TW201545976A - 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 DEG C and obtaining a carbonaceous material.

Description

Method for producing carbonaceous material for nonaqueous electrolyte secondary battery

The present invention relates to a method for producing a carbonaceous material, which is suitable for use in a negative electrode of a nonaqueous electrolyte secondary battery typified by a lithium ion secondary battery.

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

The non-graphitizable carbon can be obtained by, for example, petroleum pitch, coal pitch, phenol resin, or plant as a carbon source. Among these carbon sources, the plant system can be obtained at a low cost by cultivating a raw material which is continuously supplied stably, and thus attracts attention. In addition, since a carbon material obtained by firing a carbon material derived from a plant has a large number of pores, it is expected to have a large charge and discharge capacity (for example, Patent Document 1 and Patent Document 2).

On the other hand, in recent years, concerns about environmental protection have increased, and the development of lithium ion secondary batteries for use in vehicles has been carried out and put into practical use.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 9-161801

Patent Document 2: Japanese Patent Publication No. 10-21919

In particular, a carbonaceous material used in a lithium ion battery for use in an in-vehicle use is excellent in charge and discharge efficiency, and it is difficult to cause deterioration.

An object of the present invention is to provide a method for producing a carbonaceous material (carbonaceous material for a nonaqueous electrolyte secondary battery) used for a negative electrode of a nonaqueous electrolyte secondary battery (for example, a lithium ion secondary battery).

The present invention provides a method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery, comprising: a mixture of a carbon precursor and a volatile organic substance having a specific surface area of 100 to 500 m ² /g in an inert gas atmosphere at 800 to 1400 ° C; The step of obtaining a carbonaceous material.

According to the present invention, it is possible to provide a method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery which has excellent charge and discharge efficiency and is difficult to reduce charge and discharge efficiency.

[Formation of the Invention]

The description of the embodiments of the present invention is exemplified below, and the present invention is not limited to the following embodiments. In addition, in this specification, normal temperature means 25 degreeC. Further, in this specification referred to in the vicinity of the peak of 1360cm ^-1 (peak), there is not limited to the top of the peak (peak top) of the peak at 1360cm ^-1, a peak in the middle it is also included the presence of peaks at 1360cm ^-1.

(carbonaceous material for nonaqueous electrolyte secondary battery)

In the present embodiment, a mixture of a carbon precursor and a volatile organic substance is fired in an inert gas atmosphere at 800 to 1400 ° C to obtain a carbonaceous material for a nonaqueous electrolyte secondary battery.

The carbon precursor, that is, the precursor of the carbonaceous material, can be produced from a plant-derived carbon raw material (hereinafter, referred to as "plant-derived charcoal"). Further, in general, charcoal refers to a powdery solid which is obtained by heating a coal and which is not melt-softened and enriched with carbon. Here, it also means to use a powdery solid of a carbon-rich component which is not melt-softened by heating other organic substances.

As a plant which is a raw material of the plant-derived charcoal (hereinafter referred to as "plant material"), for example, coconut shell, coffee bean, tea leaf, sugar cane, fruit (for example, orange, banana), and wheat can be exemplified. Stalks, rice husks, broadleaf trees, conifers, bamboo. This example includes waste (for example, used tea leaves) for supplying the original use, or a part of the plant material (for example, the skin of banana or orange). These plant materials can be used singly or in combination of two or more. Among these plant materials, coconut shells which are easily obtained in large quantities are preferred.

As the coconut shell, for example, a coconut shell of oil palm (oil palm), coconut palm, snake fruit, sea coconut can be used. These coconut shells can Used alone or in combination. As a coconut shell, it is especially used as a food, a lotion raw material, a biodiesel raw material, etc., and a large amount of raw waste of coconut palm and oil palm.

The method of producing plant-derived charcoal from a plant material can be carried out, for example, by heat-treating a plant material in an inert gas atmosphere of 300 ° C or higher (hereinafter referred to as "temporary firing").

However, as the plant-derived charcoal, a charcoal such as commercially available coconut shell charcoal can also be used.

A carbonaceous material produced from plant-derived charcoal is basically suitable as a negative electrode material for a nonaqueous electrolyte secondary battery because it may be doped with a large amount of active material. However, plant-derived charcoal contains many metal elements contained in plants. For example, coconut shell charcoal contains about 0.3% potassium and about 0.1% iron. When such a carbonaceous material containing many metal elements is used as the negative electrode, there is a case where the electrochemical characteristics of the nonaqueous electrolyte secondary battery are adversely affected.

Further, plant-derived charcoal also includes potassium, iron, and alkali metals (for example, sodium), alkaline earth metals (for example, magnesium, calcium), transition metals (for example, copper), and the like. When the carbonaceous material contains these metal elements, there is a possibility that the battery performance of the nonaqueous electrolyte secondary battery is adversely affected.

In addition, it was confirmed by the inventors of the present invention that the pores of the carbonaceous material are immersed in ash and adversely affect the charge/discharge capacity of the battery.

Therefore, it is desirable to use the deashing treatment to contain the plant-derived charcoal before the firing for obtaining the carbonaceous material. This ash (metal elements such as alkali metals, alkaline earth metals, transition metals, etc.) is reduced. The ash removal method, for example, can extract the metal component by using acidic water containing a mineral acid such as hydrochloric acid, sulfuric acid, or the like, or an organic acid such as formic acid to remove the ash (liquid phase ash removal); The high-temperature gas phase containing a halogen-containing compound such as hydrogen chloride is carried out by a method of removing ash (gas phase deashing). Hereinafter, the preferred gas phase deashing in terms of no need for drying treatment after ash removal is described, and the intended deashing method is not limited.

