Lithium-ion battery and preparation method therefor
By controlling the particle size of the positive and negative active materials and the conductivity of the electrolyte, the structure and composition of lithium-ion batteries are optimized, solving the problem of high polarization in lithium-ion batteries and achieving high-efficiency discharge and stability of the batteries at high rates.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- EVE ENERGY CO LTD
- Filing Date
- 2025-08-22
- Publication Date
- 2026-07-09
AI Technical Summary
Existing lithium-ion batteries have a high degree of polarization, which affects their discharge capacity under high-rate loads.
By controlling the particle size of the positive and negative electrode active materials, the conductivity of the electrolyte, and combining appropriate slurry composition and preparation process, the structure and composition of lithium-ion batteries can be optimized to reduce electrochemical, ohmic, and diffusion polarization.
It significantly reduces the polarization of lithium-ion batteries, improves the battery's voltage retention and discharge capacity under high-rate loads, and enhances the battery's cycle stability and charge/discharge efficiency.
Smart Images
Figure PCTCN2025116452-APPB-I100001
Abstract
Description
Lithium-ion batteries and their preparation methods
[0001]
[0002] Priority information
[0003] This application claims priority to patent application No. 202412000209.4, filed with the China National Intellectual Property Administration on December 31, 2024, the entire contents of which are incorporated herein by reference as if copied herein. Technical Field
[0004] This application relates to the field of lithium-ion battery technology, and more specifically, to a lithium-ion battery and a method for preparing the same. Background Technology
[0005] The polarization of lithium-ion batteries can be used as a way to evaluate battery performance. The presence of polarization significantly affects the battery's discharge capacity under high-rate loads. Under high-rate discharge conditions, the smaller the battery polarization, the higher the initial voltage, thus allowing for greater capacity release. To meet the demands of higher power applications, more and more researchers are focusing on reducing lithium-ion battery polarization. Technical issues
[0006] Current research still needs to improve its effectiveness in reducing polarization in batteries. Technical solutions
[0007] The main objective of this application is to provide a lithium-ion battery and its preparation method to solve the problem of high polarization in existing lithium-ion batteries.
[0008] To achieve the above objectives, according to one aspect of this application, a lithium-ion battery is provided, comprising a positive electrode, an electrolyte, and a negative electrode. The positive electrode includes a positive active layer containing a positive active material with a D50 particle size of 4-10 μm. The negative electrode includes a negative active layer containing a negative active material with a D50 particle size of 10-20 μm. The electrolyte has a conductivity of 10.0-12.0 mS / cm.
[0009] According to another aspect of this application, a method for preparing the aforementioned lithium-ion battery is provided, the method comprising: step S1, mixing a positive electrode active material, a conductive agent, a first binder, and a first organic solvent to obtain a positive electrode slurry; step S2, mixing a negative electrode active material, a second binder, a thickener, and a second organic solvent to obtain a negative electrode slurry; step S3, coating the positive electrode slurry onto a current collector, and obtaining a positive electrode sheet after drying, rolling, and punching, and coating the negative electrode slurry onto the current collector, and obtaining a negative electrode sheet after drying, rolling, and punching; step S4, sequentially stacking the negative electrode sheet, a separator, and a positive electrode sheet to obtain a core; and step S5, loading the core into an aluminum-plastic packaging shell, injecting electrolyte into the aluminum-plastic packaging shell, and performing formation to obtain a lithium-ion battery. Beneficial effects
[0010] Applying the technical solution of this application, the polarization of lithium-ion batteries mainly includes electrochemical polarization, ohmic polarization, and diffusion polarization. Excessively large particle sizes increase the distance lithium ions need to reach the surface, while excessively small particle sizes may lead to a decrease in the mechanical properties of the material. Controlling the particle sizes of the positive and negative active materials within the aforementioned range helps shorten the lithium-ion diffusion path, thereby accelerating the insertion and extraction processes of lithium ions in the positive and negative active materials. It also helps improve the reactivity and contact area of the positive and negative active materials, thus reducing the resistance to lithium-ion transport within them, and consequently reducing electrochemical polarization. High conductivity of the electrolyte means better ion transport capabilities, enabling more effective support for rapid charge and discharge processes and reducing voltage drops caused by internal battery resistance. However, excessively high conductivity means faster ion movement in the electrolyte, which may lead to an exacerbation of side reactions. Controlling the electrolyte conductivity within the aforementioned range helps to improve electrolyte stability while accelerating lithium-ion migration, thereby reducing ohmic and diffusion polarization in lithium-ion batteries. However, as a whole, improvements to a single factor in a lithium-ion battery have limited impact on reducing polarization. This application simultaneously improves the particle size of the positive electrode active material, the particle size of the negative electrode active material, and the conductivity of the electrolyte. Through synergistic effects, these three factors significantly reduce polarization in lithium-ion batteries. Embodiments of the present invention
[0011] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.
