CN110416554B

CN110416554B - Modification method of carbon felt for all-vanadium redox flow battery electrode

Info

Publication number: CN110416554B
Application number: CN201810385706.2A
Authority: CN
Inventors: 盛伟; 张华民; 马相坤; 霍洋; 刘盛林; 倪泓; 高涛; 南明君; 徐广民
Original assignee: Dalian Rongke Power Equipment Co ltd
Current assignee: Dalian Rongke Power Equipment Co ltd
Priority date: 2018-04-26
Filing date: 2018-04-26
Publication date: 2021-02-02
Anticipated expiration: 2038-04-26
Also published as: CN110416554A

Abstract

The invention relates to the field of energy storage batteries, in particular to a method for modifying a carbon felt for an all-vanadium redox flow battery electrode. The plasma spray gun is adopted to carry out flow line treatment on the surface of the coiled carbon felt, so that the operation complexity is greatly reduced, and the hydrophilicity and the chemical stability of the carbon felt electrode are obviously improved. The invention realizes full-automatic production, the performance of the activated carbon felt is stable without obvious fluctuation, manual operation and real-time supervision are not needed, the safety, the stability and the cost are low, the yield is greatly increased, and the production flow is obviously simplified.

Description

Modification method of carbon felt for all-vanadium redox flow battery electrode

Technical Field

The invention relates to the field of energy storage batteries, in particular to the field of all-vanadium redox flow batteries, and particularly relates to a method special for modifying an electrode carbon felt of an all-vanadium redox flow battery.

Background

The all-vanadium redox flow battery is a novel large-scale energy storage battery and has the advantages of independent capacity, high power, long service life, easiness in operation and the like. The electrode is one of the key components of the flow battery, the performance of the electrode material directly affects the uniformity of electrolyte distribution, the diffusion state, the internal resistance of the battery and the rate of electrochemical reaction, and further affects the polarization degree of the electrode and the internal resistance of the battery, and finally affects the energy conversion efficiency of the battery, and the stability of the electrode material also affects the service life of the battery.

In the prior art, electrode materials of the all-vanadium redox flow battery mainly comprise glassy carbon, carbon felt, graphite felt, carbon paper, carbon cloth and the like. The carbon felt or the graphite felt is formed by weaving carbon fibers, has good mechanical strength, has a real specific surface area far larger than a collective surface area, can provide a larger electrochemical reaction area, and has good chemical stability and conductivity, so that the carbon felt or the graphite felt becomes one of research hotspots of all-vanadium flow battery electrode materials. However, if the vanadium redox flow battery is directly used, the electrochemical activity and the reversibility are low. Therefore, it is necessary to appropriately modify it to improve its hydrophilicity and electrochemical activity. At present, the main means for modifying the surface of the glass substrate are a gas oxidation method, a liquid phase oxidation method, an electrochemical oxidation method, a gamma ray method, a hydrothermal method, a surface deposition method and the like. However, in large-scale application, the problems of complex operation, unobvious modification effect, high cost and the like exist.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a method for modifying a carbon felt for an all-vanadium redox flow battery electrode, which adopts an air/oxygen/nitrogen/mixed gas plasma spray gun to carry out flow line treatment on the surface of a coiled carbon felt, greatly reduces the operation complexity and obviously improves the hydrophilicity and chemical stability of the carbon felt electrode.

The invention has the following inventive concept: the method has the advantages that the gas reacts with the high-activity amorphous carbon atoms on the surface of the carbon felt carbon fiber, and the degree of oxidation of carbon on the surface of the carbon felt carbon fiber can be controlled by adjusting the types and the flow rates of the activated gas, the power and the temperature of an ion spray gun, the distance between a spray head and the surface of the carbon felt, the traveling speed of the spray head and other factors, so that the types and the proportion of oxygen-containing functional groups growing on the surface of the carbon felt carbon fiber are optimal, and the carbon felt reaches the optimal activation.

In order to achieve the purpose, the invention adopts the following technical scheme:

conveying coiled carbon felt which is not subjected to activation treatment into an activation region through roller transmission, and performing activation treatment through a gas plasma spray gun at the temperature of 20-80 ℃ to grow oxygen-containing functional groups (-COH, -C ═ O, -COOH, -COOR and the like) on the surface of carbon fiber of the carbon felt, wherein the conditions in the activation process of the plasma spray gun are as follows: one or more than two gases of air, oxygen and nitrogen are used as gas sources, the gas flow rate is 0.1-100ml/min, the distance between a spray head and the surface of the carbon felt is 0.1-10cm, the traveling speed of the spray head is 0.1-50cm/s, and the power of a plasma spray gun is 2000-.

