Lithium intercalation and alloying effects on electronic structures of spinel lithium manganese oxides

Employing the DV-X alpha molecular orbital method, lithium intercalation effect and alloying effect have been investigated on the electronic structures of spinel MxMn2-xO4 and LiMxMn2-xO4 (M = Ti, V, Cr, Mn, Fe, Co, Ni and Cu). It is found that the lithium intercalation induces the electron transfer from Li to the surrounding O ions, and enlarges the Mn-3d/O-2p band gap greatly. Such a modification of the oxygen electronic state is probably related to the electrochemical cell voltage. This lithium intercalation effect still holds even in the alloyed systems. However, the amount of transferred charges from M to O ions changes depending on the alloying element, M. So the alloying addition modifies the oxygen electronic state and influences the lithium intercalation process indirectly. (C) 2000 Elsevier Science B.V. All rights reserved.