No abstract

Zinc anode‐based aqueous batteries have attracted considerable interest for large‐scale energy storage and wearable devices. Unfortunately, the formation of Zn dendrite, parasitic hydrogen evolution reaction (HER), and irreversible by‐products, seriously restrict their practical applications. Herein, a series of compact and uniform metal‐organic frameworks (MOFs) films with precisely controlled thickness (150–600 nm) are constructed by a pre‐oxide gas deposition (POGD) method on Zn foil. Under the protection of MOF layer with optimum thickness, the corrosion of zinc, the side reaction of hydrogen evolution, and the growth of dendrites on the zinc surface are suppressed. The symmetric cell based on Zn@ZIF‐8 anode exhibits exceptional cyclicality for over 1100 h with low voltage hysteresis of≈38 mV at 1 mA cm−2. Even at current densities of 50 mA cm−2 with an area capacity of 50 mAh cm−2 (85% Zn utilization), the electrode can keep cycling for >100 h. Besides, this Zn@ZIF‐8 anode also delivers a high average CE of 99.4% at 1 mA cm−2. Moreover, a rechargeable Zn ion battery is fabricated based on the Zn@ZIF‐8 anode and MnO2 cathode, which presents an exceptionally long lifespan with no capacity attenuation for 1000 cycles.

Employing metal anodes can greatly increase volumetric/gravimetric energy density versus a conventional ion-insertion anode. However, metal anodes are plagued by dendrites, corrosion, and interfacial side reactions issues. Herein, a compact and flexible amorphous MOF layer was successfully synthesized and used as protective layer on metal anode aqueous zinc-ion battery (AZIB). Compared with the crystalline MOF layer, the unique amorphous MOF layer can inhibit dendrite growth at the grain boundary and eliminate ions migration near the grain boundary, showing high interfacial adhesion and large ion migration number (tZn2+ = 0.82). Besides, the amorphous MOF layer can effectively depress unfavored behaviors, e.g., corrosion of zinc anode, hydrogen evolution reaction, and dendrite growth on zinc surface. The prepared Zn anode with the amorphous MOF layer exhibited an ultra-long cycle life (ten months, 7000 h) and a low voltage (< 40 mV) at 1 mA cm-2 in a symmetrical cell. Even at 10 mA cm-2, it still showed a high stability for more than 5500 cycles (1200 h). The enhanced performance is realized for full cells paired with a MnO2 cathode. Besides, a flexible symmetrical battery with the Zn@A-ZIF-8 anode exhibited a good cyclability under different bending angle (0°, 90°, and 180°). Moreover, various metal substrates were successfully coated with compact A-ZIF-8. The A-ZIF-8 layer can obviously improve the stability metal anodes, including Zn, Mg and Al. The results not only demonstrate the high potential of amorphous MOFs decorated Zn anodes for AZIBs, but also propose a new family of protective layers for metal anodes.