Battery separators, secondary batteries, and electrical devices

Abstract

This application provides a battery separator comprising a base film and a ceramic coating located on at least one side of the base film, characterized in that the difference between the contact angle of the base film and the contact angle of the ceramic coating is 15° or less. The battery separator of this application has high adhesion, high fluid retention capacity, and high ionic conductivity, and can improve the cycle characteristics and rate characteristics of the battery.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application references Chinese Patent Application No. 202311622649.2, filed on November 29, 2023, entitled "Battery Separator, Secondary Battery and Electrical Device," which is incorporated in its entirety by reference.

[0002] This application relates to the technical field of batteries, and more particularly to battery separators, secondary batteries, and electrical devices. [Background technology]

[0003] In recent years, as the range of applications for secondary batteries has expanded, they are being widely used in various fields such as energy storage and power systems including hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the significant advancements in secondary batteries, the demands on their energy density, cycle performance, and safety performance have also increased.

[0004] Currently, separator materials for secondary batteries are mainly PP and PE, which are important components of secondary batteries. Separator materials have good pore size distribution, mechanical properties, chemical stability, electrolyte impregnation, electronic insulation, and high-temperature pore sealing performance. However, current PP and PE separators are non-polar and have low surface tension, which affects the electrolyte impregnation and surface coating of the separator. Binding properties It is inferior. [Overview of the project]

[0005] This application was made in view of the above-mentioned problems, and its purpose is to address the high Binding properties The objective is to provide a secondary battery separator having a high liquid retention capacity and high ionic conductivity, as well as a secondary battery and electrical device having said separator.

[0006] A first aspect of this application provides a battery separator comprising a base film and a ceramic coating located on at least one side of the base film, characterized in that the difference between the contact angle of the base film and the contact angle of the ceramic coating is 15° or less.

[0007] Therefore, this application employs a battery separator having the above-described structure, thereby improving the impregnation of the separator into the electrolyte and the surface coating (ceramic coating). Binding properties , and the separator and the positive electrode sheet and the negative electrode sheet Binding properties To improve the separator's quality Binding properties This enables the achievement of high liquid retention capacity and high ionic conductivity.

[0008] In any embodiment, the base film is a corona-treated base film, where the corona treatment power P1 is 50W to 200W, the voltage V1 is 100V to 230V, and the time T1 is 0.1s to 4s. base film The materials used to form the film are not particularly limited, and the base film may include one or more of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, glass fiber, nonwoven fabric, and high-temperature resistant polyester film, and may optionally include one or more of polyethylene and polypropylene.

[0009] In any embodiment, the ceramic coating is a corona-treated ceramic coating, where the power P2 of the corona treatment is 50W to 500W, the voltage V2 is 100V to 230V, and the time T2 is 0.1s to 6s. Furthermore, the material forming the ceramic coating is not particularly limited, and the ceramic coating contains one or more of Al2O3, AlO(OH), SiO2, TiO2, MgO, CaO, ZnO2, ZrO2, and SnO2, and selectively contains Al2O3.

[0010] Therefore, base film orBy applying corona treatment to the ceramic coating, the surface energy of the material can be increased while preventing damage to the material being treated. By appropriately increasing the surface energy of the material, the impregnation of the separator into the electrolyte and the surface coating can be improved. Binding properties , and the separator and the positive electrode sheet and the negative electrode sheet Binding properties It can improve.

[0011] In any embodiment, the separator further includes a binding coating located on the side away from the base film of the ceramic coating, and the difference between the contact angle of the ceramic coating and the contact angle of the binding coating is 2° to 15°. The material forming the binding coating is not particularly limited and may be a polymer, specifically, one or more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene polymer, styrene-butadiene polymer, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethylcellulose, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylate, and sodium hydroxymethylcellulose, and selectively includes polyvinylidene fluoride.

[0012] By forming a bonding coating using the above materials and keeping the difference between the contact angle of the ceramic coating and the bonding coating within the above range, the surface energies of the bonding coating and the ceramic coating are brought closer together, resulting in a good surface energy. Binding effect It is possible to achieve results.

[0013] In any embodiment, the bonding coating is a corona-treated bonding coating, the power P3 of the corona treatment is 50W to 600W, the voltage V3 is 100V to 230V, and the time T3 is 0.1s to 5s.

[0014] Therefore, by setting the corona treatment to the above-mentioned conditions, surface treatment of the material can be achieved, that is, the surface energy of the material can be appropriately increased while preventing damage to the material being corona treated.

[0015] In any embodiment, the contact angle of the base film is 60° to 80°. The contact angle of the ceramic coating is 60° to 80°. The contact angle of the binder coating is 40° to 60°.

