KR102254067B1 - Binder for electrodes of secondary battery and method for manufacturing the same - Google Patents

Abstract

A disclosed binder resin for a secondary battery electrode includes: polyvinyl alcohol main chains; a side chain group derived from an acrylic monomer bonded to the polyvinyl alcohol main chains; and a crosslinking group derived from a boron-containing compound connecting the polyvinyl alcohol main chains. The binder resin improves the reliability and performance of the electrode.

Description

Binder for electrode of secondary battery and manufacturing method thereof {BINDER FOR ELECTRODES OF SECONDARY BATTERY AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a secondary battery, and more specifically, to a binder for an electrode of a secondary battery and a method of manufacturing the same.

Lithium-ion secondary batteries have a higher energy density than non-reusable primary batteries, are eco-friendly, have a long life cycle, can output high voltage, and can be miniaturized. It is widely used in portable electronic products. Recently, in addition to small cell phones, the use of electric vehicles, electric bicycles, electric scooters, electric quick boards, wireless fans, wireless chargers, and energy storage systems are rapidly increasing.

The lithium ion secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte as main components.

In the lithium ion secondary battery, the positive electrode includes lithium oxide, and the negative electrode includes a carbon-based material or a silicon-based material capable of storing lithium ions. The separator prevents direct contact between the positive electrode and the negative electrode, and the electrolyte serves as a medium to allow lithium ions to move between the positive electrode and the negative electrode.

Recently, in order to increase the reversible capacity of a lithium ion secondary battery, a technology for using a silicon-based material as a negative electrode material has been actively studied.

However, in the case of using a silicon-based material as a negative electrode material for a lithium-ion secondary battery as described above, there is a problem in that the battery life decreases due to electrode deterioration and binder peeling due to volume expansion/contraction of the silicon-based material during charging and discharging.

In order to improve this problem, research has been conducted to reduce the influence of volume change by reducing the size of the silicon particles or by modifying the silicon surface using a host material such as graphite. However, such a method is expensive to produce, and it is difficult to prevent deterioration of life in a long-term charging/discharging process.

Accordingly, from the viewpoint of increasing the adhesion between the binder and silicon and improving the physical properties, through various studies, Si-OH (silanol), which is an oxide film on the surface of the silicon particles, such as -OH, -COOH, -CONH-, and Polymers having polar functional groups capable of strongly interacting are being studied as suitable as a next-generation binder material.

Accordingly, the introduction of the polar functional group into the binder material increases the adhesion to silicon, thereby making it possible to suppress the detachment phenomenon of the silicon particles to some extent. However, polar polymers also cannot prevent deterioration of the binder material due to volume change during battery operation, and still have problems with long-term battery performance.

1. Korean Patent Publication 10-2016-0024921 2. Korean Patent Publication 10-2012-0029899 3. Korean Patent Publication 10-2014-0018124

The present invention is to solve the above problems, and to provide a binder resin capable of improving the reliability and performance of an electrode including a silicon-based negative active material.

Another object of the present invention is to provide a method for producing the binder resin.

Another object of the present invention is to provide a negative electrode for a secondary battery comprising the binder resin.

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

The binder resin for a secondary battery electrode according to an embodiment of the present invention includes a polyvinyl alcohol main chain, a side chain group derived from an acrylic monomer bonded to the polyvinyl alcohol main chain, and a crosslinking group derived from a boron-containing compound connecting the polyvinyl alcohol main chains. Includes.

According to an embodiment, the acrylic monomer includes a first acrylic monomer including a hydroxy group or a carboxylic acid group and a second acrylic monomer including an amide group.

According to an embodiment, the first acrylic monomer is acrylic acid (AA), methacrylic acid (MAA), maleic acid (MA), hydroxyethyl (meth) acrylate (Hydroxyethyl It includes at least one selected from the group consisting of (meth)acrylate) and hydroxypropyl (meth)acrylate.

According to an embodiment, the second acrylic monomer is N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide (N-methylol (meth) acrylamide) , Diaceton(meth)acrylamide, hydroxyethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide (N,N-dimethyl(meth)acrylamide) )acrylamide), N,N-diethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide (N,N-dimethylaminopropyl(meth)acrylamide) And (meth)acryloylmorpholine (Meth)acryloylmorpholine).

According to an embodiment, it is represented by the following Chemical Formula 1-1.