The gas phase is deashed, and it is preferred to heat the plant-derived charcoal in a gas phase containing a halogen-containing compound. Halogen-containing compounds are fluorine, chlorine, bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, iodine bromide, chlorine fluoride (ClF), iodine chloride (ICl), iodine bromide (IBr), bromine chloride. (BrCl). A compound which produces these halogen-containing compounds by thermal decomposition, or a mixture thereof may be used to carry out gas phase deashing. Preferred halogen-containing compounds are hydrogen chloride.

In the vapor phase deashing, the halogen-containing compound can be used in combination with an inert gas. The inert gas may be a gas that does not react with the carbon component constituting the plant-derived charcoal. As the inert gas, for example, nitrogen, helium, argon, helium, or a mixed gas thereof can be used. A preferred inert gas system is nitrogen.

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

The temperature of the gas phase deashing is, for example, 500 to 950 ° C, preferably It is 600 to 940 ° C, more preferably 650 to 940 ° C, and even more preferably 850 to 930 ° C. If the ash removal temperature is too low, the ash removal efficiency is lowered, and there is a case where the ash is not sufficiently removed. If the ash removal temperature becomes too high, there is a case where activation due to a halogen-containing compound is caused. The time for degassing in the gas phase is not particularly limited, and is, for example, 5 to 300 minutes, preferably 10 to 200 minutes, more preferably 20 to 150 minutes.

The conditions of the gas phase deashing may affect the physical properties of the carbon precursor, for example, the half value width and the specific surface area of the peak of the Raman spectrum to be described later.

The content of potassium, iron, and the like contained in the plant-derived charcoal is lowered by gas phase deashing. 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, still more 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, still more preferably 0.01% by weight or less.

When the particle size of the plant-derived charcoal which is a target for vapor phase ash removal is too small, separation of a gas phase containing potassium which has been removed, and a plant-derived charcoal becomes difficult, and therefore the average value of the particle diameter is obtained. The lower limit is preferably 100 μm or more, more preferably 300 μm or more, still more preferably 500 μm or more. Further, the upper limit of the average value of the particle diameter is preferably 10000 μm or less, more preferably 8000 μm or less, still more preferably 5,000 μm or less.

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

The degassing treatment of the carbon precursor after the gas phase deashing treatment can be carried out after the gas phase deashing is performed. For example, when a halogen-containing compound and nitrogen gas are supplied to the plant-derived charcoal, heat treatment is performed to remove the gas in the vapor phase, and only the supply of the halogen-containing compound is stopped, and the treatment is further continued while supplying nitrogen gas. Gas phase deoxidation treatment is performed.

In the Raman spectrum observed by the laser Raman spectrometry, the value of the half value width of the peak near the 1360 cm ^{-1 of the} carbon precursor preferably falls within the range of 230 to 260 cm ^-1 , more preferably in the range of 230 to 260 cm ^-1 . Range of 235~250cm ^-1 . The half value width of the peak near 1360 cm ^{-1 of the} Raman spectrum is related to the amount of amorphous carbon having a carbon precursor. When the half value width of the peak near 1360 cm ^{-1 of the} Raman spectrum is fired by the carbon precursor contained in the above range, a structure which is stable to heat 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 having few defects can contribute to suppressing the electric resistance of the nonaqueous electrolyte secondary battery.

Further, the Raman spectrum can be measured by a method described later. In the present specification, the half value width represents the full width at half maximum (FWHM). The peak near the 1360 cm ^{-1 of the} Raman spectrum is called the D band, and appears in the peak of the Raman spectrum due to the double resonance effect accompanying the inelastic scattering in the carbon precursor or the carbonaceous material.

The carbon precursor is subjected to a pulverization step and a classification step as needed, and the average particle diameter thereof is adjusted.

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

The pulverization step can be carried out 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 the fine powder contained in the carbon precursor, in the pulverization step, it is preferred to use a jet mill having a classification function. In the case of using a ball mill, a hammer mill, or a rod mill or the like, the fine powder can be removed by classification after the pulverization step.

The classification step is to screen the carbon precursor according to 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, for example, by classification using a sieve, wet classification, or dry classification. As the wet classifier, for example, a classifier using the principles of gravity classification, inertial classification, hydraulic classification, centrifugal classification, and the like can be cited. As the dry classifier, a classifier using the principles of precipitation classification, mechanical classification, centrifugal classification, and the like can be cited.

In the present embodiment, the specific surface area of the carbon precursor falls within the range of 100 to 500 m ² /g, more preferably falls within the range of 200 to 500 m ² /g, and falls within the range of 200 to 400 m ² /g depending on the case. range. By firing a 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 for a nonaqueous electrolyte secondary battery, the reaction of moisture contained in the carbonaceous material (for example, hydrolysis reaction of an electrolytic solution or electrolysis reaction of water) is hard to occur, and electrolysis is suppressed. The generation of an acid generated by hydrolysis of a liquid or a gas generated by electrolysis of water. Further, since the carbonaceous material has a small specific surface area, it is difficult to be oxidized in an air atmosphere, and it is possible to suppress a decrease in battery performance of a nonaqueous electrolyte secondary battery which is oxidized by the carbonaceous material. Further, since the carbonaceous material has a small specific surface area, the contact area between the carbonaceous material and lithium ions is small, and the reaction between the carbonaceous material and lithium ions is less likely to occur due to a decrease in the utilization efficiency of lithium ions. Thus, by using this carbonaceous material, the utilization efficiency of lithium ions in the nonaqueous electrolyte secondary battery can be improved. The specific surface area of the carbon precursor can be adjusted by controlling the temperature of the gas phase deashing. In addition, in this specification, a specific surface area means the specific surface area (BET specific surface area) determined by the BET method (nitrogen adsorption BET3 point method). Specifically, the specific surface area can be measured by a method described later.

