June 15, 2019, Research Highlights

Developing a Predictive Solubility Model for Monomeric and Oligomeric Cyclopropenium-Based Flow Battery Catholytes

Two important field-wide goals are met through this study: the development of a statistical model for the solubility of conformationally flexible molecules in acetonitrile and the operation of a high concentration (1 M) nonaqueous organic symmetric flow cell. Read More

June 13, 2019, Research Highlights

On Transferability of Performance Metrics for Redox-active Molecules

It is shown that two commonly used performance metrics for charged redoxmers in flow batteries, viz. their cycling and calendar lifetimes, generally do not correlate with each other. It is also demonstrated that the cycling stability is extremely sensitive to experimental detail; unless the conditions are tightly controlled, this metric is unsuitable as a guide for materials development. Read More

May 10, 2019, Research Highlights

Stability and Microheterogeneity in Concentrated Nonaqueous Electrolyte Solutions

We compared the molecular dynamics of two different but structurally-related electrolytes in highly concentrated solutions. One catholyte is compact and symmetrical; the other is bulkier and less symmetrical. Incoherent elastic and quasi-elastic neutron scattering measurements showed significant differences in crystallization, supercooling, and sudden microheterogeneity. Read More

May 7, 2019, Research Highlights

Enabling High Concentration Redox Electrolytes for Use in Nonaqueous Redox Flow Batteries

Building on prior collaborative JCESR research on iteratively advancing phenothiazines as charge storage materials, we developed a new class of phenothiazine derivatives with high equivalent charge concentration by increasing solubility and stability of multiple electron transfer events. Read More

March 5, 2019, Research Highlights

Redox Polymers in Electrochemical Systems: From Methods of Mediation to Energy Storage

Redox polymers were designed for mediation in sensors in the 1980s, but it was not until the last five years that researchers realized that they could play a critical role in energy storage, including redox flow batteries and supercapacitors. Read More

October 17, 2018, Research Highlights

Elucidating the Nuanced Effects of Thermal Pretreatment on Carbon Paper Electrodes for Vanadium Redox Flow Batteries

The chemical and physical properties of carbon paper electrodes treated at temperatures between 400-500 °C for 30 hours were quantified, and the subsequent impact of these properties on the performance of vanadium redox flow batteries explained. We find that the oxygen content and electrochemically active surface area, two parameters that govern the kinetic performance of the vanadium flow battery, follow opposing temperature trends; thus, optimal performance is achieved at a balance of these properties rather than a maximization of each. Read More

September 1, 2018, Research Highlights

Comparing Calendar and Cycle Life Stability of Redox Active Organic Molecules for Nonaqueous Redox Flow Batteries

Cycle and calendar lives are chemical stability metrics that reflect two regimes of redox flow battery use: (i) continuous charge/discharge cycling and (ii) long-term charge storage in external tanks. Here we examine how these two performance metrics are related to each other for negative charge carriers (anolytes) in nonaqueous flow cells. Surprisingly, little correlation was found between these two practically important metrics. Read More

July 27, 2018, Research Highlights

Quantifying the Impact of Viscosity on Mass-transfer Coefficients in Redox Flow Batteries

A methodology for and the results from quantification of the mass-transfer coefficient is demonstrated in the single-electrolyte configuration of JCESR’s Gen-2 cell using a model redox-active electrolyte (RAE) with a tunable viscosity. Read More

April 23, 2018, Research Highlights

Effect of the Backbone Tether on the Electrochemical Properties of Soluble Cyclopropenium Redox-Active Polymers

A series of cyclopropenium polymers were synthesized and evaluated as high potential active material for size-exclusion flow batteries. Read More

March 13, 2018, Research Highlights

Substituted Thiadiazoles as Energy-rich Anolytes for Nonaqueous Redox Flow Cells

2,1,3-benzothiadiazole (BzNSN) base molecules were derivatized with various electronic groups to achieve the optimal properties as the anolytes in nonaqueous redox flow batteries. It has been observed that the half-life times of those molecules are nicely correlated with redox potentials. Higher redox potentials lead to long life time or calendar life. The relationship of the molecular stability and the corresponding cycling performance was also investigated. Read More