CN102723502B - Surface modification method for raising activity of electrode material of vanadium cell - Google Patents

Abstract

The invention relates to the fields of battery manufacturing and energy storage, in particular to a surface modification method for improving the activity of vanadium battery electrode materials. First, the vanadium battery electrode materials to be used are cleaned to remove surface impurities, and then plasma is used to modify the electrode materials. The gas that generates the plasma reacts with the surface of the electrode in an ionized state and generates polar functional groups; finally, the modified electrode material is cleaned by ultrasonic cleaning for 5-30 minutes, and is cleaned at a temperature of 60-120°C. Drying, using the method of the present invention to modify the surface of the vanadium battery electrode material, not only can enhance the hydrophilic properties of the electrode surface, but also some functional groups have a better catalytic effect on the electrode reaction, which is expected to improve the energy storage efficiency of the battery; It can be used to treat the surface of materials with various shapes, and can maintain the mechanical properties of the material matrix, etc., and the experimental conditions are easy to control, and there is no pollution to the environment; it is an efficient and environmentally friendly method for surface modification of vanadium battery electrode materials.

Description

A surface modification method for improving the activity of vanadium battery electrode materials

technical field

The invention relates to the fields of battery manufacturing and energy storage, in particular to a surface modification method for improving the activity of vanadium battery electrode materials. the

Background technique

All-vanadium redox flow battery (vanadium battery) is a secondary energy system that uses redox reactions between vanadium ions in different valence states to store and convert energy. Its characteristics are: no emission pollution, adjustable capacity, long cycle life, deep high current density discharge, fast charging, and high energy conversion rate. As an energy storage power source, vanadium batteries are mainly used in power station peak regulation, large-scale photoelectric conversion, energy storage power for wind power generation, and as energy storage systems in remote areas, uninterruptible power supplies or emergency power systems. the

At present, the electrode materials used in vanadium batteries are mainly carbon-based graphite felt carbon felt, which has the advantages of low resistivity, good stability, and large specific surface area. However, the activity of the vanadium battery electrode reaction on its surface is relatively low, so it needs to be activated to improve the electrochemical activity and battery performance. the

Currently reported more activation treatment methods include: noble metal modification, acid activation treatment, electrochemical anodization treatment and so on. Noble metal modification requires complex steps and requires high-temperature sintering, so it is only limited to laboratory use. Thermal activation treatment has little flexibility in operation, and the oxidation reaction is not easy to control. Excessive oxidation reduces the stability and service life of electrode materials. The effect of acid activation treatment was not very obvious. The electrochemical treatment method is simple and easy to implement, and the effect is obvious. However, the current use of sulfuric acid as the electrolyte will lead to a more severe oxidation reaction on the fiber surface, coupled with the promotion effect of the acid medium on the oxidation degradation reaction, the etching phenomenon on the fiber surface is serious, and the service life of the material will be reduced. the

Contents of the invention

The heat treatment and acid treatment in the prior art of the present invention easily lead to the overoxidation of the material, which reduces the stability of the electrode material, the battery life and other shortcomings, as well as the complicated steps of noble metal modification and the influence of high temperature sintering, etc., the present invention The purpose is to provide a surface modification method for improving the activity of a vanadium electrode material with simple process, mild treatment conditions, easy control and no pollution to the environment. the

The technical scheme of the present invention is;

A surface modification method for improving the activity of vanadium battery electrode materials, comprising the following steps and process methods:

1) Pretreatment to remove impurities on the surface of the material;

2) Form polar functional groups on the surface of the electrode material: use plasma to modify the electrode material, and the gas that generates the plasma reacts with the electrode surface in an ionized state to generate polar functional groups. The working pressure of the plasma gas is 10~ 200Pa;

The gas for generating plasma is one or a mixture of two or more of oxygen, nitrogen, fluorine, chlorine, ammonia or sulfur-containing gases;

3) The electrode material modified in step 2) is ultrasonically cleaned for 5-30 minutes, and dried at a temperature of 60-120°C. the

