Copper foil with ultrahigh tensile strength and high elongation as well as preparation method and application of copper foil

Abstract

The invention relates to a copper foil with ultrahigh tensile strength and high elongation as well as a preparation method and application of the copper foil. The surface roughness of the copper foil and the electrochemical area have correlation degree X, and the unit is cm <-1 >; the correlation degree X meets the following conditions: X = B / A, and X is 10 <-11 >-10 <-5 > cm <-1 >; wherein A represents the electrochemical area of the copper foil, and B represents the roughness of the copper foil. The copper foil provided by the invention has ultrahigh tensile strength and high elongation at the same time, and has excellent comprehensive performance. The copper foil with high tensile strength can effectively resist the volume change of the electrode material in the charging and discharging process, and the risk of copper foil breakage is reduced, so that the cycling stability of the battery is improved; the high-elongation copper foil can better adapt to volume change in the battery charging and discharging process, material stress is reduced, and the flexibility of the battery is improved. The copper foil has a good market application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, and particularly relates to a copper foil with ultra-high tensile strength and high elongation rate, and a preparation method and application thereof. Background Art

[0002] Lithium batteries and supercapacitors, as efficient and environmentally friendly energy storage devices, especially lithium batteries, have been widely used in the fields of portable electronic devices, electric vehicles, and large-scale energy storage systems. The performance of lithium batteries depends to a large extent on the performance of their key materials - electrode materials. As the core material of the negative electrode current collector of lithium batteries, the physical properties of copper foil directly affect the electrochemical performance and mechanical stability of the battery, especially in terms of tensile strength and elongation rate. These characteristics directly affect the cycle stability and safety of lithium batteries.

[0003] Tensile strength is the ability of a material to resist tensile fracture. For conventional copper foil, its tensile strength is usually between 300 - 500 MPa. During the charge and discharge process of lithium batteries, the electrode material will experience volume expansion and contraction, which requires the copper foil to have sufficient tensile strength to resist the resulting mechanical stress and prevent the copper foil from breaking or the electrode material from falling off.

[0004] Elongation rate is the ability of a material to withstand the maximum deformation during the tensile process without breaking. A high elongation rate means that the copper foil can maintain its integrity when experiencing deformation, thereby improving the cycle stability and safety of the battery. The elongation rate of traditional copper foil is usually low, which limits its application in high-performance lithium batteries.

[0005] With the development of the energy density of lithium-ion graphite negative electrode materials reaching the limit, the application of silicon-based negative electrode materials with higher energy density and the need for long-cycle-life energy storage devices, the mechanical properties of traditional copper foil can no longer meet the development requirements of high-energy-density batteries. When the tensile strength is insufficient, under the demand of high-energy-density lithium batteries, the volume change of the electrode material intensifies. Traditional copper foil is difficult to withstand large mechanical stress, resulting in fracture or micro-short circuit, increasing the internal resistance of the battery and decreasing the energy density and cycle performance. As the thickness decreases and the tensile strength increases, the elongation rate also decreases. When the elongation rate is low, the copper foil is prone to break during the charge and discharge process of the battery, affecting the overall performance and service life of the battery. In addition, its safety issues have also received increasing attention. Insufficient mechanical properties of copper foil may lead to safety problems such as thermal runaway in the battery under extreme conditions. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a copper foil with ultra-high tensile strength and high elongation rate, and a preparation method and application thereof. This copper foil has both ultra-high tensile strength and high elongation rate, and has excellent comprehensive performance.

[0007] The present invention provides a copper foil with ultra-high tensile strength and high elongation rate, characterized in that: there is a correlation degree X between the surface roughness and the electrochemical area of the copper foil, with the unit of cm -1 ; the correlation degree X satisfies: X = B / A, and X is 10 -11 ~10 - 5 cm -1 ; wherein, A represents the electrochemical area of the copper foil (cm 2 ), and B represents the roughness of the copper foil (μm).

[0008] Microscopically, the material has an uneven surface, and the actual surface area obtained through electrochemical testing is larger than the apparent projected area, which can more accurately reflect the true area of the material. The copper foil is cut into 1 cm 2 in size and used as a working electrode for electrochemical testing in a potassium ferricyanide solution. According to the Randles-Sevcik equation, the electrochemical area of the material can be more accurately calculated. The expression of the Randles-Sevcik equation is as follows:

[0009] Ip = 0.446nFcA(nDFν / RT) 1 / 2

[0010] where Ip is the current value (A), n is the number of electron transfers, F is the Faraday constant, c is the concentration of the electroactive substance (molmL -1 ), A is the electrochemical surface area of the electrode (cm 2 ), D is the solution diffusion coefficient, ν is the scanning rate (V s -1 ), R is the gas constant, and T is the temperature.

[0011] Further, the copper foil satisfies one or more of the following (1)-(2):

[0012] (1) In the grain structure, the proportion of twin crystal grains is 15-50%;

[0013] (2) In the grain structure, the proportion of the twin crystal grain region is 30%-80%.

