Electroplating solution composite additive, electroplating solution, electrolytic copper foil and application of electroplating solution composite additive

Abstract

The invention discloses an electroplating solution composite additive, an electroplating solution, an electrolytic copper foil and application of the electroplating solution composite additive. The electroplating liquid composite additive comprises a brightening agent, a surface active agent and a leveling agent, wherein the leveling agent contains a polyoxyolefin ether group and a nitrogen-containing group. According to the embodiment of the invention, the leveling agent, a brightening agent and a surfactant are compounded and added into the electroplating liquid for preparing the copper foil, so that the ultrathin electrolytic copper foil can be prepared, meanwhile, good mechanical performance can be considered, and the energy density and safety of a battery can be improved when the leveling agent is used in a current collector of the power battery.

Description

Technical Field

[0001] The present application belongs to the technical field of copper foil materials, and specifically relates to a composite additive for electroplating solution, electroplating solution, electrolytic copper foil and applications thereof. Background Art

[0002] Electrolytic copper foil is widely used in lithium-ion batteries, electronic circuit boards and other products, especially in the electrode current collectors of lithium-ion batteries, where its thickness is getting thinner and thinner.

[0003] Lithium battery copper foil is the current collector of lithium-ion batteries and an important component of the electrode structure in lithium-ion batteries. Thinner copper foil will better improve energy density, but the thinner the copper foil, the higher the probability of fracture, thus affecting the safety of power batteries. Summary of the invention

[0004] In view of the above problems, the present application provides a plating solution composite additive, an electroplating solution, an electrolytic copper foil and applications thereof, aiming to solve the technical problem of how to prepare a thinner electrolytic copper foil with good mechanical properties.

[0005] 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 polyoxyolefin ether group and a nitrogen-containing group.

[0006] The embodiment of the present application provides a composite additive for electroplating solution, which is used to be added to the electroplating solution for preparing electrolytic copper foil. The composite additive for the electroplating solution 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 electroplating 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 the polarization ability, and the nitrogen-containing groups can reduce the deposition of copper ions, so that the leveling agent has a better leveling effect. Therefore, the embodiment of the present application can prepare an ultra-thin electrolytic copper foil by adding the leveling agent, the brightener and the surfactant in the electroplating solution, and at the same time, it can take into account good mechanical properties. It can be used in the current collector of the power battery to improve the energy density and safety of the battery.

[0007] 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:

[0008]

[0009] The above-mentioned leveling agent is compounded with a brightener and a surfactant to form a composite additive for electroplating solution. When used in the electroplating solution, it can produce a good polarization leveling effect on the surface of the copper foil through an electrochemical adsorption reaction.

[0010] In some embodiments, the mass ratio of the brightener, the surfactant and the leveling agent is 2-20:20-200:50-200.

[0011] The brightener, surfactant and leveler form 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.

[0012] In some embodiments, the brightener comprises at least one of sodium persulfate, sodium polydisulfide propane sulfonate and sodium 3-mercapto-1-propane sulfonate; and / or,

[0013] The surfactant includes at least one of polyvinyl alcohol and hydroxy cellulose.

[0014] The above-mentioned brighteners can effectively assist in enhancing the brightness and grain refinement of electrolytic copper foil, and the above-mentioned surfactants can effectively reduce the surface tension of the plating solution.

[0015] In a second aspect, an embodiment of the present application provides a plating solution for electrolytic copper foil, comprising the plating solution composite additive provided in the first aspect of the embodiment of the present application.

[0016] 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 having good mechanical properties.

[0017] In some embodiments, the plating solution includes components in the following concentrations:

[0018]

[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, 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 the electroplating solution to which a unique electroplating solution composite additive is added, so that an ultra-thin electrolytic copper foil having good mechanical properties can be prepared.

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

[0025] (1) The 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 and having good mechanical properties. It can be used in the current collector of a power battery to 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 go through treatment 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 colloid material of the colloid layer includes a maleic anhydride-modified polymer.

