Molybdenum-based transition metal oxide nanosheet electrode material, preparation method and application

Abstract

The invention relates to the technical field of electrode material preparation, in particular to a molybdenum-based transition metal oxide nanosheet electrode material, a preparation method and application, and the method comprises the following steps: preparing a precursor solution by using Ni salt, Co salt, an oxidation-state compound of Mo and urea; soaking the foamed nickel in the precursor solution, and carrying out hydrothermal reaction to obtain a prefabricated electrode material; and finally, calcining the prefabricated electrode material to obtain the molybdenum-based transition metal oxide nanosheet electrode material with a high specific surface area, so that electrochemical active sites can be fully exposed, and the specific capacity is remarkably improved. Due to the introduction of Ni and Co, the conductivity of the material is improved, and the reversibility of pseudocapacitance reaction is enhanced; cH4N2O serves as a nitrogen source, effective nitrogen doping in material lattices can be achieved, the electron conduction rate is increased, charge transfer loss is reduced, the interface bonding force between the material and a foamed nickel substrate is enhanced, the cycling stability is greatly improved, and the problem that a molybdenum-based transition metal oxide nanosheet electrode material is poor in energy storage performance is solved.

Description

Technical Field

[0001] This invention relates to the field of electrode material preparation technology, specifically to a molybdenum-based transition metal oxide nanosheet electrode material, its preparation method, and its application. Background Technology

[0002] With the continued growth of global energy demand and the accelerated transformation of the energy structure, energy storage technology has become a key component of the modern energy system. Whether it's the intermittent fluctuations of renewable energy sources (such as solar and wind power) or the urgent need for efficient energy storage systems in fields like electric vehicles and smart grids, the importance of energy storage technology for energy security, economic operation, and sustainable development is highlighted. In traditional energy storage technologies, lithium-ion batteries dominate due to their high energy density, but their low power density and limited charge-discharge lifespan make them unsuitable for scenarios requiring instantaneous high power output and rapid charge-discharge. Against this backdrop, supercapacitors, as a novel energy storage device, have gradually become a research hotspot due to their unique performance advantages.

[0003] Supercapacitors store energy through rapid and reversible redox reactions on the polarized electrolyte or surface, exhibiting characteristics such as high power density, fast charge and discharge speeds, long cycle life, and environmental friendliness. Their energy storage mechanisms are mainly divided into two categories: one is physical energy storage based on electric double-layer capacitance, which achieves charge storage through electron adsorption / desorption at the electrode-electrolyte interface; the other is chemical energy storage based on pseudocapacitance, which achieves charge transfer through reversible Faraday redox reactions on or near the surface of the electrode material, building upon electron adsorption. Compared to electric double-layer capacitors, pseudocapacitive capacitors, due to their deeper reaction depth and larger charge storage capacity, typically exhibit higher specific capacitance and energy density, thus becoming a core direction for improving the overall performance of supercapacitors.

[0004] Research on pseudocapacitive materials focuses on transition metal oxides, conductive polymers, and carbon-based composites. Among these, transition metal oxides, due to their rich valence state variations and excellent redox activity, have become a key branch of pseudocapacitive materials. The multi-valence characteristics of transition metal elements (such as molybdenum, nickel, cobalt, and manganese) enable them to achieve multi-step redox reactions through electron transfer during electrochemical processes, thereby significantly improving charge storage capacity. Furthermore, transition metal oxides typically possess high theoretical specific capacitance and good chemical stability, allowing them to adapt to wide potential windows and complex electrolyte environments, further expanding their application potential in supercapacitors.

[0005] In the research of transition metal oxides, molybdenum-based and Ni / Co-based materials have become the two mainstream directions for pseudocapacitive electrode materials due to their unique resource advantages and electrochemical properties. Among them, Ni / Co-based nanomaterials are a class of pseudocapacitive electrode materials that have attracted much attention due to their high redox activity, high theoretical capacity, and abundant resource reserves. Both nickel (Ni) and cobalt (Co) elements have multivalent state characteristics (e.g., Ni...). 2+ / Ni 3+ Co 2+ / Co 3+ / Co 4+ Ni / Co-based oxides (such as NiO, Co3O4, and NiCo2O4) can store large amounts of charge through reversible redox reactions during electrochemical processes. The spinel or layered structures of Ni / Co-based oxides provide ordered channels for ion transport, resulting in better electrochemical kinetics. However, the energy storage reaction of Ni / Co-based electrode materials is limited to the surface and is diffusion-controlled, generally exhibiting low energy density and poor electrochemical stability. While these issues can be improved by increasing conductivity and specific surface area (e.g., constructing multi-component transition metal oxides), such as binary NiCo2O4 which improves conductivity and structural stability through ion synergy, better material solutions are still needed. In contrast, molybdenum-based transition metal oxides possess higher theoretical capacity and deeper reactivity. This is because molybdenum has multiple valence states, enabling high-capacity energy storage through multi-electron transfer during electrochemical processes. Furthermore, the layered or tunnel-like crystal structure of molybdenum-based oxides provides abundant active sites and rapid diffusion channels for ion insertion / extraction, contributing to improved rate performance of electrode materials. In recent years, researchers have further optimized the electrochemical performance of molybdenum-based oxides by controlling their nanostructures. However, the precise control of its nanostructure still has significant limitations, resulting in restricted electrode conductivity and ion diffusion efficiency, making it difficult to fully realize its energy storage performance. Therefore, developing molybdenum-based transition metal oxide nanosheet electrode materials with excellent structural properties and electrochemical performance is crucial for breaking through the current bottleneck in supercapacitor energy storage performance and has significant research and application value. Summary of the Invention

