WO2018203731A1 - Negative electrode active material, negative electrode comprising negative electrode active material, secondary battery comprising negative electrode, and method for preparing negative electrode active material - Google Patents

Abstract

The present invention relates to a method for preparing a negative electrode active material, the method comprising the steps of: preparing a silicon-based compound containing SiOx (0.5<x<1.3); disposing a polymer layer containing a polymer compound on the silicon-based compound; disposing a metal catalyst layer on the polymer layer; heat-treating the silicon-based compound on which the polymer layer and the metal catalyst layer have been disposed; and removing the metal catalyst layer, wherein the polymer compound is any one selected from the group consisting of glucose, fructose, galactose, maltose, lactose, sucrose, a phenol-based resin, a naphthalene resin, a polyvinyl alcohol resin, a urethane resin, a polyimide, a furan resin, a cellulose resin, an epoxy resin, a polystyrene resin, a resorcinol-based resin, a phloroglucinol-based resin, a coal-based pitch, a petroleum-based pitch, and tar, or a mixture of two or more thereof.

Description

A negative electrode active material, a negative electrode including the negative electrode active material, a secondary battery including the negative electrode and a method of manufacturing the negative electrode active material

Citation with Related Applications

This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0057050 filed May 4, 2017 and Korean Patent Application No. 10-2018-0051920 filed May 4, 2018, and All content disclosed in the literature of a Korean patent application is included as part of this specification.

Field of technology

The present invention relates to a negative electrode active material, a negative electrode including the negative electrode active material, a secondary battery including the negative electrode and a method of manufacturing the negative electrode active material, specifically, the method of manufacturing the negative electrode active material is SiO _x (0.5 <x <1.3) Preparing a silicon-based compound comprising a; Disposing a polymer layer including a polymer compound on the silicon compound; Disposing a metal catalyst layer on the polymer layer; And heat treating the silicon-based compound having the polymer layer and the metal catalyst layer disposed thereon.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing, and the most actively researched fields are power generation and storage using electrochemical reactions.

A representative example of an electrochemical device using such electrochemical energy is a secondary battery, and its use area is gradually increasing. Recently, as the development and demand of portable devices such as portable computers, portable telephones, cameras, and the like, the demand for secondary batteries is rapidly increasing, and among such secondary batteries, high energy density, that is, high capacity lithium secondary batteries Much research has been done on the market and commercialized and widely used.

Generally, a secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material for inserting and detaching lithium ions from the positive electrode, and a silicon-based active material having a large discharge capacity may be used as the negative electrode active material. However, since the silicon-based active material is accompanied with excessive shrinkage and expansion during charging and discharging of the battery, the conductive path in the active material is blocked, thereby deteriorating cycle characteristics of the battery.

In order to solve this problem, conventionally, a carbon coating layer was formed on the surface of the silicon-based active material (see Korean Patent Publication No. 10-2016-0149862). Further, there is an attempt to further improve conductivity by allowing the carbon coating layer to include graphene. In order to arrange the graphene on the surface of the silicon-based active material, conventional chemical vapor deposition (CVD) is mainly used, but this process cannot be simplified because a separate hydrocarbon source must be used.

Accordingly, there is a need for a simplified process for disposing a carbon coating layer including graphene on the surface of a silicon-based active material.

[Preceding technical literature]

[Patent Documents]

Republic of Korea Patent Publication No. 10-2016-0149862

One problem to be solved by the present invention is to provide a method of manufacturing a negative electrode active material that can simplify the process of forming a carbon coating layer containing graphene on the surface of the silicon-based active material.

Another object of the present invention is to provide a negative electrode active material, a negative electrode, and a secondary battery capable of controlling excessive volume change of the negative electrode active material during charge and discharge of the battery.

According to one embodiment of the invention, preparing a silicon-based compound comprising SiO _x (0.5 <x <1.3); Disposing a polymer layer including a polymer compound on the silicon compound; Disposing a metal catalyst layer on the polymer layer; Heat-treating the silicon compound on which the polymer layer and the metal catalyst layer are disposed; And removing the metal catalyst layer, wherein the polymer compound is glucose, fructose, galactose, maltose, lactose, sucrose, phenolic resin, naphthalene resin, polyvinyl alcohol resin, urethane resin, polyimide, furan resin , Cellulose resin, epoxy resin, polystyrene resin, resorcinol-based resin, phloroglucinol-based resin, coal-based pitch, petroleum-based pitch and tar, any one selected from the group consisting of or a mixture of two or more thereof This is provided.

