Ball-milling-assisted construction of ternary mixed-metal oxide/g-C3N4 heterostructures for synergistic polysulfide adsorption and catalytic conversion in lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries are widely recognized as next-generation energy-storage systems; however, their practical realization remains severely constrained by sluggish redox kinetics and the dissolution and shuttling of lithium polysulfides. To address these challenges, we report a defect-enriched heterostructured material, denoted as HGN, composed of g-C3N4 and a ternary mixed-metal oxide (NiCoZn-O). It was constructed via a facile, solvent-free ball-milling strategy and employed as a multifunctional separator modifier. The intimate interfacial integration between g-C3N4 and NiCoZn-O generates a strongly coupled heterointerface that synergistically regulates polysulfide adsorption and catalytic conversion. Within this architecture, g-C3N4 supplies abundant electron-rich nitrogen sites that act as robust anchoring centers through Li–N interactions, thereby effectively suppressing polysulfide diffusion. Concurrently, the multimetallic NiCoZn–O framework furnishes redox-active Ni and Co centers, while Zn serves as a structural and electronic modulator that induces multiphase heterointerfaces and optimizes the local electronic environments. This interfacial coupling and compositional modulation collectively enhance polysulfide adsorption, accelerate redox conversion kinetics, and mitigate kinetic limitations during electrochemical reactions. Moreover, the defect-rich heterointerface promotes interfacial charge transfer via defect-assisted electronic coupling, further improving reaction reversibility and overall electrochemical performance. Benefiting from this cooperative adsorption-conversion mechanism, Li-S cells equipped with the HGN@PP separator deliver a discharge capacity of 583 mAh g-1 after 150 cycles at 1C and retain 525 mAh g-1 under a high sulfur loading of 8.0 mg cm-2 after 150 cycles at 0.1C. This work establishes a scalable interfacial engineering strategy for multifunctional separators and provides a practical pathway toward high-energy-density, long-life Li-S batteries.