JP3803084B2 - Manufacturing method of electrode sheet for electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an electric double layer capacitor to be improved in long-term durability and reliability. <P>SOLUTION: A method of manufacturing an electrode sheet for an electric double layer capacitor includes a drying process composed of two steps, one is a continuous drying step where the electrode sheet is dried up passing through a drying chamber as it is fed from a rolled-up electrode sheet and then rolled up again into the rolled-up electrode sheet, and the other is a vacuum drying step where the rolled-up electrode sheet subjected to the continuous drying step is housed in a vacuum chamber and then dried out, whereby the electrode sheet can be made extremely small in residual moisture content and residual IPA content. <P>COPYRIGHT: (C)2004,JPO&amp;NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an electrode sheet for an electric double layer capacitor, and particularly relates to an improved drying process for drying an electrode sheet.
[0002]
[Prior art]
Electric double layer capacitors (capacitors) have a farad-class large capacity and are excellent in charge / discharge cycle characteristics, so they are used as backup power sources for electrical equipment and batteries for various transport equipment including automobiles. From the viewpoint of effective energy use, use in applications such as nighttime power storage is also being considered.
[0003]
The structure of the electric double layer capacitor and the charging / discharging mechanism will be explained briefly. First, the structure is a sheet (hereinafter referred to as an electrode sheet) in which a current collector foil is sandwiched between two sheets of activated carbon (sheet electrode). ) And an insulating separator (hereinafter referred to as a separator) through which ions can permeate, a polarizable electrode for an electric double layer capacitor is immersed in an ionic solution. A voltage that does not cause electrolysis is applied to the polarizable electrode for the electric double layer capacitor, and charging and discharging are performed by making positive and negative electricity relative to the interface.
[0004]
Therefore, due to the nature of the electric double layer capacitor as described above, when a voltage is applied when moisture remains in the electrode sheet, the moisture may cause electrolysis, leading to performance degradation of the electric double layer capacitor. In the manufacturing process, a drying process is required to remove the moisture from the electrode sheet to a practically no problem level.
[0005]
As a method for producing such an electric double layer capacitor including a drying process for removing moisture, for example, a polarizable electrode for an electric double layer capacitor comprising an electrode sheet and a separator is used as a container for an electric double layer capacitor. After being accommodated in the bottom cylindrical container, the container is sealed with a lid body having a liquid injection port, and then the entire container is dried in an atmosphere having a dew point of −20 ° C. or less, and a non-aqueous electrolyte is injected from the liquid injection port. The liquid injection port is sealed (for example, see Patent Document 1).
In addition, for example, a raw material for a sheet-like electrode made of carbon-based powder, a conductive auxiliary agent, and a binder is mixed and kneaded, and the kneaded product is subjected to a moisture removal drying process (for example, see Patent Document 2). ).
[0006]
[Patent Document 1]
JP 2000-49052 A (Page 3-4)
[0007]
[Patent Document 2]
JP 2001-307964 A (page 4-5)
[0008]
[Problems to be solved by the invention]
As described above, when water is mixed in the electrode sheet when voltage is applied to the polarizable electrode for the electric double layer capacitor, this moisture causes electrolysis, so the capacitance of the electric double layer capacitor Problems such as a decrease in resistance, an increase in resistance, and a deterioration in durability.
[0009]
However, since the activated carbon (carbonaceous powder) that constitutes the electrode sheet is porous, it has a very high moisture adsorptivity, and when mixing each raw material, alcohol-based organics are used to facilitate mixing. Since a solvent is added, there is a conflicting problem that moisture necessarily exists in the raw material.
[0010]
Therefore, in order to ensure the long-term durability and reliability of the electric double layer capacitor, a drying process that makes the remaining amount of moisture and organic solvent in the electrode sheet extremely low in the manufacturing process is indispensable.
However, in Patent Document 1 described above, the polarizable electrode for an electric double layer capacitor composed of an electrode sheet and a separator is wound in a cylindrical shape and dried in a container. It is difficult to dry part well.
