(103e) Metal Complexes With Redox-Active Ligands As High Energy Density Nonaqueous Redox Flow Battery Electrolytes

Metal Complexes with Redox-active Ligands as High Energy
Density Nonaqueous Redox Flow Battery Electrolytes

by Patrick J. Cappillino, Harry D. Pratt III, Nicholas
S. Hudak, Neil C. Tomson, Travis M. Anderson, Mitchell R. Anstey

Renewable
energy sources that do not contribute to accumulation of greenhouse gases, such
as wind and solar, must become an increasing portion of the global energy
portfolio.  While abundant, these sources are intermittent due to factors such
as day-night cycles and weather.  Furthermore, their generation capabilities
are poorly matched to peak and off-peak use of electricity. Grid-scale
strategies to mitigate these challenges, such as load-shifting, require energy
storage components to supplement our current infrastructure in which
electricity is instantaneously generated and distributed.

Redox flow batteries
(RFB) have attractive features for grid-scale energy storage, including
separation of energy and power capacities and modular scalability.  Over the
last several decades, a number of technologies based on vanadium and
iron-chromium electrolytes were developed but have so far met limited
commercial success. Further advancement requires fundamentally different redox
chemistry with stable redox couples, large potential differences, and fast
redox kinetics.

Herein
we report new, non-aqueous RFB electrolytes that meet these criteria based on metal complexes containing ?redox
non-innocent? ligands (M-NIL). The abundance of well-characterized, reversible
charge transfer events exhibited by these compounds has the potential to greatly improve
their energy density over state-of-the-art, transition-metal based RFB
electrolytes.  Details on their preparation, characterization and
electrochemistry will be presented and their performance as RFB electrolytes
will be discussed.

Sandia
National Laboratories is a multi-program laboratory managed and operated by
Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation,
for the U.S. Department of Energy's National Nuclear Security Administration
under contract DE-AC04-94AL85000.