Current collector, pole piece, secondary battery, electrical device, copper foil, and method for manufacturing said copper foil

Abstract

The present invention relates to a current collector, a pole piece, a secondary battery, an electrical device, and copper foil, as well as a method for manufacturing the copper foil. The current collector contains copper foil, the average particle size of the crystal grains in the copper foil is 50 nm to 400 nm, and, based on the total number of crystal grains in the copper foil, the proportion of nanotwin crystal grains is 60% or more. The combined action of a high proportion of nanotwin structure and small crystal grain size is advantageous in maintaining the high plasticity of the current collector while simultaneously improving its mechanical strength, providing a material basis for further improvement of battery energy density and safety.

Description

Technical Field

[0001] [Cross-reference] This application cites Chinese Patent Application No. 202410146761.1, titled "Current Collector, Electrode Tab, Secondary Battery, Electrical Device, Copper Foil, and Method for Manufacturing the Copper Foil", filed on February 1, 2024, the entire content of which is incorporated herein by reference.

[0002] This application belongs to the field of battery technology, and specifically relates to a current collector, an electrode tab, a secondary battery, an electrical device, a copper foil, and a method for manufacturing the copper foil.

Background Art

[0003] In recent years, secondary batteries have been widely applied in multiple fields such as energy storage power systems such as hydropower plants, thermal power plants, wind power plants, and solar power plants, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc.

[0004] The current collector is an important component of a secondary battery. With the improvement of the requirements for the energy density and safety of secondary batteries in the market, in order to meet the needs of new-generation secondary batteries, it is urgently necessary to develop a lightweight and high-strength current collector.

Summary of the Invention

[0005] This application is made in view of the above problems, and its purpose is to provide an ultra-thin current collector with excellent mechanical properties in order to meet the requirements for the current collector of new-generation high-performance batteries.

[0006] To achieve the above object, this application provides a current collector, an electrode tab, a secondary battery, an electrical device, a copper foil, and a method for manufacturing the copper foil.

[0007] In a first aspect of the present application, a current collector is provided, the current collector comprising copper foil, the average particle size of the crystal grains in the copper foil being 50 nm to 400 nm, and the proportion of nanotwin crystal grains calculated based on the total number of crystal grains in the copper foil being 60% or more.

[0008] Twin structures are an effective means of improving metallic strength and plasticity. Twin grain boundaries are colattice interfaces with orderly atomic arrangements, improving material strength by increasing resistance to dislocation motion while simultaneously maintaining dislocation mobility. This strengthens the material while preserving its plasticity. Smaller grain sizes further increase the interfacial structure, improving the external stress required for dislocations to penetrate grain boundaries, thus achieving material strengthening. The combined effect of a high proportion of nanotwin structures and small grain sizes is advantageous in maintaining the high plasticity of copper foil while simultaneously improving its mechanical strength, providing a material foundation for further improvements in battery energy density and safety.

[0009] In any embodiment, the average particle size of the crystal grains in the copper foil is 50 nm to 300 nm.

[0010] Copper foil with an average particle size within the above range retains its high plasticity while further improving its mechanical strength, thus meeting the needs of a new generation of high-energy-density secondary batteries.

[0011] In any embodiment, based on the total number of crystal grains in the copper foil, the proportion of crystal grains with a particle diameter of less than 200 nm is 20% to 40%, and the proportion of crystal grains with a particle diameter between 200 nm and 500 nm is 50% to 80%.

[0012] In any embodiment, when calculated based on the total number of crystal grains in the copper foil, the proportion of crystal grains with a particle diameter greater than 500 nm is 5% or less.

[0013] In conventional copper foils strengthened by twinning methods, the manufacturing process often introduces micron-order twins, hindering further improvement of copper foil strength. The copper foil provided by the embodiment of this application has a high proportion of nano-twins, significantly improving the strength of the copper foil. Furthermore, the crystal grains have a small average particle size, exhibiting distortion, and the proportion of crystal grains with a particle size greater than 500 nm is very small. The fine crystal grains reduce the generation of concentrated stress during the deformation process of the copper foil and are advantageous due to the coordinated sliding of the crystal grains. Therefore, it is possible to improve the strength of the copper foil while simultaneously improving the elongation at break.

[0014] In any embodiment, when calculated based on the total number of crystal grains in the copper foil, the proportion of equiaxed crystal grains or pseudo-equixaxed crystal grains is 80% or more, and the ratio a1 of the lengths of the major axis to the minor axis of the equiaxed crystal grains or pseudo-equixaxed crystal grains satisfies 1 ≤ a1 < 2.

[0015] A large number of equiaxed or near-equaxed crystal grains are advantageous for achieving isotropy in all directions of the copper foil, and are advantageous for overall improvement of the strength and plasticity of the copper foil.

[0016] In any embodiment, when calculated based on the total number of crystal grains in the copper foil, the proportion of columnar crystal grains is less than 10%, and the ratio a2 of the lengths of the major axis to the minor axis of the columnar crystal grain satisfies a2 > 2.

[0017] The formation of columnar crystal grains easily leads to anisotropy in the mechanical properties of copper foil. Reducing the proportion of columnar crystal grains is advantageous for improving the mechanical strength and plasticity of copper foil and reduces the probability of stress concentration points forming.

[0018] In any embodiment, the proportion of the plane diffraction intensity of the (111) texture in the copper foil to the sum of the plane diffraction intensities of the (111), (200), (220), (311), and (222) textures in the copper foil is 60% to 85%.

[0019] Common textures for pure copper materials include (111), (200), (220), (311), and (222). Depending on the crystallographic properties, the (111) crystal plane has a high atomic density, high mechanical strength, and can improve the twinning strengthening effect. Copper foil in which the ratio of the crystal plane diffraction intensity of the (111) texture to the sum of the crystal plane diffraction intensities of the (111), (200), (220), (311), and (222) textures in the copper foil is within the above range is advantageous for improving the mechanical strength and plasticity of the copper foil.

[0020] In any embodiment, the copper foil has a first surface and a second surface facing each other, and the thickness of the copper foil is H. The region within the thickness range of 0.2H to 0.5H from the first surface of the copper foil is defined as the first region of the copper foil, and the region within the thickness range of 0.2H to 0.5H from the second surface of the copper foil is defined as the second region of the copper foil. In this case, the absolute value of the difference between the average particle diameter of the crystal grains in the first region and the average particle diameter of the crystal grains in the second region is 150 nm or less.

[0021] The grain size and structure of the copper foil also provide a basis for maintaining high uniformity along the thickness direction of the copper foil, allowing it to have an extremely thin thickness while still retaining high strength and high plasticity.

[0022] In any embodiment, the proportion of nanotwin crystal grains is calculated to be 65% to 90% based on the total number of crystal grains in the copper foil.

[0023] In any embodiment, the maximum surface roughness of the copper foil is 3 μm or less.

[0024] Copper foil with a maximum surface roughness of 3 μm or less has a smooth and uniform surface, making it less likely for stress concentration points to form during the cyclic force bearing process, which is advantageous for improving the mechanical strength and plasticity of the copper foil.

[0025] In any embodiment, the thickness H of the copper foil satisfies 3 μm ≤ H ≤ 15 μm.

[0026] The copper foil in question has a thin thickness, which allows for effective weight reduction of the battery and is advantageous for further improving the battery's energy density.

[0027] In any embodiment, under test conditions of room temperature, sample thickness of 6 ± 0.2 μm, and tensile speed of 50 ± 0.5 mm / min, the tensile strength of the copper foil is 600 MPa or more, and the elongation at break of the copper foil is 4% or more.

[0028] In any embodiment, under test conditions of room temperature, sample thickness of 6 ± 0.2 μm, and tensile speed of 50 ± 0.5 mm / min, the tensile strength of the copper foil is 700 MPa to 1500 MPa, and the elongation at break of the copper foil is 4.5% to 10%.

[0029] The above copper foil simultaneously possesses high strength and high plasticity, meeting the needs of high-energy-density batteries, improving the energy density of the battery while simultaneously enhancing its safety.

[0030] A second aspect of the present application provides an electrode piece including a current collector of any embodiment.

[0031] A third aspect of the present application provides a secondary battery including the electrode piece of the second aspect.

[0032] In any embodiment, the secondary battery is one of a battery cell, a battery module, or a battery pack.

[0033] In any embodiment, the maximum expansion force of the secondary battery cell is 1000 kgf or more.

[0034] In any embodiment, the maximum expansion force of the secondary battery cell is 2500 kgf or more.

[0035] In any embodiment, the maximum expansion force of the secondary battery cell is 4000 kgf or more. Conventional current collectors are prone to rupture due to the high expansion force of secondary batteries, causing safety events and limiting further improvement of the electrochemical performance of secondary batteries. The current collector provided by the embodiment of the present application combines excellent tensile strength and elongation at break, can be applied to secondary batteries with high expansion force, and is advantageous for further improving the energy density of secondary batteries.

[0036] A fourth aspect of the present application provides an electrical device including a secondary battery of the third aspect.

[0037] A fifth aspect of the present invention provides a method for manufacturing copper foil, wherein the copper foil is manufactured using an electroplating method, the electroplating method specifically includes reducing and depositing copper ions in an electroplating solution by periodically applying an electric current to the electroplating solution to form copper foil, the average particle size of the crystal grains in the copper foil being 50 nm to 400 nm, and the proportion of nanotwin crystal grains calculated based on the total number of crystal grains in the copper foil being 60% or more.

[0038] In any embodiment, the current is a pulsed current, and the pulsed current includes one or more of the following: a square wave pulsed current, a sinusoidal wave pulsed current, a triangular wave pulsed current, and a sawtooth wave pulsed current.

[0039] By applying a pulsed current to the electroplating solution and controlling the on / off switching of the current, the nucleation process of reduced copper ions and the growth of crystal grains can be controlled, further suppressing crystal grain growth and forming uniform nanocrystal grains, thereby improving the tensile strength and elongation at break of the copper foil. Compared to deposition using direct current, which is commonly used in conventional techniques, deposition using pulsed current can achieve a higher peak current density, which is advantageous for the mass nucleation of copper foil. This improves the density of the copper foil and reduces the crystal grain size of the copper foil, thereby improving the mechanical strength of the copper foil.

[0040] In any embodiment, the electroplating solution includes an additive, the additive includes one or more of a leveling agent, a wetting agent, and a brightener.

[0041] In any embodiment, the additive includes a leveling agent, a wetting agent, and a glossing agent.

[0042] Leveling agents adhere to the leading edge of copper foil, where deposition rates are high, suppressing grain growth, balancing the growth rates of pits and the leading edge, and improving the flatness of the copper foil. Wetting agents can improve the penetration of the electroplating solution into the substrate. The penetration of the electroplating solution at the cathode, combined with a high current, enables high-speed electrodeposition, improving the nucleation rate of the copper foil and reducing the average particle size of the crystal grains in the copper foil. A certain amount of brightener can make the crystal grain size of the copper foil finer, reduce the surface roughness of the copper foil, and improve the surface smoothness.

[0043] In any embodiment, the concentration of the leveling agent in the electroplating solution is 20 mg / L to 300 mg / L.

[0044] In any embodiment, the concentration of the leveling agent in the electroplating solution is 50 mg / L to 150 mg / L.

