WO2015129200A1 - Method for manufacturing carbonaceous material for non-aqueous electrolyte secondary cell - Google Patents

Abstract

　The disclosed manufacturing method is a method for manufacturing a carbonaceous material for a non-aqueous electrolyte secondary cell, including: a step of firing a mixture of a a volatile organic substance and a carbon precursor having a specific surface area of 100-500 m²/g in an inert gas atmosphere of 800-1400°C and obtaining a carbonaceous material.

Description

Method for producing carbonaceous material for non-aqueous electrolyte secondary battery

The present invention relates to a method for producing a carbonaceous material suitable for a negative electrode of a non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery.

Lithium ion secondary batteries are widely used in small portable devices such as mobile phones and laptop computers. As a negative electrode material for a lithium ion secondary battery, non-graphitizable carbon capable of doping (charging) and dedoping (discharging) lithium in an amount exceeding the theoretical capacity of 372 mAh / g of graphite has been developed (for example, Patent Document 1). ), Have been used.

Non-graphitizable carbon can be obtained using, for example, petroleum pitch, coal pitch, phenol resin, and plants as a carbon source. Among these carbon sources, plants are attracting attention because they are raw materials that can be continuously and stably supplied by cultivation and can be obtained at low cost. Moreover, since the carbonaceous material obtained by baking a plant-derived carbon raw material has many pores, it is expected to have a large charge / discharge capacity (for example, Patent Document 1 and Patent Document 2).

On the other hand, in recent years, due to increasing interest in environmental problems, development of lithium ion secondary batteries for in-vehicle applications has been promoted and is being put to practical use.

JP-A-9-161801 Japanese Patent Laid-Open No. 10-21919

Especially, a carbonaceous material used for a lithium ion battery for in-vehicle use is required to have good charge / discharge efficiency and hardly deteriorate.

The objective of this invention is providing the method suitable for manufacture of the carbonaceous material (carbonaceous material for nonaqueous electrolyte secondary batteries) used for the negative electrode of a nonaqueous electrolyte secondary battery (for example, lithium ion secondary battery). is there.

The present invention
Calcination of a mixture of a carbon precursor having a specific surface area of 100 to 500 m ² / g and a volatile organic substance in an inert gas atmosphere at 800 to 1400 ° C. to obtain a carbonaceous material;
Comprising
A method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery is provided.

According to the present invention, it is possible to provide a method suitable for the production of a carbonaceous material for a non-aqueous electrolyte secondary battery, which has good charge / discharge efficiency and is unlikely to decrease in charge / discharge efficiency.

The following is an explanation of an embodiment of the present invention, and is not intended to limit the present invention to the following embodiment. In addition, in this specification, normal temperature refers to 25 degreeC. Further, in this specification, the peak in the vicinity of 1360 cm ^-1, is not limited to the peak with a peak top present at 1360 cm ^-1, a peak is present halfway of the peak in 1360 cm ^-1 are also included.

(Carbonaceous material for non-aqueous electrolyte secondary batteries)
In the present embodiment, a carbonaceous material for a nonaqueous electrolyte secondary battery is obtained by firing a mixture of a carbon precursor and a volatile organic substance in an inert gas atmosphere at 800 to 1400 ° C.

The carbon precursor, that is, the precursor of the carbonaceous material can be produced from a plant-derived carbon material (hereinafter sometimes referred to as “plant-derived char”). In addition, char generally means a powdery solid rich in carbon that is not melt-softened, which is obtained when coal is heated, but here, the carbon content that is obtained by heating other organic substances is not melt-softened. It is used to include a rich powdery solid.

Examples of plants that serve as raw materials for plant-derived char (hereinafter sometimes referred to as “plant raw materials”) include, for example, coconut shells, peas, tea leaves, sugar cane, fruits (eg, mandarin oranges, bananas), strawberries, rice husks, Examples include hardwood, conifers, and bamboo. Examples of this include waste (for example, used tea leaves) after being used for the original use, or part of plant materials (for example, bananas and tangerine peels). These plant materials can be used alone or in combination of two or more. Among these plant materials, coconut shells that are easily available in large quantities are preferred.

As the coconut shell, for example, palm coconut shells (coconut palm), coconut palm, salak, and coconut palm can be used. These coconut shells can be used alone or in combination. As the coconut shell, coconut palm and palm palm, which are biomass wastes that are used as foods, detergent raw materials, biodiesel oil raw materials and the like and are generated in large quantities, are particularly preferable.

A method for producing a plant-derived char from a plant material can be carried out, for example, by heat-treating the plant material in an inert gas atmosphere at 300 ° C. or higher (hereinafter sometimes referred to as “temporary firing”).

However, char that is commercially available as coconut shell char or the like may be used as plant-derived char.

Carbonaceous materials produced from plant-derived char can be doped with a large amount of active material and are therefore basically suitable as negative electrode materials for non-aqueous electrolyte secondary batteries. However, plant-derived char contains a large amount of metal elements contained in plants. For example, coconut shell char contains about 0.3% potassium and about 0.1% iron. If a carbonaceous material containing a large amount of such metal elements is used as the negative electrode, it may adversely affect the electrochemical characteristics of the nonaqueous electrolyte secondary battery.

In addition, plant-derived char may contain alkali metal (for example, sodium), alkaline earth metal (for example, magnesium, calcium), transition metal (for example, copper) and the like in addition to potassium and iron. Even when the carbonaceous material contains these metal elements, the battery performance of the nonaqueous electrolyte secondary battery may be adversely affected.

Furthermore, it has been confirmed by the inventors that the pores of the carbonaceous material are blocked by ash, which may adversely affect the charge / discharge capacity of the battery.

Therefore, such ash (metal elements such as alkali metals, alkaline earth metals, and transition metals) contained in plant-derived char is reduced by decalcification before firing to obtain a carbonaceous material. It is desirable to keep it. Deashing methods include, for example, a method of extracting and deashing metal components using acidic water containing mineral acids such as hydrochloric acid and sulfuric acid, organic acids such as acetic acid and formic acid (liquid phase deashing), halogens such as hydrogen chloride It can be carried out as a method of deashing by exposing to a high temperature gas phase containing the compound (gas phase demineralization). Although not intended to limit the deashing method to be applied, gas phase deashing that is preferable in that no drying treatment is required after deashing will be described below.

