Core-shell particles, binder composition, slurry, electrode including core-shell particles, and secondary battery including electrode

Abstract

The present invention relates to core-shell particles; a binder composition, a slurry, and an electrode including the core-shell particles; and a secondary battery including the electrode. More specifically, the present invention relates to core-shell particles; a composition, a slurry, and an electrode including the core-shell particles; and a secondary battery including the electrode, wherein the core-shell particles, which contain an ammonium functional group in the shell portion thereof, are applied as a binder to improve the adhesion between an active material and a metal substrate and / or between active materials, and enhance the stability and slurry dispersibility in an electrolyte.

Description

Core-shell particles, binder compositions containing the same, slurry, and electrodes, and secondary batteries containing the same

[0001] The present invention relates to core-shell particles, a binder composition comprising the core-shell particles, a slurry, and an electrode, and a secondary battery comprising the electrode.

[0002] With the development and increasing demand for IT technologies such as laptops and mobile phones, and the expansion of the electric and hybrid vehicle markets as an alternative to environmental problems and energy shortages, the demand for lithium-ion secondary batteries is also increasing. Much research is being conducted to improve the performance of lithium-ion secondary batteries, such as long life, high output, high capacity, high density, and stability.

[0003] This phenomenon is significantly increased in materials such as silicon and tin that have high discharge capacity, so that although the initial charge / discharge capacity is high, the discharge capacity tends to decrease rapidly as the cycle progresses.

[0004] Typical lithium-ion secondary batteries use graphite as the anode active material, but the use of graphite-silicon-based active materials has been increasing recently. However, as lithium ions are inserted into the active material during charging and removed during discharge, the volume of the active material expands and contracts repeatedly, causing the active material to separate from the electrode. This reduces battery capacity and shortens its lifespan as the cycle progresses.

[0005] To prevent this phenomenon, efforts are being made to improve the stability of electrodes and battery performance by reducing the size of active materials to nano-size or changing the shape of active materials, increasing the adhesive strength of binders, and suppressing volume expansion with binders.

[0006] [Prior Art Literature]

[0007] [Patent Document]

[0008] (Patent Document 1) Republic of Korea Patent No. 10-1698745

[0009] The present invention seeks to provide a core-shell particle having a shell portion including an ammonium functional group and a binder composition including the same.

[0010] In particular, the purpose is to provide core-shell particles and a binder composition including the same, which have high initial discharge capacity and excellent charge / discharge cycle characteristics by improving the adhesion between the active material and the metal substrate and / or the active material, and improving stability and slurry dispersibility in the electrolyte.

[0011] In addition, the present invention aims to provide a slurry and electrode including the core-shell particles, and a secondary battery including the electrode.

[0012] However, the problems that the present invention seeks to solve are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0013] One aspect of the present invention provides a core-shell particle comprising a core comprising a first polymer and a shell formed on the core and comprising a second polymer, wherein the second polymer comprises an ammonium functional group.

[0014]

[0015] Another aspect of the present invention provides a binder composition comprising the core-shell particles.

[0016]

[0017] Another aspect of the present invention provides a slurry comprising the core-shell particles and an electrode active material.

[0018]

[0019] Another aspect of the present invention provides an electrode comprising a current collector and an electrode active material layer comprising the core-shell particles formed on the current collector.

[0020]

[0021] Another aspect of the present invention provides a secondary battery including the electrode.

[0022] The core-shell particles according to the present invention and the binder composition containing the same improve the adhesion between the active material and the metal substrate and / or the active material, and improve the stability and slurry dispersibility in the electrolyte, thereby enabling the securing of a secondary battery having a high initial discharge capacity and excellent charge / discharge cycle characteristics.

[0023] In addition, when using core-shell particles with excellent adhesive strength and a binder composition including the same, the internal resistance of the battery can be reduced and the capacity of the active material can be increased as the amount of binder used is reduced.

[0024] Figure 1 is a drawing showing the structure of a core-shell particle according to the present invention.

[0025] Hereinafter, the functions and effects of the invention will be described in more detail through specific examples. However, these examples are provided merely as examples of the invention and do not define the scope of the invention.

[0026] Prior to this, the terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, and should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0027] Accordingly, the configuration of the embodiments described in this specification is only one of the most preferred embodiments of the present invention and does not represent all of the technical ideas of the present invention, so it should be understood that various equivalents and modified examples that can replace them may exist at the time of filing this application.

[0028] In this specification, singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise," "include," or "have" should be understood to indicate the presence of a feature, number, step, component, or combination thereof, but not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0029]

[0030] A core-shell particle according to one aspect of the present invention comprises a core comprising a first polymer and a shell formed on the core and comprising a second polymer, wherein the second polymer may comprise an ammonium functional group.

[0031] The ammonium functional group is positively charged, and therefore, the core-shell particles can form ionic bonds with other compounds containing negatively charged functional groups through interactions between cations and anions. Since ionic bonds are much stronger than hydrogen bonds or dipole-dipole interactions, they can be used to manufacture secondary batteries with improved adhesion between active materials and metal substrates and / or active materials.

[0032]

[0033] In one embodiment of the present invention, the ammonium functional group may be derived from a (meth)acrylic acid ester monomer.

