Classifications

• • E—FIXED CONSTRUCTIONS
  • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
  • E05B—LOCKS; ACCESSORIES THEREFOR; HANDCUFFS
  • E05B65/00—Locks or fastenings for special use
  • E05B65/02—Locks or fastenings for special use for thin, hollow, or thin-metal wings
  • E05B65/025—Locks or fastenings for special use for thin, hollow, or thin-metal wings for lockers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/366—Composites as layered products
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
• • 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
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0416—Methods of deposition of the material involving impregnation with a solution, dispersion, paste or dry powder
• • 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
  • H01M4/04—Processes of manufacture in general
  • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
  • H01M4/40—Alloys based on alkali 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
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
  • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
  • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • E—FIXED CONSTRUCTIONS
  • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
  • E05B—LOCKS; ACCESSORIES THEREFOR; HANDCUFFS
  • E05B37/00—Permutation or combination locks; Puzzle locks
  • E05B37/02—Permutation or combination locks; Puzzle locks with tumbler discs or rings arranged on a single axis, each disc being adjustable independently of the others
• • E—FIXED CONSTRUCTIONS
  • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
  • E05B—LOCKS; ACCESSORIES THEREFOR; HANDCUFFS
  • E05B65/00—Locks or fastenings for special use
  • E05B65/44—Locks or fastenings for special use for furniture
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/058—Construction or manufacture
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/027—Negative electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
  • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
• • 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
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention relates to a carbonaceous material comprising a coating layer of metal-/metalloid- carbide. More particularly, the present invention relates to an anode active material comprising a carbonaceous material having improved electrochemical properties by treating it at high temperature under inert conditions, a method for preparing the same, an anode obtained by using the same and an electrochemical device comprising the same anode.
• Lithium secondary batteries are generally obtained by using materials capable of lithium ion intercalation/deintercalation as anode and cathode and filling an organic electrolyte or polymer electrolyte into the gap between the cathode and anode.
• Such lithium secondary batteries generate electric energy by redox reactions when lithium ion intercalates or deintercalates at the cathode and anode.
• a lithium secondary battery serves to transfer energy while lithium ions reciprocate between a cathode and anode like a rocking chair, it is also referred to as a "rocking chair battery".
• an anode active material such as the surface of carbon particles is reacted with an electrolyte to form a solid electrolyte interface (SEI) film at an anode.
• SEI solid electrolyte interface
• the SEI film serves to inhibit decomposition of the electrolyte on the surface of anode active material and thus to stabilize a battery.
• amount of reversible lithium decreases, followed by degradation in the battery capacity.
• irreversible capacity of an anode is large in a currently used secondary battery system whose lithium source is present at a cathode, irreversibility of the anode results in a dead volume of the cathode. Therefore, in practice, the cathode provides a capacity lower than the actual capacity applicable to the cathode, resulting in degradation in the battery capacity.
• FIG. 1 is an SEM (Scanning Electron Microscope) picture of a non-treated carbonaceous material
• FIG. 2 is an SEM picture of the carbonaceous material having a coating layer • of cobalt carbide according to Example 1
• FIG. 3 is an EDX (Energy Dispersive X-ray Spectroscopy) diagram of a non-treated carbonaceous material
• FIG. 4 is an EDX diagram of the carbonaceous material having a coating layer of cobalt carbide according to Example 1;
• Examples 1-4 and Examples 1-4 are graph showing initial charge/discharge capacity of each of the lithium secondary batteries according to Comparative Examples 1-4 and Examples 1-4, which use, as anode active materials, non-treated carbonaceous materials (artificial graphite A, artificial graphite B and natural graphite) and the same carbonaceous materials coated with cobalt carbide, respectively.
• the present invention has been made in view of the above-mentioned problems.
• a carbonaceous material coated with a metal and/or metalloid compound by a conventional coating process is surface-treated under high-temperature/inert atmosphere, a stable carbide coating layer having minimized reactivity to lithium is formed on the surface of the carbonaceous material, thereby minimizing the initial irreversible capacity of an anode. Therefore, it is an object of the present invention to provide an anode active material with improved electrochemical properties as described above and a method for preparing the same. It is another object of the present invention to provide an electrochemical device comprising an anode obtained by using the above anode active material.
