JP4254947B2 - Carbon material, method for producing the same, and secondary battery using the carbon material as a negative electrode active material - Google Patents

Description

【００６７】
実施例１、２、４および５はいずれも、芳香環を２個以上有するフェノール類を用いた多環フェノール樹脂を含有する樹脂組成物を炭化して製造された炭素材である。実施例１、２、４および５の方法で得られた炭素材は、いずれも炭素含有量が９８重量％以上であった。また、実施例１、２、４および５の方法で得られた炭素材は、いずれも細孔径が０．３３ｎｍを超える細孔の細孔容積が５ｍｌ／ｋｇ以下であった。また、実施例１、２、４および５の方法で得られた炭素材を負極活物質として用いた二次電池は、比較例の方法で得られた炭素材を負極活物質として用いた二次電池に比べて、放電容量、充放電効率において優れた特性を示した。
【００６８】
【発明の効果】
本発明によれば、リチウムイオン二次電池の電池特性を高めることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態における二次電池の構成を示す概略図である。
【符号の説明】
１０ 二次電池
１２ 負極活物質
１３ 負極
１４ 負極集電体
１６ 電解液
１８ セパレータ
２０ 正極活物質
２１ 正極
２２ 正極集電体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carbon material, a manufacturing method thereof, and a secondary battery using the carbon material as a negative electrode active material.
[0002]
[Prior art]
With the recent development of electronic technology, electronic devices are required to be smaller and lighter. As a result, power supply batteries mounted on electronic devices are also required to be further reduced in size, weight, and energy density.
[0003]
Conventionally, nickel-cadmium secondary batteries and lead secondary batteries have been used for such electronic devices, but these secondary batteries have low discharge voltage and meet the expectations of small size, light weight and high energy. Absent. Recently, as a replacement for these secondary batteries, a lithium ion secondary battery using a carbon material capable of occluding and releasing lithium for a negative electrode and a lithium composite oxide such as a lithium cobalt composite oxide for a positive electrode has been used. It has become.
[0004]
Lithium ion secondary batteries have a high discharge voltage and high energy density, and are expected to meet the demands for higher energy and smaller size and weight. Such a lithium ion secondary battery utilizes a phenomenon in which lithium intercalates / deintercalates between carbon material layers. Therefore, even if the charge / discharge cycle proceeds, dendritic lithium is not deposited on the negative electrode using the carbon material, and safety is also ensured. Furthermore, such a lithium ion secondary battery has a high energy density and exhibits excellent charge / discharge cycle characteristics.
[0005]
An example of the carbon material is natural graphite (Patent Document 1).
[0006]
Moreover, the carbon material using phenol resins, such as various cresol and various xylenol, is illustrated (patent document 2).
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 05-028996
[Patent Document 2]
JP-A-10-188978
[0008]
[Problems to be solved by the invention]
However, when graphite is used as the carbon material for the negative electrode, there is an upper limit on the theoretical charge / discharge capacity, and the cycle characteristics are poor and the battery characteristics are low. Conventionally, even when various phenol resins are used, there are problems as described later.
[0009]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a technique for improving battery characteristics of a lithium ion secondary battery.
[0010]
[Means for Solving the Problems]
JP-A-10-188978 exemplifies carbon materials using phenol resins (hereinafter referred to as normal phenol resins) such as various cresols and various xylenols. However, a carbon material using a normal phenol resin has a problem that it is difficult to reduce the pore volume of the carbon material because the three-dimensional skeleton is growing. By reducing the pore volume, when a carbon material is used as the negative electrode active material of a secondary battery, the amount of lithium reversibly released in the pores can be increased, and charge / discharge efficiency can be improved. it can. In addition, naphthol is also exemplified here as a raw material for the carbon material. However, even if a carbon material is simply produced using naphthol by a conventional method, naphthol is very soluble in a solvent when it forms a binuclear body. It became small and it became difficult to obtain a naphthol resin having a molecular weight larger than that of a binuclear body, and only a low molecular weight resin could be obtained. When a carbon material is produced using such a low molecular weight resin as a raw material, there is a problem that the yield is greatly reduced. Therefore, in the conventional method, it is difficult to efficiently form the carbon material by reducing the pore volume of the carbon material.
