JP2006264993A - Method of manufacturing carbon material, carbon material, negative electrode material for secondary cell and non-aqueous electrolyte secondary cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a carbon material capable of manufacturing a negative electrode material for a non-aqueous electrolyte secondary cell having excellent charge discharge characteristics, the carbon material obtained by the manufacturing method, the negative electrode material for the secondary cell using the carbon material and a non-aqueous electrolyte secondary cell. <P>SOLUTION: The method of manufacturing the carbon material has (a) a step for preparing a carbon material precursor which is one of a resin composition, a hardened material of the resin composition or a pre-carbonized material of them, (b) a step for supporting an alkali metal-containing compound on the surface of the carbon material precursor to make an alkali metal supported precursor, (c) a step for carbonizing the alkali metal supported precursor and (d) a step for washing the treated material after the carbonization to substantially remove the alkali metal component existing at least on the surface part of the treated material. The carbon material is manufactured by this method. The secondary negative electrode material contains the carbon material. The non-aqueous electrolyte secondary cell uses the negative electrode material for secondary cell. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a carbon material production method, a carbon material, a negative electrode material for a secondary battery, and a non-aqueous electrolyte secondary battery.

Carbon materials are used in a wide range of applications such as negative electrodes for lithium ion secondary batteries, capacitor electrodes, electrodes for electrolysis, and activated carbon, and are areas where further development is expected in the future.
These carbon materials are conventionally made from coconut shell, coal coke, coal or petroleum pitch, furan resin, phenol resin, and the like (for example, see Patent Document 1). However, the conventional carbon materials obtained from these raw materials have a large variation in pore diameter formed on the surface, and each pore volume is large, so that they are particularly used as negative electrode materials for non-aqueous electrolyte secondary batteries. In some cases, the characteristics are not sufficient in terms of charge / discharge capacity and cycleability.

JP 05-043345 A

  The present invention provides a method for producing a carbon material capable of producing a negative electrode material for a non-aqueous electrolyte secondary battery having excellent charge / discharge characteristics, a carbon material obtained by this production method, and a carbon material obtained by using this carbon material. A negative electrode material for a secondary battery and a nonaqueous electrolyte secondary battery are provided.

Such an object is achieved by the following present inventions (1) to (7).
(1) A method for producing a carbon material obtained by carbonizing a carbon material precursor,
(A) a step of preparing a carbon material precursor that is either a resin composition, a cured product of the resin composition, or a material obtained by pre-carbonizing the resin composition,
(B) a step of supporting an alkali metal-containing compound on the surface of the carbon material precursor to obtain an alkali metal-supported precursor;
(C) a step of carbonizing the alkali metal-supported precursor; and
(D) a step of washing the treated product after the carbonization treatment with water to substantially remove an alkali metal component in the treated product;
A method for producing a carbon material, comprising:
(2) The said resin composition is a manufacturing method of the carbon material as described in (1) which has 1 or more types chosen from a novolak-type phenol resin, a melamine resin, a furan resin, and an aniline resin.
(3) The production amount of the carbon material according to (1) or (2), wherein the supported amount of the alkali metal-containing compound is 0.1 to 5% by weight in terms of an alkali metal component with respect to the carbon material precursor. Method.
(4) A carbon material obtained by the production method according to any one of (1) to (3).
(5) The carbon material according to (4), wherein the carbon material has a pore volume of 1 to 100 ml / kg having a pore diameter exceeding 0.33 nm formed on a surface thereof.
(6) A negative electrode material for a secondary battery comprising the carbon material according to (4) or (5).
(7) A nonaqueous electrolyte secondary battery using the secondary battery negative electrode material according to (6).

  The present invention prepares a carbon material precursor that is either a resin composition, a cured product of the resin composition, or a pre-carbonized product thereof, and supports an alkali metal-containing compound on the surface, After the carbonization treatment, the carbonized product is washed with water, and has a step of substantially removing the alkali metal component in the treated product. By using the obtained carbon material, a negative electrode material for a non-aqueous electrolyte secondary battery excellent in charge / discharge characteristics can be obtained.

