First principles study an factors determining battery voltages of LiMO2 (M = Ti-Ni)

In order to evaluate the battery voltages of LiMO2/MO2 Systems and to understand the electronic mechanism that determines the voltages, two kinds of first principles calculations are combined, i.e., molecular orbital calculations by the discrete variational (DV)-X alpha method using model clusters and the full-potential linearized augmented plane wave (FLAPW) band-structure calculations. Electronic structures obtained by the two methods agree satisfactorily Two factors that determine battery voltages are evaluated separately by the DV-X alpha method: 1) the effective: electrostatic potential (Madelung potential) at the Li site, which corresponds to the energy required to remove a Li ion from LiMO2, 2) the energy of the highest occupied molecular orbital, which is related to the energy required to remove an electron. The sum of these two factors reproduces well the theoretical battery voltages by the FLAPW method. Moreover, they agree well with experimental open-circuit voltages.