Electrocatalytic Iodine Reduction Reaction Enabled by Aqueous Zinc‐Iodine Battery with Improved Power and Energy Densities

Abstract

Proposed are Prussian blue analogue hosts with ordered and continuous channels, and electrocatalytic functionality with open Co and Fe species, which facilitate maximum I2 utilization efficiency and direct I2 to I− conversion kinetics of the I2 reduction reaction, and free up 1/3 I− from I3−. Co[Co1/4Fe3/4(CN)6] exhibits a low energy barrier (0.47 kJ mol−1) and low Tafel slope (76.74 mV dec−1). Accordingly, the Co[Co1/4Fe3/4(CN)6]/I2//Zn battery delivers a capacity of 236.8 mAh g−1 at 0.1 A g−1 and a rate performance with 151.4 mAh g−1 achieved even at 20 A g−1. The battery delivers both high energy density and high‐power density of 305.5 Wh kg−1 and 109.1 kW kg−1, higher than I2//Zn batteries reported to date. Furthermore, solid‐state flexible batteries were constructed. A 100 mAh high capacity solid‐state I2//Zn battery is demonstrated with excellent cycling performance of 81.2 % capacity retained after 400 cycles.

Recent progress of flexible aqueous multivalent ion batteries

“…74 Ma et al prepared a binder-contained cathode with CC for flexible aqueous zinc-iodine batteries. 54 When the prepared flexible battery was subjected to various deformations such as bending, squeezing, and rolling, its capacity and Coulombic efficiency remained nearly unchanged compared to its initial state (Figure 3A), demonstrating the tough structure of the fabricated cathode. Impressively, the as-prepared flexible battery could be integrated into clothing fabrics to power the commercial light-emitting diode (Figure 3B), indicating the excellent potential of the flexible cathode for practical applications.…”

“…Zn metal is usually electrodeposited on CCs to fabricate flexible zinc ion batteries. [52][53][54][55][56][57][58][59][60] The deposited Zn on CCs is usually reported to be in the form of nanosheets, which provide more active sites for Zn nucleation and may inhibit Zn dendrite formation. 12 In practice, the CCs are often activated 61 to increase their porosity or treated with oxidizing acids 48 to improve their hydrophilicity and facilitate uniform metal deposition.…”

“…The binders are usually polyvinylidene fluoride or poly(tetrafluoroethylene), among which the former is more commonly used. CCs are the most common current collectors for the flexible cathodes prepared with binders, 40,[54][55][56][57]61,[70][71][72][73] and some other flexible substrates are also reported, such as carbon papers, 65,66 stainless-steel films, 33 and graphene oxide (GO)-CNT hybrid films. 74 Ma et al prepared a binder-contained cathode with CC for flexible aqueous zinc-iodine batteries.…”

Deciphering the Electrochemical Behaviors of the Electrode‐Electrolyte Coupling toward Advanced Electrochemical Energy Storage Device

“…To address this issue, a new kind of energy storage strategy has recently been proposed by expanding from the electrode material to the whole system based on the introduction of redox electrolytes in the energy storage system. [ 14–16 ] At this point, the electrolyte ions not only form an electric double layer (EDL) as the charge carrier, but also participate in the redox reaction as the electrochemical active sites, thus providing the extra charge storage for the device. Benefiting from the high ionic conductivities of aqueous electrolytes, the electrochemical kinetics can be optimized significantly, resulting in efficient redox reactions with short response time and realizing the higher power density.…”

“…Benefiting from the high ionic conductivities of aqueous electrolytes, the electrochemical kinetics can be optimized significantly, resulting in efficient redox reactions with short response time and realizing the higher power density. [ 5,17–18 ] On the other hand, as the additional electrolyte species, there are many redox couples with different reaction potentials that can be chosen in the system, [ 19–20 ] such as Cu 2+ /Cu + , [ 21–22 ] iodine, [ 15,23 ] hydroquinone, [ 24–25 ] and [Fe(CN) 6 ] 4– /[Fe(CN) 6 ] 3– etc., [ 26–28 ] in which the redox reactions can completely proceed even in the limited potential. Therefore, an advanced electrochemical energy storage device with high energy density and power density can be integrated via a synergistic electrode‐electrolyte coupling effect.…”