Efficient Charge Storage in Zinc-Iodine Batteries based on Pre-Embedded Iodine-Ions with Reduced Electrochemical Reaction Barrier and Suppression of Polyiodide Self-Shuttle Effect

Aqueous zinc-Iodine batteries are considered as a promising energy storage system due to their high energy/power density, and safety. However, polyiodide shuttling leads to severe active mass loss, which results in lower Coulombic efficiency and limits the cyclic life. Herein, a novel structure-limiting strategy to pre-embed iodide ions into Prussian blue (PBI) is proposed. The DFT calculations and electrochemical characterization reveal that the formation of Ferrum-Iodine bond reduces the electrochemical reaction energy barrier of subsequent iodide-ions at the pre-embedding sites, improves the I- oxidation reaction kinetic process, and suppresses the polyiodide self-shuttle. The PBI//Zn batteries exhibit a low Tafel slope (155 mV dec(-1)). Moreover, UV-vis spectroscopy confirms that the proposed strategy suppresses the polyiodide self-shuttle. As a result, the PBI//Zn battery achieves high iodide utilization and Coulomb efficiency (242 mAh g(-1) at 0.2 A g(-1), CEs approximate to 100%), as well as high multiplicity performance of 197.2 mAh g(-1) even at 10 A g(-1)(82% of initial capacity). The PBI//Zn battery also renders excellent cyclic stability with a capacity retention of 94% at 4 A g(-1) after 1500 cycles. The device exhibits a high energy density of 142 W h kg(-1) at a power density of 5538 W kg(-1).