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First Principles Study on Factors Determining Battery Voltages of LiMO 2 (M=Ti-Ni)

1999; Institute of Physics; Volume: 38; Issue: 8R Linguagem: Inglês

10.1143/jjap.38.4804

1347-4065

Yukinori Koyama, Isao Tanaka, Yang-SooKim Nishitani, HirohikoAdachi HirohikoAdachi,

Semiconductor materials and interfaces

In order to evaluate the battery voltages of LiMO 2 /MO 2 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)-Xα 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-Xα method: 1) the effective electrostatic potential (Madelung potential) at the Li site, which corresponds to the energy required to remove a Li ion from LiMO 2 , 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.