Electroplating solution composite additive, electroplating solution, and electrodeposited copper foil and use thereof

Abstract

An electroplating solution composite additive, an electroplating solution, and an electrodeposited copper foil and a use thereof. The electroplating solution composite additive comprises: a brightening agent, a surfactant, and a leveling agent, wherein the leveling agent contains a polyoxyalkylene ether group and a nitrogen-containing group. The leveling agent, the brightening agent, and the surfactant are compounded and added into the electroplating solution used for preparing the copper foil, such that an ultrathin electrodeposited copper foil can be prepared, good mechanical properties can also be achieved, and the energy density and safety of a battery can be improved when the ultrathin electrodeposited copper foil is used in a current collector of a power battery.

Description

Electroplating solution composite additive, electroplating solution and electrolytic copper foil and their applications

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 13, 2023, with application number 202311508060.X and invention name “Electroplating solution composite additives, electroplating solution and electrolytic copper foil and their applications”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the technical field of copper foil materials, and specifically relates to an electroplating solution composite additive, an electroplating solution, an electrolytic copper foil and applications thereof. Background Art

[0003] Electrolytic copper foil is widely used in lithium-ion batteries, electronic circuit boards and other products, especially in the electrode collectors of lithium-ion batteries, where its application is increasing and its thickness is becoming thinner and thinner.

[0004] Lithium battery copper foil, as the current collector in lithium-ion batteries, is a crucial component of the electrode structure. Thinner copper foil can improve energy density, but the thinner the foil, the higher the chance of breakage, which can affect battery safety.

[0005] Summary of the Invention

[0006] In view of the above problems, the present application provides an electroplating solution composite additive, an electroplating solution, an electrolytic copper foil and their applications, aiming to solve the technical problem of how to prepare a thinner electrolytic copper foil with good mechanical properties.

[0007] In a first aspect, an embodiment of the present application provides a composite additive for an electroplating solution, comprising: a brightener, a surfactant, and a leveler; wherein the leveler contains a polyoxyalkylene ether group and a nitrogen-containing group.

[0008] The embodiment of the present application provides a plating solution composite additive for adding to the plating solution for preparing electrolytic copper foil, and the plating solution composite additive includes a brightener, a surfactant, and a leveling agent; the brightener assists in enhancing the brightness and grain refinement of the electrolytic copper foil, the surfactant can reduce the surface tension of the plating solution and reduce the appearance of pinholes in the electrolytic copper foil, and the leveling agent contains polyoxyolefin ether groups and nitrogen-containing groups. The polyoxyolefin ether groups can be well adsorbed on the cathode surface during electroplating to increase polarization ability, and the nitrogen-containing groups can reduce copper ion deposition, so that the leveling agent has a better leveling effect. Therefore, the embodiment of the present application can prepare ultra-thin electrolytic copper foil by adding the leveling agent, brightener, and surfactant to the plating solution, while taking into account good mechanical properties. When used in the current collector of a power battery, it can improve the energy density and safety of the battery.

[0009] In some embodiments, the polyoxyalkylene ether group includes at least one of a polyoxyethylene ether group and a polyoxypropylene ether group, and the nitrogen-containing group includes at least one of a nitrophenyl group, an imidazole group, a 2,5-dicarbonylpyrrolidyl group, and a 2-thiothiazolyl group; optionally, the leveler includes at least one of the following molecular structures:

[0010] The above-mentioned leveling agents are compounded with brighteners and surfactants to form electroplating solution composite additives. When used in the electroplating solution, they can produce a good polarization leveling effect on the surface of the copper foil through electrochemical adsorption reaction.

[0011] In some embodiments, the mass ratio of the brightener, the surfactant, and the leveling agent is 2-20:20-200:50-200.

[0012] The brightener, surfactant and leveler are formed into a composite additive for the electroplating solution in the above mass ratio, so that the electrolytic copper foil prepared by the electroplating solution can have good mechanical properties at a low thickness of 0.8 to 2 μm.

[0013] In some embodiments, the brightener comprises at least one of sodium persulfate, sodium polydisulfide dipropane sulfonate and sodium 3-mercapto-1-propane sulfonate; and / or,

[0014] The surfactant includes at least one of polyvinyl alcohol and hydroxycellulose.

[0015] The above-mentioned brighteners can effectively assist in enhancing the brightness and grain refinement of the electrolytic copper foil, and the above-mentioned surfactants can effectively reduce the surface tension of the electroplating solution.

[0016] In a second aspect, an embodiment of the present application provides an electroplating solution for electrolytic copper foil, comprising the electroplating solution composite additive provided in the first aspect of the embodiment of the present application.

[0017] The electroplating solution of the embodiment of the present application is added with the electroplating solution composite additive of the first aspect of the embodiment of the present application. Based on the auxiliary copper plating effect of the electroplating solution composite additive, such an electroplating solution can prepare ultra-thin electrolytic copper foil by electroplating raw foil, while also taking into account good mechanical properties.

[0018] In some embodiments, the plating solution includes the following components at the following concentrations:

[0019] The electroplating solution of the above formula can be used to electroplate raw foil to prepare ultra-thin electrolytic copper foil with good mechanical properties.

[0020] In a third aspect, an embodiment of the present application provides a method for preparing an electrolytic copper foil, comprising the following steps:

[0021] preparing the electroplating solution provided in the second aspect of the embodiment of the present application;

[0022] The electroplating solution is used to electroplate raw foil to obtain electrolytic copper foil.

[0023] The method for preparing the electrolytic copper foil in the embodiment of the present application electroplates the raw foil with an electroplating solution to which a unique electroplating solution composite additive is added, thereby preparing an ultra-thin electrolytic copper foil having good mechanical properties.

[0024] The conditions for the electroplating green foil treatment include at least one of the following (1) to (4):

[0025] (1) Current is 4500-6000A;

[0026] (2) Electroplating rate 8-10m / min;

[0027] (3) Plating solution dosage 40-50m 3 / h;

[0028] (4) The plating solution temperature is 45-55°C.

[0029] By adjusting the parameters under the above-mentioned electroplating raw foil conditions, an ultra-thin electrolytic copper foil with a thickness of 0.8 to 2 μm and good mechanical properties can be prepared.