In vapor phase decalcification, it is preferable to heat-treat plant-derived char in a vapor phase containing a halogen-containing compound. Examples of the halogen-containing compound include fluorine, chlorine, bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, iodine bromide, chlorine fluoride (ClF), iodine chloride (ICl), and iodine bromide (IBr). Bromine chloride (BrCl). Gas phase decalcification may be carried out using a compound that generates these halogen-containing compounds by thermal decomposition, or a mixture thereof. A preferred halogen-containing compound is hydrogen chloride.

In the vapor phase deashing, the halogen-containing compound may be used by mixing with an inert gas. The inert gas should just be a gas which does not react with the carbon component which comprises the plant-derived char. As the inert gas, for example, nitrogen, helium, argon, krypton, or a mixed gas thereof can be used. A preferred inert gas is nitrogen.

In the gas phase deashing, the mixing ratio of the halogen-containing compound and the inert gas is not limited as long as sufficient deashing can be achieved. For example, the ratio of the halogen-containing compound to the inert gas is 0.01 to 10.0 volume. %, Preferably 0.05 to 8.0% by volume, more preferably 0.1 to 5.0% by volume.

The temperature of the vapor phase decalcification is, for example, 500 to 950 ° C., preferably 600 to 940 ° C., more preferably 650 to 940 ° C., and further preferably 850 to 930 ° C. When the deashing temperature is too low, the deashing efficiency is lowered and the deashing may not be sufficiently performed. If the deashing temperature is too high, activation by a halogen-containing compound may occur. The time for vapor phase decalcification is not particularly limited, but is, for example, 5 to 300 minutes, preferably 10 to 200 minutes, and more preferably 20 to 150 minutes.

The conditions for vapor phase demineralization may affect various physical properties of the carbon precursor, such as the half-value width and specific surface area of the Raman spectrum peak described below.

Vapor phase decalcification reduces the content of potassium, iron, etc. contained in plant-derived char. The content of potassium contained in the carbon precursor obtained after the vapor phase deashing treatment is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and further preferably 0.03% by weight or less. The content of iron contained in the carbon precursor obtained after the vapor phase deashing treatment is preferably 0.02% by weight or less, more preferably 0.015% by weight or less, and further preferably 0.01% by weight or less.

If the particle diameter of the plant-derived char that is the target of vapor phase demineralization is too small, it may be difficult to separate the gas phase containing removed potassium and the plant-derived char from the average value of the particle diameter. Is preferably 100 μm or more, more preferably 300 μm or more, and even more preferably 500 μm or more. Further, the upper limit of the average value of the particle diameter is preferably 10,000 μm or less, more preferably 8000 μm or less, and further preferably 5000 μm or less.

The apparatus used for vapor phase demineralization is not particularly limited as long as it can be heated while mixing the plant-derived char and the vapor phase containing the halogen-containing compound. For example, vapor phase deashing can be carried out by using a fluidized furnace and using a fluidized bed or the like by a continuous or batch-type in-layer flow system. The supply amount (flow amount) of the gas phase is, for example, 1 ml / min or more, preferably 5 ml / min or more, more preferably 10 ml / min or more per 1 g of plant-derived char.

After the vapor phase deashing, the carbon precursor after the vapor phase deashing treatment may be deoxidized. For example, after supplying a halogen-containing compound and nitrogen gas to a plant-derived char and performing vapor phase decalcification, the supply of the halogen-containing compound is stopped, and further treatment is performed while supplying nitrogen gas. By continuing, vapor phase deoxidation treatment can be performed.

In the Raman spectrum observed by laser Raman spectroscopy, the half-value width of the peak around 1360 cm ⁻¹ of the carbon precursor is preferably in the range of 230 to 260 cm ^{−1 and in} the range of 235 to 250 cm ^−1. It is more preferable. The full width at half maximum of the peak near 1360 cm ^{−1 of the} Raman spectrum is related to the amorphous amount of the carbon precursor. When a carbon precursor in which the half width of the peak near 1360 cm ^{−1 of the} Raman spectrum is included in the above range is fired, a thermally stable structure is formed and the crystal structure is easily developed. As a result, it is considered that the amount of fine defects contained in the carbonaceous material obtained by firing such a carbon precursor can be sufficiently reduced. Such a carbonaceous material with few defects can contribute to suppression of the electrical resistance of a nonaqueous electrolyte secondary battery.

The Raman spectrum can be measured using a method described later. In this specification, the half width indicates the full width at half maximum (FWHM). A peak in the vicinity of 1360 cm ^{−1 of the} Raman spectrum is called a D band, and is a peak that appears in the Raman spectrum due to a double resonance effect accompanied by inelastic scattering in a carbon precursor or a carbonaceous material.

The average particle diameter of the carbon precursor is adjusted as necessary through a pulverization step and a classification step.

In the pulverization step, the carbon precursor is pulverized and adjusted so that the average particle size of the carbonaceous material after the firing step is in the range of 3 to 30 μm, for example.

The pulverization step can be performed using a pulverizer such as a jet mill, a ball mill, a hammer mill, or a rod mill. In order to reduce the amount of fine powder contained in the carbon precursor, it is preferable to use a jet mill having a classification function in the pulverization step. When using a ball mill, a hammer mill, a rod mill or the like, fine powder can be removed by classification after the pulverization step.

In the classification process, the carbon precursor is selected based on the particle size. By the classification step, for example, the amount of fine powder contained in the carbon precursor can be reduced, and more specifically, particles having a particle diameter of 1 μm or less can be removed. Further, by classifying the carbon precursor, the particle diameter of the carbonaceous material obtained by firing the carbon precursor can be accurately adjusted.

The classification method can be carried out by, for example, classification using a sieve, wet classification, or dry classification. As the wet classifier, for example, a classifier using principles such as gravity classification, inertia classification, hydraulic classification, centrifugal classification, and the like can be given. Examples of the dry classifier include a classifier using a principle such as sedimentation classification, mechanical classification, and centrifugal classification.

