A preparation method and application of CuCo2O4@MoNi-LDH composite material

Abstract

This invention discloses a CuCo2O4@MoNi-LDH composite material, composed of hollow spherical CuCo2O4 and nanosheet-like MoNi-LDH, exhibiting a secondary structure. CuCo2O4 serves as the matrix material, with MoNi-LDH coated on the surface of CuCo2O4. The CuCo2O4 is prepared by first using a hydrothermal method to prepare spherical Cu-Co-gly, followed by calcination. The MoNi-LDH is prepared by using a hydrothermal method to in-situ prepare nanosheets on the surface of CuCo2O4, achieving loading. The specific preparation method includes the following steps: 1. Preparation of CuCo2O4; 2. Preparation of CuCo2O4@MoNi-LDH. As a supercapacitor electrode material, it exhibits a specific capacitance of 1200-1300 F / g at a discharge current density of 1 A / g within a charge-discharge range of 0-0.5 V; and a cycle stability of 88% after 6000 cycles. It possesses excellent material stability and excellent ion transport capabilities.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor technology, specifically to a method for preparing CuCo2O4@MoNi-LDH composite material and its application. Background Technology

[0002] Supercapacitors (SCs), as one of the most attractive electronic devices, have attracted much attention due to their high power density, long cycle stability, and safe operation, demonstrating significant application potential. Based on their energy storage principles, supercapacitors can be divided into three categories: electric double-layer capacitors (EDLCs), pseudocapacitors (also known as Faraday capacitors), and hybrid supercapacitors. Compared to EDLCs, pseudocapacitors store charge through a typical Faraday redox process and often exhibit higher specific capacitance. The performance of a supercapacitor largely depends on the electrode materials. To date, the different electrode materials used in supercapacitors can be categorized into three types: carbon materials, conductive polymers, and metal compounds. Among these, nickel, cobalt, and iron-based compounds, possessing multiple redox states, have been widely used as supercapacitor electrode materials due to their strong Faraday reactions during charge and discharge.

[0003] Spinel cobalt oxide (MCo2O4, M = Cu, Fe, Mg, etc.) in transition metal oxides possesses excellent electrochemical performance due to its abundant active sites and high conductivity, making it an important electrode material for supercapacitors. Among spinel cobalt oxides, CuCo2O4 also features low synthesis cost, high stability, and significant rate-degrading capabilities due to the synergistic effect of copper and cobalt elements.

[0004] For example, prior art 1 (Li, G., et al., Self-templated formation of CuCo2O4 triple-shelled hollow microspheres for all-solid-state asymmetric supercapacitors. Journal of Alloys and Compounds, 2019. 787: p. 694-699.) prepared a special triple-shelled hollow CuCo2O4 using a solvothermal / calcination method. This achieved the desired effect in 1 A g... -1 Under these conditions, the specific capacitance is 691 F g. -1Furthermore, the three-shell structure buffers volume expansion / contraction to enhance structural stability by reducing stress and strain during charging / discharging, resulting in only a 6% capacity loss after 2000 cycles.

[0005] Building upon this, combining CuCo2O4 with a support can further improve the rate capability and cycle performance of supercapacitors. By utilizing multidimensional effects and hollow structures such as spheres, tubes, cubes, and polyhedra, abundant internal voids are provided, resulting in high specific surface area and long diffusion channels. This allows for the regulation of electron transfer / separation efficiency and ion diffusion rate, ultimately enhancing the technical effect of improving electrochemical activity.

[0006] For example, the inventors' previous work, prior art 2 (Yang, XY, et al., Co3O4-doped two-dimensional carbon nanosheet as an electrode material for high-performance asymmetric supercapacitors. Electrochimica Acta, 2020. 335.), prepared a sea urchin-like composite material Co3O4-Ni / GO through low-temperature calcination and hydrothermal methods. By combining graphene with metal oxides, agglomeration was prevented while improving rate performance. This was achieved by utilizing the inherent high stability of carbon-based materials, resulting in a 90% capacity retention rate after 3000 cycles. However, such methods of introducing carbon-based materials to improve stability all suffer from the problem of lower specific capacitance performance due to the carbon-based materials.

[0007] To address the aforementioned issues, materials with inherently high specific capacitance can be used to replace carbon-based materials, thereby improving the specific capacitance performance of the materials.

