Binder for anode of secondary battery, anode of secondary battery and secondary battery

Abstract

The present invention relates to a binder for a secondary battery negative electrode, a secondary battery negative electrode, and a secondary battery. Specifically, embodiments of the present invention provide a binder for a negative electrode of a secondary battery comprising an acid and an aqueous dispersion of an aromatic hydrocarbon-modified resin; a method for manufacturing the same; and a negative electrode and a secondary battery manufactured using the same.

Description

Technology Field

[0001] The present invention relates to a binder for a negative electrode of a secondary battery, a negative electrode of a secondary battery, and a secondary battery. Background Technology

[0003] Secondary batteries are gaining attention as a power source for large electronic devices, such as electric vehicles and power storage devices, as well as for small electronic devices like portable computers, mobile phones, and cameras.

[0004] The negative electrode of a secondary battery comprises a current collector and a negative active material layer, wherein the negative active material layer comprises a negative active material and a binder.

[0005] Commonly known binders for the negative electrode of secondary batteries include polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), and polyolefin (PO)-based polymers.

[0006] Among these, PVDF has the advantage of high binding strength and electrochemical stability due to excellent interaction with carbon-based negative electrode active materials such as graphite. However, it lacks flexibility, which causes the bond to break down due to the shrinkage and expansion of the negative electrode active material during charging and discharging of the secondary battery, thereby degrading the cycle characteristics of the secondary battery. In addition, since a non-aqueous negative electrode slurry must be prepared using organic solvents, there is also the problem of causing environmental pollution.

[0007] SBR is a particulate polymer produced by emulsion polymerization. It is environmentally friendly and exhibits excellent bonding strength even when used in small quantities, offering the advantage of improving the capacity and initial charge / discharge efficiency of secondary batteries. However, it has drawbacks, such as weak bonding strength due to a narrow contact area with graphite and low thermal stability caused by the presence of unsaturated double bonds within the particles, which degrades the cycle characteristics of secondary batteries.

[0008] Although PO-based polymers possess excellent electrolyte resistance and thermal stability, the low adhesion of non-polar polymers leads to reduced bonding strength with the negative electrode active material and electrode current collector during charging and discharging, which causes a problem of degrading the cycle characteristics of secondary batteries. The problem to be solved

[0010] The present invention aims to provide a technology that secures excellent cycle characteristics even during long-term operation of a secondary battery by strengthening initial adhesion through the modification of a PO-based polymer while maintaining binding strength during the charge-discharge process. means of solving the problem

[0012] In embodiments of the present invention, a binder for a negative electrode of a secondary battery comprising an acid and an aqueous dispersion of an aromatic hydrocarbon-modified resin; a method for manufacturing the same; and a negative electrode and a secondary battery manufactured using the same are provided.

[0013] Specifically, the acid and aromatic hydrocarbon modified resin comprises a polyolefin, and in particular comprises an acid functional group and an aromatic hydrocarbon pendant functional group located within, at, or both of the molecule of the polyolefin.

[0014] In addition, the acid and aromatic hydrocarbon modified resin is prepared by sequentially reacting a polyolefin resin with an acid and an aromatic compound. Effects of the invention

[0016] The binder for a secondary battery negative electrode of the above embodiment induces π-π stacking interactions between the aromatic hydrocarbon-based pendant functional group in the acid and aromatic hydrocarbon modified resin and the surface of the negative electrode active material, thereby strengthening the initial adhesion while maintaining the binding strength during the charging and discharging process, so that excellent cycle characteristics can be secured even during long-term operation of the secondary battery. Specific details for implementing the invention

[0018] In the present invention, terms such as first, second, etc. are used to describe various components, and these terms are used solely for the purpose of distinguishing one component from another component.

[0019] The terms used herein are merely for describing exemplary embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0020] In this specification, where each layer or element is described as being formed "on" or "above" each layer or element, it means that each layer or element is formed directly on each layer or element, or that another layer or element may be additionally formed between each layer, on an object, or on a substrate.

[0021] In this specification, unless otherwise defined, "copolymer" may mean block copolymer, random copolymer, graft copolymer, or alternating copolymer, and "copolymer" may mean block copolymer, random copolymer, graft copolymer, or alternating copolymer.

[0022] In this specification, "binder" refers to a solid component in which a solvent, etc. is not mixed, and "binder composition" may refer to a solution in which a solvent, etc. is mixed with the "binder."

[0023] In this specification, "pendant functional group" refers to a functional group located inside a chain-type compound rather than at the chain end, and specifically, it may be understood to include functional groups directly or indirectly grafted to the side chain of a chain-type compound, and functional groups directly or indirectly bonded to the ring atom of a cyclic compound.

[0024] The present invention is capable of various modifications and may take various forms, and specific embodiments are illustrated and described in detail below. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0026] Binder for negative electrode of secondary battery

[0028] Polyolefin-based cathode binders known prior to one embodiment of the present invention attempted to enhance adhesion by introducing copolymer monomers with a low glass transition temperature (Tg), elastomer blending, or substituting polar functional groups. However, these methods had limitations in terms of storage stability, adhesive properties, etc.

[0030] To overcome such limitations, in one embodiment of the present invention, the π-π stacking interaction is introduced into a binder system.

[0031] Specifically, in one embodiment above, a binder for a negative electrode of a secondary battery is provided, comprising an acid and an aromatic hydrocarbon modified resin.

[0032] More specifically, the acid and aromatic hydrocarbon modified resin comprises a polyolefin, and an acid functional group and an aromatic hydrocarbon pendant functional group located within, at, or both of the molecule of the polyolefin.

[0034] π-π stacking interactions are possible between carbonaceous materials and aromatic hydrocarbons.

