Patent Application
20080241695
1. Field of the Invention
The invention generally relates to composite electrode materials, methods for manufacturing the same and electrodes adopting the same and, particularly, to a carbon nanotube composite electrode material, a method for manufacturing the same, and an electrode adopting the same.
2. Discussion of Related Art
Batteries of portable electronic products include lithium ion type batteries and lithium ion polymer type batteries. In the lithium ion type battery, a negative electrode is, opportunely, made of carbon materials such as graphite. However, carbon nanotubes have a large specific surface area and are increasingly being used to replace the graphite to act as the negative electrode in the lithium ion type battery. Due to the gaps between the carbon nanotubes being small, it is difficult for ions electrolytes and/or reactive materials to pass through the gaps, and thus this increase in surface area is not fully utilized. That is, when carbon nanotubes are used to make the negative electrode in a lithium ion type battery, the advantage of large specific surface area of carbon nanotubes is not exploited.
What is needed, therefore, is a carbon nanotube composite electrode material having a usable large effective specific area, a method for manufacturing the same and an electrode including the same therein.
A carbon nanotube composite electrode material includes carbon fibers and carbon nanotubes. The carbon fibers constitute a network structure. The carbon nanotubes are wrapped about and adhered to the carbon fibers.
Other advantages and novel features of the present carbon nanotube composite electrode material, a related method for manufacturing the same, and a related electrode adopting the same will become more apparent from the following detailed description of present embodiments when taken in conjunction with the accompanying drawings.
Many aspects of the present carbon nanotube composite electrode material, the related method for manufacturing the same, and the related electrode adopting the same can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present carbon nanotube composite electrode material, the related method for manufacturing the same, and the related electrode adopting the same.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one present embodiment of the carbon nanotube composite electrode material, the related method for manufacturing the same, and the related electrode adopting the same, in at least one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Reference will now be made to the drawings, in detail, to describe embodiments of the carbon nanotube composite electrode material, the method for manufacturing the same, and the electrode adopting the same.
Referring to
The carbon nanotube composite electrode material 10, opportunely, is a film or sheet. A thickness of the film or sheet is in the approximate range from 100 μm (micrometer) to 10 mm (millimeter). A diameter of the carbon fibers 12 is in the approximate range from 2 μm to 50 μm. A length of the carbon fibers 12 is in the approximate range from 500 μm to 5 mm. The carbon nanotubes 14 are single-walled carbon nanotubes or multi-walled carbon nanotubes. A diameter of the carbon nanotubes 14 is in the approximate range from 20 nm (nanometer) to 100 nm. A length of the carbon nanotubes 14 is above 110 μm. Because the diameter of the carbon fibers 12 is about 100 times larger than that of the carbon nanotubes 14, gaps between the carbon fibers 12 are also larger than that between the carbon nanotubes 14, such that the electrolyte and/or reactive materials can easily penetrate into the carbon fibers 12 and come into contact with all or nearly all of the available surface area of the carbon nanotubes 14. In other words, an effective specific surface area of the carbon nanotubes 14 is improved, and the capacity of the electrode material is also improved. As such, the capacity of batteries made using the present carbon nanotube composite electrode material 10 is also improved.
Referring to
In step (a), a diameter of the carbon fibers is in the approximate range from 2 μm˜100 μm. A length of the carbon fibers is in the approximate range from 0.5 mm˜5 mm. A required size of the carbon fibers can be obtained by cutting. The first dispersant comprises a substance selected from a group consisting of water, ethanol, acetone, dimethylformamide, and any combination thereof. The first dispersant is used to disperse the carbon fibers 12. An amount of the first dispersant can be chosen according to practical needs in the present embodiment, and only needs to maintain uniform dispersion of the carbon fibers 12 therein. A method to disperse the carbon fibers 12 in the first dispersant is high-speed mechanical agitation method. A time of the mechanical agitation is in the approximate range from 5-10 minutes to break up connections between the carbon fibers 12. After mechanical agitation, the carbon fibers 12 are dispersed in the solution A, and partial carbon fibers connect to one another.
In step (b), the second dispersant is used to disperse the carbon nanotubes 14. The second dispersant comprises a substance selected from a group consisting of water, ethanol, acetone, dimethylformamide, and any combination thereof. The composition of the second dispersant can be the same as, or different from the first dispersant. An amount of the second dispersant can be chosen according to the practical needs of the present embodiment, and should only maintain uniform dispersion of the carbon nanotubes 14 therein. A method to disperse the carbon nanotubes in the second dispersant is an ultrasonic agitation method. A power of the ultrasonic vibrator is in the approximate range from 800 W (Watt) to 1200 W. In the present embodiment, when the power of the ultrasonic vibrator is about 1000 W, the time of ultrasonic agitation is in the approximate range from 10-60 minutes to form a flocculent solution B. It is to be understood that the time of ultrasonic agitation treatment decreases, as the power of the ultrasonic vibrator increases.
In step (c), the solution A and the solution B are mixed to form a uniformly dispersed solution C. Quite usefully, a weight ratio of the carbon fibers 12 to the carbon nanotubes 14 is chosen in the approximate range from 1:1 to 10:1 by controlling the mixing ratio of the solution A to the solution B. The diameter of the carbon fibers 12 is about 100 times bigger than that of the carbon nanotubes 14.
In step (d), after a period of time of forming the solution C, most of the carbon nanotubes 14 are wrapped about and adhered to the carbon fibers 14 therein; thereby the structure shown in
In step (e), a process of removing the dispersant (the first and second dispersants combined) from the solution C can be a drying process and a drawing-infiltrating process. In the present embodiment, the solution C is put into a container to form a liquid layer, and the liquid layer has a certain thickness. After drying, the carbon nanotube composite electrode material is obtained. Quite usefully, the thickness of the carbon nanotube composite electrode material is in the approximate range from 0.1 mm to 10 mm.
It is noted that the step (a) and the step (b) can occur in reverse order at the same time.
Referring to
The electrode 30 can be obtained by attaching the carbon nanotube composite electrode material 34 to the substrate 32 by a conductive tape. In addition, the electrode 30 can also be produced/obtained by the following steps. Firstly, the solution C is spray-coated or otherwise applied on the substrate 32. Secondly, the substrate 32 with the solution C thereon is dried to form the electrode 30 including the carbon nanotube composite electrode material 34. To achieve a predetermined thickness of the electrode material, the coating step can be repeatedly several times.
It is noted that the electrode 30 can include the substrate 32 in the present embodiment. However, the substrate 32 is not necessary to the electrode 30. That is, the electrode 30 can, opportunely, be made of the carbon nanotube composite electrode material 34 without the substrate 32 and have a predetermined shape.
Compared with the conventional electrode used in a capacitor or battery, because the diameter of the carbon fibers 12 is about 100 times bigger than that of the carbon nanotubes 14, gaps between the carbon fibers 12 are also bigger than that between the carbon nanotubes 14, such that electrolyte can easily penetrate into the carbon fibers 12 contacting a greater amount of the surface area of the carbon nanotubes 14. In other words, an effective specific surface area of the carbon nanotubes 14 is improved, and capacity of the battery made by the carbon nanotube composite electrode material 10 is also improved.
Finally, it is to be understood that the above-described embodiments are intended to illustrate rather than limit the invention. Variations may be made to the embodiments without departing from the spirit of the invention as claimed. The above-described embodiments illustrate the scope of the invention but do not restrict the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200710073646.2 | Mar 2007 | CN | national |
