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.

　　The rigid composite graphite felt is based on PAN based carbon felt as the base material after above 2200 degrees high temperature graphitization treatment, and then treated through carbonization and graphitization by special adhesive composite.

　　The rigid composite graphite felt has certain rigidity, self support, the proportion of small, low thermal conductivity, no fiber shedding and the using temperature can reach 3200 DEG C. It’s suitable for various types of furnace types such as high pressure gas quenching furnace, pressure sintering furnace, polycrystalline casting furnace, single crystal growth furnace (sapphire), etc. the utility model can provide various shapes such as flat plate, disc and cylinder, etc. It has the advantages of long service life, it’s convenient to install and dismantle.

　　The biggest feature of our rigid composite graphite felt compared with the similar products are: high treatment temperature, low impurities, high purity (<200ppm) it is especially suitable for high temperature furnace which has the high furnace atmosphere requirements; high temperature heat insulation material provides excellent thermal properties and high mechanical strength, it can be customized according to the drawings; maximum standard board on the market, the utilization rate is high (1500*1200* thickness according to customer requirements, the error is + 2); coverage /coating (①Attaching the graphite sheet on the surface or putting the graphite sheet between the material, ②SiC coating on the surface , ③pasting the carbon cloth on the surface); excellent thermal insulation property; the purity is less than 200ppm after 2200 DEG C high temperature; it’s applicable to all kinds of vacuum furnace, induction furnace, polycrystalline ingot furnace; it has high corrosion resistance and it’s easy to process.

　　Our products involved in the field of aerospace, vacuum metallurgy, solar new energy, new chemical materials, we are the manufacturer which is specializing in the production of rigid composite graphite felt and high temperature and high purity graphite felt materials for domestic in China. The main products are carbon felt, graphite felt,rigid composite graphite felt and the auxiliary products such as carbon cloth, carbon rope and so on ,our products are widely used in all kinds of high temperature vacuum furnace equipments such as single crystal growth furnace, polycrystalline casting furnace, polycrystalline furnace, vacuum sintering furnace, hot pressing furnace, heat balance furnace and electric magnetic induction furnace ,non-oxidizing atmosphere high temperature equipment and high purity silicon hydrogenation furnace etc..

　　Flow battery is to achieve large-scale renewable energy application of new green secondary battery two, the performance of electrode materials has important significance for the practical application of the flow battery, PAN based graphite felt electrode material is the preferred flow battery, in order to further improve the hydrophilicity and electrochemical activity of the modified Shi Mozhan electrode materials, graphite related research in recent years the carpet has become a hot spot.

　　Energy storage technology is very conducive to the balance between energy production and consumption between the control in power, plays an important role in the integration of renewable energy and other areas, as one of the electrochemical energy storage technology flow battery, the redox flow battery, with current conversion capability, flexible structure design, reasonable cost, operation simple, is a new type of green two battery suitable for large scale electricity storage.

　　Carbon fiber, also called graphite felt, is made of carbon fiber after pre oxidation by lapping process of acupuncture, felt body made of carbonization process, graphite felt is a low strength carbon fiber products, has the advantages of low density, low linear expansion coefficient, low thermal capacity, small thermal conductivity, high temperature resistance thermal shock resistance, strong resistance, chemical corrosion resistance and excellent high temperature, is widely used in industry, energy industry, auto industry, chemical and environmental protection.

　　Graphite felt is the first choice of electrode material for liquid flow battery, but its electrochemical activity and hydrophilicity can not fully meet the requirements of liquid flow battery.

　　The electrochemical activity of graphite felt is not high and the poor hydrophilicity, so graphite felt modification has become an important means to improve the properties of electrode materials, the modified method is mainly to increase the graphite felt surface oxygen and deposited on the Shi Mozhan surface catalytic material, and surface morphology of carbon felt, produce different effects of chemical composition and electrochemical performance, and improve the properties of liquid flow battery.

　　Tiled arrangement of carbon felt and carbon fiber unidirectional arrangement of absorbing microwave absorbing properties of the composites, polyacrylonitrile based carbon fiber unidirectional arrangement is closely related to the suction arrangement spacing and wave properties of fiber and fiber content. Suction arrangement of carbon felt greatly influence the flat wave properties with carbon fiber content.

　　At present, the negative effect of electromagnetic radiation has affected all aspects of human life. It is an effective way to reduce or eliminate electromagnetic wave pollution by absorbing materials. Graphite felt is one of the most commonly used structural absorbing materials, and has been widely used.

　　By changing the cross section of the carbon fiber in the graphite felt, the surface modification of the fiber or the change of the electromagnetic parameters of the fiber by reducing the carbonization temperature of the carbon fiber were used to prepare the absorbing material for graphite felt.With the increase of carbon fiber content, the reflection attenuation of the sample decreases, and the absorbing property of the material decreases obviously.

　　In the graphite felt in the fiber, the duty ratio is about 5% to 8.6%, and third in the direction of vertical or inclined distribution of fiber. In this way, the carbon felt is not completely covered by the matrix with high viscosity in the composite with the epoxy resin, but forms a certain low filling net". If the graphite felt is compounded with other high density powder or particles, it can not only prevent the precipitation of the filler, but also help to obtain the composite material with uniform distribution.

