Cycling performance of LiMn₂O₄ cathode materials doped with Al³⁺ at elevated temperature

Cathode materials of LiMn₂O₄ and LiAl_xMn_2-xO₄ (x=0.05, 0.1, 0.3) were synthesized by solid-state reaction, respectively, and investigated by XRD and SEM. Their cycling performances were compared at elevated temperature. The results show that the powders synthesized have the structure of spinel phase, except for nominal LiAl_0.3Mn_1.7O₄ with the impurity LiAlO₂. The morphology of particle doped with Al³⁺ is smoother than that of undoped. The specific capacity of LiMn₂O₄ decreases heavily after 20 cycles at elevated temperature, with a capacity loss of 29%, mainly due to the effect of Jahn-Teller and disproportionating reaction of Mn³⁺, which can generate Mn²⁺ to be dissolved into electrolyte. But through Al³⁺ doping, cycling performance of LiMn₂O₄ is improved obviously at elevated temperature.