WO2019039856A1 - Method for producing porous silicon-carbon complex, secondary battery negative electrode comprising porous silicon-carbon complex produced by production method, and secondary battery comprising secondary battery negative electrode - Google Patents

Abstract

The present invention relates to a method for producing a porous silicon-carbon complex, a secondary battery negative electrode material produced by the production method, and a secondary battery comprising the secondary battery negative electrode material. The method for producing a porous silicon-carbon complex according to an embodiment of the present invention comprises: a step of mixing a silicon precursor with a heat dispersant and subjecting the mixture to first heat treatment, thereby producing a first mixture; a step of mixing the first mixture with a metal reducing agent, thereby producing a second mixture; a step of putting the second mixture into a reaction chamber and subjecting same to second heat treatment, thereby reducing the silicon precursor and producing a reaction product; a step of washing the reaction product and collecting porous silicon particles; a step of mixing the porous silicon particles with a carbon precursor, thereby producing a third mixture; and a step of subjecting the third mixture to third heat treatment, thereby coating the porous silicon particles with carbon.

Description

A method for producing a porous silicon-carbon composite material, a secondary battery anode including the porous silicon-carbon composite material produced by the above manufacturing method, and a secondary battery including the secondary battery anode

The present invention relates to a method for producing a porous silicon-carbon composite material, a secondary battery anode material produced by the manufacturing method, and a secondary battery including the secondary battery anode material.

Various lithium-based secondary batteries are becoming increasingly important as power sources for large-capacity energy storage devices such as electric vehicles and smart grids in the future, as well as power sources for small-sized devices. Accordingly, it is required to develop an electrode material having increased energy density, output density and stability compared to existing products.

The performance improvement of lithium-based secondary batteries is based on four core materials such as anode and cathode materials, separator, and electrolyte. As an anode material for lithium secondary batteries currently used, graphite is advantageous in that it has a low operating voltage and excellent lifetime stability. However, graphite has a low theoretical capacity of about 372 mAh / g, Charging rate) is slow and the characteristics are poor, so there is a limit to the application to a negative electrode material of a high performance secondary battery. Therefore, much research has been conducted on the metal materials of Groups IV and V such as Si, Sn, Ge, Pb, As and Bi which are electrochemically alloyed with lithium as an anode material that can replace graphite. Among them, silicon is a very abundant resource on the earth, and it is one of the materials that is currently being studied because it has a relatively low operating voltage (~ 0.4 V vs. Li / Li ⁺ ) and a high theoretical capacity (~ 3579 mAh / g) . However, silicon not only has low electrical conductivity, but also reacts with up to about four lithium ions per particle during repeated charge and discharge, resulting in large volume expansion and cracking of particles, which is close to 280%. In this process, the reaction between the newly generated silicon surface and the electrolyte continuously generates a new solid electrolyte interface (SEI), resulting in high initial irreversible capacity as well as high resistance and rapid capacity reduction, There is a short problem.

It is an object of the present invention to provide a process for producing a porous silicon-carbon composite which can be mass-produced at high yield and high purity.

It is another object of the present invention to provide a secondary battery anode and a secondary battery including the anode material by using the porous silicon-carbon composite material produced by the above-described method as a cathode material for a secondary battery.

Further, the secondary battery according to the embodiment of the present invention has excellent charging and discharging characteristics, and can absorb the volume change due to charging and discharging.

A method for producing a porous silicon-carbon composite according to an embodiment of the present invention includes:

(i) mixing a silicon precursor represented by the following formula (1) with a heat dispersing agent and subjecting the mixture to a first heat treatment to prepare a first mixture;

[Chemical Formula 1]

M _{2 / n} O · Al ₂ O ₃ · xSiO ₂ · yH ₂ O

(ii) mixing the first mixture with a metal reducing agent to prepare a second mixture; (iii) receiving the second mixture in a reaction chamber and performing a second heat treatment to reduce the silicon precursor to produce a reactant; (iv) washing the reactants to recover porous silicon particles; (v) mixing the porous silicon particles with a carbon precursor to produce a third mixture; And (vi) subjecting the third mixture to a third heat treatment to coat the porous silicon particles with carbon.

The porous silicon-carbon composites according to the embodiment of the present invention are manufactured by the above-described manufacturing method.

The secondary battery anode according to an embodiment of the present invention includes the above-described porous silicon-carbon composite.

The secondary battery according to the embodiment of the present invention includes the above-described secondary battery anode.

An electronic device according to an embodiment of the present invention includes the above-described secondary battery as a power supply source.

The process for producing a porous silicon-carbon composite according to an embodiment of the present invention can be mass-produced at a high yield and at a high purity.

Also, by using the porous silicon-carbon composite material produced by the above-described method as a negative electrode material for a secondary battery, it is possible to provide a secondary battery negative electrode and a secondary battery including the negative electrode material.

Further, the secondary battery according to the embodiment of the present invention has excellent charging and discharging characteristics, and can absorb the volume change due to charging and discharging.

1 illustrates a method of making a porous silicon-carbon composite according to an embodiment of the present invention.

FIG. 2 illustrates changes in silicon primary particles during charging and discharging in a secondary battery comprising a porous silicon-carbon composite fabricated according to an embodiment of the present invention.

3 is an SEM photograph of the zeolite Y. Fig.

4 is a TEM photograph of silicon particles contained in the porous silicon-carbon composite of Example 2. Fig.

5 is a TEM photograph of the porous silicon-carbon composite of Example 2. Fig.

FIG. 6 is a mapping photograph of Si elements in the rectangular region of FIG. 5. FIG.

7 is a mapping photograph of a C element in the rectangular area of FIG.

8 is a TEM photograph of silicon particles contained in the porous silicon-carbon composite of Example 7. Fig.

9 is a TEM photograph of silicon particles contained in the porous silicon-carbon composite of Example 8. Fig.

10 is a TEM photograph of silicon particles contained in the porous silicon-carbon composite of Comparative Example 1. Fig.

FIG. 11 shows X-ray diffraction (XRD) analysis results of porous silicon after washing with aqueous hydrochloric acid (HCl) solution in Examples 1, 7 and 8.

FIG. 12 shows the results of X-ray diffraction (XRD) analysis of porous silicon after washing with an aqueous solution of hydrochloric acid (HCl) and washing with hydrofluoric acid (HF) in Examples 1, 7 and 8.

FIG. 13 shows X-ray diffraction (XRD) analysis results of porous silicon after washing with an aqueous solution of hydrochloric acid (HCl) in the manufacturing method of Comparative Example 1. FIG.

