JP2002203742A - Redox type capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a condensed device which can be manufactured easily at a low cost and has superior input/output characteristics and has a large capacitance. SOLUTION: A redox type capacitor comprises an electrode which comprises conductive high molecules and a carrier for carrying the conductive high melecules, and a nonaqueous electrolyte which comprises an organic solvent and support salt dissolved in the organic solvent. The nonaqueous electolyte is added with a conductive high molecular monomer of the above molecules, and the conductive high molecules are formed by polymerization of the conductive high molecular monomers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor, and more particularly to a redox capacitor utilizing an oxidation-reduction reaction.

[0002]

2. Description of the Related Art In recent years, the demand for power storage devices has been increasing due to advances in microelectronics. Power storage devices are required to be smaller and thinner and have a large capacity. Attention has been paid to lithium secondary batteries and high-capacity capacitors represented by electric double-layer capacitors as such power storage devices.

In general, a lithium secondary battery has a large capacity, but can take out a large output in a short time and can charge a large amount of power in a short time. I can't say. on the other hand,
The electric double layer capacitor is expected because of its excellent short-time input / output characteristics, but has a problem of small capacity.

Normally, porous graphite is used as an active material of an electric double layer capacitor. Since an electric double layer is formed at an interface between an electrolytic solution and an active material, the larger the surface area of graphite as an active material, the larger the capacity of the capacitor. Capacity increases. In order to increase the surface area of graphite, it is sufficient to reduce the size of the pores of graphite, and in fact, it is known that as the pores are reduced and the surface area of graphite is increased, the capacitance of the capacitor increases. I have. On the other hand, when the pores are made smaller, the mobility of the electrolytic solution becomes smaller. Therefore, the internal resistance of the capacitor increases, and it becomes difficult to input and output at a large rate. That is, if the capacity is increased, the input / output characteristics originally possessed will be degraded. Therefore,
It is very difficult to realize an electric double layer capacitor having excellent input / output characteristics and large capacity.

[0005] Accordingly, a redox capacitor, which is a system in which an active material itself stores electricity by an oxidation-reduction reaction, has attracted attention. Redox capacitors are also called supercapacitors, and are expected to have large capacitance in addition to the conventional excellent input / output characteristics. As the active material, conductive polymers capable of doping / dedoping both cations and anions have been studied.

[0006]

Generally, to construct a redox capacitor using a conductive polymer, a conductive polymer is previously synthesized by a polymerization reaction, and the synthesized conductive polymer is synthesized. The method of using for an electrode is considered. However, since the conductive polymer is chemically active, when handled in the air, the conjugated system is broken and the conductivity is reduced. Therefore, the above method requires a special environment, equipment, and the like in order to assemble the capacitor, and is not practical.

In view of such a situation, the present inventor has conducted intensive studies, and as a result, instead of previously synthesizing a conductive polymer by a polymerization reaction, a conductive polymer monomer was added to an electrolytic solution constituting a capacitor. It has been found that a redox-type capacitor can be easily formed by adding and chemically or electrochemically polymerizing in a case.

[0008] The present invention has been made based on the above findings, and a conductive polymer produced by polymerization of a conductive polymer monomer is added to an electrolytic solution, and the conductive polymer is used as an electrode active material. It is an object to provide a power storage device which can be easily manufactured at low cost, has excellent input / output characteristics, and has a large capacity.

[0009]

According to the present invention, there is provided a redox capacitor comprising an electrode comprising a conductive polymer and a carrier for supporting the conductive polymer, a non-aqueous solution prepared by dissolving a supporting salt in an organic solvent. A non-aqueous electrolyte, a conductive polymer monomer being a monomer of the conductive polymer is added to the non-aqueous electrolyte, and the conductive polymer is The conductive polymer monomer is formed by polymerization.

That is, the redox capacitor of the present invention is produced by assembling components such as electrodes and then chemically or electrochemically polymerizing the conductive polymer monomer added to the non-aqueous electrolyte. A conductive polymer is used as an electrode active material.

Here, “electrochemical polymerization” means:
It means that polymerization is performed by applying a predetermined voltage. Further, “chemically polymerize” means polymerizing without applying a voltage. For example, when a transition metal composite oxide is used as the carrier, the conductive polymer monomer uses the transition metal contained in the carrier as a catalyst,
It polymerizes spontaneously without applying voltage.