The carbonaceous material of the present embodiment can be obtained by firing a mixture of a carbon precursor and a volatile organic compound. The carbon precursor is mixed with volatile organic compounds to form a carbonaceous material having a reduced specific surface area. By mixing the carbon precursor with the volatile organic compound, the amount of carbon dioxide adsorbed to the carbonaceous material can be reduced.

The volatile organic substance is in a solid state at normal temperature, and is preferably an organic substance having a residual carbon ratio of less than 5% by weight. As the volatile organic substance, a volatile substance (for example, a hydrocarbon-based gas or tar) capable of lowering the specific surface area of the carbon precursor produced from plant-derived charcoal is preferable.

As the volatile organic substance, for example, a thermoplastic resin or a low molecular organic compound can be used. Specifically, as the thermoplastic resin, polystyrene, polyethylene, polypropylene, poly(meth)acrylic acid, poly(meth)acrylate, or the like can be used. Moreover, in this specification, the general term of (meth)acrylic methacrylic acid and (meth)acrylic acid. As the low molecular organic compound, toluene, xylene, trimethylbenzene, styrene, naphthalene, phenanthrene, anthracene, anthracene or the like can be used. The volatile organic substance is preferably one which volatilizes at the firing temperature and does not oxidize the surface of the carbon precursor in the case of thermal decomposition. Therefore, as the thermoplastic resin, polystyrene, polyethylene, or polypropylene is preferably used. As the low molecular organic compound, from the viewpoint of safety, it is preferred to have a small volatility at normal temperature, and it is preferred to use naphthalene, phenanthrene, anthracene, anthracene or the like.

The residual carbon ratio is measured by quantifying the amount of carbon which has been heated at a high temperature after heating the sample at a high temperature in an inert gas. High-temperature heating means that about 1 g of volatile organic matter (the correct weight is set to W ₁ (g)) is placed in a crucible, and 20 liters of nitrogen is introduced in one minute, and the temperature is raised by an electric furnace at 10 ° C / min. The temperature was raised from normal temperature to 800 ° C, and then heated at 800 ° C for 1 hour. The residue at this time was set to a high temperature heating residue, and the weight was set to W ₂ (g).

Next, elemental analysis was carried out in accordance with the method specified in JIS (Japanese Industrial Standards) M8819:1997, and the weight ratio P ₁ (%) of carbon in the high-temperature heating residue was measured. Using these obtained values, the residual carbon ratio P ₂ (%) was calculated by the following formula.

The mixture of the carbon precursor and the volatile organic compound preferably contains a carbon precursor and a volatile organic compound in a weight ratio of 97:3 to 40:60. The weight ratio of the carbon precursor to the volatile organic compound in the mixture is preferably from 95:5 to 60:40, more preferably from 93:7 to 80:20. By using a mixture containing volatile organic compounds in the above ratio, the adsorption efficiency of the volatile organic compound 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 can be carried out by simultaneously supplying the carbon precursor and the volatile organic substance to the pulverizing apparatus. Further, it is also possible to mix the carbon precursor and the volatile organic substance after the pulverization step using a well-known mixing method. Such volatile organic compounds are preferably in the shape of particles. The average particle diameter of the volatile organic substance is preferably from 0.1 to 2000 μm, more preferably from 1 to 1000 μm, still more preferably from 2 to 600 μm, from the viewpoint of uniformly dispersing the volatile organic substance in the carbon precursor.

The mixture of carbon precursor and volatile organics may further comprise components other than carbon precursors and volatile organic compounds. As components other than the carbon precursor and the volatile organic substance, for example, natural graphite, artificial graphite, a metal-based material, an alloy-based material, or an oxide-based material can be used. The content ratio of such a component is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, still more preferably 20 parts by weight or less, based on 100 parts by weight of the mixture of the carbon precursor and the volatile organic substance. It is preferably 10 parts by weight or less.

The firing step is to burn the carbon precursor at 800~1400 °C. a mixture of substances and volatile organic compounds.

In the baking step, (a) the firing step of the mixture of the carbon precursor and the volatile organic substance may be calcined at 800 to 1400 ° C (the main firing step); and (b) may be provided at 350 ° C or more and less than 800. A step of preparing a mixture of a carbon precursor and a volatile organic substance (pre-baking step) at a temperature of ° C, and a baking step (a main baking step) of firing at 800 to 1400 ° C thereafter.

(prepared to burn)

The temperature at which the preliminary calcination step is carried out is more preferably 400 ° C or higher. The preliminary firing step is preferably carried out in an inert gas atmosphere as in the case of the main firing. The preliminary calcination step can be carried out under reduced pressure, for example, 10 kPa or less. The time for performing the preliminary calcination step is, for example, in the range of 0.5 to 10 hours, preferably in the range of 1 to 5 hours. When the preliminary calcination step is carried out, the generation of volatiles or excessive tar in the main calcination step can be reduced, and the burden on the calciner can be reduced.