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

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

[0039] The colloid 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 to a first release film;

[0042] transferring the second copper foil to the second release film;

[0043] 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.

[0044] The embodiment of the present application utilizes a release film as a carrier film to transfer the electrolytic copper foil onto the carrier film, and then directly forms a sandwich structured current collector through compounding with a colloidal material. Subsequent processing steps such as copper reduction are not required, and the current collector can be directly compounded and integrated. Therefore, a current collector with a thin thickness and good mechanical properties can be easily prepared.

[0045] In some embodiments, before applying the colloid material, 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,

[0046] 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.

[0047] Through passivation liquid treatment, the copper foil surface can be prevented from oxidation, further improving its 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 and further improve 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 the seventh aspect of the embodiment of the present application.

[0053] The battery according to the embodiment of the present application has good 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 of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0056] Figure 1 It is a schematic flow chart of a method for preparing an electrolytic copper foil according to an embodiment of the present application;

[0057] Figure 2 is a schematic diagram of the current collector structure of an embodiment of the present application;

[0058] Figure 3 1 is a schematic diagram of a method for preparing a current collector according to an embodiment of the present application;

[0059] Figure 4 This is a schematic diagram of the battery cell structure of an embodiment of a battery of the present application;

[0060] Figure 5 for Figure 4 An exploded schematic diagram of the battery cell shown;

[0061] Figure 6 This is a schematic structural diagram of an implementation scheme of a battery module according to an embodiment of the present application;

[0062] Figure 7 This is a schematic structural diagram of an implementation scheme of a battery pack according to an embodiment of the present application;

[0063] Figure 8 for Figure 7 A schematic diagram of the exploded structure of the battery pack shown;

[0064] Fig. 9 It is a schematic diagram of an implementation of an electrical device including the battery of 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 - shell; 22 - top cover assembly; 23 - electrode assembly; 30 - battery module; 40 - battery pack; 41 - upper box; 42 - lower box. DETAILED DESCRIPTION

[0068] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used 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 technicians in the technical field 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" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0070] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0071] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood 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 the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0073] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), and similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces). "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. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which 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 referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not 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 clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0076] With the decreasing traditional energy resources, the development of new energy storage devices has received more and more attention. Among them, secondary batteries have attracted much attention due to their high energy density, high theoretical capacity, good cycle stability and environmental protection characteristics. Secondary batteries can not only be used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric transportation tools. With the continuous expansion of the application field of secondary batteries as power batteries, the market demand is also constantly expanding, and at the same time, the performance requirements for battery cycle performance and other performance are becoming higher and higher.

[0077] As a type of secondary battery, lithium-ion batteries have the characteristics of high energy density, long service life, energy saving and environmental protection. However, the positive active material of lithium-ion batteries is prone to poor cycle life and rate performance due to structural changes, corrosion and dissolution of metal elements during the charge and discharge cycle, thus affecting the use of the battery.

[0078] At present, 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 and the coating source material by physical and mechanical ball milling, and then high-temperature heat treatment 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 high-temperature heat treatment is performed to achieve metal oxide coating on the surface of the positive electrode active material. However, the above coating is all based on secondary particles. In order to increase the energy density, it is generally necessary to increase the compaction density of the pole piece. After the pole piece is cold pressed or the battery cell is cycled and charged 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, it is difficult for the above coating method to achieve uniform and tight coating of the positive electrode active material, so its performance improvement effect is limited.

[0079] Based on the above considerations, in order to better coat and modify the positive electrode active material, a coating source is added during the synthesis of the positive electrode active material precursor in the solution system to coat the surface of the primary particle-formed positive electrode active material precursor with a sparingly soluble metal compound, and the final sintering can make the metal oxide uniformly and tightly coated on the surface of the positive electrode active material, thereby significantly improving its charge and discharge rate performance and cycle stability. Therefore, the following technical solution is proposed.