• an anode active material which comprises: (a) a carbonaceous material; and (b) a carbide coating layer partially or totally formed on the surface of the carbonaceous material, the carbide coating layer comprising at least one element selected from the group consisting of metals and metalloids.
• a method for preparing a carbonaceous material having a coating layer of metal- /metalloid-carbide which comprises the steps of: (a) coating the surface of a carbonaceous material with a compound comprising at least one element selected from the group consisting of metals and metalloids; and (b) heat-treating the carbonaceous material coated in step (a) under inert atmosphere at a temperature equal to or higher than a temperature where the metal-/metalloid- carbide is formed.
• the anode active material for batteries according to the present invention is characterized by comprising at least one layer of metal- and/or metalloid-carbide.
• the anode active material is prepared by coating a carbonaceous material with a metal-/metalloid-containing compound by a conventional coating process, and then heat-treating the coated carbonaceous material under inert atmosphere at a high temperature equal to or higher than a temperature where the metal-/metalloid- carbide is formed (for example, at a temperature of between 500°C and 2000 ° C), the temperature being determined by the particular metal or metalloid used as main element of the coating layer.
• the metal- or metalloid-carbide coating layer formed as described above shows stable physical properties with little electrochemical reactivity to lithium intercalated/deintercalated into/from the electrode active material during charge/discharge cycles of a battery.
• the anode active material according to the present invention can provide a battery with high capacity as well as high efficiency by virtue of the above-described characteristics. Such preferred effects of the present invention will be explained in detail hereinafter.
• (1) In general, when a carbonaceous material is used as anode active material in a lithium secondary battery, there are problems in that side reaction of the anode active material with an electrolyte results in low charge capacity and that irreversible capacity is generated during the first charge/discharge cycle, followed by degradation in cycle life characteristics.
• the present invention it is possible to minimize the initial irreversible capacity of an anode by forming a coating layer of a stable compound obtained from an inorganic substance with carbon (for example, a stable metal-/metalloid-carbon coating layer having minimized reactivity to lithium) , on the surface of carbonaceous material.
• a coating layer of a stable compound obtained from an inorganic substance with carbon for example, a stable metal-/metalloid-carbon coating layer having minimized reactivity to lithium
• the anode active material according to the present invention provides an increase in charge/discharge efficiency by about 3% to 10% or more (see, FIG. 5) .
• the carbonaceous material surface-treated with metal-/metalloid-carbide has a polarity higher than that of a conventional carbonaceous material, it is possible to provide excellent wetting effect when using an carbonate-based electrolyte formed of a polar solvent. Therefore, lithium ions can pass rapidly through the electrolyte, thereby improving rate characteristics of a battery.
• the coating layer partially or totally formed on the surface of a carbonaceous material according to the present invention comprises carbides of general metals (for example, alkali metals, alkaline earth metals, transition metals, etc.) and/or metalloids (for example, elements of Group 13, Group 14, etc.).
• general metals for example, alkali metals, alkaline earth metals, transition metals, etc.
• metalloids for example, elements of Group 13, Group 14, etc.
• the carbide is represented by the following formula 1: [Formula 1] ⁇ -C-C-C ⁇ n ⁇ C a M b ⁇ m ⁇ M x X y ⁇ (I) wherein M is at least one metal or metalloid element selected from the group consisting of alkali metals, alkaline earth metals, transition metals and elements of Group 13 and Group 14; X is an oxygen atom or nitrogen atom; each of n, m, x, a and b independently represents a natural number of 1 or more; and each of 1 and y independently represents an integer of 0 or more.
• the metal forming the carbide coating layer is cobalt (Co) , nickel (Ni) , iron (Fe) , manganese (Mn) , aluminum (Al) , magnesium (Mg) , titanium (Ti) , zinc(Zn), zirconium (Zr) , or the like.
• the metalloid is preferably, boron (B) , silicon (Si) or the like.
• the coating layer may be formed in the shape of a multiayer film, wherein at least one layer preferably comprises the metal-/metalloid-carbide as described above.
• a substrate to be coated with the metal- /metalloid-carbide according to the present invention may be currently used carbonaceous materials known to one skilled in the art.
• the carbonaceous materials include natural graphite, artificial graphite, fiber graphite, amorphous carbon or amorphous carbon-coated graphite.
