Variation of cathode properties of LiNi_(0.975)M_(0.025)O_2 (M = Ga, In and Tl) prepared by the combustion method

摘要

LiNi_(0.975)M_(0.025)O_2 (M = Ga, In and Tl) were synthesized by the combustion method (by preheating at 400 deg C for 30 min in air and then calcining in an O_2stream at 750 deg C for 36 h). XRD analyses, SEM observation and measurement of the variation of discharge capacity with the number of cycles were carried out. All the samples had the R3-bar m structure, and LiNi_(0.975)M_(0.025)O_2 contained LiInO_2 phase as an impurity. Among these samples, LaNi_(0.975)M_(0.025)O_2 had the largest first discharge capacity (172.2 mAh g~(-1)) and relatively good cycling performance (discharge capacity 140.3 mAh g~(-1) at n = 20). For LiNi_(0.975)M_(0.025)O_2 (M = Ga, In and Tl), the first discharge capacity decreased with increase in the ionic radius of the substituted element. The variation of cation mixing with the substituted element (decrease in I_(003)/I_(104) and increase in R-factor from M = Ga through M = Tl) is considered to be related to the behavior of the first discharge capacity with the substituted element.