Recent advances in sulfurized polyacrylonitrile cathodes for lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries are attractive for next-generation energy storage due to the high theoretical capacity (1675 mA h g⁻¹) and energy density (≈2600 Wh kg⁻¹) of sulfur cathodes. However, traditional sulfur cathodes suffer from severe challenges including the electrical insulation of sulfur, large volume changes upon cycling, and the notorious polysulfide shuttle effect that causes rapid capacity fade. In this regard, sulfurized polyacrylonitrile (SPAN) has emerged as a promising cathode material to overcome these issues. By chemically binding sulfur within a carbon–nitrogen polymer matrix, SPAN completely suppresses polysulfide dissolution and shuttle, enabling highly stable cycling. It is synthesized by simple thermal treatment of polyacrylonitrile with sulfur, yielding a covalently bonded S–C network that is compatible with conventional carbonate electrolytes. This review provides a comprehensive overview of SPAN cathodes, including their structural characteristics and unique solid-state redox mechanism, as well as recent advances in material design and performance optimization. We highlight key studies that elucidate the covalent bonding and lithiation chemistry of SPAN, and we survey state-of-the-art strategies from conductive composites and dopants to electrode engineering, which have elevated its electrochemical performance. Finally, remaining challenges and perspectives for practical Li–S batteries with SPAN cathodes are discussed.