Copolymer particles, binder composition comprising same, slurry, electrode, and secondary battery comprising electrode

Abstract

The present invention relates to: copolymer particles comprising a core part and a shell part surrounding the core part, the core part comprising a hard monomer unit and a soft monomer unit, and the shell part comprising an acrylic acid-based monomer unit, an acrylate-based monomer unit, an acrylamide-based monomer unit, or a combination thereof; a binder composition comprising the copolymer particles; a slurry; an electrode; and a secondary battery comprising the electrode.

Description

Copolymer particles, a binder composition containing the same, a slurry, an electrode, and a secondary battery containing the electrode

[0001] The present invention relates to copolymer particles, a binder composition comprising said copolymer particles, a slurry, an electrode, and a secondary battery comprising said electrode.

[0002] With the development of IT technologies such as laptops and mobile phones and the increasing demand, as well as the expansion of the electric and hybrid vehicle markets as alternatives to environmental issues and energy shortages, the demand for lithium-ion rechargeable batteries is also rising. Consequently, extensive research is being conducted to improve the performance of lithium-ion rechargeable batteries, including long lifespan, high output, high capacity, high density, and stability.

[0003] Typical lithium-ion rechargeable batteries use graphite as the negative electrode active material, and recently, there has been an increasing trend in the use of graphite-silicon-based active materials. However, as the process of lithium ions being inserted into the active material during charging and extracted during discharging is repeated, the volume of the active material undergoes expansion and contraction. Consequently, the active material separates from the electrode, leading to a decrease in battery capacity and a reduction in battery life as the cycle progresses.

[0004] This phenomenon is significantly increased in materials such as silicon and tin, which possess high discharge capacities; although the initial charge / discharge capacity is high, the discharge capacity tends to decrease rapidly as the cycle progresses.

[0005] Efforts are being made to improve electrode stability and battery performance by preventing this phenomenon by reducing the size of the active material to nano-size or modifying the shape of the active material, and by increasing the adhesion of the binder and suppressing volume expansion with the binder.

[0006] In particular, when using binders, if the adhesive strength of the binder is low, the charge-discharge cycle life of the secondary battery is reduced due to electrode detachment, and problems arise such as the binder acting as a resistor in the secondary battery when non-conductive binders are applied. Additionally, while multiple layers of thin-film electrodes are required to secure sufficient battery capacity, this necessitates the use of expensive separators and high-density current collectors, leading to issues regarding cost and volume. Therefore, the need for developing high-adhesion binders is being emphasized to extend the charge-discharge cycle life of the secondary battery, reduce internal resistance by decreasing binder usage, increase active material capacity, and thereby enable cost reduction of the material.

[0007] [Prior Art Literature]

[0008] [Patent Literature]

[0009] (Patent Document 1) Republic of Korea Registered Patent No. 10-1698745

[0010] The present invention aims to provide a copolymer particle comprising a core portion and a shell portion surrounding the core portion, wherein the core portion comprises hard monomer units and soft monomer units, and the shell portion comprises acrylic acid-based monomer units, acrylate-based monomer units, acrylamide-based monomer units, or a combination thereof, and a binder composition comprising the same.

[0011] In particular, the present invention aims to provide copolymer particles capable of inhibiting migration by increasing the bonding strength with an active material and a metal substrate as a result of polymerizing a copolymer comprising acrylic acid-based monomer units, acrylate-based monomer units, acrylamide-based monomer units, or a combination thereof in the shell portion.

[0012] In addition, the present invention aims to provide copolymer particles capable of improving resistance within a battery, extending battery life, and enhancing output performance by introducing a crosslinking agent into a binder.

[0013] In addition, the purpose is to provide copolymer particles and a binder composition containing the same that can produce a secondary battery having a high initial discharge capacity and excellent charge-discharge cycle characteristics, with excellent adhesion between the active material and the metal substrate and / or between the active material, excellent flexibility enabling the production of thick electrodes, and excellent stability and slurry dispersibility in the electrolyte.

[0014] In addition, the present invention aims to provide a slurry and an electrode comprising the copolymer particles, and a secondary battery comprising the electrode.

[0015] However, the problems that this invention seeks to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below.

[0016] One aspect of the present invention comprises a core portion and a shell portion surrounding the core portion, and

[0017] The above core portion includes hard monomer units and soft monomer units, and

[0018] The above shell portion comprises acrylic acid-based monomer units, acrylate-based monomer units, acrylamide-based monomer units, or a combination thereof.

[0019] Provides copolymer particles.

[0020] Another aspect of the present invention is a copolymer particle comprising,

[0021] A binder composition is provided.

[0022] Another aspect of the present invention is a copolymer particle and an electrode active material comprising,

[0023] Provides a slurry.

[0024] Another aspect of the present invention comprises an electrode active material layer comprising a current collector and copolymer particles formed on the current collector.

[0025] Provides an electrode.

[0026] Another aspect of the present invention is that the electrode comprises,

[0027] Provides a secondary battery.

[0028] The copolymer particles according to the present invention and the binder composition containing them can inhibit migration by increasing the bonding strength with the active material and the metal substrate as a result of polymerizing a copolymer comprising acrylic acid-based monomer units, acrylate-based monomer units, acrylamide-based monomer units, or a combination thereof in the shell portion.

[0029] In addition, the copolymer particles according to the present invention and the binder composition containing the same can provide copolymer particles capable of improving resistance within the battery, extending the battery life, and enhancing output performance by introducing a crosslinking agent into the binder.

[0030] In addition, the copolymer particles according to the present invention and the binder composition containing them improve the adhesion between the active material and the metal substrate and / or between the active material, enable the production of a flexible and non-breakable electrode film, and improve stability and slurry dispersibility within the electrolyte, thereby making it possible to secure a secondary battery having a high initial discharge capacity and excellent charge-discharge cycle characteristics.

[0031] In addition, when using copolymer particles with excellent adhesive strength and a binder composition containing them, only a small amount of the binder composition can be used, which can reduce the internal resistance of the secondary battery and increase the capacity of the active material.

[0032] The operation and effects of the invention will be described in more detail below through specific embodiments. However, these embodiments are merely examples of the invention and do not define the scope of the invention.

[0033] Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0034] Therefore, it should be understood that the configuration of the embodiments described in this specification is merely one of the most preferred embodiments of the present invention and does not represent all of the technical ideas of the present invention, and that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0035] In this specification, 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.

[0036] In the present specification, "a to b" and "a~b" indicating numerical ranges, "to" and "~" are defined as ≥a and ≤b.

