JP2008262991A - Composition for conductive polymer capacitor electrolyte and method for manufacturing conductive polymer capacitor electrolyte employing the composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition of a conductive polymer electrolytic capacitor electrolyte satisfying both high a withstand voltage and low impedance. <P>SOLUTION: Using a composition containing an ionic liquid where a conductive polymer monomer and anion components are represented by a general formula (1) R<SB>1</SB>-OSO<SB>3</SB><SP>-</SP>(in the formula, R<SB>1</SB>represents one of a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group or a t-butyl group), the conductive polymer capacitor electrolytic is formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a novel conductive polymer capacitor electrolyte composition using a conductive polymer monomer and an ionic liquid, a conductive polymer capacitor using the same, and a method for producing the same.

In recent years, electrolytic capacitors using a conductive polymer as an electrolyte are expanding the market due to their excellent impedance characteristics.
An electrolytic capacitor generally has a structure in which a valve metal such as aluminum, tantalum, or niobium is used as an anode metal, an oxide film formed on the surface thereof is used as a dielectric, and a cathode is formed by sandwiching an electrolyte layer formed on the dielectric. It has become. The electrolyte in this electrolytic capacitor has two important functions. One is an action of protecting and repairing an extremely thin oxide film, and the other is an action as a de facto cathode which serves to extract a capacitance from a dielectric on the anode.
The electrolytic capacitor typically uses a solid conductive polymer such as polypyrrole or a polythiophene derivative as an electrolyte. Since these conductive polymers have a much higher electrical conductivity (ie, electronic conductivity) than electrolytic capacitors using ordinary liquids as electrolytes, capacitors with these conductive polymers as electrolytes have internal impedance. In particular, it exhibits excellent characteristics as a capacitor for high-frequency circuits.

  Typical electrolytic capacitors include an aluminum electrolytic capacitor using aluminum as an anode metal and a tantalum electrolytic capacitor using tantalum as an anode metal. A tantalum electrolytic capacitor usually uses a porous electrode obtained by sintering tantalum powder. On the other hand, there are two types of aluminum electrolytic capacitors: chip capacitors and wound capacitors.

  In the manufacture of chip-type electrolytic capacitors, a conductive polymer electrolyte is formed on an anode foil by electrolytic polymerization or chemical polymerization, and then a carbon paste / silver paste is applied, and then laminated and dried to form a capacitor element. Make it. A chip-type electrolytic capacitor has a very excellent frequency characteristic because it is manufactured with the above-described configuration, but it has a drawback that the element manufacturing technique is extremely difficult and the defect rate is high.

  On the other hand, the wound electrolytic capacitor is provided with an anode foil formed of a valve metal such as aluminum having a dielectric oxide film formed on the surface, a cathode foil, and further between the cathode foil and the anode foil. A capacitor is manufactured by winding these, and then impregnating and polymerizing a monomer of a conductive polymer to form an electrolyte. Although the separator is indispensable to prevent short-circuiting of the wound capacitor, there is a problem that the impedance characteristic of the capacitor is deteriorated. The wound electrolytic capacitor is advantageous for increasing the capacity, but for high-frequency characteristics. Inferior.

  In any of the conductive polymer capacitors, the conductive polymer has essentially no ionic conductivity. Therefore, in terms of the repairability of the dielectric oxide film of the capacitor (that is, the anodic oxidation action), the conventional electrolytic solution It was inferior to the capacitor using As a result, the electrolytic capacitor has a drawback that a capacitor having a high withstand voltage cannot be produced. Specifically, in an electrolytic capacitor that normally uses aluminum as an anode, for example, when 40V conversion is performed, the actual use voltage is about 16V, and in an electrolytic capacitor that uses tantalum, for example, 24V conversion is performed. In actual use, the voltage is about 12V. Here, 40V conversion means that the DC voltage applied when the dielectric oxide film is formed on the valve metal surface is 40V, and ideally, a capacitor having a withstand voltage of 40V should be obtained. It is. In principle, it is possible to increase the withstand voltage in actual use by increasing the formation voltage, but in that case, the capacitor capacity decreases as the formation voltage increases, and even if the formation voltage is further increased, There is a problem that the withstand voltage in use does not increase proportionally.

