CN115206687A - A kind of super ionic liquid rich microporous nanofiber electrode material and its preparation method and application - Google Patents

Abstract

The invention discloses a super-hydrophilic ionic liquid microporous-rich nanofiber electrode material and a preparation method and application thereof, wherein the preparation method comprises the following steps: ultrasonically dispersing carbon nano tubes in deionized water, adding a phenol source, stirring and dissolving, then adding an aldehyde source for phenolic condensation, and performing suction filtration and washing to obtain graphite carbon @ phenolic resin nano fibers with a core-shell structure; carbonizing in inert atmosphere to obtain graphite carbon @ amorphous carbon nanofiber; under inert atmosphere, mixing graphite carbon @ amorphous carbon nanofiber and an activating agent, and carbonizing and activating to obtain the super-hydrophilic ionic liquid microporous-rich nanofiber electrode material. According to the electrode material provided by the invention, the conductivity and electrochemical properties of the material are synergistically improved by the conductive inner core carbon nano tube and the in-situ doped nitrogen atom, and the microporous carbon fiber has a super-hydrophilic liquid surface and shows high specific capacitance, high specific energy density, excellent rate capability and cycling stability when being used as a super capacitor electrode material.

Description

A kind of super ionic liquid rich microporous nanofiber electrode material and preparation method thereof application

technical field

The invention relates to the technical field of electrochemical energy storage, in particular to a super-ionic liquid-rich microporous nanofiber electrode material and a preparation method and application thereof.

Background technique

In order to adapt to the development of modern smart electronic devices, it is imperative to design supercapacitors with both high specific energy density and high specific power density. As a member of the carbon family, one-dimensional carbon nanotubes have high mechanical strength, excellent electrical conductivity, fast axial electron transport in supercapacitors, and exhibit high frequency response; however, their specific surface area is generally lower than 1000m ² g ^-1 , which is seldom simply used as a capacitor electrode material. At the same time, the surface of 1D carbon nanofibers has abundant defect active sites, which can realize fast radial ion diffusion in supercapacitors and exhibit excellent electrode/electrolyte interface wettability. Therefore, the composite structure of carbon nanotubes@carbon nanofibers is mostly used in the prior art to satisfy the efficient double conduction of electrons and ions during the charging and discharging process. lower problem.

At present, carbon nanofibers are mainly obtained by template method and electrospinning method. Yu Chengzhong's research group (Small2019, 1904310) used resorcinol and formaldehyde as carbon sources, tetraethyl silicate as silicon source, and co-assembled composite carbon nanofibers on carbon nanotubes. The silicon template needs to be etched and removed later. remove. Professor Zhou Liang's research group (Sci.Bull.2019,64,1617-1624) used cetyltrimethylammonium bromide as a soft template and inducer to obtain carbon nanofibers by hydrothermal reaction at 85 °C, and electrolyzed in 6M KOH In liquid, the specific capacitance is 380F g ^-1 , the energy density is 12.4Wh kg ^-1 , and the power density is 130W kg ^-1 at a current density of 1A g-1 . However, both the soft template method and the hard template method involve the preparation cost and removal cost of the template, and the process is cumbersome, time-consuming and labor-intensive. Lou Xiongwen's research group (Energy Environ.Sci., 2017,10,1777--1783) obtained porous carbon nanofibers by embedding imidazole molecular sieves in polyacrylonitrile by electrospinning, and in 2M H ₂ SO ₄ electrolyte Among them, the specific capacity is 307F g ^{-1 under the current density of 1A g -1 ,} the energy density is 10.96W h kg ^-1 , and the power density is 25000W kg ^-1 , but its synthesis is complicated, the spinning efficiency is low, the cost is high, and the pollution is large. , not suitable for large-scale promotion.

Based on this, it is of great significance to design and synthesize composite carbon nanofiber electrode materials with a simple synthesis strategy, high compaction density and high electrochemical performance.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a super ionic liquid rich microporous nanofiber electrode material and a preparation method and application thereof, so as to solve the problem of low compaction density and poor electrochemical performance when the existing composite carbon nanofibers are used as electrodes. The problem.

