KR101621519B1 - Anode for lithium secondary battery, lithium secondary battery comprising the anode, and method of preparing the anode - Google Patents

Abstract

The present invention relates to a negative electrode for a lithium secondary battery, and more particularly to a negative electrode for a lithium secondary battery in which the dispersibility of a conductive material on the negative electrode active material is improved by dispersing carbon nanotubes (CNT) and a negative electrode active material as a conductive material in water, And a method of manufacturing the negative electrode. According to one embodiment of the present invention, a carbonaceous nanotube (CNT) having -COOH groups is dispersed on the surface of a negative electrode active material of SiO _x (0 <x = 1) and a carbonaceous material, / RTI &gt; According to another embodiment of the present invention, there is provided a method of manufacturing a carbon nanotube (CNT), comprising: forming a carbon nanotube (CNT) having -COOH group by acid treatment of a carbon nanotube (CNT); Forming a negative electrode mixture by mixing the formed carbon nanotube (CNT) with SiO _x (0 <x = 1) and a negative electrode active material of a carbon-based material, adding water to the negative electrode mixture and stirring to form a negative electrode slurry ; Applying the formed negative electrode slurry on a current collector; And removing water from the negative electrode slurry to form a negative electrode. According to the present invention, it is possible to provide a negative electrode having a conductive material uniformly dispersed therein and a lithium secondary battery improved in life characteristics.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode for a lithium secondary battery, a lithium secondary battery including the same, and a method for manufacturing the negative electrode,

The present invention relates to a negative electrode for a lithium secondary battery, and more particularly to a negative electrode for a lithium secondary battery improved in dispersibility of a conductive material on a negative electrode active material by dispersing carbon nanotube (CNT) and a negative electrode active material as a conductive material, A secondary battery, and a method of manufacturing the negative electrode.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. The electrochemical device is one of the most remarkable fields in this respect, and development of a rechargeable secondary battery has become a focus of attention. In recent years, research and development on the design of new electrodes and batteries have been proceeding in order to improve capacity density and specific energy in developing such batteries.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as higher operating voltage and much higher energy density than conventional batteries such as N-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution .

Generally, a lithium secondary battery uses a material capable of intercalation / deintercalation or alloying / dealloying of lithium ions as a cathode and an anode, and an organic electrolyte or a polymer electrolyte is charged between a cathode and an anode And generates electrical energy by an oxidation reaction and a reduction reaction when lithium ions are inserted and removed from the positive electrode and the negative electrode.

At present, a carbon-based material is mainly used as an electrode active material constituting a cathode of a lithium secondary battery. In the case of graphite, the theoretical capacity is about 372 mAh / g, and the actual capacity of graphite commercialized at present is about 350 to 360 mAh / g. However, such a carbon-based material such as graphite is not compatible with a lithium secondary battery which requires a high-capacity negative electrode active material.

In order to satisfy such a demand, there is an example of using Si, Sn or the like, which is a metal capable of electrochemically alloying with lithium, or an alloy thereof with an anode active material, which exhibits a higher charge / discharge capacity than a carbon-based material. However, such a metal-based negative electrode active material is cracked and undifferentiated due to a large volume change accompanied by charging / discharging of lithium. Therefore, the capacity of the secondary battery using such a metal-based negative active material decreases sharply as the charge- There is a problem that the life is shortened. Accordingly, it was attempted to prevent a decrease in capacity and a decrease in cycle life caused by the use of the metal-based negative electrode active material.

Particularly, when SiO is used as the negative electrode active material, since the initial efficiency, the electric conductivity and the life characteristics are low, it is usually mixed with graphite and the conductive material is dispersed in the mixture. However, in the case of dot conductive materials such as Super P, Denka black and the like which are commonly used, when used together with the negative electrode active material having a large volume expansion during charging and discharging, The contact with the negative electrode active material is largely lowered and the cycle life is reduced. In the case of using a linear conductive material such as carbon nanotubes (CNT), the contact deterioration with the anode active material is greatly reduced as the cycle progresses, so that the cycle life is less deteriorated do.

