Traditional bulk silicon-carbon materials are prone to particle breakage during the process of creating concave and convex sections, leading to increased battery self-discharge. Conversely, spherical silicon-carbon materials have poor contact with graphite and binders, making them susceptible to sliding into the flat areas between concave and convex sections (i.e., areas not covered by the concave and convex sections) during the process, resulting in lower CB values ​​in these areas and increased susceptibility to lithium plating during battery cycling. This invention uses a combination of first and second silicon-carbon materials, forming a stable interlocking structure through specific morphological pairing. Compared to traditional silicon-carbon hybrid systems, this structure exhibits higher strength, allowing silicon-carbon particles to remain intact and unbroken during the concave and convex section creation process. The bond between the particles and graphite and binder is tighter, preventing particle slippage and resulting in high CB value consistency across the negative electrode. This further improves battery cycle stability and rate performance, and reduces battery self-discharge.

[0063] In this invention, the depth, spacing, and width of the recesses can be determined using conventional testing methods in the art, such as using a 3D profilometer. Specifically, after discharging the battery to 0% SOC, the electrode sheets are disassembled and soaked in DMC solvent for 12 hours, followed by rinsing with DMC to remove lithium salts adhering to the electrode sheets. One electrode sheet is folded, and the flatness of the first negative electrode active layer of the positive electrode is tested using a 3D profilometer. The depth of at least 10 recesses is measured through image analysis, and the average value is calculated and recorded as the depth of each recess. At least 5 groups of adjacent recesses are measured using the 3D profilometer scale, and the average value is taken as the spacing of the recesses. At least 10 recesses are measured using the 3D profilometer scale, and the average value is taken as the width of the recesses. When the number of recesses is less than 10, technicians can select a representative sample size based on the actual number. The testing methods for the height, width, and spacing of the protrusions can refer to the testing methods for the recesses.

[0064] In this invention, the battery further includes a separator, which includes a base film, a first coating on one side of the base film, and a second coating on the other side of the base film.

[0065] In this invention, the first coating includes a heat-resistant layer and an adhesive layer, wherein the heat-resistant layer is located between the base film and the adhesive layer.

[0066] In this invention, the battery further includes a positive electrode sheet, the first coating and the positive electrode sheet are arranged facing each other, and the second coating and the negative electrode sheet are arranged facing each other.

[0067] In this invention, the adhesive layer comprises a first polymer, which is a polymer formed by polymerizing one or more of the following monomers: styrene, ethylene, propylene, acrylonitrile, methyl methacrylate, butyl acrylate, isooctyl acrylate, octadecyl acrylate, ethyl acrylate, amide, and imide. The adhesive layer also includes an adhesive, which comprises at least one of polyvinylidene fluoride (PVDF), polyamide (PI), and polyacrylic acid (PAA).

[0068] In this invention, the second coating comprises filler particles and a second polymer, the second polymer comprising polymers formed by polymerizing one or more of the following monomers: vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene. The filler particles comprise at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, barium titanate, 1,3,5-triazine-2,4,6-triamine, melamine cyanurate, and melamine trithiocyanate.

[0069] In this invention, the heat-resistant layer comprises ceramic particles, which include at least one of lithium iron phosphate, alumina, boehmite, titanium dioxide, zirconium oxide, boron nitride, barium sulfate, barium titanate, and silicon dioxide.

[0070] In this invention, based on the total mass of the second coating, the mass content of the second polymer is 20% to 70%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60% or 70%.

[0071] In this invention, the area of ​​the adhesive layer projected onto the separator accounts for 5% to 80%, for example, 5%, 6%, 8%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, or 80%. Adjusting the area percentage of the adhesive layer projected onto the separator surface ensures lithium-ion transport and the adhesion of the separator.

[0072] In this invention, the adhesive layer comprises a plurality of adhesive dots, the average diameter of which is 50 μm to 200 μm, for example, 50 μm, 52 μm, 54 μm, 56 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, or 200 μm. The average spacing between the adhesive dots is 100 μm to 500 μm, for example, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm, 320 μm, 340 μm, 360 μm, 400 μm, 450 μm, or 500 μm. The term "a plurality of" refers to the number of adhesive dots being ≥2. Adjusting the average diameter and average spacing of the adhesive dots can regulate the uniformity of the membrane adhesion and the uniformity of the lithium-ion transport channels.

[0073] In this invention, the average diameter of the adhesive dots refers to the maximum distance between any two points on the orthographic projection profile of the adhesive dots on the diaphragm surface. The average spacing between the adhesive dots refers to the shortest distance between the edges of two adjacent adhesive dots.

[0074] The first polymer has a large particle size, which not only has a certain adhesive force, but also forms a certain gap between the positive electrode and the separator, increasing the electrolyte transport channels in various parts of the battery, reducing the local lithium-ion breakage phenomenon caused by electrolyte consumption during cycling, ensuring the battery appearance is flat, increasing the battery liquid retention, preventing lithium deposition at the interface in the later stages of high-temperature cycling, further improving the battery's cycle capacity retention rate and alleviating battery volume expansion and gas generation.

