ANODE ACTIVE MATERIAL AND SECONDARY BATTERY COMPRISING 1 THE SAME 5 The present invention relates to an anode active material and a secondary battery comprising the same. More specifically, the present invention relates to an anode active material for secondary batteries, capable of intercalating and .deintercalating ions, comprising: a core comprising a crystalline carbon-based material; and a composite coating layer comprising one or more materials selected from the group 10 consisting of low crystalline carbon and amorphous carbon, and silicon oxide capable of intercalating and deintercalating ions, wherein the composite coating layer comprises: a matrix comprising one component selected from one or more materials selected from the group consisting of low crystalline carbon and amorphous carbon, and silicon oxide capable of intercalating and deintercalating ions; and a filler comprising the other 15 component, incorporated in the matrix. Technological development and increased demand for mobile equipment have led to a rapid increase in demand for secondary batteries as energy sources. Among these secondary batteries, lithium secondary batteries having high energy. density and voltage, long cycle span and low self-discharge are commercially available and widely 5 used. 1 In addition, increased interest in environmental issues has brought about a great deal of research associated with electric vehicles, hybrid electric vehicles and plug-in hybrid electric vehicles as alternatives to vehicles using fossil fuels such as gasoline vehicles and diesel vehicles which are major causes of air pollution. These electric 10 vehicles generally use nickel-metal hydride (Ni-MH) secondary batteries as power sources. However, a great deal of study associated with use of lithium secondary batteries with high energy density, discharge voltage and power stability is currently underway and some are commercially available. A lithium secondary battery has a structure in which a non-aqueous electrolyte 15 comprising a lithium salt is impregnated into an electrode assembly comprising a cathode and an anode, each comprising an active material coated on a current collector, and a porous separator interposed therebetween. Lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium composite oxide and the like are generally used as cathode active materials of lithium secondary batteries and carbon-based materials are generally used as anode active I materials thereof. Use of silicon compounds, sulfur compounds and the like has also 1 5 been considered. However, lithium secondary batteries have various problems, in particular, problems associated with fabrication and driving properties of an anode. First, regarding fabrication of an anode, a carbon-based material used as an anode active material is highly hydrophobic and thus has problems of low miscibility 10 with a hydrophilic solvent in the process of preparing a slurry for electrode fabrication and low dispersion uniformity of solid components. In addition, this hydrophobicity of the anode active material complicates impregnation of highly polar electrolytes in the battery fabrication process. The electrolyte impregnation process is a kind of bottleneck in the battery fabrication process, thus greatly decreasing productivity. In order to solve these problems, addition of a surfactant to an anode, an electrolyte or the like is suggested. However, disadvantageously, the surfactant may have side effects on driving properties of batteries. Meanwhile, regarding driving properties of the anode, disadvantageously, the I carbon-based anode active material induces initial irreversible reaction, since a solid electrolyte interface (SEI) layer is formed on the surface of the carbon-based anode active material during an initial chargeldischarge process (activation process), and 5 battery capacity is reduced due to exhaustion of the electrolyte caused by removal (breakage) and regeneration of the SEI layer during a continuous chargeldischarge process. In order to solve these problems, various methods such as formation of an SEI layer through stronger bond, or formation of an oxide layer on the surface of the anode 10 active material have been attempted. These methods have properties unsuitable for commercialization such as deterioration in electrical conductivity caused by the oxide layer and deterioration in productivity caused by additional processes. Also, there still exists a problem in that growth of lithium dendrites on the surface of the anode active material may cause short-circuit. 15 Accordingly, there is an increasing need for secondary batteries capable of solving these problems. Therefore, the present invention has been made to solve the above and other technical problems that have yet to be resolved. As a result of a variety of extensive and intensive studies and experiments to solve the problems as described above, the present inventors discovered that, when an 5 anode active material is produced by forming a composite coating layer on a crystalline carbon-based core, various problems associated with anode fabrication and battery driving properties can be simultaneously solved. The present invention has been completed, based on this discovery. In accordance with one aspect of the present invention, provided is an anode active material for secondary batteries, capable of intercalating and