Preparation method and application of Co-Ni-S hollow microspherical composite material

Abstract

The application discloses a Co-Ni-S hollow microspherical composite material, which is prepared from cobalt nitrate hexahydrate, nickel nitrate hexahydrate, gallium nitrate hydrate, urea, ammonium fluoride and sodium sulfide nonahydrate as raw materials through a first step of hydrothermal reaction to prepare Co-Ni-Ga-CH, and then through a second step of hydrothermal reaction to prepare Co-Ni-S, which is abbreviated as Co-Ni-S. The micro-morphology of the Co-Ni-Ga-CH is a hollow microspherical structure, wherein the microsphere surface is composed of smooth sheets; the Co-Ni-S is composed of (Co, Ni)3S4 and NiS, and there is no Ga(OH)3 and other related compounds containing Ga element, the micro-morphology of the Co-Ni-S is still a hollow microspherical structure, and the microsphere surface is composed of fibrous porous sheets, the specific surface area of the Co-Ni-S is 20-40 m 2 g ‑1 , and the pore size distribution is 2-4 nm and 20-40 nm. The Ga element can be recycled. The preparation method comprises the following steps: 1, preparation of a Co-Ni-Ga-CH precursor; 2, preparation of the Co-Ni-S hollow microspherical composite material. As an application of the supercapacitor electrode material, the charging and discharging are carried out in a voltage window range of 0-0.5 V, and the specific capacitance is 1400-1450 F g ‑1 when the current density is 1 A g ‑1 .

Description

Technical Field

[0001] This invention relates to the field of supercapacitor technology, specifically to a method for preparing and applying a Co-Ni-S hollow microsphere composite material. Background Technology

[0002] Metal sulfides, as electrode materials for supercapacitors, exhibit superior performance compared to pseudocapacitive active materials such as transition metal oxides, hydroxides, and their complexes due to their high conductivity and chemical stability. The low electronegativity of metal sulfides significantly enhances their conductivity; however, current technical challenges include significant volume changes during cycling. Furthermore, powdered metal sulfides suffer from agglomeration issues due to the high surface energy between particles.

[0003] To address the aforementioned issues of volume change and agglomeration, the microstructure of the composite material can be improved by introducing a carrier. For example, existing technology 1 (Qiu J, Bai Z, Liu S, et al. Formation of nickel-cobaltsulphide@graphene composites with enhanced electrochemical capacitive properties[J]. RSC advances,2019,9(12):6946-6955.) successfully embedded nickel-cobalt sulfide particles Ni-Co-S into the graphene layer G by performing one-step annealing, carbonization, and sulfidation on a metallocene / metal-organic framework (MOF) hybrid, thus obtaining a Ni-Co-S@G composite material; achieving a current density of 1 Ag -1 The specific capacitance is 1463F g. -1 The existing technology demonstrates that by dispersing particles within a graphene layer support, a stacked layered structure is obtained, which can improve electrochemical performance to some extent. However, according to the SEM test results in this literature, the layered structure of the support is severely stacked, thus restricting ion diffusion between the electrolyte and the material, ultimately limiting the improvement in electrochemical performance.

[0004] To obtain a carrier with a more regular microstructure, graphene with a specific morphology can be used as the carrier. For example, prior art 2 (Jing C, Guo X, Xia L, et al. Morphologically confined hybridization of tiny CoNi2S4 nanosheets into S,P co-doped graphene leading to enhanced pseudocapacitance and rate capability[J]. Chemical Engineering Journal, 2020, 379:122305.) first prepares graphene oxide using concentrated sulfuric acid via the typical Hummer method, then modifies it using Ho Seok Park's method to obtain S and P co-doped graphene DG. Next, the carrier DG is mixed with a metal salt and subjected to a two-step hydrothermal process to obtain a precursor, which is then sulfided to obtain a composite material of CoNi2S4 nanosheets and S and P co-doped graphene, DGNCS. The resulting DGNCS electrode material, combined with modified graphene, has a wrinkled sheet structure. Because it improves the aggregation of CoNi2S4 and exposes more active sites, it provides a better 2Ag... -1 A current density of 1136.5 F g was obtained. -1 The specific capacitance is high. However, concentrated sulfuric acid is required in the preparation of graphene oxide. Since concentrated sulfuric acid is a controlled reagent, there are safety hazards and high management costs during production.

[0005] Besides graphene, MXene with an accordion-like layered morphology can also be used as a carrier. For example, existing technology 3 (Li Y, Kamdem P, Jin X J. In situ growth of chrysanthemum-like NiCo2S4 on MXenes for high-performance supercapacitors and a non-enzymatic H2O2 sensor[J]. Dalton Transactions, 2020, 49(23): 7807-7819.) first obtains MXene dispersion and chrysanthemum-like NiCo2S4 metal sulfide by strong acid etching and two-step hydrothermal method, respectively, and then stirs and mixes the two to obtain a three-dimensional sandwich structure MXene / NiCo2S4 composite electrode material, in 0.5Ag -1 1266 F g was obtained at a current density. -1The specific capacitance is low. Although this technical solution yields a chrysanthemum-shaped NiCo2S4 metal sulfide with a three-dimensional structure, the overall performance of the composite material is not significantly improved after introducing the MXene carrier due to the lack of porous or hollow structures. Furthermore, HF must be used in the preparation of MXene, and HF is also a hazardous chemical.

