Insulating composition for electrodes with excellent wet adhesion

Abstract

Insulating composition for an electrode, comprising: an aqueous binder dispersed by a non-aqueous solvent; and an inorganic particle, where the weight ratio of the inorganic particle to the aqueous binder is between 1:99 and 95:5.

Description

[Technical area]

[0001] This application claims priority based on Korean patent application No. 10-2021-0100879, filed on July 30, 2021, and Korean patent application No. 10-2022-0090835, filed on July 22, 2022.

[0002] The present disclosure relates to an insulating composition for an electrode with excellent wet adhesion. [State of the art]

[0003] As mobile device technology continues to evolve and the demand for mobile devices increases, the demand for secondary batteries as a power source is rapidly growing, and accordingly, many studies have been conducted on batteries that can meet various requirements.

[0004] There is typically high demand for thin prismatic and pouch-shaped batteries, which can be used in products such as mobile phones and similar devices. There is also high demand for lithium secondary batteries, such as lithium-cobalt polymer batteries, which are characterized by their excellent energy density, discharge voltage, and safety.

[0005] One of the most important research tasks related to secondary batteries is improving safety. Accidents related to battery safety are primarily caused by abnormally high temperatures resulting from a short circuit between a positive and a negative electrode. This means that under normal circumstances, electrical insulation is maintained because a separator is present between the positive and negative electrodes. However, existing separators have limitations in abnormal situations such as overcharging or discharging, dendritic growth of an electrode material, internal short circuits caused by foreign matter, penetration of sharp objects like nails, screws, and the like, or excessive deformation of the battery by an external force.

[0006] Generally, a microporous membrane made of a polyolefin resin is used primarily as a separator. However, its heat-resistant temperature is only around 120 to 160 °C, making its heat resistance insufficient. Therefore, if an internal short circuit occurs, the separator contracts due to the heat of the short-circuit reaction, thus increasing the extent of the short circuit and leading to thermal runaway, which generates significant heat of reaction. Since this phenomenon mainly occurs at the end of an electrode current collector coated with an electrode-active material in the electrode stack, various methods have been attempted to reduce the likelihood of an electrode short circuit caused by an external impact or high temperature.

[0007] To remedy the internal short circuit of a battery, a method has been proposed in which insulating tape or an insulating liquid is applied to the section of the uncoated part and the active material layer of an electrode to form an insulating coating layer. For example, there is a method for applying an insulating binder to the section of the uncoated part and the active material layer of a positive electrode, or for applying an insulating liquid in which a mixture of the binder and inorganic particles is dispersed in a solvent to form a structure (hereinafter referred to as an insulating coating layer).

[0008] Meanwhile, in an actual secondary battery, an electrode is immersed in a liquid electrolyte, and a conventional insulating coating layer exhibits deteriorated adhesion when immersed in a liquid electrolyte (hereinafter referred to as wet adhesion) and therefore does not block the migration of lithium ions in the superimposed region of the electrode to produce a capacity (see Fig. 1 shown). In particular, when the capacity is expressed in the superimposed region of the electrode, lithium ions may precipitate, which can compromise the safety of a battery cell.

[0009] Therefore, there is a need to develop an insulating composition with excellent wet adhesion. [Revelation][Technical Problem]

[0010] The present disclosure aims to provide an insulating composition for an electrode with excellent wet adhesion. [Technical solution]

[0011] One aspect of the present technology provides an insulating composition for an electrode that includes: an aqueous binder, which is replaced by a non-aqueous solvent, and inorganic particles. In one embodiment, the weight ratio of the inorganic particle to the aqueous binder ranges from 1:99 to 95:5.

[0012] In a specific embodiment, the weight ratio of the inorganic particle and the aqueous binder can be between 45:55 and 90:10.

[0013] In a specific embodiment, the non-aqueous organic solvent may be one or more selected from the group consisting of N-methylpyrrolidone (NMP), dimethylformamide (DMF) and dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate (BC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), acetonitrile, dimethoxyethane, tetrahydrofuran (THF), γ-butyrolactone, methyl alcohol, ethyl alcohol and isopropyl alcohol.

[0014] In another embodiment, the inorganic particles may be one or more selected from the group consisting of AlOOH, Al2O3, γ-AlOOH, Al(OH)3, Mg(OH)2, Ti(OH)4, MgO, CaO, Cr2O3, MnO2, Fe2O3, Co3O4, NiO, ZrO2, BaTiO3, SnO2, CeO2, Y2O3, SiO2, silicon carbide (SiC) and boron nitride (BN).

[0015] In another embodiment, the aqueous binder may be one or more selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, an ethylene-propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, an ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, an acrylic resin, phenolic resin, an epoxy resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropylcellulose, and diacetylcellulose.

[0016] For example, in the insulating composition for an electrode according to the present technology, the non-aqueous organic solvent can be N-methylpyrrolidone (NMP), and the aqueous binder can be styrene-butadiene rubber.

[0017] In one embodiment, the inorganic particles can have an average particle diameter of 0.01 µm to 100 µm.

[0018] In a more specific embodiment, the insulating composition according to the present technology can include first and second inorganic particles with different particle diameters and have a bimodal particle size distribution.

[0019] For example, the insulating composition can have a viscosity at 25 °C ranging from 50 cP to 50,000 cP.

