EELS analysis of electrochemically deintercalated Li1−xMn2O4 and substituted spinels LiMn1.6M0.4O4 (M = Co, Cr, Ni)

Spinel lithium manganese oxides LiMn 1.6 M 0.4 O 4 (M=Mn, Co, Cr, Ni) for the cathode materials of the lithium ion secondary batteries were studied by electron energy loss spectroscopy (EELS). The ELNES spectra at Mn L- and O K-edge of the extracted lithium or substituted to Mn 16d site with third cations were successfully obtained. Electrochemically deintercalated Li 1− x Mn 2 O 4 showed a chemical shift of both Mn L- and O K-edges to the higher energy side compared with those of the stoichiometric LiMn 2 O 4 indicating oxidation of Mn and O due to the electrochemical deintercalation of Li. Substitution of M for Mn (M=Co, Cr, Ni) also caused a similar spectral shift of Mn L- and O K-edges. These shifts suggest lowering of the energy levels of the inner atomic orbitals compared with that of LiMn 2 O 4 .