KR100587963B1 - Low resistance electric double layer capacitor and manufacturing method thereof - Google Patents

Abstract

An electric double layer capacitor capable of reducing the resistance while increasing the density of an electrode and a method of manufacturing the same are provided. According to the present invention, a poly methacrylic and carboxymethyl cellulose are mixed to form a binder, and then the activated carbon powder conductive material and the binder are mixed to form a mixture, and then the mixture is applied to the current collector. The object of the present invention is achieved by manufacturing the electrode.

In the present invention, by using a binder system in which carboxymethyl cellulose is mixed with polymethacrylic, which is a type of acryl, it is possible to increase the density of the electrode by 30% or more and to reduce the resistance by 70%. The performance of the double layer capacitor can be greatly improved.

Description

Low resistance electric double layer capacitor and its manufacturing method {Low ESR Electric Double Layer Capacitor and Process for Producing it}

The present invention relates to an electric double layer capacitor (EDLC) and a method for manufacturing the same, and more particularly, to an electric double layer capacitor (EDLC) and a method for manufacturing the same, which can increase an electrode capacity and reduce resistance.

Typically, capacitors (EDLC) or capacitors are classified into electrostatic capacitors, electrolytic capacitors, and electrochemical capacitors.

The electrostatic capacitors include ceramic capacitors, glass capacitors, and mica capacitors, and most have electrostatic capacitances of about 1.0 to 10 ㎌. The electrolytic capacitors are known as aluminum electrolytic capacitors or tantalum electrolytic capacitors. Can have up to twice the capacitance

Electrochemical capacitors, also called supercapacitors, may have capacitances ranging from about 1 mF to 10000 F if electric double layer capacitors using activated carbon and pseudo capacitors using metal oxides and conductive polymers have been developed.

The electric double layer capacitor is a capacitor that stores electric energy by using a principle of absorbing and desorbing electric charges to an electric double layer generated at an interface between an electrode and an electrolyte. Due to this principle, electric double layer capacitors have fast charging and discharging characteristics, and main power supply or auxiliary power supply of solar cell and communication equipment which require long life, fast charging, and high power, and also high capacity of electric vehicle and UPS It is suitable as a power supply

In the manufacture of electric double layer capacitors having such various uses, a method of preparing a polarizable electrode by forming a metal current collector on activated carbon fibers to date, and a method of pressing a carbon paste onto a conductive rubber or a metal current collector to activated carbon powder as a solvent Has been developed to apply the slurry on the metal current collector by mixing in

In the method of applying these slurries onto the current collector, polysaccharides such as polysacaride-based carboxymethyl cellulose (CMC) or fluorine-based polytetrafluoroethylene (PTFE) and styrene-butadiene louver (SBR) It has been used a lot. However, Carboxymethyl Cellulose (CMC) has a very large hardness and therefore is not easy to work and has very disadvantageous properties in the roll working process. On the other hand, polytetrafluoroethylene (PTFE) has superior properties to the carboxy methyl cellulose (CMC), but it is very difficult to reduce the thickness of the electrode because it can only work through the paste process, Electrode molding made by coating on the current collector has a very difficult disadvantage. Styrene betadien rubber (SBR) has a good advantage in forming the electrode, but it has a disadvantage that it is difficult to apply to electrode production due to its large electrode resistance.

In addition, the method of using activated carbon fiber has the advantages of low electrode resistance and internal resistance of capacitor, but it is difficult to achieve high energy density of capacitor due to low filling density of electrode. It is possible, but it is difficult to increase the output density by increasing the internal resistance of the electrode.

Therefore, the selection of a suitable binder has become an important factor in improving the electrode characteristics of high power high density capacitors.

The present invention is to solve the above problems, an object of the present invention is to form an electrode with a small amount of binder and improve the electrode density by using a binder mixed with polymethacryl and carboxymethyl cellulose And an electrode double layer capacitor capable of reducing resistance and a method of manufacturing the same.

In order to achieve the above object of the present invention, the present invention provides an electric double layer capacitor having an electrode including an activated carbon powder, a conductive material, and a binder for attaching the activated carbon powder and the conductive material to a current collector. do.

The present invention comprises the steps of mixing the activated carbon powder, conductive material and the binder to achieve another object of the present invention to form a mixture; Applying the mixture to a current collector to form an electrode; And it provides an electric double layer capacitor manufacturing method comprising a press molding step to maximize the density of the electrode.

In the present invention as described above, the activated carbon powder is preferably 60 to 90% by weight, the conductive material 10 to 20% by weight, the binder is selected from polymethacrylic, carboxymethyl cellulose and rubber-based polymer It is preferable to use 2 or more types.