[0016] By setting the contact angles of the base film and the ceramic coating within the above ranges, the surface energies of the base film and the ceramic coating can be made closer, and good Binding effect results can be achieved. By setting the contact angle of the binder coating within the above range, the effect of separating the separator and the electrode sheet can be realized better. Conclude

[0017] In any embodiment, the liquid absorption rate of the separator is 4.5 mm / s to 6 mm / s. When the separator has a liquid absorption rate within the above range, when the separator is immersed in the electrolyte, the electrolyte can be quickly impregnated into the separator, realizing rapid ion conduction. Thereby, the ionic conductivity of the battery can be improved, and further the cycle performance and rate characteristics of the battery can be improved.

[0018] In any embodiment, the adhesion force between the base film and the ceramic coating is 2.5 N / mm to 4 N / mm. By setting the adhesion force between the base film and the ceramic coating within the above range, the structure of the separator becomes more compact, the separator can better exert its function, and further the cycle performance and rate characteristics of the battery can be improved.

[0019] The second aspect of the present application provides a secondary battery including a positive electrode sheet, a negative electrode sheet, and a separator.

[0020] The secondary battery of the present application has high cycle characteristics and high rate characteristics by having the separator of the present application.

[0021] In any embodiment, the separator further includes a binding coating located away from the base film of the ceramic coating, wherein the difference between the contact angle of the positive electrode sheet and the contact angle of the binding coating is 20° or less, and / or the difference between the contact angle of the negative electrode sheet and the contact angle of the binding coating is 20° or less. The contact angle of the positive electrode sheet is 40° to 80°, and / or the contact angle of the negative electrode sheet is 40° to 80°.

[0022] In a secondary battery, if the separator, positive electrode sheet, and negative electrode sheet each have contact angles and contact angle differences within the above ranges, good bonding between the separator, positive electrode sheet, and negative electrode sheet can be achieved. This results in a more compact secondary battery structure and smoother ion conduction between the positive electrode sheet, negative electrode sheet, and separator, thereby achieving high cycle and high rate characteristics in the secondary battery.

[0023] In any embodiment, the secondary battery includes at least one of a lithium secondary battery and a sodium secondary battery.

[0024] A third aspect of this application provides an electrical device characterized by including the above-described secondary battery. [Modes for carrying out the invention]

[0025] The embodiments of the battery separator, secondary battery, and electrical device will be described in detail below. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and redundant explanations of identical structures may be omitted. This is to avoid unnecessarily verbose explanations, making them easy for those skilled in the art to understand.

[0026] The “range” disclosed in this application is limited by a lower and upper limit, and a given range is limited by selecting one lower limit and one upper limit, and the boundaries of a particular range are limited by the selected lower and upper limits. Such limited ranges may or may not include endpoint values ​​and can be combined arbitrarily, that is, any lower limit and any upper limit can be combined to form a single range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, the ranges 60-110 and 80-120 are also understood to be predictable. Also, if the minimum range values ​​are 1 and 2 and the maximum range values ​​are 3, 4 and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all predictable. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression for any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is merely an abbreviated representation of combinations of these numbers. Furthermore, when a parameter is described as being an integer of 2 or more, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12.

[0027] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technological solutions.

[0028] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0029] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method further includes step (c), it means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), or otherwise.

[0030] Unless otherwise specified, the terms "includes" and "incorporates" in this application represent open-ended expressions, but may also represent closed-ended expressions. For example, the terms "includes" and "incorporates" may further include or incorporate other components not listed, or may include or incorporate only the listed components.

[0031] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy the "A or B" condition: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0032] Battery separators are a crucial component of secondary batteries and significantly impact their performance. However, existing PP and PE separators are non-polar and have low surface tension, which affects their impregnation into the electrolyte and the surface coating. Binding propertiesThis is inferior. By applying surface corona treatment to the structure of each layer of the battery separator and electrode sheet, a free radical reaction is generated on the surface of the treated object, allowing the polymer to be crosslinked. The surface becomes rougher, the wettability to polar solvents improves, the molecules on the surface of the treated object are oxidized and polarized, and the surface is eroded by electric shocks of ions, improving the adhesion ability to the surface of the treated object. As a result, the liquid retention and binding properties of the battery separator to the electrode sheet are improved, and the cycle performance and rate characteristics of the secondary battery can be improved.

[0033] Based on this, this application provides a battery separator, a method for manufacturing the same, and a secondary battery and electrical device having the separator, which will be described in detail below.