The plasma process in step 2) is microwave plasma, radio frequency plasma or direct current plasma. the

The treatment time for forming polar functional groups on the surface of the electrode material by microwave plasma is 10-300S, the gas flow rate is 200mL/min-4L/min, and the power is 200-2000W. the

The parameters of using radio frequency plasma are power of 50-300W, gas flow of 10-200mL/min, and treatment time of 10-300S. the

The parameters for forming polar functional groups on the surface of the electrode material by using DC plasma are as follows: the discharge distance is controlled at 3-5 cm, the treatment time is 10-300 s, and the working voltage is 10-200 V. the

The electrode material is selected from graphite felt, carbon felt, graphite plate or carbon paper. the

The graphite felt has a thickness of 2 mm to 6 mm, and is selected as any one of polyacrylonitrile-based graphite felt, viscose-based graphite felt, cellulose-based graphite felt or pitch-based graphite felt. the

The carbon felt has a thickness of 1-20mm, and is selected from any one of polyacrylonitrile-based carbon felt, viscose-based carbon felt, cellulose-based carbon felt or pitch-based carbon felt. the

The thickness of the graphite plate is 1-10mm, which is selected from analytical pure graphite plate or spectroscopic pure graphite plate. the

The thickness of carbon paper is 0.5-10mm. the

Step 1) The pretreatment is ultrasonic immersion and cleaning in deionized water for 10-50 minutes, and then drying at 80-120° C. for 1-8 hours. the

The surface action depth of the modified electrode material is 5-200nm. the

The polar functional group includes one or more of hydroxyl, carboxyl, nitrogen-containing, fluorine-containing and/or sulfur-containing functional groups. the

The gases used in the present invention are all high-purity gases. the

The present invention has following advantage and technical effect:

1. The modification method of the electrode material for vanadium batteries proposed by the present invention can specifically change the physical and chemical properties of the electrode material surface, improve the hydrophilic properties of the material surface by introducing polar functional groups, etc., and the introduction of some polar groups It can also have a certain catalytic effect on the electrode reaction, so that the electrode reaction area is increased, the reversibility of the electrode reaction is improved, and the energy storage efficiency of the battery is improved;

2. The plasma treatment method proposed by the present invention can treat the surface of samples with various shapes. Compared with the wet chemical treatment process that is used more now, the plasma treatment process can save the indispensable drying and waste liquid treatment, etc. process, and the treatment process is simple, the parameters are easy to control, no corrosive and difficult-to-handle raw materials such as strong acid and strong alkali are used, and there is no pollution to the environment; 

3. The structure of the plasma processing equipment to be used in the present invention is relatively simple, and the electrode materials can be continuously processed, the processing efficiency is high, and it has the potential for industrial application;

4. The method of the present invention is cheap and easy to operate, can realize the controllable temperature modification on the surface of the electrode material for vanadium batteries, increase the activity of the electrode, slow down the etching of the fiber surface, and improve the service life of the electrode material. the

Description of drawings

Fig. 1 is the electron micrograph of vanadium battery electrode material in embodiment 2, and wherein Fig. 1 a is the polyacrylonitrile-based graphite felt before modification, and Fig. 1 b is the polyacrylonitrile-based graphite felt after modification;

Fig. 2 is the schematic diagram of radio frequency plasma treatment electrode material;

Fig. 3 is the comparison chart of the cyclic voltammetry of the graphite felt after the ammonia radio frequency plasma treatment and the untreated graphite felt in Example 3. the

Detailed ways

Example 1

1) The polyacrylonitrile-based carbon felt material with a thickness of 4mm was ultrasonically cleaned in deionized water for 20 minutes, dried in an oven at 75°C for 3 hours, and stored in a desiccator for later use. the

