A study on the electrochemical/ structural characteristics of Al2O3 coated LiMn2O4 as positive electrode for lithium secondary battery

Abstract

The layered oxide, LiCoO2, LiNiO2 and spinel LiMn2O4 are the most widely studied as 4V cathode material. Among these, lithium manganese oxide spinel has been extensively investigated as cathode materials for lithium secondary battery because of its low cost, easy preparation and environmental advantage. Mush work has been directed to the stabilization of the spinel structure treatment by using organic and inorganic compounds to decrease reactivity of interface between electrode and electolyte. Recently metal oxide coated LiCoO2 cathode has been to exhibit relatively good capacity retention without decrease in the orgainal capacity. Hunter postulated that the redox-type reaction occurs predominantly for the spinel. This mechanism is based on a surgace disproportional reaction of the two trivalent ion(Mn3+) soluble in the acid solution under low pH conditions and the Mn4+ ions remain in the lattice, forming MnO2. 2Mn3+ ---> Mn2+ + Mn4+ Therefore, it is quite possible that spinel treated with acidic sol solution comprise new surface after heat treatment. We investigated electrochemical characteristics and structural properties of spinel coated with Al2O3. Al2O3 coated-LiMn2O4 is prepared by using sol-gel method. AA analysis showed that comparing to bare powder. manganese and lithium dissolution were occurred during ther coating treatment. XRD patterns shows that increase in the lattice parameter of Al2O3 coated-LiMn2O4 is related to formation of solid solution formed on the surface of active materials. The cell performance was enhanced with Al2O3 coating.