[0035] The aromatic hydrocarbon-based pendant functional groups in the above acid and aromatic hydrocarbon modified resin can induce π-π stacking interactions with the surface of the cathode active material, thereby strengthening adhesion.

[0036] Here, the π-π stacking interaction corresponds to a type of van der Waals attraction rather than a chemical bond. Accordingly, as the negative electrode active material contracts and expands during the charging and discharging of the secondary battery, the aromatic hydrocarbon-based pendant functional groups within the acid and aromatic hydrocarbon modified resin can repeatedly bond and debond with the negative electrode active material.

[0037] As a result, the negative electrode binder of the above embodiment exhibits excellent initial adhesion, maintains binding strength to the negative electrode active material even during the charging and discharging process of the secondary battery, and can secure excellent cycle characteristics even during long-term operation of the secondary battery.

[0039] Hereinafter, the cathode binder of the above-mentioned embodiment will be described in more detail.

[0041] acid functional group

[0043] Excellent electrolyte resistance properties are achieved through the nonpolarity of the polyolefin, and at the same time, the nonpolar polyolefin can be dispersed in an aqueous solvent by introducing acid functional groups, such as maleic anhydride, into the molecule, terminals, or both of these of the polyolefin.

[0044] In addition, the introduction of the acid functional group has the effect of improving adhesion, but the adhesion when the acid functional group is introduced alone is insufficient compared to existing binders such as SBR, and can be supplemented by additionally introducing the aromatic hydrocarbon pendant functional group described later.

[0046] The above acid functional group may be derived from maleic anhydride.

[0047] Maleic anhydride exhibits excellent reactivity to radical attack and can form an acid moiety through ring opening, which is advantageous for providing reactivity and stability in acid denaturation reactions.

[0049] Aromatic hydrocarbon pendant functional group

[0051] As mentioned above, the aromatic hydrocarbon pendant functional group can compensate for the insufficient adhesive strength when the acid functional group is introduced alone.

[0053] The above aromatic hydrocarbon pendant functional group may be derived from a monocyclic aromatic hydrocarbon or a polycyclic aromatic hydrocarbon having a bonding energy with graphite of 40 to 100 kJ / mol.

[0054] When a pendant functional group having a binding energy with graphite within the above range exists as a functional group grafted directly or indirectly into the polyolefin molecule, specifically on the side chain, it effectively induces π-π stacking interactions with the surface of the negative electrode active material, thereby strengthening the initial adhesion and maintaining the binding strength even during the charging and discharging of the secondary battery.

[0056] Specifically, the aromatic hydrocarbon pendant functional group may be derived from one or more selected from the group consisting of benzene, naphthalene, anthracene, and pyrene. Each of the above substances has a binding energy with graphite of 48 kJ / mol (benzene), 73 kJ / mol (naphthalene), 88 kJ / mol (anthracene), and 95 kJ / mol (pyrene).

[0057] However, as long as the bonding energy with graphite is within the above range, the aromatic hydrocarbon pendant functional group is not specifically limited.

[0059] Content of each functional group

[0061] The total amount of the acid functional group and the aromatic hydrocarbon pendant functional group may be 0.5 to 15 weight%, specifically 0.5 to 10 weight%, of the acid and aromatic hydrocarbon modified resin (100 weight%).

[0062] In addition, when the total amount of the acid functional group and the aromatic hydrocarbon pendant functional group is based on 100 weight%, the content of the aromatic hydrocarbon pendant functional group may be 30 to 90 weight%, and the content of the acid functional group may be 10 to 70 weight%.

[0063] In this range, π-π stacking interactions with the surface of the negative electrode active material are induced more effectively to strengthen adhesion, and the binding strength can be maintained even during charging and discharging of the secondary battery.

[0064] For reference, the content of each of the above functional groups can be measured using equipment such as NMR.

[0066] polyolefin

[0068] The above polyolefin is not particularly limited as long as it is a homopolymer or copolymer of C3 or higher, specifically C3 to C20 olefins, and includes a tertiary hydrogen to which the pendant functional group can be substituted.

[0069] Specifically, the polyolefin may be a polypropylene-based homopolymer or copolymer. For example, the polyolefin may be one or more selected from the group comprising polypropylene homopolymer, propylene-ethylene copolymer, propylene-butylene copolymer, and ethylene-propylene-butylene terpolymer.

[0071] Structure of acid and aromatic hydrocarbon modified resins

[0073] The above acid and aromatic hydrocarbon modified resin may be represented in a structure comprising a repeating unit represented by the following chemical formula 1, a repeating unit represented by the following chemical formula 2, and a repeating unit represented by the following chemical formula 3:

[0074] [Chemical Formula 1]

[0075]

[0076] [Chemical Formula 2]

[0077]

[0078] In the above chemical formula 2,

[0079] L1 is directly bonded or NH, e.g., NH, and

[0080] L2 is directly bonded, or substituted or unsubstituted C 1-10 It is an alkylene, for example, a C1-alkylene (i.e., CH2), and

[0081] Ar1 is phenyl, naphthyl, anthracenyl, or pyrenyl, and

[0082] [Chemical Formula 3]

[0083]

[0084] R1 is a substituent represented by the following chemical formula 3-1 or 3-2, and

[0085] [Chemical Formula 3-1]

[0086]

[0087] [Chemical Formula 3-2]

[0088]

[0089] In the above chemical formulas 3-1 and 3-2, respectively, the dotted line is connected to the above chemical formula 3.

[0091] The above chemical formula 1 corresponds to an olefinic repeating unit that is not bonded to an acid and an aromatic hydrocarbon pendant functional group, the above chemical formula 2 corresponds to a portion (repeating unit) substituted by an aromatic hydrocarbon pendant functional group, and the above chemical formula 3 corresponds to a portion (repeating unit) substituted by an acid functional group.