According to another embodiment of the present invention, a silicon-based compound including SiO _x (0.5 <x <1.3); An amorphous carbon layer disposed on the silicon compound; A graphene layer disposed on the amorphous carbon layer; And a negative electrode active material including a pore layer corresponding to a spaced space between the amorphous carbon layer and the graphene layer, a negative electrode including the negative electrode active material, and a secondary battery including the negative electrode.

The manufacturing method of the negative electrode active material according to an embodiment of the present invention does not require a separate CVD process for supplying a carbon raw material when manufacturing the graphene layer. In addition, since the amorphous carbon layer and the graphene layer may be formed while the polymer layer and the metal catalyst layer are heat treated, the process may be simplified.

According to the negative electrode active material according to another embodiment of the present invention, the internal stress may be alleviated when the battery is charged and discharged by the pore layer in the negative electrode active material. Accordingly, structure collapse of the negative electrode is suppressed, and the conductive path in the negative electrode active material can be maintained, so that the cycle characteristics of the battery can be improved.

Hereinafter, the present invention will be described in more detail to aid in understanding the present invention.

The terms or words used in this specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

As used herein, the terms "comprise", "comprise" or "have" are intended to indicate that there is a feature, number, step, component, or combination thereof, that is, one or more other features, It should be understood that it does not exclude in advance the possibility of the presence or addition of numbers, steps, components, or combinations thereof.

In the present specification, the thickness of the amorphous carbon layer, the graphene layer, the polymer layer, the metal catalyst layer, etc. may be confirmed through a transmission electron microscope (TEM).

Method of manufacturing a negative electrode active material according to an embodiment of the present invention comprises the steps of preparing a silicon-based compound comprising SiO _x (0.5 <x <1.3); Disposing a polymer layer including a polymer compound on the silicon compound; Disposing a metal catalyst layer on the polymer layer; Heat-treating the silicon compound on which the polymer layer and the metal catalyst layer are disposed; And removing the metal catalyst layer, wherein the polymer compound is glucose, fructose, galactose, maltose, lactose, sucrose, phenolic resin, naphthalene resin, polyvinyl alcohol resin, urethane resin, polyimide, furan resin , Cellulose resin, epoxy resin, polystyrene resin, resorcinol-based resin, phloroglucinol-based resin, coal-based pitch, petroleum-based pitch and tar, any one selected from the group consisting of or a mixture of two or more thereof.

The silicon-based compound may include SiO _x (0.5 <x <1.3). Preparing the silicon-based compound may include reacting the SiO _x1 (0 <x1 <2) with a metal. The _{SiO x1 (0 <x1 <2} ) may be in the form containing the Si and SiO _2. That is, x and x1 correspond to the number ratio of O to Si contained in the SiO _x (0.5 <x <1.3) or the SiO _x1 (0 <x1 <2), respectively.

The silicon-based compound may further include a metal silicate. Specifically, the metal silicate may be doped into the SiO _x (0.5 <x <1.3) through reacting the SiO _x1 (0 <x1 <2) with a metal. The metal silicate may be located inside the silicon-based compound.

The metal silicate may be present in a doped state in the SiO _x (0.5 <x <1.3). The metal silicate includes at least one selected from the group consisting of Li ₂ Si ₂ O ₅ , Li ₃ SiO ₃ , Li ₄ SiO ₄ , Mg ₂ SiO ₄ , MgSiO ₃ , Ca ₂ SiO ₄ , CaSiO ₃ , and TiSiO ₄ . It may include.

The metal of the metal silicate may be included in an amount of 1 to 30 parts by weight, and specifically 2 to 20 parts by weight, based on 100 parts by weight of SiO _x (0.5 <x <1.3). When the above range is satisfied, the growth of Si grains can be suppressed and the initial efficiency can be improved.

