JP2010157534A - Electrode for electrochemical device, and electrochemical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for an electrochemical device capable of providing an electrochemical device which improves cycle characteristics by suppressing corrosion of a current collector, in the electrode for the electrochemical device employing the current collector including through-holes passing through both sides. <P>SOLUTION: The electrode for the electrochemical device includes a current collector with through-holes passing through both sides and an active material layer containing an active material and a binder. The electrode for the electrochemical device is characterized in that an antacid material is contained in the active material layer, and the electrochemical device has the electrode for the electrochemical device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrode suitable for use in an electrochemical element having high energy density and high output density, and an electrochemical element using the electrode.

  In recent years, attention has been focused on electrochemical devices in which lithium ions are doped in advance on the positive electrode and / or the negative electrode in order to achieve both high energy density and high power density. In order to dope lithium ions into the electrode in advance, powdered lithium is mixed in advance with the electrode active material powder, or the foil active lithium is in electrical contact with the electrode active material and the binder. A chemical method in which lithium is ionized and immersed in an electrode active material by immersing it in an electrolytic solution in a non-aqueous state; in a non-aqueous solvent electrolyte containing a lithium salt as an electrolyte, An electrochemical method in which an electrode including an active material layer formed of a material and a binder is placed, a lithium metal electrode is placed on the other side, current is applied, and lithium ions are doped into the electrode active material is proposed. Has been. Furthermore, in patent document 1, the proposal which assembles a cell using the electrical power collector which has a through-hole, and performs dope in a cell is made, and the feasibility is increasing. (Patent Document 1)

  However, in Patent Document 1, since a current collector having a through hole is used, reliability and life characteristics are low and further improvement is required as compared with a current collector without a through hole. Therefore, in Patent Document 2, in order to improve reliability and life characteristics, a conductive layer made of a conductive material is formed on a current collector having a through hole, and an active material layer is formed after closing the through hole. An electrode is proposed.

JP-A-2005-203115 WO2004 / 097867

  However, in the method of forming a conductive layer made of a conductive material on a current collector having a through hole and closing the through hole to form an active material layer, the effect of improving reliability, life characteristics, particularly cycle characteristics is It was insufficient.

  Accordingly, an object of the present invention is an electrochemical device including a current collector having a through-hole penetrating the front and back surfaces and an electrode made of an active material layer, and has excellent cycle characteristics without reducing productivity. An object of the present invention is to provide an electrode for an electrochemical element capable of obtaining an electrochemical element.

  As a result of intensive studies to solve the above problems, the present inventors have found that the cause of the deterioration of the life characteristics is that the current collector is corroded by the acid generated by the reaction between the impurities in the electrochemical element and the electrolytic solution, and the current collector It was found that the binding between the body-active material layers and the conductivity were lowered. In particular, in an electrode using a current collector having a through hole, the contact area between the current collector and the active material layer is small, and therefore, a current collector for cycle characteristics as compared with an electrode using a current collector without a through hole. It was found that the influence of corrosion was great.

  Therefore, as a result of further intensive studies, the present inventor has included the antacid material in the positive electrode and / or the negative electrode, so that the acid generated by the reaction between the impurities in the electrochemical element and the electrolytic solution is consumed by the antacid material. As a result, it was found that the corrosion of the current collector is suppressed and the cycle characteristics of the electrochemical device are improved. In particular, in the case of an organic electrolyte and fluorine in the electrolyte, hydrofluoric acid is generated by the reaction between the residual moisture in the electrochemical element and the electrolyte, so that the current collector is severely corroded and the antacid material It has been found that the improvement of the cycle characteristics due to the inclusion of is remarkable.

Thus, according to the present invention, the following (1) to (6) are provided.
(1) An electrode for an electrochemical device comprising a current collector having a through-hole penetrating the front and back surfaces, and an electrode made of an active material layer containing an active material and a binder, and is controlled in the active material layer. An electrode for an electrochemical element comprising an acid material.

(2) The electrode for an electrochemical element according to (1), wherein the antacid material is at least one selected from the group consisting of metal carbonates, metal organic acid salts, silicates, and alkaline hydroxides. .

(3) The content of the antacid material in the active material layer is 0.01 to 50 parts by weight with respect to 100 parts by weight of the electrode active material, for the electrochemical element according to (1) or (2) electrode.

