Ion confinement effect enabled by carboxymethyl cellulose/tannic acid hybrid hydrogel electrolyte toward stable zinc anode

Abstract

Zinc metal batteries have garnered considerable attention ascribing to its cost effectiveness, intrinsic safety, and eco-friendliness. Nevertheless, zinc metal batteries yet are confronted with service life issue arising from dendrite and side reactions. Here, a highly ionic confined and hydrogen bond-enhanced tannic acid-modified carboxymethyl cellulose-based hybrid hydrogel electrolyte is designed for regulating structure of Zn2+ solvent and inhibiting dendrites growth, and simultaneously remaining operational under severe condition like low temperature. The phenolic hydroxyl group in tannic acid and the carboxyl group in carboxymethyl cellulose can respectively engage in chelation and coordination with Zn2+ to regulate Zn2+ transportation channel for guiding uniform zinc plating/stripping. Simultaneously, the enhanced ion confinement effect changes the solvation structure of Zn2+ to reduce H2O activity, effectively alleviating corrosion and hydrogen evolution reaction induced by H2O. Based on the principles of thermodynamics and reaction kinetics combined with theoretical calculations and experimental findings, the mechanism underlying its pivotal role in attenuating hydrogen evolution and fostering zinc deposition is elucidated systematically. The carboxymethyl cellulose/tannic acid hydrogel electrolyte endows exceptional cycling longevity (2, 100 h at 0.5 mA cm−2/0.25 mAh cm−2) for Zn||Zn battery, as well as high Coulombic efficiency for Zn||Cu battery (averagely 98.31 % within 500 cycles at 1 mA cm−2/mAh cm−2. Moreover, the assembled Zn||Zn battery, Zn||NH4V4O10 battery and Zn||NH4V4O10 pouch battery utilizing carboxymethyl cellulose/tannic acid hydrogel electrolyte can even function normally under severe conditions like low temperature and bending. This study provides valuable reference to develop hydrogel electrolytes with the ability to withstand low temperature and stabilize zinc anode.