Method for preparing electrode primer composition and method for manufacturing electrode

Abstract

The present invention provides: a method for preparing an electrode primer composition, comprising a step of preparing a mixture by mixing sodium alginate and polyacrylic acid (PAA) using a high-pressure disperser; and a method for manufacturing an electrode including the composition.

Description

Method for preparing an electrode primer composition and a method for manufacturing an electrode

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0173995 filed November 28, 2024 and Korean Patent Application No. 10-2025-0159251 filed October 29, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of this specification.

[0003]

[0004] The present invention relates to a method for preparing an electrode primer composition and a method for preparing an electrode.

[0005] Rechargeable batteries are chemical batteries capable of semi-permanent use by continuously repeating charging and discharging through electrochemical reactions, and are classified into lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and lithium-ion batteries. Among these, lithium-ion batteries lead the rechargeable battery market due to their superior characteristics of high voltage and energy density compared to other batteries, and are classified according to the type of electrolyte into lithium-ion rechargeable batteries using liquid electrolytes and lithium-ion polymer rechargeable batteries using solid electrolytes.

[0006] Furthermore, the electrode of a lithium secondary battery is generally formed by laminating an active material layer onto a current collector, which is formed by binding an electrode active material and a conductive material used as needed with a binder. While the battery can increase operating voltage and improve energy density by using an organic electrolyte, the internal resistance tended to increase due to the high viscosity of the electrolyte. Therefore, it has been proposed to provide a primer between the active material layer and the current collector to reduce internal resistance and improve adhesion between the active material layer and the current collector.

[0007] Patent Document 1 (Chinese Registered Patent 112531145, March 19, 2021) describes a method of forming a protective layer for a sodium metal cathode by applying a composition containing sodium alginate and polyacrylic acid onto a copper current collector, but there is a problem in that it is difficult to form a primer layer due to the high viscosity of sodium alginate.

[0008] The present invention is intended to provide a method for preparing a low-viscosity electrode primer composition that provides an electrode having low surface resistance and charge transfer resistance and excellent adhesion between a current collector and a primer layer, and a method for manufacturing an electrode including the same.

[0009] According to one embodiment of the present invention, a method for preparing an electrode primer composition is provided, comprising the step of preparing a mixture by mixing sodium alginate and polyacrylic acid (PAA) using a high-pressure disperser.

[0010] In addition, according to another embodiment of the present invention, a method for manufacturing an electrode is provided, comprising the steps of: preparing the electrode primer composition; and forming a primer layer comprising the electrode primer composition on one surface of a current collector.

[0011] The following describes in more detail the method for preparing an electrode primer composition and the method for preparing an electrode according to specific embodiments of the invention.

[0012]

[0013] Unless it is specified that the steps constituting the manufacturing method described herein are sequential or continuous, or if there is another special class, the order in which one step and another step constituting a manufacturing method are described herein is not to be interpreted as being limited to that order. Accordingly, the order of the steps constituting the manufacturing method may be changed to the extent that it is readily understood by those skilled in the art, and in such cases, any changes that are obvious to those skilled in the art are included within the scope of the present invention.

[0014] Unless otherwise specifically stated throughout the specification, “include” or “contain” refers to the inclusion of any component (or constituent) without any particular limitation and cannot be interpreted as excluding the addition of other components (or constituents).

[0015] In addition, in this specification, weight average molecular weight (Mw) and number average molecular weight (Mn) refer to the polystyrene equivalent molecular weight (unit: Da (Dalton)) measured by gel permeation chromatography (GPC). In the process of measuring the polystyrene equivalent weight average molecular weight measured by the GPC method, commonly known analytical devices, detectors such as a refractive index detector, and analytical columns may be used, and commonly applied temperature conditions, solvents, and flow rates may be applied. Specific examples of the above measurement conditions include a temperature of 30°C, chloroform solvent, and a flow rate of 1 mL / min. As a specific example of the above measurement conditions, using a Polymer Laboratories PLgel MIX-B 300 mm long column and a Waters PL-GPC220 instrument, the evaluation temperature was 160 ℃, 1,2,4-trichlorobenzene was used as the solvent, and the flow rate was 1 mL / min. The sample was prepared at a concentration of 10 mg / 10 mL and supplied in an amount of 200 μL, and the values ​​of Mw and Mn could be determined using a calibration curve formed using polystyrene standards. Nine types of polystyrene standards with molecular weights of 2,000 / 10,000 / 30,000 / 70,000 / 200,000 / 700,000 / 2,000,000 / 4,000,000 / 10,000,000 were used.