[0006] To address the problem of poor energy storage performance of existing molybdenum-based transition metal oxide nanosheet electrode materials, this invention provides a molybdenum-based transition metal oxide nanosheet electrode material, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for preparing a molybdenum-based transition metal oxide nanosheet electrode material, comprising: Precursor solutions were prepared using Ni salts, Co salts, oxidized Mo compounds, and urea. Nickel foam is immersed in a precursor solution and subjected to a hydrothermal reaction to obtain a pre-fabricated electrode material. The pre-fabricated electrode material was calcined to obtain molybdenum-based transition metal oxide nanosheet electrode material.

[0008] Optionally, both the Ni salt and the Co salt are nitrates, and the oxidized compound of Mo is ammonium molybdate.

[0009] Optionally, the molar ratio of the Ni salt, Co salt, Mo oxidized compound and urea is 0.5:0.5:1:(6-9).

[0010] Optionally, it also includes a pretreatment process for the nickel foam, specifically: After cleaning the foamed nickel sequentially with acetone, ethanol, hydrochloric acid solution and water, it was then cleaned alternately with water and anhydrous ethanol and dried to obtain pretreated foamed nickel. The concentration of the hydrochloric acid solution was 1.5-3M.

[0011] Optionally, the hydrothermal reaction conditions are 150℃~180℃, and the hydrothermal reaction time is 8~12h.

[0012] Optionally, the calcination temperature is 400℃~500℃, and the calcination time is 2~6h.

[0013] Optionally, the heating rate during the calcination process is 3°C to 8°C / min.

[0014] Optionally, the calcination process is carried out under a nitrogen atmosphere with a nitrogen flow rate of 45–55 mL / min.

[0015] A molybdenum-based transition metal oxide nanosheet electrode material, wherein the specific capacity of the molybdenum-based transition metal oxide nanosheet electrode material reaches 832 F•g -1 After 5000 cycles, the cycle retention rate reached 97.36%.

[0016] The above-mentioned molybdenum-based transition metal oxide nanosheet electrode materials are used in the fabrication of capacitors.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing molybdenum-based transition metal oxide nanosheet electrode materials. The method involves preparing a precursor solution using Ni salt, Co salt, oxidized Mo compounds, and urea; then immersing nickel foam in the precursor solution for a hydrothermal reaction to obtain a pre-fabricated electrode material; finally, calcining the pre-fabricated electrode material yields a molybdenum-based transition metal oxide nanosheet electrode material with a high specific surface area. This significantly increases the contact area between the electrode and the electrolyte, fully exposing electrochemical active sites and significantly improving specific capacity. The introduction of Ni and Co modulates the MoO4…2- The electronic structure of the material is improved, enhancing its conductivity and reversibility of pseudocapacitive reactions. By introducing CH4N2O as a nitrogen source and combining it with an inert calcination atmosphere, effective nitrogen doping can be achieved in the material lattice, which not only improves the electron conduction rate and reduces charge transfer loss, but also enhances the interfacial bonding between the material and the nickel foam substrate, significantly improving cycle stability and solving the problems of poor energy storage performance and poor cycle performance of existing electrode materials. This method is simple, the process parameters can be flexibly adjusted, and it can adapt to the electrode performance requirements of different energy storage scenarios. The raw materials used are all conventional chemical reagents, which are low in cost and low in toxicity. The calcination temperature is moderate, and the energy consumption is lower than that of existing high-temperature preparation processes, meeting the environmental protection and economic requirements of large-scale production. This provides an ideal electrode material for high-energy-density energy storage devices.

[0018] Both the Ni and Co salts are nitrates, and the oxidized compound of Mo is ammonium molybdate. Nickel nitrate and cobalt nitrate completely dissociate in water, forming a homogeneous precursor solution, ensuring the Ni... 2+ Co 2+ With MoO4 2- The uniform mixing of NH4 provides a molecularly dispersed source of metal ions for the directional growth of nanosheets in the subsequent hydrothermal reaction, avoiding structural defects caused by local component segregation. + It can adsorb onto the crystal surface, inhibiting particle aggregation through electrostatic repulsion and promoting the formation of nanosheets. Meanwhile, NH4... + During calcination, it decomposes into NH3 and H2O, leaving a porous structure, which further increases the specific surface area and provides more active sites.

