KR102478764B1 - A Binder, Method proparing the binder and Electrochemical device comprising the same - Google Patents

Abstract

A binder having a structure of a core portion and a shell portion surrounding at least a portion of a surface of the core portion, wherein the core portion is derived from a styrene-based monomer, an ethylene-based monomer, an amide-based monomer, a carboxylic acid-based monomer, or a (meth)acrylic acid ester-based monomer A shell polymer having a repeating unit derived from at least one selected from ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, or (meth)acrylic acid ester-based monomers comprising a core polymer having one or more types of repeating units; Including, wherein the shell portion further comprises a (meth)acrylic acid ester-based monomer having at least one hydroxyl group, the binder is provided.

Description

A binder, a manufacturing method thereof, and an electrochemical device comprising the same {A Binder, Method proparing the binder and Electrochemical device comprising the same}

The present invention relates to a binder capable of improving stability, stretchability and conductivity, a manufacturing method thereof, and an electrochemical device including the same.

Recently, as the demand for electric vehicles and mobile devices increases, secondary batteries are attracting attention as a power source for driving them. Among secondary batteries, lithium secondary batteries are lightweight, can obtain high energy density and voltage, and can be rapidly charged, and are currently widely commercialized if research is active.

Similarly, a capacitor using an electric double layer formed at an interface between a polarized electrode and an electrolyte is used for a large-capacity power storage function such as a memory backup power supply or an electric vehicle power supply.

A lithium secondary battery or electric double layer capacitor includes one or more electrodes having a structure in which an electrode active material is bound to a current collector by a binder, and a separator, electrolyte, etc. are disposed between these electrodes, and intercalation and desorption of ions between the electrodes Electricity is generated, stored, or consumed by oxidation-reduction reactions or physical bonding by ions or electrons at the interface between the electrode and the electrolyte.

Here, the binder binds the active material of the electrode, and sometimes also binds additives such as a conductive material separately added to improve conductivity. The binder must maintain stable adhesive properties even in a chemical environment in contact with an electrolyte and a harsh electrochemical environment in which oxidation and reduction reactions occur. In addition, it is necessary to secure the reliability of the polymer material for the binder in the case of a medium or large-sized battery that must be operated for more than 10 years.

Currently, materials such as fluorine-based polymer binders such as organic polyvinylidene fluoride (PVdF) and polytetrafluoroethylene and water-based polymer strene butadiene rubber (SBR) have been used commercially, but charge and discharge of electrochemical devices There is still a need to develop a binder having low electrical resistance while having adhesive strength and mechanical properties capable of withstanding volume changes such as volume expansion of an active material upon application.

0001) Korean Registered Patent No. 10-0491026 (registration date: 2005.05.13)

In order to solve the conventional problems, the purpose of the present invention is to provide a binder that maintains the adhesive force of the binder even when the volume of the electrode active material changes during the charging and discharging process of the electrochemical device and improves the stability of the binder itself to maintain the binding force for a long period of time. to be

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the description below.

In order to solve the above problem, according to one embodiment of the present invention, the following binder is provided:

A binder having a structure of a core portion and a shell portion surrounding at least a portion of a surface of the core portion,

The core portion includes a core polymer having at least one repeating unit derived from a styrene-based monomer, an ethylene-based monomer, an amide-based monomer, a carboxylic acid-based monomer, or a (meth)acrylic acid ester-based monomer,

The shell part includes a shell polymer having a repeating unit derived from at least one selected from ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, and (meth)acrylic acid ester-based monomers,

The shell portion further comprises a (meth)acrylic acid ester-based monomer having at least one hydroxyl group, the binder.

In the binder, the shell polymer may further include a repeating unit derived from an acrylonitrile-based monomer, and the shell portion may further include a glycidyl methacrylate-based monomer component.

On the other hand, in the above embodiment, the shell polymer is a poly(alkylacrylate-based monomer-containing repeating unit derived from a (meth)acrylic acid alkyl ester monomer and a repeating unit derived from an acrylonitrile-based monomer in a weight ratio of 20:1 to 1:10 acrylonitrile-based monomer) may be a copolymer.

In addition, in the binder, the weight ratio of the core polymer and the shell polymer may be 0.1:99.9 to 5:5.

