WO2019059438A1 - Secondary battery anode active material and manufacturing method therefor - Google Patents

Secondary battery anode active material and manufacturing method therefor Download PDF

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Publication number
WO2019059438A1
WO2019059438A1 PCT/KR2017/010547 KR2017010547W WO2019059438A1 WO 2019059438 A1 WO2019059438 A1 WO 2019059438A1 KR 2017010547 W KR2017010547 W KR 2017010547W WO 2019059438 A1 WO2019059438 A1 WO 2019059438A1
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WIPO (PCT)
Prior art keywords
silicon
conductive wire
coating layer
carbon coating
carbon
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PCT/KR2017/010547
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French (fr)
Korean (ko)
Inventor
추연이
홍순호
이기강
송진우
박현기
이상한
김용욱
양태영
유재형
Original Assignee
엠케이전자 주식회사
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Priority to PCT/KR2017/010547 priority Critical patent/WO2019059438A1/en
Publication of WO2019059438A1 publication Critical patent/WO2019059438A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/10—Alloys containing non-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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • 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
    • 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 secondary battery, and more particularly, to a negative electrode active material for a secondary battery capable of providing high capacity and high efficiency charging / discharging characteristics, and a method of manufacturing the secondary battery.
  • the lithium secondary battery has been used as a power source for portable electronic products including mobile phones and notebook computers, as well as being used as a medium and large power source for hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (plug-in HEV) Applications are rapidly expanding. As the application field is expanded and demand is increased, the external shape and size of the battery are variously changed, and capacity, lifetime, and safety are demanded more than those required in conventional small batteries.
  • HEV hybrid electric vehicles
  • plug-in HEV plug-in hybrid electric vehicles
  • the lithium secondary battery is generally manufactured by using a material capable of intercalating and deintercalating lithium ions as a cathode and an anode, providing a porous separator between the electrodes, and then injecting an electrolyte. And electricity is generated or consumed by the redox reaction by insertion and desorption of lithium ions in the anode.
  • Graphite which is a negative electrode active material widely used in conventional lithium secondary batteries, has a layered structure and is very useful for insertion and desorption of lithium ions. Theoretically, graphite has a capacity of 372 mAh / g, but with the recent increase in demand for high capacity lithium batteries, a new electrode capable of replacing graphite is required. Accordingly, researches for commercialization of electrode active materials such as silicon (Si), tin (Sn), antimony (Sb), aluminum (Al) and the like that form an electrochemical alloy with lithium ion as a high capacity negative electrode active material are actively conducted .
  • electrode active materials such as silicon (Si), tin (Sn), antimony (Sb), aluminum (Al) and the like that form an electrochemical alloy with lithium ion as a high capacity negative electrode active material are actively conducted .
  • silicon, tin, antimony, and aluminum have the characteristics of increasing / decreasing the volume during charging / discharging through the formation of an electrochemical alloy with lithium.
  • the volume change due to such charging / The electrode cycle characteristics are deteriorated in an electrode in which an active material such as aluminum is introduced.
  • an active material such as aluminum is introduced.
  • such a change in volume causes cracks on the surface of the electrode active material, and continuous crack formation causes undifferentiation of the surface of the electrode, thereby deteriorating cycle characteristics.
  • the present invention provides a negative electrode active material for a secondary battery capable of providing a high capacity and high efficiency of charge / discharge characteristics.
  • a method for manufacturing a negative electrode active material for a secondary battery there is provided a method for manufacturing a negative electrode active material for a secondary battery.
  • a negative active material comprising: a silicon-containing particle; A first conductive wire attached on a surface of the silicon-containing particle; A carbon coating layer formed on at least a part of the surface of the silicon-containing particle or on the first conductive wire; And at least a portion of the surface of the silicon-containing particle and a second conductive wire attached to the carbon coating layer.
  • the carbon coating layer is formed on a portion of the surface of the silicon-containing particle, and the carbon coating layer may be formed on at least a portion of the first conductive wire.
  • the content of the first conductive wire included in the negative electrode active material may be about 0.1 to about 6 weight percent (wt%).
  • the content of the second conductive wire included in the negative electrode active material may be about 0.1 to about 6 wt%.
  • the silicon-containing particles may comprise a silicon-metal alloy, silicon oxide, silicon carbide, porous silicon, nanosilicon, or silicon nanowires.
  • the first conductive wire and the second conductive wire include a carbon nanotube, a carbon fiber, a graphene, a wire including carbon, a copper nanowire, a silver nanowire, or a metallic nanowire .
  • the carbon coating layer comprises an amorphous carbon material, wherein the amorphous carbon material is selected from soft carbon, hard carbon, coal pitch, petroleum pitch, mesophase pitch carbide, calcined coke and combinations thereof .
  • a negative active material comprising: a silicon-containing particle; A first conductive wire attached on a surface of the silicon-containing particle; A first carbon coating layer formed on at least a part of the surface of the silicon-containing particle or on the first conductive wire; A second conductive wire attached to at least a portion of a surface of the silicon-containing particle and the first carbon coating layer; A second carbon coating layer formed on the first carbon coating layer or the second conductive wire; And a third conductive wire formed on the second carbon coating layer.
  • the third conductive wire may be attached on the surface of the first carbon coating layer or the second carbon coating layer.
  • a method of manufacturing an anode active material including: preparing a first powder including silicon, a second powder including iron, and a third powder including a first additive element Forming a silicon-metal alloy powder including silicon, iron and a first additive element by a first mechanical alloying process; Attaching a first conductive wire on the silicon-metal alloy powder surface by a milling process using the silicon-metal alloy powder and the first conductive wire; Forming a carbon coating layer on the silicon-metal alloy powder by mixing the amorphous carbon material with the silicon-metal alloy powder to which the first conductive wire is attached; And then attaching the second conductive wire to the surface of the silicon-metal alloy powder or the surface of the carbon coating layer by a milling process using the silicon-metal alloy powder and the second conductive wire on which the carbon coating layer is formed.
  • the silicon-metal alloy powder is refined by the milling process and the first conductive wire is refined Can be uniformly dispersed and attached on the surface of the silicon-metal alloy.
  • the negative electrode active material according to the present invention includes a first conductive wire attached on the surface of the silicon-containing particle, a carbon coating layer formed on the surface of the silicon-containing particle to cover the first conductive wire, and a second conductive wire on the carbon coating layer .
  • the first and second conductive wires including, for example, carbon nanotubes and the like, provide electrical conductivity to the silicon-containing particles, and a carbon coating layer comprising an amorphous carbon material is filled with a charge
  • the negative electrode active material may exhibit high capacity retention characteristics and high-rate characteristics.
  • FIG. 1 shows a schematic cross-sectional view of a negative electrode active material according to exemplary embodiments.
  • FIG. 2 is a flowchart showing a manufacturing process of a negative electrode active material according to exemplary embodiments.
  • SEM scanning electron microscopy
  • FIG. 4 is a scanning electron microscope image of (a) and (b) before and after the charge / discharge test of the negative electrode active material according to the comparative example.
  • FIG. 5 is a scanning electron microscope image after a charge / discharge test of the negative electrode active material according to the exemplary embodiments.
  • FIG. 6 is a graph showing the electrical conductivity of negative electrode active materials according to exemplary embodiments.
  • FIG. 7 is a graph showing capacity retention characteristics of negative electrode active materials according to exemplary embodiments.
  • At% represents the number of atoms occupied by the component in the total atomic number of the whole alloy as a percentage.
  • FIG. 1 shows a cross-sectional view of a negative electrode active material according to exemplary embodiments.
  • the anode active material 100 may include a silicon-containing particle 110, a first conductive layer 120, a carbon coating layer 130, and a second conductive layer 140.
  • the first conductive layer 120 may comprise a first conductive wire and may be uniformly dispersed and disposed on the surface of the silicon-containing particles 110.
  • the carbon coating layer 130 may cover the first conductive layer 120, i.e., the first conductive wire, and may be formed on at least a portion of the surface of the silicon-containing particle 110.
  • the carbon coating layer 130 covers the first conductive layer 120, i.e., the first conductive wire and is on the surface of the silicon-containing particle 110, But is not limited thereto.
  • the second conductive layer 140 may include a second conductive wire and may be uniformly dispersed and disposed on the surface of the silicon-containing particles 110 and the surface of the carbon coating layer 130.
  • the negative electrode active material 100 is formed such that the silicon-containing composite powders including the silicon-containing particles 110, the first conductive layer 120, the carbon coating layer 130, and the second conductive layer 140 are adhered to each other, .
  • the negative electrode active material 100 may include the silicon-containing composite powder and a conductive material (not shown) and a binder (not shown) included in a predetermined amount.
  • the silicon-containing particles 110 may comprise at least one of a silicon-metal alloy, silicon oxide, silicon carbide, porous silicon, nanosilicon, or silicon nanowires.
  • the silicon-containing particle 110 when the silicon-containing particle 110 is a silicon-metal alloy particle, the silicon-containing particle 110 may comprise a single phase silicon (not shown) and a silicon - metal alloy phase (not shown).
  • the silicon-containing particles 110 comprise 60 to 90 at% of silicon (Si), 3 to 20 at% of iron (Fe), and 0 to 5 at% of a first additional element do.
  • the first additional element may be at least one element selected from the group consisting of boron (B), magnesium (Mg), aluminum (Al), manganese (Mn), cobalt (Co), chromium (Cr), tin (Sn), molybdenum (Mo), niobium At least one species selected from the group consisting of phosphorus (P), titanium (Ti), nickel (Ni), copper (Cu), zirconium (Zr) and zinc (Zn).
  • the silicon-containing particles 110 may comprise about 83.5 at% silicon, about 13.5 at% iron, about 2 at% manganese, and about 1 at% boron.
  • the first conductive layer 120 may comprise a first conductive wire and may be uniformly dispersed and disposed on the surface of the silicon-containing particles 110.
  • the first conductive wire may comprise a wire comprising carbon nanotubes, carbon fibers, graphene, or carbon.
  • the first conductive wire may comprise copper nanowires, or metallic nanowires such as silver nanowires.
  • the silicon-containing particles 110 comprise a silicon-metal alloy powder and the first conductive layer 120 comprises carbon nanotubes
  • the surface of the silicon-containing particles 110 is removed by a milling process The first conductive layer 120 may be formed.
  • the first conductive layer 120 may be formed on the surface of the silicon-containing particle 110 to a thickness of from about several angstroms to several tens of nanometers,
  • the first conductive wire may be uniformly dispersed and attached on the surface of the silicon-containing particles 110.
  • the first conductive wire constituting the first conductive layer 120 may have a short axis and a long axis (wherein the long axis is referred to as a vertical axis), and the length along the long axis may be substantially longer than the length along the short axis. As shown in FIG.
  • the first conductive wire constituting the first conductive layer 120 may be adhered such that the sidewall extending along its longitudinal axis adheres to the surface of the silicon-containing particle 110.
  • the first conductive wire constituting the first conductive layer 120 may have a length along the longitudinal axis of from about 2 nm to about 30 nm.
  • the first conductive wire constituting the first conductive layer 120 may have a side wall along its minor axis attached on the surface of the silicon-containing particle 110 and extending along the longitudinal axis thereof from the surface of the silicon- As shown in Fig.
  • the first conductive wire constituting the first conductive layer 120 may be included in the negative electrode active material 100 in an amount of about 0.1 to about 6 weight percent (wt%).
  • the carbon coating layer 130 may be disposed to cover the first conductive layer 120 on the surface of the silicon-containing particles 110.
  • the carbon coating layer 130 may be formed to have a relatively uniform thickness so as to cover the first conductive wire constituting the first conductive layer 120 on the surface of the silicon-containing particles 110.
  • the carbon coating layer 130 may be formed to cover substantially the whole surface of the silicon-containing particles 110, but the technical idea of the present invention is not limited thereto.
  • the carbon coating layer 130 is formed to a relatively uniform thickness on a portion of the surface of the silicon-containing particle 110, and a portion of the surface of the silicon-containing particle 110 is coated on the carbon coating layer 130,
  • the first conductive layer 120 or the second conductive layer 140 may be disposed on a portion of the surface of the silicon-containing particles 110 not covered by the carbon coating layer 130 It is possible.
  • the carbon coating layer 130 may comprise an amorphous carbon material.
  • the amorphous carbon material may be selected from soft carbon, hard carbon, coal pitch, petroleum pitch, mesophase pitch carbide, calcined coke and combinations thereof.
  • the carbon coating layer 130 may be formed by mixing the amorphous carbon material and the silicon-containing particles 110 and then heat-treating the silicon-containing particles 110 in an inert gas atmosphere to form a carbon- .
  • the carbon coating layer 130 may be formed to a thickness of about several nanometers to tens of nanometers on the surface of the silicon-containing particles 110, and the carbon coating layer 130 may be formed to a thickness of about 0.1 to about 6 wt. < / RTI > in the anode active material 100.
  • the second conductive layer 140 may comprise a second conductive wire and may be uniformly dispersed and disposed on the surface of the carbon coating layer 130.
  • the second conductive wire may comprise a wire comprising carbon nanotubes, carbon fibers, graphene, or carbon.
  • the second conductive wire may comprise copper nanowires, or metallic nanowires such as silver nanowires.
  • the second conductive layer 140 may be formed on the surface of the carbon coating layer 130 and / or on the surface of the silicon-containing particles 110 by a milling process.
  • the second conductive layer 140 may be formed on the surface of the carbon coating layer 130 and / or the surface of the silicon-containing particles 110 to a thickness of from about several angstroms to several tens of nanometers,
  • the second conductive wires constituting the second conductive layer 140 may be uniformly dispersed and attached on the surface of the carbon coating layer 130 and / or the surface of the silicon-containing particles 110.
  • the second conductive wire constituting the second conductive layer 140 may have a short axis and a long axis (wherein the long axis is referred to as a vertical axis), and the length along the long axis may be substantially longer than the length along the short axis. As shown in FIG.
  • the second conductive wires constituting the second conductive layer 140 may be adhered such that sidewalls extending along the longitudinal axis thereof adhere to the surface of the carbon coating layer 130.
  • the second conductive wire constituting the second conductive layer 140 may have a length along the longitudinal axis of from about 2 nm to about 30 nm.