Below, the carbon material production method of the present invention (hereinafter sometimes simply referred to as “production method”), the carbon material obtained by this production method, a negative electrode material for a secondary battery using the same, and The nonaqueous electrolyte secondary battery will be described in detail.
The production method of the present invention is a method for producing a carbon material obtained by carbonizing a carbon material precursor,
(A) a step of preparing a carbon material precursor that is either a resin composition, a cured product of the resin composition, or a material obtained by pre-carbonizing the resin composition,
(B) a step of supporting an alkali metal-containing compound on the surface of the carbon material precursor to obtain an alkali metal-supported precursor;
(C) a step of carbonizing the alkali metal-supported precursor, and
(D) a step of washing the treated product after the carbonization treatment with water to substantially remove an alkali metal component in the treated product;
It is characterized by having.
Moreover, the carbon material of the present invention is obtained by the production method of the present invention.
Moreover, the negative electrode material for secondary batteries of this invention contains the carbon material of the said this invention, It is characterized by the above-mentioned.
And the nonaqueous electrolyte secondary battery of this invention uses the said negative electrode material for secondary batteries of this invention, It is characterized by the above-mentioned.
First, the manufacturing method of this invention and the carbon material obtained by this manufacturing method are demonstrated in detail.

First, the production method of the present invention includes:
(A) A carbon material precursor that is either a resin composition, a cured product of the resin composition, or a material obtained by pre-carbonizing the resin composition is prepared.

First, the resin composition used in the production method of the present invention will be described.
Although it does not specifically limit as said resin composition, For example, what is chosen from a thermosetting resin, a thermoplastic resin, or another polymeric material (Hereafter, these may be only called "main component resin.") Can be contained. The main component resins can be used alone or in combination of two or more.
Moreover, a hardening | curing agent, an additive, etc. can be contained together with the said main component resin.

  In the present invention, the above resin composition may contain only one kind of resin as the main component resin, but for convenience, it is also referred to as a resin composition.

  Here, the thermosetting resin is not particularly limited. For example, a phenol resin such as a novolac type phenol resin or a resol type phenol resin, an epoxy resin such as a bisphenol type epoxy resin or a novolac type epoxy resin, a melamine resin, a urea resin, or aniline. Examples thereof include resins, cyanate resins, furan resins, ketone resins, unsaturated polyester resins, and urethane resins. In addition, modified resins in which these are modified with various components can also be used.

  The thermoplastic resin is not particularly limited. For example, polyethylene, polystyrene, polyacrylonitrile, acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, polypropylene, vinyl chloride, methacrylic resin, polyethylene terephthalate, Polyamide, polycarbonate, polyacetal, polyphenylene ether, polybutylene terephthalate, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polyamideimide, polyimide, polyphthalamide, and the like can be given.

  Other polymer compounds are not particularly limited, and examples thereof include polymerizable polymer compounds such as petroleum pitch, coal pitch, and spinning pitch.

When a thermosetting resin is used as the main component resin, the curing agent can be used in combination.
Although it does not specifically limit as a hardening | curing agent used here, For example, in the case of a novolak-type phenol resin, a hexamethylenetetramine, paraform, etc. can be used. In the case of epoxy resins, polyamine compounds such as aliphatic polyamines and aromatic polyamines, acid anhydrides, imidazole compounds, dicyandiamide, novolac type phenol resins and the like can be used.
In addition, even if it is a thermosetting resin that normally uses a predetermined amount of a curing agent, the resin composition used in the present invention may use a smaller amount than usual or may be used without using a curing agent. You can also

As said main component resin used for said resin composition, a thermosetting resin is preferable. Thereby, the remaining carbon rate of a carbon material can be raised more.
And among thermosetting resins, those selected from novolak type phenol resins, melamine resins, furan resins, and aniline resins are preferable. Thereby, in addition to the said effect, a carbon material can be manufactured at low cost.

In addition to the above, an additive can be blended in the resin composition.
Although it does not specifically limit as an additive used here, For example, the carbon material precursor carbonized at 200-800 degreeC, a graphite and graphite modifier, a nitrogen-containing compound, an oxygen-containing compound, an aromatic compound, and nonferrous A metal element etc. can be mentioned.
The above additives may be used alone or in combination of two or more depending on the type and properties of the main component resins used.