[0034] [Battery separator] The battery separator of this application comprises a base film and a ceramic coating located on at least one side of the base film, wherein the difference between the contact angle of the base film and the contact angle of the ceramic coating is 15° or less, and optionally further comprises a bonding coating. In this application, by subjecting each layer to surface corona treatment, the surface energy of each layer is increased, which helps to improve wettability and bonding strength.

[0035] In some embodiments, the difference between the contact angle of the base film and the contact angle of the ceramic coating is selectively within the range of 15°, 14°, 13°, 12°, 11°, 10°, 9°, 8°, 7°, 6°, 5°, 4°, 3°, 2°, 1°, or 0°, or any two of the above values.

[0036] The contact angle of the base film is adjusted by performing corona treatment on the surface of the base film. Corona treatment can increase the surface energy of the material surface and improve the polarity of the material surface. By setting the difference in the contact angles between the layers to the above range, the polarity of the base film surface is improved, and the base film and coating Bonding forceThis can improve the surface energy of the separator. By applying corona surface treatment to the coated separator again, the surface energy of the coated separator increases, and the separator Binding properties Furthermore, the impregnation properties into the electrolyte are improved.

[0037] In any embodiment, the base film is a corona-treated base film, where the power P1 of the corona treatment is 50W to 200W, the voltage V1 is 100V to 230V, and the time T1 is 0.1s to 4s. base film The materials used to form the film are not particularly limited, and the base film includes one or more of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, glass fiber, nonwoven fabric, and high-temperature resistant polyester film, and optionally includes one or more of polyethylene and polypropylene.

[0038] In some embodiments, the power P1 of the corona treatment on the base film is selectively 50W, 60W, 70W, 80W, 90W, 100W, 110W, 120W, 130W, 140W, 150W, 160W, 170W, 180W, 190W, or 200W, or a range between any two of the above values. In some embodiments, the corona treatment Voltage V 1 is selectively a range of 100V, 110V, 120V, 130V, 140V, 150V, 160V, 170V, 180V, 190V, 200V, 210V, 220V, or 230V, or any two of the above values. In some embodiments, the corona treatment time T1 is selectively a range of 0.1s, 0.5s, 1s, 1.5s, 2s, 2.5s, 3s, 3.5s, or 4s, or any two of the above values.

[0039] In any embodiment, the ceramic coating is a corona-treated ceramic coating, where the power P2 of the corona treatment is 50 to 500 W, the voltage V2 is 100 V to 230 V, and the time T2 is 0.1 s to 6 s. Furthermore, the material forming the ceramic coating is not particularly limited, and the ceramic coating contains one or more of Al2O3, AlO(OH), SiO2, TiO2, MgO, CaO, ZnO2, ZrO2, and SnO2, and selectively contains Al2O3.

[0040] In some embodiments, the power P2 for corona treatment of the ceramic coating is selectively 50W, 60W, 70W, 80W, 90W, 100W, 110W, 120W, 130W, 140W, 150W, 160W, 170W, 180W, 190W, 200W, 210W, 220W, 230W, 240W, 250W, 2 60W, 270W, 280W, 290W, 300W, 310W, 320W, 330W, 340W, 350W, 360W, 370W, 380W, 390W, 400W, 410W, 420W, 430W, 440W, 450W, 460W, 470W, 480W, 490W, or 500W, or a range between any two of the above values. In some embodiments, the corona treatment Voltage V 2 is selectively a range of 100V, 110V, 120V, 130V, 140V, 150V, 160V, 170V, 180V, 190V, 200V, 210V, 220V, or 230V, or any two of the above values. In some embodiments, the corona treatment time T2 is selectively a range of 0.1s, 0.5s, 1s, 1.5s, 2s, 2.5s, 3s, 3.5s, 4s, 4.5s, 5s, 5.5s, or 6s, or any two of the above values.

[0041] The aforementioned base film orBy applying the aforementioned corona treatment to the ceramic coating, the content of polar groups on the material surface can be increased, improving the polarity and surface energy of the material, which helps to improve the wettability and bonding strength of the material. At the same time, the corona treatment conditions described above can also prevent damage to the material being treated, such as the material shrinking due to the energy released during corona treatment, which affects its mechanical strength. By appropriately increasing the surface energy of the material, the impregnation of the separator into the electrolyte and the surface coating are improved. Binding properties , and the separator and the positive electrode sheet and the negative electrode sheet Binding properties It can improve.

[0042] In any embodiment, the separator further includes a binding coating located on the side of the ceramic coating away from the base film, and the difference between the contact angle of the ceramic coating and the contact angle of the binding coating is 2° to 15°. The material forming the binding coating is not particularly limited and may be a polymer, specifically, one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene polymer, styrene-butadiene polymer, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethylcellulose, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylate, and sodium hydroxymethylcellulose, and selectively includes polyvinylidene fluoride.