FIG. 14 shows X-ray diffraction (XRD) analysis results of porous silicon after washing with an aqueous solution of hydrochloric acid (HCl) and cleaning with hydrofluoric acid (HF) in the production method of Comparative Example 1. FIG.

Figure 15 shows the nitrogen adsorption / desorption isotherm curves of the porous composites prepared in Examples 1, 7, 8 and Comparative Example 1.

FIG. 16 shows pore size distributions of the porous composites prepared in Examples 1, 7 and 8 and Comparative Example 1. FIG.

17 is a graph showing the relationship between the charge / discharge cycle (charge / discharge cycle) of a lithium secondary battery (a half cell made of a lithium metal as a standard electrode) including a negative electrode using the porous silicon-carbon composites prepared in Examples 1 to 4 as a negative electrode material ≪ / RTI >

18 is a graph showing the relationship between the charging / discharging cycle (charge / discharge cycle) of a lithium secondary battery (a half cell made of a lithium metal as a standard electrode) including a negative electrode using the porous silicon-carbon composite material prepared in Examples 5 and 6 as a negative electrode material ≪ / RTI >

19 is a graph showing the relationship between the charge / discharge cycle (charge / discharge cycle) of a lithium secondary battery (a half cell made of a lithium metal as a standard electrode) including a negative electrode using the porous silicon-carbon composite material prepared in Examples 7 and 8 as a negative electrode material ≪ / RTI >

20 is a graph showing the relationship between the charging / discharging cycle (voltage) of a lithium secondary battery (half cell made of a lithium metal as a standard electrode) including a negative electrode using the porous silicon-carbon composite material prepared in Comparative Examples 1 to 4 as a negative electrode material ≪ / RTI >

FIG. 21 is a graph showing the charge / discharge rate (%) of a lithium secondary battery (half cell made of a lithium metal as a standard electrode) including a negative electrode using the porous silicon-carbon composites prepared in Examples 5 and 6 as a negative electrode material Fig.

22 is a graph showing the results of measurement of a lithium secondary battery including a negative electrode using the porous silicon-carbon composite material prepared in Example 3 as a negative electrode material and a positive electrode using NCM622 (LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ) cell in the charge / discharge cycle.

FIG. 23 is a graph showing the results of a comparison between a lithium secondary battery including a negative electrode using a porous silicon-carbon composite material according to an embodiment of the present invention as a negative electrode material and a positive electrode using NCM622 as a positive electrode material, a negative electrode using graphite as a negative electrode material, And the volume energy density of a lithium secondary battery (full cell) including a positive electrode using NCM622 as a cathode material.

1 illustrates a method of making a porous silicon-carbon composite according to an embodiment of the present invention.

Referring to FIG. 1, a method of manufacturing a porous silicon-carbon composite according to an embodiment of the present invention includes:

(i) mixing a silicon precursor represented by the following formula (1) with a heat dispersing agent and subjecting the mixture to a first heat treatment to prepare a first mixture;

[Chemical Formula 1]

M _{2 / n} O · Al ₂ O ₃ · xSiO ₂ · yH ₂ O

(ii) mixing the first mixture with a metal reducing agent to prepare a second mixture; (iii) receiving the second mixture in a reaction chamber and performing a second heat treatment to reduce the silicon precursor to produce a reactant; (iv) washing the reactants to recover porous silicon particles; (v) mixing the porous silicon particles with a carbon precursor to produce a third mixture; And (vi) subjecting the third mixture to a third heat treatment to coat the porous silicon particles with carbon.

In the step of preparing the first mixture by mixing the silicon precursor with a heat dispersing agent and performing a first heat treatment, M in the formula (1) represents a cation having an oxidation number of n = 1 or 2 contained in the zeolite which is a porous silicon precursor, After the ion exchange with NH ₄ -type, and the NH ₄ -type geochimyeon the fired in the air can be transformed into H-type zeolite. Specifically, M may be any one of Na, Li, K, Ca and Mg. x represents the molar ratio of SiO ₂ / Al ₂ O ₃ of the porous silicon precursor, for example zeolite, and x may have a value of theoretically 2 to infinity (when the Al content is 0), but x is 5 or more desirable. y represents the number of moles of water contained in the porous silicon precursor, for example, zeolite, and is not particularly limited because water changes reversibly depending on the humidity during storage and so on.

The silicon precursor represented by Formula 1 may be at least one of zeolite X, Y, A, Beta, ZSM-5, and crystalline aluminosilicate having a mordenite structure. The silicon precursor represented by Formula 1 may be at least one selected from the group consisting of alkali metals (alkali metals include Na, Li, K, Ca, and Mg), NH ₄ series, and H series. The average particle diameter of the zeolite particles may be 20 nm to 10 mu m.

The heat dispersing agent is an example of the zeolite and the metal reducing agent, and can perform a function of eliminating a large exothermic reaction during the process of reacting the magnesium powder. By using the heat dispersing agent as described above, agglomeration of the primary silicon particles can be prevented during the heat treatment. The heat dispersing agent may be at least one of sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl ₂ ) and magnesium chloride (MgCl ₂ ). At this time, the heat dispersing agent may be added in an amount of 100 to 1200 parts by weight, preferably 1000 parts by weight, based on 100 parts by weight of the silicon precursor.

The method of mixing the silicon precursor with the heat dispersing agent may be performed by a dry mixing method or a wet mixing method.

The first heat treatment step may be performed to remove moisture and hydroxyl groups (-OH) in the pores of the silicon precursor. Specifically, the first heat treatment step may be performed at a temperature in the range of 550 to 800 ° C, 700 < 0 > C for 4 hours to 7 hours, preferably 5 hours.

In the step of preparing the second mixture by mixing the first mixture and the metal reducing agent, the metal reducing agent may be an alkali metal or an alkaline earth metal, and may be a mixture thereof. Preferably, the metal reducing agent may be at least one of sodium (Na), magnesium (Mg), calcium (Ca), and aluminum (Al).

At this time, the metal reducing agent may be mixed in an amount of 50 to 200 parts by weight, preferably 80 parts by weight, based on 100 parts by weight of the silicon precursor.

In the step of receiving the second mixture in a reaction chamber and performing a second heat treatment to reduce a silicon precursor to produce a reactant, the second heat treatment step may be performed at a temperature of 300 to 1000 占 폚 in a reducing atmosphere, Temperature range, preferably from 650 to 750 ° C, and from 1 hour to 24 hours, preferably 5 hours. The heat treatment atmosphere may be an oxygen-free atmosphere such as an argon gas or an inert gas containing an argon / hydrogen mixed gas. The second heat treatment temperature may be set to 300 to 1000 ° C, preferably 650 to 750 ° C, in consideration of the melting temperature of the metal reducing agent. If the second heat treatment temperature is less than 300 ° C, the reduction ratio of the silicon precursor and the yield of the final porous silicon may be low. If the second heat treatment temperature is 1000 ° C or higher, sintering of the particles occurs, There is a problem that it is not formed.

