Sulfur and nitrogen co-doped carbon-coated modified Cu 1.96 Preparation method of S / NiS hollow microspheres

Abstract

The application discloses sulfur-nitrogen co-doped carbon-coated modified Cu 1.96 The application discloses a preparation method of S / NiS hollow microspheres. CuNi organic ligand precursors are synthesized by a solvothermal method, then ion exchange is carried out with thioacetamide in an ethanol solvent to obtain CuNi sulfide nanometer microspheres, finally, the target product, sulfur-nitrogen co-doped carbon-coated Cu, is prepared through dopamine polymerization coating and inert atmosphere heat treatment 1.96 The S / NiS hollow microspheres have a size of 400-500 nm, and there is an obvious cavity in the material, so that the volume effect of the material used as a negative electrode of a sodium ion battery can be effectively relieved; the outer double-doped carbon layer not only enhances the conductivity and mechanical strength of the electrode material, but also greatly increases the specific surface area, generates more sodium storage sites, and further improves the electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of double-metal sulfide-based nanomaterials, and particularly relates to a preparation method of double-atom doped carbon-coated modified double-metal sulfide and improvement of electrochemical performance thereof, and is applied to sodium ion battery negative electrode energy storage. BACKGROUND

[0002] Energy is the basis for human survival and development. The centralized consumption of traditional fossil energy has led to an increasing greenhouse effect, and the development of green new energy has become a widely shared international consensus. Among various green energy sources, chemical power sources have shown excellent application prospects due to their independence from seasonal, climatic, temporal and regional conditions; among them, lithium ion batteries, which are compact in structure, high in energy density and long in cycle life, are particularly representative. The successful commercialization of lithium ion batteries has rapidly revolutionized the portable electronic goods market, and is gradually transitioning to large and medium-sized energy storage fields, including electric vehicle power batteries, energy storage power station fixed power sources, etc.; however, the large consumption of lithium resources will inevitably lead to rising costs of lithium sources with low crust abundance and uneven distribution, and it is difficult to sustain large-scale use worldwide. Sodium and lithium are elements in the same main group, and they have similar physical and chemical properties, especially the abundant and widely distributed sodium resources, and the standard hydrogen electrode potential of sodium is about 0.3V higher than that of lithium, indicating that it is safer. Therefore, sodium ion batteries are considered to be the most promising rechargeable secondary batteries after lithium ion batteries.

[0003] In recent years, researchers have conducted extensive and in-depth research on sodium ion battery technology, and the negative electrode material is considered to be one of the key materials for improving the performance of sodium ion batteries, which has three typical reaction mechanisms: a deintercalation / intercalation mechanism, a conversion mechanism and an alloying mechanism. Transition metal sulfide (such as ZnS, NiS, CuS x , CoS x , etc.) negative electrode materials based on the conversion reaction mechanism have the advantages of high theoretical specific capacity and good electrical conductivity, and are a kind of negative electrode material with excellent prospects. However, such conversion reaction materials have a large volume expansion and shrinkage during repeated charge and discharge processes when storing sodium, which causes the material to easily powder and lose electrical contact, resulting in rapid capacity decay and service life deterioration of the battery, which seriously limits the development and application of such materials. Research shows that carbon coating is a common means to improve the volume effect, which can effectively maintain the electrical contact of the material during the cycle process and reduce the surface side reaction, while increasing the specific surface area and electrical conductivity; in addition, heterostructure design is also an effective means to improve the performance of the material. Since the potentials of two different materials for conversion reaction with sodium are different, and metal elements are generated during the sodium storage process, not only the electrical conductivity is enhanced, but also mutual support and mutual buffering effects are achieved during the charge and discharge process, thereby significantly improving the volume effect.

[0004] Accordingly, the prepared sulfur-nitrogen co-doped carbon-coated NiS / Cu 1.96 The S hollow microspheres have significant advantages; the in-situ generated double-doped carbon layer in the composite structure provides more sodium storage sites, while effectively maintaining the structural stability and electrical conductivity of the material, and the hollow heterostructure design can effectively relieve the volume effect; therefore, the composite material has more excellent sodium storage performance and is expected to be applied on a large scale. SUMMARY

[0005] The application aims to provide a novel Cu 1.96 The preparation method of the S / NiS@DC composite material is simple, has strong repeatability, and ingeniously realizes the sulfur-nitrogen co-doped carbon-coated hollow heterostructure double-metal sulfide, which effectively enriches the implementation strategy of heteroatom-doped carbon and the construction measure of hollow double-metal sulfide, and greatly improves the sodium storage performance of the sulfide used as a negative electrode of a sodium ion battery.

