WO2019171796A1 - Method for manufacturing negative electrode material for lithium ion secondary battery - Google Patents

Method for manufacturing negative electrode material for lithium ion secondary battery Download PDF

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WO2019171796A1
WO2019171796A1 PCT/JP2019/001798 JP2019001798W WO2019171796A1 WO 2019171796 A1 WO2019171796 A1 WO 2019171796A1 JP 2019001798 W JP2019001798 W JP 2019001798W WO 2019171796 A1 WO2019171796 A1 WO 2019171796A1
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Prior art keywords
negative electrode
graphite
graphite precursor
lithium ion
ion secondary
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PCT/JP2019/001798
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French (fr)
Japanese (ja)
Inventor
間所　靖
哲夫 塩出
隆太 芳賀
古川　聡
長山　勝博
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Ｊｆｅケミカル株式会社
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Priority to CN201980001005.7A priority Critical patent/CN110268562B/en
Priority to JP2019526020A priority patent/JP6585326B1/en
Publication of WO2019171796A1 publication Critical patent/WO2019171796A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/205—Preparation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a method for producing a negative electrode material for a lithium ion secondary battery.
  • Graphite particles which are negative electrode materials for lithium ion secondary batteries, are generally produced by graphitizing a graphite precursor.
  • a graphite precursor and a binder such as coal tar, pitch or synthetic resin are mixed and stirred, and a mixture is obtained.
  • the pulverized product is put into a mold and press-molded to obtain a graphite precursor molded body.
  • This graphite precursor molded body is fired (graphitized) at 2000 ° C. or higher in a non-oxidizing atmosphere, and graphitized molded body.
  • a method for producing a graphite powder by further pulverizing the graphitized compact for example, in Patent Document 1, a graphite precursor and a binder such as coal tar, pitch or synthetic resin are mixed and stirred, and a mixture is obtained. Then, the pulverized product is put into a mold and press-molded to obtain a graphite precursor molded body. This graphite precursor molded body is fired (graphitized) at 2000 ° C. or higher in a non-oxidizing atmosphere, and graphitized molded body. And a method for producing a graphite powder
  • the raw material graphite precursor powder is placed in a crucible and fired at 2000 ° C. or higher in a non-oxidizing atmosphere in the powder state (graphitization).
  • graphitization a non-oxidizing atmosphere in the powder state
  • the method of graphitizing the graphite precursor powder as a raw material in a crucible in a powder state has a lower packing density than the method of graphitizing the graphite precursor molded body described in Patent Document 1, so The amount that can be graphitized is small, and industrial productivity is not necessarily good.
  • an object of the present invention is to provide a method for producing a negative electrode material for a lithium ion secondary battery that is excellent in productivity.
  • the present inventors filled the inside of the bag with graphite precursor powder, and then degassed and decompressed the interior of the bag, It was learned that when the maintained one was graphitized, the packing density increased, and it was not necessary to grind the lump after the graphitization, and the present invention was completed.
  • the present invention provides the following [1].
  • [1] Filling the inside of the bag with graphite precursor powder, and then degassing and decompressing the interior of the bag, and maintaining the decompressed state,
  • the graphitization step of graphitizing the graphite precursor powder by heating the bag in which the graphite precursor powder obtained in the filling step is filled and maintained in a decompressed state.
  • the manufacturing method of the negative electrode material for lithium ion secondary batteries which has this.
  • a method for producing a negative electrode material for a lithium ion secondary battery having excellent productivity can be provided.
  • FIG. 1 is a schematic cross-sectional view of an evaluation battery for evaluating battery characteristics of a negative electrode.
  • the range when a range is expressed using “ ⁇ ”, the range includes both sides of “ ⁇ ”.
  • the range expressed as “A to B” includes A and B.
  • the method for producing a negative electrode material for a lithium ion secondary battery according to the present invention is such that a graphite precursor powder is filled into a bag, and then the inside of the bag is deaerated and decompressed to maintain the decompressed state. And graphite for graphitizing the graphite precursor powder obtained by heating the bag in which the graphite precursor powder obtained by the step and the filling step is filled and the state in which the pressure is reduced is maintained. The process.
  • the method for producing a negative electrode material for a lithium ion secondary battery of the present invention can achieve high productivity because the packing density of the carbon powder is increased and the mass after graphitization is not required to be crushed. It became so.
  • the graphite precursor powder that is a raw material for the graphite particles for lithium ion secondary batteries is not particularly limited as long as it is a powder material that can be graphitized.
  • tar pitches and / or resins are heat-treated at 300 ° C. to 1200 ° C. Things can be used.
  • the atmosphere during the heat treatment may be an oxidizing atmosphere such as the air or a non-oxidizing atmosphere such as nitrogen gas or argon gas. An oxidizing atmosphere is preferred.
  • tar pitch examples include coal tar, tar light oil, tar medium oil, tar heavy oil, naphthalene oil, anthracene oil, coal tar pitch, pitch oil, mesophase pitch, oxygen-crosslinked petroleum pitch and heavy oil.
  • thermoplastic resins such as polyvinyl alcohol (PVA) and polyacrylic acid
  • thermosetting resins such as phenol resin and furan resin
  • a fired product or a calcined product of mesocarbon spherules is preferable, and a fired product of mesocarbon spherules is more preferable.
  • the method for producing a negative electrode material for a lithium ion secondary battery of the present invention does not need to be pulverized after graphitization, so that the mesophase structure of the graphite particles is less likely to be broken than when pulverized after graphitization. It is hard to spoil the excellent characteristics of
  • the mesocarbon spherules are obtained by heat-treating coal tar pitch or petroleum pitch at a temperature of about 350 to 500 ° C. for 10 minutes to 6 hours. It can be obtained by extraction and filtration.
  • the mesocarbon spherules obtained here are calcined in a non-oxidizing atmosphere at a temperature of about 200 ° C. to 500 ° C. for 2 hours to 10 hours to obtain a calcined product, and 600 ° C. to 1200 ° C.
  • a fired product can be obtained by firing at a temperature of about 0 ° C. for 2 hours to 10 hours. Both the calcined product and the calcined product may be pulverized and adjusted in particle size to obtain a graphite precursor powder.
  • the graphite precursor powder as a raw material is preferably one whose particle size is adjusted by pulverization.
  • the graphite precursor may contain a volatile component.
  • the volatile matter of the graphite precursor is not particularly limited as long as it does not adversely affect the characteristics of the resulting graphite particles for lithium ion secondary batteries, but is preferably 10% by mass with respect to the total mass of the graphite precursor. Or less, more preferably 5% by mass or less, and further preferably 2% by mass or less.
  • the average particle size of the graphite precursor is not particularly limited, but is preferably 1 to 50 ⁇ m, more preferably 3 to 35 ⁇ m, and further preferably 5 to 20 ⁇ m.
  • the average particle size of the graphite precursor is the particle size (50% particle size, D50, median size) in which the cumulative frequency of the particle size distribution measured by a laser diffraction particle size distribution meter is 50% by volume. It is.
  • binder The method for producing a negative electrode material for a lithium ion secondary battery of the present invention does not require the binder to be mixed with the graphite precursor, and it is desirable that the binder is not mixed. This does not prevent the binder from being mixed within a range that does not adversely affect the binder.
  • the binder is appropriately selected from, for example, PVA, pitch, phenol resin, and the like.
  • the amount of the binder when mixing the binder with the graphite precursor is not particularly limited as long as it does not adversely affect the characteristics of the resulting graphite particles for lithium ion secondary batteries, but with respect to the total mass of the graphite precursor.
  • the content is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 2% by mass or less.
  • the method of mixing the graphite precursor and the binder is not particularly limited, but it is preferable to mix at or above the softening temperature of the binder, and the temperature varies depending on the type of binder used, but is preferably in the range of 80 to 350 ° C.
  • a graphitization catalyst may be mixed with the graphite precursor as long as the characteristics of the obtained graphite particles for a lithium ion secondary battery are not adversely affected.
  • Mixing a graphitization catalyst with a graphite precursor to graphitize has the effect of improving the crystallinity of the resulting graphite powder.
  • the graphitization catalyst for example, at least one of metals such as silicon, boron, iron, titanium and nickel and oxides or carbides of these metals can be used.
  • the amount of the graphitization catalyst in the case of mixing the graphitization catalyst with the graphite precursor is not particularly limited as long as it does not adversely affect the characteristics of the obtained graphite particles for lithium ion secondary batteries.
  • it is 10 mass% or less with respect to the total mass, More preferably, it is 5 mass% or less, More preferably, it is 2 mass% or less.
  • the filling step is a step in which the graphite precursor powder is filled into the bag, and then the bag is deaerated and decompressed to maintain the decompressed state.
  • the material of the bag filled with the graphite precursor (hereinafter sometimes referred to simply as “bag”) is not particularly limited, but the residual carbon ratio is close to zero, such as polyethylene or polypropylene, and volatilizes during graphitization. What is done is preferable.
  • the thickness of the bag is not particularly limited, but is preferably a thickness that does not break when the graphite precursor is filled.
  • the size of the bag is not particularly limited, but can be appropriately selected depending on the size of the crucible used in the graphitization step described later, the amount of graphite powder to be produced, and the like.
  • the filling amount of the graphite precursor is not particularly limited, but can be appropriately selected depending on the size of the bag, the size of the crucible used in the graphitization step described later, the amount of the graphite powder to be produced, and the like.
