Electrode material for supercapacitors and method for producing same

Abstract

The application relates to the technical field of energy storage, in particular to an electrode material for a super capacitor and a preparation method thereof, which comprises a transition metal sulfide, fullerene / heterocyclic polymer / polydopamine composite micro-nano tube and amino acid functionalized graphene quantum dots. The prepared electrode material has a high specific capacitance, an excellent capacity retention rate and good cycle stability.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, specifically to an electrode material for supercapacitors and its preparation method. Background Technology

[0002] Supercapacitors are a new type of energy storage device developed from traditional electrolytic capacitors. Due to the use of novel electrode materials and electrolyte systems, they exhibit high power density and high energy density. Supercapacitors can replace secondary batteries in fields such as mobile communications, information technology, aerospace, and defense technology, and have been extensively studied.

[0003] Among various electrode materials for supercapacitors, transition metal sulfides possess high theoretical capacity, but their poor conductivity affects ion transport rates, resulting in actual electrochemical performance far below theoretical values. To further explore the electrochemical potential of transition metal sulfides and increase their conductivity, composite materials can be prepared to improve their electrochemical performance. However, composite materials may cause volume effects, leading to material shedding and reduced stability, resulting in decreased cycle stability. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes an electrode material for supercapacitors and a method for preparing the same.

[0005] The technical solution adopted is as follows:

[0006] An electrode material for supercapacitors includes transition metal sulfides, fullerene / heterocyclic polymer / polydopamine composite micro / nanotubes, and amino acid-functionalized graphene quantum dots.

[0007] Furthermore, the weight ratio of the transition metal sulfide, fullerene / heterocyclic polymer / polydopamine composite micro / nanotubes, and amino acid functionalized graphene quantum dots is 1-5:0.1-1:1-5.

[0008] Furthermore, the transition metal sulfide is any one or more combinations of ZnCo2S4, CuCo2S4, and NiCo2S4.

[0009] Furthermore, the preparation method of the fullerene / heterocyclic polymer / polydopamine composite micro / nanotubes is as follows:

[0010] Heterocyclic polymers and polydopamine were dissolved in NMP, and fullerene micro-nanotubes were added. The mixture was then dispersed by ultrasonic oscillation to obtain a suspension. The suspension was cooled in an ice-water bath and water was added dropwise. After the addition was complete, the mixture was stirred for 24-48 hours and then centrifuged. The resulting solid was dried to remove water.

[0011] Further, the heterocyclic polymer is any one or more combinations of polypyrrole, polybenzopyrrole, polycarbazole, polythiophene, polybenzothiophene, and polydibenzothiophene.

[0012] Furthermore, the weight ratio of the heterocyclic polymer to polydopamine is 1-5:1-5.

[0013] Furthermore, the preparation method of the amino acid functionalized graphene quantum dots is as follows:

[0014] Dissolve citric acid and amino acids in water, place them in a constant temperature drying oven at 180-200℃ for 3-6 hours for pyrolysis, cool to room temperature, add water to prepare an aqueous solution, adjust the pH to 7-8 with sodium hydroxide solution, microfilter, then dialyze in ultrapure water using a dialysis bag to remove unreacted citric acid and amino acids, and finally freeze dry.

[0015] Furthermore, the amino acid is aspartic acid.

[0016] This invention also provides a method for preparing electrode materials for supercapacitors:

[0017] The mixture of transition metal sulfides and amino acid-functionalized graphene quantum dots is ball-milled, dried, and then mixed with fullerene / heterocyclic polymer / polydopamine composite micro / nanotubes.

[0018] The beneficial effects of this invention are:

[0019] This invention provides an electrode material for supercapacitors. Transition metal sulfides have high theoretical capacity, but their poor conductivity affects the ion transport rate, resulting in actual electrochemical performance that is far lower than the theoretical value.

[0020] Fullerene / heterocyclic polymer / polydopamine composite micro-nanotubes introduce cavities inside the electrode material. Due to their special structure, they have advantages such as low density, large specific surface area, excellent surface permeability and large internal storage space. They can alleviate the electrode volume effect, improve cycle stability, and allow the electrolyte to gradually penetrate into the internal pores during cycling, so that the active sites in the internal pores can be fully utilized.

[0021] On the other hand, the excellent conductivity promotes charge transfer and ion diffusion, thereby increasing the charge transfer rate between the electrode material and the electrolyte and improving its electrochemical performance. By depositing heterocyclic polymers and polydopamine on the surface of fullerene micro-nanotubes, the conductivity of the heterocyclic polymers is improved, thus exhibiting a better pseudocapacitive effect. This may be because polydopamine carries a negative charge, which can balance the positive charge of the heterocyclic polymers, thus acting as a "dopant".

[0022] Graphene quantum dots, with dimensions of only a few nanometers, exhibit strong quantum confinement and boundary effects, which are highly effective in improving the conductivity and stability of electrode materials. Citric acid forms sp... 2 The graphene sheet, composed of carbon atoms, has amide bonds formed by the condensation of amino groups in amino acid molecules with carboxyl groups at the edge of the graphene sheet, thus functionalizing the graphene and giving it better electrochemical activity. The electrode material prepared by this invention has high specific capacitance, excellent capacity retention, and good cycling stability. Attached Figure Description

[0023] Figure 1 The image shows a SEM image of CuCo2S4 prepared in Example 1.

