JPH0967112A - Solid activated carbon and method for producing the same - Google Patents

Abstract

(57) Abstract: A shape-retaining resin fills the pores of activated carbon to reduce the specific surface area, resulting in a decrease in capacity. In addition, mechanical strength is insufficient, and various requirements as solid activated carbon are not satisfied. SOLUTION: Activated carbon and at least one or more easily carbonizable resin consisting of emulsified oil droplets having a particle size larger than the pore size of the activated carbon are mixed to prepare a molding material, and then a doctor blade method or a tape is used. A molding method, a pressure molding method, or a molded body formed by combining the molding methods is carbonized in a non-oxidizing atmosphere, and the activated carbon and the carbide of the easily carbonizable resin are fired and integrated to obtain solid activated carbon.
And applying the solid activated carbon as a polarizable electrode of an electric double layer capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small and large capacity capacitor such as an electric double layer capacitor and a lithium ion battery, an electrode material used for various batteries such as a backup power source, a vehicle power source and an auxiliary power source, or The present invention relates to solid activated carbon applied as a porous activated carbon sintered body that can be generally widely used, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, carbon materials have been taken up as electrode materials for small and large-capacity capacitors and various batteries, and various studies have been made.

For example, several thousand per unit volume compared to a conventional capacitor in which an electrolyte is contained between polarizable electrodes mainly composed of carbonaceous material such as activated carbon and an electric double layer formed at the interface between the two is used. The electric double layer capacitor having double the electrostatic capacity has both the functions of the capacitor and the battery, and therefore, the demand thereof is rapidly increasing such as being applied to a backup power source.

Initially, as the electrode material, a material obtained by kneading and molding activated carbon and an organic resin was used, but as an electrode material of a capacitor or a battery, it has a particularly high capacitance and a low internal resistance. In order to satisfy the recent demand for miniaturization of electronic parts, the volume is minimized for a given capacity, and the porous structure that takes into consideration the impregnation of the electrolyte is less likely to cause cracks or damage, making it more durable. It has been required to have excellent properties and mechanical properties.

Therefore, in order to satisfy the above-mentioned various requirements, a mixture of a phenolic carbide powder and a powdered phenolic resin is fired, followed by activation treatment to obtain a polarizable electrode, activated carbon and an easily carbonizable thermosetting resin. It has been proposed to use, as an electrode material, solid activated carbon which is impregnated or kneaded with a hydrophilic resin and is molded and carbonized (see JP-A-6-69075).

[0006]

The polarizable electrode is a porous electrode having a large specific surface area within a range that does not impair durability and mechanical strength in order to increase electrostatic capacity (F / cc) per unit volume of the electrode. It is manufactured by mixing high-quality activated carbon with a shape-retaining resin made of phenolic resin and molding, and carbonizing and integrating the molded body in a non-oxidizing atmosphere. Due to the relationship with the volume, it is restricted to a certain range.

On the other hand, in order to improve the strength of the activated carbon after molding, a large amount of the shape-retaining resin is required. Generally, a resin having good moldability has low flow viscosity and good wettability. However, there is a high possibility that the pores of the activated carbon will be filled, and the specific surface area of the polarizable electrode will be further reduced and the capacity will be reduced in combination with the filling amount of the activated carbon which is restricted in the range as described above. There is.

On the contrary, a resin having poor moldability does not fill the pores of the activated carbon because the viscosity of the resin is high and the wettability is poor, but the strength of the molded article is low and the carbonized and fired body is integrated. The problem remains that the mechanical strength afterwards is also low.

Therefore, there is a trade-off relationship between the moldability and the mechanical strength and the electrostatic capacity, and both properties are optimized by making a trade-off between them, so that the above various requirements are not always satisfied. There was a problem.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its object is to realize the minimization of the volume with respect to a predetermined capacity, to form a small amount of easily carbonizable resin with excellent moldability, To provide solid activated carbon that is porous without blocking pores and can be suitably used as an electrode material for electric double layer capacitors and various batteries having excellent durability and mechanical properties, and a method for producing the same. is there.

[0011]

Means for Solving the Problems As a result of earnest research on the above problems, the present inventor has made an easily carbonizable resin into oil droplets emulsified to 10 to 1000 times the average pore diameter of activated carbon,
By mixing and molding the oil droplets and activated carbon, it becomes possible to mold without blocking the pores of the activated carbon, and the molded body is carbonized and fired to be integrated to obtain good moldability and mechanical strength. It became clear that both the specific surface area and

The solid activated carbon of the present invention comprises a mixture of at least one easily carbonizable resin comprising porous activated carbon and emulsified oil droplets having a particle size of 10 to 1000 times the average pore size of the activated carbon. As a molding material, a molding obtained from the molding material is carbonized and fired in a non-oxidizing atmosphere to be integrated, and the solid activated carbon is suitable as a polarizable electrode of an electric double layer capacitor.

