JP2794524B2 - A laminate of a material having a polar surface and a conductive polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate of a material having a polar surface such as an electrode or a solid electrolyte and a conductive polymer, which can be used in the fields of electrode materials for various electrochemical devices, electrochromic devices and the like. And a joining method.

[0002]

2. Description of the Related Art Generally, a conductive polymer can be prepared by electrolytic polymerization. Examples of the use of a conductive polymer as an electrode material include polyaniline, polypyrrole, and polyaniline, as summarized in The Society of Polymer Science, Handbook of New Polymers, 1989, published by Maruzen Co., Ltd., pp. 191-192.
Polyacetylene and the like are mentioned. Further, the conductive polymer has a feature that the color is changed by doping and undoping, and as described in JP-A-56-67881,
Utilizing this, application to an electrochromic device is also considered. In addition, polyaniline and the like are expected as electrode materials for batteries and are being developed.

[0003]

In the application of a conductive polymer to an electrochemical device, the conductive polymer has a typical non-polar surface, and is therefore strong against solid electrolytes and electrodes having a polar surface. Cannot have a strong adhesive strength. In an electrochemical device using an electrolyte solution, the bonding with the conductive polymer surface is completely maintained, but when a solid electrolyte is used, poor adhesion is a serious problem. Further, a transparent electrode such as ITO also has a polar surface in which the metal oxide on the surface contains many polar groups, and similarly has a polar surface. Therefore, it has been difficult to obtain strong adhesion between the conductive polymer and the electrode as in the case of the electrode. Electrochemical element using solid polymer electrolyte has no fear of liquid leakage,
Suitable for upsizing. However, as described above, there is a difficulty in bonding the conductive polymer to the solid electrolyte or the electrode, causing a problem such as peeling. Particularly, in the case of a large-area electrochromic device, the use of an organic solid electrolyte is desirable, but the problem of peeling is likely to occur.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, to eliminate the difference in polarity between the polar surface of an electrode or a solid electrolyte or the like and the conductive polymer, and to solidify the gap therebetween. It is another object of the present invention to provide a laminate of a material having a polar surface and a conductive polymer bonded thereto. Another object of the present invention is to have an affinity for both the polar surface and the conductive polymer without impairing the electrochemical performance of the electrode, the solid electrolyte and the conductive polymer, and to increase the adhesive strength between them. An object of the present invention is to find a surface modifier capable of modifying a polar surface or a surface of a conductive polymer so as to improve the surface condition.

[0005]

According to the present invention, in order to achieve the above object, when a conductive polymer is laminated on a material having a polar surface such as an electrode or a solid electrolyte, the bonding strength thereof is improved. For this purpose, there is provided a laminate characterized in that a compound containing an electropolymerizable group and a group having an affinity for a polar surface is provided as an intermediate layer between them. Here, the group capable of electrolytic polymerization includes aromatic conjugated monomers (phenylene, naphthalene, anthracene, azulene, etc.), heterocyclic conjugated monomers (thiophene, selenophene, pyrrole, pyridine, furan, etc.),
Monomers or multimers such as heteroatom-containing conjugated monomers (aniline, etc.), olefins having double bonds (ethylene, propylene, butadiene, etc.), and those modified by introducing an alkyl group or the like into these. The group having an affinity for a polar surface is a hydroxyl group, an acetylated hydroxyl group, a carboxyl group, an acetylated carboxyl group, an ether group, ethylene glycol, polyoxyethylene, or the like.

[0006]

