KR20110100497A - Carbon anode material for lithium secondary battery, method for preparing the same, and lithium secondary battery using the same - Google Patents

Abstract

A method for manufacturing a negative electrode material for a secondary battery according to the present invention includes: (S1) mixing a core carbon material, a low crystalline carbon, an additive, and a thickener in water and stirring at a speed of 10 to 500 rpm for 0.5 to 10 hours; (S2) drying the mixture at a temperature of 80 to 200 ° C; And (S3) heat-treating the dried mixture at 700 to 3,000 ° C. under an inert atmosphere.
The manufacturing method of the negative electrode material for a lithium secondary battery is applied by the wet method as a coating method to simultaneously coat and disperse the core carbon material, the carbon for forming the coating, and the property improving additive, thereby simplifying the process and uniformly dispersing the particles. The prepared negative electrode material has excellent electrochemical properties.

Description

Carbon anode material for lithium secondary battery and manufacturing method thereof and lithium secondary battery using same {Carbon anode material for lithium secondary battery, method for preparing the same, and lithium secondary battery using the same}

The present invention relates to a negative electrode material for a secondary battery, a method of manufacturing the same, and a secondary battery including the negative electrode.

As portable electronic devices such as video cameras, cordless phones, mobile phones, and notebook computers are rapidly spreading in daily life, the demand for secondary batteries used as a power source has increased greatly. Among them, lithium secondary batteries have high capacity and high energy density. Due to the battery characteristics, active research and development has been carried out at home and abroad, and is currently the most widely used secondary battery.

A lithium secondary battery basically consists of a positive electrode, a negative electrode, and an electrolyte. Therefore, research and development of a lithium secondary battery can be largely divided into studies on a cathode, an anode material, and an electrolyte.

Among these, natural graphite, which is used as a negative electrode material for lithium secondary batteries, exhibits excellent initial capacity but poor efficiency and cycle capacity. This is known to be due to the electrolyte decomposition reaction in the highly crystalline natural graphite edge portion.

In order to overcome this characteristic, the initial capacity is reduced by surface treatment (coating) of low-crystalline carbon on natural graphite and heat-treated at 1,000 ° C or higher to coat low crystalline carbide on the surface of natural graphite. The negative electrode material with improved characteristics was obtained.

Japanese Laid-Open Patent Publication No. 1998-021913 covers a metal oxide around a carbon material using a ball mill, and Japanese Laid-Open Patent Publication No. 1999-279785 forms a coating layer composed of an organic material and a metal compound on a graphite surface. Disclosed is a method for producing a negative electrode material. However, in order to coat the metallic material or carbon material, which is a small particle of several microns or less, on the surface of the core carbon material, a small particle is dispersed in advance by using a high energy dispersing force such as a ball mill or a wet method, and then the core carbon material There is a problem in that a complicated process of coating the surface to form a coating layer is required.

Accordingly, efforts to solve the above-mentioned problems of the prior art have been continued in the related art, and the present invention has been devised under such a technical background.

Accordingly, an object of the present invention is to provide a negative electrode material for a secondary battery having excellent electrochemical characteristics and a method for manufacturing a negative electrode material for a secondary battery having a simple manufacturing process thereof.

In addition, another object of the present invention to provide a lithium secondary battery negative electrode and a lithium secondary battery comprising the same prepared using the negative electrode material.

In order to solve the above problems, the negative electrode material for a lithium secondary battery of the present invention is a core carbon material; And a covering layer formed of the covering material and surrounding the core carbon material, wherein the covering material includes low crystalline carbon, an additive, and a thickener.

The core carbon material preferably has an average particle diameter of 10 to 20 µm, and natural graphite, artificial graphite, soft carbon, hard carbon, or the like can be used. The low crystalline carbon preferably has an average particle diameter of 0.5 to 10 µm, and pitch, tar, phenol resin, furan resin, and furfuryl alcohol may be used. Preferably, the core carbon material and the low crystalline carbon are mixed in a weight ratio of 85 to 95: 5 to 15.