[0092] Specifically, the above chemical formula 3-1 and the above chemical formula 3-2 are structures derived from un-ringed maleic anhydride and ringed maleic anhydride, respectively, and are substituted with tertiary hydrogen in the polyolefin.

[0093] In addition, the above chemical formula 2 is one in which the OH group of ring-opened maleic anhydride is substituted by an aromatic hydrocarbon pendant functional group. This can be viewed as the aromatic hydrocarbon pendant functional group substituting the tertiary hydrogen of the polyolefin via an acid functional group (specifically, ring-opened maleic anhydride).

[0095] In addition, the acid and aromatic hydrocarbon modified resin may be represented as a structure further comprising one or more of the repeating unit represented by the following chemical formula 4 and the repeating unit represented by the following chemical formula 5:

[0096] [Chemical Formula 4]

[0097]

[0098] [Chemical Formula 5]

[0099] .

[0100] The repeating unit represented by the above chemical formula 4 corresponds to an ethylene-based repeating unit, and the repeating unit represented by the above chemical formula 5 corresponds to a butylene-based repeating unit.

[0102] When the above polyolefin is a polypropylene homopolymer, the above acid and aromatic hydrocarbon modified resin may consist only of repeating units represented by Chemical Formula 1, repeating units represented by Chemical Formula 2, and repeating units represented by Chemical Formula 3.

[0103] In contrast, if the polyolefin is a propylene-ethylene copolymer, a propylene-butylene copolymer, or an ethylene-propylene-butylene terpolymer, the acid and aromatic hydrocarbon modified resin may further include one or more of the repeating unit represented by Chemical Formula 4 and the repeating unit represented by Chemical Formula 5, in addition to the repeating unit represented by Chemical Formula 1, the repeating unit represented by Chemical Formula 2, and the repeating unit represented by Chemical Formula 3.

[0104] For example, the polyolefin may be a propylene-ethylene copolymer, and the acid and aromatic hydrocarbon modified resin may include a repeating unit represented by Chemical Formula 1, a repeating unit represented by Chemical Formula 2, a repeating unit represented by Chemical Formula 3, and a repeating unit represented by Chemical Formula 4.

[0106] Aqueous solvent

[0108] The cathode binder of the above embodiment may form a composition by adding an aqueous solvent, namely water.

[0110] The above aqueous solvent may be used in an amount of about 50 to about 1,000 parts by weight, specifically about 100 to about 400 parts by weight, with respect to the stability and viscosity control of the acid and aromatic hydrocarbon modified resin. For example, it may be used so that the total solid content (TSC) of the total amount (100 wt%) of the cathode binder of the above embodiment is controlled to about 10 to about 30%.

[0111] If the above aqueous solvent is used in an excessively small amount, the stability of the above acid and aromatic hydrocarbon modified resin may be reduced, and if the solvent is used in an excessive amount, the viscosity decreases, which leads to a decrease in process characteristics, including coating properties, during the manufacture of the cathode, and consequently, a decrease in the overall performance of the battery may occur.

[0113] Method for manufacturing a binder for the negative electrode of a secondary battery

[0115] In another embodiment of the present invention, a method for manufacturing a binder for a negative electrode of a secondary battery is provided, comprising the steps of: reacting a polyolefin-based resin with an acid to produce an acid-modified resin; and reacting the acid-modified resin with an aromatic compound to produce an acid and aromatic hydrocarbon-modified resin.

[0117] This corresponds to a method for manufacturing a cathode binder comprising an acid and aromatic hydrocarbon modified resin of the aforementioned embodiment by sequentially reacting a polyolefin-based resin with an acid and an aromatic compound.

[0119] Hereinafter, descriptions that overlap with the above content will be omitted, and the manufacturing method of the above-mentioned embodiment will be described in detail.

[0121] Acid transformation stage

[0123] In the step of manufacturing the acid-modified resin, hydrogen located inside, at the ends, or both of the molecule of the polyolefin resin may be substituted by the acid.

[0124] Accordingly, an acid-modified resin comprising a polyolefin and an acid functional group located within, at, or both of the molecule of the polyolefin can be obtained.

[0126] Specifically, in the step of manufacturing the acid-modified resin, 1 to 30 parts by weight, specifically 1 to 20 parts by weight of acid, can be reacted based on 100 parts by weight of the polyolefin resin.

[0127] Within this range, an acid and aromatic hydrocarbon modified resin satisfying the aforementioned acid value can be finally obtained.

[0129] The step of preparing the acid-modified resin above may be performed in the presence of one or more solvents selected from the group consisting of toluene and xylene.

[0130] For example, it can be performed under a toluene solvent.

[0132] In addition, the step of preparing the acid-modified resin may be performed in the presence of one or more radical polymerization initiators selected from the group consisting of dicumyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, tert-butylcumyl peroxide, benzoyl peroxide, dilauryl peroxide, and cumene hydroperoxide.

[0133] For example, it can be performed in the presence of dicumyl peroxide.

[0135] In addition, in the step of manufacturing the acid-modified resin, the acid may be maleic anhydride.

[0136] The above maleic anhydride exhibits excellent reactivity to denaturation caused by radical attack of the above radical polymerization initiator, and can form an acid moiety through ring opening, which is advantageous for providing reactivity and stability of the acid denaturation reaction.

[0138] In addition, the step of preparing the acid-modified resin may be performed at a temperature range of 90 to 130 ℃, specifically 100 to 120 ℃; for 4 to 8 hours, specifically 5 to 7 hours.

[0139] Within these temperature and time ranges, hydrogen located inside, at the ends, or both of the molecules of the polyolefin resin can be effectively substituted by the acid.