[0020] In one embodiment, the insulating composition according to the present technology can be applied to a positive electrode of a secondary battery.

[0021] Another aspect is a method for producing the insulating composition for an electrode described above. In one embodiment, the method for producing the insulating composition for an electrode according to the present technology includes: mixing an aqueous binder dispersed in water and a non-aqueous solvent; and performing solvent substitution by removing the water through heat treatment.

[0022] In one embodiment, the process can further include enabling the inclusion of inorganic particles after solvent substitution.

[0023] In a specific embodiment, the weight ratio of the inorganic particle and the aqueous binder can be between 1:99 and 95:5.

[0024] In another embodiment, the heat treatment can be carried out in solvent substitution at 80 to 150 °C. [Beneficial effects]

[0025] An insulating composition for an electrode with excellent wet adhesion and a manufacturing process for it according to the present technology are provided, and since the insulating composition has excellent wet adhesion in a liquid electrolyte, the advantage is that the migration of lithium ions in the superimposed region of an electrode can be blocked in order to suppress the capacity development and the like. [Brief description of the drawings] Fig.Figure 1 is a schematic diagram showing the migration of lithium ions in a superimposed region of an electrode. Fig. Figure 2 shows the results of the measurement of the wet adhesion of a coating layer formed from an insulating composition, with examples and comparative examples. Fig. Figure 3 is a diagram obtained by measuring the discharge capacity in order to evaluate the capacity characteristics of the battery cells from examples 5 to 7 (discharge characteristics at room temperature). Fig. Figure 4 is a diagram obtained by measuring the discharge capacity to evaluate the capacity characteristics of the battery cells from examples 5 to 7 (high-temperature discharge characteristics). [Detailed description of the embodiments]

[0026] Since the present invention allows for various modifications and a multitude of embodiments, particular embodiments are described in detail in the detailed description.

[0027] However, it is not intended to limit the present invention to certain embodiments, and it should be understood that all modifications, equivalents or substitutes within the spirit and technical scope of the present invention are included in the present invention.

[0028] In the present disclosure, the terms “include” or “have” are intended only to indicate the presence of features, numbers, steps, processes, components, parts or combinations thereof, and not to exclude the possibility that one or more other features, numbers, steps, processes, components, parts or combinations thereof may be added.

[0029] Furthermore, in the present disclosure, when a section of a layer, film, region, plate, or the like is described as lying "on" another section, this includes not only the case where the section lies "directly on" it, but also the case where another section is inserted between them. Conversely, a section of a layer, film, region, plate, or the like that is described as lying "under" another section includes not only the case where the section lies "directly under" it, but also the case where another section is inserted between them. Moreover, what is described as "on" here can include being arranged not only on a top part, but also on a bottom part.

[0030] As used herein, an ‘insulating coating layer’ refers to an insulating element formed by applying at least one section of the uncoated portion of an electrode current collector to at least one section of an active material layer of the electrode and drying.

[0031] As used herein, the term "wet adhesion" refers to the adhesion of an insulating coating layer as measured in the immersed state in a liquid electrolyte. More precisely, wet adhesion can be measured by immersing a metal sample, including any insulating coating layer formed within it, in a liquid electrolyte, subjecting it to ultrasonic waves, and then determining whether the insulating coating layer has swollen or detached.

[0032] As used here, a “metal sample” is a space in which an insulating coating layer is formed and can refer to a metal current collector used in the manufacture of an electrode, in particular a metal current collector having a predetermined width and length. For example, the metal sample may be aluminum, copper, or an aluminum alloy.

[0033] As used here, a “superimposed region” can refer to a region in which an insulating coating layer is formed in an electrode. In particular, in an electrode in which an active material layer is formed, the insulating coating layer covers at least a section of an uncoated part up to at least a section of the active material layer, and a region in which an insulating coating layer is formed on the active material layer is referred to as a superimposed region.

[0034] The present invention is described in detail below. Insulation composition

[0035] One aspect of the present technology offers an insulating composition for an electrode that includes the following: an aqueous binder, which is replaced by a non-aqueous solvent, and inorganic particles. Specifically, the weight ratio of the inorganic particles to the aqueous binder is between 1:99 and 95:5.

[0036] Since the insulating composition for an electrode according to the present technology exhibits excellent wet adhesion in a liquid electrolyte, the advantage is that the migration of lithium ions in the superposition area of ​​an electrode can be blocked in order to suppress the capacitance development and the like.

[0037] In general, an electrode in a secondary battery is immersed in a liquid electrolyte. Consequently, a conventional insulating coating layer exhibits reduced wet adhesion while immersed in a liquid electrolyte and does not block the migration of lithium ions in the superimposed region of the electrode to cause capacitance development. In particular, if capacitance is expressed in the superimposed region of the positive electrode, lithium ions can precipitate, which can compromise the stability of a battery cell.

[0038] The present technology provides an insulating composition for an electrode that includes an aqueous binder, which is replaced by a non-aqueous solvent used as a solvent for an electrode slurry, and inorganic particles dispersed therein to improve the wet adhesion of a liquid electrolyte. That is, when applied to an electrode, the insulating composition improves wet adhesion, thereby suppressing the migration of lithium ions in the electrode's surface area and preventing lithium ion precipitation. Consequently, when applied to a secondary battery electrode, the insulating composition can improve the battery's stability.

