Electrode composition, electrode slurry, electrode, and lithium secondary battery

Abstract

The present invention relates to an electrode composition comprising: an electrode active material; an electrode binder; and polymer beads, wherein the polymer beads are soluble in an electrolyte solution.

Description

Technical Field

[0001] This invention relates to electrode compositions, electrode slurries, electrodes, and lithium secondary batteries.

[0002] <Cross-reference to related applications>

[0003] This application claims priority and benefit to Korean Patent Application No. 10-2024-0147183, filed with the Korean Intellectual Property Office on October 25, 2024, and Korean Patent Application No. 10-2025-0155287, filed with the Korean Intellectual Property Office on October 24, 2025, the entire contents of which are incorporated herein by reference. Background Technology

[0004] Due to the rapid increase in the use of fossil fuels, the demand for alternative or clean energy is growing, and as part of this, the most active area of ​​research is the use of electrochemical reactions for power generation and energy storage.

[0005] Currently, secondary batteries are a representative example of electrochemical devices that use this type of electrochemical energy, and their specific applications are gradually expanding.

[0006] With technological advancements and increasing demand for mobile devices, the need for secondary batteries as energy sources has risen dramatically. Among these secondary batteries, lithium-ion batteries, characterized by high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used. Furthermore, a method for manufacturing high-density electrodes with even higher energy density per unit volume for use in such high-capacity lithium-ion batteries is under active research.

[0007] Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material for inserting and de-inserting lithium ions from the positive electrode, and silicon-based particles with high discharge capacity can be used as the negative electrode active material.

[0008] However, during electrode manufacturing, the wettability between the electrode and the electrolyte solution decreases due to the application of high rolling pressure. When the electrolyte does not fully penetrate the electrode, ion transport slows down, making it difficult for the electrode reaction to occur smoothly, and thus reducing the battery's charge / discharge efficiency and capacity. Although attempts have been made to address this issue, improvements in electrode-electrolyte wettability remain limited. Furthermore, reduced ion transport degrades output and fast-charging performance, leading to overall battery performance degradation.

[0009] [List of Citations]

[0010] (Patent Document 1) Korean Patent Application Publication No. 10-2007-0076144 Summary of the Invention

[0011] Technical issues

[0012] Therefore, the present invention has made efforts to provide an electrode composition, electrode slurry, electrode, and lithium secondary battery, the lithium secondary battery comprising polymer beads capable of preventing a decrease in the wettability of the electrode and electrolyte solution caused by a high-pressure rolling process.

[0013] Technical solution

[0014] An exemplary embodiment of the present invention provides an electrode composition comprising an electrode active material; an electrode binder; and polymer beads, wherein the polymer beads are soluble in an electrolyte solution.

[0015] An exemplary embodiment of the present invention provides an electrode slurry comprising the electrode composition and a solvent.

[0016] An exemplary embodiment of the present invention provides an electrode comprising an electrode current collector layer; and an electrode active material layer comprising the electrode composition on one or both surfaces of the electrode current collector layer.

[0017] An exemplary embodiment of the present invention provides a lithium secondary battery, the lithium secondary battery including a first electrode; a second electrode; a separator disposed between the first electrode and the second electrode; and an electrolyte, wherein the first electrode or the second electrode is the electrode described above.

[0018] Beneficial effects

[0019] By dissolving the polymer beads in the electrolyte solution, the electrode composition according to an exemplary embodiment of the present invention can reduce resistance, increase output, and improve the lifespan of lithium secondary batteries. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating an electrode comprising an electrode composition according to an exemplary embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram illustrating an electrode comprising an electrode composition of the prior art.

[0022] <Explanation of Figure Markers>

[0023] 10: Electrode active materials

[0024] 20: Electrode adhesive

[0025] 30: Polymer beads Detailed Implementation

[0026] This instruction manual will now be described in more detail.

[0027] It should be understood that the terms or words used throughout the specification should not be construed as limited to their ordinary or dictionary meanings, but rather as having meanings and concepts consistent with the technical ideas of the invention, based on the inventor's ability to appropriately define the concepts of the words or terms to best illustrate the principles of the invention.

[0028] As used herein, the singular forms of terms such as “a,” “one,” and “the” are intended to also include the plural forms, unless the context clearly indicates otherwise.

[0029] In this specification, when a part is referred to as "comprising" a component, it means that the part may further include another component, but does not exclude another component, unless explicitly stated otherwise.

[0030] Throughout the specification, when an element is referred to as being "on" another element, the element may be in direct contact with the other element or there may be an intermediate element present.

[0031] In this specification, "p to q" means a range of "p or greater and q or less".