The additive is not particularly limited, but may be Si, Sn, Ag, Zn, Al, and Ge; Metal oxides of MgO, Al ₂ O ₃ , ZrO ₂ , SiO ₂ , TiO ₂ , CuO and SnO ₂ ; And carbon nanotubes that are carbon nanotubes, carbon nanofibers, vapor grown carbon fibers, and carbon black. The additive is preferably 1 to 3 parts by weight based on 100 parts by weight of the total weight of the core carbon material and the low crystalline carbon.

The thickener is not particularly limited, but carboxymethylcellulose, cellulose, starch and the like are used. Such thickener is preferably 1 to 3 parts by weight based on 100 parts by weight of the total weight of the core carbon material and the low crystalline carbon.

Method for producing a negative electrode material for a lithium secondary battery according to the present invention, (S1) mixing the core carbon material, low crystalline carbon, additives and thickeners in water and stirring at a rate of 10 to 500rpm for 0.5 to 10 hours;

(S2) drying the mixture at a temperature of 80 to 200 ° C; And

(S3) heat-treating the dried mixture at 700 to 3,000 ° C. under an inert atmosphere.

The negative electrode material of the present invention described above can be used in the negative electrode for lithium secondary batteries and lithium secondary batteries.

The negative electrode material for a lithium secondary battery of the present invention is excellent in electrochemical properties, and in the present invention, by applying a wet method as a coating method, the process is simple by simultaneously coating and dispersing a core carbon material, a carbon material for forming a coating, and a property improving additive.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical spirit of the present invention, the present invention includes matters described in such drawings. It should not be construed as limited to.
1 is an SEM photograph of Example 1.
2 is a SEM photograph of Comparative Example 1.
3 is an SEM photograph of Example 2. FIG.
4 shows EDS-mapping results of Example 2. FIG.

Hereinafter, the present invention will be described in detail. The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as a semantic concept consistent with the technical spirit of the present invention based on the principle of the present invention.

Core carbon material according to the present invention; And a coating layer formed of a coating material and surrounding the core carbon material to produce a negative electrode material for a lithium secondary battery.

First, the core carbon material, low crystalline carbon, additives and thickeners are mixed with water and stirred at a speed of 10 to 500 rpm for 0.5 to 10 hours (step S1).

As the core carbon material, natural graphite, artificial graphite, soft carbon, hard carbon, or the like may be used alone or in combination of two or more thereof. And it is preferable to use the core carbon material whose average particle diameter is 10-20 micrometers.

Although it does not specifically limit as low crystalline carbon, Pitch, tar, a phenol resin, furan resin, a full furyl alcohol, etc. can be used individually or in mixture of 2 or more of these, respectively. And as a low crystalline carbon, it is preferable to use the thing whose average particle diameter is 0.5-10 micrometers.

It is preferable that such a core carbon material and low crystalline carbon are mixed by 85-95: 5-15 weight ratio.

Additives that play a role in improving properties include metals such as Si, Sn, Ag, Zn, Al and Ge and metal oxides such as MgO, Al ₂ O ₃ , ZrO ₂ , SiO ₂ , TiO ₂ , CuO and SnO ₂ Metal-based materials for high capacity and high safety, and carbon nano materials for high power and long life characteristics such as carbon nanotubes, carbon nanofibers, vapor grown carbon fibers, and carbon black, respectively, or the like Two or more of these can be mixed and used. As such carbon nanomaterial, it is preferable to employ a vapor-grown carbon fiber having a high aspect ratio so as to provide high conductivity even in a small amount. Vapor-growth carbon fibers are carbon fibers graphitized by heat treatment at a temperature of 10 to 15000 and having an aspect ratio of each fiber filament of at least 2000 ° C. Each fiber filament of this vapor-grown carbon fiber includes a hollow extending along its central axis and includes branched carbon fiber filaments.

