Power generation element

Abstract

To provide a power generation element capable of easily performing power generation utilizing a temperature change, and provide a power generation element capable of easily performing not only power generation but also lighting control utilizing a temperature change.SOLUTION: A power generation element comprises a pair of conductive substrates, and a mixed layer of an ion liquid and water provided between the pair of conductive substrates. A perfluoropolymer layer is formed at the side of the mixed layer of the ion liquid and water in one conductive substrate of the pair of conductive substrates. A polymer layer other than a perfluoropolymer is formed at the side of the mixed layer of the ion liquid and water in the other conductive substrate of the pair of conductive substrates. The mixed layer of the ion liquid and water contains the ion liquid and water, and is a layer indicating a lower limit critical solution temperature type phase separation behavior.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power generating element and a power generating element having a light control function. [Background technology]

[0002] In recent years, the development of power generation methods suitable for various applications has progressed, and the required characteristics are also various depending on the application. For example, Patent Document 1 proposes a method of generating power by changing temperature, and proposes a mixed entropy battery in which a metal salt such as a lithium salt is added to a medium exhibiting a phase separation behavior of a lower critical solution temperature (LCST) type or an upper critical solution temperature (UCST) type. Patent Document 1 lists a medium containing an ionic liquid and water as the medium, but the mixed entropy battery of Patent Document 1 generates power by utilizing the change in salt concentration around the positive and negative electrodes as the state of the medium changes between a mixed state and a phase separation state around the critical temperature, since the solubility of the metal salt is different for two types of components in the medium. As an ionic liquid, for example, a combination of a cation and an anion described in Non-Patent Documents 1 and 2 is known, and Non-Patent Document 3 proposes a light control element in which a mixed liquid exhibiting a LCST-type phase separation behavior containing an ionic liquid and water is enclosed between a pair of light-transmitting substrates. However, although the light control element of Non-Patent Document 3 can change the light transmittance by changing the temperature, it does not have a power generation function. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-79814 A [Non-patent literature]

[0004] [Non-Patent Document 1] "Ionic Liquid Research Society Circular No. 1" (Ionic Liquid Research Society, published on September 6, 2013) [Non-Patent Document 2] Yuki, et al., “Thermoresponsive polyelectrolytes derived from ionic liquids”, Polymer Chemistry, 2015, 6, 2163-2178 [Non-Patent Document 3] Goda,et al., “Thermoresponsive Light Scattering Device Using Ionic Liquid-Water Mixture Exhibiting LCST-Type Phase Behavior”,Proc. IDW'17,LCTp2-7L,257(2017)(Proceedings of the International Display Workshops 2017) Summary of the Invention [Problem to be solved by the invention]

[0005] The first object of the present invention is to provide a power generating element that can easily generate power by utilizing temperature changes. The second object of the present invention is to provide a power generating element that can easily generate power and adjust light by utilizing temperature changes. [Means for solving the problem]

[0006] The present inventors have been developing a light control element that utilizes the LCST-type phase separation behavior of a mixture of an ionic liquid and water (see Non-Patent Document 3). The present inventors wondered whether the LCST-type phase separation behavior of a mixture of an ionic liquid and water could be used for other purposes, and after further investigation, they unexpectedly found that an electromotive force was generated by applying a perfluoropolymer to the surface of one of the substrates of the light control element that the present inventors had been developing, which contacts the mixture, and that the element could be used as a power generation element. Unlike the mixed entropy battery of Patent Document 1, this power generation element can generate electricity by a simple means of forming a perfluoropolymer layer on the substrate that serves as an electrode, and furthermore, by simply using a light-transmitting substrate as the substrate that serves as the electrode, the element can be used as a power generation element having a light control function, that is, a power generation and light control element. The present invention was thus completed.

[0007] That is, the present invention is specified by the following items. (1) A power generating element comprising a pair of conductive substrates and a mixed layer of ionic liquid and water provided between the pair of conductive substrates, wherein a perfluoropolymer layer is formed on the ionic liquid and water mixed layer side of one of the pair of conductive substrates, and a polymer layer other than perfluoropolymer is formed on the ionic liquid and water mixed layer side of the other of the pair of conductive substrates, and the ionic liquid and water mixed layer contains ionic liquid and water and is a layer that exhibits lower critical solution temperature type phase separation behavior. (2) The power generating element according to (1) above, wherein the polymer layer other than the perfluoropolymer is a polyimide layer. (3) A power generating element according to (1) or (2) above, characterized in that the pair of conductive substrates are light-transmitting conductive substrates, and the perfluoropolymer layer and the polymer layer other than perfluoropolymer are light-transmitting layers, and the power generating element has a light-adjusting function. Effect of the Invention

