Electrode and electrolyte additive synergy effect for improving the capacity and supporting a high voltage plateau of aqueous rechargeable zinc iodine batteries

Aqueous rechargeable zinc-iodine batteries (ZIBs) coupled with a metal anode are promising candidates for next-generation electrochemical energy storage systems due to their high energy density, excellent safety and low cost. In this work, we develop a facile strategy for high performance ZIBs by adopting ZnCl₂ electrolyte, KI additives and activated porous corncob carbon (APCC) as a cathode. We find that ZnCl₂ electrolyte could significantly activate the I⁰/I⁺ redox behavior, and expand traditional conversion to four-electron transfer process, leading to a high discharge voltage plateau. Moreover, the APCC with the high surface area and conductivity, and strong adsorption ability can effectively immobilize I₂. Notably, the introduction of KI additives provides more active materials. Consequently, an aqueous Zn battery based on a Zn metal anode and ZnCl₂ electrolyte delivers an ultra-flat plateau at 1.15 V, which contributes to 92.2% of the capacity and 89.2% of the energy density. Our work offers an efficient method to fabricate high-performance ZIBs with eco-friendliness.