KR20190011635A - Silicon sheet, manufacturing method thereof, and lithium secondary battery including the same - Google Patents

Abstract

The present invention relates to a silicon thin plate which has a simple manufacturing process and can be adjusted with size and thickness thereof suitable for a purpose to be expanded to various application fields, a manufacturing method thereof, and a lithium secondary battery including the same. The silicon thin plate has the thickness of 500 nm or less, and a specific surface area of 15 m^2/g or less.

Description

Technical Field [0001] The present invention relates to a silicon thin plate, a method of manufacturing the same, and a lithium secondary battery including the same. BACKGROUND OF THE INVENTION [0002]

A silicon thin plate, a method for producing the same, and a lithium secondary battery comprising the same.

Due to the explosive growth of electric vehicles and energy storage devices as well as small secondary batteries, graphite, which is being commercialized, is gradually being replaced by silicon at the time when battery specifications of high energy density are required. However, it is difficult to industrialize due to the low electrical conductivity, which is a disadvantage of the silicon material itself, and the large volume expansion occurring during charging / discharging.

Numerous studies have shown that the properties of silicon are improving. More specifically, much research has been conducted on improving the lifetime characteristics of a silicon anode by reducing the size of the material in nanometers.

A silicon thin plate, a method for producing the same, and a lithium secondary battery comprising the same.

In one embodiment of the present invention, the silicon (Si) thin plate has a thickness of 500 nm or less and a specific surface area of 15 m ² / g or less.

The silicon thin plate may be a silicon (Si) thin plate having a width and a length of 500 nm to 5 mm, respectively.

The silicon (Si) thin plate may be a silicon (Si) thin plate having an aspect ratio of 1 to 500,000.

The silicon (Si) thin plate may be a silicon (Si) thin plate made of amorphous silicon.

The silicon (Si) thin plate may be a silicon (Si) thin plate having a volume expansion of the electrode plate of 80% or less after 100 cycles.

The silicon (Si) thin plate may be a silicon (Si) thin plate, which further comprises a carbon coating layer on the silicon thin plate.

The carbon coating layer formed on the silicon (Si) thin plate may have a thickness of 1 nm to 10 nm.

A step of preparing a solid inorganic salt, a step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt, a step of dissolving the inorganic salt in which the silicon (Si) coating layer is formed in a solvent, Thereby obtaining a removed silicon (Si) thin plate.

The solvent may be water and the solid phase inorganic salt may have a solubility of 0.1 g / ml to 10 g / ml at room temperature with respect to water.

The cation in the solid phase inorganic salt may be selected from the group consisting of aluminum, barium, cadmium, cesium, calcium, cerium, cobalt, indium, iron Iron, Lithium, Magnesium, Manganese, Neodymium, Nickel, Potassium, Radium, Rubidium, Samarium, Sodium Sodium, Strontium, Yttrium, or Zinc.

The anion in the solid phase inorganic salt may be at least one selected from the group consisting of Bromide, Carbonate, Chloride, Chromate, Cyanide, Fluoride, Hydroxide, Iodide ), Molybdate, oxide, or sulfate.

The step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt may be performed using a chemical vapor deposition (CVD) method.

Silicon precursors used in the chemical vapor deposition (CVD, chemical vapor deposition) is a silane (SiH _4), disilane (Si ₂ H _6), silicon tetrachloride (SiCl _4), silane (HSiCl ₃₎ trichlorosilane, dichlorosilane ( H ₂ SiCl ₂ ), chlorosilane (H ₃ SiCl), or a combination thereof.

The step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt may be performed by chemical vapor deposition for 1 minute to 120 minutes.

The step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt may be performed by chemical vapor deposition at a temperature ranging from 300 ° C to 1000 ° C.

The step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt may be a sputtering method.

The thin plate-shaped silicon obtained by the step of obtaining a silicon (Si) thin plate from which the inorganic salt is dissolved and removed has an amorphous or crystalline (e.g., amorphous or amorphous) phase depending on the reaction temperature of the step of forming a silicon It can be controlled.

The step of obtaining a thin silicon (Si) sheet in which the inorganic salt is dissolved and removed may include the step of pulverizing silicon from which the inorganic salt has been removed.

When the reaction temperature of the step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt is less than 700 캜, the resultant silicon may be amorphous.

When the reaction temperature in the step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt is 700 ° C or higher, the obtained silicon may be crystalline.

The step of dissolving the inorganic salt in which the silicon (Si) coating layer is formed in a solvent, and the step of obtaining a silicon (Si) thin sheet from which the inorganic salt is dissolved to remove the inorganic salt in the solution in which the inorganic salt is dissolved Recycling < / RTI >

The step of reusing and recycling the inorganic salt in the solution in which the inorganic salt is dissolved may be one in which the inorganic salt is recrystallized using one or more non-solvent.

In the step of reusing and recycling the inorganic salt in the solution in which the inorganic salt is dissolved, the recycling ratio of the inorganic salt may be 90% or more.

And adjusting the particle size of the inorganic salt after preparing the solid inorganic salt.

The step of regulating the particle size of the inorganic salt may be one of regulating the size of the inorganic salt by any one method selected from pulverization, recrystallization by a solvent evaporator, recrystallization by heat treatment, ball milling and recrystallization by non-solvent.

A step of dissolving the inorganic salt in which the silicon (Si) coating layer is formed in a solvent, and a step of obtaining a silicon (Si) thin plate from which the inorganic salt is dissolved to form a carbon coating layer on the surface of the thin silicon (Si) . ≪ / RTI >

The step of forming the carbon coating layer on the surface of the silicon (Si) thin plate may be a heat treatment at a temperature of 700 ° C to 1000 ° C.

The step of forming the carbon coating layer on the surface of the silicon (Si) thin plate may be a heat treatment in the presence of a gas containing carbon.

The carbon-containing gas may be any one selected from acetylene (C ₂ H ₂ ), ethylene (C ₂ H ₄ ), ethane (C ₂ H ₆ ), and toluene.

The carbon coating layer formed by forming the carbon coating layer on the surface of the silicon (Si) thin plate may have a thickness of 1 nm to 10 nm.

In another embodiment of the present invention, the negative electrode, the positive electrode and the negative electrode including the negative electrode active material including the thin silicon plate according to one embodiment of the present invention,

And an electrolyte positioned between the cathode and the anode.

The thin silicon plate according to one embodiment of the present invention and its manufacturing method are simple in manufacturing process and can be adjusted in size and thickness to suit the purpose and can be expanded to various application fields.

In addition, when commercialized, the cost of indirect materials can be minimized through the reuse of inorganic salts.

