Development and Performance Characterization of Bipolar Electrodialysis Flow Batteries

Abstract

Energy storage is becoming increasingly important to have a consistent renewable power supply. Limitations on the cost of current energy storage technologies have prevented the mass adoption of renewable energy. This research focusses on the development of a flow battery using low-cost electrolyte materials based on bipolar electrodialysis technology. The battery operates by splitting salt water via electricity in conjunction with a bipolar membrane and ion exchange membranes to make acidic and basic solutions. The acid and base can then be neutralized at the bipolar membrane, generating voltage and current that can be used as electricity. A bipolar electrodialysis flow battery was designed, constructed, and improved to provide reliable and repeatable operation. Bipolar membranes with different membrane chemistries and materials were tested at different temperatures to understand the losses associated with bipolar electrodialysis flow batteries. A protocol was developed with an analytical framework to compare the results of the polarization curves in a simple way, without the need for fit parameters. Through the measurement of the membrane resistance and a polarization curve, ohmic and overpotential related losses could be distinguished. Links between these losses and the physical phenomena that take place within the bipolar membrane were made. This research provides insight on how to tailor improvements to the bipolar membranes for more efficient flow batteries using cost effective, sustainable electrolytes.