Fluorinated SO2-based inorganic electrolytes for enhanced electrochemical performance in Li-metal anodes

Nonflammable SO2-based inorganic liquid electrolytes have attracted attention as electrolyte candidates for Limetal batteries (LMBs), primarily because of their nonflammability, superior ionic conductivity, and wide operating temperature range. Despite these advantages, SO2-based inorganic liquid electrolytes have not yet been commercialized because of their difficulty in suppressing Li dendrite growth, which is a critical requirement for the safe and reliable operation of LMBs. In this study, we found that a new F-substituted electrolyte, LiAlCl3.7F0.3-3SO2, suppressed Li dendrite growth in LMBs across various current densities (1-3 mA/cm2) at an areal capacity of 3 mAh/cm2, thereby improving cycling stability. The AlF3-containing solid electrolyte interphase on the Li-metal anode effectively inhibited Li dendrite growth. Fluorinated SO2-based inorganic liquid electrolyte enabled considerably improved cycling performance of a Li/LiFePO4 full cell, achieving a capacity retention of 72.7 % after 1,000 cycles at a current density of 0.5 C.