Secondary battery, electric device, and current collector

Abstract

A secondary battery, an electric device, and a current collector. The secondary battery comprises electrode sheets; each electrode sheet comprises a current collector and a film layer arranged on at least one side of the current collector; the current collector comprises a metal current collector substrate and a primer layer arranged on at least one side of the metal current collector substrate; the primer layer comprises an inorganic oxide; and the film layer comprises an aqueous binder.

Description

Secondary battery, power consuming device, and current collector

[0001] Cross-reference to related applications

[0002] This application is based on the Chinese Patent Application No. 202410437980.5 entitled "Secondary battery and power consuming device" filed on April 11, 2024, which is incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of batteries, and in particular to a secondary battery, a power consuming device, and a current collector. BACKGROUND

[0004] With the increasing prominence of energy and environmental problems, new energy industries have received more and more attention. Secondary batteries have been widely used in recent years in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and the like, due to their high energy density and good cycle performance.

[0005] The pole piece is an important component of the secondary battery. How to improve the quality of the pole piece to further improve the performance of the secondary battery is a technical problem that needs to be solved in the field.

[0006] SUMMARY

[0007] The present application is made in view of the above-mentioned problem, and aims to provide a secondary battery with improved performance.

[0008] The first aspect of the present application provides a secondary battery, the secondary battery comprising a pole piece, the pole piece comprising a current collector and a film layer disposed on at least one side of the current collector, the current collector comprising a current collector substrate and a primer layer disposed on at least one side of the current collector substrate, the primer layer comprising an inorganic oxide, and the film layer comprising an aqueous binder.

[0009] The inorganic oxide has a large density and better affinity with the metal current collector substrate. Compared with the active material (such as soft carbon or hard carbon) or the conductive agent (such as conductive carbon) commonly used in the film layer, the inorganic oxide is less likely to shrink or displace under the surface tension of the slurry, which can effectively improve the coating quality of the primer layer and achieve successful coating of the liquid slurry with a large surface energy difference value on the surface of the current collector substrate. The aqueous slurry including the aqueous binder has a large surface tension, and there is often a problem of large surface energy difference value and poor coating quality when coating on the current collector substrate. The inclusion of the inorganic oxide in the primer layer can especially solve the problem of poor compatibility of the aqueous slurry with the current collector substrate and improve the coating quality of the aqueous slurry on the current collector substrate.

[0010] In any embodiment, the inorganic oxide includes one or more of aluminum oxide, boehmite, magnesium oxide, iron oxide, silicon oxide, and zirconium oxide.

[0011] In any embodiment, the mass percentage of the inorganic oxide in the base coating is 30%-60% based on the total mass of the base coating.

[0012] The inorganic oxide in the above mass range in the base coating can improve the coating quality of the pole piece, improve the adhesion strength of the pole piece, reduce the elongation rate of the pole piece during cold pressing, and effectively control the resistance of the current collector, while taking into account the electrochemical performance of the battery.

[0013] In any embodiment, the volume distribution particle size Dv50 of the inorganic oxide is less than 2 μm.

[0014] The inorganic oxide with the volume distribution particle size in the above range can be tightly attached to the metal current collector substrate, improving the forming quality of the base coating and the pole piece.

[0015] In any embodiment, the base coating further includes a particulate binder, and the particulate binder includes one or more of styrene-butadiene rubber and acrylate rubber.

[0016] The particulate binder has water-oil amphiphilicity, and can exhibit better water resistance than a linear binder that has strong affinity with water solvent, so that the base coating can remain stable during coating of the upper film layer containing active substances, further playing a role of the base coating in improving the coating quality.

[0017] In any embodiment, the mass percentage of the particulate binder in the base coating is 10%-40% based on the total mass of the base coating.

[0018] The particulate binder in the above mass range in the base coating can improve the coating quality of the pole piece, improve the adhesion strength of the pole piece, and effectively control the resistance of the current collector, while taking into account the electrochemical performance of the battery.

[0019] In any embodiment, the base coating further includes a dispersant, and the dispersant includes one or more of polyacrylic polymers.

[0020] The polyacrylic polymer is a linear polymer, can be fully dispersed in the solvent to coat the inorganic oxide, reduce agglomeration of the inorganic oxide, effectively disperse the inorganic oxide, assist the inorganic oxide to fully play its performance, further improve the forming quality of the base coating, improve the coating quality and adhesion strength of the pole piece, and reduce the elongation rate of the pole piece during cold pressing.

[0021] In any embodiment, the mass percentage of the dispersant in the base coating is 1%-8% based on the total mass of the base coating.

[0022] In any embodiment, the mass percentage of the dispersant is 1-5% based on the total mass of the primer layer.

[0023] The dispersant with the mass content in this range can effectively improve the adhesion strength between the film layer and the current collector, and reduce the adverse effects of excessive acrylic content on the water resistance of the primer layer, thereby improving the forming quality of the electrode sheet.

[0024] In any embodiment, the primer layer further comprises one or more of a conductive agent, a thickening agent, and a wetting agent.

[0025] The conductive agent can minimize the negative impact of the primer layer on the conductivity of the current collector, while taking into account the electrochemical performance of the battery. The thickening agent is beneficial for improving the dispersion of the conductive agent, and can reduce the sedimentation of the conductive agent and inorganic oxide, thereby improving the stability of the primer layer slurry and expanding the process window. The wetting agent is beneficial for improving the wetting of the film layer slurry on the current collector containing an oil film, so as to facilitate the coating of the primer layer slurry on the metal current collector substrate.

[0026] In any embodiment, the conductive agent comprises one or more of Super-P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and / or the thickening agent comprises one or more of sodium carboxymethyl cellulose, sodium alginate, xanthan gum, and carrageenan; and / or the wetting agent comprises one or more of polyethoxylated surfactants, polyether silicone surfactants, non-ionic fluorocarbon polymer surfactants, and alkyne surfactants.