The second heat treatment may be performed in a pressure range of 10 ^-3 bar to 5 bar pressure inside the reaction chamber. Thus, the conducting cone precursor such as zeolite can be reduced by being mixed with a metal reducing agent such as magnesium and being melted and being melted by a metal liquid such as magnesium or vapor.

The reduction reaction of the mixture using the metal reducing agent may be a reaction carried out under an alumina crucible and an inert gas flow but more preferably in an oxygen-free closed reactor.

In this step, the silicon precursor may be partially or wholly reduced to porous silicon, and some or all of the metal reductant (e.g., magnesium) powder is oxidized to a metal oxide (e.g., magnesium oxide (MgO)) . ≪ / RTI >

The method may further include a step of vacuum-drying the second mixture by mixing the first mixture and the metal reducing agent prior to the step of reducing the silicon precursor by the second heat treatment to produce a reactant. By including the present vacuum drying step, moisture of the second mixture can be removed. The present vacuum drying step can be carried out by heating the second mixture at 80 ° C to 200 ° C, preferably at 150 ° C for 1 to 5 hours, preferably for 2 hours.

The step of washing the reactants to recover the porous silicon particles can be performed by washing the reactants with distilled water and a dilute acid solution. The reaction product obtained in the second heat treatment may include by-products such as porous silicon, and the magnesium oxide addition failed to reduce the residual magnesium and silica powder, or magnesium silicide (Mg ₂ Si). These by-products can be removed by going through this step. The acid solution may include hydrochloric acid (HCl), acetic acid (CH ₃ COOH), hydrofluoric acid (HF), or a mixture thereof. The acid treatment time is preferably about 5 hours, .

In one embodiment, the step of washing the reactants to recover the porous silicon particles comprises: (iv-1) washing with distilled water to remove the heat dispersing agent; (iv-2) washing with an aqueous solution of hydrochloric acid (HCl) to remove by-products other than silicon; And (iv-3) etching and removing the silica residue with an aqueous solution of hydrofluoric acid (HF).

The porous silicon particles recovered through washing in the step of recovering the porous silicon particles have a specific surface area of not less than 30 m ² / g and not more than 500 m ² / g according to the BET measurement method, and a total pore volume of 0.2 and cm ³ / g to 1.0 cm ³ / g, the average particle size of individual primary particles constituting the silicon-porous silicon particles may be from 5 to 50 nm.

The step of mixing the carbon precursor with the porous silicon particles to produce a third mixture, and the third mixture to a third heat treatment to coat the carbon on the porous silicon particles, wherein the carbon precursor has a pitch, (eg, sucrose, glucose, resorcinol-formaldehyde, phenol-formaldehyde, phenolic resin, polydopamine, graphite, carbon black, carbon Nanotube, and graphene.

The step of coating the porous silicon particles with carbon may be performed by heat treatment at 600 ° C to 1000 ° C, preferably 800 ° C in an inert gas atmosphere or an inert gas and hydrogen mixed gas atmosphere.

The content of the porous silicon particles contained in the porous silicon-carbon composite produced through this step may be 20 to 80 wt% with respect to the total weight of the porous silicon-carbon composite.

FIG. 2 illustrates the variation of the silicon primary particles 110 during charging and discharging in a secondary battery comprising a porous silicon-carbon composite fabricated according to an embodiment of the present invention. The porous silicon-carbon composite particles 140 according to the present invention can absorb a large volume change accompanied by repeated pores and electrochemical charging and discharging by lithium due to many pores in the porous silicon particles 120, The carbon coating layer 130 enhances the conductivity and enables reversible charging and discharging, thereby exhibiting excellent characteristics as an electrode material. Referring to FIG. 2, it can be seen that even when the volume of the silicon primary particles 110 is changed by charging and discharging (see 210), the influence on the volume of the entire porous silicon-carbon composite particles 140 can be minimized have.

The porous silicon-carbon composites according to the embodiment of the present invention are manufactured by the above-described manufacturing method. The porous silicon-carbon composites may be used as a secondary battery anode material. The secondary battery anode according to an embodiment of the present invention may include a current collector and a porous silicon-carbon composite disposed on the current collector. The secondary battery according to the embodiment of the present invention includes the above-described secondary battery anode. In one example, the secondary battery comprises a negative electrode comprising a silicon-carbon composite produced by an embodiment of the present invention, an anode, and an electrolyte providing a path for movement of ions between the cathode and the anode, and an electrolyte disposed within the electrolyte, Ions to selectively permeate the ion-exchange membrane. An electronic device according to an embodiment of the present invention includes the above-described secondary battery as a power supply source. The electronic device is not particularly limited as long as it can include the secondary battery as a power supply source. Specifically, the electronic device may be a mobile device such as an electric vehicle, a smart phone, or a watch. The electronic device may include an electronic device such as a microprocessor, and may be powered by the secondary battery to drive the electronic device.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the following examples.

Example 1 Preparation of Porous Silicon-Carbon Composite

Step (1-1): Post-moisture removal of zeolite and sodium chloride mixed zeolite as a silicon precursor

Sodium chloride powder per 100 parts by weight of zeolite _{Y (x = SiO 2 / Al} 2 O 3 = 80) were uniformly mixed in an aqueous solution at a ratio 10 parts by weight, the solvent was evaporated.

Treated at 700 ° C for an additional 5 hours to remove moisture and hydroxyl groups (-OH) inside the zeolite pores to obtain a homogeneous mixture of zeolite and sodium chloride.

Step (1-2): thermal reduction step of zeolite

11 g (zeolite: sodium chloride weight ratio = 1: 10 wt%) of the mixture of zeolite Y and sodium chloride obtained in the step (1-1) was physically mixed with 0.8 g of magnesium powder and vacuum drying was carried out at 150 ° C for 2 hours .

The mixture was filled in a closed swarovsche tube in an argon atmosphere glove box and the zeolite was reduced by heat treatment at 750 ° C for 5 hours in a heating furnace under an argon atmosphere of 1 bar.

The product of the brown powder obtained through the heat treatment was firstly washed with distilled water to remove sodium chloride and further washed in 1 M hydrochloric acid (HCl) solution for 5 hours to remove magnesium oxide (MgO) or magnesium silicide (Mg ₂ Si) were removed. Residual silica which was not completely reduced was etched using hydrofluoric acid to obtain porous silicon.

