Composite electrode materials, their preparation methods, applications, and supercapacitors

Abstract

This invention discloses a composite electrode material, its preparation method, applications, and a supercapacitor. The preparation method of the composite electrode material includes the following steps: 1) mixing a nickel salt, an iron salt, and a dicarboxylic acid ligand in an aqueous solution of a polar solvent to obtain precursor solution A; 2) adding a coordination competition modifier to precursor solution A to obtain precursor solution B; 3) subjecting precursor solution B to a solvothermal reaction at 80–200°C for 5–24 h, followed by cooling to obtain a solid product; washing and drying the solid product to obtain the composite electrode material. The composite electrode material prepared by this invention possesses high BET specific surface area, high specific capacitance, low internal resistance, and high cycling stability.

Description

Technical Field

[0001] This invention relates to a composite electrode material, its preparation method, its uses, and a supercapacitor. Background Technology

[0002] Supercapacitors, also known as electrochemical capacitors, gold capacitors, or farad capacitors, A supercapacitor is a novel energy storage device that falls between traditional capacitors and rechargeable batteries. It possesses the rapid charging and discharging characteristics of capacitors while also exhibiting the energy storage properties of batteries. The electrodes, as the core components of a supercapacitor, directly determine its capacitance, energy density, power density, and cycle life. The energy storage of a supercapacitor primarily relies on the physical adsorption of the electric double layer at the electrode / electrolyte interface or rapid, reversible redox reactions on the electrode surface.

[0003] Metal-organic frameworks (MOFs) are a class of crystalline porous materials with a periodic network structure, formed by the self-assembly of inorganic metal centers (metal ions or metal clusters) and bridging organic ligands. Due to their ultra-high specific surface area and porous framework, these materials offer advantages such as rapid mass transfer and numerous active sites. Furthermore, MOFs can simultaneously provide both metal centers and ligands as active sites, making them widely used in the fabrication of electrode materials.

[0004] CN118668226A discloses a method for preparing CQD-doped nickel-iron MOF composite electrocatalytic materials on the surface of nickel foam. The method includes the following steps: 1) ultrasonically cleaning and drying the nickel foam; 2) preparing a mixed solution of ferric citrate and thiophene dicarboxylic acid; 3) immersing the nickel foam treated in step 1) in the mixed solution of step 2) and ultrasonically cleaning it for 10 min, then transferring it to a reaction vessel lined with polytetrafluoroethylene (PTFE), and then placing the reaction vessel in a forced-air drying oven for reaction; 4) after the reaction, removing the reacted nickel foam, cleaning and drying it, finally obtaining a CQD-doped nickel-iron MOF composite electrocatalytic material on the nickel foam. This method uses nickel foam as the nickel source and ferric citrate as the iron source and CQD source to prepare a composite electrocatalytic material with good catalytic activity.

[0005] CN111744519A discloses a method for continuous aqueous preparation of MOF materials using centrifugal technology. The method includes the following steps: S1, weighing a metal salt and dissolving it in a deionized aqueous solution at room temperature, denoted as reaction solution A; S2, weighing an organic ligand and dissolving it in an alkaline solution at room temperature, denoted as reaction solution B; S3, turning on the centrifugal reactor and simultaneously introducing reaction solution A and reaction solution B into the centrifugal reactor via a peristaltic pump to carry out a precipitation and crystallization reaction; obtaining a MOF material suspension; the centrifugal reactor is selected from an external circulation rotating packed bed reactor; S4, centrifuging, washing, activating, and drying the suspension to obtain MOF products. The product obtained by this method has high crystallinity, large specific surface area, uniform distribution of spherical particles, and regular morphology. However, this method requires a centrifugal reactor, placing stringent requirements on the reaction equipment and conditions.

[0006] NiFe electrodes are electrodes using nickel-iron (Ni-Fe) based materials as active materials. These electrode materials have become a research hotspot for high-performance capacitor electrodes due to their high theoretical specific capacitance, abundant redox activity, low cost, and environmental friendliness. NiFe-MOF electrode materials, prepared by applying MOFs to NiFe electrodes, combine the advantages of both NiFe electrodes and MOFs, showing broad application prospects. However, existing NiFe-MOF electrode materials suffer from technical problems when used as supercapacitor electrodes, including poor conductivity, excessive ligand embedding of metal active sites, and low energy density due to obstructed ion transport channels. Summary of the Invention

[0007] In view of this, one object of the present invention is to provide a method for preparing a composite electrode material, wherein the obtained composite electrode material has a high BET specific surface area and specific capacitance, a low charge transfer resistance, and good cycle stability. Another object of the present invention is to provide a composite electrode material obtained by the above method. A further object of the present invention is to provide an application of the above-mentioned composite electrode material in the preparation of a supercapacitor. Yet another object of the present invention is to provide a supercapacitor.

[0008] The present invention achieves the above objectives using the following technical solutions.

[0009] On one hand, the method for preparing the composite electrode material provided by the present invention includes the following steps: 1) Nickel salt, iron salt, and dicarboxylic acid ligand are mixed in an aqueous solution of a polar solvent to obtain precursor solution A; wherein the dicarboxylic acid ligand is selected from at least one of 2,5-thiophene dicarboxylic acid, terephthalic acid, 2,5-furan dicarboxylic acid, 2,5-pyrrole dicarboxylic acid, 3,7-dibenzothiophene dicarboxylic acid, and benzimidazole 5,6-dicarboxylic acid; the molar ratio of nickel in the nickel salt, iron in the iron salt, and dicarboxylic acid ligand is 2-6:1:3-8; in the aqueous solution of the polar solvent, the volume ratio of the polar solvent to water is 1-5:1, and the polar solvent is selected from at least one of DMF, DEF, DMSO, NMP, methanol, and ethanol; the amount of the polar solvent used is 5-20 mL, based on 1 mmol / L of dicarboxylic acid ligand; 2) Add the coordination competition modifier to the precursor solution A and mix to obtain the precursor solution B; wherein the coordination competition modifier is selected from at least one of trifluoroacetic acid, perfluorobutyric acid, formic acid, acetic acid, propionic acid, and n-butyric acid; the molar ratio of the coordination competition modifier to the dicarboxylic acid ligand is 0.15 to 0.27:1; 3) The precursor solution B is subjected to a solvothermal reaction at 80-200℃ for 5-24 hours, and then cooled to obtain a solid product; the solid product is washed and dried to obtain the composite electrode material.

