Biodegradable Electrolyte toward Green Flexible Zinc–Air Batteries

The continuous development of flexible electronics has driven researchers to intensively study zinc–air batteries with a theoretical high energy density, low cost, and high safety. However, conventional zinc–air batteries suffer from safety problems, such as electrolyte leakage. Therefore, the development of a green, renewable, and biodegradable solid electrolyte is urgently needed. In this work, a polymer electrolyte based on soybean protein isolate with high hydrophilicity, biodegradability, and ionic conductivity up to 0.024 S cm–1 is designed and applied to zinc–air batteries. The activation energy is obtained by calculating the slope of ln(σ) versus (1000/T) according to the Arrhenius equation, and OH– transport is mainly controlled by the Grotthuss mechanism. The resulting solid-state zinc–air battery has a stable discharge plateau of 1.2 V at 10 mA cm–2, a peak power density of up to 80 mW cm–2, and a long cycle stability of around 4300 min. This study provides a new option for designing green, economical, and biodegradable solid electrolyte and flexible sustainable energy storage devices from biomass.