JPH11329904A - Nonaqueous electric double layer capacitor and method of producing cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high reliability under high temperature without electrode degradation due to swelling by an electrolytic organic solvent and without damage to an electrode material by applying slurry to a collector and removing an organic solvent by drying the coating layer formed. SOLUTION: Polytetrafluorethylene is used as a binder. Although a means for drying a coating layer is not limited, drying temperature is preferably about 50 to 300 deg.C, depending on an organic solvent type, thickness of the coating film, carbon material concentration in the coating film, organic solvent content or auxiliary binder content and the like. Since a coated slurry is an organic solvent slurry, there is little problem for a capacitor and the like even though some of the organic solvent is made to remain in the electrode during drying process. That is to say, since some of the organic solvent is allowed to remain in the electrode and dose not need to be thoroughly dried, drying condition is largely alleviated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electric double layer capacitor, a lithium secondary battery and the like which can be repeatedly charged and discharged.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing an electrode of an electric double layer capacitor by a coating method, a carbon material, for example, powder of activated carbon or carbon black which is a conductive agent is mixed with a binder solution to form a slurry. A method of forming an electrode by coating and drying on a current collector is known.

[0003] The binder is used to bind a carbon material and fix it on a current collector.
Polyvinylidene fluoride (hereinafter abbreviated as PVDF) dissolved in an organic solvent such as -methyl-2-pyrrolidone is used. However, in an organic solvent-based electric double layer capacitor, PVDF swells at a high temperature when it comes into contact with a polar solvent such as sulfolane or propylene carbonate used as an electrolyte solvent. There is a problem that reliability is reduced.

Further, N-methyl-2-pyrrolidone, which is an organic solvent, is strongly adsorbed on a carbon material such as activated carbon and cannot be completely desorbed unless the drying temperature after coating is raised to 200 ° C. or higher. However, the melting point of PVDF is 1
Since the temperature is about 70 ° C., the drying temperature cannot be raised much, and there is a problem that N-methyl-2-pyrrolidone considerably remains in the electrode made of a carbon material and the capacity of the capacitor decreases.

On the other hand, polytetrafluoroethylene is extremely thermally and chemically stable, and an aqueous dispersion of polytetrafluoroethylene obtained by an emulsion polymerization method is a powdery material such as carbon powder. It has been known that when kneaded together, it becomes fibrillated (fibrilized) and exhibits an effect as a binder.

For example, in Japanese Patent Application Laid-Open No. 2-158055, polytetrafluoroethylene is used together with a thickener such as carboxymethyl cellulose in the form of an aqueous dispersion thereof as a binder for a positive electrode mixture for a secondary battery. It is described that a slurry ink suitable for coating is formed by using an aqueous dispersion.

However, in a capacitor using an organic solvent as an electrolytic solution, if undried moisture remains in the capacitor during charging, the residual moisture is electrolyzed to generate hydrogen, In order to deteriorate the performance of the capacitor, it is necessary to completely remove the water in the system in the drying step. However, when the above-mentioned aqueous dispersion of polytetrafluoroethylene is used, in the actual manufacturing process of the coated electrode, the thickness is usually about 100 μm,
Since the electrode layer is continuously applied and formed, it is quite difficult to quickly dry the moisture from such a relatively thick applied layer.
There was a problem that it had to be dropped extremely.

[0008] The problem of residual moisture in the same coating step is that a positive electrode active material such as a lithium cobalt oxide powder, a lithium nickel oxide powder, and a lithium manganate powder or a carbon-based negative electrode active material is mixed with a binder water. There is also a method of forming an electrode of a lithium ion secondary battery or the like by mixing with a dispersion to form a slurry, applying the slurry on a current collector and drying the slurry. In a non-aqueous battery such as a lithium-ion battery, when undried moisture remains, lithium produced by reduction at the negative electrode reacts with water to cause deterioration of battery performance, and a positive electrode active material such as lithium manganate is used. This is because the material is damaged only by contact with water.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to prevent the electrode from swelling and deteriorating with respect to the organic solvent of the electrolyte and to prevent the electrode active material from being damaged. It is to provide a method of manufacturing a non-aqueous electric double layer capacitor and a battery having high reliability even below.
In particular, the present invention provides a method for manufacturing the electrode easily and industrially with high productivity using a binder mainly composed of polytetrafluoroethylene without causing a problem due to residual water by a coating method. It is to be.

[0010]

According to the present invention, there is provided a non-aqueous electric device provided with an electrode body formed by forming an electrode material comprising a binder mainly composed of a carbon material and polytetrafluoroethylene on a current collector. In the method for manufacturing a double-layer capacitor, a step of mixing the carbon material and an organic solvent dispersion of polytetrafluoroethylene to form a slurry, a step of applying the slurry to the current collector, and a step of forming the formed coating layer A method for producing a non-aqueous electric double layer capacitor, wherein an electrode body is produced by a step of drying to remove an organic solvent is provided.

Further, according to the present invention, there is provided a method for manufacturing a non-aqueous battery provided with an electrode body formed by forming an electrode material comprising an electrode active material and a binder mainly composed of polytetrafluoroethylene on a current collector. In the method, a step of mixing the active material material and an organic solvent dispersion of polytetrafluoroethylene to form a slurry, a step of applying the slurry to the current collector, and drying the formed coating layer to form an organic A method for producing a non-aqueous battery, wherein an electrode body is produced by a step of removing a solvent is provided.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a method for manufacturing an electrode according to the present invention will be described in detail.

