Lithium iron phosphate battery electrode paste, preparation method thereof, positive electrode sheet, negative electrode sheet and lithium ion battery

Abstract

The application provides an electrode slurry for a lithium iron phosphate battery, a preparation method of the electrode slurry, a positive electrode sheet, a negative electrode sheet and a lithium ion battery. The electrode slurry for the lithium iron phosphate battery comprises a positive electrode slurry and a negative electrode slurry, the positive electrode slurry comprises recycled lithium iron phosphate, and the negative electrode slurry comprises recycled graphite; according to the weight parts, the positive electrode slurry comprises 96.0-99.0 parts of recycled lithium iron phosphate, 0.4-2.0 parts of a first conductive agent, 0.4-2.0 parts of a first binder, 0.2-1.0 parts of a dispersing agent and a first organic solvent; the negative electrode slurry comprises 96.0-98.0 parts of recycled graphite, 0.4-2.0 parts of a second conductive agent, 0.8-2.2 parts of a second binder, 0.6-1.8 parts of a first thickening agent, a second organic solvent and water. The positive electrode slurry and the negative electrode slurry are stable in slurry homogenization and coating processes, are uniformly dispersed and are not prone to cracking.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to an electrode slurry for lithium iron phosphate batteries and its preparation method, a positive electrode sheet, a negative electrode sheet, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are among the most widely used power batteries today. However, the average lifespan of lithium-ion batteries is only 5 to 10 years, and they contain a large number of various metal components and organic solvents that are harmful to the environment and human health, leading to new environmental problems after they are disposed of. Furthermore, spent lithium-ion batteries are rich in various valuable metal elements such as cobalt, manganese, nickel, and lithium. Therefore, in order to protect the environment and conserve resources, it is necessary to recycle lithium-ion battery materials to reduce raw material consumption, thereby improving resource utilization, reducing production costs, and minimizing environmental pollution.

[0003] The solid waste generated during the production of positive and negative electrode materials for traditional lithium-ion batteries mainly consists of positive electrode materials, negative electrode materials, electrolytes, and separators. These wastes contain a large number of valuable metal elements and active materials. Direct disposal not only wastes resources but also causes environmental pollution. Currently, the recycling and processing of lithium-ion batteries mainly focuses on recovering easily recoverable metal elements (such as Li, Co, Ni, Cu, and Al) and active materials, but the recycling and processing of active materials within the batteries remains relatively limited.

[0004] Currently, the utilization rate of recycled lithium iron phosphate and graphite cathode materials for the production of lithium iron phosphate batteries is low. Furthermore, the recycled active materials encounter problems during slurry preparation and coating, such as rapid viscosity increases, large sedimentation, coating cracking, fluctuations in areal density, and uneven dispersion leading to large particle scratches. The screening and separation processes for discarded electrode sheets mostly employ physical separation methods, without mixing and re-calcining the recycled graphite for carbonization and coating. These factors result in significant differences between the recycled materials and virgin materials in terms of particle surface groups, carbon content, and specific capacity. Summary of the Invention

[0005] The main objective of this application is to provide an electrode slurry for lithium iron phosphate batteries and its preparation method, positive electrode sheet, negative electrode sheet, and lithium-ion battery, in order to solve the problems in the prior art when recycled lithium iron phosphate and graphite are used in battery slurry, such as easy cracking during coating, uneven dispersion leading to large particle scratches, and large differences in the areal density of coating due to rapid sedimentation of slurry.

[0006] To achieve the above objectives, according to one aspect of this application, an electrode slurry for lithium iron phosphate batteries is provided, comprising separate positive electrode slurry and negative electrode slurry. The positive electrode slurry comprises recycled lithium iron phosphate, and the negative electrode slurry comprises recycled graphite, wherein the recycled lithium iron phosphate and recycled graphite are respectively derived from the scrap material of the positive and negative electrode sheets of lithium iron phosphate batteries. By weight, the positive electrode slurry comprises: 96.0–99.0 parts of recycled lithium iron phosphate, 0.4–2.0 parts of a first conductive agent, 0.4–2.0 parts of a first binder, 0.2–1.0 parts of a dispersant, and a first organic solvent. By weight, the negative electrode slurry comprises: 96.0–98.0 parts of recycled graphite, 0.4–2.0 parts of a second conductive agent, 0.8–2.2 parts of a second binder, 0.6–1.8 parts of a first thickener, a second organic solvent, and water.

[0007] Furthermore, the surface of the recycled lithium iron phosphate contains a third conductive agent and a third binder; the mass percentage of the third conductive agent in the recycled lithium iron phosphate is 0.5-1.5%, and the mass percentage of the third binder in the recycled lithium iron phosphate is 0.8-2%; and / or, the surface of the recycled graphite contains a fourth binder and a second thickener; the mass percentage of the fourth binder in the recycled graphite is 0.1-2%, and the mass percentage of the second thickener in the recycled graphite is 0.1-1.6%.

[0008] Furthermore, the solid content of the positive electrode slurry is 56-68%, and / or the solid content of the negative electrode slurry is 48-54%; and / or, after the positive and negative electrode slurries are allowed to stand for 24 hours respectively, the viscosity of the positive electrode slurry is 240,000-400,000 mPa·s, and the sedimentation rate of the positive electrode slurry is ≤4%, and / or the viscosity of the negative electrode slurry is 3,000-8,000 mPa·s, and the sedimentation rate of the negative electrode slurry is ≤1.5%.

[0009] Further, the first conductive agent and the third conductive agent are each independently selected from any one or more of conductive carbon black, acetylene black, and carbon nanotubes; the first binder and the third binder are each independently selected from polyvinylidene fluoride and / or polyvinyl butyral; and / or, the dispersant includes a first dispersant and a second dispersant, wherein the first dispersant is selected from any one or more of polyacrylic acid, polymethacrylic acid, polyester chain polymers, sodium silicate, polyoxyethylene ether, glycerol, sodium alginate, and hydroxypropyl methylcellulose; the second dispersant is selected from any one or more of polyethylene glycol, sodium dodecyl sulfate, polyvinylpyrrolidone, and polyurethane compounds; and / or, the mass ratio of the first dispersant to the second dispersant is 1 to 2.5:1.

