Electric conductor and design method thereof

Abstract

To provide a new electric conductor and a design method thereof that allow easy adjustment of electrical conduction properties.SOLUTION: The electric conductor includes a first material with electron conductivity or hole conductivity and a second material with ion conductivity, and has a composite conductive path formed through the entanglement of the first material and the second material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrical conductor and a method for designing the same. [Background technology]

[0002] Composite materials are known as composite materials made by combining multiple different materials. Conventional composite materials include those that mix conductive or insulating fillers into insulators to control physical properties such as thermal conductivity and thermal expansion, and those that improve conductivity by adding another conductive material to a conductive material.

[0003] Some composite materials are known to have both electronic and ionic conductivity as their conductive mechanisms. For example, Non-Patent Document 1 describes a technique for limiting ionic conductivity without affecting electronic conductivity by doping thallium bromide with hypervalent ions (Se, Pb). Non-Patent Document 2 describes the addition of ethylene glycol to PEDOT / PSS to improve hole conductivity due to the π-conjugated bonds of PEDOT and limit ionic conductivity due to hydration of PEDOT / PSS. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Cedric R. Leao et al., “Simultaneous Control of Ionic and Electronic Conductivity in Materials: Thallium Bromide Case Study”,2012 [Non-patent document 2] Jonathan Rivnay et al., “Structural control of mixed ionic and electronic transport in conducting polymers”,2016 Summary of the Invention [Problem to be solved by the invention]

[0005] Both of the materials described in Non-Patent Documents 1 and 2 above are materials that have two conductive mechanisms, namely, electronic conductivity and ionic conductivity. However, in order to adjust the conductivity, it is necessary to add a different material to the original material, which makes the adjustment difficult.

[0006] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to provide a novel electrical conductor whose electrical conduction characteristics can be easily adjusted, and a design method thereof. [Means for solving the problem]

[0007] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they discovered that by mixing a first material having electron conductivity or hole conductivity with a second material having ion conductivity to form a conductive path based on percolation theory (i.e., a conductive path formed by the first material and the second material becoming entangled with each other), it is possible to obtain an electrical conductor whose electrical conductivity characteristics can be easily adjusted by changing the mixing ratio of the first material and the second material, and whose conductivity mechanism as well as the conductivity can be easily adjusted, thereby resulting in the present invention.

[0008] That is, the electrical conductor of the present invention is characterized by comprising a first material having electron conductivity or hole conductivity and a second material having ion conductivity, and having a composite conductive path formed by the entanglement of the first material and the second material. By simply changing the mixing ratio of the first and second materials, the electrical conductivity of such an electrical conductor can be easily adjusted without adding any other materials. For example, increasing the mass fraction of the first material can make carrier conduction the dominant mechanism of conduction, while increasing the mass fraction of the second material can make ionic conduction the dominant mechanism of conduction. Furthermore, changing the mixing ratio can easily change the electrical conductivity.

[0009] A specific embodiment of the electrical conductor further includes a first conductive path formed only from the first material, and a second conductive path formed only from the second material.

[0010] Specific embodiments of the electrical conductor include those in which the first material and the second material are both atomic layer materials. Specifically, the first material is one or more selected from maxine, graphene, molybdenum disulfide, and tungsten (IV) selenide, and the second material is one or more selected from bentonite, montmorillonite, and layered double hydroxides. Also, the first material and the second material are both scale-like and randomly stacked. When the first and second materials have these properties, they can be easily mixed to form a composite conductive path based on percolation theory.

[0011] Specific examples of the electrical conductor include one in which carrier conduction is dominant in the composite conductive path when the ratio of the mass of the first material to the total mass of the first material and the second material is equal to or greater than a predetermined value, and one in which ionic conduction is dominant in the composite conductive path when the ratio of the mass of the first material to the total mass of the first material and the second material is less than the predetermined value.

[0012] In addition, a specific embodiment of the electrical conductor is one in which the composite conductive path is formed based on percolation theory.

