KR101960924B1 - Binder material, method for preparing same, and secondary battery or capacitor comprising the same - Google Patents

Abstract

The present invention relates to a binder, a method for producing the same, and a lithium secondary battery or an electric double layer capacitor including the same, more preferably the binder includes a graphene sheet; And the polymer particles adhered to at least one side of the graphene sheet, the stability, stretchability, long-term durability, adhesiveness and conduction performance can be remarkably improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder, a method for producing the same, and a secondary battery or capacitor including the binder,

The present invention relates to a binder capable of improving stability, stretchability and conductivity, a method for producing the same, and a secondary battery or capacitor including the same. More preferably, the present invention relates to a binder comprising a polymer adhered to at least one surface of a graphene sheet and having improved drawability, adhesiveness and conductivity, a method for producing the binder, and a secondary battery or a capacitor including the same.

2. Description of the Related Art Recently, miniaturization, lightening, and wirelessization of electronic devices have rapidly progressed, and as technology development and demand for mobile devices have increased, secondary batteries have attracted attention as driving power sources for these devices. Among secondary batteries, lithium secondary batteries are light-weighted and can obtain high energy density and voltage, can be charged rapidly, have been subjected to many researches, and nowadays, they are becoming important as power sources for vehicles, notebooks or portable terminals, Widely used.

In addition, an electric double layer capacitor using an electric double layer formed at the interface between a polarized electrode and an electrolyte is efficiently used for a large-capacity storage function such as a memory backup power source or an electric vehicle power source, and demand is rapidly increasing in recent years.

The lithium secondary battery or the electric double layer capacitor includes at least one electrode having a structure in which an electrode active material is bound to a current collector by a binder. A separation membrane, an electrolyte, or the like is disposed between the electrodes, Electricity is generated, stored, or consumed by oxidation-reduction reaction or physical coupling by ions or electrons at the interface between the electrode and the electrolyte.

In this case, the binder binds the electrode active material of several to several tens of micrometers or several nanometers to each other and sometimes binds an additive such as a conductive material separately added to improve the conductivity. The electrode slurry or the electrode coating layer thus formed forms a current collector ) To be attached well. The binder should be able to maintain stable adhesion properties without side reactions even in a chemical environment in contact with the electrolyte and in an electrochemical environment where severe oxidation / reduction reactions occur. In addition, in the middle- or large-sized battery which must be driven for 10 years or more in a high-temperature and low-temperature environment, a demand for securing reliability for polymer materials for binders is increasing. Currently, commercially available aqueous polymer binders such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene and other fluorine-based polymer binders and aqueous styrene butadiene rubber (SBR), which are dissolved in organic solvents, are mainly used.

Lithium metal, which was used as an anode active material in early lithium secondary batteries, had problems in terms of cycle life and stability. Subsequently, carbon-based cathodes were limited in their capacity to cope with a rapidly changing role as an energy source for next generation mobile devices. It was difficult. Recently, much research has been conducted on materials capable of lithium and alloys such as silicon (Si), tin (Sn), and oxides thereof as negative electrode materials showing higher capacity than carbon-based materials. However, silicon, tin, and the like cause a change in the crystal structure upon charging and discharging due to an alloy reaction with lithium, resulting in a volume expansion of about 200 to 300%, to generate an electrically isolated active material in the electrode, The capacity is sharply lowered as the charge / discharge cycle progresses due to the increase in resistance due to a large change in the interface between the negative electrode active materials and the deterioration of the negative electrode active material in the long term, Has a shortening problem.

Therefore, in order to improve the energy density of the battery gradually, the thickness and density of the electrode coating layer must be increased and the long-term reliability should be secured for more than 10 years. As the use of the electrode active material, A binder for a carbon-based negative electrode active material has a difficulty in being used as a binder for a silicon or tin-based negative electrode in terms of durability, physico-chemical stability, adhesion ability and the like. In addition, when an excessive amount of polymer is used as a binder in order to reduce the volume change during charging and discharging, the electric resistance of the negative electrode is increased by the electrically insulating polymer as a binder, thereby causing a problem of reduction in capacity and charge / discharge rate of the battery do.

Therefore, it is necessary to develop a binder having a low electrical resistance while having an adhesive force and a mechanical property capable of withstanding a large volume change of the negative electrode active material at the time of charging and discharging. Further, in the case of a conventional graphite-based lithium secondary battery, There is a need to increase the possibility of

Accordingly, the inventors of the present invention developed a composite binder having a strong binding force, mechanical properties, high conductivity, and a large elongation ratio by bonding polymer particles to graphene, which is known to have a very high electrical conductivity, I have come to completion.

Korean Registered Patent No. 10-0491026 (Registered on May 13, 2005)

An object of the present invention is to provide a binder having a strong binding force, a mechanical property, a large elongation and a high conductivity, and a method for producing the same.

It is still another object of the present invention to provide a lithium secondary battery including the binder described above and exhibiting improved battery performance, or a capacitor including the binder and exhibiting improved charging performance.

A binder according to an embodiment of the present invention includes a graphene sheet; And polymer particles attached to at least one side of the graphene sheet.

The graphene sheet may comprise at least one layer of graphene, graphene oxide (GO), reduced graphene oxide (r-GO), graphene with incorporated functional groups, And a composite graphene formed from the composite graphene.

The polymer particles may include polymer particles of poly (butyl acrylate-acrylonitrile) copolymer.

Or the polymer particle is any one selected from the group consisting of an inorganic particle, a metal particle, a core polymer particle, and a mixture of at least one thereof; And poly (butyl acrylate-acrylonitrile) copolymer shells.

The binder according to an embodiment of the present invention may contain 0.1 to 30% by weight of graphene sheet based on the total weight of the binder, the TSI (turbiscan stability index) of the binder is 0.5 or less, the Young's modulus is 5 MPa And the toughness may be 10 N or more.

The binder according to an embodiment of the present invention may include polymer particles having a particle size of less than 300 nm.

A method of manufacturing a binder according to an embodiment of the present invention includes: preparing a solution in which a graphene sheet and a monomer are mixed; And polymerizing the solution to form polymer particles polymerized with monomers on at least one side of the graphene sheet.

