First principles calculation of electrode material for lithium intercalation batteries: TiS{sub 2} and LiTi{sub 2}S{sub 4} cubic spinel structures

In the last decade there has been considerable activity in research and development of rechargeable lithium-ion batteries. The cubic spinel structures, TiS{sub 2} and LiTi{sub 2}S{sub 4}, have been fully optimized using the full-potential linearized augmented-plane-wave (LAPW) method. The comparison between band structures of TiS{sub 2} and LiTi{sub 2}S{sub 4} and the analogous oxide structures indicates that bonding in sulfides is more covalent. Bonding of both sulfides and oxides becomes more ionic after Li intercalation. The calculated average intercalation voltage of 2.16 eV (LiTi{sub 2}S{sub 4}) and 2.93 eV (LiTi{sub 2}O{sub 4}) is in good agreement with experimental data. The higher voltage of oxide is due to the larger change of enthalpy of formation between reactants and products.