[0008] The power generating element of the present invention can easily generate power by utilizing temperature changes. By using a light-transmitting conductive substrate, the power generating element of the present invention can easily generate power and adjust light by utilizing temperature changes. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of elements in the examples and comparative examples. [Diagram 2] FIG. 2 is a diagram showing the state of the element in Example 1, where (a) shows the state at 27° C. and (b) shows the state at 40° C. [Diagram 3] FIG. 3 shows the state of the element in Example 2, where (a) shows the state at 27° C. and (b) shows the state at 40° C. [Figure 4] FIG. 4 shows the state of the element in Example 3, where (a) shows the state at 27° C. and (b) shows the state at 40° C. [Diagram 5] FIG. 5 shows the state of the element in Example 4, where (a) shows the state at 27° C. and (b) shows the state at 40° C. [Figure 6] FIG. 6 shows the state of the element in Comparative Example 1, where (a) shows the state at 27° C. and (b) shows the state at 40° C. [Figure 7] FIG. 7 shows the state of the element in Comparative Example 2, where (a) shows the state at 27° C. and (b) shows the state at 40° C. [Figure 8] FIG. 8 shows the state of the element in Comparative Example 3, where (a) shows the state at 27° C. and (b) shows the state at 40° C. [Figure 9] FIG. 9 shows the state of the element in Comparative Example 4, where (a) shows the state at 27° C. and (b) shows the state at 40° C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The power generating element of the present invention is a power generating element comprising a pair of conductive substrates and a mixed layer of ionic liquid and water provided between the pair of conductive substrates, a perfluoropolymer layer is formed on the mixed layer side of the ionic liquid and water of one of the pair of conductive substrates, a polymer layer other than perfluoropolymer is formed on the mixed layer side of the ionic liquid and water of the other of the pair of conductive substrates, and the mixed layer of the ionic liquid and water is a layer that contains ionic liquid and water and exhibits a phase separation behavior of a lower critical solution temperature type. The conductive substrate in the power generating element of the present invention is not particularly limited in material, shape, etc., as long as it is a substrate that has conductivity and acts as an electrode, and examples thereof include conductive substrates used in various batteries, displays, etc. The pair of conductive substrates may both be the same type of substrate, or may be different types of substrates. When the power generating element of the present invention is used as a power generating light control element having a light control function, a light-transmitting conductive substrate is used as the conductive substrate. The light-transmitting conductive substrate is not particularly limited as long as it is a substrate that has light transparency and conductivity, and examples thereof include light-transmitting conductive substrates used in various displays, light control glass, light control elements, etc. Specifically, for example, a glass substrate, a plastic substrate, a plastic film, etc., on whose surface a conductive film such as an ITO film is formed can be mentioned. The light-transmitting conductive substrate in the present invention is preferably one having a visible light transmittance of 80% or more.