According to another embodiment of the present invention there is provided a method for producing a binder comprising the following steps:

Preparing a pre-emulsion slurry of a core polymer containing repeating units derived from at least one selected from styrene-based monomers, ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, and (meth)acrylic acid ester-based monomers (S -One);

Preparing a shell polymer pre-emulsion slurry containing repeating units derived from at least one selected from ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, and (meth)acrylic acid ester-based monomers (S-2);

mixing the pre-emulsion slurry of the core polymer and the pre-emulsion slurry of the shell polymer and adding a polymerization initiator to perform polymerization (S-3); and

Including the step (S-4) of terminating the polymerization,

The pre-emulsion slurry of the shell polymer further comprises a (meth)acrylic acid ester-based monomer having at least one or more hydroxy groups, a method for producing a binder containing core-shell polymer particles.

In the preparation method, the shell polymer may further include a repeating unit derived from an acrylonitrile-based monomer, and the shell portion may further include a glycidyl methacrylate-based monomer component.

In another embodiment of the present invention, an electrochemical device including the binder and the binder manufactured by the binder manufacturing method may be provided.

When the binder of the present invention is used in an electrochemical device, the adhesive strength of the binder is maintained even when the volume of the electrode active material changes during the charging and discharging process of the electrochemical device, and the stability of the binder itself is improved, so that the physical properties of the secondary battery can be maintained for a long time. .

1 is a bar graph showing adhesive strength data of binders prepared from Examples and Comparative Examples.
Figure 2 is a photomicrograph related to measuring the contact angle of the electrolyte of the binder prepared from Examples and Comparative Examples.

The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors can properly define the concept of terms in order to explain their invention in the best way. Based on the principle, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention. However, all technical and scientific terms used in this specification have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs unless otherwise specified.

Throughout this specification and claims, the terms comprise, comrises, comrising, unless stated otherwise, are meant to include a stated object, step or group of objects, and steps, and any other object However, it is not used in the sense of excluding a step or a group of objects or a group of steps.

On the other hand, various embodiments of the present invention can be combined with any other embodiments unless clearly indicated to the contrary. Any feature indicated as being particularly desirable or advantageous may be combined with any other features and characteristics indicated as being particularly desirable or advantageous.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The binder according to one embodiment of the present invention has a structure of a core part and a shell part surrounding at least a portion of the surface of the core part, wherein the core part comprises a styrene-based monomer, an ethylenic monomer, an amide-based monomer, a carboxylic acid-based monomer, or ( It includes a core polymer having one or more repeating units derived from meth)acrylic acid ester-based monomers, and the shell portion is at least one selected from ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, and (meth)acrylic acid ester-based monomers. It includes a shell polymer having a repeating unit derived from, and the shell polymer may further include a repeating unit derived from a (meth)acrylic acid ester-based monomer having at least one hydroxyl group.

The binder having the core-shell structure may include a core part and a shell part in a weight ratio of 0.1:99.9 to 5:5. When the core part is included in a weight ratio of less than 0.1, the size of the core part is small, and the core-shell structure may not be preferably implemented. When the core-shell structure is not preferably implemented, the uniformity of the particles having the core-shell structure is lowered, and it may be difficult to express physical properties required of the binder. In addition, when the shell part is included in a weight ratio of less than 5, the thickness of the shell polymer layer becomes thin, and basic binder functions such as binding force or adhesive performance may be deteriorated.

The shell polymer included in the shell part may further include a repeating unit derived from an acrylonitrile-based monomer. Acrylonitrile monomers may be added to improve morphological characteristics or ionic conductivity-related characteristics when a binder is used in a battery chemical device.

For example, the shell polymer is a poly(alkylacrylate-based monomer-acryloyl group comprising a repeating unit derived from a (meth)acrylic acid alkyl ester monomer and a repeating unit derived from an acrylonitrile-based monomer in a weight ratio of 20:1 to 1:10. nitrile-based monomer) may include a copolymer. Outside of the above range, when the ratio of repeating units derived from acrylonitrile monomer is 50% or more, the polymer may be precipitated in the form of powder rather than being produced in the form of latex. On the other hand, when the content of the butyl acrylate-based monomer-derived repeating unit is out of the above range, physical properties such as ion conductivity that can be imparted to the binder by the acrylonitrile-based repeating unit-derived repeating unit may be deteriorated.

In addition, the shell polymer may further include more than 0% by weight and less than 5% by weight of acrylic acid based on the total weight of the shell polymer. The content of acrylic acid may be 1% by weight or more in terms of increasing the binding force of the binder and the effect of conductivity in the battery, peeling resistance, etc., and the amount of acrylic acid added may be 5% by weight or less in terms of securing a product through emulsion polymerization. there is. Furthermore, the content of acrylic acid may be 1% by weight or more and 4% by weight or less.

