JP2007201397A - Electrode member having two undercoating layers for nonaqueous electronic part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a collector electrode member where a clearance is difficult to be produced on an interface between a collector electrode and a working electrode, and the surface of the collector electrode does not contact with a electrolytic solution even when coating and drying slurry of electrode material to manufacture an electrode member. <P>SOLUTION: The collector electrode member for an electronic parts has a conductive material and a first undercoating layer and second undercoating layer which are positioned on the surface of the conductive material in order, the first undercoating layer is a layer composed of elastomer, and the second undercoating layer is a layer which contains an auxiliary material and a binding resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a collector electrode member for an electronic component, and more particularly to a collector electrode member for an electronic component in which an electrode is immersed in an electrolytic solution.

  Electronic parts such as electric double layer capacitors, non-aqueous batteries, and electrolytic capacitors have a configuration in which an electrode member is immersed in an electrolytic solution. An electrode member refers to an assembly that introduces electricity into or removes electricity from an electrolytic cell holding an electrolytic solution. In this specification, the electrode member refers to a combined body of a collecting electrode and a working electrode. The working electrode refers to an electrode that contains an electrode active material and acts with an electrolyte during charging / discharging of an electronic component, and the collecting electrode refers to an electrode that supports the working electrode. For example, in a general electric double layer capacitor, a polarizable electrode corresponds to the working electrode.

  Patent Document 1 describes an electrode member in which a sheet of an electrode including a polarizable electrode material such as activated carbon is prepared in advance, and a collecting electrode is superimposed on the surface of the electrode sheet and integrated with a rolling roller or the like. Yes. In this case, a synthetic rubber in which a carbon material is dispersed is used as a conductive adhesive for bonding the collector electrode and the polarizable electrode sheet. However, forming the electrode sheet first and then bonding it to the collector electrode is a complicated process and increases the manufacturing cost.

  Non-Patent Document 1 describes that, instead of preparing an electrode sheet in advance, a polarizable electrode material is mixed with an adhesive to form a slurry, which is applied to a collecting electrode and dried to form an electrode member. ing. Since the coating and drying can be performed continuously, the process is simple. According to this method (hereinafter referred to as “slurry coating method”), the electrode member can be manufactured at low cost.

  According to the slurry coating method, when the same amount of electrode active material is used, it is possible to form a film much thinner than when an independent electrode sheet is formed, and the output density of the cell is improved. Further, according to the slurry application method, the amount of the adhesive can be considerably reduced as compared with the electrode sheet, and the internal resistance of the cell is lowered. Furthermore, according to the slurry application method, the density of the electrodes can be easily adjusted.

  However, when the electrode material slurry is directly applied to the collector electrode and dried, a gap is likely to be formed at the interface between the collector electrode and the polarizable electrode layer, and a portion not covered with the adhesive is likely to occur on the surface of the collector electrode. . This part of the collector electrode is in direct contact with the electrolyte in the electrolytic cell. Therefore, when a voltage is applied to the collector electrode during charging / discharging of the electric double layer capacitor, the electrolytic solution is easily decomposed or deteriorated due to an oxidation or reduction reaction.

In particular, next-generation high energy density electric double layer capacitors that use non-porous carbonaceous materials or graphite-based carbonaceous materials as polarizable electrodes have a high rated voltage, and when an electrode member formed by a slurry coating method is used, an electrolyte solution May deteriorate early and the service life may be shortened.
JP 2005-136401 A JP 2005-286178 A Ikuo Okamura "Electric Double Layer Capacitor and Power Storage System" 2nd Edition, Nikkan Kogyo Shimbun, 2001, 40-41

  The present invention solves the above-mentioned conventional problems, and the object is to create a gap at the interface between the collecting electrode and the working electrode even when an electrode member is produced by applying and drying a slurry of electrode material. It is difficult to provide a collector electrode member in which the surface of the collector electrode is not in contact with the electrolytic solution.

