Electrode insulating coating composition, electrode, and method for manufacturing electrode

Abstract

The insulating coating composition according to the present invention comprises inorganic particles, a rubber-based binder, a fluorine-based binder, a dispersant, and a solvent, and the fluorine-based binder is contained in an amount of 7 parts by weight or less per 100 parts by weight of the solid content excluding the solvent. The insulating coating composition according to the present invention has a thick wet thickness when applied to a current collector, and is effective in suppressing the sliding phenomenon in which the electrode slurry flows down, thereby significantly reducing the sliding length of the electrode active material layer.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0139255, filed on October 18, 2023.

[0002] The present invention relates to an electrode insulating coating composition for reducing the sliding length of an electrode active material layer, a method for manufacturing an electrode using the same, and the electrode. [Background technology]

[0003] In recent years, with the rapid development of technology and increasing demand for mobile devices, the demand for batteries as energy sources has been rapidly increasing, and accordingly, extensive research has been conducted on batteries that can meet various requirements. In particular, research has been actively conducted on lithium secondary batteries that have high energy density, excellent life and cycle characteristics as power sources for such devices.

[0004] A lithium secondary battery includes a positive electrode containing a positive electrode active material capable of intercalating / deintercalating lithium ions, a negative electrode containing a negative electrode active material capable of intercalating / deintercalating lithium ions, and a separator and electrolyte interposed between the positive and negative electrodes. The positive and negative electrodes have a structure in which an electrode active material layer is formed on one or both sides of an electrode current collector. In recent years, a technology has been developed to form an insulating layer on the outer periphery of the electrode active material layer to improve electrode stability. By forming an insulating layer on the outer periphery of the electrode active material layer, the electrode active material layer can be protected from heat generated during electrode operation and the insulation between the electrodes can be improved.

[0005] However, when the electrode slurry is applied to the current collector, the edge of the electrode active material layer is not perpendicular to the current collector plane but includes a sliding region that is inclined relative to the current collector plane due to the fluid properties of the electrode slurry. As the demand for high-energy density batteries increases, technical attempts are being made to reduce this sliding length.

[0006] Patent Document 1 discloses an electrode insulating coating composition containing ceramic and styrene-butadiene rubber. However, when an insulating layer is formed using this electrode insulating coating composition, the wet thickness of the insulating coating composition is not sufficiently thick, and the reduction in the sliding length of the electrode active material layer is still not satisfactory. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent Publication No. 10-2023-0012439 Summary of the Invention [Problem to be solved by the invention]

[0008] The technical idea of ​​the present invention aims to provide an insulating coating composition capable of reducing the sliding length of an electrode active material layer, a method for manufacturing an electrode using the same, and the electrode. [Means for solving the problem]

[0009] According to one embodiment of the present invention, there is provided an insulating coating composition comprising inorganic particles, a rubber-based binder, a fluorine-based binder, a dispersant, and a solvent, wherein the fluorine-based binder is included in an amount of 7 parts by weight or less per 100 parts by weight of the solid content excluding the solvent.

[0010] In one embodiment, the fluorine-based binder is contained in an amount of 2 to 6 parts by weight per 100 parts by weight of the solid content excluding the solvent.

[0011] The insulating coating composition according to one embodiment has a viscosity of 2,500 cps or more measured at 25° C. and a shear rate of 2.5 / s.

[0012] In one embodiment, the insulating coating composition has a phase angle a of 1° to 9° at 1 Hz before shearing, where the shear rate is in the range of 0.001 / s to 1,000 / s.

[0013] In one embodiment, the insulating coating composition has a phase angle b of 2° to 10° at 1 Hz after shearing, where the shear rate is in the range of 0.001 / s to 1,000 / s.

[0014] In an insulating coating composition according to one embodiment, the value of the phase angle change rate calculated according to the following formula 1 is 20% or less.

[0015] [Formula 1] Phase angle change rate (%) = {(phase angle at 1 Hz after shearing - phase angle at 1 Hz before shearing) / phase angle at 1 Hz before shearing} x 100

[0016] In the above formula 1, the shear rate of the shear is in the range of 0.001 / s to 1,000 / s.

[0017] In one embodiment, the fluorine-based binder is a PVDF-based polymer containing vinylidene fluoride (VDF) as a monomer.

[0018] In one embodiment, the rubber binder is styrene-butadiene rubber (SBR).

[0019] In one embodiment, the dispersing agent is one or more selected from the group consisting of tannic acid, baicalin, luteolin, taxifolin, myricetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, and piceatannol.

[0020] In one embodiment, the dispersant is tannic acid.

[0021] In one embodiment, the inorganic particles are one or more selected from the group consisting of AlO(OH), Al2O3, γ-AlOOH, Al(OH)3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, YO3, SrTiO3, BaTiO3, and Mg(OH)2.

[0022] In one embodiment, the inorganic particles are contained in an amount of 51 to 85 parts by weight, the rubber binder is contained in an amount of 15 to 37 parts by weight, and the dispersant is contained in an amount of 0.3 to 5 parts by weight, relative to 100 parts by weight of solids excluding the solvent.

[0023] In one embodiment, the rubber binder is contained in an amount of 65 parts by weight or less based on 100 parts by weight of the inorganic particles.

[0024] The insulating coating composition according to one embodiment has a solid content excluding the solvent of 16% by weight or more.

[0025] In one embodiment, the total weight of the rubber-based binder and the fluorine-based binder is in the range of 20% by weight to 45% by weight based on the total weight of the solid content.

[0026] In one embodiment, the solvent is one or more selected from the group consisting of acetone, tetrahydrofuran, acetonitrile, dimethylformamide, dimethylsulfoxide, dimethylacetamide, and N-Methyl-2-Pyrrolidone (NMP).

