Electrode insulating coating composition and electrode using the same

Abstract

To provide a composition for electrode insulating coating.SOLUTION: An electrode insulating coating composition according to the present invention includes boehmite particles, a dispersant, a binder, and a non-aqueous solvent, and the dispersant includes a phenolic compound having two or more aromatic rings, and is included in an amount of 1.2 to 8.8 parts by weight per 100 parts by weight of the boehmite particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0148085, filed November 1, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode insulating coating composition and an electrode using the same, and more particularly to an electrode insulating coating composition produced by adding boehmite particles and a dispersant containing a phenolic compound, and an electrode using the same. [Background technology]

[0003] In recent years, with the increasing technological development and demand for mobile devices, the demand for batteries as energy sources has increased dramatically, and as a result, 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 lifespan, and cycle characteristics as a power source 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, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. The positive electrode and the negative electrode 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 the stability of the electrode. 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] Conventional electrode insulating layers have generally been formed using binders with insulating properties. However, because binders have poor heat resistance, conventional insulating layers made of binders lose adhesive strength under high-temperature conditions during battery operation, resulting in a problem of reduced battery safety. To solve this problem, a technique has been proposed in which inorganic particles are added to an electrode insulating coating composition to improve the heat resistance of the insulating layer.

[0006] However, electrode insulating coating compositions containing inorganic particles proposed to date suffer from insufficient inorganic particle dispersibility. If the inorganic particles are not dispersed smoothly in the coating composition, they may settle to the bottom of the coating composition, resulting in an inconsistent distribution of the inorganic particles in the insulating layer after formation, which may reduce the heat resistance improvement effect. Furthermore, in this case, the inorganic particles may be concentrated in the lower part of the insulating layer, resulting in a reduced binder content in the lower part of the insulating layer, which may lead to the insulating layer being easily detached from the electrode. Furthermore, if the inorganic particles are not dispersed effectively, they may aggregate to form particles with large diameters, which increases the viscosity of the composition and may result in uneven thickness and / or surface of the insulating layer. Ultimately, these issues may result in a deterioration of the insulating performance of the insulating layer and reduced battery safety. Therefore, there is a demand for a technique that can uniformly disperse the inorganic particles in the insulating layer. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide an electrode insulating coating composition having improved dispersibility of inorganic particles, an insulating coating layer having excellent coatability and adhesiveness, and an electrode including the insulating coating layer.

[0008] The objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned above will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0009] According to one embodiment, the present invention provides a composition for an electrode insulating coating, comprising boehmite particles, a dispersant, a binder, and a non-aqueous solvent, wherein the dispersant comprises a phenolic compound having two or more aromatic rings, and is contained in an amount of 1.2 to 8.8 parts by weight per 100 parts by weight of the boehmite particles.

[0010] According to another embodiment, the present invention provides an electrode comprising a current collector, an electrode active material layer, and an insulating coating layer, the electrode active material layer and the insulating coating layer being disposed on the current collector, and the insulating coating layer being formed from the electrode insulating coating composition described above. [Effects of the Invention]

[0011] The electrode insulating coating composition according to the present invention contains boehmite particles having excellent heat resistance, and thus, when an electrode insulating coating layer is formed using the electrode insulating coating composition according to the present invention, excellent insulating performance can be maintained even under high temperature conditions, thereby further improving the safety of the battery.

[0012] Furthermore, when boehmite particles are used as inorganic particles as in the present invention, the adhesive strength to the electrode is excellent even after immersion in the electrolyte, and detachment of the insulating coating layer can be effectively prevented.

[0013] In addition, the electrode insulating coating composition according to the present invention contains a phenolic compound having two or more aromatic rings as a dispersant, which improves the dispersibility of boehmite particles, thereby realizing low viscosity characteristics, excellent storage stability, and excellent coating properties.

[0014] The insulating coating layer formed from the electrode insulating coating composition of the present invention can maintain excellent insulating performance even under high temperature conditions, and has excellent adhesion to the electrode even after impregnation with an electrolyte, thereby further improving battery safety. [Brief explanation of the drawings]

[0015] [Figure 1] 10 is a photograph showing the state of an insulating coating layer formed using the electrode insulating coating composition of Example 5 after being impregnated with an electrolyte solution. [Figure 2] 10 is a photograph showing the state of an insulating coating layer formed using the electrode insulating coating composition of Comparative Example 5 after being impregnated with an electrolyte solution. DETAILED DESCRIPTION OF THE INVENTION

[0016] The advantages and features of the present invention, as well as methods for achieving them, will become apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be embodied in various different forms. The present embodiments are provided solely to ensure complete disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art to which the present invention pertains. The present invention is defined solely by the scope of the claims. The same reference symbols refer to the same elements throughout the specification.

