A Co3S4 / WS2 composite material, its preparation method and application

Abstract

The present invention relates to the field of new generation energy materials, and provides a Co3S4 / WS2 composite material, a preparation method thereof and an application. In the present invention, cobalt acetate tetrahydrate and deionized water are dispersed in N,N-dimethylformamide to obtain solution A; terephthalic acid, deionized water and triethylamine are dispersed in N,N-dimethylformamide to obtain solution B; the solution A and solution B are mixed and stirred to obtain a reaction product, and the reaction product is centrifuged, washed and dried to obtain a Co-BDC precursor, etc., to obtain a Co3S4 / WS2 composite material. In the present invention, WS2 is introduced into Co3S4 to construct a heterostructure to improve the electron mobility of the negative electrode material, thereby enhancing the conductivity and reaction kinetics. The prepared Co3S4 / WS2 negative electrode material has a high specific capacity, good rate performance and cycle stability, and is particularly suitable for manufacturing the negative electrode of a sodium ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of new generation energy materials, and particularly to a Co3S4 / WS2 composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Fossil fuels are the most widely used energy sources in the world today, but their widespread use has also brought problems of resource shortage and environmental deterioration. Therefore, renewable clean energies such as wind energy, tidal energy, and solar energy have been developed, and the instant and discontinuous renewable energies have promoted the rapid development of large-scale energy storage systems. Rechargeable batteries are considered a viable strategy due to their flexibility, high energy conversion efficiency, and simple maintenance. Lithium-ion batteries (LIBs) have occupied an overwhelming dominant position in the power supply markets of advanced consumer electronics and even electric vehicles due to their high energy density, long life, and low maintenance cost. However, the low abundance and uneven distribution of lithium make it difficult to meet the large-scale growing energy demand in the near future.

[0003] Inspired by the similar chemical properties of sodium and lithium, sodium-ion batteries (SIBs) have been widely studied and are considered the most promising commercial alternative power technology to lithium-ion batteries, especially for large-scale energy storage applications of intermittent and renewable energies and smart grids due to the low cost and natural abundance of sodium resources. Considerable efforts have been made in applying the successful experience of LIBs systems to SIBs, especially in electrode materials. Sodium is in the same group as lithium in the periodic table, has similar properties to lithium, a redox potential close to that of lithium, and has a more abundant crustal reserve (Na: 2.8 wt%, Li: 0.0017 wt%). It is worth mentioning that sodium-ion batteries (SIBs) were also studied in the early stage of lithium-ion battery research. However, the larger ionic radius (Na + is 1.02 Å, Li + is 0.76 Å) results in slow reaction kinetics, usually leading to lower capacity, poor rate performance, poor cycle stability, and even complete loss of electrochemical activity, such as graphite carbon, the most commonly used anode material in lithium-ion batteries. Therefore, the development of high-performance SIBs electrode materials is still an urgent need for their practical applications.

[0004] Transition metal sulfides (TMSs) are a class of graphite alternative energy storage materials with great potential application prospects due to their high specific capacitance, good rate performance, long cycle life, and relatively low production cost. Nevertheless, problems related to voltage hysteresis and volume expansion associated with structural changes still need to be solved. Currently, through strategies such as nanostructure design, composition adjustment, and composite conductive / protective materials, TMSs of iron, cobalt, nickel, molybdenum, copper, etc. are being studied to improve the sodium storage performance.

[0005] Metal-Organic Frameworks (MOFs) and their derived nanomaterials, as a class of porous materials with special properties, have received extensive attention due to their high porosity, large specific surface area, unique morphology, and adjustable chemical composition. In addition, the preparation of highly controllable carbon nanostructure materials using MOFs as templates has gradually become a research hotspot in recent years. The derived cobalt-based sulfide nanomaterials have been widely studied as anode materials for sodium-ion batteries due to their relatively high theoretical capacity. However, when applying these materials to the anode of sodium-ion batteries, many challenges still remain, including relatively low electrical conductivity, slow kinetic reaction rate, significant volume expansion, and the shuttle effect of polysulfides. To overcome these problems, researchers usually adopt strategies such as nanosizing, constructing bimetallic heterostructures, and surface coating.

