Concentrated dual-salt electrolytes for improving the cycling stability of lithium metal anodes

Lithium (Li) metal is an ideal anode material for rechargeable Li batteries, due to its high theoretical specific capacity (3860 mAh/g), low density (0.534 g/cm³), and low negative electrochemical potential (-3.040 V vs. standard hydrogen electrode). In this work, the concentrated electrolytes with dual salts, composed of Li[N(SO₂F)₂] (LiFSI) and Li[N(SO₂CF₃)₂] (LiTFSI) were studied. In this dual-salt system, the capacity retention can even be maintained at 95.7% after 100 cycles in Li|LiFePO₄ cells. A Li|Li cell can be cycled at 0.5 mA/cm² for more than 600 h, and a Li|Cu cell can be cycled at 0.5 mA/cm² for more than 200 cycles with a high average Coulombi efficiency of 99%. These results show that the concentrated dual-salt electrolytes exhibit superior electrochemical performance and would be a promising candidate for application in rechargeable Li batteries.