fig4

Figure 4. (A) Scheme illustrating the distinct Na plating behaviors on bare Cu and Bi₂S₃@Cu substrates; (B and C) Ex-situ SEM images of the bare Cu substrate after Na plating (B) and stripping (C) at 1 mA cm^-2 with 1 mAh cm^-2 after 70 cycles; (D-G) Ex-situ SEM images of the Bi₂S₃@Cu substrate after Na plating (D and F) and stripping (E and G) at 1 mA cm^-2 with 1 mAh cm^-2 (D and E) after 600 cycles and at 1 mA cm^-2 with 5 mAh cm^-2 (F and G) after 120 cycles. Insets of (B-G) show the optical photographs of the electrodes after Na plating and stripping. SEM: Scanning electron microscope.