KR20200023623A - Anode for lithium secondary battery and lithium secondary battery using the same - Google Patents

Abstract

Provided are a negative electrode for a lithium secondary battery including a composite negative electrode active material and a lithium secondary battery employing the same. The lithium secondary battery including the composite anode active material has excellent initial efficiency characteristics and lifespan characteristics.

Description

Anode for lithium secondary battery and lithium secondary battery employing same {Anode for lithium secondary battery and lithium secondary battery using the same}

A negative electrode for a lithium secondary battery and a lithium secondary battery employing the same. More particularly, the present invention relates to a negative electrode for a lithium secondary battery having an improved initial efficiency, an increased reversible capacity, and an improved lifetime characteristics, and a lithium secondary battery employing the same.

Conventionally, lithium metal is used as a negative electrode active material of a lithium secondary battery. However, when lithium metal is used, a carbon-based material is often used as a negative electrode active material instead of lithium metal because a short circuit may occur due to battery shortage due to dendrite formation. have.

Examples of the carbon-based active material include crystalline carbon such as graphite and artificial graphite, and amorphous carbon such as soft carbon and hard carbon. However, although the amorphous carbon has a large capacity, there is a problem in that irreversibility is large in the charging and discharging process. Graphite is typically used as the crystalline carbon, and the theoretical limit capacity is 372 mAh / g, which has a high capacity and is used as a negative electrode active material. However, even if the graphite or carbon-based active material has a rather high theoretical capacity, it is only about 380 mAh / g, and there is a problem in that the negative electrode cannot be used in the development of a high capacity lithium secondary battery in the future.

In order to improve such a problem, a material that is currently being actively researched is a negative electrode active material based on metal or intermetallic compounds. For example, lithium secondary batteries using metals or semimetals such as aluminum, germanium, silicon, tin, zinc, and lead as negative electrode active materials have been studied. It is considered that such a material has a high energy density and high energy density, and can absorb and release more lithium ions than a negative electrode active material using a carbon-based material, thereby producing a battery having a high capacity and a high energy density. Pure silicon, for example, is known to have a high theoretical capacity of 4017 mAh / g.

However, the cycle characteristics are deteriorated compared to the carbon-based materials, which is still an obstacle to practical use. The reason is that when inorganic particles such as silicon and tin are used as lithium occlusion and release materials as they are, the volume during charge and discharge This is because the change in conductivity between the active materials or the phenomenon in which the negative electrode active material peels from the negative electrode current collector occurs due to the change.

In particular, in the case of an active material having a small particle size or a large specific surface area, the contact surface with the electrolyte is increased to increase side reactions with the electrolyte during initial lithium insertion. As a result, the initial irreversible capacity is increased, thereby lowering the initial efficiency.

On the other hand, binders such as polyvinylidene fluoride and styrene polybutadiene rubber, which are usually used in the production of a negative electrode, may not withstand the physical volume of the negative electrode active material as described above. In order to solve this problem, a method using a tough polymer binder, such as a polyimide binder, has been developed, but the tough polymer binder has excellent mechanical tensile strength and adhesive strength, but is easy to react with lithium ions electrochemically and as a result, There is a problem of lowering reversible capacity and initial efficiency.

The problem to be solved by the present invention is to provide a negative electrode for a lithium secondary battery with high initial efficiency and reversible capacity.

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

According to an aspect of the present invention to achieve the above object,

A composite negative electrode active material including a metal negative electrode active material and a water-soluble polymer coated on a surface of the metal negative electrode active material; And

Polyimide binder

There is provided a negative electrode for a lithium secondary battery comprising a.

According to another aspect of the invention,

The cathode;

anode;

A separator positioned between the cathode and the anode; And

A lithium secondary battery including an electrolyte is provided.

The negative electrode for a lithium secondary battery according to an aspect of the present invention may provide a lithium secondary battery in which initial irreversible capacity is reduced and initial efficiency is increased.