(4) The electrode for an electrochemical element according to any one of (1) to (3), wherein the electrolyte used for the electrochemical element is an organic electrolyte

(5) The electrode for an electrochemical element according to any one of (1) to (4), wherein the electrolytic solution contains fluorine as an electrolyte.

(6) An electrochemical element having the electrochemical element electrode according to any one of (1) to (5).

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to maintain the electrical contact in the interface of the collector and active material layer of the electrode for electrochemical devices using the collector which has a through-hole which penetrates front and back for a long period of time Thus, an electrode for an electrochemical device having excellent cycle characteristics can be obtained.

  An electrode for an electrochemical element of the present invention (hereinafter sometimes simply referred to as “electrode”) includes a current collector having a through-hole penetrating the front and back surfaces, and an active material layer containing an electrode active material and a binder. And an antacid material is contained in the active material layer.

<Active material layer>
The active material layer of the electrode of the present invention contains an electrode active material and a binder.

The active material used for the positive electrode may be any material that can reversibly dope lithium ions and anions such as tetrafluoroborate. Usually, an allotrope of carbon is used. The electrode active material used in the electric double layer capacitor can be widely used. In particular, those capable of forming an interface having a larger area even with the same weight, that is, those having a large specific surface area are preferred. Specifically, the specific surface area of ^{30 m} 2 / g or more, preferably preferably 500~5,000m ² / g, more preferably 1,000~3,000m ² / g. Specific examples of the allotrope of carbon include activated carbon, polyacene, carbon whisker, and graphite, and these powders or fibers can be used. A preferable electrode active material is activated carbon, and specific examples thereof include phenol-based, rayon-based, acrylic-based, pitch-based, and coconut shell-based activated carbon. These allotropes of carbon can be used alone or in combination of two or more as the active material. When carbon allotropes are used in combination, two or more types of carbon allotropes having different average particle diameters or particle size distributions may be used in combination. Further, a polyacene organic semiconductor (PAS) which is a heat-treated product of an aromatic condensation polymer and has a polyacene skeleton structure having a hydrogen atom / carbon atom atomic ratio of 0.50 to 0.05 can also be used suitably. .

  In addition, nonporous carbon having microcrystalline carbon similar to graphite and having an increased interlayer distance of the microcrystalline carbon can be used as the positive electrode active material. Such non-porous carbon is obtained by dry-distilling graphitized charcoal with microcrystals of a multilayer graphite structure at 700 to 850 ° C., then heat-treating with caustic at 800 to 900 ° C., and if necessary with heated steam. It is obtained by removing the residual alkali component.

  The active material used for the negative electrode is formed of a material that can be reversibly doped with lithium ions. Preferred examples of the negative electrode active material include carbon materials such as graphite, non-graphitizable carbon, hard carbon, and coke, and polyacene-based materials (PAS) described as the positive electrode active material. These carbon materials and PAS are obtained by carbonizing a phenol resin or the like, activated as necessary, and then pulverized.

  As the shape of the electrode active material, powder or fiber can be used.

  The volume average particle diameter of the electrode active material is 0.1 to 100 μm, preferably 1 to 50 μm, and more preferably 3 to 35 μm. It is preferable that the volume average particle diameter is in this range because the electrode can be easily molded and the capacity can be increased. The above-described electrode active materials can be used alone or in combination of two or more depending on the type of electrode for an electrochemical element. When the electrode active materials are used in combination, two or more types of electrode active materials having different average particle diameters or particle size distributions may be used in combination.

  The active material layer of the electrode of the present invention may contain a conductive auxiliary as required, and the type thereof is not particularly limited as long as it has conductivity. Specific examples include carbon allotropes or metals, and carbon allotropes are preferably used. Specifically, conductive carbon black such as furnace black, acetylene black, and ketjen black (registered trademark of Akzo Nobel Chemicals Bethloten Fennaut Shap); natural graphite, graphite such as artificial graphite; Particulate conductive aids that are: Moreover, the fibrous conductive support agent which consists of carbon allotropes, such as carbon fibers, such as a polyacrylonitrile type | system | group carbon fiber, a pitch type | system | group carbon fiber, and a vapor-grown carbon fiber; Examples of the conductive assistant made of metal include particulate conductive assistants such as titanium oxide, ruthenium oxide, aluminum, and nickel, and fibrous conductive assistants such as metal fibers. Among these, carbon black is preferable, and acetylene black and furnace black are more preferable.

