(Invited) Thiophosphate Based Solid Electrolytes and Cathodes Interfaces

Abstract

Stable high ion-conducting solid electrolytes are enablers for all solid state batteries. Among many class of materials, Lithium thiophosphate family of solid electrolytes have been investigated for their (a) superionic ion-conductivity (>10-4 S/cm), (b) mechanical softness and higher interfacial wettablity, (c) relatively simple synthesis and processing routes and (d) lower cost and earth abundance. Despite such advantages thiophosphates are known to have a narrow electrochemical stability window with a thermodynamical stability window between 1.7-2.6V (with respect to Li+/Li). Under such scenario, interfacial stability between Lithium thiophosphate/Li-metal and cathodes are primarily dictated by kinetic control by formation of a reaction passivation layer. Interfacial charge transfer depends on the detailed composition of the passivation reaction at the interface. The talk will highlight on the electrochemical performance characterization of the solid electrolyte, Li3PS4 and lithium-ion cathode such as LiFePO4. Detailed interfacial characterization between Li3PS4 and cathode interphases probed by XPS, NMR and electrochemical impedance spectroscopy (EIS) will be presented. In addition, synthesis and characterization of high capacity polysulfidophosphate cathodes based on catenation of sulfur to thiophosphate electrolytes, Li3(PS4)Sn where n = 5,8,6,3,2 will be discussed.