  • the second conductive wires constituting the second conductive layer 140 may be formed such that the side walls along the minor axis thereof are attached on the surface of the carbon coating layer 130 and extended along the longitudinal axis thereof from the surface of the carbon coating layer 130 .
  • the second conductive wire constituting the second conductive layer 140 may be included in the negative electrode active material 100 in an amount of about 0.1 to about 6 weight percent (wt%).
  • the carbon coating layer 130 may be composed of a plurality of layers, and the conductive wires may be dispersed and disposed between the plurality of carbon coating layers 130.
  • a first conductive wire is formed on the surface of the silicon-containing particle 110
  • a first carbon coating layer is formed on the silicon-containing particle 110 and the first conductive wire
  • a second carbon coating layer may be formed on the first carbon coating layer and a second conductive wire
  • a third conductive wire may be formed on the second carbon coating layer.
  • the third conductive wire may comprise a material similar to the first and second conductive wires.
  • the first conductive wire constituting the first conductive layer 120 and the second conductive wire constituting the second conductive layer 140 may be formed of a material having a high electrical conductivity, for example, a carbon nanotube Containing nanoparticles, such as carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, An electrical path may be provided.
  • Chemical properties e. G., Discharge capacity or cycle performance
  • the carbon coating layer 130 may comprise an amorphous carbon material.
  • the silicon-containing particles 110 can function as a buffer layer for buffering the volume change of the silicon-containing particles 110 due to insertion / desorption of the lithium particles during charging / discharging of the silicon-containing particles 110, And damage can be prevented.
  • side reactions or the generation of undesirable nonreversible interface material layers that may be generated between the electrolyte and the silicon-containing particle 110 surface due to the large surface area of the silicon-containing particles 110 can be avoided. Therefore, the negative electrode active material 100 can have excellent capacity retention characteristics.
  • FIG. 2 is a flowchart showing a manufacturing process of a negative electrode active material according to exemplary embodiments.
  • a silicon-metal alloy powder including silicon, iron, and a first additive element may be formed by a first mechanical alloying process (step S10).
  • Iron, and a first additive element by a first mechanical alloying process using a third powder comprising, for example, a first powder comprising silicon, a second powder comprising iron, and a first additive element, Silicon-metal alloy powder can be formed.
  • the first additional element may be at least one element selected from the group consisting of boron (B), magnesium (Mg), aluminum (Al), manganese (Mn), cobalt (Co), chromium (Cr), tin (Sn), molybdenum (Mo), niobium At least one species selected from the group consisting of phosphorus (P), titanium (Ti), nickel (Ni), copper (Cu), zirconium (Zr) and zinc (Zn).
  • B boron
  • Mg magnesium
  • Al aluminum
  • Co cobalt
  • Cr chromium
  • Sn tin
  • Mo molybdenum
  • niobium At least one species selected from the group consisting of phosphorus (P), titanium (Ti), nickel (Ni), copper (Cu), zirconium (Zr) and zinc (Zn).
  • the negative electrode active material powder to be formed in step S10 contains 60 to 90 atomic percent (at%) silicon, 3 to 20 at% iron, and 0 to 5 at%
  • the mass of the first to third powders may be weighed so as to include one additional element.
  • the first mechanical alloying process may be a vertical milling machine, a horizontal milling machine, a ball milling machine, a planetary milling machine, a vibration milling machine, a speckle milling machine, Or by a milling device such as a milling device.
  • the first mechanical alloying process can be performed using a ball milling device with a diameter of 1 m and a chrome steel ball with a diameter of 25.4 mm.
  • the first powder, the second powder, and the third powder may be injected into the milling apparatus in powder form and the first mechanical alloying process may be performed, in which case the active material is heated at a high temperature After melting and rapidly cooling to form a primary alloy (for example, a ribbon alloy), the rapid cooling method of pulverizing the primary alloy to form the negative electrode active material powder may not be used.
  • a primary alloy for example, a ribbon alloy
  • the rapid cooling method of pulverizing the primary alloy to form the negative electrode active material powder may not be used.
  • an anode active material comprising 83.5 at% of silicon, 13.5 at% of iron, 2 at% of manganese and 1 at% of boron, 21.85 kg of silicon, 7.02 kg of iron, 1.02 kg of manganese, 0.1 kg of boron are prepared and they can be injected into the ball milling apparatus.
  • the first powder comprising silicon and the second powder comprising iron are melted and cooled to form an intermediate powder comprising silicon and iron, and then the intermediate powder and the first additive element
  • the third powder may be injected into the milling apparatus to perform the first mechanical alloying process.
  • an intermediate powder including silicon, iron and a first additive element formed by melting and cooling the first powder, the second powder and the third powder is injected into the milling apparatus to perform the first mechanical alloying process can do.
  • anode active material comprising 86 at% silicon, 11 at% iron, 2 at% manganese and 1 at% boron, 20.34 kg of ferrosilicon, 1.49 kg of silicon manganese, (Fe-B) of 0.64 kg, and 7.52 kg of silicon are prepared and they can be injected into the ball milling apparatus.
  • the mixture of the powders and the milling balls are drawn into the milling vessel, and the milling energy is used to pulverize and alloy the powders in a short time.
  • the mixture of the powders can be pulverized into finer powders having a finer size.
  • forging, cold pressure welding, and crushing may repeatedly occur between the fine powders ground by the rotation of the milling balls and the impact caused by the collision.
  • the interfacial energy increase becomes a driving force in the process of mixing the fine powders, so that the solid phase diffusion of the atoms is promoted and microalloying may occur. Therefore, a silicon-metal alloy powder in which silicon, iron and a first additional element are alloyed can be formed.
  • the silicon single phase may be uniformly distributed in the silicon-metal alloy phase, and the first additive element may be substituted or interstitially contained within the silicon-metal alloy phase, It may be present at the interface between the alloy phase and the silicon single phase.
  • the silicon single phase formed in the powder can be changed into a fine silicon single phase, and a fine silicon single phase can evenly be distributed using the silicon-metal alloy phase as a matrix.
  • the first conductive layer may be formed on the silicon-metal alloy powder by a milling process using the silicon-metal alloy powder and the first conductive wire (step S20).
  • the milling process may be performed by a milling device such as a vertical-type milling device, a horizontal-type milling device, a ball milling device, a planetary milling device, a vibration milling device, a spesific milling device, .
  • a milling device such as a vertical-type milling device, a horizontal-type milling device, a ball milling device, a planetary milling device, a vibration milling device, a spesific milling device, .
  • the milling process may be performed using an impact milling device of volume 6L and a chrome steel ball of diameter 50 mm.
  • a first conductive wire comprising, for example, a graphite, a carbon nanotube, a carbon fiber, a graphen, or a wire comprising carbon, or a metallic wire is formed by a relatively uniform Can be uniformly dispersed and adhered on the surface of the silicon-metal alloy powder while being miniaturized to a length of one nanometer size.
  • the silicon-metal alloy powder can also be further refined during the milling process.
  • a carbon coating layer may be formed on the silicon-metal alloy powder by mixing the amorphous carbon material with the silicon-metal alloy powder having the first conductive layer formed on its surface (Step S30).
  • the amorphous carbon material and the silicon-metal alloy powder to which the first conductive wire is attached may be mixed in the solvent by the milling process in step S20.
  • the silicon-metal alloy powder and the amorphous carbon material can be stirred and mixed in the air atmosphere for several tens minutes to several hours.
  • the carbon coating layer may be formed on the silicon-metal alloy powder by heat-treating the mixture in an inert gas atmosphere.
  • the heat treatment process may be performed at a temperature of about 500 DEG C for several hours, for example, in a nitrogen atmosphere, but is not limited thereto.
  • the amorphous carbon material may be selected from soft carbon, hard carbon, coal pitch, petroleum pitch, mesophase pitch carbide, calcined coke, and combinations thereof, wherein the amorphous carbon material is selected from the group consisting of May be contained in the solvent to have a total content of 1 to 6 wt%, but is not limited thereto.
  • the second conductive layer may be formed on the carbon coating layer by a milling process using the silicon-metal alloy powder having the carbon coating layer formed on its surface and the second conductive wire (S40).
  • the milling process may be performed by a milling device such as a vertical-type milling device, a horizontal-type milling device, a ball milling device, a planetary milling device, a vibration milling device, a spesific milling device, .
  • a milling device such as a vertical-type milling device, a horizontal-type milling device, a ball milling device, a planetary milling device, a vibration milling device, a spesific milling device, .
  • the milling process may be performed using an impact milling device of volume 6L and a chrome steel ball of diameter 50 mm.
  • a second conductive wire comprising, for example, graphite, a carbon nanotube, carbon fiber, graphene, or carbon containing wire, or a metallic wire, is grown to a thickness of about 2 nm to about 30 nm Sized and can be uniformly dispersed and attached on the surface of the carbon coating layer and / or on the surface of the silicon-metal alloy powder.
  • the powders of silicon, iron, and the first additive element can be made finer or alloyed by the first mechanical alloying process, thereby facilitating the manufacturing process.
  • the milling process allows the silicon-metal alloy powder to be refined, while the first conductive wire can be miniaturized to a uniform nanosize length and uniformly adhered onto the surface of the silicon-metal alloy powder.
  • the carbon coating layer can be conformally formed on the surface of the silicon-metal alloy powder by the following mixing process, and then the second conductive wire is miniaturized to a uniform nano-sized length by the milling process, And can be uniformly adhered. Accordingly, the negative electrode active material containing the silicon-metal alloy composite powder can be produced by a relatively easy manufacturing process.
  • the negative electrode active materials according to Examples 1 to 4 were produced according to the method of manufacturing the negative electrode active material described with reference to FIG. Specifically, for the raw materials shown in Table 1, a mechanical alloying process was performed using a ball milling device having a diameter of 1 m and a chrome steel ball having a diameter of 25.4 mm. Thereafter, a silicon-metal alloy powder and 3 wt.% Of carbon nanotubes were injected into the abrasion milling apparatus and a milling process was performed using a chromium steel ball having a diameter of 50 mm for forming the first conductive layer.
  • the silicon-metal alloy powder having the first conductive layer formed therein was injected with a pitch of 3 wt%, mixed with stirring, and then heat-treated to form a carbon coating layer.
  • carbon nanotubes of 0, 1, 3, and 5 wt.%, Respectively were injected into the abrasion milling apparatus (each of Examples 1 to 4) Milling was performed using a 50 mm chrome steel ball to obtain an anode active material powder. The classification process was then carried out by means of a jet mill.
  • SEM scanning electron microscopy
  • Fig. 3 shows a surface morphology in which a first conductive wire including carbon nanotubes is uniformly adhered to the surface of a silicon-metal alloy powder. It can be confirmed that carbon nanotubes extending in one direction on the surface of the substantially spherical or elliptic particles of the silicon-metal alloy powder uniformly adhere so as to cover substantially the whole surface of the spherical or elliptical particles.
  • FIG. 4 is a scanning electron microscopic image of the negative active material according to the comparative example before and after the charge / discharge test
  • FIG. 5 is a scanning electron microscope image after the charge / discharge test of the negative active material according to the exemplary embodiments. Image.
  • the negative electrode active material according to the comparative example has an irreversible interface material layer formed by side reactions with the electrolyte inside and outside the particles in the initial state where the powder is formed, that is, before the charge and discharge (see FIG. It shows a clean morphology that is not formed at all.
  • the negative electrode active material according to the comparative example has a substantial portion of the non-reversible interfacial material layer formed not only on the outer surface of the negative electrode active material, but also on the inside thereof after 300 charge / discharge cycles (see FIG. 4 (b)).
  • the negative electrode active material according to the exemplary embodiments has no crack or irreversible interface material layers formed in the negative electrode active material after the 300 charge / discharge tests, and has a clean internal surface can confirm.
  • the irreversible interface material layers are formed into a cone shape with a very thin thickness, which is inevitably formed due to side reactions between the negative electrode active material and the electrolyte. It is presumable that the irreversible capacity of the negative electrode active material according to the exemplary embodiments is remarkably small and excellent capacity characteristics as the non-reversible interfacial material layer is maintained at a very thin thickness even after completing 300 charge / discharge tests.
  • 6 is a graph showing the electrical conductivity of negative electrode active materials according to exemplary embodiments. 6 shows the electrical conductivities of Examples 1 to 4 and Comparative Example together with the content (wt%) of each of the first conductive layer and the second conductive layer.
  • Examples 1 to 4 exhibited excellent electrical conductivity as compared with Comparative Examples, and Example 4 showed the best electrical conductivity of about 132 S / cm. Particularly, in Examples 1 to 4, the electric conductivity gradually increased as the content of the first conductive layer (or the first conductive wire) and the second conductive layer (or the second conductive wire) gradually increased. This is believed to be because both the first conductive layer and the second conductive layer in the anode active material serve to provide an effective electrical path for the silicon-containing particles in the anode active material.
  • 7 is a graph showing a capacity holding characteristic of the negative electrode active material according to the exemplary embodiments. 7 shows the capacity retention rate (%) (i.e., the ratio of 300 discharge capacities to the initial discharge capacity) in the 300 cycles of Examples 1 to 4 and the comparative example in each of the first and second conductive layers (Wt%).
  • %) i.e., the ratio of 300 discharge capacities to the initial discharge capacity
  • Example 3 and Example 4 showed capacity retention of about 85% and about 84% in a 300 cycle, while Comparative Example showed a capacity retention of about 61% in a 300 cycle. That is, a cathode (anode) including 3 wt% of a first conductive layer (3 wt% of carbon nanotubes), 3 wt% of a carbon material layer, and 3 wt% of a second conductive layer (3 wt% of carbon nanotubes), 3 wt% of a carbon material layer, and 5 wt% of a second conductive layer (5 wt% of carbon nanotubes ) (Best Mode for Carrying Out the Invention).
  • a cathode anode including 3 wt% of a first conductive layer (3 wt% of carbon nanotubes), 3 wt% of a carbon material layer, and 3 wt% of a second conductive layer (3 wt% of carbon nanotubes ) (Best Mode for Carrying Out the Invention).
  • the carbon coating layer containing the amorphous carbon material not only effectively buffer the stress caused by the volume change occurring during charging and discharging of the silicon-metal alloy powder but also the first conductive layer and the second conductive layer including the carbon nanotubes, It may be considered that the metal alloy powder is provided with electrical conductivity and exhibits excellent capacity retention characteristics.

