阅读说明：本技术 负极活性材料、包含所述负极活性材料的负极、包含所述负极的二次电池以及所述负极活性材料的制备方法 (Negative electrode active material, negative electrode comprising the same, secondary battery comprising the same, and method for preparing the same ) 是由 金东赫 金银卿 李龙珠 赵来焕 崔静贤 于 2018-03-27 设计创作，主要内容包括：本发明涉及一种负极活性材料的制备方法,所述方法包括如下步骤：准备包含SiO<Sub>x</Sub>(0.5<x<1.3)的硅类化合物；并且使用有机金属化合物作为源,通过化学气相沉积法在所述硅类化合物上形成结晶碳涂层,其中所述有机金属化合物是选自由乙酰丙酮铝、乙醇铝、苯氧化铝、乙酸铝和丁醇铝组成的组中的至少一种。(The invention relates to a preparation method of a negative electrode active material, which comprises the following steps: preparation of a composition containing SiO x (0.5<x<1.3) of silicon-based compounds; and forming a crystalline carbon coating layer on the silicon-based compound by a chemical vapor deposition method using an organic metal compound as a source, wherein the organic metal compound is at least one selected from the group consisting of aluminum acetylacetonate, aluminum ethoxide, aluminum phenoxide, aluminum acetate, and aluminum butoxide.)

1. A method of preparing an anode active material, the method comprising:

preparation of a composition containing SiO_x0.5 of the silicon-based compound of (1)<x<1.3; and

forming a crystalline carbon coating on the silicon-based compound by a chemical vapor deposition method using an organometallic compound as a source, wherein

The organic metal compound is at least one selected from the group consisting of aluminum acetylacetonate, aluminum ethoxide, aluminum phenoxide, aluminum acetate, and aluminum butoxide.

2. The method of claim 1, wherein

The silicon compound is prepared by reacting SiO_x1With metal powder containing a metal or metal gas containing a metal, wherein 0<x1<2。

3. The method of claim 2, wherein

The metal is at least one selected from the group consisting of Li, Mg, Ti and Ca.

4. The method of claim 1, wherein

The chemical vapor deposition method includes:

vaporizing said organometallic compound, and

introducing the vaporized organometallic compound into a chamber in which the silicon based compound is disposed,

wherein the organometallic compound is introduced at a rate of 1SCCM to 50 SCCM.

5. The method of claim 4, wherein

The temperature in the chamber is 300 ℃ to 1000 ℃, and

the chemical vapor deposition process is performed for 0.5 minutes to 1 hour.

6. An anode active material comprising:

comprising SiO_x0.5 of the silicon-based compound of (1)<x<1.3; and

a crystalline carbon coating disposed on the silicon based compound and configured to contain aluminum.

7. The negative electrode active material according to claim 6, wherein

The aluminum is contained in an amount of 1 to 10 parts by weight, based on 100 parts by weight of the crystalline carbon coating layer.

8. The negative electrode active material according to claim 6, wherein

The silicon-based compound further comprises a metal silicate, and

the metal silicate comprises a metal selected from the group consisting of Li₂Si₂O₅、Li₃SiO₃、Li₄SiO₄、Mg₂SiO₄、MgSiO₃、Ca₂SiO₄、CaSiO₃And TiSiO₄At least one of the group consisting of.

9. The negative electrode active material according to claim 8, wherein

Based on 100 parts by weight of SiO_xWherein 0.5<x<1.3, the metal silicate has a metal content of 1 to 30 parts by weight.

10. The negative electrode active material according to claim 6, wherein

The crystalline carbon coating has a D/G ratio of a Raman spectrum of more than 0 to less than 1, and a 2D/G ratio of a Raman spectrum of more than 0 to less than 1.

11. The anode active material according to claim 6, wherein the crystalline carbon coating layer has a thickness of 0.01 to 1 μm.

12. The negative electrode active material according to claim 6, wherein the average particle diameter (D) of the silicon-based compound₅₀) Is 0.5 μm to 10 μm.

