Nanofiber / graphite felt composite electrode material for flow battery and preparation method thereof

Abstract

The application relates to the technical field of liquid flow battery energy storage, and discloses a nanofiber / graphite felt composite electrode material for a liquid flow battery and a preparation method thereof. The electrode material comprises the following steps: taking carbon fiber graphite felt as a carrier, taking silicon powder and silicon dioxide powder as a silicon source, growing silicon carbide nanowires on the fiber surface in situ by adopting a vacuum thermal evaporation method, or taking ferrocene as a catalyst precursor, taking cyclohexane as a solvent and a reaction carbon source, and taking thiophene as an additive, growing carbon nanotubes on the fiber surface by adopting a floating catalyst chemical vapor deposition method, and carrying out steam activation on the prepared silicon carbide nanowire / graphite felt composite electrode material or carbon nanotube / graphite felt composite electrode material in an activation furnace to prepare a modified nanofiber / graphite felt composite electrode material for a liquid flow battery. The specific surface area, hydrophilicity and electrically-conductive and thermally-conductive performance of the carbon fiber graphite felt are greatly improved, and the nanofiber / graphite felt composite electrode material is applied to the field of liquid flow battery energy storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid flow battery energy storage, in particular to a nanofiber / graphite felt composite electrode material for liquid flow battery and a preparation method thereof. BACKGROUND

[0002] The electrode material of the all-vanadium redox flow battery can be divided into metal electrode material and carbon electrode material according to the material type. At present, polyacrylonitrile-based carbon felt and graphite felt have high porosity and mechanical strength, good electrical conductivity and excellent characteristics such as acid and alkali corrosion resistance, and are the most widely used carbon electrode material. However, it still has problems such as poor hydrophilicity, insufficient active sites and small specific surface area, which limits the energy storage performance of the battery. At present, the graphite felt electrode is modified by means of functional group modification, heteroatom doping and etching, although the electrocatalytic performance of the electrode to the metal ion redox reaction is enhanced, most of the methods have problems such as complex process, high cost and non-industrialization or uneven modification. The diameter of nanofiber is between 1 nm and 1000 nm, and its physical and chemical properties will change, mainly having surface effect, small size effect, quantum size effect, macroscopic quantum tunneling effect and other characteristics. Loading the nanofiber on the surface of the carbon fiber graphite felt can further improve the specific surface area, hydrophilicity and electrical conductivity, and further improve the electrochemical performance of the liquid flow battery.

[0003] Therefore, it is urgent to provide a nanofiber / graphite felt composite electrode material for liquid flow battery and a preparation method thereof to solve the above problems of the carbon fiber graphite felt electrode material. SUMMARY

[0004] Based on the above, the purpose of the present application is to provide a nanofiber / graphite felt composite electrode material for liquid flow battery and a preparation method thereof, to solve the problems of poor hydrophilicity, insufficient active sites and small specific surface area of the carbon fiber graphite felt electrode material, and to improve the electrochemical performance of the liquid flow battery.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A preparation method of a nanofiber / graphite felt composite electrode material for liquid flow battery, comprising the following steps:

[0007] The carbon fiber graphite felt is soaked in a nickel nitrate catalyst solution and then dried for use. Silicon powder and silicon dioxide powder are used as silicon source by vacuum thermal evaporation method, so that silicon carbide nanowires grow on the surface of the dried carbon fiber graphite felt, and a silicon carbide nanowire / graphite felt composite electrode material is prepared; or

[0008] The carbon fiber graphite felt is soaked in an iron nitrate-anhydrous ethanol solution and dried for use, and a carbon nanotube / graphite felt composite electrode material is prepared by growing carbon nanotubes on the surface of the dried carbon fiber graphite felt through a floating catalyst chemical vapor deposition method, with ferrocene as a catalyst precursor, cyclohexane as a solvent and a reaction carbon source, and thiophene as an additive.

[0009] The silicon carbide nanowire / graphite felt composite electrode material or the carbon nanotube / graphite felt composite electrode material is subjected to water vapor activation in an activation furnace to prepare a modified nanofiber / graphite felt composite electrode material for a flow battery.