In order to solve such problems, the present inventors have already developed an electrolyte composed of an ionic liquid and a conductive polymer. (For example, Patent Document 1) This is made by discovering that an ionic liquid has an excellent anodizing action of a valve metal and can repair defects in, for example, an aluminum oxide film. A voltage electrolytic capacitor could be realized. In the study by the present inventors, an ionic liquid having an anionic component of R′—OSO ₃ ^— (R ′ is an alkyl group having 5 to 50 carbon atoms) was relatively excellent in high withstand voltage characteristics. There was a problem that the characteristics were equal or slightly deteriorated regardless of whether or not an ionic liquid was added. Furthermore, since the viscosity increases as the alkyl chain becomes longer, there is a problem that both the withstand voltage characteristic and the impedance characteristic are deteriorated. That is, in an electrolyte composed of an ionic liquid and a conductive polymer, how to achieve both good withstand voltage characteristics and good impedance characteristics has been a major issue.
International Publication WO2005 / 012599 Pamphlet

  The present invention has been made in order to solve the above-described problems. The object of the present invention is to achieve a high withstand voltage (preferably 70% of the formation voltage without causing a decrease in impedance characteristics and capacity achievement rate. A conductive polymer capacitor electrolyte having the above and a method for producing a conductive polymer capacitor using the same.

  As a result of intensive studies in view of the above, the present inventors have found that a conductive polymer capacitor electrolyte obtained by using a composition comprising a conductive polymer monomer and an ionic liquid having a specific anion component has a high withstand voltage. The present invention has been found to show low impedance.

  That is, this invention relates to the composition for electroconductive polymer capacitor electrolytes containing the ionic liquid whose anion component is General formula (1), and a conductive polymer monomer.

R ₁ -OSO ₃ ^- ₍₁₎
(In the formula, R ₁ represents any of a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a t-butyl group.)
Moreover, this invention relates to the manufacturing method of the conductive polymer capacitor electrolyte manufactured using the said composition for conductive polymer capacitor electrolytes.

  Furthermore, the present invention provides a conductive polymer capacitor electrolyte using the above-described composition for a conductive polymer capacitor electrolyte. The present invention also provides a conductive polymer capacitor using the above-described conductive polymer capacitor electrolyte.

  By using a composition composed of a conductive polymer monomer and an ionic liquid having a specific anion component, a conductive polymer capacitor electrolyte with low impedance and high withstand voltage can be obtained, which contributes to improvement of performance. I can do it.

Hereinafter, embodiments of the present invention will be described in detail.
The conductive polymer monomer used in the present invention is not particularly limited, and examples thereof include thiophene or a derivative thereof, pyrrole or a derivative thereof, aniline or a derivative thereof. As thiophene derivatives, 3,4-ethylenedioxythiophene, 3-alkylthiophene (alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, dodecyl, etc.), fluoro Phenylthiophene, allylthiophene, 3-methoxythiophene, 3-chlorothiophene, 3-acetylthiophene, etc. are mentioned, and pyrrole derivatives include 3-methylpyrrole, 1- (dimethylamino) pyrrole, etc., and aniline derivatives O-toluidine, m-toluidine, 1,3-benzenediamine, 1,2-benzenediamine, 2-aminophenol, 3-aminophenol, 2-fluoroaniline, 3-fluoroaniline, 2-ethynylaniline, 3 -Ethynylaniline, 2-amino Nobenzonitrile, 3-aminobenzonitrile, 3-vinylaniline, 2,3-dimethylaniline, 3,5-dimethylaniline, 2,5-dimethylaniline, 2- (aminomethyl) aniline, 4-methyl-1, 2-benzenediamine, 2-methyl-1,3-benzenediamine, 4-methyl-1,3-benzenediamine, 2-methoxyaniline, 3-methoxyaniline, 2,3-diaminophenol, 5-fluoro-2- Examples thereof include methylaniline, 2-fluoro-5-methylaniline, 3-fluoro-2-methylaniline, 2-chloroaniline and the like. 3,4-ethylenedioxythiophene or pyrrole is preferred because of its high conductivity during polymer formation and stability in the air. From the viewpoint of the conductivity and heat resistance of the resulting conductive polymer, 3,4 -Ethylenedioxythiophene is particularly preferred. Two or more kinds of conductive polymer monomers may be used.

