Effect of Compression Ratio of Graphite Felts on the Performance of an All-Vanadium Redox Flow Battery

Abstract

All-vanadium redox flow batteries (VRFBs) are considered promising candidates for large-scale energy storage systems due to their flexible power scale design, high efficiency, deep discharge, long cycle life and environmental friendliness. The performance and efficiency of a VRFB is affected by many factors, including component materials, battery design, electrolyte composition and operating conditions. Among the key components, porous electrodes play a key role, as the electrochemical reaction occurs on the fiber surface of the electrode. As such, many studies have focused on improving reaction kinetics by modifying the surface of the electrode. In this work, the effect of varying the compression ratio (CR) of graphite felts on the performance and efficiency of a VRFB are investigated. The impedance of a single VRFB under varying CRs of graphite felts at various operating conditions were also measured. The results suggest that performance of a VRFB increases with increasing CR due to the decrease of area resistance and concentration overpotential. The porous electrode compressed from 6.5 to 4 mm demonstrates the optimal energy efficiency of 73% at the operating current density 80 mA cm−2 and electrolyte flow rate 100 mL min−1.

V2O5-Activated Graphite Felt with Enhanced Activity for Vanadium Redox Flow Battery

“…Consequently, carbon is the ideal material for use as a VRFB electrode. Graphite felt (GF) is the most widely used electrode material for VRFBs because of the three-dimensional network structure, large surface area, and high electrical conductivity of GF [8][9][10][11]. However, the poor electrochemical activity and hydrophobic properties of GF electrodes result in low kineticism in the redox reaction.…”

In-Situ Tools Used in Vanadium Redox Flow Battery Research—Review

“…The in situ monitoring of the impedances of VRFBs has been performed to obtain information about changes in polarization resistance associated with electrode modification, degradation of materials, and optimization of the operating parameters, etc. [118][119][120][121][122][123][124][125][126][127][128]. The measurement of full cell impedance is performed by connecting the terminals of the signal analyzer to the terminals of the cell.…”

Mass Transport Optimization for Redox Flow Battery Design

“…Subsequent experimental testing on laboratory-scale cells demonstrated improved energy efficiencies with wedge shaped cells, and a toroidal stack concept based on this concept was presented at the International Flow Battery Forum [18]. The effect of felt compression has been well documented [19,20] and other studies have applied the same theory in different ways, such as by modifying the materials instead of the cell geometry [21][22][23]. Another group has modified the cell architecture with asymmetric compression to address species crossover and associated capacity decay [24].…”