Internally connected porous PVA/PAA membrane with cross-aligned nanofiber network for facile and long-lasting ion transport in zinc–air batteries

In response to the growing interest in next-generation wearable devices, the demand for high-performance, safe, and flexible power sources has increased. Flexible zinc–air batteries (ZABs) based on gel polymer electrolytes (GPEs) have emerged as promising candidates for wearable power sources owing to their high energy density, safety, and cost efficiency. However, persistent electrolyte evaporation through the air cathode poses a significant challenge, resulting in poor lifespan characteristics that impede practical applications. In this study, we developed a polymer composite-type GPE composed of cross-aligned nanofibers (NFs) of a polyacrylic acid (PAA)-based framework embedded in a polyvinyl alcohol (PVA) matrix. Upon immersion in a liquid electrolyte (6 M KOH), the superabsorbent PAA spontaneously generated an internally connected porous (IP) structure adjacent to the aligned PAA NFs. These pores served as directional water channels, facilitating rapid hydroxide ion conduction and yielding a remarkable ionic conductivity of 235.7 mS cm−1. The PVA matrix acts as both a packaging material and the main body of the GPE, providing good dimensional stability and mitigating the swelling of PAA, even under conditions of high electrolyte uptake, while also ensuring high flexibility. The IP-PVA/PAA composite GPE demonstrated a high power output, rate performance, and excellent lifespan in flexible ZABs. Furthermore, successful operation at various bending angles provides empirical evidence supporting the viable application of flexible ZABs.