JPH06151262A - Electrochemical element - Google Patents

Abstract

PURPOSE:To provide an electrochemical element small in internal resistance, high in response speed, and hardly affected by vibrations, wherein gas is prevented from being generated from an electrode. CONSTITUTION:An electrochemical element is equipped with a first electrode 1, a high molecular electrolytic layer 3 composed of crosslinked high molecular material and liquid and arranged very close to the electrode 11, and a second electrode 2, wherein a gap between the high molecular electrolytic layer 3 and the second electrode 2 is filled with liquid medium 4, and electrochemically active ion species contained in the medium 4 and high molecular ions included in the high molecular electrolytic layer 3 are the same in polarity. By this setup, an electrochemical element which is high in response speed and low in internal resistance, functions as a rectifier in low voltage and small current can be obtained, wherein gas is hardly generated from an electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical device using an electrolyte solution, and more particularly to a device having a controllable electric conductivity, a first electrode and a first electrode which are disposed in close contact with each other and crosslinked. The present invention relates to an electrochemical device having a polymer electrolyte layer made of a polymer substance and a second electrode arranged apart from the polymer electrolyte layer.

[0002]

2. Description of the Related Art It has long been pointed out that the behavior of ions, which are charge carriers in an electrolyte solution, is similar to the behavior of electrons and holes, which are carriers in semiconductors. The electrochemical rectification element / amplification element of the above has been proposed. (For example, LETAW &BARDEEN; J. App
l. Phys. , 25 (5), 600 (1954), O
SHIDA; Phys. Soc. Japan, 15
(12), 2288 (1960), LANE & CAME
RON; Electronics, 32 (9), 53
(1959, etc.) In order to make such an electrochemical device perform the same electric conductivity control as that of a semiconductor device, it is necessary to regulate the concentration distribution of charge carriers inside the device by an appropriate method. In the initial proposal regarding this method, as a method of controlling the concentration of charge carriers, that is, ions, near the electrode, an electric current is applied to the electrode to cause an electrochemical reaction to cause concentration polarization. Then, a method has been reported in which a cation exchange resin and an anion exchange resin are brought into contact with each other to form an ion concentration distribution in a state in which no current is passed. (Eg LOV
RECEK, DESPIC &BOCKRIS; Ph
ys. Chem. , 63 , 750 (1959) LOVR
ECEK &KUNST; Nature, 189 , 804
(1961) etc.).

[0003]

The previously proposed electrochemical device described above has a drawback in that when the electrolyte is a simple liquid, the electrolyte easily flows and is easily affected by vibration. Further, in the case of an element using a solid electrolyte such as a polymer electrolyte, the movement of electrolyte ions serving as charge carriers becomes slower than in the case of a liquid electrolyte, so that there is a drawback that the response becomes slow. Further, when the electrolyte medium contains water and hydrogen ions and hydroxide ions are used as charge carriers, a faster carrier migration is observed as compared with other ordinary ions, but gas is generated by an electrode reaction from these ions. Occurs, and there is a problem that the internal resistance of the electrochemical device is not small, in addition to the problem that this gas accumulates inside the device.

The object of the present invention is to reduce the influence of vibration,
An object of the present invention is to provide an electrochemical element which does not have a problem of gas generation from electrodes and has a fast response and a small internal resistance.

[0005]

In the electrochemical device of the present invention, the gap between the polymer electrolyte layer and the second electrode is filled with a medium containing liquid as a main component, and the electrochemical element contained in the medium is filled. The electrically active ionic species has the same polarity as the polymer ion contained in the polymer electrolyte layer.

[0006]

The polymer constituting the polymer electrolyte layer of the electrochemical device of the present invention has an ionic dissociative portion in its molecular structure,
It is swollen by a solvent having a high dielectric constant and is dissociated into a polymer ion (a portion directly connected to the polymer structure and charged) and a free ion having an opposite polarity to the polymer ion.