[0043] In some embodiments, the difference between the contact angle of the ceramic coating and the contact angle of the bonding coating is selectively within the range of 15°, 14°, 13°, 12°, 11°, 10°, 9°, 8°, 7°, 6°, 5°, 4°, 3°, or 2°, or any two of the above values.

[0044] By forming a bonding coating using the above materials and keeping the difference between the contact angle of the ceramic coating and the bonding coating within the above range, the surface energies of the bonding coating and the ceramic coating are brought closer together, resulting in a good surface energy. Binding effectIt is possible to achieve results.

[0045] In any embodiment, the bonding coating is a corona-treated bonding coating, where the power P3 of the corona treatment is 50-600W, the voltage V3 is 100V-230V, and the time T3 is 0.1s-5s.

[0046] In some embodiments, the power P3 for corona treatment of the ceramic coating is selectively set to 50W, 60W, 70W, 80W, 90W, 100W, 110W, 120W, 130W, 140W, 150W, 160W, 170W, 180W, 190W, 200W, 210W, 220W, 230W, 240W, 250W, 260W, 270W, 280W, 290W, 300W, 3 10W, 320W, 330W, 340W, 350W, 360W, 370W, 380W, 390W, 400W, 410W, 420W, 430W, 440W, 450W, 460W, 470W, 480W, 490W, 500W, 510W, 520W, 530W, 540W, 550W, 560W, 570W, 580W, 590W, or 600W, or a range between any two of the above values. In some embodiments, the corona treatment Voltage V 3 is selectively a range of 100V, 110V, 120V, 130V, 140V, 150V, 160V, 170V, 180V, 190V, 200V, 210V, 220V, or 230V, or any two of the above values. In some embodiments, the corona treatment time T3 is selectively a range of 0.1s, 0.5s, 1s, 1.5s, 2s, 2.5s, 3s, 3.5s, 4s, 4.5s, or 5s, or any two of the above values.

[0047] Therefore, by setting the corona treatment to the above-mentioned conditions, surface treatment of the material can be achieved, that is, the surface energy of the material can be appropriately increased while preventing damage to the material being corona treated.

[0048] In any embodiment, the contact angle of the base film is 60° to 80°. The contact angle of the ceramic coating is 60° to 80°. The contact angle of the binding coating is 40° to 60°.

[0049] In some embodiments, the contact angle of the base film is selectively 60°, 62°, 64°, 66°, 68°, 70°, 72°, 74°, 76°, 78°, or 80°, or a range between any two of the above values.

[0050] By setting the contact angle between the base film and the ceramic coating within the above range, the surface energies of the base film and the ceramic coating can be brought closer together, resulting in good contact between the two. Binding effect This can be achieved. By setting the contact angle of the bonding coating within the above range, the separator and the electrode sheet can be brought together. Conclude This allows for a more effective realization of the desired effect.

[0051] In any embodiment, the liquid absorption rate of the separator is 4.5 mm / s to 6 mm / s. Having a liquid absorption rate within this range allows the separator to be quickly impregnated with the electrolyte when immersed in it, enabling rapid ion conduction. This improves the ionic conductivity of the battery and further enhances its cycle performance and rate characteristics.

[0052] In some embodiments, the liquid absorption rate of the separator is selectively set to 4.5 mm / s, 4.6 mm / s, 4.7 mm / s, 4.8 mm / s, 4.9 mm / s, 5 mm / s, 5.1 mm / s, and 5.2 mm / s. 、 The range is 5.3 mm / s, 5.4 mm / s, 5.5 mm / s, 5.6 mm / s, 5.7 mm / s, 5.8 mm / s, 5.9 mm / s, or 6 mm / s, or any two of the above values.

[0053] In any embodiment, the bonding force between the base film and the ceramic coating is 2.5 N / mm to 4 N / mm. By setting the bonding force between the base film and the ceramic coating within this range, the separator structure becomes more compact, the separator can perform its function more effectively, and the battery's cycle performance and rate characteristics can be improved.

[0054] In some embodiments, the bonding force between the base film and the ceramic coating is selectively within the range of 2.5 N / mm, 2.6 N / mm, 2.7 N / mm, 2.8 N / mm, 2.9 N / mm, 3 N / mm, 3.1 N / mm, 3.2 N / mm, 3.3 N / mm, 3.4 N / mm, 3.5 N / mm, 3.6 N / mm, 3.7 N / mm, 3.8 N / mm, 3.9 N / mm, or 4 N / mm, or any two of the above values.