[0010] As a preferred solution of the preparation method of the nanofiber / graphite felt composite electrode material for a flow battery, the diameter of the carbon fiber graphite felt is 2.5-6 mm.

[0011] As a preferred solution of the preparation method of the nanofiber / graphite felt composite electrode material for a flow battery, the porosity of the carbon fiber graphite felt is 65%-90%, and the heat treatment temperature of the carbon fiber graphite felt is 2200-2800°C.

[0012] As a preferred solution of the preparation method of the nanofiber / graphite felt composite electrode material for a flow battery, the mass ratio of the silicon powder to the silicon dioxide powder is (1-1.5):(0.5-1).

[0013] As a preferred solution of the preparation method of the nanofiber / graphite felt composite electrode material for a flow battery, the reaction temperature of the vacuum thermal evaporation method is 1250-1400°C, and the reaction time is 15-60 min.

[0014] As a preferred solution of the preparation method of the nanofiber / graphite felt composite electrode material for a flow battery, the concentration of the iron nitrate solution is 0.025-0.1 mol / L.

[0015] As a preferred solution of the preparation method of the nanofiber / graphite felt composite electrode material for a flow battery, the mass ratio of the ferrocene, the cyclohexane, and the thiophene is 1:(0.2-0.6):(0.05-0.1); the concentration of the ferrocene is not higher than 10 g / L, and the volume fraction of the thiophene is not higher than 0.2 vol%.

[0016] As a preferred solution of the preparation method of the nanofiber / graphite felt composite electrode material for a flow battery, the reaction temperature of the floating catalyst chemical vapor deposition method is 800-1000°C.

[0017] As a preferred scheme of the preparation method of the nanofiber / graphite felt composite electrode material for a flow battery, the reaction temperature of the water vapor activation process is 750-900 DEG C, and the reaction time is 1-5 h.

[0018] A nanofiber / graphite felt composite electrode material for a flow battery is prepared by the preparation method of any one of the above.

[0019] The present application has the following beneficial effects:

[0020] The present application provides a nanofiber / graphite felt composite electrode material for a flow battery and a preparation method thereof. Silicon nanowires or carbon nanotubes are loaded on carbon fiber graphite felt, so that the nanofiber / graphite felt composite electrode material has good micropores, large capillary force, increased hydrophilicity, and a three-dimensional conductive and heat-conductive network formed by the silicon nanowires or carbon nanotubes in the graphite felt system, thereby increasing the conductivity and thermal conductivity. The nanofiber / graphite felt composite material is then subjected to water vapor activation to load various types of oxygen functional groups and increase its hydrophilicity. Finally, a high-performance nanofiber / graphite felt composite electrode material is obtained. In addition, the nanofiber loaded on the carbon fiber graphite felt has the characteristics of surface effect, small size effect, and quantum size effect, thereby further increasing the specific surface area and conductivity of the carbon fiber graphite felt. Therefore, the nanofiber / graphite felt composite electrode material prepared by the present application has excellent specific surface area, hydrophilicity, and conductivity, and can be applied in a flow battery energy storage system and has high electrochemical performance. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present application, the present application will be described more fully below. The present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of the present application more thorough and comprehensive. Unless otherwise defined, all technical and scientific terms used in the present application belong to the technical field of the present application.

[0022] In the present embodiment, the present application provides a preparation method of a nanofiber / graphite felt composite electrode material for a flow battery, which comprises the following steps:

[0023] S100, after the carbon fiber graphite felt is soaked in a nickel nitrate catalyst solution and dried, silicon powder and silicon dioxide powder are used as a silicon source to grow silicon nanowires on the surface of the dried carbon fiber graphite felt by vacuum thermal evaporation, thereby preparing a silicon nanowire / graphite felt composite electrode material;

[0024] Specifically, the diameter of the carbon fiber graphite felt is 2.5-6 mm, and the diameter of the carbon fiber graphite felt can be specifically set to 2.5 mm or 4 mm or 6 mm. The porosity of the carbon fiber graphite felt is 65%-90%, and the heat treatment temperature of the carbon fiber graphite felt is 2200 DEG C-2800 DEG C.

