Solid-state supercapacitor fiber electrode and preparation method thereof

Abstract

The present application provides a solid-state supercapacitor fiber electrode and a preparation method thereof, which belongs to the field of supercapacitors. The preparation method sprays a metal hydroxide solution on a graphene oxide film, then rolls the film onto a fiber, and then performs high-temperature activation and calcination to obtain a graphene porous fiber, and then electrochemically deposits MnO2 on the graphene porous fiber to obtain a supercapacitor fiber electrode MnO2@aRGOF. The preparation process conditions of the present invention are simple, and the porous graphene fiber is obtained by high-temperature activation and calcination, which is beneficial to the transmission and storage of ions. The subsequent electrochemical deposition to obtain the MnO2@aRGOF electrode further improves the energy storage performance of the material. This composite electrode material shows the advantages of superior performance and good cycle stability as a supercapacitor fiber electrode, and has broad application prospects in the field of energy storage.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor technology, specifically to a solid-state supercapacitor fiber electrode and its preparation method. Background Technology

[0002] Supercapacitors, as efficient and environmentally friendly energy storage devices, have attracted much attention due to their rapid charge-discharge and cycle stability. Currently, electronic products are becoming increasingly lightweight and flexible, making the emergence of fiber-based solid-state supercapacitors inevitable. Solid-state supercapacitors possess advantages such as high power density, stable cycle life, and rapid charge-discharge, making them highly promising energy storage devices. However, the energy density of current solid-state supercapacitors remains very low. To address this issue, improving the specific capacitance of supercapacitor electrode materials is urgently needed.

[0003] Patent CN 105810456 A discloses an activated graphene / needle-shaped nickel hydroxide nanocomposite material and its preparation method. This method uses graphene prepared by a redox method as a raw material and KOH or NaOH as an activating agent to prepare activated graphene. Then, needle-shaped nickel hydroxide nanoparticles are loaded onto the surface of the activated graphene to prepare the activated graphene / needle-shaped nickel hydroxide nanocomposite material. However, this preparation method is complex and uses graphene as a raw material, resulting in high costs.

[0004] In view of this, it is necessary to design a solid-state supercapacitor fiber electrode and its preparation method to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a solid-state supercapacitor fiber electrode and its preparation method. The preparation method involves spraying a metal hydroxide onto a graphene oxide film, rolling it onto fibers, and then activating and calcining it at high temperature to obtain porous graphene fibers (Activated RGOF or aRGOF). Subsequently, MnO2 is electrochemically deposited on the porous graphene fibers to obtain a solid-state supercapacitor fiber electrode, MnO2@aRGOF. The preparation process of this invention is simple. The use of high-temperature activation and calcination to obtain porous graphene fibers is beneficial for ion transport and storage. The subsequent electrochemical deposition of the MnO2@aRGOF electrode further improves the energy storage performance of the material. This composite electrode material, as a supercapacitor fiber electrode, exhibits superior performance and good cycle stability, and has broad application prospects in the field of energy storage.

[0006] This application achieves simultaneous reduction and activation by high-temperature calcination of the precursor (a mixture of graphene oxide and metal oxide fibers), simplifying the synthesis process. Furthermore, using redox graphene significantly reduces costs compared to using graphene as a raw material.

[0007] In a first aspect, embodiments of this application provide a method for preparing a fiber electrode for a solid-state supercapacitor, comprising the following steps:

[0008] S1, spread an aqueous solution of graphene oxide with a concentration of 1-40 mg / ml in a mold and place it in a fume hood to obtain a dry graphene oxide film;

[0009] S2, prepare a metal hydroxide solution, and repeatedly spray the metal hydroxide solution onto the dried graphene oxide film obtained in step S1; then, twist the graphene oxide film containing metal hydroxide, roll it into fibers, and dry it for later use; wherein, the mass ratio of graphene oxide to metal hydroxide is 1:(6~16).

[0010] S3. The dried sample obtained in step S2 is activated and calcined at high temperature in an argon atmosphere in a tube furnace, then ultrasonically washed with deionized water, and finally dried to obtain graphene porous fibers.

