Unlocking Low-Melting-Point and High-Conductivity Molten Salts via High-Entropy Strategy with Demonstration in Thermal Batteries.

The development of advanced molten salt electrolytes for thermal batteries has long been hindered by an intrinsic trade-off between low melting point and high ionic conductivity, posing a fundamental limitation to their performance optimization. To address this challenge, this work reports a high-entropy design strategy that breaks this long-standing constraint by leveraging configurational complexity to simultaneously modulate thermodynamic and transport properties. By constructing a quinary LiF-LiCl-LiBr-KBr-CsBr molten salt system, the introduction of multiple ionic species generates substantial lattice distortion and high configurational entropy, leading to a markedly reduced melting point of 229.5°C and 1.19 S cm-1 at 350°C. When implemented in thermal batteries, a prototype battery achieves ultrafast activation within 64 ms. This work establishes high-entropy design as a general pathway to advanced electrolytes for high-temperature electrochemical applications.