Electrostatic power generation element and method for manufacturing electrostatic power generation element

Abstract

To provide an electrostatic power generation element having good flexibility and processability and reducing the environmental load, and a method for manufacturing the electrostatic power generation element.SOLUTION: An electrostatic generating element includes carbon nanotube composite paper made by combining carbon nanotubes and pulp, an electrode A having the carbon nanotube composite paper on its surface, and an electrode B arranged opposite the carbon nanotube composite paper side of the electrode A.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power generating element and a method for manufacturing the power generating element. [Background technology]

[0002] The construction of IoT infrastructure requires a huge number of diverse sensors. Energy harvesting, which obtains electricity from unused energy in the environment, has attracted attention as a power source for sensors. Among them, active research has been conducted on an element that uses frictional charging called triboelectric nano-generator (TENG), which has an extremely simple structure. TENG is a power generation method that generates AC voltage by combining contact charging between two different materials and subsequent electrostatic induction.

[0003] As an example of a conventional friction charging element, Patent Document 1 discloses a contact charging member for a friction charging generator, the contact charging member including a contact layer having a contact surface and a back surface, made of a dielectric material having a friction charging series characteristic that exhibits the property of exchanging electrons upon a contact event, and an electrode layer disposed along the back surface of the contact layer, the contact surface of the contact layer being patterned to present continuous cavities, each cavity having an opening and a flexible bottom for expanding and contracting to the opening. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2021-500841 Summary of the Invention [Problem to be solved by the invention]

[0005] However, for example, in the frictional charging generator described in the above-mentioned Patent Document 1, the contact charging member is made of fluorinated ethylene propylene, polyimide, or the like, and leaves room for improvement in terms of flexibility, processability, and environmental impact.

[0006] In view of the above problems, an object of the present invention is to provide an electrostatic generating element that has good flexibility and processability and reduces the environmental load, and a method for manufacturing the electrostatic generating element. [Means for solving the problem]

[0007] The above problems can be solved by the inventions specified below. (1) Carbon nanotube composite paper made by combining carbon nanotubes and pulp; An electrode A having the carbon nanotube composite paper on its surface; An electrode B is provided so as to face the electrode A on the carbon nanotube composite paper side; An electrostatic generating element comprising: (2) The electrostatic generating element according to (1) above, wherein the pulp is wood pulp, non-wood pulp or recycled paper pulp. (3) The electrostatic generating element according to (1) or (2), wherein the carbon nanotubes are single-walled carbon nanotubes. (4) preparing a mixture of a carbon nanotube dispersion containing carbon nanotubes, a dispersant, and water, and a pulp dispersion containing pulp and water; a step of dehydrating the mixture by a papermaking method and forming the mixture into a carbon nanotube composite paper; providing the carbon nanotube composite paper on a surface of an electrode A, and providing an electrode B so as to face the carbon nanotube composite paper side of the electrode A; A method for manufacturing an electrostatic generating element comprising the steps of: Effect of the Invention

[0008] According to the present invention, it is possible to provide a photoelectric generating element having good flexibility and processability, and a method for manufacturing the photoelectric generating element, which has a reduced environmental impact. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating a configuration of an electrostatic generating element according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating the steps of a papermaking method according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a wiring diagram of an apparatus for electrostatic generation testing according to an embodiment. [Figure 4] 1 shows voltage waveforms of an oscilloscope in Examples 1 to 3 and Comparative Example 1. [Diagram 5] 1 shows voltage waveforms of an oscilloscope in Examples 4 to 7. [Figure 6] 13 shows voltage waveforms of an oscilloscope in Examples 8 to 10. [Figure 7] 1 shows voltage waveforms of an oscilloscope in Examples 11 to 13. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Next, the embodiments of the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and that appropriate changes and improvements in the design may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0011] (Configuration of electrostatic generating element) A schematic diagram showing the configuration of an electrostatic generating element according to an embodiment of the present invention is shown in Fig. 1. The electrostatic generating element according to an embodiment of the present invention includes a carbon nanotube composite paper made by combining carbon nanotubes (CNTs) and pulp, an electrode A having the carbon nanotube composite paper on its surface, and an electrode B arranged to face the carbon nanotube composite paper side of the electrode A.