In the present invention, a compound having both an electropolymerizable group and a group having an affinity for a polar surface as described above is provided between a material having a polar surface and a conductive polymer. By providing the intermediate layer, the difference in polarity between the material having a polar surface and the conductive polymer is eliminated, and strong adhesion is obtained. As a method of laminating a compound having both an electropolymerizable group and a group having an affinity for a polar surface on a conductive polymer, the method includes applying the compound on a conductive polymer film formed on an electrode. ,
A method of chemically bonding a conductive polymer with a group capable of electrolytic polymerization of the compound by an electrochemical reaction, and after forming a film of the conductive polymer on an electrode by electrolytic polymerization, including the above separately prepared compound There is a method in which a layer of the compound is formed on a conductive polymer film by further performing electrolytic polymerization in an electrolytic bath. The compound layer thus formed also functions as a conductive polymer film, and has a group having affinity for polarity, that is, has a polar group. Shows adhesion.
In addition, after applying a compound having both an electropolymerizable group and a group having an affinity for a polar surface on the electrode to form a film, electrolytic polymerization is performed using a monomer capable of electrolytic polymerization,
By forming a conductive polymer film on the film of the above compound, a conductive polymer film having good adhesion to an electrode can be obtained, and various functional electrodes such as an electrode for a battery and an electrode for an electrochromic element can be obtained. Can be used advantageously.
When the compound according to the present invention is used on the electrode surface, it is important to use it as a sufficiently thin film. When the compound is applied thickly, the conductivity of the electrode surface is lost, and subsequent use becomes difficult. The electrolyte can be included in the film of the compound by dissolving the electrolyte in a solution of the compound used for coating in advance. Thereby, the film forming speed at the time of electrolytic polymerization can be improved.

As described above, compounds used to modify the polar surface or the surface of the conductive polymer film and to improve the adhesive strength between them are as follows:

Embedded image Wherein R ₁ and R ₂ are hydrogen or an alkyl group, B is a divalent group, A is an electropolymerizable group, D is a polar group, m and n Is an integer of 1 or more.) Is preferable.

In the above general formulas (1) and (2), the group A capable of electrolytic polymerization includes aromatic conjugated monomers (phenylene, naphthalene, anthracene, azulene, etc.),
Heterocyclic conjugated monomers (thiophene, selenophene,
Groups such as pyrrole, pyridine, and furan), heteroatom-containing monomers (such as aniline), and groups based on monomers or multimers such as those modified by introducing an alkyl group or the like into them. Furthermore, these monomers or multimers can be used in combination. The polymerization degree of the multimer is not particularly specified. Although it shows solubility in a solvent up to the trimer, the solubility in the solvent decreases when the tetramer or more. Therefore, for tetramers or more, it is necessary to take measures such as introducing an alkyl chain. In particular, monomers and dimers are advantageous because they have excellent solubility and synthetic raw materials can be obtained at low cost. Further, the divalent group B in the above general formula (2)
Examples thereof include an ether group, an ester group, an amide group, a phenylene group, a urea group, and a urethane group. Among these divalent groups, monomers having a phenylene group are excellent in polymerizability, and a polymer can be obtained with a high yield of 95% or more. Further, the phenylene group is chemically stable, and does not undergo hydrolysis by ions used as a supporting electrolyte of the electrochemical device. Furthermore, examples of the polar group D in the general formula (2) include a hydroxyl group, an acetylated hydroxyl group, a carboxyl group, and an esterified carboxyl group. An acetylated hydroxyl group and an esterified carboxyl group can be converted into a hydroxyl group and a carboxyl group by hydrolysis.

Such a polymer compound is polymerized by radical polymerization. When a large conjugated system is bonded to the double bond of ethylene, the double bond of ethylene is incorporated into the conjugated system, and the energy is reduced. And the reactivity is extremely reduced because the conjugated system is electron-withdrawing. On the other hand, by sandwiching a divalent group B between a double bond and a group A in which an electropolymerizable conjugated system is developed, as in the copolymer represented by the general formula (2), Incorporation of a double bond into a conjugated system can be suppressed, and the reactivity of the double bond can be maintained. As a result, the double bond of each monomer component can be polymerized using a polymerization initiator such as a commonly used azo compound such as azobisisobutyronitrile and a peroxide such as benzoyl peroxide. In a high yield. The copolymer may be a block copolymer or a random copolymer, and the ratio of the two monomer components is variable depending on the application.

In particular, from the viewpoint of stability and polymerizability,

Embedded image The copolymer having a phenylene group represented by the general formula (3) is excellent. In the general formula (3), R ₁ , R ₂ , A, D, m and n have the same meaning as described above. These copolymers differ in solubility in solvents depending on their component ratios, and contain a large number of polar groups D and a large number of electrolytically polymerizable groups A,
The solvent to dissolve is different. In particular, when it contains many hydroxyl groups, it dissolves in polar solvents such as dimethylformamide (DMF) and dimethylsulfoxide (DMSO). When it contains many groups capable of electrolytic polymerization, it dissolves in nonpolar solvents such as chloroform and toluene. I do.