[0030] In a fourth aspect, an embodiment of the present application provides an electrolytic copper foil, which is prepared by the preparation method provided in the third aspect of the embodiment of the present application.

[0031] The electrolytic copper foil of the embodiment of the present application has the advantages of being ultra-thin while having good mechanical properties. When used in the current collector of a power battery, it can improve the energy density and safety of the battery.

[0032] In some embodiments, the thickness of the electrolytic copper foil is 0.8-2 μm.

[0033] Electrolytic copper foil with a thickness of 0.8 to 2 μm still has good mechanical properties and can improve battery energy density.

[0034] In a fifth aspect, an embodiment of the present application provides a current collector comprising a first copper foil, a second copper foil, and a colloidal layer located between the first copper foil and the second copper foil, wherein the first copper foil and / or the second copper foil is the electrolytic copper foil provided in the fourth aspect of the embodiment of the present application.

[0035] The electrolytic copper foil unique to the embodiment of the present application is used in a current collector with a sandwich structure. Such a current collector does not need to undergo processing steps such as copper reduction, and can be directly composited and integrated. It has the characteristics of thin thickness and good mechanical properties. When used in power batteries, it can improve the energy density and safety of the battery.

[0036] In some embodiments, the colloidal material of the colloidal layer includes a maleic anhydride-modified polymer.

[0037] The maleic anhydride-modified polymer has excellent adhesiveness and can adhere the first copper foil and the second copper foil together well, further improving the stability of the current collector.

[0038] In some embodiments, the thickness of the colloidal layer is 2-4 μm.

[0039] The adhesive layer with the above thickness can well adhere the first copper foil and the second copper foil together.

[0040] In a sixth aspect, an embodiment of the present application provides a method for preparing the above-mentioned current collector, comprising:

[0041] transferring the first copper foil onto a first release film;

[0042] transferring the second copper foil onto a second release film;

[0043] A colloidal material is coated on the surface of the first copper foil away from the first release film and / or on the surface of the second copper foil away from the second release film, and then the first copper foil and the second copper foil are relatively laminated and cured to obtain the colloidal layer, and the first release film and the second release film are removed to obtain the current collector.

[0044] In the embodiment of the present application, a release film is used as a carrier film to transfer the electrolytic copper foil onto the carrier film, and then a sandwich structure current collector is directly formed by compounding with a colloidal material. No subsequent processing steps such as copper reduction are required, and the current collector can be directly compounded and integrated. Therefore, a current collector with thin thickness and good mechanical properties can be easily prepared.

[0045] In some embodiments, before applying the colloid material, the process further includes treating at least the surface of the first copper foil away from the first release film and / or the surface of the second copper foil away from the second release film with a passivation solution; and / or,

[0046] After removing the first release film and the second release film, the method further includes treating at least the surface of the first copper foil away from the colloid layer and / or the surface of the second copper foil away from the colloid layer with a passivation solution.

[0047] Through passivation liquid treatment, the surface oxidation of copper foil can be prevented, further improving the service life.

[0048] In some embodiments, the passivation solution includes chromic anhydride and glucose, wherein the chromium ion concentration is 0.3-0.9 g / L and the glucose concentration is 2-8 g / L.

[0049] The hydroxyl molecules of glucose and chromium ions in the passivation solution can work together to accelerate the solidification chain strength of the colloidal material, thereby further improving the strength of the current collector.

[0050] In a seventh aspect, an embodiment of the present application provides a battery, comprising an electrode plate, wherein the electrode plate comprises a current collector provided in the fifth aspect of the embodiment of the present application and / or a current collector prepared by the preparation method provided in the sixth aspect of the embodiment of the present application.

[0051] The current collector unique to the embodiment of the present application is used in the battery pole piece, so the battery provided by the embodiment of the present application has good energy density and safety performance.

[0052] In an eighth aspect, an embodiment of the present application provides an electrical device, comprising the battery provided in an seventh aspect of the embodiment of the present application.

[0053] The battery according to the embodiment of the present application has excellent energy density and safety performance, so such electrical devices can work more effectively for a longer period of time.

[0054] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0056] FIG1 is a schematic flow chart of a method for preparing an electrolytic copper foil according to an embodiment of the present application;

[0057] FIG2 is a schematic diagram of the current collector structure of an embodiment of the present application;

[0058] FIG3 is a schematic flow chart of a method for preparing a current collector according to an embodiment of the present application;

[0059] FIG4 is a schematic diagram of a battery cell structure of an embodiment of a battery of the present application;

[0060] FIG5 is an exploded schematic diagram of the battery cell shown in FIG4 ;

[0061] FIG6 is a schematic structural diagram of an embodiment of a battery module according to the present application;

[0062] FIG7 is a schematic structural diagram of an embodiment of a battery pack according to the present application;

[0063] FIG8 is a schematic diagram of the exploded structure of the battery pack shown in FIG7 ;

[0064] FIG9 is a schematic diagram of an embodiment of an electrical device including a battery according to an embodiment of the present application as a power source.

[0065] Description of reference numerals:

[0066] 11-first copper foil; 12-second copper foil; 13-colloid layer; 131-first colloidal material; 132-second colloidal material; 14-first release film; 15-second release film;

[0067] 20 - battery cell; 21 - housing; 22 - top cover assembly; 23 - electrode assembly; 30 - battery module; 40 - battery pack; 41 - upper case; 42 - lower case. DETAILED DESCRIPTION

[0068] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0070] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0071] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0072] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0073] In the description of the embodiments of this application, the term "plurality" refers to two or more (including two). Similarly, "multiple groups" refers to two or more (including two groups), and "multiple sheets" refers to two or more (including two sheets). "At least one" refers to more than one (including one, two, three, etc.).

[0074] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0075] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0076] With the increasing depletion of traditional energy resources, the development of new energy storage devices is gaining increasing attention. Secondary batteries, in particular, have attracted considerable attention due to their high energy density, high theoretical capacity, excellent cycle stability, and environmentally friendly properties. Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, but are also widely used in a variety of fields, including electric vehicles such as electric bicycles, electric motorcycles, and electric vehicles. As the application areas of secondary batteries as power batteries continue to expand, their market demand is also growing, and the requirements for battery performance, such as cycle performance, are becoming increasingly stringent.