[0008] For example, the inventors' previous work, prior art 3 (Mao, X., et al., Core-shell structured CuCo2S4@CoMoO4 nanorods for advanced electrode materials. Journal of Alloys and Compounds, 2020. 844.), prepared CuCo2S4@CoMoO4 through a hydrothermal and low-temperature calcination process, obtaining a core-shell heterostructure. By increasing the contact area of ​​electrolyte ions, charge transfer was promoted, resulting in improved electrochemical behavior. However, after 3000 charge-discharge cycles, the specific capacitance retention rate of this technology only reached 83%, indicating room for further improvement. The inventors' research indicates that although sulfides possess good electronic conductivity and low resistance, the significant volume expansion and contraction of the sulfide-metal oxide combination during charge-discharge processes leads to decreased structural stability, resulting in poor cycle stability of the composite material.

[0009] The analysis of existing technologies above reveals that carbon materials, represented by graphene, and metal sulfides, as carriers, still have their own insurmountable technical problems. Based on this analysis, the inventors believe that selecting materials with high electrochemical performance as carriers and controlling their morphology can effectively improve the electrochemical performance and stability of composite materials.

[0010] According to existing technology 4 (Gu, TH, et al., Porous Hybrid Network of Graphene and Metal Oxide Nanosheets as Useful Matrix for Improving the ElectrodePerformance of Layered Double Hydroxides. Small, 2015. 11(32): p. 3921-31.), the combination of metal oxides and layered hydroxide LDH can provide abundant electroactive sites for redox reactions and a spacious ion library, thereby enhancing the diffusion kinetics within the electrode, which not only improves electrochemical performance but also enhances stability.

[0011] Furthermore, layered double hydroxide LDHs, besides possessing high specific surface area and excellent transport properties due to their layered structure, thus exhibiting high specific capacitance, also demonstrate synergistic effects with metal oxides when used as a support due to the tunability of their composition and morphology. Moreover, the metal elements in layered double hydroxide LDHs can also influence metal oxides; that is, the constituent metal elements of layered double hydroxide LDHs have a significant impact on the electrochemical performance of the final composite material. According to the inventors' research, molybdenum-nickel layered double hydroxide LDHs, abbreviated as MoNi-LDH, can greatly enhance the electrochemical activity of LDH during redox reactions due to their multiple oxidation states.

[0012] For example, existing technology 5 (Jeghan, SMN, N. Kim, and G. Lee, Mo-incorporated three-dimensional hierarchical ternary nickel-cobalt-molybdenum layer doublehydroxide for high-efficiency water splitting. International Journal of Hydrogen Energy, 2021. 46(43): p. 22463-22477.) demonstrates that molybdenum-nickel-based layered hydroxides not only possess high specific surface area but also exhibit high durability with almost no aggregation during the reaction process; at the same time, they can provide electroactive sites required for redox reactions.

[0013] Based on the above analysis of existing technologies, it is clear that to improve the stability of metal oxides while maintaining high electrochemical performance, the following requirements must be met simultaneously: 1. By preparing metal oxides with multidimensional effects as matrix materials, the stability of composite materials can be fundamentally improved; 2. By loading layered double hydroxides, the high specific surface area and transport characteristics of the metal hydroxides (LDHs) are utilized to achieve synergistic effects with the metal oxides. 3. During the loading process, the microstructure of the composite material is adjusted to further improve its electrochemical performance and stability. Summary of the Invention

[0014] The purpose of this invention is to provide a method for preparing CuCo2O4@MoNi-LDH composite material and its application in the field of supercapacitors.

[0015] The core technical feature for achieving the above-mentioned invention objective is controlling the morphology of metal oxides and supported metal hydroxides. The specific principle is as follows: First, an annealing and calcination method is used to form a hollow porous structure in the metal oxide. The hollow porous structure, by creating internal voids, achieves the technical effects of increasing the specific surface area and obtaining long diffusion channels, thereby achieving the technical effects of adjusting electron transfer / separation efficiency and ion diffusion rate, and ultimately achieving the technical effect of promoting electrochemical activity.

[0016] Then, a hydrothermal method is used to coat the hollow porous metal oxide CuCo2O4 with the metal hydroxide MoNi-LDH; this further increases the specific surface area of ​​the composite material and achieves the technical effect of significantly improving the electrochemical performance of the composite material.

