Quasi‐solid‐state conversion cathode materials for room‐temperature sodium–sulfur batteries

Room‐temperature sodium–sulfur batteries (NaSBs) are promising candidates for next‐generation large‐scale energy storage solutions. However, the well‐known polysulfide shuttling of soluble long‐chain sulfur intermediates still remains a limitation in NaSBs, leading to rapid capacity loss arising from the dissolution of active sulfur into the electrolyte. This problem is effectively circumvented in quasi‐solid‐state conversion cathodes by elimination of the presence of these soluble intermediates altogether, with only insoluble intermediates formed in the process. Herein, we discuss various cathode materials that undergo quasi‐solid‐state conversion when cycled in a liquid electrolyte, including chemically bonded short‐chain sulfur species, short‐chain sulfur via physical confinement, and quasi‐solid‐state conversion cathodes with long‐chain sulfur moieties. We conclude by highlighting the current challenges and possible strategies to improve the mechanistic understanding and cycling performance of NaSBs for practical applications.