[0010] According to the preparation method of the present invention, preferably, in step 1), the nickel salt is selected from at least one of nickel nitrates, sulfates, halides, and acetates; the iron salt is selected from at least one of iron nitrates, sulfates, halides, and acetates.

[0011] According to the preparation method of the present invention, preferably, in step 1), the molar ratio of nickel in the nickel salt, iron in the iron salt and dicarboxylic acid ligand is 2.5-5.5:1:3.5-6.5; and the amount of polar solvent used is 7-18 mL based on 1 mmol / L of dicarboxylic acid ligand.

[0012] According to the preparation method of the present invention, preferably, in step 2), the molar ratio of the coordination competition modifier to the dicarboxylic acid ligand is 0.16 to 0.25:1.

[0013] According to the preparation method of the present invention, preferably, in step 3), the temperature of the solvothermal reaction is 90-150°C and the time is 8-20h.

[0014] According to the preparation method of the present invention, preferably, in step 3), the washing is performed by alternating centrifugal washing with water and C2-C5 alkyl alcohols.

[0015] According to the preparation method of the present invention, preferably, in step 3), the drying temperature is 40-120°C and the time is 12-48h.

[0016] On the other hand, the present invention also provides a composite electrode material prepared by any of the above-mentioned preparation methods, preferably, the BET specific surface area of ​​the composite electrode material is at least 130 m². 2 ·g -1 The composite electrode material at 1 A·g -1 The specific capacitance at current density is at least 2300 F·g -1 The charge transfer resistance of the composite electrode material is at most 0.65Ω.

[0017] Furthermore, the invention also provides an application of the aforementioned composite electrode material in the fabrication of supercapacitors.

[0018] In another aspect, the present invention also provides a supercapacitor comprising the above-mentioned composite electrode material.

[0019] This invention introduces a coordination competition modifier into NiFe-MOF electrode material, precisely constructing ligand defects in the crystal lattice, thereby enabling the prepared composite electrode material to possess high BET specific surface area, high specific capacitance, low internal resistance, and high cycling stability. Attached Figure Description

[0021] Figure 1 The image shows the SEM image of the composite electrode material in Experiment Example 1; where (a) is Ni 0.67 Fe 0.33 -MOF, (b) is Ni 0.67 Fe 0.33 -MOF-1, (c) is Ni 0.67 Fe 0.33 -MOF-2, (d) is Ni 0.67 Fe 0.33 -MOF-3, (e) is Ni 0.67 Fe 0.33 -MOF-4.

[0022] Figure 2 The image shows the X-ray diffraction pattern of the composite electrode material in Experiment Example 1.

[0023] Figure 3 The Fourier transform infrared spectrum of the composite electrode material in Experiment Example 1 is shown.

[0024] Figure 4 The image shows the Raman spectrum of the composite electrode material in Experiment Example 1.

[0025] Figure 5 The image shows the X-ray photoelectron spectrum of the composite electrode material in Experiment Example 1.

[0026] Figure 6The X-ray photoelectron spectra of each element in the composite electrode material in Experimental Example 1 are shown below; where (a) is C 1s, (b) is S 2p, (c) is Ni 2p, (d) is Fe 2p, (e) is O 1s, and (f) is F 1s.

[0027] Figure 7 The image shows the nuclear magnetic resonance spectrum of the composite electrode material in Experimental Example 1; where (a) is the dissolution / 1 H NMR spectrum, (b) shows the dissolution / dissolution of the composite electrode material. 19 F NMR spectrum.

[0028] Figure 8 The image shows the electron paramagnetic resonance spectrum of the composite electrode material in Experiment Example 1.

[0029] Figure 9 The thermogravimetric analysis diagram of the composite electrode material in Experiment Example 1 is shown.

[0030] Figure 10 The image shows the N2 adsorption-desorption isotherm of the composite electrode material in Experiment Example 1.

[0031] Figure 11 This is a pore size distribution diagram of the composite electrode material in Experiment Example 1.

[0032] Figure 12 The cyclic voltammetry curve (10 mV·s) of the composite electrode material in Experiment Example 2. -1 ).

[0033] Figure 13 The constant current charge-discharge curve (1 A·g) of the composite electrode material in Experimental Example 2. -1 ).

[0034] Figure 14 The rate performance curve of the composite electrode material in Experiment Example 2 is shown.

[0035] Figure 15 The specific capacitance (1 A·g) of the composite electrode material in Experimental Example 2 -1 ).

[0036] Figure 16 To apply the supercapacitor in Experiment Example 1 at 100 mV·s -1 Cyclic voltammetry curves at scan rate.

[0037] Figure 17 To apply the supercapacitor in Experiment Example 1 at 1 A·g -1 Constant current charge-discharge curves at current density.

[0038] Figure 18Cyclic voltammetry curves of the supercapacitor prepared from the composite electrode material of Example 1 in Experiment 1 at different scan rates.

[0039] Figure 19 The constant current charge-discharge curves of the supercapacitor made from the composite electrode material of Example 1 in Experiment 1 are shown at different current densities.

[0040] Figure 20 This is a Lagrangian diagram of the supercapacitor used in Experiment Example 1.

[0041] Figure 21 To apply the supercapacitor in Experiment Example 1 at 5 A·g -1 Capacity retention rate of constant current charge-discharge curves after 10,000 cycles at current density.

[0042] Figure 22 The following figures show the EIS impedance detection results of the supercapacitor used in Experiment Example 1. Figure a shows the Nyquist plot of the supercapacitor, with the inset showing an enlarged view of the high-frequency region and the equivalent circuit model. Figure b shows the relationship between the real capacitance of the supercapacitor and the frequency. Figure c shows the relationship between the imaginary capacitance of the supercapacitor and the frequency. Figure d shows the relationship between the phase angle of the supercapacitor and the frequency.

[0043] Figure 23 The image shows the LED light panel illuminated by the supercapacitor made from the composite electrode material of Example 1 in Experimental Example 2. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0046] The "BET specific surface area" mentioned in this invention refers to the total internal and external surface area per unit mass of material, with units of m². 2 ·g -1 (grams per square meter); this value was determined based on the BET theory using the nitrogen adsorption-desorption method.

[0047] The "specific capacitance" mentioned in this invention refers to the capacitance value per unit mass of electrode material, with units of F·g. -1 (Faramec).

[0048] The "charge transfer resistance" mentioned in this invention refers to the dynamic resistance that needs to be overcome for charge to transfer across the phase boundary at the electrode interface, and the unit is Ω (ohm).

