Copper foil and preparation method thereof, lithium battery copper foil, current collector, pole piece, battery and electrical device

Abstract

The present invention relates to a copper foil and a preparation method thereof, a lithium battery copper foil, a current collector, a pole piece, a battery, and an electrical device. The copper foil has a first surface and a second surface opposite to each other, the glossiness of the first surface is Gs1, the glossiness of the second surface is Gs2, Gs1>Gs2, and the main diameter of the grain fitting ellipse of the cross-sectional crystal structure between the first surface and the second surface is φ ED , in μm, the φ ED Satisfy: φ ED =2*sqrt(a 2 +b 2 ), and Φ ED The copper foil has a diameter of 0.1 μm to 6.5 μm, where a and b are the major and minor radii of the fitted ellipse, respectively. This copper foil exhibits both high tensile strength and high elongation, reducing breakage and wrinkling during manufacturing and battery production and use, thereby improving battery recyclability and safety.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to copper foil and a preparation method thereof, lithium battery copper foil, current collector, pole piece, battery and electrical device. Background Art

[0002] As a green and environmentally friendly energy storage device, lithium batteries have the advantages of 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. They are an important basic technology for achieving the "dual carbon" goals.

[0003] Lithium battery copper foil, as a carrier of the negative electrode active material and a collector and transmitter of anode electron flow in lithium-ion batteries, is a key auxiliary material in lithium-ion battery components. Depending on the application, lithium battery copper foil can be divided into two categories: power battery and non-power battery (such as 3C, energy storage, etc.). The global carbon emission reduction trend is not only promoting the rapid development of new energy industries such as new energy vehicles and photovoltaics, but also driving a rapid increase in demand for lithium battery copper foil.

[0004] With the rapid update and iteration of new energy technologies and equipment electronics, higher requirements are placed on the performance and safety of lithium-ion batteries, which are the core of energy storage systems. Similarly, the demand for high-performance lithium battery copper foil has been intensified. Among them, tensile strength and elongation are important performance indicators of lithium battery copper foil. However, traditional lithium battery copper foil is difficult to have both high tensile strength and high elongation, and is in urgent need of improvement. Summary of the Invention

[0005] Based on this, the present invention provides a copper foil and its preparation method, lithium battery copper foil, current collector, electrode, battery and electrical device. The copper foil has both high tensile strength and high elongation, and can be used as lithium battery copper foil to improve battery performance.

[0006] The technical solution is as follows:

[0007] A copper foil having a first surface and a second surface opposite to each other, wherein the glossiness of the first surface is Gs1, the glossiness of the second surface is Gs2, Gs1>Gs2, and the main diameter of the grain fitting ellipse of the cross-sectional crystal structure between the first surface and the second surface is Φ ED , in μm, the Φ ED satisfy:

[0008] Φ ED =2*sqrt(a 2 +b 2 ), and Φ ED 0.1μm~6.5μm;

[0009] Among them, a and b are the major radius and minor radius obtained by fitting the ellipse, respectively.

[0010] In one embodiment, the uniformity of the grain structure in the copper foil is denoted as Γ GM , in μm, the Γ GM satisfy:

[0011] And Γ GM 0.04μm~0.30μm;

[0012] Where n is the number of grains.

[0013] In one embodiment, the proportion of twin grain boundaries in the copper foil grain structure is 55% to 75%.

[0014] In one embodiment, the proportion of twinned grain regions in the copper foil grain structure is ≥95%.

[0015] In one embodiment, at room temperature, the tensile strength of the copper foil is 30 kgf / mm 2 ~40kgf / mm 2 .

[0016] In one embodiment, at room temperature, the elongation at break of the copper foil is ≥8%.

[0017] In one embodiment, the ratio of the Vickers hardness to the elongation at break of the copper foil is ψ, and ψ is less than 10.

[0018] The present invention also provides a method for preparing the copper foil as described above, and the technical solution is as follows:

[0019] A method for preparing the copper foil as described above comprises the following steps:

[0020] The copper foil is prepared by an electrolytic method, wherein the electrolyte used in the electrolytic method includes the following components:

[0021] Copper ion 70g / L~110g / L, sulfuric acid 90g / L~130g / L, chloride ion 10ppm~30ppm, brightener 10ppm~90ppm, leveling agent 2ppm~25ppm and moving agent 1ppm~40ppm;

[0022] Wherein, the brightener includes a sulfur-containing compound, the leveler includes a nitrogen-containing compound, and the displacement agent includes a polyether compound and a nitrogen-containing heterocyclic compound.

[0023] In one embodiment, the sulfur-containing group compound includes one or more of sodium polydisulfide dipropane sulfonate, sodium 3-mercapto-1-propane sulfonate, isothiourea propane sulfonic acid inner salt and sodium 3-(benzothiazole-2-mercapto)-propane sulfonate.

[0024] In one embodiment, the nitrogen-containing compound includes one or more of collagen, gelatin, 2-amino-4-methylbenzothiazole and 2-mercaptopyridine.

[0025] In one embodiment, the displacement agent is prepared by compounding a polyether compound and a nitrogen-containing heterocyclic compound in a concentration ratio of 1:(1-5).

[0026] In one embodiment, the polyether compound includes one or more of polyethylene glycol and polypropylene glycol.