[0016]

[0017] According to one embodiment of the invention, a method for preparing an electrode primer composition is provided, comprising the step of preparing a mixture by mixing sodium alginate and polyacrylic acid (PAA) using a high-pressure disperser.

[0018] Conventionally, fluorinated polyvinylidene (PVDF), chitosan, polyacrylic acid, and sodium alginate have been used as electrode primer compositions. However, sodium alginate is difficult to apply in the primer process due to its high viscosity. Although attempts are made to mix it with polyacrylic acid, which has low viscosity and excellent adhesion, the high viscosity of the primer composition still makes coating difficult.

[0019] The inventors have completed the present invention by confirming that when a primer composition is prepared by including the step of mixing sodium alginate and polyacrylic acid using a high-pressure disperser to prepare a mixture, the sodium alginate and polyacrylic acid are uniformly sprayed and can be controlled to a low viscosity, making primer coating easy, as well as having excellent adhesion between the current collector and the primer layer, and that the electrode formed with such a primer layer has low surface resistance and charge transfer resistance, and the battery containing it has excellent discharge capacity retention rate according to the C-rate.

[0020] The high-pressure disperser described above can impart homogeneity, dispersibility, and stability as high-pressure fluid is accelerated and subjected to shear force and physical impact, causing particles to be broken down into nano-sized particles and finely refined.

[0021] Using the above-described high-pressure disperser, a pressure of 500 bar or more and 2,000 bar or less and a flow rate of 50 ml / min or more and 500 ml / min or less can be applied. For example, the pressure may be 700 bar or more, 800 bar or more, 900 bar or more, 1,000 bar or more, and 1,800 bar or less, 1,500 bar or less, and 1,300 bar or less. If the pressure is excessively high, the process operating cost may be high or the adhesion between current collectors may be low, and if the pressure is excessively low, the viscosity of the primer composition may be high, making it difficult to perform the coating process.

[0022] In addition, the flow rate of the high-pressure disperser may be 80 ml / min or more, 100 ml / min or more, 130 ml / min or more, 150 ml / min or more, 180 ml / min or more, 200 ml / min or more, and 450 ml / min or less, 400 ml / min or less, 350 ml / min or less, 300 ml / min or less, 250 ml / min or less. If the flow rate is excessively high, the process operating cost may be high or the adhesion between current collectors may be low, and if the flow rate is excessively low, the viscosity of the primer composition may be high, making it difficult to perform the coating process.

[0023] In addition, mixing using the high-pressure disperser may be performed one or more times, but to improve productivity, it is preferable to perform mixing using the high-pressure disperser only once.

[0024]

[0025] The high-pressure disperser above passes the fluid through a micro-orifice module via a high-pressure pump, causing physical forces such as impact, cavitation, and shear force to act within the fluid due to a rapid drop in pressure, thereby reducing sodium alginate and polyacrylic acid to nano-sized particles and dispersing them homogeneously, which can lower the viscosity of the primer composition, and the viscosity of the mixture at a temperature of 25°C may be 100 cP or more and 300 cP or less. For example, the viscosity of the mixture at a temperature of 25°C may be 120 cP or more, 130 cP or more, 150 cP or more, 160 cP or more, 170 cP or more, 180 cP or more, and 280 cP or less, 250 cP or less, 230 cP or less, and 200 cP or less.

[0026] Meanwhile, although the sodium alginate above exhibits a high viscosity of 1,000 cP or more at a temperature of 25 ℃, the mixture can exhibit the viscosity described above by mixing sodium alginate and polyacrylic acid using a high-pressure disperser. The sodium alginate above may have a viscosity of 1,300 cP or more, 1,500 cP or more, 1,800 cP or more, 2,000 cP or more, and 10,000 cP or less at a temperature of 25 ℃.

[0027] The above polyacrylic acid may have a weight-average molecular weight of 10,000 or more and 800,000 or less, for example, 30,000 or more, 50,000 or more, 100,000 or more, 200,000 or more, 250,000 or more, 300,000 or more, 350,000 or more, and 700,000 or less, 650,000 or less, 600,000 or less, 550,000 or less, 500,000 or less.

[0028] In addition, the polyacrylic acid may have a number average molecular weight of 10,000 or more and 800,000 or less, for example, 30,000 or more, 50,000 or more, 100,000 or more, 200,000 or more, 250,000 or more, 300,000 or more, 350,000 or more, and 700,000 or less, 650,000 or less, 600,000 or less, 550,000 or less, 500,000 or less.