[0049] The "capacity retention rate" mentioned in this invention refers to the ratio of the remaining usable capacity of a battery to its initial capacity after a certain number of charge-discharge cycles.

[0050] <Preparation Methods of Composite Electrode Materials> This invention addresses the shortcomings of existing MOF materials in supercapacitor applications, such as poor conductivity and insufficient exposure of active sites leading to low energy density. By introducing a coordination competition modifier with strong electron-withdrawing properties during the solvothermal synthesis of NiFe-MOF, and utilizing its competitive coordination with the host ligand, ligand defects are precisely constructed in the crystal lattice. This significantly widens the ion transport channels and exposes a large number of highly active coordination unsaturated metal centers while maintaining structural stability. The resulting composite electrode material possesses high BET specific surface area, high specific capacitance, low internal resistance, and high cycling stability.

[0051] The preparation method of the composite electrode material of the present invention includes a first mixing step, a second mixing step, and a solvothermal reaction step. These are described in detail below.

[0052] First mixing step Nickel salt, iron salt and dicarboxylic acid ligand are added to an aqueous solution of a polar solvent and mixed to obtain precursor solution A.

[0053] According to one embodiment of the present invention, the nickel salt may be selected from at least one of nickel nitrates, sulfates, halides, and acetates, preferably at least one of nickel nitrates, sulfates, and halides, and more preferably at least one of nickel nitrates, sulfates, chlorides, and bromides. The iron salt may be selected from at least one of iron nitrates, sulfates, halides, and acetates, preferably at least one of iron nitrates, sulfates, and halides, and more preferably at least one of iron nitrates, sulfates, chlorides, and bromides. In the present invention, the nickel salt and iron salt may be anhydrous salts or hydrated salts.

[0054] According to one embodiment of the present invention, the dicarboxylic acid ligand may be selected from at least one of 2,5-thiophene dicarboxylic acid, terephthalic acid, 2,5-furandicarboxylic acid, 2,5-pyrroledicarboxylic acid, 3,7-dibenzothiophene dicarboxylic acid, and benzimidazole 5,6-dicarboxylic acid, preferably at least one of 2,5-thiophene dicarboxylic acid, terephthalic acid, 2,5-furandicarboxylic acid, and 2,5-pyrroledicarboxylic acid, more preferably at least one of 2,5-thiophene dicarboxylic acid, 2,5-furandicarboxylic acid, and 2,5-pyrroledicarboxylic acid.

[0055] According to one embodiment of the present invention, the polar solvent in the aqueous solution can be selected from at least one of DMF (N,N-dimethylformamide), DEF (N,N-diethylformamide), DMSO (dimethyl sulfoxide), NMP (N-methylpyrrolidone), methanol, and ethanol, preferably at least one of DMF, DEF, DMSO, and NMP, and more preferably at least one of DMF, DEF, and DMSO. In the present invention, the volume ratio of the polar solvent to water can be 1 to 5:1, preferably 1.5 to 4.5:1, and more preferably 2 to 4:1. Such an aqueous solution of polar solvent is beneficial for dissolving nickel salts, iron salts, and dicarboxylic acid ligands, and is more conducive to forming structurally stable composite electrode materials.

[0056] According to one embodiment of the present invention, the molar ratio of nickel in the nickel salt, iron in the iron salt, and the dicarboxylic acid ligand can be 2–6:1:3–8, preferably 2.5–5.5:1:3.5–6.5, and more preferably 3–5:1:4–6. Based on 1 mmol / L of the dicarboxylic acid ligand, the amount of polar solvent can be 5–20 mL, preferably 7–18 mL, and more preferably 8–15 mL. This ratio is beneficial for forming a more structurally stable composite electrode material.

[0057] In this invention, the water used in each step can be at least one of deionized water, ultrapure water, and double-distilled water; preferably at least one of deionized water and ultrapure water, more preferably deionized water or ultrapure water.

[0058] Second mixing step The coordination competition regulator was added to precursor solution A and mixed to obtain precursor solution B.

[0059] According to one embodiment of the present invention, the coordination competition modifier may be selected from at least one of trifluoroacetic acid, perfluorobutyric acid, formic acid, acetic acid, propionic acid, and n-butyric acid, preferably at least one of trifluoroacetic acid, perfluorobutyric acid, formic acid, and acetic acid, and more preferably at least one of trifluoroacetic acid and perfluorobutyric acid.

[0060] According to one embodiment of the present invention, the molar ratio of the coordination competition modifier to the dicarboxylic acid ligand can be 0.15 to 0.27:1, preferably 0.16 to 0.25:1, and more preferably 0.18 to 0.22:1.

[0061] Limiting the coordination competition modifier and its dosage within the aforementioned range facilitates the competitive coordination between the modifier and the main ligand (dicarboxylic acid ligand), leading to the formation of ligand defects within the composite electrode material. This results in a three-dimensional nanoflower-like framework structure in the composite electrode material. This microstructure increases the contact between the material and electrolyte ions, significantly improving the BET specific surface area and specific capacitance of the composite electrode material, reducing its charge transfer resistance, and enhancing its cycle stability.

[0062] Solvothermal reaction steps The precursor solution B was subjected to a solvothermal reaction at 80–200 °C for 5–24 h, and then cooled to obtain a solid product. The solid product was washed and dried to obtain the composite electrode material.

[0063] According to one embodiment of the present invention, the temperature of the solvothermal reaction can be 80–200°C, preferably 90–150°C, and more preferably 100–130°C. The time of the solvothermal reaction can be 5–24 h, preferably 8–20 h, and more preferably 10–18 h. Reasonable solvothermal temperature and time are beneficial for the competitive coordination between the coordination modifier and the main ligand (dicarboxylic acid ligand), leading to the formation of ligand defects within the composite electrode material. This is more conducive to increasing the BET specific surface area and specific capacitance of the composite electrode material, reducing the charge transfer resistance of the composite electrode material, and improving the cycle stability of the composite electrode material.

[0064] In this invention, the solvothermal reaction can be carried out in a high-pressure reactor.

[0065] In this invention, cooling can be achieved using any cooling method or device known in the art, and no particular limitation is made here. For example, it can be natural cooling or air cooling. According to a preferred embodiment of the invention, cooling can be achieved to room temperature (25°C).

