Structure and dynamics of the Li ion conductor LiMn₂O₄

Abstract

A cathode material for the rechargeable lithium ion battery, LiMn₂O₄, has been studied widely from both aspects of industrial applications and scientific interests. In this study our focus lies on the analysis of lithium diffusion phenomena in the spinel-type LiMn₂O₄ structure from static and dynamic view-points, employing the molecular dynamics simulations. The lithium ion diffuses through the channel formed by oxygen tetrahedra and octahedra centred at 8a and 16c respectively. Both the expansion of bottleneck opening (the face shared by the 8a tetrahedron and 16c octahedron) and the lowering of Li-Mn Coulomb repulsive energy seem to be essential for lithium diffusion. These factors are strongly correlated with the time dependency of Mn valences. It is supposed that the e_g electron hopping triggers off the lithium diffusion.