1 is a view schematically showing a cross section of a negative electrode including a composite negative electrode active material according to an embodiment of the present invention.
2 is a graph showing initial charge and discharge curves of a battery including a composite anode active material according to Examples and Comparative Examples of the present invention.
3 is a graph showing capacity retention rate of a battery including a composite anode active material according to Examples and Comparative Examples of the present invention.

Hereinafter, the present invention will be described in more detail.

According to an aspect of the present invention, a lithium secondary battery negative electrode includes a composite negative electrode active material including a metal-based negative electrode active material and a water-soluble polymer coated on the surface of the metal-based negative electrode active material; And polyimide binders.

According to one embodiment of the present invention, by uniformly coating a metal-based negative active material having a large specific surface area using a water-soluble polymer, it is possible to suppress destruction of the electrode structure due to volume expansion / contraction of the metal-based negative electrode active material. That is, by forming an organic pre-SEI (Solid Electrolyte Interface) using a water-soluble polymer to protect the defective portion of the metal-based negative electrode active material to suppress direct contact with the electrolyte solution to suppress side reactions with the electrolyte on the surface of the metal-based negative electrode active material have. As a result, the initial efficiency of the lithium secondary battery can be improved and the reversible capacity can be increased and the energy density can be increased.

The metal-based negative active material may be used without any limitation as long as it is used in the art, for example, at least one metal selected from the group consisting of Si, Sn, Al, Ge, Pb, Zn, Ag, and Au, alloys thereof, and the like. Oxide, or a composite of these with a carbon material.

Examples of the metal-based negative active material include silicon, silicon oxide, silicon-based alloy, silicon-carbon material composite, tin, tin-based alloy, tin-carbon material composite, germanium, germanium alloy, germanium-carbon material composite, and germanium oxide. Or a combination thereof.

The carbon material may include at least one selected from carbon nanotubes, natural graphite, artificial graphite, coke, carbon fiber, spherical carbon, amorphous carbon, and graphene.

The water-soluble polymer may be a homopolymer or a copolymer, 10g or more may be dissolved with respect to 1000g of water.

The metal-based negative electrode active material may further include a metal oxide material. The metal oxide material included on the surface of the metal-based negative electrode active material may include at least one selected from lithium titanium oxide, aluminum oxide, silicon oxide, titanium oxide, and zinc oxide. The metal oxide material may improve side efficiency and lifespan characteristics by reducing side reactions between the negative electrode active material and the electrolyte on the surface of the negative electrode. Particularly, in the case of lithium titanium oxide, lithium ions are accommodated when charged but do not release lithium ions when discharged, thereby improving conductivity of the active material.

The metal oxide material may be 0.1 to 10% by weight of the composite anode active material. When it is in the said range, side reaction with electrolyte solution can be reduced and initial stage efficiency can be improved.

The water-soluble polymer is substituted with carboxymethyl cellulose, carboxymethyl cellulose sodium salt, carboxymethyl cellulose ammonium salt, methyl cellulose, hydroxy methyl cellulose, hydroxy propyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid, alkali cation or ammonium ion Poly (alkylene-maleic anhydride) copolymer substituted with polyacrylic acid, alkali cation or ammonium ion, poly (alkylene-maleic acid) copolymer substituted with alkali cation or ammonium ion, polyethylene oxide, alginic acid and sodium alginate salt It may be one or more selected from the group.

The water-soluble polymer may be 0.5 to 20% by weight of the composite anode active material. If it falls within the above range, the initial efficiency can be improved, and the reversible capacity can be increased.

1 is a view schematically showing a negative electrode according to an embodiment of the present invention.

As shown in FIG. 1, the metal-based negative active material 11 has a surface coated with a water-soluble polymer 12, and a polyimide-based binder 13 is present between the composite negative active materials including the metal-based active material coated with the surface. To form a cathode.

The polyimide-based binder can prevent the collapse of the electrode structure to improve the life characteristics of the electrode. That is, after uniformly coating a metal-based negative active material having a large specific surface area using a water-soluble polymer, the high-strength polyimide-based binder is used to suppress destruction of the electrode structure due to volume expansion / contraction of the metal-based negative electrode active material.