[0006] To avoid the technical problems arising from adjusting the morphology of the support, as seen in existing technologies 2 and 3, a three-dimensional hierarchical porous / hollow structure can be constructed on the metal sulfide itself. This achieves the technical effect of having more electroactive sites and ideal porosity, thereby improving electrochemical performance. For example, existing technology 4 (Shi Z, Shen X, Zhang Z, et al. Hierarchically urchin-like hollow NiCo2S4 prepared by a facile template-free method for high-performance supercapacitor[J]. Journal of Colloid and Interface Science, 2021, 604: 292-300.) successfully prepared sea urchin-shaped hollow NiCo2S4 microspheres using a template-free solvothermal method with isopropanol and ethanol as solvents. The microspheres are hollow inside and have a sea urchin-like exterior, composed of multi-level nanorods. Although a hollow structure is formed, the maximum specific surface area is only 34.6 m², due to the nanorod composition of its surface and the relatively uniform pore size. 2 g -1 The average pore size is 28.3 nm, resulting in the urchin-like hollow NiCo2S4 material exhibiting high porosity at 1 Ag. -1 The specific capacitance at that time was only 1398F g -1 Meanwhile, isopropanol and ethanol, organic solvents used in the material synthesis process, are flammable and hazardous materials, posing safety concerns as well. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing Co-Ni-S hollow microsphere composite materials and their applications.

[0008] This invention addresses the technical problems existing in the prior art. First, a hollow microsphere-shaped Co-Ni-Ga-CH is synthesized via hydrothermal treatment. Then, through a second hydrothermal treatment, Co-Ni-Ga-CH is sulfided to form a Co-Ni-S hollow microsphere structure without altering the hollow microsphere structure. After soaking and washing with a large amount of deionized water, Ga elements that do not provide pseudocapacitive performance are removed. The controllable hollow structure and the formation of fibrous porous sheets on the surface of the microspheres, along with the abundant pore structure, facilitate rapid electrolyte wetting and ion transport, thereby improving the supercapacitor performance of the composite material.

[0009] To achieve the aforementioned objectives, the technical solution adopted by this invention is as follows:

[0010] A Co-Ni-S hollow microsphere composite material is prepared by first preparing Co-Ni-Ga-CH through a hydrothermal reaction, and then obtaining it through a second hydrothermal reaction. It is referred to as Co-Ni-S.

[0011] The Co-Ni-Ga-CH is composed of (Ni 6.1 Co 2.9 (OH) 18.27 (CO3) 1.315 Composed of 6,7H2O and Ga(OH)3, the microstructure of Co-Ni-Ga-CH is a hollow microsphere structure, in which the surface of the microsphere is composed of smooth thin sheets;

[0012] The Co-Ni-S is composed of (Co,Ni)3S4 and NiS, and does not contain Ga(OH)3 or other related compounds containing Ga. The microstructure of Co-Ni-S is still a hollow microsphere structure, and the surface of the microsphere is composed of fibrous porous sheets.

[0013] The Ga element in the gallium nitrate hydrate can be converted back into gallium nitrate hydrate through simple operations after preparation, which means that the Ga element has the characteristic of recycling.

[0014] The specific surface area of ​​the Co-Ni-S is 30-40 m². 2 g -1 The pore size distribution is 2-4 nm and 20-40 nm.

[0015] A method for preparing a Co-Ni-S hollow microsphere composite material includes the following steps:

[0016] Step 1, Preparation of Co-Ni-Ga-CH precursor: First, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and gallium nitrate hydrate are dissolved in deionized water to obtain solution A. At the same time, urea and ammonium fluoride are dissolved in deionized water to obtain solution B. Then, solutions A and B are mixed and subjected to a hydrothermal reaction under certain conditions. Finally, the product obtained from the hydrothermal reaction is washed and dried to obtain the Co-Ni-Ga-CH precursor, abbreviated as Co-Ni-Ga-CH.

[0017] In step 1, the molar ratio of cobalt nitrate hexahydrate, nickel nitrate hexahydrate, gallium nitrate hydrate, urea, and ammonium fluoride is 0.3:1.7:2:10:15; the hydrothermal reaction conditions in step 1 are a hydrothermal temperature of 140°C and a hydrothermal time of 12 hours.

[0018] Step 2, Preparation of Co-Ni-S Hollow Microsphere Composite Material: First, the Co-Ni-Ga-CH obtained in Step 1 is placed in deionized water and stirred after sonication to obtain mixture C. At the same time, sodium sulfide nonahydrate is dissolved in deionized water to obtain solution D. Then, under stirring conditions, solution D is quickly added to mixture C and mixed. A hydrothermal reaction is then carried out under certain conditions to achieve sulfidation treatment. Finally, the product obtained from the hydrothermal reaction is soaked, washed, and dried to obtain the Co-Ni-S hollow microsphere composite material, abbreviated as Co-Ni-S.