In addition, due to the structural characteristics, the silicon thin plate provided by the present invention is vertically relaxed rather than horizontally with respect to the internal stress caused by the volume expansion of silicon upon charging / discharging. For this reason, thin-walled silicon has a low volume expansion rate and high life expectancy. Unlike the silicon of other nanostructures, the silicon thin plate has a small specific surface area and has a low side reaction, so that the efficiency of the first charge / discharge is high.

1 is a schematic view of a lithium secondary battery according to an embodiment of the present invention.
FIG. 2 is a schematic view showing a process of synthesizing a silicon (Si) thin plate of the present invention.
FIG. 3 is a scanning electron microscope (SEM) photograph of an inorganic salt whose particle size is controlled through various recrystallization methods of the present invention.
4 is a scanning electron microscope (SEM) photograph of the silicon (Si) thin plate produced according to Production Example 2-1 of the present application.
5 is a transmission electron microscope (TEM) photograph of the carbon coated silicon thin plate produced in Production Example 3-2 of the present application.
6 is an X-ray diffraction (XRD) X-ray diffraction graph of the amorphous silicon (Si) thin plate and the carbon coated silicon thin plate of the present invention.
7 is a Raman spectroscopy graph of the amorphous silicon (Si) thin plate and the carbon coated silicon (Si) thin plate of the present invention.
8 is a Brunauer-Emmett-Teller (BET) graph of a silicon (Si) thin plate produced according to Production Example 2-1 of the present application.
9 is a graph showing the first charge / discharge of the silicon (Si) thin plate of the coin cell fabricated according to Production Example 5 of the present invention by thickness.
FIG. 10 is a graph showing the charge / discharge lifetime characteristics of the silicon (Si) thin plate of the coin cell manufactured according to Production Example 5 of the present invention.
11 is a graph showing a capacity according to charge / discharge rate of a silicon (Si) thin plate of a coin cell manufactured by Production Example 5 of the present application.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

The thin silicon plate in the present invention means silicon particles in the form of a thin film. A specific thickness range will be described later.

In the present invention, the silicon thin plate can be defined as a length and a thickness. More specifically, the silicon thin plate may be projected in a rectangular parallelepiped shape to define the longest side as a length, the length of the shortest side as a thickness, and the length of the other side as a vertical length.

Throughout this specification, where a section such as a layer, film, region, plate, or the like is referred to as being "on the surface" of another part, And the like.

Throughout this specification, when an element is referred to as " comprising ", it is understood that other elements may be included, rather than excluding other elements, unless the context clearly dictates otherwise.

(One) Silicon thin plate

In one embodiment of the present invention, a silicon (Si) thin plate having a thickness of 500 nm or less and a specific surface area of 15 m ² / g or less is provided.

Although silicon can achieve high energy density, it is difficult to industrialize due to the large volume expansion that occurs during charging / discharging of silicon materials. However, the silicon thin plate has a low volume expansion rate because it is vertically relaxed rather than horizontal in relation to the internal stress during charging / discharging, and high lifetime characteristics can be expected.

The thickness of the silicon thin plate may be 10 nm to 500 nm. Specifically, it may be 50 nm to 380 nm, 50 nm to 150 nm, 50 nm to 100 nm, and 10 nm to 50 nm.

The thickness of the silicon thin plate may be controlled by controlling the process temperature, the process time, the amount of the inorganic salt, and the flow rate of the silicon precursor gas in the step of coating the inorganic salt with silicon (Si).

The thin silicon plate may have other electro-mechanical properties depending on its thickness.

When the thickness of the silicon thin plate is more than 500 nm, the polarization phenomenon becomes worse due to the low electric conductivity of the silicon material, cracks due to the large volume expansion at the time of filling, and desorption occur, and the lifetime characteristics are deteriorated. In addition, since the thickness of the silicon thin plate has a long diffusion distance of lithium ions, the resistance increases and the high charge / discharge efficiency is not good. On the other hand, the thinner the thickness of the silicon thin plate, the smaller the volume expansion during charging / discharging, the better the long-term lifetime characteristics. The shorter diffusion length of lithium ion is favorable for high charge / discharge, but if the thickness of silicon thin plate is too thin, And the initial side reaction becomes large, which may lower the initial efficiency.

The thin silicon plate may be a two-dimensional structure, It may be a thin plate structure having slight curvature.

The silicon thin plate may have a specific surface area of 0.1 m ² / g to 20 m ² / g. More specifically, 1 m ² / g to ^{15 m 2 / g, 2.42 m} 2 / g to ^{10.79 m 2 / g, 8.32 m} 2 / g to ^{10.79 m 2 / g, 9.67 m} 2 / g to 10.79 m ² / g Lt; / RTI >

When the specific surface area of the silicon particles is less than 1 m ² / g, the initial efficiency may be good due to the low specific surface area, but the electrochemical behavior such as the bulk silicon is exhibited. That is, it can not effectively cope with the volume expansion, and the life characteristics may be degraded. In addition, when the specific surface area of the silicon thin plate exceeds 15 m ² / g, the initial side reaction becomes large due to the large specific surface area, thereby causing a problem of lowering the initial efficiency.

The silicon thin plate may have a width and a length of 500 nm to 5 mm, respectively. Specifically, it may be 500 nm to 1 mm, 500 nm to 100 μm, 500 nm to 10 μm, or 500 nm to 1 μm. The width and length are ranges that can be controlled depending on the size of the inorganic salt. When the size of the inorganic salt is large, a large-area silicon thin plate can be produced.

Unlike the silicon of other nanostructures, the silicon thin plate has a small specific surface area and thus has a low side reaction. Therefore, the efficiency of the first charge / discharge is high. However, when the width and the length of the silicon thin plate are less than 500 nm, the specific surface area becomes large like other nanostructures, and the side reaction may increase, which may reduce the efficiency of the first charge / discharge.

The range is a range that can be changed depending on the lateral and vertical sizes of the inorganic salt, and the present invention is not limited thereto and can be adjusted according to the purpose.

The aspect ratio of the silicon thin plate may be 1 to 500,000. Specifically 1 to 1,000. More specifically from 10 to 200, from 5 to 100, from 3 to 67, from 1 to 26,

As the aspect ratio of the silicon thin plate increases, the volumetric expansion occurring during charge / discharge is lowered vertically rather than horizontally relative to the internal stress, resulting in a low volume expansion rate and a high lifetime characteristic.

The silicon (Si) thin plate may have a volume expansion of not less than 30% and not more than 80% after 100 cycles. This may vary depending on the cycling conditions (operating temperature, electrode composition, etc.). If the secondary battery operating temperature is higher, the charging / discharging efficiency increases to cause a larger volume expansion. If the content of the active material in the electrode composition is high, the volume expansion rate may increase. Generally, in the case of silicon, when the lithium ion is inserted, the volume expansion exceeds 300%, whereas when the silicon thin plate is used, the volume expansion is remarkably reduced as 30-80%. As described above, The efficiency and lifetime characteristics of the battery are improved.

