A twelve-electron conversion iodine cathode enabled by interhalogen chemistry in aqueous solution

Abstract

The battery chemistry aiming for high energy density calls for the redox couples that embrace multi-electron transfer with high redox potential. Here we report a twelve-electron transfer iodine electrode based on the conversion between iodide and iodate in aqueous electrolyte, which is six times than that of the conventional iodide/iodine redox couple. This is enabled by interhalogen chemistry between iodine (in the electrode) and bromide (in the acidic electrolyte), which provides an electrochemical-chemical loop (the bromide-iodate loop) that accelerates the kinetics and reversibility of the iodide/iodate electrode reaction. In the deliberately designed aqueous electrolyte, the twelve-electron iodine electrode delivers a high specific capacity of 1200 mAh g−1 with good reversibility, corresponding to a high energy density of 1357 Wh kg−1. The proposed iodine electrode is substantially promising for the design of future high energy density aqueous batteries, as validated by the zinc-iodine full battery and the acid-alkaline decoupling battery.

Advancements in aqueous zinc–iodine batteries: a review

“…Additionally, the polyvalent properties of iodine elements such as I + and I 5+ , can contribute to higher cathode capacities. 13–16…”

“…Currently, the primary focus of this research is on the conversion involving I − /I 2 /I + as the higher valence states pose greater challenges. 15 Moreover, in I − /I 2 /I + conversion, the element of chlorine (Cl) is usually introduced to stabilize I + . 14 The anode reaction during this conversion can still be illustrated by eqn (1) .…”

A cyano cobalt “electron transfer bridge” boosting the two-electron reaction of a MnO2 cathode with long lifespan in aqueous zinc batteries

“…[1][2][3][4][5] Among them, aqueous zinc batteries provide low-cost and high safety, making them promising for grid-level energy storage. [6][7][8][9][10][11] The Zn metal anode delivers high theoretical capacity (820 mA h g À1 ), low redox potential (À0.763 V vs. standard hydrogen electrode), and a highly reversible Zn/Zn 2+ process. [12][13][14] A few cathode materials have been proposed for zinc batteries, including oxides, polyanions, and organic compounds.…”

Cobalt Single‐Atom Electrocatalysts Enhanced by Hydrogen‐Bonded Organic Frameworks for Long‐Lasting Zinc‐Iodine Batteries

“…Among them, the aqueous zinc‐iodine (Zn‐I 2 ) batteries that use an aqueous solution have become a focal point of research due to their ability to offer high energy density, affordability, and safety. [ 8–10 ] In addition, Zn‐I 2 batteries show a higher operating voltage (≈1.3 V) than extant battery options, along with a substantial theoretical capacity of 211 mAh g −1 . [ 11 ] As an inorganic material, iodine is much more affordable than rare metals such as cobalt, which is employed in metal‐based electrodes, thus making Zn‐I 2 batteries an ideal choice for greener and more sustainable energy storage.…”