KR20170041994A - Silicon composite active material for lithium secondary battery and manufacturing method therof - Google Patents

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, and to a manufacturing method thereof, which comprises the following steps of: (A) bonding titanium dioxide particles to a part or a whole surface of silicon particles, to form a silicon-titanium dioxide composite; (B) coating a surface of the silicon-titanium dioxide composite with a polymeric material; and (C) carbonizing coated polymer material by heat treatment under an inert gas atmosphere, to form a carbon coating layer, thereby providing high capacity and high output of a lithium secondary battery, and being used for a long time, while having excellent thermal stability.

Description

TECHNICAL FIELD [0001] The present invention relates to a silicon composite active material for a lithium secondary battery,

The present invention relates to an anode active material for a lithium secondary battery for a lithium secondary battery, which is capable of imparting a high capacity and a high output of a lithium secondary battery and can be used for a long time and has excellent thermal stability, and a method for manufacturing the anode active material.

The silicon based anode active material has a higher capacity than the graphite based anode active material and can be replaced with a next generation anode material.

When the silicon-based anode active material is combined with lithium, the theoretical capacity is 4200 mAh / g (Li _4.4 Si), which is larger than the carbon-based anode active material (372 mAh / g, LiC ₆ ). However, when the silicon-based negative electrode active material is combined with lithium, a volume expansion of more than 300% occurs to cause pulverization of the active material, and the crushed negative active material is removed from the electrode current collector to increase the irreversible capacity And the cycle life and the battery capacity are lowered.

In addition, the silicon-based anode active material has a problem of low conductivity, so that the output characteristics of the silicon-based anode active material are lowered compared with the carbon-based active material.

In order to overcome such a problem, a conventional silicon based anode active material is prepared by simply mixing silicon, carbon, silicon and various metals, or coating, doping or alloying. Specifically, a method of coating a coating layer made of a non-graphitic carbon-based material on the surface of silicon particles (Japanese Patent Application Laid-Open No. 2004-259475), a method of producing a negative electrode by mixing graphite particles and silicon particles or lithium powder (Yoshio, M. et al., J. of Power Sources , 136 (2004) 108), a method of mixing microparticulate silicon with carbon black A method for producing an amorphous Si-CO cathode material by a method of coating carbon by pyrolysis vapor growth method (M. Yamada et al., Hitachi Maxell Ltd. , Japan), sol-gel method (T. Morita, Power Supply & Devices Lab., Toshiba Co., Japan), silicon (Silicone), graphite, and metals (Metal, Ag, Ni and Cu) Method (S. Kugino et al., Dept. of Applied Chem., Saga Univ., Japan) A method of electroless copper plating on the surface (JW Kim et al., Seoul National Univ., Korea), a method of improving the conductivity and cycle stability by doping n-type silicon with Cr ( J. Mater. Chem ., 22, 7999, 2012), a method of coating the surfaces of silicon particles with a titanium oxide, which is a metal oxide, by electrospinning and sol- ( J. Power Sources , 258, 39, 2014), and a process for producing a porous microfine fiber body of a core-shell structure of a silicon-titanium dioxide-carbon structure ( ACS Nano . , 8, 2977, 2014).

However, these methods are complicated in the manufacturing process, are difficult to commercialize, are not only costly, but also have a tendency that the electric capacity and cycle characteristics of the battery are decreased in the charge / discharge reaction of the subsequent battery because the electric conductivity is not high enough to satisfy charge / .

Therefore, there is a demand for a novel silicon-based anode active material which does not cause the aforementioned problems even when silicon particles are used.

Japanese Patent Application Laid-Open No. 2004-259475 U.S. Patent No. 5,888,430

J. of Power Sources, 136 (2004) 108 J. Mater. Chem., 22, 7999, 2012 J. Power Sources, 258, 39, 2014 ACS Nano., 8, 2977, 2014

An object of the present invention is to provide a negative electrode active material for a rechargeable lithium battery, which is capable of imparting a high capacity and a high output of a lithium secondary battery and can be used for a long time, and is excellent in thermal stability.

Another object of the present invention is to provide a method for producing the negative electrode active material.

It is still another object of the present invention to provide a lithium secondary battery using the negative electrode active material.

Still another object of the present invention is to provide an apparatus including the lithium secondary battery.

