A high catalytic activity graphite felt electrode for vanadium battery and preparation method thereof

Abstract

The present invention relates to the field of all-vanadium liquid flow battery electrodes, and discloses a high catalytically active graphite felt electrode for vanadium batteries and a preparation method thereof, comprising the following steps: preparing an aqueous carbon slurry; loading a niobium tungsten oxide precursor and a carbon material on the graphite felt; and calcining the loaded graphite felt at a high temperature to prepare a graphite felt electrode loaded with nitrogen-doped porous niobium tungsten oxide and carbon material. The present invention combines carbon material and metal oxide, and the carbon material forms a conductive network on the surface of the graphite felt to promote the transmission of electrons; the nitrogen-doped porous niobium tungsten oxide has a significant pore structure, which increases the specific surface area of ​​the metal oxide and provides more reactive centers for vanadium ions; in addition to being a porogen, the quaternary ammonium salt also forms nitrogen doping in the niobium tungsten oxide after calcination, and the nitrogen doping improves the electrical conductivity and catalytic performance of the metal oxide.

Description

Technical Field

[0001] The invention relates to the technical field of all-vanadium liquid flow battery electrodes, and in particular to a high-catalytically active graphite felt electrode for a vanadium battery and a preparation method thereof. Background Art

[0002] All-vanadium redox flow battery (VRFB) has the advantages of high safety, flexible assembly, and recyclable electrolyte. The energy storage mechanism of VRFB is based on two vanadium-based redox reactions. 2 + / VO 2+ , the negative side is V 3+ / V 2+ Graphite felt is widely used as a VRFB electrode due to its advantages such as good chemical stability, wide working potential range, three-dimensional structure, and high conductivity. However, the poor electrochemical performance and reversibility of graphite felt are obstacles to the development of VO 2 + / VO 2+ and V 3+ / V 2+ The main reason for the redox reaction. Metal oxides have been proven to have good electrocatalytic properties and can effectively increase VO 2 + / VO 2+ and V 3+ / V 2+ However, the low specific surface area, low conductivity, uneven distribution of nanoparticles, and weak interaction with electrodes still hinder the application of metal oxides in VRFB. Summary of the invention

[0003] The object of the present invention is to provide a high catalytic activity graphite felt electrode for vanadium battery and a preparation method thereof, so as to overcome the deficiencies in the prior art.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The present application discloses a method for preparing a high catalytically active graphite felt electrode for a vanadium battery, comprising the following steps:

[0006] S1. dispersing the carbon material and the adhesive into deionized water to obtain an aqueous slurry;

[0007] S2, adding ammonium metatungstate, ammonium niobium oxalate, citric acid and quaternary ammonium salt to deionized water, stirring to dissolve, then adding aqueous carbon slurry, stirring evenly, immersing graphite felt therein, then performing complex reaction, drying after the reaction is completed, and obtaining graphite felt loaded with niobium tungsten oxide precursor and carbon material;

[0008] S3. calcining the graphite felt loaded with the niobium tungsten oxide precursor and the carbon material at a high temperature to obtain the graphite felt loaded with nitrogen-doped porous niobium tungsten oxide and the carbon material.

[0009] Preferably, the carbon material in step S1 is one of carbon nanotubes, reduced graphene oxide, and carbon nanofibers.

[0010] Preferably, the adhesive in step S1 is one of polyvinyl alcohol water-based adhesive, polyurethane water-based adhesive, and epoxy resin water-based adhesive.

[0011] Preferably, in step S1, the mass ratio of the carbon material, the adhesive and the deionized water is (5-10):(1-5):100.

[0012] Preferably, the quaternary ammonium salt in step S2 is one of dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide.

[0013] Preferably, in step S2, the mass ratio of ammonium metatungstate, ammonium niobium oxalate, citric acid, quaternary ammonium salt, water and aqueous slurry is (1-3): (2-6): (5-15): (5-15): 150: (50-100).

[0014] Preferably, in step S2, the complexation reaction temperature is 50-70° C., and the reaction time is 2-4 h.

[0015] Preferably, the calcination temperature in step S3 is 400-450° C., and the calcination time is 2-3 hours.