According to another embodiment of the present invention, there is provided a method of manufacturing a binder, comprising: forming a core polymer before preparing a solution containing a graphene sheet and a monomer; And dispersing the core polymer in a mixed solution of the graphene sheet and the monomer.

The core polymer is a polymer obtained by polymerizing any one monomer selected from the group consisting of a styrenic monomer, an ethylenic monomer, a conjugated diene monomer, an amide monomer, a carboxylic acid monomer, a (meth) acrylic acid ester monomer, The core polymer comprises from 0.1 to 30% by weight based on the total weight of the binder, the monomer comprises from 40 to 99.8% by weight based on the total weight of the binder, and the graphene sheet may include from 0.1 to 30% by weight based on the total weight of the binder.

The present invention can provide a lithium secondary battery or an electric double layer capacitor including an electrode according to an embodiment, which can provide an electrode including a binder according to an embodiment, particularly a cathode.

The binder of the present invention maintains the adhesive strength of the binder to changes in the volume of the electrode active material during the charging and discharging process, and improves battery performance and electrochemical stability due to reduction in electrical resistance, thereby enhancing long-term durability and cycle characteristics.

In addition, since the binder itself has high conductivity, a high capacity lithium secondary battery or electric double layer capacitor having improved electrical performance can be manufactured.

1 is a schematic view of a binder according to an embodiment of the present invention.
2 is a TSI property value of a binder according to an embodiment of the present invention.
Figure 3 compares the extensibility of the binder according to one embodiment of the present invention.
FIG. 4 illustrates the adhesion of a binder according to an embodiment of the present invention.
5 is a schematic view of a coin-half cell type lithium secondary battery according to an embodiment of the present invention.
6 to 8 are graphs showing electrochemical characteristics of a lithium secondary battery including a binder according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular presentation includes the expression of the abdomen unless the context clearly dictates otherwise. It is to be understood that the term " comprises " or " having " in the present invention is intended to specify the presence of stated features, integers, steps, operations, elements, parts, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof.

The binder 100 according to one embodiment of the present invention includes a graphene sheet 110 as shown in FIG. 1; And polymer particles 120 attached to at least one side of the graphene sheet 110. The graft sheet 110 may include at least one layer of graphene and the polymer particles 120 may be present at one or both sides of the graphene sheet 110 or at the end of the graphene sheet, May be attached to the graphene sheet 110 through chemical bonding, physical bonding or physicochemical bonding.

The graphene sheet 110 may be composed of a hexagonal honeycomb patterned platy graphite structure of a single layer, that is, a single layer graphene, but more preferably one layer or more of graphene may be laminated. Graphene oxide (GO), reduced graphene oxide (r-GO), graphene introduced with a functionalizing agent, and a mixture of at least one of them And a composite graphene formed from the composite graphene.

The oxidized graphene (GO) can be prepared by treating the graphene surface with an acid solution and oxidizing the acid solution. The acid solution may be any one selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, Can be used. The acid-treated graphene can be selectively used by ultrasonic dispersion treatment, filtration, washing and drying. The ultrasonic dispersion is treated for 5 to 20 minutes with ultrasound and then dispersed at 70 to 90 ° C for 3 to 5 hours. Next, it is filtered, washed, and completely dried at a temperature of 70 to 90 ° C. Acid treatment of graphene forms functional groups such as -OH and -COOH on the surface, and these functional groups can form an interface with strong interaction with polymer particles through bonding by physical and chemical methods .

The functional group-introduced graphene can improve the adhesive force by the crosslinking reaction at the interface between the graphene and the polymer or the interface between the electrode active material and the binder by bonding the functional group to the graphene surface and the edge. The functionalizing group may be a group selected from the group consisting of an arene group, a tert-butyl group, a cyclohexyl group, a hydroxyl group, a lactone group, a lactam group, an ester group, an amine group, an amide group, an imine group, A nitro group, a nitro group, a pyridine group, a phosphine group, a phosphoric acid group, a phosphonic acid group, a sulfone group, a sulfonic acid group, a sulfoxide group, a thiol group, a sulfide group, a carbonyl group, an aldehyde group, a carboxyl group, An acyl halide group, a fluoro group, a chloro group, a bromo group, an iodo group, and a combination thereof, and may be selected from the group consisting of a halogen atom, Preferably, graphene having a carboxyl group introduced therein can be used. The functional group-introducing graphene may contain 0.001 to 50 parts by weight of functionalizing agent per 100 parts by weight of the entire graphene.

The graphene sheet may contain 0.1 to 30 wt%, more preferably 1 to 5 wt%, based on the total binder weight. When the graphene sheet is contained in an amount of less than 0.1 wt% based on the total weight of the binder, the electrical properties of the binder are weakened and the improvement of the electrical conductivity is difficult to expect. When the graphene sheet is used in an amount exceeding 30 wt% Basic performance such as binder adhesiveness and the like may not be exhibited or may be lowered.

The polymer particles 120 may include (a) an acrylate-based monomer unit and (b) a nitrile-based monomer unit. (Meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n (methyl methacrylate) (Meth) acrylate, n-hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl And monomer-derived monomer units, and monomer unit (b) may include monomer-derived monomer units selected from acrylonitrile.

The polymer particles 120 are selected from the group consisting of (c) a styrene monomer, an ethylenic monomer, a conjugated diene monomer, an amide monomer, a carboxylic acid monomer, a (meth) acrylic acid ester monomer, The polymer may further comprise a polymer obtained by polymerizing any one of monomers or monomers, or may further comprise inorganic particles or metal particles.

The monomer unit (c) is selected from the group consisting of styrene,? -Methylstyrene,? -Methylstyrene, p-t-butylstyrene; Ethylene, propylene; 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, p-perylene, isoprene; Acrylonitrile, methacrylonitrile; Acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl 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, lauryl methacrylate; Acrylamide, n-methylol acrylamide, n-butoxymethyl acrylamide; Methacrylamide, n-methylol methacrylamide, n-butoxymethylmethacrylamide; Acrylic acid, methacrylic acid; It may include a polymer formed by polymerizing at least one of itaconic acid, maleic acid, fumaric acid, citraconic acid, metaconic acid, glutaconic acid, tetrahydrophthalic acid, crotonic acid, isocrotonic acid, nadic acid and their monomers.

