A method for preparing transition metal sulfide supercapacitor materials

Abstract

This invention discloses a transition metal sulfide supercapacitor electrode material, its preparation method, and its applications. The material exhibits a rod-like morphology at the microscopic level and is amorphous. Its rough surface structure provides a large reaction contact area for electron and ion exchange. This invention utilizes nickel and cobalt metal salts to prepare the metal sulfide supercapacitor electrode material through a hydration reaction under ambient temperature and pressure. It possesses excellent electronic and ionic conductivity, good rate performance, and a high-quality specific capacitance of 1330.0 F / g at a current density of 1 A / g. The preparation method employed in this invention, through the ion exchange reaction of sulfur ions in a sulfur source with an oxalate precursor to obtain transition metal sulfides as supercapacitor electrode materials, is simple to operate, low in cost, safe, and environmentally friendly, providing a new approach for the development of transition metal sulfide supercapacitor electrode materials.

Description

Technical Field

[0001] This invention relates to supercapacitors, and more particularly to a high-performance transition metal sulfide supercapacitor cathode material prepared at room temperature and pressure, its preparation method, and its application. Background Technology

[0002] Electrodes are crucial for obtaining high-performance hybrid capacitors. To improve electrochemical performance, the rational design and fabrication of cathode materials is a direct way to increase the energy density of supercapacitors. Research on cathode electrode materials for hybrid supercapacitors mainly focuses on layered double hydroxides (such as NiOOH, FeOOH, Ni / Co-OOH), metal oxides (such as RuO2, MnO2, Co3O4, NiO, etc.), and sulfides (CoS, NiS, NiCo2S4). Among these, NiOOH / AC hybrid supercapacitors have been mass-produced and applied in electric buses and solar cells, but their energy density is relatively low. However, the conductivity of these oxides or hydroxides is generally low, hindering their full potential for high capacity. Appropriate crystal structure, high conductivity, and charge storage mechanism determine the electrochemical performance of electrode materials. Polymetallic sulfides can combine the Faraday reaction characteristics of two or more single metal elements, exhibiting superior performance through synergistic effects. Compared to their corresponding oxides, they significantly improve the conductivity of the material while retaining the redox characteristics of the two transition metals acting alone, thus possessing good conductivity and high electrochemical activity. However, the preparation of metal sulfide materials often requires the use of a reactor under high temperature and high pressure conditions (e.g., Wang et al., J. Alloy. Compd, 2018, 735(25):1505-1513; Zhao et al., J. Power Sources, 2016, 332(15):355-365; Li et al., Chem. Eng. J., 2020, 380(15):122544; Huang et al., Chem. Eng. J., 2021, 419(27):129643), which consumes a lot of energy, is difficult to control, and may cause production safety problems due to improper operation, making it unsuitable for actual large-scale production. Therefore, designing and preparing feasible transition metal sulfide supercapacitor electrode materials under ambient temperature and pressure conditions, maximizing the advantages of sulfide materials with minimal resource and energy consumption, and utilizing the synergistic effect of multiple metals to improve the performance of electrode materials has practical value. Summary of the Invention

[0003] The purpose of this invention is to provide a supercapacitor material and its preparation method to overcome the defects of the prior art.

[0004] To achieve the above objectives, the present invention employs the following technical methods:

[0005] (1) Add 30 ml of anhydrous ethanol to the transition metal oxalate precursor, and use ultrasound to disperse the solute particles evenly in the anhydrous ethanol; the transition metal oxalate precursor is a binary nickel-cobalt oxalate; the molecular formula of the binary nickel-cobalt oxalate is Ni x Co y C2O4, wherein 0 < x < 1, 0 < y < 1, x + y = 2; the transition metal oxalate precursor is prepared by a co-precipitation method;

[0006] (2) Mix the solution obtained in step (1) with an excess of sulfur source, stir thoroughly to obtain a uniformly mixed suspension, and observe the color change of the solution.

[0007] (3) At a certain temperature, the mixed suspension obtained in step (2) is reacted in an oil bath device for 2 hours; in order to obtain sulfide samples generated under different temperature conditions, the reaction is carried out at temperatures of 25℃, 50℃ and 85℃ respectively.

[0008] (4) After the solution from step (3) has reacted, let it stand, separate the precipitate, wash and dry it to obtain a black powder, which is the transition metal sulfide supercapacitor material.

[0009] Furthermore, the specific steps for preparing transition metal oxalate precursor materials in the above preparation method include:

[0010] (a) Dissolve the weighed soluble nickel and cobalt salts in 20 ml of ethylene glycol solution and stir well under heating at 60 °C. This solution is denoted as solution A. Dissolve 2 mmol of ammonium oxalate monohydrate ((NH4)2C2O4·H2O) in 40 ml of deionized water and stir well. This solution is denoted as solution B.

