A nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material, its preparation method and application

Abstract

A nickel disulfide / biphase titanium dioxide / carbon nanotube composite material, its preparation method, and its application are disclosed. The method comprises the following steps: (1) preparation of a MIL125 precursor; (2) dispersing the MIL125 precursor in a mixed aqueous solution of a nickel source and thioacetamide and heating it in a water bath; after the reaction is completed, filtering, drying, and calcining are performed, followed by the growth of carbon nanotubes using chemical vapor deposition to obtain a first product; (3) mixing the first product with sulfur powder and sulfiding it to obtain the nickel disulfide / biphase titanium dioxide / carbon nanotube composite material. This invention also discloses the nickel disulfide / biphase titanium dioxide / carbon nanotube composite material prepared by the above method and its application in lithium-ion battery anode materials. The composite material provided by this invention combines the advantages of each composite phase and possesses excellent electrochemical performance, thus extending the electrode's lifespan.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode material technology, and particularly relates to a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material, its preparation method and application. Background Technology

[0002] The burning of fossil fuels has led to severe environmental pollution and an energy crisis, prompting the development of new, cost-effective, and eco-friendly energy sources. Batteries can store electrical energy converted from green and renewable energy sources (such as wind, wave, and solar power), making them suitable for everyday use. For over two decades, lithium-ion batteries (LIBs) have been considered ideal energy storage devices due to their high energy density and long cycle life, and have been widely used in electric vehicles, portable electronic devices, and other fields. However, the ever-expanding market demand presents greater challenges for LIBs, and exploring new electrode materials is a key way to achieve higher-performance lithium-ion batteries. The anode material is a crucial factor determining the energy storage performance of lithium-ion batteries. Currently, the widely used graphite anode has issues with safety and stability, while TiO2, also an intercalation-type lithium storage material, exhibits a smaller volume change (<4%) during lithium insertion / extraction, demonstrating significantly better safety and stability than graphite. Furthermore, it is abundant and eco-friendly, making it a promising anode material. However, TiO2 also has two problems: 1. A relatively low theoretical capacity (335 mAh g / g). -1 2. Its low electronic / ionic conductivity severely limits its practical application value.

[0003] Researchers have employed various methods to address these issues. For example, they have used hydrothermal methods to dope TiO2 hollow spheres with phosphorus to improve conductivity, and combined TiO2 with MoS2 to achieve excellent lithium storage performance. However, these modification methods are relatively singular and offer limited improvement to TiO2 performance. Composites with materials possessing high theoretical capacity can effectively enhance the reversible capacity of composite materials. Secondly, defect modification can improve the internal conductivity of TiO2 by adjusting electron-hole pairs and optimizing the internal interface, thus accelerating charge transfer kinetics. Thirdly, external conductivity and electrochemical performance can be improved by composites with highly conductive carbon materials, such as graphene, carbon nanotubes, and porous carbon. Finally, for rapid lithium ion storage, metal-organic frameworks (MOFs) with large specific surface areas can be introduced to create abundant open channels for full contact with the electrolyte, forming more reactive sites and providing rapid ion / electron transport channels. However, existing technologies do not disclose methods for comprehensively modifying TiO2 using the aforementioned techniques.

[0004] Therefore, how to provide a means to comprehensively modify TiO2 and further expand the application of TiO2 is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention discloses the following technical solutions:

[0007] A method for preparing a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material includes the following steps:

[0008] (1) Add terephthalic acid to a mixed solution of N,N-dimethylformamide and methanol, then add titanium isopropoxide dropwise and mix well. Perform a solvothermal reaction. After the reaction is complete, wash and dry to obtain the MIL125 precursor.

[0009] (2) The MIL125 precursor was dispersed in a mixed aqueous solution of nickel source and thioacetamide and heated in a water bath. After the reaction was completed, it was filtered, dried and calcined. Then, carbon nanotubes were grown by chemical vapor deposition to obtain the first product.

[0010] (3) The first product is mixed with sulfur powder and vulcanized to obtain the nickel sulfide / dual-phase titanium dioxide / carbon nanotube composite material.

[0011] Beneficial effects: The titanium dioxide in this invention acts as a buffer layer to mitigate the volume expansion of nickel disulfide during lithium storage, and also has a certain chemical adsorption effect on polysulfides generated during charging and discharging, thereby extending the electrode lifespan. Furthermore, the external three-dimensional network constructed from highly conductive carbon nanotubes in this invention promotes rapid electron transport, and the large specific surface area it provides is also beneficial for electrolyte wetting and ion exchange. Therefore, the composite material provided by this invention exhibits superior electrochemical performance compared to any single component.

