KR102013826B1 - Negative active material for lithium secondary battery, and lithium secondary battery including the same - Google Patents

Abstract

One embodiment of the present invention is a carbon-based particle having a plurality of pores in the surface portion, porous core particles; A silicon coating layer on the porous core particle; And a carbon-based coating layer disposed on the silicon coating layer, to provide a negative active material for a lithium secondary battery and a lithium secondary battery including the same.

Description

A negative electrode active material for a lithium secondary battery, and a lithium secondary battery including the same TECHNICAL FIELD AND AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME

It relates to a negative electrode active material for a lithium secondary battery, and a lithium secondary battery comprising the same.

A lithium secondary battery is a battery which is charged and discharged by using a redox reaction of lithium ions. The lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte formed with an ion exchange membrane interposed therebetween.

For a system requiring a larger capacity battery such as a lithium secondary battery such as an electric vehicle, it is necessary to increase the capacity of the negative electrode active material and increase the output characteristics and life characteristics. To this end, it is necessary to develop for the stable use of the alloy-based material having a large capacity, rather than the existing carbon-based negative electrode material.

In the case of the conventional carbon-based negative electrode active material, the theoretical capacity is only 372 mAh / g, and due to the interlayer insertion and desorption mechanism of lithium ions during charging and discharging, its output characteristics are particularly poor at high speed charging.

In addition, the alloy-based material currently being researched and developed has a very low electrical conductivity, which causes severe plate damage due to significant volume expansion during charge and discharge, as well as a rapid decrease in capacity. Therefore, there is a great difficulty in commercialization.

It is intended to provide a negative electrode active material for a lithium secondary battery having a larger capacity than the current commercially available carbon-based negative electrode active material and excellent output characteristics and a method of manufacturing the same.

In one embodiment of the present invention, the porous core particles, which are carbon-based particles having a plurality of pores located in the surface portion; A silicon coating layer on the porous core particle; And a carbon-based coating layer disposed on the silicon coating layer.

Specifically, the porous core particles may have a BET specific surface area of 3.00 m ² / g or more.

The pores of the porous core particles may have a diameter of 10 to 70 ㎛.

The surface portion of the porous core particles may mean a region from the surface of the carbon-based particles having a diameter of 10 to 70㎛ from more than 0% to 20% of the radius.

In this regard, the porous core particles, the carbon-based particles may be etched inward from the surface, a plurality of pores formed in the region.

In the plurality of pores, a plurality of metal nanoparticles may be located. The carbon-based particles may include at least one selected from graphite, amorphous carbon, graphene, and carbon black.

Meanwhile, the silicon coating layer may have a plurality of silicon nanoparticles dispersed in an island form, a film form, or a combination thereof.

The silicon nanoparticles may be spherical particles, may be amorphous, and the diameter may be 5 to 100 nm.

The total thickness of the silicon coating layer may be 5 to 100 nm.

Independently of this, the carbon-based coating layer may be made of hard carbon, soft carbon, mesophase pitch carbide, calcined coke, and amorphous carbon selected from a mixture thereof, the total thickness May be from 5 to 100 nm.

In the negative electrode active material, the weight ratio of the silicon coating layer / porous core particles may be 3/100 to 20/100, and the weight ratio of the carbonaceous coating layer / porous core particles may be 2/100 to 10/100.

In addition, based on the total weight (100% by weight) of the negative electrode active material, the porous core particles are included 70 to 95% by weight, the silicon coating layer is contained 3 to 20% by weight, the carbon-based coating layer is to be included in the remainder Can be.

The total diameter of the negative electrode active material may be 10 to 70 ㎛.

The BET specific surface area of the negative electrode active material may be 0.3 to 7 m ² / g.

In another embodiment of the invention, the step of attaching the metal nanoparticles on the surface of the carbon-based particles; Heat treating the carbon-based particles to which the metal nanoparticles are attached to the surface to obtain carbon-based particles having a plurality of pores formed on the surface thereof as the porous core particles; Forming a silicon coating layer on the porous core particles; And forming a carbon-based coating layer on the silicon coating layer; forming the silicon coating layer; And forming the carbon-based coating layer; is performed in one reactor, which is continuously performed using a chemical vapor deposition method, to provide a method of manufacturing a negative active material for a lithium secondary battery.

Specifically, forming the silicon coating layer; And forming the carbon-based coating layer; after the metal nanoparticles form the silicon coating layer on a surface of the silicon-based precursor, the temperature of the reactor is raised, and the silicon is used by using a hydrocarbon-based precursor. It may be to form the carbon-based coating layer on the coating layer.

More specifically, the step of forming the silicon coating layer; silane (silane, SiH ₄ ), dichlorosilane (Dichlorosilane, SiH ₂ Cl ₂ ), silicon tetrafluoride (Silicon Tetrafluoride, SiF ₄ ), silicon tetra 300 to 900 ° C. using silicon-based precursors that are fluoride (Silicon Tetrachloride, SiCl ₄ ), methylsilane (Methylsilane, CH ₃ SiH ₃ ), disilane (Disilane, Si ₂ H ₆ ), or a combination In the temperature range, it may be performed for 0.1 to 10 hours.

In addition, the step of forming a carbon-based coating layer on the silicon coating layer, using a hydrocarbon precursor that is acetylene (acetylene, C ₂ H ₂ ), ethylene (ethylene, C ₂ H ₄ ), or a combination thereof, 500 to In the temperature range of 1000 ℃, it may be performed for 0.1 to 5 hours.

On the other hand, the step of attaching the metal nanoparticles on the carbon-based core particles; if the method of using a solution, it is not limited to a special method. For example, it may be performed using a solution method which is a sol-gel, reflux, spray-dry, or a combination thereof.

More specifically, for example, attaching metal nanoparticles on the porous core particles; preparing a solution including the porous core particles, a metal raw material, and a solvent; In the solution, precipitating the metal raw material onto the surface of the carbonaceous core particle; And growing the metal raw material deposited on the surface of the carbon-based core particles into the metal nanoparticles.