However, the linear conductive materials such as carbon nanotubes (CNTs) are largely dispersed in the mixture and are not uniformly distributed on the surface of the SiO 2. Uneven distribution on the surface of the SiO 2 greatly degrades the cycle performance of the battery. .

Accordingly, there is still a need for a method of manufacturing a negative electrode in which carbon nanotubes (CNTs) can be uniformly dispersed in a manufacturing process of a negative electrode and a negative electrode thereof.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing a negative electrode capable of uniformly dispersing carbon nanotubes (CNTs) and a negative electrode.

Another object of the present invention is to provide a lithium secondary battery including the negative electrode.

According to one embodiment of the present invention, a carbon nanotube (CNT) having -COOH groups is dispersed on the surface of a negative electrode active material of a carbon-based material with SiO _x (0 <x = 1) A negative electrode for a lithium secondary battery is provided. According to another embodiment of the present invention, there is provided a method of manufacturing a carbon nanotube (CNT), comprising: forming a carbon nanotube (CNT) having -COOH group by acid treatment of a carbon nanotube (CNT); Forming a negative electrode mixture by mixing the formed carbon nanotube (CNT) with SiO _x (0 <x = 1) and a negative electrode active material of a carbon-based material, adding water to the negative electrode mixture and stirring to form a negative electrode slurry ; Applying the formed negative electrode slurry on a current collector; And removing water from the negative electrode slurry to form a negative electrode.

According to the present invention, it is possible to provide a negative electrode having a conductive material uniformly dispersed therein and a lithium secondary battery improved in life characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
1 is Fourier transform-infrared spectroscopy (FT-IR) for a cathode according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the constitutions described in the drawings are merely the most preferred embodiments, and not all of the technical ideas of the present invention are described. Therefore, various equivalents which can be substituted at the time of the present application It should be understood that variations can be made.

In the case of using a silicon based negative active material, a large volume change accompanied by lithium charge / discharge causes cracks and pulverization. In a secondary battery using such an anode active material, the capacity rapidly decreases as the charge / The cycle life is shortened. To solve this problem, a negative electrode active material is used in the form of a mixture with a carbonaceous material such as graphite. In this case, a conductive material such as carbon black is used. However, such a conductive material is not uniformly distributed on the negative electrode active material There is a problem that cycle performance is deteriorated.

In order to solve this cycle performance deterioration, carbon nanotubes (CNTs) which are not carbon black conventionally used as a conductive material on the surface of SiO are used. However, in this case, water is used as a dispersing agent, and there is still a problem that carbon nanotubes (CNTs) are not uniformly dispersed on the anode active material when water is used.

Accordingly, the present inventors have found that a method of dispersing carbon nanotubes (CNTs) on the surface of a mixture of SiO _x (0 <x = 1) and a carbonaceous material using water, (CNT) can be uniformly dispersed on the anode active material by attaching a COOH group to the carbon nanotubes. Thus, the present invention has been completed.

According to an aspect of the present invention, there is provided a negative electrode for a lithium secondary battery, wherein a carbon nanotube (CNT) is dispersed on the surface of a negative electrode active material of SiO _x (0 <x = 1) and a carbonaceous material.

The carbon nanotubes (CNTs) are not particularly limited and are divided into single walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) according to their structures .

Particularly, the carbon nanotube (CNT) has a -COOH group. The -COOH group attached to the surface of the carbon nanotube (CNT) allows the carbon nanotube (CNT) to be uniformly dispersed on the anode active material. Particularly, when the carbon nanotube (CNT) is used as a conductive material, water is used as a dispersant. In this case, the -COOH group on the carbon nanotube (CNT) has a high affinity with water, And is uniformly dispersed in the space between the surface of the negative electrode active material and the negative active material without locally forming agglomerates. As described above, the uniformly dispersed carbon nanotubes (CNTs) can improve the electrical conductivity due to the electrochemical crosslinking between the anode active materials and the high electrical conductivity of the carbon nanotubes (CNTs) themselves, And life characteristics can be greatly improved.

