JP2007042571A - Carbon particle for anode of lithium secondary battery, and carbon anode for lithium secondary battery and lithium secondary battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery which has a small irreversible capacity and excellent output characteristics as compared to conventional lithium batteries, and to provide carbon particles for an anode of lithium secondary batteries and a cathode of lithium secondary batteries using the carbon particles. <P>SOLUTION: Carbon particles for an anode of lithium secondary batteries having an interplanar spacing d002 between the (002) planes of carbon determined by an X-ray diffraction device (XRD) of 0.340-0.390 nm have an He true density of 1.40-2.00 g/cc, and a CO<SB>2</SB>adsorption capacity of 0.01-5.00 cc/g. It is preferable that an oxygen concentration over the entire part of carbon particles is not more than 1 weight%, a specific surface area of N<SB>2</SB>by nitrogen adsorption measurement at 77 K is 0.30-10 m<SP>2</SP>/g, and an O/C (a surface oxygen concentration) determined by X-ray photoelectron spectroscopy (XPS) is 0.001-0.060. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a carbon particle for a lithium secondary battery negative electrode, a negative electrode for a lithium secondary battery using the same, and a lithium secondary battery. More specifically, a lithium secondary battery excellent in charge / discharge efficiency and output characteristics suitable for applications such as electric vehicles and power tools that require a secondary battery having high input / output characteristics, and a lithium secondary battery for obtaining the same The present invention relates to carbon particles for battery negative electrodes and negative electrodes for lithium secondary batteries using the carbon particles.

In recent years, development and commercialization of a hybrid electric vehicle (HEV) that uses an engine and a motor as a power source for the purpose of reducing CO ₂ emissions and improving fuel efficiency have been promoted on a global scale. One of the challenges of HEV is the development of a high output, small size, light weight and low cost battery. Currently, nickel-hydrogen secondary batteries are used, but there are problems in input / output characteristics and energy density (Non-Patent Document 1). Therefore, a lithium secondary battery having high voltage, high energy density, and excellent input / output characteristics can be reduced in size and weight, and thus is highly expected as a power source for HEV.

As a negative electrode material for a lithium secondary battery for HEV, a graphite-based carbon material is considered in the case of designing with an emphasis on energy density, and an amorphous carbon material is considered in the case of emphasizing input / output characteristics. The graphite-based carbon material has a high initial charge / discharge efficiency because of its small specific surface area, but has a problem that the capacity of 372 Ah / kg or more, which is the theoretical capacity, cannot be obtained and the input / output characteristics are inferior. On the other hand, the amorphous carbon material has low reactivity with the electrolytic solution and it is difficult to generate dendritic metallic lithium, so that it has excellent input / output characteristics, and a material having a discharge capacity per unit weight of 500 Ah / kg or more can be obtained. However, since the specific surface area is large, there is a problem that the initial charge / discharge efficiency is low (Non-patent Document 2).
Masayuki Yoshio, Akiya Ozawa "Lithium ion secondary battery second edition" p121-134 (2001) Carbon material for negative electrode for lithium ion secondary battery Realize Co., Ltd. p12

  Therefore, a lithium secondary battery having excellent input / output characteristics and a small irreversible capacity and a negative electrode material for obtaining the lithium secondary battery are required.

  The present invention relates to a lithium secondary battery having a small irreversible capacity and excellent output characteristics as compared with a conventional lithium secondary battery, carbon particles for a lithium secondary battery negative electrode for obtaining the same, and the carbon particles. An object of the present invention is to provide a negative electrode for a lithium secondary battery.

As a result of intensive studies, the inventors have controlled the true He density, CO ₂ adsorption amount, oxygen concentration, N ₂ specific surface area, surface oxygen concentration (O / C), and interplanar spacing of the carbon 002 plane of the carbon particles. The inventors have found that carbon particles suitable for a lithium secondary battery negative electrode material having a small irreversible capacity and excellent output characteristics can be obtained, and the present invention has been achieved.

That is, the present invention is characterized by the following items (1) to (10). (1) Carbon particles for a lithium secondary battery negative electrode having a carbon 002 plane spacing d002 of 0.340 to 0.390 nm determined by X-ray diffractometer (XRD) measurement, wherein the He true density is 1.40. Carbon particles for a lithium secondary battery negative electrode having ˜2.00 g / cc and CO ₂ adsorption of 0.01 to 5.00 cc / g.

(2) The carbon particles for a lithium secondary battery negative electrode according to (1), wherein the oxygen concentration of the entire carbon particles is 1% by weight or less.

(3) The carbon particles for a lithium secondary battery negative electrode according to the above (1) or (2), wherein the N ₂ specific surface area determined from nitrogen adsorption measurement at 77K is 0.30 to 10 m ² / g.

(4) The carbon particles for a lithium secondary battery negative electrode according to any one of the above (1) to (3), wherein O / C determined by X-ray photoelectron spectroscopy (XPS) is 0.001 to 0.060.

(5) Any of the above (1) to (4), wherein the carbon precursor resin is carbonized at 450 ° C. to 1000 ° C., the obtained carbide is pulverized, and the pulverized carbide is further carbonized at 900 ° C. to 2000 ° C. Carbon particles for a lithium secondary battery negative electrode according to claim 1.

(6) The carbon particles for a lithium secondary battery negative electrode according to any one of (1) to (5), wherein the carbon precursor resin having an average particle diameter of 5 to 50 μm is carbonized.

(7) The following general formula (I)

Carbon particles for a lithium secondary battery negative electrode according to any one of the above (1) to (6), wherein a resin containing a phenol derivative represented by the formula:

(8) The carbon particles for a lithium secondary battery negative electrode according to (7), wherein the resin contains 40 to 70 mol% of a phenol derivative represented by the general formula (I) in the structure.

(9) A negative electrode for a lithium secondary battery using the carbon particles for a lithium secondary battery negative electrode according to any one of (1) to (8).

