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 Li₃YBr₂Cl_3.7F_0.3 (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 dianion-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 LYBCF_0.3 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.