Entropy‐Engineered Quinary Inorganic Molten Salt Electrolyte Enables High‐Energy Supercapacitors at 75°C With Hierarchically Ordered Macroporous Carbon Electrode

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ABSTRACT All inorganic molten salt electrolytes (MSEs) are attractive for electrochemical energy storage but typically require elevated operating temperatures due to high melting points normally exceeding 120°C. Here we report a low‐melting, quinary molten salt electrolyte comprising AlCl 3 , NaCl, KCl, KOH, and LiCl (ANKKL; molar ratio 0.6:0.2:0.2:0.15:0.2) that remains liquid at near 60°C. The incorporation of multiple salt components increases configurational entropy and promotes diverse complex solvation structures, which suppress crystallization and stabilize the molten phase at reduced temperature. ANKKL exhibits high ionic conductivity (∼0.15 S cm −1 at 75°C). Ab initio molecular dynamics and Raman spectroscopy confirm the formation of multiple Al‐based complex anions (AlCl 4 − , Al 2 Cl 7 − , AlCl 3 OH − , and Al 2 Cl 6 OH − ), indicating a disordered ionic environment favorable for fast ion transport. Couple ANKKL with hierarchically ordered macroporous carbon electrode featuring interconnected micro/meso/macropores yields dual charge storage that combines electric double‐layer capacitance and nanoconfinement‐enabled pseudo‐capacitance. Devices deliver 570 F g −1 and 87.5 Wh kg −1 at 1.3 kW kg −1 (75°C), as well as excellent capabilities of thermal re‐cycling and self‐discharge suppression, retaining ∼99% capacitance after 10 000 cycles. These results demonstrate that entropy‐engineered multicomponent molten salts represent practical, thermally stable, and cost‐effective electrolyte platform for high‐energy supercapacitors operating below 100°C.

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