Modification Of The Vanadium Redox Flow Battery Electrode Materials And Structure Of The Battery Assembly Optimization

In this paper, acidification and heat treatment of carbon paper electrode for vanadium redox battery was mainly studied. Reaction mechanism ofⅤ(Ⅳ)/Ⅴ(Ⅴ) couple on the carbon paper electrode was also investigated. Used titanium net as anode current collector and contrasted with graphite plate current collector, and designed a new structure of the battery assembly, The main points can be summarized as following.The commercial accessible carbon paper (CP) that treated in sulfuric acid solution were characterized by FT-IR spectroscopy and SEM, and at the same time, their electrochemical behaviors were investigated by cyclic voltammograms, Impedance spectroscopy and charge-discharge techniques. The results showed that -COOH functional groups come into being during acidification treatment, and CP electrode eroded by sulfuric acid solution. The VRB with modified CP electrode exhibits excellent performance under a current density of 30 mA·cm^-2 . The average current efficiency reaches 96.2 % and average voltage efficiency reaches 84.5 %. The improvement of electrochemical performance for the electrode is ascribed to the -COOH group and the special surface of CP.The commercial accessible carbon paper (CP) that heated in 435℃for 10 hours were characterized by FT-IR spectroscopy,BET, and at the same time, their electrochemical behaviors were investigated by cyclic voltammograms, Impedance spectroscopy and charge-discharge techniques. The results showed that -COOH functional groups come into being heated treatment for 10H and Specific Surface Area increases significantly. The VRB with modified CP electrode exhibits excellent performance under a current density of 100 mA·cm^-2. The average current efficiency reaches 98.5 % and average voltage efficiency reaches 77.7 %.TheⅤ(Ⅳ)/Ⅴ(Ⅴ) reaction mechanism was investigated on a carbon paper (CP) electrode by means of cyclic voltammetry, polarization curve and impedance spectroscopies. Cyclic voltammetry analysis indicated thatⅤ(Ⅳ)/Ⅴ(Ⅴ) redox reaction at CP electrode was quasi-reversible. A certain chemical reaction step was suspected to follow the electron transfer step of this reaction. The diffusion coefficient forⅤ(Ⅳ) was 4.5×10^-5cm²/s and exchange current density was 6.7×10^-4mA·cm^-2.The Tafel slope value (0.127) obtained from the polarization curve agrees well with theoretical value (0.12) when the electron transfer step was supposed to be the rate-determining step. which revealed that the electron transfer step was the rate-determining step. This further confirms the conclusion obtained by polarization curve test.Using titanium net as anode current collector and contrasting with graphite plate current collector, it's demonstrated that energy efficient of titanium net cell was obviously higher, and liquid inlet and groove bottom wasn't etched. designing a new structure of the battery assembly, Basically solved the battery leakage and corrosion of current collector.