The weight ratio of the negative electrode active material to the CNT may be about 99.8: 0.2 to about 95: 5, preferably about 99.5: 0.5 to about 98: 2. When the weight ratio of the negative electrode active material to the CNT falls within the above-mentioned range, the CNTs are uniformly dispersed in the negative electrode active material and the bond between them is strengthened, and the negative electrode including the negative electrode active material and the electroconductive material has its cycle and lifetime characteristics .

Carbon-based materials include, but are not limited to, graphite, graphitizable carbon (also referred to as soft carbon), non-graphitizable carbon (also referred to as hard carbon) Carbon black, graphene, and graphene oxide, or a mixture of two or more thereof. Specifically, the graphite may be natural graphite or artificial graphite such as mesophase carbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), or the like. Examples of the carbon black include ketjen black, acetylene black, channel black, furnace black, thermal black, lamp black, ivory, Black (Ivory black), and vine black (vine black).

Further, the negative electrode may further include a binder. The binder can bind the negative electrode active material to each other or to the current collector without limitation. Examples of the binder include polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride- Polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride-co-chlorotrifluoroethylene, polymethyl methacrylate, polyvinylidene fluoride- But are not limited to, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate ), Cellulose acetate butyrate, cellulose acetate It is also possible to use cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan ), Carboxyl methyl cellulose (CMC), acrylonitrile-styrene-butadiene copolymer, polyimide, polyvinylidenefluoride, polyacrylonitrile, Polyacrylonitrile and styrene butadiene rubber (SBR), or a mixture of two or more thereof. The binder may be used within a range that does not adversely affect the dispersibility of the negative electrode active material and CNT. The content of the binder may be about 0.5 to about 5 parts by weight, preferably about 1 to about 3 parts by weight, based on 100 parts by weight of the total of the anode active material, the CNT and the binder.

In addition, the cathode may further include a thickener. This thickening agent can be added to improve the rheological properties of the conductive material and is also referred to as a rheological control agent. Non-limiting examples of such thickeners include cellulose, urethane, curdlan or beta- 1,3-glucan, tamarind, gelatin, gua gum, Pectin, locust bean gum, or carob bean gum, carrageenan, alginic acid, arabic gum, zanthan, or the like. Or a mixture of two or more of them.

Among these, examples of the cellulose thickening agent include carboxyl methyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), methyl hydroxypropyl cellulose ), Ethyl hydroxyethyl cellulose (EHEC), methyl ethyl hydroxyethyl cellulose (MEHEC), cellulose gum and the like, or two or more kinds thereof But are not limited to, mixtures.

The thickener may be included in an amount of about 0.5 to about 3 parts by weight, preferably about 1 to about 2 parts by weight, based on 100 parts by weight of the total of the negative electrode active material, the CNT and the thickener.

The negative electrode active material prepared according to the present invention can be manufactured into a negative electrode according to a manufacturing method commonly used in the art. Also, the anode according to the present invention can be produced by a conventional method in the art, like the cathode. For example, a slurry may be prepared by mixing and stirring a binder and a solvent, if necessary, with a conductive material and a dispersant, and then applying the slurry to a current collector to compress the negative electrode active material of the present invention.

Accordingly, the present invention also provides a negative electrode of a lithium secondary battery including a current collector and a negative electrode active material layer formed on at least one side of the current collector, the negative active material layer comprising a negative electrode active material A negative electrode for a lithium secondary battery is provided.

Examples of the binder include vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, A wide variety of polymers can be used.

