Copper foil and preparation method therefor, lithium battery copper foil, current collector, electrode sheet, battery and electric device

Abstract

The present invention relates to a copper foil and a preparation method therefor, a lithium battery copper foil, a current collector, an electrode sheet, a battery, and an electric device. The copper foil has a first surface and a second surface opposite to each other. The glossiness of the first surface is Gs1, and the glossiness of the second surface is Gs2, wherein Gs1>Gs2. The main diameter of a crystal grain fitting ellipse of a cross-sectional crystal structure between the first surface and the second surface is denoted as ΦED, with the unit of μm, and ΦED satisfies: ΦED = 2*sqrt(a2+b2), and ΦED is 0.1-6.5 μm, wherein a and b are respectively a long radius and a short radius obtained by fitting an ellipse. The copper foil exhibits both a high tensile strength and a high elongation, which can reduce the fracturing and wrinkling of the copper foil during the manufacturing process and the manufacturing and use process of the battery, and improves the cycling performance and safety of the battery.

Description

Copper foil and its preparation methods, lithium battery copper foil, current collectors, electrodes, batteries and electrical devices Technical Field

[0001] This invention relates to the field of battery technology, and particularly to copper foil and its preparation method, lithium battery copper foil, current collector, electrode, battery and electrical device. Background Technology

[0002] Lithium batteries, as a green and environmentally friendly energy storage device, have advantages such as high energy density, excellent cycle performance, and high safety. They have become a key support for industries such as electronic devices, power tools, large-scale energy storage, and new energy vehicles, and are an important basic technology for achieving the "dual carbon" goal.

[0003] Lithium-ion battery copper foil, serving as the carrier of the negative electrode active material and the collector and transporter of the anode electron flow, is a key auxiliary material in lithium-ion battery components. Depending on the application, lithium-ion battery copper foil can be divided into two main categories: those for power batteries and those for non-power batteries (such as 3C products and energy storage). Against the backdrop of global carbon emission reduction, the rapid development of new energy industries such as new energy vehicles and photovoltaics has been promoted, driving a surge in demand for lithium-ion battery copper foil.

[0004] With the rapid updates and iterations of new energy technologies and electronic equipment, higher requirements have been placed on the performance and safety of lithium-ion batteries, which are the core energy storage systems. Similarly, this has intensified the demand for high-performance lithium battery copper foil. Tensile strength and elongation are important performance indicators of lithium battery copper foil, but traditional lithium battery copper foil is difficult to achieve both high tensile strength and high elongation, and improvements are urgently needed.

[0005] Summary of the Invention

[0006] Based on this, the present invention provides a copper foil and its preparation method, a lithium battery copper foil, a current collector, an electrode, a battery, and an electrical device. The copper foil has both high tensile strength and high elongation, and can be used as a lithium battery copper foil to improve battery performance.

[0007] The technical solution is as follows:

[0008] A copper foil having opposing first and second surfaces, the first surface having a gloss level of Gs1 and the second surface having a gloss level of Gs2, where Gs1 > Gs2. The principal diameter of the grain-fitted ellipse of the cross-sectional crystal structure between the first and second surfaces is denoted as Φ. ED The unit is μm, the Φ ED satisfy:

[0009] Φ ED =2*sqrt(a 2 +b 2 ), and Φ EDIts range is 0.1μm to 6.5μm;

[0010] Where a and b are the major and minor radii obtained by fitting the ellipse, respectively.

[0011] In one embodiment, the uniformity of the grain structure in the copper foil is denoted as Γ. GM The unit is μm, the Γ GM satisfy:

[0012] And Γ GM The range is 0.04μm to 0.30μm;

[0013] Where n is the number of grains.

[0014] In one embodiment, the proportion of twin grain boundaries in the copper foil grain structure is 55% to 75%.

[0015] In one embodiment, the proportion of twinned grain regions in the copper foil grain structure is ≥95%.

[0016] In one embodiment, the tensile strength of the copper foil is 30 kgf / mm² at room temperature. 2 ~40kgf / mm 2 .

[0017] In one embodiment, the copper foil has a breaking elongation of ≥8% at room temperature.

[0018] In one embodiment, the ratio of the Vickers hardness to the elongation at break of the copper foil is ψ, where ψ < 10.

[0019] The present invention also provides a method for preparing the copper foil as described above, the technical solution of which is as follows:

[0020] A method for preparing copper foil as described above includes the following steps:

[0021] The copper foil is prepared by electrolysis, wherein the electrolyte used in the electrolysis method comprises the following components:

[0022] Copper ions 70g / L~110g / L, sulfuric acid 90g / L~130g / L, chloride ions 10ppm~30ppm, brightener 10ppm~90ppm, leveling agent 2ppm~25ppm and leveling agent 1ppm~40ppm;

[0023] The brightening agent includes sulfur-containing compounds, the leveling agent includes nitrogen-containing compounds, and the positioning agent includes polyether compounds and nitrogen-containing heterocyclic compounds.

[0024] In one embodiment, the sulfur-containing compound includes one or more of sodium dithiodipropane sulfonate, sodium 3-mercapto-1-propane sulfonate, isothiourea propane sulfonate inner salt, and sodium 3-(benzothiazol-2-mercapto)-propane sulfonate.

[0025] In one embodiment, the nitrogen-containing compound includes one or more of collagen, gelatin, 2-amino-4-methylbenzothiazole, and 2-mercaptopyridine.

[0026] In one embodiment, the positioning agent is a compound of a polyether compound and a nitrogen-containing heterocyclic compound in a concentration ratio of 1:(1-5).

[0027] In one embodiment, the polyether compound includes one or more of polyethylene glycol and polypropylene glycol.

[0028] In one embodiment, the molecular weight of polyethylene glycol is 4000 to 8000.

[0029] In one embodiment, the nitrogen-containing heterocyclic compound includes polyvinylpyrrolidone.