[0029] If the weight-average molecular weight and number-average molecular weight of the polyacrylic acid are excessively high, the viscosity of the mixture may increase and flowability may decrease, and if the weight-average molecular weight and number-average molecular weight of the polyacrylic acid are excessively low, the flowability of the mixture may be high but the adhesion to the battery foil may decrease.

[0030] In addition, the polyacrylic acid may have a molecular weight distribution (PDI) of 1.0 or more and 4.0 or less, for example, 1.3 or more, 1.5 or more, 1.8 or more, 2.0 or more, and 3.5 or less, 3.0 or less, 2.5 or less.

[0031]

[0032] The weight ratio of the sodium alginate and polyacrylic acid may be 1:0.1 to 1:10, for example, 1:0.3 to 1:7, 1:0.5 to 1:5, 1:0.7 to 1:3, or 1:1 to 1:2. If the content of polyacrylic acid relative to the sodium alginate is excessively high, the surface resistance and charge transfer resistance of the manufactured anode may be high, and if the content of polyacrylic acid relative to the sodium alginate is excessively low, the viscosity of the primer composition may be high, making it difficult to perform the coating process.

[0033] In addition, the total content of sodium alginate and polyacrylic acid may be 0.1 wt% or more and 30 wt% or less with respect to 100 wt% of the primer composition, for example, 0.5 wt% or more, 1.0 wt% or more, 3.0 wt% or more, 5.0 wt% or more, and 25 wt% or less, 20 wt% or less, 15 wt% or less, 10 wt% or less, and 7 wt% or less.

[0034]

[0035] The method for preparing an electrode primer composition according to the above embodiment may further include the step of mixing a carbon source into the mixture after the step of preparing a mixture by mixing sodium alginate and polyacrylic acid using a high-pressure disperser.

[0036] By including the above carbon source, the primer composition can improve structural stability and enhance coating properties through increased sedimentation stability. Additionally, the above carbon source may be one or more selected from the group consisting of carbon black, graphite, carbon nanotubes, and fullerene, provided that it is a conductive material usable in an electrode, although it is not limited thereto.

[0037] In the above method for manufacturing an electrode primer composition, it is preferable to simply mix a carbon source into the mixture after the step of preparing a mixture by mixing sodium alginate and polyacrylic acid using a high-pressure disperser. If the carbon source is mixed together with sodium alginate and polyacrylic acid using a high-pressure disperser, it is difficult for the high-pressure disperser, which has a small passage diameter of approximately 10 mm or less, to uniformly disperse them, and multiple circulations are required to achieve dispersion. In such cases, manufacturing costs may increase or material damage may occur, leading to a deterioration in physical properties. Furthermore, the viscosity may change rapidly during the high-pressure dispersion process, which may result in unstable physical properties and viscosity of the final primer composition.

[0038] In addition, the above method for preparing the electrode primer composition allows sodium alginate and polyacrylic acid to be uniformly dispersed in the mixture dispersed by the high-pressure disperser, and the viscosity of the mixture or the final primer composition can also be controlled to be low. Therefore, the carbon source can be uniformly distributed in the mixture and interact efficiently with each other simply by adding and mixing it into the mixture, without an additional dispersion process with the mixture.

[0039] Meanwhile, the carbon source may be introduced in a solid state, such as powder, or after preparing a dispersion with an additional solvent; however, to simplify the process and reduce process costs without additional processes such as preparing a dispersion, it is preferable for the carbon source to be introduced into the mixture in a solid state, such as powder, and mixed.

[0040] In addition, the carbon source may have a particle size of 10 nm or more and 500 nm or less, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 40 nm or more, 45 nm or more, 450 nm or less, 350 nm or less, 250 nm or less, 150 nm or less, 100 nm or less, 80 nm or less, and 70 nm or less.

[0041] In addition, the content of the carbon source may be 0.1 wt% or more and 30 wt% or less with respect to 100 wt% of the primer composition, for example, 0.5 wt% or more, 1.0 wt% or more, 3.0 wt% or more, 5.0 wt% or more, and 25 wt% or less, 20 wt% or less, 15 wt% or less, 10 wt% or less, and 7 wt% or less.

