ZrO₂-Nanoparticle-Modified Graphite Felt: Bifunctional Effects on Vanadium Flow Batteries

Abstract

To improve the electrochemical performance of graphite felt (GF) electrodes in vanadium flow batteries (VFBs), we synthesize a series of ZrO2-modified GF (ZrO2/GF) electrodes with varying ZrO2 contents via a facile immersion-precipitation approach. It is found that the uniform immobilization of ZrO2 nanoparticles on the GF not only significantly promotes the accessibility of vanadium electrolyte, but also provides more active sites for the redox reactions, thereby resulting in better electrochemical activity and reversibility toward the VO(2+)/VO2(+) and V(2+)/V(3+) redox reactions as compared with those of GF. In particular, The ZrO2/GF composite with 0.3 wt % ZrO2 displays the best electrochemical performance with voltage and energy efficiencies of 71.9% and 67.4%, respectively, which are much higher than those of 57.3% and 53.8% as obtained from the GF electrode at 200 mA cm(-2). The cycle life tests demonstrate that the ZrO2/GF electrodes exhibit outstanding stability. The ZrO2/GF-based VFB battery shows negligible activity decay after 200 cycles.

Comparison of Electrospun Carbon−Carbon Composite and Commercial Felt for Their Activity and Electrolyte Utilization in Vanadium Redox Flow Batteries

“…Thanks to their low cost, inertness and stability, carbon felts are commonly used as electrode material in VRFBs, but unfortunately, those felts still have poor electrochemical activity which limits the power density of the battery . To overcome this challenge, various treatments, such as thermal treatment, acid treatment, electrochemical treatment and doping with metal and metal oxides, have been reported to activate the carbon felts, however, the obtained improvements are limited and the long‐term stability of the activated felts is still under question, whereas the electrodes suffer from degradation during cycling …”

Hydrogen‐Treated Rutile TiO2 Shell in Graphite‐Core Structure as a Negative Electrode for High‐Performance Vanadium Redox Flow Batteries

“…The same authors [21] have proposed Nb 2 O 5 (W) as an electrocatalyst, demonstrating outstanding performance and leadingt oaCE of 98.5 %a nd an EE of 78.7 % at the same current density mentioned before after more than 50 cycles.T his is the best EE value ever reported in the literature. [23] Following this report, we focused on ah igh stabilityo fo ur electrode applying larger current densities. Despite the significant progress that has been made through the use of new catalystsf or high-efficiency negative electrodes in VRFBs, the electrolyte-utilization ratio (i.e., ratio of specific dischargec apacity and theoretical capacity) is quite low,a chieving am aximum of 64 %t heoretical capacity.…”

Polarization Effects of a Rayon and Polyacrylonitrile Based Graphite Felt for Iron‐Chromium Redox Flow Batteries

“…This indicates that the redox transformation of Fe 2+ /Fe 3+ couples on the surface of the graphite felt is controlled by the charge transfer and diffusion steps under the above polarization voltage. The high‐frequency semicircular portion corresponds to the charge transfer reaction at the electrode/electrolyte interface, and the low‐frequency linear portion is the result of the species diffusion process in the electrolyte . While in Figure (b), the curves of impedance spectra in the low‐frequency region are not stable.…”