Acetonitrile-driven structural change of Li3InCl6 enables amorphization of PEO-LiTFSI for enhanced room-temperature performance

Abstract

Poly(ethylene oxide) (PEO)-based electrolytes are promising for all-solid-state batteries but are typically limited to elevated temperatures due to PEO crystallinity and strong Li⁺–EO coordination. Here, we report a homogeneous PEO–LiTFSI electrolyte incorporating optimized Li3InCl6 that suppresses PEO crystallization, weakens Li⁺–TFSI⁻ coordination, and enhances Li-ion transport after acetonitrile solvent removal. This effect originates from the structural collapse of Li3InCl6 in acetonitrile, which exposes In3⁺ sites that preferentially adsorb TFSI⁻ anions, thereby disrupting the regular arrangement of PEO chains and inducing amorphization. In contrast to other oxide-based inorganic fillers, our results also found that the interface between PEO and Li3InCl6 enables efficient Li-ion transport. The resulting electrolyte achieves a high room-temperature ionic conductivity of 1.13×10⁻4 S cm-1 and excellent cycling stability with a LiNi0.8Co0.1Mn0.1O2 cathode, retaining 74 % capacity after 100 cycles at 0.3 C and 25 oC. To confirm the generality of this strategy and mechanism, we extended it to InCl3 and GaCl3 fillers, which similarly promoted amorphization in PEO–LiTFSI electrolytes. This work provides a general strategy to design amorphous polymer electrolytes for high-voltage solid-state batteries operating at room temperature.