In this embodiment, the specific surface area of the carbon precursor is in the range of 100 to 500 m ² / g, preferably in the range of 200 to 500 m ² / g, and in some cases in the range of 200 to 400 m ² / g. . By firing the carbon precursor having a specific surface area in the above range, the fine pores of the carbonaceous material can be reduced. When such a carbonaceous material is used in a non-aqueous electrolyte secondary battery, a reaction caused by moisture contained in the carbonaceous material, for example, a hydrolysis reaction of the electrolytic solution or an electrolysis reaction of water is unlikely to occur. Generation of gas generated by electrolysis of acid and water generated by decomposition is suppressed. Furthermore, since this carbonaceous material has a small specific surface area, it is difficult to oxidize in an air atmosphere, and a decrease in battery performance of the nonaqueous electrolyte secondary battery due to oxidation of the carbonaceous material can be suppressed. In addition, since this carbonaceous material has a small specific surface area, the contactable area between the carbonaceous material and lithium ions is small, and the reaction between the carbonaceous material and lithium ions, which is one of the causes of a decrease in the utilization efficiency of lithium ions. Is unlikely to occur. Therefore, the use efficiency of lithium ions in the nonaqueous electrolyte secondary battery can be improved by using this carbonaceous material. The specific surface area of the carbon precursor can be adjusted by controlling conditions such as the temperature of vapor phase decalcification. In the present specification, the specific surface area means a specific surface area (BET specific surface area) determined by a BET method (nitrogen adsorption BET three-point method). Specifically, the specific surface area can be measured using a method described later.

The carbonaceous material of the present embodiment is obtained by firing a mixture of a carbon precursor and a volatile organic substance. A carbon precursor becomes a carbonaceous material with a reduced specific surface area by being mixed with a volatile organic material and fired. The amount of carbon dioxide adsorbed on the carbonaceous material can be reduced by mixing and baking the carbon precursor and the volatile organic substance.

As the volatile organic substance, an organic substance that is in a solid state at room temperature and has a residual carbon ratio of less than 5% by weight is preferable. As a volatile organic substance, what generates the volatile substance (for example, hydrocarbon gas and tar) which can reduce the specific surface area of the carbon precursor manufactured from plant-derived char is preferable.

As the volatile organic substance, for example, a thermoplastic resin or a low molecular organic compound can be used. Specifically, polystyrene, polyethylene, polypropylene, poly (meth) acrylic acid, poly (meth) acrylic acid ester, or the like can be used as the thermoplastic resin. In this specification, (meth) acryl is a general term for methacryl and methacryl. As the low molecular weight organic compound, toluene, xylene, mesitylene, styrene, naphthalene, phenanthrene, anthracene, pyrene, or the like can be used. Such a volatile organic substance is preferably one that does not oxidize and activate the surface of the carbon precursor when it volatilizes at the firing temperature and is thermally decomposed. Therefore, it is preferable to use polystyrene, polyethylene, or polypropylene as the thermoplastic resin. As the low molecular weight organic compound, it is preferable that volatility is low at room temperature from the viewpoint of safety, and naphthalene, phenanthrene, anthracene, pyrene, or the like is preferably used.

The residual carbon ratio is measured by quantifying the carbon content of the ignition residue after the sample is ignited in an inert gas. Intense heat means that about 1 g of volatile organic substances (this exact weight is W ₁ (g)) is put in a crucible and 20 liters of nitrogen is allowed to flow for 1 minute in an electric furnace. The temperature is raised from room temperature to 800 ° C. at a heating rate of minutes, and then heated at 800 ° C. for 1 hour. The residue at this time is regarded as an ignition residue, and its weight is defined as W ₂ (g).

Next, the ignition residue is subjected to elemental analysis in accordance with the method defined in JIS (Japanese Industrial Standard) M8819: 1997, and the weight ratio P ₁ (%) of carbon in the ignition residue is measured. Using these obtained values, the residual coal rate P ₂ (%) is calculated by the following equation.

The mixture of the carbon precursor and the volatile organic substance preferably contains the carbon precursor and the volatile organic substance in a weight ratio of 97: 3 to 40:60. The weight ratio of the carbon precursor to the volatile organic substance in this mixture is more preferably 95: 5 to 60:40, and still more preferably 93: 7 to 80:20. By using the mixture in which the volatile organic substance is contained in the above ratio, the efficiency of adsorption of the volatile organic substance to the carbon precursor is improved, and the specific surface area of the obtained carbonaceous material can be sufficiently reduced.

The mixing of the carbon precursor and the volatile organic substance may be performed by supplying the carbon precursor and the volatile organic substance to the pulverizer at the same time. Further, after the pulverization step, the carbon precursor and the volatile organic material may be mixed using a known mixing method. Such volatile organic substances are preferably in the form of particles. From the viewpoint of uniformly dispersing the volatile organic substance in the carbon precursor, the average particle size of the volatile organic substance is preferably 0.1 to 2000 μm, more preferably 1 to 1000 μm, and still more preferably 2 to 600 μm.

The mixture of the carbon precursor and the volatile organic substance may further contain components other than the carbon precursor and the volatile organic substance. As components other than the carbon precursor and the volatile organic substance, for example, natural graphite, artificial graphite, metal-based material, alloy-based material, or oxide-based material can be used. The content ratio of such components is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and further preferably 20 parts by weight with respect to 100 parts by weight of the mixture of the carbon precursor and the volatile organic substance. Part or less, and most preferably 10 parts by weight or less.

In the firing step, a mixture of the carbon precursor and the volatile organic material is fired at 800 to 1400 ° C.

The firing process
(A) It may be only a firing step (main firing step) in which a mixture of a carbon precursor and a volatile organic material is fired at 800 to 1400 ° C.,
(B) comprising a step of pre-baking a mixture of a carbon precursor and a volatile organic substance at 350 ° C. or higher and lower than 800 ° C. (pre-baking step), and then a baking step (main baking step) of baking at 800 to 1400 ° C. You may do it.

(Preliminary firing)
The temperature at which the preliminary firing step is performed is more preferably 400 ° C. or higher. The pre-baking step is preferably performed in an inert gas atmosphere as in the case of the main baking. The pre-baking step can be performed under reduced pressure, for example, 10 kPa or less. The time for performing the pre-baking step is, for example, in the range of 0.5 to 10 hours, preferably in the range of 1 to 5 hours. When the pre-baking step is performed, generation of volatile components and excessive tar components in the main baking step can be reduced, and the burden on the baking machine can be reduced.

(Main firing)
The temperature for carrying out the main baking step is 800 to 1400 ° C., preferably 1000 to 1350 ° C., more preferably 1100 to 1300 ° C. The main firing step is performed in an inert gas atmosphere. In this specification, an inert gas atmosphere refers to an atmosphere that contains an inert gas as a main component, that is, a component that occupies 50% by volume or more and does not contain an oxidizing gas typified by oxygen having high activity against carbon. As the inert gas, the aforementioned gases such as nitrogen and argon can be used. The inert gas atmosphere is preferably composed of an inert gas, but may contain a halogen-containing compound or the like together with the inert gas. Moreover, this baking process can be implemented under reduced pressure, for example, 10 kPa or less. The time for performing the main baking step is, for example, 0.05 to 10 hours, preferably 0.05 to 8 hours, and more preferably 0.05 to 6 hours.

