Preparation method of hierarchical hollow microspherical nickel selenide / nitrogen-doped porous carbon composite material, and material and application thereof

Abstract

This invention relates to the field of energy storage nanomaterials technology, specifically to a method for preparing a hierarchical hollow microspherical nickel selenide / nitrogen-doped porous carbon composite material, along with its materials and applications. The method includes: preparing a basic nickel carbonate precursor solution using nickel nitrate hexahydrate, urea, and deionized water in a specified ratio, and conducting a hydrothermal reaction; washing and drying the reaction product to obtain basic nickel carbonate nanowires; preparing a 2-methylimidazole solution, ultrasonically dispersing the basic nickel carbonate nanowires in the prepared 2-methylimidazole solution, aging at room temperature, and washing and drying the aged product to obtain Ni-MOF layered nanosheets; mixing the Ni-MOF layered nanosheets with selenium powder in a specified ratio and grinding the mixture; and conducting a selenization reaction on the ground product in a protective gas environment to obtain the hierarchical hollow microspherical nickel selenide / nitrogen-doped porous carbon composite material. This invention can shorten the sodium ion transport path, alleviate the volume expansion during sodium ion insertion / extraction, and exhibits structural stability, high capacity, and high rate capability.

Description

Technical Field

[0001] This invention relates to the field of energy storage nanomaterials technology, and in particular to a method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material, as well as the material and its application. Background Technology

[0002] Sodium-ion batteries possess advantages such as abundant resources and low cost, and are expected to complement lithium-ion batteries well in low- and medium-speed electric vehicles and energy storage. However, due to the large radius of sodium ions (0.102 nm), traditional electrode materials in sodium-ion batteries exhibit slow kinetic performance. Improvements in kinetics, including rapid ion shuttle and high ion storage capacity, are urgently needed to further advance practical applications. Fundamentally, developing high-performance anode materials is one of the effective ways to improve the electrochemical performance of sodium-ion batteries.

[0003] Compared to the low sodium storage capacity of intercalation materials and the large volume expansion of alloy materials, conversion materials are a promising class of materials for sodium-ion battery anodes. These materials theoretically have high specific capacity and abundant redox reactions, providing more sodium-ion active sites. However, their poor cycle stability, low initial coulombic efficiency, and rate performance and fast-charging characteristics do not meet expectations, limiting their further commercial application. To address the problems of conversion materials, researchers have conducted extensive studies. On the one hand, they increase defects and provide more active sites through ion doping; on the other hand, they design nanostructures to shorten the electron and ion transport distance. However, ion selection and the complex nanostructure design process remain significant challenges.

[0004] Therefore, how to provide a simpler, more efficient, and safer method for preparing conversion-type negative electrode energy storage materials has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of this, in order to overcome the shortcomings of the prior art, the present invention provides a method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material, as well as the material and its application.

[0006] According to one aspect of the present invention, a method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material is provided, the method comprising:

[0007] Step 1: Preparation of basic nickel carbonate nanowire spheres

[0008] A basic nickel carbonate precursor solution was prepared by using nickel nitrate hexahydrate, urea, and deionized water in a specified ratio. The prepared basic nickel carbonate precursor solution was placed in a reaction vessel for hydrothermal reaction to obtain hydrothermal reaction product. The hydrothermal reaction product was then washed and dried to obtain basic nickel carbonate nanowire spheres.

[0009] Step 2: Preparation of nickel metal-organic framework (Ni-MOF) layered nanosheets

[0010] A 2-methylimidazole solution was prepared, and basic nickel carbonate nanowires were placed in the prepared 2-methylimidazole solution and ultrasonically dispersed. The mixture was then aged at room temperature. The aged product was washed and dried to obtain Ni-MOF layered nanosheets.

[0011] Step 3: Preparation of hierarchical hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material

[0012] Ni-MOF layered nanosheets and selenium powder were mixed according to the specified ratio and then ground. The ground product was subjected to a selenization reaction in a protective gas environment. The selenization reaction product was cooled to room temperature to prepare a fractionated hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material.