[0030] In one embodiment, the temperature of the electrolyte is 40°C to 70°C.

[0031] In one embodiment, the current applied during the electrolysis process is 15,000A to 60,000A.

[0032] This invention also provides applications of the above-mentioned copper foil, the technical solutions of which are as follows:

[0033] A lithium-ion battery copper foil, comprising the copper foil as described above or the copper foil prepared according to the copper foil preparation method described above.

[0034] In one embodiment, the lithium-ion battery copper foil further includes a first anti-oxidation layer and a second anti-oxidation layer, wherein the first anti-oxidation layer is stacked on a first surface of the copper foil, and the second anti-oxidation layer is stacked on a second surface of the copper foil.

[0035] In one embodiment, the first anti-oxidation layer and the second anti-oxidation layer each independently comprise one or more of chromic anhydride, glucose, and nitride.

[0036] A current collector comprising lithium-ion battery copper foil as described above.

[0037] An electrode comprising a current collector as described above.

[0038] A battery comprising the electrodes as described above.

[0039] An electrical device comprising a battery as described above.

[0040] The present invention has at least the following beneficial effects:

[0041] Let Φ be the principal diameter of the grain fitting ellipse in the crystal structure of the copper foil interface. ED When Φ ED When the grain size is less than 0.1 μm, the grain size is too small, the grain boundary density increases, the tensile strength increases but the plastic deformation decreases and the elongation decreases; conversely, when Φ... ED A grain size greater than 6.5 μm results in excessively large grains, reduced grain boundary density, and difficulty in accommodating the movement and accumulation of numerous dislocations within the limited space of the crystal. This leads to increased internal stress, decreased tensile strength, and an increased risk of tearing and band breakage during copper foil manufacturing and electrode preparation. The copper foil provided by this invention has a Φ... ED With a thickness of 0.1μm to 6.5μm, it can significantly improve the elongation of copper foil, giving it both high tensile strength and high elongation. This can reduce the occurrence of foil breakage and / or wrinkling during copper foil manufacturing and / or during cell manufacturing and use, thereby improving the cycle life and safety of the battery. Attached Figure Description

[0042] Figure 1 is an EBSD photograph of the cross-section of the copper foil prepared in Example 1;

[0043] Figure 2 is a hard indentation photograph of the first glossy surface (first surface, deposition surface) of the copper foil prepared in Example 2;

[0044] Figure 3 shows an EBSD photograph of the cross-section of the copper foil prepared in Comparative Example 1. Detailed Implementation

[0045] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0047] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0048] In this invention, the terms "preferredly," "more preferably," "better," and "even better" refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention. That is, in this invention, "preferredly," "more preferably," "better," and "even better" are merely descriptions of more effective implementations or examples, but do not constitute a limitation on the scope of protection of the invention.

[0049] In this invention, terms such as "further," "even more," and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0050] In this invention, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this invention, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0051] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0052] Unless otherwise specified, all steps of this invention may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0053] Unless otherwise stated, a singular term may include a plural term and should not be understood as having a quantity of one.

[0054] In this invention, "above" or "below" both include the number itself. For example, "below 1" includes 1.

[0055] In this invention, room temperature refers to 0℃ to 40℃, including but not limited to 10℃ to 40℃, or further to 20℃ to 30℃.

[0056] Tensile strength and elongation are important performance indicators for lithium-ion battery copper foil. Traditional lithium-ion battery copper foil has a tensile strength of 300MPa to 400MPa, which is already quite high, but its elongation is only between 4% and 8%. However, in the downstream lithium-ion battery industry, the thickness requirements for copper foil are becoming increasingly thinner, and the coating speed is becoming increasingly faster. Simultaneously, during cell manufacturing processes such as coating, rolling, and baking, the copper foil is exposed to high temperature and high pressure environments. This necessitates copper foil with higher elongation to prevent dents, wrinkles, or breakage during cell manufacturing, thus reducing production efficiency. Furthermore, lithium-ion batteries require expansion and contraction of active materials during charging and discharging. High-elongation copper foil can prevent active material from falling off and breaking during the expansion and contraction processes caused by charging and discharging, thereby increasing internal resistance and reducing battery capacity, cycle life, and safety.

[0057] To address the problem that traditional lithium-ion battery copper foils struggle to achieve both high tensile strength and high elongation, this invention provides a copper foil that combines high tensile strength and high elongation, which can be used as lithium-ion battery copper foil to improve battery performance.

[0058] The technical solution is as follows:

[0059] A copper foil having opposing first and second surfaces, the first surface having a gloss level of Gs1 and the second surface having a gloss level of Gs2, where Gs1 > Gs2. The principal diameter of the grain-fitted ellipse of the cross-sectional crystal structure between the first and second surfaces is denoted as Φ. ED The unit is μm, the Φ ED satisfy:

[0060] Φ ED =2*sqrt(a 2 +b 2 ), and Φ ED Its range is 0.1μm to 6.5μm;

[0061] Where a and b are the major and minor radii obtained by fitting the ellipse, respectively.

[0062] When the principal diameter of the grain-fitting ellipse in the cross-sectional crystal structure of the copper foil surface interface is less than 0.1 μm, the small grain size of the copper foil leads to increased grain boundary density, resulting in increased strength but decreased plastic deformation and elongation. Grain boundaries, as a common planar defect in polycrystalline materials, can act as both a nucleation source and an obstacle to defect movement. The essence of fine-grain strengthening in metallurgy is the interaction between grain boundaries and dislocations, hindering dislocation movement and improving strength while maintaining good plastic deformation capacity. This process does not change the overall properties of the grain boundaries, but the disordered structure of the grain boundaries makes it difficult for dislocations to slide along them. However, there exists a critical grain size. When the grain size is smaller than the critical grain size, the effect of grain boundaries inhibits the activation of dislocation sources, leading to insufficient movable dislocation sources during the deformation process, making slip difficult and resulting in reduced plastic deformation. Furthermore, when the principal diameter of the grain fitting ellipse on the surface of the copper foil is greater than 6.5 μm, the grain size of the copper foil is too large, the grain boundary density is reduced, and the limited space within the crystal is insufficient to accommodate the movement and pile-up of a large number of dislocations, resulting in increased internal stress, decreased strength, and increased risk of tearing and breakage during the manufacturing and use of the copper foil. The copper foil provided by this invention has a Φ ED With a thickness of 0.1μm to 6.5μm, it can significantly improve the elongation of copper foil, giving it both high tensile strength and high elongation, and reducing the occurrence of copper foil breakage and / or wrinkling during copper foil manufacturing and / or during cell manufacturing and use.

