(223b) Low-Cost and Highly Efficient Materials for Grid-Scale Renewable Energy Storage Devices

The rising interest in integrating intermittent renewable energy sources such as wind and solar energy into the electric grid has created an immense need for energy storage. Redox flow batteries (RFBs) are of particular interest because of their unique feature of separate power and energy outputs. In contrast to other electrochemical energy storage devices, the energy in RFBs is stored in redox active liquid electrolytes in external tanks whereas the power is dependent on the properties of the cell stack such as electrodes, membranes, and rate of charge transfer. This allows the battery to be scaled independently to meet varying energy requirements. However, the extensive use of flow batteries is limited by low energy and power densities coupled with high material costs. Current flow battery devices rely on costly transition metals specifically vanadium, an expensive perfluorinated Nafion^TM membrane, and inert carbon electrodes. Thus, for the grid-scale adaptation of redox flow batteries, the electrochemical performance and efficiency must be enhanced with cheaper electroactive materials.

My research has focused on reducing charge transfer resistances of RFBs by using redox active electrodes and improving the performance of low-cost RFB chemistries. We found that introducing redox active sites into the electrodes reduces the voltage difference and barrier to charge transfer between the electrode and the redox active species in the electrolyte. The performance of the low-cost, environmentally friendly, and highly electroactive zinc iodine (ZI) RFB was investigated using inert electrodes and then using iron functionalized carbon electrodes. It was observed from polarization analysis that the redox-active iron functionalized electrodes sustained higher discharge voltages at low flowrates and yielded a 66% increase in power density. This performance was further improved by studying the role of the cation exchange membrane (CEM) on charge transport and energy capacity. Sulfonated poly (ether ether ketone) SPEEK membranes were used as an alternative to the benchmark nafion membrane. SPEEK had higher cationic selectivity, and from battery charge-discharge cycling, higher columbic efficiencies and a 370% increase in energy density in comparison to nafion 212.

Over the course of my PhD, I have become well versed in electrochemistry, battery material (electrode, electrolyte, and membrane) design and testing and the use of several electrochemical software such as Gamry, VersaStudio and Arbin Instruments. Additionally, I gained expertise in the assembly, design, and testing of various electrochemical cells including: 3-electrode cells, half-cells, coin cells, flow cells, fuel cells, gas diffusion cells, etc. I have also learned a lot about the broad field of energy, energy storage and renewable energy generation. My research afforded me the chance to work on both material design and energy storage device engineering.

Research Interests

I look forward to pursuing further studies on the role of electrode design on the performance of batteries, including lithium ion batteries (LIBs), the alkaline battery and flow batteries. My research interests include investigating the catalytic properties of transition metals for electrodes and electrolytes. I hope to create highly efficient electrodes and materials for long cycle, high capacity, and high power batteries taking into consideration the recyclability, cost, safety and effect of the materials and devices on the environment. I am particularly interested in pursuing a career that involves designing high performance electrochemical energy storage devices, and creating testing protocols and scaling methods for grid-compatible renewable energy storage.