[0027] Another embodiment of the present invention provides a method for manufacturing an electrode, comprising the steps of applying an electrode slurry onto a current collector and applying an electrode insulating coating composition onto the current collector, the electrode insulating coating composition including inorganic particles, a rubber-based binder, a fluorine-based binder, a dispersant, and a solvent, wherein the fluorine-based binder is included in an amount of 7 parts by weight or less per 100 parts by weight of the solid content excluding the solvent.

[0028] In one embodiment, in the step of applying the insulating coating composition, the insulating coating composition is applied to one or both edges of the electrode slurry based on the lateral direction TD of the current collector, and is applied so as to overlap a part of the lateral end of the electrode slurry.

[0029] In one embodiment, the step of applying the insulating coating composition is performed simultaneously with the step of applying the electrode slurry, or after the electrode slurry is applied, the step is performed without drying the electrode slurry.

[0030] According to another embodiment of the present invention, there is provided an electrode comprising: an electrode current collector; an electrode active material layer disposed on one or both sides of the electrode current collector; and an insulating layer disposed on one or both sides of the electrode current collector, the insulating layer contacting a transverse end portion of the electrode active material layer in the TD direction and containing inorganic particles, a rubber-based binder, a fluorine-based binder, and a dispersant, the fluorine-based binder being contained in an amount of 7 parts by weight or less per 100 parts by weight of the insulating layer.

[0031] In one embodiment, the electrode active material layer is divided into a planarized region whose surface is parallel to the plane of the electrode current collector and a sliding region extending from the planarized region and whose surface is inclined with respect to the plane of the electrode current collector, and the insulating layer is in contact with the inclined surface of the sliding region.

[0032] In one embodiment, the sliding region has a total length of 2.5 mm or less.

[0033] In one embodiment, the insulating layer has a maximum thickness of 15 μm or more and a length in the overall direction of 5 mm or less. [Effects of the Invention]

[0034] The insulating coating composition according to the present invention has a thick wet thickness when applied to a current collector, and has the effect of suppressing the sliding phenomenon in which the electrode slurry flows down, thereby dramatically reducing the sliding length of the electrode active material layer.

[0035] The insulating coating composition according to the present invention has excellent coating properties even when the solid content is increased, and has the effect of improving the drying speed of the electrode as the amount of solvent is reduced.

[0036] The insulating coating composition according to the present invention has excellent adhesive strength even after impregnation with an electrolyte solution, and can prevent the insulating layer from peeling off.

[0037] The electrode manufactured according to the present invention maintains excellent insulating performance under high temperature conditions, and by including an insulating layer with excellent adhesive strength, safety is improved. Furthermore, the sliding length of the electrode active material layer is reduced, thereby providing a battery with high capacity and high energy density. [Brief explanation of the drawings]

[0038] [Figure 1] 1 is an enlarged view of one side of a cross section of an electrode to which an electrode slurry and an electrode insulating coating composition are applied according to an exemplary embodiment; [Figure 2] FIG. 2 is a top view of an electrode sheet for explaining an electrode according to an exemplary embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along the line AA' in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will now be described in more detail to aid in its understanding.

[0040] The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that an inventor can appropriately define the concept of a term in order to best describe his or her own invention.

[0041] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0042] In this specification, terms such as "comprise," "comprise," or "have" are intended to specify the presence of implemented features, numbers, steps, components, or combinations thereof, and may be understood as not precluding the presence or possible addition of one or more other features, numbers, steps, components, or combinations thereof.

[0043] As used herein, the term "combinations thereof" in Markush expressions means a mixture or combination of one or more components selected from the group of components described in the Markush expressions, and means including one or more components selected from the group of components described above.

[0044] In this specification, the phrase "A and / or B" means "A or B, or both."

[0045] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0046] In this specification, the transport direction MD of the electrode sheet and the overall width direction of the electrode are defined as the X-axis direction, the lateral direction TD of the electrode sheet and the overall length direction of the electrode are defined as the Y-axis direction, the direction perpendicular to the plane formed by the combination of the X-axis direction and the Y-axis direction are defined as the Z-axis direction, and the X-axis direction and the Y-axis direction are called the horizontal direction.

[0047] In this specification, the sliding region refers to a region of the electrode active material layer that forms an inclined surface with respect to the plane of the electrode current collector (see 120S in Figure 1), and the length of the sliding region refers to the length of the sliding region in the Y direction.

[0048] <Electrode insulating coating composition>

[0049] An electrode insulating coating composition according to one embodiment of the present invention includes inorganic particles, a rubber-based binder, a fluorine-based binder, a dispersant, and a solvent, and the fluorine-based binder may be included in an amount of 7 parts by weight or less based on 100 parts by weight of the solid content excluding the solvent.

[0050] According to the present invention, the electrode insulating coating composition has a high shear viscosity of 2,500 cps or more, specifically 3,000 cps to 8,500 cps, and when the electrode insulating coating composition is applied, the thickness of the applied film can be increased. As the thickness of the applied film of the electrode insulating coating composition increases, the effect of reducing sliding of the electrode slurry becomes more pronounced.

[0051] Each component of the electrode insulating coating composition according to the present invention will be described below.

[0052] (1) Blank particles The electrode insulating coating composition according to one embodiment of the present invention may contain inorganic particles to enhance electrical insulation and thermal stability and improve the strength of the insulating layer. The inorganic particles do not soften or melt even at high temperatures, for example, at temperatures of 900°C or higher, so when such inorganic particles are included in the electrode insulating layer, the electrode insulating properties can be maintained even at very high temperatures.

[0053] The inorganic particles may be one or more compounds selected from the group consisting of AlO(OH), Al2O3, γ-AlOOH, Al(OH)3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, YO3, SrTiO3, BaTiO3, and Mg(OH)2, preferably one or more compounds selected from the group consisting of AlO(OH), Al2O3, γ-AlOOH, and Al(OH)3, and more preferably AlO(OH).