[0034]

[0035] In one embodiment of the present invention, the (meth)acrylic acid ester monomer may be selected from [2-(acryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, or a combination thereof.

[0036]

[0037] In one embodiment of the present invention, the content of the (meth)acrylic acid ester monomer may be 2 to 10 parts by weight per 100 parts by weight of the second monomer mixture polymerized into the second polymer.

[0038] For example, the content of the (meth)acrylic acid ester monomer may be 2.5 parts by weight to 9 parts by weight, 3 parts by weight to 8 parts by weight, 3.5 parts by weight to 7 parts by weight, 4 parts by weight to 6 parts by weight, or 4.5 parts by weight to 5.5 parts by weight per 100 parts by weight of the second monomer mixture polymerized into the second polymer.

[0039] If the content of the above (meth)acrylic acid ester monomer is outside the range of the present invention, a decrease in the adhesive strength between the active material and the metal substrate and / or the active material may occur.

[0040]

[0041] In one embodiment of the present invention, the glass transition temperature of the core-shell particles may be -15°C to 10°C, and the average particle diameter of the core-shell particles may be 10 nm to 600 nm.

[0042] For example, the glass transition temperature of the core-shell particles may be -13°C to 8°C, -11°C to 6°C, -10°C to 5°C, -10°C to -8°C, -8°C to -6°C, -6°C to -4°C, -4°C to -2°C, -2°C to 0°C, 0°C to 2°C, 2°C to 5°C, and the average particle diameter of the core-shell particles may be 15 nm to 550 nm, 20 nm to 500 nm, 20 nm to 100 nm, 100 nm to 150 nm, 150 nm to 200 nm, 200 nm to 250 nm, 250 nm to 300 nm, 300 nm to 350 nm, 350 nm to 400 nm, 400 nm to 450 nm, 450 nm to 500 nm.

[0043] If the glass transition temperature of the core-shell particles exceeds the range of the present invention, the adhesive strength between the active material and the metal substrate and / or the active material may deteriorate, and if it falls below the range, the electrode coating stability may deteriorate. In addition, if the average particle diameter of the core-shell particles exceeds the range of the present invention, the electrode processability may deteriorate, and if it falls below the range, the adhesive strength between the active material and the metal substrate and / or the active material may deteriorate.

[0044]

[0045] In one embodiment of the present invention, the core-shell particle may have a multi-shell structure including two or more layers of shells within a range that does not impede the purpose of the present invention.

[0046]

[0047] In one embodiment of the present invention, the weight ratio of the second monomer mixture polymerized into the second polymer per 1 part by weight of the first monomer mixture polymerized into the first polymer may be 0.1 part by weight to 10 parts by weight.

[0048] For example, the weight ratio of the second monomer mixture polymerized into the second polymer to 1 part by weight of the first monomer mixture polymerized into the first polymer may be 0.5 parts by weight to 9 parts by weight, 1 part by weight to 7 parts by weight, or 2 parts by weight to 6 parts by weight.

[0049] If the weight ratio of the second monomer mixture per 1 part by weight of the first monomer mixture is outside the range of the present invention, it may be difficult to exhibit the performance of the core-shell structure. More specifically, if the weight ratio of the second monomer mixture per 1 part by weight of the first monomer mixture is above the range of the present invention, a decrease in stability may occur. In addition, if the weight ratio of the second monomer mixture per 1 part by weight of the first monomer mixture is below the range of the present invention, a decrease in the adhesive strength between the active material and the metal substrate and / or the active material may occur.

[0050]

[0051] In one embodiment of the present invention, the first monomer mixture polymerized into the first polymer may include 0.5 to 9.5 parts by weight of a hard monomer per 1 part by weight of a soft monomer, and the second monomer mixture polymerized into the second polymer may include 0.5 to 4.5 parts by weight of a soft monomer per 1 part by weight of a hard monomer.

[0052] For example, the first monomer mixture may contain 1.0 to 9.0 parts by weight, 1.5 to 8.5 parts by weight, or 2.0 to 8.0 parts by weight of the hard monomer per 1 part by weight of the soft monomer, and the second monomer mixture may contain 1.0 to 4.0 parts by weight, 1.5 to 3.5 parts by weight, or 2.0 to 3.0 parts by weight of the soft monomer per 1 part by weight of the hard monomer.

[0053] If the weight portion of the hard monomer to 1 part by weight of the soft monomer of the first monomer mixture exceeds the range of the present invention, the compatibility between the core and the shell may be reduced, and if it falls below the range of the present invention, the swelling degree of the electrolyte may be increased. In addition, if the weight portion of the soft monomer to 1 part by weight of the hard monomer of the second monomer mixture exceeds the range of the present invention, the stability and mechanical strength in the electrolyte may be reduced, and if it falls below the range, the dispersibility in the slurry may be reduced due to low wettability.

[0054]

[0055] In one embodiment of the present invention, the soft monomer may include a monomer having a glass transition temperature of less than 20°C, and the hard monomer may include a monomer having a glass transition temperature of 20°C or higher.

[0056]

[0057] In one embodiment of the present invention, the soft monomer may include at least one monomer selected from the group consisting of a conjugated diene monomer and an acrylic acid ester monomer, and the hard monomer may include at least one monomer selected from the group consisting of a styrene monomer, a (meth)acrylic acid ester monomer, an acrylonitrile monomer, and a (meth)acrylamide monomer.

