A core-shell structure carbon-coated metal sulfide and a preparation method and application thereof

Abstract

The application discloses a kind of carbon-coated metal sulfide of core-shell structure and its preparation method and application, it is related to new energy material technical field.In the present application, the composite material is core-shell structure, and the inner core and shell are both carbon-coated NiS / NiS2 Nanoparticle structure;The preparation method of the composite material is: nickel salt and H4ABTC are dissolved in aqueous solution consisting of N, N-dimethylacetamide and concentrated hydrochloric acid, heat preservation filtration obtains Ni-soc-MOF;Thioacetamide and Ni-soc-MOF are dispersed into ethanol and high-temperature reaction;The obtained solid product is placed in 500 DEG C argon environment and carries out high-temperature pyrolysis reaction, and the core-shell structure carbon-coated metal sulfide composite material NiS / NiS2@C is prepared.The core-shell structure NiS / NiS2@C composite material in the present application, the carbon skeleton structure outside it can significantly the mechanical strength of the composite material, its internal porosity can effectively reduce the volume expansion of the composite material during cyclic use, and the ordered framework constructed by microstructure can effectively prevent the aggregation of nanoparticle.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new energy materials, and particularly relates to a core-shell structure carbon-coated metal sulfide and a preparation method and application thereof. BACKGROUND

[0002] Supercapacitors (SCs) are a kind of electrochemical energy storage (EES) systems, which have attracted much attention due to their fast charge-discharge rate, high power density, long cycle life, high safety and low cost. In the past few decades, commercial supercapacitors have made significant progress with relatively high power density. However, compared with batteries or other energy storage devices, their energy density is relatively low, which severely limits their practical applications. Therefore, researchers have carried out a large number of studies on high-energy-density supercapacitors without reducing the power density. Although EDLCs electrodes have inherent advantages in relatively high conductivity and good cycle stability, their specific capacitance is usually limited to 300-550 F·g -1 , which limits their comprehensive application.

[0003] Transition metal-based materials are considered as electrode materials with good theoretical specific capacity due to their reversible Faraday reactions. So far, transition metal sulfides (TMS), such as CoS, MnS, FeS2 and NiS, exhibit good energy density, long cycle performance and unique physical or chemical properties. Among sulfide materials, nickel-based sulfides have high theoretical specific capacity, low price, rich valence, easy synthesis and environmental protection, and are an ideal hybrid supercapacitor energy storage electrode material. However, nickel sulfide faces the greatest challenge due to its huge volume or structural change during the cycle and inherent low conductivity, which eventually leads to slow ion diffusion kinetics and rapid capacity degradation. Therefore, it is urgent to find an effective method to inhibit the volume expansion of the material while improving the conductivity of the material. Metal-organic framework (MOF) is a new type of porous material, which is a regularly ordered inorganic-organic hybrid polymer composed of metal center ions and organic ligands. MOF has been widely used in various fields, especially in electrochemical energy storage. MOF has become a candidate supercapacitor electrode material to meet the energy demand due to its special structural characteristics such as large surface area, easy-to-control structure and rich active sites.

[0004] One strategy is to introduce components with good conductivity to form hybrid multi-component materials, and current researches are focused on the composite of carbon-based and nickel-based sulfide materials. Hybridization not only facilitates electron transmission, but also fully plays the advantages of single components. Moreover, researches have shown that the addition of carbon materials can improve the conductivity and specific surface area. At present, the research on NiS x / carbon composite materials mainly focuses on NiS x / graphene, NiS x / carbon nanotubes, the introduction of graphene or carbon nanotubes can improve the electrochemical performance of electrode materials, such as rate performance and cycle stability. However, during the water-based electrochemical reaction, due to the different polarities of carbon and pseudo-capacitor materials, NiS x It is easy to separate from the carbon base. Therefore, it is imperative to design and develop a new strategy that can form a stable and tight interfacial bond between materials with different polarities. SUMMARY

[0005] The purpose of the present application is to provide a core-shell structure carbon-coated metal sulfide and its preparation method and application. NiS / NiS2@C nanoparticles are aggregated to form a core-shell structure, and a NiS / NiS2@C / / PAC hybrid supercapacitor is prepared for energy storage, solving the problems in the prior art.

[0006] To solve the above technical problems, the present application is realized by the following technical scheme:

[0007] The present application is a kind of core-shell structure carbon-coated metal sulfide, the composite material is core-shell structure, the core and shell of the composite material are both carbon-coated NiS / NiS2 Nanoparticle structure;

[0008] The preparation method of the core-shell structure carbon-coated metal sulfide composite material mainly includes the following steps:

[0009] Step 1, dissolve nickel salt and 3,3',5,5'-azobenzene tetraacetic acid (H4ABTC) in an aqueous solution composed of N,N-dimethylacetamide, water and concentrated hydrochloric acid, and stir uniformly to obtain a mixed solution A, wherein the nickel salt is one or more of nickel sulfate, nickel nitrate and nickel chloride;

[0010] Step 2, transfer the mixed solution A to a stainless steel reaction kettle, then place the stainless steel reaction kettle in an oven for heat preservation for 2-5 days, wash the yellow powder obtained after filtration with ethanol for 3-4 times, and dry in a vacuum environment to obtain an intermediate product Ni-soc-MOF;

[0011] Step 3, disperse thioacetamide and Ni-soc-MOF into ethanol and stir uniformly to obtain a mixed solution B, then place the mixed solution B in a stainless steel reaction kettle for high-temperature reaction, and then wash the solid product obtained after filtration with ethanol and water;

[0012] Step 4, place the obtained solid product in an argon environment at 500℃ for high-temperature pyrolysis reaction to obtain a core-shell structure carbon-coated metal sulfide composite material NiS / NiS2@C.

