A lithium ion battery high-nickel positive electrode sheet and a preparation method thereof

Abstract

This invention discloses a high-nickel cathode sheet for lithium-ion batteries and its preparation method, belonging to the technical field of high-nickel cathode sheets. The invention first prepares a high-nickel cathode material precursor by doping molybdenum trioxide and aluminum fluoride. The cathode sheet is then prepared via a hydrothermal method and subjected to secondary calcination. After hydrophobic modification using KH570, itaconic anhydride, and pore-forming agents are coated onto the cathode, followed by UV curing to obtain the high-nickel cathode sheet for lithium-ion batteries. The bulk doping of anions and cations imparts good structural stability and excellent ion transport efficiency to the material. Secondary calcination repairs surface defects and avoids side reactions from water washing, improving battery cycle life. The composite microporous film can block electrolyte corrosion and can also control pore size and porosity to optimize ion transport, achieving synergistic ion and electron transport. Maleic anhydride can also coordinate and dissolve transition metals, effectively improving the battery's electrochemical performance and storage life. The high-nickel cathode sheet for lithium-ion batteries prepared by this invention exhibits long cycle life and excellent electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of high-nickel cathode technology, specifically to a high-nickel cathode for lithium-ion batteries and its preparation method. Background Technology

[0002] Lithium-ion batteries, due to their high energy density and long cycle life, have been widely used in new energy vehicles, energy storage devices, and other fields. High-nickel cathode materials, with their ultra-high specific capacity, have become a core material for improving battery energy density and have attracted much attention from the industry. However, high-nickel cathode materials still face many technical bottlenecks in practical applications: First, the increased nickel content leads to a decrease in the stability of the material's crystal structure, making it prone to volume distortion and phase transitions during cycling, and the formation of side reaction products on the surface, significantly reducing ion transport efficiency; Second, components such as fluorides in lithium-ion batteries easily react with the cathode surface, causing material corrosion and degradation, while transition metal ions easily dissolve and diffuse to the anode, leading to anode performance degradation and seriously affecting battery cycle life and storage stability; Third, in traditional preparation processes, the water washing purification step easily triggers surface side reactions, and single surface modification methods cannot simultaneously meet the requirements of structural stability, ion transport, and corrosion resistance, failing to achieve a comprehensive improvement in electrochemical performance.

[0003] Therefore, developing a high-nickel cathode material preparation technology that combines excellent structural stability, efficient ion transport capability, and resistance to electrolyte erosion has become an urgent need to promote the development of lithium-ion batteries towards higher performance. Summary of the Invention

[0004] The purpose of this invention is to provide a high-nickel positive electrode sheet for lithium-ion batteries and its preparation method, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-nickel positive electrode sheet for lithium-ion batteries, comprising the following steps: (1) Mix high-nickel cathode material precursor, molybdenum trioxide, aluminum fluoride and ethanol in a mass ratio of 1:0.01~0.02:0.005~0.01:2, ball mill the mixture for 2~4 hours at a ball-to-material ratio of 10:1, and dry it at 80℃ for 12 hours to obtain the self-made high-nickel cathode material precursor; (2) The self-made high-nickel cathode material precursor, lithium source and deionized water are mixed at a mass ratio of 1:1.05:10. After stirring at room temperature for 10 min, the mixture is transferred to a hydrothermal reactor and reacted at 200℃ for 15~24 h. After cooling naturally to room temperature, the precipitate is washed with deionized water until the pH is 7.0. After vacuum drying at 80℃ for 12 h, the high-nickel cathode material is obtained. After calcination twice, the self-made high-nickel cathode material is obtained after natural cooling to room temperature. The self-made high-nickel cathode material is prepared into a cathode slurry. The cathode slurry is evenly coated on the cathode current collector aluminum foil with a scraper to form a wet film. After vacuum drying at 80℃ for 12 h, it is compacted and cut into high-nickel cathode sheets. (3) Mix 2-vinylthiophene, itaconic anhydride, photoinitiator, pore-forming agent and organic solvent in a mass ratio of 1:0.3~0.5:0.01:0.5~0.8:10 and stir at room temperature in the dark for 1 hour to obtain a coating solution. Coat the coating solution evenly on the surface of the high nickel positive electrode sheet modified by KH570 hydrophobicity to form a wet film with a thickness of 40~60μm. Place the coated high nickel positive electrode sheet in an oven at 80℃ and dry it in the dark for 10 minutes. Place the dried high nickel positive electrode sheet in a nitrogen atmosphere and UV cure it for 2~3 minutes. Then raise the temperature to 200℃ and keep it at the temperature for 2 hours to obtain a lithium-ion battery high nickel positive electrode sheet with a surface-coated film.

[0006] Furthermore, the high-nickel cathode material precursor mentioned in step (1) is composed of Ni. 0.8 Co 0.1 Mn 0.1( High-nickel cathode material precursor (OH)2.

[0007] Furthermore, the lithium source in step (2) is LiOH·H2O.

[0008] Furthermore, the thickness of the positive current collector aluminum foil in step (2) is 20 μm.

[0009] Furthermore, the thickness of the wet film coated in step (2) is 100 μm.

