Method for improving decarburization of R angle of inner ring of high-surface-density wound lithium battery
By using a linear polyacrylic acid and styrene-butadiene rubber compound binder and a winding tension reduction process, the problem of decarburization at the inner R-angle of high areal density lithium batteries was solved, resulting in improved battery energy density and cycle performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHU ETC BATTERY LTD
- Filing Date
- 2026-01-27
- Publication Date
- 2026-05-05
AI Technical Summary
When high areal density lithium batteries are fully charged, the coating on the outer side of the inner circle R-corner decarbonizes due to tensile stress, leading to capacity decay and safety hazards. Existing technologies have not been able to effectively solve this problem.
A linear polyacrylic acid and styrene-butadiene rubber compound binder system is used, combined with a winding tension reduction process, to optimize the compaction density of the negative electrode slurry and electrode sheet, forming a stable interface and a flexible coating structure to prevent decarburization.
Without sacrificing safety and lifespan, the battery energy density has been improved, the inner ring R-corner coating has been effectively prevented from peeling off, and the battery's cycle performance and safety have been improved.
Smart Images
Figure CN121983679A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a method for improving the decarburization of the inner ring R-angle of a high areal density wound lithium battery. Background Technology
[0002] In lithium-ion battery technology, improving energy density is one of the core driving forces for its development. Increasing the areal density of electrode active materials is a direct and effective means to improve the volumetric energy density and gravimetric energy density of the battery. However, when the areal density is increased to a certain critical value (for example, for the LFP-C system, the negative electrode > 195 g / m³), a limit is reached. 2 During long-term cycling, especially at full charge (100% SOC), a new and severe failure mode emerges in batteries. This mode manifests as follows: after disassembling a faulty cell, a large area of active material coating peels off from the outer surface of the electrode sheet (the side furthest from the winding needle) in the arc-shaped transition region (R-angle) of the innermost winding (the starting point of the winding). For graphite negative electrodes, this phenomenon is known as "decarburization." This problem not only leads to a sharp decrease in capacity but also poses a serious safety hazard because the exposed current collector may cause an internal short circuit.
[0003] Existing technologies typically seek improvements from a single perspective, such as fine-tuning the amount of binder, optimizing the rolling process, or adjusting the winding tension. However, in-depth research and mechanistic analysis have revealed that the root cause of the decarburization problem at the R-corner under high areal density lies in the mismatch between the mechanical properties of the electrode and the internal mechanical stress of the cell. The failure principle is as follows: Increased areal density leads to a significant increase in the thickness and stiffness of the electrode. During full charge, the graphite negative electrode undergoes a large volume expansion (up to 10% or more), resulting in a huge radial expansion force throughout the core. The expansion of the outer electrode compresses inward and generates a bending moment on the innermost electrode, attempting to "spread" it out. This forces the radius of curvature of the inner electrode to increase. During this process, the outer surface coating of the inner R-corner is subjected to extremely high circumferential tensile stress. This stress exceeds the tensile strength of the coating and its adhesion to the current collector under traditional designs, ultimately leading to brittle fracture or interface peeling of the coating. To solve the above problems, a method for improving the decarburization of the inner R-corner of high areal density wound lithium batteries is proposed. Summary of the Invention
[0004] The purpose of this invention is to solve the problem of decarburization on the outer side of the inner circle R-corner of a high areal density electrode when fully charged, thereby achieving an effective improvement in battery energy density without sacrificing safety and lifespan. A method for improving decarburization of the inner circle R-corner of a high areal density wound lithium battery is proposed.