The thickener is for increasing the viscosity of the solution, and is not particularly limited, but carboxymethylcellulose, cellulose, starch, and the like can be used.

When these core carbon materials, low crystalline carbon, additives and thickeners are mixed with water, a paste is formed, and these are stirred to uniformly disperse the particles. At this time, it is preferable to stir for 0.5 to 10 hours, if necessary, can be stirred at a speed of 10 to 500rpm according to the characteristics of the stirrer.

Compared to the dry method in which the core carbon material is crushed and thus adversely affects the overall electrochemical properties, the present invention uses the wet method, thereby preventing the grinding of the core carbon material.

Then, the mixture is dried at a temperature of 80 to 200 ℃ (step S2).

Dry at 80-200 ° C. using a dryer such as a vacuum oven.

Then, the dried mixture is heat treated at 700 to 3,000 ° C. under an inert atmosphere to prepare a negative electrode material for a secondary battery (S3 step).

The dried mixture is subjected to a calcination process of heat treatment at 700 to 3,000 ° C. under an inert atmosphere such as a nitrogen atmosphere. In this heat treatment, the thickener is carbonized. It may also optionally be subjected to additional classification steps.

That is, the method of manufacturing a negative electrode material for a lithium secondary battery of the present invention is simpler by applying a wet method as a coating method and simultaneously coating and dispersing a core carbon material, a carbon forming material, and a property improving additive. The negative electrode material thus prepared is uniformly dispersed and has excellent electrochemical properties. The negative electrode material of the present invention prepared according to the above-described method, the core carbon material; And a coating layer formed of the coating material and surrounding the core carbon material, wherein the coating material includes low crystalline carbon, an additive, and a thickener.

The negative electrode material of the present invention prepared as described above is prepared as an active material paste by mixing with a conductive material, a binder, and an organic solvent according to a conventional negative electrode manufacturing method, and then applied to a commonly used negative electrode current collector, such as a copper foil. Next, it can be used to prepare a negative electrode for a lithium secondary battery by drying, heat treatment and compression.

In addition, as described above, the negative electrode and the lithium-based transition metal compound prepared according to the present invention are coated on the positive electrode current collector with a predetermined thickness to face the positive electrode with a separator therebetween, and the separator is impregnated with an electrolyte solution for a lithium secondary battery. It is also possible to manufacture a lithium secondary battery capable of phosphorus charging and discharging. Since such a lithium secondary battery manufacturing method is well known to those skilled in the art to which the present invention pertains, a detailed description thereof will be omitted.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

Example 1

CMC was prepared as spherical natural graphite as core carbon material and carbonaceous material for coating formation as petroleum pitch and properties improving additives.

95 wt% of spherical natural graphite (average particle size 20 μm) and 5 wt% of pitch (average particle size 5 μm) were added to a paddle mixer and mixed for 1 hour. Based on the mixture 100, 2 parts by weight of VGCF, 2 parts by weight of CMC and 70 parts by weight of distilled water were added and mixed to form a paste. In the paste state, the speed of the paddle mixer was 100 rpm and mixed for 2 hours to uniformly disperse the materials. After the dispersion was completed, the mixture was put in a vacuum oven and dried at 150 ° C. for 2 hours, and then heat-treated at 1,000 ° C. for 10 hours in a nitrogen atmosphere. After the heat treatment was completed to classify 325 Mesh to prepare a final negative electrode material.

Example 2

A negative electrode material was manufactured in the same manner as in Example 1, except that Al ₂ O ₃ powder (average particle size 100 nm) was used as the property improving additive.

Example 3

A negative electrode material was manufactured in the same manner as in Example 1, except that Si powder (average particle size: 50 nm) was used as the property improving additive.

Comparative Example 1

95% by weight of spherical natural graphite (average particle size 20µm), 5% by weight of pitch (average particle size: 5µm) and 2 parts by weight of VGCF based on 100 carbon components in a double screw type Nauta Mixer In the state, the mixer rotated at 200 rpm. Heat treatment was performed at 1,000 ° C. for 10 hours in a nitrogen atmosphere. After completion of the heat treatment, the mixture was classified into 325 Mesh to prepare a final negative electrode material.

