Covalent Organic Frameworks with Localized High Polarity via Defect Engineering for Interfacial Regulation of Aqueous Zinc Batteries

Abstract

Aqueous zinc batteries are promising energy storage systems, but face significant challenges, including zinc dendrite growth, electrochemical corrosion, and poor reversibility for large-scale applications. Herein, we design a defective fluorinated covalent organic framework (FCOF) with localized high polarity based on a truncated monomer strategy. Controllable defect design in the FCOF framework produces polar amino groups with enhanced Zn²⁺ trapping ability. Meanwhile, an additional transport pathway was formed at the well-designed defect sites, which reduced the migration energy barriers. The Zn²⁺ diffusion coefficient of the optimal defective FCOF separators (FCOF-30, with 30% defect content) was calculated to be 9.83 × 10^-10 cm s^-1 (2 times higher than FCOF). At 10 mA cm^-2 (5 mAh cm^-2), the symmetric cell using FCOF-30 exhibited excellent Zn²⁺ deposition/stripping behavior with 1200 h cycling stability. This defect engineering concept provided in-depth insights into the ion transport regulation for the electrochemical energy storage applications.