[0063] Furthermore, research has shown that the elongation of copper foil is positively correlated with its thickness, and that for every 1% increase in the elongation at break of copper foil, the cycle stability of the battery can be improved by approximately 5%. If the elongation of copper foil can be further improved while reducing its thickness, it will open up a new track for the copper foil and battery industries. According to the solution of this invention, the elongation of copper foil can be significantly improved, thereby significantly improving the cycle performance and safety of the battery.

[0064] In one embodiment, the uniformity of the grain structure in the copper foil is denoted as Γ. GM The unit is μm, the Γ GM satisfy:

[0065] And Γ GM The range is 0.04μm to 0.30μm;

[0066] Where n is the number of grains.

[0067] Γ GMThe ratio of the area to the perimeter of the ellipse fitted to the grains of a copper foil cross-section is used to quantify grain morphology and crystal structure. When metallic materials are subjected to tensile stress, from elastic deformation to plastic deformation and ultimately fracture, materials with homogeneous and heterogeneous crystal structures may have similar tensile strength. However, heterogeneous crystal materials experience early fracture during stretching; that is, compared to heterogeneous crystal materials, homogeneous crystal materials have a longer tensile plateau period. This is partly due to the presence of coarse and fine grains with significantly different sizes within heterogeneous crystal materials. As strain increases, the low-angle grain boundaries within the coarse grains gradually increase, and the lattice distortion in the regions adjacent to the coarse and fine grains increases. In contrast, in homogeneous crystal structures, the number of lattice distortions increases with increasing strain, but the distribution remains relatively uniform. Similarly, with increasing strain, stress concentration occurs on the uneven surfaces of fine-grained regions in non-uniform microstructures. As the load increases, slip increases, and uneven regions are more distributed near the surfaces of coarse and fine grains. In contrast, during the tensile process of uniform microstructures, the formation of uneven regions is more random and dispersed. Therefore, during deformation, regions with the greatest differences in non-uniform crystal structures are more prone to strain concentration and crack development, leading to earlier fracture. On the other hand, the slip system between adjacent grains in uniform crystalline materials is strain-compatible, and dislocations are more easily transferred between pairs of grains. Conversely, in non-uniform crystalline structures, dislocations cannot transfer between grains, or their movement is hindered. Therefore, under the same macroscopic strain conditions, the dislocation movement on both sides of a local region in a non-uniform crystalline material is asynchronous, resulting in significant variations in the ability to coordinate strain, leading to non-uniform deformation, asynchronous strain, and fracture, ultimately reducing the plastic deformation capacity.

[0068] Research has shown that when the uniformity of the grain structure of the copper foil cross-section is Γ GM <0.04μm, the grain boundary surface is uneven, which easily leads to stress concentration. The increased grain boundary density inhibits the activation of dislocation sources, hinders slip, and results in reduced plastic deformation and lower elongation; the uniformity of the grain structure of the copper foil cross-section is Γ GM Grain sizes >0.30 μm are too large, resulting in lower grain boundary density, increased internal stress, and limited space for dislocations within the crystal, leading to decreased strength and causing tearing and breakage of the copper foil during manufacturing and use. The copper foil described in this invention has a [missing information - likely a specific characteristic]. GM The thickness is 0.04μm to 0.30μm, including but not limited to 0.04μm, 0.06μm, 0.08μm, 0.10μm, 0.15μm, 0.20μm, 0.25μm or 0.30μm. Copper foil that meets this requirement has both high tensile strength and high elongation, which can prevent the copper foil from tearing and breaking during manufacturing and use.

[0069] Furthermore, in crystal structures, twin grains are closely related to the mechanical properties of metallic materials. Since twins can react with dislocations at the interface, they can effectively hinder dislocation movement. Moreover, as the slip surface of face-centered cubic (FCC) stacked metallic materials, dislocations can not only move on the twin interface, but coherent grain boundaries can also provide storage space for dislocations generated during deformation, thereby effectively improving the elongation of copper foil.

[0070] In one embodiment, the proportion of twin grain boundaries in the grain structure of the copper foil of the present invention is 55% to 75%, including but not limited to 55%, 60%, 65%, 70% or 75%. Copper foil that meets this requirement has both high tensile strength and high elongation, and can avoid tearing and breakage of copper foil during manufacturing and use.

[0071] In one embodiment, the proportion of twinned grain regions in the copper foil grain structure of the present invention is ≥95%, including but not limited to 95%, 96%, 97%, 98% or 99%. Copper foil that meets this requirement has both high tensile strength and high elongation, and can avoid tearing and breakage of copper foil during manufacturing and use.

[0072] In one embodiment, under room temperature conditions (e.g., 0°C to 40°C, further 10°C to 40°C, and even further 25°C), the tensile strength of the copper foil is 30 kgf / mm². 2 ~40kgf / mm 2 including but not limited to 30 kgf / mm 2 32kgf / mm 2 34kgf / mm 2 36kgf / mm 2 38kgf / mm 2 Or 40kgf / mm 2 Copper foil that meets this requirement can reduce the occurrence of foil breakage during the manufacturing process and cell fabrication, thereby improving the efficiency of copper foil manufacturing and battery production, and enhancing battery capacity and safety performance.