[0010] Further, the second conductive agent is selected from any one or more of conductive carbon black, acetylene black, and carbon nanotubes; and / or, the second binder and the fourth binder are each independently selected from any one or more of styrene-butadiene rubber, polyacrylic acid, and waterborne polyurethane; and / or, the first thickener and the second thickener are each independently selected from any one or more of carboxymethyl cellulose, hydroxyethyl cellulose, and polyvinyl alcohol; and / or, the second organic solvent is selected from any one or more of N-methylpyrrolidone, ethylene glycol, ethylene glycol ether compounds, dimethyl sulfoxide, and propylene carbonate; and / or, the mass ratio of the second organic solvent to recycled graphite is 0.3–1.5:100; and / or, the first organic solvent is N-methylpyrrolidone.

[0011] According to another aspect of this application, a method for preparing the above-mentioned electrode slurry for lithium iron phosphate batteries is provided. The method for preparing the positive electrode slurry includes: subjecting raw materials including recycled lithium iron phosphate, a first conductive agent, a first binder, a dispersant, and a first organic solvent to a first stirring to obtain a positive electrode slurry; the method for preparing the negative electrode slurry includes: subjecting raw materials including recycled graphite, a second conductive agent, a second binder, a first thickener, a second organic solvent, and water to a second stirring to obtain a negative electrode slurry.

[0012] Further, the mass ratio of recovered lithium iron phosphate to the volume ratio of the first organic solvent is 1.37–2.51 g / mL; and / or, the mass ratio of recovered graphite to the volume ratio of water is 0.92–1.16 g / mL; and / or, the rotation speeds of the first and second stirring are each independently 300–1500 rpm.

[0013] According to another aspect of this application, a positive electrode sheet is provided, comprising a current collector and a positive electrode active coating, the positive electrode active coating being prepared from a positive electrode slurry, the positive electrode slurry comprising the aforementioned positive electrode slurry.

[0014] According to another aspect of this application, a negative electrode sheet is provided, comprising a current collector and a negative electrode active coating, the negative electrode active coating being prepared from a negative electrode slurry, the negative electrode slurry comprising the aforementioned negative electrode slurry.

[0015] According to another aspect of this application, a lithium-ion battery is provided, including a positive electrode, a negative electrode, and a separator, wherein the positive electrode includes the aforementioned positive electrode and the negative electrode includes the aforementioned negative electrode.

[0016] Applying the technical solution of this application, both lithium iron phosphate and graphite recovered by physical methods still contain binders on their surfaces. While the binders on the surface of recovered lithium iron phosphate can still exert most of their adhesive properties under re-homogenization conditions, the binders on the surface of recovered graphite are essentially unable to exert their adhesive properties. Therefore, this application optimizes the composition and content of the positive and negative electrode slurries to ensure stable sedimentation and uniform dispersion during homogenization and coating processes, and to prevent cracking during coating and baking. Simultaneously, in terms of performance, the positive and negative electrode slurries of this application are essentially indistinguishable from slurries using the new materials lithium iron phosphate and graphite, and have good compatibility with production equipment, thus facilitating resource recycling and reducing raw material costs. Specifically, adding a dispersant to the positive electrode slurry not only increases the steric hindrance between lithium iron phosphate particles, preventing particle agglomeration, but also enhances the stability of the lithium iron phosphate particles and adjusts the viscosity and flowability of the positive electrode slurry, thereby helping to ensure the stability of the surface density of the positive electrode slurry during coating. Adding a second organic solvent to the negative electrode slurry can effectively separate the recycled graphite particles, thereby improving the dispersion uniformity of the recycled graphite and reducing the likelihood of the negative electrode sheet cracking. Simultaneously, the addition of the second organic solvent allows the second binder to fully dissolve, ensuring its uniform distribution around the recycled graphite particles and the second conductive agent. This enhances the adhesion between the recycled graphite particles, preventing the pulverization and detachment of the negative electrode material, and ultimately extending the battery's cycle life. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0018] As analyzed in the background section of this application, when recycled lithium iron phosphate and graphite are used in battery slurry in the prior art, there are problems such as easy cracking during the homogenization and coating process, uneven dispersion leading to large particle scratches, and rapid sedimentation of the slurry resulting in large differences in the areal density of the coating. In order to solve the above problems, this application provides an electrode slurry for lithium iron phosphate batteries and its preparation method, a positive electrode sheet, a negative electrode sheet, and a lithium-ion battery.

[0019] In a typical embodiment of this application, an electrode slurry for lithium iron phosphate batteries is provided, comprising separate positive electrode slurry and negative electrode slurry. The positive electrode slurry comprises recycled lithium iron phosphate, and the negative electrode slurry comprises recycled graphite. The recycled lithium iron phosphate and recycled graphite are respectively derived from the scrap material of the positive and negative electrode sheets of lithium iron phosphate batteries. By weight, the positive electrode slurry comprises: 96.0 to 99.0 parts of recycled lithium iron phosphate, 0.4 to 2.0 parts of a first conductive agent, 0.4 to 2.0 parts of a first binder, 0.2 to 1.0 parts of a dispersant, and a first organic solvent. By weight, the negative electrode slurry comprises: 96.0 to 98.0 parts of recycled graphite, 0.4 to 2.0 parts of a second conductive agent, 0.8 to 2.2 parts of a second binder, 0.6 to 1.8 parts of a first thickener, a second organic solvent, and water.

[0020] For lithium iron phosphate and graphite recovered by physical methods, their surfaces still contain binders. While the binders on the surface of recovered lithium iron phosphate can still exert most of their adhesive properties under re-slurry conditions, the binders on the surface of recovered graphite are essentially ineffective. Therefore, this application optimizes the composition and content of the positive and negative electrode slurries to ensure stable sedimentation and uniform dispersion during slurrying and coating, and to prevent cracking during coating and baking. Furthermore, in terms of performance, the positive and negative electrode slurries of this application are essentially indistinguishable from slurries using the new materials lithium iron phosphate and graphite, and exhibit good compatibility with production equipment, thus facilitating resource recycling and reducing raw material costs. Specifically, adding a dispersant to the positive electrode slurry not only increases the steric hindrance between lithium iron phosphate particles, preventing particle agglomeration, but also enhances the stability of the lithium iron phosphate particles and adjusts the viscosity and flowability of the positive electrode slurry, thereby ensuring the stability of the surface density of the positive electrode slurry during coating. Adding a second organic solvent to the negative electrode slurry can effectively separate the recycled graphite particles, thereby improving the dispersion uniformity of the recycled graphite and reducing the likelihood of the negative electrode sheet cracking. Simultaneously, the addition of the second organic solvent allows the second binder to fully dissolve, ensuring its uniform distribution around the recycled graphite particles and the second conductive agent. This enhances the adhesion between the recycled graphite particles, preventing the pulverization and detachment of the negative electrode material, and ultimately extending the battery's cycle life.

