Using the density functional theory based projector-augmented wave method, the electronic structure and electron conducting properties were quantitatively investigated for LiFePO4 and LiFe15/16Mg1/16PO4. Doping by the Mg atoms into the Fe sites of the LiFePO4 turned out to enhance the electron localization at the Fe sites, and consequently, the frequency of small polaron hopping was increased, while the band gap remained unchanged. Additionally, the energy barrier for diffusion of Li ions was calculated to be 0.279 eV and the corresponding diffusion coefficient was 4.5x10(-9) cm(2)/s for LiFe15/16Mg1/16PO4.

Keywords: LiFePO4; LiFe15/16Mg1/16PO4; first-principle calculations; electronic structure; electronic conductivity; cathode material; lithium ion battery