POROUS SILICON BASED PARTICLES, METHOD FOR PREPARING SAME AND ANODE ACTIVE MATERIAL COMPRISING SAME TECHNICAL FIELD [0001] The present invention relates to porous silicon-based particles, a method of preparing the same, and a lithium secondary battery including the porous silicon-based particles. BACKGROUND ART [0002] Recently, in line with miniaturization, lightweight, thin profile, and portable trends in electronic devices according to the development of information and telecommunications industry, the need for high energy density batteries used as power sources of such electronic devices has increased. Currently, research into lithium secondary batteries, as batteries that may best satisfy the above need, has actively conducted. [0003] Various types of carbon-based materials including artificial graphite, natural graphite, or hard carbon, which are capable of intercalating/deintercalating lithium, have been used as anode active materials of lithium secondary batteries. Among the carbon-based materials, since graphite provides advantages in terms of energy density of a lithium 3 battery and also guarantees long lifespan of the lithium secondary battery due to excellent reversibility, graphite has been most widely used. [0004] However, since graphite may have a low capacity in terms of energy density per unit volume of an electrode and may facilitate side reactions with an organic electrolyte at a high discharge voltage, there is a risk of fire or explosion due to malfunction and overcharge of the battery. [0005] Thus, metal-based anode active materials, such as silicon (Si), have been studied. It is known that a Si metal-based anode active material exhibits a high lithium capacity of about 4,200 mAh/g. However, the Si metal-based anode active material may cause a volumetric change of a maximum of 300% or more before and after the reaction with lithium, i.e., during charge and discharge. As a result, conductive networks in the electrode are damaged and contact resistance between particles is increased. Thus, there is a phenomenon in which a battery performance degrades. [0006] Thus, a method of reducing substantial variations in diameter according to the volumetric change by reducing the size of silicon particles to a nano size has been attempted. However, there are difficulties in developing a method of synthesizing a uniform nano-silicon anode active material and uniformly distributing the nano-silicon anode active material in a slurry, and side reactions with an electrolyte may 4 increase because a surface area is maximized. [0007] Therefore, there is a need to develop an anode active material which may replace a typical anode active material and may address limitations in the side reactions with an electrolyte, volume expansion during charge and discharge, and performance degradation of a secondary battery. [0008] Prior Art Documents [0009] [Patent Document] [0010] Korean Patent Application Laid-Open Publication No. 2012-0109080 DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM [0011] The present invention provides porous silicon-based particles which may be more easily dispersed in an anode active material slurry, may minimize side reactions with an electrolyte, and may reduce volume expansion during charge and discharge. [0012] The present invention also provides a method of preparing the porous silicon-based particles. [0013] The present invention also provides an anode active material including the porous silicon-based particles. [0014] The present invention also provides an anode and a lithium secondary battery including the anode active material. TECHNICAL SOLUTION [0015] According to an aspect of the present invention, 5 there is provided a porous silicon-based particle including a silicon (Si) or SiOx(0 [00108] Example 1 [00109] [00110] Silicon in a powder state was immersed in 8.5 M hydrogen fluoride heated to a temperature of 50°C, and then stirred for about 30 minutes. A natural oxide layer (SiO2) present on the surface of the silicon in a powder state was removed through the above process. Thus, silicon particles having the oxide layer removed therefrom were obtained by performing a surface treatment which may allow the Si or SiOx(0 [00112] A 15 mM copper sulfate (CuSO4) aqueous solution prepared at the same volume as that of the hydrogen fluoride was added to an aqueous solution including silicon