KR20190047367A - Porous Silicon-Nano Carbon-Multilayer Graphene Composite Using Multi-Layer Graphene and Metal Alloy Powder and Manufacturing Thereof - Google Patents

Abstract

The present invention relates to: a porous silicon-nano carbon layer-multilayer graphene composite which comprises a shell containing a carbon layer and graphene on a porous silicon core particle having a micro-sized first pore and a nano-sized second pore by chemically etching a metal alloy powder; and a manufacturing method thereof. In the porous silicon-nano carbon layer-graphene composite having a core-shell structure in which a carbon-coated porous silicon particle is wrapped with a graphene shell, the present invention provides the porous silicon-nano carbon layer-graphene composite in which the porous silicon comprises the first pore and the second pore having different sizes, wherein the coated carbon has a thickness of 1 to 10 nm and the graphene shell has a thickness of less than 20 nm.

Description

TECHNICAL FIELD [0001] The present invention relates to a porous silicon-nano carbon layer-multilayer graphene composite produced by using a multi-layer graphene and a metal alloy powder and a method of manufacturing the same.

The present invention relates to a porous silicon-nano carbon layer-multilayer graphene composite produced by using multi-layer graphene and a metal alloy powder and a method of manufacturing the same. More particularly, the present invention relates to a multi- Nano carbon layer-multi-layer graphene composite comprising a porous silicon core particle having a nano-sized second pore and a shell containing a carbon layer and graphene, and a method for producing the same.

The lithium secondary battery is composed of a positive electrode, a negative electrode, and an electrolyte. When lithium ions from the positive electrode active material are charged into the negative electrode active material, that is, carbon particles by charging, So that charging and discharging are possible. As the carbonaceous materials such as graphite and low-crystalline carbon, which are used in the past, have a theoretical capacity of 375 mAh / g, the capacity of the battery is limited. As a high capacity battery is required, A very large battery capacity is required. Silicon has a theoretical cell capacity of 4200 mAh / g, which is more than 10 times larger than conventional carbonaceous anode materials.

However, silicon exhibits a semiconductor characteristic lacking in electrical conductivity. Silicon particles are destroyed by volume expansion of 300% or more during charging and discharging, and the battery capacity rapidly decreases to 100 mAh / g or less after several charge / discharge cycles. In addition, silicon has a disadvantage that lithium ion is abruptly taken in and electrolyte is solidified on the surface of silicon particles to form an unstable SEI (solid electrolyte solid) layer.

Recently, in order to secure the stability of charging and discharging capacity of such a silicon cathode material, research and development using silicon particles having a particle size of 100 nm or less as an anode active material have been conducted. However, since the anode active material made of silicon nanoparticles is expensive, it is not economical to use it as an anode material of a secondary battery due to the high cost of silicon nanoparticles. When the silicon nanoparticles are used alone, the charge / The charge and discharge capacities are rapidly decreasing, and a solution is needed.

(0001) Korean Patent Publication No. 10-2014-0096581 (0002) Korean Patent Publication No. 10-2016-0059121

SUMMARY OF THE INVENTION An object of the present invention is to provide a porous silicon-nano-particle having a nanocarbon layer formed on the surface of a porous silicon particle by preparing a solution by mixing a porous silicon particle with a water-soluble carbon precursor and a graphene oxide, Carbon layer-graphene composite and a method of manufacturing the same.

In order to solve the above-mentioned problems, the present invention according to the first aspect is a porous silicon-nano carbon layer-graphene composite having a core-shell structure wrapped with a graphene shell on carbon-coated porous silicon particles Wherein the porous silicon comprises a first pore and a second pore of different sizes, the coated carbon has a thickness of 1 to 10 nm, and the graphene shell has a porous silicon-nano carbon layer having a thickness of less than 20 nm, Graphene composite.

The first pores may have an average particle size of micro-size, and the second pores may have an average particle size of nano-size.

The average particle diameter (D50) of the porous silicon-nano carbon layer-graphene composite may be less than 9 占 퐉.

