Relation between crystal structures, electronic structures, and electrode performances of LiMn2-xMxO4 (M = Ni, Zn) as a cathode active material for 4V secondary Li batteries

We investigated the relation between the electrode performance and electronic states of LiMn2-xMxO4 (M = Ni, Zn) as cathode active materials for the 4V class of lithium secondary batteries. The cycle performance is improved by substitution of Mn with Ni or Zn. We obtained the electron density distribution by XRD using the MEM/Rieweld method. Moreover, we investigated the electronic states of LiMn1.75M0.250O4 (M = Mn, Ni, Zn) using first-principles calculation by the DV-Xalpha method. The net charges of each atom, and the bond overlap populations of Li-O, Mn-O, Ni-O and Zn-O were calculated. From the results, Li has a high ionicity and the covalent bonding of the Mn-O of LiMn1.75M0.25O4 (M = Ni, Zn) is stronger than that of LiMn2O4. As a result of the DOS, the oxygen 2p orbital and Mn 3d orbital provides the overlap and the overlap of LiMn1.75M0.25O4 is greater than that of LiMn2O4. (C) 2003 Elsevier Science B.V. All rights reserved.