In the case of an electric double layer capacitor, the carbon material used as an electrode material has a specific surface area of 700 to 2500 m ² / g, preferably 1000 to 2500 in order to increase the capacity of the electric double layer capacitor and lower the internal resistance. 20
00 m ² / g of carbon material is desirable. Examples of such a carbon material include activated carbon, polyacene, carbon black and the like. As activated carbon, coconut activated carbon,
Phenol-based activated carbon, petroleum coke-based activated carbon and the like are mentioned, and those subjected to steam activation treatment and molten KOH activation treatment are preferably used. The specific surface area is a value measured by the BET method.

Most preferably, it is a carbon material comprising a mixture of the above activated carbon and carbon black as a conductive material. The content of the conductive material is 5 to 20% by weight in the electrode material.
Is preferable because the conductivity is high and the capacity is increased.

As the electrode active material of the battery, for example, in the case of a lithium ion secondary battery, the positive electrode active material is lithium cobalt oxide, lithium nickelate, or the like.
Composite oxides such as lithium manganate are preferred, and carbon materials such as artificial graphite, soil graphite, expanded graphite, flaky graphite, and coke are preferred as the negative electrode active material. In the case of a lithium primary battery, manganese dioxide powder or fluorinated carbon powder is used as a positive electrode active material. The carbon material is usually used as a powder, but preferably has a particle size of about 1 to 50 μm. In a preferred embodiment, a conductive material such as carbon black is used as the electrode active material in addition to the composite oxide. The content of the conductive material is 1 to 20% by weight in the electrode material.

The non-aqueous battery in the present invention includes, in addition to the above-mentioned lithium ion battery, a battery using another alkali metal as an active material, and includes both a primary battery and a secondary battery.

In the present invention, polytetrafluoroethylene (hereinafter abbreviated as PTFE) is used as a binder. PTFE has a melting point of 327 ° C. and high heat resistance, and does not dissolve or swell due to an organic solvent. Therefore, it is stable even at a high temperature with respect to polar solvents such as sulfolane and propylene carbonate used as a solvent for the electrolyte, and the reliability such as the life of a capacitor and the life of a battery at a high temperature is improved.

In the present invention, PTFE is dispersed in an organic solvent to form a stable organic solvent dispersion of PTFE particles, that is, a PTFE organosol. P
TFE organosols can be prepared from aqueous dispersions of PTFE, for example, from GB 1064840, JP-B-48-17.
No. 542, JP-B-48-17548, or JP-B-48-17549, which can be used to azeotropically remove water using an organic solvent.

Various commercially available PTFE aqueous dispersions are available. Preferably, tetrafluoroethylene is polymerized by an emulsion polymerization method so that the average particle size is 0.1 to 0.5 μm and the average molecular weight is about 100,000 to 20,000,000, and a polyoxyethylene alkyl allyl ether ( For example, an aqueous PTFE dispersion containing about 2 to 10% of a nonionic surfactant such as Union Carbide Triton X100) can be suitably used.
An organic solvent is added thereto and azeotropic distillation is performed to distill and remove water.

The organic solvent used here is insoluble or hardly soluble in water and forms an azeotropic composition with water. For example, benzene, toluene, xylene,
Aromatic hydrocarbons such as mesitylene, ethylbenzene, propylbenzene, cumene; ketones such as methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone; ethyl acetate, isopropyl acetate, butyl acetate, acetic acid Esters such as isobutyl are preferred.

In the azeotropic distillation operation, the above organic solvent and an aqueous dispersion of PTFE are mixed and charged into a vessel, and the mixture is heated while stirring to distill an azeotropic mixture of water and an organic solvent. Although the operation may be performed, preferably, an organic solvent is charged into a heating vessel equipped with a stirrer, a reflux condenser, and a dropping device, and the mixture is heated and boiled while stirring, and the aqueous dispersion of PTFE is gradually added to the boiling organic solvent. It is desirable to use a method of dropping the solution. The azeotropic mixture of distilled water and organic solvent is
Upon cooling, the organic layer is separated into an organic layer and an aqueous layer. The organic layer is refluxed to a heating vessel as required, and the aqueous layer is taken out of the system. Along with such an operation, a new organic solvent can be additionally charged. Thus, such heating azeotropic operation is continued until no water is found in the distillate, that is, until the distillation temperature reaches the boiling point of the organic solvent.

The concentration of the PTFE particles in the PTFE organosol is 1 to 50% by weight, preferably 3 to 40% by weight. If the concentration is lower than this, PT as a binder
If the amount of FE is not sufficient and the concentration is higher than this,
The amount of aggregation of the PTFE particles increases, and it becomes difficult to obtain a uniformly dispersed sol.

The PTFE concentration can be adjusted by adding an organic solvent to the PTFE organosol after the azeotropic operation,
Alternatively, it can be carried out by further distilling off the solvent. Note that the organic solvent to be added for concentration adjustment is not necessarily an azeotropic solvent with water.

As described above, the obtained PTFE organosol has a water content of 0.5% by weight or less, preferably 0.1% by weight or less.

In the present invention, the addition amount of PTFE is 0.1% to 2% by weight as a solid content with respect to the electrode material.
0% is preferred. If the amount is too small, the bonding strength as a binder is weak, and peeling or the like occurs in the process. On the other hand, the PTFE binder does not essentially contribute to the electrochemical reaction of the battery, and if the amount is too large, the capacity of the capacitor and the capacity of the battery are undesirably reduced.

In the present invention, the thus obtained PT
The FE organosol is mixed with, for example, a carbon material to form a carbon material-PTFE organic solvent slurry. This is the slurry for application in the case of an electric double layer capacitor. Similarly, in the case of a battery, an organic solvent slurry of the electrode active material material-PTFE is used as a slurry for application.

When the coating / drying step is performed using this coating slurry, it is practically possible to use a carbon material-PTFE organic solvent slurry or an electrode active material material-PTFE organic solvent slurry. Since the same operation is performed, in order to avoid inconvenience, the description of the coating / drying step will be described below using a carbon material-PTFE organic solvent slurry as a representative. Therefore, a necessary part should be read as "electrode active material" in "carbon material".

