Li3Y(PS4)2 and Li5PS4Cl2 : New Lithium Superionic Conductors Predicted from Silver Thiophosphates Using Efficiently Tiered Ab Initio Molecular Dynamics Simulations

We report two novel, earth-abundant lithium superionic conductors, Li3Y(PS4)2 and Li5PS4Cl2, that are predicted to satisfy the necessary combination of good phase stability, high Li+ conductivity, wide band gap and good electrochemical stability for solid electrolyte applications in all-solid-state rechargeable lithium-ion batteries. These candidates were identified from a high-throughput first principles screening of the Li-P- S ternary and Li-M-P-S (where M is a non-redox-active element) quaternary chemical spaces, including candidates obtained by replacing Ag with Li in the Ag-P-S and Ag-M-P-S chemical spaces. An efficient tiered screening strategy was developed that combines topological analysis with ab initio molecular dynamics simulations to rapidly exclude candidates unlikely to satisfy the stringent conductivity requirements of lithium superionic conductors. In particular, we find Li3Y(PS4)2 to be an extremely promising candidate exhibiting a room-temperature Li+ conductivity of 2.16 mS/cm, which can be increased multi-fold to 7.14 mS/cm and 5.25 mS/cm via aliovalent doping with Ca2+ and Zr4+, respectively. More critically, we show that the phase and electrochemical stability of Li3Y(PS4)2 is expected to be better than current state-of-the-art lithium superionic conductors.