A positive electrode material for supercapacitors, a preparation method therefor, and use thereof

Abstract

The application relates to the technical field of electrode materials, and discloses a positive electrode material for supercapacitors, a preparation method and application thereof. The positive electrode material for supercapacitors comprises a carbon-coated mixed material, and the mixed material in the carbon-coated mixed material is composed of manganese dioxide-coated carbon nanotubes and manganese dioxide-coated graphene. Through the technical scheme, the problems of low specific capacitance and poor cycle performance of the positive electrode material for supercapacitors in the related art are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electrode materials, in particular to a positive electrode material for a supercapacitor and a preparation method and application thereof. BACKGROUND

[0002] Compared with a traditional capacitor, the supercapacitor has a higher energy density, and compared with a battery, the supercapacitor has a higher power density, is a new type of power-type energy storage device, and has excellent characteristics such as short charging time, long service life, good temperature characteristics and green environmental protection.

[0003] The supercapacitor is mainly composed of positive and negative electrodes, an electrolyte and a diaphragm for preventing short circuit, and can be divided into three types, including a double-layer supercapacitor, a pseudo-capacitive supercapacitor and a hybrid supercapacitor. Among them, the hybrid supercapacitor has a higher energy density and is an important research and development direction at present.

[0004] The lithium ion supercapacitor is a typical representative of the hybrid supercapacitor, and its energy storage mechanism contains both the reversible oxidation-reduction reaction of lithium ion battery embedding / alloying / conversion and the double-layer mechanism / pseudo-capacitive reaction of the supercapacitor, and has the advantages of multiple aspects. However, the specific capacitance of the positive electrode material is low and the cycle performance is poor. SUMMARY

[0005] The application provides a positive electrode material for a supercapacitor and a preparation method and application thereof, and solves the problems of low specific capacitance and poor cycle performance of the positive electrode material for the supercapacitor in the related art.

[0006] The technical scheme of the application is as follows:

[0007] A positive electrode material for a supercapacitor, comprising a carbon-coated mixed material, wherein the mixed material in the carbon-coated mixed material is composed of manganese dioxide-coated carbon nanotubes and manganese dioxide-coated graphene.

[0008] As a further technical scheme, the preparation method of the manganese dioxide-coated carbon nanotubes comprises the following steps:

[0009] A1, dissolving manganese acetate tetrahydrate in ethanol to obtain a manganese acetate tetrahydrate solution;

[0010] A2, adding carbon nanotubes into the manganese acetate tetrahydrate solution, stirring and evaporating to be viscous, standing and aging, drying, crushing and sieving to obtain granules;

[0011] A3, calcining the granules and cooling to obtain manganese dioxide-coated carbon nanotubes.

[0012] As a further technical scheme, the preparation method of the manganese dioxide-coated graphene comprises the following steps:

[0013] B1, manganese acetate tetrahydrate is dissolved in ethanol to obtain a manganese acetate tetrahydrate solution;

[0014] B2, graphene is added to the manganese acetate tetrahydrate solution, and stirring and evaporation are performed until it becomes viscous, and then it is left to stand and age, dried, crushed and sieved to obtain granules;

[0015] B3, the granules are calcined and cooled to obtain manganese dioxide coated graphene.

[0016] The application further provides a preparation method of the positive electrode material for supercapacitors.

[0017] S1, polyacrylonitrile is dissolved to obtain a polyacrylonitrile solution;

[0018] S2, manganese dioxide coated carbon nanotubes and manganese dioxide coated graphene are added to the polyacrylonitrile solution, ultrasonic dispersion is performed to obtain an electrospinning solution, and the electrospinning solution is electrospun to obtain a spinning film;

[0019] S3, the spinning film is dried and calcined to obtain the positive electrode material for supercapacitors.

[0020] In the application, the electrostatic spinning process is used to prepare the positive electrode material for supercapacitors. First, polyacrylonitrile is dissolved to prepare a polyacrylonitrile solution, and then manganese dioxide coated carbon nanotubes and manganese dioxide coated graphene are dispersed in the polyacrylonitrile solution to prepare an electrospinning solution for electrospinning. After the spinning film is dried to remove the solvent, calcination is performed to carbonize the polyacrylonitrile, and finally, the carbon coated manganese dioxide coated carbon nanotube and manganese dioxide coated graphene material is prepared.

[0021] As a further technical solution, the concentration of the polyacrylonitrile solution is 15wt%-17wt%.

[0022] As a further technical solution, during the electrospinning, the spinning voltage is 15kV-18kV, the advancing speed is 0.0012-0.002mm / s, and the receiving distance is 16-18cm.