[0012] As analyzed in the background section of this application, lithium-ion batteries in the prior art have a high degree of polarization. In order to solve this problem, this application provides a lithium-ion battery and a method for preparing the same.
[0013] In a typical embodiment of this application, a lithium-ion battery is provided, comprising a positive electrode, an electrolyte, and a negative electrode. The positive electrode includes a positive active layer containing a positive active material with a D50 particle size of 4-10 μm. The negative electrode includes a negative active layer containing a negative active material with a D50 particle size of 10-20 μm. The electrolyte has a conductivity of 10.0-12.0 mS / cm.
[0014] The polarization of lithium-ion batteries mainly includes electrochemical polarization, ohmic polarization, and diffusion polarization. Excessively large particle sizes increase the distance lithium ions need to reach the surface, while excessively small particle sizes may lead to a decrease in the mechanical properties of the material. Controlling the particle sizes of the positive and negative active materials within the aforementioned range helps shorten the lithium-ion diffusion path, thereby accelerating the insertion and extraction processes of lithium ions in the positive and negative active materials. It also helps improve the reactivity and contact area of the positive and negative active materials, thus reducing the resistance to lithium-ion transport within them and consequently reducing electrochemical polarization. High conductivity of the electrolyte means better ion transport capabilities, enabling more effective support for rapid charge and discharge processes and reducing voltage drops caused by internal battery resistance. However, excessively high conductivity means faster ion movement within the electrolyte, which may exacerbate side reactions. Controlling the electrolyte conductivity within the aforementioned range helps improve electrolyte stability while accelerating the movement rate of lithium ions, thereby helping to reduce ohmic and diffusion polarization in lithium-ion batteries. As a whole, improvements to a single factor in a lithium-ion battery have limited impact on reducing polarization. This application simultaneously improves the particle size of the positive electrode active material, the particle size of the negative electrode active material, and the conductivity of the electrolyte. Through synergistic effects, these three factors contribute to a significant reduction in the polarization of lithium-ion batteries.
[0015] In one embodiment of this application, the ratio of the D50 particle size of the positive electrode active material to the D50 particle size of the negative electrode active material is 1:(2~2.5).
[0016] Controlling the ratio of the D50 particle size of the positive electrode active material to that of the negative electrode active material within the above range helps to achieve a good balance in the transport rate of lithium ions between the positive and negative electrode active materials. This helps to reduce polarization caused by the mismatch in lithium ion transport rates, reduces the electrode polarization resistance of the lithium-ion battery, and improves the battery's voltage retention capability under high-rate loads, thereby helping to release more capacity.
[0017] In one embodiment of this application, the areal density of the positive electrode active layer is 100~140 g / m2; and / or, the areal density of the negative electrode active layer is 50~100 g / m2.
[0018] Areal density affects the porosity of the electrode and the permeability of the electrolyte. Controlling the areal density of the positive and negative active layers within the aforementioned range helps to maintain a reasonable level of electrode porosity. Too many pores can reduce energy density, while too few pores are detrimental to electrolyte permeation. Appropriate porosity helps the electrolyte effectively wet the electrode, promotes lithium-ion transport, and improves electrochemical reaction efficiency.
[0019] In one embodiment of this application, the thickness of the positive electrode active layer is 70~100μm; and / or, the thickness of the negative electrode active layer is 70~100μm.
[0020] An excessively thick active layer can increase the path length for lithium ions to travel from the interior of the electrode material to the surface, thereby increasing electrochemical polarization and reducing the battery's charge and discharge efficiency. Conversely, an excessively thin active layer may reduce energy density. Controlling the thickness of the positive and negative active layers within the aforementioned ranges helps to improve lithium ion transport efficiency while maintaining a high energy density in lithium-ion batteries.
[0021] In one embodiment of this application, the positive electrode active layer further contains a conductive agent and a first binder; in one embodiment of this application, the mass ratio of the positive electrode active material, the conductive agent and the first binder is 100:(1~3):(1~3).