In addition, the rubber-based polymer is styrene butadiene louver, the average particle size of the activated carbon is 5 ~ 15㎛, the conductive material using carbon black, the polymethacrylic and carboxy methyl cellulose is 1 ~ 10 to the electrode By weight%, the rubber-based polymer is preferably used 1 to 5% by weight based on the electrode.

In the method of the present invention, water or an organic solvent may be used as a solvent when the mixture is mixed. In this case, it is preferable that the water is ionized water and the organic solvent is N-methyl pyrrolion. .

In addition, in the present invention, it is preferable to use aluminum etching foil and / or foamed nickel as the current collector, and the mixture applied to the current collector is preferably hot-air dried at 60 to 150 ° C.

The press molding is preferably hot pressing in a temperature range of 50 ~ 200 ℃.

In the present invention as described above, the binder serves to prevent the activated carbon from falling off the foil when applying the activated carbon on the aluminum foil, the polymer is used as a binder to facilitate the formation of the electrode. As the current collector, aluminum foil having a purity of 99.8% is used.

In the method of the present invention, when the mixture is formed, the mixture is mixed at room temperature, that is, at a temperature of 10 to 40 ° C, and water or an organic solvent used as a solvent is used 2 to 7 times compared to activated carbon. The water here is preferably ionic water and the organic solvent is N-methyl pyrrolion (NMP), because these binders dissolve well and do not cause changes in the properties of the binder.

According to a preferred embodiment of the present invention, the binder is formed by mixing polymethacryl and carboxymethyl cellulose. In this case, the binder is formed by mixing 1-10 wt% of the polymethacryl and 1-10 wt% of the carboxymethylcellulose to the electrode.

In addition, according to another preferred embodiment of the present invention, the binder is formed by further mixing the polymethacryl and the carboxymethyl cellulose in a rubber-based polymer, in which case the binder is polymethacryl, carboxymethyl cellulose and Styrene-butadiene louver (SBR), and the binder is mixed with 1-10% by weight of the polymethacryl, 1-10% by weight of the carboxymethylcellulose, and 1-5% by weight of the styrene-butadiene louver with respect to the electrode. Is formed by

According to the present invention, by applying a system in which a polysaccharide binder is mixed with a polymethacrylic binder, which is a kind of acrylic, the density of the electrode can be increased and the resistance can be greatly reduced. Therefore, the performance of the electric double layer capacitor including the electrode can be greatly improved.

In the present invention, polymethacrylic, which is a kind of acryl-based, is dispersed in water or an organic solvent, and then mixed with polysaccharide-based and styrene-butadiene louver, and used as an electrode manufacturing binder. Polymethacryl has a strong binding force between the active materials of the electrode even with a small amount, so it is possible to increase the amount of active material per unit area, and to increase the density of the electrode by preventing the increase of the electrode density and the resistance by the binder, and to manufacture a capacitor with improved output density. In order to facilitate molding, it is required to mix and use other binders such as polysaccharide-based rubber.

Conventionally, when using a polysaccharide-based or fluorine-based binder, not only electrode molding is difficult but also active materials are peeled off during thermal compression, and the binder of the entire electrode needs to be added at least 10% by weight, thereby reducing capacity and increasing resistance due to the binder. there was. In addition, when the rubber-based binder is used, it is easy to increase the electrode density by electrode forming and thermocompression, but the internal resistance of the capacitor is increased due to its large resistance. However, in the case of using acrylic polymethacryl, even if the ratio of 3% by weight or less, that is, the amount of the binder is reduced to 1/3 or less than the conventional, it may have the existing physical strength and binding strength.

Therefore, the present invention increases the amount of active material and at the same time decreases the resistance by the binder, thereby increasing the electrode density of the capacitor by 30% or more, while reducing the resistance by 70% or more, and maintaining the bonding state even by thermocompression bonding. Has the advantage of improving.

Example 1

First, an acrylic polymethacryl (PMA) and a carboxymethyl cellulose (CMC), which is a polysaccharide, are mixed to prepare a binder as shown in the following table, and then an activated carbon powder and a conductive material are uniformly mixed with the binder to prepare a mixture. Next, the mixture was applied onto a current collector, hot air dried, and a capacitor electrode was manufactured through a thermocompression bonding process, and then a capacitor was manufactured in a cylindrical type having a size of 1030.

