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CN-122025627-A - Positive electrode active material, preparation method thereof, positive electrode plate and secondary battery

CN122025627ACN 122025627 ACN122025627 ACN 122025627ACN-122025627-A

Abstract

The application relates to the technical field of secondary batteries, in particular to a positive electrode active material, a preparation method thereof, a positive electrode plate and a secondary battery, wherein the chemical formula of the positive electrode active material is Li 2‑x (Mn a M 1‑a ) x (SiO 4 ) b O 2‑4b ,0<x<1,0.5≤a≤0.95,0.05≤b≤0.5,M which is a transition metal element. By doping a proper amount of silicic acid polyanion into the lithium-rich manganese-based positive electrode material to occupy oxygen sites, the silicic acid polyanion with a tetrahedral structure is linked with the transition metal oxide with a polyhedral structure through a strong covalent bond, so that the structural stability and the electronic conductivity of the material are improved, and the defects of poor cycling stability, low specific discharge capacity and the like caused by unstable oxygen ions of the traditional lithium-rich manganese-based material can be effectively relieved. In addition, transition metal ions are restrained from migrating through the large size of the silicic acid polyanion, so that the phase transition and irreversible oxygen release of the material structure are restrained, and the battery is favorable for maintaining stable energy density in a long-term circulation process.

Inventors

  • PENG XIAOMENG
  • DONG XIAOLONG

Assignees

  • 万华化学集团电池科技有限公司
  • 万华化学(烟台)电池产业有限公司
  • 万华化学(烟台)电池材料科技有限公司
  • 万华化学集团股份有限公司

Dates

Publication Date
20260512
Application Date
20241030

Claims (11)

  1. 1. The positive electrode active material is characterized in that the chemical formula of the positive electrode active material is Li 2-x (Mn a M 1-a ) x (SiO 4 ) b O 2-4b ,0<x<1,0.5≤a≤0.95,0.05≤b≤0.5,M, and the positive electrode active material is a transition metal element.
  2. 2. The positive electrode active material according to claim 1, wherein M is one or more selected from the group consisting of iron, nickel, aluminum, cobalt, titanium, tin, molybdenum, zinc, chromium, copper, scandium, vanadium, silver, and niobium, and optionally, one or more selected from the group consisting of cobalt and nickel.
  3. 3. The positive electrode active material according to claim 1 or 2, wherein 0.2≤x≤0.9, and/or 0.6≤a≤0.95, and/or 0.06≤b≤0.2 in the chemical formula of the positive electrode active material.
  4. 4. A method for preparing the positive electrode active material according to any one of claims 1 to 3, comprising the steps of: S1, weighing a lithium source, a manganese source, an M source and silicate according to a stoichiometric ratio for standby; S2, mixing the raw materials in the step S1 with water and a complexing agent, reacting, evaporating and concentrating to obtain hydrogel, and drying and sintering the hydrogel to obtain the anode active material; optionally, the temperature of the reaction is 60-100 ℃ and the time is 4-12 hours; Optionally, the temperature of the evaporative concentration is 100-150 ℃.
  5. 5. The method according to claim 4, wherein the lithium source comprises one or more of lithium acetate, lithium oxide, lithium carbonate, lithium nitrate, lithium sulfate, lithium chloride, lithium phosphate, and/or the manganese source comprises one or more of manganese acetate, manganese carbonate, manganese nitrate, manganese sulfate, manganese chloride, manganese phosphate, and/or the M source comprises one or more of M-containing acetate, M-containing carbonate, M-containing nitrate, M-containing sulfate, M-containing chloride, and M-containing phosphate, and/or the complexing agent comprises one or more of ethylenediamine tetraacetic acid, citric acid, oxalic acid, acetic acid, amino acid, polyvinylpyrrolidone, polyacrylic acid, aminotriacetic acid, ammonium acetate, ammonium fluoride, aminophosphoric acid, and polycarboxylic acid, and/or the complexing agent has a mass of 1wt% to 10wt% of the total mass of the lithium source, the manganese source, and the M source.
  6. 6. The method for producing a positive electrode active material according to claim 4, wherein the silicate comprises one or more of sodium silicate, magnesium silicate, ammonium silicate, aluminum silicate, calcium silicate, manganese silicate, zinc silicate, barium silicate, bismuth silicate, titanium silicate, calcium aluminum silicate, magnesium aluminum silicate, sodium aluminum silicate, and magnesium calcium silicate, and optionally the silicate comprises one or more of sodium silicate, magnesium silicate, and ammonium silicate.
  7. 7. The method for preparing a positive electrode active material according to claim 4, wherein a dispersing agent is further added during the mixing process, wherein the dispersing agent comprises one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polyether ether ketone, polyether, polyurethane, polyvinyl alcohol ether, polyacrylamide, polystyrene, polymethyl methacrylate, polyether amine and polyvinyl chloride, and the dispersing agent accounts for 1-5wt% based on the mass of solid components in the preparation raw materials of the positive electrode active material.
  8. 8. The method for producing a positive electrode active material according to any one of claims 4 to 7, wherein the sintering comprises performing a first sintering at a first sintering temperature and then heating to a second sintering temperature for a second sintering, optionally, the first sintering temperature is 300 to 450 ℃ and the sintering time is 1.5 to 4 hours, the second sintering temperature is 700 to 950 ℃ and the sintering time is 6 to 20 hours, and the heating rate from the first sintering temperature to the second sintering temperature is 3 ℃ per minute to 6 ℃ per minute.
  9. 9. A positive electrode sheet, characterized by comprising: a positive electrode current collector, and A positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprising the positive electrode active material according to any one of claims 1 to 3 or the positive electrode active material manufactured by the manufacturing method according to any one of claims 4 to 8.
  10. 10. A secondary battery comprising the positive electrode tab of claim 9.
  11. 11. An electric device comprising the secondary battery according to claim 10.