[Formula 1-1]

In Formula 1-1, R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R3 represents a hydrogen atom or a hydroxyalkyl group having 1 to 5 carbon atoms, and R4 is a hydrogen atom, 1 to 5 carbon atoms Represents an alkyl group of or a hydroxyalkyl group having 1 to 5 carbon atoms. x, y, z, m, n and w are each independently a natural number.

According to an embodiment, it is represented by the following Chemical Formula 1-2.

[Formula 1-2]

In Formula 1-2, x, y, z, m, n, and w are each independently a natural number.

According to an embodiment, the boron-containing compound includes at least one selected from the group consisting of borax, boric acid, lithium borate, and potassium borate.

A method of preparing a binder resin for a secondary battery electrode according to an embodiment of the present invention comprises the steps of forming a side chain group having an acid group by reacting polyvinyl alcohol with an acrylic monomer, and adding a polyvinyl alcohol having the side chain group to a boron-containing compound. And increasing the molecular weight by reacting with and forming a crosslinked structure, and neutralizing the acid group of the side chain group with an alkali. In the synthesis, 35 to 55% by weight of the polyvinyl alcohol, 0.1 to 0.5% by weight of the boron-containing compound, and 40 to 60% by weight of the acrylic monomer are reacted with respect to the total solid content.

A negative electrode for a secondary battery according to an embodiment of the present invention includes a current collector and an active material layer bonded to at least one surface of the current collector. The active material layer includes an active material including a silicon-based active material and graphite, and a binder resin.

A lithium secondary battery according to an embodiment of the present invention includes a negative electrode, a positive electrode spaced apart from the negative electrode, a separator separating the negative electrode from the positive electrode, and an electrolyte that transfers ions to the negative electrode and the positive electrode during a charging and discharging process. .

According to the present invention, peeling due to volume expansion and contraction of an electrode having a silicon-based active material can be prevented or suppressed. In addition, the electrode can improve battery characteristics while implementing a uniform electrode density.

1 is a cross-sectional view showing a negative electrode for a secondary battery according to an embodiment of the present invention.
2 is an FT-IR analysis graph of the binder resin of Example 1. FIG.

In the present application, terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance the possibility of being added.

Binder resin for secondary battery electrode

The binder resin according to an embodiment of the present invention has a crosslinked structure obtained by reacting polyvinyl alcohol, a boron-containing compound, and a reactive acrylic monomer having a polar functional group. The binder resin may be used as a binder for an electrode containing a silicon active material.

Polyvinyl alcohol has high adhesion to the current collector and the silicone active material. The boron-containing compound may modify the polyvinyl alcohol and increase the molecular weight of the binder resin. The reactive acrylic monomer strongly interacts with Si-OH (silanol), which is an oxide film on the surface of the silicon particles, thereby improving physical properties and reliability of a binder resin and an electrode including the same.

According to an embodiment, the boron-containing compound may include borax, boric acid, lithium borate, potassium borate, and the like. Each of these may be used alone or in combination, and preferably, the boron-containing compound may contain borax.

[Borax]-Na ₂ B ₄ O ₇ *10H ₂ O

According to an embodiment, the reactive acrylic monomer may include a first acrylic monomer having a polar functional group and a second acrylic monomer having an amide group.

The polar functional group may include a carboxylic acid group, a hydroxy group, and the like. The polar functional group may strongly interact with Si-OH of the oxide film on the surface of the silicon particle. Therefore, it is possible to increase the adhesion between the binder and the silicon particles.

The binder resin having an amide group can increase the dispersibility of the slurry, thereby increasing the bonding strength between the silicon particles.

For example, the binder resin may be represented by the following Formula 1-1.

[Formula 1-1]

In Formula 1-1, R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R3 represents a hydrogen atom or a hydroxyalkyl group having 1 to 5 carbon atoms, and R4 is a hydrogen atom, 1 to 5 carbon atoms Represents an alkyl group of or a hydroxyalkyl group having 1 to 5 carbon atoms. x, y, z, m, n and w are each independently a natural number.

x, y, z, m, n, and w may have a certain range depending on the molecular weight and composition of the binder resin.

As shown, borax may form a crosslinking group connecting the main chains of polyvinyl alcohol.

Hereinafter, "(meth)acrylic" means "methacryl" or "acrylic".

For example, the first acrylic monomer having a polar functional group is acrylic acid (AA), methacrylic acid (MAA), maleic acid (MA), hydroxyethyl (meth)acrylate (Hydroxyethyl(meth)acrylate), hydroxypropyl(meth)acrylate, etc. may be included. Each of these may be used alone or in combination, and preferably, the first acrylic monomer may include acrylic acid.