[0037] A copolymer particle according to one aspect of the present invention comprises a core portion and a shell portion surrounding the core portion, wherein the core portion comprises a hard monomer unit and a soft monomer unit, and the shell portion may comprise an acrylic acid-based monomer unit, an acrylate-based monomer unit, an acrylamide-based monomer unit, or a combination thereof.

[0038] In one embodiment of the present invention, based on 100% by weight of the total weight of the copolymer particles, the content of the core portion may be 65% by weight or more and 98% by weight or less, and the content of the shell portion may be 2% by weight or more and 35% by weight or less.

[0039] For example, the content of the core part may be 70% to 95% by weight and the content of the shell part may be 5% to 30% by weight, the content of the core part may be 70% to 80% by weight and the content of the shell part may be 20% to 30% by weight, or the content of the core part may be 80% to 95% by weight and the content of the shell part may be 5% to 20% by weight.

[0040] If the content ratio of the core and shell portions exceeds or falls below the range of the present invention, the adhesion strength and capacity retention rate may decrease, and the internal resistance of the battery may increase.

[0041] In one embodiment of the present invention, the shell portion may be crosslinked with a crosslinking agent.

[0042] In one embodiment of the present invention, based on 100% by weight of the total weight of the copolymer particles, the content of the crosslinking agent may be 0.001% by weight or more and 0.015% by weight or less.

[0043] For example, based on 100% by weight of the total weight of the copolymer particles, the content of the crosslinking agent may be 0.002% by weight or more and 0.012% by weight or less, 0.002% by weight or more and 0.008% by weight or less, or 0.008% by weight or more and 0.012% by weight or less.

[0044] If the content of the above-mentioned crosslinking agent exceeds or falls below the range of the present invention, the adhesion strength and capacity retention rate may decrease, and the internal resistance of the battery may increase.

[0045] In one embodiment of the present invention, the crosslinking agent comprises a carbonyl group (-CO-), a vinyl group (-CH=CH₂), a methylvinyl group (-CH=C(CH3)₂), an ester group (-COO-), and a phosphate group (-OPO3). 2- It may include two or more functional groups selected from the group consisting of ), and sulfone groups (-SO₂-).

[0046] For example, the crosslinking agent may include a carbonyl group (-CO-) or an ester group (-COO-) as functional groups, or a methylvinyl group (-CH=C(CH3)₂), an ester group (-COO-), or a phosphate group (-OPO3 2- It may include ) or may include a vinyl group (-CH=CH₂) or a sulfone group (-SO₂-).

[0047] In one embodiment of the present invention, the crosslinking agent is divinylbenzene, divinylsulfone, methacrylic anhydride, acrylic anhydride, 1-(acryloyloxy)-3-(methacryloyloxy)-2-propanol, 1,3-butanediol dimethacrylate, bis(4-methacryloylthiophenyl) sulfide, 1,9-bis(acryloyloxy)nonane, or 1,6-hexanediol diacrylate (1,6-Hexanediol diacrylate), 1,7-Octadiene-3,5-diol diacrylate, 2,2'-Oxybis(ethyl methacrylate), 1,3-Propanediol diacrylate, Polycaprolactone triacrylate, 1,4-Cyclohexanediol diacrylate, Dipentaerythritol hexacrylate, Ethylene glycol dimethacrylate, Trimethylolpropane trimethacrylate trimethacrylate), propylene glycol diacrylate, 1,6-hexanediol trimethacrylate,Tricyclodecane dimethanol diacrylate, Allyl methacrylate, 1,4-Butanediol trimethacrylate, 1,2-Ethanediol diacrylate, Trimethylolpropane triacrylate, Butyl acrylate-methacrylic acid copolymer, Tetraethylene glycol diacrylate, Diethylene glycol diacrylate, Ethoxylated trimethylolpropane triacrylate, Pentaerythritol triacrylate triacrylate), Polyethylene glycol diacrylate, 2-Hydroxy-3-phenoxypropyl acrylate, Bisphenol A diglycidyl ether diacrylate, 2-Phenoxyethyl acrylate, Bisphenol A ethoxylate diacrylate, Neopentyl glycol diacrylate, 2-Hydroxy-3-phenoxypropyl methacrylate, Bisphenol A propoxylate dimethacrylate,Trimethylolpropane ethoxylate triacrylate, Ethoxylated bisphenol A dimethacrylate, Ethoxylated trimethylolpropane trimethacrylate, Di(pentaerythritol) hexaacrylate, Polyethylene glycol dimethacrylate, Tetrahydrofurfuryl acrylate, 1,3-Butanediol diacrylate, Propoxylated glycerol triacrylate, Pentaerythritol triacrylate, Dipentaerythritol pentaacrylate, 1,10-Decanediol diacrylate, Bis(2-(methacryloyloxy)ethyl) phosphate, 1,12-Dodecanediol diacrylate, 1,5-Pentanediol diacrylate, Glycerol ethoxylate triacrylate, Trimethylolpropane tris(2-ethylhexanoate), Bis(4-methacryloyloxyphenyl) methane (Bis(4-methacryloyloxyphenyl)methane),It may be di(trimethylolpropane) tetraacrylate, 2,2,4-trimethyl-1,3-pentanediol diacrylate, isobornyl acrylate, bisphenol A glycerolate dimethacrylate, 1,4-butanediol diacrylate, or a combination thereof, but is not limited thereto.

[0048] For example, the crosslinking agent may be divinyl benzene, divinyl sulfone, diethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, or a combination thereof.

[0049] Meanwhile, the above-mentioned crosslinking agent may be divinylbenzene.

[0050] In one embodiment of the present invention, the core portion of the copolymer particle may comprise 1.0 to 3.0 parts by weight of the soft monomer unit per 1 part by weight of the hard monomer unit.

[0051] For example, the core portion of the copolymer particle may comprise 1.0 to 2.7 parts by weight of the soft monomer unit, 1.0 to 2.3 parts by weight of the soft monomer unit, 1.0 to 2.0 parts by weight of the soft monomer unit, 1.3 to 2.0 parts by weight of the soft monomer unit, 1.3 to 1.7 parts by weight of the soft monomer unit, or 1.4 to 1.6 parts by weight of the soft monomer unit per 1 part by weight of the hard monomer unit.

[0052] If the weight ratio of the soft monomer unit and the hard monomer unit exceeds or falls below the range of the present invention, the adhesive strength and capacity retention rate may decrease, and the internal resistance of the battery may increase.

[0053] In one embodiment of the present invention, the soft monomer unit may be formed by polymerizing a conjugated diene-based monomer, an acrylate-based monomer, or a combination thereof.

[0054] In one embodiment of the present invention, the conjugated diene series monomer may be 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, or a combination thereof, but is not limited thereto.