[0032] As used herein, the description "a polymer includes a monomer as a monomeric unit" means that the monomer participates in the polymerization reaction and is included in the polymer as a repeating unit.

[0033] As used herein, when describing a polymer as containing monomers, this is interpreted in the same way as when the polymer contains monomers as monomer units.

[0034] In this specification, unless specifically indicated as 'homopolymer', the term 'polymer' is used in the broad sense, including copolymers.

[0035] In this specification, the "weight-average molecular weight (Mw)" and "number-average molecular weight (Mn)" of a compound can be determined using the compound's molecular weight and molecular weight distribution. Specifically, a sample solution with a compound concentration of 1% by weight is prepared by placing tetrahydrofuran (THF) and the compound in a 1 ml glass tube. The standard sample (polystyrene) and the sample solution are filtered through a filter (0.45 μm pore size) and injected into a GPC injector. The molecular weight and molecular weight distribution of the compound are determined by comparing the elution time of the sample solution with the calibration curve of the standard sample. In this case, an Infinity II 1260 (Agilent Technologies) can be used as the measuring device, and the flow rate and column temperature can be set to 1.00 mL / min and 40.0 °C.

[0036] In this specification, molecular weight refers to weight-average molecular weight unless otherwise specified.

[0037] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can readily implement the present invention. However, the present invention can be implemented in various different forms and is not limited to the following description.

[0038] <Electrode Composition>

[0039] An electrode composition according to an exemplary embodiment of the present invention comprises: an electrode active material; an electrode binder; and polymer beads, wherein the polymer beads are soluble in an electrolyte solution.

[0040] Electrode adhesives are insoluble adhesives that are insoluble in electrolyte solutions, and can be used to enhance the adhesion between electrode active material particles and between electrode active material particles and electrode current collectors.

[0041] Polymer beads are soluble binders that dissolve in electrolyte solutions. In the presence of an electrolyte solution, the polymer beads dissolve, creating elongated pores at their location. This allows for the formation of numerous elongated channels through which the electrolyte solution can move, thereby reducing resistance, increasing output power, shortening fast charging time, and extending the lifespan of lithium-ion batteries.

[0042] According to an exemplary embodiment of the present invention, the electrode composition further includes a solvent, and the polymer beads are insoluble in the solvent.

[0043] When the electrode is the negative electrode, the solvent can be a solvent such as water, NMP or alcohol.

[0044] Solvents are used to mix electrode binders and electrode active materials during electrode manufacturing and to form electrode slurries. When the electrode slurry is applied to the electrode current collector layer and subsequently dried to manufacture the electrode, the electrode binder improves the adhesion between electrode active material particles and between the electrode active material particles and the electrode current collector, and the polymer beads dissolve in the electrolyte solution to form pores, thereby creating numerous elongated channels through which a large number of electrolyte solutions can move.

[0045] The inventors accomplished this invention by using polymer beads that are essentially soluble only in electrolyte solutions and insoluble in other solvents, thereby forming channels through which electrolyte solutions can easily move.

[0046] Furthermore, compared to compositions that do not use polymer beads, the electrode composition using polymer beads according to this exemplary embodiment can provide a uniform, continuous, and elongated electrolyte channel within the electrode by forming pores. Moreover, it has been demonstrated that when an electrode is manufactured using the electrode composition according to the above exemplary embodiment, not only is the impregnation time shortened, but lithium ions also diffuse smoothly into the electrode, thereby reducing resistance, increasing capacity, and improving output.

[0047] According to an exemplary embodiment of the present invention, the electrode is a negative electrode, and the electrode adhesive may include at least one selected from the group consisting of fluorinated polymers, styrene polymers, polyvinyl alcohol (PVA), polyacrylonitrile (PAN), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), and sulfonated EPDM polymers.

[0048] Fluoropolymers can be polyvinylidene fluoride (PVDF), but are not particularly limited to any particular type, as long as they are fluoropolymers that are insoluble in electrolytes.

[0049] The styrene-based polymer can be styrene-butadiene rubber (SBR), but it is not particularly limited, as long as it is a styrene-based polymer that is insoluble in electrolytes.

[0050] According to an exemplary embodiment of the present invention, the solubility of the polymer beads in the solvent of the electrolyte solution is 1% w / w to 100% w / w within a temperature range of 10 °C to 70 °C. When the above range is met, elongated pores are formed when the polymer beads dissolve. The pores allow lithium (Li) ions in the electrolyte solution to flow rapidly, thereby improving output and fast charging performance. During the final manufacturing process of the lithium secondary battery, the polymer beads can be dissolved in the electrolyte and remain therein. Depending on the temperature, the polymer beads can be formed as fine particles in the region where the electrolyte is present, or they can exist as a very thin coating on the surface of materials such as active materials or separators.