[0045] In any embodiment, the concentration of the wetting agent in the electroplating solution is 10 mg / L to 200 mg / L.

[0046] In any embodiment, the concentration of the wetting agent in the electroplating solution is 30 mg / L to 100 mg / L.

[0047] In any embodiment, the concentration of the brightener in the electroplating solution is 10 mg / L to 200 mg / L.

[0048] In any embodiment, the concentration of copper ions in the electroplating solution is 30 g / L to 100 g / L.

[0049] In one embodiment, the concentration of copper ions in the electroplating solution is 45 g / L to 75 g / L.

[0050] The research results show that the combination of low copper ion concentration and high additive concentration is more advantageous than the combination of high copper ion concentration and low additive concentration for overall improvement of copper foil strength and elongation at break. Furthermore, low copper ion concentration helps reduce concentration polarization, control grain growth and deposition rates, and is advantageous for producing small-sized grains and improving the mechanical strength of copper foil.

[0051] In any embodiment, the concentration of chloride ions in the electroplating solution is 10 mg / L to 80 mg / L.

[0052] In one embodiment, the pH of the electroplating solution is 2.5 to 4.4.

[0053] In any embodiment, the leveling agent comprises one or more of gelatin and Janus Green; the wetting agent comprises one or more of hydroxyethylcellulose and polyethylene glycol; and the glossing agent comprises one or more of sodium polydithiodipropanesulfonate, sodium 3-mercapto-1-propanesulfonate, and thiourea.

[0054] In any embodiment, the wetting agent comprises hydroxyethylcellulose and polyethylene glycol.

[0055] The research results show that simultaneously adding two different wetting agents more effectively improves the mechanical strength of copper foil than adding a single type of wetting agent. Although the mechanism is still unclear, it is speculated that it may be related to the formation of competitive adsorption between the two different additives, which is advantageous for improving consistency during the deposition process of crystal grains, reducing differences in grain size in the thickness direction, and improving the uniformity of the copper foil.

[0056] In any embodiment, the mass concentration ratio of the copper ions to the leveling agent is 500:1 to 4500:1, and / or the mass concentration ratio of the copper ions to the brightener is 300:1 to 6000:1.

[0057] In some embodiments, the electroplating solution contains gelatin at a concentration of 20 mg / L to 150 mg / L, polyethylene glycol at a concentration of 15 mg / L to 100 mg / L, hydroxyethylcellulose at a concentration of 10 mg / L to 80 mg / L, sodium polydithiodipropanesulfonate at a concentration of 15 mg / L to 150 mg / L, copper ions at a concentration of 45 g / L to 90 g / L, and chloride ions at a concentration of 10 mg / L to 80 mg / L.

[0058] In any embodiment, the peak current density of the pulse current is I, and its unit is A / dm 2 The current duty cycle of the pulse current is s, and the peak current density I and the duty cycle s are 2A / dm 2 ≤I × s ≤ 18A / dm 2 It satisfies the condition.

[0059] The product of the peak current density I and the duty cycle s corresponds to the average current density in the pulse period. Since excessively high DC deposition densities cause hydrogen deposition and concentration polarization in the electroplating solution, reducing the uniformity of the copper foil during the electrodeposition process, the pulsed current deposition method ensures that the average current density in the pulse period is higher than the maximum current density achievable with DC deposition. The product of the peak current density I and duty cycle s within the above range can not only effectively reduce the grain size but also improve the uniformity of grain size in the thickness direction of the manufactured copper foil. The product of the peak current density I and duty cycle s within the above range, combined with a low copper ion concentration in the electroplating solution, further improves the concentration polarization phenomenon of the electroplating solution, enabling the production of smaller crystal grains and improving the tensile strength and elongation at break of the copper foil. In any embodiment, the peak current density I of the pulsed current is 3.3 A / dm². 2 ≤I ≤ 333A / dm2 It satisfies the condition.

[0060] In any embodiment, the duty cycle s of the pulse current satisfies 2% ≤ s ≤ 50%.

[0061] In any embodiment, the pulse width of the pulsed current is 1 ms to 50 ms.

[0062] In any embodiment, the distance between the cathode electrode and the anode electrode is 15 mm to 20 mm.

[0063] In any embodiment, the temperature of the deposition is 45°C to 60°C.

[0064] In any embodiment, the settling time is 80 seconds or longer.

[0065] In any embodiment, the electroplating method specifically includes reducing and depositing copper ions in the electroplating solution by periodically applying a pulsed current to the electroplating solution, wherein the peak current density I of the pulsed current is 100 A / dm 2 ≤I ≤ 180A / dm 2 The following conditions are met: the duty cycle s of the pulse current satisfies 2% ≤ s ≤ 10%, and the deposition time is 80s to 250s.

[0066] In any embodiment, the above manufacturing method is a continuous production method.

[0067] In a sixth aspect of the present application, a copper foil is provided, which has the same characteristics as the copper foil in the current collector described above, and its description is omitted here.

[0068] In any embodiment, the copper foil is manufactured by the manufacturing method of the fifth embodiment.

[0069] In any embodiment, the maximum width of the copper foil is 1.5 meters or more, and / or the maximum width length of the copper foil is 10,000 meters or more.

[0070] This copper foil can be manufactured on a large scale and has potential for future industrial applications. [Brief explanation of the drawing]

[0071] To further clarify the technical concept of the embodiments of the present application, the drawings used in the embodiments of the present application are briefly introduced below. Clearly, the drawings described below represent only a few embodiments of the present application, and those skilled in the art can obtain other drawings based on these without any creative work. In the drawings, the drawings are not necessarily drawn to actual scale. The reference numerals are as follows: 1, battery pack; 2, upper case; 3, lower case; 4, battery module; 5, secondary battery; 51, casing; 52, electrode assembly; 53, cover plate. [Figure 1] This is a schematic diagram of the crystal grain size distribution of the copper foil in Example 1 of the present application. [Figure 2] This is an inverse pole figure distribution diagram of the electron backscatter diffraction pattern of the copper foil in Example 1 of the present application. [Figure 3] This is a tensile curve diagram of the copper foil of Embodiment 1 of the present application. [Figure 4] Figure 4(a) shows the X-ray diffraction pattern of the copper foil of Example 2 of the present application. Figure 4(b) shows the X-ray diffraction pattern of the copper foil of Comparative Example 1 of the present application. [Figure 5] This is a schematic diagram of one embodiment of the secondary battery of the present invention. [Figure 6] This is a schematic exploded view of one embodiment of the secondary battery of the present invention. [Figure 7] This is a schematic diagram of one embodiment of the battery module of the present invention. [Figure 8] This is a schematic diagram of one embodiment of the battery pack of the present invention. [Figure 9] Figure 8 is a schematic exploded view of an embodiment of the battery pack shown. [Figure 10] This is a schematic diagram of one embodiment of an electrical device that includes the secondary battery of the present invention as a power source. [Modes for carrying out the invention]

[0072] Hereinafter, embodiments specifically disclosing the current collector, pole piece, secondary battery, electrical device, copper foil, and method for manufacturing said copper foil will be described in detail, with reference to the drawings as appropriate. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of already well-known matters and repeated explanations of substantially the same structures may be omitted. This is to avoid making the following explanation unnecessarily long and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following explanation are provided so that the present application can be fully understood by those skilled in the art and are not intended to limit the essence of what is stated in the claims.

[0073] The “range” disclosed herein is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, and the boundaries of a special range are limited by the selected lower and upper limits. The range thus limited may include or exclude the values ​​at both ends, or may be a combination of either; that is, any lower limit may be combined with any upper limit to form a single range. For example, if the ranges 60-120 and 80-110 are given for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Similarly, if the minimum range values ​​1 and 2 are given, and the maximum range values ​​3, 4 and 5 are given, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are all expected. In this application, unless otherwise stated, the numerical range “a-b” represents an abbreviated expression of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" have already been listed in this specification, and "0 to 5" is simply an abbreviation for a combination of those numbers. Also, when it is stated that a parameter is an integer ≥ 2, this is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0074] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0075] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts, and such technical concepts should be considered to be included in the disclosures of this application.

[0076] Unless otherwise specified, all steps of this invention may be performed sequentially or randomly, but it is preferable that they be performed sequentially. For example, the fact that the above method includes steps (a) and (b) means that the above method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, the fact that the above method described above may further include step (c) means that step (c) can be added to the above method in any order, for example, the above method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0077] Unless otherwise specified, the terms "include" and "incorporate" as used in this application may be open or closed. For example, the terms "include" and "incorporate" above may further include or incorporate other components not listed, or may include or incorporate only the listed components.

[0078] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by any of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0079] Unless otherwise specified, terms used in this application have the meanings generally understood by those skilled in the art.

[0080] Unless otherwise specified, the numerical values ​​of each parameter referred to herein can be measured by various test methods commonly used in the art, for example, by the test methods referred to herein. Specifically, the microstructure of the entire copper foil is characterized in the sampling area during the test process.

[0081] Unless otherwise specified, the term "active ion" in this application refers to an ion that can be repeatedly inserted into and removed from between the positive and negative electrodes of a secondary battery, and includes, but is not limited to, lithium ions.

[0082] In this application, the terms "multiple" and "multiple types" mean two or more types.

[0083] With the increasing energy density of secondary batteries, there is a need for thinner and lighter polarity current collectors. As the current collector is thinned, the maximum load it can support decreases sharply, and the thickness available for plastic deformation of the current collector is significantly reduced. This leads to a significant decrease in the tensile strength and elongation at break of the current collector, making it difficult for conventional current collectors of average strength to meet the needs of secondary batteries. When current collectors of normal strength are thinned, fatigue failure is more likely to occur in the later stages of the secondary battery cycle, and this can also cause thermal runaway in the battery core, leading to safety events. Therefore, it is necessary to thin the current collector while effectively improving its tensile strength and plasticity (elongation at break).

[0084] Conventional metal strengthening techniques often improve strength by inhibiting dislocation motion using common incoherent grain boundaries or interfaces. When a large number of incoherent grain boundaries are introduced into a material, the strength improves significantly, but with the sustained increase of dislocation motion "inhibitors," crystal lattice dislocation motion is severely inhibited, and eventually completely suppressed, making it impossible to coordinate plastic deformation, and thus the material becomes brittle. As a result, strengthening the mechanical properties of metallic materials often comes at the cost of sacrificing plasticity, and materials with excellent plasticity often have low strength.

[0085] Based on this, the present invention provides a current collector comprising copper foil, wherein the average particle size of the crystal grains in the copper foil is 50 nm to 400 nm, and the proportion of nanotwin crystal grains calculated based on the total number of crystal grains in the copper foil is 60% or more.

[0086] In this specification, the term “twin” refers to a state in which two crystals (or two parts of one crystal) form a mirror-symmetric orientation relationship along a common crystal plane (i.e., a specific orientation relationship), where these two crystals are called a “twin,” and this common crystal plane is called a twin plane. Nanotwin refers to a twin with a size of less than 1000 nanometers in each dimension.

