Power generation unit

Abstract

To provide a highly efficient power generator which can sufficiently use a power generation surface enlarged by nanostructuring.SOLUTION: A power generator includes: a porous elastic body having a carbon material on at least an inner surface of a pore; a power collection part connected to the porous elastic body; and polar liquid. Thus, the highly efficient power generator which sufficiently uses a surface area of a power generation surface can be provided since the porous elastic body includes a polarization part at least partially and the porous elastic body immersed in the polar liquid is compressed and expanded to generate power.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power generator, and more particularly to a power generator that utilizes electrostatic induction. [Background technology]

[0002] Electrostatic induction between materials with different electron affinities is being utilized to generate electricity. Electrostatic induction is a phenomenon in which, when a charged object is brought close to a conductor, a charge of the opposite polarity to that of the charged object is attracted to the side closer to the charged object, and is caused by the actual movement of charge through the conductor.

[0003] Each of these objects carries an induced charge on its surface, and by moving the two objects relative to one another while maintaining this induced charge, the charge is transported and electricity can be generated.

[0004] In order to increase the power output in the above-mentioned power generation method, it is effective to increase the surface area of ​​the power generation surface where charge transport occurs, and thus the power generation body is nano-structured.

[0005] Patent Document 1 describes a frictional electric nanogenerator that generates electricity by utilizing the kinetic energy of liquids such as waves, and discloses that by covering the two electrodes with an insulator, the electrodes do not come into contact with the liquid in the power generation environment, allowing for stable operation for long periods of time. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2016-529868 Summary of the Invention [Problem to be solved by the invention]

[0007] However, if the surface area of ​​the power generation surface is increased by nanostructuring the power generation body, the friction between the power generation surface and the liquid increases, causing the liquid to be retained inside the power generation body and making it difficult to move, and charge transport does not occur, making it difficult to further increase the power generation output by enlarging the power generation surface.

[0008] The present invention has been made in consideration of the problems associated with the conventional technology, and its purpose is to provide a highly efficient power generator that can fully utilize the power generation surface expanded by nanostructuring. [Means for solving the problem]

[0009] As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that the above-mentioned objective could be achieved by using a nanostructured porous elastomer and elastically deforming it to forcibly introduce and remove liquid through the pores of the porous elastomer, thereby completing the present invention.

[0010] That is, the power generating unit of the present invention comprises a porous elastic body having a carbon material at least on the inner surfaces of the pores, a current collecting section connected to the porous elastic body, and a polar liquid. The porous elastic body has a polarized portion at least in a part thereof, and is characterized in that the porous elastic body immersed in the polar liquid is compressed and expanded to generate electricity. Effect of the Invention

[0011] According to the present invention, power is generated by compressing and expanding a porous elastic body immersed in a polar liquid, thereby making it possible to provide a highly efficient power generator that makes full use of the surface area of ​​the power generating surface. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram illustrating the power generation mechanism of the power generating unit of the present invention. [Diagram 2] FIG. 13 is a diagram for explaining a state of power generation measurement under stress application. [Diagram 3] 1 is a graph showing the results of power generation measurement under stress in Example 1. [Figure 4] 4 is a graph showing the relationship between power generation output and stress in Example 1. [Diagram 5] 13 is a graph showing the results of power generation measurement under stress in Example 2. [Figure 6] 11 is a graph showing the relationship between power generation output and stress in Example 2. [Figure 7] 1 is a graph showing the results of power generation measurement under stress in Examples 3 and 4. [Figure 8] 13 is a graph showing the results of power generation measurement under stress in Example 5. [Figure 9] 13 is a graph showing the results of power generation measurement under stress in Example 6. [Figure 10] 13 is a graph showing the results of power generation measurement under stress in Example 7. [Figure 11] 13 is a graph showing the relationship between power generation output and stress in Example 7. [Figure 12] 13 is a graph showing the results of power generation measurement under stress in Example 8. [Figure 13] 1 is a graph showing the results of power generation measurement with stirring stopped and with stress applied in Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The power generating unit of the present invention will now be described in detail. The power generating unit of the present invention comprises a porous elastic body having a carbon material at least on the inner surfaces of the pores, a current collecting section connected to the porous elastic body, and a polar liquid. The porous elastic body has a polarized portion at least in a part thereof, and generates electricity by immersing the porous elastic body in the polar liquid and compressing and expanding it.