[0022] The addition of conductive agents helps improve the conductivity of the positive electrode, thereby increasing the transport efficiency of lithium ions between the positive electrode active material particles. The binder's role is to firmly adhere the positive electrode active material and conductive agent to the current collector, forming a stable and uniform positive electrode active layer. Excessive conductive agents and binders will occupy space in the positive electrode active material, which is detrimental to improving the energy density of the lithium-ion battery. Controlling the mass ratio of positive electrode active material, conductive agent, and the first binder within the aforementioned range helps to achieve a high energy density in the positive electrode active layer while reducing the internal resistance of the electrode, thereby reducing electrochemical polarization and improving the battery's charge-discharge performance and cycle stability at high rates.
[0023] In one embodiment of this application, the positive electrode active material is selected from any one or more of lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate; and / or, the conductive agent is selected from any one or more of carbon nanotubes, graphene, and conductive carbon black; and / or, the first binder is selected from any one or more of polytetrafluoroethylene, carboxylated polyvinylidene fluoride, and polyimide; in one embodiment of this application, the positive electrode active material is lithium cobalt oxide; and / or, the conductive agent is carbon nanotubes; and / or, the first binder is polytetrafluoroethylene.
[0024] Controlling the types of positive electrode active material, conductive agent, and first binder within the aforementioned range helps to enrich the material selectivity. In particular, controlling the positive electrode active material to be lithium cobalt oxide, the conductive agent to be carbon nanotubes, and the first binder to be polytetrafluoroethylene (PTFE) helps to optimize the battery's electrochemical performance and improve its mechanical strength, structural stability, and safety. Specifically, lithium cobalt oxide has a high operating voltage and a stable crystal structure, which helps to provide a high energy density. Carbon nanotubes have excellent conductivity and mechanical strength, which helps to enhance the electronic conductivity network of the positive electrode active layer, reduce internal resistance, and improve the battery's charge and discharge efficiency. PTFE has good chemical stability and high-temperature resistance, which helps to stably bind the active material and conductive agent under battery operating conditions and reduce bonding failure caused by environmental changes.
[0025] In one embodiment of this application, the above-mentioned negative electrode active layer further contains a second binder and a thickener; in one embodiment of this application, the mass ratio of the negative electrode active material, the second binder and the thickener is 100:(1~5):(1~5).
[0026] The negative electrode active material is a key component of battery energy storage, while the addition of the second binder and thickener affects the structural stability of the electrode and the electrolyte distribution. Controlling the mass ratio of the negative electrode active material, the second binder, and the thickener within the aforementioned range helps to improve the uniformity of the negative electrode active material distribution in the electrode, enhance the stability of the electrode structure, and thus contribute to increasing battery capacity and reducing polarization.
[0027] In one embodiment of this application, the negative electrode active material is graphite; and / or, the second binder is styrene-butadiene latex binder; and / or, the thickener is sodium carboxymethyl cellulose.
[0028] Graphite possesses high lithium storage density and good cycle stability, providing high-capacity lithium storage performance and thus increasing battery energy density. Styrene-butadiene latex binders effectively bond active materials and current collectors, improving the mechanical strength and stability of the negative electrode and reducing active material shedding during charge-discharge cycles. Sodium carboxymethyl cellulose adjusts the viscosity of the electrolyte, making its distribution in the electrode more uniform and improving lithium-ion transport efficiency. The combined use of styrene-butadiene latex binders and sodium carboxymethyl cellulose helps improve the wettability of the electrolyte between electrode materials, promoting uniform lithium-ion transport, reducing electrochemical and ohmic polarization, and the combination of styrene-butadiene latex binders and sodium carboxymethyl cellulose forms a stable gel structure, further enhancing the adhesion of electrode materials and improving electrode stability and consistency.
[0029] In another typical embodiment of this application, a method for preparing the aforementioned lithium-ion battery is provided. The method includes: step S1, mixing a positive electrode active material, a conductive agent, a first binder, and a first organic solvent to obtain a positive electrode slurry; step S2, mixing a negative electrode active material, a second binder, a thickener, and a second organic solvent to obtain a negative electrode slurry; step S3, coating the positive electrode slurry onto a current collector, drying, rolling, and punching to obtain a positive electrode sheet, and coating the negative electrode slurry onto the current collector, drying, rolling, and punching to obtain a negative electrode sheet; step S4, sequentially stacking the negative electrode sheet, a separator, and a positive electrode sheet to obtain a core; and step S5, loading the core into an aluminum-plastic packaging shell, injecting electrolyte into the aluminum-plastic packaging shell, and performing formation to obtain a lithium-ion battery.