[0054] The AlO(OH) (boehmite) contains hydroxy groups, and therefore has the advantage of being superior in adhesive strength to the current collector after impregnation with the electrolyte, compared to cases where other inorganic particles (e.g., alumina) are used.

[0055] According to one embodiment of the present invention, the average particle size D of the inorganic particles before dissolving in the solvent 50 The D of the inorganic particles before dissolution may be 0.1 μm to 2 μm, preferably 0.3 μm to 1.7 μm, and more preferably 0.5 μm to 1.4 μm. 50 When the content of the inorganic particles satisfies the above range, the occurrence of aggregation of the inorganic particles in the composition is minimized, and an insulating coating layer having a uniform thickness and surface can be formed.

[0056] The inorganic particles may be included in an amount of 51 to 85 parts by weight, preferably 53 to 83 parts by weight, and more preferably 55 to 80 parts by weight, based on 100 parts by weight of the solid content excluding the solvent. When the content of the inorganic particles satisfies the above range, aggregation of the inorganic particles is minimized, the viscosity of the insulating coating composition can be appropriately maintained, and an insulating coating layer having a uniform thickness and surface can be formed.

[0057] (2) Rubber-based binder The electrode insulating coating composition according to one embodiment of the present invention may include a rubber-based binder to improve the adhesive strength and flexibility of the insulating layer.

[0058] The rubber-based binder may be one or a mixture of two or more selected from the group consisting of styrene-butadiene rubber, styrene-butadiene latex, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, and fluororubber, and is preferably styrene-butadiene rubber (SBR) and / or styrene-butadiene latex. Styrene-butadiene rubber and styrene-butadiene latex are preferred as the rubber-based binder of the present invention because they have excellent wet adhesion and flexibility.

[0059] The electrode insulating coating composition according to the present invention contains styrene-butadiene rubber and / or styrene-butadiene latex as a rubber-based binder, and thus has the effect of effectively preventing the insulating layer from being detached in the electrolyte.

[0060] The styrene-butadiene rubber and the styrene-butadiene latex may each contain repeating units derived from styrene monomers and repeating units derived from butadiene monomers in a weight ratio of 70:30 to 30:70. The total weight of the repeating units derived from styrene monomers and repeating units derived from butadiene monomers may be 30% to 100% or 30% to 70% by weight based on the total weight of the styrene-butadiene rubber.

[0061] Examples of the styrene monomer include styrene, α-methylstyrene, p-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 1-vinylnaphthalene, 4-cyclohexylstyrene, 4-(p-methylphenyl)styrene, 1-vinyl-5-hexylnaphthalene, derivatives thereof, and mixtures thereof. Examples of the butadiene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, derivatives thereof, and mixtures thereof.

[0062] If necessary, the styrene-butadiene rubber may further contain a repeating unit derived from a monomer having a crosslinkable group, and the repeating unit derived from the monomer having a crosslinkable group may be contained in an amount of 12 parts by weight or less based on the total weight of the styrene-butadiene rubber in order to reduce the absorption rate of the electrolyte.

[0063] The rubber binder may be included in an amount of 15 to 37 parts by weight, preferably 18 to 36 parts by weight, and more preferably 20 to 35 parts by weight, based on 100 parts by weight of the solid content excluding the solvent. When the content of the rubber binder satisfies the above range, adhesive strength and flexibility can be appropriately maintained, and an insulating coating layer having a uniform thickness and surface can be formed.

[0064] The rubber binder may be contained in an amount of 65 parts by weight or less, preferably 20 to 63.5 parts by weight, and more preferably 25 to 61 parts by weight, per 100 parts by weight of the inorganic particles. When the rubber binder and the inorganic particles satisfy the above weight ratio, it is easy to appropriately control the solid content and viscosity of the insulating coating composition.

[0065] (3) Fluorine-based binder The electrode insulating coating composition according to one embodiment of the present invention contains a fluorine-based binder in addition to the rubber-based binder in order to increase the coating thickness and reduce the coating width of the insulating coating composition. Conventionally, electrode insulating coating compositions have generally contained only rubber-based binders or only fluorine-based binders, but the electrode insulating coating composition according to the present invention is characterized in that it mainly contains a rubber-based binder and a small amount of a fluorine-based binder.

[0066] The fluorine-based binder may include a PVDF-based polymer containing vinylidene fluoride (VDF) as a monomer. Specific examples of the PVDF-based polymer include a PVDF monopolymer, PVDF-HFP (Poly(vinylidene fluoride-co-hexafluoropropylene)), PVDF-CTFE (Poly(vinylidene fluoride-co-chlorotrifluoroethylene)), PVDF-TFE (Poly(vinylidene tetrafluoroethylene)), and PVDF-TrFE (Poly(vinylidene trifluoroethylene)).

[0067] According to one embodiment of the present invention, the weight-average molecular weight (Mw) of the fluorine-based binder may be 800,000 g / mol or more, preferably 850,000 g / mol to 2,000,000 g / mol, and more preferably 900,000 g / mol to 1,500,000 g / mol. When the weight-average molecular weight of the fluorine-based binder satisfies the above range, the insulating coating composition can be effectively applied with a thicker coating thickness, and the electrode sliding length can be significantly reduced.

[0068] The fluorine-based binder may be included in an amount of 7 parts by weight or less, preferably 2 to 6 parts by weight, and more preferably 3 to 5.5 parts by weight, based on 100 parts by weight of the solid content excluding the solvent. When the content of the fluorine-based binder satisfies the above range, the insulating coating composition has an appropriate viscosity range, and the coating stability of the insulating coating composition is excellent, while the sliding length reduction effect can be maximized. When the fluorine-based binder is included in an amount of more than 7 parts by weight based on 100 parts by weight of the solid content, the viscosity of the insulating coating composition may be higher than the viscosity of the electrode slurry, which is not preferable.

