Honeycomb zif-derived layered double hydroxide composites, methods of making and using the same
A honeycomb-shaped ZIF-derived layered double hydroxide composite material was prepared by ion exchange, which solved the problems of low electronic conductivity and easy agglomeration of LDH materials in supercapacitors, and achieved high specific capacity and excellent electrochemical performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTHEAST UNIV
- Filing Date
- 2023-10-16
- Publication Date
- 2026-05-12
AI Technical Summary
Layered double hydroxide (LDH) materials are limited in large-scale application in supercapacitors due to their low electronic conductivity and tendency to agglomerate, which reduces the number of active sites and blocks electrolyte ion transport channels.
A honeycomb-shaped ZIF-derived layered double hydroxide composite material was prepared by ion exchange, forming a honeycomb structure assembled from nanosheets, which avoids agglomeration and accumulation, increases the specific surface area, and shortens the electron and ion transport distance.
It improves the specific capacity and cycle stability of electrode materials, enhances electrochemical performance, and is simple to operate and easy to scale up for production.
Smart Images
Figure CN119852102B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of supercapacitor energy storage technology, specifically relating to a honeycomb-shaped ZIF-derived layered double hydroxide composite electrode, its preparation method, and its application. Background Technology
[0002] Environmental pollution and the depletion of fossil fuels are two major challenges facing humanity today, and the vigorous development of clean and renewable energy is a hot research topic worldwide. Developing supercapacitors with high conversion efficiency and long-term stability is a crucial strategy for the scientific utilization of clean energy and the sustainable development of society through renewable energy. Designing electrodes with multi-component and multi-dimensional structures is a key technology for assembling high-efficiency supercapacitors.
[0003] Layered double hydroxides (LDHs) are widely used as electrode materials for supercapacitors due to their high theoretical capacity, large specific surface area, and good redox activity. However, their practical application is hindered by low electronic conductivity and the tendency for layered aggregation, which reduces the number of exposed active sites and blocks electrolyte ion transport channels. Multi-component structures can fully utilize the synergistic effects between different components and provide multiple reversible metal-ion redox couples. Constructing a three-dimensional structure of nanosheet assembly can prevent LDH aggregation, increase the specific surface area of the material, expose more electrochemical active sites, and shorten the distance for electron and ion transport. Simultaneously, the honeycomb structure fully utilizes the internal space of the material, buffering the volume expansion of the electrode during charging and discharging, effectively improving the electrode's specific capacity and cycle stability.
[0004] Therefore, there is an urgent need to invent a new composite electrode material that can significantly improve the electrochemical performance of materials. Summary of the Invention
[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a novel honeycomb-structured layered double hydroxide composite material with excellent electrochemical performance.
[0006] The technical problem that this invention also aims to solve is to provide a method for preparing honeycomb-shaped ZIF-derived layered double hydroxide composite materials using ion exchange.
[0007] The final technical problem to be solved by this invention is to provide the application of honeycomb-structured layered double hydroxide composite electrode material in the preparation of composite electrode materials.
[0008] Technical Solution: To solve the above-mentioned technical problems, this invention provides a method for preparing a honeycomb-shaped ZIF-derived layered double hydroxide composite material, comprising the following steps:
[0009] (1) The methanol solution of dimethylimidazole was quickly added to the methanol solution of nitrate, the mixture was stirred magnetically, allowed to stand at room temperature, centrifuged, washed with methanol, and dried under vacuum to obtain polyhedron ZIF-67.
[0010] (2) ZIF-67 and Ni(NO3)2·6H2O were dispersed in ethanol with a volume fraction of 90-95%. At a certain reaction temperature, the ZIF-67 ethanol suspension was added dropwise to the nickel nitrate ethanol solution. After the reaction was completed, the sample was collected and washed with ethanol. Finally, the sample was dried under vacuum to obtain the ZIF-67@NiCo LDH honeycomb composite material.
[0011] Further research revealed that the honeycomb structure and high-performance composite material can only be obtained by reacting in ethanol with a volume fraction of 90-95%. When using ethanol with other volume fractions, such as 80%, different composite materials with different morphologies are obtained. When the volume fraction of ethanol is greater than 95%, a hollow polyhedral structure assembled from nanosheets is obtained; when the volume fraction of ethanol is between 90-95%, a honeycomb structure assembled from nanosheets is obtained; and when the volume fraction of ethanol is less than 90%, an irregular blocky material is obtained. The main reason for the different morphologies is that when the water content is low, the ion exchange rate of the sample is slow, forming a nanosheet structure. As the water content increases, the ion exchange rate accelerates, forming a honeycomb structure assembled from nanosheets. When the water content is greater than 10%, ion exchange only occurs on the surface of the material, and a nanosheet structure cannot be obtained.