[0080] At present, the thickness of the current collector copper foil is getting thinner and thinner. The thinnest mass-produced one in China has reached 3.5μm, and its tensile strength performance is close to the process limit of lithium battery production. Thinner copper foil will be able to better improve energy density. This is because the thickness of the copper foil is smaller, the mass of the lithium-ion battery is reduced, which also means smaller resistance, and the corresponding performance of the lithium-ion battery such as energy density will also be improved. However, the thinner the copper foil, the higher the probability of it breaking, which affects the safety of the battery. Therefore, low-thickness copper foil needs to have higher tensile strength at the same time.

[0081] The composite copper foil adopts a sandwich structure, and is generally primed by magnetron sputtering or evaporation before electroplating. Since the film is primed by magnetron sputtering or evaporation, the film holes and bonding strength have always been the bottleneck of the mass production of composite copper foil, especially electroplating will further expand the holes, and the yield is low.

[0082] 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 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 poor 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 scheme is proposed.

[0083] Electroplating solution composite additives

[0084] 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 polyoxyolefin ether group and a nitrogen-containing group.

[0085] 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.

[0086] Surfactant, a kind of electroplating solution additive, can also be called inhibitor. Adding such additives to the electroplating solution can reduce the surface tension of the electroplating solution, thereby enhancing the wetting effect of the electrolyte on the electroplating cathode, increasing the polarization effect, and thus reducing the appearance of pinholes in the electrolytic copper foil.

[0087] Leveling agent, adding such additives to the electroplating solution can make the deposition rate of the concave bottom greater than the deposition rate of the convex on the microscopic concave and convex surface, thereby achieving a leveling effect. In the embodiment of the present application, the leveling agent contains polyoxyolefin ether groups and nitrogen-containing groups. The polyoxyolefin ether groups can be adsorbed on the surface of the cathode roller during electroplating to increase the polarization ability, and the nitrogen-containing groups can be adsorbed in the high potential area to reduce the deposition of copper ions. Therefore, through the combined action of the polyoxyolefin ether groups and the nitrogen-containing groups, the leveling agent has a good leveling effect and also has a brightening effect.

[0088] In the embodiment of the present application, the above-mentioned leveling agent is compounded with a brightener and a surfactant to form a composite additive for the electroplating solution, which is added to the electroplating solution for preparing copper foil, so that an ultra-thin electrolytic copper foil can be prepared. At the same time, the electrolytic copper foil can have good mechanical properties. When used in the current collector of a power battery, the energy density and safety of the battery can be improved.

[0089] In some embodiments, the polyoxyalkylene ether group in the leveler 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.

[0090] In some embodiments, the leveler comprises at least one of the following molecular structures:

[0091]

[0092] Among them, n=80-250.

[0093] 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.

[0094] In some embodiments, the mass ratio of brightener, surfactant and leveling agent is 2-20:20-200:50-200. Exemplarily, the mass ratio of brightener, surfactant and leveling agent is 2:20:50, 10:100:100, 15:150:150, 20:200:200, etc. The electroplating solution composite additive is formed with the above mass ratio, and is directly mixed and added to the electroplating solution through the flow, so that the electrolytic copper foil prepared by the electroplating solution can have good mechanical properties under the condition of low thickness of 0.8 to 2 μm.

[0095] In some embodiments, the brightener includes at least one of sodium persulfate, sodium polydisulfide dipropane sulfonate and sodium 3-mercapto-1-propane sulfonate; the above-mentioned brighteners can well assist in enhancing the brightness and grain refinement of the electrolytic copper foil.

[0096] In some embodiments, the surfactant includes one or more of polyvinyl alcohol and hydroxy cellulose. The surfactant can effectively reduce the surface tension of the plating solution.

[0097] Plating solution

[0098] In a second aspect, an embodiment of the present application provides a plating solution for electrolytic copper foil, comprising the plating solution composite additive provided in the first aspect of the embodiment of the present application.

[0099] 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 having good mechanical properties.