For example, the second acrylic monomer, N-isopropyl (meth) acrylamide (N-isopropyl (meth) acrylamide), N-methylol (meth) acrylamide (N-methylol (meth) acrylamide), di Acetone(meth)acrylamide, hydroxyethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide ), N,N-diethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide (N,N-dimethylaminopropyl(meth)acrylamide), ( Meth)acryloylmorpholine (Meth)acryloylmorpholine), and the like. Each of these may be used alone or in combination, and preferably, the second acrylic monomer may include hydroxyethylacrylamide (HEAA).

For example, when the first acrylic monomer contains acrylic acid and the second acrylic monomer contains hydroxyethylacrylamide, the binder resin may be represented by Formula 1-2 below.

[Formula 1-2]

In Formula 1-2, x, y, z, m, n, and w are each independently a natural number.

The binder resin according to an embodiment may form a composition (slurry) for forming an electrode together with an active material and a conductive agent, and prevent separation (settling) by increasing the powdery properties of the slurry. It is possible to achieve a uniform electrode density. In addition, since the adhesion with the metal foil used as the current collector is excellent, the expansion of the silicon active material can be controlled to improve battery characteristics.

According to an embodiment, in order to form the binder resin, 35 to 55% by weight of polyvinyl alcohol, 0.1 to 0.5% by weight of a boron-containing compound, and 40 to 60% by weight of an acrylic monomer may be reacted with respect to the total solid content. In addition, 0.5 to 3% by weight of a redox initiator and 0.5 to 5% by weight of a neutralizing agent may be added to the total solid content for the reaction to proceed.

For example, the weight average molecular weight of the polyvinyl alcohol may be about 1,000 to 5,000, preferably about 2,000 to 4,000.

When the content of polyvinyl alcohol is less than 35% by weight, the adhesion to the metal current collector decreases, and when it exceeds 55% by weight, the rigidity decreases and the binding effect between the active material and the current collector is weakened. Therefore, it is preferable that the polyvinyl alcohol is contained in an amount of 35 to 55% by weight based on the total solid content.

If the content of the boron-containing compound is less than 0.1% by weight, the crosslinking density is lowered, resulting in a low viscosity and high molecular weight cannot be obtained, and if it exceeds 0.5% by weight, the degree of crosslinking is too high in the synthesis process and there is a risk of gelation . Therefore, borax is preferably contained in an amount of 0.1 to 0.5% by weight based on the total solid content.

When the content of the acrylic monomer is less than 40% by weight, high rigidity (high elasticity and tensile strength) cannot be achieved, the slurry dispersibility is also poor, and when it exceeds 60% by weight, there is a problem that many neutralizing agents are used when adjusting the pH. Therefore, it is preferable that the acrylic monomer having a polar group is included in an amount of 40 to 60 parts by weight based on the total solid content.

According to an embodiment, in the acrylic monomer, a weight ratio of the first acrylic monomer and the second acrylic monomer may be 4:1 to 2:1.

It is preferable to use 0.5 to 3% by weight of the redox initiator and 0.5 to 5% by weight of the neutralizing agent, but there may be slight additions or subtractions in consideration of the binder synthesis process, for example, reaction temperature and viscosity.

As the redox initiator and neutralizing agent, those known in the art may be used. For example, the neutralizing agent may include a metal hydroxide including an alkali cation such as Li+, Na+, and K+, and an initiator for polymerization of the acrylic monomer may include ammonium persulfate.

According to an embodiment, the method for synthesizing the binder resin includes reacting polyvinyl alcohol with an acrylic monomer to form a side chain group having an acid group, and reacting the polyvinyl alcohol having the side chain group with a boron-containing compound. Increasing the molecular weight and forming a crosslinked structure, and neutralizing the acid group of the side chain group with an alkali.

Through this synthesis method, it is possible to realize a variety of soft and hard physical properties by copolymerizing with various acrylic monomers, and to increase adhesion and electrical properties by putting reactive groups such as carboxyl groups, hydroxy groups, and amide groups into the binder chain. There is this. In addition, it is possible to stably control the final molecular weight and crosslinking degree of the polyvinyl alcohol resin.

The neutralized binder resin may have a pH of about 7.5 to 8.5.

Anode for secondary battery and lithium secondary battery

1 is a cross-sectional view showing a negative electrode for a secondary battery according to an embodiment of the present invention.

