A LiPO2F2/LiFSI dual-salt electrolyte enabled stable cycling of lithium metal batteries

Metallic lithium, with super high theoretical specific capacity, enjoys great potential as an anode for rechargeable batteries. However, safety issues caused by lithium dendrite growth as well as limited cycling life restrict its practical application. Herein we validate that the application of a new dual-salt electrolyte composed of Lithium difluorophosphate (LiPO2F2) and lithium bis(fluorosulfony)imide (LiFSI) in the same proportion enables the improved long-term cycling performance along with high coulombic efficiency for lithium metal batteries. With 1 M LiPO2F2 and 1 M LiFSI in 1,2-dimethoxyethane as the electrolyte, a Li/Cu cell can be cycled at 1 mA for more than 300 cycles with a deposited capacity of 1.0 mAh. It also displays that a homogeneous and dendrite free solid electrolyte interphase layer is generated on the Cu electrode, which can be ascribed to the favorable stability of LiPO2F2 and high ionic conductivity of LiFSI. These results deliver perceptions for the advancement of high-performance lithium metal anode.