[0100] In some embodiments, the plating solution includes the following components in the following concentrations:

[0101]

[0102] For example, the copper ion concentration can be 80g / L, 90g / L, 100g / L, 110g / L, 120g / L, etc. The sulfuric acid concentration can be 100g / L, 105g / L, 110g / L, 115g / L, 120g / L, etc. The hydrochloric acid concentration can be 20mg / L, 25mg / L, 30mg / L, 35mg / L, 40mg / L, etc. The brightener concentration can be 2mg / L, 5mg / L, 8mg / L, 10mg / L, 12mg / L, 15mg / L, 20mg / L, etc. The surfactant concentration can be 20mg / L, 40mg / L, 60mg / L, 80mg / L, 100mg / L, 120mg / L, 150mg / L, 160mg / L, 180mg / L, 200mg / 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.

[0103] In one embodiment, the solvent of the electroplating solution may be an aqueous solvent. For example, copper, sulfuric acid, hydrochloric acid, brightener, surfactant and leveler may be dissolved in water to prepare the electroplating solution of the above concentration; wherein copper may be first dissolved in sulfuric acid to form copper ions.

[0104] Copper ions can be electroplated to form copper foil. Sulfate ions of sulfuric acid provide solute anions, while hydrochloric acid can promote anode dissolution to avoid the appearance of loose copper powder in the coating. At the same time, hydrochloric acid and electroplating solution composite additives synergistically improve the performance of electrolytic copper foil. The copper in this application is screened by electrochemical cyclic voltammetry, and then sliced ​​in a Hull cell to determine the approximate range and compatibility of the content of each component, and simulated pilot-scale amplification experiments are performed to obtain the electroplating solution of the above formula, and the basic properties of the electrolytic copper foil are tested by electroplating raw foil to determine that an ultra-thin electrolytic copper foil with good mechanical properties can be obtained.

[0105] Electrolytic copper foil and preparation method thereof

[0106] In a third aspect, the present application provides a method for preparing an electrolytic copper foil. Figure 1 As shown, the method for preparing the electrolytic copper foil comprises the following steps:

[0107] S01: preparing the electroplating solution provided in the second aspect of the embodiment of the present application;

[0108] S02: electroplating the raw foil with the electroplating solution to obtain electrolytic copper foil.

[0109] The method for preparing the electrolytic copper foil in the embodiment of the present application electroplates the raw foil with the electroplating solution to which a unique electroplating solution composite additive is added, so that an ultra-thin electrolytic copper foil having good mechanical properties can be prepared.

[0110] In some embodiments, the current of the electroplating green foil treatment is 4500-6000 A; illustratively, the current of the electroplating green foil treatment is 4500 A, 4800 A, 5000 A, 5200 A, 5500 A, 5800 A, 6000 A, etc. Under this current condition, the thickness of the copper foil can be well controlled within the ultra-thin range of 0.8-2 μm.

[0111] 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 the electroplating rate condition, the thickness range of the copper foil can be controlled in coordination with the current parameter, and the electroplating speed is inversely proportional to the thickness of the copper foil, that is, if the thickness of the copper foil is to be increased, the electroplating rate is appropriately reduced, and if the thickness of the copper foil is to be reduced, the electroplating rate is appropriately increased.

[0112] In one embodiment, the amount of plating solution is 40-50m 3 / h; For example, the amount of plating solution is 40m 3 / h, 42m 3 / h,45m 3 / h, 48m 3 / h,50m 3 / h, etc. Under the conditions of the amount of electroplating solution, the copper ion supply can be met and the concentration polarization can be reduced.

[0113] In one embodiment, the plating solution temperature is 45-55° C., and illustratively, the plating solution temperature is 45° C., 48° C., 50° C., 52° C., 55° C., etc. Under the plating solution temperature condition, copper ions are not easy to crystallize, and molecular diffusion can be intensified to reduce concentration polarization.