[0077] Lithium-ion batteries, a type of secondary battery, boast high energy density, long service life, and are energy-efficient and environmentally friendly. However, during the charge and discharge cycles, the positive active material in lithium-ion batteries can experience structural changes, corrosion and dissolution of metal elements, and other factors, which can lead to poor cycle life and rate performance, thus impacting battery performance.

[0078] Currently, metal oxides such as aluminum oxide are used to coat the positive electrode active material to improve its performance, but the coating step is generally performed after the precursor material is prepared. For example, the current coating methods include: (1) mixing the synthesized precursor material with the coating source material by physical and mechanical ball milling, and then heat treating at high temperature to achieve metal oxide coating on the surface of the positive electrode active material. (2) The synthesized precursor is first prepared into a solution, and then the coating source material is added in the solution environment, and then dried and heat treated at high temperature to achieve metal oxide coating on the surface of the positive electrode active material. However, the above coating is all based on the secondary particles. In order to increase the energy density, it is generally necessary to increase the compaction density of the electrode. After the electrode is cold pressed or the battery cell is cycled and discharged, the secondary particles are easily broken, exposing more primary particle interfaces, thereby increasing the sites for reaction with the electrolyte, and then increasing side reactions. Therefore, the above coating methods are difficult to achieve uniform and tight coating of the positive electrode active material, and therefore their performance improvement effect is limited.

[0079] The thickness of current collector copper foil is becoming increasingly thinner. The thinnest currently in mass production in China has reached 3.5μm, and its tensile strength is approaching the process limit for lithium-ion battery production. Thinner copper foil can further improve energy density. This is because the thinner the copper foil, the lighter the mass of the lithium-ion battery, which also means lower resistance, and correspondingly improves the energy density and other performance of the lithium-ion battery. However, the thinner the copper foil, the higher the probability of fracture, which affects battery safety. Therefore, thinner copper foil must also possess higher tensile strength.

[0080] Composite copper foil adopts a sandwich structure and is generally primed with magnetron sputtering or vapor deposition before electroplating. Because the film is primed with magnetron sputtering or vapor deposition, the film's porosity and adhesion have always been bottlenecks in the mass production of composite copper foil. Electroplating, in particular, can further expand the porosity and result in low yield.

[0081] Based on this, the embodiment of the present application develops a plating solution composite additive for electrolytic copper foil. The plating solution composite additive for electrolytic copper foil is added to the plating solution, and the raw foil is electroplated to obtain an ultra-thin electrolytic copper foil that can simultaneously take into account the tensile strength to meet the requirements of lithium-ion batteries. After such an electrolytic copper foil is compounded into a composite current collector, the quality defects of traditional composite current collectors (such as magnetron sputtering holes and holes after electroplating) can be overcome, and the composite current collector does not need to be subjected to copper reduction treatment, and can be directly compounded and integrated. It has a good application prospect in battery current collectors. Therefore, the following technical solution is proposed.

[0082] Electroplating solution composite additives

[0083] In a first aspect, an embodiment of the present application provides a composite additive for an electroplating solution, comprising: a brightener, a surfactant, and a leveler; wherein the leveler contains a polyoxyalkylene ether group and a nitrogen-containing group.

[0084] Brightener is a plating solution additive. Adding such additives to the plating solution can help enhance the brightness and grain refinement of the electrolytic copper foil, thereby increasing the elongation of the electrolytic copper foil.

[0085] Surfactant, a plating solution additive, can also be called an inhibitor. Adding such additives to the plating solution can reduce the surface tension of the plating solution, thereby enhancing the wetting effect of the electrolyte on the plating cathode, increasing the polarization effect, and thus reducing the appearance of pinholes in the electrolytic copper foil.

[0086] Leveling agents, when added to the electroplating solution, can increase the deposition rate at the bottom of the concave surface compared to the convex surface, thereby achieving a leveling effect. In the embodiments of the present application, the leveling agent contains polyoxyalkylene ether groups and nitrogen-containing groups. The polyoxyalkylene ether groups can adsorb on the surface of the cathode roller during electroplating to increase polarization, while the nitrogen-containing groups can adsorb in high-potential areas to reduce copper ion deposition. Therefore, the combined action of the polyoxyalkylene ether groups and nitrogen-containing groups gives the leveling agent a good leveling effect while also providing a brightening effect.

[0087] In the embodiment of the present application, the above-mentioned leveling agent is compounded with a brightener and a surfactant to form a plating solution composite additive, which is added to the plating solution for preparing copper foil. Ultra-thin electrolytic copper foil can be prepared, and at the same time, the electrolytic copper foil can have good mechanical properties. Use in the current collector of power batteries can improve the energy density and safety of the battery.

[0088] In some embodiments, the polyoxyalkylene ether group in the leveler includes at least one of polyoxyethylene ether and polyoxypropylene ether, and the nitrogen-containing group includes at least one of nitrophenyl, imidazole, 2,5-dicarbonylpyrrolidyl, and 2-thiothiazolyl.

[0089] In some embodiments, the leveler comprises at least one of the following molecular structures:

[0090] Among them, n=80-250.

[0091] The above-mentioned leveling agents have a good leveling effect. When combined with brighteners and surfactants to form electroplating solution composite additives, they can be used in electroplating solutions to produce a good polarization leveling effect on the copper foil surface through electrochemical adsorption reactions.

[0092] In some embodiments, the mass ratio of brightener, surfactant, and leveling agent is 2-20:20-200:50-200. For example, the mass ratio of brightener, surfactant, and leveling agent is 2:20:50, 10:100:100, 15:150:150, 20:200:200, etc. The above mass ratios are used to form a composite additive for the electroplating solution, which is directly mixed and added to the electroplating solution through a flow rate, so that the electrolytic copper foil prepared from the electroplating solution can have good mechanical properties at a low thickness of 0.8 to 2 μm.

[0093] In some embodiments, the brightener includes at least one of sodium persulfate, sodium polydisulfide dipropane sulfonate, and sodium 3-mercapto-1-propane sulfonate. The brighteners of the above types can effectively assist in enhancing the brightness and grain refinement of the electrolytic copper foil.

[0094] In some embodiments, the surfactant includes one or more of polyvinyl alcohol and hydroxycellulose. The surfactant can effectively reduce the surface tension of the electroplating solution.