[0058] The above-mentioned conjugated diene monomer may include, but is not limited to, one or more monomers selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene.

[0059] The above acrylic acid ester monomer may include at least one monomer selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butylacrylate, isobutylacrylate, t-butylacrylate, n-hexylacrylate, 2-hexyl methacrylate, n-amyl acrylate, isoamyl acrylate, 2-ethylhexylacrylate, and lauryl methacrylate, but is not limited thereto.

[0060] The above styrene-based monomer may include one or more monomers selected from the group consisting of α-methylstyrene, β-methylstyrene, pt-butyl styrene, and divinylbenzene, but is not limited thereto.

[0061] The above (meth)acrylic acid ester monomer may include at least one monomer selected from the group consisting of 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, isobornyl acrylate, isovinylacrylate, and isovinyl methacrylate, but is not limited thereto.

[0062] The above acrylonitrile-based monomer may include, but is not limited to, acrylonitrile or methacrylonitrile.

[0063] The above (meth)acrylamide monomer may include one or more monomers selected from acrylamide, methacrylamide, n-methylolacrylamide, and n-butoxymethylacrylamide, but is not limited thereto.

[0064]

[0065] In one embodiment of the present invention, the first polymer, the second polymer, or the first polymer and the second polymer may include a carboxylate functional group, and the carboxylate functional group may be derived from a carboxylic acid monomer.

[0066] The above carboxylic acid monomer may include at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, citraconic acid, metaconic acid, glutaconic acid, tetrahydrophthalic acid, crotonic acid, and isocrotonic acid.

[0067]

[0068] In one embodiment of the present invention, the content of the carboxylic acid monomer may be 0.1 to 10 parts by weight per 100 parts by weight of the first monomer mixture polymerized into the first polymer or the second monomer mixture polymerized into the second polymer.

[0069] For example, the content of the carboxylic acid monomer may be 1 part by weight to 9 parts by weight, 2 parts by weight to 8 parts by weight, or 3 parts by weight to 7 parts by weight per 100 parts by weight of the first monomer mixture polymerized into the first polymer or the second monomer mixture polymerized into the second polymer.

[0070] If the content of the carboxylic acid monomer falls below the range specified herein, the stability of the binder particles may deteriorate. Furthermore, if the content of the carboxylic acid monomer exceeds the range specified herein, the viscosity may excessively increase.

[0071]

[0072] A method for producing a core-shell particle according to one aspect of the present invention comprises: forming a core comprising a first polymer; polymerizing a second polymer from a second monomer mixture to form a shell comprising the second polymer on the core; wherein the second polymer may include an ammonium functional group.

[0073]

[0074] In one embodiment of the present invention, the method for manufacturing the core-shell particle may additionally include a step of adding a carboxylic acid monomer in the step of forming the core and / or the step of forming the shell.

[0075]

[0076] In one embodiment of the present invention, the step of forming the core may include a step of adding an emulsifier to emulsify, a step of adding a first monomer mixture, a step of adding a carboxylic acid monomer and stirring to emulsify, and a step of adding an initiator to perform emulsion polymerization.

[0077]

[0078] In one embodiment of the present invention, the step of forming the shell may include a step of adding a (meth)acrylic acid ester monomer to the core, a step of adding an emulsifier to emulsify, a step of adding a second monomer mixture, a step of additionally adding a carboxylic acid monomer and stirring to emulsify, and a step of adding an initiator to perform emulsion polymerization.

[0079]

[0080] In one embodiment of the present invention, in the step of forming the shell, the content of the core particles may be 5 to 50 parts by weight, preferably 10 to 40 parts by weight, and more preferably 20 to 28 parts by weight, with respect to 100 parts by weight of the second monomer mixture.

[0081]

[0082] In one embodiment of the present invention, in the step of forming the core and / or the step of forming the shell, the content of the emulsifier may be 1 to 10 parts by weight with respect to 100 parts by weight of the first monomer mixture. In addition, a surfactant may be used as the emulsifier, and the surfactant may be an anionic surfactant, a cationic surfactant, a zwitterionic surfactant, a nonionic surfactant, etc., and preferably, an anionic surfactant may be used. Specific examples of the anionic surfactant include, but are not limited to, higher fatty acid alkali salts, N-acrylamino acid salts, alkyl ether carbonate salts, acylated peptides, alkyl sulfonates, alkylbenzenes, alkyl amino acid salts, alkyl naphthalene sulfonates, sulfosuccinates, sulfated oils, alkyl sulfates, alkyl ether sulfates, alkyl aryl ether sulfates, alkyl amide sulfates, alkyl phosphates, alkyl ethoxyphosphates, and alkyl aryl ether phosphates, and sodium dodecylbenzene sulfonate can be preferably used.

[0083]

[0084] In one embodiment of the present invention, the content of the initiator in the step of forming the core and / or the step of forming the shell may be 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the first monomer mixture, but is not limited thereto as long as the function of polymerization initiation can be achieved.

[0085]

[0086] In one embodiment of the present invention, in the step of forming the core, the emulsion polymerization reaction may be carried out at a temperature of 20°C to 100°C, preferably 30°C to 90°C. In addition, the emulsion polymerization reaction may be carried out for a time period of 30 minutes to 600 minutes, preferably 30 minutes to 300 minutes.