  The method for preparing the resin composition is not particularly limited. For example, the main component resins and other components are blended in a predetermined ratio, and these are melt-mixed. These components are used as a solvent. It can be prepared by a method of dissolving and mixing, or a method of pulverizing and mixing these components.

The apparatus for preparing the resin composition is not particularly limited. For example, when melt mixing is performed, a kneading apparatus such as a kneading roll, a single screw or a twin screw kneader can be used. Moreover, when performing melt | dissolution mixing, mixing apparatuses, such as a Henschel mixer and a disperser, can be used, for example. And when performing pulverization mixing, apparatuses, such as a hammer mill and a jet mill, can be used, for example.
The resin composition thus obtained may be one obtained by physically mixing a plurality of types of components, or a part of the resin composition is chemically treated by energy applied in the resin composition preparation stage. It may have been reacted with.

  In the production method of the present invention, the resin composition described above, a cured product of this resin composition, or a product obtained by pre-carbonizing these can be used as the carbon material precursor.

When the resin composition is used as a carbon material precursor, it is not particularly limited, but the one prepared by the above method can be used after being preferably pulverized to an appropriate particle size.
Moreover, when a thermosetting resin or a polymerizable polymer compound is used as the main component resin of the resin composition, a cured product of this resin composition can be used. The method for curing the resin composition is not particularly limited, and examples thereof include a method in which the resin composition is thermally cured by giving a heat amount capable of a curing reaction, or a method in which the main component resin and a curing agent are used in combination. It is done. And the hardened | cured material obtained by doing in this way can be grind | pulverized to an appropriate particle size preferably, and can be used.
In addition, when using a resin obtained by subjecting the resin composition or a cured product thereof to preliminary carbonization, the resin composition or the cured product is increased to 400 to 600 ° C. at 1 to 200 ° C./hour, for example. After heating and treating this for 0.1 to 50 hours, preferably 0.5 to 10 hours, it can be cooled to room temperature and then pulverized to an appropriate particle size.

The particle size in the case of using the resin composition, a cured product of the resin composition, or a material obtained by pre-carbonizing these as a carbon material precursor is not particularly limited, but preferably has an average particle size of 1 to 30 μm, more preferably It is preferable to set it as 5-20 micrometers.
As a result, the specific surface area of the particulate carbon material precursor can be increased, and when the alkali metal-containing compound is supported in the step (b) to be described later, the uniformity of the supported amount can be improved and also described later (c ) When carbonizing in the process, it is possible to increase the uniformity of the thermal history and the surface state and to form more suitable fine pores.
Moreover, the specific surface area of a carbon material precursor can be made into a suitable level by using the carbon material precursor of such a particle size. Thereby, a suitable amount of an alkali metal-containing compound can be easily supported on the surface of the carbon material precursor.

The carbon material precursor itself is preferably in a substantially infusible form with respect to heat.
Thereby, since the alkali metal-containing compound supported in the step (b) can be held as it is on the surface of the carbon material precursor, the effect of the alkali metal-containing compound when forming pores in the step (c). Can be expressed most highly.
The carbon material precursor that itself is substantially infusible to heat is not particularly limited. For example, a cured resin composition, a resin composition preliminarily carbonized, or a resin composition Examples include those obtained by pre-carbonizing a cured product.
The form of the carbon material precursor for supporting the alkali metal-containing compound can be appropriately selected from the above, for example, according to the properties of the resin composition to be used. Among these, it is preferable to support the alkali metal-containing compound at an early point after the infusible form. Specifically, for example, an alkali metal-containing compound can be supported on a product obtained by subjecting a cured product of a resin composition to a preliminary carbonization treatment, but the alkali metal-containing compound is supported at the time of the cured product of the resin composition. It is more preferable. Thereby, the effect which adds the alkali metal containing compound mentioned later can be heightened more.

Next, in the production method of the present invention,
(B) An alkali metal-containing compound is supported on the surface of the carbon material precursor to obtain an alkali metal-supported precursor.

