KR20050022577A - Electric Conduction Adhesive and Joined Electrode Using The Said Manufacturing Method thereof - Google Patents

Abstract

PURPOSE: Provided are a conductive adhesive containing binder and a conductive material used in combination of electrode adapted for electric double layered capacitor, joined electrode using the same and a process for manufacturing the same. CONSTITUTION: The process comprises adhering electrode(12) formed of activated carbon powder(15), conductive material(16) and PFTF through kneading and current collector(13) made of metallic foil by conductive adhesive(14) in slurry form; applying the conductive adhesive on cross section of the metallic foil then contacting the electrode over the applied surface; and pressing under heat the foil and the electrode to form the joined electrode(11). The conductive adhesive is applied between the current collector and the electrode to form the joined electrode.

Description

Electrically conductive adhesive and bonded electrode assembly using the same and method for manufacturing same {Electric Conduction Adhesive and Joined Electrode Using The Said Manufacturing Method}

The present invention relates to a conductive adhesive, an electrode assembly bonded using the same, and a method of manufacturing the same. More particularly, in the bonding of an electrode used in an electric double layer capacitor, the electrode is bonded using a conductive adhesive composed of a binder and a conductive material. It relates to a conjugate and a method for producing the same.

A conventional electrochemical capacitor exhibiting ultra high capacity may be represented by an electric double layer capacitor (EDLC). Unlike the battery, the electric double layer capacitor can input and output energy in a short time, and thus is applied to rectification circuits, noise reduction, and power generation pulse generation. Recently, electric double layer capacitors have been developed which have increased capacity significantly compared to the existing electrochemical capacitors used in electronic devices. The application of output pulse power and peak power for load leveling is being promoted. In addition, the use of electric double layer capacitors, which are important in terms of environment and economics due to the use of environmentally friendly materials, long life and high charging and discharging efficiency, are used for military, aerospace, medical, It is expected to be used as the main power source and auxiliary power source of high output pulse power of high value added equipment such as electric vehicle (HEV).

An electric double layer capacitor is generally configured in such a manner that a pair of polarizable electrodes or a double layer electrode of an electrolyte is disposed with a separator having excellent insulation therebetween.

In general, the electrode is composed of an active carbon for storing the capacitance and a conductive material and a binder excellent in electrical conductivity, these components are mixed in a constant ratio in consideration of the capacitance and the electrode resistance and then adhered to the metallic mesh or metallic foil.

In general, a method of manufacturing the electrode is a coating method prepared by mixing a predetermined proportion of components with a solvent to form a slurry and coating the coated metal foil, and activated carbon and a conductive material are PTFE (Polytetrafluoroethylene, hereinafter referred to as PTFE) and Kneading together can be divided into kneading method attached to the metal mesh.

Commonly used electrodes are manufactured by an application process. This is because the electrode manufactured through the coating process is superior to the electrode manufactured through the kneading process in terms of performance and price. In addition, the kneading process uses an expensive metal mesh as a current collector, and because the contact area is limited due to the use of the metal mesh in the form of a network, a problem arises in that the contact resistance between the electrode and the current collector is large. The manufacturing process of the electrode has been preferred to the coating process rather than the kneading process.

 However, in the coating process, the binder is mainly used in two or more components, so that the number of components of the electrode is large, and in order to control the mixing conditions and the thickness of the electrode, the viscosity of the slurry must be adjusted and several times of pressing and drying conditions are required after application. There is a problem that the manufacturing process is complicated.

In contrast, the kneading process uses a PFTE single binder together with activated carbon and a conductive material, so that the number of components of the electrode is small, and the chemical and thermal stability and mechanical strength of the electrode are excellent. In addition, since the binder content of PTFE can be reduced to 3wt% than the coating process, the electrode resistance can be reduced, and the capacity can be increased due to the increase of the content of activated carbon.

In addition, in bonding the electrode and the current collector with an adhesive, in order to reduce the contact resistance between the electrode and the current collector, it is necessary to use an adhesive having excellent adhesion and conductivity. However, among the commercially available adhesives, silver (Ag) paste cannot be used due to its poor adhesion and reaction with the electrolyte used in the electric double layer capacitor. In addition, the adhesive using the conductive polymer is insufficient to reduce the contact resistance because the electrical conductivity of the polymer is worse than the electrical conductivity of the electrode.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an expensive metallic mesh instead of an inexpensive metallic foil as the current collector.

In addition, another object of the present invention is to provide a conductive adhesive excellent in adhesion and conductivity in bonding the electrode and the metallic foil prepared by the kneading process.

In addition, another object of the present invention is to provide a manufacturing method for joining the electrode produced in the kneading process with the conductive adhesive and the metallic foil so as to reduce the contact resistance simply.