  • the raw material graphite precursor may be filled with one type of graphite precursor alone in one bag, or may be filled with a combination of two or more types of graphite precursors in one bag. Also good. In addition, when two or more types of graphite precursors are filled in the same bag, those obtained by adhering, embedding or combining graphite precursors may be used. Further, carbonaceous precursor materials such as carbonaceous or graphite fibers, amorphous hard carbon, organic materials, or inorganic materials may be attached to, embedded in, or combined with the graphite precursor.
  • the graphitization step is a step of graphitizing the graphite precursor powder by heating the bag obtained by the filling step and filled with the graphite precursor powder and maintaining the reduced pressure inside. .
  • the graphitization treatment is performed by heating the graphite precursor powder filled in the bag maintained in a reduced pressure state.
  • the temperature during the graphitization treatment is not particularly limited as long as it is a temperature at which the graphite precursor powder can be graphitized, but is preferably 2000 ° C. to 3200 ° C., more preferably 2500 ° C. to 3200 ° C. More preferably, it is 2800 ° C. to 3200 ° C.
  • heating temperature in the graphitization treatment is within this range, it is possible to suppress excessive development of the crystallinity of the graphite particles.
  • the time for the graphitization treatment is not particularly limited as long as the graphite precursor powder can be graphitized, but is preferably 5 minutes to 30 hours, more preferably 30 minutes to 20 hours. .
  • the atmosphere during the graphitization treatment is not particularly limited as long as it does not interfere with the graphitization of the graphite precursor powder, but is preferably a non-oxidizing atmosphere.
  • the non-oxidizing atmosphere may be an inert gas atmosphere with an inert gas such as argon gas, helium gas or nitrogen gas, or a reducing atmosphere with a reducing gas such as hydrogen gas or carbon monoxide gas. Also good.
  • a particularly preferred atmosphere is in an argon gas stream or a nitrogen gas stream.
  • the temperature profile at the time of heating and the temperature profile at the time of heating during the graphitization treatment are not particularly limited, but various forms such as a linear heating and a stepwise heating in which the temperature is held at a constant interval can be used. It is possible to take. You may hold
  • the method of the graphitization treatment is not particularly limited, but it is preferable to heat in a state of being enclosed in a graphite crucible or the like.
  • Example 1 ⁇ Preparation of negative electrode material> ⁇ Preparation of graphite precursor powder >> A coal tar containing 0.5% by mass of free carbon (quinoline insoluble matter (QI)) was heat-treated at 350 ° C. for 0.5 hours, and then further heat-treated at 450 ° C. for 0.2 hours to obtain small mesophase carbon. A sphere was generated. Pitch was extracted from coal tar after heat treatment using tar heavy oil (boiling point: 200 to 300 ° C.). From the pitch matrix, mesophase carbon microspheres were recovered by filtration separation. The obtained mesophase carbon microspheres were calcined at 500 ° C. using a rotary kiln.
  • QI quinoline insoluble matter
  • the obtained mesophase carbon microsphere calcined product (volatile content 5 mass%) was pulverized to adjust the average particle size to 15 ⁇ m.
  • the particle size-adjusted product was fired at 1000 ° C. to make the volatile content 2% by mass or less (mesophase carbon microsphere fired product).
  • the obtained fired product was put in a polyethylene (PE) bag whose dimensions were adjusted in advance so as to fit the graphite crucible, and the bag opening was fused and sealed in a vacuum degassed state.
  • PE polyethylene
  • the prepared negative electrode mixture paste was applied to a copper foil with a uniform thickness, and the solvent was evaporated and dried at 90 ° C. in a vacuum.
  • the negative electrode mixture layer was pressed by a roll press and the electrode density was 1.70 g / cm. Adjusted to 3 .
  • a copper foil and a negative electrode mixture layer were punched out into a circular shape having a diameter of 15.5 mm to produce a working electrode (negative electrode) composed of a current collector and a negative electrode mixture adhered to the current collector.
  • a non-aqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF 6 ) in a mixed solvent of 33% by volume of ethylene carbonate and 67% by volume of methyl ethyl carbonate at a concentration of 1 mol / L.
  • the prepared nonaqueous electrolytic solution was impregnated into a polypropylene porous body (thickness 20 ⁇ m) to produce a separator impregnated with the electrolytic solution.
  • a button-type secondary battery shown in FIG. 1 was prepared as an evaluation battery.
  • the exterior cup 1 and the exterior can 3 were sealed by interposing an insulating gasket 6 at the peripheral portion thereof and caulking both peripheral portions.
  • a copper current collector 7 a made of nickel net, a circular counter electrode (positive electrode) 4 made of lithium foil, a separator 5 impregnated with an electrolytic solution, and a negative electrode mixture 2 are attached inside the outer can 3 in order from the inner surface.
  • the separator 5 impregnated with the electrolytic solution was laminated between the current collector 7b and the counter electrode 4 in close contact with the current collector 7a, and then the current collector 7b was placed in the outer cup 1 4 is accommodated in the outer can 3, the outer cup 1 and the outer can 3 are combined, and further, an insulating gasket 6 is interposed between the outer peripheral portion of the outer cup 1 and the outer can 3, and both peripheral portions are caulked and sealed. And produced.
  • the process of occluding lithium ions in the negative electrode material was charged, and the process of detaching lithium ions from the negative electrode material was discharge.
  • the loss was calculated by “the charge capacity of the first cycle” ⁇ “the discharge capacity of the first cycle”. The larger the discharge capacity, the larger the battery capacity and the better the negative electrode characteristics. The smaller the loss, the better the charge / discharge efficiency and the better the negative electrode characteristics.
  • ⁇ Average particle size> The cumulative particle size distribution measured by a laser diffraction particle size distribution meter (LMS-2000e, manufactured by Seishin Enterprise Co., Ltd.) was used as the particle size (median size, 50% particle size) at 50% by volume.
  • LMS-2000e laser diffraction particle size distribution meter
  • ⁇ Volatile matter> The amount of volatile matter was measured according to “11. Fixed carbon content determination method” of JIS K 2425: 2006. That is, 1 g of a sample (graphite precursor powder) was weighed into a crucible and heated at 430 ° C. for 30 minutes without a lid. Thereafter, a double crucible was formed and heated at 800 ° C. for 30 minutes to remove the volatile matter, and the weight loss rate of the sample was taken as the volatile matter amount.
  • the filling density when filling the crucible depends on the volume of the crucible and the graphite precursor powder filled in the crucible. Calculated from the mass of The mass of the graphite precursor powder was determined as the difference between the mass of the crucible after filling and the mass of the crucible before filling. The filling density in the case of die press molding was calculated from the volume and mass of the molded product.
  • Example 2 A negative electrode mixture, a negative electrode, and a lithium ion secondary battery were prepared in the same manner as in Example 1, except that the mesocarbon microsphere calcined product in Example 1 was pulverized so as to have an average particle size of 3 ⁇ m. And characterization was performed. The evaluation results are also shown in Table 1 below.
  • Example 3 Example 1 except that the mesophase carbon microsphere calcined product (volatile content 5 mass%) obtained in Example 1 was pulverized so as to have an average particle diameter of 3 ⁇ m and no subsequent firing treatment was performed.
  • the preparation of the negative electrode mixture, the production of the negative electrode, the production of the lithium ion secondary battery and the characteristics evaluation were performed. The evaluation results are also shown in Table 1 below.
  • Example 4 Example 1 except that the mesophase carbon microsphere calcined product obtained in Example 1 (volatile content: 5% by mass) was pulverized so as to have an average diameter of 15 ⁇ m, and the subsequent baking treatment was not performed. Similarly, preparation of a negative electrode mixture, preparation of a negative electrode, preparation of a lithium ion secondary battery, and characteristic evaluation were performed. The evaluation results are also shown in Table 1 below.
  • Example 5 Example 1 except that the mesophase carbon microsphere calcined product obtained in Example 1 (volatile content: 5% by mass) was pulverized so as to have an average diameter of 10 ⁇ m and no subsequent firing treatment was performed. Similarly, preparation of a negative electrode mixture, preparation of a negative electrode, preparation of a lithium ion secondary battery, and characteristic evaluation were performed. The evaluation results are also shown in Table 1 below.
  • Example 1 Except that no filling step was performed in Example 1, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristic evaluation were performed in the same manner as in Example 1. The evaluation results are also shown in Table 1 below.
  • Example 2 Except that no filling step was performed in Example 2, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristics evaluation were performed in the same manner as in Example 2. The evaluation results are also shown in Table 1 below.
  • Example 3 The mesophase carbon microsphere fired product obtained in Example 1 (2% by mass or less of volatile content) was put in a mold and pressed with a pressure (0.5 ton / cm 2 ) to attempt molding. However, the fired product did not form a lump and could not be molded. Therefore, it was not implemented after the graphitization step.
  • the mesocarbon microsphere fired product which is a graphite precursor, has a small volatile content of 2% by mass or less, and the binder was not mixed. It is thought.
  • Example 4 The mesophase carbon microsphere calcined product (volatile content 5 mass%) obtained in Example 1 was put into a mold and molded by pressurizing with a pressure (0.5 ton / cm 2 ). Since a lump was obtained, graphitization was performed in the same manner as in Example 1. In the same manner as in Example 1, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristic evaluation were performed. The evaluation results are also shown in Table 1 below. Unlike Comparative Example 3, in Comparative Example 4, the mesocarbon microsphere fired product, which is a graphite precursor, has a relatively large volatile content of 5% by mass. It is thought that it was possible to obtain a molded body only with this.