The _{SiO x1 (0 <x1 <2} ) with reaction with the metal may be one of a metallic powder or a metallic gas and a reaction containing the metal to _{SiO x1 (0 <x1 <2} ).

The metal may be at least one selected from the group consisting of Li, Mg, Ti, and Ca, and specifically, Li and Mg. The reaction may be performed at 300 ° C. to 1000 ° C. for 1 hour to 24 hours.

The reaction may be performed while flowing an inert gas. The inert gas may be at least one selected from the group consisting of Ar, N ₂ , Ne, He, and Kr.

The preparing of the silicon-based compound may further include removing a part of the metal silicate generated during the reaction with the metal. Specifically, preparing the silicon-based compound may include removing metal silicates disposed on a surface of the silicon-based compound of the metal silicates generated during the reaction with the metal. The metal silicate can be removed using an aqueous HCl solution.

The average particle diameter (D ₅₀ ) of the silicon compound may be 0.1 μm to 20 μm, and specifically 0.5 μm to 10 μm. When the average particle diameter of the silicon compound satisfies the above range, the rate rate of the battery may be improved.

Although not necessarily limited thereto, disposing a polymer layer including a polymer compound on the silicon-based compound may include a general method. For example, the polymer layer may be thermally cured after applying the polymer compound on the silicon-based compound, or heat-treated after the carbon-containing material is applied on the silicon-based compound to form the polymer layer. More specifically, for example, when the polymer layer includes polyimide, polyacrylic acid (PAA) may be coated on the silicon compound, followed by heat treatment to form the polymer layer.

The polymer compound is glucose, fructose, galactose, maltose, lactose, sucrose, phenolic resin, naphthalene resin, polyvinyl alcohol resin, urethane resin, polyimide, furan resin, cellulose resin, epoxy resin, polystyrene resin, resorcy It may be any one selected from the group consisting of nol resin, phloroglucinol resin, coal-based pitch, petroleum-based pitch and tar, or a mixture of two or more thereof, and specifically, may be polyimide.

The polymer layer may have a thickness of 0.001 μm to 10 μm, and specifically 0.01 μm to 5 μm. If the thickness range is satisfied, a sufficient carbon source can be supplied, so that the graphene layer can be formed continuously and uniformly.

Although not necessarily limited thereto, the disposing a metal catalyst layer on the polymer layer may include the following method.

The silicon-based compound on which the polymer layer is formed may be added to a solution containing a metal salt, and then a metal catalyst layer may be disposed on the polymer layer by using an electroless plating method of adding and stirring a reducing agent.

The metal catalyst layer may include at least one selected from the group consisting of Ni, Cu, Fe, Cu, and Co, and specifically, may include Ni.

The metal catalyst layer may have a thickness of 0.001 μm to 10 μm, and specifically 0.01 μm to 5 μm. When the thickness range is satisfied, the graphene layer having high crystallinity may be continuously and uniformly formed.

In the disposing of the metal catalyst layer on the polymer layer, the weight ratio of the polymer layer and the metal catalyst layer may be 1: 1 to 20: 1, and specifically 2: 1 to 10: 1. When the weight ratio range is satisfied, the graphene layer may be formed continuously and uniformly.

The polymer layer may be carbonized through the heat treatment of the silicon-based compound in which the polymer layer and the metal catalyst layer are disposed. Accordingly, an amorphous carbon layer may be formed on the silicon compound. At the same time, a carbon source generated from a polymer layer may be supplied to the metal catalyst layer to form a graphene layer. The heat treatment may be carried out at 300 ℃ to 1000 ℃, specifically 450 ℃ to 900 ℃. When the heat treatment range is satisfied, the graphene layer having high crystallinity may be formed while silicon grain growth is suppressed. The heat treatment may be performed for 0.5 minutes to 1 hour.

Although not necessarily limited thereto, the removing of the metal catalyst layer may include the following method.

The silicon-based compound having the metal catalyst layer formed in the acidic solution may be added, and then etched and dried for a predetermined time to remove the metal catalyst layer.