[0075] Meanwhile, the second coating is positioned opposite the negative electrode. Adjusting the proportion of the second polymer in the second coating ensures good electrolyte wettability while preventing coating peeling or detachment during battery cycling, which could reduce the interfacial adhesion between the separator and the negative electrode. When the content of the second polymer is too high (e.g., >70%), the surface polarity of the second coating is high, resulting in excessive interfacial adhesion, which is detrimental to electrolyte wetting. Simultaneously, the separator has high static electricity, making it prone to attracting dust and impurities during cell manufacturing, potentially causing localized micro-short circuits. When the content of the second polymer is too low (e.g., <20%), the interfacial adhesion between the separator and the negative electrode is weak, making the coating prone to peeling and detachment during cycling. When the first silicon-carbon material and the second silicon-carbon material with different morphologies are mixed and combined in this invention, the first silicon-carbon material and the second silicon-carbon material form a tight stacked structure in the negative electrode active layer through the intercalation structure, which provides good mechanical stability for the negative electrode sheet and has a good bearing capacity for the volume expansion stress of the silicon-carbon negative electrode. The second coating, which is disposed opposite to the negative electrode side, has a strong interfacial adhesion to the negative electrode active layer and can form a stable interface. It can not only maintain good interfacial adhesion under the action of expansion stress, so that the particles inside the negative electrode sheet do not break, but also stably adhere to the second coating on the separator, and provide a stable electrolyte wetting channel at the separator-negative electrode interface. This helps to improve the cycle stability, rate performance and capacity of the battery, and suppress battery self-discharge.

[0076] In this invention, the area ratio of the orthographic projection of the adhesive layer onto the separator can be obtained by conventional testing methods in the art, for example, by the following steps: discharge the battery to 0% SOC, disassemble and remove the separator, clean it with anhydrous ethanol and dry it, take a 3cm × 3cm area of ​​the separator as a sample, fix the separator sample on the microscope mount to avoid displacement during the test; then, use a laser confocal microscope to take an image of the separator sample surface; use ImageJ software to perform threshold segmentation on the separator sample surface image obtained in the above steps to distinguish the covered area from the uncovered area, such as to perform quantitative analysis on the grayscale or texture difference of the separator; finally, calculate the orthographic projection area ratio of the adhesive layer within a unit separator area (10cm × 10cm) using the following formula: (number of pixels in the covered area / total number of pixels) × 100%.

[0077] In this invention, the average diameter of the adhesive dots can be obtained using conventional testing methods in the art, for example, by discharging the battery to 0% SOC, disassembling and removing the separator, cleaning it with anhydrous ethanol and drying it, obtaining a scanned image of the separator adhesive layer surface using SEM, using image analysis software such as Image Pro Plus to draw the smallest circle completely surrounding an adhesive dot on the obtained scanned image, taking its diameter as the diameter of the adhesive dot, measuring the diameter of any 50 adhesive dots, and taking the average of these measurements as the average diameter; taking the shortest distance between the outlines of any two adhesive dots as the spacing between the adhesive dots, measuring at least 20 groups of two adhesive dots each, and repeating the above operation. It should be noted that if 50 adhesive dots can be observed in the captured image, the average of any 50 adhesive dots in that image is taken as the average diameter of the adhesive dots; if no 50 adhesive dots are observed in the image, multiple images are captured, and the average of the total 50 adhesive dots is taken as the average diameter.

[0078] In this invention, the battery includes an electrolyte, the electrolyte includes a sulfur-containing additive, and the sulfur-containing additive includes at least one of the following structural formulas: (Formula 1) (Formula 2) (Equation 3) and (Equation 4)

[0079] In one embodiment, based on the total mass of the electrolyte, the mass content of the sulfur-containing additive is 2% to 7%, for example, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or 7%. The mass content of the sulfur-containing additive in the electrolyte can be obtained by conventional testing methods in the art, such as by gas chromatography or gas chromatography-mass spectrometry.

[0080] Introducing sulfur-containing additives into the electrolyte, especially sulfur-containing additives as shown in Formulas 1-4, helps to promote the formation of the SEI film at the negative end. In the system of the present invention that uses a mixture of first silicon-carbon material and second silicon-carbon material, the sulfur-containing additives can generate an SEI film that is compatible with the first silicon-carbon material and the second silicon-carbon material, thereby further improving the cycle stability of the battery.

[0081] In this invention, the electrolyte further includes a solvent, a lithium salt, and additives. The lithium salt may include at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(trifluorosulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium dioxaborate (LiBOB), lithium difluorooxaborate (LiDFOB), and lithium perchlorate (LiClO4). The solvent may include at least one of cyclic carbonates (such as ethylene carbonate (EC), propylene carbonate (PC), etc.), chain carbonates (such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc.), carboxylic acid esters (such as methyl acetate (MA), ethyl acetate (EA), propyl acetate (MP), ethyl propionate (EP), propyl propionate (PP), etc.) and other solvents (such as sulfolane (SL), fluoroethylene carbonate (FEC), vinylene carbonate (VC), etc.). The additive may include at least one of vinylene carbonate (VC), ethyl difluorocarbonate (DFEA), fluoroethylene carbonate (FEC), ethylene sulfate (PS), trimethyl phosphate (TMP), adiponitrile (ADN), succinate (SN), and 1,3,6-hexanetrionitrile (HTCN).