In the redox capacitor of the present invention, a conductive polymer monomer is added to a non-aqueous electrolyte constituting a capacitor, instead of using a separately synthesized conductive polymer as in the prior art. And a conductive polymer produced by polymerizing the monomer. Then, the generated conductive polymer covers the surface of the carrier, and the carrier covered with the conductive polymer functions as an electrode. Therefore, the redox capacitor of the present invention does not require the special environment and equipment described above, and is a redox capacitor that can be easily manufactured at low cost.

The conductive polymer may be a cation and / or
Alternatively, the function is exhibited by incorporating anions between molecules, not on the surface of molecular crystals. Therefore, unlike the electric double layer capacitor, the capacity of the redox capacitor of the present invention is determined not by the surface area of the active material but by the volume of the active material. That is, it is determined by the volume of the conductive polymer. Accordingly, a redox capacitor having excellent input / output characteristics and a large capacity can be obtained without the above-described problems.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a redox capacitor according to the present invention will be described in detail below with respect to respective items of electrodes, a non-aqueous electrolyte, and production of a redox capacitor.

<Electrode> (1) Conductive polymer The conductive polymer contained in the electrode constituting the redox capacitor of the present invention is a monomer of the conductive polymer added to the non-aqueous electrolyte. It is a conductive polymer formed by polymerization of a conductive polymer monomer. Here, the conductive polymer monomer to be added to the non-aqueous electrolyte is not particularly limited. For example, acetylene, acetylene derivative, thiophene, thiophene derivative, pyrrole, pyrrole derivative, naphthene, naphthene derivative, phenylvinylene , Selenophene, furan and the like can be used. Among them, acetylene, acetylene derivatives, thiophene, thiophene derivatives, pyrrole, pyrrole derivatives, naphthenes, and naphthene derivatives are preferably used from the viewpoint that polymerization proceeds relatively easily.

In consideration of conductivity, it is desirable to use acetylene or an acetylene derivative.
In particular, it is desirable to use a substituted acetylene such as 2-butyne because of easy handling. In consideration of the fact that thiophene or a thiophene derivative is more preferably used in consideration of the fact that the thiophene is more easily polymerized, it is preferable to use thiophene or a thiophene derivative. -It is desirable to use hexylthiophene. In addition, from the viewpoint that the obtained polymer shows good conductivity, it is desirable to use isothianaphthene.

The conductive polymer may be formed by chemically or electrochemically polymerizing a conductive polymer monomer which is a monomer of the conductive polymer. The polymerization method will be described later.

(2) Carrier The carrier included in the electrode constituting the redox capacitor of the present invention supports the above conductive polymer. The support is not particularly limited as long as it is a chemically and electrochemically stable material. For example, in addition to a copper plate and a platinum foil which also function as a current collector, a carbon material, a transition metal composite oxide, or the like which is supported by the current collector and forms an electrode can be used. Above all, it is desirable to use a carbon material, a transition metal composite oxide, or the like from the viewpoint that the electrode area is large and the power storage capacity is large. In this case, a mixture of a carbon material, a powder of a transition metal composite oxide, and a binder is compression-bonded to a surface of a metal mesh or foil serving as a current collector. What is necessary is just to form.

When the capacity of the capacitor is controlled by the shape of the carrier, it is preferable to use a carbon material. For example, natural graphite, spherical or fibrous artificial graphite, easily graphitizable carbon such as coke, phenol resin Non-graphitizable carbon such as a fired body can be used. When a transition metal composite oxide is used from the viewpoint that polymerization of a conductive polymer monomer can be performed more easily using a transition metal as a catalyst, for example, MnO ₂ , V ₂ O ₅ , LiC
oO ₂ , LiNiO ₂ or the like can be used. Among them,
Considering that it is inexpensive and has high polymerization activity, it is desirable to use MnO ₂ . When considering supply of ions from the carrier, LiNiO ₂
It is desirable to use In addition, materials such as a carbon material and a transition metal composite oxide may be used alone or in combination.

When a transition metal composite oxide or the like is used, it is preferable to use a mixed conductive material in order to further improve the input / output characteristics. Examples of the conductive material include Ketjen black, acetylene black, graphite, and the like. Examples of the binder that plays a role of binding the carbon material, the support such as the transition metal composite oxide, and the conductive material mixed as necessary include polytetrafluoroethylene, polyvinylidene fluoride, and fluororubber. Thermoplastic resins such as fluororesins, polypropylene and polyethylene, and aqueous binders such as carboxymethylcellulose and polyvinyl alcohol can be used.