The metal raw material may be a nickel (Ni) raw material, an iron (Fe) raw material, a cobalt (Co) raw material, a manganese (Mn) raw material, a mixture thereof, or an alloy thereof. That is, if it can be formed of metal nanoparticles that are nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), a mixture thereof, or an alloy thereof is not particularly limited.

 The metal nanoparticles may be, for example, iron-nickel alloys (Fe-Ni), cobalt-nickel alloys (Co-Ni), or mixtures thereof.

The metal nanoparticles may have a diameter of 5 to 800 nm, and may be attached so that the weight ratio of the metal nanoparticles / carbonaceous core particles is 1/100 to 30/100.

Heat-treating the carbon-based particles to which the metal nanoparticles are attached to the surface to obtain carbon-based particles having a plurality of pores formed on the surface thereof as the porous core particles; the metal nanoparticles attached to the surface of the carbon-based particles A, the surface of the carbon-based particles may be etched to form pores at the etched positions.

The heat treatment may be performed for 1 to 12 hours in a temperature range of 700 to 1200 ℃.

Heat-treating the carbon-based particles to which the metal nanoparticles are attached to the surface to obtain carbon-based particles having a plurality of pores formed on the surface thereof as porous core particles; in the pores of the obtained porous core particles, the metal Nanoparticles may remain. As described above, the silicon coating layer and the carbon-based coating layer may be formed on the surface of the porous core particle in which the metal nanoparticles remain.

Alternatively, the step of removing the metal nanoparticles remaining on the surface of the porous core particles; after, to form a silicon coating layer and a carbon-based coating layer. For example, the metal nanoparticles may be selectively etched and removed by acid treatment.

In another embodiment of the present invention, a positive electrode; cathode; And an electrolyte; wherein the negative electrode includes the above-described negative electrode active material, and provides a lithium secondary battery.

An anode active material according to an embodiment of the present invention, the porous core particles are carbon-based particles in which a plurality of pores are located on the surface portion; A silicon coating layer on the porous core particle; And a carbon-based coating layer disposed on the silicon coating layer, which is applied to a battery to contribute to improving lifespan characteristics and output characteristics.

1 schematically illustrates a lithium secondary battery according to one embodiment of the present invention.
2 is a SEM photograph of the graphite particles used in Example 1 of the present invention.
3 is a SEM photograph of graphite @ nano-Ni synthesized in Example 1 of the present invention,
FIG. 4 is an SEM photograph of graphite particles (Etched graphite, EG) whose surface is etched in Example 1 of the present invention.
5 is a SEM photograph of the negative electrode active material particles finally obtained in Example 1 of the present invention.
FIG. 6 is a SEM photograph of graphite particles (Etched graphite, EG) whose surface is etched in Example 1 of the present invention.
7 and 8 are SEM photographs of the result of etching the surface of the graphite particles by using a simple mixture of graphite particles and Ni precursor in Evaluation Example 2 of the present invention.
9 to 11 are SEM photographs of etched graphite particles (EG) whose surfaces were etched in Example 1 of the present invention. Specifically, according to Evaluation Example 2 of the present invention, the etching treatment of the graphite particles (heat treatment) The time is different from 1 hour, 6 hours, and 8 hours, and is shown in Figs. 9, 10, and 11, respectively.
FIG. 12 shows the results of evaluating the specific voltage-versus-voltage characteristic of each lithium secondary battery in Evaluation Example 2 of the present invention. FIG.
13 is a result of evaluating the output characteristics of each lithium secondary battery under constant current conditions in Evaluation Example 2 of the present invention.
Fig. 14 is a diagram showing evaluation conditions of constant current and constant voltage in Evaluation Example 2 of the present invention. It is the result of evaluating the output characteristic of each lithium secondary battery.
15 shows the results of evaluating the initial capacity of each lithium secondary battery in Evaluation Example 3 of the present invention.
16 and 17 show the results of evaluating the output characteristics of each lithium secondary battery in Evaluation Example 3 of the present invention.
18 is a result of evaluating the life characteristics of each lithium secondary battery in Evaluation Example 3 of the present invention.
19 to 22 show results of measuring BET specific surface areas of Etched graphite @ nano-Si and the negative electrode active material of Example 1 in Evaluation Example 4 of the present invention.
23 is a result of evaluating the life characteristics of each lithium secondary battery in Evaluation Example 4 of the present invention.
24 is a result of evaluating the output characteristics of each lithium secondary battery in Evaluation Example 4 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

Anode Active Material for Lithium Secondary Battery

In one embodiment of the present invention, the porous core particles, which are carbon-based particles having a plurality of pores located in the surface portion; A silicon coating layer on the porous core particle; And a carbon-based coating layer disposed on the silicon coating layer.

The porous core particles have a BET specific surface area increased by a plurality of pores present on the surface thereof, and provide a space for buffering the volume expansion of the silicon coating layer located thereon, in comparison with the general graphite particles. This contributes to the stability of the negative electrode active material.

In addition, the silicon coating layer has a higher capacity than graphite particles, contributing to the capacity improvement of the negative electrode active material.

In addition, the carbon-based coating layer, which is located on the upper portion of the silicon coating layer, suppresses the volume expansion, contributes to the improvement of electronic conductivity on the surface, and further improve the output characteristics of the battery.

As such, the anode active material is a double coating layer formed by the silicon coating layer and the carbon-based coating layer on the porous core particles, while expressing a high capacity, maintaining stability while driving the battery, and improving output and life characteristics of the battery. It can be improved.

Hereinafter, the negative electrode active material will be described in more detail.

Porous core particles

As mentioned above, the porous core particles have an increased BET specific surface area due to the large number of pores present in the surface thereof, as compared to the normal graphite particles. Specifically, the BET specific surface area may be 3.00 m ² / g or more, more specifically 0.3 m ² / g or more and 7 m ² / g or less.

For example, the porous core particle may be a carbon-based particle including at least one selected from graphite, amorphous carbon, and graphene, and may have pores formed by etching a predetermined depth from the surface thereof.

More specifically, for example, when the metal nanoparticles are uniformly attached to the surface of the carbon-based particles, the surface of the carbon-based particles may be etched by the metal nanoparticles at the site where the metal nanoparticles are attached. Can be. That is, in the porous core particle, the carbon-based particles may be etched inward from the surface thereof, and a plurality of pores may be formed in the region.

