A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery

Journal Article · Sun Jan 01 04:00:00 EST 2017 · Journal of Visualized Experiments

DOI:https://doi.org/10.3791/55171· OSTI ID:1356477

Duan, Wentao; Vemuri, Rama S.; Hu, Dehong; Yang, Zheng; Wei, Xiaoliang

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid and deployment of renewable energy technologies. Among the many flow battery chemistries, nonaqueous flow batteries have the potential to achieve high energy density because of the broad voltage windows of nonaqueous electrolytes. However, significant technical hurdles exist currently limiting nonaqueous flow batteries to demonstrate their full potential, such as low redox concentrations, low operating currents, under-explored battery status monitoring, etc. In an attempt to address these limitations, we report a nonaqueous flow battery based on a highly soluble, redox-active organic nitronyl nitroxide radical compound, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO). This redox materials exhibits an ambipolar electrochemical property with two reversible redox pairs that are moderately separated by a voltage gap of ~1.7 V. Therefore, PTIO can serve as both anolyte and catholyte redox materials to form a symmetric flow battery chemistry, which affords the advantages such as high effective redox concentrations and low irreversible redox material crossover. The PTIO flow battery shows decent electrochemical cyclability under cyclic voltammetry and flow cell conditions; an improved redox concentration of 0.5 M PTIO and operational current density of 20 mA cm-2 were achieved in flow cell tests. Moreover, we show that Fourier transform infrared (FTIR) spectroscopy could measure the PTIO concentrations during the PTIO flow battery cycling and offer reasonably accurate detection of the battery state of charge (SOC) as cross-validated by electron spin resonance measurements. This study suggests FTIR can be used as a reliable online SOC sensor to monitor flow battery status and ensure battery operations stringently in a safe SOC range.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1356477
• Report Number(s): PNNL-SA-118931; KC0208010
• Journal Information: Journal of Visualized Experiments, Journal Name: Journal of Visualized Experiments Vol. 120; ISSN 1940-087X
• Publisher: MyJoVE Corp.
• Country of Publication: United States
• Language: English

Related Subjects

FTIR
PTIO
nonaqueous
organic
redox flow battery
state of charge
symmetric