Exploring the Potential of Halide Electrolytes for Next-Generation All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) are expected to revolutionize large-scale energy storage and electric vehicles due to their exceptional safety and high energy density. Central to this technology is the development of solid electrolytes, with halide electrolytes emerging as highly promising candidates, offering high ionic conductivity, robust electrochemical stability and excellent mechanical properties. Since the breakthrough discovery of Li₃YCl₆ in 2018, research on halide electrolytes has entered a new era. However, despite continuous research efforts, practical challenges persist in their application, including the need to further enhance ionic conductivity, improve moisture resistance, and achieve better compatibility with electrode materials. This review provides a comprehensive overview of recent progress and ongoing challenges in halide electrolytes, examining crystal structures, conduction mechanisms, and scalable synthesis techniques. Various modification strategies are also explored aimed at boosting ionic conductivity and electrochemical stability, with a particular focus on improving interface stability. Finally, future perspectives are outlined for designing high-performance halide electrolyte materials, offering guidance for ongoing research efforts toward their commercial application in ASSLBs.