[0025] Specifically, the mass ratio of the silicon powder to the silicon dioxide powder is (1-1.5):(0.5-1); the reaction temperature of the vacuum thermal evaporation method is 1250-1400℃, and the reaction time is 15-60min.

[0026] S200, the silicon carbide nanowire / graphite felt composite electrode material is subjected to steam activation in an activation furnace to prepare a modified nanofiber / graphite felt composite electrode material for a flow battery.

[0027] Specifically, the reaction temperature of the steam activation process is 750-900℃, and the reaction time is 1-5h.

[0028] In another embodiment, the application further provides a preparation method of a nanofiber / graphite felt composite electrode material for a flow battery, comprising the following steps:

[0029] S100, the carbon fiber graphite felt is soaked in an iron nitrate-anhydrous ethanol solution and then dried for use; a carbon nanotube / graphite felt composite electrode material is prepared by adopting a floating catalyst chemical vapor deposition method, using ferrocene as a catalyst precursor, cyclohexane as a solvent and a reaction carbon source, and using thiophene as an additive to make the surface of the dried carbon fiber graphite felt grow carbon nanotubes.

[0030] Specifically, the diameter of the carbon fiber graphite felt is 2.5-6mm, and the diameter of the carbon fiber graphite felt can be specifically set to 2.5mm or 4mm or 6mm; the porosity of the carbon fiber graphite felt is 65%-90%, and the heat treatment temperature of the carbon fiber graphite felt is 2200-2800℃.

[0031] Specifically, the concentration of the iron nitrate solution is 0.025-0.1mol / L; the mass ratio of the ferrocene, the cyclohexane and the thiophene is 1:(0.2-0.6):(0.05-0.1); the concentration of the ferrocene is not higher than 10g / L, and the volume fraction of the thiophene is not higher than 0.2vol%; the reaction temperature of the floating catalyst chemical vapor deposition method is 800-1000℃.

[0032] S200, the carbon nanotube / graphite felt composite electrode material is subjected to steam activation in an activation furnace to prepare a modified nanofiber / graphite felt composite electrode material for a flow battery.

[0033] Specifically, the reaction temperature of the steam activation process is 750-900℃, and the reaction time is 1-5h.

[0034] The application is further described below through specific embodiments.

[0035] Embodiment 1

[0036] The 2.5 mm carbon fiber graphite felt is soaked in a nickel nitrate catalyst solution and dried for use. The silicon powder and the silicon dioxide powder are used as the silicon source to grow the silicon carbide nanowires on the surface of the dried carbon fiber graphite felt by the vacuum thermal evaporation method. The mass ratio of the silicon powder to the silicon dioxide powder is 1:1. The vacuum thermal evaporation temperature is 1300 DEG C. The holding time is 60 min. The silicon carbide nanowire / graphite felt composite electrode material is obtained.

[0037] The silicon carbide nanowire / graphite felt composite electrode material is subjected to steam activation. The activation temperature is 850 DEG C. The activation time is 2 h. The activated silicon carbide nanowire / graphite felt composite electrode material is obtained. The material is collectively referred to as the nanofiber / graphite felt composite electrode material for the flow battery.

[0038] The nanofiber / graphite felt composite electrode material is placed in a device for testing the single cell of the all-vanadium redox flow battery to test the electrochemical performance.

[0039] Example 2

[0040] The 4 mm carbon fiber graphite felt is soaked in a nickel nitrate catalyst solution and dried for use. The silicon powder and the silicon dioxide powder are used as the silicon source to grow the silicon carbide nanowires on the surface of the dried carbon fiber graphite felt by the vacuum thermal evaporation method. The mass ratio of the silicon powder to the silicon dioxide powder is 1.5:0.5. The vacuum thermal evaporation temperature is 1250 DEG C. The holding time is 15 min. The silicon carbide nanowire / graphite felt composite electrode material is obtained.

