Preparation method and application of H-NiCo2S4-coated C core-shell nanowire electrode material

Abstract

The invention discloses a preparation method of an H-NiCo2S4 (at) C core-shell nanowire electrode material and application of the H-NiCo2S4 (at) C core-shell nanowire electrode material. Firstly, cobalt chloride hexahydrate, nickel chloride hexahydrate, lauryl sodium sulfate and urea are dissolved in deionized water, carbon fiber cloth is placed in the solution to be subjected to a hydrothermal reaction, and then the carbon fiber cloth is taken out, washed and dried. And secondly, putting the loaded NiCo2 (OH) 6 into a sodium sulfide solution, and carrying out hydrothermal reaction, so as to obtain the NiCo2S4 nanowire. Then, the NiCo2S4 nanowire electrode is placed in a deposition solution composed of potassium chloride and a pyrrole monomer, and electrochemical deposition is used; and after deposition is completed, taking out a sample, washing, and sintering at low temperature to obtain the NiCo2S4-coated C nanowire. And finally, carrying out rapid Joule heat treatment on the NiCo2S4 (at) C nanowire, so that the crystallinity of a carbon layer is improved, and the H-NiCo2S4 (at) C core-shell nanowire electrode material is obtained. The H-NiCo2S4 (at) C nanowire is used as a positive electrode to assemble an asymmetric supercapacitor, the capacitance retention rate of the device still reaches up to 93.2%, and the cycling stability of the device is far better than that of most current pseudocapacitance supercapacitors under 15000 cycles of charge-discharge cycles.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor electrode material preparation, specifically relating to a preparation method and application of a core-shell structured H-NiCo2S4@C nanowire electrode material. Background Technology

[0002] As next-generation consumer electronics, biomedical diagnostic equipment, and hybrid electric vehicles iterate towards longer range, miniaturization, and longer service life, the practical demand for high-performance energy storage systems is becoming increasingly prominent. Supercapacitors, as a promising type of electrochemical energy storage device, stand out due to their superior overall performance—possessing not only a high power density of 1–10 kW·kg⁻¹ and millisecond-level fast charge / discharge response, but also an ultra-long service life exceeding 100,000 cycles—and are therefore widely considered one of the core candidate directions for next-generation green energy storage technology.

[0003] In the development of supercapacitor electrode materials, the dual transition metal sulfide NiCo2S4 has become a research hotspot due to its advantages of both high theoretical specific capacity and low economic cost. The synergistic effect of the nickel-cobalt bimetallic compound endows it with outstanding performance: nickel and cobalt ions can exhibit multiple oxidation states and participate in a wide range of redox reactions, resulting in conductivity and electrochemical activity that are at least two orders of magnitude higher than those of single metal sulfides. However, NiCo2S4 still suffers from inherent defects, such as slow electron transfer rates, sluggish electrochemical reaction kinetics, and a redox energy storage mechanism that easily leads to volume deformation. These problems severely restrict the rate performance, power density, and cycle stability of NiCo2S4-based supercapacitors. Therefore, developing NiCo2S4-based electrode materials with both excellent electrochemical performance and long cycle life remains a key challenge that urgently needs to be addressed. For example, Huang (Journal of Alloys and Compounds, 947, (2023) 169413) synthesized Co3S4 and NiCo2S4 active materials on Zif-67 polyhedra using a hydrothermal method, and Liang (Journal of Energy Storage, 42, (2021) 103105) grew NiCo2S4 in situ on self-supporting carbon cloth using a hydrothermal method. This improved the overall specific surface area of ​​the material, obtained a higher charge storage capacity, eliminated the capacitance drop caused by the shedding of conductive agents and binders during electrochemical reactions, and improved the rate performance and cycle stability of supercapacitors.

[0004] In addition to the aforementioned issues, the rapid voltage decay of NiCo2S4-based supercapacitors in the open-circuit state has become one of the core bottlenecks hindering their large-scale practical application. Currently, establishing self-discharge suppression strategies and elucidating their underlying mechanisms through structural optimization of electrode active materials or precise screening of electrolyte systems, while simultaneously improving the specific capacitance, output power, rate performance, and cycle stability of the devices, has become a key requirement for the development of practical high-performance NiCo2S4-based supercapacitors. Therefore, developing NiCo2S4-based supercapacitors with excellent comprehensive electrochemical performance, achieving effective control of the self-discharge rate and synergistic improvement of core performance such as self-discharge rate and energy density, remains a major challenge that urgently needs to be overcome in this field. Summary of the Invention

[0005] One objective of this invention is to provide a method for preparing H-NiCo2S4@C core-shell nanowire electrode material.

