Patent Publication Number: US-2015072235-A1

Title: Powder  manufacturing  apparatus  and  anode  active  material  for  secondary battery  manufactured  by  the apparatus

Description:
RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2013-0109211, filed on Sep. 11, 2013, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     1. Field 
     One or more embodiments of the present invention relate to a powder manufacturing apparatus and anode active material for secondary battery manufactured by the apparatus, and more particularly, to a powder manufacturing apparatus that can effectively adjust a particle-size distribution of the powder alloy and to an anode active material having an excellent lifespan characteristic. 
     2. Description of the Related Art 
     Recently, lithium secondary batteries have been used as power source of portable electronic products such as mobile phones, laptop computers, and the like, and also used as medium and large sized power source of hybrid electric vehicles (HEVs) and plug-in HEVs. Owing to expansion of applied fields and increase in demands, external shapes and sizes of the lithium secondary batteries are being modified variously, and superior capacity, lifespan, and safety to those of small-sized batteries are necessary. 
     A lithium secondary battery is manufactured by using materials which lithium ions can be intercalated into and deintercalated from, as an anode and a cathode, and is manufactured generally by forming a porous separation film between the anode and the cathode and injecting an electrolyte. In addition, electric current is produced or consumed by a redox reaction caused by intercalation/deintercalation of lithium ions in the anode and the cathode. 
     Graphite is widely used in conventional lithium secondary batteries as an anode active material, and has a layered structure which lithium ions can be easily intercalated into and deintercalated from. Graphite has a theoretical capacity of 372 mAh/g; however, demands for lithium batteries of high capacity have been increased recently, a new electrode that may substitute for the graphite has been required. Thus, research has been actively conducted on commercialization of an electrode active material that may form electrochemical alloy with lithium ions, such as silicon (Si), tin (Sn), antimony (Sb), and aluminum (Al), as a high-capacity anode active material. However, when silicon (Si), tin (Sn), antimony (Sb), aluminum (Al), or the like are electrochemically plated with lithium, the volume of the resultant structure increases or decreases during a charge/discharge process. Such a volume change deteriorates cycle characteristics of an electrode employing silicon (Si), tin (Sn), antimony (Sb), aluminum (Al), or the like as an anode active material. Also, such a volume change causes cracks in a surface of the electrode active material. When cracks occur repeatedly in the surface of the electrode active material, fine particles may be formed in the surface of the electrode, thereby deteriorating cyclic characteristics. 
     An anode active material having a fine structure, in which fine particles of Si or Sn are evenly dispersed in a matrix, has been developed in order to prevent the electrode active material from being damaged due to the variation in the volume. In general, examples of powder alloy manufacturing methods are an atomization method, a melt-spinning method, a rotating electrode method, a mechanical grinding method, etc. In order to manufacture a silicon-metal powder alloy or a tin-metal powder alloy that is used as an anode active material of a secondary battery, it is necessary to evenly disperse fine particles in a matrix, and thus, the powder alloy needs to be formed by using a rapid solidification method and a particle-size distribution of the powder alloy needs to be adjusted efficiently. 
     SUMMARY 
     One or more embodiments of the present invention include an apparatus for manufacturing powder capable of manufacturing a silicon-metal powder alloy adjusting a particle-size distribution of a powder alloy effectively and having excellent lifespan characteristic. 
     One or more embodiments of the present invention include an anode active material including a silicon-metal powder alloy manufactured by the apparatus for manufacturing powder. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     According to one or more embodiments of the present invention, an apparatus for manufacturing a powder alloy used as an anode active material of a secondary battery, the apparatus includes: a nozzle unit for melting and spraying an alloy; a cooling unit for cooling down the alloy sprayed from the nozzle unit; a grinding unit for grinding the alloy cooled by the cooling unit; and a first chamber accommodating the nozzle unit, the cooling unit, and the grinding unit, and maintained to be a vacuum state. 
     The nozzle unit may include: an accommodation unit for accommodating the alloy; a heating unit for melting the alloy; and a nozzle hole for spraying the alloy. 
     The accommodation unit may be formed of one of graphite, Al 2 O 3 , ZrO 2 , and a boron nitride (BN). 
     The cooling unit may be formed as a roll, and may rapidly cool the alloy sprayed from the nozzle unit while rotating in order to form a rapidly solidified strip. 
     The rapidly solidified strip may be continuously extended to the grinding unit within the first chamber. 
     The grinding unit may include a roll, and may further cool the alloy that is cooled by the cooling unit and grinds the alloy while rotating the roll. 
     The grinding unit may include one or more disk plates. 
     A rotary shaft of the grinding unit may be perpendicular to a rotary shaft of the cooling unit. 
     The grinding unit may include: a first grinding unit for firstly cooling and grinding the alloy cooled by the cooling unit; and a second grinding unit for secondly cooling and grinding the alloy ground by the first grinding unit. 
     The apparatus may further include: a dissolution unit for melting the alloy; and a second chamber accommodating the dissolution unit and maintained to be a vacuum state, wherein the alloy melted in the dissolution unit is moved into the nozzle unit. 
     The dissolution unit may include: a dissolving crucible for accommodating the alloy; and a heating unit for melting the alloy. 
     According to one or more embodiments of the present invention, an anode active material for a secondary battery, the anode active material includes a powder alloy manufactured by the apparatus for manufacturing a powder alloy, which is described above, wherein the powder alloy includes silicon single phases, each having a grain size of about 100 nm or less, are evenly distributed in a matrix of a silicon-metal alloy. 