The alkali metal-containing compound used in the step (b) is not particularly limited, but alkali metal hydroxides such as lithium hydroxide and sodium hydroxide, alkali metal carbonates such as lithium carbonate and sodium carbonate, lithium oxide, and oxidation. Examples thereof include alkali metal oxides such as sodium. These can be used alone or in combination of two or more.
Although it does not specifically limit as a form using the said alkali metal containing compound, For example, the method of using in the form grind | pulverized to the powder form, the method of dissolving in water and using it in the form of aqueous solution, etc. are applicable.
Among these, lithium metal compounds such as lithium hydroxide and lithium carbonate, and sodium metal compounds such as sodium hydroxide and sodium carbonate are preferably used in the form of an aqueous solution. These can easily prepare an aqueous solution and have high safety. Moreover, since lithium and sodium have a small molecular size among alkali metals, the alkali metal component can be supported on the surface of the carbon material precursor with higher uniformity.

The method for supporting the alkali metal-containing compound on the surface of the carbon material precursor is not particularly limited. For example, the alkali metal-containing compound is in the form of an aqueous solution, and the carbon material precursor is immersed in this, followed by vacuum dehydration or the like. Using a method of removing only water by spraying, a method of spraying the aqueous solution onto the carbon material precursor using a spray device, and similarly removing only water, or a finely pulverized solid alkali metal-containing compound And a method of mixing this with a finely pulverized carbon material precursor.
Among these, a method in which the alkali metal-containing compound is in the form of an aqueous solution, the carbon material precursor is immersed in the aqueous solution, and then only water is removed by a technique such as vacuum dehydration. Thus, the alkali metal-containing compound can be supported on the carbon material precursor surface with high uniformity by a simple method. Moreover, the load of the alkali metal containing compound with respect to a carbon material precursor can be set easily.

The amount of the alkali metal-containing compound supported in the step (b) is not particularly limited, but is preferably 0.1 to 5.0% by weight in terms of alkali metal component with respect to the carbon material precursor. More preferably, it is 0.5 to 3.0% by weight. Thereby, a suitable amount of pores can be formed on the carbon material surface in the step (c).
When the supported amount of the alkali metal-containing compound exceeds the above upper limit, the pore volume tends to be small because the effect of the alkali metal as a catalyst becomes excessive during the reaction in the step (c). On the other hand, if it is less than the above lower limit value, the effect of the alkali metal as a catalyst becomes too small, so that it is difficult for the pore volume to decrease appropriately and the pore volume tends to increase. Thus, the pore volume formed on the carbon material surface can be controlled by adjusting the amount of the alkali metal-containing compound supported on the carbon material precursor surface.

The method for measuring the amount of the alkali metal-containing compound supported can be appropriately selected depending on the method for supporting the alkali metal-containing compound. For example, in the case of a method using an aqueous solution containing a predetermined amount of an alkali metal-containing compound and removing only moisture after the supporting treatment, or a method using a predetermined amount of a solid alkali metal-containing compound, an alkali metal-supported precursor is prepared. This can be calculated from the amounts of the carbon material precursor and the alkali metal-containing compound used in the above.
In addition, when it is not possible to calculate at the stage of the alkali metal-supported precursor, such as when the support treatment of the alkali metal-containing compound is continuously performed, the alkali metal-supported precursor is ashed in air at 800 ° C. This can be calculated from the amount of the alkali metal component contained in the processed product.

Next, in the production method of the present invention,
(C) The alkali metal supported precursor is carbonized.

Although it does not specifically limit as the conditions of the carbonization process in the said (c) process, For example, it heats up at 1-200 degreeC / hour from normal temperature, 800-3000 degreeC, Preferably it is 1000-1400 degreeC, The reaction can be carried out for 50 hours, preferably 0.5 to 10 hours. As an atmosphere during the carbonization treatment, for example, an inert atmosphere such as nitrogen or helium gas, or a substantially inert atmosphere in which a trace amount of oxygen is present in the inert gas can be used.
Conditions such as temperature and time during the carbonization can be adjusted as appropriate in order to optimize the characteristics of the carbon material.