Abstract

Provided is a secondary battery anode active material capable of providing high capacity and high efficiency charge/discharge characteristics. The anode active material comprises: silicon-containing particles; a first conductive wire attached onto the surface of the silicon-containing particles; a carbon coating layer formed on at least a part of the surface of the silicon-containing particles or on the first conductive wire; and a second conductive wire attached onto at least a part of the surface of the silicon-containing particles or the carbon coating layer.

Description

이차 전지용 음극 활물질 및 그 제조 방법Negative electrode active material for secondary battery and manufacturing method thereof
본 발명의 기술적 사상은 이차 전지에 관한 것으로서, 더욱 상세하게는, 고용량, 고효율 충방전 특성을 제공할 수 있는 이차 전지용 음극 활물질 및 그 제조 방법에 관한 것이다.TECHNICAL FIELD The present invention relates to a secondary battery, and more particularly, to a negative electrode active material for a secondary battery capable of providing high capacity and high efficiency charging / discharging characteristics, and a method of manufacturing the secondary battery.
최근 리튬 이차 전지는 휴대폰, 노트북 컴퓨터 등을 비롯한 휴대용 전자제품의 전원으로 사용될 뿐만 아니라 하이브리드 전기자동차(hybrid electric vehicles, HEV), 플러그인 하이브리드 전기자동차(plug-in HEV) 등의 중대형 전원으로 사용되는 등 응용 분야가 급속히 확대되고 있다. 이와 같은 응용분야의 확대 및 수요의 증가에 따라 전지의 외형적인 모양과 크기도 다양하게 변하고 있으며, 기존의 소형전지에서 요구되는 특성보다 더욱 우수한 용량, 수명, 및 안전성이 요구되고 있다.Recently, the lithium secondary battery has been used as a power source for portable electronic products including mobile phones and notebook computers, as well as being used as a medium and large power source for hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (plug-in HEV) Applications are rapidly expanding. As the application field is expanded and demand is increased, the external shape and size of the battery are variously changed, and capacity, lifetime, and safety are demanded more than those required in conventional small batteries.
리튬 이차 전지는 리튬 이온의 삽입(intercalation) 및 탈리(deintercalation)가 가능한 물질을 음극 및 양극으로 사용하고, 상기 전극들 사이에 다공성 분리막을 설치한 후 전해액을 주입시켜 제조되는 것이 일반적이며, 상기 음극 및 양극에서 리튬 이온의 삽입 및 탈리에 의한 산화 환원 반응에 의하여 전기가 생성되거나 소비된다.The lithium secondary battery is generally manufactured by using a material capable of intercalating and deintercalating lithium ions as a cathode and an anode, providing a porous separator between the electrodes, and then injecting an electrolyte. And electricity is generated or consumed by the redox reaction by insertion and desorption of lithium ions in the anode.
종래의 리튬 이차 전지에 널리 사용되고 있는 음극 활물질인 흑연(graphite)은 층상 구조를 가지고 있어 리튬 이온의 삽입 및 탈리에 매우 유용한 특징을 지닌다. 흑연은 이론적으로 372mAh/g의 용량을 나타내지만 최근의 고용량의 리튬 전지에 대한 수요가 증가함에 따라 흑연을 대체할 수 있는 새로운 전극이 요구되고 있다. 이에 따라, 고용량의 음극 활물질로 실리콘(Si), 주석(Sn), 안티몬(Sb), 알루미늄(Al) 등과 같이 리튬 이온과 전기화학적인 합금을 형성하는 전극 활물질에 대하여 상용화를 위한 연구가 활발히 진행되고 있다. 그러나, 실리콘, 주석, 안티모니, 알루미늄 등은 리튬과의 전기화학적 합금 형성을 통한 충전/방전시 부피가 증가/감소하는 특성을 갖고 있으며, 이러한 충방전에 따른 부피 변화는 실리콘, 주석, 안티모니, 알루미늄 등의 활물질을 도입한 전극에 있어서 전극 사이클 특성을 열화시키는 문제를 갖고 있다. 또한, 이러한 부피 변화는 전극 활물질 표면에 균열을 일으키고, 지속적인 균열 형성은 전극 표면의 미분화를 가져오게 되어 사이클 특성을 열화시키는 또 다른 요인으로 작용하게 된다. Graphite, which is a negative electrode active material widely used in conventional lithium secondary batteries, has a layered structure and is very useful for insertion and desorption of lithium ions. Theoretically, graphite has a capacity of 372 mAh / g, but with the recent increase in demand for high capacity lithium batteries, a new electrode capable of replacing graphite is required. Accordingly, researches for commercialization of electrode active materials such as silicon (Si), tin (Sn), antimony (Sb), aluminum (Al) and the like that form an electrochemical alloy with lithium ion as a high capacity negative electrode active material are actively conducted . However, silicon, tin, antimony, and aluminum have the characteristics of increasing / decreasing the volume during charging / discharging through the formation of an electrochemical alloy with lithium. The volume change due to such charging / , The electrode cycle characteristics are deteriorated in an electrode in which an active material such as aluminum is introduced. Also, such a change in volume causes cracks on the surface of the electrode active material, and continuous crack formation causes undifferentiation of the surface of the electrode, thereby deteriorating cycle characteristics.
[선행기술문헌][Prior Art Literature]
[특허문헌][Patent Literature]
1. 한국공개특허 제2009-0099922호 (2009.09.23. 공개)1. Korean Patent Publication No. 2009-0099922 (Published September 23, 2009)
2. 한국공개특허 제2010-0060613호 (2010.06.07. 공개)2. Korean Patent Publication No. 2010-0060613 (Published on Jun. 7, 2010)
3. 한국공개특허 제2010-0127990호 (2010.12.07. 공개)3. Korea Patent Publication No. 2010-0127990 (Dec. 07, 2010)
본 발명의 기술적 사상이 이루고자 하는 기술적 과제는 고용량, 고효율 충방전 특성을 제공할 수 있는 이차 전지용 음극 활물질을 제공하는 것이다.SUMMARY OF THE INVENTION The present invention provides a negative electrode active material for a secondary battery capable of providing a high capacity and high efficiency of charge / discharge characteristics.
또한, 본 발명의 기술적 사상이 이루고자 하는 다른 기술적 과제는, 상기 이차 전지용 음극 활물질의 제조 방법을 제공하는 것이다.According to another aspect of the present invention, there is provided a method for manufacturing a negative electrode active material for a secondary battery.
상기 기술적 과제를 달성하기 위한 본 발명의 기술적 사상에 따른 음극 활물질은, 실리콘 함유 입자; 상기 실리콘 함유 입자의 표면 상에 부착되는 제1 도전성 와이어; 상기 실리콘 함유 입자의 표면의 적어도 일부 또는 상기 제1 도전성 와이어 상에 형성되는 카본 코팅층; 및 상기 실리콘 함유 입자의 표면의 적어도 일부 및 상기 카본 코팅층 상에 부착되는 제2 도전성 와이어를 포함한다.According to an aspect of the present invention, there is provided a negative active material comprising: a silicon-containing particle; A first conductive wire attached on a surface of the silicon-containing particle; A carbon coating layer formed on at least a part of the surface of the silicon-containing particle or on the first conductive wire; And at least a portion of the surface of the silicon-containing particle and a second conductive wire attached to the carbon coating layer.
예시적인 실시예들에서, 상기 카본 코팅층은 상기 실리콘 함유 입자의 표면 일부분 상에 형성되며, 상기 제1 도전성 와이어의 적어도 일부분 상에 상기 카본 코팅층이 형성될 수 있다.In exemplary embodiments, the carbon coating layer is formed on a portion of the surface of the silicon-containing particle, and the carbon coating layer may be formed on at least a portion of the first conductive wire.
예시적인 실시예들에서, 상기 음극 활물질에 포함되는 상기 제1 도전성 와이어의 함량은 약 0.1 내지 약 6 중량 퍼센트(wt%)일 수 있다.In exemplary embodiments, the content of the first conductive wire included in the negative electrode active material may be about 0.1 to about 6 weight percent (wt%).
예시적인 실시예들에서, 상기 음극 활물질에 포함되는 상기 제2 도전성 와이어의 함량은 약 0.1 내지 약 6 wt%일 수 있다.In exemplary embodiments, the content of the second conductive wire included in the negative electrode active material may be about 0.1 to about 6 wt%.
예시적인 실시예들에서, 상기 실리콘 함유 입자는 실리콘-금속 합금, 실리콘 산화물, 실리콘 카바이드, 다공성 실리콘, 나노 실리콘, 또는 실리콘 나노 와이어를 포함할 수 있다.In exemplary embodiments, the silicon-containing particles may comprise a silicon-metal alloy, silicon oxide, silicon carbide, porous silicon, nanosilicon, or silicon nanowires.
예시적인 실시예들에서, 상기 제1 도전성 와이어 및 상기 제2 도전성 와이어는 카본 나노 튜브, 카본 파이버, 그래핀, 카본을 포함하는 와이어, 구리 나노 와이어, 은 나노 와이어, 또는 금속성 나노 와이어를 포함할 수 있다.In exemplary embodiments, the first conductive wire and the second conductive wire include a carbon nanotube, a carbon fiber, a graphene, a wire including carbon, a copper nanowire, a silver nanowire, or a metallic nanowire .
예시적인 실시예들에서, 상기 카본 코팅층은 비정질 탄소 물질을 포함하며, 상기 비정질 탄소 물질은 소프트 카본, 하드 카본, 석탄계 피치, 석유계 피치, 메조페이스 피치 탄화물, 소성된 코크스 및 이들의 조합으로부터 선택될 수 있다.In exemplary embodiments, the carbon coating layer comprises an amorphous carbon material, wherein the amorphous carbon material is selected from soft carbon, hard carbon, coal pitch, petroleum pitch, mesophase pitch carbide, calcined coke and combinations thereof .
상기 기술적 과제를 달성하기 위한 본 발명의 기술적 사상에 따른 음극 활물질은, 실리콘 함유 입자; 상기 실리콘 함유 입자의 표면 상에 부착되는 제1 도전성 와이어; 상기 실리콘 함유 입자의 표면의 적어도 일부 또는 상기 제1 도전성 와이어 상에 형성되는 제1 카본 코팅층; 상기 실리콘 함유 입자의 표면의 적어도 일부 및 상기 제1 카본 코팅층 상에 부착되는 제2 도전성 와이어; 상기 제1 카본 코팅층 또는 상기 제2 도전성 와이어 상에 형성되는 제2 카본 코팅층; 및 상기 제2 카본 코팅층 상에 형성되는 제3 도전성 와이어를 포함한다.According to an aspect of the present invention, there is provided a negative active material comprising: a silicon-containing particle; A first conductive wire attached on a surface of the silicon-containing particle; A first carbon coating layer formed on at least a part of the surface of the silicon-containing particle or on the first conductive wire; A second conductive wire attached to at least a portion of a surface of the silicon-containing particle and the first carbon coating layer; A second carbon coating layer formed on the first carbon coating layer or the second conductive wire; And a third conductive wire formed on the second carbon coating layer.
예시적인 실시예들에서, 상기 제3 도전성 와이어는 상기 제1 카본 코팅층 또는 상기 제2 카본 코팅층의 표면 상에 부착될 수 있다.In exemplary embodiments, the third conductive wire may be attached on the surface of the first carbon coating layer or the second carbon coating layer.
상기 기술적 과제를 달성하기 위한 본 발명의 다른 기술적 사상에 따른 음극 활물질의 제조 방법은, 실리콘을 포함하는 제1 분말, 철을 포함하는 제2 분말 및 제1 첨가 원소를 포함하는 제3 분말을 사용하여 제1 기계적 합금화 공정에 의해 실리콘, 철 및 제1 첨가 원소를 포함하는 실리콘-금속 합금 분말을 형성하는 단계; 상기 실리콘-금속 합금 분말과 제1 도전성 와이어를 사용하여 밀링 공정에 의해 상기 실리콘-금속 합금 분말 표면 상에 제1 도전성 와이어를 부착하는 단계; 상기 제1 도전성 와이어가 부착된 상기 실리콘-금속 합금 분말과 비정질 탄소 물질을 혼합하여 상기 실리콘-금속 합금 분말 상에 카본 코팅층을 형성하는 단계; 상기 카본 코팅층이 형성된 상기 실리콘-금속 합금 분말과 제2 도전성 와이어를 사용하여 밀링 공정에 의해 상기 실리콘-금속 합금 분말 표면 또는 상기 카본 코팅층 표면 상에 제2 도전성 와이어를 부착하는 단계를 포함한다. According to another aspect of the present invention, there is provided a method of manufacturing an anode active material, the method including: preparing a first powder including silicon, a second powder including iron, and a third powder including a first additive element Forming a silicon-metal alloy powder including silicon, iron and a first additive element by a first mechanical alloying process; Attaching a first conductive wire on the silicon-metal alloy powder surface by a milling process using the silicon-metal alloy powder and the first conductive wire; Forming a carbon coating layer on the silicon-metal alloy powder by mixing the amorphous carbon material with the silicon-metal alloy powder to which the first conductive wire is attached; And then attaching the second conductive wire to the surface of the silicon-metal alloy powder or the surface of the carbon coating layer by a milling process using the silicon-metal alloy powder and the second conductive wire on which the carbon coating layer is formed.
예시적인 실시예들에서, 상기 실리콘-금속 합금 분말 표면 상에 상기 제1 도전성 와이어를 부착하는 단계에서, 상기 밀링 공정에 의해 상기 실리콘-금속 합금 분말이 미세화되고 상기 제1 도전성 와이어가 상기 미세화된 실리콘-금속 합금 표면 상에 균일하게 분산되어 부착될 수 있다.In the exemplary embodiments, in the step of attaching the first conductive wire on the surface of the silicon-metal alloy powder, the silicon-metal alloy powder is refined by the milling process and the first conductive wire is refined Can be uniformly dispersed and attached on the surface of the silicon-metal alloy.