The degree of polymerization of the above compound is not particularly limited. With respect to the compound represented by the general formula (3), even if m and n are 1, the object of the present invention can be achieved. When both m and n are set to 1, the solubility of the above compound increases, and the operation becomes easy. In particular, when the conductive polymer film is laminated on the surface of the conductive polymer film by electrolytic polymerization, it is important to maintain the solubility because the usable solvent is limited to nitrobenzene or the like. However, when m and n are 1, they are introduced only at the growth end of the electrolytic polymerization, and the ratio introduced into the entire surface becomes small. Further, there is a high possibility that a low molecular weight product is produced by polymerization of the above compounds. When m and n are extremely large and the molecular weight is extremely large, the solubility is reduced and the coating becomes difficult. When a high molecular weight material is formed by coating, the solubility of m and n greater than 1 varies depending on the ratio of m and n. Further, the solubility differs depending on the type of the group A capable of electrolytic polymerization. The case where the group A capable of electrolytic polymerization is thiophene will be described as an example. If m / n = 1/10, m
A copolymer having a polymerization degree of about + n = 200 is soluble in chloroform. When m / n = 1/1, the solubility decreases even when m + n = about 50. When n is increased and m / n is decreased, solubility is improved. However, if m / n is reduced, it becomes difficult to achieve the object of the present invention. In order to achieve the object of the present invention, m / n = 1/20 or more is required. Even if m / n = 1/20, practically m + n =
About 300 is considered the limit. When thiophene is alkylthiophene, m + n = 50 is sufficiently soluble in chloroform even if m / n = 1/1.

A solution of such a copolymer is prepared, applied to a conductive polymer film formed on an electrode, dried, and further subjected to an electrochemical reaction using a solid electrolyte or a normal electrolyte solution. Thereby, the conductive polymer film and the copolymer can be chemically bonded. In this case, the conductive polymer film may be formed by applying and drying a solution of a soluble conductive polymer on the electrode, or may be a film formed directly on the electrode by electrolytic polymerization. For the conductive polymer film directly formed on the electrode by electrolytic polymerization, by performing the electrolytic polymerization again in another electrolyte solution containing the compound, the film of the compound on the conductive polymer film Can be formed. The electrolyte used is not particularly limited, but LiClO ₄ , LiAsF ₆ , LiPF ₆ , Li
BF ₄ or the like is used. As a solvent for electrolytic polymerization, propylene carbonate is generally used. However, the solvent is not particularly limited as long as it has a potential window containing a potential necessary for electrolytic polymerization and can dissolve a monomer and a supporting electrolyte. The film obtained in this way has excellent adhesion to electrodes and exhibits strong adhesion.

[0013]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but it goes without saying that the present invention is not limited to the following Examples.

Example 1 Using α-methyl-p-chlorostyrene, dichloro-
Methylstyrene having a thiophene ring at the para position was synthesized by a Grignard reaction using 1,3-bis (diphenylphosphinopropane) nickel (II), monobromothiophene and magnesium. 0.534 g of methylstyrene having a thiophene ring at the para position in 3 ml of toluene
And 2.29 g of vinyl acetate, and 0.23 g of azobisisobutyronitrile as a polymerization initiator. After stirring at 65 ° C for 60 hours, hexane 500 ml
And purified by a reprecipitation method. After filtration, the resultant was dried at 110 ° C. to obtain a copolymer represented by the following formula 6 in a yield of 41.8%.

Embedded image In an electrolyte solution in which 0.2 mol / l of lithium perchlorate and 0.2 mol / l of thiophene were dissolved in benzonitrile, polythiophene was formed on ITO glass by electrolytic polymerization using a platinum plate as a counter electrode. Separately, 0.2 mol / l of lithium perchlorate in benzonitrile, 1 wt% of the above copolymer
% Of an electrolyte solution was prepared, and a thin film of the above copolymer was provided by electrolytic polymerization on the polythiophene electrolytically polymerized film on the ITO glass using a platinum plate as a counter electrode. A concentrated solution of polyvinyl alcohol and lithium perchlorate dissolved in DMSO was cast on the obtained electrolytic polymerized film, dried sufficiently, and then a stainless steel sheet was heat-pressed. This device showed a clear electrochromism of polythiophene and uniform color development. The adhesion between the conductive polymer and polyvinyl alcohol was also good.

