Fig. 3: XPS spectra with different etching depths layer for lithium foils.

Two types of lithium foils were disassembled from symmetric cells with BTT and blank electrolyte after 10 cycles with a current density of 0.5 mA cm⁻² and a capacity density of 0.5 mAh cm⁻². a S 2p, F 1s, Li 1s spectra for the BTT symmetric cell, and b for the control cell.