Next, in the production method of the present invention,
(D) The treated product after carbonization is washed with water to substantially remove the alkali metal component in the treated product.

  In the step (d), the method of washing the treated product after carbonization treatment is not particularly limited. For example, the method is a method of stirring the treated product in water, a method of washing the treated product with running water, and the like. be able to. Thereby, the alkaline gold component can be substantially dissolved and removed from the treated product surface in water, and a carbon material substantially free of impurities and foreign matters can be obtained.

The carbon material of the present invention is obtained by the production method of the present invention.
The pore volume formed on the surface of the carbon material of the present invention is not particularly limited, but the pore volume having a pore diameter exceeding 0.33 nm is preferably 1 to 100 ml / kg. More preferably, it is 1-50 ml / kg.
As a result, when used as a negative electrode material for a secondary battery, the amount of reversible pores can be optimized and the amount of irreversible pores can be reduced, so a secondary battery having high charge / discharge characteristics. A negative electrode material can be obtained.
If the pore volume is smaller than the lower limit, the reversible pores that can occlude lithium are reduced, and the charge / discharge capacity tends to be small. On the other hand, if it is larger than the above upper limit value, since lithium cannot be released after occlusion and irreversible pores are relatively increased, charge / discharge efficiency similarly decreases.

  The reason why the carbon material that can be suitably used for the negative electrode material for secondary batteries is obtained by the production method of the present invention is not clear, but is presumed as follows.

In the process of carbonizing the thermosetting resin or its cured product, pores are formed on the surface of the carbon material by three-dimensional crosslinking reaction, thermal decomposition reaction, and ring condensation reaction. The material surface is often formed, and the pore volume itself is large. This is presumed to be partly due to non-uniform progression of the series of reactions depending on the resin structure and heat treatment method.
In contrast, in the production method of the present invention, an alkali metal-containing compound is supported on the surface of the carbon material precursor and carbonized. Thereby, it is considered that the alkali metal component functions as a catalyst particularly at the stage where the thermal decomposition reaction or the ring condensation reaction occurs, and the condensation of the carbocycle forming the carbon material is promoted. By this action, it is considered that the series of reactions proceed smoothly, the uniformity of the pore diameter formed on the surface of the carbon material is improved, and the pore volume can be set to a suitable level.
Among the alkali metals used here, better characteristics can be obtained when lithium or sodium is used. The reason for this is that lithium and sodium have a relatively small molecular size among alkali metals and have strong alkalinity, so that the above catalytic action can be effectively expressed with high uniformity. It is thought that there is not.
Further, if necessary, by adjusting the amount of the alkali metal-containing compound supported on the carbon material precursor surface, the size of the pore volume formed on the carbon material surface can be controlled. It becomes possible to obtain a carbon material according to battery characteristics.

According to the production method of the present invention, for example, compared with a method of controlling the pore volume of the carbon material by means such as increasing the carbonization temperature, the carbon material that is desired is reduced by performing carbonization at a lower temperature. Can be obtained at a cost.
And the carbon material obtained in this way does not contain an impurity substantially. For this reason, when used as a negative electrode material for a secondary battery, the insertion / extraction reaction of lithium ions during charging / discharging is rarely hindered by side reactions. By using such a carbon material, a negative electrode material for a nonaqueous electrolyte secondary battery excellent in charge / discharge characteristics can be produced.

In the carbon material of the present invention, the pore volume is measured by the following method.
Using a pore distribution measuring device “ASAP2010” manufactured by Shimadzu Corporation, a measurement sample (carbon material) was preheated at 623 K under vacuum heating, and then CO ₂ (molecular diameter; 0.33 nm) was used as a measurement gas. The adsorption isotherm at .15 K was measured, and the pore volume of each adsorbed gas was calculated using the Dubinin-Radushkevic equation, and based on this, the pore volume was calculated based on the following equation.
W = W ₀ · exp [− (A / E) n], A = RT [ln (Ps / P)]
W: Energy [ml / g] occupied by adsorbed molecules
E: Adsorption characteristic energy [J / mol]
P: Parallel vapor pressure [mmHg]
T: Adsorption temperature [K]
W ₀ : pore volume [ml / g]
Ps: saturated vapor pressure [mmHg]
n: Structural index = 2 [−]

Next, the negative electrode material for secondary batteries of the present invention will be described.
The negative electrode material for secondary batteries of the present invention is characterized by containing the carbon material of the present invention.