[0019] The molar ratio of the Ni salt, Co salt, Mo oxidized compounds and urea is 0.5:0.5:1:(6-9). By precisely controlling the reactant concentration, urea decomposition kinetics and metal-oxygen coordination environment, the morphology, composition and electrochemical performance of the molybdenum-based transition metal oxide nanosheet electrode material are significantly optimized.

[0020] The process also includes a pretreatment of the nickel foam, which involves sequentially cleaning the nickel foam with acetone, ethanol, hydrochloric acid solution, and water. Acetone, as a polar aprotic solvent, can efficiently dissolve organic contaminants such as grease and rust-preventive oil (e.g., mineral oil and silicone oil) adhering to the surface of the nickel foam, preventing uneven loading or detachment of nanosheets due to oil stains hindering direct contact between the metal salt solution and the nickel substrate. Ethanol, as a neutral polar solvent, can further remove acetone residue and some inorganic salts while avoiding the introduction of new impurities. Hydrochloric acid solution can effectively dissolve the oxide layer on the surface of the nickel foam while slightly corroding the nickel foam substrate, forming a rough surface and enhancing the mechanical anchoring effect of the surface-active materials.

[0021] The hydrothermal reaction conditions are 150℃~180℃ and the hydrothermal reaction time is 8~12h. Under these reaction conditions, a uniform nanosheet array can be formed on the surface of the nickel foam, ensuring a high specific surface area of ​​the electrode material.

[0022] The calcination temperature is 400℃~500℃ and the calcination time is 2~6h. Under these temperature conditions, the amorphous components in the material gradually transform into a crystalline structure through atomic rearrangement, reducing lattice defects, lowering electron transport resistance, and improving the conductivity of the electrode material.

[0023] A molybdenum-based transition metal oxide nanosheet electrode material, as described above, exhibits a specific capacity of 832 F•g. -1 After 5,000 cycles, the cycle retention rate reached 97.36%, demonstrating excellent electrochemical performance and cycle retention rate. It achieves efficient charge storage, which is significantly better than traditional materials. It also has advantages such as low cost, easy scalability, and non-toxicity, providing a core solution for the next generation of high energy density and long life capacitors.

[0024] The above-mentioned molybdenum-based transition metal oxide nanosheet electrode material is used in the preparation of capacitors. Because the molybdenum-based transition metal oxide nanosheet electrode material prepared by this invention has higher electrochemical performance than traditional electrode materials, the prepared capacitors have high specific capacitance and energy density, ultra-long cycle life, high power density, low cost and environmental friendliness, providing theoretical support and technical reserves for the next generation of high energy density and high power density energy storage. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the preparation method of a molybdenum-based transition metal oxide nanosheet electrode material according to the present invention. Detailed Implementation

[0026] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0027] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0028] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0029] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0030] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0031] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0032] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0033] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0034] See Figure 1 This invention discloses a method for preparing molybdenum-based transition metal oxide nanosheet electrode materials, comprising: S1: A precursor solution is prepared using Ni salt, Co salt, oxidized Mo compounds, and urea, specifically as follows: Ni salt, Co salt, the oxidized form of Mo, and urea were dissolved in deionized water at a molar ratio of 0.5:0.5:1:(6-9). The solution was stirred on a magnetic stirrer at 300 r / min for 30 min until all reagents were completely dissolved, forming a homogeneous and transparent precursor solution. Optionally, the Ni salt and Co salt are both nitrates, and the oxidized form of Mo is ammonium molybdate. S2: Immerse nickel foam in a precursor solution and carry out a hydrothermal reaction to obtain the pre-fabricated electrode material, specifically: Take nickel foam (NF), cut it, and then sonicate it sequentially for 15-30 minutes each with acetone, anhydrous ethanol, 1.5-3M hydrochloric acid solution, and deionized water to remove surface oil, organic impurities, and nickel oxide layer. After treatment, rinse it alternately with anhydrous ethanol and deionized water at least three times, dry it in a vacuum oven at 60℃-80℃, weigh it, and set it aside to obtain pretreated nickel foam. The pretreated nickel foam was immersed in the precursor solution and transferred to the bottom of the polytetrafluoroethylene inner liner. After sealing the inner liner, it was placed in a hydrothermal autoclave and hydrothermally reacted at 150℃~180℃ for 8~12h. After cooling to room temperature, it was washed with deionized water more than 3 times to remove the unreacted reagents remaining on the surface. It was then dried in an oven and weighed to obtain the pre-fabricated electrode material.

[0035] S3: The pre-fabricated electrode material is calcined to obtain a molybdenum-based transition metal oxide nanosheet electrode material, specifically: The dried pre-fabricated electrode material was transferred to a quartz boat and placed in a horizontal tube furnace. High-purity nitrogen (≥99.999%) was introduced as a protective atmosphere, and the nitrogen flow rate was adjusted to 45–55 mL / min. After the air in the furnace was exhausted, the temperature was increased to 400–500℃ at a rate of 3–8℃ / min and held for 2–6 hours. After the holding period, the heating device was turned off, and the nitrogen atmosphere was maintained until the tube furnace cooled naturally to room temperature. The sample was then removed, yielding the molybdenum-based transition metal oxide nanosheet electrode material.