[0051] According to an exemplary embodiment of the present invention, the solubility of the polymer beads in the solvent at 25 °C is 1% w / w or less. When the above range is met, the polymer beads will not dissolve in the solvent during mixing and coating, and will remain in the coated electrode along with the electrode active material, so that the polymer beads can subsequently dissolve in the electrolyte solution to form pores.

[0052] According to an exemplary embodiment of the present invention, the polymer beads may have a cylindrical, spherical, or hollow structure (core-shell structure).

[0053] The polymer beads preferably have a hollow structure (core-shell structure). When the polymer beads have a hollow structure (core-shell structure), compared with other structures, the content of polymer beads dissolved in the electrolyte solution can be reduced, thereby preventing an increase in the viscosity of the electrolyte solution, which may be effective in terms of output and fast charging.

[0054] When polymer beads are used to form pores, elongated channels of any desired shape can be created based on the shape of the polymer beads. This allows for a large flow of electrolyte solution without clogging, thereby reducing resistance, increasing output, and extending the lifespan of the lithium-ion battery. However, when pores are formed from non-formed organic compound polymers dissolved in the electrode mixing solvent, it is impossible to form elongated channels of the desired shape. This results in insufficient artificial electrolyte solution flow channels, merely enlarging existing channels. Therefore, such channels may be slightly inferior to straight electrolyte solution flow channels, potentially leading to significant performance differences in electrodes subjected to high-pressure rolling.

[0055] When polymer beads are dissolved in an electrolyte solution to form pores, the electrode is not damaged compared to the case where pores are formed by sintering polymer beads through thermal decomposition. This also eliminates the risk of thermal decomposition due to heat generated during mixing, which could adversely affect the safety of the electrode slurry.

[0056] According to an exemplary embodiment of the present invention, the electrode may be a negative electrode, and the polymer beads may include at least one of the following: polyurethane, polyurea, polyamide, polyester, polycarbonate, polyacrylate, polystyrene, polymethyl methacrylate, vinylidene chloride, urea-formaldehyde resin, melamine resin, copolymers thereof, naphthalene, 1,7,7-trimethylbicyclohepta-2-one, cyclohexane-1,2-dicarboxylic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, cyclohexane-1,2,4-tricarboxylic acid, phthalic acid, aminoacetophenone, vanillin, 4-hydroxyphthalic acid, trimellitic acid, trimellitic anhydride, dimethoxyacetophenone, 5-hydroxyisophthalic acid, gallic acid, methyl gallate, 1,7-dihydronaphthalene, 4,4'-dihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, and copolymers thereof.

[0057] When the electrode is a negative electrode, the polymer beads may include at least one of, for example, polyurethane (PU) and polycaprolactone (PCL).

[0058] According to an exemplary embodiment of the present invention, based on 100 parts by weight of the electrode composition, the content of polymer beads can be 0.5 parts by weight or more and 10 parts by weight or less, preferably 0.6 parts by weight or more, 0.7 parts by weight or more, 0.8 parts by weight or more, 0.9 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, or 2 parts by weight or more, and 9.5 parts by weight or less, 9.0 parts by weight or less, 8.5 parts by weight or less, 8.0 parts by weight or less, 7.5 parts by weight or less, or 7.0 parts by weight or less. When the above ranges are met, a suitable electrode configuration ensures the structural safety of the electrode and makes the manufacture of high-performance batteries possible.

[0059] According to an exemplary embodiment of the present invention, based on the solid content of 100 parts by weight of the electrode composition, the content of the electrode binder can be from 0.5 to 10 parts by weight, and preferably can be 0.6 parts by weight or more, 0.7 parts by weight or more, 0.8 parts by weight or more, 0.9 parts by weight or more, 1 part by weight or more, 2 parts by weight or more, or 3 parts by weight or more, and 9.9 parts by weight or less, 9.8 parts by weight or less, 9.7 parts by weight or less, 9.6 parts by weight or less, 9.5 parts by weight or less, or 9 parts by weight or less. When the above ranges are met, it is possible to prevent a decrease in adhesion to the electrode active material layer due to insufficient binder or a deterioration in the electrical properties of the electrode due to excessive binder.