[0055] For example, the above conjugated diene series monomer may be 1,3-butadiene, 1,3-pentadiene, or a combination thereof.

[0056] Meanwhile, the above conjugated diene series monomer may be 1,3-butadiene.

[0057] In one embodiment of the present invention, the acrylate series monomer is methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-hexyl acrylate, 2-hexyl methacrylate, n-amyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, lauryl methacrylate, stearyl acrylate, It may be sec-butyl acrylate or a combination thereof, but is not limited thereto.

[0058] For example, the above acrylate series monomer may be methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, or a combination thereof.

[0059] Meanwhile, the above acrylate-based monomer may be ethyl acrylate.

[0060] In one embodiment of the present invention, the hard monomer unit may be formed by polymerizing a styrene-based monomer, an acrylate-based monomer, an acrylonitrile-based monomer, an acrylamide-based monomer, or a combination thereof.

[0061] In one embodiment of the present invention, the styrene-based monomer may be styrene, α-methylstyrene, β-methylstyrene, pt-butylstyrene, divinylbenzene, or a combination thereof, but is not limited thereto.

[0062] For example, the above styrene series monomer may be styrene, α-methylstyrene, divinylbenzene, or a combination thereof.

[0063] Meanwhile, the above-mentioned styrene-based monomer may be styrene.

[0064] In one embodiment of the present invention, the acrylate-based monomer is methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, It may be isobornyl acrylate, isovinyl acrylate, isovinyl methacrylate, stearyl methacrylate, sec-butyl methacrylate, or a combination thereof, but is not limited thereto.

[0065] For example, the above acrylate series monomer may be methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, or a combination thereof.

[0066] Meanwhile, the above acrylate-based monomer may be ethyl methacrylate.

[0067] In one embodiment of the present invention, the acrylonitrile-based monomer may be acrylonitrile, methacrylonitrile, or a combination thereof, but is not limited thereto.

[0068] In one embodiment of the present invention, the acrylamide-based monomer may be acrylamide, methacrylamide, n-methylolacrylamide, n-butoxymethylacrylamide, or a combination thereof, but is not limited thereto.

[0069] For example, the above-mentioned acrylamide series monomer may be methacrylamide, n-methylolacrylamide, or a combination thereof.

[0070] In one embodiment of the present invention, the core portion of the copolymer particle may be formed by polymerizing 1,3-butadiene, styrene, and ethyl methacrylate.

[0071] For example, the weight ratio of 1,3-butadiene, styrene, and ethyl methacrylate (weight of 1,3-butadiene : weight of styrene : weight of ethyl methacrylate) can be 5 to 8 : 2 to 4 : 1.

[0072] If the weight ratio of 1,3-butadiene, styrene, and ethyl methacrylate exceeds or falls below the range of the present invention, the adhesion and capacity retention rate may decrease, and the internal resistance of the battery may increase.

[0073] In one embodiment of the present invention, based on 100% by weight of the total weight of the copolymer of the shell portion, the content of the acrylic acid-based monomer unit is 50% by weight or more and 70% by weight or less, the content of the acrylate-based monomer unit is 30% by weight or more and 50% by weight or less, and the content of the acrylamide-based monomer unit is 0% by weight or more and 20% by weight or less.

[0074] For example, based on 100% by weight of the total weight of the copolymer of the shell portion, the content ratio of the acrylic acid-based monomer unit, the acrylate-based monomer unit, and the acrylamide-based monomer unit (content of acrylic acid-based monomer unit : content of acrylate-based monomer unit : content of acrylamide-based monomer unit) may be 50% to 80% by weight : 20% to 50% by weight : 0% to 15% by weight, 55% to 75% by weight : 25% to 45% by weight : 0% to 10% by weight, 58% to 72% by weight : 28% to 42% by weight : 0% to 8% by weight, or 60% to 65% by weight : 35% to 40% by weight : 0% to 5% by weight.

[0075] If the content ratio of the above acrylic acid-based monomer unit, the above acrylate-based monomer unit, and the above acrylamide-based monomer unit exceeds or falls below the range of the present invention, the adhesive strength and capacity retention rate may decrease, and the internal resistance of the battery may increase.

[0076] In one embodiment of the present invention, the acrylic acid-based monomer unit included in the shell portion may be formed by polymerizing methacrylic acid, acrylic acid, itaconic acid, or a combination thereof, but is not limited thereto.

[0077] For example, the acrylic acid-based monomer unit included in the shell portion may be formed by polymerizing methacrylic acid, acrylic acid, or a combination thereof.

[0078] Meanwhile, the acrylic acid-based monomer unit included in the shell portion can be formed by polymerizing acrylic acid.

[0079] In one embodiment of the present invention, the acrylate-based monomer unit included in the shell portion comprises polyethylene glycol monomethacrylate (containing polyethylene glycol chains with an average molecular weight of approximately 300 to 20,000), polyethylene glycol monoethyl ether acrylate (containing polyethylene glycol chains with an average molecular weight of approximately 300 to 20,000), 2-(dimethylamino)ethyl acrylate, 2-(diethylamino)ethyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate, and methyl acrylate. acrylate), ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-hexyl methacrylate, n-amyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, lauryl methacrylate,It may be formed by polymerizing 3-[[2-(acryloyloxy)ethyl]dimethylammonium]propane-1-sulfonate, mono(2-acryloyloxyethyl)succinate, stearyl acrylate, stearyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, or a combination thereof, but is not limited thereto.

[0080] For example, the acrylate-based monomer unit included in the shell portion may be formed by polymerizing ethyl acrylate, propyl acrylate, isopropyl acrylate, or a combination thereof.

[0081] Meanwhile, the acrylate-based monomer unit included in the shell portion may be formed by polymerizing ethyl acrylate.

[0082] In one embodiment of the present invention, the acrylamide-based monomer unit included in the shell portion may be formed by polymerizing acrylamide, methacrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, N-dodecylacrylamide, N-(hydroxymethyl)acrylamide, N-(hydroxyethyl)acrylamide, 6-acrylamidohexanoic acid, or a combination thereof, but is not limited thereto.

[0083] For example, the acrylamide-based monomer unit included in the shell portion may be formed by polymerizing acrylamide, methacrylamide, or a combination thereof.

[0084] In one embodiment of the present invention, the shell portion of the copolymer particle may be formed by polymerizing acrylic acid and ethyl acrylate.

[0085] For example, the weight ratio of acrylic acid and ethyl acrylate (weight of acrylic acid : weight of ethyl acrylate) can be 1 to 2 : 1.

[0086] If the weight ratio of acrylic acid and ethyl acrylate exceeds or falls below the range of the present invention, the adhesive strength and capacity retention rate may decrease, and the internal resistance of the battery may increase.

