Phytic acid cross-linked and Hofmeister effect strengthened polyvinyl alcohol hydrogels for zinc ion storage

It is a big challenge to retain the water and thus reduce the charge impedance for solid electrolytes used in flexible and wearable zinc ion batteries. Here, we propose novel phytic acid (PA) cross-linked polyvinyl alcohol (PVA) hydrogels as high-performanced solid electrolytes strengthened by the Hofmeister effect. In this approach, freeze-thawing followed by a salting-out procedure via anions to induce the Hofmeister effect can greatly improve the tensile strain and flexibility of the hydrogels. The PA addition dramatically enhances the ionic conductivity and increases the affinity between the electrolyte and zinc plate. Consequently, the PVA/PA hydrogels exhibit remarkable electrochemical performances with stable full-cell cycling in zinc ion storage and capability in inhibiting Zn dendrite growth. The mechanical strength of polyvinyl alcohol (PVA) hydrogel can be drastically boosted by Hofmeister effects and rich hydrogen bonds. The phosphate groups from phytic acid (PA) are beneficial to fast ions transport.