[0017] The specific technical solution to achieve the above-mentioned invention objective is as follows: A CuCo2O4@MoNi-LDH composite material is composed of hollow spherical CuCo2O4 and nanosheet-like MoNi-LDH. The resulting material has a secondary structure, which is a structure in which nanosheets are grown on spherical structures. CuCo2O4 is the matrix material, and its microstructure is a hollow spherical structure with a diameter of 500-550 nm, which provides the main morphology and structural stability. The MoNi-LDH is coated on the surface of CuCo2O4, and its microstructure is a hollow spherical structure with coated nanosheets with a diameter of 550-600 nm. This structure can improve the specific surface area of ​​the material, enhance the ion transport rate, and ultimately improve the electrochemical performance of the supercapacitor.

[0018] The CuCo2O4 is prepared by using copper nitrate trihydrate, cobalt nitrate hexahydrate, isopropanol and glycerol as raw materials, first preparing spherical Cu-Co-gly by hydrothermal method, and then calcining the Cu-Co-gly to form the structure; the MoNi-LDH is prepared by using nickel nitrate, sodium molybdate and urea as raw materials, preparing nanosheets in situ on the surface of CuCo2O4 by hydrothermal method, and achieving loading.

[0019] A method for preparing CuCo2O4@MoNi-LDH composite material includes the following steps: Step 1, Preparation of CuCo2O4: Copper nitrate trihydrate and cobalt nitrate hexahydrate are dissolved in isopropanol, and then glycerol is added to obtain the first hydrothermal reaction solution. Then, the first hydrothermal reaction is carried out under certain conditions. The resulting reaction product is washed with anhydrous ethanol and dried under certain conditions to obtain Cu-Co-gly. Finally, annealing is carried out under certain conditions to obtain CuCo2O4. In step 1, the ratio of copper nitrate trihydrate: cobalt nitrate hexahydrate: isopropanol: glycerol satisfies 0.25 mmol: 0.5 mmol: 30 ml: 6 ml; In step 1, the conditions for the first hydrothermal reaction are: hydrothermal temperature of 150-200 ℃ and hydrothermal time of 6-8 h; the drying conditions are: 60-80 ℃ and drying time of 20-24 h. In step 1, the annealing conditions are as follows: under air conditions, the heating rate is 1 °C / min, the annealing temperature is 300-350 °C, and the annealing time is 2-3 hours. Step 2, Preparation of CuCo2O4@MoNi-LDH: Nickel nitrate, sodium molybdate, and urea are dissolved in deionized water and stirred until a mixed solution is obtained. Then, the CuCo2O4 obtained in Step 1 is added to the mixed solution, and a second hydrothermal reaction is carried out under certain conditions. The resulting reaction product is washed with distilled water and anhydrous ethanol, and then dried under certain conditions to obtain the CuCo2O4@MoNi-LDH composite material, abbreviated as CuCo2O4@MoNi-LDH. In step 2, the ratio of nickel nitrate: sodium molybdate: urea: deionized water: CuCo2O4 satisfies 1 mmol: 1 mmol sodium molybdate: 5 mmol: 50 ml: 0.25 g; In step 2, the conditions for the second hydrothermal reaction are: hydrothermal temperature of 100-150 ℃ and hydrothermal time of 4-6 h; the drying conditions are: drying temperature of 60-80 ℃ and drying time of 20-24 h.

[0020] The application of CuCo2O4@MoNi-LDH composite material as a supercapacitor electrode material shows that, in the charging and discharging range of 0-0.5 V, the specific capacitance is 1200-1300 F / g at a discharge current density of 1 A / g. After 6000 cycles, the cycle stability is 88%.