[0013] Preferably, in the preparation method of the graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material of the present invention, in step one, a basic nickel carbonate precursor solution is prepared by using nickel nitrate hexahydrate, urea and deionized water in a certain ratio, including: when preparing the basic nickel carbonate precursor solution, every 5 mmol of nickel nitrate hexahydrate is mixed with 25 mmol of urea and 50 ml of deionized water.

[0014] Preferably, in the preparation method of the graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material of the present invention, in step one, the hydrothermal reaction temperature is 105-135℃ and the hydrothermal reaction time is 10-12h.

[0015] Preferably, in the preparation method of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material of the present invention, in step one, the hydrothermal reaction product is cleaned and dried to obtain basic nickel carbonate nanowires, including: cleaning the hydrothermal reaction product cooled to room temperature with deionized water and anhydrous ethanol in sequence, and drying the cleaned product at 80°C for 10 h to obtain basic nickel carbonate nanowires.

[0016] Preferably, in the preparation method of the graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material of the present invention, in step two, the concentration of the 2-methylimidazole solution is 3-7 mol / L, and 40 mg of basic nickel carbonate nanowires are placed in 3 ml of the prepared 2-methylimidazole solution for ultrasonic dispersion, and the aging time at room temperature is 12-72 h.

[0017] Preferably, in the preparation method of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material of the present invention, step two, in which the aged product is cleaned and dried to obtain Ni-MOF layered nanosheets, includes: cleaning the aged product with deionized water and anhydrous ethanol in sequence, and drying the cleaned product at 80°C for 10 h to obtain Ni-MOF layered nanosheets.

[0018] Preferably, in the preparation method of the graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material of the present invention, step three involves mixing Ni-MOF layered nanosheets and selenium powder according to the specified ratio and then grinding the mixture, including: mixing 1 part by weight of Ni-MOF layered nanosheets with 0.5-2 parts by weight of selenium powder, and grinding the mixed material for 10-20 minutes.

[0019] Preferably, in the preparation method of the graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material of the present invention, step three involves carrying out a selenization reaction of the ground product in a protective gas environment, including: placing the ground product in an argon environment with an argon flow rate of 20 mL / min, heating it to 400-550°C at a heating rate of 2-5°C / min, and holding it at that temperature for 2-3 hours.

[0020] According to another aspect of the present invention, the present invention provides a hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material, which is prepared according to the above method.

[0021] According to another aspect of the present invention, the present invention provides an application of a graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material as a negative electrode material for sodium-ion batteries.

[0022] The present invention relates to a method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials, as well as the materials and applications thereof, which have the following beneficial effects:

[0023] 1. This invention utilizes a hydrothermal method to first prepare basic nickel carbonate nanowire spheres, which are then converted into Ni-MOF layered nanosheets by taking advantage of their large specific surface area. The nanosheets are stacked together to enhance structural stability. At the same time, the introduction of nitrogen can create more active sites and adsorb more sodium ions, thereby improving the sodium storage capacity of the electrode material.

[0024] 2. The hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared by this invention, when applied to sodium-ion battery anode materials, can shorten the sodium ion transport path, alleviate the volume expansion during sodium ion insertion / extraction, and significantly improve electronic conductivity and sodium ion adsorption energy. When used as a sodium-ion battery anode material in the charge / discharge process, it has good structural stability, high capacity, high rate capability, and high cycle stability, ultimately improving battery performance.

[0025] 3. The graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material of the present invention has the characteristics of strong controllability, green environmental protection, simple process, high efficiency and low cost. It can be applied in the manufacturing industry of sodium-ion battery energy storage devices, which is conducive to large-scale industrial production. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The image shown is a FESEM image of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 1 of this invention.

[0028] Figure 2 The image shown is a FESEM image of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 2 of this invention.

[0029] Figure 3 This is a FESEM image of the basic nickel carbonate nanowire spheres prepared in Example 3 of the present invention;

[0030] Figure 4 This is a FESEM image of the Ni-MOF layered nanosheets prepared in Example 3 of this invention;

[0031] Figure 5 The image shown is a FESEM image of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 3 of this invention.

