KR100274233B1 - Anode active material for lithium ion secondary battery and method for preparing the same - Google Patents

Anode active material for lithium ion secondary battery and method for preparing the same Download PDF

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KR100274233B1
KR100274233B1 KR1019980018312A KR19980018312A KR100274233B1 KR 100274233 B1 KR100274233 B1 KR 100274233B1 KR 1019980018312 A KR1019980018312 A KR 1019980018312A KR 19980018312 A KR19980018312 A KR 19980018312A KR 100274233 B1 KR100274233 B1 KR 100274233B1
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active material
resin
graphite particles
fine graphite
secondary battery
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KR1019980018312A
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Korean (ko)
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KR19990085718A (en
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심규윤
윤상영
최완욱
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김순택
삼성에스디아이주식회사
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Priority to KR1019980018312A priority Critical patent/KR100274233B1/en
Priority to US09/316,766 priority patent/US6482547B1/en
Priority to JP14189399A priority patent/JP4446510B2/en
Priority to CNB991092562A priority patent/CN1276531C/en
Publication of KR19990085718A publication Critical patent/KR19990085718A/en
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    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • 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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Inorganic Chemistry (AREA)
  • Organic Chemistry (AREA)
  • Composite Materials (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

PURPOSE: Provided are an anode active material for lithium ion secondary battery having enhanced charge/discharge efficiencies, and a method for preparing the same which can easily control a particle diameter of carbon-based active material. CONSTITUTION: The method comprises the steps of (i) crushing crystalline carbon precursor to form fine graphite particles, (ii) mixing the graphite particles with solution of noncrystalline carbon precursor, (iii) heat treating the mixture, and (iv) crushing the heat treated material. The noncrystalline carbon precursor is selected from the group consisting of coal based pitch, petroleum based pitch, polyimide resin, furan resin, phenol resin, polyvinyl alcohol resin, cellulose resin, epoxy resin and polystyrene resin.

Description

리튬 이온 이차 전지용 음극 활물질 및 그 제조 방법Anode active material for lithium ion secondary battery and manufacturing method thereof

산업상 이용 분야Industrial use field

본 발명은 리튬 이온 이차 전지용 음극 활물질 및 그 제조 방법에 관한 것으로서, 더욱 상세하게는 전지용 활물질로서 성능이 떨어지는 미세한 흑연 입자를 활용하여 고성능의 음극 활물질을 제조하는 방법에 관한 것이다.The present invention relates to a negative electrode active material for a lithium ion secondary battery and a method for manufacturing the same, and more particularly, to a method for producing a high performance negative electrode active material using fine graphite particles having poor performance as a battery active material.

종래 기술Prior art

리튬 이온 이차 전지용 음극 활물질로는 탄소계 활물질이 주로 사용되고 있으며, 이 탄소계 활물질로는 결정질계 탄소 및 비정질계 탄소 등이 있다. 결정질계 탄소로는 천연 흑연이 있으며, 핏치 등을 2000℃ 이상에서 고온 소성하여 얻어지는 인조 흑연이 있다. 비정질계 탄소는 흑연화도가 낮거나, X선 회절에서 거의 회절선이 나타나지 않는 탄소로서, 석탄계 핏치 또는 석유계 핏치를 소성하여 얻는 소프트 카본, 페놀 수지 등의 고분자 수지를 소성하여 얻는 하드 카본 등이 있다.As the negative electrode active material for a lithium ion secondary battery, a carbon-based active material is mainly used, and the carbon-based active material includes crystalline carbon and amorphous carbon. Crystalline carbon includes natural graphite, and artificial graphite obtained by firing a pitch or the like at a high temperature of 2000 ° C or higher. Amorphous carbon is carbon having low graphitization degree or hardly showing diffraction lines in X-ray diffraction, and hard carbon obtained by firing polymer resin such as soft carbon or phenol resin obtained by firing coal pitch or petroleum pitch. have.

