Preparation method of molybdate-based ni al-lDH composite film and application thereof in energy storage device

Abstract

The application relates to a preparation method of a molybdate-based NiAl-LDH composite film and application of the molybdate-based NiAl-LDH composite film in energy storage devices, and aims to solve the problem of low specific capacitance of metal oxide materials in energy storage devices.The preparation method comprises the following steps: firstly, uniformly mixing cobalt nitrate, ammonium molybdate, Ni(NO3)2.6H2O and FeSO4.9H2O, grinding, dissolving in deionized water, then adding a manganese sulfate solution, carrying out constant-temperature water bath reaction, washing, drying and calcining to obtain a substrate attached with doped molybdate powder; secondly, preparing a FeNiAl-LDH precursor solution; and thirdly, preparing a doped molybdate@NiAl-LDH nano core-shell hetero film.The doped elements (Fe, Co, Ni and Mn) expose more reaction active sites, which is beneficial to the rapid transmission of ions and electrons on the surface of the electrode and the electrolyte, and the specific capacity reaches 2350 F / g when the current density is 1 A / g.

Description

Technical Field

[0001] This invention provides a method for preparing doped (Fe, Co, Ni, Mn)MoO4@NiAl-LDH nanoarray core-shell heterofilms with good electrochemical performance and controllable morphology, and its application. Background Technology

[0002] With the rapid development of industrial society, people's demand for energy is increasing day by day, causing serious environmental pollution. The development and utilization of clean and efficient renewable energy sources is urgently needed. Solar, wind, and tidal energy, among other renewable energy sources, have advantages such as abundant reserves and environmental friendliness. However, these renewable energy sources are not continuously available and are highly dependent on the natural environment, which limits their application and development. Therefore, the development and exploration of electrode materials with high electrochemical performance is of great significance for improving the performance of energy storage devices.

[0003] Molybdate materials in metal oxides possess advantages such as high redox activity, good conductivity, excellent rate performance, and cycling stability, but their specific capacitance is unsatisfactory. Layered double hydroxides (LDHs) exhibit good pseudocapacitive performance due to their large theoretical specific capacitance and high redox activity, but nanoscale materials suffer from aggregation and accumulation problems. Summary of the Invention

[0004] The purpose of this invention is to address the problem of low specific capacitance of metal oxide materials in energy storage devices, and to provide a method for preparing molybdate-based @NiAl-LDH composite films and their application in energy storage devices.

[0005] The method for preparing the molybdate-based @NiAl-LDH composite thin film of the present invention is carried out according to the following steps:

[0006] I. Preparation of Doped Molybdates

[0007] a. Add 0.5–2 mmol of cobalt nitrate (Co(NO3)2·6H2O) and 1–2 mmol of ammonium molybdate ((NH4)2·Mo7O) 24 Mix 0.8–2 mmol Ni(NO3)2·6H2O and 0.8–1.5 mmol FeSO4·9H2O evenly and grind them, dissolve them in deionized water, put them into a conductive substrate, and then add 10–25 mL of 2 mol / L manganese sulfate solution. React in a constant temperature water bath at 25–45 °C for 4–10 h to obtain a substrate with doped molybdate.

[0008] b. The substrate with doped molybdate is washed and dried, and then calcined in a muffle furnace at a temperature of 200-400°C to obtain a substrate with doped molybdate electrode material attached.

[0009] II. FeNiAl-LDH precursor solution

[0010] 0.4–1.2 mmol Fe(NO3)3·9H2O and 0.4–1.0 mmol NiSO4·6H2O were dispersed in 30–50 mL of deionized water to obtain a mixed solution. 1.5–5 g of urea and 10–25 mL of 0.5 mol / L sodium aluminate (NaAlO2) solution were added to the mixed solution. The mixture was magnetically stirred in a constant temperature water bath at 35–45 °C and then kept at 30–50 °C for 15–40 h to obtain the precursor solution.