[0042] In addition, the weight ratio (A:B) of the carbon source content (A) and the total content (B) of sodium alginate and polyacrylic acid may be 1:0.1 to 1:10, and for example, 1:0.3 to 1:7, 1:0.5 to 1:5, 1:0.7 to 1:3, or 1:1 to 1:2. If the total content (B) of sodium alginate and polyacrylic acid is excessively high compared to the carbon source content (A), the viscosity of the primer composition may be high, making it difficult to perform the coating process, and if the total content (B) of sodium alginate and polyacrylic acid is excessively low compared to the carbon source content (A), the anode surface resistance and charge transfer resistance may be high.

[0043]

[0044] The method for preparing an electrode primer composition according to the above embodiment may prepare a primer composition by further adding a solvent in addition to the carbon source, and the solvent may be distilled water, tetrahydrofuran (THF), tetramethylfuran (TMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), N-ethylpyrrolidone, N-vinylpyrrolidone, dimethylformamide (DMF), monomethylformamide (MMF), monomethylacetamide (MMA), dimethylacetamide (DMA), dimethylimidazolidinone, butyrolactone, diacetone alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, acetonitrile, hexamethylphosphamide (HMPA). It may include one or more selected from the group consisting of N-methyl-ε-carrolactam, tetramethylurea, chlorobenzene, dioxane, methyl ethyl ketone (MEK), isobutyl methyl ketone, and sulfolane.

[0045] In addition, the solid content concentration of the electrode primer composition may be 5% by weight or more and 50% by weight or less, for example, 7% by weight or more, 8% by weight or more, 10% by weight or more, and 40% by weight or less, 30% by weight or less, and 20% by weight or less. If the solid content concentration of the electrode primer composition is excessively high, the viscosity of the primer composition may be high, making it difficult to perform the coating process, and if the solid content concentration of the electrode primer composition is lower than that, the viscosity of the primer composition may be low, requiring an additional process.

[0046]

[0047] According to another embodiment of the invention, a method for manufacturing an electrode is provided, comprising the steps of: preparing the electrode primer composition described above; and forming a primer layer comprising the electrode primer composition on one surface of a current collector.

[0048] The step of preparing the electrode primer composition is as described above in the method for preparing an electrode primer composition according to one embodiment of the invention.

[0049] The current collector on which the above primer layer is formed may be an anode current collector.

[0050] The above-mentioned positive current collector can generally use aluminum (Al) foil, but is not limited thereto. Metal materials such as nickel (Ni) foil, stainless steel foil, and titanium (Ti) foil, or carbon-based current collectors such as carbon nanotubes (CNT), graphene, and carbon fibers, as well as carbon-coated aluminum foil, metal-carbon composites, and current collectors with mesh or foam structures, may be selectively used. Such current collectors improve electrical conductivity, mechanical strength, adhesion to the electrode, and electrochemical stability, thereby ensuring more stable performance of the secondary battery.

[0051] More specifically, the anode current collector may include aluminum foil and can be implemented in various forms, such as mesh-type aluminum foil or porous aluminum foam. The mesh-type foil can improve contact and electrolyte penetration relative to specific weight when applying active material and can lower internal resistance, while the foam form can increase the filling rate of the active material and expand the contact area of ​​the electrode-electrolyte interface, thereby improving electrochemical output and thermal management performance.

[0052] The thickness of the anode current collector may be 1 μm or more and 100 μm or 5 μm or more and 30 μm or less, for example, it may be 1 μm or more, 5 μm or more, 7 μm or more, and 10 μm or more, and 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, and 20 μm or less. If the thickness of the anode current collector is excessively thin, the mechanical strength may be reduced and it may break during the manufacturing process, and if the thickness of the anode current collector is excessively thick, the energy density may be reduced due to an increase in the inactive weight of the electrode.

[0053]

[0054] In addition, the method of forming the primer layer is not particularly limited, but it may be formed on the current collector by, for example, the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, brush application, etc. In addition, drying methods for the primer layer may include, for example, drying by hot air, hot air, low humidity air, vacuum drying, or drying by irradiation by (far) infrared rays or electron beams. The drying temperature and drying time are preferably a temperature and time that can completely remove the solvent in the slurry applied on the current collector, and the drying temperature may be 50 to 300°C or 80 to 250°C, and the drying time may preferably be 2 hours or less or 5 seconds to 30 minutes.

[0055] The thickness of the primer layer may be 0.1 μm or more and 10 μm or less, for example, 0.5 μm or more, 1.0 μm or more, 1.5 μm or more, 2.0 μm or more, and 9 μm or less, 7 μm or less, 5 μm or less, or 3 μm or less. If the thickness of the primer layer is excessively thick, the adhesion to the current collector may be reduced, and if the thickness of the primer layer is excessively thin, the surface resistance and charge transfer resistance of the anode may be high.