[0013] Preferably, the specific method of step 1 is: dissolving the nickel salt and 3,3',5,5'-azobenzenetetracarboxylic acid (H4ABTC) in an aqueous solution consisting of 12-15 ml of N,N-dimethylacetamide, 3-6 ml of deionized water and 200-400 ul of concentrated hydrochloric acid, stirring uniformly to obtain mixed solution A; wherein the molar ratio of the nickel salt to 3,3',5,5'-azobenzenetetracarboxylic acid is 6:1.

[0014] Preferably, the specific method of step 2 is: transferring the mixed solution A into a 50ml stainless steel reaction kettle, then placing the stainless steel reaction kettle in an oven, and incubating at a temperature of 120-160℃ for 2-5d, washing the yellow powder obtained after filtration with ethanol for 3-4 times, and drying overnight in a vacuum environment to obtain the intermediate product Ni-soc-MOF.

[0015] Preferably, the specific method of step 3 is: dispersing 200mg of thioacetamide and Ni-soc-MOF into 40ml of ethanol and continuously stirring for 20min to obtain mixed solution B, then placing the mixed solution B in a 100ml stainless steel reaction kettle for high-temperature reaction, the reaction temperature is 200℃, and the reaction time is 2-5h, and the solid product is obtained after filtration, ethanol washing and water washing.

[0016] Preferably, the structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzenetetracarboxylic acid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by ligand connection of oxygen-centered carboxylic acid and nickel trinuclear metal clusters, including two interconnected channels and a nanoscale central cage with a particle size of less than 1nm.

[0017] Preferably, the application further includes an application of the core-shell structure carbon-coated metal sulfide in a supercapacitor, and the specific process is:

[0018] A three-electrode system is formed by taking NiS / NiS2@C as the positive electrode, Pt as the counter electrode, Ag / AgCl as the reference electrode, and 2M KOH solution as the electrolyte, and when the current density is 1A·g -1 , the specific capacitance is 1082F·g -1 .

[0019] An asymmetric supercapacitor device, NiS / NiS2@C / / PAC HSC, was fabricated using NiS / NiS2@C as the positive electrode and PAC as the negative electrode. The mass ratio of NiS / NiS2@C to PAC was 1:3.6–1:3.7. In this three-electrode system, the potential windows for NiS / NiS2@C nanoparticles and PAC were 0–0.6 V and -1.0–0 V, respectively. The CV characteristics of the asymmetric supercapacitor were measured within the 0–1.6 V potential range. The asymmetric supercapacitor was tested at 800 W·kg⁻¹. -1 It has a power density of 56.5 Wh·kg -1 The energy density is 8000 W·kg -1 It still maintains 35.6 Wh·kg at high power density. -1 Energy density, at 1 A·g -1 After 5000 charge-discharge cycles at a current density, the specific capacitance retention rate is still as high as 90%.

[0020] The present invention has the following beneficial effects:

[0021] 1. The core-shell structure NiS / NiS2@C composite material of the present invention has an external carbon skeleton structure that can significantly improve the mechanical strength of the composite material, and its internal pores can effectively reduce the volume expansion of the composite material during recycling. At the same time, the ordered framework constructed by the microstructure can effectively prevent the aggregation of nanoparticles.

[0022] 2. This invention utilizes carbon and NiS x The tight connections between nanoparticles accelerate the formation of more active sites and improve electron transport efficiency, while the appropriate porous structure and large specific surface area allow for rapid transport and diffusion of electrolyte ions.

[0023] 3. The NiS / NiS2@C prepared by this invention exhibits a strength of 1082 A·g at 1 A / g. -1 The assembled NiS / NiS2@C / / PAC HSC exhibits a high specific capacity and retains 85.6% capacity after 5000 cycles. It also provides a high energy density of 56.2 Wh / kg at 800 W / kg and retains 90% capacity after 5000 cycles.

[0024] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed for the description of the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0026] Figure 1 Preparation flow chart of the NiS / NiS2@C composite material in the present application.

[0027] Figure 2 Ni-soc-MOF and simulated XRD spectrum in the present application.

[0028] Figure 3 XRD spectrum of the NiS / NiS2@C in the present application.

[0029] Figure 4 N2adsorption curve of the NiS / NiS2@C in the present application.

[0030] Figure 5 SEM and TEM images of different materials in the present application; wherein, Fig. (a) is the SEM image of the Ni-soc-MOF, Figs. (b-c) are the SEM images of the NiS / NiS2@C, and Figs. (d-f) are the TEM images of the NiS / NiS2@C.

[0031] Figure 6 XPS image of the NiS / NiS2@C composite material in the present application.

[0032] Figure 7 Electrical test image of the NiS / NiS2@C composite material in the present application; wherein, Fig. (a) is the CV curve of the composite material at different scanning rates, Fig. (b) is the logi vs.logv curve of the composite material, Fig. (c) is the capacitive contribution rate of the total current of the composite material at 10 mV / s, and Fig. (d) is the percentage of the capacitive contribution rate of the composite material at different scanning rates.

