Thermal transport mechanisms in electrolytes for all-solid-state batteries

Solid electrolytes are central to next-generation solid-state batteries due to their improved safety and compatibility with high-energy electrodes. Beyond these advantages, their thermal transport behavior critically governs heat dissipation, with direct implications for battery efficiency, durability, and operational reliability. Here, we examine the thermal transport properties of inorganic solid electrolytes, drawing from both experimental measurements and theoretical analyses. We first summarize reported thermal conductivities across major material classes, including oxides, sulfides, and halides, and highlight their characteristic glass-like behavior. We then analyze the underlying mechanisms governing intrinsically low thermal conductivity, including liquid-like phonon dynamics, complex phonon dispersions, strong lattice anharmonicity, and diffuson-mediated thermal transport. Extrinsic factors such as site disorder, porosity, aging-induced phase changes, and composite architectures are also reviewed for their roles in modifying thermal transport. In addition, the relationship between ionic transport and thermal transport in solid electrolytes is discussed. This review provides a systematic perspective on thermal transport in solid electrolytes and highlights its implications for thermal management strategies in solid-state batteries.