(formal firing)

The temperature at which the main firing step is carried out is 800 to 1400 ° C, preferably 1,000 to 1,350 ° C, more preferably 1,100 to 1,300 ° C. The formal firing step is carried out under an inert gas atmosphere. In the present specification, the inert gas atmosphere refers to a gas atmosphere in which an inert gas is a main component (that is, a component which accounts for 50% by volume or more) and does not contain an oxidizing gas represented by oxygen which has high activity for carbon. As the inert gas, the aforementioned gas such as nitrogen or argon can be used. The inert gas atmosphere is preferably composed of an inert gas, but may contain an inert gas, a halogen-containing compound, or the like. In addition, the formal firing step can be It is carried out under reduced pressure (for example, 10 kPa or less). The time for performing the main firing step is, for example, 0.05 to 10 hours, preferably 0.05 to 8 hours, more preferably 0.05 to 6 hours.

Carbonaceous material point method using nitrogen adsorption BET3 the obtained specific surface area is preferably ^{1m 2 / g ~ 10m 2 /} g, more preferably 1.2m ² /g~9.5m ² / g, and still more preferably 1.4 m ² /g~9.0m ² /g. When the specific surface area of the carbonaceous material is too small, the amount of adsorption of lithium ions to the carbonaceous material is small, and the charge capacity of the nonaqueous electrolyte secondary battery using the carbonaceous material is lowered. When 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 the nonaqueous electrolyte secondary battery using the carbonaceous material is lowered.

The carbonaceous material preferably has a mean interplanar spacing d ₀₀₂ of the (002) plane calculated by the wide-angle X-ray diffraction method using a Bragg equation falling within a range of 0.38 nm or more and 0.40 nm or less, more preferably 0.381 nm or more and 0.389 nm. The following range. When the average surface spacing d ₀₀₂ of the (002) plane of the carbonaceous material is too small, the resistance when lithium ions are doped and dedoped with the carbonaceous material may become large. As a result, there is a case where the input and output characteristics in the nonaqueous electrolyte secondary battery using the carbonaceous material are lowered. Further, since the carbonaceous material repeats expansion and contraction during lithium ion doping and dedoping, there is a case where the carbonaceous material is damaged, and the stability as a battery material is lowered. When the average surface spacing d ₀₀₂ of the (002) plane of the carbonaceous material is excessively large, the diffusion resistance of lithium ions becomes small, but the volume of the carbonaceous material becomes large, and thus the effective capacity per unit volume of the carbonaceous material changes. Small situation.

The smaller the amount of nitrogen atoms contained in the carbonaceous material, the better. However, it is preferable that the analysis value obtained by elemental analysis (the ratio of the weight of the nitrogen atom contained in the carbonaceous material to the weight of the carbonaceous material) is 0.5% by weight or less. When such a carbonaceous material is used for a nonaqueous electrolyte secondary battery, the reaction of lithium ions with nitrogen atoms contained in the carbonaceous material can be suppressed. When such a carbonaceous material is used, the reaction of a carbonaceous material containing a nitrogen atom with oxygen in the air becomes difficult to occur.

The smaller the amount of oxygen atoms contained in the carbonaceous material, the better, but it is preferably an analytical value obtained by elemental analysis (the ratio of the weight of the oxygen atom contained in the carbonaceous material to the weight of the carbonaceous material) is 0.25 by weight. %the following. 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 hardly occurs. This carbonaceous material is difficult to adsorb moisture in the air.

Value of half-value width of a peak of 1360cm ^-1 vicinity of the carbonaceous material in a Raman spectrum observed, preferably falling in the range of 155 ~ 190cm ^-1, more preferably fall within the range of 175 ~ 190cm ^-1 More preferably, it falls within the range of 175~180cm ^-1 . Since such a carbonaceous material can absorb a large amount of lithium ions and a lithium cluster, a nonaqueous electrolyte secondary battery having good battery characteristics can be obtained by using this carbonaceous material. Further, since this carbonaceous material has good conductivity, the nonaqueous electrolyte secondary battery using this carbonaceous material can have sufficient discharge characteristics (discharge capacity). Further, the lithium cluster lithium ion is bound by the interaction between lithium ions. The lithium ion is absorbed in the carbonaceous material in a state in which lithium ions or lithium are clustered, and by forming lithium clusters and absorbing them, a nonaqueous electrolyte secondary battery having better battery characteristics can be obtained. The value of the half value width of the carbonaceous material is preferably a value which is small within the above range from the viewpoint of particularly suppressing the hygroscopicity of the carbonaceous material.

The value of the half value width of the peak near 1360 cm ^-1 of the Raman spectrum observed by the Raman spectroscopic method before the carbon precursor before firing, and the vicinity of 1360 cm ^{-1 of the} carbonaceous material obtained after the firing (the difference between the value of the half value width) of the difference between the peak value of the half-value width, preferably fall within the range of ^-1 or less than 88cm 50cm ^-1. This difference between the value of half-value width is more preferably fall within the range of 50cm to 84cm ^{-1 -1} or more, still more preferably fall within the range of 55cm to 83cm ^{-1 -1} or more, and particularly preferably ^-1 or more to fall 60cm 80cm ^-1 or less. When the carbon precursor is fired so that the difference in the value of the half value width is 50 cm ^-1 or more, it is easy to form a structure which is stable to heat, and therefore 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 and 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 value of the half value width is large. In the carbonaceous material having reduced hygroscopicity, the reaction of moisture contained in the carbonaceous material is less likely to occur, and the carbonaceous material is less likely to deteriorate. However, if the difference in the value of the half value width becomes too large, there is a case where a defect is formed in the carbonaceous material in the firing step. When a carbonaceous material having defects is used, the charge and discharge efficiency of the nonaqueous electrolyte secondary battery may be lowered. Further, when the difference in the value of the half value width becomes too large, the hygroscopicity of the carbonaceous material may increase. When a carbonaceous material having high hygroscopicity is used for a nonaqueous electrolyte secondary battery, there is a case where a reaction due to moisture contained in the carbonaceous material (for example, a hydrolysis reaction of an electrolytic solution or an electrolysis reaction of water) occurs. . The acid or gas generated by these reactions, specifically, the acid generated by the hydrolysis reaction of the electrolytic solution or the gas generated by the electrolysis reaction of water, may be deteriorated by the carbonaceous material.