[0006] To solve the above technical problems, the technical scheme adopted by the application is as follows:

[0007] A sulfur-nitrogen co-doped carbon-coated Cu 1.96 The S / NiS hollow microsphere negative electrode material is characterized in that a CuNi precursor is synthesized by a liquid phase method, and then the final product is synthesized through ion exchange, polymer coating, high-temperature heat treatment and other processes.

[0008] The liquid phase method for preparing the precursor is a solvothermal method, the ion exchange is a hydrothermal method, the polymer coating is a room temperature co-precipitation method, and the high-temperature heat treatment is a conventional inert atmosphere heat treatment, and the preparation steps are as follows:

[0009] Step 1, dissolve copper salt and nickel salt in a mixed solution of isopropyl alcohol and glycerol, and fully stir to form a uniform transparent solution A;

[0010] Step 2, transfer the solution A mixed system to a high-pressure reaction kettle and seal, react at 160-200 DEG C for 6-12 hours, and after natural cooling, perform solid-liquid separation, ethanol washing and drying to obtain a brick red powder, which is the CuNi precursor;

[0011] Step 3, a certain amount of the precursor powder prepared in step 2 is dispersed in anhydrous ethanol solution, stirred and ultrasonically dispersed uniformly, then TAA is weighed according to a mass ratio of 1:1-1:1.5, and after stirring and dissolving, it is transferred to a high-pressure reaction kettle and reacted at 90-105 DEG C for 6-12 hours. After natural cooling, solid-liquid separation, washing and drying, a black powder is obtained, which is a sulfurized CuNi nanometer microsphere (CuNi-S).

[0012] Step 4, a certain amount of CuNi-S black powder prepared in step 3 is dispersed in 50-100 mL of water, and an equal amount of tris-hydroxymethyl aminomethane and dopamine hydrochloride is added in sequence, and stirred for 8-12 h, then solid-liquid separation, drying, to obtain polydopamine coated CuNi-S powder;

[0013] Step 5, the coated material prepared in step 4 is heat treated at 450-550 DEG C under inert gas for 2-4 h, and the product is collected after natural cooling, which is sulfur and nitrogen co-doped carbon coated Cu 1.96 S / NiS hollow microsphere powder; the inert atmosphere is N2 or Ar gas flow;

[0014] The copper salt is one of copper nitrate and copper acetate; the nickel salt is one of nickel nitrate and nickel acetate; the molar ratio of soluble nickel salt to copper salt is 2:1-1:2, and the volume ratio of isopropyl alcohol to glycerol is 6:1;

[0015] The sulfur and nitrogen co-doped carbon is formed by the synergistic effect of carbonization (nitrogen doping) of polydopamine at high temperature and decomposition (sulfur doping) of copper sulfide at high temperature.

[0016] The sodium ion battery negative material Cu 1.96 Compared with the prior art, the preparation method of the S / NiS@DC has the positive effect that the composite Cu 1.96 S / NiS is essentially the same as Cu2S / NiS, and in the process of preparing the nitrogen-doped coated material, specifically in step 4, it is found that the inner shell copper sulfide is partially decomposed to release sulfur, resulting in sulfur doping into the outer carbon layer, realizing the process of sulfur doping, and further realizing the generation of sulfur and nitrogen co-doped carbon.

[0017] In the technical scheme of the present application, during the coating process (specifically in step 4 of the present application), tris-hydroxymethyl aminomethane and dopamine hydrochloride will undergo polymerization to form polydopamine, and the polydopamine will be heat treated under inert atmosphere to form nitrogen-doped carbon. One of tris-hydroxymethyl aminomethane and dopamine hydrochloride cannot undergo polymerization to form polydopamine.