[0032] Figure 6 The image shown is a FESEM image of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 4 of this invention.

[0033] Figure 7 The XRD patterns are of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3 and 4 of this invention.

[0034] Figure 8 Electrochemical rate performance diagrams of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3 and 4 of this invention;

[0035] Figure 9 The hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 3 of this invention was tested at 50 mAg. -1The first five charge-discharge curves under the current density. Detailed Implementation

[0036] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0037] It should be noted that, in the absence of conflict, the following embodiments and features can be combined with each other; and, based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0038] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0039] Example 1

[0040] Preparation of hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials:

[0041] Step 1: Preparation of basic nickel carbonate nanowire spheres

[0042] A basic nickel carbonate precursor solution was prepared by using 5 mmol nickel nitrate hexahydrate, 25 mmol urea and 50 ml deionized water according to the specified ratio. The prepared basic nickel carbonate precursor solution was placed in a reaction vessel with a polytetrafluoroethylene liner for hydrothermal reaction at a temperature of 105℃ for 12 h to obtain the hydrothermal reaction product. The hydrothermal reaction product was then washed with deionized water and anhydrous ethanol after cooling to room temperature. The washed product was dried at 80℃ for 10 h to obtain basic nickel carbonate nanowire spheres.

[0043] Step 2: Preparation of Ni-MOF layered nanosheets

[0044] A 3 mol / L 2-methylimidazole solution was prepared. 40 mg of basic nickel carbonate nanowires were placed in 3 ml of the prepared 2-methylimidazole solution and ultrasonically dispersed. The mixture was aged at room temperature for 72 h. The aged product was then washed with deionized water and anhydrous ethanol in sequence. The washed product was dried at 80 °C for 10 h to obtain Ni-MOF layered nanosheets.

[0045] Step 3: Preparation of hierarchical hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material

[0046] One part by weight of Ni-MOF layered nanosheets was mixed with 0.5 parts by weight of selenium powder. The mixture was ground for 15 min. The ground product was placed in a ceramic boat in a tube furnace. The furnace was heated to 450°C at a heating rate of 4°C / min in an argon atmosphere with a flow rate of 20 mL / min and held for 2 h. The selenization product was then cooled to room temperature to prepare fractionated hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material.

[0047] Example 2

[0048] Preparation of hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials:

[0049] Step 1: Preparation of basic nickel carbonate nanowire spheres

[0050] A basic nickel carbonate precursor solution was prepared by using 5 mmol nickel nitrate hexahydrate, 25 mmol urea and 50 ml deionized water according to the specified ratio. The prepared basic nickel carbonate precursor solution was placed in a reaction vessel with a polytetrafluoroethylene liner for hydrothermal reaction at a temperature of 135℃ for 10 h to obtain the hydrothermal reaction product. The hydrothermal reaction product was then washed with deionized water and anhydrous ethanol after cooling to room temperature. The washed product was dried at 80℃ for 10 h to obtain basic nickel carbonate nanowire spheres.

[0051] Step 2: Preparation of Ni-MOF layered nanosheets

[0052] A 7 mol / L 2-methylimidazole solution was prepared. 40 mg of basic nickel carbonate nanowires were placed in 3 ml of the prepared 2-methylimidazole solution and ultrasonically dispersed. The mixture was aged at room temperature for 24 h. The aged product was then washed with deionized water and anhydrous ethanol in sequence. The washed product was dried at 80 °C for 10 h to obtain Ni-MOF layered nanosheets.

[0053] Step 3: Preparation of hierarchical hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material

[0054] One part by weight of Ni-MOF layered nanosheets was mixed with one part by weight of selenium powder. The mixture was ground for 20 min. The ground product was placed in a ceramic boat in a tube furnace. The furnace was heated to 500°C at a heating rate of 5°C / min in an argon atmosphere with a flow rate of 20 mL / min. The temperature was held for 2 h. The selenization product was cooled to room temperature to prepare fractionated hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material.