  • Example 5 The mesophase carbon microsphere calcined product (volatile content 5 mass%) obtained in Example 2 was put into a mold and molded by pressurizing with a pressure (0.5 ton / cm 2 ). Since a lump was obtained, graphitization was performed in the same manner as in Example 2. In the same manner as in Example 1, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristic evaluation were performed. The evaluation results are also shown in Table 1 below. As in Comparative Example 4, in Comparative Example 5, the mesocarbon microsphere fired product, which is a graphite precursor, has a relatively large volatile content of 5% by mass. It is thought that it was possible to obtain a molded body only with this.
  • Example 6 Except that no filling step was performed in Example 4, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristics evaluation were performed in the same manner as in Example 4. The evaluation results are also shown in Table 1 below.
  • Example 7 Except that no filling process was performed in Example 5, the preparation of the negative electrode mixture, the production of the negative electrode, the production of the lithium ion secondary battery, and the characteristics evaluation were performed in the same manner as in Example 5. The evaluation results are also shown in Table 1 below.
  • Example 1 since the packing density of the graphite precursor powder before graphitization was increased and the pulverization treatment after graphitization was not required, the productivity was excellent and the lithium ion secondary battery It is thought that the production cost of the negative electrode material can be reduced.
  • Examples 2 and 3 in spite of using a graphite precursor powder having an average particle size as small as 3 ⁇ m, the packing density can be increased and the pulverization after graphitization is not required. Since it was able to do it, it is excellent in productivity and it is thought that the production cost of the negative electrode material for lithium ion secondary batteries can be reduced.
  • Comparative Example 1 the graphite precursor powder was filled into a crucible and subjected to graphitization treatment. Although the packing density into the crucible was not low, there was a decrease in productivity due to the use of the crucible. The level required by the present invention was not reached.
  • Comparative Example 2 was obtained by filling a crucible with a graphite precursor powder having a small average particle diameter of 3 ⁇ m and performing a graphitization treatment. However, because the packing density into the crucible was as low as 0.3 g / cm 3 , There was a decrease in productivity due to the use of a crucible, and the level required by the present invention was not reached.
  • Comparative Example 3 could not be molded and could not be graphitized.
  • the negative electrode produced using the graphite particles (negative electrode material for lithium ion secondary batteries) obtained in Comparative Examples 4 and 5 as the negative electrode material corresponds to the average particle diameter, and the discharge capacity of the evaluation battery is that of the example. Although it was equivalent to 1 to 3, the loss was larger than those of Examples 1 to 3, and the negative electrode performance was inferior.
  • the method for producing a negative electrode material for a lithium ion secondary battery of the present invention compared to a method of filling a crucible with bulk graphite precursor powder or producing a molded body of graphite precursor powder by a die press. It is excellent in productivity and contributes to the reduction of manufacturing costs.

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Abstract

The present invention addresses the problem of providing a method for manufacturing a negative electrode material for a lithium ion secondary battery having excellent productivity. This method for manufacturing a negative electrode material for a lithium ion secondary battery comprises: a filling step in which the interior of a bag is filled with graphite precursor powder, and thereafter deaerated, decompressed, and kept in a decompressed state; and a graphitization step in which the graphite precursor powder is graphitized by heating the bag the interior of which is filled with the graphite precursor powder and kept in the decompressed state.

Description

リチウムイオン二次電池用負極材料の製造方法Method for producing negative electrode material for lithium ion secondary battery
　本発明は、リチウムイオン二次電池用負極材料の製造方法に関する。 The present invention relates to a method for producing a negative electrode material for a lithium ion secondary battery.
　リチウムイオン二次電池用負極材料である黒鉛粒子は、黒鉛前駆体を黒鉛化することにより製造することが一般的である。 Graphite particles, which are negative electrode materials for lithium ion secondary batteries, are generally produced by graphitizing a graphite precursor.
　原料である黒鉛前駆体粉末から製品としての黒鉛粉末を得るプロセスとしては、例えば、特許文献１には、黒鉛前駆体と、コールタール、ピッチまたは合成樹脂等のバインダーとを混合・撹拌し、混合物を粉砕し、粉砕物を金型に入れてプレス成形して黒鉛前駆体成形体とし、この黒鉛前駆体成形体を非酸化性雰囲気中で２０００℃以上で焼成（黒鉛化）して黒鉛化成形体とし、さらにこの黒鉛化成形体を粉砕して、黒鉛粉末を製造する方法が記載されている。 As a process for obtaining a graphite powder as a product from a graphite precursor powder as a raw material, for example, in Patent Document 1, a graphite precursor and a binder such as coal tar, pitch or synthetic resin are mixed and stirred, and a mixture is obtained. Then, the pulverized product is put into a mold and press-molded to obtain a graphite precursor molded body. This graphite precursor molded body is fired (graphitized) at 2000 ° C. or higher in a non-oxidizing atmosphere, and graphitized molded body. And a method for producing a graphite powder by further pulverizing the graphitized compact.
　また、特許文献１に記載された黒鉛粉末の製造方法以外には、原料である黒鉛前駆体粉末をるつぼに入れ、粉末状態のまま、非酸化性雰囲気中で２０００℃以上で焼成（黒鉛化）して、製品としての黒鉛粉末を得る方法がある。 In addition to the method for producing graphite powder described in Patent Document 1, the raw material graphite precursor powder is placed in a crucible and fired at 2000 ° C. or higher in a non-oxidizing atmosphere in the powder state (graphitization). Thus, there is a method for obtaining graphite powder as a product.
特開平１１－１７１５１９号公報JP 11-171519 A
　しかしながら、特許文献１に記載された黒鉛粉末の製造方法では、製品としての黒鉛粉末を得るには、黒鉛前駆体成形体を黒鉛化して得られる黒鉛化成形体を粉砕する必要がある。このため、製造方法が煩雑となり、生産性が劣る場合がある。
　さらに、黒鉛化成形体を粉砕する工程において黒鉛粒子が損傷し、電池特性の低下を招くおそれがある。 However, in the method for producing graphite powder described in Patent Document 1, in order to obtain graphite powder as a product, it is necessary to pulverize the graphitized molded body obtained by graphitizing the graphite precursor molded body. For this reason, a manufacturing method becomes complicated and productivity may be inferior.
Furthermore, in the step of pulverizing the graphitized molded body, the graphite particles may be damaged, leading to deterioration of battery characteristics.
　また、原料である黒鉛前駆体粉末を粉末状態のままるつぼ中で黒鉛化する方法は、特許文献１に記載の黒鉛前駆体成形体を黒鉛化する方法に比べて、充填密度が低いため、一度に黒鉛化できる量が少量となり、工業的な生産性が必ずしもよいとはいえない。 In addition, the method of graphitizing the graphite precursor powder as a raw material in a crucible in a powder state has a lower packing density than the method of graphitizing the graphite precursor molded body described in Patent Document 1, so The amount that can be graphitized is small, and industrial productivity is not necessarily good.
　そこで、本発明は、生産性に優れるリチウムイオン二次電池用負極材料の製造方法を提供することを課題とする。 Therefore, an object of the present invention is to provide a method for producing a negative electrode material for a lithium ion secondary battery that is excellent in productivity.
　本発明者らは、上記課題を解決すべく鋭意検討を重ねたところ、黒鉛前駆体粉末を袋の内部に充填し、その後、前記袋の内部を、脱気して減圧し、減圧した状態を維持したものを黒鉛化すると、充填密度が高くなり、また、黒鉛化後の塊状物の粉砕も必要ないことを知得し、本発明を完成させた。 As a result of intensive investigations to solve the above problems, the present inventors filled the inside of the bag with graphite precursor powder, and then degassed and decompressed the interior of the bag, It was learned that when the maintained one was graphitized, the packing density increased, and it was not necessary to grind the lump after the graphitization, and the present invention was completed.
　すなわち、本発明は次の［１］を提供する。
　［１］　黒鉛前駆体粉末を袋の内部に充填し、その後、上記袋の内部を、脱気して減圧し、減圧した状態を維持する充填工程と、
　上記充填工程で得られた、上記黒鉛前駆体粉末が内部に充填され、かつ、内部を減圧した状態が維持された上記袋を加熱して、上記黒鉛前駆体粉末を黒鉛化する黒鉛化工程と
を有するリチウムイオン二次電池用負極材料の製造方法。 That is, the present invention provides the following [1].
[1] Filling the inside of the bag with graphite precursor powder, and then degassing and decompressing the interior of the bag, and maintaining the decompressed state,
The graphitization step of graphitizing the graphite precursor powder by heating the bag in which the graphite precursor powder obtained in the filling step is filled and maintained in a decompressed state. The manufacturing method of the negative electrode material for lithium ion secondary batteries which has this.
　本発明によれば、生産性に優れるリチウムイオン二次電池用負極材料の製造方法を提供することができる。 According to the present invention, a method for producing a negative electrode material for a lithium ion secondary battery having excellent productivity can be provided.
図１は、負極の電池特性を評価するための評価電池の概略断面図である。FIG. 1 is a schematic cross-sectional view of an evaluation battery for evaluating battery characteristics of a negative electrode.
　本発明において、「～」を用いて範囲を表した場合、その範囲には「～」の両側を含むものとする。例えば、「Ａ～Ｂ」と表記される範囲には、ＡおよびＢを含む。 In the present invention, when a range is expressed using “˜”, the range includes both sides of “˜”. For example, the range expressed as “A to B” includes A and B.
