JP4739067B2 - Electric double layer capacitor - Google Patents

Description

  The present invention relates to an electric double layer capacitor that performs charging and discharging based on an electric double layer formed at the interface between a polarizable electrode and an electrolyte, and more specifically, a novel electrode for increasing the capacity of a capacitor. About.

  The electric double layer capacitor is composed of a polarizable electrode and an electrolytic solution, and the electrolytic solution exists between the positive and negative electrodes facing each other. An electric double layer is formed in each of the electrodes and the electrolyte solution, and is a kind of capacitor in which electric charges are accumulated in the electric double layer. This electric double layer capacitor has a long charge / discharge cycle life and has been mainly used for a backup power source of electronic equipment.

  The electric double layer capacitor is generally manufactured using materials as described below. That is, polarizable electrodes used as the positive electrode and the negative electrode have activated carbon as a main constituent material. Examples of the activated carbon include gas, water vapor, carbon dioxide gas, alkali hydroxide or zinc chloride after carbonization of various carbon-containing materials such as coconut husk, sawdust, phenol resin, polyacrylic resin, and coke of petroleum and coal. What was manufactured by activating in the presence of etc. is used. It is also known that activated carbon fibers produced by subjecting carbon-containing fibers to the same treatment as described above are preferably used. Usually, these activated carbons are granulated into powder particles and used as a material for the polarizable electrode.

  A mixture of such activated carbon powder to which a small amount of acetylene black, a binder such as polytetrafluoroethylene, polyvinylidene fluoride, or a copolymer thereof is added is pressure-bonded to a current collector, and then heated, pressurized, etc. And used as a positive electrode and a negative electrode in a coin shape or a sheet shape. (Supervised by Atsushi Nishino, Katsuhiko Naoi, Large Capacitor Technology and Materials II-Latest Trends in Electric Double Layer Capacitors and Supercapacitors-Chapter 4, Section 3, Atsushi Nishino, CMC Publishing, published January 10, 2003)

  As the electrolytic solution interposed between the positive electrode and the negative electrode, an aqueous solution such as sulfuric acid, potassium hydroxide or sodium hydroxide, or a neutral salt is used. For example, JP 2001-230163 A, JP 2001-250742 A, and JP 2003-229335 and the like. Further, a non-aqueous organic solvent in which tetraethylammonium tetrafluoroborate, triethylmethylammonium tetrafluoroborate, tetraphethylphosphonium tetrafluoroborate, or the like is dissolved in an aprotic organic solvent such as propylene carbonate or γ-butyrolactone is used. JP 2004-048005 A, JP 2002-313686 A, and the like.

It is known that a polypropylene non-woven fabric, a glass fiber non-woven fabric, or the like is used for the separator located in the electrolytic solution.
JP 2001-230163 A JP 2001-250742 A JP 2003-229335 A JP 2004-048005 A JP 2002-313686 A Supervised by Atsushi Nishino, Katsuhiko Naoi, Large Capacitor Technology and Materials II-Latest Trends in Electric Double Layer Capacitors and Supercapacitors-Chapter 4, Section 3 Atsushi Nishino, CM Publishing, January 10, 2003

  Electric double layer capacitors manufactured by these technologies are used as backup power sources for electronic devices as described above. Recently, they are used in a hybrid form with secondary batteries and solar cells, or in wind power generation. It has come to be used for storage of the obtained electricity. In order to use in these applications or wider applications, the current capacity is not fully satisfied, and further higher output, higher capacity, higher energy density, lower price, etc. are required. .

  The inventor of the present application, when producing a polarizable electrode, for example, by adding a high molecular compound having a polar part to an activated carbon material as seen in DNA molecules, an electric double layer capacitor having a high output and a high capacity is obtained. As a result, the present invention has been completed and the above-described problems have been solved.

  That is, the present invention is an electric double layer capacitor comprising at least an electrolytic solution in which an ionic substance is dissolved in water and a polarizable electrode using a carbon material as a main component, and the polarizable electrode has a hydrogen bond Alternatively, it is an electric double layer capacitor which is an electrode formed by adding a polymer having a polar part capable of coordinate bonding to the carbon material.

