An Insight into Halide Solid-State Electrolytes: Progress and Modification Strategies

Tremendous studies have been engaged in exploring the application of solid-state electrolytes (SSEs) as it provides opportunities for next-generation batteries with excellent safety and high energy density. Among the existing SSEs, newly developed halide SSEs have become a hot spot owing to their high ionic conductivity up to 1 mS cm-1 and their stability against high-voltage cathode. As a result, halide SSEs have been shown to be promising candidates for all-solid-state lithium batteries (ASSLBs). Here, we review the progress of halide SSEs and available modification strategies of halide SSE-based batteries. First, halide SSEs are divided into four different categories, including halide SSEs with divalent metal, trivalent metal, tetravalent metal, and non-metal central elements, to overview their progress in the studies of their ionic conductivity, crystal structure, conductive mechanism, and electrochemical properties. Then, based on their existing drawbacks, three sorts of modification strategies, classified as chemical doping, interfacial modification, and composite electrolytes, along with their impacts on halide SSE-based batteries, are summarized. Finally, some perspectives toward halide SSE research are put forward, which will help promote the development of halide SSE-based batteries.