Achieving Enhanced Cycle Stability in Zn–I2 Batteries with a Polyvinylpyrrolidone Binder

Iodine (I 2 ) is an attractive cathode for aqueous Zn batteries (AZBs) because of its high capacity, low cost, and environmental benignity. Nevertheless, the I 2 dissolution and the shuttling effect of polyiodide during charge–discharge processes seriously hinder the cycle stability and practical application of Zn-I 2 batteries. Herein, a water-soluble polyvinylpyrrolidone (PVP) polymer is proposed as a functional binder to address the above issues. The abundant polar groups in the PVP molecular chain serve as active sites, which can form a strong affinity with polyiodide ions, thereby effectively confining polyiodide species within the cathode. As a result, the PVP-based cathode achieves a capacity of 201 mAh g –1 at 0.1 A g –1 and retains 122 mAh g –1 at 5 A g –1 , which significantly outperforms the conventional polytetrafluoroethylene (PTFE) binder-based cathode that only delivers 176 and 100 mAh g –1 under the same current densities, respectively. Moreover, a long cycling stability of 20,000 cycles at 5 A g –1 with 97 mAh g –1 capacity was achieved. This work not only provides an efficient and low-cost strategy to mitigate the iodine shuttle problem but also sheds insights into the design of multifunctional polymer binders for high-performance Zn-I 2 batteries.