     In a particle-size distribution of the powder alloy, when a powder diameter at a point where the number of powder particles accumulated from the smallest one corresponds to 10% of the number of entire particles is defined as D0.1, and a powder diameter at a point where the number of powder particles accumulated from the smallest one corresponds to 90% of the number of entire particles is defined as D0.9, a value of D0.1 of the powder alloy may be 1 μm or greater and a value of D0.9 may be 1000 μm or less. 
     The powder alloy may be included in the anode active material in a state of alloy fine powders ground finely by a ball milling process, and in a particle-size distribution of the powder alloy, when a powder diameter at a point where the number of powder particles accumulated from the smallest one corresponds to 10% of the number of entire particles is defined as D0.1, and a powder diameter at a point where the number of powder particles accumulated from the smallest one corresponds to 90% of the number of entire particles is defined as D0.9, a value of D0.1 of the alloy fine powder may be 0.1 μm or greater and a value of D0.9 may be 100 μm or less. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic diagram of an apparatus for manufacturing powder, according to an embodiment of the present invention; 
         FIG. 2  is a schematic diagram of an apparatus for manufacturing powder according to another embodiment of the present invention; 
         FIG. 3  is a schematic diagram of an apparatus for manufacturing powder according to another embodiment of the present invention; 
         FIG. 4  is a schematic diagram of a secondary battery according to an embodiment of the present invention; 
         FIGS. 5A and 5B  are schematic diagrams of an anode and a cathode according to an embodiment of the present invention; 
         FIG. 6  is a flowchart illustrating a method of manufacturing an anode according to an embodiment of the present invention; 
         FIGS. 7A through 7C  are graphs of particle-size distributions of a silicon-metal powder alloy according to an embodiment of the present invention; 
         FIGS. 8A through 8C  are graphs of particle-size distributions of a silicon-metal alloy fine powder according to an embodiment of the present invention; 
         FIG. 9  is an image of a fine structure of a rapidly solidified strip, according to a comparative example of the present invention; 
         FIGS. 10 and 11  are images of a fine structure of a silicon-metal powder alloy, according to embodiments of the present invention; 
         FIG. 12  is graphs showing X-ray diffraction patterns of the alloy fine powder, according to embodiments of the present invention; and 
         FIGS. 13 and 14  are graphs illustrating lifespan characteristics of an anode, according to embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
       FIG. 1  is a schematic diagram of an apparatus for manufacturing powder  1  according to an embodiment of the present invention. 
     Referring to  FIG. 1 , a powder manufacturing apparatus  1  includes a vacuum chamber  10 , a nozzle unit  20 , a cooling unit  30 , and a grinding unit  40 . 
     The vacuum chamber  10  accommodates the nozzle unit  20 , the cooling unit  30 , and the grinding unit  40  therein, and an inside of the vacuum chamber  10  is maintained at a vacuum state. The vacuum chamber  10  prevents a powder alloy ribbon and powder alloy particles, which are rapidly solidified in the cooling unit  30 , from contacting the external air, so as to avoid oxidization of the powder alloy ribbon and the powder alloy particles. An operating pressure in the inside of the vacuum chamber  10  may be less than or equal to 1×10 −5  Mpa. The vacuum chamber  10  may be connected to a vacuum pump  12  in order to maintain the vacuum pressure in the vacuum chamber  10 . 
     The nozzle unit  20  may include an accommodation unit  22 , a nozzle hole  24 , and a heating unit  26 . 
     The accommodation unit  22  may accommodate an alloy therein, and may have a single-layered structure or a stacked structure of a plurality of layers of a ceramic material such as graphite, an aluminum oxide (Al 2 O 3 ), a zirconium oxide (ZrO 2 ), or a boron nitride (BN). For example, the accommodation unit  22  may be formed of a material having a low reactivity and a high thermal resistance. If there is a possibility of generating an undesired reaction due to a contact between the material forming the accommodation unit  22  and the alloy accommodated in the accommodation unit  22 , a coating layer (not shown) covering an inner wall of the accommodation unit  22  may be further formed of a material that is not reactive with the alloy. 
     The heating unit  26  may be a heating unit for melting the alloy in the accommodation unit  22 , for example, an induction coil. In  FIG. 1 , the heating unit  26  is formed to surround an outer wall of the accommodation unit  22  as the induction coil; however, the embodiments of the present invention are not limited thereto, that is, any kind of heating unit may be used provided that it may heat the accommodation unit  22 . For example, the heating unit  26  may be formed integrally with the accommodation unit  22  while surrounding the outer wall of the accommodation unit  22 . 
     The nozzle hole  24  is formed on a lower end of the accommodation unit  22 , and the alloy melted in the accommodation unit  22  may be sprayed out of the accommodation unit  22  via the nozzle hole  24 . There may be a plurality of nozzle holes  24 . In addition, a spraying pressure providing unit (not shown) may be further formed to provide a spraying pressure to spray the melted alloy in the accommodation unit  22  via the nozzle hole  24 . For example, an inert gas of a high pressure may be supplied from the spraying pressure providing unit so as to easily spray the melted alloy via the nozzle hole  24 , and in this case, an inert gas such as argon or nitrogen may be used. 
     The cooling unit  30  may cool down the melted alloy sprayed through the nozzle hole  24 . The cooling unit  30  may be formed as a roll that is connected to a cooling tank  50  so that a temperature of the roll may not rise. The roll of the cooling unit  30  may be formed of metal having a high thermal shock resistance and a high thermal conductivity such as copper (Cu), chrome (Cr), or iron (Fe). The melted alloy sprayed from the nozzle hole  24  is rapidly cooled down on contacting the roll of the cooling unit  30 , and thus, a rapidly solidified strip  90  may be formed. The melted alloy may be cooled down rapidly, for example, a cooling speed may range from 10 3  to 10 7 ° C./sec. The cooling speed may vary depending on a rotating speed, a material, and a temperature of the roll. 