As described above, the average interplanar spacing d ₀₀₂ of the (002) plane of the carbonaceous material, the specific surface area, the half value width of the peak near the 1360 cm ^-1 of the carbon precursor observed in the Raman spectrum, and the carbonaceous material The difference in the value of the half value width of the peak near 1360 cm ^{-1 is} obtained by suppressing the deterioration of the carbonaceous material and suppressing the hygroscopicity, and also using the carbonaceous material as the negative electrode of the nonaqueous electrolyte secondary battery. In the case of good charge and discharge capacity, the results were seen. Thus, the present invention is directed to a method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery, which comprises firing a carbon precursor and a volatile organic substance in an inert gas atmosphere at 800 to 1400 ° C. In the step of obtaining a carbonaceous material, the average interplanar spacing d ₀₀₂ of the (002) plane of the carbonaceous material calculated by the Bragg equation in the wide-angle X-ray diffraction method falls within a range of 0.38 to 0.40 nm, and the BET 3 point is adsorbed by nitrogen. The specific surface area of the carbonaceous material obtained by the method falls within a range of 1 to 10 m ² /g, and the value of the half value width of the peak near the 1360 cm ^{-1 of the} carbon precursor observed in the Raman spectrum and the carbon The difference in the value of the half value width of the peak near the 1360 cm ^-1 of the material is 50 to 84 cm ^-1 .

According to this aspect, it is possible to provide a method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery which has excellent charge and discharge efficiency, lower hygroscopicity, and difficulty in deterioration of a carbonaceous material.

The average particle diameter (Dv ₅₀ ) of the carbonaceous material obtained in the present embodiment is preferably from 3 to 30 μm. When the average particle diameter is too small, the ratio of the fine powder contained in the carbonaceous material increases, and the specific surface area of the carbonaceous material may become excessively large. When a carbonaceous material having a large specific surface area is used, the possibility that the carbonaceous material reacts with the electrolytic solution becomes high. When such a carbonaceous material is used for a nonaqueous electrolyte secondary battery, the irreversible capacity of the nonaqueous electrolyte secondary battery may increase. Here, the irreversible capacity means a difference between a capacity (charge capacity) for charging a non-electrolyte secondary battery and a discharge capacity. Further, when a negative electrode is produced using a carbonaceous material having an excessively small average particle diameter, voids between the carbonaceous materials become small, and there is a case where movement of lithium in the electrolytic solution in the negative electrode is restricted. Therefore, the lower limit 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 diameter is used, the resistance to diffusion of lithium in the particles of the carbonaceous material is reduced, and a nonaqueous electrolyte secondary battery which can be rapidly charged and discharged can be obtained. Further, by using a carbonaceous material having a suitable average particle diameter, the thickness of the active material coated on the current collector plate can be reduced, and the area of the electrode can be increased, and as a result, the input and output characteristics of the nonaqueous electrolyte 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 Nonaqueous Electrolyte Secondary Battery)

The negative electrode for a nonaqueous electrolyte secondary battery of the present embodiment includes the carbonaceous material for a nonaqueous electrolyte secondary battery of the present invention.

Hereinafter, a method of producing a negative electrode for a nonaqueous electrolyte secondary battery of the present embodiment will be specifically described. In the negative electrode according to the present embodiment, a binder is added to the carbonaceous material of the present invention, an appropriate amount of a solvent is added and kneaded, and an electrode mixture is prepared, and the electrode mixture is applied to a current collector plate including a metal plate or the like. After drying, the dried set The electric board is formed by press molding.

If the carbonaceous material of the present invention is used, an electrode mixture for producing an electrode having good conductivity can be prepared. By further adding a conductive auxiliary agent to the electrode mixture, an electrode having more excellent conductivity can be formed. As the conductive auxiliary agent, conductive carbon black, vapor-grown carbon fiber (VGCF), a nanotube, or the like can be used. From the viewpoint of obtaining an electrode mixture having sufficient conductivity and good dispersibility, it can be formulated in an amount of 0.5 to 10% by weight (here, the weight of the active material (carbonaceous material) + the weight of the binder + the conductivity aid The weight of the agent = 100% by weight), preferably 0.5 to 7% by weight, more preferably 0.5 to 5% by weight of the conductive auxiliary agent.

As the binder contained in the electrode mixture, PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene-butadiene-rubber) and CMC (carboxymethylcellulose) can be used. Do not react with the electrolyte. The binder is particularly preferred for use with PVDF. This is because PVDF which has adhered to the surface of the active material is less likely to impede the movement of lithium ions, so that the use of PVDF can contribute to an improvement in the input and output characteristics of the nonaqueous electrolyte secondary battery. By adding a suitable 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 a suitable amount of the binder, the bonding of the particles of the carbonaceous material of the anode material becomes better, and the combination of the carbonaceous material and the collector material is improved. Such a binder can be used by dissolving or dispersing in a solvent or the like. For example, PVDF can be used in a slurry state using a polar solvent. As such a polar solvent, N-methylpyrrolidone (NMP) or the like can be used. In the case of using such a PVDF-based binder, it is preferred to add 3 to 13% by weight based on the total weight of the electrode mixture ( More preferably, 3 to 10% by weight of a binder is added. Further, an aqueous emulsion or CMC such as SBR can be dissolved in water for use. The binder which can be dissolved in water is preferably used in a mixture of plural kinds. 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, 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 side of the current collector plate. By forming an electrode active material layer having a suitable thickness, a nonaqueous electrolyte secondary battery having a sufficient capacity and having excellent input and output characteristics can be obtained. The thickness of the active material layer (each side) is preferably from 10 to 80 μm, more preferably from 20 to 75 μm, particularly preferably from 20 to 60 μm.

