Highly Reversible and Stable Zinc Anode Enabled by a Fully Conjugated Porous Organic Polymer Protective Layer

Abstract

Zn anodes are advantageous for use in rechargeable aqueous zinc ion batteries (ZIBs) because of their high theoretical specific capacities, low redox potentials, and safety. However, Zn anodes have several challenges, such as easy corrosion and uncontrollable zinc dendrite growth, which deteriorate the long-term cycling capability and, thus, badly hinder the practical applications of ZIBs. This study demonstrates a highly reversible and stable Zn anode by constructing a positive fully conjugated porous organic polymer-based (TM–OH) multifunctional protective layer. This TM–OH-based layer can provide a stable and corrosion-resistant “wall” with fine electrolyte wettability simultaneously, which is due to the fully conjugated structure and abundant hydrophilic OH. Moreover, Zn deposits of TM–OH@Zn display horizontally rather than upright dendrite, which is probably attributed to interaction between triazine rings rich of lone pair electrons and Zn2+. Consequently, the TM–OH@Zn electrode shows ultralow voltage hysteresis (25, 28 mV at 0.1, 1 mA cm–2 in a symmetric cell, respectively), highly reversible stripping/plating behavior, and excellent cycling stability (good operation even after 1200 h at 0.1 mA cm–2, 0.05 mAh cm–2 in a symmetric cell). TM–OH@Zn//MnO2 ZIBs were fabricated and exhibited better comprehensive electrochemical performance than Zn//MnO2 ZIBs, demonstrating the potential practical application of TM–OH@Zn.