Step (1-3): Preparation of Porous Silicon-Carbon Composite Step

The porous silicon obtained above was placed in tetrahydrofuran (THF) and completely dispersed by ultrasonic vibration. A THF solution in which the porous silicon was dispersed was added to a mixed solution in which pitch carbon was completely dissolved in THF by ultrasonic vibration and stirring.

The mixture was stirred at room temperature for 3 hours and then stirred until the solvent evaporated in the temperature range of 70 to 80 ° C.

The porous silicon-carbon precursor mixture obtained by this reaction was dried overnight at 80 ° C in a drier, and the dried powder was placed in a crucible and placed in a tube furnace. The mixture was heat-treated at 800 ° C for 4 hours under an argon gas flow and then naturally cooled. At this time, the content of silicon in the porous silicon-carbon composites was 70 wt%.

Example 2 Preparation of Porous Silicon-Carbon Composite

The porous silicon-carbon composites were prepared in the same manner as in Example 1, except that the silicon content in the porous silicon-carbon composites was changed to 60 wt% in step (1-3).

Example 3 Preparation of Porous Silicon-Carbon Composite

The porous silicon-carbon composites were prepared in the same manner as in Example 1, except that the silicon content in the porous silicon-carbon composites was 50 wt% in step (1-3).

Example 4 Preparation of Porous Silicon-Carbon Composite

The porous silicon obtained through steps (1-1) and (1-2) of Example 1 was put into a small amount of distilled water and dispersed by ultrasonic vibration.

Sucrose as a carbon precursor was added to distilled water in which the porous silicon particles were dispersed, and the mixture was stirred at room temperature for 30 minutes, then sulfuric acid (98 wt%) was added, and further stirred for 30 minutes. Thereafter, the temperature was raised to 100 to 110 ° C. until the solvent evaporated, and then the mixture was further reacted in a drier at 160 ° C. for 6 hours to prepare a porous silicon-carbon precursor mixture.

The resulting porous silicon-carbon precursor mixture was placed in an alumina crucible, placed in a tube furnace, and heat-treated at 800 ° C for 4 hours in an argon gas flow, followed by natural cooling. The silicon content in the final porous silicon-carbon composite material was 76 wt%.

Example 5 Preparation of Porous Silicon-Carbon Composite

The graphite was added to the porous silicon-carbon composite obtained in the step (1-3) of Example 1 so that the weight ratio of the porous silicon-carbon composite obtained in the above step (1-3) and graphite was 60:40 wt% .

Example 6 Production of Porous Silicon-Carbon Composite

Graphite was added to the porous silicon-carbon composite material obtained in Example 2 to prepare a porous silicon-carbon composite material having a weight ratio of graphite to graphite of 60:40 wt%.

Example 7 Production of Porous Silicon-Carbon Composite

Was used for Example 1 Step (1-1), zeolite beta _{(Zeolite β, x = SiO 2} / Al 2 O 3 = 300) as the silicon precursor in the porous silicon at step (1-3) of the carbon composite material The procedure of Example 1 was repeated except that the content of silicon was 59 wt%.

Example 8 Preparation of Porous Silica-Carbon Composite 8

Example 1 was used in the step (1-1), zeolite _{ZSM-5 (x = SiO 2} / Al 2 O 3 = 150) as the silicon precursor in the porous silicon at step (1-3) of the silicon carbon composite Was made to be 62 wt% in the same manner as in Example 1.

Comparative Example 1 Production of Porous Silicon-Carbon Composite

1 g of zeolite Y was physically mixed with 0.8 g of magnesium powder as a mineral additive and heat treated at 700 ° C. for 16 hours in an open tube furnace with argon gas (300 cc / min) flow in an alumina crucible without using sodium chloride as a heat dispersant , A porous silicon-carbon composite was prepared using pitch carbon as in the step (1-3) of Example 1 above.

At this time, the content of silicon in the porous silicon-carbon composites was 67 wt%.

≪ Comparative Example 2 > Production of silicon-carbon composite

Commercial silicon nanoparticles (particle size 50 nm) were placed in tetrahydrofuran (THF) and completely dispersed by ultrasonic vibration.

Pitch carbon was completely dissolved in THF by ultrasonic vibration and stirring, and THF solution in which the silicon nanoparticles were dispersed was added. The mixture was stirred at room temperature for 3 hours and then stirred until the solvent evaporated in the temperature range of 70 to 80 ° C.

The silicon-carbon composites obtained by this reaction were dried overnight at 80 ° C in a drier, and the dried powder was placed in a crucible and placed in a tube furnace. The tube was heat-treated at 800 ° C for 4 hours under an argon gas flow and then cooled naturally.

At this time, the content of silicon in the silicon-carbon composites was 56 wt%.

≪ Comparative Example 3 > Production of silicon-carbon composite

A silicon-carbon composite was prepared in the same manner as in Example 4 except that commercially available silicon nanoparticles having a particle size of 70 to 100 nm were used. The silicon content in the silicon-carbon composite was 52 wt%.

Comparative Example 4 Production of Silicon-Carbon Composite

Commercial silicon nanoparticles having a particle size of 70 to 100 nm were put into a small amount of distilled water and dispersed by ultrasonic vibration.

Resorcinol and formaldehyde were added to distilled water containing silicon particles and dissolved at room temperature. A small amount of aqueous ammonium hydroxide solution (0.5 wt% NH4OH) was added. The mixture was placed in a fully closed reactor and stirred until a gel was formed at a temperature range of 70-90 < 0 > C.

The carbon gel containing the obtained silicon nanoparticles was maintained at 90 DEG C for an additional 16 hours. Thereafter, the resulting composite gel was dried overnight in a dryer at 80 DEG C, and the resulting gel was placed in a crucible and placed in a tube heating furnace. The tube was heat-treated at 800 DEG C for 4 hours under an argon gas flow and then naturally cooled. Silicon-carbon composites were prepared. At this time, the content of silicon in the silicon-carbon composite was adjusted to 44 wt%.

The compositions of raw materials and the reaction conditions used in the production of Examples 1 to 8 and Comparative Examples 1 to 4 are shown in Tables 1 and 2 below.

[Table 1]

[Table 2]

<Experimental Example 1> Particle size and structure analysis of porous silicon

The particle size and structure of the porous silicon of the porous silicon-carbon composites prepared in Examples 1 to 8 and Comparative Examples 1 to 4 were measured by Field Emission Scanning Electron Microscopy (FE-SEM) (JEOL JSM-35CF (JEOL JEM-2010, 200.0 kV), BET specific surface area meter, X-ray diffraction (XRD) (Rigaku model D / MAX- 50 kV, Cu-K _? Radiation,? = 1.5418?).