(non-aqueous electrolyte secondary battery)

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

When a negative electrode for a nonaqueous electrolyte secondary battery is formed using the carbonaceous material (negative electrode material) of the present invention, other materials constituting the battery such as a positive electrode material, a separator, and an electrolytic solution are not particularly limited. Various materials which are currently used as nonaqueous solvent secondary batteries or which have been proposed can be used.

For example, as the positive electrode material, a layered oxide system (expressed as LiMO ₂ , M-based metal: for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , or LiNi _x Co _y Mo _z O ₂ can be preferably used (here, x, y, z represent composition ratio)), olivine (represented by LiMPO ₄ , M-based metal: for example, LiFePO _{4 ,} etc.), spinel (expressed by LiM ₂ O ₄ , M-based metal: for example, LiMn ₂ O _4, etc.) a composite metal chalcogen compound. These chalcogenide compounds can be used by mixing a plurality of kinds as needed. The positive electrode can be formed by forming a layer on the conductive collector material by using these positive electrode materials, a suitable binder, and a carbon material for imparting conductivity to the electrode.

The nonaqueous solvent type electrolyte solution used in the nonaqueous electrolyte secondary battery is formed by dissolving an electrolyte in a nonaqueous solvent. As the nonaqueous solvent, propyl carbonate, ethyl carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2 can be used. - an organic solvent such as methyltetrahydrofuran, cyclobutane or 1,3-dioxolane. These organic solvents can be used singly 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 or LiN(SO ₃ CF ₃ ) ₂ or the like can be used.

The nonaqueous electrolyte secondary battery is formed by immersing the positive electrode and the negative electrode formed as described above and a liquid permeable separator containing a porous material (for example, a nonwoven fabric) provided between the two electrodes in an electrolytic solution. As such a separator, a non-woven fabric or another porous material which is generally used for a secondary battery can be used. It is also possible to use a solid electrolyte containing a polymer gel which has been impregnated with an electrolyte instead of or in combination with a separator.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but these examples do not limit the scope of the invention. In addition, the measurement method of the physical property value of the carbonaceous material for nonaqueous electrolyte secondary batteries is described below, but it includes The physical property value described in the present specification is a physical property value based on a value obtained by the following method.

(Measurement of specific surface area due to nitrogen adsorption)

The approximate expression derived from the formula of BET is described below.

p /[ v ( p ₀ - p )]=(1/ v _m c )+[( c -1)/ v _m c ]( p / p ₀ )

Using the above approximate expression, V _m was obtained by a three-point method by nitrogen adsorption at a liquid nitrogen temperature, and the specific surface area of the sample was calculated by the following formula.

In this case, v _m is the amount of adsorption (cm ³ /g) required to form a monolayer on the surface of the sample, v is the measured adsorption amount (cm ³ /g), p ₀ is the saturated vapor pressure, and p is the absolute pressure. , c is a constant (reflecting the heat of adsorption), and the N-type Yafot-added number is 6.022×10 ²³ , and the area occupied by the adsorbate molecules on the surface of the sample (molecular occupied cross-sectional area) is a (nm ² ).

Specifically, the amount of nitrogen adsorbed on the carbon precursor or the carbonaceous material at a liquid nitrogen temperature was measured in the following manner using "BELL Sorb Mini" manufactured by BELL Corporation of Japan. A carbon precursor or a carbonaceous material which has been pulverized to have a particle diameter of about 5 to 50 μm is filled in the sample tube, and the sample tube is cooled to -196 ° C, temporarily decompressed, and then nitrogen is supplied at a desired relative pressure ( The purity is 99.999%) adsorbed on carbon precursors or carbonaceous materials. The amount of nitrogen adsorbed to the sample at the time of reaching the equilibrium pressure at the desired relative pressure is set to the amount of adsorbed gas v.

(measured by the average slice spacing d ₀₀₂ due to the X-ray diffraction method)

The carbonaceous material powder was filled in a sample container using "MiniFlex II manufactured by Rigaku Co., Ltd.", and an X-ray diffraction pattern was obtained by using a CuK? line which was monochromated by a Ni filter as a line source. The peak position of the diffraction pattern is obtained by the center of gravity method (the method of obtaining the position of the center of gravity of the ray and determining the peak position by the corresponding 2θ value), and using the (111) plane of the high-purity yttrium powder using the standard substance. The diffraction peak is corrected. The wavelength of the CuKα line was set to 0.15418 nm, and d _{002 was} calculated by the Bragg formula described below.

(Bragg's formula)

(Raman spectroscopy)

The Raman spectrum was measured using a LabRAM ARAMIS manufactured by Risei Co., Ltd. using a light source having a laser wavelength of 532 nm. In the test, particles in three places were randomly sampled in each sample, and further measured in two places in each sampled particle. The measurement conditions were in the wavelength range of 50 to 2000 cm ^-1 , and the cumulative number of times was 1000 times, and the average value of the total of six places was calculated.

The half-value width is obtained by approximating the spectrum obtained by the above measurement conditions by a Gaussian function and performing peak separation of the D band (near 1360 cm ^-1 ) and the G band (near 1590 cm ^-1 ).

