CN111243871A - Novel NiSe2-coated mesoporous hollow carbon sphere composite, its preparation method and its application in supercapacitors - Google Patents

Abstract

The invention discloses a novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material, its preparation method and its application in supercapacitors. The present invention adopts a one-step method without any surfactant, in-situ synthesis of mesoporous carbon nanospheres with adjustable pore size and particle size under normal temperature stirring, and then uniformly deposits a layer of Ni(OH) ₂ nanosheets, and finally selenization to obtain the target product (HMCS/NiSe ₂ ), which solves the problem of excessive aggregation of pure Ni(OH) ₂ nanosheets; at the same time, the introduction of carbon also improves the conductivity of the entire material. The introduction of mesoporous carbon greatly alleviates the problem of volume expansion of pure NiSe ₂ nanosheets during the charging and discharging process of electrochemical tests. The composite material of the present invention is used as a positive electrode active material for supercapacitors, and its rate performance is very good. After 5000 cycles, 80.5% of the capacity is still maintained.

Description

Novel NiSe2-coated mesoporous hollow carbon sphere composite and its preparation method and its application in super Application of Capacitors

technical field

The invention belongs to the field of new energy materials, and in particular relates to a novel NiSe ₂ -coated mesoporous hollow carbon ball composite material, a preparation method thereof, and an application in a super capacitor.

Background technique

According to the energy formula of supercapacitor: E=1/2CV2, increasing the specific capacitance C and working voltage V of the capacitor can effectively improve the energy density of the supercapacitor. At the same time, the decomposition voltage of the electrolyte is the key factor affecting the supercapacitor. The positive and negative electrodes of traditional water-based electric double layer supercapacitors are generally activated carbon. However, due to the uneven pore size of activated carbon, many pores are closed and closed, resulting in a decrease in its specific surface area and a low material utilization rate. At the same time, due to the decomposition voltage of water itself, the working voltage of the entire supercapacitor is greatly limited. Therefore, in recent years, researchers have focused on improving the specific capacitance of the material and the voltage window of the electrolyte.

Due to its high specific surface area, abundant pore structure, and good stability, mesoporous carbon has become more and more widely used in supercapacitor electrode materials. Transition metal oxides (containing hydroxides) can obtain higher specific capacitance due to their unique energy storage principle. Ionic liquids have been increasingly used in supercapacitors in recent years due to their non-volatile, non-flammable, low toxicity and high voltage windows.

The patent application with the application number CN201610258568.2 discloses a preparation method and application of a surface selenium-enriched NiSe ₂ nanosheet. The NiSe ₂ nanosheet with selenium-enriched surface is obtained by synthesizing Ni(OH) ₂ nanosheet first, and then selenizing at high temperature, which has stable chemical properties, simple process and convenient operation, and is applied in the field of new energy. However, in the hydrothermal process, the equipment requirements are relatively high, the technical difficulty is relatively high, and the safety performance is not good. Moreover, in the high-temperature selenization process, the temperature needs to be set in sections, and the process is complicated. In addition, the patent application with the application number CN201711449574.7 discloses a method for preparing monodisperse mesoporous carbon microspheres. It first prepares SiO ₂ , and then uses it as an inorganic template agent to prepare mesoporous carbon microspheres through organic-inorganic hybrid reaction with organic precursors. The prepared mesoporous carbon microspheres have uniform particle size and controllable pore size, but the process is complicated, the preparation conditions are harsh, and the equipment requirements are high.

The present application is made for the above reasons.

SUMMARY OF THE INVENTION

In view of the above problems or defects in the prior art, the purpose of the present invention is to provide a novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material and a preparation method and application thereof.

In order to realize the above-mentioned first purpose of the present invention, the technical scheme adopted in the present invention is as follows:

A novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material, the composite material has a spherical structure as a whole, with a diameter of 400-500 nm; the NiSe ₂ is a nanosheet; the particle size of the mesoporous hollow carbon sphere is 300 nm ~400nm, the pore size distribution is concentrated in 8~12nm, and the carbon layer thickness is 20~40nm.

The second object of the present invention is to provide a method for preparing the above-mentioned novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material. The method specifically includes the following steps:

(1) Add the silicon source into the aqueous solution dissolved with ethanol and ammonia water according to the proportion, and ultrasonically disperse evenly; then add resorcinol and formaldehyde to the obtained mixed solution successively, and magnetically stir the reaction at room temperature for 20 to 30 hours. After the reaction is completed , filtered, washed and dried to obtain SiO ₂ /SiO ₂ @RF composite structure;

(2) The SiO ₂ /SiO ₂ @RF composite structure obtained in step (1) is placed in a tube furnace, and then heated to 600-800° C. in an inert gas atmosphere, and then kept for 2-5 hours to obtain SiO ₂ /SiO ₂ @CMaterial;

