Carbon nanotube dendritic polymer mixture and preparation method thereof

Abstract

The invention provides a carbon nanotube / dendritic polymer mixture, which is characterized in that the dispersibility of CNTs and the wettability of an electrode are improved by introducing a sugar dimer containing four glucose units (4-G1) on the surface of CNTs, so that the capacitive performance of a supercapacitor is remarkably improved.

Description

Technical Field

[0001] The invention relates to a novel nanocomposite material for supercapacitor electrodes, in particular to a carbon nanotube / dendritic polymer mixture and application of the mixture in supercapacitor electrodes. Background Art

[0002] As electronic devices develop towards miniaturization and high performance, the demand for high-performance electrochemical energy storage devices is growing. Supercapacitors have become a popular energy storage device due to their high power density, fast charge and discharge capabilities, and long cycle life. Carbon nanotubes (CNTs) have been widely studied as supercapacitor electrode materials due to their excellent electrical conductivity, mechanical properties, and chemical stability. However, CNTs have problems such as poor dispersibility and difficulty in electrode preparation in applications. Therefore, the development of a new type of CNTs-based electrode material with improved performance has become a research hotspot in this field. Summary of the invention

[0003] The present invention provides a carbon nanotube / dendritic polymer mixture, the core of which is to improve the dispersibility of CNTs and the wettability of electrodes by introducing a sugar dimer containing four glucose units (4-Gl) on the surface of CNTs, thereby significantly improving the capacitance performance of supercapacitors. Solution

[0004] The present invention provides a method for preparing a carbon nanotube / dendritic polymer mixture for use as a supercapacitor electrode, comprising the following steps: a) Synthesis of a sugar dimer containing four glucose units (4-Gl); b) preparing a dispersion of carbon nanotubes containing different concentrations of 4-G1 dendrimers, wherein the carbon nanotubes include at least one of MWCNT-COOH and / or MWCNT-NH2; c) depositing the dispersion obtained in step b) onto an aluminum current collector by drop casting, alternately coating MWCNT-COOH / 4-Gl and MWCNT-NH2 / 4-Gl to form a double layer, drying at 100-105°C between each layer; d) Repeat step c) until eight double-layer films are deposited to form an electrode with good cohesion and dimensional stability.

[0005] The combination of the sugar dimer and the multi-walled carbon nanotube is achieved through electrostatic interaction, which can be used to improve the dispersibility of the carbon nanotube and the wettability of the electrode.

[0006] The present invention also provides a carbon nanotube / dendritic polymer mixture used as a supercapacitor electrode obtained by the above method, characterized in that the mixture includes surface-modified multi-walled carbon nanotubes (MWCNTs) and a sugar dimer containing four glucose units (4-Gl).

[0007] Furthermore, the multi-walled carbon nanotubes (MWCNTs) include at least one of the two types of MWCNT-COOH / 4-Gl and / or MWCNT-NH2 / 4-Gl.

[0008] Furthermore, the mixture was prepared by casting two types of modified multi-walled carbon nanotubes (MWCNTs) into eight alternating double layers.

[0009] The present invention also provides a supercapacitor, characterized in that the supercapacitor comprises any of the aforementioned carbon nanotube / dendritic polymer mixtures as electrode materials.

[0010] As a further preferred embodiment, the supercapacitor further comprises a separator embedded with 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C8H11F6N3O4S2) ions as an electrolyte.

[0011] As a further preferred embodiment, the content of the dendritic polymer in the electrode is 18-20% of the content of the carbon nanotubes, which can achieve a significant increase in capacitance. DETAILED DESCRIPTION

[0012] The present invention first synthesizes a sugar dimer (4-Gl) containing four glucose units, and then mixes it with surface-modified multi-walled carbon nanotubes (MWCNTs), including two types of MWCNT-COOH and MWCNT-NH2. By mixing the two modified MWCNTs with the 4-Gl sugar dimer in a certain proportion, a stable aqueous dispersion is formed. Next, these dispersions are deposited on an aluminum current collector by drop casting, and MWCNT-COOH / 4-Gl and MWCNT-NH2 / 4-Gl are alternately coated to form a multilayer structure, and each layer is dried at 100°C to finally form an electrode with good cohesion and dimensional stability.

