Effects of Zn or Ti substitution for Ni on the electrochemical properties of LiNiO2

LiNiO2 and LiNi1−yMyO2 (M = Zn and Ti, y = 0.005, 0.01, 0.025, 0.05, and 0.1) were synthesized with a solid-state reaction method by calcination at 750 °C for 30 h under oxygen stream after preheating at 450 °C for 5 h in air. LiNi0.995Zn0.005O2 among the Zn-substituted samples and LiNi0.995Ti0.005O2 among the Ti-substituted samples showed the best electrochemical properties. For similar values of y, LiNi1−yTiyO2 had in general better electrochemical properties than LiNi1−yZnyO2. Electrochemical properties seem to be closely related to R-factor but less related to I0 0 3/I1 0 4 value. In the FT-IR absorption spectra of LiNiO2 and LiNi1−yMyO2 (M = Zn and Ti, y = 0.005, 0.01, 0.025, 0.05 and 0.1), Li2CO3 was detected even if it is not observed from XRD pattern, with the samples LiNi1−yZnyO2 (y = 0.05 and 0.1) showing Li2ZnO2 additionally. The smaller cation mixing of the Ti-substituted samples is considered to lead to their better electrochemical properties than the Zn-substituted samples.