Aqueous Rechargeable Zn–Iodine Batteries: Issues, Strategies and Perspectives

Abstract

The static aqueous rechargeable Zn–Iodine batteries (ARZiBs) have been studied extensively because of their low‐cost, high‐safety, moderate voltage output, and other unique merits. Nonetheless, the poor electrical conductivity and thermodynamic instability of the iodine cathode, the complicated conversion mechanism, and the severe interfacial reactions at the Zn anode side induce their low operability and unsatisfactory cycling stability. This review first clarifies the typical configuration of ARZiBs with a focus on the energy storage mechanism and uncovers the issues of the ARZiBs from a fundamental point of view. After that, it categorizes the recent optimization strategies into cathode fabrication, electrolyte modulation, and separator/anode modification; and summarizes and highlights the achieved progress of these strategies in advanced ARZiBs. Given that the ARZiBs are still at an early stage, the future research outlook is provided, which hopefully may guide the rational design of advanced ARZiBs.

Restraining the shuttle effect of polyiodides and modulating the deposition of zinc ions to enhance the cycle lifespan of aqueous Zn–I2 batteries

“…As a consequence of the shuttle effect, I 3 − reacts with Zn to generate I − (Zn + I 3 − ↔ Zn 2+ + 3I − ), which subsequently returns to the cathode for re-oxidation. 6 This occurrence leads to a self-discharge and depletion of Zn activity, and it is one of the primary reasons for the precipitous decline in the cycle life of zinc iodine batteries, as illustrated in Fig. 1 .…”

“…1–5 Amongst secondary batteries, aqueous zinc–iodine (Zn–I 2 ) batteries exhibit considerable appeal because of the advantages of elemental Zn and I, including ample reserves (50–60 mg iodine per L ocean ), reasonable price point, significant theoretical capacity (Zn: 820 mA h g −1 and I 2 : 211 mA h g −1 ), low redox potential of Zn (−0.76 V vs. SHE) and high redox potential of I 2 (approximately 0.53 V vs. SHE). 6 Regrettably, crucial challenges that necessitate resolution for the deployment of aqueous Zn–I 2 batteries include both the cathode and the anode. The former pertains to the low electronic conductivity of iodine monomers (10 −6 –10 −9 S m −1 ), their solubilization in iodide ion solutions, and sluggish redox kinetics, 6–8 whereas the latter refers to problems at the Zn interface ( e.g.…”

“…6 Regrettably, crucial challenges that necessitate resolution for the deployment of aqueous Zn–I 2 batteries include both the cathode and the anode. The former pertains to the low electronic conductivity of iodine monomers (10 −6 –10 −9 S m −1 ), their solubilization in iodide ion solutions, and sluggish redox kinetics, 6–8 whereas the latter refers to problems at the Zn interface ( e.g. , side reactions, Zn dendrites, etc.…”

Thermodynamics and Kinetics of Conversion Reaction in Zinc Batteries

“…The diffusive limitations of ions primarily pertain to the transport of ions between electrodes. The diffusion polarization caused by concentration gradients, stemming from the discrepancy in ion concentration between the catholyte and anolyte significantly impacts the rate of ion diffusion, in addition with zinc and iodine ions possess larger size, resulting in greater transfer resistance. , Hence, it becomes necessary to introduce supporting electrolytes with smaller dimensions to facilitate ion conduction. For instance, the introduction of smaller-sized NH 4 + and H + , or K + and Cl – as supporting electrolytes is advantageous. , These nonelectrochemically active supporting ions can be transmitted between porous membranes, enabling rapid ion conduction (Figure d).…”

Organic cathode materials for aqueous zinc-organic batteries

“…However, they also have some drawbacks, such as the safety risks, limited lithium reserves and high cost [3,4] . As a promising alternative to LIBs, aqueous zinc-ion batteries (AZIBs) have garnered significant interest owing to their excellent theoretical capacity (820 mAh•g -1 ), appropriate redox potential (-0.76 V vs. standard hydrogen electrode), inherent safety and low cost and demonstrated considerable potential for applications in stationary energy storage systems [5][6][7][8][9] .…”