Monocrystal lithium manganate positive electrode material and preparation method thereof

Abstract

The invention provides a monocrystal lithium manganate positive electrode material, which relates to the technical field of lithium ion battery positive electrode materials. The chemical formula of the single crystal lithium manganate positive electrode material is LiaMn2-b-cMbNcO4, M represents a doping element, N represents a coating element, a is greater than or equal to 1.00 and less than or equal to 1.25, b is greater than or equal to 0 and less than or equal to 0.1, c is greater than or equal to 0 and less than or equal to 0.1, the crystal form of the single crystal lithium manganate positive electrode material is similar to a sphere, and the concentration of the coating element is in gradient distribution which is gradually reduced from outside to inside. The single-crystal lithium manganate positive electrode material disclosed by the invention is good in structural stability during charging and discharging cycles; the high-temperature and normal-temperature cycle performance and the high-temperature storage performance are excellent; the preparation method is simple, easy to operate and control, and easy for industrial production.

Description

technical field [0001] The invention relates to the technical field of lithium ion battery cathode materials, in particular to a single crystal lithium manganese oxide cathode material and a preparation method thereof. Background technique [0002] As a new generation of green secondary batteries, lithium-ion batteries have the advantages of small size, light weight, large capacity, small self-discharge, long cycle life, and no memory effect. The application has attracted more and more attention, especially as a power source to replace traditional petrochemical Energy is even more concerned. [0003] The performance of lithium-ion power batteries largely depends on the positive electrode material. Among the developed positive electrode materials, lithium manganese oxide with spinel structure and lithium iron phosphate with olivine structure have good rate charge and discharge characteristics, which are large It is an excellent cathode material for high-capacity and high-pow...

AI Technical Summary

Problems solved by technology

[0004] Lithium manganese oxide with a spinel structure is considered to be one of the most ideal cathode materials for power lithium-ion batteries, but its disadvantages are poor high-temperature storage performance and serious capacity decay during cycling.

After a lot of research, it has been confirmed that the reasons for the rapid specific capacity decay of lithium manganate cathode materials at high temperatures (above 55°C) are as follows: mainly composed of Mn 3+ Cause, a small amount of water in the electrolyte and LiPF in the electrolyte 6 The reaction generates HF, resulting in Mn 3+ A disproportionation reaction occurs to generate Mn 4+ and Mn 2+ , Mn 2+ Dissolution will occur, and the dissolution rate will be faster at high temperature, which will destroy the structure of lithium manganate; during the charging process, Mn 2+ It will migrate to the negative electrode and deposit on the surface of the negative electrode to cause a short circuit; Jahn-Teller effect: when the average valence state of Mn is lower than +3.5, the crystal structure will be distorted, and the cubic system will transform to the tetragonal system, resulting in lattice distortion and polarization of the electrode The effect is enhanced, causing capacity fading

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