Hydridoborate-Based Solid Electrolytes for All-Solid-State Batteries

All-solid-state batteries (ASSBs) utilizing solid electrolytes, which replace flammable liquid electrolytes, are regarded as one of the most promising prospective energy storage devices due to their inherent safety advantages and high energy density potential. As an emerging class of electrolytes for ASSBs, hydridoborates have attracted research interest because of their attractive material properties, including superior compatibility with metal anodes, low gravimetric density, and excellent solution processability. In this review, hydridoborate-based solid electrolytes (SEs) for all-solid-state batteries, including boranuide-based SEs, arachno-hydridoborate-based SEs, nido-hydridoborate-based SEs, closo-hydridoborate-based SEs, and conjuncto-hydridoborate-based SEs, are comprehensively summarized. Specifically, the strategies to improve ion conductivity, the ion conduction mechanism, and the performance of hydridoborate-based SEs in ASSBs are discussed. Finally, the practical challenges for the application of hydridoborate SEs in ASSBs and the future development in the field are proposed. This review provides a detailed account of the advancements in hydridoborate-based solid electrolytes, not only mapping the progress made in this field but also proposing an effective strategy for researchers to innovate efficiently to realize the practical applications of hydridoborate-based SEs for the next generation of rechargeable batteries.