(10) A lithium secondary battery using the negative electrode for a lithium secondary battery according to (9) above.

  According to the present invention, a lithium secondary battery having small irreversible capacity and excellent output characteristics as compared with a conventional lithium secondary battery, carbon particles for a lithium secondary battery negative electrode for obtaining the same, and the carbon particles It becomes possible to obtain a negative electrode for a lithium secondary battery using.

  Hereinafter, the present invention will be described in detail.

The carbon particles for a lithium secondary battery negative electrode according to the present invention are carbon particles for a lithium secondary battery negative electrode having a carbon 002 plane spacing d002 of 0.340 to 0.390 nm determined by X-ray diffractometer (XRD) measurement. The true density of He is 1.40 to 2.00 g / cc, and the CO ₂ adsorption amount is 0.01 to 5.00 cc / g.

  In the carbon particles for a lithium secondary battery negative electrode of the present invention, the interplanar spacing d002 of the carbon 002 surface determined by X-ray diffraction (XRD) measurement described below is in the range of 0.340 to 0.390 nm. It is preferable that it is 350-0.385 nm, and it is more preferable that it is 0.360-0.380 nm. The carbon particles for a lithium secondary battery negative electrode in which the interplanar spacing d002 of the carbon 002 plane is in the range of 0.340 to 0.390 nm are excellent in output characteristics. On the other hand, when d002 is less than 0.340 nm, the input / output characteristics tend to be inferior, and when it exceeds 0.390 nm, the capacity per volume tends to be small.

  In addition, the true He density of the carbon particles for a lithium secondary battery negative electrode of the present invention is in the range of 1.40 to 2.00 g / cc, preferably 1.45 to 1.80 g / cc. More preferably, it is 50-1.65 g / cc. When the interplanar spacing d002 of the carbon 002 plane is 0.340 to 0.390 nm, the initial irreversible capacity can be reduced when the He true density is in the range of 1.40 to 2.00 g / cc. . On the other hand, if the He true density exceeds 2.00 g / cc, the initial irreversible capacity tends to increase, and if it is less than 1.40 g / cc, the capacity per volume tends to decrease. The true He density can be measured with a He density meter.

The CO ₂ adsorption amount of the carbon particles for the lithium secondary battery negative electrode is in the range of 0.01 to 5.00 cc / g, preferably 0.05 to 5.00 cc / g, More preferably, it is -1.00 cc / g. When the interplanar spacing d002 of the carbon 002 plane is 0.340 to 0.390 nm, the initial irreversible capacity can be reduced when the CO ₂ adsorption amount is in the range of 0.01 to 5.00 cc / g. It is. On the other hand, when the CO ₂ adsorption amount exceeds 5.00 cc / g, the initial irreversible capacity tends to increase, and when it is less than 0.01 cc / g, the capacity per volume tends to decrease. Note that the CO ₂ adsorption amount can be measured by, for example, a gas adsorption measurement device.

Usually, carbon particles having a relatively low crystallinity such that the interplanar spacing d002 of the carbon 002 plane exceeds 0.340 nm does not develop a carbon hexagonal network surface and has many pores on the surface. , The He true density exceeds 2.00 g / cc, and the CO ₂ adsorption amount exceeds 5.00 cc / g. However, the carbon particles of the present invention are low crystalline carbon particles having a carbon 002 plane spacing d002 of 0.340 to 0.390 nm, but a He true density of 1.40 to 2.00 g / cc, CO _2. Since the adsorption amount is 0.01 to 5.00 cc / g, it is considered that the surface has few pores. When such a carbon particle for a lithium secondary battery negative electrode is used as a negative electrode material for a lithium secondary battery, the carbon hexagonal network surface is not developed, so that the output characteristics are excellent and the surface has few pores. It is possible to obtain characteristics with a small irreversible capacity.

  In the carbon particles for a lithium secondary battery negative electrode of the present invention, the oxygen concentration of the entire carbon particles is preferably 1% by weight or less, more preferably 0.5% by weight or less, and 0.3% by weight. More preferably, it is particularly preferable that it does not contain oxygen. The carbon particles for a lithium secondary battery negative electrode having an oxygen concentration of 1.0% by weight or less can reduce the initial irreversible capacity because the reaction between lithium ions and oxygen is suppressed. On the other hand, if the oxygen concentration exceeds 1.0% by weight, the initial irreversible capacity tends to increase. The oxygen concentration can be measured by, for example, an oxygen / nitrogen analyzer.

Thus, in the carbon particles for a lithium secondary battery negative electrode in which the interplanar spacing d002 of the carbon 002 plane is 0.340 to 0.390 nm, the He true density is 1.40 to 2.00 g / cc, and the CO ₂ adsorption amount is When the oxygen concentration of the carbon particles obtained by 0.01 to 5.00 cc / g and elemental analysis is 1.0% by weight or less, the carbon hexagonal mesh surface is not developed, and the carbon material has a fine surface. It is considered that there are almost no pores and almost no oxygen.

In addition, the carbon particles for a lithium secondary battery negative electrode in the present invention preferably have an N ₂ specific surface area of 0.30 to 10 m ² / g determined by nitrogen adsorption measurement at 77 K, and 0.30 to 8.0 m. ² / g is more preferable, and 0.30 to 5.0 m ² / g or less is further preferable. The carbon particles for a lithium secondary battery negative electrode having an N ₂ specific surface area in the range of 0.30 to 10 m ² / g have a small irreversible capacity and good adhesion to the electrode. On the other hand, the discharge capacity N ₂ specific surface area is less than 0.30 m 2 / ^g is reduced, further, there is a tendency for electrode adhesion is lowered, tends to irreversible capacity of first time exceeds 10 m 2 / ^g is greater is there. The N ₂ specific surface area can be calculated, for example, by measuring the adsorption amount of N ₂ with a gas adsorption measurement device and using the BET theory.