[0069] In one embodiment, the total weight of the rubber binder and the fluorine-based binder is in the range of 20% by weight to 45% by weight, preferably 22% by weight to 35% by weight, and more preferably 25% by weight to 35% by weight, based on the total weight of the solids. When the total content of the rubber binder and the fluorine-based binder is in the above range, the insulating coating composition has excellent coating performance, and the electrode slurry has an excellent effect of suppressing sliding.

[0070] (4) Dispersant The electrode insulating coating composition according to one embodiment of the present invention may include a dispersant to improve the dispersibility of the inorganic particles.

[0071] The dispersing agent may be one or more selected from the group consisting of tannic acid, baicalin, luteolin, taxifolin, myricetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, and piceatannol, preferably one or more selected from the group consisting of tannic acid, quercetin, and epigallocatechin gallate, more preferably tannic acid.

[0072] The dispersant significantly improved the dispersibility of the inorganic particles, particularly boehmite particles, and significantly improved the viscosity and aging characteristics of the electrode insulating coating composition. In particular, when the dispersant is tannic acid, the tannic acid forms a coordinate bond with the current collector, allowing the electrode insulating coating composition to adhere better to the current collector. The hydroxyl groups of the tannic acid improve the flexibility of the rubber-based binder, styrene-butadiene rubber (SBR), helping to improve the adhesive strength of the electrode insulating coating composition. Ultimately, the electrode insulating coating composition can further enhance its ability to suppress electrode slurry sliding.

[0073] The dispersant may be contained in an amount of 0.3 to 5 parts by weight, preferably 0.5 to 4 parts by weight, and more preferably 1 to 3 parts by weight, per 100 parts by weight of the solid content excluding the solvent. When the content of the dispersant satisfies the above range, the coating properties of the insulating coating composition and the adhesive strength with the electrode can be appropriately maintained.

[0074] (5) Solvent The electrode insulating coating composition according to one embodiment of the present invention includes a solvent for dispersing the inorganic particles, binder, etc. It is preferable that the solvent is capable of dispersing the inorganic particles, dispersant, and binder to a certain level or more, but is a non-solvent for the electrode active material layer.

[0075] Specific examples of the solvent include one or more selected from the group consisting of acetone, tetrahydrofuran, acetonitrile, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, and N-methyl-2-pyrrolidone (NMP). These solvents are preferred as non-aqueous solvents in terms of phase stability compared to aqueous solvents.

[0076] The solvent may be included in an amount that allows the composition to have an appropriate viscosity, taking into account the coating properties of the composition, and may be included in an amount of, for example, 85 parts by weight or less, preferably 71 to 81 parts by weight, and more preferably 73 to 79 parts by weight, per 100 parts by weight of the composition.

[0077] The electrode insulating coating composition according to the present invention may have a solids content, excluding the solvent, of 16% by weight or more, preferably 18% to 30% by weight, and more preferably 20% to 27% by weight. When the solids content satisfies the above range, the composition can have a viscosity suitable for forming an insulating layer, exhibiting excellent coating performance and allowing the insulating layer to be applied with a large thickness. To increase the wet thickness, a higher solids content is advantageous.

[0078] The electrode insulating coating composition according to the present invention may be prepared by mixing the inorganic particles, rubber-based binder, fluorine-based binder, and dispersant in the solvent, and then performing a dispersion process.

[0079] First, the inorganic particles, rubber-based binder, fluorine-based binder, and dispersant are mixed in the solvent to mix the components of the composition, which may be performed using a mixing device well known in the art, such as, but not limited to, a homomixer.

[0080] Next, the composition that has undergone the mixing process may be milled to be dispersed. The milling may be performed using a ball mill, a bead mill, or a basket mill, and more specifically, a bead mill.

[0081] Meanwhile, the degree of dispersion of the composition can be adjusted by adjusting milling conditions such as the number of times the composition is passed through the ball mill, bead mill, or basket mill, and rotor speed.

[0082] The electrode insulating coating composition of the present invention as described above may have a viscosity of 2500 cps or more, preferably 3000 cps to 8500 cps, more preferably 3500 cps to 8000 cps, and most preferably 5000 cps to 7500 cps, measured at 25°C and a shear rate of 2.5 cps / s. This viscosity range is higher than the viscosity range of conventional electrode insulating coating compositions, which is 1000 cps to 2000 cps. When the electrode insulating coating composition has a viscosity within this range, the wet thickness level of the electrode insulating coating composition can be increased to the applied thickness level of the electrode slurry, and the electrode insulating coating composition can effectively function as a dam to suppress sliding of the electrode slurry, resulting in excellent coating stability of the insulating coating composition.

[0083] The electrode insulating coating composition according to the present invention has a viscosity within the above range, and therefore can have a wet thickness of 100 μm or more, preferably 120 μm to 200 μm, and more preferably 130 μm to 180 μm. Here, the wet thickness refers to the maximum height from the surface of the current collector to the surface of the electrode insulating coating composition when both the electrode slurry and the electrode insulating coating composition are applied. This wet thickness range is significantly higher than that of conventional electrode insulating coating compositions. The wet thickness of the electrode insulating coating composition, which acts as a dam, is thick enough to be similar to the thickness of the electrode slurry, effectively suppressing the sliding phenomenon in which the electrode slurry flows down.

[0084] The electrode insulating coating composition according to the exemplary embodiment may have a phase angle a at 1 Hz before shearing in the range of 1° to 9°, specifically 2° to 8°, and more specifically 3° to 7°. The electrode insulating coating composition may have a phase angle b at 1 Hz after shearing in the range of 2° to 10°, specifically 3° to 9°, and more specifically 4° to 8°. Here, the shear rate of the shearing is in the range of 0.001 / s to 1,000 / s. When the electrode insulating coating composition has phase angles before and after shearing in the above ranges, it has excellent coatability and is also excellent in reducing the sliding length of the electrode slurry.