<Experimental Example 2> TEM photograph analysis of porous silicon

3 is a SEM photograph of the zeolite Y, and Fig. 4 is a TEM photograph of the silicon particles contained in the porous silicon-carbon composite of Example 2. Fig.

As shown in FIG. 3, the zeolite Y used as a raw material has a size of 500 nm to 1 μm and has a smooth surface. As shown in FIG. 4, it can be seen that the porous silicon particles obtained in Example 2 were considerably rougher than the surface of the whole particles before reduction.

&Lt; Experimental Example 3 > SEM photograph and TEM photograph of porous silicon composite

TEM photographs and element mapping results of the porous silicon-carbon composites prepared in Example 2 are shown in FIGS. 5 to 7. FIG. 5 is a TEM photograph of the porous silicon-carbon composite of Example 2, FIG. 6 is a mapping image of Si elements in the rectangular region of FIG. 5, FIG. 7 is a mapping of C elements of the rectangular region of FIG. ) It is a photograph.

5 to 7, it is confirmed that the entire particle structure before and after the reduction is maintained without fracturing, and carbon is evenly coated around the porous silicon particles.

TEM photographs of the porous silicon prepared in Examples 7 and 8 are shown in Figs. 8 and 9, respectively. The porous silicon samples (Examples 8 and 9) obtained in Examples 7 and 8 have a particle size of about 500 nm to 1 μm similar to the porous silicon prepared in Example 1, and many pores are distributed in the particles .

A TEM photograph of the porous silicon particles prepared in Comparative Example 1 is shown in Fig. In comparison with FIGS. 4, 8 and 9, in Comparative Example 1, the sintering of the silicon particles occurred due to the high heat generation during the reduction reaction, and the silicon primary particle size was significantly increased to about 47 nm.

<Experimental Example 4> XRD analysis results of porous silicon

X-ray diffraction (XRD) analysis results of the pickling step in the manufacturing process of the porous silicon prepared in Examples 1, 7 and 8 are shown in FIGS. 11 and 12. FIG. 11 shows X-ray diffraction (XRD) analysis results of porous silicon after washing with an aqueous solution of hydrochloric acid (HCl) in the production methods of Examples 1, 7 and 8, Ray diffraction (XRD) analysis of the porous silicon after washing with an aqueous solution of hydrochloric acid (HCl) and washing with hydrofluoric acid (HF) in the production method.

The porous silicon particles prepared in Example 1 are composed of silicon primary particles having a size of about 28 nm and have pores developed therein. The porous silicon particles prepared in Examples 7 and 8 are composed of silicon primary particles of about 32 and 35 nm in size.

After magnesium reduction, it was confirmed that the zeolite was reduced to silicon and appeared as diffraction peaks (2? = 28.5 °, 47.4 °, 56.2 °, 69.2 °, and 76.6 °) of the silicon crystal. It can be seen in FIG. 12 that some amorphous residual silica which was not completely reduced at 2? = 15 to 25 ° was completely removed after HF etching.

XRD analysis results of the porous silicon produced in Comparative Example 1 are shown in Figs. 13 and 14. Fig. 13 is a graph showing the results of X-ray diffraction (XRD) analysis of porous silicon after washing with an aqueous solution of hydrochloric acid (HCl) in the manufacturing method of Comparative Example 1. Fig. And X-ray diffraction (XRD) analysis of porous silicon after washing with hydrofluoric acid (HF).

After reduction, the zeolite Y is reduced to silicon, except for the peak of magnesium by-products such as a small amount of Mg ₂ SiO ₄ , which is represented by the diffraction peak of the silicon crystal (2θ = 28.4 °, 47.3 °, 56.1 °, 69.2 °, 76.5 °) (Fig. 13) can be confirmed. Mg ₂ SiO ₄ was formed by reacting reactant SiO ₂ with product MgO, and reacted with HF during the etching of residual silica with HF, resulting in a new product, MgF ₂ , as a byproduct, resulting in lower purity of silicon 14). According to the XRD analysis, the size of the primary particles of the porous silicon produced in Comparative Example 1 was as large as 47 nm.

<Experimental Example 5> BET analysis results of porous silicon

BET analysis results of the porous silicon produced in Examples 1, 7 and 8 and Comparative Example 1 are shown in Figs. 15 and 16. Fig. Fig. 15 shows the nitrogen adsorption / desorption isotherm curves of the porous composites prepared in Examples 1, 7 and 8 and Comparative Example 1, and Fig. 16 shows the isothermal absorption curves of the porous composite prepared in Examples 1, 7 and 8 and Comparative Example 1 Lt; RTI ID = 0.0 &gt; pore &lt; / RTI &gt; size distribution of the porous composite. The BET surface area, pore volume, and average pore size are shown in Table 3 below.

[Table 3]

Referring to FIGS. 15 and 16, it can be seen that the porous silicon according to Examples 1, 7, and 8 has a higher nitrogen adsorption amount than that of Comparative Example 1, and the pores are developed inside the particles.

15, 16, and Table 3, the porous silicon produced in Examples 1, 7, and 8 had a much larger BET surface area, pore volume, and size than the porous silicon produced in Comparative Example 1. [ That is, in Comparative Example 1, since sodium chloride, which is a heat dispersing agent, is not used, it can be seen that sintering of silicon particles occurs due to a high reaction heat generated during the reaction.

PREPARATION EXAMPLE 1 Preparation of Lithium Secondary Cell (half cell)

The silicon-carbon composites prepared in Examples 1 to 4, Examples 5 to 8 and Comparative Examples 1 to 4 were used as the electrode active material, and carbon black as a conductive material and PVA (poly vinyl acetate, DMSO sulfoxide) was used. The silicon-carbon composite, the conductive material and the polymer binder were mixed at a weight ratio of 80:10:10 to obtain a slurry-like mixture.

The slurry was applied to a copper plate current collector having a thickness of 10 mu m as 50 mu m, dried at 80 DEG C for 2 hours, put into a compressor, and compressed to 30 mu m. Thereafter, it was vacuum-dried at 80 DEG C for 2 hours and cut into 1.54 cm &lt; ² &gt; to prepare an electrode.

The composite working electrode and the lithium metal reference electrode were laminated in a 2032 coin cell in a glove box in an argon atmosphere and a 2.54 cm ² polypropylene (PP) separator was placed therebetween.

