Li-Ion Transport and Mechanics of Li–S–P–B–I Glassy Electrolytes

This work employs molecular dynamics simulations with a machine learning force field (MLFF) to reveal how the competition between B-S and P-S networks governs the properties of 30Li₂S - 25B₂S₃ - 45LiI - aP₂S₅ (LSPBI) glasses across a full composition range (from 0 P₂S₅ to 100 P₂S₅). We demonstrate that the introduction of P₂S₅ into a B₂S₃-based glass induces a critical structural transformation, which non-monotonically optimizes both ionic conductivity and mechanical nano-ductility. At moderate P₂S₅ contents, incorporated PS₄ units depolymerize the rigid boron framework, creating percolative diffusion pathways that enhance ionic conductivity. Concurrently, the emergence of flexible P-S-P configurations enables energy dissipation through bond bending, shifting fracture behavior from brittle to ductile. However, excessive P₂S₅ promotes condensed polyphosphates (e.g., P₂S₆, P₂S₇), which re-polymerize the network and ultimately impede Li⁺ mobility.<br/>