[0141] Aromatic hydrocarbon modification process

[0143] After the step of preparing the acid-modified resin, the tertiary hydrogen located inside the acid-modified resin molecule can be substituted with an aromatic hydrocarbon pendant functional group by reacting with an aromatic compound.

[0144] Accordingly, an acid and aromatic hydrocarbon modified resin comprising a polyolefin and an acid functional group and an aromatic hydrocarbon pendant functional group located within, at, or both of the molecule of the polyolefin can be obtained.

[0146] Based on 100 parts by weight of the above acid-modified resin, 1 to 30 parts by weight, specifically 1 to 20 parts by weight of an aromatic compound can be reacted.

[0147] Within this range, an acid and aromatic hydrocarbon modified resin satisfying the content of the aforementioned aromatic hydrocarbon pendant functional group can be finally obtained.

[0149] The step of preparing the above acid and aromatic hydrocarbon modified resin can be performed under a toluene solvent.

[0151] In addition, in the step of preparing the acid and aromatic hydrocarbon modified resin, the aromatic compound may be a monocyclic aromatic hydrocarbon or a polycyclic aromatic hydrocarbon having a bonding energy with graphite of 40 to 100 kJ / mol.

[0152] For example, it may be one or more selected from the group consisting of benzyl amine, naphthyl methylamine, anthracene methylamine, and pyrene methylamine.

[0154] In addition, the step of preparing the acid and aromatic hydrocarbon modified resin may be performed at a temperature range of 90 to 130 ℃, specifically 100 to 120 ℃; for 1 to 5 hours, specifically 2 to 4 hours.

[0155] Within these temperature and time ranges, the tertiary hydrogen located inside the molecule of the acid-modified resin can be effectively substituted by the aromatic hydrocarbon.

[0157] Water dispersion preparation step

[0159] After the step of preparing the acid and aromatic hydrocarbon modified resin, the method may further include the step of preparing an aqueous dispersion containing the acid and aromatic hydrocarbon modified resin using an evaporation method.

[0160] In other words, by further including this step, a composition comprising an aqueous solvent together with the acid and the aromatic hydrocarbon modified resin (hereinafter, depending on the case, may be referred to as an 'aqueous dispersion' or 'aqueous dispersion') can be obtained.

[0161] The aqueous dispersion obtained in this way can be used to implement an aqueous cathode. Here, an aqueous cathode refers to a cathode prepared using a cathode composite slurry composition that does not contain a non-aqueous solvent and contains an aqueous solvent.

[0162] Compared to a cathode manufactured using a cathode composite slurry composition containing a non-aqueous solvent (non-aqueous cathode), such an aqueous cathode is environmentally friendly as there is no concern about the generation of harmful substances during the cathode manufacturing process.

[0164] The step of preparing an aqueous dispersion comprising the above acid and aromatic hydrocarbon modified resin comprises: mixing the above acid and aromatic hydrocarbon modified resin with a low-boiling point solvent having a boiling point of 100°C or lower and then raising the temperature to prepare a solution in which the above acid and aromatic hydrocarbon modified resin is dissolved; adding a basic solution dropwise to the solution in which the above acid and aromatic hydrocarbon modified resin is dissolved; and, after adding the basic solution, adding distilled water dropwise while simultaneously removing the low-boiling point solvent The method may further include the step of dispersing the acid and aromatic modified resin in water while distilling.

[0165] The above low-boiling point solvent is a solvent with a boiling point (100°C) or lower than that of water, which is the final dispersion solvent, specifically 90°C or lower, 80°C or lower, or 70°C or lower, and although the lower limit is not specifically limited, it may be 10°C or higher, 20°C or higher, 30°C or higher, or 40°C or higher.

[0166] As the above low-boiling point solvent, acetone (boiling point: 56.5 °C), tetrahydrofuran (THF, boiling point: 66 °C), or a mixture thereof may be used, for example, tetrahydrofuran.

[0168] In the step of preparing a solution in which the acid and aromatic hydrocarbon modified resin are dissolved, the temperature can be increased until it reaches a temperature range of 50 to 90 ℃, specifically 60 to 80 ℃, so that the acid and aromatic hydrocarbon modified resin can be completely dissolved in the tetrahydrofuran.

[0170] Subsequently, in the step of dropping the basic solution, a basic solution comprising 0.1 to 10 parts by weight, specifically 0.5 to 5 parts by weight, based on 100 parts by weight of the acid and aromatic hydrocarbon modified resin in the solution in which the acid and aromatic hydrocarbon modified resin are dissolved, may be dropped.

[0171] Here, the basic substance is N,N-dimethylethanolamine, and the basic solution may be a solution in which N,N-dimethylethanolamine is dissolved in tetrahydrofuran (THF).

[0172] By adding the above basic solution dropwise, the acid substituent is converted into a water-soluble amine substituent form and its solubility in water is increased, thereby producing a stable water-dispersible solution.

[0174] After the step of water-dispersing the acid and aromatic hydrocarbon modified resin, the method may further include the step of cooling the water dispersion of the acid and aromatic hydrocarbon modified resin to room temperature; and the step of filtering the cooled water dispersion of the acid and aromatic hydrocarbon modified resin.

[0175] By further including these steps, unreacted materials remaining in the aqueous dispersion of the acid and aromatic hydrocarbon modified resin can be removed.

[0177] cathode

[0179] In another embodiment of the present invention, a cathode is provided comprising: a cathode current collector; and a cathode composite layer positioned on the cathode current collector and comprising the binder of the above embodiment and the cathode active material.

[0181] Except for the cathode binder of the above embodiment, the cathode composite, the cathode active material used in the cathode, the cathode current collector, etc., may each include generally known components.