[0066] According to a preferred embodiment of the present invention, washing can be performed by alternating centrifugal washing with water and C2-C5 alkyl alcohols. In this invention, the C2-C5 alkyl alcohols can be C2-C4 alkyl alcohols, preferably C2-C3 alkyl alcohols, and more preferably at least one of ethanol and isopropanol. In this invention, one wash using water or a C2-C5 alkyl alcohol alone is counted as one wash; for example, one wash using water or a C2-C5 alkyl alcohol alternately is counted as two washes. The total number of washes can be 2-6 times, preferably 2-5 times, and more preferably 3-5 times.

[0067] In this invention, the rotation speed for each centrifugal wash can be 5000-15000 rpm, preferably 6000-12000 rpm, and more preferably 6500-10000 rpm. The time for each centrifugal wash can be 3-20 min, preferably 5-15 min, and more preferably 8-12 min.

[0068] According to one embodiment of the present invention, the drying temperature can be 40–120°C, preferably 50–100°C, and more preferably 55–90°C. The drying time can be 12–48 hours, preferably 18–40 hours, and more preferably 20–32 hours. Drying can be carried out using any drying equipment known in the art, which will not be described in detail here. For example, a vacuum oven can be used.

[0069] Reasonable drying conditions are conducive to the formation of a three-dimensional nanoflower framework structure in composite electrode materials, which is more conducive to improving the BET specific surface area and specific capacitance of composite electrode materials, reducing the charge transfer resistance of composite electrode materials, and improving the cycle stability of composite electrode materials.

[0071] <Composite Electrode Materials> The composite electrode material of the present invention is prepared by the above method.

[0072] The composite electrode material of this invention exhibits a three-dimensional nanoflower framework structure due to the competitive coordination between the coordination modifier and the host ligand (dicarboxylic acid ligand). This results in ligand defects forming within the material. Such a composite electrode material can significantly increase its BET specific surface area, effectively widening ion transport channels and greatly reducing charge transfer resistance. The ligand defects transform previously saturated metal nodes into a coordination-unsaturated state, exposing a large number of highly active Ni / Fe centers, directly driving a significant leap in the specific capacitance of the composite electrode material.

[0073] According to one embodiment of the present invention, the BET specific surface area of ​​the composite electrode material can be at least 130 m². 2 ·g -1 Preferably at least 132m 2 ·g -1 More preferably at least 135m 2 ·g -1 Composite electrode materials at 1 A·g -1 The specific capacitance at current density can be at least 2300 F·g -1 Preferably, it is at least 2350 F·g -1 More preferably at least 2380 F·g -1 The charge transfer resistance of the composite electrode material can be at most 0.65Ω, preferably at most 0.63Ω, and more preferably at most 0.6Ω.

[0075] <Applications and Supercapacitors> The present invention also provides an application of the above-mentioned composite electrode material in the fabrication of a supercapacitor. The present invention further provides a supercapacitor comprising the above-mentioned composite electrode material.

[0076] According to one embodiment of the present invention, the supercapacitor has a power density of 790.8 W·kg -1 The energy density at that time can be at least 88 Wh·kg -1 Preferably at least 89 Wh·kg -1 More preferably at least 89.2 Wh·kg -1 Supercapacitors at 5 A·g -1 At a current density, after 10,000 constant current charge-discharge cycles, the capacity retention rate can be at least 80%, preferably at least 83%, and more preferably at least 85%.

[0077] In this invention, thanks to the stability of the three-dimensional nanoflower skeleton structure of the composite electrode material, the supercapacitor has high energy density and capacity retention, good energy storage performance and cycle stability, and has high practical application value.

[0078] <Testing Method> SEM inspection: Performed using a ZEISS Sigma 360 field emission scanning electron microscope (Germany).

[0079] XRD analysis was performed using an XPert3 Powder X-ray diffractometer from Panaco (Netherlands); a copper target was used. Ka The radiation source was tested at a wavelength of 1.5418 Å.

[0080] FTIR detection: A Nexus 870 Fourier transform infrared spectrometer from Nicolet Instruments (USA) was used; the test range was 4000–400 cm⁻¹. -1 The sample was prepared using the potassium bromide tableting method. The sample and potassium bromide were mixed at a weight ratio of 1:20 and pressed into a disc with a diameter of 10 mm for testing.

[0081] XPS detection: The X-ray photoelectron spectrometer was used by Thermo Fisher Scientific ESCALAB 250 Xi.

[0082] NMR analysis was performed using a Bruker AV400 nuclear magnetic resonance spectrometer (Switzerland); the material was analyzed at a concentration of 1 mol·L⁻¹. -1 Digestion was carried out in a mixed solution of NaOH and D2O, followed by testing. 1 H NMR and 19 F NMR.

[0083] EPR detection: performed using the EMX Plus electron paramagnetic resonance spectrometer from Bruker GmbH, Germany.

[0084] Thermogravimetric analysis was performed using a TG series thermogravimetric analyzer from Netzsch GmbH, Germany.

[0085] BET specific surface area and pore size testing: Autosorb-6 fully automatic specific surface area and pore size distribution measuring instrument from CANTA Corporation, USA.

[0086] Cyclic voltammetry was performed using a CS350 electrochemical workstation from Wuhan Koster Instruments Co., Ltd.

[0087] Constant current charge-discharge testing: was performed using a CS350 electrochemical workstation from Wuhan Koster Instruments Co., Ltd.

[0088] EIS impedance testing was performed using a CS350 electrochemical workstation from Wuhan Koster Instruments Co., Ltd.

[0089] <Ingredient Description> Unless otherwise specified, all raw materials used in the following examples are commercially available products.

[0090] Some of the raw material information is shown in Table 1 below.

[0091] Table 1. Some of the raw materials used in the examples

[0092] Example 1 and Comparative Examples 1-4 Preparation of composite electrode materials Mix 4.5 mL of DMF with 1.5 mL of deionized water to obtain an aqueous DMF solution. Add 0.4 mmol of nickel nitrate hexahydrate, 0.1 mmol of ferric nitrate nonahydrate, and 0.5 mmol of 2,5-thiophene dicarboxylic acid to the aqueous DMF solution, mix and dissolve to obtain precursor solution A.

[0093] Trifluoroacetic acid (TFA) was added to precursor solution A to obtain precursor solution B.

[0094] Precursor solution B was placed in a 50 mL polytetrafluoroethylene-lined stainless steel autoclave and subjected to a solvothermal reaction at 110 °C for 12 h. The mixture was then allowed to cool naturally to room temperature to obtain a solid product. The solid product was washed three times alternately by centrifugation with deionized water and anhydrous ethanol (water-ethanol-water), each time at 8000 rpm for 10 min, to obtain a precipitate. The precipitate was then placed in a vacuum oven and dried at 60 °C for 24 h to obtain the composite electrode material.