The carbon may be amorphous carbon, and the graphene may be multi-layer graphene.

The carbon and the graphene may be contained in an amount of 1 to 80% by weight based on the porous silicon.

The present invention according to the second aspect also provides a negative electrode active material comprising a porous silicon-nano carbon layer-graphene composite.

According to a third aspect of the present invention, there is also provided a method of manufacturing a semiconductor device, comprising the steps of: (a) preparing a mixed solution of a water soluble carbon precursor and a multilayer graphene on dried silicon particles from which impurities have been removed; (b) drying the mixed solution to prepare a porous silicon-carbon precursor-multilayer graphene composite; And (c) a porous silicon-nano carbon layer having a core-shell structure wrapped with carbon-coated porous silicon particles in a multi-layer graphene shell by heat treating the porous silicon-carbon precursor-multi- Nano carbon layer-graphene composite comprising the step of forming a porous silicon-nano carbon layer-graphene composite.

Wherein the dried silicon particles from which the impurities have been removed contain at least one element selected from Na, K, Mg, Ca, Cr, Mn, Fe, Ni, Fe, Ni, Cu, Zn Al, The sludge can be produced by chemical nicking with one or more acids selected from nitric acid, hydrochloric acid, phosphoric acid or hydrofluoric acid.

(I) dispersing graphite having a size of 5 to 80 占 퐉 in at least one organic solvent or water to prepare a graphite solution; (ii) adding a nonionic surfactant to the graphite solution, and using the mechanical shear force to produce multilayer graphene; (iii) acid-treating the multi-layer graphene.

The carbon precursor may include at least one selected from glucose, sucrose, polyacrylonitrile, polyacrylamide, and polyacrylic acid.

The porous silicon-nano carbon layer-multi-layer graphene composite prepared by using the multi-layer graphene and the metal alloy powder according to the present invention and the manufacturing method thereof can be manufactured through a simple and efficient method compared with the conventional anode active material using silicon nano- And the porous silicon-carbon composite particles have a micro size, uniform insertion and desorption reaction with lithium ions, uniform SEI formation, and electric conductivity are increased in the electrode structure A negative electrode active material can be provided.

FIG. 1 is a flow chart of a process for producing a porous silicon-nano carbon layer-multi-layer graphene composite prepared from a solution in which a carbon precursor and a multi-layer graphene are mixed, after manufacturing porous silicon and multi-layer graphene according to an embodiment of the present invention to be.
FIG. 2 shows the results of analysis of surface area and average pore size of a metal alloy powder, a chemical etching result, and a porous silicon-nano carbon layer-multilayer graphene according to an embodiment of the present invention by the BET method.
FIG. 3 shows the results of analysis by Raman spectroscopy and transmission electron microscopy (TEM) of multilayer graphenes used in the present invention.
FIG. 4 shows the result of analysis of the porous silicon used in the present invention by a scanning electron microscope (SEM).
FIG. 5 is a result of transmission electron microscopy (TEM) analysis of porous silicon-carbon composites and porous silicon-carbon-multilayer graphenes according to an embodiment of the present invention.
6 is a graph showing electrochemical characteristics of porous silicon, porous silicon-carbon composites and porous silicon-nano carbon layer-multilayer graphene composites according to an embodiment of the present invention.
FIG. 7 is a graph showing electrochemical characteristics of a porous silicon-nano carbon layer-multilayer graphene composite according to an embodiment of the present invention according to graphene content.

Hereinafter, preferred embodiments of the present invention will be described in detail. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Throughout the specification, when an element is referred to as " including " an element, it means that it can include other elements, not excluding other elements, unless specifically stated otherwise.

The present invention is capable of various modifications and various embodiments and is intended to illustrate and describe the specific embodiments in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms used in the description are used only to describe certain embodiments and are not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present invention, terms such as comprise, having, or the like are intended to designate the presence of stated features, integers, steps, operations, elements, parts or combinations thereof, and may include one or more other features, , But do not preclude the presence or addition of one or more other features, elements, components, components, or combinations thereof.