In order to achieve the above object, the technical scheme of the present invention is achieved in this way:

A preparation method of a super ionic liquid rich microporous nanofiber electrode material, comprising the following steps:

S1, ultrasonically dispersing carbon nanotubes in deionized water, adding a phenol source, stirring and dissolving, then adding an aldehyde source to carry out phenolic condensation, and obtaining core-shell structure graphitic carbon@phenolic resin nanofibers after washing with suction;

S2, under inert atmosphere, carbonize described graphitic carbon@phenolic resin nanofibers to obtain graphitic carbon@amorphous carbon nanofibers;

S3. In an inert atmosphere, the graphitic carbon@amorphous carbon nanofibers are mixed with an activator, and activated by carbonization to obtain a super-ionic liquid-rich microporous nanofiber electrode material.

According to the above scheme, in step S1, the mass ratio of the carbon nanotubes, the phenol source and the aldehyde source is (0.005-0.05):1:1.5.

According to the above scheme, the phenol source includes one of m-aminophenol, o-aminophenol and p-aminophenol, and the aldehyde source includes formaldehyde or acetaldehyde.

According to the above scheme, in step S1, the reaction temperature of the phenolic condensation reaction is 20-100° C., and the reaction time is 10-60 min.

According to the above scheme, in step S2, the carbonization conditions include: 500-1400°C, carbonization time 100-200min, and heating rate 2-10°Cmin ^-1 .

According to the above scheme, in step S3, the mass ratio of the carbon nanofibers and the activator is in the range of 1:2 to 1:5.

According to the above scheme, the activator includes potassium hydroxide or potassium bicarbonate.

According to the above scheme, in step S3, the carbonization activation conditions include: activation temperature of 700-800°C, time of 60-180min, and heating rate of 2-5°Cmin ^-1 .

On the basis of the above scheme, the second object of the present invention is to provide a super ionic liquid rich microporous nanofiber electrode material, which is obtained by the above-mentioned preparation method of the super ionic liquid rich microporous nanofiber electrode material.

On the basis of the above scheme, the third object of the present invention is to provide the application of the above-mentioned super ionic liquid-rich microporous nanofiber electrode material as an active material for supercapacitors.

Compared with the prior art, the present invention has the following advantages:

(1) The super-ionic liquid-rich microporous nanofiber electrode material of the present invention has a dense 3D skeleton, high compaction density, carbon nanotubes are used as the conductive core, and the microporous carbon is used as the capacitor shell, which can realize rapid electronic ion dual At the same time, the microporous carbon fiber has a super ionic liquid surface, the contact angle is almost zero, and the micropore size is slightly larger than the ion size in the ionic liquid electrolyte, showing high specific capacitance and high specific energy when used as supercapacitor electrode material density, excellent rate capability and cycling stability.

(2) The preparation method provided by the present invention has the advantages of simple operation, short preparation time, low cost, simple and green synthesis process, and no need to remove templates; in addition, the reaction is carried out in a pure water system, without the addition of organic solvents, and is suitable for industrial production.

Description of drawings

In order to illustrate the present invention or the technical solutions in the prior art more clearly, the following briefly introduces some drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are the For some embodiments of the invention, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the synthesis mechanism diagram of super ionic liquid rich microporous nanofiber electrode material according to the present invention;

2 is the SEM images (a) and TEM images (b, c) of the core-shell structure graphitic carbon@phenolic resin nanofibers according to Example 1 of the present invention, and the SEM images of the core-shell structure graphitic carbon@amorphous nitrogen-doped carbon nanofibers (d) and TEM images (e, f), SEM images (g), TEM images (h, i) and EDS spectra (j) of superionic liquid-rich microporous nanofibers;

3 is the XRD patterns of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3 of the present invention;

4 is the Raman spectrum of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3 of the present invention;

Fig. 5 is the adsorption-desorption curve and pore size distribution curve diagram of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3 of the present invention;

6 is the XPS spectrum of the superionic liquid-rich microporous nanofiber electrode material according to Example 1 of the present invention;

7 is a wettability test chart of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3 of the present invention;

8 is a cyclic voltammetry diagram of the superionic liquid-rich microporous nanofiber electrode material according to Example 1 of the present invention;

9 is a cyclic voltammetry diagram of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3 of the present invention;

10 is a charge-discharge curve diagram of the super-ionic liquid-rich microporous nanofiber electrode material according to Example 1 of the present invention under different current densities;

FIG. 11 is the rate curve of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3 of the present invention;

12 is a cycle curve of the super-ionic liquid-rich microporous nanofiber electrode material according to Example 1 of the present invention;

13 is the SEM images of the phenolic resin microspheres according to Example 3 of the present invention (a, d), the SEM images of the nitrogen-doped carbon microspheres (b, e), and the SEM images of the rich microporous nitrogen-doped carbon microspheres (c, d). f);

14 is a charge-discharge curve diagram of carbon nanotubes after carbonization and activation according to Example 4 of the present invention.