[0087] The average particle size of crystal grains in copper foil can be tested using methods known in this field. For example, the cross-section of copper foil is measured using an electron backscatter diffraction (EBSD) and a scanning electron microscope. A copper foil range of 5 mm × 5 mm or larger and 8 mm × 8 mm or smaller is selected, and an inverse pole figure distribution map of the copper foil is obtained. The average diameter of the equivalent circle of the crystal grains is taken as the crystal grain size. The crystal grain sizes within this range are statistically calculated to create a quantity distribution map. As shown in Figure 1, the skewness is used for fitting, and the length corresponding to the peak value is taken as the average particle size of the crystal grains.

[0088] In some embodiments, the average grain size of the copper foil is selectively a numerical range of 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, or any two of these.

[0089] In some embodiments, the average particle size of the crystal grains in the copper foil is 50 nm to 300 nm.

[0090] Copper foil with an average particle size within the above range retains its high plasticity while further improving its mechanical strength, thus meeting the needs of a new generation of high-energy-density secondary batteries.

[0091] In some embodiments, based on calculations using the total number of crystal grains in the copper foil, the proportion of crystal grains with a particle diameter of less than 200 nm is 20% to 40%, and the proportion of crystal grains with a particle diameter between 200 nm and 500 nm is 50% to 80%.

[0092] In some embodiments, when calculated based on the total number of crystal grains in the copper foil, the percentage of crystal grains with a particle size of less than 200 nm is selectively a numerical range of 20%, 24%, 28%, 32%, 36%, 40%, or any two of these.

[0093] In some embodiments, when calculated based on the total number of crystal grains in the copper foil, the proportion of crystal grains with a particle diameter between 200 nm and 500 nm is selectively a numerical range of 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any two of these.

[0094] In some embodiments, when calculated based on the total number of crystal grains in the copper foil, the number of crystal grains with a particle diameter greater than 500 nm is 5% or less, and selectively 2% or less.

[0095] In some embodiments, when calculated based on the total number of crystal grains in the copper foil, the percentage of crystal grains with a particle diameter greater than 500 nm is selectively a numerical range of 0.5%, 1%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any two of these.

[0096] The copper foil crystal grains provided by the embodiments of this application have a small average particle size, exhibit a degree of distortion in the particle size, and have a very small proportion of crystal grains with a particle size greater than 500 nm. The fine crystal grains reduce the generation of concentrated stress during the deformation process of the copper foil and are advantageous for the coordinated sliding of the crystal grains. Therefore, it is possible to improve the strength of the copper foil and simultaneously improve the elongation at break.

[0097] In this application, the proportion of nanotwin grains can be tested by methods known in this field. For example, a cross-section of a copper foil can be observed using a combination of electron backscatter diffraction (EBSD) and scanning electron microscopy. A copper foil range of 5 mm × 5 mm or larger and 8 mm × 8 mm or smaller can be selected to obtain an inverse pole figure distribution map of the copper foil, where different colors represent different grain orientations. As an example, in Figure 2, the red lines inside the grains represent twin grain boundaries and indicate the presence of a twin structure. The size and number of twins can be statistically analyzed using analysis software set with an electron backscatter diffractometer, and the proportion of nanotwin grains can be calculated. As an example, grain characteristics can be analyzed using an Oxford C-Nano+ electron backscatter diffractometer and its associated software.

[0098] In some embodiments, when calculated based on the total number of crystal grains in the copper foil, the percentage of nanotwin crystal grains is selectively a numerical range of 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or any two of these.

[0099] Twin structures are an effective means of improving metallic strength and plasticity. Twin grain boundaries are colattice interfaces where the atomic arrangement is orderly, and by improving the resistance to dislocation motion, they can improve material strength while maintaining dislocation mobility, thereby strengthening the material and maintaining its plasticity. However, in conventional methods, copper foil strengthened by twin strengthening often introduces micron-order twins during the manufacturing process, which hinders further improvement of copper foil strength. The copper foil provided by the embodiment of this application has a high proportion of nano-twins, improving the plasticity of the copper foil while significantly improving its strength. The small grain size further increases the interface structure, improving the external stress required for dislocations to penetrate grain boundaries, and thus achieving material strengthening. The combined action of a high proportion of nano-twin structures and small grain size is advantageous in maintaining the high plasticity of the copper foil while improving its mechanical strength, providing a material basis for further improvement of battery energy density and safety.

[0100] In this specification, the term “equixaxen grain or pseudo-equixaxen grain” refers to a grain in which the major axis and minor axis are equal or have little difference. In some embodiments, the ratio a1 of the lengths of the major axis to the minor axis of an equiaxen grain or pseudo-equixaxen grain satisfies 1 ≤ a1 < 2.

[0101] In some embodiments, when calculated based on the total number of crystal grains in the copper foil, the proportion of equiaxed crystal grains or pseudo-equixaxed crystal grains is 80% or more, selectively 90% or more, and the ratio a1 of the lengths of the major axis to the minor axis of the equiaxed crystal grains or pseudo-equixaxed crystal grains satisfies 1 ≤ a1 < 2.

[0102] In this application, the proportion of equiaxed grains or pseudo-equixaxed grains can be tested using methods known in the art. For example, a cross-section of a copper foil can be observed using a combination of electron backscatter diffraction (EBSD) and scanning electron microscopy. A copper foil range of 5 mm × 5 mm or larger and 8 mm × 8 mm or smaller can be selected to obtain an inverse pole figure distribution map of the copper foil, and the proportion of equiaxed grains or pseudo-equixaxed grains can be statistically calculated using analysis software.

[0103] A large number of equiaxed or near-equilibrium crystal grains are advantageous for achieving grain refinement and uniformity in copper foil, and the properties of the equiaxed or near-equilibrium crystal grains are the same or similar in each direction, which is advantageous for overall improvement of the strength and plasticity of copper foil.

[0104] In some embodiments, when calculated based on the total number of crystal grains in the copper foil, the percentage of equiaxed or near-equixaxed crystal grains is a numerical range of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any two of these.

[0105] In some embodiments, when calculated based on the total number of crystal grains in the copper foil, the proportion of columnar crystal grains is less than 10%, and the ratio a2 of the lengths of the major axis to the minor axis of the columnar crystal grain satisfies a2 > 2.

[0106] The formation of columnar crystal grains easily leads to anisotropy in the mechanical properties of copper foil. Reducing the proportion of columnar crystal grains is advantageous for improving the mechanical strength and plasticity of copper foil and reduces the probability of stress concentration points forming.

[0107] In some embodiments, the direction of the long axis of the columnar crystal grain is the direction of the thickness of the copper foil.

[0108] In some embodiments, the proportion of the crystal plane diffraction intensity of the (111) texture in the copper foil to the total crystal plane diffraction intensities of the (111), (200), (220), (311), and (222) textures in the copper foil is 60% or more, and selectively between 60% and 85%.

[0109] In this specification, the term "texture" refers to a phenomenon in which, during the formation process of a crystal, each crystal grain within a polycrystalline material is regularly arranged along a certain direction, exhibiting a somewhat statistically heterogeneous distribution, that is, they appear to be aligned in a certain direction, and as a result, the probability of orientation in these directions increases significantly. This is also called preferential arrangement or preferential orientation.

[0110] In this application, the crystal plane diffraction intensity of the texture in copper foil can be tested using methods known in the art. For example, copper foil is tested with an X-ray diffractometer, and the X-ray spectrum of standard copper powder (PDF No. 04-0836) is referenced. The diffraction peak area at a peak position of 40° to 45° is defined as the (111) crystal plane diffraction intensity of the texture, the diffraction peak area at a peak position of 47° to 52° is defined as the (200) crystal plane diffraction intensity of the texture, the diffraction peak area at a peak position of 70° to 75° is defined as the (220) crystal plane diffraction intensity of the texture, the diffraction peak area at a peak position of 85° to 95° is defined as the (311) crystal plane diffraction intensity of the texture, and the diffraction peak area at a peak position of 103° to 107° is defined as the (222) crystal plane diffraction intensity of the texture.

[0111] In some embodiments, the proportion of the plane diffraction intensity of the (111) texture in the copper foil to the sum of the plane diffraction intensities of the (111), (200), (220), (311), and (222) textures in the copper foil is selectively a numerical range of 60%, 65%, 70%, 75%, 80%, 85%, or any two of these.

[0112] Common textures for pure copper materials include (111), (200), (220), (311), and (222). Depending on the crystallographic properties, the (111) crystal plane has a high atomic density, high mechanical strength, and can improve the twinning strengthening effect. A copper foil containing a high proportion of (111) texture is advantageous for improving the mechanical strengthening and plasticity reinforcement effects of the copper foil.

[0113] In some embodiments, the copper foil has a first surface and a second surface facing each other, and the thickness of the copper foil is H. The region within the thickness range of 0.2H to 0.5H from the first surface of the copper foil is defined as the first region of the copper foil, and the region within the thickness range of 0.2H to 0.5H from the second surface of the copper foil is defined as the second region of the copper foil. In this case, the absolute value of the difference between the average particle diameter of the crystal grains in the first region and the average particle diameter of the crystal grains in the second region is 150 nm or less.

[0114] In some embodiments, the absolute value of the difference between the average particle diameter of the crystal grains in the first region and the average particle diameter of the crystal grains in the second region is a numerical range of 1 nm, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 150 nm, or any two of these.

[0115] The crystal grain size and structure of the copper foil also exhibit high uniformity along the thickness direction, which ensures uniform deposition at different stages of deposition and indicates that the electroplating solution does not undergo significant polarization during the deposition process, providing a foundation for maintaining high strength and high plasticity while having an extremely thin thickness.

[0116] In some embodiments, the proportion of nanotwin crystal grains is calculated to be 65% to 90% based on the total number of crystal grains in the copper foil.

[0117] In some embodiments, the maximum surface roughness of the copper foil is 3 μm or less.

[0118] The maximum surface roughness of copper foil can reflect the uniformity and smoothness of the copper foil surface. The maximum surface roughness of copper foil can be tested by methods known in this field. For example, a stylus roughness tester can be used. The surface of the copper foil is wiped with alcohol, the copper foil is placed flat on a horizontal surface, and the stylus roughness tester is placed on the surface of the copper foil. The measuring needle is brought into contact with the surface of the copper foil, and the measuring needle is lightly rubbed along the surface. The roughness of the copper foil is obtained by the measurement taken by the instrument. The test is performed five times on different parts of the copper foil, and the maximum value of the measured values ​​is taken as the maximum surface roughness of the copper foil.

[0119] In some embodiments, the maximum surface roughness of the copper foil is selectively 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or a numerical range between any two of these.

[0120] The copper foil with a maximum surface roughness of 3 μm or less has a smooth and uniform surface, is less likely to form stress concentration points during the cycle force receiving process, and is advantageous for improving the mechanical strength and plasticity of the copper foil.

[0121] In some embodiments, the thickness H of the copper foil satisfies 3 μm ≤ H ≤ 15 μm, and selectively 3 μm ≤ H ≤ 8 μm.

[0122] In some embodiments, the thickness H of the copper foil is selectively 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a numerical range between any two of these.

[0123] In the present application, the thickness of the copper foil can be tested by methods known in the art. As an example, a sample of 20×15 cm 2 is cut, the cut sample piece is placed on an electronic balance and weighed to obtain the weight of the sample piece. Further, based on the density ρ of the copper foil being 8.96 g / cm 3 the volume of the sample piece is calculated. The length and width of the sample piece are known, and thus the thickness of the sample piece can be calculated.

