Alloying effect on electronic structures of lithium intercalation compounds

The alloying effect on the electronic structures of spinel LiMxMn2−xO4 (M=Ti, Cr, Mn, Fe, Co, Ni, Cu and Zn) has been investigated by the DV-Xα molecular orbital method. Following the addition of alloying element M, new M-3d bands in the density of states appeared additionally compared with that in pure LiMn2O4. As the new M-3d bands appeared, the new O-2p bands also emerged accordingly in the same positions around Fermi energy due to M–O interaction. If alloying element M leads to emergence of O-2p band in low energy position, withdrawal of Li electrons from this low O-2p band would results in high electrochemical cell voltage. The mechanism of high voltage occurrence due to alloying in lithium intercalation compounds can be attributed to the low oxygen levels near Fermi energy modified by neighbor alloying element.