[0060] According to an exemplary embodiment of the present invention, the weight-average molecular weight of the electrode adhesive can be 100,000 g / mol or greater and 1,500,000 g / mol or less. When the weight-average molecular weight of the electrode adhesive falls within the above range, the electrode adhesive exhibits excellent mechanical strength and high intermolecular interaction, resulting in excellent adhesion of the electrode. Furthermore, when the above range is satisfied, the viscosity of the electrode adhesive can be set within an appropriate range, thereby resulting in excellent coatability of the electrode when it is used to manufacture the electrode.

[0061] The electrode binder can be a negative electrode binder.

[0062] Electrode adhesives can be water-based adhesives.

[0063] When aqueous binders are used in electrode compositions, they enable rapid dissolution, ease of processing, and high efficiency. They also allow for stable control of the electrode slurry viscosity, ensuring long-term cycling and providing additional advantages such as high adhesion under various operating temperature conditions.

[0064] To manufacture water-based adhesives, polymerization initiators are used, and examples of polymerization initiators may include, but are not limited to, ammonium persulfate.

[0065] According to an exemplary embodiment of the present invention, the electrolyte solution may include, but is not limited to, one or more solvents selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC).

[0066] The electrolyte solution may include, but is not limited to, one or more electrolyte solutions selected from, for example, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), butenyl carbonate (BC), γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, trimethoxymethane, dioxolane derivatives, 1,3-dimethyl-2-imidazolinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0067] Specifically, among carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are high-viscosity organic solvents and can be preferably used because they have high dielectric constants to effectively dissociate lithium salts. When cyclic carbonates are mixed and used in appropriate proportions with low-viscosity and low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate, electrolytes with high conductivity can be prepared and can therefore be used more preferably.

[0068] The electrode active material can be a negative electrode active material.

[0069] According to an exemplary embodiment of the present invention, the electrode active material may include one or more selected from the group consisting of silicon-based active materials and carbon-based active materials.

[0070] Based on the solid content of 100 parts by weight of the electrode composition, the content of the electrode active material can be 90 parts by weight or more and 98 parts by weight or less, preferably 92 parts by weight or more and 97.5 parts by weight or less.

[0071] According to an exemplary embodiment of the present invention, the silicon-based active material may include materials selected from Si and SiO2. x One or more of the group consisting of (0 < x < 2), Si / C, and Si alloys. Silicon-based active materials have a capacity at least 10 times higher than carbon-based active materials, and therefore, when silicon-based active materials are used in electrodes, especially negative electrodes, electrodes with high energy density can be achieved even with reduced thickness compared to cases involving only carbon-based active materials.

[0072] Electrode active materials may include silicon-based active materials, and silicon-based active materials may include those selected from Si and SiO2. x One or more of the groups consisting of (0 < x < 2).

[0073] Silicon-based active materials may use only pure silicon (Si) as the silicon-based active material. Using pure silicon (Si) as the silicon-based active material means that, based on 100 parts by weight of the total silicon-based active material described above, pure Si particles that are not bonded to other particles or elements are included in the above range.

[0074] Silicon-based active materials can exist in a crystalline or amorphous form. Specifically, the silicon particles in silicon-based active materials are preferably spherical, but not limited to this.

[0075] In SiO x The value of x is excluded because SiO2 with x equal to 2 does not react with lithium ions and therefore cannot store lithium. Therefore, x is preferably within the range described above.

[0076] Silicon-based active materials can be Si / C, composed of Si and C complexes. For example, each peak of Si and C can be observed using elemental analysis methods such as XRD or NMR. Silicon-carbon composites can be represented as Si / C, and can consist of Si and C that are not bonded to each other, but may also contain other components as needed. For example, silicon-carbon composites may contain or not contain silicon carbide, represented by SiC. When silicon-carbon composites contain silicon carbide, its content is 3% by weight or less. Silicon-carbon composites can exist in a crystalline, amorphous, or mixed state. According to one example, C in a silicon-carbon composite can exist in an amorphous state.

[0077] According to an exemplary embodiment of the present invention, carbon-based active materials may include one or more selected from the group consisting of artificial graphite, natural graphite, hard carbon, and soft carbon.

[0078] When the electrode active material is composed of silicon-based and carbon-based active materials, the ratio of silicon-based to carbon-based active materials can be in the range of 2:98 to 30:70. Electrode active materials that meet the above range mainly contain carbon-based active materials as the main component. Therefore, they exhibit small volume expansion during charging and discharging, resulting in reduced swelling, and also have the additional effect of excellent conductive connectivity.

[0079] The positive electrode active material can be a commonly used positive electrode active material. Specifically, the positive electrode active material can be a layered compound such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2) or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides represented by O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxides (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; and those represented by the chemical formula LiNi. 1-c2 M c2 O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01 ≤ c2 ≤ 0.3) represents a Ni-site type lithium nickel oxide; LiMn 2-c3 M c3Lithium manganese composite oxides represented by O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≤c3≤0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn); LiMn2O4, where part of the Li in the chemical formula is replaced by an alkaline earth metal ion, etc., but not limited thereto.