[0095] Comparative Example 1 did not contain trifluoroacetic acid, while Comparative Examples 2, 1, 3, and 4 contained 0.05 mmol, 0.10 mmol, 0.15 mmol, and 0.20 mmol of trifluoroacetic acid, respectively, to prepare composite electrode materials. The corresponding composite electrode materials are denoted as Ni... 0.67 Fe 0.33 -MOF (Comparative Example 1), Ni 0.67 Fe 0.33 -MOF-1 (Comparative Example 2), Ni 0.67 Fe 0.33 -MOF-2 (Example 1), Ni 0.67 Fe 0.33 -MOF-3 (Comparative Example 3) and Ni 0.67 Fe 0.33 -MOF-4 (Comparative Example 4).

[0096] Experimental Example 1 The composite electrode materials prepared in Example 1 and Comparative Examples 1-4 were examined by SEM (scanning electron microscopy), and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the composite electrode material (Ni) prepared in Comparative Example 1 without the introduction of a coordination competition modifier... 0.67 Fe 0.33 -MOF) exhibits a nanoflower structure composed of interwoven nanosheets. Meanwhile, the composite electrode material (Ni) prepared by introducing trifluoroacetic acid in Example 1... 0.67 Fe 0.33 The MOF-2 nanosheets maintain a good three-dimensional nanoflower framework, and the nanosheet surface becomes rougher with slightly curled edges and larger spacing between nanosheets. This optimized microstructure can increase the full contact between the material and electrolyte ions.

[0097] The phase and crystal structure of the composite electrode materials prepared in Example 1 and Comparative Examples 1-4 were characterized and analyzed by X-ray diffraction (XRD), and the results are as follows: Figure 2 As shown. By Figure 2 It can be seen that Ni 0.67 Fe 0.33 -MOF-2 still retains its connection with Ni 0.67 Fe 0.33 The consistent strong diffraction peaks of the MOF demonstrate that the main framework of the MOF remains intact and has good structural stability even when ligand defects are introduced.

[0098] The Fourier transform infrared (FTIR) spectra of the composite electrode materials prepared in Examples 1 and 1-4 are as follows: Figure 3As shown, compared with the infrared characteristic peaks of H2TDC, the spectrum of the composite electrode material is significantly different in the range of 2500–3100 cm⁻¹. -1 No stretching vibration peak of hydroxyl (-OH) was observed in the range, but rather at 3600 cm⁻¹. -1 The presence of a hydroxyl peak associated with water molecules confirms the successful binding of the organic ligand to the metal center during the hydrothermal treatment process. (This is in contrast to Ni.) 0.67 Fe 0.33 -MOF comparison: After introducing trifluoroacetic acid ligands, the composite electrode material showed a 1658 cm⁻¹... -1 An absorption peak associated with an undissociated carboxyl group was observed at 1364 cm⁻¹, indicating the presence of free ligands in the composite electrode material. -1 and 1572cm -1 The spectral peaks at 485 cm⁻¹ correspond to the symmetric and asymmetric stretching vibrations of the carboxylate group (-COO), indicating that the oxygen atom in the carboxylate group participates in coordination. Notably, the peak at 485 cm⁻¹... -1 The Ni-O vibration peaks appearing at 580 cm⁻¹ and 580 cm⁻¹ -1 The Fe-O at the location confirms the successful coordination of H2TDC with the metal center. The above FTIR data demonstrate that this invention successfully synthesized a composite electrode material.

[0099] The Raman spectra of the composite electrode materials prepared in Example 1 and Comparative Examples 1-4 are as follows: Figure 4 As shown in the figure, the characteristic absorption peak of the composite electrode material is consistent with the vibrational characteristics of Ni-MOF. At 1472 cm⁻¹... -1 The characteristic peak at 1135 cm⁻¹ represents the symmetric stretching vibration of the carboxylate group (COO⁻), indicating coordination between the organic ligand and the metal node. -1 and 805cm -1 The absorption peaks at 688 cm⁻¹ correspond to the stretching vibration of the CO bond and the bending vibration of the CH bond, respectively. Furthermore, at 688 cm⁻¹... -1 The characteristic peak observed at this location is the stretching vibration of the CS bond on the thiophene ring, confirming the integrity of the thiophene functional group in the MOF framework. Comparison of the Raman spectra of different composite electrode materials reveals that Ni... 0.67 Fe 0.33 The peak positions of -MOF and Ni-MOF are basically the same, indicating that Fe doping did not change the coordination environment of the ligands. For Ni... 0.67 Fe 0.33 -MOF-1 and Ni 0.67 Fe 0.33 -MOF-2, the position and relative intensity of its characteristic peaks remain intact, indicating that the host chemical bonding structure of MOF was not disrupted while ligand defects were introduced. However, with further increases in the amount of trifluoroacetic acid introduced, Ni... 0.67 Fe 0.33-MOF-3 and Ni 0.67 Fe 0.33 The Raman characteristic peak intensity of MOF-4 showed a significant decrease, and the peak shape broadened slightly. This reduction in spectral intensity is generally attributed to a decrease in the degree of order in the crystal structure and a reduction in the number of effective ligands per unit volume (i.e., high concentration of ligand deficiency). This further confirms that excessive trifluoroacetic acid leads to excessive corrosion of the framework and collapse of local structures, thereby reducing the crystallinity and stability of the material.

[0100] X-ray photoelectron spectroscopy (XPS) of the composite electrode materials prepared in Examples 1 and 1-4 are as follows: Figure 5 As shown, the F1s spectrum exhibits a characteristic peak at 688.6 eV, confirming the successful introduction of the CF3 group. The nuclear magnetic resonance (NMR) spectra of the composite electrode materials prepared in Examples 1 and Comparative Examples 1-4 are shown below. Figure 6 and Figure 7 As shown, nuclear magnetic resonance 19 The presence of a characteristic peak at -75.4 ppm in the F NMR spectrum further confirms the successful introduction of the CF3 group.

[0101] The electron paramagnetic resonance (EPR) spectra of the composite electrode materials prepared in Example 1 and Comparative Example 1 are shown below. Figure 8 As shown, by applying Ni 0.67 Fe 0.33 -MOF and Ni 0.67 Fe 0.33 Comparing the electron paramagnetic signals of -MOF-2, it can be found that both groups of materials exhibit a symmetrical resonance absorption peak at g=2.003, which is attributed to the unpaired electron signal trapped by oxygen vacancies in the lattice. The Ni after introducing trifluoroacetic acid as a modifier... 0.67 Fe 0.33 -MOF-2 material has a higher signal intensity than Ni 0.67 Fe 0.33 -MOF materials, which directly proves that ligand defects effectively induce higher concentrations of oxygen vacancies, thus confirming the successful regulation of the local electronic structure of the material by defects.