［リチウムイオン二次電池用負極材料の製造方法］
　本発明のリチウムイオン二次電池用負極材料の製造方法は、黒鉛前駆体粉末を袋の内部に充填し、その後、上記袋の内部を、脱気して減圧し、減圧した状態を維持する充填工程と、上記充填工程で得られた、上記黒鉛前駆体粉末が内部に充填され、かつ、内部を減圧した状態が維持された上記袋を加熱して、上記黒鉛前駆体粉末を黒鉛化する黒鉛化工程とを有する。 [Method for producing negative electrode material for lithium ion secondary battery]
The method for producing a negative electrode material for a lithium ion secondary battery according to the present invention is such that a graphite precursor powder is filled into a bag, and then the inside of the bag is deaerated and decompressed to maintain the decompressed state. And graphite for graphitizing the graphite precursor powder obtained by heating the bag in which the graphite precursor powder obtained by the step and the filling step is filled and the state in which the pressure is reduced is maintained. The process.
　本発明のリチウムイオン二次電池用負極材料の製造方法は、炭素粉末の充填密度を高めたこと、また、黒鉛化後の塊状物の粉砕が必要ではなくなったことから、高い生産性を達成できるようになった。 The method for producing a negative electrode material for a lithium ion secondary battery of the present invention can achieve high productivity because the packing density of the carbon powder is increased and the mass after graphitization is not required to be crushed. It became so.
〈原料および添加物〉
　原料である黒鉛前駆体粉末、ならびに黒鉛前駆体と混合して本発明の製造方法に供することができるバインダーおよび黒鉛化触媒について説明する。 <Raw materials and additives>
The raw material graphite precursor powder, and the binder and graphitization catalyst that can be mixed with the graphite precursor and used for the production method of the present invention will be described.
《黒鉛前駆体粉末》
　リチウムイオン二次電池用黒鉛粒子の原料である黒鉛前駆体粉末は、黒鉛化できる粉末材料であれば特に制限はなく、例えば、タールピッチ類および／または樹脂類を３００℃～１２００℃で熱処理したもの等を使用することができる。熱処理の際の雰囲気は、大気中等の酸化性雰囲気中であってもよいし、窒素ガス中またはアルゴンガス中等の非酸化性雰囲気であってもよいが、７００℃以上で熱処理する場合は、非酸化性雰囲気が好ましい。 <Graphite precursor powder>
The graphite precursor powder that is a raw material for the graphite particles for lithium ion secondary batteries is not particularly limited as long as it is a powder material that can be graphitized. For example, tar pitches and / or resins are heat-treated at 300 ° C. to 1200 ° C. Things can be used. The atmosphere during the heat treatment may be an oxidizing atmosphere such as the air or a non-oxidizing atmosphere such as nitrogen gas or argon gas. An oxidizing atmosphere is preferred.
　上記タールピッチ類としては、例えば、コールタール、タール軽油、タール中油、タール重油、ナフタリン油、アントラセン油、コールタールピッチ、ピッチ油、メソフェーズピッチ、酸素架橋石油ピッチおよびヘビーオイル等が挙げられる。 Examples of the tar pitch include coal tar, tar light oil, tar medium oil, tar heavy oil, naphthalene oil, anthracene oil, coal tar pitch, pitch oil, mesophase pitch, oxygen-crosslinked petroleum pitch and heavy oil.
　上記樹脂類としては、例えば、ポリビニルアルコール（ＰＶＡ）およびポリアクリル酸等の熱可塑性樹脂、ならびにフェノール樹脂およびフラン樹脂等の熱硬化性樹脂が挙げられる。 Examples of the resins include thermoplastic resins such as polyvinyl alcohol (PVA) and polyacrylic acid, and thermosetting resins such as phenol resin and furan resin.
　黒鉛前駆体としては、メソカーボン小球体の焼成品または仮焼品が好ましく、メソカーボン小球体の焼成品がより好ましい。本発明のリチウムイオン二次電池用負極材料の製造方法は、黒鉛化の後に粉砕する必要がないので、黒鉛化の後に粉砕する場合に比べて、黒鉛粒子のメソフェーズ構造が壊れにくく、負極材料としての優れた特性を損ないにくい。 As the graphite precursor, a fired product or a calcined product of mesocarbon spherules is preferable, and a fired product of mesocarbon spherules is more preferable. The method for producing a negative electrode material for a lithium ion secondary battery of the present invention does not need to be pulverized after graphitization, so that the mesophase structure of the graphite particles is less likely to be broken than when pulverized after graphitization. It is hard to spoil the excellent characteristics of
　メソカーボン小球体は、例えば、コールタールピッチまたは石油系ピッチを、３５０～５００℃程度の温度で１０分～６時間加熱処理してピッチ中に生成した光学的異方性小球体を、溶剤により抽出し、ろ過することにより得ることができる。
　ここで得られたメソカーボン小球体を、非酸化性雰囲気中で、２００℃～５００℃程度の温度で２時間～１０時間仮焼することにより仮焼品を得ることができ、６００℃～１２００℃程度の温度で２時間～１０時間焼成することにより焼成品を得ることができる。仮焼品および焼成品のいずれも、粉砕および粒度調整を行って、黒鉛前駆体粉末としてもよい。 The mesocarbon spherules, for example, are obtained by heat-treating coal tar pitch or petroleum pitch at a temperature of about 350 to 500 ° C. for 10 minutes to 6 hours. It can be obtained by extraction and filtration.
The mesocarbon spherules obtained here are calcined in a non-oxidizing atmosphere at a temperature of about 200 ° C. to 500 ° C. for 2 hours to 10 hours to obtain a calcined product, and 600 ° C. to 1200 ° C. A fired product can be obtained by firing at a temperature of about 0 ° C. for 2 hours to 10 hours. Both the calcined product and the calcined product may be pulverized and adjusted in particle size to obtain a graphite precursor powder.
　本発明の製造方法においては、原料である黒鉛前駆体粉末は、粉砕により粒度調整したものであることが好ましい。 In the production method of the present invention, the graphite precursor powder as a raw material is preferably one whose particle size is adjusted by pulverization.
（黒鉛前駆体の揮発分）
　上記黒鉛前駆体は、揮発分を含んでいてもよい。
　黒鉛前駆体の揮発分は、得られるリチウムイオン二次電池用黒鉛粒子の特性に悪影響を与えない範囲内であれば特に限定されないが、黒鉛前駆体の合計質量に対して、好ましくは１０質量％以下であり、より好ましくは５質量％以下であり、さらに好ましくは２質量％以下である。 (Volatile content of graphite precursor)
The graphite precursor may contain a volatile component.
The volatile matter of the graphite precursor is not particularly limited as long as it does not adversely affect the characteristics of the resulting graphite particles for lithium ion secondary batteries, but is preferably 10% by mass with respect to the total mass of the graphite precursor. Or less, more preferably 5% by mass or less, and further preferably 2% by mass or less.
（黒鉛前駆体の平均粒子径）
　黒鉛前駆体の平均粒子径は、特に限定されないが、好ましくは１～５０μｍであり、より好ましくは３～３５μｍであり、さらに好ましくは５～２０μｍである。
　なお、本発明において、黒鉛前駆体の平均粒子径は、レーザー回折式粒度分布計により測定した粒度分布の累積度数が体積百分率で５０％となる粒子径（５０％粒子径、Ｄ５０、メジアン径）である。 (Average particle diameter of graphite precursor)
The average particle size of the graphite precursor is not particularly limited, but is preferably 1 to 50 μm, more preferably 3 to 35 μm, and further preferably 5 to 20 μm.
In the present invention, the average particle size of the graphite precursor is the particle size (50% particle size, D50, median size) in which the cumulative frequency of the particle size distribution measured by a laser diffraction particle size distribution meter is 50% by volume. It is.
《バインダー》
　本発明のリチウムイオン二次電池用負極材料の製造方法は、黒鉛前駆体にバインダーを混合することを必要とせず、混合しないことが望ましいが、得られるリチウムイオン二次電池用黒鉛粒子の特性に悪影響を与えない範囲でバインダーを混合することを妨げるものではない。
　上記バインダーとしては、例えば、ＰＶＡ、ピッチおよびフェノール樹脂等から適宜選択される。
　黒鉛前駆体にバインダーを混合する場合のバインダーの量は、得られるリチウムイオン二次電池用黒鉛粒子の特性に悪影響を与えない範囲内であれば特に限定されないが、黒鉛前駆体の合計質量に対して、好ましくは１０質量％以下であり、より好ましくは５質量％以下であり、さらに好ましくは２質量％以下である。
　黒鉛前駆体とバインダーを混合する方法は、特に限定されないが、バインダーの軟化温度以上で混合することが好ましく、その温度は使用するバインダーの種類によって異なるが、８０～３５０℃の範囲が好ましい。 "binder"
The method for producing a negative electrode material for a lithium ion secondary battery of the present invention does not require the binder to be mixed with the graphite precursor, and it is desirable that the binder is not mixed. This does not prevent the binder from being mixed within a range that does not adversely affect the binder.
The binder is appropriately selected from, for example, PVA, pitch, phenol resin, and the like.
The amount of the binder when mixing the binder with the graphite precursor is not particularly limited as long as it does not adversely affect the characteristics of the resulting graphite particles for lithium ion secondary batteries, but with respect to the total mass of the graphite precursor. The content is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 2% by mass or less.
The method of mixing the graphite precursor and the binder is not particularly limited, but it is preferable to mix at or above the softening temperature of the binder, and the temperature varies depending on the type of binder used, but is preferably in the range of 80 to 350 ° C.