[0080] According to an exemplary embodiment of the present invention, the electrode composition may include an electrode conductive material, and based on 100 parts by weight of the electrode composition, the content of the electrode conductive material may be 0.03 parts by weight or more and 40 parts by weight or less. Specifically, based on 100 parts by weight of the electrode composition, the electrode conductive material may be included in an amount of 0.03 parts by weight or more and 40 parts by weight or less, preferably 0.05 parts by weight or more and 30 parts by weight or less, more preferably 0.5 parts by weight or more and 25 parts by weight or less.

[0081] According to an exemplary embodiment of the present invention, the electrode composition may include an electrode conductive material, and the electrode conductive material may include one or more selected from the group consisting of point conductive materials, planar conductive materials and linear conductive materials.

[0082] Electrode conductive materials can include dot-shaped conductive materials and linear conductive materials.

[0083] Dot-like conductive materials refer to dot-shaped or spherical conductive materials that can be used to improve the conductivity of electrodes and have conductivity without causing chemical changes. Specifically, dot-like conductive materials can be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking black, conductive fibers, fluorocarbons, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium dioxide, and polyphenylene derivatives. From the perspective of achieving high conductivity and excellent dispersibility, they preferably include carbon black and / or artificial graphite.

[0084] Planar conductive materials can improve conductivity by increasing the planar contact between silicon particles in the electrode, while simultaneously suppressing the interruption of conductive paths due to volume expansion. Planar conductive materials can be represented as plate-like conductive materials or bulk conductive materials. Examples of planar conductive materials may include at least one selected from the group consisting of plate-like graphite, graphene, graphene oxide, and graphite sheets, and preferably plate-like graphite.

[0085] Linearly conductive materials can be carbon nanotubes. Carbon nanotubes can be bundled carbon nanotubes. Bundled carbon nanotubes can comprise multiple carbon nanotube units. Specifically, here, the term "bundle-type" refers to, unless otherwise specified, a bundle-like or rope-like secondary shape in which multiple carbon nanotube units are aligned or entangled side-by-side along a direction substantially the same as the longitudinal axis of the carbon nanotube units. The carbon nanotube units have cylindrical graphite sheets with nanometer-sized diameters and sp... 2 Bonded structure. In this case, the properties of conductive or semiconductor materials can be expressed based on the curling angle and structure of the graphite sheet. Compared to entangled-type carbon nanotubes, bundled carbon nanotubes can be more uniformly dispersed during the fabrication of the negative electrode and can form a conductive network more smoothly in the negative electrode, thereby improving the conductivity of the negative electrode.

[0086] The electrode conductive material can be a negative electrode conductive material.

[0087] The negative conductive material is applied to the negative electrode and has a structure that is completely separate from the positive conductive material applied to the positive electrode. That is, the negative conductive material is used to support the contact points between the silicon-based active materials, which undergo significant volume expansion due to charging and discharging, while the positive conductive material is used to impart partial conductivity and acts as a buffer when wound. Therefore, the structures and functions of the negative and positive conductive materials are different from each other.

[0088] Positive electrode conductive materials are used to impart conductivity to the electrodes and are used without particular limitations, as long as they are electronically conductive without causing a chemical change in the battery to be configured. Specific examples may include graphite such as natural and artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium dioxide; or conductive polymers such as polyphenylene derivatives, etc., and any one of them or a mixture of two or more of them may be used.

[0089] According to an exemplary embodiment of the present invention, the electrode composition may further include a thickener, the type and amount of which are not particularly limited, and carboxymethyl cellulose (CMC) can be used as a thickener, for example.

[0090] <Method for Manufacturing Electrode Compositions>

[0091] A method for manufacturing an electrode composition is provided, comprising the steps of: preparing an electrode active material; preparing an electrode binder; preparing polymer beads; and adding an electrode conductive material. In this specification, the above can be applied to electrode active materials, electrode binders, polymer beads, and conductive materials. In the case of polymer beads, they are added and mixed in powder form. However, in the case of mixing, since thorough mixing is required, the polymer beads are added and mixed for a sufficiently long time (approximately 20 minutes or longer).

[0092] <Electrode Paste>

[0093] The electrode slurry according to an exemplary embodiment of the present invention comprises the electrode composition described above and a solvent.

[0094] Solvents may include those known in the art. For example, solvents may be water (e.g., distilled water) or N-methyl-2-pyrrolidone (NMP), but are not limited thereto.

