Green synthesis of renewable biomass-derived porous carbon hosts for superior aqueous zinc-iodine batteries

• Green synthesis of hierarchical porous carbon through direct carbonization of natural biomass-cotton with unique structure. • Ultra-long cycle performance of 10,000 cycles and 88 % capacity retention. • Highly mass loaded electrode (20.3 mg cm −2 ) with area capacity up to 1.8 mAh cm −2 . Natural biomass-derived carbon materials, renowned for their inherent porosity and distinctive structural attributes, have become the focus of extensive research and application. The incorporation of heteroatom doping further amplifies their appeal due to the inherent advantages it confers. A hierarchical porous carbon framework derived from biomass was synthesized by direct carbonization of cotton. The strategic optimization of the synthesis parameters during thermochemical treatment to preserve the inherent tubular fiber structure of cotton and regulate the pore structure to effectively mitigate the inherent shuttle effect of zinc-iodine batteries (ZIBs). The electrochemical performance of the synthesized cathode material is impressive. The SPC 750 -2/I 2 (spiral porous carbon) electrode exhibits robust performance with 88 % capacity retention after 10,000 cycles at a current density of 2 A/g. This durability and stability at a high current density suggests that the material has potential for high-performance energy storage applications and is important for the sustainable utilization of low-cost, excess biomass.