Preparation of Waterproof and Air-Permeable Membrane by Water Surface Spreading Method for Metal-Air Battery

The electrochemical performance of metal–air batteries is sensitive to environmental humidity, which significantly limits its wide application in an air environment. In this paper, a waterproof and breathable polydimethylsiloxane (PDMS) composite membrane has been successfully synthesized by the water spreading method for metal–air batteries. The effects of spreading times and fillers (hydrophobic SiO2 and silicalite-1) on the water vapor and air permeability of the PDMS membrane were investigated. The results demonstrate that increasing the spreading times and adding an appropriate amount of hydrophobic SiO2 can improve the waterproof quality and air permeability of the PDMS membrane. The optimized membrane was assembled into a metal–air battery, and the effects of the membrane on the running resistance, cycle number, and polarization voltage of the battery were evaluated. The hydrophobic SiO2–PDMS membrane significantly reduces the running resistance of the battery and improves the cycle number of lithium–air batteries by 25% and that of zinc–air batteries by 100% in an air environment (40% RH, 25 °C). The polarization voltage is also significantly reduced, indicating great potential in applications.