The shell polymer may further include an acrylate-based monomer unit and a nitrile-based monomer unit. The monomer unit is acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutal (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, and mixtures thereof.

Meanwhile, the shell polymer may further include a repeating unit derived from a (meth)acrylic acid ester-based monomer having at least one hydroxyl group. Representative examples of (meth)acrylic acid ester-based monomers having at least one hydroxy group include 2-hydroxyethyl acrylate (2-HEA), 2-hydroxy methacrylate (2-HEMA), and 4-hydroxy butyl acrylate. Hydroxyalkyl (meth)acrylates, such as late (4-HBA), are mentioned.

The binder according to one embodiment of the present invention contains a (meth)acrylic acid ester-based monomer having a hydroxyl functional group and has an effect of improving adhesive strength. The effect of improving adhesion can be inferred as a physical property of contact angle. According to the binder according to one embodiment of the present invention, 15% or more, and further 20% or more compared to a binder not containing a (meth)acrylic acid ester monomer having a hydroxyl group. It shows the effect of improving the contact angle.

The contact angle refers to the angle between the solid surface and the tangent drawn to the liquid surface from the contact point of the three phases of the solid, liquid, and gas when a stationary liquid is placed on the solid surface, and is an indicator of wettability between the solid and the liquid. A decrease in contact angle indicates an improvement in surface wettability, which means an increase in surface free energy. Therefore, these contact angle properties can be a major indicator for inferring the interfacial penetration and adhesion enhancement of materials with which the binder contacts.

In the present invention, the contact angle is measured by preparing a binder film from a binder solution, fixing it to a contact angle measuring device, and then dropping one drop of the electrolyte contained in the microsilage to measure the contact angle.

In addition, the shell part may further include a glycidyl methacrylate-based monomer component. The glycidyl methacrylate-based monomer component is for the shape stability of the shell part and can help maintain the shape of the shell part when the core part is entirely surrounded by the shell part. Depending on the environment of the electrochemical device, the core polymer of the core part can be dissolved, but when the shape of the shell part stably surrounds the core part, the problem of loss of binder properties can be solved.

In the core-shell structure, the core portion at least partially surrounded by the shell portion is a core polymer having at least one repeating unit derived from a styrene-based monomer, an ethylene-based monomer, an amide-based monomer, a carboxylic acid-based monomer, or a (meth)acrylic acid ester-based monomer. can include

The core part may further include inorganic particles or metal particles in addition to the core polymer. Examples of inorganic particles include any one selected from SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZnO ₂ , BaTiO ₃ , BaSrTiO ₃ , V ₂ O ₃ , La ₂ O ₃ , HfO ₂ , SrTiO ₃ and Nb ₂ O ₅ Or two or more may be included, and examples of the metal particles include copper (Cu), silver (Ag), nickel (Ni), gold (Au), platinum (Pt), ruthenium (Ru), iron (Fe), cobalt ( Co), indium (In), tin (Sn), tungsten (W), or a single metal particle or metal oxide containing a metal selected from zinc (Zn) may be included.

Examples of the styrenic repeating unit included in the core polymer may include styrene, *j methyl styrene, *j methyl styrene, and p-t-butyl styrene. Examples of the ethylene-based repeating unit included in the core polymer may include ethylene, propylene, and the like, and examples of the conjugated diene-based repeating unit include 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1, 3-pentadiene, p-perylene, isoprene and the like may be included.

The repeating unit derived from the (meth)acrylic acid ester monomer included in the core polymer includes methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate , isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, hydroxypropyl acrylate, lauryl acrylate; Methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl Methacrylate, 2-ethylhexyl methacrylate, hydroxypropyl methacrylate, and lauryl methacrylate may be included.

Examples of repeating units derived from amide-based monomers included in the core polymer include acrylamide, n-methylolacrylamide, n-butoxymethylacrylamide, methacrylamide, n-methylolmethacrylamide, and n-butoxymethyl Methacrylamide and the like may be included.

Repeating units derived from carboxylic acid monomers included in the core polymer may include itaconic acid, maleic acid, fumaric acid, citraconic acid, methaconic acid, glutaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, nadic acid, and the like. .