  The volume average particle diameter of the conductive auxiliary agent is preferably smaller than the volume average particle diameter of the electrode active material, and is usually in the range of 0.001 to 10 μm, preferably 0.05 to 5 μm, more preferably 0.01 to 1 μm. It is. When the particle size of the conductive assistant is within this range, high conductivity can be obtained with a smaller amount of use. These conductive assistants can be used alone or in combination of two or more.

  The amount of the conductive assistant is usually 0.1 to 50 parts by weight, preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. By forming the electrode for an electrochemical element containing an amount of the conductive aid in this range, the capacity of the capacitor can be increased and the internal resistance can be decreased.

  The binder is a compound that can bind an electrode active material, a conductive aid, and the like. Examples of the binder include polymer compounds such as a fluorine polymer, a diene polymer, an acrylate polymer, polyimide, polyamide, and polyurethane. Among them, the binder is preferably an acrylate polymer, and has good binding properties with a current collector, improvement in electrode density by pressing, and internal resistance and flexibility of the obtained electrode. These binders can be used alone or in combination of two or more. Further, the binder may be a binder having a core-shell structure obtained by stepwise polymerization of a mixture of two or more monomers.

  The fluorine-based polymer is a polymer containing a monomer unit containing a fluorine atom. Specific examples of the fluoropolymer include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, ethylene / tetrafluoroethylene copolymer, ethylene / chlorotri Fluoroethylene copolymer and perfluoroethylene / propene copolymer may be mentioned. Among them, it is preferable to include polytetrafluoroethylene because it is easy to fibrillate and retain the electrode active material.

  The diene polymer is a homopolymer of a conjugated diene or a copolymer obtained by polymerizing a monomer mixture containing a conjugated diene, or a hydrogenated product thereof. The proportion of the conjugated diene in the monomer mixture is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more. Specific examples of the diene polymer include conjugated diene homopolymers such as polybutadiene and polyisoprene; aromatic vinyl / conjugated diene copolymers such as carboxy-modified styrene / butadiene copolymer (SBR); Examples thereof include vinyl cyanide / conjugated diene copolymers such as acrylonitrile / butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

  The acrylate polymer is preferably an acrylate polymer containing a monomer unit obtained by polymerizing an acrylic ester and / or a methacrylic ester, usually 50% by weight or more, preferably 70% by weight or more, and has high heat resistance. And the internal resistance of the electrode for electrochemical devices obtained can be made small. Specific examples of the acrylate polymer include, for example, 2-ethylhexyl acrylate / methacrylic acid / acrylonitrile copolymer, 2-ethylhexyl acrylate / methacrylic acid / methacrylonitrile copolymer, butyl acrylate / acrylonitrile copolymer. , Butyl acrylate / acrylic acid copolymer, 2-ethylhexyl acrylate / styrene / methacrylic acid copolymer, and butyl acrylate / methyl methacrylate / methacrylic acid copolymer, acrylic acid-2-ethylhexyl / acrylonitrile / itacon An acid copolymer etc. are mentioned.

  The glass transition temperature (Tg) of the binder is 50 ° C. or lower, preferably in the range of −100 to 0 ° C. When the Tg of the binder is within this range, the binding property is excellent with a small amount of use, the electrode strength is high, the flexibility is high, and the electrode density can be easily increased by a pressing process during electrode formation.

  The shape of the binder is most preferably particulate in order to minimize binding, increase in electrode capacity, and increase in internal resistance, for example, a binder such as latex. In a state in which the above particles are dispersed in a solvent, and powders obtained by drying such a dispersion.

  The particle size of the binder is not particularly limited, but is usually 0.001 to 100 μm, preferably 0.01 to 10 μm, more preferably 0.05 to 1 μm. When the average particle size of the binder is within this range, an excellent binding force can be imparted to the active material layer even when a small amount of the binder is used.

  The method for producing the binder is not particularly limited, and a known polymerization method such as an emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method, or a solution polymerization method can be employed. Among them, it is preferable to produce by an emulsion polymerization method because the particle diameter of the binder is easy to control.

  The usage-amount of a binder is 1-20 weight part normally with respect to 100 weight part of active materials, Preferably it is the range of 3-15 weight part.