[0087] In one embodiment of the present invention, the glass transition temperature of the soft monomer unit may be less than 20°C, and the glass transition temperature of the hard monomer unit may be 20°C or higher.

[0088] The above glass transition temperatures were each measured using TA's DSC.

[0089] In one embodiment of the present invention, the glass transition temperature (Tg) of the copolymer particles may be -20 ℃ to 10 ℃.

[0090] The above glass transition temperatures were each measured using TA's DSC.

[0091] For example, the glass transition temperature (Tg) of the copolymer particles may be -18 ℃ to 8 ℃, -18 ℃ to 7 ℃, -17 ℃ to 7 ℃, -16 ℃ to 7 ℃, -15 ℃ to 6 ℃, or -14 ℃ to 5 ℃.

[0092] The above copolymer particles have a low glass transition temperature (Tg) of -20°C to 10°C, and because they are hydrophobic compared to copolymers used as binders in conventional batteries, migration is suppressed and the film formation speed is fast, resulting in high adhesion.

[0093] In addition, since the copolymer particles are highly crosslinked, they have high elasticity and excellent adhesion, as well as excellent flexibility due to their low glass transition temperature (Tg). Therefore, the copolymer particles can be used in the production of thick electrodes.

[0094] If the glass transition temperature (Tg) of the copolymer particles exceeds the range of the present invention, a decrease in adhesion between the active material and the metal substrate and / or between the active material may occur, and if it falls below, the stability of the electrode coating may decrease.

[0095] In one embodiment of the present invention, the average particle size of the copolymer particles may be 200 nm to 900 nm.

[0096] The average particle size of the above copolymer particles was measured using Malvern's Mastersizer and SEM.

[0097] For example, the average particle size of the copolymer particles may be 200 nm to 850 nm, 200 nm to 800 nm, 200 nm to 400 nm, 400 nm to 800 nm, 200 nm to 250 nm, 250 nm to 300 nm, 300 nm to 500 nm, 500 nm to 700 nm, 700 nm to 800, or 800 nm to 850 nm.

[0098] If the average particle size (average diameter) of the copolymer particles exceeds the range of the present invention, slurry stability may be reduced and electrode processability may be reduced, and if it falls below, a decrease in adhesion between the active material and the metal substrate and / or between the active material may occur.

[0099] In one embodiment of the present invention, the degree of gelation measured by solidifying the binder containing the copolymer particles may be 80% or more and 99% or less.

[0100] At this time, the degree of gelation measures the extent to which the solidified binder containing the copolymer particles does not leach out in the solvent. For example, the solvent may be tetrahydrofuran (THF).

[0101] In one embodiment of the present invention, the acidity of the binder solution containing the copolymer particles may be pH 7 or higher and pH 10 or lower.

[0102] pH was measured using a pH meter from TOA.

[0103] If the pH of the copolymer particles exceeds the range of the present invention, deterioration of the binder may occur.

[0104] In one embodiment of the present invention, the mixture may include an emulsifier, and the content of the emulsifier may be 1 to 10 parts by weight per 100 parts by weight of the first monomer mixture. In addition, a surfactant may be used as the emulsifier, and the surfactant may be anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants, and preferably, anionic surfactants may be used.

[0105] Specific examples of the above-mentioned anionic surfactants include, but are not limited to, alkali salts of higher fatty acids, N-acryl amino acids, alkyl ether carbonates, acylated peptides, alkyl sulfonates, alkylbenzenes, alkyl amino acids, alkyl naphthalene sulfonates, sulfosuccinates, sulfated oils, alkyl sulfates, alkyl ether sulfates, alkyl aryl ether sulfates, alkyl amide sulfates, alkyl phosphates, alkyl ethriphosphates, and alkyl aryl ether triphosphates, and preferably, sodium dodecylbenzene sulfonate may be used.

[0106] A binder composition according to one aspect of the present invention may include one or more of the copolymer particles.

[0107] A slurry according to one aspect of the present invention may include one or more of the copolymer particles and an electrode active material.

[0108] In one embodiment of the present invention, the slurry may include organic solvents such as carboxymethylcellulose, NMP (N-methylpyrrolidone), DMF (dimethylformamide), acetone, dimethylacetamide, or water as a solvent, and preferably, carboxymethylcellulose may be used. In addition, the slurry may include one or more solvents.

[0109] The above carboxymethylcellulose may have a degree of substitution of hydroxyl (-OH) groups by carboxymethyl groups (-CH2CO2H) of 0.7 to 1.2, a molecular weight (Mn) of 500,000 to 900,000, and a pH of 6.5 to 8.0.

[0110] In one embodiment of the present invention, the slurry may contain the copolymer particles in an amount of 0.1% to 10% by weight per 100% by weight of the slurry. For example, the slurry may contain the copolymer particles in an amount of 0.1% to 8% by weight, 0.1% to 6% by weight, 0.1% to 4% by weight, or 0.1% to 3% by weight per 100% by weight of the slurry. Additionally, the slurry may include carboxymethylcellulose (CMC) and an electrode active material capable of intercalation and deintercalation of lithium ions.

[0111]

[0112] An electrode according to one aspect of the present invention may include a current collector and an electrode active material layer comprising copolymer particles formed on the current collector. The electrode may be a positive electrode or a negative electrode.

[0113] In one embodiment of the present invention, the adhesion strength of the cathode using the cathode slurry containing the copolymer particles may be 30 gf / cm or more.

[0114] For example, it may be 30 gf / cm or more, 60 gf / cm or less, 35 gf / cm or more, 55 gf / cm or less, 40 gf / cm or more, 55 gf / cm or less, 42.1 gf / cm or more, 50.1 gf / cm or less, 42.1 gf / cm or more, 47.6 gf / cm or less, 47.6 gf / cm or more, 50.1 gf / cm or less, 40 gf / cm or more, 43 gf / cm or less, 43 gf / cm or more, 48 gf / cm or less, or 48 gf / cm or more, 55 gf / cm or less.

[0115] In one embodiment of the present invention, the binding force gradient of the cathode using the cathode slurry containing the copolymer particles may be 60% or more.

[0116] For example, it may be 60% or more and 98% or less, 65% or more and 95% or less, 70% or more and 95% or less, 75% or more and 95% or less, 80% or more and 95% or less, 82% or more and 95% or less, 82% or more and 90% or less, 90% or more and 95% or less, 80% or more and 85% or less, 85% or more and 91% or less, or 91% or more and 95% or less.