[0036] This invention enables the preparation of Ni with high specific surface area by precisely controlling hydrothermal parameters. 1 / 2 Co 1 / 2Compared to existing hydrothermal processes, the MoO4 / nanosheet structure can fully expose electrochemical active sites, significantly improving specific capacity. Introducing CH4N2O as a nitrogen source and combining it with an inert calcination atmosphere enables effective nitrogen doping in the material lattice, which not only improves electron conduction rate and reduces charge transfer loss, but also enhances the interfacial bonding between the material and the nickel foam substrate, greatly improving cycle stability and solving the problem of poor cycle performance of existing materials. During the preparation process, the process parameters can be flexibly adjusted to adapt to the electrode performance requirements of different energy storage scenarios, and the pretreatment process of the nickel foam substrate is simple, achieving close loading of the material without complex modification. At the same time, the raw materials used are all conventional chemical reagents, which are low in cost and low in toxicity. The calcination temperature is moderate, and the energy consumption is lower than that of existing high-temperature preparation processes, meeting the environmental protection and economic requirements of large-scale production.

[0037] Example 1 Step 1: Take 1.5 mm thick nickel foam (NF) and cut it into 1 cm × 2 cm and 1 cm × 1 cm sheets, placing them in a 500 mL beaker. Sonicate the beaker sequentially with 50 mL acetone, 50 mL anhydrous ethanol, 50 mL 2 M hydrochloric acid solution, and 50 mL deionized water for 20 min each to remove surface oil, organic impurities, and the nickel oxide layer. After treatment, rinse five times alternately with anhydrous ethanol and deionized water, then dry in a 60℃ vacuum oven for 24 h. Weigh the product for later use.

[0038] Step 2: Measure 50 mL of deionized water and add 0.5 mmol Ni(NO3)2·6H2O, 0.5 mmol Co(NO3)2·6H2O, 1 mmol (NH4)2MoO4·4H2O, and 7 mmol NH2CONH2 sequentially. Stir on a magnetic stirrer at 300 r / min for 30 min until all reagents are completely dissolved, forming a homogeneous and transparent precursor solution. Place the pretreated NF at the bottom of a 100 mL polytetrafluoroethylene (PTFE) liner, slowly pour in the above precursor solution to saturate the NF, seal the liner, and place it in a hydrothermal autoclave. React in a 160℃ oven for 8 h.

[0039] Step 3: After the reaction is complete, cool to room temperature, remove NF, wash 6 times with deionized water to remove unreacted reagents, and dry in a 55℃ oven for 24 h, then weigh. Transfer the dried sample to a quartz boat and place it in a horizontal tube furnace. Purge with high-purity nitrogen (≥99.999%) as a protective atmosphere, adjusting the nitrogen flow rate to 50 mL / min. After the air in the furnace is exhausted (after 30 min of purging), heat to 400℃ at a rate of 5℃ / min and hold for 2 h. After holding, turn off the heating device and maintain the nitrogen atmosphere until the tube furnace cools naturally to room temperature. Remove the sample to obtain Ni. 1 / 2 Co 1 / 2MoO4 / NF electrode material (molybdenum-based transition metal oxide nanosheet electrode material, denoted as NCM-1).

[0040] Example 2 Step 1: Take 1.5 mm thick nickel foam (NF) and cut it into 1 cm × 2 cm and 1 cm × 1 cm sheets, placing them in a 500 mL beaker. Sonicate the beaker sequentially with 50 mL acetone, 50 mL anhydrous ethanol, 50 mL 2 M hydrochloric acid solution, and 50 mL deionized water for 20 min each to remove surface oil, organic impurities, and the nickel oxide layer. After treatment, rinse five times alternately with anhydrous ethanol and deionized water, then dry in a 60℃ vacuum oven for 24 h. Weigh the product for later use.

[0041] Step 2: Measure 50 mL of deionized water and add 0.5 mmol Ni(NO3)2·6H2O, 0.5 mmol Co(NO3)2·6H2O, 1 mmol (NH4)2MoO4·4H2O, and 7 mmol NH2CONH2 sequentially. Stir on a magnetic stirrer at 300 r / min for 30 min until all reagents are completely dissolved, forming a homogeneous and transparent precursor solution. Place the pretreated NF at the bottom of a 100 mL polytetrafluoroethylene (PTFE) liner, slowly pour in the above precursor solution to saturate the NF, seal the liner, and place in a hydrothermal autoclave. React in a 180℃ oven for 8 h.

[0042] Step 3: After the reaction is complete, cool to room temperature, remove NF, wash 6 times with deionized water to remove unreacted reagents, and dry in a 55℃ oven for 24 h, then weigh. Transfer the dried sample to a quartz boat and place it in a horizontal tube furnace. Purge with high-purity nitrogen (≥99.999%) as a protective atmosphere, adjusting the nitrogen flow rate to 50 mL / min. After the air in the furnace is exhausted (after 30 min of purging), heat to 400℃ at a rate of 5℃ / min and hold for 2 h. After holding, turn off the heating device and maintain the nitrogen atmosphere until the tube furnace cools naturally to room temperature. Remove the sample to obtain Ni. 1 / 2 Co 1 / 2 MoO4 / NF electrode material (molybdenum-based transition metal oxide nanosheet electrode material, denoted as NCM-2).