[0011]
The inventor of the present application uses a polycyclic phenol resin such as a naphthol resin as a raw material for a carbon material, and by devising a production method, the regularity of the resin structure can be improved, and a carbon material having a small pore volume can be obtained. I found out that it can be manufactured. Thus, by using a carbon material having a small pore volume and a high regularity of the resin structure as the negative electrode active material, the charge / discharge capacity and the charge / discharge efficiency of the lithium ion secondary battery can be increased.
[0012]
  According to the present invention, a carbon material used for a negative electrode active material of a secondary battery, which is obtained by carbonizing a polycyclic phenol resin synthesized by reacting a polycyclic phenol containing two or more aromatic rings with an aldehyde. A plurality of pores are formed on the surface, and the pore volume of the pores is0.01 ml / kg or more 2.3A carbon material that is less than or equal to ml / kg is provided.
[0013]
Here, the pore volume is CO₂Can be measured as an adsorbed gas, and can have a pore diameter exceeding 0.33 nm. By forming a resin by using a polycyclic phenol as a raw material to form a carbon material, the pore volume can be reduced in this way. By setting the pore volume to 50 ml / kg or less, the amount capable of reversibly releasing lithium occluded in the pores increases, and the charge / discharge capacity and charge / discharge efficiency of the secondary battery can be increased.
[0014]
When a phenol resin is formed using polycyclic phenols as raw materials, the polynuclear phenol monomers and the binuclear component of polycyclic phenols generated at the beginning of the reaction are uniformly dissolved, and the dinuclear component of polycyclic phenols is It is necessary to select a solvent that can keep the dinuclear component dissolved until it reaches a melting temperature and can be polymerized. Thereby, a high molecular weight resin can be obtained. By using such a high molecular weight resin as a raw material, a carbon material having a small pore volume can be efficiently formed. As such a solvent, a solvent having a boiling point capable of maintaining the reflux reaction in a temperature range of 100 ° C. to 200 ° C. where the dinuclear component of the polycyclic phenol melts is preferably used. Examples of such solvents include ketones such as methyl isobutyl ketone, cyclohexanone and ethyl butyl ketone, alcohols such as ethylene glycol, pentanol, butanol and cyclohexanol, amides such as dimethylformamide and dimethylacetamide, toluene, Petroleum such as xylene can be exemplified.
[0015]
  In the carbon material of the present invention, the carbon content of the carbon material can be 95% by weight or more.
[0016]
When the carbon content of the carbon material is in such a range, lithium ions can be prevented from being electrically adsorbed to the carbon material, and the charge / discharge efficiency of the secondary battery can be increased. By forming a resin from polycyclic phenols as a raw material to form a carbon material, a carbon material having a high carbon content can be formed.
[0017]
In the carbon material of the present invention, the polycyclic phenols can contain a condensed ring. Thereby, the regularity of a resin structure can be improved and a carbon material with a small pore volume can be formed. Here, the condensed ring can have a naphthalene skeleton. Thereby, the regularity of the resin structure can be enhanced, and the carbon material having a small pore volume can be formed because the ring condensation easily proceeds.
[0018]
In the carbon material of the present invention, the polycyclic phenols may include naphthols, anthracenes, or binaphthols.
[0019]
According to the present invention, a secondary battery using the above carbon material as a negative electrode active material is provided. Thereby, the charge / discharge capacity and charge / discharge efficiency of the secondary battery can be increased.
[0020]
According to the present invention, there is provided a method for producing a carbon material used for a negative electrode active material of a secondary battery, wherein polycyclic phenols containing two or more aromatic rings and aldehydes are used in a solvent having a boiling point of 100 ° C. or higher. Disclosed is a method for producing a carbon material comprising a step of producing a phenol resin composition by dissolving and reacting a polycyclic phenol and an aldehyde at 100 ° C. or higher, and a step of heat-treating the phenol resin composition. .
[0021]
As described above, when a phenol resin is formed from a polycyclic phenol as a raw material, the polycyclic phenol monomer and the binuclear component of the polycyclic phenol generated at the beginning of the reaction are uniformly dissolved, and the polycyclic phenol It is necessary to select a solvent that can remain in the reaction system up to a temperature at which the binuclear component melts and can further polymerize the polycyclic phenols. Since the dinuclear component of polycyclic phenols melts at about 100 ° C. to 200 ° C., by dissolving polycyclic phenols containing two or more aromatic rings and aldehydes in a solvent having a boiling point of 100 ° C. or higher. A high molecular weight polycyclic phenol resin can be obtained. By using such a high molecular weight polycyclic phenol resin as a raw material, a carbon material having a small pore volume can be efficiently formed.
