Flexible, fiber-shaped, quasi-solid-state Zn-polyaniline batteries with methanesulfonic acid-doped aqueous gel electrolyte

Although quasi-solid-state fiber-shaped Zn-polyaniline batteries (Fs-ZPBs) are safe and potentially wearable power sources, they exhibit severe capacity degradation due to the inherently low electrolyte conductivity, soluble quinone formation in the cathode, and anode corrosion. In this study, these problems are mitigated by supplementing a polyvinyl alcohol-based gel-type electrolyte with methanesulfonic acid, which forms intermolecular hydrogen bonds to connect polyvinyl alcohol chains with each other and link the polyaniline surface with the electrolyte. The establishment of these linkages increases the ionic conductivity of the electrolyte and enhances charge transfer at the polyaniline/electrolyte interface. The relatively large molecular size of methanesulfonic acid hinders the access of water to the active materials (polyaniline and Zn) while allowing polyaniline to be efficiently doped with small-radius Cl⁻ anions. The effects of dual anion doping and water capture suppress polyaniline degradation and Zn corrosion, resulting in excellent battery performance, namely, 88.1% capacity retention after 2000 cycles and 92.7% capacity retention after 500 bending cycles at a 2.5 mm bending radius. Furthermore, an all-carbon-yarn Fs-ZPB is developed for applications requiring practical wearability.