As the cathode active material, a lithium-containing transition metal oxide may be preferably used. For example, Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), Li _x MnO _{2 x <1.3), Li x Mn} 2 O 4 (0.5 <x <1.3), Li x (Ni a Co b Mn c) O 2 (0.5 <x <1.3, 0 <a <1, 0 <b <1, Li _x Co _{1- y} Mn _y O ₂ (where 0 <c <1, a + b + c = 1), Li _x Ni _1-y Co _y O ₂ 0.5 <x <1.3, 0≤y < 1), Li x Ni 1 -y Mn y O 2 (0.5 <x <1.3, O≤y <1), Li x (Ni a Co b Mn c) O 4 ( (0.5 <x <1.3, 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li _x Mn _{2 -z} Ni _z O ₄ (0.5 <x <1.3, 0 <z <2), Li _x CoPO ₄ (0.5 <x <1.3) and Li _x FePO ₄ (0.5 <z <2), Li _x Mn _{2 -z} Co _z O ₄ x < 1.3), or a mixture of two or more thereof. The lithium-containing transition metal oxide may be coated with a metal such as aluminum (Al) or a metal oxide. In addition to the lithium-containing transition metal oxide, sulfide, selenide and halide may also be used.

When the electrode is manufactured, a lithium secondary battery having a separator interposed between the positive electrode and the negative electrode and an electrolyte, which is conventionally used in the art, can be manufactured using the electrode.

Accordingly, in the present invention, it is possible to provide a lithium secondary battery comprising a positive electrode, the negative electrode described above, and a separator interposed between the positive electrode and the negative electrode.

In the electrolyte used in the present invention, the lithium salt that may be included as the electrolyte may be any of those conventionally used in an electrolyte for a lithium secondary battery. For example, examples of the anion of the lithium salt include F ^- , Cl ^- , Br ^{- _{, I -, NO 3 -,}} N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 _{^{PF 2 -, (CF 3)}} 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N _{^{-, CF 3 CF 2 (CF}} 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

As the organic solvent contained in the electrolytic solution used in the present invention, the organic solvent commonly used for the electrolyte for a lithium secondary battery can be used without limitation, and examples thereof include propylene carbonate (PC), ethylene carbonate (ethylene carbonate) EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxy Ethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran, or a mixture of two or more thereof. In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have high permittivity as a high-viscosity organic solvent and dissociate the lithium salt in the electrolyte well. To such a cyclic carbonate, dimethyl carbonate and diethyl When a low viscosity, low dielectric constant linear carbonate such as carbonate is mixed in an appropriate ratio, an electrolyte having a high electric conductivity can be prepared, and thus it can be more preferably used.

Alternatively, the electrolytic solution stored in accordance with the present invention may further contain an additive such as an overcharge inhibitor or the like contained in an ordinary electrolytic solution.

As the separator, a conventional porous polymer film conventionally used as a separator, for example, a polyolefin such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer A porous polymer film made of a high molecular weight polymer may be used alone or in a laminated manner, or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point, a polyethylene terephthalate fiber or the like may be used. It is not.

The battery case used in the present invention may be of any type that is commonly used in the art, and is not limited in its external shape depending on the use of the battery. For example, a cylindrical case, a square type, a pouch type, (coin) type or the like.

According to another aspect of the present invention, there is provided a method of manufacturing a lithium secondary battery including the steps of forming a carbon nanotube (CNT) (S1), forming a negative electrode slurry (S2), applying a negative electrode slurry (S3) A method of manufacturing a negative electrode for a secondary battery is provided.

In step S1, carbon nanotubes (CNTs) are treated with an acid. The acid treatment may be performed by mixing the acid solution with carbon nanotubes (CNT) at a temperature of about 70 to about 90 DEG C to form a mixture, and the mixture may be stirred for about 1 to about 10 hours. Preferably, the acid treatment temperature and duration may be from about 75 ° C to about 85 ° C and from about 2 to about 5 hours, respectively.

The acid solution may be, but is not limited to, one selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and the like, or a mixture of two or more thereof.

The acid treatment forms a CNT-containing mixture containing carbon nanotubes (CNT) having -COOH groups. Carbon nanotubes (CNTs) are as previously described with respect to cathodes herein.