Table 1

PMA (% by weight) CMC (wt%) Resistance (Ω㎠) Electrode Density (g / cm 3) Experimental Example 1 3 2 2 0.67 Experimental Example 2 3 6 8 0.57 Experimental Example 3 5 2 4 0.61 Experimental Example 4 5 6 14 0.54 Experimental Example 5 7 2 6 0.59 Experimental Example 6 7 6 16 0.51

     Activated carbon powder, conductive material, and solvent were mixed in the same composition, and the electrode thickness was adjusted to the same thickness after coating and thermocompression. As the amount of binder in the electrode manufacturing increases, the electrode density decreases while the resistance decreases. It showed higher characteristics.

Although the total amount of binder used was the same as in Experimental Examples 2 and 5, the electrode using a lot of polymethacryl (PMA) was able to obtain favorable results in terms of low resistance and density, and also compared with the same amount of carboxymethyl cellulose (CMC). After crimping, less electrode peeling occurs and resistance is higher.

In case of Experiment 1, electrode production was possible with the smallest amount of binder, and electrode density and resistance were also excellent.

Example 2

3% by weight of acryl-based polymethacryl (PMA) is mixed, and 2% by weight of carboxymethyl cellulose, 4% by weight, and 1% by weight of styrene butadiene louver (SBR), 3% by weight, and 5% by weight, respectively. Binder was prepared by adding Table 2 below.

[Table 2]

PMA (% by weight) CMC (wt%) SBR (wt%) Resistance (Ω㎠) Electrode Density (g / cm 3) Experimental Example 1 3 2 One 2 0.69 Experimental Example 2 3 2 3 8 0.60 Experimental Example 3 3 2 5 16 0.58 Experimental Example 4 3 4 One 6 0.60 Experimental Example 5 3 4 3 14 0.57 Experimental Example 6 3 4 5 18 0.51

     As shown in the table above, as the amount of binder used decreases, the electrode characteristics are improved, that is, the resistance is lowered, and the electrode density is increased. It was found that the use of a large amount caused the increase of resistance. The capacitance and equivalent series resistance (ESR) were measured by manufacturing a 1030 cylindrical size capacitor manufactured according to Experimental Example 1 with the best electrode characteristics. The results showed values of 14F and 20mΩ, respectively, which are about 9F and 60mΩ of the capacitance and resistance of capacitors made of carboxymethyl cellulose (CMC) and polytetrafluoroethylene (PTFE). It can be seen that it has a significantly improved performance compared to

According to the present invention, the polysaccharide binder is mixed with a binder of polymethacrylic, which is a kind of acrylic, and then the rubber is used as an styrene butadiene louver to increase the density of the electrode by 30% or more and at the same time the resistance to 70% or less. Can be reduced. An electric double layer capacitor employing such an electrode can greatly improve energy density and output density.

Claims (11)

70 to 89% by weight of activated carbon powder and 10 to 20% by weight of conductive material, and selected from polymethacryl, carboxymethylcellulose and rubber-based polymers to apply the activated carbon powder and conductive material onto a current collector An electric double layer capacitor characterized in that it comprises an electrode in 1 to 10% by weight of two or more binders. delete The electric double layer capacitor of claim 1, wherein the rubber polymer is styrene butadiene louver. The electric double layer capacitor according to claim 1, wherein an average particle size of the activated carbon is 5 to 15 µm, and the conductive material is carbon black.  According to claim 2 or 3, wherein the polymethacryl and carboxymethyl cellulose is 1 to 10% by weight relative to the total electrode composed of activated carbon, conductive material and binder, the rubber-based polymer is 1 to An electric double layer capacitor, characterized in that ~ 5% by weight is used. A method for producing the electrical double layer capacitor according to any one of claims 1 to 5, wherein 70 to 89% by weight of activated carbon powder and 10 to 20% by weight of conductive material are combined with polymethacryl, carboxymethylcellulose and Preparing a mixture by mixing 1-10 wt% of two or more binders selected from rubber polymers using water or an organic solvent as a solvent (S1); Forming an electrode by applying the mixture in the step S1 to a current collector; And Method of manufacturing an electric double layer capacitor, characterized in that the press forming step (S3) to maximize the electrode density after the step (S2). delete The method of claim 6, wherein the water is ionized water and the organic solvent is N-methyl pyrrolion. The method of manufacturing an electric double layer capacitor according to claim 6, wherein an aluminum etching foil and / or a foamed nickel are used as the current collector in step S2. The method of claim 6 or 9, wherein the mixture applied to the current collector in the step (S2) is hot air dried at 60 ~ 150 ℃. The method of claim 6, wherein the press molding in the step S3 is performed by thermocompression in a temperature range of 50 to 200 ° C. 8.