[0085] The phase angle is a parameter that can evaluate the viscoelastic properties of the insulating coating composition, and can be calculated according to the following Equation 2.

[0086] [Formula 2] δ=tan -1 (G” / G')

[0087] In the above formula 2, δ is the phase angle (°), G' is the storage modulus value measured at a temperature of 25°C, and G'' is the loss modulus value measured at a temperature of 25°C.

[0088] The storage modulus (G'), loss modulus (G"), phase angle, etc. can be measured and calculated using a concentric cylinder (CC) rheometer. Specifically, a certain amount of the insulating coating composition is placed in a cup, and the gap between the cup and the rod is adjusted to 4,000 μm, and then the rheology can be measured at a constant temperature of 25°C. In this case, shear is applied for 900 seconds within the above shear rate range, and an oscillation test before and after shear is performed, and the phase angle can be measured as a result.

[0089] The phase angle is a measure of whether a composition is more liquid or more solid. Smaller phase angles indicate more solid properties, while larger phase angles indicate more liquid properties.

[0090] The electrode insulating coating composition according to the exemplary embodiment may have a phase angle change rate calculated according to the following formula 1 of 20% or less, specifically in the range of 1% to 18%, more specifically 3% to 16%, and even more specifically 5% to 15%.

[0091] [Formula 1] Phase angle change rate (%) = {(phase angle at 1 Hz after shearing - phase angle at 1 Hz before shearing) / phase angle at 1 Hz before shearing} x 100

[0092] In the above formula 1, the shear rate of the shear is in the range of 0.001 / s to 1,000 / s.

[0093] In this specification, the method for calculating the rate of change in the phase angle is as follows. First, a vibration frequency of 1 Hz is applied to the insulating coating composition, and the resulting phase angle is measured. This is defined as the phase angle before shearing. Then, shear is applied to the insulating coating composition while increasing the shear rate in the range of 0.001 / s to 1,000 / s. Then, a vibration frequency of 1 Hz is applied to the insulating coating composition after shearing, and the resulting phase angle is measured. This is defined as the phase angle after shearing. These values ​​are then substituted into the above formula 1 to calculate the rate of change in the phase angle.

[0094] Typically, electrode slurries and insulating coating compositions are coated using a slit die coater, and the insulating coating composition discharged from the slit of the slit die coater is subjected to shear force due to the discharge pressure. For an insulating coating composition, a small phase angle change rate before / after shear means that the rate of phase change due to the discharge pressure is small or that the composition has a strong tendency to maintain its original phase. An insulating coating composition whose phase angle change rate falls within the above range has a strong tendency to maintain its original phase even when subjected to the discharge pressure, and therefore has a strong support force for the electrode slurry and is highly effective in suppressing the sliding phenomenon of the electrode slurry.

[0095] The electrode insulating coating composition according to the present invention has a higher viscosity than conventional electrode insulating coating compositions, which allows for a thicker wet thickness and reduces the sliding length of the electrode slurry to a level of 2.5 mm or less, more specifically 0.1 mm to 2 mm, and even more specifically 0.5 mm to 1.8 mm. Considering that the sliding length was about 5 mm when electrodes were manufactured using conventional insulating coating compositions, the insulating coating composition according to the present invention can be evaluated as dramatically reducing the sliding length.

[0096] As described above, the electrode insulating coating composition according to the present invention has an appropriate viscosity and solid content, and thus suppresses the sliding phenomenon of electrode slurry flowing down, thereby significantly reducing the sliding length. Furthermore, the electrode insulating coating composition according to the present invention has superior wet adhesion strength compared to insulating coating compositions containing only a fluorine-based binder, thereby preventing detachment of the insulating layer and improving battery safety.

[0097] <Electrode manufacturing method>

[0098] The method for producing an electrode according to the present invention will be described below.

[0099] A method for manufacturing an electrode according to an embodiment of the present invention may include a step of applying an electrode slurry onto a current collector, and a step of applying an electrode insulating coating composition onto the current collector.

[0100] In the method for manufacturing an electrode according to one embodiment of the present invention, in order to shorten the sliding length of the electrode active material layer, the electrode insulating coating composition includes inorganic particles, a rubber-based binder, a fluorine-based binder, a dispersant, and a solvent, and the fluorine-based binder is included in an amount of 7 parts by weight or less per 100 parts by weight of the solid content excluding the solvent.

[0101] The composition of the electrode insulating coating composition has been explained in detail above, so a duplicate explanation will be omitted.

[0102] 1 and 2 are views showing an electrode manufactured according to a manufacturing process of an electrode according to one embodiment of the present invention. Referring to Fig. 1, the insulating coating composition 130CD may be applied to one or both edges of the electrode slurry 120SE based on the transverse direction TD (Y-axis direction) of the current collector 110. In addition, the insulating coating composition 130CD is applied so as to overlap a part of the transverse direction TD end 120S of the electrode slurry 120SE.

[0103] According to an embodiment of the present invention, the step of applying the insulating coating composition may be performed simultaneously with the step of applying the electrode slurry, or may be performed after the electrode slurry has been applied, without the electrode slurry being dried.

[0104] Typically, when an electrode slurry is applied to a current collector, the end of the applied electrode slurry may be formed with a slope, known as a sliding portion. When an insulating coating composition is applied simultaneously with the electrode slurry or when the insulating coating composition is applied before the electrode slurry has dried, the insulating coating composition 130CD acts as a dam to prevent the electrode slurry 120SE from flowing down, thereby reducing the sliding length (see FIG. 1). This effect of reducing the sliding length is even greater when the electrode slurry and the insulating coating composition are applied simultaneously.

[0105] <Electrode>

[0106] The electrode according to the present invention will now be described.