[0011] III. Preparation of Doped Molybdate@NiAl-LDH Nanocore-Shell Heterofilms

[0012] The substrate of the attached doped molybdate electrode material obtained in step one was added to the precursor solution, ultrasonically dispersed, and reacted in a constant temperature water bath at 50-70°C. After washing and drying, a doped molybdate@NiAl-LDH nanocore-shell heterostructure film was obtained on the substrate.

[0013] The application of the doped molybdate@NiAl-LDH nanocore-shell heterostructure thin film of this invention is to use the doped molybdate@NiAl-LDH nanocore-shell heterostructure thin film as a positive electrode material in supercapacitors.

[0014] This invention designs a (Fe, Co, Ni, Mn)MoO4@NiAl-LDH nanoarray hybrid core-shell structure composite material. By constructing a special morphology and utilizing the synergistic effect between multiple metals, the electrochemical performance of the electrode material is significantly improved, thereby enhancing the electrochemical performance of energy storage devices. Furthermore, the prepared composite thin-film electrode shows broad application prospects in lithium batteries, supercapacitors, zinc-ion batteries, and other fields.

[0015] This invention synthesizes a (Fe, Co, Ni, Mn)MoO4@NiAl-LDH nanoarray core-shell heterostructure thin film on a conductive substrate using a simple two-step room-temperature stirring method. During the preparation process, doping elements are used to improve the defect degree of (Fe, Co, Ni, Mn)MoO4@NiAl-LDH. The core-shell structure forms a unique core-void-shell morphology, expanding the specific surface area of ​​the material. The doping elements (Fe, Co, Ni, Mn) expose more reactive sites, which facilitates the rapid transport of ions and electrons on the electrode and electrolyte surfaces. Simultaneously, the ordered multi-level void structure can mitigate the expansion effect of the material during charge and discharge, ensuring the morphology of the material during the charge and discharge strokes and reducing the structural damage caused by ion and electron insertion and extraction during the reaction. Furthermore, the nanoscale material shortens the diffusion path of ions and electrons, accelerating ion and electron conduction. This increases the conductivity and carrier collection of the composite material, optimizes the chemical properties of the thin film, improves volume changes during electrochemical reactions, and enhances stability. Tests have shown that this composite thin-film electrode can efficiently store energy in electrochemical reactions, and it is expected to have excellent practical value and significance in the research of new materials in the field of energy storage in the future.

[0016] The method for preparing molybdate-based @NiAl-LDH composite films of the present invention has the following beneficial effects:

[0017] 1. The preparation process of the molybdate-based @NiAl-LDH composite thin film of this invention is safe, pollution-free, and relatively simple. The well-ordered structural units of the doped core-shell nanoarray facilitate the directional and rapid transfer of charge within the electrode. Simultaneously, this structure provides a large specific surface area, hindering the agglomeration process of the material nanoparticles during electrochemical reactions, thereby maintaining a fast chemical reaction rate for the nanoparticles and improving the electrochemical performance of the sample.

[0018] 2. The obtained molybdate-based @NiAl-LDH composite material exhibits excellent cycle stability.

[0019] 3. The combination of molybdate and layered double hydroxide forms a core-shell structure, which increases the conductivity of the composite material and the collection of charge carriers, and reduces the volume change of the active material during the reaction process.

[0020] 4. By making reasonable use of the synergistic effect between multiple metals, the resulting composite material has excellent specific capacity, reaching 2350 F / g when the current density is 1 A / g. Attached Figure Description

[0021] Figure 1 The specific capacity test results of the doped molybdate-based @NiAl-LDH composite thin film obtained in the example are shown in the figure at different current densities.

[0022] Figure 2 The image shows the cycle stability test results of the doped molybdate-based @NiAl-LDH composite film obtained in the example.

[0023] Figure 3 The image shown is an electron microscope image of the doped molybdate-based @NiAl-LDH composite film obtained in the example.