[0019] In step 2, the mass ratio of Co-Ni-Ga-CH and sodium sulfide nonahydrate is 1:5; the hydrothermal reaction conditions in step 2 are: hydrothermal temperature of 160℃ and hydrothermal time of 12h.

[0020] The specific conditions for soaking and washing in step 2 are as follows: deionized water is used, and the soaking time is 0.5-1h to achieve complete removal of Ga element.

[0021] The application of a Co-Ni-S hollow microsphere composite material as an electrode material for supercapacitors was demonstrated, exhibiting charge-discharge performance within a voltage window of 0-0.5V and at a current density of 1A g. -1 At that time, the specific capacitance was 1400-1450F g -1 .

[0022] The technical effects of this invention have been tested experimentally, and the specific details are as follows:

[0023] XRD testing of this invention revealed that Co-Ni-Ga-CH exhibited (Ni) 6.1 Co 2.9 (OH) 18.27 (CO3) 1.315The characteristic peaks of 6.7H2O and Ga(OH)3 were observed; however, Co-Ni-S only showed characteristic peaks of (Co,Ni)3S4 and NiS, while the characteristic peaks of Ga-related compounds disappeared.

[0024] According to SEM testing, Co-Ni-Ga-CH has a hollow microsphere structure, wherein the surface of the microsphere is composed of smooth thin sheets; Co-Ni-S also has a hollow microsphere structure, wherein the surface of the microsphere is composed of fibrous porous sheets.

[0025] EDS testing of this invention shows that Ga is present in Co-Ni-Ga-CH; however, Ga is absent in Co-Ni-S, proving that Ga has been successfully removed.

[0026] The N2 isothermal adsorption / desorption test showed that the Co-Ni-S hollow microsphere composite material has a specific surface area of ​​30-40 m². 2 g -1 The pore size distribution is 2-4 nm and 20-40 nm.

[0027] Electrochemical detection of this invention shows that, in 6M KOH solution, within a charge-discharge window range of 0-0.5V, at 1Ag... -1 At a current density of 1400-1450 F g, the specific capacitance of the Co-Ni-S hollow microsphere composite material is 1400-1450 F g. -1 .

[0028] Therefore, the Co-Ni-S hollow microsphere composite material of the present invention has the following advantages over the prior art:

[0029] 1. This invention does not require the introduction of a carrier. The microstructure of the composite material can be controlled by adjusting the synthesis ratio. The hollow microsphere composite material obtained has a microsphere surface composed of fibrous porous sheets, which can provide more active sites and improve the electrochemical performance of the material.

[0030] 2. This invention uses water as a solvent to control the microstructure of composite materials, avoiding the use of hazardous reagents and improving safety and reliability;

[0031] 3. The synthesis and post-processing of the Co-Ni-S hollow microsphere composite material of this invention are simple and suitable for mass production;

[0032] 4. The unique hollow structure of the Co-Ni-S hollow microsphere composite material of this invention, as well as the porous structure formed by the fibrous structure on the surface, exhibit a large specific surface area, which exposes more active sites in the composite material, facilitating rapid wetting of the electrolyte and rapid ion transport. Moreover, it can effectively control the volume expansion of the material during the Faraday reaction process, avoid structural collapse, and thus improve the electrochemical performance of the composite material.

[0033] Therefore, this invention has broad application prospects in the field of electrode materials for supercapacitors. Attached image description:

[0034] Figure 1 The XRD test results are for Co-Ni-Ga-CH in Example 1;

[0035] Figure 2 The results are EDS measurements of Co-Ni-Ga-CH in Example 1.

[0036] Figure 3 The results are SEM measurements of Co-Ni-Ga-CH in Example 1.

[0037] Figure 4 The results are SEM measurements of Co-Ni-Ga-CH in Example 1.

[0038] Figure 5 The results are SEM measurements of Co-Ni-Ga-CH in Example 1.

[0039] Figure 6 The BET test results are for Example 1 and Comparative Example 1.

[0040] Figure 7 This is an aperture distribution diagram of Example 1 and Comparative Example 1;

[0041] Figure 8 As Example 1, Comparative Example 1 was prepared in 1 Ag. -1 Charge-discharge curves at current density;

[0042] Figure 9 The XRD test results of Co-Ni-S in Example 1 are shown.

[0043] Figure 10 The results are EDS measurements of Co-Ni-S in Example 1.

[0044] Figure 11 The results are SEM measurements of Co-Ni-S in Example 1.

[0045] Figure 12 The results are SEM measurements of Co-Ni-S in Example 1.

[0046] Figure 13 The XRD test results are for Co-Ni-CH in Comparative Example 1;

[0047] Figure 14 The results are SEM measurements of Co-Ni-CH in Comparative Example 1.

[0048] Figure 15 The results are SEM measurements of Co-Ni-CH in Comparative Example 1.

[0049] Figure 16 The SEM test results are for Co-S prepared in Comparative Example 2.