More preferably, the polymer particles 120 may further comprise (c) polymer particles formed by polymerizing a styrene monomer or monomer such as styrene,? -Methylstyrene,? -Methylstyrene, pt-butylstyrene.

The inorganic particles may be at least one selected from the group consisting of 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 And the metal particles may be at least one selected from the group consisting of copper (Cu), silver (Ag), nickel (Ni), gold (Au), platinum (Pt), ruthenium (Ru), iron (Fe), cobalt (Co) , Tin (Sn), tungsten (W), or zinc (Zn).

The total content of these monomer units may be at least 50% by weight, preferably at least 70% by weight, more preferably at least 90% by weight, based on the total weight of the binder. If the monomer total content is less than 50% by weight based on the total binder weight, the adhesive force by the polymer particles is weakened (i.e., the shell thickness becomes too thin), and the binder binding force may be weakened.

The polymer particles 120 may be any one selected from the group consisting of emulsion polymer particles, copolymer polymer particles, core-shell polymer particles, and composite polymer particles containing at least one thereof. Preferably, the polymer particles 120 may be in the form of copolymeric polymers or emulsion polymers of monomeric units (a) and monomeric units (b). The polymer particles 120 may be polymer particles in the form of a core-shell, preferably composed of a core polymer composed of a monomer unit (c) and a copolymer shell polymer of a monomer unit (a) and a monomer unit (b).

When the polymer particles containing two kinds of monomers are prepared, 10 to 200 parts by weight of the monomer unit (b) may be contained per 100 parts by weight of the monomer unit (a).

When polymer particles containing two or more monomers are prepared, 10 to 200 parts by weight of the monomer unit (b) and 1 to 50 parts by weight of the monomer unit (c) are added to 100 parts by weight of the monomer unit (a) .

The core polymer is a polymer obtained by polymerizing any one monomer selected from the group consisting of a styrenic monomer, an ethylenic monomer, a conjugated diene monomer, an amide monomer, a carboxylic acid monomer, a (meth) acrylic acid ester monomer, The core polymer comprises from 0.1 to 30% by weight based on the total weight of the binder, the monomer comprises from 40 to 99.8% by weight based on the total weight of the binder, and the graphene sheet may include from 0.1 to 30% by weight based on the total weight of the binder.

When the content of the core polymer is less than 0.1% by weight based on the total weight of the binder, or when the amount of the monomer forming the shell polymer is more than 99.8% by weight based on the total weight of the binder, the core polymer is too small to cause the core- , The uniformity of the particle size in the core-shell structure may deteriorate and the physical properties of the binder may deteriorate. When the content of the core polymer is more than 30% by weight, or when the amount of the monomer forming the shell polymer is less than 40% by weight, the shell polymer may be too thin and the function of the basic binder such as adhesion performance may be deteriorated.

In the case of the graphene sheet, if the amount is less than 0.1% by weight based on the total weight of the binder, it is difficult to expect improvement in the electrical conductivity of the binder. If the amount exceeds 30% by weight, have.

According to a preferred embodiment of the present invention, the polymer particles may comprise poly (butyl acrylate-acrylonitrile) water-dispersed emulsion copolymer polymer particles.

According to another preferred embodiment of the present invention, the polymer particles are composed of a styrene monomer, an ethylenic monomer, a conjugated diene monomer, an amide monomer, a carboxylic acid monomer, a (meth) acrylic acid ester monomer, A core polymer formed by polymerizing any one of monomers selected from the group consisting of: And poly (butyl acrylate-acrylonitrile) copolymer shells. More preferably a core polymer obtained by polymerizing any one monomer selected from the group consisting of styrene,? -Methylstyrene,? -Methylstyrene, p-t-butylstyrene, and mixtures thereof; And poly (butyl acrylate-acrylonitrile) copolymer shells.

The polymer particles may be at least 50% or more of the spherical particles having a particle size of less than 300 nm. When the polymer particles exceed 300 nm in size or spherical particles are contained in less than 50%, the adhesive force due to the point contact may decrease.

The turbidity stability index (TSI) of the binder 100 according to an embodiment of the present invention is 0.5 or less (on a daily basis), preferably 0.3 or less on a daily basis, more preferably 0.1 to 0.2 )to be. Young's modulus of the binder 100 is 5 MPa or more and toughness is 10 N or more, more preferably 50 N or more.

A method of manufacturing a binder according to an embodiment of the present invention includes: preparing a solution in which a graphene sheet and a monomer are mixed; And polymerizing the solution to form polymer particles polymerized with monomers on at least one side of the graphene sheet. More preferably, the method for producing a binder includes: dispersing graphene in distilled water; Preparing a mixed solution by mixing an emulsifier and a monomer capable of forming polymer particles in a graphene dispersion solution; Introducing a reaction initiator while raising the temperature of the mixed solution to 50 to 100 캜 to form polymer particles by emulsion-polymerizing monomers on at least one side of the graphene sheet; And terminating the reaction.

The description of the graphene sheet and the monomers is as described above.

The method of polymerizing monomers to produce polymer particles is not particularly limited, but can be obtained by copolymerizing the respective monomers by a known polymerization method such as emulsion polymerization, suspension polymerization, dispersion polymerization or solution polymerization. Among them, the emulsion polymerization method may be preferable because the control of the particle diameter of the copolymer is easy.

The emulsion polymerization may be carried out using a conventionally used emulsion polymerization reactor, and preferably a five-necked flask reactor equipped with a stirrer, a condenser, a sample inlet, a thermometer and a burette for introducing an initiator may be used. A wing shape stirrer may be further included. The reaction temperature can be controlled by using a thermostat or a heat plate, and the reaction can be carried out in an oxygen-cut atmosphere by adjusting the nitrogen flow to 0 to 100 ml / min.

The step of forming the polymer particles may further include any one additive selected from the group consisting of a polymerization initiator, an emulsifier, a dispersant, and a mixture thereof.

