WO2023080367A1 - Slurry composition for negative electrode of lithium secondary battery - Google Patents

Slurry composition for negative electrode of lithium secondary battery Download PDF

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WO2023080367A1
WO2023080367A1 PCT/KR2022/006203 KR2022006203W WO2023080367A1 WO 2023080367 A1 WO2023080367 A1 WO 2023080367A1 KR 2022006203 W KR2022006203 W KR 2022006203W WO 2023080367 A1 WO2023080367 A1 WO 2023080367A1
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negative electrode
carbon nanotubes
secondary battery
lithium secondary
active material
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PCT/KR2022/006203
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French (fr)
Korean (ko)
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곽우헌
윤기봉
곽성훈
송세호
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주식회사 나노신소재
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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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • 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
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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

Definitions

  • the present invention relates to a slurry composition for a negative electrode of a lithium secondary battery having improved electrical conductivity and dispersibility.
  • a representative example of an electrochemical device using electrochemical energy may be a secondary battery, and its use area is gradually expanding.
  • a secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator.
  • the positive electrode and the negative electrode generally consist of an electrode current collector and an electrode active material layer formed on the electrode current collector, and the electrode active material layer is coated with an electrode slurry composition containing an electrode active material, a conductive material, a binder, etc. on the electrode current collector , it is manufactured by rolling after drying.
  • a dotted conductive material such as carbon black has been mainly used as a conductive material for a secondary battery, but in the case of such a dotted conductive material, there is a problem in that the effect of improving electrical conductivity is not sufficient.
  • a linear conductive material such as carbon nanotubes (CNT) or carbon nanofibers (CNF) are being actively conducted.
  • linear conductive materials such as carbon nanotubes and carbon nanofibers have excellent electrical conductivity, but due to the nature of the material itself, which grows in a bundle type or entangle type, its dispersibility in the slurry is poor, resulting in poor coating and processability, and electrode There is a problem in that the coating layer is not evenly distributed on the surface of the active material.
  • attempts have been made to improve dispersibility by introducing a functional group into a linear conductive material, but in this case, there is a problem in that the presence of a functional group causes a side reaction on the surface and deteriorates the electrochemical properties. .
  • the present invention was derived to solve the above problems, so that carbon nanotubes can cover the entire surface of an active material for a negative electrode evenly, and dramatically increase the physical and chemical stability of the active material for a negative electrode and the electrical conductivity of the electrode. It is an object of the present invention to provide a slurry composition for a negative electrode of a lithium secondary battery capable of improving the lifespan characteristics of a battery.
  • the present invention for solving the above problems relates to a slurry composition for a negative electrode of a lithium secondary battery, and more specifically, by mixing an active material for a negative electrode coated with carbon nanotubes and having a carbon nanotube layer formed on the surface, and a binder characterized in that it is manufactured.
  • another aspect of the present invention relates to a slurry composition for a negative electrode of a lithium secondary battery, more specifically, an active material for a negative electrode coated with carbon nanotubes and having a carbon nanotube layer formed on the surface, carbon black and It is characterized in that it is prepared by mixing a binder.
  • an active material for a negative electrode coated with carbon nanotubes is prepared in advance and then mixed with a binder to prepare a slurry for a negative electrode of a lithium secondary battery,
  • the carbon nanotubes allow the entire surface of the negative electrode active material to be evenly coated, thereby increasing the physical and chemical stability of the negative electrode active material.
  • the contact resistance is further lowered to significantly increase the electrical conductivity, and as a result, there is an effect of improving the lifespan characteristics of the lithium secondary battery.
  • TEM transmission electron microscope
  • FIG. 2 shows a scanning electron microscope measurement result for an active material for a silicon-based negative electrode having a carbon nanotube layer formed on the surface according to an embodiment of the present invention.
  • FIG. 3 is a graph showing the results of a charge/discharge test for half coin cells manufactured using the negative electrode slurry compositions of each of Examples and Comparative Examples of the present invention.
  • SEM 4 relates to a scanning electron microscope (SEM) photograph after removing the active material of the negative electrode active material having a carbon nanotube layer formed on its surface.
  • TEM 5 relates to a transmission electron microscope (TEM) photograph of a carbon nanotube layer remaining after the active material is removed.
  • One aspect of the present invention relates to a slurry composition for a negative electrode of a lithium secondary battery. do.
  • another aspect of the present invention relates to a slurry composition for a negative electrode of a lithium secondary battery, more specifically, an active material for a negative electrode coated with carbon nanotubes and having a carbon nanotube layer formed on the surface, carbon black and It may be prepared by mixing a binder.
  • the active material for a negative electrode having a carbon nanotube layer formed on the surface is pre-prepared by coating the carbon nanotubes, and then mixed with the binder, thereby simultaneously mixing the existing active material for the negative electrode, the carbon nanotubes, and the binder at once.
  • the carbon nanotubes can cover the entire surface of the active material for the negative electrode more evenly than the electrode, thereby further increasing the physical and chemical stability of the active material for the negative electrode, and at the same time lowering the contact resistance, thereby increasing the electrical conductivity. can be significantly increased.
  • the negative electrode active material is a negative electrode active material commonly used in the field of lithium secondary batteries, and includes carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of being alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metal oxides capable of doping and undoping lithium, such as SiOx (0 ⁇ x ⁇ 2), SnO 2 , vanadium oxide, and lithium vanadium oxide; or a composite including the metallic compound and a carbonaceous material, such as a Si—C composite or a Sn—C composite, and any one or a mixture of two or more of these may be used.
  • carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon
  • metallic compounds capable of being alloyed with lithium, such as Si, Al, Sn, Pb, Zn
  • the silicon-based compound may be, for example, a mixture of silicon-based oxide (SiOx) and a carbonaceous material.
  • the active material for the negative electrode is characterized by using a carbon nanotube layer formed on the surface coated with carbon nanotubes as a conductive material.
  • a carbon nanotube layer formed on the surface coated with carbon nanotubes as a conductive material.
  • single-walled carbon nanotubes or multi-walled carbon nanotubes may be used as the carbon nanotubes, but a more robust carbon nanotube layer is formed on the surface of the active material so that the active material can be easily contracted and expanded during battery operation.
  • the carbon nanotubes preferably include at least one selected from the group consisting of single-walled carbon nanotubes and five-walled or less multi-walled carbon nanotubes, and furthermore, the single-walled carbon nanotubes It may be more preferable to use at least one content selected from the group consisting of nanotubes and multi-walled carbon nanotubes with five or less walls, which is 30% by weight or more relative to the total weight of the carbon nanotubes coated with the negative electrode active material, Furthermore, in order to achieve the electrical conductivity and dispersibility desired by the present invention and at the same time sufficiently secure the stability of the active material, the mass ratio of the active material for the negative electrode and the carbon nanotubes coated on the surface of the active material for the negative electrode is not particularly limited. , preferably from 100:0.01 to 100:10.