[0006] The second objective of this invention is to provide the H-NiCo2S4@C core-shell nanowire electrode material prepared by the above method as a positive electrode material for asymmetric supercapacitors.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing H-NiCo2S4@C core-shell nanowire electrode material, comprising the following steps:

[0009] S1: Cobalt chloride hexahydrate (CoCl2∙6H2O), nickel chloride hexahydrate (NiCl2∙6H2O), sodium dodecyl sulfate (SDS), and urea were dissolved in ultrapure water and stirred with a magnetic stirrer to obtain a pink precursor solution. The treated carbon fiber cloth was immersed in the precursor solution and placed together in a Teflon reactor for hydrothermal reaction. After cooling to room temperature, the carbon fiber cloth was washed, dried, and then sodium sulfide nonahydrate was dissolved in ultrapure water. The carbon fiber containing the NiCo2S4 precursor was arranged in the mixed solution and subjected to hydrothermal reaction to obtain NiCo2S4 nanowires with carbon fiber cloth as substrate.

[0010] S2: Potassium chloride and pyrrole monomer were stirred and mixed to form a deposition solution. NiCo2S4 nanowires were placed in this deposition solution and deposited using a constant potential. After deposition, the carbon fiber cloth was removed, washed, and dried. Subsequently, the NiCo2S4@Ppy carbon fibers were arranged in a ceramic crucible, and the ceramic crucible was placed in a tube furnace for low-temperature carbonization. Then, N2 was introduced into the tube furnace for low-temperature heating treatment. Finally, it was cooled to room temperature to obtain core-shell nanowires NiCo2S4@C. Rapid sintering heating was then performed on a rapid Joule heating instrument under an Ar atmosphere. First, the carbon fiber cloth was clamped on the sample stage, a vacuum was drawn, and the current and heating time were adjusted.

[0011] Preferably, the molar ratio of cobalt chloride hexahydrate, nickel chloride hexahydrate, sodium dodecyl sulfate, and urea in step S1 is 2.5:1.25:1:9.

[0012] Preferably, the temperature of the hydrothermal reaction in step S1 is 80~120°C, and the heating time is 5~12h.

[0013] Preferably, the concentration of sodium sulfide nonahydrate in step S1 is 0.04 mol / L. -1 .

[0014] Preferably, in step S1, the temperature of the hydrothermal reaction in the second step is 80~120°C, and the heating time is 5~12h.

[0015] Preferably, in step S2, the mixed solution contains 0.15 g of potassium chloride, 0.3-0.5 ml of pyrrole monomer, and 60-100 ml of ultrapure water.

[0016] Preferably, the electrodeposition voltage in step S2 is 0.8V and the deposition time is 10-120s.

[0017] Preferably, in step S2, the heating in the tube furnace is carried out under N2 atmosphere at a rate of 2°C / min to 400~600°C, and held at that temperature for 1 hour;

[0018] Preferably, in step S2, during the high-temperature shock process, a constant voltage of 3200V and a current of 28A-35A are selected, and the high-temperature thermal shock time is kept constant at 4-10s.

[0019] Secondly, the present invention provides a supercapacitor comprising a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode is a carbon fiber cloth with H-NiCo2S4@C core-shell nanowires grown on it, the negative electrode is nickel foam coated with commercial activated carbon (YP-80F), and the electrolyte is 6.0 M potassium hydroxide (KOH), thereby assembling a supercapacitor.

[0020] This invention uses H-NiCo2S4@C core-shell nanowire electrode material as the positive electrode of a supercapacitor, which improves the cycling stability and self-discharge rate of the supercapacitor.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) In this invention, H-NiCo2S4@C core-shell nanowires are used as the positive electrode material of supercapacitors, and the carbon layer is controlled by electrodeposition.

[0023] (2) The present invention uses H-NiCo2S4@C core-shell nanowires as the positive electrode material of supercapacitors. The capacitance retention rate of the capacitor is 93.2% after 15,000 cycles, which effectively improves the cycle stability of supercapacitors.

[0024] (3) The present invention uses H-NiCo2S4@C nanowires with a core-shell structure as the positive electrode material of the supercapacitor, which effectively prolongs the self-discharge time of the supercapacitor and exhibits excellent electrochemical performance. Attached Figure Description

[0025] Figure 1 The image shows a scanning electron microscope (SEM) image of the H-NiCo2S4@C core-shell nanowires prepared in Example 1.

[0026] Figure 2 The image shows a transmission electron microscope (TEM) image of the H-NiCo2S4@C core-shell nanowires prepared in Example 1.