[0124] The copper foil has a thin thickness, can achieve effective weight reduction of the battery, and is advantageous for further improving the battery energy density.

[0125] In some embodiments, under test conditions of room temperature, sample thickness of 6±0.2 μm, and tensile speed of 50±0.5 mm / min, the tensile strength of the copper foil is 600 MPa or more, and the elongation at break of the copper foil is 4% or more. Selectively, the tensile strength of the copper foil is 700 MPa to 1500 MPa, more selectively, 800 MPa to 1000 MPa, and the elongation at break of the copper foil is 4.5% to 10%, and more selectively, 5% to 8%.

[0126] In this specification, the term "room temperature" refers to 20 ± 10°C.

[0127] In this specification, the term "tensile strength" refers to the maximum load-bearing strength of a sample when it is continuously loaded until it breaks.

[0128] In this specification, the term "elongation at break" refers to the ratio of the change in length to the original length when a material undergoes plastic deformation from the time it is subjected to a force until it breaks. It is usually expressed as a percentage and is an important parameter for evaluating the deformation capacity of a material under stress during a tensile process.

[0129] In this application, the tensile strength and elongation at break of copper foil can be tested according to methods known in the art, for example, the GB / T 5230-1995 "Electrolytic Copper Foil" standard. As an example, at least four samples measuring 200 ± 0.5 mm in length, 15 ± 0.25 mm in width, and 6 ± 0.2 μm in thickness are cut, and a load is continuously applied to the samples at a tensile speed of 50 ± 0.5 mm / min at room temperature until fracture occurs. The tensile strength of the sample is defined as the maximum load divided by the cross-sectional area of ​​the sample. The cross-sectional area of ​​the sample can be calculated by dividing the mass of the sample by the product of the length and density of the sample, and the density of the copper foil sample is 8.9 g / cm³. 3 It can be done this way.

[0130] In some embodiments, under test conditions of room temperature, sample thickness of 6 ± 0.2 μm, and tensile speed of 50 ± 0.5 mm / min, the tensile strength of the copper foil is selectively within a numerical range of 600 MPa, 700 MPa, 800 MPa, 900 MPa, 1000 MPa, 1100 MPa, 1200 MPa, 1300 MPa, 1400 MPa, 1500 MPa, or any two of these, and the elongation at break of the copper foil is selectively within a numerical range of 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of these.

[0131] The above copper foil simultaneously possesses high strength and high plasticity, meeting the needs of high-energy-density batteries, improving the energy density of the battery while simultaneously enhancing its safety.

[0132] This invention further provides a method for manufacturing copper foil, wherein the copper foil is manufactured using an electroplating method, and the electroplating method specifically includes reducing and depositing copper ions in an electroplating solution by periodically applying an electric current to the electroplating solution to form copper foil, wherein the average particle size of the crystal grains in the copper foil is 50 nm to 400 nm, and based on the total number of crystal grains in the copper foil, the proportion of nanotwin crystal grains is 60% or more, and selectively 65% ​​or more.

[0133] In this specification, the term "electroplating method" refers to a method of depositing a metal or alloy onto the surface of a workpiece using the principle of electroplating to form a metal layer.

[0134] In some embodiments, the current is a pulsed current, and the pulsed current includes one or more of the following: a square wave pulsed current, a sinusoidal wave pulsed current, a triangular wave pulsed current, and a sawtooth wave pulsed current.

[0135] In some embodiments, the pulsed current includes a square wave pulsed current.

[0136] In this specification, the term "pulsed current" refers to a periodically repeating pulse of current or voltage.

[0137] By applying a pulsed current to the electroplating solution and controlling the on / off switching of the current, the nucleation process of reduced copper ions and the growth of crystal grains can be controlled, further suppressing crystal grain growth and forming uniform nanocrystal grains, thereby improving the tensile strength and elongation at break of the copper foil. Compared to deposition using direct current, which is commonly used in conventional techniques, deposition using pulsed current can achieve a higher peak current density, which is advantageous for the mass nucleation of copper foil. This improves the density of the copper foil and reduces the crystal grain size of the copper foil, thereby improving the mechanical strength of the copper foil.

[0138] In some embodiments, the electroplating solution contains copper ions and chloride ions.

[0139] In some embodiments, the concentration of copper ions in the electroplating solution is 30 g / L to 100 g / L, and selectively 45 g / L to 75 g / L.

[0140] In some embodiments, the concentration of copper ions in the electroplating solution is 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, or a numerical range between any two of these.

[0141] The research results show that the combination of low copper ion concentration and high additive concentration is more advantageous than the combination of high copper ion concentration and low additive concentration for overall improvement of copper foil strength and elongation at break. Furthermore, low copper ion concentration helps control the growth and deposition rate of crystal grains, which is advantageous for producing small crystal grains and improving the mechanical strength of copper foil.

[0142] In some embodiments, the chloride ion concentration is 10 mg / L to 80 mg / L.

[0143] In some embodiments, the chloride ion concentration is a numerical range of 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L, or any two of these.

[0144] In some embodiments, the electroplating solution further comprises additives, the additives comprising one or more of leveling agents, wetting agents, and brighteners.

[0145] In this specification, the term "leveling agent" refers to a substance that can be added to an electroplating solution to improve the flatness of the plated layer.

[0146] In this specification, the term "wetting agent" refers to a substance that reduces the interfacial tension between the electroplating solution / electrode and improves the adhesion between the plating layer and the substrate.

[0147] In this specification, the term "brightener" refers to a substance that improves the smoothness of a plated layer and reduces surface roughness.

[0148] Leveling agents adhere to the leading edge of copper foil, where deposition rates are high, suppressing grain growth, balancing the growth rates of pits and the leading edge, and improving the flatness of the copper foil. Wetting agents can improve the penetration of the electroplating solution into the substrate. The penetration of the electroplating solution at the cathode, combined with a high current, enables high-speed electrodeposition, improving the nucleation rate of the copper foil and reducing the average particle size of the crystal grains in the copper foil. Brighteners can make the crystal grain size of the copper foil finer and reduce the surface roughness of the copper foil, improving the surface smoothness.

[0149] In some embodiments, the additives include leveling agents, wetting agents, and glossing agents.

[0150] Research results show that when multiple types of additives are added simultaneously, a synergistic effect can be achieved, effectively improving the strength and plasticity of copper foil.

[0151] In some embodiments, the leveling agent comprises one or more of gelatin and Janus Green; the wetting agent comprises one or more of hydroxyethylcellulose and polyethylene glycol; and the glossing agent comprises one or more of sodium polydithiodipropanesulfonate, sodium 3-mercapto-1-propanesulfonate, and thiourea.

[0152] In some embodiments, the wetting agent comprises hydroxyethylcellulose and polyethylene glycol.

[0153] The research results show that simultaneously adding two different wetting agents more effectively improves the mechanical strength of copper foil than adding a single type of wetting agent. Although the mechanism is still unclear, it is speculated that it may be related to the formation of competitive adsorption between the two different additives, which is advantageous for improving consistency during the deposition process of crystal grains, reducing differences in grain size in the thickness direction, and improving the uniformity of the copper foil.

[0154] In some embodiments, the concentration of the leveling agent in the electroplating solution is 20 mg / L to 300 mg / L, and selectively 50 mg / L to 150 mg / L.

[0155] In some embodiments, the concentration of the leveling agent in the electroplating solution is a numerical range of 20 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, 300 mg / L, or any two of these.

[0156] In some embodiments, the concentration of the wetting agent in the electroplating solution is 10 mg / L to 200 mg / L, and selectively 30 mg / L to 100 mg / L.

[0157] In some embodiments, the concentration of the wetting agent in the electroplating solution is 10 mg / L, 30 mg / L, 50 mg / L, 80 mg / L, 100 mg / L, 130 mg / L, 150 mg / L, 180 mg / L, 200 mg / L, or a numerical range between any two of these.

[0158] In some embodiments, the concentration of the brightener in the electroplating solution is 10 mg / L to 200 mg / L.

[0159] In some embodiments, the concentration of the brightener in the electroplating solution is 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L, 90 mg / L, 100 mg / L, 110 mg / L, 120 mg / L, 130 mg / L, 140 mg / L, 150 mg / L, 160 mg / L, 170 mg / L, 180 mg / L, 190 mg / L, 200 mg / L, or a numerical range between any two of these.

[0160] In some embodiments, the pH of the electroplating solution is 2.5 to 4.4.

[0161] In some embodiments, the pH of the electroplating solution is a numerical range of 2.5, 2.7, 2.9, 3.1, 3.3, 3.5, 3.7, 3.9, 4.1, 4.4, or any two of these.

[0162] In some embodiments, the mass concentration ratio of the copper ions to the leveling agent is 500:1 to 4500:1, and / or the mass concentration ratio of the copper ions to the brightener is 300:1 to 6000:1.

[0163] In some embodiments, the mass concentration ratio of the copper ions to the leveling agent is selectively a numerical range of 500:1, 1000:1, 1500:1, 2000:1, 2500:1, 3000:1, 3500:1, 4000:1, 4500:1, or any two of these.

[0164] In some embodiments, the mass concentration ratio of copper ions to the brightener is selectively a numerical range of 300:1, 1000:1, 2000:1, 3000:1, 4000:1, 5000:1, 6000:1, or any two of these.

[0165] In some embodiments, the electroplating solution contains gelatin at a concentration of 20 mg / L to 150 mg / L, polyethylene glycol at a concentration of 15 mg / L to 100 mg / L, hydroxyethylcellulose at a concentration of 10 mg / L to 80 mg / L, sodium polydithiodipropanesulfonate at a concentration of 15 mg / L to 150 mg / L, copper ions at a concentration of 45 g / L to 90 g / L, and chloride ions at a concentration of 10 mg / L to 80 mg / L.

[0166] In some embodiments, the peak current density of the pulse current is I, and its unit is A / dm 2 The current duty cycle of the pulse current is s, and the peak current density I and the duty cycle s are 2A / dm 2 ≤I × s ≤ 18A / dm 2 It satisfies the condition.

[0167] In this specification, the term "current duty cycle of a pulsed current" refers to the ratio of the current conduction time to the total pulse period in a pulsed current.

[0168] In some embodiments, the product I × s of the peak current density I and the duty cycle s is 2A / dm 2 , 4A / dm 2 , 6A / dm 2 , 8A / dm 2 , 10A / dm 2 , 12A / dm 2 , 14A / dm 2 , 16A / dm 2 , 18A / dm 2 Or a numerical range between any two of these.

[0169] The product of the peak current density I and the duty cycle s corresponds to the average current density in the pulse period. Since excessively high DC deposition density causes hydrogen deposition and concentration polarization in the electroplating solution, reducing the uniformity of the copper foil during the electrodeposition process, the pulsed current deposition method ensures that the average current density in the pulse period is higher than the maximum current density achievable with DC deposition. By controlling the on / off state of the current using the product of the peak current density I within the above range and the duty cycle s, a dynamic balance of consumed and replenished copper ions in the electroplating solution can be achieved. This reduces the concentration difference between the copper ion deposition site and other parts of the electroplating solution, preventing significant concentration polarization in the electroplating solution and improving the uniformity of the grain size in the thickness direction of the manufactured copper foil. Furthermore, the product of the peak current density I within the above range and the duty cycle s controls the core formation and growth rate of the crystal grains, enabling the production of crystal grains with smaller particle sizes and thereby improving the mechanical strength of the copper foil.