  • the dispersion particle size of the single-walled carbon nanotubes is not particularly limited, but is preferably 1 to 20 ⁇ m. This is because when the dispersion particle size of the single-walled carbon nanotubes is less than 1 ⁇ m, it is difficult to uniformly cover the entire surface of the active material for the negative electrode, resulting in an excessively high contact resistance, and when the dispersion particle size exceeds 20 ⁇ m, carbon This is because the dispersion stability of the nanotube slurry is poor, and thus the reproducibility of resistance during coating is poor.
  • the single-walled carbon nanotubes have a dispersed particle size of 5 to 10 ⁇ m.
  • the active material for a negative electrode having a carbon nanotube layer formed on the surface may preferably have a powder resistance value of 1 to 1000 ⁇ cm in order to achieve the electrical conductivity and dispersibility desired by the present invention.
  • the binder is added to secure adhesion between active materials for electrodes or between an active material and a current collector, for example, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), poly Vinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and the like, and one of them may be used alone or a mixture of two or more thereof.
  • PVDF-co-HFP vinylidene fluoride-hexafluoropropylene copolymer
  • CMC carboxymethylcellulose
  • EPDM ethylene-propylene-diene polymer
  • SBR styrene-but
  • the content of the binder is not particularly limited, but is preferably 10% by weight or less, more preferably 0.1 to 5% by weight, based on the total weight of the negative electrode slurry composition in order to secure excellent electrode grip while minimizing the increase in electrode resistance. there is.
  • a method for preparing a slurry composition for a negative electrode of a lithium secondary battery according to the present invention will be described as follows.
  • the negative electrode active material coated with carbon nanotubes and having a carbon nanotube layer formed on the surface is prepared by mixing and stirring the negative electrode active material, the carbon nanotube slurry, and a solvent to form a mixture, and then drying the mixture.
  • drying of the mixture may be performed by drying in an oven or spraying using a spray dryer.
  • IPA isopropyl alcohol
  • the negative electrode active material having the carbon nanotube layer formed on the surface prepared above and the binder are mixed and stirred to finally prepare a slurry composition for a negative electrode of a lithium secondary battery according to the present invention.
  • the slurry composition for a negative electrode of a lithium secondary battery by mixing an active material for a negative electrode having a carbon nanotube layer formed by coating the surface with carbon nanotubes and a binder, it is more effective than an electrode using conventional carbon nanotubes. It has the advantage of increasing the electrical conductivity of the electrode and improving the dispersibility so that the conductive material can be uniformly and continuously distributed in the electrode, and furthermore, the stability of the negative active material during battery operation can be further improved.
  • Another aspect of the present invention relates to a lithium secondary battery including a negative electrode prepared using the slurry composition for a negative electrode.
  • another aspect of the present invention relates to an active material for a negative electrode of a lithium secondary battery coated with carbon nanotubes and having a carbon nanotube layer formed on the surface, wherein the carbon nanotubes are single-walled carbon nanotubes and five-walled or less It includes at least one selected from the group consisting of multi-walled carbon nanotubes, and the content of at least one selected from the group consisting of single-walled carbon nanotubes and five-walled or less multi-walled carbon nanotubes coats an active material for a negative electrode. It is characterized in that more than 30% by weight relative to the weight of the total carbon nanotubes.
  • Carbon nanotube slurry (water-based, 35 g of solid content (0.4%) and 165 g of isopropyl alcohol (IPA) as a solvent were weighed and placed in a stirring container, and then stirred at 5,000 rpm for 5 minutes using a high shear mixer to form a mixture. Next, the resulting mixture is put in a drying container and dried in an oven at 200 ° C. for 8 hours, or the resulting mixture is sprayed using a spray dryer at 150 ° C. at a rate of 10 ml / min to form single-walled carbon nanotubes.
  • the mass ratio of the active material for the negative electrode and the single-walled carbon nanotubes coated on the surface of the active material for the negative electrode is 100:0.1.
  • 1 shows a transmission electron microscope (TEM) photograph of single-walled carbon nanotubes used in an embodiment of the present invention
  • FIG. 2 is a silicon-based cathode having a carbon nanotube layer formed on the surface according to an embodiment of the present invention. It shows the scanning electron microscope measurement result for the active material.
  • SBR Styrene butadiene rubber
  • a slurry composition for a negative electrode of a lithium secondary battery by mixing SiOx, a single-walled carbon nanotube, and styrene butadiene rubber (SBR) as a binder in the amount shown in Table 2 below, relative to the total weight of the negative electrode slurry composition, and stirring was manufactured.
  • Example comparative example Capacity retention rate after the 50th cycle (%) 98.3 95.8
  • Figure 4 relates to a scanning electron microscope (SEM) photograph after removing the active material of the negative electrode active material on which the carbon nanotube layer is formed on the surface. According to Figure 7, the active material is removed and only the carbon nanotube layer covering the active material remains. You can check.
  • SEM scanning electron microscope
  • FIG. 5 relates to a transmission electron microscope (TEM) photograph of a carbon nanotube layer remaining after the active material is removed.
  • TEM transmission electron microscope
  • the present invention relates to a slurry composition for a negative electrode of a lithium secondary battery, and since it can be used for manufacturing a negative electrode of a lithium secondary battery, it has industrial applicability.

Abstract

The present invention relates to a slurry composition for a negative electrode of a lithium secondary battery, and more specifically, to a slurry composition characterized by being produced by mixing: a negative electrode active material which is coated with a carbon nanotube and thus has a carbon nanotube layer formed on the surface thereof; and a binder. According to a slurry composition for a negative electrode of a lithium secondary battery according to the present invention, mixing a binder and a negative electrode active material, the surface of which is coated with a carbon nanotube and which has a carbon nanotube layer formed thereon, can improve dispersibility while increasing the electrical conductivity of an electrode compared to conventional electrodes to which a carbon nanotube is applied, whereby there is the effect that a conductive material can be uniformly and continuously distributed in the electrode. In addition, according to the slurry composition for a negative electrode of a lithium secondary battery according to the present invention, there is an effect of increasing the stability of a negative electrode active material during battery operation.

Description

리튬이차전지의 음극용 슬러리 조성물Slurry composition for negative electrode of lithium secondary battery
본 발명은 전기 전도도 및 분산성이 개선된 리튬이차전지의 음극용 슬러리 조성물에 관한 것이다.The present invention relates to a slurry composition for a negative electrode of a lithium secondary battery having improved electrical conductivity and dispersibility.
