Lithium fluoride additive for inorganic LiAlCl4·3SO2 electrolyte toward stable lithium metal anode

Abstract

Lithium metal is considered to be one of the most promising anode materials for next-generation energy storage systems. However, low Coulombic efficiency and dendrite growth during cycling limit the practical applications of lithium metal. In this work, a non-combustible inorganic electrolyte-LiAlCl4·3SO2 is modified with LiF additive to achieve a more stable lithium metal anode. By adding 0.3 wt% LiF to LiAlCl4·3SO2, the ionic conductivity and lithium ion transference number of LiAlCl4·3SO2 are increased, and lithium ion migration through the solid electrolyte interface (SEI) film of lithium metal anode is easier. Thus, a more stable lithium metal anode is achieved. Therefore, at 2.0 mA cm−2 and 2.0 mAh·cm−2, Li|Cu cells with LiAlCl4·3SO2 containing 0.3 wt% LiF can provide a stable cycling for 310 h with an average Coulombic efficiency up to 97.0%. Moreover, the addition of 0.3 wt% LiF in LiAlCl4·3SO2 can also improve the electrochemical performance of Li-SO2 full-cell. With an areal capacity of 2 mAh·cm−2, Li-SO2 cell with LiAlCl4·3SO2 containing 0.3 wt% LiF can deliver ∼900 mAh·g (carbon)−1 at a discharge current densities of 0.5 A g (carbon)−1. Therefore, we believe that a simple and effective solution is provided in this work to improve the stability of lithium metal anode with LiAlCl4·3SO2 inorganic electrolyte.