Preparation And Characterization Of LiNi_1/3Co_1/3Mn_1/3O₂ Cathode Material For Lithium-ion Batteries

Sony crop developed lithium-ion battery in 1990 and realized its commercialization in 1991. The proceeding of commercialization had achieved fast development during the ten years followed. The prospect of lithium-ion batteries’ application is very positive because of its high ratio of performance to price.LiCoO2 is widely used, but Co belongs to the scare resources and is very expensive. What’s more, it is toxic and easy to cause environmental pollution. And the stability of LiNiO2 is poor and it is so difficult to prepare that we must synthesis it under oxygen atmosphere. Manganese cathode materials draw attention with abundant resources, low cost and non-poison. But the layered LiMnO2 is a kind of thermodynamic instable system. Although it has high capacity, the layered structure transforms into spinel structure in the process of charge-discharge, which leads to the decreasing in cycle performance and electrochemical stability. The dissolution of Manganese and the decomposition of the electrolyte under high pressure caused by Jahn-Teller effect of LiMn2O4 lead to capacity fade in lithium-ion batteries. LiFeO4 is called the anode of zero pollution. It has many advantages, such as cheap price, high energy density, environmental innocuousness and high security, etc. It has been widely researched and applied in recent years. But the application is limited due to its high power resistance and tap density. A layered ternary material composited of LiCoO2, LiNiO2 and LiMnO2 cumulates the merits of all of them. They have strong complementarity in the structure and performance. It is considered as one of the most developed prospects of the anode materials on account of its high discharge capacity, static cycle life, low cost and good safety performance.In this thesis, LiNi1/3Co1/3Mn1/3O2 powders were obtained through high temperature mechanochemistry technology with Li2CO3, NiO, Co3O4 and MnO2. XRD, SEM, constant charge-discharge instrument and electrochemical workstation were utilized to analyze the influence factors in the process of preparation, including ball milling temperature, time, molar ratio of Li/(Ni+Co+Mn) and balls/material weight ratio. The results show that when the reaction temperature is 750℃, the reaction time is 15 h, the mole ratio of Li/(Ni+Co+Mn) is 1.05, and balls/material weight ratio is 10:1, particles are evenly distributed, small and show a unitary structure. The battery is fabricated with the material as cathode. The initial discharge specific capacity is 137.5 mAh/g at 0.1 C. The discharge specific capacity is 132.9 mAh/g over 20 cycles at 0.1 C, and the capacity retention ratio is up to 96.65%.