To improve the transport of active species in the carbon nano-fibrous electrodes of a vanadium flow battery (VFB), a free-standing carbon nano-fibrous web with ultra large pores has been designed and fabricated through the horizontally-opposed blending electrospinning method in this study. The morphology, surface chemistry and electrochemical performances of the highly porous nano-fibrous web have been investigated and compared with the carbon nano-fibrous web prepared by traditional electrospinning. Benefiting from the much larger pore size and higher porosity of the carbon nano-fibrous web prepared by horizontally-opposed blending electrospinning, the concentration polarization of the vanadium flow battery is effectively reduced. As indicated by the single cell tests, the battery using horizontally-opposed blending electrospun carbon nano-fibrous web electrodes delivers much improved performance, especially at high current density. The voltage efficiency is 10.3% higher than that of the traditional electrospun carbon nano-fibrous web electrodes and the electrolyte utilization efficiency is twice as much as that of the traditional electrospun carbon nano-fibrous web electrodes at 60 mA cm(-2). The results suggest that expanding the pore size could be one effective strategy to facilitate carbon nano-fibrous materials' applications for VRBs, and that the horizontally-opposed blending electrospun carbon nano-fibrous web is a promising electrode candidate for VFBs.