(3) placing the SiO ₂ /SiO ₂ @C material obtained in step (2) in concentrated nitric acid for acidification, then suction filtration, washing, and drying to obtain pretreated SiO ₂ /SiO ₂ @C;

(4) ultrasonically dispersing the pretreated SiO ₂ /SiO ₂ @C obtained in step (3) in deionized water, then adding nickel nitrate hexahydrate and urea in sequence, and heating in a water bath to 70-90° C. for constant temperature reaction after mixing for 4- 6h, after the reaction, suction filtration, washing, drying to obtain SiO ₂ /SiO ₂ @C/Ni(OH) ₂ material;

(5) the SiO ₂ /SiO ₂ @C/Ni(OH) ₂ material obtained in step (4) is placed in the middle of the porcelain boat, selenium powder is placed on both sides of the porcelain boat, and then the porcelain boat is placed in a tube furnace, In an inert gas atmosphere, the temperature is raised to 300～500℃ and kept for 1～3h to obtain SiO ₂ /SiO ₂ @C/NiSe ₂ material;

(6) placing the SiO ₂ /SiO ₂ @C/NiSe ₂ material obtained in step (5) in a NaOH aqueous solution for 20-30 h to obtain the NiSe ₂ -coated mesoporous hollow carbon sphere composite material (HMCS/NiSe ₂ ).

Further, in the above technical solution, the silicon source in step (1) is tetraethyl orthosilicate (TEOS), propyl orthosilicate (TPOS), methyl orthosilicate (TMOS) or sodium silicate (Na ₂ SiO ₃ ) any one or more of the above.

Further, in the above technical solution, the dosage ratio of the silicon source described in step (1) to ethanol, ammonia water and deionized water is 2mmol:60ml:3ml:20ml.

Further, in the above technical solution, 2 mmol of the silicon source and resorcinol in step (1): (0.3-0.5) g.

Further, in the above technical solution, the molar ratio of formaldehyde to resorcinol described in step (1) is 1-2:1.

Further, in the above technical solution, the ultrasonic dispersion time in step (1) is not limited, as long as the uniform dispersion of the silicon source in the aqueous solution is achieved, and the ultrasonic dispersion time is generally preferably 10-20 min.

Specifically, in the above technical solution, the ethanol in step (1) is used as a solvent, the ammonia water is used to provide alkaline conditions for the condensation reaction, the resorcinol is used to provide phenolic hydroxyl groups, and the formaldehyde is used to provide aldehyde hydroxyl groups .

The reaction mechanism of the above-mentioned step (1) of the present invention is as follows: during the stirring process at room temperature, the hydrolysis and condensation reaction of the silicon source generates SiO ₂ , which firstly nucleates internally (made up of countless SiO ₂ monomers), and then continues to generate SiO ₂ At the same time as a monomer, the two hydrogen atoms on the ortho-position of the resorcinol hydroxyl group are relatively active, and combine with the oxygen atom on the formaldehyde group to form a water molecule, and the rest are connected to form a polymer compound - phenolic resin (RF), which is The SiO ₂ generated after nucleation is embedded in the phenolic resin as a template for subsequent mesopores, and finally self-assembles to form a spherical SiO ₂ /SiO ₂ @RF composite structure.

Further, in the above technical solution, the purpose of high temperature calcination in step (2) is to completely carbonize the phenolic resin (RF) in the SiO ₂ /SiO ₂ @RF composite structure to obtain SiO ₂ /SiO ₂ @C.

Further, in the above technical solution, the acidification in step (3) is preferably carried out at 70-90° C., and the acidification time is preferably 10-20 min. The purpose of acidification in this step is to increase the hydrophilic functional groups on the surface of the mesoporous carbon.

Further, in the above technical solution, the nickel nitrate hexahydrate in step (4) is used as a nickel source, and the urea provides enough OH ⁻ for generating Ni(OH) ₂ .

Further, in the above technical solution, the molar ratio of nickel nitrate hexahydrate and urea in step (4) is 1:1 to 3, more preferably 1:2.

Further, in the above technical solution, the purpose of high temperature calcination in step (5) is to ensure that the selenium powder is reduced, thereby obtaining the target product HMCS/NiSe ₂ .

Further, in the above technical solution, the mass ratio of the SiO ₂ /SiO ₂ @C/Ni(OH) ₂ material to the selenium powder in step (5) is 1:2-5, more preferably 1:3.

Further, in the above technical scheme, the concentration of the aqueous NaOH solution in step (6) is 1-5 mol/L.

Further, in the above technical scheme, in step (6), the SiO ₂ /SiO ₂ @C/NiSe ₂ material is placed in an aqueous NaOH solution for etching, and the purpose is to use the NaOH aqueous solution to etch the SiO ₂ /SiO ₂ @C/NiSe ₂ material The _SiO2 in the middle is all etched away.