[0082] In this invention, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the surface of the positive current collector. The positive active layer includes a positive active material, which includes at least one of lithium cobalt oxide (LCO), nickel cobalt manganese ternary material (NCM), nickel cobalt aluminum ternary material (NCA), nickel cobalt manganese aluminum quaternary material (NCMA), lithium iron phosphate (LFP), lithium manganese phosphate (LMP), lithium vanadium phosphate (LVP), lithium manganese oxide (LMO), lithium nickel oxide, lithium nickel manganese oxide binary material, lithium-rich manganese-based material, and lithium manganese iron phosphate.

[0083] In one embodiment, the positive electrode active material includes lithium cobalt oxide.

[0084] In this invention, the negative electrode sheet further includes a negative electrode conductive agent, which includes carbon black and / or carbon nanotubes, and the carbon nanotubes may be multi-walled carbon nanotubes.

[0085] In this invention, the diameter of the carbon nanotubes is 5nm to 50nm, for example, 5nm, 6nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, or 50nm. The aspect ratio of the carbon nanotubes is 500 to 2000, for example, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1600, 1800, or 2000.

[0086] The diameter of the carbon nanotube refers to its outer diameter.

[0087] Carbon nanotubes with aspect ratios within the aforementioned range exhibit higher mechanical strength, which is beneficial for buffering the lithium intercalation expansion of silicon-carbon particles. They can also be dispersed within the negative electrode active layer, bridging the silicon-carbon material, graphite, and binder to form a dense conductive network, thereby improving the overall conductivity of the negative electrode. Combined with the first and second silicon-carbon materials of this invention, the mechanical stability and conductivity of the negative electrode can be further improved, thereby enhancing the rate performance and cycle stability of the battery.

[0088] In this invention, the term "0%SOC" refers to a discharge at 0.1C to the lower limit voltage (e.g., 3.0V).

[0089] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0090] 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.

[0091] In the following examples, unless otherwise specified, all materials used are commercially available analytical grade.

[0092] The following examples illustrate the battery of the present invention.

[0093] Example 1: (1) Preparation of the positive electrode: Lithium cobalt oxide, PVDF, acetylene black, and carbon nanotubes (CNTs) were mixed in a mass ratio of 96:2:1.5:0.5 and then added to N-methylpyrrolidone (NMP) solvent. The mixture was stirred under vacuum for 5 hours to ensure the uniformity of the slurry, and the resulting positive electrode slurry was coated onto both sides of an aluminum foil. The slurry was then dried in a vacuum drying oven at 120°C for 8 hours, and finally rolled and slit to obtain the positive electrode sheet.

[0094] (2) Preparation of the negative electrode: A first silicon-carbon material (α = 135°, average particle size = 8.7 μm), a second silicon-carbon material (N = 6 lines, 14 faces, the included angle between any two intersecting edges is 120°, average particle size = 5.5 μm), artificial graphite, sodium carboxymethyl cellulose (CMC-Na), polyacrylonitrile-butyl acrylate copolymer, and carbon nanotubes (diameter = 35 nm, aspect ratio = 1562) were mixed in a mass ratio of 9:11:76.5:1.6:1.6:0.3, and NMP was added and stirred. The negative electrode slurry is mixed and then evenly coated onto both sides of the copper foil using a coating machine to form the first and second negative electrode active layers. After drying at 89°C for 12 hours, the negative electrode sheet is obtained by rolling and slitting. The negative electrode sheet is then processed using a special roller with protrusions to form several concave parts on the surface of the first negative electrode active layer and several convex parts on the surface of the second negative electrode active layer. The width of the concave parts is 3 mm, the depth is 25 μm, and the spacing is 2.5 mm. The width of the convex parts is 3 mm, the depth is 25 μm, and the spacing is 2.5 mm.

[0095] The α / N ratio is 22.5. All silicon-carbon materials have a carbon coating layer on their surface, with a thickness of 26 nm. The content of porous carbon matrix, silicon, and carbon coating layer in the silicon-carbon material is 47%, 50%, and 3%, respectively. The specific surface area of ​​the percarbonized material is 0.82 m². 2 / g, pore volume is 0.0011cm³ 3 / g, true density is 1.97cm³ 3 / g, the silicon content in the negative electrode active layer is 9.7%.

[0096] (3) Preparation of electrolyte: Under the protection of argon atmosphere, PC, EP, PP and DEC are mixed in a weight ratio of 2:1:3:3 to obtain a solvent. Based on the total weight of the electrolyte, 12% FEC, 4.6% sulfur-containing additive (Formula 4), 3.5% HTCN and 12% lithium hexafluorophosphate (LiPF6) are added and stirred evenly to obtain the electrolyte.

[0097] (4) Preparation of the diaphragm: PVDF and organic solvent DMAC were blended and thoroughly stirred to dissolve. Boehmite was then added and stirred to disperse evenly to obtain a mixed slurry with a solid content of 8% by mass. The mass ratio of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) to filler particles was 4:6. The mixed slurry was coated onto the first surface of a polyethylene (PE) porous base film using a gravure roller. The organic solvent was extracted in a water bath to create pores, and then the film was dried in a multi-section oven at 60°C to form a second coating.

