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

Abstract

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 structurelimiting 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 ≈ 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 .

Aqueous Zinc‐Iodine Batteries: From Electrochemistry to Energy Storage Mechanism

“…Xie et al prepared a novel electrode material by pre-embedding iodide ions into Prussian blue (PB), which is denoted as PBI. [62] As depicted by the CV curves, both PB and PBI electrodes show a pair of peaks, corresponding to the Fe 3+ /Fe 2+ redox reaction (Figure 8e). However, compared with PB, PBI exhibits more evident peaks at 0.46 V and 0.37 V versus saturated calomel electrode (SCE), corresponding to I 3 − /I − redox reaction, which suggests that the PBI electrode is more favorable for iodine conversion.…”

“…Reproduced with permission. [62] Copyright 2023, Wiley-VCH. h) Schematic illustration of the mechanism of Zn─I 2 batteries.…”

“…g) The Gibbs free-energy diagrams of IOR in PB and PBI. Reproduced with permission [62]. Copyright 2023, Wiley-VCH.…”

Metal–iodine batteries: achievements, challenges, and future

“…In addition to carbon-based hosts and organic polymer hosts, several other types of materials have been taken into consideration for their utilization as iodine hosts, including Prussian blue analogues (PBAs), Prussian blue (PB) and MXenes. 83,190,191 Generally, PBAs possess adequate porosity, continuous and ordered micropore channels, and transition-metal species with electrochemical catalytic functions, which endow PBAs with the promising potential to act as iodine hosts. Accordingly, the rate capability of the Co[Co 1/4 Fe 3/4 (CN) 6 ]/I 2 ‖Zn cell can reach to 151.4 mA h g −1 even at 20 A g −1 .…”

“…192,193 Similarly, the PB cathode with pre-embedded iodide ions had a short lifetime of 1500 cycles at 4 A g −1 . 191 On the other hand, MXenes could also be considered as iodine hosts on account of their exceptional electrical conductivity, abundant surface terminations (O, –F, –OH, etc. ), periodic layered microstructure, and arrayed interlayer gap.…”