Grid-scale energy storage has the potential to alleviate the variability and unpredictability of renewable energy sources, such as wind or solar, while also improving electrical grid stability and national infrastructure security. This research project investigates organic electrochemical redox flow battery systems and one of their major limiting factors: electrode performance losses that contribute to a decrease in efficiency to the overall system. In most electrochemical systems, ions must move to store or release electricity in the electrode. If ionic transport is slow, then the system's ability to deliver power at high efficiency suffers. The research team will address the synthesis of the electrode material, mathematical simulations of the electrode formation mechanisms, and characterization of the electrochemical performance of the electrode in a flow battery application. The electrode material has a porous structure that is designed so that the transport of liquid electrolyte is facilitated and improves the power and efficiency of the whole battery system. The mathematical simulation component of this research is expected to contribute to a broader understanding of how fluids move in porous structure. Such knowledge will be useful in oil and gas production, groundwater hydrodynamics, and other electrochemical reactors. The research will be integrated into a broad range of educational and outreach activities that include research dissemination through graduate and undergraduate courses, a pre-college summer program, and video clips of experimental demonstrations and simulation results for YouTube dissemination.
The goal of this research project is to accelerate ionic transport in organic electrochemical systems and to reduce ion transport loss via directionally-porous graphene aerogel (DGA) electrodes. Studies will lead to an understanding of the fundamental physics that define the relationship between viscous flow, porosity, pore morphology, and mass and ionic transport. The research will complement current research in organic redox electrochemical systems including identification of promising electrochemical redox couples and suitable separators. The project involves cyclic integration between molecular dynamics simulations of synthesis conditions, synthesis of DGA electrodes via freeze-templating, material property assessment, and electrode demonstration in an operating organic redox flow battery (biphenyl anode, sulfide/polysulfide cathode, and sodium triflate as charge carrier). Molecular dynamics simulations will focus on the effects of freezing conditions on electrode structure and ionic (biphenyl radical, sulfide, and sodium ion) transport in the presence of electrolyte convection. DGA electrodes will be synthesized under a variety of conditions for comparison with simulation results and implementation in a biphenyl/polysulfide redox flow battery. Physical properties including stiffness, porosity, and surface area, and electrode-relevant properties including electrochemical surface area, electronic and thermal conductivities, and effective permeability will be assessed. A novel characterization technique will directly measure changes in effective liquid-phase ionic conductivity using the same foundational principle underlying the standard four-point probe test used to measure solid-phase ionic conductivity (e.g. ion exchange membranes). The new diagnostic will measure liquid phase ionic conductivity, with and without a porous electrode, and with or without convective flux. Liquid phase ionic conductivity will be benchmarked against aqueous sodium chloride with a conventional carbon felt electrode.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