상기 결정질계 탄소인 천연 흑연 또는 인조 흑연을 전지용 활물질로 사용하기 위해서는 분쇄 공정을 실시하는데, 이때 적당한 입도의 흑연 입자만 얻어지는 것이 아니라, 도 2에서 보이는 바와 같이 입경이 10㎛ 이하인 것이 전체 입자의 약 80부피%에 이르며 상당히 넓은 입도 분포의 흑연 입자가 얻어진다.In order to use the natural crystalline carbon or artificial graphite, which is the crystalline carbon, as a battery active material, a pulverization process is performed. At this time, not only graphite particles having an appropriate particle size are obtained, but as shown in FIG. Graphite particles of up to 80% by volume and a fairly wide particle size distribution are obtained.

이들 흑연 입자 중에서 전지용 활물질로서 적당한 입도의 것을 선별하고 나면 미세한 흑연 입자가 남게 된다. 특히 인조 흑연을 분쇄, 분급한 후 남게 되는 미세한 인조 흑연 입자는 표면 특성이 열화되어 이를 전지에 적용할 경우 충방전 효율이 상당히 저하된다. 또한, 미세한 천연 또는 인조 흑연 입자를 전지에 적용할 경우, 충방전시 부반응의 발생이 크고, 극판의 충진 밀도가 낮아 활물질의 로딩 레벨(loading level)이 저하된다. 이와 같이 활물질 가공 공정에서 활물질로 사용하기에 부적합한 미세한 흑연 입자가 생성되므로 이는 결국, 자원의 낭비를 초래한다.Fine graphite particles remain after the particles having a suitable particle size are selected as active materials for batteries from these graphite particles. In particular, the fine artificial graphite particles remaining after pulverizing and classifying artificial graphite deteriorates the surface properties, and when applied to the battery, the charge and discharge efficiency is significantly reduced. In addition, when the fine natural or artificial graphite particles are applied to the battery, side reactions are largely generated during charge and discharge, and the packing density of the electrode plate is low, thereby lowering the loading level of the active material. As such, fine graphite particles, which are not suitable for use as the active material in the active material processing process, are generated, which in turn causes waste of resources.

상기 문제점을 해결하기 위한 것으로서, 본 발명의 목적은 자원의 낭비를 방지할 수 있도록 미세한 흑연 입자를 활용하는 방법을 제공하는 것이다.In order to solve the above problems, an object of the present invention is to provide a method of utilizing the fine graphite particles to prevent the waste of resources.

본 발명의 다른 목적은 충방전 효율이 향상된 탄소계 활물질을 제공하는 것이다.Another object of the present invention is to provide a carbon-based active material having improved charge and discharge efficiency.

본 발명의 또 다른 목적은 최종적으로 수득하는 탄소계 활물질의 입도를 용이하게 제어할 수 있는 활물질 제조 방법을 제공하는 것이다.Still another object of the present invention is to provide an active material manufacturing method capable of easily controlling the particle size of the finally obtained carbon-based active material.

도 1은 본 발명의 일 실시예에 따른 활물질의 단면도.1 is a cross-sectional view of an active material according to an embodiment of the present invention.

도 2는 종래 기술에 따른 활물질의 입도 분포도.2 is a particle size distribution diagram of an active material according to the prior art.

도 3은 본 발명의 일 실시예에 따른 활물질의 입도 분포도.Figure 3 is a particle size distribution of the active material according to an embodiment of the present invention.

상기 본 발명의 목적을 달성하기 위하여, 본 발명은 결정질계 탄소를 분쇄하여 미세한 흑연 입자를 형성하고, 이 미세한 흑연 입자를 비정질 탄소 전구체 용액과 혼합한 후, 이를 열처리하고, 분쇄함으로써 미세한 흑연 입자들을 비정질계 탄소를 매개로 결합(binding)시킨 리튬 이온 이차 전지용 음극 활물질을 제공한다.In order to achieve the object of the present invention, the present invention is pulverized crystalline carbon to form fine graphite particles, the fine graphite particles are mixed with an amorphous carbon precursor solution, and then heat treated and pulverized fine graphite particles Provided is a negative electrode active material for a lithium ion secondary battery, which is bound through amorphous carbon.

이하, 본 발명을 더욱 상세히 설명한다.Hereinafter, the present invention will be described in more detail.

