Continuous Amorphous Metal-Organic Frameworks Layer Boosts the Performance of Metal Anodes

Employing metal anodes can greatly increase the volumetric/gravimetric energy density versus a conventional ion-insertion anode. However, metal anodes are plagued by dendrites, corrosion, and interfacial side reaction issues. Herein, a continuous and flexible amorphous MOF layer was successfully synthesized and used as a protective layer on metal anodes. Compared with the crystalline MOF layer, the continuous amorphous MOF layer can inhibit dendrite growth at the grain boundary and eliminate ion migration near the grain boundary, showing high interfacial adhesion and a large ion migration number (t_Zn²⁺ = 0.75). In addition, the continuous amorphous MOF layer can effectively solve several key challenges, e.g., corrosion of the zinc anode, hydrogen evolution reaction, and dendrite growth on the zinc surface. The prepared Zn anode with the continuous amorphous MOF (A-MOF) layer exhibited an ultralong cycling life (around one year, more than 7900 h) and a low overpotential (<40 mV), which is 12 times higher than that of the crystalline MOF protective layer. Even at 10 mA cm^-2, it still showed high stability for more than 5500 cycles (1200 h). The enhanced performance is realized for full cells paired with a MnO₂ cathode. In addition, a flexible symmetrical battery with the Zn@A-ZIF-8 anode exhibited good cyclability under different bending angles (0°, 90°, and 180°). More importantly, various metal substrates were successfully coated with compact A-ZIF-8. The A-ZIF-8 layer can obviously improve the stability of other metal anodes, including those of Mg and Al. These results not only demonstrate the high potential of amorphous MOF-decorated Zn anodes for AZIBs but also propose a type of protective layer for metal anodes.