WO2012029920A1

WO2012029920A1 - Process for production of porous carbon material, porous carbon material, electrode for capacitor, and capacitor

Info

Publication number: WO2012029920A1
Application number: PCT/JP2011/069936
Authority: WO
Inventors: 貴彦井戸; 真利梅村; 俊光国貞
Original assignee: イビデン株式会社
Priority date: 2010-09-02
Filing date: 2011-09-01
Publication date: 2012-03-08

Abstract

This process for producing a porous carbon material is a process for producing a porous carbon material having fine pores formed therein, and is characterized by comprising a heating step of heating a first composite material or a second composite material at a temperature not lower than a temperature at which a part of a porogen can be decomposed and gasified and not higher than 2000˚C, wherein the first composite material comprises a first organic material having a porogen-containing modifying group bound to a polymeric chain that constitutes the first organic material and the second composite material comprises a porogen-containing inorganic sol and a second organic material.

Description

Porous carbon material manufacturing method, porous carbon material, capacitor electrode, and capacitor

The present invention relates to a method for producing a porous carbon material, a porous carbon material, a capacitor electrode, and a capacitor.

In recent years, with the growing awareness of resource saving and environmental issues, the development of power storage devices has been promoted rapidly. Among power storage devices, capacitors such as electric double layer capacitors (EDLC) and lithium ion capacitors (LIC) are attracting attention.

The electric double layer capacitor is composed of a pair of polarizable electrodes sandwiching a separator, a case for housing them, an electrolytic solution as an electrolyte, and a current collector. In an electric double layer capacitor, electricity is stored in an electric double layer formed at the polarizable electrode / electrolyte interface.
In the lithium ion capacitor, the same material as the electric double layer capacitor is used as the positive electrode material, whereas a carbon-based material capable of occluding lithium ions is used as the negative electrode material. And the energy density is improved by adding lithium ion to the carbonaceous material which is a negative electrode material.

A material constituting a polarizable electrode of an electric double layer capacitor and a positive electrode of a lithium ion capacitor (hereinafter simply referred to as a capacitor electrode) is required to have a high specific surface area, and is a porous material made of activated carbon. Carbonaceous materials are known.

The porous carbon material made of activated carbon includes pores having a pore diameter smaller than 2 nm (hereinafter also referred to as micropores), pores having a pore diameter of 2 to 50 nm (hereinafter also referred to as mesopores), and pores. Fine pores having a diameter exceeding 50 nm (hereinafter also referred to as macropores) are formed.

Since the macropores contain air holes, the porous carbon material becomes bulky due to the presence of the air holes, and in the capacitor electrode using the porous carbon material, the charged amount per unit volume (below) , Also simply referred to as electrode density).

On the other hand, although the micropore has a large specific surface area, it is considered that the size of the pore is too small to allow the electrolyte to enter sufficiently. In addition, in the electrolyte solution composed of propylene carbonate and tetrabutylammonium ions, the electrolyte ions are estimated to form a solvation having a diameter of about 0.86 nm. However, most of the micropores consist of pores with a pore diameter smaller than 1 nm, so the diameter of the electrolyte ions is close to the width of the micropores, and the electrolyte ions are sufficiently adsorbed by the micropores due to the ion sieve effect of the micropores. It is thought not to.
Therefore, when a porous carbon material made of activated carbon is used for a capacitor electrode, it cannot be said that the charge / discharge characteristics are sufficiently high.

As a porous carbon material considering such a problem, for example, Patent Document 1 discloses a porous carbon material in which many mesopores are formed, and a manufacturing method thereof.
In the method for producing a porous carbon material described in Patent Document 1, a step of preparing a composite of inorganic particles such as silica and a carbon precursor such as phenol, and heating the composite at 600 to 1500 ° C. It describes that it includes a step of carbonizing the carbon precursor and a step of etching the remaining inorganic particles with a base or acid.

JP-T-2004-503456

In the method for producing a porous carbon material described in Patent Document 1, mesopores having a desired size can be obtained by controlling the particle diameter of the inorganic particles.
Such a porous carbon material has a high specific surface area due to a small number of macropores, and a capacitor electrode using such a porous carbon material is considered to have a high electrode density.

In the method for producing a porous carbon material described in Patent Document 1, pores are formed in the space initially occupied by the inorganic particles by etching the remaining inorganic particles with a base or acid.
However, in order to form pores, it is necessary to perform etching using a dangerous chemical such as sodium hydroxide or a hydrofluoric acid solution, so that there is a problem in safety.
Further, in order to form the pores, it is necessary to separately perform a process called etching, which leads to an increase in manufacturing time and cost.

The present invention has been made to solve the above-described problems, and is a safer method for producing a porous carbon material that can omit the step of forming pores, and the production method thereof. It is an object to provide a carbon material. Another object of the present invention is to provide a capacitor electrode made of the carbon material and a capacitor including the capacitor electrode.

As a result of intensive studies to solve the above-mentioned problems, the present inventors removed the pore source by heating the composite material including the pore source at a predetermined temperature when producing the porous carbon material. The inventors have found that pores can be formed and completed the present invention.

That is, the method for producing the porous carbon material of the present invention includes:
A method for producing a porous carbon material, comprising:
A first composite material in which a modifying group containing a pore source is bonded to a polymer chain constituting the first organic material, or a first composite material comprising an inorganic sol or metal alkoxide containing a pore source and a second organic material. And a heating step of heating the composite material at a temperature of 2200 ° C. or lower and a temperature at which a part of the pore source is decomposed and vaporized.

In the method for producing a porous carbon material of the present invention, as the material containing the pore source, the first composite material in which the modifying group containing the pore source is bonded to the polymer chain constituting the first organic material, or A second composite material made of an inorganic sol or metal alkoxide and a second organic material is used.
By the heating step, first, the first composite material or the second composite material can be carbonized. Further, the pore source can be removed from the composite material by the heating step. As a result, pores can be formed.

When the first composite material is used as the material including the pore source, it is considered that pores are formed by the following mechanism.
For example, when the modifying group contained in the first composite material is an organosilicon compound, in the heating step, a part of silica generated by desorbing the organosilicon compound from the first composite material or the detached organic A part of the silicon compound is vaporized. As a result, pores are formed.