The present invention provides a collector electrode member for an electronic component having a conductive material, a first undercoat layer sequentially provided on the surface of the conductive material, and a second undercoat layer, wherein the first undercoat layer is made of an elastomer. Layer,
The second undercoat layer provides a collector electrode member for an electronic component, which is a layer comprising a conductive auxiliary agent and a binding resin, whereby the above object is achieved.

The collector electrode member for electronic parts of the present invention is
Preparing a conductive material;
Forming a first undercoat layer made of an elastomer on the surface of the conductive material; and forming a second undercoat layer comprising a conductive additive and a binding resin on the surface of the first undercoat layer;
It is preferable to manufacture by the method of including.

  When the collector electrode member of the present invention is used, the electrolyte solution hardly deteriorates even when used at a high voltage, and the cycle characteristics and the service life of the electronic component are improved.

  As the conductive material, a material having a form normally used as a collecting electrode of an electronic component is used. The form of the collecting electrode may be a sheet shape, a prismatic shape, a cylindrical shape, or the like. When the electronic component is an electric double layer capacitor, the material of the collector electrode may be aluminum, copper, silver, nickel, titanium, or the like. A preferred form is a sheet or foil, and a preferred material is aluminum. This is because aluminum has a low electric resistance as a metal, and the withstand voltage is less deteriorated in an assembled state as an electric double layer capacitor.

  The first undercoat layer is provided to inhibit contact between the conductive material and the electrolytic solution. The first undercoat layer is excellent in the electrolyte barrier property, oxidation-reduction resistance, and chemical resistance, and needs to exhibit good stability over the life of the electric double layer capacitor. Furthermore, the first undercoat layer needs to electrically connect the conductive material and the second undercoat layer.

  A preferred material for constituting the first undercoat layer is an elastomer, more preferably a synthetic rubber. Specific examples of the synthetic rubber include isoprene rubbers such as isoprene rubber (polyisoprene); butadiene rubbers such as butadiene rubber (cis-1,4-polybutadiene) and styrene-butadiene rubber (SBR); nitrile rubber (NBR) And diene special rubbers such as chloroprene rubber; olefin rubbers such as ethylene / propylene rubber, ethylene / propylene / diene rubber and acrylic rubber; hydrin rubber; urethane rubber; fluorine rubber;

  Among the above synthetic rubbers, SBR having various varieties is inexpensive and suitable. Furthermore, as SBR, a glass transition temperature (Tg) of −5 ° C. to 30 ° C., particularly 0 ° C. to 10 ° C. is more preferable. When the TBR of SBR is less than −5 ° C., the blocking property of the electrolyte is insufficient, and when it exceeds 30 ° C., the conductivity is insufficient. Here, TBR of SBR is a value measured in accordance with JISK 7121.

  The first undercoat layer is formed by applying and drying a liquid containing the synthetic rubber and the dispersion medium. The application method is not particularly limited, but is usually applied by a gravure printing method or a die head method. The thickness of the first undercoat layer is 1 to 5 μm, preferably 1 to 2 μm in a dry state. When the thickness of the first undercoat layer is less than 1 μm, the barrier property of the electrolytic solution is insufficient, and when it exceeds 5 μm, the conductivity is insufficient.

  The dispersion medium is not particularly limited, but water and lower alcohols (methanol, ethanol, n-propanol, isopropanol, etc.) are preferable. In general, synthetic rubbers are not dissolved or dispersed in these dispersion media as they are, so that a known surfactant or a water-soluble polymer for forming a protective colloid may be added.

Of the above synthetic rubbers, latex may be used for those for which latex is easily available. For example, latex such as SBR and NBR is common. In this case, all of the conductive adhesive dispersion medium may be derived from latex, or a dispersion medium may be added separately.

  The second undercoat layer is provided to reduce the contact resistance between the conductive material and the polarizable electrode.