[0017] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in a manner commonly understood by those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless otherwise clearly defined.

[0018] The terms used in this specification are for the purpose of describing the embodiments and are not intended to limit the present invention. In this specification, the singular form includes the plural form unless otherwise specified in the phrase. The words "comprise," "have," and "include" used in this specification do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0019] In this specification, when a part is said to include a certain component, this does not mean that it may further include other components, unless otherwise specified.

[0020] In this specification, the phrase "A and / or B" means A, or B, or A and B. In this specification, "%" means % by weight unless expressly indicated otherwise.

[0021] In this specification, D 50 means the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve, and D 90 means the particle size corresponding to 90% of the cumulative volume in the particle size distribution curve. 50 and D 90 can be measured using, for example, a laser diffraction method, which generally allows measurement of particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution.

[0022] The present invention will be specifically described below. Electrode insulating coating composition An electrode insulating coating composition according to one embodiment of the present invention includes boehmite (γ-AlO(OH)) particles, a dispersant, a binder, and a non-aqueous solvent, and the dispersant includes a phenolic compound having two or more aromatic rings, and is included in an amount of 1.2 to 8.8 parts by weight per 100 parts by weight of the boehmite particles.

[0023] Hereinafter, each component of the electrode insulating coating composition according to the present invention will be described. (1) Boehmite particles The boehmite particles are included in the electrode insulating coating composition to increase the heat resistance of the insulating coating layer. Inorganic particles such as boehmite do not soften or melt even at high temperatures, for example, at temperatures of 900°C or higher. Therefore, when such inorganic particles are included in the electrode insulating layer, the electrode insulating properties can be maintained even at very high temperatures.

[0024] It is clear that when boehmite particles are used as inorganic particles, the adhesive strength with the current collector after immersion in the electrolyte is superior to when other inorganic particles (e.g., alumina) are used. This effect is believed to be due to the influence of hydroxy groups contained in boehmite.

[0025] According to one embodiment of the present invention, the D of the boehmite particles before dissolving in the non-aqueous solvent 50 The D of the boehmite particles before dissolution may be 0.1 μm to 1.0 μm, preferably 0.1 μm to 0.7 μm, and more preferably 0.1 μm to 0.5 μm. 50 When the content of the boehmite particles satisfies the above range, the occurrence of agglomeration of the boehmite particles in the composition is minimized, and an insulating coating layer having a uniform thickness and surface can be formed.

[0026] The boehmite particles may be included in an amount of 10 to 25 parts by weight, preferably 10 to 20 parts by weight, and more preferably 15 to 20 parts by weight, based on 100 parts by weight of the insulating coating composition. When the content of the boehmite particles is within this range, the occurrence of agglomeration of the boehmite 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.

[0027] (2) Dispersant The dispersant is used to improve the dispersibility of the boehmite particles in the electrode insulating coating composition.

[0028] In the present invention, the dispersant contains a phenolic compound containing two or more aromatic rings. Preferably, the dispersant contains one or more structures selected from the group consisting of a phenol structure, a catechol structure, a gallol structure, and a naphthol structure in one or more of the aromatic rings, and more preferably, the dispersant contains one or more structures selected from the group consisting of a catechol structure and a gallol structure in one or more of the aromatic rings.

[0029] In this case, the phenol structure is a structure in which one hydroxy group is bonded to a benzene ring, the catechol structure is a structure in which two hydroxy groups are bonded to a benzene ring, the gallol structure is a structure in which three hydroxy groups are bonded to a benzene ring, and the naphthol structure is a structure in which one hydroxy group is bonded to naphthalene.

[0030] According to one embodiment of the present invention, the dispersing agent is one or more selected from the group consisting of baicalin, luteolin, taxifolin, myricetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, piceatannol, and tannic acid, preferably, the dispersing agent is one or more selected from the group consisting of tannic acid, quercetin, and epigallocatechin gallate, more preferably, the dispersing agent may be tannic acid.

[0031] According to the research of the present inventors, it has become clear that when a phenolic compound containing two or more aromatic rings is used as a dispersant in a composition containing boehmite particles, the dispersibility of the boehmite particles is significantly improved, and the viscosity and aging characteristics of the electrode insulating coating composition are significantly improved.