The present invention in the adhesion of the electrode and the current collector,

It is characterized by a conductive adhesive in a slurry state in which at least one binder having adhesiveness and at least one conductive material having conductivity are mixed.

The binder is CMC (Carboxymethylcellulose), PVA (Polyvinyl alcohol), PVDF (Polyvinyliene fluoride), PVP (Polyvinylpyrrolidone), MC (methyl cellulose), latex-based ethylene-vinyl chloride copolymer resin, vinylidene chloride latex, chlorinated resin, acetic acid One or both of vinyl resin, polyvinyl butyral, polyvinyl formal, bisphenol-based epoxy resin and Styrene Butadiene Rubber (SBR) -based butadiene rubber, isoprene rubber, nitrile butadiene rubber, urethane rubber, silicone rubber, acrylic rubber The above is characterized by being mixed.

The conductive material includes SPB (Super P Black), Carbon black, Activated carbon, Hard carbon, Soft carbon, Graphite, Metal powder (Al, Pt, Ni, Cu, Au, Stainless steel or one or more kinds of metals described above Alloy) and one or more of the powders coated on carbon black, activated carbon, hard carbon, soft carbon, and graphite by electroless plating.

The mixing ratio of the binder and the conductive material of the conductive adhesive has a composition range of 10 to 80% when the particle size of the conductive material is 1 μm or less, and the range of the binder when the particle size of the conductive material is 1 μm or more. Characterized in that the composition range of 10 to 40%.

In addition, the present invention in the electrode assembly consisting of the adhesion of the electrode and the current collector,

An electrode made of activated carbon, a conductive material and a PFTE and manufactured by kneading, a current collector formed of a metallic foil, and

The conductive adhesive is applied between the electrode and the current collector and adhered thereto.

The metallic foil is characterized by an electrode assembly made of aluminum foil.

In addition, the present invention is bonded to the electrode consisting of activated carbon, conductive material and PFTE and manufactured by kneading and the current collector formed of metallic foil using the conductive adhesive,

The conductive adhesive in the slurry state is applied to the cross section of the metallic foil, and the electrode assembly is characterized in that the electrode bonding method for adhering by the bonding process by hot pressing after the correspondingly.

The hot pressing process is characterized in that the pressing step by increasing the temperature step by step up to 150 ℃ at room temperature.

The electrode is characterized in that applied to at least one of the electric double layer capacitor or the primary and secondary batteries.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration and operation according to an embodiment of the present invention.

1 is a cross-sectional view of an electrode assembly in which an electrode is attached to a metal foil according to the present invention.

The electrode assembly 11 is manufactured by pressing an electrode 12 having a thickness of 100 μm through a kneading process using a conductive adhesive 14 on a metallic foil 13 having a thickness of 20 μm. The electrode 12 is preferably manufactured by kneading after mixing the activated carbon powder 15, the conductive material 16 and PTFE (not shown), the metallic foil 13 is to use an aluminum foil desirable.

The conductive adhesive 14 should exhibit excellent adhesion and electrical conductivity, but the existing conductive adhesive has an electrode resistance of 20 Ωcm or more. It is composed of an activated carbon powder 15, a conductive material 16 and a binder of PTFE (not shown) and exhibits a resistance value higher than about 3 Ωcm, which is a resistance value of the electrode 14 manufactured by the kneading process. Increasing the internal resistance or equivalent series resistance (hereinafter referred to as ESR) of the capacitor results in lowering the output characteristics of the capacitor. Therefore, the electrical resistivity of the conductive adhesive 14 is obtained by the kneading process. It should be lower than the specific resistance of the electrode 12, it is preferable that the contact resistance is also lowered by improving the adhesion of the conductive adhesive 14.

Referring to the preferred components and manufacturing method of the conductive adhesive in detail,

Conductive adhesive 14 according to the present invention is composed of components each responsible for the adhesion and conductivity. As the conductive adhesive 14, the same binder used for the electric double layer capacitor or the electrodes of the primary and secondary batteries is used. For the conductivity, the conductive material of the electric double layer capacitor or the electrode for the primary and secondary batteries, the metal powder or the conductive having excellent conductivity. It is preferable to mix the metal-coated powder on the surface of the ash.

The components of the conductive adhesive 14 must be uniformly mixed in consideration of adhesion and conductivity. In the case of the conductive powder 16, since the conductive path between the electrode 12 and the current collector 13 manufactured through the kneading process is provided, the contact resistance between the powders is configured to be controlled to a minimum. When the size of the particles of the conductive powder 16 is small, the number of particles increases in the direction perpendicular to the plane of the current collector 13, so that the contact resistance increases, so as to reduce the contact resistance, the conductivity is maintained within the range of maintaining the adhesive force. The thickness of the adhesive 14 is controlled to a minimum, and the component ratio between the components is also preferably adjusted according to the particle size.