[0011] S4. Prepare a mixed solution of sodium sulfite and manganese sulfate, and perform electrochemical deposition of MnO2 using a three-electrode structure: the working electrode is the graphene porous fiber obtained in step S3, the counter electrode is a Pt electrode, and the reference electrode is a calomel electrode. The prepared mixed solution of sodium sulfite and manganese sulfate is used as the electrolyte for constant current deposition. After deposition, the fiber electrode is thoroughly washed with deionized water and dried to obtain a solid supercapacitor fiber electrode.

[0012] In the technical solution of this application embodiment, a metal hydroxide is introduced during fiber preparation. The metal hydroxide is then activated and calcined at high temperature to create pores within the graphene oxide layer, resulting in porous graphene fibers (Activated RGOF or aRGOF). This facilitates ion transport and storage. MnO2 is then electrochemically deposited on the Active RGOF to provide pseudocapacitance, further increasing the energy storage performance of the fiber electrode. The Active RGOF achieves an energy storage capacity of 0.4 mA·cm⁻¹. -2 At a current density, it can provide an areal capacitance of 414.53 mF·cm⁻¹. -2 After electrochemical deposition of MnO2 by activated RGOF (MnO2@aRGOF), it can provide 516.13 mF·cm⁻¹ within the operating voltage range of 0–1.2 V. -2 The specific capacity per square meter (0.08 A·cm³) -3 At a current density of 60.49 F·cm³, the volumetric capacitance is 60.49 F·cm³. -3 ).

[0013] Preferably, in step S4, the deposition current in the constant current deposition process is 200–800 μA·cm. -2 The deposition time is 5 to 30 minutes.

[0014] In the technical solution of this application embodiment, MnO2 is deposited on aRGOF under constant current for 5-40 min, which increases pseudocapacitance and improves electrochemical performance.

[0015] Preferably, in step S3, the temperature control method for the high-temperature activation calcination is as follows: increasing the temperature at 2-20°C / min to 200-400°C, holding for 10-120 min, and then increasing the temperature at 2-20°C / min to 300-1000°C and holding for 10-120 min. More preferably, the temperature control method for the high-temperature activation calcination is as follows: increasing the temperature at 2°C / min to 280°C, holding for 30 min, and then increasing the temperature at 5°C / min to 650°C and holding for 30 min.

[0016] Preferably, the heating rate in the second stage is greater than the heating rate in the first stage.

[0017] In the technical solution of this application embodiment, the obtained graphene porous fiber has a three-dimensional porous structure distribution (it has mesopores, which facilitate ion transport; at the same time, micropores further increase the energy storage performance of the material) while maintaining the integrity of the fiber.

[0018] Preferably, in step S2, the metal hydroxide solution contains metal hydroxide:deionized water in a ratio of (1-20g):(50-500mL).

[0019] Preferably, the metal hydroxide solution is a sodium hydroxide solution or a potassium hydroxide solution.

[0020] Preferably, in step S4, the concentration of sodium sulfite is 0.5–5 mol / L; the mass ratio of sodium sulfite to manganese sulfate is (5–50):1.

[0021] Preferably, in step S2, the drying temperature range is 20–200°C, and the drying time is 12–48 h.

[0022] Preferably, in step S1, the mold is made of polytetrafluoroethylene. The settling time is 12–36 hours.

[0023] Secondly, embodiments of this application provide a solid-state supercapacitor fiber electrode, prepared using the aforementioned technical solution. This solid-state supercapacitor fiber electrode comprises graphene porous fibers and MnO2 uniformly loaded on the surface of the graphene porous fibers. This solid-state supercapacitor fiber electrode can provide 516.13 mF·cm⁻¹ within a working voltage range of 0–1.2 V. -2 The specific capacity per square meter (0.08 A·cm³) -3 At a current density of 60.49 F·cm³, the volumetric capacitance is 60.49 F·cm³. -3).

[0024] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0026] Figure 1 This is a scanning electron microscope image of the solid supercapacitor fiber electrode prepared in Example 1 of the present invention.

[0027] Figure 2 The CV curve of the solid supercapacitor fiber electrode prepared in Example 1 of the present invention at voltage scan rates of 10 mV / s to 500 mV / s.

