KR20220059764A - Aqeous dispersion binder composition for secondary battery electrode, electrode comprising the same and secondary battery using the same - Google Patents

Abstract

The present invention relates to a water-dispersible binder composition for a secondary battery electrode, an electrode including the same, and a secondary battery including the same. More specifically, the secondary battery using a water-dispersible binder composition for a secondary battery electrode containing carboxylic acid-modified polyolefin has excellent heat resistance and mechanical properties, improves binding force, and can improve the charge/discharge life characteristics and performance of the secondary battery due to improved adhesion of the electrode according to the present invention.

Description

Aqueous dispersion binder composition for secondary battery electrode, electrode for secondary battery comprising same, and secondary battery using same

The present invention relates to an aqueous dispersion binder composition for a secondary battery electrode, an electrode for a secondary battery comprising the same, and a secondary battery including the electrode. In detail, it relates to a secondary battery having improved electrode adhesion and binding force, including the aqueous dispersion binder composition for an electrode according to the present invention.

In addition, according to the electrode according to the present invention, the charge and discharge life characteristics of the secondary battery can be improved, and the battery performance can be improved due to the low resistance.

Lithium secondary battery is an electrode material constituting the positive and negative electrodes. It consists of a positive electrode and a negative electrode material, an electrolyte that conducts lithium ions between electrodes, and a separator that prevents short circuits so that the positive and negative electrodes do not come into direct contact with each other. It can be divided into components, and the negative electrode material and the positive electrode material are each composed of a metal current collector, an active material, a conductive material, a binder, and other additives.

Graphite or an activated carbon-based material is mainly used as the active material of the negative electrode, and activated carbon is used as the conductive material. The binder is mainly used to secure the adhesion or binding force between the electrode active material and the electrode current collector, and is also used as a buffer against the expansion and contraction of the active material according to the insertion and desorption of lithium ions.

A basic requirement of a polymer material used as a binder is that there should be no chemical and electrochemical side reactions with organic electrolytes, and at the same time, stable adhesive properties must be maintained. As the negative electrode binder, oil-based PVDF, water-based SBR/CMC, or acrylic binders are mainly used. Due to the problem of dissociation of ions and the problem of corrosion of the aluminum current collector, PVDF, which is a planetary type, is mainly used.

However, in the case of oil-based systems, there is a problem of increased facility investment and manufacturing cost due to the recovery of the used solvent, as well as aggregation problem of active material and low adhesion to the current collector due to the high molecular weight of PVDF.

Therefore, as a binder material applicable to both anode material and cathode material, while solving the above problems, it prevents deterioration due to separation of the active material even when the volume of the electrode changes due to charging/discharging due to its strong adhesive force, and There is a demand for a new binder for secondary battery electrodes that can improve the life and performance of the battery.

Korean Patent Publication No. 10-2012-0106041 (2012.09.26)

An object of the present invention to solve the above problems is to improve the mechanical properties and adhesive properties of the binder, and suppress the increase in resistance to improve the life and performance of the battery, and an aqueous dispersion binder composition for secondary battery electrodes, an electrode comprising the same, and An object of the present invention is to solve the above problem by providing a secondary battery using the same.

It is also an object of the present invention to provide a binder for a secondary battery electrode with improved durability by improving the adhesion of the electrode binder and preventing peeling and detachment of the electrode, a secondary battery electrode including the same, and a secondary battery using the same.

Another object of the present invention is to provide a binder material applicable to both the anode material and the cathode material.

Another object of the present invention is to provide a secondary battery to which the binder according to the present invention is applied, in which voltage stability is remarkably improved because a change in current is insignificant when a voltage up to 7V is applied.

Another object of the present invention is to provide an electrode including the binder of the present invention and a secondary battery using the same to improve adhesion, thereby providing a secondary battery with improved charge/discharge lifespan characteristics and performance.

The aqueous dispersion binder composition for secondary battery electrodes according to an aspect of the present invention provides an aqueous dispersion binder composition for secondary battery electrodes comprising a carboxylic acid-modified polyolefin.

In the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention, the carboxylic acid-modified polyolefin may be a polyolefin modified with maleic anhydride or (meth)acrylic acid.