In addition, when the second composite material is used as the material including the pore source, pores are considered to be formed by the following mechanism.
For example, in the second composite material, when the inorganic sol is dispersed in the second organic material, the inorganic compound contained in the inorganic sol is vaporized in the heating step. As a result, pores are formed.

Thus, in the method for producing a porous carbon material of the present invention, the carbonization of the composite material and the formation of pores can be performed by the heating step. Therefore, the process of forming pores can be omitted, and the manufacturing process can be simplified. As a result, manufacturing time and cost can be reduced.
Furthermore, in the method for producing a porous carbon material of the present invention, pores can be formed by heating the first composite material or the second composite material, so that dangerous chemicals such as hydrofluoric acid are handled. And the porous carbon material can be produced safely.

In the method for producing a porous carbon material of the present invention, the first composite material or the second composite material is heated at a temperature not lower than 2200 ° C. and not lower than a temperature at which a part of the pore source decomposes and vaporizes. Many effective mesopores can be formed by heating the first composite material or the second composite material in the above temperature range.
When the first composite material or the second composite material is heated below a temperature at which a part of the pore source vaporizes, the pore source is not sufficiently removed from the composite material, so that mesopores are not formed. On the other hand, when the first composite material or the second composite material is heated at a temperature exceeding 2200 ° C., the shrinkage (for example, graphitization) of the carbon material proceeds and pores are reduced.

The porous carbon material produced by the method for producing a porous carbon material of the present invention has a low bulk because many effective mesopores are formed. And the electrode for capacitors using this porous carbon material becomes high in electrode density.
Thus, in the method for producing a porous carbon material of the present invention, a porous carbon material suitable for the material constituting the capacitor electrode can be produced.

In the method for producing a porous carbon material of the present invention, the temperature in the heating step is preferably more than 1500 ° C. and not more than 2200 ° C. Further, the temperature in the heating step is more preferably 1600 to 2200 ° C.
By heating the first composite material or the second composite material in the above temperature range, a porous carbon material suitable for the material constituting the capacitor electrode can be produced.

In the method for producing a porous carbon material of the present invention, it is desirable that the modifying group contained in the first composite material is an organosilicon compound. Furthermore, the organosilicon compound is more preferably an alkoxysilane.
Organosilicon compounds such as alkoxysilanes are easily bonded to a polymer chain constituting the first organic material.

In the method for producing a porous carbon material of the present invention, the inorganic sol contained in the second composite material is desirably a silica sol, an alumina sol, or a magnesia sol.
Inorganic sols such as silica sol are excellent in availability and handling.

In the method for producing a porous carbon material of the present invention, the metal alkoxide contained in the second composite material is preferably an alkoxysilane.

In the method for producing a porous carbon material of the present invention, the first organic material or the second organic material is a phenol resin, an epoxy resin, a polyimide resin, a melamine resin, or a polyamideimide resin. It is desirable to be. Furthermore, the first organic material or the second organic material is more preferably a phenol resin or a polyimide resin having a network skeleton.

The method for producing a porous carbon material of the present invention may further include a post-treatment step of treating the obtained porous carbon material with a base or an acid after the heating step.
As described above, in the conventional method for producing a porous carbon material, the pore source is removed only by etching using a base or an acid. On the other hand, in the method for producing a porous carbon material of the present invention, the pore source is removed in the heating step.
In the method for producing a porous carbon material of the present invention, after removing most of the pore sources by the heating step, the pore sources can be reliably removed by performing a post-treatment step with a base or acid.

The porous carbon material of the present invention is produced by any one of the methods for producing a porous carbon material of the present invention.

The capacitor electrode of the present invention is characterized by comprising a porous carbon material produced by any one of the methods for producing a porous carbon material of the present invention.

The capacitor of the present invention includes a capacitor electrode including a porous carbon material produced by any one of the methods for producing a porous carbon material of the present invention.

Note that the mechanism by which pores are formed in the first composite material or the second composite material described above is merely an estimation mechanism. Therefore, as long as pores are formed by the configuration of the present invention, another mechanism may be used, and the mechanism is not construed as being limited to the above mechanism.

FIG. 1 is a cross-sectional view schematically showing an example of the lithium ion capacitor of the present invention.

Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and can be applied with appropriate modifications without departing from the scope of the present invention.

(1) Manufacturing method of porous carbon material The manufacturing method of the porous carbon material which concerns on embodiment of this invention is the following.
A method for producing a porous carbon material, comprising:
A first composite material in which a modifying group containing a pore source is bonded to a polymer chain constituting the first organic material, or a first composite material comprising an inorganic sol or metal alkoxide containing a pore source and a second organic material. And a heating step of heating the composite material at a temperature of 2200 ° C. or lower and a temperature at which a part of the pore source is decomposed and vaporized.

(First composite material)
First, the first composite material in which a modifying group containing a pore source is bonded to a polymer chain constituting the first organic material will be described.
In this case, a modifying group (for example, an organosilicon compound) included in the first composite material becomes a pore source.
In the case of using the first composite material, a part of silica generated by desorbing an organosilicon compound or the like from the first composite material or a part of the desorbed organosilicon compound is vaporized in the heating step described later. . As a result, it is considered that pores are formed.

A thermosetting resin is mentioned as a 1st organic material. Examples of thermosetting resins include phenolic resins, epoxy resins, polyimide resins, melamine resins, polyamideimide resins, urethane resins, amino resins, unsaturated polyester resins, diallyl phthalate resins, alkyds. Resin, silicon resin and the like. Among these resins, phenol-based resins, epoxy-based resins, polyimide-based resins, melamine-based resins, or polyamide-imide-based resins are preferable, and phenol-based resins or polyimide-based resins having a network skeleton are particularly preferable.
In the present specification, the phenolic resin refers to a phenol resin and a resin containing a phenol resin as a main component (for example, a modified phenol resin). The epoxy resin refers to an epoxy resin and a resin mainly composed of an epoxy resin. The same applies to other resins.

Examples of the modifying group include an organosilicon compound. Moreover, the organosilicon compound has functional groups such as a vinyl group, a methacryl group, an epoxy group, an amino group, a nitrogen-containing group, a sulfur-containing alkyl group, and a hydroxyl group.
Specific examples of the organosilicon compound include alkoxysilanes (for example, alkoxysilane compounds, alkoxysilane oligomers, polyalkoxysilanes, silane coupling agents, and the like).

