关键词: Li(Mn_1/3Co_1/3Ni_1/3)O₂, 高温固相合成, 晶体结构, 表面分析, 电化学性能

Abstract The cathode material for lithium batteries Li(Mn_1/3Co_1/3Ni_1/3)O₂ has been synthesized by sol-gel technique followed by high temperature solid state reaction. The crystalline structure, ionic value and electrochemical properties of the material were investigated via X-ray photoelectron spectra, X-ray diffraction, cyclic voltammetry and charge-discharge cycling. The hexagonal lattice parameters of the compound by calcining the precursor at 950 ℃ are: a＝0. 2864 nm, c＝1. 4235 nm. XPS studies indicate that the oxidation states of manganese, nickel and cobalt in the Li(Mn_1/3Co_1/3Ni_1/3)O₂ surface region are largely 4＋, 2＋ and 3＋ respectively with small content of Ni^2＋ ion. Initial discharge capacity of 195 mAh/g at 55 ℃ was obtained in the range 2.5～4.6 V and at a specific current of 28 mA/g and under the same conditions 170 mAh/g was retained at the end of the 10th cycles. From the voltage profile and cyclic voltammetry, the redox processes occurring at ～3.7 and ～4.4 V were assigned to the Ni^2＋/4＋ and Co^3＋/4＋ couples, respectively.

Key words: Li(Mn_1/3Co_1/3Ni_1/3)O₂, high temperature solid state reaction, crystal structure, surface analysis, electrochemical property