[0021] The present invention experimentally tested the obtained structurally stable CuCo2O4@MoNi-LDH composite material, and the results are as follows: The structurally stable CuCo2O4@MoNi-LDH composite material was tested by X-ray diffraction (XRD). The diffraction crystal planes corresponding to different diffraction peaks showed that the composite material was composed of two substances: CuCo2O4 and MoNi-LDH. Scanning electron microscopy (SEM) analysis revealed that the spherical CuCo2O4@MoNi-LDH composite material was uniformly coated with nanosheets of MoNi-LDH material, forming a uniform structure of long nanosheets on spheres. This indicates that the structurally stable CuCo2O4@MoNi-LDH composite material was successfully prepared. Transmission electron microscopy (TEM) analysis revealed that the structurally stable CuCo2O4@MoNi-LDH composite material has a hollow core-shell structure inside CuCo2O4 and a hollow core-shell structure with MoNi-LDH nanosheets on the surface. This indicates that a structurally stable CuCo2O4@MoNi-LDH composite material was successfully prepared. Nitrogen adsorption-desorption tests showed that the specific surface area of ​​the structurally stable CuCo2O4@MoNi-LDH composite material was generally better than that of CuCo2O4. Electrochemical testing and electrochemical cycling stability testing of structurally stable CuCo2O4@MoNi-LDH composite materials: Charge and discharge within the range of 0-0.5V, with a discharge current density of 1 A g. -1 At that time, the specific capacitance of the structurally stable CuCo2O4@MoNi-LDH composite material was 1200-1300 F / g, and the specific capacitance retention rate was 88% after 6000 cycles.

[0022] The above experiments show that, The role of the CuCo2O4 matrix is ​​as follows: 1. CuCo2O4 has a uniformly sized hollow structure. The hollow structure of CuCo2O4 makes its structure more stable, and its unique hollow structure increases its specific surface area, allowing it to contact and react with the electrolyte to a greater extent. 2. The combination of oxides and hydroxides enhances the electrochemical activity of hydroxides, and the combination of the two results in a larger specific capacitance and better rate characteristics.

[0023] The function of the MoNi-LDH load is: 1. It solves the problems of structural degradation and low conductivity of metal oxides directly exposed to electrolytes during rapid charging / discharging processes; 2. Nanosheets loaded with MoNi-LDH have a larger contact area with the electrolyte, thus providing more active sites; 3. Interconnected LDH nanosheets help shorten the distance of electron diffusion and enhance the electrochemical reaction to generate more pseudocapacitance.

[0024] Therefore, the CuCo2O4@MoNi-LDH composite material of the present invention has the following advantages over the prior art: 1. The hollow structure of CuCo2O4 gives metal oxides a greater structural advantage, which not only improves the stability of the material, but also increases its specific surface area due to its unique hollow structure, allowing for greater contact and reaction with the electrolyte. 2. A core-shell structure with MoNi-LDH as the "shell" and CuCo2O4 as the "core" was successfully synthesized by hydrothermal method with metal hydroxide MoNi-LDH and metal oxide CuCo2O4. This structure can provide more active sites in the subsequent reaction process. At the same time, the interconnected LDH nanosheets help to shorten the distance of electron diffusion and enhance the electrochemical reaction to generate more pseudocapacitance. Therefore, the core-shell composite material of metal oxide and metal hydroxide of the present invention improves ion transport capability and has broad application prospects in the field of supercapacitors. Attached image description: Figure 1 X-ray diffraction patterns of CuCo2O4@MoNi-LDH in Example 1, CuCo2O4 prepared in step 1 of Example 1, and MoNi-LDH prepared in Comparative Example 1; Figure 2 The image shows a scanning electron microscope image of CuCo2O4 prepared in step 1 of Example 1 at a scale bar length of 100 nm. Figure 3 The scanning electron microscope image of MoNi-LDH prepared for Comparative Example 1 at a scale bar length of 1 μm; Figure 4 This is a scanning electron microscope image of CuCo2O4@MoNi-LDH prepared in Example 1 at a scale bar length of 100 nm; Figure 5 This is a transmission electron microscope (TEM) image of CuCo2O4@MoNi-LDH prepared in Example 1 with a scale bar length of 200 nm. Figure 6 Scanning electron microscope image of CuCo2O4@MoNi-LDH 2:1 prepared for Comparative Example 2 at a scale bar length of 100 nm; Figure 7 Scanning electron microscope image of CuCo2O4@MoNi-LDH 1:2 prepared for Comparative Example 3 at a scale bar length of 100 nm; Figure 8 The nitrogen adsorption-desorption curves are shown for CuCo2O4 prepared in step 1 of Example 1 and CuCo2O4@MoNi-LDH composite material prepared in Example 1. Figure 9Charge-discharge curves of the structurally stable CuCo2O4@MoNi-LDH composite material prepared in Example 1; Figure 10 Cycle life curve of the structurally stable CuCo2O4@MoNi-LDH composite material prepared in Example 1; Figure 11 Charge-discharge curves of the structurally stable CuCo2O4@MoNi-LDH composite material prepared in Example 1 and the CuCo2O4 composite material prepared in step 1 of Example 1; Figure 12 Charge-discharge curves of the structurally stable CuCo2O4@MoNi-LDH composite material prepared in Example 1 and the MoNi-LDH composite material prepared in Comparative Example 1; Figure 13 Charge-discharge curves of the structurally stable CuCo2O4@MoNi-LDH composite material prepared in Example 1, CuCo2O4@MoNi-LDH 2:1 prepared in Comparative Example 2, and CuCo2O4@MoNi-LDH 1:2 prepared in Comparative Example 3. Detailed Implementation