[0095] electroplating solution

[0096] In a second aspect, an embodiment of the present application provides an electroplating solution for electrolytic copper foil, comprising the electroplating solution composite additive provided in the first aspect of the embodiment of the present application.

[0097] The electroplating solution of the embodiment of the present application is added with the electroplating solution composite additive of the first aspect of the embodiment of the present application. Based on the auxiliary copper plating effect of the electroplating solution composite additive, such an electroplating solution can prepare ultra-thin electrolytic copper foil by electroplating raw foil, while also taking into account good mechanical properties.

[0098] In some embodiments, the plating solution includes the following components at the following concentrations:

[0099] For example, the copper ion concentration can be 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, etc. The sulfuric acid concentration can be 100 g / L, 105 g / L, 110 g / L, 115 g / L, 120 g / L, etc. The hydrochloric acid concentration can be 20 mg / L, 25 mg / L, 30 mg / L, 35 mg / L, 40 mg / L, etc. The brightener concentration can be 2 mg / L, 5 mg / L, 8 mg / L, 10 mg / L, 12 mg / L, 15 mg / L, 20 mg / L, etc. The surfactant concentration can be 20 mg / L, 40 mg / L, 60 mg / L, 80 mg / L, 100 mg / L, 120 mg / L, 150 mg / L, 160 mg / L, 180 mg / L, 200 mg / L, etc. The surfactant concentration can be 50 mg / L, 60 mg / L, 80 mg / L, 100 mg / L, 120 mg / L, 150 mg / L, 160 mg / L, 180 mg / L, 200 mg / L, etc.

[0100] In one embodiment, the solvent of the electroplating solution may be water. For example, copper, sulfuric acid, hydrochloric acid, a brightener, a surfactant, and a leveler may be dissolved in water to prepare an electroplating solution of the aforementioned concentration. The copper may first be dissolved in sulfuric acid to form copper ions.

[0101] Copper ions can be electroplated to form copper foil. The sulfate ions in sulfuric acid provide solute anions, while hydrochloric acid can promote anodic dissolution, preventing the appearance of loose copper powder in the coating. At the same time, hydrochloric acid and the electroplating solution composite additive synergistically improve the performance of electrolytic copper foil. This application uses electrochemical cyclic voltammetry for screening, followed by Hull cell sheeting to determine the approximate range and compatibility of the content of each component. A simulated pilot-scale scale-up experiment is conducted to obtain the electroplating solution with the above formula. The basic properties of the electrolytic copper foil are then tested by electroplating raw foil to determine that an ultra-thin electrolytic copper foil with good mechanical properties can be obtained.

[0102] Electrolytic copper foil and preparation method thereof

[0103] In a third aspect, an embodiment of the present application provides a method for preparing an electrolytic copper foil. As shown in FIG1 , the method for preparing an electrolytic copper foil comprises the following steps:

[0104] S01: preparing the electroplating solution provided in the second aspect of the embodiment of the present application;

[0105] S02: electroplating the raw foil with the electroplating solution to obtain electrolytic copper foil.

[0106] The method for preparing the electrolytic copper foil in the embodiment of the present application electroplates the raw foil with an electroplating solution to which a unique electroplating solution composite additive is added, thereby preparing an ultra-thin electrolytic copper foil having good mechanical properties.

[0107] In some embodiments, the current of the electroplating green foil process is 4500-6000 A. For example, the current of the electroplating green foil process is 4500 A, 4800 A, 5000 A, 5200 A, 5500 A, 5800 A, 6000 A, etc. Under this current condition, the copper foil thickness can be well controlled within the ultra-thin range of 0.8-2 μm.

[0108] In one embodiment, the electroplating rate is 8-10 m / min; illustratively, the electroplating rate is 8 m / min, 8.5 m / min, 9 m / min, 9.5 m / min, 10 m / min, etc. Under these electroplating rate conditions, the thickness range of the copper foil can be controlled in conjunction with the current parameters, and the electroplating speed is inversely proportional to the thickness of the copper foil. That is, to increase the thickness of the copper foil, the electroplating rate is appropriately reduced, and to reduce the thickness of the copper foil, the electroplating rate is appropriately increased.

[0109] In one embodiment, the amount of plating solution is 40-50m 3 / h; For example, the plating solution dosage is 40m 3 / h,42m 3 / h,45m 3 / h,48m 3 / h,50m 3 / h, etc. Under the conditions of the plating solution dosage, the copper ion supply can be met and the concentration polarization can be reduced.

[0110] In one embodiment, the plating solution temperature is 45-55° C., illustratively, the plating solution temperature is 45° C., 48° C., 50° C., 52° C., 55° C., etc. Under this plating solution temperature condition, copper ions are less likely to crystallize, and molecular diffusion can be promoted, thereby reducing concentration polarization.

[0111] In one embodiment, the conditions for electroplating the raw foil with the electroplating solution include: a current of 4500-6000A; an electroplating rate of 8-10m / min; and an electroplating solution volume of 40-50m 3 / h; plating solution temperature 45-55 ° C. Under such electroplating conditions, ultra-thin electrolytic copper foil with a thickness of 0.8-2 μm and good mechanical properties can be produced.

[0112] In a fourth aspect, embodiments of the present application provide an electrolytic copper foil, which is prepared by the preparation method provided in the third aspect of the embodiments of the present application. The electrolytic copper foil of the embodiments of the present application has the advantages of being ultra-thin while also having good mechanical properties. Its use in current collectors of power batteries can improve the energy density and safety of the batteries.

[0113] In some embodiments, the thickness of the electrolytic copper foil is 0.8 to 2 μm, for example, 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm, 2 μm, etc. Electrolytic copper foil with a thickness of 0.8 to 2 μm still has good mechanical properties and can improve battery energy density.

[0114] Current collector and preparation method thereof

[0115] In the fifth aspect, an embodiment of the present application provides a current collector, as shown in Figure 2, including a first copper foil 11, a second copper foil 12 and a colloidal layer 13 located between the first copper foil 11 and the second copper foil 12, the first copper foil 11 and / or the second copper foil 12 is the electrolytic copper foil provided in the fourth aspect of the embodiment of the present application.

