The property of graphite felt used in redox flow battery has a significance to the widely use of redox flow battery.and the Pan base material is the first choice to make the graphite/carbon felt because of the competitive price and good conductivity, chemical stability etc.
The electrode material is core component of the redox flow battery,the stability of the electrode material can decide the service time of the battery.now the PAN graphite/carbon felt is widely used as a commercial.
The PAN graphite/carbon felt still has a disadvantage,the chemical activity and hydrophilia is not enough,so it need a chemical modification before used in the battery.
The main way to modify the graphite/carbon felt as below:
And it devides into air oxidation style,liquid oxidation style and the electrochemical oxidation.
The main purpose is to increase the number of oxygen containing functional groups,such as
—COH、—C=O、—COOH and —COOR etc.it can help increase the hydrophilia of the redox flow battery to enlarge the energy efficiency.
Currently used for commercial production way is air oxidation style,and it used for Vanadium redox flow battery and Fe/ Cr redox flow battery.The reaction conditions of liquid oxidation style is more calm,and the number of oxygen containing functional groups is more than the air oxidation style,but it need strongly acidic oxidant to modify the graphite/carbon felt,it has a badly corrosion to the equipments,so it’s not suitable for industrial production.
Besides of the oxidation style,it also can use Oxygen plasma, γ ray method, hydrothermal method Surface deposition etc.
Redox flow battery is a novel kind of secondary batteries to achieve large-scale renewable energy application,and the research and the development on the graphite/carbon felt modification has an important significance.