[0011]
Further, in Patent Document 2 described above, drying is performed at the stage of mixing and kneading the raw material of the sheet-like electrode instead of the electrode sheet. Thereafter, the kneaded product is rolled to produce a sheet-like electrode. There is a problem that the sheet-like electrode absorbs moisture again until the electrode is laminated on the foil to complete the electrode sheet.
[0012]
The present invention has been made in view of the above circumstances, and its purpose is to make the remaining amount of moisture and the like in the electrode sheet extremely low, so that electrolysis of water does not occur during actual use, and for a long time. An object of the present invention is to provide a method of manufacturing an electrode sheet for an electric double layer capacitor that can maintain durability and reliability.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the method for producing an electrode sheet for an electric double layer capacitor according to the present invention includes a step of mixing and kneading raw materials containing a carbonaceous powder, a conductive auxiliary agent and a binder to produce a molding material, and this molding. A step of forming and rolling a material to form a long sheet-shaped electrode, a step of bonding the sheet-shaped electrode and a current collector foil to create an electrode sheet, and a drying step of drying the electrode sheet In particular, in the drying process, the electrode sheet was continuously dried by passing through the drying chamber of the continuous dryer while feeding out the electrode sheet, and the roll-shaped electrode sheet that had undergone this continuous drying was not completely removed by the continuous drying. In order to remove the moisture, it includes vacuum drying in which it is housed in a vacuum chamber and dried (claim 1).
[0014]
According to this configuration, the drying process is performed after the electrode sheet is formed, that is, the electrode sheet itself is dried in a completed state, and the drying process is performed in a state where the electrode sheet is spread and continuous drying and vacuum drying. Therefore, the remaining amount of moisture and organic solvent in the electrode sheet can be set to a very low value.
[0015]
By the way, the sheet-like electrode is normally dried by blowing heated air from the nozzle onto the sheet-like electrode. Metal fines in the pipe (for example, a pipe connecting the heater and the nozzle) or heating lines in the heater are applied to the heated air. In such a case, the deteriorated powder or the like may be mixed, and in this case, they adhere to the electrode sheet surface and become impurities, which contributes to a decrease in durability of the electric double layer capacitor.
[0016]
Therefore, in order to ensure long-term durability and reliability of the electric double layer capacitor, when heating air is used in the electrode sheet drying process, it is also very important to strictly control the amount of impurities mixed in the heating air. It becomes important to.
In this regard, in the present invention, the continuous drying is performed by blowing heated air through a hepa filter (Claim 2). Therefore, even if impurities such as deteriorated powder of the heater are included in the heated air, 0 Since the impurities can be removed by a hepa filter having the ability to collect 99.97% or more of particles of 3 μm or more, the impurities do not adhere to the electrode sheet.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a manufacturing process for manufacturing an electrode sheet for an electric double layer capacitor (hereinafter referred to as an electrode sheet). The raw materials for producing the sheet-like electrode constituting the electrode sheet are activated carbon as a carbonaceous powder, carbon black as a conductive auxiliary, PTFE (polytetrafluoroethylene) powder as a binder, and liquid IPA as a binder auxiliary ( Isopropyl alcohol).
[0018]
First, each raw material is weighed. Next, activated carbon and carbon black are put into a container of a mixer, and these are mixed by a rotating stirring blade. Thereby, activated carbon and carbon black are mixed as uniformly as possible.
And PTFE and IPA are thrown in in the container of the said mixer, and these and the mixture of the said activated carbon and carbon black are mixed. As a result, the activated carbon, carbon black, and PTFE are mixed, and the PTFE is fiberized to entangle the activated carbon and carbon black.
[0019]
Next, the mixed mixture is placed in a container of a kneader (kneader), covered with a lid, and kneaded by rotating the blade while pressing the mixture with the lid. By this kneading, the mixture is kneaded in a clay state, and PTFE is further fibrillated so that activated carbon and carbon black are bound. At this time, the temperature of the container, lid, and blade of the kneader is controlled to be 90 ° C., for example.