When a medium mainly composed of a liquid and containing the low molecular weight ions is brought into contact with the above-mentioned polymer electrolyte layer, the low molecular weight ions move across the interface. At this time, the polymer ions do not move because they are fixed by crosslinking. Therefore, when the Donnan equilibrium is established at the interface between the polymer electrolyte layer and the medium, the shadow of the low molecular electrolyte that has moved across the interface /
The amounts of cations are not equal to each other.

Low molecular weight ions having the opposite sign to the polyelectrolyte ions can pass through the interface relatively freely, whereas ions having the same sign as the polyelectrolyte pass only a small amount through the interface. Thus, among the low molecular weight ions contained in the medium, the ions having the same sign as the polymer electrolyte are excluded from the polymer electrolyte layer.

If an ion that is electrochemically active, that is, an electron that exchanges electrons with the electrode and directly participates in a redox reaction is used as the ion that is excluded from the above-mentioned polymer electrolyte layer, The electron transfer reaction rates at the first electrode in contact with the molecular electrolyte layer and the second electrode in contact with the medium are different, reflecting the difference in the concentration of the ions on the surface of each electrode. Therefore, when an electric current is passed between the first and second electrodes, the magnitude of the polarization voltage generated on the electrode surface varies depending on the direction of the electric current, so that a rectifying action appears.

As described above, the concentration of the electrochemically active ions in the polymer electrolyte layer is low, but the concentration of the polymer ions and the free ions having the opposite polarity are sufficiently high. The electric resistance can be kept low. On the other hand, in a medium mainly composed of a liquid, the concentration of the electrochemically active ion and the ion having the opposite polarity can be increased, so that the electric resistance of the medium can be suppressed low.

Since the element of the present invention is a device for controlling conductivity by using ions in the electrolytic solution as charge carriers and controlling the concentration of ions near the electrodes, the electrolytic solution, that is, the medium, has electronic conductivity. Is not preferable. The solvent used for the medium is preferably one having a high dielectric constant and practically no dissociation property, and acetonitrile, ethylene glycol, propylene carbonate, dimethylacetamide, dimethylformamide and the like can be used. However, even a solvent that slightly dissociates into ions can be used if the ions generated from the solvent do not practically undergo an electrode reaction under the operating conditions of the device. For example, even if water is used as a solvent, one electrolyte ion is used as a charge carrier.
If more than x10 ^-6 mol 1/1 is added, and the electrode reaction of the carrier precedes the electrolytic reaction of water, a practical device can be manufactured.

The medium mainly containing a liquid in the electrochemical device of the present invention may be an ordinary liquid alone, but it is possible to maintain a stable distance between the crosslinked polymer electrolyte layer and the second electrode. A suitable solid spacer or porous material may be inserted into the liquid, or a bridging molecule swollen with the liquid may be used instead of the liquid because it is effective for stabilizing the operating characteristics.

From practical requirements, it should be ensured that the device will not be consumed even if a current is continuously applied to the device. In order to achieve this, the present electrochemical device is required to have no deterioration or elution of electrodes due to energization and no decomposition or consumption of the electrolytic solution due to energization.

In order to prevent the deterioration of the electrode, the electrode used in the device of the present invention needs to be made of a conductor which is electrochemically inactive under the normal use condition of the device. Materials that satisfy these conditions include electrochemically noble metals such as gold, platinum, and rhodium, graphite,
Examples include amorphous carbon.

