Hydrogel integrated ion channels in porous membrane for stabilizing zinc anode of aqueous zinc-ion batteries

Abstract

Aqueous zinc ion batteries (AZBs) are characterized by high capacity, environmental friendliness and low cost. However, the dendrites and parasitic reactions (e.g., corrosion and hydrogen evolution) on the Zn anode restrict the advancement of AZBs. The separator offers the requisite channel for ion transport during battery operation and exerts a considerable influence on the electrode/electrolyte interfacial chemistry and electrode stability. However, the heterogeneity of the pores and framework in common porous separators is not favorable for the uniform ion diffusion/deposition at the interface, which readily causes concentration gradients and induces dendrites. This work establishes a functional composite membrane with hydrogel-integrated ion channels exploiting the Hofmeister effect. Thanks to the robust hydrogen bond network within the polyvinyl alcohol (PVA) hydrogel and its strong interaction with the porous skeleton, the integrated pore-surface ion channel is uniform and stable. This distinctive channel, filled with the highly conductive, zinc-philic and hydrophilic PVA, expedites and homogenizes the diffusion/deposition kinetics of Zn²⁺ and mitigates electrode corrosion caused by reactive water. The PVA-tailored membranes remarkably enhance the stability of the Zn anode, enabling robust cycling for more than 2000 h at 10 mA cm^-2 and 1 mAh cm^-2 with a relatively small polarization voltage. This research offers valuable perspectives for the fabrication of functional membranes and the development of advanced AZBs featuring superior performance.

Keywords: AZBs; Hofmeister effect; Integrated ion channels; PVA hydrogel; Porous membrane; Zinc anode.