Monocrystal ternary positive electrode material and preparation method thereof

Abstract

The invention provides a monocrystal ternary positive electrode material, which has a chemical formula of LiaNixCoyMnzMbO2, wherein a is greater than or equal to 1.02 and less than or equal to 1.25, x + y + z + b is equal to 1, the average valence state of Ni, Co and Mn is 3.0+/-0.1, the molar ratio of Co is 0-20%, the molar ratio of Mn is greater than or equal to 20%, the molar ratio of Ni is 40-75%, the doped metal M is selected from at least one of Al, W, Ti, Mg, Zr, Ba and La, and the molar ratio of the doped metal M is less than 1%. The preparation method selects a medium-nickel low-cobalt ternary precursor,andcomprises the following steps: 1, mixing a lithium source, sintering to prepare a ternary positive electrode material with a large specific surface area and a single-crystal-like structure, and then crushing the ternary positive electrode material into primary monocrystal or monocrystal-like small particles which are relatively small in particle size and are uniformly dispersed; and 2, continuously mixing the primary small particles with a lithium source, carrying out element M doping, sintering at a higher temperature, and carrying out mechanical depolymerization to obtain the monocrystal-morphology positive electrode material with relatively good dispersibility. According to the invention, the problems that monocrystal particles of the low-cobalt and high-manganese-content ternary material are difficult to grow, Li/Ni mixed arrangement is high, and the rate capability is reduced are solved.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a single-crystal nickel-cobalt-manganese ternary positive electrode material with high electrochemical activity, low cobalt and high manganese content and a preparation method thereof. Background technique [0002] At present, lithium-ion batteries are widely used in electric vehicles, portable electronic devices and other fields due to their high energy density, high specific capacity, high specific power, long cycle life, and fast charge and discharge rates. Due to the continuous improvement of the demand for energy density, the ternary cathode material (LiNi) with high specific capacity, good safety and low cost x co y mn z o 2 , x+y+z=1), has gradually become a research hotspot in the field of cathode materials. The development needs of power battery enterprises in the development of ternary cathode materials include high-nickel ternary systems, high-voltage...

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Problems solved by technology

Among the ternary materials, the low-cobalt ternary positive electrode system has certain defects, mainly as follows: 1. It is difficult to form a single crystal morphology and requires a higher sintering temperature; 2. The nickel content remains unchanged, the cobalt content decreases, and the manganese content will increase, then the reduction of trivalent cobalt content and the increase of tetravalent manganese content will lead to the increase of divalent nickel content, which will aggravate the problem of lithium-nickel mixing in materials, and the layered order of materials will become lower, resulting in Ionic conductivity and electronic conductivity become worse; 3. Precursors with scattered primary particles and loose morphology are easy to sinter into single crystal morphology, while precursors with dense primary particles are not easy to sinter and form aggregates; 4 , With the reduction of cobalt content, the rate performance becomes worse, and it is more difficult to delithiate the positive electrode material

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