  The carbon particles for a lithium secondary battery negative electrode in the present invention have an O / C (= oxygen abundance ratio atomic% / carbon abundance ratio atomic%) determined by X-ray photoelectron spectroscopy (XPS) of 0.001 to 0.00. 060 is preferable, 0.001 to 0.050 is more preferable, and 0.001 to 0.045 is even more preferable. Carbon particles for a lithium secondary battery negative electrode whose O / C determined by X-ray photoelectron spectroscopy (XPS) is in the range of 0.001 to 0.060 have a small initial irreversible capacity and excellent life characteristics. On the other hand, if O / C exceeds 0.060, the first irreversible capacity tends to increase, and the life characteristics tend to be inferior.

There is no particular limitation on method for producing a lithium secondary battery negative electrode carbon particles of the present invention, for example, a carbon precursor resin N _2, Ar, under inert gas atmosphere such as He, calcined at 900 ° C. to 2000 ° C. It can be obtained by (carbonization). As a method for firing the carbon precursor resin, the temperature may be raised once up to the maximum temperature and fired, or after the primary firing at a relatively low temperature, the secondary firing may be performed at the maximum temperature.

  When firing to the maximum temperature at a time, it is preferable to use a carbon precursor resin having an average particle size adjusted to 5 to 50 μm in advance. In this case, the average particle size of the carbon precursor resin is more preferably 5 to 40 μm, and further preferably 5 to 30 μm. Carbon particles for lithium secondary battery negative electrodes obtained by firing a carbon precursor resin having an average particle size of less than 5 μm tend to have a large irreversible capacity and a poor contact between the particles, resulting in poor input / output characteristics. It is in. On the other hand, the carbon particles for a lithium secondary battery negative electrode obtained by firing a carbon precursor resin having an average particle size exceeding 50 μm are likely to have irregularities on the electrode surface, causing a short circuit of the battery, and the particle surface. Since the diffusion distance of lithium from the inside to the inside becomes long, the input / output characteristics tend to deteriorate.

  Moreover, as a maximum temperature at the time of baking carbon precursor resin, 900-2000 degreeC is preferable, 1100 degreeC-1500 degreeC is more preferable, 1200 degreeC-1300 degreeC is further more preferable. When the firing temperature is less than 900 ° C., the initial irreversible capacity tends to increase when used as a negative electrode material for a lithium secondary battery, and when it exceeds 2000 ° C., the discharge capacity tends to decrease.

  On the other hand, when the secondary firing is performed up to the maximum temperature after the primary firing at a relatively low temperature, the carbon precursor resin is primarily fired at 450 ° C. to 1000 ° C., and the obtained carbide is pulverized. It is preferable to raise the temperature to the maximum temperature and perform secondary firing to adjust the particle size of the obtained carbon particles.

  The firing temperature for the primary firing is preferably 450 ° C to 1000 ° C, more preferably 700 ° C to 1000 ° C, and still more preferably 800 ° C to 1000 ° C. The firing temperature (maximum temperature) for secondary firing is preferably 900 to 2000 ° C, more preferably 1100 ° C to 1500 ° C, and still more preferably 1200 ° C to 1300 ° C. When the firing temperature is less than 900 ° C., the initial irreversible capacity tends to increase when used as a negative electrode material for a lithium secondary battery, and when it exceeds 2000 ° C., the discharge capacity tends to decrease.

  The method for pulverizing the carbide after the primary firing is not particularly limited, and for example, known methods such as a jet mill, a vibration mill, a pin mill, a cutter mill, and a hammer mill can be used.

  Moreover, there is no restriction | limiting in particular as a method of adjusting the particle size of the carbon particle obtained after baking, However, Known methods, such as a sieve and a classifier, can be used. Moreover, as an average particle diameter of carbon particle, 5-50 micrometers is preferable, 5-40 micrometers is more preferable, 5-30 micrometers is further more preferable. The carbon particles for negative electrodes of lithium secondary batteries having an average particle size of less than 5 μm have a large irreversible capacity, are liable to deteriorate the contact between the particles, and tend to deteriorate input / output characteristics. On the other hand, the carbon particles for lithium secondary battery negative electrodes having an average particle size exceeding 50 μm are liable to generate irregularities on the electrode surface, causing a short circuit of the battery and increasing the diffusion distance of lithium from the particle surface to the inside. Therefore, the input / output characteristics tend to deteriorate.

The carbon particles obtained by simply firing the carbon precursor resin usually have different carbon properties on the surface and inside, and the inside has a denser structure than the surface. Therefore, as described above, before firing, the particle size of the carbon precursor resin is adjusted in advance, or after the primary firing, a pulverization treatment is performed to bring the inside having a dense structure to the surface and further firing. By doing so, it becomes possible to produce the carbon particles for a lithium secondary battery negative electrode of the present invention satisfying various physical properties (interplanar spacing of the carbon 002 plane, He true density, CO ₂ adsorption amount, etc.).

  As carbon precursor resin, for example, ethylene heavy end pitch, crude oil pitch, coal tar pitch, asphalt cracking pitch, pitch generated by pyrolyzing polyvinyl chloride, etc., and naphthalene are polymerized in the presence of a super strong acid. Synthetic pitches, thermoplastic synthetic resins such as polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, and polyvinyl butyral, natural products such as starch and cellulose, phenol resins, and the like can be used.

Among them, it is preferable to use a phenol resin as the carbon precursor resin, more preferably a resin containing a phenol derivative represented by the following general formula (I) in the structure, and a phenol derivative represented by the following general formula (I). It is particularly preferable to use a resin containing 40 to 70 mol% in the structure.

  Examples of the substituent X of the phenol derivative represented by the general formula (I) include a methyl group, an ethyl group, a butyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a sec-butyl group. Tert-butyl group, octyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, heptyl group and the like. Moreover, as an aryl group, a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group etc. are mentioned, for example. These aryl groups may have a substituent.

Moreover, the phenol derivative represented by the following general formula (II) may be contained in an amount of 30 mol% or less in the structure of the phenol resin.