[0023] As a further technical solution, during the ultrasonic dispersion, the power of the ultrasonic is 150-350W, the frequency of the ultrasonic is 30-50kHz, the temperature of the ultrasonic is 40-50℃, and the time of the ultrasonic is 20-40min.

[0024] As a further technical solution, the mass ratio of the manganese dioxide coated carbon nanotubes, the manganese dioxide coated graphene and the polyacrylonitrile solution is 1-4:6-9:100, and preferably 2.5:7.5:100.

[0025] As a further technical scheme, the temperature of the calcination is 1300-1500 DEG C, and the time of the calcination is 10-20 min.

[0026] As a further technical scheme, step S2 is specifically:

[0027] S21, the manganese dioxide coated carbon nanotube is added into the polyacrylonitrile solution, and is ultrasonically dispersed to obtain a core layer electrospinning solution;

[0028] S22, the manganese dioxide coated graphene is added into the polyacrylonitrile solution, and is ultrasonically dispersed to obtain a shell layer electrospinning solution;

[0029] S23, the core layer electrospinning solution and the shell layer electrospinning solution are coaxially electrospun to obtain a spinning film.

[0030] In the application, the coaxial electrospinning process is adopted to prepare the positive electrode material for supercapacitors, the manganese dioxide coated carbon nanotube is used as the core layer, and the carbon nanotube is oriented along the direction of the electric field under the action of the electric field, so that mechanical support and a conductive framework are provided for the positive electrode material, the manganese dioxide coated graphene is used as the shell layer, the specific surface area is maximized, and the specific capacitance and the cycle life of the positive electrode of the supercapacitor are further improved.

[0031] As a further technical scheme, in step S21, the mass ratio of the manganese dioxide coated carbon nanotube to the polyacrylonitrile solution is 7.5:100.

[0032] As a further technical scheme, in step S22, the mass ratio of the manganese dioxide coated graphene to the polyacrylonitrile solution is 7.5:100.

[0033] As a further technical scheme, in the coaxial electrospinning process, the advancing speed of the core layer electrospinning solution is 0.0004-0.0006 mm / s, and the advancing speed of the shell layer electrospinning solution is 0.0012-0.0018 mm / s.

[0034] As a further technical scheme, in the coaxial electrospinning process, the spinning voltage is 15 kV-18 kV, and the receiving distance is 16-18 cm.

[0035] The application further discloses application of the positive electrode material for supercapacitors or the positive electrode material for supercapacitors prepared by the preparation method in lithium ion supercapacitors.

[0036] The working principle and beneficial effects of the application are as follows:

[0037] The manganese dioxide is respectively coated on the carbon nanotube and the graphene, and then is mixed to form a carbon-coated composite material, which is used as a positive electrode material of a supercapacitor, so that the specific capacitance and cycle life of the positive electrode of the supercapacitor can be significantly improved. On one hand, the graphene and the carbon nanotube have extremely high electronic transmission capacity, can provide an electronic channel, greatly reduce the overall electrode resistance, and make the high specific capacitance of the manganese dioxide fully play; on the other hand, the carbon layer coating can inhibit the volume expansion of the manganese dioxide in the charging and discharging process, prevent the active material from falling off, and at the same time, the mechanical toughness of the carbon nanotube / graphene network provides support for the positive electrode material, maintains the structural integrity of the positive electrode material, and significantly prolongs the cycle life. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0039] In the following examples and comparative examples:

[0040] The preparation method of the manganese dioxide-coated carbon nanotube is as follows:

[0041] A1, 0.75 parts of manganese acetate tetrahydrate by weight is dissolved in 35 parts of ethanol to obtain a manganese acetate tetrahydrate solution;

[0042] A2, 8.7 parts of single-walled carbon nanotubes (outer diameter 2 nm, length 1-2 μm, purchased from Xuzhou Jet Innovation Material Technology Co., Ltd.) are added to the above manganese acetate tetrahydrate solution, and the solution is evaporated to be viscous while stirring at 90°C. After standing at room temperature for 2 hours, it is transferred to a 90°C oven for drying, crushed through a 2000 mesh sieve to obtain granules;

[0043] A3, the granules are calcined at 450°C for 4 hours in an air atmosphere, and then cooled to obtain manganese dioxide-coated carbon nanotubes;

[0044] The preparation method of the manganese dioxide-coated graphene is as follows:

[0045] B1, 0.75 parts of manganese acetate tetrahydrate by weight is dissolved in 35 parts of ethanol to obtain a manganese acetate tetrahydrate solution;

[0046] B2, 8.7 parts of graphene (thickness 1-3 nm, diameter 3-5 μm, number of layers 2-5 layers, purchased from Zhejiang Zhitian Micro New Material Co., Ltd.) are added to the above manganese acetate tetrahydrate solution, and the solution is evaporated to be viscous while stirring at 90°C. After standing at room temperature for 2 hours, it is transferred to a 90°C oven for drying, crushed through a 2000 mesh sieve to obtain granules;

[0047] B3, calcining the granules at 450℃ for 4h under air atmosphere, and cooling to obtain manganese dioxide coated graphene.