The polymerization initiator may be a water-soluble persulfate system such as Ammonium persulfate (APS), Potassium persulfate (KPS), Sodium persulfate (NPS) or the like; Ammonium persulfate; Organic peroxides such as benzo peroxide and cumene hydroperoxide can be used alone or in combination with a reducing agent such as ascorbic acid as a redox polymerization initiator. Also, there may be mentioned 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy- 4-dimethylvaleronitrile), dimethyl 2,2'-azobisisobutyrate, and 4,4'-azobis (4-cyanopentanoic acid); Azobis (N, N'-dimethyleneisobutylamidine), 2,2'-azobis (N, N'- N'-dimethyleneisobutylamidine) dihydrochloride, or the like may be used alone or in combination of two or more. The amount of the polymerization initiator to be used is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total amount of the monomers. When the content of the polymerization initiator is less than 0.1 part by weight based on 100 parts by weight of the total amount of the monomers, polymerization and polymer conversion of the monomer may be lowered, and if it exceeds 5 parts by weight, peel adhesion strength may be lowered.

Emulsifiers include lauryl sulfate systems such as sodium lauryl sulfate (SLS), ammonium lauryl sulfate, and potassium lauryl sulfate; Sulfate systems such as sodium 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; Benzenesulfonic acid sodium salt such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethanesulfonate; Sodium alkylsulfate such as sodium lauryl sulfate and sodium tetradodecylsulfate; Sodium sulfosuccinate sodium salt such as sodium dioctylsulfosuccinate and sodium hexylsulfosuccinate sodium; Fatty acid sodium salts such as sodium laurate; ethoxy sulfate sodium salts such as polyoxyethylene lauryl ether sulfate sodium salt and polyoxyethylene nonylphenyl ether sulfate sodium salt; Alkyl ether phosphate ester sodium salt; Sodium polyacrylate, and the like may be used alone or in combination of two or more. The amount of the emulsifier to be added may be arbitrarily set, and may be usually about 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of the monomers, but may not be separately included depending on polymerization conditions.

According to another aspect of the present invention, there is provided a method of manufacturing a binder, comprising: forming a core; Preparing a solution in which a core, a graphen sheet, and a monomer are mixed; And polymerizing the solution to form polymer particles in the form of core-shell polymerized monomers on the core polymer surface on at least one side of the graphene sheet.

The step of forming the core may include the step of producing a core formed of an inorganic particle, a metal particle, a core polymer particle, and a mixture thereof.

The inorganic particles may be at least one selected from the group consisting of 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 And the metal particles may be at least one selected from the group consisting of copper (Cu), silver (Ag), nickel (Ni), gold (Au), platinum (Pt), ruthenium (Ru), iron (Fe), cobalt (Co) , Tin (Sn), tungsten (W), or zinc (Zn).

The core polymer is prepared by polymerizing any one monomer or monomer selected from the group consisting of a styrenic monomer, an ethylenic monomer, a conjugated diene monomer, an amide monomer, a carboxylic acid monomer, a (meth) acrylic acid ester monomer, And a step of forming a core polymer. More preferably, the step of forming the core polymer comprises polymerizing any one of styrene monomers selected from the group consisting of styrene,? -Methylstyrene,? -Methylstyrene, pt-butylstyrene, and mixtures thereof to form a polystyrene polymer To form core particles comprising the core particles.

The shell polymer may include a step of forming a copolymer polymer composed of the monomer unit (a) and the monomer unit (b) described above on the core polymer, more preferably a poly (butyl acrylate-acrylonite Lt; RTI ID = 0.0 > (II) < / RTI > copolymer) shell.

In the step of forming the core-shell type polymer particles, the shell polymer may be contained in an amount of 10 to 900 parts by weight based on 100 parts by weight of the core polymer. When the shell polymer is less than 10 parts by weight or more than 900 parts by weight based on 100 parts by weight of the core polymer, the desired core-shell polymer particles can not be formed and physical properties such as adhesiveness and toughness may be deteriorated.

In the binder manufacturing step of the present invention, the core polymer is selected from the group consisting of a styrenic monomer, an ethylenic monomer, a conjugated diene monomer, an amide monomer, a carboxylic acid monomer, a (meth) acrylic acid ester monomer, Or may be a core polymer obtained by polymerizing any one of monomers. More preferably 0.1 to 30% by weight, based on the total weight of the binder, of any one of the core polymers selected from the group consisting of styrene,? -Methylstyrene,? -Methylstyrene, pt-butylstyrene and mixtures thereof, The monomer capable of forming a polymer may be contained in an amount of 40 to 99.8% by weight based on the total weight of the binder, and the graphene sheet may be contained in an amount of 0.1 to 30% by weight based on the total weight of the binder.

The binder preparation step of the present invention can be produced by reacting at a temperature in the range of 0 to 100 占 폚 and a pressure range of 0.1 to 1.5 atm for 1 minute to 24 hours. If the reaction conditions are out of the range, the polymer particles may not adhere to at least one side of the graphene sheet, or the monomers may not be polymerized into the polymer particles, thereby deteriorating the physical properties of the binder.

According to another embodiment of the present invention, there is provided a lithium secondary battery including an electrode and an electrode including a binder according to an embodiment of the present invention. Specifically, the lithium secondary battery includes a positive electrode including a positive electrode active material disposed opposite to each other, a negative electrode including a negative electrode active material, and an electrolyte interposed between the positive electrode and the negative electrode. The positive electrode or negative electrode may be an electrode including the binder have. The lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and electrolyte used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type.

The lithium secondary battery can be manufactured by disposing a separator between a cathode, an anode and a cathode and a separator between the anode and the cathode to prepare an electrode assembly, placing it in a case, injecting an electrolyte, and impregnating the anode, the anode and the separator.

A conductive lead member for collecting a current generated when the battery operates can be attached to the cathode and the anode, respectively, and the lead member can guide current generated in the anode and the cathode to the cathode terminal and the cathode terminal, respectively.

The negative electrode may be prepared by preparing a composition for forming a negative electrode active material layer by mixing a negative electrode active material, a binder, a solvent and an optional conductive agent, and then applying the composition to a negative electrode current collector such as a copper foil.

