Carbon nanotubes interpenetrating ordered micro-mesoporous carbon spheres embedded with Fe3C nanocrystals for anchoring polyiodides in ZnI2 batteries

Zinc-iodine (Zn I 2 ) batteries have become one of the research hotspots in recent years in the field of energy storage due to their abundant resources, environmental friendliness, low price, high theoretical capacity (211 mAh g −1 ), and low redox potential. However, the polyiodide shuttle effect is a key challenge. In this work, carbon nanotubes interpenetrating ordered micro mesoporous carbon spheres embedded with fine Fe 3 C nanocrystals (Fe 3 C/CNTs/OMMC) were synthesized by a simple method and used to act as an iodine host material. Benefiting from the unique micro mesoporous structure of OMMC and fine Fe 3 C nanocrystals with abundant active sites, Fe 3 C/CNTs/OMMC has achieved physical confinement and chemical adsorption/catalysis of polyiodides. Meanwhile, highly conductive CNTs facilitate rapid electron conduction and accelerate the reaction. Thus, the Zn I 2 battery using Fe 3 C/CNTs/OMMC-I 2 exhibited excellent cycling stability and good electrochemical performance. It was found that the initial specific capacity was high at a current density of 5 A g −1 , and that 164 mAh g −1 capacity remained after 10,000 cycles. The capacity retention percentage was 82 % after 17,000 cycles at a current density of 10 A g −1 .