[0022]
Examples of such solvents include one or more selected from methyl isobutyl ketone, cyclohexanone, ethyl butyl ketone, ethylene glycol, pentanol, butanol, cyclohexanol, dimethylformamide, dimethylacetamide, toluene, and xylene. Is done.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic diagram showing the configuration of the secondary battery of the present invention. The secondary battery 10 includes a negative electrode 13 composed of a negative electrode active material 12 and a negative electrode current collector 14, an electrolyte solution 16, a separator 18, and a positive electrode 21 composed of a positive electrode active material 20 and a positive electrode current collector 22. Including.
[0024]
In the negative electrode 13, as the negative electrode current collector 14, for example, a copper foil or a nickel foil can be used.
[0025]
Next, the negative electrode active material (negative electrode material) 12 of the present invention will be described. As the negative electrode active material 12, a carbon material described below is used.
[0026]
The carbon material of the present invention is formed by carbonizing a resin composition containing a polycyclic phenol resin synthesized from polycyclic phenols having two or more aromatic rings and aldehydes.
[0027]
Examples of the polycyclic phenols used in the synthesis of the polycyclic phenol resin include naphthols such as α-naphthol and β-naphthol, α-naphthohydroquinone (4,4-naphthalenediol), and β-naphthohydroquinone (1 , 2-naphthalenediol) and the like, binaphthols such as 1,1′-bi-2-naphthol and 1,1-methylene-bi-2-naphthol, α-anthrol or β-ant Monooxyanthracenes such as roll, dioxyanthracenes such as 1,2-dioxyanthracene, or 9,10-dioxyanthracene (anthraquinol), p-benzylphenol, 4,4′-isopropylidenediphenol, Or benzylphenols such as bisphenol F, or p-phenyl Phenol, or 4,4-phenyl phenols such as biphenol, and the like. Among these, it can use individually or in combination of 2 or more types. Among these, naphthols, dioxynaphthalenes, binaphthols, monooxyanthracenes, or dioxyanthracenes are particularly preferably used. Thereby, the regularity of the resin structure can be enhanced, and the carbon material having a small pore volume can be formed because the ring condensation easily proceeds. Benzylphenols are also preferably used.
[0028]
In addition to such polycyclic phenols, phenols other than these can also be used in combination. In this case, the blending amount of phenols other than polycyclic phenols is preferably small so as not to impair the characteristics of the carbon material of the present invention.
[0029]
Examples of aldehydes used in the synthesis of polycyclic phenol resins include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, furfural, glyoxal, n-butyraldehyde, caproaldehyde, allylaldehyde, benzaldehyde, Examples include crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, and salicylaldehyde. Among these, it can use individually or in combination of 2 or more types.
[0030]
The polycyclic phenol resin is produced, for example, by blending polycyclic phenols and aldehydes and reacting them using an acidic or basic catalyst. As for the reaction molar ratio of the monomers, for example, the number of moles of the aldehyde (F) relative to the polycyclic phenol (P) can be 0.3 to 3.0 in terms of the molar ratio (F / P). Among these, for example, when producing a novolac type polycyclic phenol resin using an acidic catalyst, the reaction molar ratio can be set to 0.3 to 1.0, preferably 0.6 to 0.8. In addition, as an acidic and basic catalyst, the known thing used for the synthesis | combination of a phenol resin can be used.
[0031]
When polycyclic phenols and aldehydes are reacted, a binuclear component of polycyclic phenols is generated at the initial stage of the reaction. Thereafter, the temperature of the reaction system is raised to remove water from the reaction system, and the polynuclear phenolic binuclear body is melted and reacted in a homogeneous system to be polymerized. In the case of producing a phenol resin using a conventional phenolic monomer as a raw material, the raw material is in a liquid state, and the produced binuclear component is dissolved in the reaction system, so that the reaction is allowed to proceed as it is without particularly using a solvent. be able to. However, when a polycyclic phenol resin is produced using a solid polycyclic phenol monomer as a raw material as in the present invention, it is necessary to select an appropriate solvent in order to dissolve the solid monomer. In addition, the dinuclear component generated at the initial stage of the reaction has a property that it cannot be dissolved in a solvent at a low temperature and precipitates. If the binuclear component is not dissolved in the solvent, the binuclear component will precipitate, and cannot be melted and reacted in a homogeneous system, and the reaction for polymerizing further will not proceed substantially. End up.