<Non-Aqueous Electrolyte> Redox-type capacitor of the present invention
The non-aqueous electrolyte that constitutes Pashita dissolves the supporting salt in
It is understood. Dissolved in organic solvent as supporting salt
What dissociates and dissociates may be used. For example, LiB
F_Four, LiPF₆, LiClO_Four, LiCF_ThreeSO _Three, Li
AsF₆, LiN (CF_ThreeSO_Two)_Two, LiN (C_TwoF_FiveSO
_Two)_TwoSuch as lithium salt, NaPF₆, NaBF_Four, NaCl
O_FourSodium salts, such as NH_FourPF₆, NH_FourBF_Four, NH_Four
ClO_FourAnd the like. In particular,
Because of its large separation and good solubility, Li
PF₆It is desirable to use In addition, these supporting salts
May be used alone, or these
Of these, two or more of them can be used in combination. In addition,
If the concentration of the supporting salt in the electrolyte is good ionic conductivity
For this reason, 0.5 to 1.5M is desirable.
No. If the concentration of the supporting salt is less than 0.5 M, sufficient
Amount cannot be obtained, and if it exceeds 1.5M,
Does the ionic conductivity decrease because the viscosity of the liquid increases?
It is.

It is desirable to use an aprotic organic solvent as the organic solvent for dissolving the supporting salt. When using a protic solvent represented by an aqueous or alcoholic,
This is because it is sometimes difficult to electrochemically polymerize the conductive polymer monomer due to the limited potential window. Further, when chemical polymerization is performed, there is a problem that active points are easily deactivated.

As the aprotic organic solvent, it is possible to use, for example, one or a mixture of two or more of cyclic carbonate, chain carbonate, cyclic ester, cyclic ether and chain ether. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate.Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.Examples of the cyclic ester include gamma butyrolactone, Examples of gamma valerolactone include cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, and examples of linear ethers include dimethoxyethane and ethylene glycol dimethyl ether. Any one of these can be used alone, or two or more can be used in combination.

The electrolyte has a high dielectric constant to promote dissociation of the supporting salt, has a low viscosity so as not to hinder the movement of ions, and has a resistance to electrochemical oxidation-reduction. High performance is required. Therefore, in particular,
Carbonates are suitable as the solvent. For example, it is desirable to use a mixture of ethylene carbonate or the like as a high dielectric constant solvent and diethyl carbonate or the like as a low viscosity solvent.

The non-aqueous electrolyte constituting the redox capacitor of the present invention further contains the above-mentioned conductive polymer monomer. The proportion of the conductive polymer monomer added to the non-aqueous electrolyte is desirably 0.5 to 10% by volume when the total volume of the non-aqueous electrolyte is 100%. 0.5
If the content is less than% by volume, the conductive high molecular weight to be formed is smaller than that in the appropriate range, so that a sufficient function as a capacitor may not be achieved. On the other hand, if it is more than 10% by volume, the amount of the conductive polymer formed is larger than that in the appropriate range, so that the conductive polymer may be formed so as to straddle between the electrodes and short-circuit may occur. It is. In particular, in order to apply the conductive polymer to the entire surface of the carrier and exhibit a sufficient function as a capacitor, it is desirable that the addition ratio of the conductive polymer monomer be 0.5 to 5% by volume. Note that the conductive polymer monomer is easily dissolved in the electrolytic solution, and thus may be added to the electrolytic solution at the time of manufacturing the capacitor.

<Preparation of Redox Capacitor> (1) Assembly of Capacitor In the redox capacitor of the present invention, an electrode body is formed by facing at least two or more electrodes including the above-described carrier. Each electrode may use the same kind of carrier or may use different kinds of carriers. Then, a separator is interposed between the electrodes. The separator may be any as long as it separates the electrodes and holds the electrolytic solution. For example, microporous polyethylene, microporous polypropylene, a nonwoven fabric of polyethylene or polypropylene, a nonwoven fabric made of paper, or the like can be used.

Then, the electrode body is housed in a predetermined case,
A connection between the electric body and a terminal leading to the outside is made by using a current collecting lead or the like, the electrode body is impregnated with the non-aqueous electrolyte, and the case is closed to assemble a redox capacitor.