[0012] Secondly, the composite material in this invention incorporates a MOF precursor during preparation. During the water bath process, the synergistic effect of nickel acetate and thioacetamide results in a unique yolk-shell structure. Abundant pores and a large specific surface area ensure sufficient contact with the electrolyte, thereby generating more electrochemical reaction active sites. Simultaneously, it alleviates volume expansion during lithium insertion / extraction, significantly improving stability. Furthermore, thioacetamide also acts as a nitrogen dopant for TiO2. Nitrogen doping introduces abundant oxygen vacancies, effectively optimizing the electronic structure of titanium dioxide, increasing its internal conductivity, and the resulting lattice distortion facilitates lithium-ion transport, accelerating reaction kinetics.

[0013] Furthermore, the present invention involves heat treatment at 650°C, which enables the coexistence of anatase TiO2 and rutile TiO2 in the final product. The introduction of the anatase-rutile heterostructure not only facilitates the tight bonding between TiO2 and the carbon layer, improving the electronic conductivity of the composite material, but also reduces Li... + The migration energy barrier is reduced, and at the same time, the two-phase titanium dioxide can increase the defect density in the TiO2 lattice. The abundant oxygen vacancies and enhanced electronic conductivity can accelerate the electron / ion transport of the electrode.

[0014] Preferably, the ratio of the amount of terephthalic acid, N,N-dimethylformamide, methanol and titanium isopropoxide added in step (1) is (1-2)g∶27ml∶3ml∶(0.5-1)ml.

[0015] Beneficial effects: Under the above ratio conditions, a disk-shaped MOF structure can be generated. The disk-shaped MOF has a small size and is also conducive to the formation of subsequent hollow structures.

[0016] Preferably, the solvothermal reaction temperature in step (1) is 100-180℃ and the time is 9-20h.

[0017] Beneficial effects: The above-mentioned solvothermal parameter range can limit the growth of MOF to a certain extent, control its size, and help shorten the transport path of electrons / ions inside.

[0018] Preferably, the ratio of the amount of MIL125 precursor, nickel source, thioacetamide and water added in step (2) is (160-200) mg: (114.5-457.8) mg: (69.1-276.4) mg: 121 ml.

[0019] Beneficial effects: The water bath reaction at the above raw material addition ratio can effectively promote MOF hydrolysis, forming a hollow yolk shell structure, which is conducive to electrolyte wetting and promotes ion transport.

[0020] Preferably, the nickel source in step (2) is nickel acetate, and the water bath heating temperature is 50-70℃ for 3-5 hours;

[0021] The calcination is carried out under a protective atmosphere at a temperature of 400-600℃ for 1-3 hours.

[0022] Beneficial effects: The nickel acetate in this invention makes the aqueous solution weakly acidic, which is conducive to the hydrolysis of MOF, and the above-mentioned calcination temperature can ensure the occurrence of carbothermic reaction, thereby forming nickel metal particles as a catalyst, which is beneficial to the subsequent chemical vapor deposition growth of carbon nanotubes.

[0023] Preferably, in the chemical vapor deposition process described in step (2), the carbon source is introduced by bubbling, the protective atmosphere is argon with a flow rate of 100-300 sccm, and the reducing atmosphere is hydrogen with a flow rate of 10-30 sccm.

[0024] In the chemical vapor deposition process, the carbon source is added in a 100-500 ml bubble bottle with 50-300 ml of solution.

[0025] The chemical vapor deposition method has a reaction temperature of 650℃ and a reaction time of 0.5-3 hours.

[0026] The carbon source is ethanol.

[0027] Beneficial effects: The chemical vapor deposition method in this invention can controllably form carbon nanotubes. At the same time, the above parameters can ensure that the growth amount of carbon nanotubes is within a suitable range, which can improve the overall conductivity of the electrode without causing the proportion of other active materials to be too low and reduce the capacity.

[0028] Preferably, in step (3), the mass ratio of the first product to sulfur powder is 1:(1-4), the sulfidation reaction temperature is 300-600℃, and the reaction time is 1-3h.

[0029] Beneficial effects: Under the above conditions, sulfidation can be fully completed to obtain the desired product NiS2.

[0030] A method for preparing a nickel disulfide / diphase titanium dioxide / carbon nanotube composite material.