[0032] This effect is believed to be due to the bulky structure generated by two or more aromatic rings and the influence of the hydroxy group contained in the phenol group.

[0033] However, when a phenolic compound containing only one aromatic ring (e.g., dopamine, gallic acid, pyrogallol, catechol, etc.) is used as a dispersant, the effect of preventing aggregation of boehmite particles and the effect of improving dispersibility are insufficient.

[0034] The dispersant may be included in an amount of 1.2 to 8.8 parts by weight, preferably 1.2 to 7.6 parts by weight, and more preferably 1.4 to 7.0 parts by weight, per 100 parts by weight of the boehmite particles. If the dispersant content is outside this range, the coating properties of the insulating coating layer and its adhesion to the electrode may be reduced. Specifically, if the dispersant content is less than 1.2 parts by weight per 100 parts by weight of the boehmite particles, the boehmite particles may not be sufficiently dispersed in the composition, resulting in agglomerated particles, which may prevent the coating process. Even if coating is possible, the coating may not be uniformly formed, resulting in line defects. Furthermore, if the dispersant content is more than 8.8 parts by weight per 100 parts by weight of the boehmite particles, air bubbles may form craters during coating layer formation, and the adhesion between the insulating coating layer and the current collector may be reduced after immersion in the electrolyte, resulting in detachment of the insulating coating layer.

[0035] (3) Binder The binder then serves to adhere the insulating coating layer to the current collector and / or electrode active material layer.

[0036] The binder may be formed from a compound of components that are not easily dissolved by the electrolyte of the secondary battery. The binder is not particularly limited as long as it is a polymer binder used in the art, and representative examples thereof include aqueous or non-aqueous polymers including a single substance or a mixture of two or more substances selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene (PVdF-CTFE), polymethyl methacrylate, polyvinyl acetate, ethylene-co-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, styrene butadiene copolymer (Styrene Butadiene Rubber, SBR), acrylonitrile styrene butadiene copolymer, and polyimide. Among these, polyvinylidene fluoride (PVdF) is particularly preferable.

[0037] The binder may be included in an amount of 1 to 5 parts by weight, preferably 1 to 3 parts by weight, and more preferably 1.5 to 3 parts by weight, based on 100 parts by weight of the electrode insulating coating composition. When the content of the binder satisfies the above range, excellent adhesion between the insulating coating layer and the electrode is exhibited.

[0038] (4) Non-aqueous solvents Next, the non-aqueous solvent dissolves the boehmite particles, dispersant, and binder, and ensures the coatability of the insulating coating layer formed from the composition.

[0039] The non-aqueous solvent is preferably a solvent that can dissolve the boehmite particles, dispersant, and binder to a certain level or more, but is a non-solvent for the electrode active material layer. If an aqueous solvent is used, part of the electrode active material layer may aggregate, which may reduce the phase stability of the electrode active material layer.

[0040] Specific examples of the non-aqueous solvent include acetone, tetrahydrofuran, acetonitrile, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, and N-methyl-2-pyrrolidone (NMP), which may be used alone or in combination. Among these, N-methyl-2-pyrrolidone (NMP), which is suitable for dissolving non-aqueous binders (e.g., polyvinylidene fluoride), is particularly preferred.

[0041] The non-aqueous solvent may be included in an amount that allows the composition to have an appropriate viscosity, taking into consideration the coatability of the composition, for example, 70 to 90 parts by weight, preferably 75 to 85 parts by weight, per 100 parts by weight of the composition. Preferably, the electrode insulating coating composition according to the present invention may have a solids content of 10 to 30% by weight, preferably 15 to 25% by weight, and more preferably 17 to 23% by weight. When the solids content satisfies this range, the composition can have an appropriate viscosity for forming a coating layer while minimizing the occurrence of agglomeration of boehmite particles in the composition.

[0042] The electrode insulating coating composition of the present invention as described above can be prepared by mixing boehmite particles, a dispersant, and a binder in a non-aqueous solvent, and then performing a dispersion process.

[0043] First, the boehmite particles, dispersant, and binder are mixed in a non-aqueous solvent to mix the components of the composition. In this case, the mixing may be performed using a mixing device known in the art, such as, but not limited to, a homomixer.

[0044] Next, the composition that has undergone the mixing process is milled to be dispersed. The milling may be performed using a ball mill, a bead mill, or a basket mill, and more specifically, may be performed using a bead mill.