[0028] Figure 3 The results of constant current charge-discharge test of the solid supercapacitor fiber electrode prepared in Example 1 of this invention.

[0029] Figure 4 The AC impedance test results are for the solid supercapacitor fiber electrode prepared in Example 1 of this invention. Detailed Implementation

[0030] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0032] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0033] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0034] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0035] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0036] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0037] In a first aspect, embodiments of this application provide a method for preparing a fiber electrode for a solid-state supercapacitor, comprising the following steps:

[0038] S1, spread an aqueous solution of graphene oxide with a concentration of 1-40 mg / ml in a mold and place it in a fume hood to obtain a dry graphene oxide film;

[0039] The mold is made of polytetrafluoroethylene. The settling time is 12–36 hours.

[0040] S2, prepare a metal hydroxide solution, and repeatedly spray the metal hydroxide solution onto the dried graphene oxide film obtained in step S1; then, twist the graphene oxide film containing metal hydroxide, roll it into fibers, and dry it for later use; wherein, the mass ratio of graphene oxide to metal hydroxide is 1:(6~16).

[0041] In this metal hydroxide solution, the ratio of metal hydroxide to deionized water is (1–20 g): (50–500 mL). The metal hydroxide solution is either a sodium hydroxide solution or a potassium hydroxide solution.

[0042] During the drying process, the drying temperature range is 20–200℃, and the drying time is 12–48 hours. Preferably, the drying temperature range is 60–80℃.

[0043] S3. The dried sample obtained in step S2 is activated and calcined at high temperature in an argon atmosphere in a tube furnace, then ultrasonically washed with deionized water, and finally dried to obtain graphene porous fibers.

[0044] Specifically, the temperature control method for high-temperature activation calcination is a two-stage control: raise the temperature to 200-400℃ at a rate of 2-20℃ / min, hold for 10-120min, and then raise the temperature to 300-1000℃ at a rate of 2-20℃ / min and hold for 10-120min.

[0045] Preferably, the heating rate in the second stage is greater than that in the first stage; specifically, the temperature control method for high-temperature activation calcination is as follows: heat to 280°C at 2° / min, hold for 30 min, then heat to 650°C at 5° / min and hold for 30 min.

[0046] S4. Prepare a mixed solution of sodium sulfite and manganese sulfate, and perform electrochemical deposition of MnO2 using a three-electrode structure: the working electrode is the graphene porous fiber obtained in step S3, the counter electrode is a Pt electrode, and the reference electrode is a calomel electrode. The prepared mixed solution of sodium sulfite and manganese sulfate is used as the electrolyte for constant current deposition. After deposition, the fiber electrode is thoroughly washed with deionized water and dried to obtain a solid supercapacitor fiber electrode.

[0047] Specifically, in the constant current deposition process, the deposition current is 200–800 μA·cm. -2 The deposition time is 5 to 30 minutes.

[0048] The concentration of sodium sulfite is 0.5–5 mol / L; the mass ratio of sodium sulfite to manganese sulfate is (5–50):1.

[0049] Secondly, embodiments of this application provide a solid-state supercapacitor fiber electrode, prepared by the aforementioned method. The resulting solid-state supercapacitor fiber electrode comprises graphene porous fibers and MnO2 uniformly loaded on the surface of the graphene porous fibers. This solid-state supercapacitor fiber electrode can provide 516.13 mF·cm⁻¹ in an operating voltage range of 0–1.2 V. -2 The specific capacity per square meter (0.08 A·cm³) -3 At a current density of 60.49 F·cm³, the volumetric capacitance is 60.49 F·cm³. -3 ).

[0050] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0051] Example 1

[0052] This embodiment provides a method for preparing a fiber electrode for a solid-state supercapacitor, including the following steps:

[0053] S1, the concentration of graphene oxide in the aqueous solution was measured to be 7 mg / ml. 20 ml of the solution was sonicated for 2 hours and then spread on a custom polytetrafluoroethylene mold (100×100×10mm). The solution was left to stand in a fume hood overnight to obtain a dry graphene oxide film.