[0098] A ceramic slurry with a solid content of 35% by mass is obtained by blending alumina, polyacrylate, carboxymethyl cellulose (CMC), sodium dodecylbenzenesulfonate, and deionized water. The mass ratio of alumina, polyacrylate, CMC, and sodium dodecylbenzenesulfonate is 94.5:5:0.4:0.1 based on 100% solid mass. After thorough stirring and dispersion, the slurry is coated onto the second surface of a porous base film using a gravure roller and dried in a multi-section oven at 60°C to form a heat-resistant layer.

[0099] Weigh out polymethyl methacrylate (PMMA) powder, styrene-butadiene latex (adhesive), n-butanol (dispersant), sodium carboxymethyl cellulose (thickener), and ethylene oxide polymer (surfactant) in a ratio of 15:2.5:1:1.5:0.2 (mass ratio). Add deionized water and stir for 10 minutes. Heat to 50°C and mix thoroughly to obtain a slurry with a viscosity of 2 Pa·s and a solid content of 20.2%. Apply the water-based PMMA granular adhesive layer to the heat-resistant layer and substrate surface using a multi-point spraying method. The coating thickness is 2 μm. In the dot-coated adhesive layer, the average diameter of the adhesive dots is 163 μm, the average spacing between adjacent adhesive dots is 132 μm, and the proportion of the orthogonal projection area of ​​the adhesive layer on the membrane surface is 25%.

[0100] (5) Battery fabrication: The obtained positive electrode sheet, separator and negative electrode sheet are stacked in sequence, wound into a bare cell and then packed into an aluminum-plastic composite film and sealed. The first coating of the separator is opposite to the positive electrode and the second coating is opposite to the negative electrode. Electrolyte is injected under vacuum conditions and vacuum sealed. The battery is obtained through standing, formation and sorting processes.

[0101] Example 2: (1) Preparation of the positive electrode: Lithium cobalt oxide, PVDF, acetylene black, and CNT were mixed in a mass ratio of 96:2:1.5:0.5 and then added to NMP solvent. The mixture was stirred under vacuum for 5 hours to ensure the uniformity of the slurry, and the resulting positive electrode slurry was coated onto both sides of an aluminum foil. The slurry was then dried in a vacuum drying oven at 120°C for 8 hours, and finally rolled and slit to obtain the positive electrode sheet.

[0102] (2) Preparation of the negative electrode: A first silicon-carbon material (α = 145°, average particle size = 7.2 μm), a second silicon-carbon material (N = 8 lines, 18 faces, the included angle between any two intersecting edges is 135°, average particle size = 2.6 μm), artificial graphite, CMC-Na, polyacrylonitrile-butyl acrylate copolymer, and carbon nanotubes (diameter = 5 nm, aspect ratio = 53) were mixed in a mass ratio of 6:14:76.5:1.6:1.6:0.3, and NMP was added and stirred to form a negative electrode slurry. The slurry is evenly coated onto both sides of the copper foil using a coating machine to form the first negative electrode active layer and the second negative electrode active layer. After drying at 89°C for 12 hours, the negative electrode sheet is obtained by rolling and slitting. The negative electrode sheet is then processed using a special roller with protrusions to form several concave parts on the surface of the first negative electrode active layer and several convex parts on the surface of the second negative electrode active layer. The width of the concave parts is 0.5 mm, the depth is 3 μm, and the spacing is 0.8 mm. The width of the convex parts is 0.5 mm, the depth is 3 μm, and the spacing is 0.8 mm.

[0103] The α / N ratio is 18.1. All silicon-carbon materials have a carbon coating layer on their surface, with a thickness of 10 nm. The contents of the porous carbon matrix, silicon, and carbon coating layer in the silicon-carbon materials are 48%, 50%, and 2%, respectively. The specific surface area of ​​the percarbonized material is 0.93 m². 2 / g, pore volume is 0.0014cm³ 3 / g, true density is 1.96cm³ 3 / g, the silicon content in the negative electrode active layer is 9.7%.

[0104] (3) Preparation of electrolyte: Under the protection of argon atmosphere, PC, EP, PP and DEC are mixed in a weight ratio of 2:1:3:3 to obtain a solvent. Based on the total weight of the electrolyte, 12% FEC, 2.2% sulfur-containing additive (Formula 4), 3.5% HTCN and 12% LiPF6 are added and stirred evenly to obtain the electrolyte.

[0105] (4) Preparation of the diaphragm: PVDF and organic solvent DMAC are blended and thoroughly stirred to dissolve. Boehmite is then added and stirred to disperse evenly to obtain a mixed slurry with a solid content of 8% by mass. The mass ratio of PVDF-HFP to filler particles is 4:6. The mixed slurry is coated onto the first surface of a PE porous base film using a gravure roller. The organic solvent is extracted in a water bath to create pores, and then the film is dried in a multi-section oven at 60°C to form a second coating.

[0106] Alumina, polyacrylate, CMC, sodium dodecylbenzenesulfonate, and deionized water were blended to obtain a ceramic slurry with a solid content of 35% by mass. The mass ratio of alumina, polyacrylate, CMC, and sodium dodecylbenzenesulfonate was 94.5:5:0.4:0.1 based on 100% solid mass. After thorough stirring and dispersion, the slurry was coated onto the second surface of a porous base film using a gravure roller and dried in a multi-section oven at 60°C to form a heat-resistant layer.