상기 비정질계 탄소 전구체로는 석탄계 핏치와 석유계 핏치의 혼합물, 석탄계 핏치 또는 석유계 핏치 등을 유기 용매로 처리하여 테트라하이드로퓨란 불용성 성분을 제거한 테트라하이드로퓨란 가용성 핏치를 사용할 수 있으며, 폴리이미드 수지, 퓨란 수지, 페놀 수지, 폴리비닐알콜 수지, 셀룰로즈 수지, 에폭시 수지, 폴리스티렌 수지 등의 고분자 수지를 사용할 수도 있다.The amorphous carbon precursor may be a mixture of a coal-based pitch and a petroleum-based pitch, a coal-based pitch, or a petroleum-based pitch using an organic solvent to remove a tetrahydrofuran insoluble component. Polymer resins, such as a furan resin, a phenol resin, polyvinyl alcohol resin, a cellulose resin, an epoxy resin, and a polystyrene resin, can also be used.

상기 미세 흑연 입자로는 천연 흑연 또는 인조 흑연을 분쇄, 분급하는 공정에서 발생하는 부산물로서, 평균 길이 또는 입경이 15㎛ 미만인 섬유형, 구형 또는 플레이크형 미세 흑연 입자를 사용할 수 있다. 물론, 이들 미세 흑연 입자를 일부 포함하는 결정성 흑연을 상기 비정질 탄소 전구체 용액과의 혼합 공정에 투입할 수도 있다.As the fine graphite particles, by-products generated in the process of pulverizing and classifying natural graphite or artificial graphite, fibrous, spherical or flake fine graphite particles having an average length or particle diameter of less than 15 μm may be used. Of course, crystalline graphite containing some of these fine graphite particles may be added to the mixing step with the amorphous carbon precursor solution.

상기 비정질 탄소 전구체와 미세 흑연 입자는 1:1-1:8의 중량비로 혼합할 수 있으며, 바람직하게는 1:4-1:6의 중량비로 혼합한다. 비정질 탄소 전구체의 양이 미세 흑연 입자의 양보다 큰 경우, 최종적으로 수득되는 활물질에서 비정질 탄소 부분이 과다해지므로 이 활물질을 채용하는 전지의 전압 평탄성이 불량해질 우려가 있다. 비정질 탄소 전구체의 양이 미세 흑연 입자의 1/8 미만인 경우, 비정질 탄소 전구체가 미세 흑연 입자들을 효과적으로 결합(binding)시킬 수 없다는 문제점이 발생한다.The amorphous carbon precursor and the fine graphite particles may be mixed in a weight ratio of 1: 1-1: 8, preferably in a weight ratio of 1: 4-1: 6. If the amount of the amorphous carbon precursor is larger than the amount of the fine graphite particles, there is a risk that the voltage flatness of the battery employing the active material is poor because the amorphous carbon portion becomes excessive in the finally obtained active material. When the amount of the amorphous carbon precursor is less than 1/8 of the fine graphite particles, a problem arises in that the amorphous carbon precursor cannot effectively bind the fine graphite particles.

상기 비정질 탄소 전구체와 미세 흑연 입자 또는 미세 흑연 입자를 포함하는결정성 흑연의 혼합물에 테트라하이드로퓨란 등의 유기 용매를 첨가하여 교반한 후, 이를 증류시킴으로써 다수개의 미세 흑연 입자 또는 미세 흑연 입자를 포함하는 결정성 흑연이 비정질 탄소 전구체에 의해서 결합된 형태의 물질을 얻을 수 있다.An organic solvent such as tetrahydrofuran is added to the mixture of the amorphous carbon precursor and the fine graphite particles or the crystalline graphite containing the fine graphite particles, followed by stirring, followed by distillation to include a plurality of the fine graphite particles or the fine graphite particles. It is possible to obtain a material in the form in which crystalline graphite is bound by an amorphous carbon precursor.

이 물질을 질소 분위기하에서 약 400-500℃, 바람직하게는 430-450℃에서 10시간 이상 가열하여 미세 흑연 입자간의 바인더(binder)로 작용하는 비정질 탄소 전구체를 100% 메조페이스로 전환시킨다. 상기 질소 분위기하 열처리 공정으로 최종 활물질의 비정질 탄소 층이 상대적으로 두껍게 형성되며, 이 공정을 실시하지 않으면 최종 활물질의 비정질 탄소 층이 상대적으로 얇아질 수 있다.The material is heated under nitrogen atmosphere at about 400-500 ° C., preferably 430-450 ° C. for at least 10 hours to convert the amorphous carbon precursor, which acts as a binder between fine graphite particles, to 100% mesophase. The amorphous carbon layer of the final active material is formed relatively thick by the heat treatment process under the nitrogen atmosphere, and if the process is not performed, the amorphous carbon layer of the final active material may be relatively thin.

