POROUS AMORPHOUS SILICON, METHOD FOR PRODUCING POROUS AMORPHOUS SILICON, AND SECONDARY BATTERY

Abstract

A porous amorphous silicon which enables improvement in battery performances such as charge/discharge efficiency and battery capacity when used as the anode material; a method for producing a porous amorphous silicon, capable of producing a porous amorphous silicon composed entirely of amorphous silicon at relatively low cost in a short time; and a secondary battery using the porous amorphous silicon as the anode material. A molten metal containing metal and silicon is cooled at a cooling rate of 10.sup.6 K/sec or more to form an eutectic alloy including the metal and the silicon, and then the metal is selectively eluted from the eutectic alloy with an acid or an alkali to obtain a porous amorphous silicon. The porous amorphous silicon has a lamellar or columnar structure having a mean lamellar diameter or a mean column diameter of 1 nm to 100 nm.

Claims

1. A porous amorphous silicon which has a lamellar or columnar structure having a mean lamellar diameter or a mean column diameter of 1 nm to 100 nm.

2. The porous amorphous silicon according to claim 1, which has a lamellar structure having a spacing between adjacent lamellae of 1 nm to 100 nm or a columnar structure having a spacing between adjacent columns of 1 nm to 100 nm.

3. The porous amorphous silicon according to claim 1, which has a mean porosity of 10% to 99%.

4. The porous amorphous silicon according to claim 1, wherein the mean lamellar diameter or the mean column diameter is 1 nm to 50 nm.

5. The porous amorphous silicon according to claim 1, which has a bicontinuous structure.

6. A method for producing a porous amorphous silicon, which comprises cooling a molten metal containing metal and silicon at a cooling rate of 10.sup.6 K/sec or more to form an eutectic alloy comprising the metal and the silicon, and selectively eluting the metal from the eutectic alloy with an acid or an alkali to obtain a porous amorphous silicon.

7. The method for producing a porous amorphous silicon according to claim 6, wherein the eutectic alloy is produced by a single roll rapid quenching method or a twin roll rapid quenching method, and has a ribbon or foil shape having a mean thickness of 0.1 μm to 1 mm.

8. The method for producing a porous amorphous silicon according to claim 6, wherein the eutectic alloy is produced by a gas atomization method or a water atomization method, and has a powder shape having a mean lamellar diameter of 10 nm to 30 μm.

9. The method for producing a porous amorphous silicon according to claim 6, wherein a phase of the silicon in the structure of the eutectic alloy has a domain size of 1 nm to 100 nm.

10. The method for producing a porous amorphous silicon according to claim 6, wherein a phase of the metal in the structure of the eutectic alloy has a domain size of 1 nm to 100 nm.

11. The method for producing a porous amorphous silicon according to claim 6, wherein a phase of the silicon in the structure of the eutectic alloy has a domain size of 1 nm to 50 nm.

12. The method for producing a porous amorphous silicon according to claim 6, wherein the eutectic alloy is an Al—Si alloy.

13. The method for producing a porous amorphous silicon according to claim 12, which contains an atomic percentage of Si between 1% to 50%.

14. The method for producing a porous amorphous silicon according to claim 6, wherein the eutectic alloy is an Fe—Si alloy, an Ni—Si alloy, a Cr—Si alloy, an Ag—Si alloy or a Cu—Si alloy.

15. The method for producing a porous amorphous silicon according to claim 14, which contains an atomic percentage of Si between 50% to 90%.

16. The method for producing a porous amorphous silicon according to claim 6, wherein the eutectic alloy is a two- or multi-component eutectic alloy represented by M.sub.1-Si (M.sub.1 represents one or more elements selected from Al, Ag, As, Au, Be, Ca, Cr, Cu, Mg, Pd, Pt, Y, Co, Fe, Mn, Ti and Zr).

17. The method for producing a porous amorphous silicon according to claim 6, wherein the eutectic alloy is a three- or multi-component eutectic alloy represented by M.sub.2-Al—Si (M.sub.2 represents one or more elements selected from Ca, Cu, Ge, P, Mn, Na, Sb, Sn, Sc, Sr and Ti).