[0012] In step (1), the concentration of the methanol solution of cobalt nitrate is 50-100 g / L, and the concentration of the methanol solution of 2-methylimidazole is 10-50 g / L.
[0013] In step (2), the mass ratio of ZIF-67 to Ni(NO3)2·6H2O is 1:(2-3).
[0014] In step (2), the concentration of ZIF-67 in the ZIF-67 suspension is 1-4 g / L.
[0015] In step (2), the concentration of Ni(NO3)2·6H2O in the nickel nitrate ethanol solution is 5-15 g / L.
[0016] In step (2), the reaction temperature is 25-35℃ and the reaction time is 1-9 hours.
[0017] The specific preparation method of this invention is as follows:
[0018] (1) Quickly add 10-50 g / L dimethylimidazolium methanol solution to 50-100 g / L cobalt nitrate methanol solution, stir magnetically for 1 hour, let stand at room temperature for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain ZIF-67 polyhedron.
[0019] (2) Disperse ZIF-67 at a concentration of 1-4 g / L in 30 mL of ethanol, and dissolve Ni(NO3)2·6H2O at a relative content of 5-15 g / L in 10 mL of ethanol, with the volume fraction of ethanol used being 90%-95%. Then, add the ZIF-67 dispersion to the Ni(NO3)2·6H2O solution under stirring, and stir the reaction at 25-35℃ for 1-9 hours. After the reaction is completed, collect the sample and wash it with ethanol, and vacuum dry it for 12 hours to obtain ZIF-67@NiCo LDH honeycomb composite material.
[0020] (3) The ZIF-67@NiCo LDH honeycomb composite material was uniformly mixed with polytetrafluoroethylene and acetylene black at a mass ratio of 8:1:1 to form a slurry, which was then coated onto the pretreated nickel foam as the working electrode of the supercapacitor. The platinum sheet was used as the counter electrode, mercury oxide was used as the reference electrode, and potassium hydroxide was used as the electrolyte. The electrode performance of the supercapacitor was then tested.
[0021] The present invention also includes the ZIF-67@NiCo LDH honeycomb composite material prepared by the aforementioned preparation method.
[0022] The present invention also includes the application of the ZIF-67@NiCo LDH honeycomb composite material in the preparation of composite electrodes.
[0023] The preparation of the composite electrode includes: uniformly mixing the ZIF-67@NiCo LDH honeycomb composite material with polytetrafluoroethylene and acetylene black to form a slurry, and coating it onto pretreated nickel foam. The slurry loading is 0.8-1.5 mg / cm³. 2 .
[0024] The present invention also includes a ZIF-67@NiCo LDH composite electrode, wherein the composite electrode comprises the ZIF-67@NiCo LDH honeycomb composite material.
[0025] In this invention, electrochemical testing is conducted in an environment with potassium hydroxide electrolyte, wherein the concentration of potassium hydroxide electrolyte is 2-6 mol / L. The prepared composite electrode is used as the working electrode, the platinum sheet is used as the counter electrode, and mercury / mercury oxide is used as the reference electrode, forming a three-electrode system for electrochemical testing.
[0026] The reaction mechanism of this invention: This invention uses nickel ions to etch ZIF-67, and obtains a ZIF-derived ZIF-67@NiCo LDH honeycomb structure in situ by controlling the etching time, etching temperature, and solvent water content. Specifically, when the ethanol volume fraction is 90-95%, a honeycomb structure assembled from nanosheets is obtained. The honeycomb structure assembled from nanosheets avoids the aggregation and accumulation of LDH, increases the specific surface area of the material, exposes more electrochemical active sites, and shortens the distance of electron and ion transport. At the same time, the honeycomb structure makes full use of the internal space of the material and buffers the volume expansion of the electrode during charging and discharging, effectively improving the specific capacity and cycle stability of the electrode. Therefore, this material can fully utilize the synergistic effect between different materials to improve the specific capacity of the electrode. The composite material prepared by this invention has a honeycomb structure, which is assembled from nanosheet structures. The honeycomb structure of this invention can increase the contact area between the electrode and the electrolyte, improve the active sites of electrochemical reaction, increase the electron transport channels and improve conductivity, and solve the problems of easy agglomeration and accumulation of layered double hydroxides and structural collapse during cycling, thereby improving the cycling performance of the electrode material and thus improving the electrochemical performance of the electrode material.