In order to accomplish the above object, the present invention provides a method of manufacturing an anode active material for a lithium secondary battery, comprising the steps of: (A) suppressing undifferentiation of silicon generated during charging / discharging of a lithium secondary battery and acting as a buffer matrix for suppressing volume expansion, Forming a silicon-titanium dioxide composite by bonding titanium dioxide particles to part or whole of the surface of the silicon particles to improve capacity and cycle life of the secondary battery by improving battery life and rate characteristics;

(B) coating the surface of the silicon-titanium dioxide composite with a polymeric material; And

(C) heat treating the coated polymeric material in an inert gas atmosphere to carbonize the coated polymeric material to form a carbon coating layer. By the carbon layer coated in the silicon-titanium dioxide-carbon composite structure, a stable passivation film is formed on the surface of the electrode and the side reaction is suppressed to increase the cycle efficiency and the electrochemical characteristics are improved by improving the conductivity, thereby improving the performance of the lithium secondary battery.

In the step (A), the silicon particles and the titanium dioxide particles may be mixed in a weight ratio of 5: 1 to 110: 1.

In the step (B), the polymer material may be at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polymethyl methacrylate, polyacrylonitrile, polyaniline, The resin may be selected from the group consisting of sucrose, polyimide, polyvinyl alcohol, polyvinyl chloride, epoxy resin, citric acid, phenolresonosinol formaldehyde resin ( phenolresorcinol-formaldehyde resin, phenol-formaldehyde resin, or a mixture thereof.

In the step (B), the silicon-titanium dioxide complex and the polymer material may be mixed at a weight ratio of 1:99 to 99: 1.

In the step (C), the heat treatment is performed by raising the temperature from T1 to T2, T1 is any temperature between 70 and 90 degrees Celsius, and T2 is any temperature between 600 and 900 degrees Celsius.

In the step (C), the heat treatment may be performed at a temperature raising rate of 3 to 10 ° C / min and may be maintained at the same temperature for 1 to 10 hours after the temperature rise to T2.

The silicone-titanium dioxide-polymer composite coated with the polymer material at T1 may be dried before the heat treatment in the step (C).

In the step (C), the inert gas may be a helium gas, an argon gas, a nitrogen gas, a neon gas, or a mixture of two or more gases.

According to another aspect of the present invention, there is provided a negative electrode active material according to the above method, A silicon-titanium dioxide composite to which titanium dioxide particles are applied on a part or entire surface of the silicon particles; And a carbon coating layer coated on the surface of the silicon-titanium dioxide composite.

According to another aspect of the present invention, there is provided a lithium secondary battery including: a positive electrode including a positive electrode active material; A negative electrode comprising the negative active material and the binder; A separation membrane for preventing a short circuit between the anode and the cathode; And an electrolyte comprising a lithium salt.

The binder is selected from the group consisting of polyacrylic acid, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butadiene rubber, isoprene rubber, polysulfide rubber, chloroprene rubber, polyurethane rubber, silicone rubber, ethylene propylene diene methylene ), An acrylic rubber, and a fluoroelastomer.

The cathode may further include a conductive material that is conductive carbon, a conductive metal, or a conductive polymer.

The lithium salt may be at least one selected from the group consisting of LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiSbF ₆ and LiAsF ₆ .

According to another aspect of the present invention, there is provided an apparatus including the lithium secondary battery according to the present invention, which may be a transport device or an energy storage device including the lithium secondary battery.

The silicon-titanium dioxide-carbon composite of the present invention exhibits a volume expansion during charging / discharging, an unstable solid electrolyte interface (SEI) formation, an active material pulverization and a low electric conductivity, which are generated in the conventional silicon based anode active material Can be solved. Specifically, the silicon-titanium dioxide-carbon composite of the present invention forms a solid electrolyte interfacial layer (SEI) that is stable during charging / discharging by the carbon coating layer, thereby increasing cycle efficiency and improving electrical conductivity in the secondary battery. In addition, in the present invention, the silicon-titanium dioxide composite structure suppresses volume expansion during charging / discharging, and carbon coating on the surface of the silicon-titanium dioxide composite can stably maintain the carbon coating layer in the volume expansion of silicon.

The charge / discharge efficiency and cycle characteristics are improved by forming a stable solid electrolyte interface film and improving the electrical conductivity on the silicon-titanium dioxide-carbon composite of the present invention.

In addition, since the present invention can provide a negative electrode active material having improved charging / discharging characteristics and a high capacity retention ratio as well as a simple manufacturing process and a low cost, it is easy to improve the performance and mass production of the lithium secondary battery.