[0024] Figure 4 The graph shows the rate performance test results of the doped molybdate-based @NiAl-LDH composite material obtained in the example. Detailed Implementation

[0025] Specific Implementation Method 1: The preparation method of the molybdate-based @NiAl-LDH composite film in this implementation method is carried out according to the following steps:

[0026] I. Preparation of Doped Molybdates

[0027] a. Add 0.5–2 mmol of cobalt nitrate (Co(NO3)2·6H2O) and 1–2 mmol of ammonium molybdate ((NH4)2·Mo7O) 24 Mix 0.8–2 mmol Ni(NO3)2·6H2O and 0.8–1.5 mmol FeSO4·9H2O evenly and grind them, dissolve them in deionized water, put them into a conductive substrate, and then add 10–25 mL of 2 mol / L manganese sulfate solution. React in a constant temperature water bath at 25–45 °C for 4–10 h to obtain a substrate with doped molybdate.

[0028] b. The substrate with doped molybdate is washed and dried, and then calcined in a muffle furnace at a temperature of 200-400°C to obtain a substrate with doped molybdate electrode material attached.

[0029] II. FeNiAl-LDH precursor solution

[0030] 0.4–1.2 mmol Fe(NO3)3·9H2O and 0.4–1.0 mmol NiSO4·6H2O were dispersed in 30–50 mL of deionized water to obtain a mixed solution. 1.5–5 g of urea and 10–25 mL of 0.5 mol / L sodium aluminate (NaAlO2) solution were added to the mixed solution. The mixture was magnetically stirred in a constant temperature water bath at 35–45 °C and then kept at 30–50 °C for 15–40 h to obtain the precursor solution.

[0031] III. Preparation of Doped Molybdate@NiAl-LDH Nanocore-Shell Heterofilms

[0032] The substrate of the attached doped molybdate electrode material obtained in step one was added to the precursor solution, ultrasonically dispersed, and reacted in a constant temperature water bath at 50-70°C. After washing and drying, a doped molybdate@NiAl-LDH nanocore-shell heterostructure film was obtained on the substrate.

[0033] This embodiment utilizes a (Fe, Co, Ni, Mn)MoO4@NiAl-LDH nanoarray hybrid core-shell structure to construct a composite material. By constructing a unique morphology and leveraging the synergistic effect between multiple metals, it significantly enhances the electrochemical performance of the electrode material, thereby increasing the energy density of energy storage devices. The method is simple, controllable, and produces a smooth, high-performance thin film. Furthermore, the prepared composite thin-film electrode shows promising applications in lithium batteries, supercapacitors, and zinc-ion batteries.

[0034] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that in step one, step a involves mixing and grinding 0.5–2 mmol cobalt nitrate Co(NO3)2·6H2O, 1–2 mmol ammonium molybdate, 0.8–2 mmol Ni(NO3)2·6H2O, and 0.8–1.5 mmol FeSO4·9H2O evenly, and then dissolving them in 20 mL of deionized water.

[0035] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that step a in step 1 is carried out in a constant temperature water bath at 30-40℃ for 6-8 hours.

[0036] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that step b in step one involves calcination treatment at a temperature of 300-400°C in air for 2-3 hours.

[0037] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that in step 2, 0.4–0.8 mmol Fe(NO3)3·9H2O and 0.8–1.0 mmol NiSO4·6H2O are dispersed in 30–50 mL of deionized water to obtain a mixed solution. 2–3 g of urea and 10–20 mL of sodium aluminate (NaAlO2) solution with a concentration of 0.5 mol / L are then added to the mixed solution.

[0038] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that step two involves magnetic stirring for 2 hours in a constant temperature water bath at 40°C.

[0039] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Five in that step two involves constant temperature treatment at 35-45°C for 25-35 hours.

[0040] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the reaction in step three is carried out in a constant temperature water bath at 50-70°C for 1.5-2.5 hours.

[0041] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the thickness of the doped molybdate@NiAl-LDH nanocore-shell heterofilm in step three is 150–300 μm.