[0107] Weigh PMMA powder, styrene-butadiene latex (adhesive), n-butanol (dispersant), sodium carboxymethyl cellulose (thickener), and ethylene oxide polymer (surfactant) in a ratio of 15:2.5:1:1.5:0.2 (mass ratio). Add deionized water and stir for 10 minutes. Heat to 50°C and mix thoroughly to obtain a slurry with a viscosity of 2 Pa·s and a solid content of 20.2%. Apply the water-based PMMA granule adhesive layer to the heat-resistant layer and substrate surface using a multi-point spraying method. The coating thickness is 2 μm. In the dot-coated adhesive layer, the average diameter of the adhesive dots is 52 μm, the average spacing between adjacent adhesive dots is 101 μm, and the proportion of the orthogonal projection area of ​​the adhesive layer on the membrane surface is 10%.

[0108] (5) Battery fabrication: The obtained positive electrode sheet, separator and negative electrode sheet are stacked in sequence, wound into a bare cell and then packed into an aluminum-plastic composite film and sealed. The first coating of the separator is opposite to the positive electrode and the second coating is opposite to the negative electrode. Electrolyte is injected under vacuum conditions and vacuum sealed. The battery is obtained through standing, formation and sorting processes.

[0109] Example 3: (1) Preparation of the positive electrode: Lithium cobalt oxide, PVDF, acetylene black, and CNT were mixed in a mass ratio of 96:2:1.5:0.5 and then added to NMP solvent. The mixture was stirred under vacuum for 5 hours to ensure the uniformity of the slurry, and the resulting positive electrode slurry was coated onto both sides of an aluminum foil. The slurry was then dried in a vacuum drying oven at 120°C for 8 hours, and finally rolled and slit to obtain the positive electrode sheet.

[0110] (2) Preparation of the negative electrode: A first silicon-carbon material (α = 110°, average particle size = 9.8 μm), a second silicon-carbon material (N = 6 lines, number of faces = 12, the included angle between any two intersecting edges = 110°, average particle size = 7.7 μm), artificial graphite, CMC-Na, polyacrylonitrile-butyl acrylate copolymer, and carbon nanotubes (diameter = 48 nm, aspect ratio = 1985) were mixed in a mass ratio of 10:10:76.5:1.6:1.6:0.3, and NMP was added and stirred to form a negative electrode. The slurry is evenly coated onto both sides of the copper foil using a coating machine to form the first negative electrode active layer and the second negative electrode active layer. After drying at 89°C for 12 hours, the negative electrode sheet is obtained by rolling and slitting. The negative electrode sheet is then processed using a special roller with protrusions to form several concave parts on the surface of the first negative electrode active layer and several convex parts on the surface of the second negative electrode active layer. The width of the concave parts is 7.5 mm, the depth is 47 μm, and the spacing is 5 mm. The width of the convex parts is 7.5 mm, the depth is 47 μm, and the spacing is 5 mm.

[0111] The α / N ratio is 18.3. All silicon-carbon materials have a carbon coating layer on their surface, with a thickness of 48 nm. The content of porous carbon matrix, silicon, and carbon coating layer in the silicon-carbon material is 45%, 50%, and 5%, respectively. The specific surface area of ​​the percarbonized material is 0.67 m². 2 / g, pore volume is 0.0008cm³ 3 / g, true density is 1.98cm³ 3 / g, the silicon content in the negative electrode active layer is 9.7%.

[0112] (3) Preparation of electrolyte: Under the protection of argon atmosphere, PC, EP, PP and DEC are mixed in a weight ratio of 2:1:3:3 to obtain a solvent. Based on the total weight of the electrolyte, 12% FEC, 6.7% sulfur-containing additive (Formula 4), 3.5% HTCN and 12% LiPF6 are added and stirred evenly to obtain the electrolyte.

[0113] (4) Preparation of the diaphragm: PVDF and organic solvent DMAC are blended and thoroughly stirred to dissolve. Boehmite is then added and stirred to disperse evenly to obtain a mixed slurry with a solid content of 8% by mass. The mass ratio of PVDF-HFP to filler particles is 4:6. The mixed slurry is coated onto the first surface of a PE porous base film using a gravure roller. The organic solvent is extracted in a water bath to create pores, and then the film is dried in a multi-section oven at 60°C to form a second coating.

[0114] Alumina, polyacrylate, CMC, sodium dodecylbenzenesulfonate, and deionized water were blended to obtain a ceramic slurry with a solid content of 35% by mass. The mass ratio of alumina, polyacrylate, CMC, and sodium dodecylbenzenesulfonate was 94.5:5:0.4:0.1 based on 100% solid mass. After thorough stirring and dispersion, the slurry was coated onto the second surface of a porous base film using a gravure roller and dried in a multi-section oven at 60°C to form a heat-resistant layer.