《黒鉛化触媒》
　本発明のリチウムイオン二次電池用負極材料の製造方法は、得られるリチウムイオン二次電池用黒鉛粒子の特性に悪影響を与えない範囲で黒鉛前駆体に黒鉛化触媒を混合してもよい。黒鉛化触媒を黒鉛前駆体と混合して黒鉛化すると、得られる黒鉛粉末の結晶性が向上する効果がある。
　上記黒鉛化触媒としては、例えば、ケイ素、ホウ素、鉄、チタンおよびニッケル等の金属ならびにこれらの金属の酸化物または炭化物等の少なくとも１種を使用することができる。
　黒鉛前駆体に黒鉛化触媒を混合する場合の黒鉛化触媒の量は、得られるリチウムイオン二次電池用黒鉛粒子の特性に悪影響を与えない範囲内であれば特に限定されないが、黒鉛前駆体の合計質量に対して、好ましくは１０質量％以下であり、より好ましくは５質量％以下であり、さらに好ましくは２質量％以下である。 《Graphitization catalyst》
In the method for producing a negative electrode material for a lithium ion secondary battery of the present invention, a graphitization catalyst may be mixed with the graphite precursor as long as the characteristics of the obtained graphite particles for a lithium ion secondary battery are not adversely affected. Mixing a graphitization catalyst with a graphite precursor to graphitize has the effect of improving the crystallinity of the resulting graphite powder.
As the graphitization catalyst, for example, at least one of metals such as silicon, boron, iron, titanium and nickel and oxides or carbides of these metals can be used.
The amount of the graphitization catalyst in the case of mixing the graphitization catalyst with the graphite precursor is not particularly limited as long as it does not adversely affect the characteristics of the obtained graphite particles for lithium ion secondary batteries. Preferably it is 10 mass% or less with respect to the total mass, More preferably, it is 5 mass% or less, More preferably, it is 2 mass% or less.
〈充填工程および黒鉛化工程〉
　本発明の製造方法における充填工程および黒鉛化工程について説明する。 <Filling process and graphitization process>
The filling step and graphitization step in the production method of the present invention will be described.
《充填工程》
　充填工程は、黒鉛前駆体粉末を袋の内部に充填し、その後、袋の内部を、脱気して減圧し、減圧した状態を維持する工程である。 《Filling process》
The filling step is a step in which the graphite precursor powder is filled into the bag, and then the bag is deaerated and decompressed to maintain the decompressed state.
（黒鉛前駆体を充填する袋）
　黒鉛前駆体を充填する袋（以下、単に「袋」という場合がある。）の材質は、特に限定されないが、ポリエチレンまたはポリプロピレンなどのように残炭率がゼロに近く、黒鉛化の際に揮発してしまうものが好ましい。
　また、袋の厚みは、特に限定されないが、黒鉛前駆体を充填した際に破れない厚みのものが好ましい。
　また、袋のサイズは、特に限定されないが、後述する黒鉛化工程で使用するるつぼの大きさ、製造する黒鉛粉末の量などにより、適宜選択することができる。
　また、黒鉛前駆体の充填量は、特に限定されないが、袋のサイズ、後述する黒鉛化工程で使用するるつぼの大きさ、製造する黒鉛粉末の量などにより、適宜選択することができる。 (Bag filled with graphite precursor)
The material of the bag filled with the graphite precursor (hereinafter sometimes referred to simply as “bag”) is not particularly limited, but the residual carbon ratio is close to zero, such as polyethylene or polypropylene, and volatilizes during graphitization. What is done is preferable.
Moreover, the thickness of the bag is not particularly limited, but is preferably a thickness that does not break when the graphite precursor is filled.
The size of the bag is not particularly limited, but can be appropriately selected depending on the size of the crucible used in the graphitization step described later, the amount of graphite powder to be produced, and the like.
Moreover, the filling amount of the graphite precursor is not particularly limited, but can be appropriately selected depending on the size of the bag, the size of the crucible used in the graphitization step described later, the amount of the graphite powder to be produced, and the like.
（充填）
　充填工程においては、原料である黒鉛前駆体は、１つの袋に１種類の黒鉛前駆体を単独で充填してもよいし、１つの袋に２種類以上の黒鉛前駆体を組み合わせて充填してもよい。
　また、２種類以上の黒鉛前駆体を同一の袋に充填する場合は、黒鉛前駆体どうしを、付着、埋設または複合したものを用いてもよい。
　さらに、黒鉛前駆体に、炭素質もしくは黒鉛質の繊維、非晶質ハードカーボンなどの炭素質前駆体材料、有機材料または無機材料を、付着、埋設または複合して用いてもよい。 (filling)
In the filling step, the raw material graphite precursor may be filled with one type of graphite precursor alone in one bag, or may be filled with a combination of two or more types of graphite precursors in one bag. Also good.
In addition, when two or more types of graphite precursors are filled in the same bag, those obtained by adhering, embedding or combining graphite precursors may be used.
Further, carbonaceous precursor materials such as carbonaceous or graphite fibers, amorphous hard carbon, organic materials, or inorganic materials may be attached to, embedded in, or combined with the graphite precursor.
（脱気・減圧状態の維持）
　黒鉛前駆体が充填された袋の内部を脱気して減圧することにより、黒鉛前駆体の充填密度を上昇させ、充填密度を上昇させた状態で、袋をシールして、袋の内部を減圧した状態を維持する。
　脱気は、例えば、バキュームコンパクター（壽環境機材社製）などを用いて行うことができる。脱気して減圧した袋の内部の気圧は、０Ｐａ～２０００Ｐａ程度とすることが好ましい。 (Maintaining deaeration and decompression)
By degassing and depressurizing the inside of the bag filled with the graphite precursor, the packing density of the graphite precursor is increased, and the bag is sealed while the packing density is increased, and the inside of the bag is depressurized. Maintain the state.
Deaeration can be performed using, for example, a vacuum compactor (manufactured by Sakai Environmental Equipment Co., Ltd.). The pressure inside the bag deaerated and depressurized is preferably about 0 to 2000 Pa.
《黒鉛化工程》
　黒鉛化工程は、充填工程で得られた、黒鉛前駆体粉末が内部に充填され、かつ、内部を減圧した状態が維持された袋を加熱して、黒鉛前駆体粉末を黒鉛化する工程である。 《Graphitization process》
The graphitization step is a step of graphitizing the graphite precursor powder by heating the bag obtained by the filling step and filled with the graphite precursor powder and maintaining the reduced pressure inside. .
　減圧状態が維持された袋の内部に充填された黒鉛前駆体粉末を加熱することにより黒鉛化処理を行う。 The graphitization treatment is performed by heating the graphite precursor powder filled in the bag maintained in a reduced pressure state.
　黒鉛化処理の際の温度（加熱温度）は、黒鉛前駆体粉末を黒鉛化できる温度であれば特に限定されないが、好ましくは２０００℃～３２００℃であり、より好ましくは２５００℃～３２００℃であり、さらに好ましくは２８００℃～３２００℃である。黒鉛化処理の際の加熱温度がこの範囲内であると、黒鉛粒子の結晶性が過度に発達することを抑制することができる。 The temperature during the graphitization treatment (heating temperature) is not particularly limited as long as it is a temperature at which the graphite precursor powder can be graphitized, but is preferably 2000 ° C. to 3200 ° C., more preferably 2500 ° C. to 3200 ° C. More preferably, it is 2800 ° C. to 3200 ° C. When the heating temperature in the graphitization treatment is within this range, it is possible to suppress excessive development of the crystallinity of the graphite particles.
　黒鉛化処理の際の時間（加熱時間）は、黒鉛前駆体粉末を黒鉛化できる時間であれば特に限定されないが、好ましくは５分～３０時間であり、より好ましくは３０分～２０時間である。 The time for the graphitization treatment (heating time) is not particularly limited as long as the graphite precursor powder can be graphitized, but is preferably 5 minutes to 30 hours, more preferably 30 minutes to 20 hours. .
　黒鉛化処理の際の雰囲気は、黒鉛前駆体粉末の黒鉛化に差し支えないものであれば特に限定されないが、好ましくは非酸化性雰囲気である。
　非酸化性雰囲気は、アルゴンガス、ヘリウムガスまたは窒素ガス等の不活性ガスによる不活性ガス雰囲気であってもよいし、水素ガスまたは一酸化炭素ガス等の還元性ガスによる還元性雰囲気であってもよい。特に好ましい雰囲気は、アルゴンガス気流中または窒素ガス気流中である。 The atmosphere during the graphitization treatment is not particularly limited as long as it does not interfere with the graphitization of the graphite precursor powder, but is preferably a non-oxidizing atmosphere.
The non-oxidizing atmosphere may be an inert gas atmosphere with an inert gas such as argon gas, helium gas or nitrogen gas, or a reducing atmosphere with a reducing gas such as hydrogen gas or carbon monoxide gas. Also good. A particularly preferred atmosphere is in an argon gas stream or a nitrogen gas stream.
　黒鉛化処理の際の、昇温時の温度プロファイルおよび加熱時の温度プロファイルは、特に限定されないが、直線的な昇温、一定間隔で温度をホールドする段階的な昇温などの様々な形態をとることが可能である。２０００℃以下の温度で所定時間保持してもよい。 The temperature profile at the time of heating and the temperature profile at the time of heating during the graphitization treatment are not particularly limited, but various forms such as a linear heating and a stepwise heating in which the temperature is held at a constant interval can be used. It is possible to take. You may hold | maintain for a predetermined time at the temperature of 2000 degrees C or less.
　黒鉛化処理の方法は、特に限定されないが、黒鉛るつぼ等に封入した状態で加熱することが好ましい。 The method of the graphitization treatment is not particularly limited, but it is preferable to heat in a state of being enclosed in a graphite crucible or the like.