[0050] Figure 17 Comparative Example 2 at 1A g -1 Charge-discharge curves at current density;

[0051] Figure 18 The SEM test results are for Ni-S prepared in Comparative Example 3.

[0052] Figure 19 Comparative Example 3 at 1A g -1 Charge-discharge curves at current density.

[0053] Figure 20 The SEM test results are for Co-Ni-S-1 prepared in Comparative Example 4.

[0054] Figure 21 Comparative Example 4 at 1A g -1 Charge-discharge curves at current density;

[0055] Figure 22 The SEM test results are for Co-Ni-S-2 prepared in Comparative Example 5.

[0056] Figure 23 Comparative Example 5 at 1A g -1 Charge-discharge curves at current density. Detailed Implementation

[0057] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0058] Example 1

[0059] A method for preparing a Co-Ni-S hollow microsphere composite material includes the following steps:

[0060] Step 1, Preparation of Co-Ni-Ga-CH precursor: First, 0.3 mmol of cobalt nitrate hexahydrate, 1.7 mmol of nickel nitrate hexahydrate, and 2 mmol of gallium nitrate hydrate were dissolved in 30 ml of deionized water to obtain solution A. Simultaneously, 10 mmol of urea and 15 mmol of ammonium fluoride were dissolved in 20 ml of deionized water to obtain solution B. Then, solutions A and B were mixed and subjected to a hydrothermal reaction at a hydrothermal temperature of 140℃ for 12 h. Finally, the product obtained from the hydrothermal reaction was washed and dried to obtain the Co-Ni-Ga-CH precursor, abbreviated as Co-Ni-Ga-CH.

[0061] To verify the composition and reaction mechanism of the obtained Co-Ni-Ga-CH, XRD analysis was performed on the Co-Ni-Ga-CH obtained in step 1. The test results are as follows: Figure 1 As shown, Co-Ni-Ga-CH simultaneously contains (Ni 6.1 Co 2.9 (OH) 18.27 (CO3) 1.315 Characteristic peaks of 6.7H2O and Ga(OH)3.

[0062] To further confirm the composition of Co-Ni-Ga-CH, EDS testing was performed. The test results are as follows: Figure 2 As shown, Co-Ni-Ga-CH contains Co, Ni, Ga, and O elements. The EDS test results are consistent with the XRD test results.

[0063] To demonstrate the microstructure of Co-Ni-Ga-CH, SEM analysis was performed on the Co-Ni-Ga-CH obtained in step 1. The test results are as follows: Figure 3 As shown, Co-Ni-Ga-CH has a microspherical structure; further magnification reveals... Figure 4 As shown, the surface of the Co-Ni-Ga-CH microspheres consists of smooth thin sheets.

[0064] To further demonstrate the internal structure of Co-Ni-Ga-CH, the microspherical Co-Ni-Ga-CH structure was ultrasonicated and then subjected to SEM testing. The test results are as follows: Figure 5 As shown, Co-Ni-Ga-CH has a hollow structure.

[0065] Therefore, the SEM test results show that Co-Ni-Ga-CH has a hollow microsphere structure.

[0066] To demonstrate the microporous structure of Co-Ni-Ga-CH, an N2 isothermal adsorption-desorption BET test was performed on the Co-Ni-Ga-CH obtained in step 1. The test results are as follows: Figure 6As shown, the specific surface area of ​​Co-Ni-Ga-CH is 28 m². 2 g -1 The pore size distribution test results are as follows: Figure 7 As shown, the pore size distribution of Co-Ni-Ga-CH is 3.57 nm, 19.99 nm and 30.99 nm.

[0067] To compare with the Co-Ni-S hollow microsphere composite material obtained in step 2, electrochemical tests were performed on the Co-Ni-Ga-CH. The specific method for the electrochemical test was as follows: the test material was used as the working electrode, and a Hg / HgO electrode and a platinum sheet electrode were used as the reference and counter electrodes, respectively. The material was immersed in a 6M KOH solution, and its specific capacitance was measured in a three-electrode system. The test results are as follows: Figure 8 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1A g -1 At that time, the specific capacitance of Co-Ni-Ga-CH was 878 Fg. -1 .

[0068] Step 2, Preparation of Co-Ni-S Hollow Microsphere Composite Material: First, 0.1g of Co-Ni-Ga-CH obtained in Step 1 is placed in 20ml of deionized water and stirred for 3 minutes to obtain mixture C. Simultaneously, 0.5g of sodium sulfide nonahydrate is dissolved in 20ml of deionized water to obtain solution D. Then, under stirring conditions, solution D is rapidly added to mixture C and mixed. Hydrothermal reaction is carried out at a hydrothermal temperature of 160℃ for 12 hours to achieve sulfidation treatment. Finally, the product obtained from the hydrothermal reaction is soaked, washed, and dried to obtain the Co-Ni-S hollow microsphere composite material, abbreviated as Co-Ni-S.