[0006] Compared with single-component metal sulfides, heterostructured multi-component metal sulfides have obvious advantages. For example, heterointerfaces with a large number of lattice mismatches, distortions, and defects can greatly affect the behavior of charge carrier transport. At the same time, different coupled components can greatly promote the interfacial reaction kinetics and accelerate electron / ion transport through the internal electric field on the heterointerfaces. In addition, the synergistic effect of different components will effectively avoid the aggregation of the generated products and relieve the pressure of sodium ions during the insertion / extraction process. Therefore, it is necessary to construct heterostructures to greatly improve the sodium storage electrochemical performance of materials. Summary of the Invention

[0007] To solve the above problems, the present invention provides a Co3S4 / WS2 composite material, its preparation method and application. The preparation method provided by the present invention is simple and convenient to operate and has a low cost; the Co3S4 / WS2 composite material has a low cost and excellent performance; when the Co3S4 / WS2 composite material is used to prepare a sodium-ion battery, it has a high specific capacity, fast charge and discharge speed, and long cycle life.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The present invention provides a preparation method of a Co3S4 / WS2 composite material, comprising the following steps:

[0010] 1) Dissolve cobalt acetate tetrahydrate and deionized water in N,N-dimethylformamide to obtain solution A;

[0011] Dissolve terephthalic acid, deionized water, and triethylamine in N,N-dimethylformamide to obtain solution B;

[0012] Mix and stir solution A and solution B to obtain a reaction product, and centrifuge, wash, and dry the reaction product to obtain a Co-BDC precursor;

[0013] 2) Carbonize the Co-BDC precursor obtained in step 1) under a nitrogen atmosphere to obtain a Co@C precursor;

[0014] 3) Disperse the Co@C precursor obtained in step 2), sodium tungstate dihydrate, and thioacetamide in deionized water and perform ultrasonic treatment to obtain a mixed solution;

[0015] 4) Perform a hydrothermal reaction on the mixed solution obtained in step 3) to obtain a reaction product, and centrifuge, wash, and dry the reaction product to obtain a Co3S4 / WS2 composite material.

[0016] Preferably, the mass ratio of cobalt acetate tetrahydrate, the volume of deionized water, and the volume of N,N-dimethylformamide in step 1) is 964 mg: 1 - 3 ml: 25 ml;

[0017] The mass ratio of terephthalic acid, the volume of deionized water, the volume of triethylamine, and the volume of N,N-dimethylformamide is 250 mg: 1 - 3 ml: 1 - 3 ml: 20 ml.

[0018] Preferably, the mixing method in step 1) includes stirring, and the stirring time is 1 - 3 h;

[0019] The conditions for centrifugation include: a rotation speed of 8000 rpm and a time of 2 min;

[0020] Wash with absolute ethanol;

[0021] The conditions for drying include: a temperature of 60 °C and a time of 12 h.

[0022] Preferably, the conditions for carbonization treatment in step 2) include: a temperature of 500 - 600 °C and a time of 2 h.

[0023] Preferably, the mass ratio of the Co@C precursor, sodium tungstate dihydrate, thioacetamide, and the volume of deionized water in step 3) is 30 mg: 150 - 180 mg: 150 - 200 mg: 60 ml;

[0024] The time for ultrasonic treatment is 30 min.

[0025] Preferably, the conditions for the hydrothermal reaction in step 4) include: a temperature of 180 - 200 °C and a time of 10 - 20 h.

[0026] Preferably, the conditions for centrifugation in step 4) include: a rotation speed of 8000 rpm and a time of 2 min;

[0027] Wash with absolute ethanol;

[0028] The drying conditions include: a temperature of 60 °C and a time of 12 h.

[0029] The present invention also provides a Co3S4 / WS2 composite material prepared by the preparation method described in the above technical solution.

[0030] The present invention also provides the application of the Co3S4 / WS2 composite material described in the above technical solution in the preparation of the negative electrode of a sodium-ion battery.

