Cycling performance of LiNi1−yMyO2 (M=Ni, Ga, Al and/or Ti) synthesized by wet milling and solid-state method

Abstract

The LiNi1−yMyO2 specimens with compositions of LiNiO2, LiNi0.975Ga0.025O2, LiNi0.975Al0.025O2, LiNi0.995Ti0.005O2, and LiNi0.990Al0.005Ti0.005O2 were synthesized by wet milling and a solid-state reaction method. Among all the specimens, LiNi0.990Al0.005Ti0.005O2 has the largest first discharge capacity of 196.3 mAh/g at a rate of 0.1 C. At n=50, LiNiO2 has the largest discharge capacity of 126.7 mAh/g. LiNiO2 has the best cycling performance, its degradation rate of discharge capacity being 0.73 mAh/g/cycle. LiNi0.975Al0.025O2 shows the lowest decrease rate of the first discharge capacity with C rate. An equation describing the variation of the discharge capacity with the number of charge-discharge cycles, n, is obtained. The Williamson-Hall method is applied to calculate the crystallite size and the strain of the samples before and after charge-discharge cycling.