Grain-Boundary-Free Glassy Solid Electrolytes based on Sulfide Materials: Effects of Oxygen and Nitrogen Doping on Electrochemical Performance

While much of the current research on glassy solid electrolytes (GSEs) has focused on the binary Li₂S+P₂S₅ system, compositions with Si are of interest because Si promotes stronger glass formation and allows low-cost melt-quenching (MQ) synthesis under ambient pressure. Another advantage is that they can be formed in homogeneous and continuous glass forms, as a result they are free of grain boundaries. In this work, we have examined the structures and electrochemical properties of bulk glass pieces of sulfide and oxy-sulfide GSE compositions and have also expanded the study by using LiPON glass as a dopant to produce an entirely new class of nitrogen doped mixed oxy-sulfide nitride (MOSN) GSEs. Upon doping with oxygen and nitrogen, the solid electrolyte interface (SEI) is stabilized and the doped MOSN GSE exhibits a critical current density (CCD) of 1.8 mA cm⁻² at 100 °C. We also report on improving the glass quality, the SEI engineering and its limitations, and future plans of improving the electrochemical performance of these homogeneous MQ MOSN GSEs. These fundamental results can help to understand the structures and doping effects of the bulk GSEs, and as such can provide a guide to design improved homogeneous grain-boundary-free GSEs.