The silicon thin plate may be amorphous or controlled to be crystalline depending on the reaction temperature of the silicon coating or carbon coating step.

If the silicon coating step is performed at a temperature of less than 700 캜, the formed silicon thin plate is amorphous, and if the silicon coating step is performed at 700 캜 or higher, the silicon thin plate formed may be crystalline. When the reaction temperature in the carbon coating step is 700 ° C to 1,000 ° C, the crystallinity of the silicon thin plate may vary from amorphous to polycrystalline.

The thin silicon plate may further comprise a carbon coating layer on the silicon surface. By further including the carbon coating layer, the electrochemical performance of the thin silicon plate can be improved. Specifically, the carbon coating on the silicon thin plate surface can improve the low electrical conductivity of the silicon and reduce the side reaction of the silicon surface, so that a more stable SEI layer can be formed. In addition, it becomes a physical protective film at the time of volume expansion, and life characteristics can be improved.

The carbon coating step may be a heat treatment at a temperature of 700 ° C to 1000 ° C, and the silicon may be controlled from amorphous to polycrystalline according to the heat treatment temperature of the carbon coating step.

The temperature of the carbon coating step may vary depending on the carbon precursor gas. Coating is possible at over 900 ° C for CH ₄ gas, over 800 ° C for C ₂ H ₄ , and over 700 ° C for C ₂ H ₂ . However, silicon carbide (SiC) may be formed when the temperature of the carbon coating step exceeds 1000 캜.

The thickness of the coated carbon layer can be controlled by the amount of the material to be coated, the flow rate of the carbon precursor gas to be coated, the reaction temperature, and the process time, and the thickness of the coated carbon layer may be 1 nm to 10 nm. Specifically, it may be 3 nm to 7 nm. If the carbon coating layer is less than 1 nm, the above-described carbon coating effect may be insufficient. If the carbon coating layer is more than 10 nm, the capacity per unit weight or volume of the electrode may be decreased.

(2) Manufacturing method of silicon thin plate

According to an embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of preparing a solid inorganic salt, forming a silicon (Si) coating layer on the surface of the solid inorganic salt, dissolving the inorganic salt in which the silicon , And a step of obtaining a silicon (Si) thin plate from which the inorganic salt has been dissolved to remove the silicon (Si) thin sheet.

More specifically, the present invention provides a method for producing a silicon thin plate using an inorganic salt as a mold.

Specifically, in the step of obtaining a silicon (Si) thin plate from which the inorganic salt has been dissolved and dissolved, a thin silicon plate according to one embodiment of the present invention described above can be obtained.

Since the method for producing this thin silicon plate is to produce a thin silicon plate using an inorganic salt as a mold, the inorganic salt should be stable regardless of the synthesis temperature, time, and voltage, and preferably has a melting point of 600 ° C or higher.

The cation in the solid phase inorganic salt may be at least one selected from the group consisting of aluminum, barium, cadmium, cesium, calcium, cerium, cobalt, indium, iron Iron, lanthanum, magnesium, manganese, neodymium, nickel, potassium, radium, rubidium, samarium, sodium, For example, sodium, strontium, yttrium, or zinc.

The anion in the solid inorganic salt may be at least one selected from the group consisting of Bromide, Carbonate, Chloride, Chromate, Cyanide, Fluoride, Hydroxide, Iodide, Molybdate, Oxide, or Sulfate.

The solid inorganic salt may have a solubility of 100 g / L to 10,000 g / L at room temperature with respect to the solvent. This is for the removal of inorganic salts after coating the surface of the inorganic salt with silicon. The solubility range refers to the range in which the inorganic salt can form a saturated state in the solvent.

According to one embodiment of the present invention, the solid inorganic salt may have a solubility of 0.1 g / ml to 10 g / ml at room temperature with respect to water.

In one embodiment of the present invention, the solvent and non-solvent may be selected as the solubility of the inorganic salt used for each solvent and non-solvent. For example, when a specific inorganic salt is selected, the solvent is selected to have a sufficiently high solubility in the inorganic salt, and the non-solvent can be selected to have a sufficiently low solubility in the inorganic salt.

More specifically, when the inorganic salt is selected as sodium chloride, water can be selected as the solvent. The solubility of sodium chloride in water is 360 g / L. The non-solvent may be methanol, ethanol, dimethylformamide, 1-propanol, sulfolane, 1-butanol, 2-propanol, 1-pentanol, acetonitrile, acetone and combinations thereof. The above-mentioned non-solvent is very low in solubility in sodium chloride of about 0.4 to 0.00042 g / L.

Hereinafter, a method of manufacturing a silicon thin plate according to an embodiment of the present invention will be described in detail.

First, the step of preparing a solid phase inorganic salt may be preparing an inorganic salt which forms a frame of the silicon coating layer. This may further comprise the step of adjusting the particle size of the inorganic salt after the step of preparing the solid inorganic salt.

The step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt may be to form a silicon (Si) coating layer on the whole or part of the inorganic salt surface.

The step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt may be performed using chemical vapor deposition (CVD).

The silicon precursor used in the chemical vapor deposition (CVD) may be a silane-based compound. Specifically, a silane (SiH _4), disilane (Si ₂ H _6), silicon tetrachloride (SiCl _4), trichlorosilane (HSiCl _3), dichlorosilane (H ₂ SiCl _2), chlorosilane (H ₃ SiCl), Or a combination thereof, and the present invention is not limited thereto.

The step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt may be performed by chemical vapor deposition at a temperature ranging from 300 ° C to 1000 ° C. In the chemical vapor deposition method, the temperature at which silicon can be decomposed and deposited in the silane compound used as a silicon precursor may be set to the lower limit of the reaction temperature, and the melting point of the inorganic salt used as the upper limit of the reaction temperature may be performed. Therefore, when the reaction temperature is less than 300 ° C., silicon is not sufficiently decomposed from the silicon precursor to deposit, and when the reaction temperature exceeds 1000 ° C., the melting point of the inorganic salt used exceeds the melting point. do.

The silicon coating layer may be crystalline or amorphous depending on the reaction temperature of the step of coating the surface of the solid inorganic salt with silicon (Si), and the degree of crystallization of the silicon coating layer may be controlled by controlling the reaction temperature.

As shown in the following Production Examples, amorphous silicon is coated when the reaction temperature is 700 ° C or less, and crystalline can be formed when the reaction temperature is 700 ° C or more.