[0039] In a specific embodiment, the insulating composition for an electrode according to the present technology has a composition in which inorganic particles and an aqueous binder are mixed in a ratio of 1:99 to 95:5. When an insulating coating layer is formed from the insulating composition for an electrode, the wet adhesion can be excellent.

[0040] Meanwhile, the wet adhesion of the insulating coating layer can be measured by immersing a metal sample, including an insulating coating layer formed within it, in a liquid electrolyte, sonicating it with ultrasonic waves, and then determining whether the insulating coating layer formed in the metal sample has swollen or detached.

[0041] The liquid electrolyte used to measure wet adhesion can include an organic solvent and an electrolyte salt, and the electrolyte salt can be a lithium salt. Any lithium salt typically used in a non-aqueous liquid electrolyte for a lithium secondary battery can be used without restriction. For example, an anion of the lithium salt can include one, two, or more from the group consisting of F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , CF3(CF2)7SO3 - , CF3CO2 -, CH3CO2 - , SCN - and (CF3CF2SO2)2N - .

[0042] Since the organic solvent described above is contained within the liquid electrolyte, any organic solvent typically used in a liquid electrolyte for a lithium secondary battery can be used without restriction. For example, an ether, an ester, an amide, a linear carbonate, a cyclic carbonate, or the like can be used alone or in combination with two or more of them. Typically, a cyclic carbonate, a linear carbonate, or a carbonate compound that is a mixture of these can be used.

[0043] Furthermore, the insulating composition for an electrode according to the present technology can be applied to a positive electrode, and the non-aqueous organic solvent can be one or more selected from the group consisting of N-methylpyrrolidone (NMP), dimethylformamide (DMF) and dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMV), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate (BC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), acetonitrile, dimethoxyethane, tetrahydrofuran (THF), γ-butyrolactone, methyl alcohol, ethyl alcohol and isopropanol.

[0044] In a specific embodiment, the non-aqueous organic solvent may be one or more selected from the group consisting of NMP, DMF, DMAc and DMSO, and in particular one or more selected from the group consisting of NMP, DMF, and DMAc.

[0045] For example, the non-aqueous organic solvent can be an amide-based organic solvent, and the same solvent used to prepare a slurry for a positive electrode can be used. The non-aqueous organic solvent can be NMP.

[0046] In a specific embodiment, the insulating composition, when applied as an insulating coating layer of a positive electrode, can be applied and dried simultaneously with an active material layer of the positive electrode, according to the present technology. If, in this case, the same solvent used as a solvent for the positive electrode slurry is used as the solvent for the insulating composition, differences in drying rates and the like are reduced, thus preventing cracks and similar defects that occur at the interface between the insulating coating layer and the active material layer of the positive electrode. In particular, the NMP solvent can be used as a substitute solvent, and the aqueous binder can be present as an NMP-substituted binder.

[0047] Furthermore, the aqueous binder may be one or more selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile butadiene rubber, acrylonitrile butadiene styrene rubber, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, an ethylene-propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, an ethylene-propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, an acrylic resin, phenolic resin, an epoxy resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropylcellulose, and diacetylcellulose.In a specific embodiment, the aqueous binder can be one or more selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber. For example, the aqueous binder can be styrene-butadiene rubber.

[0048] Conventionally, polyvinylidene fluoride (hereinafter referred to as PVDF) has been used as a binder for an insulating coating layer of a positive electrode, but PVDF exhibits reduced wet adhesion when immersed in a liquid electrolyte. Accordingly, in the present technology, styrene-butadiene rubber (SBR) can be used as the binder polymer. When SBR is used as the binder, water can be used as the solvent. However, in this case, if an insulating composition is applied simultaneously with a positive electrode slurry, gelation of PVDF, an organic binder used as a positive electrode binder, may occur between the insulating composition and the positive electrode slurry.

[0049] Furthermore, the insulating composition can enhance battery safety by incorporating inorganic particles, and the strength of the insulating coating layer can also be increased. The quantity of inorganic particles can be appropriately adjusted, taking into account the viscosity of the insulating composition, thermal resistance, insulating properties, filling effect, dispersibility, stability, and other factors. Generally, as the size of the inorganic particles increases, the viscosity of the composition, including the particles, also increases, as does the potential for sedimentation within the insulating composition. Conversely, as the size of the inorganic particles decreases, thermal resistance also increases. Therefore, considering the above points, a suitable type and size of inorganic particles can be selected, and if necessary, at least two types of inorganic particles can be used.

[0050] In a specific embodiment, the inorganic particles may be one or more selected from the group consisting of AlOOH, Al₂O₃, γ-AlOOH, Al(OH)₃, Mg(OH)₂, Ti(OH)₄, MgO, CaO, Cr₂O₃, MnO₂, Fe₂O₃, Co₃O₄, NiO, ZrO₂, BaTiO₃, SnO₂, CeO₂, Y₂O₃, SiO₂, silicon carbide (SiC), and boron nitride (BN), in particular one or more selected from the group consisting of AlOOH, Al₂O₃, γ-AlOOH, and Al(OH)₃. For example, the inorganic particles may be AlOOH.