As the polyimide-based binder, one or more selected from the group consisting of polyimide, polyamideimide, polyetherimide, and the like may be used.

As said polyimide, various well-known polyimide can be mentioned, Any of thermoplastic polyimide and thermosetting polyimide can be used. In the case of a thermosetting polyimide, any of a condensation type polyimide and an addition type polyimide may be sufficient. The reason for having good electron mobility and the like is one having an aromatic ring in the molecular chain, that is, an aromatic polyimide. Polyimide may use only 1 type and may use 2 or more types together.

As polyamideimide, various well-known polyamideimide is mentioned. Also in polyamideimide, the same thing as polyimide has an aromatic ring in a molecular chain, ie, an aromatic polyamideimide. Polyamideimide may use only 1 type, and may use 2 or more types together.

As polyamide, various polyamides, such as nylon 66, nylon 6, and aromatic polyamide (nylon MXD6 etc.), can be used, for example. Also in polyamide, for the same reason as polyimide, what has an aromatic ring in a molecular chain, ie, an aromatic polyamide, is mentioned. Polyamide may use only 1 type and may use 2 or more types of polyamide together.

The water-soluble polymer in the negative electrode for the lithium secondary battery may be present in an amount of 0.5 to 20% by weight of the composite negative electrode active material. If it falls within the above range, it is possible to increase the initial efficiency and increase the reversible capacity.

The polyimide binder may be present in an amount of 5 to 30% by weight of the negative electrode for the lithium secondary battery. If it is in the above range can maintain excellent life characteristics.

According to another aspect of the invention, the negative electrode for a lithium secondary battery comprises the steps of preparing a mixture comprising a metal-based negative electrode active material particles, a water-soluble polymer and water; Drying the mixture to prepare a composite anode active material; Preparing a slurry including the composite anode active material, a polyimide binder, and an organic solvent; And coating the slurry onto a current collector.

At this time, instead of coating the slurry directly on the current collector, the negative electrode may be manufactured by casting the slurry on a separate support and laminating the film peeled from the support onto the copper current collector.

When the metal-based negative electrode active material, the water-soluble polymer, and the polyimide binder are mixed at the same time, the compatibility of the water-soluble polymer and the polyimide-based binder is poor, and thus a desired negative electrode layer cannot be formed. Therefore, in the method of manufacturing a negative electrode according to an embodiment of the present invention, a composite negative electrode active material having a water-soluble polymer coated on the surface of a metal negative electrode active material is prepared by first preparing a mixture including metal-based negative electrode active material particles, a water-soluble polymer, and water. Is obtained first and then mixed with a polyimide-based binder and an organic solvent to obtain a slurry. The slurry can then be cast onto a current collector or coated on a support and then dried to obtain a negative electrode layer.

N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide and the like can be used as the organic solvent.

Lithium secondary battery according to another aspect of the present invention the negative electrode; anode; A separator existing between the cathode and the anode; And electrolyte solutions.

The positive electrode may be prepared by mixing a positive electrode active material, a conductive agent, a binder, and a solvent to prepare a positive electrode active material composition, and then coating and drying the positive electrode active material directly on an aluminum current collector. Alternatively, the cathode active material composition may be cast on a separate support, and then a film obtained by peeling from the support may be laminated on the aluminum current collector.

The positive electrode active material may be any lithium-containing metal oxide, without limitation, as long as it is commonly used in the art, for example, LiCoO ₂ , LiMn _x O _2x , LiNi _x-1 Mn _x O _2x (x = 1, 2 ), LiNi _1-xy Co _x Mn _y O ₂ (0 ≦ _x ≦ 0.5, 0 ≦ _y ≦ 0.5), and the like. Carbon black may be used as the conductive agent in the positive electrode active material composition, and vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, and polytetrafluoro And ethylene and mixtures thereof, and styrene butadiene rubber polymers. N-methylpyrrolidone, acetone, water, etc. can be used as a solvent. At this time, the content of the positive electrode active material, the conductive agent, the binder, and the solvent is at a level commonly used in lithium batteries.

In some cases, a plasticizer is further added to the positive electrode active material composition to form pores in the electrode plate.