As the negative electrode active material, any of the materials used for manufacturing the negative electrode can be selectively used, and the binder is the same as that described above. In addition, preferred examples of the solvent include dimethyl sulfoxide (DMSO), alcohol, N-methylpyrrolidone (NMP), acetone or water.

The conductive material is used for imparting conductivity to the electrode. Any electrically conductive material that does not cause chemical changes in the battery may be used. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as fibers, copper, nickel, aluminum, and silver, metal fibers, and the like, and at least one conductive material such as polyphenylene derivatives may be used.

The collector may be any metal selected from the group consisting of copper, aluminum, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof, and stainless steel may be carbon, nickel, And an aluminum-cadmium alloy may be preferably used as the alloy. In addition, a non-conductive polymer surface-treated with a conductive material, a conductive polymer, or the like may be used.

The method of applying the collector for forming the anode active material layer to the collector may be selected from known methods in consideration of the characteristics of the material and the like or may be carried out by a new appropriate method. For example, it is preferable that the composition for forming the anode active material layer is dispersed on a current collector and then uniformly dispersed using a doctor blade or the like. In some cases, a method of performing the distribution and distribution processes in a single process may be used. In addition, methods such as die casting, comma coating, and screen printing may be used.

The positive electrode may be prepared by preparing a composition for forming a positive electrode active material layer by mixing a positive electrode active material, a conductive agent and a binder in the same manner as the negative electrode, applying the composition for forming a positive electrode active material layer to a positive current collector such as aluminum foil, have. It is also possible to produce the positive electrode plate by casting the positive electrode active material composition on a separate support, then peeling the film from the support, and laminating the film on the metal current collector.

As the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used. Specifically, a lithium-containing transition metal oxide can be preferably used. For example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , Li (Ni _a Co _b Mn _c ) O ₂ (where 0 <a < (1? 0 <c <1, a + b + c = 1), LiNi _{1 -y} Co _y O 2, LiCo _{1 - y} Mn _y O ₂ , LiNi _{1 - y} Mn _y O _{2 1), Li (Ni a Co} b Mn c) O 4 ( However, 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn 2 - z Ni z O ₄ , LiMn _{2 - z} Co _z O ₄ (where 0 <z <2), LiCoPO ₄ and LiFePO ₄ , or a mixture of two or more thereof. In addition to these oxides, sulfide, selenide and halide may be used.

The conductive agent and the binder are the same as those described above in the cathode.

The electrolyte may comprise an organic solvent and a lithium salt.

The organic solvent can be used without particular limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may be an ester solvent, an ether solvent, a ketone solvent, an aromatic hydrocarbon solvent, an alkoxyalkane solvent, or a carbonate solvent, and these solvents may be used singly or in combination of two or more.

Specific examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, But are not limited to, ethyl propionate,? -Butyrolactone, decanolide,? -Valerolactone, mevalonolactone,? -Caprolactone, caprolactone, 隆 -valerolactone, 竜 -caprolactone, and the like.

Specific examples of the ether-based solvent include dibutyl ether, tetraglyme, 2-methyltetrahydrofuran, tetrahydrofuran, and the like.

Specific examples of the ketone-based solvent include cyclohexanone and the like. Specific examples of the aromatic hydrocarbon organic solvent include benzene, fluorobenzene, chlorobenzene, iodobenzene, toluene, fluorotoluene, xylene, (xylene), and the like. Examples of the alkoxyalkane solvent include dimethoxy ethane and diethoxy ethane.

Specific examples of the carbonate solvent include dimethylcarbonate (DMC), diethylcarbonate (DEC), dipropylcarbonate (DPC), methylpropylcarbonate (MPC), ethylpropylcarbonate (EPC) (MEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), propylenecarbonate (PC), butylenecarbonate (BC), or fluoroethylenecarbonate , FEC), and the like.

Among them, it is preferable to use a carbonate-based solvent as an organic solvent. Among the carbonate-based solvents, a carbonate-based organic solvent having a high ionic conductivity and a high ionic conductivity capable of improving the charge- It may be preferable to use a mixture of a carbonate-based organic solvent having a low viscosity capable of appropriately controlling the viscosity of the solvent. Specifically, an organic solvent having a high dielectric constant selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof, and an organic solvent having a low viscosity selected from the group consisting of ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, Can be mixed and used. More preferably, the organic solvent having a high dielectric constant and the organic solvent having a low viscosity are mixed in a volume ratio of 2: 8 to 8: 2, and more specifically, ethylene carbonate or propylene carbonate; Ethyl methyl carbonate; And dimethyl carbonate or diethyl carbonate in a volume ratio of 5: 1: 1 to 2: 5: 3, preferably 3: 5: 2.

The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (C ₂ F ₅ SO ₃ ) ₂ , _{LiN (C 2 F 5 SO 2} ) 2, LiN (CF 3 SO 2) 2, LiN (C a F 2a + 1 SO 2) (C b F 2b + 1 SO 2) ( However, a and b are natural numbers, Preferably 1? A? 20 and 1? B? 20), LiCl, LiI, LiB (C ₂ O ₄ ) _2, and mixtures thereof. Preferably, lithium hexafluoro It is preferable to use phosphate (LiPF ₆ ).

When the lithium salt is dissolved in the electrolyte, the lithium salt functions as a supply source of lithium ions in the lithium secondary battery and can promote the movement of lithium ions between the positive and negative electrodes. Accordingly, the lithium salt is preferably contained in the electrolyte at a concentration of about 0.6 mol% to 2 mol%. If the concentration of the lithium salt is less than 0.6 mol%, the conductivity of the electrolyte may be lowered and the electrolyte performance may be deteriorated. If the concentration exceeds 2 mol%, the viscosity of the electrolyte may increase and the lithium ion mobility may be lowered. Considering the conductivity of the electrolyte and the mobility of the lithium ion, it is more preferable that the lithium salt is adjusted to approximately 0.7 mol% to 1.6 mol% in the electrolyte.

The electrolyte may further include additives (hereinafter, referred to as "other additives") which can be generally used for electrolytes in order to improve the lifetime characteristics of the battery, suppress the reduction of the battery capacity, and improve the discharge capacity of the battery in addition to the electrolyte components have.

