Wide-temperature zinc-iodine batteries enabling by a Zn-ion conducting covalent organic framework buffer layer

Abstract

Aqueous zinc-iodine batteries (ZIBs) are attractive energy storage devices owing to their safety and low cost, but polyiodide shuttling and poor wide-temperature operation limit their scalability. Herein, a sulfonated zinc-grafted covalent organic framework (COF) (denoted TpPa-Zn) was designed and served as the buffer layer on the surface of glass fiber (GF) to enhance ZIBs’ performance. The TpPa-Zn structure exhibits single zinc-ion conductivity, with its nanopores and sulfonic acid groups effectively suppressing polyiodide shuttling. In-situ Raman and X-ray photoelectron spectroscopy tests revealed that the TpPa-Zn modified separator promotes polyiodide conversion, reducing self-discharge and enhancing cycle stability. The upgraded ZIBs were demonstrated with ultra-stable operation over a wide temperature ranging from 0 to 65 ℃, retaining 90.5 % and 90.7 % capacity retention rate at 65 ℃ (500 cycles) and 0 ℃ (2000 cycles), respectively. Moreover, high-iodine-loading tests demonstrated practical applicability, with a retention rate of 87 % at 3 mg cm⁻² and 93 % at 5 mg cm⁻². This study elucidates that the TpPa-Zn buffer layer significantly improves the temperature adaptability of ZIBs, potentially inspiring the rational design of COF-based wide-temperature batteries.