  When a thermoplastic resin is used as the carbon precursor resin, a crosslinking reaction occurs and the carbonization rate can be increased by performing a curing treatment of the resin before firing. The curing method in the present invention is not particularly limited. For example, a method of performing a crosslinking reaction with aldehydes under an acid catalyst such as hydrochloric acid, sulfuric acid, nitric acid, etc., mixing with a crosslinking agent and heating to 180 ° C. to 200 ° C. Examples thereof include a method of performing a crosslinking reaction by melting, a method of using a mixture with a resol resin without using a crosslinking agent, and the like.

  A method of performing a crosslinking reaction with an aldehyde under an acid catalyst is a wet reaction, and is suitable for curing, for example, a fiber-shaped precursor resin. Moreover, the method of performing a crosslinking reaction by mixing with a crosslinking agent and heat-melting at 180-200 degreeC is suitable for producing a powder phenol resin, for example. As the crosslinking agent, for example, a substance serving as a formalin supply source such as hexamethylenetetramine and paraformaldehyde can be used.

  Further, the shape of the carbon precursor resin is not particularly limited, and bead-shaped resin particles may be used, and the resin lump may be a jet mill, a vibration mill, a pin mill, a cutter mill, a hammer mill, or the like. You may use what was used and grind | pulverized.

  The negative electrode for a lithium ion secondary battery of the present invention is not particularly limited. For example, the carbon particles for a negative electrode of the lithium ion secondary battery of the present invention, an organic binder, and various additives added as necessary. Kneading with a stirrer, ball mill, super sand mill, pressure kneader, etc. together with a solvent to prepare a paste-like negative electrode slurry, for example, metal mask printing method, electrostatic coating method, dip coating method, spray coating method, It can be formed by applying and drying on a current collector by a known method such as a roll coating method, a doctor blade method, a gravure coating method, a screen printing method, and if necessary, by compression molding by a molding method such as a roll press. it can. Alternatively, the paste-like coating material for the negative electrode layer can be formed into a sheet shape, a pellet shape, or the like and integrated with the current collector by a forming method such as a roll press.

  Examples of the organic binder include styrene-butadiene copolymer, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylonitrile, hydroxyethyl (meth) acrylate, butyl ( Ethylenically unsaturated carboxylic acid esters such as (meth) acrylates, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid, and polymer compounds having a large ion conductivity can be used. As the polymer compound having a high ionic conductivity, polyvinylidene fluoride, polyethylene oxide, polyepichlorohydrin, polyphosphazene, polyacrylonitrile and the like can be used. The content of the organic binder is preferably 1 to 20 parts by weight with respect to 100 parts by weight of the mixture of carbon particles and the organic binder.

  Moreover, you may mix a conductive support agent as said additive. Examples of the conductive auxiliary agent include carbon black, graphite, acetylene black, or an oxide or nitride that exhibits conductivity. The usage-amount of a conductive support agent should just be about 1 to 15 weight% of the carbon particle of this invention.

  Furthermore, you may mix the thickener of a negative electrode slurry as said additive. Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), oxidized starch, phosphorylated starch, and casein.

  The material and shape of the current collector are not particularly limited in the case of a negative electrode, and a strip-shaped one made of aluminum, copper, nickel, titanium, stainless steel, etc. in a foil shape, a punched foil shape, a mesh shape, or the like. Use it. A porous material such as porous metal (foamed metal) or carbon paper can also be used.

  The lithium ion secondary battery of the present invention can be obtained, for example, by arranging the negative electrode for a lithium ion secondary battery and the positive electrode of the present invention facing each other via a separator and injecting an electrolytic solution.

  The positive electrode can be obtained by forming a positive electrode material layer on the current collector surface in the same manner as the negative electrode. In this case, the current collector may be a band-shaped material made of a metal or an alloy such as aluminum, titanium, or stainless steel in a foil shape, a punched foil shape, a mesh shape, or the like.

Examples of the positive electrode material used for the positive electrode is not particularly limited, for _{example, LiNiO 2, LiCoO 2, LiMn} 2 O 4, Cr 3 O 8, Cr 2 O 5, V 2 O 5, V 6 O 13, VO 2, MnO ₂ , TiO ₂ , MoV ₂ O ₈ , TiS ₂ , V ₂ S ₅ , VS ₂ , MoS ₂ , MoS ₃ , conductive polymer such as polyaniline and polypyrrole, porous carbon, etc. are used alone or in combination. be able to.

Examples of the electrolyte include lithium salts such as LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSO ₃ CF ₃ , ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, cyclopentanone, sulfolane, 3- Methyl sulfolane, 2,4-dimethyl sulfolane, 3-methyl-1,3-oxazolidine-2-one, γ-butyrolactone, diethyl carbonate, dimethoxyethane, dimethyl carbonate, methyl propyl carbonate, methyl ethyl carbonate, butyl ethyl carbonate, dipro Bil carbonate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, etc. A so-called organic electrolytic solution dissolved in a non-aqueous solvent such as a fraction mixture can be used.

  As the separator, for example, a nonwoven fabric mainly composed of polyolefin such as polyethylene and polypropylene, cloth, microporous film, or a combination thereof can be used. In addition, when it is set as the structure where the positive electrode and negative electrode of a lithium secondary battery to produce do not contact directly during use, it is not necessary to use a separator.

  The structure of the lithium secondary battery of the present invention is not particularly limited. Usually, a positive electrode and a negative electrode, and a separator provided as necessary, are wound into a flat spiral shape to form a wound electrode plate group. Are generally laminated to form a laminated electrode plate group, and the electrode plate group is enclosed in an exterior body. The lithium secondary battery of the present invention is not particularly limited, but can be used as a paper-type battery, a button battery, a coin-type battery, a stacked battery, a cylindrical battery, or the like.

  The lithium secondary battery of the present invention thus obtained has a small irreversible capacity compared to a lithium secondary battery using conventional carbon particles as a negative electrode, and also has output characteristics, rapid charge / discharge characteristics, and safety. It will be excellent.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples.