[0027] In one embodiment, the molecular weight of polyethylene glycol is 4000-8000.

[0028] In one embodiment, the nitrogen-containing heterocyclic compound includes polyvinylpyrrolidone.

[0029] In one embodiment, the temperature of the electrolyte is 40°C to 70°C.

[0030] In one embodiment, the current applied during the electrolysis process is 15,000A to 60,000A.

[0031] The present invention also provides an application of the above copper foil, and the technical solution is as follows:

[0032] A lithium battery copper foil comprises the copper foil as described above or a copper foil prepared according to the method for preparing the copper foil as described above.

[0033] In one embodiment, the lithium 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 the first surface of the copper foil, and the second anti-oxidation layer is stacked on the second surface of the copper foil.

[0034] In one embodiment, the first anti-oxidation layer and the second anti-oxidation layer independently include one or more of chromic anhydride, glucose and nitride.

[0035] A current collector includes the lithium battery copper foil described above.

[0036] A pole piece includes the current collector as described above.

[0037] A battery comprises the electrode sheet described above.

[0038] An electrical device comprises the battery as described above.

[0039] The present invention has at least the following beneficial effects:

[0040] The main diameter of the grain fitting ellipse in the copper foil interface crystal structure is Φ ED , when Φ ED When the particle 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; on the contrary, when Φ ED If the diameter is larger than 6.5 μm, the grain size is too large, the grain boundary density is reduced, and the limited space in the crystal is difficult to accommodate the movement and accumulation of a large number of dislocations, resulting in increased internal stress, decreased tensile strength, and an increased risk of tearing and breaking during the copper foil manufacturing and electrode preparation process. ED The thickness of the copper foil is 0.1 μm to 6.5 μm, which can significantly improve the elongation of the copper foil, so that the copper foil has both high tensile strength and high elongation. It can reduce the phenomenon of broken foil and / or wrinkling during the copper foil manufacturing process and / or in the battery cell process and use, and improve the cycle and safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is an EBSD photograph of the cross section of the copper foil prepared in Example 1;

[0042] Figure 2 This is a photo of the hardness indentation of the first shiny surface (first surface, deposition surface) of the copper foil prepared in Example 2;

[0043] Figure 3 This is the EBSD photograph of the copper foil cross section prepared in Comparative Example 1. DETAILED DESCRIPTION

[0044] To facilitate understanding of the present invention, the present invention will be described more fully below, along with preferred embodiments thereof. 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 more thorough and comprehensive understanding of the disclosure of the present invention.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0046] Where “including,” “having,” and “comprising” are used herein, it is intended to cover a non-exclusive inclusion, and another component may also be added unless a clear limiting term such as “only,” “consisting of,” etc. is used.

[0047] The words "preferably", "more preferably", "preferably", "better", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the statement of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention. That is, in the present invention, "preferably", "more preferably", "preferably", "better", etc. are only used to describe implementation methods or examples with better effects, but do not constitute a limitation on the scope of protection of the present invention.

[0048] In the present invention, “further”, “further”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of the present invention.

[0049] In the present invention, "at least one" means more than one, such as one, two, or more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layer" means at least two layers, such as two, three, etc., unless otherwise specifically defined. In the description of the present invention, "several" means at least one, such as one, two, etc., unless otherwise specifically defined.

[0050] 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 such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0051] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0052] Unless mentioned otherwise, terms in the singular may include plural forms and should not be construed as having one number.

[0053] In the present invention, "above" or "below" includes the number itself. For example, "1 or below" includes 1.

[0054] In the present invention, room temperature refers to 0°C to 40°C, including but not limited to 10°C to 40°C, or further 20°C to 30°C.

[0055] Tensile strength and elongation are important performance indicators of lithium battery copper foil. The tensile strength of traditional lithium battery copper foil is 300MPa to 400MPa, which has reached a relatively high level, but the elongation is only between 4% and 8%. However, in the downstream lithium battery industry production process, the thickness of copper foil is required to be thinner and the coating speed is getting faster and faster. At the same time, during the battery cell process such as coating, rolling, and baking, the copper foil will be in a high temperature and high pressure environment. This requires the copper foil to have a higher elongation to prevent dents, wrinkles or broken strips during the battery cell process, which reduces production efficiency. In addition, lithium-ion batteries need to be accompanied by the expansion and contraction of active materials during charging and discharging. High-elongation copper foil can prevent the active material from falling off and breaking during the expansion and contraction caused by charging and discharging of the electrode, thereby increasing internal resistance and reducing the battery capacity, cycle life and safety.

[0056] In view of the problem that traditional lithium battery copper foil is difficult to have both high tensile strength and high elongation, the present invention provides a copper foil with both high tensile strength and high elongation, which can be used as lithium battery copper foil to improve battery performance.

[0057] The technical solution is as follows:

[0058] A copper foil having a first surface and a second surface opposite to each other, wherein the glossiness of the first surface is Gs1, the glossiness of the second surface is Gs2, Gs1>Gs2, and the main diameter of the grain fitting ellipse of the cross-sectional crystal structure between the first surface and the second surface is Φ ED , in μm, the Φ ED satisfy:

[0059] Φ ED =2*sqrt(a 2 +b 2 ), and Φ ED 0.1μm~6.5μm;

[0060] Among them, a and b are the major radius and minor radius obtained by fitting the ellipse, respectively.