[0069] To verify the composition and reaction mechanism of the obtained Co-Ni-S, XRD analysis was performed on the Co-Ni-S obtained in step 2. The test results are as follows: Figure 9 As shown, Co-Ni-S contains characteristic peaks of both (Co,Ni)3S4 and NiS, but lacks characteristic peaks of Ga(OH)3 and other compounds containing Ga. Comparison with the XRD results from step 1 shows that Ga(OH)3 was successfully removed in step 2. Based on existing knowledge, Ga is converted from Ga(OH)3 into water-soluble Ga2S3, which is removed in step 2. Subsequent simple operations can convert the Ga in the solution into gallium nitrate hydrate for recycling.

[0070] To further confirm the presence of Ga, EDS analysis was performed on Co-Ni-S. The test results are as follows: Figure 10As shown, Co-Ni-S contains only Co, Ni, and S elements, but not Ga. The EDS test results are consistent with the XRD test results, indicating that Ga(OH)3 was successfully removed through step 2.

[0071] To demonstrate the microstructure of Co-Ni-S and its changes during the reaction process, the Co-Ni-S obtained in step 2 was subjected to SEM analysis after ultrasonication. The test results are as follows: Figure 11 As shown, Co-Ni-S still retains its hollow microsphere structure; further magnification reveals... Figure 12 As shown, the surface of Co-Ni-S is composed of fibrous porous sheets.

[0072] By comparing the SEM test results of Co-Ni-Ga-CH obtained in step 1, it can be seen that Co-Ni-S obtained after sulfurization of Co-Ni-Ga-CH retains the original hollow microsphere structure. However, the sheet structure of Co-Ni-Ga-CH hollow microspheres is a smooth sheet, while the sheet structure of Co-Ni-S hollow microspheres is a fibrous porous sheet.

[0073] The results from XRD, EDS, and SEM show that after hydrothermal sulfidation in step 2, the (Ni) in Co-Ni-Ga-CH 6.1 Co 2.9 (OH) 18.27 (CO3) 1.315 ·6.7 H2O and Ga(OH)3 are sulfided to form (Co,Ni)3S4, NiS and Ga2S3 in Co-Ni-S. Since Ga2S3 dissolves slowly in water, after Co-Ni-Ga-CH is sulfided and soaked in a large amount of deionized water and vacuum filtered multiple times, the Ga2S3 formed on the surface of the hollow microspheres slowly dissolves in water. Therefore, the sheet-like structure on the surface of the Co-Ni-S hollow microspheres fibroses to form a porous structure.

[0074] To demonstrate the microporous structure of Co-Ni-S and its changes during the reaction process, the Co-Ni-S obtained in step 2 was subjected to a BET test. The test results are as follows: Figure 6 As shown, the specific surface area of ​​Co-Ni-S is 37 m². 2 g -1 The pore size distribution test results are as follows: Figure 7 As shown, the pore size distribution is 2.97 nm, 3.31 nm, 3.61 nm, 21.18 nm and 31.35 nm.

[0075] By comparing the BET test results of Co-Ni-Ga-CH obtained in step 1, it can be seen that the specific surface area of ​​Co-Ni-S is larger than that of Co-Ni-Ga-CH, and the pore structure is more diverse.

[0076] Combining the XRD, EDS, SEM, and BET test results of Co-Ni-Ga-CH and Co-Ni-S, it can be seen that Co-Ni-Ga-CH transforms into Co-Ni-S with (Co,Ni)3S4, NiS, and Ga2S3 after hydrothermal sulfidation in step 2. However, since Ga2S3 is soluble in water, after soaking in a large amount of deionized water and repeated vacuum filtration, the Ga2S3 in Co-Ni-S slowly dissolves in the water, and the Ga element disappears. Therefore, the lamellar structure on the surface of the hollow microspheres of Co-Ni-S becomes fibrous, forming a porous structure, which further increases the specific surface area of ​​Co-Ni-S and makes the pore structure more diverse.

[0077] The electrochemical performance test results of Co-Ni-S are as follows: Figure 8 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1Ag... -1 At that time, the specific capacitance of the Co-Ni-S composite material as a supercapacitor electrode was 1438 F g. -1 Comparison with the electrochemical performance test results from step 1 shows that the specific capacitance of Co-Ni-S is improved by 63.78%.

[0078] Based on the above test results, analysis of the reasons for the performance improvement reveals three significant changes during the vulcanization process in step 2:

[0079] 1. The microstructure of the composite material remains the original hollow microsphere structure, thus eliminating the influence of the basic morphology on the capacitance performance.

[0080] 2. Since Ga only has one oxidation state (+3), Ga2S3 will not undergo redox reactions and cannot provide pseudocapacitive performance. Therefore, the Ga element was successfully removed in the sulfidation treatment in step 2, thus improving the specific capacitance performance.

[0081] 3. The formed bimetallic sulfide Co-Ni-S not only improves the Faraday capacitance, but the hollow microspheres and fibrous porous structure can further improve the pseudocapacitance.

[0082] To demonstrate the influence of each element, namely Ga, Co, and Ni, on the properties of the composite material, Comparative Examples 1, 2, and 3 are provided, which are composite materials prepared without the addition of gallium nitrate hydrate, nickel nitrate hexahydrate, and cobalt nitrate hexahydrate, respectively.