     The rapidly solidified strip  90  may be formed as a ribbon or a flake. A length and/or a thickness of the rapidly solidified strip  90  may vary depending on a size of the nozzle hole  24 , a rotating speed of the roll of the cooling unit  30 , and a temperature of the roll. For example, the roll may rotate at a speed ranging from about 1000 to about 5000 revolutions per minute (rpm) by a rotating unit (not shown) such as a motor. Also, the length and/or the thickness of the rapidly solidified strip  90  may vary depending on a distance between the cooling unit  30  and the nozzle hole  24 . For example, if the nozzle hole  24  and the cooling unit  30  are too close to each other, some of the sprayed melted alloy is cooled down around the nozzle hole  24 , and thereby reducing a diameter of the nozzle hole  24  or blocking an inlet of the nozzle hole  24 . If the nozzle hole  24  and the cooling unit  30  are too far from each other, a time for the melted alloy sprayed from the nozzle hole  24  to reach the roll of the cooling unit  30  is increased, and the cooling speed of the melted alloy may be reduced. Accordingly, silicon particles precipitated in a matrix may be coalesced, and thus, a rapid solidification effect may be degraded. 
     The grinding unit  40  may grind the rapidly solidified strip  90  cooled by the cooling unit  30  to form a power alloy  92 . In one or more embodiments of the present invention, the grinding unit  40  may be located so that the rapidly solidified strip  90  generated by the cooling unit  30  glides directly to the grinding unit  40  in the vacuum chamber  10 . Therefore, the rapidly solidified strip  90  may be continuously extended toward the grinding unit  40  in the vacuum chamber  10 . Although not shown in  FIG. 1 , a guide (not shown) may be formed between the grinding unit  40  and the cooling unit  30  so that the rapidly solidified strip  90  generated by the cooling unit  30  may be easily located on the grinding unit  40 . 
     According to the present embodiment, the grinding unit  40  may include two grinding rollers  42  and  44 . The grinding rollers  42  and  44  that are adjacent to each other rotate in different directions from each other to ground the rapidly solidified strip  90  introduced into a space between the grinding rollers  42  and  44  to generate the powder alloy  92 . For example, the grinding rollers  42  and  44  may rotate at a speed ranging from about 1000 to about 3000 rpm by a rotating unit (not shown) such as a motor. 
     According to the present embodiment, the grinding rollers  42  and  44  may include a disk plate that is rotated. In  FIG. 1 , the two grinding rollers  42  and  44  are included in the grinding unit  40 ; however, only one grinding roller may be included in the grinding unit  40 . Also, the grinding rollers  42  and  44  are formed as disks; however, one or more embodiments of the present invention are not limited thereto. In addition, a rotary shaft of the grinding unit  40  may be disposed perpendicularly to a rotating shaft of the cooling unit  30 ; however, relative locations of the grinding unit  40  and the cooling unit  30  are not limited thereto. 
     Selectively, the grinding rollers  42  and  44  may be connected to a cooling tank  50 . In this case, the rapidly solidified strip  90  may be additionally cooled down while being ground to fine powder. In general, the melted silicon-metal alloy sprayed from the nozzle hole  24  is instantly solidified on contacting the roll of the cooling unit  30  to form the rapidly solidified strip  90  of a ribbon shape, and thus, the rapid solidification may be performed effectively when a contact area between the melted alloy and the roll of the cooling unit  30  is increased. If a size (thickness or length) of the rapidly solidified strip  90  is too large, a ratio of an area contacting the roll with respect to the entire area of the rapidly solidified strip  90  may be reduced, and accordingly, a temperature difference between a surface and an inside of the rapidly solidified strip  90 , or a temperature difference between a lower surface (i.e., a surface contacting the roll) and an upper surface (i.e., a surface opposite to the surface contacting the roll) of the rapidly solidified strip  90  may be generated. That is, a temperature of the lower surface of the rapidly solidified strip  90 , which directly contacts the cooling unit  30 , may be lower than that of inside the rapidly solidified strip  90 . Therefore, the lower surface of the rapidly solidified strip  90  may have a fine structure, in which silicon single phase particles of fine sizes, for example, a diameter of a few nm to tens of nm, are evenly distributed in a silicon-metal alloy matrix, due to the rapid cooling operation. On the other hand, the inside or the upper surface of the rapidly solidified strip  90  may not be rapidly cooled down, and thus, the silicon single phase particles grows (grain growth) and may be coalesced. However, according to the present embodiment, the grinding unit  40  is formed to be adjacent to the cooling unit  30 , and the grinding unit  40  is connected to the cooling tank  50  to be maintained at a low temperature. Therefore, the rapidly solidified strip  90  may be ground to the power alloy  92  of smaller size in the grinding unit  40 , and the powder alloy  92  is additionally cooled down. Therefore, the powder alloy  92  may have a fine structure, in which the silicon single phase particles of fine and uniform sizes are distributed in the silicon-alloy matrix. 
     Also, the grinding unit  40  is located in the vacuum chamber  10  in which the cooling unit  30  is also located, and thus, oxidation of the surface of the rapidly solidified strip  90  due to the air may be prevented during the grinding process of the rapidly solidified strip  90  into the powder alloy  92 . 
     According to the present embodiment, the powder alloy  92  may have a diameter of about 1 to 1000 μm. The diameter of the powder alloy  92  may vary depending on the rotating speed of the grinding rollers  42  and  44  of the grinding unit  40 . 
     According to the powder manufacturing apparatus  1  of the present embodiment, the silicon-metal powder alloy capable of adjusting the particle-size distribution effectively and having excellent lifespan characteristic may be manufactured. 
       FIG. 2  is a schematic diagram of a powder manufacturing apparatus  1   a  according to another embodiment of the present invention. The powder manufacturing apparatus  1   a  shown in  FIG. 2  is the same as the powder manufacturing apparatus  1  shown in  FIG. 1 , except for further including a dissolution unit  70  and a dissolving chamber  60 . 
     Referring to  FIG. 2 , the powder manufacturing apparatus  1   a  may further include a dissolving chamber  60  connected to an upper portion of the vacuum chamber  10 . The dissolving chamber  60  may be connected to a vacuum pump  62  to maintain an inside thereof at a vacuum state. 
     The dissolution unit  70  may include a dissolving crucible  72  and a heating unit  74 , and accommodates an alloy in the dissolution unit  70  to melt the alloy. The dissolution unit  70  is located in the dissolving chamber  60 , and maintained at a vacuum state to prevent an oxidation of melted alloy due to the air during melting the alloy. 
