Improvement of vanadium redox flow battery performance obtained by compression and laser perforation of electrospun electrodes

Abstract

Flow battery electrodes made of electrospun carbon fibers were synthesized with substantially lower porosity than typical electrospun mats by applying compression during the stabilization stage. The objective was to create flow battery electrodes with higher volumetric surface area to support the electrochemical reaction. The physical, structural, and transport properties of these novel mats were characterized extensively. A porosity reduction of 12% was attained by this method, yielding a 50% increase volumetric surface area, while the in-plane permeability and tortuosity were found to remain relatively consistent. On the other hand, the fibers near the surfaces were somewhat compacted, which hurt the through-plane permeability, so holes were created using a CO2 laser to perforate the structure. The loss of specific surface area caused by laser perforation was quite negligible and still showed improvement compared to the uncompressed control sample. Flow battery performance tests were conducted on all samples. All electrospun samples outperformed commercial carbon mats, with the compressed samples without and without laser perforations showing markedly better performance in the activation region. The non-perforated compressed sample showed mass transfer limitations at higher current density, while the laser perforations largely eliminated this effect, yield the best performance over the entire range of current density.