［実施例１］
〈負極材料の作製〉
《黒鉛前駆体粉末の調製》
　フリーカーボン（キノリン不溶分（ＱＩ））を０．５質量％含有するコールタールを、３５０℃で０．５時間加熱処理した後、さらに４５０℃で０．２時間加熱処理して、メソフェーズカーボン小球体を生成させた。
　タール重油（沸点：２００～３００℃）を用いて、加熱処理後のコールタールからピッチを抽出した。ピッチマトリックス中から、ろ過分離により、メソフェーズカーボン小球体を回収した。
　得られたメソフェーズカーボン小球体を、ロータリーキルンを用いて５００℃で仮焼した。得られたメソフェーズカーボン小球体仮焼品（揮発分５質量％）を粉砕して、平均粒子径を１５μｍに調整した。この粒度調整品を１０００℃で焼成し揮発分を２質量％以下（メソフェーズカーボン小球体焼成品）とした。 [Example 1]
<Preparation of negative electrode material>
<< Preparation of graphite precursor powder >>
A coal tar containing 0.5% by mass of free carbon (quinoline insoluble matter (QI)) was heat-treated at 350 ° C. for 0.5 hours, and then further heat-treated at 450 ° C. for 0.2 hours to obtain small mesophase carbon. A sphere was generated.
Pitch was extracted from coal tar after heat treatment using tar heavy oil (boiling point: 200 to 300 ° C.). From the pitch matrix, mesophase carbon microspheres were recovered by filtration separation.
The obtained mesophase carbon microspheres were calcined at 500 ° C. using a rotary kiln. The obtained mesophase carbon microsphere calcined product (volatile content 5 mass%) was pulverized to adjust the average particle size to 15 μm. The particle size-adjusted product was fired at 1000 ° C. to make the volatile content 2% by mass or less (mesophase carbon microsphere fired product).
《充填工程》
　得られた焼成品を、あらかじめ黒鉛るつぼに合うように寸法を調整したポリエチレン（ＰＥ）製袋に入れ、減圧脱気した状態で袋の開口部を融着封止した。 《Filling process》
The obtained fired product was put in a polyethylene (PE) bag whose dimensions were adjusted in advance so as to fit the graphite crucible, and the bag opening was fused and sealed in a vacuum degassed state.
《黒鉛化工程》
　この状態で黒鉛るつぼに封入し、アルゴン雰囲気下、昇温速度１０００℃／時間で昇温し、３０００℃で３時間かけて黒鉛化処理を行った。黒鉛化工程で袋は分解消失し、得られた黒鉛粉末は篩目５３μｍの振動篩で粗粒を除去し、負極材料を作製した。 《Graphitization process》
In this state, it was sealed in a graphite crucible, heated in an argon atmosphere at a heating rate of 1000 ° C./hour, and graphitized at 3000 ° C. for 3 hours. In the graphitization step, the bag was decomposed and disappeared, and the obtained graphite powder was coarsely removed with a vibrating sieve having a mesh size of 53 μm to produce a negative electrode material.
〈負極合剤ペーストの作製〉
　作製した負極材料９８質量部と、カルボキシメチルセルロースを１質量部と、スチレン－ブタジエンゴム１質量部とを水に入れ、撹拌して負極合剤ペーストを作製した。 <Preparation of negative electrode mixture paste>
98 parts by mass of the prepared negative electrode material, 1 part by mass of carboxymethylcellulose, and 1 part by mass of styrene-butadiene rubber were put in water and stirred to prepare a negative electrode mixture paste.
〈作用電極（負極）の作製〉
　作製した負極合剤ペーストを、銅箔に均一な厚さで塗布し、真空中９０℃で溶剤を揮発させて乾燥し、負極合剤層をロールプレスによって加圧し電極密度を１．７０ｇ／ｃｍ3に調整した。銅箔と負極合剤層を直径１５．５ｍｍの円形状に打抜いて、集電体と、該集電体に密着した負極合剤とからなる作用電極（負極）を作製した。 <Production of working electrode (negative electrode)>
The prepared negative electrode mixture paste was applied to a copper foil with a uniform thickness, and the solvent was evaporated and dried at 90 ° C. in a vacuum. The negative electrode mixture layer was pressed by a roll press and the electrode density was 1.70 g / cm. Adjusted to 3 . A copper foil and a negative electrode mixture layer were punched out into a circular shape having a diameter of 15.5 mm to produce a working electrode (negative electrode) composed of a current collector and a negative electrode mixture adhered to the current collector.
〈対極（正極）の作製〉
　リチウム金属箔をニッケルネットに押付け、直径１５．５ｍｍの円形状に打抜いて、ニッケルネットからなる集電体と、この集電体に密着したリチウム金属箔（厚み０．５ｍｍ）からなる対極（正極）を作製した。 <Preparation of counter electrode (positive electrode)>
A lithium metal foil is pressed against a nickel net and punched into a circular shape with a diameter of 15.5 mm. A current collector made of nickel net and a counter electrode made of a lithium metal foil (thickness 0.5 mm) adhered to the current collector ( Positive electrode) was prepared.
〈電解液、セパレータ〉
　エチレンカーボネート３３体積％－メチルエチルカーボネート６７体積％の混合溶剤に、ヘキサフルオロリン酸リチウム（ＬｉＰＦ6）を１ｍｏｌ／Ｌとなる濃度で溶解させ、非水電解液を調製した。
　調製した非水電解液をポリプロピレン多孔質体（厚み２０μｍ）に含浸させ、電解液が含浸したセパレータを作製した。 <Electrolyte, separator>
A non-aqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF 6 ) in a mixed solvent of 33% by volume of ethylene carbonate and 67% by volume of methyl ethyl carbonate at a concentration of 1 mol / L.
The prepared nonaqueous electrolytic solution was impregnated into a polypropylene porous body (thickness 20 μm) to produce a separator impregnated with the electrolytic solution.
〈評価電池の作製〉
　評価電池として図１に示すボタン型二次電池を作製した。
　外装カップ１と外装缶３は、その周縁部において絶縁ガスケット６を介在させ、両周縁部をかしめて密閉した。その内部に外装缶３の内面から順に、ニッケルネットからなる集電体７ａ、リチウム箔よりなる円形状の対極（正極）４、電解液が含浸されたセパレータ５、負極合剤２が付着した銅箔からなる集電体（負極）７ｂが積層された電池系である。
　前記評価電池は電解液を含浸させたセパレータ５を集電体７ｂと、集電体７ａに密着した対極４との間に挟んで積層した後、集電体７ｂを外装カップ１内に、対極４を外装缶３内に収容して、外装カップ１と外装缶３とを合わせ、さらに、外装カップ１と外装缶３との周縁部に絶縁ガスケット６を介在させ、両周縁部をかしめて密閉して作製した。 <Production of evaluation battery>
A button-type secondary battery shown in FIG. 1 was prepared as an evaluation battery.
The exterior cup 1 and the exterior can 3 were sealed by interposing an insulating gasket 6 at the peripheral portion thereof and caulking both peripheral portions. A copper current collector 7 a made of nickel net, a circular counter electrode (positive electrode) 4 made of lithium foil, a separator 5 impregnated with an electrolytic solution, and a negative electrode mixture 2 are attached inside the outer can 3 in order from the inner surface. This is a battery system in which a current collector (negative electrode) 7b made of foil is laminated.
In the evaluation battery, the separator 5 impregnated with the electrolytic solution was laminated between the current collector 7b and the counter electrode 4 in close contact with the current collector 7a, and then the current collector 7b was placed in the outer cup 1 4 is accommodated in the outer can 3, the outer cup 1 and the outer can 3 are combined, and further, an insulating gasket 6 is interposed between the outer peripheral portion of the outer cup 1 and the outer can 3, and both peripheral portions are caulked and sealed. And produced.
〈負極特性〉
　充放電特性は以下の方法により測定した。結果を表１に示した。
　回路電圧が１ｍＶに達するまで０．９ｍＡの定電流充電を行った後、回路電圧が１ｍＶに達した時点で定電圧充電に切替え、さらに電流値が２０μＡになるその間の通電量から充電容量（単位：ｍＡｈ／ｇ）を求めた。その後、１０分間休止した。次に０．９ｍＡの電流値で、回路電圧が１．５Ｖに達するまで定電流放電を行い、この間の通電量から放電容量（単位：ｍＡｈ／ｇ）を求めた。これを第１サイクルとした。
　なおこの試験では、リチウムイオンを負極材料に吸蔵する過程を充電、負極材料からリチウムイオンが脱離する過程を放電とした。
　ロスは、「第１サイクルの充電容量」－「第１サイクルの放電容量」で計算した。
　放電容量が大きいほど、電池容量が大きく、負極特性が優れる。
　ロスが小さいほど、充放電の効率がよく、負極特性が優れる。 <Negative electrode characteristics>
The charge / discharge characteristics were measured by the following method. The results are shown in Table 1.
After constant current charging of 0.9 mA until the circuit voltage reaches 1 mV, switching to constant voltage charging is performed when the circuit voltage reaches 1 mV, and the current capacity becomes 20 μA. : MAh / g). Then, it rested for 10 minutes. Next, constant current discharge was performed at a current value of 0.9 mA until the circuit voltage reached 1.5 V, and the discharge capacity (unit: mAh / g) was determined from the amount of electricity supplied during this period. This was the first cycle.
In this test, the process of occluding lithium ions in the negative electrode material was charged, and the process of detaching lithium ions from the negative electrode material was discharge.
The loss was calculated by “the charge capacity of the first cycle” − “the discharge capacity of the first cycle”.
The larger the discharge capacity, the larger the battery capacity and the better the negative electrode characteristics.
The smaller the loss, the better the charge / discharge efficiency and the better the negative electrode characteristics.
