Carbon-based metal oxide electrode material and capacitor

Abstract

The application relates to the technical field of capacitors, in particular to an electrode material based on carbon metal oxide and a capacitor. The electrode material is made of MOFs and benzoxazine monomers, and the weight ratio of the MOFs and the benzoxazine monomers is 1-5:1-5. The prepared electrode material has a higher specific capacitance value, a higher capacitance retention rate and good cycle stability.

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, specifically to an electrode material and capacitor based on carbon-based metal oxides. Background Technology

[0002] Supercapacitors typically consist of positive and negative electrodes, an electrolyte solution, and a separator. The electrodes are the core component of a supercapacitor, forming the basis for efficient electrochemical energy conversion and storage. Therefore, research on electrode materials is crucial for the development of supercapacitors.

[0003] Transition metal oxides (TMOs) are another major class of supercapacitor electrode materials, characterized by high specific capacitance, high energy density, and excellent pseudocapacitive properties. According to relevant literature, TMO electrodes can generate large specific capacitance and high energy density at low scan rates and low current densities. However, due to electronic structure defects, most TMOs exhibit very low conductivity. High resistivity increases sheet resistance and charge transfer resistance, especially at high current densities, leading to significant voltage losses and severely impacting practical applications. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes an electrode material and capacitor based on carbon-based metal oxides.

[0005] The technical solution adopted is as follows:

[0006] An electrode material based on carbon-based metal oxides is made of MOFs and benzoxazine monomers in a weight ratio of 1-5:1-5.

[0007] Furthermore, the MOFs are rare earth element modified Zn / Co-MOFs.

[0008] Furthermore, the preparation method of the rare earth element modified Zn / Co-MOFs is as follows:

[0009] Water-soluble zinc salt, water-soluble cobalt salt, nitrogen-containing heterocyclic ligand and polyaryl aromatic carboxylic acid ligand are added to an alcohol solvent and mixed well. The resulting mixture is then subjected to a solvothermal reaction at 120-140℃ for more than 4 hours. The product is collected and dispersed in an alcohol solvent. Water-soluble rare earth salt is added, and the mixture is heated to reflux for more than 24 hours.

[0010] Furthermore, the water-soluble rare earth salt is a water-soluble terbium salt or a water-soluble europium salt.

[0011] Furthermore, the molar ratio of the water-soluble zinc salt, water-soluble cobalt salt, and water-soluble rare earth salt is 1:2:0.1-0.5.

[0012] Furthermore, the molar ratio of the nitrogen-containing heterocyclic ligand to the polyaryl aromatic carboxylic acid ligand is 1-5:1-5.

[0013] Furthermore, the structural formula of the benzoxazine monomer is shown below:

[0014]

[0015] Wherein, R is any one of hydrogen, hydroxyl, carboxyl, amino, cyano, or sulfonic acid groups.

[0016] Furthermore, the benzoxazine monomer is one of the following compounds:

[0017]

[0018]

[0019] Furthermore, the preparation method of the above-mentioned carbon-based metal oxide-based electrode material is as follows:

[0020] The benzoxazine monomer was dissolved in a mixed solvent of N,N-dimethylformamide and n-propanol, and MOFs were added. The mixture was ultrasonically vibrated for more than 30 minutes, and the solvent was removed by vacuum evaporation to obtain the precursor. The precursor was heated to 200-250℃ and kept at that temperature for 1-3 hours. Then, under nitrogen protection, the temperature was raised to 550-600℃ and kept at that temperature for 1-3 hours. The resulting product was mixed with KOH and ground. Then, under a mixed atmosphere of nitrogen and hydrogen, the temperature was raised to 850-950℃ and kept at that temperature for 1-3 hours. The product was washed with water until neutral and then dried.

[0021] The present invention also provides a capacitor comprising the above-described carbon-based metal oxide-based electrode material.

[0022] The beneficial effects of this invention are:

[0023] This invention provides an electrode material based on carbon-based metal oxides. Rare earth element-modified Zn / Co-MOFs serve as the core, and rare earth element-doped Zn / Co bimetallic oxides are obtained during carbonization. Compared with monometals, bimetallic oxides have more redox reaction sites and generate larger ion transport channels, thereby significantly improving the electrochemical activity of the material. By using covalent post-synthesis modification to modify the framework of organic ligands in MOFs with rare earth elements, the porosity is increased while maintaining the original topology. Rare earth elements play a good role in regulating the electronic properties of bimetallic oxides, and the resulting carbonized products have more tunable valence sites, better conductivity, and higher stability.