[0012] The electrostatic generating element according to the embodiment of the present invention is a contact-separation type electrostatic generating element. In such a contact-separation type electrostatic generating element, the moment that electrode A and electrode B approach each other and come into contact, electrons move to one electrode, creating an opposite potential (charging). Next, when electrode A and electrode B are separated, the electrostatic field generated by the separated frictional charges is balanced, and a current pulse is generated. When the gap between electrode A and electrode B is closed again by an external force, the frictional charges between the carbon nanotube composite paper on the surface of electrode A and electrode B become closer, the frictional potential difference disappears, and electrons flow back into the circuit to generate an opposite current pulse.

[0013] In the electrostatic generating element according to an embodiment of the present invention, the carbon nanotube composite paper on the surface of electrode A contains conductors called carbon nanotubes in the pulp, and is therefore able to transmit electricity efficiently to electrode A. Furthermore, the pulp inside the carbon nanotube composite paper has a three-dimensional mesh structure, with the carbon nanotubes clinging to this three-dimensionally expanding pulp. When electrode A and electrode B come close to each other and come into contact, the carbon nanotube composite paper is compressed. At this time, the pulp itself inside the carbon nanotube composite paper is also compressed, amplifying the charge. This makes it possible to generate electrostatic charge with high efficiency.

[0014] The carbon nanotube composite paper of the electrostatic generating element according to the embodiment of the present invention is composed of a composite of carbon nanotubes and pulp. Carbon nanotubes are a substance made of carbon, and have many excellent properties such as high electrical conductivity, light weight, high strength, large specific surface area, and flexibility. By combining carbon nanotubes with such properties and pulp, which is easy to process and familiar to many people, it is expected that the paper will be used in various fields as described below.

[0015] Carbon nanotubes are carbon-based materials consisting of graphene sheets rolled into a cylindrical shape, and are classified as single-walled carbon nanotubes and multi-walled carbon nanotubes based on the number of surrounding walls. The use of single-walled carbon nanotubes increases the flexibility of the carbon nanotube composite paper. On the other hand, the use of multi-walled carbon nanotubes increases the strength of the carbon nanotube composite paper. Single-walled carbon nanotubes and multi-walled carbon nanotubes can be appropriately selected depending on the application of the actuator. Furthermore, the carbon nanotubes in the carbon nanotube composite paper may have a chiral (spiral) type, zigzag type, armchair type, or other structure due to differences in the structure of the graphene sheets.

[0016] The carbon nanotube composite paper of the electrostatic generating element according to the embodiment of the present invention preferably contains 0.1 to 30 mass % of carbon nanotubes. In the carbon nanotube composite paper of the electrostatic generating element, good conductivity is obtained when the carbon nanotubes are contained in 1 mass % or more. Furthermore, even if the carbon nanotube composite paper of the electrostatic generating element contains more than 30 mass % of carbon nanotubes, it becomes difficult to further improve the conductivity, and there is a tendency that it is disadvantageous in terms of cost. In the carbon nanotube composite paper of the electrostatic generating element according to the embodiment of the present invention, the carbon nanotubes are more preferably contained in 5 to 30 mass %, and even more preferably contained in 10 to 30 mass %.

[0017] The thickness of the carbon nanotube composite paper of the electrostatic generating element according to the embodiment of the present invention is not particularly limited, but may be, for example, 0.05 to 1 mm.

[0018] The pulp for the carbon nanotube composite paper is not particularly limited, but may be wood pulp (coniferous pulp or hardwood pulp such as eucalyptus), non-wood pulp (kenaf pulp, cotton pulp, bamboo pulp, bagasse pulp, abaca pulp, seaweed pulp, straw pulp, bark pulp, mulberry pulp, reed pulp, fruit pulp, etc.), or recycled paper pulp.