Detailed ways

In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

It should be noted that, in the description of the embodiments of the present application, the description of the term "some specific embodiments" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment of the present invention or in the example. In this specification, schematic representations of the above terms do not necessarily refer to the same implementation or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In this embodiment, "within the range" includes the terminal values at both ends, for example, "within the range of 1 to 100" includes the values at both ends of 1 and 100.

An embodiment of the present invention provides a method for preparing a super-ionic liquid-rich microporous nanofiber electrode material, comprising the following steps:

S1. Under the pure water system, ultrasonically disperse carbon nanotubes in deionized water, add a small amount of phenol source and stir to dissolve, then put into aldehyde source for phenolic condensation, after suction filtration and washing, a gray core-shell structure graphitic carbon@phenolic resin is obtained Nanofibers;

S2. In an inert atmosphere, carbonize the core-shell structure graphitic carbon@phenolic resin nanofibers in one step to obtain black core-shell structure graphitic carbon@amorphous carbon nanofibers;

S3. In an inert atmosphere, mix the black core-shell structure graphitic carbon@amorphous carbon nanofibers with an activator, and carbonize and activate to obtain black core-shell structure graphitic carbon@microporous carbon nanofibers, that is, super ionic liquid rich microporous carbon nanofibers. Porous Nanofiber Electrode Materials.

Combining with Fig. 1, the synthesis mechanism of super ionic liquid-rich microporous nanofiber electrode material is as follows: carbon nanotubes modified with surface oxygen functional groups can be uniformly dispersed in aqueous solution due to hydrogen bonding, when m-aminophenol and formaldehyde are added. , The carbon nanotubes modified by the uniformly dispersed surface oxygen functional groups can effectively reduce the nucleation barrier of phenolic condensation as a heterogeneous nucleation site. Carbon@phenolic resin nanofibers; because the fiber surface is rich in amino and hydroxyl functional groups, it is dominated by hydrogen bond forces during the carbonization process, and the three-dimensional fiber frame is compressed and becomes dense, and finally compressed micropore-rich can be obtained after activation Three-dimensional carbon frame nanofiber electrode material.

Specifically, in step S1, the mass ratio of carbon nanotubes, phenol source and aldehyde source is (0.005-0.05):1:1.5. The phenol source includes one of m-aminophenol, o-aminophenol and p-aminophenol, and the aldehyde source includes formaldehyde or acetaldehyde. Further, the phenol source is preferably m-aminophenol, and the aldehyde source is preferably formaldehyde.

Wherein, in order to improve the reaction efficiency, the reaction temperature of the phenolic condensation reaction is 20-100° C., and the reaction time is 10-60 min.

The core-shell structure is a microporous nanostructure, which greatly increases the specific surface area and improves the wettability between the electrolyte and the electrode material; in addition, the core-shell structure forms a three-dimensional interwoven network structure, which is beneficial to the electrons inside the electrode material during the redox process. As well as the rapid transport of ions, the specific capacitance of the electrode material is further improved.

Specifically, in step S2, the conditions for one-step carbonization include: 500-1400° C., carbonization time 100-200 min, and heating rate 2-10° C. min ⁻¹ . Preferably, the carbonization temperature is 800° C., the carbonization time is 120 min, and the heating rate is 2° C. min ⁻¹ .

The doping of nitrogen elements can improve the active sites and show better performance. The conductive core carbon nanotubes and in-situ doped nitrogen atoms synergistically improve the electrical conductivity and electrochemical performance of the material.

In step S3, the mass ratio of the carbon nanofibers and the activator is in the range of 1:2 to 1:5, wherein the activator is preferably potassium hydroxide.

Further, the conditions for carbonization activation include: activation temperature of 700-800° C., time of 60-180 min, and heating rate of 2-5° C. min ⁻¹ . Preferably, the activation temperature is 750° C., the time is 120 min, and the heating rate is 3° C. min ⁻¹ .