[0027] In any embodiment, the mass percentage of the conductive agent is 10-40% based on the total mass of the primer layer; the mass percentage of the thickening agent is 0.5-4%; and the mass percentage of the wetting agent is 0.2-1%.

[0028] In any embodiment, the thickness of the primer layer is 0.5-3 μm.

[0029] The primer layer with a thickness in the appropriate range can take into account the forming quality and electrochemical performance of the battery.

[0030] In any embodiment, the current collector substrate is a metal current collector substrate, and the metal current collector substrate is prepared by a calendering method.

[0031] The metal current collector substrate prepared by the calendering method has low cost, and can further reduce the overall cost of the battery. However, after calendering, the oil film is inevitably left on the surface of the metal current collector substrate. The present application is particularly suitable for such a metal current collector substrate, and can comprehensively reduce the cost of the secondary battery.

[0032] In any embodiment, the daN value of the current collector substrate is 20 mN / cm-35 mN / cm.

[0033] The daN value of water is greater than 70 mN / cm, and the difference between the daN value of the aqueous slurry and the above-mentioned metal current collector substrate is large, which is not easy to realize uniform coating on the surface thereof. The embodiment of the present application can effectively improve the coating quality of the aqueous slurry on the above-mentioned metal current collector substrate, which is beneficial to widen the selection range of the current collector substrate, and further realize the reduction of the battery cost.

[0034] In any embodiment, the current collector substrate comprises a metal current collector substrate, and the metal current collector substrate comprises at least one of a copper foil, an aluminum foil, a stainless steel foil, a titanium foil, and a nickel foil.

[0035] In any embodiment, the film layer further comprises a negative electrode active material, and the negative electrode active material comprises one or more of hard carbon, soft carbon, graphite, and silicon; and / or the aqueous binder comprises one or more of styrene-butadiene rubber (SBR) and acrylate rubber.

[0036] In any embodiment, the secondary battery comprises one or more of a sodium secondary battery and a lithium secondary battery.

[0037] In any embodiment, the secondary battery comprises a sodium ion battery, and a single cell of the sodium ion battery comprises: a battery shell, an upper portion of the battery shell being provided with an opening; a top cover assembly, the top cover assembly being arranged at the opening of the battery shell, and the top cover assembly being sealed and electrically connected with the battery shell; and an electrode assembly, the electrode assembly being used for electrical connection and being arranged on the top cover assembly; wherein the top cover assembly comprises a top cover plate, and the electrode assembly and the top cover plate are configured as a single integral member made of metal aluminum or alloy aluminum.

[0038] The sodium ion battery realizes the optimized design of the battery top cover assembly under the premise of maintaining the performance of the battery, and by integrating the electrode assembly onto the top cover assembly and configuring the electrode assembly and the top cover plate as a single integral member made of metal aluminum or alloy aluminum, the number of structural members can be reduced, the manufacturing cost can be further reduced, and the connection of the battery shell and the electrode assembly can be electrified, thereby reducing the possibility of corrosion of the battery shell.

[0039] The second aspect of the present application provides a power utilization device, and the power utilization device comprises the secondary battery of any embodiment.

[0040] The third aspect of the present application provides a current collector, and the current collector comprises a current collector substrate and a primer layer arranged on at least one side of the current collector substrate, and the primer layer comprises an inorganic oxide.

[0041] In any embodiment, the inorganic oxide comprises one or more of aluminum oxide, boehmite, magnesium oxide, iron oxide, silicon oxide, and zirconium oxide.

[0042] In any embodiment, the primer layer further includes a particulate binder, the particulate binder including one or more of a styrene butadiene emulsion, an acrylic emulsion.

[0043] In any embodiment, the primer layer further includes a dispersant, the dispersant including one or more of a polyacrylic polymer.

[0044] In any embodiment, the current collector substrate is a metallic current collector substrate, the metallic current collector substrate having a dyne value of 20 mN / cm to 35 mN / m.

[0045] In any embodiment, the current collector substrate is a metallic current collector substrate, the metallic current collector substrate including an aluminum foil. BRIEF DESCRIPTION OF DRAWINGS

[0046] FIG. 1 is a schematic view of a secondary battery according to an embodiment of the present application.

[0047] FIG. 2 is an exploded view of the secondary battery according to an embodiment of the present application shown in FIG. 1.

[0048] FIG. 3 is a schematic view of a battery module according to an embodiment of the present application.

[0049] FIG. 4 is a schematic view of a battery pack according to an embodiment of the present application.

[0050] FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4.

[0051] FIG. 6 is a schematic view of an electric device using the secondary battery according to an embodiment of the present application as a power source.

[0052] BRIEF DESCRIPTION OF DRAWINGS 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: secondary battery; 51: case; 52: electrode assembly; 53: top cap assembly. DETAILED DESCRIPTION

[0053] Hereinafter, embodiments of the secondary battery, the electric device, and the current collector according to the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there can be cases where unnecessary detailed descriptions are omitted. For example, there can be cases where detailed descriptions of matters well known in the art, repeated descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0054] The "ranges" disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner are generally inclusive and can be combined arbitrarily, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values ​​listed are 1 and 2, and if the maximum range values ​​listed are 3, 4, and 5, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise specified, the numerical range "ab" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely an abbreviation for these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0055] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0056] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0057] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0058] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0059] If not specifically stated, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": 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).