[0114] In one embodiment, the conditions for electroplating the raw foil with the electroplating solution include: a current of 4500-6000A; an electroplating rate of 8-10 m / min; and an amount of electroplating solution of 40-50 m 3 / h; the plating solution temperature is 45-55° C. Under such electroplating conditions, an ultra-thin electrolytic copper foil with a thickness of 0.8-2 μm and good mechanical properties can be prepared.

[0115] 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. The electrolytic copper foil of the embodiment of the present application has the advantages of being ultra-thin and having good mechanical properties, and can be used in the current collector of a power battery to improve the energy density and safety of the battery.

[0116] In some embodiments, the thickness of the electrolytic copper foil is 0.8-2 μm. The electrolytic copper foil with a thickness of 0.8-2 μm still has good mechanical properties and can improve the energy density of the battery.

[0117] Current collector and preparation method thereof

[0118] In a fifth aspect, the present application provides a current collector, such as Figure 2 As shown, it includes a first copper foil 11, a second copper foil 12 and a colloid 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 by the fourth aspect of the embodiment of the present application.

[0119] 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 go through treatment 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.

[0120] 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 the present application; or, the second copper foil 12 is the electrolytic copper foil provided in the fourth aspect of the embodiment of the present application. Further, in the current collector of the embodiment of the present application, the first copper foil 11 and the second copper foil 12 are both the electrolytic copper foils provided in the fourth aspect of the embodiment of the present application.

[0121] In some embodiments, the colloidal material of the colloidal layer includes a maleic anhydride-modified polymer. The maleic anhydride-modified polymer has good adhesion and can well 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 on the market or modified by a modification method commonly used in the art.

[0122] In some embodiments, the thickness of the colloid layer is 2-4 μm. The colloid layer with the above thickness can well adhere the first copper foil and the second copper foil together.

[0123] In a sixth aspect, an embodiment of the present application provides a method for preparing the above-mentioned current collector, comprising:

[0124] transferring the first copper foil onto the first release film;

[0125] transferring the second copper foil onto the second release film;

[0126] 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 attached to each other, cured, and the first and second release films are removed to obtain a current collector.

[0127] The embodiment of the present application utilizes a release film as a carrier film to transfer the electrolytic copper foil onto the carrier film, and then directly forms a sandwich structured current collector through compounding with a colloidal material. Subsequent processing steps such as copper reduction are not required, and the current collector can be directly compounded and integrated. Therefore, a current collector with a thin thickness and good mechanical properties can be easily prepared.

[0128] Specifically, the amount of colloidal material for forming a colloidal layer can be coated on the surface of the first copper foil away from the first release film, and then the first copper foil and the second copper foil are relatively laminated for curing. Alternatively, the amount of colloidal material for forming a colloidal layer can be coated on the surface of the second copper foil away from the second release film, and then the second copper foil and the first copper foil are relatively laminated for curing.

[0129] Alternatively, a portion of the colloid material used to form a colloid layer, i.e., the first colloid material, may be coated on the surface of the first copper foil away from the first release film, and another portion of the colloid material used to form a colloid layer, i.e., the second colloid material, may be coated 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 may be bonded to each other for curing. In this way, the first colloid material and the second colloid material are bonded and cured to each other, and the curing temperature reaches the glass state temperature of the colloid material, so that the two copper foils have strong adhesion and can be better adhered together.

[0130] like Figure 3 As shown: 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, and then relatively affix the first copper foil 11 and the second copper foil 12 for curing treatment, and the first colloid material 131 and the second colloid material 132 are bonded and cured to form a colloid layer 13. Finally, remove the first release film 14 and the second release film 15 to obtain the current collector.

[0131] In some embodiments, the curing conditions include: the temperature is controlled at 60-80° C. and the curing time is 48-72 hours. Under such conditions, the colloid material can be cured well, so that the first copper foil 11 and the second copper foil 12 are tightly attached together.

[0132] 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 is 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.

[0133] 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, thereby further improving the service life.