[0055] Example 3

[0056] Preparation of hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials:

[0057] Step 1: Preparation of basic nickel carbonate nanowire spheres

[0058] A basic nickel carbonate precursor solution was prepared by using 5 mmol nickel nitrate hexahydrate, 25 mmol urea and 50 ml deionized water according to the specified ratio. The prepared basic nickel carbonate precursor solution was placed in a reaction vessel with a polytetrafluoroethylene liner for hydrothermal reaction at a temperature of 120°C for 12 h to obtain the hydrothermal reaction product. The hydrothermal reaction product was then washed with deionized water and anhydrous ethanol after cooling to room temperature. The washed product was dried at 80°C for 10 h to obtain basic nickel carbonate nanowire spheres.

[0059] Step 2: Preparation of Ni-MOF layered nanosheets

[0060] A 5 mol / L 2-methylimidazole solution was prepared. 40 mg of basic nickel carbonate nanowires were placed in 3 ml of the prepared 2-methylimidazole solution and ultrasonically dispersed. The mixture was aged at room temperature for 12 h. The aged product was then washed with deionized water and anhydrous ethanol in sequence. The washed product was dried at 80 °C for 10 h to obtain Ni-MOF layered nanosheets.

[0061] Step 3: Preparation of hierarchical hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material

[0062] One part by weight of Ni-MOF layered nanosheets was mixed with two parts by weight of selenium powder. The mixture was ground for 10 min. The ground product was placed in a ceramic boat in a tube furnace. The furnace was heated to 550°C at a heating rate of 2°C / min in an argon atmosphere with a flow rate of 20 mL / min. The temperature was held for 2 h. The selenization product was cooled to room temperature to prepare fractionated hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material.

[0063] Example 4

[0064] Preparation of hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials:

[0065] Step 1: Preparation of basic nickel carbonate nanowire spheres

[0066] A basic nickel carbonate precursor solution was prepared by using 5 mmol nickel nitrate hexahydrate, 25 mmol urea and 50 ml deionized water according to the specified ratio. The prepared basic nickel carbonate precursor solution was placed in a reaction vessel with a polytetrafluoroethylene liner for hydrothermal reaction at a temperature of 130℃ for 11 h to obtain the hydrothermal reaction product. The hydrothermal reaction product was then washed with deionized water and anhydrous ethanol after cooling to room temperature. The washed product was dried at 80℃ for 10 h to obtain basic nickel carbonate nanowire spheres.

[0067] Step 2: Preparation of Ni-MOF layered nanosheets

[0068] A 5 mol / L 2-methylimidazole solution was prepared. 40 mg of basic nickel carbonate nanowires were placed in 3 ml of the prepared 2-methylimidazole solution and ultrasonically dispersed. The mixture was aged at room temperature for 48 h. The aged product was then washed with deionized water and anhydrous ethanol in sequence. The washed product was dried at 80 °C for 10 h to obtain Ni-MOF layered nanosheets.

[0069] Step 3: Preparation of hierarchical hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material

[0070] One part by weight of Ni-MOF layered nanosheets was mixed with 1.5 parts by weight of selenium powder. The mixture was ground for 10 min. The ground product was placed in a ceramic boat in a tube furnace. The furnace was heated to 400°C at a heating rate of 3°C / min in an argon atmosphere with a flow rate of 20 mL / min and held for 3 h. The selenization product was then cooled to room temperature to prepare fractionated hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material.

[0071] Example 5

[0072] The microstructure of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3, and 4, as well as the basic nickel carbonate nanowires and Ni-MOF layered nanosheets prepared in Example 3, was observed using a thermal field emission scanning electron microscope (FESEM) manufactured by Zeiss AG, Germany. The experimental procedure and parameters included: taking a small amount of powder material samples prepared in each example, attaching the samples to the sample stage with conductive adhesive, and observing them with the instrument. The accelerating voltage was 5 kV.

[0073] The microstructure of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 1 is shown in [reference needed]. Figure 1 The magnification is 50,000 times; the microstructure of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 2 is shown in [reference needed]. Figure 2The magnification is 50,000 times; the microstructure of the basic nickel carbonate nanowire spheres prepared in Example 3 is shown in [reference needed]. Figure 3 The magnification is 50,000 times; the microstructure of the Ni-MOF layered nanosheets prepared in Example 3 is shown in [reference needed]. Figure 4 The magnification is 50,000 times; the microstructure of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 3 is shown in [reference needed]. Figure 5 The magnification is 50,000 times; the microstructure of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 4 is shown in [reference needed]. Figure 6 The magnification is 50,000 times.