[0170] In some embodiments, the peak current density I of the pulsed current is 3.3 A / dm 2 ≤I ≤ 333A / dm 2 It satisfies the condition.

[0171] In some embodiments, the peak current density I of the pulsed current is 3.3 A / dm 2 , 8.35 A / dm 2 , 10A / dm 2 , 100A / dm 2 , 150A / dm 2 , 167 A / dm 2 , 180A / dm 2 , 200A / dm 2 , 300A / dm 2 , 333A / dm 2 Or a numerical range between any two of these.

[0172] In some embodiments, the duty cycle s of the pulse current is 2% to 50%.

[0173] In some embodiments, the duty cycle s of the pulse current is a numerical range of 2%, 3.30%, 5%, 10%, 20%, 30%, 40%, 50%, or any two of these.

[0174] In some embodiments, the pulse width of the pulsed current is 1 ms to 50 ms.

[0175] In this specification, the term "pulse width" refers to the duration of time during which the electric current is sustained within a pulse period.

[0176] In some embodiments, the pulse width of the pulsed current is a numerical range of 1 ms, 5 ms, 10 ms, 15 ms, 20 ms, 25 ms, 30 ms, 35 ms, 40 ms, 45 ms, 50 ms, or any two of these.

[0177] In some embodiments, the distance between the cathode electrode and the anode electrode is 15 mm to 20 mm.

[0178] In some embodiments, the distance between the cathode electrode and the anode electrode is a numerical range of 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or any two of these.

[0179] In some embodiments, the deposition temperature is 45°C to 60°C.

[0180] In some embodiments, the deposition temperature is selectively a numerical range of 45°C, 50°C, 55°C, 60°C, or any two of these.

[0181] In some embodiments, the cathode electrode is a titanium drum or titanium plate.

[0182] In some embodiments, the anode electrode is a titanium substrate plate.

[0183] In some embodiments, the settling time is 80 seconds or longer.

[0184] In some embodiments, the settling time is selectively a numerical range of 80s, 100s, 200s, 220s, 240s, 280s, 300s, 400s, 500s, 800s, 1000s, or any two of these.

[0185] In some embodiments, the electroplating method specifically includes periodically applying a pulsed current to an electroplating solution to reduce and deposit copper ions in the electroplating solution, wherein the peak current density I of the pulsed current is 100 A / dm². 2 ≤I ≤ 180A / dm 2 The following conditions are met: the duty cycle s of the pulse current satisfies 2% ≤ s ≤ 10%, and the deposition time is 80s to 250s.

[0186] In some embodiments, the above manufacturing method is a continuous production method.

[0187] In some embodiments, the manufacturing method is a drum deposition method. Its operating principle is that a cathode drum is connected to the negative electrode of a power supply, and an anode bath is connected to the positive electrode of the power supply. After an electroplating solution containing copper ions is introduced into the anode bath, an electric field is formed between the positive and negative electrodes. Under the action of the electric field, copper ions migrate to the surface of the cathode drum and deposit. The deposited copper foil is then peeled from the cathode drum and wound onto another drum. The electroplating solution is continuously added in a cycle, and copper ions continuously deposit on the cathode drum under the action of the electric field, continuously peeled off, and wound onto a winding shaft. This manufacturing method can significantly improve the continuous production of copper foil and offers potential for industrial applications.

[0188] This invention further provides a copper foil, which has the same characteristics as the copper foil in the current collector described above, and its explanation is omitted here.

[0189] In any embodiment, the copper foil is manufactured by the manufacturing method of any of the embodiments described above.

[0190] In some embodiments, the maximum width of the copper foil is 1.5 meters or more, and / or the maximum width length of the copper foil is 10,000 meters or more.

[0191] In some embodiments, the maximum width of the copper foil is a numerical range of 1.5 meters, 2 meters, 2.5 meters, 3 meters, 3.5 meters, 4 meters, 6 meters, 8 meters, 10 meters, or any two of these.

[0192] In some embodiments, the maximum width and length of the copper foil is a numerical range of 10,000 meters, 15,000 meters, 20,000 meters, 25,000 meters, 30,000 meters, 60,000 meters, 100,000 meters, or any two of these.

[0193] The copper foil provided by the embodiment of this application can be manufactured on a large scale and has potential for industrial applications.

[0194] pole piece The present invention further provides a pole piece comprising a current collector according to any embodiment.

[0195] In some embodiments, the pole piece is a negative pole piece, and the current collector is a negative current collector.

[0196] In some embodiments, the negative electrode piece includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0197] In some embodiments, the negative electrode film layer includes a negative electrode active material. In some embodiments, the negative electrode active material includes, but is not limited to, one or more of ordinary natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include one or more of elemental silicon, silicon oxide, silicon carbon composites, silicon nitrogen composites, and silicon alloy materials. The tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials.

[0198] In some embodiments, the electrode piece is a negative electrode piece, and the negative electrode piece includes a current collector and a negative electrode film layer installed on at least one side of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a silicon-based material, and the tensile elongation at room temperature of the negative electrode piece is 2% or more, and selectively 3% to 5%.

[0199] In this specification, the term "room temperature" refers to 20 ± 10°C.

[0200] In this specification, the term "tensile elongation at fracture" refers to the ratio of the change in length of a material to its original length when it deforms from the time it is subjected to a force until it fractures. It is usually expressed as a percentage and is an important parameter for evaluating the deformation capacity of a material under stress during a tensile process.

[0201] The tensile elongation at break of the negative electrode piece can be tested by methods known in the field. As an example, at least four samples measuring 200 ± 0.5 mm in length and 15 ± 0.25 mm in width are cut from the negative electrode piece. Using a pneumatic chuck, the air pressure is set to 0.2 MPa, the electrode piece is inserted through the upper and lower chucks, and the air valve is pressed to clamp it. First, the upper chuck is clamped to maintain a weak connection (i.e., the sample's natural curvature is maintained and no external force is applied), then the lower chuck is clamped, and a load is continuously applied to the sample at a tensile speed of 2 mm / min until it breaks, with a gauge length of 50 mm. The tensile elongation at break of the negative electrode piece is defined as the length of the gauge length of the sample before tensile fracture divided by the length of the gauge length of the sample before tensile fracture.

[0202] In some embodiments, the tensile elongation at room temperature of the negative electrode piece is selectively a numerical range of 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any two of these.

[0203] In some embodiments, the thickness of the negative electrode piece is 100 μm to 150 μm and is measured directly using a micrometer.

[0204] The negative electrode portion of the secondary battery has a large tensile elongation rate, which provides sufficient stretching space during the later stages of the secondary battery's cycle and allows it to withstand the reciprocal expansion of the secondary battery during the cycle. As a result, secondary batteries made of silicon-based materials have high energy density while simultaneously extending safety and cycle life.

[0205] In some embodiments, the bonding density of the negative electrode piece is 1.5 g / cm³. 3 Furthermore, the cold pressure elongation rate of the above-mentioned negative electrode piece is 0.1% or less, and selectively between 0.06% and 0.1%.

[0206] In this application, the bonding density of the negative electrode piece has a meaning known in the art and can be tested by methods known in the art. The bonding density of the negative electrode piece = surface density of the negative electrode film layer / thickness of the negative electrode film layer. The thickness of the negative electrode film layer has a meaning known in the art and can be tested by methods known in the art, for example, by employing a micrometer (e.g., Mitutoyo 293-100 type, with an accuracy of 0.1 μm). The surface density of the negative electrode film layer can be tested by methods known in the art. For example, take a negative electrode piece after cold pressing or a negative electrode piece obtained by disassembling a battery (if it is a double-sided coated negative electrode piece, the negative electrode film layer on one side can be wiped off first), punch it out into a small circular sheet with an area of ​​S1, weigh it, and mark it as M1. Then, wipe off the negative electrode film layer of the weighed negative electrode piece, weigh the negative electrode current collector, and mark it as M0. The surface density of the negative electrode piece = (M1 - M0) / S1.

[0207] In some embodiments, the bonding density of the negative electrode piece is selectively set to 1.5 g / cm³. 3 1.55 g / cm³ 3 1.6 g / cm³ 3 1.65 g / cm³ 3 1.7 g / cm³ 3 1.75 g / cm³ 3 1.8 g / cm³ 3 1.85 g / cm³ 3 1.9 g / cm³ 3 1.95 g / cm³ 3 2.0 g / cm³ 3 Or a numerical range between any two of these.

[0208] The cold-pressure elongation of the negative electrode piece can be tested by methods known in this art. For example, two points are taken on the surface of the negative electrode piece before cold pressing along the (MD) direction perpendicular to the cold-pressure drum, and the distance between them L1 is measured. After cold pressing, the distance between the two points L2 is measured on the negative electrode piece, and (L2-L1) / L1 is taken as the cold-pressure elongation of the negative electrode piece. At least five different locations are measured, and the average value is taken as the cold-pressure elongation of the negative electrode piece. It should be understood that the cold-pressure elongation of the negative electrode piece can also be obtained by characterizing the secondary battery after disassembly. For example, a secondary battery is disassembled to obtain the negative electrode piece, and the difference between the current collector break elongation in the coated area of ​​the negative electrode film layer and the current collector break elongation in the uncoated area is tested. This difference can also be used to represent the cold-pressure elongation of the negative electrode piece.

[0209] In some embodiments, the cold pressure elongation of the negative electrode piece is selectively a numerical range of 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or any two of these.

[0210] The negative electrode of this secondary battery achieves a high crimping density while simultaneously exhibiting a low stretch rate during the cold pressurization process. This reserves more usable space for the expansion of the electrode during the secondary battery's cycle, which is advantageous for further extending the safety and cycle life of the secondary battery. Furthermore, the low cold pressurization stretch rate reduces the risk of wrinkles forming on the tab of the negative electrode during the cold pressurization process. Moreover, it eliminates the need for the current pre-stretching process, which is used to reduce the probability of wrinkles forming on the tab during cold pressurization, thereby improving production efficiency.

[0211] In some embodiments, the bonding density of the negative electrode piece is 1.5 g / cm³. 3 ~2.0g / cm 3 That is the case.

[0212] Silicon-based materials have higher hardness and relatively lower sliding properties compared to carbon-based active materials commonly used in negative electrodes. Therefore, a higher cold pressing pressure is required to achieve the same bonding density. The silicon-containing negative electrode of this secondary battery has high stretchability and can reach high bonding densities, extending the safety and lifespan of the battery while simultaneously improving the energy density of the secondary battery.

[0213] In some embodiments, the mass content of the silicon-based material is calculated to be between 5% and 100% based on the total mass of the negative electrode film layer.

[0214] In some embodiments, when calculated based on the total mass of the negative electrode film layer, the mass content of the silicon-based material is selectively 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or a numerical range between any two of these.

[0215] In some embodiments, the mass content of the silicon-based material is calculated to be between 10% and 60% based on the total mass of the negative electrode film layer.

