In situ preparation of zincophilic covalent–organic frameworks with low surface work function and high rigidity to stabilize zinc metal anodes

Abstract

Zinc-ion batteries (ZIBs) are inexpensive and safe, but side reactions on the Zn anode and Zn dendrite growth hinder their practical applications. In this study, 1,3,5-triformylphloroglycerol (Tp) and various diamine monomers (p-phenylenediamine (Pa), benzidine (BD), and 4,4′’-diamino-p-terphenyl (DATP)) were used to synthesize a series of two-dimensional covalent-organic frameworks (COFs). The resulting COFs were named TpPa, TpBD, and TpDATP, respectively, and they showed uniform zincophilic sites, different pore sizes, and high Young’s moduli on the Zn anode. Among them, TpPa and TpBD showed lower surface work functions and higher ion transfer numbers, which were conducive to uniform galvanizing/stripping zinc and inhibited dendrite growth. Theoretical calculations showed that TpPa and TpBD had wider negative potential region and greater adsorption capacity for Zn²⁺ than TpDATP, providing more electron donor sites to coordinate with Zn²⁺. Symmetric cells protected by TpPa and TpBD stably cycled for more than 2300 h, whereas TpDATP@Zn and the bare zinc symmetric cells failed after around 150 and 200 h. The full cells containing TpPa and TpBD modification layers also showed excellent cycling capacity at 1 A/g. This study provides comprehensive insights into the construction of highly reversible Zn anodes via COF modification layers for advanced rechargeable ZIBs.