By removing the metal catalyst layer, a pore layer corresponding to a spaced space between the amorphous carbon layer and the metal catalyst layer may be formed. Accordingly, since the volume of the negative electrode active material may be prevented from being excessively changed during charging and discharging of the battery, a conductive path in the negative electrode active material may be secured, thereby improving cycle characteristics.

A negative active material according to another embodiment of the present invention, a silicon-based compound containing SiO _x (0.5 <x <1.3); An amorphous carbon layer disposed on the silicon compound; A graphene layer disposed on the amorphous carbon layer; And a pore layer corresponding to a spaced space between the amorphous carbon layer and the graphene layer. Here, the silicon-based compound including SiO _x (0.5 <x <1.3) is the same as described above, and thus description thereof is omitted.

The amorphous carbon layer may be disposed on the silicon compound. The amorphous carbon layer may include amorphous carbon, and specifically, may be made of amorphous carbon. By the amorphous carbon layer, the rate (rate) characteristics of the battery can be improved.

The amorphous carbon layer may have a thickness of 0.001 μm to 10 μm, and specifically 0.01 μm to 5 μm. When the thickness range is satisfied, it is possible to manufacture a battery having excellent rate characteristics without reducing the initial efficiency.

The graphene layer may be disposed on the amorphous carbon layer. The graphene layer may include graphene, and specifically, may be made of graphene. In the present invention, graphene means a carbonaceous structure having a thickness of 0.2 nm or less, including carbon atoms constituting a hexagonal lattice, having flexibility, and having a thin film form. By the graphene layer, since the volume expansion of the silicon-based compound can be controlled during charge and discharge, the conductive path (block) can be prevented from being blocked to improve the cycle characteristics of the battery.

The graphene layer may have a thickness of 0.5 nm to 200 nm, and specifically 1 nm to 100 nm. If the thickness range is satisfied, the cycle characteristics of the battery may be improved.

The amorphous carbon layer and the graphene layer may be formed by carbonizing the above-described polymer layer.

The pore layer may be located between the amorphous carbon layer and the graphene layer. Specifically, the pore layer corresponds to a spaced space between the amorphous carbon layer and the graphene layer. The void layer may be one spaced space or two or more spaced spaces. That is, the pore layer may exist on at least a portion of the surface of the amorphous carbon layer, and in the case of two or more spaced spaces, they may be scattered on the surface of the amorphous carbon layer. The pore layer is not formed only by removing the metal catalyst layer. Specifically, the pore layer may be implemented because the polymer layer is contracted while being carbonized (pyrolyzed) by the heat treatment. That is, after the polymer layer and the metal catalyst layer are sequentially formed according to the manufacturing method of the present invention, the heat treatment proceeds, so that the pore layer may be formed. The pore layer may play a role of alleviating internal stress caused by a change in volume of the silicon-based compound during charge and discharge of the battery, thereby maintaining a conductive path of the negative electrode active material.

The average thickness of the pore layer may be 0.5nm to 200nm, specifically, may be 100nm to 200nm. When the thickness is satisfied, a sufficient area for alleviating the internal stress caused by the volume change of the silicon-based compound during charge and discharge of the battery is secured, so that the conductive path of the negative electrode active material can be more smoothly maintained.

The negative electrode according to another embodiment of the present invention may include a negative electrode active material, wherein the negative electrode active material is the same as the negative electrode active material described above. Specifically, the negative electrode may include a current collector and a negative electrode active material layer disposed on the current collector. The negative electrode active material layer may include the negative electrode active material. Furthermore, the negative electrode active material layer may further include a binder and / or a conductive material. In addition, the negative electrode may further include graphite particles, and the graphite particles may be included in the negative electrode active material layer.

The binder is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (polyvinylidene fluoride (PVDF)), polyacrylonitrile, polymethylmethacrylate (polymethylmethacrylate) , Polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM) , Sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, poly acrylic acid (poly acrylic acid) and hydrogen may be included at least one selected from the group consisting of substances substituted with Li, Na or Ca and the like. And also various copolymers thereof.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, farnes black, lamp black and thermal black; Conductive fibers such as carbon fibers and metal fibers; Conductive tubes such as carbon nanotubes; Metal powders such as fluorocarbon, aluminum and nickel powders; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The graphite-based active material particles may be at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesocarbon microbeads. By using the graphite active material particles together with the secondary particles, the charge and discharge characteristics of the battery can be improved.