[0025] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0026] Example 1 A method for preparing CuCo2O4@MoNi-LDH composite material includes the following steps: Step 1, Preparation of CuCo2O4: 0.25 mmol copper nitrate trihydrate and 0.5 mmol cobalt nitrate hexahydrate were dissolved in 30 ml isopropanol, and then 6 ml glycerol was added to obtain the first hydrothermal reaction solution. The first hydrothermal reaction was then carried out at a hydrothermal temperature of 180 °C for 6 h. The resulting reaction product was washed with anhydrous ethanol and dried at a drying temperature of 60 °C for 24 h to obtain Cu-Co-gly. Finally, under air conditions, the product was annealed at a heating rate of 1 °C / min, an annealing temperature of 350 °C, and an annealing time of 2 h to obtain CuCo2O4. Step 2, Preparation of CuCo2O4@MoNi-LDH: 1 mmol nickel nitrate, 1 mmol sodium molybdate, and 5 mmol urea were dissolved in 50 ml deionized water and stirred until a mixed solution was obtained. Then, 0.25 g of CuCo2O4 obtained in Step 1 was added to the mixed solution, and a second hydrothermal reaction was carried out at a hydrothermal temperature of 120 ℃ for 4 h. The resulting reaction product was washed with distilled water and anhydrous ethanol, and then dried at a drying temperature of 60 ℃ for 24 h to obtain the CuCo2O4@MoNi-LDH composite material, abbreviated as CuCo2O4@MoNi-LDH.

[0027] To demonstrate the role of MoNi-LDH in the composite material, in addition to characterizing and testing the CuCo2O4@MoNi-LDH obtained in step 2, the CuCo2O4 obtained in step 1 and the step itself were also characterized and tested.

[0028] To verify the composition and reaction mechanism of the obtained CuCo2O4@MoNi-LDH, XRD tests were performed on the CuCo2O4 prepared in step 1 of Example 1, the CuCo2O4@MoNi-LDH obtained in step 2, and the MoNi-LDH in Comparative Example 1. The test results are as follows: Figure 1 As shown, The CuCo2O4 test detected the characteristic peak of CuCo2O4, indicating that CuCo2O4 was successfully synthesized in step 1; The MoNi-LDH test detected characteristic peaks of the LDH structure, indicating that Comparative Example 1 successfully synthesized MoNi-LDH. At the same time, the broad diffraction peaks indicate that the stable combination of Ni and Mo and the low crystallinity can form a synergistic effect in subsequent electrochemical performance. The CuCo2O4@MoNi-LDH test simultaneously detected characteristic peaks of both CuCo2O4 and LDH structures, indicating that step 2 successfully synthesized CuCo2O4@MoNi-LDH.

[0029] To demonstrate the microstructure of the obtained CuCo2O4@MoNi-LDH and its changes during the reaction process, SEM tests were performed on CuCo2O4 prepared in step 1 of Example 1, CuCo2O4@MoNi-LDH obtained in step 2 of Example 1, and MoNi-LDH in Example 1, respectively. TEM tests were also performed on CuCo2O4@MoNi-LDH obtained in step 2 of Example 1. The results are as follows: Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown: The SEM test results of CuCo2O4 are as follows: Figure 2 As shown, the microstructure is a spherical structure with a size range of 500-550 nm; SEM test results of MoNi-LDH are as follows Figure 3 As shown, the microstructure is a nanosheet structure with a size range of 1-2 μm; SEM test results of CuCo2O4@MoNi-LDH are as follows: Figure 4 As shown, the microstructure is a spherical structure with uniformly coated nanosheets, ranging in size from 550 to 600 nm; the TEM test results of CuCo2O4@MoNi-LDH are as follows. Figure 5 As shown, the sphere has a hollow interior and an overall core-shell structure with MoNi-LDH as the "shell" and CuCo2O4 as the "core".