Next, after the kneaded material kneaded by the kneader is accommodated in a container of the kneader 9 and made into fine particles, it is put into a calendering machine, and this mixture is formed into a sheet by two rollers. The formed sheet-like molded body is wound up by a winding roller. At this time, the thickness of the sheet-like molded body is, for example, 200 μm.
[0020]
Next, in the roll rolling step, the sheet-like formed body is rolled through two rollers. By performing this roll rolling process a plurality of times, a sheet-like electrode having a predetermined thickness, for example, 160 μm is formed. Incidentally, in the final step of the roll rolling, both end portions in the width direction of the sheet-like electrode are cut with a cutter. What has been described above is the step of forming the sheet-like electrode.
Then, in the lamination step, the sheet electrode that is rolled to form an electrode sheet laminated on an aluminum foil as a current collector foil. This is the process of creating the electrode sheet. And the drying process which consists of continuous drying and vacuum drying is implemented to this roll-shaped electrode sheet.
[0021]
Here, the details of the continuous drying and the vacuum drying in the above-described drying step will be described with reference to FIGS.
First, as shown in FIG. 2, in the continuous drying apparatus 2 for the electrode sheet 1, the continuous drying is performed by passing the electrode sheet 1 wound up in a roll shape through the drying chamber 3 while being fed out from one roller, and this drying. The electrode sheet 1 thus formed is wound with another roller to be rolled again.
[0022]
In this case, the roller that feeds the electrode sheet 1 performs tension control that applies a braking force according to the roll diameter (winded thickness) of the electrode sheet 1, and also rolls the dried electrode sheet 1 again. The roller 4 before one stage performs edge control for displacing the electrode sheet 1 in the width direction so that the tension of the electrode sheet 1 is constant in each part in the width direction.
[0023]
In the drying chamber 3 described above, a plurality of nozzles 5 for blowing heated air from above and below the electrode sheet 1 that is continuously dried are provided. The number of the nozzles 5 is not limited as long as it is sufficient to dry the electrode sheet 1. The heating air is generated by the first heating air supply means 6 having a heater 6a and a fan 6b as shown in FIG. It is sent to the nozzle 5 through the heated air supply means 8.
[0024]
The hepa filter 7 has a capability of collecting 99.97% of particles having a size of 0.3 μm or more by improving the dust collection area by forming a resin fiber non-woven fabric into a pleated shape, and the heated air passing through the hepa filter 7 is in the pipe. The metal powder and the deteriorated powder of the heater are removed. However, since the hepa filter 7 has a very high density due to its high collection capability, the momentum of the heating air is reduced due to its resistance. Further, the hepa filter 7 has a high heat capacity because of its density, and the temperature of the heated air that has passed through the hepa filter 7 also decreases. Therefore, in this embodiment, the heated air passing through the hepa filter 7 is again sprayed from the nozzle 5 onto the electrode sheet 1 after increasing the temperature and pressure using the second heated air supply means 8. Yes.
[0025]
As described above, since the heated air that has passed through the hepa filter 7 has very little impurities in the air, the pipe connecting the second heated air supply means 8 and the nozzle 5 in this embodiment is made of corrosion-resistant stainless steel, Further, for example, a nichrome wire as the heater 8b is covered with the same corrosion-resistant stainless steel pipe to prevent dust generation.
[0026]
For this reason, although the heating air from the 2nd heating air supply means 8 also has very few impurities, the structure which produces | generates a heating air is not necessarily limited to this by the environment of a drying process.
[0027]
As described above, the moisture and the IPA residue contained in the electrode sheet 1 are effectively removed by continuous drying performed by spreading the electrode sheet 1.
The temperature of the heating air when sprayed on the electrode sheet 1 is, for example, about 120 ° C. This is because when the temperature is higher than this temperature, a problem of deterioration of the adhesive or the like occurs.
In the drying chamber 3, the electrode sheet 1 is meandered and dried while being folded several times, or a far-infrared device or the like is installed in the drying chamber 3 while spraying heated air. There is no problem even if the drying capacity is further increased.