[0033] Figure 8 Electrical test image of the NiS / NiS2@C composite material in the present application; wherein, Fig. (a) is the charge-discharge curve of the composite material, Fig. (b) is the specific capacity of the composite material at different current densities, Fig. (c) is the cycle stability test image of the composite material, and Fig. (d) is the impedance image of the composite material.

[0034] Figure 9The different material electric test diagram in the application; wherein, figure (a) is the CV curve diagram of AC and NiS / NiS2@C at 20mV / s, figure (b) is the CV curve diagram of NiS / NiS2@C / / PAC hybrid supercapacitor at different potential window with the scanning rate of 50mV / s, figure (c) is the CV curve diagram of the composite material at different scanning rates, and figure (d) is the GCD curve diagram of different current densities in the potential window of 0-1.6V.

[0035] Figure 10 Figure (a) is the retention rate diagram of 5000 cycles at the scanning rate of 1A / g, and figure (b) is the Ragone diagram of energy density and power density. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the application will be apparently and completely described below with reference to the drawings in the embodiments of the application, and obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0037] Example 1: a core-shell structure carbon-coated metal sulfide and a preparation method thereof

[0038] Please refer to Figures 1-10 The application is a core-shell structure carbon-coated metal sulfide, the composite material is a core-shell structure, and the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structures.

[0039] The preparation method of the core-shell structure carbon-coated metal sulfide composite material is as follows: NiCl2·4H2O and 3,3',5,5'-azobenzene-4-carboxylic acid (H4ABTC) are dissolved in 12ml N,N-dimethylacetamide and 3ml deionized water, 300ul concentrated hydrochloric acid is added, the mixture is placed in a 150℃ oven for 2 days to obtain Ni-soc-MOF, 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed in 40ml ethanol, stirred for 20 minutes, and then kept at 200℃ for 2 hours, the product is filtered and dried, and pyrolysis is carried out in an argon environment at 500℃, thereby successfully preparing the core-shell structure NiS / NiS2@C composite material.

[0040] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene-4-carboxylic acid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by connecting together carboxylic acids with oxygen as the center and nickel trinuclear metal clusters through ligands, including two interconnected channels and a nanoscale central cage with a particle size of less than 1nm.

[0041] Example 2 A core-shell structure carbon-coated metal sulfide and a preparation method

[0042] The present application is a kind of core-shell structure carbon-coated metal sulfide, the composite material is core-shell structure, the inner core and shell of the composite material are carbon-coated NiS / NiS2 Nanoparticle structure;

[0043] The preparation method of the core-shell structure carbon-coated metal sulfide composite material, the specific method is: NiCl2·4H2O and 3,3',5,5'-azobenzene tetracarboxylic acid (H4ABTC) are dissolved in 12ml N,N-dimethylacetamide and 4ml deionized water, then 300ul concentrated hydrochloric acid is added, the mixture is placed in 150℃ oven for 2 days to obtain Ni-soc-MOF, then 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed into 40ml ethanol, stirred for 20 minutes, and then kept at 200℃ for 2 hours, the product is obtained after filtration and drying, and pyrolysis is carried out in argon environment at 500℃, to successfully prepare the core-shell structure NiS / NiS2@C composite material;

[0044] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene tetracarboxylic acid and nickel ions;The specific structure of the Ni-soc-MOF is a three-dimensional framework formed by carboxylic acid with oxygen as the center and nickel trinuclear metal clusters connected together by ligands, including two interconnected channels and a nanoscale central cage with a particle size of less than 1nm.

[0045] Example 3 A core-shell structure carbon-coated metal sulfide and a preparation method

[0046] The present application is a kind of core-shell structure carbon-coated metal sulfide, the composite material is core-shell structure, the inner core and shell of the composite material are carbon-coated NiS / NiS2 Nanoparticle structure;

[0047] The preparation method of the core-shell structure carbon-coated metal sulfide composite material, the specific method is: NiCl2·4H2O and 3,3',5,5'-azobenzene tetracarboxylic acid (H4ABTC) are dissolved in 12ml N,N-dimethylacetamide and 4ml deionized water, then 300ul concentrated hydrochloric acid is added, the mixture is placed in 150℃ oven for 2 days to obtain Ni-soc-MOF, then 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed into 40ml ethanol, stirred for 20 minutes, and then kept at 200℃ for 2 hours, the product is obtained after filtration and drying, and pyrolysis is carried out in argon environment at 500℃, to successfully prepare the core-shell structure NiS / NiS2@C composite material;

[0048] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene-4-carboxylic acid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by ligand connection of oxygen-centered carboxylic acid and nickel trinuclear metal clusters, including two interconnected channels and a nanoscale central cage with a particle size of less than 1 nm.

[0049] Example 4: A core-shell structure carbon-coated metal sulfide and a preparation method thereof

[0050] The present application is a core-shell structure carbon-coated metal sulfide, the composite material is a core-shell structure, the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structures.

