Redox Flow Battery
Objective: Further the understanding and state-of-the-art of nonaqueous redox flow batteries through examination of cell components such as the electrolytes, electrodes and separators..
Summary: Summary: Demand for large scale grid energy storage grew significantly in recent years due to a variety of factors ranging from new regulations like California’s storage mandate in 2013  to highly publicised failures in natural gas storage facilities in 2015 . Redox flow batteries (RFBs), which store energy in liquid electrolytes rather than traditional solid electrodes, offer long-lived, lower-lifetime-cost alternatives to traditional Li-ion batteries. While Li-ion systems dominate volume or weight constrained applications like mobile electronics or vehicles, stationary large-scale grid electricity storage can sustain the lower energy density and specific energy of state-of-the-art aqueous Vanadium RFBs. However, Li-ion systems still illustrate a potential area of improvement for redox flow batteries: construction of nonaqueous systems can enhance performance of these battery systems.
While nonaqueous systems can offer higher cell voltages, improved reaction kinetics, and lower viscosities among other performance improvements, they require a different cost model than aqueous systems. Contrary to aqueous vanadium systems where redox-active species dominate electrolyte cost, nonaqueous systems will have substantial solvent and supporting electrolyte cost. Therefore, nonaqueous systems must be selected which deliver sufficient performance improvements to counteract areas of increased cost. On this topic, our research focuses on low-cost symmetric redox-active species. Lower active species cost is achieved through higher voltages than aqueous vanadium delivered by V(acac)3 chemistry , increased coulombs accessible per molecule delivered by the Cr(acac)3 chemistry , and use of inexpensive organic waste streams such for the redox active chemistries . Symmetry provides another cost saving and performance enhancing by allowing the use of inexpensive, high-rate compatible porous separators rather than expensive, resistive fluorinated ion exchange membranes.
 J. St. John. 17/10/2013. GreenTechMedia. Cells used to charge/discharge the system
 J. St. John. 02/06/2016. GreenTechMedia.
 A. Shinkle, et al., J. Power Sources. 2012.
 Q. Liu, et al., Electrochem. Comm. 2010.
 J. Saraidaridis, et al. Meeting Abstracts of ECS EEC&S 2015. 2015.
Cells used to charge/discharge the system
Mass Transport in Flow Battery
Objective: Measure interactions between diffusing species across the membrane in aqueous-all-vanadium redox flow batteries.
Summary: Aqueous-all-vanadium redox flow batteries are a promising technology for large capacity, efficient energy storage. Currently there is a broad research effort in creating sophisticated models of redox flow batteries capable of predicting their performance. An important parameter in these models is the interaction between diffusing species in the membrane of redox flow batteries. The main two species of interest are vanadyl sulfate, which is one of the four oxidation states of vanadium storing charge in the battery, and sulfuric acid, which serves to reduce the ohmic losses in the electrolyte. To measure the diffusional interactions, an interdiffusion is conducted, where initially pure vanadyl sulfate and sulfuric acid are placed on either side of the membrane and allowed to diffuse across. Interdiffusion of the species results in an exponential decay in concentration on either side towards equilibrium. The measured decay constant can then be used to compute the diffusional interaction parameter for vanadyl sulfate and sulfuric acid.
A redox flow battery in the glovebox.