Description

Positive electrode active material, preparation method thereof, positive electrode plate and secondary battery Technical Field The application relates to the technical field of secondary batteries, in particular to a positive electrode active material, a preparation method thereof, a positive electrode plate and a secondary battery. Background Along with the gradual exhaustion of fossil energy, the search of green and environment-friendly renewable energy sources becomes one of the hot spots of people research, and ideal green energy sources such as wind energy, solar energy and the like have strong discontinuity, so that people are forced to develop various energy storage devices for controllable storage and release of energy sources. In recent years, due to the characteristics of small volume, large specific energy, good cycle stability and the like, lithium batteries become research hotspots of people, and in combination with different energy storage mechanisms, lithium secondary batteries in various forms including lithium metal batteries, lithium ion batteries, lithium-air batteries, lithium-sulfur batteries and the like have been developed, but in consideration of cost and mass production limitations and commercial practical requirements, the lithium batteries are currently most popular as lithium ion batteries, and the higher energy density and the small size of the lithium batteries also make the lithium batteries widely applied to digital electronic products and precise instruments. Currently, various positive electrode active materials have been developed for the storage and release mechanism of lithium ions, such as layered lithium cobalt oxide, multi-lithium composite materials (e.g., nickel cobalt manganese ternary materials), lithium iron phosphate, lithium manganate, and the like. With the continuous research of lithium ion positive electrode active materials, the capacity of the conventional positive electrode active materials currently developed gradually approaches the limit, and the development of a novel positive electrode active material with higher theoretical capacity is gradually one of research hotspots of related researchers. Compared with the current commercial anode material, the lithium-rich manganese-based material (xLi2MnO3·(1-x)LiMO2 (0 < x <1, M is a transition metal element and a combination thereof)) has higher theoretical specific capacity (> 250mAh g -1), and meanwhile, the main body of the material is manganese with lower price, so that the lithium-rich manganese-based material attracts attention of researchers at home and abroad. However, research on lithium-rich manganese-based materials has been conducted for decades, and so far there is no commercially viable lithium-rich manganese-based material, which is resulted from the poor structural stability of the lithium-rich manganese-based material. The ideal lithium-rich manganese-based material is of a lamellar phase structure, however, in the battery cycle process, transition metal ions can irreversibly migrate and occupy lithium vacancies in the material crystal lattice, so that the original crystal structure of the transition metal ions is changed, and irreversible oxygen release occurs, thereby further accelerating the migration of the transition metal ions, and as the cycle is continuously carried out, more and more transition metal ions occupying the lithium vacancies after the migration cause the crystal structure of the material to gradually change from the original lamellar phase to the spinel phase, which directly causes the discharge voltage of the device to be reduced, obvious voltage drop problems occur, and simultaneously the device capacity is continuously reduced. Therefore, developing a lithium-rich manganese-based positive electrode material that is stable in structure is critical to achieving commercial applications thereof. Disclosure of Invention The application provides a positive electrode active material, a preparation method thereof, a positive electrode plate and a secondary battery, and aims to solve the problems of poor structural stability and poor cycle performance of a lithium-rich manganese-based positive electrode material in the prior art. In a first aspect, the present application provides a positive electrode active material having a chemical formula Li2-x(MnaM1-a)x(SiO4)bO2-4b,0<x<1,0.5≤a≤0.95,0.05≤b≤0.5,M as a transition metal element. In an alternative embodiment, the M is selected from one or more of iron, nickel, aluminum, cobalt, titanium, tin, molybdenum, zinc, chromium, copper, scandium, vanadium, silver, niobium; In an alternative embodiment, the M is selected from one or more of cobalt, nickel. In an alternative embodiment, 0.2≤x≤0.9 in the chemical formula of the positive electrode active material. In an alternative embodiment, 0.6≤a≤0.95 in the chemical formula of the positive electrode active material. In an alternative embodiment, 0.06≤b≤0.2 in the chemical formula of t