Dual-Mechanism Anchoring of Iodine Species by Pitch-Derived Porous Carbon for Enhanced Zinc–Iodine Battery Performance

Abstract

Aqueous Zn-I₂ battery is an overwhelming candidate for sustainable energy storage systems due to its high safety, low cost, and environmental friendliness. However, the serious self-discharge and the shuttle effect initiated by soluble polyiodides significantly hinder further development. Herein, a pitch-derived carbon (PPC_MK) with a unique micro-/mesopores structure and abundant oxygen-containing functional groups is prepared, with dual-mechanism anchoring of iodine species to effectively confine the polyiodides for alleviating the above problems. The rich micropores of PPC_MK (0.62 nm) function to inhibit the formation of I₃⁻, and the large specific surface area enables a high I₂ uptake of 64.51%. Moreover, oxygen-containing functional groups of PPC_MK further enhance the interaction with I₃⁻ to strengthen the polyiodide confinement. Therefore, the Zn-I₂ batteries exhibit a high specific capacity of 236.76 mAh g⁻¹ (4 mg_iodine cm⁻²) with an average Coulombic efficiency of 99.73% at 1 C, low self-discharge rate of 18.18% capacity loss after one-week resting, and superior durability of 20 000 cycles at 20 C with 95.08% retentive capacity. Especially, the pouch cell exhibits a superior area capacitance of 5.51 mAh cm⁻² at a high-loading (30 mg_iodine cm⁻²). This study provides an economically effective solution for the large-scale production of high-performance Zn-I₂ batteries.