a, b Voltage profiles for Li plating/stripping on a Cu working electrode cycled in 1 M LiTFSI-FEC/FDMA and 1 M LiPF6-EC/DMC at a current density of 1 mA cm−2. c Li plating/stripping Coulombic efficiency in Li||Cu cells using different electrolytes. Li was electrodeposited at 1 mA cm−2 to a total capacity of 1 mAh cm−2 followed by stripping to a cut-off voltage of 1.0 V vs. Li+/Li. d Positive linear sweep voltammograms (LSV) sweep to gauge the oxidation stabilities of the different electrolytes as evaluated on Li||stainless-steel cells at a scanning rate of 5 mV s−1. e, f Cyclic voltammetry (CV) curves of Li||Cu cells in 1 M LiTFSI-FEC/FDMA and 1 M LiPF6-EC/DMC electrolytes at a scanning rate of 1 mV s−1. The insets show the enlarged view regions.