[0045] Meanwhile, the degree of dispersion of the composition can be adjusted by adjusting milling conditions such as the number of passes (hereinafter referred to as "pass number") of the composition through the ball mill, bead mill, or basket mill, and rotor speed.

[0046] According to one embodiment of the present invention, the D of the solid particles in the composition 50 may be 0.4 μm to 1.3 μm, preferably 0.4 μm to 1.0 μm, and more preferably 0.4 μm to 0.7 μm. Here, the solid particles may include at least one of boehmite particles, a dispersant, and a binder. Specifically, the solid particles may be in a form in which the boehmite particles are bound to each other, or in a form in which the boehmite particles are bound to the dispersant and / or the binder.

[0047] When the particle size of the solid particles in the composition satisfies the above range, the dispersibility of the boehmite particles in the composition is improved, and the coatability and adhesiveness of the insulating coating layer can be significantly improved.

[0048] Meanwhile, the degree of dispersion of the solid particles in the composition can be adjusted by adjusting the solid content in the composition, the type and content of the dispersant, and / or the dispersion process conditions.

[0049] electrode Next, an electrode including the insulating coating layer according to the present invention will be described. The electrode includes a current collector, an electrode active material layer, and an insulating coating layer. The electrode active material layer and the insulating coating layer can be disposed on the current collector. In this case, the insulating coating layer may be formed from the above-described composition for electrode insulation coating.

[0050] The current collector is not particularly limited as long as it does not induce a chemical change in the battery and has conductivity. For example, as the current collector, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used.

[0051] Next, 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. As the positive electrode active material, well-known positive electrode active materials in the technical field may be used without limitation. For example, lithium cobalt-based oxides, lithium nickel-based oxides, lithium manganese-based oxides, lithium iron phosphate, lithium nickel manganese cobalt-based oxides, or combinations thereof may be used. Specifically, as the positive electrode active material, LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, and LiNi a Mn b Co c O2 (where 0 < a, b, c < 1) etc. may be used, but not limited thereto.

[0052] As the negative electrode active material, natural graphite, artificial graphite, carbonaceous materials; lithium-containing titanium composite oxides (LTO), Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or metals (Me) such as Fe; alloys composed of the metals (Me); oxides (MeO x ); and one or more negative electrode active materials selected from the group consisting of composites of the metals (Me) and carbon may be mentioned.

[0053] Meanwhile, the electrode active material layer may further include a conductive material and a binder in addition to the active materials such as the positive electrode active material and the negative electrode active material. The conductive material is not particularly limited as long as it does not induce chemical changes in the battery and is conductive, and examples thereof 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 (Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, etc.), ketjen black, EC-based products (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (Timcal).

[0054] The binder is a component that aids in binding the active material and conductive material, etc., and in binding to 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-butylene rubber, fluororubber, and various copolymers.

[0055] Next, the insulating coating layer is formed by applying the electrode insulating coating composition onto the current collector and then drying it. The insulating coating layer may be formed on a non-coated portion of the current collector where the electrode active material layer is not formed, and in this case, the insulating coating layer may be formed to partially overlap an end of the electrode active material layer.

[0056] The insulating coating layer may be formed to a uniform thickness on the current collector and the electrode active material layer. In this case, the thickness of the insulating coating layer may be 10 μm to 30 μm, preferably 15 μm to 25 μm, and more preferably 17 μm to 23 μm. When the thickness of the insulating coating layer satisfies the above range, the adhesion of the insulating coating layer to the current collector and / or the electrode active material layer may be further improved.

[0057] Meanwhile, the insulating coating layer according to one embodiment of the present invention has superior coating properties and adhesion compared to conventional insulating coating layers. Specifically, the insulating coating layer has excellent coating properties due to its uniform thickness and / or surface. Furthermore, the boehmite particles are uniformly dispersed on the insulating coating layer, and sufficient binder is present at the bottom of the insulating coating layer, resulting in excellent adhesion of the insulating coating layer.

[0058] The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0059] Example 1 80 parts by weight of NMP solution as a non-aqueous solvent, D 50 is 0.2 μm, and the specific surface area is 17 m 217 parts by weight of 1 / g boehmite (product name: ACTILOX200SM, manufacturer: Nabaltec), 0.3 parts by weight of tannic acid (TA, manufacturer: Sigma Aldrich) as a dispersant, and 2.7 parts by weight of PVdF (product name: KF9700, manufacturer: KUREHA) as a binder were mixed to prepare 1 kg of a mixture, which was then mixed for 1 hour using a homomixer (product name: Dispermat LC, manufacturer: VMA).