[0013] The supercapacitor is assembled, wherein the supercapacitor includes the above carbon nanotube / dendrimer mixture as an electrode material and a separator embedded with 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide (C8H11F6N3O4S2) ions as an electrolyte.

[0014] Beneficial effects: By introducing dendritic polymers into the electrode, especially when the content of dendritic polymers reaches 20% of the carbon nanotube content, the capacitance performance of the supercapacitor is significantly improved compared to the capacitor without dendritic polymers, and the capacitance is increased by 600%. This significant performance improvement is attributed to the steric hindrance of the dendritic polymers, which helps to form a three-dimensional porous conduit network that is conducive to the rapid transport of ions and electrons, and the chemical affinity of the dendritic polymers for the ionic liquid electrolyte, which improves the wettability of the electrode. Example

[0015] In a specific embodiment, a carbon nanotube / dendritic polymer mixture electrode is prepared by the following steps: Glycodimer synthesis: First, a glycodimer containing four glucose units (4-Gl) is synthesized.

[0016] Preparation of carbon nanotube dispersion: MWCNT-COOH and MWCNT-NH2 were ultrasonically treated in deionized water for 2 h to obtain stable carbon nanotube aqueous dispersions. Then, an appropriate amount of 4-Gl dendrimer was added to each dispersion and stirred at room temperature for 30 min to ensure that the dendrimer was fully dissolved and interacted with the carbon nanotube surface.

[0017] Electrode preparation: The prepared MWCNT-COOH / 4-Gl and MWCNT-NH2 / 4-Gl dispersions were alternately deposited onto the aluminum current collector by drop casting and dried at 100 °C between each layer until an 8-layer double-layer structure was formed.

[0018] Supercapacitor assembly: The electrodes prepared above and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C8H11F6N3O4S2) ionic liquid were used as electrolyte to assemble a supercapacitor.

[0019] Performance Testing The electrochemical performance of the prepared supercapacitor was tested at a current density of 0.5 A g-1. Its performance was evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant current charge-discharge (GCD) tests.

[0020] At a scan rate of 10 mV / s, the supercapacitor containing 20 wt% dendrimer exhibited a nearly rectangular CV curve with no obvious redox peak, indicating that it mainly exhibited capacitive behavior. The specific capacitance reached 57.0 F g-1, which increased by 600% compared with the capacitor without dendrimer.

[0021] EIS test results show that the supercapacitor containing 20 wt% dendrimer has the smallest interfacial charge transfer resistance and lower equivalent series resistance (ESR), which indicates its excellent electrochemical kinetics and high ion transport efficiency.

[0022] At 0.5 A g -1 At a current density of 1.5 200 MHz, the supercapacitor exhibited a symmetrical linear charge-discharge curve, indicating good capacitance performance and high energy efficiency. After 2,000 charge-discharge cycles, the device still maintained more than 90% of its initial capacitance, showing excellent cycle stability.

[0023] The carbon nanotube / dendritic polymer mixture provided by the present invention is used as a supercapacitor electrode material. By introducing a dendritic polymer on the surface of CNTs, not only the dispersibility of CNTs and the wettability of the electrode are improved, but also the capacitance performance of the supercapacitor is significantly improved. The introduction of the dendritic polymer, especially when its content reaches 20% of the carbon nanotube content, can significantly increase the capacitance and improve the interaction between the electrode and the electrolyte, thereby enhancing the electrochemical performance. In addition, the high cycle stability and excellent electrochemical kinetic performance exhibited by the mixed electrode make it a very promising high-performance supercapacitor electrode material.

