Fig. 3.

Mechanism of improved wettability on planar Cu by coating the substrate with abietic resin. a EPMA image of the bottom surface of ultrathin Li when it peeled off from the Cu substrate. b Elemental distribution image of O and C on the bottom surface. c Fourier infrared spectra of ultrathin Li on the bottom surface of the substrate. d Elemental distribution of Li⁺ and C⁺ probed via Tof-SIMS. e Elemental distribution map of Li⁺ on the bottom surface of ultrathin Li after etching 50 layers. f Elemental distribution map of Li⁺ on the bottom layer of ultrathin Li after etching 179 layers. g XPS spectra of C 1s for the abietic resin coating. XPS spectra of C 1s (h) and Li 1s (i) on the bottom surface of ultrathin Li layer when peeled off from the Cu substrate. j XPS spectra of Li 1s for the bottom surface of ultrathin Li after the carbon-enriched layer was removed by DOL. Scale bars are 20 µm in a, b, e, f