• carbonaceous materials that may be used include carbonaceous materials composed of carbon atoms only and heat-treated at a temperature of 2000 ° C or higher so as to provide a completely ordered structure, such as Kish graphite (KG), SFG series (SFG- ⁇ , SFG-15, etc.), highly oriented pyrolytic graphite, MPCF (mesophase pitch based carbon fiber), MCMB series (MCMB 2800, MCMB 2700, MCMB 2500, etc.) or the like.
• the carbonaceous material comprising a metal- /metalloid-carbide coating layer is formed by heat treating a carbonaceous material under inert atmosphere at a temperature equal to or higher than the temperature where the metal-/metalloid-carbide is formed.
• the heat treatment temperature is 500 ° C or higher, preferably ranges from 500 ° C to 2000 ° C and more preferably ranges from 800 ° C to 2000 ° C. If the heat treatment temperature is lower than 500 ° C, it is not possible to obtain a significant improvement in terms of anode efficiency. If the heat treatment temperature is higher than 2000 ° C, there is a possibility of dissolution of metal-/metalloid carbide, resulting in phase separation from the carbonaceous material. Additionally, as the inert atmosphere, low reactive gas known to one skilled in the art may be used.
• such gas includes at least one inert gas selected from the group consisting of nitrogen, argon, helium and xenon.
• inert gas may be used in the form of a mixture with hydrogen gas in order to facilitate reduction reaction.
• inert gas suitably has a purity of between 50 and 99.999%.
• the surface of a carbonaceous material is coated with a compound comprising at least one element selected from the group consisting of metals and metalloids and then the coated carbonaceous material is heat-treated under inert atmosphere at a temperature equal to or higher than the temperature where the corresponding metal-/metalloid-carbide is formed (for example, at a temperature of between 500 ° C and 2000 ° C).
• the method used for coating the- surface of a carbonaceous material with a metal- /metalloid-containing compound may be any method known to one skilled in the art.
• Non-limiting examples of the methods include general coating methods such as solvent evaporation method, co-precipitation method, precipitation method, sol-gel method, adsorption and filtering method, sputtering method, CVD (chemical vapor deposition) method, etc. There is no particular limitation in selection of the coating method.
• the step for coating the surface of a carbonaceous material with a metal-/metalloid-containing compound includes the steps of: (i) dispersing or dissolving a metal and/or metalloid compound comprising at least one element selected from the group consisting of cobalt (Co) , nickel (Ni) , iron (Fe) , aluminum (Al) , magnesium (Mg) , boron (B) , titanium (Ti) , zirconium (Zr) and silicon (Si) into a solvent to provide a dispersion or solution containing the same compound; and (ii) adding the dispersion or solution obtained from step (i) to a carbonaceous material, stirring the resultant mixture and drying the mixture.
• a metal and/or metalloid compound comprising at least one element selected from the group consisting of cobalt (Co) , nickel (Ni) , iron (Fe) , aluminum (Al) , magnesium (Mg) , boron (B) , titanium (T
• the metal/metalloid compound that may be used includes a water soluble or water insoluble compound comprising cobalt (Co) , manganese (Mn) , nickel (Ni) , iron (Fe) , aluminum (Al), magnesium (Mg) , boron (B) , titanium (Ti) , zirconium (Zr) or silicon (Si), or two or more of said elements.
• a water soluble or water insoluble compound comprising cobalt (Co) , manganese (Mn) , nickel (Ni) , iron (Fe) , aluminum (Al), magnesium (Mg) , boron (B) , titanium (Ti) , zirconium (Zr) or silicon (Si), or two or more of said elements.
• the metal, metalloid compound is dissolved in a solvent such as water or alcohols and then the resultant solution is added to a carbonaceous material, followed by stirring and drying.
• a solvent such as water or alcohols
• the solution or dispersion in which the metal and/or metalloid is dissolved is added to a carbonaceous material
• the solution or dispersion is added in such an amount that the weight ratio of metal (M) to carbonaceous material (C) , i.e., M/C (or S/C, in the case of metalloids (S) ) ranges from 0.5 to 20 wt%, more preferably from 0.5 to 10 wt%.
• the coated carbonaceous material may be dried by using a method currently used in the art .