Ethylene carbonate, ethylmethyl carbonate, and diethyl carbonate, to which 10 vol% of fluoroethylene carbonate was added, were mixed with an organic solvent containing 1.0 M LiPF ₆ lithium salt as an electrolyte solution. ) Was mixed in a volume ratio of 30:40:30 to prepare a lithium secondary cell (half cell).

&Lt; Preparation Example 2 > Preparation of lithium secondary battery (full cell)

Carbon black as a conductive material, and 5 wt% solution of PVA (polyvinyl acetate, DMSO (dimethyl sulfoxide)) as a polymer binder were used as the anode active material, the silicon-carbon composite material prepared in Example 3, and the conductive material. The silicon-carbon composite, the conductive material and the polymer binder were mixed at a weight ratio of 80:10:10 to obtain a slurry-like mixture.

The slurry was coated on a copper plate current collector having a thickness of 10 탆 and dried at 80 캜 for 2 hours and then compressed. Thereafter, it was vacuum-dried at 80 DEG C for 2 hours and cut into 1.54 cm &lt; ² &gt; to prepare an electrode.

The composite working electrode and the lithium metal reference electrode were laminated in a Swarovsk cell in a glove box in an argon atmosphere and a 2.54 cm ² polypropylene (PP) separator was placed therebetween.

Ethylene carbonate and ethylmethyl carbonate in which 10 vol% of fluoroethylene carbonate was added to an organic solvent containing 1.2 M LiPF ₆ lithium salt as an electrolyte were mixed at a volume ratio of 30:70 A half cell was prepared using the mixed solution, and a pretreatment for reducing irreversible energy of the negative electrode active material was performed by charging / discharging the battery for one cycle.

Commercial NCM 622 as a cathode active material, carbon black as a conductive material, and a 5 wt% solution in PVdF (N-methyl-2-pyrrolidone) were used as a binder) in a ratio of 85: : 7.5 weight ratio to obtain a slurry-like mixture.

The slurry was coated on an aluminum plate current collector having a thickness of 20 탆, dried at 80 캜 for 2 hours and compressed. Thereafter, it was vacuum-dried at 120 DEG C for 12 hours, and cut to 1.13 cm &lt; ² &gt; to prepare an electrode.

In the glove box of argon atmosphere, the pre-treated composite anode and NCM active material anode were laminated on a 2032 coin cell, and a 2.54 cm ² polypropylene (PP) separator was placed therebetween.

Ethylene carbonate and ethylmethyl carbonate in which 10 vol% of fluoroethylene carbonate was added to an organic solvent containing 1.2 M LiPF ₆ lithium salt as an electrolyte were mixed at a volume ratio of 30:70 A lithium secondary battery (full cell) was prepared using the mixed solution.

Experimental Example 6 Electrochemical Characterization of Lithium Secondary Cell (half cell)

In order to analyze the electrochemical characteristics of the lithium secondary battery, charging and discharging cycle characteristics were analyzed by a constant current method.

FIGS. 17 to 21 show results of analysis of charging and discharging cycle characteristics of the composite prepared in Examples 1 to 4, Examples 5 to 8 and Comparative Examples 1 to 4 as the electrode active material. 17 to 21, the charging and discharging cycle characteristic analysis was performed at a current density of 50 mA / g in a voltage range of 0.01 to 1.5 V for 5 cycles at a current density of 100 mA / g after one cycle test, At 500 mA / g, or 5 cycles at a current density of 100 mA / g and 500 mA / g from a subsequent cycle. FIG. 21 shows the results of testing the rate characteristics of the electrode made of the electrode active material according to Examples 5 and 6. FIG. At this time, the charge current density was kept constant at 100 mA / g and the discharge current density was varied at 100, 500, 1,000, 2,000, 5,000 and 10,000 mA / g.

17 is a graph showing the relationship between the charge / discharge cycle (charge / discharge cycle) of a lithium secondary battery (a half cell made of a lithium metal as a standard electrode) including a negative electrode using the porous silicon-carbon composites prepared in Examples 1 to 4 as a negative electrode material &Lt; / RTI &gt; Referring to FIG. 17, Example 1 was prepared so that the silicon content of the porous silicon-carbon composites was 70 wt%, and the initial coulombic efficiency was as high as 81.3%. At a current density of 100 mA / g, the charge capacity was found to be 1700 to 1760 mAh / g. After the rapid decrease of charge capacity to 1150 mAh / g until 6 cycles at a current density of 500 mA / , And showed a high capacity of about 1000 mAh / g.

Also, the porous silicon-carbon composites according to Example 2 had a silicon content of 60 wt%, and the initial coulombic efficiency was 75.3%. At a current density of 100 mA / g, the charge capacity was 1360 to 1390 mAh / g. After that, the charge capacity was reduced to 930 mAh / g until 7 cycles at a current density of 500 mA / / g. &lt; / RTI &gt;

In addition, the porous silicon-carbon composites according to Example 3 had a silicon content of 50 wt%, indicating an initial coulombic efficiency of 77.6%. At a current density of 100 mA / g, the charging capacity was 1050 to 1065 mAh / g. After that, the charging capacity was reduced to 687 mAh / g until 9 cycles at a current density of 500 mA / / g. &lt; / RTI &gt;

In addition, the porous silicon-carbon composites according to Example 4 had a silicon content of 76 wt%, which was lower than that of carbon coating with a pitch of 70% at an initial coulombic efficiency. At a current density of 100 mA / g, the charge capacity was 1005 to 1020 mAh / g, and then at a current density of 500 mA / g, the charge capacity rapidly decreased to 648 mAh / g until 11 cycles. Capacity and retention rate.

18 shows the charge / discharge cycle characteristics of the porous silicon-carbon composites prepared in Examples 5 and 6. FIG. The electrode active material according to Example 5 is obtained by mixing the porous silicon-carbon composite material prepared in Example 1 with graphite in a ratio of 60:40 wt%, and the silicon content in the electrode active material is 42 wt%. As a result, the initial coulombic efficiency was as high as 85% and the reversible capacity was 1018 mAh / g. At a current density of 100 mA / g, the charge capacity was above 1050 mAh / g, and then at 150 mA / g current density, the capacity was higher than 660 mAh / g after 150 cycles.

The electrode active material according to Example 6 is obtained by mixing the porous silicon-carbon composites prepared in Example 2 with graphite in a ratio of 60:40 wt%, and the silicon content in the electrode active material is 36 wt%. As a result, the initial coulombic efficiency was 79.5% and the reversible capacity was 959 mAh / g. At a current density of 100 mA / g, the charge capacity was more than 911 mAh / g, and then at 500 mA / g current density, it showed an excellent capacity of more than 620 mAh / g after 150 cycles.