전기화학적 에너지를 이용하는 전기화학 소자의 대표적인 예로 이차 전지를 들 수 있으며, 점점 더 그 사용 영역이 확대되고 있는 추세이다. 최근에는 휴대용 컴퓨터, 휴대용 전화기, 카메라 등의 휴대용 기기에 대한 기술 개발과 수요가 증가함에 따라 에너지원으로서 이차전지의 수요가 급격히 증가하고 있고, 그러한 이차 전지 중 높은 에너지 밀도, 즉 고용량의 리튬 이차전지에 대해 많은 연구가 행해져 왔고, 또한 상용화되어 널리 사용되고 있다.A representative example of an electrochemical device using electrochemical energy may be a secondary battery, and its use area is gradually expanding. Recently, as technology development and demand for portable devices such as portable computers, mobile phones, and cameras increase, the demand for secondary batteries as an energy source is rapidly increasing. A lot of research has been done on it, and it is also commercialized and widely used.
일반적으로 이차 전지는 양극, 음극, 전해질, 및 분리막으로 구성된다. 양극 및 음극은 일반적으로 전극 집전체와, 전극 집전체 상에 형성된 전극 활물질층으로 이루어지며, 상기 전극 활물질층은 전극 활물질, 도전재, 바인더 등을 포함하는 전극 슬러리 조성물을 전극 집전체 상에 도포, 건조한 후 압연하는 방식으로 제조된다.In general, a secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode and the negative electrode generally consist of an electrode current collector and an electrode active material layer formed on the electrode current collector, and the electrode active material layer is coated with an electrode slurry composition containing an electrode active material, a conductive material, a binder, etc. on the electrode current collector , it is manufactured by rolling after drying.
한편, 종래에는 이차 전지용 도전재로 카본 블랙과 같은 점형 도전재가 주로 사용되었으나, 이러한 점형 도전재의 경우 전기 전도성 향상 효과가 충분하지 않다는 문제점이 있었다. 이와 같은 문제점을 개선하기 위해 탄소나노튜브(Carbon NanoTube, CNT)나 탄소나노파이버(Carbon NanoFiber, CNF)와 같은 선형 도전재를 적용하는 방안에 대한 연구들이 활발하게 진행되고 있다.On the other hand, conventionally, a dotted conductive material such as carbon black has been mainly used as a conductive material for a secondary battery, but in the case of such a dotted conductive material, there is a problem in that the effect of improving electrical conductivity is not sufficient. In order to improve this problem, researches on methods of applying a linear conductive material such as carbon nanotubes (CNT) or carbon nanofibers (CNF) are being actively conducted.
그러나, 탄소나노튜브나 탄소나노파이버와 같은 선형 도전재의 경우, 전기 전도성은 우수하지만, 번들 타입 또는 인탱글 타입으로 성장하는 소재 자체의 특성상 슬러리 내에서의 분산성이 떨어져 코팅성 및 공정성이 떨어지고, 전극 활물질의 표면에 피복층으로 고르게 분포하지 않게 되는 문제점이 있다. 이와 같은 문제점을 개선하기 위해, 선형 도전재에 관능기 등을 도입하여 분산성을 향상시키고자 하는 시도들이 잇었으나, 이 경우, 관능기 존재에 의해 표면 부반응이 발생하여 전기화학 특성이 떨어진다는 문제점이 있다.However, linear conductive materials such as carbon nanotubes and carbon nanofibers have excellent electrical conductivity, but due to the nature of the material itself, which grows in a bundle type or entangle type, its dispersibility in the slurry is poor, resulting in poor coating and processability, and electrode There is a problem in that the coating layer is not evenly distributed on the surface of the active material. In order to improve such a problem, attempts have been made to improve dispersibility by introducing a functional group into a linear conductive material, but in this case, there is a problem in that the presence of a functional group causes a side reaction on the surface and deteriorates the electrochemical properties. .
본 발명은 상기와 같은 문제점을 해결하기 위해 도출된 것으로, 탄소나노튜브가 음극용 활물질의 표면을 전체적으로 고르게 피복 할 수 있도록 하고, 음극용 활물질의 물리·화학적 안정성과 전극의 전기 전도도를 획기적으로 높일 수 있으며, 전지의 수명 특성을 향상시킬 수 있는 리튬이차전지의 음극용 슬러리 조성물을 제공하는 것을 그 목적으로 한다.The present invention was derived to solve the above problems, so that carbon nanotubes can cover the entire surface of an active material for a negative electrode evenly, and dramatically increase the physical and chemical stability of the active material for a negative electrode and the electrical conductivity of the electrode. It is an object of the present invention to provide a slurry composition for a negative electrode of a lithium secondary battery capable of improving the lifespan characteristics of a battery.
상기와 같은 과제를 해결하기 위한 본 발명은 리튬이차전지의 음극용 슬러리 조성물에 관한 것으로, 보다 구체적으로 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질 및 바인더를 혼합하여 제조되는 것을 특징으로 한다.The present invention for solving the above problems relates to a slurry composition for a negative electrode of a lithium secondary battery, and more specifically, by mixing an active material for a negative electrode coated with carbon nanotubes and having a carbon nanotube layer formed on the surface, and a binder characterized in that it is manufactured.
또한, 본 발명의 다른 양태는 리튬이차전지의 음극용 슬러리 조성물에 관한 것으로, 보다 구체적으로 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질, 카본블랙(carbon black) 및 바인더를 혼합하여 제조되는 것을 특징으로 한다.In addition, another aspect of the present invention relates to a slurry composition for a negative electrode of a lithium secondary battery, more specifically, an active material for a negative electrode coated with carbon nanotubes and having a carbon nanotube layer formed on the surface, carbon black and It is characterized in that it is prepared by mixing a binder.
본 발명에 따른 리튬이차전지의 음극용 슬러리 조성물에 의하면, 탄소나노튜브로 피복된 음극용 활물질을 선행 제조 한 후 바인더와 혼합하여 리튬이차전지의 음극용 슬러리를 제조함으로써, 기존의 음극용 활물질, 탄소나노튜브 및 바인더를 한 번에 동시에 혼합하여 제조되는 전극 보다 탄소나노튜브가 음극용 활물질의 표면을 전체적으로 고르게 피복할 수 있도록 하며, 이로 인해 음극용 활물질의 물리·화학적 안정성이 더욱 더 높아지게 되는 것은 물론 접촉 저항이 더욱 더 낮아져 전기 전도도를 현저히 높일 수 있으며, 결과적으로 리튬이차전지의 수명 특성을 향상시킬 수 있는 효과가 있다.According to the slurry composition for a negative electrode of a lithium secondary battery according to the present invention, an active material for a negative electrode coated with carbon nanotubes is prepared in advance and then mixed with a binder to prepare a slurry for a negative electrode of a lithium secondary battery, Compared to an electrode manufactured by mixing carbon nanotubes and a binder at once, the carbon nanotubes allow the entire surface of the negative electrode active material to be evenly coated, thereby increasing the physical and chemical stability of the negative electrode active material. Of course, the contact resistance is further lowered to significantly increase the electrical conductivity, and as a result, there is an effect of improving the lifespan characteristics of the lithium secondary battery.
도 1은 본 발명의 실시예에 사용된 단일벽 탄소나노튜브에 대한 투과전자현미경(TEM) 사진을 나타낸 것이다.1 shows a transmission electron microscope (TEM) picture of a single-walled carbon nanotube used in an embodiment of the present invention.
