Synergistic polysulfide regulation and redox catalysis via CeSe2@TiSe2-C separator for practical high-loading lithium-sulfur batteries

Abstract The widespread commercialization of lithium–sulfur (Li–S) batteries is severely impeded by rapid capacity fading, polysulfide shuttling, and sluggish redox kinetics, particularly under the high sulfur loading and lean electrolyte conditions required for practical applications. This work reports a multifunctional separator that addresses these critical challenges by leveraging a CeSe 2 @TiSe 2 –C heterostructure (synthesized via an MXene-templated strategy) as a coating layer. The CeSe 2 component supplies abundant redox-active sites, enabling reversible polysulfide anchoring and catalytic conversion, while the TiSe 2 –C scaffold provides high electronic conductivity and robust mechanical support. This dual-function interlayer achieves effective polysulfide regulation and accelerates sulfur redox kinetics, as demonstrated by suppressed shuttle effect, reduced interfacial resistance, and enhanced lithium-ion transport. Li–S cells equipped with the CeSe 2 @TiSe 2 –C coated separator deliver outstanding electrochemical performance across both fundamental and application-relevant regimes. At a low sulfur loading of 1 mg⋅cm⁻ 2 , the system exhibits an initial discharge capacity of 1650 mAh·g⁻ 1 at 0.2C. Under practical conditions, i.e., high sulfur loading (5 mg⋅cm⁻ 2 ) and lean electrolyte ( E / S = 6.5 μL⋅mg⁻ 1 ), the cell achieves an initial capacity of 964 mAh⋅g⁻ 1 at 0.2C, retaining 729 mAh⋅g⁻ 1 after 100 cycles (75.6% retention) and maintaining a high average Coulombic efficiency of 97.9%. The charge-transfer resistance remains low (27.4 Ω), and comparative studies reveal superior suppression of polysulfide migration, enhanced redox kinetics, and significantly reduced capacity decay relative to TiSe 2 –C, CeSe 2 , or uncoated separators. These results establish a scalable and versatile separator design paradigm for Li–S batteries, integrating redox catalysis with conductive frameworks, and provide critical insights for the development of high-energy-density, long-life batteries for next-generation energy storage and electric mobility. Graphical abstract