[0027] Figure 3 The image shows the rapid charge and discharge of the supercapacitor constructed in Example 1 at different current densities.

[0028] Figure 4 The graph shows the specific capacitance and voltage drop of the supercapacitor constructed in Example 1 under different current densities.

[0029] Figure 5 The leakage current test diagram of the supercapacitor constructed in Example 1.

[0030] Figure 6 The supercapacitor constructed for Example 1 at 1 A g -1 Diagram of open-circuit voltage test during charging.

[0031] Figure 7 The supercapacitor constructed for Example 1 was tested at a current density of 10 A g. -1 Cyclic stability curve of the lower electrode.

[0032] Figure 8 The energy density and power density of the supercapacitor constructed for Example 1. Detailed Implementation

[0033] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0034] Example 1

[0035] H-NiCo2S4@C nanowires with a core-shell structure grown on carbon fiber cloth were prepared by the following steps:

[0036] S1: Weigh 594.83 mg CoCl2∙6H2O, 297.09 mg NiCl2∙6H2O, 288.38 mg sodium dodecyl sulfate (SDS), and 540.54 mg urea, dissolve them in 45 mL of distilled water, and continuously stir magnetically until a uniform pink solution is formed. Then pour the solution into a Teflon autoclave and heat at 100°C for 5 hours. Clean the carbon fiber cloth containing the NiCo2S4 precursor sequentially with ultrapure water and ethanol. After cleaning, dry it in an oven at 60°C for 12 hours. Place the carbon fiber cloth in a solution containing 0.04 mol L... -1 The instrument was placed in a sodium sulfide nonahydrate solution and then heated in an oven at a constant temperature of 120°C for 7 hours. After cooling to room temperature, it was removed and cleaned with ultrapure water and ethanol. After cleaning, it was dried in an oven at 60°C overnight to finally obtain carbon fiber cloth containing NiCo2S4 nanowires.

[0037] S2: A carbon fiber cloth with NiCo2S4 nanowires grown on it is placed in a deposition solution containing potassium chloride and pyrrole monomer, wherein 0.3 g of potassium chloride and 0.3 ml of pyrrole monomer are dissolved in 100 ml of ultrapure water. Electrodeposition was performed using a three-electrode system. A carbon fiber cloth containing NiCo2S4 nanowires was placed in the deposition solution and used as the working electrode. Ag / AgCl was used as the reference electrode, and a platinum sheet was used as the counter electrode. Electrochemical workstation was used to deposit the nanowires at a constant voltage of 0.8V for 40s. The carbon fiber cloth containing the NiCo2S4@Ppy precursor was cleaned with ultrapure water and ethanol. After cleaning, it was dried in an oven at 60°C for 12h. The carbon fibers containing NiCo2S4@Ppy were arranged in a ceramic crucible, which was then placed in a tube furnace and heated to 400°C at a rate of 2°C / min under a N2 atmosphere for 2h. Subsequently, it was heated on a rapid heating instrument with Ar introduced at a voltage of 3200V and a current of 28A for 4s. Finally, it was cooled to room temperature with the instrument to obtain H-NiCo2S4@C core-shell nanowires with carbon fiber cloth as the substrate.

[0038] Figure 1 The scanning electron microscope (SEM) image of the H-NiCo2S4@C core-shell nanowires prepared in Example 1 shows that the prepared nanowires are nanowires.

[0039] Figure 2 The transmission electron microscope (TEM) image of the H-NiCo2S4@C core-shell nanowires prepared in Example 1 shows that the prepared material has a core (NiCo2S4)-shell (C) structure.

[0040] Example 2

[0041] The carbon fiber cloth with core-shell structured H-NiCo2S4@C nanowires was prepared by the following steps:

[0042] S1: Weigh 800 mg CoCl2∙6H2O, 400 mg NiCl2∙6H2O, 500 mg sodium dodecyl sulfate (SDS), and 700 mg urea, dissolve them in 50 mL of distilled water, and continuously stir magnetically until a uniform pink solution is formed. Then pour the solution into a Teflon autoclave and heat at 100°C for 9 hours. Clean the carbon fiber cloth containing the NiCo2S4 precursor sequentially with ultrapure water and ethanol. After cleaning, dry it in an oven at 60°C for 12 hours. Place the carbon fiber cloth in a solution containing 0.04 mol L... -1 The instrument was placed in a sodium sulfide nonahydrate solution and then heated in an oven at a constant temperature of 120°C for 7 hours. After cooling to room temperature, it was cleaned with ultrapure water and ethanol and then dried in an oven at 60°C for 12 hours to finally obtain carbon fiber cloth containing NiCo2S4 nanowires.