도 2는 본 발명의 실시예에 따른 표면에 탄소나노튜브층이 형성된 실리콘계 음극용 활물질에 대한 주사전자현미경 측정 결과를 나타낸 것이다.FIG. 2 shows a scanning electron microscope measurement result for an active material for a silicon-based negative electrode having a carbon nanotube layer formed on the surface according to an embodiment of the present invention.
도 3은 본 발명의 실시예 및 비교예 각각의 음극용 슬러리 조성물을 이용하여 제조된 하프 코인 셀에 대한 충방전 시험 결과를 나타낸 그래프이다.3 is a graph showing the results of a charge/discharge test for half coin cells manufactured using the negative electrode slurry compositions of each of Examples and Comparative Examples of the present invention.
도 4는 표면에 탄소나노튜브층이 형성된 음극용 활물질의 활물질을 제거한 후의 주사전자현미경(SEM) 사진에 관한 것이다.4 relates to a scanning electron microscope (SEM) photograph after removing the active material of the negative electrode active material having a carbon nanotube layer formed on its surface.
도 5는 활물질이 제거된 후 잔존하는 탄소나노튜브층에 대한 투과전자현미경(TEM) 사진에 관한 것이다.5 relates to a transmission electron microscope (TEM) photograph of a carbon nanotube layer remaining after the active material is removed.
본 발명의 일 양태는 리튬이차전지의 음극용 슬러리 조성물에 관한 것으로, 보다 구체적으로 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질 및 바인더를 혼합하여 제조되는 것을 특징으로 한다. 또한, 본 발명의 다른 양태는 리튬이차전지의 음극용 슬러리 조성물에 관한 것으로, 보다 구체적으로 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질, 카본블랙(carbon black) 및 바인더를 혼합하여 제조되는 것일 수 있다. 본 발명은 탄소나노튜브를 피복 처리하여 표면에 탄소나노튜브층이 형성된 음극용 활물질을 선행 제조한 후 바인더와 혼합함으로써, 기존의 음극용 활물질, 탄소나노튜브 및 바인더를 한 번에 동시에 혼합하여 제조되는 전극 보다 탄소나노튜브가 음극용 활물질의 표면을 전체적으로 고르게 피복할 수 있도록 하며, 이로 인해 음극용 활물질의 물리·화학적 안정성을 더욱 더 높일 수 있고, 동시에 접촉 저항을 더욱 더 낮출 수 있어 전기 전도도를 현저히 높일 수 있게 된다.One aspect of the present invention relates to a slurry composition for a negative electrode of a lithium secondary battery. do. In addition, another aspect of the present invention relates to a slurry composition for a negative electrode of a lithium secondary battery, more specifically, an active material for a negative electrode coated with carbon nanotubes and having a carbon nanotube layer formed on the surface, carbon black and It may be prepared by mixing a binder. In the present invention, the active material for a negative electrode having a carbon nanotube layer formed on the surface is pre-prepared by coating the carbon nanotubes, and then mixed with the binder, thereby simultaneously mixing the existing active material for the negative electrode, the carbon nanotubes, and the binder at once. The carbon nanotubes can cover the entire surface of the active material for the negative electrode more evenly than the electrode, thereby further increasing the physical and chemical stability of the active material for the negative electrode, and at the same time lowering the contact resistance, thereby increasing the electrical conductivity. can be significantly increased.
본 발명에서 상기 음극용 활물질은 리튬이차전지 분야에서 통상적으로 사용되는 음극 활물질로서, 인조흑연, 천연흑연, 흑연화 탄소섬유, 비정질탄소 등의 탄소질 재료; Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si합금, Sn합금 또는 Al합금 등 리튬과 합금화가 가능한 금속질 화합물; SiOx(0<x<2), SnO2, 바나듐 산화물, 리튬 바나듐 산화물과 같이 리튬을 도프 및 탈도프할 수 있는 금속산화물; 또는 Si-C 복합체 또는 Sn-C 복합체과 같이 상기 금속질 화합물과 탄소질 재료를 포함하는 복합물 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. 본 발명은 상기 음극용 활물질로서 실리콘계 화합물을 사용하는 것이 에너지 밀도 측면에서 바람직하며, 상기 실리콘계 화합물은 예를 들면 실리콘계 산화물(SiOx)과 탄소질 재료의 혼합물일 수 있다.In the present invention, the negative electrode active material is a negative electrode active material commonly used in the field of lithium secondary batteries, and includes carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of being alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metal oxides capable of doping and undoping lithium, such as SiOx (0<x<2), SnO 2 , vanadium oxide, and lithium vanadium oxide; or a composite including the metallic compound and a carbonaceous material, such as a Si—C composite or a Sn—C composite, and any one or a mixture of two or more of these may be used. In the present invention, it is preferable to use a silicon-based compound as the active material for the negative electrode in terms of energy density, and the silicon-based compound may be, for example, a mixture of silicon-based oxide (SiOx) and a carbonaceous material.
본 발명에서 상기 음극용 활물질은 도전재인 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있는 것을 사용하는 것을 특징으로 한다. 본 발명은 상기 음극용 활물질의 외부 표면을 탄소나노튜브로 피복함으로써, 음극용 활물질의 지나친 부피 변화를 억제하여 안정성을 높임과 동시에 강한 도전성 경로를 확보할 수 있으며, 전극 활물질의 탈리를 억제하여 전극 접착력이 크게 향상될 수 있다.In the present invention, the active material for the negative electrode is characterized by using a carbon nanotube layer formed on the surface coated with carbon nanotubes as a conductive material. In the present invention, by covering the outer surface of the active material for the negative electrode with carbon nanotubes, an excessive volume change of the active material for the negative electrode can be suppressed to increase stability and at the same time, a strong conductive path can be secured, and detachment of the electrode active material can be suppressed to form an electrode. Adhesion can be greatly improved.
본 발명에서 상기 탄소나노튜브는 단일벽 탄소나노튜브나 다중벽 탄소나노튜브가 사용될 수 있으나, 활물질의 표면에 보다 견고하게 탄소나노튜브층을 형성하여, 전지의 구동 시 활물질의 수축·팽창에도 쉽게 탄소나노튜브층이 탈리되지 않도록 하기 위해 상기 탄소나노튜브는 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상을 포함하는 것이 바람직하고, 나아가 상기 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상의 함량이 음극용 활물질을 피복한 전체 탄소나노튜브의 중량 대비 30 중량% 이상인 것을 사용하는 것이 더욱 더 바람직할 수 있으며, 더 나아가 본 발명이 목적하는 전기전도성 및 분산성을 달성하고, 동시에 활물질의 안정성을 충분히 확보하기 위해서는 상기 음극용 활물질과 상기 음극용 활물질의 표면에 피복된 탄소나노튜브의 질량비는 특별히 제한적인 것은 아니나, 100 : 0.01 내지 100 : 10 인 것이 바람직하다.In the present invention, single-walled carbon nanotubes or multi-walled carbon nanotubes may be used as the carbon nanotubes, but a more robust carbon nanotube layer is formed on the surface of the active material so that the active material can be easily contracted and expanded during battery operation. In order to prevent the carbon nanotube layer from detaching, the carbon nanotubes preferably include at least one selected from the group consisting of single-walled carbon nanotubes and five-walled or less multi-walled carbon nanotubes, and furthermore, the single-walled carbon nanotubes It may be more preferable to use at least one content selected from the group consisting of nanotubes and multi-walled carbon nanotubes with five or less walls, which is 30% by weight or more relative to the total weight of the carbon nanotubes coated with the negative electrode active material, Furthermore, in order to achieve the electrical conductivity and dispersibility desired by the present invention and at the same time sufficiently secure the stability of the active material, the mass ratio of the active material for the negative electrode and the carbon nanotubes coated on the surface of the active material for the negative electrode is not particularly limited. , preferably from 100:0.01 to 100:10.
