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

Abstract

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.