As the separator, any of those commonly used in lithium batteries can be used. In particular, it is preferable that it is low resistance with respect to the ion movement of electrolyte, and is excellent in electrolyte-moisture capability. For example, the material selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), and mixtures thereof may be in the form of nonwoven or woven fabric. In more detail, a lithium ion battery uses a rollable separator made of a material such as polyethylene or polypropylene, and a lithium ion polymer battery uses a separator having excellent organic electrolyte impregnation ability. It can be manufactured according to the method.

That is, a separator composition is prepared by mixing a polymer resin, a filler, and a solvent, and then the separator composition is directly coated and dried on an electrode to form a separator film, or the separator composition is cast and dried on a support, and then the support The separator film peeled off can be laminated on the electrode and formed.

The polymer resin is not particularly limited, and for example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate or a mixture thereof may be used. In particular, it is preferable to use vinylidene fluoride / hexafluoropropylene copolymers having a hexafluoropropylene content of 8 to 25% by weight.

The separator is disposed between the positive electrode and the negative electrode as described above to form a battery structure. The battery structure is wound or folded, placed in a cylindrical battery case or a square battery case, and then injected with an organic electrolyte to complete a lithium ion battery. Alternatively, the battery structure is stacked in a bi-cell structure, and then impregnated in the organic electrolyte, and the resultant is placed in a pouch and sealed to complete a lithium ion polymer battery.

The organic electrolyte solution includes a lithium salt, a mixed organic solvent consisting of a high dielectric constant solvent and a low boiling point solvent, and may further include various additives such as an overcharge preventing agent if necessary.

The high dielectric constant solvent used in the organic electrolyte is not particularly limited as long as it is commonly used in the art, and for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate or gamma-butyrolactone may be used. have.

In addition, low boiling point solvents are also commonly used in the art, such as dimethyl carbonate and ethylmethyl carbonate. Diethyl carbonate, chain carbonates such as dipropyl carbonate, dimethoxyethane, diethoxyethane or fatty acid ester derivatives may be used, and the like is not particularly limited.

One or more hydrogen atoms present in the high dielectric constant solvent and the low boiling point solvent may be substituted with a halogen atom, and the halogen atom is preferably fluorine.

It is preferable that the mixing volume ratio of the high dielectric constant solvent and the low boiling point solvent is 1: 1 to 1: 9, and when it is out of the range, it is not preferable in terms of discharge capacity and charge and discharge life.

In addition, any lithium salt used in the organic electrolyte may be used as long as it is conventionally used in lithium batteries, LiClO ₄ , LiCF ₃ SO ₂ , LiPF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiBF ₄ , LiC (CF Preference is given to at least one compound selected from the group consisting of ₃ SO ₂ ) ₃ , and LiN (C ₂ F ₅ SO ₂ ) ₂ .

It is preferable that the concentration of the lithium salt in the organic electrolyte is about 0.5 to 2 M. If it falls within the above range, the mobility of lithium ions can be maintained and the conductivity of the electrolyte can be prevented from decreasing.

Hereinafter, the present invention will be described in more detail with reference to Examples, but these are not intended to limit the present invention.

Preparation Example 1

4 g of polyisobutylene-maleic anhydride copolymer (purchased from Kuraray, product name: ISOBAM, weight average molecular weight 300,000 to 350,000), and 1.245 g of LiOH were mixed in 96 g of deionized water, followed by stirring at about 70 ^° C. for 24 hours. Proceeding to obtain a polymer composition containing polyisobutylene-maleic anhydride and deionized water substituted with lithium.

Preparation Example 2

4 g of polyacrylic acid (purchased by Aldrich, viscosity average molecular weight 450,000) and 1.35 g of LiOH were mixed in 96 g of deionized water, followed by stirring at about 70 ^° C. for 24 hours to carry out lithium substitution of polyacrylic acid and deionized water. A polymer composition containing was obtained.