The conductive adhesive 14 may be applied not only to electric double layer capacitors but also to primary and secondary batteries, which are similar technologies in manufacturing processes, and the electric double layer capacitors or primary and secondary batteries using these technologies are inexpensive and have excellent output characteristics. do.

In order to improve the adhesive strength of the conductive adhesive 14 composed of the conductive material 16 and the binder (not shown), the adhesion process between the electrode and the current collector is important in addition to the adhesive force of the binder.

Looking at the bonding process, the conductive adhesive is prepared in a slurry state by dissolving the binder of the electric double layer capacitor or the electrode for the primary and secondary batteries in a solvent and then mixing the conductive material (16). The slurry is applied to be adjusted to a thickness of about 10 μm or less and bonded to the electrode in the liquid phase. The conductive adhesive 14 in the liquid state partially penetrates into the pores of the electrode 12 and solidifies through constant pressing and drying conditions. The surface of the electrode 12 is composed of activated carbon 15 having a particle size of several μm and a conductive material 16 having a diameter of about 0.1 μm, so that bending occurs, and a conductive adhesive penetrating into the pores of the electrode 12 ( 14 fills these voids to widen the contact area with the current collector 13, thereby reducing the contact resistance between the electrode 12 and the current collector 13.

In addition, crimping conditions are important to improve ligation. The slurry of the said conductive adhesive 14 is a state containing the solvent, and it removes by a natural state or heating after crimping. However, drying in a non-squeezed state decreases the electrode density to increase the contact resistance, so that in order to improve the electrode density and improve the adhesive force, the conductive adhesive 14, which has been heated in the pressing process and removes the solvent, fills the voids and collects the current collector. It is desirable to improve the adhesive force due to the increase in the contact area with (13).

Table 1 below shows the DC and AC resistivity of the conductive adhesive prepared by changing the components.

Table 1

Table 1 shows the weight ratio between the components and components of the conductive adhesive developed in the present invention, and shows the electrical resistivity of the sheet prepared by drying and pressing after applying the slurry mixed with the solvent. The electrical resistivity is preferably measured by a DC or AC 4-terminal sheet of a certain size sheet.

In Table 1, 101S and CMC (carboxymethylcellulose, hereinafter referred to as CMC) represent commercially available binders, and SPB (Super P Black, Belgium MMM Carbon, hereinafter referred to as SPB) represents a commercially available conductive material. For comparison of the conductive adhesive for each component, the weight ratio of the conductive material to the binder was fixed at 70:30.

In Table 1, when the SPB is mixed with the binder, the CMC shows lower electrical resistivity, and when the same CMC binder is used, the SPB shows lower electrical resistivity than the graphite. On the other hand, when the conductive material plated with electroless Ni on the surface of SPB and mixed with the CMC it can be seen that the electrical resistivity is the lowest.

2 is a graph showing the change in specific resistance of the conductive adhesive according to the composition ratio of the CMC.

In FIG. 2, the electrical resistivity is measured by the DC 4-terminal method as described in Table 1. FIG.

The dotted line represents the electrical resistivity of the electrode manufactured through the kneading process.

In the graph of FIG. 2, the SPB shows the lowest value at 30% of the composition of the CMC, and as the composition of the CMC increases, the electrical resistivity increases. In the case of graphite, the electrical resistivity increases linearly as the composition of CMC increases.

Therefore, according to these results, it is possible to consider the specific resistance value due to the relationship between the particle specific surface area and the binder content according to the particle size of the conductive material dispersed in the CMC. The SPB has a particle size of about 0.1 μm and a CMC of 30% or less has a large specific surface area of the particles, which indicates that the resistance is large due to a lack of adhesion due to the binder. It is considered that the contact area between the conductive materials is reduced due to the increase in content. However, graphite has a particle size of about 1㎛, and CMC is considered to be relatively less affected by the specific surface area of the conductive material powder when 10% or more is added. These results show that the SPB has a lower electrical resistivity than that of Graphite, and the conductive material adhesive of SPB: CMC is lower than the electrical resistivity of the kneaded electrode within the composition range examined in the graph of FIG.

3 is a graph showing a change in the specific capacitance (F / g) according to the current density of each capacitor.

Specific capacity is the capacitance of a capacitor divided by the weight of active carbon throughout the cell.

In the graph of FIG. 3, the capacitor using the conductive adhesive of 101S: SPB shows a sharp decrease as the current density during discharge increases. However, the capacitor using the CMC: SPB conductive adhesive has a small decrease with the increase of the current density, and the conductive adhesive obtained by mixing the conductive powder of Ni coated with electroless plating on the surface of the SPB is mixed with the CMC. It can be seen that the capacitors using are smaller in width. These results reflect the results of the electrical resistivity of the conductive adhesive for each component shown in Table 1, indicating that the lower the resistance of the conductive adhesive, the lower the contact resistance between the electrode and the current collector.

