Bioinspired oxygen selective membrane for Zn–air batteries

Zn–air and other metal–air batteries suffer from limited shelf life due to carbonization by CO₂ and evaporation of water through the cathode. Bioinspired oxygen selective membranes (OSMs) with common similarities to lungs alveoli were prepared and applied as an oxygen selective passive membrane on the cathode of the Zn–air batteries, which limit CO₂ and H₂O transport while actively supporting O₂ flux. The OSMs were prepared from polycarbonate and iron(II) phthalocyanine in volatile chlorogenic solvent (“breath figures self-assembly” mechanism) under controlled humidity conditions. Membranes were characterized by scanning electron microscopy, UV–visible spectroscopy, and gas chromatography. These membranes contain polycarbonate in a pulmonary alveolus-like structure of 0.2–4.0 microns thick, inclosing iron(II) phthalocyanine as an oxygen carrier molecule. The electrochemical measurements are performed to evaluate the membrane O₂ permeability in both half- and full-cell Zn–air configurations. The effect of relative humidity, iron(II) phthalocyanine, and polycarbonate content is investigated during the optimization of membrane permeabilities and selectivity results. By installing the OSM on top of the cathode of a Zn–air prototype cell, we were able to reduce the water evaporation by 88% while supporting an oxygen limiting current of 73 mA cm⁻²_OSM with an OSM (PC 11%, FePc 9.1%). Graphical abstract: In this contribution, we present an oxygen selective membrane (OSM) to increase the shelf life of the Zn–air cell. By applying OSM on top of the Zn–air cell cathode, we successfully demonstrated the reduction in the water evaporation by 88% while supporting an oxygen limiting current of 73 mA cm⁻²_OSM. [Figure not available: see fulltext.].