Further, in the above technical solution, the etching temperature in step (6) is preferably 60-90°C.

Further, in the above technical solution, the inert gas described in step (2) and step (5) is preferably argon whose volume percentage is greater than or equal to 99.95%.

The third object of the present invention is to provide the application of the above-mentioned novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material as a positive electrode material in supercapacitors.

A supercapacitor, comprising the above-mentioned novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material of the present invention.

An asymmetric supercapacitor, comprising a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, an electrolyte and a casing, wherein the positive electrode is coated and/or mixed with a positive electrode active material, a conductive agent and a binder. Or filled on the surface of the current collector to form; the negative electrode is formed by mixing the negative electrode active material with a conductive agent and a binder and then coating and/or filling it on the surface of the current collector; wherein: the positive electrode active material is the above-mentioned A novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material; the negative active material is the mesoporous hollow carbon sphere HCMS; the electrolyte is EMIMBF ₄ ionic liquid.

Further, in the above technical scheme, the mesoporous hollow carbon sphere HCMS is prepared by the following method, and the steps are as follows:

(i) adding the silicon source into the aqueous solution dissolved with ethanol and ammonia water according to the proportion, and ultrasonically dispersing evenly; then adding resorcinol and formaldehyde to the obtained mixed solution successively, and magnetically stirring the reaction at room temperature for 20 to 30 hours, and after the reaction finishes , filtered, washed and dried to obtain SiO ₂ /SiO ₂ @RF composite structure;

(ii) placing the SiO ₂ /SiO ₂ @RF composite structure obtained in step (i) in a tube furnace, and then heating the temperature to 600-800° C. under an inert gas atmosphere and holding the temperature for 2-5 hours to obtain SiO ₂ /SiO ₂ @CMaterial;

(iii) At room temperature, the SiO ₂ /SiO ₂ @C material obtained in step (ii) is placed in an aqueous NaOH solution for 20-30 hours, and then suction filtered, washed, and dried to obtain the mesoporous hollow carbon spheres HMCS.

Further, in the above technical solution, the concentration of the aqueous NaOH solution in step (iii) is 1-5 mol/L.

Further, in the above technical solution, in step (iii), the SiO ₂ /SiO ₂ @C material is placed in a NaOH aqueous solution for reaction, and the purpose is to use the NaOH aqueous solution to etch away all SiO ₂ in the SiO ₂ /SiO ₂ @C material.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The mesoporous carbon materials prepared by the present invention have all open pores in size. In addition, the new NiSe ₂ -coated mesoporous hollow carbon sphere composite material of the present invention is also coated with nano-flaky NiSe ₂ on the surface of the mesoporous carbon. , which can greatly increase its surface area and improve the utilization rate of materials.

(2) The present invention adopts a simple water bath method to synthesize Ni(OH) ₂ nanosheets, and the selenization process is simple and feasible.

(3) The present invention adopts a one-step method without any surfactant, in-situ synthesis of mesoporous carbon nanospheres with adjustable pore size and particle size at room temperature, and then uniformly deposit a layer of Ni on the surface of the water bath using a simple chemical precipitation method (OH) ₂ nanosheets, the method is simple and feasible, and the safety performance is good. The problem of excessive aggregation of pure Ni(OH) ₂ nanosheets is solved, and the introduction of carbon also improves the conductivity of the entire material. The introduction of mesoporous carbon largely alleviates the problem of volume expansion of pure NiSe ₂ nanosheets during the charge-discharge process of electrochemical tests. Therefore, as a positive electrode active material for a supercapacitor, the present invention has good rate performance, and still maintains 80.5% of the capacity after 5000 cycles.

(4) The present invention uses NaOH to etch SiO ₂ , which greatly reduces the risk of experiments. The whole preparation process is relatively simple, easy to operate and has high safety performance. In addition, the supercapacitor prepared by the present invention is green and environmentally friendly, and the specific capacitance and stability are greatly improved, and the energy density is high, which improves the disadvantage of the low energy density of the supercapacitor to a certain extent.

Description of drawings

1 is a schematic structural diagram of a NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2) of Example 1 of the present invention;

2 is the XRD diffraction pattern of the mesoporous hollow carbon spheres (HMCS) prepared in step (1) of Example 1 of the present invention and the NiSe ₂ -coated mesoporous hollow carbon spheres composite (HMCS/NiSe ₂ ) prepared in step (2) ;

Fig. 3 is the SEM photograph of the mesoporous hollow carbon sphere (HMCS) prepared in step (1) of Example 1 of the present invention;

4 is a SEM photograph of the NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2) of Example 1 of the present invention;

5 is a TEM photograph of the mesoporous hollow carbon sphere (HMCS) prepared in step (1) of Example 1 of the present invention;

6 is a TEM photograph of the NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2) of Example 1 of the present invention;

Fig. 7 is the nitrogen adsorption, desorption and pore size distribution diagram of the NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2) of Example 1 of the present invention; wherein: the inset is the pore size distribution picture;

8 is a Raman diagram of the mesoporous hollow carbon spheres (HMCS) prepared in step (1) of Example 1 of the present invention and the NiSe ₂ -coated mesoporous hollow carbon spheres composite (HMCS/NiSe ₂ ) prepared in step (2);

Fig. 9 is the rate performance test result diagram of the battery prepared by Application Example 1;

FIG. 10 is a graph showing the test results of the cycle performance of the battery prepared in Application Example 1. FIG.