FIG. 1A is a view illustrating a process of bonding silicon particles and titanium dioxide particles according to an embodiment of the present invention.
1B is a view illustrating a process of coating a polymeric material on a surface of a silicon-titanium dioxide composite according to an embodiment of the present invention.
1C is an image of a silicon-dioxide-carbon composite anode active material prepared according to an embodiment of the present invention.
1D is an image of a silicon-titanium dioxide-carbon composite anode active material prepared according to another embodiment of the present invention.
2A is a TEM image of silicon particles, and FIG. 2B is a TEM image of titanium dioxide particles.
FIGS. 3A and 3B are TEM images of silicon-titanium dioxide-carbon composites prepared according to an embodiment of the present invention, according to the magnification. FIG.
FIGS. 3c and 3d are TEM images of silicon-titanium dioxide-carbon composites prepared according to another embodiment of the present invention, according to the magnification.
3E and 3F are TEM images of the silicon-titanium dioxide-carbon composite prepared according to another embodiment of the present invention, measured according to the magnification.
Figures 3g and 3h are TEM images of silicon-titanium dioxide-carbon composites prepared according to yet another embodiment of the present invention, measured according to magnification.
4A-4F are graphs illustrating charge / discharge characteristics of a half-cell fabricated according to Examples and Comparative Examples of the present invention.

The present invention relates to a negative electrode active material for a lithium secondary battery, which is capable of imparting a high capacity and a high output of a lithium secondary battery and can be used for a long time, and also has excellent thermal stability, and a method for manufacturing the same.

In addition, the present invention overcomes the problems of volume expansion and low conductivity of a silicon anode active material with a silicon-titanium dioxide-carbon composite.

Hereinafter, the present invention will be described in detail.

The method for producing an anode active material for a lithium secondary battery according to the present invention comprises the steps of: (A) bonding a titanium dioxide particle to a part or whole surface of a silicon particle to form a silicon-titanium dioxide composite (FIG. (B) coating the surface of the silicon-titanium dioxide composite with a polymeric material (FIG. 1B); And (C) heating the coated polymeric material in an inert gas atmosphere to carbonize the coated polymeric material, thereby forming a carbon coating layer.

In step (A), a silicon-titanium dioxide composite is formed by physically bonding titanium dioxide particles to a part or whole surface of the silicon particles.

The physical coupling means ball milling, in which titanium dioxide particles are bonded to the surface of the silicon particles through ball milling. The physical bonding between the silicon particles and the titanium dioxide particles suppresses an exothermic reaction occurring between the lithiated silicon and the (Li _4.4 Si) electrolyte during charging / discharging of the lithium secondary battery, thereby improving the thermal stability, Lithium is inserted into the titanium dioxide particles during discharge to improve the electrical conductivity and reduce the irreversible reaction of the silicon. The anatase titanium dioxide reversibly reacts with lithium in the range of about 1.5-2.0 V (vs. Li + / Li) and exhibits an electrical conductivity of 10 ^-9 to 10 ^-7 Scm ^-1 . When lithium is incorporated into the titanium dioxide (Li _x TiO ₂ ) electrical conductivity is improved.

The silicon-titanium dioxide composite produced by the physical bonding of the silicon particles and the titanium dioxide particles forms small pores in the structure to shorten the movement path of lithium, thereby improving the rate characteristics and charge / discharge cycle characteristics of the lithium secondary battery .

The physical coupling serves as a buffer matrix that suppresses the volume expansion, which is a structural change that may occur during charging / discharging of silicon.

The silicon particles and the titanium dioxide particles are combined in a weight ratio of 5: 1 to 110: 1, preferably 15: 1 to 20: 1.

When the content of the silicon particles is out of the above range on the basis of the titanium dioxide particles, the thermal characteristics and the structural stability of the lithium secondary battery can be obtained, but the capacity and cycle performance of the lithium secondary battery are deteriorated.

Next, in the step (B), the surface of the silicon-titanium dioxide composite is coated with a polymer material.

The silicon-titanium dioxide complex and the polymer material are mixed at a weight ratio of 1:99 to 99: 1, preferably 70:30 to 99: 1. When the content of the polymer material is more than 1:99 by weight, the content of the polymer material is high. Therefore, the pores formed in the silicon-titanium dioxide composite are blocked to reduce the pore size or reduce the pores, Deg.] C. If the content of the polymer material is less than 99: 1 by weight, the content of the polymer material may be low and the carbon layer may be unevenly formed, thereby deteriorating the performance of the secondary battery.