또한, 상기 단일벽 탄소나노튜브의 분산입도는 특별히 제한적인 것은 아니나, 1 내지 20 ㎛인 것이 바람직하다. 이는 상기 단일벽 탄소나노튜브의 분산입도가 1 ㎛ 보다 작을 경우에는 음극용 활물질 표면을 전체적으로 고르게 피복하기 어려우므로, 접촉 저항이 지나치게 높아지는 문제가 발생하고, 분산입도가 20 ㎛ 를 초과할 경우에는 탄소나노튜브 슬러리의 분산 안정성이 떨어지므로 피복 시 저항의 재현성이 떨어지는 문제가 있기 때문이다. 특히, 표면에 탄소나노튜브층이 형성되어 있는 단결정 음극용 활물질의 분체저항을 현저하게 낮추기 위해서는 상기 단일벽 탄소나노튜브의 분산입도가 5 내지 10 ㎛인 것이 보다 더 바람직하다. In addition, the dispersion particle size of the single-walled carbon nanotubes is not particularly limited, but is preferably 1 to 20 μm. This is because when the dispersion particle size of the single-walled carbon nanotubes is less than 1 μm, it is difficult to uniformly cover the entire surface of the active material for the negative electrode, resulting in an excessively high contact resistance, and when the dispersion particle size exceeds 20 μm, carbon This is because the dispersion stability of the nanotube slurry is poor, and thus the reproducibility of resistance during coating is poor. In particular, in order to remarkably lower the powder resistance of an active material for a single crystal negative electrode on which a carbon nanotube layer is formed on the surface, it is more preferable that the single-walled carbon nanotubes have a dispersed particle size of 5 to 10 μm.
또한, 본 발명에서 상기 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질은 본 발명이 목적하는 전기전도성 및 분산성을 달성하기 위해 분체저항 값이 1 내지 1000 Ωㆍcm 인 것이 바람직할 수 있다.In addition, in the present invention, the active material for a negative electrode having a carbon nanotube layer formed on the surface may preferably have a powder resistance value of 1 to 1000 Ω·cm in order to achieve the electrical conductivity and dispersibility desired by the present invention. .
본 발명에서 상기 바인더는 전극용 활물질들 간 또는 활물질과 집전체 간의 접착력을 확보하기 위해 첨가하는 것으로, 예를 들면, 비닐리덴플루오라이드-헥사플루오로프로필렌 코폴리머(PVDF-co-HFP), 폴리비닐알코올, 폴리아크릴로니트릴(polyacrylonitrile), 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 폴리머(EPDM), 술폰화-EPDM, 스티렌 부타디엔 고무(SBR), 불소고무, 또는 이들의 다양한 공중합체 등을 들 수 있으며, 이들 중 1종 단독 또는 2종 이상의 혼합물이 사용될 수 있다.In the present invention, the binder is added to secure adhesion between active materials for electrodes or between an active material and a current collector, for example, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), poly Vinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and the like, and one of them may be used alone or a mixture of two or more thereof.
상기 바인더는 함량이 특별히 제한적인 것은 아니나, 전극 저항 증가를 최소화하면서 우수한 전극 접지력을 확보하기 위해서 음극용 슬러리 조성물 전체 중량 대비 10 중량% 이하인 것이 바람직하며, 보다 바람직하게는 0.1 내지 5 중량%일 수 있다.The content of the binder is not particularly limited, but is preferably 10% by weight or less, more preferably 0.1 to 5% by weight, based on the total weight of the negative electrode slurry composition in order to secure excellent electrode grip while minimizing the increase in electrode resistance. there is.
본 발명에 따른 리튬이차전지의 음극용 슬러리 조성물의 제조방법에 대해 설명하면 다음과 같다.A method for preparing a slurry composition for a negative electrode of a lithium secondary battery according to the present invention will be described as follows.
먼저, 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질은 음극용 활물질, 탄소나노튜브 슬러리 및 용매를 혼합하고 교반하여 혼합물을 생성한 후, 상기 혼합물을 건조시켜 제조될 수 있다. 여기서, 상기 혼합물에 대한 건조는 오븐에서 건조시키거나, 분무건조기를 사용하여 분무함으로써 이루어질 수 있다. 본 발명에서 상기 탄소나노튜브 슬러리는 단일벽 탄소나노튜브가 물에 혼합된 것을 사용하는 것이 바람직하다. 또한, 상기 용매로는 아이소프로필알코올(IPA)을 사용하는 것이 바람직하다.First, the negative electrode active material coated with carbon nanotubes and having a carbon nanotube layer formed on the surface is prepared by mixing and stirring the negative electrode active material, the carbon nanotube slurry, and a solvent to form a mixture, and then drying the mixture. can Here, drying of the mixture may be performed by drying in an oven or spraying using a spray dryer. In the present invention, it is preferable to use a mixture of single-walled carbon nanotubes in water as the carbon nanotube slurry. In addition, it is preferable to use isopropyl alcohol (IPA) as the solvent.
다음으로, 상기에서 제조된 표면에 탄소나노튜브층이 형성된 음극용 활물질과 바인더를 혼합한 후 교반하여 최종적으로 본 발명에 따른 리튬이차전지의 음극용 슬러리 조성물을 제조한다.Next, the negative electrode active material having the carbon nanotube layer formed on the surface prepared above and the binder are mixed and stirred to finally prepare a slurry composition for a negative electrode of a lithium secondary battery according to the present invention.