Detailed ways

The present invention will be described in further detail below by means of an example of implementation. This example is implemented on the premise of the technology of the present invention. Now, the detailed implementation and specific operation process are given to illustrate the inventiveness of the present invention, but the protection scope of the present invention is not limited to the following examples of implementation.

From the information contained in this application, various changes to the precise description of the present invention can be readily made by those skilled in the art without departing from the spirit and scope of the appended claims. It is to be understood that the scope of the invention is not limited to the processes, properties or components defined, as these embodiments and other descriptions are intended to be illustrative only of particular aspects of the invention. Indeed, various modifications of the embodiments of the invention that are obvious to those skilled in the art or related fields are intended to be within the scope of the appended claims.

For a better understanding of the invention and not to limit the scope of the invention, all numbers expressing amounts, percentages, and other numerical values used in this application should in all cases be understood as modified by the word "about". Accordingly, unless expressly stated otherwise, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At a minimum, each numerical parameter shall be deemed to have been obtained from the reported significant digits and by conventional rounding methods.

The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

Example 1

The preparation method of a novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material in this embodiment specifically includes the following steps:

(1) Preparation of mesoporous hollow carbon spheres

(i) Using propyl orthosilicate (TPOS) and ethyl orthosilicate (TEOS) as silicon sources, ultrasonically dispersed in an aqueous solution of ethanol (solvent) and ammonia (alkaline conditions) for 10 min, and then adding isophthalic acid Phenol (used to provide phenolic hydroxyl groups) and formaldehyde (used to provide aldehyde hydroxyl groups), and then the resulting mixture was magnetically stirred at room temperature for 20 h, and finally filtered, washed, and dried to obtain a SiO ₂ /SiO ₂ @RF composite structure. Wherein the consumption of TPOS, TEOS is respectively 0.5mmol, 1.5mmol; The consumption of ethanol, ammoniacal liquor, deionized water is successively 60ml, 3ml, 20ml, the consumption of resorcinol is 0.4g, and the consumption of formaldehyde is 0.56ml ( The density of described formaldehyde is 300mg/ml);

(ii) The SiO ₂ /SiO ₂ @RF composite structure prepared by the method in step (i) is placed in a high temperature tube furnace, and kept in an argon atmosphere for 2 hours to completely carbonize the phenolic resin, and its carbonization temperature remains At 700°C, SiO ₂ /SiO ₂ @C material was obtained.

(iii) at room temperature, put the SiO ₂ /SiO ₂ @C material prepared by the method in step (ii) into an aqueous NaOH solution for 30 hours to ensure that all SiO ₂ in the material is etched by NaOH, and finally suction filtration and washing , and dried; the concentration of the NaOH aqueous solution used was 1 mol/L, and finally hollow mesoporous carbon nanospheres (HMCS) were obtained.

(2) Preparation of NiSe ₂ -coated mesoporous hollow carbon sphere composites

(a) Take 0.1 g of the SiO ₂ /SiO ₂ @C material prepared in the above step (ii), ultrasonically disperse it in 50 ml of concentrated nitric acid, then heat to 80 °C and stir for 15 min to increase the hydrophilic functional groups on the surface of mesoporous carbon. Then, deionized water and absolute ethanol are used for suction filtration, washing, and finally drying to obtain pretreated hollow mesoporous carbon nanospheres.

(b) ultrasonically disperse all the pretreated hollow mesoporous carbon nanospheres obtained in step (a) in 100 ml of deionized water, add 0.29 g of nickel nitrate hexahydrate (nickel source) after ultrasonication for 30 min, and heat to 80 °C under magnetic stirring 15min, then add 1.2g urea (provide enough OH ^- ), continue to heat in a water bath at 80°C for 5h, finally suction filter, wash, collect the solid product, and dry to obtain SiO ₂ /SiO ₂ @C/Ni(OH) ₂ materials.