The mixing of the carbon material and the PTFE organosol completely disperses the carbon material particles and the PTFE particles in each other.
In order to mix and promote fibrillation of PTFE, it is preferable to mix or knead while applying a shearing force. As such a shear mixer, for example, kneaders such as a kneader mixer, a Muller mixer, a ball mill, a roll mill, a pebble mill, an internal Misaki, and a pony mixer are preferably used. By shear mixing
The PTFE is fibrillated, and the obtained slurry becomes a paste. PTF thus fibrillated
When E is applied, the particles of the carbon material can be strongly bound on the current collector, as described later. In addition, for the shear mixing, an organic solvent is further added so as to have an appropriate viscosity.
It may be carried out after dilution.

The mixing is carried out without applying a shearing force, and the obtained slurry for coating is coated and dried on a current collector, and this is strongly pressed by passing it through a pressure roller. It is also possible to fibrillate the PTFE and bind the carbon material.

The mixing time may vary depending on the type of mixer, PTFE sol concentration, type and amount of carbon material, etc.
Usually, it is about 5 minutes to 3 hours.

In the present invention, PT is used as the binder.
FE is used as a main component, but when applied to a relatively smooth current collector surface other than a porous current collector such as a wire mesh or punched metal or expanded metal, PTFE alone has an adhesive property. May not be enough. In such a current collector having a smooth surface, an auxiliary binder component can be used in order to improve the adhesion to the surface. As such an auxiliary binder component,
Resin components other than PTFE, for example, methyl cellulose, carboxymethyl cellulose, ethyl cellulose,
Sodium polyacrylate, PVDF, fluoro rubber, EPD
It is preferable to use M rubber, styrene butadiene rubber, neoprene rubber, polyimide, polyamide imide, epoxy resin, urethane resin, or the like.

In particular, EPDM rubber, carboxymethylcellulose, ethylcellulose and PVDF are PTF
It has good miscibility with the E organosol, and improves adhesion to smooth surfaces such as aluminum foil and copper foil. These resins can be used as a solution or an organic solvent dispersion in any form depending on the situation, but it is particularly preferable to add them to the slurry during the above-mentioned shear mixing.

The amount of these auxiliary binder resins to be added in addition to PTFE is 0.1% by weight based on the carbon material.
1% to 5% is preferred. If the amount is too small, the effect of enhancing the adhesion is weak, and if the amount is too large, the capacity of the capacitor and the capacity of the battery are undesirably reduced.

In the present invention, the thus prepared
A slurry in which a carbon material and PTFE are well dispersed in an organic solvent (a slurry in which a carbon material is uniformly dispersed in a PTFE organosol) is applied as a coating slurry on a current collector to form a coating layer. As the material of the current collector, aluminum, iron, nickel, titanium, copper, or a single metal or alloy such as stainless steel is used. As the current collector of the electrode of the electric double layer capacitor and the positive electrode of the battery, Aluminum is preferred because it is light and has low electrical resistance. The shape is arbitrary such as a plate shape, a foil shape, a wire mesh shape, a punched metal shape, an expanded metal shape, and the like.
Above all, a foil-like metal with a thickness of about 20 to 100 μm,
The formation of a wound electrode body or a laminated electrode body is easy and preferable.
When a metal foil is used as a current collector, its surface is chemically and
It is preferable to roughen the surface by electrochemical or physical etching, because the adhesion between the electrode material and the metal foil is improved.

As a means for applying the coating slurry to the current collector, various known coating apparatuses can be employed.

For example, application of bar coater, die coater, slot orifice coater, bead coater, (reverse) roll coater, squeeze roll coater, pickup roll coater, dip roll coater, air doctor coater, knife over roll coater, rod coater, etc. Is possible.

The thickness of the coating layer is not particularly limited, but is usually 10 to 300 μm, preferably 20 to 100 μm.
It is about μm.

The application step can be performed continuously, preferably by applying the composition using a bar coater or the like while running the current collector in the longitudinal direction.

By drying the coating layer thus formed and removing the organic solvent, the carbon material becomes PTF
The electrode body bound to the current collector surface by the binder mainly composed of E is formed. That is, the particles of the carbon material become fibrillated PTFE in the process of removing the organic solvent.
Into the fiber, is firmly fixed, and electrical
It is considered that it is physically fixed and joined to the current collector surface reliably.

The drying means for drying the coating layer is not particularly limited, but may be a box dryer, a tunnel dryer, a band dryer, a hot air dryer, a nozzle / jet dryer, an infrared dryer, or the like. However, it is possible to suitably apply a dryer conventionally used for drying a sheet material or a coating film. Most of these are hot air circulation systems that circulate and use hot air.

The drying temperature (or hot air temperature) can vary depending on the type of the organic solvent, the thickness of the coating film, the carbon material concentration in the coating film, the content of the organic solvent, the content of the auxiliary binder, and the like. It is preferably performed at about ° C.
In particular, if the temperature is near or above the boiling point of the organic solvent, drying is performed in a very short time. For example, when the solvent is toluene, drying is easily completed in about several minutes by using a hot air circulation system at 150 ° C. Since the hot air contains vaporized organic solvent vapor, it is preferable to extract a portion of the hot air out of the system, cool it with a condenser, condense the solvent, and recover the hot air.

In a non-aqueous electric double layer capacitor or battery, even if a small amount of water remains in the electrode during the drying step, the performance of the capacitor or battery is significantly reduced as described above. In the present invention,
Basically, the coating slurry is an organic solvent slurry,
Even if some organic solvent remains in the electrode in the drying step, there is no significant problem for the capacitor and the like. That is, since a small amount of the organic solvent is allowed, it is not necessary to completely dry the organic solvent, so that the drying conditions are greatly eased.