본 발명에 따른 리튬이차전지의 음극용 슬러리 조성물에 의하면, 표면에 탄소나노튜브가 피복되어 탄소나노튜브층이 형성되어 있는 음극용 활물질과 바인더를 혼합함으로써, 기존의 탄소나노튜브를 적용하는 전극보다 전극의 전기 전도도를 높일 수 있으면서, 분산성을 향상시켜 도전재가 전극 내에서 균일하게 지속적으로 분포할 수 있도록 하는 이점이 있으며, 나아가 전지 구동 시 음극용 활물질의 안정성을 한층 더 높일 수 있다.According to the slurry composition for a negative electrode of a lithium secondary battery according to the present invention, by mixing an active material for a negative electrode having a carbon nanotube layer formed by coating the surface with carbon nanotubes and a binder, it is more effective than an electrode using conventional carbon nanotubes. It has the advantage of increasing the electrical conductivity of the electrode and improving the dispersibility so that the conductive material can be uniformly and continuously distributed in the electrode, and furthermore, the stability of the negative active material during battery operation can be further improved.
본 발명의 또 다른 양태는 상기의 음극용 슬러리 조성물을 이용하여 제조되는 음극을 포함하는 리튬이차전지에 관한 것이다.Another aspect of the present invention relates to a lithium secondary battery including a negative electrode prepared using the slurry composition for a negative electrode.
또한, 본 발명의 또 다른 양태는 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있는 리튬이차전지의 음극용 활물질에 관한 것으로, 상기 탄소나노튜브는 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상을 포함하고, 상기 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상의 함량이 음극용 활물질을 피복한 전체 탄소나노튜브의 중량 대비 30 중량% 이상인 것을 특징으로 한다.In addition, another aspect of the present invention relates to an active material for a negative electrode of a lithium secondary battery coated with carbon nanotubes and having a carbon nanotube layer formed on the surface, wherein the carbon nanotubes are single-walled carbon nanotubes and five-walled or less It includes at least one selected from the group consisting of multi-walled carbon nanotubes, and the content of at least one selected from the group consisting of single-walled carbon nanotubes and five-walled or less multi-walled carbon nanotubes coats an active material for a negative electrode. It is characterized in that more than 30% by weight relative to the weight of the total carbon nanotubes.
이하, 본 발명을 실시예를 통해 설명하도록 한다. 하기 실시예는 본 발명을 설명하기 위한 일 예에 지나지 않으며, 이에 의해 본 발명의 범위가 제한되는 것은 아니다.Hereinafter, the present invention will be described through examples. The following examples are only examples for explaining the present invention, and the scope of the present invention is not limited thereby.
<실시예><Example>
1. 표면에 탄소나노튜브층이 형성된 실리콘계 음극용 활물질의 제조1. Preparation of an active material for a silicon-based negative electrode having a carbon nanotube layer formed on the surface thereof
실리콘계 음극용 활물질인 천연흑연-SiOx 혼합물(천연흑연 : SiOx의 질량비는 9 : 1) 200g, 단일벽 탄소나노튜브의 함량이 95 중량%인 탄소나노튜브가 함유된 탄소나노튜브 슬러리(물 기반, 고형분 0.4%) 35g, 용매인 아이소프로필알코올(IPA) 165g을 각각 계량하여 교반 용기에 담은 후 하이 쉐어 믹서(High shear mixer)를 이용하여 5,000rpm 으로 5분 동안 교반하여 혼합물을 생성하였다. 다음으로, 생성된 혼합물을 건조 용기에 담아 오븐에서 200℃로 8시간 동안 건조시키거나, 상기 생성된 혼합물을 분무건조기를 이용하여 150℃에서 10ml/min의 속도로 분무하여 단일벽 탄소나노튜브가 피복되어 표면에 탄소나노튜브층이 형성된 음극용 활물질을 제조하였다. 여기서, 상기 음극용 활물질과 상기 음극용 활물질의 표면에 피복된 단일벽 탄소나노튜브의 질량비는 100 : 0.1 이다. 도 1은 본 발명의 실시예에 사용된 단일벽 탄소나노튜브에 대한 투과전자현미경(TEM) 사진을 나타낸 것이고, 도 2는 본 발명의 실시예에 따른 표면에 탄소나노튜브층이 형성된 실리콘계 음극용 활물질에 대한 주사전자현미경 측정 결과를 나타낸 것이다.Carbon nanotube slurry (water-based, 35 g of solid content (0.4%) and 165 g of isopropyl alcohol (IPA) as a solvent were weighed and placed in a stirring container, and then stirred at 5,000 rpm for 5 minutes using a high shear mixer to form a mixture. Next, the resulting mixture is put in a drying container and dried in an oven at 200 ° C. for 8 hours, or the resulting mixture is sprayed using a spray dryer at 150 ° C. at a rate of 10 ml / min to form single-walled carbon nanotubes. An active material for a negative electrode having a carbon nanotube layer formed on the surface thereof was prepared. Here, the mass ratio of the active material for the negative electrode and the single-walled carbon nanotubes coated on the surface of the active material for the negative electrode is 100:0.1. 1 shows a transmission electron microscope (TEM) photograph of single-walled carbon nanotubes used in an embodiment of the present invention, and FIG. 2 is a silicon-based cathode having a carbon nanotube layer formed on the surface according to an embodiment of the present invention. It shows the scanning electron microscope measurement result for the active material.
2. 리튬이차전지의 음극용 슬러리 조성물의 제조2. Preparation of slurry composition for negative electrode of lithium secondary battery
음극용 슬러리 조성물의 전체 중량 대비 상기에서 제조된 표면에 탄소나노튜브층이 형성된 실리콘계 음극용 활물질 및 바인더인 스티렌 부타디엔 고무(SBR)를 하기의 표 1에 나타난 함량으로 혼합한 후 교반하여 최종적으로 본 발명에 따른 리튬이차전지의 음극용 슬러리 조성물을 제조하였다.Styrene butadiene rubber (SBR), which is an active material for a silicon-based negative electrode having a carbon nanotube layer formed on the surface and a binder, was mixed in the contents shown in Table 1 below, compared to the total weight of the negative electrode slurry composition, and then stirred to finally A slurry composition for a negative electrode of a lithium secondary battery according to the present invention was prepared.
표면에 on the surface 탄소나노튜브층이layer of carbon nanotubes 형성된 음극용 활물질 Formed active material for negative electrode 바인더bookbinder
(SBR)(SBR)
실시예Example 98 중량%98% by weight 2 중량%2% by weight
<비교예><Comparative Example>
음극용 슬러리 조성물의 전체 중량 대비 실리콘계 음극용 활물질 SiOx, 단일벽탄소나노튜브, 바인더인 스티렌 부타디엔 고무(SBR)를 하기의 표 2에 나타난 함량으로 혼합한 후 교반하여 리튬이차전지의 음극용 슬러리 조성물을 제조하였다.A slurry composition for a negative electrode of a lithium secondary battery by mixing SiOx, a single-walled carbon nanotube, and styrene butadiene rubber (SBR) as a binder in the amount shown in Table 2 below, relative to the total weight of the negative electrode slurry composition, and stirring was manufactured.
