posted on 2020-03-18, 14:43authored byJingchao Chai, Amir Lashgari, Zishu Cao, Caroline K. Williams, Xiao Wang, Junhang Dong, Jianbing “Jimmy” Jiang
Non-aqueous
redox flow batteries (RFBs) are promising energy storage devices owing
to the broad electrochemical window of organic solvents. Nonetheless,
the wide application of these batteries has been limited by the low
stability and limited solubility of organic materials, as well as
the insufficient ion conductivity of the cell separators in non-aqueous
electrolytes. In this study, two viologen analogues with poly(ethylene
glycol) (PEG) tails are designed as anolytes for non-aqueous RFBs.
The PEGylation of viologen not only enhances the solubility in acetonitrile
but also increases the overall molecular size for alleviated crossover.
In addition, a composite nanoporous aramid nanofiber separator, which
allows the permeation of supporting ions while inhibiting the crossover
of the designer viologens, is developed using a scalable doctor-blading
method. Paired with ferrocene, the full organic material-based RFB
presents excellent cyclability (500 cycles) with a retention capacity
per cycle of 99.93% and an average Coulombic efficiency of 99.3% at
a current density of 2.0 mA/cm2. The high performance of
the PEGylated viologen validates the potential of the PEGylation strategy
for enhanced organic material-based non-aqueous RFBs.