[0107] 1 to 3, an electrode 100 according to one embodiment of the present invention includes an electrode current collector 110, an electrode active material layer 120 disposed on one or both sides of the electrode current collector, and an insulating layer 130 disposed on one or both sides of the electrode current collector, and the insulating layer 130 is configured to contact an end portion in the lateral direction TD (Y-axis direction) of the electrode active material layer 120. The end portion is an end portion of one or both side edges of the electrode active material layer 120 based on the lateral direction TD (Y-axis direction) of the electrode sheet ES or the overall length direction (Y-axis direction) of the electrode 100.

[0108] 1 and 2, an electrode active material layer 120 is formed in the center of an electrode sheet ES, which serves as the base material of the electrode 100, in the lateral direction (Y-axis direction), and insulating layers 130 are formed on both side edges of the electrode sheet ES in the lateral direction. Outside the insulating layer 130, there is a plain area that is not covered by the electrode active material layer 120 or the insulating layer 130. The electrode 100 shown in FIG. 3 can be manufactured by notching and cutting along the notching lines (dotted lines) shown on the electrode sheet ES. While FIG. 2 shows an electrode in which insulating layers 130 are applied to both side edges of the electrode active material layer 120, the present invention is not limited thereto, and the insulating layer 130 may be applied to only one side edge of the electrode active material layer 120.

[0109] 1 and 3, the electrode active material layer 120 may be formed by drying an electrode slurry 120SE coated on a current collector 110, and the insulating layer 130 may be formed by drying the electrode insulating coating composition 130CD. The insulating layer 130 includes inorganic particles, a rubber-based binder, a fluorine-based binder, a dispersant, and a solvent, and the fluorine-based binder is included in an amount of 7 parts by weight or less based on 100 parts by weight of the solid content excluding the solvent. The inorganic particles, rubber-based binder, fluorine-based binder, and dispersant constituting the insulating layer have been described in detail above, so a repeated description will be omitted.

[0110] 1 and 3, an electrode 100 according to an embodiment may be divided into a planarized region 120A in which the surface of an electrode active material layer 120 formed from an electrode slurry 120SE is parallel to the plane of the electrode current collector 110, and a sliding region 120S extending from the planarized region 120A and having a surface inclined toward the plane of the electrode current collector 110. The sliding region 120S may be located at one end and the other end of the electrode active material layer 120 in the overall length direction (Y-axis direction).

[0111] In the electrode 100 according to one embodiment, the insulating coating composition 130CD prevents the electrode slurry 120SE from spreading along the current collector, and the sliding length of the electrode active material layer 120 is shorter than that of conventional electrodes.

[0112] The insulating coating composition according to the present invention has a thicker wet thickness when applied to a current collector than conventional insulating coating compositions, and is more effective in reducing the sliding length of the electrode slurry, thereby reducing the overall length of the sliding region of the electrode active material layer to 2.5 mm or less, more specifically, 0.1 mm to 2 mm, and even more specifically, 0.5 mm to 1.8 mm. Here, the wet thickness refers to the thickness of the insulating coating composition after it is applied and before it is dried.

[0113] By having the above-mentioned composition, the insulating coating composition of the present invention has an appropriate viscosity and solid content within a range in which coating properties are not impaired, and the wet thickness of the insulating coating composition can be increased. As a result, the thickness of the insulating layer formed by drying the insulating coating composition is also thicker than that of insulating layers formed from conventional insulating coating compositions.

[0114] The insulating layer has a maximum thickness of 15 μm or more, specifically 17 μm to 40 μm, and more specifically 20 μm to 35 μm. The insulating layer has a length in its overall length direction (Y-axis direction) of 5 mm or less, preferably 4 mm or less, and more preferably 3 mm or less. Here, the thickness of the insulating layer means the thickness after drying. Here, the thickness of the insulating layer means the thickness of the insulating layer only.

[0115] The current collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery, and examples of the current collector include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0116] The electrode active material layer may be a positive electrode active material layer containing a positive electrode active material or a negative electrode active material layer containing a negative electrode active material.

[0117] The positive electrode active material is not particularly limited, and any compound known in the art that allows reversible intercalation and deintercalation of lithium may be used without limitation. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; 1+x Mn 2-x O4 (where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O; and the chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3) 2-x M x Lithium manganese composite oxides represented by Li2Mn3MO8 (where M=Co, Ni, Fe, Cr, Zn, or Ta, and x=0.01 to 0.1) or Li2Mn3MO8 (where M=Fe, Co, Ni, Cu, or Zn); LiNi x Mn 2-x Examples of lithium manganese composite oxides include, but are not limited to, lithium manganese oxides with a spinel structure represented by O4; LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; lithium iron phosphate compounds represented by LiFePO4; disulfide compounds; and Fe2(MoO4)3.

[0118] The above negative electrode active material is not particularly limited, and examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, TD, Si alloy, Sn alloy, or Al alloy; SiO x (0 < X < 2), metal oxides capable of doping and undoping lithium such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the above metallic compounds and carbonaceous materials such as Si-C composites or Sn-C composites, etc. Among these, mixtures of any one or two or more thereof can be used. A thin film of metallic lithium can also be used as the above negative electrode active material.

[0119] On the other hand, the above electrode active material layer can contain a conductive material and a binder in addition to active materials such as a positive electrode active material and a negative electrode active material.

[0120] The conductive material is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. Examples of such conductive materials include graphite; carbon black, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers, such as carbon fiber and metal fiber; metal powders, such as carbon fluoride, aluminum, and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials, such as polyphenylene derivatives. Specific examples of commercially available conductive materials include acetylene black-based products (such as those from Chevron Chemical Company, Denka Singapore Private Limited, and Gulf Oil Company), Ketjenblack, EC-based products (products from Armak Company), Vulcan XC-72 (products from Cabot Company), and Super P (products from Timcal).

[0121] The binder is a component that aids in bonding the active material and conductive material and the current collector, and is typically added in an amount of 1 to 30 wt % based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymerization agents.