A secondary battery according to another embodiment of the present invention may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the negative electrode is the same as the negative electrode described above. Since the cathode has been described above, a detailed description thereof will be omitted.

The positive electrode may include a positive electrode active material. The cathode active material may be a cathode active material that is commonly used. Specifically, the cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + y 1} Mn _{2-y 1} O ₄ (0 ≦ _{y 1} ≦ 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , V ₂ O ₅ , Cu ₂ V ₂ O _7, and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _1-y2 M _y2 O ₂ , wherein M is Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and satisfies 0.01 ≦ y2 ≦ 0.3; LiMn _2-y3 M _y3 O ₂ , wherein M is Co, Ni, Fe, Cr, Zn or Ta, and satisfies 0.01 ≦ y3 ≦ 0.1; or Li ₂ Mn ₃ MO ₈ , wherein M is Fe, Lithium manganese composite oxide represented by Co, Ni, Cu, or Zn .; LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions, etc. may be mentioned, but is not limited thereto. The anode may be Li-metal.

The separator separates the negative electrode from the positive electrode and provides a passage for lithium ions, and can be used without particular limitation as long as the separator is used as a separator in a secondary battery. In particular, it has a low resistance to ion migration of the electrolyte and an excellent ability to hydrate the electrolyte. It is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer or the like Laminate structures of two or more layers may be used. In addition, conventional porous nonwoven fabrics such as nonwoven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers and the like may be used. In addition, a coated separator including a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be optionally used as a single layer or a multilayer structure.

The electrolyte may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like, which can be used in manufacturing a lithium secondary battery, but are not limited thereto.

Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

As the non-aqueous organic solvent, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butylo lactone, 1,2-dime Methoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolon, formamide, dimethylformamide, dioxoron, acetonitrile, nitromethane, methyl formate, Methyl acetate, phosphate triester, trimethoxy methane, dioxorone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, pyrion An aprotic organic solvent such as methyl acid or ethyl propionate can be used.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, may be preferably used as high-viscosity organic solvents because they have high dielectric constants to dissociate lithium salts well, such as dimethyl carbonate and diethyl carbonate. When the same low viscosity, low dielectric constant linear carbonate is mixed and used in an appropriate ratio, an electrolyte having a high electrical conductivity can be made, and thus it can be more preferably used.

The metal salt may be a lithium salt, the lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, is in the lithium salt anion ^{F -, Cl -, I -} , NO 3 -, N (CN _{^{) 2 -, BF 4 -,}} ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF - ^{_{, (CF 3) 6 P -}} , CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 _{^{CO -, (CF 3 SO 2}} ) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO ₂ ^-, SCN ^- can be used at least one member selected from the group consisting of ^- and _{(CF 3 CF 2 SO 2)} 2 N.

In addition to the electrolyte components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoro ethylene carbonate, pyridine, tri, etc. for the purpose of improving battery life characteristics, reducing battery capacity, and improving discharge capacity of the battery. Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imida One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol or aluminum trichloride may be included.

According to another embodiment of the present invention, a battery module including the secondary battery as a unit cell and a battery pack including the same are provided. Since the battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and cycle characteristics, a medium-large device selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system It can be used as a power source.

Hereinafter, preferred embodiments are provided to aid in understanding the present invention, but the above embodiments are merely illustrative of the present disclosure, and it is apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present disclosure. It is natural that such variations and modifications fall within the scope of the appended claims.

Examples and Comparative Examples

Preparation Example 1 Preparation of Silicon Compound

After mixing 20 g of SiO powder and 2 g of metal lithium powder were accommodated in a reaction vessel of a chamber, the temperature of the chamber was then raised to 800 ° C. At this time, Ar was used as the inert gas. Thereafter, after the heat treatment for 2 hours, the chamber temperature was reduced to room temperature to collect the product in the reaction vessel. The collected product was acid treated with HCl. Thereafter, the acid-treated product was milled to have an average particle diameter (D ₅₀ ) of 5 μm to prepare a silicon compound. As measured by XRD, the silicon-based compound includes Li ₂ Si ₂ O ₅ and Li ₂ SiO ₃ , which are metal silicates, and lithium of Li ₂ Si ₂ O ₅ and Li ₂ SiO ₃ is 100 weight of the silicon-based compound. It was confirmed that the total amount included 5 parts by weight.