In addition, in general, the latent heat of vaporization of organic solvents is much smaller than that of water (eg, the latent heat of vaporization of water: 540).
(cal / g, toluene: 86 cal / g), so that the solvent contained in the binder liquid can be more easily removed by drying as compared with drying water, and the productivity is improved.

The PTFE-based binder of the present invention can be used arbitrarily for only the positive electrode, only the negative electrode, or both electrodes of the electrodes.

The element configuration of an electric double layer capacitor having the electrode body formed by the coating method as described above as a polarizable electrode or a battery having a positive electrode or a negative electrode is not particularly limited. For example, a pair of disc-shaped electrodes in which this electrode body is formed in a disc shape, a coin-shaped structure in which a coin-shaped container is housed together with an electrolytic solution through a separator, and a pair of strip-shaped electrodes formed in a strip shape through a separator A cylindrical structure, which is wound and housed in a bottomed cylindrical container together with the electrolytic solution. The electrode body formed in a square shape is used as a positive electrode and a negative electrode, and a plurality of layers are alternately laminated via a separator and housed in a rectangular container together with the electrolytic solution. Any of the rectangular structures described above can be suitably applied. Note that a current collecting terminal is formed or joined in advance to the current collector or the electrode body so that the current collecting terminal is electrically joined to a positive electrode or a negative electrode of a capacitor or a battery.

The separator may be any porous separator that transmits ions, such as a microporous polyethylene film, a microporous polypropylene film, or a microporous PTFE.
Film, polyethylene nonwoven fabric, polypropylene nonwoven fabric, glass fiber mixed nonwoven fabric, nylon nonwoven fabric, polyester nonwoven fabric, polyurethane nonwoven fabric, glass mat filter and the like can be suitably used. Separator thickness is 20-2
It is preferably set to 00 μm.

As the electrolyte, an organic solvent-based electrolyte is preferably used. In the case of an electric double layer capacitor,
Examples of the electrolyte include BF ₄ salts, such as quaternary ammonium ions and quaternary phosphonium ions, ClO ₄ salts and PF ₆ salts, and LiBF ₄ , LiClO ₄ and NaP
A salt such as F ₆ or LiPF ₆ is used. On the other hand, in the case of a lithium ion battery or the like, for example, LiBF ₄ , LiC
_{lO 4, LiPF 6, LiAsF 6} , LiSbF 6, L
Using salts such as iCF ₃ SO ₃ and LiCF ₃ CO ₂ , these salts include propylene carbonate, ethylene carbonate, γ-butyrolactone, acetonitrile, dimethylformamide, sulfolane, 1,2-dimethoxyethane, nitromethane, dimethyl carbonate, A solution of one or more organic solvents such as diethyl carbonate, ethyl methyl carbonate, diethyl methyl carbonate, dimethyl ethyl carbonate and the like is preferably used. The concentration of the salt is about 0.1 to 3.0 mol / l.

[0048]

According to the present invention, in which the organic solvent dispersion of PTFE is used as the binder, the coating layer of the electrode material can be dried more easily than the method using PTFE as the aqueous dispersion.
It is considered that since the productivity of the electrode body is improved and the moisture in the electrode can be surely removed, a non-aqueous electric double layer capacitor having high stability and high reliability even in long-term charging can be obtained. In addition, a non-aqueous battery having a long cycle life and high reliability can be obtained.

The non-aqueous electric double layer capacitors and batteries produced by the present invention can be used for various electronic devices, toys, cameras,
The present invention can be widely applied to relatively small applications such as electric tools and medical devices, or relatively large applications such as electric vehicles and power storage systems.

[0050]

The present invention will be described below with reference to examples. However, these are examples of the present invention, and the present invention is not limited to these.

[Example 1] (Preparation of PTFE sol) Toluene 1k was placed in a 2 liter heating vessel equipped with a stirrer, a reflux condenser and a dropping device.
g, and bring to a boil while heating and stirring.
FE aqueous dispersion (Fluon (registered trademark) AD1 (containing 60% resin content) manufactured by Asahi ICI Fluoropolymers) 1
00 g was gradually added dropwise, and water in the system was removed by azeotropic distillation with toluene. The distillate initially has two phases, a toluene layer and an aqueous layer, but as the amount of water in the system decreases,
The water layer disappears, and substantially becomes only the toluene layer. The water content by the Karl Fischer method was 0.05% by weight.

[0052] Toluene was further added to adjust the concentration to obtain a 30% by weight toluene dispersion of PTFE (organosol).

(Preparation of coating slurry) A carbon material comprising 80 parts by weight of activated carbon having a BET specific surface area of 2000 m ² / g and 10 parts by weight of carbon black as a conductive agent, 34 parts by weight of a 30% by weight toluene dispersion of PTFE, and toluene 300 parts by weight were charged into a ball mill pot using alumina balls and mixed for 10 minutes to obtain a coating slurry containing 24% by weight of a solid content of activated carbon, carbon black and PTFE. The composition of the solid content is 80% by weight of activated carbon,
It was 10% by weight of carbon black and 10% by weight of PTFE.

(Coating / Drying) This slurry was applied to a 30 μm-thick perforated aluminum plate as a current collector.
Apply with a bar coater to a film thickness of 50 μm,
It was dried at 150 ° C. for 5 minutes in a box dryer. After drying,
Similarly, application and drying were performed on the back surface to obtain an electrode body.

(Assembly of Capacitor) The following assembling work of the electric double layer capacitor was performed in a nitrogen stream at a dew point of -50 ° C. The thickness of the separator was 25 μm.
Was used. Prior to assembling, the electrode body was dried at a temperature of 200 ° C. under a reduced pressure of 0.1 torr for 8 hours.