Therefore, the preparation process provided by the present invention is simple and green, does not need to remove the template, and has low cost; in addition, the reaction is carried out in a pure water system without the addition of an organic solvent, which is suitable for industrial production.

On the basis of the above scheme, another embodiment of the present invention provides a super ionic liquid rich microporous nanofiber electrode material, which is prepared by the above-mentioned preparation method of the super ionic liquid rich microporous nanofiber electrode material.

On the basis of the above solution, another embodiment of the present invention provides the application of the above-mentioned super ionic liquid rich microporous nanofiber electrode material as an active material of a supercapacitor.

The super ionic liquid rich microporous nanofiber electrode material provided by the invention has a dense 3D skeleton and high compaction density, and uses carbon nanotubes as a conductive core, microporous carbon as a capacitor shell, and the conductive core carbon nanotubes and in-situ The doped nitrogen atoms synergistically enhance the electrical conductivity and electrochemical properties of the material, and can achieve fast electron-ion double conduction; at the same time, the microporous carbon fiber has well-developed micropores and mesopores, and the size of the micropores is slightly larger than that of the ionic liquid electrolyte. The medium ion size, the contact angle with the electrolyte is almost zero, and it has a super ionic liquid surface, which shows high specific capacitance, high specific energy density, excellent rate performance and stable cycling performance as a supercapacitor electrode material.

On the basis of the above embodiments, the present invention provides the following specific examples to further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In the following examples, the experimental methods without specific conditions are generally in accordance with the conditions suggested by the manufacturer. Unless otherwise stated, percentages and parts are by mass.

Example 1

This embodiment provides a method for preparing a super-ionic liquid-rich microporous nanofiber electrode material, comprising the following steps:

1) Disperse 25mg carbon nanotubes in 300mL deionized water, add 2.475g m-aminophenol to dissolve, add 3.42mL formaldehyde to react for 0.5h, and obtain gray core-shell structure graphite carbon@phenolic resin nanofibers ( CNT@APF);

2) The dried CNT@APF was carbonized at 800 °C for 2 h under nitrogen atmosphere, and the heating rate was 2 °C min ^-1 to obtain black core-shell structure graphitic carbon@amorphous nitrogen-doped carbon nanofibers (CNT@NC);

3) Mix CNT@NC and KOH according to the mass ratio of 1:4, activate at 750 °C for 1 h under nitrogen atmosphere, and the heating rate is 2 °C min ^-1 . The activated sample is washed with dilute hydrochloric acid to remove impurities, and then washed with water until Neutral, the super ionic liquid microporous-rich nanofiber electrode material-black core-shell structure graphitic carbon@microporous-rich nitrogen-doped carbon nanofibers (CNT@NC-A) was obtained.

Example 2

This embodiment provides a method for preparing a nanofiber electrode material, comprising the following steps:

1) Disperse 25mg carbon nanotubes in 300mL deionized water, add 2.475g m-aminophenol to dissolve, add 3.42mL formaldehyde to react for 0.5h, and obtain gray core-shell structure graphite carbon@phenolic resin nanofibers ( CNT@APF);

2) The dried CNT@APF was carbonized at 800 °C for 2 h under nitrogen atmosphere with a heating rate of 2 °C min ^-1 to obtain black core-shell structured graphitic carbon@amorphous nitrogen-doped carbon nanofibers (CNT@NC).

The difference between this example and the electrode material prepared in Example 1 is that the core-shell structure graphitic carbon@amorphous nitrogen-doped carbon nanofiber in this example is not activated by potassium hydroxide.

Example 3

This embodiment provides a method for preparing a nanofiber electrode material, comprising the following steps:

1) In 300mL deionized water, add 2.475g m-aminophenol to dissolve, add 3.42mL formaldehyde to react for 0.5h, and obtain yellow phenolic resin microspheres (APF) after suction filtration, washing and drying;

2) The dried APF was carbonized at 800 °C for 2 h in a nitrogen atmosphere, and the heating rate was 2 °C min ^-1 to obtain black nitrogen-doped carbon microspheres (NCS);

3) Mix NCS and KOH according to a mass ratio of 1:4, activate at 750 °C for 1 h under nitrogen atmosphere, and the heating rate is 2 °C min ^-1 , wash the activated sample with dilute hydrochloric acid to remove impurities, and then wash with water until neutral , black microporous nitrogen-doped carbon microspheres (NCS-A) were obtained.