  Next, the ionic liquid used in the present invention will be described. An ionic liquid, also called a room temperature molten salt, refers to a liquid that is liquid at room temperature despite being composed only of ions, and is composed of a combination of a cation such as imidazolinium and an appropriate anion. The ionic liquid is not partially ionized and dissociated like a normal organic solvent, but is considered to be formed from only ions and 100% ionized. As described above, the ionic liquid is usually a liquid at room temperature, but the ionic liquid used in the present invention does not necessarily have to be a liquid at room temperature, and becomes a liquid during the aging process or heat treatment of the capacitor. Any material that spreads and becomes a liquid by Joule heat generated during the repair of the dielectric oxide film may be used.

The ionic liquid used in the present invention has an anionic component represented by the general formula (1);
R ₁ -OSO ₃ ^- ₍₁₎
In the formula (1), R ₁ may be a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a t-butyl group, or the like. A methyl group, an ethyl group, a propyl group, an isopropyl group, and an n-butyl group are particularly preferable from the viewpoint of achieving both impedance characteristics. In general, the alkoxysulfonic acid anion represented by the above formula (1) is difficult to stabilize with an alkyl group having a small R ₁ , that is, a methyl group or an ethyl group, and generates a corresponding acid over time by hydrolysis. Therefore, it was considered unsuitable for the purpose of the present invention. However, when applied to a conductive polymer capacitor electrolyte by the present inventors, it is surprising that not only is it stable without generating an acid corresponding to it, but also both of a high withstand voltage characteristic and a low impedance characteristic that have been difficult in the past. It was found to give

  The cation component of the ionic liquid includes ammonium and its derivatives, imidazolinium and its derivatives, pyridinium and its derivatives, pyrrolidinium and its derivatives, pyrrolinium and its derivatives, pyrazinium and its derivatives, pyrimidinium and its derivatives, triazonium and its derivatives, triazinium And derivatives thereof, triazine and derivatives thereof, quinolinium and derivatives thereof, isoquinolinium and derivatives thereof, indolinium and derivatives thereof, quinoxalinium and derivatives thereof, piperazinium and derivatives thereof, oxazolinium and derivatives thereof, thiazolinium and derivatives thereof, morpholinium and derivatives thereof Derivatives, piperazine and its derivatives, In order to achieve both high pressure resistance characteristics, imidazolium derivatives are preferable, and imidazolium derivatives are preferably diethyl imidazolium, ethyl butyl imidazolium, and dimethyl imidazolium, and particularly preferably ethyl methyl imidazolium and methyl butyl imidazolium. is there.

  Of course, the composition of the present invention may contain, for example, a surfactant as an optional component in addition to the ionic liquid and the monomer of the conductive polymer. Examples of the surfactant include sodium linear alkylbenzene sulfonate, tetraalkyl ammonium, sodium lauryl sulfate, triisopropyl naphthalene sulfonic acid, alkyl sulfonic acid, dodecyl benzene sulfonic acid, hexadodecyl trimethyl ammonium bromide, and particularly preferably dodecyl. Benzenesulfonic acid.

  In addition, although the composition of this invention contains a solvent (dispersion medium) normally as an arbitrary component, of course, the ionic liquid and the solvent (dispersion medium) do not need to be mutually compatible. The solvent used may be a known solvent and is not particularly limited. For example, methanol, ethanol, butanol, 2-propanol, acetone, diethyl ether, ethyl acetate, THF, DMF, acetonitrile, DMSO, dimethyl carbonate, ethylene Examples include carbonate, propylene carbonate, hexane, toluene, chloroform, and the like, and particularly preferred is butanol.