Thus, the plurality of pores formed may include a plurality of the metal nanoparticles. As will be described later, the metal nanoparticles may be removed or may be located in a plurality of pores in the porous core particles without being removed.

The diameter of the metal nanoparticles and the depth etched thereby determine the surface portion of the porous core particles. Here, the surface portion of the porous core particles, from the surface of the carbon-based particles having a diameter of 10 to 70 ㎛, will mean a region from more than 0% to 20% of the radius, specifically 1% to 20% or less Can be. In this range, the BET specific surface area of the porous core particles has an advantage compared to that of ordinary graphite particles. The larger the diameter of the silicon nanoparticles, the wider the surface portion, which will be described later.

However, when pores are formed in a region exceeding 20% of the radius of the carbon-based particles, there is a problem that the BET specific surface area is too large, causing performance degradation when applied to the battery. In contrast, when pores are formed in a region of less than 1% of the radius of the carbon-based particle, the increase in BET specific surface area is minimal.

On the other hand, when the shape of the metal nanoparticles are spherical, the shape of the pores formed by etching may also be spherical. In addition, the diameter of the metal nanoparticles may determine the pore diameter of the porous core particles, the pore diameter of the porous core particles may be 5 to 800 nm. The larger the diameter of the silicon nanoparticles, the larger the pore diameter, which will be described later.

Silicone coating layer

Meanwhile, the silicon coating layer may have a plurality of silicon nanoparticles dispersed in an island form, a film form, or a combination thereof. As will be described later, an appropriate silicon-based precursor may be used, and a chemical vapor deposition method may be used to form a silicon coating layer on which the film form and the island form are mixed on the graphene coating layer.

Specifically, when using the chemical vapor deposition method. The silicon coating layer begins to be formed in the island form, and the island form is a form suitable for the volume expansion of the silicon nanoparticles included in the silicon coating layer.

However, as the deposition amount increases, the film form is formed, and finally, the deposition may be completed in a state in which the film form and the island form are mixed. In this case, the capacity per weight of the silicon particles can be improved, and the chemical conversion efficiency can be improved.

In contrast, in the case of using a physical vapor deposition method such as ball milling, the silicon nanoparticles are simply attached onto the first carbon coating layer by a physical strong force in the process of mixing each raw material, whereby the distribution of the silicon nanoparticles is uniform. It is almost impossible to attach and adjust it. In addition, pulverization occurs simultaneously with the mixing of the respective raw materials, and at this time, destruction of the carbon material occurs, which may cause performance degradation when applied to the battery.

The silicon nanoparticles formed by the chemical vapor deposition method may be spherical particles having a diameter of 5 to 100 nm, and may be amorphous. The amorphous silicon nanoparticles have a large capacity per weight of the particles, significantly less stress due to volume expansion during charging (ie alloying with lithium), alloying with lithium and The high dealloying speed is advantageous for the charge / discharge rate.

The total thickness of the silicon coating layer may be 5 to 100 nm.

Carbon coating layer

The carbon-based coating layer may be made of hard carbon, soft carbon, mesophase pitch carbide, calcined coke, and amorphous carbon selected from a mixture thereof, and the total thickness is 5 to 100. Nm.

As will be described later, after the silicon coating layer is formed, a carbon-based coating layer may be formed on the silicon coating layer by using a chemical vapor deposition method in succession using a suitable hydrocarbon precursor in the same device.

Total anode active material

In the negative electrode active material, the weight ratio of the silicon coating layer / porous core particles may be 3/100 to 20/100, and the weight ratio of the carbonaceous coating layer / porous core particles may be 2/100 to 10/100.

In addition, based on the total weight (100% by weight) of the negative electrode active material, the porous core particles are included 70 to 95% by weight, the silicon coating layer is contained 3 to 20% by weight, the carbon-based coating layer is to be included in the remainder Can be.

The total diameter of the negative electrode active material may be 10 to 70 ㎛.

BET specific surface area of the negative electrode active material is. 0.3 to 7 m ² / g.

When this is satisfied, the negative electrode active material may express high capacity of 440 to 900 mAh / g, but may have excellent life characteristics and stability.

Manufacturing method of negative electrode active material for lithium secondary battery

In another embodiment of the invention, the step of attaching the metal nanoparticles on the surface of the carbon-based particles; Heat treating the carbon-based particles to which the metal nanoparticles are attached to the surface to obtain carbon-based particles having a plurality of pores formed on the surface thereof as the porous core particles; Forming a silicon coating layer on the porous core particles; And forming a carbon-based coating layer on the silicon coating layer; forming the silicon coating layer; And forming the carbon-based coating layer; is performed in one reactor, which is continuously performed using a chemical vapor deposition method, to provide a method of manufacturing a negative active material for a lithium secondary battery.

This is one of the methods of manufacturing the above-mentioned negative electrode active material. Specifically, after forming a plurality of pores in the surface portion of the carbon-based core particles to obtain a porous core particles, and after forming a silicon coating layer using a chemical vapor deposition (CVD) in the same reactor followed by carbon It is a series of process of forming a system coating layer (henceforth "continuous process").

Hereinafter, a detailed description of the negative electrode active material will be omitted, and the features of each step will be described in detail.

Continuous process

Prior to explaining the manufacturing process of the porous core particles, the continuous process will be described.

According to the continuous process, the silicon coating layer and the carbon-based coating layer can be formed in one reactor, in contrast to the discontinuous process (for example, when the process of forming the silicon coating layer and the carbon-based coating layer is different), the process operation There are advantages in terms of cost, time, etc. In addition, since the continuous process is based on the CVD method, it is possible to form each coating layer by exchanging only precursors at an appropriate time without using a solvent.

Specifically, forming the silicon coating layer; And forming the carbon-based coating layer; after the metal nanoparticles form the silicon coating layer on a surface of the silicon-based precursor, the temperature of the reactor is raised, and the silicon is used by using a hydrocarbon-based precursor. It may be to form the carbon-based coating layer on the coating layer.