[0060] Next, a dispersion process was carried out using a bead mill (product name: LS-1, manufacturer: NETZSCH) at a rotor speed of 3300 RPM, a discharge rate of 540 g / min per pass, and 8 passes to prepare a composition for electrode insulating coating.

[0061] Example 2 An electrode insulating coating composition was prepared in the same manner as in Example 1, except that 0.6 parts by weight of the dispersant and 2.4 parts by weight of the binder were mixed.

[0062] Example 3 An electrode insulating coating composition was prepared in the same manner as in Example 1, except that 1 part by weight of the dispersant and 2 parts by weight of the binder were mixed.

[0063] Example 4 An electrode insulating coating composition was prepared in the same manner as in Example 2, except that the dispersion process was carried out with 9 passes.

[0064] Example 5 An electrode insulating coating composition was prepared in the same manner as in Example 2, except that the dispersion process was carried out with 6 passes.

[0065] Comparative Example 1 An electrode insulating coating composition was prepared in the same manner as in Example 2, except that no dispersant was used and 3 parts by weight of binder was mixed.

[0066] Comparative Example 2 An electrode insulating coating composition was prepared in the same manner as in Example 2, except that H-NBR (product name: THERBAN 3400, manufacturer: ARLANXEO) was used as the dispersant instead of TA.

[0067] Comparative Example 3 An electrode insulating coating composition was prepared in the same manner as in Example 2, except that 0.1 parts by weight of the dispersant and 2.9 parts by weight of the binder were mixed.

[0068] Comparative Example 4 An electrode insulating coating composition was prepared in the same manner as in Example 5, except that 2 parts by weight of the dispersant and 1 part by weight of the binder were mixed.

[0069] Comparative Example 5 An electrode insulating coating composition was prepared in the same manner as in Example 5, except that alumina (product name: AES-11, manufacturer: Sumitomo) was used instead of boehmite as the inorganic particles.

[0070] [Table 1]

[0071] Experimental Example 1 - Particle size measurement Using a particle size analyzer (product name: MASTERSIZER 3000, manufacturer: Malvern), the particle size D of the solid particles in the electrode insulating coating compositions prepared in Examples 1 to 5 and Comparative Examples 1 to 5 was measured. 10 , D 50 , and D 90 The measurement results are shown in Table 2 below.

[0072] Experimental Example 2 - Viscosity Measurement The viscosity of each of the electrode insulating coating compositions prepared in Examples 1 to 5 and Comparative Examples 1 to 5 was measured, and the measurement results are shown in Table 2 below. The viscosity of the composition was measured using a viscometer (product name: viscometer TV-22, manufacturer: TOKI) at 25°C and 1 rpm.

[0073] Experimental Example 3 - Evaluation of storage stability (aggregation) The electrode insulating coating compositions prepared in Examples 1 to 5 and Comparative Examples 1 to 5 were stored in 50 ml vials for 24 hours, and then the presence or absence of precipitation was visually observed and evaluated as follows. The evaluation results are shown in Table 2. ○: No precipitation occurs ×: Precipitation occurs

[0074] Experimental Example 4 - Evaluation of coating properties The electrode insulating coating compositions prepared in Examples 1 to 5 and Comparative Examples 4 to 5 were coated on aluminum foil to a thickness of 20 μm and then dried to form insulating coating layers.

[0075] The formed insulating layer was visually inspected for defects and evaluated as follows. The evaluation results are shown in Table 2 below. ○: No poor line quality or craters due to air bubbles were observed ×: Poor line quality or craters due to air bubbles are observed On the other hand, the electrode insulating coating compositions of Comparative Examples 1 to 3 had excessively high viscosities, making it impossible to form an insulating coating layer by coating.

[0076] Experimental Example 5 - Evaluation of Adhesion The electrode insulating coating compositions prepared in Examples 1 to 5 and Comparative Examples 4 to 5 were coated on aluminum foil to a thickness of 20 μm and then dried to form an insulating coating layer, which was then cut into 20 mm × 100 mm pieces and immersed in an electrolyte (LiPF61M, EC / EMC=3 / 7 (vol%)) at 60°C for 24 hours. The presence or absence of detachment from the aluminum foil substrate was visually inspected and evaluated as follows. The evaluation results are shown in Table 2.