18. A secondary battery whose anode material comprises the porous amorphous silicon according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 includes (a) a scanning electron microscopic (SEM) photograph; (b) a SEM photograph taken at a higher magnification than that of (a); and (c) a SEM photograph taken at a higher magnification than that of (b); of a porous amorphous silicon produced using an Al—Si alloy, which is fabricated by mixing at a ratio of Si:Al=20:80 (atomic %) using a single roll rapid quenching method, by the method for producing a porous amorphous silicon according to an embodiment of the present invention.

[0040] FIG. 2 includes (a) an electron transmission microscopic (TEM) photograph; and (b) a TEM photograph taken at a higher magnification than that of (a) and a Fourier-transformed image (inserted figure); of the porous amorphous silicon shown in FIG. 1.

[0041] FIG. 3 includes (a) a scanning electron microscopic (SEM) photograph, (b) a SEM photograph taken at a higher magnification than that of (a); (c) a SEM photograph taken at a higher magnification than that of (b); and (d) a SEM photograph of the part different from that of (b) taken at a higher magnification than that of (a); of a porous amorphous silicon produced using an Al—Si alloy powder, which is fabricated by mixing at a ratio of Si:Al=20:80 (atomic %) through gas atomization using He gas, by the method for producing a porous amorphous silicon according to an embodiment of the present invention.

[0042] FIG. 4 includes (a) a scanning electron microscopic (SEM) photograph; and (b) a SEM photograph taken at a higher magnification than that of (a); of a porous amorphous silicon produced using an Al—Si—Ti alloy powder, which is fabricated by mixing at a ratio of Si:Al:Ti=19.5:79.5:1.0 (atomic %) through gas atomization using He gas, by the method for producing a porous amorphous silicon according to an embodiment of the present invention.

[0043] FIG. 5 illustrates XRD spectra of (a) the porous amorphous silicon shown in FIG. 1; (b) the porous amorphous silicon shown in FIG. 3; (c) the porous amorphous silicon shown in FIG. 4; and (d) a crystalline substance Si nanopowder of Comparative Example.

[0044] FIG. 6 includes (a) a scanning electron microscopic (SEM) photograph, (b) a SEM photograph taken at a higher magnification than that of (a); (c) a SEM photograph taken at a higher magnification than that of (b); and (d) a SEM photograph taken at a higher magnification than that of (c); of a porous amorphous silicon produced using an Al—Si alloy powder, which is fabricated by mixing at a ratio of Si:Al=3:97 (atomic %) through gas atomization using He gas, by the method for producing a porous amorphous silicon according to an embodiment of the present invention.

[0045] FIG. 7 includes (a) a scanning electron microscopic (SEM) photograph; (b) a SEM photograph taken at a higher magnification than that of (a); and (c) a SEM photograph taken at a higher magnification than that of (b); of a porous amorphous silicon produced using an Al—Si alloy powder, which is fabricated by mixing at a ratio of Si:Al=12.5:87.5 (atomic %) through gas atomization using Ar gas, by the method for producing a porous amorphous silicon according to an embodiment of the present invention.

[0046] FIG. 8 includes (a) a scanning electron microscopic (SEM) photograph; and (b) a SEM photograph taken at a higher magnification than that of (a); of a porous amorphous silicon produced using an Al—Si alloy powder, which is fabricated by mixing at a ratio of Si:Al=12.5:87.5 (atomic %) using a single roll rapid quenching method, by the method for producing a porous amorphous silicon according to an embodiment of the present invention.

[0047] FIG. 9 includes (a) a scanning electron microscopic (SEM) photograph; and (b) a SEM photograph taken at a higher magnification than that of (a); of a porous amorphous silicon produced using an Al—Si alloy powder, which is fabricated by mixing at a ratio of Si:Al=30:70 (atomic %) using a single roll rapid quenching method, by the method for producing a porous amorphous silicon according to an embodiment of the present invention.

[0048] FIG. 10 includes (a) a scanning electron microscopic (SEM) photograph; and (b) a SEM photograph taken at a higher magnification than that of (a); of a porous amorphous silicon produced using an Al—Si alloy powder, which is fabricated by mixing at a ratio of Si:Al=40:60 (atomic %) using a single roll rapid quenching method, by the method for producing a porous amorphous silicon according to an embodiment of the present invention.

[0049] FIG. 11 illustrates an XRD spectrum of the porous amorphous silicon shown in FIG. 8.