(Elemental analysis)

Elemental analysis was carried out using an oxygen-nitrogen-hydrogen analyzer EMGA-930 manufactured by Seisakusho Co., Ltd. The detection method of the device uses oxygen: inert gas melting-non-dispersive infrared absorption method (NDIR); nitrogen-inert Gas Melting - Thermal Conductivity (TCD); Hydrogen: Inert Gas Melting - Non-Dispersive Infrared Absorption (NDIR). The calibration system was carried out using (oxygen-nitrogen) Ni capsules, TiH2 (H standard sample), and SS-3 (N, O standard sample), and 20 mg of water having been measured at 250 ° C for about 10 minutes as a pretreatment. The sample was placed in a Ni capsule and measured by degassing in an elemental analysis apparatus for 30 seconds. The analysis was performed with 3 samples, and the average value of the obtained 3 samples was taken as an analysis value.

(Measurement of residual carbon ratio)

The residual carbon ratio is measured by quantifying the amount of carbon of the high-temperature heating residue after heating the sample at a high temperature in an inert gas. High-temperature heating means that about 1 g of volatile organic matter (the correct weight is set to W ₁ (g)) is placed in a crucible, and 20 liters of nitrogen is introduced in one minute while heating at a rate of 10 ° C / min in an electric furnace. The crucible was heated from normal temperature to 800 ° C, and then heated at 800 ° C for 1 hour. The residue at this time was set to a high temperature heating residue, and the weight was set to W ₂ (g).

Next, elemental analysis was carried out in accordance with the method specified in JIS (Japanese Industrial Standards) M8819:1997, and the weight ratio P ₁ (%) of carbon in the high-temperature heating residue was measured. Using these obtained values, the residual carbon ratio P ₂ (%) was calculated by the following formula.

(Modulation example 1)

The coconut shell was broken up and subjected to dry distillation at 500 ° C to obtain coconut shell charcoal having a particle diameter of 2.360 to 0.850 mm (containing 98% by weight of the particle size). 2.360~0.850mm particles). To 100 g of this coconut shell charcoal, a gas phase deashing treatment was carried out at 870 ° C for 50 minutes while supplying nitrogen gas containing 1% by volume of hydrogen chloride gas at a flow rate of 10 L/min. Thereafter, the supply of hydrogen chloride gas was stopped, and while supplying nitrogen gas at a flow rate of 10 L/min, the gas phase deoxidation treatment was further carried out at 900 ° C for 30 minutes to obtain a carbon precursor.

The carbon precursor obtained was coarsely pulverized into an average particle diameter of 10 μm using a ball mill, and then pulverized and classified by a small jet mill (CoJet System α-mkIII, manufactured by Seishin Co., Ltd.) to obtain a carbon precursor having an average particle diameter of 9.6 μm. Things. The value of the half value width of the peak near 1360 cm ^-1 of the Raman spectrum observed by the Raman spectroscopic method of the obtained carbon precursor was 245 cm ^-1 .

(Modulation example 2)

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

(Modulation Example 3)

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

(Modulation Example 4)

A carbon precursor was obtained in the same manner as in Preparation Example 1 except that the gas phase deashing treatment temperature and the vapor phase deoxidation treatment temperature were changed to 980 °C. The value of the half value width of the peak near 1360 cm ^-1 of the Raman spectrum observed by the Raman spectroscopic method of the obtained carbon precursor was 220 cm ^-1 .

(Modulation Example 5)

A carbon precursor was obtained in the same manner as in Preparation Example 1 except that the gas phase deashing treatment temperature and the vapor phase deoxidation treatment temperature were changed to 800 °C. The value of the half value width of the peak near 1360 cm ^-1 of the Raman spectrum observed by the Raman spectroscopic method of the obtained carbon precursor was 267 cm ^-1 . The specific surface area of the obtained carbon precursor was 520 m ² /g.

(Modulation Example 6)

A carbon precursor was obtained in the same manner as in Preparation Example 2 except that the gas phase deashing treatment temperature and the vapor phase deoxidation treatment temperature were changed to 950 °C. The specific carbon surface 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 Kogyo Co., Ltd., average particle diameter: 400 μm, residual carbon ratio: 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 in a high-speed heating furnace manufactured by Motoyama Co., Ltd., at a nitrogen flow rate of 5 L per minute, at a temperature increase rate of 60 ° C per minute. After raising the temperature to 1290 ° C, it was kept at 1290 ° C (baking temperature) for 11 minutes and naturally cooled. It was confirmed that the temperature in the furnace was lowered to 200 ° C or lower, and the carbonaceous material was taken out from the furnace. The recovered carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(Example 2)

Except for the carbon precursor prepared by Modulation Example 1, and Example 1 The same was carried out to obtain a carbonaceous material. The recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(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 recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(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 recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(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 recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(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 recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(Example 7)

The same as in the first embodiment except that the firing temperature was changed to 1350 °C. The ground is carried out to obtain a carbonaceous material. The recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(Example 8)

A carbonaceous material was obtained in the same manner as in Example 2 except that the firing temperature was changed to 1,350 °C. The recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(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 recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(Embodiment 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 recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(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 recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(Embodiment 12)

In addition to changing the hold time at 1290 ° C to 23 minutes, The carbonaceous material was obtained in the same manner as in Example 9. The recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(Comparative Example 1)

9.1 g of the carbon precursor prepared in Preparation Example 4 and 0.9 g of polystyrene (manufactured by Sekisui Kogyo Co., Ltd., average particle diameter: 400 μm, residual carbon ratio: 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 in a high-speed heating furnace manufactured by Motoyama Co., Ltd., at a nitrogen flow rate of 5 L per minute, at a temperature increase rate of 60 ° C per minute. The temperature was raised to 1290 ° C, and then kept at 1290 ° C (baking temperature) for 11 minutes, and then naturally cooled. It was confirmed that the temperature in the furnace was lowered to 200 ° C or lower, and the carbonaceous material was taken out from the furnace. The recovered carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(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 recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(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 recovery amount of the carbonaceous material was 8.1 g, and the recovery rate relative to the carbon precursor was 89%. The physical properties of the obtained carbonaceous material are shown in Table 1.

