Air electrodes performance in zinc-air batteries for portable devices

Summary form only given as follows. Zinc-air batteries operate by using oxygen from the air at the positive electrode and oxidation of zinc metal at the negative electrode. Oxygen from the air is reduced at the air electrode and the zinc electrode oxidizes to form zinc oxide (ZnO). This process generates the electrochemical energy of the system. The zinc-air system is unique in that zinc-air cells must be exposed to air in order to discharge. This exposure to ambient air, if not properly controlled, can severely shorten the system's operating life due to the negative effects of water vapor transpiration and carbon dioxide adsorption on the electrolyte and the air electrode. The zinc electrode in zinc-air cells behaves similarly to the zinc electrode in typical alkaline cells. This electrode is not a limiting factor in the transition of zinc-air technology into portable devices. However, air electrodes for typical zinc-air cells have not been designed to provide high power density. This is because the application where zinc-air is most widely used is hearing aid button cells. These cells are not required to deliver high power density and they have very restrictive air access openings to delay the onset of cell dry out or flooding. In order to move zinc-air battery technology into the realm of power for portable devices two fundamental issues must be addressed. The first of these is the power capability of the air electrode and the second is the isolation of the cells from the external environment when not in use. AER Energy has developed solutions to both of these issues that can enable the use of zinc-air batteries in portable devices. This paper discusses the latest developments in both of these areas.