KR20050092976A - Electrodes and capacitors composed with porous 3-dimensional current collector, and their fabrication methods - Google Patents

Abstract

The present invention relates to an electrode in which an electrode active material is uniformly distributed in pores of a porous three-dimensional current collector, a capacitor using the same, and a method of manufacturing the same. The electrode according to the present invention is excellent in electrical conductivity, the potential distribution on the surface of the electrode is maintained constant, and the separation of the electrode active material is prevented, so the utilization rate, cycle life and high rate charge and discharge characteristics of the electrode active material is excellent.

Description

ELECTRODES AND CAPACITORS COMPOSED WITH POROUS 3-DIMENSIONAL CURRENT COLLECTOR, AND THEIR FABRICATION METHODS}

The present invention relates to an electrode and a capacitor using a porous three-dimensional current collector, and a method for manufacturing the same. Electrode active material particles in the pores of a porous three-dimensional current collector, such as copper, nickel, stainless steel, aluminum, or silver, a conductive material, a binder , Paste together with solvent to uniformly fill the pores of the current collector by paste application method, and press to prepare electrodes in which the electrode active material is uniformly distributed in the pores of the three-dimensional current collector, thereby increasing the conductivity of the electrodes and Electrodes and capacitors using porous three-dimensional current collectors that increase the utilization and cycle life of active materials and improve high rate charge and discharge characteristics by maintaining the potential distribution on the surface and preventing the separation of electrode active materials. It is about.

Conventional electrochemical capacitors can be roughly classified into pseudo capacitors and electric double layer capacitors. Pseudocapacitors use metal oxides as electrode active materials, and over 10 years of development of pseudocapacitors using metal oxides, most of the studies are made of ruthenium oxide, iridium oxide, Tantalum oxide, vanadium oxide, and the like are used. The pseudocapacitor has a disadvantage in that the dislocation of the potential distribution of the metal oxide electrode is uneven and the utilization rate of the electrode active material is lowered. In addition, since the electrode uses an expanded foil, a punched foil, or a non-porous foil as a current collector, which has a two-dimensional structure, there is a disadvantage in that high rate charge and discharge characteristics and utilization rate of the electrode active material are reduced.

In the case of an electric double layer capacitor, porous carbon-based materials having high electrical conductivity, thermal conductivity, low density, suitable corrosion resistance, low thermal expansion rate, and high purity are used as electrode active materials. However, in order to increase the performance of the capacitor, the production of a new electrode active material, the surface modification of the electrode active material, the performance of the membrane and electrolyte, the performance of the organic solvent electrolyte, to increase the utilization rate and cycle life of the electrode active material, and to improve the high rate charge and discharge characteristics Many studies have been conducted on performance improvement.

In the case of capacitors currently being studied, current collectors of both electrodes are made of aluminum or titanium foil, expanded aluminum or titanium foil current collectors, and other perforated aluminum or Punched aluminum or titanium Various types of current collectors such as foil are used. These current collectors are two-dimensional current collectors, and in order to increase the binding force between the electrode active material and the current collector, a large amount of binder must be used in the manufacture of the electrode, or the surface of the current collector must be modified, and the electrode active material can be thickened. It has the same disadvantage as none. As a result, the utilization rate and cycle life of the electrode active material are revealed, and the high rate charge / discharge characteristics are somewhat low, and the improvement thereof is necessary.

Accordingly, it is an object of the present invention to provide a new electrode for a capacitor which improves the utilization of the active material by reducing the amount of the binder while increasing the amount of the electrode active material.

In addition, another object of the present invention is to provide a new capacitor which increases the cycle life and improves high rate charge and discharge characteristics.

Other objects and features of the present invention will appear more specifically in the following detailed description.

       The present invention provides a capacitor electrode comprising a porous three-dimensional current collector and a mixture of an electrode active material, a binder and a conductive material filled in the pores of the current collector.

The porous three-dimensional current collector may be in the form of, for example, a foam, a fiber structure, a porous structure, an etched structure, and a recessed structure.