In the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention, the carboxylic acid modification may be 0.01 to 5% by weight.

In the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention, the weight average molecular weight of the carboxylic acid-modified polyolefin may be 50,000 to 200,000 g/mol.

The aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention may include an amino alcohol neutralizing agent.

In the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention, the particle size of the aqueous dispersion of the carboxylic acid-modified polyolefin may be 50 to 500 nm.

In the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention, the aqueous dispersion binder composition for secondary battery electrodes further includes any one or two or more selected from an acrylic binder, an olefin-based elastomer binder, and a cellulose-based binder. can do.

An embodiment of the present invention may provide a composition for a secondary battery electrode comprising an electrode active material, a conductive material, and the above-described aqueous dispersion binder composition for secondary battery electrodes.

In the composition for a secondary battery electrode according to an embodiment of the present invention, the content of the carboxylic acid-modified polyolefin may be 0.1 to 15% by weight based on the electrode active material.

An embodiment of the present invention may include a current collector and an electrode active material layer disposed on the current collector, wherein the electrode active material layer may provide an electrode for a secondary battery made of the composition for a secondary battery electrode described above.

One embodiment of the present invention is a negative electrode; anode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte, wherein the negative electrode may provide a secondary battery that is the secondary battery electrode described above.

In the secondary battery according to an embodiment of the present invention, the adhesive force of the negative electrode may be 9.5 gf/10mm or more.

In the secondary battery according to an embodiment of the present invention, the secondary battery may have a capacity retention rate of 80% or more after 500 cycles of charging and discharging.

An object of the present invention to solve the above problems is to improve the mechanical properties and adhesive properties of the binder, and suppress the increase in resistance to improve the life and performance of the battery, and an aqueous dispersion binder composition for secondary battery electrodes, an electrode comprising the same, and It is possible to provide a secondary battery including the same.

The aqueous dispersion binder composition for a secondary battery electrode according to an embodiment of the present invention, an electrode including the same, and a secondary battery including the same improve the adhesion of the electrode binder, and prevent peeling and detachment of the electrode, thereby improving durability there is

The water-dispersible binder for an electrode according to an embodiment of the present invention has the advantage of being applicable to both the anode material and the cathode material.

In the secondary battery to which the water-dispersible binder for electrodes is applied according to an embodiment of the present invention, when a voltage is applied up to 7V, the change in current is insignificant, so that voltage stability is remarkably improved.

The secondary battery according to an embodiment of the present invention has the effect of improving the adhesion of the electrode, thereby improving the charge/discharge life characteristics and performance.

Hereinafter, the present invention will be described in more detail through embodiments or examples including the accompanying drawings. However, the following specific examples or examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of effectively describing particular embodiments only and is not intended to limit the invention.

Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise.

Also, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

An object of the present invention to solve the above problems is to improve the mechanical properties and adhesive properties of the binder, and suppress the increase in resistance to improve the life and performance of the battery, and the binder for the secondary battery electrode, the electrode comprising the same, and an electrode comprising the same A secondary battery may be provided.

In addition, the present invention was completed by discovering that the water-dispersible binder for secondary battery electrodes according to an embodiment of the present invention can provide a secondary battery with improved charge/discharge life characteristics and performance due to improved adhesion.

The aqueous dispersion binder composition for a secondary battery electrode according to an embodiment of the present invention may include a carboxylic acid-modified polyolefin.

The polyolefin is not limited as long as it is a commonly used known polyolefin, and for example, may be selected from polyethylene, polypropylene, polybutene, and the like.

In the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention, the carboxylic acid-modified polyolefin is a polyolefin modified with maleic anhydride or (meth)acrylic acid.

In the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention, the carboxylic acid modification may be 0.01 to 5% by weight, specifically, 0.05 to 4% by weight, preferably It may be modified to 1 to 3.5 wt%, but is not limited thereto. In this case, the carboxylic acid modification means a value measured through FT-IR modified with maleic anhydride or (meth)acrylic acid described above. The water-dispersible binder for an electrode comprising a carboxylic acid-modified polyolefin satisfying the above range has an effect of improving adhesion and thus improving battery durability, and preventing peeling and detachment of the electrode.