In order to prevent the deterioration of the electrolytic solution, the charge carriers present in the electrolytic solution undergo a reversible electrochemical reaction on the above-mentioned inert electrode material, and the carriers oxidized at the anode of the device become the cathode. It should be one that can be reduced by the reverse reaction. Carriers suitable for such a reversible oxidation / reduction reaction include iron (III) / iron (II), copper (II) / copper (I), cerium (IV) / cerium (I
II), transition metal ions having a plurality of oxidation states, halogen ions such as iodine and bromine, quinone compounds such as hydroquinone and naphthohydroquinone, and phenothiazine compounds such as thionine, N-methylphenothiazine and methylene blue. . These electrochemically active ions may form a complex in the presence of a ligand. Of course, be careful of the combination of carrier, electrode material, and electrolyte solvent so that the components of the electrolyte solution other than the electrode material and carrier do not undergo a deterioration reaction at the redox potential where the oxidation or reduction reaction involving these ions proceeds. Should be selected. That is, the material used as the carrier must be one that is reduced at a potential nobler than that of the electrode material and the electrolyte solution solvent and is oxidized at a base potential.

The carrier must be soluble in the solvent in both its oxidized and reduced state. The carrier does not have to be an ion in both the oxidized state and the reduced state, and may be an ion in either state and may be a neutral molecule in the other state. Particularly, when one of the states is a neutral molecule, the neutral molecule can move freely without receiving Coulomb force from the fixed ions of the polymer electrolyte layer, which is preferable for the electrochemical device of the present invention.

The polymer constituting the polymer electrolyte layer is used for the purpose of holding the electrolytic solution and for fixing ions having the same sign as carrier ions in the electrolytic solution. By holding the electrolytic solution and preventing its flow, stirring of the electrolytic solution does not occur even when shock or vibration is applied to the element. Therefore, the carrier concentration in the vicinity of the electrodes is prevented from being disturbed by vibration and impact, and the operation of the element is stabilized.

Such a polyelectrolyte layer is composed of a crosslinked polyelectrolyte and a liquid that swells it. The crosslinked polyelectrolyte plays a role of supplying ions at an appropriate concentration in the polyelectrolyte layer, preventing flow inside the polyelectrolyte layer, and stabilizing the position of the polyelectrolyte layer in the device. In order not to slow down the movement of carriers in the polymer electrolyte layer, the ratio of the polymer to the liquid should be small. When the proportion of the polymer increases, the number of liquid molecules that are adsorbed around the polymer chains and are restricted in movement increases, and the dissolved free ions become difficult to move. In order for the free ions to move in the same manner as in the liquid, it is necessary that the liquid be present in at least about the same weight as the polymer.

When the weight ratio of the liquid to the polymer is 100 times or more, the crosslinked polyelectrolyte layer becomes very soft and the purpose of stabilizing the position of the layer cannot be achieved. For the above reasons, the crosslinked polyelectrolyte layer is required to be composed of a crosslinked polyelectrolyte swollen by a liquid at a magnification of 100 times or more.

The polymer constituting the polymer electrolyte layer has an ionic dissociative portion in its molecule. For the operation of the electrochemical device of the present invention, it is essential to have the effect of eliminating the electrochemically active ions that are charge carriers from the polymer electrolyte layer, as described above. The sex moiety must be such that upon dissociation, a charge of the same sign as the electrochemically active ion appears on the polymer side.

In the above-mentioned ion dissociative portion, a sulfonic acid group, a phosphoric acid group, a carboxyl group or the like can be used as the anion, and a quaternary aluminium, amine or the like can be used as the cation. A polymer electrolyte having an appropriate ion dissociable portion may be selected according to the sign of the electrochemically active ion used.

The device of the present invention preferably has a container for holding the first and second electrodes, the polymer electrolyte layer and the medium in order to stabilize the operation. This container firstly prevents the liquid from being lost from the device, secondly from the outside to prevent moisture and electrolyte ions from invading the inside of the device, and thirdly, fixedly holds the relative position of each part in the device. Play a role. The material of the container is such that water, a solvent such as an electrolytic solution, electrolyte ions, etc. are difficult to penetrate, it is electrochemically inert, it has a suitable hardness, and it is an electrically insulating material. I have to. From such a point of view, glass, various ceramics, plastics and the like can be selected as the material of the container.