[0043] Example 3 Step 1: Take 1.5 mm thick nickel foam (NF) and cut it into 1 cm × 2 cm and 1 cm × 1 cm sheets, placing them in a 500 mL beaker. Sonicate the beaker sequentially with 50 mL acetone, 50 mL anhydrous ethanol, 50 mL 2 M hydrochloric acid solution, and 50 mL deionized water for 20 min each to remove surface oil, organic impurities, and the nickel oxide layer. After treatment, rinse five times alternately with anhydrous ethanol and deionized water, then dry in a 60℃ vacuum oven for 24 h. Weigh the product for later use.

[0044] Step 2: Measure 50 mL of deionized water and add 0.5 mmol Ni(NO3)2·6H2O, 0.5 mmol Co(NO3)2·6H2O, 1 mmol (NH4)2MoO4·4H2O, and 7 mmol NH2CONH2 sequentially. Stir on a magnetic stirrer at 300 r / min for 30 min until all reagents are completely dissolved, forming a homogeneous and transparent precursor solution. Place the pretreated NF at the bottom of a 100 mL polytetrafluoroethylene (PTFE) liner, slowly pour in the above precursor solution to saturate the NF, seal the liner, and place it in a hydrothermal autoclave. React in a 160℃ oven for 12 h.

[0045] Step 3: After the reaction is complete, cool to room temperature, remove NF, wash 6 times with deionized water to remove unreacted reagents, and dry in a 55℃ oven for 24 h, then weigh. Transfer the dried sample to a quartz boat and place it in a horizontal tube furnace. Purge with high-purity nitrogen (≥99.999%) as a protective atmosphere, adjusting the nitrogen flow rate to 50 mL / min. After the air in the furnace is exhausted (after 30 min of purging), heat to 400℃ at a rate of 5℃ / min and hold for 2 h. After holding, turn off the heating device and maintain the nitrogen atmosphere until the tube furnace cools naturally to room temperature. Remove the sample to obtain Ni. 1 / 2 Co 1 / 2 MoO4 / NF electrode material (molybdenum-based transition metal oxide nanosheet electrode material, denoted as NCM-3).

[0046] Example 4 Step 1: Take 1.5 mm thick nickel foam (NF) and cut it into 1 cm × 2 cm and 1 cm × 1 cm sheets, placing them in a 500 mL beaker. Sonicate the beaker sequentially with 50 mL acetone, 50 mL anhydrous ethanol, 50 mL 2 M hydrochloric acid solution, and 50 mL deionized water for 20 min each to remove surface oil, organic impurities, and the nickel oxide layer. After treatment, rinse five times alternately with anhydrous ethanol and deionized water, then dry in a 60℃ vacuum oven for 24 h. Weigh the product for later use.

[0047] Step 2: Measure 50 mL of deionized water and add 0.5 mmol Ni(NO3)2·6H2O, 0.5 mmol Co(NO3)2·6H2O, 1 mmol (NH4)2MoO4·4H2O, and 7 mmol NH2CONH2 sequentially. Stir on a magnetic stirrer at 300 r / min for 30 min until all reagents are completely dissolved, forming a homogeneous and transparent precursor solution. Place the pretreated NF at the bottom of a 100 mL polytetrafluoroethylene (PTFE) liner, slowly pour in the above precursor solution to saturate the NF, seal the liner, and place it in a hydrothermal autoclave. React in a 160℃ oven for 8 h.

[0048] Step 3: After the reaction is complete, cool to room temperature, remove NF, wash 6 times with deionized water to remove unreacted reagents, and dry in a 55℃ oven for 24 h, then weigh. Transfer the dried sample to a quartz boat and place it in a horizontal tube furnace. Purge with high-purity nitrogen (≥99.999%) as a protective atmosphere, adjusting the nitrogen flow rate to 50 mL / min. After the air in the furnace is exhausted (after 30 min of purging), heat to 500℃ at a rate of 5℃ / min and hold for 2 h. After holding, turn off the heating device and maintain the nitrogen atmosphere until the tube furnace cools naturally to room temperature. Remove the sample to obtain Ni. 1 / 2 Co 1 / 2 MoO4 / NF electrode material (molybdenum-based transition metal oxide nanosheet electrode material, denoted as NCM-4).

[0049] Example 5 Step 1: Take 1.5 mm thick nickel foam (NF) and cut it into 1 cm × 2 cm and 1 cm × 1 cm sheets, placing them in a 500 mL beaker. Sonicate the beaker sequentially with 50 mL acetone, 50 mL anhydrous ethanol, 50 mL 2 M hydrochloric acid solution, and 50 mL deionized water for 20 min each to remove surface oil, organic impurities, and the nickel oxide layer. After treatment, rinse five times alternately with anhydrous ethanol and deionized water, then dry in a 60℃ vacuum oven for 24 h. Weigh the product for later use.