Taking the super ionic liquid microporous nanofiber electrode material prepared in Example 1 as an example, the morphology and structure of CNT@APF, CNT@NC and CNT@NC-A were characterized, and the results shown in Figures 2-7 were obtained. picture.

Figure 2 shows the SEM images (a) and TEM images (b, c) of CNT@APF, the SEM images (d) and TEM images (e, f) of CNT@NC, and the SEM images (g) of CNT@NC-A. , TEM images (h, i) and EDS spectrum (j), it can be seen from Fig. 2 that the synthesized graphitic carbon@phenolic resin nanofibers CNT@APF are in a state of mutual cross-linking, the fiber size is about 60nm, and the core layer carbon The diameter of the nanotubes is 5-10 nm, and the three-dimensional network is loose and porous at this time. During the carbonization process, the adjacent fibers approached each other under the force of hydrogen bonding, which reduced the proportion of useless cavities, improved the network density, and slightly reduced the fiber diameter. After the activation treatment, due to the excellent thermal stability and etching resistance of phenolic resin-based carbon, the fiber diameter did not change much, but a rich microporous structure was formed inside the fiber. The C and O elements are uniformly distributed on the fiber, while the N element is relatively less distributed in the carbon nanotubes, which reflects the distribution of carbon nanotubes in the fiber.

In order to further illustrate the effect of carbon nanotubes on superionic liquid-rich microporous nanofiber electrode materials, the data in Table 1 were obtained by comparing the synthesis yield, carbonization yield, and activation yield of porous carbon spheres and porous carbon fibers.

Table 1 Yield table of nitrogen-doped porous carbon materials

It can be seen from Table 1 that, compared with the samples without carbon nanotubes, the addition of trace carbon nanotubes not only increases the electrical conductivity of the material, induces the transformation of resin nucleation growth from three-dimensional to one-dimensional, but also improves the production of precursors. Compared with porous carbon spheres (NCS-A), the final product yield of porous carbon fibers (CNT@NC-A) was increased by 43.1% under the same conditions.

FIG. 3 is the XRD patterns of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3. It can be seen from FIG. 3 that the CNT@NC-A prepared in Example 1, the CNT@NC prepared in Example 2, the The two large envelope peaks at 24° and 43° of NCS-A prepared in Example 3 correspond to the diffraction patterns of amorphous carbon at (002) and (100) crystal planes, indicating its amorphous structure. Compared with CNT@NC, the diffraction peak intensities of the activated NCS-A and CNT@NC-A are weakened.

Figure 4 is the Raman diagram of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3. It can be seen from Figure 4 that the CNT@NC-A prepared in Example 1 and the CNT@NC prepared in Example 2 are at 1360 cm ^-1 and 1580 cm ^-1 correspond to the typical amorphous and graphitized peaks of carbon materials, wherein the G peak intensity is high due to the existence of carbon nanotubes, and there is a typical 2D peak at 2700 cm ^-1 . The NCS-A prepared in Example 3 corresponds to the typical amorphous peaks (D peaks) and graphitization (G peaks) of carbon materials at 1360 cm ^-1 and 1580 cm ^-1 . Due to the absence of carbon nanotubes, D peaks and G peaks The ratio is about 1, indicating that the activated material has a certain degree of graphitization while maintaining the amorphous structure.

Figure 5 shows the adsorption-desorption curves and pore size distribution curves of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3. It can be seen from Figure 5 that the specific surface area of the CNT@NC-A material prepared in Example 1 It reaches 2059m2g ^-1 , the micropore volume is 0.69cm3g ^-1 , has abundant micropore and mesopore structure, and the micropore size is slightly larger than the ion size in the ionic liquid electrolyte, and all the pores are ion-reachable effective pores. The specific surface area of the CNT@NC material prepared in Example 2 reached 358 m 2g ^-1 , and the micropore volume was 0.04 cm 3g ^-1 , indicating that the micropores were not developed without activation. The specific surface area of the NCS-A material prepared in Example 3 reaches 770m2g ^-1 , the micropore volume is 0.24cm3g ^-1 , and it has abundant micropores.