[0056]

[0057] The electrode manufacturing method according to the other embodiment above may include the step of forming a positive active material layer on the primer layer after forming a primer layer.

[0058] The above-mentioned cathode active material may include various lithium transition metal oxides, such as, for example, lithium iron phosphate (LiFePO4, LFP), nickel-cobalt-manganese (NCM) system, nickel / cobalt / aluminum (NCA) system, lithium cobalt oxide (LiCoO2, LCO), lithium manganese oxide (LiMn2O4, LMO), etc.

[0059] For example, a battery using a lithium iron phosphate (LFP) cathode has the advantage of being cheaper and having higher structural stability compared to a conventional nickel-cobalt-manganese (NCM) ternary battery, but it has the disadvantage that the capacity of the LFP cathode is about 150 mAh / g, which is lower than the capacity of the Ni-based cathode, which is about 200 mAh / g. However, by applying the primer layer described above, the interfacial resistance can be reduced and the output characteristics can be improved.

[0060] In addition, nickel-based ternary (NCM, NCA) cathode active materials exhibit high capacity (200 mAh / g or more) and are suitable for high-energy-density batteries, but they have low structural stability and high interfacial reactivity with the electrolyte, which may pose a risk of thermal runaway. By using the primer layer described above, the interfacial instability described above can be mitigated, and the electron transfer efficiency between the current collector and the active material layer can be improved, thereby enhancing cycle life and safety.

[0061] In addition, high-voltage cathode active materials such as LiCoPO4 and LiNi 0.5 Mn 1.5 O4, etc., can operate at 4.5V or higher, but insufficient interfacial stability can lead to problems such as electrolyte decomposition and increased electrode resistance. By using the primer layer described above, the interfacial stability with the high-voltage anode described above is improved, thereby enabling excellent output characteristics even when operating at high voltage.

[0062]

[0063] Additionally, a battery comprising a negative electrode, the positive electrode, and a separator may be provided, and the battery may include an electrode assembly comprising the negative electrode, the positive electrode, and a separator interposed between the negative electrode and the positive electrode, and an electrolyte providing ion mobility between the positive electrode and the negative electrode.

[0064] The above separator may be selected from, for example, glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and may be in the form of a nonwoven or woven fabric. For example, polyolefin-based polymer separators such as polyethylene and polypropylene may be mainly used in lithium secondary batteries, and separators coated with a composition containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength. Optionally, they may be used in a single-layer or multi-layer structure, and while it is acceptable to use separators known in the relevant art field, the present invention is not limited thereto.

[0065] The above-mentioned anode includes the contents regarding the anode active material layer described above.

[0066] The above-mentioned cathode can be manufactured in a form in which a cathode active material is bonded to a cathode current collector according to conventional methods known in the art. At this time, the cathode active material is carbon such as, for example, non-graphitizable carbon, graphite-based carbon; Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8)의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5등의 산화물; 폴리아세틸렌 등의 도전성 고분 자; Li-Co-Ni계 재료 등을 사용할 수 있다. 특히, 전지의 우수한 용량 및 수명 성능 등을 달성하기 위해 상기 음극은 리튬 금속을 포함한 활물질층을 포함할 수 있다.

[0067] Meanwhile, the above-mentioned negative current collector is not particularly limited and may include, for example, a thin film form made of copper (Cu) foil, nickel (Ni) foil, stainless steel (SUS) foil, titanium (Ti) foil, and alloys thereof. Among these, copper foil can be most widely used because it has excellent electrical conductivity and is inexpensive, while nickel foil and stainless steel foil may be advantageous in high-voltage systems or long-life batteries where corrosion resistance is required.

[0068] In addition, the negative electrode current collector may have a foam structure in addition to a simple thin film, and, for example, copper foam or nickel foam may be used. The foam current collector has a three-dimensional porous structure, which can increase the filling rate of the active material, improve the penetration of the electrolyte into the electrode, and enhance mechanical stability. This structure is particularly advantageous for batteries requiring high-capacity negative electrode designs and rapid charge / discharge characteristics.

[0069] The above-mentioned cathode current collector may further include a surface treatment process. For example, chemical etching, plasma treatment, or sandblasting may be performed to impart roughness to the surface of the current collector, thereby strengthening the physical and chemical bonding between the active material layer and the current collector. In addition, carbon coating, metal oxide coating (ZnO, TiO₂, etc.), or conductive polymer coating may be applied, and such coatings can improve electronic conductivity and enhance electrode-electrolyte interface stability.