Example 1

Silicon (average particle size 4㎛, Aldrich) and carbon nanotubes (Hanhwa Chemical Co., Ltd.) were mixed in a weight ratio of 50:50, and then silicon / carbon composite particles were prepared using a high energy mill for 30 minutes.

75 parts by weight of the silicon / carbon composite particles prepared by the above method and 125 parts by weight of an aqueous solution of polyisobutylene-maleic anhydride copolymer (Li-1.0-PIBMA) substituted with lithium prepared in Preparation Example 1 were then uniformly mixed. After drying in an oven at 80 ° C., a composite negative electrode active material having a polyisobutylene-maleic anhydride copolymer substituted with lithium coated on a silicon / carbon composite surface was prepared.

After preparing a slurry by mixing 400 parts by weight of a solution of polyamideimide binder (purchased: Solvay Solexis, product name: Torlon4000T) in N-methylpyrrolidone at 5% by weight to the composite anode active material prepared above, a slurry was prepared. It was coated on the current collector to be about 75 μm. The electrode thus prepared was dried in a hot air dryer at about 100 ° C. for 2 hours, and once again vacuum dried at about 120 ° C. for 2 hours to prepare a cathode from which moisture was completely removed. The prepared negative electrode was rolled through a rolling mill so that the final thickness of the active material layer was about 40 μm to prepare a final negative electrode.

Example 2

75 parts by weight of the silicon / carbon composite particles prepared in the same manner as in Example 1 and 125 parts by weight of polyacrylic acid (Li-PAA) substituted with lithium of Preparation Example 2 were uniformly mixed, and then dried in an 80 ° C. oven. A composite anode active material in which polyacrylic acid substituted with lithium was coated on the silicon / carbon composite particle surface was prepared. The composite anode active material was mixed with 400 parts by weight of a solution of polyamideimide binder (purchased: Solvay Solexis, product name: Torlon4000T) in N-methylpyrrolidone at 5% by weight to prepare a slurry, and then coated on a copper current collector. An electrode was prepared.

Example 3

75 parts by weight of the silicon / carbon composite particles prepared in the same manner as in Example 1 and 10 parts by weight of polyvinyl alcohol (PVA) (purchased: Kanto Chemical, product name: Polyvinyl alcohol # 2,000) 50 parts by weight of an aqueous solution After drying in an oven at 80 ° C., a composite negative electrode active material having a polyvinyl alcohol coated on a silicon / carbon composite surface was prepared. The composite anode active material was mixed with 400 parts by weight of a solution of polyamideimide binder (purchased: Solvay Solexis, product name: Torlon4000T) in N-methylpyrrolidone at 5% by weight to prepare a slurry, and then coated on a copper current collector. An electrode was prepared.

Example 4

75 parts by weight of the silicon / carbon composite particles prepared in the same manner as in Example 1 and 250 parts by weight of 2% by weight of an aqueous solution of sodium alginate (Na-Alginate), and then dried in an oven at 80 ℃ and sodium alginate silicon A composite anode active material coated on the / carbon composite surface was prepared. The composite anode active material was mixed with 400 parts by weight of a solution of polyamideimide binder (purchased: Solvay Solexis, product name: Torlon4000T) in N-methylpyrrolidone at 5% by weight to prepare a slurry, and then coated on a copper current collector. An electrode was prepared.

Example 5

75 parts by weight of the silicon / carbon composite particles prepared in the same manner as in Example 1 and 2 parts by weight of carboxymethylcellulose sodium salt (purchased: Daicel, product name: CMC 1260) 250 parts by weight of an aqueous solution was uniformly mixed, then 80 ℃ Drying in an oven prepared a composite anode active material in which carboxymethylcellulose sodium salt was coated on the silicon / carbon composite surface. The composite anode active material was mixed with 400 parts by weight of a solution of polyamideimide binder (purchased: Solvay Solexis, product name: Torlon4000T) in N-methylpyrrolidone at 5% by weight to prepare a slurry, and then coated on a copper current collector. An electrode was prepared.