In the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention, the weight average molecular weight of the carboxylic acid-modified polyolefin may be 30,000 to 300,000 g/mol. Specifically, the weight average molecular weight may be 50,000 to 150,000 g/mol. In a range where the weight average molecular weight satisfies the above range, adhesion may be further improved, but the present invention is not limited thereto.

In the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention, the secondary battery electrode binder may include an amino alcohol neutralizing agent.

The amino alcohol neutralizing agent may be a compound represented by the following formula (1).

[Formula 1]

In Formula 1, R is (C1-C5) alkylene. As a specific example, it may be monoethanolamine (MEA), but is not limited thereto.

The amino alcohol neutralizing agent may improve dispersibility by neutralizing the acidity of the polyolefin modified with carboxylic acid. That is, there is an effect that it is easy to control the particle size of the aqueous dispersion of the modified polyolefin.

In the aqueous dispersion binder composition for a secondary battery electrode according to an embodiment of the present invention, the particle size of the aqueous dispersion of the carboxylic acid-modified polyolefin may be 50 to 500 nm, specifically 100 to 450 nm, More specifically, it may be 150 to 400 nm, but is not limited thereto.

The aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention may further include any one or two or more selected from an acrylic binder, an olefin-based elastomer binder, and a cellulose-based binder.

The acrylic binder may be any acrylic binder known in the art, for example, specifically methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, It is not limited as long as it is a binder of a polymer resin prepared from a monomer such as 2-ethylhexyl methacrylate.

The olefinic type of the olefin-based elastomer binder may be styrene-based, and specifically, the styrene-based monomer may be an unsubstituted styrene monomer or a substituted styrene monomer.

The substituted styrene monomer may be styrene substituted with a substituent including an aliphatic hydrocarbon or a hetero atom in a benzene ring or a vinyl group. Preferably, styrene substituted with (C1-C4) alkyl or halogen can be used. The styrenic monomer of the present invention may preferably be at least one selected from the group consisting of styrene, α-methylstyrene, 4-methylstyrene, 4-bromostyrene, 4-chlorostyrene and vinyltoluene, Most preferably, styrene may be used, and a preferred example of the olefin-based elastomer binder may be styrene-butadiene-based-rubber, but is not limited thereto.

The cellulosic binder is a cellulosic polymer, and is selected from the group consisting of carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, methyl hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, methyl ethyl hydroxyethyl cellulose, and cellulose gum. One or more may be used, and more preferably, carboxymethyl cellulose may be used, but is not limited thereto.

An embodiment of the present invention may provide a composition for a secondary battery electrode comprising an electrode active material, a conductive material, and the above-described aqueous dispersion binder composition for secondary battery electrodes.

The content of the carboxylic acid-modified polyolefin may be 0.1 to 15 wt% based on the electrode active material. Specifically, it may be 0.3 to 14% by weight, and more specifically, it may be 0.5 to 13% by weight, but the content of the carboxylic acid-modified polyolefin within the range in which the performance of the secondary battery is not reduced is not particularly limited.

The electrode active material includes a negative electrode active material and a positive electrode active material, and the negative active material includes any one or two selected from graphite-based active material, platinum, palladium, silicon-based active material, silver, aluminum, bismuth, tin, zinc, or a combination thereof. It may be more than, preferably, since it may exhibit a better effect on a silicon-based active material or a negative active material containing a silicon-based active material, it may be preferred, but is not limited thereto.

The positive electrode active material may be any positive electrode active material known in the art. For example, it is preferable to use a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. The present invention is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical change in the battery constituted can be used. Graphite-based conductive material, carbon black-based conductive material, metal or metal compound At least one selected from a conductive material may be used. Examples of the graphite-based conductive material include artificial graphite, natural graphite, and the like, and examples of the carbon black-based conductive material include acetylene black, ketjen black, denka black, thermal black, and channel black. black) and the like, and examples of the metal-based or metal compound-based conductive material include perovskite materials such as tin, tin oxide, tin phosphate (SnPO ₄ ), titanium oxide, potassium titanate, LaSrCoO ₃ , and LaSrMnO ₃ . . However, it is not limited to the above-listed conductive materials.