Referring to FIG. 1, a negative electrode for a secondary battery may include a current collector 10 and an active material layer 20.

The current collector 10 may include a conductive material such as a carbon-based material or a metal. According to an embodiment, the current collector may include stainless steel, aluminum, nickel, titanium, copper, or an alloy thereof, and may have a shape such as a film, sheet, foil, or porous body. For example, the thickness of the current collector 10 may be 5 μm to 300 μm.

The active material layer 20 may include an active material 22, a binder resin 24 and a conductive material 26.

The active material 22 serves to generate electricity by allowing electrons (current) to flow while reversibly absorbing or releasing lithium ions provided from the positive electrode of the lithium ion secondary battery.

According to an embodiment, the active material 22 may include a silicon-based active material 22a and a carbon-based active material 22b. The carbon-based active material 22b may include natural graphite, artificial graphite, soft carbon, and the like.

For example, the silicon-based active material may include silicon, silicon oxide (SiOx), silicon carbide (SiC), and silicon alloy. For example, when the content of the silicon-based active material is insufficient, it is difficult to implement a high-capacity electrode, and when the content of the silicon-based active material is excessive, the volume expansion due to charging increases excessively, and the electrode may be deformed and the lifespan may be significantly reduced.

According to an embodiment, the active material 22 may include graphite and silicon in a weight ratio of 2:1 to 5:1.

For example, the conductive material 26 is a carbon-based conductive material such as graphene, carbon black, acetylene black, etc., nickel, copper, titanium, vanadium, chromium, manganese, iron, cobalt, zinc, molybdenum, tungsten, silver , A metal such as gold, a conductive polymer such as polyaniline, polythiophene, polyacetylene, polypyrrole, or a combination thereof.

For example, a weight ratio of the active material 22 and the conductive material 26 may be 10:1 to 30:1.

In order to form the active material layer 20, an active material slurry composition may be applied on the current collector 10 and dried or cured.

The binder resin 24 has a crosslinked structure obtained by reacting polyvinyl alcohol, borax, and a reactive acrylic monomer having a polar functional group. Since the specific configuration of the binder resin 24 is the same as the previously described binder resin, a detailed description will be omitted.

The active material slurry composition may include an active material, a conductive material, a binder resin, and a solvent.

The binder resin may be water-soluble or dispersed in water. Therefore, the solvent may preferably include an aqueous solvent such as water. In another embodiment, the solvent is NN-dimethylformamide, NN-dimethylacetamide, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, methyl cellosolve , Butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, diethylene glycol dimethyl ether, toluene, xylene, or a combination thereof, or a mixture of these and water.

According to an embodiment, the solid content of the active material slurry composition may be 30% by weight to 60% by weight, and the content of the binder resin may be 1% by weight to 10% by weight based on the total weight of the solid content. In addition, the content of the conductive material may be 1% by weight to 10% by weight based on the total weight of the solid content.

According to an embodiment, the active material slurry composition may further include a crosslinking agent to further form a crosslinking bond of the binder resin. In addition, additives such as a dispersant, a thickener, and a filler may be further included in order to improve properties.

A lithium secondary battery according to an embodiment of the present invention may include a positive electrode, a separator, a negative electrode, an electrolyte, and a storage container for sealing them.

The positive electrode may include a current collector and an active material layer. The active material layer of the positive electrode may include a lithium transition metal oxide as an active material.

For example, the lithium transition metal oxide may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, or a combination thereof.

The separator may prevent contact between the anode and the cathode. For example, the separator is a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or These may be laminated and used, or a nonwoven fabric made of high melting point glass fibers, polyethylene terephthalate fibers, or the like may be used, but is not limited thereto.

The electrolyte may transfer ions to the negative electrode and the positive electrode during a charging and discharging process. Propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran , N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (GBL), fluoroethylene carbonate (FEC), methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate , Propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, butyl propionate, or a combination thereof. In addition, the electrolyte may further contain a lithium salt.

According to the present invention, it is possible to prevent cracking, tearing, peeling, and detachment of the negative electrode including the silicon active material, and to improve the charge/discharge battery characteristics and discharge maintenance rate of the electrode by minimizing the change in the electrode structure resulting from the change in the volume of the silicon active material. I can.

Hereinafter, preparation examples and effects of the present invention will be described in detail through specific comparative examples, examples, and experiments.

