Fig. 4: Electrochemical performance of Li | |Cu half cells, in situ ECCS observations, and chemical compositions of SEI.
a Long-term Li plating/stripping CE test performed at 0.5 mA cm-2 and 1 mAh cm-2 in 1.2 m BMC+ (The inset is results obtained within 10 cycles in various electrolytes). b Comparisons of Li plating/stripping CE with previously reported ether-based and carbonate-based electrolytes that are in the form of normal concentration electrolytes, HCEs and LHCEs (Additional details can be referenced in Supplementary Table 4). SEM and optical images for the surface of Li electrodeposits after the first plating on the Cu foil at 0.5 mA cm-2 and 3 mAh cm-2 in (c) 1.2 m DME+ and (d) 1.2 m BMC + . In situ ECCS observations for evolution processes of Li plating/stripping in (e) 1.2 m DME + , (f) LB010+ and (g) 1.2 m BMC+ (In the case of LB010 + , since no Li plating occurred in the first cycle within the observed range, the test was specially extended to 3 cycles. Complete evolution processes of Li plating/stripping and more details can be found in Supplementary Fig. 34 and Supplementary Movies 6–8). C1s and F1s XPS patterns of the Cu substrates with various durations of Ar+ sputtering after one cycle of Li plating/stripping in (h) 1.2 m DME + , (i) LB010+ and (j) 1.2 m BMC + . k TOF-SIMS 3D reconstruction for the sputtered volume of the Cu substrate after one cycle of Li plating/stripping in 1.2 m BMC + .
