The final poster highlighted is Kassia’s…

Stability testing of radical cations for energy storage applications.

Kassia Symstad, Dr. Thomas F. Guarr

Electron donor molecules must be stable in both the neutral and radical cation form to be viable as shuttles for overcharge protection in lithium ion batteries or as part of a larger donor-acceptor system for use in redox flow batteries.  In this work we report stability testing on a variety of carbazole and phenothiazine-5,5-dioxide derivatives.  Conversion of the neutral molecule to its radical cation state was accomplished either by chemical oxidation or electrolysis in a spectroelectrochemical cell.  The radical cations of these donor molecules have a differect UV-vis spectra than the neutral molecules, which provides an effective means to monitor their generation and persistence.  The voltage that resulted in the maximum rate of conversion to the radical cation form was found this way.  that voltage was them applied for a longer period of time, either in a spectroelectrochemical cell or a conventional H-cell for bulk electrolysis to effect complete conversion.  This allows the radical cation to be studied on time scales ranging from seconds to months.  These stability studies are useful for the evaluation of preliminary data from a linked donor-acceptor system in a prototype RFB cell.

We had a total of seven posters presented at the Schaap Symposium.  Our next presenter is Anthony Porath…

Building blocks for multi-electron linked systems for organic redox flow batteries

Anthony Porath, Adina Dumitrascu, Dan Henton, Jason G. Gillmore, Thomas F. Guarr

A series of redox-active compounds were synthesized and electrochemically assessed for their potential use in nonaqueous redox flow batteries (RFBs).  These include electron donating species, the donors, and electron accepting species, the acceptors.  The donor and acceptor moieties are separated with an expensive ion-exchange membrane in traditional RFBs, but when covalently-linked a simple separator is able to be utilized.  The donor/acceptor systems exist in three stable oxidation states during RFB operation: reduced (anolyte), neutral, and oxidized (catholyte) forms.  The pursuit of multi-electron redox-active species would serve to further lower costs.  Decreasing the cost as much as possible is important as it would make it much more economical to introduce RFBs in a large-scale grid storage role.  The synthesis, characterization and preliminary electrochemical investigation of these molecules will be described.

Andy also presented a poster at the Schaap Symposium…

Cyclopropenium Donors for Linked Donor-Acceptor Systems for Symmetric Nonaqueous Redox Flow Batteries

Andrew Rajewski, Adina Dumitrascu, Jason G. Gillmore, Thomas F. Guarr

A series of molecules containing electron donor (D) and electron acceptor (A) moieties are being explored for future use in symmetric organic redox flow batteries (RFBs).  The synthesis, characterization and preliminary electrochemical investigation of these molecules will be described.  Past studies in the group have looked at heterocyclic donors.  This work focuses on the synthesis of cyclopropenium donors for use in linked donor-acceptor systems.  Cyclopropenium donors have been studied in recent years and have shown promising properties for use in RFBs (>=0.8 V vs. Fc/Fc+, <3% loss of storage capacity over 200 cycles).)  Linking these donors to acceptors in linked systems allows for a symmetric RFB that eliminates the ubiquitous and expensive ion exchange membrane used in typical RFBs.  Because the membrane can account for up to 40% of cell costs, this could represent an important opportunity to improve the economics of employing flow batteries for grid-level energy storage applications.

1. Sanford, Adv. Energy Mater., 2016 7(5), 1602027

Mike will be finishing up his engineering degree at Hope College this fall and continuing his work with us throughout the year.  He joined us this summer to work on supercapacitor applications.

Nickel (II) and Copper (II) tetraaminophthalocyanines for Supercapacitor Applications

Michael T Giurini, Kevin Klunder, Thomas F. Guarr

As the world embraces renewable energy sources and moves away from fossil fuels, the demand for efficient ways to store energy has increased substantially.  Supercapacitors can be used to enhance energy efficiency.  While they store less energy than batteries, they can absorb and release it at a much faster rate.  Conductive polymers produced from nickel, copper, and cobalt tetraaminophthalocyanines can be used to fabricate electrochemical double layer capacitors (EDLC) with unique electric storage properties.  Using cyclic voltammetry, these compounds can be electropolymerized to form thin films, which can then be conditioned with an annealing process to act as EDLC’s.  Studies to determine the optimal conditions for electropolymerization and conditioning will be reported.  The polymerization and annealing process was tested with various electrolytes, solvents, and electrode surfaces.  Resulting polymer films were analyzed electrochemically and by scanning electron microscopy (SEM) to determine the impact of these variables on EDLC formation.