<Preparation of carbon particles for lithium secondary battery negative electrode>
Example 1
In a 2 L three-necked flask equipped with a stirrer, a reflux condenser, and a temperature system, 217 g of m-cresol (reagent special grade: manufactured by Wako Pure Chemical Industries, Ltd.), 38% formaldehyde aqueous solution (reagent special grade: Wako Pure Chemical Industries, Ltd.) 97 g, 1 mol / l hydrochloric acid (for volumetric analysis: Wako Pure Chemical Industries, Ltd.) 20 g was added, heated to 100 ° C., and held for 1 hour. Thereafter, the mixture was heated to reflux at 150 ° C. for 4 hours, and residual monomers and water in the system were removed at 180 ° C. 100 g of the obtained phenol resin was weighed and pulverized and mixed with 10 g of hexamethylenetetramine (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.). The obtained powder mixture was transferred to a polytetrafluoroethylene vat and cured while being mixed on a 200 ° C. hot plate. The cured resin was completely cured by heat treatment at 180 ° C. for 4 hours in a hot air dryer. The obtained cured resin was pulverized for 30 seconds using a cutter mill.

The pulverized resin was passed through a continuous firing furnace at 900 ° C. to perform carbonization. The obtained carbide was pulverized for 30 seconds using a cutter mill and then sieved with a 250 mesh sieve. By heating the sieved carbide from room temperature (25 ° C.) to 500 ° C. for 30 minutes and from 500 ° C. to 1200 ° C. at a heating rate of 5.8 ° C./min and holding at 1200 ° C. for 1 hour under N ₂ atmosphere. Carbon particles were produced.

(Example 2)
In a 2 L three-necked flask equipped with a stirrer, a reflux condenser, and a temperature system, 217 g of m-cresol (reagent special grade: manufactured by Wako Pure Chemical Industries, Ltd.), 38% formaldehyde aqueous solution (reagent special grade: Wako Pure Chemical Industries, Ltd.) 97 g, 1 mol / l hydrochloric acid (for volumetric analysis: Wako Pure Chemical Industries, Ltd.) 20 g was added, heated to 100 ° C., and held for 1 hour. Thereafter, the mixture was heated to reflux at 150 ° C. for 4 hours, and residual monomers and water in the system were removed at 180 ° C. 100 g of the obtained phenol resin was weighed and pulverized and mixed with 10 g of hexamethylenetetramine (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.). The obtained powder mixture was transferred to a polytetrafluoroethylene vat and cured while being mixed on a 200 ° C. hot plate. The cured resin was completely cured by heat treatment at 180 ° C. for 4 hours in a hot air dryer. The obtained cured resin was pulverized for 30 seconds using a cutter mill.

The pulverized resin was passed through a continuous firing furnace at 900 ° C. to perform carbonization. The obtained carbide was pulverized for 30 seconds using a cutter mill and then sieved with a 250 mesh sieve. By heating the sieved carbide in a N ₂ atmosphere from room temperature (25 ° C.) to 500 ° C. for 30 minutes and from 500 ° C. to 1300 ° C. at a heating rate of 5.8 ° C./min and holding at 1300 ° C. for 1 hour. Carbon particles were produced.

(Example 3)
In a 2 L three-necked flask equipped with a stirrer, a reflux condenser, and a temperature system, 217 g of m-cresol (reagent special grade: manufactured by Wako Pure Chemical Industries, Ltd.), 38% formaldehyde aqueous solution (reagent special grade: Wako Pure Chemical Industries, Ltd.) 97 g, 1 mol / l hydrochloric acid (for volumetric analysis: Wako Pure Chemical Industries, Ltd.) 20 g was added, heated to 100 ° C., and held for 1 hour. Thereafter, the mixture was heated to reflux at 150 ° C. for 4 hours, and residual monomers and water in the system were removed at 180 ° C. 100 g of the obtained phenol resin was weighed and pulverized and mixed with 10 g of hexamethylenetetramine (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.). The obtained powder mixture was transferred to a polytetrafluoroethylene vat and cured while being mixed on a 200 ° C. hot plate. The cured resin was completely cured by heat treatment at 180 ° C. for 4 hours in a hot air dryer. The obtained cured resin was pulverized for 30 seconds using a cutter mill.

The pulverized resin was passed through a continuous firing furnace at 900 ° C. to perform carbonization. The obtained carbide was pulverized for 30 seconds using a cutter mill and then sieved with a 250 mesh sieve. By heating the sieved carbide in a N ₂ atmosphere from room temperature (25 ° C.) to 500 ° C. for 30 minutes, from 500 ° C. to 1400 ° C. at a heating rate of 5.8 ° C./min, and holding at 1400 ° C. for 1 hour. Carbon particles were produced.

Example 4
In a 2 L three-necked flask equipped with a stirrer, a reflux condenser, and a temperature system, 217 g of m-cresol (reagent special grade: manufactured by Wako Pure Chemical Industries, Ltd.), 38% formaldehyde aqueous solution (reagent special grade: Wako Pure Chemical Industries, Ltd.) 97 g, 1 mol / l hydrochloric acid (for volumetric analysis: Wako Pure Chemical Industries, Ltd.) 20 g was added, heated to 100 ° C., and held for 1 hour. Thereafter, the mixture was heated to reflux at 150 ° C. for 4 hours, and residual monomers and water in the system were removed at 180 ° C. 100 g of the obtained phenol resin was weighed and pulverized and mixed with 10 g of hexamethylenetetramine (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.). The obtained powder mixture was transferred to a polytetrafluoroethylene vat and cured while being mixed on a 200 ° C. hot plate. The cured resin was completely cured by heat treatment at 180 ° C. for 4 hours in a hot air dryer. Subsequently, the obtained cured resin was pulverized for 30 seconds using a cutter mill, then pulverized for 5 minutes using a vibration mill, and sieved with a 250 mesh sieve.

