Production and characterization of bi-functional cathodes for secondary zinc-air batteries

Abstract

One of the major drawbacks for today’s energy market of renewable energy production is that there is no cost efficient possibility to store produced energy for times when renewable energy production is less then energy consumption. The EU funded Project “ZAS – Zinc Air Secondary batteries based on innovative nanotechnology for efficient energy storage” has the goal to overcome this drawback by developing a new generation of secondary zinc-air batteries. Zinc based metal-air batteries have the advantages of metal batteries, which is a high energy density due to fact that oxygen from ambient air, is used and therefore has not to be stored inside the battery. Because of that lighter batteries can be build and the only limiting factor is the amount of reversible active usable zinc inside the battery. Besides this, zinc has even more advantages, zinc is a cheap metal which is commonly occurring in the environment, production of Zn-Air batteries can be done in any atmosphere which makes it cheap in production and zinc is environmentally benign. Because of all these advantages these Zn-Air batteries are of high interest for stationary energy storage systems. However, before Zn-Air batteries can be used as storage units some obstacles have to be overcome. The low cyclability of state of the art Zn-air batteries is due to the high passivation rate and dendrite growth of zinc, carbonization of alkaline electrolyte and corrosion of cathode materials. One of the goals of ZAS! is to develop a scalable production technique for cathodes up to to a single cell size of 110 cm². The electrochemical testing of cells in different stages of development was carried out in half- and full-cells with an aqueous alkaline electrolyte. Varying sizes of the used testing-cells showed scalability and (electrochemical) stability of the prepared cathodes. The main focus of this work was to identify the main preparation parameters that have high impact on the structure and morphology of the prepared electrodes and therefore on the performance of the cathode. To get a better understanding of the contributions of the different parameters, several test cells were developed and physical and electrochemical characterizations (CV, PC, EIS) were performed.