Preparation method of layered double hydroxide electrode material with nanosheet structure

Abstract

The invention belongs to the technical field of supercapacitor electrode materials, and discloses a preparation method of a layered double hydroxide electrode material with a nanosheet structure. Aiming at the problems of small specific surface area and low utilization rate of active sites caused by easy aggregation of a layered double hydroxide material, NiFe-MOF is uniformly coated on the surface of NiFe-LDH through a process of combining a hydrothermal method and a secondary hydrothermal method to form the core-shell structure composite electrode material. The preparation process is simple and controllable, the cost is low, the specific surface area of the obtained NiFe-LDH-coated MOF composite electrode material is remarkably increased, active sites are rich, the electron transfer rate is high, and the NiFe-LDH-coated MOF composite electrode material shows ultrahigh specific capacitance, good rate capability and cycling stability when applied to supercapacitors.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor electrode material technology, specifically relating to a method for preparing a layered double hydroxide electrode material with a nanosheet structure. Background Technology

[0002] With the global energy crisis and environmental problems becoming increasingly prominent, the development of efficient and clean energy storage devices has become a research hotspot. Supercapacitors, as a novel energy storage device, possess significant application value in new energy vehicles, smart grids, and portable electronic devices due to their advantages such as high power density, long cycle life, and rapid charge / discharge. However, the low energy density of traditional supercapacitors restricts their large-scale application, and the performance of electrode materials is the core factor determining the energy density of supercapacitors.

[0003] Layered double hydroxide electrode materials are characterized by low cost, relatively easy fabrication, and high theoretical specific capacitance. Their unique layered structure, tunable host metal ions, and exchangeable interlayer anions give them great potential in energy storage applications. However, layered double hydroxide materials suffer from problems such as easy aggregation leading to small specific surface area and low utilization of active sites.

[0004] This invention provides a layered double hydroxide electrode material with a nanosheet structure. By combining the NiFe-LDH@MOF electrode material with nickel foam, a binder-free integrated electrode is prepared, thereby improving the specific capacitance and structural stability. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a layered double hydroxide electrode material with a nanosheet structure. This method is characterized by its environmentally friendly and rapid preparation process, low cost, and the resulting layered double hydroxide electrode material exhibits advantages such as uniform distribution of active sites, large specific capacitance, stable microstructure, and excellent electrochemical performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a layered double hydroxide electrode material with a nanosheet structure: Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, NH4F and CO(NH2)2 are added to deionized water to form a homogeneous solution; then, NiFe-LDH electrode material is obtained by hydrothermal process; then, NiFe-MOF is uniformly grown on the surface of NiFe-LDH by secondary hydrothermal method to form NiFe-LDH@MOF composite electrode material.

[0007] Furthermore, the preparation method specifically includes the following main steps: (1) Clean the nickel foam thoroughly and dry it for later use; (2) Dissolve Ni(NO3)2·6H2O and Fe(NO3)3·9H2O in deionized water, add NH4F and CO(NH2)2 to form a homogeneous solution; (3) Transfer the solution obtained in step (2) to the reaction vessel, put in the cleaned nickel foam, carry out hydrothermal reaction, take out the nickel foam, rinse it clean and dry it to obtain NiFe-LDH electrode material; (4) Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and terephthalic acid are dissolved in a mixed solution of deionized water, anhydrous ethanol and N,N-dimethylformamide to form a homogeneous solution. NiFe-LDH electrode material is placed in the solution and subjected to a hydrothermal reaction. After rinsing and drying, NiFe-LDH@MOF composite electrode material is obtained.

[0008] Furthermore, in step (2), the molar ratio of nickel and iron ions is 1~3:1~3.

[0009] Furthermore, in step (3), the hydrothermal reaction is carried out at 120°C for 8 hours.

[0010] Furthermore, the amount of terephthalic acid added in step (4) is 0.9 mmol.

[0011] Furthermore, in step (4), the hydrothermal reaction is carried out at 120°C for 8 hours.

[0012] Furthermore, in step (4), the loading of the NiFe-LDH@MOF composite material on the electrode is 1.0~2.5 mg / cm³. 2 .

[0013] The layered double hydroxide electrode material with a nanosheet structure was prepared by the method described above.

[0014] Application: The layered double hydroxide electrode material with nanosheet structure described above is used in supercapacitors.

[0015] Beneficial effects: The NiFe-LDH@MOF electrode material of this invention features a layered double hydroxide electrode with a nanosheet structure uniformly distributed on nickel foam, providing numerous reaction sites, thereby enabling efficient adsorption of OH- from alkaline solutions. - It stores charge and exhibits excellent specific capacitance.