[0115] Weigh PMMA powder, styrene-butadiene latex (adhesive), n-butanol (dispersant), sodium carboxymethyl cellulose (thickener), and ethylene oxide polymer (surfactant) in a ratio of 15:2.5:1:1.5:0.2 (mass ratio). Add deionized water and stir for 10 minutes. Heat to 50°C and mix thoroughly to obtain a slurry with a viscosity of 2 Pa·s and a solid content of 20.2%. Apply the water-based PMMA granule adhesive layer to the heat-resistant layer and substrate surface using a multi-point spraying method. The coating thickness is 2 μm. In the dot-coated adhesive layer, the average diameter of the adhesive dots is 197 μm, the average spacing between adjacent adhesive dots is 485 μm, and the proportion of the orthogonal projection area of ​​the adhesive layer on the diaphragm surface is 5%.

[0116] (5) Battery fabrication: The obtained positive electrode sheet, separator and negative electrode sheet are stacked in sequence, wound into a bare cell and then packed into an aluminum-plastic composite film and sealed. The first coating of the separator is opposite to the positive electrode and the second coating is opposite to the negative electrode. Electrolyte is injected under vacuum conditions and vacuum sealed. The battery is obtained through standing, formation and sorting processes.

[0117] Example 4 group: This set of examples is used to verify the impact of changes in "α / N", as detailed below: Example 4a is based on Example 1, except that α is 62° in the first silicon-carbon material and N is 8 in the second silicon-carbon material, with 20 faces. Example 4b is based on Example 1, except that α is 149° in the first silicon-carbon material and N is 6 in the second silicon-carbon material, with 4 faces.

[0118] Example 5 group: This set of examples is used to verify the impact of changes in the "quantity ratio of the first silicon-carbon material and the second silicon-carbon material", as detailed below: Example 5a, based on Example 1, except that the negative electrode slurry is formed by mixing a first silicon carbide material, a second silicon carbide material, artificial graphite, CMC-Na, polyacrylonitrile-butyl acrylate copolymer and carbon nanotubes in a mass ratio of 12:8:76.5:1.6:1.6:0.3, and then adding NMP and stirring. Example 5b is based on Example 1, except that the negative electrode slurry is formed by mixing a first silicon carbide material, a second silicon carbide material, artificial graphite, CMC-Na, polyacrylonitrile-butyl acrylate copolymer and carbon nanotubes in a mass ratio of 4:16:76.5:1.6:1.6:0.3 and adding NMP and stirring.

[0119] Example 6: Based on Example 1, the difference is that a plurality of protrusions are formed on the surface of the first negative electrode active layer and a plurality of concave portions are formed on the surface of the second negative electrode active layer.

[0120] Example 7: Based on Example 1, the difference is that the negative electrode slurry is formed by mixing a first silicon-carbon material, a second silicon-carbon material, artificial graphite, CMC-Na, SBR and carbon nanotubes in a mass ratio of 9:11:76.5:1.6:1.6:0.3, and then adding deionized water and stirring.

[0121] Example 8 group: This set of examples is used to verify the impact of changes in the "adhesive dot settings". It is based on Example 1, except that the adhesive dots are not dot matrix coatings and are unevenly distributed, as detailed below: Example 8a is based on Example 1, except that the diameter and spacing of the adhesive dots are not unique, and the area of ​​the adhesive layer projected onto the diaphragm surface accounts for 25%. Example 8b is based on Example 1, except that the diameter and spacing of the adhesive dots are not unique, and the area of ​​the adhesive layer projected onto the diaphragm surface accounts for 79%. Example 8c is based on Example 1, except that the diameter and spacing of the adhesive dots are not unique, and the area of ​​the adhesive layer projected onto the diaphragm surface accounts for 82%.

[0122] Example 9: Based on Example 1, the difference is that the first coating of the diaphragm is opposite to the negative electrode, and the second coating is opposite to the positive electrode.

[0123] Example 10 group: This set of examples is used to verify the impact of changes in "sulfur-containing additives", as detailed below: Example 10a is based on Example 1, except that the sulfur-containing additive is replaced by the compound shown in Formula 4 with an equal mass of the compound shown in Formula 1; Example 10b is based on Example 1, except that the sulfur-containing additive is replaced by the compound shown in Formula 4 with an equal mass of the compound shown in Formula 2; Example 10c is based on Example 1, except that the sulfur-containing additive is replaced by the compound shown in Formula 4 with an equal mass of the compound shown in Formula 3; Example 10d is based on Example 1, except that the sulfur-containing additive is replaced by an equal mass of 1,3-propanesulfonate lactone instead of the compound shown in Formula 4.

[0124] Example 11 group: This set of examples is used to verify the impact of changes in the "mass content of silicon in the negative electrode active layer", as detailed below: Example 11a, based on Example 1, except that the negative electrode slurry is obtained by mixing a first silicon-carbon material, a second silicon-carbon material, artificial graphite, CMC-Na, polyacrylonitrile-butyl acrylate copolymer, and carbon nanotubes in a mass ratio of 2.25:2.75:91.5:1.6:1.6:0.3. In this case, the contents of porous carbon matrix, silicon element, and carbon coating layer in the silicon-carbon material are 57%, 40%, and 3%, respectively, and the content of silicon element in the negative electrode active layer is 1.9%. Example 11b is based on Example 1, except that the negative electrode slurry is obtained by mixing a first silicon-carbon material, a second silicon-carbon material, artificial graphite, CMC-Na, polyacrylonitrile-butyl acrylate copolymer and carbon nanotubes in a mass ratio of 36:44:16.5:1.6:1.6:0.3. In this case, the contents of porous carbon matrix, silicon element and carbon coating layer in the silicon-carbon material are 37%, 60% and 3% respectively, and the content of silicon element in the negative electrode active layer is 46.3%.