[0005] A method for improving carbon decarburization at the inner radius (R-angle) of a high areal density wound lithium battery includes the following steps: S1. Preparation of negative electrode slurry: The negative electrode active material, conductive agent, binder, dispersant and solvent are mixed to prepare a negative electrode slurry, wherein the binder is a compound of linear polyacrylic acid and styrene-butadiene rubber, and the proportion of the binder in the negative electrode slurry is 1.5%-2.5%; S2. Preparation of negative electrode sheet: The negative electrode slurry is coated onto the current collector, dried, and rolled to obtain the negative electrode sheet. The compacted density of the negative electrode sheet is controlled at 1.45 g / cm³. 3 Up to 1.52 g / cm 3 between; S3, wound cell: The negative electrode sheet, positive electrode sheet, and separator are wound together to form a wound cell by using a method of decreasing winding tension.
[0006] Preferably, in step S1, the method for preparing the negative electrode slurry includes: (1) First, dry mix the negative electrode active material, dispersant and conductive agent, and stir at a low speed of 15-20 rpm for 30 minutes to achieve preliminary uniform mixing through mechanical friction; (2) Then add binder and some solvent, control the solid content of slurry at 66% to 68%, disperse at 20 rpm for 60 min, so that the large particles in the powder material are broken into small particles; (3) Add the remaining solvent and control the solid content of the slurry to 49% to 54%. Disperse at high speed of 1200-1800 rpm for 120 min to ensure that each component is fully dispersed in water and forms a stable suspension.
[0007] Preferably, the ratio of negative electrode active material, conductive agent, binder, dispersant and solvent in the negative electrode slurry is 96.8:0.5:2.2:0.5:100.
[0008] Preferably, the ratio of linear polyacrylic acid to styrene-butadiene rubber in the adhesive is 1.7:0.5.
[0009] Preferably, the negative electrode active material is graphite, and the conductive agent is conductive carbon black.
[0010] Preferably, the dispersant is sodium carboxymethyl cellulose and the solvent is deionized water.
[0011] Preferably, in step S2, the current collector is an ultra-thin electrolytic copper foil of 5-6 μm.
[0012] Preferably, in step S3, the winding tension is reduced in the following manner: when the innermost 5 to 10 turns are wound, the winding tension is linearly reduced from the initial tension value F1 to between 0.3F1 and 0.5F1.
[0013] The present invention also proposes a lithium-ion battery prepared by the above method.
[0014] Compared with existing technologies, the advantages of this invention are: 1. This invention solves the problem of powder shedding and decarbonization caused by tensile stress on the outer coating of the innermost R-corner of the cell under high areal density by deeply coupling material system optimization and manufacturing process control, ensuring the structural integrity of the electrode sheet, so that the battery can achieve higher energy density without sacrificing its cycle life and safety performance.
[0015] 2. This invention uses a combination of linear PAA binder and high-elasticity SBR binder to form a stable interface, which effectively prevents decarbonization and helps to improve battery cycle life. The improvement measures can all be implemented on existing battery production lines without major equipment investment, making it easy to promote and apply quickly. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the process of the present invention.
[0017] Figure 2 This is a photograph of the battery cell after disassembly in Embodiment 1 of the present invention.
[0018] Figure 3 This is a photograph of the battery cell after disassembly in Embodiment 2 of the present invention.
[0019] Figure 4 This is a photograph of the battery cell after disassembly in Comparative Example 1 of this invention.
[0020] Figure 5 This is a photograph of the battery cell after disassembly in Comparative Example 2 of this invention.
[0021] Figure 6 This is a photograph of the battery cell after disassembly in Comparative Example 3 of this invention.
[0022] Figure 7 This is a photograph of the battery cell after disassembly in Comparative Example 4 of this invention.
[0023] Figure 8 This is a photograph of the battery cell after disassembly in Comparative Example 5 of this invention.
[0024] Figure 9 This is a photograph of the battery cell after disassembly in Comparative Example 6 of this invention. Detailed Implementation
[0025] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.