[0030] Therefore, through Figure 2 CuCo2O4, Figure 3 MoNi-LDH, Figure 4 Comparative microstructure tests of CuCo2O4@MoNi-LDH revealed that the surface of CuCo2O4 with spherical structure is uniformly coated with MoNi-LDH nanosheets. Figure 2 CuCo2O 4、 Figure 4 The changes in the morphology of CuCo2O4@MoNi-LDH further prove that CuCo2O4@MoNi-LDH was successfully synthesized.

[0031] The specific electrochemical testing method used in this invention is as follows: 0.008 g of CuCo2O4@MoNi-LDH composite material, 0.001 g of acetylene black and 0.001 g of polytetrafluoroethylene micro powder are weighed and placed in a small agate mortar. 0.5 mL of ethanol is added for grinding. The ground sample is pressed with a 1 mm thick nickel foam current collector under a pressure of 10 kPa. The sample is dried in air at room temperature and cut into 2 cm × 2 cm pieces to obtain a supercapacitor electrode. The electrode is then immersed in a 6 M KOH solution. A calomel electrode and a platinum electrode are used as the reference electrode and the counter electrode, respectively. The specific capacitance GCD performance is tested in a three-electrode system.

[0032] The specific capacitance test results of CuCo2O4 are as follows: Figure 11 As shown, charging and discharging within the range of 0-0.5 V, with a discharge current density of 1 A g. -1 At that time, the specific capacitance was 200 F g -1 ; The specific capacitance test results of MoNi-LDH are as follows: Figure 12 As shown, charging and discharging within the range of 0-0.5V, with a discharge current density of 1 A g. -1At that time, the specific capacitance was 830 F g -1 ; The specific capacitance test results of CuCo2O4@MoNi-LDH are as follows: Figure 9 As shown, charging and discharging are performed within the range of 0-0.5V, with a discharge current density of 1 A g. -1 At that time, the specific capacitance was 1286 F g. -1 The results of the CuCo2O4@MoNi-LDH cycle test are as follows: Figure 10 As shown, the capacitance retention rate is 88% after 6000 cycles. The reason why the curve shows a decrease followed by an increase is that the material structure is a core-shell structure. After the cyclic reaction, some of the LDH coating falls off, exposing CuCo2O4, which works synergistically to increase the specific capacitance again.

[0033] By comparing CuCo2O4 with CuCo2O4@MoNi-LDH, it can be seen that after loading MoNi-LDH, at a discharge current density of 1 A g -1 At that time, the performance increased from 200 F g -1 Increased to 1286 F g -1 The specific capacitance has been increased to 643%.

[0034] By comparing MoNi-LDH with CuCo2O4@MoNi-LDH, it can be seen that after being combined with CuCo2O4, the discharge current density is 1 A g. -1 At that time, the performance was 830 F g -1 Increased to 1286 F g -1 The specific capacitance is increased to 155%.

[0035] Therefore, the above experiments show that, The role of CuCo2O4 is to facilitate the transport of electrons in the internal structure. In addition, the growth of MoNi-LDH nanosheets on CuCo2O4 nanospheres can effectively prevent the aggregation of nanosheets, thereby improving the stability of the overall structure while obtaining a larger contact surface with the electrolyte. The role of MoNi-LDH is to provide more active sites through the combination of transition metals Ni and Mo, thereby improving conductivity. In addition, the interconnection of LDH nanosheets helps to shorten the distance of electron diffusion and provides nanochannels and suitable mesoporous structures to promote ion transport, allowing more electroactive parts to participate in Faraday redox reactions, thereby effectively improving specific capacitance performance.