According to another embodiment of the present invention, a method for preparing a binder including core-shell polymer particles is provided.

A method for preparing a binder containing core-shell polymer particles according to another embodiment of the present invention is:

(S-1) a core polymer pre-emulsion slurry containing repeating units derived from at least one selected from styrene-based monomers, ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, and (meth)acrylic acid ester-based monomers manufacturing;

(S-2) preparing a shell polymer pre-emulsion slurry containing repeating units derived from at least one selected from ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, and (meth)acrylic acid ester-based monomers;

(S-3) performing polymerization by mixing the pre-emulsion slurry of the core polymer and the pre-emulsion slurry of the shell polymer and adding a polymerization initiator; and

(S-4) terminating the polymerization,

The pre-emulsion slurry of the shell polymer further includes a (meth)acrylic acid ester-based monomer having at least one or more hydroxyl groups.

At this time, the shell polymer may further include a repeating unit derived from an acrylonitrile-based monomer. In addition, the shell part may further include a glycidyl methacrylate-based monomer component.

The method for preparing a binder containing the core-shell polymer particles is a so-called process in which a pre-emulsion slurry of a core polymer and a pre-emulsion slurry of a shell polymer are prepared in steps (S-1) and (S-2), respectively, and polymerized. As a two-step process, polymerization stability is higher than that of the conventional one-step process in which core polymer components and shell polymer components are simultaneously introduced and polymerized, and as a result, core-shell structured particles can be produced stably. Efficiency can be high.

The method for producing polymer particles by polymerization of the above monomers is not particularly limited, but may be obtained by copolymerizing the respective monomers by a known polymerization method such as emulsion polymerization, suspension polymerization, dispersion polymerization, or solution polymerization. . Among these polymerization methods, the emulsion polymerization method may be preferable in view of facilitating control of the particle diameter.

For the emulsion polymerization reaction by the emulsion polymerization method, a commonly used emulsion polymerization machine may be used, and preferably a 5-necked separate flask reactor equipped with a stirrer, a cooler, a sample inlet, a thermometer, and a burette for initiator input may be used. In addition, a reactor further comprising a wing-shaped stirrer may be used to perform the stirring function during the reaction. The reaction temperature can be adjusted using a thermostat or a heat plate, etc., and the reaction can be carried out in an oxygen-blocking atmosphere by adjusting the flow of nitrogen to 0 to 100 ml/min.

In the step of forming polymer particles, one or more additives selected from the group consisting of polymerization initiators, emulsifiers, dispersants, and mixtures thereof may be further added.

Polymerization initiator is ammonium sulfate polymerization initiator is ammonium persulfate (Ammonium persulfate, APS), potassium persulfate (Potasium persulfate, KPS), sodium persulfate (Sodium persulfate, NPS); ammonium persulfate; Organic peroxides such as benzo peroxide and cumene hydroperoxide may be used alone or in combination with a reducing agent such as ascorbic acid as a redox polymerization initiator. In addition, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2, azo monomers such as 4-dimethylvaleronitrile), dimethyl-2,2'-azobisisobutyrate, and 4,4'-azobis(4-cyanopentanoic acid); 2,2'-azobis(2-aminodipropane)dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis(N, Amidine monomers, such as N'-dimethylene isobutylamidine) dihydrochloride, etc. can also be used individually or in combination of 2 or more types. The amount of polymerization initiator used may be 0.01 to 10 parts by weight, and further 0.1 to 5 parts by weight based on 100 parts by weight of the total amount of monomers. When the content of the polymerization initiator is less than 0.1 parts by weight based on 100 parts by weight of the total amount of monomers, polymerization of monomers and polymer conversion rate may be lowered, and when it exceeds 10 parts by weight, peel strength may be lowered.

Emulsifier is sodium lauryl sulfate (SLS), ammonium lauryl sulfate

lauryl sulfate systems such as pate and potassium lauryl sulfate; Sodium dodecyl sulfate (Sodium

sulfate systems such as dodecyl sulfate (SDS); nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene sorbitan lauryl ester, and polyoxyethylene-polyoxypropylene block copolymer; gelatin, maleic anhydride-ethylene copolymer, polyvinylpyrrolidone; sodium salts of benzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate; Alkyl sulfate sodium salts, such as sodium lauryl sulfate and sodium tetradodecyl sulfate; sulfosuccinate sodium salts such as sodium dioctyl sulfosuccinate and sodium dihexyl sulfosuccinate; fatty acid sodium salts such as sodium laurate: ethoxysulfate sodium salts such as polyoxyethylene lauryl ether sulfate sodium salt and polyoxyethylene nonylphenyl ether sulfate sodium salt; Alkyl ether phosphoric acid ester sodium salt; Sodium polyacrylate etc. can be used individually or in combination of 2 or more types. The addition amount of the emulsifier may be set arbitrarily, and may include 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of monomers, but may not be included separately depending on polymerization conditions.