[0050] Step 2: Measure 50 mL of deionized water and add 0.5 mmol Ni(NO3)2·6H2O, 0.5 mmol Co(NO3)2·6H2O, 1 mmol (NH4)2MoO4·4H2O, and 7 mmol NH2CONH2 sequentially. Stir on a magnetic stirrer at 300 r / min for 30 min until all reagents are completely dissolved, forming a homogeneous and transparent precursor solution. Place the pretreated NF at the bottom of a 100 mL polytetrafluoroethylene (PTFE) liner, slowly pour in the above precursor solution to saturate the NF, seal the liner, and place it in a hydrothermal autoclave. React in a 160℃ oven for 8 h.

[0051] Step 3: After the reaction is complete, cool to room temperature, remove NF, wash 6 times with deionized water to remove unreacted reagents, and dry in a 55℃ oven for 24 h, then weigh. Transfer the dried sample to a quartz boat and place it in a horizontal tube furnace. Purge air as a protective atmosphere, adjust the nitrogen flow rate to 50 mL / min, and after the air in the furnace is exhausted (after 30 min of purging), heat to 400℃ at a rate of 5℃ / min and hold for 2 h. After holding, turn off the heating device and maintain the nitrogen atmosphere until the tube furnace cools naturally to room temperature. Remove the sample to obtain Ni. 1 / 2 Co 1 / 2 MoO4 / NF electrode material (molybdenum-based transition metal oxide nanosheet electrode material, denoted as NCM-5).

[0052] Comparative Example 1 Step 1: Take 1.5 mm thick nickel foam (NF) and cut it into 1 cm × 2 cm and 1 cm × 1 cm sheets, placing them in a 500 mL beaker. Sonicate the beaker sequentially with 50 mL acetone, 50 mL anhydrous ethanol, 50 mL 2 M hydrochloric acid solution, and 50 mL deionized water for 20 min each to remove surface oil, organic impurities, and the nickel oxide layer. After treatment, rinse five times alternately with anhydrous ethanol and deionized water, then dry in a 60℃ vacuum oven for 24 h. Weigh the product for later use.

[0053] Step 2: Measure 50 mL of deionized water and add 0.5 mmol Ni(NO3)2·6H2O, 0.5 mmol Co(NO3)2·6H2O, and 1 mmol (NH4)2MoO4·4H2O sequentially. Stir on a magnetic stirrer at 300 r / min for 30 min until all reagents are completely dissolved, forming a homogeneous and transparent precursor solution. Place the pretreated NF at the bottom of a 100 mL polytetrafluoroethylene (PTFE) liner, slowly pour in the above precursor solution to saturate the NF, seal the liner, and place it in a hydrothermal autoclave. React in a 160℃ oven for 8 h.

[0054] Step 3: After the reaction is complete, cool to room temperature, remove NF, wash 6 times with deionized water to remove unreacted reagents, and dry in a 55℃ oven for 24 h, then weigh. Transfer the dried sample to a quartz boat and place it in a horizontal tube furnace. Purge with high-purity nitrogen (≥99.999%) as a protective atmosphere, adjusting the nitrogen flow rate to 50 mL / min. After the air in the furnace is exhausted (after 30 min of purging), heat to 400℃ at a rate of 5℃ / min and hold for 2 h. After holding, turn off the heating device and maintain the nitrogen atmosphere until the tube furnace cools naturally to room temperature. Remove the sample to obtain Ni. 1 / 2 Co 1 / 2MoO4 / NF electrode material (molybdenum-based transition metal oxide nanosheet electrode material, denoted as NCM).

[0055] To further illustrate the beneficial effects of the present invention, the electrode materials prepared in Examples 1 to 5 and Comparative Example 1 were tested, and the test results are shown in the table below:

[0056] It can be seen that process parameters have a significant impact on Ni 1 / 2 Co 1 / 2 MoO4 / NF electrode material performance is significantly affected: Example 1 has the best overall performance, with a specific capacity of 832 F•g. -1 The cycle retention rate was 97.36%. Hydrothermal treatment at 150℃ formed a well-defined nanosheet structure. The nitrogen source provided by NH2CONH2 achieved nitrogen doping of the material under an N2 atmosphere, which enhanced conductivity, reduced charge transfer resistance, and inhibited the dissolution and loss of active materials. In Example 2, hydrothermal treatment at 180℃ caused nanosheet aggregation due to excessively high temperature, reducing active sites and causing the specific capacity to plummet to 365 F•g. -1 Example 3 involved hydrothermal treatment at 150°C for 12 hours. Due to the excessively long reaction time, the nanosheets over-growthed, forming a bulk structure, and the specific capacity decreased to 592 F•g. -1 Example 4: Calcination at 500℃ resulted in MoO4... 2- Decomposition occurs, the crystal structure collapses, and the specific capacity is only 134 F•g. -1 Example 5: Due to the oxidizing atmosphere, the nitrogen-doped structure is destroyed, and an inactive Co3O4 impurity phase is easily generated. Specific capacity: 210 F•g -1 The cycle retention rate was only 78.03%; Comparative Example 1, without NH2CONH2 and calcined in air, lacked nitrogen doping and conductive enhancement sites, and the air atmosphere caused material oxidation and degradation, resulting in a specific capacity of only 48 F•g. -1 The cycle retention rate of 65.8% fully demonstrates the key role of nitrogen doping and appropriate hydrothermal / calcination parameters in the material properties.