Example 1 Preparation of Anode Active Material

(1) polymer layer formation

The silicon compound of Preparation Example 1 was added to a dimethylacetamide (DMAC) solution containing poly acrylic acid (PAA), and stirred for 1 hour in a reducing atmosphere. At this time, Ar gas was used for formation of a reducing atmosphere. Thereafter, the silicon-based compound was extracted through centrifugation, and then PAA-coated silicon-based compound was obtained by vacuum drying. The PAA-coated silicon-based compound was imidized by heat treatment at 300 ° C. for 60 minutes in a reducing atmosphere to form a polyimide layer having a thickness of 1 μm on the silicon-based compound.

(2) Formation of Metal Catalyst Layer

The silicon compound on which the polyimide layer was formed was introduced into an aqueous potassium hydroxide (KOH) solution at 50 ° C., followed by stirring for 10 minutes. Thereafter, the silicon compound was extracted by centrifugation. The extracted silicon compound was added to a nickel sulfate (Ni ₂ SO ₄ ) aqueous solution, stirred for 10 minutes, and then rinsed. Thereafter, the silicon compound was added to an aqueous borohydride solution at 50 ° C., and stirred for 30 minutes to prepare particles having a nickel catalyst layer having a thickness of 100 nm formed on the polyimide layer.

(3) heat treatment

The particles were introduced into a tube furnace and heat-treated at 600 ° C. for 10 minutes in a reducing atmosphere to form an amorphous carbon layer from the polyimide layer; And a graphene layer disposed on the nickel catalyst layer and including a plurality of graphenes. At this time, Ar gas was used for the reducing atmosphere. The amorphous carbon layer had a thickness of 300 nm and the graphene layer had a thickness of 50 nm.

(4) removal of the metal catalyst layer

The silicon-based compound having the amorphous carbon layer and the graphene layer formed on the surface of the 1M FeCl ₃ aqueous solution was etched for 2 hours, and then dried with ethanol to remove the nickel catalyst layer. As the nickel catalyst layer was removed, a gap layer corresponding to a space in which the amorphous carbon layer and the graphene layer were spaced apart from each other was formed between the amorphous carbon layer and the graphene layer. The thickness of the pore layer was 100 nm to 200 nm.

Example 2: Preparation of Anode Active Material

A negative electrode active material of Example 2 was prepared in the same manner as in Example 1, except that the nickel catalyst layer was formed to have a thickness of 50 nm. The thickness of the amorphous carbon layer in the prepared negative active material was 150nm, the thickness of the graphene layer was 25nm. In addition, the thickness of the said void layer was 50 nm or more and less than 100 nm.

Comparative Example 1: Preparation of Anode Active Material

(1) amorphous carbon layer formation

100 g of the silicon compound of Preparation Example 1 and 7 g of coal tar pitch were mixed and then heat treated at 950 ° C. to form a negative electrode active material having an amorphous carbon layer having a thickness of 300 nm disposed on the surface of the silicon compound.

Comparative Example 2: Preparation of Anode Active Material

(1) amorphous carbon layer formation

After mixing 100 g of the silicon-based compound of Preparation Example 1 and 7 g of coal tar pitch, and heat treatment at 950 ° C, an amorphous carbon layer having a thickness of 300 nm was formed on the surface of the silicon-based compound.

(2) crystalline carbon layer formation

Specifically, the silicon compound in which the amorphous carbon layer is disposed was placed in a reaction vessel of a chamber, and the temperature of the chamber was raised to 950 ° C. At this time, the atmospheric pressure of the chamber was maintained at 10 mTorr using a rotary pump. Thereafter, after injecting methane gas for 5 minutes, the temperature of the chamber was reduced to room temperature. Thereafter, the product in the reaction vessel was collected to form a crystalline carbon layer having a thickness of 50 nm on the amorphous carbon layer. There was no spaced space between the amorphous carbon layer and the crystalline carbon layer.

