Waste coffee grounds-derived micropores carbon framework as an efficient iodine host for zinc iodine battery

Aqueous zinc-iodine batteries (AZIBs) have attracted significant attention as the most promising next-generation energy storage technology due to their low cost, inherent safety, and high energy density. However, their practical application is hindered by the poor electronic conductivity of iodine cathodes and the severe shuttling effect of intermediate polyiodides. Here, we report a novel micropores carbon framework (MCF) synthesized from waste coffee grounds via a facile carbonization-activation process. The resultant MCF features an ultrahigh specific surface area and a high density of micropores, which not only physically confine iodine species to minimize iodine loss but also enhance the electronic conductivity of the composite cathode. Furthermore, biomass-derived heteroatom dopings (nitrogen functionalities) facilitate effective chemical anchoring of polyiodide intermediates, thereby mitigating the shuttle effect. UV–visible spectroscopy and electrochemical kinetic analyses further confirm the rapid transformation and inhibition mechanism of iodine species by MCF. Consequently, the MCF/I₂ cathode delivers superior specific capacities of 238.3 mA h g⁻¹ at 0.2 A g⁻¹ and maintains outstanding cycling performance with a capacity retention of 85.2% after 1200 cycles at 1.0 A g⁻¹. This work not only provides an important reference for the design of high-performance iodine-host porous carbon materials but also explores new paths for the sustainable, high-value utilization of waste biomass resources.