The organosilicon compound has a reactive functional group such as a vinyl group, a methacryl group, an epoxy group, an amino group, a nitrogen-containing group, a sulfur-containing alkyl group, and a hydroxyl group.
Therefore, the first composite material is formed by bonding a modifying group such as an organosilicon compound to the first organic material via these functional groups.

Examples of the alkoxysilane compound include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, and tetrabutoxysilane; trialkoxysilanes; or a polymer thereof.
The alkoxysilane compound to be bonded is preferably an alkoxysilane oligomer that is a polymer. Among the alkoxysilane compounds, tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane or polymers thereof are preferable.

Of the alkoxysilane compounds, tetramethoxysilane or a polymer thereof is represented by chemical formula (1).

In chemical formula (1), R represents a methyl group or a methoxy group. N is an integer of 0 or more.

In addition, an alkoxysilane oligomer in which n in the chemical formula (1) is 2 to 10 can be used by reducing the polymerization degree of the alkoxysilane compound. In this case, the alkoxysilane oligomer can form a large number of bonds with the first organic material such as a phenol resin, and a large number of uniform mesopores can be formed after the heating step.

Examples of the silane coupling agent include vinyltriethoxysilane, vinyltrimethoxysilane, tris (β-methoxyethoxy) vinylsilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, β- (3 , 4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyl Trimethoxysilane, (N-phenyl-γ-aminopropyl) trimethoxysilane, γ-ureidopropyltriethoxysilane, γ-isocyanatopropyltriethoxysilane, γ-isocyanatopropyltrimethoxysilane, γ-mercap Trimethoxysilane, bis (3-triethoxysilylpropyl) tetrasulfane, bis (3-triethoxysilylpropyl) disulfane, octyltriethoxysilane, methyltriethoxysilane, methyl trimethoxysilane.

The silane coupling agent undergoes an addition reaction with the first organic material such as a phenol resin through the functional group to form a first composite material. Silane coupling agents are those in which a hydrolyzable group that easily binds inorganic components and a functional group that easily bonds organic components are bonded to silicon atoms (Si), and are usually used as resin modifiers. It is. By the chemical reaction of the functional group of the silane coupling agent, it bonds with the first organic material, and a crosslinked structure by the silane coupling agent is formed in the first organic material.

Hereinafter, as specific examples of the first composite material, a phenol resin modified with an alkoxysilane compound, a polyamideimide resin modified with an alkoxysilane compound, and a polyimide resin modified with an alkoxysilane compound will be described.

A phenol resin modified with an alkoxysilane compound can be produced by reacting a phenol resin with an alkoxysilane oligomer that does not have a highly reactive functional group.
Chemical formula (2) shows the chemical structure of a phenol resin modified with an alkoxysilane compound. In addition, the coupling | bonding site | part of a phenol resin and an alkoxysilane compound can be selected arbitrarily.

In chemical formula (2), R represents a methyl group or a methoxy group. M is an integer of 1 or more.

The phenolic resin modified with the alkoxysilane compound is mixed with a curing reagent and cured by heating at about 170 ° C. for about 30 minutes, at about 100 ° C. for about 30 minutes, at about 220 ° C. for about 120 minutes, etc. You may let them.
Examples of the curing reaction agent include hexamethylenetetramine, 2-ethyl-4-methyl-imidazole, formaldehyde and the like.

Polyamideimide resin modified with alkoxysilane compound is a sol-gel cure (alkoxysilane hydrolysis and condensation reaction) by reacting amide bond of polyamic acid and aromatic carboxylic acid with alkoxysilane (alkoxysilane oligomer). After that, the obtained gel is heat-cured at 120 to 250 ° C.

Chemical formula (3) shows the chemical structure of a polyamide-imide resin modified with an alkoxysilane compound. Note that the alkoxysilane compound can be bonded to any part of the polyamideimide resin.

In chemical formula (3), X represents an alkyl spacer. M is an integer of 1 or more, and n is an integer of 1 or more.

A polyimide resin modified with an alkoxysilane compound is a method for preparing a polyamideimide resin modified with an alkoxysilane compound described above, except that a polyamic acid is used instead of an amide conjugate of a polyamic acid and an aromatic carboxylic acid. It can be prepared by the same method.
That is, a polyimide resin modified with an alkoxysilane compound is obtained by performing sol-gel curing (alkoxysilane hydrolysis and condensation reaction) by reacting polyamic acid with alkoxysilane (alkoxysilane oligomer), and then obtained. The gel can be produced by heating at 120 to 430 ° C. for imidization.

Chemical formula (4) shows the chemical structure of a polyimide resin modified with an alkoxysilane compound. Note that the alkoxysilane compound can be bonded to any part of the polyimide resin.

In chemical formula (4), x is an integer of 1 or more, y is an integer of 1 or more, and n is an integer of 1 or more.

In order to form a first composite material by reacting an alkoxysilane (alkoxysilane oligomer) with a first organic material such as a phenol resin, an alkoxysilane (alkoxysilane oligomer) is added to the mixture in the sol state. The polysiloxane is bonded to the first organic material by performing a polymerization reaction together with the hydrolysis.
Then, for example, heating is performed at a temperature of 100 to 200 ° C. to form a bridge between the first organic materials by a sol-gel reaction, and the sol state is cured to the gel state.

In addition, an alkoxysilane (alkoxysilane oligomer) can be bonded to an arbitrary portion of the first organic material such as a phenol resin at a uniform interval, and the polysiloxane in the first organic material can be crosslinked and cured. Can be uniformly distributed.

In addition, the size and quantity of the pores can be controlled by adjusting the molecular weight and bonding point of the polysiloxane bonded in the first organic material such as phenol resin.
For example, if the number of bonding points of alkoxysilane (alkoxysilane oligomer) is increased in the first organic material, a large number of polysiloxane bonds in the first organic material. On the other hand, if the bonding points of alkoxysilane (alkoxysilane oligomer) are reduced, the bonding points of polysiloxane are reduced. As a result, the fine structure of the carbon obtained by the heating process, that is, the pore size and the number of pores are adjusted by the bonding point and bonding amount of the polysiloxane.