[0116] The electrolytic copper foil unique to the embodiment of the present application is used in a current collector with a sandwich structure. Such a current collector does not need to undergo processing steps such as copper reduction, and can be directly composited and integrated. It has the characteristics of thin thickness and good mechanical properties. When used in power batteries, it can improve the energy density and safety of the battery.

[0117] Specifically, in the current collector, the first copper foil 11 is bonded to one surface of the colloid layer 13, and the second copper foil 12 is bonded to the other surface of the colloid layer 13. The first copper foil 11 is the electrolytic copper foil provided in the fourth aspect of the embodiment of this application; alternatively, the second copper foil 12 is the electrolytic copper foil provided in the fourth aspect of the embodiment of this application. Furthermore, in the current collector of this embodiment of this application, both the first copper foil 11 and the second copper foil 12 are the electrolytic copper foil provided in the fourth aspect of the embodiment of this application.

[0118] In some embodiments, the colloidal material of the colloidal layer includes a maleic anhydride-modified polymer. The maleic anhydride-modified polymer has excellent adhesion and can effectively adhere the first copper foil and the second copper foil together, further improving the stability of the current collector. For example, the maleic anhydride-modified polymer can be maleic anhydride-modified polyethylene terephthalate (PET) or maleic anhydride-modified polypropylene (PP). These colloidal materials can be purchased commercially or modified using modification methods commonly used in the art.

[0119] In some embodiments, the thickness of the colloid layer is 2-4 μm. The colloid layer of the above thickness can well adhere the first copper foil and the second copper foil together.

[0120] In a sixth aspect, an embodiment of the present application provides a method for preparing the above-mentioned current collector, comprising:

[0121] transferring the first copper foil onto the first release film;

[0122] transferring the second copper foil onto the second release film;

[0123] A colloidal material is coated on the surface of the first copper foil away from the first release film and / or on the surface of the second copper foil away from the second release film, and then the first copper foil and the second copper foil are relatively laminated, cured, and the first and second release films are removed to obtain a current collector.

[0124] In the embodiment of the present application, a release film is used as a carrier film to transfer the electrolytic copper foil onto the carrier film, and then a sandwich structure current collector is directly formed by compounding with a colloidal material. No subsequent processing steps such as copper reduction are required, and the current collector can be directly compounded and integrated. Therefore, a current collector with thin thickness and good mechanical properties can be easily prepared.

[0125] Specifically, the surface of the first copper foil away from the first release film can be coated with a colloidal material to form a colloidal layer, and then the first copper foil and the second copper foil can be placed relative to each other for curing. Alternatively, the surface of the second copper foil away from the second release film can be coated with a colloidal material to form a colloidal layer, and then the second copper foil and the first copper foil can be placed relative to each other for curing.

[0126] Alternatively, a portion of the colloid material used to form the colloid layer, i.e., the first colloid material, can be applied to the surface of the first copper foil away from the first release film, and another portion of the colloid material used to form the colloid layer, i.e., the second colloid material, can be applied to the surface of the second copper foil away from the second release film. The first and second copper foils can then be bonded together and cured. This allows the first and second colloid materials to bond and cure, with the curing temperature reaching the glass transition temperature of the colloid materials, resulting in strong adhesion and better adhesion between the two copper foils.

[0127] As shown in Figure 3: Step (1): Transfer the first copper foil 11 to the first release film 14; Step (2): Transfer the second copper foil 12 to the second release film 15; Step (3): Coat the first colloid material 131 on the surface of the first copper foil 11 away from the first release film 14, and coat the second colloid material 132 on the surface of the second copper foil 12 away from the second release film 15. Then, the first copper foil 11 and the second copper foil 12 are relatively bonded and cured. The first colloid material 131 and the second colloid material 132 are bonded and cured to form a colloid layer 13. Finally, the first release film 14 and the second release film 15 are removed to obtain the current collector.

[0128] In some embodiments, the curing conditions include: controlling the temperature at 60-80° C. for 48-72 hours. Under these conditions, the colloid material can be cured well, thereby firmly bonding the first copper foil 11 and the second copper foil 12 together.

[0129] In some embodiments, before applying the colloid material, at least the surface of the first copper foil 11 away from the first release film 14 and / or the surface of the second copper foil 12 away from the second release film 14 are treated with a passivation solution. Treating the first copper foil 11 and / or the second copper foil 12 with the passivation solution can prevent oxidation of the copper foil surface inside the current collector, further improving the service life.

[0130] In some embodiments, after removing the first release film 14 and the second release film 15, at least the surface of the first copper foil 11 away from the colloid layer 13 and / or the surface of the second copper foil 12 away from the colloid layer 13 are treated with a passivation solution. Treating the first copper foil 11 and / or the second copper foil 12 with the passivation solution can prevent oxidation of the copper foil surface exposed to the current collector, further improving the service life.

[0131] In some embodiments, the passivation solution includes chromic anhydride and glucose. Glucose, a molecule containing hydroxyl groups, provides chromium oxide ions that react with metal ions on the metal surface. The chromium ion concentration in the passivation solution is 0.3-0.9 g / L, and the glucose concentration is 2-8 g / L. The passivation solution, primarily composed of chromic anhydride and glucose, accelerates the solidification chain strength of the colloidal material, further enhancing the strength of the current collector.

[0132] This invention utilizes an electrolytic copper foil method, which makes it difficult to remove ultra-thin copper foil compared to traditional electrolytic copper foil. The copper foil is transferred to a base film at room temperature using a carrier film, then passed through a passivation solution to prevent surface oxidation. Simultaneously, the ultra-thin copper foil is transferred to the carrier film. This method utilizes a carrier film to transfer the copper foil, resulting in a finished composite copper foil without a film carrier.

[0133] In some embodiments, the first release film 14 and the second release film 15 may be commonly used UV adhesive-reducing films or other types of release films, and the specific thickness may be 12 to 25 microns.

[0134] Battery

[0135] In a seventh aspect, an embodiment of the present application provides a battery, comprising an electrode plate, the electrode plate comprising the current collector provided in the fifth aspect of the embodiment of the present application and / or the current collector prepared by the preparation method provided in the sixth aspect of the embodiment of the present application.

[0136] The current collector unique to the embodiment of the present application is used in the battery pole piece, so the battery provided by the embodiment of the present application has good energy density and safety performance.

[0137] Specifically, the battery electrode can be a positive electrode or a negative electrode.