(2) Formation of Conductive Polymer The conductive polymer contained in the electrode constituting the redox capacitor of the present invention is formed by chemically or electrochemically adding a conductive polymer monomer added to a non-aqueous electrolyte. It is formed by polymerizing to. The polymerization method is, for example, when a transition metal composite oxide is used as a carrier, the transition metal acts as a catalyst for polymerization, so that no voltage is applied after assembling the capacitor, and the 60
This can be done by leaving it for about a minute. Also,
When the transition metal composite oxide is not used as the support,
After assembling the capacitor, polymerization can be performed by applying a predetermined voltage by a general charging method. In this case, it is desirable to apply a voltage of about 3 to 4.5 V using lithium as a reference electrode.

<Allowance of Other Embodiments> The embodiments of the redox capacitor of the present invention have been described above.
The above-described embodiment is merely an embodiment, and the redox capacitor of the present invention can be implemented in various forms including various modifications and improvements based on the knowledge of those skilled in the art, including the above-described embodiment. it can.

It is to be noted that the capacitor is formed not in the case that is a component of the capacitor but in a separate container using an electrode in which a conductive polymer is formed by chemically or electrolytically polymerizing a conductive polymer monomer separately. A configuration is also conceivable. The redox capacitor of the present invention also includes a capacitor composed of an electrode using the conductive polymer formed as described above. However, since the conductive polymer produced by polymerization is chemically unstable as described above, it is necessary to pay sufficient attention to handling. In such an embodiment, the manufacturing process of the capacitor itself becomes complicated. . Therefore, it is more desirable to carry out in the above embodiment.

[0031]

EXAMPLES Based on the above embodiment, various redox capacitors having different conductive polymer monomers added to the non-aqueous electrolyte were manufactured. For comparison, a redox capacitor in which a conductive polymer monomer was not added to the non-aqueous electrolyte was also manufactured. Then, the capacity of each capacitor was evaluated. Hereinafter, the fabricated redox capacitors and the evaluation of their capacitance will be described in order.

<Prepared Redox Capacitor> (1) An electrode was formed using MnO ₂ as the redox capacitor carrier of Example 1. 5 parts by weight of polytetrafluoroethylene as a binder was mixed with 95 parts by weight of powdered MnO ₂ , and this mixed powder was applied to the surface of a Ni mesh serving as a current collector by about 4 ton / cm ^2.
And dried at 120 ° C. for 5 hours to obtain an electrode. The size of the electrode was 10 mmφ. Two of these electrodes have a thickness of 2
The electrodes were opposed to each other via a 5 μm, 19 mmφ polyethylene separator.

The electrode body was inserted into a case (30 mmφ × 3 mm), impregnated with 500 μL of a non-aqueous electrolyte, and then the case was closed to assemble a redox capacitor. The non-aqueous electrolyte is prepared by mixing LiP in a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 3: 7.
The F ₆ was dissolved at a concentration of 1M, it was made by adding further thiophene as a conductive polymer monomer in a proportion of 2.5% by volume. After assembling the capacitor, it was left for about 30 minutes to polymerize the conductive polymer monomer to form a conductive polymer on the surface of the carrier. The capacitor manufactured in this manner was used as a redox capacitor of Example 1.

(2) Redox capacitors of Examples 2 to 4 In the redox capacitors of Example 1, only the type of conductive polymer monomer added to the non-aqueous electrolyte was changed as follows, Was manufactured. That is, the capacitor in which thiophene was changed to 2-butyne was used in Example 2, the capacitor in which thiophene was changed to 3-hexylthiophene was Example 3, and the capacitor in which thiophene was changed to isothianaphthene was used as the redox capacitor of Example 4. .

(3) Redox Capacitor of Comparative Example 1 In the redox capacitor of Example 1, except that the conductive polymer monomer was not added to the non-aqueous electrolyte, the capacitor was manufactured in the same manner as in Example 1. The redox capacitor of Comparative Example 1 was manufactured.

(4) An electrode was formed using LiNiO ₂ as the redox capacitor carrier of Example 5. Example 1 except that LiNiO ₂ was used as the carrier.
A capacitor manufactured in the same manner as the capacitor of Example 5 was used as a redox capacitor of Example 5.