[0055] In any embodiment, the separator further includes a binding coating located on the side of the ceramic coating away from the base film, wherein the difference between the contact angle of the positive electrode sheet and the contact angle of the binding coating is 20° or less, and / or the difference between the contact angle of the negative electrode sheet and the contact angle of the binding coating is 20° or less. The contact angle of the positive electrode sheet is 40° to 80°, and / or the contact angle of the negative electrode sheet is 40° to 80°.

[0056] In some embodiments, the difference between the contact angle of the positive electrode sheet and / or the negative electrode sheet and the contact angle of the bonding coating is selectively 20°, 19°, 18°, 17°, 16°, 15°, 14°, 13°, 12°, 11°, 10°, 9°, 8°, 7°, 6°, 5°, 4°, 3°, 2°, 1°, or 0°, and the contact angle of the positive electrode sheet and / or the negative electrode sheet is selectively 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, or 80°, or in the range of any two of the above values.

[0057] In the separator described in this application, the separator, positive electrode sheet, and negative electrode sheet in the secondary battery have contact angles and contact angle differences within the above ranges, thereby achieving good bonding between the separator, positive electrode sheet, and negative electrode sheet. This results in a more compact secondary battery structure and smoother ion conduction between the positive electrode sheet, negative electrode sheet, and separator, thereby achieving high cycle characteristics and high rate characteristics for the secondary battery.

[0058] [Positive electrode sheet] The positive electrode sheet includes a positive electrode current collector and positive electrode film layers provided on both sides of the positive electrode current collector, the positive electrode film layers containing positive electrode active material.

[0059] For example, a positive electrode current collector has two opposing surfaces in the thickness direction of itself, and the positive electrode film layer is provided on the two opposing surfaces of the positive electrode current collector.

[0060] In some embodiments, a metal foil or a composite current collector can be used as the positive electrode current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0061] In some embodiments, the positive electrode active material can be a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of a lithium-containing phosphate having an olivine structure, a lithium transition metal oxide, and modified compounds of each of them. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of the lithium transition metal oxide include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel manganese cobalt oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which may simply be called NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which may simply be called NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which may simply be called NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which may simply be called NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which may simply be called NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05It may include, but is not limited to, at least one of O2) and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure include, but is not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may also be simply called LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (e.g., LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0062] In some embodiments, the positive electrode film layer selectively further comprises a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0063] In some embodiments, the cathode film layer further selectively comprises a conductive agent (Super P). For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0064] In some embodiments, the positive electrode sheet can be manufactured as follows: The above-mentioned components for manufacturing the positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, the positive electrode slurry is coated onto a positive electrode current collector, and the positive electrode sheet can be obtained through processes such as oven drying and cold pressing.

[0065] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector and negative electrode film layers provided on both surfaces of the negative electrode current collector, the negative electrode film layers containing a negative electrode active material.

[0066] For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on the two surfaces of the negative electrode current collector.

[0067] In some embodiments, a metal foil or a composite current collector can be used as the negative electrode current collector. For example, copper foil may be used as the metal foil. The composite current collector consists of a polymer material substrate layer and a polymer material substrate. layer The composite current collector may include a metal layer formed on at least one surface. The composite current collector can be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0068] In some embodiments, the negative electrode active material can be any negative electrode active material known in the art for batteries. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxygen compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials usable as negative electrode active materials for batteries may be used. These negative electrode active materials may be used individually or in combination of two or more types.

[0069] In some embodiments, the negative electrode film layer further selectively comprises a binder. The binder may be at least one selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0070] In some embodiments, the negative electrode film layer further selectively comprises a conductive agent. The conductive agent may be at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0071] In some embodiments, the negative electrode film layer further comprises other additives, such as a selective thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0072] In some embodiments, the negative electrode sheet can be manufactured as follows: The above-mentioned components for manufacturing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, the negative electrode slurry is coated onto a negative electrode current collector, and the negative electrode sheet can be obtained through processes such as oven drying and cold pressing.

[0073] [Electrolyte] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. In this application, the type of electrolyte is not specifically limited and can be selected as needed. For example, the electrolyte may be liquid, gel-like, or all-solid.

[0074] In some embodiments, an electrolyte solution is used as the electrolyte. The electrolyte solution comprises an electrolyte salt and a solvent.

[0075] In some embodiments, the electrolyte salt may be at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0076] In some embodiments, the solvent may be at least one selected from ethylene carbonate, propylene carbonate, ethylmethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethylmethyl sulfone, and diethyl sulfone.

[0077] In some embodiments, the electrolyte further selectively includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may further include additives that can improve certain aspects of the battery's performance, such as additives that can improve the battery's overcharge performance, or additives that can improve the battery's high-temperature or low-temperature performance.