[0014] Further, at room temperature, the copper foil has a tensile strength of 700-900 MPa and a fracture elongation rate ≥ 3%.

[0015] Further, the thickness of the copper foil is 3-6 μm.

[0016] The present invention also provides a preparation method for a copper foil with ultra-high tensile strength and high elongation rate, comprising the following steps:

[0017] The ultra-high tensile strength and high elongation copper foil is prepared by an electrolysis method; wherein, the copper sulfate electrolyte used in the electrolysis method comprises the following components:

[0018] Copper ions 70 g / L to 110 g / L, sulfuric acid 90 g / L to 130 g / L, chloride ions 10 - 50 ppm, component A 80 - 240 ppm, component B 30 - 150 ppm, and component C 15 - 100 ppm; the component A is an organic divalent sulfur compound; the component B comprises a polyether compound and a nitrogen-containing heterocyclic compound; the component C is a nitrogen-containing compound.

[0019] Preferably, the organic divalent sulfur compound comprises one or more of sodium poly-dithiopropanesulfonate, sodium 3-mercapto-1-propanesulfonate, and sodium alkanethiolate propane sulfonate.

[0020] Preferably, the mass ratio of the polyether compound to the nitrogen-containing heterocyclic compound is 1:(1 - 10); the polyether compound comprises one or more of polyethylene glycol and polypropylene glycol; the nitrogen-containing heterocyclic compound comprises polyvinylpyrrolidone.

[0021] Preferably, the nitrogen-containing compound comprises one or more of gelatin, collagen, polyethyleneimine, and tetrahydrothiazolethione.

[0022] Preferably, the temperature of the copper sulfate electrolyte is 40 - 70 °C; the current applied during the electrolysis process is 15000 A - 70000 A.

[0023] The present invention also provides an application of the ultra-high tensile strength and high elongation copper foil in a current collector.

[0024] The present invention also provides a pole piece, comprising the current collector as described above.

[0025] The present invention also provides a battery, comprising the pole piece as described above.

[0026] The present invention also provides an electrical device, comprising the battery as described above.

[0027] One of the key points of the present invention provides a method for quantifying the surface characteristics of a copper foil, defining the correlation degree X between roughness and electrochemical area, and the control range of X is 10 -11 ~10 -5 cm -1。The electrochemical area is determined by the surface characteristics of the material. The hydrophilicity of the copper foil is related to its own organizational structure and surface roughness, which directly affects the contact ability, adhesion ability, electrode manufacturing process and electrode quality with the active material of the battery negative electrode. Therefore, the correlation between the roughness of the copper foil and the electrochemical area must meet a certain range, especially for silicon-based negative electrode materials with a larger coefficient of thermal expansion. When the surface characteristic X of the copper foil is too small (<10 -11 cm -1 ), the negative electrode active material is not easily adhered to the surface of the copper foil. During the manufacturing process and cycling process of the battery cell, the active material is likely to fall off, increasing the internal resistance of the battery, reducing the energy density and cycle life of the battery, etc. When the surface characteristic X of the copper foil is too large (>10 - 5 cm -1 ), with the increase in the surface roughness of the copper foil, the adhesion of the negative electrode coating material to the copper foil shows polarization. The surface that is easily wetted becomes even easier to wet and has better hydrophilicity, while the surface of the material with low wettability is more difficult to wet and has worse hydrophilicity. Substances such as graphite and silicon-based negative electrode active materials have poor contact and low adhesion with the electrolytic copper foil with large surface roughness and are prone to falling off, directly affecting the cycle life of the battery.

[0028] The second key point of the present invention is to characterize the grain structure with ultra-high tensile strength. In the crystal structure, the proportion of twin crystal grains is 15%-50%, and the proportion of the twin crystal grain region is 30%-80%. The coherent twin boundary interface energy of Cu is 0.025 J / m 2 , and the grain boundary interface energy is very low, about 1 / 10 of the ordinary grain boundary interface energy and is very stable. The twin crystal interface energy of the ultra-high tensile strength copper foil is low, and the grains are finer than those of the conventional copper foil. According to the smooth fine grain theory, the finer the grains, the higher the tensile strength. In addition, the interaction between the coherent grain boundaries and dislocation defects inside the twin crystals. On the one hand, the twin crystal interface can effectively hinder the movement of dislocations. When the stress is high enough, the dislocations react with the twin crystal interface and cross the twin crystal interface; on the other hand, the twin crystal interface is also the slip plane of fcc-packed metal materials. Dislocations can not only move on the twin crystal interface, but also the coherent grain boundaries can provide storage space for the dislocations generated during deformation, thereby effectively improving the elongation of the copper foil.