본 발명에 따른 음극 활물질은 실리콘 함유 입자의 표면 상에 부착되는 제1 도전성 와이어, 실리콘 함유 입자의 표면 상에서 제1 도전성 와이어를 커버하도록 형성되는 카본 코팅층, 및 카본 코팅층 상의 제2 도전성 와이어를 포함한다. 예를 들어 카본 나노 튜브 등을 포함하는 제1 및 제2 도전성 와이어가 실리콘 함유 입자에 전기 전도성을 제공하며, 비정질 탄소 물질을 포함하는 카본 코팅층이 상기 실리콘 함유 입자에 리튬 이온이 삽입 또는 탈리되는 충전 및 방전 단계 동안에 발생할 수 있는 상기 실리콘 함유 입자의 부피 변화에 의한 스트레스를 효과적으로 완충할 수 있다. 상기 음극 활물질은 높은 용량 유지 특성을 보이는 한편 우수한 고율(high-rate) 특성을 보일 수 있다. The negative electrode active material according to the present invention includes a first conductive wire attached on the surface of the silicon-containing particle, a carbon coating layer formed on the surface of the silicon-containing particle to cover the first conductive wire, and a second conductive wire on the carbon coating layer . The first and second conductive wires including, for example, carbon nanotubes and the like, provide electrical conductivity to the silicon-containing particles, and a carbon coating layer comprising an amorphous carbon material is filled with a charge And the stress due to the volume change of the silicon-containing particles that may occur during the discharging step can be effectively buffered. The negative electrode active material may exhibit high capacity retention characteristics and high-rate characteristics.
도 1은 예시적인 실시예들에 따른 음극 활물질의 개략적인 단면도를 나타낸다.1 shows a schematic cross-sectional view of a negative electrode active material according to exemplary embodiments.
도 2는 예시적인 실시예들에 따른 음극 활물질의 제조 공정을 나타내는 플로우 차트이다. 2 is a flowchart showing a manufacturing process of a negative electrode active material according to exemplary embodiments.
도 3은 예시적인 실시예들에 따른 음극 활물질의 주사 전자 현미경(scanning electron microscopy, SEM) 이미지이다.3 is a scanning electron microscopy (SEM) image of an anode active material according to exemplary embodiments.
도 4는 비교예에 따른 음극 활물질의 충방전 테스트 이전(a) 및 이후(b)의 주사 전자 현미경 이미지이다.FIG. 4 is a scanning electron microscope image of (a) and (b) before and after the charge / discharge test of the negative electrode active material according to the comparative example.
도 5는 예시적인 실시예들에 따른 음극 활물질의 충방전 테스트 이후의 주사 전자 현미경 이미지이다.5 is a scanning electron microscope image after a charge / discharge test of the negative electrode active material according to the exemplary embodiments.
도 6은 예시적인 실시예들에 따른 음극 활물질들의 전기 전도도를 나타내는 그래프이다.6 is a graph showing the electrical conductivity of negative electrode active materials according to exemplary embodiments.
도 7은 예시적인 실시예들에 따른 음극 활물질들의 용량 유지 특성을 나타내는 그래프이다.7 is a graph showing capacity retention characteristics of negative electrode active materials according to exemplary embodiments.
이하, 첨부된 도면을 참조하여 본 발명의 바람직한 실시예를 상세히 설명하기로 한다. 본 발명의 실시예들은 당해 기술 분야에서 통상의 지식을 가진 자에게 본 발명의 기술적 사상을 더욱 완전하게 설명하기 위하여 제공되는 것이며, 하기 실시예는 여러 가지 다른 형태로 변형될 수 있으며, 본 발명의 기술적 사상의 범위가 하기 실시예에 한정되는 것은 아니다. 오히려, 이들 실시예는 본 개시를 더욱 충실하고 완전하게 하고, 당업자에게 본 발명의 기술적 사상을 완전하게 전달하기 위하여 제공되는 것이다. 본 명세서에서 사용된 바와 같이, 용어 "및/또는"은 해당 열거된 항목 중 어느 하나 및 하나 이상의 모든 조합을 포함한다. 동일한 부호는 시종 동일한 요소를 의미한다. 나아가, 도면에서의 다양한 요소와 영역은 개략적으로 그려진 것이다. 따라서, 본 발명의 기술적 사상은 첨부한 도면에 그려진 상대적인 크기나 간격에 의해 제한되지 않는다. 본 발명의 실시예들에서, at%(원자%)는 전체 합금의 원자 총 개수에서 해당 성분이 차지하는 원자 개수를 백분율로 표시한 것이다.Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. The scope of technical thought is not limited to the following examples. Rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the scope of the invention to those skilled in the art. As used herein, the term " and / or " includes any and all combinations of one or more of the listed items. The same reference numerals denote the same elements at all times. Further, various elements and regions in the drawings are schematically drawn. Accordingly, the technical spirit of the present invention is not limited by the relative size or spacing depicted in the accompanying drawings. In the embodiments of the present invention, at% (atomic%) represents the number of atoms occupied by the component in the total atomic number of the whole alloy as a percentage.
도 1은 예시적인 실시예들에 따른 음극 활물질의 단면도를 나타낸다.1 shows a cross-sectional view of a negative electrode active material according to exemplary embodiments.
도 1을 참조하면, 음극 활물질(100)은 실리콘 함유 입자(110), 제1 도전층(120), 카본 코팅층(130), 및 제2 도전층(140)을 포함할 수 있다. 제1 도전층(120)은 제1 도전성 와이어를 포함할 수 있고, 실리콘 함유 입자(110)의 표면 상에 균일하게 분산되어 배치될 수 있다. 카본 코팅층(130)은 제1 도전층(120), 즉 제1 도전성 와이어를 커버하며 실리콘 함유 입자(110)의 표면의 적어도 일부 상에 형성될 수 있다. 예를 들어, 도 1에서는 카본 코팅층(130)이 제1 도전층(120), 즉 제1 도전성 와이어를 커버하며 실리콘 함유 입자(110)의 표면 상에 된 것이 예시적으로 도시되었으나, 본 발명이 이에 한정되는 것은 아니다. 제2 도전층(140)은 제2 도전성 와이어를 포함할 수 있고, 실리콘 함유 입자(110)의 표면 및 카본 코팅층(130) 표면 상에 균일하게 분산되어 배치될 수 있다. 음극 활물질(100)은 실리콘 함유 입자(110), 제1 도전층(120), 카본 코팅층(130), 및 제2 도전층(140)을 포함하는 실리콘 함유 복합체 분말이 서로 부착되고 응집되어 형성될 수 있다. 도시되지는 않았지만, 음극 활물질(100)은 상기 실리콘 함유 복합체 분말과, 소정의 함량으로 포함된 도전재(도시 생략) 및 바인더(도시 생략)를 포함할 수도 있다.Referring to FIG. 1, the anode active material 100 may include a silicon-containing particle 110, a first conductive layer 120, a carbon coating layer 130, and a second conductive layer 140. The first conductive layer 120 may comprise a first conductive wire and may be uniformly dispersed and disposed on the surface of the silicon-containing particles 110. The carbon coating layer 130 may cover the first conductive layer 120, i.e., the first conductive wire, and may be formed on at least a portion of the surface of the silicon-containing particle 110. For example, although it is illustrated in FIG. 1 that the carbon coating layer 130 covers the first conductive layer 120, i.e., the first conductive wire and is on the surface of the silicon-containing particle 110, But is not limited thereto. The second conductive layer 140 may include a second conductive wire and may be uniformly dispersed and disposed on the surface of the silicon-containing particles 110 and the surface of the carbon coating layer 130. The negative electrode active material 100 is formed such that the silicon-containing composite powders including the silicon-containing particles 110, the first conductive layer 120, the carbon coating layer 130, and the second conductive layer 140 are adhered to each other, . Although not shown, the negative electrode active material 100 may include the silicon-containing composite powder and a conductive material (not shown) and a binder (not shown) included in a predetermined amount.
예시적인 실시예들에 있어서, 실리콘 함유 입자(110)는 실리콘-금속 합금, 실리콘 산화물, 실리콘 카바이드, 다공성 실리콘, 나노 실리콘, 또는 실리콘 나노와이어 중 적어도 하나를 포함할 수 있다. 예를 들어 실리콘 함유 입자(110)가 실리콘-금속 합금 입자일 때, 실리콘 함유 입자(110)는 실리콘 단일상(도시 생략), 및 상기 실리콘 단일상과 계면을 이루며 상기 실리콘 단일상을 둘러싸는 실리콘-금속 합금상(도시 생략)을 포함한다. 예시적인 실시예들에 있어서, 실리콘 함유 입자(110)는 60 내지 90 at%의 실리콘(Si), 3 내지 20 at%의 철(Fe), 및 0 내지 5 at%의 제1 첨가 원소를 포함한다. 상기 제1 첨가 원소는 보론(B), 마그네슘(Mg), 알루미늄(Al), 망간(Mn), 코발트(Co), 크롬(Cr), 주석(Sn), 몰리브덴(Mo), 니오븀(Nb), 인(P), 티타늄(Ti), 니켈(Ni), 구리(Cu), 지르코늄(Zr) 및 아연(Zn)으로 구성되는 군으로부터 선택되는 적어도 하나의 종일 수 있다. 예를 들어, 실리콘 함유 입자(110)는 약 83.5 at%의 실리콘, 약 13.5 at%의 철, 약 2 at%의 망간 및 약 1 at%의 보론을 포함할 수 있다. In exemplary embodiments, the silicon-containing particles 110 may comprise at least one of a silicon-metal alloy, silicon oxide, silicon carbide, porous silicon, nanosilicon, or silicon nanowires. For example, when the silicon-containing particle 110 is a silicon-metal alloy particle, the silicon-containing particle 110 may comprise a single phase silicon (not shown) and a silicon - metal alloy phase (not shown). In exemplary embodiments, the silicon-containing particles 110 comprise 60 to 90 at% of silicon (Si), 3 to 20 at% of iron (Fe), and 0 to 5 at% of a first additional element do. The first additional element may be at least one element selected from the group consisting of boron (B), magnesium (Mg), aluminum (Al), manganese (Mn), cobalt (Co), chromium (Cr), tin (Sn), molybdenum (Mo), niobium At least one species selected from the group consisting of phosphorus (P), titanium (Ti), nickel (Ni), copper (Cu), zirconium (Zr) and zinc (Zn). For example, the silicon-containing particles 110 may comprise about 83.5 at% silicon, about 13.5 at% iron, about 2 at% manganese, and about 1 at% boron.
예시적인 실시예들에서, 제1 도전층(120)은 제1 도전성 와이어를 포함할 수 있고, 실리콘 함유 입자(110)의 표면 상에 균일하게 분산되어 배치될 수 있다. 예시적인 실시예들에서, 제1 도전성 와이어는 카본 나노 튜브, 카본 파이버, 그래핀, 또는 카본을 포함하는 와이어를 포함할 수 있다. 다른 실시예들에서, 제1 도전성 와이어는 구리 나노와이어, 또는 은 나노와이어와 같은 금속성 나노 와이어를 포함할 수도 있다. 예를 들어, 실리콘 함유 입자(110)가 실리콘-금속 합금 분말을 포함하고, 제1 도전층(120)이 카본 나노 튜브를 포함할 때, 밀링 공정에 의해 실리콘 함유 입자(110)의 표면 상에 제1 도전층(120)이 형성될 수 있다. In the exemplary embodiments, the first conductive layer 120 may comprise a first conductive wire and may be uniformly dispersed and disposed on the surface of the silicon-containing particles 110. In exemplary embodiments, the first conductive wire may comprise a wire comprising carbon nanotubes, carbon fibers, graphene, or carbon. In other embodiments, the first conductive wire may comprise copper nanowires, or metallic nanowires such as silver nanowires. For example, when the silicon-containing particles 110 comprise a silicon-metal alloy powder and the first conductive layer 120 comprises carbon nanotubes, the surface of the silicon-containing particles 110 is removed by a milling process The first conductive layer 120 may be formed.
예시적인 실시예들에서, 제1 도전층(120)은 실리콘 함유 입자(110)의 표면 상에 약 수 옹스트롬 내지 수십 나노미터의 두께로 형성될 수 있고, 제1 도전층(120)을 구성하는 제1 도전성 와이어는 실리콘 함유 입자(110)의 표면 상에 균일하게 분산되어 부착될 수 있다. 예를 들어 제1 도전층(120)을 구성하는 제1 도전성 와이어는 단축과 장축(여기서 상기 장축을 종축으로 지칭함)을 가지며, 상기 장축을 따른 길이가 상기 단축을 따른 길이보다 상당히 크도록 상기 장축을 따라 연장되는 구조를 가질 수 있다. 제1 도전층(120)을 구성하는 제1 도전성 와이어는 그 종축을 따라 연장되는 측벽이 실리콘 함유 입자(110)의 표면과 접착하도록 부착될 수 있다. 예시적인 실시예들에 있어서, 제1 도전층(120)을 구성하는 제1 도전성 와이어는 그 종축을 따라 약 2 nm 내지 약 30 nm의 길이를 가질 수 있다. 그러나 이와는 달리, 제1 도전층(120)을 구성하는 제1 도전성 와이어는 그 단축에 따른 측벽이 실리콘 함유 입자(110)의 표면 상에 부착되어 그 종축을 따라 실리콘 함유 입자(110) 표면으로부터 길게 연장되도록 배치될 수도 있다. 예시적인 실시예들에서, 제1 도전층(120)을 구성하는 제1 도전성 와이어는 약 0.1 내지 약 6 중량 퍼센트(wt%)의 함량으로 음극 활물질(100) 내에 포함될 수 있다.In exemplary embodiments, the first conductive layer 120 may be formed on the surface of the silicon-containing particle 110 to a thickness of from about several angstroms to several tens of nanometers, The first conductive wire may be uniformly dispersed and attached on the surface of the silicon-containing particles 110. [ For example, the first conductive wire constituting the first conductive layer 120 may have a short axis and a long axis (wherein the long axis is referred to as a vertical axis), and the length along the long axis may be substantially longer than the length along the short axis. As shown in FIG. The first conductive wire constituting the first conductive layer 120 may be adhered such that the sidewall extending along its longitudinal axis adheres to the surface of the silicon-containing particle 110. In exemplary embodiments, the first conductive wire constituting the first conductive layer 120 may have a length along the longitudinal axis of from about 2 nm to about 30 nm. Alternatively, the first conductive wire constituting the first conductive layer 120 may have a side wall along its minor axis attached on the surface of the silicon-containing particle 110 and extending along the longitudinal axis thereof from the surface of the silicon- As shown in Fig. In exemplary embodiments, the first conductive wire constituting the first conductive layer 120 may be included in the negative electrode active material 100 in an amount of about 0.1 to about 6 weight percent (wt%).
