Unraveling (electro)-chemical stability and interfacial reactions of Li10SnP2S12 in all-solid-state Li batteries

Li10SnP2S12 (LSPS) with high ionic conductivity and moderate price is a promising solid electrolyte for all-solid-state batteries. However, the instability of LSPS and LSPS/electrodes interfaces would cause poor cycle performance issues in the LSPS-based all-solid-state batteries, which have not been well understood. Herein, we address and unravel the decomposition products of LSPS and their Li+ transfer characteristics, especially on the surface of LSPS/electrodes by using solid-state nuclear magnetic resonance (ss NMR) spectroscopy coupled with X-ray photoelectron spectroscopy (XPS). The results reveal that the high mechanical energy during ball-milling process leads to the decomposition of LSPS into Li4SnS4 and Li3PS4. During charge/discharge cycling, specific capacity fading of batteries originates from the formation of new interfacial layer at LSPS/Acetylene black cathode and LSPS/Li metal anode interfaces. Furthermore, our results demonstrate that the rough and porous morphology of the interface formed after cycling, rather than the decomposition products, is the critical factor which results in the increases of the interfacial resistance at LSPS/Li interface and serious formation of Li dendrite. Our results highlight the significant roles of (electro)chemical and interfacial stability of sulfide solid electrolyte in the development of all-solid-state batteries.