All vanadium redox flow battery, using vanadium ion solution as positive and negative electrode active material, the cathode is V (IV) /V (V) of V cathode, (II) /V (III) on the electric potential difference, the standard is about 1.25 V. The battery has the advantages of large capacity, long service life, deep discharge and no damage to the battery, and can realize the instantaneous recharging. At present, the development of vanadium battery is hindered by the electrode material, and the electrode material target is PAN base felt.
At present, the production of PAN carbon felt is mainly used as thermal insulation material, the conductivity and electrochemical activity can not meet the requirements of the battery. The effect of heat treatment temperature on the graphitization of graphite felt was further studied.
In the heat treatment of graphite felt, the optimum temperature of heat treatment is about 550 DEG C, and the Shi Mozhan resistance is the lowest and the exchange current is the maximum. In the process of charging and discharging, the coulomb efficiency can reach more than 90% by using the graphite felt electrode prepared by the optimum temperature.
Electrode material is one of the key materials for all vanadium redox flow batteries. Due to the large surface area and good stability, the graphite felt is dominant. However, the graphite felt material has poor hydrophilicity, and its electrochemical activity is not good enough. This paper on the graphite felt electrode respectively chromic acid oxidation method, mixed acid electrochemical oxidation method and hydrothermal ammoniation method for processing vanadium redox flow battery to improve its activity.
The reason lies in the improvement of electrode active carbon fiber surface increased nitrogen content of functional groups and nitrogen functional groups to enhance the positive charge density of the alkaline carbon fiber and its adjacent carbon atoms, accelerate the electrode / solution interface of vanadium ion and electron transfer rate, improve the vanadium ion diffusion process, reduces the electron transfer resistance.