[0041] The silicon carbide nanowire / graphite felt composite electrode material is subjected to steam activation. The activation temperature is 750 DEG C. The activation time is 5 h. The activated silicon carbide nanowire / graphite felt composite electrode material is obtained. The material is collectively referred to as the nanofiber / graphite felt composite electrode material for the flow battery.

[0042] The nanofiber / graphite felt composite electrode material is placed in a device for testing the single cell of the all-vanadium redox flow battery to test the electrochemical performance.

[0043] Example 3

[0044] The 6 mm carbon fiber graphite felt is soaked in a nickel nitrate catalyst solution and dried for use. The silicon powder and the silicon dioxide powder are used as the silicon source to grow the silicon carbide nanowires on the surface of the dried carbon fiber graphite felt by the vacuum thermal evaporation method. The mass ratio of the silicon powder to the silicon dioxide powder is 1:0.5. The vacuum thermal evaporation temperature is 1400 DEG C. The holding time is 40 min. The silicon carbide nanowire / graphite felt composite electrode material is obtained.

[0045] The silicon carbide nanowire / graphite felt composite electrode material is subjected to steam activation, the activation temperature is 900 DEG C, and the activation time is 1h, to obtain the activated silicon carbide nanowire / graphite felt composite electrode material, collectively referred to as a nanofiber / graphite felt composite electrode material for a flow battery;

[0046] The nanofiber / graphite felt composite electrode material is placed in a device for testing a single cell of a vanadium flow battery to perform electrochemical performance testing.

[0047] Example 4

[0048] The 2.5mm carbon fiber graphite felt is soaked in an iron nitrate-anhydrous ethanol solution and then dried for use. A floating catalyst chemical vapor deposition method is used, ferrocene is used as a catalyst precursor, cyclohexane is used as a solvent and a reaction carbon source, and thiophene is used as an additive to grow carbon nanotubes on the surface of the dried carbon fiber graphite felt. The concentration of the iron nitrate solution is 0.025mol / L, the reaction temperature of the floating catalyst chemical vapor deposition method is 800 DEG C, the mass ratio of ferrocene, cyclohexane and thiophene is 1:0.2:0.05, the concentration of ferrocene is 5g / L, and the volume fraction of thiophene is 0.2vol%, to obtain a carbon nanotube / graphite felt composite electrode material.

[0049] The carbon nanotube / graphite felt composite electrode material is subjected to steam activation, the activation temperature is 850 DEG C, and the activation time is 2h, to obtain the activated carbon nanotube / graphite felt composite electrode material, collectively referred to as a nanofiber / graphite felt composite electrode material for a flow battery;

[0050] The nanofiber / graphite felt composite electrode material is placed in a device for testing a single cell of a vanadium flow battery to perform electrochemical performance testing.

[0051] Example 5

[0052] The 4mm carbon fiber graphite felt is soaked in an iron nitrate-anhydrous ethanol solution and then dried for use. A floating catalyst chemical vapor deposition method is used, ferrocene is used as a catalyst precursor, cyclohexane is used as a solvent and a reaction carbon source, and thiophene is used as an additive to grow carbon nanotubes on the surface of the dried carbon fiber graphite felt. The concentration of the iron nitrate solution is 0.05mol / L, the reaction temperature of the floating catalyst chemical vapor deposition method is 900 DEG C, the mass ratio of ferrocene, cyclohexane and thiophene is 1:0.6:0.1, the concentration of ferrocene is 8g / L, and the volume fraction of thiophene is 0.1vol%, to obtain a carbon nanotube / graphite felt composite electrode material.

[0053] The carbon nanotube / graphite felt composite electrode material is subjected to steam activation, the activation temperature is 750 DEG C, and the activation time is 5h, to obtain the activated carbon nanotube / graphite felt composite electrode material, collectively referred to as a nanofiber / graphite felt composite electrode material for a flow battery;

[0054] The nanofiber / graphite felt composite electrode material is placed in a device for testing a single cell of a vanadium redox flow battery to perform electrochemical performance testing.

