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 longterm 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 Zn 2+ . 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//MnO 2 ZIBs were fabricated and exhibited better comprehensive electrochemical performance than Zn//MnO 2 ZIBs, demonstrating the potential practical application of TM− OH@Zn.

Covalent Organic Frameworks in Aqueous Zinc‐Ion Batteries

“…Subsequently, Mi et al constructed a fully conjugated COF multifunctional protective layer (TM-OH) generated from 2,4,6-trimethyl-1,3,5-triazine and 2,5-dihydroxyterephthalic aldehyde to achieve a highly reversible and stable zinc anode (Figure 7c). [87] Since TM-OH has a fully conjugated structure, the TM-OH@Zn anode exhibits good corrosion resistance, where the pre-designed abundant hydrophilic -OH groups ensure the penetration of the electrolyte and deliver uniform zinc deposition conditions. Of great importance, the lone pair electron-rich triazine ring can strongly interact with Zn 2 + and affect the growth orientation of Zn, resulting in horizontal dendrites rather than upright dendrites in Zn deposits (Figure 7d).…”

Advances in functional organic material-based interfacial engineering on metal anodes for rechargeable secondary batteries

“…The introduction of artificial SEI layer can effectively avoid the direct contact between the liquid electrolyte and metal anode, reducing the loss of active substances and electrolyte. [17][18][19] Finally, the construction of gel/solid-state electrolytes (SSEs). This method inhibits dendrite growth and reduces side reactions, further improving the battery safety.…”

Suppressing Side Reaction and Dendritic Growth via Interfacial Cyclization Molecule for Stable Zn Metal Anodes

“…To solve the aforementioned problems, enormous efforts have been made in recent years, mainly including: (i) electrolyte optimization, such as high concentration electrolyte, introducing additives; , (ii) modifying a coating layer on the Zn metal surface, e.g., CaCO 3 layer, SiO 2 layer, porous carbon layer, reduced graphene oxide layer, porous organic polymers layer, and so forth; − (iii) using alloyed Zn anode, such as Zn–Al alloys; (iv) adopting gel electrolyte or all solid state electrolyte; (v) electrode structure design, e.g., zincophilic modification; and (vi) construction of a novel separator . The simplest and most straightforward method to achieve practical application among these tactics is to introduce electrolyte additives.…”