Comparative Example 3: Preparation of Anode Active Material

(1) amorphous carbon layer formation

After mixing 100 g of the silicon-based compound of Preparation Example 1 and 7 g of coal tar pitch, and heat treatment at 950 ° C, an amorphous carbon layer having a thickness of 300 nm was formed on the surface of the silicon-based compound.

(2) Formation of Metal Catalyst Layer

The silicon compound on which the amorphous carbon layer was formed was added to an aqueous potassium hydroxide (KOH) solution at 50 ° C., followed by stirring for 10 minutes. Thereafter, the silicon compound was extracted by centrifugation. The extracted silicon compound was added to a nickel sulfate (Ni ₂ SO ₄ ) aqueous solution, stirred for 10 minutes, and then rinsed. Thereafter, the silicon-based compound was added to an aqueous solution of borohydride at 50 ° C., and stirred for 30 minutes to prepare particles having a nickel catalyst layer having a thickness of 100 nm formed on the amorphous carbon layer.

(3) Formation of Graphene Layer

Specifically, the silicon-based compound having the nickel catalyst layer and the amorphous carbon layer disposed on the surface thereof was placed in the reaction vessel of the chamber, and the temperature of the chamber was raised to 950 ° C. At this time, the atmospheric pressure of the chamber was maintained at 10 mTorr using a rotary pump. Thereafter, after injecting methane gas for 5 minutes, the temperature of the chamber was reduced to room temperature. Thereafter, the product in the reaction vessel was collected to form a graphene layer having a thickness of 50 nm on the amorphous carbon layer. There is no spaced space between the amorphous carbon layer and the graphene layer.

Examples 3, 4 and Comparative Examples 4, 5, 6: Preparation of Secondary Battery

Secondary batteries of Examples 3 and 4 and Comparative Examples 4, 5 and 6 were prepared using the negative electrode active materials of Examples 1 and 2 and Comparative Examples 1, 2 and 3, respectively.

Specifically, Examples 1, 2 and Comparative Examples 1, 2, and 3 each of the negative electrode active material, natural graphite, and carbon black, CMC, and styrene butadiene rubber (SBR) having an average particle diameter (D ₅₀ ) of 65 nm were 9.6: 86.2: A negative electrode slurry with a mixture solid content of 45% was prepared by adding and mixing the solvent with distilled water at 1.0: 1.7: 1.5.

Each of the negative electrode slurry was applied to a copper (Cu) metal thin film which is a negative electrode current collector having a thickness of 20 μm at a loading of 160 mg / 25 cm ² and dried. At this time, the temperature of the air circulated was 70 ℃. Subsequently, a negative electrode was prepared by rolling and applying the slurry to which the slurry was applied and dried, and drying in a vacuum oven at 130 ° C. for 8 hours.

Each of the negative electrodes was cut into 1.4875 cm ² circles to form a negative electrode, and a positive electrode was used for Li-metal. An electrolyte solution containing LiPF ₆ dissolved in a concentration of 1 M was injected into a mixed solution having a mixing volume of 7: 3 of ethyl methyl carbonate (EMC) and ethylene carbonate (EC) through a separator of porous polyethylene between the positive electrode and the negative electrode. A coin-half-cell including a metal and a negative electrode was prepared one by one.

Test Example 1: Evaluation of Capacity Retention Rate

For each of the secondary batteries of Examples 3 and 4 and Comparative Examples 4, 5 and 6, the capacity retention rate was evaluated in the following manner, and then shown in Table 1.

For each of the secondary batteries of Examples 3 and 4 and Comparative Examples 4, 5 and 6, the capacity retention rate was evaluated in the following manner, and then shown in Table 3.

One cycle was charged at 0.1 C and discharged at 0.1 C. The charge was charged at 0.5 C and discharged at 0.5 C from two cycles to 50 cycles.

Charging Conditions: CC (Constant Current) / CV (Constant Voltage) (5mV / 0.005C current cut-off)

Discharge condition: CC (constant current) condition 1.0 V

Dose retention rates were each derived by the following calculations.