[0011] The mixed layer of ionic liquid and water in the present invention is provided between the pair of conductive substrates. The mixed layer of ionic liquid and water in the present invention exhibits lower critical solution temperature (LCST) type phase separation behavior. The mixed layer of ionic liquid and water in the present invention exhibits LCST type phase separation behavior, and therefore exhibits a one-phase state at temperatures below the LCST, and exhibits a phase-separated state into two phases at temperatures above the LCST. This is believed to be because hydrogen bonds are formed between the ionic liquid and water at temperatures below the LCST, and the hydrogen bonds are broken at temperatures above the LCST. The ionic liquid in the present invention is not particularly limited as long as it exhibits LCST type phase separation behavior when mixed with water, and examples of cations of the ionic liquid in the present invention include tetraalkylphosphonium ([Pn,m,l,k ] + : n, m and l are 4 or 6, k is 4, 6, 8 or 14), tetraalkylammonium ([N n,m,l,k ] + : n, m and l are 4, k is 3, 4, 12, 14 or 16), 1,2,3-trialkylimidazolium ([C n C m C l im] + : m is 1, l is 0 or 1, n is 1, 4, 5, 8 or 10), and the anion is CF3COO - , SCN - , Br - , I - , PF6 - , HOOC-CH=CH-COO - ([Mal] - ), HO-C6H4-COO - ([Sal] - ), styrene sulfonate ([SS] - ), 3-sulfopropyl methacrylate ([MC3S] - ), 2,4,6-trimethylbenzenesulfonate ([TMBS] - As the ionic liquid in the present invention, a combination of these cations and anions can be used. As the ionic liquid in the present invention, for example, [P 4,4,4,4 ]CF3COO,[N 4,4,4,3 ]I, [C4C1im]PF6, [P 4,4,4,4 ][Mal], [N 4,4,4,4 [TMBS], [P 4,4,4,8 ]Br,[P 4,4,4,4 ][Sal], [P 4,4,4,6[MC3S], phosphonium phosphate type zwitterions, etc. can be mentioned. The notation [ ] in the above is an abbreviation generally used in technical fields related to ionic liquids, and conforms to the description in Non-Patent Documents 1 and 2. The mixing ratio of the ionic liquid and water in the present invention is not particularly limited as long as it is a ratio that shows LCST-type phase separation behavior, and for example, the volume ratio of ionic liquid:water can be 1:12.5 to 1:65, and preferably 1:25 to 1:50. The mixed layer of ionic liquid and water in the present invention may be composed only of ionic liquid and water, or may contain other components within a range that does not inhibit the LCST-type phase separation behavior. In addition, the ionic liquid in the mixed layer of ionic liquid and water may be one type, or two or more types. The LCST is not particularly limited and may be selected according to the environment in which it is used, but for example, 20 to 40°C can be mentioned, and 25 to 35°C is preferable when used for daily light control. The ionic liquid in the present invention is preferably one that has an LCST of 20 to 40°C when mixed with water, and more preferably one that has an LCST of 25 to 35°C.

[0012] In the power generating element of the present invention, a perfluoropolymer layer is formed on the mixed layer side of the ionic liquid and water of one of the pair of conductive substrates. The perfluoropolymer layer is preferably in contact with the mixed layer of the ionic liquid and water. The perfluoropolymer in the present invention is not particularly limited, and may be a crystalline perfluoropolymer or an amorphous perfluoropolymer. As the perfluoropolymer in the present invention, from the viewpoint of facilitating the formation of a perfluoropolymer layer on the surface of the conductive substrate, a liquid or soluble in a solvent such as a fluorine solvent is preferable, and when light transmittance is required, an amorphous perfluoropolymer is preferable from the viewpoint of increasing light transmittance. As the crystalline perfluoropolymer, there is no particular limit, but examples thereof include polytetrafluoroethylene and polyvinylidene fluoride. As the amorphous perfluoropolymer, there is no particular limit, but examples thereof include amorphous perfluoropolymer having an aliphatic ring in the main chain. The aliphatic ring may contain an oxygen atom. Examples of the amorphous perfluoropolymer in the present invention include amorphous perfluoropolymers having a repeating unit of the following chemical formula (1) in the main chain, and amorphous perfluoropolymers having a repeating unit of the following chemical formula (2) in the main chain.

[0013] [ka]

[0014] In chemical formula (1), R1, R2, R3 and R4 each independently represent F or a C1-C6 fluoroalkyl group which may contain one or more oxygen atoms, where C1-C6 means that the number of carbon atoms is 1 to 6.

[0015] [ka]

[0016] In chemical formula (2), R1, R2, R3, R4, R5 and R6 each independently represent F or a C1-C6 fluoroalkyl group which may contain one or more oxygen atoms, where C1-C6 represents the number of carbon atoms being 1 to 6. Q and R represent O or CF2.

[0017] Specific examples of the amorphous perfluoropolymer in the present invention include Hyflon (registered trademark) AD40HS (SOLVAY), Cytop (registered trademark) CTL-809M (AGC Corporation), etc. Hyflon (registered trademark) AD40HS (SOLVAY) contains a repeating unit in which R1 is -O-CF3 and R2 to R3 are F in the chemical formula (1), and Cytop (registered trademark) CTL-809M (AGC Corporation) contains a repeating unit in which R1 to R6 are F, Q is O, and R is CF2 in the chemical formula (2). In addition, Cytop (registered trademark) CTL-809M (AGC Corporation) has terminal functional groups of -CONH to Si(OR)n.