[0031] Beneficial effects: First, the introduction of the MOF precursor limits the size of the composite material to a certain extent, keeping it at the micrometer level; simultaneously, due to the tunable structure, a unique porous yolk-shell structure is obtained through a simple water bath reaction. Second, compared to nitrogen doping during heat treatment, nitrogen doping during MOF hydrolysis allows nitrogen doping to occur more within the titanium dioxide lattice rather than on the surface layer, thus more effectively introducing lattice defects. Finally, this invention allows anatase TiO2 and rutile TiO2 to coexist in the final product through heat treatment at 650℃; the introduction of the anatase-rutile heterostructure facilitates the tight bonding between TiO2 and the carbon layer.

[0032] Application of a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material in lithium-ion battery anode materials.

[0033] The unique porous yolk-shell structure of this invention provides abundant channels and a large specific surface area, ensuring sufficient contact with the electrolyte and thus generating more electrochemical reaction active sites. Simultaneously, it alleviates volume expansion during lithium insertion / extraction processes, significantly improving stability. Furthermore, nitrogen doping during the water bath process introduces abundant oxygen vacancies, effectively optimizing the electronic structure of titanium dioxide, increasing its internal conductivity, and the resulting lattice distortion facilitates lithium-ion transport, accelerating reaction kinetics.

[0034] Furthermore, the introduction of the anatase-rutile heterostructure not only facilitates the tight bonding between TiO2 and the carbon layer, improving the electronic conductivity of the composite material, but also reduces Li... + The migration energy barrier is reduced, and at the same time, the two-phase titanium dioxide can increase the defect density in the TiO2 lattice. The abundant oxygen vacancies and enhanced electronic conductivity can accelerate the electron / ion transport of the electrode.

[0035] Compared with existing technologies, this invention discloses a nickel disulfide / biphase titanium dioxide / carbon nanotube composite material, its preparation method, and its applications. The product provided by this invention combines the advantages of each composite phase, possessing both the excellent stability of titanium dioxide and the high reversible capacity of nickel disulfide. This invention uses a Ti-based metal-organic framework MIL125 as a precursor, obtains a uniform yolk-shell structure through a water bath, introduces nickel metal particles, and uses CVD technology to catalyze the growth of carbon nanotubes with a size of approximately 500-2000 nm. Finally, the composite material is obtained through sulfidation. Nickel disulfide in this invention is a material with a high theoretical capacity (870 mAh g⁻¹). -1 This invention significantly improves the reversible capacity of the composite material. After low-temperature heat treatment, TiO2 typically exists in anatase form. Through high-temperature heat treatment, some anatase TiO2 transforms into rutile TiO2, forming a biphase TiO2. Furthermore, the thioacetamide added during the water bath process can dope TiO2 with nitrogen, increasing its internal conductivity. The external three-dimensional network constructed from highly conductive carbon nanotubes enhances the overall conductivity of the composite material. Simultaneously, the introduction of the MOF structure ensures the overall size of the composite material remains at the micrometer level, effectively increasing the contact area between the active material and the electrolyte, thereby further promoting ion migration. The various modification methods employed in this invention optimize the practical application value of TiO2 from both electrochemical performance and electrode reaction kinetics perspectives. Attached Figure Description

[0036] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0037] Figure 1 The images are scanning electron microscope (SEM) images of the nickel / titanium dioxide / carbon composite β prepared in Example 1 at different magnifications.

[0038] Figure 2 SEM images of the nickel / dual-phase titanium dioxide / carbon nanotube composite γ prepared in Example 1 at different magnifications;

[0039] Figure 3 SEM images of the nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite prepared in Example 1 at different magnifications;

[0040] Figure 4 The X-ray diffraction (XRD) pattern of the nickel disulfide / dual-phase titanium dioxide / carbon nanotubes prepared in Example 1;

[0041] Figure 5 The nitrogen element X-ray photoelectron spectroscopy (XPS) of the nickel disulfide / biphase titanium dioxide / carbon nanotubes prepared in Example 1;

[0042] Figure 6 SEM images of the nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite prepared in Example 2 at different magnifications;

[0043] Figure 7 SEM image of nickel disulfide / dual-phase titanium dioxide / carbon prepared in Comparative Example 1;

[0044] Figure 8 The XRD diffraction pattern of the nickel disulfide / dual-phase titanium dioxide / carbon prepared in Comparative Example 1 is shown.