deintercalating ions, comprising: a core comprising a crystalline carbon-based material; and a composite coating layer comprising one or more materials selected from the group consisting of low crystalline carbon and amorphous carbon, and silicon oxide capable of intercalating 15 and deintercalating ions, wherein the composite coating layer comprises: a matrix comprising one component selected fiom (a) the one or more materials selected fiom the group consisting of low crystalline carbon and amorphous carbon and (b) the silicon F oxide capable of intercalating and deintercalating ions; and a filler comprising the other component, incorporated in the matrix. I As such, the anode active material having a structure in which the core comprising a crystalline carbon-based material is coated with the composite coating 5 layer having a matridfiller structure comprising one or more materials selected from the group consisting of low crystalline carbon and amorphous carbon, and silicon oxide capable of intercalating and deintercalating ions can solve the problems in the related art, based on specific active material structure and components. First, the surface of the silicon oxide capable of intercalating and 10 deintercalating ions comprised as a matrix or filler component in the composite coating layer exhibits high miscibility with a hydrophilic solvent in a slurry for fabrication of an anode according to the type of materials used, thus improving dispensability in solid components in the slurry. Accordingly, when an anode is fabricated by applying this slurry to a current collector, distribution uniformity between components such as a 15 binder and the anode active material can be improved and superior electrode properties can thus be obtained. The improvement in uniformity caused by the hydrophilic material can minimize a decrease in bonding strength between the slurry and the partial current d collector which occurs on the non-uniform electrode. The hydrophilic material .improves affinity between the active material layer and the surface of the current collector, bonding strength between the active material layer and the current collector and thereby solves a problem of increase in internal resistance caused by separation of 5 the active material layer from the current collector. Similarly, the silicon oxide capable of intercalating and deintercalating ions comprised in the composite coating layer imparts relatively high hydrophilicity to at least a part of the anode active material, thereby greatly reducing impregnation time of the highly polar electrolyte in the electrode fabrication process and considerably 10 improving battery productivity. Second, the silicon oxide capable of intercalating and deintercalating ions comprised in the composite coating layer previously forms a layer that has the same function as SEI having a strong chemical bond and has a stronger bond on the surface of the anode, thereby reducing an amount of irreversible ions required for formation of the 15 SEI layer, minimizes collapse of the SEI layer during repeated charge and discharge and ultimately improves battery lifespan. Third, the silicon oxide capable of intercalating and deintercalating ions comprised as a matrix or filler in the composite coating layer minimizes deterioration in i) electrical conductivity which may be induced by presence of materials incapable of intercalating and deintercalating ions. I Also, in the case of a lithium secondary battery, growth of lithium dendrites may occur, since the crystalline carbon-based material serving as a core has a similar 5 electric potential to lithium, but this growth can be inhibited by coating silicon oxide capable of intercalating and deintercalating ions on the surface of the crystalline carbonbased material at a high oxidation-reduction potential. Hereinafter, the present invention will be described in detail. As described above, the anode active material according to the present invention comprises: a core comprising a crystalline carbon-based material; and a composite coating layer comprising: a matrix comprising one component (for example, amorphous carbon) selected from one or more materials selected from the group consisting of low crystalline carbon and amorphous carbon, and silicon oxide capable of 15 intercalating and deintercalating ions; and a filler comprising the other component (for example, silicon oxide capable of intercalating and deintercalating ions), incorporated in the matrix. . . 8b Generally, a carbon-based material is classified into graphite having a complete layered crystal structure such as natural graphite, soft carbon having a low-crystalline layered crystal structure (graphene structure in which hexagonal honeycomb shaped planes of carbon are arrayed in the form of a layer), and hard carbon having a structure 5 in which the low-crystalline structures are mixed with non-crystalline parts. In a preferred embodiment, the core component of the present invention, the crystalline carbon-based material may be graphite, or a mixture of graphite and low crystalline carbon, and one of the composite coating layer components may be lowcrystalline carbon, amorphous carbon or a mixture thereof. 