• the carbonaceous material dried as described above has a metal-/metalloid-oxide coating layer on its surface.
• the metal- /metalloid-oxide coating layer is converted into a metal-/metalloid-carbide coating layer having reinforced interfacial bonding force with the carbonaceous material, from the top surface.
• the temperature where the carbide is formed depends on characteristics of each metal/metalloid, as described particularly in the following alloy phase diagram.
• the process of converting a metal-/metalloid- oxide into a metal-/metalloid-carbide results from a chemical reaction specific to each metal and can be seen from the phase diagram of each metal element.
• Co maintains its oxide state at a temperature of up to 400 ° C under reductive atmosphere because cobalt oxide is not decomposed or broken at the same temperature.
• Co is reduced by the reaction of the surrounding carbon, thereby forming a metal-carbide composite maintaining the form of Co-carbide.
• Si maintains a metal oxide state at a temperature of up to about 1400 ° C under reductive atmosphere in the presence of carbon.
• Si is bonded with carbon and thus maintains a metal (metalloid) - carbide form. Because such metal (metalloid) -carbides generated by heat treatment are electrochemically inactive to Li, they can minimize the irreversible amount of lithium needed for the formation of an SEI film during the first charge cycle and thus can realize high capacity and high efficiency of a battery.
• the carbide coating layer according to the present invention can be formed by bonding a metal-/metalloid-carbide directly onto the surface of a carbonaceous material through a sputtering or CVD (chemical vapor deposition) process .
• the present invention also provides an electrochemical device comprising: (a) a cathode; (b) an anode using an anode active material having the above-mentioned metal-/metalloid-carbide coating layer; (c) a separator; and (d) a non-aqueous electrolyte.
• the electrochemical device includes all devices carrying out electrochemical reactions and particular examples thereof include all kinds of primary and secondary batteries, etc.
• the electrochemical devices are lithium secondary batteries, which include lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries or lithium ion polymer secondary batteries.
• any conventional method known to one skilled in the art may be used.
• the separator is interposed between two electrodes to form an assembly into which the nonaqueous electrolyte is then injected.
• the cathode and anode according to the present invention may be prepared according to any conventional method known in the art.
• slurry for each electrode i.e., each of slurry containing a cathode active material and slurry containing an anode active material is formed, the formed slurry is applied on each current collector, and the solvent or dispersant contained in the slurry is removed by drying, etc., to cause the active material particles to be bound to the collector as well as among themselves.
• a small amount of conductive agent and/or binder may be added to the slurry.
• the anode active material is the carbonaceous material comprising a metal-/metalloid-carbide coating layer according to the present invention.
• the cathode active material includes conventional cathode active materials that can be used in conventional electrochemical devices.
• the cathode active material include, but are not limited to, lithium intercalation materials such as lithium manganese oxides, lithium cobalt oxides, lithium nickel oxides, lithium iron oxides or composite oxides formed by combination of them (for example, LiCo0 2 , LiNi0 2 , LiC10 4 , LiCF 3 S0 3 , LiPF 6 , LiBF 4 , LiAsF 6 , LiN(CF 3 S0 2 ) 2 or LiMn 2 0 4 ) .
• the conductive agent may be any electroconductive material that does not undergo a chemical change in a finished battery.
• Non-limiting examples of a cathode current collector include foil formed of aluminum, nickel or a combination thereof.
• Non-limiting examples of an anode current collector include foil formed of copper, gold, nickel, copper alloys or a combination thereof.
• the electrolyte that may be used in the present invention includes a salt represented by the formula of A + B ⁇ , wherein A + represents an alkali metal cation selected from the group consisting of Li + , Na + , K + and combinations thereof, and B " represents an anion selected from the group consisting of PF 6 ⁇ , BF 4 " , Cl “ , Br “ , I “ , C10 4 ⁇ , AsF 6 “ , CH3CO2 “ , CF3SO 3 " , N(CF 3 S0 2 ) 2 " , C(CF 2 S0 2 ) 3 _ and combinations thereof, the salt being dissolved or dissociated in an organic solvent selected from the group consisting of propylene carbonate (PC) , ethylene carbonate (EC) , diethyl carbonate (DEC) , dimethyl carbonate (DMC) , dipropyl carbonate (DPC) , dimethyl sulfoxide, acetonitrile, dimethoxyethane
• the electrolyte that may be used in the present invention is not limited to the above examples.
