Relation between Crystal Structure, Electronic Structures and Electrode Performances of LiMn_2－xZn_xO₄ (x=0.05, 0.10) as a Cathode Active Material for Li Secondary Battery

Abstract

We have been studied the relation between crystal structures, electronic structures, thermodynamic stability and cycle performances of LiMn_2－xZn_xO₄(x=0.05, 0.10) as cathode active materials for 4 V class Li secondary battery. The crystal structures are Fd-3m and the bond lengths of (Mn, Zn)-O of LiMn_{1. 9}Zn_0.lO₄ decrease in comparison with that of LiMn₂O₄. The cycle performance improves on increasing Zn content. The heat of dissolution of the samples was measured. These samples are more stable thermodynamically with increasing Zn content. Moreover, we calculated the net charge of each atom, the bond overlap population of Li-O, Mn-O, Zn-O, the density of states, and the electron density of Li Mn_1.75M_0.25O₄ (M=Mn, Zn) using first principles calculation by DV-Xαmethod. Li ionicity always keeps high and the covalent bonding of Mn-O in the octahedron of LiMn_1.75Zn_0.25O₄ is stronger than that of LiMn₂O₄.