[0016] Beneficial effects of the present invention:

[0017] 1. The present invention combines carbon materials and metal oxides. The carbon materials improve the conductivity of the metal oxides, form a conductive network on the surface of the graphite felt, promote the transmission of electrons, and improve the voltage efficiency and energy efficiency of the battery.

[0018] 2. The nitrogen-doped porous niobium tungsten oxide prepared by the present invention has a distinct pore structure, which increases the specific surface area of ​​the metal oxide, provides more reactive centers for vanadium ions, and improves the capacity retention rate;

[0019] 3. In addition to being a porogen, the quaternary ammonium salt will also form nitrogen doping in the niobium tungsten oxide after calcination. Nitrogen doping improves the electrical conductivity and catalytic performance of the metal oxide, thereby improving the voltage efficiency and energy efficiency of the battery;

[0020] 4. The quaternary ammonium salt provides more nucleation sites for the in-situ growth of niobium tungsten oxide on the surface of carbon materials and graphite felt, solving the problem of uneven distribution of nanoparticles. At the same time, the adhesive enhances the interaction between nanoparticles and graphite felt, prevents the catalyst from falling off during the cycle, and improves the capacity retention rate of graphite felt. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope image of the nitrogen-doped porous niobium tungsten oxide and carbon nanotube graphite felt prepared in Example 1 of the present invention;

[0022] Figure 2 This is a mapping diagram of the nitrogen-doped porous niobium tungsten oxide and carbon nanotube graphite felt prepared in Example 1 of the present invention;

[0023] Figure 3 The cyclic voltammetry curves are shown when the graphite felt is used as the positive and negative electrodes in Example 1 of the present invention and Comparative Example 1, respectively. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below through the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0025] A method for preparing a high catalytically active graphite felt electrode for a vanadium battery comprises the following steps:

[0026] S1. Dispersing 5-10 parts by mass of carbon material and 1-5 parts by mass of adhesive into 100 parts by mass of deionized water to obtain an aqueous slurry;

[0027] S2. Add 1-3 parts by mass of ammonium metatungstate, 2-6 parts by mass of ammonium niobium oxalate, 5-15 parts by mass of citric acid and 5-15 parts by mass of quaternary ammonium salt to 150 parts by mass of deionized water, stir to dissolve, then add 50-100 parts by mass of aqueous carbon slurry, stir evenly and immerse in graphite felt. Then carry out complexation reaction at 50-70°C for 2-4 hours. After the reaction is completed, dry at 100°C for 2 hours to obtain graphite felt loaded with niobium tungsten oxide precursor and carbon material;

[0028] S3. calcining the graphite felt loaded with the niobium tungsten oxide precursor and the carbon material at 400-450° C. for 2-3 h at a heating rate of 10° C. / min in air to obtain the graphite felt loaded with nitrogen-doped porous niobium tungsten oxide and the carbon material.

[0029] Embodiment 1: This embodiment is specifically obtained by the following operations:

[0030] S1, dispersing 5 g of carbon nanotubes and 1 g of polyvinyl alcohol aqueous adhesive into 100 g of deionized water to obtain an aqueous slurry;

[0031] S2. Add 1g of ammonium metatungstate, 2g of ammonium niobium oxalate, 5g of citric acid and 5g of dodecyltrimethylammonium bromide to 150g of deionized water, stir to dissolve, then add 50g of aqueous carbon slurry, stir evenly and immerse in graphite felt. Then carry out complexation reaction at 50°C for 2h. After the reaction is completed, dry at 100°C for 2h to obtain graphite felt loaded with niobium tungsten oxide precursor and carbon nanotubes;

[0032] S3, calcining the graphite felt loaded with the niobium tungsten oxide precursor and the carbon nanotubes at 400° C. for 2 h in air at a heating rate of 10° C. / min to obtain the graphite felt loaded with nitrogen-doped porous niobium tungsten oxide and carbon nanotubes;