[0014] Specifically, by immersing a porous elastic body in a polar liquid, the polar liquid enters the pores of the porous elastic body. Then, triggered by the polarized parts of the porous elastic body, the electric charges of the polar liquid tend to be oriented on the inner surfaces of the pores of the porous elastic body as shown in Figure 1, and the inner surfaces of the pores are polarized so as to cancel out the electric charges of the polar liquid, and the entire porous elastic body becomes charged.

[0015] When the porous elastic body is compressed to push out the polar liquid from within the pores, the charge in the carbon material that was polarized to cancel out the charge of the polar liquid becomes excessive, causing a transfer of charge. Conversely, when the polar liquid enters the pores, the charge in the carbon material becomes insufficient, causing a transfer of charge, and this transfer of charge is then extracted to the outside to generate electricity.

[0016] In this way, the power generating unit of the present invention does not transfer charges by the kinetic energy of the liquid itself, but rather transfers charges by applying external kinetic energy directly to the porous elastic body, compressing and expanding the porous elastic body, thereby increasing or decreasing the amount of polar liquid contained in the porous elastic body.

[0017] Therefore, even if the frictional force between the power generation surface and the polar liquid increases as the power generation surface expands, the liquid is retained in the porous elastomer and the flow of the polar liquid is not impeded, making it possible to generate power with high efficiency.

[0018] The porous elastomer may have a carbon material at least on its inner surface, and may be formed of porous carbon in which the carbon material itself has elasticity, or may have a carbon material on the inner surface of the pores of a porous substrate having elasticity such as rubber.

[0019] The polarized portion is formed of a carbon material and a material having an electronegativity different from that of the carbon material. The polarized portion may include a material having an electronegativity different from that of the carbon material, and the polarized portion may be formed in the carbon material itself, or a porous substrate or a binder in contact with the carbon material may include a material having an electronegativity different from that of the carbon material, and the porous elastic body as a whole may form the polarized portion.

[0020] By providing the polarized portions, the charge of the carbon material is biased, which in turn makes it easier for the charge of the polar liquid in the pores to be oriented, and the porous elastic body becomes more easily charged.

[0021] Examples of binders and porous substrates with different electronegativities that can be used include CMC (carboxymethyl cellulose), polyacrylic acid, cellulose nanofiber, polyvinylidene fluoride, and polytetrafluoroethylene.

[0022] As the carbon material, porous carbon having π electrons can be used, such as activated carbon, carbon black, acetylene black, graphene meso sponge (GMS), carbon meso sponge (CMS), carbon nanotube (CNT), etc.

[0023] Among these, graphene mesosponge (GMS), carbon mesosponge (CMS) and carbon nanotubes (CNT) are preferably used because they themselves have flexibility that allows elastic deformation.

[0024] In other words, porous carbon particles such as carbon black do not themselves elastically deform, so even if the porous substrate elastically deforms when stress is applied, changing the pore volume of the porous substrate, the position of the porous carbon particles only changes, and power generation cannot be achieved by utilizing the micropores that the porous carbon particles themselves possess.

[0025] In contrast, the graphene meso sponge (GMS), carbon meso sponge (CMS) and carbon nanotubes (CNT) described above undergo elastic deformation when stress is applied, changing the volume of their micropores, making it possible to generate electricity using these micropores and improving power output.

[0026] The carbon material preferably has a bulk modulus of 1000 MPa or less. If the bulk modulus exceeds 1000 MPa, the carbon material will be difficult to elastically deform, making it difficult to generate electricity using the micropores in the carbon material.