Example 6

80 parts by weight of the silicon / carbon composite particles prepared in the same manner as in Example 1 and 150 parts by weight of an aqueous solution of 2% by weight of carboxymethylcellulose sodium salt (purchase: Daicel, product name: CMC 1330) were uniformly mixed, followed by 80 ° C. Drying in an oven produced a composite anode active material in which carboxymethylcellulose sodium salt (CMC 1330) was coated on the silicon / carbon composite surface. The composite anode active material was mixed with 340 parts by weight of a solution of polyamideimide binder (Buy: Solvay Solexis, product name: Torlon4000T) in N-methylpyrrolidone at 5% by weight to prepare a slurry, and then coated on a copper current collector. An electrode was prepared.

Example 7

80 parts by weight of the silicon / carbon composite particles prepared in the same manner as in Example 1 and 150 parts by weight of an aqueous solution of 2% by weight of carboxymethylcellulose ammonium salt (Daicel, product name: DN-100L) were uniformly mixed, followed by 80 ° C. Drying in an oven prepared a composite anode active material in which carboxymethyl cellulose ammonium salt (DN-100L) was coated on the silicon / carbon composite surface. The composite anode active material was mixed with 340 parts by weight of a solution of polyamideimide binder (Buy: Solvay Solexis, product name: Torlon4000T) in N-methylpyrrolidone at 5% by weight to prepare a slurry, and then coated on a copper current collector. An electrode was prepared.

Comparative Example 1

80 parts by weight of the silicon / carbon composite particles prepared in the same manner as in Example 1 and a polyamideimide binder (purchased from Solvay Solexis, product name: Torlon4000T) at 5% by weight in 400 parts by weight of a solution dissolved in N-methylpyrrolidone After mixing to prepare a slurry, it was coated on a copper current collector to prepare an electrode.

Comparative Example 2

80 parts by weight of the silicon / carbon composite particles prepared in the same manner as in Example 1 and 500 parts by weight of polyacrylic acid (Li-PAA) substituted with lithium of Preparation Example 2 uniformly mixed to prepare a slurry, The electrode was prepared by coating on the whole.

Comparative Example 3

75 parts by weight of the silicon / carbon composite particles prepared in the same manner as in Example 1 and 125 parts by weight of polyacrylic acid (Li-PAA) substituted with lithium of Preparation Example 2 and a polyamideimide binder (purchased: Solvay Solexis, product name : 400 parts by weight of a solution of Torlon4000T) dissolved in N-methylpyrrolidone at 5% by weight was mixed together. Since the solvent of the polyacrylic acid aqueous solution substituted with lithium is water, and the solvent of polyamideimide is N-methylpyrrolidone, since the binder materials are nonsolvents to each other, a polymer material precipitates and an electrode slurry cannot be prepared. .

The electrodes prepared in Examples and Comparative Examples were used as the cathode, Li metal as the counter electrode, polyethylene as the separator, and 1.3M LiPF ₆ + EC / DEC / FEC = 2/6/2 (v / v) ( 3: 7 weight ratio) The coin half cell (CR2032) was prepared using an electrolyte, and then charged and discharged under the following conditions.

After charging with constant current to 0.001V at 130 mA / g, it charged to 65 mA / g at constant voltage. The discharge was performed at a constant current up to 1.5 V at 130 mA / g. This was repeated 50 times to evaluate the charge and discharge characteristics.

Initial efficiency is calculated by the following equation.

Initial Efficiency (%) = (One Discharge Capacity / One Charge Capacity) x 100

Table 1 shows the charge and discharge capacity, initial efficiency, and capacity retention rate of the batteries according to Examples and Comparative Examples. 2 shows the charge and discharge capacity of the lithium secondary battery including the negative electrode according to the embodiment and the comparative example of the present invention. 3 shows the capacity retention rate of the lithium secondary battery including the negative electrode according to the Examples and Comparative Examples of the present invention.