The step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt may be performed by chemical vapor deposition for 1 minute to 120 minutes. Specifically, it may be performed by chemical vapor deposition for 10 minutes to 90 minutes, 10 minutes to 20 minutes, 15 minutes to 20 minutes, or 1 minute to 10 minutes. The silicon coating layer formation time range can be controlled according to the thickness of the required silicon thin plate.

The step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt may be a sputtering method. However, the present invention is not limited thereto, and any of those commonly used in the art can be applied without limitation.

The thickness of the silicon thin plate obtained by controlling the process time of the step of coating silicon (Si) on the surface of the solid inorganic salt can be adjusted, and the electrochemical characteristics may be changed according to the thickness of the silicon thin plate as described above.

The step of dissolving the inorganic salt in which the silicon (Si) coating layer has been formed in a solvent and the step of obtaining a silicon (Si) thin sheet in which the inorganic salt is dissolved and dissolved to remove the inorganic salt is dissolved in a solvent in the inorganic salt in which the silicon coating layer is formed , Filtering the solution to obtain silicon (Si) from which inorganic salts have been removed, and then pulverizing the obtained silicon (Si) to obtain a silicon (Si) thin plate.

The solvent may be water or a mixture of water and alcohol, but is not limited thereto, and may be varied depending on the kind of inorganic salt used as described above.

Dissolving the inorganic salt in which the silicon (Si) coating layer is formed in a solvent; And obtaining a silicon (Si) thin sheet from which the inorganic salt is dissolved and removed, and then recycling the inorganic salt in the solution in which the inorganic salt is dissolved to recycle it.

The present invention provides a method for recycling an inorganic salt used for forming a silicon thin plate, and the inorganic salt can be recycled at 90% or more, so that there is an advantage that consumption cost of an indirect material necessary during a synthesis process can be reduced.

In one embodiment of the present invention, a silicon coating layer is formed on the surface of an inorganic salt, and then the inorganic salt is dissolved and removed by using a solvent. After filtration, a thin silicon plate is obtained, and then the collected solution is recrystallized using a non- Lt; / RTI >

The step of reusing the inorganic salt in the solution in which the inorganic salt is dissolved to recycle can be carried out using one or more non-solvent. The non-solvent may vary depending on the kind of inorganic salt and the type and solubility of the solvent.

The step of preparing the solid phase inorganic salt may further include the step of adjusting the particle size of the solid phase inorganic salt.

The step of adjusting the particle size of the solid inorganic salt may be carried out by adjusting the size of the inorganic salt by any one method selected from pulverization, recrystallization by a solvent evaporator, recrystallization by heat treatment, ball milling and recrystallization by non-solvent . (Si) thin plate obtained according to the size of the inorganic salt is varied depending on the size of the thin silicon (Si) plate, as described above, Properties may vary.

The method of recrystallizing the solid inorganic salt may vary the particle size of the inorganic salt depending on the type of non-solvent, amount of non-solvent, reaction temperature, and reaction time. Since the solubility of the solvent in the inorganic salt is different from the solubility of the non-solvent, the particle size of the inorganic salt to be precipitated may vary depending on the type of the non-solvent. The larger the difference between the solubility of the non-solvent in the inorganic salt and the solubility of the solvent, the smaller the particle size of the inorganic salt to be precipitated. Further, the larger the amount of the non-solvent to deposit the inorganic salt, the smaller the particle size of the inorganic salt. The reaction temperature is generally a factor for increasing the solubility. The solubility of the solvent in the inorganic salt is greatly increased, while the solubility of the non-solvent is slightly increased, and the difference may be large. When the temperature is raised, . The reaction time refers to the stirring time after the non-solvent is added. As the reaction time becomes longer, the growth time of the nucleus of the inorganic salt to be precipitated becomes longer, and inorganic salts having a large particle size can be precipitated.

Dissolving the inorganic salt in which the silicon (Si) coating layer is formed in a solvent; And a step of obtaining a silicon (Si) thin plate from which the inorganic salt has been dissolved to form a carbon coating layer on the surface of the silicon (Si) thin plate. Specifically, the recycling ratio of the inorganic salt is 90% to 100%, 97.9% to 99.7%, 98.0% to 99.7%, 98.3% to 99.7%, 98.5% to 99.7%, 98.7% to 99.7%, 99.0% , 99.4% to 99.7%, 99.6% to 99.7%.

The step of forming the carbon coating layer on the surface of the silicon (Si) thin plate may be a heat treatment at a temperature of 700 ° C to 1000 ° C. The reaction temperature may vary depending on the carbon precursor gas in the carbon coating layer formation step. A carbon coating layer is formed at 900 ° C or higher for CH ₄ gas, 800 ° C or higher for C ₂ H ₄ , and 700 ° C or higher for C ₂ H ₂ . However, since the silicon carbide (SiC) may be formed when the temperature exceeds 1000 캜, the carbon coating is performed at a temperature lower than that.

By controlling the reaction temperature and time in the carbon coating layer forming step, the crystallinity of the thin silicon plate and the thickness of the carbon coating layer can be controlled.

The carbon coating layer formed by forming the carbon coating layer on the surface of the silicon (Si) thin plate may have a thickness of 1 nm to 10 nm. If a carbon coating layer is formed, the low electrical conductivity of silicon may be complemented and the initial efficiency may be increased. In addition, since carbon is coated on the silicon surface forming the unstable SEI layer, a more stable film can be formed to improve the lifetime characteristics, and it can serve as a protective layer capable of physically supporting the silicon that expands upon charging / discharging .

When the thickness of the carbon coating layer is 1 nm or less, the effect of carbon coating is insufficient. In other words, the low electrical conductivity of silicon can not be compensated for, and an unstable SEI layer can be formed, and it is not a structure that physically compensates for volume expansion. If it is 10 nm or more, the capacity per volume or volume of the battery can be reduced.

As described above, the electrochemical characteristics of the silicon thin plate can be improved by coating the silicon thin plate with the carbon layer, and the electrochemical characteristics can be changed depending on the thickness of the carbon coating layer.

The step of forming the carbon coating layer on the surface of the silicon (Si) thin plate may be a heat treatment in the presence of a gas containing carbon. The carbon-containing gas may be any one selected from acetylene (C ₂ H ₂ ), ethylene (C ₂ H ₄ ), ethane (C ₂ H ₆ ), and toluene, It is not limited.

(3) Lithium secondary battery

In another embodiment of the present invention, there is provided a negative electrode comprising a negative electrode active material including the above-mentioned silicon (Si) thin plate; anode; And an electrolyte positioned between the cathode and the anode.