　　The bipolar plate used therein are required to achieve higher electrical conductivity due to the requirements for redox flow batteries have become more and more stringent in recent years.and thus A bipolar plate composed of an electrically conductive composite achieves a higher electrical conductivity by increasing the conductive filler content in the material.

　　Graphite was used as one of the main bipolar plate material in redox flow batteries due to its high electrical conductivity ,low weight and good chemical stability in the past.Graphite blocks were produced by sintering process and plates were machined to desired sizes.The main limitation of this method was the porosity of produced graphite plates.

　　At present, our company provides a bipolar plate for a redox flow battery , the bipolar late including an electrically conductive composite prepared by mixing a thermoplastic resin ,a carbonaceous material selected from graphite and carbon black ,and a carbon nano-tube.

　　Our current business is extended from the overall solution of the material to the manufacture of bipolar plates, and thus provides the following three VRB assembly services:

　　1).The bipolar plate (we can provide punch service. The thickness of the bipolar plate now can be processed are 0.6/0.8/1.0 /1.2/1.3mm.

　　2).The composite of the bipolar plate and the electrode, the advantage is that the electrode felt is fully combined with the felt in the plate, it greatly reduces the theoretical value of the contact resistance to the felt.

　　3).The bipolar plate ,the electrode and outline border. Three in one frame after embedding flow

　　box (precision injection), it’s the way which improve the reliability greatly compared with the above 1 and 2.

　　Although the density of carbon fiber is lower than that of aluminum, its strength is higher than that of steel. Carbon fiber is not only the inherent "hard" characteristic of carbon materials, but also the machinability of textile fiber.

　　A carbon fiber woven graphite felt has good conductivity, mechanical properties, electrochemical reaction activity, acid resistance, corrosion resistance and oxidation resistance, is a good electrode material, compared with metal, graphite powder and various electrode materials, more suitable for the electrode storage battery.

　　At present, the domestic production of graphite felt is mainly used to make thermal insulation material, and its conductivity and electrochemical activity can not meet the requirements of the use of battery electrode materials, therefore, the need for carbon fiber felt surface treatment. The commonly used surface treatment methods include heat treatment, acid treatment and electrochemical oxidation treatment.

　　The operation of heat treatment in air atmosphere, and after the heat treatment,the conductive ability of graphite felt has been improved, in the heat treatment of graphite felt, if the temperature is too low, resulting in electrochemical active graphite felt low, unable to meet the requirements of use as electrode materials; but if the heat treatment temperature is too high, it will cause the graphite felt surface etching, serious excessive oxidation, fiber breakage and breakage, resulting in the the electrical conductivity and mechanical properties decreased sharply, seriously affecting their life.

　　With the heat treatment temperature increased gradually from 450 degrees to 600 degrees Celsius, the impurities of graphite felt surface are gradually disappear, with the further oxidation of the holes, grooves and other defects; carbon fiber structure with the oxidation degree also changed gradually from the turbostratic structure of two dimensional ordered structure transformation three.

　　Polyacrylonitrile (PAN) based graphite felt , made of PAN precursor in an inert gas in high temperature and antipyretic have a variety of forms, such as continuous products, carbon fiber, short carbon fiber and short carbon fiber. It has many applications in engineering because of its excellent physical and chemical properties and electrical conductivity. Continuous carbon fibers are often used in resin matrix composites as reinforcements.

　　The most widely used short cut carbon fiber is a small amount of chopped carbon fiber mixed with concrete, forming carbon fiber concrete, which has a variety of functional characteristics such as pressure sensitivity, temperature sensitivity, thermoelectric and electrothermal effects. Based on the above features, carbon fiber reinforced concrete materials can be used in the temperature and deformation self diagnosis and adaptive aspects of concrete structures, such as intelligent deicing and snow melting system of concrete pavement [5]. But the production process of continuous carbon fiber is relatively complex, the price is higher; and the short cut carbon fiber mixed with concrete, need the chopped carbon fiber completely uniformly dispersed in the concrete, it is a big problem in materials, the functional properties of carbon fiber reinforced concrete material is affected, especially the heating effects the size based conductive network formation in carbon fiber, namely by carbon fiber components reduce the concrete resistance and Joule heat.

　　Graphite felt is a soft cloth formed by the bonding of chopped carbon fibers, and each fiber forms a conductive network with each other. In the concrete smart materials, because the carbon fiber felt easily cut into the desired shape size, sample only need to be paved in concrete.

　　PAN based graphite felt with electrothermal effect good and stable; the thermal efficiency of carbon fiber of different types are different, therefore, can choose the optimal thickness, to achieve efficient and economic purposes; in a certain temperature range, the temperature stability of PAN based graphite felt the rise and the input power is proportional to the input power can be selected according to the need the temperature rise; graphite felt with a temperature sensitive effect, linear resistivity increased with the temperature of graphite felt decreases, this effect can be used for temperature detection structure; combined with temperature sensitive effect and heating effect, is expected to realize the adaptive temperature regulating structure.

