CN102263221B - Oriented CNT (carbon nano tube)/polymer composite membrane as well as preparing method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of lithium ion batteries, and in particular relates to a carbon nanotube/polymer composite film and a preparation method and application thereof. The invention uses epoxy resin embedding solution, toughening agent and carbon nanotube array as raw materials to obtain carbon nanotube/polymer composite film through curing, compounding and slicing. The carbon nanotubes in the film are evenly distributed, so that the upper and lower surfaces of the film have good electrical conductivity, and at the same time it has good flexibility and strength, and there are a large number of open ends of carbon nanotubes on the film surface. The height of the open ends is The orientation structure makes it widely used in lithium-ion batteries. In the present invention, the vertical orientation carbon nanotube/polymer composite film is exemplified as the application in button-type lithium-ion batteries and polymer lithium-ion batteries, and is also suitable for In other forms of lithium-ion batteries.

Description

Oriented carbon nanotube/polymer composite film and its preparation method and application

technical field

The invention belongs to the technical field of lithium ion batteries, and in particular relates to a carbon nanotube/polymer composite film and a preparation method and application thereof.

Background technique

The discovery of carbon nanotubes is a milestone in the history of world science. Since the discovery of carbon nanotubes (Carbon Nanotubes, CNTs) by Iijima in Japan in 1991[1], carbon nanotubes have been characterized by their unique high tensile strength, high elasticity, electronic properties from metal to semiconductor, high current load capacity and high thermal conductivity. As well as the unique quasi-one-dimensional tubular molecular structure, it has many potential application values in the future high-tech field and has become the focus of attention. Carbon nanotubes have been widely studied to be added to polymers to prepare composite materials, but because carbon nanotubes are randomly distributed in polymers, the practical performance of composite materials is not ideal. With the in-depth study of carbon nanotube arrays (ACNTs), the macroscopic length of nanotube arrays is sufficient to allow a single carbon tube to penetrate the entire material in a composite material. Using the ordered nature of carbon nanotube arrays to prepare uniformly dispersed and flexible carbon nanotube/polymer composites has become a new research hotspot. At present, there are two main methods for preparing carbon nanotube/polymer composites: in-situ polymerization and polymer infiltration. Composite materials with anisotropy can be prepared, and their superior electrical and mechanical properties show very good application potential [2] [3].

New energy technology plays a vital role in the sustainable development of human society in the future. Lithium-ion batteries were developed in the 1990s. They have high specific energy, long cycle life, good safety performance, no memory effect, and are environmentally friendly. And other advantages, it has been widely used in portable electrical appliances such as mobile phones, notebook computers, and camcorders, and is expected to be widely used in electric vehicles and storage of clean electric energy such as solar energy and wind energy. Since the commercialization of lithium-ion batteries, electrode materials have always been a research hotspot in the field of batteries. In the lithium intercalation reaction of lithium-ion batteries, LiC6 was once considered to be the highest composition of lithium-carbon compounds, but since 1994, the report of nano-carbon materials exceeding the theoretical capacity has led people to start the exploration of a new generation of lithium-ion battery anode materials. Among them, the research on carbon nanotubes has made important progress. Ideally, carbon nanotubes are seamless, hollow tubes rolled from layers of graphite. Carbon nanotubes have a very high surface area and excellent mechanical and electrical properties, and have been the focus of material science research since their inception. Studies have found that the charge and discharge capacity of carbon nanotubes can exceed twice the theoretical capacity of graphite lithium intercalation compounds. However, the random accumulation of carbon tubes is not conducive to lithium intercalation and deintercalation. How to effectively play the role of carbon tubes in lithium-ion batteries has become a direction that has attracted widespread attention [4][5].

Aiming at how to effectively play the role of carbon tubes in lithium-ion batteries, the present invention addresses the problems existing in existing lithium-ion battery systems by using vertically oriented carbon tubes/polymer composite film electrode materials. The carbon tubes in this electrode material maintain a high degree of order, thereby improving the conductivity of the electrode material, and all the carbon tubes are kept open at both ends of the film to facilitate the improvement of lithium storage performance. Due to the immobilization of polymers, electrodes made of carbon tube materials have the advantages of long life, good safety, high specific capacity, and superior rate performance; by optimizing the composition and process of this composite membrane electrode in lithium-ion battery applications, Preparation of new lithium-ion batteries with high energy density and high safety.

