Li2S Anti-Passivation Deposition Guided by Electrochemically Self-Generated Thiophosphate Molecular Mediators for Lithium-Sulfur Batteries.

The practical deployment of high-energy lithium-sulfur (Li-S) batteries is critically impeded by low sulfur utilization, primarily due to the shuttle effect of soluble polysulfides and, less investigated, the passivation of the deposited Li2S film. To address these challenges, we report an electrochemically in situ self-generated Li3PS4 molecules that serve as novel molecular mediators to guide the nucleation of Li2S preferentially on Li3PS4, forming a 3D assembly film composed of Li3PS4@Li2S molecular clusters with an optimized stoichiometry ratio (1:6), thereby effectively suppressing the aggregation and passivation of bulk Li2S. The Li3PS4 mediators were cyclically generated during discharge from a cathode composed of a 3D phosphorus-sulfur covalent inorganic framework (P-S CIF) grown on Ti3C2Tx nanosheets (TNS). The P-S CIF features a tetrahedral architecture with phosphorus atoms at vertices interconnected by sulfur chains, spatially confining sulfur species to minimize long-chain polysulfides (Li2Sn, n≥6) generation. Benefiting from the synergistic effect of Li3PS4-mediated Li2S nucleation plus the spatial confinement provided by the P-S CIF, and the strong polysulfide anchoring capability of TNS, the TNS/P-S CIF cathode achieves exceptional stability and kinetics, delivering an initial capacity of 967 mAh g-1 at 0.1 A g-1 and retaining 673 mAh g-1 after 1000 cycles at 1 A g-1 (decay rate: 0.022% per cycle). Notably, the electrode maintains an areal capacity of 6.24 mAh cm-2 under a high loading of 9.8 mg cm-2, surpassing commercial benchmarks. This work establishes a molecular-level design paradigm for sulfur hosts, integrating structural precision with electrochemical functionality to advance the practical realization of high-performance Li-S batteries.