[0102] Thermogravimetric analysis (TGA) diagrams of the composite electrode materials prepared in Example 1 and Comparative Examples 1-4 are shown below. Figure 9 As shown, with the addition of trifluoroacetic acid, the ligand decomposition weight loss rate decreased significantly, which thermodynamically verified that the composite electrode material generates ligand defects.

[0103] The N2 adsorption-desorption isotherms of the composite electrode materials prepared in Examples 1 and 4 are as follows: Figure 10 As shown, all composite electrode materials exhibit type IV isotherm characteristics with an H3-type hysteresis loop, indicating the presence of a mesoporous structure within the material. With the introduction of trifluoroacetic acid, Ni... 0.67Fe 0.33 The specific surface area of ​​MOF-1 increased to 91 m². 2 ·g -1 Because the amount of trifluoroacetic acid introduced is relatively small, the ligand competition effect is weak, and Ni 0.67 Fe 0.33 The MOF-1 framework largely maintains a relatively complete crystal structure. As the trifluoroacetic acid concentration increases, Ni... 0.67 Fe 0.33 The specific surface area of ​​-MOF-2 is from Ni 0.67 Fe 0.33 -MOF reaches 135m 2 ·g -1 With further increases in the amount of trifluoroacetic acid introduced, Ni 0.67 Fe 0.33 The specific surface area of ​​MOF-3 begins to decrease, dropping to 10¹ m². 2 ·g -1 At this point, the excessive loss of ligands leads to instability in the local coordination environment, and some structures may collapse, resulting in the loss of effective porous structure. Ni 0.67 Fe 0.33 The specific surface area of ​​MOF-4 continued to decrease to 96 m². 2 ·g -1 In high concentrations of trifluoroacetic acid, competitive coordination generates a large number of amorphous phases that block the originally open pores, resulting in a decrease in specific surface area.

[0104] The pore size distribution diagram of the composite electrode material is shown below. Figure 11 As shown, based on the DFT pore size distribution curves, all materials exhibit large mesopores / macropores. Ni 0.67 Fe 0.33 The pore size distribution peak of MOF-1 is centered at 30.5 nm, with relatively low peak intensity. Due to its relatively large and intact grain size, it enhances electrolyte penetration. Ni 0.67 Fe 0.33 The main peak of the MOF-2 pore size distribution shifts to 34.2 nm, and the integrated pore volume reaches its maximum value. Ni 0.67 Fe 0.33 The MOF-3 pore size peak position shifted further to 30.1 nm, but the peak height began to decrease. Although the pore size increased, the total number of pores decreased. Ni 0.67 Fe 0.33 -MOF-4 exhibits a broad and low distribution peak, centered at approximately 25.1 nm. The extremely broad distribution indicates that the uniformity of the pore structure has been disrupted.

[0105] Experimental Example 2 Cyclic voltammetry and constant current charge-discharge tests were performed on the composite electrode materials prepared in Example 1 and Comparative Examples 1-4, respectively. In the constant current charge-discharge (GCD) analysis, a constant current value was used to charge and discharge the electrode material in a three-electrode system. During the charging phase, electrical energy was input to the capacitor device according to a set constant current, causing corresponding redox reactions to occur on its electrodes to store charge. During the discharging phase, the device released the stored electrical energy with the same constant current, causing the electrodes to undergo reverse redox reactions. In this experimental example, the composite electrode material was used as the positive electrode of the capacitor device for testing. The specific capacitance was calculated according to the formula shown in Equation (1-1):

[0106] in, C Specific capacitance (F·g) -1 ), I Current (A) Δt Δ is the discharge time (s). V Let F be the voltage difference (F) and m be the electrode material loading (g).

[0107] Test results as follows Figures 12-15 As shown, Figure 12 Comparison at 10 mV·s -1 Cyclic voltammetry curves of various composite electrode materials at different scan rates, within the same voltage window for Ni 0.67 Fe 0.33 The current response of -MOF-2 is significantly enhanced. This enhancement is attributed to the fact that ligand defects increase the exposed metal active sites, thereby improving conductivity. Figure 13 The performance of various composite electrode materials at 1 A·g was compared. -1 Constant current charge-discharge curves at current density, Ni 0.67 Fe 0.33 -MOF-2 materials exhibit the longest discharge time. The specific capacitance of each composite electrode material was calculated, and its rate performance is as follows: Figure 14 As shown, Ni 0.67 Fe 0.33 -MOF-2 exhibits 2385 F·g -1 The specific capacitance. This value exceeds that of Ni. 0.67 Fe 0.33 -MOF(1306F·g) -1 ), Ni 0.67 Fe 0.33 -MOF-1 (1738F·g) -1 ), Ni 0.67 Fe 0.33 -MOF-3 (1774F·g) -1) and Ni 0.67 Fe 0.33 -MOF-4 (1480 F g) -1 ) Specific capacitance data at other current densities are shown in Table 2. Rate curves show that the specific capacitance of each composite electrode material decreases with increasing current density. This decrease can be attributed to insufficient electrode resistance and the inadequacy of the Faraday redox reaction at high current densities. Figure 15 A direct comparison was made at 1 A·g -1 The specific capacitance of each composite electrode material at current density. These electrochemical data indicate that the composite electrode materials significantly improve their electrochemical performance by introducing ligand defects and oxygen vacancies.

[0108] Table 2 Specific capacitance data of composite electrode materials

[0109] Note: The unit of specific capacitance is F·g. -1 .

[0110] Application Example 1 and Comparative Application Examples 1-4 The specific method for preparing a supercapacitor is as follows: 1. Pretreatment of nickel foam (1) Cut the nickel foam into 1×1.5cm pieces. 2 Small rectangular pieces are used to obtain nickel foam blocks; (2) Use nickel foam blocks with a concentration of 6 mol·L⁻¹ -1 The primary nickel foam carrier A was obtained by ultrasonic cleaning with hydrochloric acid solution for 10 min. (3) The primary nickel foam carrier A was ultrasonically cleaned with acetone for 10 min to obtain the primary nickel foam carrier B; (4) The primary nickel foam carrier B was ultrasonically cleaned with alternating ethanol and deionized water 3 times each, for 10 minutes each time, to obtain the primary nickel foam carrier C. (5) Place the primary nickel foam carrier C in a vacuum drying oven and dry it at 60°C for 12 hours to obtain the nickel foam carrier.

