Improvement of Cycling Stability of $LiMn_2O_4$ Cathode by $Al_2O_3$ Surface Coating for Li-Ion Batteries

The effect of the $Al_2O_3$ coating on the charge-discharge cycling performance of spinel powder ($LiMn_2O_4$) was investigated in the range of 3.5-4.5 V at 1C. The $Al_2O_3$ coating on the surface of the spinel powder was carried out using the solution method, followed by 500C for 6 h in air. Powder X-ray diffraction pattern of the $Al_2O_3$-coated spinel $LiMn_2O_4$ showed that the $Al_2O_3$ coating medium was not incorporated in the spinel bulk structure. Scanning electron microscopy results showed that the $Al_2O_3$ coating particles were homogeneously distributed on the surface of $LiMn_2O_4$ powder particles. The $Al_2O_3$-coated $LiMn_2O_4$ retained 92.3% of its original capacity after 30 cycles, showing much better cycle ability than the bare lithium manganese oxide. The improvement of electrochemical performance is attributed to suppression of $Mn^{2+}$ dissolution into electrolyte via $Al_2O_3$ layer.