[0019] The pulp for the carbon nanotube composite paper is not particularly limited, but mechanical pulp (MP), chemical pulp (CP), and the like can be used.

[0020] Mechanical pulp is pulp made by breaking down wood using physical forces. Types of mechanical pulp include groundwood pulp (GP), refiner ground pulp (RGP), thermo-mechanical pulp (TMP), and chemi-thermo-mechanical pulp (CTMP).

[0021] Chemical pulp is pulp made by chemically decomposing wood (which must be crushed into chips) and separating lignin, etc. (called cooking). Types of chemical pulp include kraft pulp (KP), sulfide pulp (SP), and alkaline pulp (AP).

[0022] Furthermore, inorganic fibers, glass fibers, fibers derived from minerals, etc. may be used as the pulp for the carbon nanotube composite paper.

[0023] As described above, the carbon nanotube composite paper of the electrostatic generating element according to the embodiment of the present invention is formed by combining carbon nanotubes, which have many excellent properties such as high electrical conductivity, light weight, high strength, large specific surface area, and flexibility, with pulp, which is easy to process and is familiar to many people. Carbon nanotube composite paper having such a configuration is flexible and can be designed to any size, and can be applied to suit the shape of the site even after production. It can also be easily produced in large quantities and over a large area. It is also environmentally friendly and can be disposed of by incineration.

[0024] The electrodes A and B of the electrostatic generating element according to the embodiment of the present invention are preferably made of a material having good electrical conductivity. Examples of such materials include metals (aluminum, copper, silver, gold, platinum, iron, nickel, chromium, molybdenum, indium, etc.), metal alloys, semiconductors (doped silicon, etc.), metal oxides (indium tin oxide (ITO), etc.), and conductive polymers (PEDOT-PSS, etc.). The electrodes A and B may be made of the same material or different materials. The plate shapes of the electrodes A and B are not particularly limited, but are preferably plate-shaped.

[0025] The electrostatic generating element according to the embodiment of the present invention is used in a vibrating environment, and the vibration is used to repeatedly contact and separate electrode A, which has carbon nanotube composite paper on its surface, and electrode B, which is disposed so as to face the carbon nanotube composite paper side of electrode A. At this time, by electrically connecting conductors to electrodes A and B of the electrostatic generating element, a pulsed current can be obtained by electrostatic generation.

[0026] The electrostatic power generation element according to the embodiment of the present invention only requires an environment with vibration, and can therefore become an energy harvester that can easily obtain energy when combined with equipment that generates vibrations, such as washing machines, or busy corridors indoors, or with busy bridges or mobility such as airplanes or automobiles outdoors. It can also be used for furniture, interior applications, outdoor applications, disaster prevention, devices and mobility that constantly generate vibrations, etc.

[0027] (Method of manufacturing electrostatic generating element) Next, a method for manufacturing an electrostatic generating element according to an embodiment of the present invention will be described. First, carbon nanotubes, a dispersant, and water are ultrasonically dispersed to prepare a CNT dispersion.

[0028] Examples of dispersants that can be used include DNA, catechin, pyrene-based dispersants, phthalocyanine-based dispersants, porphyrin-based dispersants, naphthalocyanine-based dispersants, surfactants, etc. Examples of surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants.

[0029] Specific examples of dispersants include sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, cetylpyridinium chloride, dodecyltrimethylammonium bromide, polyoxyethylene (100) stearyl ether, polyoxyethylene (10) octylphenyl ether, methyltriphenylsulfonium bromide, and sodium salt of β-naphthalenesulfonic acid formalin condensate.

[0030] Next, the pulp and water are mixed to prepare a pulp dispersion. Next, the CNT dispersion and the pulp dispersion prepared as described above are mixed together to prepare a mixture. The liquid temperatures during the preparation of the above-mentioned CNT dispersion liquid, pulp dispersion liquid, and mixed liquid may be room temperature (about 25° C.) or may be heated.