[0030] This application demonstrates that lithium-ion batteries with low polarization can be prepared using conventional lithium-ion battery preparation steps.
[0031] Including but not limited to, the first organic solvent is selected from any one or more of N-methyl-2-pyrrolidone, polyvinylpyrrolidone, and triethyl phosphite; the second organic solvent is selected from any one or more of anhydrous ethanol, N-methyl-2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide; the diaphragm is selected from any one or more of polyethylene diaphragm, polypropylene diaphragm, and glass fiber diaphragm; and the current collector is selected from copper foil and / or aluminum foil.
[0032] In one embodiment of this application, the solid content of the positive electrode slurry is 70-75%; and / or, the viscosity of the positive electrode slurry is 4000-6000 cP; and / or, the solid content of the negative electrode slurry is 45-50%; and / or, the viscosity of the negative electrode slurry is 3000-5000 cP.
[0033] Controlling the solid content and viscosity of the positive electrode slurry and the negative electrode slurry within the above range helps to improve the wettability of the active layer and promote the uniform distribution of the electrolyte, thereby helping to optimize the transport path and speed of lithium ions in the positive and negative electrodes and reduce ohmic polarization and diffusion polarization of the battery.
[0034] In one embodiment of this application, the electrolyte comprises a lithium salt, a third organic solvent, and an additive. In one embodiment of this application, the lithium salt is lithium hexafluorophosphate; and / or, the third organic solvent is selected from any one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate; and / or, the additive is vinyl carbonate.
[0035] The beneficial effects of this application will be further illustrated below with reference to the embodiments.
[0036] Example 1
[0037] Positive electrode sheet: Lithium cobalt oxide with a D50 particle size of 4μm, carbon nanotubes and polytetrafluoroethylene are mixed with N-methyl-2-pyrrolidone in a mass ratio of 100:1:3 to obtain a positive electrode slurry. The solid content of the positive electrode slurry is 70% and the viscosity is 4000cP. The positive electrode slurry is coated on copper foil, and after drying, rolling and punching, a positive electrode sheet is obtained. The areal density of the positive electrode active layer in the positive electrode sheet is 100g / m2 and the thickness is 70μm.
[0038] Negative electrode sheet: Graphite with a D50 particle size of 10μm, styrene-butadiene latex binder, and sodium carboxymethyl cellulose are mixed with N-methyl-2-pyrrolidone in a mass ratio of 100:1:5 to obtain a negative electrode slurry. The solid content of the negative electrode slurry is 45%, and the viscosity of the negative electrode slurry is 3000cP. The negative electrode slurry is coated on copper foil, and after drying, rolling and punching, a negative electrode sheet is obtained. The areal density of the negative electrode active layer in the negative electrode sheet is 50g / m2, and the thickness is 70μm.
[0039] Electrolyte: Ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate are mixed in a volume ratio of 30:50:20 to obtain a mixed organic solvent. Lithium hexafluorophosphate and vinyl carbonate are added to the mixed organic solvent to obtain the electrolyte. The mass percentage of lithium hexafluorophosphate in the electrolyte is 13%, and the conductivity of the electrolyte is 10.0 mS / cm.
[0040] Battery: The above-mentioned negative electrode sheet, polyethylene separator and positive electrode sheet are stacked in sequence to obtain a core. After the core is put into an aluminum-plastic packaging shell, electrolyte is injected into the aluminum-plastic packaging shell to form a lithium-ion battery.
[0041] Example 2
[0042] The difference from Example 1 is that the D50 particle size of lithium cobalt oxide is 10 μm, and the D50 particle size of graphite is 20 μm, ultimately resulting in a lithium-ion battery.
[0043] Example 3
[0044] The difference from Example 1 is that the D50 particle size of lithium cobalt oxide is 4 μm, and the D50 particle size of graphite is 10 μm, ultimately resulting in a lithium-ion battery.
[0045] Example 4
[0046] The difference from Example 1 is that the D50 particle size of lithium cobalt oxide is 10 μm and the D50 particle size of graphite is 10 μm, ultimately resulting in a lithium-ion battery.