[0027] Although there is no particular lower limit for the bulk modulus of the carbon material, if the bulk modulus is too small, durability is likely to decrease, so the substantial lower limit is 30 MPa. The bulk modulus of a carbon material can be determined by using a mercury porosimeter to measure the volume change of a sample relative to the pressure applied to mercury during mercury injection.

[0028] In addition, the carbon material preferably contains an n-type or p-type dopant. By including a dopant, the carbon material itself is polarized, and the output of the power generating unit can be improved.

[0029] The n-doped carbon material is rich in electrons, and it is believed that as the cations in the polar liquid decrease with compression, the electrons stored in the carbon material maintain electrical neutrality, and thus the electrons move to an external circuit, generating electricity.

[0030] Examples of n-type dopants include inorganic compounds such as nitrogen (N), silicon dioxide (SiO2), molybdenum disulfide (MoS2), and selenium-substituted molybdenum sulfide (MoSSe).

[0031] Similarly, the p-doped carbon material is electron deficient, and it is believed that electricity is generated by the transfer of electrons from an external circuit to maintain the electrical neutrality of the electron-deficient carbon material as the number of cations in the polar liquid decreases upon compression.

[0032] As the p-type dopant, fullerene (C 60 Examples of the electron-accepting material include electron donor (E), boron (B), and the like.

[0033] The porous elastic body preferably has an average pore size of 1 to 50 nm. By having the average pore size within the above range, it is possible to achieve both an enlarged power generation surface area and a high bulk modulus. Specifically, if the average pore size is too small, the porous elastic body will be less likely to undergo elastic deformation, whereas if the average pore size is too large, the power generation surface area will decrease, tending to reduce the power output.

[0034] The porous elastic body preferably has a porosity of 30 to 90% by volume. By setting the porosity within the above range, it is possible to achieve both improved power generation output and durability. If the porosity is too small, the amount of polar liquid that enters the pores is reduced, so that the amount of change in the polar liquid therein caused by the elastic deformation of the porous elastic body is reduced. If the porosity is too large, the pores are easily crushed, and durability is easily reduced. The porosity of the porous elastic body can be calculated from the total pore volume in an uncompressed state measured by a nitrogen adsorption method and the true density of the carbon.

[0035] The polar liquid may be water, a solution containing a salt, or an ionic liquid (room temperature molten salt). Since ionic liquids generally have high viscosity, it is preferable for them to contain a salt.

[0036] Examples of the salt include inorganic salts such as lithium salts, potassium salts, sodium salts, and magnesium salts, as well as organic salts.

[0037] Solvents for the salts include aqueous and non-aqueous solvents, with water being preferred since it is a good solvent for salts and it is easy to increase the ion concentration in the liquid.

[0038] The current collector may be made of a material that is conductive and does not change due to the polar liquid, such as stainless steel. EXAMPLES

[0039] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0040] [Example 1] Using γ-Al2O3 nanoparticles (SBa-200) with an average particle size of 7 nm as a template, CVD was performed at 900°C using CH4 as the carbon source, and the template was then removed with hydrofluoric acid to obtain carbon meso sponge (CMS). The bulk modulus of this CMS was 83 MPa.

[0041] The CMS was heat-treated at 1800°C to produce graphene meso sponge (GMS), which was then mixed with polytetrafluoroethylene (PTFE) in a ratio of 95:5 to produce a sheet-shaped porous elastomer. The bulk modulus of the GMS was 252 MPa, the average pore size of the porous elastomer was 5.8 nm, and the porosity was 0.85.

[0042] A current collector (SUS) and a cellulose separator were attached to one side of the porous elastic body, and the body was immersed in a 4M NaCl aqueous solution to obtain a power generating unit.

[0043] The power generating unit was placed in a cylinder made of polyether ketone resin, and a pressure of 30 to 300 MPa was applied to the power generating unit using a compression tester. The pressure was then released to compress and expand the porous elastic body, thereby generating electricity.