Figure 6 is the XPS energy spectrum of the super ionic liquid-rich microporous nanofiber electrode material CNT@NC-A prepared in Example 1. It can be seen from Figure 6 that the composition of the CNT@NC-A material is C (91.80 at.% ), N (3.24 at.%) and O (4.96 at.%), high nitrogen content will greatly improve the electrochemical performance, in addition, through peak fitting, N species mainly exist in the form of pyrrole nitrogen.

Fig. 7 and Fig. 9 are cyclic voltammetry graphs of the wettability test charts of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3, respectively. It can be seen from Fig. 7 that the CNT@NC- The initial contact angle of material A and the electrolyte is 39.6°, and the contact angle after 4 min is 0°, which is in a fully wetted state. Good interface wettability will greatly benefit the electrochemical performance. The initial contact angle of the CNT@NC material prepared in Example 2 in contact with the electrolyte was 59.9°, and the contact angle changed little after 4 min, indicating that the electrode material of this example was essentially wet with the electrolyte, but due to the microscopic The pores are underdeveloped and have limited wettability, exhibiting less than ideal capacitive performance (Figure 9). The initial contact angle of the NCS-A material prepared in Example 3 in contact with the electrolyte was 85.3°, and the contact angle after 4 min was 58.0°, indicating that the electrode material of this example is essentially wet with the electrolyte, but due to the spherical shape The structure and electrolyte wettability are inferior to the three-dimensional network structure, and the specific surface area is less than that, showing the capacitance performance inferior to that of Example 1 (Fig. 9).

The application of the super ionic liquid microporous carbon nanofiber electrode material prepared in Example 1 as the supercapacitor electrode material is as follows: the production process of the electrode sheet uses the super ionic liquid microporous carbon nanofiber as the active material, and acetylene black as the Conductive agent, PTFE as binder, the three are mixed in a mortar with a mass ratio of 8:1:1, and pressed into a roller to make an electrode sheet, ionic liquid EMIMBF ₄ is used as the electrolyte, and a cellulose diaphragm is used to assemble into a button-type Battery. By analogy, the electrode materials prepared in Examples 2 and 3 were also assembled into batteries. Electrochemical tests were performed on the assembled button cells, respectively, and the result diagrams shown in Figures 8-12 were obtained.

Figure 8 is a cyclic voltammetry diagram of the superionic liquid microporous-rich nanofiber electrode material CNT@NC-A prepared in Example 1. It can be seen from Figure 8 that the superionic liquid microporous-rich carbon nanofibers in different It exhibits a rectangular-like shape at scan rate, indicating its electrochemical capacitive behavior.

Fig. 9 is the cyclic voltammetry curves of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3. It can be seen from The capacitance of the battery assembled with A is much higher than that of the CNT@NC-assembled battery prepared in Example 2, which was pre-activated, and higher than that of the NCS-A prepared in Example 3 without the addition of carbon nanotubes.

Figures 10 and 12 are respectively the charge-discharge curves and cycle curves of the super-ionic liquid-rich microporous nanofiber electrode material CNT@NC-A prepared in Example 1 at different current densities. At a current density of 1A g ^-1 , the superionic liquid microporous carbon nanofibers have a specific capacitance as high as 219F g ^-1 , and at a current density of 10A g ^-1 , the capacity retention rate is as high as 95% after 20000 cycles (attached). Figure 12), which benefits from the good wettability of the electrode/electrolyte interface. According to further conversion, its energy density is 108.8Wh kg ^-1 , and the power density can reach 946.3W kg ^-1 .

Figure 11 shows the rate curves of the nitrogen-doped porous carbon materials described in Examples 1, 2 and 3. It can be seen from Figure 11 that the specific capacitance of the CNT@NC-A battery prepared in Example 1 is at a current density of 50A g ^-1 It is still as high as 160F g ^-1 , which is much higher than that of the CNT@NC battery prepared in Example 2 and the NCS-A battery prepared in Example 3. The excellent rate performance is due to nitrogen doping and the efficient electron-ion dual conduction of the structure. .

Fig. 13 is the SEM images (a, d) of the phenolic resin microspheres APF described in Example 3, the SEM images (b, e) of the nitrogen-doped carbon microspheres NCS, and the rich microporous nitrogen-doped carbon microspheres NCS-A The SEM images (c, f) of the phenolic resin microspheres are shown in Figure 13. The phenolic resin microspheres are monodisperse spheres with a diameter of 600 nm. During the carbonization process, the small molecule precursors escape, and the resin shrinks to obtain monodisperse carbons with a diameter of 500 nm. Microspheres, nitrogen-doped carbon microspheres, under the action of alkali etching during the activation process, the rich microporous nitrogen-doped carbon microspheres maintain a stable monodisperse state with a size of 450nm.