10 Meanwhile, silicon oxide capable of intercalating and deintercalating ions which is another component constituting the composite coating layer in the present invention exhibits relatively high hydrophilicity and polarity to one or more materials selected from the group consisting of low crystalline carbon and amorphous carbon and thus provides improved properties in terms of mix preparation or electrolyte 15 impregnation. A preferred example of the silicon oxide is a substance represented by SiO,. For example, SiOz intercalates and deintercalates very few lithium ions used for lithium secondary batteries. Accordingly, in the formula, x satisfies 0.1 < x < 1.5 and is more -9- 9 preferably 0.5 < x < 1.3 in order to maintain the structure of silicon oxide and facilitate intercalation and deintercalation of ions. In the present invention, the structure of the composite coating layer may be determined, depending on matrix and filler components. In a first exemplary structure, a filler comprising silicon oxide capable of intercalating and deintercalating ions is incorporated in a matrix comprising one or more materials selected from the group consisting of low crystalline carbon and amorphous carbon. In a second exemplary structure, a filler comprising one or more materials 10 selected from the group consisting of low crystalline carbon and amorphous carbon is incorporated in a matrix comprising silicon oxide capable of intercalating and deintercalating ions. In the composite coating layer, since the matrix has a structure, components of which have a continuous phase and the filler has a structure, components of which have 15 independent phases, the content of the matrix component is not necessarily greater than the content of the filler component. In the composite coating layer, the content of one or more materials selected from the group consisting of low crystalline carbon and amorphous carbon, and the -10- b content of the silicon oxide capable of intercalating and deintercalating ions are not particularly limited so long as the intended effects of the present invention (described above) can be exerted. In a preferred embodiment, the content of one or more materials selected fiom the group consisting of low crystalline carbon and amorphous 5 carbon may be 10 to 95% by weight, based on the total amount of the composite coating layer and the content of silicon oxide capable of intercalating and deintercalating ions may be 5 to 90% by weight, based on the total amount of the composite coating layer. The amount (coating amount) of the composite coating layer is preferably 0.1 to 20% by weight, based on the total amount of the anode active material. When the 10 amount of the composite coating layer is excessively low or the thickness thereof is excessively small, effects caused by formation of the composite coating layer may not be obtained and, on the other hand, when the amount of the composite coating layer is excessively high or the thickness thereof is excessively great, disadvantageously, the desired core-composite coating layer structure may not be formed and capacity may be 15 deteriorated. The present invention also provides an anode mix comprising the anode active material. The anode mix according to the present invention comprises 1 to 20% by weight of a binder, and optionally comprises 0 to 20% by weight of a conductive material, based on the total weight of the anode mix. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene 5 fluoride (PVdF), cellulose, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinyl pyrollidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymers (EPDM), sulfonated EPDM, styrene butadiene rubbers, fluoro-rubbers, various , copolymers, and polymer-saponified polyvinyl alcohol. Any conductive material may be used without particular limitation so long as it has suitable conductivity without causing chemical changes in the fabricated battery. Examples of conductive materials include graphite; carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers such as carbon fibers and metallic fibers; metallic powders such 15 as carbon fluoride powder, aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives. Specific examples of commercially available conductive materials may include various acetylene black products (available from Chevron Chemical Company, Denka Singapore Private Limited and Gulf Oil Company), Ketjen Black EC series (available fiom Armak Company), Vulcan XC-72 (available fiom Cabot Company) and Super P (Timcal Co.). If desired, a filler is optionally added to inhibit expansion of the anode. Any filler may be used without particular limitation so long as it does not cause adverse 5 chemical changes in the manufactured battery and is a fibrous material. Examples of the filler include olefin polymers such as polyethylene and polypropylene; and fibrous materials such as glass fibers and carbon fibers. Other components such as viscosity controllers or adhesion promoters may be added alone or in combination. The viscosity controller is a component to control the viscosity of the electrode mix and thereby facilitate mixing of the electrode mix and application of the same to a current collector and is present in an amount of 30% by weight or less, based on the total weight of the anode mix. Examples of the viscosity controller include, but are not limited to, carboxymethyl cellulose and polyvinylidene fluoride. In some cases, the 15 afore-mentioned solvent may also act as the viscosity controller. The adhesion promoter is an auxiliary ingredient to improve