[0051] The weight ratio of the inorganic particle to the aqueous binder can range from 1:99 to 95:5, particularly between 45:55 and 90:10 or 50:50 and 90:10. For example, the weight ratio of the inorganic particle to the aqueous binder in the insulating composition can be 50:50. However, if the amount of aqueous binder is too low, it may be difficult to achieve the desired insulating effect in the present technology, and adhesion to an electrode may be impaired. Conversely, if the amount of aqueous binder is too high, the insulating composition may drip into an overlying region where an electrode is coated, thereby compromising the safety of a battery cell.

[0052] The inorganic particles can have an average particle diameter of 0.01 µm to 100 µm, specifically 0.5 µm to 80 µm, 1 µm to 50 µm, 2 µm to 30 µm, 3 µm to 20 µm, or 5 µm to 10 µm. If the size of the inorganic particles falls within the range described above, they can be uniformly distributed in the electrode, minimizing the resistance of the lithium ions and ensuring the performance of a lithium secondary battery.

[0053] In another embodiment, the insulating composition can include first and second inorganic particles with different particle diameters and can have a bimodal particle size distribution. This means that the inorganic particles consist of a mixture of small and large particles, and small second inorganic particles can fill the voids between large first inorganic particles, and an appropriate amount of inorganic particles can be dispersed. However, the present invention is not limited to this.

[0054] Meanwhile, in the insulating composition for an electrode according to the present technology, the inorganic particles and SBR may be included in amounts of 1 to 50 parts by weight, 5 to 40 parts by weight or 10 to 40 parts by weight, based on 100 parts by weight of the NMP solvent.

[0055] The insulating composition can have a viscosity at 25 °C of 50 cP to 50,000 cP, 100 cP to 45,000 cP, 1,000 cP to 40,000 cP, 2,000 cP to 35,000 cP, 3,000 cP to 30,000 cP, 4,000 cP to 20,000 cP, or 5,000 cP to 10,000 cP. Within the range described above, adhesion to an active electrode material layer can be improved, as well as coatability, processability, and the like.

[0056] In one embodiment, the insulating composition for an electrode according to the present technology can be produced by mixing an aqueous binder dispersed in water and a non-aqueous solvent, and by carrying out solvent substitution through the removal of the water by heat treatment. According to the present technology, an insulating coating layer enclosing the aqueous binder can be applied to a moisture-sensitive positive electrode by forming an aqueous binder substituted with a non-aqueous solvent.

[0057] In another embodiment, the process further includes, after solvent substitution, the ability to encapsulate inorganic particles. Specifically, the weight ratio of the inorganic particle to the aqueous binder is between 1:99 and 95:5. The mixing ratio of the inorganic particle and the aqueous binder is as described above.

[0058] In one embodiment, the heat treatment can be carried out in solvent substitution at 80 to 150 °C. The heat treatment is designed to remove a water component contained in the aqueous binder by evaporation. The heat treatment can be carried out at atmospheric pressure (1 atm) and also under vacuum or reduced pressure conditions (0.1 atm or more and less than 1 atm) for rapid evaporation of water. The heat treatment is intended to effectively evaporate water and can be carried out at 80 to 150 °C or 100 to 130 °C. Electrode for secondary battery

[0059] Another aspect of the present technology offers an electrode for a secondary battery, which includes the following: a metal current collector; an active material layer provided on the metal current collector; and an insulating coating layer that covers at least one section of a non-coating part where the active material layer is not present, up to at least one section of the active material layer, wherein the metal current collector includes the uncoated part, and The insulating coating layer includes inorganic particles and an aqueous binder, which is substituted by a non-aqueous organic solvent.

[0060] The electrode for a secondary battery according to the present technology has the advantage that the migration of lithium ions in the superimposed region of the electrode can be blocked in order to suppress the capacity development and the like, by the insulating coating layer having excellent wet adhesion.

[0061] In a specific embodiment, the inorganic particles of the insulating coating layer can be one or more selected from the group consisting of AlOOH, Al2O3, γ-AlOOH, Al(OH)3, Mg(OH)2, Ti(OH)4, MgO, CaO, Cr2O3, MnO2, Fe2O3, Co3O4, NiO, ZrO2, BaTiO3, SnO2, CeO2, Y2O3, SiO2, silicon carbide (SiC) and boron nitride (BN), in particular one or more selected from the group consisting of AlOOH, Al2O3, γ-AlOOH and Al(OH)3. For example, the inorganic particles can be AlOOH.

[0062] Furthermore, the aqueous binder may be one or more selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile butadiene rubber, acrylonitrile butadiene styrene rubber, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, an ethylene-propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, an ethylene-propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, an acrylic resin, phenolic resin, an epoxy resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropylcellulose, and diacetylcellulose.In a specific embodiment, the aqueous binder can be one or more selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber. For example, the aqueous binder can be styrene-butadiene rubber.

[0063] In a specific embodiment, the aqueous binder can be an aqueous binder substituted with a non-aqueous organic solvent, or styrene-butadiene rubber substituted with an amide-based solvent, for example, styrene-butadiene rubber substituted with an NMP solvent. In particular, the insulating coating layer can be formed by applying the insulating composition described above to an electrode of a secondary battery such that the insulating composition covers at least a section of the uncoated portion up to at least a section of the active material layer and dries at approximately 50 to 300 °C.In this case, a solvent is removed from the insulating coating layer during the drying process, and the styrene-butadiene rubber dispersed in the solvent is substituted with NMP, thus NMP-substituted styrene-butadiene rubber may be present.