FIG. 19 shows charge / discharge cycle characteristics of the porous silicon-carbon composites prepared in Examples 7 and 8. FIG. As a result, the porous silicon-carbon composite according to Example 7 had a silicon content of 59 wt%. The initial coulombic efficiency was as high as 83.9% and the reversible capacity was 1040 mAh / g. At a current density of 100 mA / g, the charging capacity was 1015 to 1030 mAh / g. After that, the charging capacity was reduced to 580 mAh / g until 10 cycles at a current density of 500 mA / / g or more.

In addition, the porous silicon-carbon composites according to Example 8 had a silicon content of 62 wt%. The initial coulombic efficiency was as high as 80.7% and the reversible capacity was 1171 mAh / g. At a current density of 100 mA / g, the charging capacity was about 1160 mAh / g. After that, the charging capacity was reduced from 720 mAh / g to 8 cycles at a current density of 500 mA / g. &lt; / RTI &gt;

20 shows charge / discharge cycle characteristics of the porous silicon-carbon composites prepared in Comparative Example 1 and the commercial silicon-carbon composites prepared in Comparative Examples 2 to 4. FIG. Referring to this, Comparative Example 1 was prepared to have a silicon content of 67 wt% in the porous silicon-carbon composite material, and the initial coulombic efficiency was as high as 87.4%. At a current density of 100 mA / g, the charge capacity was more than 1100 mAh / g. Then, at a current density of 500 mA / g, the charge capacity rapidly decreased from 550 mAh / g to 11 cycles, g or more. In other words, the initial cool dragon efficiency and cycle stability are comparatively good, but the cycle capacity is low at 500 mA / g because the sintering of the particles causes insufficient void space in the silicon particles due to sintering of the particles.

In addition, the commercial silicon nanoparticle-carbon composite according to Comparative Example 2 of FIG. 20 had an initial coulombic efficiency of 87.4%. At a current density of 100 mA / g, the charge capacity was about 2100 mAh / g. At a current density of 500 mA / g, the cycle capacity rapidly decreased and decreased to 860 mAh / g at 54 cycles.

In addition, the commercial Silicon nanoparticle-carbon composite according to Comparative Example 3 of FIG. 20 showed an initial coulombic efficiency as low as 72.8%. At a current density of 100 mA / g, the charge capacity was more than 1140 mAh / g. After that, the cycle capacity decreased drastically under the current density of 500 mA / g and decreased to 120 mAh / g at 70 cycles.

In addition, the commercial Silicon nanoparticle-carbon composite according to Comparative Example 4 of FIG. 20 had a relatively high initial coulombic efficiency of 81.8%. At a current density of 100 mA / g, the charge capacity was as high as 1504 mAh / g. After that, the charge capacity was reduced to 1092 mAh / g until 6 cycles at a current density of 500 mA / g. And then the capacity rapidly decreased to 575 mAh / g in 70 cycles.

That is, the cyclic characteristics of the commercial silicon nano-particle-carbon composites according to Comparative Examples 3 to 4 were significantly lower than those of the porous silicon-carbon composites due to the side effect of not effectively absorbing the volume expansion of silicon internally have.

FIG. 21 is a graph showing the charge / discharge rate (%) of a lithium secondary battery (half cell made of a lithium metal as a standard electrode) including a negative electrode using the porous silicon-carbon composites prepared in Examples 5 and 6 as a negative electrode material Fig. The current density during charging was fixed at 100 mA / g and the discharge current density was varied at 100, 500, 1,000, 2,000, 5,000 and 10,000 mA / g. As a result, the porous silicon-carbon composites according to Example 5 exhibited high capacities of 1,010, 1,000, 975, 943 and 882 mAh / g at current densities of 100, 500, 1,000, 2,000 and 5,000 mA / The capacity was greatly decreased at 10,000 mA / g, but the capacity was in the range of 440-550 mAh / g, which exceeded the theoretical capacity of commercial graphite (372 mAh / g). However, when the current density was gradually decreased to 100 mA / g, rapid capacity recovery showed excellent electrochemical reversibility.

The porous silicon-carbon composite according to Example 6 exhibited a high capacity of more than 920 mAh / g even when the current density increased from 100 mA / g to 5,000 mA / g, and reached about 750 mAh / g even at a current density of 10,000 mA / Respectively. Then, when the current density was gradually decreased from 10,000 mA / g to 100 mA / g, fast capacity recovery was achieved, indicating excellent electrochemical reversibility.

Table 4 below shows the capacity retention ratios of the composite prepared in Examples 1 to 3 and 5 to 8 with respect to the characteristics of the charge / discharge cycle as the electrode active material, Shows the capacity retention rate according to the characteristics analysis of the charge / discharge cycle of the composite prepared in Comparative Examples 1 to 4.

[Table 4]

[Table 5]

As shown in Table 4, in the case of Examples 1 to 3 and Examples 5 to 8, the capacity retention ratio of 18 to 70 cycles was 88% or more at a current density of 500 mA / g, Except for Example 1 and Example 8, most of the capacity was not reduced.

Also, in Examples 5 and 6 prepared by mixing the porous silicon-carbon composite with graphite, the capacity retention ratio at 18 to 150 cycles was 100%, which shows very stable cycle characteristics. In the case of Examples 7 and 8, the retention ratios of 18 to 150 cycles were relatively high as 94.3 and 73.7%, respectively, while the retention ratios of 18 to 70 cycles of Comparative Example 1 were somewhat low as 76% (Table 5).

In addition, in Comparative Example 2 made of commercially available silicon nanoparticles having a diameter of about 50 nm, the capacity retention ratio of 18 to 54 cycles was 80%. However, Comparative Example 2 made of commercially available silicon nanoparticles having a diameter of 70 to 100 nm 3 and Comparative Example 4, the capacity retention ratios of 18 to 70 cycles were remarkably lowered to 20% and 51%, respectively (Table 5).

EXPERIMENTAL EXAMPLE 7 Electrochemical Characterization of Lithium Secondary Cell (full cell)

In order to analyze the electrochemical characteristics of the lithium secondary battery prepared above, charge / discharge cycle characteristics were analyzed by a constant current method.