이어서, 이를 감압하에서 가열하여 이 물질 내에 존재하는 저분자체를 제거한 후, 900-1200℃에서 열처리한다. 이어서, 전지용 활물질로서 적정 입도를 가지도록 즉, 평균 입경이 15-40㎛이 되도록 분쇄 가공하여 도 1에 보이는 바와 같이, 비정질계 탄소(2)를 매개로 결합된 미세 흑연 입자들(1)로 이루어진 활물질을 수득한다. 더욱이, 본 발명의 활물질은 결정질계 탄소인 미세 흑연 입자를 비정질계 탄소로 코팅한 형태이므로 전해질의 코-인터칼레이션이 방지되어 음극의 비가역 용량을 감소시킬 수 있다. X-선 회절 분석 결과, 상기 비정질계 탄소의 (002) 플레인 층간 거리(d2)는 3.4-3.8Å이며, 상기 미세 흑연 입자의 (002) 플레인 층간 거리(d2)는 3.35-3.4Å인 것이 바람직함을 알 수 있었다. 또한, 본 발명의 방법으로 제조한 음극 활물질은 도 3에서 보이는 바와 같이 입경이 10㎛ 이하인 것이 전체 활물질의 약 20부피% 정도로서 본 발명에 따른 재가공으로 미세 흑연 입자의 입경이 약 5-25㎛ 가량 성장되었음을 알 수 있다.Subsequently, it is heated under reduced pressure to remove the low molecular weight present in this material, and then heat-treated at 900-1200 ° C. Subsequently, as the active material for a battery, grinding is performed to have an appropriate particle size, that is, an average particle diameter of 15-40 μm, and as the fine graphite particles 1 bonded through the amorphous carbon 2 as shown in FIG. 1. Obtained active material is obtained. In addition, since the active material of the present invention is a form in which fine graphite particles, which are crystalline carbon, are coated with amorphous carbon, co-intercalation of the electrolyte is prevented, thereby reducing the irreversible capacity of the negative electrode. As a result of X-ray diffraction analysis, the (002) plane interlayer distance (d 2 ) of the amorphous carbon was 3.4-3.8 μs, and the (002) plane interlayer distance (d 2 ) of the fine graphite particles was 3.35-3.4 μm. It was found that it is preferable. In addition, the negative electrode active material prepared by the method of the present invention has a particle diameter of 10 μm or less, as shown in FIG. 3, about 20% by volume of the entire active material. It can be seen that it has grown.

본 기술 분야의 당업자는 상기 본 발명의 음극 활물질을 사용하여 공지된 전지 제조 방법에 따라 용이하게 리튬 이온 이차 전지를 제조할 수 있을 것이다.Those skilled in the art will be able to easily manufacture a lithium ion secondary battery according to a known battery manufacturing method using the negative electrode active material of the present invention.

상기 리튬 이온 이차 전지에서, 양극 활물질로는 LiCoO2, LiNiO2, LiMn2O4, LiNixCo1-xOy(0〈x〈1, 0〈y≤2) 등의 리튬 전이 금속 산화물이 바람직하며, 세퍼레이터로는 폴리프로필렌 계열의 다공성 고분자를 사용하는 것이 바람직하다. 또한, 본 발명의 음극 활물질의 표면이 비정질계 탄소이므로 전해질로서 LiPF6, LiClO4등의 리튬염을 용해시킨 프로필렌 카보네이트를 사용할 수 있다.In the lithium ion secondary battery, a lithium transition metal oxide such as LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiNi x Co 1-x O y (0 <x <1, 0 <y ≦ 2) may be used. It is preferable to use a polypropylene-based porous polymer as the separator. In addition, since the surface of the anode active material of the present invention is amorphous carbon, propylene carbonate in which lithium salts such as LiPF 6 and LiClO 4 are dissolved can be used as the electrolyte.