[0031] Preferably, the components of the sodium-ion battery include the Co3S4 / WS2 composite material, Ketjen black, and polyvinylidene fluoride;

[0032] The mass ratio of the Co3S4 / WS2 composite material, Ketjen black, and polyvinylidene fluoride is 7:2:1.

[0033] The present invention constructs a Co-based metal-organic nanomaterial, obtains a carbon skeleton with controllable morphology through high-temperature carbonization, and constructs a Co3S4 / WS2 bimetallic heterostructure on the carbon substrate to solve the problems of large volume expansion and poor cycle stability existing in transition metal sulfides, so as to obtain a new negative electrode material for sodium-ion batteries with long cycle life and high specific capacity, providing feasible ideas and methods for exploring new energy storage electrode materials.

[0034] In the present invention, the present invention first selects a bimetallic sulfide derived from the carbonization of Co-BDC as the negative electrode material. This type of material has a high specific capacity, and the derived carbon material has a nanoscale structure, rich heteroatom doping, and ideal conductivity. Among the metal sulfides, transition metal cobalt-based and tungsten-based are selected. Because cobalt trisulfide derived from Co-BDC has a high theoretical capacity, and secondly, a WS2 heterostructure is introduced on Co3S4, thereby reducing the resistance of sodium ions to embed / extract in the positive and negative electrodes, improving the electron mobility of the negative electrode material, and further improving the sodium storage reaction kinetic performance of the obtained sample.

[0035] Advantages of the present invention:

[0036] In the present invention, a WS2 heterostructure is introduced into Co3S4 to improve the electron mobility of the negative electrode material, thereby enhancing the conductivity and reaction kinetics. The prepared Co3S4 / WS2 negative electrode material has a high specific capacity, good rate performance, and cycle stability, and is particularly suitable for manufacturing the negative electrode of a sodium-ion battery. Description of the drawings

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments.

[0038] Figure 1Field emission scanning electron microscopy (SEM) image of the Co-BDC precursor prepared in Example 1;

[0039] Figure 2 Field emission scanning electron microscopy (SEM) image of the Co3S4 / WS2 composite material prepared in Example 1;

[0040] Figure 3 Cycling performance graph of the Co3S4 / WS2 electrode material prepared in Example 1 as the anode material of a sodium-ion battery at a current density of 2 A g -1 for 100 cycles;

[0041] Figure 4 Cycling performance graph of the Co3S4 / WS2 composite material prepared in Example 1 as the anode material of a sodium-ion battery at a current density of 2 A g -1 for 200 cycles. Detailed implementation mode

[0042] The present invention provides a preparation method of a Co3S4 / WS2 composite material, comprising the following steps:

[0043] 1) Dissolve cobalt acetate tetrahydrate and deionized water in N,N-dimethylformamide to obtain solution A;

[0044] Dissolve terephthalic acid, deionized water and triethylamine in N,N-dimethylformamide to obtain solution B;

[0045] Mix and stir solution A and solution B to obtain a reaction product, and centrifuge, wash and dry the reaction product to obtain a Co-BDC precursor;

[0046] 2) Carbonize the Co-BDC precursor obtained in step 1) under a nitrogen atmosphere to obtain a Co@C precursor;

[0047] 3) Disperse the Co@C precursor obtained in step 2), sodium tungstate dihydrate and thioacetamide in deionized water and perform ultrasonic treatment to obtain a mixed solution;

[0048] 4) Perform a hydrothermal reaction on the mixed solution obtained in step 3) to obtain a reaction product, and centrifuge, wash and dry the reaction product to obtain a Co3S4 / WS2 composite material.