[0044] For the stress-applied power generation measurement, as shown in Figure 2, a gold-plated stainless steel electrode was used as the working electrode, a counter electrode was used as the counter electrode, and a Ag / AgCl electrode was used as the reference electrode. The electrodes were connected to a potentio-galvanostat, and pressure was repeatedly applied and released every 90 seconds. The plating of the working electrode in the portion that contacts the porous elastic body was removed to expose the SUS material.

[0045] The results of the power generation measurement under stress are shown in FIG. 3, and the relationship between the power generation output and stress is shown in FIG. It can be seen from Fig. 3 that electricity is generated in response to the elastic deformation of the porous elastic body, and from Fig. 4 that the maximum output is achieved at a pressure of about 200 MPa.

[0046] [Example 2] A power generating unit was obtained in the same manner as in Example 1, except that the CMS was not heat-treated. The results of the power generation measurement under stress are shown in FIG. 5, and the relationship between the power generation output and stress is shown in FIG. It can be seen from Fig. 5 that electricity is generated in response to the elastic deformation of the porous elastic body, as in Example 1. It can also be seen from Fig. 6 that the maximum output is achieved at a pressure of about 150 MPa.

[0047] [Example 3] A power generating unit was obtained in the same manner as in Example 1, except that GMS was replaced with activated carbon (YP-50F, manufactured by Kuraray Co., Ltd.).

[0048] [Example 4] A power generating unit was obtained in the same manner as in Example 1, except that GMS was replaced with acetylene black (Denka Black, manufactured by Denka Corporation).

[0049] The results of the power generation measurement under stress in Examples 3 and 4 are shown in FIG. The amount of electricity generated in Example 3 was lower than that in Example 1. This result shows that the shape of the pores, the strength, and the flexibility of the carbon material are involved in the amount of electricity generated. Moreover, the amount of electricity generated in Example 4 was lower than that in Example 3. Since acetylene black has a smaller specific surface area than activated carbon, it is understood that the size of the specific surface area is related to the amount of electricity generated.

[0050] [Example 5] A power generating unit was obtained in the same manner as in Example 1, except that the 4M NaCl aqueous solution was replaced with pure water. The results of the power generation measurement under stress of 50 MPa are shown in FIG.

[0051] From FIG. 8, it can be seen that the change in current value was low in the compression power generation test in pure water, and that sodium ions and chloride ions have an effect on power generation.

[0052] [Example 6] A power generating unit was obtained in the same manner as in Example 1, except that the 4M NaCl aqueous solution was replaced with a 1M Et4NBF4 propylene carbonate solution. The results of the power generation measurements under stresses of 30, 50, and 75 MPa are shown in FIG.

[0053] The change in current value in the nonaqueous electrolyte of Example 6 was approximately one order of magnitude lower than the change in current value in the aqueous electrolyte of Example 1. This is presumably because the organic ion species have a large ionic radius and a small capacitance, resulting in a decrease in output.

[0054] [Example 7] 2.0 g of Al2O3 nanoparticles (Taimei Chemical Industry Co., Ltd.: TM300: average primary particle diameter 7 nm) and 6.7 g of quartz sand (Fujifilm Wako Pure Chemical Industries, Ltd.) as a spacer were mixed (weight ratio 3:10). The quartz sand used was soaked overnight in 0.1 M hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd.), washed with ultrapure water, heated in an air atmosphere in a muffle furnace at 900°C for 1 h, and sieved (180 μm).

[0055] This mixture of TM300 and quartz sand was placed in a quartz reaction tube, and CVD was carried out under the following conditions using CH3CN (Fujifilm Wako Pure Chemical Industries, Ltd.) as the carbon source.

[0056] The temperature was increased to 650° C. at a rate of 10° C. / min while flowing Ar gas at 225 mL / min. Thereafter, the temperature was maintained at 650° C. for 30 min and stabilized. Since CH3CN is a volatile liquid at room temperature and pressure, the flow path was changed so that CH3CN was bubbled with Ar gas, allowing CH3CN to flow through the system and CVD was performed for 1 hour. After that, the sample was stabilized at 600°C for 30 minutes, then heated to 900°C, annealed for 60 minutes, and naturally cooled to room temperature.