[0057] Example 6 Step 1: Take 1.5 mm thick nickel foam (NF) and cut it into 1 cm × 2 cm and 1 cm × 1 cm sheets, placing them in a 500 mL beaker. Sonicate the beaker sequentially with 50 mL acetone, 50 mL anhydrous ethanol, 50 mL 2 M hydrochloric acid solution, and 50 mL deionized water for 20 min each to remove surface oil, organic impurities, and the nickel oxide layer. After treatment, rinse five times alternately with anhydrous ethanol and deionized water, then dry in a 60℃ vacuum oven for 24 h. Weigh the product for later use.

[0058] Step 2: Measure 50 mL of deionized water and add 0.5 mmol Ni(NO3)2·6H2O, 0.5 mmol Co(NO3)2·6H2O, 1 mmol (NH4)2MoO4·4H2O, and 6 mmol NH2CONH2 sequentially. Stir on a magnetic stirrer at 300 r / min for 30 min until all reagents are completely dissolved, forming a homogeneous and transparent precursor solution. Place the pretreated NF at the bottom of a 100 mL polytetrafluoroethylene (PTFE) liner, slowly pour in the above precursor solution to saturate the NF, seal the liner, and place it in a hydrothermal autoclave. React in a 170℃ oven for 10 h.

[0059] Step 3: After the reaction is complete, cool to room temperature, remove NF, wash 6 times with deionized water to remove unreacted reagents, and dry in a 55℃ oven for 24 h, then weigh. Transfer the dried sample to a quartz boat and place it in a horizontal tube furnace. Purge with high-purity nitrogen (≥99.999%) as a protective atmosphere, adjusting the nitrogen flow rate to 45 mL / min. After the air in the furnace is exhausted (after 30 min of purging), heat to 450℃ at a rate of 3℃ / min and hold for 3 h. After holding, turn off the heating device and maintain the nitrogen atmosphere until the tube furnace cools naturally to room temperature. Remove the sample to obtain Ni. 1 / 2 Co 1 / 2 MoO4 / NF electrode material.

[0060] Example 7 Step 1: Take 1.5 mm thick nickel foam (NF) and cut it into 1 cm × 2 cm and 1 cm × 1 cm sheets, placing them in a 500 mL beaker. Sonicate the beaker sequentially with 50 mL acetone, 50 mL anhydrous ethanol, 50 mL 1.5 M hydrochloric acid solution, and 50 mL deionized water for 20 min each to remove surface oil, organic impurities, and the nickel oxide layer. After treatment, rinse five times alternately with anhydrous ethanol and deionized water, then dry in a 60℃ vacuum oven for 24 h. Weigh the product for later use.

[0061] Step 2: Measure 50 mL of deionized water and add 0.5 mmol Ni(NO3)2·6H2O, 0.5 mmol Co(NO3)2·6H2O, 1 mmol (NH4)2MoO4·4H2O, and 8 mmol NH2CONH2 sequentially. Stir on a magnetic stirrer at 300 r / min for 30 min until all reagents are completely dissolved, forming a homogeneous and transparent precursor solution. Place the pretreated NF at the bottom of a 100 mL polytetrafluoroethylene (PTFE) liner, slowly pour in the above precursor solution to saturate the NF, seal the liner, and place it in a hydrothermal autoclave. React in a 165℃ oven for 9 h.

[0062] Step 3: After the reaction is complete, cool to room temperature, remove NF, wash 6 times with deionized water to remove unreacted reagents, and dry in a 55℃ oven for 24 h, then weigh. Transfer the dried sample to a quartz boat and place it in a horizontal tube furnace. Purge with high-purity nitrogen (≥99.999%) as a protective atmosphere, adjusting the nitrogen flow rate to 55 mL / min. After the air in the furnace is exhausted (after 30 min of purging), heat to 500℃ at a rate of 8℃ / min and hold for 3 h. After holding, turn off the heating device and maintain the nitrogen atmosphere until the tube furnace cools naturally to room temperature. Remove the sample to obtain Ni. 1 / 2 Co 1 / 2 MoO4 / NF electrode material (molybdenum-based transition metal oxide nanosheet electrode material, denoted as NCM-1).

[0063] Example 8 Step 1: Take 1.5 mm thick nickel foam (NF) and cut it into 1 cm × 2 cm and 1 cm × 1 cm sheets, placing them in a 500 mL beaker. Sonicate the beaker sequentially with 50 mL acetone, 50 mL anhydrous ethanol, 50 mL 3M hydrochloric acid solution, and 50 mL deionized water for 20 min each to remove surface oil, organic impurities, and the nickel oxide layer. After treatment, rinse five times alternately with anhydrous ethanol and deionized water, then dry in a 60℃ vacuum oven for 24 h. Weigh the product for later use.