[0018] The size of the internal cavity of the material, the thickness of the carbon layer and the proportion of metal elements are highly controllable and adjustable by using the technical scheme of the present application; the material has a obvious internal cavity, which can effectively relieve the volume effect of the material as a sodium ion battery negative electrode, and the two sulfides in the heterostructure play the roles of mutual support and mutual buffering; in particular, the present application ingeniously realizes the co-doping of sulfur and nitrogen atoms in the outer carbon shell, which greatly improves the conductivity and specific surface area of the material, and constructs more sodium storage sites.

[0019] Therefore, the composite material is significantly improved in sodium storage performance as a negative electrode of a sodium ion battery, and provides a new solution for development and application of metal sulfide negative electrode materials of the sodium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Cu prepared in Example 1 1.96 X-ray diffraction (XRD) spectrum of the S / NiS@DC powder.

[0021] Figure 2 Cu prepared in Example 1 1.96 XPS spectrum of the C element of the S / NiS@DC powder.

[0022] Figure 3 Cu prepared in Example 1 1.96 Scanning electron microscope (SEM) image of the S / NiS@DC powder.

[0023] Figure 4 Cu prepared in Example 1 1.96 Transmission electron microscope (TEM) image of the S / NiS@DC powder, A and B are TEM images at different magnifications.

[0024] Figure 5 Cu prepared in Example 1 1.96 Cyclic voltammetry and charge-discharge curve of the S / NiS@DC powder as a negative electrode of a sodium ion battery, A is a cyclic voltammetry graph, and B is a charge-discharge curve graph.

[0025] Figure 6 Cu prepared in Example 1 1.96 Rate performance graph of the S / NiS@DC powder as a negative electrode of a sodium ion battery.

[0026] Figure 7 Cu prepared in Example 2 1.96 Scanning electron microscope (SEM) image of the S / NiS@DC powder, A and B are TEM images at different magnifications.

[0027] Figure 8 Cu prepared in Example 3 1.96 Scanning electron microscope (SEM) image of the S / NiS@DC powder, A and B are TEM images at different magnifications.

[0028] Figure 9 Cu prepared in Example 4 1.96 Rate performance graph of the S / NiS powder as a negative electrode of a sodium ion battery.

[0029] Figure 10 Cu prepared in Example 51.96 Transmission electron microscope (TEM) and high-resolution transmission electron microscope (HR-TEM) images of S / NiS powder.

[0030] Figure 11 Cu prepared in Example 5 without carbon coating 1.96 Rate performance graph of S / NiS powder used as a negative electrode of a sodium ion battery.

[0031] Figure 12 Cu prepared in Example 6 with reversed metal molar ratio 1.96 Cyclic voltammetry and rate performance graph of S / NiS@DC material used as a negative electrode of a sodium ion battery, A is a cyclic voltammetry graph, and B is a charge-discharge curve graph. DETAILED DESCRIPTION

[0032] The following examples facilitate a better understanding of the present application, but do not limit the present application. In the following examples, the experimental methods are conventional methods unless otherwise specified. The test materials used in the following examples are commercially available or self-made, and are commercially purchased unless otherwise specified.

[0033] Example 1

[0034] Step 1, 1.0 mmol Cu(CH3COO)2·H2O and 0.5 mmol Ni(CH3COO)2·4H2O were dissolved in 120 mL of isopropyl alcohol and 20 mL of glycerol mixed organic solvent, and a uniform transparent solution A was formed under constant stirring at room temperature;

[0035] Step 2, the mixed system of solution A was transferred to a high-pressure reaction kettle and sealed, and reacted at 160°C for 12 h. After natural cooling, solid-liquid separation, ethanol washing and drying, a brick red powder was obtained, which was CuNi organic precursor;

[0036] Step 3, a certain amount of the precursor powder prepared in step 2 was dispersed in anhydrous ethanol solution, and stirred and ultrasonically dispersed uniformly. Then, TAA was weighed according to a mass ratio of 1:1.5, and after stirring and dissolving, it was transferred to a high-pressure reaction kettle and reacted at 90°C for 12 h. After natural cooling, solid-liquid separation, washing and drying, a black powder was obtained, which was CuNi-S powder.

[0037] Step 4, 200 mg of the CuNi-S black powder prepared in step 3 was dispersed in 100 mL of water, and 100 mg of tris-hydroxymethyl aminomethane and 100 mg of dopamine hydrochloride were added in sequence. After constant stirring at room temperature for 10 h, solid-liquid separation and drying, a polydopamine coated CuNi-S powder was obtained.