[0061] When the main 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 copper foil grains are too small, the grain boundary density increases, the strength increases, but the plastic deformation decreases, and the elongation decreases. Grain boundaries, as surface defects commonly found in polycrystalline materials, can serve as defect nucleation sources and hinder the movement of defects. The essence of fine grain strengthening in metallurgy is the interaction between grain boundaries and dislocations, which hinders the movement of dislocations, improving strength while ensuring good plastic deformation capacity. This process does not change the properties of the overall grain boundaries, but the disordered structure of the grain boundaries makes it difficult for dislocations to slide along them. However, there is a critical grain size. When the grain size is smaller than the critical grain size, the action of the grain boundaries inhibits the activation of dislocation sources, resulting in a lack of movable dislocation sources during the deformation process, making it difficult for slip to proceed, resulting in reduced plastic deformation. In addition, when the main 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 difficult to accommodate the movement and accumulation of a large number of dislocations, resulting in increased internal stress, reduced strength, and an increased risk of tearing and breaking during the manufacture and use of the copper foil. ED The thickness of the copper foil is 0.1 μm to 6.5 μm, which can significantly improve the elongation of the copper foil, so that the copper foil has both high tensile strength and high elongation, and reduces the phenomenon of copper foil breaking and / or wrinkling during the copper foil manufacturing process and / or in the battery cell process and use.

[0062] Furthermore, research has shown that copper foil elongation is positively correlated with thickness fitting, and that for every 1% increase in copper foil elongation at break, battery cycling stability improves by approximately 5%. If copper foil elongation can be further increased while reducing thickness, it will open up a new path for the copper foil and battery industries. The solution of the present invention can significantly increase copper foil elongation, thereby significantly improving battery cycling and safety.

[0063] In one embodiment, the uniformity of the grain structure in the copper foil is denoted as Γ GM , in μm, the Γ GM satisfy:

[0064] And Γ GM 0.04μm~0.30μm;

[0065] Where n is the number of grains.

[0066] Γ GMIt is the ratio of the area to the perimeter of the ellipse fitted by the grain of the copper foil cross section, and can be used to quantify the morphology and crystal structure of the grains. When metal materials are subjected to tensile stress, from elastic deformation to plastic deformation and finally fracture, materials with uniform crystal structures and materials with non-uniform crystal structures may have similar tensile strengths, but metal materials with non-uniform crystal structures will experience early fracture during the tensile process, that is, compared with metal materials with non-uniform crystal structures, metal materials with uniform crystal structures have a longer tensile plateau period. On the one hand, due to the presence of coarse grains and fine grains with large size differences in materials with non-uniform crystal structures, as the strain increases, the low-angle grain boundaries within the coarse grains gradually increase, and the lattice distortion in the adjacent areas of the coarse grains and fine grains increases. In contrast, with the increase of strain, the amount of lattice distortion in the uniform crystal structure increases, but the distribution is relatively uniform. Similarly, as strain increases, the surface irregularities of fine-grained regions in heterogeneous microstructures cause stress concentration. As the load continues to increase, slip increases, and the irregularities are more distributed near the coarse-grained and fine-grained surfaces. In contrast, during the tensile process of a homogeneous microstructure, the formation of irregularities is more random and dispersed. Therefore, during deformation, regions with the greatest differences in the heterogeneous crystal structure are more likely to form strain concentrations and develop cracks, leading to earlier fracture. On the other hand, the slip system between adjacent grains in a homogeneous crystal structure is strain-compatible, and dislocations are more easily transferred between pairs of grains. In contrast, dislocations between grains in a heterogeneous crystal structure cannot transfer between these grains, or their motion is hindered. Therefore, under the same macroscopic strain conditions, dislocations on both sides of a local region in a heterogeneous crystal structure are asynchronous, resulting in significant variations in the ability to coordinate strain, leading to uneven deformation, strain asynchrony, and fracture, resulting in a decrease in plastic deformation capacity.

[0067] The research found that when the grain structure uniformity of the copper foil cross section is Γ GM <0.04μm, the grain boundary surface is uneven, which is prone to stress concentration, and the grain boundary density increases, which inhibits the start of dislocation sources, making it difficult for slip to proceed, resulting in reduced plastic deformation and low elongation; the grain structure uniformity of the copper foil cross section is Γ GM >0.30μm, the grain size is too large, the grain boundary density is reduced, the stress in the crystal is increased, the space for accommodating dislocations in the crystal is limited, and the strength is reduced, causing the copper foil to tear and break during manufacturing and use. GM The thickness of the copper foil is 0.04 μm to 0.30 μm, including but not limited to 0.04 μm, 0.06 μm, 0.08 μm, 0.10 μm, 0.15 μm, 0.20 μm, 0.25 μm or 0.30 μm. The copper foil meeting this requirement has both high tensile strength and high elongation, which can avoid tearing and breaking of the copper foil during manufacturing and use.

[0068] Furthermore, in the crystal structure, twin grains are closely related to the mechanical properties of metal materials. Since twins can react with dislocations at the interface, they can effectively hinder the movement of dislocations. In addition, the twin interface serves as the slip plane of face-centered cubic (FCC) stacked metal materials. Not only can dislocations move on the twin interface, but the coherent grain boundary can also provide storage space for dislocations generated during deformation, thereby effectively improving the elongation of the copper foil.