(Second composite material)
Next, a second composite material composed of an inorganic sol containing a pore source or a metal alkoxide and a second organic material will be described.
In this case, the inorganic compound contained in the inorganic sol or the second organic material becomes the pore source.

For example, when the inorganic compound is silica and the second organic material is a phenol resin, the structure of the second composite material may be a structure in which silica particles are dispersed in the phenol resin. A structure in which is dispersed in a phenol resin crosslinked with a silica portion is also conceivable. Thus, “silica” means not only ceramic silica (SiO ₂ ) but also Si—O units in organic materials. The same applies to other inorganic compounds other than silica.
In the case of using the second composite material, in the heating step described later, the inorganic compound contained in the inorganic sol is vaporized or vaporized after the inorganic compound contained in the second organic material is desorbed. As a result, it is considered that pores are formed.

Examples of the inorganic sol include silica sol, alumina sol, magnesia sol, zirconia sol, and titania sol. Among these, silica sol, alumina sol, or magnesia sol is desirable, and silica sol is more desirable from the viewpoint of evaporability.
Silica sol includes organosilica sol.
Examples of the metal alkoxide include alkoxysilanes.

An example of the second organic material is a thermosetting resin. Examples of thermosetting resins include phenolic resins, epoxy resins, polyimide resins, melamine resins, polyamideimide resins, urethane resins, amino resins, unsaturated polyester resins, diallyl phthalate resins, alkyds. Resin, silicon resin and the like. Among these resins, phenol-based resins, epoxy-based resins, polyimide-based resins, melamine-based resins, or polyamide-imide-based resins are preferable, and phenol-based resins or polyimide-based resins having a network skeleton are particularly preferable.

The second organic material may be a first composite material.

The second composite material having a structure in which inorganic compound particles contained in the inorganic sol are dispersed in the second organic material is a mixture of an inorganic sol such as an organosilica sol and a second organic material such as a phenol resin. And it can produce | generate by disperse | distributing inorganic sol to a 2nd organic material.

(Heating process)
Hereinafter, a heating process for obtaining a porous carbon material by heating the first composite material or the second composite material containing the pore source at a temperature not lower than 2200 ° C. and not lower than a temperature at which a part of the pore source decomposes and vaporizes will be described. To do.

A heating process is performed in inert gas atmosphere, such as nitrogen and argon.
Although the pressure in a heating process is not specifically limited, Usually, it is desirable that it is about a normal pressure.
The heating time in the heating step is not particularly limited, but is preferably 1 to 100 hours, and more preferably 2 to 10 hours.
The temperature in the heating step is not less than the temperature at which a part of the pore source contained in the first composite material or the second composite material is decomposed and vaporized, and not more than 2200 ° C. Therefore, the temperature in the heating step is appropriately determined according to the type of the first composite material or the second composite material and other heating conditions (temperature rise temperature, heating time, etc.), but exceeds 1500 ° C. It is preferably 2200 ° C. or lower, more preferably 1600 to 2200 ° C., and particularly preferably 1600 to 2000 ° C.
The temperature rising rate in the heating step is usually about 10 to 400 ° C./hour, and preferably about 20 to 200 ° C./hour.
Further, it is considered that the pore source can be efficiently vaporized by increasing the CO partial pressure in the heating step.

(Other processes)
In the method for producing a porous carbon material according to the embodiment of the present invention, a post-treatment step of treating the obtained porous carbon material with a base or acid may be performed after the heating step.
Residual components can be removed by the post-treatment process.

In the post-treatment process, etching is performed using a base such as sodium hydroxide (NaOH) or an acid such as hydrofluoric acid (HF).
For example, when performing an etching treatment using hydrofluoric acid, it is desirable to stir the porous carbon material in a 20 to 50% hydrofluoric acid solution for 0.5 to 10 hours.

In the method for producing a porous carbon material according to the embodiment of the present invention, a pulverization step for obtaining a carbon powder having a predetermined particle diameter may be performed by pulverizing the produced porous carbon material.
The pulverization of the porous carbon material can be performed using an ultrafine pulverizer, a ball mill, a jet mill or the like.
The particle diameter (D50) of the carbon powder after the pulverization step is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.
When the particle diameter of the carbon powder is 1 to 5 μm, a uniform electrode can be formed even when the thickness is small when used as an electrode for a capacitor.
The particle size of the porous carbon material can be obtained by measuring a pulverized carbon powder suspension with a particle size distribution measuring device and a particle size distribution measuring device (laser diffraction type).

In the method for producing a porous carbon material according to the embodiment of the present invention, after the heating step, a step of pulverizing the obtained porous carbon material (post-heating pulverization step) is performed, and the material obtained by the pulverization step is obtained. You may perform the process (additional heating process) heated at the temperature higher than the temperature in a heating process.
After removing most of the pore sources by the heating step, the obtained material is pulverized and the pulverized material is heated again, so that the remaining pore sources can be reliably removed.

In the additional heating step, the other conditions are the same as those in the heating step except that the material obtained in the post-heating pulverization step is heated at a temperature higher than the temperature in the heating step.
The temperature in the additional heating step is preferably from the heating temperature (temperature in the heating step) to 2200 ° C.

Moreover, you may perform the post-processing process which etches the material obtained by the post-heating grinding process or the additional heating process with a base or an acid after the post-heating grinding process.
Each condition in the post-processing step is the same as each condition in the post-processing step performed after the heating step.

In the method for producing a porous carbon material according to the embodiment of the present invention, before the heating step, the material containing the pore source is heated at a temperature lower than the temperature in the heating step (preheating step), A step of crushing the material obtained by the preheating step (pre-heating crushing step) may be performed.
After removing a part of the pore source in the preheating step, the obtained material is pulverized, and the pulverized material is heated again, so that the pore source can be reliably removed.

In the preheating step, other conditions are the same as those in the heating step, except that the material including the pore source is heated at a temperature lower than the temperature in the heating step.
The temperature in the preheating step is desirably 400 ° C. to heating temperature (temperature in the heating step).

Moreover, you may perform the post-processing process which etches the material obtained by the pre-heating grinding process or the heating process with a base or an acid after the pre-heating grinding process.
Each condition in the post-processing step is the same as each condition in the post-processing step performed after the heating step.

