JPH011220A - Polarizable electrode and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a polarizable electrode used for energy storage devices such as electric double layer capacitors and secondary batteries, and counter electrodes of electrochromic display elements, and a method for manufacturing the same. It is related to.

BACKGROUND ART Conventionally, for example, take an electric double layer capacitor as an example, a polarizable electrode used therein is shown in FIG. That is, it has a layer 1o1 formed by depositing aluminum metal on the surface of a cloth 1oo made of activated carbon fibers by plasma spraying. A coin-type electric double layer capacitor has been developed using this pair of polarizable electrodes, separator 102, cases 103 and 104, and gasket ring 105. Activated carbon fiber 100 and separator 10
2 is impregnated with an electrolyte solution in which an electrolyte such as tetraethylammonium verchlorate is dissolved in a solvent such as propylene carbonate. Here metal layer: 1
', lie 7 (cloth 10o made of tricarbon fiber and case 103
, 104, and by lowering the contact resistance between the two, the electric double layer capacity accumulated on the activated carbon fiber surface can be efficiently drawn out.
and achieve low internal resistance of the capacitor.

Problems to be Solved by the Invention Figure 6 shows the changes in capacitance and resistance over time when a capacitor with polarizable electrodes having the conventional configuration described above is maintained under conditions of 2.8 V applied in series and 86°C. This shows that. As can be seen from this figure, the initial large capacity and low resistance value changes with the time of the life test, and after 1000 hours, the capacitance value is -15%.

The resistance value has changed to +300%. Possible causes of such changes in characteristics include the formation of voids 112 at the interface between the activated carbon fiber layer 11o and the metal layer 111, and the formation of an oxide layer 113 on the metal surface, as shown in FIG. . Such voids and oxidized layers are accelerated under conditions of high temperature and voltage application, and trace decomposition gas of the electrolyte generated at this time is localized in these voids and between the metal layer 111 and the case 114 and further Deterioration of the above characteristics may be accelerated.

The present invention strengthens the contact between the metal current collecting layer and the activated carbon fiber layer, minimizes the change in contact resistance even during high-temperature load tests, and maintains the initial high performance values of capacitance and resistance over a long period of time. The present invention provides a polarizable electrode structure and a method for manufacturing the same.

Means for Solving the Problems The present invention is a polarizable electrode composed of carbon or activated carbon, a mixed layer of metal and carbon atoms on the surface thereof, and a metal layer on this mixed layer.

Furthermore, while irradiating the carbon surface with an ion beam of an inert gas such as nitrogen or argon, Ta, Ti, and A
fi, f(f, Nb, Zr, Si) A mixed layer of the metal and carbon is formed on the carbon surface by depositing a metal such as Nb, Zr, or Si by vapor deposition or sputtering. The present invention relates to a method for manufacturing a polarizable electrode, which is characterized by forming a layer.

Function According to the present invention, since there is a mixed layer between the metal current collecting layer and the activated carbon fiber layer, which is generated by injecting metal into the surface of the activated carbon, mutual physical and electrical contact forces are reduced. becomes strong, and the adhesion between the two layers remains almost unchanged even when used under high-temperature loads.As a result, the high performance of electric double layer capacitors, batteries, and electrochromic display elements using this material is maintained over a long period of time. be done.

EXAMPLES Before describing specific examples of the present invention, the basic idea of the present invention and the method of forming a carbon/metal mixed layer will be described in detail.

In order to efficiently collect current from the electric double layer capacity on the surface of activated carbon fibers, a current collecting color layer has conventionally been formed by a method such as plasma spraying or vapor deposition at A° C., as described above. An enlarged and schematic representation of this interface is shown in FIG. 6, where the AI metal layer 121 is only formed in physical contact with the surface of the carbon layer 120, and the carbon atoms 122 and There is no layer in which An atoms 123 coexist, and the bonding force between them is
It's just Humandeavmarska. When plasma spraying is used, the molten 82 is embedded into the carbon fibers, resulting in a so-called "anchor effect" that results in stronger adhesion than other forming methods, but if you look at the contact area microscopically, it is the same as shown in Figure 6. It is. In contrast, the interface of the polarizable electrode of the present invention has a schematic configuration shown in FIG. That is, carbon layer 1
It is composed of a carbon and metal mixed layer 2 that exists continuously with this layer, and a metal layer 3 on top of this layer.As can be seen from the figure, the mixed layer 2 contains, for example, aluminum atoms 4
and carbon atom 6 are mixed.

In this mixed layer 2, the composition ratio of carbon atoms and metal atoms in the depth direction between the carbon layer 1 and the metal layer 3 can be arbitrarily controlled depending on the conditions at the time of formation, and the optimum strength can be maintained.

The degree of this mixing may be either a physical mixture of both elements or a so-called metal carbide compound, and this also depends on the conditions during production.

