fig4

Figure 4. Mg20Bi alloy anode after cycling in Mg20Bi | MBN-Br | Mg20Bi symmetric cell. SEM of Mg20Bi alloy anode: (A) 50 h; (B) 200 h and (C) 600 h; (D) EDS mapping of Figure 4C; (E) XPS spectra at different etching times: Mg 2p and Bi 4f in Mg20Bi alloy anode after 600 h stripping/plating; (F) Variations in Bi^III proportion in the Mg20Bi alloy at different cycling and etching times. MBN-Br: Mg(BH₄)₂·1.9NH₃-32 wt.% MgBr₂·2NH₃; SEM: Scanning electron microscopy; EDS: Energy-dispersive X-ray spectrometer; XPS: X-ray photograph spectroscopy.