[0024] The introduction of polyaryl aromatic carboxylic acid ligands overcomes the disadvantage of unstable skeletons when using nitrogen-containing heterocyclic ligands alone. The rigid groups strengthen the skeleton structure of MOFs, and the carboxylic acid can combine with rare earth elements to form a stable skeleton structure, thus exhibiting coordination diversity.

[0025] The polymer of benzoxazine monomer after thermosetting is coated on the surface of MOFs. After carbonization, it exhibits a certain spherical morphology, with extremely high specific surface area and hierarchical porous structure. These structural characteristics are beneficial to the improvement of conductivity, ion / mass transport, charge or ion aggregation at the electrode-electrolyte interface, and the generation of pseudocapacitance, thus giving the material high capacitance performance.

[0026] Adding KOH for activation can generate a large amount of gas during carbonization. At high temperatures, these gases etch carbon materials and expand the pore volume, thereby increasing the contact area between the electrolyte and the pores, enhancing the double layer effect, and improving electrochemical activity. Hydrogen has strong reducing properties, and carbonization in a mixed atmosphere of nitrogen and hydrogen can reduce some metal ions to a lower valence state. At the same time, oxygen vacancies are introduced into the generated bimetallic oxide, thereby improving conductivity.

[0027] Tests have shown that the electrode material prepared by this invention has a high specific capacitance value and a high capacitance retention rate, exhibiting good cycle stability. Attached Figure Description

[0028] Figure 1 The image shows a SEM image of the electrode material prepared in Example 1.

[0029] Figure 2 This is a magnified SEM image of the electrode material prepared in Example 1. Detailed Implementation

[0030] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0031] Example 1:

[0032] A method for preparing electrode materials based on carbon-based metal oxides:

[0033] 5.68 g zinc nitrate (0.03 mol), 10.97 g cobalt nitrate (0.06 mol), 12.32 g 2-methylimidazole (0.15 mol), and 24.9 g terephthalic acid (0.15 mol) were added to 250 ml methanol and mixed well. The resulting mixture was transferred to a polytetrafluoroethylene reactor, sealed, and heated to 135 °C for a solvothermal reaction for 8 h. The product was collected, washed with methanol, dried, and added to 500 ml methanol. The mixture was ultrasonically dispersed for 30 min, and then 0.005 mol terbium nitrate was added. The mixture was heated to reflux and reacted for 48 h to obtain Tb-modified Zn / Co-MOFs.

[0034] 1.5 mol paraformaldehyde, 750 mmol furfural and 100 ml toluene were added to a three-necked flask and stirred at room temperature for 1 h. Then 750 mmol m-methylphenol was dissolved in 200 ml toluene and added. The mixture was stirred and refluxed for 6 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction solution was washed three times with deionized water. 3 L of n-hexane was added dropwise to the organic phase. The mixture was cooled to 5 °C and stirred to crystallize for 10 h. The mixture was filtered, the product was collected and dried to obtain benzoxazine monomer.

[0035]

[0036] 10g of benzoxazine monomer was dissolved in a mixed solvent consisting of 50ml of N,N-dimethylformamide and 50ml of n-propanol. Then, 10g of Tb-modified Zn / Co-MOFs were added. The mixture was ultrasonically vibrated for 45min, and the solvent was removed by vacuum evaporation to obtain the precursor. The precursor was heated to 200℃ and held for 2h for curing. Then, under nitrogen protection, the temperature was raised to 600℃ and held for 2h. The obtained product was mixed with 40g of KOH and ground evenly. Then, under a mixed atmosphere of nitrogen and hydrogen in a volume ratio of 5:1, the temperature was raised to 950℃ and held for 2h. The product was washed with water until neutral and then dried.

[0037] Example 2:

[0038] A method for preparing electrode materials based on carbon-based metal oxides:

[0039] 5.68 g zinc nitrate (0.03 mol), 10.97 g cobalt nitrate (0.06 mol), 12.32 g 2-methylimidazole (0.15 mol), and 24.9 g terephthalic acid (0.15 mol) were added to 250 ml methanol and mixed well. The resulting mixture was transferred to a polytetrafluoroethylene reactor, sealed, and heated to 135 °C for a solvothermal reaction for 8 h. The product was collected, washed with methanol, dried, and added to 500 ml methanol. The mixture was ultrasonically dispersed for 30 min, and then 0.005 mol terbium nitrate was added. The mixture was heated to reflux and reacted for 48 h to obtain Tb-modified Zn / Co-MOFs.

