Lithium ion battery positive electrode material and preparation method therefor

Abstract

The invention discloses a positive electrode material of LiNi1 / 3Co1 / 3Mn1 / 3O4 coated by an Al2O3-MgF2 composite film. The positive electrode material comprises an active material and a surface coating layer, wherein the active material is LiNi1 / 3Co1 / 3Mn1 / 3O4 and the surface coating layer is a composite film of Al2O3 and MgF2. In the experiment, with the sol-gel method, the surface of LiNi1 / 3Co1 / 3Mn1 / 3O4 of the positive electrode material is coated with a gel layer of (H7C3O3)3Al-O-Al (H7C3O3)3 and a material coated with Al2O3 is obtained after carrying out thermal treatment. The obtained powder and MgF2 are dissolved into anhydrous ethanol, and the wanted material is obtained after the mixture is evaporated and calcinated. The irreversible reaction between the active particle surface and the electrolyte can be inhibited by coating a composite film of Al2O3 and MgF2 over the surface of the active material, so that the surface structure stability of the active material and the service life are increased.

Description

technical field [0001] The invention belongs to the field of lithium ion batteries, in particular, the invention relates to a lithium ion battery cathode material and a preparation method thereof. Background technique [0002] At present, the commonly used cathode materials for lithium-ion batteries are LiCoO 2 , LiMn 2 o 4 , LiNiO 2 and LiFePO 4 . However, these materials have disadvantages that cannot be ignored: LiCoO 2 Co element in nature is low in content, expensive, and pollutes the environment; although Mn is rich in resources, LiMn 2 o 4 The structure is unstable, the Jahn-Teller effect is prone to occur, the cycle performance is poor, and the capacity is also low; LiNiO 2 The synthesis process is difficult, and the ideal crystal form generally needs to be formed in an oxygen atmosphere. In addition, due to the similar radius of nickel ions and lithium ions, ion mixing is easy to occur, and the cycle stability is poor; LiFePO 4 The conductivity is low, so i...

AI Technical Summary

Problems solved by technology

However, these materials have disadvantages that cannot be ignored: LiCoO 2 Co element in nature is low in content, expensive, and pollutes the environment; although Mn is rich in resources, LiMn 2 o 4 The structure is unstable, the Jahn-Teller effect is prone to occur, the cycle performance is poor, and the capacity is also low; LiNiO 2 The synthesis process is difficult, and the ideal crystal form generally needs to be formed in an oxygen atmosphere. In addition, due to the similar radius of nickel ions and lithium ions, ion mixing is easy to occur, and the cycle stability is poor; LiFePO 4 Low conductivity, so its rate performance is poor, and low temperature performance is not good

[0004] Studies have shown that the initial charge-discharge capacity of the material under high voltage is improved, but the capacity decays faster and the cycle performance is poor

The reason may be: when the cut-off voltage is high, the electrolyte will decompose to produce a small amount of HF, the active particles on the surface of the positive electrode material will be eroded by HF, and the transition metal ions will dissolve, resulting in the collapse of the surface layered structure and deterioration of cycle performance.

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