[0026] Numerous specific details are set forth in the following description to provide a thorough understanding of this application, and preferred embodiments of this application are shown in the accompanying drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application. This application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application; therefore, this application is not limited to the specific embodiments disclosed below. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified. It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intervening element present. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementations. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is only for describing particular implementations and is not intended to be limiting of this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0027] Reference Figure 1 As shown, a method for improving the decarburization of the inner ring R-angle of a high areal density wound lithium battery includes the following steps: S1. Preparation of Negative Electrode Slurry: A negative electrode active material, conductive agent, binder, dispersant, and solvent are mixed to prepare a negative electrode slurry. The binder is a blend of linear polyacrylic acid (PAA) and styrene-butadiene rubber (SBR). The ratio of linear polyacrylic acid to SBR in the binder is 1.7:0.5. The design mechanism of this blend is to leverage the synergistic effect of the two binders: the carboxyl groups (-COOH) in the linear polyacrylic acid (PAA) molecular chain can form strong chemical bonds (-COOLi, -COO-Cu) with the oxides on the surface of graphite particles and copper current collectors. This strong chemical bond not only provides extremely high interfacial bonding strength but also constructs a stable, cross-linked three-dimensional network framework structure within the coating, significantly improving the coating's integrity, elastic modulus, and crack resistance. However, coatings formed by pure linear polyacrylic acid (PAA) systems are often excessively rigid and brittle. To address this, highly elastic styrene-butadiene rubber (SBR) is introduced as a complementary material. SBR molecular chains consist of styrene hard segments and butadiene soft segments, exhibiting excellent flexibility and resilience. It can absorb and release stress during deformation like a spring, imparting higher elongation at break and toughness to the electrode coating. By compounding linear polyacrylic acid (PAA) with SBR, a perfect combination of a "rigid skeleton" and an "elastic matrix" is achieved. This results in a coating that possesses both high strength to resist tensile stress and the ability to buffer and disperse localized stress concentrations through its own flexible deformation, fundamentally improving the structural integrity of the coating under complex stress conditions. The preferred binder dosage is 1.5%-2.5% to achieve the optimal balance between adhesion and electrochemical performance.
[0028] S2. Preparation of negative electrode sheet: The negative electrode slurry is coated onto the current collector, dried, and rolled to obtain the negative electrode sheet. The compacted density of the negative electrode sheet is controlled at 1.45 g / cm³. 3 Up to 1.52 g / cm 3 In between, this design provides space for the expansion of active material particles by retaining an appropriate amount of porosity, making the electrode change from "rigid" to "flexible". It can effectively absorb and release stress through micro-deformation, avoiding brittle peeling caused by stress concentration. S3, wound cell: The negative electrode sheet, positive electrode sheet, and separator are wound together to form a wound cell by using a method of decreasing winding tension.
[0029] In step S1, the method for preparing the negative electrode slurry includes: (1) First, the negative electrode active material, dispersant and conductive agent are dry mixed and stirred at a low speed of 15-20 rpm for 30 minutes. The initial uniform mixing is achieved through mechanical friction. This gentle mixing process avoids excessive breakage and agglomeration of the conductive agent. At the same time, the conductive agent is initially attached to the surface of the graphite particles through mechanical friction, laying the foundation for the subsequent formation of a continuous conductive network. (2) Then add binder and some solvent, control the solid content of slurry at 66% to 68%, disperse at 20 rpm for 60 min, so that the large particles in the powder material are broken into small particles. The main purpose of this stage is to break up the powder agglomeration through appropriate shear force, so that the binder can begin to wet and coat the particle surface. The relatively low rotation speed avoids the breakage of the binder molecular chain caused by excessive shear. (3) Add the remaining solvent and control the solid content of the slurry to 49% to 54%. Disperse at high speed of 1200-1800 rpm for 120 minutes to ensure that all components are fully dispersed in water and form a stable suspension. The main functions of this stage are: first, to fully disperse all components and ensure the uniformity of the slurry; second, to fully extend the molecular chains of the binder through high-speed shearing and promote its uniform distribution in the slurry; third, to break up the remaining agglomerates and refine the particle size distribution; and fourth, to adjust the rheological properties of the slurry to obtain a suitable viscosity and thixotropy for coating.