The negative electrode includes the above-described negative electrode active material. For example, the negative electrode active material composition, the binder and optionally the conductive agent are mixed in a solvent to prepare a negative electrode active material composition, ) To the negative electrode current collector.

The binder used in the negative electrode active material composition is a component that assists in bonding of the active material and the conductive agent to the binder and bonding to the collector, and is added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the negative active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

Since the negative electrode active material itself provides a conductive path, the negative electrode need not use a conductive agent. However, the negative electrode may further include a conductive agent in order to further improve the electrical conductivity. As the conductive agent, any material conventionally used for a lithium battery can be used. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black and carbon fiber; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; A conductive polymer such as a polyphenylene derivative, or a conductive material including a mixture thereof. The content of the conductive material can be appropriately adjusted.

As the solvent, N-methylpyrrolidone (NMP), acetone, water and the like can be used. The solvent is used in an amount of 1 to 10 parts by weight based on 100 parts by weight of the negative electrode active material. When the content of the solvent is within the above range, the work for forming the active material layer is easy.

Further, the negative electrode collector is generally made to have a thickness of 5 to 20 mu m. The negative electrode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, sintered carbon, surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The prepared negative electrode active material composition may be directly coated on the current collector to prepare a negative electrode plate, or a negative electrode plate may be obtained by laminating the negative electrode active material film, which is cast on a separate support and separated from the support, to a copper foil current collector. The negative electrode is not limited to the above-described form, but may be in a form other than the above-described form.

The negative electrode active material composition may be used not only for the production of electrodes of a lithium battery but also for the production of a printable battery by printing on a flexible electrode substrate.

Separately, a cathode active material composition in which a cathode active material, a conductive agent, a binder, and a solvent are mixed is prepared in order to manufacture the anode.

As the cathode active material, lithium-containing metal oxides can be used as long as they are commonly used in the art. For example, LiCoO ₂ , LiMn _x O ₂ x (x = 1, 2), LiNi _1-x Mn _x O ₂ (0 <x <1), or LiNi _1-xy Co _x Mn _y O ₂ 0.5, 0? Y? 0.5). For example, it is a compound capable of intercalating / deintercalating lithium such as LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , V ₂ O ₅ , TiS or MoS.

As the conductive agent, the binder and the solvent in the positive electrode active material composition, the same materials as those of the above-mentioned negative electrode active material composition may be used. In some cases, a plasticizer may be further added to the cathode active material composition and the anode active material composition to form pores inside the electrode plate. The content of the cathode active material, the conductive agent, the binder and the solvent is a level commonly used in a lithium battery.

The positive electrode current collector is not particularly limited as long as it has a thickness of 10 to 20 占 퐉 and has high conductivity without causing chemical change in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, Or a surface treated with carbon, nickel, titanium or silver on the surface of aluminum or stainless steel can be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The prepared cathode active material composition can be directly coated on the cathode current collector and dried to produce a cathode plate. Alternatively, the positive electrode active material composition may be cast on a separate support, and then the film obtained by peeling from the support may be laminated on the positive electrode collector to produce a positive electrode plate.

The positive electrode and the negative electrode may be separated by a separator, and the separator may be any as long as it is commonly used in a lithium battery. Particularly, it is preferable to have a low resistance against the ion movement of the electrolyte and an excellent ability to impregnate the electrolyte. For example, a material selected from a glass fiber, a polyester, a Teflon, a polyethylene, a polypropylene, a polytetrafluoroethylene (PTFE), and a combination thereof may be used in the form of a nonwoven fabric or a woven fabric. The separator has a pore diameter of 0.01 to 10 mu m and a thickness of 5 to 300 mu m.

The lithium salt-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and lithium. As the non-aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte and the like are used.

Examples of the non-aqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, But are not limited to, lactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, Nitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives , Tetrahydrofuran derivatives, ether, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation groups, and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides, sulfates, silicates and the like of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt may be any of those conventionally used in lithium batteries and may be dissolved in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , _{LiPF 6, LiCF 3 SO 3,} LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, lithium chloro borate, lower aliphatic carboxylic Lithium borate, lithium perborate, lithium tetraborate, lithium imide, and the like.

The lithium battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and the electrolyte used. The lithium battery can be classified into a cylindrical shape, a square shape, a coin shape, a pouch shape, And can be divided into a bulk type and a thin film type. Also, a lithium primary battery and a lithium secondary battery are both possible.

The manufacturing method of these batteries is well known in the art, and thus a detailed description thereof will be omitted.

1 schematically illustrates a typical structure of a lithium battery according to an embodiment of the present invention.

1, the lithium battery 30 includes a positive electrode 23, a negative electrode 22, and a separator 24 disposed between the positive electrode 23 and the negative electrode 22. The positive electrode 23, the negative electrode 22 and the separator 24 described above are wound or folded and accommodated in the battery container 25. Then, an electrolyte is injected into the battery container 25 and sealed with a sealing member 26, thereby completing the lithium battery 30. The battery container 25 may have a cylindrical shape, a rectangular shape, a thin film shape, or the like. The lithium battery may be a lithium ion battery.

The lithium battery is suitable for applications requiring a high capacity, high output and high temperature driving such as an electric vehicle in addition to a conventional cellular phone, a portable computer, and the like, and can be used in combination with a conventional internal combustion engine, a fuel cell, a supercapacitor, A hybrid vehicle or the like. In addition, the lithium battery can be used for all other applications requiring high output, high voltage and high temperature driving.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Fabrication and evaluation of silicon thin plate

Production Example 1: Preparation of inorganic salt whose particle size is controlled by recrystallization

500 g of NaCl was dissolved in 1,388 ml of water to prepare a saturated solution. Ethanol (2,776 ml) corresponding to twice the amount of water was added thereto and stirred rapidly. At this time, 133 g of NaCl precipitated and was obtained through the filter.

NaCl having an average particle diameter of 10 mu m was uniformly prepared by the recrystallization method of the inorganic salt. When the particle size of the inorganic salt is regulated through recrystallization, an inorganic salt having a uniform particle size can be produced.

As described above, the type of non-solvent and the difference in solubility, the ratio of the solvent to the solvent, the temperature (the solubility of the inorganic salt is changed), the stirring time (the longer the agitation time is, ), The particle size of the inorganic salt is changed.

FIG. 3 is a scanning electron microscope (SEM) photograph of NaCl with particle diameters controlled by various methods.

Commercial NaCl is a cube with one side of 1 mm. NaCl having an average particle size of about 500 μm was obtained by crushing it with a mortar, and NaCl having a mean particle size of about 300 μm was obtained through a solvent drier in a saturated NaCl solution. After the heat treatment, NaCl having an average particle diameter of 200 mu m was obtained by dry ball milling and NaCl having an average particle diameter of about 150 mu m was obtained by recrystallization using a non-solvent as described in Production Example 1, NaCl having an average particle size was obtained. In the case of the recrystallization method using the non-solvent, not only the grain size can be reduced but also NaCl having a uniform size can be obtained.