[0073] In one embodiment, under room temperature conditions (e.g., 0°C to 40°C, further 10°C to 40°C, and even further 25°C), the elongation at break of the copper foil is ≥8%, including but not limited to 8%, 10%, 12%, 15%, 18%, or 20%. If the elongation at break of the copper foil is <8%, and it is used as a current collector for lithium-ion batteries, when a material with a high expansion rate is selected as the active material for the battery, the electrode may crack or break during the charging and discharging process of the lithium secondary battery due to insufficient elongation with the expansion of the cell volume, increasing internal resistance and reducing the battery's capacity, cycle life, and safety.

[0074] Furthermore, from the perspective of the microstructure and deformation mechanism of materials, in metallic materials, hardness is mainly determined by the hindering effect of grain interfaces and the resistance to dislocation movement. If the ratio of Vickers hardness to fracture elongation of copper foil is too high, the hardness of the metallic material is high. The interaction between grain boundaries and dislocations is also affected. The disordered structure of grain boundaries makes it difficult for dislocations to slide along them, and the resistance to grain boundary and dislocation movement is greater. At the same time, grain boundaries inhibit the activation of dislocation sources, making it more difficult for the material to undergo plastic deformation under stress, resulting in a decrease in elongation.

[0075] In one embodiment, the Vickers hardness of the copper foil of the present invention is 40Hv or higher, and further, the Vickers hardness of the copper foil of the present invention is 45Hv or higher, which has high hardness and wear resistance.

[0076] In one embodiment, the ratio of the Vickers hardness to the elongation at break of the copper foil of the present invention is ψ (e.g., if the Vickers hardness of the copper foil is 48.7 Hv and the elongation at break is 15.7%, then ψ is 48.7 / 15.7 = 3.1), ψ < 10, including but not limited to 1, 2, 3, 4, 5, 6, 7, 8 or 9. Copper foil that meets this requirement has both high tensile strength and high elongation, which can prevent tearing and breakage of the copper foil during manufacturing and use.

[0077] In one embodiment, the thickness of the copper foil is 6 μm to 12 μm, more specifically 8 μm to 10 μm. Understandably, for electrolytic copper foil, the thickness can be controlled by the current and linear velocity during the preparation process.

[0078] Understandably, this invention does not impose any special limitations on the method for analyzing the crystal structure of copper foil cross-sections; conventional characterization and analysis methods in the art are sufficient. Optionally, this invention employs backscattered diffraction (EBSD) testing to characterize the grain structure of the copper foil. Further, a C-Swift EBSD detector manufactured by Oxford Instruments, UK, is used to observe and characterize the crystal structures of the samples in each embodiment and comparative example. To clearly observe the grain boundary contours of the samples, the cross-sections are pre-polished using an ion mill for 20 minutes. Further, In this context, 'n' represents the number of grains detected by EBSD on the copper foil cross-section. In one embodiment of this invention, it is the number of grains in the entire field of view at a magnification of 3000. The number can be directly detected and counted using Aztec Crystal software. In short, it is the total number of grains seen in the field of view at a magnification of 3000 when observing the copper foil cross-section.

[0079] Understandably, this invention does not impose any special limitations on the testing methods for the tensile strength and elongation of copper foil; conventional testing methods in the art can be used. Optionally, in the embodiments of this invention, the tensile strength and elongation of the samples are tested using a HY-0230 universal testing machine manufactured by Shanghai Hengyi Precision Instruments Co., Ltd., according to the testing methods of GB / T29847-2013, at room temperature and a strain rate of 50 mm / min.

[0080] Understandably, this invention does not impose any special limitations on the Vickers hardness testing method for copper foil; conventional testing methods in the art can be used. Optionally, in the embodiments of this invention, the Vickers hardness (HV) test is conducted according to the test method of GB / T 4340.1-2009, using a touchscreen micro Vickers hardness tester manufactured by Shanghai Taishuo Testing Instruments Co., Ltd., to test the Vickers hardness value (HV) of the sample at room temperature and under the conditions of applying a pressure of 50g for 5 seconds. The measurement is repeated at five different locations on the sample, and the average value is taken as the final Vickers hardness value (HV) of the sample.

[0081] The present invention also provides a method for preparing the copper foil as described above, the technical solution of which is as follows:

[0082] A method for preparing copper foil as described above includes the following steps:

[0083] The copper foil is prepared by electrolysis, wherein the electrolyte used in the electrolysis method comprises the following components:

[0084] Copper ions 70g / L~110g / L, sulfuric acid 90g / L~130g / L, chloride ions 10ppm~30ppm, brightener 10ppm~90ppm, leveling agent 2ppm~25ppm and leveling agent 1ppm~40ppm;

[0085] The brightening agent includes sulfur-containing compounds, the leveling agent includes nitrogen-containing compounds, and the positioning agent includes polyether compounds.

[0086] The electrolytic deposition process for forming copper foil results in a preferential orientation phenomenon (texture) due to the different growth rates of each crystal facet. From a crystallographic perspective, it is generally believed that textured growth along the (220) plane is beneficial to improving elongation. This invention uses organic composite electrolyte additives to enable the copper sulfate electrolyte to obtain relatively large and uniform grains during the deposition process, which also benefits the improvement of elongation. Specifically, in this invention, a certain proportion of brightener, leveling agent, and positioning agent are added to the electrolyte (or plating solution) as organic additives, which can change the deposition rate of the copper foil and improve its mechanical properties. The brightener is mainly composed of sulfur-containing compounds, whose primary function is to promote the nucleation of copper ions. The leveling agent is mainly composed of nitrogen-containing compounds, which promote face-centered cubic growth of copper foil, making the grains smoother. When organic sulfide brighteners and nitrogen-containing compound (such as nitrogen-containing polymer) leveling agents are used in combination, the copper foil crystal structure becomes smoother and denser, generating a large number of nanocrystalline regions, which enhances the fine grain strengthening effect. The excellent structure of fine grains and nanotwins interacts to improve the tensile strength and elongation of the copper foil. The positioning agent is mainly composed of ether compounds and nitrogen-containing heterocyclic compounds, which can form a more stable and uniform barrier layer, thereby effectively restricting certain growth directions of copper crystals. It interacts with other additives to act uniformly on various parts of the copper foil, making the grains finer and more uniform. In addition, polyether compounds can effectively inhibit grain growth at high temperatures, reduce grain nucleation size, generate more interfaces, absorb and release thermal stress, and improve the stability of copper foil under high-temperature conditions. Understandably, some compounds have multiple functions. For example, 2-amino-4-methylbenzothiazole can be used as both a leveling agent and a positioning agent.