The polymer material is not particularly limited as long as it is a material capable of being carbonized upon heat treatment at a high temperature to form a carbon coating layer. Preferably, the material is polyvinylidene fluoride-co-hexafluoropropylene, But are not limited to, polymethyl methacrylate, polyacrylonitrile, polyaniline, sucrose, polyimide, polyvinyl alcohol, polyvinyl chloride, epoxy resin for example, epoxy resin, citric acid, phenolresorcinol-formaldehyde resin, phenol-formaldehyde resin or mixtures thereof.

 The polymeric material is dissolved in an organic solvent to coat the surface of the titanium-silicon dioxide composite. The organic solvent having a low boiling point is preferable for obtaining a uniform carbon coating layer and for easy solvent removal. Examples of the organic solvent having a low boiling point include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) ethanol, acetone, water or mixtures thereof.

 Next, in the step (C), the coated polymeric material layer is heat-treated in an inert gas atmosphere to carbonize the coated polymeric material layer at a high temperature to form a carbon-coated layer to form a silicon-titanium dioxide-carbon composite.

The polymeric material layer may be dried at T1 prior to carbonization at elevated temperatures. The T1 is any temperature between 70 and 90 ° C. If the drying temperature is lower than the lower limit of the above range, the carbon coating layer may not be dried and may not be carbonized. If the drying temperature is above the upper limit, And then the carbonized portion at the time of carbonization at a high temperature may be lowered in strength and the performance of the secondary battery may be deteriorated.

The heat treatment is performed by raising the temperature from T1 to T2, preferably from 600 to 900 DEG C, preferably from 750 to 800 DEG C at T1 at a temperature raising rate of 3 to 10 DEG C / min so that carbon forms a dense coating layer. After the temperature is raised to one temperature (T2) and the temperature is reached to T2, the polymer coating layer is carbonized by maintaining the temperature for 1 to 10 hours to convert it to a carbon coating layer. At this time, when the drying process is not performed, T1 is room temperature (25 to 27 DEG C).

When the temperature of T2 is lower than the lower limit, the carbon coating layer may be non-dense and non-uniformly formed. If the temperature is above the upper limit, the carbon coating layer may not be formed. Further, when carbonization is carried out by continuously raising the temperature at T2 without maintaining the temperature, the strength of the carbon coating layer is lowered and the carbon coating layer is not formed densely.

If the active gas is used instead of the inert gas, the polymer material layer may not be carbonized into the carbon coating layer but may be converted into another material layer, thereby deteriorating the performance of the secondary battery.

Examples of the inert gas include helium gas, argon gas, nitrogen gas, neon gas, or a mixture of two or more gases.

Also, the negative electrode active material for a lithium secondary battery of the present invention can be provided.

The negative electrode active material for a lithium secondary battery of the present invention can be produced according to the above production method, and specifically, as shown in Fig. A silicon-titanium dioxide composite to which titanium dioxide particles are applied on a part or entire surface of the silicon particles; And a carbon coating layer coated on the surface of the silicon-titanium dioxide composite.

The thus prepared silicon-titanium dioxide-carbon composite anode active material has a longer life and excellent thermal stability than carbon-based materials such as graphite. High electric conductivity, high power and high capacity as compared with the case where carbon particles are applied.

In addition, the silicon-titanium dioxide-carbon composite of the present invention forms a solid electrolyte interface film (SEI) which is stable during charging / discharging by the carbon coating layer, thereby increasing cycle efficiency and improving electrical conductivity in the secondary battery. However, in the conventional technique, the carbon coating layer coated on the silicon has not been able to function as the original carbon coating layer due to the collapse of the carbon coating layer due to the excessive volume expansion of the silicon upon charging / discharging. However, in the present invention, the silicon-titanium dioxide composite structure suppresses the volume expansion during charging / discharging, and the carbon coating is coated on the surface of the silicon-titanium dioxide composite, so that the carbon coating layer can be stably maintained in the volume expansion of silicon.

The charge / discharge efficiency and cycle characteristics are improved by forming a stable solid electrolyte interface film and improving the electrical conductivity on the silicon-titanium dioxide-carbon composite of the present invention.

The present invention is based on the synthesis of a negative electrode active material in a macroscopic size of a silicon-titanium dioxide-carbon composite structure starting from a nano-sized silicon active material. The size of the negative electrode active material itself is nano- Characteristics can be improved, the charge / discharge characteristics can be improved, and the capacity retention ratio can be increased, thereby improving the performance and mass production of the lithium secondary battery.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

Example 1.