A current collecting terminal is attached to the two electrode bodies, and a positive electrode body,
The separator, the negative electrode body, and the separator were superposed and wound in this order to obtain an electrode-wound element body. After the electrolyte was impregnated with the solution, the battery was inserted into a SUS316 case having a cylindrical bottom, and the current collecting terminal was electrically connected to the positive electrode and the negative electrode, and then sealed via a safety valve and packing. Height 65m
m, and an electric double layer capacitor having a capacity of 120 F was manufactured.

Here, a propylene carbonate solution in which 1 mol / liter tetraethylammonium tetrafluoroborate was dissolved was used as the electrolytic solution.

(Test) During the assembly of the capacitor, almost no drop of the electrode material from the electrode body was observed. Further, even after the electrode body was immersed in an electrolyte solution at 80 ° C. for 24 hours, the electrode body was pulled up and rubbed against the surface, and no dropping of the electrode material was observed, and the binding property was stable.

The battery is charged to 2.5 V and charged at 1.0 A with a current of 10 A.
The operation to discharge to V was performed to measure the duration, and this was defined as the initial duration. Further, at 70 ° C. for 100 days.
After applying a voltage of 5 V, an operation of discharging to 1.0 V at a current of 10 A was performed to measure the duration, and the ratio of the duration after applying a 2.5 V voltage for 100 days to the initial duration is shown in Table 1. Was.

Example 2 BET specific surface area 2000 m ² /
g of activated carbon and 10 parts by weight of carbon black, 34 parts by weight of a 30% by weight toluene dispersion of PTFE used in Example 1, 5 parts by weight of ethyl cellulose, 225 parts by weight of toluene and 75 parts by weight of ethanol Was charged into a ball mill pot using alumina balls, mixed for 10 minutes, and activated carbon, carbon black, P
25% by weight of solid content consisting of TFE and ethyl cellulose
A slurry for application was obtained. The composition of solids is activated carbon 7
6.2% by weight, carbon black 9.5% by weight, PTF
E 9.5% by weight and ethyl cellulose 4.8% by weight.

This slurry was applied and coated in the same manner as in Example 1.
After drying, an electrode body was obtained.

Using this electrode body, a capacitor was assembled in the same manner as in Example 1.

As in the case of the first embodiment, the electrode material was hardly dropped from the electrode body during the assembling operation.
In addition, even if the electrode body was immersed in an electrolyte solution at 80 ° C. for 24 hours and then pulled up, the surface of the electrode body was rubbed, and the electrode material did not fall off, and the binding property was stable.

Further, the same test as in Example 1 was performed.
The results are shown in Table 1.

Comparative Example 1 BET specific surface area 2000 m ² /
g of activated carbon and 10 parts by weight of carbon black, N-methyl-2-pyrrolidone and PV
200 parts by weight of a solution in which 5% by weight of DF was dissolved (Kyner (registered trademark) 500, manufactured by Penwald) were added and mixed in a ball mill similar to that in Example 1 for 10 minutes.
34.5 solids composed of carbon black and PVDF
A slurry for coating containing 1% by weight was obtained. The solid content is 80% by weight activated carbon, 10% by weight carbon black, PVD
F10% by weight.

This slurry was prepared in the same manner as in Example 1,
A 50 μm thick film is formed on a 20 μm thick aluminum foil as a current collector.
It was applied to a thickness of μm and dried at 150 ° C. for 10 minutes. After drying, application and drying were similarly performed on the back surface to obtain an electrode body.

Using this electrode body, a capacitor was assembled in the same manner as in Example 1. In addition, the same test as in Example 1 was performed, and the results are shown in Table 1.

Although there was almost no dropout of the electrode material during the assembling work, the electrode body was immersed in an electrolyte solution at 80 ° C., then lifted up, and rubbed lightly on the surface. As a result, PVDF as a binder was swollen by the electrolyte solution. Then, the electrode material was easily dropped.

Comparative Example 2 The same test as in Example 1 was performed, except that an aqueous dispersion of PTFE was used in place of the toluene dispersion of PTFE.

That is, a BET specific surface area of 2000 m ² / g
A carbon material comprising 80 parts by weight of activated carbon and 10 parts by weight of carbon black, 16 parts by weight of a PTFE aqueous dispersion (Fluon (registered trademark) AD1 (containing 60% resin content) manufactured by Asahi ICI Fluoropolymers Co., Ltd.) and 320 parts by weight of water The parts were mixed for 10 in the same manner as in Example 1 to obtain a coating slurry containing 23.5% by weight of a solid content composed of activated carbon, carbon black, and PTFE. The solid content is 80.4% by weight of activated carbon, 10% by weight of carbon black, PT
FE was 9.6% by weight.

The slurry was applied and dried in the same manner as in Example 1 to obtain an electrode body.

However, the drying rate in this case was lower than that in Example 1. After drying for 5 minutes, the sample was further dried at 150 ° C. for 3 hours to dry until no weight loss due to residual moisture was observed.

Using the two electrode bodies prepared as described above, a capacitor was assembled in the same manner as in Example 1. Further, a test similar to that in Example 1 was conducted. The results are shown in Table 1. .

[0074]

[Table 1]

Example 3 (Preparation of Slurry for Coating) A cathode active material composed of 90 parts by weight of lithium cobalt oxide and 5 parts by weight of carbon black as a conductive agent, 30% by weight of PTFE used in Example 1 dispersed in toluene. 17 parts by weight of the liquid and 100 parts by weight of toluene were charged into a ball mill pot using alumina balls and mixed for 120 minutes to obtain a slurry for coating a positive electrode containing 47% by weight of a solid content of lithium cobaltate, carbon black and PTFE. Was. The composition of the solid content is lithium cobaltate 90% by weight, carbon black 5% by weight, P
TFE was 5% by weight.