According to a first aspect of the present invention, there is provided a porous silicon-nano carbon layer-graphene composite having a core-shell structure wrapped in a carbon-coated porous silicon particle with a graphene shell, Nanocarbon layer-graphene composite having a first pore and a second pore, the coated carbon having a thickness of 1 to 10 nm, and the graphene shell having a thickness of less than 20 nm.

In the present invention, the porous silicon may include first pores and second pores having different sizes. The first pore average particle size may have a micro size, and may have a size of 1 to 500 mu m. The second pores may have an average particle size of nano-sized particles, and preferably have a size of 1 to 500 nm. If the average particle diameter of the first pores and the second pores is out of the above range, physical properties of the negative electrode active material including the composite may be deteriorated and the activity of the negative electrode may be decreased.

In the present invention, it is preferable that the average particle diameter (D50) of the porous silicon-nano carbon layer-graphene composite is less than 9 mu m. When the average particle diameter exceeds 9 탆, the particle size of the negative electrode active material including the composite increases, and the negative electrode activity may decrease as the surface area decreases.

In the present invention, the carbon may be amorphous carbon. Amorphous carbon is carbon which does not have a crystal structure, and amorphous carbon is preferably used since the reactivity is high and bonding property with porous silicon and graphene is good. The graphene may be multi-layer graphene, and preferably 2-5 layers of graphene may be used. When using single-layer graphene, the thickness of the graphene is thinned and durability is poor. When the graphene having 6 layers or more is used, the thickness of the graphene may become thick and porosity may be lowered. The carbon and graphene may be contained in an amount of 1 to 80% by weight, and preferably 20 to 60% by weight, based on the porous silicon. When the content of carbon and graphene is less than 1 wt%, the effect of coating of carbon and graphene is difficult to expect. When the content of carbon and graphene is more than 80 wt%, the thickness of the shell portion becomes thick, Falls.

The present invention according to the second aspect also relates to a negative electrode active material comprising a porous silicon-nano carbon layer-graphene composite. The silicon-nano carbon layer-graphene composite has porosity, uniform insertion and desorption reaction with lithium ions, and uniform SEI formation, so that it can be used as a negative electrode active material instead of the conventional nanosilicon.

Hereinafter, the present invention will be described in detail with reference to a porous silicon-nano carbon layer-graphene composite manufacturing method.

According to a third aspect of the present invention, there is provided a method for producing a silicon nitride film, comprising the steps of: (a) preparing a solution in which a water soluble carbon precursor and a multilayer graphene are mixed with dry silicon particles from which impurities have been removed; (b) drying the mixed solution to prepare a porous silicon-carbon precursor-multilayer graphene composite; And (c) a porous silicon-nano carbon layer having a core-shell structure wrapped with carbon-coated porous silicon particles in a multi-layer graphene shell by heat treating the porous silicon-carbon precursor-multi- Nano carbon layer-graphene composite comprising the steps of: preparing a porous silicon-nano carbon layer-graphene composite.

In the present invention, the dried silicon particles from which the impurities have been removed may contain one or more elements selected from Na, K, Mg, Ca, Cr, Mn, Fe, Ni, Fe, Ni, Cu, The powdered sludge may be prepared by chemically treating the waste alloy sludge with one or more acids selected from nitric acid, hydrochloric acid, phosphoric acid or hydrofluoric acid. The clogging sludge produced in the coke reduction process contains a large amount of Group 1 element, Group 2 element and transition metal, and also contains a large amount of silicon. Therefore, considerable cost reduction can be expected when porous silicon is manufactured using the same.

At this time, it is preferable that the clogging sludge is treated with strong acid to remove elements of Group 1 and Group 2 and transition metals except silicon. The strong acid may be one or more acid acids which are recovered in nitric acid, hydrochloric acid, phosphoric acid or hydrofluoric acid, preferably a first treatment with an aqueous solution of hydrochloric acid, sulfuric acid or nitric acid, followed by a second treatment with hydrofluoric acid. During the primary treatment, the Group 1 and Group 2 elements and the transition metal are removed, and during the secondary treatment, the silica on the surface of the porous silicon is removed.