In addition, itaconic acid may be further added as an additive for shape stability of the final core-shell polymer particles.

According to another embodiment of the present invention, an electrochemical device including the prepared binder is provided.

The electrochemical device may be a lithium ion secondary battery or an electric double layer capacitor. The binder may be included in the electrode slurry of the electrochemical device to enhance binding force between the current collector and the active material constituting the electrode. It can also be used to strengthen the binding force between the electrode active material and the active material.

[Example]

Example 1

An emulsifier solution was prepared by adding 6 g (4 pt/M) of sodium lauryl sulfate (SLS) as an emulsifier to 100 g of distilled water and stirring. A pre-emulsion solution was prepared by pouring 150 g of styrene monomer into the emulsifier solution in small portions while stirring. 30% of the prepared pre-emulsion solution was put into a reactor into which 230 g of distilled water was added, and the temperature was raised to 75° C. and purged with nitrogen. After confirming that the temperature of the reactor reached 75° C., 30% of the initiator solution was added and stirred for 40 minutes. The initiator solution is a mixture of 0.6 g (0.4 pt/M) of ammonium persulfate (APS) in 20 g of distilled water. After stirring, the mixed solution of the pre-emulsion solution and the initiator solution remaining in the reactor was continuously introduced for 2 hours using a metering pump. Thereafter, the temperature of the reactor was raised to 85° C., the reaction was further continued for 1 hour, and then the reaction was terminated by cooling to room temperature. Through the above process, a solution containing a polystyrene core polymer having a total solid concentration (TSC) of 30% was prepared.

A solution in which 0.9 g of itaconic acid was dissolved in 113.33 g of distilled water and 66.7 g (20 g of solid content) of a solution containing a polystyrene core polymer having a solid content of 30% prepared by the method for preparing the core polymer solution were introduced into the reactor.

After adding 3.6 g (2pt/M) of sodium lauryl sulfate as an emulsifier to 120 g of distilled water and stirring to prepare an emulsifier solution, 180 g of shell monomer was poured into the emulsifier solution in small portions and stirred to prepare a pre-emulsion solution. The composition of the shell monomer is shown in Table 1.

After putting 30% of the prepared pre-emulsion solution into a reactor and purging the reactor internal conditions with nitrogen gas, the temperature of the reactor was raised to 75° C. and stirred for 1 hour and 30 minutes. 0.9 g (0.5 pt/M) of ammonium sulfate as an initiator was added to the remaining pre-emulsion and mixed, and the mixed solution was added continuously for 2 hours and 30 minutes using a metering pump. After the introduction was completed, an initiator solution (a mixed solution of 20 g of distilled water and 0.9 g of ammonium sulfate) was introduced into the reactor. Thereafter, the temperature of the reactor was raised to 85° C., the reaction was further continued for 1 hour, and then the reaction was terminated by cooling to room temperature.

Through the above reaction, a binder including core-shell polymer particles having a total solid content of 40% and a core/shell molar ratio of 1:9 was prepared.

Example 2 and Example 3

A binder containing core-shell polymer particles was prepared in the same manner as in Example 1, except that the composition of the shell monomer was changed to that shown in Table 1.

Comparative Example 1

A binder containing core-shell polymer particles was prepared in the same manner as in Example 1, except that the composition of the shell monomer was changed to that shown in Table 1.

division Shell Monomer 180g butyl acrylate Acrylonitrile Contains hydroxyl group
acrylic acid ester GMA Example 1 99.6g 58.8g 2-HEA (18g) 3.6g Example 2 99.6g 58.8g 2-HEMA (18g) 3.6g Example 3 99.6g 58.8g 4-HBAs (18g) 3.6g Comparative Example 1 117.6g 58.8g - 3.6g

*2-HEA; 2-Hydroxyethyl acetate.

*2-HEMA; 2-Hydroxymethacrylate.

*4-HBA; 2-Hydroxybutyl acrylate.