〈平均粒子径〉
　レーザー回折式粒度分布計（ＬＭＳ－２０００ｅ，セイシン企業社製）により測定した粒度分布の累積度数が、体積百分率で５０％となる粒子径（メジアン径、５０％粒子径）とした。 <Average particle size>
The cumulative particle size distribution measured by a laser diffraction particle size distribution meter (LMS-2000e, manufactured by Seishin Enterprise Co., Ltd.) was used as the particle size (median size, 50% particle size) at 50% by volume.
〈比表面積〉
　粉体分析装置（Ｍａｃｓｏｒｂ（登録商標），マウンテック社製）を用いて、窒素ガス吸着によるＢＥＴ１点法で求めた。 <Specific surface area>
Using a powder analyzer (Macsorb (registered trademark), manufactured by Mountec Co., Ltd.), the BET one-point method by nitrogen gas adsorption was used.
〈揮発分〉
　揮発分量はＪＩＳ　Ｋ　２４２５：２００６の「１１．固定炭素分定量方法」に準拠して測定した。すなわち、試料（黒鉛前駆体粉末）１ｇをるつぼに量り取り、蓋をしないで４３０℃で３０分間加熱した。その後、二重るつぼとし、８００℃で３０分間加熱して揮発分を除き、試料の減量率を揮発分量とした。 <Volatile matter>
The amount of volatile matter was measured according to “11. Fixed carbon content determination method” of JIS K 2425: 2006. That is, 1 g of a sample (graphite precursor powder) was weighed into a crucible and heated at 430 ° C. for 30 minutes without a lid. Thereafter, a double crucible was formed and heated at 800 ° C. for 30 minutes to remove the volatile matter, and the weight loss rate of the sample was taken as the volatile matter amount.
〈充填密度〉
　るつぼに充填した場合（袋（黒鉛前駆体粉末入り）をるつぼに充填した場合も粉をるつぼに充填した場合もともに）の充填密度は、るつぼ内容積と、るつぼ内に充填した黒鉛前駆体粉末の質量から算出した。なお、黒鉛前駆体粉末の質量は、充填後のるつぼの質量と充填前のるつぼの質量の差として求めた。
　金型プレス成形した場合の充填密度は、成形品の体積および質量から算出した。 <Filling density>
The filling density when filling the crucible (both when the bag (with graphite precursor powder) is filled into the crucible and when the powder is filled into the crucible) depends on the volume of the crucible and the graphite precursor powder filled in the crucible. Calculated from the mass of The mass of the graphite precursor powder was determined as the difference between the mass of the crucible after filling and the mass of the crucible before filling.
The filling density in the case of die press molding was calculated from the volume and mass of the molded product.
〈黒鉛化後の粉砕の要否の判断基準〉
　黒鉛化後の粉砕の要否は、軽く振動を与えて、塊状の黒鉛粉末が崩れたものについて、「不要」と判断し、崩れなかったものについて、「要」と判断した。 <Criteria for determining the necessity of pulverization after graphitization>
The necessity of pulverization after graphitization was determined as “unnecessary” when the massive graphite powder was broken by applying light vibrations, and “necessary” when it was not broken.
［実施例２］
　実施例１においてメソカーボン小球体仮焼品を平均粒子径が３μｍとなるように粉砕したこと以外は、実施例１と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。 [Example 2]
A negative electrode mixture, a negative electrode, and a lithium ion secondary battery were prepared in the same manner as in Example 1, except that the mesocarbon microsphere calcined product in Example 1 was pulverized so as to have an average particle size of 3 μm. And characterization was performed. The evaluation results are also shown in Table 1 below.
［実施例３］
　実施例１において得られたメソフェーズカーボン小球体仮焼品（揮発分５質量％）を平均粒子径が３μｍとなるように粉砕し、かつその後の焼成処理を行わなかったこと以外は、実施例１と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。 [Example 3]
Example 1 except that the mesophase carbon microsphere calcined product (volatile content 5 mass%) obtained in Example 1 was pulverized so as to have an average particle diameter of 3 μm and no subsequent firing treatment was performed. In the same manner as above, the preparation of the negative electrode mixture, the production of the negative electrode, the production of the lithium ion secondary battery and the characteristics evaluation were performed. The evaluation results are also shown in Table 1 below.
［実施例４］
　実施例１において得られたメソフェーズカーボン小球体仮焼品（揮発分５質量％）を平均径が１５μｍとなるように粉砕し、かつその後の焼成処理を行わなかったこと以外は、実施例１と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。 [Example 4]
Example 1 except that the mesophase carbon microsphere calcined product obtained in Example 1 (volatile content: 5% by mass) was pulverized so as to have an average diameter of 15 μm, and the subsequent baking treatment was not performed. Similarly, preparation of a negative electrode mixture, preparation of a negative electrode, preparation of a lithium ion secondary battery, and characteristic evaluation were performed. The evaluation results are also shown in Table 1 below.
［実施例５］
　実施例１において得られたメソフェーズカーボン小球体仮焼品（揮発分５質量％）を平均径が１０μｍとなるように粉砕し、かつその後の焼成処理を行わなかったこと以外は、実施例１と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。 [Example 5]
Example 1 except that the mesophase carbon microsphere calcined product obtained in Example 1 (volatile content: 5% by mass) was pulverized so as to have an average diameter of 10 μm and no subsequent firing treatment was performed. Similarly, preparation of a negative electrode mixture, preparation of a negative electrode, preparation of a lithium ion secondary battery, and characteristic evaluation were performed. The evaluation results are also shown in Table 1 below.
［比較例１］
　実施例１において充填工程を何ら行わなかったこと以外は、実施例１と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。 [Comparative Example 1]
Except that no filling step was performed in Example 1, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristic evaluation were performed in the same manner as in Example 1. The evaluation results are also shown in Table 1 below.
［比較例２］
　実施例２において充填工程を何ら行わなかったこと以外は、実施例２と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。 [Comparative Example 2]
Except that no filling step was performed in Example 2, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristics evaluation were performed in the same manner as in Example 2. The evaluation results are also shown in Table 1 below.
［比較例３］
　実施例１において得られたメソフェーズカーボン小球体焼成品（揮発分２質量％以下）を金型に入れ、圧力（０．５ｔｏｎ／ｃｍ2）で加圧して成形を試みた。しかし、焼成品は塊状にならず、成形できなかった。
　そのため、黒鉛化工程以降は実施しなかった。
　なお、比較例３においては、黒鉛前駆体であるメソカーボン小球体焼成品の揮発分量が２質量％以下と少なく、バインダーも混合しなかったため、金型プレスだけでは成形体とすることができなかったと考えられる。 [Comparative Example 3]
The mesophase carbon microsphere fired product obtained in Example 1 (2% by mass or less of volatile content) was put in a mold and pressed with a pressure (0.5 ton / cm 2 ) to attempt molding. However, the fired product did not form a lump and could not be molded.
Therefore, it was not implemented after the graphitization step.
In Comparative Example 3, the mesocarbon microsphere fired product, which is a graphite precursor, has a small volatile content of 2% by mass or less, and the binder was not mixed. It is thought.
［比較例４］
　実施例１において得られたメソフェーズカーボン小球体仮焼品（揮発分５質量％）を金型に入れ、圧力（０．５ｔｏｎ／ｃｍ2）で加圧して成形した。塊状物が得られたので、実施例１と同様に黒鉛化処理を行った。実施例１と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。
　なお、比較例３と異なり、比較例４においては、黒鉛前駆体であるメソカーボン小球体焼成品の揮発分量が５質量％と比較的多いため、別途バインダーを混合しなくても、金型プレスだけで成形体とすることができたと考えられる。 [Comparative Example 4]
The mesophase carbon microsphere calcined product (volatile content 5 mass%) obtained in Example 1 was put into a mold and molded by pressurizing with a pressure (0.5 ton / cm 2 ). Since a lump was obtained, graphitization was performed in the same manner as in Example 1. In the same manner as in Example 1, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristic evaluation were performed. The evaluation results are also shown in Table 1 below.
Unlike Comparative Example 3, in Comparative Example 4, the mesocarbon microsphere fired product, which is a graphite precursor, has a relatively large volatile content of 5% by mass. It is thought that it was possible to obtain a molded body only with this.
［比較例５］
　実施例２において得られたメソフェーズカーボン小球体仮焼品（揮発分５質量％）を金型に入れ、圧力（０．５ｔｏｎ／ｃｍ2）で加圧して成形した。塊状物が得られたので、実施例２と同様に黒鉛化処理を行った。実施例１と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。
　なお、比較例４と同様、比較例５においても、黒鉛前駆体であるメソカーボン小球体焼成品の揮発分量が５質量％と比較的多いため、別途バインダーを混合しなくても、金型プレスだけで成形体とすることができたと考えられる。 [Comparative Example 5]
The mesophase carbon microsphere calcined product (volatile content 5 mass%) obtained in Example 2 was put into a mold and molded by pressurizing with a pressure (0.5 ton / cm 2 ). Since a lump was obtained, graphitization was performed in the same manner as in Example 2. In the same manner as in Example 1, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristic evaluation were performed. The evaluation results are also shown in Table 1 below.
As in Comparative Example 4, in Comparative Example 5, the mesocarbon microsphere fired product, which is a graphite precursor, has a relatively large volatile content of 5% by mass. It is thought that it was possible to obtain a molded body only with this.
［比較例６］
　実施例４において充填工程を何ら行わなかったこと以外は、実施例４と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。 [Comparative Example 6]
Except that no filling step was performed in Example 4, preparation of the negative electrode mixture, preparation of the negative electrode, preparation of the lithium ion secondary battery, and characteristics evaluation were performed in the same manner as in Example 4. The evaluation results are also shown in Table 1 below.