Contents of the invention

The purpose of the present invention is to provide an oriented carbon nanotube/polymer composite film with excellent electrical conductivity, excellent flexibility and strength, and its preparation method and application. the

The invention provides a method for preparing an aligned carbon nanotube/polymer composite film. It mainly uses the mixed solution of epoxy resin monomer and toughening agent and carbon nanotube array as raw materials, and through the method of infiltration, the resin monomer is immersed in the array, and then it is cured by heating to form a composite material. Finally, the carbon nanotube/polymer composite film was obtained by slicing with a microtome. The innovation of this method is that it realizes the production of vertically oriented carbon nanotube film, so that the upper and lower surfaces of the film are connected by a single carbon nanotube, so as to better exert the electrical properties of carbon nanotubes.

The concrete steps of the inventive method are as follows:

Immerse the carbon nanotube array in the mixed solution of epoxy resin monomer and toughening agent, infiltrate and embed it; then cure it in an oven at 55-65 ^o C for 12-40 hours to obtain the embedded block; use a microtome Composite thin slices with different thicknesses are cut to obtain a carbon nanotube/polymer composite film, and the thickness of the composite film ranges from 50 nanometers to 50 microns.

The method of the present invention completely fixes the carbon nanotube array in the epoxy resin, and the carbon nanotubes in the film obtained after slicing are completely evenly distributed, and all are perpendicular to the surface of the film, so there are a large number of single tubes between the upper and lower surfaces of the film. The carbon nanotubes are interconnected and have excellent electrical conductivity, and the surface of the film has a large number of open ends of the carbon nanotubes.

In the present invention, the carbon nanotube array can be prepared by the following method:

The catalyst structure for the synthesis of carbon nanotube arrays is Si/SiO ₂ /Al ₂ O ₃ /Fe, wherein the thickness of SiO ₂ is 300-1000 μm, the thickness of Al ₂ O ₃ is 10-30 nm, and the thickness of Fe is 0.5-1.5 nm, Al ₂ O ₃ is located between the silicon wafer and Fe, as a buffer layer, and Fe as a catalyst, which are prepared by depositing a nanometer-thick film on a silicon wafer by an electron beam evaporation coating device; using chemical vapor deposition method, Using ethylene as the carbon source and argon and hydrogen as the carrier gas, synthesize highly oriented carbon nanotube arrays on Si substrates with an oxide layer; the flow of ethylene is 190-290 sccm, the flow of argon is 400-620 sccm, and the flow of hydrogen The flow rate was 20-48 sccm and the tube furnace was grown for 5-100 min.

The carbon nanotube/polymer composite film prepared by the above method can be used as an electrode material and loaded into a lithium ion battery to prepare a high-performance secondary lithium ion battery. The composite film can also be used as a sensitive element to prepare a gas sensor to obtain a sensitive device with high sensitivity, high stability and short recovery time. the

1. Button lithium-ion battery installation steps

(1) First clean the battery stainless steel case with distilled water, then use distilled water to sonicate for 15-25 minutes in an ultrasonic cleaner, then use anhydrous ethanol to sonicate for 15-25 minutes, and finally dry it in an oven at 75-85°C .

(2) Use a 1-50um thick oriented carbon nanotube/polymer composite film as the negative plate, and dry it in a blast oven at 75-85°C for 4-8 hours.

(3) Under an inert gas protection environment, install in the order of stainless steel shell, carbon nanotube/epoxy resin composite film, diaphragm, absorbent paper, lithium sheet, current collector, and stainless steel cover. The electrolyte is added dropwise in the middle, so that the electrolyte fully infiltrates the electrode and separator materials.

(4) Place the installed lithium-ion battery in a ventilated and dark place for more than 20 hours.

2. The production of polymer lithium-ion batteries based on aligned carbon nanotubes/polymer composite films as electrode materials, the specific steps are as follows:

(1) Preparation of oriented carbon nanotube/polymer composite film with the designed size of the battery product.

(2) Cut the appropriate size diaphragm.

(3) Prepare the battery core, put it in the order of positive electrode/diaphragm/negative electrode/diaphragm/positive electrode or the order of negative electrode/diaphragm/positive electrode/diaphragm, and make the battery core by winding/stacking.

(4) Assemble into a battery, and inject electrolyte or sol electrolyte and seal the four edges.

(5) Formation and storage: slow charging and formation, and after several weeks of storage, qualified products are screened out.