[0030] The ratio of negative electrode active material, conductive agent, binder, dispersant and solvent in the negative electrode slurry is 96.8:0.5:2.2:0.5:100. The negative electrode active material is graphite, the conductive agent is conductive carbon black (SP), the dispersant is sodium carboxymethyl cellulose, and the solvent is deionized water.
[0031] In step S2, the current collector is made of 5-6μm ultrathin electrolytic copper foil, whose excellent ductility can further help buffer stress.
[0032] In step S3, the winding tension is reduced in the following way: when the innermost 5 to 10 turns are wound, the winding tension is linearly reduced from the initial tension value F1 to between 0.3F1 and 0.5F1. This is to avoid applying excessive pre-stretch stress to the most vulnerable inner electrode during the manufacturing stage, thereby leaving a margin for the expansion and stretching stress generated when fully charged, and preventing the two from exceeding the standard by superposition.
[0033] Example 1 Negative electrode slurry preparation: Negative electrode active material, conductive agent, binder, dispersant and solvent are mixed to prepare negative electrode slurry. The ratio of negative electrode active material, conductive agent, binder, dispersant and solvent in negative electrode slurry is 96.8:0.5:2.2:0.5:100, wherein the ratio of linear polyacrylic acid (PAA) to styrene-butadiene rubber (SBR) in the binder is 1.7:0.5. The method for preparing negative electrode slurry is as follows: (1) First, dry mix the negative electrode active material, dispersant and conductive agent, and stir at low speed for 30 minutes (about 15-20 rpm) to achieve preliminary uniform mixing through mechanical friction; (2) Then add binder and some solvent, control the solid content of slurry at 66% to 68%, disperse at 20 rpm for 60 min, so that the large particles in the powder material are broken into small particles; (3) Add the remaining solvent and control the solid content of the slurry to 49% to 54%. Disperse at high speed for 120 minutes (about 1200-1800 rpm) to fully disperse each component in water and form a stable suspension.
[0034] Preparation of negative electrode sheet: The negative electrode slurry was uniformly coated onto a 6μm ultrathin copper foil, and the negative electrode sheet was obtained after drying and rolling. The negative electrode areal density was 210 g / m². 2 The compaction density of the negative electrode sheet is 1.52 g / cm³. 3 ; Winding process: The winding tension is controlled by decreasing tension. The initial tension is 4.5N. When the innermost 4 turns are wound, the tension decreases by 0.05N per turn. The negative electrode, positive electrode and separator are wound together to form the battery cell.
[0035] After the wound battery cell is charged to 100% SOC at a 1C current, it is disassembled for observation. Figure 2 As shown, the outermost R-corner (located on the left side of the figure) has a complete coating with uniform color, and only extremely small, almost invisible coating particles have peeled off at the edge (the peeled area is estimated to be less than 1%).
[0036] Example 2 The difference between Example 2 and Example 1 is that the negative electrode surface density is adjusted to 220 g / m³. 2 The compaction density of the negative electrode sheet was adjusted to 1.50 g / cm³. 3 It uses 5μm ultrathin copper foil; The negative electrode slurry composition, ratio, and preparation process are the same, and the winding process is identical. After the wound cells are charged to 100% SOC with a 1C current, they are disassembled for observation. Figure 3 As shown, after increasing the negative electrode surface density, the inner ring R angle of the cell remained intact after full charging, and no visible decarburization or powder shedding was observed.
[0037] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that only linear polyacrylic acid (PAA) was used as the adhesive, while the other processes were the same. After the wound battery cell was charged to 100% SOC at a 1C current, it was disassembled for observation. Figure 4As shown, significant coating peeling occurred on the outer side of the innermost radius corner of the coil core, exposing the bright copper foil substrate. The boundaries of the peeling area were clear, exhibiting typical interfacial adhesion failure between the coating and the current collector. This is because although the pure PAA system provides extremely high bond strength, the coating is too rigid and brittle, lacking the flexibility to adapt to deformation. Under the tensile stress generated by full-fill expansion, the brittle coating cannot release stress through deformation, leading to brittle fracture at the stress concentration point and complete peeling from the current collector. The decarburized area ratio is significantly greater than 15%.