Silicon-Titanium Dioxide-Carbon Composite

A silicon-titanium dioxide composite was prepared by ball milling 3 g of silicon having an average particle size of 100 nm and 0.03 g of titanium dioxide (silicon particles: titanium dioxide particles = 100: 1 by weight) at 300 rpm for 2 hours. The weight of the beads used is 20 times the weight of the mixture.

2 g of polyvinylidene fluoride-co-hexafluoropropylene (PVDF) and 8 g of acetone were mixed and stirred for 12 hours to dissolve. Then, 1 g of the prepared silicon-titanium dioxide composite and 1 g of the PVDF solution 1.5 g are mixed and homogeneously mixed for 12 hours.

The mixed silicon-titanium dioxide-PVDF composite was dried in an oven at 80 ° C. for 6 hours, then heated to 800 ° C. at a heating rate of 5 ° C./min and then heat-treated at 800 ° C. for 3 hours to obtain a silicon- . After the reaction is completed, the temperature is dropped at the same rate, and when the temperature is reached, the compound is recovered.

Silicon electrode

0.3 g of the prepared silicon-titanium dioxide-carbon composite anode active material, 0.1 g of Denka black as a conductive agent, 0.28 g of a 35% PAA (polyacrylacid) solution as a binder and 1 g of ethanol were mixed and stirred at 4000 rpm for 30 minutes. Although there is no limitation on the viscosity, it is preferable that the viscosity is not too high or low for an electrode having a constant thickness. The prepared slurry was applied to a copper foil having a thickness of 10 mu m to a thickness of 100 mu m using a doctor blade method to prepare a silicon electrode.

Coin-type battery

The prepared silicon-titanium dioxide-carbon composite cathode electrode and a lithium metal electrode were laminated, and a polypropylene (PP) separator was provided between the two electrodes. Ethylcarbonate / ethylmethyl carbonate was used as an electrolyte at a volume ratio of 3: 7 A coin-type battery was prepared by adding 5% fluoroethyl carbonate (FEC) to a mixed organic solvent (EC / EMC) and injecting an electrolyte solution containing 1 M LiPF ₆ dissolved therein.

The capacity of the completed coin-type battery at the time of charging and discharging was measured at a voltage range of 0.05 to 2 V, and the capacity change according to the C-rate was measured.

Example 2.

A silicon-titanium dioxide-carbon composite, an electrode and a battery were prepared in the same manner as in Example 1 except that 0.15 g of titanium dioxide (silicon particles: titanium dioxide particles = 20: 1 weight ratio) was used.

Example 3.

A silicon-titanium dioxide-carbon composite, an electrode and a battery were prepared in the same manner as in Example 1 except that 0.3 g of titanium dioxide (silicon particles: titanium dioxide particles = 10: 1 weight ratio) was used.

Example 4.

A silicon-titanium dioxide-carbon composite, an electrode and a battery were prepared in the same manner as in Example 1 except that 0.45 g of titanium dioxide (silicon particles: titanium dioxide particles = 6.6: 1 weight ratio)

Comparative Example 1

The untreated pure silicon negative electrode active material was prepared and used in the same manner as in Example 1 to prepare an electrode and a battery.

< Test Example >

Test Example  One. TEM  shooting

FIG. 2 and FIG. 3 are images observed through a transmission electron microscope (TEM) to confirm that the carbon coating layer is well formed in the silicon-titanium dioxide-carbon composite material.

2A is a TEM image of silicon particles, and FIG. 2B is a TEM image of titanium dioxide particles.

FIGS. 3A and 3B are TEM images of a silicon-titanium dioxide-carbon composite prepared according to Example 1, measured according to magnification; FIG. FIGS. 3c and 3d are TEM images of the silicon-titanium dioxide-carbon composite prepared according to Example 2, measured according to the magnification; FIG. Figures 3e and 3f are TEM images of the silicon-titanium dioxide-carbon composites prepared according to Example 3, measured according to magnification; FIGS. 3G and 3H are TEM images of the silicon-titanium dioxide-carbon composite prepared according to Example 4, according to the magnification.

As shown in FIGS. 2 and 3, the TEM image of FIGS. 3A-H shows a comparison between the silicon-titanium dioxide-carbon composite . Further, as shown in the TEM image of Figs. 3A-h, it was confirmed that the carbon coating layer was uniformly formed.