  A preferable material for constituting the second undercoat layer is a binder resin in which a conductive auxiliary agent is dispersed. Specific examples of conductive aids include graphite having high conductivity due to the presence of delocalized π electrons; carbon black which is a spherical aggregate in which several layers of graphitic carbon microcrystals gather to form a turbulent structure (Acetylene black, ketjen black, other furnace blacks, channel blacks, thermal lamp blacks, etc.); Hydrocarbons such as methane, propane, acetylene, etc. are vapor-phase pyrolyzed and deposited in a thin film on the blackboard as a substrate And pyrolytic graphite. Among them, flaky graphite [particularly natural graphite (scaly graphite)] is also a acetylene because it has a relatively small particle size and a relatively good conductivity because it can ensure high conductivity. Black is preferred.

  The resin in which the conductive auxiliary agent is dispersed is generally used when a slurry is prepared, and may be any resin that is stable in an organic electrolyte and electrochemically stable. Examples include isoprene rubbers such as isoprene rubber (polyisoprene); butadiene rubbers such as butadiene rubber (cis-1,4-polybutadiene) and styrene-butadiene rubber (SBR); dienes such as nitrile rubber (NBR) and chloroprene rubber Olefin rubbers such as ethylene / propylene rubber, ethylene / propylene / diene rubber, and acrylic rubber; hydrin rubber; urethane rubber; fluorine rubber; A thickener such as carboxymethyl cellulose (CMC) may be used alone, or a mixture of CMC and the above synthetic rubber may be used.

  The amount (based on solid content) of the conductive auxiliary agent in the second undercoat layer is, for example, preferably 50 to 99% by mass, 80 to 99% by mass, 90 to 99% by mass, particularly 95 to 99% by mass. When the amount of the conductive auxiliary is less than 50% by mass, it is difficult to ensure conductivity, and when it exceeds 99% by mass, the coating property is deteriorated.

  The second undercoat layer is formed in the same manner as the first undercoat layer except that the liquid containing the conductive auxiliary agent, the binding resin, and the dispersion medium is used. The thickness of the second undercoat layer is 1 to 5 μm, preferably 1 to 3 μm in a dry state. If the thickness of the second undercoat layer is less than 1 μm, it is difficult to ensure conductivity, and if it exceeds 5 μm, the volume of the working electrode layer effective as an electrode decreases.

  The collector member thus obtained can be used to manufacture electrode members for electronic parts such as electric double layer capacitors. For example, a sheet-like electrode member is a mixture of a polarizable electrode material, a binding resin, and a conductive auxiliary agent, and dispersed in an appropriate dispersion medium to obtain a slurry of the electrode material, which is applied to the surface of the collector electrode member, It is formed by drying until the dispersion medium is completely evaporated.

  The collector electrode member is preferably heated after the second undercoat layer is formed. It is because the electrical conductivity between the working electrodes is improved by heating. The step of heating the collector electrode member may be performed before the working electrode is formed, or may be performed after the working electrode is formed. Moreover, you may carry out simultaneously with the process of evaporating a dispersion medium.

  The heating temperature is generally 100 to 220 ° C, preferably 130 to 190 ° C. When the heating temperature is less than 100 ° C., the conductivity of the current collecting station member is not sufficiently improved, and when it exceeds 220 ° C., the deterioration of other electrode constituent materials proceeds. The heating time is generally 1 to 12 hours, preferably 4 to 8 hours. When the heating time is less than 1 hour, the conductivity is not improved sufficiently, and various properties are not improved even if the heat treatment is performed for more than 12 hours.

  As the polarizable electrode material, a carbonaceous material usually used for electric double layer capacitors such as activated carbon can be used. The polarizable electrode material may include a carbon material that substantially expands when the electric double layer capacitor is charged. Expandable carbon is graphite-like microcrystalline carbon, and when a voltage is applied, electrolyte ions intercalate with a solvent between the layers of graphite-like microcrystalline carbon, resulting in substantial expansion of the electrode. It is thought to occur.

  A preferable non-porous carbon is, for example, described in Patent Document 2, and can be produced as follows.