[0060] With the increasing demand for battery cost reduction, the urgency of using low-cost current collector substrates is increasing. However, low-cost current collector substrates often use low-cost production processes, such as calendering, in the manufacturing process. An oil film is coated on the surface of the current collector substrate during the rolling process to reduce surface damage to the substrate. However, the oil film on the surface of the current collector substrate is not easy to remove, so that when the aqueous slurry is coated on the surface of the current collector substrate, it cannot fully infiltrate the surface of the current collector substrate, resulting in difficulty in achieving coating of the aqueous slurry on the surface of the current collector substrate. Taking a sodium secondary battery as an example, since sodium ions do not alloy with aluminum metal like lithium ions, there are more choices for negative current collector materials. For example: the negative electrode of a sodium ion battery can use low-cost foils such as aluminum foil to replace the copper foil used in the prior art to achieve further cost reduction. As an example, the surface of the aluminum foil prepared by calendering will have a layer of oil film, making it difficult for the negative aqueous slurry to be coated on its surface, and it cannot be applied to the negative electrode sheet.

[0061] The first aspect of the present application provides a secondary battery, the secondary battery comprising an electrode sheet, the electrode sheet comprising a current collector and a film layer disposed on at least one side of the current collector, the current collector comprising a current collector substrate and a primer layer disposed on at least one side of the current collector substrate, the primer layer comprising an inorganic oxide, and the film layer comprising an aqueous binder.

[0062] The inorganic oxide refers to an inorganic compound composed of oxygen atoms and one or more metal or non-metal elements.

[0063] The inorganic oxide in the primer layer can be tested using any known testing method. As an example, the decomposition products in the film layer are analyzed by Raman spectroscopy, X-ray diffractometer, transmission electron microscope, etc. testing instrument; or combined with energy spectrum for component analysis.

[0064] The aqueous binder refers to a binder using an aqueous medium as a dispersant, and thus a film layer including the aqueous binder is often prepared by a water-based slurry. The aqueous binder is classified into a linear binder and a particulate binder according to the dispersion morphology of the binder in a solvent. The linear binder has a linear morphology in the solvent, and can achieve high molecular chain stretching in the solvent, and thus presents a coating state to an active material in the film layer, including, for example, but not limited to, polyacrylic acid, polymethyl acrylate. The particulate binder refers to a binder having a dot-like morphology in the solvent, and is mostly a latex particle, including, for example, but not limited to, butadiene styrene rubber, propylene butadiene rubber.

[0065] The inorganic oxide has a large density and a better affinity to the current collector substrate, and is less likely to shrink or displace under the surface tension of the slurry compared to an active material (such as soft carbon or hard carbon) or a conductive agent (such as conductive carbon) commonly used in the film layer, and thus can effectively improve the coating quality of the base coating layer.

[0066] The aqueous slurry including the aqueous binder has a large surface tension, and often has a large surface energy difference value and poor coating quality when coated on the current collector substrate, and the inclusion of the inorganic oxide in the base coating layer can particularly solve the poor compatibility of the aqueous slurry with the current collector substrate and improve the coating quality of the aqueous slurry on the current collector substrate. It can be understood that the pole piece herein can be a positive pole piece or a negative pole piece, and the embodiments of the present application can achieve corresponding technical effects for different battery systems. As an example, for a positive pole piece using an aqueous film layer slurry, the current collector provided by the embodiments of the present application can also provide improved pole piece coating quality. It should be noted that the secondary battery herein is not limited to a sodium secondary battery, but also includes a lithium secondary battery.

[0067] It can be understood that the material of the current collector is not particularly limited, as long as it does not cause chemical changes in the secondary battery and has conductivity, and the current collector includes a metal foil with a pure metal content of 95% or more, such as at least one of a copper foil, an aluminum foil, a stainless steel foil, a titanium foil, and a nickel foil, and also includes an alloy foil of at least two main metals, such as an alloy foil of at least two main elements of copper, aluminum, nickel, titanium, and iron, and can also include copper, aluminum cadmium alloy, iron, or stainless steel, etc. which is surface treated with carbon, nickel, titanium, silver, copper, etc. In addition, the adhesion to the negative active material can be enhanced by forming fine concaves and convexes on the surface, and can be used in various forms such as a film, a sheet, a foil, a mesh, a porous body, a foam, a non-woven fabric, etc.

[0068] In some embodiments, the inorganic oxide includes one or more of aluminum oxide, boehmite, magnesium oxide, iron oxide, silicon oxide, and zirconium oxide.

[0069] In some embodiments, the inorganic oxide includes one or more of aluminum oxide and boehmite.

[0070] The two inorganic oxides have more excellent adhesion on aluminum foil, and can further improve the forming quality and bonding strength of the pole piece.

[0071] In some embodiments, the mass percentage of the inorganic oxide is 30%-60% based on the total mass of the primer layer.

[0072] In some embodiments, the mass percentage of the inorganic oxide is selected from 30%, 35%, 40%, 45%, 50%, 55%, 60% or any numerical range between any two of them, based on the total mass of the primer layer.

[0073] The inorganic oxide in the above mass range in the primer layer can not only improve the coating quality of the pole piece, but also improve the bonding strength of the pole piece, reduce the elongation rate of the pole piece during cold pressing, and effectively control the resistance of the current collector, and take into account the electrochemical performance of the battery.

[0074] In some embodiments, the volume distribution particle size Dv50 of the inorganic oxide is less than 2 microns (μm).

[0075] The volume distribution particle size Dv50 refers to the particle size corresponding to the cumulative volume distribution percentage of 50% from the small particle size side in the particle size volume distribution graph.

[0076] The volume distribution particle size Dv50 can be tested by any known method in the art. For example, refer to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, and use a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK for determination.

[0077] The inorganic oxide with the volume distribution particle size in the above range can be tightly attached to the metal current collector substrate, improving the forming quality of the primer layer and the pole piece.

[0078] In some embodiments, the primer layer further comprises a particulate binder, and the particulate binder comprises one or more of styrene-butadiene rubber and acrylate rubber.

[0079] The particulate binder refers to a binder that appears as a point in the primer layer. Such a binder generally appears as a granular distribution in a solvent, and is mostly a latex particle.