[0054] S2, weigh 5.04g of KOH, pour it into 30ml of deionized water, mix well to obtain a KOH aqueous solution; then, repeatedly spray the KOH aqueous solution onto the dried graphene oxide film obtained in S1; then carefully peel off the film with tweezers, twist the KOH-containing graphene oxide film, roll it into fibers, and dry it at 60℃ for 24h; wherein, the mass ratio of graphene oxide to KOH is 1:12.

[0055] S3. The dried sample was calcined in an argon atmosphere in a tube furnace, heated to 280°C at 2° / min and held for 30 min, then heated to 650°C at 5° / min and held for 30 min. The sample was then ultrasonically washed three times with deionized water for 20 min each time, and finally dried at 60°C for 12 h to obtain graphene porous fibers (aRGOF).

[0056] S4, weigh 12.19 g of anhydrous sodium sulfite, pour it into 70 ml of deionized water and stir well. Then add 1.06 g of anhydrous manganese sulfate, mix and stir continuously. Electrochemical deposition of MnO2 is performed using a three-electrode structure: the working electrode is aRGOF obtained in step S3, the counter electrode is a Pt electrode (10 × 10 × 0.1 mm), and the reference electrode is a calomel electrode (3MKCl). 400 μA·cm⁻¹ is applied over 20 min. -2 The constant current.

[0057] After deposition, the fiber electrode for the solid supercapacitor is thoroughly washed with deionized water and dried to obtain the solid supercapacitor fiber electrode.

[0058] Examples 2-6 and Comparative Examples 1-3

[0059] Examples 2-6 and Comparative Examples 1-3 provide a method for preparing fiber electrodes for solid-state supercapacitors. Compared with Example 1, the differences are that the mass ratio of graphene oxide to metal hydroxide in step S2 is changed, the type of metal hydroxide is changed, and the constant current deposition time in step S4 is changed, as shown in the table below. The rest is roughly the same as in Example 1 and will not be repeated here.

[0060]

[0061]

[0062] Experiments show that among the samples prepared in Examples 1-6, the sample prepared in Example 1 has the best electrochemical performance.

[0063] Figure 1 The image shows a scanning electron microscope (SEM) image of the solid-state supercapacitor fiber electrode prepared in Example 1. Image b is a magnified view of image a. Image a shows that MnO2 is uniformly attached to the fiber surface; image b shows that the graphene fiber surface has a porous structure with needle-like MnO2 particles. This morphology increases the number of sites on the material surface where redox reactions can occur, resulting in better capacitance.

[0064] Figure 2 The CV curves of the solid-state supercapacitor fiber electrode prepared in Example 1 are shown in the voltage scan rate range of 10 mV / s to 500 mV / s. It can be seen that the shape of the CV curves is close to rectangular, indicating that the material exhibits excellent capacitive behavior.

[0065] Figure 3 The results of the constant current charge-discharge test of the solid-state supercapacitor fiber electrode prepared in Example 1 are shown. It can be seen that at 0.4 mA·cm⁻¹... -2 At a current density of 516.13 mF·cm⁻¹, the electrode material can provide 516.13 mF·cm⁻¹. -2The area-to-capacity ratio, even at a current density of 4 mA·cm², is high. -2 Below, the electrode material still has 219.71 mF·cm⁻¹ -2 It exhibits excellent electrochemical performance due to its high area specific capacity.

[0066] Figure 4 The AC impedance test results are for the solid-state supercapacitor fiber electrode prepared in Example 1 of this invention. The curves show that the material has a low diffusion resistance, indicating good conductivity. The porous graphene fiber structure is beneficial for ion transport and storage within the material.

[0067] In Comparative Example 1, when GO:KOH = 1:20, the mixed graphene oxide and KOH fiber material is over-activated after high-temperature calcination in step S3, resulting in a very brittle fiber material with a low yield, which cannot be used as an electrode for the next deposition step.

[0068] In Comparative Example 2, when GO:KOH = 1:2, the fibers obtained after calcination were not sufficiently activated and had virtually no porous structure.

[0069] In Comparative Example 3, when the constant current deposition time was 40 min, the MnO2 on the fiber surface of the obtained fiber electrode agglomerated, resulting in a significant decrease in its energy storage capacity as an electrode. The reason is that the deposition time was too long, leading to excessive nucleation and growth of MnO2, which eventually completely covered the fiber surface and agglomerated.