Comparative Example 2

95% by weight of spherical natural graphite (average particle size: 20 µm), pitch (average particle size: 5 µm) weight percent, and 2 parts by weight of Al ₂ O ₃ powder, based on the carbon component 100, in a mixer equipped with a high-speed rotating impeller In the state, the impeller rotated at 6,000 rpm and mixed. Heat treatment was performed at 1,000 ° C. for 10 hours in a nitrogen atmosphere. After the heat treatment, the mixture was classified into 325 Mesh to prepare a final negative electrode material.

Comparative Example 3

95% by weight of spherical natural graphite (average particle size 20 µm), pitch (average particle size 5 µm) weight percent and 2 parts by weight of Si powder based on the carbon component 100 are placed in a mixer equipped with a high speed impeller (impeller) in a dry state. The rotational speed of 6,000rpm was mixed. Heat treatment was performed at 1,000 ° C. for 10 hours in a nitrogen atmosphere. After the heat treatment, the mixture was classified into 325 Mesh to prepare a final negative electrode material.

Test Example 1. Measurement of Properties

Particle Size Distribution Measurement: The particle size analyzer using the laser scattering method measured the average particle size of the negative electrode material of Example 1-3 and Comparative Example 1-3 is shown in Table 1 below.

Specific Surface Area (SSA) Measurement: The specific surface areas of the negative electrode materials of Examples 1-3 and Comparative Examples 1-3 using nitrogen adsorption BET method are shown in Table 1 below.

Test Example 2 Measurement of Electrochemical Properties

100 g of the negative electrode material prepared in Examples 1-3 and Comparative Examples 1-3 was placed in a 500 ml reactor, and a small amount of N-methylpytolidone (NMP) and PVDF (binder) were added thereto, followed by mixing to prepare a slurry. . The slurry was uniformly applied to a copper foil having a thickness of 12 μm, and vacuum dried at 120 ° C. to prepare a negative electrode for a lithium secondary battery. Using the prepared negative electrode and lithium foil as a positive electrode, a coin-type half cell was prepared using Celgard 2400 as a separator and 1 M LiPF ₆ mixed with EC: DEC = 3: 7 as a nonaqueous electrolyte.

Charge and discharge test was performed using the prepared half cell. The charge / discharge test regulates the potential in the range of 0 to 1.5V, charges to 0.01V with the charging current of 0.5mA / cm ² , maintains the voltage of 0.01V, and when the charging current becomes 0.02mA / cm ^2. Charging continued until. The discharge current was discharged up to 1.5 V at 0.5 mA / cm ² . In Table 1, the charge and discharge efficiency represents the ratio of the discharged capacitance to the charged capacitance.

Test Example 3. SEM Photo

SEM pictures of Example 1-2 and Comparative Example 1 are shown in Figures 1-3. In addition, the EDS-mapping results of Example 2 are shown in FIG.

Looking at the case of Example 1 and Comparative Example 1, it can be seen by the results of Table 1 that the electrochemical properties are also improved as the VGCF dispersion of Example 1 is well, looking at the SEM photograph of Figure 1 and 2, In the case of FIG. 2 of Comparative Example 1 manufactured by the dry method, some VGCF agglomeration phenomena were found, while in the case of FIG. 1 of Example 1 to which the wet method of the present invention was applied, the VGCF agglomeration was significantly reduced.

In addition, in the case of Example 2-3, as in Example 1, when the metal or metal oxide nanomaterials are also dispersed by the wet method of the present invention, it can be seen that uniform dispersion is possible. However, even in the case of Comparative Example 2-3 using the dry method of mixing at high speed, uniform material dispersion is possible, but it is accompanied by the grinding of the core carbon material, which adversely affects the overall electrochemical properties.