[0216] By using silicon-based materials within the above content range, secondary batteries possess a combination of good energy density, safety, and cycle stability.

[0217] In some embodiments, the thickness of the current collector is 2 μm to 10 μm.

[0218] In some embodiments, the thickness of the current collector is selectively 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any two of these numerical ranges. The thickness of the current collector can be obtained by testing using any known method in the art. For example, the thickness of the current collector can be obtained by testing with a thickness tester. Alternatively, the current collector can be punched into a small circular sheet, weighed, and then the surface density of the sample is obtained by dividing the mass of the sample by the surface area of ​​the sample. The thickness of the current collector can then be calculated by dividing the surface density of the sample by the density of the current collector material (for example, if the current collector is copper foil, the density of the current collector is 8.9 g / cm³). 3 The density of the current collector material can be characterized and tested using a composition testing machine.

[0219] In some embodiments, the negative electrode film layer further selectively contains a negative electrode conductive agent. The present application is not particularly limited to the type of negative electrode conductive agent, and as an example, the negative electrode conductive agent may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0220] In some embodiments, the negative electrode film layer further selectively includes a negative electrode adhesive. The present application is not particularly limited to the type of negative electrode adhesive, and as an example, the negative electrode adhesive may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0221] In some embodiments, the negative electrode film layer further selectively includes other auxiliary agents. For example, the other auxiliary agents may include thickeners such as sodium carboxymethylcellulose (CMC) or PTC thermistor material.

[0222] The above-mentioned negative electrode film layer is generally formed by applying a negative electrode slurry to a negative electrode current collector, drying it, and applying cold pressure. The above-mentioned negative electrode slurry is usually formed by dispersing a negative electrode active material, a selective conductive agent, a selective adhesive, and other selective auxiliary agents in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0223] The negative electrode piece described above does not exclude any additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode piece described in this application further includes a conductive primer layer (e.g., consisting of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and placed on the surface of the negative electrode current collector, and in some embodiments, the negative electrode piece described in this application further includes a protective layer covering the surface of the negative electrode film layer.

[0224] secondary battery The present invention further provides a secondary battery, the form of which the secondary battery is optionally a battery cell, a battery module, or a battery pack.

[0225] In some embodiments, the maximum expansion force of the secondary battery cell is 1000 kgf or more.

[0226] In some embodiments, the maximum expansion force of the secondary battery cell is 2500 kgf or more.

[0227] In some embodiments, the maximum expansion force of the secondary battery cell is 4000 kgf or more.

[0228] Of these, 1 kgf is the gravitational force acting on a 1-kilogram object at sea level at 45 degrees north latitude. 1 kgf is approximately 9.8 Newtons. The expansion force of the secondary battery cell is sensed by pressure sensors in clamps placed on both sides of the large surface of the polarity of the secondary battery cell.

[0229] Conventional current collectors are prone to rupture due to the high expansion force of secondary batteries, causing safety incidents and limiting further improvement of the electrochemical performance of secondary batteries. The current collector provided by the embodiment of the present invention possesses excellent tensile strength and elongation at break, and can be applied to secondary batteries with high expansion force, which is advantageous for further improving the energy density of secondary batteries.

[0230] This application does not particularly limit the type of secondary battery, and for example, the secondary battery may be a lithium-ion battery. Typically, a secondary battery includes a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the secondary battery, active ions are repeatedly inserted into and removed from the positive electrode and the negative electrode, and the electrolyte plays a role in conducting active ions between the positive electrode and the negative electrode. This application does not particularly limit the type of electrolyte, and can be selected according to actual needs. For example, the electrolyte may be at least one selected from a solid electrolyte and a liquid electrolyte (i.e., an electrolyte solution). In secondary batteries employing an electrolyte solution, and in some secondary batteries employing a solid electrolyte, a separator film may be further included, which is placed between the positive electrode and the negative electrode and serves to isolate them.

[0231] [Positive electrode piece] In some embodiments, the positive electrode piece includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0232] The positive electrode current collector may be a metal foil or a composite current collector. Copper foil can be used as an example of a metal foil. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0233] The positive electrode film layer typically comprises a positive electrode active material, a selective adhesive, and a selective conductive agent. The positive electrode film layer is typically formed by applying a positive electrode slurry to the positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, a selective conductive agent, a selective adhesive, and any other components in a solvent and stirring uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP). As an example, the adhesive used for the positive electrode film layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. As an example, the conductive agent used in the positive electrode film layer includes one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0234] The above-mentioned positive electrode active material can be a positive electrode active material for secondary batteries known in this field.

[0235] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and modified compounds thereof. Examples of the lithium transition metal oxide include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. As an example of the lithium-containing phosphate, it may include, but is not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and modified compounds thereof.

[0236] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material used in the lithium-ion battery may include one or more of lithium transition metal oxides having the general formula Li a Ni b Co c M d O e A f and modified compounds thereof. 0.8 ≦ a ≦ 1.2, 0.5 ≦ b < 1, 0 < c < 1, 0 < d < 1, 1 ≦ e ≦ 2, 0 ≦ f ≦ 1, M is one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is one or more selected from N, F, S, and Cl.

[0237] In some embodiments, as an example, the positive electrode active material used in the lithium-ion battery is LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 It may contain one or more of O2, LiFePO4, and LiMnPO4.

[0238] In this application, each of the modified compounds for the above-mentioned cathode active materials can be used to perform doping modification and / or surface coating modification on the above-mentioned cathode active materials.

[0239] [Electrolyte] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0240] The types of electrolyte salts mentioned above are not particularly limited and can be selected according to actual needs.

[0241] If the secondary battery of this application is a lithium-ion battery, as an example, the electrolyte salt may include one or more of the following: lithium hexafluoride phosphate (LiPF6), lithium tetraborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoride arsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxaletborato (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatriate (LiDFOP), and lithium tetrafluorooxalatriate (LiTFOP).

[0242] The type of solvent mentioned above is not particularly limited and can be selected according to actual needs. In some examples, the solvent may include, for instance, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0243] In some embodiments, the electrolyte further selectively includes additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives that can improve specific performance of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high-temperature performance of the secondary battery, and additives that improve the low-temperature output performance of the secondary battery.

[0244] [Separator film] This application does not impose any special restrictions on the type of separator film, and any known porous separator film having good chemical and mechanical stability can be selected.

[0245] In some embodiments, the material of the separator film may include one or more of the following: glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film may be a single-layer film or a multilayer composite film. If the separator film is a multilayer composite film, the materials of each layer may be the same or different.

[0246] In some embodiments, the positive electrode piece, the separator film, and the negative electrode piece can form an electrode assembly by a winding process or a lamination process.

[0247] In some embodiments, the secondary battery may include an outer packaging. This outer packaging is used to enclose the electrode assembly and electrolyte.

[0248] In some embodiments, the outer packaging may be a rigid casing, such as a rigid plastic casing, an aluminum casing, or a steel casing. The outer packaging may also be a pouch, such as a bag-shaped pouch. The material of the pouch may be one or more of the following plastics: polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0249] This application does not impose any particular restrictions on the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 5 shows a rectangular secondary battery 5 as an example.

[0250] In some embodiments, as shown in Figure 6, the outer packaging may include a casing 51 and a cover plate 53. The casing 51 may include a base plate and side plates connected to the base plate, with the base plate and side plates surrounding each other to form a housing cavity. The casing 51 has an opening that communicates with the housing cavity, and the cover plate 53 is used to cover the opening to seal the housing cavity. The positive electrode piece, negative electrode piece, and separator film can be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed in the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and can be adjusted according to the needs.

[0251] The method for manufacturing the secondary battery of the present invention is known. In some embodiments, a secondary battery may be formed by assembling a positive electrode piece, a separator film, a negative electrode piece, and an electrolyte. For example, an electrode assembly may be formed by winding or laminating the positive electrode piece, a separator film, and a negative electrode piece, the electrode assembly may be placed in an outer package, the electrolyte may be injected after drying, and a secondary battery may be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0252] In some embodiments of the present invention, the secondary battery may be assembled into a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0253] Figure 7 is a schematic diagram of an example battery module 4. As shown in Figure 7, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, they may be arranged according to any other method. Furthermore, the multiple secondary batteries 5 may be fixed by fastening members.

[0254] Selectively, the battery module 4 may further include an outer casing having a housing space, in which a plurality of secondary batteries 5 are housed.

[0255] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0256] Figures 8 and 9 are schematic views of a battery pack 1 as an example. As shown in Figures 8 and 9, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper case 2 and a lower case 3. The upper case 2 is covered on the lower case 3 and is used to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box according to any method.

[0257] Electrical equipment The present application further provides an electrical device, which includes at least one of the secondary battery, battery module or battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source of the electrical device, or may be used as an energy storage unit of the electrical device. The electrical device may be a mobile device (such as a mobile phone, tablet computer, notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, hybrid electric vehicle, plug-in hybrid electric vehicle, electric bicycle, electric scooter, electric golf cart, electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0258] The electrical device can select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0259] Figure 10 is a schematic view of an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the needs of high output and high energy density of the electrical device, a battery pack or a battery module can be adopted.

[0260] Another example of the electrical device may be a mobile phone, a tablet, a notebook computer, etc. The electrical device is usually required to be thin and lightweight, and a secondary battery can be adopted as a power source.

[0261] [Examples] The following examples will explain the content disclosed by this application in more detail. However, since it is obvious to those skilled in the art to make various modifications and changes within the scope of the content disclosed by this application, these examples are for the purpose of illustration only. Unless otherwise specified, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples may be commercially available, or may be synthesized according to ordinary methods, and can be directly used without further treatment. Also, all equipment used in the examples may be commercially available products.

[0262] Example 1 (1) Production of copper foil Dissolve a copper plate or copper wire with a purity of 99.9% or more in a sulfuric acid solution to produce a copper sulfate pentahydrate solution, use it as a copper source, add additives and oxalic acid, and prepare an electroplating solution at 60°C. The additives include gelatin, polyethylene glycol, hydroxyethyl cellulose, and sodium chloride. The pH of the electroplating solution is 3.5. Among them, the concentration of each component is as follows: the copper ion concentration is 45 g / L, the gelatin concentration is 90 mg / L, the polyethylene glycol concentration is 50 mg / L, the hydroxyethyl cellulose concentration is 30 mg / L, the chloride ion concentration is 80 mg / L, and the sodium polydithiodipropanesulfonate concentration is 75 mg / L. The rest is deionized water.

[0263] Using a square wave pulse current waveform, apply the current periodically to act on the polished cathode titanium drum. The area of the titanium drum located in the electroplating solution is 0.3 dm 2 and the rotation speed of the titanium drum is 2 m / min. Apply a pulse current, the current density is 167 A / dm 2 and the duty ratio is 5%, the pulse width is 1 ms, the distance between the cathode and the anode is 20 mm, and the deposition temperature is 60°C. The electroplating time is 224 s, deposit the copper foil on the titanium drum, and the thickness of the copper foil is 6 μm.

[0264] (2) Battery manufacturing Positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and adhesive polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5, and after thorough stirring to achieve a uniform mixture, a positive electrode slurry is obtained. Subsequently, the positive electrode slurry is uniformly applied to the positive electrode current collector, and then dried, cold-pressed, and fractured to obtain a positive electrode piece.