More specifically, the step of forming the silicon coating layer; silane (silane, SiH ₄ ), dichlorosilane (Dichlorosilane, SiH ₂ Cl ₂ ), silicon tetrafluoride (Silicon Tetrafluoride, SiF ₄ ), silicon tetra 300 to 900 ° C. using silicon-based precursors that are fluoride (Silicon Tetrachloride, SiCl ₄ ), methylsilane (Methylsilane, CH ₃ SiH ₃ ), disilane (Disilane, Si ₂ H ₆ ), or a combination In the temperature range, it may be performed for 0.1 to 10 hours.

In addition, forming a carbon-based coating layer on the silicon coating layer; 500, using a hydrocarbon precursor that is acetylene (acetylene, C ₂ H ₂ ), ethylene (ethylene, C ₂ H ₄ ), or a combination thereof, In the temperature range of to 1000 ℃, it may be performed for 0.1 to 5 hours.

The silicon-based precursor and the hydrocarbon-based precursor may be liquid or gaseous.

For example, the liquid or gaseous silicon precursor is vaporized and the silicon coating layer is formed by chemical vapor deposition, and then the temperature is raised only in the same reactor, and thus the liquid or gaseous hydrocarbons. The carbon precursor may be formed by using a chemical vapor deposition method based on a precursor. In this case, gas such as hydrogen (H ₂ ), argon (Ar), nitrogen (N ₂ ) and the like may flow in a reactor in which chemical vapor deposition occurs.

In the case of using the chemical vapor deposition method, the silicon nanoparticles included in the silicon coating layer may be amorphous, and the silicon coating layer may be deposited in a mixture of a film form and an island form. Accordingly, the capacity per weight of the silicon particles can be improved, and the chemical conversion efficiency can be improved.

Porous Core Particle Manufacturing Process

On the other hand, the porous core particles may be prepared by etching the surface of the carbon-based particles using metal nanoparticles.

In this case, as mentioned above, the metal nanoparticles are grown on the surface of the carbon-based particles by mixing the raw material, which is a precursor of the metal nanoparticles, and the carbon-based particles in a solution.

That is, the step of attaching the metal nanoparticles on the carbon-based core particles; if the method of using a solution, is not limited to a particular method of performing. For example, it may be performed using a solution method which is a sol-gel, reflux, spray-dry, or a combination thereof.

More specifically, for example, attaching metal nanoparticles on the porous core particles; preparing a solution including the porous core particles, a metal raw material, and a solvent; In the solution, precipitating the metal raw material onto the surface of the carbonaceous core particle; And growing the metal raw material deposited on the surface of the carbon-based core particles into the metal nanoparticles.

The metal raw material is not particularly limited as long as it can be formed of metal nanoparticles that are nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), or a combination thereof. Nickel alloys (Fe-Ni), cobalt-nickel alloys (Co-Ni) or a combination thereof may be included.

The metal nanoparticles may have a diameter of 5 to 800 nm, and may be attached so that the weight ratio of the metal nanoparticles / carbonaceous core particles is 1/100 to 30/100. The diameter of the metal nanoparticles and the weight of the metal nanoparticles relative to the carbon-based core particles determine the depth (that is, the surface area of the porous core particle) and the pore size at which the carbon-based particles are etched.

Specifically, as the metal nanoparticle diameter and the weight ratio increase within each range, the depth of the surface portion becomes deeper, and the pore size of the porous core particle increases.

However, when exceeding each of the above ranges, the carbon-based particles are deeply etched, the pore size is increased, the BET specific surface area of the obtained porous core particles may be excessively increased. On the contrary, when less than each of the above ranges, the carbonaceous leaf is etched shallowly, the pore size becomes small, and the BET specific surface area of the obtained porous core particles may be excessively reduced. The problem with the BET specific surface area is as described above.

On the other hand, by heat-treating the carbon-based particles attached to the surface of the metal nanoparticles, to obtain the carbon-based particles having a plurality of pores in the surface portion as a porous core particle; in the metal attached to the surface of the carbon-based particles Nanoparticles, by etching the surface of the carbon-based particles, pores may be formed in the etched position.

The heat treatment may be performed for 1 to 12 hours in a hydrogen gas atmosphere, the temperature range of 700 to 1200 ℃. In the temperature range, as the heat treatment time increases, the depth of the surface portion becomes deeper, and the pore size of the porous core particles increases.

However, when the heat treatment temperature and time range are exceeded, the carbon-based particles are deeply etched and the pore size is increased, so that the BET specific surface area of the obtained porous core particles may be excessively increased. On the contrary, when the heat treatment temperature and time range are less than, the carbonaceous leaf is etched shallowly, the pore size becomes small, and the BET specific surface area of the obtained porous core particles may be excessively reduced. The problem with the BET specific surface area is as described above.

Heat treating the carbon-based particles to which the metal nanoparticles are attached to the surface to obtain carbon-based particles having a plurality of pores formed on the surface thereof as the porous core particles; In the pores of the obtained porous core particles, the metal nanoparticles may remain. As described above, the silicon coating layer and the carbon-based coating layer may be formed on the surface of the porous core particle in which the metal nanoparticles remain.

Alternatively, the step of removing the metal nanoparticles remaining on the surface of the porous core particles; after, to form a silicon coating layer and a carbon-based coating layer. For example, the metal nanoparticles may be selectively etched and removed by acid treatment.

Lithium secondary battery

In another embodiment of the present invention, a positive electrode; cathode; And an electrolyte; wherein the negative electrode provides a lithium secondary battery including the negative electrode active material described above.

This includes the above-described negative electrode active material, and thus high capacity characteristics are stably expressed even after repeated charging and discharging, which corresponds to a lithium secondary battery having excellent life characteristics and stability.

Description of the negative electrode active material is omitted as described above, and other components of the lithium secondary battery will be described in detail.

Specifically, a separator may be further included between the anode and the cathode.

1 schematically illustrates a lithium secondary battery according to one embodiment of the present invention. The lithium secondary battery 1 includes a battery container 5 including a positive electrode 3, a negative electrode 2, and an electrolyte solution impregnated in a separator 4 existing between the positive electrode 3 and the negative electrode 2; And a sealing member 6 for sealing the battery container 5.