having the oxide layer (SiO2) removed therefrom that was obtained in step (i), in which 8.5 M hydrogen fluoride was mixed, and stirred for about 3 hours to perform etching. Copper was deposited on the surface of the silicon having the oxide layer (SiO2) removed therefrom through the above process, and simultaneously, the etching was performed. [00113] In the aqueous solution state, the remaining hydrogen fluoride was removed by washing porous silicon particles several times using a filter press capable of simultaneously filtering, washing, and dehydrating. Thereafter, the solution thus obtained was filtered, dehydrated, and dried at about 150°C for about 1 hour to obtain porous silicon particles in which nonlinear pores were connected to one another. [00114] In order to remove copper remaining on the porous silicon particles prepared by the above method, nitric acid was heated to a temperature of 50°C, and the porous silicon particles were then immersed in the nitric acid for about 2 hours to remove the copper. 30 [00115] Examples 2 to 6 [00116] Porous silicon particles were prepared in the same manner as in Example 1 except that a 15 mM copper sulfate (CuSO4) aqueous solution prepared at the same volume as that of the hydrogen fluoride was added to an aqueous solution including silicon having the oxide layer (SiO2) removed therefrom that was obtained in step (i), in which 8.5 M hydrogen fluoride was mixed, and stirred for about 6 hours, 9 hours, 12 hours, 18 hours, and 24 hours, respectively. [00117] Example 7 [00118] [00119] Silicon in a powder state was immersed in 17.5 M hydrogen fluoride heated to a temperature of 50°C, and then stirred for about 30 minutes. A natural oxide layer (SiO2) present on the surface of the silicon in a powder state was removed through the above process. Thus, silicon particles having the oxide layer removed therefrom were obtained by performing a surface treatment which may allow the Si or SiOx(0 [00121] A 30 mM copper sulfate (CuSO4) aqueous solution prepared at the same volume as that of the hydrogen fluoride was added to an aqueous solution, in which 17.5 M hydrogen fluoride and silicon having the oxide layer (SiO2) removed therefrom that was obtained in step (i) were mixed, and stirred for about 1 hour. Copper was uniformly deposited on the surface of the silicon having the oxide layer (SiO2) removed therefrom through the above process. [00122] In the aqueous solution including silicon having the oxide layer (SiO2) removed therefrom in which 17.5 M hydrogen fluoride was mixed, a 0.5 M phosphite (H3PO3) aqueous solution was prepared to have 1/3 of the volume of the hydrogen fluoride, and was then added to the aqueous solution including the copper-deposited silicon that was obtained in the above metal deposition step. When this mixture was mixed at 50°C for about 21 hours, a portion deposited with copper and a surface oxidized by phosphite were only selectively etched by chemical etching, and thus, porous silicon was prepared in which nonlinear pores were connected to one another. 32 [00123] In this case, the copper deposited on the silicon was used as a catalyst reducing silicon and the phosphite was used as a weak oxidant oxidizing the silicon to increase a chemical etching rate. [00124] That is, the phosphite used as a weak oxidant may increase the size of the pore formed by the copper or may form additional pores through the oxidation of the silicon. [00125] Comparative Example 1 [00126] Porous silicon particles were prepared in the same manner as in Example 1 except that a silver nitrate aqueous solution was used instead of a copper sulfate (CuSO4) aqueous solution in step (ii) of Example 1. [00127] Comparative Example 2 [00128] Porous silicon particles were prepared in the same manner as in Example 7 except that an iron nitrate (Fe(NO3)3) (or other strong oxidants) was used instead of a 0.5 M phosphite (H3PO3) aqueous solution in step (ii) of Example 7. [00129] Comparative Example 3 [00130] Porous silicon particles were prepared in the same manner as in Example 1 except that etching was performed for 28 hours in step (ii) of Example 1. 