[0078] [Method for manufacturing battery separators] The battery separator of this application is manufactured by the following method: The battery separator of this application comprises a base film, a ceramic coating, and a selective Binding The process involves several steps. First, corona treatment is applied to the surface of the base film to improve the polarity of the base film surface, and the base film and coating are connected. Bonding forceTo improve the surface energy of the coated separator, the surface energy of the coated separator is increased by applying corona surface treatment again. Binding properties Furthermore, it improves the impregnation properties of the electrolyte.

[0079] [Secondary battery] Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During charging and discharging of the battery, active ions repeatedly insert and remove between the positive and negative electrode sheets. The electrolyte plays a role in conducting ions between the positive and negative electrode sheets. The separator is placed between the positive and negative electrode sheets and primarily serves to prevent short circuits between the positive and negative electrodes, while also allowing ions to pass through.

[0080] The secondary battery of this application has high cycle characteristics and high rate characteristics by having the separator described in this application. [Examples]

[0081] Examples of the present application are described below. The examples described below are illustrative and are for interpretive purposes only, and should not be understood as limiting this application. Unless otherwise specified in the examples, specific techniques or conditions are followed in accordance with the techniques or conditions described in the literature in the art, or in the specifications of the products. Unless otherwise specified, the reagents or equipment used are common commercially available products.

[0082] 1. Manufacturing method Example 1 1) Separator Polyethylene was used as the base film, with a length of 100 cm and a width of 10 cm. The base film was subjected to corona treatment, with a power P1 of 200 W, a voltage V1 of 150 V, and a time T1 of 3.5 s.

[0083] A fixed amount of Al2O3, a ceramic material, was weighed and dispersed in water to obtain a ceramic material slurry. The ceramic material slurry was spray-coated onto both opposing surfaces of a corona-treated polyethylene base film to produce a ceramic coating. After the spray coating was completed, it was baked in a 60°C oven for 30 minutes. The surface of the baked ceramic coating was corona-treated with a power P2 of 500W, a voltage V2 of 220V, and a time T2 of 5s.

[0084] A fixed amount of polyvinylidene fluoride, a binder, was weighed and dissolved in N-methyl-2-pyrrolidone, a solvent, to obtain a binder slurry. This slurry was then spray-coated onto opposing surfaces of a corona-treated ceramic coating to produce a binder coating. After the spray coating was completed, the mixture was baked in a 60°C oven for 30 minutes. The surface of the baked binder coating was corona-treated with a power P3 of 589W, a voltage V3 of 200V, and a time T3 of 4s to obtain a separator.

[0085] 2) Electrolyte In a glove box filled with argon (moisture content less than 10 ppm, oxygen content less than 1 ppm), ethylene carbonate and ethylmethyl carbonate (volume ratio 3:7) were uniformly mixed in a constant ratio, and then an appropriate amount of LiPF6 was slowly added to a non-aqueous organic solvent. After the lithium salt was completely dissolved, a 1 mol / L electrolyte was obtained. The conductivity of the electrolyte was 8.5 mS / cm.

[0086] 3) Manufacturing of positive electrode sheets LiNi 0.5 Co 0.2 Mn 0.3O2, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5. N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred in a vacuum until the reaction system was homogeneous, yielding a positive electrode slurry with a solid content of 65 wt%. The positive electrode slurry was applied to the aluminum foil current collector, oven-dried at 85°C, then cold-pressed, followed by edge cutting, thinning, and slitting. Subsequently, the sheet was oven-dried at 85°C under vacuum conditions for 4 hours to produce a positive electrode sheet.

[0087] 4) Manufacturing of negative electrode sheets The negative electrode active material is graphite, a certain amount of silicon, the conductive agent is Super P, the thickener is CMC, and Binding agent Styrene-butadiene rubber (SBR) was mixed in a mass ratio of 90:4:3:3 and dissolved in deionized water to prepare a negative electrode slurry. The negative electrode slurry was obtained using a vacuum mixer, and the solid content in the negative electrode slurry was 55 wt%. The negative electrode slurry was applied to the copper foil of the current collector, and after oven drying at 85°C, it was cold-pressed, edge-cut, thin-cut, and slit, and then oven-dried at 120°C under vacuum conditions for 12 hours to prepare a negative electrode sheet.

[0088] 5) Battery manufacturing The manufactured positive electrode sheet, separator, and negative electrode sheet were stacked in this order, with the separator positioned between the positive and negative electrode sheets to isolate them. The stack was then wound to obtain a bare cell, tabs were welded, the bare cell was set in an outer casing, the electrolyte manufactured above was injected into the dried cell, and packaging, standing, chemical conversion, molding, and capacity testing were performed to obtain the lithium secondary battery of Example 1.