[0043] S2: Carbon fibers with NiCo2S4 nanowires were arranged in a deposition solution of potassium chloride and pyrrole monomer, wherein the mass of potassium chloride was 0.3 g, the volume of ultrapure water was 100 mL, and the volume of pyrrole monomer was 0.3 mL. The carbon fiber cloth was placed in the deposition solution and used as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. Deposition was performed at a constant voltage of 0.8 V for 20 s using an electrochemical workstation. The carbon fiber cloth containing the NiCo2S4@Ppy precursor was then washed sequentially with ultrapure water and ethanol. After cleaning, the nanowires were dried in an oven at 60°C for 12 hours. Carbon fibers containing NiCo2S4@Ppy were arranged in a ceramic crucible, which was then placed in a tube furnace. The furnace was heated to 450°C at a rate of 2°C / min under a nitrogen atmosphere and held for 2 hours. Subsequently, the nanowires were subjected to thermal shock on a high-temperature shock apparatus under vacuum. Ar was introduced at 3200V and 32A for 4 seconds, and the furnace was allowed to cool to room temperature with the apparatus. This yielded H-NiCo2S4@C core-shell nanowires with a carbon fiber cloth substrate. The SEM and TEM images of the H-NiCo2S4@C core-shell nanowires prepared in this example are similar to those in Example 1.

[0044] Example 3

[0045] The carbon fiber cloth with core-shell structured H-NiCo2S4@C nanowires was prepared by the following steps:

[0046] S1: Weigh 400 mg CoCl2∙6H2O, 200 mg NiCl2∙6H2O, 200 mg sodium dodecyl sulfate (SDS), and 500 mg urea, dissolve them in 40 mL of distilled water, and continuously stir magnetically until a uniform pink solution is formed. Then pour the solution into a Teflon autoclave and heat at 120°C for 5 hours. Clean the carbon fiber cloth containing the NiCo2S4 precursor sequentially with ultrapure water and ethanol. After cleaning, dry it in an oven at 60°C for 12 hours. Place the carbon fiber cloth in a solution containing 0.04 mol L... -1 The instrument was placed in a sodium sulfide nonahydrate solution and then heated in an oven at a constant temperature of 120°C for 7 hours. After cooling to room temperature, it was cleaned with ultrapure water and ethanol and then dried in an oven at 60°C for 12 hours to finally obtain carbon fiber cloth containing NiCo2S4 nanowires.

[0047] S2: Carbon fibers with NiCo2S4 nanowires were arranged in a deposition solution of potassium chloride and pyrrole monomer, wherein the mass of potassium chloride was 0.3 g, the volume of ultrapure water was 80 mL, and the volume of pyrrole monomer was 0.3 mL. The carbon fiber cloth was placed in the deposition solution and used as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. Deposition was performed at a constant voltage of 0.8 V for 20 s using an electrochemical workstation. The carbon fiber cloth containing the NiCo2S4@Ppy precursor was then washed sequentially with ultrapure water and ethanol. The carbon fibers containing NiCo2S4@Ppy were dried in an oven at 60°C for 12 hours. The carbon fibers were then arranged in a ceramic crucible, which was placed in a tube furnace and heated to 450°C at a rate of 2°C / min under a N2 atmosphere for 2 hours. Subsequently, rapid Joule heating was performed on a rapid Joule heating instrument. A vacuum was drawn, and Ar was introduced at a voltage of 3200V and a current of 32A for 4 seconds. Finally, the mixture was cooled to room temperature with the instrument, yielding H-NiCo2S4@C core-shell nanowires with a carbon fiber cloth substrate. The SEM and TEM images of the H-NiCo2S4@C core-shell nanowires prepared in this example are similar to those in Example 1.

[0048] Using carbon fiber cloth with H-NiCo2S4@C core-shell nanowires grown in Example 1 as the positive electrode (1*1cm), commercial activated carbon (YP-80F) coated on nickel foam as the negative electrode (1*1cm), 6.0 M KOH as the electrolyte, and cellulose paper as the separator, a supercapacitor system was constructed, and its electrochemical performance was tested at room temperature.

[0049] Figure 3 The image shows the rapid charge and discharge diagrams of the supercapacitor prepared in Example 1 at different current densities.

[0050] Figure 4The specific capacitance and voltage drop of the supercapacitor prepared in Example 1 at different current densities.

[0051] Figure 5 The image shows the leakage current test result of the supercapacitor prepared in Example 1.

[0052] Figure 6 The image shows the open-circuit voltage test result of the supercapacitor prepared in Example 1.