If the size of the clogging sludge is larger than that of the porous silicon used in the present invention, it may be pulverized to an appropriate size through a milling process or the like. When the size of the sludge is small, They may be used in combination.

The concentration of the acid used in the strong acid treatment may be 1 to 10 M, preferably 3 to 4 M in the primary and secondary treatments. The amount of the acid used is 1 to 100 parts by weight per 1 part by weight of the pulverized sludge, And 2 to 10 parts by weight in the secondary treatment can be used. The amount of the acid used can be increased or decreased depending on the content of the metal impurities and the silica in the sludge.

It is preferable that the primary acid treatment and the secondary acid treatment are performed at room temperature, and it is more preferable to maintain the room temperature using a cooling device because a lot of heat is generated during the acid treatment. The primary acid treatment is preferably performed for 8 to 12 hours, and the secondary acid treatment is preferably performed for 30 to 60 minutes.

The porous silicon after the acid treatment can be washed with an organic solvent to remove remaining impurities. The organic solvent used herein may be any organic solvent that does not cause damage to the silicon particles while removing impurities, and any organic solvent may be used without limitation, but benzene, toluene, xylene, carbon tetrachloride, hydrocarbon, isopropyl alcohol, alcohol or phenol is preferably used And more preferably an alcohol can be used. After the cleaning, the porous silicon particles may be dried using a drying method commonly used to dry the porous silicon particles. In order to shorten the processing time, it is preferable to dry the porous silicon particles in a dry oven at 80 ° C for 12 hours.

In the step (a), the mixed solution may include 1 wt% of the porous silicon, 0.2-2 wt% of the carbon precursor, and 0.01-0.1 wt% of graphene, and preferably 1 wt% of the porous silicon, 0.5% by weight, and 0.01% by weight of graphene.

The carbon precursor is a substance which is heat-treated to form a carbon layer on the porous silicon surface, and at least one selected from water-soluble compounds such as glucose, sucrose, polyacrylonitrile, polyacrylamide and polyacrylic acid can be used. The carbon precursor is coated on the surface of the silicon particles and carbonized to form a fine coating layer.

(I) dispersing graphite having a size of 5 to 80 탆 in an organic solvent or water to prepare a graphite solution; (ii) adding a nonionic surfactant to the graphite solution, and using the mechanical shear force to produce multilayer graphene; (iii) acid-treating the multi-layer graphene.

The graphite used in the production of the multi-layer graphene has a size of 5 to 80 탆, preferably 15 to 45 탆. If the size of the graphite is less than 5 탆, the area of the graphene becomes small and it is difficult to uniformly adhere. When the size exceeds 80 탆, the size of the graphite becomes larger than that of the porous silicon particles.

Further, the graphite solution may be prepared using an organic solvent or water, preferably water. The surfactant may be a nonionic surfactant, preferably Tween 20, Tween 80, or Triton X-100 .

The graphite solution was prepared by adding 0.05 to 0.1 wt% of a surfactant to water to make a total volume of 200 to 1000 mL, uniformly peeling for 30 to 150 min using a cone type ultrasonic machine, and centrifuging at 1500 rpm for 15 minutes And then centrifuged.

The drying in the step (b) may be carried out by passing the sprayed droplets through a tubular heating furnace using a transportation gas. At this time, the temperature of the tubular furnace can be controlled to control the particle size of the porous silicon-carbon precursor-multilayer graphene composite. The drying temperature is preferably 100 to 200 ° C.

The heat treatment in the step (c) may be performed in an inert gas atmosphere using nitrogen or argon gas, and the temperature of the heating furnace is preferably 500 to 800 ° C. The heat treatment time can be from 60 to 180 minutes.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. And certain features shown in the drawings are to be enlarged or reduced or simplified for ease of explanation, and the drawings and their components are not necessarily drawn to scale. However, those skilled in the art will readily understand these details.