Specific surface area determined by nitrogen adsorption BET3 point method of the carbonaceous material is preferably ^{1m 2 / g ~ 10m 2 /} g, more preferably 1.2m ² /g~9.5m ² / g, further preferably from 1.4m ² /g~9.0m ² / g. If the specific surface area of the carbonaceous material is too small, the amount of lithium ions adsorbed on the carbonaceous material is reduced, and the charge capacity of a non-aqueous electrolyte secondary battery using this carbonaceous material may be reduced. If the specific surface area is too large, lithium ions react on the surface of the carbonaceous material, and the utilization efficiency of lithium ions in a nonaqueous electrolyte secondary battery using the carbonaceous material may be reduced.

The carbonaceous material preferably has an average interplanar spacing d ₀₀₂ of (002) plane calculated from the wide-angle X-ray diffraction method using the Bragg equation in the range of 0.38 nm to 0.40 nm, and 0.381 nm. More preferably, it is in the range of 0.389 nm or less. When the average spacing d ₀₀₂ of (002) plane of the carbonaceous material is too small, there is the resistance when the lithium ion to the carbon material to doping and dedoping increases. As a result, the input / output characteristics of the nonaqueous electrolyte secondary battery using the carbonaceous material may be deteriorated. In addition, since the carbonaceous material repeatedly expands and contracts when lithium ions are doped and dedoped, the carbonaceous material may be damaged, and the stability as a battery material may be reduced. When the average interplanar spacing d ₀₀₂ of the (002) plane of the carbonaceous material is too large, the diffusion resistance of lithium ions is reduced, but the volume of the carbonaceous material is increased, so that the effective capacity per volume of the carbonaceous material is increased. May become smaller.

The smaller the amount of nitrogen atoms contained in the carbonaceous material, the better, but the analytical value obtained by elemental analysis (ratio of the weight of nitrogen atoms contained in the carbonaceous material to the weight of the carbonaceous material) is 0.5 weight. % Or less is preferable. When such a carbonaceous material is used for a nonaqueous electrolyte secondary battery, the reaction between lithium ions and nitrogen atoms contained in the carbonaceous material can be suppressed. When such a carbonaceous material is used, the reaction between the carbonaceous material containing nitrogen atoms and oxygen in the air is less likely to occur.

The smaller the amount of oxygen atoms contained in the carbonaceous material, the better, but the analytical value obtained by elemental analysis (the ratio of the weight of oxygen atoms contained in the carbonaceous material to the weight of the carbonaceous material) is 0.25 weight. % Or less is preferable. When such a carbonaceous material is used for a nonaqueous electrolyte secondary battery, the reaction between lithium ions and oxygen atoms contained in the carbonaceous material is unlikely to occur. Such carbonaceous materials are difficult to adsorb moisture in the air.

The half-width value of the peak around 1360 cm ^{−1 of the} carbonaceous material observed in the Raman spectrum is preferably in the range of 155 to 190 cm ⁻¹ , more preferably in the range of 175 to 190 cm ⁻¹ . More preferably, it is in the range of 175 to 180 cm ⁻¹ . Since such a carbonaceous material can occlude more lithium ions and lithium clusters, a nonaqueous electrolyte secondary battery having good battery characteristics can be obtained by using this carbonaceous material. Moreover, since this carbonaceous material has favorable electroconductivity, the nonaqueous electrolyte secondary battery using this carbonaceous material can have sufficient discharge characteristics (discharge capacity). The lithium cluster is a combination of lithium ions due to the interaction between lithium ions. Lithium ions are occluded in the carbonaceous material in the form of lithium ions or lithium clusters, but by forming the lithium clusters and occluded, a nonaqueous electrolyte secondary battery with better battery characteristics can be obtained. From the viewpoint of particularly suppressing the hygroscopicity of the carbonaceous material, the half-value width of the carbonaceous material is preferably a small value within the above range.

The half-width value of the peak near 1360 cm ^{−1 of the} Raman spectrum observed by laser Raman spectroscopy of the carbon precursor before firing, and the half-width value of the peak near 1360 cm ^{−1 of the} carbonaceous material obtained after firing. (The difference in half-value width) is preferably in the range of 50 cm ^{−1 to} 88 cm ⁻¹ . Difference between the value of the half width is more preferably in the range of 50 cm ^-1 or more 84cm ^-1 or less, more preferably in the range of 55cm ^-1 or 83cm ^-1 or less, 60cm ^-1 or 80 cm ^-1 The following range is particularly preferable. When the carbon precursor is fired so that the difference in the half-value width is 50 cm ⁻¹ or more, a thermally stable structure is easily formed, and it is considered that a carbonaceous material having high crystallinity can be obtained. Such a carbonaceous material can contribute to the improvement of the charge / discharge efficiency of the non-electrolyte secondary battery. From the viewpoint of particularly suppressing the hygroscopicity of the carbonaceous material, it is preferable that the difference in the half-value width is large. In a carbonaceous material with reduced hygroscopicity, a reaction due to moisture contained in the carbonaceous material is unlikely to occur, and the carbonaceous material is unlikely to deteriorate. However, if the difference in half-value width is too large, defects may be formed in the carbonaceous material in the firing step. If a carbonaceous material having defects is used, the charge / discharge efficiency of the nonaqueous electrolyte secondary battery may be reduced. Moreover, if the difference in the half-value width is too large, the hygroscopicity of the carbonaceous material may increase. When a highly hygroscopic carbonaceous material is used in a non-aqueous electrolyte secondary battery, a reaction caused by moisture contained in the carbonaceous material, for example, a hydrolysis reaction of an electrolytic solution or an electrolysis reaction of water may occur. The carbonaceous material may be deteriorated by an acid or gas generated by these reactions, specifically, an acid generated by a hydrolysis reaction of an electrolytic solution or a gas generated by an electrolysis reaction of water.