[0087] In one embodiment, the sulfur-containing compound includes one or more of sodium polydisulfide dipropane sulfonate (SPS), sodium 3-mercapto-1-propane sulfonate (MPS), isothiourea propane sulfonate inner salt (UPS), and sodium 3-(benzothiazol-2-mercapto)-propane sulfonate (ZPS). Further, the brightener is a compound of sodium polydisulfide dipropane sulfonate and sodium 3-mercapto-1-propane sulfonate. Even further, the brightener is a compound of sodium polydisulfide dipropane sulfonate and sodium 3-mercapto-1-propane sulfonate at a concentration ratio of (0.5–3):1.

[0088] In one embodiment, the nitrogen-containing compound includes one or more of collagen, gelatin, 2-amino-4-methylbenzothiazole, and 2-mercaptopyridine.

[0089] In one embodiment, the positioning agent is a compound of a polyether compound and a nitrogen-containing heterocyclic compound in a concentration ratio of 1:(1-5).

[0090] In one embodiment, the polyether compound includes one or more of polyethylene glycol (PEG) and polypropylene glycol (PPG). Further, the polyethylene glycol has a molecular weight of 4000 to 8000.

[0091] In one embodiment, the nitrogen-containing heterocyclic compound is polyvinylpyrrolidone (PVP).

[0092] In one embodiment, the leveling agent includes at least polyethylene glycol. The leveling agent is a compound of polyethylene glycol and nitrogen-containing heterocyclic compounds, which can form a more stable and uniform barrier layer, thereby effectively restricting certain growth directions of copper crystals. It interacts uniformly with other additives on various parts of the copper foil, making the grains finer and more uniform, improving the uniformity of the grains, and enabling the copper foil to have both high tensile strength and high elongation. This can prevent the copper foil from tearing and breaking during manufacturing and use.

[0093] In one embodiment, the temperature of the electrolyte is 40°C to 70°C.

[0094] In one embodiment, the current applied during the electrolysis process is 15,000A to 60,000A.

[0095] In one embodiment, the method for manufacturing copper foil as described above includes the following steps:

[0096] Using copper plates and / or copper wires with a purity of 99.8% or higher as raw materials, copper sulfate electrolyte is prepared by dissolving them in sulfuric acid solution under high-temperature air. The electrolyte is then purified through three-stage filtration. An insoluble material is used as the anode, and a cathode roller with a titanium ring as its surface is used as the cathode. The bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte in an electrolytic cell, and electrolysis is performed by constant rotation. The amount of copper foil electrodeposited on the cathode roller surface is controlled according to the cathode current density and the cathode roller rotation speed. After the copper foil is removed from the liquid surface by the roller, it is continuously peeled off from the cathode roller, and after oxidation prevention, drying, and winding, the original foil is formed. The electrolyte contains the following components: copper ions 70 g / L–110 g / L, sulfuric acid 90 g / L–130 g / L, chloride ions 10 ppm–30 ppm, brightener 10 ppm–90 ppm, leveling agent 2 ppm–25 ppm, and leveling agent 1 ppm–40 ppm.

[0097] Understandably, for copper foil prepared by electrolysis, during the preparation process, the deposited surface with high gloss is the rough surface (corresponding to the first surface described in this invention), while the roller surface that is in direct contact with the cathode roller surface and has low gloss is the smooth surface (corresponding to the second surface described in this invention).

[0098] This invention also provides applications of the above-mentioned copper foil, the technical solutions of which are as follows:

[0099] (1) A lithium-ion battery copper foil, comprising the copper foil as described above or the copper foil prepared according to the copper foil preparation method described above. Understandably, the lithium-ion battery copper foil has the advantages of the copper foil described in this invention, with uniform grains, moderate grain size, and both high tensile strength and high elongation, thereby reducing the breakage and wrinkling of the lithium-ion battery copper foil during manufacturing and battery manufacturing and use, and improving the cycle life and safety of the battery.

[0100] In one embodiment, the lithium-ion battery copper foil further includes a first anti-oxidation layer and a second anti-oxidation layer, wherein the first anti-oxidation layer is stacked on a first surface of the copper foil, and the second anti-oxidation layer is stacked on a second surface of the copper foil.

[0101] In one embodiment, the first anti-oxidation layer and the second anti-oxidation layer each independently comprise one or more of chromic anhydride, glucose, and nitrides. It is understood that the first and second anti-oxidation layers of the present invention are independent of each other; therefore, the material and dosage ratio of the first anti-oxidation layer can be the same as or different from those of the second anti-oxidation layer.

[0102] (2) A current collector comprising the lithium-ion battery copper foil as described above. Understandably, the current collector possesses the advantages of the lithium-ion battery copper foil described in this invention, exhibiting both high tensile strength and high elongation, thereby reducing cell breakage and wrinkling during manufacturing and use, and improving battery cycle life and safety. In one example, after cell cycle charging and discharging, the tensile strength of the current collector is 30 kgf / mm². 2 ~40kgf / mm 2 Elongation ≥ 3%.