[0050] FIG. 12 is a graph showing the test results of the evaluation of battery cycle properties of (a) a lithium ion battery using the porous amorphous silicon shown in FIG. 1 as the anode material; and (b) a lithium ion battery using crystalline Si particles of Comparative Example as the anode material.

DETAILED DESCRIPTION OF THE INVENTION

[0051] Embodiments of the present invention will be described below with reference to Examples.

[0052] The porous amorphous silicon according to an embodiment of the present invention has a lamellar or columnar structure having a mean lamellar diameter or a mean column diameter of 1 nm to 100 nm. The porous amorphous silicon according to an embodiment of the present invention has a lamellar structure having a spacing between adjacent lamellae of 1 nm to 100 nm or a columnar structure having a spacing between adjacent columns of 1 nm to 100 nm. The porous amorphous silicon according to an embodiment of the present invention is suitably produced by the method for producing a porous amorphous silicon according to an embodiment of the present invention.

[0053] In the method for producing a porous amorphous silicon according to an embodiment of the present invention, first, a molten metal containing metal and silicon is cooled at a cooling rate of 10.sup.6 K/sec or more to form an eutectic alloy comprising the metal and the silicon. Subsequently, the metal is selectively eluted from the eutectic alloy with an acid or an alkali. This makes it possible to obtain a porous amorphous silicon.

[0054] In the method for producing a porous amorphous silicon according to an embodiment of the present invention, the eutectic alloy may be produced, for example, by a single roll rapid quenching method or a twin roll rapid quenching method. In this case, the eutectic alloy to be produced preferably has a ribbon or foil shape having a mean thickness of 0.1 μm to 1 mm. The eutectic alloy may also be produced by a gas atomization method or a water atomization method. In this case, the eutectic alloy to be produced preferably has a powder shape having a mean particle diameter of 10 nm to 30 μm.

[0055] In the method for producing a porous amorphous silicon according to an embodiment of the present invention, the eutectic alloy may be, for example, an Al—Si alloy. In this case, the eutectic alloy preferably contains an atomic percentage of Si between 1% to 50%. This makes it possible to produce a porous amorphous silicon having a mean porosity of 50% to 99%. The eutectic alloy may be an Fe—Si alloy, an Ni—Si alloy, a Cr—Si alloy, an Ag—Si alloy or a Cu—Si alloy. In this case, the eutectic alloy preferably contains an atomic percentage of Si between 50% to 90%. This makes it possible to produce a porous amorphous silicon having a mean porosity of 10% to 50%.

[0056] The eutectic alloy may be a two- or multi-component eutectic alloy represented by M.sub.1-Si (M.sub.1 represents one or more elements selected from Al, Ag, As, Au, Be, Ca, Cr, Cu, Mg, Pd, Pt, Y, Co, Fe, Mn, Ti and Zr), or a three- or multi-component eutectic alloy represented by M.sub.2-Al—Si (M.sub.2 represents one or more elements selected from Ca, Cu, Ge, P, Mn, Na, Sb, Sn, Sc, Sr and Ti). The eutectic alloy may also be an amorphous alloy.

[0057] The actions will be described below.

[0058] In the method for producing a porous amorphous silicon according to an embodiment of the present invention, a molten metal containing metal and silicon is cooled at a cooling rate of 10.sup.6 K/sec or more when an eutectic metal is formed, thus making it possible to adjust a domain size of a silicon phase in the structure of the eutectic alloy in a range of 1 nm to 100 nm, and to adjust a domain size of a metal phase in the structure of the eutectic alloy in a range of 1 nm to 100 nm. The selective elution of the metal from this eutectic alloy makes it possible to produce a porous amorphous silicon according to an embodiment of the present invention which has a mean lamellar diameter or a mean column diameter of 1 nm to 100 nm and has a lamellar structure having a spacing between adjacent lamellae of 1 nm to 100 nm or a columnar structure having a spacing between adjacent columns of 1 nm to 100 nm.

[0059] The method for producing a porous amorphous silicon according to the present invention is capable of producing a porous amorphous silicon composed entirely of amorphous silicon by cooling a molten metal at a cooling rate of 10.sup.6 K/sec or more. Further increase in cooling rate enables the domain size of a silicon phase in the structure of the eutectic alloy to be reduced to a range of 1 nm to 50 nm, thus producing a porous amorphous silicon having a mean lamellar diameter or a mean column diameter of 1 nm to 50 nm.