[0064] In one embodiment, the insulating coating layer can have a thickness of 0.2 µm to 100 µm, in particular 1 µm to 50 µm, and even more specifically 1 µm to 30 µm, 2 µm to 30 µm, 3 µm to 20 µm, or 5 µm to 15 µm. If the coating layer is too thin, it may be difficult to expect an improvement in safety from applying the insulating coating layer.

[0065] Furthermore, the electrode for a secondary battery can be a positive electrode.

[0066] Furthermore, the active material layer can include an active material of the positive electrode. In a particular embodiment, any commonly used active material can be used for the positive electrode, and lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide produced by a combination thereof can be used, but the present invention is not limited thereto.

[0067] Furthermore, the amount of active material in the positive electrode can be 85 to 95 parts by weight, in particular 88 to 95 parts by weight, 90 to 95 parts by weight, 86 to 90 parts by weight or 92 to 95 parts by weight, based on 100 parts by weight of the active material layer.

[0068] Additionally, conductive material can be used to improve the performance, such as the electrical conductivity, of the positive electrode, and one or more materials can be selected from the group consisting of natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, and carbon fiber. For example, the conductive material can include acetylene black.

[0069] Furthermore, the conductive material can be included in an amount of 1 to 10 parts by weight, in particular 2 to 8 parts by weight or 2 to 6 parts by weight, based on 100 parts by weight, of the active material layer.

[0070] Furthermore, the binder may include one or more resins selected from the group consisting of a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, and a copolymer thereof. For example, the binder may include polyvinylidene fluoride.

[0071] Furthermore, the binder can be included in an amount of 1 to 10 parts by weight, in particular 2 to 8 parts by weight or 2 to 6 parts by weight, based on 100 parts by weight, of the active material layer.

[0072] Although there is no particular limit to the average thickness of the active material layer, the average thickness can be, in particular, 0.1 µm to 20 µm and, more specifically, 0.1 µm to 15 µm, 0.1 µm to 10 µm, 2 µm to 10 µm, 4 µm to 10 µm or 5 µm to 9 µm.

[0073] Meanwhile, according to the present technology, any current collector that does not cause any chemical changes within the battery and exhibits high conductivity can be used as the positive electrode current collector for a lithium secondary battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or similar materials, as well as aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or similar substances, can also be used. Furthermore, fine irregularities can be formed on the surface of the current collector to increase the adhesion of the active material of the positive electrode, and various forms such as a film, sheet, foil, mesh, porous material, foam, and non-woven fabric are possible.Furthermore, the average thickness of the current collector can be appropriately applied in a range of 3 to 500 µm, taking into account the conductivity and the total thickness of a positive electrode to be produced. Lithium secondary battery

[0074] Another aspect of the present technology is a lithium secondary battery including the electrode described above for a secondary battery according to the present technology.

[0075] As described above, the electrode for a secondary battery can be used as the positive electrode in the lithium secondary battery according to the present technology.

[0076] The lithium secondary battery according to the present technology can include the positive electrode described above, a negative electrode and a separator arranged between the positive electrode and the negative electrode.

[0077] The lithium secondary battery based on the present technology has the particular advantage that the migration of lithium ions in the superimposed region of the electrode can be blocked in order to suppress capacity development and the like, since the insulating coating layer exhibits excellent wet adhesion in a liquid electrolyte. Accordingly, the lithium secondary battery based on the present technology can exhibit improved stability.

[0078] In this case, the negative electrode can include a negative electrode current collector and a layer of active material applied to the current collector. Specifically, the negative electrode is fabricated by depositing active material onto a negative electrode current collector, followed by drying and pressing. If required, the negative electrode can further include a conductive material, an organic binder polymer, a filler, and the like, as described above.

[0079] Examples of active materials for the negative electrode include carbon and graphite materials such as graphite, which has a fully layered crystal structure (like natural graphite); soft carbon, which has a layered crystal structure with low crystallinity (graphene structure; a structure in which hexagonal honeycomb-like planes of carbon are arranged in layers); hard carbon, in which these structures are mixed with amorphous parts; artificial graphite; expanded graphite; carbon fibers; non-graphitizable carbon; carbon black; carbon nanotubes; fullerenes; activated carbon; and the like; as well as metal compound oxides such as Li x Fe2O3 (0≤x≤1), Li x WO2 (0≤x≤1), Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, group 2 and group 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8); Lithiummetall; Lithiumlegierungen; Legierungen auf Siliziumbasis; Legierungen auf Zinnbasis; Metalloxide wie SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 und Bi2O5; leitfähige Polymere wie Polyacetylen und dergleichen; Materialien auf Li-Co-Ni-Basis; Titanoxid; Lithiumtitanoxid und dergleichen können verwendet werden.

[0080] In one embodiment, the active material of the negative electrode can include both graphite and silicon (Si)-containing particles. The graphite can be one or more natural graphites with a layered crystal structure and artificial graphites with an isotropic structure; the silicon (Si)-containing particles can be silicon (Si) particles, silicon oxide (SiO2) particles, or a mixture of silicon (Si) particles and silicon oxide (SiO2) particles, which are particles containing silicon (Si) as a major metal component.

