| How to make graphite felt better for vanadium redox flow battery |
| vanadium redox flow battery，graphite felt |
Electrode material is one of the key materials for all vanadium redox flow battery. Graphite felt material due to the large real surface area, good stability and occupy the leading position.
But the graphite felt material is poor in hydrophilicity, and the electrochemical activity is not good enough. Graphite felt electrode were chromic acid by liquid phase oxidation, mixed acid electrochemical oxidation and hydrothermal ammoniation treatment, to improve as the activity of the vanadium redox flow battery.
The main conclusions are as follows: by chromic acid liquid phase oxidation and graphite felt electrode hydrophilicity and electrochemical activity was significantly enhanced, the optimum processing time for 5 hours. Chromate treatment of graphite felts loaded into the battery, at 10 to the characteristics exhibited good charge discharge performance, at 10 mA / cm2, battery voltage efficiency 90.9%, energy efficiency reached 79.4%. FT-IR and SEM test showed that the treated carbon fiber oxygen containing functional groups increased and increased surface gully, the former increases the carbon fiber surface is involved in active points VO2+/VO2+ electrode reaction of the and the latter increases the vanadium ion and the electrode contact area. After electrochemical anodic oxidation treatment of sulfuric acid and phosphoric acid, the hydrophilicity and electrochemical activity of graphite felt electrode were also significantly enhanced. The optimal treatment conditions were as follows: current density was 50 mA/cm2, and the treatment time was 4min. Will handle Houshi graphite felt fitted into the battery, in the 10 to 50 MA / cm2 showed better charge discharge performance, at 20 mA / cm2, battery voltage rate was 88.2%, energy efficiency reached 79.6%. FT-IR and SEM tests showed that the surface roughness of carbon fiber was increased with the increase of oxygen functional groups on the surface of carbon fiber. The XRD results show that the carbon fiber crystallite size and interplanar spacing decreased, indicating that electrochemical oxidation etching the outermost graphite crystallite, the carbon fiber surface roughness increases.
First proposed in 180 DEG C water heat ammoniation treatment of graphite felt electrode, graphite felt electrode hydrophilicity and electrochemical activity was significantly enhanced and the optimum processing time for 15 hours. The processing of graphite felt is loaded into the battery, charge and discharge can be stabilized in 20 to 60 in the range of mA/cm2. In 20mA/cm2, the voltage efficiency can reach 83.7% and the energy efficiency can reach 85.3%. And improve the activity of electrode is carbon fiber surface containing the increase of nitrogen content of functional groups, containing nitrogen functional groups enhances the alkalinity of carbon fiber and its adjacent carbon atoms of the positive charge density, accelerating electrode / solution interface of vanadium ions and electrons transfer speed, improve the vanadium ion diffusion process, reduces the electron transfer resistance |
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