예시적인 실시예들에서, 카본 코팅층(130)은 실리콘 함유 입자(110)의 표면 상에서 제1 도전층(120)를 커버하도록 배치될 수 있다. 예를 들어, 카본 코팅층(130)은 실리콘 함유 입자(110)의 표면 상에서 제1 도전층(120)을 구성하는 제1 도전성 와이어를 커버하도록 상대적으로 균일한 두께로 형성될 수 있다. 도 1에 도시된 바와 같이, 카본 코팅층(130)은 실리콘 함유 입자(110)의 표면의 실질적으로 전체를 커버하도록 형성될 수 있으나, 본 발명의 기술적 사상이 이에 한정되는 것은 아니다. 도 1에 도시된 것과는 달리, 카본 코팅층(130)은 실리콘 함유 입자(110)의 표면의 일부분 상에 상대적으로 균일한 두께로 형성되고, 실리콘 함유 입자(110)의 표면 일부분은 카본 코팅층(130)에 의해 커버되지 않고 외부로 노출될 수 있으며, 카본 코팅층(130)에 의해 커버되지 않은 실리콘 함유 입자(110)의 표면 일부분 상에는 제1 도전층(120) 또는 제2 도전층(140)이 배치될 수도 있다.In the exemplary embodiments, the carbon coating layer 130 may be disposed to cover the first conductive layer 120 on the surface of the silicon-containing particles 110. For example, the carbon coating layer 130 may be formed to have a relatively uniform thickness so as to cover the first conductive wire constituting the first conductive layer 120 on the surface of the silicon-containing particles 110. 1, the carbon coating layer 130 may be formed to cover substantially the whole surface of the silicon-containing particles 110, but the technical idea of the present invention is not limited thereto. 1, the carbon coating layer 130 is formed to a relatively uniform thickness on a portion of the surface of the silicon-containing particle 110, and a portion of the surface of the silicon-containing particle 110 is coated on the carbon coating layer 130, The first conductive layer 120 or the second conductive layer 140 may be disposed on a portion of the surface of the silicon-containing particles 110 not covered by the carbon coating layer 130 It is possible.
예시적인 실시예들에서, 카본 코팅층(130)은 비정질 탄소 물질을 포함할 수 있다. 상기 비정질 탄소 물질은 소프트 카본, 하드 카본, 석탄계 피치, 석유계 피치, 메조페이스 피치 탄화물, 소성된 코크스 및 이들의 조합으로부터 선택될 수 있다. 예를 들어, 카본 코팅층(130)은 상기 비정질 탄소 물질과 실리콘 함유 입자(110)를 혼합한 후, 비활성 가스 분위기에서 열처리하는 공정에 의해 실리콘 함유 입자(110)의 표면 상에 콘포말한 두께로 형성될 수 있다. 예시적인 실시예들에서, 카본 코팅층(130)은 실리콘 함유 입자(110)의 표면 상에 약 수 나노미터 내지 수십 나노미터의 두께로 형성될 수 있고, 카본 코팅층(130)은 약 0.1 내지 약 6 wt%의 함량으로 음극 활물질(100) 내에 포함될 수 있다.In the exemplary embodiments, the carbon coating layer 130 may comprise an amorphous carbon material. The amorphous carbon material may be selected from soft carbon, hard carbon, coal pitch, petroleum pitch, mesophase pitch carbide, calcined coke and combinations thereof. For example, the carbon coating layer 130 may be formed by mixing the amorphous carbon material and the silicon-containing particles 110 and then heat-treating the silicon-containing particles 110 in an inert gas atmosphere to form a carbon- . In exemplary embodiments, the carbon coating layer 130 may be formed to a thickness of about several nanometers to tens of nanometers on the surface of the silicon-containing particles 110, and the carbon coating layer 130 may be formed to a thickness of about 0.1 to about 6 wt. < / RTI > in the anode active material 100.
예시적인 실시예들에서, 제2 도전층(140)은 제2 도전성 와이어를 포함할 수 있고, 카본 코팅층(130)의 표면 상에 균일하게 분산되어 배치될 수 있다. 예시적인 실시예들에서, 제2 도전성 와이어는 카본 나노 튜브, 카본 파이버, 그래핀, 또는 카본을 포함하는 와이어를 포함할 수 있다. 다른 실시예들에서, 제2 도전성 와이어는 구리 나노 와이어, 또는 은 나노 와이어와 같은 금속성 나노 와이어를 포함할 수도 있다. 예를 들어, 밀링 공정에 의해 카본 코팅층(130)의 표면 및/또는 실리콘 함유 입자(110)의 표면 상에 제2 도전층(140)이 형성될 수 있다. In the exemplary embodiments, the second conductive layer 140 may comprise a second conductive wire and may be uniformly dispersed and disposed on the surface of the carbon coating layer 130. In exemplary embodiments, the second conductive wire may comprise a wire comprising carbon nanotubes, carbon fibers, graphene, or carbon. In other embodiments, the second conductive wire may comprise copper nanowires, or metallic nanowires such as silver nanowires. For example, the second conductive layer 140 may be formed on the surface of the carbon coating layer 130 and / or on the surface of the silicon-containing particles 110 by a milling process.
예시적인 실시예들에서, 제2 도전층(140)은 카본 코팅층(130)의 표면 및/또는 실리콘 함유 입자(110)의 표면 상에 약 수 옹스트롬 내지 수십 나노미터의 두께로 형성될 수 있고, 제2 도전층(140)을 구성하는 제2 도전성 와이어는 카본 코팅층(130)의 표면 및/또는 실리콘 함유 입자(110)의 표면 상에 균일하게 분산되어 부착될 수 있다. 예를 들어 제2 도전층(140)을 구성하는 제2 도전성 와이어는 단축과 장축(여기서 상기 장축을 종축으로 지칭함)을 가지며, 상기 장축을 따른 길이가 상기 단축을 따른 길이보다 상당히 크도록 상기 장축을 따라 연장되는 구조를 가질 수 있다. 제2 도전층(140)을 구성하는 제2 도전성 와이어는 그 종축을 따라 연장되는 측벽이 카본 코팅층(130)의 표면과 접착하도록 부착될 수 있다. 예시적인 실시예들에 있어서, 제2 도전층(140)을 구성하는 제2 도전성 와이어는 그 종축을 따라 약 2 nm 내지 약 30 nm의 길이를 가질 수 있다. 그러나 이와는 달리, 제2 도전층(140)을 구성하는 제2 도전성 와이어는 그 단축에 따른 측벽이 카본 코팅층(130)의 표면 상에 부착되어 그 종축을 따라 카본 코팅층(130) 표면으로부터 길게 연장되도록 배치될 수도 있다. 예시적인 실시예들에서, 제2 도전층(140)을 구성하는 제2 도전성 와이어는 약 0.1 내지 약 6 중량 퍼센트(wt%)의 함량으로 음극 활물질(100) 내에 포함될 수 있다.In exemplary embodiments, the second conductive layer 140 may be formed on the surface of the carbon coating layer 130 and / or the surface of the silicon-containing particles 110 to a thickness of from about several angstroms to several tens of nanometers, The second conductive wires constituting the second conductive layer 140 may be uniformly dispersed and attached on the surface of the carbon coating layer 130 and / or the surface of the silicon-containing particles 110. For example, the second conductive wire constituting the second conductive layer 140 may have a short axis and a long axis (wherein the long axis is referred to as a vertical axis), and the length along the long axis may be substantially longer than the length along the short axis. As shown in FIG. The second conductive wires constituting the second conductive layer 140 may be adhered such that sidewalls extending along the longitudinal axis thereof adhere to the surface of the carbon coating layer 130. In exemplary embodiments, the second conductive wire constituting the second conductive layer 140 may have a length along the longitudinal axis of from about 2 nm to about 30 nm. However, the second conductive wires constituting the second conductive layer 140 may be formed such that the side walls along the minor axis thereof are attached on the surface of the carbon coating layer 130 and extended along the longitudinal axis thereof from the surface of the carbon coating layer 130 . In exemplary embodiments, the second conductive wire constituting the second conductive layer 140 may be included in the negative electrode active material 100 in an amount of about 0.1 to about 6 weight percent (wt%).
다른 실시예들에 있어서, 카본 코팅층(130)은 복수의 층으로 구성될 수 있고, 복수의 카본 코팅층(130) 사이에 도전성 와이어들이 분산되어 배치될 수 있다. 예를 들어, 실리콘 함유 입자(110)의 표면 상에 제1 도전성 와이어가 형성되고, 제1 카본 코팅층이 실리콘 함유 입자(110)와 제1 도전성 와이어 상에 형성되며, 제2 도전성 와이어가 제1 카본 코팅층 상에 형성되고, 제2 카본 코팅층이 제1 카본 코팅층 및 제2 도전성 와이어 상에 형성되고, 제3 도전성 와이어가 제2 카본 코팅층 상에 형성될 수 있다. 제3 도전성 와이어는 제1 및 제2 도전성 와이어와 유사한 물질을 포함할 수 있다.In other embodiments, the carbon coating layer 130 may be composed of a plurality of layers, and the conductive wires may be dispersed and disposed between the plurality of carbon coating layers 130. [ For example, a first conductive wire is formed on the surface of the silicon-containing particle 110, a first carbon coating layer is formed on the silicon-containing particle 110 and the first conductive wire, A second carbon coating layer may be formed on the first carbon coating layer and a second conductive wire, and a third conductive wire may be formed on the second carbon coating layer. The third conductive wire may comprise a material similar to the first and second conductive wires.
예시적인 실시예들에 있어서, 제1 도전층(120)을 구성하는 제1 도전성 와이어와 제2 도전층(140)을 구성하는 제2 도전성 와이어는 전기 전도도가 높은 물질, 예를 들어 카본 나노 튜브, 카본 파이버, 그래핀, 또는 카본을 포함하는 와이어, 또는 구리 나노 와이어, 또는 은 나노 와이어와 같은 금속성 나노 와이어를 포함할 수 있고, 이에 따라 상기 도전성 와이어를 통해 인접한 실리콘 함유 입자(110) 사이의 전기적 경로가 제공될 수 있다. 제1 도전층(120)과 제2 도전층(140)이 실리콘 함유 입자(110) 내부에서 생성된 전자의 빠른 이동을 용이하게 하는 전기적 경로로 작용함에 따라, 상기 음극 활물질(100)은 향상된 전기 화학적 특성(예를 들어, 방전 용량 또는 사이클 성능)을 가질 수 있다. In exemplary embodiments, the first conductive wire constituting the first conductive layer 120 and the second conductive wire constituting the second conductive layer 140 may be formed of a material having a high electrical conductivity, for example, a carbon nanotube Containing nanoparticles, such as carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, carbon nanotubes, An electrical path may be provided. As the first conductive layer 120 and the second conductive layer 140 act as electrical paths facilitating rapid transfer of electrons generated within the silicon containing particles 110, Chemical properties (e. G., Discharge capacity or cycle performance).
또한, 예시적인 실시예들에서, 카본 코팅층(130)은 비정질 탄소 물질을 포함할 수 있다. 이에 따라 실리콘 함유 입자(110)의 충방전시 리튬 입자의 삽입/탈리에 따른 실리콘 함유 입자(110)의 부피 변화를 완충하는 버퍼층으로 작용할 수 있고, 이러한 부피 변화에 의한 음극 활물질(100)의 크랙 및 손상을 방지할 수 있다. 또한, 실리콘 함유 입자(110)의 넓은 표면적에 기인하여 전해액과 실리콘 함유 입자(110) 표면 사이에서 생성될 수 있는 부반응(또는 원치 않는 비가역적 계면 물질층들의 생성)을 방지할 수 있다. 따라서, 상기 음극 활물질(100)은 우수한 용량 유지 특성을 가질 수 있다.Further, in the exemplary embodiments, the carbon coating layer 130 may comprise an amorphous carbon material. As a result, the silicon-containing particles 110 can function as a buffer layer for buffering the volume change of the silicon-containing particles 110 due to insertion / desorption of the lithium particles during charging / discharging of the silicon-containing particles 110, And damage can be prevented. In addition, side reactions (or the generation of undesirable nonreversible interface material layers) that may be generated between the electrolyte and the silicon-containing particle 110 surface due to the large surface area of the silicon-containing particles 110 can be avoided. Therefore, the negative electrode active material 100 can have excellent capacity retention characteristics.
도 2는 예시적인 실시예들에 따른 음극 활물질의 제조 공정을 나타내는 플로우 차트이다.2 is a flowchart showing a manufacturing process of a negative electrode active material according to exemplary embodiments.
도 2를 참조하면, 제1 기계적 합금화 공정에 의해 실리콘, 철 및 제1 첨가 원소를 포함하는 실리콘-금속 합금 분말을 형성할 수 있다(S10 단계). 예를 들어 실리콘을 포함하는 제1 분말, 철을 포함하는 제2 분말 및 제1 첨가 원소를 포함하는 제3 분말을 사용하여 제1 기계적 합금화 공정에 의해 실리콘, 철 및 제1 첨가 원소를 포함하는 실리콘-금속 합금 분말을 형성할 수 있다. 상기 제1 첨가 원소는 보론(B), 마그네슘(Mg), 알루미늄(Al), 망간(Mn), 코발트(Co), 크롬(Cr), 주석(Sn), 몰리브덴(Mo), 니오븀(Nb), 인(P), 티타늄(Ti), 니켈(Ni), 구리(Cu), 지르코늄(Zr) 및 아연(Zn)으로 구성되는 군으로부터 선택되는 적어도 하나의 종일 수 있다. Referring to FIG. 2, a silicon-metal alloy powder including silicon, iron, and a first additive element may be formed by a first mechanical alloying process (step S10). Iron, and a first additive element by a first mechanical alloying process using a third powder comprising, for example, a first powder comprising silicon, a second powder comprising iron, and a first additive element, Silicon-metal alloy powder can be formed. The first additional element may be at least one element selected from the group consisting of boron (B), magnesium (Mg), aluminum (Al), manganese (Mn), cobalt (Co), chromium (Cr), tin (Sn), molybdenum (Mo), niobium At least one species selected from the group consisting of phosphorus (P), titanium (Ti), nickel (Ni), copper (Cu), zirconium (Zr) and zinc (Zn).