A negative electrode active material comprising 90 parts by weight of graphite having an average particle diameter of 10 μm, 33 parts by weight of a 30% by weight toluene dispersion of PTFE, and 100 parts by weight of toluene were mixed in the same manner for 120 minutes, and graphite and PTFE were mixed. A negative electrode slurry containing 45% by weight of a solid content was obtained. The composition of the solid content was 90% by weight of graphite and 10% by weight of PTFE.

(Coating / Drying) The slurry for coating the positive electrode is
A 30 μm-thick perforated aluminum foil, which is a positive electrode current collector, is coated with a bar coater so as to have a thickness of 100 μm, and dried in a box-type drier at 150 ° C. for 5 minutes. And dried to obtain a positive electrode body.

A negative electrode slurry was applied to a 30 μm-thick perforated copper foil as a negative electrode current collector by a bar coater so as to have a thickness of 70 μm. After drying at 5 ° C. for 5 minutes, coating and drying were similarly performed on the back surface to obtain a negative electrode body.

(Assembling of Battery) The following assembling work of the battery was performed in a glove box under a dry argon atmosphere at a dew point of −50 ° C. The thickness of the separator is 25
A micron microporous polyethylene film was used.

A current collecting terminal was attached to each electrode body, and a positive electrode body, a separator, a negative electrode body, and a separator were superposed and wound in this order to obtain an electrode wound element body. After impregnating the electrolyte solution, the battery was placed in an aluminum case having a cylindrical bottom, and the current collecting terminal was electrically connected to the positive electrode and the negative electrode, and then sealed with a safety valve and packing. 5mm, height 6
A 5 mm lithium ion secondary battery was manufactured.

As the electrolytic solution, a solution in which LiPF ₆ at a concentration of 1 mol / liter was dissolved in a mixed solvent of ethyl methyl carbonate and ethylene carbonate at a volume ratio of 1: 1 was used.

(Test) During the battery assembling operation, almost no dropout of the electrode active material from the positive electrode body and the negative electrode body was observed. In addition, even after the electrode body was immersed in an electrolyte solution at 80 ° C. for 24 hours, the electrode body was pulled up and rubbed against the surface, and no fall-off of the active material was observed.

A charge-discharge cycle test in which an operation of charging at a constant voltage and a constant current of 4.2 V and a maximum current of 1000 mA for 2 hours in an atmosphere of 60 ° C. for 2 hours, and then discharging at a constant current of 1000 mA to 2.75 V is repeated. And the cycle number at which the discharge capacity decreased to 60% or less of the initial value was defined as the cycle life. The cycle life of this battery was 550 cycles.

Example 4 A positive electrode active material comprising 90 parts by weight of lithium cobalt oxide and 5 parts by weight of carbon black, 13 parts by weight of a 30% by weight toluene dispersion of PTFE used in Example 1, and 80 parts by weight of toluene Was charged into a ball mill pot using alumina balls, mixed for 30 minutes, and then mixed with N-methyl-2-pyrrolidone by PVDF.
Was dissolved in 5% by weight (Kyner (registered trademark) 500, manufactured by Penwald) and 20 parts by weight were added.
Mix for 0 minutes, lithium cobalt oxide, carbon black,
A slurry for coating a positive electrode containing 48% by weight of a solid content composed of PTFE and PVDF was obtained. The composition of the solid content is lithium cobaltate 90% by weight, carbon black 5% by weight, PT
FE was 4% by weight and PVDF was 1% by weight.

Further, a negative electrode active material comprising 90 parts by weight of coke having an average particle diameter of 10 μm, 20 parts by weight of a 30% by weight toluene dispersion of PTFE, and 100 parts by weight of toluene were mixed in the same manner for 30 minutes. N-methyl-
Solution 4 in which 5% by weight of PVDF is dissolved in 2-pyrrolidone
0 parts by weight and mixed for another 120 minutes, coke,
A negative electrode coating slurry containing 39% by weight of a solid content composed of PTFE and PVDF was obtained. The composition of solid content is coke 9
2% by weight, 6% by weight of PTFE, and 2% by weight of PVDF.

The slurry for coating the positive electrode was coated and dried on a 20 μm-thick aluminum foil as a positive electrode current collector in the same manner as in Example 3 to obtain a positive electrode body.

Further, the slurry for coating the negative electrode was applied and dried on a copper foil having a thickness of 20 μm as a negative electrode current collector in the same manner as in Example 3 to obtain a negative electrode body.

A lithium ion secondary battery was manufactured in the same manner as in Example 3 using the positive electrode body and the negative electrode body.

During the assembling work of the battery, almost no dropout of the electrode active material from the positive electrode body and the negative electrode body was recognized. Further, 580 cycle life was obtained even at 60 ° C.

Example 5 A positive electrode active material comprising 90 parts by weight of lithium cobaltate and 5 parts by weight of carbon black, 13 parts by weight of a 30% by weight toluene dispersion of PTFE used in Example 1, and 100 parts by weight of toluene Was charged into a ball mill pot using alumina balls, and mixed for 30 minutes. Then, 10 parts by weight of an ethyl cellulose solution in which 10% by weight was dissolved in a mixed solvent of 80% by weight of toluene and 20% by weight of ethanol was added, and further 120 minutes. Mix,
A slurry for coating a positive electrode containing 46% by weight of a solid content composed of lithium cobaltate, carbon black, PTFE, and ethyl cellulose was obtained. The composition of the solid content is lithium cobaltate 90% by weight, carbon black 5% by weight, PTFE
4% by weight and 1% by weight of ethyl cellulose.