[0045] Figure 9 The rate performance comparison chart shows the nickel disulfide / dual-phase titanium dioxide / carbon nanotubes and nickel disulfide / dual-phase titanium dioxide / carbon prepared in Example 1 and Comparative Example 1.

[0046] Figure 10 The impedance comparison diagrams are shown for nickel disulfide / dual-phase titanium dioxide / carbon nanotubes and nickel disulfide / dual-phase titanium dioxide / carbon prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] Example 1

[0050] A method for preparing a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material includes the following steps:

[0051] (1) 1.5 g of terephthalic acid was added to a mixed solution of 27 ml N,N-dimethylformamide and 3 ml methanol. After stirring thoroughly for about 40 minutes, a transparent mixed solution A was obtained. Then, 0.78 ml of titanium isopropoxide was added dropwise, and the mixture was stirred continuously for 5 minutes to obtain a transparent solution B. The transparent solution B was then placed in a 100 ml reaction vessel and subjected to a solvothermal reaction at 150 °C for 12 h. After the reaction was completed, the precipitate was collected and washed three times with anhydrous ethanol. After drying for 12 hours, Ti was obtained. 4+ Using terephthalic acid as the central ion, the MIL125 precursor with terephthalic acid as the organic ligand was obtained;

[0052] (2) Dissolve 228.9 mg of nickel acetate and 138.2 mg of thioacetamide in 121 ml of deionized water, then add 180 mg of the MIL125 precursor obtained in step (1), sonicate for 5 minutes, and then perform water bath treatment at 60 °C for 4 hours to obtain a mixed suspension. After filtration, wash the precipitate with deionized water several times, and then dry it for 12 hours to obtain a light green powder α. Calcine the light green powder α at 500 °C for 2 hours in a nitrogen atmosphere to obtain a black powder β.

[0053] (3) Under an argon-hydrogen mixture, ethanol was introduced into a 300ml bubbling bottle containing 100ml of ethanol as a carbon source using a bubbling method. In-situ converted nickel metal particles were used as catalysts to grow carbon nanotubes on black powder β by chemical vapor deposition (CVD) at 650℃. Argon was used as the protective atmosphere (flow rate: 150sccm) and hydrogen was used as the reducing atmosphere (flow rate: 15sccm). The growth time was 1h to obtain a nickel / biphase titanium dioxide / carbon nanotube composite γ.

[0054] (4) The above-mentioned nickel / biphase titanium dioxide / carbon nanotube composite γ was mixed with sulfur powder at a mass ratio of 1:2 and sulfided at 350°C for 2 hours to obtain the final product, nickel disulfide / biphase titanium dioxide / carbon nanotube composite material, namely NiS2 / TiO2 / CNTs.

[0055] Figure 1 Parts a and b are SEM images of the nickel / titanium dioxide / carbon composite β at different magnifications. A clear hollow yolk shell structure can be observed, with a size between 500-1000 nm.

[0056] like Figure 2 As shown in parts a and b, after CVD technology, carbon nanotubes grow significantly, encapsulating the yolk shell structure, and their size is approximately 500-2000 nm.

[0057] Figure 3 Parts a and b are SEM images of the nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material at different magnifications. It can be seen that the morphology does not change much after sulfidation.

[0058] Figure 4 The XRD diffraction pattern of the nickel disulfide / biphase titanium dioxide / carbon nanotubes prepared in Example 1 is shown. It can be seen that the phase of nickel disulfide / biphase titanium dioxide / carbon nanotubes is further identified by X-ray diffraction as a mixture of rutile and anatase two-phase titanium dioxide (JCPDS 72-1148, JCPDS 99-0008) and nickel disulfide (JCPDS 89-1495). The presence of carbon nanotubes can be confirmed by the above SEM image.

[0059] Figure 5 The XPS spectrum of N element in the nickel disulfide / dual-phase titanium dioxide / carbon nanotube prepared in Example 1 is shown. The valence state of N on the surface of Example 1 was detected. It can be seen that N has a characteristic peak of N-Ti-O at 401.7 eV, indicating that N is obviously present in the titanium dioxide lattice, which proves the successful incorporation of N.