[0117]

[0118] In one embodiment of the present invention, the current collector is a part where electron movement occurs in the electrochemical reaction of the active material, and depending on the type of electrode, there are negative current collectors and positive current collectors. The current collector may strengthen the bonding force of the electrode active material by forming fine irregularities on its surface, and can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0119] The above negative current collector can generally be formed with a thickness of 5 μm to 30 μm. Such a negative current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof may be used.

[0120] The above positive current collector can generally be formed with a thickness of 3 μm to 500 μm. The above positive current collector is not particularly limited as long as it has high conductivity 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., aluminum-cadmium alloy, etc. may be used.

[0121]

[0122] In one embodiment of the present invention, the electrode active material is a material capable of causing an electrochemical reaction and is used in the manufacture of cathode and anode slurries, and depending on the type of electrode, there is a cathode active material and an anode active material.

[0123]

[0124] The above-mentioned negative electrode active material may be selected from one or more of the group consisting of carbon and graphite materials capable of intercalation and deintercalation of lithium ions, Si-based materials, metals and compounds capable of alloying with lithium, composites of metals and their compounds with carbon and graphite materials, lithium-containing nitrides, etc.

[0125] Carbon and graphite materials include natural graphite, synthetic graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotubes, fullerene, activated carbon, hard carbon, and soft carbon. Si-based materials include Si and SiO.x (0 <x<2), Si-Y 합금(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 또는 이들의 조합이다.), Si-C 복합체 또는 이들의 조합의 Si계 화합물 등이 있다. 리튬과 합금이 가능한 금속 및 원소로는 Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt, Ti 등이 있다. 상기 음극 슬러리는 상기 음극 활물질을 상기 음극 슬러리 100 중량부에 대하여 20 내지 80중량부의 함량으로 포함할 수 있다.

[0126]

[0127] As for the above positive electrode active material, a lithium transition metal oxide may be used alone, or in some cases, other positive electrode active materials capable of absorbing and releasing lithium ions may be mixed and used.

[0128] For example, the above-mentioned positive 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+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-y Ni-site type lithium nickel oxide represented by MyO2 (where M is Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y = 0.01 to 0.3); chemical formula LiMn 2-yLithium manganese complex oxides represented by MyO2 (where M = Co, Ni, Fe, Cr, Zn or Ta and y = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the Li of the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc. may be used, but are not limited to these.

[0129] In addition, the above-mentioned positive active material is Li a Ni x Mn y Co z O2(0.8≤a<1.2, 0.2≤x<1, 0 <y<1, 0<z<1, x+y+z=1이다)로 표시되는 리튬 니켈-망간 코발트 산화물 및 LiCoO2를 포함할 수 있다. 상기 화학식 1로 표시되는 리튬 전이금속 산화물은 높은 방전 용량을 나타내는 바, 전체 양극 활물질에 대하여 적어도 20 중량 % 이상의 함량으로 포함되어 있는 것이 바람직하고, 더욱 바람직하게는 20 중량 % 내지 90 중량 %로 포함될 수 있다. LiCoO2는 양극 활물질 전체 중량을 기준으로 20 중량 % 내지 80 중량 %로 포함될 수 있다.

[0130]

[0131] A secondary battery according to one aspect of the present invention may include the electrode.

[0132]

[0133] In one embodiment of the present invention, the internal resistance of the secondary battery including a cathode using a cathode slurry containing the copolymer particles may be 248 mΩ or less.

[0134] For example, the internal resistance of the above secondary battery may be 240 mΩ or more and 248 mΩ or less, 242 mΩ or more and 248 mΩ or less, 244.3 mΩ or more and 247.2 mΩ or less, 244.3 mΩ or more and 245.1 mΩ or less, 245.1 mΩ or more and 247.2 mΩ or less, 243 mΩ or more and 245 mΩ or less, 245 mΩ or more and 246 mΩ or less, or 246 mΩ or more and 248 mΩ or less.

[0135] That is, in the case of a secondary battery manufactured using copolymer particles in which the weight ratio of the core and shell portions and the content of the crosslinking agent satisfy the scope of the present invention, excellent adhesion between the active material and the metal substrate and / or between the active material is achieved even with the use of a smaller amount of copolymer particles, and there is an effect of reducing the resistance value inside the battery as measured by DC-IR.

[0136]

[0137] In one embodiment of the present invention, the capacity retention rate of the secondary battery including a cathode using a cathode slurry containing the copolymer particles may be 95% or higher.

[0138] For example, the capacity retention rate of the above secondary battery may be 95% or more and 99% or less, 96% or more and 98% or less, 97.1% or more and 98.1% or less, 98.1% or more and 98.5% or less, or 97.1% or more and 98.5% or less.

[0139]

[0140] In one embodiment of the present invention, the secondary battery may include a separator. The separator may be an insulating thin film having high ion permeability and mechanical strength, interposed between the positive electrode and the negative electrode. The pore diameter of the separator may generally be 0.01 μm to 10 μm, and the thickness may generally be 5 μm to 300 μm. For example, an olefin-based polymer such as chemically resistant and hydrophobic polypropylene; a sheet or nonwoven fabric made of glass fiber or polyethylene, etc. may be used as such a separator. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as the separator.

[0141] The above lithium salt-containing non-aqueous electrolyte consists of an electrolyte and a lithium salt, and the electrolyte may be a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, etc.

[0142] As the above-mentioned non-aqueous organic solvent, for example, aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfranc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, ethyl propionate, etc. may be used.

[0143] 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.

[0144] As the above-mentioned inorganic solid electrolyte, for example, nitrides, halides, and 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.

[0145] 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 10 LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, imide, etc. may be used.

[0146] In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., the electrolyte may also be supplemented 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 included, and carbon dioxide may be further included to improve high-temperature preservation characteristics, and fluoro-ethylene carbonate (FEC), propene sultone (PRS), fluoro-propylene carbonate (FPC), ethylene carbonate (EC), ethyl methyl carbonate, diethyl carbonate, etc. may be further included.

[0147]

[0148] In one embodiment of the present invention, the secondary battery can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells used as a power source for a medium-to-large device.

[0149] Preferred examples of the above medium-to-large devices include, but are not limited to, power tools that are powered by an electric motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); and electric golf carts.

[0150] The present invention will be explained in more detail below through examples. However, the following examples are intended to explain the invention more specifically, and the scope of the invention is not limited by the following examples.

[0151]

[0152] Examples and Comparative Examples: Preparation of Copolymer Particles

[0153] [Example 1]

[0154] Manufacturing of the core part

[0155] 60 g of 1,3-butadiene, 30 g of styrene, and 10 g of ethyl methacrylate monomer were each added to 200 g of distilled water, and 0.5 g of sodium dodecylbenzene sulfonate was added as an anionic surfactant to emulsify and then stirred. 1 g of potassium sulfite, a decomposition initiator, was added to carry out the polymerization reaction to produce polymer particles that serve as the core.