[0087]

[0088] In one embodiment of the present invention, in the step of forming the shell, the emulsion polymerization reaction may be carried out at a temperature of 20°C to 100°C, preferably 30°C to 90°C. In addition, the emulsion polymerization reaction may be carried out for a time of 10 minutes to 500 minutes, preferably 30 minutes to 400 minutes.

[0089]

[0090] In one embodiment of the present invention, the step of forming the shell may be performed by a seed polymerization method performed by adding the core particles as seeds.

[0091] Specifically, the step of forming the shell may include a process of adding a portion of a first monomer mixture, an emulsifier, and an initiator to an aqueous solution and polymerizing the mixture to obtain a reaction mixture in which seeds having a particle size of 10 nm to 100 nm are formed, and a process of adding a second monomer mixture and an initiator to the obtained reaction mixture and polymerizing the mixture.

[0092] The above seed polymerization method is a method in which seeds are first manufactured and then a polymerization reaction is initiated using the seeds. The particle size of the final core-shell particles is not controlled by the amount of emulsifier used, but can be controlled by the size and number of seed particles participating in the initial reaction. Therefore, the particle size can be easily controlled and the reaction can be conveniently controlled.

[0093] In the above seed polymerization, a surfactant may be used as the emulsifier, and the surfactant may be an anionic surfactant, a cationic surfactant, a zwitterionic surfactant, a nonionic surfactant, etc., and preferably, an anionic surfactant may be used. Specific examples of the anionic surfactant include, but are not limited to, higher fatty acid alkali salts, N-acrylamino acid salts, 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 ethoxyphosphates, and alkyl aryl ether phosphates, and preferably, sodium dodecylbenzene sulfonate may be used.

[0094] In the above seed polymerization, a decomposition initiator or a redox initiator may be used as the initiator, and preferably a decomposition initiator may be used. The decomposition initiator may be at least one selected from the group consisting of potassium persulfate, ammonium persulfate, sodium hydrosulfite, potassium sulfite, sodium persulfate, and sodium bipersulfate.

[0095] In the above seed polymerization, a process of adding a chelating agent may be additionally included. The chelating agent may be at least one selected from the group consisting of ethylenediaminetetraacetic acid, hydroxyethyl ditetraacetic acid, and propanediaminetetraacetic acid.

[0096]

[0097] A binder composition according to one aspect of the present invention may include any one of the core-shell particles.

[0098]

[0099] A slurry according to one aspect of the present invention may include any one of the core-shell particles and an electrode active material.

[0100]

[0101] In one embodiment of the present invention, the slurry may include an organic solvent such as carboxymethylcellulose, NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide, or water as a solvent, and preferably carboxymethylcellulose may be used. In addition, the slurry may include one or more solvents.

[0102] The above carboxymethyl cellulose may have a degree of substitution of a hydroxyl group (-OH) by a carboxymethyl group (-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.

[0103]

[0104] In one embodiment of the present invention, the slurry may contain the core-shell particles in an amount of 0.1 wt% to 10 wt% based on 100 wt% of the slurry. For example, the slurry may contain the core-shell particles in an amount of 0.1 wt% to 8 wt%, 0.1 wt% to 6 wt%, 0.1 wt% to 4 wt%, or 0.1 wt% to 3 wt% based on 100 wt% of the slurry. In addition, the slurry may contain carboxymethyl cellulose (CMC) and an electrode active material capable of intercalating and deintercalating lithium ions.

[0105]

[0106] An electrode according to one aspect of the present invention may include a current collector and an electrode active material layer including the core-shell particles formed on the current collector. The electrode may be a positive electrode or a negative electrode.

[0107]

[0108] In one embodiment of the present invention, the adhesive strength of the negative electrode using the negative electrode slurry containing 1.8 parts by weight of the core-shell particles based on 100 parts by weight of the total weight of the negative electrode slurry may be 18 gf / cm or more. In addition, the adhesive strength of the negative electrode using the negative electrode slurry containing 1.3 parts by weight of the core-shell particles based on 100 parts by weight of the total weight of the negative electrode slurry may be 13 gf / cm or more.

[0109]

[0110] In one embodiment of the present invention, the current collector is a portion where electrons move in the electrochemical reaction of the active material, and a negative current collector and a positive current collector exist depending on the type of electrode. The current collector may form fine irregularities on its surface to strengthen the bonding strength of the electrode active material, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0111] The above negative electrode current collector can generally be formed to a thickness of 5 μm to 30 μm. The negative electrode current collector is not particularly limited as long as it has conductivity and does not cause 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 can be used.

[0112] The positive electrode current collector can generally be formed to a thickness of 3 μm to 500 μm. The positive electrode 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. can be used.

[0113]

[0114] 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 negative electrode and positive electrode slurries, and a negative electrode active material and a positive electrode active material exist depending on the type of electrode.

[0115]

[0116] The above negative electrode active material may be selected from 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.

[0117] Carbon and graphite materials include natural graphite, artificial 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, SiOx(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.

[0118]

[0119] As the positive electrode active material, the lithium transition metal oxide represented by the chemical formula 1 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.