[0095] The electrode paste can be a negative electrode paste, and therefore the electrode composition can be used for a negative electrode paste.

[0096] The positive electrode slurry includes the above-mentioned positive electrode composition and solvent.

[0097] In some cases, by appropriately adjusting the average particle size (D50) or specific surface area of ​​the silicon-based active material to control the viscosity of the electrode paste within a suitable range, the dispersibility of the components (e.g., conductive materials, binders, silicon-based active materials, and carbon-based active materials) in the electrode paste can be improved. This improves the contact area between components, allowing the conductive network to be maintained, increasing capacity retention, and preventing non-uniformity in current density during charging and discharging.

[0098] Furthermore, in some cases, the viscosity of the electrode paste can be adjusted to 5000 cps to 6000 cps. When the viscosity is within this range, it exhibits excellent storage stability and good coating performance when the electrode paste is applied to one or both surfaces of the electrode current collector layer.

[0099] <Electrode>

[0100] An electrode according to an exemplary embodiment of the present invention comprises an electrode current collector layer; and an electrode active material layer comprising the above-described electrode composition on one or both surfaces of the electrode current collector layer.

[0101] The electrode can be a negative electrode, and therefore, the electrode current collector layer, electrode paste, and electrode active material layer are all used as negative electrodes.

[0102] The negative electrode current collector layer typically has a thickness of 1 μm to 100 μm. There are no particular limitations on such a layer, as long as it possesses high conductivity without causing chemical changes within the battery. For example, materials such as copper, stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum alloys, and copper or stainless steel treated with carbon, nickel, titanium, silver, etc., on each surface can be used. Furthermore, the negative electrode current collector layer can have microscopic irregularities formed on its surface to enhance the adhesion of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, or nonwoven fabrics.

[0103] This invention provides a negative electrode for a lithium secondary battery, wherein the thickness of the negative electrode current collector layer is 1 μm or greater and 100 μm or less, and the thickness of the negative electrode active material layer is 20 μm or greater and 500 μm or less. However, this thickness can vary depending on the type and application of the negative electrode used, and is not limited thereto.

[0104] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including positive electrode active material.

[0105] In the positive electrode, there are no particular restrictions on the positive current collector, as long as it is conductive and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel with surface treatments of carbon, nickel, titanium, silver, etc., can be used. Furthermore, the thickness of the positive current collector can typically range from 3 μm to 500 μm, and microscopic irregularities can be formed on its surface to enhance the adhesion of the positive electrode active material. For example, the positive current collector can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, or nonwoven fabrics.

[0106] The positive electrode can be Li-metal.

[0107] The positive electrode active material layer may include the aforementioned positive electrode active material, as well as the positive electrode conductive material and the positive electrode binder.

[0108] <Lithium secondary batteries>

[0109] An exemplary embodiment of the present invention provides a lithium secondary battery, comprising: a first electrode; a second electrode; a separator disposed between the first electrode and the second electrode; and an electrolyte, wherein the first electrode or the second electrode is the electrode described above.

[0110] Specifically, the first electrode can be a negative electrode and the second electrode can be a positive electrode, or the first electrode can be a positive electrode and the second electrode can be a negative electrode.

[0111] Specifically, a lithium secondary battery may include a negative electrode, a positive electrode, a separator inserted between the positive and negative electrodes, and an electrolyte, wherein the negative electrode is the same as the negative electrode described above. Since the negative electrode has already been described, its detailed description is omitted.

[0112] The separator is used to separate the negative electrode from the positive electrode and to provide a migration path for lithium ions. Any separator can be used without particular limitation, as long as it is commonly used in secondary batteries. However, separators with high electrolyte water retention capacity and low electrolyte ion migration resistance are preferred. Specifically, porous polymer membranes can be used, such as porous polymer membranes made of polyolefin-based polymers, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers; or stacked structures having two or more layers. Alternatively, conventional porous nonwoven fabrics can be used, such as nonwoven fabrics made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc. Furthermore, coated separators containing ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and separators with single-layer or multi-layer structures can be selectively used.

[0113] Examples of electrolytes may include, but are not limited to, organic-based liquid electrolytes, inorganic-based liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, or molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0114] Specifically, electrolytes can include metal salts.

[0115] Lithium salts can be used as metal salts, and these lithium salts are readily soluble in non-aqueous electrolytes, such as those selected from F. - Cl - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH -(SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - One or more of the groups can be used as anions of lithium salts.

