Janus Binder Chemistry for Synchronous Enhancement of Iodine Species Adsorption and Redox Kinetics toward Sustainable Aqueous Zn–I₂ Batteries

Abstract

Currently, the desired research focus in energy storage technique innovation has been gradually shifted to next-generation aqueous batteries holding both high performance and sustainability. However, aqueous Zn-I₂ batteries have been deemed to have great sustainable potential, owing to the merits of cost-effective and eco-friendly nature. However, their commercial application is hindered by the serious shuttle effect of polyiodides during reversible operations. In this work, a Janus functional binder based on chitosan (CTS) molecules was designed and prepared; the polar terminational groups impart excellent mechanical robustness to hybrid binders; meanwhile, it can also deliver isochronous enhancement on physical adsorption and redox kinetics toward I₂ species. By feat of highly effective remission to shuttle effect, the CTS cell exhibits superb electrochemical storage capacities with long-term robustness, specifically, 144.1 mAh g^-1, at a current density of 0.2 mA g^-1 after 1500 cycles. Simultaneously, the undesired self-discharging issue could be also well-addressed; the Coulombic efficiency could remain at 98.8 % after resting for 24 h. More importantly, CTS molecules endow good biodegradability and reusable properties; after iodine species were reloaded, the recycled devices could also deliver specific capacities of 73.3 mAh g^-1, over 1000 cycles. This Janus binder provides a potential synchronous solution to realize high comprehensive performance with high iodine utilization and further make it possible for sustainable Zn-I₂ batteries.