  The active material layer of the electrode of the present invention may further contain a cellulose derivative. The cellulose derivative is a compound obtained by etherifying or esterifying at least a part of the hydroxyl group of cellulose, and is preferably water-soluble. The cellulose derivative used in the present invention usually does not have a glass transition point. Specific examples include carboxymethyl cellulose, carboxymethyl ethyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. These salts can also be used. Examples of the salt include ammonium salt and alkali metal salt. Among them, a salt of carboxymethyl cellulose is preferable, and an ammonium salt of carboxymethyl cellulose and a sodium salt of carboxymethyl cellulose are particularly preferable.

  The degree of etherification of the cellulose derivative is preferably 0.5 to 2, more preferably 0.5 to 1.5. Here, the degree of etherification is a value representing how many hydroxyl groups contained per 3 glucose units of cellulose are etherified on average. When the degree of etherification is within this range, the stability of the slurry containing the active material and the binder is high, and solid matter sedimentation and aggregation are unlikely to occur. Furthermore, by using a cellulose derivative, the coating property and fluidity of the slurry during electrode production are improved.

  Although the usage-amount of a cellulose derivative is suitably selected according to the kind of electrode manufactured, it is 0.1-10 weight part normally with respect to 100 weight part of active materials, Preferably it is 0.5-5 weight part.

<Antiacid material>
The antacid material used in the present invention is not particularly limited as long as it consumes acid and does not corrode the current collector metal. Among them, metal carbonates, metal organic acid salts, silicates It is preferably at least one selected from the group consisting of alkaline hydroxides.
Specific examples of the metal carbonate include magnesium carbonate and calcium carbonate.
Specific examples of the metal organic acid salt include sodium carboxylate, potassium carboxylate, sodium sulfonate, potassium sulfonate, sodium benzoate, potassium benzoate and the like.
Specific examples of the silicate include sodium silicate, potassium silicate, aluminum silicate, magnesium silicate, silicon dioxide and the like.
A specific example of the alkaline hydroxide is magnesium hydroxide.
Among these antacids, the amount of water remaining in the electrode can be reduced, so that the solubility in water is low, or no hydrate is formed or even if a hydrate is formed, it is dehydrated below the electrode drying temperature. What can be done is preferred. Specifically, examples of the antacid material having low solubility in water include magnesium carbonate, calcium carbonate, and silicon dioxide, which do not form a hydrate or dehydrate at a temperature lower than the electrode drying temperature even if a hydrate is formed. Examples of those that can be used include sodium silicate and potassium silicate.

  In the present invention, the content of the antacid material in the active material layer is not particularly specified, but an electrode excellent in the balance between the effect of inhibiting corrosion of the current collector and the initial electrical property value can be obtained. Preferably it is 0.01-50 weight part with respect to 100 weight part of electrode active materials, More preferably, it is 0.1-20 weight part, More preferably, it is 1-10 weight part. The volume average particle diameter of the antacid material is not particularly specified, but is preferably 100 μm or less, more preferably 10 μm or less because a high inhibitory effect on current collector corrosion can be obtained.

<Current collector>
The material of the current collector having through holes penetrating the front and back surfaces used in the present invention (hereinafter sometimes simply referred to as “current collector”) is, for example, metal, carbon, conductive polymer, or the like. Preferably, a metal is used. As the current collector metal, aluminum, copper, platinum, nickel, tantalum, titanium, stainless steel, other alloys and the like are usually used.

  Examples of the shape of the through hole of the current collector include a quadrangle, a rhombus, a turtle shell shape, a hexagon, a round shape, a star shape, and a cross shape. Specific examples of the sheet-like current collector having pores include expanded metal obtained by expanding a flat plate into a rhombus or turtle shell-shaped net, punched metal obtained by perforating a flat plate, and the like.

  The aperture ratio of the current collector is not particularly specified, but is preferably 10 to 90 area%, more preferably 40 to 60 area%, because the strength and the molding speed can be increased. The opening diameter is not particularly defined, but is usually 0.01 to 10 μm, more preferably 1 to 5 μm because the molding speed can be increased. The opening diameter here is a diameter of a circumscribed circle of the opening. The diameter of the circumscribed circle is obtained by observing the surface of the current collector with a laser microscope or a tool microscope, fitting the circumscribed circle to the opening, and averaging the results. The thickness of the current collector is appropriately selected according to the purpose of use, but is usually 1 to 200 μm, preferably 5 to 100 μm, more preferably 10 to 60 μm from the viewpoint of achieving both high strength and low resistance. .