[0032]
Therefore, in producing a polycyclic phenol resin, the boiling point is such that the reflux reaction can be continued in a temperature range of 100 to 200 ° C. in which the raw polycyclic phenol monomers are dissolved and the binuclear component can be dissolved. It is preferred to select a solvent having In addition, the solvent used here is, after the reflux reaction, when the temperature of the reaction system is further increased to remove the solvent and water, the dinuclear component is melted until the temperature reaches, for example, 110 to 150 ° C. It is preferable that it has a function of assisting the melting of the binuclear body so that the remaining binuclear component does not precipitate. Examples of such a solvent include ketones such as methyl isobutyl ketone, cyclohexanone, and ethyl butyl ketone, alcohols such as ethylene glycol, pentanol, butanol, and cyclohexanol, amides such as dimethylformamide and dimethylacetamide, And petroleum such as toluene and xylene. Using such a solvent, the polycyclic phenol resin can be produced by reacting at the above reaction temperature for 0.1 to 5 hours and then performing a dehydration reaction.
[0033]
In addition to the polycyclic phenol resin, the carbon material of the present invention includes phenol resins other than the polycyclic phenol resins, thermosetting resins such as furan resins and epoxy resins, and thermoplastic resins such as polystyrene, polyamide, and polypropylene. , Petroleum pitch, coal pitch, spinning pitch and the like can be blended. These materials can be used alone or in combination of two or more. As the resin other than the polycyclic phenol resin, it is preferable to use a resin containing a large number of rings originally contained in the monomers constituting each resin or rings derived from substituents in the monomers.
[0034]
In addition to the resin, the carbon material of the present invention includes addition of a resin curing agent, various monomer components, a carbon material precursor carbonized at 200 to 800 ° C., a metal, a metal compound, graphite, a graphite modifier, and the like. An agent etc. can be mix | blended and manufactured.
[0035]
The phenol resin composition of the present invention preferably contains 50% by weight or more, more preferably 80% by weight or more of the polycyclic phenol resin.
[0036]
When the carbon material of the present invention is produced using a plurality of types of resins as raw materials, they may be chemically reacted or physically mixed by a kneading apparatus such as a kneading roll, a twin-screw kneader, or a kneader. You can also.
[0037]
After producing a polycyclic phenol resin as described above, a curing treatment is performed. The curing treatment can be performed using a method such as heat curing, acid curing, acid anhydride curing, or amine curing.
[0038]
After the curing treatment, carbonization treatment by heat treatment is performed. The carbonization treatment is performed, for example, at a temperature of 800 ° C. or higher and 1500 ° C. or lower for 0.1 hour or longer and 50 hours or shorter, more preferably 1 hour or longer and 15 hours or shorter. The carbonization treatment can be performed in an inert gas atmosphere such as nitrogen or helium, or in a gas atmosphere in which a trace amount of oxygen is present in the inert gas. The characteristics of the carbon material can be adjusted to the optimum by the temperature, time, etc. during such carbonization treatment.
[0039]
The carbon content of the carbon material of the present invention is preferably 95% by weight or more, more preferably 97% by weight or more. Thereby, a negative electrode active material with high charging / discharging efficiency can be obtained. When the carbon content is lower than the above lower limit, the content of highly polar atoms other than carbon atoms increases, so the possibility that lithium ions will be electrically adsorbed to the carbon material increases, and as a result Discharge efficiency tends to be low.
[0040]
In the carbon material of the present invention, a plurality of pores are formed on the surface of the carbon material. Here, the pores are CO₂Is used as an adsorbed gas, and has a pore diameter exceeding 0.33 nm. The pore volume is preferably 0.01 to 50 ml / kg, more preferably 0.1 to 5 ml / kg.