As described above, the average spacing d ₀₀₂ of the (002) plane of the carbonaceous material, the specific surface area, the half-width value of the peak near 1360 cm ^{−1 of the} carbon precursor observed in the Raman spectrum, and the carbonaceous material The difference from the half-width value of the peak near 1360 cm ⁻¹ is good when the carbonaceous material is suppressed from deterioration and hygroscopicity, and when this carbonaceous material is used as the negative electrode of a nonaqueous electrolyte secondary battery. It is effective in obtaining charge / discharge capacity. Therefore, the present invention from another aspect thereof,
A method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery, comprising:
A step of firing a carbon precursor and a volatile organic substance in an inert gas atmosphere at 800 to 1400 ° C. to obtain a carbonaceous material;
Comprising
The average interplanar spacing d ₀₀₂ of the (002) plane of the carbonaceous material calculated using the Bragg equation in the wide-angle X-ray diffraction method is in the range of 0.38 to 0.40 nm,
The specific surface area of the carbonaceous material determined by the nitrogen adsorption BET three-point method is in the range of 1 to 10 m ² / g,
The difference between the half-width value of the peak near 1360 cm ^{−1 of the} carbon precursor observed in the Raman spectrum and the half-width value of the peak near 1360 cm ^{−1 of the} carbonaceous material is 50 to 84 cm ⁻¹ . is there,
A method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery is provided.

According to this aspect, it is possible to provide a method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery that has good charge / discharge efficiency and lower hygroscopicity and is less likely to cause deterioration of the carbonaceous material. .

The average particle diameter (Dv ₅₀ ) of the carbonaceous material obtained in the present embodiment is preferably 3 to 30 μm. If the average particle size is too small, the proportion of fine powder contained in the carbonaceous material increases, and the specific surface area of the carbonaceous material may become too large. When a carbonaceous material having a large specific surface area is used, the possibility that the carbonaceous material and the electrolytic solution react with each other increases. When such a carbonaceous material is used for a non-aqueous electrolyte secondary battery, the irreversible capacity of the non-aqueous electrolyte secondary battery may increase. Here, the irreversible capacity is the difference between the capacity (charge capacity) charged in the non-electrolyte secondary battery and the discharge capacity. In addition, when a negative electrode is produced using a carbonaceous material having an average particle size that is too small, the voids between the carbonaceous materials may be reduced, and movement of lithium in the electrolyte solution in the negative electrode may be restricted. . Accordingly, the lower limit value of the average particle diameter of the carbonaceous material is more preferably 4 μm or more, and particularly preferably 5 μm or more. In addition, when a carbonaceous material having an appropriate average particle size is used, a non-aqueous electrolyte secondary battery capable of rapid charge and discharge can be obtained because resistance due to diffusion of lithium in the particles of the carbonaceous material is reduced. . In addition, by using a carbonaceous material having an appropriate average particle size, the thickness of the active material applied to the current collector plate can be reduced, and the area of the electrode can be increased. The input / output characteristics of the secondary battery can be improved. Therefore, the upper limit of the average particle diameter of the carbonaceous material is preferably 30 μm or less, more preferably 19 μm or less, still more preferably 17 μm or less, still more preferably 16 μm or less, and most preferably 15 μm or less.

(Negative electrode for non-aqueous electrolyte secondary battery)
The negative electrode for a nonaqueous electrolyte secondary battery according to this embodiment includes the carbonaceous material for a nonaqueous electrolyte secondary battery according to the present invention.

Hereinafter, a method for producing a negative electrode for a non-aqueous electrolyte secondary battery according to this embodiment will be described in detail. In the negative electrode of this embodiment, a binder (binder) is added to the carbonaceous material of the present invention, an appropriate amount of an appropriate solvent is added and kneaded to prepare an electrode mixture, and this electrode mixture is made of a metal plate or the like. After applying and drying the current collector plate, the current collector plate after drying can be produced by pressure molding.

When the carbonaceous material of the present invention is used, an electrode mixture for producing an electrode having good conductivity can be prepared. By adding a conductive additive to the electrode mixture, an electrode having better conductivity can be formed. As the conductive assistant, conductive carbon black, vapor grown carbon fiber (VGCF), nanotube, or the like can be used. From the viewpoint of obtaining an electrode mixture having sufficient conductivity and good dispersibility, 0.5 to 10% by weight (wherein the weight of the active material (carbonaceous material) + the weight of the binder + the weight of the conductive assistant) = 100% by weight), preferably 0.5 to 7% by weight, more preferably 0.5 to 5% by weight.

As the binder contained in the electrode mixture, PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene / butadiene / rubber) and CMC (carboxymethylcellulose) and the like that does not react with an electrolyte solution. Can be used. As the binder, it is particularly preferable to use PVDF. This is because PVDF adhering to the surface of the active material hardly inhibits migration of lithium ions, and thus PVDF can contribute to improvement of input / output characteristics of the nonaqueous electrolyte secondary battery. By adding an appropriate amount of the binder, the resistance value of the electrode and the internal resistance of the battery can be suppressed, and a nonaqueous electrolyte secondary battery having good battery characteristics can be obtained. Further, by adding an appropriate amount of the binder, the bonding between the particles of the carbonaceous material as the negative electrode material becomes good, and the bonding between the carbonaceous material and the current collector becomes good. Such a binder can be used by dissolving or dispersing in a solvent or the like. For example, PVDF can be used by forming a slurry state using a polar solvent. As such a polar solvent, N-methylpyrrolidone (NMP) or the like can be used. When such a PVDF-based binder is used, the binder is preferably added in an amount of 3 to 13% by weight, more preferably 3 to 10% by weight based on the total weight of the electrode mixture. In addition, an aqueous emulsion such as SBR or CMC can be used by dissolving in water. It is preferable to use a mixture of a plurality of types of binders that can be used by dissolving in water. In this case, the ratio of the total weight of the binder to the total weight of the electrode mixture is preferably in the range of 0.5 to 5% by weight, and more preferably in the range of 1 to 4% by weight.

The electrode active material layer is generally formed on both surfaces of the current collector plate, but may be formed only on one surface of the current collector plate. By forming an electrode active material layer having an appropriate thickness, a nonaqueous electrolyte secondary battery having sufficient capacity and good input / output characteristics can be obtained. The thickness of the active material layer (per one side) is preferably 10 to 80 μm, more preferably 20 to 75 μm, and particularly preferably 20 to 60 μm.

(Non-aqueous electrolyte secondary battery)
The nonaqueous electrolyte secondary battery of this embodiment includes the negative electrode for a nonaqueous electrolyte secondary battery of the present invention. The nonaqueous electrolyte secondary battery using the negative electrode for a nonaqueous electrolyte secondary battery using the carbonaceous material of the present invention exhibits excellent output characteristics and excellent cycle characteristics.