[0027] Beneficial Effects: Compared with existing technologies, this invention fully leverages the synergistic effect between different materials to improve the specific capacity of the electrode. This invention utilizes an ion exchange method to directly obtain a honeycomb-shaped ZIF-derived layered double hydroxide composite material. This method is simple to operate, has good reproducibility, and is easy to scale up for production. The electrode prepared from the ZIF-67@NiCo LDH honeycomb composite material of this invention exhibits excellent electrochemical performance. Attached Figure Description
[0028] Figure 1 Scanning electron microscope image of the sample in Example 3;
[0029] Figure 2 Charge-discharge curves of sample in Example 3;
[0030] Figure 3 Scanning electron microscope image of sample 1 (Comparative Example 1). Detailed Implementation
[0031] To better understand the present invention, the following embodiments are provided to further illustrate the invention, but the scope of the invention is not limited to the examples below.
[0032] Example 1: Preparation and performance testing of ZIF-67@NiCo LDH
[0033] 1. Preparation of ZIF-67@NiCo LDH
[0034] (1) Add 95 mL of 20 g / L dimethylimidazole methanol solution to 45 mL of 50 g / L cobalt nitrate methanol solution, stir magnetically for 1 hour, let stand at room temperature for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain ZIF-67 polyhedron.
[0035] (2) ZIF-67 with a concentration of 1 g / L was dispersed in 30 mL of ethanol, and Ni(NO3)2·6H2O with a concentration of 6 g / L was dissolved in 10 mL of ethanol. The volume fraction of ethanol used was 90%. Then, the ZIF-67 dispersion was added to the Ni(NO3)2·6H2O solution under stirring. The reaction was carried out at 30 °C for 3 hours. After the reaction was completed, the sample was collected, washed with ethanol, and vacuum dried for 12 hours to obtain ZIF-67@NiCo LDH honeycomb composite material.
[0036] 2. Preparation of ZIF-67@NiCo LDH honeycomb composite electrode material
[0037] ZIF-67@NiCo LDH honeycomb composite material was uniformly mixed with polytetrafluoroethylene and acetylene black at a mass ratio of 8:1:1 to form a slurry. The slurry was prepared at a concentration of 1 mg / cm³. 2 The platinum sheet is coated onto the pretreated nickel foam and used as the working electrode of the supercapacitor. The platinum sheet is used as the counter electrode, the mercury oxide is used as the reference electrode, and the electrolyte is a 2 mol / L potassium hydroxide solution.
[0038] 3. Performance Testing
[0039] The ZIF-67@NiCo LDH honeycomb composite electrode material was tested for supercapacitor electrode performance. At 1 A / g, the specific capacitance of the ZIF-67@NiCo LDH honeycomb composite electrode material reached 1620 Farads / gram, and the capacitance retention was 68% at a current density of 10 A / g. After 10,000 cycles at a current density of 10 A / g, the capacitance retention of the ZIF-67@NiCoLDH honeycomb composite material was 73%.
[0040] Example 2: Preparation and Performance Testing of ZIF-67@NiCo LDH Honeycomb Composite Electrode Material
[0041] 1. Preparation of ZIF-67@NiCo LDH
[0042] (1) Add 95 mL of 30 g / L dimethylimidazolium methanol solution to 45 mL of 65 g / L cobalt nitrate methanol solution, stir magnetically for 1 hour, let stand at room temperature for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain ZIF-67 polyhedron.
[0043] (2) ZIF-67 with a concentration of 3 g / L was dispersed in 30 mL of ethanol, and Ni(NO3)2·6H2O with a concentration of 10 g / L was dissolved in 10 mL of ethanol. The volume fraction of ethanol used was 95%. Then, the ZIF-67 dispersion was added to the Ni(NO3)2·6H2O solution under stirring. The reaction was carried out at 30 °C for 4 hours. After the reaction was completed, the sample was collected, washed with ethanol, and vacuum dried for 12 hours to obtain ZIF-67@NiCo LDH honeycomb composite material.
[0044] 2. Preparation of ZIF-67@NiCo LDH honeycomb composite electrode material
[0045] ZIF-67@NiCo LDH honeycomb composite material was uniformly mixed with polytetrafluoroethylene and acetylene black at a mass ratio of 8:1:1 to form a slurry. The slurry was prepared at a concentration of 1 mg / cm³. 2 The platinum sheet is coated onto the pretreated nickel foam and used as the working electrode of the supercapacitor. The platinum sheet is used as the counter electrode, the mercury oxide is used as the reference electrode, and the electrolyte is a 3 mol / L potassium hydroxide solution.