［比較例７］
　実施例５において充填工程を何ら行わなかったこと以外は、実施例５と同様に負極合剤の調製、負極の作製、リチウムイオン二次電池の作製および特性評価を行った。評価結果を同じく下表１に示した。 [Comparative Example 7]
Except that no filling process was performed in Example 5, the preparation of the negative electrode mixture, the production of the negative electrode, the production of the lithium ion secondary battery, and the characteristics evaluation were performed in the same manner as in Example 5. The evaluation results are also shown in Table 1 below.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
［結果の説明］
　実施例１は、黒鉛化前の黒鉛前駆体粉末の充填密度を高くし、かつ、黒鉛化処理後の粉砕処理を不要とすることができたことから、生産性に優れ、リチウムイオン二次電池用負極材料の生産コストを低減することができると考えられる。
　実施例２、３は、平均粒子径が３μｍと小さい黒鉛前駆体粉末を用いたにもかかわらず、充填密度を高くすることができ、かつ、黒鉛化処理後の粉砕処理を不要とすることができたことから、生産性に優れ、リチウムイオン二次電池用負極材料の生産コストを低減することができると考えられる。 [Explanation of results]
In Example 1, since the packing density of the graphite precursor powder before graphitization was increased and the pulverization treatment after graphitization was not required, the productivity was excellent and the lithium ion secondary battery It is thought that the production cost of the negative electrode material can be reduced.
In Examples 2 and 3, in spite of using a graphite precursor powder having an average particle size as small as 3 μm, the packing density can be increased and the pulverization after graphitization is not required. Since it was able to do it, it is excellent in productivity and it is thought that the production cost of the negative electrode material for lithium ion secondary batteries can be reduced.
　黒鉛前駆体として平均粒子径の異なるメソフェーズカーボン小球体仮焼品を用いた実施例４、５の場合でも黒鉛化前の黒鉛前駆体粉末の充填密度を高くし、かつ、黒鉛化処理後の粉砕処理を不要とすることができたことから、生産性に優れ、リチウムイオン二次電池用負極材料の生産コストを低減することができると考えられる。
　さらに、実施例１～５により得られた黒鉛粒子（リチウムイオン二次電池用負極材料）を負極材料として用いて作製した負極は、平均粒径に対応して、従来品である比較例１、２、６、７と同等の放電容量とロスが得られた。なお、ロスの値は黒鉛粒子の平均粒子径に依存するので、ロスの値を比較する際は、ほぼ同じ平均粒子径で比較する必要がある。 Even in Examples 4 and 5 using mesophase carbon microsphere calcined products having different average particle diameters as the graphite precursor, the packing density of the graphite precursor powder before graphitization is increased, and pulverization after graphitization is performed. Since the treatment can be eliminated, it is considered that the productivity is excellent and the production cost of the negative electrode material for a lithium ion secondary battery can be reduced.
Furthermore, the negative electrode produced by using the graphite particles (negative electrode material for lithium ion secondary battery) obtained in Examples 1 to 5 as the negative electrode material corresponds to the average particle size of Comparative Example 1, which is a conventional product. Discharge capacity and loss equivalent to 2, 6, and 7 were obtained. Since the loss value depends on the average particle diameter of the graphite particles, it is necessary to compare with the same average particle diameter when comparing the loss values.
　比較例１は、黒鉛前駆体粉末をるつぼに充填して黒鉛化処理を行ったものであるが、るつぼへの充填密度は低くはなかったものの、るつぼを使用することによる生産性の低下があり、本発明の要求する水準には達していなかった。 In Comparative Example 1, the graphite precursor powder was filled into a crucible and subjected to graphitization treatment. Although the packing density into the crucible was not low, there was a decrease in productivity due to the use of the crucible. The level required by the present invention was not reached.
　比較例２は、平均粒子径が３μｍと小さい黒鉛前駆体粉末をるつぼに充填して黒鉛化処理を行ったものであるが、るつぼへの充填密度が０．３ｇ／ｃｍ3と低かったために、るつぼを使用することによる生産性の低下があり、本発明の要求する水準には達していなかった。 Comparative Example 2 was obtained by filling a crucible with a graphite precursor powder having a small average particle diameter of 3 μm and performing a graphitization treatment. However, because the packing density into the crucible was as low as 0.3 g / cm 3 , There was a decrease in productivity due to the use of a crucible, and the level required by the present invention was not reached.
　比較例６、７でも、るつぼへの充填密度がそれぞれ０．７ｇ／ｃｍ3、０．５ｇ／ｃｍ3と低かったために、るつぼを使用することによる生産性の低下があり、本発明の要求する水準には達していなかった。 Even Comparative Examples 6 and 7, for the packing density of the crucible was low, respectively 0.7 g / cm 3, and 0.5 g / cm 3, there is decrease in productivity due to the use crucible and requirements of the invention The level was not reached.
　比較例３は、成形することができず、黒鉛化処理を行うことができなかった。 Comparative Example 3 could not be molded and could not be graphitized.
　比較例４、５は、黒鉛前駆体粉末の成形体の充填密度は低くはなかったが、黒鉛化処理後に粉砕処理を必要としたことから、生産性の低下があり、本発明の要求する水準には達していなかった。 In Comparative Examples 4 and 5, the packing density of the graphite precursor powder compact was not low, but the pulverization treatment was required after the graphitization treatment, resulting in a decrease in productivity and the level required by the present invention. Was not reached.
　なお、比較例４、５により得られた黒鉛粒子（リチウムイオン二次電池用負極材料）を負極材料として用いて作製した負極は、平均粒子径に対応して、評価電池の放電容量は実施例１～３と同等であったが、ロスは実施例１～３よりも大きくなり、負極性能は劣っていた。 In addition, the negative electrode produced using the graphite particles (negative electrode material for lithium ion secondary batteries) obtained in Comparative Examples 4 and 5 as the negative electrode material corresponds to the average particle diameter, and the discharge capacity of the evaluation battery is that of the example. Although it was equivalent to 1 to 3, the loss was larger than those of Examples 1 to 3, and the negative electrode performance was inferior.
　本発明のリチウムイオン二次電池用負極材料の製造方法によれば、るつぼにバルクの黒鉛前駆体粉末を充填したり、金型プレスにより黒鉛前駆体粉末の成形体を作製したりする方法に比べて、生産性に優れ、製造コストの低減に寄与する。 According to the method for producing a negative electrode material for a lithium ion secondary battery of the present invention, compared to a method of filling a crucible with bulk graphite precursor powder or producing a molded body of graphite precursor powder by a die press. It is excellent in productivity and contributes to the reduction of manufacturing costs.
１　　外装カップ
２　　負極合剤
３　　外装缶
４　　対極（正極）
５　　セパレータ
６　　絶縁ガスケット
７ａ　　集電体
７ｂ　　集電体（負極） DESCRIPTION OF SYMBOLS 1 Exterior cup 2 Negative electrode mixture 3 Exterior can 4 Counter electrode (positive electrode)
5 Separator 6 Insulating gasket 7a Current collector 7b Current collector (negative electrode)

Claims (1)

  1. 　黒鉛前駆体粉末を袋の内部に充填し、その後、前記袋の内部を、脱気して減圧し、減圧した状態を維持する充填工程と、
    　前記充填工程で得られた、前記黒鉛前駆体粉末が内部に充填され、かつ、内部を減圧した状態が維持された前記袋を加熱して、前記黒鉛前駆体粉末を黒鉛化する黒鉛化工程と
    を有するリチウムイオン二次電池用負極材料の製造方法。     Filling the inside of the bag with graphite precursor powder, then degassing and reducing the pressure inside the bag, and maintaining the reduced pressure,
    The graphitization step of graphitizing the graphite precursor powder by heating the bag, which is obtained in the filling step, the inside of which the graphite precursor powder is filled and the inside of which is decompressed is maintained. The manufacturing method of the negative electrode material for lithium ion secondary batteries which has this.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02157158A (en) * 1988-12-08 1990-06-15 Kanto Yakin Kogyo Kk Production of carbon fiber molded body for use at high temperature
JPH03197363A (en) * 1989-12-25 1991-08-28 Kobe Steel Ltd Production of carbon fiber-reinforced carbon composite material
JPH05208876A (en) * 1992-01-30 1993-08-20 Dainippon Ink & Chem Inc Production of cylindrical porous carbon molded product
JPH1167201A (en) * 1997-08-19 1999-03-09 Petoca:Kk Carbon material for lithium ion secondary battery negative electrode and its manufacture

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5055243A (en) * 1990-02-27 1991-10-08 Kantoyaking Kogyo K.K. Method of preparing carbon fiber-reinforced carbon modules
CN106892428A (en) * 2017-03-27 2017-06-27 凤城市宝山炭素有限公司 A kind of method that short route produces isotropic hyperfine structure isostatic pressing formed graphite

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02157158A (en) * 1988-12-08 1990-06-15 Kanto Yakin Kogyo Kk Production of carbon fiber molded body for use at high temperature
JPH03197363A (en) * 1989-12-25 1991-08-28 Kobe Steel Ltd Production of carbon fiber-reinforced carbon composite material
JPH05208876A (en) * 1992-01-30 1993-08-20 Dainippon Ink & Chem Inc Production of cylindrical porous carbon molded product
JPH1167201A (en) * 1997-08-19 1999-03-09 Petoca:Kk Carbon material for lithium ion secondary battery negative electrode and its manufacture

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