  In order to reduce the contact resistance with the active material layer or to improve the adhesion to the active material layer, the current collector is subjected to surface chemical treatment and surface roughening treatment as necessary. It may be. Examples of the surface chemical treatment include acid treatment and chromate treatment. Examples of the surface roughening treatment include electrochemical etching treatment and etching treatment with acid or alkali.

  Moreover, you may use what applied the conductive adhesive to the surface as a collector. As the conductive adhesive, known ones can be used. Among them, a conductive adhesive obtained by dissolving or dispersing a conductive agent, a binder, and a thickener in a solvent is preferable.

<Method for producing electrode for electrochemical device>
The electrode for an electrochemical element of the present invention can be obtained by forming an active material layer on a current collector by wet molding or dry molding.
Specifically, wet molding is a slurry obtained by dispersing or dissolving an essential component of an electrode active material, a binder, and an antacid material and an optional component such as a conductive additive and a cellulose derivative in water or an organic solvent. Is prepared, and the prepared slurry is applied onto a current collector and dried to form an active material layer on the current collector.
Dry molding is a concept for the above-mentioned wet molding, and a step of obtaining a mixture containing the electrode active material, the binder, and the essential components of the antacid material and the above-mentioned optional components, and the resulting mixture in the form of a sheet Forming the active material layer. Specific examples include an extrusion molding method, a roll rolling method, a powder molding method, and a pressure molding method.

  The mixture may be in the form of particles containing the above components in a composite form (hereinafter sometimes referred to as composite particles). The production method of the composite particles is not particularly limited, and is a spray drying granulation method, a rolling bed granulation method, a compression granulation method, a stirring granulation method, an extrusion granulation method, a crushing granulation method, a fluidized bed granulation method. It can be produced by a known granulation method such as a granulation method, a fluidized bed multifunctional granulation method, or a melt granulation method.

  In the case where the electrochemical device electrode of the present invention is produced by wet molding, the slurry to be used can be produced by mixing water and each of the aforementioned components using a mixer. As the mixer, a ball mill, a sand mill, a pigment disperser, a pulverizer, an ultrasonic disperser, a homogenizer, a planetary mixer, a Hobart mixer, and the like can be used. Also, the electrode active material and the conductivity imparting material are first mixed using a mixer such as a crusher, a planetary mixer, a Henschel mixer, and an omni mixer, and then the binder composition is added and mixed uniformly. Is also preferable. By adopting this method, a uniform slurry can be easily obtained.

  The viscosity of the slurry varies depending on the type of coating machine and the shape of the coating line, but is usually 100 to 100,000 mPa · s, preferably 1,000 to 50,000 mPa · s, and more preferably 5,000 to 5,000. It is 20,000 mPa · s.

  The method for applying the slurry to the current collector is not particularly limited. Examples thereof include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method.

  Examples of the method for drying the slurry applied on the current collector include drying with hot air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. Among these, a drying method by irradiation with far infrared rays is preferable.

  The drying temperature and the drying time are preferably a temperature and a time at which the solvent in the slurry applied to the current collector can be completely removed. The drying temperature is usually 100 to 300 ° C, preferably 120 to 250 ° C. The drying time is usually 10 minutes to 100 hours, preferably 20 minutes to 20 hours.

  You may heat-press after drying. By performing the pressing, an electrode having a smooth surface and a uniform surface can be obtained. Further, it is preferable to press after the heat treatment because the electrode density can be easily increased.

  The hot pressing method is preferably a die press or roll press.

  The temperature of the hot press is preferably 50 ° C to 150 ° C, and more preferably 80 ° C to 130 ° C.

  The thickness of the active material layer of the obtained electrode is preferably 10 μm to 1000 μm, more preferably 20 to 500 μm. The density of the active material layer of the obtained electrode is preferably 0.4 g / cc to 1.0 g / cc, more preferably 0.5 g / cc to 0.7 g / cc.