[0021] In addition, the weight percentage of recovered lithium iron phosphate can be 96.0 parts, 97.0 parts, 98.0 parts or 99.0 parts. Of course, the weight percentage of recovered lithium iron phosphate can be any value within the range of 96.0 to 99.0 parts, which will not be elaborated here.

[0022] The weight percentage of the first conductive agent can be 0.4 parts, 0.5 parts, 1.0 parts, 1.5 parts or 2.0 parts. Of course, the weight percentage of the first conductive agent can be any value within the range of 0.4 to 2.0 parts, which will not be elaborated here.

[0023] The weight percentage of the first adhesive can be 0.4 parts, 0.5 parts, 1.0 parts, 1.5 parts or 2.0 parts. Of course, the weight percentage of the first adhesive can be any value within the range of 0.4 to 2.0 parts, which will not be elaborated here.

[0024] The weight percentage of the dispersant can be 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts or 1.0 parts. Of course, the weight percentage of the dispersant can be any value within the range of 0.2 to 1.0 parts, which will not be elaborated here.

[0025] The weight percentage of recycled graphite can be 96.0, 97.0, or 98.0 parts. Of course, the weight percentage of recycled graphite can be any value within the range of 96.0 to 98.0 parts, which will not be elaborated here.

[0026] The weight percentage of the second conductive agent can be 0.4 parts, 0.5 parts, 1.0 parts, 1.5 parts or 2.0 parts. Of course, the weight percentage of the second conductive agent can be any value within the range of 0.4 to 2.0 parts, which will not be elaborated here.

[0027] The weight percentage of the second adhesive can be 0.8 parts, 1.2 parts, 1.6 parts, 1.8 parts or 2.2 parts. Of course, the weight percentage of the second adhesive can be any value within the range of 0.8 to 2.2 parts, which will not be elaborated here.

[0028] The weight percentage of the first thickener can be 0.6 parts, 1.0 parts, 0.6 parts, 1.4 parts or 1.8 parts. Of course, the weight percentage of the first thickener can be any value within the range of 0.6 to 1.8 parts, which will not be elaborated here.

[0029] In one embodiment of this application, the surface of the recycled lithium iron phosphate contains a third conductive agent and a third binder; the mass percentage of the third conductive agent in the recycled lithium iron phosphate is 0.5-1.5%, and the mass percentage of the third binder in the recycled lithium iron phosphate is 0.8-2%; and / or, the surface of the recycled graphite contains a fourth binder and a second thickener; the mass percentage of the fourth binder in the recycled graphite is 0.1-2%, and the mass percentage of the second thickener in the recycled graphite is 0.1-1.6%.

[0030] For recycled lithium iron phosphate containing a third conductive agent and a third binder within the above-mentioned range, and for recycled graphite containing a fourth binder and a second thickener within the above-mentioned range, this application optimizes the composition and content of the positive electrode slurry and the negative electrode slurry, which helps the slurry to settle stably and disperse evenly during homogenization and coating processes, and is less prone to cracking during coating and baking.

[0031] In addition, the mass percentage of the third conductive agent in the recovered lithium iron phosphate can be 0.5%, 0.8%, 1.2%, or 1.5%. Of course, the mass percentage of the third conductive agent in the recovered lithium iron phosphate can be any value within the range of 0.5% to 1.5%, which will not be elaborated here.

[0032] The mass percentage of the third binder in the recycled lithium iron phosphate can be 0.8%, 1.2%, 1.6%, or 2%. Of course, the mass percentage of the third binder in the recycled lithium iron phosphate can be any value within the range of 0.8% to 2%, which will not be elaborated here.

[0033] The mass percentage of the fourth binder in the recycled graphite can be 0.1%, 0.5%, 1.0%, 1.5%, or 2%. Of course, the mass percentage of the fourth binder in the recycled graphite can be any value within the range of 0.1% to 2%, which will not be elaborated here.

[0034] The mass percentage of the second thickener in the recycled graphite can be 0.1%, 0.5%, 1.0%, 1.3%, or 1.6%. Of course, the mass percentage of the second thickener in the recycled graphite can be any value within the range of 0.1% to 1.6%, which will not be elaborated here.

[0035] In one embodiment of this application, the solid content of the positive electrode slurry is 56-68%, and / or the solid content of the negative electrode slurry is 48-54%; and / or, after the positive electrode slurry and the negative electrode slurry are respectively allowed to stand for 24 hours, the viscosity of the positive electrode slurry is 240,000-400,000 mPa·s, and the sedimentation rate of the positive electrode slurry is ≤4%, and / or, the viscosity of the negative electrode slurry is 3,000-8,000 mPa·s, and the sedimentation rate of the negative electrode slurry is ≤1.5%.

[0036] Preferably controlling the solid content of the positive and negative electrode slurries within the aforementioned range helps the active material particles form a more compact and ordered arrangement during the coating process, thereby improving the uniformity and consistency of the coating and reducing the risk of cracking during the drying process. Simultaneously, it helps the viscosity and sedimentation rate of the positive and negative electrode slurries reach the aforementioned range after standing for 24 hours, thus minimizing localized structural defects in the electrodes caused by particle sedimentation and improving the consistency of the lithium-ion battery.

[0037] In addition, the solid content of the cathode slurry can be 56%, 60%, 64% or 68%. Of course, the solid content of the cathode slurry can be any value within the range of 56% to 68%, which will not be elaborated here.

[0038] The solid content of the negative electrode slurry can be 48%, 50%, 52% or 54%. Of course, the solid content of the negative electrode slurry can be any value within the range of 48% to 54%, which will not be elaborated here.