Further, after the acid treatment step, the formed CNT-containing mixture may be filtered and dried under vacuum at a temperature of about 100 to about 200 DEG C for about 5 to about 20 hours. Preferably, the drying temperature and duration may be from about 125 to about 175 DEG C and from about 7 to about 15 hours, respectively. The filtration can be carried out by a method customary in the art, for example, filtration with distilled water or the like.

In step S2, a carbon nanotube (CNT) formed in the step S1 is mixed with _{SiO x (0 <x = 1} ) and the negative electrode active material of a carbonaceous substance to form a negative electrode mixture. Then, water is added to the negative electrode mixture and stirred to form a negative electrode slurry. In general, the anode active material may be dispersed using a dispersing device known in the art. The dispersing apparatus is not particularly limited as long as it is an apparatus for dispersing a substance to be dispersed in a solvent or a dispersion medium. Examples thereof include a stirrer, an ultrasonic dispersing apparatus, a magnetic stirrer, and a spray dryer.

Alternatively, the carbon nanotube (CNT) may be mixed with a carboxyl methyl cellulose (CMC) solution before mixing with the negative electrode mixture to form a CNT-CMC solution. Here, the carboxymethyl cellulose (CMC) solution may contain about 0.5 to about 3 wt%, preferably about 1 to about 2 wt% of carboxymethyl cellulose (CMC).

The negative electrode mixture may further comprise a binder or a thickener. These binders and thickeners are as previously described herein for the negative electrode.

In step S3, the negative electrode slurry formed in step S2 is applied on the current collector. This application can be carried out by a method commonly known in the art. The current collector is as previously described with respect to the cathode herein.

In step S4, water is removed from the negative electrode slurry to form a negative electrode. Removal of water can be accomplished by drying at a temperature of about 100 to about 200 DEG C for about 5 to about 20 hours. Preferably, the removal temperature and duration may be from about 125 to about 175 DEG C and from about 7 to about 15 hours, respectively. The removal of the water can be carried out by a method customary in the art.

The weight ratio of the negative electrode active material to the CNT may be about 99.8: 0.2 to about 95: 5, preferably about 99.5: 0.5 to about 98: 2. The reason for this is as described above with respect to the cathode in the present invention.

In addition, the carbon-based material is as described above with respect to the negative electrode in the present invention.

Hereinafter, embodiments of the present invention will be described in detail to facilitate understanding of the present invention. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the following embodiments. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

< Example  1>

(Step 1) Anode active material  Produce

25 g of a nitric acid solution (60% purity) and 25 g of a sulfuric acid solution (60% purity) were placed in a beaker and the temperature was raised to 80 DEG C on a hot plate and 1 g of CNT was added and stirred for 4 hours for acid treatment. Thereafter, the mixture was filtered with distilled water, and vacuum dried at about 130 ° C for 10 hours to prepare acid-treated carbon nanotubes (CNTs).

(Step 2) Negative electrode manufacturing

The negative electrode was prepared using the acid-treated carbon nanotube (CNT) prepared in the step 1 as a conductive material. SiO 2 and graphite were used as an anode active material in an amount of 10:90 wt%, and the acid-treated carbon nanotubes (CNT) as a conductive material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) 96.8: 1: 1: 1.2, and water was added to prepare an anode slurry. The prepared negative electrode slurry was applied to a copper foil, vacuum dried at about 130 캜 for 10 hours, and then a negative electrode of 1,4875 cm 2 was prepared.

(Step 3) Production of secondary battery

A metal lithium foil of 1.8 cm &lt; 2 &gt; was used as an anode, and an electrode assembly was manufactured through a polyethylene separator between the anode and the cathode. A non-aqueous electrolyte was prepared by adding 1 M LiPF ₆ to a non-aqueous electrolyte solvent in which ethylene carbonate (EC) and diethylene carbonate (DEC) were mixed at a volume ratio of 1: 2, and then injected into the electrode assembly to form a coin- A battery was prepared.