[0057] After cooling, the sample was collected, the quartz sand spacers were removed using a sieve, and the sample was suspended in pure water. The suspension was poured into hydrofluoric acid and stirred for 1 hour to dissolve the Al2O3 particles, and then suction filtered while washing with ultrapure water.

[0058] The same operation was repeated with the stirring time changed to 3 hours, and after completely removing the Al2O3 particles, the mixture was suspended in acetone and left overnight. After that, the mixture was suction filtered and the acetone was completely removed using a dryer to obtain nitrogen-doped CMS.

[0059] Except for using this nitrogen-doped n-doped CMS, a power generating unit was obtained in the same manner as in Example 1. The results of the power generation measurement under stress are shown in FIG.

[0060] Example 7 showed a maximum output of 0.19 μW at 250 MPa. This value is approximately twice as high as the maximum output of 0.10 μW in Example 2, and it is understood that adding electrons by doping can generate electricity.

[0061] [Example 8] Fullerene (C 60 2.5 mg of the graphene meso sponge (GMS) was dispersed in 100 ml of toluene, 50 mg of graphene meso sponge (GMS) was added, and the mixture was ultrasonically dispersed for 30 minutes and stirred for 30 minutes. The mixture was then dried by evaporation at 70°C to obtain p-doped GMS with electron-accepting fullerenes supported on its surface.

[0062] Except for using this p-doped GMS doped with fullerene, a power generator was obtained in the same manner as in Example 1. The results of power generation measurement under stress application at 50 MPa are shown in FIG. In Example 8, the current changed in the negative direction and the potential changed in the positive direction during power generation due to compression, showing the opposite behavior to Example 7. The output was 0.021 μW, about twice as high as the value of Example 1 (0.0093 μW).

[0063] [Comparative Example 1] A 0.4 mg CMS sheet was used as the working electrode, a 20 mg YP-50F activated carbon sheet as the counter electrode, and a silver / silver chloride reference electrode as the reference electrode, and a power generation test was performed in a 4M NaCl aqueous solution.

[0064] The NaCl aqueous solution was stirred at 300 rpm and stopped every 60 seconds, and the changes in potential and current were measured without compressing the CMS sheet. Figure 13 shows the changes in potential and current when the CMS sheet was compressed at 30 to 50 MPa.

[0065] As shown in Figure 13, changes in current and potential were observed with stirring, but the amount of change was small, and the maximum generated power was 0.014 μW / cm 2 That was about it. Maximum output when compressed is 0.35μW / cm 2 This demonstrates the superiority of poroelastic materials and power generation through compression and expansion. [Explanation of symbols]

[0066] 1 Poroelastic bodies 11 Pore 2 polar liquid 3 Current collector (SUS) 4 Separator (cellulose) 5 Mesh (Pt) 6 Exposed part (SUS)

Claims

1. a porous elastic body having a carbon material on at least the inner surfaces of the pores; A power generating unit including a current collector connected to the porous elastic body and a polar liquid, The porous elastic body has a polarized portion at least in a part thereof, A power generating unit which generates power by compressing and expanding the porous elastic body immersed in the polar liquid.

2. 2. The power generating unit according to claim 1, wherein the carbon material is at least one selected from the group consisting of graphene meso sponge (GMS), carbon meso sponge (CMS) and carbon nanotube (CNT).

3. 3. The power generating unit according to claim 2, wherein the bulk modulus of the carbon material is 30 to 1000 MPa.

4. 4. The power generating unit according to claim 2, wherein the carbon material contains an n-type or p-type dopant.

5. 5. The power generating unit according to claim 1, wherein the porous elastic body has an average pore size of 1 to 50 nm.

6. 6. The power generating unit according to claim 1, wherein the porosity of the porous elastic body is 30 to 90 volume %.

7. 7. The power generating unit according to claim 1, wherein the polar liquid contains a salt.

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