[0039] After the positive electrode slurry and negative electrode slurry are allowed to stand for 24 hours, the viscosity of the positive electrode slurry can be 240,000 mPa·s, 260,000 mPa·s, 275,000 mPa·s, 294,000 mPa·s, 340,000 mPa·s, 375,000 mPa·s, or 400,000 mPa·s. Of course, the viscosity of the positive electrode slurry can be any value within the range of 240,000 to 400,000 mPa·s. The sedimentation rate of the positive electrode slurry can be 0.26%, 0.50%, 0.92%, 1.56%, 2.30%, 2.80%, 3.30%, 3.75%, or 4%. Of course, the sedimentation rate of the positive electrode slurry can be any value within the range of ≤4%. The viscosity of the negative electrode slurry can be 3000 mPa·s, 3500 mPa·s, 4000 mPa·s, 4800 mPa·s, 5700 mPa·s, 6980 mPa·s, 7500 mPa·s, or 8000 mPa·s. Of course, the viscosity of the negative electrode slurry can be any value within the range of 3000 to 8000 mPa·s. The sedimentation rate of the negative electrode slurry can be 0.22%, 0.45%, 0.56%, 0.74%, 1.15%, 1.25%, or 1.5%. Of course, the sedimentation rate of the negative electrode slurry can be any value within the range of ≤1.5%, which will not be elaborated here.

[0040] In one embodiment of this application, the first conductive agent and the third conductive agent are each independently selected from any one or more of conductive carbon black, acetylene black, and carbon nanotubes; the first binder and the third binder are each independently selected from polyvinylidene fluoride (PVDF) and / or polyvinyl butyral; and / or, the dispersant includes a first dispersant and a second dispersant, wherein the first dispersant is selected from any one or more of polyacrylic acid, polymethacrylic acid, polyester chain polymers, sodium silicate, polyoxyethylene ether, glycerol, sodium alginate, and hydroxypropyl methylcellulose; the second dispersant is selected from any one or more of polyethylene glycol, sodium dodecyl sulfate, polyvinylpyrrolidone, and polyurethane compounds; and / or, the mass ratio of the first dispersant to the second dispersant is 1 to 2.5:1.

[0041] Preferably controlling the types of the first and third conductive agents within the aforementioned range helps improve the conductivity of the positive electrode. Having the same type of first and third conductive agent further enhances the conductivity of the positive electrode. Preferably controlling the types of the first and third binders within the aforementioned range helps minimize active material shedding, enhance the structural stability of the positive electrode, and reduce the battery's internal resistance. Having the same type of first and third binder further enhances the structural stability of the positive electrode.

[0042] Preferably, the type of the first dispersant is controlled within the aforementioned range. Its molecular chain structure helps to form an effective coating layer on the surface of lithium iron phosphate particles. On the one hand, its chain structure helps to increase the steric hindrance between lithium iron phosphate particles, thereby minimizing the agglomeration of lithium iron phosphate particles due to their proximity. On the other hand, the interaction between the first dispersant and the surface of lithium iron phosphate particles helps to improve the dispersibility of lithium iron phosphate particles in the slurry, thereby accommodating more lithium iron phosphate particles and increasing the solid content of the cathode slurry. Preferably, the type of the second dispersant is controlled within the aforementioned range. This helps to form a strong interaction with the surface of lithium iron phosphate particles, thereby enhancing the stability of lithium iron phosphate particles in the slurry and making them less prone to sedimentation or stratification when left to stand or subjected to certain external forces. At the same time, the addition of the second dispersant helps to adjust the rheological properties of the cathode slurry, giving the cathode slurry suitable viscosity and flowability, which is beneficial to the stability of the coating surface density during the coating process and improves the long-term preservation ability of the cathode slurry. Preferably controlling the mass ratio of the first dispersant and the second dispersant within the above range helps to further enhance the synergistic effect between the two, thereby further improving the dispersion uniformity of lithium iron phosphate particles, improving the stability and solid content of the cathode slurry, thereby improving coating performance, and thus optimizing the consistency of lithium-ion batteries.

[0043] Furthermore, the mass ratio of the first dispersant to the second dispersant can be 1:1, 1.5:1, 2:1, or 2.5:1. Of course, the mass ratio of the first dispersant to the second dispersant can be any value within the range of 1 to 2.5:1, which will not be elaborated here.

[0044] In one embodiment of this application, the second conductive agent is selected from any one or more of conductive carbon black, acetylene black, and carbon nanotubes; and / or, the second binder and the fourth binder are each independently selected from any one or more of styrene-butadiene rubber (SBR), polyacrylic acid, and waterborne polyurethane; and / or, the first thickener and the second thickener are each independently selected from any one or more of carboxymethyl cellulose (CMC), hydroxyethyl cellulose, and polyvinyl alcohol; and / or, the second organic solvent is selected from any one or more of N-methylpyrrolidone, ethylene glycol, ethylene glycol ether compounds, dimethyl sulfoxide, and propylene carbonate; and / or, the mass ratio of the second organic solvent to recycled graphite is 0.3 to 1.5:100; and / or, the first organic solvent is N-methylpyrrolidone.

[0045] Preferably controlling the type of the second conductive agent within the above-mentioned range helps to improve the conductivity of the negative electrode sheet. Preferably controlling the types of the second and fourth binders within the above-mentioned range helps to minimize the shedding of active material and enhance the structural stability of the negative electrode sheet. Preferably controlling the types of the first and second thickeners within the above-mentioned range helps to adjust the viscosity of the negative electrode slurry and minimize sedimentation.

[0046] Preferably controlling the type of the second organic solvent and the mass ratio of the second organic solvent to recycled graphite within the aforementioned range helps to further improve the dispersion effect, thereby contributing to the surface smoothness and uniform thickness of the coated negative electrode sheet. This facilitates the uniform insertion and extraction of lithium ions into the electrode, ultimately improving the electrochemical performance of the lithium-ion battery. Its main mechanism lies in the adsorption of second organic solvent molecules on the surface of recycled graphite particles, forming a solvation layer, which helps to reduce the mutual attraction between recycled graphite particles. Simultaneously, the binder has good solubility in the second organic solvent, allowing binder molecules to be evenly distributed around the recycled graphite particles and conductive agents, thus better encapsulating the surface of the recycled graphite particles, enhancing the adhesion between the recycled graphite particles, and thus stabilizing the sedimentation of the negative electrode slurry as much as possible. Preferably, the type of the first organic solvent is within the aforementioned range, which helps to uniformly disperse the recycled lithium iron phosphate in the first organic solvent, thereby improving the coating quality.