[0011] (b) Slowly add solution A obtained in step (1) to solution B, continue stirring for 4 hours, and then let stand for 1 hour. Then wash the obtained precipitate three times each with deionized water and anhydrous ethanol, and dry it overnight in an electric heating drying oven.

[0012] Furthermore, the binary metal nickel-cobalt oxalate Ni mentioned in the above steps x Co y C2O4 has a nickel-cobalt ratio of x:y = 1:2, 1:1 and 2:1.

[0013] Furthermore, the sulfur source mentioned in the above steps is a sodium sulfide solution with a concentration of approximately 0.2 mol / L; the sodium sulfide solution is prepared by weighing 2 mmol of sodium sulfide nonahydrate (Na2S·9H2O) and dissolving it in 10 ml of deionized water, stirring thoroughly, and mixing evenly.

[0014] Furthermore, the soluble nickel salt used in the preparation method of the transition metal oxalate precursor is nickel nitrate (Ni(NO3)2) or nickel acetate (Ni(CH3COO)2), and the soluble cobalt salt is cobalt nitrate (Co(NO3)2) or cobalt acetate (Ni(CH3COO)2).

[0015] Compared with the prior art, the advantages of the present invention are as follows:

[0016] 1. The raw materials used in this invention are readily available, inexpensive, environmentally friendly, and have low energy consumption;

[0017] 2. The preparation method of the present invention differs from the existing general preparation methods that require a high temperature and high pressure environment. It obtains transition metal sulfides as cathode materials for supercapacitors through the ion exchange reaction between sulfur ions in the sulfur source and oxalate precursor at room temperature. The reaction environment is easy to form, the preparation process is simple and easy to control, and it is highly safe.

[0018] 3. The amorphous transition metal sulfide material with a rough nanowire morphology prepared by this invention exhibits excellent superelectric properties and high specific capacitance. Hybrid devices made using the material prepared by this invention demonstrate good high energy density and excellent cycling performance. Attached Figure Description

[0019] Figure 1 The X-ray diffraction (XRD) spectrum of the transition metal sulfide material provided in Embodiment 2 of the present invention;

[0020] Figure 2 This is a scanning electron microscope (SEM) image of the transition metal sulfide material provided in Embodiment 2 of the present invention;

[0021] Figure 3 The electrochemical test curves of the transition metal sulfide materials prepared with different nickel-cobalt ratios provided in Example 1 of the present invention are shown. (a) is the cyclic voltammetry (CV) curve of the transition metal sulfide material at a scan rate of 20 mV / s, and (b) is the galvanostatic charge-discharge (GCD) curve of the transition metal sulfide material at a current density of 1 A / g.

[0022] Figure 4 The electrochemical test curves of the transition metal sulfide materials obtained at different sulfidation temperatures provided in Example 2 of the present invention are shown. (a) is the cyclic voltammetry (CV) curve of the transition metal sulfide material at a scan rate of 20 mV / s, and (b) is the galvanostatic charge-discharge (GCD) curve of the transition metal sulfide material at a current density of 1 A / g. Detailed Implementation

[0023] To facilitate understanding of the present invention, a more comprehensive and detailed description of the invention will be provided below in conjunction with the accompanying drawings and preferred embodiments. However, the scope of protection of the present invention is not limited to the specific embodiments described below. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Various raw materials, reagents, instruments, and equipment used in the embodiments can be purchased commercially or prepared by existing methods.

[0024] Example 1:

[0025] A method for preparing a transition metal sulfide supercapacitor material according to the present invention includes the following steps:

[0026] (1) Weigh 0.2g of Ni prepared by the co-precipitation method with nickel-cobalt ratios x:y = 1:2, 1:1 and 2:1 respectively. x Co y The C2O4 precursor was placed in 100 mL of anhydrous ethanol and magnetically stirred for 10 min to obtain a uniformly dispersed suspension.

[0027] (2) Weigh 1.0g of sodium sulfide nonahydrate (Na2S·9H2O) and add it to the above suspension. Continue to stir magnetically for 2h to mix the two raw materials evenly. React at 25℃ for 2h.

[0028] (3) Wash the reaction product obtained in step (2) with deionized water and anhydrous ethanol in sequence. Then, centrifuge the washed sample and place it in a vacuum drying oven to dry at 60°C for 12 hours to obtain a black powder, which is the target product, transition metal sulfide supercapacitor material.