Claims (17)

Core carbon material; And a coating layer formed of a coating material and surrounding the core carbon material, the negative electrode material for a lithium secondary battery comprising:
The coating material includes a low crystalline carbon, an additive and a thickener negative electrode material for a lithium secondary battery. The method of claim 1,
The core carbon material is a negative electrode material for a lithium secondary battery, characterized in that the average particle diameter of 10 to 20 ㎛. The method of claim 1,
The core carbon material is a negative electrode material for a lithium secondary battery, characterized in that the compound of one or a mixture of two or more selected from natural graphite, artificial graphite, soft carbon and hard carbon. The method of claim 1,
The low crystalline carbon is an anode material for a lithium secondary battery, characterized in that the average particle diameter is 0.5 to 10 ㎛. The method of claim 1,
The low crystalline carbon is a negative electrode material for a lithium secondary battery, characterized in that one compound selected from pitch, tar, phenol resin, furan resin, and furfuryl alcohol or a mixture of two or more kinds. The method of claim 1,
The core carbon material and the low crystalline carbon are mixed in a weight ratio of 85 to 95: 5 to 15, the negative electrode material for a lithium secondary battery. The method of claim 1,
The additives are metals of Si, Sn, Ag, Zn, Al and Ge; Metal oxides of MgO, Al ₂ O ₃ , ZrO ₂ , SiO ₂ , TiO ₂ , CuO and SnO ₂ ; And at least one compound selected from carbon nanotubes, carbon nanofibers, vapor grown carbon fibers, and carbon black carbon nanomaterials, or a mixture of two or more thereof. The method of claim 1,
The additive is a negative electrode material for a lithium secondary battery, characterized in that 1 to 3 parts by weight based on 100 parts by weight of the total weight of the core carbon material and low crystalline carbon. The method of claim 1,
The thickener is a negative electrode material for a lithium secondary battery, characterized in that one or a mixture of two or more selected from carboxymethylcellulose (cellulose), cellulose and starch. The method of claim 1,
The thickener is 1 to 3 parts by weight based on 100 parts by weight of the total weight of the core carbon material and low crystalline carbon negative electrode material for a lithium secondary battery. (S1) mixing the core carbon material, the low crystalline carbon, the additive and the thickener into water and stirring;
(S2) drying the mixture at a temperature of 80 to 200 ° C; And
(S3) heat-treating the dried mixture at 700 to 3,000 ° C. under an inert atmosphere;
Method for producing a negative electrode material for a lithium secondary battery comprising a. 12. The method of claim 11,
The core carbon material is a method for producing a negative electrode material for a lithium secondary battery, characterized in that the compound of one or a mixture of two or more selected from natural graphite, artificial graphite, soft carbon and hard carbon. 12. The method of claim 11,
The low crystalline carbon is a method for producing a negative electrode material for a lithium secondary battery, characterized in that the compound selected from pitch, tar, phenol resin, furan resin, and furfuryl alcohol or a mixture of two or more kinds. 12. The method of claim 11,
The additives are metals of Si, Sn, Ag, Zn, Al and Ge; Metal oxides of MgO, Al ₂ O ₃ , ZrO ₂ , SiO ₂ , TiO ₂ , CuO and SnO ₂ ; And at least one compound selected from carbon nanotubes, carbon nanofibers, vapor grown carbon fibers, and carbon black carbon nanomaterials, or a mixture of two or more kinds thereof. 12. The method of claim 11,
The thickener is a method for producing a negative electrode material for a lithium secondary battery, characterized in that one or a mixture of two or more selected from carboxymethylcellulose, cellulose and starch. In the negative electrode for a lithium secondary battery formed by coating a negative electrode material and a binder on the negative electrode current collector,
The negative electrode material is a negative electrode material for a lithium secondary battery, characterized in that the negative electrode material manufactured by the manufacturing method of any one of claims 11 to 15. In a lithium secondary battery comprising a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte solution,
The negative electrode is a lithium secondary battery, characterized in that the negative electrode according to claim 16.

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