다음은 본 발명의 이해를 돕기 위하여 바람직한 실시예를 제시한다. 그러나 하기의 실시예들은 본 발명을 보다 쉽게 이해하기 위하여 제공되는 것일 뿐 본 발명이 하기의 실시예에 한정되는 것은 아니다.The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

실시예 1Example 1

석탄계 핏치 또는 석유계 핏치를 테트라하이드로퓨란에 용해시킨 후 증류시켜서 테트라하이드로퓨란 가용성 핏치를 제조하였다.A tetrahydrofuran soluble pitch was prepared by dissolving a coal pitch or a petroleum pitch in tetrahydrofuran and distilling it out.

이 테트라하이드로퓨란 가용성 핏치를 최대 입경이 5㎛인 플레이크형 미세 흑연 입자와 1:6의 중량비로 혼합한 후, 적정량의 테트라하이드로퓨란을 첨가하고 교반하였다. 이 혼합 용액을 증류시켜서 얻은 물질을 질소 분위기하 430℃에서 10시간 정도 가열하고, 이어서 감압하에서 열처리하였다. 이어서, 1000℃에서 2시간 열처리한 후 분쇄하여 평균 입경이 15-40㎛인 활물질을 제조하였다.This tetrahydrofuran soluble pitch was mixed with flake type fine graphite particles having a maximum particle diameter of 5 µm in a weight ratio of 1: 6, and then an appropriate amount of tetrahydrofuran was added and stirred. The substance obtained by distilling this mixed solution was heated at 430 degreeC for about 10 hours in nitrogen atmosphere, and then heat-processed under reduced pressure. Subsequently, the resultant was heat-treated at 1000 ° C. for 2 hours and then ground to prepare an active material having an average particle diameter of 15-40 μm.

상기 음극 활물질과 바인더로서 폴리 비닐리덴 플루오라이드를 N-메틸 피롤리돈에 용해시켜서 슬러리를 제조한 후 이를 집전체에 코팅하여 극판을 제조하였다.As the negative electrode active material and the binder, polyvinylidene fluoride was dissolved in N-methyl pyrrolidone to prepare a slurry, and then coated on a current collector to prepare an electrode plate.

상기 극판, 이에 대한 대극으로서 리튬 금속 박편 및 전해질로서 LiPF6, LiClO4등의 리튬염을 용해시킨 에틸렌 카보네이트와 디메틸 카보네이트의 혼합물을 사용하여 코인형 리튬 이온 전지를 제조한 후, 초기 충전 용량, 방전 용량, 충방전 효율을 측정하여 측정하여 표 1에 나타내었다. 이때, 충방전 효율은 충전 용량에 대한 방전 용량의 비율을 나타낸 것이다.After preparing a coin-type lithium ion battery using a mixture of ethylene carbonate and dimethyl carbonate in which lithium electrode flakes such as LiPF 6 and LiClO 4 were dissolved as an electrode, a lithium metal flake as an electrode, and an electrolyte therein, an initial charge capacity and a discharge Capacity and charge and discharge efficiency were measured and measured, and are shown in Table 1. At this time, the charge and discharge efficiency represents the ratio of the discharge capacity to the charge capacity.

실시예 2Example 2

테트라하이드로퓨란 가용성 핏치를 최대 입경이 5㎛인 플레이크형 미세 흑연 입자와 1:4의 중량비로 혼합한 것을 제외하고는 실시예 1과 동일하게 실시하였다.Tetrahydrofuran soluble pitch was carried out in the same manner as in Example 1 except that the flake-shaped fine graphite particles having a maximum particle size of 5 µm were mixed at a weight ratio of 1: 4.

실시예 3Example 3

테트라하이드로퓨란 가용성 핏치를 최대 입경이 5㎛인 플레이크형 미세 흑연 입자와 1:1의 중량비로 혼합한 것을 제외하고는 실시예 1과 동일하게 실시하였다.Tetrahydrofuran soluble pitch was carried out in the same manner as in Example 1 except that the flake-shaped fine graphite particles having a maximum particle diameter of 5 µm were mixed at a weight ratio of 1: 1.