[0051] The preparation method of the core-shell structure carbon-coated metal sulfide composite material is as follows: NiCl2·4H2O and 3,3',5,5'-azobenzene-4-carboxylic acid (H4ABTC) are dissolved in 14ml N,N-dimethylacetamide and 3ml deionized water, 300ul concentrated hydrochloric acid is added, the mixture is placed in a 150℃ oven for 2 days to obtain Ni-soc-MOF, then 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed in 40ml ethanol, stirred for 20 minutes, and then heated at 200℃ for 2 hours, filtered and dried to obtain the product, and pyrolysis is carried out in an argon environment at 500℃ to successfully prepare the core-shell structure NiS / NiS2@C composite material.

[0052] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene-4-carboxylic acid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by ligand connection of oxygen-centered carboxylic acid and nickel trinuclear metal clusters, including two interconnected channels and a nanoscale central cage with a particle size of less than 1 nm.

[0053] Example 5: A core-shell structure carbon-coated metal sulfide and a preparation method thereof

[0054] The present application is a core-shell structure carbon-coated metal sulfide, the composite material is a core-shell structure, the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structures.

[0055] The preparation method of the core-shell structure carbon-coated metal sulfide composite material is as follows: NiCl2.4H2O and 3,3',5,5'-azobenzene tetracarboxylic acid (H4ABTC) are dissolved in 15ml N,N-dimethylacetamide and 3ml deionized water, 300ul concentrated hydrochloric acid is added, the mixture is placed in a 150 DEG C oven for 2 days to obtain Ni-soc-MOF, 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed in 40ml ethanol, stirring is carried out for 20 minutes, and then the product is obtained by drying after being kept at 200 DEG C for 2 hours, and pyrolysis is carried out under an argon environment at 500 DEG C, so that the core-shell structure NiS / NiS2@C composite material is successfully prepared.

[0056] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene tetracarboxylic acid and nickel ions; and the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by connecting together an oxygen-centered carboxylic acid and a nickel trinuclear metal cluster through a ligand, including two interconnected channels and a nanoscale central cage with a particle size of less than 1nm.

[0057] Example 6: A core-shell structure carbon-coated metal sulfide and a preparation method thereof

[0058] The present application is a core-shell structure carbon-coated metal sulfide, the composite material is a core-shell structure, and the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structures.

[0059] The preparation method of the core-shell structure carbon-coated metal sulfide composite material is as follows: NiCl2.4H2O and 3,3',5,5'-azobenzene tetracarboxylic acid (H4ABTC) are dissolved in 15ml N,N-dimethylacetamide and 3ml deionized water, 300ul concentrated hydrochloric acid is added, the mixture is placed in a 150 DEG C oven for 2 days to obtain Ni-soc-MOF, 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed in 40ml ethanol, stirring is carried out for 20 minutes, and then the product is obtained by drying after being kept at 200 DEG C for 2 hours, and pyrolysis is carried out under an argon environment at 500 DEG C, so that the core-shell structure NiS / NiS2@C composite material is successfully prepared.

[0060] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene tetracarboxylic acid and nickel ions; and the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by connecting together an oxygen-centered carboxylic acid and a nickel trinuclear metal cluster through a ligand, including two interconnected channels and a nanoscale central cage with a particle size of less than 1nm.

[0061] Example 7: A core-shell structure carbon-coated metal sulfide and a preparation method thereof

[0062] The application is a kind of core-shell structure carbon-coated metal sulfide, the composite material is a core-shell structure, the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structure;

[0063] The preparation method of the core-shell structure carbon-coated metal sulfide composite material is as follows: NiCl2·4H2O and 3,3',5,5'-azobenzene tetracarboxylic acid (H4ABTC) are dissolved in 12ml N,N-dimethylacetamide and 3ml deionized water, 300ul concentrated hydrochloric acid is added, the mixture is placed in a 140℃ oven for 2 days to obtain Ni-soc-MOF, 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed in 40ml ethanol, stirred for 20 minutes, and then kept at 200℃ for 2 hours, the product is filtered and dried, and pyrolysis is carried out in an argon environment at 500℃, thereby successfully preparing a core-shell structure NiS / NiS2@C composite material;

[0064] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene tetracarboxylic acid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by connecting together carboxylic acids with oxygen as the center and nickel trinuclear metal clusters through ligands, including two interconnected channels and a nanoscale central cage with a particle size of less than 1nm.

[0065] Example 8: A kind of core-shell structure carbon-coated metal sulfide and a preparation method

[0066] The application is a kind of core-shell structure carbon-coated metal sulfide, the composite material is a core-shell structure, the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structure;

[0067] The preparation method of the core-shell structure carbon-coated metal sulfide composite material is as follows: NiCl2·4H2O and 3,3',5,5'-azobenzene tetracarboxylic acid (H4ABTC) are dissolved in 12ml N,N-dimethylacetamide and 3ml deionized water, 300ul concentrated hydrochloric acid is added, the mixture is placed in a 160℃ oven for 2 days to obtain Ni-soc-MOF, 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed in 40ml ethanol, stirred for 20 minutes, and then kept at 200℃ for 2 hours, the product is filtered and dried, and pyrolysis is carried out in an argon environment at 500℃, thereby successfully preparing a core-shell structure NiS / NiS2@C composite material;

[0068] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene-4-carboxylic acid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by ligand connection of oxygen-centered carboxylic acid and nickel trinuclear metal clusters, including two interconnected channels and a nanoscale central cage with a particle size of less than 1 nm.