Test Example  2. Charge / discharge characteristics (2)

4A-4F are graphs illustrating charge / discharge characteristics of a half-cell fabricated according to Examples and Comparative Examples of the present invention. 4A to 4C are graphs showing the discharge capacity when the processes of <0.2C, 0.2D>, <0.5C, 0.5D>, and <1C, 1D> Respectively. Cycle characteristics after 0.2C, 0.5C, and 1C-rate changes after 2 cycles of initial charge / discharge 0.05C and 0.1C charge / discharge cycles, respectively (FIGS. 4A, 4b and 4c).

4D-f show the charge / discharge curves according to the change of the c-rate, and the charge / discharge curves at the fifteenth cycle after the c-rate sufficiently progressed. 4D is a charge / discharge curve in the 15th cycle of the 0.2C 50-charge / discharge cycle test, FIG. 4E is the charge / discharge curve of the 15th cycle in the 0.5C 50-time test, Charge / discharge curve of the 15th cycle in the cycle test.

As shown in Fig. 4, it was confirmed that Example 2 was superior in charge / discharge characteristics to Examples 1, 3 and 4 and Comparative Example 1. The titanium dioxide particles bonded to the surface of the silicon particles serve as a buffer matrix for suppressing the expansion of the silicon volume caused by charging / discharging, and it was confirmed that the titanium dioxide content in Example 2 was the optimum amount to suppress the volume expansion compared with the other groups .

Claims (14)

(A) bonding the titanium dioxide particles to a part or whole surface of the silicon particles to form a silicon-titanium dioxide composite;
(B) coating the surface of the silicon-titanium dioxide composite with a polymeric material; And
(C) heat treating the coated polymeric material in an inert gas atmosphere to carbonize the coated polymeric material to form a carbon coating layer, and a method for manufacturing the negative active material for a lithium secondary battery. The method of claim 1, wherein in step (A), the silicon particles and the titanium dioxide particles are used in a weight ratio of 5: 1 to 110: 1. The method of claim 1, wherein the polymer material is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polymethyl methacrylate, polyacrylonitrile Polyaniline, sucrose, polyimide, polyvinyl alcohol, polyvinyl chloride, epoxy resin, citric acid, phenol, A phenol-formaldehyde resin, a phenol-formaldehyde resin, or a mixture thereof. 2. A method for producing a negative electrode active material for a lithium secondary battery according to claim 1, wherein the negative active material is a phenol-formaldehyde resin. The method of claim 1, wherein the silicon-titanium dioxide complex and the polymer material are used in a weight ratio of 1:99 to 99: 1 in the step (B). The method of claim 1, wherein in the step (C), the heat treatment is performed by increasing the temperature from T1 to T2, T1 is any temperature between 70 and 90 degrees Celsius, T2 is any temperature between 600 and 900 degrees Celsius Wherein the negative electrode active material is a negative active material. The method according to claim 1, wherein in the step (C), the heat treatment is performed at a temperature raising rate of 3 to 10 ° C / min, a temperature is increased to T2 and maintained at the same temperature for 1 to 10 hours, Wherein the negative electrode active material is at any one temperature. The method of claim 1, wherein in step (C), the silicon-titanium dioxide composite coated with the polymer material is dried at T1 before heat treatment, and T1 is any temperature between 70 and 90 ° C. A method for manufacturing a negative electrode active material for a secondary battery. The method of claim 1, wherein the inert gas in the step (C) is a helium gas, an argon gas, a nitrogen gas, a neon gas, or a mixture gas of two or more thereof. Silicon particles;
A silicon-titanium dioxide composite to which titanium dioxide particles are applied on a part or entire surface of the silicon particles; And
And a carbon coating layer coated on the surface of the silicon-titanium dioxide composite. A cathode comprising a cathode active material;
A negative electrode comprising the negative electrode active material of claim 9 and a binder;
A separation membrane for preventing a short circuit between the anode and the cathode; And
A lithium secondary battery comprising an electrolyte comprising a lithium salt. The method of claim 10, wherein the binder is selected from the group consisting of polyacrylic acid, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butadiene rubber, isoprene rubber, polysulfide rubber, chloroprene rubber, polyurethane rubber, Wherein the polymer is at least one selected from the group consisting of ethylene propylene diene methylene (EPDM), acrylic rubber, and fluoroelastomer. The lithium secondary battery according to claim 10, wherein the negative electrode further comprises a conductive material that is conductive carbon, a conductive metal, or a conductive polymer. The lithium secondary battery according to claim 10, wherein the lithium salt is at least one selected from the group consisting of LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiSbF ₆ and LiAsF ₆ . An apparatus comprising the lithium secondary battery according to any one of claims 10 to 13,
Wherein the device is a transport device or an energy storage device.

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