[0046] 3. Performance Testing
[0047] The ZIF-67@NiCo LDH honeycomb composite electrode material was tested for supercapacitor electrode performance. At 1 A / g, the specific capacitance of the ZIF-67@NiCo LDH honeycomb composite electrode material reached 1680 Farads / gram, and the capacitance retention was 70% at a current density of 10 A / g. After 10,000 cycles at a current density of 10 A / g, the capacitance retention of the ZIF-67@NiCoLDH honeycomb composite material was 75%.
[0048] Example 3: Preparation and performance testing of ZIF-67@NiCo LDH
[0049] 1. Preparation of ZIF-67@NiCo LDH
[0050] (1) Add 95 mL of 40 g / L dimethylimidazolium methanol solution to 45 mL of 70 g / L cobalt nitrate methanol solution, stir magnetically for 1 hour, let stand at room temperature for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain ZIF-67 polyhedron.
[0051] (2) ZIF-67 with a concentration of 2 g / L was dispersed in 30 mL of ethanol, and Ni(NO3)2·6H2O with a concentration of 14 g / L was dissolved in 10 mL of ethanol. The volume fraction of ethanol used was 95%. Then, the ZIF-67 dispersion was added to the Ni(NO3)2·6H2O solution under stirring. The reaction was carried out at 30 °C for 5 hours. After the reaction was completed, the sample was collected, washed with ethanol, and vacuum dried for 12 hours to obtain ZIF-67@NiCo LDH honeycomb composite material.
[0052] 2. Preparation of ZIF-67@NiCo LDH honeycomb composite electrode material
[0053] ZIF-67@NiCo LDH honeycomb composite material was uniformly mixed with polytetrafluoroethylene and acetylene black at a mass ratio of 8:1:1 to form a slurry. The slurry was prepared at a concentration of 1 mg / cm³. 2 The platinum sheet is coated onto the pretreated nickel foam and used as the working electrode of the supercapacitor. The platinum sheet is used as the counter electrode, the mercury oxide is used as the reference electrode, and the electrolyte is a 6 mol / L potassium hydroxide solution.
[0054] 3. Performance Testing
[0055] The ZIF-67@NiCo LDH honeycomb composite electrode material was tested for supercapacitor electrode performance. At 1 A / g, the specific capacitance of the ZIF-67@NiCo LDH honeycomb composite electrode material reached 1730 Farads / gram, and the capacitance retention was 76% at a current density of 10 A / g. After 10,000 cycles at a current density of 10 A / g, the capacitance retention of the ZIF-67@NiCoLDH honeycomb composite material was 82%.
[0056] Example 4: Preparation and performance testing of ZIF-67@NiCo LDH
[0057] 1. Preparation of ZIF-67@NiCo LDH
[0058] (1) Add 95 mL of 50 g / L dimethylimidazolium methanol solution to 45 mL of 90 g / L cobalt nitrate methanol solution, stir magnetically for 1 hour, let stand at room temperature for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain ZIF-67 polyhedron.
[0059] (2) ZIF-67 with a concentration of 4 g / L was dispersed in 30 mL of ethanol, and Ni(NO3)2·6H2O with a concentration of 14 g / L was dissolved in 10 mL of ethanol. The volume fraction of ethanol used was 95%. Then, the ZIF-67 dispersion was added to the Ni(NO3)2·6H2O solution under stirring. The reaction was carried out at 30 °C for 6 hours. After the reaction was completed, the sample was collected, washed with ethanol, and vacuum dried for 12 hours to obtain ZIF-67@NiCo LDH honeycomb composite material.
[0060] 2. Preparation of ZIF-67@NiCo LDH honeycomb composite electrode material
[0061] ZIF-67@NiCo LDH honeycomb composite material was uniformly mixed with polytetrafluoroethylene and acetylene black at a mass ratio of 8:1:1 to form a slurry, which was then coated onto pretreated nickel foam as the working electrode of the supercapacitor. A platinum sheet was used as the counter electrode, mercury oxide was used as the reference electrode, and the electrolyte was a 6 mol / L potassium hydroxide solution.