[0010] Furthermore, the high-nickel cathode sheet mentioned in step (2) is a high-nickel cathode sheet with an areal density of 20 mg / cm².

[0011] Furthermore, the photoinitiator in step (3) is Irgacure 819.

[0012] Furthermore, the pore-forming agent in step (3) is PEG 1000.

[0013] Furthermore, the organic solvent in step (3) is N-methylpyrrolidone.

[0014] Furthermore, the lithium-ion battery high-nickel cathode sheet with a surface-coated thin film in step (3) is a lithium-ion battery high-nickel cathode sheet with a surface film pore size of 0.5~1μm and a porosity of 30~40%.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are: This invention achieves long cycle life and excellent electrochemical performance by coating a high-nickel cathode sheet prepared from a self-made high-nickel cathode material precursor with a self-made composite microporous film.

[0016] This invention prepares a high-nickel cathode sheet using molybdenum trioxide and aluminum fluoride as raw materials. After a second calcination treatment, surface defects are repaired, side reactions caused by water washing are avoided, and the stability of the material is further improved, thereby enhancing battery cycle life. Then, KH570 is used to hydrophobically modify the surface of the high-nickel cathode sheet, which is then coated with a mixture of 2-vinylthiophene, itaconic anhydride, and a pore-forming agent. Finally, after UV curing and removal of the pore-forming agent, a high-nickel cathode sheet for lithium-ion batteries with a composite microporous film coated on the surface is obtained. The doping of molybdenum trioxide and aluminum fluoride gives the high-nickel cathode sheet excellent ion transport efficiency in addition to good structural stability. The composite microporous film formed by the KH570 hydrophobic layer and the coating of 2-vinylthiophene and itaconic anhydride not only prevents electrolyte erosion of the cathode material and extends battery storage life, but the presence of micropores also optimizes ion transport efficiency, achieving synergistic transport of ions and electrons, greatly improving electrochemical performance. Simultaneously, itaconic anhydride can coordinate with transition metals dissolved from the high-nickel cathode sheet, preventing them from diffusing to the negative electrode and causing damage. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The testing methods for various indicators of the high-nickel positive electrode sheet for lithium-ion batteries prepared in the following embodiments are as follows: Electrochemical performance testing: Using a lithium-indium alloy sheet as the negative electrode (50% lithium atom percentage, 60 μm thickness), high-nickel positive electrode sheets prepared in Examples 1-5 and Comparative Examples 1-7 were pressed onto both sides of an LLZO solid electrolyte layer under 70 standard atmospheres to assemble a 2032 type coin-type all-solid-state battery. The DC internal resistance and AC internal resistance (frequency range 1 Hz to 106 Hz) of the high-nickel composite positive electrode sheet were tested at 60 °C using a dual-probe method. The DC internal resistance reflects the electronic conductivity of the electrode sheet, while the AC internal resistance reflects the lithium-ion conductivity. To improve testing accuracy, gold plating was performed on the top and bottom of the sample before testing. Rate discharge tests were conducted on the all-solid-state battery at 60 °C with a voltage range of 2.7–4.1 V, at discharge rates of 0.1C, 0.3C, 1.0C, and 1.5C. Cycle life performance testing: High-nickel cathode sheets prepared in Examples 1-5 and Comparative Examples 1-7 were used as cathodes, and lithium-indium alloy sheets (55% lithium atom percentage, 50 μm thickness) were used as anodes to prepare coin-type all-solid-state lithium batteries. The assembled all-solid-state lithium batteries were cycled for 3 weeks at room temperature within the range of 4.4V-3.0V, with a cycle current of 0.2C. Then, within the same voltage range, they were subjected to constant current and constant voltage charge-discharge cycles at a rate of 0.2C for 50 cycles. The internal resistance of the batteries was measured using electrochemical impedance spectroscopy (EIS) in the frequency range of 0.1 Hz to 1 MHz, with an applied voltage amplitude of 5 mV. Example 1