13. An anode containing the anode active material according to claim 6.

14. The negative electrode according to claim 13, further comprising graphite-based particles.

15. A secondary battery comprising:

the negative electrode according to claim 14;

a positive electrode;

a separator disposed between the positive electrode and the negative electrode; and

an electrolyte.

Technical Field

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of korean patent application No. 10-2017-0057049 filed in the korean intellectual property office at 5, 4, 2017, the disclosure of which is incorporated herein by reference in its entirety.

Background

As the use of fossil fuels is rapidly increasing, the demand for the use of alternative energy or clean energy is increasing, and as a part of this trend, the most active research field is the field of power generation and storage using electrochemical reactions.

Currently, a typical example of an electrochemical device using such electrochemical energy is a secondary battery, and the field of use thereof is increasing. In recent years, with the technical development and increased demand of portable devices such as portable computers, mobile phones, and cameras, the demand for secondary batteries as an energy source has increased significantly. Among these secondary batteries, lithium secondary batteries having high energy density, i.e., lithium secondary batteries having high capacity, have been studied in large quantities and also commercialized and widely used.

In general, a secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The anode contains an anode active material for intercalating and deintercalating lithium ions from the cathode, and as the anode active material, a silicon-based active material having a high discharge capacity can be used. However, the silicon-based active material has a problem in that its initial efficiency is low. In order to solve such a problem, a method of reducing a part of the silicon-based active material is used.

However, during the reduction process, silicate-based by-products are generated, which react with moisture inside or outside the manufactured secondary battery to generate gas, resulting in a problem of deterioration in the life span and stability of the secondary battery.

Therefore, the following method is used: a carbon coating layer is formed on the reduced silicon-based active material by a chemical vapor deposition method to prevent water from reacting with by-products, while the carbon coating layer is formed as a crystalline layer to improve surface conductivity of the active material. However, in order to form a crystalline carbon coating layer on the particles by a chemical vapor deposition method, a metal catalyst should be first provided on the particles. In this case, however, a step of providing a metal catalyst and a step of removing the metal catalyst after forming the crystalline carbon coating layer are required. Therefore, the process becomes complicated.

Therefore, it is required to develop a method for preparing an anode active material capable of simplifying the process by not using a separate metal catalyst in the process of forming a crystalline carbon coating layer on a silicon-based compound.

[ Prior art documents ]

[ patent document ]

(patent document 1) Korean patent laid-open publication No. 10-2008-0111809

Disclosure of Invention

Technical problem

An aspect of the present invention provides a method of preparing an anode active material capable of simplifying a process by not using a separate metal catalyst in forming a crystalline carbon coating layer on a silicon-based compound.

Another aspect of the present invention provides an anode active material, an anode, and a secondary battery capable of minimizing gas generation due to moisture.

Technical scheme

According to an aspect of the present invention, there is provided a method of preparing an anode active material, the method including: preparation of a composition containing SiO_x(0.5<x<1.3) of silicon-based compounds; forming a crystalline carbon coating on the silicon-based compound by a chemical vapor deposition method using an organic metal compound as a source, wherein the organic metal compound is at least one selected from the group consisting of aluminum acetylacetonate (aluminum acetylacetonate), aluminum ethoxide (aluminum ethoxide), aluminum phenoxide (aluminum phenoxide), aluminum acetate, and aluminum butoxide (aluminum tributoxide).

According to another aspect of the present invention, there are provided an anode active material, an anode including the anode active material, and a secondary battery including the anode, wherein the anode active material includes SiO-containing_x(0.5<x<1.3) of silicon-based compounds; and a crystalline carbon coating layer disposed on the silicon-based compound and configured to contain aluminum.

Advantageous effects

The method of preparing the anode active material according to one embodiment of the present invention may form the crystalline carbon coating layer without using a separate metal catalyst by using an organometallic compound as a CVD source when forming the crystalline carbon coating layer. Therefore, a metal catalyst deposition process, a metal catalyst removal process, and the like can be omitted, thereby simplifying the process of preparing the anode active material. In addition, the anode active material according to another embodiment of the present invention can minimize gas generation caused by a reaction of external moisture and a byproduct in the silicon-based compound by including the crystalline carbon coating layer. Accordingly, the life characteristics and stability of a secondary battery including the anode active material may be improved.

Drawings

Fig. 1 shows a raman spectrum of a carbon coating layer of an anode active material of example 3 of the present invention, and a raman spectrum of a carbon coating layer of an anode active material of comparative example 1 of the present invention.

Detailed Description

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

It should be understood that the words or terms used in the specification and claims should not be construed as meaning defined in commonly used dictionaries. It will be further understood that the words or terms should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and technical concepts of the present invention, based on the principle that the inventor may appropriately define the meaning of the words or terms in order to best explain the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. In the specification, unless otherwise indicated, terms in the singular may include the plural.

It will be further understood that the terms "comprises," "comprising," or "having," when used in this specification, specify the presence of stated features, integers, steps, elements, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, elements, or groups thereof.

The method of preparing the anode active material according to one embodiment of the present invention may be a method of preparing the anode active material, the method including: preparation of a composition containing SiO_x(0.5<x<1.3) of silicon-based compounds; make itForming a crystalline carbon coating layer on the silicon-based compound by a chemical vapor deposition method using an organic metal compound as a source, wherein the organic metal compound is at least one selected from the group consisting of aluminum acetylacetonate, aluminum ethoxide, aluminum phenoxide, aluminum acetate, and aluminum butoxide.

The silicon-based compound may comprise SiO_x(0.5<x<1.3). The preparing the silicon based compound may include reacting SiO_x1(0<x1<2) React with the metal. SiO 2_x1(0<x1<2) And SiO_x(0.5<x<1.3) may be in the form of a composition comprising Si and SiO₂In the form of (1). That is, x and x1 correspond to SiO, respectively_x(0.5<x<1.3) or SiO_x1(0<x1<2) The quantitative ratio of O to Si contained in (1).

The silicon-based compound may comprise a metal silicate. In particular, by subjecting the SiO_x1(0<x1<2) Reacting with a metal, the metal silicate may be doped into SiO_x(0.5<x<1.3). The metal silicate may be located within the silicon-based compound.

The SiO_x1(0<x1<2) The reaction with the metal may be carried out by reacting SiO_x1(0<x1<2) With a metal powder or a metal gas containing the metal.

The metal may be at least one selected from the group consisting of Li, Mg, Ti, and Ca, and may be particularly Li and Mg. The reaction may be carried out at a temperature of 300 ℃ to 1000 ℃ for 1 hour to 24 hours.

The reaction may be carried out while flowing an inert gas. The inert gas may be selected from Ar, N₂And Ne, He, and Kr.

The preparing the silicon based compound may further include removing a portion of the metal silicate generated during the reaction with the metal.

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

In the formation of the crystalline carbon coating, the chemical vapor deposition method may include vaporizing (vaporizing) the organometallic compound and introducing the vaporized organometallic compound into a chamber in which a silicon-based compound is disposed.

The organic metal compound may be at least one selected from the group consisting of aluminum acetylacetonate, aluminum ethoxide, aluminum phenoxide, aluminum acetate, and aluminum butoxide.

Generally, in order to form a crystalline carbon coating on particles by a chemical vapor deposition method, a metal catalyst should be first provided on the particles. In this case, however, a step of providing the metal catalyst and a step of removing the metal catalyst after forming the crystalline carbon coating layer are required. This complicates the process. On the other hand, when the crystalline carbon coating layer is formed according to one embodiment of the present invention, in the case of using an organometallic compound as a CVD source, the crystalline carbon coating layer may be formed without using a separate metal catalyst. Specifically, the metal component of the organometallic compound may be used as a catalyst, and the carbon component of the organometallic compound may be used as a carbon source. Therefore, the metal catalyst deposition step and the metal catalyst removal step can be omitted.

This can simplify the process.

The rate of introduction of the organometallic compound can be 1SCCM to 50SCCM, specifically 5SCCM to 20 SCCM. When this introduction rate is satisfied, a uniform and highly crystalline carbon coating can be formed.

The temperature in the chamber is 300 ℃ to 1000 ℃, and specifically may be 400 ℃ to 900 ℃. In addition, the chemical vapor deposition process may be performed for 0.5 minutes to 1 hour, specifically 1 minute to 10 minutes, more specifically 2 minutes to 5 minutes. When this temperature and time range is satisfied, a uniform and highly crystalline carbon coating can be formed while suppressing the growth of silicon crystal grains.

The negative active material according to another embodiment of the present invention may include a negative electrode material including SiO_x(0.5<x<1.3) of silicon-based compounds; and a crystalline carbon coating layer disposed on the silicon-based compound, wherein the crystalline carbon coating layer may contain aluminum.

Average particle diameter (D) of the silicon compound₅₀) Can be 0.1 μm to 20 μm, specifically 0.5 μm to 10 μm. When the average particle diameter of the silicon-based compound satisfies the above range, rate characteristics of the battery may be improved.

The silicon-based compound may further comprise a metal silicate. In particular, the metal silicate may be doped in SiO_x(0.5<x<1.3). The metal silicate may comprise a metal selected from the group consisting of Li₂Si₂O₅、Li₃SiO₃、Li₄SiO₄、Mg₂SiO₄、MgSiO₃、Ca₂SiO₄、CaSiO₃And TiSiO₄At least one of the group consisting of.

Based on 100 parts by weight of SiO_x(0.5<x<1.3), the metal of the metal silicate may be contained in an amount of 1 to 30 parts by weight, specifically 2 to 20 parts by weight. When the above range is satisfied, the growth of silicon crystal grains can be suppressed and the initial efficiency can be improved.

The crystalline carbon coating may comprise crystalline carbon. The crystalline carbon coating may have a D/G ratio of raman spectrum of more than 0 to less than 1, specifically 0.1 to 0.9. Further, the 2D/G ratio of the raman spectrum of the crystalline carbon coating may be more than 0 to less than 1, specifically 0.1 to 0.9. Here, the D/G ratio is a ratio of a D band peak to a G band peak in the raman spectrum, and the 2D/G ratio is a ratio of a 2D band peak to a G band peak in the raman spectrum. The D band peak, the G band peak and the 2D band peak are respectively corresponding to the Raman spectrum and are positioned at 1350cm^-1、1590cm^-1、2700cm^-1The peak at (c). Satisfying the above ratio means forming a crystalline carbon coating layer.

The thickness of the crystalline carbon coating may be 0.01 μm to 1 μm, specifically 0.1 μm to 0.9 μm. When the thickness of the crystalline carbon coating layer satisfies the above range, gas generation caused by the reaction of external moisture and by-products in the silicon-based compound can be minimized without lowering initial efficiency.

The crystalline carbon coating may comprise aluminum. The aluminum may be derived from an organometallic compound used as a chemical vapor deposition source in a manufacturing method of the anode active material. The content of the aluminum may be 0.1 to 10 parts by weight, specifically 0.5 to 5 parts by weight, based on 100 parts by weight of the crystalline carbon coating layer. When the aluminum satisfies the above range, it means that an appropriate amount of the organometallic compound is used as a source for CVD. Thereby, the reaction of the moisture with the by-product of the silicon-based compound can be prevented, and the initial efficiency and rate characteristics can be maintained.

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

The binder may include at least one selected from the group consisting of: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and materials in which hydrogen is replaced with Li, Na, Ca, or the like. In addition, the adhesive may comprise various copolymers thereof.

The conductive agent is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, as the conductive agent, there can be used: graphite such as natural graphite or artificial graphite; carbonaceous materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon powders, aluminum powders, 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.

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

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

The positive electrode may include a positive electrode active material. The positive electrode active material may be a positive electrode active material commonly used in the art. Specifically, the positive electrode active material may be: layered compounds, e.g. lithium cobalt oxide (LiCoO)₂) And lithium nickel oxide (LiNiO)₂) Or a compound substituted with one or more transition metals; lithium manganese oxides, e.g. Li_1+y1Mn_2-y1O₄(0≤y1≤0.33)、LiMnO₃、LiMn₂O₃And LiMnO₂(ii) a Lithium copper oxide (Li)₂CuO₂) (ii) a Vanadium oxides such as LiV₃O₈、V₂O₅And Cu₂V₂O₇(ii) a From the formula LiNi_1-y2M_y2O₂Ni-site type lithium nickel oxide represented (wherein M is any one of Co, Mn, Al, Cu, Fe, Mg, B or Ga, and 0.01. ltoreq. y 2. ltoreq.0.3); of the formula LiMn_2-y3M_y3O₂(wherein M is any one of Co, Ni, Fe, Cr, Zn or Ta, and 0.01. ltoreq. y 3. ltoreq.0.1) or a formula of Li₂Mn₃MO₈(wherein M is any one of Fe, Co, Ni, Cu, or Zn); LiMn in which a part of Li is replaced with an alkaline earth metal ion₂O₄And the like, but are not limited thereto. The positive electrode may be Li metal.

The separator is used to separate the anode and the cathode and provide a moving path for lithium ions. Any separator may be used without particular limitation so long as it is generally used as a separator in a secondary battery. In particular, a separator having excellent moisture-containing properties of the electrolyte and low resistance to ion movement in the electrolyte is preferable. Specifically, a porous polymer film, for example, a porous polymer film manufactured using a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or a laminated structure having two or more layers thereof may be used. In addition, a typical porous nonwoven fabric, such as a nonwoven fabric formed of glass fibers having a high melting point or polyethylene terephthalate fibers, etc., may be used as the separator. In addition, the coated separator including a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may be selectively used in a single layer or a multi-layer structure.

The electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a melt-type inorganic electrolyte, etc., which may be used in the manufacture of a lithium secondary battery, but is not limited thereto.

Specifically, the electrolyte may include a nonaqueous organic solvent and a lithium salt.

As the non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ -butyrolactone, 1, 2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1, 3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphotriester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1, 3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate and ethyl propionate may be used.

In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, may be preferably used because they are high-viscosity organic solvents having a high dielectric constant, and can well dissociate lithium salts. In addition, since a cyclic carbonate may be mixed with a linear carbonate having a low viscosity and a low dielectric constant, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio to prepare an electrolyte having high conductivity, it may be more preferable to use such a cyclic carbonate in combination with the linear carbonate.

As the metal salt, a lithium salt may be used. The lithium salt is a material that is easily soluble in the non-aqueous electrolyte. For example, as the anion of the lithium salt, one or more selected from the group consisting of: f^-、Cl^-、I^-、NO₃ ^-、N(CN)₂ ^-、BF₄ ^-、ClO₄ ^-、PF₆ ^-、(CF₃)₂PF₄ ^-、(CF₃)₃PF₃ ^-、(CF₃)₄PF₂ ^-、(CF₃)₅PF^-、(CF₃)₆P^-、CF₃SO₃ ^-、CF₃CF₂SO₃ ^-、(CF₃SO₂)₂N^-、(FSO₂)₂N^-、CF₃CF₂(CF₃)₂CO^-、(CF₃SO₂)₂CH^-、(SF₅)₃C^-、(CF₃SO₂)₃C^-、CF₃(CF₂)₇SO₃ ^-、CF₃CO₂ ^-、CH₃CO₂ ^-、SCN^-And (CF)₃CF₂SO₂)₂N^-。

In order to improve the life characteristics of the battery, suppress the reduction in the capacity of the battery, and improve the discharge capacity of the battery, the electrolyte may further contain one or more additives other than the above-mentioned electrolyte components, for example, halogenated alkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glymeHexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substitutedOxazolidinone, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, or the like.

According to another embodiment of the present invention, there are provided a battery module including the secondary battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having high capacity, high rate performance, and cycle characteristics, and thus, may be used as a power source for medium and large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

Hereinafter, preferred embodiments of the present invention will be described in detail to facilitate understanding of the present invention. However, these embodiments are merely illustrative of the present invention, and thus, it is apparent to those skilled in the art that various modifications and changes can be made without departing from the scope and spirit of the present invention disclosed in the appended claims. It is apparent that such changes and modifications fall within the scope of the appended claims.