2) Put the processed electrode material in step 1) into a radio frequency plasma surface modification device. The structure of the radio frequency plasma surface modification device is shown in Figure 2, wherein a sample stage is installed in the reaction chamber d, and the ground terminal of the radio frequency generator a is externally connected to the bottom of the sample stage through the radio frequency electrode c, and the other end of the radio frequency generator a is connected to Electrode connections above the sample stage in reaction chamber d. When modifying the electrode material, put the electrode material as sample b on the sample stage. The reaction chamber is evacuated through the gas supply and vacuum system, and then the reaction gas oxygen is introduced to maintain the pressure of the reaction chamber gas system at 100Pa, the processing time is 100S, the gas flow rate is 50mL/min, and the power of the instrument is controlled at 100W. the

3) The carbon felt material after step 2) is ultrasonically cleaned for 5 minutes, taken out and dried in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Example 2

The difference with embodiment 1 is:

1) Put a polyacrylonitrile-based graphite felt with a thickness of 4mm into deionized water for ultrasonic cleaning for 20 minutes, put it in an oven and dry it at 75°C for 3 hours, and store it in a desiccator for later use. the

2) Put the processed electrode material in step 1) into a radio frequency plasma surface modification device. The reaction chamber is evacuated through the gas supply and vacuum system, and then the reaction gas nitrogen is introduced to maintain the pressure of the reaction chamber gas system at 150Pa, and the processing time is from 100S. The gas flow rate is 100mL/Min. The instrument power is controlled at 200W. the

3) Ultrasonic cleaning the graphite felt in step 2) for 5 minutes, taking it out and drying it in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Example 3

The difference with embodiment 1 is:

1) Put a polyacrylonitrile-based graphite felt with a thickness of 4mm into deionized water for ultrasonic cleaning for 20 minutes, put it in an oven and dry it at 75°C for 3 hours, and store it in a desiccator for later use. the

2) Put the processed electrode material in step 1) into the radio frequency plasma surface modification device, evacuate the reaction chamber through the gas supply and vacuum system, and then feed the reaction gas ammonia to maintain the reaction chamber gas system Pressure 100Pa, processing time from 300S. The gas flow rate is 100ml/min. The power of the instrument is controlled at 200w. the

3) Ultrasonic cleaning the graphite felt material in step 2) for 5 minutes, taking it out and drying it in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Example 4

1) Put a polyacrylonitrile-based graphite felt with a thickness of 4mm into deionized water for ultrasonic cleaning for 20 minutes, put it in an oven and dry it at 75°C for 3 hours, and store it in a desiccator for later use. the

2) Put the processed electrode material in step 1) into the radio frequency plasma surface modification device, evacuate the reaction chamber through the gas supply and vacuum system, and then feed the reaction gas chlorine to maintain the pressure of the reaction chamber gas system 50Pa, processing time from 100S. The gas flow rate is 50ml/min. The instrument power is controlled at 100w. the

3) Ultrasonic cleaning the graphite felt in step 2) for 5 minutes, taking it out and drying it in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Example 5

1) Put the polyacrylonitrile-based graphite felt material with a thickness of 4 mm into deionized water for ultrasonic cleaning for 20 minutes, put it into an oven for drying at 75° C. for 3 hours, and store it in a desiccator for later use. the

2) Put the processed electrode material in step 1) into a radio frequency plasma surface modification device. The reaction chamber is evacuated through the gas supply and vacuum system, and then the mixed gas of oxygen and nitrogen is introduced into the reaction gas, the gas ratio is 1:1. Before the gas is introduced, the gas is fully mixed in the gas mixing tank. Keep the reaction chamber gas system pressure at 200Pa, and the processing time from 100S. The gas flow rate is 60ml/min. The instrument power is controlled at 100w. the

3) Ultrasonic cleaning the graphite felt material in step 2) for 5 minutes, taking it out and drying it in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Example 6

1) Put polyacrylonitrile-based carbon paper materials with a thickness of 1 mm into deionized water for ultrasonic cleaning for 30 minutes, put them in an oven and dry them at 100° C. for 1 hour, and store them in a desiccator for later use. the

2) Put the processed electrode material in step 1) into a radio frequency plasma surface modification device. The reaction chamber is evacuated through the gas supply and vacuum system, and then the reaction gas nitrogen is introduced to maintain the pressure of the reaction chamber gas system at 100Pa, and the processing time is from 200S. The gas flow rate is 100ml/min. The instrument power is controlled at 300w. the