비교예 1Comparative Example 1

음극 활물질로서 결정질계 탄소인 미세 흑연 입자를 사용하고, 전해질로서 LiPF6, LiClO4등의 리튬염을 용해시킨 에틸렌 카보네이트 및 디메틸 카보네이트의 혼합물을 사용한 것을 제외하고는 실시예 1과 동일한 방법으로 극판 및 전지를 제조하였다.Except for using the fine graphite particles of crystalline carbon as a negative electrode active material and a mixture of ethylene carbonate and dimethyl carbonate in which lithium salts such as LiPF 6 and LiClO 4 were dissolved as the electrolyte, the electrode plate and The battery was prepared.

비교예 2Comparative Example 2

석탄계 핏치를 테트라하이드로퓨란에 용해시킨 후 증류시켜서 테트라하이드로퓨란 가용성 핏치를 제조하였다.The coal-based pitch was dissolved in tetrahydrofuran and then distilled to prepare a tetrahydrofuran soluble pitch.

이 테트라하이드로퓨란 가용성 핏치를 질소 분위기하 430℃에서 10시간 정도 가열하고, 다시 감압하에서 열처리하였다. 이어서, 1000℃에서 2시간 열처리, 2800℃에서 흑연화한 후 분쇄, 분급하여 음극 활물질을 제조하였다.This tetrahydrofuran soluble pitch was heated at 430 ° C. for about 10 hours in a nitrogen atmosphere, and further heat-treated under reduced pressure. Subsequently, the negative electrode active material was prepared by heat treatment at 1000 ° C. for 2 hours and graphitization at 2800 ° C., followed by grinding and classification.

음극 활물질로서 상기 제조한 음극 활물질을 사용하고, 전해질로서 LiPF6, LiClO4등의 리튬염을 용해시킨 에틸렌 카보네이트 및 디메틸 카보네이트의 혼합물을 사용한 것을 제외하고는 실시예 1과 동일한 방법으로 극판 및 전지를 제조하였다.A negative electrode and a battery were prepared in the same manner as in Example 1 except that the negative electrode active material prepared above was used as the negative electrode active material, and a mixture of ethylene carbonate and dimethyl carbonate in which lithium salts such as LiPF 6 and LiClO 4 were dissolved as the electrolyte. Prepared.

상기 실시예 및 비교예에서 제조한 전지의 특성을 하기 표 1에 나타낸다.The characteristics of the batteries prepared in the above Examples and Comparative Examples are shown in Table 1 below.

충전용량(㎃h/g)Charge capacity (h / g) 방전용량(㎃h/g)Discharge capacity (㎃h / g) 충방전 효율(%)Charge / discharge efficiency (%) 실시예 1Example 1 404404 372372 92.192.1 실시예 2Example 2 410410 368368 89.889.8 실시예 3Example 3 415415 370370 89.289.2 비교예 1Comparative Example 1 431431 345345 80.080.0 비교예 2Comparative Example 2 452452 320320 70.870.8

상기 표 1에서 보이듯이, 실시예 1, 2, 3은 비교예 1, 2에 비해 충방전 효율이 매우 우수함을 알 수 있다. 이것은 실시예 1, 2, 3의 경우, 미세 흑연 입자의 표면이 비정질 탄소에 의해 코팅되므로 전해액과의 부반응이 감소하여 방전 용량 및 비가역 용량이 증가하기 때문이다.As shown in Table 1, Examples 1, 2, 3 can be seen that the charge and discharge efficiency is very excellent compared to Comparative Examples 1, 2. This is because in the case of Examples 1, 2, and 3, the surface of the fine graphite particles is coated with amorphous carbon, so that the side reaction with the electrolyte decreases, thereby increasing the discharge capacity and irreversible capacity.

상기한 바와 같이, 본 발명은 결정질계 탄소 물질의 가공 공정에서 발생하는 부산물인 미세 흑연 입자를 적정 입도를 가지는 활물질로 재가공함으로써 활물질 가공 공정상의 손실을 최소화한다.As described above, the present invention minimizes the loss in the active material processing process by reprocessing the fine graphite particles, which are by-products generated in the processing of the crystalline carbon material, into an active material having an appropriate particle size.