(2) Porous carbon material A porous carbon material according to an embodiment of the present invention is manufactured by the above-described method for manufacturing a porous carbon material.

In the porous carbon material of the present embodiment, pores are formed. Specifically, in the differential pore volume distribution curve obtained by analyzing the adsorption isotherm obtained by the N ₂ adsorption method by the BJH method, pores included in the pore diameter range of 2 to 200 nm are formed.
The BJH method used here is a method proposed by Barrett, Joyner, Halenda for determining the distribution of mesopores (EP Barrett, LG Joyner and PP Halenda, J. et al. Am. Chem. Soc., 73, 373, (1951)).

In the differential pore volume distribution curve, the total value A of the pore volumes included in the pore diameter range of 2 to 15 nm is equal to the total value B of the pore volumes included in the pore diameter range of 2 to 200 nm. It is desirable to occupy 80% or more.

In the porous carbon material of the present embodiment, the total value B of the pore volumes included in the pore diameter range of 2 to 200 nm is desirably 0.3 cm ³ / g or more, and 0.4 to 1. More desirably, it is 2 cm ³ / g.
When the total value B is 0.3 cm ³ / g or more, there are many pores for the electrolyte to enter, and the capacitor electrode using such a porous carbon material further improves the charge / discharge characteristics. be able to.
In addition, when the total value B exceeds 1.2 cm ³ / g, the bulk density (weight per unit volume) of the porous carbon material decreases, and in the capacitor electrode using such a porous carbon material, the electrode density Becomes lower.

Further, the porous carbon material of the present embodiment may further contain silicon carbide.
If silicon carbide is contained in the porous carbon material, the porous carbon material can be easily pulverized, and the particle diameter of the carbon powder formed by pulverizing the porous carbon material can be more uniform.

(3) Capacitor Electrode and Capacitor A capacitor electrode according to an embodiment of the present invention is characterized by comprising a porous carbon material produced by the above-described method for producing a porous carbon material.
In addition, a capacitor according to an embodiment of the present invention includes a capacitor electrode including the porous carbon material manufactured by the above porous carbon material manufacturing method.

Here, a lithium ion capacitor electrode which is a kind of hybrid capacitor electrode will be described as an example of the capacitor electrode, and a lithium ion capacitor which is a kind of hybrid capacitor will be described as an example of the capacitor.

A lithium ion capacitor 1 shown in FIG. 1 includes an electrode for a lithium ion capacitor (a positive electrode is denoted by reference numeral 2 and a negative electrode is denoted by reference numeral 3), a separator 4 and an electrolytic solution (not shown).
Specifically, in the lithium ion capacitor 1, the positive electrode 2 and the negative electrode 3 are provided so as to face each other with the separator 4 interposed therebetween.

The positive electrode 2 includes the porous carbon material of the present embodiment described above.
The positive electrode 2 includes an electrode composition made of the porous carbon material of the present embodiment, a positive electrode current collector 2a on which the electrode composition is formed, and a positive electrode tab 2b attached to the positive electrode current collector 2a. The positive electrode tab 2b is taken out from the casing 5 to the outside.

The thickness of the positive electrode 2 is preferably 30 to 300 μm, more preferably 40 to 200 μm, and still more preferably 50 to 150 μm.

The positive electrode current collector 2a is preferably made of metal, carbon, conductive polymer, etc., and more preferably made of metal.
As the metal for the positive electrode current collector 2a, aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, other alloys, or the like can be used.
Among these, it is preferable to use copper, aluminum or an aluminum alloy from the viewpoint of electrical conductivity and voltage resistance.

Examples of the shape of the positive electrode current collector 2a include current collectors such as metal foils and metal edged foils, and current collectors having through-holes such as expanded metal, punching metal, and net-like, but reduce diffusion resistance of electrolyte ions. In addition, a positive electrode current collector having a through-hole is preferable in that the output density of the lithium ion capacitor can be improved, and among them, expanded metal or punching metal is more preferable in that the electrode strength is further excellent.

The ratio of the holes of the positive electrode current collector 2a is preferably 10 to 80 area%, more preferably 20 to 60 area%, and still more preferably 30 to 50 area%. When the ratio of the penetrating holes is within this range, the diffusion resistance of the electrolytic solution is reduced, and the internal resistance of the lithium ion capacitor is reduced.
In addition, the hole of a positive electrode electrical power collector should just be provided only in the case of a lithium ion capacitor, and the hole need not be provided in the case of an electric double layer capacitor.

The thickness of the positive electrode current collector 2a is preferably 5 to 100 μm, more preferably 10 to 70 μm, and still more preferably 20 to 50 μm. *

The negative electrode 3 is an electrode including a negative electrode active material that can occlude and release lithium ions.
The negative electrode 3 is provided with a negative electrode current collector 3a. A negative electrode tab 3b is attached to the negative electrode current collector 3a, and the negative electrode tab 3b is taken out from the casing 5 to the outside.
The negative electrode current collector 3b is made of, for example, copper, nickel, stainless steel, and alloys thereof.

The negative electrode 3 is preferably preliminarily occluded with lithium ions.
Lithium ions can be occluded in the negative electrode by a chemical method or an electrochemical method.

Examples of the chemical method include a method of immersing lithium ions by immersing in an electrolytic solution in a state where a negative electrode and a necessary amount of lithium metal are in contact with each other and applying heat. Examples of the electrochemical method include a method in which lithium ions are occluded by making a negative electrode and lithium metal face each other through a separator and charging with constant current in an electrolytic solution.

The separator 4 is not particularly limited as long as it can insulate between lithium ion capacitor electrodes and allow ions to pass therethrough.
Specifically, a polyolefin such as polyethylene or polypropylene, a microporous membrane made of rayon or glass fiber, a nonwoven fabric made of rayon or glass fiber, a porous membrane made mainly of pulp (commonly called electrolytic capacitor paper), or the like is used. be able to.
The thickness of the separator 4 is preferably 1 to 100 μm, more preferably 10 to 80 μm, and still more preferably 20 to 60 μm.

The casing 5 may be formed of a laminate film, a metal case, a resin case, a ceramic case, or the like.
The shape is not particularly limited, and may be a coin shape, a cylindrical shape, a square shape, or the like.