  The negative electrode material for a secondary battery of the present invention is not particularly limited. For example, a fluorine-based polymer containing polyethylene, polypropylene, etc., a rubbery polymer such as butyl rubber, butadiene rubber, etc. with respect to 100 parts by weight of the carbon material of the present invention. 1 to 30 parts by weight of an organic polymer binder and an appropriate amount of a viscosity adjusting solvent such as N-methyl-2-pyrrolidone and dimethylformamide are added and kneaded to form a paste-like mixture by compression molding, roll molding, etc. Can be obtained by molding into a sheet shape, a pellet shape or the like. Moreover, it can also obtain by apply | coating-molding the mixture made into the slurry form with the solvent for viscosity adjustments on collectors, such as copper foil and nickel foil.

Next, the nonaqueous electrolyte secondary battery of the present invention will be described.
The nonaqueous electrolyte secondary battery of the present invention is characterized by using the secondary battery negative electrode material of the present invention.

When the above-mentioned negative electrode material for a secondary battery is applied to the nonaqueous electrolyte secondary battery of the present invention, it is not particularly limited.For example, the negative electrode material for a secondary battery is disposed to face the positive electrode material via a separator, A nonaqueous electrolyte secondary battery can be obtained by using the electrolytic solution.
Although it does not specifically limit as a positive electrode material, For example, conductive polymers, such as complex oxides, such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide, polyaniline, polypyrrole, etc. can be used. Although it does not specifically limit as a separator, For example, microporous films, such as polyethylene and a polypropylene, a nonwoven fabric, etc. can be used. Although it does not specifically limit as electrolyte solution, For example, what melt | dissolved lithium salt used as electrolyte in a non-aqueous solvent can be used. No particular limitation is imposed on the electrolyte, for _example, it can be used LiClO 4, lithium metal salt such as LiPF _6, tetraalkylammonium salts, and the like. The non-aqueous solvent is not particularly limited. For example, a mixture of cyclic esters such as propylene carbonate, ethylene carbonate and γ-butyrolactone, chain esters such as dimethyl carbonate and diethyl carbonate, ethers such as dimethoxyethane, and the like. Can be used. A solid electrolyte in which the above salts are mixed with polyethylene oxide, polyacrylonitrile or the like may be used, but is not particularly limited.

  Hereinafter, the present invention will be described by way of examples. However, the present invention is not limited to the examples. In the examples and comparative examples, “part” indicates “part by weight”, and “%” indicates “% by weight”.

The raw materials used in the examples and comparative examples are as follows.
(1) Novolac type phenolic resin: “PR-53195” manufactured by Sumitomo Bakelite Co., Ltd., weight average molecular weight of about 3000

1. Production of carbon material <Example 1>
(1) Preparation of carbon material precursor (cured product of resin composition) 100 parts of a novolak type phenol resin and 10 parts of hexamethylenetetramine were pulverized and mixed to prepare a resin composition. The obtained resin composition was heated from 100 ° C. over 5 hours, reached 200 ° C., further held for 1 hour and cured, and then pulverized to a mean particle size of 20 μm by a vibration ball mill, A material precursor was obtained.
(2) Preparation of Alkali Metal-Supported Precursor 100 parts of the carbon material precursor obtained above was immersed in an alkaline aqueous solution in which 6 parts of sodium hydroxide was dissolved in 100 parts of water for 1 hour. Thereafter, only water was removed using a vacuum dehydrator to obtain an alkali metal-supported precursor.
(3) Production of Carbon Material The alkali metal-supported precursor obtained above was heated from room temperature at 100 ° C./hour, and after reaching 1200 ° C., it was further held for 10 hours for carbonization treatment. Then, after cooling to normal temperature and using 10 weight part of water with respect to 1 weight part of carbon material, stirring and washing for about 10 minutes, filtration and drying were performed to obtain a carbon material.