[0081] In this case, the active material of the negative electrode can include 80 to 95 parts by weight of graphite and 1 to 20 parts by weight of silicon (Si)-containing particles per 100 parts by weight of the active material of the negative electrode. With the present technology, lithium consumption and irreversible capacity loss during the initial charging and discharging of the battery can be reduced, and the charging capacity per unit mass increased, by adjusting the amounts of graphite and silicon (Si)-containing particles incorporated into the active material of the negative electrode within the ranges described above.

[0082] Furthermore, the active material layer of the negative electrode can have an average thickness of 100 µm to 200 µm, in particular 100 µm to 180 µm, 100 µm to 150 µm, 120 µm to 200 µm, 140 µm to 200 µm or 140 µm to 160 µm.

[0083] Furthermore, the current collector of the negative electrode is not particularly limited, as long as it does not cause any chemical changes in the battery and exhibits high conductivity. For example, copper, stainless steel, nickel, titanium, calcined carbon, or similar materials can be used, and copper or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like can also be used.

[0084] Furthermore, the current collector for the negative electrode, like the current collector for the positive electrode, can have fine irregularities on its surface to increase the adhesion of the active material of the negative electrode, and various forms are possible, such as a film, sheet, foil, mesh, porous body, foam, and nonwoven fabric. The average thickness of the current collector of the negative electrode can also be appropriately set in a range of 3 to 500 µm, taking into account the conductivity and the overall thickness of the negative electrode to be manufactured.

[0085] Additionally, the separator is inserted between the positive and negative electrodes and is an insulating thin film with high ion permeability and mechanical strength. While the separator is not particularly restricted as long as it is commonly used in engineering, a film or nonwoven fabric made of chemically resistant and hydrophobic polypropylene, glass fiber, polyethylene, or the like can be used. In some cases, a composite separator can be used, in which a porous polymer substrate such as the film or nonwoven fabric containing inorganic / organic particles is coated with an organic binder polymer. If a solid electrolyte such as a polymer or similar material is used, the solid electrolyte can also serve as the separator.Furthermore, the separator can have an average pore diameter of 0.01 to 10 µm and an average thickness of 5 to 300 µm.

[0086] Meanwhile, the positive electrode and the negative electrode can be housed in a cylindrical battery, a prismatic battery, or a pouch-like battery, while being wound in the form of a jelly roll design or housed in a foldable or stackable form in a pouch-like battery, but the present invention is not limited thereto.

[0087] Furthermore, according to the present technology, the lithium salt-containing liquid electrolyte can consist of a liquid electrolyte and a lithium salt. The liquid electrolyte can be a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, or similar.

[0088] For example, a non-aqueous organic solvent such as N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfrance, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methylformate, methyl acetate, phosphate triesters, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, ethyl propionate, or similar substances can be used.

[0089] Examples of organic solid electrolytes that can be used include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers including ionic dissociation groups, or similar materials.

[0090] Examples of inorganic solid electrolytes that can be used include nitrides, halides or sulfates of Li, such as Li3N, LiI, Li5Ni2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, Li3PO4-Li2S-SiS2 or similar.

[0091] Lithium salts are substances that are readily soluble in non-aqueous electrolytes, and examples include LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB10Cl. 10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, Chlorborolithium, Lithium of a lower aliphatic carboxylic acid, Lithium tetraphenylborate, Imide, or similar.

[0092] Furthermore, to improve charging / discharging properties, flame retardancy, and the like, the liquid electrolyte may contain, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glymes, hexaphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, or the like. In some cases, a halogenated solvent such as carbon tetrachloride, ethylene trifluoride, or the like may also be included to ensure non-flammability; carbon dioxide gas may be included to improve high-temperature storage properties; and fluoroethylene carbonate (FEC), propensultone (PRS), or the like may be further included.

[0093] Meanwhile, another aspect of the present technology provides a battery module that includes the secondary battery described above as a unit cell, and also provides a battery pack that includes the battery module.

[0094] The battery pack can be used as an energy source for medium to large devices that require high temperature stability and high performance characteristics such as long cycle life. Specific examples of medium to large devices include: power tools driven by electric motors; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; electric two-wheelers, including electric bicycles (e-bikes) and electric scooters (e-scooters); electric golf carts; energy storage systems, and the like. More specific examples of these include HEVs, but the present invention is not limited to these.

[0095] Furthermore, the positive and negative electrodes can be housed in a cylindrical battery, a prismatic battery, or a pouch-like battery, while they can be wound in a jelly-roll design or folded or stacked within a pouch-like battery. For example, the lithium secondary battery according to the present technology can be a pouch-like battery.

[0096] As described above, the lithium secondary battery, which incorporates the active material of the positive electrode according to the present technology, can be used in a battery module or battery pack that includes multiple batteries as a single unit cell. In particular, the lithium secondary battery is useful for portable devices such as mobile phones, laptops, digital cameras, and the like, as well as for electric vehicles such as hybrid electric vehicles (HEVs).

[0097] The present invention will be described in more detail below with reference to examples and experimental examples.

[0098] However, it should be understood that the following examples and experimental examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Example 1.