[0013] Furthermore, the method for designing an electrical conductor of the present invention is characterized in that a first material having electron conductivity or hole conductivity and a second material having ion conductivity are mixed at different mass ratios, and the first material and the second material are intertwined to form a composite conductive path, thereby designing electrical conductors with different electrical conductivity properties. Such a method for designing an electrical conductor can achieve the same effects as the electrical conductor of the present invention described above. [Effects of the Invention]

[0014] According to the present invention configured as described above, it is possible to provide a novel electrical conductor whose electrical conduction characteristics can be easily adjusted, and a method for designing the same. [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B are diagrams illustrating the configuration of an electrical conductor according to one embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the electrical conduction characteristics of an electrical conductor (a mixture of bentonite and Maxine) according to one embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing the electrical conduction characteristics of an electrical conductor (a mixture of graphene and maxine) according to one embodiment of the present invention. [Figure 4] 3A to 3C are diagrams illustrating an example of the principle of multi-sensing using an electrical conductor according to the embodiment. [Figure 5] 3A to 3C are diagrams illustrating an example of the principle of multi-sensing using an electrical conductor according to the embodiment. [Figure 6] FIG. 4 is a diagram showing electrochemical properties of the electrical conductor according to the embodiment. [Figure 7] 4A and 4B are diagrams showing control of light absorption rate by an electrical conductor according to the embodiment; [Figure 8] FIG. 4 is a diagram showing modulation of IV characteristics due to temperature change of an electrical conductor according to the embodiment. [Figure 9] FIG. 4 is a diagram showing the IV characteristic modulation due to humidity change of the electrical conductor according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, the configuration, manufacturing method, and use example of an electrical conductor according to one embodiment of the present invention will be described with reference to the drawings.

[0017] (1) Structure of electrical conductors The electrical conductor of this embodiment is used, for example, in a battery electrode, and includes a first material having electrical conductivity or hole conductivity and a second material having ion conductivity. The electrical conductor may have any shape, such as a thin film or a plate.

[0018] Both the first material and the second material are atomic layer materials (also referred to as two-dimensional materials). Specifically, the first material is, for example, one or more selected from MXene, graphene, molybdenum disulfide, and tungsten(IV) selenide, and the second material is, for example, one or more selected from bentonite, montmorillonite, and layered double hydroxides. The first material and the second material may each be composed of a single atomic layer material, or at least one or both of the first material and the second material may be composed of multiple atomic layer materials. For example, the first material may include MXene and graphene, and the second material may include bentonite. Note that the first material and the second material are not limited to the examples given above and may be any atomic layer material. Furthermore, the combination of the first material and the second material is not limited to the examples given above and may be any combination.

[0019] Both the first material and the second material are scaly. The first material having electrical conductivity or hole conductivity has, for example, an average flake thickness of 1 nm or more and 10 nm or less, and an average particle size of, for example, 1 nm or more and 50 nm or less. The second material having ion conductivity has, for example, an average flake thickness of 1 nm or more and 10 nm or less, and an average particle size of, for example, 1 nm or more and 50 nm or less.

[0020] The electrical conductor of this embodiment is formed by randomly stacking a first material and a second material, as shown in Fig. 1. That is, in this electrical conductor, the first material and the second material are randomly arranged in the stacking direction and in a planar direction perpendicular to the stacking direction. The first material and the second material are bonded to each other by intermolecular forces.

[0021] This electrical conductor has a composite conductive path formed by the entanglement of the first material and the second material, a first conductive path formed only of the first material, and a second conductive path formed only of the second material. This composite conductive path is formed according to percolation theory.

[0022] The electrical conduction characteristics of this electrical conductor change depending on the mixing ratio (mass ratio) of the contained first material and second material. Specifically, the conductive mechanism of this electrical conductor changes depending on the mixing ratio of the first material and the second material. As shown in Figures 2 and 3, when the ratio of the mass of the first material to the total mass of the first material and the second material is equal to or greater than a predetermined value, carrier conduction becomes dominant in the composite conductive path. On the other hand, when the ratio of the mass of the first material to the total mass of the first material and the second material is less than the predetermined value, ionic conduction becomes dominant in the composite conductive path.

[0023] Furthermore, the conductivity (electrical conductivity) of this electrical conductor changes depending on the mixing ratio of the first material and the second material. Specifically, as shown in Figures 2 and 3, when the ratio of the mass of the first material to the total mass of the first and second materials is equal to or greater than a predetermined value, the electrical conductivity improves as the ratio of the mass of the first material increases, whereas when the ratio of the mass of the first material to the total mass of the first and second materials is less than the predetermined value, the electrical conductivity improves as the ratio of the mass of the first material decreases.