[0024] The carbon nanotube / dendritic polymer mixture electrode material of the present invention is not only suitable for supercapacitors, but may also be suitable for other electrochemical energy storage and conversion devices, such as batteries, fuel cells, etc.

[0025] The embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and changes to the present invention without departing from the spirit and scope of the present invention. For example, although the present invention mainly describes the embodiments using a specific dendritic polymer (a sugar dimer containing four glucose units), those skilled in the art will appreciate that other types of dendritic polymers or functionalized polymers may also be used for similar purposes to improve the dispersibility of carbon nanotubes, the wettability of electrodes, and the electrochemical performance.

[0026] Furthermore, although the present invention describes an embodiment using a specific ionic liquid (1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide) as an electrolyte, other types of ionic liquids or conventional electrolytes may be used as long as they can provide the required electrochemical window and conductivity to meet the performance requirements of the supercapacitor.

[0027] The embodiments of the present invention also demonstrate a method for preparing an electrode by drop casting, but those skilled in the art will appreciate that other electrode preparation techniques, such as spraying, printing or roll coating, can also be used to prepare the carbon nanotube / dendritic polymer mixture electrode described in the present invention to adapt to different manufacturing processes and application requirements.

[0028] Finally, the carbon nanotube / dendritic polymer mixture electrode material of the present invention is not only suitable for supercapacitors due to its excellent performance, but may also play an important role in other fields, such as sensors, electrocatalysts and energy conversion devices.

[0029] The technical contents and embodiments described in this specification are for reference only, and the protection scope of the present invention shall be subject to the attached claims. Those skilled in the art may make various modifications, changes or equivalent substitutions to the present invention without departing from the spirit and scope of the present invention, and these modifications, changes or equivalent substitutions shall be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall not be limited to the specific embodiments in the specification, but shall be determined according to the contents of the attached claims.

Claims

1. A carbon nanotube / dendritic polymer mixture for use as a supercapacitor electrode, characterized in that: The mixture includes surface-modified multi-walled carbon nanotubes (MWCNTs) and a sugar dimer containing four glucose units (4-Gl).

2. The mixture according to claim 1, characterized in that The multi-walled carbon nanotubes (MWCNTs) include at least one of the two types of MWCNT-COOH / 4-Gl and / or MWCNT-NH2 / 4-Gl.

3. The mixture according to claim 1 or 2, characterized in that The mixture was prepared by casting two types of modified multi-walled carbon nanotubes (MWCNTs) into eight alternating bilayers.

4. A supercapacitor, characterized in that: The supercapacitor comprises a carbon nanotube / dendrimer mixture according to any preceding claim as electrode material.

5. The supercapacitor according to claim 4, characterized in that: The supercapacitor further includes a separator in which 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonimide (C8H11F6N3O4S2) ions are embedded as an electrolyte.

6. The supercapacitor according to claim 4 or 5, characterized in that: The content of the dendritic polymer in the electrode accounts for 18-20% of the content of the carbon nanotubes.

7. A method for preparing a carbon nanotube / dendritic polymer mixture for use as a supercapacitor electrode, characterized in that The following steps are involved: a) Synthesis of a sugar dimer containing four glucose units (4-Gl); b) preparing carbon nanotube dispersions containing different concentrations of 4-Gl dendrimers, wherein the carbon nanotubes include two types: MWCNT-COOH and MWCNT-NH2; c) depositing the dispersion obtained in step b) onto an aluminum current collector by drop casting, coating MWCNT-COOH / 4-Gl and MWCNT-NH2 / 4-Gl alternately to form a double layer, drying at 100°C between each layer; d) Step c) is repeated until eight bilayers are deposited to form an electrode with good cohesion and dimensional stability.

8. The preparation method according to claim 7, characterized in that: The binding of the sugar dimer to the multi-walled carbon nanotube is achieved through electrostatic interaction.

9. Use of a supercapacitor using the carbon nanotube / dendritic polymer mixture according to any one of claims 1 to 3 as an electrode material.