Two-dimensional nitrogen-rich organic–inorganic heterostructure enables shuttle-free durable Zn–I2 batteries

Aqueous zinc–iodine (Zn–I2) batteries have attracted significant attention due to their high safety, cost-effectiveness, and considerable theoretical capacity. However, their practical performance is severely hindered by the shuttle effect of soluble polyiodide intermediates and sluggish I2/I− conversion kinetics. Herein, we report an organic–inorganic heterostructure composite of poly(1,5-diaminonaphthalene) and few-layer graphene via a ball-milling method as iodine host materials to boost the performance of Zn–I2 batteries. Unique, two-dimensional morphology of few-layer graphene and abundant polar nitrogen-containing groups in the poly(1,5-diaminonaphthalene) can effectively capture and confine iodine species by physical adsorption and strong chemical anchoring. Density functional theory calculations further reveal that the synergistic interaction of the organic and inorganic components benefits electron transport and lowers energy barrier for iodine reduction reaction (I2/I−), thereby accelerating redox kinetics. Benefiting from these advantages, the two-dimensional organic–inorganic heterostructure composite as a cathode of Zn–I2 batteries delivers a high specific capacity of 247.3 mAh g−1 at 0.4 A g−1 and achieves an ultra-long cycling stability with over 25 000 cycles at 6 A g−1. Furthermore, a high areal capacity of 2.46 mAh cm−2 is attained under a high iodine mass loading of 15.93 mg cm−2. This work provides a feasible strategy for designing host materials for high-performance Zn–I2 batteries.