[0080] Styrene-butadiene rubber (SBR) is also known as polystyrene butadiene copolymer.

[0081] Acrylate rubber is an elastomer obtained by copolymerization of acrylate as a main monomer. The main monomers include methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, etc. In some embodiments, the acrylate rubber includes styrene-acrylate rubber (SAR). Styrene-acrylate rubber (SAR) is also known as styrene acrylate copolymer.

[0082] The particulate binder has water-oil amphiphilicity, and can exhibit better water resistance than linear binders with strong affinity to water solvent, so that the base coating can remain stable during coating of the upper film layer containing active substances, and further play a role of the base coating in improving coating quality.

[0083] In some embodiments, the particulate binder includes acrylate rubber.

[0084] The acrylate rubber has stronger adhesion to the metal current collector substrate than other particulate binders, and can further improve the coating quality and adhesion strength of the pole piece.

[0085] In some embodiments, the mass fraction of the particulate binder is 10%-40% based on the total mass of the base coating.

[0086] In some embodiments, the mass fraction of the particulate binder is selected from 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any numerical range between any two of them, based on the total mass of the base coating.

[0087] The particulate binder in the above mass range in the base coating can not only improve the coating quality of the pole piece, but also improve the adhesion strength of the pole piece, and effectively control the resistance of the current collector, and take into account the electrochemical performance of the battery.

[0088] In some embodiments, the base coating further includes a dispersant, and the dispersant includes one or more of polyacrylic polymers.

[0089] The polyacrylic polymer refers to a polymer obtained by polymerization of acrylic acid or acrylic acid derivatives as monomers or by copolymerization of acrylic acid or acrylic acid derivatives as main monomers and other unsaturated compounds. It can be understood that the polyacrylic polymer can include homopolymers and copolymers.

[0090] In some embodiments, the polyacrylic polymer includes one or more of polyacrylic acid, polymethylacrylic acid, polyacrylamide, poly(acrylic acid-acrylamide), poly(acrylic acid-acrylonitrile), and poly(acrylic acid-acrylonitrile-acrylamide).

[0091] The polyacrylic polymer is a linear polymer, which can be fully dispersed in a solvent to coat the inorganic oxide, reduce the agglomeration of the inorganic oxide, effectively disperse the inorganic oxide, assist the inorganic oxide to fully exert its performance, further improve the forming quality of the base coating, improve the coating quality and bonding strength of the pole piece, and reduce the elongation rate of the pole piece during cold pressing.

[0092] In some embodiments, the mass percentage of the dispersant is 1-8% based on the total mass of the base coating.

[0093] In some embodiments, the mass percentage of the dispersant is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or any numerical range between any two of the above values, based on the total mass of the base coating.

[0094] The dispersant with the mass content in the range can effectively improve the bonding strength between the film layer and the current collector, reduce the adverse effects of the reduction of water resistance of the base coating caused by the excessive content of acrylic acid, and comprehensively improve the forming quality of the pole piece.

[0095] In some embodiments, the base coating further comprises one or more of a thickening agent, a conductive agent, and a wetting agent.

[0096] In some embodiments, the conductive agent comprises one or more of Super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] The conductive agent can minimize the negative impact of the base coating on the conductivity of the current collector, while taking into account the electrochemical performance of the battery.

[0098] In some embodiments, the thickening agent comprises one or more of sodium carboxymethyl cellulose, sodium alginate, xanthan gum, and carrageenan.

[0099] The thickening agent can help to improve the dispersion of the conductive agent, reduce the sedimentation of the conductive agent and the inorganic oxide, improve the stability of the base coating slurry, and expand the process window.

[0100] In some embodiments, the wetting agent comprises one or more of a polyethoxylated surfactant, a polyether silicone surfactant, a non-ionic fluorocarbon polymer surfactant, and an alkyne surfactant.

[0101] The wetting agent can help to improve the wetting of the film layer slurry on the current collector containing an oil film, so as to coat the base coating slurry on the metal current collector substrate.

[0102] In some embodiments, the mass percentage of the conductive agent is 10%-40%, the mass percentage of the thickening agent is 0.5%-4%, and the mass percentage of the wetting agent is 0.2%-1%, based on the total mass of the primer layer.

[0103] In some embodiments, the mass percentage of the conductive agent is 10%, 20%, 30%, 40%, or any numerical range between any two of the above values, based on the total mass of the primer layer.

[0104] In some embodiments, the mass percentage of the thickening agent is 0.5%, 1%, 2%, 3%, 4%, or any numerical range between any two of the above values, based on the total mass of the primer layer.

[0105] In some embodiments, the mass percentage of the wetting agent is 0.2%, 0.4%, 0.6%, 0.8%, 1%, or any numerical range between any two of the above values.

[0106] In some embodiments, the thickness of the primer layer is 0.5-3 μm.

[0107] In some embodiments, the thickness of the primer layer is 0.5 μm, 1 μm, 2 μm, 3 μm, or any numerical range between any two of the above values.

[0108] The primer layer with a thickness within a suitable range can balance the forming quality and electrochemical performance of the battery.

[0109] In some embodiments, the primer layer is prepared by mixing the inorganic oxide and the dispersant in an aqueous solvent, stirring until uniform, adding the thickening agent, and then adding the conductive agent, the binder, and the wetting agent in sequence to form a primer slurry; coating the primer slurry on a metal current collector substrate, and after drying, cold pressing, and other processes, a current collector containing the primer layer is obtained.

[0110] In some embodiments, the film layer further comprises a negative active material, and the negative active material comprises one or more of hard carbon, soft carbon, graphite, and silicon.

[0111] In some embodiments, the aqueous binder comprises one or more of styrene-butadiene rubber (SBR) and acrylate rubber.