[0024] (2) Manufacturing method Next, an example of a method for manufacturing such an electrical conductor according to this embodiment will be described. Here, an example of a method for manufacturing a thin-film electrical conductor will be described. The method for manufacturing the electrical conductor according to this embodiment includes (i) a vacuum filtration (suction filtration) step and (ii) a transfer step.

[0025] (i) Vacuum filtration step In this process, a filter holder is first placed on top of a suction filter bottle. Then, a dispersion of the first material (maxine or graphene) and the second material (bentonite) in a dispersion medium is poured into the filter holder, and the pressure inside the suction filter bottle is reduced. This deposits a thin film of electrical conductor on the filter.

[0026] (ii) Transfer process Next, the thin film of electrical conductor is transferred onto a substrate. Specifically, the filter obtained in the vacuum filtration process is first immersed in water, and this fully wetted filter is placed on a glass substrate with the thin film facing downwards. Next, the glass substrate with the filter attached is placed in a vacuum chamber or the like and a vacuum is drawn. As the water that has soaked into the filter dries, the filter naturally peels off, leaving the thin film attached to the substrate, and a substrate with a thin film formed on it is obtained.

[0027] (3) Usage example Next, an example of use of the electrical conductor of this embodiment will be described.

[0028] (i) Negative electrode of secondary battery The electrical conductor of this embodiment can be used as a negative electrode of a secondary battery. When a thin film of a nanomaterial alone that exhibits electronic conductivity is used as the negative electrode of a secondary battery as in the past, large ions (e.g., Na + There is a problem that ions are difficult to adsorb, resulting in a decrease in battery capacity. In addition, when a thin film of a single nanomaterial is used, there is also a problem that processing such as introducing defects is required to control the conductivity. In contrast, by using the electrical conductor of this embodiment as a negative electrode, it becomes possible to promote ion adsorption through ionic conduction, thereby improving battery capacity. In addition, Li + Na, which is larger in size than + This makes it possible to adsorb ions such as lithium ion and sodium ion, making it applicable to not only lithium ion batteries but also sodium ion batteries. Furthermore, by simply changing the mixing ratio of the first and second materials in the electrical conductor, the conductivity of the electrode and the governing conductive mechanism can be adjusted, thereby enabling the electrode performance to be tuned.

[0029] (ii) Multi-sensing device The electrical conductor of this embodiment can also be applied to a multi-sensing device. For example, in various fields such as medicine, the chemical industry, and agriculture, multi-sensing is being carried out, in which multiple sensors are used to acquire multiple environmental data (such as temperature and humidity).However, this multi-sensing has the problem of requiring larger devices and higher costs due to the use of multiple sensors.

[0030] In contrast, the electrical conductor of this embodiment has both carrier conductivity and ion conductivity as its conduction mechanism, and these carrier conductivity and ion conductivity have the property of changing in response to environmental changes such as temperature and humidity, and external stimuli such as tension and compression. Therefore, by using the electrical conductor of this embodiment as a sensor, it is possible to simultaneously sense multiple environmental changes (e.g., temperature and humidity) and multiple changes in external stimuli (e.g., tension and compression) with a single sensor by measuring changes in both carrier conductivity and ion conductivity. Furthermore, by changing the mixing ratio of the first material and the second material in the electrical conductor, it is possible to adjust the conduction mechanism, improve sensing function, and adjust sensing sensitivity.

[0031] - For measuring temperature, humidity, etc. For example, as shown in Figure 4, by utilizing the fact that the change in electrical resistance differs depending on temperature and humidity, it is possible to simultaneously sense both humidity and temperature from the actually observed IV curve. Also, by utilizing the fact that the carrier mobility differs greatly between ionic conduction and carrier conduction, it is thought that it may be possible to evaluate temperature and humidity by evaluating the mobility in a thin film (electrical conductor).

[0032] Equivalent circuit analysis method Furthermore, by utilizing the difference in conduction speed between carrier conduction in atomic layer materials and ionic conduction between layers, it is possible to investigate changes in conductivity due to the adsorption of atoms or ions at the interface, as well as carrier changes due to light irradiation, using equivalent circuit analysis with a sweep of frequency, as shown in Figure 5. This allows the conduction component related to ionic conduction to be detected primarily at low frequencies, while the carrier conduction component is detected at high frequencies. This makes it possible to separate the ionic conduction and carrier conduction components, and to realize multi-sensing based on changes in each external factor.