[0111] 2. Preparation of positive electrode 1.5 mg of the composite electrode material prepared in Example 1 and Comparative Examples 1-4 were placed between two nickel foam carriers. The positive electrode was then prepared by using an FYC-25 benchtop powder press at a pressure of 10 MPa for 30 s.

[0112] 3. Negative electrode preparation Activated carbon (YEC-8), conductive carbon black (ACET), and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 8:1:1 and stirred for 30 minutes to obtain a negative electrode material slurry. The negative electrode material slurry was then uniformly coated onto a nickel foam substrate. The coated nickel foam substrate was then vacuum dried at 60°C for 12 hours to obtain the negative electrode.

[0113] 4. Fabrication of Supercapacitors Assemble in the following order: The order from top to bottom is: positive electrode shell, stainless steel sheet, positive electrode, separator, negative electrode, stainless steel sheet, negative electrode shell.

[0114] Next, the concentration was 1 mol·L -1 KOH electrolyte was evenly dropped onto the positive and negative electrodes and the separator, and then a hydraulic button cell sealing machine was used to press and close the electrodes to obtain a supercapacitor.

[0115] The supercapacitors produced need to stand for 12 hours before electrochemical testing.

[0116] The supercapacitors prepared from the composite electrode materials of Example 1 and Comparative Examples 1-4 are respectively denoted as Ni 0.67 Fe 0.33 -MOF (Application Comparison Example 1), Ni 0.67 Fe 0.33 -MOF-1 (Comparative Application Example 2), Ni 0.67 Fe 0.33 -MOF-2 (Application Example 1), Ni 0.67 Fe 0.33 -MOF-3 (Comparative Application Example 3) and Ni 0.67 Fe 0.33 -MOF-4 (Comparative Application Example 4).

[0118] Application Experiment Example 1 Cyclic voltammetry, constant current charge-discharge testing, and EIS impedance testing were performed on the supercapacitors prepared in Application Example 1 and Comparative Examples 1 to 4, respectively.

[0119] The constant current charge-discharge characteristic analysis (GCD) is the same as in Experimental Example 2. In this application experiment, the supercapacitors prepared in Application Example 1 and Comparative Examples 1-4 were used as capacitor devices for testing.

[0120] Electrochemical Impedance Spectroscopy (EIS) is used to analyze the characteristics of the supercapacitor. During the measurement, a small-amplitude sinusoidal AC signal with a frequency range from 0.01 Hz to 100 kHz is applied. The system's response to this AC signal, i.e., the change in current or potential, is measured simultaneously. By changing the frequency of the AC signal, the system's impedance (including resistance and reactance) at different frequencies is recorded. The real capacitance (C′(ω)) and imaginary capacitance (C″(ω)) calculated from the EIS data are given by the following formulas: Where C( w ) represents the complex capacitance (F) at the corresponding frequency response, C'( w ) represents the real capacitance (F) at the corresponding frequency, C''( w ) represents the imaginary capacitance (F) at the corresponding frequency, j is the imaginary unit, √-1, Z'(w) and Z''(w) are the real and imaginary parts of the impedance (Ω) respectively, |Z( w )| represents the magnitude (Ω) of the complex impedance.

[0121]

[0122] Where τ0 is the relaxation time constant (s), f0 is the characteristic frequency (Hz), and the corresponding imaginary capacitance C'' is... w The frequency at which the peak value is reached.

[0123] The power density and energy density in this application example are obtained through calculation. C is calculated based on constant current charge and discharge detection, and the power density and energy density are obtained by substituting C into formulas (1-6) and (1-7).

[0124]

[0125] In the formula, E Energy density of electrode materials (Wh·kg) -1 ), C The specific capacitance (F·g) calculated by equation (1-1) -1 ), V For voltage difference (F), P The power density of the electrode material (W·kg) -1 ), Δ t The discharge time is denoted as s.

[0126] Test results as follows Figures 16-22 As shown. Figure 16 As shown, at 100 mV·s -1 Cyclic voltammetry curves at scan rates, Ni0.67 Fe 0.33 -MOF-2 has the largest scan area, indicating that Ni 0.67 Fe 0.33 -MOF-2 possesses excellent charge storage capabilities. For example... Figure 17 As shown, at 1A·g -1 The constant current charge-discharge curves at current densities show that Ni 0.67 Fe 0.33 -MOF-2 has the longest discharge time, demonstrating its high storage capacity among various supercapacitors. Figure 18 Ni was showcased 0.67 Fe 0.33 -MOF-2 in 20–100 mV·s -1 Cyclic voltammetry curves at the scan rate. Figure 19 Ni was showcased 0.67 Fe 0.33 -MOF-2 in 1~10 A·g -1 Constant current charge-discharge curves at current density. At 1 A·g -1 At current density, Ni 0.67 Fe 0.33 -MOF, Ni 0.67 Fe 0.33 -MOF-1, Ni 0.67 Fe 0.33 -MOF-2, Ni 0.67 Fe 0.33 -MOF-3 and Ni 0.67 Fe 0.33 The specific capacitance of MOF-4 was calculated to be 215.8 F·g. -1 287.1 F·g -1 389.6 F·g -1 242.6 F·g -1 and 215.1 F·g -1 The energy density and power density of each supercapacitor are calculated using formulas 1-6 and 1-7. For example... Figure 20 As shown in the diagram, with Ni 0.67 Fe 0.33 A supercapacitor assembled using MOF-4 as the electrode material achieved a power density of 790.8 W·kg⁻¹. -1 At that time, the energy density reached 89.2 Wh·kg -1 This demonstrates superior performance compared to supercapacitors made from electrode materials in existing technologies (as shown in Table 3), indicating that ligand defects have a significant advantage in promoting energy storage. At 5 A·g -1 A 10,000-cycle stability test was conducted at a current density as follows: Figure 21As shown, the supercapacitors exhibited capacitance retention rates of 74%, 76%, 85%, 76%, and 67%, respectively.