[0019] (1) The composition is Ni 0.8 Co 0.1 Mn 0.1( The high-nickel cathode material precursor (OH)2, molybdenum trioxide, aluminum fluoride and ethanol were mixed in a mass ratio of 1:0.01:0.005:2 and ball-milled for 2 hours at a ball-to-material ratio of 10:1 at a ball-milling speed of 500 rpm. After ball milling, the slurry was dried at 80°C for 12 hours to remove ethanol and then sieved through a 400-mesh sieve to obtain the self-made high-nickel cathode material precursor. (2) The self-made high-nickel cathode material precursor, LiOH·H2O and deionized water were mixed at a mass ratio of 1:1.05:10. After stirring at 500 rpm for 10 min at room temperature, the mixture was transferred to a 1 L polytetrafluoroethylene hydrothermal reactor with a filling degree of 75% and a reaction temperature of 200℃ for 15 h. After naturally cooling to room temperature, the precipitate was washed with deionized water until the pH was 7.0. After drying at 80℃ and a vacuum degree of 0.01 MPa for 12 h, the high-nickel cathode material was obtained. Under an oxygen atmosphere, the temperature was increased to 500℃ at a heating rate of 5℃ / min and held for 2 h to remove surface residues. Then the temperature was increased to 700℃ at a heating rate of 2℃ / min and held for 8 h to repair surface defects. After naturally cooling to room temperature, the mixture was sieved through a 400 mesh to obtain the self-made high-nickel cathode material. (3) The self-made high-nickel cathode material, conductive carbon SP and binder PVDF are mixed evenly in the solvent N-methylpyrrolidone at a mass ratio of 95:2:3 to prepare a cathode slurry with a solid content of 40wt%. The cathode slurry is evenly coated on a cathode current collector aluminum foil with a thickness of 20μm using a scraper. The wet film thickness is 100μm. It is dried at 80℃ and vacuum degree of 0.01MPa for 12h. It is then compacted by a roller press with a pressure of 5MPa and cut into high-nickel cathode sheets with a surface density of 20mg / cm². (4) Heat 2g of high-nickel positive electrode sheet to 200℃ at a heating rate of 2℃ / min and keep it at that temperature for 1h. Then cool it naturally to room temperature for later use. Mix KH570 and anhydrous ethanol at a mass ratio of 1:10. Stir at 500rpm for 10min at room temperature. Then add 0.1M glacial acetic acid at a rate of 2mL / min to adjust the pH to 4.0 to obtain a modified solution. Mix the prepared high-nickel positive electrode sheet and the modified solution at a mass ratio of 1:2. Let it stand at room temperature for 2h. Take out the positive electrode sheet, wipe the surface with anhydrous ethanol to remove excess solution, and dry it at 60℃ and 0.01MPa vacuum for 3h to obtain a high-nickel positive electrode sheet with hydrophobic surface modification. (5) Mix 2-vinylthiophene, itaconic anhydride, Irgacure 819, PEG 1000 and N-methylpyrrolidone in a mass ratio of 1:0.3:0.01:0.5:10 and stir at 300 rpm for 1 h at room temperature in the dark to obtain a coating solution. Use a micro-scraper to evenly coat the coating solution onto the surface of the hydrophobically modified high-nickel cathode sheet, controlling the wet film thickness to 40 μm. Place the coated high-nickel cathode sheet in an oven at 80 °C and dry in the dark for 10 min to evaporate most of the solvent and pre-shape the coating to prevent flow during subsequent UV curing. Place the dried high-nickel cathode sheet in a nitrogen atmosphere and irradiate it with a UV light source with a wavelength of 365 nm and a power of 100 mW / cm² for 2 min. Then heat it to 200 °C at a heating rate of 5 °C / min and hold it for 2 h to remove the pore-forming agent PEG. 1000, a high-nickel cathode sheet for lithium-ion batteries with a surface film pore size of 0.5μm and a porosity of 30% was obtained. Example 2

[0020] (1) The composition is Ni 0.8 Co 0.1 Mn 0.1( The high-nickel cathode material precursor (OH)2, molybdenum trioxide, aluminum fluoride and ethanol were mixed at a mass ratio of 1:0.012:0.006:2 and ball-milled for 2.5 h at a ball-to-material ratio of 10:1 at a ball-milling rate of 500 rpm. After ball milling, the slurry was dried at 80 °C for 12 h to remove ethanol and then sieved through a 400-mesh sieve to obtain the self-made high-nickel cathode material precursor. (2) The self-made high-nickel cathode material precursor, LiOH・H2O and deionized water were mixed at a mass ratio of 1:1.05:10. After stirring at 500 rpm for 10 min at room temperature, the mixture was transferred to a 1 L polytetrafluoroethylene hydrothermal reactor with a filling degree of 75% and a reaction temperature of 200℃ for 18 h. After naturally cooling to room temperature, the precipitate was washed with deionized water until the pH was 7.0. After drying at 80℃ and a vacuum degree of 0.01 MPa for 12 h, the high-nickel cathode material was obtained. Under an oxygen atmosphere, the temperature was increased to 500℃ at a heating rate of 5℃ / min and held for 2 h to remove surface residues. Then, the temperature was increased to 700℃ at a heating rate of 2℃ / min and held for 8 h to repair surface defects. After naturally cooling to room temperature, the mixture was sieved through a 400 mesh to obtain the self-made high-nickel cathode material. (3) The self-made high-nickel cathode material, conductive carbon SP and binder PVDF are mixed evenly in the solvent N-methylpyrrolidone at a mass ratio of 95:2:3 to prepare a cathode slurry with a solid content of 40wt%. The cathode slurry is evenly coated on a cathode current collector aluminum foil with a thickness of 20μm using a scraper. The wet film thickness is 100μm. It is dried at 80℃ and vacuum degree of 0.01MPa for 12h. It is then compacted by a roller press with a pressure of 5MPa and cut into high-nickel cathode sheets with a surface density of 20mg / cm². (4) Heat 2g of high-nickel positive electrode sheet to 200℃ at a heating rate of 2℃ / min and keep it at that temperature for 1h. Then cool it naturally to room temperature for later use. Mix KH570 and anhydrous ethanol at a mass ratio of 1:10. Stir at 500rpm for 10min at room temperature. Then add 0.1M glacial acetic acid at a rate of 2mL / min to adjust the pH to 4.0 to obtain a modified solution. Mix the prepared high-nickel positive electrode sheet and the modified solution at a mass ratio of 1:2. Let it stand at room temperature for 2.5h. Take out the positive electrode sheet, wipe the surface with anhydrous ethanol to remove excess solution, and dry it at 60℃ and 0.01MPa vacuum for 3h to obtain a high-nickel positive electrode sheet with hydrophobic surface modification. (5) Mix 2-vinylthiophene, itaconic anhydride, Irgacure 819, PEG 1000 and N-methylpyrrolidone in a mass ratio of 1:0.35:0.01:0.55:10 and stir at 300 rpm for 1 h at room temperature in the dark to obtain a coating solution. Use a micro-scraper to evenly coat the coating solution onto the surface of the hydrophobically modified high-nickel cathode sheet, controlling the wet film thickness to be 45 μm. Place the coated high-nickel cathode sheet in an oven at 80 °C and dry in the dark for 10 min to evaporate most of the solvent and pre-shape the coating to prevent flow during subsequent UV curing. Place the dried high-nickel cathode sheet in a nitrogen atmosphere and irradiate it with a UV light source with a wavelength of 365 nm and a power of 100 mW / cm² for 2.2 min. Then heat it to 200 °C at a heating rate of 5 °C / min and hold it for 2 h to remove the pore-forming agent PEG. 1000, a high-nickel cathode sheet for lithium-ion batteries with a surface film pore size of 0.6 μm and a porosity of 32% was obtained. Example 3