[0099] To 100 g of a styrene-butadiene rubber (hereinafter referred to as SBR, BM451B, available from ZEON Chemicals) dispersed in water as solvent in a 60:40 ratio (by weight), 500 g of an N-methyl-2-pyrrolidone (NMP) solvent were added and stirred. The stirred mixture was then heated at 100 to 120 °C for 2 hours to completely evaporate the water and produce an NMP-substituted SBR binder. The NMP-substituted SBR binder and inorganic particles were then mixed in a 50:50 weight ratio and stirred to produce an insulating composition. The resulting insulating composition had a viscosity of 5,000 cP. Examples 2 to 4 and comparative examples 1 and 2.

[0100] An insulating composition was obtained in the same way as in Example 1, except that the amounts of inorganic particles and a binder were changed in the preparation of an insulating composition.

[0101] Specific compositions of examples 1 to 4 and of comparative examples 1 and 2 are shown in the following Table 1. [Table 1] Classification Insulation composition solvent Inorganic particles binder Inorganic particles:binder (weight ratio) Example 1 NMP ALOOH SBR 50:50 Example 2 NMP ALOOH SBR 60:40 Example 3 NMP ALOOH SBR 75:25 Example 4 NMP ALOOH SBR 80:20 Comparison example 1 NMP ALOOH PVDF 80:20 Comparison example 2 NMP ALOOH PVDF 88:12 Experiment 1. Measurement of the wet adhesion of the insulating coating layer

[0102] To evaluate the adhesion of an insulating coating layer according to the present technology, an experiment was carried out as follows. Metal sample including the insulating coating layer formed therein

[0103] Each of the insulating compositions prepared in Examples 1 to 4 and Comparative Examples 1 and 2 was applied to an aluminum foil and dried to prepare a metal sample in which an insulating coating layer approximately 10 µm thick had formed. The metal sample, including the insulating coating layer formed within it, was punched to a size of 2 cm × 2 cm using a punching device for adhesion measurement. Application of ultrasound waves

[0104] 200 g of a liquid electrolyte (EC / EMC = 3 / 7 (Vol %)) were placed in a 250 ml beaker, and the metal sample, including the insulating layer formed within it, was immersed in the liquid electrolyte. To control the movement of the metal sample, it was fixed in place with a device.

[0105] The liquid electrolyte in which the metal sample was immersed was then sonicated using an ultrasonic device (4200, commercially available from BANDELIN). The conditions for the application of ultrasonic waves in this case were as follows. - Frequency: 20 kHz - Tip diameter: 13 mm (TS-113) - Amplitude: 100%

[0106] (when using a 13 mm tip, tip-to-tip 132 µm)

[0107] The results are shown in Table 2 below and Fig. 2 shown. [Table 2] Classification Example 1 Example 2 Example 3 Example 4 Comparative example 1 Comparative example 2 Composition: AlOOH:SBR=50:50 AlOOH:SBR=60:40 AlOOH:SBR=75:25 AlOOH:SBR=80:20 AlOOH:PVDF=80:20 AlOOH:PVDF=88:12 Time (minutes) 19 19 19 15 5 10 Final temperature (°C) 109 109 109 100 71 87 Comparison of wet adhesion no swelling and no detachment no swelling and no detachment no swelling and no detachment no swelling and no detachment Swelling Swelling and detachment

[0108] Fig. Figure 2 is a diagram showing the results of the wet adhesion measurement of insulating coating layers from Examples 1 and 4 and the comparison examples 1 and 2. Referring to Table 2 and Fig.Figure 2 shows that the electrode sample from Example 1 exhibits no swelling or detachment of the insulating coating layer. However, in the case of Example 1, the measurement was stopped upon reaching 109 °C because the measurement environment had changed due to the evaporation of a solvent resulting from the temperature rise of a liquid electrolyte caused by the application of ultrasonic waves and the EMC boiling point of 107.5 °C.

[0109] Although not shown in the figure, the electrode specimens of Examples 2 and 3, like Example 1, also showed no swelling or delamination of the insulating coating layer. However, when 109 °C was reached, the measurement was stopped because the measurement environment changed due to the evaporation of the solvent, which has an EMC boiling point of 107.5 °C.

[0110] In the case of Example 4, no swelling or detachment of the electrode specimen occurred during the 15-minute application of ultrasound waves in a liquid electrolyte. However, although not shown in the figure, swelling and detachment of the electrode specimen did occur when the temperature of the liquid electrolyte reached 108 °C due to the continuous application of ultrasound waves.

[0111] Furthermore, in comparison examples 1 and 2, swelling and detachment of the electrode specimens occurred within only 5 minutes after the application of ultrasound waves in a liquid electrolyte.

[0112] Based on the above results, it could be confirmed that the insulating coating layers of the examples exhibited excellent wet adhesion compared to the insulating coating layers of comparison examples 1 and 2. Experimental example 2. Evaluation of the battery cell's capacity

[0113] To evaluate the performance of the positive electrode, which includes an insulating coating layer according to the present technology, a half-cell was manufactured and the capacity was subsequently evaluated. Production of the half-cell

[0114] 96 parts by weight LiNi 0,8 Co 0,1 Mn 0,1O2 as the active material of the positive electrode, 2 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and 2 parts by weight of carbon black as a conductive material were weighed and mixed in an N-methylpyrrolidone (NMP) solvent to produce a slurry for the active material layer of the positive electrode. The positive electrode slurry was then applied to an aluminum foil, dried, and roll-pressed to produce a positive electrode including the active material layer (average thickness: 130 µm).