[0138] In some embodiments, the battery electrode is a negative electrode electrode, which includes the above-mentioned current collector and a negative electrode active layer bonded to the current collector. The negative electrode active material of the negative electrode active layer includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, etc. It may also optionally include a binder. The binder may be selected from at least one of 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). The negative electrode active layer may also optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the negative electrode active layer may also optionally include other additives, such as dispersants, thickeners (such as sodium carboxymethyl cellulose), etc.

[0139] In some embodiments, the battery further comprises a positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode active layer combined with the positive electrode current collector. The positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0140] In some embodiments, the positive electrode active material in the positive electrode active layer may be a lithium ion active material, such a positive electrode active material can be used in a lithium ion secondary battery, or the positive electrode active material may be a sodium ion active material, such a positive electrode active material can be used in a sodium ion secondary battery. Specifically, taking lithium ion active materials as an example, they may include lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), and ternary materials (lithium nickel cobalt manganese oxide (NCM) or lithium nickel cobalt aluminum oxide (NCA).

[0141] In some embodiments, the positive electrode active layer may further optionally include a binder. As an 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. The positive electrode active layer may further optionally include a conductive agent. As an 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.

[0142] Specifically, the battery includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The battery also includes an electrolyte.

[0143] In some embodiments, the separator may be made of materials commonly known in the art for battery separators. For example, the separator substrate may include one or more of polyethylene, polypropylene, and polyvinylidene fluoride.

[0144] In some embodiments, the electrolyte includes an electrolyte salt and a solvent. If the secondary battery is a lithium ion battery, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate. If the secondary battery is a sodium ion battery, the corresponding electrolyte salt is replaced with a sodium salt.

[0145] In some embodiments, the solvent in the electrolyte can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl 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, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0146] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0147] In some embodiments, the battery of the embodiments of the present application may include a secondary battery, specifically any one of a battery cell, a battery module, and a battery pack of the secondary battery.

[0148] A battery cell is a battery cell comprising a battery housing and a cell encapsulated within the housing. The shape of a battery cell is not particularly limited and can be cylindrical, square, or any other shape. A square-shaped battery cell 20 is shown in FIG4 .

[0149] In some embodiments, the battery of the embodiments of the present application may include a secondary battery, specifically any one of a battery cell, a battery module, and a battery pack of the secondary battery.

[0150] A battery cell is a battery cell comprising a battery housing and a cell encapsulated within the housing. The shape of a battery cell is not particularly limited and can be cylindrical, square, or any other shape. A square-shaped battery cell 20 is shown in FIG4 .

[0151] In some embodiments, as shown in Figure 5, the outer packaging of the battery cell 20 may include a shell 21 and a top cover assembly 22. The shell 21 may 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 shell 21 has an opening connected to the receiving cavity, and the top cover assembly 22 is used to cover the opening to close the receiving cavity. The positive electrode sheet, isolation membrane and pole sheet contained in the secondary battery of the embodiment of the present application can be formed into an electrode assembly 23 through a winding process and / or a lamination process. The electrode assembly 23 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 23. The number of electrode assemblies 23 contained in the battery cell 20 can be one or more, which can be adjusted according to actual needs.

[0152] The preparation method of the battery cell 20 is well known. In some embodiments, the electrode sheet, separator, and electrolyte can be assembled to form the battery cell 20. As an example, the electrode sheet, separator, and electrode sheet can be wound or laminated to form the electrode assembly 23. The electrode assembly 23 is then placed in an outer package, dried, and then injected with electrolyte. The battery cell 20 is then vacuum packaged, allowed to stand, formed, and shaped.

[0153] A battery module is assembled from the battery cells 20 , that is, it may contain a plurality of battery cells 20 , and the specific number can be adjusted according to the application and capacity of the battery module.

[0154] In some embodiments, FIG6 is a schematic diagram of an exemplary battery module 30. As shown in FIG6 , in the battery module 30, multiple battery cells 20 may be arranged sequentially along the length of the battery module 30. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 20 may be secured using fasteners.

[0155] Optionally, the battery module 30 may further include a housing having an accommodation space, and the plurality of battery cells 20 may be accommodated in the accommodation space.

[0156] A battery pack is assembled from the battery cells 20 described above, and may contain multiple battery cells 20, wherein multiple battery cells 20 may be assembled into the battery module 30 described above. The specific number of battery cells 20 or battery modules 30 contained in a battery pack may be adjusted according to the application and capacity of the battery pack.

[0157] In the embodiment, Figures 7 and 8 are schematic diagrams of an exemplary battery pack 40. The battery pack 40 may include a battery box and multiple battery modules 30 disposed within the battery box. The battery box includes an upper box body 41 and a lower box body 42. The upper box body 41 covers the lower box body 42 and forms an enclosed space for accommodating the battery modules 30. The multiple battery modules 30 may be arranged in any manner within the battery box.

[0158] Electrical devices

[0159] In an eighth aspect, embodiments of the present application further provide an electrical device comprising the battery provided in the seventh aspect of the present application. The battery can serve as both a power source and an energy storage unit for the electrical device. Consequently, the electrical device of the present application embodiment has a high capacity retention rate and excellent operational stability and safety.

[0160] Electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc. These electrical devices may use secondary batteries, battery modules, or battery packs based on their usage requirements.

[0161] Figure 9 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0162] As another example, the electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a secondary battery as a power source.

[0163] Example

[0164] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0165] Example 1

[0166] A plating solution comprising the following components in the following concentrations:

[0167] Among them, the brightener is sodium polydisulfide dipropylene sulfonate, the surfactant is polyvinyl alcohol, and the leveling agent is:

[0168] n=130.

[0169] A method for preparing an electrolytic copper foil, comprising:

[0170] Add the prepared electroplating solution to the foil machine, adjust the current of the foil machine to 6000A, and perform electroplating. The electroplating line speed is 8m / min, and the amount of electroplating solution is 40m 3 / h, temperature 45 ° C. The cathode roller in the foil machine has a diameter of 2.7 mm and a titanium surface roughness Ra value of 0.2-0.3 μm.

[0171] The electrolytic copper foil produced by the above preparation method can be peeled off from the cathode roller through the UV adhesive reduction film.