[0116] In addition to the electrolyte components mentioned above, one or more additives, such as halogenated alkyl carbonate compounds like ethylene difluorocarbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether, triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, can be further included in the electrolyte to improve battery life characteristics, inhibit battery capacity reduction, increase battery discharge capacity, etc.

[0117] An exemplary embodiment of the present invention provides a battery module and a battery pack, wherein the battery module includes a lithium secondary battery as a unit cell, and the battery pack includes the battery module. Alternatively, a battery pack including a lithium secondary battery is provided. Because the battery module and battery pack include a secondary battery with high capacity, high rate performance, and high cycle characteristics, the battery module and battery pack can be used as a power source for medium to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems.

[0118] Figure 1 This is a schematic diagram illustrating an electrode comprising an electrode composition according to an exemplary embodiment of the present invention, and Figure 2 This is a schematic diagram illustrating an electrode comprising a prior art electrode composition according to another exemplary embodiment of the present invention. Figure 1 It can be confirmed that when electrode binders and polymer beads are used and introduced into the electrolyte solution, effects such as reduced resistance, improved output, and increased lifespan are achieved. However, according to... Figure 2 It can be confirmed that when only one type of binder is used and introduced into the electrolyte solution, no effect of reduced resistance, improved output, or increased lifespan is obtained.

[0119] Best mode

[0120] Preferred embodiments are provided below to better understand the present invention. It will be apparent to those skilled in the art that these embodiments are merely illustrative of the invention, and various modifications and changes can be made within the scope and spirit of the invention. These modifications and changes naturally fall within the scope of this document.

[0121] <Preparation of Negative Electrode Adhesives and Polymer Beads>

[0122] Example 1-1

[0123] In a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet pipe, a negative electrode binder of styrene-butadiene rubber (SBR) was prepared at a content of 2.3% w / w, and polymer beads of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) were added and prepared at a content of 2% w / w. A negative electrode composition having the composition and content (based on % w / w) shown in Table 1 below was then prepared.

[0124] Examples 1-2

[0125] In a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet pipe, a negative electrode binder, styrene-butadiene rubber (SBR), was prepared at a content of 2.3% w / w, and polymer beads, polyurethane (PU), were added and prepared at a content of 2%. A negative electrode composition having the composition and content (based on % w / w) shown in Table 1 below was then prepared.

[0126] Comparative Example 1-1

[0127] The negative electrode binder was prepared using the same method as in Preparation Examples 1-1, except that polymer beads were not prepared, and the negative electrode binder, which was styrene-butadiene rubber (SBR), was prepared at a content of 4.3% w / w. Then, negative electrode compositions having the composition and content (based on % w / w) shown in Table 1 below were prepared.

[0128] [Table 1]

[0129]

[0130] <Preparation of Electrodes and Lithium Secondary Batteries>

[0131] Example 2-1: Preparation of Electrodes and Lithium Secondary Batteries

[0132] A negative electrode slurry was prepared by adding a negative electrode composition having the composition of Examples 1-1 in Table 1 to distilled water as a solvent. Subsequently, a negative electrode active material layer was coated onto a copper foil with a thickness of 8 μm to a thickness of 38 μm, wherein the negative electrode loading was 76.34 mg / 25 cm⁻². 2Then, it is dried at 130 °C for 12 hours and rolled to prepare the negative electrode.

[0133] A lithium secondary battery is prepared by using lithium metal as the positive electrode, inserting a polyolefin separator between the negative electrode and the lithium metal, and injecting an electrolyte containing 1M LiPF6 in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in a volume ratio of 30:70.

[0134] Example 2-2: Preparation of Electrodes and Lithium Secondary Batteries

[0135] Electrodes and lithium secondary batteries were prepared in the same manner as in Example 2-1, except that a negative electrode with the composition of Examples 1-2 in Table 1 was used.

[0136] Comparative Example 2-1: Preparation of Electrodes and Lithium Secondary Batteries

[0137] Electrodes and lithium secondary batteries were prepared in the same manner as in Example 2-1, except that a negative electrode with the composition of Comparative Example 1-1 in Table 1 was used.

[0138] <Experimental Example: Evaluation of Battery Characteristics>

[0139] Experimental Example 1: Initial Capacity Efficiency and Energy Efficiency

[0140] The lifetime and capacity retention of the lithium secondary batteries prepared in Examples 2-1 and 2-2, and Comparative Example 2-1, were evaluated using an electrochemical charge / discharge tester. The lithium secondary batteries were tested for three cycles at 4.2–2.5 V and 0.3C / 0.3C, and the charging capacity and energy, as well as the discharging capacity and energy, were measured in the third cycle to evaluate efficiency. The results are shown in Table 2 below.