[0183] The cathode binder of the above embodiment may be included in an amount of 1% to 10% by weight, specifically 1% to 5% by weight, of the total weight (100% by weight) of the cathode composite. When this is satisfied, the content of the cathode active material can be relatively increased, and the discharge capacity of the cathode can be further improved.

[0184] Meanwhile, the cathode binder of the above embodiment has excellent characteristics regarding binding strength and mechanical properties, so it can maintain binding strength between cathode active materials and between cathode active materials and cathode current collectors, and can suppress the expansion of the cathode active material through its own mechanical properties, even when a graphite-based cathode active material is used as the cathode active material of the cathode composite, or when a cathode active material with a higher capacity is used.

[0185] Since the cathode binder of the above embodiment is suitable for application not only with graphite-based cathode active materials but also with cathode active materials having a higher capacity, the type of cathode active material is not particularly limited in the above embodiment of the present invention.

[0186] Specifically, the above-mentioned negative electrode active material is carbon such as non-graphitizable carbon, graphite-based carbon, etc.; Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5 등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물; 리튬 티타늄 산화물 등을 사용할 수 있다.

[0187] The negative electrode current collector is generally made with a thickness of 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, fine irregularities may be formed on the surface to strengthen the bonding strength of the negative electrode active material, and it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0188] The above cathode is manufactured by applying a cathode composite containing a cathode active material and the binder onto a cathode current collector, followed by drying and rolling, and, if necessary, may be manufactured by further adding a conductive material, a filler, etc.

[0189] The above conductive material is used to impart conductivity to the negative electrode, and any electronically conductive material that does not cause chemical changes in the battery being constructed may be used. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fibers; metal-based materials such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; conductive polymers such as polyphenylene derivatives; or conductive materials comprising a mixture thereof.

[0190] The above filler is optionally used as a component to suppress the expansion of the negative electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery, for example, olivine-based polymers such as polyethylene and polypropylene; or fibrous materials such as glass fibers and carbon fibers may be used.

[0192] secondary battery

[0194] In another embodiment of the present invention, a secondary battery comprising the negative electrode of the aforementioned embodiment is provided. Such a secondary battery may be in a form comprising a positive electrode; an electrolyte; and a negative electrode, and may be implemented as a lithium secondary battery.

[0196] The above lithium secondary battery can be manufactured by impregnating an electrode assembly comprising a positive electrode, a separator, and a negative electrode with a non-aqueous electrolyte.

[0198] The above-mentioned cathode is as described above, and the remaining components are explained below.

[0200] anode

[0202] The above-mentioned positive electrode comprises a positive electrode active material, wherein the positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x O 4　(where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); LiNi x Mn 2-x Examples include lithium manganese complex oxides with a spinel structure represented by O4; LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc., but are not limited to these.

[0203] The above positive current collector is generally made with a thickness of 3 μm to 500 μm. Such a positive current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The current collector may also form fine irregularities on its surface to increase the adhesion of the positive active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.

[0204] The above conductive material is not particularly limited as long as it possesses conductivity without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives may be used.

[0206] A generally known binder may be used in the anode above. Representative examples include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc., but are not limited thereto.

[0208] The above-mentioned cathode and anode may each be manufactured by mixing an active material and a binder, and in some cases, a conductive material, a filler, etc., in a solvent to form a slurry-type electrode mixture, and then applying this electrode mixture to each electrode current collector. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof will be omitted in this specification.

[0210] In the case of the above-mentioned separator, any material commonly used in lithium batteries to separate the negative and positive electrodes and provide a pathway for the movement of lithium ions may be used. That is, a material with low resistance to the movement of electrolyte ions and excellent electrolyte wettability may be used. For example, it may be selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, and may be in the form of a non-woven or woven fabric. For example, polyolefin-based polymer separators such as polyethylene and polypropylene are mainly used in lithium-ion batteries, and coated separators containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0211] In some cases, a gel polymer electrolyte may be coated on the separator to increase the stability of the battery. Representative examples of such gel polymers include polyethylene oxide, polyvinylidene fluoride, and polyacrylonitrile.

[0212] However, if a solid electrolyte other than the above-mentioned non-aqueous electrolyte is used, the solid electrolyte may also serve as a separator.

[0213] The above-mentioned non-aqueous electrolyte may be a liquid electrolyte comprising a non-aqueous organic solvent and a lithium salt. The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0214] The above-mentioned non-aqueous electrolytes include non-aqueous electrolytes, organic solid electrolytes, and inorganic solid electrolytes.

[0215] The above-mentioned non-aqueous electrolyte includes, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfranc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, Aprotic organic solvents such as tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate may be used.

[0216] The above organic solid electrolyte may be, for example, a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, a polymer containing an ionic dissociator, etc.

[0217] As the above-mentioned inorganic solid electrolyte, for example, nitrides, halides, sulfates of Li such as Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, Li3PO4-Li2S-SiS2 may be used.

[0218] The above lithium salt is a substance that dissolves well in the above-mentioned non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, etc. may be used.

[0219] In addition, for the purpose of improving charge / discharge characteristics and flame retardancy, the electrolyte may be further enriched with, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. In some cases, to impart non-flammability, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be further enriched, carbon dioxide may be further enriched to improve high-temperature storage characteristics, and FEC (fluoro-ethylene carbonate), PRS (propene sultone), FPC (fluoro-propylene carbonate), etc.

[0220] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but also as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0222] Preferred embodiments are presented below to aid in understanding the invention. However, the following embodiments are intended only to illustrate the invention and do not limit the invention to these embodiments.

[0224] <Example>

[0226] Example 1

[0227] (1) Preparation of a binder composition for a cathode

[0228] 1) Preparation of acid-modified polyolefin resin

[0229] 300g of polyolefin resin (poly(propylene-ethylene) copolymer, softening point 50℃, weight-average molecular weight 160,000 g / mol), 30g of maleic anhydride, and 450g of toluene were completely dissolved while uniformly stirring at 110℃ under a nitrogen atmosphere.