The conductive material is not particularly limited, and its content may be appropriately adjusted depending on the purpose of use, but preferably used in an amount of 1 to 30% by weight based on the electrode active material.

The solvent is a solvent for forming the aqueous dispersion binder composition for secondary battery electrodes, and a water-soluble solvent such as water may be used. The solvent is preferably used in an amount such that the composition has an appropriate viscosity in consideration of the applicability and coatability of the composition for secondary battery electrodes.

The solid content of the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention may be 20% by weight or more, but is not limited thereto.

In addition, the aqueous dispersion binder composition for secondary battery electrodes according to an embodiment of the present invention may be provided as a composition for secondary battery electrodes, including an electrode active material and a conductive material, wherein the solid content of the composition for secondary battery electrodes is It may be 20% by weight or more, preferably 25% by weight or more, but is not limited thereto.

An embodiment of the present invention may include a current collector and an electrode active material layer disposed on the current collector, wherein the electrode active material layer may provide an electrode for a secondary battery made of the composition for a secondary battery electrode described above.

The current collector may be selected from an aluminum foil, a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, and combinations thereof, but is limited thereto it is not going to be

One embodiment of the present invention is a negative electrode; anode; a separator interposed between the positive electrode and the negative electrode; and a secondary battery including an electrolyte. The cathode is the same as the electrode described above.

The positive electrode includes a current collector and a positive electrode active material layer formed by applying a composition for a positive electrode including a positive electrode active material on the current collector.

The current collector may be the current collector described above, and any material known in the art may be used, but the present invention is not limited thereto.

The positive electrode active material layer includes a positive electrode active material, and may optionally further include a binder and a conductive material. The positive active material may be any positive active material known in the art, and is the same as described above.

As the binder and the conductive material, the above-described aqueous dispersion binder composition and conductive material for secondary battery electrodes may be used, and a material known in the art may be used, but the present invention is not limited thereto.

The separator may be selected from, for example, glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and may be in the form of a nonwoven fabric or a woven fabric. For example, a polyolefin-based polymer separator such as polyethylene or polypropylene may be mainly used for a lithium secondary battery, and a separator coated with a composition containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, optionally It can be used in a single-layer or multi-layer structure, and it is not limited when a separator known in the art is used, but the present invention is not limited thereto.

The electrolyte is an electrolyte, and includes an organic solvent and a lithium salt.

The organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move, and for example, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. The organic solvents may be used alone or in mixture of two or more, and when two or more kinds are mixed and used, the mixing ratio may be appropriately adjusted according to the desired battery performance. On the other hand, if an organic solvent known in the art is used, it may be used, but the present invention is not limited thereto.

The lithium salt is a material that is dissolved in an organic solvent, acts as a source of lithium ions in the battery, enables basic lithium secondary battery operation, and promotes movement of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₃ C ₂ F ₅ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN(CxF ₂ x+1SO ₂ )(CyF ₂ y+1SO ₂ ) (x and y are natural numbers), LiCl, LiI, LiB(C ₂ O ₄ ) ₂ or a combination thereof. However, the present invention is not limited thereto.

The concentration of the lithium salt may be used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, since the electrolyte has appropriate conductivity and viscosity, excellent electrolyte performance may be exhibited, and lithium ions may move effectively.

In addition, in order to improve charge/discharge characteristics and flame retardancy characteristics, the electrolyte solution is pyridine, triethyl phosphate, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, if necessary. , sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol, aluminum trichloride, etc. may be further included. . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included to impart incombustibility, and FEC (fluoro-ethylene carbonate), PRS (propene sulfone), FPC ( fluoro-propylene carbonate) and the like may be further included.

The adhesive strength of the negative electrode of the secondary battery according to an embodiment of the present invention may be 9.5 gf/10mm or more. More specifically, it may be 9.7 gf/10mm, and more preferably 10.0 gf/10mm or more. The secondary battery according to an embodiment of the present invention has an effect of improving adhesion through the binder according to the present invention and improving durability by preventing peeling and detachment of electrodes.