<Example 2>
Example 1 (2) In the preparation of an alkali metal-supported precursor, the same procedure as in Example 1 was used, except that an aqueous alkali metal solution in which sodium hydroxide was reduced to 3 parts and dissolved in 100 parts of water was used. Thus, a carbon material precursor, an alkali metal carrying precursor, and a carbon material were obtained.

<Example 3>
Example 1 (2) In the preparation of an alkali metal-supported precursor, Example 1 and Example 1 were used except that an aqueous alkali metal solution in which sodium hydroxide was reduced to 0.5 part and dissolved in 100 parts of water was used. Similarly, a carbon material precursor, an alkali metal carrying precursor, and a carbon material were obtained.

<Example 4>
Example 1 (2) In the preparation of the alkali metal-supported precursor, the same procedure as in Example 1 was used, except that an aqueous alkali metal solution in which sodium hydroxide was increased to 8 parts and dissolved in 100 parts of water was used. Thus, a carbon material precursor, an alkali metal carrying precursor, and a carbon material were obtained.

<Example 5>
Example 1 (2) In the preparation of the alkali metal-supported precursor, Example 1 and Example 1 were used except that an alkali metal aqueous solution in which 10 parts of lithium hydroxide was dissolved instead of sodium hydroxide with respect to 100 parts of water was used. Similarly, a carbon material precursor, an alkali metal carrying precursor, and a carbon material were obtained.

<Example 6>
(1) Preparation of carbon precursor (prepared carbonized cured resin composition)
A resin composition was prepared by pulverizing and mixing 100 parts of a novolac-type phenol resin and 10 parts of hexamethylenetetramine. The obtained resin composition was heated from 100 ° C. over 5 hours, and after reaching 200 ° C., it was further cured by holding for 1 hour, and then pulverized to an average particle size of 20 μm with a vibration ball mill, A cured product of the composition was obtained.
The cured product of the obtained resin composition was heated from room temperature at 100 ° C./hour, and after reaching 600 ° C., it was further maintained for 10 hours to perform preliminary carbonization treatment to obtain a carbon material precursor.
After that, using the obtained carbon material precursor, in Example 1 (2) Preparation of alkali metal-supported precursor, an alkali metal aqueous solution in which 7 parts of sodium hydroxide was dissolved in 100 parts of water was used. An alkali metal-supported precursor and a carbon material were obtained in the same manner as in Example 1 except that they were used.

<Comparative example>
(1) Preparation of composition 100 parts of novolak type phenol resin and 10 parts of hexamethylenetetramine were pulverized and mixed to prepare a resin composition.
The obtained resin composition was heated from 100 ° C. over 5 hours, and after reaching 200 ° C., it was further cured by holding for 1 hour, and then pulverized to an average particle size of 20 μm with a vibration ball mill, A cured product of the composition was obtained.
(2) Production of carbon material The cured product of the resin composition obtained above was heated from room temperature at 10 ° C./hour, reached 1200 ° C., and held for another 10 hours for carbonization treatment, I got the material.

2. Evaluation of Resin Composition and Carbon Material The following evaluation was performed on the alkali metal-supported precursor and the carbon material obtained in Examples and Comparative Examples.
The results are shown in Table 1.

(1) Blending of resin composition The blending of resin compositions used in Examples and Comparative Examples was shown.

(2) Amount of alkali metal component supported in alkali metal-supported precursor The amount was calculated from the amount of carbon material precursor used in preparing the alkali metal-supported precursor and the amount of alkali metal-containing compound.