[0070] In Example 6, KOH was replaced with NaOH, and the resulting fiber material also had a porous structure, with similar properties.

[0071] Comparative Example 4

[0072] Comparative Example 4 provides a method for preparing a solid supercapacitor fiber electrode. Compared with Example 1, the difference is that the high-temperature calcination control method in step S3 is replaced by: raising the temperature to 650°C at 2° / min and holding it for 30min.

[0073] Experiments show that when using a one-stage heating method, the fiber material obtained after high-temperature calcination is very brittle and has a low yield, making it unsuitable as an electrode for further deposition.

[0074] Comparative Example 5

[0075] Comparative Example 5 provides a method for preparing a solid supercapacitor fiber electrode. Compared with Example 1, the difference is that the high-temperature calcination control method in step S3 is replaced by: raising the temperature to 1050°C at 2° / min and holding for 30min.

[0076] Experiments show that the fiber material obtained after high-temperature calcination is very brittle and has a low yield, making it unsuitable as an electrode for further deposition.

[0077] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a fiber electrode for a solid-state supercapacitor, characterized in that, Includes the following steps: S1, spread an aqueous solution of graphene oxide with a concentration of 1-40 mg / ml in a mold and place it in a fume hood to obtain a dry graphene oxide film; S2, prepare a metal hydroxide solution, and repeatedly spray the metal hydroxide solution onto the dried graphene oxide film obtained in step S1; then, twist the graphene oxide film containing the metal hydroxide, roll it into fibers, and dry it for later use; wherein, the mass ratio of the graphene oxide to the metal hydroxide is 1:(6~16). S3. The dried sample obtained in step S2 is activated and calcined at high temperature in an argon atmosphere in a tube furnace, then ultrasonically washed with deionized water, and finally dried to obtain graphene porous fibers. S4. Prepare a mixed solution of sodium sulfite and manganese sulfate, and perform electrochemical deposition of MnO2 using a three-electrode structure: the working electrode is the graphene porous fiber obtained in step S3, the counter electrode is a Pt electrode, the reference electrode is a calomel electrode, and the prepared mixed solution of sodium sulfite and manganese sulfate is used as the electrolyte for constant current deposition. After deposition, the material is thoroughly washed with deionized water and dried to obtain a solid supercapacitor fiber electrode.

2. The method for preparing the fiber electrode of a solid-state supercapacitor according to claim 1, characterized in that, In step S4, during the constant current deposition process, the deposition current is 200–800 μA·cm. -2 The deposition time is 5 to 30 minutes.

3. The method for preparing the fiber electrode of a solid-state supercapacitor according to claim 1, characterized in that, In step S3, the temperature control method for the high-temperature activation calcination is as follows: the temperature is increased to 200-400℃ at a rate of 2-20℃ / min, held for 10-120min, and then increased to 300-1000℃ at a rate of 2-20℃ / min and held for 10-120min.

4. The method for preparing the fiber electrode of a solid-state supercapacitor according to claim 3, characterized in that, The heating rate in the second stage is greater than that in the first stage.

5. The method for preparing the fiber electrode of a solid-state supercapacitor according to claim 1, characterized in that, In step S2, the metal hydroxide solution contains metal hydroxide:deionized water in a ratio of (1-20g):(50-500mL).

6. The method for preparing the fiber electrode of a solid-state supercapacitor according to claim 1, characterized in that, The metal hydroxide solution is a sodium hydroxide solution or a potassium hydroxide solution.

7. The method for preparing the fiber electrode of a solid-state supercapacitor according to claim 1, characterized in that, In step S4, the concentration of sodium sulfite is 0.5–5 mol / L; the mass ratio of sodium sulfite to manganese sulfate is (5–50):

1.

8. The method for preparing the fiber electrode of a solid-state supercapacitor according to claim 1, characterized in that, In step S2, the drying temperature range is 20 to 200°C, and the drying time is 12 to 48 hours.

9. The method for preparing a solid-state supercapacitor fiber electrode according to claim 1, characterized in that, In step S1, the mold is made of polytetrafluoroethylene.

10. A fiber electrode for a solid-state supercapacitor, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

Images