[0064] Step 2: Measure 50 mL of deionized water and add 0.5 mmol Ni(NO3)2·6H2O, 0.5 mmol Co(NO3)2·6H2O, 1 mmol (NH4)2MoO4·4H2O, and 7 mmol NH2CONH2 sequentially. Stir on a magnetic stirrer at 300 r / min for 30 min until all reagents are completely dissolved, forming a homogeneous and transparent precursor solution. Place the pretreated NF at the bottom of a 100 mL polytetrafluoroethylene (PTFE) liner, slowly pour in the above precursor solution to saturate the NF, seal the liner, and place it in a hydrothermal autoclave. React in a 160℃ oven for 8 h.

[0065] Step 3: After the reaction is complete, cool to room temperature, remove NF, wash 6 times with deionized water to remove unreacted reagents, and dry in a 55℃ oven for 24 h, then weigh. Transfer the dried sample to a quartz boat and place it in a horizontal tube furnace. Purge with high-purity nitrogen (≥99.999%) as a protective atmosphere, adjusting the nitrogen flow rate to 50 mL / min. After the air in the furnace is exhausted (after 30 min of purging), heat to 400℃ at a rate of 5℃ / min and hold for 2 h. After holding, turn off the heating device and maintain the nitrogen atmosphere until the tube furnace cools naturally to room temperature. Remove the sample to obtain Ni. 1 / 2 Co1 / 2 MoO4 / NF electrode material (molybdenum-based transition metal oxide nanosheet electrode material, denoted as NCM-1).

[0066] A molybdenum-based transition metal oxide nanosheet electrode material, as described above, exhibits a specific capacity of 832 F•g. -1 After 5,000 cycles, the cycle retention rate reached 97.36%, demonstrating excellent electrochemical performance and cycle retention rate. It achieves efficient charge storage, which is significantly better than traditional materials. It also has advantages such as low cost, easy scalability, and non-toxicity, providing a core solution for the next generation of high energy density and long life capacitors.

[0067] The above-mentioned molybdenum-based transition metal oxide nanosheet electrode material is used in the preparation of capacitors. Because the molybdenum-based transition metal oxide nanosheet electrode material prepared by this invention has higher electrochemical performance than traditional electrode materials, the prepared capacitors have high specific capacitance and energy density, ultra-long cycle life, high power density, low cost and environmental friendliness, providing theoretical support and technical reserves for the next generation of high energy density and high power density energy storage.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for preparing a molybdenum-based transition metal oxide nanosheet electrode material, characterized in that, include: Precursor solutions were prepared using Ni salts, Co salts, oxidized Mo compounds, and urea. Nickel foam is immersed in a precursor solution and subjected to a hydrothermal reaction to obtain a pre-fabricated electrode material. The pre-fabricated electrode material was calcined to obtain molybdenum-based transition metal oxide nanosheet electrode material.

2. The method for preparing the molybdenum-based transition metal oxide nanosheet electrode material according to claim 1, characterized in that, Both the Ni and Co salts are nitrates, and the oxidized compound of Mo is ammonium molybdate.

3. The method for preparing the molybdenum-based transition metal oxide nanosheet electrode material according to claim 1, characterized in that, The molar ratio of the Ni salt, Co salt, the oxidized Mo compound and urea is 0.5:0.5:1:(6-9).

4. The method for preparing the molybdenum-based transition metal oxide nanosheet electrode material according to claim 1, characterized in that, It also includes a pretreatment process for nickel foam, specifically: After cleaning the foamed nickel sequentially with acetone, ethanol, hydrochloric acid solution and water, it was then cleaned alternately with water and anhydrous ethanol and dried to obtain pretreated foamed nickel. The concentration of the hydrochloric acid solution was 1.5-3M.

5. The method for preparing the molybdenum-based transition metal oxide nanosheet electrode material according to claim 1, characterized in that, The hydrothermal reaction conditions are 150℃~180℃, and the hydrothermal reaction time is 8~12h.

6. The method for preparing the molybdenum-based transition metal oxide nanosheet electrode material according to claim 5, characterized in that, The calcination temperature is 400℃~500℃, and the calcination time is 2~6h.

7. The method for preparing the molybdenum-based transition metal oxide nanosheet electrode material according to claim 1, characterized in that, The heating rate during the calcination process is 3℃~8℃ / min.

8. The method for preparing the molybdenum-based transition metal oxide nanosheet electrode material according to claim 1, characterized in that, The calcination process is carried out under a nitrogen atmosphere with a nitrogen flow rate of 45–55 mL / min.

9. A molybdenum-based transition metal oxide nanosheet electrode material according to any one of claims 1-8, characterized in that, The molybdenum-based transition metal oxide nanosheet electrode material has a specific capacity of 832 F•g. -1 After 5000 cycles, the cycle retention rate reached 97.36%.

10. The application of the molybdenum-based transition metal oxide nanosheet electrode material according to claim 9 in the fabrication of capacitors.

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