33 [00131] Comparative Example 4 [00132] Porous silicon particles were prepared in the same manner as in Example 1 except that etching was performed for 1 hour in step (ii) of Example 1. [00133] [00134] Example 8 [00135] The porous silicon-based particles prepared in Example 1 were used as an anode active material. The anode active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed at a weight ratio of 70:10:20, and the mixture was mixed with a N-methyl- 2-pyrrolidone solvent to prepare a slurry. One surface of a copper current collector was coated with the prepared slurry to a thickness of 30 μm, dried, and rolled. Then, an anode was prepared by punching into a predetermined size. [00136] 10 wt% fluoroethylene carbonate based on a total weight of an electrolyte solution was added to a mixed solvent, which includes 1.0 M LiPF6 and an organic solvent prepared by mixing ethylene carbonate and diethyl carbonate at a weight ratio of 30:70, to prepare a non-aqueous electrolyte solution. [00137] A lithium foil was used as a counter electrode, a polyolefin separator was disposed between both electrodes, and a coin-type half cell was then prepared by injecting the 34 electrolyte solution. [00138] Examples 9 to 14 [00139] Coin-type half cells were prepared in the same manner as in Example 8 except that the porous silicon-based particles prepared in Examples 2 to 7 were used as an anode active material instead of using the porous silicon-based particles prepared in Example 1. [00140] Example 15 [00141] A coin-type half cell was prepared in the same manner as in Example 8 except that the porous silicon particles prepared in Example 5 were coated with 10 wt% of carbon and an anode active material was used in which the carbon-coated porous silicon particles and graphite were mixed at a ratio of 50:50. [00142] Comparative Example 5 [00143] A coin-type half cell was prepared in the same manner as in Example 8 except that pure Si particles were used as an anode active material instead of using the porous siliconbased particles prepared in Example 1. [00144] Comparative Examples 6 to 9 [00145] Coin-type half cells were prepared in the same manner 35 as in Example 8 except that the porous silicon-based particles prepared in Comparative Examples 1 to 4 were used as an anode active material instead of using the porous silicon-based particles prepared in Example 1. [00146] Comparative Example 10 [00147] A coin-type half cell was prepared in the same manner as in Example 8 except that the porous silicon particles prepared in Comparative Example 4 were coated with 10 wt% of carbon and an anode active material was used in which the carbon-coated porous silicon particles and graphite were mixed at a ratio of 50:50. [00148] Experimental Example 1 [00149] < Scanning Electron Microscope (SEM) Images> [00150] Surface morphologies of nonlinear pores included in the porous silicon-based particles obtained in Examples 1 to 6 according to etching time were identified with an SEM. The results thereof are presented in FIG. 3. [00151] Referring to FIG. 3, it may be confirmed that pores were formed in the surface of the porous silicon-based particle of Example 1 in which the etching was performed for 3 hours, and the formation degree and diameter of the pores, which were formed in the particle, tended to increase as the etching time increased to 6 hours, 9 hours, 12 hours, 18 36 hours, and 24 hours as in Examples 2 to 6. [00152] Also, it may be confirmed that at least two or more pores of the nonlinear pores included in the porous siliconbased particles of Examples 2 to 6, in which the etching was performed for 6 hours or more, were connected to each other. [00153] With respect to Example 6 in which the etching was performed for about 24 hours, it may be confirmed that the nonlinear pores included in the porous silicon particles were almost connected to one another, and it was also confirmed that a depth of the pore was the largest in Example 6 in which the etching was performed for about 24 hours. [00154] It was considered that the depth of the nonlinear pore of the particle was increased because the size of copper, as a metal catalyst, deposited on the surface of silicon was increased by hydrogen fluoride as the etching time increased. [00155] Surface morphologies of the porous silicon particles of Example 7, in which etching was performed using phosphite (H3PO3) as a weak oxidant, were identified with an SEM. The results thereof are presented in FIG. 4. [00156] As illustrated in FIG. 4, it may be observed that a plurality of nonlinear pores was formed on the entire porous silicon particles, and the