(c) get 0.1g of SiO ₂ /SiO ₂ @C/Ni(OH) ₂ material prepared by the method described in step (b) and put it into the middle of the porcelain boat, and put 0.15g (total 0.3g) selenium powder on both sides of the porcelain boat , and then put the porcelain boat into the tube furnace, heated to 400 ℃ under the argon atmosphere, and then continued to keep at 400 ℃ in the argon atmosphere for 2 hours to ensure that the selenium powder was reduced to obtain SiO ₂ /SiO ₂ @C /NiSe ₂ material.

(d) The SiO ₂ /SiO ₂ @C/NiSe ₂ material obtained in step (c) was placed in 100 ml of NaOH aqueous solution with a concentration of 4 mol/L, heated to 80 °C for constant temperature etching for 20 h, to obtain the new NiSe _2. Coated mesoporous hollow carbon sphere composites (HMCS/NiSe ₂ ).

Figure 1 is a schematic structural diagram of the NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2) of Example 1 of the present invention; it can be seen from the figure that the entire composite structure has abundant voids and voids. A thin layer of NiSe ₂ nanosheets is also grown on the outside of the carbon layer. The porous structure has a good inhibitory effect on the volume expansion of NiSe ₂ during charge and discharge. In addition, the introduction of the carbon shell makes NiSe ₂ expose more active sites, which further improves its performance.

2 is the XRD diffraction pattern of the mesoporous hollow carbon spheres (HMCS) prepared in step (1) of Example 1 and the NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2). According to the standard card JCPDS No.41-1445, the positions of the diffraction peaks (2θ=29.95°, 33.58°, 36.89°, 42.86°, 50.74°, 53.17°, 55.52°, 57.81°, 62.23°) correspond to the crystal planes ( (200), (210), (211), (220), (311), (222), (023), (321), (400), according to the lattice constant a=b=c=5.9604, it is determined to be Cubic NiSe ₂ with a broad carbon peak at 2θ=24.9°, confirming the product as pure HMCS/NiSe ₂ without other impurities.

Figure 3 is an SEM photo of the mesoporous hollow carbon sphere (HMCS) prepared in step (1) of Example 1. It can be seen that its overall shape is spherical, its size is similar, and its dispersibility is good.

Figure 4 is a SEM photo of the NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2) of Example 1. It can be seen from this figure that the NiSe ₂ -coated NiSe 2 prepared in this example The mesoporous hollow carbon sphere composite material is a spherical structure with NiSe ₂ nanosheets growing on the surface. Located around 10nm, the carbon layer thickness is around 30nm. It can also be seen that the NiSe ₂ nanosheets are uniformly coated on the surface of the hollow spheres, exposing more active sites, making it have a higher specific capacitance. In addition, the existence of hollow mesopores in the composite also lays the foundation for the subsequent excellent electrochemical performance.

5 is a TEM photo of the mesoporous hollow carbon sphere (HMCS) prepared in step (1) of Example 1. It can be clearly seen that it has a pore structure, and a thin layer of carbon shell on the outer edge is clearly seen. The pore structure can alleviate the volume expansion problem of the material due to the rapid adsorption and desorption of ions in high current discharge.

6 is a TEM photograph of the NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2) of Example 1 of the present invention. It can be confirmed from Fig. 5 that the shape of the composite material remains spherical with nanosheets on the surface, which fully conforms to the above description.

7 is a graph of nitrogen adsorption, desorption and pore size distribution of the NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2) of Example 1 of the present invention. After testing, the surface area of the composite is 381.4m ² g ^-1 , far exceeding that of pure NiSe ₂ nanosheets, which further confirms that the introduction of mesoporous carbon can expose more active sites. It can also be clearly seen from Figure 6 that it has a typical IV-type curve, indicating the existence of mesopores. It can also be seen intuitively from the pore size distribution that there are a large number of mesopores around 10 nm, which are very beneficial for ion storage. .

8 is a Raman diagram of the mesoporous hollow carbon spheres (HMCS) prepared in step (1) of Example 1 of the present invention and the NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2). As can be seen from Fig. 7, two distinct peaks of HMCS at 1300 cm ^-1 and 1580 cm ^-1 match with D-band (disordered carbon) and G-band (graphitic carbon). The intensity of D-band: G-band (ID/IG )=0.98, which further indicates that it is amorphous carbon and has fewer defects. Compared with the Raman curve of HMCS/NiSe ₂ , its ratio increases to 1.2, which further indicates that after the two materials are combined, the defects are further increased and the degree of graphitization is higher. , the conductivity is higher, and the electron transfer for subsequent electrochemical performance tests is faster.