<Electrochemical element>
The electrochemical element of the present invention has the above-described electrode for an electrochemical element of the present invention. The electrochemical element can be produced according to a conventional method using the electrode of the present invention, an electrolytic solution, and parts such as a separator. Specifically, for example, the electrode is cut into an appropriate size, and then the electrodes are overlapped through a separator, and then wound, folded, laminated, etc., and then put into a container, and an electrolyte is injected into the container. Can be manufactured by sealing.

  The electrolytic solution used in the present invention is not particularly limited as long as the electrolytic solution solvent is generally used as an electrolytic solution solvent, but is preferably an organic electrolytic solution that can be used at a high voltage. Specifically, carbonates such as propylene car boat, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone; sulfolanes; nitriles such as acetonitrile; These can be used alone or as a mixed solvent of two or more. Of these, carbonates are particularly preferable.

Examples of the electrolyte used for the electrolytic solution include LiI, LiCOlO ₄ , LiAsF ₆ , LiBF ₄ , LiPF _{6 and the} like that do not cause electrolysis even at a high voltage and can stably exist lithium ions. Of these, those containing fluorine such as LiBF ₄ and LiPF ₆ are particularly preferable. When an electrolyte containing fluorine is used as the electrolyte, the storage capacity can be increased and the internal resistance can be decreased. The concentration of the electrolyte in the electrolytic solution is preferably at least 0.1 mol / L or more in order to reduce the internal resistance due to the electrolytic solution, and more preferably in the range of 0.5 to 1.5 mol / L. preferable.
The electrode for an electrochemical element of the present invention is suitable for an electrochemical element that uses the organic electrolytic solution, and is more suitable for an electrochemical element that contains fluorine as an electrolyte constituting the electrolytic solution.

  As the separator used in the present invention, for example, a microporous film or non-woven fabric made of polyolefin such as polyethylene or polypropylene, or a porous film mainly made of pulp called electrolytic capacitor paper can be used. Moreover, it can replace with a separator and a solid electrolyte can also be used.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, the part and% in a present Example are a basis of weight unless there is particular notice.

The tests and evaluations in the examples and comparative examples were performed by the following methods.
(Measurement of active material layer thickness)
The thickness of the active material layer is 2 cm using an eddy current displacement sensor (sensor head unit EX-110V, amplifier unit unit EX-V02: manufactured by Keyence Corporation) after forming the active material layer on both sides of the current collector. The thickness of each active material layer was measured at intervals, and the average value thereof was defined as the thickness of the active material layer.

(Electrical characteristics of electrochemical devices)
The obtained electrochemical device starts to be charged at a constant current of 1.5 A. When the charging voltage reaches 3.8 V, the voltage is maintained to be constant voltage charging, and charging is performed when constant voltage charging is performed for 20 minutes. Completed. Next, the operation of discharging until reaching 2.1 V at a constant current of 1.5 A immediately after completion of charging was defined as one cycle, and charging and discharging were performed for 5 cycles as conditioning, and thereafter, charging and discharging for 1000 cycles were performed. The cell characteristics in the first cycle after conditioning were defined as initial characteristics, and the cell characteristics after 1000 cycles were defined as characteristics after 1000 cycles. The cell characteristics were evaluated by the cell capacity and internal resistance.

  The cell capacity was calculated from the amount of electricity at the time of discharge, and the internal resistance was calculated from the relationship of R = ΔV / I by obtaining the voltage drop ΔV from the voltage at 0.1 seconds after the discharge.

The rate of change in resistance was calculated by (internal resistance value after 1000 cycles−initial internal resistance value) / (initial internal resistance value) × 100.
The capacity change rate was calculated by (cell capacity after 1000 cycles−initial cell capacity) / (initial cell capacity) × 100.

<Example 1>
(Preparation of positive electrode for electrochemical devices)
Carboxymethyl cellulose ammonium salt having a degree of etherification of 0.6 and a 1% aqueous solution having a viscosity of 30 mPa · s is dissolved in 213.2 parts of ion-exchanged water, and a volume average particle diameter is used as a conductivity-imparting agent. 50 parts of 0.035 μm acetylene black (Denka black powder: manufactured by Denki Kagaku Kogyo Co., Ltd.) was added and mixed and dispersed using a planetary mixer to obtain a conductivity imparting agent dispersion having a solid content concentration of 20%.