Further, the gas flow rate is 20-100ml/min, the distance between the spray head and the surface of the carbon felt is 1-10cm, the travel speed of the spray head is 20-50cm/s, and the power of the plasma spray gun is 2500-.

In the flow process, one or more plasma spray guns can be arranged according to the production efficiency requirement, and the plasma spray guns can be arranged in a horizontal or vertical manner.

Preferably, the percentage content ratio of oxygen-containing functional groups on the surface of the carbon felt for the all-vanadium redox flow battery electrode is-C ═ O: -COH: -COOR ═ 2:1: 1.

As a preferred embodiment, when the air source is air and nitrogen, the flow rate ratio of air to nitrogen is 9:1, the total flow rate is 20ml/min, the surface of the spray head and the carbon felt is set to be 1cm, and the travel speed of the spray head is 20 cm/s.

As a preferred embodiment, when the gas sources are oxygen and nitrogen, the flow rate ratio of oxygen to nitrogen is 1:1, the total flow rate is 50ml/min, the surface of the spray head and the carbon felt is set to be 5cm, and the travel speed of the spray head is 50 cm/s.

The traditional carbon felt modification method has many limitations, for example, the gas oxidation method has strict requirements on temperature and time, the temperature of the gas oxidation method is generally 400 ℃, and excessive oxidation etching of the surface of the carbon felt can be caused by too high temperature or long time. The temperature and time of the traditional gas oxidation method are not easy to accurately control, and the method is difficult to apply in the industrial continuous production process, especially in the flow operation. However, the method is used for modifying the all-vanadium redox flow battery electrode carbon felt by adopting a plasma spraying method for the first time. The modification method can be operated at normal temperature, the conditions are all manually controllable, the oxygen content can be adjusted and the activation conditions can be controlled by controlling the flow rate of the spraying gas, the traveling speed and the power of the spray head, the carbon felts containing different types and proportions of oxygen-containing functional groups can be prepared, and the design of the all-vanadium flow battery can be adapted to different requirements. The method is more suitable for continuous flow production and industrial production no matter from the aspects of production cost, operation mode or modification effect.

Compared with the prior art, the invention has the beneficial effects that:

1. compared with the traditional activation mode, the method has the advantages that full-automatic production is realized, assembly line operation is adopted, the performance of the activated carbon felt is stable without obvious fluctuation, manual operation and real-time supervision are not needed, the safety, stability and cost are low, the yield is greatly increased, and the production flow is obviously simplified.

2. Compared with the traditional oxidation activation mode in a high-temperature furnace, the plasma positive ions have extremely high excited states and are more easily combined with carbon on the surface of the carbon felt carbon fiber to generate a large number of oxygen-containing functional groups. The types and the proportion of oxygen-containing functional groups on the surface of the carbon fiber of the carbon felt can be controlled by simply changing the activation parameters, so that the overall performance of the carbon felt is controlled, and electrodes with different requirements can be prepared.

3. The optimal activation condition is confirmed through a series of experiments, and the performance of the activated carbon felt is obviously improved compared with that of the traditional activation method.

Drawings

FIG. 1 is a schematic view of a modified carbon felt plasma spraying device. Wherein a is a perspective view and b is a front view.

Detailed Description

The invention is described in more detail below with reference to specific examples, without limiting the scope of the invention. Unless otherwise specified, the experimental methods adopted by the invention are all conventional methods, and experimental equipment, materials, reagents and the like used in the experimental method can be obtained from commercial sources.

Example 1

And (3) putting the finished carbon felt which is not activated into a coil and has a thickness of 3mm into an uncoiler assembly line for acting, conveying the finished carbon felt into an activation area through the transmission of a rolling shaft, and activating the carbon felt by adopting a plasma spray gun for blowing, wherein the activation area is at normal temperature. The output power of the plasma is set to be 3500w, the flow rate ratio of air to nitrogen is 9:1, the total flow rate is 20ml/min, the surface of the spray head and the carbon felt is set to be 1cm, and the running speed of the spray head is 20 cm/s.

Example 2

And (3) putting a finished carbon felt which is 5mm thick and is not activated into an uncoiler assembly line, conveying the finished carbon felt into an activation area through rolling shaft transmission, and activating the carbon felt by adopting a plasma spray gun for blowing, wherein the activation area is at normal temperature. The output power of the plasma is set to be 5000w, the flow rate ratio of oxygen to nitrogen is 1:1, the total flow rate is 50ml/min, the nozzle and the surface of the carbon felt are set to be 5cm, and the nozzle speed is 50 cm/s.

