Ab initio studies on n-type and p-type Li₄Ti₅O₁₂

This paper studies the structure and electronic properties of Li₄Ti₅O₁₂, as anode material for lithium ion batteries, from first principles calculations. The results suggest that there are two kinds of unit cell of Li₄Ti₅O₁₂: n-type and p-type. The two unit cells have different structures and electronic properties: the n-type with two 16d site Li ions is metallic by electron, while the p-type with three 16d Li ions is metallic by hole. However, the Li₄Ti₅O₁₂ is an insulator. It is very interesting that one n-type cell and two p-type cells constitute one Li₄Ti₅O₁₂ supercell which is insulating. The results show that the intercalation potential obtained with a p-type unit cell with one additional electron is quite close to the experimental value of 1.5~V.