Structural transitions in positive electrodes for Li-ion batteries the vibronic approach

We present the vibrational properties of manganese dioxides and lithiated oxides with either spinel-type and layered-type structure used as positive electrodes in Li-ion batteries. The local structure in γ-MnO₂ is investigated as a function of the intergrowth rate, Pr, of pyrolusite in the ramsdellite matrix and the phase evolution as a function of the degree of intercalation or deintercalation in 4-volt electrode materials Li_1−xCoO₂ and Li_1−xMn₂O₄. Lattice dynamics are studied using either a classical group theoretical analysis or a local environment model. Raman and FTIR bands are identified on the basis of vibrational modes of polyhedral units which are building the structure. Structural modifications induced by intercalation-deintercalation process are examined. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.