Zn2+-crosslinking enhanced natural gelatinizer binders for low self-discharge and long-life Zn-I2 batteries

A series of natural gelatinizers is evaluated as alternative binders to replace the conventional PVDF binder. • The waterborne binders can improve both cycling stability and anti-self-discharge performance. • The optimized binder slows the 200 h self-discharge rate from 37% down to 16%, while prolonging the lifetime by ∼ 2.6 times. Aqueous zinc-iodine (Zn-I 2 ) batteries have been identified as one kind of promising energy storage device, but still suffer from self-discharge and short lifetime problems due to polyiodide shuttling. To improve the polyiodide confining ability of the I 2 cathodes, a series of natural gelatinizers, including carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyanionic cellulose (PAC), xanthan gum (XG), and sodium alginate (SA), are evaluated as alternative binders to replace the conventional polyvinylidene fluoride (PVDF). Experimental results suggest that all these water-borne binders can improve the cycling stability of the electrodes by forming a flexible hydrogel skeleton. In addition, the abundant heteroatoms in the binders can effectively adsorb polyiodide and suppress the shuttle effect. As a result, the adoption of these water-borne binders can significantly slow down the self-discharge rate of the resulting Zn-I 2 batteries, compared to the traditional PVDF binder (capacity loss: 16–21% vs. 37%, after 200 h). Among these binders, SA endows the cathodes with the best anti-self-discharging performance (capacity loss: 23.7% vs. 49.3% after 500 h, compared with the PVDF-binder battery). This strategy opens a new avenue to enhance the anti-self-discharge performance of Zn-I 2 batteries with natural polymers. Download: Download high-res image (149KB) Download: Download full-size image