adhesion of an active material to a current collector and is present in an amount of 10% by weight, based on the binder and examples thereof include oxalic acid, adipic acid, formic acid, acrylic acid derivatives and itaconic acid derivatives. The present invention also provides an anode for secondary batteries in which the anode mix is applied to a current collector. For example, the anode is produced by adding an anode material containing an anode active material, a binder or the like to a solvent such as NMP to prepare a slurry, and applying the slurry to an anode current collector, followed by drying and pressing. The anode current collector is generally fabricated to have a thickness of 3 to 500 pm. Any anode current collector may be used without particular limitation so long 10 as it has suitable conductivity without causing adverse chemical changes in the fabricated battery. Examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, and copper or stainless steel surface-treated with carbon, nickel, titanium or silver, and aluminum-cadmium alloys. The anode current collector includes fine irregularities on the surface thereof so as to 15 enhance adhesion of anode active materials. In addition, the current collectors may be used in various forms including films, sheets, foils, nets, porous structures, foams and non-woven fabrics. * The present invention also provides a secondary battery comprising the anode and the battery is preferably a lithium secondary battery. The lithium secondary battery has a structure in which a lithium salt-containing non-aqueous electrolyte is impregnated into an electrode assembly comprising a 5 separator interposed between the cathode and the anode. For example, the cathode is prepared by applying a cathode active material to a cathode current collector, followed by drying and pressing and further optionally comprises other components such as binders or conductive materials as described above associated with the configuration of the anode. The cathode current collector is generally manufactured to have a thickness of 3 to 500 p. Any cathode current collector may be used without particular limitation so long as it has suitable conductivity without causing adverse chemical changes in the fabricated battery. Examples of the cathode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, and aluminum or stainless steel surface- 15 treated with carbon, .nickel, titanium or silver. Similar to the anode current collector, the cathode current collectors include fine irregularities on the surface thereof so as to enhance adhesion to the cathode active material. In addition, the cathode current 3 collector may be used in various forms including films, sheets, foils, nets, porous structures, foams and non-woven fabrics. The cathode active material is a lithium transition metal oxide comprising two or more transition metals as a substance that causes electrochemical reaction, and 5 examples thereof include, but are not limited to, layered compounds such as lithium cobalt oxide (LiCo02) or lithium nickel oxide (LiNiO;?) substituted by one or more transition metals; lithium manganese oxide substituted by one or more transition metals; lithium nickel oxide represented by the formula of LiNil.,MYO2 (in which M = Co, Mn, Al, Cu, Fe, Mg, By Cr, Zn or Ga, the lithium nickel oxide including one or more 10 elements among the elements, 0.011yL0.7); lithium nickel cobalt manganese composite oxides represented by Lil+zNibM&Col-(b+,+d)Msdu0ch( 2a-s eL)ilA+eZ Nil/3Col,3Mnl,@2 or Lil+zNio,4Mno.4Coo.2(0i2n which -0.51~50.5, 0.11b50.8, O.l An anode active material which had been coated with a carbon/silicon oxide composite prepared in Example 1 and had been further coated with carbon was produced and a coin-type half cell was fabricated in the same manner as in Example 1. An anode active material was produced and a coin-type half cell was fabricated in the same manner as in Example 1, except that silicon dioxide (SO2) having a mean particle diameter of about 100 nm was used, instead of silicon oxide (SiO). An anode active material was produced and a coin-type half cell was fabricated 10 in the same manner as in Example 1, except that the hydrophilic material (C) was not used. Electrolyte impregnation properties of the electrodes fabricated in accordance with Example 1 and Comparative Examples 1 to 3 were evaluated. The electrode was 15 roll-pressed to have a porosity of about 23% and a time taken for 1 microliter (pe) of a 1M LiPF6 electrolyte solution in a carbonate solvent dropped on the surface of the J electrode to completely permeate into the surface was measured. Results are shown in Table 1 below. As can be seen from Table 1, the electrode using an anode active material 5 coated with a carbodmetal composite according to Example 1 of the present invention exhibited considerably short electrolyte impregnation times, as compared to Comparative Examples 1 to 3 of electrodes using an anode active material coated with carbon alone. The reason for this is that the surface of the anode active material was coated with a hydrophilic material, thus enabling a highly polar electrolyte to be rapidly 10 permeated into particles. Impregnation time (sec) Chargeldischarge properties were evaluated using the coin-type half cells fabricated in accordance with Example 1 and Comparative Examples 1 to 3. Specifically, during charge, the