[0038] Step 5, the CuNi-S@PDA powder prepared in step 4 was heat-treated at 550°C for 2h under N2 in a tube furnace, and the polydopamine was carbonized. After natural cooling, the product was collected, and Cu 1.96 S / NiS@DC black powder;

[0039] Figure 1 Cu1.96S / NiS@DC composite material prepared in this embodiment 1.96 XRD pattern of the Cu1.96S / NiS@DC bimetallic sulfide composite material. The phase diffraction peak is relatively sharp and consistent with the standard card, and there is no obvious impurity diffraction peak, indicating that the prepared material has high purity and crystallinity, and no carbon peak is detected, indicating that it exists in amorphous form.

[0040] Figure 2 Cu1.96S / NiS@DC powder prepared in this embodiment 1.96 XPS spectrum of C element of the Cu1.96S / NiS@DC powder. The carbon-sulfur bond and carbon-nitrogen bond in the figure can effectively confirm that the sulfur and nitrogen atoms successfully doped into the carbon.

[0041] Figure 3 Cu1.96S / NiS@DC powder prepared in this embodiment 1.96 SEM image of the Cu1.96S / NiS@DC composite material. The powder is uniform in size secondary sub-microspheres (about 500nm), and there are obvious small particles on the rough surface, which is the material formed by the thermal decomposition of copper sulfide at high temperature.

[0042] Figure 4 Cu1.96S / NiS@DC powder prepared in this embodiment 1.96 TEM image of the Cu1.96S / NiS@DC composite material. The microspheres have obvious cavities inside, and the decomposed copper sulfide material can be clearly seen in the outer carbon layer.

[0043] Figure 5 Cu1.96S / NiS@DC powder prepared in this embodiment 1.96 Cyclic voltammogram and charge-discharge curve of the Cu1.96S / NiS@DC composite material used as a negative electrode of a sodium ion battery. The oxidation-reduction peak is relatively obvious at a scan rate of 0.2mV / s, and the coincidence is good except for the first cycle. The initial discharge specific capacity of the material is about 730mAh / g at a current density of 0.2A / g, and the stable reversible capacity is about 520mAh / g.

[0044] Figure 6 Rate cycle performance of the Cu1.96S / NiS@DC composite material prepared in this embodiment used as a negative electrode of a sodium ion battery. The novel nitrogen and sulfur double-doped carbon-coated bimetallic sulfide negative electrode material has relatively excellent rate cycle performance.

[0045] Example 2

[0046] Step 1, 2.0 mmol Cu(CH3COO)2·H2O and 1.0 mmol Ni(CH3COO)2·4H2O were dissolved in 180 mL of isopropyl alcohol and 30 mL of glycerol mixed organic solvent, and a uniform transparent solution A was formed under stirring at room temperature;

[0047] Step 2, the solution A mixed system was transferred to a high-pressure reaction kettle and sealed, and reacted at 180℃ for 8h. After natural cooling, solid-liquid separation, ethanol washing and drying, a brick red powder was obtained, which was the CuNi organic precursor;

[0048] Step 3, a certain amount of the precursor powder prepared in step 2 was dispersed in anhydrous ethanol solution, and stirred and ultrasonically dispersed uniformly. Then, TAA was weighed according to the mass ratio of 1:1.5, and after stirring and dissolving, it was transferred to a high-pressure reaction kettle and reacted at 100℃ for 8h. After natural cooling, solid-liquid separation, washing and drying, a black powder was obtained, which was the CuNi-S powder.

[0049] Step 4, 200mg of the CuNi-S black powder prepared in step 3 was dispersed in 100mL of water, and 100mg of tris-hydroxymethyl aminomethane and 100mg of dopamine hydrochloride were added in sequence, and stirred at room temperature for 10h. Then, solid-liquid separation and drying were performed to obtain the polydopamine coated CuNi-S powder;

[0050] Step 5, the CuNi-S@PDA powder prepared in step 4 was heat-treated at 500℃ for 3h under Ar gas in a tube furnace to carbonize the polydopamine, and the product was collected after natural cooling to obtain the Cu 1.96 S / NiS@DC black powder;

[0051] Figure 7 The SEM image of the prepared Cu 1.96 S / NiS@DC composite material showed that the size of the nanometer microspheres was also about 500nm, and rough small particles could also be seen on the surface, and the morphology characteristics were almost the same as those of Example 1.