[0069] Example 9: A core-shell structure carbon-coated metal sulfide and a preparation method thereof

[0070] The present application is a core-shell structure carbon-coated metal sulfide, the composite material is a core-shell structure, the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structures.

[0071] The preparation method of the core-shell structure carbon-coated metal sulfide composite material is as follows: NiCl2·4H2O and 3,3',5,5'-azobenzene-4-carboxylic acid (H4ABTC) are dissolved in 12ml N,N-dimethylacetamide and 3ml deionized water, 200ul concentrated hydrochloric acid is added, the mixture is placed in a 150℃ oven for 2 days to obtain Ni-soc-MOF, then 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed in 40ml ethanol, stirred for 20 minutes, and then heated at 200℃ for 2 hours, filtered and dried to obtain the product, and pyrolysis is carried out in an argon environment at 500℃ to successfully prepare a core-shell structure NiS / NiS2@C composite material.

[0072] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene-4-carboxylic acid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by ligand connection of oxygen-centered carboxylic acid and nickel trinuclear metal clusters, including two interconnected channels and a nanoscale central cage with a particle size of less than 1 nm.

[0073] Example 10: A core-shell structure carbon-coated metal sulfide and a preparation method thereof

[0074] The present application is a core-shell structure carbon-coated metal sulfide, the composite material is a core-shell structure, the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structures.

[0075] The preparation method of the core-shell structure carbon-coated metal sulfide composite material is as follows: NiCl2.4H2O and 3,3',5,5'-azobenzene tetracarboxylic acid (H4ABTC) are dissolved in 12ml N,N-dimethylacetamide and 3ml deionized water, 400ul concentrated hydrochloric acid is added, the mixture is placed in a 150℃ oven for 2 days to obtain Ni-soc-MOF, then 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed in 40ml ethanol, stirred for 20 minutes, and then kept at 200℃ for 2 hours, the product is obtained after filtration and drying, and pyrolysis is carried out at 500℃ in an argon environment, thereby successfully preparing the core-shell structure NiS / NiS2@C composite material.

[0076] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene tetracarboxylic acid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by connecting together carboxylic acid with oxygen as the center and nickel trinuclear metal clusters through ligands, including two interconnected channels and a nanoscale central cage with a particle size of less than 1nm.

[0077] Example 11: A core-shell structure carbon-coated metal sulfide and a preparation method thereof

[0078] The present application is a core-shell structure carbon-coated metal sulfide, the composite material is a core-shell structure, and the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structures.

[0079] The preparation method of the core-shell structure carbon-coated metal sulfide composite material is as follows: NiCl2.4H2O and 3,3',5,5'-azobenzene tetracarboxylic acid (H4ABTC) are dissolved in 12ml N,N-dimethylacetamide and 3ml deionized water, 400ul concentrated hydrochloric acid is added, the mixture is placed in a 150℃ oven for 2 days to obtain Ni-soc-MOF, then 200mg thioacetamide and Ni-soc-MOF microspheres are dispersed in 40ml ethanol, stirred for 20 minutes, and then kept at 200℃ for 2 hours, the product is obtained after filtration and drying, and pyrolysis is carried out at 500℃ in an argon environment, thereby successfully preparing the core-shell structure NiS / NiS2@C composite material.

[0080] The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene tetracarboxylic acid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by connecting together carboxylic acid with oxygen as the center and nickel trinuclear metal clusters through ligands, including two interconnected channels and a nanoscale central cage with a particle size of less than 1nm.

[0081] The X-ray powder diffraction (XRD) result of the Ni-soc-MOF precursor corresponds to previous reportsFigure 2 ), indicating their exact preparation. As Figure 3 shown. The XRD pattern of MOF-derived NiS / NiS2@C nanocomposites shows strong characteristic peaks and is consistent with NiS (JCPDS No. 02-1280) and NiS2 (JCPDS No. 11-0099).

[0082] The Brunauer-Emmett-Teller (BET) surface area and pore size distribution of NiS / NiS2@C composites were also explored by N2adsorption-desorption isotherms, as Figure 4 shown. NiS / NiS2@C exhibits a typical IV adsorption isotherm and mesoporous structure with pore size concentrated in the range of 2-4 nm. NiS / NiS2@C has a core-shell structure with a high nitrogen adsorption amount and a specific surface area of 58.4 mg -1 cm-3, large specific surface area and rich porosity are beneficial to the diffusion of electrolyte in the material, thus obtaining better electrochemical performance.

[0083] After the sulfuration and carbonization process, the Ni-soc-MOF precursor was successfully converted into uniform carbon-modified core-shell spheres, as Figure 5 shown. In addition, the enlarged SEM images clearly identify the core-shell structure of NiS / NiS2@C. At the same time, TEM images show that the microspheres present an obvious hollow structure between the core and shell, and the microstructure of the microspheres is further verified by HRTEM observation. Obviously, all the NiS / NiS2 nanoparticles are coated by a thin carbon shell with a thickness of 1.6 nm. The measured interplanar spacings are 0.26 nm and 0.288 nm, which are attributed to the (101) plane of NiS and the (200) plane of NiS2.