[0103] (3) An electrode sheet comprising the current collector as described above. Understandably, the electrode sheet has the advantages of the current collector described in this invention, possessing both high tensile strength and high elongation, thereby reducing cell breakage and wrinkling during manufacturing and use, and improving battery cycle life and safety.

[0104] Furthermore, the electrode comprises a first active material layer, a current collector, and a second active material layer stacked together. Even further, the first active material layer comprises at least one or more combinations of graphite-based materials, silicon-based materials, and alloy materials, and the second active material layer comprises at least one or more combinations of graphite-based materials, silicon-based materials, and alloy materials. It is understood that in this invention, the first active material layer and the second active material layer are independent of each other, and the raw materials, dosage ratios, and layer thicknesses used in each can be the same or different, without special limitations.

[0105] In one embodiment, the electrode is an anode electrode.

[0106] (4) A battery comprising the electrodes as described above.

[0107] (5) An electrical device comprising the battery as described above. It is understood that the electrical device is a conventional electrical device in the art, including but not limited to digital products, lighting products, vehicles, etc.

[0108] The present invention will be illustrated by the following specific embodiments.

[0109] 1. The testing method is as follows:

[0110] (1) Backscattered diffraction (EBSD) test: The crystal structure of each example and comparative example sample was observed and characterized using a C-Swift EBSD detector manufactured by Oxford Instruments, UK. To clearly observe the grain boundary contours of the samples, the cross-section was polished for 20 minutes using an ion mill. The magnification was 3000x, where n is the total number of grains observed on the copper foil cross-section at 3000x magnification, a and b are the major and minor radii obtained from the fitted ellipse, respectively, and the average Φ... ED The value refers to the average of the principal diameters of the fitted ellipse of n grains detected under a 3000x field of view.

[0111] (2) Tensile strength and elongation test: According to the test method GB / T29847-2013, the tensile strength and elongation of the samples were tested using a HY-0230 universal testing machine manufactured by Shanghai Hengyi Precision Instruments Co., Ltd., under the conditions of room temperature and strain rate of 50 mm / min. The tensile test specimens were strip specimens with a distance of 50 mm between the clamps. The samples were measured ten times and the average value was taken as the final tensile strength and elongation of the sample. Specifically, the measured tensile strength and elongation were the average values ​​of the transverse and longitudinal directions. Five copper foil strips with a size of 15*100 mm were cut in both the transverse and longitudinal directions. The tensile strength and elongation of the samples were tested under the conditions of room temperature and strain rate of 50 mm / min, and the average value of the ten copper foil strips in both the transverse and longitudinal directions was taken as the final tensile strength and elongation value of the sample.

[0112] (3) Vickers Hardness (HV) Test: According to the test method GB / T4340.1-2009, a touch screen micro Vickers hardness tester manufactured by Shanghai Taishuo Testing Instruments Co., Ltd. was used to test the Vickers hardness (HV) of the sample at room temperature and under the conditions of applying a pressure of 50g for 5s. The sample was measured repeatedly at five different locations and the average value was taken as the final Vickers hardness (HV) of the sample.

[0113] 2. Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0114] Example 1

[0115] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution consisted of 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives. The brightener comprised 40 ppm SPS and 45 ppm MPS, the leveling agent comprised 10 ppm PEG and 20 ppm PVP (PEG molecular weight 4000), and the leveling agent comprised 5 ppm gelatin. These were diluted and added to the copper sulfate electrolyte. The electrolyte temperature was 55℃, and the electrolyte flowed through a pipe at the bottom of the electrolytic cell at a rate of 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0116] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness of the copper foil were tested. The test results are shown in Table 1.

[0117] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil of this embodiment using a scraper, and then rolled and cut to form an anode sheet. Subsequently, the anode sheet and the prepared cathode sheet are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode sheet is <300ppm. The electrolyte of a lithium secondary battery was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 minutes, the elongation was measured. The test results are shown in Table 1.

[0118] Example 2

[0119] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution consisted of 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives. The brightener comprised 45 ppm SPS and 40 ppm MPS, the leveling agent comprised 7 ppm PEG and 25 ppm PVP (PEG molecular weight 4000), and the leveling agent comprised 5 ppm gelatin. These were diluted and added to the copper sulfate electrolyte. The electrolyte temperature was 55℃, and the electrolyte flowed through a 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0120] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken from each roll and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness were tested. The test results are shown in Table 1.

[0121] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil in this embodiment using a scraper, and then rolled and cut to form an anode electrode. Subsequently, the anode electrode and the prepared cathode electrode are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode electrode is <300ppm. The electrolyte of a lithium secondary battery was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 minutes, the elongation was measured. The test results are shown in Table 1.

[0122] Example 3

[0123] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution consisted of 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives. The brightener comprised 45 ppm SPS and 30 ppm MPS, the leveling agent comprised 7 ppm PEG and 25 ppm PVP (PEG molecular weight 4000), and the leveling agent comprised 10 ppm gelatin. These were diluted and added to the copper sulfate electrolyte. The electrolyte temperature was 55℃, and the electrolyte flowed through a 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0124] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken from each roll and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness were tested. The test results are shown in Table 1.

[0125] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil in this embodiment using a scraper, and then rolled and cut to form an anode electrode. Subsequently, the anode electrode and the prepared cathode electrode are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode electrode is <300ppm. The electrolyte for lithium secondary batteries was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 minutes, the elongation was measured. The test results are shown in Table 1.

[0126] Example 4

[0127] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution consisted of 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives. The brightening agent comprised 40 ppm SPS and 40 ppm UPS, the leveling agent comprised 7 ppm PEG and 20 ppm PVP (PEG molecular weight 6000), and the leveling agent comprised 5 ppm collagen. After dilution, these were added to the copper sulfate electrolyte. The electrolyte temperature was 55℃, and the electrolyte flowed through a 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0128] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness of the copper foil were tested. The test results are shown in Table 1.