Fig. 22 is a graph showing the results of the evaluation of the properties of the porous silicon-carbon composites (Example 3) prepared in Example 3 using a negative electrode and negative electrode using NCM622 (LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ) FIG. 5 is a graph showing charge / discharge cycle performance of a lithium secondary battery. FIG. At this time, the complete lithium rechargeable battery prepared using graphite as the negative electrode active material was used as a control, and the capacity was expressed based on the weight of the cathode material. In FIG. 22, charge / discharge cycle characteristics analysis is performed at a voltage range of 2.0 to 4.2 V, at 5 cycles at a C-rate of 0.1 C, and at a C-rate of 0.5 C from a subsequent cycle. As a result, the complete pore of the porous silicon-carbon composite according to Example 3 as the negative electrode active material exhibited a capacity equal to or higher than that of the control pore under the initial 0.1C condition. Then, It is confirmed that the cycle stability is equal to or higher than that of the comparative example.

FIG. 23 is a graph showing a relationship between a lithium secondary battery including a negative electrode using a porous silicon-carbon composite material according to an embodiment of the present invention as a negative electrode material and a positive electrode using NCM 622 as a positive electrode material, a negative electrode using graphite as a negative electrode material, The weight and the volume energy density of a lithium secondary battery including a positive electrode used as a material. At this time, only the total weight and the total volume of the anode and the anode active material were considered in calculating the weight and the volume energy density, respectively. As a result, a lithium secondary battery using a high-capacity porous silicon-carbon composite as a negative electrode active material exhibits an energy density of about 1.3 times higher and a density of energy per volume of about 1.7 times higher than that of a lithium secondary battery using a commercial graphite as an anode active material can confirm. Therefore, the lithium secondary battery using the high-capacity porous silicon-carbon composite as the negative electrode active material has a cycle stability equal to or higher than that of the lithium secondary battery using the commercial graphite as the negative electrode active material, and it is confirmed that the energy density of the lithium secondary battery can be greatly improved .

Claims (19)

1. (i) mixing a silicon precursor represented by the following formula (1) with a heat dispersing agent and subjecting the mixture to a first heat treatment to prepare a first mixture;

   [Chemical Formula 1]

   M _{2 / n} O · Al ₂ O ₃ · xSiO ₂ · yH ₂ O

   (ii) mixing the first mixture with a metal reducing agent to prepare a second mixture;

   (iii) receiving the second mixture in a reaction chamber and performing a second heat treatment to reduce the silicon precursor to produce a reactant;

   (iv) washing the reactants to recover porous silicon particles;

   (v) mixing the porous silicon particles with a carbon precursor to produce a third mixture; And

   (vi) subjecting the third mixture to a third heat treatment to coat the porous silicon particles with carbon

   A method for producing a porous silicon-carbon composite.
2. The method according to claim 1,

   The silicon precursor represented by Formula 1 is at least one of zeolite X, Y, A, Beta, ZSM-5, and crystalline aluminosilicate having a mordenite structure.

   A method for producing a porous silicon - carbon composite.
3. The method according to claim 1,

   Wherein the silicon precursor represented by Formula 1 is at least one selected from the group consisting of alkali metals (alkali metal is any of Na, Li, K, Ca, and Mg), NH ₄ series,

   A method for producing a porous silicon - carbon composite.
4. The method according to claim 1,

   Wherein x is 2 or more,

   A method for producing a porous silicon - carbon composite.
5. The method according to claim 1,

   Wherein the heat dispersing agent is at least one of sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl ₂ ) and magnesium chloride (MgCl ₂ )

   A method for producing a porous silicon - carbon composite.
6. The method according to claim 1,

   In the step of preparing the first mixture,

   Wherein the heat dispersing agent is added in a ratio of 100 to 1200 parts by weight based on 100 parts by weight of the silicon precursor.

   A method for producing a porous silicon - carbon composite.
7. The method according to claim 1,

   Wherein the first heat treatment step is performed for 4 hours to 7 hours at a temperature in the range of 550 ° C to 800 ° C in a moisture-free gas atmosphere to remove moisture and hydroxyl groups (-OH) in the silicon precursor pores,

   A method for producing a porous silicon-carbon composite.
8. The method according to claim 1,

   Wherein the metal reducing agent is at least one of sodium (Na), magnesium (Mg), and aluminum (Al)

   A method for producing a porous silicon - carbon composite.
9. The method according to claim 1,

   In the step of preparing the second mixture,

   Wherein the metal reducing agent is mixed in a ratio of 50 to 200 parts by weight based on 100 parts by weight of the silicon precursor,

   A method for producing a porous silicon - carbon composite.
10. The method according to claim 1,

    Wherein the second heat treatment step is performed in an oxygen-free reaction chamber at a temperature in the range of 300 DEG C to 1000 DEG C and in a range of 1 hour to 24 hours,

    A method for producing a porous silicon-carbon composite.
11. The method according to claim 1,

    Wherein the second heat treatment is performed at a pressure within the reaction chamber of from 10 &lt; ^-3 &gt; bar to 5 bar.

    A method for producing a porous silicon-carbon composite.
12. The method according to claim 1,

    The step of washing the reactants to recover the porous silicon particles comprises:

    (iv-1) washing with distilled water to remove the heat dispersing agent;

    (iv-2) washing with an aqueous solution of hydrochloric acid (HCl) to remove by-products other than silicon; And

    (iv-3) etching the silica residue with an aqueous solution of hydrofluoric acid (HF).

    A method for producing a porous silicon-carbon composite.
13. The method according to claim 1,

    In the step of recovering the porous silicon particles,

    The specific surface area according to the BET measurement method is not less than 30 m ² / g and not more than 500 m ² / g,

    The total pore volume according to the BET measurement is from 0.2 cm ³ / g to 1.0 cm ³ / g,

    Wherein the individual silicon primary particles constituting the porous silicon particles have an average particle diameter of 5 to 50 nm,

    A method for producing a porous silicon-carbon composite.
14. The method according to claim 1,

    The carbon precursor may be selected from the group consisting of pitch, sucrose, glucose, resorcinol-formaldehyde, phenol-formaldehyde, phenolic resin, At least one of polyphenylene, polydopamine, graphite, carbon black, carbon nanotubes, and graphene,

    A method for producing a porous silicon-carbon composite.
15. 15. The method of claim 14,

    Wherein the step of coating carbon on the porous silicon particles comprises:

    In an inert gas atmosphere or an atmosphere of an inert gas and a hydrogen gas, at a temperature of 600 to 1000 占 폚,

    A method for producing a porous silicon-carbon composite.
16. A porous silicon-carbon composite produced by the method of claim 1.
17. A secondary battery anode comprising the porous silicon-carbon composite of claim 16.
18. A secondary battery comprising the secondary battery anode of claim 17.
19. An electronic device comprising the secondary battery of claim 18 as a power source.

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