Example 2

The preparation method of a novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material in this embodiment specifically includes the following steps:

(1) Preparation of mesoporous hollow carbon spheres

(i) Ultrasonic dispersion of methyl orthosilicate (TMOS) as silicon source in an aqueous solution dissolved in ethanol (solvent) and ammonia (alkaline conditions) for 15 min, followed by addition of resorcinol (for providing phenolic hydroxyl groups) and formaldehyde (used to provide aldehyde hydroxyl group), and then the obtained mixed solution was magnetically stirred at room temperature for 25 h, and finally suction filtered, washed, and dried to obtain a SiO ₂ /SiO ₂ @RF composite structure. Wherein the consumption of described TMOS is 2mmol; The consumption of ethanol, ammoniacal liquor, deionized water is successively 60ml, 3ml, 20ml, the consumption of resorcinol is 0.3g, the consumption of formaldehyde is 0.56ml (the density of described formaldehyde is 300mg /ml);

(ii) The SiO ₂ /SiO ₂ @RF composite structure prepared by the method of step (i) was kept in a high temperature tube furnace under argon atmosphere for 3 hours, and the phenolic resin was completely carbonized, and the carbonization temperature was kept at 800° C. , the SiO ₂ /SiO ₂ @C material was obtained.

(iii) at room temperature, put the SiO ₂ /SiO ₂ @C material prepared by the method in step (ii) into an aqueous NaOH solution for 25 hours to ensure that all SiO ₂ in the material is etched by NaOH, and finally suction filtration and washing , and dried; the concentration of the NaOH aqueous solution used was 2 mol/L, and finally hollow mesoporous carbon nanospheres (HMCS) were obtained.

(2) Preparation of NiSe ₂ -coated mesoporous hollow carbon sphere composites

(a) Take 0.1 g of the SiO ₂ /SiO ₂ @C material prepared in the above step (ii), ultrasonically disperse it in 50 ml of concentrated nitric acid, then heat to 70 °C and stir for 20 min to increase the hydrophilic functional groups on the surface of mesoporous carbon. Then use deionized water and anhydrous ethanol to perform suction filtration, washing, and finally drying to obtain pretreated SiO ₂ /SiO ₂ @C.

(b) ultrasonically disperse all the pretreated SiO ₂ /SiO ₂ @C obtained in step (a) in 100 ml of deionized water, add 0.29 g of nickel nitrate hexahydrate (nickel source) after ultrasonication for 30 min, and heat to 80 °C under magnetic force Stir for 15min, then add 1.8g urea (provide enough OH ^- ), continue to heat in a water bath at 70°C for 6h, finally filter, wash, collect the solid product, and dry to obtain SiO ₂ /SiO ₂ @C/Ni(OH ) ₂ materials.

(c) take 0.1g of SiO ₂ /SiO ₂ @C/Ni(OH) ₂ material prepared by the method described in step (b) and put it into the middle of the porcelain boat, and put 0.1g (total 0.2g) selenium powder on both sides of the porcelain boat , and then put the porcelain boat into the tube furnace, heated to 500 ℃ under the argon atmosphere, and continued to keep the temperature at 500 ℃ for 1 h under the argon atmosphere to ensure that the selenium powder was reduced, and obtained SiO ₂ /SiO ₂ @C/ NiSe ₂ material.

(d) The SiO ₂ /SiO ₂ @C/NiSe ₂ material obtained in step (c) was placed in 100 ml of NaOH aqueous solution with a concentration of 2 mol/L, heated to 90 ° C for constant temperature etching for 30 h, to obtain the new type of NiSe _2. Coated mesoporous hollow carbon sphere composites (HMCS/NiSe ₂ ).

Example 3

The preparation method of a novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material in this embodiment specifically includes the following steps:

(1) Preparation of mesoporous hollow carbon spheres

(i) ultrasonically disperse sodium silicate (Na ₂ SiO ₃ ) as a silicon source in an aqueous solution dissolved in ethanol (solvent) and ammonia (alkaline conditions) for 20 min, followed by adding resorcinol (for providing phenolic hydroxyl groups) and formaldehyde (used to provide aldehyde hydroxyl groups), and then the resulting mixture was stirred magnetically for 30 h at room temperature, and finally filtered, washed, and dried to obtain a SiO ₂ /SiO ₂ @RF composite structure. Wherein the consumption of the sodium silicate is 2mmol; the consumption of ethanol, ammonia water, deionized water is successively 60ml, 3ml, 20ml, the consumption of resorcinol is 0.5g, and the consumption of formaldehyde is 0.56ml (the density of the formaldehyde 300mg/ml);

(ii) The SiO ₂ /SiO ₂ @RF composite structure prepared by the method of step (i) was kept in a high temperature tube furnace under argon atmosphere for 5 hours, and the phenolic resin was completely carbonized, and the carbonization temperature was kept at 600° C. , the SiO ₂ /SiO ₂ @C material was obtained.

(iii) at room temperature, put the SiO ₂ /SiO ₂ @C material prepared by the method in step (ii) into an aqueous NaOH solution for 20 hours to ensure that all SiO ₂ in the material is etched by NaOH, and finally suction filtration and washing , and dried; the concentration of the NaOH aqueous solution used was 3 mol/L, and finally hollow mesoporous carbon nanospheres (HMCS) were obtained.