[0230] While maintaining the temperature inside the flask at 110℃, 6g of dicumyl peroxide, a radical polymerization initiator, was slowly added over 1 hour. Subsequently, the reaction was carried out for an additional 5 hours or more to ensure that the radical polymerization reaction could proceed completely.

[0231] After the reaction was completed, the product was cooled to room temperature, and then the product was added to a large amount of acetone to precipitate an acid-modified polyolefin resin. The acid-modified resin obtained in this way was washed with acetone three times to completely remove unreacted materials. Subsequently, it was dried under reduced pressure at 60°C.

[0232] 2) Preparation of acid and aromatic hydrocarbon modified polyolefin resins

[0233] 400g of toluene was added to 200g of the above acid-modified polyolefin resin and heated to 110℃ to completely dissolve it. A solution of 10g of naphthyl methylamine dissolved in 40g of toluene was added and reacted at 110℃ for 3 hours.

[0234] After the reaction was completed, the product was cooled to room temperature, and then the product was added to a large amount of acetone to precipitate an acid and aromatic hydrocarbon modified polyolefin resin. The resulting acid and aromatic hydrocarbon modified polyolefin resin was washed with acetone three times to completely remove unreacted materials. Subsequently, it was dried under reduced pressure at 60°C.

[0235] 3) Preparation of an aqueous dispersion of polyolefin resin (Preparation of cathode binder composition)

[0236] 100g of THF was added to 150g of the acid and aromatic hydrocarbon modified polyolefin resin in a reactor equipped with a reflux condenser and a Dean-Stark apparatus, and the temperature was raised to 70°C to completely dissolve it. A solution of 4.5g of N,N-dimethylethanolamine dissolved in 30g of THF as a basic compound was added dropwise over 1 hour. Subsequently, 600g of distilled water was added dropwise over 1 hour while the THF was slowly distilled through a Dean-Stark trap to perform water dispersion. After cooling to room temperature, the mixture was filtered through a 300-mesh sieve to prepare a final aqueous dispersion of the polyolefin resin with a solid content of 20%.

[0237] (2) Preparation of the cathode

[0238] Using water as a dispersion medium, 95 g of artificial graphite, 1.5 g of acetylene black, 100 g of carboxymethyl cellulose (solid content 1.0 wt%) as a thickener, and 12.5 g of the cathode binder composition of Example 1 (solid content 20 wt%) were mixed and stirred for 1 hour to prepare a cathode composite slurry composition having a total solid content of 45 wt%.

[0239] A copper foil with a thickness of 10 μm is prepared and used as a cathode current collector, and using a comma coater, the cathode composite slurry composition is applied to one surface of the cathode current collector at a concentration of 8.0 mg / cm² 2 After applying to both sides with a loading amount, the material was hot-air dried in an oven at 80°C for 10 minutes, and then rolled to a total thickness of 190 μm. Accordingly, the cathode of Example 1 was obtained.

[0240] (3) Manufacturing of lithium-ion batteries

[0241] LiNi as the positive active material0.6 Mn 0.2 Co 0.2 O290 g, 5.0 g of acetylene black, and 50 g of polyvinylidene fluoride (PVDF) as a binder (solid content 10 wt%) were used, and these were stirred in NMP, a solvent, for 1 hour to prepare an anode composite slurry composition with a total solid content of 70 wt%.

[0242] Prepare an aluminum foil with a thickness of 20 μm and use it as an anode current collector, and using a comma coater, apply the anode composite slurry composition to one surface of the anode current collector at a concentration of 15.6 mg / cm² 2 After applying to both sides with a loading amount, the material was hot-air dried in an 80°C oven for 10 minutes, and then rolled to a total thickness of 190 μm. Accordingly, the anode of Example 1 was obtained.

[0243] As the electrolyte, LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) (weight ratio of EC:PC:DEC = 3:2:5) to a concentration of 1.3 M, and 10 wt% of the additive fluoroethylene carbonate (FEC) was added to the total weight of the electrolyte.

[0245] Example 2

[0246] A cathode binder composition was prepared in the same manner as in Example 1, except that 6.4g of naphthyl methylamine was used instead of 10g of Example 1 in the aromatic hydrocarbon modification step, and 5.9g of N,N-dimethylethanolamine, a basic compound of Example 1, was used instead of 4.5g in the step of preparing the aqueous dispersion of the aromatic modified polyolefin resin. The cathode and lithium-ion battery manufacturing were carried out using the same process as in Example 1.

[0248] Example 3

[0249] A cathode binder composition was prepared in the same manner as in Example 1, except that 16g of naphthyl methylamine was used instead of 10g of Example 1 in the aromatic hydrocarbon modification step, and 1.8g of N,N-dimethylethanolamine, a basic compound of Example 1, was used instead of 4.5g in the step of preparing the aqueous dispersion of the aromatic modified polyolefin resin. The cathode and lithium-ion battery manufacturing were carried out using the same process as in Example 1.

[0251] Example 4

[0252] A cathode binder composition was prepared in the same manner as in Example 1, but 7g of benzyl amine was used instead of 10g of naphthyl methylamine in Example 1 during the aromatic hydrocarbon modification step. The cathode and lithium-ion battery manufacturing were carried out using the same process as in Example 1.

[0254] Example 5

[0255] A cathode binder composition was prepared in the same manner as in Example 4 above, but 24g of maleic anhydride was used instead of 30g in the acid modification step, 4g of benzyl amine was used instead of 7g of Example 4 in the aromatic hydrocarbon modification step, and 2.7g of N,N-dimethylethanolamine, a basic compound of Example 4, was used instead of 4.5g in the step of preparing the aqueous dispersion of the aromatic modified polyolefin resin. The cathode and lithium-ion battery manufacturing were carried out using the same process as in Example 1.