[0021] (1) The composition is Ni 0.8 Co 0.1 Mn 0.1( The high-nickel cathode material precursor, molybdenum trioxide, aluminum fluoride and ethanol were mixed at a mass ratio of 1:0.015:0.0075:2 and ball-milled for 3 hours at a ball-to-material ratio of 10:1 at a ball-milling speed of 500 rpm. After ball milling, the slurry was dried at 80°C for 12 hours to remove ethanol and then sieved through a 400-mesh sieve to obtain the self-made high-nickel cathode material precursor. (2) The self-made high-nickel cathode material precursor, LiOH·H2O and deionized water were mixed at a mass ratio of 1:1.05:10. After stirring at 500 rpm for 10 min at room temperature, the mixture was transferred to a 1 L polytetrafluoroethylene hydrothermal reactor with a filling degree of 75% and a reaction temperature of 200℃ for 20 h. After naturally cooling to room temperature, the precipitate was washed with deionized water until the pH reached 7.0. After drying at 80℃ and a vacuum degree of 0.01 MPa for 12 h, the high-nickel cathode material was obtained. Under an oxygen atmosphere, the temperature was increased to 500℃ at a heating rate of 5℃ / min and held for 2 h to remove surface residues. Then, the temperature was increased to 700℃ at a heating rate of 2℃ / min and held for 8 h to repair surface defects. After naturally cooling to room temperature, the mixture was sieved through a 400 mesh to obtain the self-made high-nickel cathode material. (3) The self-made high-nickel cathode material, conductive carbon SP and binder PVDF are mixed evenly in the solvent N-methylpyrrolidone at a mass ratio of 95:2:3 to prepare a cathode slurry with a solid content of 40wt%. The cathode slurry is evenly coated on a cathode current collector aluminum foil with a thickness of 20μm using a scraper. The wet film thickness is 100μm. It is dried at 80℃ and vacuum degree of 0.01MPa for 12h. It is then compacted by a roller press with a pressure of 5MPa and cut into high-nickel cathode sheets with a surface density of 20mg / cm². (4) Heat 2g of high-nickel positive electrode sheet to 200℃ at a heating rate of 2℃ / min and keep it at that temperature for 1h. Then cool it naturally to room temperature for later use. Mix KH570 and anhydrous ethanol at a mass ratio of 1:10. Stir at 500rpm for 10min at room temperature. Then add 0.1M glacial acetic acid at a rate of 2mL / min to adjust the pH to 4.0 to obtain a modified solution. Mix the prepared high-nickel positive electrode sheet and the modified solution at a mass ratio of 1:2. Let it stand at room temperature for 3h. Take out the positive electrode sheet, wipe the surface with anhydrous ethanol to remove excess solution, and dry it at 60℃ and 0.01MPa vacuum for 3h to obtain a hydrophobically modified high-nickel positive electrode sheet. (5) Mix 2-vinylthiophene, itaconic anhydride, Irgacure 819, PEG 1000 and N-methylpyrrolidone in a mass ratio of 1:0.4:0.01:0.65:10 and stir at 300 rpm for 1 h at room temperature in the dark to obtain a coating solution. Use a micro-scraper to evenly coat the coating solution onto the surface of the hydrophobically modified high-nickel cathode sheet, controlling the wet film thickness to 50 μm. Place the coated high-nickel cathode sheet in an oven at 80 °C and dry in the dark for 10 min to evaporate most of the solvent and pre-shape the coating to prevent flow during subsequent UV curing. Place the dried high-nickel cathode sheet in a nitrogen atmosphere and irradiate it with a UV light source with a wavelength of 365 nm and a power of 100 mW / cm² for 2.5 min. Then heat it to 200 °C at a heating rate of 5 °C / min and hold it for 2 h to remove the pore-forming agent PEG. 1000, a high-nickel cathode sheet for lithium-ion batteries with a surface film pore size of 0.8 μm and a porosity of 35% was obtained. Example 4