When the carbonaceous material (negative electrode material) of the present invention is used to form a negative electrode for a non-aqueous electrolyte secondary battery, other materials constituting the battery such as a positive electrode material, a separator, and an electrolytic solution are particularly limited. It is possible to use various materials conventionally used or proposed as a nonaqueous solvent secondary battery.

For example, as the cathode material, one represented layered oxide (LiMO _2, M is a metal: for example _{LiCoO 2, LiNiO 2, LiMnO 2} , or _{LiNi x Co y Mo z O 2} ( where x, y , Z represents a composition ratio)), olivine system (represented by LiMPO ₄ , M is a metal: for example, LiFePO _4, etc.), spinel system (represented by LiM ₂ O ₄ , M is a metal: for example, LiMn ₂ O _4, etc. ) Can be preferably used. These chalcogen compounds may be used in combination of a plurality of types as required. A positive electrode is formed by forming a layer on a conductive current collector using these positive electrode materials and a carbon material for imparting conductivity to an appropriate binder and electrode.

A non-aqueous solvent electrolyte used for a non-aqueous electrolyte secondary battery is formed by dissolving an electrolyte in a non-aqueous solvent. Nonaqueous solvents include organic solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyllactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, or 1,3-dioxolane. Can be used. These organic solvents can be used alone or in combination of two or more. As the electrolyte, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiCl, LiBr, LiB (C ₆ H ₅ ) ₄ , LiN (SO ₃ CF ₃ ) _2, or the like can be used.

A nonaqueous electrolyte secondary battery includes a positive electrode and a negative electrode formed as described above, and a liquid-permeable separator made of a porous material (for example, non-woven fabric) disposed between the two electrodes, and is immersed in the electrolytic solution. Is formed. As such a separator, a non-woven fabric or other porous material usually used for a secondary battery can be used. Instead of the separator or in combination with the separator, a solid electrolyte made of a polymer gel impregnated with an electrolytic solution can also be used.

Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention. In addition, although the measuring method of the physical-property value of the carbonaceous material for nonaqueous electrolyte secondary batteries is described below, the physical-property value described in this specification including an Example is the value calculated | required by the following method. Is based.

(Specific surface area measurement by nitrogen adsorption method)
An approximate expression derived from the BET expression is described below.

Using the above approximate equation, _vm was determined by a three-point method by nitrogen adsorption at liquid nitrogen temperature, and the specific surface area of the sample was calculated by the following equation.

In this case, v _m adsorption amount necessary to form a monomolecular layer on the surface of the sample (cm ³ / g), v adsorption amount is measured _{^{(cm 3 / g), p}} 0 is saturation vapor pressure, p Is an absolute pressure, c is a constant (reflecting heat of adsorption), N is Avogadro's number 6.022 × 10 ²³ , and a (nm ² ) is an area occupied by the adsorbate molecule on the sample surface (molecular occupation cross section).

Specifically, the amount of nitrogen adsorbed on the carbon precursor or carbonaceous material at the liquid nitrogen temperature was measured using “BELL Sorb Mini” manufactured by BELL Japan, as follows. A carbon precursor or a carbonaceous material pulverized to a particle size of about 5 to 50 μm is filled in a sample tube, and the sample tube is cooled to −196 ° C., and the pressure is once reduced. Nitrogen (purity 99.999%) was adsorbed on the carbonaceous material. The amount of nitrogen adsorbed on the sample when the equilibrium pressure was reached at the desired relative pressure was defined as the amount of adsorbed gas v.

(Measurement of average layer surface distance d ₀₀₂ by X-ray diffraction method)
Using “MiniFlexII, manufactured by Rigaku Corporation”, an X-ray diffraction pattern was obtained using CuKα rays filled with a carbonaceous material powder in a sample holder and monochromated by a Ni filter as a radiation source. The peak position of the diffraction pattern is obtained by the barycentric method (a method of obtaining the barycentric position of the diffraction line and obtaining the peak position by the corresponding 2θ value), and using the diffraction peak on the (111) plane of the high-purity silicon powder for standard materials. Corrected. The wavelength of the CuKα ray was 0.15418 nm, and d ₀₀₂ was calculated according to the Bragg formula described below.

(Raman spectrum)
Using a LabRAM ARAMIS manufactured by HORIBA, Ltd., a Raman spectrum was measured using a light source having a laser wavelength of 532 nm. In the test, three particles were randomly sampled in each sample, and two points were measured in each sampled particle. The measurement conditions were a wavelength range of 50 to 2000 cm ⁻¹ , an integration count of 1000 times, and an average value at a total of 6 locations was calculated as a measurement value.
The full width at half maximum is measured after fitting the spectrum obtained under the above measurement conditions with a Gaussian function for peak separation between the D band (near 1360 cm ⁻¹ ) and the G band (near 1590 cm ⁻¹ ). did.

(Elemental analysis)
Elemental analysis was performed using an oxygen / nitrogen / hydrogen analyzer EMGA-930 manufactured by HORIBA, Ltd. The detection method of the apparatus is oxygen: inert gas melting-non-dispersive infrared absorption method (NDIR), nitrogen: inert gas melting-thermal conductivity method (TCD), hydrogen: inert gas melting-non-dispersive infrared ray. Absorption method (NDIR) was used. Calibration is performed with (oxygen / nitrogen) Ni capsules, TiH2 (H standard sample), SS-3 (N, O standard sample), and 20 mg of the sample whose moisture content was measured at 250 ° C. for about 10 minutes as a pretreatment The measurement was performed after taking the capsule and degassing it in the elemental analyzer for 30 seconds. Three samples were analyzed, and the average value of the three samples obtained was used as the analysis value.

(Measurement of residual coal rate)
The residual carbon ratio was measured by quantifying the carbon content of the ignition residue after the sample was ignited in an inert gas. Ignition is about 1 g of volatile organics (this exact weight is W ₁ (g)) in a crucible, and 20 liters of nitrogen is allowed to flow for 1 minute in an electric furnace at 10 ° C./min. The temperature was increased from room temperature to 800 ° C. at a temperature increase rate of 1, and then heated at 800 ° C. for 1 hour. The residue at this time was regarded as an ignition residue, and its weight was defined as W ₂ (g).
Subsequently, the ignition residue was subjected to elemental analysis in accordance with the method defined in JIS (Japanese Industrial Standard) M8819: 1997, and the weight ratio P ₁ (%) of carbon in the ignition residue was measured. Using these obtained values, the remaining coal rate P ₂ (%) was calculated by the following equation.