[0042] Example: The preparation method of the molybdate-based @NiAl-LDH composite film in this example is carried out according to the following steps:

[0043] I. Preparation of Doped Molybdates

[0044] a. Add 0.8 mmol of cobalt nitrate (Co(NO3)2·6H2O) and 1.5 mmol of ammonium molybdate ((NH4)2·Mo7O) 24 Mix 0.8 mmol Ni(NO3)2·6H2O and 1.2 mmol FeSO4·9H2O evenly and grind them, dissolve them in 20 mL of deionized water, put them into a conductive carbon cloth substrate, and then add 15 mL of 2 mol / L manganese sulfate solution. React in a constant temperature water bath at 30 °C for 6 h to obtain a substrate with doped molybdate.

[0045] b. The substrate with doped molybdate is washed and dried (drying temperature is 60℃), and then heat-treated in a muffle furnace at 280℃ for 2 hours to obtain a substrate with doped molybdate electrode material attached.

[0046] II. FeNiAl-LDH precursor solution

[0047] 0.6 mmol Fe(NO3)3·9H2O and 0.9 mmol NiSO4·6H2O were dispersed in 40 mL of deionized water to obtain a mixed solution. 2.2 g of urea and 12 mL of sodium aluminate (NaAlO2) solution with a concentration of 0.5 mol / L were added to the mixed solution. The mixture was magnetically stirred in a constant temperature water bath at 40 °C for 2 h, and then kept at 38 °C for 40 h to obtain the precursor solution.

[0048] III. Preparation of Doped Molybdate@NiAl-LDH Nanocore-Shell Heterofilms

[0049] The substrate of the attached doped molybdate electrode material obtained in step one was added to the precursor solution. First, it was ultrasonically vibrated for 30 min, and then reacted in a constant temperature water bath at 70℃ for 2 h. After washing and drying, a doped molybdate@NiAl-LDH nanocore-shell heterostructure film was obtained on the conductive substrate, wherein the particle size of the (Fe, Co, Ni, Mn)MoO4@NiAl-LDH core-shell structure nanoparticles was 200 nm.

[0050] The 3000-cycle stability test result of the molybdate-based @NiAl-LDH composite thin film material in this embodiment is shown in the figure below. Figure 2 As shown.

[0051] Component assembly:

[0052] The asymmetric device is assembled using molybdate-based @NiAl-LDH electrode material as the positive electrode, an electrolyte, and carbon nanotubes as the negative electrode. The molybdate-based @NiAl-LDH electrode measures 1.0 cm × 1.0 cm and has a mass of 1.9 mg / cm³. -2 The carbon nanotube electrode also has an area of ​​1.0 cm × 1.0 cm and a mass of 1.6 mg / cm². -2 The electrolyte was prepared as follows: 6g of polyvinyl alcohol (PVA) and 5.6g of KOH were added to 50mL of deionized water at 80℃, and stirred continuously until the mixture became a clear gel. The positive and negative electrode materials and the separator were immersed in the prepared gel electrolyte for 5 minutes, then removed and assembled into a positive electrode-separator-negative electrode device. The prepared device was placed in air for 24 hours. The specific capacity, energy density, and power density of the prepared asymmetric device were calculated as the sum of the active masses of the positive and negative electrodes. The device thickness was 1.15-1.34mm.

[0053] Device testing conditions: A two-electrode system was used at room temperature.

[0054] Device test data:

[0055] At a current density of 1 A / g, the specific capacity of the molybdate-based @NiAl-LDH / / CNTs asymmetric device is 2350 F / g. At a current density of 15 A / g, the specific capacity still reaches 1154 F / g. The molybdate-based @NiAl-LDH / / CNTs asymmetric device exhibits good stability, retaining 92.1% of its capacity after 5000 cycles. At a current density of 1 A / g, the device has a power density of 11530 W / kg and an energy density of 62.3 Wh / kg.