cells were charged in a CC mode at a current density of 15 0.1C to 5 mV and then maintained in a CV mode at 5 mV, charging was completed Ex. 1 9 1 when current density reached 0.01C. During discharge, the cells were discharged in a Comp. Ex. 3 142 Comp. Ex. 1 13 8 Comp. Ex. 2 93 (D CC mode at a current density of 0.1 C to 1.5V. As a result, chargeldischarge capacity and efficiency of a first cycle were obtained. Then, chargeldischarge was repeated 50 times wider the same conditions as above, except that the current density was changed to 0.5C. Results are shown in Table 2 below. As can be seen from Table 2 above, the anode active materials coated with a composite containing silicon oxide (SiO) as a hydrophilic material according to Example 1 of the present invention exhibited high capacity maintenance after 50 chargeldischarge cycles and high efficiency, as compared to Comparative Example 2 10 using silicon dioxide (Si02) as a hydrophilic material. The reason for this is that when silicon dioxide is used, a content of oxygen that irreversibly reacts with lithium is high, Comp. Ex. 3 385.1 356.6 92.6 7 8 Comp. Ex. 2 387.7 357.1 92.1 82 Charge capacity (mAWg) Discharge capacity Efficiency (%) Capacity maintenance (%) after 50 chargeldischarge cycles Ex. 1 398.3 368.1 92.4 89 Comp. Ex. 1 392.1 360.7 92.0 84 * efficiency is decreased and lithium oxide produced during this reaction increases surface resistance of the anode active material. Also, it could be seen that the anode active material according to Example 1 exhibited considerably high capacity maintenance after 50 chargeldischarge cycles, as 5 compared to the anode active materials surface-coated with only carbon of Comparative Examples 1 and 3. The reason for this is that the hydrophilic material performing the same function as SEI forms a strong bond with a core material via carbon and thereby inhibits removal of the SEI layer in the repeated chargeldischarge process. Also, a material having high chargeldischarge voltage is coated, thereby preventing 10 precipitation of lithium and improving ion conductivity. As apparent from the fore-going, the anode active material according to the present invention is effective in greatly improving a battery fabrication process, minimizing deterioration in electrical conductivity and considerably inhibiting 15 deterioration in battery lifespan through a specific core/composite coating layer structure and can minimize performance and safety problems associated with lithium precipitation through presence of a material having a high oxidation-reduction potential on the surface of the active material. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. (claim 1] An anode active material for secondary 'batteries, capable of intercalating and deintercalating ions, the7anode active material comprising: a core comprising a crystalline carbon-based material; and 5 a composite coating layer comprising one or more materials selected from the group consisting of low crystalline carbon and amorphous carbon, and silicon oxide capable of intercalating and deintercalating ions, wherein the composite coating layer comprises: a matrix comprising one component selected from (a) the one or more 10 materials selected from the group consisting of low crystalline carbon and amorphous carbon and (b) the silicon oxide capable of intercalating and deintercalating ions; and a filler comprising the other component, incorporated in the matrix. (claim 2] The anode active material according to claim 1, wherein the crystalline carbon-based material comprises one or more of graphite and soft carbon. (IC [claim 3] The anode active material according to claim 1, wherein the silicon oxide capable of intercalating and deintercalating ions is a compound represented by the following formula: SiO, 5 wherein x satisfies 0.1 < x < 1.5. [claim 4] The anode active material according to claim 3, wherein x satisfies 0.5 < x < 1.3. [claim 5] The anode active material according to claim 1, wherein the composite coating layer has a structure in which the filler comprising the silicon oxide 10 capable of intercalating and deintercalating ions is incorporated in the matrix comprising the one or more materials selected from the group consisting of low crystalline carbon and amorphous carbon. [claim 6] The anode active material according to claim 1, wherein the composite coating layer has a structure in which the filler comprising the one or more 15 materials selected fiom the group consisting of low crystalline carbon and amorphous carbon is incorporated in the matrix comprising the silicon oxide capable of intercalating and deintercalating ions. [claim7] The anode active material according to claim 1, wherein an amount of the composite coating layer is 0.1 to 20% by weight, based on the total amount of the anode active material. [claim 8] An anode mix comprising the anode active material according to any - one of claims 1 to 7. [claim 9] An anode for secondary batteries in which the anode mix according to - claim 8 is applied to a current collector. [claim 10] A secondary battery comprising the anode for secondary batteries according to claim 9. [claim 11] The secondary battery according to claim 10, wherein the battery is a lithium secondary battery. [claim 12] A middle- or lake-sized battery pack cbmprising the secondary battery-according to claim - 1 1 as a unit cell.