[0120] For example, the above cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), 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; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-y Ni-site type lithium nickel oxide represented by MyO2 (wherein M is Co, Mn, Al, Cu, Fe, Mg, B or Ga and y = 0.01 to 0.3); chemical formula LiMn 2-y Lithium manganese composite oxides expressed as MyO2 (wherein, M = Co, Ni, Fe, Cr, Zn or Ta, and y = 0.01 to 0.1) or Li2Mn3MO8 (wherein, M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc. can be used, but are not limited thereto.

[0121] The above positive electrode active material is preferably Li a Ni x Mn y Co zChemical formula 1 of O2 (in the above formula, 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.

[0122]

[0123] A secondary battery according to one aspect of the present invention may include the electrode.

[0124]

[0125] In one embodiment of the present disclosure, the internal resistance of the secondary battery including the negative electrode using the negative electrode slurry including 1.3 parts by weight of the core-shell particles based on 100 parts by weight of the total weight of the negative electrode slurry may be 255 mΩ or less. For example, the internal resistance of the secondary battery may be 251 mΩ or less, 247 mΩ or less, or 243 mΩ or less. That is, in the case of a secondary battery manufactured using the core-shell particles of the present disclosure including an ammonium functional group, excellent adhesion between the active material and the metal substrate and / or the active material is achieved even with a smaller amount of core-shell particles, and there is an effect of reducing the internal resistance value of the battery measured through DC-IR.

[0126]

[0127] In one embodiment of the present invention, the capacity retention rate of the secondary battery including the negative electrode using the negative electrode slurry including 1.8 parts by weight of the core-shell particles based on 100 parts by weight of the total weight of the negative electrode slurry may be 96% or more.

[0128]

[0129] In one embodiment of the present invention, the secondary battery may include a separator. The separator is interposed between the positive and negative electrodes, and a thin insulating film with high ion permeability and mechanical strength may be used. The pore diameter of the separator is generally 0.01 μm to 10 μm, and the thickness may be generally 5 μm to 300 μm. Examples of such a separator include a chemically resistant and hydrophobic olefin polymer such as polypropylene; a sheet or nonwoven fabric made of glass fiber or polyethylene; and the like. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also function as the separator.

[0130] The above lithium salt-containing non-aqueous electrolyte is composed of an electrolyte and a lithium salt, and a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, etc. can be used as the electrolyte.

[0131] As the above non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, ethyl propionate, etc. can be used. there is.

[0132] As the organic solid electrolyte, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymerizers containing ionic dissociation groups, etc. can be used.

[0133] 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, etc. can be used.

[0134] The above lithium salt is a substance that is easily dissolved in the 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 carboxylic acid, lithium tetraphenylborate, imide, etc. can be used.

[0135] In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., the electrolyte may be added with, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. In some cases, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be further included to provide non-flammability, carbon dioxide gas 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.

[0136]

[0137] 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 be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells used as a power source for a medium- to large-sized device.

[0138] Preferred examples of the above medium- to large-sized devices include, but are not limited to, power tools 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; and electric golf carts.

[0139]

[0140] Hereinafter, the present invention will be described in more detail through examples. However, the following examples are intended to further illustrate the present invention, and the scope of the present invention is not limited by the following examples.

[0141]

[0142] Synthesis example: Preparation of core particles

[0143] A first monomer mixture that is polymerized into a first polymer was prepared by mixing 1,3-butadiene, a soft monomer, and styrene, a hard monomer, in a weight ratio of 1:8.

[0144] 1 part by weight of sodium dodecylbenzene sulfonate as an anionic surfactant was added to 200 parts by weight of distilled water, relative to 100 parts by weight of the first monomer mixture, and emulsified. Then, 100 parts by weight of the first monomer mixture was added, and 3 parts by weight of acrylic acid was further added, stirred, and emulsified. To this, 1 part by weight of potassium sulfite, a decomposition initiator, was added relative to 100 parts by weight of the first monomer mixture, and an emulsion polymerization reaction was performed, thereby producing core particles.

[0145]

[0146] Examples and Comparative Examples: Preparation of Core-Shell Particles

[0147] [Example 1]

[0148] A second monomer mixture that is polymerized into a second polymer was prepared by mixing 1,3-butadiene, a soft monomer, and styrene, a hard monomer, in a weight ratio of 3:1.

[0149] 25 parts by weight of the core particles (synthetic example) as seeds were added to 200 parts by weight of distilled water relative to 100 parts by weight of the second monomer mixture, and 5 parts by weight of [2-(acryloyloxy)ethyl]trimethylammonium chloride was added relative to 100 parts by weight of the second monomer mixture.

[0150] Then, 0.5 parts by weight of sodium dodecylbenzene sulfonate as a surfactant was added to 100 parts by weight of the second monomer mixture, emulsified, and then 100 parts by weight of the second monomer mixture and 4 parts by weight of acrylic acid were added and stirred. Here, 1 part by weight of potassium sulfite as a decomposition initiator was added to 100 parts by weight of the second monomer mixture, and a polymerization reaction was performed to produce core-shell structured polymer particles.

[0151]

[0152] [Example 2]

[0153] In Example 2, core-shell structured polymer particles were prepared in the same manner as in Example 1, except that 5 parts by weight of [2-(methacryloyloxy)ethyl]trimethylammonium chloride was added instead of [2-(acryloyloxy)ethyl]trimethylammonium chloride per 100 parts by weight of the second monomer mixture.