The electrolytic solution is composed of an electrolyte and a solvent.
A lithium salt can be used as the electrolyte. Therefore, lithium ions can be used as cations. As anions, PF ₆ ⁻ , BF ₄ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , N (RfSO ₃ ) ²⁻ , C (RfSO ₃ ) ³⁻ , RfSO ₃ ⁻ (Rf is 1 to 12 carbon atoms, respectively) F ⁻ , ClO ₄ ⁻ , AlCl ₄ ⁻ , AlF ₄ ^{− and the} like can be used.
These electrolytes can be used alone or in combination of two or more.
The concentration of the lithium salt as the electrolyte is preferably 0.1 to 2.5 mol / l.

A solvent will not be specifically limited if it is a non-aqueous electrolyte solution which can be used for a capacitor or a lithium ion capacitor.
Specific examples include carbonates such as propylene boat, ethylene carbonate, butylene carbonate, dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone; sulfolanes; nitriles such as acetonitrile. These solvents can be used alone or as a mixed solvent of two or more. Of these, carbonates are preferred.

The electrode for a lithium ion capacitor of this embodiment can be manufactured through the following steps.

First, a positive electrode composition preparation step of preparing a positive electrode composition slurry is performed by mixing a carbon powder made of the porous carbon material of the present embodiment, a conductive material, a binder and water.

The porous carbon material of the present embodiment is pulverized to obtain carbon powder having a predetermined particle size.
The particle diameter (D50) of the carbon powder is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

Examples of the binder include polytetrafluoroethylene, styrene butadiene rubber, polytetrafluoroethylene, styrene butadiene rubber (SBR), and polyvinylidene fluoride (PVDF). These binders can be used alone or in combination of two or more. As the binder, polytetrafluoroethylene is preferable.
In addition, the binder is preferably a powder in order to facilitate the moldability.
The amount of the binder used is preferably, for example, 1 to 30 parts by weight with respect to 100 parts by weight of the carbon powder.

The conductive material is made of particulate carbon that has almost no pores that can form an electric double layer. For example, furnace black, acetylene black, and ketjen black (registered by Akzo Nobel Chemicals Bethloten Fennaut Shap) Trade name) and the like. Among these, acetylene black and furnace black are preferable.
These conductive materials can be used alone or in combination of two or more.

The average particle size of the conductive material is preferably smaller than the average particle size of the carbon powder made of the porous carbon material, more preferably 0.001 to 10 μm, still more preferably 0.05 to 5 μm, and particularly preferably 0.00. 01 to 1 μm. When the average particle diameter of the conductive material is within this range, high electrical conductivity can be obtained.
The amount of the conductive material is preferably in the range of 0.1 to 50 parts by weight, more preferably 0.5 to 15 parts by weight, and further preferably 1 to 10 parts by weight with respect to 100 parts by weight of the carbon powder.
When the amount of the conductive material is within this range, the capacity of the lithium ion capacitor using the obtained lithium ion capacitor electrode can be increased, and the internal resistance can be decreased.

Next, the positive electrode composition slurry is applied on the positive electrode current collector 2a, and then dried to produce a positive electrode.
The positive electrode 2 can be produced by such a wet molding method.
As other methods, a method of laminating a positive electrode composition molded into a sheet shape on a positive electrode current collector (kneading sheet molding method), preparing composite particles of the positive electrode composition, forming a sheet on the positive electrode current collector, Examples thereof include a roll press method (dry molding method). Among these, a wet molding method and a dry molding method are preferable, and a wet molding method is more preferable.

The negative electrode 3 is formed by mixing a negative electrode active material, a binder, and a conductive material, adding this to a solvent to prepare a slurry for a negative electrode composition, applying the slurry to the negative electrode current collector 3a, and drying the slurry. be able to.
In addition, the negative electrode may be produced by a kneading sheet molding method or a dry molding method.

The negative electrode active material may be any material that can reversibly carry lithium ions.
Specifically, electrode active materials used in the negative electrode of lithium ion secondary batteries can be widely used.
Among these, crystalline carbon materials such as graphite and non-graphitizable carbon, carbon materials such as hard carbon and coke, and polyacene-based substances (PAS) are preferable. These carbon materials and PAS are obtained by carbonizing a phenol resin or the like, activated as necessary, and then pulverized.
The same binder and conductive material as the positive electrode can be used.

Next, a method for manufacturing the capacitor of this embodiment will be described.
Here, the manufacturing method of a capacitor is demonstrated taking the lithium ion capacitor mentioned above as an example.

First, the positive electrode 2 is attached to the upper casing, and the negative electrode 3 is attached to the lower casing.
Then, the separator 4 is installed between the positive electrode 2 and the negative electrode 3, and after impregnating with electrolyte solution, a casing is sealed.
Thereby, the lithium ion capacitor of this embodiment can be manufactured.

Below, the manufacturing method of the porous carbon material of this embodiment, the porous carbon material, the electrode for capacitors, and the effect of a capacitor are described.

(1) In the method for producing a porous carbon material of the present embodiment, the first composite material in which a modifying group containing a pore source is bound to the polymer chain constituting the first organic material, or the pore source is used. A heating step is included in which the second composite material including the inorganic sol or metal alkoxide and the second organic material is heated at a temperature not lower than the temperature at which a part of the pore source is decomposed and vaporized but not higher than 2200 ° C.
By the heating step, first, the first composite material or the second composite material can be carbonized. Further, the pore source can be removed from the composite material by the heating step. As a result, pores can be formed.
Thus, in the manufacturing method of the porous carbon material of this embodiment, carbonization of a composite material and formation of pores can be performed by a heating process. Therefore, the process of forming pores can be omitted, and the manufacturing process can be simplified. As a result, manufacturing time and cost can be reduced.
Furthermore, in the method for producing the porous carbon material of the present embodiment, since the pores can be formed by heating the first composite material or the second composite material, dangerous chemicals such as hydrofluoric acid are handled. A porous carbon material can be produced safely without any problems.

(2) In the method for producing a porous carbon material of the present embodiment, the first composite material or the second composite material is heated at a temperature not lower than 2200 ° C. and not lower than a temperature at which a part of the pore source is decomposed and vaporized.
Many effective mesopores can be formed by heating the first composite material or the second composite material in the above temperature range.