[0022] (1) The composition is Ni 0.8 Co 0.1 Mn 0.1( The high-nickel cathode material precursor (OH)2, molybdenum trioxide, aluminum fluoride and ethanol were mixed at a mass ratio of 1:0.018:0.008:2 and ball-milled for 3.5 hours at a ball-to-material ratio of 10:1 at a ball-milling rate of 500 rpm. After ball milling, the slurry was dried at 80°C for 12 hours to remove ethanol and then sieved through a 400-mesh sieve to obtain the self-made high-nickel cathode material precursor. (2) The self-made high-nickel cathode material precursor, LiOH·H2O and deionized water were mixed at a mass ratio of 1:1.05:10. After stirring at 500 rpm for 10 min at room temperature, the mixture was transferred to a 1 L polytetrafluoroethylene hydrothermal reactor with a filling degree of 75% and a reaction temperature of 200℃ for 22 h. After naturally cooling to room temperature, the precipitate was washed with deionized water until the pH reached 7.0. The mixture was then dried at 80℃ and a vacuum degree of 0.01 MPa for 12 h to obtain the high-nickel cathode material. The mixture was heated to 500℃ at a heating rate of 5℃ / min under an oxygen atmosphere and held for 2 h to remove surface residues. The mixture was then heated to 700℃ at a heating rate of 2℃ / min and held for 8 h to repair surface defects. After naturally cooling to room temperature, the mixture was sieved through a 400 mesh to obtain the self-made high-nickel cathode material. (3) The self-made high-nickel cathode material, conductive carbon SP and binder PVDF are mixed evenly in the solvent N-methylpyrrolidone at a mass ratio of 95:2:3 to prepare a cathode slurry with a solid content of 40wt%. The cathode slurry is evenly coated on a cathode current collector aluminum foil with a thickness of 20μm using a scraper. The wet film thickness is 100μm. It is dried at 80℃ and vacuum degree of 0.01MPa for 12h. It is then compacted by a roller press with a pressure of 5MPa and cut into high-nickel cathode sheets with a surface density of 20mg / cm². (4) Heat 2g of high-nickel positive electrode sheet to 200℃ at a heating rate of 2℃ / min and keep it at that temperature for 1h. Then cool it naturally to room temperature for later use. Mix KH570 and anhydrous ethanol at a mass ratio of 1:10. Stir at 500rpm for 10min at room temperature. Then add 0.1M glacial acetic acid at a rate of 2mL / min to adjust the pH to 4.0 to obtain a modified solution. Mix the prepared high-nickel positive electrode sheet and the modified solution at a mass ratio of 1:2. Let it stand at room temperature for 3.5h. Take out the positive electrode sheet, wipe the surface with anhydrous ethanol to remove excess solution, and dry it at 60℃ and 0.01MPa vacuum for 3h to obtain a high-nickel positive electrode sheet with hydrophobic surface modification. (5) Mix 2-vinylthiophene, itaconic anhydride, Irgacure 819, PEG 1000 and N-methylpyrrolidone in a mass ratio of 1:0.45:0.01:0.75:10 and stir at 300 rpm for 1 h at room temperature in the dark to obtain a coating solution. Use a micro-scraper to evenly coat the coating solution onto the surface of the hydrophobically modified high-nickel cathode sheet, controlling the wet film thickness to be 55 μm. Place the coated high-nickel cathode sheet in an oven at 80 °C and dry in the dark for 10 min to evaporate most of the solvent and pre-shape the coating to prevent flow during subsequent UV curing. Place the dried high-nickel cathode sheet in a nitrogen atmosphere and irradiate it with a UV light source with a wavelength of 365 nm and a power of 100 mW / cm² for 2.8 min. Then heat it to 200 °C at a heating rate of 5 °C / min and hold it for 2 h to remove the pore-forming agent PEG. 1000, a high-nickel cathode sheet for lithium-ion batteries with a surface film pore size of 0.9 μm and a porosity of 38% was obtained. Example 5