• the separator that may be used includes a porous separator that serves to interrupt internal short circuit between both electrodes and is impregnated with an electrolyte.
• Non-limiting examples of such porous separators include polypropylene-based, polyethylene- based and polyolefin-based porous separators.
• the electrochemical device obtained by the method according to the present invention, preferably a lithium secondary battery may have a cylindrical, prismatic or pouch-like shape with no particular limitation.
• Example 1 Carbonaceous Material Comprising Metal-/Metalloid-Carbide Coating Layer and Manufacture of Lithium Secondary Battery Using the Same Example 1 1-1. Carbonaceous Material Having Cobalt Carbide Coating Layer (1) Cobalt acetate (Co (CH 3 C00) 2 '4H 2 0) was dissolved in distilled water to provide aqueous cobalt acetate solution. The solution was added to artificial graphite
• a (artificial graphite series) as carbonaceous material in the amount of 4 wt%, as expressed in the weight ratio (Co/C) of cobalt to carbonaceous material. Then, the resultant mixture was stirred and the solvent was evaporated. After removing the solvent completely, the resultant carbonaceous powder was dried in a vacuum oven for 12 hours . The dried powder was surface-treated in an electric furnace at 800 ° C for 2 hours to obtain a carbonaceous material coated with cobalt carbide. 1-2.
• EC ethylene carbonate
• EMC ethylmethyl carbonate
• Example 4 Example 1 was repeated to provide a carbonaceous material (4) having a silicon carbide coating layer and a lithium secondary battery using the same as anode active material, except that artificial graphite B (artificial graphite series) was used instead of artificial graphite A as carbonaceous material, and that silicon acetate (Si (CH 3 COO) 4 ) was used instead of cobalt acetate while adjusting a weight ratio of Si/C to 0.5 wt% and setting a reaction temperature to 1400 ° C.
• Comparative Examples 1-4 Comparative Examples 1-3.
• Manufacture of Lithium Secondary Battery Example 1 was repeated to provide a lithium secondary battery, except that each of the carbonaceous materials used in Examples 1-3, i.e., artificial graphite A (Comparative Example 1) , artificial graphite
• lithium secondary batteries using carbonaceous materials having a cobalt carbide coating layer according to Examples 1-3 showed an increase of charge/discharge efficiency by about 3-9% compared to the batteries using the same non-treated carbonaceous materials as anode active materials according to Comparative Examples 1-3 (see, FIG. 5 and Table 1).
• the battery using artificial graphite B coated with a coating layer of cobalt carbide according to Example 2 showed a significant increase in charge/discharge efficiency by 8.4% compared to the battery using the same carbonaceous material according to Comparative Example 2 (see, Table 1) .
• the battery using a carbonaceous material coated with a coating layer of cobalt oxide obtained by coating a carbonaceous material with a cobalt compound and then heat treating the resultant material in the air at 400 ° C shows a decrease in charge/discharge efficiency by 3.6% compared to the battery according to Comparative Example 2 using the same non-treated carbonaceous material (see, FIG. 5 and Table 1) .
• the carbonaceous material having a coating layer of metal-/metalloid- carbide according to the present invention can decrease the initial irreversible capacity of an anode and thus can significantly increase the charge/discharge efficiency of a battery, when used as anode active material in a lithium secondary battery. Additionally, the surface modification method carried out under high temperature/inert atmosphere according to the present invention results in excellent reinforcement of qualities of an anode. [Table 1]
• the carbonaceous material according to the present invention has a coating layer of metal- and/or metalloid-carbide formed on the surface thereof, the metal- and/or metalloid-carbide being electrochemically inactive to lithium.
• the carbonaceous material is used as anode active material of a lithium secondary battery, the lithium secondary battery can realize an increase in the initial charge/discharge efficiency and can provide reinforced qualities of an anode.

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• 2005
  • 2005-04-22 TW TW094112872A patent/TWI275197B/zh active
  • 2005-04-22 KR KR1020050033622A patent/KR100666822B1/ko active IP Right Grant
  • 2005-04-22 EP EP05764713.3A patent/EP1738425B1/en active Active
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