[0122] The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only and the scope of the present invention is not limited to these examples.

[0123] Example 1

[0124] The inorganic particles were boehmite (AlO(OH) product name: AOH60), the rubber binder was SBR (styrene butadiene rubber) (BM-L302, manufacturer: ZEON), and the fluorine binder was PVDF (KF9700, manufacturer: Kureha, weight average molecular weight (Mw): 8.8 × 10). 5 g / mol) and tannic acid (TA, manufacturer: Sigma Aldrich) as a dispersant in a weight ratio of 74:22:2:2, and added to N-methylpyrrolidone (NMP) to make the solid content about 25 wt% to prepare an insulating coating composition.

[0125] <Examples 2 and 3>

[0126] An insulating coating composition was prepared in the same manner as in Example 1, except that the weight ratios of the inorganic particles, rubber-based binder, fluorine-based binder, and dispersant were changed as shown in Table 1.

[0127] Example 4

[0128] An insulating coating composition was prepared in the same manner as in Example 1, except that the weight proportions and solid contents of the inorganic particles, rubber-based binder, fluorine-based binder, and dispersant in Example 1 were changed as shown in Table 1.

[0129] <Comparative Example 1>

[0130] An insulating coating composition was prepared by mixing boehmite (AlO(OH) product name: AOH60) as inorganic particles, SBR (styrene butadiene rubber) (BM-L302, manufacturer: ZEON) as a rubber binder, and tannic acid (TA, manufacturer: Sigma Aldrich) as a dispersant in a weight ratio of 57.5:40:2.5, and adding this to N-methylpyrrolidone (NMP) to make the solid content approximately 16.4 wt%.

[0131] <Comparative Example 2>

[0132] An insulating coating composition was prepared by mixing boehmite (AlO(OH) product name: AOH60) as inorganic particles, SBR (styrene butadiene rubber) (BM-L302, manufacturer: ZEON) as a rubber binder, and tannic acid (TA, manufacturer: Sigma Aldrich) as a dispersant in a weight ratio of 76:22:2, and adding this to N-methylpyrrolidone (NMP) to make the solid content approximately 25% by weight.

[0133] <Comparative Example 3>

[0134] The inorganic particles were boehmite (AlO(OH) product name: AOH60), and the fluorine-based binder was PVDF (KF9700, manufacturer: Kureha, weight-average molecular weight (Mw): 8.8 × 10 5 g / mol) and tannic acid (TA, manufacturer: Sigma Aldrich) as a dispersant in a weight ratio of 85:13.5:1.5, and added to N-methylpyrrolidone (NMP) to make the solid content about 20 wt% to prepare an insulating coating composition.

[0135] <Experimental Example 1: Viscosity Measurement>

[0136] The viscosity of each of the insulating coating compositions produced in Examples 1 to 4 and Comparative Examples 1 to 3 was measured. The results are shown in Table 1.

[0137] Specifically, the insulating coating compositions prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were cooled for 1 hour at room temperature and a relative humidity of 1%, and then the viscosity of the positive electrode slurry composition was measured at 25°C and a shear rate of 2.5 / s using a Brookfield viscometer. The viscosity measurement was carried out within 2 hours, including the cooling time, after the preparation of the positive electrode slurry composition.

[0138] <Experimental Example 2: Measuring the length of the electrode sliding area>

[0139] (Production of electrode slurry) Lithium nickel cobalt manganese aluminum (NCMA) composite oxide (NCMA), binder (PVDF, Poly(vinylidene fluoride)) (KF9700, manufactured by Kureha, weight average molecular weight (Mw): 8.8 × 10 5 g / mol) and a conductive material (carbon nanotubes, CNT) were mixed in a weight ratio of 97:1.5:1.5 (NCMA:PVDF:CNT) and dispersed in N-methylpyrrolidone (NMP) to a solid content of approximately 70 wt% to prepare a slurry for the positive electrode.

[0140] (Electrode manufacturing) The electrode slurry and the insulating coating composition of Example 1 were simultaneously coated onto an aluminum metal foil (thickness 10 μm), and the insulating coating composition was applied to both side edges of the electrode slurry application area based on the transverse direction TD (Y-axis direction) of the metal foil. At this time, the electrode slurry and the insulating coating composition were each adjusted to a coating thickness of 150 μm.

[0141] Thereafter, the electrode was dried at a temperature of 130°C and rolled to complete the production of the electrode.

[0142] In the produced electrode, the sliding length, which is the length in the lateral direction (Y-axis direction) of the sliding region of the electrode active material layer, was measured. The results are shown in Table 1.

[0143] For each of the insulating coating compositions of Examples 2 to 4 and Comparative Examples 1 to 3, electrode slurries and electrodes were prepared in the same manner as above, and the sliding length of the electrode active material layer in each electrode was measured. The results are shown in Table 1.

[0144] [Table 1]

[0145] Referring to Table 1, it can be seen that the insulating coating compositions according to the examples of the present invention have a reduced sliding length compared to the insulating coating compositions of Comparative Examples 1 to 3. In particular, the insulating coating compositions according to Examples 2 and 3, which contain 3.5 to 5 parts by weight of fluorine-based binder among the solid content, have a high viscosity and are more effective in reducing the sliding length.

[0146] Comparing Example 2 and Example 4, which have the same fluorine-based binder content, it was found that the insulating coating composition of Example 2, which has a higher solid content, is more effective in reducing the sliding length of the electrode slurry.

[0147] The insulating coating compositions according to Comparative Examples 1 and 2 do not contain a fluorine-based binder, and therefore their wet thickness is thinner than that of the insulating coating compositions of the Examples, and it is analyzed that their effect of reducing the sliding of the electrode slurry is also smaller than that of the insulating coating compositions of the Examples.