[0016] Beneficial effects: The NiFe-LDH@MOF electrode material of this invention possesses a unique nanosheet structure. A secondary hydrothermal method achieves uniform coating of NiFe-MOF on the surface of the NiFe-LDH electrode material, forming a core-shell structure. This effectively alleviates the aggregation problem of the NiFe-LDH electrode material. As the reaction proceeds, electrolyte ions further move into the interior of the structure, further releasing the specific capacitance of the electrode material. Furthermore, this electrode material overcomes the disadvantage of reduced specific surface area caused by the stacked sheet-like structure of layered double hydroxides. Attached Figure Description

[0017] Figure 1 SEM images of (a) NiFe-LDH electrode; (b) NiFe-MOF electrode; (c) NiFe-LDH@MOF electrode; Figure 2 The image shows the XRD pattern of the NiFe-LDH@MOF electrode material prepared according to this invention. Figure 3 This is a schematic diagram of the cyclic voltammetric (CV) curves of the NiFe-LDH@MOF electrode material prepared in this invention; Figure 4 Charge-discharge curves of the NiFe-LDH@MOF electrode material prepared in this invention under different discharge currents; Figure 5 This is a rate performance diagram of the NiFe-LDH@MOF electrode material prepared in this invention; Figure 6 The diagram shows the cycling performance of the NiFe-LDH@MOF electrode material prepared in this invention. Detailed Implementation

[0018] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0019] Example 1 (1) Clean the nickel foam with acetone, hydrochloric acid, deionized water and anhydrous ethanol, and then dry it at 60°C for 10 hours.

[0020] (2) Dissolve 0.500 mmol Ni(NO3)2·6H2O in 30 mL of deionized water. Dissolve Fe(NO3)3·9H2O in the solution according to the molar ratio of nickel to iron metal ions of 1:2. Then add 1.000 mmol NH4F and 3.000 mmol CO(NH2)2 to form a homogeneous solution.

[0021] (3) Transfer the solution obtained in step (2) to a stainless steel reactor lined with polytetrafluoroethylene, add the treated nickel foam, and place the reactor in an oven at 120°C for 8 hours. Remove the nickel foam, rinse with deionized water and anhydrous ethanol, and dry at 60°C for 10 hours to obtain the NiFe-LDH electrode.

[0022] (4) Dissolve 0.500 mmol Ni(NO3)2·6H2O, 0.500 mmol Fe(NO3)3·9H2O, and 0.900 mmol terephthalic acid in a mixed solution of 2 mL deionized water, 2 mL anhydrous ethanol, and 26 mL N,N-dimethylformamide. Mix thoroughly and transfer the solution to a stainless steel reactor lined with polytetrafluoroethylene. Place the NiFe-LDH electrode inside. Place the reactor in an oven at 120°C for 8 h. Remove the nickel foam, rinse with deionized water and anhydrous ethanol, and dry at 60°C for 10 h. Obtain a NiFe-LDH@MOF electrode with a nickel to iron ion molar ratio of 1:2.

[0023] Example 2 (1) Clean the nickel foam with acetone, hydrochloric acid, deionized water and anhydrous ethanol, and then dry it at 60°C for 10 hours.

[0024] (2) Dissolve 0.500 mmol Ni(NO3)2·6H2O in 30 mL of deionized water. Dissolve Fe(NO3)3·9H2O in the solution at a nickel to iron metal ion molar ratio of 2:1. Then add 1.000 mmol NH4F and 3.000 mmol CO(NH2)2 to form a homogeneous solution.

[0025] (3) Transfer the solution obtained in step (2) to a stainless steel reactor lined with polytetrafluoroethylene, add the treated nickel foam, and place the reactor in an oven at 120°C for 8 hours. Remove the nickel foam, rinse with deionized water and anhydrous ethanol, and dry at 60°C for 10 hours to obtain the NiFe-LDH electrode.

[0026] (4) Dissolve 0.500 mmol Ni(NO3)2·6H2O, 0.500 mmol Fe(NO3)3·9H2O, and 0.900 mmol terephthalic acid in a mixed solution of 2 mL deionized water, 2 mL anhydrous ethanol, and 26 mL N,N-dimethylformamide. Mix thoroughly and transfer the solution to a stainless steel reactor lined with polytetrafluoroethylene. Place the NiFe-LDH electrode inside. Place the reactor in an oven at 120°C for 8 h. Remove the nickel foam, rinse with deionized water and anhydrous ethanol, and dry at 60°C for 10 h. Obtain a NiFe-LDH@MOF electrode with a nickel to iron ion molar ratio of 2:1.

[0027] Example 3 (1) Clean the nickel foam with acetone, hydrochloric acid, deionized water and anhydrous ethanol, and then dry it at 60°C for 10 hours.

[0028] (2) Dissolve 0.500 mmol Ni(NO3)2·6H2O in 30 mL of deionized water. Dissolve Fe(NO3)3·9H2O in the solution at a nickel to iron metal ion molar ratio of 1:1. Then add 1.000 mmol NH4F and 3.000 mmol CO(NH2)2 to form a homogeneous solution.

[0029] (3) Transfer the solution obtained in step (2) to a stainless steel reactor lined with polytetrafluoroethylene, add the treated nickel foam, and place the reactor in an oven at 120°C for 8 hours. Remove the nickel foam, rinse with deionized water and anhydrous ethanol, and dry at 60°C for 10 hours to obtain the NiFe-LDH electrode.