The content of the mixture is suitably 70-95% by weight relative to the total weight of the electrode. In addition, the mixture has a range of 70 to 99% by weight, 0.5 to 10% by weight and 0.5 to 20% by weight of the electrode active material, the binder and the conductive material, respectively. The content of the binder and the conductive material is about 1 to 5%, the conductive material is reduced by about 5 to 10% compared with the prior art.

In addition, the present invention is to prepare a porous three-dimensional current collector, paste the mixture of the electrode active material, the binder and the conductive material in a uniform state using a solvent, filling the paste into the pores of the porous three-dimensional current collector, It provides a method for manufacturing an electrode for a capacitor comprising the drying and high temperature compression of the porous three-dimensional current collector.

According to the present invention, by increasing the conductivity of the electrode, maintaining the potential distribution of the electrode surface is constant, and preventing the separation of the electrode active material to increase the utilization and cycle life of the active material, and improves the high-rate charge and discharge characteristics. In addition, the present invention can be easily filled with the electrode active material in the pores of the porous three-dimensional current collector, while reducing the amount of the binder can increase the amount of the electrode active material, in some cases the amount of the conductive material can also be reduced There is this.

An electrode and a capacitor using a porous three-dimensional current collector according to the present invention will be described in detail as follows.

       1A and 1B are schematic views showing planes and cross sections of the electrode of the present invention, respectively, showing that the electrode active materials 1 and 3 are uniformly distributed in the pores of the porous three-dimensional current collectors 2 and 4. In the electrode manufacturing method, a porous three-dimensional current collector is manufactured from materials such as copper, nickel, stainless steel, aluminum, titanium, and silver.

The porous three-dimensional current collector is formed of a foamed metal, a metal fiber, a porous metal, an etched metal, a back and forth uneven metal, and the like. (The uneven shape of the front and back means that the bottom or front and back surfaces of the current collector are uneven.) The material is nickel (Ni), copper (Cu), stainless steel (SUS), titanium (Ti), and vanadium. (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), zinc (Zn), molybdenum (Mo), tungsten (W), silver (Ag), gold (Au), ruthenium (Ru), platinum (Pt), iridium (Ir), aluminum (Al), tin (Sn), bismuth (Bi), antimony (Sb), and the like.

Electrode active material particles are formed in the pores of the porous 3D current collector together with a conductive material, a binder, and an organic solvent to be uniformly filled in the current collector pores by a paste coating method. After drying it, the electrode is manufactured by pressing at a pressure of 10 kg / cm 2 -100 ton / cm 2 using a roll press or a flat press at a high temperature of 80 ° C. to 150 ° C.

Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), carboxymethylcellulose (CMC), hydropropylmethylcellulose (HPMC), polyvinyl alcohol (PVA), polyvinyl chloride (PVC) And the like, but is not limited to this, any kind of binder that can be used in the manufacture of conventional electrodes may be used.

As the conductive material, acetylene black, ketjen black, graphite (sfg 6) or super-P may be used, but is not limited thereto.

The organic solvent may be ethyl alcohol, methyl alcohol, isopropyl alcohol, acetone and the like, but is not limited thereto.

When the electrode of the present invention is manufactured, the electrical conductivity of the electrode is improved, the current and potential distribution are constant, local overcharge reaction is suppressed, and the separation of the electrode active material is prevented, thereby increasing the utilization rate and cycle life of the electrode, and high rate charge and discharge. Characteristics are improved. In particular, the effect is large in large capacitors and batteries.

As the electrode active material used for the electrode of the present invention, any active material known in the art as a capacitor active material can be used. For example, porous carbon materials such as activated carbon, carbon aerogels, carbon nanotubes, and carbon nanofibers may be used in the electric double layer capacitor, and ruthenium oxide, iridium oxide, tantalum oxide, vanadium oxide, and the like in the case of pseudocapacitors. In the case of a metal oxide and a conductive polymer capacitor, a conductive polymer such as polyaniline, polypyrrole, and polyacene may be used.

