Capitalizing on the Iodometric Reaction for Energetic Aqueous Energy Storage

Iodometric and iodimetric titrations represent a prevailing technique to determine the concentration of Cu²⁺ ions in aqueous solutions; However, their utilization in electrochemical energy storage has been overlooked due to the poor reversibility between CuI and Cu²⁺ related to the shuttling effect of I₃^- species. In this work, we developed a 4A zeolite separator capable of suppressing the free shuttling of I₃^- 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 I₃^- ions, as a result of electrostatic interaction between them. To explore the practical potential, a hybrid cell of Zn∥I₂ consisting of Cu²⁺ 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 I₂, 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 Cu²⁺-mediated cell design that could potentially double the capacity and energy of conventional aqueous battery systems.