[0055] Example 6

[0056] The 6mm carbon fiber graphite felt is soaked in a ferric nitrate-absolute ethanol solution and dried for use. A floating catalyst chemical vapor deposition method is used to grow carbon nanotubes on the surface of the dried carbon fiber graphite felt, with ferrocene as a catalyst precursor, cyclohexane as a solvent and a reaction carbon source, and thiophene as an additive. The ferric nitrate solution has a concentration of 0.1 mol / L, the reaction temperature of the floating catalyst chemical vapor deposition method is 1000°C, the mass ratio of ferrocene, cyclohexane, and thiophene is 1:0.2:0.05 (in other examples, the mass ratio of ferrocene, cyclohexane, and thiophene can also be set to 1:0.6:0.05), the ferrocene concentration is 10 g / L, and the volume fraction of thiophene is 0.05 vol%, to obtain a carbon nanotube / graphite felt composite electrode material.

[0057] The carbon nanotube / graphite felt composite electrode material is subjected to steam activation, with an activation temperature of 900°C and an activation time of 1h, to obtain an activated carbon nanotube / graphite felt composite electrode material, which is collectively referred to as a nanofiber / graphite felt composite electrode material for a redox flow battery.

[0058] The nanofiber / graphite felt composite electrode material is placed in a device for testing a single cell of a vanadium redox flow battery to perform electrochemical performance testing.

[0059] To further illustrate the key of the present patent, a comparative example is added for illustration.

[0060] Comparative Example 1

[0061] The 2.5mm carbon fiber graphite felt is subjected to steam activation, with an activation temperature of 850°C and an activation time of 2h, to obtain an activated carbon fiber graphite felt, which can be used as an electrode material and placed in a device for testing a single cell of a vanadium redox flow battery to perform electrochemical performance testing.

[0062] The electrode materials prepared in the examples and the comparative example are subjected to electrochemical performance testing, and the performance and electrochemical performance (current density 80mA / cm 2 ) of the materials are tested. The test results are shown in Table 1.

[0063] Table 1 Electrochemical test results

[0064]

[0065] It can be obtained from the above test results that the volume density and porosity of the examples and the comparative examples are not much different, indicating that the modification of the silicon carbide nanowires and the carbon nanotubes has less influence on the volume density and porosity of the carbon fiber graphite felt, and the nanofiber / graphite felt composite electrode material prepared in the application has excellent specific surface area and energy efficiency, and can be applied in the liquid flow battery energy storage system.

[0066] The above are only the preferred embodiments of the present application and the technical principles applied, and those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above examples, the present application is not limited to the above examples only, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A method for preparing a nanofiber / graphite felt composite electrode material for flow batteries, characterized in that, Includes the following steps: After immersing carbon fiber graphite felt in a nickel nitrate catalyst solution and drying it for later use, silicon powder and silicon dioxide powder were used as silicon sources by vacuum thermal evaporation to grow silicon carbide nanowires on the surface of the dried carbon fiber graphite felt, thus preparing a silicon carbide nanowire / graphite felt composite electrode material. The silicon carbide nanowire / graphite felt composite electrode material was activated with water vapor in an activation furnace to prepare a modified nanofiber / graphite felt composite electrode material for flow batteries. The mass ratio of the silicon powder to the silicon dioxide powder is (1-1.5):(0.5-1); The reaction temperature of the vacuum thermal evaporation method is 1250℃-1400℃, and the reaction time is 15-60min.

2. The method for preparing the nanofiber / graphite felt composite electrode material for flow batteries according to claim 1, characterized in that, The porosity of the carbon fiber graphite felt is 65%-90%.

3. The method for preparing the nanofiber / graphite felt composite electrode material for flow batteries according to claim 1, characterized in that, The reaction temperature for the steam activation process is 750-900℃, and the reaction time is 1-5h.

4. A nanofiber / graphite felt composite electrode material for flow batteries, characterized in that, It is prepared by the preparation method according to any one of claims 1-3.

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