The capacity retention rate after 500 cycles of charging and discharging of the secondary battery according to an embodiment of the present invention may be 80% or more. Preferably it may be 88% or more, and more preferably it may be 91% or more. In the secondary battery according to an embodiment of the present invention, it is possible to maintain a high capacity retention rate after charging and discharging, and improve the adhesion of the electrode, thereby improving the charge/discharge lifespan characteristics and performance of the secondary battery.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the following examples and comparative examples are merely examples for explaining the present invention in more detail, and the present invention is not limited by the following examples and comparative examples.

The physical properties of the following Examples and Comparative Examples of the present invention were measured in the following manner.

[Weight Average Molecular Weight]

GPC (Agilent Technologies' Agilent 1100S GPC Reflective Index detector) was used for measurement, and the test standard was carried out in accordance with KS M ISO 13885-1. For GPC column, 2 x TSKgel SupermultiporeHZ-M + TSKgel SuperHZ-2500 (4.6 x 150 mm) was used, THF solution was used as the solvent, polystyrene was used as the standard, and analysis was performed at 35 ° C, flow rate of 0.35 mL/min. did The results are shown in Table 1 below.

[Adhesive force test]

For the negative electrode of Example prepared above, the adhesive force was measured using UTM equipment. ASTM D903 was used as the test standard, and double-sided tape (3M VHB) was attached to a 76 x 26 mm slide glass for the specimen, and then the rolled anode surface was attached to the tape, and the sample was 30mm/min at an angle of 180°. The adhesive force was evaluated by measuring the force at the time of tearing off at a speed. The results are shown in Table 1 below.

[Battery Characteristics]

1) Discharge and charge capacity: With respect to the lithium secondary battery of the above-prepared embodiment, using WBCS 3000 (WonA Tech. Co.), the charge/discharge capacity is measured at room temperature by a galvanostatic mode method with a current rate of 0.1C. The results are shown in Table 1 below.

2) Resistance measurement: 1 x 1 cm ² with a constant current source using HMS-3000 (Ecopia), a Hall effect measuring instrument, and terminal switching using Van der Poh’s law Find the surface resistance and specific resistance of the electrode of the size. The results of electrode resistivity are shown in Table 1 below.

3) Capacity retention rate (lifetime characteristics)

Using the same method as the charging and discharging capacity, the capacity after repeated charging and discharging of 500 cycles at room temperature with a constant current of 0.5C current density was expressed as a percentage of the initial capacity. The results are shown in Table 1 below.

[Example 1]

[Manufacturing of binders]

100 g of polypropylene (Eastman, weight average molecular weight 350,000 g/mol) was put in a 1L reactor, and 1000 g of toluene as an organic solvent was heated and melted at a temperature of 180° C. or higher under a nitrogen atmosphere. Then, 30 g of maleic anhydride and organic 1 g of dicumyl peroxide, which is a peroxide, was added and reacted for 1 hour or more to prepare a polypropylene resin modified with maleic anhydride. The denaturation rate of the modified polypropylene resin was confirmed to be 3.3 wt.% as measured by FT-IR.

After that, 500 g of ultrapure water (DI water) and 300 g of organic solvent tetrahydrofuran (THF) were added to 100 g of the maleic acid-modified polypropylene resin prepared in a 1L pressure reactor, and 20 g of monoethanolamine (MEA) was added as a neutralizing agent. After dispersing at room temperature, it is made aqueous while heating at 100° C. or less for 2 hours and 30 minutes, and then cooled to room temperature. In order to remove the organic solvent from the cooled polypropylene-modified aqueous dispersion solution with maleic acid, distillation is performed under reduced pressure of 0.05 Mpa or higher while reheating to 40 ° C or higher to recover tetrahydrofuran (THF), an organic solvent, and maleic acid. to obtain an aqueous dispersion of polypropylene resin modified with At this time, the particle size of the aqueous dispersion of polypropylene resin modified with maleic acid was 250 nm.