  The powder of needle coke green powder is baked at 500 to 900 ° C., preferably 600 to 800 ° C., more preferably 650 to 750 ° C. for 2 to 4 hours in an inert atmosphere, for example, an atmosphere of nitrogen or argon. It is considered that a crystal structure of a carbon structure is formed in this firing step.

  The calcined carbon powder is mixed with an alkali hydroxide having a weight ratio of 1.8 to 2.2 times, preferably about 2 times. The powder mixture is calcined at 650 to 850 ° C., preferably 700 to 750 ° C. for 2 to 4 hours under an inert atmosphere. This process is called alkali activation, and it is considered that alkali metal atom vapor penetrates the carbon structure and has the effect of relaxing the crystal structure of carbon.

  The resulting powder mixture is then washed to remove the alkali hydroxide. In the washing, for example, particles are collected from the carbon after the alkali treatment, filled in a stainless steel column, 120 to 150 ° C., 10 to 100 kgf, preferably 10 to 50 kgf of pressurized water vapor is introduced into the column, This can be done by continuing to introduce pressurized steam until the pH is ˜7 (usually 6-10 hours). After completion of the alkali removal step, an inert gas such as argon or nitrogen is passed through the column and dried to obtain the desired non-porous carbon powder.

  In addition to carbon black, powder graphite or the like can be used as the conductive auxiliary agent for the working electrode. In addition to PTFE, PVDF, PE, PP, or the like can be used as the binding resin. In this case, the blending ratio of non-porous carbon, conductive auxiliary agent (carbon black) and binder resin (PTFE) is generally about 10: 1: 0.5-10: 0.5-0.25. is there.

  The electrode member of the present invention can be used for conventionally known electronic components such as electric double layer capacitors. An electric double layer capacitor can be assembled by, for example, forming a positive electrode and a negative electrode by overlapping sheet-like electrode members with a separator interposed therebetween, and then impregnating the electrolyte.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “part” or “%” is based on weight unless otherwise specified.

Example 1
The potassium hydroxide pellets were pulverized in advance with a mill to obtain powder. Nippon Steel-made coal-based needle coke green powder (NCGP) was calcined at about 800 ° C. for 3 hours in an alumina crucible while circulating nitrogen in a muffle furnace and naturally cooled. Next, the roughly fired product was mixed with 1.5 times the potassium hydroxide powder per weight ratio. Each was put in a nickel crucible and covered with a nickel lid to shut off the outside air. This was activated for 4 hours at 750 ° C. while circulating nitrogen in a muffle furnace. The fired product was taken out, washed lightly with pure water, and then washed by applying ultrasonic waves. The time is 1 minute. Next, water was separated using a Buchner funnel. The same washing operation was repeated until the pH of the washing water reached around 7. This was dried in a vacuum dryer at 200 ° C. for 10 hours.

The obtained carbon was pulverized for 1 hour with 10 mmφ alumina balls using a ball mill (AV-1 manufactured by Fujiwara Seisakusho). When the particle size was measured with a Coulter counter, all of them became powdery with a center particle diameter of about 10 microns. It was 80 m < ² > / g when the specific surface area of the obtained powdery carbon was measured by BET method. The pore volume with a pore diameter of 0.8 nm or less was 0.04 ml / g.

  SBR was applied as a first layer with a thickness of 5 μm. Next, a slurry in which acetylene black was dispersed in an aqueous CMC solution in an amount of 97% by mass based on the solid content was applied as a second layer with a thickness of 5 μm. Next, a slurry was prepared by adding SBR to a dispersion of powdered carbon in a CMC aqueous solution to adjust the viscosity. The slurry was applied to the third layer as a working electrode layer. The obtained coated product was pressed with a press machine to obtain a coated electrode having a thickness of 100 microns. The completed electrode layer was heat-treated at 160 ° C. for 6 hours and dried to produce a coated electrode.