     The dissolving crucible  72  may receive the alloy therein, and may be formed to have a single-layered structure or a stacked structure of a plurality of layers formed of a ceramic material such as graphite, an aluminum oxide (Al 2 O 3 ), a boron nitride (BN), and the like. For example, a material for forming the dissolving crucible  72  may be a structurally and chemically stabilized material at a temperature higher than a melting temperature of the alloy. If there is a possibility of generating an undesired reaction between the material forming the dissolving crucible  72  and the alloy received in the dissolving crucible  72 , a coating layer (not shown) covering an inner wall of the dissolving crucible  72  may be further formed of a material that is not reactive with the alloy. 
     The heating unit  74  may be a unit for melting the alloy in the dissolving crucible  72 , for example, an induction coil. In  FIG. 2 , the heating unit  74  is formed as an induction coil that surrounds an outer wall of the dissolving crucible  72 ; however, the embodiments of the present invention are not limited thereto, that is, any kind of heating unit may be used provided that the dissolving crucible  72  may be heated. For example, the heating unit  74  may be formed integrally with the dissolving crucible  72  while surrounding the outer wall of the dissolving crucible  72 . 
     The alloy melted in the dissolution unit  70  may be moved to the nozzle unit  20  in the vacuum chamber  10  via an injection hole  64 . For example, if a pressure in the dissolving chamber  60  and a pressure in the vacuum chamber  10  are different from each other, the alloy may move along the injection hole  64  due to the pressure difference. After that, the melted alloy is sprayed to the cooling unit via the nozzle unit  20  in the vacuum chamber  10  to form the rapidly solidified strip  90 . 
       FIG. 2  shows that one dissolution unit  70  is formed in the dissolving chamber  60 ; however, one or more dissolution units  70  may be provided in the dissolving chamber  60 . Otherwise, one or more dissolving chambers  60 , each including one or more dissolution units  70 , may be provided. 
     According to the present embodiment, the dissolution unit  70  and the nozzle unit  20  are separately provided, and thus, a capacity of the dissolution unit  70  may be flexibly adjusted according to an amount of the alloy that is to be melted. Also, since the alloy is injected into the nozzle unit  20  in a melted state, a time for receiving the melted alloy in the nozzle unit  20  may be reduced. According to the powder manufacturing apparatus  1   a  of the present embodiment, the powder alloy may be mass produced, and thereby reducing manufacturing costs and improving productivity. 
       FIG. 3  is a schematic diagram of a powder manufacturing apparatus  1   b  according to another embodiment of the present invention. The powder manufacturing apparatus  1   b  of  FIG. 3  is the same as the powder manufacturing apparatus  1  shown in  FIG. 1 , except for further including a plurality of grinding units  40  and  80 . 
     Referring to  FIG. 3 , a first grinding unit  40  and a second grinding unit  80  are provided in the vacuum chamber  10 . The first grinding unit  40  and the second grinding unit  80  may grind the rapidly solidified strips  90  introduced into grinding rollers  42 ,  44 ,  82 , and  83  thereof, and accordingly, the powder alloy  92  may be manufactured. 
     In the present embodiment, the first and second grinding units  40  and  80  may be disposed so that rotary shafts thereof may be perpendicular to each other. In this case, while the rapidly solidified strip  90  is introduced into the first grinding unit  40 , scattered parts of the rapidly solidified strip  90  may be ground by the second grinding unit  80 , and thus, the grinding efficiency of the rapidly solidified strip  90  may be improved. 
     According to one or more embodiments of the present invention, the first grinding unit  40  and the second grinding unit  80  may be disposed so that the powder alloy  92  that is obtained by passing through the first grinding unit  40  may pass through the second grinding unit  80  again. In this case, the powder alloy  92  may be ground twice in the same vacuum chamber  10 , and thus, damage of the powder alloy  92  such as surface oxidation due to the air may be prevented. 
     In addition, the first and second grinding units  40  and  80  are respectively connected to the cooling tank  50  to improve the cooling effect. 
       FIG. 4  is a schematic diagram of a secondary battery  100  according to an embodiment of the present invention. 
     Referring to  FIG. 4 , a secondary battery  100  may include an anode  110 , a cathode  120 , a separator  130  disposed between the anode  110  and the cathode  120 , a battery container  140 , and a sealing member  150 . Also, the secondary battery  100  may further include an electrolyte (not shown) with which the anode  110 , the cathode  120 , and the separator  130  are impregnated. In addition, the anode  110 , the cathode  120 , and the separator  130  are sequentially stacked and wound as a spiral shape to be accommodated in the battery container  140 . The battery container  140  may be sealed by the sealing member  150 . 
     The secondary battery  100  may be a lithium secondary battery using lithium as a medium, and may be classified as a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery according to a kind of the separator  130  and the electrolyte. In addition, the secondary battery  100  may be formed as a coin type, a button type, a sheet type, a cylinder type, a flat type, and an angular type according to a shape thereof, and may be classified as a bulk type and a thin film type according to a size thereof. The secondary battery  100  shown in  FIG. 4  is a cylinder type secondary battery as an example, and one or more embodiments of the present invention are not limited thereto. 
       FIG. 5A  is a schematic diagram of the anode  110  according to the embodiment of the present invention. The anode  110  shown in  FIG. 5A  may be the anode  110  included in the secondary battery  100  of  FIG. 4 . 
     Referring to  FIG. 5A , the anode  110  may include a negative current collector  111 , and an anode active material layer  112  located on the negative current collector  111 . The anode active material layer  112  may include an anode active material  113 , a binder  114 , and a conductive material  115 . 
     The negative current collector  111  may include a conductive material, for example, may be a thin conductive foil. For example, the negative current collector  111  may include Cu, gold (Au), nickel (Ni), stainless, titanium (Ti), or an alloy thereof. In addition, the negative current collector  111  may include a conductive polymer, and may be formed by compressing an anode active material. 