[0265] The negative electrode slurry is prepared by dissolving artificial graphite, a conductive agent (acetylene black), an adhesive (styrene-butadiene rubber (SBR)), and a thickener (carboxymethylcellulose sodium (CMC)) in deionized water, a solvent, in a weight ratio of 90:4:4:2, and mixing them uniformly. Next, the negative electrode slurry is uniformly applied to copper foil, which is the negative electrode current collector, one or more times, and after drying, a negative electrode film sheet is obtained. Then, negative electrode pieces are obtained by cold pressing and splitting.

[0266] In an argon gas-atmosphered glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), fluoroethylene carbonate (FEC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC), which are organic solvents, are uniformly mixed in a mass ratio of 1:2:7, and 12.5 wt% of LiPF6 lithium salt is added and dissolved in the organic solvent. Next, 2.0 wt% of fluoroethylene carbonate, 0.5 wt% of 1,3-propanesultone, and 0.5 wt% of succinic anhydride are added to the above organic solvent as additives, mixed and stirred uniformly to obtain an electrolyte.

[0267] A polypropylene film is used as the separator film.

[0268] An electrode assembly is obtained by sequentially stacking a positive electrode piece, a separator film, and a negative electrode piece, and winding them together, so that the separator film is positioned between the positive electrode piece and the negative electrode piece to separate them. The electrode assembly is then placed in a battery casing, dried, and then injected with electrolyte. A lithium-ion battery is then manufactured through further processes such as chemical conversion and settling.

[0269] Examples 2-8 The manufacturing methods in Examples 2 to 8 are basically the same as those in Example 1, but differ in that the components or concentration of the electrolyte, or the parameters of deposition by pulsed current are changed, as shown in Table 1.

[0270] Example 9 The manufacturing method of Example 9 is basically the same as that of Example 1, but differs in that the mixing ratio of the negative electrode pieces is changed. Specifically, silicon carbon (silicon content 20 wt% to 50 wt%), artificial graphite, acetylene black as a conductive agent, styrene-butadiene rubber (SBR) as an adhesive, and sodium carboxymethylcellulose (CMC) as a thickener are dissolved in deionized water as a solvent in a mass ratio of 10:86:1:1.5:1.5, and after uniform mixing, a negative electrode slurry is produced. Next, the negative electrode slurry is uniformly applied to copper foil, which is a negative electrode current collector, once or multiple times, and after drying, a negative electrode film sheet is obtained. Further cold pressing and division are performed to obtain negative electrode pieces.

[0271] Example 10 Example 10 is basically the same as Example 9, differing in that the components in the negative electrode film layer are kept unchanged, while the blending ratio of each component in the negative electrode film layer is adjusted. Specifically, the blending ratio of the negative electrode film layer is 30:66:1:1.5:1.5 for silicon carbon (negative electrode active material), artificial graphite, acetylene black (conductive agent), styrene-butadiene rubber (SBR) (adhesive), and sodium carboxymethylcellulose (CMC) (thickener).

[0272] Example 11 Example 11 is basically the same as Example 10, but is different in that the crimping density of the negative electrode sheet film layer is adjusted, specifically as shown in Table 4.

[0273] Comparative Example 1 The manufacturing method of Comparative Example 1 is basically the same as that of Example 1, but the electroplating method is changed to deposit with direct current, and the deposition current density is 8.35 A / dm 2 which is different, specifically as shown in Table 1.

[0274] Comparative Example 2 The manufacturing method of Comparative Example 2 is basically the same as that of Example 9, but a conventional copper foil of the prior art is used as the current collector, and its thickness is 6 μm. Under the test conditions of room temperature, sample thickness of 6 ± 0.2 μm, and tensile speed of 50 ± 0.5 mm / min, the tensile strength of the copper foil is 350 MPa and the elongation at break is 6.2%, which is different.

[0275] Comparative Example 3 The manufacturing method of Comparative Example 3 is basically the same as that of Comparative Example 2, but is different in that a preliminary stretching process is added before cold pressing in the manufacturing process of the negative electrode sheet. Specifically, a preliminary stretching drum is added before cold pressing, and the tension of the drum is 400 N to 700 N. By pre-stretching the empty area of the copper foil after coating, the film area is stretched during the cold pressing process, but the empty area is not stretched to avoid the problem of wrinkles occurring.

[0276]

Table 1

[0277] Performance testing (1) Thickness test 20×15 cm 2 samples are taken, and their thickness is calculated using the weighing method. Specifically, the cut sample pieces are placed on an electronic balance and weighed to obtain the weight of the sample pieces. Furthermore, the density ρ of the copper foil is 8.96 g / cm 3Based on this, the volume of the sample piece can be calculated, and since the length and width of the sample piece are known, the thickness of the sample piece can be calculated.

[0278] (2) Mechanical performance test According to GB / T 5230-1995 "Electrolytic Copper Foil," a tensile sample piece with a length L0 of 200 mm and a width of 15 mm was cut. The sample was weighed on a balance and recorded as mass m. A universal testing machine was used to test the tensile performance at 25°C, with the tensile speed set to 50 mm / min.

[0279] Cross-sectional area of ​​the tensile sample The image is JPEG2026524204000003.jpg10170, and of which ρ is 8.96 g / cm³. 3 The unit of m is grams, and the unit of L0 is centimeters.

[0280] The sample is continuously loaded until it breaks, the maximum load F is read from the load cell or tensile curve, and the tensile strength σ is calculated according to Equation I. b Calculate.

[0281] JPEG2026524204000004.jpg22170

[0282] The distance between two lines after the sample has been fractured is L1, which is measured on the sample or read from the tensile curve. L1 can be measured using the linear method or the shift method, and the elongation at fracture δ can be calculated using Equation II.

[0283] JPEG2026524204000005.jpg22170

[0284] (3) Testing of the crystal grain properties of copper foil Cross-sections of copper foil are observed using a combination of electron backscatter diffraction (EBSD) and scanning electron microscopy, with the backscatter diffraction instrument being an Oxford C-Nano+. Inverse pole figure distribution maps are obtained, and the grain size of each crystal is measured. The diameter of the equivalent circle of the crystal grain is defined as the crystal grain size, and distribution statistics are performed on the crystal grain size. Strain is used for fitting, and the particle size corresponding to the peak value is defined as the average particle size of the crystal grains in the copper foil. Numerical statistics are performed on twins using the inverse pole figure, with different colors representing different crystal grain orientations. The red lines inside the crystal grains represent twin grain boundaries and indicate the presence of a twinned structure. The proportion of nanotwin crystal grains is statistically calculated using analysis software that is part of the Oxford C-Nano+ backscatter diffraction instrument. The proportion of equiaxed or near-equilibrium crystal grains is measured using a similar method.

[0285] (4) Maximum surface roughness test The surface of the copper foil is wiped with alcohol, the copper foil is placed flat on a horizontal surface, and a stylus-type roughness tester is placed on the surface of the copper foil. The measuring needle is brought into contact with the surface of the copper foil, and the measuring needle is lightly rubbed along the surface. The roughness of the copper foil is obtained by the measurement taken by the instrument. The test is performed five times on different parts of the copper foil, and the maximum value measured is taken as the maximum surface roughness of the copper foil.

[0286] (5) State of Health (SOH) for crack failures At 25°C, the battery is charged with a constant current of 1C until the voltage reaches 3.8V, then charged again with a constant voltage of 3.8V until the current is ≤0.05C, and then discharged with a constant current of 1C until the voltage reaches 2.5V. This constitutes one charge-discharge cycle. This charge-discharge cycle is repeated, and then it is determined whether or not a crack has occurred inside the battery using electronic computed tomography (CT). If a crack has occurred inside the battery, the battery is disassembled after the failure caused by the crack during the cycle, the negative electrode piece inside the battery is disassembled, a sample is taken from a location where no crack has occurred, the elongation at break of the sample is measured using the method for measuring elongation at break described above, and the SOH value of the battery at this time is obtained by performing a simulation calculation.

[0287] (6) Cycle simulation calculation: A fracture model is established based on finite element analysis, the battery core is modeled using a wound core (JR) after hot pressure welding, the pole tensile curve is input as a mechanical parameter, and finally, the free rebound of the JR size is benchmarked using the expansion force data of the battery core alone and input as a crack model. The state of health (SOH) corresponding to when pole fracture occurs in the battery core during a long cycle is simulated and analyzed, using the criterion that the pole elongation rate under the expansion force of the battery core alone is greater than the pole fracture elongation rate.

[0288] (7) Observation of the tab region after cold pressurization: If wrinkles occur in the empty area of ​​the pole piece, it is determined that wrinkles have occurred in the tab. If the empty area of ​​the pole piece remains flat and there are no abnormal phenomena, it is determined that wrinkles have not occurred in the tab.

[0289] Test results [Table 2]

[0290] [Table 3]

[0291] The test results for the examples and comparative examples are shown in Tables 1 to 3.

[0292] As can be seen from the comparison between the examples and comparative examples, the average particle size of the crystal grains in the copper foil provided by this application is 50 nm to 400 nm, and when calculated based on the total number of crystal grains in the copper foil, the proportion of twinned crystal grains is 60% or more. This combines excellent tensile strength and elongation at break, can reduce the state of health (SOH) value corresponding to battery crack failure, and contributes to battery safety and extending cycle life.

[0293] Figure 1 is a schematic diagram showing the grain size distribution of the copper foil according to Example 1, Figure 2 is a distribution diagram of the inverse pole figure of the electron backscatter diffraction pattern of the copper foil of Example 1, and Figure 3 is a tensile curve diagram of the copper foil of Example 1. Referring to Figures 1 and 2, the average particle size of the crystal grains in the copper foil of Example 1 is 200 nm, the minimum crystal grain size is approximately 10 nm, and based on the total number of crystal grains in the copper foil, the proportion of crystal grains with a particle size of 200 nm or less is 34%, the proportion of crystal grains with a particle size of 200 to 500 nm is approximately 65%, and the proportion of crystal grains with a particle size greater than 500 nm is 2% or less, and the maximum surface roughness of the copper foil is 0.12 μm. Figure 4a shows the X-ray diffraction pattern of the copper foil of Example 2. The crystal plane diffraction intensity of the (111) texture in the copper foil is 80.06% of the sum of the crystal plane diffraction intensities of the (111), (200), (220), (311), and (222) textures in the copper foil. Compared to the copper foil in Comparative Example 1 in Figure 4b, the proportion of the crystal plane diffraction intensity of the (111) texture in the copper foil to the sum of the crystal plane diffraction intensities of the (111), (200), (220), (311), and (222) textures in the copper foil is significantly improved.

[0294] As can be seen from Table 3, when the additives in the electroplating solution simultaneously contain a certain amount of leveling agent, wetting agent, and brightener, the maximum surface roughness of the copper foil can be reduced, and the tensile strength and elongation at break of the copper foil can be further improved at the same time.

[0295] As can be seen from the comparison of Examples 1, 2, and 8, an electroplating solution containing a low concentration of copper ions and a high concentration of additives can further improve the tensile strength and elongation at break of the copper foil compared to an electroplating solution containing a high concentration of copper ions and a low concentration of additives.