(3) Evaluation of pore volume of carbon material The pore diameter and pore volume were measured by the following methods.
Using a pore distribution measuring device “ASAP2010” manufactured by Shimadzu Corporation, pre-vacuum heating pretreatment with a measurement sample (carbon material) 623K, then using CO ₂ (molecular diameter: 0.33 nm) as a measurement gas 273. The adsorption isotherm at 15 K was measured, and the pore volume of each adsorbed gas was calculated using the Dubinin-Radushkevic equation, and based on this, the pore volume was calculated based on the following equation.
W = W ₀ · exp [− (A / E) n], A = RT [ln (Ps / P)]
W: Energy [ml / g] occupied by adsorbed molecules
E: Adsorption characteristic energy [J / mol]
P: Parallel vapor pressure [mmHg]
T: Adsorption temperature [K]
W ₀ : pore volume [ml / g]
Ps: saturated vapor pressure [mmHg]
n: Structural index = 2 [−]
R: Gas constant

3. Evaluation as negative electrode material for secondary battery (1) Production of bipolar coin cell for secondary battery evaluation 10 parts of polyvinylidene fluoride as a binder with respect to 100 parts of carbon material obtained in Examples and Comparative Examples, diluted An appropriate amount of N-methyl-2-pyrrolidone as a solvent was added and mixed to prepare a slurry-like negative electrode mixture. The prepared negative electrode slurry-like mixture was applied to both sides of 18 μm copper foil, and then vacuum-dried at 110 ° C. for 1 hour. After vacuum drying, the electrode was pressure-formed by a roll press. This was cut out as a circle having a diameter of 16.156 mm to produce a negative electrode.
The positive electrode was evaluated with a bipolar coin cell using lithium metal. As the electrolytic solution, a solution obtained by dissolving 1 mol / liter of lithium perchlorate in a mixed solution of ethylene carbonate and diethyl carbonate having a volume ratio of 1: 1 was used.

(2) Evaluation of charging capacity and discharging capacity The charging condition was that charging was terminated at a constant current of 25 mA / g until it reached 1 mV, and then the current was attenuated to 1.25 mA / g or less with 1 mV holding. . The discharge conditions were set until the current was attenuated to 1.25 mAh / g or less. The cut-off potential under discharge conditions was 1.5V.

(3) Evaluation of charge / discharge efficiency Based on the value obtained in the above (2), the charge / discharge efficiency was calculated by the following formula.
Charge / discharge efficiency (%) = [discharge capacity / charge capacity] × 100

Each of Examples 1 to 6 is a carbon material obtained by the production method of the present invention, and in the evaluation using the carbon material using the carbon material as a negative electrode material of a secondary battery, a comparative example which is a conventional production method The charge / discharge efficiency was higher than
In particular, Examples 1 to 4 were excellent in the balance of these characteristics because the amount and method of supporting the alkali metal component of the alkali metal supporting precursor were optimal.
Since the comparative example did not use an alkali metal-containing compound, the pore volume was large and the charge capacity was larger than that of the example, but the discharge capacity was relatively small, so the charge / discharge efficiency was at a low level.

The carbon material obtained by the method for producing a carbon material according to the present invention can be suitably used for various purposes such as a negative electrode for a lithium ion secondary battery, an electrode for a capacitor, an electrode for electrolysis, and activated carbon. .

Claims (7)

A method for producing a carbon material obtained by carbonizing a carbon material precursor,
(A) a step of preparing a carbon material precursor that is either a resin composition, a cured product of the resin composition, or a material obtained by pre-carbonizing the resin composition,
(B) a step of supporting an alkali metal-containing compound on the surface of the carbon material precursor to obtain an alkali metal-supported precursor;
(C) a step of carbonizing the alkali metal-supported precursor; and
(D) a step of washing the treated product after the carbonization treatment with water to substantially remove an alkali metal component in the treated product;
A method for producing a carbon material, comprising: The method for producing a carbon material according to claim 1, wherein the resin composition has at least one selected from a novolac type phenol resin, a melamine resin, a furan resin, and an aniline resin. The method for producing a carbon material according to claim 1 or 2, wherein the supported amount of the alkali metal-containing compound is 0.1 to 5% by weight in terms of an alkali metal component with respect to the carbon material precursor. A carbon material obtained by the production method according to claim 1. The carbon material according to claim 4, wherein the carbon material has a pore volume of 1 to 100 ml / kg having a pore diameter of more than 0.33 nm formed on a surface thereof. A negative electrode material for a secondary battery, comprising the carbon material according to claim 4 or 5. A nonaqueous electrolyte secondary battery using the negative electrode material for a secondary battery according to claim 6.