[0048] In the uniaxial electrospinning, the spinning needle was of 23G type, with an inner diameter of 0.33mm and an outer diameter of 0.63mm.

[0049] In the coaxial electrospinning, the spinning needle was of 15G / 20G type.

[0050] The polyacrylonitrile had a weight average molecular weight of 140,000.

[0051] Example 1

[0052] The preparation method of the positive electrode material for supercapacitors comprises the following steps:

[0053] S1, dissolving the polyacrylonitrile in N,N-dimethylformamide to obtain a 15wt% polyacrylonitrile solution;

[0054] S2, adding the manganese dioxide coated carbon nanotubes and the manganese dioxide coated graphene into the polyacrylonitrile solution (the mass ratio of the manganese dioxide coated carbon nanotubes, the manganese dioxide coated graphene and the polyacrylonitrile solution was 1:9:100), and ultrasonic dispersing for 20min, with a power of 350W, a frequency of 30kHz and a temperature of 50℃, to obtain an electrospinning solution, which was transferred to a needle tube for uniaxial electrospinning, with a spinning voltage of 15kV, a pushing speed of 0.0012mm / s and a receiving distance of 16cm, to obtain a spinning film;

[0055] S3, drying the spinning film and calcining at 1300℃ for 20min to obtain the positive electrode material for supercapacitors.

[0056] Example 2

[0057] The preparation method of the positive electrode material for supercapacitors comprises the following steps:

[0058] S1, dissolving the polyacrylonitrile in N,N-dimethylformamide to obtain a 15wt% polyacrylonitrile solution;

[0059] S2, adding the manganese dioxide coated carbon nanotubes and the manganese dioxide coated graphene into the polyacrylonitrile solution (the mass ratio of the manganese dioxide coated carbon nanotubes, the manganese dioxide coated graphene and the polyacrylonitrile solution was 1:9:100), and ultrasonic dispersing for 20min, with a power of 350W, a frequency of 30kHz and a temperature of 50℃, to obtain an electrospinning solution, which was transferred to a needle tube for uniaxial electrospinning, with a spinning voltage of 15kV, a pushing speed of 0.0012mm / s and a receiving distance of 16cm, to obtain a spinning film;

[0060] S3, drying the spinning film, calcining at 1500℃ for 10min, to obtain a positive electrode material for supercapacitors.

[0061] Example 3

[0062] The difference from Example 1 is that the mass ratio of manganese dioxide coated carbon nanotubes, manganese dioxide coated graphene, and polyacrylonitrile solution is 2.5:7.5:100.

[0063] Example 4

[0064] The difference from Example 1 is that the mass ratio of manganese dioxide coated carbon nanotubes, manganese dioxide coated graphene, and polyacrylonitrile solution is 4:6:100.

[0065] Example 5

[0066] A method for preparing a positive electrode material for supercapacitors includes the following steps:

[0067] S1, dissolving polyacrylonitrile in N,N-dimethylformamide to obtain a 15wt% polyacrylonitrile solution;

[0068] S21, adding manganese dioxide coated carbon nanotubes to the polyacrylonitrile solution (mass ratio of manganese dioxide coated carbon nanotubes to polyacrylonitrile solution is 7.5:100), ultrasonic dispersion for 20min, ultrasonic power is 350W, ultrasonic frequency is 30kHz, ultrasonic temperature is 50℃, to obtain a core layer electrospinning solution;

[0069] S22, adding manganese dioxide coated graphene to the polyacrylonitrile solution (mass ratio of manganese dioxide coated graphene to polyacrylonitrile solution is 7.5:100), ultrasonic dispersion for 20min, ultrasonic power is 350W, ultrasonic frequency is 30kHz, ultrasonic temperature is 50℃, to obtain a shell layer electrospinning solution;

[0070] S23, transferring the core layer electrospinning solution and the shell layer electrospinning solution to needle tubes respectively, and performing coaxial electrospinning, spinning voltage is 15kV, the pushing speed of the core layer electrospinning solution is 0.0004mm / s, the pushing speed of the shell layer electrospinning solution is 0.0012mm / s, receiving distance is 16cm, to obtain a spinning film;

[0071] S3, drying the spinning film, calcining at 1300℃ for 20min, to obtain a positive electrode material for supercapacitors.