[0024] Figure 2 This is a TEM image of the fullerene / polypyrrole / polydopamine composite micro / nanotubes prepared in Example 1.

[0025] Figure 3 This is a TEM image of the amino acid-functionalized graphene quantum dots prepared in Example 1. Detailed Implementation

[0026] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0027] Example 1:

[0028] An electrode material for supercapacitors comprises CuCo2S4 in a weight ratio of 5:0.5:2.5, fullerene / polypyrrole / polydopamine composite micro / nanotubes, and amino acid-functionalized graphene quantum dots.

[0029] Using porous nickel foam as the current collector, the nickel foam was first cut into 1cm×1cm electrode sheets. Since nickel foam is easily oxidized in air to form an oxide film, the nickel foam was ultrasonically cleaned in acetone and anhydrous ethanol for 1 hour. CuCo2S4 and amino acid functionalized graphene quantum dots were mixed and ball-milled for 5 hours, then dried and mixed with fullerene / heterocyclic polymer / polydopamine composite micro-nanotubes to obtain the electrode material. The electrode material, acetylene black and polytetrafluoroethylene (PTFE, 60% water emulsion) were mixed evenly at a mass ratio of 8:1:1 with anhydrous ethanol as a liquid phase additive to obtain a slurry. The slurry was uniformly coated on the nickel foam using a repeated coating-drying method. Then the nickel foam was placed in a vacuum drying oven and vacuum dried at 80℃ for 24 hours. The nickel foam was then pressed into sheets at 10MPa to obtain the electrode. The electrode thickness was about 0.15mm, and the amount of active material in each electrode sheet was about 7mg.

[0030] The preparation method of CuCo2S4 is as follows:

[0031] Mix 0.2 mol cobalt nitrate hexahydrate, 0.1 mol copper nitrate trihydrate, and 0.9 mol thiourea, then add 5000 ml of a mixed solution of water and isopropanol (volume ratio 1:1). Stir thoroughly until completely dissolved. Pour the solution into a hydrothermal reactor and seal it for 24 h at 180 °C. After the reaction is complete, filter out the product, wash it with water, and then dry it in a vacuum drying oven at 40 °C for 10 h.

[0032] The preparation method of fullerene / polypyrrole / polydopamine composite micro / nanotubes is as follows:

[0033] Fullerene micro / nanotubes were prepared according to the methods described in the references below:

[0034] Han Zhu, Li Guibao, Pu Guangzhe. Fullerene C 60 Synthesis and growth mechanism of nanotubes [J]. Journal of Qingdao University of Science and Technology (Natural Science Edition), 2010, (No. 2);

[0035] Dissolve 1g of polypyrrole and 1g of polydopamine in 250ml of NMP, then add 0.5g of fullerene micro-nanotubes. After ultrasonic oscillation for 30min, disperse the mixture to obtain a suspension. Cool the suspension in an ice-water bath and add 2500ml of water dropwise. After the addition is complete, stir for 24h and centrifuge. Dry the resulting solid at 80℃ for 48h to remove water.

[0036] The preparation method of amino acid-functionalized graphene quantum dots is as follows:

[0037] Dissolve 25g of citric acid and 18g of DL-aspartic acid in 200ml of water, place in a constant temperature drying oven at 200℃ for 5h, cool to room temperature, add 1000ml of water to prepare an aqueous solution, adjust the pH to 7 with 1M sodium hydroxide solution, filter through a 0.22μm microporous membrane, and then dialyze in ultrapure water for 24h using a dialysis bag with a molecular weight cutoff of 3kDa to remove unreacted citric acid and DL-aspartic acid, and finally freeze dry.

[0038] Example 2:

[0039] The method is basically the same as in Example 1, except that the weight ratio of CuCo2S4, fullerene / polypyrrole / polydopamine composite micro / nanotubes and amino acid functionalized graphene quantum dots is 5:1:5.

[0040] Example 3:

[0041] The results are basically the same as in Example 1, except that the weight ratio of CuCo2S4, fullerene / polypyrrole / polydopamine composite micro / nanotubes and amino acid functionalized graphene quantum dots is 5:0.5:5.

[0042] Example 4:

[0043] The results are basically the same as in Example 1, except that the weight ratio of CuCo2S4, fullerene / polypyrrole / polydopamine composite micro / nanotubes and amino acid functionalized graphene quantum dots is 5:0.1:5.

[0044] Comparative Example 1:

[0045] It is basically the same as Example 1, except that it does not include fullerene / polypyrrole / polydopamine composite micro / nanotubes and amino acid-functionalized graphene quantum dots.

[0046] Comparative Example 2:

[0047] It is basically the same as Example 1, except that it does not include fullerene / polypyrrole / polydopamine composite micro / nanotubes.