[0084] The surface elemental composition and chemical bond properties of NiS / NiS2@C were analyzed by X-ray photoelectron spectroscopy (XPS). As shown, Ni, C, O, and S elements have been clearly identified on the surface of the prepared nanocomposites. Figure 6 b presents the Cls XPS spectrum can be divided into three types of peaks at 285.4, 287.0, 289.1 eV, which are respectively attributed to C-C / C=C, C-N, and -C=O bonds. The peaks of S2p at about 161.9 and 163.0 eV correspond to S2p 3 / 2 and S2p 1 / 2 , indicating the presence of Ni-S bonds. In Figure 6 c, the Ni 2p spectrum is decomposed into four spin-orbit peaks of 2p 3 / 2 and 2p 1 / 2 , as well as two typical satellite peaks (labeled "Sat.", 861.8 eV and 880.6 eV). The results show that the Ni2+ (853.9ev and 871.1ev) and Ni 3+ (857.3ev and 875.5ev) coexist on the surface of NiS / NiS2@C.

[0085] Embodiment 12 Application of a core-shell structure carbon-coated metal sulfide in a supercapacitor

[0086] The application also includes an application of a core-shell structure carbon-coated metal sulfide in a supercapacitor, and the specific process is as follows:

[0087] A three-electrode system is formed by taking NiS / NiS2@C as a positive electrode, Pt as a counter electrode, and Ag / AgCl as a reference electrode, and a 2M KOH solution is taken as an electrolyte, and when the current density is 1A·g -1 , the specific capacitance is 1082F·g -1 .

[0088] A hybrid supercapacitor device NiS / NiS2@C / / PAC HSC is prepared by taking NiS / NiS2@C as a positive electrode and mesoporous activated carbon (PAC) as a negative electrode, the mass ratio of NiS / NiS2@C to PAC is 1:3.6-1:3.7, the potential window of NiS / NiS2@C nanoparticles and PAC in a three-electrode system is 0-0.6V and -1.0-0V respectively, and the CV characteristic measurement of the asymmetric supercapacitor is carried out in a potential range of 0-1.6V, the asymmetric supercapacitor has an energy density of 56.5Wh·kg -1 at a power density of 800W·kg -1 , still maintains an energy density of 35.6Wh·kg -1 at a high power density of 8000W·kg -1 , and the specific capacitance retention rate is still as high as 90% after 5000 charge-discharge cycles at a current density of 1A·g -1 .

[0089] The electrochemical behavior of NiS / NiS2@C in a conventional three-electrode system is studied by using CV, GCD and EIS. At a scan rate of 20mV·s -1 , the cyclic voltammetry curve (CV) of the NiS / NiS2@C electrode is studied from 0 to 0.5V. It is obvious that the CV curve of the NiS / NiS2@C material has two symmetrical redox peaks, indicating that the redox reaction is reversible. The optimized NiS / NiS2@C electrode material has a maximum integrated area and higher redox peak intensity, indicating that the NiS / NiS2@C electrode material has better electrochemical performance. These significant electrochemical characteristics come from its unique core-shell structure and large surface area. By changing the scan rate from 4mV·s -1Change to 40 mV s -1 The CVs related to NiS / NiS2@C were investigated in detail, as shown in Fig. Figure 7 a. A pair of redox peaks for NiS / NiS2@C electrode can be observed on the curve, which might be due to the reversible oxidation-reduction process between Ni 2+ and Ni 3+ :

[0090] NiS2+ OH-→ NiS2OH + e -

[0091] NiS2OH → NiS2O + H2O + e -

[0092] NiS + OH - → NiSOH + e -

[0093] NiSOH → NiSO + H2O + e -

[0094] As shown in Fig. Figure 7 b, the relationship between log(i) and log(V) was obtained from the CV curves of NiS / NiS2@C, and the b value was calculated from the equation (i = a v b, log i = blog v + log a). Generally, when b = 1.0, the reaction is a capacitive-controlled redox process, while b = 0.5, the reaction is a diffusion-controlled reaction. The b values of the redox peaks of NiS / NiS2@C were 0.55 and 0.59, respectively, indicating that the electrochemical reaction of NiS / NiS2@C composite was the result of the combined action of diffusion control and capacitive control Figure 7 c). The contribution rate of the two processes can be further calculated according to the following equation:

[0095] i(V) = k1 v + k2 v 1 / 2

[0096] where I, v represent the current and scan rate, respectively, and k1 v and k2 v 1 / 2 represent the relative contribution of the capacity and diffusion-controlled process. At a lower scan rate of 4 mV -1 ( Figure 7 d), the diffusion-controlled process contributed 75% of the total charge storage, indicating that the diffusion-controlled charge storage mechanism of NiS / NiS2@C at a lower scan rate. As expected, the ratio of surface capacitance contribution gradually increased with the increase of scan rate, indicating that the NiS / NiS2@C electrode was mainly a pseudo-capacitance behavior. Such a high pseudo-capacitance contribution might be due to the rich porous structure, which is beneficial to the high-rate performance of NiS / NiS2@C.