[0033] Figure 1 This is a scanning electron microscope image of the graphite felt loaded with nitrogen-doped porous niobium tungsten oxide and carbon nanotubes in Example 1. It can be seen that the surface of the graphite felt is covered with a large amount of niobium tungsten oxide and carbon nanotubes, and the three are tightly combined. The surface of the niobium tungsten oxide has an obvious pore structure, which makes the active specific surface area larger;

[0034] Figure 2 (a), (b), (c), and (d) are scanning electron microscope images, N element distribution diagrams, Nb element distribution diagrams, and W element distribution diagrams of the nitrogen-doped porous niobium tungsten oxide and carbon nanotube graphite felt prepared in Example 1, respectively. It can be seen that the niobium tungsten oxide contains nitrogen doping, indicating that the addition of quaternary ammonium salt not only forms a porous structure in the niobium tungsten oxide, but also forms nitrogen doping in the oxide, thereby improving the catalytic efficiency.

[0035] Embodiment 2: This embodiment is obtained by the following operations:

[0036] S1. Dispersing 7.5 g of reduced graphene oxide and 3 g of polyurethane water-based adhesive into 100 g of deionized water to obtain an aqueous slurry;

[0037] S2. Add 2g of ammonium metatungstate, 4g of ammonium niobium oxalate, 10g of citric acid and 10g of tetradecyltrimethylammonium bromide to 150g of deionized water, stir to dissolve, then add 75g of aqueous carbon slurry, stir evenly and immerse in graphite felt. Then carry out complexation reaction at 60°C for 3h. After the reaction is completed, dry at 100°C for 2h to obtain graphite felt loaded with niobium tungsten oxide precursor and reduced graphene oxide;

[0038] S3. calcining the graphite felt loaded with niobium tungsten oxide precursor and reduced graphene oxide at 425° C. for 2.5 h in air at a heating rate of 10° C. / min to obtain graphite felt loaded with nitrogen-doped porous niobium tungsten oxide and reduced graphene oxide.

[0039] Embodiment 3: This embodiment is obtained by the following operations:

[0040] S1, dispersing 10g of carbon nanofibers and 5g of epoxy resin water-based adhesive into 100g of deionized water to obtain an aqueous slurry;

[0041] S2. Add 3g of ammonium metatungstate, 6g of ammonium niobium oxalate, 15g of citric acid and 15g of hexadecyltrimethylammonium bromide to 150g of deionized water, stir to dissolve, then add 100g of aqueous carbon slurry, stir evenly and immerse in graphite felt. Then carry out complexation reaction at 70°C for 4h. After the reaction is completed, dry at 100°C for 2h to obtain graphite felt loaded with niobium tungsten oxide precursor and carbon nanofibers;

[0042] S3. calcining the graphite felt loaded with the niobium tungsten oxide precursor and the carbon nanofibers at 425° C. for 2.5 h in air at a heating rate of 10° C. / min to obtain the graphite felt loaded with nitrogen-doped porous niobium tungsten oxide and carbon nanofibers.

[0043] Comparative Example 1: This comparative example is a blank control group, that is, untreated blank graphite felt is used. Figure 3 (a) and (b) are cyclic voltammetry curves when the graphite felt is used as the positive electrode in Comparative Example 1 and Example 1, respectively. Figure 3 (c) and (d) are the cyclic voltammetry curves when the graphite felt is used as the negative electrode in Comparative Example 1 and Example 1, respectively. Figure 3 It can be seen that the graphite felt loaded with nitrogen-doped porous niobium tungsten oxide and carbon nanotubes has a larger redox peak, indicating that the graphite felt loaded with catalyst has higher kinetic activity for the vanadium battery system and is beneficial to the redox reaction of vanadium ions.

[0044] Comparative Example 2: The preparation process of this comparative example is different from that of Example 1 only in that no aqueous carbon slurry is added in step S2.

[0045] Comparative Example 3: The preparation process of this comparative example is different from that of Example 1 only in that ammonium metatungstate and ammonium niobium oxalate are not added in step S2.

[0046] Comparative Example 4: The preparation process of this comparative example is different from that of Example 1 only in that no quaternary ammonium salt is added in step S2.