[0030] (4) Dissolve 0.500 mmol Ni(NO3)2·6H2O, 0.500 mmol Fe(NO3)3·9H2O, and 0.900 mmol terephthalic acid in a mixed solution of 2 mL deionized water, 2 mL anhydrous ethanol, and 26 mL N,N-dimethylformamide. Mix thoroughly and transfer the solution to a stainless steel reactor lined with polytetrafluoroethylene. Place the NiFe-LDH electrode inside. Place the reactor in an oven at 120°C for 8 h. Remove the nickel foam, rinse with deionized water and anhydrous ethanol, and dry at 60°C for 10 h. Obtain a NiFe-LDH@MOF electrode with a nickel to iron ion molar ratio of 1:1.

[0031] Figure 1 Image a is a scanning electron microscope (SEM) image of the NiFe-LDH electrode material after the first hydrothermal step in Example 1. Numerous smooth, stacked nanosheets are attached to the nickel foam framework. Figure 1 Image b is a scanning electron microscope (SEM) image of the NiFe-MOF electrode material prepared hydrothermally on the surface of nickel foam according to the conditions of step (4) in Example 1. The nickel foam skeleton has a uniformly attached surface with extremely high roughness and contains a large number of nano-bulbs with uniform pore size. Figure 1 Image c is a scanning electron microscope (SEM) image of the NiFe-LDH@MOF electrode material after secondary hydrothermal treatment in Example 1. After secondary hydrothermal treatment, NiFe-MOF is uniformly attached to the original NiFe-LDH electrode material in a sheet-like manner, without obvious agglomerates, thus combining the structural support of NiFe-LDH with the porous characteristics of NiFe-MOF.

[0032] Figure 2The image shows the XRD pattern of the NiFe-LDH@MOF electrode material. No other impurity peaks are clearly visible in the spectrum, indicating that the prepared NiFe-LDH@MOF electrode material has high purity.

[0033] Figure 3 Cyclic voltammetry curves of NiFe-LDH@MOF electrode materials prepared with different nickel and iron ion molar ratios at a scan rate of 20 mV / s are shown. The capacitance performance of the electrode material prepared in Example 1 is significantly higher than that of the electrode materials prepared in Example 2 and Example 3.

[0034] Figure 4 The figures show the charge-discharge curves of the NiFe-LDH@MOF electrode material prepared in Example 1 at different current densities. It can be seen that the electrode material's potential can reach 0.50, and at a current density of 1 A / g, the specific capacitance is as high as 2640.6 F / g. This provides a research direction for assembling high-energy-density batteries formed by two electrodes.

[0035] Figure 5 A comparison of the specific capacitance of NiFe-LDH@MOF electrode materials prepared for different molar ratios of nickel and iron ions is shown. It can be seen that the specific capacitance performance of the electrode material prepared in Example 1 is significantly higher than that of the electrode materials prepared in Example 2 and Example 3.

[0036] Figure 6 The figure shows the cycling stability curve of the NiFe-LDH@MOF electrode material prepared in Example 1. The cycling curves show that the capacitance retention of the electrode begins to decrease with increasing cycle number. After 5000 cycles, the capacitance retention of the NiFe-LDH@MOF(1:2) electrode still reaches 80.8%, overcoming the deficiency of insufficient stability in layered double hydroxide electrode materials.

[0037] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a layered double hydroxide electrode material having a nanosheet structure, characterized by: Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, NH4F and CO(NH2)2 are added into deionized water to form a uniform solution; then a NiFe-LDH electrode material is obtained through a hydrothermal process; and then a NiFe-MOF is uniformly grown on the surface of the NiFe-LDH through a secondary hydrothermal method to form a NiFe-LDH@MOF composite electrode material.

2. The method of claim 1, wherein: Specifically, the following main steps are included: (1) Clean the foamed nickel and dry for use; (2) Dissolve Ni(NO3)2·6H2O and Fe(NO3)3·9H2O in deionized water, add NH4F and CO(NH2)2 to form a uniform solution; (3) Transfer the solution obtained in step (2) into a reaction kettle, put in the cleaned foamed nickel, and perform a hydrothermal reaction; take out the foamed nickel, rinse it clean, and dry to obtain a NiFe-LDH electrode material; (4) Dissolve Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and terephthalic acid in a mixed solution of deionized water, anhydrous ethanol and N,N-dimethylformamide to form a uniform solution, put in the NiFe-LDH electrode material, perform a hydrothermal reaction, rinse it clean, and dry to obtain a NiFe-LDH@MOF composite electrode material.

3. The method of claim 2, wherein: In step (2), the molar ratio of nickel and iron metal ions is 1-3:1-3.

4. The method of claim 2, wherein: In step (3), the hydrothermal reaction is performed at a temperature of 120℃ for 8h.

5. The method of claim 2, wherein: In step (4), the amount of terephthalic acid added is 0.9 mmol.

6. The method of claim 2, wherein: In step (4), the hydrothermal reaction is performed at a temperature of 120℃ for 8h.

7. The method of claim 2, wherein: The electrode in step (4) has a loading of 1.0 to 2.5 mg / cm 2 .

8. A layered double hydroxide electrode material with nanosheet structure prepared by the preparation method according to any one of claims 1-7.

9. Application of the layered double hydroxide electrode material with nanosheet structure according to claim 8 in supercapacitors.

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