As described above, the negative electrode of the lithium secondary battery includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material. Since the description of the negative electrode active material is as described above, it will be omitted.

The negative electrode active material layer also includes a binder, and optionally may further include a conductive material.

The binder adheres the anode active material particles to each other well, and also serves to adhere the anode active material to the current collector well. As the binder, a water-insoluble binder, a water-soluble binder or a combination thereof can be used.

The water-insoluble binder includes polyvinyl chloride, carboxylated polyvinylchloride, polyvinyl fluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride , Polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

Examples of the water-soluble binder include styrene-butadiene rubber, acrylated styrene-butadiene rubber, polyvinyl alcohol, sodium polyacrylate, propylene and olefin copolymers having 2 to 8 carbon atoms, and (meth) acrylic acid and (meth) acrylic acid alkyl esters. Copolymers or combinations thereof.

When using the water-soluble binder as the negative electrode binder, it may further include a cellulose-based compound that can impart viscosity. As this cellulose type compound, carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, these alkali metal salts, etc. can be used in mixture of 1 or more types. Na, K or Li may be used as the alkali metal. The amount of such thickener used may be 0.1 to 3 parts by weight based on 100 parts by weight of the binder.

The conductive material is used to impart conductivity to the electrode, and any battery can be used as long as it is an electronic conductive material without causing chemical change in the battery. For example, natural graphite, artificial graphite, carbon black, acetylene black, and ketjen. Carbon-based materials such as black and carbon fibers; Metal materials such as metal powder or metal fibers such as copper, nickel, aluminum and silver; Conductive polymers such as polyphenylene derivatives; Or a conductive material containing a mixture thereof.

The current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

The positive electrode includes a current collector and a cathode active material layer formed on the current collector. As the cathode active material, a compound (lithiated intercalation compound) capable of reversible intercalation and deintercalation of lithium may be used. Specifically, at least one of a complex oxide of metal and lithium selected from cobalt, manganese, nickel, and a combination thereof can be used. More specific examples may be used a compound represented by any one of the following formula.

Li _a A _{1 - b} X _b D ₂ (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5); _{Li a A 1 - b X b} O 2 - c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); _{LiE 1 - b X b O 2} - c D c (0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); _{LiE 2 - b X b O 4} - c D c (0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); _{Li a Ni 1 -b- c Co b} X c Dα (0.90 ≤ a ≤1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); _{Li a Ni 1 -b- c Co b} X c O 2 - α Tα (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); _{Li a Ni 1 -b- c Co b} X c O 2 - αT 2 (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _{1- b- c} Mn _b X _c Dα (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 <α ≦ 2); Li _a Ni _{1- bc} Mn _b X _c 0 _2-α Tα (0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b X _c 0 _2-α T ₂ (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 (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 G _e O ₂ (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 0 ₂ (0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); Li _a CoG _b O ₂ (0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); Li _a MnG _b O ₂ (0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); Li _a Mn ₂ G _b O ₄ (0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); Li _a MnG _b PO ₄ (0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiZO 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); LiFePO ₄

In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

Of course, what has a coating layer on the surface of this compound can also be used, or the compound and the compound which have a coating layer can also be used in mixture. The coating layer may include at least one coating element compound selected from the group consisting of oxides of the coating elements, hydroxides, oxyhydroxides of the coating elements, oxycarbonates of the coating elements and hydroxycarbonates of the coating elements. The compounds constituting these coating layers may be amorphous or crystalline. As the 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 forming process may use any coating method as long as it does not adversely affect the physical properties of the positive electrode active material by using such elements in the compound (for example, spray coating, dipping, etc.). Details that will be well understood by those in the field will be omitted.

The positive electrode active material layer also includes a binder and a conductive material.

The binder adheres positively to the positive electrode active material particles, and also serves to adhere the positive electrode active material to the current collector well, and examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and polyvinyl. Chloride, carboxylated polyvinylchloride, polyvinylfluoride, polymer comprising ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene- Butadiene rubber, acrylic styrene-butadiene rubber, epoxy resin, nylon and the like can be used, but is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and any battery can be used as long as it is an electronic conductive material without causing chemical change in the battery. For example, natural graphite, artificial graphite, carbon black, acetylene black, and ketjen. Metal powder, metal fiber, etc., such as black, carbon fiber, copper, nickel, aluminum, silver, etc. can be used, and 1 type (s) or 1 or more types can be mixed and conductive materials, such as a polyphenylene derivative, can be used.

Al may be used as the current collector, but is not limited thereto.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. Since such an electrode manufacturing method is well known in the art, detailed description thereof will be omitted. N-methylpyrrolidone may be used as the solvent, but is not limited thereto.

In the nonaqueous electrolyte secondary battery according to one embodiment of the present invention, the nonaqueous electrolyte includes a nonaqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the cell can move.

Depending on the type of lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. As the separator, polyethylene, polypropylene, polyvinylidene fluoride or two or more multilayer films thereof may be used, and polyethylene / polypropylene two-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene / poly It goes without saying that a mixed multilayer film such as a propylene three-layer separator can be used.

Hereinafter, preferred embodiments of the present invention are described. However, the following examples are only some of the preferred embodiments of the present invention, and the present invention is not limited to the following examples.

Example  1 (negative active material of etched graphite @ nano-Si @ C structure)

(1) Preparation of Anode Active Material

1) raw material

Graphite particles having a diameter of 20 μm and a BET specific surface area of 0.32 m ² / g are used as carbon particles (FIG. 2), and silane (SiH ₄ ) gas is used as a silicon precursor. As the hydrocarbon precursor, acetylene (C ₂ H ₂ ) gas was used.

2) carbon-based particle surface Etching  Process (Porous Core Particle Manufacturing Process)

First, the surface of the carbon-based particles was etched to form a plurality of pores on the surface portion, which was obtained as porous core particles.