[0115] The positive electrode was then coated with each insulating composition obtained in Examples 1 to 3 using the dipping process and subsequently dried in a convection oven (130 °C) to form a 10 µm thick insulating coating layer on the positive electrode. A lithium foil as the negative electrode and a liquid electrolyte to which 1 M LiPF6 in a solvent (EC:DMC:DEC=1:2:1) was added were used to fabricate a coin-type half-cell. [Table 3] Insulating coating layer battery Example 1 Example 5 Example 2 Example 6 Example 3 Example 7 Measurement of the drainage capacity

[0116] The discharge behavior of the batteries in examples 5 to 7 was evaluated under the following conditions. Furthermore, the discharge characteristics were measured at room temperature (25 °C) and high temperature (45 °C). -Discharge: 0.1C, 0.33C, 0.5C, 1.0C, 2.5V, shutdown

[0117] To compare the capacity of each battery, a battery cell containing an electrode without an insulating coating layer was used as a comparison example 3. The results are shown in Tables 4 and 5 and the Fig. 3 and Fig. 4 shown. [Table 4] Classification Insulation composition Drainage rate at room temperature (%) solvent Inorganic particles binder Inorganic particles:binder (weight ratio) 0,1C 0,33C 0,5C 1,0C Comparative example 3 - - - - 100,00 100,00 100,00 100,00 Example 5 NMP ALOOH SBR 50:50 0,33 0,06 0,05 0,00 Example 6 NMP ALOOH SBR 60:40 0,60 0,09 0,05 0,03 Example 7 NMP ALOOH SBR 75:25 0,27 0,06 0,03 0,00 [Table 5] Classification Insulation composition Drainage rate at high temperatures (%) solvent Inorganic particles binder Inorganic particles:binder (weight ratio) 0,1C 0,33C 0,5C 1,0C Comparative example 3 - - - - 100,00 100,00 100,00 100,00 Example 5 NMP ALOOH SBR 50:50 2,23 0,21 0,15 0,05 Example 6 NMP ALOOH SBR 60:40 1,41 0,18 0,15 0,03 Example 7 NMP ALOOH SBR 75:25 15,35 0,18 0,15 0,03

[0118] Referring to Tables 4 and 5 and Fig. 3 and Fig. Figure 4 shows that the battery of example 7 showed a partially expressed capacity when discharged at a high temperature (45 °C) at 0.1 C, while the batteries of examples 5 and 6 showed hardly any expressed capacity when discharged at room temperature (25 °C).

[0119] It is assumed that the above result is due to the insulating coating layer preventing the migration of lithium ions in the superimposed region of the electrode, thus suppressing capacity degradation and similar effects during discharge by exhibiting excellent wet adhesion in a liquid electrolyte. Accordingly, in lithium secondary batteries using this technology, capacity degradation corresponding to an increase in cycle life can be suppressed, and safety can be improved.

[0120] Although the present invention has been described above with reference to the exemplary embodiments, the person skilled in the art may assume that various modifications and changes can be made without departing from the spirit and technical scope of the present invention as described in the attached claims.

[0121] Therefore, the technical scope of the present invention should be defined by the attached claims and not limited by the detailed description of the specification. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] KR 10-2021-0100879

[0001] KR 10-2022-0090835

[0001]

Claims

[1] Insulating composition for an electrode, comprising: an aqueous binder dispersed by a non-aqueous solvent; and an inorganic particle, where the weight ratio of the inorganic particle to the aqueous binder is between 1:99 and 95:

5. [2] Insulating composition according to claim 1, wherein the weight ratio of the inorganic particle to the aqueous binder is between 45:55 and 90:

10. [3] Insulating composition according to claim 1, wherein the non-aqueous organic solvent is one or more selected from the group consisting of N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate (BC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), acetonitrile, dimethoxyethane, tetrahydrofuran (THF), γ-butyrolactone, methyl alcohol, ethyl alcohol and isopropyl alcohol. [4] Insulating composition according to claim 1, wherein the inorganic particles are one or more selected from the group consisting of AlOOH, Al2O3, γ-AlOOH, Al(OH)3, Mg(OH)2, Ti(OH)4, MgO, CaO, Cr2O3, MnO2, Fe2O3, Co3O4, NiO, ZrO2, BaTiO3, SnO2, CeO2, Y2O3, SiO2, silicon carbide (SiC) and boron nitride (BN). [5] Insulating composition according to claim 1, wherein the aqueous binder is one or more selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, an ethylene-propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, an ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, an acrylic resin, phenolic resin, an epoxy resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropylcellulose and diacetylcellulose. [6] Insulating composition according to claim 1, wherein the non-aqueous organic solvent is N-methylpyrrolidone (NMP) and the aqueous binder is styrene-butadiene rubber. [7] Insulating composition according to claim 6, wherein the insulating composition includes first and second inorganic particles with different particle diameters and has a bimodal particle size distribution. [8] Insulating composition according to claim 1, wherein the insulating composition has a viscosity at 25 °C of 50 cP to 50,000 cP. [9] Secondary battery comprising the insulating composition according to claim 1 and a positive electrode, wherein the insulating composition is applied to the positive electrode.

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