[0049] In the present invention, cobalt acetate tetrahydrate and deionized water are dispersed in N,N-dimethylformamide to obtain solution A; terephthalic acid, deionized water and triethylamine are dispersed in N,N-dimethylformamide to obtain solution B; the solution A and solution B are mixed and stirred to obtain a reaction product, and the reaction product is centrifuged, washed and dried to obtain a Co-BDC precursor. In the present invention, the mass ratio of cobalt acetate tetrahydrate to the volume of deionized water and DMF is preferably 964 mg: 1-3 ml: 25 ml, more preferably 964 mg: 3 ml: 25 ml. In the present invention, the mass ratio of terephthalic acid, the volume of deionized water, the volume of triethylamine to the volume of N,N-dimethylformamide is 250 mg: 1-3 ml: 1-3 ml: 20 ml, more preferably 250 mg: 3 ml: 2 ml: 20 ml. In the present invention, the stirring time is preferably 1-3 h. In the present invention, the centrifugation conditions preferably include: a rotation speed of 8000 rpm and a time of 2 min. The present invention preferably uses absolute ethanol for washing. In the present invention, the drying conditions preferably include: a temperature of 60 °C and a time of 12 h.

[0050] In the present invention, the obtained Co-BDC precursor is carbonized under a nitrogen atmosphere to obtain a Co@C precursor. In the present invention, the carbonization conditions preferably include: a temperature of 500-600 °C and a time of 2 h.

[0051] In the present invention, the obtained Co@C precursor, sodium tungstate dihydrate and thioacetamide are dispersed in deionized water and ultrasonicated to obtain a mixed solution. In the present invention, the mass ratio of the Co@C precursor, the mass of sodium tungstate dihydrate, the mass of thioacetamide to the volume of deionized water is preferably 30 mg: 150-180 mg: 150-200 mg: 60 ml, more preferably 30 mg: 165 mg: 150 mg: 60 ml. In the present invention, the ultrasonic time condition is preferably 30 min.

[0052] The mixed solution obtained in the present invention is subjected to a hydrothermal reaction to obtain a reaction product, and the reaction product is centrifuged, washed and dried to obtain a Co3S4 / WS2 composite material. In the present invention, the hydrothermal reaction conditions preferably include: a temperature of 180-200 °C and a time of 10-20 h. In the present invention, the centrifugation conditions preferably include: a rotation speed of 8000 rpm and a time of 2 min. The present invention preferably uses absolute ethanol for washing. In the present invention, the drying conditions preferably include: a temperature of 60 °C and a time of 12 h.

[0053] The present invention also provides a Co3S4 / WS2 composite material prepared by the preparation method described in the above technical solution.

[0054] The present invention also provides an application of the Co3S4 / WS2 composite material described in the above technical solution in the preparation of the negative electrode of a sodium-ion battery. In the present invention, the components of the sodium-ion battery preferably include the Co3S4 / WS2 composite material, Ketjen black, and polyvinylidene fluoride. In the present invention, the mass ratio of the Co3S4 / WS2 composite material, Ketjen black, and polyvinylidene fluoride is preferably 7:2:1. The present invention has no special limitation on the sources of the Ketjen black and polyvinylidene fluoride, and commercially available products for the conventional preparation of sodium-ion batteries can be used.

[0055] To further illustrate the present invention, the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0056] Example 1: A preparation method of a Co3S4 / WS2 composite material, the steps are as follows:

[0057] 1. Dissolve 964 mg of cobalt acetate tetrahydrate and 3 ml of deionized water in 25 ml of N,N-dimethylformamide (abbreviated as DMF) and denote it as solution A; dissolve 250 mg of terephthalic acid, 3 ml of deionized water, and 2 ml of triethylamine in 20 ml of DMF and denote it as solution B; pour solution A into solution B and stir at room temperature for 3 hours to obtain a purple solution. Centrifuge the purple solution at 8000 rpm for 2 min and wash it with absolute ethanol. Then dry the obtained precipitate in a blast drying oven at 60 °C for 12 h to obtain Co-BDC powder;

[0058] 2. Load 300 mg of the prepared Co-BDC powder into a crucible and carbonize it at 600 °C for 2 h in a tubular furnace under a N2 atmosphere to obtain a Co@C precursor;

[0059] 3. Then disperse 30 mg of the obtained Co@C precursor, 165 mg of sodium tungstate dihydrate, and 150 mg of thioacetamide in 60 ml of deionized water and ultrasonically treat it for 0.5 h to obtain a mixed solution;

