First-principles investigation of the new phases and electrochemical properties of MoSi2 as the electrode materials of lithium ion battery

Abstract

Although Si is a promising anode material, the worse electric conductivity and volume expansion of Si are key bottlenecks. To solve these problems, we apply the ab-initio calculations to explore the structural feature, electrochemical and electronic properties of MoSi2. Two novel MoSi2 orthorhombic phases: TiSi2-type(Fmmm) and ZrSn2-type(Fddd) are predicted. MoSi2 markedly improves the elastic stiffness and volume deformation resistance of Si due to the formation of MoSi bond. The calculated volume of MoSi2 is smaller than that of Si. Importantly, the calculated average open circuit voltage(Voc) of hexagonal(P6222), tetragonal(I4/mmm), orthorhombic(Fmmm) and orthorhombic(Fddd) structures is 2.87 V, 1.23 V, 1.25 V and 2.47 V, respectively. The reason is that the introduction of Mo improves the charge overlap between the conduction band and the valence band. The tetragonal and orthorhombic structures exhibit metallic behavior due to the localized hybridization between Mo-d state and Si-p state. Our work provides a new path to improve the electrochemical and electronic properties of Si.