[0036] Based on the CuCo2O4@MoNi-LDH of Example 1, the CuCo2O4 of step 1 in Example 1, and the MoNi-LDH of Comparative Example 1, the following conclusions can be drawn: 1. When CuCo2O4 is used as a precursor to coat the surface of MoNi-LDH, the specific capacitance performance of the composite material is greatly improved compared with the case of single loading. The reason is that CuCo2O4 as the substrate material has a decisive influence on the overall morphology of CuCo2O4@MoNi-LDH composite material. Using CuCo2O4 as a conductive substrate not only facilitates the ultra-high-speed transport of electrons, but also increases the contact area between CuCo2O4@MoNi-LDH composite material and electrolyte, thereby accelerating ion diffusion. 2. The role of MoNi-LDH nanosheets in composite materials is to improve the specific capacitance of the composite material; the direct growth of MoNi-LDH nanosheets on CuCo2O4 nanospheres can prevent the aggregation of nanosheets. The interconnection of LDH nanosheets is beneficial to shorten the distance of electron diffusion and provides nanochannels and suitable mesoporous structures to promote ion transport.

[0037] To demonstrate the role of CuCo2O4 in composite materials, Comparative Example 1, MoNi-LDH without CuCo2O4, is provided.

[0038] Comparative Example 1 A method for preparing MoNi-LDH material, the steps unless otherwise specified are the same as in Example 1, except that step 1 is not performed, and CuCo2O4 is not added in step 2, and the resulting material is MoNi-LDH.

[0039] MoNi-LDH SEM test results are as follows: Figure 3 As shown, the microstructure is a nanosheet structure with a size range of 1-2 μm; Electrochemical test results of MoNi-LDH are as follows: Figure 12 As shown, charging and discharging within the range of 0-0.5V, with a discharge current density of 1 A g. -1 At that time, the specific capacitance was 830 F g -1 Compared with the CuCo2O4@MoNi-LDH example, it can be seen that after being combined with CuCo2O4, the discharge current density is 1 A g. -1 At that time, the performance was 830 F g -1 Increased to 1286 F g -1 The specific capacitance is increased to 155%.

[0040] Therefore, the role of MoNi-LDH nanosheets in composite materials is to improve the specific capacitance of the composite material; through the combination of transition metals Ni and Mo, more active sites are provided, thereby improving conductivity; in addition, the interconnection of LDH nanosheets helps to shorten the distance of electron diffusion and provides nanochannels and suitable mesoporous structures to promote ion transport, allowing more electroactive parts to participate in Faraday redox reactions, thereby effectively improving specific capacitance performance.

[0041] To demonstrate the effect of the Mo:Ni ratio on the performance of MoNi-LDH, Comparative Examples 2 and 3 are provided, with Mo:Ni ratios of 2:1 and 1:2, respectively, for CuCo2O4@MoNi-LDH.

[0042] Comparative Example 2 A method for preparing CuCo2O4@MoNi-LDH with a Mo:Ni ratio of 2:1 is described. The steps are the same as those in Example 1 unless otherwise specified. The difference is that the amount of sodium molybdate added in step 2 is changed from 1 mmol to 2 mmol. The resulting material is named CuCo2O4@MoNi-LDH 2:1.

[0043] The SEM test results of CuCo2O4@MoNi-LDH 2:1 are as follows: Figure 6 As shown, the microstructure is a spherical structure with a small number of nanosheets attached to the surface, with a size range of 550-600 nm. The electrochemical performance test results of CuCo2O4@MoNi-LDH 2:1 are as follows: Figure 13 As shown, charging and discharging within the range of 0-0.5V, with a discharge current density of 1 A g. -1 At that time, the specific capacitance was 800 F g -1 A comparison with CuCo2O4@MoNi-LDH shows that the specific capacitance decreased by nearly 400 F g. -1 .

[0044] Comparative Example 3 A method for preparing CuCo2O4@MoNi-LDH material with a Mo:Ni ratio of 1:2 is described. The steps are the same as those in Example 1 unless otherwise specified. The difference is that the amount of nickel nitrate added in step 2 is changed from 1 mmol to 2 mmol. The resulting material is named CuCo2O4@MoNi-LDH 1:2.

[0045] The test results of CuCo2O4@MoNi-LDH 1:2 are as follows: Figure 7 As shown, the microstructure is a spherical structure with a small number of nanosheets attached to the surface, with a size range of 550-600 nm. The electrochemical performance test results of CuCo2O4@MoNi-LDH 1:2 are as follows: Figure 13 As shown, charging and discharging within the range of 0-0.5V, with a discharge current density of 1 A g. -1 At that time, the specific capacitance was 714 F g. -1 Compared with CuCo2O4@MoNi-LDH, the specific capacitance decreased by nearly 500 F g. -1 .