예시적인 실시예들에 있어서, S10 단계에서 형성될 음극 활물질 분말이 최종 음극 활물질에 대하여 각각 60 내지 90 원자 퍼센트(at%)의 실리콘, 3 내지 20 at%의 철 및 0 내지 5 at%의 제1 첨가 원소를 포함하도록 상기 제1 내지 제3 분말의 질량이 칭량될 수 있다. 예시적인 실시예들에 있어서, 상기 제1 기계적 합금화 공정은 수직형 어트리션 밀링 장치, 수평형 어트리션 밀링 장치, 볼 밀링 장치, 유성형 밀링 장치, 진동 밀링 장치, 스펙스 밀링 장치, 또는 고에너지 밀링 장치과 같은 밀링 장치에 의해 수행될 수 있다. 예를 들어, 직경 1 m의 볼 밀링 장치와 직경 25.4 mm의 크롬 스틸 볼을 사용하여 상기 제1 기계적 합금화 공정이 수행될 수 있다. In the exemplary embodiments, the negative electrode active material powder to be formed in step S10 contains 60 to 90 atomic percent (at%) silicon, 3 to 20 at% iron, and 0 to 5 at% The mass of the first to third powders may be weighed so as to include one additional element. In the exemplary embodiments, the first mechanical alloying process may be a vertical milling machine, a horizontal milling machine, a ball milling machine, a planetary milling machine, a vibration milling machine, a speckle milling machine, Or by a milling device such as a milling device. For example, the first mechanical alloying process can be performed using a ball milling device with a diameter of 1 m and a chrome steel ball with a diameter of 25.4 mm.
예시적인 실시예들에서, 상기 제1 분말, 상기 제2 분말 및 상기 제3 분말을 분말 형태로 상기 밀링 장치 내에 주입하고 상기 제1 기계적 합금화 공정을 수행할 수 있고, 이러한 경우에 활물질을 고온에서 용융하고 급속 냉각하여 일차 합금(예를 들어, 리본 합금)을 형성한 이후에, 상기 일차 합금을 분쇄하여 음극 활물질 분말을 형성하는 급속 냉각 방식을 사용하지 않을 수 있다. 예를 들어, 83.5 at%의 실리콘, 13.5 at%의 철, 2 at%의 망간 및 1 at%의 보론을 포함하는 음극 활물질을 형성하기 위하여, 실리콘 21.85 kg, 철 7.02 kg, 망간 1.02 kg, 및 보론 0.1 kg이 준비되고, 이들이 상기 볼 밀링 장치 내에 주입될 수 있다. In exemplary embodiments, the first powder, the second powder, and the third powder may be injected into the milling apparatus in powder form and the first mechanical alloying process may be performed, in which case the active material is heated at a high temperature After melting and rapidly cooling to form a primary alloy (for example, a ribbon alloy), the rapid cooling method of pulverizing the primary alloy to form the negative electrode active material powder may not be used. For example, to form an anode active material comprising 83.5 at% of silicon, 13.5 at% of iron, 2 at% of manganese and 1 at% of boron, 21.85 kg of silicon, 7.02 kg of iron, 1.02 kg of manganese, 0.1 kg of boron are prepared and they can be injected into the ball milling apparatus.
다른 실시예들에서, 실리콘을 포함하는 상기 제1 분말 및 철을 포함하는 상기 제2 분말을 용융하고 냉각하여 실리콘 및 철을 포함하는 중간 분말을 형성하고, 이후 상기 중간 분말과 제1 첨가 원소를 포함하는 상기 제3 분말을 상기 밀링 장치 내에 주입하여 상기 제1 기계적 합금화 공정을 수행할 수 있다. 또한, 상기 제1 분말, 상기 제2 분말 및 상기 제3 분말을 용융하고 냉각하여 형성된 실리콘, 철 및 제1 첨가 원소를 포함하는 중간 분말을 상기 밀링 장치 내에 주입하여 상기 제1 기계적 합금화 공정을 수행할 수 있다. 예를 들어, 86 at%의 실리콘, 11 at%의 철, 2 at%의 망간 및 1 at%의 보론을 포함하는 음극 활물질을 형성하기 위하여, 페로실리콘 20.34 kg, 실리콘망간 1.49 kg, 철-보론(Fe-B) 0.64 kg, 및 실리콘 7.52 kg이 준비되고, 이들이 상기 볼 밀링 장치 내에 주입될 수 있다. In other embodiments, the first powder comprising silicon and the second powder comprising iron are melted and cooled to form an intermediate powder comprising silicon and iron, and then the intermediate powder and the first additive element The third powder may be injected into the milling apparatus to perform the first mechanical alloying process. Further, an intermediate powder including silicon, iron and a first additive element formed by melting and cooling the first powder, the second powder and the third powder is injected into the milling apparatus to perform the first mechanical alloying process can do. For example, to form an anode active material comprising 86 at% silicon, 11 at% iron, 2 at% manganese and 1 at% boron, 20.34 kg of ferrosilicon, 1.49 kg of silicon manganese, (Fe-B) of 0.64 kg, and 7.52 kg of silicon are prepared and they can be injected into the ball milling apparatus.
상기 제1 기계적 합금화 공정에서, 밀링 용기 내부에 상기 분말들의 혼합물과 밀링 볼을 인입하고, 밀링 에너지에 의해 단시간에 상기 분말들을 분쇄 및 합금화시킬 수 있다. 상기 분말들의 혼합물은 더욱 미세한 사이즈를 갖는 미세 분말들로 분쇄될 수 있다. 특히, 밀링볼의 회전 및 충돌에 의한 충격에 의해 분쇄된 미세 분말들 사이의 미세 단조(forging), 냉간 압접(cold pressure welding), 파쇄(crushing)가 반복적으로 발생할 수 있다. 이에 따라, 미세 분말들이 혼합되는 과정에서 계면 에너지 증가가 구동력이 되어 원자의 고상 확산(solid phase diffusion)이 촉진되며 미세 합금화가 발생할 수 있다. 따라서, 실리콘, 철 및 제1 첨가 원소가 합금화된 실리콘-금속 합금 분말이 형성될 수 있다. 상기 실리콘-금속 합금 분말 내에서, 실리콘 단일상이 실리콘-금속 합금상 내부에 균일하게 분포할 수 있고, 제1 첨가 원소는 실리콘-금속 합금상 내부에 치환형 또는 침입형으로 포함되거나 실리콘-금속 합금상과 실리콘 단일상의 계면에 존재할 수 있다.In the first mechanical alloying process, the mixture of the powders and the milling balls are drawn into the milling vessel, and the milling energy is used to pulverize and alloy the powders in a short time. The mixture of the powders can be pulverized into finer powders having a finer size. Particularly, forging, cold pressure welding, and crushing may repeatedly occur between the fine powders ground by the rotation of the milling balls and the impact caused by the collision. As a result, the interfacial energy increase becomes a driving force in the process of mixing the fine powders, so that the solid phase diffusion of the atoms is promoted and microalloying may occur. Therefore, a silicon-metal alloy powder in which silicon, iron and a first additional element are alloyed can be formed. In the silicon-metal alloy powder, the silicon single phase may be uniformly distributed in the silicon-metal alloy phase, and the first additive element may be substituted or interstitially contained within the silicon-metal alloy phase, It may be present at the interface between the alloy phase and the silicon single phase.
미세 합금화가 진행될수록 상기 분말 내에 형성되는 실리콘 단일상이 미세한 실리콘 단일상으로 변화될 수 있고, 실리콘-금속 합금상을 매트릭스로 하여 미세한 실리콘 단일상이 고르게 분포할 수 있다. As the microalloying progresses, the silicon single phase formed in the powder can be changed into a fine silicon single phase, and a fine silicon single phase can evenly be distributed using the silicon-metal alloy phase as a matrix.
이후, 실리콘-금속 합금 분말과 제1 도전성 와이어를 사용하여 밀링 공정에 의해 실리콘-금속 합금 분말 상에 제1 도전층을 형성할 수 있다(S20 단계).Thereafter, the first conductive layer may be formed on the silicon-metal alloy powder by a milling process using the silicon-metal alloy powder and the first conductive wire (step S20).
예를 들어, 상기 밀링 공정은 수직형 어트리션 밀링 장치, 수평형 어트리션 밀링 장치, 볼 밀링 장치, 유성형 밀링 장치, 진동 밀링 장치, 스펙스 밀링 장치, 또는 고에너지 밀링 장치과 같은 밀링 장치에 의해 수행될 수 있다. 예를 들어, 용적 6L의 어트리션 밀링 장치와 직경 50 mm의 크롬 스틸 볼을 사용하여 상기 밀링 공정이 수행될 수 있다.For example, the milling process may be performed by a milling device such as a vertical-type milling device, a horizontal-type milling device, a ball milling device, a planetary milling device, a vibration milling device, a spesific milling device, . For example, the milling process may be performed using an impact milling device of volume 6L and a chrome steel ball of diameter 50 mm.
상기 밀링 공정에 의해, 예를 들어 흑연, 카본 나노 튜브, 카본 파이버, 그래핀, 또는 카본을 포함하는 와이어, 또는 금속성 와이어를 포함하는 제1 도전성 와이어가 약 2 nm 내지 약 30 nm의 상대적으로 균일한 나노 사이즈의 길이로 미세화되는 한편, 실리콘-금속 합금 분말의 표면 상에 균일하게 분산되어 부착될 수 있다. 또한, 상기 밀링 공정 동안 실리콘-금속 합금 분말 또한 더욱 미세화될 수 있다.By the milling process, a first conductive wire comprising, for example, a graphite, a carbon nanotube, a carbon fiber, a graphen, or a wire comprising carbon, or a metallic wire is formed by a relatively uniform Can be uniformly dispersed and adhered on the surface of the silicon-metal alloy powder while being miniaturized to a length of one nanometer size. In addition, the silicon-metal alloy powder can also be further refined during the milling process.
이후, 표면에 제1 도전층이 형성된 실리콘-금속 합금 분말과 비정질 탄소 물질을 혼합하여 실리콘-금속 합금 분말 상에 카본 코팅층을 형성할 수 있다(S30 단계).Then, a carbon coating layer may be formed on the silicon-metal alloy powder by mixing the amorphous carbon material with the silicon-metal alloy powder having the first conductive layer formed on its surface (Step S30).
예시적인 실시예들에서, S20 단계에서의 상기 밀링 공정에 의해 제1 도전성 와이어가 부착된 실리콘-금속 합금 분말과, 비정질 탄소 물질이 용매 내에서 혼합될 수 있다. 예를 들어 실리콘-금속 합금 분말과, 비정질 탄소 물질은 대기 분위기에서 수십 분 내지 수 시간 동안 교반 혼합될 수 있다. 이후, 상기 혼합물을 비활성 가스 분위기에서 열처리함에 의해 실리콘-금속 합금 분말 상에 카본 코팅층이 형성될 수 있다. 상기 열처리 공정은 예를 들어 질소 분위기에서 약 500℃의 온도에서 수 시간 수행될 수 있으나, 이에 한정되는 것은 아니다. 예를 들어, 상기 비정질 탄소 물질은 소프트 카본, 하드 카본, 석탄계 피치, 석유계 피치, 메조페이스 피치 탄화물, 소성된 코크스 및 이들의 조합으로부터 선택될 수 있고, 상기 비정질 탄소 물질은 음극 활물질 질량에 대하여 총 1 내지 6 wt%의 함량을 갖도록 상기 용매 내에 포함될 수 있으나, 이에 한정되는 것은 아니다. In the exemplary embodiments, the amorphous carbon material and the silicon-metal alloy powder to which the first conductive wire is attached may be mixed in the solvent by the milling process in step S20. For example, the silicon-metal alloy powder and the amorphous carbon material can be stirred and mixed in the air atmosphere for several tens minutes to several hours. Thereafter, the carbon coating layer may be formed on the silicon-metal alloy powder by heat-treating the mixture in an inert gas atmosphere. The heat treatment process may be performed at a temperature of about 500 DEG C for several hours, for example, in a nitrogen atmosphere, but is not limited thereto. For example, the amorphous carbon material may be selected from soft carbon, hard carbon, coal pitch, petroleum pitch, mesophase pitch carbide, calcined coke, and combinations thereof, wherein the amorphous carbon material is selected from the group consisting of May be contained in the solvent to have a total content of 1 to 6 wt%, but is not limited thereto.
이후, 표면에 카본 코팅층이 형성된 실리콘-금속 합금 분말과 제2 도전성 와이어를 사용하여 밀링 공정에 의해 카본 코팅층 상에 제2 도전층을 형성할 수 있다(S40 단계).Thereafter, the second conductive layer may be formed on the carbon coating layer by a milling process using the silicon-metal alloy powder having the carbon coating layer formed on its surface and the second conductive wire (S40).
예를 들어, 상기 밀링 공정은 수직형 어트리션 밀링 장치, 수평형 어트리션 밀링 장치, 볼 밀링 장치, 유성형 밀링 장치, 진동 밀링 장치, 스펙스 밀링 장치, 또는 고에너지 밀링 장치과 같은 밀링 장치에 의해 수행될 수 있다. 예를 들어, 용적 6L의 어트리션 밀링 장치와 직경 50 mm의 크롬 스틸 볼을 사용하여 상기 밀링 공정이 수행될 수 있다.For example, the milling process may be performed by a milling device such as a vertical-type milling device, a horizontal-type milling device, a ball milling device, a planetary milling device, a vibration milling device, a spesific milling device, . For example, the milling process may be performed using an impact milling device of volume 6L and a chrome steel ball of diameter 50 mm.
상기 밀링 공정에 의해, 예를 들어 흑연, 카본 나노 튜브, 카본 파이버, 그래핀, 또는 카본을 포함하는 와이어, 또는 금속성 와이어를 포함하는 제2 도전성 와이어가 약 2 nm 내지 약 30 nm의 상대적으로 균일한 나노사이즈의 길이로 미세화되는 한편, 카본 코팅층의 표면 및/또는 실리콘-금속 합금 분말의 표면 상에 균일하게 분산되어 부착될 수 있다. By the milling process, a second conductive wire comprising, for example, graphite, a carbon nanotube, carbon fiber, graphene, or carbon containing wire, or a metallic wire, is grown to a thickness of about 2 nm to about 30 nm Sized and can be uniformly dispersed and attached on the surface of the carbon coating layer and / or on the surface of the silicon-metal alloy powder.
