Fig. 4. Cycling performance in carbonate electrolyte and study of failure mechanisms.

(A) Coulombic efficiency versus cycle number plots of Cu, HCS, and ALD Al₂O₃/HCS in 30 μl of EC/DEC electrolyte with 1 M LiPF₆, 1% VC, and 10% FEC. (B to E) Voltage versus capacity plot during 1st, 2nd, 25th, and 100th cycles. (F) SEM characterization of HCS electrodes after 25 cycles. Images were acquired after the last lithium stripping half-cycle. (G) SEM characterization of ALD Al₂O₃/HCS electrodes after 25 cycles. Images were acquired after the last lithium stripping half-cycle. (H) Cycling performance of repeated electrochemical Li plating/stripping on HCS electrodes with different amounts of EC/DEC electrolyte containing 1 M LiPF₆, 1% VC, and 10% FEC. All electrodes were cut open for viewing using FIB. SEM images were taken with a sample rotation angle of 52°.