[0156]

[0157] Preparation of core-shell type copolymer particles

[0158] Afterwards, 50 g of distilled water was added to the polymer particles that form the core part, 10 g of ethyl acrylate, 15 g of acrylic acid, 0.01 g of divinyl benzene as a crosslinking agent, and 0.2 g of potassium sulfite as an initiator were added and stirred further to form a shell part, thereby producing core-shell type copolymer particles.

[0159] Finally, the acidity was adjusted to pH 7–9 using an aqueous sodium hydroxide solution.

[0160] At this time, the weight ratio of the core part to the shell part was manufactured as 80:20.

[0161]

[0162] [Example 2]

[0163] Copolymer particles were prepared according to Example 1, except that the content of each monomer and the content of the crosslinking agent (52 g of 1,3-butadiene and 26 g of styrene, 9 g of ethyl methacrylate, 15 g of ethyl acrylate, 24 g of acrylic acid, and 0.015 g of divinylbenzene as a crosslinking agent) were changed.

[0164] At this time, the weight ratio of the core part to the shell part was manufactured as 70:30.

[0165]

[0166] [Example 3]

[0167] Copolymer particles were prepared according to Example 1, except that the content of each monomer and the content of the crosslinking agent (70 g of 1,3-butadiene and 35 g of styrene, 12 g of ethyl methacrylate monomer, 2.5 g of ethyl acrylate, 4 g of acrylic acid, and 0.0025 g of divinyl benzene as a crosslinking agent) were changed.

[0168] At this time, the weight ratio of the core part to the shell part was manufactured to be 95:5.

[0169]

[0170] [Comparative Example 1]

[0171] Copolymer particles were prepared according to Example 1, except that a shell portion was not formed.

[0172] That is, copolymer particles consisting only of a core part and not a shell part of Example 1 were prepared.

[0173]

[0174] [Comparative Example 2]

[0175] Copolymer particles were prepared by adding 10 g of ethyl acrylate, 15 g of acrylic acid, 0.01 g of divinyl benzene as a crosslinking agent, and 0.2 g of potassium sulfite as an initiator to 200 g of distilled water and stirring.

[0176] Finally, the acidity was adjusted to pH 7–9 using an aqueous sodium hydroxide solution.

[0177]

[0178] [Comparative Example 3]

[0179] Copolymer particles were prepared according to Example 1, except that the content of each monomer and the content of the crosslinking agent (38 g of 1,3-butadiene and 19 g of styrene, 6 g of ethyl methacrylate monomer, 25 g of ethyl acrylate, 40 g of acrylic acid, and 0.025 g of divinyl benzene as a crosslinking agent) were changed.

[0180] At this time, the weight ratio of the core part and the shell part was manufactured to be 50:50.

[0181]

[0182] [Comparative Example 4]

[0183] Copolymer particles were prepared according to Example 1, except that the content of each monomer and the content of the crosslinking agent (22 g of 1,3-butadiene and 11 g of styrene, 7 g of ethyl methacrylate monomer, 35 g of ethyl acrylate, 52 g of acrylic acid, and 0.035 g of divinyl benzene as a crosslinking agent) were changed.

[0184] At this time, the weight ratio of the core part to the shell part was manufactured to be 30:70.

[0185]

[0186] Table 1 below shows the relative weight ratio of the core and shell portions constituting the copolymer particles in Examples 1 to 3 and Comparative Examples 1 to 4.

[0187] In addition, the average particle size of the copolymer particles in Examples 1 to 3 and Comparative Examples 1 to 4 was shown.

[0188]

[0189] Core part : Shell part (Weight ratio) Average particle size (nm) Example 1 80 : 20 400 Example 2 70 : 30 800 Example 3 95 : 5 200 Comparative Example 1 100 : 0 150 Comparative Example 20 : 100 180 Comparative Example 3 50 : 50 1000 Comparative Example 4 30 : 70 1200

[0190]

[0191] Preparation Example: Preparation of cathode slurry, cathode, and battery

[0192] A cathode slurry was prepared by mixing 97 parts by weight of graphite as a cathode active material, 1.8 parts by weight of copolymer particles of Examples 1 to 3 and Comparative Examples 1 to 4, and 1.2 parts by weight of carboxymethylcellulose with distilled water.

[0193] The above cathode slurry was uniformly coated onto a Cu thin film with a thickness of 10 μm using an applicator, and then dried at a temperature of 100°C for 30 minutes to produce a cathode.

[0194] A positive electrode was prepared by mixing lithium nickel-manganese cobalt oxide as the positive active material, acetylene black as the conductive material, and polyvinylidene fluoride (PVDF) as the positive binder in a weight ratio of 92:4:4 and coating the mixture onto an aluminum collector. An electrolyte was prepared by dissolving LiPF6 to a concentration of 1M in a non-aqueous solvent having a composition of ethylene carbonate (EC):ethylmethyl carbonate (EMC):diethyl carbonate (DEC) = 1:2:1. A full cell was prepared using a porous polyethylene film as the separator.

[0195] Table 2 below shows the types of copolymer particles used for each battery.

[0196]

[0197] Copolymer particles used Preparation Example 1 Example 1 Preparation Example 2 Example 2 Preparation Example 3 Example 3 Comparative Preparation Example 1 Comparative Example 1 Comparative Preparation Example 2 Comparative Example 2 Comparative Preparation Example 3 Comparative Example 3 Comparative Preparation Example 4 Comparative Example 4

[0198]

[0199] [Evaluation Example]

[0200] Evaluation Example 1: Measurement of Electrode Adhesion (UTM)

[0201] The cathodes of Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 4, prepared using the copolymer particles of Examples 1 to 3 and Comparative Examples 1 to 4, were cut to a size of 25 mm in width and 100 mm in length.

[0202] A double-sided tape with a width of 20 mm and a length of 40 mm was attached to an acrylic plate with a width of 40 mm and a length of 100 mm. After attaching the prepared electrode to the double-sided tape, it was lightly pressed 5 times with a hand roller. It was then mounted on a UTM (20 kgf Load cell) to peel off approximately 25 mm of one side of the cathode. The cathode was then secured to the upper clip of the tensile strength tester, and the tape attached to one side of the cathode was secured to the lower clip. The electrode was peeled off at a speed of 100 mm / min, and the force required to detach the electrode in the 180° direction was measured. At least 5 specimens were prepared and measured per sample, and the average value was calculated. The results are shown in Table 3 below.