(1) Production of porous silicon

The waste sludge produced in the coke reduction process was first treated with 3M hydrochloric acid for 10 hours and then subjected to secondary treatment with 3M hydrofluoric acid for 40 minutes to obtain a porous silicon powder. Thereafter, the porous silicon powder was washed with alcohol, and then dried in an oven at 80 ° C for 12 hours to prepare a porous silicon powder.

(2) a carbon precursor

Polyacrylonitrile was purchased and used in the market.

(3) Multi-layer graphene

Graphite having a size of 30 mu m and 0.1 wt% of a surfactant (Tween 20) were mixed with ultrapure water through an ion exchange device to obtain a total volume of 1000 ml to prepare a graphite solution. The membrane was homogeneously peeled off using a cone type ultrasonic machine for 100 minutes and centrifuged at 1500 rpm for 15 minutes in a centrifuge. The precipitated multi-layer graphene was dried in a constant temperature drier at 150 DEG C for 24 hours to prepare it.

Example 1

1 g of the dry porous silicon powder from which impurities were removed and 0.5 g of polyacrylonitrile as a carbon precursor were dispersed in 100 mL of distilled water and 0.01 g of the multi-layer graphene was mixed to prepare a 100 mL mixed solution.

Ultrasonic treatment was performed for 30 minutes by using an ultrasonic dispersing machine to prepare a mixed solution in which carbon precursor and multi-layer graphene were dispersed on the surfaces of the porous silicon particles.

The porous silicon-carbon precursor-multilayer graphene composite spray-dried in a tubular furnace having a temperature of 150 ° C was heat-treated for 2 hours in a heating furnace at 700 ° C in a nitrogen gas atmosphere to carbonize the polyacrylonitrile, A porous silicon-nano carbon layer-graphene composite in which multi-layer graphene was dispersed in the prepared porous silicon particles was prepared.

Example 2

1 g of the dry porous silicon powder from which impurities were removed and 1 g of polyacrylonitrile as a carbon precursor were dispersed in 100 mL of distilled water, and 0.01 g of multi-layer graphene was mixed to prepare a 100 mL mixed solution.

Ultrasonic treatment was performed for 30 minutes by using an ultrasonic dispersing machine to prepare a mixed solution in which carbon precursor and multi-layer graphene were dispersed on the surfaces of the porous silicon particles.

The porous silicon-carbon precursor-multilayer graphene composite spray-dried in a tubular furnace having a temperature of 150 ° C was heat-treated for 2 hours in a heating furnace at 700 ° C in a nitrogen gas atmosphere to carbonize the polyacrylonitrile, A porous silicon-nano carbon layer-graphene composite in which multi-layer graphene was dispersed in the prepared porous silicon particles was prepared.

Comparative Example 1

1 g of the dried porous silicon powder from which impurities were removed and 1 g of glucose as a carbon precursor were dispersed in 100 mL of distilled water, and then 0.01 g of multilayer graphene was mixed to prepare a 100 mL mixed solution.

Ultrasonic treatment was performed for 30 minutes by using an ultrasonic dispersing machine to prepare a mixed solution in which carbon precursor and multi-layer graphene were dispersed on the surfaces of the porous silicon particles.

The porous silicon-carbon precursor-multilayer graphene composite spray-dried in a tubular heating furnace having a temperature of 150 ° C was heat-treated for 2 hours in a heating furnace at 700 ° C in a nitrogen gas atmosphere to carbonize the glucose, A porous silicon-nano carbon layer-graphene composite having multi-layer graphenes dispersed therein was prepared.

Comparative Example 2

1 g of the dry porous silicon powder from which impurities were removed and 1 g of polyacrylonitrile as a carbon precursor were dispersed in 100 mL of distilled water to prepare a 100 mL mixed solution.

Ultrasonic treatment was performed for 30 minutes using an ultrasonic dispersing machine to prepare a mixed solution in which the carbon precursor was dispersed on the surfaces of the porous silicon particles.