[0047] Example 5
[0048] The difference from Example 1 is that the conductivity of the electrolyte was adjusted to 12.0 mS / cm by adjusting the mass ratio of vinyl carbonate, and a lithium-ion battery was finally obtained.
[0049] Example 6
[0050] The difference from Example 1 is that the areal density of the positive electrode active layer is 140 g / m2 and the areal density of the negative electrode active layer is 100 g / m2, ultimately resulting in a lithium-ion battery.
[0051] Example 7
[0052] The difference from Example 1 is that the areal density of the positive electrode active layer is 160 g / m2 and the areal density of the negative electrode active layer is 120 g / m2, resulting in a lithium-ion battery.
[0053] Example 8
[0054] The difference from Example 1 is that the thickness of the positive electrode active layer is 100 μm and the thickness of the negative electrode active layer is 100 μm, resulting in a lithium-ion battery.
[0055] Example 9
[0056] The difference from Example 1 is that the thickness of the positive electrode active layer is 130 μm and the thickness of the negative electrode active layer is 110 μm, resulting in a lithium-ion battery.
[0057] Example 10
[0058] The difference from Example 1 is that the mass ratio of lithium cobalt oxide, carbon nanotubes and polytetrafluoroethylene is 100:3:1, resulting in a lithium-ion battery.
[0059] Example 11
[0060] The difference from Example 1 is that the mass ratio of lithium cobalt oxide, carbon nanotubes and polytetrafluoroethylene is 100:4:1, resulting in a lithium-ion battery.
[0061] Example 12
[0062] The difference from Example 1 is that the mass ratio of graphite, styrene-butadiene latex binder and sodium carboxymethyl cellulose is 100:5:1, resulting in a lithium-ion battery.
[0063] Example 13
[0064] The difference from Example 1 is that the mass ratio of graphite, styrene-butadiene latex binder, and sodium carboxymethyl cellulose is 100:6:1, resulting in a lithium-ion battery.
[0065] Example 14
[0066] The difference from Example 1 is that the solid content of the positive electrode slurry is 75% and the viscosity of the positive electrode slurry is 6000 cP, while the solid content of the negative electrode slurry is 50% and the viscosity of the negative electrode slurry is 5000 cP, ultimately yielding a lithium-ion battery.
[0067] Example 15
[0068] The difference from Example 1 is that the solid content of the positive electrode slurry is 80% and the viscosity of the positive electrode slurry is 8000 cP, the solid content of the negative electrode slurry is 55% and the viscosity of the negative electrode slurry is 6000 cP, and finally a lithium-ion battery is obtained.
[0069] Comparative Example 1
[0070] The difference from Example 1 is that the D50 particle size of lithium cobalt oxide is 15 μm, and the D50 particle size of graphite is 5 μm, ultimately resulting in a lithium-ion battery.
[0071] Comparative Example 2
[0072] The difference from Example 1 is that the D50 particle size of the graphite is 5 μm and the conductivity of the electrolyte is 15.0 mS / cm, ultimately resulting in a lithium-ion battery.
[0073] Comparative Example 3
[0074] The difference from Example 1 is that the D50 particle size of lithium cobalt oxide is 15 μm, the conductivity of the electrolyte is 15.0 mS / cm, and a lithium-ion battery is finally obtained.
[0075] The lithium-ion batteries prepared in the above examples and comparative examples were first discharged at 25°C to 3.0V at 1C, then charged at 1C constant current and constant voltage to 4.2V, with a cutoff current of 0.02C, and then discharged at 11.4C. The initial voltage value was tested, and the initial discharge capacity at 11.4C was recorded. The batteries were then charged at 1C and discharged at 4A for 300 cycles. The capacity retention rate after 300 cycles was tested, and the test results are shown in Table 1.
[0076] Table 1
[0077]
[0078] As can be seen from Table 1, the initial voltage of the comparative example at high rates is lower than that of the present application, indicating that the battery polarization of the present application is lower. The cycle capacity retention rate of the embodiment is similar to that of the comparative example, indicating that the cycle stability of the battery of the present application is not affected.