음극용 활물질Active material for cathode
(SiOx)(SiOx) 		단일벽 탄소나노튜브single-walled carbon nanotubes
(SWCNT)(SWCNTs) 		바인더bookbinder
(SBR)(SBR)
비교예comparative example 97.95 중량%97.95% by weight 0.05 중량%0.05% by weight 2 중량%2% by weight
<실험예><Experimental example>
1. 수명 특성 실험1. Life characteristics test
상기 실시예 및 비교예의 음극용 슬러리 조성물 각각을 전극 집전체 상에 도포하고, 건조한 후 압연하여 제조된 음극, 분리막(PE Separator, SB16C), 전해질 (1 M LiPF6, EC/DEC/FEC (Ethylene carbonate/Diethylcarbonate/Fluoroethylene carbonate = 25/70/5 by volume), 1% VC(vinylene carbonate))을 이용하여 하프 코인 셀(Half coin cell)을 각각 조립한 후 수명 특성을 비교하는 실험을 실시하였으며, 그 결과는 표 3 및 도 3에 나타난 바와 같다. 충방전 시험은 WBCS 3000 Battery Cycler (Won A Tech)를 이용하여 충방전 시험을 진행하였고, 수명 테스트는 상온 및 1C에서 테스트를 진행하였다.Anode, separator (PE Separator, SB16C), electrolyte (1 M LiPF 6 , EC / DEC / FEC (Ethylene After assembling half coin cells using carbonate/Diethylcarbonate/Fluoroethylene carbonate = 25/70/5 by volume, 1% VC (vinylene carbonate)), an experiment was conducted to compare lifespan characteristics. The results are shown in Table 3 and FIG. 3. The charge/discharge test was conducted using a WBCS 3000 Battery Cycler (Won A Tech), and the life test was performed at room temperature and 1C.
[실험 조건][Experiment conditions]
- Charge : 0.5C, 0.01V & 0.01C cutoff- Charge : 0.5C, 0.01V & 0.01C cutoff
- Rest : 10min - Rest : 10min
- Discharge : 1.0C, 1.5V cutoff- Discharge : 1.0C, 1.5V cutoff
하기 표 3의 결과 값은 50번째 사이클 이후의 용량 보존율을 나타내고 있으며, 표 3 및 도 3에 의하면, 본 발명의 실시예의 음극용 슬러리 조성물로 제조된 하프 코인 셀이 비교예의 음극용 슬러리 조성물로 제조된 하프 코인 셀에 비해 전지의 수명 유지율이 더 높은 것을 알 수 있다. The result values in Table 3 below show the capacity retention rate after the 50th cycle, and according to Table 3 and FIG. 3, the half coin cell prepared with the slurry composition for negative electrode of Example of the present invention was prepared with the slurry composition for negative electrode of Comparative Example It can be seen that the life retention rate of the battery is higher than that of the half-coin cell.
실시예 Example 비교예 comparative example
50번째 사이클 이후의 용량 보존율(%)Capacity retention rate after the 50th cycle (%) 98.398.3 95.895.8
2. 활물질에 피복된 2. coated with active material 탄소나노튜브층의of carbon nanotube layer 분석 analyze
상기에서 제조된 표면에 탄소나노튜브층이 형성된 음극용 활물질 50g, 실리콘 에천트(etchant) 450g을 각각 원심분리기용 바틀에 담은 후 원심분리기를 이용하여 6,000rpm으로 5분 동안 교반하여 음극용 활물질을 제거하였다.50 g of the negative electrode active material and 450 g of the silicon etchant having the carbon nanotube layer formed on the surface prepared above were placed in a bottle for a centrifugal separator, and then stirred at 6,000 rpm for 5 minutes using a centrifuge to obtain an active material for the negative electrode. Removed.
다음으로, 물 500g을 상기 원심분리기용 바틀에 추가하여 6,000rpm으로 5분동안 교반하여 원심분리 및 추가 세척을 한 후, 세척이 완료된 샘플을 주사전자현미경(SEM) 및 투과전자현미경(TEM)으로 확인하였으며, 그 결과는 도 4 및 5에 나타난 바와 같다.Next, 500 g of water was added to the centrifuge bottle, stirred at 6,000 rpm for 5 minutes, centrifuged and additionally washed, and the washed sample was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was confirmed, and the results are as shown in FIGS. 4 and 5.
도 4는 표면에 탄소나노튜브층이 형성된 음극용 활물질의 활물질을 제거한 후의 주사전자현미경(SEM) 사진에 관한 것으로서, 도 7에 의하면 활물질이 제거되어 활물질을 피복하던 탄소나노튜브층만 잔존하는 것을 확인할 수 있다.Figure 4 relates to a scanning electron microscope (SEM) photograph after removing the active material of the negative electrode active material on which the carbon nanotube layer is formed on the surface. According to Figure 7, the active material is removed and only the carbon nanotube layer covering the active material remains. You can check.
나아가, 도 5는 활물질이 제거된 후 잔존하는 탄소나노튜브층에 대한 투과전자현미경(TEM) 사진에 관한 것으로서, 도 5에 의하면 음극용 활물질을 피복하던 탄소나노튜브층은 대부분이 단일벽 탄소나노튜브로 이루어져 있음을 확인할 수 있다.Furthermore, FIG. 5 relates to a transmission electron microscope (TEM) photograph of a carbon nanotube layer remaining after the active material is removed. According to FIG. 5, most of the carbon nanotube layer covering the negative electrode active material is single-walled carbon nano It can be seen that it consists of a tube.
본 발명은 리튬이차전지의 음극용 슬러리 조성물에 관한 것으로, 리튬이차전지의 음극 제조에 이용될 수 있으므로, 산업상 이용가능성이 있다.The present invention relates to a slurry composition for a negative electrode of a lithium secondary battery, and since it can be used for manufacturing a negative electrode of a lithium secondary battery, it has industrial applicability.

Claims (19)

  1. 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질 및 바인더를 혼합하여 제조되는 리튬이차전지의 음극용 슬러리 조성물.A slurry composition for a negative electrode of a lithium secondary battery prepared by mixing an active material for a negative electrode coated with carbon nanotubes and having a carbon nanotube layer formed on the surface thereof, and a binder.
  2. 제 1항에 있어서,According to claim 1,
    상기 탄소나노튜브는 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상을 포함하는 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.The carbon nanotube is a slurry composition for a negative electrode of a lithium secondary battery, characterized in that it comprises at least one selected from the group consisting of single-walled carbon nanotubes and five-walled or less multi-walled carbon nanotubes.
  3. 제 2항에 있어서,According to claim 2,
    상기 단일벽 탄소나노튜브의 분산입도가 1 내지 20㎛ 인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.A slurry composition for a negative electrode of a lithium secondary battery, characterized in that the dispersion particle size of the single-walled carbon nanotubes is 1 to 20 μm.
  4. 제 2항에 있어서,According to claim 2,
    상기 탄소나노튜브는 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상의 함량이 음극용 활물질을 피복한 전체 탄소나노튜브의 중량 대비 30 중량% 이상인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.In the carbon nanotubes, the content of at least one selected from the group consisting of single-walled carbon nanotubes and multi-walled carbon nanotubes of 5 or less layers is 30% by weight or more relative to the weight of the total carbon nanotubes coated with an active material for a negative electrode. A slurry composition for a negative electrode of a lithium secondary battery.
