First principles study of the elastic properties of Li2MnSiO4−ySy

Abstract

First principles calculations were performed to investigate the elastic properties of Li₂MnSiO_4−yS_y (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 Li₂MnSiO_4−yS_y. This study provides an alternative way for improving the electrochemical performance of silicate materials.