[0257] Example 6

[0258] A negative electrode binder composition was prepared in the same manner as in Example 1, except that 18g of pyrene methylamine was used instead of 10g of naphthyl methylamine in Example 1 during the aromatic hydrocarbon modification step. The manufacturing of the negative electrode and the lithium-ion battery were carried out using the same process as in Example 1.

[0260] Comparative Example 1

[0261] After preparing an acid-modified polyolefin resin in the same manner as in Example 1, an aqueous dispersion (anode binder composition) was prepared directly without aromatic hydrocarbon modification. The aqueous dispersion was prepared in the same manner as in Example 1, but 9g of the basic compound N,N-dimethylethanolamine was used instead of 4.5g. The manufacture of the anode and the lithium-ion battery were carried out using the same process as in Example 1.

[0263] Comparative Example 2

[0264] Instead of the cathode binder composition of Example 1 above, 6.25 g of water-dispersed SBR latex (solid content 40%, styrene:butadiene = 60:40 wt%) was used to manufacture a cathode and a lithium-ion battery using the same process as in Example 1.

[0266] Experimental Example: Evaluation of Cathode and Secondary Battery

[0267] For the above Examples 1 to 6 and Comparative Examples 1 to 2, the negative electrode and lithium secondary battery were evaluated under the following conditions, and the results were recorded in Table 1 below.

[0268] (1) Cathode adhesion

[0269] In a constant temperature chamber at 25°C, the cathode composite layer of each cathode was adhered to a glass substrate, and when the cathode was pulled at a peeling speed of 5 mm / min and a peeling angle of 180˚, the force by which the cathode composite layer of the cathode peeled from the glass substrate was measured.

[0270] (2) Rate of change in cathode thickness

[0271] Each of the above-prepared cathodes was immersed in the electrolyte for 24 hours, and the cathode thickness before and after immersion was measured using a thickness gauge, respectively, to evaluate the rate of change in cathode thickness according to [Equation 1] below. Here, the electrolyte used was an electrolyte of the same composition as that used in the manufacture of each lithium-ion battery.

[0272] [Equation 1] Rate of change in cathode thickness (%) = 100 × [Difference in thickness before and after electrolyte immersion] / [Thickness before electrolyte immersion]

[0273] (3) Battery capacity retention rate after 1,000 cycles

[0274] In a constant temperature chamber at 25°C, each lithium-ion battery was charged at 36 A in CC / CV mode to 4.15 V, and then discharged in CC mode to 3.0 V, constituting one cycle, with a 20-minute rest period between the charging and discharging, for a total of 1,000 cycles. The ratio of the discharge capacity measured in the 1,000th cycle to the discharge capacity measured in the first cycle was calculated according to [Equation 2] below.

[0275] [Equation 2] Capacity Retention Rate (%) = 100 × [Discharge Capacity after 1000 Cycles] / [Discharge Capacity after 1 Cycle]

[0277] Cathode adhesion (gf / cm) Cathode thickness change rate (%) Capacity retention rate (%) of secondary battery after 1,000 cycles Example 1 40 0.1 91 Example 2 37 0.1 90 Example 3 38 0.1 88 Example 4 36 0.1 89 Example 5 35 0.1 84 Example 6 39 0.1 90 Comparative Example 1 30 0.1 85 Comparative Example 2 35 1.5 86

[0278] As shown in Table 1 above, compared to Comparative Examples 1 and 2, Examples 1 to 6 show excellent cathode adhesion, thickness change rate, and capacity retention rate of the secondary battery after 1,000 cycles.

[0280] Specifically, in the case of SBR (Comparative Example 2) generally known in the industry, the initial adhesion strength is secured to be relatively high, but it is confirmed that there is a significant change in thickness before and after electrolyte loading.

[0281] In particular, significant changes in thickness before and after electrolyte impregnation indicate that the SBR expands as the electrolyte is impregnated, resulting in a loss of binding force to the negative electrode active material.

[0282] Although it was evaluated up to 1,000 cycles at the laboratory scale, it is predicted that when operating for a long period exceeding this, the electrolyte-impregnated SBR will further lose its binding strength to the negative electrode active material due to the shrinkage and expansion of the negative electrode active material, thereby impairing the cycle characteristics of the secondary battery.

[0284] Meanwhile, in the case of a polyolefin resin modified only by acid (Comparative Example 1), compared to SBR (Comparative Example 2), the change in thickness before and after electrolyte loading was reduced, but it was confirmed to have low initial adhesion.

[0285] In this regard, excellent electrolyte resistance is achieved due to the non-polarity of the polyolefin, but the effect of improving adhesion by introducing the acid functional group alone is confirmed to be lower than that of SBR (Comparative Example 2).

[0287] On the other hand, in the case of acid and aromatic hydrocarbon modified resins (Examples 1 to 6), it is confirmed that high initial adhesion is secured while changes in cathode thickness are suppressed.

[0288] This means that excellent electrolyte resistance is achieved through the non-polarity of the polyolefin, while the insufficient adhesion resulting from the introduction of acid functional groups alone is compensated for through aromatic hydrocarbon-based pendant functional groups.

[0289] In summary, by introducing acid functional groups and aromatic hydrocarbon pendant functional groups into the interior, terminals, or both of the polyolefin molecule, it is possible to simultaneously achieve excellent initial adhesion and electrolyte resistance characteristics. Through this, it is possible to maintain binding strength during the charge-discharge process and secure excellent cycle characteristics even during long-term operation of the secondary battery.