[0134] In some embodiments, the passivation solution includes chromic anhydride and glucose. Glucose is a molecule containing hydroxyl groups. Chromic anhydride can provide chromium oxide ions to 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 main components of the passivation solution are chromic anhydride and glucose, which can accelerate the solidification chain strength of the colloidal material and further improve the strength of the current collector.

[0135] The present invention adopts the electrolytic copper foil method, which is different from the traditional electrolytic copper foil. The reason why the ultra-thin copper foil cannot be torn off is that the copper foil is transferred to the base film at room temperature by using a carrier film, and the surface of the copper foil is prevented from being oxidized by a passivation solution. At the same time, the ultra-thin copper foil has been transferred to the carrier film. The copper foil of this scheme uses a carrier film to transfer the copper foil, and the final composite copper foil product has no thin film carrier.

[0136] In some embodiments, the first release film 14 and the second release film 15 may be commonly used UV anti-adhesion films or other types of release films, and the specific thickness may be 12 to 25 microns.

[0137] Battery

[0138] In a seventh aspect, an embodiment of the present application provides a battery, comprising an electrode plate, the electrode plate comprising 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.

[0139] 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.

[0140] Specifically, the battery electrode may be a positive electrode or a negative electrode.

[0141] In some embodiments, the battery pole piece is a negative pole piece, and the negative pole piece includes the above-mentioned current collector and a negative active layer combined with the current collector. The negative active material of the negative 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 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 active layer may also optionally include other additives, such as dispersants, thickeners (such as sodium carboxymethyl cellulose), etc.

[0142] In some embodiments, the battery further comprises a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active layer combined with the positive current collector. The positive current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. 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.

[0143] 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, lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), and ternary materials (nickel cobalt manganese oxide NCM or nickel cobalt aluminum oxide NCA) may be included.

[0144] In some embodiments, the positive electrode active layer may also 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 also 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.

[0145] 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, and also includes an electrolyte.

[0146] In some embodiments, the separator may be made of materials known in the art for battery separators. As an example, the separator substrate may include one or more of polyethylene, polypropylene, and polyvinylidene fluoride.

[0147] In some embodiments, the electrolyte includes an electrolyte salt and a solvent. For a secondary battery that is a lithium ion battery, the electrolyte salt may 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorobis(oxalate phosphate) and lithium tetrafluorooxalate phosphate. For a secondary battery that is a sodium ion battery, the corresponding electrolyte salt is replaced with a sodium salt.

[0148] 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, methyl propyl carbonate, ethyl propyl 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.

[0149] In some embodiments, the electrolyte may further include additives, such as 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, additives that improve battery high or low temperature performance, etc.

[0150] In some embodiments, the battery of the embodiments of the present application may include a secondary battery, and specifically may include any one of a battery cell, a battery module, and a battery pack of a secondary battery.

[0151] The battery cell refers to a battery housing and a battery cell encapsulated in the battery housing. The shape of the battery cell is not particularly limited and can be cylindrical, square or any other shape. Figure 4 The battery cell 20 shown has a square structure.

[0152] In some embodiments, the battery of the embodiments of the present application may include a secondary battery, and specifically may include any one of a battery cell, a battery module, and a battery pack of a secondary battery.

[0153] The battery cell refers to a battery housing and a battery cell encapsulated in the battery housing. The shape of the battery cell is not particularly limited and can be cylindrical, square or any other shape. Figure 4 The battery cell 20 shown has a square structure.

[0154] In some embodiments, Figure 5 As shown, 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, the isolation membrane and the pole sheet contained in the secondary battery of the embodiment of the present application can form 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 may be one or more, which can be adjusted according to actual needs.

[0155] The preparation method of the battery cell 20 is well known. In some embodiments, the pole piece, the separator, the pole piece and the electrolyte can be assembled to form the battery cell 20. As an example, the pole piece, the separator and the pole piece can be formed into the electrode assembly 23 through a winding process or a lamination process, and the electrode assembly 23 is placed in an outer package, dried and injected with electrolyte, and then vacuum packaged, left to stand, formed, shaped and other processes are performed to obtain the battery cell 20.