[0023] (1) The composition is Ni 0.8 Co 0.1 Mn 0.1( The high-nickel cathode material precursor (OH)2, molybdenum trioxide, aluminum fluoride and ethanol were mixed in a mass ratio of 1:0.02:0.01:2 and ball-milled for 4 hours at a ball-to-material ratio of 10:1 at a ball-milling speed of 500 rpm. After ball milling, the slurry was dried at 80℃ for 12 hours to remove ethanol and then sieved through a 400-mesh sieve to obtain the self-made high-nickel cathode material precursor. (2) The self-made high-nickel cathode material precursor, LiOH·H2O and deionized water were mixed at a mass ratio of 1:1.05:10. After stirring at 500 rpm for 10 min at room temperature, the mixture was transferred to a 1 L polytetrafluoroethylene hydrothermal reactor with a filling degree of 75% and a reaction temperature of 200℃ for 24 h. After naturally cooling to room temperature, the precipitate was washed with deionized water until the pH was 7.0. After drying at 80℃ and a vacuum degree of 0.01 MPa for 12 h, the high-nickel cathode material was obtained. Under an oxygen atmosphere, the temperature was increased to 500℃ at a heating rate of 5℃ / min and held for 2 h to remove surface residues. Then, the temperature was increased to 700℃ at a heating rate of 2℃ / min and held for 8 h to repair surface defects. After naturally cooling to room temperature, the mixture was sieved through a 400 mesh to obtain the self-made high-nickel cathode material. (3) The self-made high-nickel cathode material, conductive carbon SP and binder PVDF are mixed evenly in the solvent N-methylpyrrolidone at a mass ratio of 95:2:3 to prepare a cathode slurry with a solid content of 40wt%. The cathode slurry is evenly coated on a cathode current collector aluminum foil with a thickness of 20μm using a scraper. The wet film thickness is 100μm. It is dried at 80℃ and vacuum degree of 0.01MPa for 12h. It is then compacted by a roller press with a pressure of 5MPa and cut into high-nickel cathode sheets with a surface density of 20mg / cm². (4) Heat 2g of high-nickel positive electrode sheet to 200℃ at a heating rate of 2℃ / min and keep it at that temperature for 1h. Then cool it naturally to room temperature for later use. Mix KH570 and anhydrous ethanol at a mass ratio of 1:10. Stir at 500rpm for 10min at room temperature. Then add 0.1M glacial acetic acid at a rate of 2mL / min to adjust the pH to 4.0 to obtain a modified solution. Mix the prepared high-nickel positive electrode sheet and the modified solution at a mass ratio of 1:2. Let it stand at room temperature for 4h. Take out the positive electrode sheet, wipe the surface with anhydrous ethanol to remove excess solution, and dry it at 60℃ and vacuum degree 0.01MPa for 3h to obtain a high-nickel positive electrode sheet with hydrophobic surface modification. (5) Mix 2-vinylthiophene, itaconic anhydride, Irgacure 819, PEG 1000 and N-methylpyrrolidone in a mass ratio of 1:0.5:0.01:0.8:10 and stir at 300 rpm for 1 h at room temperature in the dark to obtain a coating solution. Use a micro-scraper to evenly coat the coating solution onto the surface of the hydrophobically modified high-nickel cathode sheet, controlling the wet film thickness to 60 μm. Place the coated high-nickel cathode sheet in an oven at 80 °C and dry in the dark for 10 min to evaporate most of the solvent and pre-shape the coating to prevent flow during subsequent UV curing. Place the dried high-nickel cathode sheet in a nitrogen atmosphere and irradiate it with a UV light source with a wavelength of 365 nm and a power of 100 mW / cm² for 3 min. Then heat it to 200 °C at a heating rate of 5 °C / min and hold it for 2 h to remove the pore-forming agent PEG. 1000, a high-nickel cathode sheet for lithium-ion batteries with a surface film pore size of 1μm and a porosity of 40% was obtained.

[0024] Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that step (1) is omitted, and step (2) is changed to: the composition is Ni. 0.8 Co 0.1 Mn 0.1 ( The high-nickel cathode material precursor (OH)2, LiOH・H2O, and deionized water were mixed at a mass ratio of 1:1.05:10. After stirring at 500 rpm for 10 min at room temperature, the mixture was transferred to a 1 L polytetrafluoroethylene hydrothermal reactor with a filling degree of 75%. The reaction was carried out at 200℃ for 20 h. After naturally cooling to room temperature, the precipitate was washed with deionized water until the pH reached 7.0. The mixture was then dried at 80℃ and a vacuum of 0.01 MPa for 12 h to obtain the high-nickel cathode material. The mixture was heated to 500℃ at a heating rate of 5℃ / min under an oxygen atmosphere and held for 2 h to remove surface residues. The mixture was then heated to 700℃ at a heating rate of 2℃ / min and held for 8 h to repair surface defects. After naturally cooling to room temperature, the mixture was sieved through a 400-mesh sieve to obtain the self-made high-nickel cathode material. The remaining steps were the same as in Example 3.

[0025] Comparative Example 2 The difference between Comparative Example 2 and Example 3 lies in step (2). Step (2) is changed to: mixing the self-made high-nickel cathode material precursor, LiOH·H2O and deionized water at a mass ratio of 1:1.05:10, stirring at 500 rpm for 10 min at room temperature, transferring to a 1L polytetrafluoroethylene hydrothermal reactor with a filling degree of 75%, reacting at 200℃ for 20 h, naturally cooling to room temperature, washing the precipitate with deionized water until the pH is 7.0, drying at 80℃ and a vacuum degree of 0.01 MPa for 12 h to obtain the high-nickel cathode material, naturally cooling to room temperature, and sieving through a 400-mesh sieve to obtain the self-made high-nickel cathode material. The remaining steps are the same as in Example 3.