[0079] As can be seen from the above description, the embodiments of this application achieve the following technical effects:
[0080] The polarization of lithium-ion batteries mainly includes electrochemical polarization, ohmic polarization, and diffusion polarization. Excessively large particle sizes increase the distance lithium ions need to reach the surface, while excessively small particle sizes may lead to a decrease in the mechanical properties of the material. Controlling the particle sizes of the positive and negative active materials within the aforementioned range helps shorten the lithium-ion diffusion path, thereby accelerating the insertion and extraction processes of lithium ions in the positive and negative active materials. It also helps improve the reactivity and contact area of the positive and negative active materials, thus reducing the resistance to lithium-ion transport within them and consequently reducing electrochemical polarization. High conductivity of the electrolyte means better ion transport capabilities, enabling more effective support for rapid charge and discharge processes and reducing voltage drops caused by internal battery resistance. However, excessively high conductivity means faster ion movement within the electrolyte, which may exacerbate side reactions. Controlling the electrolyte conductivity within the aforementioned range helps improve electrolyte stability while accelerating the movement rate of lithium ions, thereby helping to reduce ohmic and diffusion polarization in lithium-ion batteries. As a whole, improvements to a single factor in a lithium-ion battery have limited impact on reducing polarization. This application simultaneously improves the particle size of the positive electrode active material, the particle size of the negative electrode active material, and the conductivity of the electrolyte. Through synergistic effects, these three factors contribute to a significant reduction in the polarization of lithium-ion batteries.
[0081] The above are merely embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A lithium-ion battery, comprising a positive electrode, an electrolyte, and a negative electrode, characterized in that, The positive electrode includes a positive active layer containing a positive active material with a D50 particle size of 4-10 μm; the negative electrode includes a negative active layer containing a negative active material with a D50 particle size of 10-20 μm; and the electrolyte has a conductivity of 10.0-12.0 mS / cm.
2. The lithium-ion battery according to claim 1, characterized in that, The ratio of the D50 particle size of the positive electrode active material to the D50 particle size of the negative electrode active material is 1:(2~2.5).
3. The lithium-ion battery according to claim 1 or 2, characterized in that, The areal density of the positive electrode active layer is 100~140 g / m2; and / or, the areal density of the negative electrode active layer is 50~100 g / m2.
4. The lithium-ion battery according to any one of claims 1 to 3, characterized in that, The thickness of the positive electrode active layer is 70~100μm; and / or, the thickness of the negative electrode active layer is 70~100μm.
5. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The positive electrode active layer also contains a conductive agent and a first binder; preferably, the mass ratio of the positive electrode active material, the conductive agent and the first binder is 100:(1~3):(1~3).
6. The lithium-ion battery according to claim 5, characterized in that, The positive electrode active material is selected from any one or more of lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate; and / or, the conductive agent is selected from any one or more of carbon nanotubes, graphene, and conductive carbon black; and / or, the first binder is selected from any one or more of polytetrafluoroethylene, carboxylated polyvinylidene fluoride, and polyimide. Preferably, the positive electrode active material is lithium cobalt oxide; and / or, the conductive agent is carbon nanotubes; and / or, the first binder is polytetrafluoroethylene.
7. The lithium-ion battery according to any one of claims 1 to 6, characterized in that, The negative electrode active layer also contains a second binder and a thickener; preferably, the mass ratio of the negative electrode active material, the second binder and the thickener is 100:(1~5):(1~5).
8. The lithium-ion battery according to claim 7, characterized in that, The negative electrode active material is graphite; and / or, the second binder is styrene-butadiene latex binder; and / or, the thickener is sodium carboxymethyl cellulose.
9. A method for preparing a lithium-ion battery according to any one of claims 1 to 8, characterized in that, The preparation method includes: Step S1: Mix the positive electrode active material, conductive agent, first binder and first organic solvent to obtain positive electrode slurry; Step S2: Mix the negative electrode active material, the second binder, the thickener, and the second organic solvent to obtain the negative electrode slurry; Step S3: The positive electrode slurry is coated onto the current collector, and after drying, rolling and punching, a positive electrode sheet is obtained. The negative electrode slurry is coated onto the current collector, and after drying, rolling and punching, a negative electrode sheet is obtained. Step S4: The negative electrode, the separator, and the positive electrode are stacked sequentially to obtain a wound core; Step S5: After loading the core into the aluminum-plastic packaging shell, inject electrolyte into the aluminum-plastic packaging shell to perform formation and obtain the lithium-ion battery.
10. The preparation method according to claim 9, characterized in that, The positive electrode slurry has a solid content of 70-75%; and / or, the viscosity of the positive electrode slurry is 4000-6000 cP; and / or, the solid content of the negative electrode slurry is 45-50%; and / or, the viscosity of the negative electrode slurry is 3000-5000 cP.