Preparation And Doping Modification Of High Nickel Ternary Materials LiNi_0.8Co_0.1Mn_0.1O₂

In recent years,the rapid development of power vehicles and hybrid vehicles has placed higher demands on the energy density and production cost of lithium ion batteries.As a limiting factor and a major cost source for lithium-ion batteries,it is especially important to develop high-capacity and low-cost cathode materials.LiNi_0.8Co_0.1Mn_0.1O₂high-nickel ternary cathode material has high specific capacity and low cost,which meets the long range requirements of electric vehicles and hybrid vehicles,and is in line with the development trend of ternary materials with high nickel and low cobalt.LiNi_0.8Co_0.1Mn_0.1O₂ is the most promising lithium ion battery cathode material in the stage.However,as the nickel content increases,the difficulty in the synthesis of the material increases and the cycle stability decreases.This is an urgent problem for researchers to solve.In this paper,Li(Ni_0.8Co_0.1Mn_0.1)OH₂ precursor materials are synthesized by co-precipitation method which suitable for industrial production.Then,it is mixed with lithium hydroxide and sintered under an oxygen atmosphere to obtain a ternary product.By studying the concentration of complexing agent,the pH value of the reaction solution and the amount of lithium mixed on the morphology and electrochemical properties of the ternary materials,the optimum conditions for the synthesis of LiNi_0.8Co_0.1Mn_0.1O₂were sought.The experimental results demonstrate that the optimum complexing agent concentration is 3 M,the pH is 11 and the optimum lithium mixing amount is 5%lithium excess.The synthesized LiNi_0.8Co_0.1Mn_0.1O₂ cathode material has a first discharge specific capacity of 211 mAh/g at 0.1 C,and the first cycle coulomb efficiency is 90.3%.However,the cycle efficiency was not very satisfactory,and the capacity retention after200 cycles was 57%.In order to improve the cycle stability of LiNi_0.8Co_0.1Mn_0.1O₂,element doping is employed.In this experiment,the elements copper and aluminum,which are the anode and cathode current collectors,are selected as doping elements,which can also solve the problem of impurity removal during the recovery process of lithium ion batteries.The doping of both copper and aluminum improves the cycle properties of the material,but the mechanism of action of the two elements is different.The doping of copper can reduce the cation mixing phenomenon of the material,increase the diffusion coefficient of lithium ions and reduce the impedance.The doping of Al can improve the layered structure of the material,improve the structural stability and cyclic reversibility of the material.Doping can also improve the thermal stability of the material.By studying the electrochemical properties of materials under different element doping levels,the final optimum element doping amount is Cu=1%and Al=1%.After doping,the capacity retention of the cathode material cycled 100 times at 1 C increased from 70.5%to 89.9%.