[0040] 1.5 mol paraformaldehyde, 750 mmol furfural and 100 ml toluene were added to a three-necked flask and stirred at room temperature for 1 h. Then 750 mmol m-methylphenol was dissolved in 200 ml toluene and added. The mixture was stirred and refluxed for 6 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction solution was washed three times with deionized water. 3 L of n-hexane was added dropwise to the organic phase. The mixture was cooled to 5 °C and stirred to crystallize for 10 h. The mixture was filtered, the product was collected and dried to obtain benzoxazine monomer.

[0041]

[0042] 10g of benzoxazine monomer was dissolved in a mixed solvent of 50ml N,N-dimethylformamide and 50ml n-propanol. Then, 10g of Tb-modified Zn / Co-MOFs were added. The mixture was ultrasonically vibrated for 45min, and the solvent was removed by vacuum evaporation to obtain the precursor. The precursor was heated to 250℃ and cured for 3h. Then, under nitrogen protection, the temperature was raised to 600℃ and kept for 3h. The obtained product was mixed with 40g of KOH and ground evenly. Then, under a mixed atmosphere of nitrogen and hydrogen in a volume ratio of 5:1, the temperature was raised to 950℃ and kept for 3h. The product was washed with water until neutral and then dried.

[0043] Example 3:

[0044] A method for preparing electrode materials based on carbon-based metal oxides:

[0045] 5.68 g zinc nitrate (0.03 mol), 10.97 g cobalt nitrate (0.06 mol), 12.32 g 2-methylimidazole (0.15 mol), and 24.9 g terephthalic acid (0.15 mol) were added to 250 ml methanol and mixed well. The resulting mixture was transferred to a polytetrafluoroethylene reactor, sealed, and heated to 135 °C for a solvothermal reaction for 8 h. The product was collected, washed with methanol, dried, and added to 500 ml methanol. The mixture was ultrasonically dispersed for 30 min, and then 0.005 mol terbium nitrate was added. The mixture was heated to reflux and reacted for 48 h to obtain Tb-modified Zn / Co-MOFs.

[0046] 1.5 mol paraformaldehyde, 750 mmol furfural and 100 ml toluene were added to a three-necked flask and stirred at room temperature for 1 h. Then 750 mmol m-methylphenol was dissolved in 200 ml toluene and added. The mixture was stirred and refluxed for 6 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction solution was washed three times with deionized water. 3 L of n-hexane was added dropwise to the organic phase. The mixture was cooled to 5 °C and stirred to crystallize for 10 h. The mixture was filtered, the product was collected and dried to obtain benzoxazine monomer.

[0047]

[0048] 10g of benzoxazine monomer was dissolved in a mixed solvent of 50ml N,N-dimethylformamide and 50ml n-propanol. Then, 10g of Tb-modified Zn / Co-MOFs were added. The mixture was ultrasonically vibrated for 45min, and the solvent was removed by vacuum evaporation to obtain the precursor. The precursor was heated to 250℃ and cured for 1h. Then, under nitrogen protection, the temperature was raised to 600℃ and kept for 1h. The obtained product was mixed with 40g of KOH and ground evenly. Then, under a mixed atmosphere of nitrogen and hydrogen in a volume ratio of 5:1, the temperature was raised to 850℃ and kept for 3h. The product was washed with water until neutral and then dried.

[0049] Comparative Example 1:

[0050] The method is basically the same as in Example 1, except that Zn / Co-MOFs are used instead of Tb to modify Zn / Co-MOFs;

[0051] The preparation method of Zn / Co-MOFs is as follows:

[0052] 5.68 g zinc nitrate (0.03 mol), 10.97 g cobalt nitrate (0.06 mol), 12.32 g 2-methylimidazole (0.15 mol) and 24.9 g terephthalic acid (0.15 mol) were added to 250 ml methanol and mixed well. The resulting mixture was transferred to a polytetrafluoroethylene reactor, sealed, and heated to 135 °C for a solvothermal reaction for 8 h. The product was collected, washed with methanol, and dried.

[0053] Comparative Example 2:

[0054] The example is basically the same as in Example 1, except that polystyrene is used instead of benzoxazine monomer.

[0055] The preparation method of the electrode material is as follows:

[0056] 5.68 g zinc nitrate (0.03 mol), 10.97 g cobalt nitrate (0.06 mol), 12.32 g 2-methylimidazole (0.15 mol), and 24.9 g terephthalic acid (0.15 mol) were added to 250 ml methanol and mixed well. The resulting mixture was transferred to a polytetrafluoroethylene reactor, sealed, and heated to 135 °C for a solvothermal reaction for 8 h. The product was collected, washed with methanol, dried, and added to 500 ml methanol. The mixture was ultrasonically dispersed for 30 min, and then 0.005 mol terbium nitrate was added. The mixture was heated to reflux and reacted for 48 h to obtain Tb-modified Zn / Co-MOFs.