[0069] In one embodiment, the proportion of twin grain boundaries in the grain structure of the copper foil described in the present invention is 55% to 75%, including but not limited to 55%, 60%, 65%, 70% or 75%. The copper foil that meets this requirement has both high tensile strength and high elongation, which can avoid tearing and breaking of the copper foil during manufacturing and use.

[0070] In one embodiment, the proportion of twin grain areas in the grain structure of the copper foil described in the present invention is ≥95%, including but not limited to 95%, 96%, 97%, 98% or 99%. The copper foil that meets this requirement has both high tensile strength and high elongation, which can avoid tearing and breaking of the copper foil during manufacturing and use.

[0071] In one embodiment, at room temperature (such as 0°C to 40°C, further 10°C to 40°C, further 25°C), the tensile strength of the copper foil is 30 kgf / mm 2 ~40kgf / mm 2 , including but not limited to 30kgf / 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 phenomenon of copper foil breaking during the preparation process and the battery cell preparation process, improve the efficiency of copper foil manufacturing and battery production, and improve the capacity and safety performance of the battery.

[0072] In one embodiment, at room temperature (e.g., 0°C to 40°C, further 10°C to 40°C, and even further 25°C), the copper foil has an elongation at break of 8% or greater, including but not limited to 8%, 10%, 12%, 15%, 18%, or 20%. If the copper foil has an elongation at break of less than 8%, when used as a lithium battery copper foil current collector, and when the battery active material is a material with a high expansion rate, during the charge and discharge process of the lithium secondary battery, the electrode sheet may crack or break due to insufficient elongation as the battery cell expands in volume, thereby increasing internal resistance and reducing the battery capacity, cycle life, and safety.

[0073] Furthermore, from the perspective of the material's microstructure and deformation mechanism, in metal materials, hardness is primarily determined by the obstruction of grain boundaries and the resistance to dislocation movement. If the ratio of the copper foil's Vickers hardness to its elongation at break is too high, the metal material's hardness increases, and the interaction between grain boundaries and dislocations, along with the disordered structure of grain boundaries, makes it difficult for dislocations to slide along them. This creates greater resistance to movement between grain boundaries and dislocations. 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, leading to reduced elongation.

[0074] In one embodiment, the Vickers hardness of the copper foil of the present invention is greater than 40 Hv. Furthermore, the Vickers hardness of the copper foil of the present invention is greater than 45 Hv, which is relatively high in hardness and wear-resistant.

[0075] In one embodiment, the numerical ratio of the Vickers hardness to the elongation at break of the copper foil of the present invention is ψ (for example, 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. The copper foil that meets this requirement has both high tensile strength and high elongation, and can avoid tearing and breaking of the copper foil during manufacturing and use.

[0076] In one embodiment, the thickness of the copper foil is 6 μm to 12 μm, further 8 μm to 10 μm. It is understandable that for electrolytic copper foil, the thickness of the copper foil can be controlled by the current and line speed during the preparation process.

[0077] It is understandable that the present invention does not impose any special restrictions on the method for analyzing the crystal structure of the copper foil cross section, and conventional characterization and analysis methods in the field can be used. Optionally, the present invention uses backscatter diffraction (EBSD) testing to characterize the grain structure of the copper foil of the present invention. Further, a C-Swift EBSD detector manufactured by Oxford Instruments in the United Kingdom is used to observe and characterize the crystal structure of each embodiment and comparative example sample. In order to clearly observe the grain boundary contour of the sample, the cross section is polished for 20 minutes using an ion milling machine in advance. Further, Where n is the grain count detected by EBSD on the copper foil cross section. In one embodiment of the present 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 by 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.

[0078] It is understood that the present invention does not impose any particular limitation on the testing methods for the tensile strength and elongation of copper foil, and conventional testing methods in the art may be used. Alternatively, in an embodiment of the present invention, the tensile strength and elongation of the sample were tested at room temperature and a strain rate of 50 mm / min using a HY-0230 universal material testing machine manufactured by Shanghai Hengyi Precision Instrument Co., Ltd., in accordance with the test method of GB / T29847-2013.

[0079] It is understood that the present invention does not impose any particular restrictions on the Vickers hardness test method for copper foil, and conventional test methods in the art can be used. Optionally, in an embodiment of the present invention, the Vickers hardness (HV) test is based on the GB / T 4340.1-2009 test method, using a touch screen micro Vickers hardness tester manufactured by Shanghai Taishuo Testing Instrument Co., Ltd., and testing the Vickers hardness value (HV) of the sample at room temperature and using a pressure value of 50g for 5s. Repeat the measurement at five different locations of the sample and take the average value as the final Vickers hardness value (HV) of the sample.

[0080] The present invention also provides a method for preparing the copper foil as described above, and the technical solution is as follows:

[0081] A method for preparing the copper foil as described above comprises the following steps:

[0082] The copper foil is prepared by an electrolytic method, wherein the electrolyte used in the electrolytic method includes the following components:

[0083] Copper ion 70g / L~110g / L, sulfuric acid 90g / L~130g / L, chloride ion 10ppm~30ppm, brightener 10ppm~90ppm, leveling agent 2ppm~25ppm and moving agent 1ppm~40ppm;

[0084] Wherein, the brightener includes a sulfur-containing compound, the leveler includes a nitrogen-containing compound, and the displacement agent includes a polyether compound.