(3) The porous carbon material of this embodiment is manufactured by the method for manufacturing a porous carbon material of this embodiment.
Since the porous carbon material manufactured by the method for manufacturing the porous carbon material of the present embodiment has many effective mesopores, the bulk is low. And the electrode for capacitors using this porous carbon material becomes high in electrode density.

(4) The capacitor electrode of the present embodiment is characterized by comprising a porous carbon material manufactured by the method for manufacturing a porous carbon material of the present embodiment. A capacitor using such an electrode has a high electrode density.

(5) The capacitor according to the present embodiment includes a capacitor electrode including the porous carbon material manufactured by the method for manufacturing a porous carbon material according to the present embodiment. Since such a capacitor includes an electrode having a high electrode density, the capacitor has a high electrode density.

Hereinafter, examples that more specifically disclose the embodiments of the present invention will be shown, but the present embodiments are not limited to these examples.

(1) Production of porous carbon material (Example 1)
A phenol resin modified with an alkoxysilane compound (Sumilite Resin (registered trademark) PR-54529, manufactured by Sumitomo Bakelite Co., Ltd.) and hexamethylenetetramine as a curing reaction agent are mixed with phenol resin: curing reaction agent = 5: 1. The mixture was mixed at a weight ratio to obtain a curing reaction agent mixture.

The obtained curing reaction agent mixture was placed on a PET sheet fixed on a glass plate.
Next, using a glass rod, the curing reaction agent mixture was formed into a film on a PET sheet, and cured in a dryer at 170 ° C. for 30 minutes.
The obtained film was cut into a predetermined size and heated at 1800 ° C. for 2 hours under heating conditions in an N ₂ atmosphere.
The porous carbon material of Example 1 was manufactured through the above steps.

(Example 2)
A porous material was produced in the same manner as in Example 1 except that the heating condition was changed to 1600 ° C. for 10 hours in an N ₂ atmosphere.

(Example 3)
A porous material was produced in the same manner as in Example 1 except that the heating condition was changed to N ₂ atmosphere at 2000 ° C. for 2 hours.

Example 4
2200 ° C. The heating conditions, it is 2 hours, except that the N ₂ atmosphere to prepare a porous material in the same manner as in Example 1.

(Example 5)
A polyamide-imide resin modified with an alkoxysilane compound synthesized by introducing siloxane into the basic skeleton of an aromatic polyamide-imide synthesized from trimellitic anhydride and diphenylmethane-4,4′-diisocyanate was used.
A film was obtained in the same manner as in Example 1 for the polyamideimide resin modified with the alkoxysilane compound.
The obtained film was cut into a predetermined size and heated at 1600 ° C. for 2 hours under heating conditions in an N ₂ atmosphere.
By passing through the above process, the porous carbon material of Example 5 was manufactured.

(Example 6)
A polyimide resin (HBPI-SiO2-A, manufactured by Ibiden Resin Co., Ltd.) modified with an alkoxysilane compound was prepared, and a film was obtained in the same manner as in Example 1.
The obtained film was cut into a predetermined size and heated at 1800 ° C. for 2 hours under heating conditions in an N ₂ atmosphere.
The porous carbon material of Example 6 was manufactured through the above steps.

(Example 7)
Organosilica sol (manufactured by Nissan Chemical Industries, Ltd., particle size 10 nm, silica concentration 20%) and phenolic resin (manufactured by Sumitomo Bakelite Co., Ltd., novolak type) in organosilica sol: phenolic resin = 5: 4 (weight ratio) The composite material was obtained by mixing and dispersing the organosilica sol in the phenol resin.
10 g of the obtained composite material and 0.8 g of hexamethylenetetramine as a curing reaction agent were mixed to obtain a curing reaction agent mixture.

The obtained curing reaction agent mixture was placed on a PET sheet fixed on a glass plate.
Next, using a glass rod, the curing reaction agent mixture was formed into a film on a PET sheet, and cured in a dryer at 170 ° C. for 30 minutes.
The obtained film was cut into a predetermined size and heated at 1800 ° C. for 2 hours under heating conditions in an N ₂ atmosphere.
The porous carbon material of Example 7 was manufactured through the above steps.

(Comparative Example 1)
A porous material was produced in the same manner as in Example 1 except that the heating conditions were changed to N ₂ atmosphere at 1450 ° C. for 2 hours.
(Comparative Example 2)
2250 ° C. The heating conditions, it is 2 hours, except that the N ₂ atmosphere to prepare a porous material in the same manner as in Example 1.

(Comparative Example 3)
A porous carbon material was produced in the same manner as in Example 1 except that the film was heated at 800 ° C. for 2 hours in an N ₂ atmosphere and then treated with 48% hydrofluoric acid (HF aqueous solution) for 24 hours.

(Comparative Example 4)
As the porous carbon material of Comparative Example 4, commercially available activated carbon (Calgon Carbon Japan Co., Ltd., Diasorb (registered trademark) F 100D) was used.

(2) Evaluation of porous carbon material The porous carbon material manufactured by each Example and the comparative example was evaluated with the following method.
The porous carbon material produced in each example and comparative example was placed in a ball mill and pulverized with an alumina ball for 10 hours to produce a carbon powder having a particle diameter (D50) of 3 μm. Each evaluation was performed using.

(Preparation of differential pore volume distribution curve)
Using the carbon powder, the adsorption amount of N ₂ was measured, and an adsorption isotherm was prepared.
For the measurement of the N ₂ adsorption amount, AUTOSORB-1MP manufactured by Cantachrome was used.
The obtained adsorption isotherm was analyzed by the BJH method to obtain a differential pore volume distribution curve.
As a result, the porous carbon material produced in each example and comparative example had pores included in the pore diameter range of 2 to 200 nm.
In addition, for the porous carbon materials produced in each of the examples and comparative examples, the total pore volume A included in the pore diameter range of 2 to 15 nm is the pores included in the pore diameter range of 2 to 200 nm. The proportion of the total volume B was determined. The results are shown in Table 1.

(Measurement of BET specific surface area)
About the porous carbon material manufactured by each Example and the comparative example, the BET specific surface area was calculated | required by BET method using the adsorption isotherm obtained by the said operation. The results are shown in Table 1.
The BET specific surface area was measured by a capacity method and a multipoint method according to JIS Z 8830 (2001).