The porous silicon-carbon precursor complex spray-dried in a tubular furnace having a temperature of 150 ° C was heat-treated for 2 hours in a heating furnace at 700 ° C in a nitrogen gas atmosphere to carbonize the polyacrylonitrile to form a porous silicon- .

Comparative Example 3

1 g of the dry porous silicon powder from which impurities were removed and 1 g of polyacrylonitrile as a carbon precursor were dispersed in 100 mL of distilled water, and then 0.3 g of multilayer graphene was mixed to prepare a 100 mL mixed solution.

Ultrasonic treatment was performed for 30 minutes by using an ultrasonic dispersing machine to prepare a mixed solution in which carbon precursor and multi-layer graphene were dispersed on the surfaces of the porous silicon particles.

The porous silicon-carbon precursor-multilayer graphene composite spray-dried in a tubular furnace having a temperature of 150 ° C was heat-treated for 2 hours in a heating furnace at 700 ° C in a nitrogen gas atmosphere to carbonize the polyacrylonitrile, A porous silicon-nano carbon layer-graphene composite in which multi-layer graphene was dispersed in the prepared porous silicon particles was prepared.

Experimental Example

FIG. 2 shows the results of analysis of surface area and average pore size using the BET method of the metal alloy powder, the metal alloy powder after the acid treatment, and the porous silicon-nano carbon layer-multilayer graphene.

The specific surface area of the metal alloy powder not subjected to the acid treatment was 2.03 m 2 / g. Using hydrochloric acid, the primary etching showed 109 m2 / g and the secondary etching with hydrofluoric acid showed 251 m2 / g. Through this, the sub - micron size and nano - sized pores are formed through chemical etching, and the specific surface area is increased.

The average pore size of porous silicon was 13.9 m2 / g before etching and 18 m2 / g after etching. Therefore, the surface area and porosity of the porous silicon increased through the chemical etching of the metal alloy powder. On the other hand, porous silicon - carbon - graphene composites with multi - layer graphene dispersed on carbon - coated porous silicon particles showed that the porous silicon surface was coated with carbon and graphene by the reduction of specific surface area and pore size.

FIG. 3 shows the result of analysis by Raman spectroscopy and transmission electron microscopy (TEM) of multilayer graphene.

Tip Raman spectra of multi-layer graphene prepared using NMP, water and non-ionic surfactant in an ultrasonic machine. Raman spectra are known to be an important measuring instrument for measuring defects and thicknesses of fabricated multi-layer graphenes. The D band at 1350 cm-1 and the 2D band at G band and 2700 cm-1 at 1590 cm-1. The ratio of the D / G band intensity to the ungraded graphite was less than 0.06, while the ratio of the D / G band intensity to the multi - layer graphene peeled with an ultrasonic machine increased to 0.4 to 0.6. From these results, it can be seen that multi-layer graphene was formed from graphite. Dry multi-layer graphene was dispersed in ethanol solvent and multi-layer graphene was coated on TEM grid. TEM observation revealed that the multilayer graphene of 1 micrometer or more was formed in the left photograph of FIG. 3 (b), and it was confirmed that the graphene layer was less than 10 layers in the corner portion (right image of FIG. 3 (b)).

4 shows the result of analysis of porous silicon with a scanning electron microscope (SEM). Porosity below micron size was observed after primary and secondary etching. The average pore size and specific surface area of the porous silicon increased more than two times after the second etching compared to the first etching of the metal alloy powder. Porous silicon showed the increase of specific surface area and pore size of metal alloy powder.

FIG. 5 is a transmission electron microscopic (TEM) analysis result of a porous silicon-nano carbon layer composite and a porous silicon-nano carbon layer-multilayer graphene composite according to an embodiment of the present invention. Polyacrylonitrile was used as the carbon precursor. It was confirmed that the nano carbon layer and the multi-layer graphene were coated on the porous silicon particles.

