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 I<inf>2</inf> utilization efficiency and direct I<inf>2</inf> to I⁻ conversion kinetics of the I<inf>2</inf> reduction reaction, and free up 1/3 I⁻ from I<inf>3</inf>⁻. Co[Co<inf>1/4</inf>Fe<inf>3/4</inf>(CN)<inf>6</inf>] exhibits a low energy barrier (0.47 kJ mol⁻¹) and low Tafel slope (76.74 mV dec⁻¹). Accordingly, the Co[Co<inf>1/4</inf>Fe<inf>3/4</inf>(CN)<inf>6</inf>]/I<inf>2</inf>//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 I<inf>2</inf>//Zn batteries reported to date. Furthermore, solid-state flexible batteries were constructed. A 100 mAh high capacity solid-state I<inf>2</inf>//Zn battery is demonstrated with excellent cycling performance of 81.2 % capacity retained after 400 cycles.