The method for producing solid activated carbon of the present invention is
Porous activated carbon and the particle size is 1 of the average pore size of the activated carbon.
At least one or more easily carbonizable resin consisting of emulsified oil droplets, which is 0 to 1000 times, is mixed and sludge is formed from the mixture, or a granulated body obtained by further drying and granulating the sludge is formed. After being prepared as a material, when the slurry is used as a molding material, a doctor blade method or a tape molding method is used, or when the granule is used, a pressure molding method is used, or those molding materials are each molded into After being molded into a sheet-shaped or block-shaped molded body by a composite molding method in which the above methods are combined, the molded body is carbonized in a non-oxidizing atmosphere, and the activated carbon and the carbide of the easily carbonizable resin are fired and integrated. It is characterized by that.

The activated carbon of the present invention has a specific surface area of 300 m ^2.
If it is at least / g, the precursor and means for activation are not particularly limited.

That is, examples of the precursor include coal-based bituminous coal, creosote oil, coal tar, petroleum-based pitch oil, bottom oil, saccharides, coconut husk, and cellulose. It is preferable to use coconut husk as a precursor from the viewpoint of size and easiness of crushing.Furthermore, from the viewpoint of self-discharge characteristics, a synthetic resin containing no metal impurities and relatively easy to obtain a relatively pure substance was used as the activated carbon raw material. Things are also desirable.

Further, the activation, that is, the activation of the precursor is
Known methods can be adopted, and specific examples thereof include a method of dry distillation using zinc chloride, phosphoric acid, or the like, or a method of treating with high temperature steam,
Activated carbon activated with water vapor having a low residual content is preferable in terms of excellent conductivity of the carbonized electrode and avoiding aging of the electrode due to a substance soluble in the electrolytic solution.

Further, the shape of the activated carbon is not particularly limited, but it is preferably granular or flaky from the viewpoint of packing efficiency, and the average particle size thereof is also 2 to 50 from the same viewpoint.
μm is preferred.

That is, in the case of activated carbon having an average particle size of less than 2 μm, the specific surface area of the particles increases, the amount of binder required for molding increases, and the activated carbon content decreases relatively. If the particle size exceeds 50 μm, the smoothness of the electrode surface is inferior, and therefore they are not preferable.

The average pore diameter of the activated carbon referred to in the present invention is the average value of the pore diameters that contribute to the capacity of the electric double layer, and is specifically the open pores of the activated carbon and 1 to 300 nm.
Which can be measured by the mercury penetration method or the amount of adsorption of a specific molecule. When the pore size is less than 1 nm, it is almost impossible to move the ions that become electric charges. If it exceeds 300 nm, the specific surface area of the pores becomes very small, and neither contributes to the capacity of the electric double layer.

Further, the average pore diameter of the activated carbon for an electric double layer capacitor is, based on the principle of the electric double layer capacitor, the pore diameter is 3 times or more of the ion diameter so that ions as electric charges can easily move. Is required, and it depends on the type of charge and the type of solvent used, but it is about 1 nm or more, but within 50 nm, the apparent specific surface area of activated carbon, that is, Since the electric capacity becomes the largest, 1 to 50 nm is more desirable.

The method for controlling the pore diameter can be carried out by a known method, and specifically, it is known that it can be controlled by the kinds of the precursor and activated carbon and the activation conditions.

Next, the easily carbonizable resin of the present invention is a resin which has a nonvolatile content of 40% by weight or more when heated in vacuum at 600 ° C. or more, and is not particularly limited, but examples thereof include phenol. Resin, epoxy resin, urethane resin,
Aromatic carbonate resins, cellulose resins, acetonitrile resins, various resins such as coal tar oil and pitch oil are listed, and among them, phenol resin, aromatic carbonate resin, coal tar, etc. in which the nonvolatile content remains at 60% by weight or more are preferable. is there.

Further, in order to improve the binding force with activated carbon, it is preferable to use a binder in which a monomer having a reactive group is copolymerized, and the reactive group is specifically a vinyl group, an acrylic group or a nitrile group. And may contain a silanate or titanate-based compound.

Further, a part or all of the binder can be substituted with a monomer for synthesizing the resin by a polymerization reaction, and a mixture or copolymer of several resins can be used.

In the present invention, the particle size of the emulsified oil droplets of the easily carbonizable resin is 1 of the average pore size of activated carbon.
If it is less than 0 times, the oil droplets are deformed and enter the pores to easily fill the pore diameter, and the carbonization treatment thereafter makes the pores closed, resulting in a decrease in capacitance.

On the other hand, if the particle size exceeds 1000 times, the surface of the pores of activated carbon will be largely covered, and as a result, the pores will be blocked.