[0074] Figure 1 The image shown is a FESEM image of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 1 of this invention. Figure 1 As shown, the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material is composed of nickel selenide nanoparticles and nitrogen-doped porous carbon with a diameter of 1-2 μm. After the selenization reaction, the surface is relatively rough and has a large specific surface area, which increases the number of active sites, which is conducive to the adsorption of sodium ions and helps to improve the capacity of sodium-ion batteries.

[0075] Figure 2 The image shown is a FESEM image of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 2 of this invention. Figure 2 As shown, with the increase of selenium powder ratio, the number of nickel selenide nanoparticles on the nitrogen-doped carbon framework increases, which is beneficial to further improve the capacity of sodium-ion batteries.

[0076] Figure 3 The image shown is a FESEM image of the basic nickel carbonate nanowire spheres prepared in Example 3 of this invention. Figure 3 As shown, the basic nickel carbonate prepared in Example 3 is composed of nanowire spheres. The nanowire spheres are bonded together and support each other, which enhances the structural stability during the electrochemical reaction process and avoids the structural collapse caused by sodium ions during insertion and extraction.

[0077] Figure 4 The image shown is a FESEM image of the Ni-MOF layered nanosheets prepared in Example 3 of this invention. Figure 4 As shown, after aging in 2-methylimidazole solution, basic nickel carbonate nanowires are transformed into Ni-MOF layered nanosheets. The nanosheets have many pores, which facilitates the penetration of sodium-ion battery electrolyte, thereby better contacting the negative electrode material, shortening the ion transport path and accelerating the electrochemical reaction rate.

[0078] Figure 5 The image shown is a FESEM image of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 3 of this invention. Figure 5 As shown, by adjusting the concentration of the 2-methylimidazole solution, the selenized hierarchical hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material have a suitable specific surface area and uniform morphology, which is beneficial to the rapid insertion and extraction of sodium ions. According to the Kirkendall effect, relative motion occurs in the Ni cation. 2+ and anion Se 2- Triggered between them, both actively move towards the boundary, further forming nickel selenide grains. With the assistance of high temperature, the particles connect with each other to form a shell. The shell is attached to the interior of nitrogen-doped carbon obtained by 2-methylimidazolium carbide. These advantages help to alleviate the volume expansion during the sodium ion insertion and extraction process, trigger more redox reactions, and make the ion shuttle speed faster.

[0079] Figure 6 The image shown is a FESEM image of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 4 of this invention. Figure 6 As shown, with the increase of heat preservation time, the large internal cavity originating from the Kirkendall effect can be seen more intuitively, thus forming more hierarchical hollow structures, which helps to alleviate the volume expansion caused by electrochemical charging and discharging.

[0080] Example 6

[0081] The phase composition of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3, and 4 was analyzed using an XRD-6000 (3KW) XRD instrument manufactured by Shimadzu Corporation, Japan. The experimental procedure and parameter settings included: placing the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in each example into a glass slide groove (2.0*2.0cm), ensuring the groove was just filled, and then placing it in the XRD instrument. The X-ray source was Cu target Kα rays (λ=0.15418nm), the scanning range was 10-80°, the scanning rate was 4° / min, the tube voltage was 40kV, and the tube current was 30mA. The test results are shown in [reference needed]. Figure 7 .

[0082] Figure 7 The XRD patterns of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3, and 4 of this invention are shown below. Figure 7 As shown, the XRD patterns of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3 and 4 correspond to the standard PDF card NiSe2-JCPDS#88-1711, indicating that NiSe2 was successfully prepared.