3) Ultrasonic cleaning the carbon paper material in step 2) for 5 minutes, taking it out and drying it in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Example 7

1) Put polyacrylonitrile-based carbon paper materials with a thickness of 1 mm into deionized water for ultrasonic cleaning for 30 minutes, put them in an oven and dry them at 100° C. for 1 hour, and store them in a desiccator for later use. the

2) Put the processed electrode material in step 1) into the microwave plasma surface modification device, evacuate the reaction chamber through the gas supply and vacuum system, and then pass in the reaction gas nitrogen to maintain the pressure of the reaction chamber gas system 150Pa, processing time from 50S. The gas flow rate is 200mL/min. The instrument power is controlled at 500w. the

3) Ultrasonic cleaning the carbon paper material in step 2) for 5 minutes, taking it out and drying it in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Example 8

1) Put the spectrally pure graphite plate material with a thickness of 4 mm into deionized water and ultrasonically clean it for 30 minutes, put it in an oven and dry it at 100°C for 1 hour, and store it in a desiccator for later use. the

2) Put the processed electrode material in step 1) into microwave plasma. surface modification device. The reaction chamber is evacuated through the gas supply and vacuum system, and then the reaction gas nitrogen is introduced to maintain the pressure of the reaction chamber gas system at 100Pa, and the processing time is from 200S. The gas flow rate is 400mL/min. The instrument power is controlled at 400w. the

3) Ultrasonic cleaning the graphite plate material in step 2) for 2 minutes, taking it out and drying it in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Example 9

1) Put the spectrally pure graphite plate material with a thickness of 4 mm into deionized water and ultrasonically clean it for 30 minutes, put it in an oven and dry it at 100°C for 1 hour, and store it in a desiccator for later use. the

2) Put the processed electrode material in step 1) into the DC plasma surface modification device, evacuate the reaction chamber through the gas supply and vacuum system, and then pass in the reaction gas nitrogen to maintain the pressure of the reaction chamber gas system 30Pa, the discharge distance is 5cm, the working voltage is 100V, and the processing time is from 100S. the

3) Ultrasonic cleaning the graphite plate material in step 2) for 2 minutes, taking it out and drying it in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Example 10

1) The polyacrylonitrile-based carbon paper material with a thickness of 1mm was ultrasonically cleaned in deionized water for 30 minutes, dried in an oven at 100°C for 1 hour, and stored in a desiccator for later use. the

2) Put the processed electrode material in step 1) into a DC plasma surface modification device. The reaction chamber is evacuated through the gas supply and vacuum system, and then the reaction gas nitrogen is introduced to maintain the pressure of the reaction chamber gas system at 160Pa, the discharge distance is 4cm, the working voltage is 200V, and the processing time is 300S. the

3) Ultrasonic cleaning the carbon paper material in step 2) for 5 minutes, taking it out and drying it in an oven at 100°C for 3 hours, then it can be used as the electrode material of the vanadium battery, and the battery can be assembled. the

Experimental example 1

Electron scanning microscope observation is carried out before and after electrode modification in embodiment 1-10, sees that Fig. 1 shows the electron micrograph that is the electrode material of vanadium battery in embodiment 2, and Fig. 1 a is used graphite felt material, and Fig. 1 b is plasma The treated graphite felt material can be seen that the treated carbon fiber surface is rougher, thereby increasing its specific surface area, providing more reaction sites for vanadium ions, and improving the electrochemical activity of the electrode. the

Other examples have the same results as Example 2, which shows that the electrode material treated by the method of the present invention can increase its surface area, which is beneficial to improve the electrochemical activity of the electrode. the

Experimental example 2

Cyclic voltammetry test was carried out before and after modification of the electrodes in Examples 1-10, scanning speed: 5mv/s. the