[0097] To further investigate the electrochemical performance of the electrode, such as Figure 8 As shown in figure a, the NiS / NiS2@C composite material at 1 A·g -1 Constant current charge-discharge (GCD) analysis was performed within the 0-0.4V potential window, revealing that the NiS / NiS2@C composite material exhibited a longer discharge time. This indicates that the NiS / NiS2@C material performs well. The GCD curves show typical charge-discharge plateaus, reflecting typical battery behavior of the electrode material. The specific capacities of the NiS / NiS2@C electrode at different current densities were 1082, 1021, 999, 883, 840, 790, 729, and 676 F·g. -1 (2706, 2553, 2498, 2400, 2208, 2100, 1975, 1823 and 1690 F·g) -1 Furthermore, the specific capacity of NiS / NiS2@C ranges from 1 to 20 A·g. -1 The percentage remained at 62.4%. Figure 8 b). Cyclic performance of NiS / NiS2@C at 5 A·g -1 Next step ( Figure 8 c) It retains 85.6% of its charge-discharge performance after 5000 charge-discharge cycles, demonstrating excellent cycle stability and electrochemical stability.

[0098] To further understand the charge transfer characteristics and ion diffusion mechanism of the material, EIS tests were performed. Figure 8 d describes NiS / NiS2@C and NiS x The Nyquist plot of the electrode. In the low-frequency region, the slope of the NiS / NiS2@C is very sharp, indicating a low Warburg impedance (Wo). A steeper slope indicates a faster diffusion rate of ions from the electrolyte to the electrode surface. The intercept of the real part of the impedance in the high-frequency region reflects the series resistance (Rs), which originates from the interfacial contact resistance at the electrolyte and electrolyte / collector ionic resistance. The NiS / NiS2@C electrode is very small, only 0.5 ohms, indicating good conductivity. Therefore, NiS / NiS2@C has the lowest resistance and the highest charge transfer capability, which is beneficial for improving specific capacity and rate performance.

[0099] To accurately study the practicality of NiS / NiS2@C electrode materials, a NiS / NiS2@C / / PAC HSC device with a wide operating voltage window was fabricated using the NiS / NiS2@C composite material as the positive electrode and PAC as the negative electrode, as shown in the figure. According to the GCD curve, activated carbon exhibits EDLC behavior at 1 A·g-1. -1 Under the given conditions, the capacitance of PAC is calculated to be 260 F·g. -1To achieve the best electrochemical performance of the device, according to the formula, the mass ratio of the positive and negative electrodes is about 1:4.2. Figure 9 a shows the CV curves of NiS / NiS2@C and AC electrodes at 10 mV·s -1 -1V and 0-0.6V, respectively. The optimal working voltage of the HSC device can be extended to 1.6V Figure 9 b). When the working potential window of the NiS / NiS2@C / / PAC HSC is extended to 1.7V, the CV curve is obviously fast, and oxygen is released, indicating that significant polarization or some irreversible reactions may have occurred. Therefore, the 0-1.6V window is chosen as the most suitable potential window. Based on the above CV performance at different scan rates of 10-70 mV·s -1 -1V and 0-0.6V, respectively. The optimal working voltage of the HSC device can be extended to 1.6V Figure 9 c). With the increase of scan rate, HSC shows EDLC and battery behavior, which contributes to the specific capacity of NiS / NiS2@C / / PAC HSC. At the same time, the shape of the curve is maintained, which proves the structural stability of HSC. As shown in Figure 9 d, the approximate symmetric distribution of GCD indicates that the NiS / NiS2@C / / PAC HSC device has a high coulombic efficiency. According to the discharge curve and formula calculation, the specific capacity of the HSC device at 1, 2, 3, 5, 7, 8, 10 and 12 A·g -1 -1V and 0-0.6V, respectively. The optimal working voltage of the HSC device can be extended to 1.6V -1 , showing excellent rate capability. It is worth noting that the capacity retention of the NiS / NiS2@C / / PAC HSC device at 1 A·g -1 -1V and 0-0.6V, respectively. The optimal working voltage of the HSC device can be extended to 1.6V Figure 10 a).

[0100] In addition, the power density and energy density of the NiS / NiS2@C / / PAC HSC device are summarized, and the Ragone plot is shown in Figure 10 b, which shows superior energy storage advantages. Encouragingly, the NiS / NiS2@C / / PAC HSC can provide an energy density of 56.5 Wh·kg -1 at a power density of 800 w·kg -1 , and still maintains a capacity of 35.6 Wh·kg -1 at a maximum power density of 8000 w·kg -1The energy density of the NiS / NiS2@C / / AC HSC is 56.5 Wh kg-1 at a power density of 800 W kg-1. The capacity retention rate is 90% after 5000 charge-discharge cycles. These results indicate that the Ni-soc-MOF derived core-shell structured NiS / NiS2@C electrode has a very broad application prospect in energy storage devices.

[0101] In summary, by combining hydrothermal sulfuration synthesis with high-temperature carbonization process, and using Ni-soc-MOF as a sacrificial template, carbon-coated NiS / NiS2 microspheres with core-shell structure are successfully synthesized, which have high porosity, abundant redox active sites, large specific surface area, and a synergistic effect between Ni atoms and C atoms. Therefore, the MOF derived NiS / NiS2@C electrode has very high electrochemical performance. At 1 A g-1, the NiS / NiS2@C electrode shows an ideal specific capacity of 1082 F·g-1; at 5 A g-1, the capacity retention rate is 85.6%. In addition, the assembled NiS / NiS2@C / / AC HSC has an energy density of 56.5 Wh kg-1 at a power density of 800 W kg-1, and has a long service life, with a capacity retention rate of 90% after 5000 charge-discharge cycles. These results indicate that the Ni-soc-MOF derived core-shell structured NiS / NiS2@C electrode has a very broad application prospect in energy storage devices. -1 -1 -1 -1 -1

[0102] In the description of the present specification, the description referring to the terms "one embodiment", "an example", "a specific example" and the like means that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Illustrative expressions of the above terms in the present specification do not necessarily refer to the same embodiment or example. Also, the specific feature, structure, material or characteristic described can be combined in any appropriate manner in one or more embodiments or examples.

