Redox flow batteries (RFBs) are highly efficient electrochemical energy storage (EES) devices
for large-scale electricity generated from renewable energy sources like solar, wind etc. The
energy-power decoupling makes the RFBs unique from other EES devices. Vanadium redox
flow battery (VRFB) is one of the most studied RFB due to its several advantages, e.g. long
cycle life, avoidable cross-contamination of electroactive species, safe to use etc.1 Electrodes
plays a significant role in VRFB which provides a suitable site for the electrochemical reactions
that in turn decides the performance of the battery. Graphite felt (GF) and carbon paper (CP)
are the most common electrode material for VRFB. Due to hydrophobicity and less
electroactive surface area of these electrodes, it is necessary to activate the electrodes and/or
coat suitable electrocatalyst for better performance of the battery.2 Thermal activation3 and
sulfuric acid4 activation are the widely accepted methods for such electrodes. A lot of
electrocatalysts such a carbon material, metal, metal oxides etc. have also been studied.5 Still,
there is a lot more scope to increase the energy efficiency (EE), electrolyte utilization, cycle
life of the VRFB.
On the other hand, commercialization of VRFB is limited by its high cost. About 35-50 % of
its cost is from its active material, i.e. vanadium due to its scarcity.6 Hence, the cost of the
battery can be minimized by replacing vanadium using organic electroactive species. Quinone
based electroactive species are widely studied for organic aqueous flow batteries. However,
they face many challenges related to side reactions, instability, low solubility etc.7
In this seminar, a literature survey on electroactive materials for various aqueous acidic
RFBs and my work on VRFB will be discussed.
References:
1. Vivona et al., J. Electrochem. Soc., 167, 110534 (2020)
2. Liu et al., ACS Appl. Mater. Interfaces, 9, 4626-4633 (2017)
3. Sun et al., Electrochim. Acta, 37, 1253–1260 (1992).
4. Sun et al., Electrochim. Acta, 37, 2459–2465 (1992).
5. Gencten et al., Int. J. Energyg Res., 44, 7903-7923 (2020)
6. Li et al., Natl. Sci. Rev., 4, 91-105 (2017)
7. Zhong et al., Front. Chem., 8:451 (2020)