[0127] Table 3 Power density and energy density of supercapacitors based on different composite electrode materials

[0128] Note: The references are as follows: 1.Lin S., Guo X., Cai W., et al. Binder-free defective bimetallicmetal-organic framework nanostructures with lattice distortion as hybridsupercapacitor electrodes[J]. ACS Applied Nano Materials, 2024, 7(1): 1078-1088. 2.Yao J., Ji Y., Lu F., et al. Facile route to high-mass-loadingamorphous NiCo-MOFs as high-performance electrode materials for asymmetricsupercapacitors[J]. New Journal of Chemistry, 2023, 47(9): 4182-4186. 3.Pan Y., Han Y., Chen Y., et al. Benzoic acid-modified 2D Ni-MOF for high-performance supercapacitors[J]. Electrochimica Acta, 2022, 403: 139679. 4.Mofokeng TP, Ipadeola AK, Tetana Z N., et al. Defect-engineered nanostructured Ni / MOF-derived carbons for an efficient aqueousbattery-type energy storage device[J]. ACS Omega, 2020, 5(32): 20461-20472. 5.Sahoo MK, Mane P., Chakraborty B., et al. Three-dimensional Ni-MOF as a high-performance supercapacitoranode material; experimental and theoretical insight[J]. Inorganic Chemistry, 2024, 63(14): 6383-6395. EIS impedance test results are as follows: Figure 22 As shown. To study the charge transfer characteristics of various composite electrode materials, EIS was analyzed and fitted as follows. Figure 22 As shown in Figure a, the curve exhibits incomplete semicircles and linear tailing characteristics. The fitted data are shown in Table 4. Ni 0.67 Fe 0.33 The charge transfer resistance (Rct) of MOF-2 is reduced to 0.6Ω, while that of Ni... 0.67 Fe 0.33 The Rct of the MOF is 0.8 Ω, while its internal resistance (Rs) decreases from 1.3 Ω to 1.0 Ω. This indicates that ligand defects can enhance electronic conductivity and promote charge transfer. Furthermore, the relationship between the real capacitance (C') and the imaginary capacitance (C'') and frequency is calculated according to Equation 1-2. Figure 22 Figure b shows the relationship between the real capacitance of the composite electrode material and frequency in each supercapacitor, which is consistent with the previously calculated specific capacitance trend. Figure 22 Figure c shows the relationship between the imaginary capacitance of the composite electrode material and frequency in various supercapacitors. The time constant is calculated using formulas 1-6. 0.67 Fe 0.33 The τ0 of -MOF-2 is 5.1 seconds, which is significantly smaller than that of Ni. 0.67 Fe 0.33 The 10.0 s⁻¹ of the -MOF indicates that it possesses superior K⁺ diffusion kinetics. Furthermore, Ni... 0.67 Fe 0.33 -MOF-2 exhibits a frequency response closer to 90 in the low-frequency range. ° phase angle ( Figure 22 The d-plot further demonstrates its excellent capacitive behavior and fast electrochemical response.

[0129] Table 4. Impedance values ​​obtained by fitting each composite electrode material using ZView.

[0130] Application Experiment Example 2 The supercapacitors prepared in Application Example 1 were fully charged, and then connected to the LED light panel via wires according to the corresponding positive and negative terminals, as follows. Figure 23 As shown, the supercapacitor successfully illuminated the lamp panel. This indicates that the supercapacitor prepared from the composite electrode material of this invention can stably output electrical energy, and the voltage can meet the requirements of small loads. The composite electrode material and device assembly effect is good, demonstrating potential for practical application.

[0131] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for preparing a composite electrode material, characterized in that, Includes the following steps: 1) Nickel salt, iron salt, and dicarboxylic acid ligand are mixed in an aqueous solution of a polar solvent to obtain precursor solution A; wherein the dicarboxylic acid ligand is selected from at least one of 2,5-thiophene dicarboxylic acid, terephthalic acid, 2,5-furan dicarboxylic acid, 2,5-pyrrole dicarboxylic acid, 3,7-dibenzothiophene dicarboxylic acid, and benzimidazole 5,6-dicarboxylic acid; the molar ratio of nickel in the nickel salt, iron in the iron salt, and dicarboxylic acid ligand is 2-6:1:3-8; in the aqueous solution of the polar solvent, the volume ratio of the polar solvent to water is 1-5:1, and the polar solvent is selected from at least one of DMF, DEF, DMSO, NMP, methanol, and ethanol; the amount of the polar solvent used is 5-20 mL, based on 1 mmol / L of dicarboxylic acid ligand; 2) Add the coordination competition modifier to the precursor solution A and mix to obtain the precursor solution B; wherein the coordination competition modifier is selected from at least one of trifluoroacetic acid, perfluorobutyric acid, formic acid, acetic acid, propionic acid, and n-butyric acid; the molar ratio of the coordination competition modifier to the dicarboxylic acid ligand is 0.15 to 0.27:1; 3) The precursor solution B is subjected to a solvothermal reaction at 80-200℃ for 5-24 hours, and then cooled to obtain a solid product; the solid product is washed and dried to obtain the composite electrode material.

2. The preparation method according to claim 1, characterized in that, In step 1), the nickel salt is selected from at least one of nickel nitrates, sulfates, halides, and acetates; the iron salt is selected from at least one of iron nitrates, sulfates, halides, and acetates.

3. The preparation method according to claim 1, characterized in that, In step 1), the molar ratio of nickel in the nickel salt, iron in the iron salt, and dicarboxylic acid ligand is 2.5–5.5:1:3.5–6.5; and the amount of polar solvent used is 7–18 mL, based on 1 mmol / L of dicarboxylic acid ligand.

4. The preparation method according to claim 1, characterized in that, In step 2), the molar ratio of the coordination competition regulator to the dicarboxylic acid ligand is 0.16 to 0.25:

1.

5. The preparation method according to claim 1, characterized in that, In step 3), the temperature of the solvothermal reaction is 90–150°C, and the time is 8–20 h.

6. The preparation method according to claim 1, characterized in that, In step 3), the washing process involves alternating centrifugal washing with water and C2-C5 alkyl alcohols.

7. The preparation method according to claim 1, characterized in that, In step 3), the drying temperature is 40–120°C and the time is 12–48 hours.

8. A composite electrode material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The composite electrode material has a BET specific surface area of ​​at least 130 m². 2 ·g -1 The composite electrode material at 1 A·g -1 The specific capacitance at current density is at least 2300 F·g -1 The charge transfer resistance of the composite electrode material is at most 0.65Ω.

9. The use of the composite electrode material according to claim 8 in the preparation of supercapacitors.

10. A supercapacitor, characterized in that, The supercapacitor comprises the composite electrode material as described in claim 8.

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