Cost-Effective and Humid Air-Stable Fluoride Solid Electrolyte with High Ionic Conductivity Induced by Microstructural Modulation
Xianhui Nie, Lei Meng, Jiulin Hu, Chilin Li
Abstract
Among halide solid-state electrolytes (SSEs), fluorides show distinct advantages in chemical and electrochemical stability but are plagued by inadequate room-temperature (RT) ionic conductivity. Herein, we propose a cost-effective and humid air-stable fluoride SSE Li 2 TiF 6 synthesized by a simple hydrothermal method, exhibiting a high ionic conductivity of 9.69 × 10 –5 S/cm at RT and outstanding humidity tolerance. The enhanced ionic conductivity is demonstrated to originate from microstrain-induced crystal lattice expansion. Furthermore, a stable Li + -conductive and intimate interface between halide electrolyte and lithium metal is constructed by introducing a poly(ethylene oxide) protective layer, resulting in the symmetric cell exhibiting a long lifespan with stable cycling over 1000 h at 0.1 mA/cm 2 as well as the solid-state lithium metal batteries based on the LiFePO 4 cathode reversibly operated for at least 250 cycles at 0.5 C. This work provides fresh perspectives on resolving the cost and various stability issues encountered with halide SSEs.