[0062] 3. Performance Testing
[0063] The ZIF-67@NiCo LDH honeycomb composite electrode material was tested for supercapacitor electrode performance. At 1 A / g, the specific capacitance of the ZIF-67@NiCo LDH honeycomb composite electrode material reached 1700 Farads / gram, and the capacitance retention was 75% at a current density of 10 A / g. After 10,000 cycles at a current density of 10 A / g, the capacitance retention of the ZIF-67@NiCoLDH honeycomb composite material was 80%.
[0064] Comparative Example
[0065] 1. Preparation of ZIF-67@NiCo LDH bulk materials
[0066] (1) Add 95 mL of 40 g / L dimethylimidazolium methanol solution to 45 mL of 70 g / L cobalt nitrate methanol solution, stir magnetically for 1 hour, let stand at room temperature for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain ZIF-67 polyhedron.
[0067] (2) ZIF-67 with a concentration of 2 g / L was dispersed in 30 mL of ethanol, and Ni(NO3)2·6H2O with a concentration of 14 g / L was dissolved in 10 mL of ethanol. The volume fraction of ethanol used was 80%. Then, the ZIF-67 dispersion was added to the Ni(NO3)2·6H2O solution under stirring. The reaction was carried out at 30 °C for 5 hours. After the reaction was completed, the sample was collected, washed with ethanol, and vacuum dried for 12 hours to obtain ZIF-67@NiCo LDH block material.
[0068] 2. Preparation of ZIF-67@NiCo LDH electrode material
[0069] ZIF-67@NiCo LDH block composite material was uniformly mixed with polytetrafluoroethylene and acetylene black at a mass ratio of 8:1:1 to form a slurry. The slurry was prepared at a concentration of 1 mg / cm³. 2 The platinum sheet is coated onto the pretreated nickel foam and used as the working electrode of the supercapacitor. The platinum sheet is used as the counter electrode, the mercury oxide is used as the reference electrode, and the electrolyte is a 6 mol / L potassium hydroxide solution.
[0070] 3. Performance Testing
[0071] The ZIF-67@NiCo LDH electrode material was tested for its supercapacitor electrode performance. At 1 A / g, the specific capacitance of the ZIF-67@NiCo LDH electrode material was approximately 800 Farads / gram, and the capacitance retention was 50% at a current density of 10 A / g. After 10,000 cycles at a current density of 10 A / g, the capacitance retention of the ZIF-67@NiCo LDH bulk composite material was 40%.
Claims
1. A method for preparing a honeycomb-shaped ZIF-derived layered double hydroxide composite material, characterized in that, Includes the following steps: (1) The methanol solution of dimethylimidazole was quickly added to the methanol solution of cobalt nitrate, and the mixture was stirred magnetically. The mixture was allowed to stand at room temperature, centrifuged, washed with methanol, and dried under vacuum to obtain polyhedron ZIF-67. (2) ZIF-67 and Ni(NO3)2∙6H2O were dispersed in 95% ethanol. At a certain reaction temperature, the ZIF-67 ethanol suspension was added dropwise to the nickel nitrate ethanol solution. After the reaction was completed, the sample was collected and washed with ethanol. Finally, the sample was dried under vacuum to obtain ZIF-67@NiCo LDH honeycomb composite material. In step (1), the concentration of the methanol solution of cobalt nitrate is 50-100 g / L, and the concentration of the methanol solution of 2-methylimidazole is 10-50 g / L. In step (2), the mass ratio of ZIF-67 to Ni(NO3)2∙6H2O is 1:(2-3). In step (2), the concentration of ZIF-67 in the ZIF-67 suspension is 1-4 g / L. In step (2), the concentration of Ni(NO3)2∙6H2O in the nickel nitrate ethanol solution is 5-15 g / L. In step (2), the reaction temperature is 25-35 ℃, and the reaction time is 1-9 hours.
2. The ZIF-67@NiCo LDH honeycomb composite material prepared by the preparation method according to claim 1.
3. The application of the ZIF-67@NiCo LDH honeycomb composite material according to claim 2 in the preparation of composite electrodes.
4. The application according to claim 3, characterized in that, The preparation of the composite electrode includes: uniformly mixing the ZIF-67@NiCo LDH honeycomb composite material with polytetrafluoroethylene and acetylene black to form a slurry, and coating it onto pretreated nickel foam. The loading of the slurry is 0.8-1.5 mg / cm³. 2 .
5. A ZIF-67@NiCo LDH composite electrode, characterized in that, The composite electrode comprises the ZIF-67@NiCo LDH honeycomb composite material as described in claim 2.