     The anode active material  113  may include a material which lithium ions may be reversibly intercalated into/deintercalated from. According to one or more embodiments of the present invention, the anode active material  113  may include a silicon-metal alloy material, and the silicon-metal alloy material may include silicon particles of a few nm to hundreds of nm dispersed evenly in a silicon-metal matrix. The metal may be a transition metal, or at least one of Al, Cu, Zr, Ni, Ti, Co, Cr, V, Mn, and Fe. In addition, instead of using the silicon, Sn, Al, or Sb may be used. The anode active material  113  may include a powder alloy that is manufactured by using the powder manufacturing apparatus described with reference to  FIGS. 1 through 3 . Selectively, the anode active material  113  may include alloy fines that are obtained by additionally performing a fine grinding of the alloy particles by a ball-milling method or an air-jet milling method. 
     The binder  114  may bind the particles of the anode active material  113  together, and bind the anode active material  113  with the negative current collector  111 . The binder  114  may be, for example, a polymer, such as polyimide, polyamideimide, polybenzimidazole, polyvinyl alcohol, carboxyl methylcellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene, acrylated styrene-butadiene, or epoxy resin. 
     The conductive material  115  may increase conductivity of the anode  110 , and may be a conductive material that does not cause a chemical change in the secondary battery  100 . For example, the conductive material  115  may include a carbon-based material, e.g., graphite, carbon black, acetylene black, or carbon fiber; a metal material, e.g., copper, nickel, aluminum, or silver; a conductive polymeric material, e.g., a polyphenylene derivative; or a conductive material including a mixture thereof. 
       FIG. 5B  is a schematic diagram of the cathode  120  included in the secondary battery  100  of  FIG. 4 . 
     Referring to  FIG. 5B , the cathode  120  includes a positive current collector  121 , and a cathode active material layer  122  located on the positive current collector  121 . The cathode active material layer  122  includes a cathode active material  123  and a positive binder  124  for binding the cathode active material  123 . Also, the cathode active material layer  122  may selectively further include a cathode conductive material  125 . Also, although not shown in  FIG. 5B , the cathode active material layer  122  may further include an additive such as a filler or a dispersing agent. The cathode  120  may be formed by mixing the cathode active material  123 , the cathode binder  124 , and/or the cathode conductive material  125  in a solvent to obtain a cathode active material composition, and applying the composition on the positive current collector  121 . 
     The positive current collector  121  may be a thin conductive foil, and may include, for example, a conductive material. The positive current collector  121  may include Al, Ni, or an alloy thereof, for example. Otherwise, the positive current collector  121  may include a polymer including conductive metal, or the positive current collector  121  may be formed by compressing an anode active material. 
     The cathode active material  123  may be, for example, a cathode active material for a lithium secondary battery, and may include a material which lithium ions may be reversibly intercalated into/deintercalated from. The cathode active material  123  may include a lithium-containing transition metal oxide, a lithium-containing transition metal sulfide, or the like, for example, at least one selected from the group consisting of LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li(Ni a Co b Mn c )O 2  (0&lt;a&lt;1, 0&lt;b&lt;1, 0&lt;c&lt;1, a+b+c=1), LiNi 1-y Co y O 2 , LiCo 1-y Mn y O 2 , LiNi 1-y Mn y O 2  (0≦y&lt;1), Li(Ni a Co b Mn c )O 4  (0&lt;a&lt;2, 0&lt;b&lt;2, 0&lt;c&lt;2, a+b+c=2), LiMn 2-z Ni z O 4 , and LiMn 2-z Co z O 4  (0&lt;z&lt;2), LiCoPO 4 , and LiFePO 4 . 
     The cathode binder  124  may bind particles of the cathode active material  123  and also binds the cathode active material  123  with the positive current collector  121 . The cathode binder  124  may be, for example, a polymer, such as polyimide, polyamideimides, polybenzimidazole, polyvinyl alcohol, carboxylmethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene, acrylated styrene-butadiene, or epoxy resin. 
     The cathode conductive material  125  may increase conductivity of the cathode  120 , and may be a conductive material that does not cause a chemical change in the secondary battery  100 . For example, the cathode conductive material  125  may include a carbon-based material, e.g., graphite, carbon black, acetylene black, or carbon fiber; a metal material, e.g., copper, nickel, aluminum, or silver; a conductive polymeric material, e.g., a polyphenylene derivative; or a conductive material including a mixture thereof. 
     Referring back to  FIG. 4 , the separator  130  may be a porous material, and may be a single film or a multi-layered film including two or more layers. The separator  130  may include a polymeric material, e.g., at least one selected from the group consisting of a polyethylene-based polymer, a polypropylene-based material, a polyvinylidene fluoride-based polymer, and a polyolefin-based polymer. 
     The electrolyte with which the anode  110 , the cathode  120 , and the separator  130  are impregnated may include a non-aqueous solvent and electrolyte salt. The type of the non-aqueous solvent is not limited if it may be used for a general non-aqueous electrolyte solution. Examples of the non-aqueous solvent may include a carbonated solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, or a nonprontonic solvent. A non-aqueous solvent or a mixture of two or more non-aqueous solvents may be used. When the mixture of two or more non-aqueous solvents is used, a mixing ratio of the two or more non-aqueous solvents may be appropriately adjusted according to a desired performance of a battery. 
     The type of the electrolyte salt is not limited if it may be used for a general non-aqueous electrolytic solution. For example, the electrolyte salt may be salt having an A + B −  structure. Here, ‘A + ’ may denote alkaline metal positive ions, e.g., as Li + , Na + , or K + , or a combination thereof. ‘B − ’ may denote negative ions, e.g., PF 6   − , BF 4   − , Cl − , Br − , I − , ClO 4   − , AsF 6   − , CH 3 CO 2   − , CF 3 SO 3   − , N(CF 3 SO 2 ) 2   − , or C(CF 2 SO 2 ) 3   − , or a combination thereof. For example, the electrolyte salt may be lithium-based salt, e.g., at least one selected from the group consisting of LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiN(SO 2 C 2 F 5 ) 2 , Li(CF 3 SO 2 ) 2 N, LiN(SO 3 C 2 F 5 ) 2 , LiC 4 F 9 SO 3 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ), LiCl, LiI, and LiB(C 2 O 4 ) 2 . Here, ‘x’ and ‘y’ each denote a natural number. 
