Dopant-controlled early-stage stability of LLZO/Li13Si4 interfaces for thermal batteries

This is the authors' abstract. We don't add key points for this paper.

Thermal batteries operate above 500 °C, where molten-salt electrolytes are prone to leakage, volumetric expansion, and interfacial corrosion. Garnet-type Li 7 La 3 Zr 2 O 12 (LLZO) has been proposed as a solid-electrolyte alternative, but its performance depends on solid–solid interfacial reactions whose early-stage evolution is difficult to probe experimentally. Here, ab initio molecular dynamics simulations at 500 °C are used to examine how Al, Ga, and Ta dopants affect the early-stage structural and electronic response of LLZO/Li 13 Si 4 interfaces. Because the low-energy LLZO surface differs in orientation or termination among the compositions, the comparison reflects dopant chemistry together with surface configuration rather than dopant identity alone. Although the overall charge transfer is comparable across all systems, within the 8 ps trajectories the Ta-doped interface shows charge redistribution extending more broadly into the LLZO interior. In contrast, the Ga-doped interface shows charge redistribution localized near the interface together with greater dopant displacement and local structural rearrangement, and the Al-doped interface lies between the two. The early-stage interfacial response is thus characterized by the spatial distribution of the redistributed charge and the accompanying thermally activated atomic rearrangement, not by the magnitude of charge transfer. These features may serve as descriptors for LLZO-based interfaces at high temperature.