[0172] Example 2

[0173] The difference from Example 1 is that the concentrations of the components of the electroplating solution are as follows:

[0174] Example 3

[0175] The difference from Example 1 is that the leveling agent is

[0176] n=136.

[0177] Example 4

[0178] The difference from Example 1 is that the leveling agent is

[0179] n=144.

[0180] Example 5

[0181] The difference from Example 1 is that the leveling agent is

[0182] n=180.

[0183] Example 6

[0184] The difference from Example 1 is that the leveling agent is

[0185] n=226.

[0186] Comparative Example 1

[0187] The difference from Example 1 is that the leveling agent is gelatin.

[0188] Comparative Example 2

[0189] The difference from Example 1 is that the leveling agent is collagen.

[0190] Performance Testing

[0191] (1) Mechanical properties test of electrolytic copper foil

[0192] 1.1 Tensile strength and elongation at break test

[0193] The determination can be carried out according to the GB / T 1040.3-2006 method. The specific steps are as follows:

[0194] The electrolytic copper foil was punched into samples with a width of 15 mm and a length of 150 mm. The tensile test was performed using a high-speed rail tensile tester at room temperature and pressure (25°C, 0.1 MPa). The initial length of the high-speed rail tensile tester was set to 50 mm. The tensile test was performed at a tensile rate of 5 mm / min until the sample broke. The maximum tensile force F (N) and the device displacement y (mm) at the time of tensile fracture were recorded. Finally, the elongation at break was calculated as (y / 50) × 100%. The tensile strength of the current collector was calculated according to T = F / S. Where S is the initial cross-sectional area of ​​the sample, which is equal to the product of the width of the sample and the thickness of the sample.

[0195] 1.2 Pinhole test

[0196] Lay a flat, wrinkle-free electrolytic copper foil sample on a backlit screen. Turn on the backlight and visually circle the three largest pinholes within a 33cm x 33cm area. Remove and retain the sample from the circled area. Place the removed sample on a CCD and measure the pinhole diameters of the three samples. Take the average of the three sample diameters.

[0197] 1.3 Thickness test

[0198] First calculate the surface density of electrolytic copper foil, then convert the unit. Use a punching machine and a special die to punch the copper foil into 10×10cm along the width direction. 2 Take 3 samples. Turn on the electronic balance, place the sample in the electronic balance for testing, and record the data after the value stabilizes.

[0199] Surface density (mg / cm 2 )=weight data ÷ punching area; thickness=area density / copper density, copper density is 8.95g / cm 3 .

[0200] The final results are shown in Table 1.

[0201] Table 1

[0202] (2) Current collector test

[0203] The electrolytic copper foils of the above embodiment and comparative example are prepared into a sandwich structure to form a current collector, and the steps are as follows:

[0204] S1) cutting the electrolytic copper foil prepared above into two sections, each 1000 m long and 300 mm wide, to serve as a first copper foil and a second copper foil, respectively;

[0205] S2) transferring the first copper foil onto the first release film; transferring the second copper foil onto the second release film;

[0206] S3): Coat maleic acid-modified polypropylene on the surface of the first copper foil away from the first release film, and coat maleic acid-modified polypropylene on the surface of the second copper foil away from the second release film. Then, the first copper foil and the second copper foil are relatively laminated and cured (temperature 70°C, time 72h) to form a colloidal layer with a thickness of 2 μm. Then, the first release film and the second release film are torn off to obtain a current collector.

[0207] Performance tests on the current collector's elongation at break, tensile strength, adhesion, and resistance to battery electrolyte.

[0208] 2.1 Tensile strength test of current collector

[0209] The determination can be carried out according to the GB / T 1040.3-2006 method. The specific steps are as follows:

[0210] The current collector was punched into samples with a width of 15 mm and a length of 150 mm. The tensile test was performed using a high-speed rail tensile test machine at room temperature and pressure (25°C, 0.1 MPa). The initial length of the high-speed rail tensile test machine was set to 50 mm. The tensile test was performed at a tensile rate of 5 mm / min until the sample broke. The maximum tensile force F (N) and the device displacement y (mm) at the time of tensile fracture were recorded. Finally, the elongation at break was calculated as (y / 50) × 100%. The tensile strength of the current collector was calculated according to T = F / S. Where S is the initial cross-sectional area of ​​the sample, which is equal to the product of the width of the sample and the thickness of the sample.

[0211] 2.2 Current collector adhesion test

[0212] Sampling: Use a steel ruler to cut a 2cm wide current collector sample. Wipe the steel plate clean with alcohol. Apply 2cm of 3M double-sided tape evenly to the steel plate. Place the sample evenly on the tape, trimming any excess current collector. Center and evenly apply 2cm of wrinkle tape to the current collector, with one end attached to a piece of A4 paper (insulating sheet). (Do not allow the wrinkle tape to directly contact the steel plate.) Roll the sample back and forth twice using a 2kg roller.

[0213] Test: Turn on the high-speed rail tensile testing machine and clamp the sample steel plate vertically in the lower fixture (with the A4 paper end facing downward). Then, flip the A4 paper end upward and clamp it vertically in the upper fixture. Open the test software, select the insulation film peel force test, set the tensile speed to 500mm / min, and manually pull the sample off 2mm-4mm. Click the reset button to reset the zero, then click the run button and pull the sample off 100mm. Observe whether any material falls off and adheres to the wrinkle adhesive. If the wrinkle adhesive does not adhere to any falling material, it is considered qualified; otherwise, it fails.

[0214] 2.3 Hole Testing

[0215] A metallographic microscope was used in the backlight mode with a 50x objective lens to observe whether there were holes in the base film of the current collector.

[0216] 2.4 Resistance to battery electrolyte

[0217] Take the current collector sample, put the sample into the bag sealed with aluminum plastic film, add electrolyte, seal for 7 days, and observe whether the base film of the current collector falls off or peels off after 7 days of soaking.

[0218] The test results are shown in Table 2.