(2) Preparation of NiSe ₂ -coated mesoporous hollow carbon sphere composites

(a) Take 0.1 g of the SiO ₂ /SiO ₂ @C material prepared in the above step (ii), ultrasonically disperse it in 50 ml of concentrated nitric acid, then heat to 90 °C and stir for 10 min to increase the hydrophilic functional groups on the surface of mesoporous carbon. Then, deionized water and absolute ethanol are used for suction filtration, washing, and finally drying to obtain pretreated hollow mesoporous carbon nanospheres.

(b) ultrasonically disperse the pretreated (0.1 g) SiO ₂ /SiO ₂ @C obtained in step (a) in 100 ml of deionized water, add 0.29 g of nickel nitrate hexahydrate (nickel source) after ultrasonication for 30 min, and heat to Magnetic stirring at 80°C for 15min, then add 0.9g urea (provide enough OH ^- ), continue heating in a water bath at 70°C for 6h, finally filter, wash, collect the solid product, and dry to obtain SiO ₂ /SiO ₂ @C /Ni(OH) ₂ material.

(c) take 0.1g of SiO ₂ /SiO ₂ @C/Ni(OH) ₂ material prepared by the method described in step (b) and put it into the middle of the porcelain boat, and put 0.25g (total 0.5g) selenium powder on both sides of the porcelain boat , and then put the porcelain boat into the tube furnace, heat it to 300 ℃ in an argon atmosphere, and continue to keep it in an argon atmosphere at 300 ℃ for 3 hours to ensure that the selenium powder is reduced to obtain SiO ₂ /SiO ₂ @C/NiSe ₂ Material.

(d) placing the SiO ₂ /SiO ₂ @C/NiSe ₂ material obtained in step (c) in 100ml of NaOH aqueous solution with a concentration of 5mol/L, heating to 60°C for constant temperature etching for 25h, to obtain the new type of NiSe _2. Coated mesoporous hollow carbon sphere composites (HMCS/NiSe ₂ ).

Application Example 1

This embodiment provides an asymmetric supercapacitor, including a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, an electrolyte, and a casing. Acetylene black and PTFE are mixed and coated on the surface of nickel foam to form; the negative electrode is formed by mixing the negative electrode active material with acetylene black and PTFE in a mass ratio of 8:1:1 and then coated on the surface of nickel foam; wherein: The positive active material is the novel NiSe ₂ -coated mesoporous hollow carbon sphere composite (HMCS/NiSe ₂ ) prepared in step (2) of Example 1; the negative active material is the hollow hollow carbon prepared in step (1) of Example 1. Mesoporous carbon nanospheres (HMCS); the separator is a PTFE film; the electrolyte is an ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF ₄ ). Asymmetric supercapacitors were assembled using CR 2032 button cells for electrochemical performance testing.

FIG. 9 is a graph of the test results of the rate performance of the asymmetric supercapacitor prepared in this application example. It can be clearly seen from Figure 9 that as the current density increases, the capacity decreases slowly, which is basically consistent with the analysis and prediction of its performance in the description of the material structure above. It is further explained that the introduction of mesoporous carbon can not only play a buffering role, so that the material deformation is smaller under high current density. At the same time, its conductivity is improved as a whole, more ions are transmitted in the same time, and more energy is stored.

FIG. 10 is a graph of the cycle performance test results of the asymmetric supercapacitors prepared in this application example. It can be seen from Figure 10 that after 5000 cycles, the capacity decays less and still maintains 80.5% of the capacity, indicating that its stability is relatively good, which further confirms the above.

Claims (10)