Production Example 2-1: Production of thin silicon plate (Chemical Vapor Deposition (CVD))

25 g of NaCl having a particle size of 10 탆 prepared in Preparation Example 1 was placed in an electric furnace and maintained at 550 캜 and then SiH ₄ gas was flowed at a rate of 50 cc / min for 10 minutes, 15 minutes, 20 minutes, and 90 minutes A silicon (Si) coating layer is formed on the surface of NaCl.

After completion of the reaction, the mixture is cooled to room temperature, and NaCl having a silicon coating layer is dissolved in water and stirred. Then, the mixture is filtered through a filter to obtain a silicon (Si) coating layer from which NaCl has been removed. The resultant NaCl-removed silicon (Si) coating layer was crushed to prepare a silicon thin plate.

The thickness of the silicon thin plate may be 50 nm, 100 nm, 150 nm, and 380 nm, respectively, depending on the reaction time of the silicon (Si) coating layer forming step, and the lateral length may be from 500 nm to 10 m. The synthesized silicon is also amorphous.

Regarding the horizontal and vertical lengths of the obtained silicon thin plate, as described above, the initially coated silicon is equal to the length and breadth of the inorganic salt, but is pulverized during the stirring and the obtaining process to have various sizes ranging from 500 nm to 10 μm.

4 is a scanning electron microscope (SEM) photograph of a silicon thin plate produced according to Production Example 2-1, wherein silicon coating steps were carried out for 10 minutes, 15 minutes, 20 minutes, and 90 minutes, respectively, 50 nm, 100 nm, 150 nm, and 380 nm.

The silicon thin plates of 50 nm, 100 nm, 150 nm, and 380 nm thick produced by Production Example 2-1 had an aspect ratio of 10 to 200, 5 to 100, 3 to 67, 1 to 26 to be.

The specific surface areas of the silicon thin plates of 50 nm, 100 nm, 150 nm, and 380 nm thick prepared by the above production example are 10.79 m ² / g, 9.67 m ² / g, 8.32 m ² / g and 2.42 m ² / g, respectively.

Production Example 2-2: Production of thin silicon plate (sputtering method)

1 g of 10 탆 NaCl prepared in Preparation Example 1 was placed on a silicon wafer and placed in a RF magnetron sputter sample chamber. After that, argon gas is flowed at 20 cc / min, and is deposited at 300 W for 1 hour. The subsequent procedure was the same as in Production Example 2-1, and a silicon thin plate having a thickness of 100 nm, a width of 10 μm or less and a specific surface area of 15 m ² / g or less was prepared.

Evaluation Example 2-1: Brunauer-Emmett-Teller (BET)

8 is a Brunauer-Emmett-Teller (BET) graph of the silicon thin plate produced in Production Example 2-1. The specific surface area of the thin silicon plates of 50 nm, 100 nm, 150 nm and 380 nm thickness was 10.79 m ² / g, 9.67 m ² / g, 8.32 m ² / g, and 2.42 m ² / g.

Production Example 3-1: Carbon-coated silicon (Si) thin plate (carbon coating step temperature 750 ° C)

Silicon thin plates having thicknesses of 50 nm, 100 nm, 150 nm, and 380 nm manufactured in Production Example 2-1 were prepared.

And a carbon coating layer is formed on the silicon thin plate by performing heat treatment for 10 minutes at a temperature of 750 ° C in a state where C ₂ H ₂ gas is introduced at 500 sccm. At this time, the thickness of the formed carbon coating layer is 3 nm.

Production Example 3-2: Carbon-coated silicon (Si) thin plate (carbon coating step temperature 900 ° C)

Silicon thin plates having thicknesses of 50 nm, 100 nm, 150 nm, and 380 nm manufactured in Production Example 2-1 were prepared.

C ₂ H ₂ gas is introduced at a flow rate of 500 sccm and is then heat-treated at a temperature of 900 ° C. for 8 minutes to form a carbon coating layer on the thin silicon plate. At this time, the thickness of the formed carbon coating layer is 3 nm.

5 is a TEM photograph of a silicon thin plate having a thickness of 50 nm coated with carbon at 900 ° C according to Production Example 3-2, showing a sufficiently wide transverse length compared with the thickness, It can be confirmed that the structure of FIG.

Evaluation Example 3-1: X-ray diffraction (XRD)

6 is a graph showing the results of X-ray diffraction (XRD) analysis of an amorphous silicon (Si) thin plate having a thickness of 50 nm prepared in Production Example 2-1 and a carbon-coated silicon thin plate prepared in Production Examples 3-1 and 3-2 (XRD) X-ray diffraction graph.

In the case of the amorphous silicon of 50 nm prepared in Production Example 2-1, the silicon peak is not observed on the XRD, but there is a crystalline silicon peak as the crystallinity increases during the heat treatment process of 750 ° C. and 900 ° C. in the carbon coating step. That is, as the heat treatment is performed at a higher temperature, a larger peak appears, so that the crystallinity of silicon is increased.

Evaluation Example 3-2: Raman spectroscopy

7 is a Raman spectroscopy graph of an amorphous silicon (Si) thin plate (Production Example 2-1) having a thickness of 50 nm and silicon thin plates (Production Examples 3-1 and 3-2) carbon-coated at 750 ° C and 900 ° C to be.

In Raman spectroscopy, the raman shift corresponding to Si-Si bonding appears at about 480-520 cm ^-1 . The more amorphous shows a broad peak in the near and 480cm ^-1, the more close to a single crystal 520cm ^-1, is displayed a sharp peak.

The amorphous silicon thin plate having a thickness of 50 nm (Production Example 2-1) shows a peak corresponding to Si-Si bonding around 493.0 cm ^-1 in Raman spectroscopy.

Raman spectroscopy shows a peak corresponding to Si-Si bonding centered at 506.7 cm ^-1 at 750 ° C. This shows that the amorphous silicon thin plate with a thickness of 50 nm (Production Example 2 -1), which is higher in crystallinity than Si-Si

Silicon-coated silicon (Si) foil at 900 ° C (Production Example 3-2) shows a peak corresponding to Si-Si bonding centered at 516.7 cm ^-1 in Raman spectroscopy, which shows an amorphous silicon thin plate Si-Si bonds at a higher temperature than that of the carbon thin film (Production Example 3-1) at 750 ° C.