[0085] During the electrolytic deposition process to form copper foil, due to the different growth rates of each crystal plane, a phenomenon of preferential orientation (texture) will occur. From a crystallographic perspective, it is generally believed that texture growth along the (220) plane is beneficial to improving elongation. The present invention uses an organic composite electrolyte additive to enable the copper sulfate electrolyte to obtain relatively large and uniform grains during the deposition process, which is also beneficial to improving elongation. Specifically, in the present invention, a certain proportion of brightener, leveler 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 the mechanical properties of the copper foil. Among them, brighteners are mainly composed of sulfur-containing compounds, and their main function is to promote the nucleation of copper ions; levelers are mainly composed of nitrogen-containing compounds, which can promote the face-centered growth of copper foil grains, making the grains flatter. When organic sulfide brighteners and nitrogen-containing compounds (such as nitrogen-containing polymers) levelers are used in combination, the copper foil crystal structure becomes flatter and denser, producing a large number of nanocrystalline regions, enhancing the fine grain strengthening effect. The excellent structure of fine crystals and nanotwins interacts with each other to improve the tensile strength of the copper foil while increasing the elongation. 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 evenly with other additives in various parts of the copper foil, making the grains smaller and more uniform. In addition, polyether compounds can effectively inhibit the growth of grains at high temperatures, reduce the size of grain nucleation, generate more interfaces, absorb and release thermal stress, and improve the stability of the copper foil under high temperature conditions. It is understandable that some compounds have multiple functions, such as 2-amino-4-methylbenzothiazole, which can be used as both a leveling agent and a moving agent.

[0086] In one embodiment, the sulfur-containing compound includes one or more of sodium polydisulfide propanesulfonate (SPS), sodium 3-mercapto-1-propanesulfonate (MPS), isothiourea propanesulfonic acid inner salt (UPS), and sodium 3-(benzothiazole-2-mercapto)-propanesulfonate (ZPS). Furthermore, the brightener is compounded from sodium polydisulfide propanesulfonate and sodium 3-mercapto-1-propanesulfonate. Furthermore, the brightener is compounded from sodium polydisulfide propanesulfonate and sodium 3-mercapto-1-propanesulfonate at a concentration ratio of (0.5-3):1.

[0087] In one embodiment, the nitrogen-containing compound includes one or more of collagen, gelatin, 2-amino-4-methylbenzothiazole and 2-mercaptopyridine.

[0088] In one embodiment, the displacement agent is prepared by compounding a polyether compound and a nitrogen-containing heterocyclic compound in a concentration ratio of 1:(1-5).

[0089] In one embodiment, the polyether compound includes one or more of polyethylene glycol (PEG) and polypropylene glycol (PPG), and the molecular weight of the polyethylene glycol is 4,000 to 8,000.

[0090] In one embodiment, the nitrogen-containing heterocyclic compound is polyvinylpyrrolidone (PVP).

[0091] In one embodiment, the positioning agent includes at least polyethylene glycol. The positioning agent is a compound of polyethylene glycol and a nitrogen-containing heterocyclic compound, which can form a more stable and uniform barrier layer, thereby effectively limiting certain growth directions of copper crystals. It interacts evenly with other additives on various parts of the copper foil, making the grains smaller and more uniform, improving the uniformity of the grains, and making the copper foil have both high tensile strength and high elongation, thereby avoiding tearing and breaking of the copper foil during manufacturing and use.

[0092] In one embodiment, the temperature of the electrolyte is 40°C to 70°C.

[0093] In one embodiment, the current applied during the electrolysis process is 15,000A to 60,000A.

[0094] In one embodiment, the method for manufacturing the copper foil comprises the following steps:

[0095] Copper plates and / or copper wires with a purity of 99.8% or higher are used as raw materials, which are dissolved in a sulfuric acid solution through a flow of high-temperature air to prepare a copper sulfate electrolyte. The purified copper sulfate electrolyte is then filtered through three stages. An insoluble material is then used as the anode, and a cathode roller with a titanium ring as the roller 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 the roller rotates at a constant speed for electrolysis. The amount of copper foil electrodeposited on the surface of the cathode roller is controlled by the cathode current density and the roller speed. After the copper foil is rotated out of the liquid surface with the roller, it is continuously peeled from the cathode roller, subjected to oxidation protection, drying, and winding to produce raw foil. The electrolyte contains the following components: 70g / L to 110g / L copper ions, 90g / L to 130g / L sulfuric acid, 10ppm to 30ppm chloride ions, 10ppm to 90ppm brightener, 2ppm to 25ppm leveler, and 1ppm to 40ppm displacement agent.

[0096] It can be understood that for copper foil prepared by electrolysis, during the preparation process, for the copper foil, the deposition surface with high gloss is the rough surface (corresponding to the first surface described in the present invention), and the roller surface that is in direct contact with the cathode roller surface and has low gloss is the glossy surface (corresponding to the second surface described in the present invention).

[0097] The present invention also provides an application of the above copper foil, and the technical solution is as follows:

[0098] (1) A lithium battery copper foil, comprising the copper foil as described above or a copper foil prepared according to the method for preparing the copper foil as described above. It is understood that the lithium battery copper foil has the advantages of the copper foil described in the present invention, with uniform grains, moderate grain size, high tensile strength and high elongation, thereby reducing the breakage and wrinkling of the lithium battery copper foil during the manufacturing process and during battery manufacturing and use, thereby improving the recyclability and safety of the battery.