[0018] In the power generating element of the present invention, a polymer layer other than perfluoropolymer (hereinafter also referred to as "other polymer layer") is formed on the mixed layer side of the ionic liquid and water of the other conductive substrate of the pair of conductive substrates, i.e., the conductive substrate on which the perfluoropolymer layer is not formed. Here, the perfluoropolymer in the above "other than perfluoropolymer" refers to the whole perfluoropolymer, and does not mean anything other than the perfluoropolymer formed on one of the conductive substrates. The other polymer layer is preferably in contact with the mixed layer of the ionic liquid and water. The polymer forming the other polymer layer is not particularly limited, and examples thereof include polyimide, polyvinyl alcohol, polycarbonate, polymethyl methacrylate, liquid crystal polymer, polystyrene, and copolymers of these polymers. The other polymer layer in the present invention is preferably formed of polyimide, and more preferably formed of polyimide having an alkyl side chain. When the power generating element of the present invention is used as a power generating light control element having a light control function, it is preferable that the other polymer layer is a perfluoropolymer layer and another polymer layer having light transparency, and these layers are preferably formed of amorphous perfluoropolymer and another polymer (polymer) having light transparency. In addition, when the device is used as a power-generating light control element, the other polymer layer is preferably formed of polyimide, and more preferably formed of polyimide having an alkyl side chain.

[0019] In the present invention, it is considered that at a temperature above the LCST, the anions of the ionic liquid are adsorbed to the perfluoropolymer layer by intermolecular interactions, so that the perfluoropolymer layer side becomes negatively charged, generating a potential difference and acting as a power generating element. When a polyimide having an alkyl side chain is used for the other polymer layer, the force of the alkyl group in the cation of the ionic liquid to adsorb to the polyimide becomes stronger, so that the potential difference becomes large and the phase separation state can be maintained. Specific examples of polymers forming the other polymer layer include RN-1199A (Nissan Chemical Industries, Ltd.) as a polyimide, SunEver (registered trademark) SE-4811 (Nissan Chemical Industries, Ltd.) as a polyimide having an alkyl side chain, and Denka Poval (registered trademark) K-24E (Denka Co., Ltd.) as a polyvinyl alcohol. The thickness of the perfluoropolymer layer and the other polymer layer is not particularly limited as long as it is within a range that does not inhibit the function of the conductive substrate as an electrode or does not inhibit light transmittance, and examples thereof include 1 μm or less, 0.1 to 0.7 μm, etc. The distance between the pair of conductive substrates in the power generating element of the present invention (the distance from the outer surface of the perfluoropolymer layer to the outer surface of the other polymer layer) is not particularly limited, and examples thereof include 5 to 100 μm, 5 to 70 μm, etc., and when used as a power generating light control element, examples thereof include 5 to 50 μm, 10 to 40 μm, etc. When used as a power generating light control element, the distance between the pair of conductive substrates is preferably 10 to 40 μm from the viewpoint of increasing the opacity at temperatures above the LCST and the transparency (transmittance) at temperatures below the LCST.

[0020] The method for producing the power generation element of the present invention is not particularly limited, but for example, the power generation element can be produced by preparing a pair of conductive substrates, applying a perfluoropolymer to one surface of one of the conductive substrates to form a perfluoropolymer layer, applying a polymer other than perfluoropolymer to one surface of the other conductive substrate to form another polymer layer, arranging the surface with the perfluoropolymer layer and the surface with the other polymer layer opposite each other, and sealing a mixed liquid of an ionic liquid and water between them. EXAMPLES

[0021] The present invention will be described in detail below with reference to examples of the present invention. The present invention is not limited to these examples.

[0022] [Example 1] (Fabrication of element) Two light-transmitting conductive substrates were prepared, each having an ITO film (100Ω / □) formed as a light-transmitting conductive film on soda glass (20 mm long x 20 mm wide, 1.1 mm thick). Light-transmitting polymer 1 described in Table 1 was applied to one side of one of the light-transmitting conductive substrates, and light-transmitting polymer 2 described in Table 1 was applied to one side of the other light-transmitting conductive substrate to form a light-transmitting polymer layer. The device shown in FIG. 1 was fabricated using two light-transmitting conductive substrates on which light-transmitting polymer layers were formed (hereinafter referred to as light-transmitting conductive substrates with polymer layers). The distance between the two light-transmitting conductive substrates with polymer layers was 20 μm, and an ionic liquid aqueous solution was sealed between the substrates as a mixed layer of ionic liquid and water. The ionic liquid aqueous solution was prepared by mixing tetrabutylphosphonium hydroxide ([P 4,4,4,4 The LCST of the ionic liquid solution was 30°C.

[0023] (Element evaluation) The fabricated element was placed on an ITO heater (KM-1, KITAZATO), and the voltage was measured using a digital multimeter (34461A, KYESIGHT). A load resistance of 10 kΩ was used. The measurement was evaluated as the potential difference between the voltage at 27°C, a temperature below the LCST, and the voltage at 40°C, a temperature above the LCST. The results are shown in Table 1.