There is also a problem that increasing the particle size of the emulsified oil droplets is not desirable from the viewpoint of stability of emulsion particles and adhesive strength of activated carbon.

Therefore, the particle size of the oil droplets of the easily carbonizable resin emulsified is 10 to 10 of the average pore size of the activated carbon.
00 times, and more preferably 100 to 1000 times from the viewpoint of securing pores of activated carbon as open pores.

The particle size of the oil droplets emulsified with the easily carbonizable resin is specifically determined by measuring the micro-Brownian motion of the oil droplets by measuring the Doppler effect of laser light or by light scattering. It can be measured by a known method such as a method for measuring.

Further, the emulsification of the easily carbonizable resin can be prepared by a known method, and specifically, a method in which the resin is polymerized (interfacial polymerization) in an emulsion can be employed.

In emulsifying the resin, any surfactant or polymerization initiator can be used.

Further, after adding a solvent to the resin obtained by the bulk polymerization method and emulsifying it with a homogenizer or manton-goline in a dispersion medium which is substantially insoluble in the solvent and has a higher vapor pressure than the solvent, It is also possible to obtain an emulsion by reducing the pressure and evaporating the solvent.

On the other hand, as a method for controlling the particle size of the emulsion, it is known that it can be easily controlled by controlling the amount of the dispersant or the HLB value at the time of emulsification, and an arbitrary HLB value can be obtained. It is preferable to use a nonionic dispersant that is easy to use.

Further, the dispersion medium used for emulsifying the easily carbonizable resin may be one that is substantially incompatible with the resin. Specifically, it is an oil-soluble solvent such as acrylonitrile or coal tar. As the binder, water can be used as a dispersion medium, and a water-soluble polymer can also be used for stabilizing the emulsion, and dibutyl can be used to reduce the viscosity of the dispersoid and accelerate the emulsification. It is also possible to add a plasticizer such as phthalate ester.

On the other hand, in emulsifying a water-soluble binder such as polyphenol, an aliphatic oil such as decane can be used as a dispersion medium.

Incidentally, in order to improve the moldability as necessary and to secure continuous pores after carbonization, a resin which is easily pyrolyzed can be added to the easily carbonizable resin.

The easily heat decomposable resin is 600 in vacuum.
When heated to 0 ° C., the residual carbon content is 10% or less, more preferably 5% or less.

That is, if the residual carbon content exceeds 10%, the pores of the activated carbon are filled, and the solid activated carbon does not meet the desired requirements.

Examples of the easily thermally decomposable resin include acrylic resin, butyral resin, α-methylstyrene, etc. The method of adding the resin is to add it to the emulsion of the easily carbonizable resin, or to prepare it as an emulsion. It can be mixed with the emulsion of the easily carbonizable resin or can be mixed in a state of being dissolved in the dispersion medium of the emulsion of the easily carbonizable resin, and further, these addition forms can be used together.

[0040]

According to the present invention, the easily carbonizable resin is added to the porous activated carbon in the form of emulsified oil droplets having a particle diameter much larger than the pore diameter of the activated carbon, and the mixture is added and mixed.
By carbonizing in a non-oxidizing atmosphere and firing and integrating, the easily carbonizable resin efficiently adheres to the surface of the activated carbon particles to improve moldability, and it is effectively used for bonding between activated carbon particles and strength. In addition, the easily carbonizable resin does not block the pores of the activated carbon, the surface area of the activated carbon is not reduced, and high capacitance can be maintained as solid activated carbon.

Furthermore, when the solid activated carbon is used as a polarizable electrode of an electric double layer capacitor, the easily carbonizable resin is emulsified and localized in the electrode. As a result, the crystallinity after carbonization of the resin is increased. It is accelerated and the electric resistance value of the electrode is lowered.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the solid activated carbon of the present invention and the method for producing the same will be described in detail based on Examples.

The solid activated carbon of the present invention includes porous activated carbon having a specific surface area of 300 m ² / g or more, represented by coconut husk charcoal, and at least one or more easily carbonizable substances such as phenol resin, aromatic carbonate resin and coal tar. The resin is emulsified to obtain an average diameter of open pores of the activated carbon of 10 to 10
Mixing with oil droplets adjusted to have a particle size of 00 times,
After preparing a slurry for molding from the mixture, or after preparing a granule by drying and granulating the slurry of the mixture, in the case of using a slurry as a molding material, a doctor blade method or a tape molding method, When the granulated material is used as a molding material, a pressure molding method is used, or after tape molding is performed using sludge as a molding material, pressure molding is further performed with a roll or the like, and molding is performed by combining the above molding methods. The obtained molded body is heat-treated in a non-oxidizing atmosphere to carbonize the easily carbonizable resin, and the activated carbon and the carbide of the easily carbonizable resin are fired to be integrated.