[0099] In one embodiment, the lithium 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 the first surface of the copper foil, and the second anti-oxidation layer is stacked on the second surface of the copper foil.

[0100] In one embodiment, the first and second anti-oxidation layers independently comprise one or more of chromic anhydride, glucose, and nitride. It is understood that the first and second anti-oxidation layers of the present invention are independent of each other. Therefore, the material and usage ratio of the first anti-oxidation layer can be the same as or different from the material and usage ratio of the second anti-oxidation layer.

[0101] (2) A current collector, comprising the lithium battery copper foil as described above. It is understood that the current collector has the advantages of the lithium battery copper foil described in the present invention, and has both high tensile strength and high elongation, thereby reducing the breakage and wrinkling of the battery cell during manufacturing and use, and improving the cycle performance and safety of the battery. In one example, after the battery cell is cyclically charged and discharged, the tensile strength of the current collector is 30kgf / mm 2 ~40kgf / mm 2 , elongation ≥3%.

[0102] (3) A pole piece comprising the current collector described above. It is understood that the pole piece has the advantages of the current collector described in the present invention, with both high tensile strength and high elongation, thereby reducing breakage and wrinkling of the battery cell during manufacturing and use, and improving the cycle performance and safety of the battery.

[0103] Furthermore, the electrode sheet includes a first active material layer, a current collector, and a second active material layer stacked together. Furthermore, the first active material layer comprises at least one or a combination of graphite, silicon, and alloy materials, and the second active material layer comprises at least one or a combination of graphite, silicon, and alloy materials. It will be understood that in the present invention, the first and second active material layers are independent of each other, and the raw materials, dosage ratios, and layer thicknesses used can be the same or different, without particular limitation.

[0104] In one embodiment, the electrode piece is an anode electrode piece.

[0105] (4) A battery comprising the electrode as described above.

[0106] (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, cars, etc.

[0107] Specific embodiments are listed below to illustrate the present invention.

[0108] 1. The test method is as follows:

[0109] (1) EBSD test: The crystal structure of each embodiment and comparative example sample was observed and characterized using a C-Swift EBSD detector manufactured by Oxford Instruments, UK. In order to clearly observe the grain boundary contours of the sample, the cross section was polished for 20 minutes using an ion milling machine in advance. The observation magnification was 3000 times. n is the total number of grains observed in the copper foil cross section at 3000 times the field of view. a and b are the major and minor radii obtained by fitting the ellipse, respectively. The average Φ ED The value refers to the average of the main diameters of the n grain fitting ellipses detected under a 3000x field of view.

[0110] (2) Tensile strength and elongation test: According to the test method GB / T29847-2013, the HY-0230 universal material testing machine manufactured by Shanghai Hengyi Precision Instrument Co., Ltd. was used to test the tensile strength and elongation of the sample at room temperature and a strain rate of 50 mm / min. The tensile test specimen was a strip specimen with a distance of 50 mm between the clamps. The sample was 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 of 15*100 mm in size were cut in the transverse and longitudinal directions. The tensile strength and elongation of the sample were tested at room temperature and a strain rate of 50 mm / min, and the average value of a total of 10 copper foil strips in the transverse and longitudinal directions was taken as the final tensile strength and elongation value of the sample.

[0111] (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 Instrument Co., Ltd. was used to test the Vickers hardness (HV) of the sample at room temperature and with a pressure of 50g for 5s. Repeat the measurement at five different locations on the sample and take the average value as the final Vickers hardness (HV) of the sample.

[0112] 2. If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0113] Example 1

[0114] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, among which the brightener is composed of 40ppm SPS and 45ppm MPS, the moving agent is composed of 10ppm PEG and 20ppm PVP, and the PEG molecular weight is 4000, and the leveling agent is 5ppm gelatin, which are diluted and added to the copper sulfate electrolyte. The electrolyte temperature is 55℃, and the electrolyte is heated at 43m3 / min through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0115] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken and baked at 150°C for 10 minutes. The tensile strength, elongation and hardness of the copper foil were tested. The test results are shown in Table 1.

[0116] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0117] Example 2

[0118] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, among which the brightener is composed of 45ppm SPS and 40ppm MPS, the moving agent is composed of 7ppm PEG and 25ppm PVP, and the PEG molecular weight is 4000, and the leveling agent is 5ppm gelatin, which are diluted and added to the copper sulfate electrolyte. The electrolyte temperature is 55℃, and the electrolyte is heated at 43m3 / min through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0119] Three rolls of 2000 m copper foil were produced in batches. Three full-width original foil samples were taken from each roll. After baking at 150°C for 10 min, tensile strength, elongation and hardness tests were performed. The test results are shown in Table 1.

[0120] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0121] Example 3

[0122] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, among which the brightener is composed of 45ppm SPS and 30ppm MPS, the moving agent is composed of 7ppm PEG and 25ppm PVP, and the PEG molecular weight is 4000, and the leveling agent is 10ppm gelatin, which are diluted and added to the copper sulfate electrolyte. The electrolyte temperature is 55℃, and the electrolyte is heated at 43m3 / min through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0123] Three rolls of 2000 m copper foil were produced in batches. Three full-width original foil samples were taken from each roll. After baking at 150°C for 10 min, tensile strength, elongation and hardness tests were performed. The test results are shown in Table 1.