[0047] The graphite felts prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were assembled into battery stacks, and charge and discharge tests were performed under the same test conditions to record the battery coulombic efficiency, voltage efficiency, energy efficiency, and capacity retention rate after 100 cycles. The test results are shown in Table 1:

[0048] Table 1. Test results of graphite felt performance in examples and comparative examples

[0049]

[0050] As can be seen from Table 1, compared with Comparative Examples 1 to 3, Examples 1 to 3 have higher voltage efficiency, energy efficiency and capacity retention rate, mainly because the present invention combines carbon materials and metal oxides, the carbon materials improve the electrical conductivity of the metal oxides, form a conductive network on the surface of graphite felt, promote the transmission of electrons, and improve the voltage efficiency and energy efficiency of the battery, and the nitrogen-doped porous niobium tungsten oxide has a significant pore structure, which increases the specific surface area of ​​the metal oxide, provides more reactive centers for vanadium ions, and improves the capacity retention rate; compared with Comparative Example 4, Examples 1 to 3 have higher voltage efficiency, energy efficiency and capacity retention rate, mainly because the quaternary ammonium salt, in addition to being a porogen, also forms nitrogen doping in the niobium tungsten oxide after calcination, and nitrogen doping improves the electrical conductivity and catalytic performance of the metal oxide, thereby improving the voltage efficiency and energy efficiency of the battery, and the quaternary ammonium salt provides more nucleation sites for the in-situ growth of niobium tungsten oxide on the surface of carbon materials and graphite felt, solving the problem of uneven distribution of nanoparticles. At the same time, the adhesive enhances the interaction between the nanoparticles and the graphite felt, preventing the catalyst from falling off during the cycle and improving the capacity retention rate of the graphite felt.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high catalytically active graphite felt electrode for a vanadium battery, characterized in that: The following steps are involved: S1. dispersing the carbon material and the adhesive into deionized water to obtain an aqueous slurry; S2, adding ammonium metatungstate, ammonium niobium oxalate, citric acid and quaternary ammonium salt to deionized water, stirring to dissolve, then adding aqueous carbon slurry, stirring evenly, immersing graphite felt therein, then performing complex reaction, drying after the reaction is completed, and obtaining graphite felt loaded with niobium tungsten oxide precursor and carbon material; S3. calcining the graphite felt loaded with niobium tungsten oxide precursor and carbon material at high temperature to obtain graphite felt loaded with nitrogen-doped porous niobium tungsten oxide and carbon material; the calcination temperature is 400-450° C., and the calcination time is 2-3 hours.

2. The method for preparing a high catalytic activity graphite felt electrode for vanadium battery according to claim 1, characterized in that: In the step S1, the carbon material is one of carbon nanotubes, reduced graphene oxide, and carbon nanofibers.

3. The method for preparing a high catalytic activity graphite felt electrode for vanadium battery according to claim 1, characterized in that: The adhesive in step S1 is one of polyvinyl alcohol water-based adhesive, polyurethane water-based adhesive, and epoxy resin water-based adhesive.

4. The method for preparing a high catalytic activity graphite felt electrode for vanadium battery according to claim 1, characterized in that: In step S1, the mass ratio of the carbon material, the adhesive and the deionized water is (5-10): (1-5):

100.

5. The method for preparing a high catalytic activity graphite felt electrode for vanadium battery according to claim 1, characterized in that: In step S2, the quaternary ammonium salt is one of dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide.

6. The method for preparing a high catalytic activity graphite felt electrode for vanadium battery according to claim 1, characterized in that: In step S2, the mass ratio of ammonium metatungstate, ammonium niobium oxalate, citric acid, quaternary ammonium salt, water and aqueous slurry is (1-3): (2-6): (5-15): (5-15): 150: (50-100).

7. The method for preparing a high catalytic activity graphite felt electrode for vanadium battery according to claim 1, characterized in that: In step S2, the complexation reaction temperature is 50-70° C., and the reaction time is 2-4 hours.

8. A high catalytic activity graphite felt electrode for vanadium battery, characterized in that: The high catalytic activity graphite felt electrode is prepared by the preparation method of the high catalytic activity graphite felt electrode for vanadium battery as described in any one of claims 1 to 7.

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