(Preparation Example 1)
The coconut shell was crushed and dry-distilled at 500 ° C. to obtain coconut shell char having a particle size of 2.360 to 0.850 mm (containing 98% by weight of particles having a particle size of 2.360 to 0.850 mm). A vapor phase deashing process was performed for 50 minutes at 870 ° C. while supplying nitrogen gas containing 1% by volume of hydrogen chloride gas at a flow rate of 10 L / min to 100 g of this coconut shell char. Thereafter, only the supply of hydrogen chloride gas was stopped, and while supplying nitrogen gas at a flow rate of 10 L / min, vapor phase deoxidation treatment was further performed at 900 ° C. for 30 minutes to obtain a carbon precursor.
The obtained carbon precursor was roughly pulverized to an average particle size of 10 μm using a ball mill, and then pulverized and classified using a compact jet mill (manufactured by Seishin Enterprise Co., Ltd., Kodget System α-mkIII) to obtain an average particle size. A carbon precursor of 9.6 μm was obtained. The full width at half maximum of the peak near 1360 cm ^{−1 of the} Raman spectrum observed by laser Raman spectroscopy of the obtained carbon precursor was 245 cm ⁻¹ .

(Preparation Example 2)
A carbon precursor was obtained in the same manner as in Preparation Example 1 except that the vapor phase deashing treatment temperature and the vapor phase deoxidation treatment temperature were changed to 900 ° C. The half-width value of the peak near 1360 cm ^{−1 of the} Raman spectrum observed by laser Raman spectroscopy of the obtained carbon precursor was 237 cm ⁻¹ . The specific surface area of the obtained carbon precursor was 210 m ² / g.

(Preparation Example 3)
A carbon precursor was obtained in the same manner as in Preparation Example 2, except that the vapor phase deashing temperature and the vapor phase deoxidation temperature were changed to 870 ° C. The specific surface area of the obtained carbon precursor was 350 m ² / g.

(Preparation Example 4)
A carbon precursor was obtained in the same manner as in Preparation Example 1 except that the vapor phase deashing temperature and the vapor phase deoxidation temperature were changed to 980 ° C. The full width at half maximum of the peak around 1360 cm ^{−1 of the} Raman spectrum observed by laser Raman spectroscopy of the obtained carbon precursor was 220 cm ⁻¹ .

(Preparation Example 5)
A carbon precursor was obtained in the same manner as in Preparation Example 1, except that the vapor phase deashing temperature and the vapor phase deoxidation temperature were changed to 800 ° C. The half width of the peak near 1360 cm ^{−1 of the} Raman spectrum observed by laser Raman spectroscopy of the obtained carbon precursor was 267 cm ⁻¹ . The specific surface area of the obtained carbon precursor was 520 m ² / g.

(Preparation Example 6)
A carbon precursor was obtained in the same manner as in Preparation Example 2, except that the vapor phase deashing temperature and the vapor phase deoxidation temperature were changed to 950 ° C. The specific surface area of the obtained carbon precursor was 70 m ² / g.

Example 1
9.1 g of the carbon precursor prepared in Preparation Example 2 and 0.9 g of polystyrene (manufactured by Sekisui Plastics Co., Ltd., average particle size of 400 μm, residual carbon ratio of 1.2% by weight) were mixed. 10 g of this mixture was placed in a graphite sheath (length 100 mm, width 100 mm, height 50 mm) and 1290 at a heating rate of 60 ° C. per minute under a nitrogen flow rate of 5 L per minute in a fast heating furnace manufactured by Motoyama Co., Ltd. After raising the temperature to 0 ° C., the mixture was kept at 1290 ° C. (calcination temperature) for 11 minutes and naturally cooled. After confirming that the furnace temperature had dropped to 200 ° C. or less, the carbonaceous material was taken out of the furnace. The recovered carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Example 2)
A carbonaceous material was obtained in the same manner as in Example 1 except that the carbon precursor prepared in Preparation Example 1 was used. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

Example 3
A carbonaceous material was obtained in the same manner as in Example 1 except that the firing temperature was changed to 1270 ° C. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

Example 4
A carbonaceous material was obtained in the same manner as in Example 2 except that the firing temperature was changed to 1270 ° C. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Example 5)
A carbonaceous material was obtained in the same manner as in Example 1 except that the firing temperature was changed to 1300 ° C. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Example 6)
A carbonaceous material was obtained in the same manner as in Example 2 except that the firing temperature was changed to 1300 ° C. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Example 7)
A carbonaceous material was obtained in the same manner as in Example 1 except that the firing temperature was changed to 1350 ° C. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Example 8)
A carbonaceous material was obtained in the same manner as in Example 2 except that the firing temperature was changed to 1350 ° C. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

Example 9
A carbonaceous material was obtained in the same manner as in Example 1 except that the carbon precursor prepared in Preparation Example 3 was used. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Example 10)
A carbonaceous material was obtained in the same manner as in Example 9 except that the firing temperature was changed to 1270 ° C. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Example 11)
A carbonaceous material was obtained in the same manner as in Example 1 except that the holding time at 1290 ° C. was changed to 23 minutes. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

Example 12
A carbonaceous material was obtained in the same manner as in Example 9 except that the holding time at 1290 ° C. was changed to 23 minutes. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Comparative Example 1)
9.1 g of the carbon precursor prepared in Preparation Example 4 and 0.9 g of polystyrene (manufactured by Sekisui Plastics Co., Ltd., average particle size of 400 μm, residual carbon ratio of 1.2% by weight) were mixed. 10 g of this mixture was placed in a graphite sheath (length 100 mm, width 100 mm, height 50 mm) and 1290 at a heating rate of 60 ° C. per minute under a nitrogen flow rate of 5 L per minute in a fast heating furnace manufactured by Motoyama Co., Ltd. The temperature was raised to 0 ° C., then held at 1290 ° C. (calcination temperature) for 11 minutes, and then naturally cooled. After confirming that the furnace temperature had dropped to 200 ° C. or less, the carbonaceous material was taken out of the furnace. The recovered carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Comparative Example 2)
A carbonaceous material was obtained in the same manner as in Comparative Example 1 except that the carbon precursor prepared in Preparation Example 5 was used. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Comparative Example 3)
A carbonaceous material was obtained in the same manner as in Comparative Example 1 except that the carbon precursor prepared in Preparation Example 6 was used. The recovered amount of the carbonaceous material was 8.1 g, and the recovery rate with respect to the carbon precursor was 89%. Table 1 shows the physical properties of the obtained carbonaceous material.