Specific examples of the other additives include vinylene carbonate (vinylenecarbonate, VC), methyl fluoride (metal fluoride, for example, LiF, RbF, TiF, AgF , AgF 2, BaF 2, CaF 2, CdF 2, FeF 2, HgF ₂ , Hg ₂ F ₂ , MnF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF ₃ , GaF _{3, GdF 3, FeF 3,} HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF 3, YF 3, _{YbF 3, TIF 3, CeF 4} , GeF 4, HfF 4, SiF 4, SnF 4, TiF 4, VF 4, ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6 , WF ₆ , CoF ₂ , CoF ₃ , CrF ₂ , CsF, ErF ₃ , PF ₃ , PbF ₃ , PbF ₄ , ThF ₄ , TaF ₅ and SeF ₆ ), glutaronitrile Succinonitrile (SN), adiponitrile (AN), 3,3'-thiodipropionitrile (TPN), vinylethylene carbonate (VEC) Fluoroethylene Carbonate fluoroethylene carbonate (FEC), difluoroethylenecarbonate, fluorodimethylcarbonate, fluoroethylmethylcarbonate, lithium bis (oxalato) borate, LiBOB, , Lithium difluoro (oxalate) borate, LiDFOB, lithium (malonatooxalato) borate (LiMOB), and the like. Or a mixture of two or more species. Other additives may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

The separator is not particularly limited as long as it can be used as a separator in a lithium secondary battery. Particularly, it is preferable that the separator is low in resistance against ion movement of the electrolyte and excellent in electrolyte wettability.

Specifically, porous polymer films such as ethylene homopolymers, propylene homopolymers, ethylene / propylene copolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers, A porous polymer film may be used alone or in a laminated form, or a nonwoven fabric made of a conventional porous nonwoven fabric, for example, a glass fiber having a high melting point, polyethylene terephthalate fiber or the like may be used, but the present invention is not limited thereto.

Although the cylindrical lithium secondary battery has been described as an example in the present embodiment, the present invention is not limited to the cylindrical lithium secondary battery, and any shape can be used as long as it can operate as a battery.

According to another embodiment of the present invention, there is provided an electric double layer capacitor including an electrode including a binder according to an embodiment of the present invention.

The electric double layer capacitor electrode can be prepared by preparing a composition for an electric double layer capacitor electrode containing a binder and an electrode active material of the present invention and optionally containing a thickener and a conductivity imparting agent and applying the composition to a current collector, .

As the electrode active material for the electric double layer capacitor electrode, a carbonaceous material having a specific surface area of 30 m 2 / g or more, preferably 500 to 5,000 m 2 / g, more preferably 1,000 to 3,000 m 2 / g is suitably used. Specific examples of the carbonaceous substance include activated carbon, polyacene, carbon whisker, graphite and the like, and powders or fibers thereof can be used. The electrode active material is preferably activated carbon, and specifically, activated carbon such as phenol-based, rayon-based, acrylic-based, pitch-based or coconut shell-based activated carbon may be used. The non-porous carbon having the graphite-like microcrystalline carbon described in Japanese Patent Application Laid-Open No. 1999-317333 and Japanese Patent Application Laid-Open No. 2002-25867 and the interlayer distance of the microcrystalline carbon is enlarged can also be used as the electrode active material. When the electrode active material is a powder, the particle diameter is preferably 0.1 to 100 占 퐉, more preferably 1 to 20 占 퐉, because it is easy to make the capacitor electrode thin and the electrostatic capacity can be increased.

The binder may contain 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the electrode active material. If the amount of the binder is too small, the electrode active material or the conductivity imparting material tends to fall off from the electrode. On the contrary, if the amount of the binder is too large, the electrode active material may be covered with the binder and the internal resistance of the electric double layer capacitor may increase.

The thickener for the electric double layer capacitor electrode can improve the coating and fluidity of the electrode slurry. The kind of the thickener is not particularly limited, but a water-soluble polymer is preferable. Specific examples of the water-soluble polymer include cellulosic polymers such as carboxyl methyl cellulose, methyl cellulose and hydroxypropyl cellulose, and ammonium and alkali metal salts thereof; (Meth) acrylate such as poly (meth) acrylate, polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, a copolymer of acrylic acid or an acrylate and a vinyl alcohol, maleic anhydride or maleic acid or a copolymer of fumaric acid and vinyl alcohol Modified polyvinyl alcohol, modified polyacrylic acid, polyethylene glycol, polycarboxylic acid, oxidized starch, phosphoric acid starch, casein, various modified starches and the like. Among them, preferably used are cellulose-based polymers and salts thereof, and more preferably ammonium salts of cellulose-based polymers. The thickener may be used in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of the electrode active material.

As the conductivity imparting material for the electric double layer capacitor electrode, conductive carbon such as acetylene black, KETJENBLACK, or carbon black can be used, and they are mixed with the electrode active material. The electrical contact between the electrode active materials is further improved by using the conductivity imparting material in combination, the internal resistance of the electric double layer capacitor can be lowered, and the capacitance density can be also increased. The amount of the conductivity-imparting agent may be 0.1 to 20 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the electrode active material.

The current collector for the electric double layer capacitor electrode is not particularly limited as long as it is a conductive and electrochemically durable material. From the viewpoint of heat resistance, a metal material such as aluminum, titanium, tantalum, stainless steel, And aluminum and platinum are particularly preferable. The shape of the current collector is not particularly limited, but a sheet having a thickness of usually about 0.001 to 0.5 mm is used.