nonlinear pores were formed as open pores in the surfaces of the particles. Also, it was confirmed that an average diameter of the nonlinear pores was 37 in a range of about a few tens to a few hundreds of nanometers. [00157] When compared to silver used as a catalyst of a typical chemical etching method, there was a similarity in that only a portion contacted with the catalyst was etched. However, in the case that silver was used as a catalyst, since etching occurred in a direction perpendicular to the surface of the silicon, pores in the form of a linear wire may be formed (see FIGS. 2 and 6). [00158] In contrast, in the case in which copper was used as a catalyst as in the embodiment of the present invention, it may be confirmed that since the shape of copper crystals was rectangular, copper deposition may occur in the form of a rectangle. It may be also confirmed that since etching is not affected by the crystallinity of silicon, the etching may occur in the form of nonlinear pores having no directionality. [00159] FIG. 5 is an electron microscope image showing an internal cross-section of the porous silicon particle obtained in Example 7 after sectioning. [00160] In order to identify morphologies of the internal cross-section of the porous silicon particle prepared in Example 7, the porous silicon particle was cross-sectioned using an argon (Ar)-ion milling apparatus and the internal cross-section was then analyzed with an electron microscope. 38 [00161] Referring to FIG. 5, it was confirmed that pores of the porous silicon particle prepared in Example 7 were formed up to the inside of the particle, and it may be confirmed that the nonlinear pores having no directionality were connected to one another in the porous silicon particle. [00162] When comparing average diameters of the pores formed in the inside/outside of the porous silicon particle, it was confirmed that the average diameter of the pores formed in the inside thereof tended to be smaller than the average diameter of the pores formed in the outside thereof. [00163] It was considered that there was no effect on the copper catalyst due to the crystal direction of silicon, the etching occurred without directionality, and the etching occurred in which an etched portion was in the shape of a nonlinear corn as it gradually moves in the direction of the center of the porous silicon particle. [00164] Also, it may be estimated that the average diameter of the internal pores tended to be gradually decreased in the direction of the center of the particle in comparison to the surface of the porous silicon particle due to the additional pore formation and the active connection between the pores by the phosphite. [00165] In contrast, referring to FIG. 6 illustrating an internal cross-section of the silicon-based particle prepared in Example 1, it may be confirmed that since the etching 39 occurred in a direction perpendicular to the surface of the silicon, pores may be linearly formed. [00166] Experimental Example 2: Measurements of Physical Properties of Porous Silicon-based Particles [00167] Tap densities (g/cc), total mercury intrusion volumes (mL/g), bulk densities (g/cc), and porosities (%) of the porous silicon-based particles prepared in Examples 1 to 6 were measured and the results thereof are presented in Table 1 below. [00168] [00169] The porous silicon-based particles obtained in Examples 1 to 6 were respectively charged into a container and, as the tap density of the particles, an apparent density of the particles was measured by vibrating under a predetermined condition. [00170] [00171] The total mercury intrusion volumes (mL/g) were measured by using a mercury porosimeter (AutoPore VI 9500, Micromerities, USA). [00172] The mercury porosimetry uses a capillary phenomenon by which a liquid infiltrates into a fine pore. A nonwetting liquid, such as mercury, can infiltrate when a 40 pressure is applied from the outside, and the smaller the size of the pore is, the higher the pressure is required. The measurement results may be represented by a function of a cumulative volume of mercury intruded according to the pressure (or size of the pore). [00173] Operating Principle [00174] Porous silicon particles were put in a penetrometer and sealed, and a vacuum was then applied and mercury was filled. When the pressure was applied to the penetrometer, the mercury infiltrated