A high-pressure induced stable phase of Li2MnSiO4 as an effective poly-anion cathode material from simulations

Abstract

Search for novel cathode materials is of current interest. Among them, Li₂MnSiO₄ shows promise as a cathode material in the poly-anion family due to its structural diversity, abundance, low cost, and high theoretical capacity (330 mA h g⁻¹). However, it suffers from low electronic and ionic conductivity, limited reversible capacity, and poor cycling performance. To overcome these deficiencies, using a global structure search at high pressure, we find a new phase with a group symmetry of Cc, which is the ground-state at a pressure of 50 Gpa, and remains stable when the pressure is released. This new phase exhibits many attractive features such as a high energy density of 612 Wh kg⁻¹ with a reversible capacity of 170 mA h g⁻¹, a high average discharge voltage of 3.6 V, improved electronic conductivity, coexistence of anionic and cationic redox, and superior ionic conductivity due to unique diffusion channels with reduced steric hindrance and coulombic repulsion. All these features endow the new phase of Li₂MnSiO₄ with potential for use as a high performance cathode material.