  5. 제 1항에 있어서,According to claim 1,
    상기 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질은 분체저항 값이 1 내지 1000 Ωㆍcm 인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.A slurry composition for a negative electrode of a lithium secondary battery, characterized in that the active material for a negative electrode having a carbon nanotube layer formed on the surface has a powder resistance value of 1 to 1000 Ω·cm.
  6. 제 4항에 있어서,According to claim 4,
    상기 음극용 활물질과 상기 음극용 활물질의 표면에 피복된 탄소나노튜브의 질량비는 100 : 0.01 내지 100 : 10 인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.The slurry composition for a negative electrode of a lithium secondary battery, characterized in that the mass ratio of the active material for the negative electrode and the carbon nanotubes coated on the surface of the active material for the negative electrode is 100: 0.01 to 100: 10.
  7. 제 1항에 있어서,According to claim 1,
    상기 음극용 활물질은 실리콘계 화합물인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.The active material for the negative electrode is a slurry composition for a negative electrode of a lithium secondary battery, characterized in that the silicon-based compound.
  8. 제 1항에 있어서,According to claim 1,
    상기 바인더는 폴리비닐리덴플루오라이드(PVdF), 폴리비닐리덴플루오라이드-헥사플루오로프로필렌 코폴리머(PVdF-co-HFP), 폴리비닐알코올, 폴리아크릴로니트릴(polyacrylonitrile), 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 폴리머(EPDM), 술폰화-EPDM, 스티렌 부타디엔 고무(SBR), 불소고무 또는 이들의 다양한 공중합체인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.The binder is polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose ( CMC), starch, hydroxypropylcellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluorine A slurry composition for a negative electrode of a lithium secondary battery, characterized in that it is rubber or various copolymers thereof.
  9. 제 1항 내지 제 8항 중 어느 한 항의 음극용 슬러리 조성물을 이용하여 제조되는 음극을 포함하는 리튬이차전지.A lithium secondary battery comprising a negative electrode prepared using the slurry composition for a negative electrode according to any one of claims 1 to 8.
  10. 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질, 카본블랙 및 바인더를 혼합하여 제조되는 리튬이차전지의 음극용 슬러리 조성물.Carbon black, an active material for negative electrodes coated with carbon nanotubes and having a carbon nanotube layer formed on the surface And a slurry composition for a negative electrode of a lithium secondary battery prepared by mixing a binder.
  11. 제 10항에 있어서,According to claim 10,
    상기 탄소나노튜브는 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상을 포함하는 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.The carbon nanotube is a slurry composition for a negative electrode of a lithium secondary battery, characterized in that it comprises at least one selected from the group consisting of single-walled carbon nanotubes and five-walled or less multi-walled carbon nanotubes.
  12. 제 11항에 있어서,According to claim 11,
    상기 단일벽 탄소나노튜브의 분산입도가 1 내지 20㎛ 인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.A slurry composition for a negative electrode of a lithium secondary battery, characterized in that the dispersion particle size of the single-walled carbon nanotubes is 1 to 20 μm.
  13. 제 11항에 있어서,According to claim 11,
    상기 탄소나노튜브는 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상의 함량이 음극용 활물질을 피복한 전체 탄소나노튜브의 중량 대비 30 중량% 이상인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.In the carbon nanotubes, the content of at least one selected from the group consisting of single-walled carbon nanotubes and multi-walled carbon nanotubes of 5 or less layers is 30% by weight or more relative to the weight of the total carbon nanotubes coated with an active material for a negative electrode. A slurry composition for a negative electrode of a lithium secondary battery.
  14. 제 10항에 있어서,According to claim 10,
    상기 표면에 탄소나노튜브층이 형성되어 있는 음극용 활물질은 분체저항 값이 1 내지 1000 Ωㆍcm 인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.A slurry composition for a negative electrode of a lithium secondary battery, characterized in that the active material for a negative electrode having a carbon nanotube layer formed on the surface has a powder resistance value of 1 to 1000 Ω·cm.
  15. 제 13항에 있어서,According to claim 13,
    상기 음극용 활물질과 상기 음극용 활물질의 표면에 피복된 탄소나노튜브의 질량비는 100 : 0.01 내지 100 : 10 인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.The slurry composition for a negative electrode of a lithium secondary battery, characterized in that the mass ratio of the active material for the negative electrode and the carbon nanotubes coated on the surface of the active material for the negative electrode is 100: 0.01 to 100: 10.
  16. 제 10항에 있어서,According to claim 10,
    상기 음극용 활물질은 실리콘계 화합물인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.The active material for the negative electrode is a slurry composition for a negative electrode of a lithium secondary battery, characterized in that the silicon-based compound.
  17. 제 10항에 있어서,According to claim 10,
    상기 바인더는 폴리비닐리덴플루오라이드(PVdF), 폴리비닐리덴플루오라이드-헥사플루오로프로필렌 코폴리머(PVdF-co-HFP), 폴리비닐알코올, 폴리아크릴로니트릴(polyacrylonitrile), 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 에틸렌-프로필렌-디엔 폴리머(EPDM), 술폰화-EPDM, 스티렌 부타디엔 고무(SBR), 불소고무 또는 이들의 다양한 공중합체인 것을 특징으로 하는 리튬이차전지의 음극용 슬러리 조성물.The binder is polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose ( CMC), starch, hydroxypropylcellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluorine A slurry composition for a negative electrode of a lithium secondary battery, characterized in that it is rubber or various copolymers thereof.
  18. 제 10항 내지 제 17항 중 어느 한 항의 음극용 슬러리 조성물을 이용하여 제조되는 음극을 포함하는 리튬이차전지.A lithium secondary battery comprising a negative electrode prepared using the slurry composition for a negative electrode according to any one of claims 10 to 17.
  19. 탄소나노튜브로 피복되어 표면에 탄소나노튜브층이 형성되어 있되,It is coated with carbon nanotubes and a carbon nanotube layer is formed on the surface,
    상기 탄소나노튜브는 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상을 포함하고, 상기 단일벽 탄소나노튜브 및 5중벽 이하의 다중벽 탄소나노튜브로 이루어진 군으로부터 선택된 어느 하나 이상의 함량이 음극용 활물질을 피복한 전체 탄소나노튜브의 중량 대비 30 중량% 이상인 리튬이차전지의 음극용 활물질.The carbon nanotubes include at least one selected from the group consisting of single-walled carbon nanotubes and five-walled or less multi-walled carbon nanotubes, and are composed of the single-walled carbon nanotubes and five-walled or less multi-walled carbon nanotubes. An active material for a negative electrode of a lithium secondary battery in which the content of at least one selected from the group is 30% by weight or more based on the weight of the total carbon nanotubes coated with the active material for a negative electrode.
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