[0124] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0125] Example 4

[0126] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, among which the brightener is composed of 40ppm SPS and 40ppm UPS, the moving agent is composed of 7ppm PEG and 20ppm PVP, and the PEG molecular weight is 6000, and the leveling agent is 5ppm collagen, which are diluted and added to the copper sulfate electrolyte. The electrolyte temperature is 55℃, and the electrolyte is heated at 43m3 / min through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0127] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken and baked at 150°C for 10 minutes. The tensile strength, elongation and hardness of the copper foil were tested. The test results are shown in Table 1.

[0128] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0129] Example 5

[0130] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, among which the brightener is composed of 45ppm UPS and 40ppm ZPS, the moving agent is composed of 5ppm PEG and 20ppm PVP, and the PEG molecular weight is 8000, and the leveling agent is composed of 6ppm collagen and 3ppm gelatin. After dilution, add them to the copper sulfate electrolyte. The electrolyte temperature is 55℃, and the electrolyte is heated at 43m3 / s through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0131] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken and baked at 150°C for 10 minutes. The tensile strength, elongation and hardness of the copper foil were tested. The test results are shown in Table 1.

[0132] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0133] Example 6

[0134] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, among which the brightener is composed of 45ppm ZPS and 35ppm MPS, the moving agent is composed of 10ppm PEG and 15ppm PVP, and the PEG molecular weight is 8000, and the leveling agent is 10ppm gelatin, which are diluted and added to the copper sulfate electrolyte. The electrolyte temperature is 55℃, and the electrolyte is heated at 43m3 / min through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0135] Three rolls of 2000m copper foil were produced in batches. Three full-width original foil samples were taken and baked at 150°C for 10 minutes. The tensile strength, elongation and hardness of the copper foil were tested. The test results are shown in Table 1.

[0136] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0137] Comparative Example 1

[0138] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, which are composed of 25ppm SPS and 20ppm MPS as brighteners, 30ppm PEG with a molecular weight of 4000 as a moving agent, and 5ppm collagen as a leveling agent. After dilution, they are added to the copper sulfate electrolyte. The electrolyte temperature is 55℃ and the electrolyte is heated at 43m through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0139] Three rolls of 2000 m copper foil were produced in batches. Three full-width original foil samples were taken from each roll. After baking at 150°C for 10 min, tensile strength, elongation and hardness tests were performed. The test results are shown in Table 1.

[0140] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0141] Comparative Example 2

[0142] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, among which the brightener is 85ppm SES, the moving agent is composed of 10ppm PEG and 20ppm PVP, and the PEG molecular weight is 4000), and the leveling agent is 7ppm Janus Green, which are diluted and added to the copper sulfate electrolyte. The electrolyte temperature is 55℃, and the electrolyte is heated at 43m3 / min through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0143] Three rolls of 2000 m copper foil were produced in batches. Three full-width original foil samples were taken from each roll. After baking at 150°C for 10 min, tensile strength, elongation and hardness tests were performed. The test results are shown in Table 1.

[0144] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0145] Comparative Example 3

[0146] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, among which the brightener is composed of 60ppm SES and 20ppm ZPS, the moving agent is 25ppm PVP, and the leveling agent is composed of 5ppm collagen and 5ppm Jianna Green. After dilution, they are added to the copper sulfate electrolyte. The electrolyte temperature is 55℃ and the electrolyte is heated at 43m3 / s through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0147] Three rolls of 2000 m copper foil were produced in batches. Three full-width original foil samples were taken from each roll. After baking at 150°C for 10 min, tensile strength, elongation and hardness tests were performed. The test results are shown in Table 1.

[0148] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0149] Comparative Example 4

[0150] Copper plates and copper wires with a purity of 99.8% or more are mixed in a 1:1 weight ratio, introduced with hot air, and dissolved in a sulfuric acid solution to prepare a copper sulfate electrolyte. The pure copper sulfate electrolyte is then filtered through three stages. An insoluble material is used as the anode, and a cathode roller with a titanium ring as the roller surface is used as the cathode. In the electrolytic cell, the bottom semicircle of the cathode roller is immersed in the copper sulfate electrolyte, and a current of 35,000A is applied and the roller rotates at a constant speed for electrolysis. The copper sulfate electrolyte contains 85g / L of Cu 2+ , 105g / L sulfuric acid, 17ppm chloride ions and organic composite electrolyte additives, among which the brightener is composed of 45ppm SPS and 35ppm SES, the moving agent is 25ppm PEG with a molecular weight of 4000, and the leveling agent is composed of 5ppm gelatin and 5ppm Janus green. After dilution, add them to the copper sulfate electrolyte. The electrolyte temperature is 55℃, and the electrolyte is heated at 43m3 / min through the bottom pipe of the electrolytic cell. 3 The copper foil is fed into the electrolysis system at a rate of 1000 t / h. After the copper foil is removed from the liquid by the rollers, it is continuously peeled off from the cathode rollers, treated with a passivation solution containing chromic anhydride and glucose for oxidation prevention, dried, and wound up to produce raw foil, which is subsequently used as lithium battery copper foil.

