Lithium-rich manganese-based positive electrode material and preparation method thereof

Abstract

The invention provides a lithium-rich manganese-based positive electrode material and a preparation method thereof. The lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based core and a surface modification layer, wherein the lithium-rich manganese-based core comprises a chemical component with a general formula Li<1+x>Mn<y>M<z>O<r>, wherein M is at least one of Ni, Co, Al, Mg, Ti, Fe, Cu, Cr, Mo, Zr, Ru, Sn or V, x is smaller than or equal to 1 and greater than 0, y is smaller than or equal to 1 and greater than 0, z is smaller than 1 and greater than or equal to 0 and r smaller than or equal to 3 and greater than or equal to 1.8; the surface modification layer comprises a vanadium-doped gradient layer and a coating layer of a lithium vanadium oxide. The positive electrode material has a low initial charge-discharge irreversible capacity loss and excellent cycle performance and rate capability. According to the method, the bonding strength between the lithium vanadium oxide of the surface modification layer and the core of the lithium-rich manganese-based positive electrode material can be improved, the total alkali content of the material is reduced through reaction of the vanadium oxide and the residual lithium on the surface of the lithium-rich manganese-based positive electrode material is reduced and the problem of high-pressure cycle expansion of a battery is solved.

Description

technical field [0001] The invention relates to the technical field of preparation of positive electrode materials for lithium ion batteries, in particular to a lithium-rich manganese-based positive electrode material and a preparation method thereof. Background technique [0002] As a new type of high-energy green battery, lithium-ion batteries are widely used in portable electronic products such as notebook computers and mobile phones, and are expanding to large and medium-sized energy storage equipment and new energy electric vehicles. This has a great impact on the energy density of lithium-ion batteries. , cycle life, cost and safety put forward higher requirements. Cathode materials are an important part of lithium-ion batteries, accounting for about 30%-40% of the total cost of the entire battery. Therefore, improving the performance and reducing the cost of cathode materials is extremely critical for the development of lithium-ion batteries. [0003] In recent year...

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Problems solved by technology

However, there are still some problems with this system material as a candidate material for high-energy lithium-ion batteries: first, the lithium ion diffusion coefficient of the system material (10 -15 ~10 -12 cm 2 the s -1 ) and electronic conductivity (10 -7 ~10 -8 S cm -1 ) is much lower than the traditional layered cathode material, resulting in a significant decrease in the capacity of the material at a higher rate of ≥1C and a worsening cycle performance, which cannot meet the performance requirements of the electrode material for the practical application of lithium-ion batteries

However, in the above two articles, the liquid-phase method was used to prepare the surface-modified materials. The surface structure of the lithium-rich manganese-based positive electrode material is easily damaged, resulting in a decrease in structural stability, and its low heat treatment stability makes it difficult for vanadium ions to enter the core layer. Diffusion properties play a role in stabilizing the bulk structure of the material

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