Sieved resin under _{N 2} was heated at 2.9 ° C. / min to room temperature to 200 DEG ° C., 2 hours hold at 200 ° C., then to 900 ° C. at a heating rate of 20 ° C. / h from 200 ° C. Carbonization was performed by heating and holding at 900 ° C. for 1 hour. Next, without pulverizing the obtained carbide, the temperature was raised from room temperature (25 ° C.) to 500 ° C. for 30 minutes under N ₂ atmosphere to 1200 ° C. at a heating rate of 300 ° C./h from 500 ° C. to 1200 ° C. The carbon particles were produced by holding for 1 hour.

(Comparative Example 1)
In a 2 L three-necked flask equipped with a stirrer, reflux condenser, and temperature system, phenol (reagent special grade: manufactured by Wako Pure Chemical Industries, Ltd.) 188 g, 38% formaldehyde aqueous solution (reagent special grade: manufactured by Wako Pure Chemical Industries, Ltd.) 97 g, 1 mol / l hydrochloric acid (reagent special grade: Wako Pure Chemical Industries, Ltd.) 20 g was added, heated to 100 ° C. and held for 1 hour. Thereafter, the mixture was heated to reflux at 150 ° C. for 4 hours, and residual monomers and water in the system were removed at 180 ° C. 100 g of the obtained novolac resin was weighed and pulverized and mixed with 10 g of hexamethylenetetramine (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.). The obtained powder mixture was transferred to a polytetrafluoroethylene vat and cured while being mixed on a 200 ° C. hot plate. The cured resin was completely cured by heat treatment at 180 ° C. for 4 hours in a hot air dryer. The obtained cured resin was pulverized for 30 seconds using a cutter mill.

The pulverized resin was passed through a continuous firing furnace at 900 ° C. to perform carbonization. The obtained carbide was pulverized for 30 seconds using a cutter mill and then sieved with a 250 mesh sieve. By heating the sieved carbide from room temperature (25 ° C.) to 500 ° C. for 30 minutes and from 500 ° C. to 1200 ° C. at a heating rate of 5.8 ° C./min and holding at 1200 ° C. for 1 hour under N ₂ atmosphere. Carbon particles were produced.

(Comparative Example 2)
In a 2 L three-necked flask equipped with a stirrer, a reflux condenser, and a temperature system, 132 g of phenol (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.) and pt-butylphenol (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.) ) 90g, 38% formaldehyde aqueous solution (reagent special grade: Wako Pure Chemical Industries, Ltd.) 97g, 1mol / l hydrochloric acid (for volumetric analysis: Wako Pure Chemical Industries, Ltd.) 20g, heated to 100 ° C, one hour Retained. Thereafter, the mixture was heated to reflux at 150 ° C. for 4 hours, and residual monomers and water in the system were removed at 180 ° C. 100 g of the obtained phenol resin was weighed and pulverized and mixed with 10 g of hexamethylenetetramine (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.). The obtained powder mixture was transferred to a polytetrafluoroethylene vat and cured while being mixed on a 200 ° C. hot plate. The cured resin was completely cured by heat treatment at 180 ° C. for 4 hours in a hot air dryer. The obtained cured resin was pulverized for 30 seconds using a cutter mill.

The pulverized resin was passed through a continuous baking furnace at 900 ° C. and carbonized. The obtained carbide was pulverized for 30 seconds using a cutter mill and then sieved with a 250 mesh sieve. By heating the sieved carbide in a N ₂ atmosphere from room temperature (25 ° C.) to 500 ° C. for 30 minutes, from 500 ° C. to 1100 ° C. at a heating rate of 5.8 ° C./min, and holding at 1100 ° C. for 1 hour. Carbon particles were produced.

(Comparative Example 3)
In a 2 L three-necked flask equipped with a stirrer, a reflux condenser, and a temperature system, 132 g of phenol (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.) and pt-butylphenol (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.) ) 90g, 38% formaldehyde aqueous solution (reagent special grade: Wako Pure Chemical Industries, Ltd.) 97g, 1mol / l hydrochloric acid (for volumetric analysis: Wako Pure Chemical Industries, Ltd.) 20g, heated to 100 ° C, one hour Retained. Thereafter, the mixture was heated to reflux at 150 ° C. for 4 hours, and residual monomers and water in the system were removed at 180 ° C. 100 g of the obtained phenol resin was weighed and pulverized and mixed with 10 g of hexamethylenetetramine (special reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.). The obtained powder mixture was transferred to a polytetrafluoroethylene vat and cured while being mixed on a 200 ° C. hot plate. The cured resin was subjected to a heat treatment by heating at 180 ° C. for 4 hours in a hot air dryer. The obtained cured resin was pulverized for 30 seconds using a cutter mill, then pulverized for 5 minutes using a vibration mill, and sieved with a 250 mesh sieve.

The temperature of the sieved resin is raised from room temperature to 200 ° C. at 2.9 ° C./min under N ₂ atmosphere and held at 200 ° C. for 2 hours, and then from 200 ° C. to 900 ° C. at a heating rate of 20 ° C./h. Carbonization was performed by heating and holding at 900 ° C. for 1 hour. Next, without pulverizing the obtained carbide, the temperature was raised from room temperature (25 ° C.) to 500 ° C. for 30 minutes under N ₂ atmosphere to 1200 ° C. at a heating rate of 300 ° C./h from 500 ° C. to 1200 ° C. The carbon particles were produced by holding for 1 hour.

<Evaluation>
He true density of carbon particles for lithium secondary battery negative electrodes obtained in Examples 1 to 4 and Comparative Examples 1 to 3, CO ₂ adsorption amount, carbon 002 plane spacing d002, oxygen concentration, N ₂ specific surface area and O ₂ / C was measured by the following method. The results are shown in Table 1.

