Aqueous fibrous membrane electrolyte for ultrathin flexible Zinc-air batteries

Membrane electrolytes are key to constructing planar energy storage devices of low thickness and high flexibility, requesting simultaneous optimization of ionic conductivity and mechanical stability. Herein, aqueous phase electrospinning (APE) was implemented to co-spin polyvinyl alcohol and pullulan polysaccharide for fabricating crosslinked fibrous membrane electrolytes. While the hydroxyl-rich polymeric backbone grafted with quaternary ammonium endows a strong hydrogen-bonding network affording a large ionic conductivity of 30.2 mS cm- 1, the cellulose-braced fibrous structure manifests a high tensile strength of 4.6 MPa. What's more, the porous structure of the membrane electrolyte with enhanced charge mobility and uniformity helps to guide homogeneous Zn plating/stripping with suppressed dendrite growth. As a result, the assembled ultrathin flexible ZAB delivers a superb round-trip energy efficiency of 59.8 %, a maximum power density of 102 mW cm- 2 and a long-term cycling stability over 100 h at 5 mA cm- 2. By innovating the concept and methodology of aqueous fibrous membrane electrolytes, this study opens up a new chapter on the development of solid electrolytes in aqueous battery systems for powering wearable electronics.