Table 2 below shows the internal resistance (ESR) of the test capacitor for each conductive adhesive.

TABLE 2

Table 2 shows the internal resistance or equivalent series resistance (ESR) of the capacitor in Figure 3. In Table 2, it can be seen that the smaller the electrical resistivity of the conductive adhesive, the smaller the ESR of the manufactured capacitor. As the electrical resistivity of the conductive adhesive decreases, the internal resistance (ESR) of the bonded electrode and the electric double layer capacitor manufactured using the same decreases.

In the detailed description according to the present invention has been described with respect to specific embodiments and those skilled in the art will understand that various modifications are possible without departing from the scope of the technical spirit of the present invention.

The scope of the present invention should not be limited to the above-described embodiments, but should be defined by the claims below and equivalents thereof.

As described above, the present invention has an effect of providing an expensive metallic mesh with an inexpensive metallic foil as the current collector.

In addition, the present invention has the effect of providing a conductive adhesive excellent in adhesion and conductivity in bonding the electrode and the metallic foil prepared by the kneading process.

In addition, the present invention has the effect of providing a manufacturing method for joining the electrode produced in the kneading process with the conductive adhesive and the metallic foil to reduce the contact resistance simply.

In addition, the present invention simplifies the manufacturing process to lower the cost of the electrode and reduce the electrode resistance, to improve the output characteristics of the electric double-layer capacitor or primary and secondary batteries to be applied in the future and to increase the product competitiveness through the price reduction electrode assembly It is effective to provide.

1 is a cross-sectional view of an electrode assembly in which an electrode is attached to a metal foil according to the present invention.

2 is a graph showing the specific resistance change of the conductive adhesive according to the composition ratio of the CMC.

3 is a graph showing a change in the specific capacitance (F / g) according to the current density of each capacitor.

<Description of the symbols for the main parts of the drawings>

11 electrode assembly 12 electrode

13: current collector (metallic foil) 14: conductive adhesive

15: activated carbon powder 16: conductive powder (conductive material)

Claims (9)

In the conductive adhesive for bonding the electrode and the current collector, A conductive adhesive comprising a slurry in which at least one binder having an adhesive property and at least one conductive material having conductivity are mixed. The method of claim 1, The binder is CMC (Carboxymethylcellulose), PVA (Polyvinyl alcohol), PVDF (Polyvinyliene fluoride), PVP (Polyvinylpyrrolidone), MC (methyl cellulose), latex-based ethylene-vinyl chloride copolymer resin, vinylidene chloride latex, chlorinated resin, acetic acid One or both of vinyl resin, polyvinyl butyral, polyvinyl formal, bisphenol-based epoxy resin and Styrene Butadiene Rubber (SBR) -based butadiene rubber, isoprene rubber, nitrile butadiene rubber, urethane rubber, silicone rubber, acrylic rubber The above is mixed and comprised, The electrically conductive adhesive characterized by the above-mentioned. The method of claim 1, The conductive material includes SPB (Super P Black), Carbon black, Activated carbon, Hard carbon, Soft carbon, Graphite, Metal powder (Al, Pt, Ni, Cu, Au, Stainless steel or one or more kinds of metals described above Alloy) and the metal described above by electroless plating, one or two or more kinds of powders coated on carbon black, activated carbon, hard carbon, soft carbon, and graphite are mixed. The method of claim 1, The mixing ratio of the binder and the conductive material of the conductive adhesive is a composition range of 10 to 80% when the particle size of the conductive material is 1 μm or less, and the binder range is 10 when the particle size of the conductive material is 1 μm or more. A conductive adhesive, characterized in that the composition range of ~ 40%. In the electrode assembly consisting of the adhesion of the electrode and the current collector, An electrode composed of activated carbon, a conductive material and PFTE and manufactured by kneading A current collector formed of a metallic foil, and Electrode assembly comprising the conductive adhesive is applied between the electrode and the current collector to adhere it. The method of claim 5, The metallic foil is an electrode assembly, characterized in that consisting of aluminum foil. In bonding an electrode made of activated carbon, a conductive material and PFTE and manufactured through kneading, and a current collector formed of a metallic foil using the conductive adhesive, The conductive adhesive in the slurry state is applied to the cross section of the metallic foil, and the electrode is bonded to each other and then bonded by a bonding process by hot pressing. The method of claim 7, wherein The bonding process by the hot pressing is an electrode assembly manufacturing method characterized in that the pressing step by increasing the temperature step by step up to 150 ℃ at room temperature. The method according to any one of claims 5 to 8, And the electrode is applied to at least one of the electric double layer capacitor or the primary and secondary batteries.