[0029] Example 2:

[0030] A method for preparing a transition metal sulfide supercapacitor material according to the present invention includes the following steps:

[0031] (1) Weigh 0.2g of Ni prepared by the co-precipitation method with a nickel-cobalt ratio of x:y = 2:1. x Co y The C2O4 precursor was placed in 100 mL of anhydrous ethanol and magnetically stirred for 10 min to obtain a uniformly dispersed suspension.

[0032] (2) Weigh 1.0g of sodium sulfide nonahydrate (Na2S·9H2O) and add it to the above suspension. Continue to stir magnetically for 2h to mix the two raw materials evenly. Set three different temperature conditions of 25℃, 50℃ and 80℃ respectively and react for 2h.

[0033] (3) Wash the reaction product obtained in step (2) with deionized water and anhydrous ethanol in sequence. Then, centrifuge the washed sample and place it in a vacuum drying oven to dry at 60°C for 12 hours to obtain a black powder, which is the target product, transition metal sulfide supercapacitor material.

[0034] Example 3:

[0035] An application of the transition metal sulfide supercapacitor of the present invention includes the following steps:

[0036] Using nickel foam as the carrier fluid, the nickel foam was cut to an appropriate size and ultrasonically cleaned sequentially in acetone, ethanol, and deionized water for 10 minutes before use. At a mass ratio of 8:1:1, 0.08g of the supercapacitor material obtained in this invention example, 0.01g of binder (PVDF), and 0.01g of conductive agent (acetylene black) were weighed out and thoroughly dispersed in an agate mortar with 0.5ml of NMP. This mixture was then evenly coated onto the nickel foam, with a coating area of ​​approximately 1cm². 2 After preparation, the tablets are dried at 60°C and then compressed.

[0037] A three-electrode system was adopted. The working electrode of the foamed nickel sheet prepared in this example was a platinum sheet as the counter electrode and Hg / HgO as the reference electrode. The electrolyte used was a 1 mol / L sodium sulfate solution.

Claims

1. A method for producing a transition metal sulfide electrode material, characterized by, The method comprises the following steps: (1) adding 30 ml of anhydrous ethanol into a transition metal oxalate precursor, and dispersing the solute microparticles uniformly in the anhydrous ethanol by ultrasonic waves; the transition metal oxalate precursor is a binary metal nickel-cobalt oxalate; the molecular formula of the binary metal nickel-cobalt oxalate is Ni x Co y C2O4, wherein 0 < x < 1, 0 < y < 1, and x + y = 2; the transition metal oxalate precursor is prepared by a coprecipitation method; (2) mixing the solution obtained in step (1) with an excess of a sulfur source, stirring thoroughly to obtain a uniformly mixed suspension, and observing the color change of the solution; (3) reacting the mixed suspension obtained in step (2) in an oil bath device at a certain temperature for 2 hours; in order to obtain sulfide samples generated under different temperature conditions, the reaction is carried out at temperatures of 25℃, 50℃ and 85℃, respectively; (4) allowing the solution after the reaction in step (3) to stand, separating the precipitate, washing and drying to obtain black powder, which is a transition metal sulfide electrode material.

2. The production method according to claim 1, wherein The specific steps for preparing the transition metal oxalate precursor material in step (1) include: (a) dissolving a weighed amount of soluble nickel salt and cobalt salt in 20 ml of ethylene glycol solution, stirring uniformly under heating at 60℃, and recording as solution A; dissolving 2 mmol of ammonium oxalate monohydrate ((NH4)2C2O4·H2O) in 40 ml of deionized water, stirring uniformly, and recording as solution B; (b) slowly adding the solution A obtained in step (1) to solution B, continuing to stir for 4 hours and then standing for 1 hour; then washing the obtained precipitate with deionized water and anhydrous ethanol each for three times, and placing it in an electric heating air drying oven for drying overnight.

3. The production method according to claim 1, wherein The binary metal nickel cobalt oxalate Ni x Co y C2O4, the ratio of nickel cobalt is x:y = 1:2, 1:1 or 2:

1.

4. The production method according to claim 1, wherein The sulfur source in step (2) is a sodium sulfide solution with a concentration of 0.2 mol / L; the method for preparing the sodium sulfide solution is to weigh 2 mmol of sodium sulfide nonahydrate (Na2S·9H2O) and dissolve it in 10 ml of deionized water, stirring thoroughly and mixing uniformly.

5. The production method according to claim 2, wherein The soluble nickel salt used in step (a) is nickel nitrate (Ni(NO3)2) or nickel acetate (Ni(CH3COO)2), and the soluble cobalt salt is cobalt nitrate (Co(NO3)2) or cobalt acetate.

Images