< Example  2>

0.5 g of carbon nanotubes (CNT) and 11.17 g of distilled water are put into SUS can and mixed thoroughly for 1 hour using a spex mill. At this time, 15 balls (ball 15 weight, 6.55g) of 4.6mm SUS material were used. Thereafter, 8.33 g of a CMC solution in which carboxymethylcellulose (CMC) was dispersed in water in an amount of 1.2 wt% was added to the SUS can, and the mixture was sufficiently mixed for 1 hour to prepare a CNT-CMC solution. At this time, in the CNT-CMC solution, the CNT content was 2.5 wt% and the CMC content was 0.5 wt%.

A coin-type half-cell was prepared in the same manner as in Example 1, except that the CNT-CMC solution was added so that the CNT content was 1 weight ratio and the CNT-CMC solution was used as the conductive material.

< Comparative Example  1>

A coin-type half-cell was fabricated in the same manner as in Example 1, except that Super P was used as the conductive material.

< Comparative Example  2>

A coin-type half-cell was fabricated in the same manner as in Example 1, except that carbon nanotubes (CNTs) not treated with acid as the conductive material were used.

Table 1 below shows the first discharge capacity, initial efficiency, and capacity retention rate of the batteries manufactured in Examples 1 and 2 and Comparative Examples 1 and 2.

The first discharge capacity (mAh / g) Initial efficiency (%) Capacity retention rate (%) Example 1 474 88.2 94 Example 2 475 88.2 95 Comparative Example 1 473 88.3 85 Comparative Example 2 473 88.2 82 Initial efficiency = (first discharge capacity) / (first charge capacity) x 100
Capacity retention rate = (50th discharge capacity) / (first discharge capacity) x 100

As shown in Table 1, the batteries of Examples 1 and 2 manufactured according to the present invention had substantially the same first discharge capacity and initial efficiency as those of the batteries prepared in Comparative Examples 1 and 2, Able to know.

Claims (23)