[0112] The above particulate binder is different from linear binders such as polyacrylic acid, and can effectively alleviate the gel phenomenon of the film layer slurry and improve the brittleness of the film layer. The improvement effect is particularly significant for slurry containing negative active materials such as hard carbon, soft carbon, and graphite.

[0113] In some embodiments, the current collector substrate is a metal current collector substrate, and the metal current collector substrate is prepared by a calendering method.

[0114] The metal current collector substrate prepared by calendering method has low cost, and can further reduce the overall cost of the battery. However, after calendering, oil film inevitably remains on the surface of the metal current collector substrate, and the present application is particularly suitable for such metal current collector substrate, and comprehensively reduces the cost of the secondary battery.

[0115] In some embodiments, the dyne value of the current collector substrate is 20 millinewton per meter (mN / m) to 35 mN / m.

[0116] In some embodiments, the dyne value of the current collector substrate can be selected from 20 mN / m, 25 mN / m, 30 mN / m, 35 mN / m, or any numerical range between any two of them.

[0117] The dyne value also refers to the surface tension coefficient, which mainly represents the size of the surface tension, that is, the force per unit length between two adjacent parts of the liquid surface. The dyne value can be used to reflect the wetting ability of the current collector substrate, and the higher the dyne value, the better the wetting ability of the current collector substrate. The dyne value can be obtained by any known method in the art, for example, using a dyne pen to draw on the surface of the current collector substrate to test the dyne value of the current collector substrate.

[0118] The dyne value of water is greater than 70 mN / m, and the dyne value of the aqueous slurry is quite different from that of the above-mentioned current collector substrate, and it is not easy to achieve uniform coating on its surface. The embodiments of the present application can effectively improve the coating quality of the aqueous slurry on the above-mentioned current collector substrate, which is beneficial to widen the selection range of the current collector substrate and further reduce the cost of the battery. In some embodiments, the current collector substrate comprises a metal current collector substrate, and the metal current collector substrate comprises at least one of a copper foil, an aluminum foil, a stainless steel foil, a titanium foil, and a nickel foil.

[0119] In some embodiments, the metal current collector substrate comprises an aluminum foil.

[0120] The aluminum foil spontaneously generates an aluminum oxide film on the surface, so that the oxide of the primer layer in the embodiments of the present application has higher affinity with it, which can further improve the coating quality and bonding strength of the electrode sheet.

[0121] In some embodiments, the film layer can also optionally comprise a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0122] In some embodiments, the film layer can also optionally comprise other auxiliary agents, such as thickening agents (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0123] In some embodiments, the electrode sheet can be prepared by dispersing the above-mentioned components for preparing the electrode sheet, such as the active material, the conductive agent, the binder and any other components, in a solvent (e.g., deionized water) to form a film layer slurry; coating the film layer slurry on the current collector, and after processes such as drying, cold pressing, etc., the electrode sheet can be obtained.

[0124] In some embodiments, the secondary battery includes one or more of a sodium secondary battery, a lithium secondary battery.

[0125] In some embodiments, the secondary battery is a sodium ion battery, and the electrode sheet is a negative electrode sheet.

[0126] In some embodiments, the secondary battery is a negative electrode-free battery, which can be a sodium negative electrode-free battery or a lithium negative electrode-free battery.

[0127] The negative electrode-free secondary battery refers to a battery that is not actively provided with a negative active material layer on the negative electrode side during the manufacturing process of the battery, for example, a battery that is not provided with a metal or carbon active material layer on the negative electrode by coating or deposition during the manufacturing process of the battery to form a negative active material layer. During the first charging, active ions obtain electrons on the anode side to deposit in the form of metal on the surface of the current collector to form a metal phase, and during discharging, the metal can be converted into active ions to return to the positive electrode, realizing cyclic charging and discharging. Therefore, the negative electrode-free battery is also a metal battery. Compared with other secondary batteries, the negative electrode-free secondary battery can obtain higher energy density because it does not need to be provided with a negative active material layer in advance.

[0128] Although the negative electrode-free secondary battery does not need to be provided with a metal or carbon active material layer by coating or deposition to form a negative active material layer, the negative electrode-free secondary battery is often provided with a primer layer containing a conductive material to achieve the function of inducing deposition. Due to the large difference in surface tension, the coating of the aqueous primer layer of the negative electrode-free secondary battery on the current collector substrate with a low surface tension value also has the problem of being difficult to form. The primer layer provided by the embodiments of the present application is also applicable to the negative electrode-free secondary battery, improves the coating quality, and the inorganic oxide can further play the role of inducing metal deposition, which is conducive to further improving the uniformity of metal deposition.

[0129] In some embodiments, the secondary battery includes a sodium ion battery, and a single cell of the sodium ion battery includes: a battery shell, an upper portion of the battery shell being provided with an opening; a top cover assembly, the top cover assembly being arranged at the opening of the battery shell, the top cover assembly being sealed and electrically connected with the battery shell; and an electrode assembly, the electrode assembly being used for electrical connection, the electrode assembly being arranged on the top cover assembly; wherein the top cover assembly includes a top cover plate, and the electrode assembly and the top cover plate are configured as a single whole member made of metal aluminum or alloy aluminum.

[0130] The sodium ion battery realizes the optimized design of the battery top cover assembly under the premise of maintaining the battery performance, by integrating the electrode assembly on the top cover assembly, the electrode assembly is constructed as a single whole member made of metal aluminum or alloy aluminum, the number of structural members can be reduced, the manufacturing cost is further reduced, the connection of the battery shell and the electrode assembly is charged, and the possibility of corrosion of the battery shell is reduced.

[0131] In some embodiments, the secondary battery further includes a positive electrode tab including a positive electrode current collector and a positive electrode active material layer formed on at least a portion of a surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, the positive electrode active material can include at least one of a layered transition metal oxide, a polyanion compound, and a Prussian blue compound.