[0057] Dissolve 10g of polystyrene in 100ml of toluene, then add 10g of Tb-modified Zn / Co-MOFs, sonicate for 45min, remove the solvent under reduced pressure to obtain the precursor, heat the precursor to 200℃ and keep it at that temperature for 2h, then heat it to 600℃ and keep it at that temperature for 2h under nitrogen protection, mix the obtained product with 40g of KOH and grind it evenly, then heat it to 950℃ and keep it at that temperature for 2h under a mixed atmosphere of nitrogen and hydrogen in a volume ratio of 5:1, wash the product with water until neutral and then dry it.

[0058] Performance testing:

[0059] The electrochemical performance of the electrode materials prepared in Examples 1-3 and Comparative Examples 1-2 of this invention was tested using a three-electrode system.

[0060] The working electrode was prepared by dissolving electrode materials (mass ratio 8:1:1), acetylene black, and polytetrafluoroethylene in ethanol, grinding and mixing them, coating them onto 1cm×1cm nickel foam, and then drying and compacting them. A saturated calomel electrode was used as the reference electrode, a platinum sheet as the counter electrode, and 1mol / L H2SO4 as the electrolyte to form a three-electrode system. The specific capacitance of the three-electrode system at a current density of 1A / g and the capacitance retention rate after 10,000 cycles were tested using a CH1760D electrochemical workstation. The test results are shown in Table 1.

[0061] Table 1:

[0062]

[0063] As shown in Table 1 above, the electrode material prepared by the present invention has a high specific capacitance value and a high capacitance retention rate, exhibiting good cycle stability.

[0064] A comparison of the data from Example 1 and Comparative Example 1 shows that Tb modification plays a positive role in improving the specific capacitance and cycle stability of the electrode material. This may be because Tb atoms play a good role in regulating the electronic properties of metal oxides, and the resulting carbide products have more tunable valence sites, better conductivity, and higher stability.

[0065] A comparison of the data from Example 1 and Comparative Example 2 shows that the carbonized product after curing benzoxazine monomer is more suitable as an electrode material for capacitors than polystyrene.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrode material based on carbon-based metal oxides, characterized in that, It is made of MOFs and benzoxazine monomers in a weight ratio of 1-5:1-5; The MOFs are rare earth element modified Zn / Co-MOFs; The benzoxazine monomer is one of the following compounds: The preparation method of the rare earth element modified Zn / Co-MOFs is as follows: Water-soluble zinc salt, water-soluble cobalt salt, nitrogen-containing heterocyclic ligand and polyaryl aromatic carboxylic acid ligand are added to an alcohol solvent and mixed well. The resulting mixture is then subjected to a solvothermal reaction at 120-140℃ for more than 4 hours. The product is collected and dispersed in an alcohol solvent. Water-soluble rare earth salt is added, and the mixture is heated to reflux for more than 24 hours. The water-soluble rare earth salt is a water-soluble terbium salt or a water-soluble europium salt; The electrode material is prepared as follows: The benzoxazine monomer was dissolved in a mixed solvent of N,N-dimethylformamide and n-propanol, and MOFs were added. The mixture was ultrasonically vibrated for more than 30 minutes, and the solvent was removed by vacuum evaporation to obtain the precursor. The precursor was heated to 200-250℃ and kept at that temperature for 1-3 hours. Then, under nitrogen protection, the temperature was raised to 550-600℃ and kept at that temperature for 1-3 hours. The resulting product was mixed with KOH and ground. Then, under a mixed atmosphere of nitrogen and hydrogen, the temperature was raised to 850-950℃ and kept at that temperature for 1-3 hours. The product was washed with water until neutral and then dried.

2. The electrode material based on carbon-based metal oxides as described in claim 1, characterized in that, The molar ratio of the water-soluble zinc salt, water-soluble cobalt salt, and water-soluble rare earth salt is 1:2:0.1-0.

5.

3. The electrode material based on carbon-based metal oxides as described in claim 1, characterized in that, The molar ratio of the nitrogen-containing heterocyclic ligand to the polyaryl aromatic carboxylic acid ligand is 1-5:1-5.

4. A capacitor, characterized in that, Including the carbon-based metal oxide-based electrode material as described in any one of claims 1-3.

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