into the pores of the porous silicon particles to reduce the height of the mercury of the penetrometer. When the reduction was measured as a function of the pressure, the volume of the mercury infiltrated into the pores may be obtained. The mercury intrusion results may be represented by a pore radius or intrusion pressure and a cumulative intrusion volume per sample weight. [00175] Since the mercury intruded into the pores between the particles when the pressure was low, the size of the pore may decrease as the pressure increased. In a sample formed of porous powder, a cumulative intrusion curve may be a bimodal curve due to these pores. [00176] [00177] The bulk density of the porous silicon-based particles may be obtained by using a total intrusion volume 41 when the pressure was maximum during the mercury porosimetry, i.e., when the mercury intrusion did not occur anymore. [00178] [00179] The porosities of the porous silicon-based particles obtained in Examples 1 to 6 were calculated by using Equation 1 below. [00180] [Equation 1] [00181] Porosity (%) = {1-(bulk density of the porous silicon particles of Examples 1 to 6/bulk density of pure silicon particle)} × 100. [00182] [Table 1] Sample Etching time (h) Tap density (g/cc) Total mercury intrusion volume (mL/g) Bulk density (g/cc) Porosity (%) Example 1 3 0.90 0.64 0.75 11.7 Example 2 6 0.84 0.72 0.68 19.2 Example 3 9 0.81 0.76 0.66 22.2 Example 4 12 0.75 0.84 0.62 26.2 Example 5 18 0.65 1.05 0.53 37.7 Example 6 24 0.63 1.19 0.51 39.2 Si particles 0 1.02 0.53 0.85 0 Comparative Example 1 3 0.91 0.62 0.77 9.5 42 Comparative Example 2 21 0.68 0.91 0.60 29.4 Comparative Example 3 28 0.80 0.75 0.65 23.5 Comparative Example 4 1 0.94 0.59 0.79 7.1 [00183] As illustrated in Table 1, porosities of the porous silicon-based particles of Examples 1 to 6, in which nonlinear pores were formed by etching for 3 hours to 24 hours, were in a range of about 11% to about 39%. In particular, with respect to the porous silicon-based particles of Example 6 in which nonlinear pores were formed by etching for 24 hours, the porosity was close to about 40% in comparison to pure Si particles in which a treatment for forming pores was not performed. [00184] The Si particles had a tap density of 1.02 (g/cc) and a bulk density of 0.85 (g/cc). In contrast, the porous silicon-based particles of Examples 1 to 6 had lower tap densities and bulk densities than the above tap density and bulk density. [00185] Also, a total mercury intrusion volume of the Si particles was 0.53 g/cc and total mercury intrusion volumes of the porous silicon-based particles of Examples 1 to 6 were in a range of 0.64 g/cc to 1.19 g/cc. Thus, the total mercury intrusion volumes of the porous silicon-based particles of Examples 1 to 6 were significantly increased in 43 comparison to that of the Si particles. [00186] In particular, with respect to Examples 5 and 6 in which the etching was respectively performed for 18 hours and 24 hours, the total mercury intrusion volumes were respectively 1.05 g/cc and 1.19 g/cc. Thus, the total mercury intrusion volumes were increased by 2 times or more in comparison to that of the Si particles. [00187] In contrast, with respect to Comparative Example 1 in which the etching time was the same as that of Example 1 but a silver nitrate aqueous solution was used, the porosity was 9.5%, and thus, it may be understood that the porosity was significantly reduced in comparison to that of Example 1. [00188] With respect to Comparative Example 3 in which the etching was performed for 28 hours, the etching solution was only consumed but there was no effect due to the excessive etching time. With respect to Comparative Example 4 in which the etching was performed for only 1 hour, the porosity was 7.1%, and thus, pores were not sufficiently formed. [00189] Also, since the tap densities and the bulk densities of Examples 1 to 6 of the present invention were decreased and the total mercury intrusion volumes thereof were increased in comparison to those of the pure Si particles, it was considered that the depths of the formed nonlinear pores were increased and the plurality of nonlinear pores were 44 formed according to an increase in the etching time. [00190] In order to identify physical properties of the porous silicon particles obtained in Example 7 in which the etching was performed by using the