  The molar ratio of the ionic liquid to the conductive polymer monomer is not particularly limited as long as the obtained capacitor gives good results in impedance and withstand voltage characteristics, but preferably the conductive polymer monomer: ion When the liquid is 1: 0.01 to 0.6 and the ionic liquid is 0.01 or more, the withstand voltage is excellent, and when it is 0.6 or less, the low resistance is excellent. That is, the ratio of ionic liquid / conductive polymer monomer is preferably 0.01 or more from the viewpoint of withstand voltage, and preferably 0.60 or less from the viewpoint of low resistance. If it is less than that, the effect is lowered, and if it is more than the range, the resistance is increased, which is not preferable. Particularly preferably, it is 0.01 or more and 0.5 or less.

  Next, the manufacturing method of the conductive polymer capacitor in this invention is demonstrated. The manufacturing method of the conductive polymer capacitor including the electrolyte and the electrode of the present invention is not particularly limited. For example, from a valve action metal in which a dielectric oxide film is formed on the surface of a wound type conductive polymer aluminum electrolytic capacitor. A capacitor element constituted by winding an anode foil and a cathode foil with a separator interposed therebetween, and an electrolyte made of a conductive polymer and an ionic liquid between the anode foil and the cathode foil. For example, after the element is housed in a bottomed cylindrical aluminum case, an aluminum electrolytic capacitor can be configured by sealing the opening of the aluminum case with a sealing agent.

  In the present invention, the electrolyte can be prepared by chemical polymerization or by electrolytic polymerization.

  First, a method by chemical polymerization will be described. The chemical polymerization method is a method in which a conductive polymer monomer such as pyrrole is polymerized and synthesized in the presence of an appropriate oxidizing agent. Examples of the oxidizing agent include ferric paratoluenesulfonate, ferric naphthalenesulfonate, ferric n-butylnaphthalenesulfonate, ferric triisopropylnaphthalenesulfonate, persulfate, hydrogen peroxide, diazonium salt. , Halogens and halides, or transition metal salts such as iron, copper, and manganese can be used. A conductive polymer synthesized by chemical polymerization can obtain a polymer having conductivity in a one-step reaction by incorporating an anion of an oxidant into the polymer as a dopant in the polymerization process. It is preferable to use ferric paratoluenesulfonate containing paratoluenesulfonate ions having high mobility as an oxidizing agent.

  In the case of the polymerization, it is preferable to add an oxidizing agent to a solution containing a conductive polymer monomer and the ionic liquid. In this case, the viscosity and concentration may be adjusted by adding a solvent. As the polymerization solvent used in the polymerization, at least one kind or two or more kinds are selected from the solvents contained in the composition, but they may be the same as or different from the solvent contained in the composition. The polymerization conditions may be known polymerization conditions, and the temperature range is from -100 ° C to 200 ° C, particularly preferably from -30 ° C to 150 ° C. The polymerization time is 1 minute to 120 hours, particularly preferably 1 minute to 1440 minutes. The polymerization may be repeated a plurality of times.

  Next, a method for forming an electrolyte by electrolytic polymerization will be described. The electrolytic polymerization method is a method in which a conductive polymer is dissolved in a solvent and anodized to dehydrogenate the conductive polymer. Electropolymerization is, for example, a method in which a pyrrole monomer is dissolved in a solvent together with a supporting electrolyte and subjected to dehydrogenation polymerization by anodic oxidation, whereby polypyrrole, which is a conductive polymer, can be deposited on the anode. In general, since the oxidation-reduction potential of a polymer is lower than that of a monomer, the oxidation of the polymer skeleton proceeds further in the polymerization process, and accordingly, the anion of the supporting electrolyte is incorporated into the polymer as a dopant. In electropolymerization, such a mechanism has an advantage that a polymer having conductivity can be obtained without adding a dopant later. In addition, when electrolytic polymerization is performed in an ionic liquid, the anionic component of the ionic liquid may be taken into the conductive polymer as a dopant, which is particularly preferable for the purpose of the present invention. When synthesizing a conductive polymer by electrolytic polymerization, the oxide film on the valve metal is a dielectric, so a conductive film is formed on the dielectric beforehand to make it conductive, Electropolymerization is performed by applying a voltage. As the conductive film used for such a purpose, a conductive polymer synthesized by chemical polymerization, pyrolytic manganese dioxide, or the like can be used.