[0028]
In order to prevent dust generation on the electrode sheet 1, not only the heater of the second heating air supply means 8 but also the first heating air supply means 6 is covered with a heater coated with stainless steel or the like. Piping may be used.
In the vacuum drying, the electrode sheet 1 wound up in a roll shape after continuous drying is accommodated in the vacuum chamber 10 of the vacuum drying device 9 and dried in a roll state.
[0029]
The vacuum chamber 10 adjusts the degree of vacuum by a vacuum pipe 11 and a purge pipe 12 connected to a vacuum pump (not shown) or adjusts the air flow in the vacuum chamber, and the degree of vacuum can be measured using a vacuum gauge 13. it can. The door 15 to which the observation window 14 is attached seals the vacuum chamber 10 and is opened and closed by a handle 15a.
A heater 16 is provided on the peripheral wall of the vacuum chamber 10, and the temperature in the vacuum chamber 10 is controlled by the heater 16. A core support 17 is provided on the inner wall surface of the vacuum chamber 10, and the core support 17 can support a core 19 passed through a bobbin (winding core) 18 of the roll-shaped electrode sheet 1.
[0030]
Since the roll-shaped electrode sheet 1 supported by the core 19 and the core support 17 in the vacuum chamber 10 is placed under vacuum while being heated as described above, the moisture that cannot be removed by continuous drying, and IPA is removed.
As described above, since the electrode sheet 1 is dried not during its formation but after completion, it is possible to remove moisture and IPA contained in the electrode sheet 1 (sheet-like electrode) as much as possible, and thus high quality. An electric double layer capacitor can be manufactured.
[0031]
Here, the electrode sheet 1 that has been vacuum-dried is inspected for its residual moisture content, residual IPA content, overall appearance, etc. The residual moisture content is, for example, 2000 ppm or less, and the residual IPA content is 900 ppm. The following.
[0032]
In addition, the process of winding the electrode sheet 1 after continuous drying into a roll shape is provided with a dry bath (dew point lower than that in a dry area of −20 ° C. or lower) in the dry chamber 3. By performing the above, re-adsorption of moisture or the like may be prevented when the electrode sheet 1 is wound.
[Brief description of the drawings]
FIG. 1 is a view showing a method of manufacturing an electrode sheet for an electric double layer capacitor according to an embodiment of the present invention. FIG. 2 is a side view showing a drying chamber. FIG. 3 is a supply flow of heating air in the drying chamber. [Fig. 4] Perspective view showing the vacuum chamber [Explanation of symbols]
In the figure, 1 is an electrode sheet, 2 is a continuous drying device, 3 is a drying chamber, 4 is a roller, 5 is a nozzle, 6 is a first heated air supply means, 6a is a heater, 6b is a fan, 7 is a hepa filter, 8 Is a second heating air supply means, 8a is a heater, 8b is a fan, 9 is a vacuum dryer, 10 is a vacuum chamber, 11 is a vacuum pipe, 12 is a purge nozzle, 13 is a vacuum gauge, 14 is an observation window, 15 is a door , 15a is a handle, 16 is a heater, 17 is a core support, 18 is a bobbin (winding core), and 19 is a core.

Claims (2)

Mixing and kneading raw materials including carbonaceous powder, conductive auxiliary agent and binder, and forming a molding material;
Forming and rolling the molding material to form a long sheet electrode;
A process of creating an electrode sheet by laminating the sheet electrode and the current collector foil;
A method of producing an electrode sheet for an electric double layer capacitor by performing a drying step of drying the electrode sheet,
The drying step is continuous drying in which the electrode sheet is passed through a drying chamber while being fed, and
The electrode sheet wound in a roll shape through this continuous drying includes vacuum drying in which the electrode sheet is housed in a vacuum chamber and dried in order to remove moisture that could not be removed by the continuous drying. A method for producing an electrode sheet for an electric double layer capacitor. 2. The method for producing an electrode sheet for an electric double layer capacitor according to claim 1, wherein the continuous drying is performed by spraying heated air that has passed through a hepa filter onto the electrode sheet in a drying chamber.

Images