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 (PPCMK) 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 PPCMK (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 PPCMK 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 mgiodine 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 mgiodine cm−2). This study provides an economically effective solution for the large-scale production of high-performance Zn-I2 batteries.