[0060] Since the method for producing a porous amorphous silicon according to the present invention comprises the steps of rapid quenching a molten metal and eluting metal with an acid or an alkali, a porous amorphous silicon can be produced at relatively low costs in a short time without using an expensive device. Silicon having the highest Clarke number excluding oxygen is used as the material, and a porous amorphous silicon can be produced at low cost by using metal having higher Clarke number, such as aluminum. Therefore, this makes it easy to economically scale up for mass production.

[0061] Since the porous amorphous silicon according to the present invention is composed of a sufficiently grown porous amorphous silicon, it is possible to improve battery performances such as charge/discharge efficiency and battery capacity when used as the anode material. When the porous amorphous silicon according to the present invention is used as the anode material for lithium ion batteries, even if silicon is alloyed with lithium to cause volume expansion, there is almost no change in appearance because expansion occurs to fill pores of holes. The porous amorphous silicon according to an embodiment of the present invention can have both high strength and high elasticity compared to a crystalline substance, and is resistant to the volume expansion when silicon is alloyed with lithium. As mentioned above, when the porous amorphous silicon according to the present invention is used as the anode material for lithium ion batteries, it is possible to prevent the anode material from being pulverized.

[0062] The porous amorphous silicon according to the present invention is not limited to the anode material for lithium ion batteries, and can also be used as thermoelectric materials, solar batteries, electronic device members, filter materials and optical materials. The porous amorphous silicon according to the present invention preferably has a bicontinuous structure. It is preferable that the porous amorphous silicon according to the present invention is amorphous silicon having a three-dimensional network structure and also includes continuous pores. The ratio of silicon is preferably 90% or more in terms of a ratio of an element excluding oxygen.

Example 1

[0063] Using the method for producing a porous amorphous silicon according to an embodiment of the present invention, a porous amorphous silicon was produced. First, silicon (massive, purity of 99.999% or higher) was mixed with aluminum at a ratio of Si:Al=20:80 (atomic %) and the mixture was arc-melted in a vacuum furnace in a state of being purged with argon gas to obtain a molten metal. Using a single roll caster, a ribbon-shaped Al—Si alloy having a thickness of about 15 μm was fabricated from the molten metal by a single roll rapid quenching method. This Al—Si alloy is an eutectic alloy comprising Al and Si. This Al—Si alloy was immersed in hydrochloric acid having the concentration of 5 N at a temperature of 60° C. for 24 hours to elute Al, thus producing a porous body composed of silicon.

[0064] A scanning electron microscopic (SEM) photograph and an electron transmission microscopic (TEM) photograph of the porous body thus obtained are respectively shown in FIG. 1 and FIG. 2. FIG. 2(b) shows, as an inserted figure, a Fourier-transformed image of a TEM photograph. As shown in FIG. 1 and FIG. 2, the substance thus obtained has a porous structure having a mean lamellar diameter and a mean column diameter of about 10 nm, and particularly it has been confirmed from FIG. 1(c) that the substance has a lamellar structure of about 10 nm. It has also been confirmed that the lamellar structure had a spacing between adjacent lamellae of several tens of nm or less. It has been confirmed that the substance is amorphous since the Fourier-transformed image in FIG. 2(b) exhibits a halo pattern.

[0065] The measurement results by an X-ray diffraction (XRD) method of the porous body thus obtained are shown in FIG. 5(a). The measurement results by an X-ray diffraction (XRD) method of a commercially available crystalline substance Si nanopowder as Comparative Example are shown in FIG. 5(d). As shown in FIG. 5(a), it has been confirmed that the porous body thus obtained is not a crystalline substance but amorphous since an XRD spectrum has no sharp peaks and exhibits a gentle shape. The above results reveal that the substance shown in FIG. 1 and FIG. 2 is a porous amorphous silicon.

Example 2

[0066] Silicon (massive, purity of 99.9% or higher) was mixed with aluminum at a ratio of Si:Al=20:80 (atomic %) and the mixture was arc-melted in a vacuum furnace in a state of being purged with argon gas to obtain a molten metal at 1,400° C. Using the gas atomizer shown in Patent Literature 2, the molten metal was ground by helium gas under 10 MPa to fabricate an Al—Si alloy powder having a particle diameter of about 10 μm or less. This Al—Si alloy is an eutectic alloy comprising Al and Si. This Al—Si alloy was immersed in hydrochloric acid having the concentration of 5 N at a temperature of 60° C. for 24 hours to elute Al, thus producing a porous body composed of silicon.