(5) Redox capacitors of Examples 6 to 8 In the redox capacitors of Example 5, only the type of conductive polymer monomer added to the non-aqueous electrolyte was changed as follows, Was manufactured. That is, the capacitor in which thiophene was changed to 2-butyne was used in Example 6, the capacitor in which thiophene was changed to 3-hexylthiophene was Example 7, and the capacitor in which thiophene was changed to isothianaphthene was used as the redox capacitor of Example 8. .

(6) Redox Capacitor of Comparative Example 2 In the redox capacitor of Example 5, except that the conductive polymer monomer was not added to the nonaqueous electrolyte, a capacitor was prepared in the same manner as in Example 5. The redox capacitor of Comparative Example 2 was manufactured.

<Evaluation of Capacitance> The capacitance of each of the fabricated redox capacitors of Examples 1 to 8 and Comparative Examples 1 and 2 was measured using cyclic voltammetry (CV). The measurement conditions were as follows: at 25 ° C., a scanning speed of 1 mV / s,
The voltage range was -1 to 1V. And the obtained current-
The capacity of each capacitor was calculated from the voltage curve. The capacity is
It was determined as the quantity of electricity per unit weight of the active material (support + conductive polymer) at the electrode of each capacitor. Table 1 shows the results.

[0040]

[Table 1]

From Table 1, it can be seen that the capacitors of Comparative Examples 1 and 2 in which the conductive polymer monomer was not added have extremely small capacities. That is, the capacitors of Comparative Examples 1 and 2 are merely electric double layer capacitors. In contrast, the capacitors of Examples 1 to 8 in which the conductive polymer monomer was added to the non-aqueous electrolyte had a large capacity, and the conductive polymer monomer added to the non-aqueous electrolyte was polymerized and formed on the surface of the carrier. It was confirmed that the obtained conductive polymer effectively functioned as an active material.

Further, the capacitance of the capacitors of Examples 1 to 4 was as large as about 4 to 5 times the capacitance of the capacitors of Examples 5 to 8. The reason is that Mn as a carrier
This is probably because O ₂ has a higher catalytic activity for monomer polymerization than LiNiO ₂ .

[0043]

According to the redox capacitor of the present invention, a conductive polymer monomer is added to an electrolytic solution, and a conductive polymer produced by polymerization of the conductive polymer monomer is used as an electrode active material. It can be easily manufactured at low cost,
The power storage device has excellent input / output characteristics and a large capacity.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 4/62 H01G 9/00 301A 10/40 9/22 (72) Inventor Yoshio Ukyo Yoshikatsu Ukyo Aichi-gun Aichi-gun Nagakute No. 41, Machidai-Cho, Chumichi Yokomichi 1 F-term in Toyota Central R & D Laboratories, Inc. (Reference) 5H029 AJ02 AJ03 AJ14 AK16 AL16 AM02 AM03 AM05 AM07 BJ04 DJ07 DJ13 EJ04 EJ05 HJ07 5H050 AA02 AA08 AA19 BA00 CA20 CB20 DA04 EA01 EA08 FA02 FA02

Claims (6)

[Claims] 1. A redox capacitor comprising an electrode comprising a conductive polymer and a carrier for supporting the conductive polymer, and a non-aqueous electrolyte in which a supporting salt is dissolved in an organic solvent. A conductive polymer monomer that is a monomer of the conductive polymer is added to the non-aqueous electrolyte, and the conductive polymer is formed by polymerizing the conductive polymer monomer. A redox-type capacitor, characterized in that: 2. The carrier according to claim 1, wherein the carrier is at least one selected from a carbon material and a transition metal composite oxide.
4. A redox capacitor according to claim 1. 3. The redox capacitor according to claim 1, wherein the supporting salt is at least one selected from a lithium salt, a sodium salt, and an ammonium salt. 4. The redox capacitor according to claim 1, wherein the organic solvent is a carbonic acid ester. 5. The conductive polymer monomer according to claim 1, wherein the conductive polymer monomer is at least one selected from acetylene, acetylene derivatives, thiophene, thiophene derivatives, pyrrole, pyrrole derivatives, naphthenes, and naphthene derivatives. 4. A redox capacitor according to claim 1. 6. The method according to claim 1, wherein the conductive polymer monomer is added in an amount of 0.5 to 10% by volume (100% by volume of the entire nonaqueous electrolyte). Redox capacitors.