[0151] Three rolls of 2000 m copper foil were produced in batches. Three full-width original foil samples were taken from each roll. After baking at 150°C for 10 min, tensile strength, elongation and hardness tests were performed. The test results are shown in Table 1.

[0152] The first active material layer and the second active material layer of this embodiment are composed 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, mixed into a slurry by weight. The slurry is applied to the two opposite surfaces of the lithium battery copper foil of this embodiment using a scraper, and then cut into anode pieces by rolling. The pieces are then wound with the prepared cathode pieces in the order of cathode, diaphragm and anode into an 18650 single cell and baked in an oven for 24 hours. The water content of the anode pieces is less than 300ppm. The lithium secondary battery electrolyte was injected into the prepared single cell. After standing, formation, and capacity separation, 10 PCS 18650 batteries with a capacity of 1.1Ah were prepared. The cells were charged at a voltage of 4.2V and discharged at a voltage of 3.2V, and charged and discharged at a rate of 1C at room temperature (25°C). After 3000 charge and discharge cycles, the cells were disassembled in an empty state. The active material of the electrode was dissolved in pure water to obtain the anode current collector after cyclic charge and discharge. After baking at 105°C for 10 minutes, samples were taken to measure their elongation. The test results are shown in Table 1.

[0153] The performance data of the comparative examples of the above embodiments are shown in Table 1 below.

[0154] Table 1 Performance results of comparative examples of various embodiments

[0155]

[0156] Figure 1 This is the EBSD photo of the copper foil cross section prepared in Example 1. Figure 1 It can be seen that the twin area is large, the grain size difference is small, the grain boundary can effectively hinder the dislocation movement, and the elongation is high.

[0157] Figure 2 This is a photo of the hardness indentation of the first glossy surface of the copper foil prepared in Example 2. Figure 2 It can be seen that the indentation is a straight-sided quadrilateral with a short diagonal length and high hardness.

[0158] Figure 3 This is the EBSD photo of the copper foil cross section prepared in Comparative Example 1. Figure 3 It can be seen that the grain size varies greatly, a large number of fine grains exist locally, and the grain boundary density is too high, which easily leads to strain concentration and development into cracks, resulting in low elongation.

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

[0160] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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 above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall 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 glossiness of the first surface is Gs1, the glossiness of the second surface is Gs2, Gs1>Gs2, and the main diameter of the grain fitting ellipse of the cross-sectional crystal structure between the first surface and the second surface is Φ ED , in μm, the Φ ED satisfy: Φ ED = 2 * sqrt(a 2 + b 2 ), and Φ ED is from 0.1 μm to 6.5 μm; Among them, a and b are the major radius and minor radius obtained by fitting the ellipse respectively; The uniformity of the grain structure in the copper foil is denoted as Γ GM , in μm, the Γ GM satisfy: and Γ GM is 0.04 μm to 0.30 μm; Where n is the number of grains.

2. The copper foil according to claim 1, wherein 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 twinned grain regions is ≥95%.

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

4. The copper foil according to any one of claims 1 to 2, characterized in that The numerical ratio of the Vickers hardness to the elongation at break of the copper foil is ψ, and ψ is less than 10.

5. The copper foil according to claim 1, wherein The copper foil has a Vickers hardness of 40 Hv or more.

6. A method for preparing the copper foil according to any one of claims 1 to 5, characterized in that: The steps include: The copper foil is prepared by an electrolytic method, wherein the electrolyte used in the electrolytic method includes the following components: Copper ion 70g / L~110g / L, sulfuric acid 90g / L~130g / L, chloride ion 10ppm~30ppm, brightener 10ppm~90ppm, leveling agent 2ppm~25ppm and moving agent 1ppm~40ppm; Wherein, the brightener includes a sulfur-containing compound, the leveler includes a nitrogen-containing compound, and the displacement agent includes a polyether compound and a nitrogen-containing heterocyclic compound; The sulfur-containing group compound includes one or more of sodium polydisulfide dipropane sulfonate, sodium 3-mercapto-1-propane sulfonate, isothiourea propane sulfonic acid inner salt and sodium 3-(benzothiazole-2-mercapto)-propane sulfonate; The nitrogen-containing compound includes one or more of collagen, gelatin, 2-amino-4-methylbenzothiazole and 2-mercaptopyridine; The moving agent is prepared by compounding a polyether compound and a nitrogen-containing heterocyclic compound in a concentration ratio of 1: (1-5); The polyether compound includes one or more of polyethylene glycol and polypropylene glycol; The nitrogen-containing heterocyclic compound includes polyvinyl pyrrolidone.

7. The preparation method according to claim 6, characterized in that The brightener is prepared by compounding sodium polydisulfide dipropane sulfonate and sodium 3-mercapto-1-propane sulfonate in a concentration ratio of (0.5-3):

1.

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

9. A lithium battery copper foil, characterized in that The invention comprises the copper foil according to any one of claims 1 to 5 or the copper foil prepared according to the method for preparing the copper foil according to any one of claims 6 to 8.

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

11. A pole piece, characterized in that: The present invention comprises the current collector according to claim 10.

12. A battery, characterized in that: Including the pole piece according to claim 11.

13. An electrical device, characterized in that: Including the battery according to claim 12.

Images