전술한 S10 내지 S40 단계를 순차적으로 수행함에 의해, 도 1을 참조로 설명한 실리콘 함유 입자(110), 제1 도전층(120), 카본 코팅층(130) 및 제2 도전층(140)을 포함하는 실리콘-금속 합금 복합체 분말이 완성될 수 있다.The above steps S10 to S40 are sequentially performed to form the silicon-containing particles 110, the first conductive layer 120, the carbon coating layer 130, and the second conductive layer 140 described with reference to FIG. Silicon-metal alloy composite powder can be completed.
상기 음극 활물질 제조 방법에 따르면, 실리콘, 철 및 제1 첨가 원소 각각의 분말들을 제1 기계적 합금화 공정에 의해 미세화하거나 합금화할 수 있으므로 제조 공정이 용이할 수 있다. 또한, 밀링 공정에 의해 실리콘-금속 합금 분말이 미세화되는 한편, 제1 도전성 와이어가 균일한 나노 사이즈의 길이로 미세화되어 실리콘-금속 합금 분말의 표면 상에 균일하게 부착될 수 있다. 뒤따르는 혼합 공정에 의해 실리콘-금속 합금 분말 표면 상에 카본 코팅층이 콘포말하게 형성될 수 있고, 이후 밀링 공정에 의해 제2 도전성 와이어가 균일한 나노 사이즈의 길이로 미세화되어 카본 코팅층의 표면 상에 균일하게 부착될 수 있다. 따라서, 상대적으로 용이한 제조 공정에 의해 실리콘-금속 합금 복합체 분말을 포함하는 음극 활물질이 제조될 수 있다. According to the method for manufacturing the negative electrode active material, the powders of silicon, iron, and the first additive element can be made finer or alloyed by the first mechanical alloying process, thereby facilitating the manufacturing process. In addition, the milling process allows the silicon-metal alloy powder to be refined, while the first conductive wire can be miniaturized to a uniform nanosize length and uniformly adhered onto the surface of the silicon-metal alloy powder. The carbon coating layer can be conformally formed on the surface of the silicon-metal alloy powder by the following mixing process, and then the second conductive wire is miniaturized to a uniform nano-sized length by the milling process, And can be uniformly adhered. Accordingly, the negative electrode active material containing the silicon-metal alloy composite powder can be produced by a relatively easy manufacturing process.
아래의 표 1에서는 도 2를 참조로 설명한 음극 활물질의 제조 방법에 따른 실시예들의 제조 조건에 대하여 설명하도록 한다. In Table 1 below, the manufacturing conditions of the embodiments according to the method of manufacturing the negative electrode active material described with reference to FIG. 2 will be described.
조성(at%)Composition (at%) 제조공정Manufacture process 비고Remarks
비교예Comparative Example Si83.5-Fe13.5-Mn2-B1Si83.5-Fe13.5-Mn2-B1 1) 기계적 합금화 공정: 볼밀 장치2) 분급 공정: 제트밀 장치1) Mechanical alloying process: Ball mill 2) Classification process: Jet mill device 실리콘-금속 합금 분말Silicon-metal alloy powder
실시예 1Example 1 (Si83.5-Fe13.5-Mn2-B1)-CNT1 3 wt%(Si83.5-Fe13.5-Mn2-B1) -CNT1 3 wt% 1) 기계적 합금화 공정: 비교예와 동일2) 제1 도전층 형성 공정: 어트리션 밀링 장치, 카본 나노 튜브 3 wt%3) 카본 코팅층 형성 공정: - 피치 3 wt%를 교반 혼합 후 500℃ 2시간 열처리4) 분급 공정: 비교예와 동일1) Mechanical Alloying Process: Same as Comparative Example 2) First Conductive Layer Formation Process: Attrition Milling Device, Carbon Nanotube 3 wt% 3) Carbon Coating Layer Formation Process: 3 wt% Time heat treatment 4) Classification process: Same as the comparative example 제1 도전층/카본 코팅층을 형성Forming a first conductive layer / carbon coating layer
실시예 2Example 2 (Si83.5-Fe13.5-Mn2-B1)-CNT1 3 wt%-CNT2 1 wt%(Si83.5-Fe13.5-Mn2-B1) -CNT1 3 wt% -CNT2 1 wt% 1) 기계적 합금화 공정: 비교예와 동일2) 제1 도전층 형성 공정: 실시예 1과 동일3) 카본 코팅층 형성 공정:실시예 1과 동일4) 제2 도전층 형성 공정: 어트리션 밀링 장치, 카본 나노 튜브 1 wt%5) 분급 공정: 비교예와 동일1) Mechanical Alloying Process: Same as Comparative Example 2) First Conductive Layer Formation Process: Same as Example 1 3) Carbon Coating Layer Formation Process: Same as Example 1 4) Second Conductive Layer Formation Process: , 1 wt% of carbon nanotubes 5) Classifying step: Same as the comparative example 제1 도전층/카본 코팅층/제2 도전층을 형성Forming a first conductive layer / a carbon coating layer / a second conductive layer
실시예 3Example 3 (Si83.5-Fe13.5-Mn2-B1)- CNT1 3 wt%-CNT2 3 wt%(Si83.5-Fe13.5-Mn2-B1) - CNT1 3 wt% -CNT2 3 wt% 1) 기계적 합금화 공정: 비교예와 동일2) 제1 도전층 형성 공정: 실시예 1과 동일3) 카본 코팅층 형성 공정:실시예 1과 동일4) 제2 도전층 형성 공정: 어트리션 밀링 장치, 카본 나노 튜브 3 wt%5) 분급 공정: 비교예와 동일1) Mechanical Alloying Process: Same as Comparative Example 2) First Conductive Layer Formation Process: Same as Example 1 3) Carbon Coating Layer Formation Process: Same as Example 1 4) Second Conductive Layer Formation Process: , Carbon nanotubes 3 wt% 5) Classifying step: Same as the comparative example 제1 도전층/카본 코팅층/제2 도전층을 형성Forming a first conductive layer / a carbon coating layer / a second conductive layer
실시예 4Example 4 (Si83.5-Fe13.5-Mn2-B1)- CNT1 3 wt%-CNT2 5 wt%(Si83.5-Fe13.5-Mn2-B1) - CNT1 3 wt% -CNT2 5 wt% 1) 기계적 합금화 공정: 비교예와 동일2) 제1 도전층 형성 공정: 실시예 1과 동일3) 카본 코팅층 형성 공정:실시예 1과 동일4) 제2 도전층 형성 공정: 어트리션 밀링 장치, 카본 나노 튜브 5 wt%5) 분급 공정: 비교예와 동일1) Mechanical Alloying Process: Same as Comparative Example 2) First Conductive Layer Formation Process: Same as Example 1 3) Carbon Coating Layer Formation Process: Same as Example 1 4) Second Conductive Layer Formation Process: , 5 wt% of carbon nanotubes) Classifying step: Same as the comparative example 제1 도전층/카본 코팅층/제2 도전층을 형성Forming a first conductive layer / a carbon coating layer / a second conductive layer
표 1을 참조하면, 실시예 1 내지 실시예 4에 따른 음극 활물질이 도 2를 참조로 설명한 음극 활물질의 제조 방법에 따라 제조되었다. 구체적으로, 표 1에 기재된 원재료에 대하여 직경 1 m의 볼 밀링 장치와 직경 25.4 mm의 크롬 스틸 볼을 사용하여 기계적 합금화 공정이 수행되었다. 이후 제1 도전층 형성을 위하여, 어트리션 밀링 장치 내에 실리콘-금속 합금 분말과 3 wt의 카본 나노 튜브를 주입하고, 직경 50 mm의 크롬 스틸 볼을 사용하여 밀링 공정이 수행되었다. 이후, 용매 내에 제1 도전층이 형성된 실리콘-금속 합금 분말과 3 wt%의 피치를 주입하여 교반 혼합하고 이후 열처리하여 카본 코팅층을 형성하였다. 이후 제2 도전층 형성을 위하여, 어트리션 밀링 장치 내에 실리콘-금속 합금 분말과 각각 0, 1, 3, 및 5 wt의 카본 나노 튜브를 주입하고(각각 실시예 1 내지 4의 경우), 직경 50 mm의 크롬 스틸 볼을 사용하여 밀링 공정이 수행되어 음극 활물질 분말이 얻어졌다. 이후 분급 공정은 제트밀 장치에 의해 수행되었다.Referring to Table 1, the negative electrode active materials according to Examples 1 to 4 were produced according to the method of manufacturing the negative electrode active material described with reference to FIG. Specifically, for the raw materials shown in Table 1, a mechanical alloying process was performed using a ball milling device having a diameter of 1 m and a chrome steel ball having a diameter of 25.4 mm. Thereafter, a silicon-metal alloy powder and 3 wt.% Of carbon nanotubes were injected into the abrasion milling apparatus and a milling process was performed using a chromium steel ball having a diameter of 50 mm for forming the first conductive layer. Thereafter, the silicon-metal alloy powder having the first conductive layer formed therein was injected with a pitch of 3 wt%, mixed with stirring, and then heat-treated to form a carbon coating layer. In order to form the second conductive layer, carbon nanotubes of 0, 1, 3, and 5 wt.%, Respectively, were injected into the abrasion milling apparatus (each of Examples 1 to 4) Milling was performed using a 50 mm chrome steel ball to obtain an anode active material powder. The classification process was then carried out by means of a jet mill.
도 3은 예시적인 실시예들에 따른 음극 활물질의 주사 전자 현미경(scanning electron microscopy, SEM) 이미지이다. 3 is a scanning electron microscopy (SEM) image of an anode active material according to exemplary embodiments.
도 3은 실리콘-금속 합금 분말 표면에 카본 나노 튜브를 포함하는 제1 도전성 와이어가 균일하게 부착된 표면 모폴로지를 나타낸다. 실리콘-금속 합금 분말의 대략 구형 또는 타원형 입자의 표면 상에, 일 방향으로 길게 연장되는 카본 나노 튜브가 상기 구형 또는 타원형 입자의 실질적으로 전체 표면을 덮도록 균일하게 부착됨을 확인할 수 있다.Fig. 3 shows a surface morphology in which a first conductive wire including carbon nanotubes is uniformly adhered to the surface of a silicon-metal alloy powder. It can be confirmed that carbon nanotubes extending in one direction on the surface of the substantially spherical or elliptic particles of the silicon-metal alloy powder uniformly adhere so as to cover substantially the whole surface of the spherical or elliptical particles.
도 4는 비교예에 따른 음극 활물질의 충방전 테스트 이전(a) 및 이후(b)의 주사 전자 현미경 이미지이고, 도 5는 예시적인 실시예들에 따른 음극 활물질의 충방전 테스트 이후의 주사 전자 현미경 이미지이다.FIG. 4 is a scanning electron microscopic image of the negative active material according to the comparative example before and after the charge / discharge test, and FIG. 5 is a scanning electron microscope image after the charge / discharge test of the negative active material according to the exemplary embodiments. Image.
도 4를 참조하면, 비교예에 따른 음극 활물질은 충방전 이전에(도 4의 (a) 참조), 즉 분말이 형성된 초기 상태에 입자 내부 및 외부에 전해액과의 부반응에 의한 비가역 계면 물질층이 전혀 형성되지 않은 깨끗한 모폴로지를 보인다. 그러나, 비교예에 따른 음극 활물질은 300회의 충방전 이후에(도 4의 (b) 참조), 음극 활물질 외부 표면뿐만 아니라 내부에도 비가역 계면 물질층이 상당 부분 형성되었음을 확인할 수 있다. 이는 충방전에 의하여 음극 활물질 내부의 실리콘 함유 입자의 반복적 수축 및 팽창에 의해 음극 활물질 내에 미세 크랙이 발생하게 되고, 상기 미세 크랙을 통해 전해액이 상기 음극 활물질 내부로 침투하여 비가역 계면 물질층이 지속적으로 형성되기 때문으로 생각될 수 있다. 이러한 비가역 계면 물질층 형성에 의해 비가역 용량이 점차적으로 증가될 수 있다. 또한 음극 활물질 입자의 일부분이 인접한 음극 활물질 입자 또는 호일 등의 전극 물질로부터 박리되어, 큰 간격으로 물리적으로 분리되어 있음을 확인할 수 있다. 이는 음극 활물질 내부의 실리콘 함유 입자의 반복적 수축 및 팽창에 따른 스트레스에 기인한 것으로서, 음극 활물질과 이에 인접한 음극 활물질 입자 사이의, 또는 전극 물질까지의 전기적 경로가 단절되어 상기 음극 활물질이 더 이상 충방전을 위한 액티브 영역으로 작용하지 못할 수 있다. Referring to FIG. 4, the negative electrode active material according to the comparative example has an irreversible interface material layer formed by side reactions with the electrolyte inside and outside the particles in the initial state where the powder is formed, that is, before the charge and discharge (see FIG. It shows a clean morphology that is not formed at all. However, it can be seen that the negative electrode active material according to the comparative example has a substantial portion of the non-reversible interfacial material layer formed not only on the outer surface of the negative electrode active material, but also on the inside thereof after 300 charge / discharge cycles (see FIG. 4 (b)). This causes microcracks in the negative electrode active material due to repeated shrinkage and expansion of the silicon-containing particles in the negative electrode active material due to charge / discharge, and the electrolyte penetrates into the negative active material through the microcracks, As shown in FIG. By forming such an irreversible interface material layer, the irreversible capacity can be gradually increased. It can also be confirmed that a part of the negative electrode active material particles are peeled from the adjacent electrode active material particles or foil or the like and are physically separated at large intervals. This is because of the stress caused by repeated shrinkage and expansion of the silicon-containing particles in the negative electrode active material, and the electric path between the negative electrode active material and the adjacent negative electrode active material particles or to the electrode material is cut off, It may not act as an active region for
반면, 도 5를 참조하면, 예시적인 실시예들에 따른 음극 활물질은 300회의 충방전 테스트를 수행한 이후에도 음극 활물질 내부에 크랙 또는 비가역 계면 물질층들이 형성되지 않으며, 손상되지 않고 깨끗한 내부 표면을 가짐을 확인할 수 있다. 음극 활물질 입자의 최외곽 표면에서는 비가역 계면 물질층들이 매우 얇은 두께로 콘포말하게 형성되어 있으며, 이는 음극 활물질과 전해액 사이의 부반응에 의해 불가피하게 형성되는 것이다. 300회의 충방전 테스트를 완료한 이후에도 비가역 계면 물질층이 매우 얇은 두께로 유지됨에 따라, 예시적인 실시예들에 따른 음극 활물질의 비가역 용량이 현저히 작으며, 우수한 용량 특성을 가질 것으로 추측할 수 있다. On the other hand, referring to FIG. 5, the negative electrode active material according to the exemplary embodiments has no crack or irreversible interface material layers formed in the negative electrode active material after the 300 charge / discharge tests, and has a clean internal surface can confirm. On the outermost surface of the negative electrode active material particles, the irreversible interface material layers are formed into a cone shape with a very thin thickness, which is inevitably formed due to side reactions between the negative electrode active material and the electrolyte. It is presumable that the irreversible capacity of the negative electrode active material according to the exemplary embodiments is remarkably small and excellent capacity characteristics as the non-reversible interfacial material layer is maintained at a very thin thickness even after completing 300 charge / discharge tests.