  In a preferred aspect of the present invention, the polymer compound is an electric double layer capacitor, wherein the polymer compound is a polymer compound having at least one polar portion per molecular weight of 400 on average.

  In a more preferred embodiment, the present invention is an electric double layer capacitor in which the polymer compound is a polymer having a base capable of hydrogen bonding as a polar moiety.

  More specifically, the present invention is an electric double layer capacitor in which the base capable of hydrogen bonding is a nitrogen fluorinated base.

  More specifically, the present invention is an electric double layer capacitor in which the nitrogen fluorinated cyclic base is a base selected from adenine, guanine, cytosine, uracil or thymine.

  More specifically, the present invention is an electric double layer capacitor in which the polymer compound is a natural product-derived or synthesized DNA, RNA or a salt thereof.

  From another viewpoint, the present invention is an electric double layer capacitor in which the amount of the polymer compound added is in the range of 0.5 to 10 wt% with respect to the carbon material.

  In a preferred embodiment, the present invention is an electric double layer capacitor in which the carbon material is activated carbon.

  Further, the present invention provides an electric double layer capacitor, wherein the polarizable electrode using a carbon material as the main component is an electrode containing polytetrafluoroethylene, polyvinylidene fluoride or a copolymer thereof as a binder. is there.

  More specifically, the present invention is an electric double layer capacitor in which the content of the binder is in the range of 0.5 to 10 wt% of the total amount of the carbon material and the polymer compound.

  Furthermore, the present invention is an electric double layer capacitor in which the electrolytic solution further contains an alcohol.

  Moreover, this invention is an electric double layer capacitor whose pH of the said electrolyte solution is the range of 1-12.

  In a polarizable electrode prepared by adding a polymer compound having a polar part according to the present invention to activated carbon particles, the electrolyte is contained in the electrode because the polar part of this type of polymer compound is hydrophilic. It is thought that the area of the electric double layer interface formed at the interface between the activated carbon and the electrolytic solution increases easily by entering the pores and grain boundaries. As a result, the amount of adsorbed and desorbed ions from the electrolyte on the activated carbon surface corresponding to charge accumulation increases, and the rate of adsorption and desorption increases, resulting in high output and high capacitance. Is considered to be obtained. An electric double layer capacitor configured using such an electrode is suitable for use in a hybrid form with a secondary battery or a solar battery, for storing electricity obtained by wind power generation, or the like. It is used suitably for a use.

  Hereinafter, an electric double layer capacitor having an electrode prepared by adding a polymer compound having a polar part capable of hydrogen bonding or coordination bonding according to the present invention to the carbon material will be described in detail.

  The present invention relates to an electric double layer capacitor comprising at least an electrolytic solution in which an ionic substance is dissolved in water and a polarizable electrode using a carbon material as a main component, and the polarizable electrode has a hydrogen bond Alternatively, it is an electric double layer capacitor which is an electrode formed by adding a polymer compound having a polar part capable of coordination bonding to the carbon material. As mentioned immediately above, the hydrophilicity of the polar part of this type of polymer compound facilitates the entry of the electrolyte into the pores and grain boundaries within the electrode, and thus the activated carbon surface corresponding to charge accumulation. It is considered that the amount of ions adsorbed and desorbed from within the electrolyte increases, and the rate of adsorption and desorption increases, and high output and high capacitance can be achieved.

As the polymer compound having a polar part, a polymer compound having at least one polar part per molecular weight of 400 on average is suitably used. If the polar portion is small, sufficient hydrophilicity cannot be obtained, and the original purpose cannot be achieved. Therefore, the described ratio is required for the existence ratio of the polar portion.
As the polar moiety, atoms such as nitrogen, oxygen, sulfur, and phosphorus are preferably used, and substituents such as a hydroxyl group, a nitro group, a sulfonic acid group, a carboxyl group, and a phosphinic acid group, an ether bond, a thioether bond, and a disulfide bond. Bond structures such as ketones can be used. For example, the presence of a nitrogen heterocyclic structure such as an azole in a polymer compound chain or as a side chain can also be effectively used as a polar moiety. Such a polar part preferably has a structural form capable of hydrogen bonding or coordination bond, and more preferably a polar part capable of hydrogen bonding. Among them, a polymer compound having a base capable of hydrogen bonding as a polar moiety as a side chain is more preferably used.