[0072] Example 6

[0073] A method for preparing a positive electrode material for supercapacitors includes the following steps:

[0074] S1, dissolving polyacrylonitrile in N, N-dimethylformamide to obtain a 15wt% polyacrylonitrile solution;

[0075] S21, adding manganese dioxide coated carbon nanotubes into the polyacrylonitrile solution (the mass ratio of manganese dioxide coated carbon nanotubes to polyacrylonitrile solution is 7.5:100), ultrasonic dispersion for 20 min, the power of ultrasonic is 350 W, the frequency of ultrasonic is 30 kHz, and the temperature of ultrasonic is 50℃, to obtain a shell layer electrospinning solution;

[0076] S22, adding manganese dioxide coated graphene into the polyacrylonitrile solution (the mass ratio of manganese dioxide coated graphene to polyacrylonitrile solution is 7.5:100), ultrasonic dispersion for 20 min, the power of ultrasonic is 350 W, the frequency of ultrasonic is 30 kHz, and the temperature of ultrasonic is 50℃, to obtain a core layer electrospinning solution;

[0077] S23, transferring the core layer electrospinning solution and the shell layer electrospinning solution into needle tubes respectively, and performing coaxial electrospinning, the spinning voltage is 15kV, the advancing speed of the core layer electrospinning solution is 0.0004mm / s, the advancing speed of the shell layer electrospinning solution is 0.0012mm / s, and the receiving distance is 16cm, to obtain a spinning film;

[0078] S3, drying the spinning film, and calcining at 1300℃ for 20 min to obtain a positive electrode material for supercapacitors.

[0079] Comparative Example 1

[0080] The preparation method of the positive electrode material for supercapacitors comprises the following steps:

[0081] S1, dissolving polyacrylonitrile in N, N-dimethylformamide to obtain a 15wt% polyacrylonitrile solution;

[0082] S2, adding manganese dioxide coated carbon nanotubes into the polyacrylonitrile solution (the mass ratio of manganese dioxide coated carbon nanotubes to polyacrylonitrile solution is 1:10), ultrasonic dispersion for 20 min, the power of ultrasonic is 350 W, the frequency of ultrasonic is 30 kHz, and the temperature of ultrasonic is 50℃, to obtain an electrospinning solution, transferring the electrospinning solution into a needle tube, and performing uniaxial electrospinning, the spinning voltage is 15kV, the advancing speed is 0.0012mm / s, and the receiving distance is 16cm, to obtain a spinning film;

[0083] S3, drying the spinning film, and calcining at 1300℃ for 20 min to obtain a positive electrode material for supercapacitors.

[0084] Comparative Example 2

[0085] The preparation method of the positive electrode material for supercapacitors comprises the following steps:

[0086] S1, dissolving polyacrylonitrile in N, N-dimethylformamide to obtain a 15wt% polyacrylonitrile solution;

[0087] S2, adding manganese dioxide coated graphene to the above polyacrylonitrile solution (mass ratio of manganese dioxide coated graphene to polyacrylonitrile solution is 1:10), ultrasonic dispersion for 20 min, ultrasonic power is 350 W, ultrasonic frequency is 30 kHz, ultrasonic temperature is 50℃, to obtain an electrospinning solution, the electrospinning solution is transferred to a needle tube, and uniaxial electrospinning is carried out, the spinning voltage is 15kV, the pushing speed is 0.0012mm / s, and the receiving distance is 16cm, to obtain a spinning film;

[0088] S3, drying the above spinning film, calcining at 1300℃ for 20 min to obtain a positive electrode material for supercapacitors.

[0089] Application example

[0090] The preparation method of the electrode is as follows:

[0091] (1) Put PVDF, conductive carbon black and the above positive electrode material into a marquis mortar according to a mass ratio of 10:10:80, drop NMP solution, and grind thoroughly for 5 min to obtain a slurry with a solid content of 60%;

[0092] (2) uniformly coat the above slurry on an Al foil current collector, dry and roll, and punch into a circular electrode piece (Φ=1.4cm, electrode piece area density=2.8mg / cm 2 ), assemble into a button lithium ion supercapacitor in a glove box protected by Ar atmosphere, use a metal lithium sheet (Φ=1.5cm, thickness 200μm) as a counter electrode; PE / PP separator; liquid lithium ion battery electrolyte (DMC:EC:PC=1:1:1, LiPF6=1.3mol / L).