[0132] The transition metal in the layered transition metal oxide can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Optionally, the layered transition metal oxide is, for example, NaxMO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0

[0133] The polyanion compound can be a compound having a metal ion, a transition metal ion, and a tetrahedral (YO4) n- The anion unit is a type of compound. The metal ion can be selected from one of a sodium ion, a lithium ion, a potassium ion, and a zinc ion; the transition metal can be selected from at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, In, Ge, Ga, Sn, Hf, Ta, W, and Pb; Y can be selected from at least one of P, S, and Si; and n represents the valence state of (YO4) n- .

[0134] As an optional embodiment of the present application, the chemical formula of the polyanion compound can be Na x-a A a V y-b M b (PO4) 2-2c (DO4)2 c F z-d Q d, wherein the A element represents an alkali metal element doped to replace the Na element, the M element represents a metal element replacing the V element, the D element represents a doping element replacing the P element, and the Q element represents a doping element replacing the F element. The D element includes at least one of Si and S, and the Q element includes at least one of Cl and O. 3.5≤x≤4.5, 0≤a≤0.15x, 0.8≤y≤1.1, 0≤b≤0.3y, 0≤c≤0.15, 0.8≤z≤1.1, and 0≤d≤0.2z. Optionally, the A element includes at least one of K and Li; and the M element includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0135] As an optional embodiment of the present application, the chemical formula of the polyanionic compound can be Na x R y (PO4)2P2O7, wherein x=3.5-4.5, y=2.75-3.25, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0136] As an optional embodiment of the present application, the chemical formula of the polyanionic compound can be Na 4+x R 3-y P 4-m O 15 / C; where 0 <x<0.5、0<y≤0.5、0<m≤0.2,R包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、In、Ga、Sn、Hf、Ta、W和Pb中的至少一种。

[0137] As an optional embodiment of the present application, the chemical formula of the polyanionic compound can be Na m Fe x (PO4) y P2O7 / C; wherein, 3.6≤m≤4.4, 2.8≤x≤3, 2≤y≤2.1. Prussian blue compounds can be compounds having sodium ions, transition metal ions and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0138] In some embodiments, the positive electrode active material layer may further include a conductive agent to improve the conductivity of the positive electrode. The conductive agent may be selected from one or more of Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0139] In some embodiments, the positive electrode active material layer may further include a binder to firmly bond the positive electrode active material and the optional conductive agent to the positive electrode current collector. The binder may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0140] In some embodiments, the positive electrode current collector may be a conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet may be selected from one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate may each be independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector may be a composite current collector formed by combining a metal foil with a polymer base film.

[0141] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0142] [Electrolytes]

[0143] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0144] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0145] In some embodiments, the electrolyte salt may be selected from at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.

[0146] In some embodiments, the electrolyte comprises an ester solvent, and the ester solvent comprises at least one selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, and fluoroethylene carbonate.

[0147] In some embodiments, the electrolyte comprises an ether solvent, and the ether solvent comprises one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ether.

[0148] In some embodiments, the electrolyte comprises an ether solvent, and the ether solvent comprises one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0149] In some embodiments, the electrolyte can further optionally comprise an additive. For example, the additive can comprise a negative electrode film-forming additive, a positive electrode film-forming additive, and can further comprise an additive capable of improving certain properties of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, and the like.

[0150] In some embodiments, the secondary battery further comprises a separator. The type of the separator is not particularly limited in the present application, and any known porous separator having good chemical stability and mechanical stability can be used.

[0151] In some embodiments, the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0152] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to make an electrode assembly by a winding process or a stacking process.

[0153] In some embodiments, the secondary battery can comprise an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0154] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, and the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, and the like can be listed.

[0155] The shape of the secondary battery is not particularly limited, and can be cylindrical, square, or any other shape. For example, FIG. 1 is a square structure of a secondary battery 5 as an example.

[0156] In some embodiments, referring to FIG. 2, the outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be arranged on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be selected by a person skilled in the art according to specific actual needs.

[0157] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0158] FIG. 3 is a battery module 4 as an example. Referring to FIG. 3, in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0159] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0160] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0161] FIGS. 4 and 5 are a battery pack 1 as an example. Referring to FIGS. 4 and 5, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0162] In addition, the application also provides a power utilization device comprising at least one of the secondary battery, the battery module, or the battery pack provided by the application. The secondary battery, the battery module, or the battery pack can be used as a power supply of the power utilization device, and can also be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0163] As the power utilization device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirement thereof.

[0164] FIG. 6 is a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the secondary battery for the power utilization device, a battery pack or a battery module can be used.

[0165] As another example of the device, it can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a secondary battery can be used as a power supply.

[0166] Further, the application also provides a current collector comprising a metal current collector substrate and a primer layer provided on at least one side of the metal current collector substrate, wherein the primer layer comprises an inorganic oxide.

[0167] It can be understood that the current collector comprises the current collector features of the secondary battery in any of the embodiments.

[0168] Embodiments

[0169] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0170] Embodiment 1

[0171] 1) Preparation of the current collector

[0172] Preparation of the primer slurry: 40 parts of alumina and 5 parts of polyacrylic acid were mixed in an aqueous solution, and after being stirred uniformly, 2 parts of thickening agent CMC-Na was added to form a uniform and stable alumina dispersion liquid; after being stirred and dispersed uniformly by adding 29.7 parts of Super-P, 28 parts of punctiform adhesive styrene-butadiene emulsion was added and dispersed for 30 min, and finally 0.3 parts of wetting agent polyoxyethylene ether was added and dispersed for 30 min to form a primer slurry with a solid content of 18%.

[0173] Coating of the primer slurry: the above primer slurry was uniformly coated on the aluminum metal current collector substrate, and after drying, a primer layer was obtained, with a coating mass of 140 mg / 1540.25 mm 2 The dyne value of the aluminum metal current collector substrate was 20 mN / m-35 mN / m.