6 is a graph showing the results of measurement of a porous silicon-carbon composite (a) porous silicon (b) porous silicon-carbon composite (Comparative Example 2) Graph showing the electrochemical properties of a silicon-nano carbon layer-graphene composite. The negative electrode had an anode active material: conductor: binder ratio of 8: 1: 1 and a binder PAA. CR2032 coin cell was fabricated with 0.8mg / ㎠ of anode active material. The amount of current was measured at 0.3 C with 1 C of 1000 mAh / g. The charge / discharge capacity of the porous silicon (P-Si) was drastically reduced as a result of 10 charge / discharge cycles. The porous silicon-carbon composite (P-Si @ C) and the porous silicon-carbon-multilayer graphene composite (PS @ C @ G) initially showed about 1100 mAh / g, Carbon - multilayer graphene composites (PS @ C @ G) showed stable charge and discharge capacities.

(PS @ C @ G) prepared in Example 2 and a porous silicon-carbon-multilayer graphene composite (PS @ C @ G) having an increased amount of the multilayer graphene prepared in Comparative Example 3, G-2), and the results are shown in FIG. The electrochemical characterization is the same as in FIG. 6, except that the charging / discharging characteristics in which the amount of multilayer graphene was increased 30 times showed a stable cyclic characteristic in the beginning, but the charging / discharging capacity was decreased. The porous silicon-carbon-multilayer graphene composite of Example 2 showed the best capacity.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (10)

A porous silicon-nano carbon layer-graphene composite having a core-shell structure that is wrapped with a graphene shell in a porous silicon particle coated with carbon,
Wherein the porous silicon comprises a first pore and a second pore of different sizes,
The coated carbon has a thickness of 1 to 10 nm, and the graphene shell has a thickness of less than 20 nm.
The method according to claim 1,
The first pores have an average particle size of micro-size,
Wherein the second pores have an average particle size of nanosize. ≪ RTI ID = 0.0 > 21. < / RTI >
The method according to claim 1,
Wherein said porous silicon-nano carbon layer-graphene composite has an average particle size (D50) of less than 9 microns.
The method according to claim 1,
Wherein the carbon is amorphous carbon and the graphene is a multi-layer graphene.
The method according to claim 1,
Wherein the carbon and the graphene are contained in an amount of 1 to 80 wt% based on the porous silicon.
A negative electrode active material comprising the porous silicon-nano carbon layer-graphene composite of any one of claims 1 to 5.
(a) preparing a solution in which a water soluble carbon precursor and a multilayer graphene are mixed with dry silicon particles from which impurities have been removed;
(b) drying the mixed solution to prepare a porous silicon-carbon precursor-multilayer graphene composite; And
(c) heat treating the porous silicon-carbon precursor-multi-layer graphene composite to form a porous silicon-nano carbon layer-graphene having a core-shell structure wrapped with carbon-coated porous silicon grains in a multi-layer graphene shell Producing a complex;
Lt; RTI ID = 0.0 > silicon-nano-carbon < / RTI > layer-graphene composite.
8. The method of claim 7,
Wherein the dried silicon particles from which the impurities have been removed contain at least one element selected from Na, K, Mg, Ca, Cr, Mn, Fe, Ni, Fe, Ni, Cu, Zn Al, Characterized in that the sludge is chemically nicked with one or more acids selected from nitric acid, hydrochloric acid, phosphoric acid or hydrofluoric acid.
8. The method of claim 7,
The multi-
(i) dispersing graphite having a size of 5 to 80 占 퐉 in at least one organic solvent or water to prepare a graphite solution;
(ii) adding a nonionic surfactant to the graphite solution, and using the mechanical shear force to produce multilayer graphene;
(iii) acid-treating the multi-layer graphene;
Wherein the porous silicon-nano carbon layer-graphene composite is produced by the process comprising:
8. The method of claim 7,
Wherein the carbon precursor comprises at least one selected from the group consisting of glucose, sucrose, polyacrylonitrile, polyacrylamide and polyacrylic acid.

Images