[0052] Example 3

[0053] Step 1, 2.0 mmol Cu(CH3COO)2·H2O and 1.0 mmol Ni(CH3COO)2·4H2O were dissolved in 180 mL of isopropyl alcohol and 30 mL of glycerol mixed organic solvent, and a uniform transparent solution A was formed under stirring at room temperature;

[0054] Step 2, the solution A mixed system was transferred to a high-pressure reaction kettle and sealed, and reacted at 180℃ for 8h. After natural cooling, solid-liquid separation, ethanol washing and drying, a brick red powder was obtained, which was the CuNi organic precursor;

[0055] Step 3, take a certain amount of precursor powder prepared in step 2 and disperse it in anhydrous ethanol solution, stir and ultrasonically disperse it uniformly, then weigh TAA according to a mass ratio of 1:1.5, stir and dissolve it, then transfer it to a high-pressure reaction kettle and react at 105°C for 4h. After natural cooling, solid-liquid separation, washing and drying, a black powder is obtained, which is CuNi-S powder.

[0056] Step 4, take 200mg of CuNi-S black powder prepared in step 3 and disperse it in 100mL of water, then add 100mg of tris-hydroxymethyl aminomethane and 100mg of dopamine hydrochloride in sequence, fully stir and react at room temperature for 10h, then perform solid-liquid separation and drying to obtain polydopamine-coated CuNi-S powder;

[0057] Step 5, take CuNi-S@PDA powder prepared in step 4, perform heat treatment at 550°C for 4h under N2 in a tube furnace, carbonize the polydopamine, and after natural cooling, collect the product to obtain Cu 1.96 S / NiS@DC black powder;

[0058] Figure 8 The SEM image of the prepared Cu 1.96 S / NiS@DC composite material is shown in FIG. 6, and the size of the nanometer microspheres is also about 500nm, and the surface can also be seen to be rough and small particles, and the morphology characteristics are almost the same as those of Example 1.

[0059] Example 4

[0060] Step 1, dissolve 1.0mmol of Cu(CH3COO)2·H2O and 0.5mmol of Ni(CH3COO)2·4H2O in 120mL of isopropyl alcohol and 20mL of glycerol mixed organic solvent, fully stir to form a uniform transparent solution A at room temperature;

[0061] Step 2, transfer the mixed system of solution A to a high-pressure reaction kettle and seal, react at 160°C for 12h, after natural cooling, perform solid-liquid separation, ethanol washing and drying to obtain a brick red powder, which is CuNi organic precursor;

[0062] Step 3, take a certain amount of precursor powder prepared in step 2 and disperse it in anhydrous ethanol solution, stir and ultrasonically disperse it uniformly, then weigh TAA according to a mass ratio of 1:1.5, stir and dissolve it, then transfer it to a high-pressure reaction kettle and react at 90°C for 12h. After natural cooling, solid-liquid separation, washing and drying, a black powder is obtained, which is CuNi-S powder.

[0063] Step 4, take CuNi-S powder prepared in step 3, perform heat treatment at 550°C for 2h under N2 in a tube furnace, enhance the crystallinity of the powder, and after natural cooling, collect the product to obtain Cu 1.96S / NiS black powder;

[0064] Figure 9 CuNi-S powder prepared without carbon coating 1.96 The rate cycling performance of the S / NiS mixed sulfide material used as a negative electrode of a sodium ion battery is compared with that of the Cu Figure 6 CuNi-S powder prepared without carbon coating 1.96 The advantages of the S / NiS@DC electrode material.

[0065] Example 5

[0066] The raw materials are metered and scaled up, and the equipment is also an equipment that can be commonly purchased in the art and is suitable for the reaction conditions.

