Rapid Thermal Annealing of Cathode-Garnet Interface toward High-Temperature Solid State Batteries

High-temperature batteries require the battery components to be thermally stable and function properly at high temperatures. Conventional batteries have high-temperature safety issues such as thermal runaway, which are mainly attributed to the properties of liquid organic electrolytes such as low boiling points and high flammability. In this work, we demonstrate a truly all-solid-state high-temperature battery using a thermally stable garnet solid-state electrolyte, a lithium metal anode, and a V₂O₅ cathode, which can operate well at 100 °C. To address the high interfacial resistance between the solid electrolyte and cathode, a rapid thermal annealing method was developed to melt the cathode and form a continuous contact. The resulting interfacial resistance of the solid electrolyte and V₂O₅ cathode was significantly decreased from 2.5 × 10⁴ to 71 Ω·cm² at room temperature and from 170 to 31 Ω·cm² at 100 °C. Additionally, the diffusion resistance in the V₂O₅ cathode significantly decreased as well. The demonstrated high-temperature solid-state full cell has an interfacial resistance of 45 Ω·cm² and 97% Coulombic efficiency cycling at 100 °C. This work provides a strategy to develop high-temperature all-solid-state batteries using garnet solid electrolytes and successfully addresses the high contact resistance between the V₂O₅ cathode and garnet solid electrolyte without compromising battery safety or performance.