Capacity retention rate (%) = (50 discharge capacity / 1 1.0V discharge capacity) × 100

	Example 3	Example 4	Comparative Example 4	Comparative Example 5	Comparative Example 6
Capacity retention	96	91	75	85	87

Referring to Table 1, in the case of the batteries of Examples 3 and 4 using the negative electrode active material prepared according to the manufacturing method of the present invention, the capacity retention rate is significantly higher than that of the battery of Comparative Example 4 using the negative electrode active material containing no graphene High. In addition, the batteries of Examples 3 and 4 have a higher capacity retention rate than the batteries of Comparative Examples 5 and 6 including the negative electrode active material prepared by a general method of sequentially forming an amorphous carbon layer and a crystalline carbon layer (or graphene layer). You can see that. This is because, in the case of the negative electrode active materials of Examples 1 and 2, the pore layer plays a role of suppressing structural collapse of the negative electrode active material and maintaining a conductive path.

Claims (15)

1. Silicon-based compounds comprising SiO _x (0.5 <x <1.3);

   An amorphous carbon layer disposed on the silicon compound;

   A graphene layer disposed on the amorphous carbon layer; And

   An anode active material comprising a pore layer corresponding to the spaced space between the amorphous carbon layer and the graphene layer.
2. The method according to claim 1,

   The anode active material has an average thickness of 0.5nm to 200nm.
3. The method according to claim 1,

   The amorphous carbon layer has a thickness of 0.001 μm to 10 μm.
4. The method according to claim 1,

   The thickness of the graphene layer is a negative electrode active material is 0.5nm to 200nm.
5. Preparing a silicon compound including SiO _x (0.5 <x <1.3);

   Disposing a polymer layer including a polymer compound on the silicon compound;

   Disposing a metal catalyst layer on the polymer layer;

   Heat-treating the silicon compound on which the polymer layer and the metal catalyst layer are disposed; And

   Removing the metal catalyst layer;

   The polymer compound is glucose, fructose, galactose, maltose, lactose, sucrose, phenolic resin, naphthalene resin, polyvinyl alcohol resin, urethane resin, polyimide, furan resin, cellulose resin, epoxy resin, polystyrene resin, resorcy A method for producing a negative electrode active material, which is any one selected from the group consisting of nol resin, fluoroglucinol resin, coal pitch, petroleum pitch and tar, or a mixture of two or more thereof.
6. The method according to claim 5,

   The silicon compound further includes a metal silicate,

   The metal silicate includes at least one selected from the group consisting of Li ₂ Si ₂ O ₅ , Li ₃ SiO ₃ , Li ₄ SiO ₄ , Mg ₂ SiO ₄ , MgSiO ₃ , Ca ₂ SiO ₄ , CaSiO ₃ , and TiSiO ₄ . The manufacturing method of the negative electrode active material containing.
7. The method according to claim 6,

   The metal of the metal silicate is 1 part by weight to 30 parts by weight with respect to 100 parts by weight of the SiO _x (0.5 <x <1.3) is a manufacturing method of the negative electrode active material.
8. The method according to claim 5,

   The polymer layer has a thickness of 0.001 μm to 10 μm.
9. The method according to claim 5,

   The metal catalyst layer is a method for producing a negative electrode active material including at least one selected from the group consisting of Ni, Cu, Fe, Cu and Co.
10. The method according to claim 5,

    The metal catalyst layer has a thickness of 0.001 μm to 10 μm.
11. The method according to claim 5,

    The weight ratio of the polymer layer and the metal catalyst layer is 1: 1 to 20: 1 method of producing a negative electrode active material.
12. The method according to claim 5,

    The heat treatment is a method for producing a negative electrode active material is performed at 300 ℃ to 1000 ℃ 0.5 minutes to 1 hour.
13. A negative electrode comprising the negative electrode active material of claim 1.
14. The method according to claim 13,

    A negative electrode further comprising graphite particles.
15. A negative electrode of claim 13;

    anode;

    A separator interposed between the anode and the cathode; And

    Secondary battery comprising an electrolyte.