  Typical examples of the polymer having a polar moiety described above that can be used in the present invention include DNA, RNA, and salts thereof. Nucleic acids modified in various forms can also be used. A polymer compound in which a base having a structure different from that of natural DNA (for example, azoles) is introduced into the base part, a polymer compound having a nucleobase in the side chain, but the polymer backbone is not sugar-phosphate A polymer compound in which a substituent is introduced into this base is preferably used. In addition, a polymer compound in which the phosphate portion of the DNA main chain is converted to a long-chain quaternary ammonium salt is also preferably used.

また、例えば特開２００４−３３１５７４や特開２００３−３３５７９４のような方法を利用して、核酸塩基にカルボニル基やメチレン基を介して下記の式(II)及び式(III) で表される基やチオール基を導入した通常の塩基に置換基を導入した高分子化合物を合成して利用することができる。

(ただし、Ｘ及びＹはＨ又はＢｒを表す。)

また、ＤＮＡ主鎖のリン酸部分を長鎖の４級アンモニウム塩化した高分子化合物として、例えば下記の式(IV)でリン酸部分を４級アンモニウム塩化した高分子化合物などが好適に用いられる。

(岡畑恵雄、川崎剛美、未来材料第３巻第３号４６〜５１頁(２００３)発行(株)エヌ・ティー・エス) Nucleic acids modified in various forms as described above can be obtained by known methods.
In order to prepare a polymer compound having a nucleobase in the side chain but the polymer main chain skeleton is not sugar-phosphate, the following formula (I ) Can be obtained and added to the electrode of the electric double layer capacitor of the present invention.

In addition, for example, groups represented by the following formulas (II) and (III) can be used for the nucleobase via a carbonyl group or a methylene group using a method such as JP-A-2004-331574 or JP-A-2003-335794. Alternatively, a polymer compound in which a substituent is introduced into a normal base into which a thiol group is introduced can be synthesized and used.

(However, X and Y represent H or Br.)

Further, as a polymer compound obtained by subjecting the phosphate portion of the DNA main chain to a long-chain quaternary ammonium salt, for example, a polymer compound obtained by subjecting the phosphate portion to a quaternary ammonium salt according to the following formula (IV) is preferably used.

(Mr. Okahata, Takemi Kawasaki, Future Materials, Vol. 3, No. 3, pp. 46-51 (2003), NTT)

  In addition, a base selected from adenine, guanine, cytosine, uracil or thymine so as to be present in DNA or RNA derived from natural products is also preferably used. Any of DNA, RNA, or salts thereof derived from natural products or synthesized is preferably used. As a natural product-derived DNA, RNA or a salt thereof, the organism derived from the natural product is not particularly limited, but those extracted from camellia or camellia are preferably used at low cost.

  If the amount of the hydrophilic polymer compound, DNA or salt thereof added is 0.5 weight percent or less, the hydrophilic effect of these additives will be insufficient, resulting in high output and high electrostatic capacity of the electric double layer capacitor. Capacitance can be suppressed. In addition, when the weight is 10.0 weight percent or more, the weight of the activated carbon in the polarizable electrode decreases, and in the polarizable electrode in which activated carbon particles are used, electron transfer based on direct contact between the activated carbon particles As a result, the high output and high capacitance of the electric double layer capacitor are hindered. For this reason, the addition amount of the polymer compound is preferably in the range of 0.5 to 10 wt% with respect to the carbon material.

  As the carbon material used as the main material of the polarizable electrode used as the positive electrode and the negative electrode in the present invention, known activated carbon is used. Moreover, the thing which grind | pulverized the activated carbon fiber as activated carbon and was made into the particle | grains is used suitably.

