Effect of Ga doping on the structural, electrochemical and thermal properties of LiCo0.975Ga0.025O2 as cathode materials for lithium ion batteries

Layered LiCo0.975Ga0.025O2 was prepared by a sol-gel method and its structure, electrochemical and thermal properties were compared with those of LiCoO2 synthesized by the same method. The results showed that gallium doping improved the capacity retention of LiCoO2 while it lowered the initial discharge capacity. The improvement of capacity retention was prominent when the cycle tests were carried out at higher cut-off voltage and larger current rate. Cyclic voltammetry test indicated that the phase transition of LiCoO2 was suppressed by gallium doping. XRD of LixCo0.975Ga0.025O2 indicated that gallium doping brought about fewer changes in the c-axis during charge. Furthermore, the gallium doping also significantly enhanced the chemical diffusivity of Li+, suppressed the Co dissolution, limited the decomposition of electrolyte and improved the thermal stability of LiCoO2 during cycling.