Claims

Claim 1 A binder for a negative electrode of a secondary battery comprising an acid and aromatic hydrocarbon modified resin, wherein the acid and aromatic hydrocarbon modified resin comprises a polyolefin and an acid functional group and an aromatic hydrocarbon pendant functional group located within, at, or both of the molecule of the polyolefin, wherein the aromatic hydrocarbon pendant functional group is derived from one or more selected from the group consisting of naphthalene, anthracene, and pyrene, and the aromatic hydrocarbon pendant functional group is substituted on the olefin via the acid functional group. Claim 2 delete Claim 3 A binder for the negative electrode of a secondary battery, wherein the acid functional group is derived from maleic anhydride. Claim 4 A binder for a negative electrode of a secondary battery, wherein the polyolefin is a homopolymer or copolymer of a C3 to C20 olefin having tertiary hydrogen. Claim 5 A binder for a negative electrode of a secondary battery, wherein the polyolefin is one or more selected from the group comprising polypropylene homopolymer, propylene-ethylene copolymer, propylene-butylene copolymer, and ethylene-propylene-butylene terpolymer. Claim 6 In claim 1, the acid and aromatic hydrocarbon modified resin comprises a repeating unit represented by the following Chemical Formula 1, a repeating unit represented by the following Chemical Formula 2, and a repeating unit represented by the following Chemical Formula 3, a binder for a negative electrode of a secondary battery: [Chemical Formula 1] [Chemical Formula 2] In the above chemical formula 2, L1 is directly bonded or NH, e.g., NH, and L2 is directly bonded, or substituted or unsubstituted C 1-10 It is an alkylene, e.g., C1-alkylene (i.e., CH2), and Ar1 is naphthyl, anthracenyl, or pyrenyl, [Chemical Formula 3] R1 is a substituent represented by the following chemical formula 3-1 or 3-2, [Chemical Formula 3-1] [Chemical Formula 3-2] In the above chemical formulas 3-1 and 3-2, respectively, the dotted line is connected to the above chemical formula 3. Claim 7 A binder for a negative electrode of a secondary battery according to claim 1, wherein the acid and aromatic hydrocarbon modified resin further comprises one or more of a repeating unit represented by the following chemical formula 4 and a repeating unit represented by the following chemical formula 5: [Chemical Formula 4] [Chemical Formula 5] . Claim 8 A binder for a negative electrode of a secondary battery according to claim 1, wherein the total amount of the acid functional group and the aromatic hydrocarbon pendant functional group is 0.5 to 15 weight% of the acid and aromatic hydrocarbon modified resin (100 weight%). Claim 9 A binder for a negative electrode of a secondary battery, wherein the binder composition further comprises an aqueous solvent in the first paragraph. Claim 10 A method for manufacturing a binder for a negative electrode of a secondary battery according to claim 1 comprises the steps of: reacting a polyolefin-based resin with an acid to produce an acid-modified resin; and reacting the acid-modified resin with an aromatic compound to produce an acid and aromatic hydrocarbon-modified resin. Claim 11 A method for manufacturing a binder for a negative electrode of a secondary battery, wherein, in the step of manufacturing the acid-modified resin according to claim 10, 1 to 30 parts by weight of acid is reacted based on 100 parts by weight of the polyolefin-based resin. Claim 12 A method for manufacturing a binder for a negative electrode of a secondary battery, wherein, in claim 10, the step of manufacturing the acid-modified resin is performed in a temperature range of 90 to 130 ℃. Claim 13 In claim 10, the step of preparing the acid and aromatic hydrocarbon modified resin involves reacting 1 to 30 parts by weight of an aromatic compound based on 100 parts by weight of the acid modified resin, a method for preparing a binder for a negative electrode of a secondary battery. Claim 14 A method for manufacturing a binder for a negative electrode of a secondary battery, wherein, in claim 10, the step of manufacturing the acid and aromatic hydrocarbon modified resin is performed in a temperature range of 90 to 130 ℃. Claim 15 A method for manufacturing a binder for a negative electrode of a secondary battery, further comprising, in claim 10, a step of preparing an aqueous dispersion containing the acid and aromatic hydrocarbon modified resin using an evaporation method after the step of preparing the acid and aromatic hydrocarbon modified resin. Claim 16 A method for manufacturing a negative electrode binder for a secondary battery, wherein the step of preparing an aqueous dispersion containing the acid and aromatic hydrocarbon modified resin comprises: a step of mixing the acid and aromatic hydrocarbon modified resin with a low-boiling point solvent having a boiling point of 100°C or lower and then raising the temperature to prepare a solution in which the acid and aromatic hydrocarbon modified resin is dissolved; a step of adding a basic solution dropwise to the solution in which the acid and aromatic hydrocarbon modified resin is dissolved; and a step of dispersing the acid and aromatic modified resin in water while adding distilled water dropwise and simultaneously distilling the low-boiling point solvent after adding the basic solution. Claim 17 A method for manufacturing a binder for a negative electrode of a secondary battery, wherein, in claim 16, the low-boiling point solvent is acetone, tetrahydrofuran, or a mixture thereof. Claim 18 A method for manufacturing a binder for a negative electrode of a secondary battery, further comprising, in claim 16, a step of cooling the aqueous dispersion of the acid and aromatic hydrocarbon modified resin to room temperature after the step of dispersing the acid and aromatic hydrocarbon modified resin; and a step of filtering the cooled aqueous dispersion of the acid and aromatic hydrocarbon modified resin. Claim 19 A negative electrode of a secondary battery comprising: a negative electrode current collector; and a negative electrode composite layer located on the negative electrode current collector and comprising the binder of claim 1 and a negative electrode active material. Claim 20 A secondary battery comprising the cathode of claim 19; the anode; and the electrolyte.

Images