26 parts of the resulting conductivity imparting agent dispersion, 100 parts of activated carbon powder having an average particle size of 5 μm and a specific surface area of 2000 m ² / g as the positive electrode active material, 3 parts of calcium carbonate (CaCO ₃ ) as the antacid material, acrylate weight An appropriate amount of water was added to 7.5 parts of an aqueous dispersion having a solid content concentration of 40% and 1 part of carboxymethyl cellulose ammonium salt having a degree of etherification of 0.6 and a viscosity of 1% aqueous solution of 900 mPa · s. The mixture was dispersed using a Lee mixer to obtain a positive electrode slurry for an electrochemical device having a viscosity of between 5,000 and 20,000 mPa · s. As the acrylate polymer, a copolymer having a Tg of −20 ° C. obtained by emulsion polymerization of 76 parts of 2-ethylhexyl acrylate, 20 parts of acrylonitrile and 4 parts of itaconic acid was used.

  As the current collector, an aluminum expanded metal (manufactured by Nippon Metal Industry Co., Ltd.) having a thickness of 35 μm, an aperture ratio of 50%, and an aperture diameter of 1 mm was used. A carbon-based conductive paint (Nippon Graphite Industries Co., Ltd., Bunny Height T-702A) with a solid content concentration of 15% is applied to both sides of this current collector and dried at 120 ° C. for 5 minutes to conduct electricity with a thickness of 4 μm on one side. A current collector with a conductive adhesive layer on which a conductive adhesive layer was formed was obtained.

  The positive electrode slurry for electrochemical devices is applied to both sides of the current collector using a roll coater on the current collector with the conductive adhesive layer, dried at 60 ° C. for 20 minutes, and then heat-treated at 120 ° C. for 20 minutes. After that, roll pressing was performed at a roll temperature of 100 ° C. to obtain a positive electrode for an electrochemical element having a single-sided active material layer thickness of 150 μm.

(Preparation of negative electrode for electrochemical devices)
A 0.5 mm thick phenolic resin molded plate is placed in a siliconite electric furnace, heated to 500 ° C. at a rate of 50 ° C./hour, and further at a rate of 10 ° C./hour to 660 ° C. in a nitrogen atmosphere, followed by heat treatment. Polyacene was synthesized. The polyacene plate thus obtained was pulverized with a disk mill and sieved to obtain a polyacene powder having an average particle diameter of 5 μm. The polyacene powder had an H / C ratio of 0.21. 100 parts of the resulting polyacene powder, 3 parts of calcium carbonate as an antacid material, 7.5 parts of an aqueous dispersion of an acrylate polymer with a solid content of 40%, and a 1% aqueous solution with a degree of etherification of 0.6 An anode slurry for an electrochemical device in which an appropriate amount of water is added to 1 part of carboxymethylcellulose ammonium salt of 900 mPa · s, mixed and dispersed using a planetary mixer, and the viscosity falls between 5,000 and 20,000 mPa · s. Got.

  A conductive adhesive is applied to both sides of a copper expanded metal (made by Nippon Metal Industry Co., Ltd.) having a thickness of 35 μm, an aperture ratio of 50%, and an aperture diameter of 1 mm, and collecting current with a conductive adhesive layer. Got the body. The negative electrode slurry for electrochemical devices was applied to both sides of the current collector using a roll coater on this current collector, dried at 60 ° C. for 20 minutes, then heat-treated at 120 ° C. for 20 minutes, and then at a roll temperature of 100 ° C. Roll pressing was performed to obtain a positive electrode for an electrochemical element having a thickness of 60 μm on one side of the active material layer.

(Preparation of measurement cell)
In the produced electrode sheet, the uncoated portion where the conductive adhesive layer and the active material layer are not formed is left 2 cm × 2 cm wide, and the portion where the active material layer is formed is 5 cm × 5 cm wide. (The uncoated part is formed so as to extend one side of a 5 cm × 5 cm square on which the conductive adhesive layer and the active material layer are formed). 10 sets of electrode sheets cut out in this way are prepared for the positive electrode and 11 sets for the negative electrode, and the uncoated portions are welded with ultrasonic waves respectively. The measurement electrodes were vacuum-dried at 200 ° C. for 20 hours. Using a 35 μm-thick cellulose / rayon mixed nonwoven fabric as a separator, the positive electrode sheet and the negative electrode sheet are arranged so that the terminal welds are on opposite sides, and the positive electrode and the negative electrode are alternated, and stacked electrodes All the outermost electrodes are laminated so as to be the negative electrode. Separators were placed on the top and bottom, and four sides were taped.