[0070] The thickness of the above-mentioned cathode current collector may be 1 μm or more and 100 μm or 5 μm or more and 30 μm or less, for example, it may be 1 μm or more, 5 μm or more, 7 μm or more, and 10 μm or more, and 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, and 20 μm or less. If the thickness of the above-mentioned cathode current collector is excessively thin, the mechanical strength may be reduced and it may break during the manufacturing process, and if the thickness of the above-mentioned cathode current collector is excessively thick, the energy density may be reduced due to an increase in the inactive weight of the electrode.

[0071]

[0072] The above-described battery may be manufactured by a conventional battery manufacturing method and is not limited to a specific method. For example, the method includes the steps of: manufacturing an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; loading the battery assembly into a battery case; preparing an electrolyte; and pouring the electrolyte into the battery case.

[0073] In addition, the above electrode assembly can be manufactured by winding it into a jelly-roll form according to the final use of the battery, or by stacking multiple electrode assemblies to form a stack / folding type, then loading it into a suitable battery case, and then preparing an electrolyte and injecting it into the battery case.

[0074] The above electrolyte may use a non-aqueous electrolyte including a non-aqueous electrolyte. As the above-mentioned non-aqueous electrolyte, for example, non-protic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butylolactone, 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.

[0075] According to the present invention, a method for preparing a low-viscosity electrode primer composition and a method for manufacturing an electrode including the same can be provided, which provides an electrode having low surface resistance and charge transfer resistance and excellent adhesion between a current collector and a primer layer.

[0076] According to the present invention, the primer layer formed using the primer composition has low viscosity, making the coating process easy, and can also be controlled to have a uniformly thin thickness, thereby improving the energy density of the electrode. In addition, as the primer layer is formed homogeneously, the stability of the electrode-current collector interface is improved, which suppresses the increase in resistance during charge-discharge cycles and improves the lifespan characteristics of the battery.

[0077] Furthermore, according to the above electrode manufacturing method, thermal stability can be ensured by lowering the surface resistance and charge transfer resistance of the electrode to reduce heat generation, thereby improving the safety of the battery. Moreover, according to the above electrode manufacturing method, desired viscosity and composition can be secured through a simple mixing process using a high-pressure disperser, which increases manufacturing efficiency and reduces electrode manufacturing costs.

[0078] Furthermore, the electrode provided by the above electrode manufacturing method exhibits excellent capacity retention even during high-rate discharge, making it suitable for application fields requiring high output, such as electric vehicles, power tools, and energy storage systems (ESS). Moreover, the primer layer can be applied not only to lithium iron phosphate (LFP) cathode active materials but also to various series of active materials, such as nickel-cobalt-manganese (NCM), nickel-cobalt-aluminum (NCA), and high-voltage cathode active materials, thereby expanding the range of applications for next-generation lithium secondary battery electrodes.

[0079]

[0080] Figure 1 is a graph showing the measurement results of surface resistance and charge transfer resistance of the example and comparative example.

[0081] Figure 2 is a graph showing the results of measuring the discharge retention rate according to the C-rate of the examples and comparative examples.

[0082]

[0083] The invention is described in more detail in the following examples. However, the following examples are merely illustrative of the invention, and the scope of the invention is not limited by the following examples.

[0084]

[0085] <Examples and Comparative Examples>

[0086] Example 1

[0087] A mixture was prepared by dispersing (mixing) 2.5 g of polyacrylic acid (Mw: 450,000) and 2.5 g of sodium alginate (viscosity at 25 ℃ and 2 wt% in H2O concentration: 2,000 cp) using a high-pressure disperser (model name MN400BOF, PICOMAX). At this time, the operating pressure of the high-pressure disperser was 1,000 bar and the flow rate was 200 ml / min, and mixing was performed only once using the high-pressure disperser. Subsequently, 5.0 g of carbon black (average particle size: 48 nm) and 90 ml of distilled water were added to the mixture and mixed to prepare an electrode primer composition.

[0088]

[0089] Example 2

[0090] An electrode primer composition was prepared in the same manner as in Example 1, except that it was mixed twice with a high-pressure disperser instead of once with a high-pressure disperser.

[0091]

[0092] Example 3

[0093] An electrode primer composition was prepared in the same manner as in Example 1, except that it was mixed three times with a high-pressure disperser instead of once with a high-pressure disperser.