The capacitor can be manufactured by combining the prepared electrodes. Electrode according to the present invention is a capacitor using a separator such as polypropylene (polypropylene), polyethylene (polyethylene), for a polymer electrolyte type capacitor using a polymer electrolyte impregnated with an aqueous solution or an organic solution, and a solid electrolyte using a solid electrolyte There is an advantage that can be used as an electrode for a body capacitor.

When the porous three-dimensional current collector of the present invention is a nano material active material, the effect is great. In the case of a nano-material active material, as the active material is nano-ized, the surface area of the active material increases, and accordingly, the amount of the conductive material and the binder increases, so that the amount of the electrode active material is relatively small and the resistance is increased, thereby reducing the electrode capacity and high rate charge / discharge characteristics. There is a possibility of deterioration. On the other hand, when the porous three-dimensional current collector according to the present invention can be used to produce an electrode by reducing the amount of the binder and the electrical conductivity occurs in three dimensions, so the conductive material can be used less electrode capacity using the nano-material active material And high rate charge / discharge characteristics can be improved. Therefore, if the nano-material active material is developed and commercialized in the future, the role of the porous three-dimensional current collector of the present invention is considered to be very important and its effect is also very large.

The following are examples and comparative examples in which electrodes and capacitors are manufactured using the manufacturing method of the present invention and performance tests are performed. However, the present invention will be described in more detail, but these examples are only illustrative of the present invention. This is not limited to this.

Example 1

5.5 g of activated carbon, 0.4 g of acetylene black, and 0.5 g of polytetrafluoroethylene are mixed with an appropriate amount of 1-methyl-2-pyrrolidinone and acetone, and when the appropriate viscosity is obtained, the paste is foamed nickel ) After filling in the pores of the current collector and drying, heat rolling was performed to obtain a carbon electrode.

A capacitor was formed by stacking a carbon electrode, a PP separator, and a carbon electrode, and injected an ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethylmethyl carbonate (EMC) solution in which 1 M LiPF ₆ was dissolved, and then 240 mA (each). 10 mA / cm ² ) and 480 mA (20 mA / cm ² ) of constant current were charged to 1-2 V to investigate electrode capacity and voltage drop.

Example 2

5.5 g of activated carbon, 0.4 g of acetylene black, and 0.5 g of polytetrafluoroethylene were mixed with an appropriate amount of 1-methyl-2-pyrrolidinone and acetone, and when the appropriate viscosity was obtained, the paste was mixed with nickel fiber (Ni fiber ) After filling in the pores of the current collector and drying, heat rolling was performed to obtain a carbon electrode.

A capacitor was formed by stacking a carbon electrode, a PP separator, and a carbon electrode, and injected an ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) solution in which 1 M LiPF ₆ was dissolved, and then 240 mA ( 10 mA / cm ² ) and 480 mA (20 mA / cm ² ) were charged to 1-2 V to investigate the electrode capacity and voltage drop.

Example 3

5.5 g of activated carbon, 0.4 g of acetylene black, and 0.5 g of polytetrafluoroethylene are mixed with an appropriate amount of 1-methyl-2-pyrrolidinone and acetone, and when the appropriate viscosity is obtained, the paste is made of porous aluminum. ) After filling in the pores of the current collector and drying, heat rolling was performed to obtain a carbon electrode.

A capacitor was formed by stacking a carbon electrode, a PP separator, and a carbon electrode, and injected an ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) solution in which 1 M LiPF ₆ was dissolved, and then 240 mA ( 10 mA / cm ² ) and 480 mA (20 mA / cm ² ) were charged to 1-2 V to investigate the electrode capacity and voltage drop.

Example 4

5.5 g of activated carbon, 0.4 g of acetylene black, and 0.5 g of polytetrafluoroethylene are mixed with an appropriate amount of 1-methyl-2-pyrrolidinone and acetone, and when the appropriate viscosity is obtained, the paste is etched Al) was filled in the pores of the current collector and dried, and then heated and rolled to obtain a carbon electrode.