[0067] Step 1: 20 mol of Cu(CH3COO)2·H2O and 10 mol of Ni(CH3COO)2·4H2O were dissolved in 1.8 L of isopropanol and 0.3 L of glycerol mixed organic solvent, and a uniform transparent solution A was formed under stirring at room temperature;

[0068] Step 2: The solution A mixed system was transferred to a high-pressure reaction kettle and sealed, and reacted at 200°C for 4 h. After natural cooling, solid-liquid separation, ethanol washing and drying, a brick red powder was obtained, which was the CuNi organic precursor;

[0069] Step 3: A certain amount of the precursor powder prepared in step 2 was dispersed in anhydrous ethanol solution, and stirred and ultrasonically dispersed uniformly. Then TAA was weighed according to a mass ratio of 1:1.5, and after stirring and dissolving, it was transferred to a high-pressure reaction kettle and reacted at 90°C for 4 h. After natural cooling, solid-liquid separation, washing and drying, a black powder was obtained, which was the CuNi-S powder.

[0070] Step 4: The CuNi-S powder prepared in step 3 was heat-treated at 550°C for 2 h under Ar gas in a tube furnace to enhance the crystallinity of the powder. After natural cooling, the product was collected, and the Cu 1.96 S / NiS black powder.

[0071] Figure 10 CuNi-S powder prepared without carbon coating 1.96 The TEM image of the S / NiS mixed sulfide material is a secondary sub-microsphere composed of primary nanoparticles, and the microsphere has obvious cavities inside. The crystal lattice fringes of the two materials are clearly visible, proving the unique heterostructure.

[0072] Figure 11 CuNi-S powder prepared without carbon coating 1.96 The rate cycling performance of the S / NiS mixed sulfide material used as a negative electrode of a sodium ion battery is compared with that of the Cu Figure 6The rate performance comparison in the above table shows that Cu 1.96 The advantages of S / NiS@DC electrode materials.

[0073] Example 6

[0074] Step 1: Dissolve 1.0 mmol Cu(CH3COO)2·H2O and 2.0 mmol Ni(CH3COO)2·4H2O in 180 mL of isopropyl alcohol and 30 mL of glycerol mixed organic solvent, and stir at room temperature to form a uniform transparent solution A;

[0075] Step 2: Transfer the mixed solution A into a high-pressure reaction kettle and seal, and react at 160°C for 12 h. After natural cooling, perform solid-liquid separation, ethanol washing and drying to obtain a brick red powder, which is the CuNi organic precursor;

[0076] Step 3: Take a certain amount of the precursor powder prepared in step 2 and disperse it in anhydrous ethanol solution, and stir and ultrasonically disperse it uniformly. Then, weigh TAA according to a mass ratio of 1:1.5, and after stirring and dissolving, transfer it into a high-pressure reaction kettle and react at 90°C for 12 h. After natural cooling, perform solid-liquid separation, washing and drying to obtain a black powder, which is the CuNi-S powder.

[0077] Step 4: Take 200 mg of the CuNi-S black powder prepared in step 3 and disperse it in 100 mL of water, and then add 100 mg of tris-hydroxymethyl aminomethane and 100 mg of dopamine hydrochloride, respectively, and stir at room temperature for 10 h. Then, perform solid-liquid separation and drying to obtain the polydopamine-coated CuNi-S powder;

[0078] Step 5: Take the CuNi-S@PDA powder prepared in step 4 and heat treat it at 550°C for 2 h under N2 gas in a tube furnace to carbonize the polydopamine. After natural cooling, collect the product to obtain the Cu1.96S / NiS@DC material with reversed metal molar ratio. 1.96 The S / NiS@DC black powder, although the molar ratio of the two changes, the phase does not change after the preparation process of the present application.

[0079] Figure 12 The cyclic voltammograms and rate performance of the prepared Cu1.96S / NiS@DC material with reversed metal molar ratio as the negative electrode of a sodium ion battery are compared with those of the Cu1.96S / NiS@DC material in Example 1 Figure 5 and 6 It can be found that the Cu1.96S / NiS@DC electrode materials with different metal ratios all have excellent electrochemical performance.

[0080] In the above examples, the preparation of the sodium ion battery electrode pole piece is as follows: the negative electrode active material (nitrogen and sulfur double-doped carbon-coated double-metal sulfide composite material prepared in different schemes), natural carbon black and binder PVDF (polyvinylidene fluoride) are mixed at a specified mass ratio (7:2:1) to prepare a slurry, and after drying and cutting, a sodium ion battery negative electrode test pole piece is obtained.

[0081] Electrochemical performance test: the prepared button cell in the glove box is respectively placed in a blue electric battery test system for testing, the charge and discharge interval is set to 0.01-3V, and the current density is set to 0.1-2.0A / g.