[0026] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that step (4) is omitted, and step (5) is changed to: 2-vinylthiophene, itaconic anhydride, Irgacure 819, PEG 1000 and N-methylpyrrolidone are mixed in a mass ratio of 1:0.4:0.01:0.65:10 and stirred at 300 rpm for 1 h at room temperature in the dark to obtain a coating solution. The coating solution is uniformly coated on the surface of the high-nickel positive electrode using a micro scraper, and the wet film thickness is controlled to be 50 μm. The coated high-nickel positive electrode is placed in an oven at 80°C and dried in the dark for 10 min. The purpose is to evaporate most of the solvent, so that the coating is initially shaped and avoids flow during subsequent UV curing. The dried high-nickel positive electrode is irradiated for 2.5 min by a UV light source with a wavelength of 365 nm and a power of 100 mW / cm² under a nitrogen atmosphere, and then heated to 200°C at a heating rate of 5°C / min and held for 2 h to remove the pore-forming agent PEG. 1000, and a high-nickel cathode sheet for lithium-ion batteries with a surface film pore size of 0.8 μm and a porosity of 35% is obtained. The remaining steps are the same as in Example 3.

[0027] Comparative Example 4 The difference between Comparative Example 4 and Example 3 lies in step (5). Step (5) is changed to: mixing itaconic anhydride, Irgacure 819, PEG 1000 and N-methylpyrrolidone in a mass ratio of 0.4:0.01:0.65:10, stirring at 300 rpm for 1 h at room temperature in the dark to obtain a coating solution. The coating solution is uniformly coated on the surface of the hydrophobically modified high-nickel positive electrode using a micro-scraper, and the wet film thickness is controlled to be 50 μm. The coated high-nickel positive electrode is placed in an oven at 80°C and dried in the dark for 10 min. The purpose is to evaporate most of the solvent, so that the coating is initially shaped and avoids flow during subsequent UV curing. The dried high-nickel positive electrode is then irradiated for 2.5 min under a nitrogen atmosphere with a UV light source with a wavelength of 365 nm and a power of 100 mW / cm², and then heated to 200°C at a heating rate of 5°C / min and held for 2 h to remove the pore-forming agent PEG. 1000, and a high-nickel cathode sheet for lithium-ion batteries with a surface film pore size of 0.8 μm and a porosity of 35% is obtained. The remaining steps are the same as in Example 3.

[0028] Comparative Example 5 The difference between Comparative Example 5 and Example 3 lies in step (5). Step (5) is changed to: 2-vinylthiophene, Irgacure 819, PEG 1000 and N-methylpyrrolidone are mixed at a mass ratio of 1:0.01:0.65:10 and stirred at 300 rpm for 1 h at room temperature in the dark to obtain a coating solution. The coating solution is uniformly coated on the surface of the hydrophobically modified high-nickel positive electrode using a micro-scraper, and the wet film thickness is controlled to be 50 μm. The coated high-nickel positive electrode is placed in an oven at 80°C and dried in the dark for 10 min. The purpose is to evaporate most of the solvent, so that the coating is initially shaped and avoids flow during subsequent UV curing. The dried high-nickel positive electrode is then irradiated for 2.5 min at a UV light source with a wavelength of 365 nm and a power of 100 mW / cm² under a nitrogen atmosphere, and then heated to 200°C at a heating rate of 5°C / min and held for 2 h to remove the pore-forming agent PEG. 1000, and a high-nickel cathode sheet for lithium-ion batteries with a surface film pore size of 0.8 μm and a porosity of 35% is obtained. The remaining steps are the same as in Example 3.

[0029] Comparative Example 6 The difference between Comparative Example 6 and Example 3 lies in step (5). Step (5) is changed to: 2-vinylthiophene, itaconic anhydride, Irgacure 819 and N-methylpyrrolidone are mixed in a mass ratio of 1:0.4:0.01:10 and stirred at 300 rpm for 1 h at room temperature in the dark to obtain a coating solution. The coating solution is uniformly coated on the surface of the hydrophobically modified high-nickel positive electrode using a micro-scraper, and the wet film thickness is controlled to be 50 μm. The coated high-nickel positive electrode is placed in an oven at 80°C and dried in the dark for 10 min. The purpose is to evaporate most of the solvent, so that the coating is initially shaped and avoids flow during subsequent UV curing. The dried high-nickel positive electrode is then irradiated for 2.5 min in a nitrogen atmosphere with a UV light source with a wavelength of 365 nm and a power of 100 mW / cm². The temperature is then increased to 200°C at a heating rate of 5°C / min and held for 2 h to remove the pore-forming agent PEG. 1000, and a high-nickel cathode sheet for lithium-ion batteries with a surface film pore size of 0.8 μm and a porosity of 35% is obtained. The remaining steps are the same as in Example 3.

[0030] Comparative Example 7 The difference between Comparative Example 7 and Example 3 is that the composition is Ni. 0.8 Co 0.1 Mn 0.1( A high-nickel cathode material precursor (OH)2, conductive carbon SP (conductive agent), and PVDF (binder) were mixed uniformly in N-methylpyrrolidone (N-methylpyrrolidone) at a mass ratio of 95:2:3 to prepare a cathode slurry with a solid content of 40 wt%. The cathode slurry was uniformly coated onto a 20 μm thick aluminum foil for cathode current collector using a scraper, resulting in a wet film thickness of 100 μm. The film was dried at 80 °C and a vacuum of 0.01 MPa for 12 h, then compacted using a roller press at a pressure of 5 MPa and cut into high-nickel cathode sheets for lithium-ion batteries with an areal density of 20 mg / cm².