[0038] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that only styrene-butadiene rubber (SBR) was used as the adhesive, while the other processes were the same. After the wound battery cell was charged to 100% SOC at a 1C current, it was disassembled for observation. Figure 5 As shown, obvious coating peeling also appeared on the outer side of the innermost R corner of the core, exposing the copper foil. However, unlike the whole peeling in Comparative Example 1, the peeling here may be accompanied by more powdery powder. This is because although the pure SBR system has excellent flexibility, its chemical bonding with the active material and current collector is weak, and the interfacial adhesion strength is insufficient. Under tensile stress, the coating is prone to slippage or peeling from the interface, which also cannot meet the requirements of high stress scenarios. The decarburized area ratio is greater than 10%.
[0039] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the ratio of linear polyacrylic acid (PAA) to styrene-butadiene rubber (SBR) in the binder is 1.3:0.9 (a lower ratio than in Example 1). Other processes are the same. After the wound cells are charged to 100% SOC at 1C, they are disassembled for observation. Figure 6 As shown, coating peeling occurred on the outer side of the innermost radius corner of the core. Although the situation may be slightly better than pure SBR due to the presence of a small amount of PAA, the overall strength and modulus of the coating are low due to insufficient "rigid skeleton" components, resulting in weak tensile strength. Under stress, it is still prone to excessive deformation leading to failure.
[0040] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the ratio of linear polyacrylic acid (PAA) to styrene-butadiene rubber (SBR) in the binder is 1.9:0.2 (a higher ratio than in Example 1). All other processes are the same. After the wound cells are charged to 100% SOC at 1C, they are disassembled for observation. Figure 7 As shown, some coating peeled off from the outer edge of the innermost R-angle of the core. At this point, the coating is too rigid and lacks toughness, approaching the brittle behavior of Comparative Example 1. Under cyclic stress, it is prone to microcracks that propagate, leading to localized peeling.
[0041] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the winding tension of Comparative Example 5 is 4.5N throughout the winding process, and the negative electrode sheet, positive electrode sheet, and separator are wound together to form the battery cell. The other processes are the same. After the wound battery cell is charged to 100% SOC at a 1C current, it is disassembled for observation. Figure 8 As shown, despite the use of optimized slurry and compaction density, a small amount of clear coating peeling still occurred on the outer side of the innermost R-angle of the core. This confirms that the constant high prestress applied during the manufacturing stage significantly depleted the safety margin of the inner coating stress, making it more prone to reaching the failure critical point under the subsequent superposition of full-fill expansion stress.
[0042] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the compaction density of the negative electrode sheet was adjusted to 1.80 g / cm³. 3 Other cells, using the same process, were charged to 100% SOC at a 1C current, then disassembled for observation. Figure 9 As shown, the coating peeled off on the outer side of the innermost R-angle of the core. The excessively high compaction density greatly compressed the pores of the electrode sheet, causing it to lose its flexibility and return to a "rigid" state. It could not effectively buffer the expansion stress, resulting in stress concentration and coating damage.
[0043] As can be seen from Examples 1-2 and Comparative Examples 1-6, a composite of linear polyacrylic acid (PAA) and styrene-butadiene rubber (SBR) in a ratio of 1.7:0.5 is required for good results in the binder. However, excessive compaction density and variations in the winding process can reduce the decarburization prevention effect of the negative electrode sheet. Therefore, the method of the present invention can achieve an areal density exceeding 200 g / m². 2 When fully charged, the inner R-corner area of the lithium battery remains intact, effectively preventing carbon decarbonization. At the same time, the battery exhibits excellent cycle performance and safety, providing a reliable technical path for further improving the energy density of lithium batteries.
