Characterizing the Stability and Kinetics of Hybrid Oxide-Sulfide Solid Electrolyte Cells

Abstract

Growing energy applications and markets demand safer and higher performance Li-ion batteries. All solid-state batteries (ASSBs) represent a significant step forward in Li-ion battery technology. We have recently described the production of Li6.25La3Al0.25Zr2O12 (LLZO) solid state electrolyte (SSE). LLZO provides high room temperature ionic conductivities as well as chemical and mechanical stability towards metallic Li, which has 10X the specific capacity of a carbon anode. Sulfide based SSEs have high room temperatures conductivities, but their chemical and mechanical stability towards metallic Li has not been well defined. Here, we describe the construction of ASSBs with a metallic Li anode, a solid oxide electrolyte (LLZO), and a composite cathode consisting of an 75Li2S:25P2S5 sulfide electrolyte and TiS2 cathode. This architecture isolates the Li anode from the sulfide SSE and allows for facile assembly with a cold-pressed composite cathode powder. Electrochemical impedance spectroscopy (EIS) was used to probe the electrochemistry of the LLZO/Li2S:P2S5 interface as a function of temperature, pressure, and current density. DC cycling at 70°C and post mortem materials characterization were performed to determine the long-term stability of the hybrid oxide/sulfide interface.