As shown in Figure 3, it is the result of Example 3, wherein 1# represents the untreated electrode, and 2# represents the electrode after ammonia plasma treatment, as can be seen from Figure 3, the graphite after plasma modification Felt material, the oxidation peak current increased from 28.62 mA to 30.63 mA, and the reduction peak current increased from -18.62 mA to -27.53 mA. The peak potential difference is less from 640 mV to 433 mV. The peak values of the reduction peak and the oxidation peak of the electrode after 2# plasma treatment are basically equal, and the oxidation wave and the reduction wave are in a symmetrical state. It can be seen that the electrochemical activity of the treated graphite felt material has been greatly improved, and has a good The reversibility of the electrode is very conducive to the reaction of the electrode active material on it, which is expected to improve the energy storage efficiency of the battery. the

The test results of other embodiments also have the peak value of the reduction peak and the oxidation peak are substantially equal, and the oxidation wave and the reduction wave are in a symmetrical state; the electrochemical activity of the treated graphite felt material is greatly improved, and it has good reversibility. It is very beneficial for the electrode active material to react on it. the

Claims (9)

1. A surface modification method improving the activity of vanadium battery electrode material, is characterized in that: comprise following steps and processing method: 1) Pretreatment to remove impurities on the surface of the material; 2) Form polar functional groups on the surface of the electrode material: the electrode material is modified by plasma, and the gas that generates the plasma reacts with the electrode surface in an ionized state to generate polar functional groups. The working pressure of the plasma gas is 10~ 200Pa; The gas for generating plasma is one or a mixture of two or more of oxygen, nitrogen, fluorine, chlorine, and ammonia; 3) The electrode material modified in step 2) is ultrasonically cleaned for 5-30 minutes, and dried at a temperature of 60-120°C; The plasma process in step 2) is microwave plasma, radio frequency plasma or direct current plasma; The treatment time for forming polar functional groups on the surface of electrode materials by microwave plasma is 10~300S, the gas flow rate is 200mL/min~4L/min, and the power is 200~2000W; The parameters of using radio frequency plasma are power 50~300W, gas flow 10~200mL/min, processing time 10~300S; The parameters for forming polar functional groups on the surface of electrode materials using DC plasma are: the discharge distance is controlled at 3-5cm, the treatment time is 10-300S, and the working voltage is 10-200V. 2. The surface modification method for improving the activity of vanadium battery electrode materials according to claim 1, characterized in that: the electrode materials are selected from graphite felt, carbon felt, graphite plate or carbon paper. 3. the surface modification method that improves vanadium battery electrode material activity according to claim 2, is characterized in that: described graphite felt thickness is 2mm～6mm, is selected as polyacrylonitrile-based graphite felt, viscose-based graphite felt, Any one of cellulose-based graphite felt or pitch-based graphite felt. 4. The surface modification method for improving the activity of vanadium battery electrode materials according to claim 2, characterized in that: the carbon felt thickness is 1 ~ 20mm, selected from polyacrylonitrile-based carbon felt, viscose-based carbon felt, cellulose Any one of base carbon felt or pitch-based carbon felt. 5. The surface modification method for improving the activity of vanadium battery electrode materials according to claim 2, characterized in that: the thickness of the graphite plate is 1-10mm, which is selected from analytical pure graphite plate or spectrally pure graphite plate. 6. The surface modification method for improving the activity of vanadium battery electrode materials according to claim 2, characterized in that: the thickness of the carbon paper is 0.5-10mm. 7. The surface modification method for improving the activity of vanadium battery electrode materials according to claim 1, characterized in that: step 1) pretreatment is ultrasonic immersion and cleaning in deionized water for 10-50 minutes, and then drying at 80-120 °C , The drying time is 1~8 hours. 8. The surface modification method for improving the activity of the electrode material of the vanadium battery according to claim 1, characterized in that: the surface action depth of the modified electrode material is 5-200nm. 9. The surface modification method for improving the activity of vanadium battery electrode materials according to claim 1, characterized in that: the polar functional groups include one or more of hydroxyl, carboxyl, nitrogen-containing, and fluorine-containing functional groups.

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