As described above, the lithium secondary battery or the electric double layer capacitor including the binder according to the present invention can stably exhibit excellent discharge capacity and high cycle life characteristics. Therefore, it is possible to provide a lithium secondary battery or an electric double layer capacitor including a binder, (HEVs), plug-in HEVs (PHEVs), and mid- to large-sized energy storage systems.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[ Example  One]

0.675 g of graphene sheet powder (0.5% by weight based on the weight of the monomer) was added to 200 g of distilled water and ultrasonically dispersed for 4 hours. A mixture of dispersed graphene solution and 5 pt / M of sodium dodecyl sulfate (SDS) as an emulsifier and acrylonitrile (AN) and butyl acrylate (BA) as monomers at a weight ratio of 1: 2 g, and the mixture was charged into a stirrer, and nitrogen gas was blown in to remove oxygen, followed by stirring at room temperature for 30 minutes. 1 pt / M of potassium persulfate (KPS) was added as an initiator, and the internal temperature of the stirrer was raised to 70 캜 and in situ emulsion polymerization was carried out for 4 hours under a nitrogen atmosphere. Thereafter, the temperature was raised to 80 DEG C and the reaction was further continued for 2 hours, and the reaction was terminated by cooling to room temperature to contain the poly (butyl acrylate-acrylonitrile) water-dispersed emulsion copolymer particles adhered on the graphene sheet Lt; / RTI &gt;

The step of preparing the poly (butyl acrylate-acrylonitrile) copolymer by the reaction of acrylonitrile and butyl acrylate can be represented by the following formula (1).

[ Example  2]

A binder was prepared in the same manner as in Example 1 except that 1.35 g of graphene sheet powder (1 wt% based on the weight of the monomers) was added.

[ Example  3]

A binder was prepared in the same manner as in Example 1, except that 2.7 g of graphene sheet powder (2 wt% based on the weight of the monomers) was added.

[ Example  4]

3 g (2 pt / M) of emulsifier sodium lauryl sulfate (SLS) was added to 100 g of distilled water and stirred to prepare an emulsifier solution. A pre-emulsion solution was prepared by pouring 150 g of styrene monomer into the emulsifier solution in small amounts. Half of the prepared preemulsion solution was placed in a reactor charged with 230 g of distilled water, and the temperature was raised to 75 DEG C and nitrogen purged. When the reactor temperature reached 75 ° C, 50% of the initiator solution containing 0.6 g (0.4 pt / M) of initiator ammonium persulfate (APS) was added to 20 g of distilled water and stirred for 40 minutes. Thereafter, a mixed solution of the pre-emulsion solution and initiator solution remaining in the reactor was continuously introduced for 2 hours by a metering pump. The temperature of the reactor was raised to 85 ° C, and the reaction was further continued for 1 hour. The reaction was terminated by cooling to room temperature to prepare a polystyrene core polymer having a total solid concentration (TSC) of 30%.

(2 pt / M) of 5 wt% sodium laurylsulfate (SLS) as an emulsifier was added to 200 g of distilled water by adding 1.35 g of graphene sheet powder (1 wt% 45 g of acrylonitrile (AN) as a monomer, 90 g of butyl acrylate (BA) and 50 g of a polystyrene core polymer having a TSC content of 30% (solid content 15 g) were charged into a stirrer and stirred at a speed of 200 rpm. After stirring, the temperature of the reactor was raised to 70 캜, purged with nitrogen gas, and stirred for 1 hour. Then 45 g of ammonium persulfate (APS) was added as an initiator and emulsion polymerization was carried out for 4 hours. Thereafter, the temperature was raised to 85 占 폚 and the reaction was further continued for 1 hour, and then the reaction was terminated by cooling to room temperature to prepare a binder containing core-shell polymer particles adhered on the graphene sheet.

[ Comparative Example  One]

A commercially available 480B binder from Zeon was prepared and compared.

[ Comparative Example  2]

A binder containing poly (butyl acrylate-acrylonitrile) water-dispersed emulsion copolymer particles was prepared, except that the graphene sheet was dispersed in the binder manufacturing method of Example 1.

[ Experimental Example  One]

To measure the stability and homogeneity of the binder dispersion solution, the Turbiscan Stability Index (TSI) was measured using a dispersion stabilizer (Turbiscan) and shown in FIG.

Turbiscan generates 880 nm of near infrared wavelength light from a light source and measures the intensity of light measured through a transmission detector located on the opposite side of the light source and a backscattering detector at a 45 ^° angle of the light source intensity,%) of the sample, and calculating the dispersion stability behavior of the entire sample by calculating the following equation (1).

(i = number of scans, H = total height of sample, h = scan height, scan ₀ (h) = intensity of backscattered light (BS (%))

As shown in FIG. 2, the TSI values of Examples 1 to 3 were 0.5 or less, more preferably 0.1 to 0.2, even after one day at 30.degree. C., indicating a relatively stable dispersion state. However, as the content of the graphene sheet in the binder increases as in Examples 2 and 3, the stability is gradually lowered. At this time, the binder solutions of Examples 1 to 3 used a solution in which the high-component content was 20 to 50%.

[ Experimental Example  2]

The binder polymer was poured into a Petri dish and then dried overnight at 40 ° C. and further dried in a 60 ° C. vacuum oven for 6 hours to obtain a film dried to a thickness of about 250 μm. The binder film was cut to a size of 1 x 4 cm and stretched at a force of 50 N / 60 mm / min using a tensometer (TA-Plus, Lloyd Instruments Ltd.) to measure the toughness and elasticity of the binder The comparison is shown in Figure 3 and in Table 1 below (the limit of the device was 350 mm).

As can be seen from the results of FIG. 3, the 480B film of Comparative Example 1 failed to withstand the force acting, the film was torn, and the toughness was about 6 N. On the other hand, the BA20 film of Comparative Example 2 is much more resistant to tensile test and is not torn, so it is judged to have a toughness of 50 N or more which is the mechanical limit. Comparative Example 2 After the experiment, the plastic deformation of the film was severe, and the film did not return to the initial state even after removing the tensile force.

However, the binder films of Examples 1 to 3, in which the polymer particles were evenly dispersed and adhered on the graphene sheet, were not torn during the test, and were restored to their original shape in a short time after the test. As described above, it was confirmed that the Young's modulus of the films of Examples 1 to 3 was improved as compared with Comparative Examples 1 and 2.

Degree of break Young's modulus (MPa) Toughness (N) Comparative Example 1 O 1.35 5.92 Comparative Example 2 X 15.99 > 50 Example 1 X 6.49 > 50 Example 2 X 6.75 > 50 Example 3 X 5.65 > 50

As described above, it was confirmed that the binder of Examples 1 to 3 had a Young's modulus of 5 MPa or more and a toughness of 10 N or more.