[0053] Figure 7 The supercapacitor constructed for Example 1 was tested at a current density of 10 A g. -1 The lower electrode cycling stability curve shows a capacitance retention of 93.2% and a coulombic efficiency of 100% after 15,000 cycles. This demonstrates reliable electrochemical stability and coulombic efficiency.

[0054] Figure 8 The power density and energy density of the supercapacitor constructed in Example 1 are shown. This supercapacitor possesses an excellent energy density (40.3 Wh kg). -1 ) and high power density (14860 (W kg) -1 ).

[0055] The specific embodiments described herein are merely illustrative of the spirit of the invention and do not limit the scope of protection of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing an H-NiCo2S4@C core-shell nanowire electrode material, the method comprising the following steps: S1: Cobalt chloride hexahydrate, nickel chloride hexahydrate, sodium dodecyl sulfate, and urea were dissolved in water and stirred to obtain a precursor solution. Carbon fiber cloth was immersed in the precursor solution for a hydrothermal reaction. After cooling to room temperature, the solution was washed and dried. Then, the carbon fibers containing the NiCo2S4 precursor were arranged in an aqueous solution containing sodium sulfide nonahydrate for a second hydrothermal vulcanization treatment. After cooling to room temperature, the solution was washed and dried. Finally, NiCo2S4 nanowires with carbon fiber cloth as a substrate were obtained. S2: NiCo2S4 nanowires were placed in a deposition solution of potassium chloride and pyrrole monomers and electrochemically deposited using a three-electrode system. A carbon fiber cloth containing NiCo2S4 nanowires was used as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. Electrodeposition was performed using a constant voltage method. After deposition, the working electrode was washed and dried to obtain NiCo2S4@Ppy. Then, the NiCo2S4@Ppy carbon fiber cloth was placed in a ceramic crucible, which was then placed in a tube furnace. N2 was introduced into the tube furnace for low-temperature heating treatment to obtain NiCo2S4@C core-shell nanowires with a carbon fiber cloth substrate. Finally, the carbon fibers containing NiCo2S4@C were arranged on the sample stage of a rapid Joule heating instrument, evacuated, and then Ar was introduced into the instrument for rapid Joule heating treatment to obtain H-NiCo2S4@C core-shell nanowires with a carbon fiber cloth substrate.

2. The method for preparing an H-NiCo2S4@C core-shell nanowire electrode material according to claim 1, characterized in that, The molar ratio of cobalt chloride hexahydrate, nickel chloride hexahydrate, sodium dodecyl sulfate, and urea in step S1 is 2.5:1.25:1:

9.

3. The method for preparing an H-NiCo2S4@C core-shell nanowire electrode material according to claim 1, characterized in that, The hydrothermal reaction in step S1 is carried out at a temperature of 80~120°C for 5~12 hours.

4. The method for preparing an H-NiCo2S4@C core-shell nanowire electrode material according to claim 1, characterized in that, The concentration of sodium sulfide nonahydrate in step S1 is 0.04 mol / L. -1 .

5. The method for preparing an H-NiCo2S4@C core-shell nanowire electrode material according to claim 1, characterized in that, In step S1, the temperature of the second hydrothermal reaction is 80~120°C, and the heating time is 5~12h.

6. The method for preparing an H-NiCo2S4@C core-shell nanowire electrode material according to claim 1, characterized in that, In step S2, the mixed solution contains 0.15g-0.5g of potassium chloride, 0.3-0.5ml of pyrrole monomer, and 60-100ml of ultrapure water.

7. The method for preparing an H-NiCo2S4@C core-shell nanowire electrode material according to claim 1, characterized in that, The electrodeposition voltage in step S2 is 0.8V, and the deposition time is 10-120s.

8. The method for preparing an H-NiCo2S4@C core-shell nanowire electrode material according to claim 1, characterized in that... In step S2, heating in the tube furnace involves raising the temperature to 400-600°C at a rate of 2°C / min under a N2 atmosphere and holding it at that temperature for 1 hour.

9. The method for preparing an H-NiCo2S4@C core-shell nanowire electrode material according to claim 1, characterized in that... In step S2, during the rapid Joule heating process, a constant voltage of 3200V is selected, the current is selected as 20A-38A, and the thermal shock time is kept constant at 4-10s.

10. A supercapacitor, the supercapacitor comprising a positive electrode, a negative electrode, an electrolyte, and a separator, characterized in that, The positive electrode is a carbon fiber cloth with NiCo2S4@C core-shell nanowires grown on it, prepared by the preparation method according to any one of claims 1 to 8.

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