Specifically, in 100 g of powder composed of graphite particles, 25 g of Ni (II) chloride (NiCl ₂ 6H ₂ O), a Ni compound, was dissolved as a metal precursor, and these were dissolved in a methanol / deionized water mixed solution, followed by sodium hydroxide (NaOH). ) And 10 ml of hydrazine (N ₂ H ₄ H ₂ O) were added to synthesize the nickel nanoparticles on the graphite surface. The carbon-based particles having nickel nanoparticles attached to the surface were heat-treated at 1000 ° C. in a hydrogen (H ₂ ) gas atmosphere for 6 hours to obtain carbon-based particles having a large number of pores formed on the surface thereof as porous core particles. 4). In this case, the BET specific surface area of the porous core particles was measured to be 3.85 m ² / g.

3) Silicon coating layer forming process ( Evaluation example  1 standard)

On the surface of the obtained porous core particles, silicon nanoparticles were dispersed by CVD to form a silicon coating layer.

Specifically, the obtained porous core particles were mounted on a CVD apparatus (manufactured by Daemyung), and silane (silane, SiH ₄ ) gas was flowed at a flow rate of 50 sccm, and treated at 450 ° C. for 0.5 hour. As a result, it was confirmed that a silicon coating layer having a total thickness of 15 nm was formed in a form in which silicon nanoparticles having a diameter of 15 nm were uniformly dispersed on the surface of the porous core particle.

4) Carbon based coating layer forming process

The silicon coating layer formed particles were left in the reactor, acetylene (C ₂ H ₂ ) gas flowed at a flow rate of 150 sccm, and was treated at 900 ℃ for 0.5 hours. As a result, it was confirmed that carbon was uniformly coated on the surface of the silicon coating layer to form a carbon coating layer having a total thickness of 10 nm.

(2) Preparation of Cathode

The prepared negative active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener were prepared and mixed in a weight ratio of 95.8: 1: 4.5: 1.7 (negative active material: binder: thickener). Then, the negative electrode active material composition was prepared by dispersing in distilled water from which ions were removed.

The composition was applied to a Cu-foil current collector, and then dried and rolled according to a conventional method to prepare a negative electrode having an electrode density of 1.6 g / cm ³ and an active material loading level of 10 mg / cm ³ .

(3) fabrication of a lithium secondary battery

A coin-type 2032 half cell was produced according to a conventional method using the cathode as the working electrode and lithium metal as the counter electrode.

At this time, a separator made of a porous polypropylene film is inserted between the working electrode and the counter electrode, and LiPF having a concentration of 1 M in a mixed solution having a mixed volume ratio of 7: 3 of ethyl methyl carbonate (EMC) and ethylene carbonate (EC) as an electrolyte solution is 7: 3. ₆ And 10% by weight of fluoroethylene carbonate (FEC) additives were used.

Evaluation example  One ( Example On 1 fair  According to BET Specific surface area  Change assessment)

In Example 1, as each process proceeds, the aspect in which the BET specific surface area changes is analyzed and recorded in Table 1 below. In addition, SEM photographs according to the respective process conditions were taken and shown in FIGS. 2 to 5.

1) Specifically, untreated graphite particles (Bare graphite), the BET specific surface area was measured to 0.32 m ² / g, the surface characteristics can be seen in FIG.

2) Meanwhile, in the first step of Example 1, nickel nanoparticles were attached to the surface of graphite particles (graphite @ nano-Ni) such that the weight ratio of graphite particles to nickel nanoparticles was 100: 3.1, and the surface characteristics thereof were shown in FIG. See Figure 3. Specifically, in FIG. 3, it can be seen that nickel nanoparticles having a diameter of 200 nm are uniformly attached to the graphite particle surface.

3) As the graphite nanoparticles to which the nickel nanoparticles were attached were heat-treated in a hydrogen atmosphere, the surface of the graphite particles was etched at the portion where the nickel nanoparticles were attached (Etched graphite, EG). The surface-etched graphite particles (Etched graphite, EG) is a porous core particle of Example 1, the surface characteristics can be seen in FIG.

When comparing FIG. 4 with FIG. 2 (Bare graphite), pores are formed in the area | region up to 10% of a graphite particle radius from the surface of a graphite particle, and it can be confirmed that a pore diameter is 200 nm. In addition, the BET specific surface area was measured at 3.85 m ² / g, and it can be seen that the specific surface area of the untreated negative active material (Bare graphite) was significantly increased.

4) With respect to the porous core particles, the weight ratio of graphite particles to silicon nanoparticles was 100: 5.2 to disperse the silicon nanoparticles having a diameter of 15 nm to form a silicon coating layer having a total thickness of 15 nm. The carbon coating layer was formed on the surface of the silicon coating layer thus formed, and its surface characteristics can be seen in FIG. 5.

The negative electrode active material of Example 1 thus obtained had a BET specific surface area of 2.85 m ² / g and a BET specific surface area was reduced by the coating than the porous core particle, but was compared to the untreated negative electrode active material (Bare graphite). It can still be seen that the BET specific surface area is quite large.

Bare graphite graphite @ nano-Ni Etched graphite (EG) Etched graphite @ nano-Si @ C
( Example  One) BET
( m ² g ^-One ) 0.32 - 3.85 2.85 Ni content ( part by weight ) 0.0% 3.1% 3.1 3.1 Si content ( parts by weight 0.0% 0.0% 0.0 5.2 * Note: Each content of Ni and Si was measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and is based on 100 parts by weight of etched graphite (EG).

Evaluation example  2 (carbon-based particle surface Etching  Evaluation of process)

In this evaluation example, only the carbon-based particle surface etching process is evaluated in the Example 1 process. for teeth, By performing different etching methods and times, only the surface of the graphite particles was etched, and the following evaluation was performed while the silicon coating layer and the carbon-based coating layer were not formed on the surface.

( 1) etching  Sick leave according to how the process is performed

Bare graphite, which is a raw material of Example 1, was mixed with a Ni precursor at a weight ratio of 4: 1 and heat-treated at 1000 ° C. for 6 hours in a hydrogen gas atmosphere to obtain a result.

SEM images were taken of the resultant obtained by treating a simple mixture of the graphite particles and the Ni precursor, and the graphite particles whose surfaces were etched in Example 1, and the surface properties thereof were observed.