[0024] [Examples 2 to 4] Elements of Examples 2 to 4 were prepared and evaluated in the same manner as in Example 1, except that the light-transmitting polymers 1 and 2 were replaced with the combinations shown in Table 1. The results are shown in Table 1.

[0025] [Comparative Examples 1 to 4] Elements of Comparative Examples 1 to 4 were prepared and evaluated in the same manner as in Example 1, except that the light-transmitting polymers 1 and 2 were replaced with the combinations shown in Table 2. The results are shown in Table 2.

[0026] In Tables 1 and 2, Hyflon (registered trademark) refers to Hyflon AD40HS (SOLVAY), Cytop (registered trademark) refers to Cytop CTL-809M (AGC Corporation), SE-4811 refers to Sunever (registered trademark) SE-4811 (Nissan Chemical Industries, Ltd.), RN-1199A refers to RN-1199A (Nissan Chemical Industries, Ltd.), and K-24E refers to Denka Poval (registered trademark) K-24E (Denka Company, Ltd.).

[0027] [Table 1]

[0028] [Table 2]

[0029] (Microscopic Observation) The elements of Examples 1 to 4 and Comparative Examples 1 to 4 were observed with an optical microscope (BX-60, OLYMPUS) using a 5x objective lens at a temperature of 27°C, which is below the LCST, and at a temperature of 40°C, which is above the LCST. Observation was performed from the outside of the light-transmitting conductive substrate with two polymer layers, with the element placed on the microscope stage with the light-transmitting conductive substrate with two polymer layers facing up. The results are shown in Figures 2 to 9. (Naked eye observation) All of Examples 1 to 4 and Comparative Examples 1 to 4 were transparent when observed at 27°C, but when observed at 40°C, Examples 1 and 4 and Comparative Examples 1 and 2 appeared completely cloudy and blocked the transmission of light. Example 2 and Comparative Example 3 appeared semi-cloudy, Example 3 appeared slightly cloudy, and Comparative Example 4 was unchanged from the state at 27°C. These are due to differences in the state of phase separation, as can be seen from Figs. 2 to 9 showing the results of microscope observation.

[0030] From the results of Tables 1 and 2, a potential difference occurred in the elements of Examples 1 to 4, whereas no significant potential difference occurred in the elements of Comparative Examples 1 to 4. Furthermore, as can be seen from the results of microscopic observation and naked eye observation of Examples 1 to 4, in the present invention, the light transmittance at temperatures above the LCST can be adjusted by changing the combination of polymers used. [Industrial Applicability]

[0031] The power generating element and the power generating element having a dimming function of the present invention can generate electricity and / or dimming by temperature change, and therefore can be suitably used in fields where power generation and / or dimming by temperature change is required or can be utilized. For example, they can be used as temperature sensors, power sources for wearable devices, and the like. As a temperature sensor, for example, a mechanism can be created in which an external circuit is turned on and a signal is transmitted when the temperature exceeds the LCST and power is generated. As a power source for wearable devices, for example, a mechanism can be created in which power is generated when the temperature exceeds the LCST, a voltage is supplied to a body sensor, and recording is started. In addition, the power generating element having a dimming function of the present invention can be used as dimming glass simply by replacing the window glass of an existing building, commercial facility, house, etc., and can generate power, so there is no need to secure new installation space for a power generating device or battery, and dimming and power generation can be performed simultaneously with one element.

Claims

1. A pair of conductive substrates and a mixed layer of an ionic liquid and water provided between the pair of conductive substrates, a perfluoropolymer layer is formed on the mixed layer side of the ionic liquid and water of one of the pair of conductive substrates, a polymer layer other than a perfluoropolymer is formed on the mixed layer side of the ionic liquid and water of the other conductive substrate of the pair of conductive substrates; The mixed layer of ionic liquid and water is a power generating element that contains an ionic liquid and water and exhibits a lower critical solution temperature type phase separation behavior.

2. 2. The power generating element according to claim 1, wherein the polymer layer other than the perfluoropolymer is a polyimide layer.

3. 3. The power generating element according to claim 1 or 2, wherein the pair of conductive substrates are light-transmitting conductive substrates, and the perfluoropolymer layer and the polymer layer other than the perfluoropolymer are light-transmitting layers, and the power generating element has a light-adjusting function.

Images