Furthermore, carbon-coated silicon (Si) thin plate when the (Preparation Example 3-1, 3-2) by the carbon in the D band, G band peak shown at 1350cm ^-1 and 1580cm ^-1 at 750 ℃ and 900 ℃ It can be seen that the silicon thin plate surface is coated with carbon.

Production Example 4: Recycling of Inorganic Salt

In Production Example 2-1, NaCl in which a silicon coating layer is formed is dissolved in water, and the solution is filtered through a filter to obtain a silicon (Si) coating layer from which NaCl has been removed, followed by drying the filtered solution to obtain NaCl.

A saturated solution was prepared by dissolving in 1,388 ml of 500 g of NaCl water. Ethanol (2,776 ml) corresponding to twice the amount of water was added thereto and stirred rapidly. At this time, 133 g of NaCl was precipitated and obtained through the filter, and 362 g of NaCl was passed through the filter while being dissolved in water. The solution passed through the filter was dried again to obtain NaCl particles. At the same time, saturated salt water was prepared at room temperature. Two times of ethanol was added to the volume of the water to be added, and NaCl was precipitated and filtered and dried repeatedly. On average, during the recycling process, there may be a loss of about 1.2%.

If the non-solvent such as ethanol is added to the solution after filtration, the NaCl precipitates in the initial state again. In this case, however, the NaCl precipitate may not be saturated and the uniformity of the precipitated NaCl particle is lowered. Therefore, it is possible to produce NaCl having a uniform particle size by sufficiently drying the filtered solution to obtain NaCl, and then forming a saturated solution and precipitating again as a non-solvent.

Evaluation Example 4-1: Recycling rate of inorganic salt

The inorganic salt was recycled by using NaCl as an inorganic salt by the method of Production Example 4, and the results as shown in Table 1 were obtained.

salt is the amount of salt precipitated, solution is the amount remaining in salt water without precipitation, and loss is experimentally lost amount. The amount of salt and solution can be recycled, which is represented by sum, and is represented by recycling rate (%) and loss rate (loss (%))

No. Recyclability (%) loss (%) salt solution sum One 26.6 72.4 99.0 1.0 2 27.8 70.2 98.0 2.0 3 23.9 75.5 99.4 0.6 4 21.4 77.6 99.0 1.0 5 30.7 67.6 98.3 1.6 6 27.5 72.2 99.7 0.2 7 31.8 66.9 98.7 1.3 8 26.6 71.9 98.5 1.6 9 30.2 67.7 97.9 2.1 10 29.6 69.7 99.3 0.7 Avg. 27.6 71.2 98.8 1.2

Preparation and Evaluation of Coin Cells Containing Silicon Thin Plate

Production Example 5: Production of Coin Cell

A coin cell was prepared by the following method.

The silicon thin plate having thicknesses of 50, 100, 150, and 380 nm synthesized in Preparation Example 2-1 was coated with a carbon layer according to Production Example 3-2 to be used as a negative electrode material for a lithium secondary battery. A negative electrode slurry is prepared by dispersing 80 wt% of the active material, 10 wt% of the binder (PAA / CMC, 1/1, weight ratio) and 10 wt% of the conductive material (super-P) in water. Lithium metal was used as a counter electrode, a polyethylene separator was interposed between the cathode and the counter electrode, and a mixed solvent of ethylene carbonate and dimethyl carbonate (EC / DEC, 3/7 by volume) in which 1.3 M LiPF ₆ was dissolved was used as an electrolytic solution Thereby producing a coin cell.

Evaluation Example 5-1: First charge / discharge experiment by thickness of silicon (Si) thin plate

9 is a graph showing the first charge / discharge with respect to the thickness of the silicon (Si) thin plate.

The first charge / discharge test was carried out with the coin cell manufactured in Production Example 5. At this time, the charge / discharge rate was fixed to 0.05C-rate, and the operating voltage was set to 0.005V to 1.5V.

Charging capacity (mAh / g) Discharge capacity (mAh / g) Initial efficiency (%) 50nm 2410.8 2169.9 90.0 100 nm 2255.6 2082.4 92.3 150 nm 2315.0 2064.8 89.2 380 nm 2331.1 1078.7 46.3

Evaluation Example 5-2: Charge / discharge life characteristic test by thickness of silicon (Si) thin plate

FIG. 10 shows the result of the first cycle charging / discharging test through Evaluation Example 5-1 with the coin cell made in Production Example 5, and then the evaluation of the life cycle of 50 cycles in Evaluation Example 5-2. The charge / discharge rate is 0.2C-rate, and the operating voltage is 0.01V-1.2V.

The thicker the thickness of the silicon thin plate, the better the lifetime characteristics. This is because the thick thin plate repeatedly expands and shrinks in volume during the cycle, and is desorbed from the electrode.

Evaluation Example 5-3: Capacity Experiment According to Charge / Discharge Rate of Thin Silicon (Si) Thickness

FIG. 11 is a graph of a capacity according to charge / discharge speed of a silicon (Si) thin plate.

After the first charging / discharging was carried out through the coin cell evaluation example 5-1 made in the production example 5, the rate characteristics of the battery were confirmed in the evaluation example 5-3.

The charge / discharge rate is 0.2C-rate, and the cell is stabilized by 10 cycles. The discharge rate is adjusted to 0.5, 1, 3, 5, 7, 10, and 20C- And checked again to return to 0.2C-rate.

At this time, the thinner the thickness, the better the speed-rate characteristic, and it can be seen that the efficiency is better when the thin sheet is rapidly charged / discharged.

Evaluation Example 5-4: Thickness measurement after 0, 1, 10, 50, 100 cycles of electrode plates of silicon (Si) thin plate having thickness of 50 nm and 100 nm

In order to measure the electrode thickness in the charging / discharging evaluation conducted in Evaluation Example 5-2, the coin cell was disassembled to calculate the volume expansion rate of the electrode in the discharge state after 0, 1, 10, 50, and 100 cycle charge / discharge.

12 is a graph showing the thicknesses of the electrodes after 0, 1, 10, 50, and 100 cycles of an electrode plate of a silicon (Si) thin plate having a thickness of 50 nm and a thickness of 100 nm.

The electrodes of silicon foil with a thickness of 50 nm swelled 1%, 2.4%, 27.3%, and 49.3% after 1, 10, 50, and 100 cycles charge / discharge respectively.

In the case of the electrode of thin silicon plate having a thickness of 100 nm, it expanded by 1%, 12.5%, 47.3%, and 68.3% after 1, 10, 50 and 100 cycles charge / discharge respectively.