Specifically, in Example 1, the surface-etched graphite particles, in the SEM photograph of FIG. 6, are uniformly etched on each graphite particle surface, and nickel nanoparticles are uniformly attached to each etched particle surface, and In the state, you can see that they are not agglomerated with each other.

On the other hand, in the case of the result of treating the mixture, in the SEM photographs of Figures 7 and 8, it can be seen that the surface of each graphite particle is not evenly etched, even Ni metal and graphite particles are agglomerated.

This is a difference according to the etching method. In contrast to the case where the simple mixture of the graphite particles and the Ni precursor is heat-treated in a hydrogen gas atmosphere, even if the same material is used, the nickel nanoparticles are applied to the surface of the graphite particles as in Example 1. When attached and then treated, it means that the surface of the graphite nanoparticles may be etched at the site where the nickel nanoparticles are attached.

( 2) etching  Evaluation based on process run time 1

In Example 1, the heat treatment temperature during the carbon-based particle surface etching is the same, but by changing the heat treatment time to 1 hour, 6 hours, and 8 hours, three samples were prepared (Etched graphite-1 hour, 6 hour, and 8 hour, respectively), the results of each evaluation are reported in Table 2 below. In addition, SEM pictures of each sample were taken and shown in FIGS. 9 to 11.

Specifically, referring to FIGS. 9 to 11 and Table 2, it can be seen that as the execution time increases under the same conditions, the BET specific surface area increases and the etched depth also increases.

Etched graphte-1 hour Etched graphite-6 hour Etched graphite-8 hour BET (m ² g ^-1 ) 1.01 3.85 4.67 Etched Depth 0.2 μm 1.5 μm > 3.0 μm Note: Etched Depth is the average value measured directly from the cross-sectional SEM image.

( 3) etching  Evaluation based on process run time 2 ( Specific quantity  Contrast voltage characteristics)

In Example 1, two samples were prepared (Etched graphite-1 hour and 6 hour, respectively) with the same heat treatment temperature during carbon-based particle etching but with different heat treatment times of 1 hour and 6 hours. Each of these two samples and the untreated negative electrode active material (Bare graphite) were applied as the negative electrode active material, respectively, to prepare respective lithium secondary batteries.

For each lithium secondary battery, electrochemical analysis was performed under the following conditions, and the results are shown in Table 3 and FIG. 12.

-Cut off Voltage (V): 0.005V-1.5V

-C-rate (C): 0.1C lithiation, 0.1C delithiation

According to Table 3 and FIG. 12, it can be seen that the initial efficiency value varies depending on the etching process execution time. Specifically, in the case of etching compared to Bare, there is an advantage that the overvoltage during the charging and discharging process is reduced due to the increase of the edge surface active to lithium, which can be confirmed through the CV section is significantly shortened in FIG. Even in the case of etching, 6 hours is much smaller than 1 hour, and the CV section length is also different.

Sample Charge Capacity Discharge Capacity Initial Coulombic  efficiency ( I.C.E ) Bare graphite 333 mAh / g 323 mAh / g 96.9% Etched graphite-1 hour 332 mAh / g 322 mAh / g 96.9% Etched graphite-6 hour 343 mAh / g 322 mAh / g 93. 7 %

( 4) etching  Evaluation according to process run time 3 (output characteristics under constant current conditions)

In Example 1, two samples were prepared (Etched graphite-1 hour and 6 hour, respectively) with the same heat treatment temperature during carbon-based particle etching but with different heat treatment times of 1 hour and 6 hours. Each of these two samples and the untreated negative electrode active material (Bare graphite) were applied as the negative electrode active material, respectively, to prepare respective lithium secondary batteries.

For each lithium secondary battery, electrochemical analysis was performed under the following conditions, and the results are shown in Table 4 and FIG. 13. This is controlled by a constant current to check the output characteristics of each sample. For reference, the graphite-based negative active material is conventionally known in the art, and then flows through a constant current and then lithiated through constant voltage control.

-Cut off Voltage (V): 0.005V-1.0V

-C-rate (C): 0.1C-5.0C Lithiation, 0.5C Delithiation

According to Table 4 and Figure 13, it can be seen that the output characteristics are improved according to the etching process execution time, specifically, when the etching compared to Bare, the overvoltage during the charging and discharging process is reduced due to the increase of the edge surface active to lithium There is an advantage, which can be seen through the improved output characteristics in FIG. 13. Even in the case of etching, 6 hours compared to 1 hour has a much smaller overvoltage and there is a big difference in the output characteristics.

( 4) etching  Evaluation according to process run time 4 (output characteristics under constant current and constant voltage conditions)

In Example 1, the heat treatment temperature during the carbon-based particle surface etching was the same, but the heat treatment time was changed to 6 hours, to prepare a sample (Etched graphite-1 hour). Each lithium secondary battery was produced by the method of Example 1 using this sample and the untreated negative electrode active material (Bare graphite) as a negative electrode active material, respectively.

About each lithium secondary battery, the electrochemical analysis was performed on condition of the following, and the result is shown in FIG. In order to check the lithiation characteristics of each sample within the time limit, it is lithiated in constant current and constant voltage modes, and then cut-off with reaction time. will be.

Voltage (V): 0.005V-1.0V

-Cut off Voltage (V): 0.005V (1 / 100C cut-off)

-C-rate (C): 0.1C-5.0C Lithiation, 0.5C Delithiation

According to FIG. 14, it can be seen that when etching compared to Bare, an overvoltage is reduced due to an increase in the edge surface active to lithium ions, thereby improving output characteristics.

Evaluation example  3 (Evaluation of Continuous Process Using CVD Method)

In this evaluation example, in Example 1 process, the advantage of the process of forming a silicon coating layer and a carbon type coating layer continuously in the same reactor by a CVD method (henceforth "continuous process") is evaluated. for teeth, The untreated graphite particles (Bare graphite) and the negative electrode active material particles obtained in Example 1 will be compared.

Specifically, by applying the untreated graphite particles (Bare graphite) as a negative electrode active material, a lithium secondary battery was produced by the method of Example 1, compared with the lithium secondary battery of Example 1, the following evaluation was performed. .