[0125] Example 12 group: This set of examples is used to verify the impact of changes in "filler particles in the second coating of the diaphragm", as detailed below: Example 12a is based on Example 1, except that the filler particles are replaced with boehmite of the same mass fraction. Example 12b is based on Example 1, except that the filler particles are replaced with an equal mass fraction of melamine cyanurate instead of boehmite.

[0126] Comparative Example 1: This set of proportions is used to verify the impact of changes in "α / N", as detailed below: Comparative Example 1a is based on Example 1, except that α is 52° in the first silicon-carbon material; Comparative Example 1b is based on Example 2, except that α is 163° in the first silicon-carbon material; Comparative Example 1c is based on Example 4a, except that the second silicon-carbon material has 5 N lines and 6 faces. Comparative Example 1d is based on Example 4a, except that the second silicon-carbon material has 10 N lines and 22 faces.

[0127] Comparative Example 2: This set of comparative models is used to verify the impact of changes in "silicon-carbon materials", as detailed below: Comparative Example 2a, based on Example 1, except that the negative electrode slurry was prepared by mixing a first silicon-carbon material, artificial graphite, CMC-Na, polyacrylonitrile-butyl acrylate copolymer and carbon nanotubes in a mass ratio of 20:76.5:1.6:1.6:0.3. Comparative Example 2b is based on Example 1, except that the negative electrode slurry is prepared by mixing a second silicon carbide material, artificial graphite, CMC-Na, polyacrylonitrile-butyl acrylate copolymer and carbon nanotubes in a mass ratio of 20:76.5:1.6:1.6:0.3. Comparative Example 2c, based on Example 1, differs in that the negative electrode slurry is obtained by mixing spherical silicon carbon, bulk silicon carbon, artificial graphite, CMC-Na, polyacrylonitrile-butyl acrylate copolymer and carbon nanotubes in a mass ratio of 10:10:76.5:1.6:1.6:0.3, wherein the spherical silicon carbon and bulk silicon carbon are conventional materials in the art.

[0128] Comparative Example 3: Based on Example 1, the difference is that the average particle size of the first silicon-carbon material is 5.5 μm and the average particle size of the second silicon-carbon material is 8.7 μm.

[0129] It should be noted that in Examples 1 to 11, the included angle between any two intersecting edges of the second silicon-carbon material is greater than or equal to 90°.

[0130] Test example: (1) Cyclic capacity retention: The batteries obtained in the embodiments and comparative examples of this invention were charged at 0.7C constant current and constant voltage to 4.53V at 25℃±2℃, cut off at 0.05C, and then discharged at 0.2C constant current to 3.0V. The initial discharge capacity was recorded as C0. After resting for 10 minutes, the cycle was as follows: 3C constant current and constant voltage charging to 4.25V, cut off at 2C, then 2C constant current and constant voltage charging to 4.48V, cut off at 1.5C, then 1.5C constant current and constant voltage charging to 4.53V, cut off at 0.18C, rested for 5 minutes, and then discharged at 0.7C to 3.0V. After 800 cycles, the batteries were charged at 0.7C constant current and constant voltage to 4.53V, cut off at 0.05C, and then discharged at 0.2C constant current to 3.0V. The discharge capacity at this point was recorded as C1. The test results are recorded in Table 1. Capacity retention rate: C=(C1 / C0)×100%. The results are recorded in Table 1.

[0131] (2) Ratio performance: The batteries obtained in the embodiments and comparative examples of the present invention were tested for rate performance using a Xinwei battery tester at an environment of 25℃±2℃, according to the following steps: (i) Charge at 0.2C to the upper limit voltage of 4.53V (cutoff at 0.02C), then discharge at 0.2C to the lower limit voltage of 3.0V, and record the discharge capacity as Q1; (ii) Charge at 0.2C to the upper limit voltage of 4.53V (cutoff at 0.02C), then discharge at 0.5C to the lower limit voltage of 3.0V, and record the discharge capacity as Q2; (iii) The capacity retention rate of the battery at a 0.5C discharge rate is Q2 / Q1. The higher the capacity retention rate, the better the battery's rate performance. The results are recorded in Table 1.

[0132] (3) Self-discharge test: The batteries obtained in the embodiments and comparative examples of this invention were charged to 4.53V at a constant current and constant voltage of 1C at an environment of 25℃±2℃, cut off at 0.02C, and left to stand for 5 minutes. The open-circuit voltage OCV1 (unit: volts V) of the battery was then tested. The batteries were then left to stand open-circuit for 24 hours at (25±2)℃, and the voltage OCV2 after the standby was tested. The self-discharge coefficient K value of the battery was calculated as: K = (OCV1 - OCV2) / 24. The normal range for the self-discharge coefficient K value is -0.02 to 0.08. Batteries exceeding this range are considered to have a poor K value. The total number of battery samples tested was 50. The K value yield results are recorded in Table 1.