       FIG. 6  is a flowchart illustrating a method of fabricating an anode, according to an embodiment of the present invention. 
     Referring to  FIG. 6 , silicon and a metal material are melted together to form a molten mixture (operation S10). The silicon and the metal material may be melted together, for example, by generating induced heat of the silicon or the metal material through high-frequency induction using a high-frequency induction furnace. Otherwise, the molten mixture may be generated by using an arc melting process. For example, the silicon-metal powder alloy may be silicon-nickel-titanium powder alloy; however, one or more embodiments of the present invention are not limited thereto. That is, any kind of material which lithium ions intercalated into/deintercalated from to act as an anode material may be used. For example, when the powder manufacturing apparatus described with reference to  FIGS. 1 through 3  is used, silicon and metal are inserted in the nozzle unit of the vacuum chamber and heat is applied to the silicon and metal via the heating unit to form the silicon-metal alloy molten mixture. Otherwise, the silicon-metal alloy molten mixture may be formed in a dissolving unit of the dissolution chamber. 
     After that, the silicon-metal alloy molten mixture is cooled down to form a rapidly solidified strip (operation S20). In the embodiments of the present invention, the cooling operation may be performed by using the powder manufacturing apparatus described with reference to  FIGS. 1 through 3 . For example, the molten mixture sprayed from the nozzle unit is rapidly cooled when contacting the roll of the cooling unit to form the rapidly solidified strip. 
     The rapidly solidified strip is ground to generate silicon-metal powder alloy (operation S30). In the embodiments of the present invention, the grinding process may be performed by using the powder manufacturing apparatus described with reference to  FIGS. 1 through 3 . For example, the rapidly solidified strip that is cooled down by the cooling unit is captured by the grinding unit, and one or more grinding units may grind the rapidly solidified strip to form the silicon powder alloy. The grinding process may be performed in the chamber where the cooling process is performed, and the chamber is maintained at the vacuum state so that the oxidation on the rapidly solidified strip or the silicon-metal powder alloy due to the air. In the embodiments of the present invention, the ground silicon-metal powder alloy has a diameter ranging from about 1 to 1000 μm. For example, the ground silicon-metal powder alloy has a diameter of about 50 to about 500 μm. However, the diameter of the powder alloy is not limited to the above examples, and may vary depending on a size of the rapidly solidified strip and a rotating speed of the grinding unit. For example, in a grain size distribution of the powder alloy, when a powder diameter at which a ratio of powder particles accumulated from the smallest one corresponds to 10% is defined as D0.1 and a powder diameter at which a ratio of the accumulated powder particles corresponds to 90% is defined as D0.9, a value of D0.1 of the powder alloy may be 1 μm or greater and a value of D0.9 of the powder alloy may be 1000 μm or less. 
     Then, the silicon-metal powder alloy is finely ground to generate silicon-metal alloy fine powder (operation S40). In the embodiments of the present invention, the fine grinding process may be performed by a ball milling process or an air-jet milling process. In an example of using the ball milling process, the silicon-metal powder alloy and a zirconia ball are inserted in a milling container, and then the ball milling process may be performed for about 10 to 100 hours at a speed of about 100 to 500 rpm. In another embodiment, the fine grinding process may be performed by using the powder manufacturing apparatus described with reference to  FIGS. 1 to 3 . In this case, in the powder manufacturing apparatus including one or more grinding units, the silicon-metal powder alloy that is ground by a first grinding unit is captured by a second grinding unit and finely ground, and then, the silicon-metal alloy fine powder may be manufactured. In the embodiments of the present invention, the silicon-metal alloy fine powder has a diameter of 0.1 to 100 μm. However, the diameter of the fine powder is not limited thereto, and the diameter of the fine powder may vary depending on the diameter of the silicon-metal powder alloy used in the fine grinding, a usage amount of the zirconia ball, a rotating speed of the ball milling, and the rotation speed of the grinding unit. For example, a value of D0.1 of the silicon-metal alloy fine powder may be 0.1 μm or greater, and a value of D0.9 may be 100 μm or less. 
     After that, the silicon-metal alloy fine powder is mixed with a conductive material of a predetermined concentration and a binder to form slurry, and the slurry is applied and dried on a negative current collector, thereby fabricating the anode shown in  FIG. 5A . 
     EXPERIMENTAL EXAMPLES 
     1. Preparing Experimental Examples 
     Anode active materials prepared by experimental examples 1 through 9 were manufactured by differentiating rotation speeds of the roll of the cooling unit and rotation speeds of the grinding rollers in the grinding unit as shown in following Table 1. In experimental examples 1 through 9, the powder manufacturing apparatus of  FIG. 1  was used, the rotation speed of the roll in the cooling unit was set as 1600 rpm, 1800 rpm, and 2000 rpm, and the rotation speed of the grinding roller in the grinding unit was set as 1600 rpm, 1800 rpm, and 2000 rpm. As a comparative example, a rapidly solidified strip was fabricated by using a cooling roll having a rotation speed of 1800 rpm without using the grinding unit. 
     2. Particle-Size Distribution of the Powder Alloy 
     The particle-size distribution of the powder alloy was measured by using MASTERSIZER 2000 of Malvern, Inc. In a graph showing a distribution of the number of particles with respect to the powder diameter, a powder diameter at a point where the accumulated number of powder particles corresponds to 10% of the number of entire particles is determined as D0.1. Also, powder diameters at points where the accumulated number of the powder particles corresponds to 50% and 90% of the number of entire particles are respectively defined as D0.5 and D0.9. That is, D0.5 denotes a median value in the particle-size distribution, and D0.1 and D0.9 respectively denote particles sizes corresponding to 10% from the lowest and 10% from the highest. Table 1 shows particles sizes D0.1, D0.5, and D0.9 of the powder alloy obtained through the experimental examples 1 through 9. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Rotation 
                 Rotation 
                   