(1) Initial capacity assessment

For each lithium secondary battery, the electrochemical properties were evaluated under the following conditions, and the results are reported in Table 4 and FIG. 15.

-Cut off Voltage (V): 0.005 V-1.5 V

-Cut off Voltage (V): 0.005V (1 / 100C cut-off)

-C-rate (C): 0.1 C

According to Table 4 and Figure 15, when the silicon coating layer and the carbon-based coating layer formed by a continuous process compared to Bare it can be seen that not only the specific cost of the material increases significantly but also the overvoltage also decreases.

Charge capacity Discharge capacity Initial C.E . Bare graphite 333 323 96.7% Etched graphite @ nano-Si @ C
( Example  One) 508 470 92.5%

(1) output characteristic evaluation

For each lithium secondary battery, the electrochemical properties were evaluated under the following conditions, and the results were recorded in FIGS. 16 (Lithiation) and 17 (Delithiation).

Voltage (V): 0.005V-1.0V

-Cut off Voltage (V): 0.005V (1 / 100C cut-off)

C-rate (C): 0.1C-5.0C Lithiation, 0.5C Delithiation

According to FIG. 16 (Lithiation) and FIG. 17 (Delithiation), when the silicon coating layer and the carbon-based coating layer are formed by the continuous process compared to the bare, it can be seen that the charge and discharge output characteristics are greatly improved due to the reduction of overvoltage. have.

(2) Life characteristics evaluation

For each lithium secondary battery, the electrochemical properties were evaluated under the following conditions, and the results are recorded in FIG. 18.

Voltage (V): 0.005V-1.0V

-Cut off Voltage (V): 0.005V (1 / 100C cut-off)

-C-rate (C): 0.5 C-rate

According to FIG. 18, in the case of forming the silicon coating layer and the carbon-based coating layer by a continuous process, it can be seen that the advantage of having the life characteristics equivalent to that of Bare.

Evaluation example  4 (evaluation based on the presence or absence of carbon-based coating layer)

In this evaluation example, the final process of Example 1, ie, the presence or absence of carbon-based coating, was evaluated. To this end, the carbon-based coating process of Example 1 is omitted, and the particles having only a silicon coating layer formed on the surface of the graphite particles whose surfaces are etched are used as a negative electrode active material (hereinafter referred to as "Etched graphite @ nano-Si"). The following evaluation was performed as compared with the negative electrode active material of Example 1.

(1) surface properties and BET Specific surface area  compare

The SEM photographs of the etched graphite @ nano-Si and the negative electrode active material of Example 1 are shown in Figs. 19 to 22, respectively, and the BET specific surface area was measured.

19 and 20, before forming the carbon-based coating layer in Example 1, it can be seen that the silicon nanoparticles are uniformly attached to the surface of the graphite particles etched surface. The carbon-based coating layer is formed on the silicon nanoparticles attached as described above, and specific surface properties thereof can be seen in FIGS. 21 and 22. The surface area was measured at 2.49 m ² / g, and the negative active material of Example 1 having the carbon-based coating layer formed thereon was measured to have a BET specific surface area of 2.85 m ² / g, which was determined by forming the carbon-based coating layer. It is slightly increased and still has a significantly increased BET specific surface area compared to bare graphite.

(2) Life characteristics evaluation

Etched graphite @ nano-Si was applied as a negative electrode active material, and a lithium secondary battery was manufactured by the method of Example 1. In comparison with the lithium secondary battery of Example 1, the electrochemical properties were evaluated under the following conditions, and the results are recorded in FIG. 23.

Voltage (V): 0.005V-1.0V

-Cut off Voltage (V): 0.005V (1 / 100C cut-off)

-C-rate (C): 0.5 C-rate

According to FIG. 23, when the negative electrode active material of Example 1, in which a carbon-based coating layer was further formed on the surface thereof, compared to Etched graphite @ nano-Si, it can be seen that the life characteristics are more excellent. It can be inferred that the carbon layer not only protects the silicon surface from electrolyte exposure but also is due to an excellent electrical conductivity supply.

(3) output characteristic evaluation

Etched graphite @ nano-Si was applied as a negative electrode active material, and a lithium secondary battery was manufactured by the method of Example 1. In comparison with the lithium secondary battery of Example 1, the electrochemical properties were evaluated under the following conditions, and the results are recorded in FIG. 24.

Voltage (V): 0.005V-1.0V

-Cut off Voltage (V): 0.005V (1 / 100C cut-off)

C-rate (C): 0.1C-5.0C Lithiation, 0.5C Delithiation

According to FIG. 24, when the negative electrode active material of Example 1, in which a carbon-based coating layer was further formed on the surface thereof, compared to Etched graphite @ nano-Si, it can be seen that the output characteristics are more excellent. Again, it can be inferred that the carbon layer not only protects the silicon surface from electrolyte exposure, but also is due to an excellent electrical conductivity supply.

The present invention is not limited to the above embodiments and may be manufactured in various forms, and those skilled in the art to which the present invention pertains may change to other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that it may be practiced. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

1: lithium secondary battery 2: negative electrode
3: anode 4: separator
5: battery container 6: sealing member

Claims (4)

Porous core particles, which are carbon-based particles in which a plurality of pores are located at the surface portion;
A silicon coating layer positioned on a surface portion of the porous core particle; And
And a carbon-based coating layer on the silicon coating layer.
The carbon-based coating layer and the silicon coating layer is a film (film) form,
Metal nanoparticles are included in the pores located on the surface portion of the porous core particles,
The metal nanoparticles,
Nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn), or combinations thereof,
The surface portion of the porous core particles,
A negative electrode active material for a lithium secondary battery, which is an area of more than 0% and up to 20% of the radius from the surface of the carbon-based particles.
The method of claim 1,
The porous core particles,
BET specific surface area is 3.00 m ² / g or more,
Anode active material for lithium secondary battery.
The method of claim 1,
The carbon-based particles,
The diameter is 10 to 70 ㎛,
Anode active material for lithium secondary battery.
anode;
cathode; And
An electrolyte;
The negative electrode, the negative electrode active material according to any one of claims 1 to 3,
Lithium secondary battery.

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