[0031] Example of effect Table 1 below presents the performance analysis results of the high-nickel cathode sheets for lithium-ion batteries using Examples 1 to 5 and Comparative Examples 1 to 7 of the present invention.

[0032] Table 1 A comparison of the experimental data on the electrochemical performance of the examples and comparative examples reveals that the present invention first prepares a high-nickel cathode material precursor by doping molybdenum trioxide with aluminum fluoride. After preparing the cathode sheet via a hydrothermal method and performing a second calcination, KH570 is used for hydrophobic modification. Then, 2-vinylthiophene, itaconic anhydride, and pore-forming agents are coated onto the cathode, followed by UV curing to obtain the high-nickel cathode sheet for lithium-ion batteries. The bulk doping of anions and cations gives the high-nickel cathode sheet excellent ion transport efficiency in addition to good structural stability. The composite microporous film formed by the KH570 hydrophobic layer and the grafted maleic anhydride polythiophene allows for precise control of the pore size and porosity of the surface microporous film. This optimizes ion transport efficiency, achieving synergistic transport of ions and electrons, and greatly improving electrochemical performance. A comparison of the capacity retention data from the examples and comparative examples after 50 cycles reveals that the two-stage calcination treatment in this invention repairs surface defects, avoids side reactions caused by water washing, and further improves material stability, thereby enhancing battery cycle life. The composite microporous film formed by the KH570 hydrophobic layer and the grafted maleic anhydride polythiophene can also prevent the electrolyte from eroding the positive electrode material, extending battery storage life. Simultaneously, maleic anhydride can coordinate with transition metals dissolved from the high-nickel positive electrode, preventing their diffusion to the negative electrode and causing damage.

[0033] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A high-nickel positive electrode sheet for lithium-ion batteries, characterized in that, Includes the following steps: (1) Mix high-nickel cathode material precursor, molybdenum trioxide, aluminum fluoride and ethanol in a mass ratio of 1:0.01~0.02:0.005~0.01:2, ball mill the mixture for 2~4 hours at a ball-to-material ratio of 10:1, and dry it at 80℃ for 12 hours to obtain the self-made high-nickel cathode material precursor; (2) The self-made high-nickel cathode material precursor, lithium source and deionized water are mixed at a mass ratio of 1:1.05:

10. After stirring at room temperature for 10 min, the mixture is transferred to a hydrothermal reactor and reacted at 200℃ for 15~24 h. After cooling naturally to room temperature, the precipitate is washed with deionized water until the pH is 7.

0. After vacuum drying at 80℃ for 12 h, the high-nickel cathode material is obtained. After calcination twice, the self-made high-nickel cathode material is obtained after natural cooling to room temperature. The self-made high-nickel cathode material is prepared into a cathode slurry. The cathode slurry is evenly coated on the cathode current collector aluminum foil with a scraper to form a wet film. After vacuum drying at 80℃ for 12 h, it is compacted and cut into high-nickel cathode sheets. (3) Mix 2-vinylthiophene, itaconic anhydride, photoinitiator, pore-forming agent and organic solvent in a mass ratio of 1:0.3~0.5:0.01:0.5~0.8:10 and stir at room temperature in the dark for 1 hour to obtain a coating solution. Coat the coating solution evenly on the surface of the high nickel positive electrode sheet modified by KH570 hydrophobicity to form a wet film with a thickness of 40~60μm. Place the coated high nickel positive electrode sheet in an oven at 80℃ and dry it in the dark for 10 minutes. Place the dried high nickel positive electrode sheet in a nitrogen atmosphere and UV cure it for 2~3 minutes. Then raise the temperature to 200℃ and keep it at the temperature for 2 hours to obtain a lithium-ion battery high nickel positive electrode sheet with a surface-coated film.

2. The high-nickel positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The high-nickel cathode material precursor mentioned in step (1) is composed of Ni. 0.8 Co 0.1 Mn 0.1( High-nickel cathode material precursor (OH)2.

3. The high-nickel positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The lithium source in step (2) is LiOH·H2O.

4. The high-nickel positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The thickness of the positive current collector aluminum foil in step (2) is 20 μm.

5. The high-nickel positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The thickness of the wet film coated in step (2) is 100 μm.

6. The high-nickel positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The high-nickel cathode sheet mentioned in step (2) is a high-nickel cathode sheet with an areal density of 20 mg / cm².

7. A high-nickel positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The photoinitiator in step (3) is Irgacure 819.

8. A high-nickel positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The pore-forming agent in step (3) is PEG 1000.

9. A high-nickel positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The organic solvent in step (3) is N-methylpyrrolidone.

10. A high-nickel positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery high-nickel cathode sheet with a surface-coated thin film in step (3) is a lithium-ion battery high-nickel cathode sheet with a surface film pore size of 0.5~1μm and a porosity of 30~40%.

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