[0082] Through the above examples, the following conclusions can be drawn:

[0083] The application provides a sulfur-nitrogen co-doped carbon-coated Cu 1.96 The preparation method of the S / NiS hollow microspheres is controllable and adjustable in morphology, size and metal sulfide ratio, and there is an obvious cavity in the microspheres, which can effectively relieve the volume effect of the material used as a sodium ion battery negative electrode, and the composite microsphere product exhibits more excellent electrochemical performance than the original unmodified material as a sodium ion battery negative electrode material; in particular, the sulfur-nitrogen double-atom in-situ doped carbon-coated Cu 1.96 The S / NiS hollow microspheres effectively enrich the method of carbon doping and the construction idea of mixed metal sulfide heterojunction, the method is novel and innovative, meanwhile, the preparation method is easy to expand, has good reproducibility and batch stability, effectively promotes the development of high specific capacity sodium ion battery negative electrode materials, and has certain application prospect.

Claims

1. A sulfur-nitrogen co-doped carbon-coated modified Cu 1.96 The method for preparing S / NiS hollow microspheres is characterized by, The preparation steps are as follows: Step 1: Dissolve copper salt and nickel salt in a mixed solution of isopropanol and glycerol, and stir thoroughly to form a homogeneous solution A. The volume ratio of isopropanol to glycerol is 5-10:

1. Step 2: Solution A is subjected to a hydrothermal reaction to obtain CuNi precursor powder. The hydrothermal reaction temperature is 160℃~200℃, and the reaction time is 6~12h. Step 3: Disperse the CuNi precursor powder from Step 2 in anhydrous ethanol solution, add TAA, and then perform a hydrothermal reaction again to obtain sulfide CuNi nanospheres, abbreviated as CuNi-S; the hydrothermal reaction temperature is 90℃~105℃, and the reaction time is 6~12h. Step 4: Disperse the CuNi-S obtained in Step 3 in water, add tris(hydroxymethyl)aminomethane and dopamine hydrochloride in sequence, and react under stirring. After solid-liquid separation and drying, the obtained product is CuNi-S powder coated with polydopamine. Step 5: After heat-treating the polydopamine-coated CuNi-S powder obtained in Step 4 under an inert gas atmosphere, collect the product, which is the sulfur-nitrogen co-doped carbon-coated Cu. 1.96 S / NiS hollow microsphere powder.

2. The sulfur-nitrogen co-doped carbon-coated modified Cu according to claim 1 1.96 The method for preparing S / NiS hollow microspheres is characterized by, The copper salt is one of copper nitrate and copper acetate; the nickel salt is one of nickel nitrate and nickel acetate; the molar ratio of nickel salt to copper salt is 0.5-2:

1.

3. The sulfur-nitrogen co-doped carbon-coated modified Cu according to claim 1 1.96 The method for preparing S / NiS hollow microspheres is characterized by, In step 3, the mass ratio of CuNi precursor powder to TAA is 1:1 to 1:1.

5.

4. The sulfur-nitrogen co-doped carbon-coated modified Cu according to claim 1 1.96 The method for preparing S / NiS hollow microspheres is characterized by, In step 4, the mass ratio of CuNi-S, tris(hydroxymethyl)aminomethane, and dopamine hydrochloride is 2:0.5-1:0.5-1.

5. The sulfur-nitrogen co-doped carbon-coated modified Cu according to claim 1 1.96 The method for preparing S / NiS hollow microspheres is characterized by, In step 5, during the heat treatment process, the inert gas is N2 or Ar gas flow; the heat treatment temperature is 450~550℃, and the heat treatment time is 2~4h.

6. A sulfur-nitrogen co-doped carbon-coated modified Cu 1.96 S / NiS hollow microspheres, characterized in that... Sulfur-nitrogen co-doped carbon-coated modified Cu prepared by the method according to any one of claims 1-5 1.96 S / NiS hollow microspheres.

7. A sulfur-nitrogen co-doped carbon-coated modified Cu according to claim 6 1.96 Application of S / NiS hollow microspheres in the anode of alkali metal secondary batteries.

8. The application according to claim 7, characterized in that, The alkali metal is selected from any one of lithium, sodium, and potassium.

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