[0093] Electrochemical performance test:

[0094] Charge and discharge the above button lithium ion supercapacitor between 1.5V~4.4V, current density is 2.6A / g, and cycle test is carried out at 20℃. The test results are recorded in Table 1.

[0095] Table 1 Electrochemical performance test results of button lithium ion supercapacitor

[0096]

[0097] As can be seen from Table 1, the positive electrode material for supercapacitors provided by the application has high specific capacitance and good cycle stability. The specific capacitance and capacity retention rate after 10000 cycles of the positive electrode material obtained in Examples 1-6 are higher than those of Comparative Examples 1-2, indicating that the manganese dioxide is coated on the carbon nanotubes and graphene respectively, and then mixed to form a carbon-coated composite material, which can significantly improve the specific capacitance and cycle life of the positive electrode of the supercapacitor.

[0098] The above only describes preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A positive electrode material for a supercapacitor, characterized in that, The carbon-coated mixed material comprises a mixed material consisting of manganese dioxide-coated carbon nanotubes and manganese dioxide-coated graphene. The preparation method of the positive electrode material for supercapacitors comprises the following steps: S1, dissolving polyacrylonitrile to obtain a polyacrylonitrile solution; S21, adding manganese dioxide-coated carbon nanotubes into the polyacrylonitrile solution and ultrasonically dispersing to obtain a core layer electrospinning solution; S22, adding manganese dioxide-coated graphene into the polyacrylonitrile solution and ultrasonically dispersing to obtain a shell layer electrospinning solution; S23, coaxially electrospinning the core layer electrospinning solution and the shell layer electrospinning solution to obtain a spinning film; S3, drying and calcining the spinning film to obtain the positive electrode material for supercapacitors.

2. The positive electrode material for supercapacitors according to claim 1, characterized in that, The preparation method of the manganese dioxide-coated carbon nanotubes comprises the following steps: A1, dissolving manganese acetate tetrahydrate in ethanol to obtain a manganese acetate tetrahydrate solution; A2, adding carbon nanotubes into the manganese acetate tetrahydrate solution, stirring and evaporating to be viscous, standing and aging, drying, crushing and sieving to obtain granules; A3, calcining the granules and cooling to obtain the manganese dioxide-coated carbon nanotubes.

3. The positive electrode material for supercapacitors according to claim 1, characterized in that, The preparation method of the manganese dioxide-coated graphene comprises the following steps: B1, dissolving manganese acetate tetrahydrate in ethanol to obtain a manganese acetate tetrahydrate solution; B2, adding graphene into the manganese acetate tetrahydrate solution, stirring and evaporating to be viscous, standing and aging, drying, crushing and sieving to obtain granules; B3, calcining the granules and cooling to obtain the manganese dioxide-coated graphene.

4. A method for producing a positive electrode material for a supercapacitor, for producing the positive electrode material for a supercapacitor according to any one of claims 1 to 3, characterized by, The preparation method of the positive electrode material for supercapacitors comprises the following steps: S1, dissolving polyacrylonitrile to obtain a polyacrylonitrile solution; S21, adding manganese dioxide-coated carbon nanotubes into the polyacrylonitrile solution and ultrasonically dispersing to obtain a core layer electrospinning solution; S22, adding manganese dioxide-coated graphene into the polyacrylonitrile solution and ultrasonically dispersing to obtain a shell layer electrospinning solution; S23, coaxially electrospinning the core layer electrospinning solution and the shell layer electrospinning solution to obtain a spinning film; S3, drying and calcining the spinning film to obtain the positive electrode material for supercapacitors.

5. The method according to claim 4, wherein the method is characterized by, In the ultrasonic dispersion in steps S21 and S22, the power of the ultrasonic is 150-350 W, the frequency of the ultrasonic is 30-50 kHz, the temperature of the ultrasonic is 40-50℃, and the time of the ultrasonic is 20-40 min.

6. The method of claim 4, wherein the method further comprises the step of: The calcining temperature is 1300-1500℃. ​ 7. The method according to claim 4, wherein the method is characterized by, In the coaxial electrospinning process, the pushing speed of the core layer electrospinning solution is 0.0004-0.0006 mm / s, and the pushing speed of the shell layer electrospinning solution is 0.0012-0.0018 mm / s.

8. The positive electrode material for supercapacitors according to any one of claims 1-3 or prepared by the preparation method according to any one of claims 4-7 is applied in lithium ion supercapacitors.

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