(Production method of electrode)
Using the carbonaceous materials obtained in Examples 1 to 12 and Comparative Examples 1 to 3, negative electrodes were prepared according to the following procedure.
92 parts by mass of the carbonaceous material for negative electrode, 2 parts by mass of acetylene black, 6 parts by mass of PVDF (polyvinylidene fluoride) and 90 parts by mass of NMP (N-methylpyrrolidone) were mixed to obtain a slurry. The obtained slurry was applied to a copper foil having a thickness of 14 μm, dried and pressed to obtain an electrode having a thickness of 60 μm. The density of the obtained electrode was 0.9 to 1.1 g / cm ³ .

(Battery initial capacity and charge / discharge efficiency)
The electrode produced above was used as a working electrode, and metallic lithium was used as a counter electrode and a reference electrode. As the solvent, ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 3: 7. In this solvent, 1 mol / L LiPF ₆ was dissolved as an electrolyte. A glass fiber nonwoven fabric was used for the separator. Using these, a lithium secondary battery was produced in a glove box under an argon atmosphere.

Using the lithium secondary battery having the above configuration, a charge / discharge test was performed using a charge / discharge test apparatus (“TOSCAT” manufactured by Toyo System Co., Ltd.). Lithium was doped at a rate of 70 mA / g with respect to the mass of the active material, and was doped until 1 mV with respect to the lithium potential. Further, a constant voltage of 1 mV with respect to the lithium potential was applied for 8 hours to complete the doping. The capacity (mAh / g) at this time was defined as the charge capacity. Next, dedoping was performed at a rate of 70 mA / g with respect to the weight of the active material until 2.5 V with respect to the lithium potential, and the capacity discharged at this time was defined as the discharge capacity. The percentage of discharge capacity / charge capacity was defined as charge / discharge efficiency (initial charge / discharge efficiency), and used as an index of lithium ion utilization efficiency (lithium efficiency) in the battery. Further, after 7 days, the same battery performance was measured again, and the discharge capacity, charge capacity, and charge / discharge efficiency were measured. The value of the charge / discharge efficiency after 7 days with respect to the initial value of the charge / discharge efficiency was defined as the efficiency maintenance rate (%), which was used as an index of durability against deterioration of the carbonaceous material. The obtained battery performance is shown in Table 2.

In Table 1, the difference between the half width values is the difference between the half width value before firing (half width value of the carbon precursor) and the half width value after firing (the half width value of the carbonaceous material). It is. In the table, the nitrogen content of the carbonaceous material means an analytical value obtained by elemental analysis (ratio of the weight of nitrogen atoms contained in the carbonaceous material to the weight of the carbonaceous material). Similarly, the oxygen content of the carbonaceous material means an analytical value obtained by elemental analysis.

When the carbonaceous materials obtained in Examples 1 to 12 were used, the charge capacity and the discharge capacity were equivalent to those of the carbonaceous materials obtained in Comparative Examples 1 to 3. This value was satisfactory. Furthermore, the value of the efficiency maintenance rate, which is an index of the resistance against oxidative deterioration of the carbonaceous material, was also good. Further, the moisture absorption of the carbonaceous materials obtained in Examples 1 to 12 could be reduced more than the moisture absorption of the carbonaceous materials obtained in Comparative Examples 1 to 3. Furthermore, when the carbonaceous materials obtained in Examples 1 to 12 were used, the charge / discharge efficiency was good, and the efficiency maintenance rate after 7 days was also good.

The non-aqueous electrolyte secondary battery using the carbonaceous material of the present invention has good charge / discharge efficiency and lower hygroscopicity, and the carbonaceous material is unlikely to deteriorate. Therefore, it can be used particularly for in-vehicle applications such as hybrid vehicles (HEV) and electric vehicles (EV) that require a long life.

Claims (7)

1. Calcining a mixture of a carbon precursor having a specific surface area of 100 to 500 m ² / g and a volatile organic substance in an inert gas atmosphere at 800 to 1400 ° C. to obtain a carbonaceous material;
   Comprising
   A method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery.
2. The carbon precursor is derived from a plant,
   The manufacturing method of the carbonaceous material for nonaqueous electrolyte secondary batteries of Claim 1.
3. The volatile organic matter is in a solid state at room temperature, and the residual carbon ratio is less than 5% by weight.
   The manufacturing method of the carbonaceous material for nonaqueous electrolyte secondary batteries of Claim 1.
   Here, the residual carbon ratio is obtained by heating 1 g of the volatile organic matter from an ordinary temperature to 800 ° C. at a temperature rising rate of 10 ° C./min in an inert gas, and then ashing at 800 ° C. for 1 hour. It is a numerical value determined by the product of the weight of the residue and the carbon content of the residue.
4. The average interplanar spacing d ₀₀₂ of the (002) plane of the carbonaceous material calculated using the Bragg equation by wide-angle X-ray diffraction is in the range of 0.38 to 0.40 nm,
   The specific surface area of the carbonaceous material determined by the nitrogen adsorption BET three-point method is in the range of 1 to 10 m ² / g.
   The manufacturing method of the carbonaceous material for nonaqueous electrolyte secondary batteries of Claim 1.
5. The difference between the half-width value of the peak near 1360 cm ^{−1 of the} carbon precursor observed in the Raman spectrum and the half-width value of the peak near 1360 cm ^{−1 of the} carbonaceous material is 50 to 88 cm ⁻¹ . is there,
   The manufacturing method of the carbonaceous material for nonaqueous electrolyte secondary batteries of Claim 1.
6. The half-value width of the peak around 1360 cm ^{−1 of the} carbonaceous material observed in the Raman spectrum is in the range of 155 to 190 cm ⁻¹ .
   The manufacturing method of the carbonaceous material for nonaqueous electrolyte secondary batteries of Claim 1.
7. The half-width value of the peak near 1360 cm ^{−1 of the} carbon precursor observed in the Raman spectrum is in the range of 230 to 260 cm ⁻¹ .
   The manufacturing method of the carbonaceous material for nonaqueous electrolyte secondary batteries of Claim 1.