Example 3

And (3) putting a finished carbon felt which is 7mm thick and is not activated into an uncoiler assembly line, conveying the finished carbon felt into an activation area through rolling shaft transmission, and activating the carbon felt by adopting a plasma spray gun for blowing, wherein the activation area is at normal temperature. The plasma output power is set to be 8000w, the air flow rate is 100ml/min, the spray head and the surface of the carbon felt are set to be 8cm, and the travel speed of the spray head is 30 cm/s.

Comparative example 1

And (3) putting the finished carbon felt which is 5mm thick and is not activated into an uncoiler assembly line, conveying the finished carbon felt into an activation area through rolling shaft transmission, and activating the carbon felt by adopting a plasma spray gun for blowing. The output power of the plasma is set to be 5000w, the flow rate ratio of oxygen to nitrogen is 1:1, the total flow rate is 250ml/min, the nozzle and the surface of the carbon felt are set to be 5cm, and the nozzle moving speed is 50 cm/s.

Comparative example 2

And (3) putting the finished carbon felt which is 5mm thick and is not activated into an uncoiler assembly line, conveying the finished carbon felt into an activation area through rolling shaft transmission, and activating the carbon felt by adopting a plasma spray gun for blowing. The output power of the plasma is set to be 5000w, the flow rate ratio of oxygen to nitrogen is 1:1, the total flow rate is 50ml/min, the surfaces of the spray head and the carbon felt are set to be 25cm, and the running speed of the spray head is 50 cm/s.

Comparative example 3

The carbon felt is treated by a traditional hot air oxidation method. The thickness of the carbon felt is 3mm, the flow rate of dry air is 100ml/min, and the heat treatment is carried out for 4 hours at 400 ℃.

Comparative example 4

The carbon felt is treated by adopting a traditional concentrated sulfuric acid oxidation method. The thickness of the carbon felt is 3mm, the carbon felt electrode is soaked in 4mol/L concentrated sulfuric acid for 12 hours, then is washed by deionized water, and is dried for 12 hours at 80 ℃.

The modified products of examples 1 to 3 and comparative examples 1 to 4 were subjected to the following property analyses.

TABLE 1 analysis of properties

Means of characterisation	Performance index
		Heat weight change	Carbon content
XPS	Type and content of oxygen-containing functional group
		Resistivity of	Resistivity tester
Efficiency of battery	Single cell test system

The test results are shown in table 2.

TABLE 2 examples and comparative examples Performance parameters

According to the experimental data, the gas flow rate, the nozzle traveling speed, the surface distance between the nozzle and the carbon felt and the power all play a vital role in modifying the carbon felt, and all parameters are closely related. The carbon felts with oxygen-containing functional groups of different types and proportions can be obtained by adjusting the parameters, products with different single cell voltage efficiencies, energy efficiencies and resistivities can be obtained, and the design of the all-vanadium redox flow battery is suitable for different requirements. In conclusion, the method is more suitable for continuous flow operation and is suitable for modifying large-batch carbon felts.

The above description is only for the purpose of creating a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the technical scope of the present invention.

Claims

1. A modification method of a carbon felt for an all-vanadium redox flow battery electrode is characterized by comprising the following steps: sending coiled carbon felt which is not subjected to activation treatment into an activation area through roller transmission, and growing oxygen-containing functional groups on the surface of carbon fiber of the carbon felt through gas plasma spray gun activation treatment, wherein the conditions in the plasma spray gun activation process are as follows: taking air and nitrogen, oxygen and one of nitrogen, air and oxygen as a gas source, wherein the gas flow rate is 0.1-100ml/min, the distance between the spray head and the surface of the carbon felt is 0.1-10cm, the travelling speed of the spray head is 0.1-50cm/s, and the power of the plasma spray gun is 2000-25000W; the oxygen-containing functional group comprises-COH, -C = O, -COOH, -COOR; the percentage content ratio of the oxygen-containing functional groups is-C = O: -COH: -COOR =2:1: 1; when the air source is air and nitrogen, the flow rate ratio of the air to the nitrogen is 9:1, the total flow rate is 20ml/min, the nozzle and the surface of the carbon felt are set to be 1cm, and the nozzle moving speed is 20 cm/s; when the gas source is oxygen and nitrogen, the flow rate ratio of the oxygen to the nitrogen is 1:1, the total flow rate is 50ml/min, the nozzle and the surface of the carbon felt are set to be 5cm, and the nozzle running speed is 50 cm/s; the temperature in the activation zone is 20-80 ℃.

2. The modification method as claimed in claim 1, wherein air and nitrogen, oxygen and one of nitrogen, air and oxygen are used as gas sources, the gas flow rate is 20-100ml/min, the distance between the nozzle and the carbon felt surface is 1-10cm, the nozzle speed is 20-50cm/s, and the plasma spray gun power is 2500- > 8000W.