[0067] A scanning electron microscopic (SEM) photograph of the porous body thus obtained is shown in FIG. 3. As shown in FIG. 3, it has been confirmed that the substance thus obtained has a porous lamellar structure having a mean lamellar diameter and a mean column diameter of about 20 to 30 nm (see FIG. 3(b) and FIG. 3(c)) and a columnar structure having a mean column diameter of about 100 nm (see FIG. 3(d)). It has also been confirmed that the lamellar structure has a spacing between adjacent lamellae of several tens of nm or less and the columnar structure has a spacing between adjacent columns of 100 nm or less. The columnar structure shown in FIG. 3(d) has a length of about 1 μm and an aspect ratio of about 10.

[0068] The measurement results by an X-ray diffraction (XRD) method of the porous body thus obtained are shown in FIG. 5(b). As shown in FIG. 5(b), it has been confirmed that the porous body thus obtained is almost entirely amorphous since a slight peak appears on the wide-angle side, but an XRD spectrum has no sharp peak and exhibits almost gentle shape. The above results reveal that the substance shown in FIG. 3 is a porous amorphous silicon.

Example 3

[0069] Silicon (massive, purity of 99.9% or higher) was mixed with aluminum and titanium at a ratio of Si:Al:Ti=19.5:79.5:1.0 (atomic %) and the mixture was arc-melted in a vacuum furnace in a state of being purged with argon gas to obtain a molten metal at 1,400° C. Using the gas atomizer shown in Patent Literature 2, the molten metal was ground by helium gas under 10 MPa to fabricate an Al—Si—Ti alloy powder having a particle diameter of about 10 μm or less. This Al—Si—Ti alloy is an eutectic alloy comprising Al, Si and Ti. This Al—Si—Ti alloy was immersed in hydrochloric acid having the concentration of 5 N at a temperature of 60° C. for 24 hours to elute Al and Ti, thus producing a porous body composed of silicon.

[0070] A scanning electron microscopic (SEM) photograph of the porous body thus obtained is shown in FIG. 4. As shown in FIG. 4, it has been confirmed that the substance thus obtained has a porous lamellar structure having a mean lamellar diameter and a mean column diameter of about 80 to 100 nm or less. It has also been found that the lamellar structure has a spacing between adjacent lamellae of 50 nm or less.

[0071] The measurement results by an X-ray diffraction (XRD) method of the porous body thus obtained are shown in FIG. 5(c). As shown in FIG. 5(c), it has been confirmed that the porous body thus obtained is not a crystalline substance but amorphous since an XRD spectrum has no sharp peak and exhibits a gentle shape. The above results reveal that the substance shown in FIG. 4 is a porous amorphous silicon.

Example 4

[0072] Silicon (massive, purity of 99.9% or higher) was mixed with aluminum at various ratios to fabricate an eutectic alloy and then Al was eluted to produce a porous body composed of silicon. A mixing ratio of Si and Al included the following four types: [Si:Al]=[3:97], [12.5:87.5], [30:70] and [40:60] (atomic %). In the case of [Si:Al]=[3:97], an eutectic alloy was fabricated by a gas atomization method using He gas. In the case of [Si:Al]=[12.5:87.5], an eutectic alloy was fabricated by a gas atomization method using Ar gas. In the case of the following three types: [Si:Al]=[12.5:87.5], [30:70] and [40:60], an eutectic alloy was fabricated by a single roll rapid quenching method.

[0073] When using the gas atomization method, like Example 2, first, a mixture obtained by mixing Si and Al at a predetermined ratio was arc-melted in a vacuum furnace in a state of being purged with argon gas, and then the molten metal was ground by He gas or Ar gas under 10 MPa using the gas atomizer shown in Patent Literature 2 to fabricate an eutectic alloy composed of an Al—Si alloy powder having a particle diameter of about 10 μm or less. When using the single roll rapid quenching method, like Example 1, first, a mixture obtained by mixing Si and Al at a predetermined ratio was arc-melted in a vacuum furnace in a state of being purged with argon gas, and then an eutectic alloy composed of a ribbon-shaped Al—Si alloy having a thickness of about 15 μm was fabricated from the molten metal using a single roll caster. The eutectic alloy fabricated by each method was immersed in hydrochloric acid having the concentration of 5 N at a temperature of 60° C. for 24 hours to elute Al, thus producing a porous body composed of silicon.