[Measurement method of He true density]
After impregnating He gas into carbon particles for a lithium secondary battery negative electrode, which was previously dried under reduced pressure at 200 ° C. for 2 hours under the following conditions, using a He true density meter (MUPU-13T QUANTOMECOM), Measurements were made.
-Run mode: Multi Run
・ Number of analysis: 20 times ・ Number of recruitment analysis: 10 times ・ Allowable% deviation: 0.050%
・ Purge mode: Pulse mode Pulse 2500 times

[Measurement method of CO ₂ adsorption amount]
It was carried out by the following method using a gas adsorption device (manufactured by AUTSORB-1 Quantachrome). 3 g of carbon particles for a lithium secondary battery negative electrode were weighed into a quartz sample tube, and pretreated at 200 ° C. for 6 hours under reduced pressure on a pretreatment stage provided. The sample tube after the pretreatment was replaced with a measurement stage, and CO ₂ adsorption / desorption measurement was performed. Measurement was performed under the following measurement conditions, and the adsorption amount at a measurement pressure of 9.75 × 10 ⁻¹ mmHg was defined as the CO ₂ adsorption amount.
・ Measurement temperature: 273K
Measurement pressure: Adsorption 1.0 × 10 ^{−5 to} 9.75 × 10 ⁻¹ mmHg
: Desorption 9.75 × 10 ^{−1 to} 2.5 × 10 ⁻² mmHg

[Measurement method of d002 spacing between carbon 002 planes]
The carbon particles for the negative electrode of the lithium secondary battery were filled in the concave portion of the quartz sample holder and set on the measurement stage. Measurement was performed with a wide-angle X-ray diffractometer (manufactured by Rigaku Corporation) under the following measurement conditions.
-Radiation source: CuKα ray (wavelength λ = 0.15418 nm)
・ Output: 40kV, 20mA
・ Sampling width: 0.010 °
-Scanning range: 10-35 °
・ Number of integration: 1 time ・ Scanning speed: 0.5 ° / min
The peak position (2θ) of the obtained 002 diffraction line is externally corrected using the 111 diffraction line of the high-purity silicon powder for standard materials, and the interplanar spacing of the carbon 002 plane using the CuKα ray wavelength λ and Bragg equation d002 was calculated.

[Measurement method of oxygen concentration]
The oxygen concentration of the carbon particles for a lithium secondary battery negative electrode was measured using an oxygen / nitrogen analyzer (TC436: manufactured by LECO). The temperature in the furnace was set to about 1600 ° C. by setting the impulse furnace to 5400 W. 0.1 g to 0.2 g of carbon particles for a lithium secondary battery negative electrode were heated in an inert gas stream (helium), and oxygen was measured with an infrared detector. The oxygen content of the negative electrode material for a lithium secondary battery was calculated by comparing the obtained spectrum with a reference material (yttrium oxide) whose oxygen content was known.

[Measurement method of N ₂ specific surface area]
The N ₂ specific surface area was measured by the following method using AUTSORB-1 (manufactured by Quantachrome). 1 g of the carbon particles for a lithium secondary battery negative electrode was weighed into a quartz sample tube, and pretreated at 200 ° C. for 6 hours under reduced pressure on a pretreatment stage provided. Transfer the sample tube after the pretreatment in the measurement stage, was N ₂ adsorption-desorption measurements under the following conditions.
・ Measurement temperature: 77K
Measurement pressure: Adsorption 1.0 × 10 ^{−4 to} 9.95 × 10 ⁻¹ mmHg
: Desorption 9.95 × 10 ^{−1 to} 5.0 × 10 ⁻² mmHg
From the obtained isotherm, a value of relative pressure of 1.0 × 10 ^{−4 to} 1.5 × 10 ⁻¹ was applied to the BET theory to obtain an N ₂ specific surface area.

[O / C measurement method]
The measurement of O / C was performed under the following measurement conditions using an X-ray photoelectron spectrometer (AXSIS-165, manufactured by Shimadzu / Kratos).
X-ray source: AlKα 45 to 150 W (3 to 10 mA, 15 kV)
・ Detection angle: 90 degrees ・ Analysis area: 0.3 × 0.7 mm ²
・ Qualitative analysis PE: 160 eV
・ Quantitative analysis PE: 10 eV
As a measurement sample, an electrode prepared for measurement of charge / discharge characteristics described later was used. An element abundance ratio (atomic%) is calculated from the spectrum area of the detected spectrum (C1s, O1s, F1s), and O / C (= oxygen abundance ratio atomic% / carbon abundance ratio) using the abundance ratio of carbon and oxygen. a
tmic%).

  Lithium secondary batteries having negative electrodes for lithium secondary batteries in which the carbon particles for lithium secondary battery negative electrodes obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were applied as negative electrode materials were prepared, and their charge / discharge characteristics and Input / output characteristics were measured by the following method. The results are shown in Table 2.

[Measurement method of charge / discharge characteristics]
A coin-type lithium secondary battery for charge / discharge characteristic measurement was produced by the following procedure. First, 90% by weight of the obtained carbon particles for a negative electrode of a lithium secondary battery (negative electrode carbon material) were added with 10% by weight of polyvinylidene fluoride (PVDF) dissolved in N-methyl-2-pyrrolidone and kneaded. A paste was prepared. Next, using a 200 μm thick mask with a 9.2 mm diameter hole, the paste obtained above was applied in a circular shape on a 42 μm thick electrolytic copper foil, which was further dried at 105 ° C. A test electrode was obtained by removing N-methyl-2pyrrolidone.

Next, the obtained test electrode was placed in an electrolyte solution (LiPF ₆ in a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (EC and MEC are in a volume ratio of 1: 3) at a concentration of 1 mol / l. A coin-type lithium secondary battery was manufactured by placing a lithium metal electrode facing the polyethylene microporous membrane separator impregnated with a solution so dissolved.