                   
                   
                   
               
               
                   
                 speed of 
                 speed of 
                 Particle 
                 Particle 
                 Particle 
                   
               
               
                   
                 cooling  
                 grinding 
                 size 
                 size 
                 size 
                 D0.9- 
               
               
                   
                 roll 
                 unit  
                 (D 0.1) 
                 (D 0.5) 
                 (D 0.9) 
                 D0.1 
               
               
                   
                 [rpm] 
                 [rpm] 
                 [μm] 
                 [μm] 
                 [μm] 
                 [μm] 
               
               
                   
               
             
            
               
                 Comparative 
                 1800 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 example 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 1600 
                 1600 
                 47.6 
                 147.4 
                 455.4 
                 407.8 
               
               
                 example 1 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 1600 
                 1800 
                 45.2 
                 134.5 
                 389.2 
                 344 
               
               
                 example 2 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 1600 
                 2000 
                 43.2 
                 123.7 
                 332.8 
                 289.6 
               
               
                 example 3 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 1800 
                 1600 
                 42.7 
                 116.8 
                 289.4 
                 246.7 
               
               
                 example 4 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 1800 
                 1800 
                 40.6 
                 100.1 
                 234.5 
                 193.9 
               
               
                 example 5 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 1800 
                 2000 
                 38.1 
                 73.8 
                 178.3 
                 140.2 
               
               
                 example 6 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 2000 
                 1600 
                 26.1 
                 51.2 
                 93.1 
                 67 
               
               
                 example 7 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 2000 
                 1800 
                 25.8 
                 50.9 
                 92.1 
                 66.3 
               
               
                 example 8 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 2000 
                 2000 
                 25.4 
                 50.2 
                 90.5 
                 65.1 
               
               
                 example 9 
                   
                   
                   
                   
                   
                   
               
               
                   
               
            
           
         
       
     
     Referring to Table 1, when the rotation speed of the cooling roll increases, a value of D0.5 is increased, and a value of D0.9-D0.1 is reduced. That is, if the rotation speed of the cooling roll is increased, a size of the rapidly solidified strip is reduced, and the ground alloy powder may have fine and uniform distribution. Also, if the rotation speed of the grinding roll is increased, the value of D0.5 is reduced, and the value of D0.9-D0.1 is reduced. That is, when the rotation speed of the grinding roll is increased, a grinding performance of grinding the rapidly solidified strip into the powder alloy is improved, and the powder alloy may have fine and uniform distribution. 
       FIGS. 7A through 7C  are graphs showing particle-size distributions of the silicon-metal powder alloy according to embodiments of the present invention.  FIGS. 7A ,  7 B, and  7 C are graphs respectively showing the particle-size distributions of the power alloys that were manufactured according to the experimental examples 1, 5, and 9, respectively. 
     Referring to  FIGS. 7A through 7C , the powder alloys according to the experimental examples 1, 5, and 9 respectively have D0.5 values of 147.4 μm, 100.1 μm, and 50.2 μm. Also, with respect to the dispersity of the distribution, the powder alloys of the experimental examples 1, 5, and 9 respectively have values of D0.9-D0.1, that is, 407.8 μm, 193.9 μm, and 65.1 μm. Therefore, it is identified that when the rotation speeds of the cooling roll and the grinding roll are increased, the powder alloy may have fine and uniform particle distribution. 
     3. Particle-Size Distribution of Alloy Fine Powder 
     The powder alloys according to the experimental examples 1 through 9 shown in Table 1 were additionally ground to manufacture silicon-metal alloy fine powder, and particle-size distribution of the silicon-metal alloy fine powder is shown in Table 2. 
     The above fine grinding process was performed by using a ball milling process. The power alloy and a zirconia ball having a diameter of 5 mm were inserted in a milling container having a capacity of 500 ml, and the ball milling process was performed for 48 hours at a speed of 200 rpm to manufacture the silicon-metal alloy fine powders according to the experimental examples 1 through 9. According to a comparative example, a rapidly solidified strip and a zirconia ball were inserted in the milling container, and the ball milling process was performed. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Particle  
                 Particle 
                 Particle  
                   
                   
                   
               
               
                   
                 size  
                 size 
                 size 
                 D0.9- 
                 Grain 
                   
               
               
                   
                 (D 0.1) 
                 (D 0.5)  
                 (D 0.9) 
                 D0.1 
                 size 
                 Lattice 
               
               
                   
                 [μm] 
                 [μm] 
                 [μm] 
                 [μm] 
                 [nm] 
                 strain 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Comparative 
                 0.6 
                 2.9 
                 19.7 
                 19.1 
                 43.9 
                 0.321 
               
               
                 example 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 0.7 
                 4.0 
                 18.1 
                 17.4 
                 44.1 
                 0.319 
               
               
                 example 1 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 0.7 
                 3.9 
                 17.9 
                 17.2 
                 43.3 
                 0.328 
               
               
                 example 2 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental  
                 0.8 
                 3.8 
                 15.6 
                 14.8 
                 42.8 
                 0.331 
               
               
                 example 3 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental 
                 0.8 
                 3.6 
                 13.6 
                 12.8 
                 41.9 
                 0.339 
               
               
                 example 4 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental  
                 0.8 
                 3.6 
                 12.0 
                 11.2 
                 41.2 
                 0.341 
               
               
                 example 5 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental  
                 0.8 
                 3.4 
                 12.4 
                 11.6 
                 40.6 
                 0.350 
               
               
                 example 6 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental  
                 0.7 
                 3.3 
                 12.2 
                 11.5 
                 40.1 
                 0.354 
               
               
                 example 7 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental  
                 0.8 
                 3.1 
                 12.1 
                 11.3 
                 39.7 
                 0.359 
               
               
                 example 8 
                   
                   
                   
                   
                   
                   
               
               
                 Experimental  
                 0.8 
                 3.0 
                 10.6 
                 9.8 
                 38.6 
                 0.365 
               
               
                 example 9 
                   
                   
                   
                   
                   
                   
               
               
                   
               
            
           
         
       
     