[0141] Experiment Example 2: Resistance

[0142] The SOC was set to 50%, and pulses of 0.3C, 0.5C, 1C, and 1.5C were applied for 10 seconds each in the charging and discharging directions. The average DC internal resistance (DCIR) was derived to evaluate the resistance. The results are shown in Table 2 below.

[0143] Experiment Example 3: Charging Output

[0144] The prepared lithium secondary battery was discharged at 2.5C in the discharge direction at 25 °C and 40% SOC until the voltage reached 2.5V. The discharge output was evaluated by measuring the time required to reach the end of the discharge. The results are shown in Table 2 below:

[0145] [Table 2]

[0146]

[0147] According to Table 2, Examples 2-1 and 2-2 include polymer beads, which are soluble binders in the electrolyte solution, and elongated pores are formed at the locations where the polymer beads are present. Therefore, elongated channels through which a large amount of electrolyte solution can move in a desired shape can be formed, thereby reducing resistance, increasing capacity, and improving output. Conversely, in Comparative Example 2-1, since no polymer beads were used, no pores were formed, resulting in increased resistance and decreased capacity and output.

Claims

1. An electrode composition comprising: Electrode active materials; Electrode adhesive; and polymer beads, The polymer beads are soluble in an electrolyte solution.

2. The electrode composition according to claim 1, wherein the electrode composition further comprises a solvent, and the polymer beads are insoluble in the solvent.

3. The electrode composition according to claim 1, wherein... The electrode is a negative electrode, and The electrode adhesive comprises at least one selected from the group consisting of fluorinated polymers, styrene polymers, polyvinyl alcohol (PVA), polyacrylonitrile (PAN), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), and sulfonated EPDM polymers.

4. The electrode composition according to claim 1, wherein the solubility of the polymer beads in the solvent of the electrolyte solution is from 1% w / w to 100% w / w in a temperature range of 10°C to 70°C.

5. The electrode composition according to claim 2, wherein the solubility of the polymer beads in the solvent at 25 °C is 1% w / w or less.

6. The electrode composition according to claim 1, wherein the polymer beads have a cylindrical, spherical, or hollow structure (core-shell structure).

7. The electrode composition according to claim 1, wherein... The electrode is a negative electrode, and The polymer beads comprise at least one of the following: polyurethane, polyurea, polyamide, polyester, polycarbonate, polyacrylate, polystyrene, polymethyl methacrylate, vinylidene chloride, urea-formaldehyde resin, melamine resin, copolymers thereof, naphthalene, 1,7,7-trimethylbicyclohepta-2-one, cyclohexane-1,2-dicarboxylic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, cyclohexane-1,2,4-tricarboxylic acid, phthalic acid, aminoacetophenone, vanillin, 4-hydroxyphthalic acid, trimellitic acid, trimellitic anhydride, dimethoxyacetophenone, 5-hydroxyisophthalic acid, gallic acid, methyl gallate, 1,7-dihydronaphthalene, 4,4'-dihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, and copolymers thereof.

8. The electrode composition according to claim 1, wherein, based on 100 parts by weight of the electrode composition, the content of the polymer beads is 0.5 parts by weight or more and 10 parts by weight or less.

9. The electrode composition according to claim 1, wherein the electrolyte solution comprises one or more solvents selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC).

10. The electrode composition according to claim 1, wherein the electrode active material comprises one or more selected from the group consisting of silicon-based active materials and carbon-based active materials.

11. The electrode composition according to claim 10, wherein the silicon-based active material comprises selected from Si, SiO x (0 < x < 2), one or more of the group consisting of Si / C and Si alloys.

12. The electrode composition of claim 10, wherein the carbon-based active material comprises one or more selected from the group consisting of artificial graphite, natural graphite, hard carbon, and soft carbon.

13. The electrode composition of claim 1, wherein the electrode composition comprises an electrode conductive material, and the electrode conductive material is included in an amount of 0.03 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the electrode composition.

14. An electrode paste, comprising: The electrode composition according to any one of claims 1-13, and Solvent.

15. An electrode comprising: Electrode current collector layer; and An electrode active material layer comprising the electrode composition according to any one of claims 1 to 13 on one or both surfaces of the electrode current collector layer.

16. A lithium secondary battery, comprising: First electrode; Second electrode; A partition plate disposed between the first electrode and the second electrode; and Electrolytes, The first electrode or the second electrode is the electrode described in claim 15.

17. A battery module comprising the lithium secondary battery according to claim 16.

18. A battery pack comprising the lithium secondary battery according to claim 16.

19. A battery pack comprising the battery module according to claim 17.

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