[Lithium secondary battery manufacturing]

150 g of a mixed negative electrode active material composed of 15 wt% of SiOx (0<x<1) and 85 wt% of artificial graphite was added, and using a planetary mixer, 10 g of a carbon black conductive material, and the binder prepared above (with maleic acid) 3.3 g of the modified polypropylene resin aqueous dispersion) and 3.3 g of a carboxymethylcellulose binder (Daiichi Kogyo Seiyaku, molecular weight 110,000) were mixed in a weight ratio of 90:6:2:2, and 111 g of water was added so that the solid content was 33 wt%. was added and mixed at 45 rpm for 40 minutes to prepare a composition for a negative electrode of a secondary battery. Zirconia balls were put into the composition for a negative electrode of a secondary battery, and kneaded and defoamed for 30 minutes in a non-bubbling kneader.

Then, the composition for a negative electrode was applied to a negative electrode current collector (copper foil) having a thickness of 20 μm so that the electrode loading (mg/cm ² ) was 10.9 mg per unit area, dried in a vacuum oven at 70° C. for 10 hours, and then 50 A negative electrode having a total thickness of 85.0 μm including the current collector and the active material was prepared by rolling at a pressure of 15 MPa between rolls heated to ℃. Physical properties are listed in Table 1 below.

150 g of positive electrode active material NMC (nickel-based composite oxide, nickel-manganese-cobalt, LMO (Li ₂ MnO ₃ )), 10 g of carbon black conductive material, 3.3 g of the binder prepared above (aqueous dispersion of polypropylene resin modified with maleic acid), and 3.3 g of carboxymethyl cellulose binder was mixed in a weight ratio of 90:6:2:2, mixed with a solvent N-methyl-2 pyrrolidone so that the solid content was 33 wt%, and mixed at 45 rpm for 40 minutes for a secondary battery positive electrode A composition was prepared. Thereafter, zirconia balls were put into the composition for a positive electrode of a secondary battery, and kneaded and defoamed for 30 minutes in a non-bubbling kneader.

The prepared composition for a positive electrode was applied to a positive electrode current collector (aluminum foil) having a thickness of 15 μm so that the electrode loading (mg/cm ² ) was 10.9 mg per unit area, dried in a vacuum oven at 120° C. for 10 hours, and then 80 A positive electrode having a total thickness of 74.0 μm including a current collector and an active material was prepared by rolling between rolls heated to ℃ at a pressure of 15 MPa.

The prepared negative electrode and positive electrode and the porous polyethylene separator were assembled using a stacking method, and the electrolyte (ethylene carbonate (EC)/ethylmethyl carbonate (EMC) = 1/2 (volume ratio), lithium hexa A lithium secondary battery was prepared by injecting fluorophosphate (1 mol of LiPF ₆ ) The physical properties are listed in Table 1 below.

[Example 2]

[Manufacturing of binders]

Using a twin extruder, 10 kg of polyethylene resin (Honeywell, molecular weight 410,000 g/mol) and 0.5 kg of maleic anhydride are mixed well with a mixing mixer, and then 50 g of dicumyl peroxide as an initiator is added and mixed and dispersed. The mixed raw materials were put into an extruder (TWIN SCREW, L/D 40) heated to a high temperature of 180 ° C, adjusted to a screw speed of 150 rpm or less, and passed through 250 mesh to prepare a polyethylene resin modified with maleic acid under high temperature and pressure. The denaturation rate of the modified polyethylene resin was confirmed to be 3.3 wt.% as measured by FT-IR. In the subsequent process, a binder was prepared in the same manner as in Example 1, and a secondary battery was manufactured in the same manner using the binder. Physical properties are listed in Table 1 below.

[Example 3]

With respect to Example 1, the same method except for replacing the binder with a mixture of the binder prepared in Example 1 and a SBR (styrene butadiene rubber) binder (Xeon Corporation, molecular weight 130,570 g/mol) in a weight ratio of 1:1 to prepare a binder, and a secondary battery was manufactured in the same manner using the binder. Physical properties are listed in Table 1 below.

[Comparative Example 1]

A secondary battery was manufactured in the same manner as in Example 1, except that the binder was replaced with a mixture of SBR binder (Xeon, molecular weight 150,500 g/mol) and CMC binder in a 1:1 weight ratio. Physical properties are listed in Table 1 below.

[Comparative Example 2]

A secondary battery was manufactured in the same manner as in Example 1, except that the binder was replaced with a mixture of an acrylic binder (JSR, molecular weight 77,000 g/mol) and a CMC binder in a 1:1 weight ratio. Physical properties are listed in Table 1 below.

