Phase-transition-mediated interfacial reconstruction for adaptive ion transport in high-temperature solid-state batteries

Lithium-ion conductor as Li 5 AlO 4 (LAO) with strongly temperature-dependent ionic transport behavior is selected as the representative to build the new types of high-temperature battery. • A phase-transition-mediated interfacial engineering strategy is proposed to reconstruct rigid solid-solid interfaces into adaptive solid-liquid junctions. • Cell FeS 2 ||LiCl-KCl||LAO||Li-B delivers a high discharge capacity of 648.9 mAh g −1 at 400 °C and 10 mA cm −2 . • This work establishes a general strategy for mitigating interfacial polarization and enabling high-rate operation in high-temperature batteries. High-temperature solid-state batteries are promising power sources for aerospace, defense, and extreme-environment applications because of their intrinsic safety and high-power capability. However, conventional solid electrolytes often remain ionically conductive at room temperature, might resulting in capacity degradation cause by unintended lithium-ion transport prior to battery operation. In this work, Li 5 AlO 4 (LAO) is newly selected as the representative solid electrolytes which exhibit strongly temperature-dependent ionic transport behavior, making them suitable for high-temperature batteries with reduced self-discharge risk under battery storage conditions. In addition, we also propose a phase-transition-mediated interfacial engineering strategy, to overcome the high interfacial polarization resistance under practical high-current operation, mainly originated from the rigid and non-reconfigurable solid-solid interface between the electrode and electrolyte. The result indicates that the originally discrete solid-solid interface can be reconstructed into a dynamically adaptive solid-liquid-solid ion-transport junction by introducing a thermally responsive LiCl-KCl interlayer that remains solid during battery assembly but undergoes in situ liquefaction at the operating temperature. This interface rebuilt approach significantly improves interfacial contact, reduces interfacial resistance, and facilitates more efficient ionic flux transfer across the cathode/electrolyte interface. As a result, the internal resistance is dramatically reduced from 37.26 Ω to 0.81 Ω, while the optimized FeS 2 ||LiCl-KCl||LAO||Li-B cell delivers a high specific capacity of 648.9 mAh g −1 at 400 °C and 10 mA cm −2 . This work demonstrates that phase-transition-mediated interfacial reconstruction provides an effective strategy for regulating interfacial ion transport and mitigating polarization in high-temperature solid-state batteries, offering a promising route toward safe and high-power electrochemical energy systems for extreme environments. Download: Download high-res image (232KB) Download: Download full-size image