weak oxidant, tap density (g/cc), BET specific surface area (m2/g), and particle size distribution were measured, and the results thereof are presented in Table 2 below. [00191] [00192] In this case, the tap density measurement was performed in the same manner as in the porous silicon-based particles of Examples 1 to 6. [00193] [00194] The specific surface area of the porous silicon-based particles of Example 7 may be measured by a BET method. For example, the specific surface area was measured by a 6-point BET method according to a nitrogen gas adsorption-flow method using a porosimetry analyzer (Belsorp-II mini by Bell Japan Inc.). [00195] [00196] Dmin, D10, D50, D90, and Dmax were measured as an average particle size distribution of the porous silicon-based 45 particles for the particle size distribution of the porous silicon-based particles of Example 7, and Dmin, D10, D50, D90, and Dmax were denoted as particle diameters at less than 10%, 10%, 50%, 90%, and greater than 90% in a cumulative particle diameter distribution, respectively. [00197] The particle size distribution of the porous siliconbased particles of Example 7 was measured by using a laser diffraction method (Microtrac MT 3000). [00198] [Table 2] Sample Tap density (g/cc) BET specific surface area (m2/g) Particle size distribution (μm) Dmin D10 D50 D90 Dmax Example 7 0.61 20.87 2.312 3.55 4.63 6.14 10.09 Si particles 1.02 1.56 2.312 3.57 4.65 6.15 10.09 [00199] As illustrated in Table 2, tap density of the porous silicon particles obtained in Example 7 was 0.61 g/cc and tap density of the Si particles was 1.02 g/cc. Thus, it may be confirmed that the tap density of the porous silicon particles of Example 7 was decreased by about 0.41 g/cc in comparison to that of the Si particles. [00200] Accordingly, as illustrated in the SEM image of Experimental Example 1, it may be estimated that pores were formed in the porous silicon particles obtained in Example 7. [00201] As illustrated in Table 2, a BET specific surface 46 area of the porous silicon particles obtained in Example 7 was 20.87 m2/g, and a BET specific surface area of the Si particles was 1.56 m2/g. Thus, the BET specific surface area of the porous silicon particles prepared in Example 7 was increased by about 13 times in comparison to that of the Si particles. [00202] Since Example 7 and the Si particles exhibited the same particle size distribution, it was considered that the increase in the specific surface area was due to the formation of the pores. [00203] Experimental Example 3: Hg Porosimetry Analysis [00204] FIG. 7 illustrates pore distributions of the porous silicon-based particles prepared in Examples 1 to 6 through mercury porosimetry analysis. [00205] Referring to FIG. 7, a rate of change in volume of mercury intruded into the pore, which was measured by mercury porosimetry of the porous silicon-based particles, had peaks in an average pore diameter range of about 30 nm to about 2,500 nm. [00206] When examining two enlarged graphs of a graph of Example 7, the peaks respectively appeared in average pore diameter ranges of 800 nm to 2,000 nm and 50 nm to 600 nm. Herein, the peak in an average pore diameter range of 800 nm to 2,000 nm was a peak corresponding to pores between the 47 porous silicon particles and the peak in an average pore diameter range of 50 nm to 600 nm was a peak corresponding to the nonlinear pores included in the porous silicon particles. [00207] It may be confirmed that a total mercury intrusion volume in the average pore diameter range of 50 nm to 600 nm was in a range of 0.5 mL/g to 1.2 mL/g. [00208] Also, referring to FIG. 7, it may be confirmed that the pore volume was increased as the etching time was increased to 3 hours, 6 hours, 9 hours, 12 hours, 18 hours, and 24 hours as in Examples 1 to 6. In particular, it may be confirmed that the porous silicon particles of Example 6, in which the etching was performed for 24 hours, exhibited the largest pore volume. [00209] In the porous silicon particles of Examples 1 to 6, it was confirmed that the average diameter distribution of the pores was in a form in which mesopores having an average diameter of 20 nm to 100 nm and macropores coexisted until the etching time was in a range of 3 hours to 18 hours, and the distribution of macropores having an average diameter of 50 nm or more was increased as the etching time