[0046] Based on the above examples 1 CuCo2O4@MoNi-LDH, 2 CuCo2O4@MoNi-LDH 2:1, and 3 CuCo2O4@MoNi-LDH 1:2, the following conclusions can be drawn: For layered metal hydroxide nanosheets coated on metal oxides, the electrochemical performance and morphology can be affected by adjusting the metal ratio.

[0047] pass Figure 13 Electrochemical tests comparing performance show that the electrochemical performance is best when the ratio of Mo to Ni is 1:1. Further analysis using... Figure 4 CuCo2O4@MoNi-LDH, Figure 5 CuCo2O4@MoNi-LDH 2:1 Figure 6 Scanning electron microscopy (SEM) images of CuCo2O4@MoNi-LDH 1:2 show that when the metal ratio of Mo to Ni is 1:1, the nanosheet structure loaded on the surface of the spherical CuCo2O4 is most uniformly distributed, effectively preventing the stacking of nanosheet structures and thus increasing the specific surface area of ​​the material.

Claims

1. A method for preparing CuCo2O4@MoNi-LDH composite material, characterized in that... Includes the following steps: Step 1, Preparation of CuCo2O4: Copper nitrate trihydrate and cobalt nitrate hexahydrate are dissolved in isopropanol, and then glycerol is added to obtain the first hydrothermal reaction solution. Then, the first hydrothermal reaction is carried out under certain conditions. The resulting reaction product is washed with anhydrous ethanol and dried under certain conditions to obtain Cu-Co-gly. Finally, annealing is carried out under certain conditions to obtain CuCo2O4. In step 1, the ratio of copper nitrate trihydrate: cobalt nitrate hexahydrate: isopropanol: glycerol satisfies 0.25 mmol: 0.5 mmol: 30 ml: 6 ml; In step 1, the conditions for the first hydrothermal reaction are: hydrothermal temperature of 150-200 ℃ and hydrothermal time of 6-8 h; the drying conditions are: 60-80 ℃ and drying time of 20-24 h. In step 1, the annealing conditions are as follows: under air conditions, the heating rate is 1 ℃ / min, the annealing temperature is 300-350 ℃, and the annealing time is 2-3 hours. Step 2, Preparation of CuCo2O4@MoNi-LDH: Nickel nitrate, sodium molybdate, and urea are dissolved in deionized water and stirred to obtain a mixed solution. Then, the CuCo2O4 obtained in Step 1 is added to the mixed solution, and a second hydrothermal reaction is carried out under certain conditions. The resulting reaction product is washed with distilled water and anhydrous ethanol, and then dried under certain conditions to obtain the CuCo2O4@MoNi-LDH composite material, abbreviated as CuCo2O4@MoNi-LDH. In step 2, the ratio of nickel nitrate: sodium molybdate: urea: deionized water: CuCo2O4 satisfies 1 mmol: 1 mmol: 5 mmol: 50 mL: 0.25 g; In step 2, the conditions for the second hydrothermal reaction are: hydrothermal temperature of 100-150 ℃ and hydrothermal time of 4-6 h; the drying conditions are: drying temperature of 60-80 ℃ and drying time of 20-24 h. CuCo2O4 is the matrix material, and its microstructure is a hollow spherical structure with a diameter of 500-550 nm, which provides the main morphology and structural stability. The MoNi-LDH coating on the CuCo2O4 surface provides the effect of increasing the specific surface area of ​​the material and improving the ion transport rate, and ultimately improving the electrochemical performance of the supercapacitor. The obtained CuCo2O4@MoNi-LDH composite material is composed of hollow spherical CuCo2O4 and nanosheet-like MoNi-LDH, forming a core-shell structure with MoNi-LDH as the "shell" and CuCo2O4 as the "core".

2. The application of the CuCo2O4@MoNi-LDH composite material obtained by the preparation method according to claim 1 as a supercapacitor electrode material, characterized in that: When charged and discharged within the range of 0-0.5 V, the specific capacitance is 1200-1300 F / g at a discharge current density of 1 A / g.

3. The application of the CuCo2O4@MoNi-LDH composite material obtained by the preparation method according to claim 1 as a supercapacitor electrode material, characterized in that: After 6000 cycles, the cycle stability is 88%.

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