[0083] Comparative Example 1

[0084] A method for preparing a composite material without adding gallium nitrate hydrate, wherein the steps not specifically described in the details are the same as step 1 in Example 1, except that gallium nitrate hydrate is not added to solution A in step 1, and the resulting material is named Co-Ni-CH.

[0085] The XRD test results of Co-Ni-CH are as follows: Figure 13 As shown, Co-Ni-CH simultaneously contains Ni 0.985 Co 0.015 (OH)2, Ni(OH)2 and (Ni 6.1 Co 2.9 (OH) 18.27 (CO3) 1.315 • 6.7 H₂O characteristic peak. Compared with Example 1, it can be seen that, in addition to the absence of the characteristic peak of Ga(OH)₃ due to the lack of Ga element introduction, the existence forms of Ni and Co elements have also been substantially changed. Therefore, the test results show that the introduction of Ga element can change the composition of the material.

[0086] SEM test results of Co-Ni-CH are as follows: Figure 14 As shown, Co-Ni-CH has a flower-like structure; further magnification reveals... Figure 15 As shown, the flower-like structure surface of Co-Ni-CH consists of loose, smooth flakes.

[0087] By comparing the SEM test results with those of Example 1, it can be seen that the introduction of Ga element can make Co-Ni-Ga-CH form microspheres composed of sheet-like structures that are more compact. Furthermore, the sheet-like structures on the surface are smaller, while the internal structure is hollow. That is, Ga element has a decisive influence on microstructure.

[0088] The BET test results of Co-Ni-CH are as follows: Figure 6 As shown, the specific surface area of ​​Co-Ni-CH is 7m². 2 g -1 The pore size distribution of Co-Ni-CH is as follows: Figure 7 As shown, the pore size distribution of Co-Ni-CH is 3.53 nm. Compared with Example 1, the specific surface area of ​​Co-Ni-Ga-CH is increased by 300%, and it has a more diverse pore structure. Therefore, the introduction of Ga can significantly improve the specific surface area of ​​the material. This is evident from the combination of SEM and BET test results; changes in microstructure directly affect the specific surface area performance.

[0089] The electrochemical performance test results of Co-Ni-CH are as follows: Figure 8 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1Ag... -1At that time, the specific capacitance of Co-Ni-CH was 81 F g. -1 Compared to Example 1, the specific capacitance of Co-Ni-Ga-CH is increased by 983.95% compared to Co-Ni-CH. Therefore, the introduction of Ga can significantly improve the specific capacitance of the composite material.

[0090] By comparing the above test results with those of Example 1, the following conclusions can be drawn:

[0091] 1. Introducing Ga can change the composition of composite materials;

[0092] 2. Introducing Ga can change the microstructure of composite materials, thereby increasing the specific surface area;

[0093] The specific capacitance performance is significantly improved through the combined effect of composition and microstructure.

[0094] The reasons are as follows: The introduction of Ga transforms the loosely structured, smooth, flake-like Co-Ni-CH flower-like structure into a more compact Co-Ni-Ga-CH microsphere structure composed of smaller flakes, and also creates a hollow structure within the microspheres. This change in microstructure affects the formation of pores during the subsequent hydrothermal sulfidation of Co-Ni-Ga-CH to form Co-Ni-S, ultimately increasing the specific surface area of ​​the composite material. Based on common knowledge in the field, the differences in pore structure and specific surface area resulting from differences in microstructure have a decisive impact on the electrochemical performance of materials. Increased specific surface area exposes more active sites in the composite material, facilitating rapid electrolyte wetting and ion transport. Simultaneously, it effectively controls the volume expansion during the Faraday reaction, preventing structural collapse and thus improving the electrochemical performance of the composite material.

[0095] Comparative Example 2

[0096] A method for preparing a composite material without adding nickel nitrate hexahydrate is provided. The steps not specifically described in the details are the same as those in Example 1, except that nickel nitrate hexahydrate is not added to solution A in step 1. To control variables, the amount of cobalt nitrate hexahydrate added is 2 mmol. The material obtained in step 2 is named Co-S.

[0097] The SEM test results of Co-S are as follows: Figure 16 As shown, Co-S has a plate-like structure, and its shape is irregular and its size varies.

[0098] By comparing the SEM test results with those of Example 1, it can be seen that the introduction of Ni element can transform the microstructure of Co-Ni-S composite material from a plate-like structure to a hollow microsphere structure, thus achieving the effect of adjusting the microstructure of the composite material.

[0099] The electrochemical performance test results of Co-S are as follows: Figure 17 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1A g -1 At that time, the specific capacitance of Co-S was 364 F g. -1 Compared with Example 1, the specific capacitance of Co-Ni-S is increased by 295.05% compared with Co-S. The test results show that the introduction of Ni can significantly improve the specific capacitance of the composite material.

[0100] A comparison of the above test results with those of Example 1 shows that the introduction of Ni can significantly improve the specific capacitance performance by changing the microstructure of the composite material.