[0044]

EXAMPLES When evaluating the solid activated carbon of the present invention and the method for producing the same, the activated carbon detailed in Table 2 and the emulsified easily carbonizable resin and easily decomposable resin so that the composition shown in Table 1 is obtained. The binder was mixed to prepare a slurry, which was then spray-dried by a spray-drying method and granulated to prepare a granule raw material for molding.

The preparation of the easily carbonizable resin emulsion used in the examples was carried out by adding 100 g of the easily carbonizable resin shown in Table 2 as a dispersoid and 100 tetrahydrofuran as a solvent.
g and 50 g of dibutyl phthalate ester as a plasticizer are added and dissolved by heating.

On the other hand, 200 g of water as a dispersion medium and 3 g of dodecylbenzene polyethylene glycol as a nonionic dispersant are mixed and dissolved.

Then, the dispersion medium and the dispersoid are mixed,
Using a homogenizer, set the rotation speed to 12000 rpm and stir for 30 minutes to emulsify. While stirring, depressurize the system to volatilize and remove tetrahydrofuran of the solvent added to the dispersoid, and then further evaporate under reduced pressure. Add stripped water. Then, a predetermined amount of activated carbon was added to finally prepare an emulsion solution in which the activated carbon was mixed.

[0048]

[Table 1]

[0049]

[Table 2]

Next, the obtained emulsion solution is spray-dried to prepare granules, and the granule raw material is pressure-molded using a pressure press machine, and then the molded body is subjected to 80% vacuum.
Carbonized and fired at a temperature of 0 ° C for 2 hours, length 50 mm, width 50 m
An activated carbon substrate for evaluation having a thickness of m and a thickness of 3 mm was obtained.

A sample prepared in the same manner without adding the easily carbonizable resin was used as a comparative example.

Using the thus obtained activated carbon substrate for evaluation, the three-point bending strength was measured according to the JIS-R-1601 standard, and the specific surface area was measured by the BET method with N _2, and the capacitance was evaluated as described above. 4 for activated carbon substrate for electrodes
It was measured by charging and discharging in a 0% sulfuric acid aqueous solution, and the internal resistance was calculated from the difference between the charging current and the discharging current.

[0053]

[Table 3]

As a result of the above, the sample No. 4 in which the ratio of the particle size of the emulsified oil droplets to the average pore size of the activated carbon is less than 10 times, and the sample No. 11 of the comparative example in which the easily carbonizable resin is not used, The capacitance is as small as 10 F / cc or less,
The internal resistance is extremely high at 29Ω or higher, while
Sample No. 10 having a particle size ratio of more than 1000 times had an extremely low strength of 10 g / mm ² and could not be put to practical use.

On the other hand, the sample according to the present invention has a high strength of 30 g / mm ² or more and a specific surface area of 250 m ²
/ G or more, the capacitance is as large as 30 F / cc or more, and the internal resistance is as low as 17 Ω or less, all of which have satisfactory characteristics as solid activated carbon and are suitable as electric double layer capacitors. I know there is.

The present invention is not limited to the above embodiment.

[0057]

As described above in detail, according to the solid activated carbon and the method for producing the same of the present invention, it is possible to realize a reduction in volume with respect to a predetermined capacity and to easily and stably carry out the forming and carbonizing production steps. It is possible to obtain solid activated carbon that is porous and is excellent in durability and mechanical properties, and can be suitably used as an electrode material for electric double layer capacitors and various batteries. Use this solid activated carbon as a polarizable electrode. In this case, the surface area in contact with the electrolytic solution as an electrode increases, and the electric path through which the charge passes also increases, so a simple structure with an extremely large capacitance per unit volume, efficient, durable and compact size The electric double layer capacitor can be obtained.

Claims (3)

[Claims] 1. Activated carbon and an average pore diameter of the activated carbon of 10 to 10.
Solid activated carbon in which a molded body obtained from a mixture of at least one or more easily carbonizable resin consisting of emulsified oil droplets having a particle size of 1000 times is carbonized and fired in a non-oxidizing atmosphere to be integrated. 2. The solid activated carbon according to claim 1, wherein the solid activated carbon is a polarizable electrode of an electric double layer capacitor. 3. Activated carbon and an average pore diameter of the activated carbon of 10 to 10.
After mixing with at least one or more easily carbonizable resin consisting of emulsified oil droplets having a particle size of 1000 times, and preparing a slurry or a granule from the mixture, a doctor blade method or a tape molding method, or A molded body is produced by a pressure molding method or a combination molding method thereof, the molded body is carbonized in a non-oxidizing atmosphere, and the activated carbon and the carbide of the easily carbonizable resin are fired and integrated. A method for producing solid activated carbon.