This coated electrode was punched into a 20 mmφ disk and assembled into a three-electrode cell as shown in FIG. As the reference electrode, “# 1711” activated carbon manufactured by Kureha Chemical Co., Ltd. was dispersed in a CMC solution, the viscosity was adjusted with SBR, and a slurry was prepared to be a coated electrode. These cells were dried in a vacuum at 220 ° C. for 24 hours and cooled. An electrolyte solution was prepared by dissolving spirobipyrrolidinium tetrafluoroborate (SBPBF ₄ ) in propylene carbonate so as to be 2.0 mol%. And the obtained electrolyte solution was inject | poured into the cell, and the electrical double layer capacitor was produced.

  Power system charge / discharge test device “CDT-RD20” is connected to the assembled electric double layer capacitor, and after electric field activation, the ambient temperature is kept at 25 ° C. and constant current charging is performed at 5 mA for 7200 seconds. After reaching the set voltage, constant current discharge at 5 mA was performed. The set voltage was 4.2 V, 3 cycles were performed, and the data for the third cycle was adopted.

The capacity (F / cc) was calculated from the discharge power.
The DC resistance (Ω) was calculated from the IR drop during constant current discharge.

  Next, the ambient temperature was raised to 70 ° C., and charging and discharging under the above conditions were performed 100 cycles. Thereafter, the ambient temperature was returned to 25 ° C., charge and discharge were performed for 3 cycles, the capacity retention rate was measured, and the internal resistance increase rate (%) was calculated by the following formula. Table 1 shows the capacity retention rate (%) and the internal resistance increase rate (%) after 106 cycles of the electric double layer capacitor.

Example 2
An electric double layer capacitor was prepared and tested in the same manner as in Example 1 except that NBR was used for the first undercoat layer. The test results are shown in Table 1.

Comparative Example 1
An electric double layer capacitor was produced and tested in the same manner as in Example 1 except that an electrode layer having no undercoat was used. The test results are shown in Table 1.

容量維持率（％）＝Ｃ１０６／Ｃ３×１００
抵抗増加率（％）＝（Ｒ１０６／Ｒ３−１）×１００
Ｃ３:３サイクル目容量(２５℃)、Ｃ１０６:１０６サイクル目容量(２５℃)
Ｒ３:３サイクル目抵抗(２５℃)、Ｒ１０６:１０６サイクル目抵抗(２５℃) [Table 1]

Capacity maintenance rate (%) = C106 / C3 × 100
Resistance increase rate (%) = (R106 / R3-1) × 100
C3: 3rd cycle capacity (25 ° C), C106: 106th cycle capacity (25 ° C)
R3: 3rd cycle resistance (25 ° C), R106: 106th cycle resistance (25 ° C)

It is an assembly drawing which shows the structure of the electric double layer capacitor of an Example.

Explanation of symbols

1, 11 ... Insulating washer,
2 ... Top cover,
3 ... Spring,
4, 8 ... collector electrode,
5, 7 ... carbonaceous electrode,
6 ... separator,
9 ... Guide,
10, 13 ... O-ring,
12 ... the body,
14 ... Presser plate,
15 ... Reference electrode,
16 ... Bottom cover.

The first undercoat layer is formed by applying and drying a liquid containing the elastomer and the dispersion medium. The application method is not particularly limited, but is usually applied by a gravure printing method or a die head method. The thickness of the first undercoat layer is 1 to 5 μm, preferably 1 to 2 μm in a dry state. When the thickness of the first undercoat layer is less than 1 μm, the barrier property of the electrolytic solution is insufficient, and when it exceeds 5 μm, the conductivity is insufficient.

The present invention relates to electrode member nonaqueous electronic components, for the non-aqueous electrode of the electronic component member, particularly formed by electrodes immersed in the electrolyte.

Non-aqueous electronic components such as electric double layer capacitors, non-aqueous batteries, and electrolytic capacitors have a configuration in which an electrode member is immersed in an electrolytic solution. An electrode member refers to an assembly that introduces electricity into or removes electricity from an electrolytic cell holding an electrolytic solution. In this specification, the electrode member refers to a combined body of a collecting electrode and a working electrode. The working electrode refers to an electrode that contains an electrode active material and acts with an electrolyte during charging / discharging of a non-aqueous electronic component , and the collecting electrode refers to an electrode that supports the working electrode. For example, in a general electric double layer capacitor, a polarizable electrode corresponds to the working electrode.