[0101] Comparative Example 3

[0102] A method for preparing a composite material without adding cobalt nitrate hexahydrate is provided. The steps not specifically described in the details are the same as those in Example 1, except that cobalt nitrate hexahydrate is not added to solution A in step 1. To control the variables, the amount of nickel nitrate hexahydrate added is 2 mmol. The material obtained in step 2 is named Ni-S.

[0103] The SEM test results of Ni-S are as follows: Figure 18 As shown, Ni-S has a solid spherical structure, and the surface of the microspheres is composed of plates of varying sizes.

[0104] By comparing the SEM test results with those of Example 1, it can be seen that the introduction of Co element can transform the microstructure of the composite material from a solid sphere-like structure to a hollow sphere-like structure, thus achieving the effect of adjusting the microstructure of the composite material.

[0105] The electrochemical performance test results of Ni-S are as follows: Figure 19 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1A g -1 At that time, the specific capacitance of Ni-S was 1366 F g. -1 Compared to Example 1, the specific capacitance of Co-Ni-S is increased by 5.27% compared to Ni-S. The test results show that introducing Co can improve the specific capacitance of the composite material.

[0106] A comparison of the above test results with those of Example 1 shows that the introduction of Co can change the microstructure of the composite material and improve its specific capacitance performance.

[0107] To demonstrate the effect of the Co to Ni ratio on the morphology and properties of Co-Ni-S, Comparative Examples 4 and 5 are provided, with Co / Ni ratios of 1:1 and 1:3, respectively, for Co-Ni-S composite materials.

[0108] Comparative Example 4

[0109] A method for preparing a Co-Ni-S composite material with a Co / Ni ratio of 1:1 is provided. The steps not specifically described in the details are the same as those in Example 1, except that: the amount of cobalt nitrate hexahydrate added to solution A in step 1 is 1 mmol, the amount of nickel nitrate hexahydrate added is 1 mmol, and the material obtained in step 2 is named Co-Ni-S-1.

[0110] The SEM test results of Co-Ni-S-1 are as follows: Figure 20 As shown, Co-Ni-S-1 has a plate-like structure with irregular shapes and varying sizes, but some microsphere-like structures appear. Comparison with the SEM test results of Example 1 shows that even with the introduction of Ni, a low proportion cannot completely form a spherical structure. Specifically, a Co / Ni ratio of 1:1 is insufficient to transform the composite material's microstructure into a hollow microsphere structure. Therefore, it can be demonstrated that the ratio of Co to Ni has a significant impact on the microstructure.

[0111] The electrochemical performance test results of Co-Ni-S-1 are as follows: Figure 21 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1Ag... -1 At that time, the specific capacitance of Co-Ni-S-1 was 1086 F g. -1 Compared to Example 1, the specific capacitance of Co-Ni-S is increased by 32.41% compared to Co-Ni-S-1. The test results show that adjusting the ratio of Co and Ni can significantly improve the specific capacitance of the material.

[0112] A comparison of the above test results with those of Example 1 shows that adjusting the ratio of Co and Ni can change the microstructure of the composite material and achieve a significant improvement in specific capacitance performance.

[0113] Comparative Example 5

[0114] A method for preparing a Co-Ni-S composite material with a Co / Ni ratio of 1:3 is provided. The steps not specifically described in the details are the same as those in Example 1, except that: in step 1, the amount of cobalt nitrate hexahydrate added to solution A is 0.5 mmol, and the amount of nickel nitrate hexahydrate added is 1.5 mmol. The material obtained in step 2 is named Co-Ni-S-2.

[0115] The SEM test results of Co-Ni-S-2 are as follows: Figure 22 As shown, Co-Ni-S-2 has a solid microsphere-like structure with a surface composed of sheet-like structures.

[0116] Comparison with the SEM test results of Example 1 shows that, with a Co / Ni ratio of 1:3, the microstructure of Co-Ni-S-2 is a quasi-microsphere structure, failing to form a hollow microsphere structure. However, in Example 1, when more Ni source was introduced, i.e., a Co / Ni ratio of 3:17, the resulting Co-Ni-S exhibited a hollow microsphere structure, and the lamellar structure on the microsphere surface became fibrous, forming a porous structure. Therefore, it can be demonstrated that the ratio of Co to Ni has a significant impact on the microstructure.

[0117] The electrochemical performance test results of Co-Ni-S-2 are as follows: Figure 23 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1Ag... -1 At that time, the specific capacitance of Co-Ni-S-2 was 1278 F g. -1 Compared to Example 1, the specific capacitance of Co-Ni-S is increased by 12.51% compared to Co-Ni-S-2. The test results show that adjusting the ratio of Co to Ni can improve the specific capacitance of the material.

[0118] Comparing the above test results with those of Example 1, it can be seen that adjusting the ratio of Co and Ni can change the microstructure of the composite material. After introducing more Ni source, the Co-Ni-S in Example 1 tends to form a hollow microsphere structure with a surface composed of fibrous porous sheets, thereby improving the specific capacitance performance.