The form of the electrochemical device of the present invention is not limited to that shown in FIG. Hereinafter, another embodiment of the electrochemical element according to the present invention will be illustrated with reference to the drawings.

FIG. 2 shows another form of the electrochemical device of the present invention. In particular, when forming a small element having a small capacity, if the first and second electrodes are arranged on the same surface as shown in the figure, it is easy to form the electrode pattern by a printing technique. This element is different from the element of FIG. 1 in that carriers flow in the lateral direction, but the principle that the voltage / current characteristics appear asymmetrically with respect to the origin is the same as in the case of FIG.

FIG. 3 shows a structure similar to that of FIG. 2 in which a plurality of elements elongated in one direction are provided side by side, and the current capacity can be increased even in the form of laterally moving carriers.

FIG. 4 shows the electrodes arranged concentrically. Since there is no electrode end because the electrode is circular,
The carrier concentration distribution is not disturbed at the electrode end, and good operation can be expected.

Next, an example in which the electrochemical device of the present invention is actually prepared will be described.

Example 1 In a nitrogen atmosphere, two glass plates were horizontally opposed to each other with a polyester film as a spacer at a distance of 50 μm, and N, N-dimethylacrylamide-2-acrylamido-2-methylpropanesulfone was interposed therebetween. Sodium acid
N, N-methylenebisacrylamide · N, N, N ′,
Weight ratio of N'-tetramethylethylenediamine / ammonium persulfate / water 400: 400: 100: 1: 2: 3
The mixed solution of 200 was filled and the polymerization was allowed to stand. The water-containing film obtained was thoroughly washed with water and then immersed in an aqueous solution of 0.06% by weight of bromine and 0.24% by weight of potassium bromide. Two glass plates with a platinum pattern having a width of 100 μm and a length of 10 mm formed on the surface are prepared, and the glass fiber filter paper containing the bromine / potassium bromide solution is placed on one of the glass plates. Overlaid. The water-containing film was placed on this, and another glass plate was placed thereon so that the platinum pattern was substantially aligned with the position of the platinum pattern of the lower glass plate. As a result, the electrochemical device of the present invention using the platinum pattern of the upper glass plate as the first electrode, the platinum pattern of the lower glass plate as the second electrode, the hydrous film as the polymer electrolyte layer, and bromine ion as the carrier was obtained. Been formed.

When the voltage / current characteristics of this element were measured with the voltage applied from the second electrode to the first electrode in the positive direction, the rectifying property as shown in FIG. 5 was observed.

Example 2 In a nitrogen atmosphere, two glass plates are horizontally opposed to each other with a polyester film as a spacer at a distance of 100 μm, and N, N-dimethylacrylamide / sodium acrylate / N, N-methylene is interposed therebetween. Bisacrylamide
N, N, N ', N'-tetramethylethylenediamine
Ammonium persulfate / water weight ratio 400: 400: 10
The first water-containing film was prepared by static polymerization by filling a mixed solution of 0: 1: 2: 3200. Similarly, the weight ratio of N, N-dimethylacrylamide / N, N-methylenebisacrylamide / N, N, N ', N-tetramethylethylenediamine / ammonium persulfate / water is 800: 10.
A second hydrous film was prepared from a mixed solution of 0: 1: 2: 3200. Both of the obtained films were washed with water and then immersed in an aqueous solution containing 0.01% by weight of iodine and 0.05% by weight of potassium iodide. The first water-containing film was laid on a platinum plate having a size of 10 mm × 10 mm, the second film was laid on this, and another platinum plate of 10 mm × 10 mm was laid on it to give an electrochemical device of the present invention. In this device, the first film serves as a polymer electrolyte layer and the second film serves as a medium, and serves as an electrochemical device having the structure shown in FIG.