Description of drawings

Figure 1, a is the physical picture of the carbon nanotube array embedded in resin, and Figures b-f are the morphological views of the carbon nanotube/polymer composite film after different forms of bending or folding.

Figure 2, Schematic diagram of the working principle of the battery.

Figure 3, the structural diagram of the button lithium-ion battery.

Figure 4, polymer lithium battery manufacturing process.

Detailed ways

The specific process of preparation is as follows:

First, the synthesis of aligned carbon nanotube arrays.

Vertically grown carbon nanotube arrays were synthesized using a typical chemical vapor deposition method in a quartz tube of a tube furnace with Fe(1 nm)/Al ₂ O ₃ (10 nm)/SiO ₂ /Si as catalyst. In the catalyst, Al ₂ O ₃ is located between the silicon wafer and Fe, as a buffer layer, and Fe as a catalyst, which are prepared by depositing a nanometer-thick film on the silicon wafer by an electron beam evaporation coating device. Using chemical vapor deposition method, ethylene is used as carbon source, argon and hydrogen are used as carrier gas, and highly oriented carbon nanotube arrays are synthesized on Si substrate with oxide layer. The details of the synthesis and the self-assembly of carbon tubes in fibers can be referred to the existing literature reports.

Second, preparation of embedding stock solution.

The formula used for embedding is the classic "EPON 812" formula. The present invention is based on this formula and adds an appropriate amount of toughening agent. The specific preparation method is as follows: First, configure solution A and solution B. Liquid A is composed of epoxy resin (SPI-Pon 812) and dodecenylsuccinic anhydride (DDSA) in a volume ratio (60-65): 100; liquid B is composed of epoxy resin (SPI-Pon 812) and Nadic methyl anhydride (NMA) is composed at a volume ratio of 100: (86-90). Prepared liquid A and liquid B are ultrasonically dispersed in an ultrasonic cleaner for 10-30 minutes to disperse evenly. The toughening agent is DT-2 type purchased from Shenyang Southeast Chemical Research Institute. Then mix liquid A and liquid B at a volume ratio of 2:8 (liquid A: liquid B = 2:8), then add a toughening agent with a total volume of 8%--12% of the total volume of liquid A and liquid B, and finally add the total 1% to 2% of the volume of the curing accelerator 2, 4, 6 tris (dimethylaminomethyl) phenol (DMP-30), ultrasonic 10-30 minutes, fully mixed. Finally, the embedding stock solution was obtained. Put the array into the embedding-shaped mold, then inject the embedding stock solution, and cure in a polymerization box at 60 degrees Celsius for 36 hours under normal pressure to obtain a carbon nanotube array embedded with epoxy resin. the

Third, section the embedded sample.

The embedded samples were trimmed, and then sliced with a Leica microtome to obtain carbon nanotube/polymer composite films of different thicknesses. The thickness of the slices ranged from 50 nm to 100 µm.

Fourth, battery assembly:

1. Button lithium-ion battery installation steps:

(1) Clean the stainless steel case of the battery with distilled water first, then use distilled water in an ultrasonic cleaner for 20 minutes, then use anhydrous ethanol for 20 minutes, and dry it in an oven at 80°C.

(2) The oriented carbon nanotube/polymer composite film with a thickness of 1-50 um is used as the negative plate, and it is dried in a vacuum oven at 80° C. for 6 hours as before in a blast oven.

(3) Under the protective environment of inert gas, the stainless steel shell, carbon nanotube/epoxy resin composite film, diaphragm, absorbent paper, lithium sheet, current collector, and stainless steel cover are installed in sequence. The electrolyte is added dropwise in the middle, so that the electrolyte fully infiltrates the electrode and separator materials.

(4) Place the installed lithium-ion battery in a ventilated and dark place to age for about 24 hours. The charging and discharging performance of the battery was tested by the timing point method of the electrochemical workstation CHI660.

2. The production of polymer lithium-ion batteries based on aligned carbon nanotubes/polymer composite films as electrode materials, the specific steps are as follows:

(1) Preparation of oriented carbon nanotube/polymer composite film with the designed size of the battery product.

(2) Cut the appropriate size diaphragm.

(3) Prepare the battery core, put it in the order of positive electrode/diaphragm/negative electrode/diaphragm/positive electrode or the order of negative electrode/diaphragm/positive electrode/diaphragm d, and make a battery core by winding/stacking.

(4) Assemble into a battery, and inject electrolyte or sol electrolyte and seal the four edges.