[0129] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil of this embodiment using a scraper, and then rolled and cut to form an anode sheet. Subsequently, the anode sheet and the prepared cathode sheet are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode sheet is <300ppm. The electrolyte of a lithium secondary battery was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 minutes, the elongation was measured. The test results are shown in Table 1.

[0130] Example 5

[0131] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution contains 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives. The brightener consists of 45 ppm UPS and 40 ppm ZPS; the leveling agent consists of 5 ppm PEG and 20 ppm PVP (PEG molecular weight 8000); and the leveling agent consists of 6 ppm collagen and 3 ppm gelatin. These are diluted and added to the copper sulfate electrolyte. The electrolyte temperature is 55℃, and the electrolyte is pumped through a pipe at the bottom of the electrolytic cell at a flow rate of 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0132] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness of the copper foil were tested. The test results are shown in Table 1.

[0133] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil of this embodiment using a scraper, and then rolled and cut to form an anode sheet. Subsequently, the anode sheet and the prepared cathode sheet are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode sheet is <300ppm. The electrolyte of a lithium secondary battery was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 minutes, the elongation was measured. The test results are shown in Table 1.

[0134] Example 6

[0135] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution consisted of 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives. The brightener comprised 45 ppm ZPS and 35 ppm MPS, the leveling agent comprised 10 ppm PEG and 15 ppm PVP (PEG molecular weight 8000), and the leveling agent comprised 10 ppm gelatin. These were diluted and added to the copper sulfate electrolyte. The electrolyte temperature was 55℃, and the electrolyte flowed through a 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0136] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness of the copper foil were tested. The test results are shown in Table 1.

[0137] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil of this embodiment using a scraper, and then rolled and cut to form an anode sheet. Subsequently, the anode sheet and the prepared cathode sheet are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode sheet is <300ppm. The electrolyte for lithium secondary batteries was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 min, the elongation was measured. The test results are shown in Table 1.

[0138] Comparative Example 1

[0139] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution consisted of 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives, including 25 ppm SPS and 20 ppm MPS as brighteners, 30 ppm PEG (molecular weight 4000) as a leveling agent, and 5 ppm collagen as a leveling agent. After dilution, these were added to the copper sulfate electrolyte. The electrolyte temperature was 55℃, and the electrolyte flowed through a pipe at the bottom of the electrolytic cell at a rate of 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0140] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken from each roll and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness were tested. The test results are shown in Table 1.

[0141] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil in this embodiment using a scraper, and then rolled and cut to form an anode sheet. Subsequently, the anode sheet and the prepared cathode sheet are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode sheet is <300ppm. The electrolyte of a lithium secondary battery was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 minutes, the elongation was measured. The test results are shown in Table 1.

[0142] Comparative Example 2

[0143] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution consisted of 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives. The brightener was 85 ppm SES, the leveling agent was composed of 10 ppm PEG and 20 ppm PVP (PEG molecular weight 4000), and the leveling agent was 7 ppm Janus Green. These were diluted and added to the copper sulfate electrolyte. The electrolyte temperature was 55℃, and the electrolyte flowed through a 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0144] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken from each roll and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness were tested. The test results are shown in Table 1.

[0145] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil in this embodiment using a scraper, and then rolled and cut to form an anode electrode. Subsequently, the anode electrode and the prepared cathode electrode are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode electrode is <300ppm. The electrolyte of a lithium secondary battery was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 minutes, the elongation was measured. The test results are shown in Table 1.

[0146] Comparative Example 3

[0147] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution consisted of 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives. The brightener comprised 60 ppm SES and 20 ppm ZPS, the leveling agent 25 ppm PVP, and the leveling agent 5 ppm collagen and 5 ppm Janus Green. These were diluted and added to the copper sulfate electrolyte. The electrolyte temperature was 55℃, and the electrolyte flowed through a 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0148] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken from each roll and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness were tested. The test results are shown in Table 1.

[0149] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil in this embodiment using a scraper, and then rolled and cut to form an anode electrode. Subsequently, the anode electrode and the prepared cathode electrode are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode electrode is <300ppm. The electrolyte of a lithium secondary battery was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 minutes, the elongation was measured. The test results are shown in Table 1.

[0150] Comparative Example 4

[0151] Copper sulfate electrolyte was prepared by dissolving copper plates and wires with a purity of 99.8% or higher in a sulfuric acid solution at a 1:1 weight ratio with high-temperature air. The electrolyte was then purified through three-stage filtration. An insoluble material was used as the anode, and a cathode roller with a titanium ring as its surface was used as the cathode. The bottom semicircle of the cathode roller was immersed in the copper sulfate electrolyte in the electrolytic cell, and electrolysis was performed under a current of 35000A and constant rotation. The copper sulfate electrolyte contained 85 g / L of Cu. 2+ The electrolyte solution consisted of 105 g / L sulfuric acid, 17 ppm chloride ions, and organic composite electrolyte additives. The brightener comprised 45 ppm SPS and 35 ppm SES, the leveling agent was 25 ppm PEG with a molecular weight of 4000, and the leveling agent was 5 ppm gelatin and 5 ppm Janus Green. These were diluted and added to the copper sulfate electrolyte. The electrolyte temperature was 55℃, and the electrolyte flowed through a pipe at the bottom of the electrolytic cell at a rate of 43 m... 3 A flow rate of / h is supplied to the electrolysis system. After the copper foil is discharged from the liquid by the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution containing chromium anhydride and glucose, dried, wound up, and the original foil is generated. This copper foil is then used as lithium battery copper foil.

[0152] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken from each roll and baked at 150℃ for 10 minutes. The tensile strength, elongation and hardness were tested. The test results are shown in Table 1.

