Complementary chemical adsorption of iodine species on MXene/carboxylated CNTs for high loading zinc–iodine batteries

Zinc-iodine rechargeable batteries offer inherent safety and abundant reserves, making them promising for energy storage applications. However, the poor interfacial stability of the zinc anode and the shuttle effect, both caused by the diffusion of soluble polyiodides in aqueous media, significantly compromise device stability, especially at high mass loadings. This work proposes a complementary chemical adsorption strategy to achieve high-loading zinc-iodine batteries, utilizing a composite material of Ti₃C₂T_<i>x</i> MXene and carboxylated multi-walled carbon nanotubes (c-MCNTs) as an iodine carrier. Carboxylated multi-walled carbon nanotubes (c-MCNTs) form C-I bonds with initial I^- ions through chemical interactions, while Ti₃C₂T_<i>x</i> MXene effectively chemically adsorbs the byproduct I₃^- ions formed during charging and discharging, enabling the adsorption of a substantial amount of iodine species. Therefore, even at a high areal mass loading of 33.27 mg cm^-2, the prepared zinc-iodine battery delivers a high areal capacity of 2.82 mAh cm^-2 at a current density of 5 mA cm^-2, surpassing most previously reported zinc-iodine batteries, while maintaining excellent cycling stability with a capacity retention of 99.04% after 300 cycles. Moreover, it exhibits outstanding rate performance, retaining an areal capacity of 1.52 mAh cm^-2 even at a high current density of 50 mA cm^-2. This strategy is also potentially extendable to the design of other high-loading metal-iodine batteries.