[0148] The insulating coating composition of Comparative Example 3 did not contain a rubber-based binder, and therefore had a very low viscosity compared to the insulating coating compositions of the Examples, and was shown to have no effect on reducing the sliding length of the electrode slurry. [Explanation of symbols]

[0149] 100: Electrode 110: Current collector 120: Electrode active material layer 130: Insulating layer 120SE: Electrode slurry 130CD: Insulation coating composition

Claims

1. Contains inorganic particles, rubber binder, fluorine binder, dispersant and solvent, The electrode insulating coating composition contains the fluorine-based binder in an amount of 7 parts by weight or less per 100 parts by weight of the solid content excluding the solvent.

2. 2. The electrode insulating coating composition according to claim 1, wherein the fluorine-based binder is contained in an amount of 2 to 6 parts by weight per 100 parts by weight of the solid content excluding the solvent.

3. 2. The electrode insulating coating composition according to claim 1, wherein the electrode insulating coating composition has a viscosity of 2,500 cps or more when measured at 25[deg.] C. and a shear rate of 2.5 / s.

4. 2. The electrode insulating coating composition according to claim 1, wherein the electrode insulating coating composition has a phase angle a of 1° to 9° at 1 Hz before shearing, a phase angle b of 2° to 10° at 1 Hz after shearing, and a shear rate of the shearing in the range of 0.001 / s to 1,000 / s.

5. The electrode insulating coating composition has a phase angle change rate calculated according to the following formula 1 of 20% or less, [Formula 1] Phase angle change rate (%) = {(phase angle at 1 Hz after shearing - phase angle at 1 Hz before shearing) / phase angle at 1 Hz before shearing} × 100 2. The electrode insulating coating composition according to claim 1, wherein in said formula 1, the shear rate of said shear is in the range of 0.001 / s to 1,000 / s.

6. 2. The electrode insulating coating composition according to claim 1, wherein the fluorine-based binder is a PVDF-based polymer containing vinylidene fluoride (VDF) as a monomer.

7. 2. The electrode insulating coating composition according to claim 1, wherein the rubber binder is styrene-butadiene rubber (SBR).

8. 2. The electrode insulating coating composition according to claim 1, wherein the dispersant is one or more selected from the group consisting of tannic acid, baicalin, luteolin, taxifolin, myricetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, and piceatannol.

9. 2. The electrode insulating coating composition according to claim 1, wherein the dispersing agent is tannic acid.

10. The inorganic particles include AlO(OH), Al ２ O ３ , γ-AlOOH, Al(OH) ３ , SiO ２ , TiO ２ , SnO ２ , CeO ２ , MgO, NiO, CaO, ZnO, ZrO ２ , Y ２ O ３ , SrTiO ３ , BaTiO ３ and Mg(OH) ２ 2. The electrode insulating coating composition according to claim 1, wherein the composition is one or more selected from the group consisting of:

11. For 100 parts by weight of the solid content excluding the solvent, the inorganic particles are 51 to 85 parts by weight, the rubber binder is 15 to 37 parts by weight, 2. The electrode insulating coating composition according to claim 1, wherein the dispersant is contained in an amount of 0.3 to 5 parts by weight.

12. The electrode insulating coating composition according to claim 1 , wherein the rubber binder is contained in an amount of 65 parts by weight or less relative to 100 parts by weight of the inorganic particles.

13. 2. The electrode insulating coating composition according to claim 1, wherein the electrode insulating coating composition has a solid content excluding the solvent of 16% by weight or more.

14. 2. The electrode insulating coating composition according to claim 1, wherein the total weight of the rubber-based binder and the fluorine-based binder is in the range of 20% by weight to 45% by weight based on the total weight of the solid content.

15. 2. The electrode insulating coating composition according to claim 1, wherein the solvent is one or more selected from the group consisting of acetone, tetrahydrofuran, acetonitrile, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, and N-methyl-2-pyrrolidone (NMP).

16. applying an electrode slurry onto a current collector; and applying an electrode insulating coating composition onto the current collector, The electrode insulating coating composition includes inorganic particles, a rubber-based binder, a fluorine-based binder, a dispersant, and a solvent, The method for producing an electrode, wherein the fluorine-based binder is contained in an amount of 7 parts by weight or less per 100 parts by weight of the solid content excluding the solvent.

17. 17. The method for manufacturing an electrode according to claim 16, wherein in the step of applying the electrode insulating coating composition, the electrode insulating coating composition is applied to one or both edges of the electrode slurry based on a transverse direction (TD) of the current collector, and is applied so as to overlap a part of an end of the electrode slurry in the transverse direction.

18. 17. The method for manufacturing an electrode according to claim 16, wherein the step of applying the electrode insulating coating composition is performed simultaneously with the step of applying the electrode slurry, or is performed after the electrode slurry is applied without drying the electrode slurry.

19. Electrode current collector, an electrode active material layer disposed on one or both surfaces of the electrode current collector; and an insulating layer disposed on one or both surfaces of the electrode current collector; the insulating layer contacts a lateral direction (TD) end of the electrode active material layer, the insulating layer includes inorganic particles, a rubber-based binder, a fluorine-based binder, and a dispersant; The fluorine-based binder is contained in an amount of 7 parts by weight or less relative to 100 parts by weight of the insulating layer.

20. the electrode active material layer is divided into a planarized region in which the surface of the electrode active material layer is parallel to the plane of the electrode current collector, and a sliding region extending from the planarized region and in which the surface of the electrode active material layer is inclined with respect to the plane of the electrode current collector; 20. The electrode of claim 19, wherein the insulating layer contacts an angled surface of the sliding region.

21. 21. The electrode of claim 20, wherein the sliding region has an overall length of 2.5 mm or less.

22. The maximum thickness of the insulating layer is 15 μm or more, 20. The electrode of claim 19, wherein the insulating layer has a total length of 5 mm or less.

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