[0083] Example 7

[0084] The graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3, and 4 were mixed with conductive agent Super P and polyvinylidene fluoride in a mass ratio of 8:1:1 and stirred evenly to obtain a mixed product. Then, N-methylpyrrolidone was added to the mixed product as a solvent and stirred evenly to obtain a slurry with suitable viscosity. Finally, the slurry was coated onto a copper foil with a thickness of 9 μm using an SZQ type four-sided preparation tool (150 μm thickness) produced by Tianjin Jinghai District Kexin Testing Machine Factory. The coated copper foil was then vacuum dried at 80°C for 12 h to obtain the electrode sheet made of the graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3, and 4.

[0085] The graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite electrode sheets prepared in Examples 1, 2, 3, and 4 were cut into sheets using a tablet press manufactured by Shenzhen Kejing Materials Technology Co., Ltd. The experimental process and parameters included: cutting the materials prepared in each example into 12mm diameter circular sheets as electrode materials; using a CR2025 battery casing and 1M NaCF3SO3 in… Diglyme (100%) electrolyte, glass fiber separator, and sodium metal sheet were placed together in a glove box with a water and oxygen content of less than 0.1 ppm. The electrode material was placed in the center of the positive electrode shell, and two drops of electrolyte were added to fully wet the electrode material. Then, the glass fiber separator was covered onto the electrode sheet with tweezers. The sodium metal sheet, gasket, spring sheet, and negative electrode shell were then placed in sequence. Finally, the battery was sealed using a battery sealing machine of model PX-HS-20 produced by Shenzhen Kejing Materials Technology Co., Ltd., to obtain a sodium-ion battery composed of graded hollow microspherical nickel selenide / nitrogen-doped porous carbon composite material prepared in Examples 1, 2, 3, and 4 as the negative electrode material.

[0086] Example 8

[0087] Electrochemical tests were conducted on sodium-ion batteries assembled from hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3, and 4 using a CT3002A Blue Electric Battery Testing System manufactured by Wuhan Blue Electric Electronics Co., Ltd. The experimental procedures and parameters included: current densities of 0.05 A g / g. -1 0.1Ag -1 0.2Ag -1 0.5Ag -1 1.0Ag -1 2.0Ag -1 5.0Ag -1 and 10.0Ag-1 The electrochemical performance of each embodiment was reflected by constant current charge-discharge testing.

[0088] Figure 8 The electrochemical rate performance diagrams are shown for the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3, and 4 of this invention. Figure 8 As shown, the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1, 2, 3 and 4 have good sodium storage performance, and the charge and discharge capacity overlap is high under different current densities, with the efficiency maintained at around 100%.

[0089] Figure 9 The sodium-ion battery assembled from the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared in Example 3 of this invention achieved a performance of 50 mAg. -1 The first five charge-discharge curves under current density, with the first charge cycle showing a capacity of 603.69 mAh / g. -1 The discharge capacity is 623.27 mAh g. -1 The efficiency in the first lap was as high as 96.86%.

[0090] Sodium-ion batteries assembled using the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1 to 4 achieved a performance of 50 mA g. -1 The first charge-discharge capacity and first coulombic efficiency under current density are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] As can be seen from Table 1, the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials prepared in Examples 1-4 of this invention exhibit excellent electrochemical performance when used as anode materials for sodium-ion batteries. Among them, the anode material prepared in Example 3 shows particularly good performance at 50 mAg. -1 The initial charge-discharge specific capacity under current density testing was 603.69 / 623.27 mAh g. -1 The initial coulombic efficiency reached 96.86%, and the remaining embodiments all had high charge-discharge specific capacity, with initial coulombic efficiencies all above 90%.

[0095] The present invention relates to a method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite materials, as well as the materials and applications thereof, which have the following beneficial effects:

[0096] 1. This invention utilizes a hydrothermal method to first prepare basic nickel carbonate nanowire spheres, which are then converted into Ni-MOF layered nanosheets by taking advantage of their large specific surface area. The nanosheets are stacked together to enhance structural stability. At the same time, the introduction of nitrogen can create more active sites and adsorb more sodium ions, thereby improving the sodium storage capacity of the electrode material.