도 6은 예시적인 실시예들에 따른 음극 활물질들의 전기 전도도를 나타내는 그래프이다. 도 6에는 실시예 1 내지 4와 비교예의 전기 전도도를, 제1 도전층 및 제2 도전층 각각의 함량(wt%)과 함께 도시하였다. 6 is a graph showing the electrical conductivity of negative electrode active materials according to exemplary embodiments. 6 shows the electrical conductivities of Examples 1 to 4 and Comparative Example together with the content (wt%) of each of the first conductive layer and the second conductive layer.
도 6을 참조하면, 실시예 1 내지 4 모두 비교예에 비하여 우수한 전기 전도도를 나타냈으며, 실시예 4의 경우 약 132 S/cm의 가장 우수한 전기 전도도를 나타냈다. 특히, 실시예 1 내지 4에서는 제1 도전층(또는 제1 도전성 와이어)과 제2 도전층(또는 제2 도전성 와이어)의 함량이 점차 증가됨에 따라 점점 증가되는 전기 전도도를 나타냈다. 이는 음극 활물질 내의 제1 도전층과 제2 도전층 모두가 음극 활물질 내의 실리콘 함유 입자에 대하여 효과적인 전기적 경로를 제공하는 역할을 하기 때문인 것으로 생각될 수 있다.Referring to FIG. 6, Examples 1 to 4 exhibited excellent electrical conductivity as compared with Comparative Examples, and Example 4 showed the best electrical conductivity of about 132 S / cm. Particularly, in Examples 1 to 4, the electric conductivity gradually increased as the content of the first conductive layer (or the first conductive wire) and the second conductive layer (or the second conductive wire) gradually increased. This is believed to be because both the first conductive layer and the second conductive layer in the anode active material serve to provide an effective electrical path for the silicon-containing particles in the anode active material.
도 7은 예시적인 실시예들에 따른 음극 활물질의 용량 유지 특성을 나타내는 그래프이다. 구체적으로, 도 7에는 실시예 1 내지 4와 비교예의 300회 사이클에서의 용량 유지율(%)(즉, 초기 방전 용량 대비 300회 방전 용량의 비율)이 제1 도전층 및 제2 도전층 각각의 함량(wt%)과 함께 표시되었다. 7 is a graph showing a capacity holding characteristic of the negative electrode active material according to the exemplary embodiments. 7 shows the capacity retention rate (%) (i.e., the ratio of 300 discharge capacities to the initial discharge capacity) in the 300 cycles of Examples 1 to 4 and the comparative example in each of the first and second conductive layers (Wt%).
도 7을 참조하면, 실시예 1 내지 실시예 4는 모두 비교예에 비하여 우수한 용량 유지 특성을 나타냈다. 특히, 실시예 3 및 실시예 4는 300회 사이클에서 약 85% 및 약 84%의 용량 유지율을 나타낸 반면, 비교예는 300회 사이클에서 약 61%의 용량 유지율을 나타냈다. 즉, 3 wt%의 제1 도전층(3 wt%의 카본 나노 튜브), 3 wt%의 카본 물질층, 및 3 wt%의 제2 도전층(3 wt%의 카본 나노 튜브)을 포함하는 음극 활물질(실시예 3) 또는 3 wt%의 제1 도전층(3 wt%의 카본 나노 튜브), 3 wt%의 카본 물질층, 및 5 wt%의 제2 도전층(5 wt%의 카본 나노 튜브)을 포함하는 음극 활물질(실시예 4)에서 가장 우수한 용량 유지 특성이 확인되었다. 이는 비정질 탄소 물질을 포함하는 카본 코팅층이 실리콘-금속 합금 분말의 충방전시 발생하는 부피 변화에 따른 스트레스를 효과적으로 완충할 뿐만 아니라 카본 나노 튜브를 포함하는 제1 도전층과 제2 도전층이 실리콘-금속 합금 분말에 전기 전도도를 제공하여 우수한 용량 유지 특성을 나타낸 것으로 생각될 수 있다.Referring to FIG. 7, all of Examples 1 to 4 exhibited excellent capacity holding characteristics as compared with Comparative Examples. In particular, Example 3 and Example 4 showed capacity retention of about 85% and about 84% in a 300 cycle, while Comparative Example showed a capacity retention of about 61% in a 300 cycle. That is, a cathode (anode) including 3 wt% of a first conductive layer (3 wt% of carbon nanotubes), 3 wt% of a carbon material layer, and 3 wt% of a second conductive layer (3 wt% of carbon nanotubes), 3 wt% of a carbon material layer, and 5 wt% of a second conductive layer (5 wt% of carbon nanotubes ) (Best Mode for Carrying Out the Invention). This is because the carbon coating layer containing the amorphous carbon material not only effectively buffer the stress caused by the volume change occurring during charging and discharging of the silicon-metal alloy powder but also the first conductive layer and the second conductive layer including the carbon nanotubes, It may be considered that the metal alloy powder is provided with electrical conductivity and exhibits excellent capacity retention characteristics.
이상에서 설명한 본 발명의 기술적 사상이 전술한 실시예 및 첨부된 도면에 한정되지 않으며, 본 발명의 기술적 사상을 벗어나지 않는 범위 내에서 여러 가지 치환, 변형 및 변경이 가능하다는 것은, 본 발명의 기술적 사상이 속하는 기술분야에서 통상의 지식을 가진 자에게 있어 명백할 것이다.It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. Will be apparent to those of ordinary skill in the art.

Claims (10)

  1. 실리콘 함유 입자; Silicon-containing particles;
    상기 실리콘 함유 입자의 표면 상에 부착되는 제1 도전성 와이어; A first conductive wire attached on a surface of the silicon-containing particle;
    상기 실리콘 함유 입자의 표면의 적어도 일부 또는 상기 제1 도전성 와이어 상에 형성되는 카본 코팅층; 및A carbon coating layer formed on at least a part of the surface of the silicon-containing particle or on the first conductive wire; And
    상기 실리콘 함유 입자의 표면의 적어도 일부 및 상기 카본 코팅층 상에 부착되는 제2 도전성 와이어를 포함하는 음극 활물질.And at least a part of the surface of the silicon-containing particle and a second conductive wire adhering to the carbon coating layer.
  2. 제1항에 있어서,The method according to claim 1,
    상기 카본 코팅층은 상기 실리콘 함유 입자의 표면 일부분 상에 형성되며, 상기 제1 도전성 와이어의 적어도 일부분 상에 상기 카본 코팅층이 형성되는 것을 특징으로 하는 음극 활물질.Wherein the carbon coating layer is formed on a part of the surface of the silicon-containing particle, and the carbon coating layer is formed on at least a part of the first conductive wire.
  3. 제1항에 있어서,The method according to claim 1,
    상기 음극 활물질에 포함되는 상기 제1 도전성 와이어의 함량은 0.1 내지 6 중량 퍼센트(wt%)이며,The content of the first conductive wire included in the negative electrode active material is 0.1 to 6 weight percent (wt%),
    상기 음극 활물질에 포함되는 상기 제2 도전성 와이어의 함량은 0.1 내지 6 wt%인 것을 특징으로 하는 음극 활물질.Wherein the content of the second conductive wire in the negative electrode active material is 0.1 to 6 wt%.
  4. 제1항에 있어서,The method according to claim 1,
    상기 실리콘 함유 입자는 실리콘-금속 합금, 실리콘 산화물, 실리콘 카바이드, 다공성 실리콘, 나노 실리콘, 또는 실리콘 나노 와이어를 포함하는 것을 특징으로 하는 음극 활물질.Wherein the silicon-containing particles comprise a silicon-metal alloy, silicon oxide, silicon carbide, porous silicon, nanosilicon, or silicon nanowires.
  5. 제1항에 있어서,The method according to claim 1,
    상기 제1 도전성 와이어 및 상기 제2 도전성 와이어는 카본 나노 튜브, 카본 파이버, 그래핀, 카본을 포함하는 와이어, 구리 나노 와이어, 은 나노 와이어, 또는 금속성 나노 와이어를 포함하는 것을 특징으로 하는 음극 활물질.Wherein the first conductive wire and the second conductive wire include a carbon nanotube, a carbon fiber, a graphene, a wire including carbon, a copper nanowire, a silver nanowire, or a metallic nanowire.
  6. 제1항에 있어서,The method according to claim 1,
    상기 카본 코팅층은 비정질 탄소 물질을 포함하며,Wherein the carbon coating layer comprises an amorphous carbon material,
    상기 비정질 탄소 물질은 소프트 카본, 하드 카본, 석탄계 피치, 석유계 피치, 메조페이스 피치 탄화물, 소성된 코크스 및 이들의 조합으로부터 선택되는 것을 특징으로 하는 음극 활물질.Wherein the amorphous carbon material is selected from soft carbon, hard carbon, coal pitch, petroleum pitch, mesophase pitch carbide, calcined coke, and combinations thereof.
  7. 실리콘 함유 입자; Silicon-containing particles;
    상기 실리콘 함유 입자의 표면 상에 부착되는 제1 도전성 와이어; A first conductive wire attached on a surface of the silicon-containing particle;
    상기 실리콘 함유 입자의 표면의 적어도 일부 또는 상기 제1 도전성 와이어 상에 형성되는 제1 카본 코팅층;A first carbon coating layer formed on at least a part of the surface of the silicon-containing particle or on the first conductive wire;
    상기 실리콘 함유 입자의 표면의 적어도 일부 및 상기 제1 카본 코팅층 상에 부착되는 제2 도전성 와이어;A second conductive wire attached to at least a portion of a surface of the silicon-containing particle and the first carbon coating layer;
    상기 제1 카본 코팅층 또는 상기 제2 도전성 와이어 상에 형성되는 제2 카본 코팅층; 및A second carbon coating layer formed on the first carbon coating layer or the second conductive wire; And
    상기 제2 카본 코팅층 상에 형성되는 제3 도전성 와이어를 포함하는 음극 활물질.And a third conductive wire formed on the second carbon coating layer.
  8. 제7항에 있어서,8. The method of claim 7,
    상기 제3 도전성 와이어는 상기 제1 카본 코팅층 또는 상기 제2 카본 코팅층의 표면 상에 부착되는 것을 특징으로 하는 음극 활물질.And the third conductive wire is attached on the surface of the first carbon coating layer or the second carbon coating layer.
  9. 실리콘을 포함하는 제1 분말, 철을 포함하는 제2 분말 및 제1 첨가 원소를 포함하는 제3 분말을 사용하여 제1 기계적 합금화 공정에 의해 실리콘, 철 및 제1 첨가 원소를 포함하는 실리콘-금속 합금 분말을 형성하는 단계;Iron, and a silicon-metal containing a first additive element by a first mechanical alloying process using a third powder comprising a first powder containing silicon, a second powder containing iron, and a first additive element, Forming an alloy powder;
    상기 실리콘-금속 합금 분말과 제1 도전성 와이어를 사용하여 밀링 공정에 의해 상기 실리콘-금속 합금 분말 표면 상에 제1 도전성 와이어를 부착하는 단계;Attaching a first conductive wire on the silicon-metal alloy powder surface by a milling process using the silicon-metal alloy powder and the first conductive wire;
    상기 제1 도전성 와이어가 부착된 상기 실리콘-금속 합금 분말과 비정질 탄소 물질을 혼합하여 상기 실리콘-금속 합금 분말 상에 카본 코팅층을 형성하는 단계;Forming a carbon coating layer on the silicon-metal alloy powder by mixing the amorphous carbon material with the silicon-metal alloy powder to which the first conductive wire is attached;
    상기 카본 코팅층이 형성된 상기 실리콘-금속 합금 분말과 제2 도전성 와이어를 사용하여 밀링 공정에 의해 상기 실리콘-금속 합금 분말 표면 또는 상기 카본 코팅층 표면 상에 제2 도전성 와이어를 부착하는 단계를 포함하는 음극 활물질의 제조 방법. Metal alloy powder and the second conductive wire on which the carbon coating layer is formed, by a milling process; and adhering the second conductive wire to the surface of the silicon-metal alloy powder or the surface of the carbon coating layer using the silicon- ≪ / RTI >
  10. 제9항에 있어서,10. The method of claim 9,
    상기 실리콘-금속 합금 분말 표면 상에 상기 제1 도전성 와이어를 부착하는 단계에서, 상기 밀링 공정에 의해 상기 실리콘-금속 합금 분말이 미세화되고 상기 제1 도전성 와이어가 상기 미세화된 실리콘-금속 합금 표면 상에 균일하게 분산되어 부착되는 것을 특징으로 하는 음극 활물질의 제조 방법.Wherein the step of attaching the first conductive wire on the surface of the silicon-metal alloy powder comprises the steps of: finishing the silicon-metal alloy powder by the milling process and forming the first conductive wire on the micronized silicon- Wherein the negative electrode active material is uniformly dispersed and adhered.
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