[0133] Table 1: As can be seen from Table 1, the lithium-ion battery prepared by this invention, compared with the comparative example, balances rate performance, cycle stability and high K-value yield.

[0134] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The battery includes a negative electrode sheet, the negative electrode sheet includes a negative current collector and a negative active layer located on at least one side surface of the negative current collector, the negative active layer includes a negative active material, the negative active material includes a silicon-carbon material, and the silicon-carbon material includes a first silicon-carbon material and a second silicon-carbon material. The cross-sectional profile of the first silicon-carbon material includes at least two included angles, the average angle of which is α, and α is 60°~150°; The second silicon-carbon material has a plurality of edges and faces formed by the edges, the number of edges forming the faces is N, N≥6 and N is an integer, the included angle between any two intersecting edges is greater than or equal to 90°, and the number of faces is greater than or equal to 4. α and N satisfy: 7.5 ≤ α / N ≤ 25; The average particle size of the first silicon-carbon material is greater than that of the second silicon-carbon material.

2. The battery according to claim 1, wherein, α and N satisfy: 18 ≤ α / N ≤ 23; And / or, the number of the first silicon-carbon materials accounts for 30% to 50% of the total number of silicon-carbon materials; And / or, the number of the second silicon-carbon material accounts for 50% to 70% of the total number of silicon-carbon materials; Preferably, the average particle size of the first silicon-carbon material is 7 μm to 10 μm; Preferably, the average particle size of the second silicon-carbon material is 2 μm to 8 μm.

3. The battery according to claim 1 or 2, wherein, The silicon-carbon material includes a porous carbon matrix and silicon particles located in the pores inside the porous carbon matrix. Preferably, at least a portion of the outer surface of the silicon-carbon material is provided with a coating layer; More preferably, the coating layer comprises amorphous carbon.

4. The battery according to claim 3, wherein, Based on the total mass of the silicon-carbon material, the mass content of the porous carbon matrix is ​​38%~55%; And / or, based on the total mass of the silicon-carbon material, the mass content of silicon element is 40% to 60%; And / or, based on the total mass of the silicon-carbon material, the mass content of the coating layer is 2% to 5%; And / or, based on the total mass of the negative electrode active layer, the mass content of silicon element is 1% to 50%.

5. The battery according to claim 1 or 2, wherein, The negative electrode active layer includes a negative electrode binder, which includes a polyacrylonitrile-alkane acrylate copolymer. And / or, the negative electrode active layer is formed of a negative electrode active slurry, the negative electrode active slurry comprising an oily solvent; Preferably, the oily solvent includes N-methylpyrrolidone and / or dimethylacetamide.

6. The battery according to claim 1 or 2, wherein, The negative electrode active layer includes a first negative electrode active layer and a second negative electrode active layer. The first negative electrode active layer and the second negative electrode active layer are disposed opposite to each other along the thickness direction of the negative electrode sheet. The length of the first negative electrode active layer is greater than the length of the second negative electrode active layer. And / or, the outer surface of the first negative electrode active layer has a plurality of recesses, and the outer surface of the second negative electrode active layer has a plurality of protrusions, wherein the recesses correspond one-to-one with the protrusions; And / or, the depth of the recess is 3μm~50μm, the width of the recess is 0.3mm~8mm, and the spacing between the recesses is 0.5mm~5mm.

7. The battery according to claim 1 or 2, wherein, The battery also includes a separator, which includes a base film, a first coating on one side of the base film, and a second coating on the other side of the base film. And / or, the first coating includes a heat-resistant layer and an adhesive layer, the heat-resistant layer being located between the base film and the adhesive layer; Preferably, the battery further includes a positive electrode, with the first coating and the positive electrode facing each other, and the second coating and the negative electrode facing each other.

8. The battery according to claim 7, wherein, The adhesive layer includes a first polymer, which comprises a polymer formed by polymerizing one or more of the following monomers: styrene, ethylene, propylene, acrylonitrile, methyl methacrylate, butyl acrylate, isooctyl acrylate, octadecyl acrylate, ethyl acrylate, amide, and imide. And / or, the second coating comprises filler particles and a second polymer, the second polymer comprising a polymer formed by polymerizing one or more of the following monomers: vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene; Preferably, the filler particles include at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, barium titanate, 1,3,5-triazine-2,4,6-triamine, melamine cyanurate, and melamine trithiocyanate. Preferably, the mass content of the second polymer is 20% to 70% based on the total mass of the second coating.

9. The battery according to claim 7, wherein, The area of ​​the adhesive layer projected onto the diaphragm accounts for 5% to 80% of the total area. And / or, the adhesive layer comprises a plurality of adhesive dots, the average diameter of which is 50 μm to 200 μm; And / or, the average spacing between the adhesive dots is 100μm~500μm.

10. The battery according to claim 1 or 2, wherein, The battery includes an electrolyte, the electrolyte including a sulfur-containing additive, the sulfur-containing additive comprising at least one of the following structural formulas: , , and ; Preferably, the mass content of the sulfur-containing additive is 2% to 7% based on the total mass of the electrolyte.

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