Thermal Stability Landscape of Solid-State Batteries

Solid-state batteries (SSBs) with lithium metal anodes promise to offer high energy densities, enabling applications such as long-range electric vehicles and electric aviation. While various challenges related to transport, chemomechanics, and interfacial morphology have been extensively investigated, the thermal stability of the underlying solid/solid interfaces still requires comprehensive assessment. In this Perspective, we present mechanistic insights into the coupled influence of electrode–electrolyte interactions, heterogeneities, and gas-evolution dynamics in governing distinct thermal instability pathways in inorganic SSBs. The critical role of interphase chemistry and lithium morphology in thermal runaway at the anode/solid electrolyte interface and cathode-driven phenomena such as oxygen release, state-of-charge effects, pressure buildup, and crosstalk reactions are discussed. We further examine how operating conditions including pressure, current density, temperature, and moisture exposure modulate thermo-kinetic pathways and the exothermic behavior of SSBs. Key scientific gaps are identified, providing a foundation for future research toward the development of thermally stable and safe SSBs.