[0296] As can be seen from the comparison between Examples 1, 4, and 6 and Example 5, the product of a high peak current density and duty cycle slightly increases the average particle size of the copper foil crystal grains and slightly reduces the mechanical properties, but it is superior to Comparative Example 1.

[0297] [Table 4]

[0298] As can be seen from the comparison between Examples 9-11 and Comparative Example 3, the secondary battery includes a negative electrode piece, the negative electrode piece includes a negative electrode current collector and a negative electrode film layer installed on at least one side of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the tensile elongation at room temperature of the negative electrode piece is 2% or more, and the SOH corresponding to the fracture of the electrode piece of the battery core can be reduced and the battery life can be extended.

[0299] As can be seen from the comparison between Examples 9-11 and Comparative Example 2, when the current collector of this embodiment is used and applied to a secondary battery containing silicon-based material, and the pre-stretching process is canceled when manufacturing the negative electrode piece, no wrinkles occur in the tab, the battery production process is optimized, and production efficiency is improved.

[0300] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any embodiment that has substantially the same configuration as the technical idea and achieves the same function and effect within the scope of the technical proposal of this application is included within the scope of this application. Furthermore, various modifications that can be added to the embodiments and that can be conceived by a person skilled in the art, as long as they do not depart from the gist of this application, as well as other forms that are formed by combining some of the components of the embodiments, are also included within the scope of this application.

Claims

1. A current collector comprising copper foil, wherein the average particle size of the crystal grains in the copper foil is 50 nm to 400 nm, and the proportion of nanotwin crystal grains calculated based on the total number of crystal grains in the copper foil is 60% or more. Current collector.

2. The crystal grains in the copper foil are (1) The average particle size of the crystal grains in the copper foil is 50 nm to 300 nm, (2) Based on the total number of crystal grains in the copper foil, the proportion of crystal grains with a particle diameter of less than 200 nm is 20% to 40%, and the proportion of crystal grains with a particle diameter between 200 nm and 500 nm is 50% to 80%. (3) Based on the total number of crystal grains in the copper foil, the proportion of crystal grains with a particle diameter greater than 500 nm is 5% or less, (4) Based on the total number of crystal grains in the copper foil, the proportion of equiaxed crystal grains or pseudo-equaxed crystal grains is 80% or more, and the ratio a1 of the lengths of the major axis to the minor axis of the equiaxed crystal grains or pseudo-equaxed crystal grains satisfies 1 ≤ a1 < 2, (5) Based on the total number of crystal grains in the copper foil, the proportion of columnar crystal grains is less than 10%, and the ratio a2 of the lengths of the major axis to the minor axis of the columnar crystal grain satisfies a2 > 2, (6) The proportion of the crystal plane diffraction intensity of the (111) texture in the copper foil to the sum of the crystal plane diffraction intensities of the (111) texture, (200) texture, (220) texture, (311) texture, and (222) texture in the copper foil is 60% to 85%. (7) The copper foil has a first surface and a second surface facing each other, and the thickness of the copper foil is H, the region within a thickness range of 0.2H to 0.5H from the first surface of the copper foil is defined as the first region of the copper foil, and the region within a thickness range of 0.2H to 0.5H from the second surface of the copper foil is defined as the second region of the copper foil, wherein the absolute value of the difference between the average particle diameter of the crystal grains in the first region and the average particle diameter of the crystal grains in the second region is 150 nm or less, (8) Based on the total number of crystal grains in the copper foil, the proportion of nanotwin crystal grains is 65% to 90%, and the copper foil satisfies one or more of these characteristics. The current collector according to claim 1.

3. The aforementioned copper foil is (1) The maximum surface roughness of the copper foil is 3 μm or less, (2) The thickness H of the copper foil satisfies 3 μm ≤ H ≤ 15 μm, (3) Under test conditions of room temperature, sample thickness of 6 ± 0.2 μm, and tensile speed of 50 ± 0.5 mm / min, the tensile strength of the copper foil is 600 MPa or more, and the elongation at break of the copper foil is 4% or more. (4) The copper foil is characterized by satisfying one or more of the following characteristics: under test conditions of room temperature, sample thickness of 6 ± 0.2 μm, and tensile speed of 50 ± 0.5 mm / min, the tensile strength of the copper foil is 700 MPa to 1500 MPa, and the elongation at break of the copper foil is 4.5% to 10%. The current collector according to claim 1 or 2.

4. A current collector comprising the current collector described in any one of claims 1 to 3, Pole piece.

5. A feature comprising the polar piece described in claim 4, Secondary battery.

6. The maximum expansion force of the secondary battery cell is characterized by being 1000 kgf or more. The secondary battery according to claim 5.

7. The maximum expansion force of the secondary battery cell is characterized by being 2500 kgf or more. The secondary battery according to claim 5.

8. The maximum expansion force of the secondary battery cell is characterized by being 4000 kgf or more. The secondary battery according to claim 5.

9. The electrode piece is a negative electrode piece, and the negative electrode piece comprises the current collector and a negative electrode film layer installed on at least one side of the current collector, the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprises a silicon-based material, and the tensile elongation at room temperature of the negative electrode piece is 2% or more. A secondary battery according to any one of claims 5 to 8.

10. The negative electrode piece is characterized by having a tensile elongation at room temperature of 3% to 5%. The secondary battery according to claim 9.

11. The compression density of the negative electrode piece is 1.5 g / cm². ３ The above is true, and the cold pressure stretching rate of the negative electrode piece is 0.1% or less. The secondary battery according to claim 9.

12. The cold pressure elongation rate of the negative electrode piece is characterized by being 0.06% to 0.1%. The secondary battery according to claim 11.

13. The compression density of the negative electrode piece is 1.5 g / cm². ３ ~2.0 g / cm ３ Characterized by, The secondary battery according to claim 9 or 10.

14. Based on the total mass of the negative electrode film layer, the mass content of the silicon-based material is characterized by being 5% to 100%. A secondary battery according to any one of claims 9 to 13.

15. Based on the total mass of the negative electrode film layer, the mass content of the silicon-based material is characterized by being 10% to 60%. A secondary battery according to any one of claims 9 to 14.

16. The thickness of the current collector is characterized by being 2 μm to 10 μm. A secondary battery according to any one of claims 9 to 15.

17. A secondary battery comprising any one of claims 5 to 16, Electrical device.

18. A method for manufacturing copper foil, comprising manufacturing the copper foil using an electroplating method, wherein the electroplating method specifically includes periodically applying an electric current to an electroplating solution to reduce and deposit copper ions in the electroplating solution, thereby forming copper foil, wherein the average particle size of the crystalline particles in the copper foil is 50 nm to 400 nm, and the proportion of nanotwin crystal grains, calculated based on the total number of crystalline grains in the copper foil, is 60% or more. Manufacturing method.

19. The current is a pulsed current, and the pulsed current is characterized by including one or more types of square wave pulsed current, sinusoidal wave pulsed current, triangular wave pulsed current, and sawtooth wave pulsed current. The manufacturing method according to claim 18.

20. The electroplating solution contains an additive, and the additive is characterized by containing one or more of a leveling agent, a wetting agent, and a brightener. The manufacturing method according to claim 18 or 19.

21. The additive is characterized by comprising a leveling agent, a wetting agent, and a glossing agent. The manufacturing method according to any one of claims 18 to 20.

22. The aforementioned electroplating solution is (1) The concentration of the leveling agent in the electroplating solution is 20 mg / L to 300 mg / L, (2) The concentration of the leveling agent in the electroplating solution is 50 mg / L to 150 mg / L, (3) The concentration of the wetting agent in the electroplating solution is 10 mg / L to 200 mg / L, (4) The concentration of the wetting agent in the electroplating solution is 30 mg / L to 100 mg / L, (5) The concentration of the brightener in the electroplating solution is 10 mg / L to 200 mg / L, (6) The concentration of copper ions in the electroplating solution is 30 g / L to 100 g / L, (7) The concentration of copper ions in the electroplating solution is 45 g / L to 75 g / L, (8) The concentration of chloride ions in the electroplating solution is 10 mg / L to 80 mg / L, (9) The electroplating solution has a pH of 2.5 to 4.4, and is characterized by satisfying one or more of these conditions. The manufacturing method according to claim 20 or 21.

23. The leveling agent comprises one or more of gelatin and Janus green; the wetting agent comprises one or more of hydroxyethylcellulose and polyethylene glycol; and the glossing agent comprises one or more of sodium polydithiodipropanesulfonate, sodium 3-mercapto-1-propanesulfonate, and thiourea. The manufacturing method according to any one of claims 20 to 22.

24. The aforementioned wetting agent is characterized by comprising hydroxyethylcellulose and polyethylene glycol. The manufacturing method according to any one of claims 20 to 23.

25. The mass concentration ratio of the copper ions to the leveling agent is 500:1 to 4500:1, and / or The mass concentration ratio of the copper ions to the brightener is characterized by being 300:1 to 6000:

1. The manufacturing method according to any one of claims 22 to 24.

26. The electroplating solution is characterized by containing gelatin at a concentration of 20 mg / L to 150 mg / L, polyethylene glycol at a concentration of 15 mg / L to 100 mg / L, hydroxyethylcellulose at a concentration of 10 mg / L to 80 mg / L, sodium polydithiodipropanesulfonate at a concentration of 15 mg / L to 150 mg / L, copper ions at a concentration of 45 g / L to 90 g / L, and chloride ions at a concentration of 10 mg / L to 80 mg / L. The manufacturing method according to any one of claims 20 to 25.

27. The peak current density of the pulsed current is I, and its unit is A / dm ２ The current duty cycle of the pulse current is s, and the peak current density I and the duty cycle s are 2 A / dm ２ ≦I×s≦18A / dm ２ A feature that satisfies the following conditions: The manufacturing method according to any one of claims 19 to 26.

28. The aforementioned electroplating method is (1) The peak current density I of the pulse current is 3.3 A / dm ２ ≦I≦333A / dm ２ The conditions must be met, (2) The duty cycle s of the pulse current satisfies 2% ≤ s ≤ 50%, (3) The pulse width of the pulse current is 1 ms to 50 ms, (4) The distance between the cathode electrode and the anode electrode is 15 mm to 20 mm, (5) The temperature of the deposition is 45°C to 60°C, (6) The settling time is 80 s or more, and the product is characterized by satisfying one or more of these conditions. The manufacturing method according to any one of claims 19 to 27.

29. Specifically, the electroplating method includes periodically applying a pulsed current to an electroplating solution to reduce and deposit copper ions in the electroplating solution. Among them, the peak current density I of the pulsed current is 100 A / dm ２ ≦ I ≦ 180 A / dm ２ satisfies the condition, the duty ratio s of the pulsed current satisfies 2% ≦ s ≦ 10%, and the deposition time is 80 s to 250 s, which is characterized by The manufacturing method according to any one of claims 19 to 28.

30. The above manufacturing method is characterized by being a continuous production method. The manufacturing method according to any one of claims 18 to 29.

31. A copper foil, wherein the copper foil is manufactured by the manufacturing method described in any one of claims 18 to 30. copper foil.

32. The maximum width of the copper foil is 1.5 meters or more, and / or the maximum length of the copper foil is 10,000 meters or more. The copper foil according to claim 31.

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