Example 3 A platinum electrode having a width of 50 μm and a length of 5 mm was 10 μm on a glass plate.
Two pieces are formed in parallel while being separated by m. The glass plate was immersed in a 1: 100 mixture of γ-methacryloxypropyltrimethoxysilane and water for 3 hours and then heat-treated at 100 ° C. for 5 minutes. 0.5m on 5μm thick polyester film
A mx4 mm wide window was cut out and placed on the glass plate so that the window corresponded to the position of the platinum electrode. Acrylamide-3-methacrylaminopropyltrimethylammonium chloride-N, N'-methylenebisacrylamide-N, N, N ', N'-tetramethylethylenediamine-riboflavin-water weight ratio 500
A solution was prepared by mixing at a ratio of 0: 30: 1250: 120: 1: 100000, and this solution was dropped into the hole portion of the film on the glass plate, and the glass plate was covered with another glass plate from above. Then, the solution sealed in the window portion was irradiated with ultraviolet light having a wavelength of 366 mm by using an optical mask to photopolymerize the solution in a predetermined portion to form a crosslinked polymer electrolyte layer as shown in FIG. . After that, remove the glass plate lid and wash with water, and further ferrous chloride 1.5x10 ^-3
After washing with an aqueous solution of mol / 1 and ferric chloride 8 × 10 ⁻⁵ mol / 1, the element was sealed with a small amount of the iron chloride solution by covering with a cover of polycarbonate resin to complete an electrochemical element.

Example 4 0.41 g of 4-styrenesulfonic acid, 0.1 g of divinylbenzene and 0.01 g of 2,2'-azobis (2,4-dimethylvaleronitrile) were dissolved in 1 ml of methanol to prepare a monomer mixture solution. After freezing and degassing, the glass plate is filled with a space of 50 μm and left at room temperature for standing polymerization. After washing the obtained film with water,
Ionic equilibrium is obtained by washing with an aqueous solution containing 0.1% by weight of bromine and 0.002 mol of potassium bromide. Using this film and a bromine / potassium bromide solution, and using the same platinum electrode as in Example 1,
An electrochemical device similar to the above was formed.

[0033]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the space between the polymer electrolyte layer and the second electrode is filled with a medium mainly containing a liquid, and the electrochemically active ionic species contained in the medium is filled. By having the same polarity as the polymer ions of the polymer electrolyte layer, it exhibits a rectifying action at a low voltage and a small current, has a relatively simple structure and does not require a high-purity constituent material, and a printing technique. It is possible to produce a small-sized one using, and there is an effect that an electrochemical element which is not easily affected by vibration, has no problem of gas generation from the electrode, has a fast response, and has a low internal resistance.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the basic configuration of an electrochemical device of the present invention.

FIG. 2 is a schematic cross-sectional view showing the constitution of the electrochemical device of another embodiment.

FIG. 3 is a schematic plan view showing the configuration of an electrochemical device of another example of the present invention.

FIG. 4 is a schematic plan view showing a configuration of an electrochemical device of the present invention in which each electrode is coaxially arranged.

FIG. 5 shows the voltage of the electrochemical device according to the first embodiment of the present invention.
It is a current curve.

[Explanation of symbols]

 1 1st electrode 2 2nd electrode 3 Crosslinked polymer electrolyte layer 4 Medium 5 Container

Claims (3)

[Claims] 1. A first electrode, a polymer electrolyte layer which is disposed in close contact with the first electrode and is composed of a crosslinked polymer substance and a liquid, and is disposed apart from the polymer electrolyte layer. In an electrochemical device having a second electrode, a gap between the polymer electrolyte layer and the second electrode is filled with a medium mainly containing a liquid, and the electrochemically active substance contained in the medium is activated. Ionic species,
An electrochemical device having the same polarity as the polymer ions contained in the polymer electrolyte layer. 2. The electrochemical device according to claim 1, wherein the content of the liquid in the polymer electrolyte layer is 50% by weight or more. 3. The electrochemical device according to claim 1 or 2, wherein the substance forming a redox pair with the electrochemically active ionic species is a neutral molecule.