Based on the above results, it can be seen that the thinner the thickness of the silicon thin plate, the lower the volume expansion rate of the silicon electrode.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

30: Lithium battery
22: cathode
23: anode
24: Separator
25: Battery container
26:

Claims (30)

A silicon (Si) thin plate having a thickness of 500 nm or less and a specific surface area of 15 m ² / g or less.
The method according to claim 1,
The above-
And a width and a length of 500 nm to 5 mm, respectively,
Silicon (Si) foil.
The method according to claim 1,
The thin silicon (Si)
And the aspect ratio of the transverse length / thickness is 1 to 500,000.
Silicon (Si) foil.
The method according to claim 1,
The thin silicon (Si)
Lt; RTI ID = 0.0 &gt; amorphous &lt; / RTI &
Silicon (Si) foil.
The method according to claim 1,
The thin silicon (Si)
And the volume expansion of the electrode plate after 100 cycles is 80% or less.
Silicon (Si) foil.
The method according to claim 1,
The thin silicon (Si)
And further comprising a carbon coating layer on the silicon (Si) thin plate.
Silicon (Si) foil.
The method according to claim 6,
The thickness of the carbon coating layer formed on the silicon (Si)
1 nm to 10 nm.
Silicon (Si) foil.
Preparing a solid inorganic salt;
Forming a silicon (Si) coating layer on the surface of the solid inorganic salt;
Dissolving the inorganic salt in which the silicon (Si) coating layer is formed in a solvent; And
Obtaining a silicon (Si) thin sheet from which the inorganic salt has been dissolved and removed;
(Si). &Lt; / RTI &gt;
9. The method of claim 8,
The solvent is water,
Wherein the solid phase inorganic salt has a solubility of 0.1 g / ml to 10 g / ml at room temperature with respect to water.
9. The method of claim 8,
The cations in the inorganic salt of the solid phase,
Aluminum, barium, cadmium, cesium, calcium, cerium, cobalt, indium, iron, lithium, Magnesium, manganese, neodymium, nickel, potassium, radium, rubidium, samarium, sodium, strontium, Yttrium, or Zinc,
The anion in the solid inorganic salt may be,
It can be used in the form of Bromide, Carbonate, Chloride, Chromate, Cyanide, Fluoride, Hydroxide, Iodide, Molybdate, Wherein the substrate is an oxide, a sulfate, or a sulfate.
9. The method of claim 8,
Forming a silicon (Si) coating layer on the surface of the solid inorganic salt;
Wherein the heat treatment is performed using chemical vapor deposition (CVD).
12. The method of claim 11,
The silicon precursor used for the chemical vapor deposition (CVD)
(SiH ₄ ), disilane (Si ₂ H ₆ ), silicon tetrachloride (SiCl ₄ ), trichlorosilane (HSiCl ₃ ), dichlorosilane (H ₂ SiCl ₂ ), chlorosilane (H ₃ SiCl) &Lt; RTI ID = 0.0 &gt; (Si) &lt; / RTI &gt;
12. The method of claim 11,
Forming a silicon (Si) coating layer on the surface of the solid inorganic salt,
Wherein the heat treatment is performed by chemical vapor deposition for 1 to 120 minutes.
12. The method of claim 11,
Forming a silicon (Si) coating layer on the surface of the solid inorganic salt,
Wherein the heat treatment is performed by chemical vapor deposition at a temperature ranging from 300 ° C to 1000 ° C.
9. The method of claim 8,
Forming a silicon (Si) coating layer on the surface of the solid inorganic salt;
Wherein a sputtering method is used.
9. The method of claim 8,
(Si) thin sheet obtained by dissolving the inorganic salt to obtain a thin plate-like silicon,
(Si) coating layer on the surface of the solid inorganic salt is controlled to be amorphous or crystalline depending on the reaction temperature.
9. The method of claim 8,
Wherein the silicon obtained is amorphous when the reaction temperature of the step of forming a silicon (Si) coating layer on the surface of the solid inorganic salt is less than 700 캜.
9. The method of claim 8,
Wherein the silicon obtained is crystalline when the reaction temperature of forming the silicon (Si) coating layer on the surface of the solid inorganic salt is 700 ° C or higher.
9. The method of claim 8,
Dissolving the inorganic salt in which the silicon (Si) coating layer is formed in a solvent; And obtaining a silicon (Si) thin plate from which the inorganic salt is dissolved and removed,
And recycling the inorganic salt in the solution in which the inorganic salt is dissolved to recycle the inorganic salt.
20. The method of claim 19,
Recycling the inorganic salt in the solution in which the inorganic salt is dissolved to recycle
Wherein the inorganic salt is recrystallized using at least one non-solvent.
20. The method of claim 19,
Recycling the inorganic salt in the solution in which the inorganic salt is dissolved to recycle
Wherein the recycling ratio of the inorganic salt is 90% or more.
A method of manufacturing a silicon (Si) thin plate.
9. The method of claim 8,
Preparing the solid inorganic salt,
And adjusting the particle size of the inorganic salt.
23. The method of claim 22,
Wherein the step of adjusting the particle size of the inorganic salt comprises:
Wherein the particle size of the inorganic salt is controlled by any one method selected from pulverization, recrystallization by a solvent evaporator, recrystallization by heat treatment, ball milling and recrystallization by non-solvent.
A method of manufacturing a silicon (Si) thin plate.
9. The method of claim 8,
Dissolving the inorganic salt in which the silicon (Si) coating layer is formed in a solvent; And obtaining a silicon (Si) thin plate from which the inorganic salt is dissolved and removed,
And forming a carbon coating layer on the surface of the silicon (Si) thin plate.
25. The method of claim 24,
Forming a carbon coating layer on the silicon (Si) thin plate surface;
Wherein the heat treatment is performed at a temperature of 700 캜 to 1000 캜.
25. The method of claim 24,
Forming a carbon coating layer on the silicon (Si) thin plate surface;
Wherein the heat treatment is performed under the condition that a gas containing carbon is present.
27. The method of claim 26,
The gas containing carbon
A method of producing a thin silicon (Si) sheet according to any one of the preceding claims, wherein the substrate is any one selected from acetylene (C ₂ H ₂ ), ethylene (C ₂ H ₄ ), ethane (C ₂ H ₆ ), and toluene.
25. The method of claim 24,
Forming a carbon coating layer on the surface of the silicon (Si) thin plate;
And a thickness of 1 nm to 10 nm.
9. The method of claim 8,
Obtaining a silicon (Si) thin sheet from which the inorganic salt has been dissolved to remove;
Wherein the inorganic salt has been removed.
A method of manufacturing a silicon (Si) thin plate.
A negative electrode comprising a negative electrode active material comprising a thin silicon plate according to any one of claims 1 to 7,
Anode and
An electrolyte positioned between the cathode and the anode;
&Lt; / RTI &gt;

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