A negative electrode comprising a negative electrode active material and a conductive material,
The negative electrode active material is a mixture of SiOx (0 <x = 1) and a carbonaceous material, and the conductive material is a carbon nanotube (CNT) having a -COOH group, and the carbon nanotube having a -COOH group is a negative active material Dispersed on the surface,
The weight ratio of the negative electrode active material and the conductive material is 99.8: 0.2 to 95: 5,
The negative electrode is formed by removing water from a negative electrode slurry obtained by mixing a negative electrode active material, a conductive material, and water. delete The method according to claim 1,
Wherein the carbon-based material is selected from the group consisting of graphite, graphitizable carbon, non-graphitizable carbon, carbon black, graphene and graphene oxide Wherein the negative electrode is a selected one kind of material or a mixture of two or more thereof. The method according to claim 1,
Wherein the negative electrode further comprises a binder. 5. The method of claim 4,
Wherein the binder is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride- Polyvinylidene fluoride-co-chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate (also referred to as polyvinylpyrrolidone), polyvinylpyrrolidone polyvinyl acetate, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate ), Cyanoethylpullulan, cyano But are not limited to, polyvinyl alcohol, cyanoethylpolyvinylalcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose (CMC), acrylonitrile-styrene-butadiene (1) selected from the group consisting of acrylonitrile-styrene-butadiene copolymer, polyimide, polyvinylidene fluoride, polyacrylonitrile and styrene butadiene rubber Or a mixture of two or more thereof. The method according to claim 1,
Wherein the negative electrode further comprises a thickener. The method according to claim 6,
Wherein the thickener is selected from the group consisting of cellulose, urethane, curdlan, tamarind, gelatin, gua gum, pectin, LBG (locust bean gum), carrageenan wherein the negative electrode is one selected from the group consisting of carrageenan, alginic acid, arabic gum and zanthan, or a mixture of two or more thereof. The method according to claim 6,
Wherein the thickener is selected from the group consisting of carboxyl methyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), methylhydroxypropyl cellulose (MHPC) Is selected from the group consisting of ethyl hydroxyethyl cellulose (EHEC), methyl ethyl hydroxyethyl cellulose (MEHEC) and cellulose gum, or a mixture of two or more thereof And a negative electrode for a lithium secondary battery. The method according to claim 6,
Wherein the thickener is included in an amount of 0.5 to 3 parts by weight based on 100 parts by weight of the total of the negative electrode active material, the CNT, and the thickener. A lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
10. The lithium secondary battery according to any one of claims 1 to 9, wherein the negative electrode is a negative electrode. Forming carbon nanotubes (CNTs) having -COOH groups by acid-treating carbon nanotubes (CNTs);
Forming a negative electrode mixture by mixing the formed carbon nanotube (CNT) with SiO _x (0 <x = 1) and a negative electrode active material of a carbon-based material, adding water to the negative electrode mixture and stirring to form a negative electrode slurry ;
Applying the formed negative electrode slurry on a current collector; And
Removing water from the negative electrode slurry to form a negative electrode
/ RTI &gt;
Wherein the weight ratio of the negative electrode active material to the CNT is 99.8: 0.2 to 95: 5. 12. The method of claim 11,
The acid treatment step may be carried out by mixing a carbon nanotube (CNT) having -COOH groups by mixing an acid solution with carbon nanotubes (CNT) at a temperature of 70 to 90 ° C to form a mixture, and stirring the mixture for 1 to 10 hours. Wherein the CNT-containing mixture is formed on the surface of the cathode. 12. The method of claim 11,
After the acid treatment step, the formed CNT-containing mixture is filtered and dried under vacuum at a temperature of 100 to 200 DEG C for 5 to 20 hours. delete 12. The method of claim 11,
Wherein the carbon-based material is selected from the group consisting of graphite, graphitizable carbon, non-graphitizable carbon, carbon black, graphene and graphene oxide Wherein the negative electrode is a selected one kind of substance or a mixture of two or more thereof. 12. The method of claim 11,
The CNT-CMC solution is formed by mixing the carbon nanotube (CNT) with a carboxyl methyl cellulose (CMC) solution before mixing with the negative electrode mixture. 17. The method of claim 16,
Wherein the carboxyl methyl cellulose (CMC) solution comprises 0.5 to 3% by weight of carboxymethyl cellulose (CMC). 12. The method of claim 11,
Wherein the negative electrode mixture further comprises a binder. 19. The method of claim 18,
Wherein the binder is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride-co-trichloroethylene, polyvinylidene fluoride- Polyvinylidene fluoride-co-chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate (also referred to as polyvinylpyrrolidone), polyvinylpyrrolidone polyvinyl acetate, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate ), Cyanoethylpullulan, cyano But are not limited to, polyvinyl alcohol, cyanoethylpolyvinylalcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose (CMC), acrylonitrile-styrene-butadiene (1) selected from the group consisting of acrylonitrile-styrene-butadiene copolymer, polyimide, polyvinylidene fluoride, polyacrylonitrile and styrene butadiene rubber Or a mixture of two or more thereof. 12. The method of claim 11,
Wherein the negative electrode mixture further comprises a thickener. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; 21. The method of claim 20,
Wherein the thickener is selected from the group consisting of cellulose, urethane, curdlan, tamarind, gelatin, gua gum, pectin, LBG (locust bean gum), carrageenan wherein the electrolyte is one selected from the group consisting of carrageenan, alginic acid, arabic gum and zanthan, or a mixture of two or more thereof. 21. The method of claim 20,
Wherein the thickener is included in an amount of 0.5 to 3 parts by weight based on 100 parts by weight of the total of the negative electrode mixture and the thickener. A negative electrode produced by the method for manufacturing a negative electrode for a lithium secondary battery according to any one of claims 11 to 13, 15 to 22.

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