[0089] In this application, the contact angle of the material surface was measured as follows:

[0090] An electrode sheet or film was fixed to a standard glass sheet and placed on a mounting stage. The needle was inserted into deionized water, the deionized water was slowly drawn into a syringe, the needle was pointed upward, the piston was pressed to expel the air from the syringe, and then the needle was placed on the mounting base. The height of the sample stage was adjusted, the sample stage was raised to receive the expelled droplet, and the droplet was dropped onto the powder surface to form a droplet. The contact angle was automatically measured using a contact angle meter (SINDIN, model SDC-200S), its magnitude was determined by fitting, and the contact angle was recorded.

[0091] The secondary batteries of Examples 2-15 and Comparative Examples 1-3 were manufactured in the same manner as the secondary battery of Example 1, except for the corona treatment parameters of the base film, ceramic coating, and bonding coating, or the contact angle of the positive / negative electrode sheet. Details of the product parameters are shown in Table 1.

[0092] 2. Performance Test 1. Separator performance testing 1) Test of bonding strength Sampling was performed using a sampler measuring 100 mm in length and 20 mm in width. After wiping the stainless steel plate with alcohol, standard width double-sided tape (standard 3M9730-100) was applied flat to the steel plate. The other side of the double-sided tape was peeled off, the separator was applied flat, a jig was attached, and the base film and coating of the separator were tested on a tensile testing machine (model: INSTRON, model: 3365). Bonding force We conducted tests on this topic.

[0093] 2) Test of liquid absorption capacity Samples were taken using a sampler measuring 100 mm in length and 20 mm in width. The samples were immersed in a 1 mol / L LiPF6 / EC:DEC = 1:1 electrolyte solution at 60°C for 4 hours. After that, the separators were removed and suspended for 30 seconds. The weight of the separators before and after immersion was measured using an electronic balance ((weight after immersion - weight before immersion) / weight before immersion).

[0094] 3) Test of liquid absorption rate Sampling was performed using a sampler measuring 100 mm in length and 5 mm in width. The sample was fixed (suspended horizontally), and one drop of electrolyte (1 mol / L LiPF6 / EC:DEC=1:1) was added to the sample using a dropper. The length of the absorption stripe on the sample after 60 seconds was recorded. The ratio of this length to time was defined as the absorption rate.

[0095] 2. Battery performance test 1) Cycle performance The manufactured lithium secondary battery was charged with a constant current at 25°C at a rate of 0.33C up to 3.65V, and then at 0.05C. to After constant voltage charging, the device was left standing for 10 minutes, and then discharged at a constant current of 0.33C down to 2.5V, with the discharge capacity recorded as C0. Following the above charge / discharge process... 500 A cycle was performed. 500 The discharge capacity after cycling was defined as C1, and the battery's cycle capacity retention rate was calculated as C1 / C0 × 100%.

[0096] 2) Fast charging performance The manufactured lithium secondary battery was charged with a constant current at 2C at 25°C up to 3.65V, and then at 0.05C. to Constant voltage charging was performed. The charging capacity at this time was defined as C1. After that, it was left for 10 minutes, and then discharged at a constant current of 1C down to 2.5V, and the discharge capacity was recorded as C0. The fast charging performance is reflected in the C0 / C1 value, and a larger value indicates better fast charging performance.

[0097] 3. Analysis of the test results of each example and comparative example. Batteries for each example and comparative example were manufactured according to the method described above, and each performance parameter was measured. The results are shown in Table 1 below.

[0098] [Table 1]

[0099] According to Table 1, the separators of Examples 1 to 15 of this application include a base film and a ceramic coating located on at least one side of the base film, with a difference of 15° or less between the contact angle of the base film and the contact angle of the ceramic coating. Batteries manufactured using this separator all exhibited high capacity retention after 500 cycles, as well as excellent rapid charging performance. The main reasons for this are as follows: The base film of the separator , ceramic coating and bonding coating By applying the corona treatment described in this application, the polarity and surface energy of the base film, ceramic coating, and bonding coating are improved. Specifically, the contact angles between each layer are within the range described in this application, improving the bonding between layers and thus improving the battery's cycle performance and rapid charging performance.

[0100] Furthermore, the inventors have found through their research that in the later stages of a secondary battery cycle, battery decay is largely influenced by the amount of electrolyte retained. Therefore, increasing the amount of electrolyte retained by the separator helps improve cycle performance, and the improvement in bonding strength and the increase in electrolyte retained is advantageous for rate performance because it helps improve the interface state of the electrode sheet. In Examples 1 to 15 of this application, after corona treatment of the separator film layer, the polarity of the material surface is improved, and similarly, the affinity with the electrolyte, which is a polar substance, is improved. As a result, the electrolyte absorption rate of the separator increases, and the electrolyte retention rate improves, which also helps improve the cycle performance and rapid charging performance of the battery.

