Elucidating the effects of −OH content on phase transition and Li-ion transport of anti-perovskite solid electrolytes

Anti-perovskite materials such as Li₂(OH)Cl have garnered considerable interest as solid electrolytes due to their numerous advantages. However, the low ionic conductivity of the orthorhombic Li₂(OH)Cl near room temperature presents a significant challenge for the application. In this study, we intricately modulate the −OH content in Li₂(OH)Cl through a controlled heat treatment process. This method effectively increases the cubic phase content and lowers the phase transition temperature, thereby enhancing the ionic conductivity at 30 °C by more than an order of magnitude. Theoretical calculations illustrate that the removal of −OH content significantly reduces the barrier for phase transition, leading to substantial alterations in the Li-ion transport pathway and migration barrier. Furthermore, LiHClO-600 demonstrates exceptional resistance to lithium reduction and is compatible with lithium metal and LiFePO₄, rendering it a viable solid electrolyte for batteries. Both experimental findings and theoretical calculations cohesively highlight the pivotal role of −OH content in driving phase transition and facilitating Li-ion transport in anti-perovskite solid electrolytes, paving the way for their potential utilization in all-solid-state batteries.