High-Performance Zn-I2 Batteries Enabled by a Metal-Free Defect-Rich Carbon Cathode Catalyst

Aqueousiodine-zinc (Zn-I-2) batteriesbased on I-2 conversion reaction are one of the promisingenergy storage devices due to their high safety, low-cost zinc metalanode, and abundant I-2 sources. However, the performanceof Zn-I-2 batteries is limited by the sluggish I-2 conversion reaction kinetics, leading to poor rate capabilityand cycle performance. Herein, we develop a defect-rich carbon asa high-performance cathode catalyst for I-2 loading andconversion, which exhibits excellent iodine reduction reaction (IRR)activity with a high reduction potential of 1.248 V (vs Zn/Zn2+) and a high peak current density of 20.74 mA cm(-2), superior to a nitrogen-doped carbon. The I-2-loaded defect-richcarbon (DG1100/I-2) cathode achieves a large specific capacityof 261.4 mA h g(-1) at 1.0 A g(-1), a high rate capability of 131.9 mA h g(-1) at 10A g(-1), and long-term stability with a high retentionof 88.1% over 3500 cycles. Density functional theory calculationsindicated that the carbon seven-membered ring (C7) defect site possessesthe lowest adsorption energies for iodine species among several defectsites, which contributes to the high catalytic activity for IRR andthe corresponding electrochemical performance of Zn-I-2 batteries. This work offers a defect engineering strategy for boostingthe performance of Zn-I-2 batteries.