From Cation Solvation to Anion Coordination: Lewis-Acidic Boranes Enable Halide Salt Electrolytes

Ion solvation in battery electrolytes involves supramolecular host–guest interactions and is most often enabled by Lewis basic coordination of cations, sometimes at the expense of cation mobility. Here, we investigate anion-centered solvation using Lewis acidic supramolecular hosts. We introduce a class of small-molecule boranes that selectively coordinate anions, enabling systematic interrogation of how anion binding strength governs salt dissociation and ion transport. A family of readily accessible boranes spanning a wide range of Lewis acidities was synthesized and evaluated with Li- and Na-based salts. Increasing borane Lewis acidity strongly correlated with enhanced dissociation and ionic conductivity of otherwise poorly soluble halide salts (Cl –, F – ), yielding order-of-magnitude conductivity enhancements and, in some cases, performance exceeding that of TFSI-based electrolytes. These results establish anion coordination strength as a powerful and tunable handle for regulating ion transport and expand supramolecular host–guest chemistry to the rational design of electrolyte solvation environments.