[0047] Furthermore, the mass ratio of the second organic solvent to the recycled graphite can be 0.3:100, 0.5:100, 1.0:100, or 1.5:100. Of course, the mass ratio of the second organic solvent to the recycled graphite can be any value within the range of 0.3 to 1.5:100, which will not be elaborated here.

[0048] In another typical embodiment of this application, a method for preparing the above-mentioned electrode slurry is provided. The method for preparing the positive electrode slurry includes: first stirring a raw material comprising recycled lithium iron phosphate, a first conductive agent, a first binder, a dispersant and a first organic solvent to obtain a positive electrode slurry; the method for preparing the negative electrode slurry includes: second stirring a raw material comprising recycled graphite, a second conductive agent, a second binder, a first thickener, a second organic solvent and water to obtain a negative electrode slurry.

[0049] The above-described method for preparing the positive electrode slurry achieves stable and uniform dispersion of recycled lithium iron phosphate. After 24 hours of settling, the difference in solid content between the upper and lower layers of the positive electrode slurry decreases from 10% to less than 1%, ensuring the stability of the coating surface density during coating and improving the long-term preservation capability of the positive electrode slurry. Furthermore, the viscosity of the positive electrode slurry increases steadily during the first stirring process, preventing the formation of unusable gel-like states. In addition, the addition of the first and second dispersants improves the dispersibility of the recycled lithium iron phosphate particles, thereby increasing the solid content of the positive electrode slurry and reducing the amount of the first organic solvent used. Similarly, the addition of the second organic solvent to the negative electrode slurry prepared using the above method not only ensures uniform dispersion of the recycled graphite particles, guaranteeing a smooth and uniform surface and thickness of the coated negative electrode sheet, but also facilitates the uniform insertion and extraction of lithium ions into the electrode, thus improving the electrochemical performance of the lithium-ion battery. Simultaneously, the binder, dissolved in the second organic solvent, better coats the surface of the recycled graphite particles, enhancing the adhesion between them. In addition, the addition of a second organic solvent helps to lower the boiling point of the solvent water in the negative electrode slurry and increase the evaporation rate of the solvent water, thereby inhibiting the cracking of the negative electrode sheet.

[0050] In one embodiment of this application, the mass ratio of recovered lithium iron phosphate to the volume ratio of the first organic solvent is 1.37 to 2.51 g / mL; and / or, the mass ratio of recovered graphite to the volume ratio of water is 0.92 to 1.16 g / mL; and / or, the rotation speeds of the first and second stirring are each independently 300 to 1500 rpm.

[0051] Preferably controlling the ratio of the mass of recovered lithium iron phosphate to the volume of the first organic solvent and the rotation speed of the first stirring within the aforementioned ranges helps to uniformly disperse the recovered lithium iron phosphate in the first organic solvent, thereby improving the coating quality. Preferably controlling the ratio of the mass of recovered graphite to the volume of water and the rotation speed of the second stirring within the aforementioned ranges helps to uniformly disperse the recovered graphite in the water, thereby improving the coating quality.

[0052] Furthermore, the ratio of the mass of recovered lithium iron phosphate to the volume of the first organic solvent can be 1.37 g / mL, 1.42 g / mL, 1.53 g / mL, 1.82 g / mL, 2.05 g / mL, or 2.51 g / mL. Of course, the ratio of the mass of recovered lithium iron phosphate to the volume of the first organic solvent can be any value within the range of 1.37 to 2.51 g / mL, which will not be elaborated further here.

[0053] The mass ratio of recovered graphite to water volume can be 0.92 g / mL, 1.02 g / mL, 1.04 g / mL, 1.10 g / mL, or 1.16 g / mL. Of course, the mass ratio of recovered graphite to water volume can be any value within the range of 0.92 to 1.16 g / mL, which will not be elaborated here.

[0054] The speed of the first and second stirring can be independently 300 rpm, 600 rpm, 1000 rpm or 1500 rpm. Of course, the speed of the first and second stirring can be any value within 300 to 1500 rpm, which will not be elaborated here.

[0055] In another typical embodiment of this application, a positive electrode sheet is provided, including a current collector and a positive electrode active coating, the positive electrode active coating being prepared from a positive electrode slurry, the positive electrode slurry including the above-mentioned positive electrode slurry.

[0056] The positive electrode sheet including the above-mentioned positive electrode slurry has good structural stability and electrochemical performance. At the same time, the peeling force of the positive electrode sheet reaches 0.2 to 0.6 N. The peeling force of the positive electrode sheet can be 0.2 N, 0.3 N, 0.4 N, 0.5 N or 0.6 N. Of course, the peeling force of the positive electrode sheet can be any value within the range of 0.2 to 0.6 N, which will not be elaborated here.

[0057] In another typical embodiment of this application, a negative electrode sheet is provided, including a current collector and a negative electrode active coating, the negative electrode active coating being prepared from a negative electrode slurry, the negative electrode slurry including the aforementioned negative electrode slurry.

[0058] The negative electrode sheet including the above-mentioned negative electrode slurry can suppress volume expansion during charging and discharging, and has good rate performance and cycle performance. At the same time, the peeling force of the negative electrode sheet reaches 0.15 to 0.5N. The peeling force of the negative electrode sheet can be 0.15N, 0.25N, 0.35N, 0.45N or 0.5N. Of course, the peeling force of the negative electrode sheet can be any value within the range of 0.15 to 0.5N, which will not be elaborated here.

[0059] In another typical embodiment of this application, a lithium-ion battery is provided, including a positive electrode, a negative electrode, and a separator, wherein the positive electrode includes the aforementioned positive electrode and the negative electrode includes the aforementioned negative electrode.

[0060] Lithium-ion batteries, including the aforementioned positive and negative electrode plates, exhibit excellent electrochemical and cycle performance.