[0074] Scanning electron microscopic (SEM) photographs of each porous body thus obtained are respectively shown in FIG. 6 to FIG. 10. As shown in FIG. 6, it has been confirmed that the porous body obtained by mixing at a ratio of [Si:Al]=[3:97] through the gas atomization method using He gas has a columnar structure having a mean column diameter of about 100 nm (see FIG. 6(d)).

[0075] As shown in FIG. 7, it has been confirmed that the porous body obtained by mixing at a ratio of [Si:Al]=[12.5:87.5] through a gas atomization method using Ar gas has a porous lamellar structure having a mean lamellar diameter and a mean column diameter of about 100 nm (see FIG. 7(c)). It has also been confirmed that the lamellar structure has a spacing between adjacent lamellae of about 100 nm. As shown in FIG. 8, it has been confirmed that the porous body obtained by mixing at the same ratio of [Si:Al]=[12.5:87.5] through a single roll rapid quenching method has a columnar structure having a mean column diameter of about 100 nm or less (see FIG. 8(b)). The measurement results by an X-ray diffraction (XRD) method of this porous body are shown in FIG. 11. As shown in FIG. 11, it has been confirmed that the porous body thus obtained is not a crystalline substance but amorphous since an XRD spectrum has no sharp peaks and exhibits a gentle shape. These results reveal that the substance shown in FIG. 8 is a porous amorphous silicon.

[0076] As shown in FIG. 9, it has been confirmed that the porous body obtained by mixing at a mixing ratio of [Si:Al]=[30:70] through a single roll rapid quenching method has a porous lamellar structure having a mean lamellar diameter and a mean column diameter of about several tens of nm (see FIG. 9(b)). It has also been confirmed that the lamellar structure has a spacing between adjacent lamellae of several tens of nm or less.

[0077] As shown in FIG. 10, it has been confirmed that the porous body obtained by mixing at a mixing ratio of [Si:Al]=[40:60] through a single roll rapid quenching method has a porous lamellar structure having a mean lamellar diameter and a mean column diameter of about 100 nm or less (see FIG. 10(b)). It has also been confirmed that the lamellar structure has a spacing between adjacent lamellae of several tens of nm or less.

Example 5

[0078] A lithium ion battery using the porous amorphous silicon shown in FIG. 1 and FIG. 2 as the anode material was produced, and then a test for the evaluation of cycle properties of the battery was performed. First, porous amorphous silicon particles, a carbon black conductive assistant and a polyimide binder were dispersed in N-methyl-2-pyrrolidone to obtain a uniform slurry. The slurry was unfirmly coated on a rolled copper foil so that a coating amount became about 1 to 2 mg/cm.sup.2, and then dried and solidified by heating in a vacuum at 450° C. Using this coated rolled copper foil as an anode, pure lithium as a counter electrode, and a solution having a concentration of 1 mol/liter prepared by dissolving lithium hexafluorophosphate in fluoroethylene carbonate as an electrolyte, a 2032 coin type half-cell battery was produced. A lithium ion battery using crystalline Si particles having a diameter of 100 nm as an anode material was also produced as Comparative Example.

[0079] With respect to each lithium ion battery thus produced, the delithiation capacity at each cycle was measured by repeating charge/discharge cycle for 100 cycles at a current density of 0.5 C for a porous amorphous silicon electrode and 0.25 C (1 C is 3,579 mA/g) for crystalline silicon particles at a voltage in a range of 0.005 V to 1 V. The measurement results are shown in FIG. 12. As shown in FIG. 12, it has been confirmed that the battery using the porous amorphous silicon exhibited the maximum capacity of about 2,000 mAh/g Si and the capacity of 1,600 to 1,700 mAh/g Si after 100 cycles, and a decrease in capacity is suppressed to about 15 to 20% even after 100 cycles. To the contrary, it has been confirmed that, in the case of the battery using crystalline Si particles of Comparative Example, the original maximum capacity of about 2,350 mAh/g Si is decreased to 500 mAh/g Si or less after 80 cycles. As mentioned above, it is possible to say that the lithium ion battery using the porous amorphous silicon as the anode material has satisfactory cycle properties and high battery capacity.