In summary, the super ionic liquid microporous nanofiber electrode material prepared by the present invention has a microporous-rich carbon fiber size of 40 nm, a specific surface area of up to 2059m2 g ^-1 , and an electrode sheet density of 2.6 g cm ^-2 . The ionic liquid electrolyte exhibits excellent wettability (θ-0°), and as a supercapacitor electrode material exhibits high specific capacitance, high specific energy-power density, excellent rate capability and stable cycling performance.

Example 4

The present embodiment provides a method for preparing carbon nanotubes, comprising the following steps:

100 mg of carbon nanotubes were dispersed in 1200 mL of deionized water, washed and dried by suction, carbonized at 800 °C for 2 h under nitrogen atmosphere, and the heating rate was 2 °C min ^-1 , and then mixed with KOH according to the mass ratio of 1:4, under nitrogen atmosphere Activated at 750℃ for 1h under the atmosphere, the heating rate was 2℃min ^-1 . The activated sample was washed with dilute hydrochloric acid to remove impurities, and then washed with water until neutral to obtain black activated carbon nanotubes (CNT-A).

Fig. 14 is the charge-discharge curve of carbon nanotubes CNT-A after carbonization and activation described in Example 4. It can be seen from Fig. 14 that under the current density of 1A g ^-1 , the specific capacitance of the activated carbon nanotubes is 25.2 F g ^-1 , which exhibits extremely limited capacitive performance.

Although the disclosure of the present invention is as above, the protection scope of the disclosure of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims (10)

1. A preparation method of a super-hydrophilic ionic liquid microporous-rich nanofiber electrode material is characterized by comprising the following steps:

s1, ultrasonically dispersing carbon nano tubes in deionized water, adding a phenol source, stirring and dissolving, then adding an aldehyde source for phenolic condensation, and performing suction filtration and washing to obtain graphite carbon @ phenolic resin nano fibers with a core-shell structure;

s2, carbonizing the graphite carbon @ phenolic resin nanofiber in an inert atmosphere to obtain graphite carbon @ amorphous carbon nanofiber;

and S3, mixing the graphite carbon @ amorphous carbon nanofiber with an activating agent in an inert atmosphere, and carbonizing and activating to obtain the super-hydrophilic ionic liquid microporous-rich nanofiber electrode material.

2. The production method according to claim 1, wherein in step S1, the mass ratio of the carbon nanotube, the phenol source, and the aldehyde source is (0.005-0.05): 1:1.5.

3. the method of claim 1 or 2, wherein the phenol source comprises one of m-aminophenol, o-aminophenol and p-aminophenol, and the aldehyde source comprises formaldehyde or acetaldehyde.

4. The method according to claim 3, wherein in step S1, the reaction temperature of the phenolic aldehyde condensation reaction is 20 to 100 ℃ and the reaction time is 10 to 60min.

5. The production method according to claim 1, wherein in step S2, the carbonization conditions include: the carbonization temperature is 500-1400 ℃, the carbonization time is 100-200min, and the heating rate is 2-10 ℃ for min ^-1 。

6. The production method according to claim 1, wherein in step S3, the mass ratio of the carbon nanofibers and the activating agent is in the range of 1.

7. The method of claim 6, wherein the activator comprises potassium hydroxide or potassium bicarbonate.

8. The production method according to claim 6, wherein in step S3, the carbonization activation conditions include: the activation temperature is 700-800 deg.C, the activation time is 60-180min, and the heating rate is 2-5 deg.C for min ^-1 。

9. A super-hydrophilic ionic liquid microporous nanofiber electrode material, which is characterized by being prepared by the preparation method of the super-hydrophilic ionic liquid microporous nanofiber electrode material as claimed in any one of claims 1-8.

10. The application of the super-hydrophilic ionic liquid microporous-rich nanofiber electrode material obtained by the preparation method according to any one of claims 1-8 or the super-hydrophilic ionic liquid microporous-rich nanofiber electrode material according to claim 9 as an active material of a super capacitor.

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