No. Charge capacity
(mAh / g) Discharge capacity
(mAh / g) Initial efficiency
(%) Capacity retention
(%) Comparative Example 1 1,984 1,366 68.9 89.2 Comparative Example 2 2,180 1,525 71.0 55.2 Example 1 2,366 1,666 70.5 90.0 Example 2 2,115 1,492 70.5 89.3 Example 3 2,100 1,480 70.5 89.5 Example 4 2,350 1,657 70.5 90.3 Example 5 2,366 1,710 72.3 90.2 Example 6 2,285 1,635 71.6 90.8 Example 7 2,271 1,636 72.1 90.6

In Comparative Example 2 in Table 1, the initial efficiency was slightly higher than that of Examples 1 to 4 as an example of not using polyamideimide as a binder, but the capacity retention ratio was rapidly decreased. This can be seen that the binder of Comparative Example 2 does not correspond to the volume expansion and contraction of the active material during charging and discharging, and the life characteristics are sharply degraded because the electrode is not firmly held. As described above, in the case of the lithium secondary battery including the negative electrode including the composite negative active material according to the present invention, the initial efficiency is high, the capacity retention rate is increased, and the lifespan characteristics are improved. In particular, it can be seen that the reversible capacity is increased when using a water-soluble polymer substituted with a metal.

11: metal negative active material
12: water soluble polymer
13: polyimide binder

Claims (11)

A composite negative electrode active material including a metal-based negative electrode active material including a composite in which a plurality of metal particles and a carbon material are mixed and a water-soluble polymer coated on a surface of the metal-based negative electrode active material; And
It comprises a polyimide-based binder,
The metal-based negative active material is selected from silicon-carbon material composites, tin-carbon material composites, germanium-carbon material composites, and combinations thereof,
The carbon material includes at least one selected from carbon nanotubes, natural graphite, artificial graphite, carbon fiber, spherical carbon, and graphene,
The water-soluble polymer is a negative electrode for a lithium secondary battery contained in an amount of 3.6 to 20% by weight of the composite negative electrode active material. The method of claim 1,
The water-soluble polymer is substituted with carboxymethyl cellulose, carboxymethyl cellulose sodium salt, carboxymethyl cellulose ammonium salt, methyl cellulose, hydroxy methyl cellulose, hydroxy propyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid, alkali cation or ammonium ion Poly (alkylene-maleic anhydride) copolymer substituted with polyacrylic acid, alkali cation or ammonium ion, poly (alkylene-maleic acid) copolymer substituted with alkali cation or ammonium ion, polyethylene oxide, alginic acid and sodium alginate salt At least one lithium secondary battery negative electrode selected from the group. The method of claim 1,
The water-soluble polymer is a negative electrode for a lithium secondary battery contained in the amount of 3.61 to 20% by weight of the composite negative electrode active material. The method of claim 1,
The water-soluble polymer is a negative electrode for a lithium secondary battery contained in an amount of 3.6 to 6.3% by weight of the composite negative electrode active material. The method of claim 1,
The water-soluble polymer is a negative electrode for a lithium secondary battery contained in the amount of 3.61 to 6.25% by weight of the composite negative electrode active material. The method of claim 1,
The negative electrode for a lithium secondary battery further comprises a metal oxide material on the surface of the metal-based negative electrode active material. The method of claim 6,
The metal oxide material is at least one selected from lithium titanium oxide, aluminum oxide, silicon oxide, titanium oxide and zinc oxide negative electrode for a lithium secondary battery. The method of claim 1,
The polyimide-based binder is a lithium secondary battery negative electrode contained in the amount of 5 to 30% by weight of the negative electrode for the lithium secondary battery. The method of claim 1,
The polyimide-based binder is at least one selected from polyamideimide, polyamide and polyimide negative electrode for a lithium secondary battery. Preparing a mixture including metal-based negative active material particles, a water-soluble polymer, and water, including a composite in which a plurality of metal particles and a carbon material are mixed;
Drying the mixture to prepare a composite anode active material;
Preparing a slurry including the composite anode active material, a polyimide binder, and an organic solvent; And
Coating the slurry onto a current collector
Method for manufacturing a negative electrode for a lithium secondary battery according to claim 1 comprising a. anode;
The negative electrode according to any one of claims 1 to 9;
A separator positioned between the positive electrode and the negative electrode; And
Lithium secondary battery containing an electrolyte solution.

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