　　Ammonia decomposition produced by urea nitrogen doping on graphite felt, preparation of nitrogen doped graphite felt, compared with nitrogen doped graphite felt and graphite felt has more excellent electrochemical performance, and doping temperature and doping time have influence on the electrochemical activity of graphite felt.

　　Proton exchange membrane fuel cell (PEMFC) has many advantages, such as high power density, low working temperature, fast start and long service life, but hydrogen storage is used as fuel.

　　Graphite felt is the main cathode material of direct flow methanol fuel cell, and its performance is very important for direct flow methanol fuel cell. Graphite felt has the advantages of good stability, large surface area under unit cost, good fluid permeability, etc. but its application is limited because of its poor hydrophilicity and low electrochemical activity.

　　Commonly used acid treatment, heat treatment, electrochemical oxidation, nitrogen doping and other methods. Due to nitrogen doping not only improves the surface chemical activity of graphite felt, but also on the electronic structure of regulation, so in recent years, nitrogen doped graphite felt in many electrochemical devices exhibited electrocatalytic properties better than graphite felt no nitrogen doping of this study is based on previous achievements.

　　The ammonia produced by hydrolysis of urea by nitrogen doping treatment on graphite felt, has an important influence on the electrochemical activity of the cathode temperature,nitrogen doping does not change the crystal structure of graphite felt, but will affect the crystallite parameter.

　　there will not be much affected the overall morphology of nitrogen doped under certain conditions on the graphite felt mat, the nitrogen content of graphite are improved in nitrogen doped after nitrogen increased mainly pyrrolic nitrogen and pyridine type nitrogen, indicating the increase of no contribution even inhibit the electrochemical activity of graphite nitrogen on graphite felt, pyrrolic nitrogen and pyridine type nitrogen is the main reason to enhance the electrochemical activity of graphite felt the.

　　Vanadium battery is a new type of energy storage battery developed in recent years, because of its high energy efficiency and long service life.

　　Environmental friendly and cheap, operating and maintenance costs low, many of the characteristics of the rapid development of. But at present, there are some problems in vanadium battery. There are many factors that affect the performance of vanadium battery, including the electrode material performance, the positive and negative electrode reaction is an important factor.

　　Graphite felt has a series of excellent properties, such as high specific strength, high specific modulus, high temperature resistance, corrosion resistance, conductivity and thermal expansion coefficient, so it is used in the field of vanadium battery. However, it is found that the active surface area is smaller than the surface area, the surface energy is low, and the wettability is poor.

　　By low temperature liquid phase oxidation method for surface oxidation of graphite felt, with different concentration and Potassium Permanganate solution at different temperature and acid solution on Potassium Permanganate graphite felt for processing, to obtain the performance of graphite felt electrode material excellent. The graphite felt surface becomes smooth after Potassium Permanganate solution treatment.

　　The surface polar groups of the graphite felt treated by different Potassium Permanganate solution increased, and the hydrophilicity was improved. Graphite felt on the surface in the process of Potassium Permanganate solution deposition on the Potassium Permanganate, is not conducive to V (IV) in the above reaction.

　　Another way to improve the activity of graphite felt is to deposit metal or metal oxide on the surface of graphite felt. Transition metal oxide or semiconductor compound.

　　The graphite felt electrode used for vanadium redox flow battery was used in the electrochemical treatment, the activity of the electrode was improved, the voltage efficiency was increased, and the current efficiency was improved. After electrochemical treatment, the O/C ratio of graphite felt surface increases, and the main increase is COOH functional group.

　　The analysis results show that the surface of carbon fiber is etched, and the specific surface area is increased. The increase of the electrode activity is attributed to the increase of the number of COOH functional groups on the surface of carbon fiber and the increase of specific surface area.

　　The small capacity of the battery has been successfully applied in human life, further research and development of new environmentally friendly battery suitable for large-scale energy storage, development and utilization of new energy sources, will have great social and economic significance.

　　All vanadium redox flow battery can be regarded as the representative of the new energy storage battery, compared with other batteries, it has a unique advantage, and has been the attention of scientists at home and abroad, at present, the vanadium battery has been abroad applied to wind power plant, peak load regulation of power grid and solar photovoltaic power station demonstration operation. However, the development of vanadium battery is still limited, and the electrode material is a very important factor.

　　The electrode material is mainly divided into metal electrode and carbon electrode, wherein the carbon electrode with good stability reflects the greater advantage, and the carbon electrode, graphite felt materials with its advantages of real surface area is much larger than the geometric surface area and occupies the dominant position, the graphite felt were activated by concentrated sulfuric acid by liquid phase oxidation and air oxidation method, that can greatly improve the electrochemical performance of vanadium battery.

　　Although the process is simple, the process is simple, the operation is small, and the oxidation reaction is not easy to control. Concentrated sulfuric acid oxidation process is very dangerous, industrial production is very difficult. The electrochemical oxidation method, which is easy to control, easy to control, and easy to realize industrialized operation, is easy to control.