[0031] Regarding the composition of the CNT dispersion liquid when a surfactant is used as a dispersant, the amount of CNT contained in the water is determined by the type of surfactant based on a specified critical micelle concentration. The CNT content in the mixture depends on the desired electrical conductivity of the CNT composite paper. In particular, the CNT content relative to the pulp has a large effect on the electrical conductivity of the CNT composite paper. Increasing the CNT content relative to the pulp improves the electrical conductivity of the CNT composite paper.

[0032] Next, a specified formwork is placed on the net, the mixed liquid is poured into the formwork and dehydrated, then the formwork is removed and the mixture is shaped and dried by a hot press (papermaking method). Alternatively, the mixed liquid may simply be poured into the formwork and the water may be evaporated. This produces carbon nanotube composite paper in which carbon nanotubes and pulp are mixed three-dimensionally. Figure 2 shows a schematic diagram illustrating the steps of the papermaking method. At this time, heat pressing may or may not be performed. By heat pressing, it is possible to produce a compactly compressed carbon nanotube composite paper. If heat pressing is not performed, the density of the carbon nanotube composite paper decreases, but the compression ratio of the carbon nanotube composite paper increases when the electrostatic generating element generates electricity, allowing for more efficient power generation.

[0033] Next, an electrostatic generating element according to an embodiment of the present invention is produced by providing the carbon nanotube composite paper on the surface of electrode A, and providing electrode B so as to face the carbon nanotube composite paper side of electrode A. As a means for providing the carbon nanotube composite paper on the surface of electrode A, the carbon nanotube composite paper may be attached to the surface of electrode A using a known conductive double-sided tape or conductive paste. EXAMPLES

[0034] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0035] <Test Example 1> (Examples 1 to 7 and Comparative Example 1) Carbon nanotubes (CNTs), sodium dodecyl sulfate (SDS) as a dispersant, and water in the amounts shown in Table 1 were mixed in a beaker and subjected to ultrasonic dispersion for 1 hour to prepare a CNT dispersion. The types of CNTs shown in Table 1 are as follows: "SG101" Zeon Corporation single-walled CNT: SG101 "NC7000" Nanocyl single-walled CNT: NC7000 "(6,5)" Single-walled CNT with chirality (6,5) "(7,6)" Single-walled CNT with chirality (7,6)

[0036] Next, eucalyptus as a pulp material and water were mixed in the amounts shown in Table 1 in a beaker and stirred for one hour to prepare a pulp dispersion. Next, a rectangular mold was placed on top of the net, and the CNT dispersion and pulp dispersion were poured into the mold to create a mixed liquid. After dehydration, the mold was removed and the mixture was molded and dried using a hot press to produce CNT composite paper. Next, the CNT composite paper was cut into a square with each side measuring 3 cm, which was used as a sample.

[0037] [Table 1]

[0038] Next, the film thickness and sheet resistance of each sample were measured. The sheet resistance was calculated using the following formula. The measurement results are shown in Table 2. Sheet resistance (Ω / sq.) = (V / I) x (W / L) [V: observed voltage, I: applied current, W: sample width, L: sample length]

[0039] [Table 2]

[0040] Next, two aluminum plates each measuring 4 cm x 4 cm x 0.3 mm in length x width x thickness were prepared, and the sample was attached to the surface of one of the aluminum plates with conductive double-sided tape to create an electrostatic generating element.

[0041] Next, the electrostatic power generation element, a constant vibration generator made with a 3D printer, and an oscilloscope were connected according to the wiring diagram shown in FIG. 3. The maximum separation distance between the two Al plates was 0.7 cm, and the constant vibration generator caused the upper Al plate to approach and contact one of the Al plates to which the lower CNT composite paper sample was attached, and then move away. After the upper Al plate moves away and reaches the maximum separation distance, it again approaches and contacts the lower Al plate. This was repeated multiple times, and the power generation output by electrostatic power generation was confirmed with an oscilloscope. Vibration by the constant vibration generator (tapping of the Al plate) was performed for about 15 minutes. The voltage waveforms of the oscilloscope for each example and comparative example are shown in FIG. 4 and FIG. 5.