Example 2 Monobromobithiophene, magnesium, dichloro-
Using 1,3-bis (diphenylphosphinopropane) nickel (II) and p-chlorostyrene, a vinyl compound having bithiophene at the para-position of the benzene ring was synthesized by a Grignard reaction. In 3 ml of toluene, 0.5 g of the vinyl compound and 2.31 g of vinyl acetate were copolymerized with 0.20 g of azobisisobutyronitrile as a polymerization initiator. Stir at 65 ° C for 72 hours, hexane 500ml
And purified by a reprecipitation method. After filtration, at 110 ° C 1
After drying for 0 hour, a copolymer represented by the following formula 7 was synthesized.

Embedded image 1 wt% of polyoctylthiophene is dissolved in toluene,
A film was formed by casting on ITO glass, and the above copolymer was dissolved in DMSO and cast on the polyoctylthiophene film. Using an electrolyte solution obtained by dissolving 0.2 mol / l of lithium perchlorate in benzonitrile, the color extinction of polyoctylthiophene by electrochromism was repeated several times and then dried. A concentrated solution in which 1.5 wt% of polyvinyl alcohol and 1.5 wt% of lithium perchlorate were dissolved in DMSO was cast on the obtained electrolytic polymerized film, dried sufficiently, and then a stainless steel plate was heat-pressed. This device showed a clear electrochromism of polythiophene and uniform color development. The adhesion between the conductive polymer and polyvinyl alcohol was also good.

[0016]

As described above, the laminate according to the present invention comprises:
When a conductive polymer is laminated on a material having a polar surface such as an electrode or a solid electrolyte, a compound containing an electropolymerizable group and a group having an affinity for the polar surface is provided as an intermediate layer between them. Because, without impairing the electrochemical performance of electrodes, solid electrolytes and conductive polymers,
The difference in the polarities can be eliminated, and strong joining can be achieved without problems such as poor adhesion and peeling. In addition, the compound layer thus formed also functions as a conductive polymer film, and the obtained laminate is advantageously used in various electrochemical devices as an electrochromic device or its counter electrode, or a battery electrode. Can be used.

Claims (7)

(57) [Claims] 1. A compound having a group capable of electrolytic polymerization and a group having an affinity for a polar surface is provided as an intermediate layer between a material having a polar surface such as an electrode and a solid electrolyte and a conductive polymer. A laminate of a material having a polar surface and a conductive polymer. 2. An intermediate layer between a material having a polar surface and a conductive polymer as shown below. Wherein R ₁ and R ₂ are hydrogen or an alkyl group, A is an electropolymerizable group, D is a group having an affinity for a polar surface, and m and n are integers of 1 or more. 2. The laminate according to claim 1, wherein a compound represented by the formula: is used. 3. An intermediate layer between a material having a polar surface and a conductive polymer as shown below. Wherein R ₁ and R ₂ are hydrogen or alkyl groups, B is a divalent group, A is an electropolymerizable group, D is a group having an affinity for a polar surface, m and n Is an integer of 1 or more.) The laminate according to claim 1, wherein the compound is represented by the following formula: 4. As an intermediate layer between a material having a polar surface and a conductive polymer, The compound according to claim 1, wherein a compound represented by the formula: wherein R is hydrogen or an alkyl group, and k, m and n are integers of 1 or more. 5. A compound containing an electropolymerizable group and a group having an affinity for a polar surface is provided as an intermediate layer between a material having a polar surface and a conductive polymer, and the compound is formed by an electrochemical reaction. 2. A chemical bond is formed between an electropolymerizable group and a conductive polymer.
The laminate according to any one of claims 1 to 4. 6. After forming a conductive polymer on an electrode surface by electrolytic polymerization, electrolytic polymerization is further performed in an electrolyte solution in which a compound containing a group having an electrolytically polymerizable group and a group having an affinity for a polar surface is dissolved. The laminate according to any one of claims 1 to 4, wherein a surface of the electropolymerized film is modified and then bonded to a solid electrolyte. 7. A film containing a compound containing an electropolymerizable group and a group having an affinity for a polar surface is formed on an electrode, and then subjected to electrolytic polymerization using an electropolymerizable monomer. The laminate according to any one of claims 1 to 4, wherein a conductive polymer is formed on the film.