[0048] Comparative Example 3:

[0049] It is basically the same as Example 1, except that it does not include amino acid-functionalized graphene quantum dots.

[0050] Comparative Example 4:

[0051] The example is basically the same as Example 1, except that polypyrrole is used instead of polydopamine, that is, fullerene / polypyrrole composite micro-nanotubes are used instead of fullerene / polypyrrole / polydopamine composite micro-nanotubes.

[0052] The preparation method of fullerene / polypyrrole composite micro / nanotubes is as follows:

[0053] Dissolve 2g of polypyrrole in 250ml of NMP, then add 0.5g of fullerene micro / nanotubes. Disperse the solution by ultrasonic oscillation for 30min to obtain a suspension. Cool the suspension in an ice-water bath and add 2500ml of water dropwise. After the addition is complete, stir for 24h and centrifuge. Dry the resulting solid at 80℃ for 48h to remove moisture.

[0054] Comparative Example 5:

[0055] The example is basically the same as Example 1, except that polydopamine is used instead of polypyrrole, that is, fullerene / polydopamine composite micro-nanotubes are used instead of fullerene / polypyrrole / polydopamine composite micro-nanotubes.

[0056] The preparation method of fullerene / polydopamine composite micro / nanotubes is as follows:

[0057] Dissolve 2g of polydopamine in 250ml of NMP, then add 0.5g of fullerene micro-nanotubes. Disperse the mixture by ultrasonic oscillation for 30min to obtain a suspension. Cool the suspension in an ice-water bath and add 2500ml of water dropwise. After the addition is complete, stir for 24h and centrifuge. Dry the resulting solid at 80℃ for 48h to remove water.

[0058] Comparative Example 6:

[0059] The method is basically the same as in Example 1, except that commercially available graphene quantum dots (Beike Nano) are used instead of amino acid-functionalized graphene quantum dots.

[0060] Performance testing:

[0061] The electrochemical performance of the electrodes prepared in Examples 1-4 and Comparative Examples 1-6 of this invention was tested using a three-electrode system.

[0062] A three-electrode system was formed using a saturated calomel electrode as the reference electrode, a platinum sheet as the counter electrode, and 1 mol / L H2SO4 as the electrolyte. The specific capacitance of the three-electrode system at a current density of 1 A / g and the capacitance retention rate after 10,000 cycles were tested using a CHI760D electrochemical workstation.

[0063] The test results are shown in Table 1:

[0064] Table 1:

[0065]

[0066] As shown in Table 1 above, the electrode material prepared by the present invention has a high specific capacitance and excellent capacity retention, exhibiting good cycle stability.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrode material for supercapacitors, characterized in that, Including transition metal sulfides, fullerene / heterocyclic polymer / polydopamine composite micro / nanotubes, and amino acid-functionalized graphene quantum dots; The heterocyclic polymer is any one or more combinations of polypyrrole, polybenzopyrrole, polycarbazole, polythiophene, polybenzothiophene, and polydibenzothiophene.

2. The electrode material for a supercapacitor as described in claim 1, characterized in that, The weight ratio of the transition metal sulfide, fullerene / heterocyclic polymer / polydopamine composite micro / nanotubes, and amino acid-functionalized graphene quantum dots is 1-5: 0.1-1：1-5。 3. The electrode material for a supercapacitor as described in claim 1, characterized in that, The transition metal sulfide is any one or a combination of ZnCo2S4, CuCo2S4, and NiCo2S4.

4. The electrode material for a supercapacitor as described in claim 1, characterized in that, The preparation method of the fullerene / heterocyclic polymer / polydopamine composite micro / nanotubes is as follows: Heterocyclic polymers and polydopamine were dissolved in NMP, and fullerene micro-nanotubes were added. The mixture was then dispersed by ultrasonic oscillation to obtain a suspension. The suspension was cooled in an ice-water bath and water was added dropwise. After the addition was complete, the mixture was stirred for 24-48 hours and then centrifuged. The resulting solid was dried to remove water.

5. The electrode material for a supercapacitor as described in claim 4, characterized in that, The weight ratio of the heterocyclic polymer to polydopamine is 1-5:1-5.

6. The electrode material for a supercapacitor as described in claim 1, characterized in that, The preparation method of the amino acid functionalized graphene quantum dots is as follows: Dissolve citric acid and amino acids in water, place them in a constant temperature drying oven at 180-200℃ for 3-6 hours for pyrolysis, cool to room temperature, add water to prepare an aqueous solution, adjust the pH to 7-8 with sodium hydroxide solution, microfilter, then dialyze in ultrapure water using a dialysis bag to remove unreacted citric acid and amino acids, and finally freeze dry.

7. The electrode material for a supercapacitor as described in claim 6, characterized in that, The amino acid in question is aspartic acid.

8. A method for preparing an electrode material for a supercapacitor as described in any one of claims 1-7, characterized in that, The mixture of transition metal sulfides and amino acid-functionalized graphene quantum dots is ball-milled, dried, and then mixed with fullerene / heterocyclic polymer / polydopamine composite micro / nanotubes.

Images