In the present invention, a binder can be used to bind the carbon material in preparing the polarizable electrode. Various kinds of natural or synthetic known binders can be used as the binder. Among them, polytetrafluoroethylene, polyvinylidene fluoride, or a copolymer thereof is extremely suitable because of its adhesive effect and ease of handling. Used for.
These binders are indispensable for binding activated carbon, which is the main constituent material, as an electrode. On the other hand, these compounds are hydrophobic, so if the amount added is too large, the activity in the electrode will be increased. The area of the interface where the carbonized carbon and the electrolytic solution are in contact with each other to form the electric double layer is not sufficiently obtained, and therefore, the amount of adsorption of ions in the electrolytic solution necessary for charge accumulation to the activated carbon is not sufficient, The electric resistance of the polarizable electrode increases, and high electrostatic capacity and high output cannot be achieved due to electric loss. On the other hand, if the addition amount of the binder is too small, the adhesion becomes insufficient, the mechanical properties of the electrode become poor, and it becomes difficult to maintain the shape. An addition amount of 0.5 to 10.0 weight percent of the total weight of the molecular compound is preferably used.

The electric double layer capacitor of the present invention uses an aqueous solution as an electrolyte as described above. As the water-soluble electrolyte, it is effective if it contains a cation and an anion, and any known organic, inorganic acid, base, or salt solution can be used. In the electric double layer capacitor of the present invention, In the case where the pH is 0 or less or 14.0 or more, the polar polymer compound added to the carbon material may be decomposed by a side reaction such as hydrolysis. Preferably used. For this reason, a salt is used more suitably among an acid, a base, and a salt. As the salt, any of strong acid, strong base, weak acid, and weak base salts can be used. Among them, NaCl, NaBr, NH ₄ Cl, NH ₄ ClO ₄ , Na ₂ SO ₃ , Na ₂ SO ₄ , NaHCO _3, or these Mixtures are preferably used.
An aqueous solution having a pH in the range of 1 to 12 has low corrosivity, low danger to the human body, no flammability or ignitability, and is cheaper and easier to handle than an organic electrolyte. So practicality is high.

  Furthermore, in order to improve incidental characteristics such as freezing prevention at a low temperature, such an electrolytic solution can contain an organic solvent compatible with water as long as flammability and ignitability do not occur. As the organic solvent, alcohols such as ethylene glycol and glycol ether are particularly preferably used.

  A cross-sectional view of a preferred embodiment of the electric double layer capacitor of the present invention is shown in FIG. A filter paper 3 (separator) impregnated with an electrolytic solution is located between the positive electrode 1 and the negative electrode 2. The positive electrode 1 and the negative electrode 2 are in contact with and electrically connected to current collectors 4 and 5 made of an insoluble metal, respectively. An insulating chamber frame gasket 6 is disposed to seal the electrolyte. All of these are pressed by the insulating end plate 7 using bolts 8 and 9.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples, Arbitrary deformation | transformation can be made within the range of the technical idea of this invention.

Example 1
Adhesion to activated carbon powder (average particle size: about 5 μm, BET surface area: 800 m ² / g, pore volume: 0.36 ml / g, average pore size: 1.8 nm, acidic group content: 2.2 meq / g) DNA-Na salt prepared by extraction from polytetrafluoroethylene and powdery camellia white powder were mixed at a mass ratio of 95: 2: 3, pressed into a film, and a diameter of 1.2 cm Cut out into a circle. The amount of this mixture used was 30 mg per 1.2 cm diameter disk. This film was bonded to a 1.2 cm diameter circular current collector made of an insoluble metal foil to produce an electrode, and a glass fiber filter paper (Toyo Filter Paper GB) impregnated with an electrolyte as a separator between the two electrodes. −100R) and pressed with an insulating end plate, an electric double layer capacitor having the structure shown in FIG. 1 was assembled. A 3.5 mol / l NaBr aqueous solution (pH: 5.2) was used as the electrolytic solution. After performing pre-charging / discharging 200 times at a current density of ^2.5 mA / cm ² in a voltage range of 0.9 to 0.0 V at 25 ° C., 20 mA / in a voltage range of 0.9 to 0.0 V. The electrostatic capacity in the discharging process at the 1000th cycle when charging / discharging at a current density of cm ² was 3.8F.

Example 2
As a result of experimenting under the same conditions as in Example 1 except that the current density during charging / discharging of the electric double layer capacitor was set to 5 mA / cm ² , the capacitance of the electric double layer capacitor was 6.4F.