[0033] (iii) Other sensors Furthermore, when the electrical conductor of this embodiment is irradiated with light, carriers are generated in the carrier-conducting material (first material) such as maxine or graphene. Therefore, by connecting an ammeter to the electrical conductor of this embodiment and detecting the photocurrent, it can also be used as an optical sensor. In addition, changes in pH and gas concentration can cause the H + Amount or OH - The amount of ionic conduction in the electrical conductor changes, as does the gas concentration in the solution. This changes the amount of ionic conduction in the electrical conductor, which in turn changes the electrical resistivity. By detecting this, the material can be used as a pH sensor or gas sensor.

[0034] (iv) Reservoir element The rapid increase in IoT devices is driving demand for edge computing (a method of processing information on the sensor side) that reduces communication load. The fusion of edge computing and reservoir computing makes it possible to achieve ultra-low power consumption. Using physical phenomena in the reservoir makes it possible to implement an ultra-low power machine learning computer in hardware, and nonlinear response to input is crucial to realizing an "ultra-low power computer." The electrical conductor of this embodiment is expected to exhibit highly nonlinear response due to the complex coupling of carrier conduction and ion conduction, and can be used as a reservoir element for reservoir computing, making it possible to realize ultra-low-power computers.

[0035] Furthermore, experiments were carried out to confirm (a) electrochemical properties, (b) light absorption control, (c) IV characteristic modulation due to temperature changes, and (d) IV characteristic modulation due to humidity changes of the electrical conductor of this embodiment.

[0036] As shown in Figure 6, it was confirmed that adding graphene to bentonite can promote the redox reaction while maintaining ionic conductivity (the redox current value was increased by approximately 10 times). This confirmed that the electrical conductor of this embodiment has potential for application as a secondary battery with adjustable electronic and ionic conductivity.

[0037] As shown in Figure 7, it was confirmed that mixing Maxin and bentonite provides the light absorption properties specific to Maxin, and that the light absorption rate can be adjusted by adjusting the ratio of Maxin to bentonite. This confirmed that the electrical conductor of this embodiment can be applied to functional thin films and optical sensors that have the characteristics of Maxin thin films (such as electromagnetic wave shielding performance).

[0038] As shown in Figure 8, it was confirmed that the IV characteristics change with temperature, and that the current value decreases when there is a large amount of bentonite, which exhibits ionic conductivity, and increases when there is a large amount of maxine, which exhibits electronic conductivity. This confirms that the electrical conductor of this embodiment can be applied to temperature sensors with different performance depending on the thin film composition.

[0039] As shown in Figure 9, it was confirmed that the nonlinearity of the IV characteristics improved as the amount of bentonite increased. This confirmed that the electrical conductor of this embodiment can be applied to a reservoir element with adjustable nonlinearity. It was also confirmed that the IV characteristics changed with changes in humidity. This confirmed that the electrical conductor of this embodiment can be applied to a temperature sensor.

Claims

1. An electrical conductor comprising a first material having electron conductivity or hole conductivity and a second material having ion conductivity, the first material and the second material being entangled to form a composite conductive path.

2. a first conductive path formed only of the first material; The electrical conductor of claim 1 further comprising a second conductive path formed solely of the second material.

3. The electrical conductor of claim 1 , wherein the first material and the second material are both atomic layer materials.

4. 4. The electrical conductor of claim 3, wherein the first material is one or more selected from maxine, graphene, molybdenum disulfide, and tungsten (IV) selenide, and the second material is one or more selected from bentonite, montmorillonite, and layered double hydroxides.

5. 2. The electrical conductor according to claim 1, wherein the first material and the second material are both scale-like and randomly laminated.

6. 2. The electrical conductor of claim 1, wherein carrier conduction is dominant in the composite conductive path when the ratio of the mass of the first material to the total mass of the first material and the second material is equal to or greater than a predetermined value, and ionic conduction is dominant in the composite conductive path when the ratio of the mass of the first material to the total mass of the first material and the second material is less than the predetermined value.

7. 2. The electrical conductor according to claim 1, wherein the composite conductive paths are formed based on percolation theory.

8. A method for designing electrical conductors with different electrical conductivity properties by mixing a first material having electron conductivity or hole conductivity with a second material having ion conductivity at different mass ratios, and intertwining the first material with the second material to form a composite conductive path.

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