[0060] Example 2

[0061] A method for preparing a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material includes the following steps:

[0062] (1) 1.5 g of terephthalic acid was added to a mixed solution of 27 ml N,N-dimethylformamide and 3 ml methanol. After stirring thoroughly for about 40 minutes, a transparent mixed solution A was obtained. Then, 0.78 ml of titanium isopropoxide was added dropwise, and stirring was continued for 5 minutes to form a transparent solution B. The transparent solution B was then placed in a 100 ml reaction vessel and subjected to a solvothermal reaction at 150 °C for 12 h. After the reaction was completed, the precipitate was collected and washed three times with anhydrous ethanol. After drying for 12 hours, Ti was obtained. 4+ Using terephthalic acid as the central ion, the MIL125 precursor with terephthalic acid as the organic ligand was obtained;

[0063] (2) Dissolve 228.9 mg of nickel acetate and 138.2 mg of thioacetamide in 121 ml of deionized water, then add 180 mg of the MIL125 precursor obtained in step (1), sonicate for 5 minutes, and then perform water bath treatment at 60 °C for 4 hours to obtain a mixed suspension. After filtration, wash the obtained precipitate with deionized water several times, and dry it for 12 hours to obtain a light green powder α. Calcine the light green powder α at 500 °C for 2 hours in a nitrogen atmosphere to obtain a black powder β.

[0064] (3) Under an argon-hydrogen mixture, ethanol was introduced into a 300ml bubbling bottle containing 100ml of ethanol as a carbon source using a bubbling method. In-situ converted nickel metal particles were used as catalysts to grow carbon nanotubes on black powder β by chemical vapor deposition (CVD) at 650℃. Argon was used as the protective atmosphere (flow rate: 150sccm) and hydrogen was used as the reducing atmosphere (flow rate: 10sccm). The growth time was 0.5h, and a nickel / biphase titanium dioxide / carbon nanotube composite γ was obtained.

[0065] (4) The above-mentioned nickel / biphase titanium dioxide / carbon nanotube composite γ was mixed with sulfur powder at a mass ratio of 1:2 and sulfided at 350°C for 2 hours to obtain the final product, nickel disulfide / biphase titanium dioxide / carbon nanotube composite material, namely NiS2 / TiO2 / CNTs.

[0066] Figure 6 Parts a and b are SEM images of the nickel disulfide / biphase titanium dioxide / carbon nanotube composite prepared in Example 2 at different magnifications. It can be seen that during the CVD reaction, reducing the reaction time significantly inhibited the growth of carbon nanotubes, and the grown carbon nanotubes were relatively sparse.

[0067] Example 3

[0068] A method for preparing a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material includes the following steps:

[0069] (1) 1.5 g of terephthalic acid was added to a mixed solution of 27 ml N,N-dimethylformamide and 3 ml methanol. After stirring thoroughly for about 40 minutes, a transparent mixed solution A was obtained. Then, 0.78 ml of titanium isopropoxide was added dropwise, and stirring was continued for 5 minutes to form a transparent solution B. The transparent solution B was then placed in a 100 ml reaction vessel and subjected to a solvothermal reaction at 150 °C for 12 h. After the reaction was completed, the precipitate was collected and washed three times with anhydrous ethanol. After drying for 12 hours, Ti was obtained. 4+ Using terephthalic acid as the central ion, the MIL125 precursor with terephthalic acid as the organic ligand was obtained;

[0070] (2) Dissolve 228.9 mg of nickel acetate and 138.2 mg of thioacetamide in 121 ml of deionized water, then add 180 mg of the MIL125 precursor obtained in step (1), sonicate for 5 minutes, and then perform water bath treatment at 60 °C for 4 hours to obtain a mixed suspension. After filtration, wash the obtained precipitate with deionized water several times, and dry it for 12 hours to obtain a light green powder α. Calcine the light green powder α at 500 °C for 2 hours in a nitrogen atmosphere to obtain a black powder β.

[0071] (3) Under an argon-hydrogen mixture, ethanol was introduced into a 300ml bubbling bottle containing 100ml of ethanol as a carbon source using a bubbling method. In-situ converted nickel metal particles were used as catalysts to grow carbon nanotubes on black powder β by chemical vapor deposition (CVD) at 650℃. Argon was used as the protective atmosphere (flow rate: 150sccm) and hydrogen was used as the reducing atmosphere (flow rate: 10sccm). The growth time was 2h to obtain a nickel / biphase titanium dioxide / carbon nanotube composite γ.

[0072] (4) The above-mentioned nickel / biphase titanium dioxide / carbon nanotube composite γ was mixed with sulfur powder at a mass ratio of 1:2 and sulfided at 350°C for 2 hours to obtain the final product, nickel disulfide / biphase titanium dioxide / carbon nanotube composite material, namely NiS2 / TiO2 / CNTs.