  As a lithium electrode, a lithium metal foil (thickness 82 μm, length 5 cm × width 5 cm) bonded to an 80 μm-thick stainless steel mesh is used, and the lithium electrode is laminated so as to completely face the outermost negative electrode One each was placed on the top and bottom. In addition, the terminal welding part (two sheets) of the lithium electrode current collector was resistance welded to the negative electrode terminal welding part.

Laminate with the above lithium foil arranged at the top and bottom is placed inside the deep drawn lower exterior film, covered with the exterior laminate film and fused on the three sides, and then ethylene carbonate, diethyl carbonate and propylene carbonate as electrolytes A solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / l in a mixed solvent with a weight ratio of 3: 4: 1 was vacuum impregnated, and then the other side was fused to form a film capacitor (electrochemical element). Produced. Table 1 shows the results of evaluating the electrical characteristics of the obtained electrochemical device.

<Example 2>
An electrode for an electrochemical device was produced in the same manner as in Example 1 except that the amount of calcium carbonate contained in the positive electrode active material layer and the negative electrode active material layer was 0.1 part. Table 1 shows the results of evaluating the electrical characteristics of the obtained electrode for electrochemical devices.

<Example 3>
An electrode for an electrochemical device was produced in the same manner as in Example 1, except that the amount of calcium carbonate contained in the positive electrode active material layer and the negative electrode active material layer was 1.2 parts. Table 1 shows the results of evaluating the electrical characteristics of the obtained electrode for electrochemical devices.

<Example 4>
An electrode for an electrochemical device was produced in the same manner as in Example 1 except that the amount of calcium carbonate contained in the positive electrode active material layer and the negative electrode active material layer was 9 parts. Table 1 shows the results of evaluating the electrical characteristics of the obtained electrode for electrochemical devices.

<Example 5>
In Example 1, an electrode for an electrochemical element was produced in the same manner as in Example 1 except that the amount of calcium carbonate contained in the positive electrode active material layer and the negative electrode active material layer was 20 parts. Table 1 shows the results of evaluating the electrical characteristics of the obtained electrode for electrochemical devices.

<Example 6>
In Example 1, the same manner as in Example 1 except that sodium silicate (Na ₂ SiO ₃ ) was used instead of calcium carbonate as the antacid material contained in the positive electrode active material layer and the negative electrode active material layer. A chemical element electrode was prepared. Table 2 shows the results of evaluating the electrical characteristics of the obtained electrode for electrochemical devices.

<Comparative Example 1>
In Example 1, an electrode for an electrochemical device was obtained in the same manner as in Example 1 except that the positive electrode active material layer and the negative electrode active material layer did not contain calcium carbonate as an antacid material. Table 1 shows the results of evaluating the electrical characteristics of the obtained electrode for electrochemical devices.

  By using the electrode for an electrochemical element of the present invention, deterioration of capacity and internal resistance after long-term cycle charge / discharge use can be suppressed, and the life of the electrochemical element can be extended. Therefore, it can be suitably used for various applications such as an application to an electric vehicle or a hybrid vehicle, a solar power generation energy storage system combined with a solar battery, and a load leveling power source combined with a battery.

Claims (6)

An electrode for an electrochemical element comprising a current collector having a through-hole penetrating the front and back surfaces, and an active material layer containing an electrode active material and a binder, and containing an antacid material in the active material layer An electrode for an electrochemical element. 2. The electrode for an electrochemical element according to claim 1, wherein the antacid material is at least one selected from the group consisting of metal carbonates, metal organic acid salts, silicates, and alkaline hydroxides. 3. The electrode for an electrochemical element according to claim 1, wherein the content of the antacid material in the active material layer is 0.01 to 50 parts by weight with respect to 100 parts by weight of the electrode active material. The electrode for an electrochemical element according to any one of claims 1 to 3, wherein the electrolytic solution used for the electrochemical element is an organic electrolytic solution. The electrode for an electrochemical element according to claim 4, wherein the electrolytic solution contains fluorine as an electrolyte. The electrochemical element which has an electrode for electrochemical elements in any one of Claims 1-5.