[0156] The battery module is assembled from the battery cells 20 , that is, it may contain a plurality of the battery cells 20 , and the specific number can be adjusted according to the application and capacity of the battery module.

[0157] In some embodiments, Figure 6 FIG. 3 is a schematic diagram of a battery module 30 as an example. Figure 6 As shown, in the battery module 30, the plurality of battery cells 20 may be arranged in sequence along the length direction of the battery module 30. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 20 may be fixed by fasteners.

[0158] 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.

[0159] A battery pack is composed of the above-mentioned battery cells 20, that is, it may contain multiple battery cells 20, wherein multiple battery cells 20 may be assembled into the above-mentioned battery module 30. The specific number of battery cells 20 or battery modules 30 contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0160] As in the embodiment, Figure 7and Figure 8 4 is a schematic diagram of an exemplary battery pack 40. The battery pack 40 may include a battery box and a plurality of battery modules 30 disposed in the battery box. The battery box includes an upper box body 41 and a lower box body 42, wherein the upper box body 41 is used to cover the lower box body 42 and form a closed space for accommodating the battery modules 30. The plurality of battery modules 30 may be arranged in the battery box in any manner.

[0161] Electrical devices

[0162] In an eighth aspect, the present application embodiment further provides an electric device, the electric device comprising the battery provided in the seventh aspect of the present application embodiment. The battery can be used as a power source for the electric device, or as an energy storage unit for the electric device. Therefore, the electric device in the present application embodiment has a high capacity retention rate, good stability and safety in use.

[0163] The electrical device may be, but is not limited to, a mobile device (such as a mobile phone, a laptop 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. The electrical device may select a secondary battery, a battery module or a battery pack according to its use requirements.

[0164] Fig. 9 Schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements of the electric device for high power and high energy density, a battery pack or a battery module may be used.

[0165] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a secondary battery may be used as a power source.

[0166] Example

[0167] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0168] Example 1

[0169] A plating solution comprising the following components in concentrations:

[0170]

[0171] Among them, the brightener is sodium polydisulfide dipropane sulfonate, the surfactant is polyvinyl alcohol, and the leveling agent is: n=130.

[0172] A method for preparing an electrolytic copper foil, comprising:

[0173] Add the prepared electroplating solution to the foil machine, adjust the current of the foil machine to 6000A, and perform electrodeposition. The electrodeposition 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.

[0174] The electrolytic copper foil produced by the above preparation method can be peeled off from the cathode roller through the UV anti-adhesion film.

[0175] Example 2

[0176] The difference from Example 1 is that the concentrations of the components of the electroplating solution are as follows:

[0177] Example 3

[0178] The difference from Example 1 is that the leveling agent is n=136.

[0179] Example 4

[0180] The difference from Example 1 is that the leveling agent is n=144.

[0181] Example 5

[0182] The difference from Example 1 is that the leveling agent is n=180.

[0183] Example 6

[0184] The difference from Example 1 is that the leveling agent is n=226.

[0185] Comparative Example 1

[0186] The difference from Example 1 is that the leveling agent is gelatin.

[0187] Comparative Example 2

[0188] The difference from Example 1 is that the leveling agent is collagen.

[0189] Performance Testing

[0190] (1) Mechanical properties test of electrolytic copper foil

[0191] 1.1 Tensile strength and elongation at break test

[0192] The determination can be carried out according to the GB / T 1040.3-2006 method. The specific steps are as follows:

[0193] 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 machine at room temperature and pressure (25°C, 0.1 MPa). The initial length of the high-speed rail tensile machine was set to 50 mm. The tensile test was performed at a tensile rate of 5 mm / min until the sample broke and the tensile test was stopped. The maximum tensile force F (N) borne by the sample when it was pulled apart and the equipment displacement y (mm) when the tensile fracture occurred were recorded. Finally, the elongation at break was calculated to be (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.

