2003 Volume 71 Issue 12 Pages 1145-1147
We investigated the electronic states of LiyMn2−xMxO4 (M = Mn, Mg, Ni, Co) as cathode active materials for the 4 V class lithium secondary battery. We calculated the electronic states of LiyMn1.75M0.25O4 (M = Mn; y = 0, Mg, Ni; y = 0.5, Co; y = 0.25) using first-principles calculations by the DV-Xα method. The net charge of each atom, and the bond overlap populations of Mn-O and M-O were calculated. The strong covalency between Mn and O existed in the Li defect model and LiyMn1.75M0.25O4 (M = Mg, Ni, Co). The bonding change in Mn-O is small and maintained the spinel structure during the charge-discharge process by substitution of Mn with M (= Mg, Ni, Co).