Fig. 4

Surface morphology and mechanical property of the SEI layers formed from the different electrolytes. AFM images (10 × 10 µm2 scan size) of the C-SEI layer (a), S-SEI layer (b), and PST-90-SEI layer (c). Indentation curves of the C-SEI layer (d), S-SEI layer (e), and PST-90-SEI layer (f). The SEI layers were obtained after 100 cycles of Li plating/stripping, and Li was stripped completely before the AFM characterization