First principles study of the elastic properties of Li2MnSiO4-ySy

First principles calculations were performed to investigate the elastic properties of Li2MnSiO4-ySy (y = 0, 0.5, 1, 2, 4) with the aim of improving the structural stability of silicate materials during charge/discharge cycles. Computational results show that the material ductility has been overall improved by sulfur substitution for oxygen. In particular, the Pugh ratios B/G of MnSiO3S and MnSiO2S2 are 1.97 and 2.79, respectively, significantly larger than the critical value 1.75 that separates ductile and brittle materials. In this sense, the ductile-brittle transition during delithiation can be suppressed and the reversible deinsertion of two Li ions per formula unit would be achieved in Li2MnSiO4-ySy. This study provides an alternative way for improving the electrochemical performance of silicate materials.