[0060] 4. Finally, transfer the mixed solution to a 100 ml sealed autoclave lined with polytetrafluoroethylene and react at 200 °C for 20 h; wait until it cools to room temperature, wash the solvothermal product with absolute ethanol multiple times, and then dry it in a blast drying oven at 60 °C for 12 h to obtain a Co3S4 / WS2 composite material;

[0061] The prepared Co3S4 / WS2 battery anode material, Ketjen black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 7:2:1 in N-methyl-2-pyrrolidone (NMP) solvent. After mixing and stirring, a uniform slurry was obtained and coated on a copper foil current collector, then dried overnight in a vacuum oven at 120 °C. After cooling to room temperature, the slices were taken out, weighed, placed in a glove box for 8 h of equilibration, and then assembled into a sodium-ion battery to test the electrochemical performance of the battery.

[0062] Example 2: A preparation method of Co3S4 / WS2 composite material, the steps are as follows:

[0063] 1. Dissolve 964 mg of cobalt acetate tetrahydrate and 1 ml of deionized water in 25 ml of DMF, denoted as solution A; dissolve 250 mg of terephthalic acid, 1 ml of deionized water, and 1 ml of triethylamine in 20 ml of DMF, denoted as solution B; pour solution A into solution B and stir at room temperature for 1 hour to obtain a purple solution. The purple solution was centrifuged at 8000 rpm for 2 min and washed with absolute ethanol. Then the obtained precipitate was dried in a forced-air drying oven at 60 °C for 12 h to obtain Co-BDC powder;

[0064] 2. Load the prepared 300 mg of Co-BDC powder into a crucible, and carbonize it at 500 °C for 2 h in a tubular furnace under N2 atmosphere to obtain a Co@C precursor;

[0065] 3. Then disperse 30 mg of the obtained Co@C precursor, 180 mg of sodium tungstate dihydrate, and 200 mg of thioacetamide in 60 ml of deionized water, and ultrasonically treat for 0.5 h to obtain a mixed solution;

[0066] 4. Finally, transfer the mixed solution to a 100 ml sealed autoclave with a polytetrafluoroethylene liner and react at 180 °C for 10 h; after cooling to room temperature, wash the solvothermal product with absolute ethanol multiple times, and then dry it in a forced-air drying oven at 60 °C for 12 h to obtain the Co3S4 / WS2 composite material;

[0067] The prepared Co3S4 / WS2 battery anode material, Ketjen black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 7:2:1 in N-methyl-2-pyrrolidone (NMP) solvent. After mixing and stirring, a uniform slurry was obtained and coated on a copper foil current collector, then dried overnight in a vacuum oven at 120 °C. After cooling to room temperature, the slices were taken out, weighed, placed in a glove box for 8 h of equilibration, and then assembled into a sodium-ion battery to test the electrochemical performance of the battery.

[0068] Example 3: A preparation method of Co3S4 / WS2 composite material, the steps are as follows:

[0069] 1. Dissolve 964 mg of cobalt acetate tetrahydrate and 2 ml of deionized water in 25 ml of DMF, denoted as solution A; dissolve 250 mg of terephthalic acid, 1 ml of deionized water and 3 ml of triethylamine in 20 ml of DMF, denoted as solution B; pour solution A into solution B and stir at room temperature for 1 hour to obtain a purple solution. Centrifuge the purple solution at 8000 rpm for 2 min and wash it with absolute ethanol. Then dry the obtained precipitate in a forced-air drying oven at 60 °C for 12 h to obtain Co-BDC powder;

[0070] 2. Load 300 mg of the prepared Co-BDC powder into a crucible and carbonize it at 550 °C for 2 h in a tubular furnace under N2 atmosphere to obtain a Co@C precursor;

[0071] 3. Then disperse 30 mg of the obtained Co@C precursor, 150 mg of sodium tungstate dihydrate and 200 mg of thioacetamide in 60 ml of deionized water and ultrasonically treat for 0.5 h to obtain a mixed solution;

[0072] 4. Finally, transfer the mixed solution to a 100 ml sealed autoclave lined with polytetrafluoroethylene and react at 190 °C for 15 h; after cooling to room temperature, wash the solvothermal product with absolute ethanol multiple times, and then dry it in a forced-air drying oven at 60 °C for 12 h to obtain a Co3S4 / WS2 composite material;

[0073] Mix the prepared Co3S4 / WS2 battery anode material, Ketjen black and polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1 in N-methyl-2-pyrrolidone (NMP) solvent, mix and stir to obtain a uniform slurry, apply it on a copper foil current collector, and dry it overnight in a vacuum oven at 120 °C. After cooling to room temperature, take out the slice, weigh it, put it in a glove box to equilibrate for 8 h, and then assemble it into a sodium-ion battery to test the electrochemical performance of the battery.