[Comparative Example 3]

A secondary battery was manufactured in the same manner as in Example 1, except that the binder was replaced with a PVDF binder (Kureha, molecular weight 280,000 g/mol). Physical properties are listed in Table 1 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 bookbinder
characteristic Weight average molecular weight (Mw, g/mol) 90,192 56,284 141,570 150,000 78,000 280,000 Electrode characteristics Electrode adhesion (gf/10mm) 10.1 9.5 10.2 8.7 8.1 8.3 Cell Chemistry Discharge capacity (%) 94.5 94.4 94.3 94.2 94.3 94.2 Charging capacity (%) 90.7 90.8 90.8 90.5 90.3 90.4 Room temperature resistance (MΩ) 0.90 0.95 0.91 1.12 1.01 1.05 Low temperature resistance (MΩ) 8.4 8.5 8.6 9.0 8.7 8.9 Capacity retention rate (%) 91.1 89.1 92.5 88.1 80.5 82.2

In Table 1, when an electrode is manufactured using the electrode binder according to the present invention, the adhesiveness of the binder is improved to improve the bonding force between the electrode and the separator, and the effect of preventing peeling and detachment of the electrode can be obtained.

In addition, Examples 1 to 3, which are binders for electrodes according to the present invention, have significantly lower resistance at room temperature and low temperature compared to Comparative Examples 1 to 3, which is expected to obtain a great effect in improving the capacity and performance of the battery, 500 After the charge/discharge cycle, the capacity retention rate was also high, indicating that the charge/discharge life characteristics and performance retention rate were also high.

Through this, the binder for an electrode according to the present invention improves the binding force between the electrode and the separator, and can obtain the effect of preventing peeling and detachment of the electrode, and has the effect of improving the charge/discharge lifespan characteristics and performance of the secondary battery .

As described above, the present invention has been described by specific matters and limited examples, but these are provided to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and the field to which the present invention belongs Various modifications and variations are possible from these descriptions by those of ordinary skill in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims to be described later, but also all those with equivalent or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (13)

An aqueous dispersion binder composition for a secondary battery electrode comprising a carboxylic acid-modified polyolefin. The method of claim 1,
The carboxylic acid-modified polyolefin is an aqueous dispersion binder composition for secondary battery electrodes that is modified with maleic anhydride or (meth)acrylic acid in polyolefin. The method of claim 1,
The carboxylic acid modification is an aqueous dispersion binder composition for a secondary battery electrode that is modified to 0.01 to 5% by weight. The method of claim 1,
The carboxylic acid-modified polyolefin has a weight average molecular weight of 30,000 to 300,000 g/mol of an aqueous dispersion binder composition for a secondary battery electrode. The method of claim 1,
The aqueous dispersion binder composition for secondary battery electrodes is an aqueous dispersion binder composition for secondary battery electrodes comprising an amino alcohol neutralizing agent. The method of claim 1,
The aqueous dispersion of the carboxylic acid-modified polyolefin has a particle size of 50 to 500 nm, an aqueous dispersion binder composition for a secondary battery electrode. The method of claim 1,
The aqueous dispersion binder composition for secondary battery electrodes further comprises any one or two or more selected from an acrylic binder, an olefin-based elastomer binder, and a cellulose-based binder. A composition for a secondary battery electrode comprising an electrode active material, a conductive material, and an aqueous dispersion binder composition for secondary battery electrodes according to any one of claims 1 to 7. 9. The method of claim 8,
The content of the carboxylic acid-modified polyolefin is 0.1 to 15% by weight based on the electrode active material composition for a secondary battery electrode. It includes a current collector and an electrode active material layer disposed on the current collector,
The electrode active material layer is an electrode for a secondary battery prepared from the composition for a secondary battery electrode according to claim 8. cathode; anode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte;
The negative electrode is the electrode according to claim 10 . 12. The method of claim 11,
The adhesive strength of the negative electrode is 9.5 gf / 10mm or more of the secondary battery. 12. The method of claim 11,
The secondary battery has a capacity retention rate of 80% or more after 500 cycles of charging and discharging.