[0154]

[0155] [Comparative Example 1]

[0156] The core particles (synthetic example) as seeds were added to 200 parts by weight of distilled water in an amount of 17 parts by weight based on 100 parts by weight of the second monomer mixture, and in the case of Comparative Example 1, [2-(acryloyloxy)ethyl]trimethylammonium chloride was added in an amount of 13 parts by weight based on 100 parts by weight of the second monomer mixture.

[0157] Other than this, core-shell particles were manufactured in the same manner as in Example 1.

[0158]

[0159] [Comparative Example 2]

[0160] The core particles (synthetic example) as seeds were added to 200 parts by weight of distilled water in an amount of 17 parts by weight based on 100 parts by weight of the second monomer mixture, and in the case of Comparative Example 2, instead of [2-(acryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]trimethylammonium chloride was added in an amount of 13 parts by weight based on 100 parts by weight of the second monomer mixture.

[0161] Other than this, core-shell particles were manufactured in the same manner as in Example 1.

[0162]

[0163] [Comparative Example 3]

[0164] The core particles (synthetic example) as seeds were added to 200 parts by weight of distilled water in an amount of 29 parts by weight relative to 100 parts by weight of the second monomer mixture, and in the case of Comparative Example 3, [2-(acryloyloxy)ethyl]trimethylammonium chloride was added in an amount of 1 part by weight relative to 100 parts by weight of the second monomer mixture.

[0165] Other than this, core-shell particles were manufactured in the same manner as in Example 1.

[0166]

[0167] [Comparative Example 4]

[0168] The core particles (synthetic example) as seeds were added to 200 parts by weight of distilled water in an amount of 29 parts by weight based on 100 parts by weight of the second monomer mixture, and in the case of Comparative Example 4, instead of [2-(acryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]trimethylammonium chloride was added in an amount of 1 part by weight based on 100 parts by weight of the second monomer mixture.

[0169] Other than this, core-shell particles were manufactured in the same manner as in Example 1.

[0170]

[0171] [Comparative Example 5]

[0172] Core-shell particles were prepared in the same manner as in Example 1, except that 30 parts by weight of the core particles (synthetic example) were added as seeds to 200 parts by weight of distilled water relative to 100 parts by weight of the second monomer mixture, and (meth)acrylic acid ester monomer was not added.

[0173]

[0174] Manufacturing examples: Manufacturing of cathode slurry, cathode, and battery

[0175] [Manufacturing Example 1]

[0176] A negative electrode slurry was prepared by mixing 97 parts by weight of graphite as a negative electrode active material, 1.8 parts by weight of the core-shell particles of Examples 1 and 2 and Comparative Examples 1 to 5, and 1.2 parts by weight of carboxymethylcellulose with distilled water.

[0177] The above cathode slurry was uniformly applied to a Cu thin film having a thickness of 10 ㎛ using an applicator, and then dried at a temperature of 100°C for 30 minutes to manufacture a cathode.

[0178] A cathode was manufactured by mixing lithium nickel-manganese cobalt oxide as a cathode active material, acetylene black as a conductive agent, and polyvinylidene fluoride (PVDF) as a cathode binder in a weight ratio of 92:4:4 and applying the mixture to an aluminum collector. An electrolyte was manufactured by dissolving LiPF6 in a non-aqueous solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) = 1:2:1 to a concentration of 1 M. A battery (full cell) was manufactured using a porous polyethylene film as a separator.

[0179] The types of core-shell particles used are shown in Table 1 below.

[0180]

[0181] Types of core-shell particles Manufacturing example 1-1 Example 1 Manufacturing example 1-2 Example 2 Manufacturing example 1-3 Comparative example 1 Manufacturing example 1-4 Comparative example 2 Manufacturing example 1-5 Comparative example 3 Manufacturing example 1-6 Comparative example 4 Manufacturing example 1-7 Comparative example 5

[0182] [Manufacturing Example 2]

[0183] A negative electrode slurry was prepared by mixing 97 parts by weight of graphite as a negative electrode active material, 1.3 parts by weight of the core-shell particles of Examples 1 and 2 and Comparative Examples 1 to 5, and 1.7 parts by weight of carboxymethylcellulose with distilled water.

[0184] Other than this, the negative electrode and battery were manufactured using the same method and conditions as in Manufacturing Example 1.

[0185] The types of core-shell particles used are shown in Table 2 below.

[0186]

[0187] Types of Core-Shell Particles Manufacturing Example 2-1 Example 1 Manufacturing Example 2-2 Example 2 Manufacturing Example 2-3 Comparative Example 3 Manufacturing Example 2-4 Comparative Example 4

[0188] [Evaluation example]

[0189] Evaluation Example 1: Measurement of the adhesive strength of the cathode

[0190] The cathodes manufactured in Manufacturing Examples 1-1 to 1-7 and Manufacturing Examples 2-1 to 2-4 were cut to a size of 25 mm in width and 100 mm in length. A double-sided tape with an area of ​​20 mm in width and 40 mm in length was attached to an acrylic plate with an area of ​​40 mm in width and 100 mm in length. The prepared electrode was attached to the double-sided tape, lightly pressed 5 times with a hand roller, and mounted on a UTM (20 kgf Load cell). After peeling off about 25 mm of one side of the cathode, the cathode was fixed to the upper clip of the tensile strength tester, and the tape attached to one side of the cathode was fixed to the lower clip. While peeling at a speed of 100 mm / min, the force at which the electrode fell in the 180° direction was measured. At least 5 specimens were manufactured for each sample, measured, and the average value was calculated. The results are shown in Tables 3 and 4 below.