The present invention solves the above-mentioned conventional problems, and the object is to create a gap at the interface between the collecting electrode and the working electrode even when an electrode member is produced by applying and drying a slurry of electrode material. It is difficult to provide an electrode member in which the surface of the collecting electrode is not in contact with the electrolytic solution.

The present invention relates to a non-aqueous electronic component having a conductive material, a first undercoat layer sequentially provided on the surface of the conductive material, a second undercoat layer, and a working electrode layer formed by a slurry coating method. a use electrode member,
The first undercoat layer is a layer made of an elastomer formed by applying and drying a liquid containing latex of synthetic rubber .
Second undercoat layer is Ru layer der comprising a conductive auxiliary agent and a binder resin, there is provided a nonaqueous electronic component electrode member, the objects can be achieved.

The electrode member for non-aqueous electronic components of the present invention is
Preparing a conductive material;
Forming a first undercoat layer made of an elastomer by applying and drying a liquid containing latex of synthetic rubber on the surface of the conductive material;
Forming a second undercoat layer comprising a conductive additive and a binding resin on the surface of the first undercoat layer; and
Forming a working electrode layer on the surface of the second undercoat layer by a slurry coating method;
It is preferable to manufacture by the method of including.

When the electrode member of the present invention is used, the electrolyte solution hardly deteriorates even when used at a high voltage, and the cycle characteristics and the useful life of the non-aqueous electronic component are improved.

As the conductive material, a material having a form normally used as a collecting electrode of a non-aqueous electronic component is used. The form of the collecting electrode may be a sheet shape, a prismatic shape, a cylindrical shape, or the like. When the non-aqueous electronic component is an electric double layer capacitor, the material for the collector electrode may be aluminum, copper, silver, nickel, titanium, or the like. A preferred form is a sheet or foil, and a preferred material is aluminum. This is because aluminum has a low electric resistance as a metal, and the withstand voltage is less deteriorated in an assembled state as an electric double layer capacitor.

The thus obtained collector electrode member can be used for manufacturing an electrode member of a non-aqueous electronic component such as an electric double layer capacitor. For example, a sheet-like electrode member is a mixture of a polarizable electrode material, a binding resin, and a conductive auxiliary agent, and dispersed in an appropriate dispersion medium to obtain a slurry of the electrode material, which is applied to the surface of the collector electrode member, It is formed by drying until the dispersion medium is completely evaporated.

The electrode member of the present invention can be used for conventionally known non-aqueous electronic components such as an electric double layer capacitor. An electric double layer capacitor can be assembled by, for example, forming a positive electrode and a negative electrode by overlapping sheet-like electrode members with a separator interposed therebetween, and then impregnating the electrolyte.

Claims (6)

In a collector electrode member for an electronic component having a conductive material, a first undercoat layer sequentially provided on the surface of the conductive material, and a second undercoat layer,
The first undercoat layer is an elastomer layer;
A collector electrode member for electronic parts, wherein the second undercoat layer is a layer comprising a conductive additive and a binding resin.   The collector electrode member for electronic parts according to claim 1, wherein the elastomer is a synthetic rubber.   The electrode member for electronic components which has a layer of a working electrode on the surface of the collector electrode member of Claim 1 or 2. Preparing a conductive material;
Forming a first undercoat layer made of an elastomer on the surface of the conductive material; and forming a second undercoat layer comprising a conductive additive and a binding resin on the surface of the first undercoat layer;
The manufacturing method of the collector electrode member for electronic components containing this.   The manufacturing method of the electrode member for electronic components including the process of forming the layer of a working electrode on the surface of the collector electrode member of Claim 1 or 2. The manufacturing method of the electrode member for electronic components which further includes the process of heating the electrode member for electronic components of Claim 5.

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