[0174] 2) Preparation of the negative electrode tab

[0175] The negative electrode active material hard carbon, conductive carbon black, water-based binder styrene-butadiene rubber (SBR), and thickening agent sodium carboxymethyl cellulose (CMC-Na) were fully stirred in a deionized water solvent system at a mass ratio of 96:2:1:1, and after being mixed uniformly, a negative electrode slurry was obtained; the negative electrode slurry was uniformly coated on the negative electrode current collector prepared in the above step, and then was subjected to drying, cold pressing, and slitting to obtain a negative electrode tab.

[0176] The preparation method of Example 2-8 was basically the same as that of Example 1, except that the specific components of the primer layer were adjusted, as shown in Table 1. In Example 4, the conductive agent was carbon nanotubes.

[0177] Comparative Example 1

[0178] The negative electrode active material hard carbon, conductive carbon black, binder styrene-butadiene rubber (SBR), and thickening agent sodium carboxymethyl cellulose (CMC-Na) were fully stirred in a deionized water solvent system at a mass ratio of 96:2:1:1, and after being mixed uniformly, a negative electrode slurry was obtained; the negative electrode slurry was uniformly coated on the surface of an aluminum foil, and then was subjected to drying, cold pressing, and slitting to obtain a negative electrode tab.

[0179] The preparation method of Comparative Example 2 was basically the same as that of Example 1, except that the specific components of the primer layer were adjusted, as shown in Table 1.

[0180] Table 1

[0181] II. Battery performance test

[0182] 1. Water resistance test of the negative electrode current collector

[0183] The negative electrode current collector coated with the primer layer prepared above was punched using a punch press to obtain a negative electrode current collector with an area of about 2 mm 2The sample was baked at 120°C for 5 min after 0.2 g of water was evenly dropped on the surface of the bottom coating layer side of the sample. The sample was observed by a CCD microscope. If the exposed current collector substrate existed in the sample, it was determined as unqualified; if the film layer was torn or the bottom coating layer appeared outward migration and diffusion but the substrate was not exposed, it was determined as qualified; if the film layer did not change significantly, it was determined as good.

[0184] 2. Coating quality test of the negative electrode tab

[0185] The coating quality of the prepared negative electrode tab was observed; if serious edge shrinkage and large-area coating leakage occurred, it was determined as unqualified; if a small amount of sawtooth edge shrinkage and a small amount of point coating leakage occurred, it was determined as qualified; if there was no edge shrinkage and coating leakage, the film layer surface was flat and uniform, and it was determined as good.

[0186] 3. Adhesion strength test

[0187] According to the test method in the national standard GB T 2791-1995, the peeling strength between the negative electrode film layer and the current collector provided with the bottom coating layer was tested.

[0188] 4. Tab elongation test

[0189] The negative electrode tab was taken, the tab ear area was removed, three mark points were made transversely at intervals of three meters along the tab direction, the length of two mark points was accurately to 0.1 mm, and the length of the distance between two adjacent points was recorded as a; the left and right gaps and the tonnage of the press roll between 20 tons and 79 tons were adjusted, and the thickness of the cold pressing was adjusted to make the tab reach the ideal compactness density; the compactness density of the tab was measured to be 0.95 g / cm 3 The length b of the tab mark after cold pressing. That is, the cold pressing elongation η = (b / a-1)*100%. Two sections were taken for each sample, three samples were taken, and the average value of the six data obtained by the test was taken as the tab elongation.

[0190] 5. Current collector resistance test

[0191] The current collector with bottom coating was tested by a tab resistance meter (Yuan Neng Technology), five samples were taken for parallel test, and the average value measured was the film resistance of the current collector.

[0192] III. Analysis of test results of each embodiment and comparative example

[0193] The batteries of each embodiment and comparative example were prepared according to the above method, and each performance parameter was measured, and the results are shown in Table 2 below.

[0194] Table 2

[0195] As can be seen from the comparison of the examples and the comparative examples, the secondary battery provided by the bottom coating layer of the present application includes inorganic oxide, which can realize the coating of the water-based film layer slurry on the surface of the aluminum foil, and is conducive to further reducing the cost of the sodium secondary battery. As can be seen from the comparison between examples 1, 3 and 4, when the mass percentage of inorganic oxide in the bottom coating layer is 30%-60%, the bottom coating layer not only can improve the coating quality of the water-based slurry on the current collector substrate, but also can improve the mechanical interlocking force with the film layer by means of the rivet effect between the inorganic oxide and the negative active material, thereby increasing the bonding strength between the film layer and the current collector; it can reduce the driving effect of the film layer extension on the current collector during cold pressing, and reduce the elongation rate of the current collector during cold pressing.

[0196] Table 3

[0197] As can be seen from Table 3, when the mass percentage of inorganic oxide is 30%-60% and the mass percentage of particulate binder is 10%-30%, the coating quality, bonding strength and elongation rate of the pole piece can be improved while the resistance is considered, and the electrochemical performance of the secondary battery can be considered while the cost is reduced.

[0198] Although the coating quality of the pole piece is improved in examples 6 and 7, the edge of the coating layer is slightly serrated and a small amount of point-shaped coating leakage occurs, so that the bonding strength and elongation rate of the pole piece cannot be accurately measured, therefore, the performance is not detected.

[0199] As can be seen from the comparison between examples 1, 2, 5 and example 6, when the mass percentage of the dispersant is 1%-5% based on the total mass of the bottom coating layer, the interaction force between the water molecules in the water-based negative film layer slurry and the polyacrylic acid dispersant in the bottom coating layer is kept at a suitable level, so that the water molecules are not easy to insert between the molecules of the bottom coating layer, the bottom coating layer has good water resistance, and the coating appearance of the pole piece is further improved.

