4 research outputs found
Hydrophilic Channel Alignment of Perfluoronated Sulfonic-Acid Ionomers for Vanadium Redox Flow Batteries
It is known that uniaxially drawn
perfluoronated sulfonic-acid ionomers (PFSAs) show diffusion anisotropy
because of the aligned water channels along the deformation direction.
We apply the uniaxially stretched membranes to vanadium redox flow
batteries (VRFBs) to suppress the permeation of active species, vanadium
ions through the transverse directions. The aligned water channels
render much lower vanadium permeability, resulting in higher Coulombic
efficiency (>98%) and longer self-discharge time (>250 h). Similar
to vanadium ions, proton conduction through the membranes also decreases
as the stretching ratio increases, but the thinned membranes show
the enhanced voltage and energy efficiencies over the range of current
density, 50–100 mA/cm<sup>2</sup>. Hydrophilic channel alignment
of PFSAs is also beneficial for long-term cycling of VRFBs in terms
of capacity retention and cell performances. This simple pretreatment
of membranes offers an effective and facile way to overcome high vanadium
permeability of PFSAs for VRFBs