A negative electrode active material comprising 90 parts by weight of graphite having an average particle diameter of 10 μm, 30 parts by weight of a 30% by weight toluene dispersion of PTFE, and 100 parts by weight of toluene were used.
Similarly, after mixing for 30 minutes, 10 parts by weight of an ethylcellulose solution in which 10% by weight was dissolved in the above-mentioned mixed solvent of 80% by weight of toluene and 20% by weight of ethanol was added, and the mixture was further mixed for 120 minutes to obtain graphite, PTFE, and ethylcellulose. , A slurry for coating the negative electrode containing 43% by weight of a solid content was obtained. The composition of the solid content is 90% by weight of graphite, PTFE 9
% By weight and 1% by weight of ethylcellulose.

The slurry for coating the positive electrode and the negative electrode was coated and dried in the same manner as in Example 4 to obtain a positive electrode body and a negative electrode body. To produce a lithium ion secondary battery.

During the assembling work of the battery, almost no dropout of the electrode active material from the positive electrode body and the negative electrode body was recognized. Further, 570 cycle life was obtained even at 60 ° C.

Example 6 A cathode active material comprising 90 parts by weight of lithium cobaltate and 5 parts by weight of carbon black, 13 parts by weight of a 30% by weight toluene dispersion of PTFE used in Example 1, and 1 part by weight of EPDM rubber 100 parts by weight of toluene and 100 parts by weight were charged into a ball mill pot using alumina balls and mixed for 120 minutes to obtain a slurry for coating a positive electrode containing 48% by weight of a solid content of lithium cobaltate, carbon black, PTFE, and EPDM rubber. The composition of the solid content was 90% by weight of lithium cobalt oxide, 5% by weight of carbon black, 4% by weight of PTFE, and 1% by weight of EPDM rubber.

A negative electrode active material comprising 90 parts by weight of graphite having an average particle size of 10 μm, 20 parts by weight of a 30% by weight toluene dispersion of PTFE, 1 part by weight of EPDM rubber and 100 parts by weight of toluene were similarly mixed for 120 minutes. The mixture was mixed to obtain a negative electrode coating slurry containing 46% by weight of a solid content composed of graphite, PTFE, and EPDM rubber. The composition of the solid content was 93% by weight of graphite, 6% by weight of PTFE, and 1% by weight of EPDM rubber.

The slurry for coating the positive electrode and the negative electrode was coated and dried in the same manner as in Example 4 to obtain a positive electrode body and a negative electrode body. An ion secondary battery was manufactured.

During the assembling work of the battery, almost no dropout of the electrode active material from the positive electrode body and the negative electrode body was observed. Further, 570 cycle life was obtained even at 60 ° C.

Example 7 A positive electrode active material comprising 90 parts by weight of lithium cobalt oxide and 5 parts by weight of carbon black, 13 parts by weight of a 30% by weight toluene dispersion of PTFE used in Example 1 and 100 parts by weight of toluene were used. Was mixed in a ball mill pot using alumina balls for 30 minutes, and then a fluororubber (Aflas (registered trademark) 20 manufactured by Asahi Glass Co., Ltd.) dissolved in tetrahydrofuran at 5% by weight was used.
0) 20 parts by weight were added and mixed for further 120 minutes to obtain a positive electrode coating slurry containing 44% by weight of a solid content composed of lithium cobalt oxide, carbon black, PTFE, and fluororubber. The composition of the solid content is lithium cobaltate 90
% By weight, 5% by weight of carbon black, 4% by weight of PTFE, and 1% by weight of fluoro rubber.

Further, 20 parts by weight of a negative electrode active material comprising 90 parts by weight of graphite having an average particle diameter of 10 μm, 20 parts by weight of a 30% by weight toluene dispersion of PTFE and 100 parts by weight of toluene were mixed in the same manner for 30 minutes. Was added and mixed for further 120 minutes to obtain a slurry for negative electrode coating containing 40% by weight of a solid content of graphite, PTFE and fluororubber. The composition of the solid content was 92% by weight of graphite, 6% by weight of PTFE, and 2% by weight of fluororubber.

The slurry for coating the positive electrode and the negative electrode was coated and dried in the same manner as in Example 4 to obtain a positive electrode body and a negative electrode body. An ion secondary battery was manufactured.

During the battery assembling work, almost no dropout of the electrode active material from the positive electrode body and the negative electrode body was observed. Further, 570 cycle life was obtained even at 60 ° C.

Comparative Example 3 A cathode active material comprising 90 parts by weight of lithium cobaltate and 5 parts by weight of carbon black, N-methyl-2-pyrrolidone and 5% by weight of PVDF
100 parts by weight of the dissolved solution (Kyner (registered trademark) 500, manufactured by Penwald) are charged into a ball mill pot using alumina balls, mixed for 10 minutes, and the solid content of lithium cobaltate, carbon black, and PVDF is reduced to 51 parts by weight. Thus, a slurry for coating the positive electrode containing about 10% by weight was obtained. The composition of the solid content was 90% by weight of lithium cobaltate, 5% by weight of carbon black, and 5% by weight of PVDF.

A negative electrode active material comprising 90 parts by weight of coke having an average particle diameter of 10 μm, 20 parts by weight of a 30% by weight toluene dispersion of PTFE, and 20 parts by weight of toluene were similarly mixed for 10 minutes. 200 parts by weight of a solution in which 5% by weight of PVDF was dissolved was added to the mixture, and the mixture was further mixed for 120 minutes, and coke, PTFE,
A slurry for coating a negative electrode containing PVDF with a solid content of 32% by weight was obtained. Here, the composition of the solid content was 85% by weight of coke, 6% by weight of PTFE, and 9% by weight of PVDF.

The slurry for coating the positive electrode was applied to a 20 μm-thick aluminum foil as a positive electrode current collector by a bar coater so as to have a thickness of 100 μm.
After drying at 0 ° C. for 120 minutes, application and drying were performed on the back surface to obtain a positive electrode body.