[0041]
Thereby, charge capacity can be ensured and charging / discharging efficiency can be made favorable. When the pore volume of the pore having such a pore diameter is smaller than 0.01 ml / kg, the reversible pores capable of occluding and releasing lithium are reduced, so the charge / discharge capacity is small. Tend to be. Further, when the pore volume of the pore having such a pore diameter is larger than 50 ml / kg, more lithium can be occluded but more irreversible pores that are difficult to release, resulting in lower charge / discharge efficiency. It becomes like this. Moreover, when the pore volume of the pores having a pore diameter in the range is smaller than 5 ml / kg, the occluded lithium can be released more efficiently, thereby increasing the charge / discharge efficiency.
[0042]
Since the carbon material of the present invention contains a polycyclic phenol resin synthesized from the above polycyclic phenols as a main component, the process of pore formation during curing and carbonization is based on a normal phenol resin as the main component. In contrast, it is possible to produce a carbon material having a high regularity of the resin structure and a small pore volume. Thereby, when the carbon material of the present invention is used as a negative electrode active material of a lithium ion secondary battery, excellent characteristics are exhibited, and high charge / discharge capacity and charge / discharge efficiency of the lithium ion secondary battery can be ensured.
[0043]
In addition, it can modify | denature with the material etc. which can become a metal or another carbon material at the time of manufacture of the carbon material of this invention, and other additives, such as a pigment, a lubricant, an antistatic agent, and antioxidant, can also be added.
[0044]
The negative electrode 13 of the present invention is manufactured, for example, as follows.
1 to 30 parts by weight of organic polymer binder (fluorine polymer including polyethylene, polypropylene, etc., rubbery polymer such as butyl rubber, butadiene rubber, etc.) and an appropriate amount of viscosity with respect to 100 parts by weight of the carbon material. An adjustment solvent (N-methyl-2-pyrrolidone, dimethylformamide, etc.) is added and kneaded, and the paste-like mixture is formed into a sheet, pellet, or the like by compression molding, roll molding, or the like, and the negative electrode active material 12 is manufactured and laminated with the negative electrode current collector 14.
[0045]
Further, 1 to 30 parts by weight of an organic polymer binder (fluorine polymer including polyethylene, polypropylene, etc., rubbery polymer such as butyl rubber, butadiene rubber, etc.) and an appropriate amount with respect to 100 parts by weight of the carbon material. A viscosity adjusting solvent (N-methyl-2-pyrrolidone, dimethylformamide, etc.) is added and kneaded, and the mixture in the form of a slurry is applied to a current collector such as a copper foil or a nickel foil to be manufactured. You can also.
[0046]
As the electrolytic solution 16 in the present invention, an aqueous or non-aqueous solution can be used, but a non-aqueous solution is usually used. As the non-aqueous electrolyte solution 16, for example, a solution obtained by dissolving a lithium salt serving as an electrolyte in a non-aqueous solvent is used. As the non-aqueous solvent, a mixture of cyclic esters such as propylene carbonate, ethylene carbonate and γ-butyrolactone, chain esters such as diethyl carbonate, ethers such as dimethoxyethane, and the like can be used. As an electrolyte, LiClO₄, LiPF₆Lithium metal salts such as, tetraalkylammonium salts and the like can be used. A solid electrolyte obtained by mixing the above salts with polyethylene oxide, polyacrylonitrile, or the like can also be used.
[0047]
As the separator 18, for example, a microporous film such as polyethylene or polypropylene, a nonwoven fabric, or the like can be used.
[0048]
In the positive electrode 11, the positive electrode active material (positive electrode material) 20 is not particularly limited, but is lithium cobalt oxide (LiCoO).₂), Lithium nickel oxide (LiNiO)₂), Lithium manganese oxide (LiMn)₂O₄) And the like, and conductive polymers such as polyaniline and polypyrrole can be used. As the positive electrode current collector 22, for example, an aluminum foil can be used. The positive electrode 21 of the present invention is manufactured by a known positive electrode manufacturing method.
[0049]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to an Example.