[0094]

[0095] Comparative Example 1

[0096] An electrode primer composition was prepared by adding and mixing 5.0 g of sodium alginate (viscosity at 25 ℃ and 1 wt% in H2O concentration: 12 cp), 5.0 g of carbon black (average particle size: 48 nm), and 90 ml of distilled water.

[0097]

[0098] Comparative Example 2

[0099] An electrode primer composition was prepared by adding and mixing 5.0 g of sodium alginate (viscosity at 25 ℃ and 2 wt% in H2O concentration: 2,000 cp), 5.0 g of carbon black (average particle size: 48 nm), and 90 ml of distilled water.

[0100]

[0101] Comparative Example 3

[0102] An electrode primer composition was prepared by adding and mixing 5.0 g of polyacrylic acid (Mw: 450,000), 5.0 g of carbon black (average particle size: 48 nm), and 90 ml of distilled water.

[0103]

[0104] Comparative Example 4

[0105] An electrode primer composition was prepared by adding and mixing 2.5 g of sodium alginate (viscosity at 25 ℃ and 2 wt% in H2O concentration: 2,000 cp), 2.5 g of polyacrylic acid (Mw: 450,000), 5.0 g of carbon black (average particle size: 48 nm), and 90 ml of distilled water.

[0106]

[0107] evaluation

[0108] 1. Viscosity evaluation

[0109] The viscosity of the electrode primer compositions of the examples and comparative examples was measured using a Brookfield viscometer (Anton Paar) at a temperature of 25°C and is shown in Table 1 below.

[0110]

[0111] 2. Measurement of primer layer thickness

[0112] The electrode primer compositions of the examples and comparative examples were applied onto an aluminum foil (thickness: 12 μm) and dried to produce a current collector with a primer layer formed thereon, and the thickness of the primer layer was measured using a digital micrometer (measurable to 0.001 mm) and is shown in Table 1 below.

[0113]

[0114] 3. Surface Resistance Evaluation

[0115] The electrode primer compositions of the examples and comparative examples were applied onto aluminum foil (thickness: 12 μm) and dried to produce a current collector with a primer layer formed thereon. A surface resistance measurement probe was placed on the primer layer, and a current was applied using a milliohm meter (HIOKI) to measure the surface resistance. The results are shown in Table 1 below. Meanwhile, Figure 1 is a graph showing the surface resistance measurement results of the examples and comparative examples.

[0116]

[0117] 4. Evaluation of Primer Layer Peel Strength

[0118] The electrode primer compositions of the examples and comparative examples were applied to an aluminum foil (thickness: 12 μm) to a thickness of 1 to 2 μm and dried to produce a current collector with a primer layer formed thereon. Then, a 3M adhesive tape (width: 1.8 cm) was pressed onto the primer layer using a 50 g rubber roller, and then 180° peeled at a speed of 50 mm / min using a UTM (Instron 68SC-1) to measure the 180° peel strength, and the results are shown in Table 1 below.

[0119]

[0120] 5. Evaluation of Charge Transfer Resistance

[0121] The charge transfer resistance of a battery including an electrode using the electrode primer compositions of the examples and comparative examples was evaluated, and the results are shown in Table 1 below.

[0122] Specifically, the electrode primer compositions of the examples and comparative examples were applied onto an aluminum foil (thickness: 12 μm) and dried to produce a current collector with a primer layer formed thereon, and an active material composition containing LiFePO4 as an active material was formed on the primer layer to form an active material layer and produce an anode.

[0123] Subsequently, a coin cell was fabricated using a separator (Celgard 2325) between the anode and the artificial graphite cathode. After inserting the coin cell into an aluminum pouch, 40 μl of electrolyte (1M LiPF6in EC / EMC / DMC 1:1:1 + 2wt% VC + 5wt% FEC electrolyte) was injected to fabricate the cell. Subsequently, the charge transfer resistance (R) of the coin cell was measured using an electrochemical impedance spectroscopy instrument. ct ) measured.

[0124] Figure 1 is a graph showing the measurement results of charge transfer resistance of the example and comparative example.

[0125]

[0126] 6. Evaluation of Discharge Retention Rate According to C-Rate

[0127] The discharge retention rate according to the C-rate of a battery including an electrode using the electrode primer compositions of the examples and comparative examples was evaluated, and the results are shown in Table 1 below.

[0128] Specifically, a cell was manufactured as described in '5. Evaluation of Charge Transfer Resistance' above, and the capacitance was measured in the order of C-rate 0.2 C / 0.1 C -> 0.2 C / 0.2 C -> 0.2 C / 0.5 C -> 0.2 C / 1.0 C -> 0.2 C / 2.0 C -> 0.2 C / 3.0 C -> 0.2 C / 5.0 C, and the capacitance retention rates of other C-rates were measured based on 0.2 C / 0.1 C (100%), and the results are shown in Table 1 below.