increased. This was considered due to the fact that the formed pores were connected to one another as the etching time increased. [00210] Furthermore, it was confirmed that the porous silicon particles of Example 5, which were etched for 18 hours, had a pore distribution in which macropores having an average 48 diameter of 50 nm or more were mostly formed. [00211] It was considered that the porous silicon particles of Example 6, which were etched for 24 hours, had a pore shape in which pores were almost combined and connected to one another. [00212] Experimental Example 4: Life Characteristics and Thickness Change Rate Analysis [00213] The following experiments were performed in order to investigate life characteristics and thickness change rates of the secondary batteries prepared in Examples 8 to 15 and Comparative Examples 5 to 10. [00214] Life characteristics of each secondary battery were measured by performing charge and discharge at 0.1 C in a first cycle and performing charge and discharge at 0.5 C in subsequent cycles. The life characteristics were represented as a ratio of discharge capacity in a 49th cycle to the first cycle discharge capacity. Each secondary battery was disassembled in a charge state of a 50th cycle and a thickness of an electrode was measured. Then, a thickness change rate was obtained by comparing the above thickness with a thickness of the electrode before the first cycle. [00215] The following Table 3 presents life characteristics and thickness change rates of the secondary batteries 49 prepared in Examples 8 to 15 and Comparative Examples 5 to 10. [00216] [Table 3] Examples Remarks Life characteristics (%) Thickness change rate (%) Example 8 3 hr etching 65 250 Example 9 6 hr etching 70 230 Example 10 9 hr etching 75 200 Example 11 12 hr etching 80 180 Example 12 18 hr etching 85 170 Example 13 24 hr etching 85 150 Example 14 21 hr etching, use H3PO3 85 150 Example 15 18 hr etching + 10 wt% carbon coating (50/50 mixed anode) 90 120 Comparative Example 5 Pure Si 55 300 Comparative Example 6 3 hr etching, use AgNO3 65 270 Comparative Example 7 21 hr etching, use strong oxidant 75 180 Comparative Example 8 28 hr etching 70 200 Comparative Example 9 1 hr etching 60 300 Comparative Example 10 1 hr etching + 10 wt% carbon coating (50/50 mixed anode) 70 180 [00217] - Life characteristics: (discharge capacity in a 49th 50 cycle/ first cycle discharge capacity) x 100 [00218] - Thickness change rate: (electrode thickness in a charge state of a 50th cycle – electrode thickness before a first cycle)/ electrode thickness before the first cycle x 100 [00219] As illustrated in Table 3, it may be confirmed that the secondary batteries of Examples 8 to 15 of the present invention had significantly better life characteristics and thickness change rate than those of Comparative Examples 5 to 10. [00220] Specifically, when particularly comparing Example 8 and Comparative Example 6 in which the etching was performed for 3 hours, it may be confirmed that the thickness change rate of Example 8 using the copper sulfate aqueous solution as a metal catalyst was decreased in comparison to that of Comparative Example 6 using silver nitrate. [00221] Also, when comparing Example 14 and Comparative Example 7 in which the etching was performed for 21 hours, it may be confirmed that both the life characteristics and the thickness change rate of Example 14 using phosphite as a weak oxidant were better than those of Comparative Example 7 using iron nitrate as a strong oxidant. [00222] In the case that graphite and the porous silicon particles coated with 10 wt% carbon were mixed as in Example 15, the life characteristics was 90% and the thickness change 51 rate was 120%. Thus, it may be understood that the performance of the secondary battery was significantly improved. [00223] In contrast, with respect to Example 9 in which the etching was performed for only 1 hour, the thickness change rate was 300%, and thus, it may be confirmed that the volume expansion was not reduced due to the insufficient formation of the pores. INDUSTRIAL APPLICABILITY [00224] Porous silicon-based particles according to an embodiment of the present invention may be more easily dispersed in an anode active material slurry, may minimize side reactions with an electrolyte, and may reduce volume expansion during charge and discharge by including Si or SiOx(0