A capacitor was formed by stacking a carbon electrode, a PP separator, and a carbon electrode, and injected an ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) solution in which 1 M LiPF ₆ was dissolved, and then 240 mA ( 10 mA / cm ² ) and 480 mA (20 mA / cm ² ) were charged to 1-2 V to investigate the electrode capacity and voltage drop.

Example 5

5.5 g of activated carbon, 0.4 g of acetylene black, and 0.5 g of polytetrafluoroethylene were mixed with an appropriate amount of 1-methyl-2-pyrrolidinone and acetone, and when the appropriate viscosity was obtained, the paste was unevenly rolled back and forth. After filling and drying in the pores of an electrical power collector, it heat-rolled and obtained the carbon electrode.

A capacitor was formed by stacking a carbon electrode, a PP separator, and a carbon electrode, and injected an ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) solution in which 1 M LiPF ₆ was dissolved, and then 240 mA ( 10 mA / cm ² ) and 480 mA (20 mA / cm ² ) were charged to 1-2 V to investigate the electrode capacity and voltage drop.

Example 6

5.5 g of activated carbon, 0.4 g of acetylene black, and 0.5 g of polytetrafluoroethylene were mixed with an appropriate amount of 1-methyl-2-pyrrolidinone and acetone, and when the appropriate viscosity was obtained, the paste was unevenly rolled back and forth. After filling and drying in the pores of an electrical power collector, it heat-rolled and obtained the carbon electrode.

A capacitor was formed by stacking a carbon electrode, a PP separator, and a carbon electrode, and injected an ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) solution in which 1 M LiPF ₆ was dissolved, and then 240 mA ( 10 mA / cm ² ) and 480 mA (20 mA / cm ² ) were charged to 1-2 V to investigate the electrode capacity and voltage drop.

Comparative Example 1

5.5 g of activated carbon, 0.4 g of acetylene black, and 0.5 g of polytetrafluoroethylene (hereinafter referred to as "PTFE") with an appropriate amount of 1-methyl-2-pyrrolidinone (hereinafter referred to as "NMP") and acetone When the mixture was mixed and the proper viscosity was obtained, the paste was filled into the pores of the expanded aluminum foil current collector and dried, and then heated and rolled to obtain a carbon electrode.

A capacitor was formed by stacking a carbon electrode, a PP separator, and a carbon electrode, and injected an ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) solution in which 1 M LiPF ₆ was dissolved, and then 240 mA ( 10 mA / cm ² ) and 480 mA (20 mA / cm ² ) were charged to 1-2 V to investigate the electrode capacity and voltage drop.

The results of charging and discharging at 240 mA of the capacitors s1 to s6 of Examples 1 to 6 and the capacitors of Comparative Example 1 (b1) are shown in FIG. 2. From this, it can be seen that the electrode capacitance characteristics of the capacitor according to the present invention are superior to those of the capacitor of the comparative example.

The results of charging and discharging at 480 mA of the capacitors s1 to s6 of Examples 1 to 6 and the capacitors of Comparative Example 1 (b1) are shown in FIG. 3. It can be seen that the high rate discharge characteristic of the capacitor according to the present invention is superior to that of the capacitor of Comparative Example 1.

The capacitances of the capacitors s1 to s6 of Examples 1 to 6 and the capacitors of Comparative Example 1 (b1) are compared with each other, and are shown in FIG. 4. It can be seen that the capacity characteristics of the capacitor according to the present invention are superior to those of the capacitor of Comparative Example 1.

Table 1 shows the voltage drop characteristics of the capacitors s1 to s6 of Examples 1 to 6 and the capacitors of Comparative Example 1 (b1). It can be seen that the voltage drop phenomenon of the capacitor according to the present invention is significantly reduced.