[0050]
1. Carbon material manufacturing
Example 1
100 parts by weight of β-naphthol, 40 parts by weight of 37% formaldehyde aqueous solution, 2 parts by weight of 25% sulfuric acid aqueous solution, and 150 parts by weight of methyl isobutyl ketone were placed in a three-necked flask equipped with a stirrer and a condenser tube, and then at 100 ° C. for 3 hours. After the reaction, the reaction temperature was raised to 150 ° C. for dehydration to obtain 90 parts by weight of a polycyclic phenol resin. A mixture obtained by adding 10 parts by weight of hexamethylenetetramine to 100 parts by weight of the obtained polycyclic phenol resin was ground and mixed, and then cured at 200 ° C. for 5 hours. After the curing treatment, the temperature was raised in a nitrogen atmosphere, and carbonization treatment was performed for 10 hours after reaching 1000 ° C. to obtain a carbon material.
[0051]
(Example 2)
A carbon material was obtained by the same method as in Example 1 except that the carbonization condition was changed to 10 hours after reaching 1200 ° C.
[0053]
(Example 4)
A carbon material was obtained in the same manner as in Example 1 except that 135 parts by weight of anthraquinol was used instead of 100 parts by weight of β-naphthol.
[0054]
(Example 5)
A carbon material was obtained in the same manner as in Example 1 except that 120 parts by weight of paraphenylphenol was used instead of 100 parts by weight of β-naphthol.
[0055]
(Comparative Example 1)
A carbon material was obtained in the same manner as in Example 1 except that a phenol resin synthesized from phenol and formaldehyde (“PR-217” manufactured by Sumitomo Bakelite Co., Ltd.) was used instead of the polycyclic phenol resin.
[0056]
(Comparative Example 2)
Instead of polycyclic phenolic resin, a solution prepared by dissolving 1 part by weight of sodium hydroxide in 5 parts by weight of water per 100 parts by weight of phenolic resin ("PR-217" manufactured by Sumitomo Bakelite Co., Ltd.) synthesized from phenol and formaldehyde A carbon material was obtained in the same manner as in Example 1, except that the mixture was dissolved and mixed and stirred for 1 hour.
[0057]
2. Evaluation of carbon content
After drying at 110 ° C. for 3 hours, the composition ratio of carbon, hydrogen, and nitrogen was measured using an elemental analyzer (manufactured by Perkin Elmer).
[0058]
3. Evaluation of pore volume
The measuring method of the pore diameter and the pore volume in the carbon material of the present invention is as follows.
[0059]
Using a pore distribution measuring device (ASAP2010, manufactured by Shimadzu Corporation), the measurement sample was subjected to preheating treatment at 623 K and then CO as a measurement gas.₂(Molecular diameter: 0.33 nm) was used to measure the adsorption isotherm at 273.15 K, and the pore volume of each adsorbed gas was calculated using the Dubinin-Radushkevich equation. The pore volume of pores having a diameter exceeding 0.33 nm was calculated based on the following formulas 1 and 2.
[0060]
W = W₀Xexp [-(A / E) n] (Formula 1)
A = RT [ln (Ps / P)] (Formula 2)
W: Energy [ml / g] occupied by adsorbed molecules
E: Adsorption characteristic energy [J / mol]
P: Parallel vapor pressure [mmHg]
T: Adsorption temperature [K]
W₀: Pore volume [ml / g]
Ps: saturated vapor pressure [mmHg]
n: Structural index = 2 [−]
[0061]
4). Evaluation as a negative electrode active material for secondary batteries
<Manufacture of secondary batteries>
(1) Production of negative electrode: 10 parts by weight of polyvinylidene fluoride as a binder and an appropriate amount of N-methyl-2-pyrrolidone as a diluent solvent are added to 100 parts by weight of the carbon material produced in each of the examples and comparative examples. By mixing, a slurry-like mixture for negative electrode active material was prepared. The prepared mixture for negative electrode active material was applied on both sides of 18 μm copper foil, and the solvent was dried and removed under vacuum at 110 ° C. for 1 hour. Subsequently, the negative electrode active material mixture was compression-molded with a roller press to produce a strip-shaped negative electrode. This was cut out as a circle having a diameter of 16.156 mm to produce a negative electrode.