[0061] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0062] Example 1

[0063] Preparation of positive electrode slurry: 96.0 parts by weight of recycled lithium iron phosphate, 1.5 parts by weight of conductive carbon black (first conductive agent), 2.0 parts by weight of PVDF (first binder), 0.1 parts by weight of polyester chain polymer HY-24000 (first dispersant), 0.5 parts by weight of polyvinylpyrrolidone (second dispersant), and 56 mL by weight of N-methylpyrrolidone (first organic solvent) were stirred at 1000 rpm in a dual planetary mixer to obtain the positive electrode slurry. The recycled lithium iron phosphate was a physically recycled lithium iron phosphate material. The surface of the recycled lithium iron phosphate contained conductive carbon black (third conductive agent) and PVDF (third binder). The mass percentage of conductive carbon black in the recycled lithium iron phosphate was 0.5%, the mass percentage of PVDF was 2%, and the mass ratio of the recycled lithium iron phosphate to the volume of N-methylpyrrolidone was 1.53 g / mL.

[0064] Negative electrode slurry preparation: 96.0 parts by weight of recycled graphite, 1.0 part by weight of conductive carbon black (second conductive agent), 2.0 parts by weight of SBR (second binder), 1.5 parts by weight of CMC (first thickener), N-methylpyrrolidone (second organic solvent), and 96 mL by weight of deionized water were stirred for the second time at 800 rpm in a dual planetary mixer to obtain the negative electrode slurry. The recycled graphite was physically recycled graphite material, and its surface contained SBR (fourth binder) and CMC (second thickener). The recycled lithium iron phosphate contained 0.1% SBR (fourth binder) and 1.6% CMC (second thickener). The mass ratio of N-methylpyrrolidone (second organic solvent) to recycled graphite was 0.3:100, and the mass ratio of recycled graphite to deionized water was 1.02 g / mL.

[0065] Example 2

[0066] Preparation of positive electrode slurry: 97.0 parts by weight of recycled lithium iron phosphate, 0.4 parts by weight of conductive carbon black (first conductive agent), 1.5 parts by weight of PVDF (first binder), 0.3 parts by weight of polyacrylic acid (first dispersant), 0.3 parts by weight of sodium dodecyl sulfate (second dispersant), and 56 mL by weight of N-methylpyrrolidone (first organic solvent) were stirred at 300 rpm in a dual planetary mixer to obtain the positive electrode slurry. The recycled lithium iron phosphate was a physically recycled lithium iron phosphate material. The surface of the recycled lithium iron phosphate contained conductive carbon black (third conductive agent) and PVDF (third binder). The mass percentage of conductive carbon black in the recycled lithium iron phosphate was 1%, the mass percentage of PVDF was 1.5%, and the mass ratio of the recycled lithium iron phosphate to the volume of N-methylpyrrolidone was 1.51 g / mL.

[0067] Negative electrode slurry preparation: 97.0 parts by weight of recycled graphite, 2.0 parts by weight of conductive carbon black (second conductive agent), 0.8 parts by weight of SBR (second binder), 0.6 parts by weight of CMC (first thickener), ethylene glycol (second organic solvent), and 96 mL by weight of deionized water were stirred for the second time at 300 rpm in a dual planetary mixer to obtain the negative electrode slurry. The recycled graphite was physically recycled graphite material, and its surface contained SBR (fourth binder) and CMC (second thickener). The recycled lithium iron phosphate contained 1% by mass of SBR and 1% by mass of CMC. The mass ratio of ethylene glycol to recycled graphite was 1:100, and the mass ratio of recycled graphite to deionized water was 1.04 g / mL.

[0068] Example 3

[0069] Preparation of positive electrode slurry: 99.0 parts by weight of recycled lithium iron phosphate, 2.0 parts by weight of conductive carbon black (first conductive agent), 0.4 parts by weight of PVDF (first binder), 0.5 parts by weight of polyoxyethylene ether (first dispersant), 0.1 parts by weight of polyvinylpyrrolidone (second dispersant), and 56 mL by weight of N-methylpyrrolidone (first organic solvent) were stirred at 1500 rpm in a dual planetary mixer to obtain the positive electrode slurry. The recycled lithium iron phosphate was a physically recycled lithium iron phosphate material. The surface of the recycled lithium iron phosphate contained conductive carbon black (third conductive agent) and PVDF (third binder). The mass percentage of conductive carbon black in the recycled lithium iron phosphate was 1.5%, the mass percentage of PVDF was 0.8%, and the mass ratio of the recycled lithium iron phosphate to the volume of N-methylpyrrolidone was 1.82 g / mL.

[0070] Negative electrode slurry preparation: 98.0 parts by weight of recycled graphite, 0.4 parts by weight of conductive carbon black (second conductive agent), 0.8 parts by weight of SBR (second binder), 1.8 parts by weight of CMC (first thickener), dimethyl sulfoxide (second organic solvent), and 96 mL by weight of deionized water were stirred for the second time in a dual planetary mixer at 1500 rpm to obtain the negative electrode slurry. The recycled graphite was physically recycled graphite material, and its surface contained SBR (fourth binder) and CMC (second thickener). The recycled lithium iron phosphate contained 2% by mass of SBR, 0.1% by mass of CMC, and the mass ratio of dimethyl sulfoxide to recycled graphite was 1.5:100. The mass ratio of recycled graphite to deionized water was 1.06 g / mL.

[0071] Example 4

[0072] The difference from Example 1 is that the preparation of the positive electrode slurry: the mass ratio of the first dispersant, polyester chain polymer HY-24000, and the second dispersant, polyvinylpyrrolidone, is 2.5:1.

[0073] Preparation of negative electrode slurry: The mass ratio of the second organic solvent N-methylpyrrolidone and recycled graphite is 1.5:100, and the negative electrode slurry is finally obtained.

[0074] Example 5

[0075] The difference from Example 1 is that the positive electrode slurry is prepared in the following way: the mass ratio of the first dispersant, polyester chain polymer HY-24000, and the second dispersant, polyvinylpyrrolidone, is 3.5:1, and the positive electrode slurry is finally obtained.

[0076] Preparation of negative electrode slurry: The mass ratio of the second organic solvent N-methylpyrrolidone and recycled graphite is 2.5:100, and the negative electrode slurry is finally obtained.

[0077] Example 6

[0078] The difference from Example 1 is in the preparation of the positive electrode slurry: the mass ratio of recovered lithium iron phosphate to the volume ratio of the first organic solvent N-methylpyrrolidone is 2.51 g / mL, the first stirring speed is 1500 rpm, and finally the positive electrode slurry is obtained.

