Interfacial engineering of Li-B anodes with in situ formed LiAl alloy for high-performance molten salt electrolyte thermal batteries

Molten salt electrolyte thermal batteries are widely employed in military applications, particularly as power sources for guided missiles. The novel LiCl-LiF-Li 2 SO 4 electrolyte, with its wide electrochemical window, enables high-energy-density electrochemical systems when paired with high-voltage cathodes. However, severe negative reactions occur between this electrolyte and Li-B anodes, forming a reactant layer that degrades the discharge performance. In this study, a dense LiAl alloy layer that enables simultaneous ion and electron transport was in situ formed on the Li-B anode via cold pressing to suppress the negative interfacial reactions, thereby mitigating the deterioration of discharge performance. Discharge tests reveal that with a current density of 100 mA cm −2 , the modified Li-B-10Al anode (10-μm-Al-modified Li-B) achieves a specific discharge capacity of 2356.9 ± 18.4 mAh g −1 in a single cell, far exceeding the 1131.1 ± 25.6 mAh g −1 for the unmodified Li-B anode. Moreover, when paired with a high-voltage NiF 2 cathode, the cell using Li-B-10Al anode delivers a higher specific capacity (374.8 ± 5.4 vs . 231.9 ± 4.9 mAh g −1 ) and lower polarization compared to the cell with a Li-B anode. This study provides an innovative strategy to address interfacial issues in molten salt electrolyte/Li-B anode and opens a new route toward next-generation high-performance thermal batteries.