Zinc-slurry preparation and characterization for a zinc-air redox-flow battery

Abstract

The Zinc air redox flow battery is one of the redox flow batteries which are promising candidates for large scale energy storage. The battery comprises of a separate tank containing active species in which the energy capacity is stored, and the cell stack where power can be independently scaled. However, oxygen can be directly picked from air leading to cost, safety and space saving benefits as it avoids the need of another storage tank. This study was aimed at formulating and preparing the zinc slurry, an active species for the zinc air redox flow batteries. The formula was developed containing zinc particles, zinc oxide, water, polyacrylic acid and potassium hydroxide. The variation in the sample slurries was due to the difference in the molecular weights of the several polyacrylic acid samples used. Flow rate test were carried out on the prepared test samples and it was observed that slurries composed of Polyacrylic acid of average molecular weight 1.250.000 and 4.000.000 showed better flow properties. To these slurries containing the high average molecular weight Polyacrylic acid, Electrochemical Impedance Spectroscopy was carried at a frequency range of 0.1 Hz to 100 kHz with an AC amplitude of 20mV. The slurries reported improved discharge performance as the current density increased. Future work has been suggested in order to improve the performance of the slurries in the battery.