[0079] Preparation of negative electrode slurry: The ratio of the mass of recycled graphite to the volume of deionized water was 1.16 g / mL, the second stirring speed was 1500 rpm, and the negative electrode slurry was finally obtained.

[0080] Example 7

[0081] The difference from Example 1 is in the preparation of the positive electrode slurry: the mass ratio of recovered lithium iron phosphate to the volume ratio of the first organic solvent N-methylpyrrolidone is 3 g / mL, the first stirring speed is 250 rpm, and finally the positive electrode slurry is obtained.

[0082] Preparation of negative electrode slurry: The ratio of the mass of recycled graphite to the volume of deionized water is 1.5 g / mL, the second stirring speed is 250 rpm, and finally the negative electrode slurry is obtained.

[0083] Example 8

[0084] The difference from Example 1 is that the solid content of the positive electrode slurry is 68% and the solid content of the negative electrode slurry is 54%.

[0085] Example 9

[0086] The difference from Example 1 is that the solid content of the positive electrode slurry is 75% and the solid content of the negative electrode slurry is 65%.

[0087] Comparative Example 1

[0088] Preparation of positive electrode slurry: 96.0 parts by weight of lithium iron phosphate, 1.5 parts by weight of conductive carbon black (first conductive agent), 2.0 parts by weight of PVDF (first binder), and 56 mL by weight of N-methylpyrrolidone (first organic solvent) were stirred at 1000 rpm in a dual planetary mixer to obtain the positive electrode slurry. Lithium iron phosphate is a new material, and its surface does not contain conductive agents or binders.

[0089] Negative electrode slurry preparation: 96.0 parts by weight of graphite, 1.0 part by weight of conductive carbon black (second conductive agent), 2.0 parts by weight of SBR (second binder), 1.5 parts by weight of CMC (first thickener), and 96 mL by weight of deionized water were stirred for the second time at 800 rpm in a dual planetary mixer to obtain the negative electrode slurry. Graphite is a novel material whose surface does not contain binders, thickeners, or conductive agents.

[0090] Comparative Example 2

[0091] The difference from Example 1 is that the positive electrode slurry is prepared as follows: 96.0 parts by weight of recycled lithium iron phosphate, 2.5 parts by weight of the first conductive agent conductive carbon black, 2.5 parts by weight of the first binder PVDF and 56 mL by weight of the first organic solvent N-methylpyrrolidone are stirred at 1000 rpm in a double planetary mixer to obtain the positive electrode slurry.

[0092] Negative electrode slurry preparation: According to the weight parts, 96.0 parts of recycled graphite, 2.5 parts of the second conductive agent conductive carbon black, 2.5 parts of the second binder SBR, 2 parts of the first thickener CMC and 96 mL of deionized water were stirred for the second time in a double planetary mixer at 800 rpm to obtain the negative electrode slurry.

[0093] Test method:

[0094] Positive electrode preparation: The positive electrode slurry of the above examples and comparative examples is uniformly coated on the aluminum foil current collector, dried, cold pressed, and die-cut into strips to form positive electrode sheets.

[0095] Negative electrode preparation: The negative electrode slurry of the above examples and comparative examples is uniformly coated on the copper foil current collector, dried, cold pressed, and die-cut into strips to form negative electrode sheets.

[0096] The positive electrode, negative electrode, and separator are wound into a core pack using a winding device. The core pack is then welded to the top cover assembly, installed in an aluminum shell, and injected with lithium hexafluorophosphate electrolyte to form a cell. The cell then undergoes formation and capacity testing processes during charging and discharging to obtain a lithium-ion battery.

[0097] Slurry viscosity test: The viscosity was measured using a rotational viscometer.

[0098] Slurry settling rate test: The solid content measurement method was adopted. After the slurry was left to stand for 24 hours, the upper and lower slurry layers were baked. The slurry before and after drying were weighed and the solid content and the solid content difference (i.e., 24-hour settling) were calculated.

[0099] Peel force test of electrode: The peel force of the electrode is tested by peel test method using a tensile testing machine.

[0100] Battery internal resistance test: The test was conducted using a voltage internal resistance tester under a 1kHz sinusoidal current.

[0101] Battery cycle capacity retention test: (1) Prepare a constant temperature and humidity test chamber and set its temperature to 25℃; select the battery and record its basic parameters such as appearance, size and weight; (2) Use a high-precision charge and discharge device to perform the first charge and discharge cycle of the battery at a rate of 0.5C in an environment of 25℃. When charging, first charge at a constant current of 0.5C to 3.65V, and then switch to constant voltage charging until the current drops below 0.05C, and let it rest for 60 minutes; when discharging, discharge at a constant current of 0.5C to the battery cutoff voltage of 2.5V, let it rest for 60 minutes, and record the capacity, voltage plateau and other data of the first charge and discharge; (3) Perform 0.5C charge and discharge cycle, and after the battery performance is stable, take the maximum discharge capacity in the first 10 cycles as the initial performance data; (4) Continue the cycle test (such as 0.5C charging and discharging in step 2) until the battery capacity decays to a certain percentage of the initial capacity (such as 80% or 70%) or reaches the set maximum number of cycles. Capacity retention rate = 0.5C discharge capacity of this cycle number / initial discharge capacity.

[0102] The test results are shown in Tables 1 and 2.

[0103] Table 1

[0104]

[0105] Table 2

[0106]

[0107]

[0108] As shown in Table 1, the slurry performance of Example 1, which uses recycled lithium iron phosphate and recycled graphite, shows no significant difference in viscosity and 24-hour sedimentation rate compared to Comparative Example 1, which uses new active materials. As shown in Table 2, the peeling force of the positive and negative electrode sheets in Example 1 is superior to that in Comparative Example 1, and the cycle performance of Example 1 remains at a high level.

