Hierarchically porous hydrogel electrolyte prepared from interpenetrating polymer networks for flexible Zn-Air batteries

Gel polymer electrolyte (GPE) based flexible zinc-air batteries (ZABs) are considered promising power sources for next-generation wearable devices because of their high specific energy density, low cost, high safety, and environmental friendliness. However, the liquid component in GPE is susceptible to evaporation through the air cathode, drastically reducing the cell performance and lifetime. Poly(vinyl alcohol) (PVA) is the most widely adopted ion conductive polymer, but its poor water retention and low ionic conductivity hinder the widespread commercialization of flexible ZABs. A hierarchically porous (HP) PVA and poly(acrylic acid) (PAA) hybrid GPE is developed to address the aforementioned issues. The polymerization of acrylic acid in a PVA matrix forms a semi-interpenetrating polymer network involving a unique HP structure inside the membrane. The PAA-rich lotus-seed-like pores fundamentally improve electrolyte uptake and retention properties, and enhance ionic conductivity. The HP-PVA/PAA hybrid GPE delivers excellent cycling stability, rate characteristics, and power output in ZABs. Furthermore, HP-PVA/PAA based flexible ZABs incorporated into the customized strap demonstrates their feasibility for powering the wearable smart watch.