[0200] As can be seen from the comparison between examples 1, 2, 8 and example 7, when the mass percentage of the particulate binder is greater than 10% based on the total mass of the bottom coating layer, the particulate binder can provide sufficient adhesion in the bottom coating layer, so that the water molecules are not easy to insert between the molecules of the bottom coating layer, the bottom coating layer has good water resistance, and the coating appearance of the pole piece is further improved.

[0201] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications to the embodiments, or by combining part of the configurations of the embodiments, which can be conceived by those skilled in the art without departing from the spirit of the present application, are also included in the scope of the present application.

Claims

1. A secondary battery, characterized in that: The secondary battery includes a pole piece, which includes a current collector and a film layer arranged on at least one side of the current collector. The current collector includes a current collector substrate and a primer layer arranged on at least one side of the current collector substrate. The primer layer includes an inorganic oxide, and the film layer includes an aqueous binder.

2. The secondary battery according to claim 1, wherein The inorganic oxide includes one or more of aluminum oxide, boehmite, magnesium oxide, iron oxide, silicon oxide, and zirconium oxide.

3. The secondary battery according to claim 1 or 2, characterized in that Based on the total mass of the primer layer, the mass proportion of the inorganic oxide is 30%-60%.

4. The secondary battery according to any one of claims 1 to 3, characterized in that The volume distribution particle size Dv50 of the inorganic oxide is less than 2 μm.

5. The secondary battery according to any one of claims 1 to 4, characterized in that The primer layer further includes a particulate binder, and the particulate binder includes one or more of styrene-butadiene rubber and acrylic rubber.

6. The secondary battery according to claim 5, characterized in that The mass proportion of the particulate binder is 10% to 40% based on the total mass of the primer layer.

7. The secondary battery according to any one of claims 1 to 6, characterized in that The base coating layer further includes a dispersant comprising one or more polyacrylic acid polymers.

8. The secondary battery according to claim 7, wherein Based on the total mass of the primer layer, the mass proportion of the dispersant is 1%-8%.

9. The secondary battery according to any one of claims 1 to 8, characterized in that Based on the total mass of the primer layer, the mass proportion of the dispersant is 1%-5%.

10. The secondary battery according to claim 8, wherein The primer layer further comprises one or more of a conductive agent, a thickener, and a wetting agent; the conductive agent comprises one or more of Super-P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and / or The thickener includes one or more of sodium carboxymethyl cellulose, sodium alginate, xanthan gum, and carrageenan; and / or The wetting agent includes one or more of polyoxyethylene surfactants, polyether silicone surfactants, nonionic fluorocarbon polymer surfactants, and acetylene surfactants.

11. The secondary battery according to claim 10, wherein: Based on the total mass of the primer layer, the mass proportion of the conductive agent is 10%-40%; the mass proportion of the thickener is 0.5%-4%; and the mass proportion of the wetting agent is 0.2%-1%.

12. The secondary battery according to any one of claims 1 to 11, characterized in that: The thickness of the primer layer is 0.5 μm-3 μm.

13. The secondary battery according to any one of claims 1 to 12, characterized in that: The current collector substrate is a metal current collector substrate, and the metal current collector substrate is prepared by a calendering method.

14. The secondary battery according to any one of claims 1 to 13, characterized in that The dyne value of the current collector substrate is 20 mN / m-35 mN / m.

15. The secondary battery according to any one of claims 1 to 14, characterized in that The current collector substrate includes a metal current collector substrate, and the metal current collector substrate includes at least one of copper foil, aluminum foil, stainless steel foil, titanium foil, and nickel foil.

16. The secondary battery according to any one of claims 1 to 15, characterized in that The film layer further comprises a negative electrode active material, wherein the negative electrode active material comprises one or more of hard carbon, soft carbon, graphite, and silicon; and / or The aqueous binder includes one or more of styrene-butadiene rubber (SBR) and acrylic rubber.

17. The secondary battery according to any one of claims 1 to 16, characterized in that: The secondary battery includes one or more of a sodium secondary battery and a lithium secondary battery.

18. The secondary battery according to any one of claims 1 to 17, characterized in that The secondary battery includes a sodium ion battery, and the monomer of the sodium ion battery includes: A battery housing, wherein an opening is provided at an upper portion of the battery housing; a top cover assembly, the top cover assembly being disposed at the opening of the battery housing, the top cover assembly being sealed and electrically connected to the battery housing; as well as an electrode assembly, the electrode assembly being used for electrical connection and being disposed on the top cover assembly; The top cover assembly includes a top cover plate, and the electrode assembly and the top cover plate are constructed as a single integral component made of metal aluminum or alloy aluminum.

19. An electrical device, characterized in that: The electric device includes the secondary battery according to any one of claims 1 to 18.

20. A current collector, characterized in that: The current collector includes a current collector substrate and a primer layer disposed on at least one side of the current collector substrate, wherein the primer layer includes an inorganic oxide.

21. The current collector according to claim 20, characterized in that The inorganic oxide includes one or more of aluminum oxide, boehmite, magnesium oxide, iron oxide, silicon oxide, and zirconium oxide.

22. The current collector according to claim 20 or 21, characterized in that: The primer layer further includes a particulate binder, and the particulate binder includes one or more of styrene-butadiene emulsion and acrylic emulsion.

23. The current collector according to any one of claims 20 to 22, characterized in that The base coating layer further includes a dispersant comprising one or more polyacrylic acid polymers.

24. The current collector according to any one of claims 20 to 23, characterized in that The current collector substrate is a metal current collector substrate, and the dyne value of the metal current collector substrate is 20mN / m-35mN / m.

25. The current collector according to any one of claims 20 to 24, characterized in that The current collector substrate is a metal current collector substrate, and the metal current collector substrate includes aluminum foil.

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