[0042] In Examples 1 to 7, a power generation output of about 75 mV was obtained on the positive and negative sides. In Comparative Example 1, an element was used in which eucalyptus paper containing no CNT was attached to an Al plate, so only noise was observed, and compared to Examples 1 to 7, no static electricity was generated. In Example 4, metallic CNT (NC7000) was used, but a power generation output similar to that of semiconducting CNT (SG101) was obtained. In Examples 5 to 7, the amount of SDS added was half that used in Examples 1 to 3, but no significant difference was observed in the power generation output.

[0043] <Test Example 2> In Test Example 1, when the upper Al plate was tapped by the constant vibration generator, the opposing lower Al plate with the CNT composite paper attached floated, making it impossible to tap evenly, reducing the contact area and decreasing the power generation output. In contrast, in Test Example 2, by adjusting the balance of the constant vibration generator, when the upper Al plate was tapped, it was made to come into uniform contact with the lower Al plate with the CNT composite paper attached, increasing the contact area and thereby improving the power generation output. The sample of CNT composite paper was prepared by the same procedure as in Test Example 1. The composition of the CNT dispersion and pulp dispersion used in Test Example 2 is shown in Table 3.

[0044] [Table 3]

[0045] Next, the film thickness and sheet resistance of each sample were measured. The sheet resistance was calculated using the same formula as in Test Example 1. The measurement results are shown in Table 4.

[0046] [Table 4]

[0047] Next, in the same manner as in Test Example 1, an electrostatic generating element was made using the two Al plates and the sample. Next, in the same manner as in Test Example 1, the electrostatic power generation element, the constant vibration generator made with a 3D printer, and the oscilloscope were connected according to the wiring diagram shown in FIG. 3. In Test Example 2, the constant vibration generator was balanced so that when the upper Al plate was tapped, it was uniformly contacted with the lower Al plate to which the CNT composite paper was attached, increasing the contact area. The power generation output by electrostatic power generation at this time was confirmed with an oscilloscope. The voltage waveforms of the oscilloscope for each example are shown in FIG. 6 and FIG. 7. The vibration by the constant vibration generator (tapping of the Al plate) was performed for about 15 minutes.

[0048] In Examples 8 to 13, a power generation output of about 300 mV was obtained on the positive and negative sides. In Examples 8 to 10, the amount of eucalyptus was twice as much as in Examples 11 to 13, and the power generation output was slightly increased compared to Examples 11 to 13. In Examples 8 to 13, little deterioration of the CNT composite paper was observed after tapping for about 15 minutes, and the power generation output was stable. This indicates that the CNT composite paper has high durability.

Claims

1. A carbon nanotube composite paper made by combining carbon nanotubes and pulp; An electrode A having the carbon nanotube composite paper on its surface; an electrode B provided opposite the electrode A on the carbon nanotube composite paper side; An electrostatic generating element comprising:

2. The electrostatic generating element according to claim 1 , wherein the pulp is wood pulp, non-wood pulp or recycled paper pulp.

3. The electrostatic generating element according to claim 1 or 2, wherein the carbon nanotubes are single-walled carbon nanotubes.

4. A step of preparing a mixture of a carbon nanotube dispersion containing carbon nanotubes, a dispersant, and water, and a pulp dispersion containing pulp and water; a step of dehydrating the mixture by a papermaking method and forming the mixture into a carbon nanotube composite paper; providing the carbon nanotube composite paper on a surface of an electrode A, and providing an electrode B so as to face the carbon nanotube composite paper side of the electrode A; A method for manufacturing an electrostatic generating element comprising the steps of:

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