LiCl-LiBr-KBr-KF electrolyte with low-melting-point and high electrical-conductivity for molten salt thermal batteries

Developing molten salt electrolytes with a low melting point and high electrical conductivity is critical for advanced thermal batteries. A novel LiCl-LiBr-KBr-KF (15.0-55.0-25.0-5.0 mol%) molten salt electrolyte was designed and validated through phase diagram calculation and experimental measurements. Compared with the LiCl-LiBr-KBr system, the melting point of the LiCl-LiBr-KBr-KF system decreased by 8.0 °C, the electrical conductivity increased by 0.25 S/cm, and the electrochemical window widened by 0.1 V at 500.0 °C. The mass loss of LiCl-LiBr-KBr-KF electrolytes at 830.0 °C is only 3.0 wt%, and its density at 500.0 °C is 2.36 g/cm 3 , i.e., 0.07 g/cm 3 higher than that of LiCl-LiBr-KBr. Practically, its lower melting point can reduce the activation energy of thermal batteries. Meanwhile, enhanced electrical conductivity and Li + diffusion coefficient can improve the power density and response speed of the thermal battery. LiCl-LiBr-KBr-KF electrolyte exhibits superior comprehensive performance. This result not only enriches the high-performance molten salt materials but also provides a novel strategy for designing next-generation thermal battery electrolytes.