Interfacial instabilities in halide-based solid-state batteries

All-solid-state batteries have emerged as a promising technology for energy storage, offering improved safety and potential for higher energy density. Halide-based batteries have gained popularity due to the advantageous characteristics of electrolytes, including decent ion conductivity, good formability, high-voltage stability, and moisture resistivity. Despite the impressive cycle life observed in halide-based batteries under high stack pressures or at elevated temperatures, poor cathode–electrolyte stabilities still pose a significant challenge that results in rapid capacity decay under ambient temperature and low pressure. The poor stability at the halide–anode interface further limits the choice of electrode materials for high-energy applications. This article presents a review of interfacial instability in halide-based solid-state batteries, addressing both the chemical, electrochemical, and mechanical origins of these instabilities at the cathode–electrolyte and anode–electrolyte interfaces. We also discuss state-of-the-art approaches to mitigate interfacial instabilities and highlight their limitations. Finally, we propose perspectives and future directions for resolving interfacial instabilities in halide-based solid-state batteries. Graphical abstract