[0073] Example 4

[0074] A method for preparing a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material includes the following steps:

[0075] A method for preparing a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material includes the following steps:

[0076] (1) 1.5 g of terephthalic acid was added to a mixed solution of 27 ml N,N-dimethylformamide and 3 ml methanol. After stirring thoroughly for about 40 minutes, a transparent mixed solution A was obtained. Then, 0.78 ml of titanium isopropoxide was added dropwise, and stirring was continued for 5 minutes to form a transparent solution B. The transparent solution B was then placed in a 100 ml reaction vessel and subjected to a solvothermal reaction at 150 °C for 12 h. After the reaction was completed, the precipitate was collected and washed three times with anhydrous ethanol. After drying for 12 hours, Ti was obtained. 4+ Using terephthalic acid as the central ion, the MIL125 precursor with terephthalic acid as the organic ligand was obtained;

[0077] (2) Dissolve 114.5 mg of nickel acetate and 69.1 mg of thioacetamide in 121 ml of deionized water, then add 180 mg of the MIL125 precursor obtained in step (1), sonicate for 5 minutes, and then perform water bath treatment at 60 °C for 4 hours to obtain a mixed suspension. After filtration, wash the obtained precipitate with deionized water several times, and dry it for 12 hours to obtain a light green powder α. Calcine the light green powder α at 500 °C for 2 hours in a nitrogen atmosphere to obtain a black powder β.

[0078] (3) Under an argon-hydrogen mixture, ethanol was introduced into a 300ml bubbling bottle containing 100ml of ethanol as a carbon source using a bubbling method. In-situ converted nickel metal particles were used as catalysts to grow carbon nanotubes on black powder β by chemical vapor deposition (CVD) at 650℃. Argon was used as the protective atmosphere (flow rate: 150sccm) and hydrogen was used as the reducing atmosphere (flow rate: 10sccm). The growth time was 0.5h, and a nickel / biphase titanium dioxide / carbon nanotube composite γ was obtained.

[0079] (4) The above-mentioned nickel / biphase titanium dioxide / carbon nanotube composite γ was mixed with sulfur powder at a mass ratio of 1:2 and sulfided at 350°C for 2 hours to obtain the final product, nickel disulfide / biphase titanium dioxide / carbon nanotube composite material, namely NiS2 / TiO2 / CNTs.

[0080] Example 5

[0081] A method for preparing a nickel disulfide / dual-phase titanium dioxide / carbon nanotube composite material includes the following steps:

[0082] (1) 1.5 g of terephthalic acid was added to a mixed solution of 27 ml N,N-dimethylformamide and 3 ml methanol. After stirring thoroughly for about 40 minutes, a transparent mixed solution A was obtained. Then, 0.78 ml of titanium isopropoxide was added dropwise, and stirring was continued for 5 minutes to form a transparent solution B. The transparent solution B was then placed in a 100 ml reaction vessel and subjected to a solvothermal reaction at 150 °C for 12 h. After the reaction was completed, the precipitate was collected and washed three times with anhydrous ethanol. After drying for 12 hours, Ti was obtained. 4+ Using terephthalic acid as the central ion, the MIL125 precursor with terephthalic acid as the organic ligand was obtained;

[0083] (2) Dissolve 457.8 mg of nickel acetate and 276.4 mg of thioacetamide in 121 ml of deionized water, then add 180 mg of the MIL125 precursor obtained in step (1), sonicate for 5 minutes, and then perform water bath treatment at 60 °C for 4 hours to obtain a mixed suspension. After filtration, wash the precipitate with deionized water several times, and dry it for 12 hours to obtain a light green powder α. Calcine the light green powder α at 500 °C for 2 hours in a nitrogen atmosphere to obtain a black powder β.

[0084] (3) Under an argon-hydrogen mixture, ethanol was introduced into a 300ml bubbling bottle containing 100ml of ethanol as a carbon source using a bubbling method. In-situ converted nickel metal particles were used as catalysts to grow carbon nanotubes on black powder β by chemical vapor deposition (CVD) at 650℃. Argon was used as the protective atmosphere (flow rate: 150sccm) and hydrogen was used as the reducing atmosphere (flow rate: 10sccm). The growth time was 0.5h, and a nickel / biphase titanium dioxide / carbon nanotube composite γ was obtained.