(How to make the electrode)

Using the carbonaceous materials obtained in Examples 1 to 12 and Comparative Examples 1 to 3, the negative electrode was produced in the following procedure.

92 parts by mass of a carbonaceous material for a 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 pressurized 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 and discharge efficiency)

The electrode fabricated above was used as a working electrode, and metallic lithium was used as a counter electrode and a reference electrode. The solvent was used by mixing ethyl carbonate and ethyl methyl carbonate in a volume ratio of 3:7. In this solvent, 1 mol/L of LiPF _{6 was} dissolved as an electrolyte. The separator is made of fiberglass non-woven fabric. Using them, a lithium secondary battery was fabricated in a kit of hands under an argon atmosphere.

A charge and discharge test was performed using a charge and discharge tester ("TOSCAT" manufactured by Toyo Systems Co., Ltd.) using a lithium secondary battery having the above configuration. The doping of lithium was carried out at a rate of 70 mA/g with respect to the mass of the active material, and was doped until it became 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, and the doping was ended. The capacity (mAh/g) at this time is set as the charging capacity. Next, dedoping was performed at a rate of 70 mA/g with respect to the weight of the active material until the lithium potential was 2.5 V, and the capacity at this time was set as the discharge capacity. The percentage of the discharge capacity/charge capacity is set as the charge/discharge efficiency (initial charge and discharge efficiency), and is used as an index of the utilization efficiency (lithium efficiency) of lithium ions in the battery. Further, the same battery performance was measured again after 7 days, and the discharge capacity, the charge capacity, and the charge and discharge efficiency were measured. Will be charged after 7 days The value of the discharge efficiency is set to the efficiency retention rate (%) as the value of the initial charge and discharge efficiency, and is an index of durability against deterioration of the carbonaceous material. The obtained battery performance is shown in Table 2.

The difference in the value of the half value width in Table 1 is the value of the half value width before firing (the value of the half value width of the carbon precursor) and the value of the half value width after the firing (half value of the carbonaceous material) The difference in the width value). Further, in the table, the nitrogen content of the carbonaceous material means an analytical value (ratio of the weight of the nitrogen atom contained in the carbonaceous material to the weight of the carbonaceous material) obtained by elemental analysis. The oxygen content of the carbonaceous material also means the analytical value obtained by elemental analysis.

When the carbonaceous materials obtained in Examples 1 to 12 were used, the charging capacity and the discharge capacity were the same as those of the carbonaceous materials obtained in Comparative Examples 1 to 3. This value is a level that can be met. In addition, the value of the efficiency retention rate with respect to the resistance index of oxidative degradation of the carbonaceous material is also improved. Further, the moisture absorption amount of the carbonaceous materials obtained in Examples 1 to 12 was smaller than the moisture absorption amount of the carbonaceous materials obtained in Comparative Examples 1 to 3. Further, when the carbonaceous materials obtained in Examples 1 to 12 were used, the charge and discharge efficiency was good, and the efficiency retention rate after 7 days was also improved.

[Industrial availability]

The nonaqueous electrolyte secondary battery using the carbonaceous material of the present invention has good charge and discharge efficiency and lower hygroscopicity, and deterioration of the carbonaceous material hardly occurs. Therefore, it can be used particularly for long life Automotive applications such as hybrid electric vehicles (HEV) and electric vehicles (EV).

Claims (7)

A method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery, which comprises firing a mixture of a carbon precursor and a volatile organic substance having a specific surface area of 100 to 500 m ² /g in an inert gas atmosphere at 800 to 1400 ° C The step of carbonaceous materials. The method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the carbon precursor is derived from a plant. The method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the volatile organic substance is in a solid state at a normal temperature, and the residual carbon ratio is less than 5% by weight, wherein the residual carbon ratio is determined by In the inert gas, the weight of the residue obtained by raising 1 g of the volatile organic substance from room temperature to 800 ° C at a temperature increase rate of 10 ° C /min, and then ashing at 800 ° C for 1 hour and the carbon content of the residue The value determined by the product. The method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the average surface interval d ₀₀₂ of the (002) plane of the carbonaceous material calculated by the Bragg equation by the wide angle X-ray diffraction method falls on In the range of 0.38 to 0.40 nm, the specific surface area of the carbonaceous material determined by the nitrogen adsorption BET 3 point method falls within the range of 1 to 10 m ² /g. The method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery according to claim 1, wherein a value of a half value width of a peak near the 1360 cm ^-1 of the carbon precursor observed in the Raman spectrum, and the carbonaceous material The difference in the value of the half value width of the peak near the 1360 cm ^{-1 of the} material is 50 to 88 cm ^-1 . The method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery according to claim 1, wherein a value of a half value width of a peak near 1360 cm ^-1 of the carbonaceous material observed in the Raman spectrum falls between 155 and 190 cm The range of ^-1 . The method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery according to claim 1, wherein a value of a half value width of a peak near 1360 cm ^-1 of the carbon precursor observed in the Raman spectrum falls at 230 to 260 cm The range of ^-1 .