Improved stability against moisture and lithium metal by doping F into Li3InCl6

The halide Li3InCl6 (LIC) has emerged as a promising solid electrolyte for its high ionic conductivity and oxidation stability, while the development of applicable LIC for solid-state Li batteries is severely hampered by the poor stability against moisture and lithium metal. In this work, fluorine doping of LIC is proposed to solve the aforementioned issues. The doping of fluorine into the LIC lattice can be simply achieved by ball-milling with low-temperature annealing. The ionic conductivity of optimized F-doped LIC (Li3InCl5.6F0.4, LICF0.4) reaches 1.37 × 10−3 S cm−1 at 30 °C. Benefiting from the in-situ formed F-rich interface, the Li symmetric cells with LICF0.4 electrolytes exhibit lower resistance and smaller polarization than those with LIC electrolytes. Moreover, the LICF0.4 shows enhanced moisture-stability owing to the formation of Li–F bond in the crystal structure. This work indicates that fluorine doping is a simple and effective way to improve the stability of Li3InCl6 against moisture and Li metal, which is helpful for the real application of Li3InCl6