As shown in Table 1, in the porous carbon materials of Examples 1 to 6 in which the first composite material in which the modifying group was bonded to the organic material was heated at 1600 to 2200 ° C., the pore diameter range was 2 to 15 nm. The total value A of the pore volumes contained in 80% to 87% of the total value B of the pore volumes contained in the pore diameter range of 2 to 200 nm.
Therefore, it can be seen that the porous carbon materials produced in Examples 1 to 6 have sufficiently more mesopores with a high specific surface area than macropores with a low specific surface area.

Further, in the porous carbon materials of Examples 1 to 6, the total value B of the pore volumes included in the pore diameter range of 2 to 200 nm is 0.3 to 0.63 cm ³ / g.
Further, in the porous carbon materials of Examples 1 to 6, the BET specific surface area is 301 to 428 m ² / g.
Therefore, the porous carbon materials produced in Examples 1 to 6 are sufficiently low in bulk, and it is considered that the capacitor electrode using the porous carbon material has a high electrode density. In addition, many mesopores of a size that is easy for electrolyte to enter are formed, and it is considered that the surface of the capacitor electrode using such a porous carbon material can be effectively used as an electric double layer.

It can also be seen that the porous carbon material of Example 7 using the second composite material composed of the inorganic sol and the organic material can provide the same results as the porous carbon material of Examples 1 to 6.

Meanwhile, the porous carbon material of Comparative Example 1 in which the first composite material in which the modifying group was bonded to the organic material was heated at 1450 ° C., and the porous material in Comparative Example 2 in which the composite material to which the modifying group was bonded were heated at 2250 ° C. In the carbonaceous material, the total value A of the pore volume included in the range of the pore diameter of 2 to 15 nm is 82 to 85% of the total value B of the pore volume included in the range of the pore diameter of 2 to 200 nm. is occupying.
However, in the porous carbon materials of Comparative Examples 1 and 2, the total value B of the pore volumes included in the pore diameter range of 2 to 200 nm is a low value of 0.03 to 0.24 cm ³ / g. The BET specific surface area is also a low value of 135 to 195 m ² / g.
Therefore, when the porous carbon material manufactured in Comparative Examples 1 and 2 is used for a capacitor electrode, the electrode density is considered to be low.

Further, in the porous carbon material of Comparative Example 3 subjected to hydrofluoric acid treatment, the total value A of the pore volumes included in the pore diameter range of 2 to 15 nm is included in the fine pore diameter range of 2 to 200 nm. The ratio of the pore volume to the total value B is the same as that of the porous carbon materials of Examples 1 to 5. The BET specific surface area is superior to the porous carbon materials of Examples 1 to 5.
However, in the porous carbon material of Comparative Example 3, the total value B of the pore volumes included in the pore diameter range of 2 to 200 nm is a high value of 1.25 cm ³ / g. Therefore, it is considered that the bulk density of the porous carbon material is lowered, and when such a porous carbon material is used for a capacitor electrode, the electrode density is lowered.

In the porous carbon material of Comparative Example 4 using activated carbon, the BET specific surface area is superior to the porous carbon materials of Examples 1 to 5.
However, in the porous carbon material of Comparative Example 4 using activated carbon, the total value A of the pore volumes included in the pore diameter range of 2 to 15 nm is the pores included in the pore diameter range of 2 to 200 nm. Only 44% of the total volume B is occupied. Therefore, it is considered that the mesopores are not sufficiently formed in the porous carbon material of Comparative Example 4.
Further, in the porous carbon material of Comparative Example 4, the total value B of pore volumes included in the pore diameter range of 2 to 200 nm is a high value of 1.41 cm ³ / g. Therefore, it is considered that the bulk density of the porous carbon material is lowered, and when such a porous carbon material is used for a capacitor electrode, the electrode density is lowered.

As described above, many mesopores were formed by heating the first composite material in which the modifying group was bonded to the organic material or the second composite material composed of the inorganic sol and the organic material in a predetermined temperature range. It is considered that a porous carbon material can be produced.

DESCRIPTION OF SYMBOLS 1 Lithium ion capacitor 2 Positive electrode 2a Positive electrode collector 2b Positive electrode tab 3 Negative electrode 3a Negative electrode collector 3b Negative electrode tab 4 Separator 5 Casing

Claims

A method for producing a porous carbon material, comprising:
A first composite material in which a modifying group containing a pore source is bonded to a polymer chain constituting the first organic material, or a first composite material comprising an inorganic sol or metal alkoxide containing a pore source and a second organic material. 2. A method for producing a porous carbon material, comprising a heating step of heating the composite material 2 at a temperature not lower than a temperature at which a part of the pore source is decomposed and vaporized but not higher than 2200 ° C.
The method for producing a porous carbon material according to claim 1, wherein the temperature in the heating step is higher than 1500 ° C and not higher than 2200 ° C.
The method for producing a porous carbon material according to claim 2, wherein the temperature in the heating step is 1600 to 2200 ° C.
The method for producing a porous carbon material according to any one of claims 1 to 3, wherein the modifying group contained in the first composite material is an organosilicon compound.
The method for producing a porous carbon material according to claim 4, wherein the organosilicon compound is an alkoxysilane.
The method for producing a porous carbon material according to any one of claims 1 to 3, wherein the inorganic sol contained in the second composite material is silica sol, alumina sol, or magnesia sol.
The method for producing a porous carbon material according to any one of claims 1 to 3, wherein the metal alkoxide contained in the second composite material is an alkoxysilane.
The first organic material or the second organic material is a phenol resin, an epoxy resin, a polyimide resin, a melamine resin, or a polyamideimide resin. A method for producing a porous carbon material.
The method for producing a porous carbon material according to claim 8, wherein the first organic material or the second organic material is a phenol resin or a polyimide resin having a network skeleton.
The method for producing a porous carbon material according to any one of claims 1 to 9, further comprising a post-treatment step of treating the obtained porous carbon material with a base or an acid after the heating step.
A porous carbon material produced by the method for producing a porous carbon material according to any one of claims 1 to 10.
A capacitor electrode comprising the porous carbon material produced by the method for producing a porous carbon material according to any one of claims 1 to 10.
A capacitor comprising a capacitor electrode comprising a porous carbon material produced by the method for producing a porous carbon material according to any one of claims 1 to 10.