Wet Chemical Synthesis of Dianion-Doped Halide Solid-State Electrolytes for Improved Interface Stability

Abstract

Halide Li3YCl6 (LYC) is receiving great attention due to its low raw material price and wide electrochemical window. However, its low ionic conductivity and poor lithium metal stability hinder its practical application in all-solid-state lithium batteries. Herein, a halide electrolyte Li3YBr2Cl3.7F0.3（σ=2.38 mS cm-1）containing three halogen elements is synthesized by wet chemistry synthesis. The interfacial protection mechanism is investigated by scanning electron microscopy and X-ray photoelectron spectroscopy, and the fluorine-rich interfacial layer is generated in situ, allowing for smaller polarization and reduction inhibition, thus making the cycling process more stable. The lithium plating/stripping test of the lithium-symmetric battery shows that the interface stability between bihalogen-doped halide and lithium metal is significantly improved, and the cycle test time can be stably maintained for more than 1600 h at 0.1 mA cm-2. Moreover, the LYBCF0.3 based all-solid-state battery maintains a stable discharge capacity of 70 mAh g-1 at 0.3 C for 100 cycles at room temperature, demonstrating excellent electrochemical performance. This study presents a simple and economical wet chemical synthesis route for the preparation of fluorine-doped multi-component high performance halide electrolytes and demonstrates their potential for large scale production.

Keywords: Halide solid electrolytes, All-solid-state batteries, Wet-chemistry, Electrolyte modification