[0077] ○: No separation or lifting occurs ×: Detachment or lifting occurs On the other hand, the electrode insulating coating compositions of Comparative Examples 1 to 3 had excessively high viscosities, making it impossible to form an insulating coating layer by coating.

[0078] FIG. 1 is a photograph showing the state of an insulating coating layer formed using the electrode insulating coating composition of Example 5 after being impregnated with an electrolyte solution, and FIG. 2 is a photograph showing the state of an insulating coating layer formed using the electrode insulating coating composition of Comparative Example 5 after being impregnated with an electrolyte solution.

[0079] 1 and 2, it can be seen that the insulating coating layer formed from the electrode insulating coating composition of Example 5, which used boehmite as inorganic particles, maintained the coating layer without peeling or floating even after impregnation in the electrolyte, whereas the insulating coating layer formed from the electrode insulating coating composition of Comparative Example 5, which used alumina, suffered peeling and floating after impregnation in the electrolyte.

[0080] [Table 2]

[0081] From Table 2, it can be seen that the electrode insulating coating compositions of Examples 1 to 5, which use boehmite as inorganic particles and a phenolic compound containing two or more aromatic rings as a dispersant, and which contain the dispersant in an amount of 1.2 to 8.8 parts by weight per 100 parts by weight of the boehmite particles, exhibit little particle aggregation in the composition, have excellent storage stability, and are excellent in coatability. Furthermore, it can be seen that when an insulating coating layer is formed from the electrode insulating coating compositions of Examples 1 to 5, excellent adhesive strength is maintained even after immersion in an electrolyte solution.

[0082] In contrast, the electrode insulating coating composition of Comparative Example 1, which did not use a dispersant, experienced severe particle aggregation in the composition, which resulted in an excessively high viscosity, making it impossible to carry out the coating process.

[0083] In addition, the electrode insulating coating composition of Comparative Example 2, which used H-NBR as a dispersant, showed lower particle aggregation and viscosity than Comparative Example 1, but the viscosity was still too high, making it impossible to carry out the coating process.

[0084] On the other hand, the electrode insulating coating compositions of Comparative Examples 3 and 4, in which the content of the dispersant in the composition was outside the range of the present invention, exhibited poor coating properties, adhesion, and / or storage stability.

[0085] Furthermore, as shown in FIG. 2 and Table 2, when an insulating coating layer was formed using the electrode insulating coating composition of Comparative Example 5, which used alumina instead of boehmite as inorganic particles, the adhesive strength with the current collector after immersion in the electrolyte solution was significantly reduced.

Claims

1. Boehmite particles; a dispersant; and Binder and a non-aqueous solvent; Including, The dispersant includes a phenolic compound having two or more aromatic rings, and is contained in an amount of 1.2 to 8.8 parts by weight based on 100 parts by weight of the boehmite particles.

2. 2. The electrode insulating coating composition according to claim 1, wherein the phenolic compound containing two or more aromatic rings contains one or more structures selected from the group consisting of a phenol structure, a catechol structure, a gallol structure, and a naphthol structure in one or more of the aromatic rings.

3. 3. The electrode insulating coating composition according to claim 2, wherein the phenolic compound containing two or more aromatic rings contains one or more structures selected from the group consisting of a catechol structure and a gallol structure in one or more of the aromatic rings.

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

5. 5. The electrode insulating coating composition according to claim 4, wherein the phenolic compound having two or more aromatic rings is one or more selected from the group consisting of tannic acid, quercetin, and epigallocatechin gallate.

6. 6. The electrode insulating coating composition according to claim 5, wherein the phenolic compound containing two or more aromatic rings is tannic acid.

7. 2. The electrode insulating coating composition according to claim 1, wherein the binder is polyvinylidene fluoride.

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

9. For 100 parts by weight of the electrode insulating coating composition, 10 to 25 parts by weight of the boehmite particles; 0.2 to 1.5 parts by weight of the dispersant; 1 to 5 parts by weight of the binder; 2. The electrode insulating coating composition according to claim 1, further comprising 70 to 90 parts by weight of the non-aqueous solvent.

10. 2. The electrode insulating coating composition according to claim 1, wherein the solid content of the electrode insulating coating composition is 10% by weight to 30% by weight.

11. a current collector, an electrode active material layer, and an insulating coating layer; the electrode active material layer and the insulating coating layer are disposed on the current collector; An electrode, wherein the insulating coating layer is formed from the electrode insulating coating composition according to claim 1 .

Images