[0085] (4) The above-mentioned nickel / biphase titanium dioxide / carbon nanotube composite γ was mixed with sulfur powder at a mass ratio of 1:2 and sulfided at 350°C for 2 hours to obtain the final product, nickel disulfide / biphase titanium dioxide / carbon nanotube composite material, namely NiS2 / TiO2 / CNTs.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that the CVD process in step (3) is not included, and the remaining steps remain unchanged to obtain a composite of nickel disulfide / dual-phase titanium dioxide / carbon, namely NiS2 / TiO2 / C.

[0088] Figure 7 The SEM images of nickel disulfide / dual-phase titanium dioxide / carbon prepared in Comparative Example 1 show that no carbon nanotubes were found in the powder that was not subjected to CVD.

[0089] Figure 8 The XRD diffraction pattern of the nickel disulfide / biphase titanium dioxide / carbon prepared in Comparative Example 1 further confirms that the phases are nickel disulfide and anatase and rutile biphase titanium dioxide.

[0090] Technical effect

[0091] The composite materials obtained in Examples 1-5 and Comparative Example 1 were mixed with Super P and polyvinylidene fluoride (PVDF) at a mass ratio of 7:2:1, respectively. After grinding for 30 minutes and stirring for 2 hours, a slurry was prepared and coated onto copper foil. After thorough drying, it was pressed into a disc to serve as the electrode for the lithium-ion battery to be assembled. The assembled coin-type lithium-ion battery uses a lithium sheet as the negative electrode, the above-mentioned electrode as the positive electrode, and a microporous polypropylene membrane as the separator. 1 mol L of [aluminum oxide] was dropped onto both sides of the separator.-1 The electrolyte consisted of LiPF6 as the solute and ethylene carbonate (EC) and dimethyl carbonate (DMC) in a 1:1 volume ratio as the solvent. After the assembled lithium-ion batteries were allowed to stand, electrochemical tests were performed. The charge / discharge voltage was 3V-0.01V, and the rate performance and impedance of the negative electrode were measured at 25±1℃.

[0092] With changes in chemical composition and parameters during preparation, lithium-ion batteries exhibit different electrochemical performances. The maximum discharge capacity of lithium-ion batteries assembled from the composite materials used in Examples 1-5 and Comparative Example 1 at different current densities is shown in Table 1.

[0093] Table 1

[0094]

[0095] It can be seen that changing the parameters in the preparation process has a significant impact on the electrochemical performance of lithium-ion batteries. These changed parameters include the reaction time in the CVD technology and the amounts of nickel acetate and thioacetamide. When the CVD reaction time is significantly reduced (Example 2), the growth of carbon nanotubes is significantly inhibited, resulting in a sparse conductive network, as observed in the scanning electron microscope image. Capacity is high at low currents, but decays rapidly at high currents. When the CVD reaction time is increased (Example 3), the amount of carbon nanotubes grown is greater, leading to a decrease in the proportion of high-capacity active material. Consequently, the capacity is lower at various currents, but stability is improved. Without using CVD technology, the specific capacity of Comparative Example 1 at different current densities is lower than that of Examples 1-3, indicating that the presence of carbon nanotubes can significantly improve the poor conductivity of the composite material, thereby enhancing rate performance.

[0096] Figure 9 and Figure 10 The graphs show a comparison of rate performance and impedance of the nickel disulfide / dual-phase titanium dioxide / carbon nanotube and nickel disulfide / dual-phase titanium dioxide / carbon nanotubes prepared in Example 1 and Comparative Example 1. (Combined with...) Figure 9 and Figure 10 It is easy to see that the presence of carbon nanotubes can not only improve the electrochemical performance of composite materials, but also reduce interfacial impedance, increase lithium ion migration rate, and accelerate reaction kinetics.

[0097] Examples 4 and 5, which varied the amounts of nickel acetate and thioacetamide, yielded products exhibiting the worst electrochemical performance. Reducing the amounts of nickel acetate and thioacetamide (Example 4) resulted in a significant decrease in both nickel and nitrogen doping content, leading to a substantial reduction in the high specific capacitance of nickel disulfide and the nitrogen content of TiO2 doping, thus exhibiting poor rate performance. However, when the amounts of nickel acetate and thioacetamide were significantly increased, Example 5 displayed the worst electrochemical performance. This is likely because increasing the amounts of nickel acetate and thioacetamide significantly promoted the hydrolysis of the precursor MIL125, causing structural instability or collapse, thus disrupting the MOF structure and resulting in a sharp decrease in electrochemical performance.

