Improved Cycling Stability of Lithium‐Metal Anode with Concentrated Electrolytes Based on Lithium (Fluorosulfonyl)(trifluoromethanesulfonyl)imide

A new type of concentrated electrolyte composed of Li[(FSO2)N(SO2CF3)] (LiFTFSI), Li[N(SO2F)2] (LiFSI), and ether solvents can improve the cycling stability of lithium (Li) metal and inhibit Li‐metal dendritic growth. The high average coulombic efficiency of >95 % and excellent cycling performance of >250 cycles for the Li|copper cells have been achieved, even at a high current density of 3 mA cm−2. Moreover, the Li|LiFePO4 cell exhibits superior cycling stability with capacity retention of >92 % at 0.2 C for more than 200 cycles and excellent C‐rate capability.