또한, 본 발명에 따른 음극 활물질은 결정질계 탄소를 비정질계 탄소로 코팅한 형태이므로 전해질의 코-인터칼레이션이 방지되어 음극의 비가역 용량을 감소시킬 수 있다. 따라서, 상대적으로 양극의 투입량을 증가시킬 수 있어서 전지의 고용량화가 가능하며, 우수한 충방전 효율을 가진 전지를 제공할 수 있다. 또한, 프로필렌 카보네이트 전해질의 사용이 가능하므로 저온 특성이 우수하며, 장수명, 저가의 전지를 제공할 수 있다.In addition, since the negative active material according to the present invention is coated with crystalline carbon with amorphous carbon, co-intercalation of the electrolyte can be prevented, thereby reducing the irreversible capacity of the negative electrode. Therefore, it is possible to increase the amount of the positive electrode to be relatively increased, thereby enabling a high capacity of the battery, and providing a battery having excellent charge and discharge efficiency. In addition, it is possible to use a propylene carbonate electrolyte, it is excellent in low temperature characteristics, it is possible to provide a battery of long life, low cost.

Claims (7)

결정질계 탄소를 분쇄하여 미세한 흑연 입자를 형성하는 공정과;Grinding the crystalline carbon to form fine graphite particles; 상기 미세한 흑연 입자를 비정질 탄소 전구체 용액과 혼합하는 공정과;Mixing the fine graphite particles with an amorphous carbon precursor solution; 상기 혼합물을 열처리하는 공정; 및Heat treating the mixture; And 상기 열처리된 물질을 분쇄하는 공정을 포함하는 리튬 이온 이차 전지용 음극 활물질 제조 방법.Method for producing a negative electrode active material for a lithium ion secondary battery comprising the step of grinding the heat-treated material. 제 1항에 있어서, 상기 비정질 탄소 전구체는 석탄계 피치, 석유계 핏치, 폴리이미드 수지, 퓨란 수지, 페놀 수지, 폴리비닐알콜 수지, 셀룰로즈 수지, 에폭시 수지 및 폴리스티렌 수지로 이루어진 군에서 선택되는 하나 이상인 리튬 이온 이차 전지용 음극 활물질 제조 방법.The method of claim 1, wherein the amorphous carbon precursor is at least one selected from the group consisting of coal pitch, petroleum pitch, polyimide resin, furan resin, phenol resin, polyvinyl alcohol resin, cellulose resin, epoxy resin and polystyrene resin A negative electrode active material manufacturing method for an ion secondary battery. 제 1항에 있어서, 상기 비정질 탄소 전구체와 미세 흑연 입자의 중량비는 1:1-1:8인 리튬 이온 이차 전지용 음극 활물질 제조 방법.The method of claim 1, wherein the weight ratio of the amorphous carbon precursor to the fine graphite particles is 1: 1-1: 8. 제 1항에 있어서, 상기 혼합 공정과 상기 열처리 공정 사이에 테트라하이드로퓨란을 첨가하여 교반하는 공정을 더욱 포함하는 리튬 이온 이차 전지용 음극 활물질 제조 방법.The method of manufacturing a negative electrode active material for a lithium ion secondary battery according to claim 1, further comprising a step of adding and stirring tetrahydrofuran between the mixing step and the heat treatment step. 제 1항에 있어서, 상기 열처리 공정은 900-1200℃에서 탄소화하는 공정인 리튬 이온 이차 전지용 음극 활물질 제조 방법.The method of claim 1, wherein the heat treatment step is a step of carbonizing at 900-1200 ° C. 6. 평균 입경이 15㎛ 미만인 미세한 흑연 입자 또는 상기 미세한 흑연 입자를 포함하는 결정질계 탄소 활물질이 비정질계 탄소를 매개로 결합(binding)된 형태의 리튬 이온 이차 전지용 음극 활물질.A negative active material for a lithium ion secondary battery having a fine graphite particle having an average particle diameter of less than 15 μm or a crystalline carbon active material including the fine graphite particle is bound through an amorphous carbon. 제 6항에 있어서, 상기 음극 활물질의 평균 입경은 15-40㎛인 리튬 이온 이차 전지용 음극 활물질.The negative electrode active material of claim 6, wherein an average particle diameter of the negative electrode active material is 15-40 μm.
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