Experimental example

Measurement of electrode adhesive strength

The adhesive strength of the binders prepared in Examples 1 to 3 and Comparative Example 1 to the electrode was compared.

An electrode composition was prepared by mixing 1.4% of the binder, 97.6% of the negative electrode active material, and 1.0% of carboxymethylcellulose (CMC) prepared in Examples and Comparative Examples. The electrode composition was applied to a current collector specimen cut to a width of 4 cm, and dried at 80 ° C. for 24 hours to prepare an electrode.

The prepared electrode was attached to a stainless steel (SUS) plate using double-sided tape. The portion adhered to the double-sided tape was the portion to which the electrode composition was applied. The electrode was attached to the double-sided tape by pressing it back and forth twice at a speed of 300 mm/min using a 1 kg roller.

Then, the specimen was bitten on a texture analyzer and peeled off at a speed of 300 mm/min to measure the adhesive strength.

A graph showing the measurement result of the contact angle is attached to FIG. 1 .

Measurement of contact angle

The binder solutions of Examples 1 to 3 and Comparative Example were placed in a Teflon dish and dried at 70° C. for 24 hours to prepare a binder film (thickness of 10 ± 0.1 μm).

After punching a part of the prepared binder film and fixing it to a contact angle measuring instrument (contact angle equipment), a drop of the electrolyte contained in the microsilage was dropped to measure the contact angle.

As the electrolyte, a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate 1:1:1 was used.

Since the contact angle may change as the electrolyte gets wet into the binder composition or evaporates into the air, the contact angle after 0.1 seconds after the electrolyte falls on the binder film is set as the initial contact angle, and the contact angle changes as time (seconds, s) changes was continuously measured and shown.

The measured contact angles are shown in Table 2, and a photograph of the measurement is attached to FIG. 2.

Contact angle (°) Example 1 Example 2 Example 3 comparative example initial contact angle 44.6 56.4 43.5 68.8 Contact angle after 150 seconds 32.4 43 31.4 55.6

When the binder according to the present invention is used, adhesion between the current collector, the electrode active material, and the active material is improved, so that a secondary battery with superior performance and stability can be manufactured.

Claims (9)

A binder having a structure of a core portion and a shell portion surrounding at least a portion of a surface of the core portion,
The core portion includes a core polymer having at least one repeating unit derived from a styrene-based monomer, an ethylene-based monomer, an amide-based monomer, a carboxylic acid-based monomer, or a (meth)acrylic acid ester-based monomer,
The shell portion includes a shell polymer having repeating units derived from at least one selected from ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, and (meth)acrylic acid ester-based monomers,
The shell part further comprises a (meth)acrylic acid ester-based monomer having at least one hydroxyl group,
The shell polymer is a binder that further comprises a repeating unit derived from an acrylonitrile-based monomer. delete The binder according to claim 1, wherein the shell part further comprises a glycidyl methacrylate-based monomer component. The method of claim 1, wherein the shell polymer is a poly(alkylacrylate-based monomer-including a repeating unit derived from a (meth)acrylic acid alkyl ester monomer and a repeating unit derived from an acrylonitrile-based monomer in a weight ratio of 20:1 to 1:10 An acrylonitrile-based monomer) copolymer, which is a binder. The binder according to claim 1, wherein the weight ratio of the core polymer and the shell polymer is 0.1:99.9 to 5:5. Preparing a core polymer pre-emulsion slurry containing repeating units derived from at least one selected from styrene-based monomers, ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, and (meth)acrylic acid ester-based monomers;
Preparing a pre-emulsion slurry of shell polymers containing repeating units derived from at least one selected from ethylene-based monomers, amide-based monomers, carboxylic acid-based monomers, and (meth)acrylic acid ester-based monomers;
mixing the pre-emulsion slurry of the core polymer and the pre-emulsion slurry of the shell polymer and adding a polymerization initiator to perform polymerization; and
Including the step of terminating the polymerization,
The pre-emulsion slurry of the shell polymer further includes a (meth)acrylic acid ester-based monomer having at least one hydroxyl group,
The shell polymer further comprises a repeating unit derived from an acrylonitrile-based monomer, the method for producing a binder according to any one of claims 1 and 3 to 5 comprising core-shell polymer particles. delete The method of claim 6, wherein the shell part further comprises a glycidyl methacrylate-based monomer component. An electrochemical device comprising the binder according to any one of claims 1 and 3 to 5.

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