HCl-Free Mechanochemical Synthesis of Lithium Niobium Oxychlorides

초록

Halide-based oxychloride electrolytes, including LiNbOCl4, are promising candidates for all-solid-state batteries (ASSBs) due to their high ionic conductivity and compatibility with oxide cathodes. Common synthesis using LiOH and NbCl5 produces corrosive HCl gas, raising environmental and safety concerns. Here, we report an alternative route using mixtures of oxides and chlorides that eliminates HCl byproduct. LiNbOCl4 synthesized via this method forms a crystalline phase without postannealing and exhibits an ionic conductivity of 11.8 mS cm-1 at 25 degrees C. The soft lattice and flexible [NbOCl4]- chains facilitate rapid Li+ diffusion with low activation energy, enhancing ionic transport. Electrochemical tests demonstrate that LiNbOCl4 functions effectively as a catholyte with high-nickel cathodes (LiNi0.8Co0.1Mn0.1O2) in a dual-electrolyte architecture, underscoring its practical applicability. This work establishes a safe and environmentally friendly, HCl-free mechanochemical synthesis pathway and highlights the critical role of precursor selection in achieving high-conductivity oxyhalide solid electrolytes without postannealing for next-generation ASSBs.

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