[0044] In summary, by using a combination of high-strength linear polyacrylic acid (PAA) binder and high-elasticity styrene-butadiene rubber (SBR) binder to construct a three-dimensional reinforcing network, the coating's tensile strength and toughness are improved, enabling it to withstand greater tensile stress and adapt to greater deformation without detachment. Appropriately reducing the compaction density enhances the electrode's flexibility, allowing it to buffer and disperse stress through deformation. Furthermore, controlling the decreasing winding tension eliminates the pre-stress applied to the inner ring during manufacturing, thereby reducing the peak total stress at full charge. This provides sufficient technical margin for improving the energy density of lithium-ion batteries.
[0045] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
[0046] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.
[0047] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.
Claims
1. A method for improving carbon decarburization at the inner radius (R-angle) of a high areal density wound lithium battery, characterized in that: Includes the following steps: S1. Preparation of negative electrode slurry: The negative electrode active material, conductive agent, binder, dispersant and solvent are mixed to prepare a negative electrode slurry, wherein the binder is a compound of linear polyacrylic acid and styrene-butadiene rubber, and the proportion of the binder in the negative electrode slurry is 1.5%-2.5%; S2. Preparation of negative electrode sheet: The negative electrode slurry is coated onto the current collector, dried, and rolled to obtain the negative electrode sheet. The compacted density of the negative electrode sheet is controlled at 1.45 g / cm³. 3 Up to 1.52 g / cm 3 between; S3, wound cell: The negative electrode sheet, positive electrode sheet, and separator are wound together to form a wound cell by using a method of decreasing winding tension.
2. The method for improving carbon decarburization of the inner ring R-angle of a high areal density wound lithium battery according to claim 1, characterized in that: In step S1, the method for preparing the negative electrode slurry includes: (1) First, dry mix the negative electrode active material, dispersant and conductive agent, and stir at a low speed of 15-20 rpm for 30 min to achieve preliminary uniform mixing through mechanical friction; (2) Then add binder and some solvent, control the solid content of slurry at 66% to 68%, disperse at 20 rpm for 60 min, so that the large particles in the powder material are broken into small particles; (3) Add the remaining solvent and control the solid content of the slurry to 49% to 54%. Disperse at high speed of 1200-1800 rpm for 120 min to ensure that each component is fully dispersed in water and forms a stable suspension.
3. The method for improving carbon decarburization at the inner ring R-angle of a high areal density wound lithium battery according to claim 1, characterized in that: The ratio of negative electrode active material, conductive agent, binder, dispersant and solvent in the negative electrode slurry is 96.8:0.5:2.2:0.5:
100.
4. The method for improving decarburization of the inner ring R-angle of a high areal density wound lithium battery according to claim 1, characterized in that: The ratio of linear polyacrylic acid to styrene-butadiene rubber in the adhesive is 1.7:0.
5.
5. The method for improving carbon decarburization at the inner R-angle of a high areal density wound lithium battery according to claim 1, characterized in that: The negative electrode active material is graphite, and the conductive agent is conductive carbon black.
6. The method for improving decarburization of the inner ring R-angle of a high areal density wound lithium battery according to claim 1, characterized in that: The dispersant is sodium carboxymethyl cellulose, and the solvent is deionized water.
7. The method for improving decarburization of the inner ring R-angle of a high areal density wound lithium battery according to claim 1, characterized in that: In step S2, the current collector is an ultra-thin electrolytic copper foil of 5-6 μm.
8. The method for improving decarburization of the inner ring R-angle of a high areal density wound lithium battery according to claim 1, characterized in that: In step S3, the winding tension is reduced in the following way: when the innermost 5 to 10 turns are wound, the winding tension is linearly reduced from the initial tension value F1 to between 0.3F1 and 0.5F1.
9. A lithium-ion battery, characterized in that, It is prepared by the method described in any one of claims 1-8.