The obtained lithium secondary battery was subjected to a charge / discharge test by a two-terminal method, and the charge / discharge capacity was measured. Between the sample electrode and the lithium metal electrode, the battery was charged to 0 V (V vs. Li / Li ⁺ ) with a constant current of 0.2 mA / cm ^{2 with} respect to the area of the sample electrode, and then the current was supplied with a constant voltage of 0 V. The battery was charged to 0.02 mA / cm ² . Next, after a 30-minute rest period, a one-cycle test was performed to discharge to 1.5 V (V vs. Li / Li ⁺ ) at a constant current of 0.2 mA / m ² , and the discharge capacity and charge / discharge efficiency were measured. The charge / discharge efficiency was calculated as (discharge capacity) / (charge capacity) × 100.

[Measurement method of output characteristics]
A wound cylindrical lithium secondary battery for measuring output characteristics was produced by the following procedure. First, 87% by weight of the obtained carbon particles for a negative electrode of a lithium secondary battery, 5% by weight of carbon black as a conductive auxiliary agent, and polyvinylidene fluoride (PVDF) dissolved in N-methyl-2-pyrrolidone in a solid content. A paste was prepared by adding 8% by weight and kneading. Next, this paste was applied to an electrolytic copper foil having a thickness of 40 μm using a coating machine (Chibi Coater: Sunk Co., Ltd.) so that the clearance was 4.5 mg / cm ² per unit area. Then, it was dried at 130 ° C. to remove N-methyl-2-pyrrolidone, and compression molding was performed with a roll press so that the composite density was 1.0 g / cm ³ , thereby producing a negative electrode.

Next, 94% by weight of lithium cobaltate having a particle diameter of 5 μm as a positive electrode active material, 3% by weight of carbon black as a conductive auxiliary agent, and polyvinylidene fluoride (PVDF) dissolved in N-methyl-2-pyrrolidone as a solid content. Was added to 3 wt% and kneaded to prepare a paste. Next, this paste was applied to an electrolytic aluminum foil having a thickness of 20 μm using a coating machine (Chibi Coater: Sunk Co., Ltd.) so that the coating amount per unit area was 8.0 mg / cm ² . N-methyl-2-pyrrolidone was removed by drying at 130 ° C., and compression molding was performed with a roll press machine so that the composite density was 2.5 g / cm ³ , thereby producing a positive electrode.

Next, the produced negative electrode was cut out to 54 mm × 360 mm square and the positive electrode was cut into 50 mm × 30 mm square, and laminated so that the respective coating portions faced with a separator therebetween, and then a 1 mm thick PTFE (polytetrafluoroethylene) plate The diameter was adjusted by winding. The separator was used by superposing two polyethylene microporous membranes with a thickness of 20 μm. Next, the electrode plate group was put into a steel can, and LiPF ₆ was added to a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (EC and MEC are 1: 3 in a volume ratio) of 1.5 mol / l. 3 ml of the electrolytic solution dissolved so as to have a concentration was put in a sealed can to produce a wound cylindrical lithium secondary battery.

The output characteristics of the obtained lithium secondary battery were measured by the following method. First, the battery prepared above was charged to 4.15 V with a constant current of 100 mA in a constant temperature bath at 25 ° C., further charged with a constant voltage of 4.15 V until the current became 10 mA, and after 100 minutes of rest, 100 mA was charged. The battery was discharged to 2.75 V at a constant current of. Next, after a 30-minute pause, the battery was charged to 4.15 V at a constant current of 100 mA, and further charged to a current of 10 mA at a constant voltage of 4.15 V, so that the SOC (charged state) was 100%. Then, after a 30-minute rest, the battery was discharged for 10 seconds under a constant current of 500 mA, and the voltage drop (ΔV) at that time was measured. The DC resistance value obtained by the quotient of this voltage drop (ΔV) and the discharge current value (500 mA) was taken as the output characteristic.

  As can be seen from Tables 1 and 2, lithium secondary batteries having negative electrodes to which the carbon particles for negative electrodes of lithium secondary batteries of Examples 1 to 4 are applied as negative electrode materials are excellent in charge / discharge efficiency and output characteristics.

Claims (10)

A carbon particle for a lithium secondary battery negative electrode having a carbon 002 plane spacing d002 of 0.340 to 0.390 nm determined by X-ray diffractometer (XRD) measurement, wherein the He true density is 1.40 to 2. Carbon particles for a lithium secondary battery negative electrode having 00 g / cc and a CO ₂ adsorption amount of 0.01 to 5.00 cc / g.   The carbon particle for a lithium secondary battery negative electrode according to claim 1, wherein the oxygen concentration of the entire carbon particle is 1 wt% or less. The carbon particle for a lithium secondary battery negative electrode according to claim 1 or 2, wherein the N ₂ specific surface area obtained by measuring nitrogen adsorption at 77K is 0.30 to 10 m ² / g.   The O / C obtained by X-ray photoelectron spectroscopy (XPS) is 0.001 to 0.060. The carbon particles for a lithium secondary battery negative electrode according to any one of claims 1 to 3.   The lithium precursor according to any one of claims 1 to 4, wherein the carbon precursor resin is carbonized at 450 ° C to 1000 ° C, the obtained carbide is pulverized, and the pulverized carbide is further carbonized at 900 ° C to 2000 ° C. Carbon particles for secondary battery negative electrode.   The carbon particles for a lithium secondary battery negative electrode according to any one of claims 1 to 5, wherein a carbon precursor resin having an average particle size of 5 to 50 µm is carbonized. The following general formula (I)

The carbon particle for lithium secondary battery negative electrodes in any one of Claims 1-6 formed by carbonizing the resin which contains the phenol derivative represented by these as a carbon precursor resin.   The carbon particles for a lithium secondary battery negative electrode according to claim 7, wherein the resin contains 40 to 70 mol% of a phenol derivative represented by the general formula (I) in its structure.   The negative electrode for lithium secondary batteries using the carbon particle for lithium secondary battery negative electrodes in any one of Claims 1-8.   A lithium secondary battery using the negative electrode for a lithium secondary battery according to claim 9.