[0194] 1.2 Pinhole test

[0195] Take a flat, wrinkle-free electrolytic copper foil sample and lay it flat on the backlight screen. Turn on the backlight screen and visually circle the three largest pinholes within the range of 33cm×33cm. Remove the samples in the circled area and keep them. Remove the removed samples and place them on the CCD to measure the pinhole diameters of the three samples respectively. The pinhole diameter is the average of the diameters of the three samples.

[0196] 1.3 Thickness test

[0197] First calculate the surface density of the electrolytic copper foil, and then convert the unit. Use a punching machine and a special die cutter to punch the copper film into 10×10cm along the width direction. 2 Take 3 samples. Turn on the electronic balance, put the samples into the electronic balance for testing, and record the data after the value stabilizes.

[0198] Surface density (mg / cm 2 )=weight data÷punching area; thickness=surface density / copper density, copper density is 8.95g / cm 3 .

[0199] The final results are shown in Table 1.

[0200] Table 1

[0201]

[0202] (2) Current collector test

[0203] The electrolytic copper foils of the above examples and comparative examples 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 with a length of 1000 m and a width of 300 mm, 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 laminate the first copper foil and the second copper foil relative to each other for curing treatment (temperature 70° C., time 72 h) to form a colloidal layer with a thickness of 2 μm, then tear off the first release film and the second release film 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 Current collector tensile strength test

[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 machine at room temperature and pressure (25°C, 0.1 MPa). The initial length of the high-speed rail tensile machine was set to 50 mm. The tensile test was performed at a tensile rate of 5 mm / min until the sample broke and the tensile test was stopped. The maximum tensile force F (N) borne by the sample when it was broken and the device displacement y (mm) when the tensile fracture occurred 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 out a 2cm wide current collector sample, wipe the steel plate clean with alcohol; stick 3M double-sided tape (2cm) evenly on the steel plate, stick the sample evenly on the double-sided tape, cut off the excess current collector, and then stick the wrinkled tape (2cm) evenly on the current collector in the center, and stick one end of it on an A4 paper sample (insulating sheet) strip (the wrinkled tape cannot directly contact the steel plate). Then use a 2KG roller to roll the sample back and forth twice.

[0213] Test: Turn on the high-speed rail tensile machine, clamp the sample steel plate vertically on the lower fixture (A4 paper side facing downward), then flip the A4 paper side up and clamp it vertically on the upper fixture. Open the test software, select the insulation film peeling force, set the tensile speed to 500mm / min, first manually pull off the sample by 2mm-4mm, click the reset button to reset, click the run button, pull off the sample by 100mm, and observe whether there is any material falling off and adhering to the wrinkle glue. If there is no material adhering to the wrinkle glue, it is qualified, otherwise it is unqualified.

[0214] 2.3 Hole Test

[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 a current collector sample, put the sample into a 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 immersion.

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

[0219] (3) Secondary battery cell performance test

[0220] The current collector prepared as above is used as the negative 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 (CNT), 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 an 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 negative electrode slurry; the negative electrode slurry is evenly coated on the above-prepared current collector, double-sided coating is performed, and the negative electrode sheets are obtained after sufficient drying, cold pressing, and slitting.

[0223] Preparation of battery electrolyte: At room temperature, ethylene carbonate (EC) / diethyl carbonate (DEC) are mixed in a volume ratio of 1:1, and LiPF6 is 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 sheet and negative electrode sheet 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 the 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 a charge and discharge cycle, and the discharge capacity of this time is the discharge capacity of the first cycle. Perform 1000 charge and discharge cycles on 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]

[0231] From the data in Table 1 and Table 2, it can be seen that the electrolytic copper foil prepared in the embodiment of the present application has an ultra-thin electrolytic copper foil and can also have good mechanical properties. Therefore, the current collector prepared with this electrolytic copper foil has good mechanical properties, is resistant to battery electrolyte, and the copper foil is not easy to fall off, thereby improving the cycle performance and safety of the secondary battery.

[0232] 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 replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate 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.

Images