  As the anode of the conductive polymer capacitor of the present invention, a conventionally known capacitor can be preferably used. For example, as the anode metal, the surface of an electrode foil such as aluminum is etched to form an etching hole, or tantalum. By using a powder electrode made of, for example, and combining a dielectric made of an oxide film formed by a method such as anodic oxidation on the surface of the anode metal, an anode made of an anode metal and a dielectric oxide film can be formed. The above anodic oxidation can be performed by immersing the anode metal in, for example, an aqueous solution of ammonium adipate and applying a conversion voltage.

  As the cathode, for example, carbon paste and silver paste can be formed by a conventionally known method. The anode and cathode are each connected to a terminal. Thus, a conductive polymer capacitor having at least an anode, an electrolyte, and a cathode can be formed.

  In the conductive polymer capacitor of the present invention using the electrolyte formed by the above method, the constituent elements of the capacitor not particularly mentioned are not particularly limited, and conventionally known ones can be appropriately applied. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.

<Ionic liquid: ILs>
First, a method for synthesizing or obtaining an ionic liquid used as an example will be described.
(ILs-1)

Purchased from MERCK.
(ILs-2)

Purchased from Solvent Innovation.
(ILs-3)

Chem. Lett. , 32, 654 (2003).

(Measurement of liquid capacity of restoration chemical conversion aluminum foil)
The volume in the liquid was calculated from the slope of the graph obtained in a constant current charge / discharge test of 50 μA between 0 and 4 V using solartron, model number “1480” manufactured by Toyo Technica.

(Measurement of initial capacity of electrode)
The obtained foil was used as a sample, and after aging at 20 V for 1 hour, the initial capacity was measured using the mercury cell shown in FIG.
A solartron manufactured by Toyo Technica, model number “1480” was used as the apparatus, a constant current charge / discharge test of 50 μA was performed in the range of 0 to 4 V, and the capacity was calculated from the slope of the obtained graph.

(Volume expression rate)
(Volume in liquid / initial volume) × 100 was defined as “capacity expression rate (%)”, and the variation in the liquid capacity of the repaired and formed aluminum foil to be used was normalized.

(Impedance measurement)
After the initial capacity measurement, impedance was measured using the mercury cell shown in FIG. Electrochemical Analyzer Model 608B (ALS / [H] CH Instruments) was used as the apparatus, and measurement was performed in the range of 1 Hz to 1 MHz under the conditions of DC Potential: 0 V and AC Amplitude: 100 V. The impedance value of 10 kHz was defined as the electrode impedance.

(Withstand voltage measurement)
After measuring the impedance, the withstand voltage (V) was measured using the mercury cell shown in FIG. The device was model number “TR6143” manufactured by Advantest Corporation, and the voltage was increased at a rate of 20 mV / sec. The withstand voltage value was defined as the voltage at which a current of 10 mA flowed.

Example 1
A conductive polymer aluminum electrolytic capacitor was produced by forming a conductive polymer obtained by chemical polymerization of 3,4-ethylenedioxythiophene on an aluminum oxide film.
That is, an aluminum etched foil having an effective area of 10 mm × 10 mm is dipped in a 1% ammonium adipate aqueous solution, first raised from 0 to 45 V at a rate of 20 mV / sec, and then a constant voltage of 45 V is applied for 40 minutes, A dielectric film was formed on the surface of the aluminum etched foil.
Next, this foil was washed with running deionized water for 3 minutes and then dried at 120 ° C. for 1 hour. The volume of the aluminum etched foil obtained at this time was 25 μF.