[0129] Figure 2 is a graph showing the results of measuring the discharge retention rate according to the C-rate of the examples and comparative examples.

[0130]

[0131] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Viscosity (cP, 25 ℃) 190 180 160 180 800 180 500 Thickness (㎛) 22 22 525 Surface Resistance (Ω cm) 0.5 0.6 0.6 0.7 0.9 0.7 50.8 Peel Strength (N cm -1 )3.12.82.32.03.52.23.0 Charge transfer resistor R ct (Ω cm 2 Discharge retention rate (%) by C-rate vs. 0.2C / 0.1C 0.2C / 0.1C 100 100 100 100 100 100 100 0.2C / 0.2C 98.7 98.6 98.5 98.7 98.8 98.4 98.8 0.2C / 0.5C 94.8 94.6 95.5 94.5 95.0 94 94.2 0.2C / 1.0C 90.8 90.79 1.590.489.789.489.50.2C / 2.0C84.084.184.283.481.982.181.80.2C / 3.0C 78.878.979.274.674.175.571.80.2C / 5.0C70.570.771.167.666.867.765.9

[0132] Referring to Table 1 and Figures 1 and 2 above, it was confirmed that Examples 1 to 3 have low viscosity, resulting in excellent coating processability, and that the primer layer is formed uniformly and thinly, thereby reducing surface resistance and charge transfer resistance, while maintaining excellent capacity retention even during high-rate discharge. In addition, the peel strength was also stably secured, which had the effect of sufficiently maintaining the adhesion between the primer layer and the current collector.

[0133] On the other hand, Comparative Example 1, which used only low-viscosity sodium alginate, showed low peel strength due to insufficient adhesion, while Comparative Examples 2 and 4, which used only high-viscosity sodium alginate or did not use a high-pressure disperser, had high viscosity, making it difficult to form a uniform and thin primer layer. As a result, surface resistance increased, and they exhibited inferior performance compared to the examples in terms of charge transfer resistance and high-rate discharge retention rate.

Claims

1. A step of preparing a mixture by mixing sodium alginate and polyacrylic acid (PAA) using a high-pressure disperser; comprising, Method for preparing an electrode primer composition.

2. In Paragraph 1, A method for preparing an electrode primer composition by applying a pressure of 500 bar or more and 2,000 bar or less and a flow rate of 50 ml / min or more and 500 ml / min or less using the above-mentioned high-pressure disperser.

3. In Paragraph 1, A method for preparing an electrode primer composition, wherein mixing using the above-mentioned high-pressure disperser is performed only once.

4. In Paragraph 1, A method for preparing an electrode primer composition, wherein the above mixture has a viscosity of 100 cP or more and 300 cP or less at a temperature of 25 ℃.

5. In Paragraph 1, A method for preparing an electrode primer composition, wherein the sodium alginate above has a viscosity of 1,000 cP or more at a temperature of 25 ℃.

6. In Paragraph 1, A method for preparing an electrode primer composition in which the weight ratio of the sodium alginate and polyacrylic acid is 1:0.1 to 1:

10.

7. In Paragraph 1, A method for preparing an electrode primer composition, further comprising the step of mixing a carbon source into the above mixture.

8. In Paragraph 7, A method for preparing an electrode primer composition, wherein the carbon source is one or more selected from the group consisting of carbon black, graphite, carbon nanotubes, and fullerene.

9. In Paragraph 7, A method for preparing an electrode primer composition, wherein the content of the carbon source is 0.1% by weight or more and 30% by weight or less with respect to 100% by weight of the primer composition.

10. In Paragraph 7, A method for preparing an electrode primer composition, wherein the weight ratio (A:B) of the carbon source content (A) and the total content (B) of sodium alginate and polyacrylic acid is 1:0.1 to 1:

10.

11. A step of preparing an electrode primer composition according to claim 1; and A method for manufacturing an electrode, comprising the step of forming a primer layer containing the electrode primer composition on one surface of the current collector.

12. In Paragraph 11, A method for manufacturing an electrode, wherein the thickness of the primer layer is 0.1 μm or more and 10 μm or less.

13. In Paragraph 11, A method for manufacturing an electrode in which a positive active material layer composed of lithium iron phosphate is formed on the above primer layer.

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