Tuning Zn2+ coordination tunnel by hierarchical gel electrolyte for dendrite-free zinc anode

We report a highly-confined and hydrogen bond-strengthened tannic acid (TA) modified sodium alginate (SA) composite hydrogel electrolyte (TA-SA). The coordination and chelation of carboxyl groups and phenolic hydroxyl groups of electrolyte toward zinc ions successfully guide the Zn deposition and realize ameliorated self-discharge stability. The intermolecular hydrogen bonds between carbonyl and hydroxyl groups also improve the low-temperature performance. Aqueous zinc-ion batteries (ZIBs) are perceived as one of the most upcoming grid-scale storage systems. However, the issues of electrode dissolution, dendrite formation, and corrosion in traditional liquid electrolytes have plagued its progress. In this work, Zn dendrite growth and side reactions are effectively suppressed by a highly-confined tannic acid (TA) modified sodium alginate (SA) composite gel electrolyte (TA-SA). The ion-confinement effect is enhanced by divalent zinc ions coordinated with carboxyl groups and chelated with phenolic hydroxyl groups, thus guiding and regulating Zn deposition to achieve steady zinc plating/stripping behavior. As a consequence, the Zn/TA-SA/NH 4 V 4 O 10 full cells deliver a high specific capacity of 238.6 mAh g −1 and maintain 94.51% over 900 cycles at 2 A g −1 . Notably, after resting over 5 d, the capacity can be stabilized with a capacity retention of 97.25% after 200 cycles at 2 A g −1 . This highly-confined and hydrogen bond-strengthened gel electrolyte may provide an effective strategy for the future development of quasi-solid-state metal batteries.