[0074] Measure the electrochemical performance of the three Co3S4 / WS2 battery anode materials prepared in Example 1 (denoted as a), 2 (denoted as b), and 3 (denoted as c) at a current density of 2 A g -1 The electrochemical performance at a current density. Table 1 shows the characterization results of the Co3S4 / WS2 battery anode materials prepared in Examples 1, 2, and 3. From the data in Table 1, it can be seen that the Co3S4 / WS2 battery anode materials (a), (b), and (c) obtained by the preparation method of the present invention still exhibit 764.321 mAh g -1 at a high current density of 2 A g after cycling 100 times -1 、327.235 mAh g -1 、730.163 mAh g -1 excellent sodium storage performance.

[0075] AsFigure 2 As can be seen from the field emission scanning electron microscope image of the Co3S4 / WS2 battery anode material prepared in Example 1, its morphology is irregular spherical.

[0076] Such as Figure 3 As can be seen from the cycling performance graph of the Co3S4 / WS2 composite material prepared in Example 1 as the anode material for sodium-ion batteries at a current density of 2 A g -1 for 100 cycles.

[0077] Such as Figure 4 As can be seen from the cycling performance graph of the Co3S4 / WS2 composite material prepared in Example 1 as the anode material for sodium-ion batteries at a current density of 2 A g -1 for 200 cycles. It can be concluded from Figure 4 that the fluctuation starts at about the 103rd cycle (specific capacity of 747.314 mAh g -1 ) and continues to decay. By about the 200th cycle, the specific capacity is 573.783 mAh g -1 .

[0078] Table 1 Characterization results of the Co3S4 / WS2 battery anode material

[0079]

[0080] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. Application of Co3S4 / WS2 composite material in preparing a negative electrode for improving the specific capacity of a sodium-ion battery; The components of the sodium-ion battery are the Co3S4 / WS2 composite material, Ketjen black, and polyvinylidene fluoride; The mass ratio of the Co3S4 / WS2 composite material, Ketjen black, and polyvinylidene fluoride is 7:2:1; The Co3S4 / WS2 composite material is prepared by the following method: 1) Dissolve 964 mg of cobalt acetate tetrahydrate and 3 ml of deionized water in 25 ml of N,N-dimethylformamide, denoted as solution A; dissolve 250 mg of terephthalic acid, 3 ml of deionized water, and 2 ml of triethylamine in 20 ml of DMF, denoted as solution B; pour solution A into solution B and stir at room temperature for 3 hours to obtain a purple solution; centrifuge the purple solution at 8000 rpm for 2 minutes and wash with absolute ethanol; then dry the obtained precipitate in a blast drying oven at 60 °C for 12 h to obtain Co-BDC powder; 2) Place 300 mg of the prepared Co-BDC powder in a crucible and carbonize it in a tubular furnace under a N2 atmosphere at a temperature of 600 °C for 2 h to obtain a Co@C precursor; 3) Then disperse 30 mg of the obtained Co@C precursor, 165 mg of sodium tungstate dihydrate, and 150 mg of thioacetamide in 60 ml of deionized water and ultrasonically treat for 0.5 h to obtain a mixed solution; 4) Finally, transfer the mixed solution to a 100 ml sealed autoclave lined with polytetrafluoroethylene and react at 200 °C for 20 h; after cooling to room temperature, wash the solvothermal product with absolute ethanol multiple times, and then dry it in a blast drying oven at 60 °C for 12 h to obtain the Co3S4 / WS2 composite material.

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