[0062]
(2) Fabrication of positive electrode: LiCoO₂And 6.6 parts by weight of graphite as a conductive agent and 100% by weight of N-methoxymethylated amide resin having a methoxymethyl group substitution rate of 30% (Toresin EF-30T, Teikoku Sangyo ( A suitable amount of N-methyl-2-pyrrolidone was added and mixed with 3.3 parts by weight of a diluent solvent, to prepare a slurry-like mixture for positive electrode active material. The adjusted mixture for positive electrode active material was applied to both sides of an aluminum foil having a thickness of 10 μm, and the solvent was dried and removed under vacuum. Subsequently, the mixture for positive electrode active material was compression-molded by a roller press to produce a belt-like positive electrode. This was cut out as a circle having a diameter of 16.156 mm to produce a positive electrode.
[0063]
(3) Manufacture of secondary batteries (bipolar coin cells)
Using the negative electrode and positive electrode produced as described above and a separator made of a microporous polypropylene film having a thickness of 25 μm and a width of 44 mm, a negative electrode, a separator, and a positive electrode were laminated in this order to produce a bipolar coin cell. As the electrolytic solution, a solution in which 1 mol / liter of lithium perchlorate was dissolved in a mixed solution of ethylene carbonate and diethylene carbonate having a volume ratio of 1: 1 was used.
[0064]
(4) Measuring method of secondary battery characteristics
  First charge capacity and discharge capacity, charge condition is current 25mA /The constant current of g is 1 mV and the discharge condition is 1.25 m.A /It was measured as the current was attenuated to g or less. The cut-off potential under discharge conditions was 1.5V. The charge / discharge efficiency is (ReleaseElectric capacity /ChargeCapacity)× 100 (%)Calculated by
[0065]
Table 1 shows the results of the characteristic evaluation of the carbon material obtained by the above method and the bipolar coin cell.
[0066]
[Table 1]

[0067]
  Example1, 2, 4 and 5All are carbon materials produced by carbonizing a resin composition containing a polycyclic phenol resin using a phenol having two or more aromatic rings. Example1, 2, 4 and 5The carbon materials obtained by this method all had a carbon content of 98% by weight or more. Examples1, 2, 4 and 5All of the carbon materials obtained by the above method had a pore volume of pores having a pore diameter exceeding 0.33 nm of 5 ml / kg or less. Examples1, 2, 4 and 5The secondary battery using the carbon material obtained by the above method as a negative electrode active material has a higher discharge capacity and charge / discharge efficiency than the secondary battery using the carbon material obtained by the method of the comparative example as a negative electrode active material. It showed excellent characteristics.
[0068]
【The invention's effect】
According to the present invention, the battery characteristics of a lithium ion secondary battery can be enhanced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a secondary battery in an embodiment of the present invention.
[Explanation of symbols]
10 Secondary battery
12 Negative electrode active material
13 Negative electrode
14 Negative electrode current collector
16 Electrolyte
18 Separator
20 Cathode active material
21 Positive electrode
22 Positive current collector

Claims (7)

A carbon material used for a negative electrode active material of a secondary battery,
It is obtained by carbonizing a polycyclic phenol resin synthesized by reacting polycyclic phenols containing two or more aromatic rings with aldehydes. A carbon material having a pore volume of 0.01 ml / kg or more and 2.3 ml / kg or less. -Carbon content is 95 wt% or more, the carbon material according to claim 1. In the carbon material according to claim 1 or 2,
The polycyclic phenol is a carbon material containing a condensed ring. In the carbon material according to any one of claims 1 to 3,
The polycyclic phenol is a carbon material containing naphthols, anthracenes, or binaphthols.   A secondary battery using the carbon material according to claim 1 as a negative electrode active material. A method for producing a carbon material used for a negative electrode active material of a secondary battery,
A polycyclic phenol containing two or more aromatic rings and an aldehyde are dissolved in a solvent having a boiling point of 100 ° C. or higher, and the polycyclic phenol and the aldehyde are reacted at 100 ° C. or higher to obtain a phenol resin composition. Manufacturing process;
Heat treating the phenolic resin composition;
The manufacturing method of the carbon material containing this. In the manufacturing method of the carbon material of Claim 6,
Production of carbon material, wherein the solvent is one or more solvents selected from methyl isobutyl ketone, cyclohexanone, ethyl butyl ketone, ethylene glycol, pentanol, butanol, cyclohexanol, dimethylformamide, dimethylacetamide, toluene, xylene Method.

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