(5) Formation and storage: slow charging and formation, and after several weeks of storage, qualified products are screened out.

references

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Claims (7)

1. a preparation method for alignment carbon nano tube/polymer composite membrane, is characterized in that concrete steps are as follows:

The mixed solution that carbon nano pipe array is immersed to epoxy monomer and flexibilizer, permeates, embedding; 55--65 ℃ of curing 12--40 hour in baking oven, obtains embedded block again; With slicing machine, be cut into different-thickness compound foil, obtain carbon nanotube/polymer composite membrane, the thickness range of composite membrane is 50 nanometers to 50 micron;

The compound method of described mixed solution is as follows:

First, configuration solution A and solution B; A liquid is by epoxy resin and dodecenylsuccinic acid acid anhydride (60-65) by volume: 100 ratio forms; B liquid is by epoxy resin and methyl carbic anhydride by volume 100: the ratio of (86-90) forms; The A liquid preparing and B liquid make dispersed at ultrasonic cleaning machine the inside ultrasonic 10-30 minute; Then A liquid and B liquid are mixed with the volume ratio of 2:8, then the flexibilizer that adds A liquid and B liquid cumulative volume 8%--12%, 1%～2% curing accelerator 2,4,6 three (dimethylamino methyl) phenol that finally adds cumulative volume, ultrasonic 10-30 minute, fully mixes; Finally obtain embedding stoste.

2. the preparation method of alignment carbon nano tube/polymer composite membrane according to claim 1, is characterized in that wherein the synthesis step of carbon nano-tube is:

Use structure is Si/SiO ₂/ Al ₂o ₃/ Fe is catalyst, adopts chemical vapour deposition technique, with ethene, does carbon source, usings argon gas and hydrogen as carrier gas, is having synthetic height-oriented carbon nano pipe array on oxide layer Si substrate; Therein ethylene flow is 190-290 sccm, and argon flow amount is 400-620 sccm, and hydrogen flowing quantity is 20-48 sccm, and 5-100 min grows in tube furnace; In catalyst, SiO ₂thickness is 300-1000 μ m, Al ₂o ₃thickness is 10-30 nm, and Fe thickness is 0.5-1.5 nm, Al ₂o ₃be positioned at the centre of silicon chip and Fe, as resilient coating, Fe is as catalyst, and the film preparation that they deposit one deck nano thickness by electron beam evaporation deposition instrument respectively on silicon chip obtains.

3. an alignment carbon nano tube/polymer composite membrane, it adopts preparation method's preparation as claimed in claim 1.

4. a lithium ion battery, it adopts alignment carbon nano tube/polymer composite membrane as claimed in claim 3 as electrode material.

5. a gas sensor, it adopts alignment carbon nano tube/polymer composite membrane as claimed in claim 3 as senser.

6. a kind of lithium ion battery as claimed in claim 4, is characterized in that described lithium ion battery is fastening lithium ionic cell,

Fastening lithium ionic cell installation steps are:

(1) first battery stainless steel case is cleaned with distilled water, then in ultrasonic cleaner, use the ultrasonic 15--25 minute of distilled water, then use the ultrasonic 15--25 minute of absolute ethyl alcohol, finally 75--85 ℃ of oven dry in baking oven;

(2) with the thick alignment carbon nano tube/polymer composite membrane of 1～50um, be negative plate, dry 75--86 ℃ of dry 4-8 hour in convection oven;

(3) under inert gas shielding environment, according to stainless steel casing, carbon nano tube/epoxy resin composite membrane, barrier film, waterleaf paper, lithium sheet, collector, the order of stainless steel cover is installed; The middle electrolyte that drips, makes electrolyte fully infiltrate electrode and diaphragm material;

(4) mounted lithium ion battery being positioned over to ventilation lucifugal place changes into more than 20 hours.

7. as according to a kind of lithium ion battery claimed in claim 4, it is characterized in that described lithium ion battery is film lithium ion battery,

Film lithium ion battery installation steps are:

(1) prepare the alignment carbon nano tube/polymer composite membrane of battery product design size;

(2) cutting suitable dimension barrier film;

(3) prepare battery, according to the order of the order of positive pole/barrier film/negative pole/barrier film/positive pole or negative pole/barrier film/positive pole/barrier film, put well, through coiling/lamination, make battery;

(4) be assembled into battery, and inject four edge seals after electrolyte or sol-electrolyte;

(5) change into and place: charging changes at a slow speed, and places after several weeks, filters out qualified products.

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