Next, a method for manufacturing the polarizable electrode of the present invention will be described. FIG. 2 shows an example of an apparatus for forming the polarizable electrode of the present invention. 10- in advance in Pelger 1o
A high vacuum of 7 Torr is maintained, and argon gas is introduced from the gas introduction hole 11. While irradiating the activated carbon fiber cloth 14 held on the base 13 with an Ar ion beam ionized by the ionization unit 12, the aluminum powder 16 placed in the heating boat 15 is heated and evaporated, and the carbon fibers are simultaneously irradiated with the ion beam. A film is formed on the cloth 14. At this time, the carbon is being hit by the ion beam, so the aluminum atoms that evaporate and fly penetrate deep into the constituent carbon atoms (approximately 100 people), forming a two-layer mixed layer on the carbon, and this continues until the ion beam no longer enters. A mixed layer is formed followed by an A2 deposited layer. As a result, a polarizable electrode having a cross-sectional configuration as shown in FIG. 1 is formed. 17 is a rotor IJ-pump, 18 is a diffusion pump, 19 is a power source and control unit for ion generation, and 2o is a power source and control unit for vapor deposition. For this purpose, for example, an IVD device manufactured by Nissin Electric Co., Ltd. can be used.

In addition to such an apparatus, a method of directly implanting ions such as 2 into carbon with an ion beam is also possible.

Next, specific examples of the present invention will be described.

Example 1 Weight: 160 y/n? A mixed layer and a single layer of Al1 were formed on the surface of a cloth made of phenolic activated carbon fibers using the rVD apparatus described above. The thickness of the mixed layer was 1000 mm, and the thickness of the single layer was 9 mm.

Example 2 A second layer of 100 μm was further formed on the surface of the material obtained in Example 1 by plasma spraying.

Example 3 The surface of the same activated carbon fiber cloth as in Example 1 was ion beam implanted with A4 to a depth of 100 mm.

On top of this, a plasma sprayed A2 layer of 100 μm is further formed.

The polarizable electrodes obtained in each example were punched out to a diameter of 5 rm, and assembled into a capacitor having the configuration shown in FIG.

Comparative Example 1 A capacitor was assembled by punching a cloth made of phenolic activated carbon fiber with a fabric weight of 150 y/m'' to a diameter of 51 mm.

Comparative Example 2 A 100 μm thick A2 layer was formed on the surface of a cloth cut from phenolic activated carbon fiber with a basis weight of 150 y/m by plasma spraying, and then punched out to a diameter of 5 mm to assemble a capacitor.

Table 1 lists the initial and life characteristics of the capacitors obtained through the above experiments.

Effects of the Invention As described above, according to the present invention, since there is a mutual diffusion layer between the carbon and metal layers at the interface, the adhesive force between the two is greater than mere physical adhesion, and the bonding force between the two at the interface increases. Peeling and oxidation of the metal layer are less likely to occur, and the characteristics of electric double layer capacitors using this material are greatly improved.

In this example, only activated carbon fibers were described as the carbon material, but the same effect can be obtained for carbon fibers, carbon in the form of plates, pellets, membranes, sheets, porous bodies, etc., and activated carbon. Needless to say, you can get it. Metal is also A
Valve metals other than 2 (Ta, Hf, Ti, Nb, Zr)
or SL may also be used. Furthermore, the present invention is also effective for polarizable electrode applications other than capacitors, such as Li secondary batteries and counter electrodes of electrochromic display elements.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of a polarizable electrode of the present invention, Fig. 2 is a diagram showing an example of a device for producing the metal mixed layer and metal layer used in the invention, and Fig. 3 is a diagram of a conventional polarizable electrode. A diagram showing the state of deterioration, Figure 4 is a cross-sectional configuration diagram of an electric double layer capacitor, Figure 5 is a life characteristic diagram of a conventional electric double layer capacitor, and Figure 6 is a schematic cross-sectional diagram of a conventional polarizable electrode. . 1... Carbon layer, 2... Metal carbon mixed layer,
3...-metal layer, 4...-metal atom, 6-
...Carbon atom. Name of agent: Patent attorney Toshio Nakao and one other person
Size O
L5 sect Law sect 4th sect

Claims (5)

[Claims] (1) A polarizable electrode composed of carbon or activated carbon, a mixed layer of metal and carbon atoms on the surface, and a metal layer on this mixed layer. (2) The polarizable electrode according to claim 1, wherein the carbon or activated carbon has the shape of a plate, sheet, fiber, or porous molded body. (3) The metal is Ta, Al, Hf, Zr, Ti, Nb, S
The polarizable electrode according to claim 1, characterized in that it is made of one or more of the following. (4) The polarizable electrode according to claim 1, wherein the mixed layer is either a compound layer of carbon and metal or a physical mixed layer of carbon and metal elements. (5) While irradiating the surface of carbon with an ion beam of inert gas such as nitrogen or argon,
, Hf, Zr, and Si by vapor deposition or sputtering to form a mixed layer of the metal and carbon on the carbon surface, and further to form the metal layer successively on this mixed layer. A method for manufacturing a polarizable electrode, characterized by: