KR20200131793A - Composite anode active material, a method of preparing the composite anode material, and Lithium secondary battery comprising the composite anode active material - Google Patents

Abstract

The present invention relates to a composite negative electrode active material comprising: a plurality of silicon particles; a silicon oxide coating layer disposed on each of the plurality of silicon particles; and a carbonaceous material disposed to separate the plurality of silicon particles from each other. A lithium secondary battery comprising a negative electrode using the composite negative electrode active material has high capacity and excellent service life properties.

Description

Composite anode active material, a method of preparing the composite anode material, and Lithium secondary battery comprising the composite anode active material}

It relates to a composite negative electrode active material, and a negative electrode and a lithium battery including the same.

Lithium batteries are used in various applications by having high voltage and high energy density. For example, electric vehicles (HEV, PHEV) and the like can operate at high temperatures, charge or discharge a large amount of electricity, and be used for a long time, so lithium batteries with high discharge capacity and excellent life characteristics are required. .

Carbon-based materials are porous and are stable due to little change in volume during charging and discharging. However, in general, carbon-based materials have low battery capacity due to the porous structure of carbon. For example, the theoretical capacity of highly crystalline graphite is 372 mAh/g in the LiC ₆ composition. In addition, the high rate characteristics are low.

In addition to the carbon-based material, a metal alloyable with lithium may be used as an anode active material having a high electric capacity. For example, lithium alloyable metals are Si, Sn, Al, and the like. Among them, active research is being conducted on an anode active material using ball-milled Si particles together with a carbon-based material.

However, since the silicon particles cause a volume change of 400% during charging and discharging, the negative electrode active material including the silicon particles may be cracked. When a crack occurs in the negative active material, a side reaction proceeds due to penetration of the electrolyte into the negative active material, resulting in deterioration of the negative active material. Since the deterioration of the negative electrode active material leads to a decrease in the capacity of the lithium secondary battery including the same, there is a need for suppressing the deterioration of the negative electrode active material due to the volume change of the silicon particles.

One aspect is to provide a novel negative active material.

Another aspect is to provide a method of manufacturing the negative active material.

Another aspect is to provide a lithium secondary battery including a negative electrode employing the negative electrode active material.

According to one aspect,

A plurality of silicon particles;

A silicon oxide coating layer disposed on each of the plurality of silicon particles; And

Including a carbonaceous material disposed to separate the plurality of silicon particles from each other,

The carbonaceous material is a carbonaceous matrix,

It includes a bimodal pore structure including first pores and second pores, the first pore has a diameter of 1 to 5 nm, the second pore has a diameter of 10 to 200 nm, A composite cathode active material having a higher distribution ratio than that of the second pore is provided.

According to the other side,

Pulverizing the silicon in an organic solvent and/or an aqueous solvent to provide silicon particles including a silicon oxide coating layer;

Uniformly mixing the silicon particles, a carbon precursor, and a non-aqueous solvent to obtain a mixed composition; And

Firing the mixed composition to obtain a composite negative electrode active material;

There is provided a method for producing a composite negative electrode active material comprising a.

According to another aspect,

A negative electrode including the negative electrode active material,

Anode, and

A lithium secondary battery containing an electrolyte is provided.

A lithium secondary battery including a negative electrode employing the composite negative electrode active material according to one aspect has high capacity and excellent lifespan characteristics.

1 is a perspective view schematically showing a cross section of a composite cathode active material according to an embodiment of the present invention.
2 is a transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS) photograph showing the distribution of Si atoms and O atoms contained in silicon oxide among silicon particles including silicon oxide obtained in Preparation Examples 4 to 6.
3(a) is a charge/discharge curve of a half cell manufactured according to Comparative Examples 1 to 3 of the present invention, and FIG. 3(b) is a graph of electrochemical evaluation data.
4(a) is a charge/discharge curve of a half cell manufactured according to Examples 1 to 2 and Comparative Example 4 of the present invention, and FIG. 4(b) is a graph of electrochemical evaluation data.
5(a) is a charge/discharge curve of a half cell manufactured according to Examples 1 and 3 and Comparative Example 5 of the present invention, and FIG. 5(b) is a graph of electrochemical evaluation data.
6 is a graph of electrochemical evaluation data of lithium secondary batteries manufactured in Example 10 and Comparative Examples 9 to 10 of the present invention.
7 is a graph of electrochemical evaluation data of lithium secondary batteries manufactured in Example 10 and Comparative Example 11 of the present invention.
8 is a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) photograph of a cross section of a cathode after 100 charge/discharge cycles of a half cell fabricated according to Example 13 of the present invention.
9 is a graph showing changes in pore distribution and volume of composite cathode active materials obtained in Preparation Examples 11 and 15 of the present invention.
10 is a schematic diagram of a lithium secondary battery according to an exemplary embodiment.
<Explanation of symbols for major parts of drawings>
1: lithium battery 2: negative electrode
3: anode 4: separator
5: battery case 6: cap assembly

The present inventive concept described below may apply various transformations and may have various embodiments. Specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, this is not intended to limit the present creative idea to a specific embodiment, it is to be understood as including all transformations, equivalents or substitutes included in the technical scope of the present creative idea.

The terms used below are only used to describe specific embodiments, and are not intended to limit the present inventive idea. Singular expressions include plural expressions unless the context clearly indicates otherwise. Hereinafter, terms such as "comprises" or "have" are intended to indicate the existence of features, numbers, steps, actions, components, parts, components, materials, or a combination thereof described in the specification. It is to be understood that the above other features, or the possibility of the presence or addition of numbers, steps, actions, components, parts, components, materials, or combinations thereof, are not excluded in advance.

Hereinafter, "one silicon particle" and "other silicon particle" are used only to indicate different silicon particles, and are not to be understood as limiting specific silicon particles.

In the following, "about" or "approximately" is a value presented within an acceptable error range for a specific value determined by the technician, taking into account the measurement error and the error associated with the measurement of a specific amount (ie, the limit of the measurement system). And the average. For example, “about” can mean one or more standard deviations, or within ±30%, 20%, 10% or 5% of a given value.

Unless otherwise defined, all terms (technical terms and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. In addition, terms such as those defined in a commonly used dictionary should be interpreted as meanings corresponding to their meanings in the context of the relevant technical field and the present application, and unless specifically defined herein, they are interpreted as ideal or excessively formal meanings. It shouldn't be.

In the drawings, the thickness is enlarged or reduced in order to clearly express various layers and regions. The same reference numerals are assigned to similar parts throughout the specification. Throughout the specification, when a part such as a layer, film, region, plate, etc. is said to be "on" or "on" another part, this includes not only the case directly above the other part, but also the case where there is another part in the middle. . The terms are used only for the purpose of distinguishing one component from another. On the other hand, the fact that one component is "directly on" another component means that there is no intervening component between them.

Hereinafter, a lithium secondary battery including a composite anode active material according to exemplary embodiments and a negative electrode employing the composite cathode active material will be described in more detail.

A composite negative electrode active material according to an embodiment will be described in detail with reference to FIG. 1.

Referring to FIG. 1, a composite cathode active material 10 according to an embodiment includes a plurality of silicon particles 11; A silicon oxide coating layer 12 disposed on each of the plurality of silicon particles 11; And a carbonaceous material 13 separating one silicon particle and the other silicon particle from each other among the plurality of silicon particles.

Since the composite cathode active material 10 includes a plurality of silicon particles 11, it has a higher capacity than a conventional carbon-based anode active material, and by providing a silicon oxide coating layer 12 on the silicon particles 11, silicon Particle expansion is suppressed. Furthermore, by arranging the carbonaceous material 13 between the plurality of silicon particles 11, not only the expansion of the silicon particles is further suppressed and the expansion stress is buffered, but also the anode active material due to collision between the expanded silicon particles. Cracks are suppressed.

According to one embodiment, the composite cathode active material may include a bimodal pore structure. For example, the composite cathode active material may include pores having different size ranges.

According to one embodiment, the bimodal pore structure may include first pores having a diameter of 1 to 5 nm, and second pores having a diameter of 10 to 200 nm.

According to one embodiment, the first pores are distributed in the composite cathode active material at a higher ratio than the second pores that may cause side reactions due to impregnation of the electrolyte. Accordingly, deterioration of the negative electrode active material due to a side reaction with the electrolyte can be prevented.

According to one embodiment, the volume of the first pores may be about 20% by volume or less with respect to the total volume of the bimodal pore structure. For example, the volume of the first pores is about 19 vol% or less, about 18 vol% or less, about 17 vol% or less, about 16 vol% or less, about 15 vol% or less with respect to the total volume of the bimodal pore structure. , About 14% by volume or less, about 13% by volume or less, about 12% by volume or less, about 11% by volume or less, about 10% by volume or less, about 9% by volume or less, about 8% by volume or less, about 7% by volume or less, about It may be 6% by volume or less, about 5% by volume or less, about 4% by volume or less, about 3% by volume or less, about 2% by volume or less, or about 1% by volume or less.

When the volume of the first pores falls within the above range, deterioration of battery performance due to impregnation of the electrolyte and side reactions with the electrolyte may be prevented.

According to one embodiment, the composite cathode active material may further include a carbon coating layer. The carbon coating layer may be formed on the surface of the composite cathode active material by chemical vapor deposition of a carbon source. In the process of forming the carbon coating layer on the surface of the composite cathode active material, the first pores are filled with a carbon source, so that the volume occupied by the first pores is reduced. As a result, the specific surface area of the composite cathode active material can be remarkably reduced. For example, the specific surface area of the composite cathode active material may be reduced by 90% or more compared to before including the carbon coating layer. This proves that the first pores are predominantly distributed in the composite cathode active material.

According to one embodiment, the specific surface area of the composite cathode active material may be 1 to 20 cm ² /g.

According to one embodiment, the silicon oxide coating layer includes a compound represented by Formula 1 below.

<Formula 1>

SiO _x (0<x≤2)

In this case, the silicon oxide coating layer may be amorphous. Since the amorphous silicon oxide coating layer is inert with respect to lithium ions, the transfer rate of lithium is high. In addition, the silicon oxide coating layer may uniformly absorb and buffer stress generated by silicon expansion. Therefore, by accepting the expansion of the silicon particles, it is possible to improve the life characteristics of the negative electrode active material.

According to one embodiment, the silicon particles and the silicon oxide coating layer may be disposed in contact with each other. By disposing the silicon oxide coating layer on the surface of the silicon particles, the volume expansion of the silicon particles can be more effectively accommodated.

According to one embodiment, the silicon oxide coating layer and the carbonaceous material may be disposed to contact each other. In other words, the carbonaceous material may be disposed to be interposed between the silicon oxide coating layers. By disposing a carbonaceous material on the surface of the silicon oxide coating layer, volume expansion of the silicon particles can be further suppressed.

According to one embodiment, one surface of the silicon oxide coating layer may be in contact with the silicon particles, and the other surface of the silicon oxide coating layer may be disposed to contact the carbonaceous matrix. Through this structure, it is possible to improve the stability and durability of the negative electrode active material by effectively receiving the stress caused by the volume expansion of the silicon particles.

According to one embodiment, a silicon oxide coating layer is included on the surface of the silicon particle, and the silicon oxide coating layer may be continuous on the surface of the silicon particle. That is, the silicon oxide coating layer completely covers the circumference of the silicon particles, thereby preventing deterioration due to direct contact between the electrolyte and the silicon particles, and sufficiently accommodates the volume expansion of the silicon particles.

According to one embodiment, a silicon oxide coating layer is included on the surface of the silicon particles, and the silicon oxide coating layer may have a thickness of about 10 nm to about 20 nm. For example, the silicon oxide coating layer is about 10 nm to about 19 nm, about 10 nm to about 18 nm, about 10 nm to about 17 nm, about 10 nm to about 16 nm, about 10 nm to about 15 nm, about 10 nm to about 14 nm, about 10 nm to about 13 nm , About 10 nm to about 12 nm, about 10 nm to about 11 nm, about 11 nm to about 20 nm, about 12 nm to about 20 nm, about 13 nm to about 20 nm, about 14 nm to about 20 nm, about 15 nm to about 20 nm, about 16 nm to about 20 nm, about It may have a thickness of 17 nm to about 20 nm, about 18 nm to about 20 nm, or about 19 nm to about 20 nm.

According to one embodiment, the carbonaceous material may be formed from a carbon precursor having elasticity after firing.

For example, the carbon precursor is not particularly limited, and rayon-based carbon fiber, PAN-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon, carbon fiber, graphite, polymer , Coal tar pitch, petroleum pitch, meso-phase pitch, isotropic pitch, coke, low molecular weight heavy oil, coal-based pitch, phenol resin, naphthalene resin, epoxy resin, vinyl chloride resin, polyimide, polybenzimidazole, polyacrylonitrile, polyethylene Glycol, polyvinyl alcohol, polyvinyl chloride, furfuryl alcohol, furan, cellulose, glucose, sucrose, acetic acid, malic acid, citric acid, organic acids, and at least one selected from the group consisting of combinations thereof.

For example, the carbonaceous material may include artificial graphite, for example, plate-like graphite. For example, at least a portion of the carbonaceous material may be made of plate-like graphite.

The carbonaceous material may have a carbonization degree of 99% or more. For example, the carbonaceous material may substantially not contain elements other than carbon and hydrogen. By setting the carbonization degree of the carbonaceous material to be 99% or more, it is possible to manufacture a composite cathode active material having a sufficient stress buffering effect and a compact structure and excellent in conductivity.

According to one embodiment, the silicon particles may be nanoparticles. According to one embodiment, the median particle diameter (D ₅₀ ) of the silicon nanoparticles may be about 10 nm to 200 nm, and may be an arbitrary range expressed by two arbitrary values selected within the above range.

For example, the median particle diameter of the silicon particles is about 10 nm to about 200 nm, about 10 nm to about 150 nm, about 10 nm to about 125 nm, about 10 nm to about 100 nm, about 10 nm to about 90 nm, about 10 nm to about 80 nm, about 10 nm to It may be about 70 nm, about 10 nm to about 60 nm, about 10 nm to about 50 nm, about 10 nm to about 40 m, about 10 nm to about 30 nm, or about 10 nm to about 20 nm. By configuring the median particle diameter of the silicon particles within the above range, it is possible to minimize stress generated by volume expansion of the silicon.

According to one embodiment, the shape of the silicon particles is not particularly limited, and may include a spherical shape, a tube shape, a plate shape, or a combination thereof.

According to one embodiment, the carbonaceous material may be included in an amount of 30% to 70% by weight based on the total weight of the composite cathode active material. When the carbonaceous material is included in the above range of the composite cathode active material, the volume expansion of the silicon particles can be suppressed while sufficiently separating the silicon particles. In addition, the carbonaceous material functions as a matrix for the silicon particles, thereby fixing the silicon particles and preventing desorption, thereby having excellent life characteristics.

Hereinafter, a method of manufacturing a composite negative electrode active material according to an embodiment will be described.

A method of manufacturing a composite negative electrode active material according to one embodiment,

Pulverizing silicon in an organic solvent and/or an aqueous solvent to provide silicon particles including a silicon oxide coating layer;

Uniformly mixing the silicon particles, a carbon precursor, and a non-aqueous solvent to obtain a mixed composition; And

Firing the mixed composition to obtain a composite negative electrode active material;

Includes.

According to one embodiment, the grinding may be a mechanical grinding method. For example, the mechanical grinding method may be a ball milling process. For example, the ball milling process may be a planetary ball mill, a high energy ball mill, or a stirred ball mill, but is not limited thereto. In the ball milling process, the grinding ball mill does not react with silicon, and, for example, a zirconia ball mill may be used. In addition, the ball milling process time may be performed for an appropriate time in consideration of the desired final particle size, for example, may be performed for about 1 minute to about 20 hours.

The ball milling process includes wet or dry ball milling, and a person of ordinary skill in the art may select an appropriate ball milling process according to the size and use of the desired lithium alloyable metal particles.

An organic solvent may be used as an example of the medium used for wet ball milling. For example, the medium includes an isopropyl alcohol solvent, but is not limited thereto, and any medium that can be used for wet ball milling in the art may be used.

The ball milling process may be performed at a temperature lower than room temperature. For example, the ball milling process may be performed at a temperature of 25°C or less.

According to one embodiment, the silicon oxide coating layer may have a thickness of 10 nm to 20 nm.

According to one embodiment, the carbon precursor may be included in an amount of 30% to 70% by weight based on the total weight of the mixed composition. For example, when the carbon precursor is included in the above range with respect to the total weight of the mixed composition, it is possible to obtain a carbonaceous elastic matrix composed of a carbonaceous material capable of receiving volume expansion of the silicon particles while sufficiently separating the silicon particles. have.

According to one embodiment, the non-aqueous solvent is tetrahydrofuran, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbo Nate, gamma-butyrolactone, 1,2-dimethoxy ethane, tetrahydroxy franc (franc), 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolone, formamide, dimethylformamide, Dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate tryester, trimethoxymethane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, Propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, and ethyl propionate may include at least one selected from the group consisting of, but is not limited thereto, and dissolving the aforementioned carbon precursor, and at the same time Any solvent capable of dispersing the silicon particles may be included.

According to one embodiment, before the step of firing the mixed composition, the step of removing the non-aqueous solvent may be further included. The step of removing the non-aqueous solvent may be evaporated by standing at room temperature, or dried in a vacuum oven at 50 to 200°C.

By removing the non-aqueous solvent, it is possible to increase the density of the negative electrode active material obtained through the subsequent firing process.

According to one embodiment, the firing may be performed at about 800°C to about 1200°C. If the sintering process is performed at a temperature of less than 800°C, the carbonization reaction of the carbon precursor is not sufficiently performed, resulting in a carbon material having a low carbonization degree. Due to poor conductivity, it may act as resistance. Due to the reaction between silicon and silicon oxide, capacity and life characteristics may be deteriorated due to reduction of the oxide layer and generation of silicon carbide.

According to one embodiment, the firing may be performed for about 2 hours to about 6 hours. For example, the firing is about 2 hours to about 5 hours, about 2 hours to about 5.5 hours, about 2 hours to about 4.5 hours, about 2 hours to about 4 hours, about 2 hours to about 3.5 hours, about 2 hours To about 3 hours, about 2 hours to about 2.5 hours, about 2.5 hours to about 6 hours, about 3 hours to about 6 hours, about 3.5 hours to about 6 hours, about 4 hours to about 6 hours, about 4.5 hours to about 6 hours, about 5 hours to about 6 hours, or about 5.5 hours to about 6 hours.

A negative electrode for a lithium secondary battery according to an aspect includes a negative electrode current collector; And a negative electrode active material layer disposed on at least one surface of the negative electrode current collector and including the above-described composite negative electrode active material.

The negative electrode may include a binder between the negative electrode current collector and the negative electrode active material layer or in the negative electrode active material layer. For the binder, refer to the bar described later.

The negative electrode and a lithium secondary battery including the same may be manufactured by the following method.

The negative electrode includes the above-described composite negative electrode active material, for example, after preparing a composite negative electrode active material composition by mixing the above-described composite negative electrode active material, a binder, and optionally a conductive material in a solvent, it is molded into a certain shape, or copper foil It can be manufactured by applying it to a current collector such as (copper foil).

The binder used in the composite negative electrode active material composition is a component that assists in binding of the composite negative electrode active material to the conductive material and bonding to the current collector, and may be included between the negative electrode current collector and the negative electrode active material layer or in the negative electrode active material layer, It is added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the composite cathode active material. For example, the binder may be added in an amount of 1 to 30 parts by weight, 1 to 20 parts by weight, or 1 to 15 parts by weight based on 100 parts by weight of the composite cathode active material.

Examples of such a binder include polyvinylidene fluoride, polyvinylidene chloride, polybenzimidazole, polyimide, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydride Roxypropylcellulose, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile butadiene styrene, phenol resin, epoxy resin, polyethylene Terephthalate, polytetrafluoroethylene, polyphenylene sulfide, polyamideimide, polyetherimide, polyethersulfone, polyamide, polyacetal, polyphenylene oxide, polybutylene terephthalate, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, and various copolymers.

The negative electrode may optionally further include a conductive material to further improve electrical conductivity by providing a conductive path to the composite negative electrode active material described above. As the conductive material, anything generally used for lithium batteries may be used, and examples thereof include carbon-based materials such as carbon black, acetylene black, ketjen black, and carbon fiber (eg, vapor-grown carbon fiber); Metal-based materials such as metal powder or metal fibers such as copper, nickel, aluminum, and silver; A conductive material containing a conductive polymer such as a polyphenylene derivative, or a mixture thereof can be used.

As the solvent, N-methylpyrrolidone (NMP), acetone, water, and the like may be used. The content of the solvent is 1 to 10 parts by weight based on 100 parts by weight of the composite cathode active material. When the content of the solvent is in the above range, the operation for forming the active material layer is easy.

In addition, the current collector is generally made to have a thickness of 3 to 500 μm. The current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. Surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, and the like may be used. In addition, it is possible to enhance the bonding strength of the composite cathode active material by forming fine irregularities on the surface, and can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

A negative electrode plate may be prepared by directly coating the prepared composite negative electrode active material composition on a current collector, or a negative electrode plate may be obtained by casting on a separate support and laminating a composite negative electrode active material film separated from the support on a copper foil current collector. The negative electrode is not limited to the shapes listed above, but may have a shape other than the above shape.

The composite cathode active material composition may be used not only to manufacture an electrode of a lithium battery, but also to be printed on a flexible electrode substrate and used to manufacture a printable battery.

Next, the anode is prepared.

For example, a positive electrode active material composition in which a positive electrode active material, a conductive material, a binder, and a solvent are mixed is prepared. The positive electrode active material composition is directly coated on a metal current collector to prepare a positive electrode plate. Alternatively, the positive electrode active material composition may be cast on a separate support, and then a film peeled from the support may be laminated on a metal current collector to prepare a positive electrode plate. The anode is not limited to the shapes listed above, but may be in a shape other than the above shape.

The positive electrode active material is a lithium-containing metal oxide and may be used without limitation as long as it is commonly used in the art. For example, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

For example, the positive electrode active material is a lithium-containing metal oxide, Li _a A _1-b B ¹ _b D ¹ ₂ (in the above formula, 0.90≦a≦1.8, and 0≦b≦0.5); Li _a E _1-b B ¹ _b O _2-c D ¹ _c (in the above formula, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05); LiE _2-b B ¹ _b O _4-c D ¹ _c (where 0≦b≦0.5, 0≦c≦0.05); Li _a Ni _1-bc Co _b B ¹ _c D ¹ _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Co _b B ¹ _c O _2-α F ¹ _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b B ¹ _c D ¹ _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Mn _b B ¹ _c O _2-α F ¹ _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1); Li _a NiG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a CoG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a MnG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90≦a≦1.8 and 0.001≦b≦0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiI ¹ O ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0≦f≦2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≦f≦2); A compound represented by any one of the formulas of LiFePO ₄ can be used:

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or combinations thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

For example, LiCoO ₂ , LiMn _x O _2x (x=1, 2), LiNi _1-x Mn _x O _2x (0<x<1), LiNi _1-xy Co _x Mn _y O ₂ (0≤x≤ 0.5, 0≤y≤0.5), LiFePO ₄ and the like.

Of course, one having a coating layer on the surface of the compound may be used, or a mixture of the compound and a compound having a coating layer may be used. The coating layer may contain a coating element compound of oxide, hydroxide, oxyhydroxide of coating element, oxycarbonate of coating element, or hydroxycarbonate of coating element. The compound constituting these coating layers may be amorphous or crystalline. As a coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. The coating layer formation process may be any coating method as long as the compound can be coated by a method that does not adversely affect the physical properties of the positive electrode active material by using these elements (e.g. spray coating, dipping method, etc.). Since the content can be well understood by those engaged in the relevant field, detailed description will be omitted.

In the positive electrode active material composition, a conductive material, a binder, and a solvent may be the same as those of the negative electrode active material composition.

The contents of the positive electrode active material, the conductive material, the binder, and the solvent are the levels commonly used in lithium secondary batteries. One or more of the conductive material, the binder, and the solvent may be omitted depending on the use and configuration of the lithium battery.

Next, a separator to be inserted between the positive and negative electrodes is prepared.

Any of the separators can be used as long as they are commonly used in lithium batteries. Those having low resistance to ion migration of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, as selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, it may be a non-woven fabric or a woven fabric. For example, a woundable separator such as polyethylene or polypropylene may be used for a lithium ion battery, and a separator having excellent organic electrolyte impregnation ability may be used for a lithium ion polymer battery. For example, the separator may be manufactured according to the following method.

A polymer resin, a filler, and a solvent are mixed to prepare a separator composition. The separator composition may be directly coated and dried on an electrode to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled off from the support may be laminated on an electrode to form a separator.

The polymer resin used for manufacturing the separator is not particularly limited, and all materials used for the bonding material of the electrode plate may be used. For example, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof may be used.

Next, the electrolyte is prepared.

For example, the electrolyte may be an organic electrolyte. In addition, the electrolyte may be a solid electrolyte. For example, the solid electrolyte may include a sulfide-based solid electrolyte containing Li ₂ S. For example, the solid electrolyte is ThioLISICON (Li _3.25 Ge _0.25 P _0.75 S ₄ ), Li ₂ S, Li ₂ SP ₂ S ₅ , Li ₂ S-SiS ₂ , Li ₂ S-GeS ₂ , Li ₂ SB ₂ S ₅ , Li ₂ S-Al ₂ S ₅ , LPSX(Li _x P _y S _z X, X = Cl, Br, I), LGPS(Li ₁₀ GeP ₂ S ₁₂ ), LPS(Li ₇ P ₃ S ₁₁ ), It may be boron oxide, lithium oxynitride, or the like, but is not limited thereto, and any one that can be used as a solid electrolyte in the art may be used. The solid electrolyte may be formed on the negative electrode by a method such as sputtering.

For example, the organic electrolyte may be prepared by dissolving a lithium salt in an organic solvent.

The organic solvent may be used as long as it can be used as an organic solvent in the art. For example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate , Benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethylsulfoxide , Dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

The lithium salt may also be used as long as it can be used as a lithium salt in the art. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (where x,y are natural numbers), LiCl, LiI, or a mixture thereof.

As shown in FIG. 9, the lithium battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2 and the separator 4 described above are wound or folded to be accommodated in the battery case 5. Subsequently, an organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium battery 1. The battery case 5 may be cylindrical, rectangular, thin-film, or the like. For example, the lithium battery 1 may be a thin film type battery. The lithium battery 1 may be a lithium ion battery.

A separator may be disposed between the positive electrode and the negative electrode to form a battery structure. After the battery structure is stacked in a bi-cell structure, it is impregnated with an organic electrolyte, and the resulting product is accommodated in a pouch and sealed to complete a lithium ion polymer battery.

In addition, a plurality of the battery structures are stacked to form a battery pack, and the battery pack may be used in all devices requiring high capacity and high output. For example, it can be used for laptop computers, smart phones, electric vehicles, and the like.

In addition, since the lithium secondary battery has excellent life characteristics and high rate characteristics, it can be used in an electric vehicle (EV). For example, it can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in a field requiring a large amount of power storage. For example, it can be used for electric bicycles, power tools, and the like.

The present invention will be described in more detail through the following Preparation Examples, Examples and Comparative Examples. However, the examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Example

(Production of silicon particles including a silicon oxide coating layer)

Manufacturing Example 1

Bulk silicon available on the market was put into a ball mill device together with an isopropyl alcohol (IPA) medium, and pulverized for 0.5 hours at room temperature and a ball mill rotation speed of 3000 to 4000 rpm to obtain ball milled silicon nanoparticles.

Manufacturing Example 2

Ball-milled silicon nanoparticles were obtained in the same manner as in Preparation Example 1, except that the grinding time was set to 1 hour.

Manufacturing Example 3

Ball-milled silicon nanoparticles were obtained in the same manner as in Preparation Example 1, except that the grinding time was set to 2 hours.

Manufacturing Example 4

Ball-milled silicon nanoparticles were obtained in the same manner as in Preparation Example 1, except that the grinding time was set to 3 hours.

Manufacturing Example 5

Ball milled silicon nanoparticles were obtained in the same manner as in Preparation Example 1, except that the grinding time was 5 hours and a small amount of water was additionally added as a medium.

Manufacturing Example 6

Ball milled silicon nanoparticles were obtained in the same manner as in Preparation Example 1, except that the grinding time was set to 10 hours and a small amount of water was additionally added as a medium.

(Manufacture of composite cathode active material)

Manufacturing Example 7

It was mixed and homogeneously dispersed in 50% by weight of silicone particles obtained in Preparation Example 1, 50% by weight of coal tar pitch, and tetrahydrofuran to obtain a mixed composition. The mixed composition was dried in a vacuum chamber to remove the solvent. Then, the mixed composition was fired at 900°C to obtain a composite negative electrode active material.

Manufacturing Example 8

A composite negative electrode active material was prepared in the same manner as in Preparation Example 7, except that the silicon particles obtained in Preparation Example 2 were used instead of the silicon particles obtained in Preparation Example 1.

Manufacturing Example 9

A composite negative electrode active material was prepared in the same manner as in Preparation Example 7, except that the silicon particles obtained in Preparation Example 3 were used instead of the silicon particles obtained in Preparation Example 1.

Manufacturing Example 10

A composite negative electrode active material was prepared in the same manner as in Preparation Example 7, except that the silicon particles obtained in Preparation Example 4 were used instead of the silicon particles obtained in Preparation Example 1.

Manufacturing Example 11

A composite cathode active material was prepared in the same manner as in Preparation Example 7, except that the silicon particles obtained in Preparation Example 5 were used instead of the silicon particles obtained in Preparation Example 1.

Manufacturing Example 12

A composite cathode active material was prepared in the same manner as in Preparation Example 7, except that the silicon particles obtained in Preparation Example 6 were used instead of the silicon particles obtained in Preparation Example 1.

Manufacturing Example 13

It was mixed and homogeneously dispersed in 80% by weight of silicone particles obtained in Production Example 5, 20% by weight of coal tar pitch, and tetrahydrofuran to obtain a mixed composition. The mixed composition was dried in a vacuum chamber to remove the solvent. Then, the mixed composition was fired at 900°C to obtain a composite negative electrode active material.

Manufacturing Example 14

A composite negative electrode active material was prepared in the same manner as in Preparation Example 13, except that the coal tar pitch was used at 33.3% by weight.

Manufacturing Example 15

The composite cathode active material obtained in Preparation Example 11 was prepared, and acetylene (C ₂ H ₂ ) (g) was vapor-deposited for 30 minutes at a rate of 50 sccm under conditions of 900° C. to obtain a composite anode active material including an additional carbon coating layer. Was prepared.

Evaluation Example 1: Analysis of Silicon Oxide Coating Layer

The surfaces of the silicon particles including the silicon oxide coating layer prepared in Preparation Examples 4 to 6 were confirmed by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), and the photographs are shown in FIG. 2.

According to FIG. 2, it was confirmed that the silicon oxide coating layer of the silicon particles prepared in Preparation Examples 4 to 6 was made of Si and O. In addition, from Preparation Example 4 to the silicon oxide coating layer prepared in Preparation Example 6, the effect of increasing the ratio of O could be confirmed.

Evaluation Example 2: Porosity Analysis of Composite Cathode Active Material

The surface of the composite cathode active material obtained in Preparation Examples 11 and 15 was observed with SEM to measure the size and volume of pores. The results are shown in FIG. 9.

9, in the case of the composite cathode active material obtained in Preparation Example 11, the volume of pores having a size of 1 to 5 nm is within 20% of the total pore volume, whereas in the case of the composite cathode active material obtained in Preparation Example 15, 1 to 5 It can be seen that the volume of the pores of the nm size is almost 0%. On the other hand, changes in the volume of pores with a size of 10 nm or more showed similar behavior regardless of the presence or absence of a carbon coating layer. In view of this, it can be seen that the gaseous carbon coating process selectively blocked pores with a size of 1 to 5 nm.

In addition, the specific surface area of the composite negative electrode active material obtained in Preparation Example 11 was 14.6 cm ² /g, and the specific surface area of the composite negative electrode active material obtained in Preparation Example 15 was confirmed to be 1.42 cm ² /g, and the specific surface area decreased by about 90% or more. It can be seen that

(Production of half cell)

Example 1

The composite negative electrode active material obtained in Preparation Example 11 was used to prepare a slurry in a ratio of a negative electrode active material: a conductive material: a binder in a ratio of 96:1:3. Here, Super P was used as the conductive material, and carboxymethylcellulose (CMC) and styrene-butadiene-rubber (SBR) were used as the binder.

The slurry was uniformly applied to copper foil, dried in an oven at 80° C. for about 2 hours, roll pressed, and dried in a vacuum oven at 110° C. for about 12 hours to prepare a negative electrode.

Mixing in which the prepared negative electrode is used as a working electrode, lithium foil is used as a counter electrode, a polyethylene film is inserted as a separator between the negative electrode and the counter electrode, and EC/EMC/DEC is mixed in a volume ratio of 3/5/2 A CR2032 half cell was manufactured according to a commonly known process using a liquid electrolyte in which 10.0% by weight of FEC was added to the solvent and LiPF ₆ was added to a concentration of 1.3 M as a lithium salt.

Example 2

A CR2032 half cell was manufactured in the same manner as in Example 1, except that the composite negative electrode active material obtained in Preparation Example 12 was used instead of the composite negative electrode active material obtained in Preparation Example 11.

Comparative Examples 1 to 4

A CR2032 half cell was manufactured in the same manner as in Example 1, except that the composite negative electrode active materials obtained in Preparation Examples 7 to 10 were used, respectively, instead of the composite negative electrode active material obtained in Preparation Example 11.

Example 3

A CR2032 half cell was manufactured in the same manner as in Example 1, except that the composite negative electrode active material obtained in Preparation Example 14 was used instead of the composite negative electrode active material obtained in Preparation Example 11.

Comparative Example 5

A CR2032 half cell was manufactured in the same manner as in Example 1, except that the composite negative electrode active material obtained in Preparation Example 13 was used instead of the composite negative electrode active material obtained in Preparation Example 11.

Evaluation Example 3: Evaluation of electrochemical properties (1)

Start charging the half-cells manufactured according to Examples 1 and 2 and Comparative Examples 1 to 4 at a charging rate of 0.1 C-rate at 25° C., and charge the voltage to 0.005 V, at which time to have a constant voltage at a constant current. After that, charge it with a certain voltage until it becomes less than a certain current (0.01C). Thereafter, discharge was performed with a constant current until reaching 1.5V at a discharge rate of 0.1C-rate. After passing through two charge/discharge cycles in this way, the voltage section is set to 0.005V to 1V at a charge/discharge rate of 0.5C-rate, and the charge/discharge cycles are continuously repeated 100 times. Some of the results of the charging and discharging experiments are shown in Table 1 below, and graphs of the charging and discharging test results are shown in FIGS. 3 and 4.

The initial efficiency was calculated from Equation 1 below.

<Equation 1>

The initial efficiency (%) = [discharge capacity / charge capacity at 1 ^st cycle at 1 ^st cycle] ㅧ 100

Initial capacity
[mAh/g] Initial efficiency
[%] Comparative Example 1 2426 91.5 Comparative Example 2 2233 91.0 Comparative Example 3 2126 90.5 Comparative Example 4 1533 87.8 Example 1 1402 84.5 Example 2 1400 83.6

As shown in Table 1, the composite cathode active material included in Examples 1 and 2 includes a silicon oxide coating layer of 10 nm or more, so that the initial capacity and initial efficiency are compared to Comparative Examples 1 to 4 including a thinner silicon oxide coating layer. Was lower. However, as shown in Figures 3 and 4, it can be seen that the capacity retention rate is significantly improved compared to Comparative Examples 1 to 4. In particular, when comparing Examples 1 and 2 with Comparative Example 4, it is true that some loss in the initial reversible capacity is lost, but the capacity retention rate is significantly improved in subsequent cycles, and Examples 1 and 2 are Comparative Examples after a certain cycle. It is predicted to have a higher reversible capacity compared to 4.

Evaluation Example 4: Evaluation of electrochemical properties (2)

The half-cells manufactured according to Examples 1 and 3 and Comparative Example 5 were started charging at 25° C. at a charging rate of 0.1 C-rate, and the voltage was charged to 0.005 V, and at this time, after charging to have a constant voltage at a constant current, Charge it with a certain voltage until it reaches a certain current or less (0.01C). Thereafter, discharge was performed with a constant current until reaching 1.5V at a discharge rate of 0.1C-rate. After passing through two charge/discharge cycles in this way, the voltage section is set to 0.005V to 1 at a charge/discharge rate of 0.5C-rate, and the charge/discharge cycles are continuously repeated 100 times. Some of the results of the charge/discharge experiment are shown in Table 2 below, and a graph of the charge/discharge experiment result is shown in FIG.

Initial capacity
[mAh/g] Initial efficiency
[%] Example 1 1402 84.5 Example 3 1702 85.7 Comparative Example 5 1887 84.9

As shown in Table 2, in Example 1, 50% by weight coal tar pitch was mixed, but in Example 3 and Comparative Example 5, 33.3% by weight and 20% by weight were mixed, respectively, to sufficiently separate the silicon particles. Since the matrix is not formed and the stress buffering effect due to expansion is insufficient, it is thought that cracking of the anode active material occurs due to silicon expansion, resulting in a decrease in life characteristics and capacity. In addition, Examples 1 and 3 and Comparative Example 5 In comparison, it is true that there is a slight loss in the initial reversible capacity due to the increase of the inert carbon content, but the capacity retention rate is significantly improved in subsequent cycles, and after a certain cycle, Examples 1 and 3 are higher than that of Comparative Example 5. It is predicted to have a reversible capacity.

(Production of full cell)

(Manufacture of cathode)

Example 5

The composite negative electrode active material obtained in Preparation Example 11 and spherical graphite (having a capacity of 360mAh/g) were mixed in a weight ratio of 50:50 to be used as a negative electrode active material, super.P as a conductive material, CMC as a thickener, and SBR as a binder. And the negative electrode active material/conductor/thickener/binder in a weight ratio of 96:1:1.5:1.5 to prepare a slurry. The slurry was applied on a copper current collector having a thickness of 18 μm using a conventional method. The current collector to which the slurry was applied was dried at room temperature, and then dried at 120° C., followed by rolling and punching to prepare a negative electrode to be applied to the cell.

Comparative Examples 6 to 8

A negative electrode was manufactured in the same manner as in Example 5, except that the composite negative electrode active material obtained in Preparation Examples 7, 10, and 14 was used instead of the composite negative electrode active material obtained in Preparation Example 4.

(Manufacture of anode)

Example 9

A mixture of lithium cobalt oxide (LCO) cathode active material, carbon conductor (super.P), and polyvinylidene fluoride (PVdF) in a weight ratio of 94:3:3 was mixed with N-methylpyrrolidone (NMP). Together, a positive electrode active material slurry was prepared by mixing through a homogenizer. Apply the positive electrode active material slurry to a thickness of about 120 μm using a doctor blade on a 15 μm-thick aluminum current collector, dry it at room temperature, and dry it again under vacuum and 120° C. conditions, and roll-press it onto the current collector. A positive electrode having a positive electrode active material layer disposed thereon was prepared.

(Manufacture of lithium secondary battery)

Example 10

The negative electrode prepared in Example 5 was wound in a circular shape of 16 mm, the positive electrode was wound in a circular shape of 15 mm, and a separator was disposed between the positive electrode and the negative electrode to prepare a 2032 type coin full cell.

As the separator, a 14 µm-thick polyethylene-polypropylene copolymer separator was used.

As an electrolytic solution, 10.0% by weight of FEC was added to a mixed solvent in which EC/EMC/DEC was mixed at a volume ratio of 3/5/2, and LiPF ₆ was added as a lithium salt to a concentration of 1.3 M, and a liquid electrolytic solution was used.

Comparative Examples 9 to 11

A 2032-type coin full cell was manufactured in the same manner as in Example 8, except that the negative electrode obtained in Comparative Examples 6 to 8 was used instead of the negative electrode prepared in Example 5.

Evaluation Example 5: Evaluation of electrochemical properties (3)

The full cells prepared according to Example 10 and Comparative Examples 9 to 11 were started charging at a charging rate of 0.2 C-rate at 25° C., and the voltage was charged to 4.2 V. At this time, after charging to have a constant voltage at a constant current, a constant Charge until the voltage reaches a certain current or less (0.05C). Thereafter, discharge was performed with a constant current until it reached 2.5V at a discharge rate of 0.1C-rate. After passing through two charge/discharge cycles as described above, charging at 1 C-rate and discharging at 0.5 C-rate, the voltage section is 4.2V to 2.7V, and 200 charge/discharge cycles are continuously repeated. Graphs of the charging and discharging experiment results are shown in FIGS. 6 and 7.

6 and 7, in contrast to Examples 10 and 11, in the case of Comparative Example 7, the thickness of the silicon oxide coating layer was not thick enough to alleviate the silicon expansion volume, and thus the lifespan characteristics were remarkably deteriorated. In addition, it can be seen that in Examples 12 and 13, it is possible to prevent cracking of the negative electrode active material due to volume expansion of silicon due to the introduction of sufficient carbonaceous material.

Evaluation Example 6: Observation of the cathode surface after 100 cycles

The full coin cell manufactured according to Example 13 was subjected to 100 cycles of charging and discharging, and then the cathode was cut and the cross section was observed through a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS), and the photograph is shown in FIG. Is shown in

According to FIG. 8, no cracks were found inside the negative electrode even after 100 charging and discharging, and the F element found in the SEI layer formed by reaction with the electrolyte was observed only on the outer surface of the negative electrode active material, and not inside. Can be seen. This is thought to indirectly show that the electrolyte did not penetrate into the negative electrode because no crack was generated in the negative electrode.

In the above, preferred embodiments according to the present invention have been described with reference to the drawings and embodiments, but these are only exemplary, and various modifications and other equivalent embodiments are possible from those of ordinary skill in the art. You will be able to understand. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims (18)

A plurality of silicon particles;
A silicon oxide coating layer disposed on each of the plurality of silicon particles; And
Including a carbonaceous material disposed to separate the plurality of silicon particles from each other,
The carbonaceous material is a carbonaceous matrix,
It includes a bimodal pore structure including first pores and second pores, the first pore has a diameter of 1 to 5 nm, the second pore has a diameter of 10 to 200 nm, A composite cathode active material with a higher distribution ratio than that of the second pore. The method of claim 1,
The composite cathode active material, wherein the volume of the first pores is 20% by volume or less with respect to the total volume of the bimodal pore structure. The method of claim 1,
The composite cathode active material further comprises a carbon coating layer. The method of claim 1,
The specific surface area of the composite negative electrode active material is 1 to 20 cm ² /g, the composite negative electrode active material. The method of claim 1,
The silicon oxide coating layer comprises a compound represented by the following formula (1), a composite cathode active material.
<Formula 1>
SiO _x (0<x≤2) The method of claim 1,
The silicon particles and the silicon oxide coating layer are disposed in contact with each other, a composite cathode active material. The method of claim 1,
One surface of the silicon oxide coating layer is in contact with the silicon particles, and the other surface of the silicon oxide coating layer is disposed to contact the carbonaceous material. The method of claim 1,
Including a silicon oxide coating layer on the surface of the silicon particles,
The silicon oxide coating layer is continuous on the surface of the silicon particles, the composite cathode active material. The method of claim 1,
Including a silicon oxide coating layer on the surface of the silicon particles,
The silicon oxide coating layer has a thickness of 10nm to 20nm, composite cathode active material. The method of claim 1,
The carbonaceous material is formed from a carbon precursor having elasticity after firing, the composite cathode active material. The method of claim 10,
The carbon precursor is rayon carbon fiber, PAN based carbon fiber, pitch based carbon fiber, vapor-grown carbon, carbon fiber, graphite, polymer, coal tar pitch, petroleum pitch, meso-phase Pitch, isotropic pitch, coke, low molecular weight heavy oil, coal-based pitch, phenol resin, naphthalene resin, epoxy resin, vinyl chloride resin, polyimide, polybenzimidazole, polyacrylonitrile, polyethylene glycol, polyvinyl alcohol, polyvinyl chloride, Furfuryl alcohol, furan, cellulose, glucose, sucrose, acetic acid, malic acid, citric acid, organic acid, and a composite cathode active material comprising at least one selected from the group consisting of a combination thereof. The method of claim 1,
The carbonaceous material has a carbonization degree of 99% or more, a composite cathode active material. The method of claim 1,
The median particle diameter (D ₅₀ ) of the silicon particles is 10 nm to 200 nm, a composite cathode active material. Pulverizing the silicon in an organic solvent and/or an aqueous solvent to provide silicon particles including a silicon oxide coating layer;
Uniformly mixing the silicon particles, a carbon precursor, and a non-aqueous solvent to obtain a mixed composition; And
Firing the mixed composition to obtain a composite negative electrode active material;
Containing, a method for producing a composite negative electrode active material. The method of claim 14,
The pulverization is a mechanical pulverization method, a method for producing a composite cathode active material. The method of claim 14,
A method for producing a composite negative electrode active material, further comprising removing the non-aqueous solvent prior to firing the mixed composition. The method of claim 14,
The firing is carried out at 800°C to 1200°C, a method for producing a composite cathode active material. anode;
A negative electrode comprising the composite negative electrode active material according to any one of claims 1 to 13; And
Lithium secondary battery comprising an electrolyte.

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