[0191]

[0192] Adhesive strength (gf / cm) Manufacturing example 1-120 Manufacturing example 1-220.6 Manufacturing example 1-39.7 Manufacturing example 1-410.1 Manufacturing example 1-515.6 Manufacturing example 1-616.1 Manufacturing example 1-712.9

[0193] As a result of the measurement, as shown in Table 3, it was confirmed that the negative electrodes of Preparation Examples 1-1 and 1-2, which were manufactured by including 1.8 parts by weight of the core-shell particles of Examples 1 and 2, had a high adhesive strength of 18 gf / cm or more. That is, in the case of the negative electrodes of Preparation Examples 1-1 and 1-2, which were manufactured by including 1.8 parts by weight of the core-shell particles of Examples 1 and 2, it was confirmed that they had a higher adhesive strength when compared to the negative electrodes of Preparation Examples 1-3 to 1-7, which were manufactured by including 1.8 parts by weight of the core-shell particles of Comparative Examples 1 to 5. This means that when the content of the (meth)acrylic acid ester monomer satisfies the range of the present invention of 2 parts by weight or more and 10 parts by weight or less, a negative electrode having a better adhesive strength between the active material and the metal substrate can be obtained.

[0194]

[0195] Adhesive strength (gf / cm) Manufacturing example 2-1 13.1 Manufacturing example 2-2 13.4 Manufacturing example 2-3 10.7 Manufacturing example 2-4 10.9 Manufacturing example 1-7 12.9

[0196] As a result of the measurement, as shown in Table 4, it was confirmed that the negative electrodes of Manufacturing Examples 2-1 and 2-2, which were manufactured by including 1.8 parts by weight of the core-shell particles of Examples 1 and 2, had a high adhesive strength of 13 gf / cm or more. That is, in the case of the negative electrodes of Manufacturing Examples 2-1 and 2-2, which were manufactured by including 1.3 parts by weight of the core-shell particles of Examples 1 and 2, it was confirmed that they had a higher adhesive strength when compared to the negative electrodes of Manufacturing Examples 2-3 and 2-4, which were manufactured by including 1.3 parts by weight of the core-shell particles of Comparative Examples 3 and 4, and the negative electrode of Manufacturing Example 1-7, which was manufactured by including 1.8 parts by weight of the core-shell particles of Comparative Example 5. This means that when the content of the (meth)acrylic acid ester monomer satisfies the range of the present invention of 2 parts by weight or more and 10 parts by weight or less, a negative electrode having better adhesive strength between the active material and the metal substrate can be obtained.

[0197]

[0198] Evaluation Example 2: Measurement of battery capacity retention rate

[0199] For the batteries manufactured in Manufacturing Examples 1-1 to 1-7, charging and discharging were performed twice at 25°C with a charge and discharge current density of 0.1C, a charge end voltage of 4.2 V, and a discharge stop voltage of 2.8 V.

[0200] Afterwards, 100 charge / discharge cycles were performed with a charge / discharge current density of 1C, a charge end voltage of 4.2 V, and a discharge end voltage of 2.8 V.

[0201] All discharges were performed under constant current / constant voltage conditions, and the terminal current of the constant voltage discharge was set to 0.005 C.

[0202] At this time, the capacity retention rate was calculated according to the following mathematical formula 1.

[0203]

[0204] <Mathematical Formula 1>

[0205] Capacity retention rate [%] = [Discharge capacity of the 100th cycle / Discharge capacity of the 1st cycle] X 100

[0206]

[0207] The results of measuring the capacity retention rate of the batteries manufactured in Manufacturing Examples 1-1 to 1-7 are shown in Table 5.

[0208]

[0209] Capacity Retention (%, @100 cycles) Manufacturing Example 1-196.2 Manufacturing Example 1-296.3 Manufacturing Example 1-393.5 Manufacturing Example 1-493.9 Manufacturing Example 1-595.1 Manufacturing Example 1-695.3 Manufacturing Example 1-794.6

[0210] As a result of the measurement, as shown in Table 5, it was confirmed that the batteries of Preparation Examples 1-1 and 1-2, which were manufactured by including 1.8 parts by weight of the core-shell particles of Examples 1 and 2, had a high capacity retention rate of 96% or more. That is, in the case of the batteries of Preparation Examples 1-1 and 1-2, which were manufactured by including 1.8 parts by weight of the core-shell particles of Examples 1 and 2, it was confirmed that they had a higher capacity retention rate when compared to the batteries of Preparation Examples 1-3 to 1-7, which were manufactured by including 1.8 parts by weight of the core-shell particles of Comparative Examples 1 to 5. This means that when the content of the (meth)acrylic acid ester monomer satisfies the range of the present invention of 2 parts by weight or more and 10 parts by weight or less, a battery having better life characteristics can be obtained.