[0101] Furthermore, as shown in Table 1, in Comparative Examples 1 to 3, the separator in Comparative Example 1 had no corona treatment applied to the base film and ceramic coating, the separator in Comparative Example 2 had no corona treatment applied to the ceramic coating and binding coating, and the separator in Comparative Example 3 had no corona treatment applied to the base film and binding coating. As a result, the secondary batteries manufactured using these separators suffered from significantly reduced cycle characteristics and rapid charging characteristics, and failed to meet the requirements of this application.

[0102] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and all embodiments having substantially the same technical idea and achieving the same function and effect within the scope of the technical solution of this application are included in the technical scope of this application. Furthermore, other forms that are constructed by adding various modifications to the embodiments that a person skilled in the art could conceive of, and by combining some of the components of the embodiments, are also included in the scope of this application, without departing from the gist of this application.

Claims

1. The base film comprises a ceramic coating located on at least one side of the base film, A separator characterized in that the difference between the contact angle of the base film and the contact angle of the ceramic coating is 15° or less, preferably 10° or less.

2. The separator according to claim 1, characterized in that the base film is a corona-treated base film, the power P1 of the corona treatment is 50W to 200W, the voltage V1 is 100V to 230V, and the time T1 is 0.1s to 4s.

3. The separator according to claim 1 or 2, characterized in that the ceramic coating is a corona-treated ceramic coating, the power P2 of the corona treatment is 50W to 500W, the voltage V2 is 100V to 230V, and the time T2 is 0.1s to 6s.

4. The separator according to any one of claims 1 to 3, further comprising a binding coating located on the side of the ceramic coating away from the base film, wherein the difference between the contact angle of the ceramic coating and the contact angle of the binding coating is 2° to 15°.

5. The separator according to any one of claims 1 to 4, characterized in that the bonding coating is a bonding coating that has been corona-treated, the power P3 of the corona treatment is 50W to 600W, the voltage V3 is 100V to 230V, and the time T3 is 0.1s to 5s.

6. The separator according to any one of claims 1 to 5, characterized in that the contact angle of the base film is 60° to 80°.

7. The separator according to any one of claims 1 to 6, characterized in that the contact angle of the ceramic coating is 60° to 80°.

8. The separator according to any one of claims 1 to 7, characterized in that the contact angle of the bonding coating is 40° to 60°.

9. The separator according to any one of claims 1 to 8, wherein the base film comprises one or more of polyethylene, polypropylene, polyimide, polyamide, polyethylene terephthalate, glass fiber, nonwoven fabric, and high-temperature resistant polyester film, and is characterized in that it selectively comprises one or more of polyethylene and polypropylene.

10. The ceramic coating contains one or more of Al ２ O ３ , AlO(OH), SiO ２ , TiO ２ , MgO, CaO, ZnO ２ , ZrO ２ , SnO ２ , and selectively contains Al ２ O ３ . The separator according to any one of claims 1 to 9, characterized in that it contains Al

11. The separator according to any one of claims 1 to 10, wherein the binding coating comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene polymer, styrene-butadiene polymer, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethylcellulose, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylate, and sodium hydroxymethylcellulose, and selectively comprises polyvinylidene fluoride.

12. The separator according to any one of claims 1 to 11, characterized in that the liquid absorption rate of the separator is 4.5 mm / s to 6 mm / s.

13. The separator according to any one of claims 1 to 12, characterized in that the bonding force between the base film and the ceramic coating is 2.5 N / mm to 4 N / mm.

14. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, and a separator according to any one of claims 1 to 13.

15. The separator further includes a binding coating located on the side of the ceramic coating away from the base film, wherein the difference between the contact angle of the positive electrode sheet and the contact angle of the binding coating is 20° or less, and / or The secondary battery according to claim 14, characterized in that the difference between the contact angle of the negative electrode sheet and the contact angle of the bonding coating is 20° or less.

16. The secondary battery according to claim 14 or 15, characterized in that the contact angle of the positive electrode sheet is 40° to 80°, and / or the contact angle of the negative electrode sheet is 40° to 80°.

17. The secondary battery according to any one of claims 14 to 16, characterized in that the secondary battery includes at least one of a lithium secondary battery and a sodium secondary battery.

18. An electrical device characterized by including a secondary battery according to any one of claims 14 to 17.

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