A kind of positive electrode of lithium ion battery and preparation method thereof

Abstract

The invention provides a positive electrode of a lithium ion battery and a preparation method thereof, wherein the active material of the positive electrode is LiMn x N 2‑X o 4 , 0.9≤x≤1, N is selected from Ni, Co, Ti, Cr, Zr, Ca, Mg, Cu, Al; the positive electrode includes a bottom layer, a middle layer and a surface layer, and the average particle size of the bottom active material is X1 , the average particle diameter of the middle layer is X2, the average particle diameter of the surface layer is X3, wherein the X1 is 1.5-1.7 μm, and X3 is 2.4-2.6 μm, wherein X2=k*(n*X1+m *X3), wherein k, n, m are adjustment coefficients, k=0.21-0.23, n=2.8-3.2, m=2.0-2.2; the thickness of the bottom layer is Y1, and the thickness of the middle layer is Y2, so The thickness of the surface layer is Y3, wherein Y2=y*(Y1+Y3); when the bottom layer of the positive electrode, the average particle diameter and the thickness of the active material in the middle layer and the surface layer satisfy the above relational formula, the coating of the active material layer The performance is good, the stress between each layer is uniform, and the structure is stable, which can avoid the collapse of the active material layer structure caused by long-term circulation, prevent the active material from falling off, and improve the cycle life.

Description

technical field [0001] The invention relates to a positive electrode of a lithium ion battery and a preparation method thereof. Background technique [0002] Compared with other secondary batteries, lithium-ion batteries have significant advantages such as high working voltage and energy density, long cycle life, small size, light weight, low self-discharge rate, no memory effect and no pollution. Among them, due to the rich manganese resources, low price, environmental friendliness, and good safety, the unique three-dimensional tunnel structure of lithium manganese oxide is conducive to the insertion and extraction of lithium ions. LiMn 2 o 4 Become a promising green energy material in the 21st century. In recent years, the research on lithium manganese oxide has been the focus of developing new cathode materials for lithium-ion batteries at home and abroad. However, the Jahn-Teller effect will occur in the material during cycling, resulting in structural damage and rapi...

AI Technical Summary

Problems solved by technology

In the prior art, the active materials that have been developed include LiMn x N 2- X o 4 , 0.9≤x≤1, N is selected from Ni, Co, Ti, Cr, Zr, Ca, Mg, Cu, Al; the problem of capacity fading has basically been solved, but, as the charge and discharge progress, due to the active material layer The volume change of the active material layer is prone to collapse, which leads to the shedding of the active material and reduces the cycle life.

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