[0153] The first and second active material layers of this embodiment are, by weight, made of 96 parts of commercially available natural graphite, 2 parts of conductive carbon black, 1.5 parts of styrene-butadiene rubber (SBR), 0.5 parts of carboxymethyl cellulose (CMC), and 210 parts of deionized water to form a slurry. The slurry is applied to the two opposing surfaces of the lithium-ion battery copper foil in this embodiment using a scraper, and then rolled and cut to form an anode electrode. Subsequently, the anode electrode and the prepared cathode electrode are wound together in the order of cathode, separator, and anode to form an 18650 single cell and then baked in an oven for 24 hours. The water content of the anode electrode is <300ppm. The electrolyte of a lithium secondary battery was injected into the prepared single cell. After standing, formation, and capacity testing, 10 PCS of 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at 4.2V and discharged at 3.2V, at a 1C charge-discharge rate at room temperature (25℃), and after 3000 charge-discharge cycles, they were disassembled in the empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cycle charging and discharging. After baking at 105℃ for 10 minutes, the elongation was measured. The test results are shown in Table 1.

[0154] The comparative performance data of the above embodiments are shown in Table 1 below.

[0155] Table 1 Performance results of the comparative products in each embodiment

[0156] Figure 1 is an EBSD photograph of the cross-section of the copper foil prepared in Example 1. As can be seen from Figure 1, the twinning region is large, the grain size difference is small, the grain boundaries can effectively hinder dislocation movement, and the elongation is high.

[0157] Figure 2 is a photograph of the first gloss surface hardness indentation of the copper foil prepared in Example 2. As can be seen from Figure 2, the indentation is a straight-edged quadrilateral with a low diagonal length and high hardness.

[0158] Figure 3 shows the cross-sectional EBSD photograph of the copper foil prepared in Comparative Example 1. As can be seen from Figure 3, the grain size difference is large, there are a large number of fine grains in some areas, the grain boundary density is too high, which easily leads to strain concentration and crack development, resulting in low elongation.

[0159] In summary, the copper foil provided by this invention has a moderate grain size, good uniformity, moderate grain boundary density, high tensile strength and high elongation, and high hardness. It can reduce the occurrence of foil breakage and / or wrinkling during the copper foil manufacturing process and / or during the cell manufacturing process and use, thereby improving the cycle life and safety of the battery.

[0160] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0161] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A copper foil, characterized in that, The copper foil has a first surface and a second surface opposite to each other. The gloss of the first surface is Gs1, and the gloss of the second surface is Gs2, where Gs1 > Gs2. Let Φ be the principal diameter of the grain fitting ellipse of the cross-sectional crystal structure between the first surface and the second surface. ED The unit is μm, the Φ ED Satisfy: Φ ED =2*sqrt(a 2 +b 2 ), and Φ ED Its range is 0.1μm to 6.5μm; Where a and b are the major and minor radii obtained by fitting the ellipse, respectively.

2. The copper foil according to claim 1, characterized in that, Let the uniformity of the grain structure in the copper foil be Γ. GM The unit is μm, the Γ GM satisfy: And Γ GM The range is 0.04μm to 0.30μm; Where n is the number of grains.

3. The copper foil according to claim 1, characterized in that, The copper foil satisfies one or more of the following (1) to (2): (1) In the grain structure, the proportion of twin grain boundaries is 55% to 75%; (2) In the grain structure, the proportion of twin grain regions is ≥95%.

4. The copper foil according to any one of claims 1 to 3, characterized in that, The copper foil satisfies one or more of the following (1) to (2): (1) At room temperature, the tensile strength of the copper foil is 30 kgf / mm². 2 ~40kgf / mm 2 ; (2) At room temperature, the elongation at break of the copper foil is ≥8%.

5. The copper foil according to any one of claims 1 to 3, characterized in that, The ratio of the Vickers hardness to the elongation at break of the copper foil is ψ, where ψ < 10.

6. A method for preparing copper foil according to any one of claims 1 to 5, characterized in that, Includes the following steps: The copper foil is prepared by electrolysis, wherein the electrolyte used in the electrolysis method comprises the following: The components shown are: Copper ions 70g / L~110g / L, sulfuric acid 90g / L~130g / L, chloride ions 10ppm~30ppm, brightener 10ppm~90ppm, leveling agent 2ppm~25ppm and leveling agent 1ppm~40ppm; The brightening agent includes sulfur-containing compounds, the leveling agent includes nitrogen-containing compounds, and the positioning agent includes polyether compounds and nitrogen-containing heterocyclic compounds.

7. The preparation method according to claim 6, characterized in that, Satisfy one or more of the following conditions (1) to (5): (1) The sulfur-containing compound includes one or more of sodium polydithiopropane sulfonate, sodium 3-mercapto-1-propane sulfonate, isothiourea propane sulfonate inner salt and sodium 3-(benzothiazol-2-mercapto)-propane sulfonate; (2) The nitrogen-containing compounds include one or more of collagen, gelatin, 2-amino-4-methylbenzothiazole and 2-mercaptopyridine; (3) The positioning agent is composed of polyether compounds and nitrogen-containing heterocyclic compounds in a concentration ratio of 1:(1-5); (4) The polyether compounds include one or more of polyethylene glycol and polypropylene glycol; (5) The nitrogen-containing heterocyclic compound includes polyvinylpyrrolidone.

8. The preparation method according to claim 6 or 7, characterized in that, Satisfy one or more of the following conditions (1) to (2): (1) The temperature of the electrolyte is 40℃~70℃; (2) The current applied during the electrolysis process is 15000A to 60000A.

9. A lithium-ion battery copper foil, characterized in that, This includes copper foil as described in any one of claims 1 to 5, or copper foil prepared by any one of claims 6 to 8.

10. A current collector, characterized in that, Including the lithium-ion battery copper foil as described in claim 9.

11. An electrode sheet, characterized in that, Includes the current collector as described in claim 10.

12. A battery, characterized in that, Includes the electrode as described in claim 11.

13. An electrical appliance, characterized in that, Includes the battery as described in claim 12.

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