Capitalizing on the Iodometric Reaction for Energetic Aqueous Energy Storage.

Iodometric and iodimetric titrations represent a prevailing technique to determine the concentration of Cu 2+ ions in aqueous solutions; However, their utilization in electrochemical energy storage has been overlooked due to the poor reversibility between CuI and Cu 2+ related to the shuttling effect of I 3 - species. In this work, we developed a 4A zeolite separator capable of suppressing the free shuttling of I 3 - ions, thus achieving a record-high capacity retention of 95.7% upon 600 cycles. Theoretical and experimental studies reveal that the negatively charged zeolite can effectively impede the approach and penetration of I 3 - ions, as a result of electrostatic interaction between them. To explore the practical potential, a hybrid cell of Zn∥I 2 consisting of Cu 2+ redox agent has been assembled with a discharge capacity of 356 mA h g -1 . The cell affords a specific energy of 443 W h kg -1 based on I 2 , or 193 W h kg -1 based on both electrodes. This work offers insight on the energy utilization of the iodometric reactions and advocates a Cu 2+ -mediated cell design that could potentially double the capacity and energy of conventional aqueous battery systems.