[0119] Based on the comparison of the test results of Comparative Examples 1, 2, 3, 4, and 5 with those of Example 1, the following conclusions can be drawn:

[0120] 1. Introducing Ga can change the composition and microstructure of composite materials. This is because it makes the material form Co-Ni-Ga-CH microspheres with a compact sheet-like structure on the surface, and makes the interior of the microspheres form a hollow structure. After removing Ga, the surface of the microspheres forms fibrous porous sheets. The change in pore structure ultimately increases the specific surface area of ​​the composite material.

[0121] 2. The introduction of Ni can change the microstructure of composite materials. The reason is that after the introduction of Ni, the microstructure of composite materials changes from a plate-like structure to a hollow microsphere structure.

[0122] 3. The introduction of Co can change the microstructure of composite materials. The reason is that after the introduction of Co, the microstructure of composite materials changes from a solid sphere structure to a hollow microsphere structure.

[0123] 4. By adjusting the Co / Ni ratio, the microstructure of the composite material can be changed, so that the composite material forms a hollow microsphere structure and the surface is composed of fibrous porous sheets.

[0124] The specific capacitance performance is significantly improved through the combined effect of composition and microstructure.

Claims

1. A Co-Ni-S hollow microsphere composite material, characterized in that: Co-Ni-Ga-CH precursor is prepared by first-step hydrothermal reaction using cobalt nitrate hexahydrate, nickel nitrate hexahydrate, gallium nitrate hydrate, urea, and ammonium fluoride as raw materials. Then, Co-Ni-Ga-CH precursor and sodium sulfide nonahydrate are prepared by second-step hydrothermal reaction. Co-Ni-S is abbreviated as Co-Ni-S.

2. The Co-Ni-S hollow microsphere composite material according to claim 1, characterized in that: The Co-Ni-Ga-CH is composed of (Ni 6.1 Co 2.9 (OH) 18.27 (CO3) 1.315 Composed of 6,7H2O and Ga(OH)3, the microstructure of Co-Ni-Ga-CH is a hollow microsphere structure, in which the surface of the microsphere is composed of smooth thin sheets; The Co-Ni-S is composed of (Co, Ni)3S4 and NiS, and does not contain Ga(OH)3 or other related compounds containing Ga. The microstructure of Co-Ni-S is still a hollow microsphere structure, and the surface of the microsphere is composed of fibrous porous sheets.

3. The Co-Ni-S hollow microsphere composite material according to claim 1, characterized in that: The specific surface area of ​​the Co-Ni-S is 30-40 m². 2 g -1 The pore size distribution is 2-4 nm and 20-40 nm.

4. A method for preparing a Co-Ni-S hollow microsphere composite material, characterized in that... Includes the following steps: Step 1, Preparation of Co-Ni-Ga-CH precursor: First, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and gallium nitrate hydrate are dissolved in deionized water to obtain solution A. At the same time, urea and ammonium fluoride are dissolved in deionized water to obtain solution B. Then, solutions A and B are mixed and subjected to a hydrothermal reaction under certain conditions. Finally, the product obtained from the hydrothermal reaction is washed and dried to obtain the Co-Ni-Ga-CH precursor, abbreviated as Co-Ni-Ga-CH. Step 2, Preparation of Co-Ni-S hollow microsphere composite material: First, the Co-Ni-Ga-CH obtained in Step 1 is placed in deionized water and stirred after sonication to obtain mixture C. At the same time, sodium sulfide nonahydrate is dissolved in deionized water to obtain solution D. Then, under stirring conditions, solution D is quickly added to mixture C and mixed. Hydrothermal reaction is carried out under certain conditions to achieve sulfidation treatment. Finally, the product obtained from the hydrothermal reaction is soaked, washed, and dried to obtain the Co-Ni-S hollow microsphere composite material, abbreviated as Co-Ni-S. The Ga element in gallium nitrate hydrate is recycled.

5. The preparation method according to claim 4, characterized in that: In step 1, the molar ratio of cobalt nitrate hexahydrate, nickel nitrate hexahydrate, gallium nitrate hydrate, urea, and ammonium fluoride is 0.3:1.7:2:10:

15.

6. The preparation method according to claim 4, characterized in that: The conditions for the hydrothermal reaction in step 1 are: hydrothermal temperature of 140℃ and hydrothermal time of 12 h.

7. The preparation method according to claim 4, characterized in that: In step 2, the mass ratio of Co-Ni-Ga-CH and sodium sulfide nonahydrate is 1:5; the hydrothermal reaction conditions in step 2 are: hydrothermal temperature of 160℃ and hydrothermal time of 12 h.

8. The preparation method according to claim 4, characterized in that: The specific conditions for soaking and washing in step 2 are as follows: deionized water is used, and the soaking time is 0.5-1 h to achieve complete removal of Ga element.

9. The application of a Co-Ni-S hollow microsphere composite material as a supercapacitor electrode material, characterized in that: Charge and discharge are performed within a voltage window of 0-0.5 V, at a current density of 1 A g. -1 At that time, the specific capacitance was 1400-1450 F g -1 .

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