[0203]

[0204] Adhesion strength of cathode electrode (gf / cm) (UTM) Preparation Example 150.1 Preparation Example 247.6 Preparation Example 342.1 Comparative Preparation Example 126.7 Comparative Preparation Example 210.1 Comparative Preparation Example 317.1 Comparative Preparation Example 415.8

[0205]

[0206] As a result of the measurement, as shown in Table 3 above, it was confirmed that the cathodes of Preparation Examples 1 to 3 had a high adhesion strength of 42.1 gf / cm or higher. That is, in the case of the cathodes of Preparation Examples 1 to 3 prepared including the copolymer particles of Examples 1 to 3, it was confirmed that they had a higher adhesion strength when compared to the cathodes of Comparative Preparation Examples 1 to 4 prepared including the copolymer particles of Comparative Examples 1 to 4.

[0207] In addition, when comparing the adhesion strength measured at the cathodes of Preparation Examples 1 to 3, the cathode of Preparation Example 1 had the highest adhesion strength of 50.1 gf / cm, indicating that the adhesion strength is higher when the weight ratio of the core part to the shell part in the copolymer particles used to manufacture each electrode approaches 80:20, and it was also confirmed that the adhesion strength is higher when the content of the crosslinking agent approaches 0.008 wt% based on 100 wt% of the total weight of the copolymer particles.

[0208] This means that when the weight ratio of the core and shell portions and the content of the crosslinking agent satisfy the range of the present invention, a cathode having superior adhesion between the active material and the metal substrate can be obtained.

[0209]

[0210] Evaluation Example 2: Evaluation of Bonding Gradient (Layered Bonding)

[0211] The binding force gradient of the cathodes of Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 4, prepared using the copolymer particles of Examples 1 to 3 and Comparative Examples 1 to 4, was measured using a surface and interfacial cutting analysis system (SAICAS).

[0212] To measure the adhesion gradient, the adhesion strength was measured at a depth of 30% and 90% from the surface of the cathode (composite layer), respectively, and then the adhesion gradient was calculated according to the following mathematical formula 1.

[0213]

[0214] [Mathematical Formula 1]

[0215] Bonding Gradient [%] = (Binding strength at 90% depth from the surface of the composite layer / Bonding strength at 30% depth from the surface of the composite layer) × 100

[0216]

[0217] The calculated binding force gradient is shown in Table 4 below.

[0218]

[0219] Cathode Adhesion Gradient (%) Preparation Example 190.0 Preparation Example 294.4 Preparation Example 382.1 Comparative Preparation Example 153.7 Comparative Preparation Example 235.0 Comparative Preparation Example 333.3 Comparative Preparation Example 429.9

[0220]

[0221] As a result of measurement, as shown in Table 4 above, it was confirmed that the cathodes of Preparation Examples 1 to 3 had a high binding strength gradient of 82.1% or higher. That is, in the case of the cathodes of Preparation Examples 1 to 3 prepared including the copolymer particles of Examples 1 to 3, it was confirmed that they had a higher binding strength gradient when compared to the cathodes of Comparative Preparation Examples 1 to 4 prepared including the copolymer particles of Comparative Examples 1 to 4.

[0222] In addition, when comparing the binding strength gradients measured at the cathodes of Preparation Examples 1 to 3, the cathode of Preparation Example 2 had the highest binding strength gradient of 94.4%, indicating that the binding strength gradient is higher as the weight ratio of the core part to the shell part in the copolymer particles used to manufacture each electrode approaches 70:30, and it was also confirmed that the binding strength gradient is higher as the content of the crosslinking agent approaches 0.012 wt% based on 100 wt% of the total weight of the copolymer particles.

[0223] This means that when the weight ratio of the core and shell portions and the content of the crosslinking agent satisfy the range of the present invention, a cathode having superior adhesion between the active material and the metal substrate can be obtained.

[0224]

[0225] Evaluation Example 3: Measurement of battery capacity retention rate

[0226] For the batteries prepared in Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 4, the charge termination voltage was set to 4.2V and the discharge termination voltage to 2.8V at 25°C, and the charge / discharge current density was changed sequentially to 0.1C, 0.2C, and 0.5C, and a total of 3 charge / discharge cycles were performed once each.

[0227] Afterwards, 100 charge-discharge cycles were performed with a charge-discharge current density of 1C, a charge termination voltage of 4.2V, and a discharge termination voltage of 2.8V.

[0228] All discharges were performed under constant current / constant voltage conditions, and the termination current of the constant voltage discharge was set to 0.005C.

[0229] At this time, the capacity retention rate was calculated according to the following mathematical formula 2.

[0230]

[0231] [Mathematical Formula 2]

[0232] Capacity retention rate [%] = [Discharge capacity of the 100th cycle / Discharge capacity of the 1st cycle] x 100

[0233]

[0234] The results of measuring the capacity retention rate of the batteries prepared in Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 4 are shown in Table 5 below.

[0235]

[0236] Battery Capacity Retention Rate (%, @100 cycles) Preparation Example 198.5 % Preparation Example 298.1 % Preparation Example 397.1 % Comparative Preparation Example 193.2 % Comparative Preparation Example 288.2 % Comparative Preparation Example 385.6 % Comparative Preparation Example 476.3 %

[0237]

[0238] As a result of measurement, as shown in Table 5 above, it was confirmed that the batteries of Preparation Examples 1 to 3 had a high capacity retention rate of 97% or higher. That is, in the case of the batteries of Preparation Examples 1 to 3 prepared including the copolymer particles of Examples 1 to 3, it was confirmed that they had a higher capacity retention rate when compared to the batteries of Comparative Preparation Examples 1 to 4 prepared including the copolymer particles of Comparative Examples 1 to 4.

[0239] In addition, when comparing the capacity retention rates measured in the batteries of Preparation Examples 1 to 3, the battery of Preparation Example 1 had the highest capacity retention rate of 98.5%, indicating that the capacity retention rate is higher when the weight ratio of the core part to the shell part in the copolymer particles used to manufacture each battery approaches 80:20, and it was also confirmed that the capacity retention rate is higher when the content of the crosslinking agent approaches 0.008 wt% based on 100 wt% of the total weight of the copolymer particles.

[0240] This means that a battery with superior lifespan characteristics can be obtained when the weight ratio of the core and shell parts and the content of the crosslinking agent satisfy the range of the present invention.

[0241]

[0242] Evaluation Example 4: Measurement of internal resistance of a battery

[0243] After the initial formation of the batteries prepared in Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 4, the internal resistance of the batteries was measured using the DC-IR (Direct Current Internal Resistance) method under the condition that they were charged at a rate of 0.3C at a voltage corresponding to 50% of the SOC in CC / CV mode, and then discharged at a rate of 3C at 2.75V. At this time, the temperature of the chamber was 25 ℃.