[ Experimental Example  3]

A binder composition prepared by mixing 1.4% of the binder of Example 4 and Comparative Example 1, 97.4% of BTR, and 1.2% of CMC was applied, peeling force necessary for peeling the binder film produced by drying at 180 캜, The peelability of the binder and the peelability of the binder are compared in FIG.

4, when the binder of Comparative Example 1 was used, the binder was peeled off when a force of 0.354 N / cm ² was applied, but when the binder of Example 4 was used, the force of 0.367 N / cm ² .

[ Experimental Example  4]

A lithium secondary battery having a simple structure as shown in the schematic view of the coin-and-half cell shown in FIG. 5 was manufactured. 5% by weight of each of the binders of Examples 1 to 3 and Comparative Examples 1 and 2, 3% by weight of carboxymethyl cellulose (CMC) as a thickener, 90% by weight of graphite as a negative electrode active material, And 2% by weight of a vapor grown carbon fiber (VGCF) was applied to a copper current collector to form a cathode 330. [

A positive electrode slurry composition was prepared by mixing NMC532 cathode active material, Super-P conductive material and KF1100 binder in a N-methyl pyrrolidone solvent in a weight ratio of 94: 3: 3 as an anode, Thereby forming the anode 310. The electrode assembly is manufactured through the porous polyethylene separator 320 between the prepared anode and cathode, the electrode assembly is placed inside the case 210 to 250, and then the electrolytic solution is injected into the case, as shown in FIG. 6 A coin-half cell type lithium secondary battery was manufactured. At this time, the electrolytic solution was prepared by mixing ethylene carbonate (EC): dimethyl carbonate (EMC) at a weight ratio of 3: 7, adding 1 M of lithium hexafluorophosphate (LiPF ₆ ).

And more particularly to a battery laminate comprising a positive electrode 310, a negative electrode 330 and a separator 320 surrounded by a cap 210, a wave spring 220, a spacer 230, a gasket 240 and a case 250 And an electrolyte (not shown) was injected into the gasket 240 to prepare a coin-half cell type lithium secondary battery.

In order to examine the initial efficiency and cycle characteristics of secondary batteries manufactured using the binders of Examples 1 to 3 and Comparative Examples 1 and 2, The cycle of discharging was repeated twice, and the cycle of charging and discharging to 0.5 C was repeated 48 times. The discharge capacity (mAh / g) was measured for each cycle and is shown in Fig.

6, it was confirmed that the discharge capacity of the battery using the binders of Examples 1 to 3 was maintained at a high level during the repetition of 50 cycles as compared with Comparative Example 1. In particular, as in Example 2, , It was confirmed that the electrochemical characteristics were maintained at a high level.

[ Experimental Example  5]

Electrochemical impedance spectroscopy (EIS) was carried out by measuring the impedance and the resistance value at the cycle repetition using the battery prepared in the same manner as in Experimental Example 4 using the binders of Examples 1 to 3 and Comparative Examples 1 and 2, 7 are shown in Fig.

After measuring the weight of the negative electrode on the electrode plate, the theoretical capacity (1C) of the coin cell according to the content of the negative electrode active material was calculated, and the charging and discharging of the battery was performed based on the theoretical capacity. In order to uniformly form the solid electrolyte membrane in the electrode, the initial charge and discharge were carried out twice with 0.1 C current, and the remaining three times at 0.5 C, and the electrochemical impedance was compared. As a result, in Comparative Examples 1 and 2 The charge transfer resistance values of Examples 1 to 3 were maintained at a low level.

[ Experimental Example  6]

A negative electrode prepared by mixing the positive electrode active material as described in Experimental Example 4: positive electrode conductive material: binder in a weight ratio of 94: 3: 3, and negative electrode active material: thickener: binder in a weight ratio of 97.6: 1: (MAh) of the battery was measured while repeating 1080 cycles of high-speed charge-discharge (3C) with respect to the battery prepared by using an electrolyte containing 2% by weight of VC, and the battery life was compared 8. At this time, the binder of Example 1 and Example 4 were used as the negative electrode binder, respectively.

As shown in FIG. 8, the initial recovery rate was 79.4% when the binder of Example 1 was used and 73.7% when the binder of Example 4 was used, and the initial capacity was high when the binder of Example 4 was used. Also, after 1080 cycles, the battery life was maintained at a relatively high rate of 51.8% when the binder of Example 1 was used, compared with the initial capacity, indicating that the long-term durability of the battery was maintained even at high charge / discharge cycles there was.

As described above, the binder according to Examples 1 to 4 of the present invention has stronger bonding force, higher mechanical properties, and higher conductivity than those of Comparative Examples 1 and 2, and when used as a binder for the negative electrode, And it was confirmed that it has a high electrochemical characteristic through peeling resistance and the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

100: binder
110: graphene sheet 120: polymer particles
210: cap 220: wave spring
230: spacer 240: gasket
250: Case 310: Anode
320: separator 330: cathode

Claims (12)

Graphene sheets; And
And polymer particles adhered to at least one side of the graphene sheet,
The polymer particles may be polymer particles of poly (butyl acrylate-acrylonitrile) copolymer,
Shell polymer particles comprising a core comprising polystyrene polymer particles and a poly (butyl acrylate-acrylonitrile) copolymer shell, wherein the core-
The turbidity stability index (TSI) is 0.5 or less, the Young's modulus is 5 MPa or more, the toughness is 10 N or more,
bookbinder. The method according to claim 1,
The graphene sheet may include at least one layer of graphene, graphene oxide (GO), reduced graphene oxide (r-GO), graphene introduced with functional groups, Wherein the binder is selected from the group consisting of mixed graphenes. delete delete delete The method according to claim 1,
Wherein the polymer particles are less than 300 nm in size. The method according to claim 1,
And 0.1 to 30% by weight of the graphene sheet based on the total weight of the binder. delete An electrode comprising the binder of claim 1. 10. The electrode according to claim 9, wherein the electrode is a cathode. A secondary battery comprising the electrode of claim 9. A capacitor comprising the electrode of claim 9.

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