Polysulfides immobilization and conversion by nitrogen-doped porous carbon/graphitized carbon nitride heterojunction for high-rate lithium-sulfur batteries

Improving efficiency of solid-liquid-solid multiphase conversion of sulfur to Li2S and suppressing lithium polysulfide shuttle phenomenon are crucial tasks for industrialization of lithium-sulfur batteries. In this study, a novel honeycomb-like nitrogen-doped porous carbon/graphitized carbon nitride (HPCG) heterojunction nanocatalyst is prepared using truncated rhombic dodecahedral zeolitic imidazolate framework-8 (TRD-ZIF-8) nanoparticles as a synthesis template. A unique hierarchical porous structure and abundant active catalytic sites of HPCG can effectively immobilize polysulfides, accelerate long-chain polysulfide conversion and promote Li2S nucleation, thereby inhibiting the shuttle effect. HPCG cells exhibit good rate performance and excellent high-rate cycling stability with only 0.073% capacity decay per cycle after 1000 cycles at 5 C. Specifically, a cell with a low electrolyte/sulfur (E/S) ratio of 9.6 µL mg−1 demonstrates stable operation over 300 cycles at 1C. This work is expected to deepen the understanding of interphase conversion process of complex lithium polysulfides and provide new ideas for designing sulfur host materials of lithium-sulfur batteries.