[0098] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a nickel disulfide / biphasic titanium dioxide / carbon nanotube composite material, characterized by, The preparation method comprises the following steps: (1) adding terephthalic acid into a mixed solution of N, N-dimethylformamide and methanol, then adding titanium isopropoxide dropwise and mixing uniformly, and performing a solvothermal reaction, and then washing and drying after the reaction to obtain a MIL125 precursor; (2) dispersing the MIL125 precursor in a mixed aqueous solution of a nickel source and thioacetamide, and performing water bath heating, and then filtering, drying and calcining after the reaction, and then growing carbon nanotubes by using a chemical vapor deposition method to obtain a first product; the reaction temperature of the chemical vapor deposition method is 650 ℃; (3) mixing the first product with sulfur powder to perform sulfuration, and obtaining the nickel disulfide / biphasic titanium dioxide / carbon nanotube composite material.

2. The method for preparing a nickel disulfide / biphasic titanium dioxide / carbon nanotube composite material according to claim 1, characterized by, In step (1), the adding amount ratio of the terephthalic acid, N, N-dimethylformamide, methanol and titanium isopropoxide is (1-2) g: 27 ml: 3 ml: (0.5-1) ml.

3. The method of claim 1, wherein the nickel disulfide / biphasic titanium dioxide / carbon nanotube composite is prepared by the steps of: (a) mixing nickel disulfide, biphasic titanium dioxide, and carbon nanotubes in a solvent; (b) drying the mixture; (c) mixing the dried mixture with a binder; (d) molding the mixture; and (e) sintering the mixture. In step (1), the solvothermal reaction temperature is 100-180 ℃, and the time is 9-20 h.

4. The method of claim 1, wherein the nickel disulfide / biphasic titanium dioxide / carbon nanotube composite is prepared by the steps of: (a) mixing nickel disulfide, biphasic titanium dioxide, and carbon nanotubes in a solvent; (b) drying the mixture; (c) mixing the dried mixture with a binder; (d) molding the mixture; and (e) sintering the mixture. In step (2), the adding amount ratio of the MIL125 precursor, the nickel source, thioacetamide and water is (160-200) mg: (114.5-457.8) mg: (69.1-276.4) mg: 121 ml.

5. The method of claim 1, wherein the nickel disulfide / biphasic titanium dioxide / carbon nanotube composite is prepared by the steps of: (a) mixing nickel disulfide, biphasic titanium dioxide, and carbon nanotubes in a solvent; (b) drying the mixture; (c) mixing the dried mixture with a binder; (d) molding the mixture; and (e) sintering the mixture. In step (2), the nickel source is nickel acetate, the water bath heating temperature is 50-70 ℃, and the time is 3-5 h. The calcination is performed in a protective atmosphere, the calcination temperature is 400-600 ℃, and the calcination time is 1-3 h.

6. The method of claim 1, wherein the nickel disulfide / biphasic titanium dioxide / carbon nanotube composite is prepared by the steps of: (a) mixing nickel disulfide, biphasic titanium dioxide, and carbon nanotubes in a solvent; (b) drying the mixture; (c) heating the dried mixture; and (d) cooling the heated mixture. In step (2), a bubbling method is used to introduce a carbon source in the chemical vapor deposition method, the protective atmosphere is argon, the argon flow rate is 100-300 sccm, the reducing atmosphere is hydrogen, and the hydrogen flow rate is 10-30 sccm. The reaction time of the chemical vapor deposition method is 0.5-3 hours. The carbon source comprises ethanol.

7. The method of claim 1, wherein the nickel disulfide / biphasic titanium dioxide / carbon nanotube composite is prepared by the steps of: (a) mixing nickel disulfide, biphasic titanium dioxide, and carbon nanotubes in a solvent; (b) drying the mixture; (c) heating the dried mixture; and (d) cooling the heated mixture. In step (3), the mass ratio of the first product to sulfur powder is 1: (1-4), the sulfuration reaction temperature is 300-600 ℃, and the reaction time is 1-3 h.

8. The nickel disulfide / biphasic titanium dioxide / carbon nanotube composite material prepared by the preparation method of any one of claims 1-7.

9. The nickel disulfide / biphasic titanium dioxide / carbon nanotube composite material in claim 8 in the application of a lithium ion battery negative electrode material.

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