[0211]

[0212] Evaluation Example 3: Measurement of internal resistance of a battery

[0213] After the initial formation of the batteries manufactured in Manufacturing Examples 2-1 to 2-4 and Manufacturing Example 1-7, the internal resistance of the batteries was measured using the DC-IR (Direct Current Internal Resistance) method under the conditions of charging at a 0.3C rate at a voltage corresponding to 50% of the SOC in CC / CV mode and then discharging at a 2C rate at 2.75 V. The temperature of the chamber at this time was 25°C.

[0214]

[0215] The results of measuring the internal resistance of the batteries manufactured in Manufacturing Examples 2-1 to 2-4 and Manufacturing Example 1-7 are shown in Table 6.

[0216]

[0217] Internal resistance (DC-IR, mΩ) Manufacturing example 2-1239.9 Manufacturing example 2-2241.1 Manufacturing example 2-3257.2 Manufacturing example 2-4256.1 Manufacturing example 1-7300.2

[0218] As a result of the measurement, it was confirmed that the batteries of Preparation Examples 2-1 and 2-2, which were manufactured by including 1.3 parts by weight of the core-shell particles of Examples 1 and 2, had low internal resistances of 255 mΩ or less, as shown in Table 6. That is, in the case of the batteries of Preparation Examples 2-1 and 2-2, which were manufactured by including 1.3 parts by weight of the core-shell particles of Examples 1 and 2, it was confirmed that they had lower internal resistance values ​​when compared with the negative electrodes of Preparation Examples 2-3 and 2-4, which were manufactured by including 1.3 parts by weight of the core-shell particles of Comparative Examples 3 and 4, and the negative electrode of Preparation Example 1-7, which was manufactured by including 1.8 parts by weight of the core-shell particles of Comparative Example 5. This means that when the content of the (meth)acrylic acid ester monomer satisfies the range of the present invention of 2 parts by weight or more and 10 parts by weight or less, a battery with excellent performance with reduced power loss due to internal resistance can be obtained.

[0219]

[0220] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0221]

[0222] The core-shell particles according to the present invention and the binder composition containing the same improve the adhesion between the active material and the metal substrate and / or the active material, and improve the stability and slurry dispersibility in the electrolyte, thereby enabling the securing of a secondary battery having a high initial discharge capacity and excellent charge / discharge cycle characteristics.

[0223] In addition, when using core-shell particles with excellent adhesive strength and a binder composition including the same, the internal resistance of the battery can be reduced and the capacity of the active material can be increased as the amount of binder used is reduced.

Claims

1. A core comprising a first polymer; and A shell formed on the core and comprising a second polymer; Includes, The second polymer comprises an ammonium functional group, Core-shell particles.

2. In paragraph 1, The above ammonium functional group is derived from a (meth)acrylic acid ester monomer. Core-shell particles.

3. In paragraph 2, The above (meth)acrylic acid ester monomer is selected from [2-(acryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, or a combination thereof. Core-shell particles.

4. In paragraph 2, The content of the above (meth)acrylic acid ester monomer is 2 to 10 parts by weight per 100 parts by weight of the second monomer mixture polymerized into the second polymer. Core-shell particles.

5. In paragraph 1, The glass transition temperature is -15 ℃ to 10 ℃, The average particle diameter is 10 nm to 600 nm, Core-shell particles.

6. In paragraph 1, The weight ratio of the second monomer mixture polymerized into the second polymer per 1 part by weight of the first monomer mixture polymerized into the first polymer is 0.1 part by weight to 10 parts by weight, Core-shell particles.

7. In paragraph 1, The first monomer mixture polymerized with the first polymer comprises 0.5 to 9.5 parts by weight of a hard monomer per 1 part by weight of a soft monomer, The second monomer mixture polymerized with the second polymer comprises 0.5 to 4.5 parts by weight of a soft monomer per 1 part by weight of a hard monomer. Core-shell particles.

8. In paragraph 7, The above soft monomer includes a monomer having a glass transition temperature of less than 20°C, The above rigid monomer includes a monomer having a glass transition temperature of 20°C or higher. Core-shell particles.

9. In paragraph 7, The above soft monomer comprises at least one monomer selected from the group consisting of a conjugated diene monomer and an acrylic acid ester monomer, The above rigid monomer comprises at least one monomer selected from the group consisting of a styrene monomer, a (meth)acrylic acid ester monomer, an acrylonitrile monomer, and a (meth)acrylamide monomer. Core-shell particles.

10. In paragraph 1, wherein the first polymer, the second polymer, or the first polymer and the second polymer comprise a carboxylate functional group, The above carboxylate functional group is derived from a carboxylic acid monomer, The above carboxylic acid monomer comprises at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, citraconic acid, metaconic acid, glutaconic acid, tetrahydrophthalic acid, crotonic acid, and isocrotonic acid. Core-shell particles.

11. In paragraph 10, The content of the carboxylic acid monomer is 0.1 to 10 parts by weight per 100 parts by weight of the first monomer mixture polymerized into the first polymer or the second monomer mixture polymerized into the second polymer. Core-shell particles.

12. Comprising a core-shell particle of any one of claims 1 to 11, Binder composition.

13. A core-shell particle according to any one of claims 1 to 11; and containing an electrode active material; Slurry.

14. The entire house; and An electrode active material layer comprising a core-shell particle of any one of claims 1 to 11 formed on the above-described collector; electrode.

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

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