Next, the chemical polymerization composition used for electrolyte formation was prepared with the following compounding ratio.
As a monomer of the conductive polymer, 0.2 g of 3,4-ethylenedioxythiophene (hereinafter abbreviated as EDOT; manufactured by HC Starck-V TECH) and iron paratoluenesulfonate (hereinafter referred to as oxidant) are used. 0.40 g) (abbreviated as p-TsO), 0.60 g of 1-butanol as a solvent, and 0.18 g of ionic liquid (ILs-1) were used. These formulations are in a molar ratio of EDOT: p-TsO: ionic liquid = 1: 0.5: 0.5.
This chemical polymerization composition was mixed in a well-dried beaker, and then the aluminum etched foil was immersed in the polymerization solution in the polymerization solution, and after being pulled up, heat treatment was performed at 120 ° C. for 1 hour. The same treatment was repeated four times so that the surface of the foil was uniformly covered with the electrolyte.
The initial capacity of the foil thus obtained was measured using the mercury cell shown in FIG. Moreover, impedance and withstand voltage (V) were measured. Table 1 shows the characteristics of the obtained electrode. The results in Table 1 are average values of three electrodes. As a result, a capacity expression rate of 77%, an impedance of 0.253Ω, and a withstand voltage of 58V were obtained.

(Example 2)
A capacitor of the present invention was produced in the same manner as in Example 1 except that 0.19 g of ionic liquid ILs-2 was used. Table 1 shows the characteristics of the obtained capacitor. As a result, the capacity expression rate was 79%, the impedance was 0.250Ω, and the withstand voltage was 56V.

(Comparative Example 1)
A capacitor of the present invention was produced in the same manner as in Example 1 except that 0.22 g of ionic liquid ILs-3 was used. Table 1 shows the characteristics of the obtained capacitor of the present invention. As a result, a capacity expression rate of 78%, an impedance of 1.65Ω, and a withstand voltage of 57V were obtained.

(Comparative Example 2)
A capacitor of the present invention was produced in the same manner as in Example 1 except that no ionic liquid was used. Table 1 shows the characteristics of the obtained capacitor of the present invention. As a result, the capacity expression rate was 65%, the impedance was 2.23Ω, and the withstand voltage was 39V.

  As described above, the conductive polymer capacitor electrolyte composition according to the present invention can provide an electrolytic capacitor electrolyte having a high capacity achievement rate and a high withstand voltage and a method for producing the same without causing an increase in impedance. It is useful.

Conceptual diagram of electropolymerization equipment Mercury cell for measuring electrodes

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymerization start electrode 2 Anode metal 3 Dielectric film 4 Conductive layer 5 Electrolytic polymerization layer 6 Electrolytic solution 7 Cathode

Claims (7)

A conductive polymer capacitor electrolyte composition comprising an ionic liquid having an anionic component represented by general formula (1) and a conductive polymer monomer.
R ₁ -OSO ₃ ^- ₍₁₎
(In the formula, R ₁ represents any of a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a t-butyl group.)   2. The composition for a conductive polymer capacitor electrolyte according to claim 1, wherein the conductive polymer monomer contains at least one or more selected from the group consisting of pyrrole, aniline, thiophene, and derivatives thereof. .   The cation component of the ionic liquid is ammonium and derivatives thereof, imidazolinium and derivatives thereof, pyridinium and derivatives thereof, pyrrolidinium and derivatives thereof, pyrrolinium and derivatives thereof, pyrazinium and derivatives thereof, pyrimidinium and derivatives thereof, triazonium and derivatives, triazinium and derivatives thereof Derivatives thereof, triazine and derivatives thereof, quinolinium and derivatives thereof, isoquinolinium and derivatives thereof, indolinium and derivatives thereof, quinoxalinium and derivatives thereof, piperazinium and derivatives thereof, oxazolinium and derivatives thereof, thiazolinium and derivatives thereof, morpholinium and derivatives thereof , Selected from the group consisting of piperazine and derivatives thereof, 1 or a conductive polymer capacitor electrolyte composition according to claim 2.   A conductive polymer capacitor electrolyte comprising the composition for a conductive polymer capacitor electrolyte according to any one of claims 1 to 3, and a method for producing the same.   The method for producing a conductive polymer capacitor electrolyte according to claim 4, wherein the conductive polymer capacitor electrolyte is formed by chemical polymerization.   The method for producing a conductive polymer capacitor electrolyte according to claim 4, wherein the conductive polymer capacitor electrolyte is formed by electrolytic polymerization.   A conductive polymer capacitor using the conductive polymer capacitor electrolyte according to claim 4.