[0109] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0110] For lithium iron phosphate and graphite recovered by physical methods, their surfaces still contain binders. While the binders on the surface of recovered lithium iron phosphate can still exert most of their adhesive properties under re-slurry conditions, the binders on the surface of recovered graphite are essentially ineffective. Therefore, this application optimizes the composition and content of the positive and negative electrode slurries to ensure stable sedimentation and uniform dispersion during slurrying and coating, and to prevent cracking during coating and baking. Furthermore, in terms of performance, the positive and negative electrode slurries of this application are essentially indistinguishable from slurries using the new materials lithium iron phosphate and graphite, and exhibit good compatibility with production equipment, thus facilitating resource recycling and reducing raw material costs. Specifically, adding a dispersant to the positive electrode slurry not only increases the steric hindrance between lithium iron phosphate particles, preventing particle agglomeration, but also enhances the stability of the lithium iron phosphate particles and adjusts the viscosity and flowability of the positive electrode slurry, thereby ensuring the stability of the surface density of the positive electrode slurry during coating. Adding a second organic solvent to the negative electrode slurry can effectively separate the recycled graphite particles, thereby improving the dispersion uniformity of the recycled graphite and reducing the likelihood of the negative electrode sheet cracking. Simultaneously, the addition of the second organic solvent allows the second binder to fully dissolve, ensuring its uniform distribution around the recycled graphite particles and the second conductive agent. This enhances the adhesion between the recycled graphite particles, preventing the pulverization and detachment of the negative electrode material, and ultimately extending the battery's cycle life.

[0111] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrode slurry for lithium iron phosphate batteries, comprising separate positive electrode slurry and negative electrode slurry, wherein the positive electrode slurry comprises recycled lithium iron phosphate, and the negative electrode slurry comprises recycled graphite, wherein... The recycled lithium iron phosphate and the recycled graphite are respectively derived from the scrap materials of the positive and negative electrode sheets of lithium iron phosphate batteries; characterized in that, The positive electrode slurry comprises, by weight parts: 96.0~99.0 parts of the recovered lithium iron phosphate; 0.4 to 2.0 parts of the first conductive agent; 0.4 to 2.0 parts of the first adhesive; 0.2 to 1.0 parts of dispersant; and First organic solvent; The dispersant includes a first dispersant and a second dispersant. The first dispersant is selected from any one or more of polyacrylic acid, polymethacrylic acid, polyester chain polymers, sodium silicate, polyoxyethylene ether, glycerol, sodium alginate, and hydroxypropyl methylcellulose. The second dispersant is selected from any one or more of polyethylene glycol, sodium dodecyl sulfate, polyvinylpyrrolidone, and polyurethane compounds. The negative electrode slurry comprises, by weight parts: 96.0 to 98.0 parts of the recovered graphite; 0.4 to 2.0 parts of a second conductive agent; 0.8 to 2.2 parts of the second adhesive; 0.6 to 1.8 parts of the first thickener; and The second organic solvent and water; The second organic solvent is selected from any one or more of N-methylpyrrolidone, ethylene glycol, ethylene glycol ethers, dimethyl sulfoxide, and propylene carbonate.

2. The electrode slurry for lithium iron phosphate batteries according to claim 1, characterized in that, The surface of the recycled lithium iron phosphate contains a third conductive agent and a third binder; the mass percentage of the third conductive agent in the recycled lithium iron phosphate is 0.5-1.5%, and the mass percentage of the third binder in the recycled lithium iron phosphate is 0.8-2%. And / or, the surface of the recycled graphite contains a fourth binder and a second thickener; the mass percentage of the fourth binder in the recycled graphite is 0.1-2%, and the mass percentage of the second thickener in the recycled graphite is 0.1-1.6%.

3. The electrode slurry for lithium iron phosphate batteries according to claim 1 or 2, characterized in that, The solid content of the positive electrode slurry is 56-68%, and / or the solid content of the negative electrode slurry is 48-54%. And / or, after the positive electrode slurry and the negative electrode slurry have been allowed to stand for 24 hours, the viscosity of the positive electrode slurry is 240,000~400,000 mPa·s and the sedimentation rate of the positive electrode slurry is ≤4%, and / or, the viscosity of the negative electrode slurry is 3,000~8,000 mPa·s and the sedimentation rate of the negative electrode slurry is ≤1.5%.

4. The electrode slurry for lithium iron phosphate batteries according to claim 2, characterized in that, The first conductive agent and the third conductive agent are each independently selected from conductive carbon black and / or carbon nanotubes; the conductive carbon black is acetylene black; the first binder and the third binder are each independently selected from polyvinylidene fluoride and / or polyvinyl butyral. And / or, the mass ratio of the first dispersant to the second dispersant is 1~2.5:

1.

5. The electrode slurry for lithium iron phosphate batteries according to claim 2, characterized in that, The second conductive agent is conductive carbon black and / or carbon nanotubes; the conductive carbon black is acetylene black; and / or, the second binder and the fourth binder are each independently selected from any one or more of styrene-butadiene rubber, polyacrylic acid, and waterborne polyurethane; and / or, the first thickener and the second thickener are each independently selected from any one or more of carboxymethyl cellulose, hydroxyethyl cellulose, and polyvinyl alcohol. And / or, the mass ratio of the second organic solvent to the recycled graphite is 0.3~1.5:100; And / or, the first organic solvent is N-methylpyrrolidone.

6. A method for preparing the electrode slurry for lithium iron phosphate batteries according to any one of claims 1 to 5, characterized in that, The method for preparing the positive electrode slurry includes: subjecting raw materials including recycled lithium iron phosphate, a first conductive agent, a first binder, a dispersant and a first organic solvent to a first stirring to obtain the positive electrode slurry; The method for preparing the negative electrode slurry includes: subjecting raw materials comprising recycled graphite, a second conductive agent, a second binder, a first thickener, a second organic solvent, and water to a second stirring to obtain the negative electrode slurry.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the recovered lithium iron phosphate to the volume ratio of the first organic solvent is 1.37~2.51 g / mL; and / or, the mass ratio of the recovered graphite to the volume ratio of the water is 0.92~1.16 g / mL; And / or, the rotation speed of the first stirring and the second stirring is independently 300~1500 rpm.

8. A positive electrode sheet, comprising a current collector and a positive electrode active coating, wherein the positive electrode active coating is prepared from a positive electrode slurry, characterized in that, The positive electrode slurry includes the positive electrode slurry according to any one of claims 1 to 5.

9. A negative electrode sheet, comprising a current collector and a negative electrode active coating, wherein the negative electrode active coating is prepared from a negative electrode slurry, characterized in that, The negative electrode slurry includes the negative electrode slurry according to any one of claims 1 to 5.

10. A lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator, characterized in that, The positive electrode includes the positive electrode as described in claim 8, and the negative electrode includes the negative electrode as described in claim 9.

Images