Example 1

45 g of PVA (KURARAY Corp. POVAL, molecular weight 2,400) and 500 g of water were added to a 1L 5-neck flask, and the temperature was raised to 90°C to completely dissolve. After confirming complete dissolution, the temperature was cooled to 50° C., 1) 1 g of APS (ammonium persulfate) was dissolved in 10 g of water, and 2) 0.3 g of NaHSO 3 g dissolved in 3 g of water was sequentially added and maintained for 10 minutes. While nitrogen was added, 40 g of AA (acrylic acid), 15 g of HEAA (Hydroxyethyl acrylamide), and 250 g of water were mixed, and then slowly added dropwise for 60 minutes and maintained for 6 hours. After the maintenance reaction, 0.5 g of borax was dissolved in 10 g of water and added thereto, followed by holding for 2 hours. Next, an aqueous solution in which 0.5 g of NaOH was dissolved in 4.5 g of water was gradually added while adjusting the pH to 8.0 to obtain an aqueous binder for the negative electrode.

The synthesized binder A1 had a solid content of 10.8%, a viscosity of 5,200 cps, and a pH of 8.1.

2 is an FT-IR analysis graph of the binder resin of Example 1. FIG.

2 is an analysis graph after the final neutralization reaction. Referring to FIG. 2, it can be seen that a salt was formed by reacting NaOH and COOH at ^{~1570cm -1.}

Example 2

A binder resin was synthesized in the same manner as in Example 1, except that the PVA was changed (KURARAY Corp. POVAL, molecular weight 1,700), and the binder resin had a solid content of 11.3%, a viscosity of 4,500 cps, and a pH of 7.9.

Example 3

A binder resin was synthesized in the same manner as in Example 1, except that acrylamide (Acrylamide, Sigma Aldrich reagent, 99% purity) was used instead of HEAA.In the binder resin, the solid content was 11.0%, the viscosity was 5,700 cps, and the pH was It was 7.7.

Comparative Example 1

Physical properties were compared with a commercially available PAA (Polyacrylic acid) Solution (35 wt% in H ₂ O, average molecular weight 100,000, Sigma Aldrich) solution.

Comparative Example 2

It was compared with the commercially available SBR-CMC aqueous binder, which is a binder mainly used when applying the graphite-based active material alone, the anode material of the current secondary battery. Styrene-butadiene rubber (SBR) 40wt% (ZEON) and carboxymethyl cellulose (CMC) 2wt% (Dicel) were mixed in a ratio of 50:50 to the solid content to compare the physical properties.

Slurry composition

As the negative electrode active material, 1) POS-H3 grade (d50=16.8㎛) natural graphite of POSCO Chemtech is used, and 2) DMSO-C05 SiOx (d50=1~6㎛) of Daeju Electronics is used for silicon. Graphite: silicon Mixing at a weight ratio of 8:2, and using Timcal's Super-P black as a conductive material, a slurry composition was prepared by mixing an active material: a conductive material: a binder in a weight ratio of 90:5:5. At this time, the content of water as a solvent was adjusted in consideration of coating properties, viscosity, and solid content. The viscosity of the obtained slurry composition was 500 to 2,000 cps, and the solid content was 50%.

The adhesion and bending test results of the slurry composition are shown in Table 1 below. For the evaluation of adhesion, the slurry composition was coated on a copper foil having a thickness of 18 μm, dried (1st: 80°C×3 hours, 2nd: aging×24 hours at room temperature), and then peeled at 90° with a UTM device (10cm×15mm). Thickness) was measured, and for the bending test, the specimen was bent to a thickness of 1 Φ and then cracked with an electron microscope was checked.

Table 1

Battery manufacturing and battery characteristic evaluation

The slurry composition was coated on a copper foil having a thickness of 18 μm and dried, thereby forming an active material layer having a thickness of 40 μm on one side of the copper foil, and punching into a circle having a diameter of 14 Φ to prepare a test electrode (cathode), and a thickness of 0.3 as a positive electrode. A metal lithium foil of mm was used. A 0.1mm-thick porous polyethylene sheet was used as a separator, and a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 as an electrolyte, and LiPF ₆ as a lithium salt at a concentration of about 1 mol/L. Dissolved in was used.

The negative electrode, the positive electrode, the separator, and the electrolyte were sealed in a stainless steel container to prepare a coin cell for evaluation of a general shape having a thickness of 2 mm and a diameter of 32 mm.

The coin cell was charged with a constant current of 0.05C until the voltage reached 0.01V, and discharged with a constant current of 0.05C until the voltage became 1.5V to obtain the discharge capacity and initial efficiency. The capacity retention test was carried out by conducting a constant current in the same voltage range as above, and the results are shown in Table 2 below.

