Armoring the Cathode with Starch Gel Enables Shuttle-Free Zinc-Iodine Batteries

Abstract

Zinc-iodine batteries (ZIBs) have been recognized as a promising energy storage device due to their high energy density, low cost and environmental friendliness. However, the development of ZIBs is hindered by the shuttle effect of polyiodides which results in capacity degradation and poor cycling performance. Taking inspiration from the ability of starch to form inclusion compounds with iodine, we propose to use a starch gel on the cathode to suppress the shuttle of polyiodides. Herein, porous carbon is utilized as iodine host and provide an excellent conductive network, while starch gel is used as another host to suppress polyiodides shuttle, resulting in an improved battery performance. The testing results demonstrate that the conversion between I− and I0 in the cathode and the effective inclusion role of starch suppress the shuttle of polyiodides during the charging process. Meanwhile, based on the electrochemical tests and theoretical DFT calculations, it is found that starch has a stronger ability for adsorbing polyiodides compared with carbon materials, which enables effective confinement of polyiodides. The ZIBs used the cathode with starch gel exhibites high coulombic efficiency (>95% at 0.2 A g−1) and low self-discharge (86.8% after rest 24h). This strategy is characterized by its simplicity, low cost and high applicability, making it meaningful for the research of high-performance ZIBs.

Keywords: Zinc-iodine battery, shuttle-free, starch gel, dual-ion