[Table 1] Voltage drop characteristics of capacitors according to Examples and Comparative Examples [unit: V]

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 120 mA 0.134 0.174 0.145 0.154 0.091 0.151 0.210 240 mA 0.279 0.349 0.300 0.319 0.183 0.311 0.411 480 mA 0.587 0.710 0.636 0.658 0.372 0.639 0.815

According to the present invention, an electrode in which an electrode active material is uniformly distributed in pores of a porous three-dimensional current collector, a capacitor using the same, and a method of manufacturing the same are provided. Electrode according to the present invention is excellent in electrical conductivity, utilization of electrode active materials, cycle life and high rate charge and discharge characteristics, can be applied to various industrial fields, such as for various small electronic devices, communication devices and power supply of electric vehicles, localization of various devices This can lead to import substitution and export increase.

       1A and 1B are schematic cross-sectional views of an electrode composed of a porous three-dimensional current collector of the present invention.

2 is a graph showing charge and discharge results at 240 mA of a capacitor and a capacitor of Comparative Example 1 according to the embodiments of the present invention.

3 is a graph showing charge and discharge results at 480 mA of a capacitor according to the embodiments of the present invention and a capacitor of Comparative Example 1. FIG.

4 is a graph comparing capacitance characteristics of a capacitor according to embodiments of the present invention and a capacitor of Comparative Example 1. FIG.

*** Explanation of symbols for main parts of drawing ***

1: electrode active material 2: porous 3D current collector

3: electrode active material 4: porous 3D current collector

Claims (12)

Porous three-dimensional current collector, A capacitor electrode comprising a mixture of an electrode active material, a binder and a conductive material filled in the pores of the current collector. The electrode for a capacitor according to claim 1, wherein the content of the mixture is 70 to 95 wt% based on the total weight of the electrode. The electrode of claim 1, wherein the mixture contains 70 to 99 wt%, 0.5 to 10 wt%, and 0.5 to 20 wt% of an electrode active material, a binder, and a conductive material, respectively. The electrode of claim 1, wherein the porous three-dimensional current collector is any one selected from a foam, a fiber structure, a porous structure, an etched structure, and a recessed structure. The method of claim 1, wherein the material of the porous three-dimensional current collector is nickel (Ni), copper (Cu), stainless steel (SUS), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn) , Iron (Fe), cobalt (Co), zinc (Zn), molybdenum (Mo), tungsten (W), silver (Ag), gold (Au), ruthenium (Ru), platinum (Pt), iridium (Ir) , An electrode for a capacitor, which is any one selected from the group consisting of aluminum (Al), tin (Sn), bismuth (Bi), antimony (Sb), and the like. The method of claim 1, wherein the electrode active material is a porous carbon material selected from activated carbon, carbon aerogel, carbon nanotube, carbon nanofiber in the case of an electric double layer capacitor, ruthenium oxide, iridium oxide, tantalum in the case of pseudocapacitor In the case of a metal oxide selected from an oxide and a vanadium oxide, and a conductive polymer capacitor, an electrode for a capacitor which is a conductive polymer such as polyaniline, polypyrrole, or polyacene. The electrode of claim 1, wherein the conductive material is selected from the group consisting of acetylene black, ketjen black, graphite (sfg 6), and super-P. The electrode of claim 1, wherein the binder is selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, carboxymethylcellulose, hydropropylmethylcellulose and polyvinyl alcohol. Prepare a porous three-dimensional current collector, The mixture of the electrode active material, the binder and the conductive material is pasted into a uniform state using a solvent, Filling the paste in the pores of the porous three-dimensional current collector, Electrode manufacturing method for a capacitor comprising the drying and high-temperature pressing the porous three-dimensional current collector. 10. The method of claim 9, wherein the high temperature pressing is performed at a pressure of 10 kg / cm 2-100 t / cm 2 at a temperature of 80 ° C-150 ° C. A capacitor comprising the electrode according to claim 1, and a separator or an electrolyte. The method of claim 11, wherein the capacitor is a capacitor using a polypropylene or polyethylene separator, a polymer electrolyte capacitor using a polymer electrolyte impregnated with an aqueous solution or an organic solution, or an all-solid capacitor using a solid electrolyte, characterized in that Capacitor.