Table 2

Referring to Tables 1 and 2, in the case of the PAA binder of Comparative Example 1, the adhesive strength is significantly lower than that of Examples 1 to 3, the Tg of the binder is high, so the coating film is rigid, and as charging/discharging proceeds, the active material and copper foil As the binding effect between the cells is reduced, the battery characteristic value is also low.

In addition, in the case of the SBR-CMC binder of Comparative Example 2, when the silicon active material and graphite were mixed, the physical properties were decreased due to the decrease in the dispersibility of the graphite and silicon due to the rapid volume expansion of the silicon during charging and discharging, and the decrease in adhesion to the copper foil. .

On the other hand, the binder resin according to the embodiment of the present invention has high adhesion to the current collector, and it can be confirmed that the capacity retention rate, the expansion rate, and the electrolyte resistance are all excellent.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the present invention described in the following claims. You will understand that you can.

The present invention can be used to manufacture an electrode assembly, a lithium secondary battery, and the like.

Claims (10)

It is obtained by reacting 35 to 55% by weight of polyvinyl alcohol, 0.1 to 0.5% by weight of a boron-containing compound, and 40 to 60% by weight of an acrylic monomer, based on the total solid content,
A binder resin for a secondary battery electrode comprising a polyvinyl alcohol main chain, a side chain group derived from the acrylic monomer bonded to the polyvinyl alcohol main chain, and a crosslinking group derived from the boron-containing compound connecting the polyvinyl alcohol main chains. The binder resin for an electrode according to claim 1, wherein the acrylic monomer comprises a first acrylic monomer containing a hydroxy group or a carboxylic acid group and a second acrylic monomer containing an amide group. The method of claim 2, wherein the first acrylic monomer is acrylic acid (AA), methacrylic acid (MAA), maleic acid (MA), hydroxyethyl (meth)acrylate (Hydroxyethyl (meth) acrylate) and hydroxypropyl (meth) acrylate (Hydroxypropyl (meth) acrylate), characterized in that it comprises at least one selected from the group consisting of a secondary battery electrode binder resin. The method of claim 2, wherein the second acrylic monomer is N-isopropyl (meth)acrylamide, N-methylol (meth)acrylamide (N-methylol(meth)acrylamide) , Diaceton(meth)acrylamide, hydroxyethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide (N,N-dimethyl(meth)acrylamide) )acrylamide), N,N-diethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide (N,N-dimethylaminopropyl(meth)acrylamide) And (meth)acryloylmorpholine (Meth)acryloylmorpholine). The binder resin for secondary battery electrodes according to claim 1, which is represented by the following Chemical Formula 1-1.
[Formula 1-1]

(In Formula 1-1, R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R3 represents a hydrogen atom or a hydroxyalkyl group having 1 to 5 carbon atoms, and R4 is a hydrogen atom, It represents an alkyl group of 5 or a hydroxyalkyl group of 1 to 5 carbon atoms. x, y, z, m, n and w are each independently a natural number.) The binder resin for secondary battery electrodes according to claim 1, which is represented by the following Chemical Formula 1-2.
[Formula 1-2]

(In Formula 1-2, x, y, z, m, n, and w are each independently a natural number.) The binder resin according to claim 1, wherein the boron-containing compound contains at least one selected from the group consisting of borax, boric acid, lithium borate, and potassium borate. Reacting polyvinyl alcohol with an acrylic monomer to form a side chain group having an acid group;
Reacting the polyvinyl alcohol having the side chain group with a boron-containing compound to increase molecular weight and form a crosslinked structure; And
Neutralizing the acid group of the side chain group with an alkali,
A method for producing a binder resin for a secondary battery electrode, characterized in that 35 to 55% by weight of the polyvinyl alcohol, 0.1 to 0.5% by weight of the boron-containing compound, and 40 to 60% by weight of the acrylic monomer are reacted with respect to the total solid content . Current collector; And
It includes an active material layer bonded to at least one surface of the current collector,
The active material layer,
An active material including a silicon-based active material and graphite; And
A negative electrode for a secondary battery comprising any one binder resin selected from claim 1 to claim 7. The negative electrode of claim 9;
An anode spaced apart from the cathode;
A separator separating the cathode and the anode; And
Lithium secondary battery comprising an electrolyte that transfers ions to the negative electrode and the positive electrode during charging and discharging.

Images