       FIGS. 8A through 8C  are graphs showing particle-size distributions of silicon-metal alloy fine powders according to the embodiments of the present invention.  FIGS. 8A ,  8 B, and  8 C are graphs respectively showing the particle-size distributions of the alloy fine powders that are obtained by finely grinding the powder alloys manufactured according to the comparative example, the experimental example 5, and the experimental example 9. 
     Referring to  FIGS. 8A through 8C , the alloy fine powders according to the comparative example, the experimental example 5, and the experimental example 9 respectively have D0.5 values of 2.9 μm, 3.6 μm, and 3.0 μm. In addition, with respect to a dispersity in the distribution, the alloy fine powders according to the comparative example, the experimental example 5, and the experimental example 9 respectively have D0.9-D0.1 values of 19.1 μm, 11.2 μm, and 9.8 μm. In particular, the comparative example has a wide distribution of particles, which denotes that a ratio between a fine particle and a large particle from among the entire fine particles is relatively large, when being compared with the experimental examples. According to the experimental examples 1 and 9, the alloy fine powders have uniform distribution, when compared with the comparative example. In addition, when the power alloy before performing the fine grinding process has the fine and uniform distribution, the fine and uniform particle distribution may be obtained after performing the fine grinding process by using the ball milling process. 
     4. Observation of Fine Structures of Power Alloy and Alloy Fine Powder 
       FIG. 9  is an image showing a fine structure of a rapidly solidified strip, according to a comparative example. As shown in Table 1, the rapidly solidified strip was obtained in a cooled state by the cooling roll having a rotation speed of 1800 rpm, and the rapidly solidified strip had a ribbon shape having a thickness of about 11.3 μm. The rapidly solidified strip has a fine structure, in which silicon single phases of a few to tens of nm are evenly distributed in a silicon-metal alloy matrix. In  FIG. 9 , black fine particles denote the silicon single phases. 
     A lower portion of the rapidly solidified strip (3.02 μm from a bottom surface) has a fine structure that is different from that of remaining part in the rapidly solidified strip. Since the lower portion contacting the cooling roll is cooled down at the fastest speed, the silicon single phases having fine sizes that are unable to be observed are precipitated. 
       FIGS. 10 and 11  are images showing fine structures of silicon-metal alloy fine powders according to the embodiments of the present invention. 
       FIG. 10  is a scanning electron microscopy (SEM) image of the powder alloy according to the experimental example 1, that is, the power alloy ground by the cooling roll and the grinding roll. The powder alloy has a diameter of hundreds of nm to 10 μm, and black silicon single phases are uniformly distributed in the power alloy. 
       FIG. 11  is a transmission electron microscopy (TEM) image of an alloy fine powder according to the experimental example 9, that is, the alloy fine powder obtained by finely grinding the power alloy that is ground by the grinding roll by using the ball milling process. The alloy fine powder has a fine structure, in which the silicon single phases are uniformly distributed in a silicon-metal alloy matrix, and the silicon single phases may have a diameter of a few nm to tens of nm. 
       FIG. 12  is graphs showing X-ray diffraction patterns of the alloy fine powders according to the embodiments of the present invention. In  FIG. 12 , the X-ray diffraction patterns of the alloy fine powders according to the comparative example ((a) and (b)), the experimental example 5 ((c) and (d)), and the experimental example 9 ((e) and (f)) are shown. In (b), (d), and (f) of  FIG. 12 , diffraction patterns of the silicon single phases having peaks between 28° and 29° are expanded. Table 2 shows average grain sizes (nm) of the silicon single phases and lattice strain values calculated based on the X-ray diffraction patterns of  FIG. 12 . Referring to  FIG. 12  and Table 2, the experimental examples of the present invention have an average grain size of about 38.6 nm to about 44.1 nm, and have a lattice strain value of about 0.319 to about 0.365. 
     5. Evaluation of Electrochemical Characteristics 
     A secondary battery half-cell was manufactured in order to evaluate electrochemical characteristics of the alloy powder according to the embodiments of the present invention. A coin cell was manufactured by using metal lithium as a reference electrode, the alloy fine powders according to the experimental examples 1 and 9, and the comparative example as measurement electrodes, and the separator formed of a polyethylene film. 
     An initial discharge capacity, an initial efficiency, and a capacity retention rate of the half-cell were measured. Here, first and second charging/discharging operations were performed at a current density of 0.1 C and 0.2 C, and third through fiftieth charging/discharging operations were performed at a current density of 1.0 C. 
       FIGS. 13 and 14  are graphs showing cyclic characteristics of the anode according to the embodiments of the present invention.  FIG. 13  shows discharge capacities of anodes using the alloy fine powders according to the comparative example, the experimental example 5, and the experimental example 9 to 50 cycles, and  FIG. 14  shows charging/discharging efficiencies to the 50 cycles. 
     Referring to  FIGS. 13 and 14 , the anode using the silicon-metal alloy fine powder according to the experimental examples of the present invention has superior charging/discharging characteristics and superior discharge capacity to those of the comparative example. In particular, the anode according to the experimental example 9 shows a high capacity retention rate of 97.5% and a high charging/discharging efficiency (a ratio of a discharge capacity with respect to a charge capacity) after 52 charging/discharging cycles. 
     In general, when silicon (Si), tin (Sn), antimony (Sb), aluminum (Al), or the like are electrochemically plated with lithium, the volume of the resultant structure increases or decreases during a charge/discharge process. Such a volume change deteriorates cycle characteristics of an electrode employing silicon (Si), tin (Sn), antimony (Sb), aluminum (Al), or the like as an anode active material. Also, such a volume change causes cracks in a surface of the electrode active material. When cracks occur repeatedly in the surface of the electrode active material, fine particles may be formed in the surface of the electrode, thereby deteriorating cyclic characteristics. However, according to the alloy fine powder of the embodiments of the present invention, the silicon single phases of fine sizes are evenly distributed in the silicon-metal alloy matrix, and thus, the volume change of the silicon single phases may be buffered by the matrix, and thereby reducing a stress caused by the volume change. Therefore, the anode active material according to the embodiments of the present invention may have an excellent cyclic characteristic. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Comparative 
                 Experimental 
                 Experimental 
               
               
                   
                 example 
                 example 5 
                 example 9 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 First charging capacity 
                 1081 
                 1094 
                 1075 
               
               
                 [mAh/g] 
               
               
                 First discharging capacity 
                 870 
                 857 
                 847 
               
               
                 [mAh/g] 
               
               
                 First charging/discharging 
                 80.6 
                 81.9 
                 84.7 
               
               
                 efficiency [%] 
               
               
                 Third discharging capacity 
                 824 
                 841 
                 839 
               
               
                 [mAh/g] 
               
               
                 52nd discharging capacity 
                 728 
                 768 
                 818 
               
               
                 [mAh/g] 
               
               
                 Capacity retention rate [%] 
                 87.9 
                 91.3 
                 97.5 
               
               
                 (52nd/3rd) 
               
               
                 52nd charging/discharging 
                 98.9 
                 98.7 
                 99.5 
               
               
                 efficiency [%] 
               
               
                   
               
            
           
         
       
     
     According to the powder manufacturing apparatus of the present invention, the nozzle unit, the cooling unit, and the grinding unit are included in a first chamber so as to effectively adjust a particle-size distribution of the powder alloy and manufacture silicon-metal powder alloy having excellent lifespan characteristic. A secondary battery including the anode active material that is formed by using the powder alloy has an extended cycle-life. 
     It should be understood that the exemplary embodiments described therein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     While one or more embodiments of the present invention have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.