1. A novel NiSe ₂ -coated mesoporous hollow carbon sphere composite material, characterized in that: the composite material has a spherical structure as a whole, with a diameter of 400-500 nm; the NiSe ₂ is a nanosheet; the mesoporous hollow carbon The particle size of the ball is 300-400 nm, the pore size distribution is concentrated at 8-12 nm, and the thickness of the carbon layer is 20-40 nm. 2. the preparation method of NiSe ₂ coating mesoporous hollow carbon sphere composite material according to claim 1, is characterized in that: (1) Add the silicon source into the aqueous solution dissolved with ethanol and ammonia water according to the proportion, and ultrasonically disperse evenly; then add resorcinol and formaldehyde to the obtained mixed solution successively, and magnetically stir the reaction at room temperature for 20 to 30 hours. After the reaction is completed , filtered, washed and dried to obtain SiO ₂ /SiO ₂ @RF composite structure; (2) The SiO ₂ /SiO ₂ @RF composite structure obtained in step (1) is placed in a tube furnace, and then heated to 600-800° C. in an inert gas atmosphere, and then kept for 2-5 hours to obtain SiO ₂ /SiO ₂ @CMaterial; (3) placing the SiO ₂ /SiO ₂ @C material obtained in step (2) in concentrated nitric acid for acidification, then suction filtration, washing, and drying to obtain pretreated SiO ₂ /SiO ₂ @C; (4) ultrasonically dispersing the pretreated SiO ₂ /SiO ₂ @C obtained in step (3) in deionized water, then adding nickel nitrate hexahydrate and urea in sequence, and heating in a water bath to 70-90° C. for constant temperature reaction after mixing for 4- 6h, after the reaction, suction filtration, washing, drying to obtain SiO ₂ /SiO ₂ @C/Ni(OH) ₂ material; (5) the SiO ₂ /SiO ₂ @C/Ni(OH) ₂ material obtained in step (4) is placed in the middle of the porcelain boat, selenium powder is placed on both sides of the porcelain boat, and then the porcelain boat is placed in a tube furnace, In an inert gas atmosphere, the temperature is raised to 300～500℃ and kept for 1～3h to obtain SiO ₂ /SiO ₂ @C/NiSe ₂ material; (6) placing the SiO ₂ /SiO ₂ @C/NiSe ₂ material obtained in step (5) in a NaOH aqueous solution for 20-30 h to obtain the NiSe ₂ -coated mesoporous hollow carbon sphere composite material HMCS/NiSe ₂ . 3. The preparation method of NiSe ₂ coated mesoporous hollow carbon sphere composite material according to claim 2, characterized in that: the silicon source described in step (1) is ethyl orthosilicate, propyl orthosilicate, ortho-silicon Any one or more of methyl ester or sodium silicate. 4 . The preparation method of NiSe ₂ coated mesoporous hollow carbon sphere composite material according to claim 2 , wherein the molar ratio of formaldehyde and resorcinol in step (1) is 1-2:1. 5 . 5 . The preparation method of NiSe ₂ coated mesoporous hollow carbon sphere composite material according to claim 2 , wherein the molar ratio of nickel nitrate hexahydrate and urea in step (4) is 1:1-3. 6 . 6. The preparation method of NiSe ₂ coated mesoporous hollow carbon sphere composite material according to claim 2, characterized in that: SiO ₂ /SiO ₂ @C/Ni(OH) ₂ material and selenium described in step (5) The mass ratio of powder is 1:2～5. 7. Application of the NiSe ₂ -coated mesoporous hollow carbon sphere composite material according to claim 1 or the NiSe ₂ -coated mesoporous hollow carbon sphere composite material prepared by the method of any one of claims 2 to 6 in supercapacitors . 8. A supercapacitor positive electrode, characterized in that it comprises the NiSe ₂ -coated mesoporous hollow carbon sphere composite material according to claim 1 or the NiSe ₂ -coated mesoporous composite material prepared by the method according to any one of claims 2 to 6 Hollow carbon sphere composite. 9. An asymmetrical supercapacitor, characterized in that: comprising a positive electrode, a negative electrode, a diaphragm, an electrolyte and a shell that are arranged between the positive and negative electrodes, and the positive electrode is to mix the positive electrode active material with a conductive agent and an adhesive. After being uniformly coated and/or filled on the surface of the current collector, the negative electrode is formed by mixing the negative electrode active material with a conductive agent and a binder and then coating and/or filling it on the surface of the current collector; wherein: the positive electrode is active The material is the NiSe ₂ -coated mesoporous hollow carbon sphere composite material according to claim 1 or the NiSe ₂ -coated mesoporous hollow carbon sphere composite material prepared by the method according to any one of claims 2 to 6; the negative electrode active material It is mesoporous hollow carbon sphere HCMS; the electrolyte is EMIMBF ₄ ionic liquid. 10. The asymmetric supercapacitor according to claim 9, wherein the mesoporous hollow carbon sphere HCMS is prepared by the following method, and the steps are as follows: (i) adding the silicon source into the aqueous solution dissolved with ethanol and ammonia water according to the proportion, and ultrasonically dispersing evenly; then adding resorcinol and formaldehyde to the obtained mixed solution successively, and magnetically stirring the reaction at room temperature for 20 to 30 hours, and after the reaction finishes , filtered, washed and dried to obtain SiO ₂ /SiO ₂ @RF composite structure; (ii) placing the SiO ₂ /SiO ₂ @RF composite structure obtained in step (i) in a tube furnace, and then heating the temperature to 600-800° C. under an inert gas atmosphere and holding the temperature for 2-5 hours to obtain SiO ₂ /SiO ₂ @CMaterial; (iii) At room temperature, the SiO ₂ /SiO ₂ @C material obtained in step (ii) is placed in an aqueous NaOH solution for 20-30 hours, and then suction filtered, washed, and dried to obtain the mesoporous hollow carbon spheres HMCS.

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