[0097] 2. The hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material prepared by this invention, when applied to sodium-ion battery anode materials, can shorten the sodium ion transport path, alleviate the volume expansion during sodium ion insertion / extraction, and significantly improve electronic conductivity and sodium ion adsorption energy. When used as a sodium-ion battery anode material in the charge / discharge process, it has good structural stability, high capacity, high rate capability, and high cycle stability, ultimately improving battery performance.

[0098] 3. The graded hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material of the present invention has the characteristics of strong controllability, green environmental protection, simple process, high efficiency and low cost. It can be applied in the manufacturing industry of sodium-ion battery energy storage devices, which is conducive to large-scale industrial production.

[0099] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material, characterized in that, The method includes: Step 1: Preparation of basic nickel carbonate nanowire spheres A basic nickel carbonate precursor solution was prepared by using nickel nitrate hexahydrate, urea, and deionized water in a specified ratio. The prepared basic nickel carbonate precursor solution was placed in a reaction vessel for hydrothermal reaction to obtain hydrothermal reaction product. The hydrothermal reaction product was then washed and dried to obtain basic nickel carbonate nanowire spheres. Step 2: Preparation of Ni-MOF layered nanosheets A 2-methylimidazole solution was prepared, and basic nickel carbonate nanowires were placed in the prepared 2-methylimidazole solution and ultrasonically dispersed. The mixture was then aged at room temperature. The aged product was washed and dried to obtain Ni-MOF layered nanosheets. Step 3: Preparation of hierarchical hollow microspheres of nickel selenide / nitrogen-doped porous carbon composite material Ni-MOF layered nanosheets and selenium powder were mixed according to the specified ratio and then ground. The ground product was subjected to a selenization reaction in a protective gas environment. The selenization reaction product was cooled to room temperature to prepare a fractionated hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material.

2. The method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material according to claim 1, characterized in that, In step one, a basic nickel carbonate precursor solution is prepared by using nickel nitrate hexahydrate, urea, and deionized water in the specified ratio. This includes preparing the basic nickel carbonate precursor solution by mixing 5 mmol of nickel nitrate hexahydrate with 25 mmol of urea and 50 ml of deionized water.

3. The method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material according to claim 1, characterized in that, In step one, the hydrothermal reaction temperature is 105-135℃, and the hydrothermal reaction time is 10-12h.

4. The method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material according to claim 1, characterized in that, In step one, the hydrothermal reaction product is cleaned and dried to obtain basic nickel carbonate nanowires. This includes: cleaning the hydrothermal reaction product cooled to room temperature with deionized water and anhydrous ethanol in sequence, and drying the cleaned product at 80°C for 10 hours to obtain basic nickel carbonate nanowires.

5. The method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material according to claim 1, characterized in that, In step two, the concentration of the 2-methylimidazole solution is 3-7 mol / L. Each 40 mg of basic nickel carbonate nanowires is placed in 3 ml of the prepared 2-methylimidazole solution and ultrasonically dispersed. The aging time at room temperature is 12-72 h.

6. The method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material according to claim 1, characterized in that, In step two, the aged product is cleaned and dried to obtain Ni-MOF layered nanosheets, including: cleaning the aged product with deionized water and anhydrous ethanol in sequence, and drying the cleaned product at 80°C for 10 hours to obtain Ni-MOF layered nanosheets.

7. The method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material according to claim 1, characterized in that, In step three, Ni-MOF layered nanosheets and selenium powder are mixed according to the formula and then ground, including: mixing 1 part by weight of Ni-MOF layered nanosheets with 0.5-2 parts by weight of selenium powder, and grinding the mixed material for 10-20 minutes.

8. The method for preparing hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material according to claim 1, characterized in that, In step three, the grinding product is subjected to a selenization reaction in a protective gas environment, including: placing the grinding product in an argon environment with an argon flow rate of 20 mL / min, heating it to 400-550℃ at a heating rate of 2-5℃ / min, and holding it at that temperature for 2-3 hours.

9. A hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material, characterized in that, The hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material is prepared by the method according to any one of claims 1 to 8.

10. An application of a hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material, characterized in that, The application of the hierarchical hollow microsphere nickel selenide / nitrogen-doped porous carbon composite material as described in claim 9 as a negative electrode material for sodium-ion batteries.

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