A four-electron Zn-I<sub>2</sub> aqueous battery enabled by reversible I<sup>-</sup>/I<sub>2</sub>/I<sup>+</sup> conversion.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33419999.
- Also identified by DOI 10.1038/s41467-020-20331-9 and PMC identifier 7794333.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Electrochemically reversible redox couples that embrace more electron transfer at a higher potential are the eternal target for energy storage batteries. Here, we report a four-electron aqueous zinc-iodine battery by activating the highly reversible I<sub>2</sub>/I<sup>+</sup> couple (1.83 V vs. Zn/Zn<sup>2+</sup>) in addition to the typical I<sup>-</sup>/I<sub>2</sub> couple (1.29 V). This is achieved by intensive solvation of the aqueous electrolyte to yield ICl inter-halogens and to suspend its hydrolysis. Experimental characterization and modelling reveal that limited water activity and sufficient free chloride ions in the electrolyte are crucial for the four-electron process. The merits of the electrolyte also afford to stabilize Zn anode, leading to a reliable Zn-I<sub>2</sub> aqueous battery of 6000 cycles. Owing to high operational voltage and capacity, energy density up to 750 Wh kg<sup>-1</sup> based on iodine mass was achieved (15-20 wt% iodine in electrode). It pushes the Zn-I<sub>2</sub> battery to a superior level among these available aqueous batteries.