The slurry for coating the negative electrode was applied to a 20 μm thick copper foil as a negative electrode current collector by a bar coater so as to have a thickness of 70 μm.
After drying at 0 ° C. for 5 minutes, the back surface was similarly coated and dried to obtain a negative electrode body.

A lithium ion secondary battery was produced in the same manner as in Example 3 using the positive electrode body and the negative electrode body.

During the assembly of the battery, the electrode active material was hardly dropped from the positive and negative electrode bodies. However, after the electrode body was immersed in an electrolytic solution at 80 ° C., it was pulled up and the surface was rubbed lightly. And PVDF as a binder swelled in the electrolytic solution, and the electrode material was easily dropped off. As a result of a charge / discharge cycle test at 60 ° C., 180
In the cycle, the discharge capacity was reduced to 60% or less of the initial value.

Comparative Example 4 The same experiment as in Example 3 was conducted, except that an aqueous dispersion of PTFE was used instead of the 30% by weight toluene dispersion of PTFE.

That is, a positive electrode active material comprising 90 parts by weight of lithium cobalt oxide and 5 parts by weight of carbon black;
8 parts by weight of PTFE aqueous dispersion (Fluon (registered trademark) AD1 (containing 60% resin content) manufactured by Asahi ICI Fluoropolymers Co., Ltd.) and 100 parts by weight of water are charged into a ball mill pot using alumina balls, and mixed for 10 minutes. , Lithium cobaltate, carbon black, PTFE
Of slurry containing 49% by weight of a solid content consisting of The composition of the solid content was 90% by weight of lithium cobaltate, 5% by weight of carbon black, and 5% by weight of PTFE.

A negative electrode active material comprising 90 parts by weight of coke having an average particle diameter of 10 μm, 18 parts by weight of the above-mentioned aqueous PTFE dispersion Fluon (registered trademark) AD and 100 parts by weight of water were mixed in the same manner for 10 minutes, and coke and PTFE were mixed. , A slurry for coating a negative electrode containing 48% by weight of a solid content was obtained. The composition of the solid content is coke 95% by weight, PTFE5
% By weight.

The slurry for coating the positive electrode was applied to a 30-μm-thick perforated aluminum foil serving as a positive electrode current collector so as to have a thickness of 100 μm by a bar coater, and was heated at 150 ° C. in a box-type drier. After drying for 5 minutes, a positive electrode body was obtained.

However, the drying speed in this case was lower than that in Example 3. After drying for 5 minutes, the sample was further dried at 150 ° C. for 2 hours to dry it until no weight loss due to residual moisture was observed.

Further, a slurry for coating the negative electrode was applied to a 30 μm-thick perforated copper foil as a negative electrode current collector by a bar coater so as to have a thickness of 70 μm. Drying was performed at 5 ° C. for 5 minutes to obtain a negative electrode body.

Using these electrode bodies, a lithium-ion secondary battery was fabricated in the same manner as in Example 3, and a cycle test was performed.
The cycle life at 0 ° C. was as low as 75 cycles.

[0115]

According to the present invention, an electrode slurry is obtained by applying and drying a coating slurry obtained by mixing a dispersion of PTFE in an organic solvent with a carbon material or an electrode active material on a current collector. And a method for producing a highly reliable electric double layer capacitor or battery having stability during charging even at a high temperature without swelling and deterioration in an electrolyte solvent.

Further, since PTFE dispersed in an organic solvent is used as a binder, an electrode can be formed industrially easily and with high productivity without causing a problem due to residual water.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuya Hiratsuka Asahi Glass Co., Ltd. 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa

Claims (8)

[Claims] 1. A method for manufacturing a non-aqueous electric double layer capacitor including an electrode body formed by forming an electrode material comprising a carbon material and a binder mainly composed of polytetrafluoroethylene on a current collector. Mixing a material and an organic solvent dispersion of polytetrafluoroethylene to form a slurry, applying the slurry to the current collector,
And a method for producing a non-aqueous electric double layer capacitor, wherein the electrode body is produced by a step of drying the formed coating layer to remove the organic solvent. 2. The method according to claim 1, wherein the content of polytetrafluoroethylene in the electrode material is 0.1 to 20% by weight. 3. The non-aqueous electrolyte according to claim 1, wherein the organic solvent dispersion of polytetrafluoroethylene is obtained by azeotropically dehydrating an aqueous dispersion of polytetrafluoroethylene with the organic solvent. A method for manufacturing a double-layer capacitor. 4. The method for producing a nonaqueous electric double layer capacitor according to claim 1, wherein the mixing of the carbon material and the organic solvent dispersion of polytetrafluoroethylene is performed while applying a shearing force. 5. A method for manufacturing a non-aqueous battery including an electrode body formed by forming an electrode material comprising an electrode active material and a binder mainly composed of polytetrafluoroethylene on a current collector. A step of mixing a material and an organic solvent dispersion of polytetrafluoroethylene to form a slurry, a step of applying the slurry to the current collector, and a step of drying the formed coating layer to remove the organic solvent. A method for producing a non-aqueous battery, comprising producing an electrode body. 6. The method according to claim 5, wherein the polytetrafluoroethylene in the electrode material is 0.1 to 20% by weight. 7. The nonaqueous battery according to claim 5, wherein the organic solvent dispersion of polytetrafluoroethylene is obtained by azeotropically dehydrating an aqueous dispersion of polytetrafluoroethylene with the organic solvent. Manufacturing method. 8. The method for producing a nonaqueous battery according to claim 5, wherein the mixing of the carbon material and the organic solvent dispersion of polytetrafluoroethylene is performed while applying a shearing force.