Comparative Example 1
Example of manufacturing a polarizable electrode of an electric double layer capacitor, except that the mass was 95: 5 of polytetrafluoroethylene in activated carbon powder and the electrode was prepared without adding a DNA-Na salt. As a result of experimenting under the same condition as 1, the capacitance of the electric double layer capacitor was 0.51F.

Example 3
As a result of experimenting under the same conditions as in Example 1 except that a 4.0 mol / l NaCl aqueous solution (pH: 5.9) was used as the electrolyte when producing the electric double layer capacitor, the capacitance of the electric double layer capacitor was 2 .8F.

Comparative Example 2
As a result of experiments under the same conditions as in Comparative Example 1 except that a 4.0 mol / l NaCl aqueous solution (pH: 5.9) was used as the electrolytic solution for charging and discharging the electric double layer capacitor, The electric capacity was 1.3F.

Example 4
As a result of experiments under the same conditions as in Example 1 except that a 2.0 mol / l NH ₄ BF ₄ aqueous solution (pH: 2.0) was used as the electrolytic solution during the production of the electric double layer capacitor, the electrostatic capacitance of the electric double layer capacitor was The capacity was 2.8F.

Comparative Example 3
As a result of experiments under the same conditions as in Comparative Example 1 except that a 2.0 mol / l NH ₄ BF ₄ aqueous solution (pH: 2.0) was used as the electrolytic solution during the production of the electric double layer capacitor, the electrostatic capacitance of the electric double layer capacitor was The capacity was 1.1F.

Example 5
As a result of experiments under the same conditions as in Example 1 except that a 1.8 mol / l Na ₂ SO ₃ aqueous solution (pH: 10.8) was used as the electrolyte during the production of the electric double layer capacitor, the electrostatic capacitance of the electric double layer capacitor was The capacity was 4.9F.

Example 6
EXAMPLE Polyvinylidene fluoride was used as an adhesive when preparing a polarizable electrode, and after adding and kneading an adhesive and a DNA-Na salt of activated carbon to activated carbon powder, the sheet dried in a sheet form was polarizable. As a result of experimenting under the same conditions as in Example 1 except that they were used as electrodes, the capacitance of the electric double layer capacitor was 3.2F.

Example 7
As a result of experiments under the same conditions as in Example 1 except that the blending ratio of activated carbon powder, adhesive, and DNA-Na salt was 90: 5: 5 when producing a polarizable electrode, The capacitance was 2.8F.

Example 8
As a result of experiments under the same conditions as in Example 1 except that the electrode was prepared using a fibrous DNA-Na salt in place of the DNA-Na salt when producing a polarizable electrode, The electric capacity was 2.9F.

Example 9
When preparing a polarizable electrode, it was carried out except that the electrode was prepared using a polymer compound in which the phosphoric acid portion of the DNA was quaternary ammonium salted by the above formula (IV) instead of the DNA-Na salt. As a result of experimenting under the same conditions as in Example 1, the capacitance of the electric double layer capacitor was 3.9F.

It is sectional drawing of the electric double layer capacitor to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Current collector 5 Current collector 6 Gasket 7 End plate 8 Tightening bolt 9 Nut

Claims (7)

An electric double layer capacitor comprising at least an electrolytic solution in which an ionic substance is dissolved in water and a polarizable electrode using a carbon material as a main component, wherein the polarizable electrode contains DNA or a salt thereof as the carbon material An electric double layer capacitor, an electrode made by adding to The electric double layer capacitor according to claim 1 , wherein the amount of the DNA or salt thereof added is in the range of 0.5 to 10 wt% with respect to the carbon material. The electric double layer capacitor according to claim 1 or 2, wherein the carbon material is activated carbon. The electricity according to any one of claims 1 to 3 , wherein the polarizable electrode using a carbon material as the main component is an electrode containing polytetrafluoroethylene, polyvinylidene fluoride or a copolymer thereof as a binder. Double layer capacitor. The electric double layer capacitor according to any one of claims 1 to 4 , wherein a content of the binder is in a range of 0.5 to 10 wt% of a total amount of the carbon material and the polymer. The electric double layer capacitor according to any one of claims 1 to 5 , wherein the electrolytic solution contains alcohols. The electric double layer capacitor according to any one of claims 1 to 6 , wherein a pH of the electrolytic solution is in a range of 1 to 12.

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