[0244]

[0245] The results of measuring the internal resistance of the batteries prepared in Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 4 are shown in Table 6 below.

[0246]

[0247] Battery Internal Resistance (DC-IR, mΩ) Preparation Example 1244.3 Preparation Example 2245.1 Preparation Example 3247.2 Comparative Preparation Example 1250.1 Comparative Preparation Example 2280.4 Comparative Preparation Example 3301.1 Comparative Preparation Example 4330.6

[0248]

[0249] As a result of measurement, as shown in Table 6 above, it was confirmed that the batteries of Preparation Examples 1 to 3 had a low internal resistance value of 247.2 mΩ or less. That is, in the case of the batteries of Preparation Examples 1 to 3 prepared including the copolymer particles of Examples 1 to 3, it was confirmed that they had a lower internal resistance value when compared to the batteries of Comparative Preparation Examples 1 to 4 prepared including the copolymer particles of Comparative Examples 1 to 4.

[0250] In addition, when comparing the internal resistance values ​​measured in the batteries of Preparation Examples 1 to 3, the battery of Preparation Example 1 had the lowest internal resistance value of 244.3 mΩ, indicating that the internal resistance value is lower as the weight ratio of the core part to the shell part in the copolymer particles used to manufacture each battery approaches 80:20, and it was also confirmed that the internal resistance value is lower as the content of the crosslinking agent approaches 0.008 wt% based on 100 wt% of the total weight of the copolymer particles.

[0251] This means that when the relative weight ratio of the core and shell parts and the content of the crosslinking agent satisfy the scope of the present invention, a battery of excellent performance with reduced power loss due to internal resistance can be obtained.

[0252]

[0253] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention.

[0254] The copolymer particles according to the present invention and the binder composition containing them can inhibit migration by increasing the bonding strength with the active material and the metal substrate as a result of polymerizing a copolymer comprising acrylic acid-based monomer units, acrylate-based monomer units, acrylamide-based monomer units, or a combination thereof in the shell portion.

[0255] In addition, the copolymer particles according to the present invention and the binder composition containing the same can provide copolymer particles capable of improving resistance within the battery, extending the battery life, and enhancing output performance by introducing a crosslinking agent into the binder.

[0256] In addition, the copolymer particles according to the present invention and the binder composition containing them improve the adhesion between the active material and the metal substrate and / or between the active material, enable the production of a flexible and non-breakable electrode film, and improve stability and slurry dispersibility within the electrolyte, thereby making it possible to secure a secondary battery having a high initial discharge capacity and excellent charge-discharge cycle characteristics.

[0257] In addition, when using copolymer particles with excellent adhesive strength and a binder composition containing them, only a small amount of the binder composition can be used, which can reduce the internal resistance of the secondary battery and increase the capacity of the active material.

Claims

1. Core part; and Includes a shell portion surrounding the core portion; The above core portion includes hard monomer units and soft monomer units, and The above shell portion comprises acrylic acid-based monomer units, acrylate-based monomer units, acrylamide-based monomer units, or a combination thereof. Copolymer particles.

2. In Paragraph 1, Based on 100% by weight of the total weight of the copolymer particles, The content of the above core part is 65 weight% or more and 98 weight% or less, and The content of the shell portion is 2 weight% or more and 35 weight% or less, Copolymer particles.

3. In Paragraph 1, The above shell part is cross-linked with a cross-linking agent, Copolymer particles.

4. In Paragraph 3, Based on 100% by weight of the total weight of the copolymer particles, The content of the above crosslinking agent is 0.001 weight% or more and 0.015 weight% or less, Copolymer particles.

5. In Paragraph 1, The core portion comprises 1.0 to 3.0 parts by weight of the soft monomer unit per 1 part by weight of the hard monomer unit, Copolymer particles.

6. In Paragraph 1, The above soft monomer unit is formed by polymerizing a conjugated diene series monomer, an acrylate series monomer, or a combination thereof. Copolymer particles.

7. In Paragraph 6, The above conjugated diene series monomer is 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, or a combination thereof, and The above acrylate-based monomers include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-hexyl methacrylate, n-amyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, lauryl methacrylate, stearyl acrylate, and sec-butyl acrylate. acrylate) or a combination thereof, Copolymer particles.

8. In Paragraph 1, The above hard monomer unit is formed by polymerizing a styrene-based monomer, an acrylate-based monomer, an acrylonitrile-based monomer, an acrylamide-based monomer, or a combination thereof. Copolymer particles.

9. In Paragraph 8, The above styrene series monomer is styrene, α-methylstyrene, β-methylstyrene, pt-butylstyrene, divinylbenzene, or a combination thereof, and The above acrylate-based monomers are methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and isobornyl methacrylate. acrylate), isovinyl acrylate, isovinyl methacrylate, stearyl methacrylate, sec-butyl methacrylate, or a combination thereof, The above acrylonitrile-based monomer is acrylonitrile, methacrylonitrile, or a combination thereof, and The above acrylamide series monomer is acrylamide, methacrylamide, n-methylolacrylamide, n-butoxymethylacrylamide, or a combination thereof, Copolymer particles.

10. In Paragraph 1, The acrylic acid-based monomer unit included in the shell portion is formed by polymerizing methacrylic acid, acrylic acid, itaconic acid, or a combination thereof, and The acrylate-based monomer units included in the shell portion are polyethylene glycol monomethacrylate, polyethylene glycol monoethyl ether acrylate, 2-(dimethylamino)ethyl acrylate, 2-(diethylamino)ethyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, and n-butyl acrylate. acrylate), isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-hexyl methacrylate, n-amyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, lauryl methacrylate, 3-[[2-(acryloyloxy)ethyl]dimethylammonium]propane-1-sulfonate, mono(2-acryloyloxyethyl)succinate,It is formed by polymerizing Stearyl acrylate, Stearyl methacrylate, Sec-butyl acrylate, Sec-butyl methacrylate, or a combination thereof, and The acrylamide-based monomer unit included in the shell portion is formed by polymerizing acrylamide, methacrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, N-dodecylacrylamide, N-(hydroxymethyl)acrylamide, N-(hydroxyethyl)acrylamide, 6-acrylamidohexanoic acid, or a combination thereof. Copolymer particles.

11. In Paragraph 1, Having an average particle size of 200 nm to 900 nm, Copolymer particles.

12. A copolymer particle comprising any one of claims 1 to 11, Binder composition.

13. A copolymer particle of any one of claims 1 to 11; and Electrode active material; comprising, Slurry.

14. The entire house; and An electrode active material layer formed on the above-mentioned current collector and comprising copolymer particles of any one of claims 1 to 11; comprising, electrode.

15. Including the electrode of claim 14, Secondary battery.