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 under stand the electronic mechanism that determines the voltages, two kinds of f irst principles calculations are combined, i.e., molecular orbital calculat ions by the discrete variational (DV)-X alpha method using model clusters a nd the full-potential linearized augmented plane wave (FLAPW) band-structur e calculations. Electronic structures obtained by the two methods agree sat isfactorily Two factors that determine battery voltages are evaluated separ ately by the DV-X alpha method: 1) the effective: electrostatic potential ( Madelung potential) at the Li site, which corresponds to the energy require d to remove a Li ion from LiMO2, 2) the energy of the highest occupied mole cular orbital, which is related to the energy required to remove an electro n. The sum of these two factors reproduces well the theoretical battery vol tages by the FLAPW method. Moreover, they agree well with experimental open -circuit voltages.