Claims

1. A method for preparing molybdate-based @NiAl-LDH composite thin films, characterized in that... The preparation method is carried out according to the following steps: I. Preparation of Doped Molybdates a. Mix and grind 0.5~2 mmol cobalt nitrate Co(NO3)2·6H2O, 1~2 mmol ammonium molybdate, 0.8~2 mmol Ni(NO3)2·6H2O and 0.8~1.5 mmol FeSO4·9H2O evenly, dissolve in deionized water, place in a conductive substrate, then add 10~25 mL of 2 mol / L manganese sulfate solution, react in a constant temperature water bath at 25~45℃ for 4~10 h to obtain a substrate with doped molybdate; b. The substrate with doped molybdate is washed and dried, and then calcined in a muffle furnace at a temperature of 200~400℃ to obtain a substrate with doped molybdate electrode material attached. II. FeNiAl-LDH precursor solution 0.4–1.2 mmol Fe(NO3)3·9H2O and 0.4–1.0 mmol NiSO4·6H2O were dispersed in 30–50 mL of deionized water to obtain a mixed solution. 1.5–5 g of urea and 10–25 mL of sodium aluminate solution with a concentration of 0.5 mol / L were added to the mixed solution. The mixture was magnetically stirred in a constant temperature water bath at 35–45 °C and then kept at 30–50 °C for 15–40 h to obtain the precursor solution. III. Preparation of Molybdate-Based @NiAl-LDH Composite Thin Films The substrate of the attached doped molybdate electrode material obtained in step one was added to the precursor solution, ultrasonically dispersed, and reacted in a constant temperature water bath at 50~70℃. After washing and drying, a molybdate-based @NiAl-LDH composite film was obtained on the substrate.

2. The method for preparing molybdate-based @NiAl-LDH composite thin films according to claim 1, characterized in that... In step one, step a involves mixing and grinding 0.5-2 mmol cobalt nitrate Co(NO3)2·6H2O, 1-2 mmol ammonium molybdate, 0.8-2 mmol Ni(NO3)2·6H2O, and 0.8-1.5 mmol FeSO4·9H2O evenly, and then dissolving them in 20 mL of deionized water.

3. The method for preparing molybdate-based @NiAl-LDH composite thin films according to claim 1, characterized in that... In step one, step a is carried out in a constant temperature water bath at 30~40℃ for 6~8 hours.

4. The method for preparing molybdate-based @NiAl-LDH composite thin films according to claim 1, characterized in that... In step one, step b involves calcining the material in an air atmosphere at a temperature of 300-400℃ for 2-3 hours.

5. The method for preparing molybdate-based @NiAl-LDH composite thin films according to claim 1, characterized in that... In step two, 0.4-0.8 mmol Fe(NO3)3·9H2O and 0.8-1.0 mmol NiSO4·6H2O are dispersed in 30-50 mL of deionized water to obtain a mixed solution. 2-3 g of urea and 10-20 mL of sodium aluminate solution with a concentration of 0.5 mol / L are then added to the mixed solution.

6. The method for preparing molybdate-based @NiAl-LDH composite thin films according to claim 1, characterized in that... In step two, the mixture is magnetically stirred in a constant temperature water bath at 40℃ for 2-3 hours.

7. The method for preparing molybdate-based @NiAl-LDH composite thin films according to claim 1, characterized in that... In step two, the temperature is kept constant at 35~45℃ for 25~35 hours.

8. The method for preparing molybdate-based @NiAl-LDH composite thin films according to claim 1, characterized in that... In step three, the reaction is carried out in a constant temperature water bath at 50~70℃ for 1.5~2.5 h.

9. The method for preparing molybdate-based @NiAl-LDH composite thin films according to claim 1, characterized in that... In step three, the thickness of the molybdate-based @NiAl-LDH composite film is 150~300μm.

10. The application of the molybdate-based @NiAl-LDH composite film prepared by the method described in claim 1, characterized in that... Molybdate-based @NiAl-LDH composite films are used as positive electrode materials in supercapacitors.

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