[0219] (3) Secondary battery cell performance test

[0220] The prepared current collector is used as the negative electrode current collector in a secondary battery cell. The secondary battery cell includes an electrode assembly formed by a positive electrode sheet, a separator, and a negative electrode sheet, and also includes a battery electrolyte. The preparation steps are as follows:

[0221] Preparation of positive electrode sheets: Using methyl pyrrolidone (NMP) as a solvent, lithium iron phosphate, carbon nanotubes (CNTs), and polyvinylidene fluoride (PVDF) are mixed and dissolved in the solvent in a mass ratio of 97:2:1 to prepare a first positive electrode slurry with a solid content of 80%; the first positive electrode slurry is evenly coated on aluminum foil, double-sided coating is performed, drying, and slitting are performed to obtain positive electrode sheets.

[0222] Preparation of negative electrode sheets: Using water as solvent, artificial graphite, conductive carbon black, sodium carboxymethyl cellulose dispersant, and styrene-butadiene rubber binder are mixed in a mass ratio of 96:1:1:2 to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on the above-prepared current collector, double-sided coating is performed, and after sufficient drying, cold pressing, and slitting, the negative electrode sheets are obtained.

[0223] Preparation of battery electrolyte: At room temperature, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1, and LiPF6 was added to the mixed solution to obtain a solution with a concentration of 1 mol / L as the electrolyte.

[0224] Battery assembly: The positive electrode sheets and negative electrode sheets prepared above are stacked and wound in the order of "positive electrode sheet-separator membrane-negative electrode sheet" to form an electrode assembly, and then filled with electrolyte to assemble into a lithium-ion secondary battery cell.

[0225] Then carry out secondary battery cycle performance test:

[0226] Test method: At 45°C, charge the lithium-ion secondary battery at a constant current rate of 1C to 4.2V, then charge at a constant voltage until the current is less than or equal to 0.05C, and then discharge at a constant current rate of 1C to 2.8V. This is one charge-discharge cycle, and the discharge capacity at this rate is the discharge capacity of the first cycle. Perform 1000 charge-discharge cycles of the lithium-ion secondary battery according to the above method, and record the discharge capacity of the 1000th cycle.

[0227] Capacity retention rate (%) of the lithium ion secondary battery after 1000 cycles = discharge capacity at the 1000th cycle / discharge capacity at the 1st cycle × 100%.

[0228] The test results are shown in Table 2.

[0229] Table 2

[0230] The data in Tables 1 and 2 demonstrate that the electrolytic copper foil prepared in the examples of this application is ultra-thin and also exhibits excellent mechanical properties. Therefore, the current collector prepared from this electrolytic copper foil exhibits excellent mechanical properties, is resistant to battery electrolyte, and is not prone to copper foil shedding, thereby improving the cycling performance and safety of the secondary battery.

[0231] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A composite additive for electroplating solution, characterized in that: include: Brightener, surfactant and leveler; wherein the molecular structure of the leveler contains polyoxyalkylene ether group and nitrogen-containing group.

2. The electroplating solution composite additive according to claim 1, characterized in that: The polyoxyalkylene ether group includes at least one of a polyoxyethylene ether group and a polyoxypropylene ether group, and the nitrogen-containing group includes at least one of a nitrophenyl group, an imidazole group, a 2,5-dicarbonylpyrrolidyl group and a 2-thiothiazolyl group; optionally, the leveler includes at least one of the following molecular structures:

3. The electroplating solution composite additive according to claim 1 or 2, characterized in that: The mass ratio of the brightener, the surfactant and the leveling agent is 2-20:20-200:50-200.

4. The electroplating solution composite additive according to any one of claims 1 to 3, characterized in that: The brightener comprises at least one of sodium persulfate, sodium polydisulfide dipropane sulfonate and sodium 3-mercapto-1-propane sulfonate; and / or, The surfactant includes at least one of polyvinyl alcohol and hydroxy cellulose.

5. An electroplating solution for electrolytic copper foil, characterized in that: The electroplating solution comprises the composite additive according to any one of claims 1 to 4.

6. The electroplating solution according to claim 5, characterized in that The electroplating solution includes the following components in concentration:

7. A method for preparing an electrolytic copper foil, comprising the following steps: Prepare the electroplating solution according to claim 5 or 6; The electroplating solution is used to electroplate raw foil to obtain electrolytic copper foil.

8. The preparation method according to claim 7, characterized in that: The conditions for the electroplating green foil treatment include at least one of the following (1) to (4): (1) The current is 4500-6000A; (2) Electroplating rate 8-10m / min; (3) Plating solution dosage 40-50m 3 / h; (4) The plating solution temperature is 45-55°C.

9. An electrolytic copper foil, characterized in that: The electrolytic copper foil is prepared by the preparation method described in claim 7 or 8.

10. The electrolytic copper foil according to claim 9, characterized in that: The thickness of the electrolytic copper foil is 0.8-2 μm.

11. A current collector, characterized in that: The invention comprises a first copper foil, a second copper foil and a colloid layer located between the first copper foil and the second copper foil, wherein the first copper foil and / or the second copper foil is the electrolytic copper foil according to claim 9 or 10.

12. The current collector according to claim 11, characterized in that: The colloid material of the colloid layer includes a maleic anhydride-modified polymer.

13. The current collector according to claim 11 or 12, characterized in that: The thickness of the colloid layer is 2-4 μm.

14. A method for preparing a current collector according to any one of claims 11 to 13, characterized in that: include: transferring the first copper foil to a first release film; transferring the second copper foil to the second release film; A colloid material is coated on the surface of the first copper foil away from the first release film and / or on the surface of the second copper foil away from the second release film, and then the first copper foil and the second copper foil are relatively bonded and cured to obtain the colloid layer, and the first release film and the second release film are removed to obtain the current collector.

15. The preparation method according to claim 14, characterized in that: Before the colloid material is applied, at least the surface of the first copper foil away from the first release film and / or the surface of the second copper foil away from the second release film is treated with a passivation solution; and / or, After removing the first release film and the second release film, the method further includes treating at least a surface of the first copper foil away from the colloid layer and / or a surface of the second copper foil away from the colloid layer with a passivation solution.

16. The preparation method according to claim 15, characterized in that: The passivation solution comprises chromic anhydride and glucose, wherein the chromium ion concentration is 0.3-0.9 g / L and the glucose concentration is 2-8 g / L.

17. A battery, comprising an electrode plate, characterized in that: The electrode plate comprises the current collector according to any one of claims 11 to 13 and / or the current collector prepared by the preparation method according to any one of claims 14 to 16.

18. An electrical device, characterized in that: Comprising the battery of claim 17.

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