[0103] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all of the details of the application, and the application is not limited to the specific embodiments described. Obviously, many modifications and variations can be made in light of the contents of the specification. The embodiments are selected and specifically described in the specification in order to better explain the principles and practical application of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.​​​​​

Claims

1. A core-shell structured carbon-coated metal sulfide composite material, characterized by, The composite material is a core-shell structure, and the inner core and the outer shell of the composite material are both carbon-coated NiS / NiS2 nanoparticle structures; The preparation method of the core-shell structure carbon-coated metal sulfide composite material mainly comprises the following steps: Step 1, dissolve nickel salt and 3,3',5,5'-azobenzene tetraacid in an aqueous solution composed of N,N-dimethylacetamide, water and concentrated hydrochloric acid, and prepare a mixed solution A after stirring uniformly; Step 2, transfer the mixed solution A into a stainless steel reaction kettle, then place the stainless steel reaction kettle in an oven for heat preservation for 2-5 days, obtain a yellow powder after filtration, wash the yellow powder with ethanol for 3-4 times, and dry in a vacuum environment to obtain an intermediate product Ni-soc-MOF; Step 3, disperse thioacetamide and Ni-soc-MOF into ethanol and stir uniformly to obtain a mixed solution B, then place the mixed solution B in a stainless steel reaction kettle for high-temperature reaction, and obtain a solid product after filtration, ethanol washing and water washing; Step 4, place the obtained solid product in an argon environment at 500 DEG C for high-temperature pyrolysis reaction to prepare the core-shell structure carbon-coated metal sulfide composite material NiS / NiS2@C; The specific method of step 3 is: disperse 200 mg of thioacetamide and Ni-soc-MOF into 40 ml of ethanol and continuously stir for 20 min to obtain a mixed solution B, then place the mixed solution B in a 100 ml stainless steel reaction kettle for high-temperature reaction, the reaction temperature is 200 DEG C, the reaction time is 2-5 h, and a solid product is obtained after filtration, ethanol washing and water washing; The structure of the Ni-soc-MOF is composed of 3,3',5,5'-azobenzene tetraacid and nickel ions; the specific structure of the Ni-soc-MOF is a three-dimensional framework formed by carboxylic acid with oxygen as the center and nickel trinuclear metal clusters connected together through ligands, including two interconnected channels and a nanoscale central cage with a particle size less than 1 nm; The application of the above-mentioned core-shell structure carbon-coated metal sulfide in supercapacitors, the specific process is: A three-electrode system was formed by taking NiS / NiS2@C as a positive electrode, Pt as a counter electrode, and Ag / AgCl as a reference electrode, and taking 2M KOH solution as an electrolyte, and when the current density was 1 A·g -1 , the specific capacitance was 1082 F·g -1 . A hybrid supercapacitor device NiS / NiS2@C / / PAC HSC is prepared with NiS / NiS2@C as a positive electrode and mesoporous activated carbon PAC as a negative electrode, the mass ratio of NiS / NiS2@C to mesoporous activated carbon is 1:3.6-1:3.7, the potential window of NiS / NiS2@C nanoparticles and PAC in a three-electrode system is 0-0.6 V and-1.0-0 V respectively, the CV characteristic measurement of the asymmetric supercapacitor is carried out in a potential range of 0-1.6 V, the asymmetric supercapacitor has an energy density of 56.5 Wh·kg -1 -1 at a power density of 800 W·kg -1 -1, still maintains an energy density of 35.6 Wh·kg -1 -1 at a high power density of 8000 W·kg -1 -1, and the specific capacitance retention rate is still as high as 90% after 5000 charge-discharge cycles at a current density of 1 A·g -1 .

2. The core-shell structured carbon-coated metal sulfide composite material according to claim 1, characterized in that, The specific method of step 1 is: dissolve nickel salt and 3,3',5,5'-azobenzene tetraacid in an aqueous solution composed of 12-15 ml of N,N-dimethylacetamide, 3-6 ml of deionized water and 200-400 ul of concentrated hydrochloric acid, and prepare a mixed solution A after stirring uniformly; wherein the molar ratio of the nickel salt to 3,3',5,5'-azobenzene tetraacid is 6:

1.

3. The core-shell structured carbon-coated metal sulfide composite material according to claim 1, characterized in that, The specific method of step 2 is: transfer the mixed solution A into a 50 ml stainless steel reaction kettle, then place the stainless steel reaction kettle in an oven for heat preservation at a temperature of 120-160 DEG C for 2-5 days, obtain a yellow powder after filtration, wash the yellow powder with ethanol for 3-4 times, and dry overnight in a vacuum environment to obtain an intermediate product Ni-soc-MOF.

4. The core-shell structured carbon-coated metal sulfide composite material according to claim 1 or 2, characterized in that, The nickel salt is one or more of nickel sulfate, nickel nitrate and nickel chloride.

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