[0029] The third key point of the present invention is that the copper foil has an ultra-high tensile strength of 700-900 MPa, while ensuring an elongation rate greater than 3%. Under the condition of ultra-high tensile strength, it can carry active materials with higher energy density and larger volume expansion and contraction ratio, which helps to improve the energy density and cycle stability of the battery. At the same time, the tensile strength and the elongation rate are inversely proportional. When the tensile strength is too high, it is often accompanied by brittleness and low elongation rate. When the elongation rate > 3%, it can meet the coating and rolling efficiency in current commercial production, avoid the phenomenon of tape breakage, and thus improve production efficiency. At the same time, as the negative electrode current collector of the lithium battery, due to its better mechanical properties, it provides better protection when the battery is impacted or pressed, reducing the safety risk.

[0030] The fourth key point of the present invention is that the copper foil has an extremely thin thickness, which is 3-6 μm. A thinner copper foil means lighter mass and smaller resistance, and the energy density and safety of the battery will be further improved. At the same time, it can effectively reduce the raw material cost of the copper foil. If the 8-μm copper foil used is replaced with a 6-μm or 4.5-μm copper foil, compared with the lithium battery using the 8-μm copper foil, the thinning of the copper foil significantly improves the energy density of the battery by 5% (6-μm copper foil) and 9.1% (4.5-μm copper foil) respectively; when the copper price increases by 10,000 per ton, the copper raw material costs saved by switching from 8 μm to 6 μm and from 6 μm to 4.5 μm will increase by 2.81 million and 1.13 million per GWh respectively.

[0031] The fifth key point of the present invention is the use of a composite organic additive composed of three components A, B, and C as the additive for foil formation. Component A is composed of sulfur-containing group compounds, and its main function is to promote the nucleation of copper ions; Component C is mainly composed of nitrogen-containing compounds, which can promote the face-centered growth of the copper foil grains, making the grains smoother; when the A agent of the organic sulfide and the C component of the nitrogen-containing compound (such as nitrogen-containing polymers) are used in combination, the crystal structure of the copper foil is more flat and dense, generating a large number of nanocrystalline regions, strengthening the effect of fine grain strengthening. The excellent structures of the fine grains and nano-twins interact with each other to improve the tensile strength of the copper foil while increasing the elongation rate. Component B is mainly composed of ether compounds and nitrogen-containing heterocyclic compounds, which can form a more stable and uniform hindrance layer, thereby effectively restricting certain growth directions of copper crystals, and interacting uniformly with other additives in various parts of the copper foil, making the grains finer and more uniform.

[0032] The sixth key point of the present invention is a current collector having the advantages of the lithium battery copper foil of the present invention, a current collector having ultra-high tensile strength and high elongation rate, which reduces the phenomena of fracture and wrinkling during the manufacturing and use of the battery core, improves production efficiency, and enhances the cycle performance and safety of the battery.

[0033] The seventh key point of the present invention is a pole piece having the advantages of the lithium-ion copper foil of the present invention, a pole piece having ultra-high tensile strength and high elongation rate, which can coat more and / or higher silicon-containing ratio and other anode active materials with higher shrinkage and expansion coefficients, improve the battery energy and extend the battery service life, and enhance the battery safety.

[0034] The eighth key point of the present invention is a lithium battery having the advantages of the lithium-ion copper foil of the present invention, having ultra-high energy density, longer cycle life and higher safety.

[0035] Beneficial effects

[0036] The copper foil of the present invention simultaneously has ultra-high tensile strength and high elongation rate, and has excellent comprehensive performance. The copper foil with high tensile strength can effectively resist the volume change of the electrode material during charge and discharge, reduce the risk of copper foil fracture, and thus improve the cycle stability of the battery; when the battery is subjected to external impact or mechanical stress, the copper foil with high tensile strength can maintain the structural integrity and reduce the possibility of battery damage; with the optimization of the electrode material, the copper foil with high tensile strength can adapt to the battery design with higher energy density and promote the performance improvement of lithium batteries; the copper foil with high elongation rate can better adapt to the volume change during charge and discharge of the battery, reduce the material stress, and improve the flexibility of the battery; when the battery is subjected to extreme conditions such as overcharge, over-discharge or short circuit, the copper foil with high elongation rate can slow down the fracture of the material and reduce the safety risk; the copper foil with high elongation rate reduces the material fatigue of the battery during long-term use and extends the service life of the battery. This copper foil has good market application prospects. Description of the Drawings

[0037] Figure 1 EBSD diagram of the copper foil prepared for Example 6.

[0038] Figure 2 Photo of the battery anode pole piece with the copper foil prepared in Example 8 as the current collector.

[0039] Figure 3 EBSD diagram of the copper foil prepared for Comparative Example 1.

[0040] Figure 4 Photo of the battery anode pole piece with the copper foil prepared in Comparative Example 3 as the current collector. Detailed Embodiments

[0041] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0042] The test methods are as follows:

[0043] (1) Electrochemical test: A three-electrode system is adopted, with a potassium ferricyanide solution as the electrolyte and an electrolytic copper foil as the working electrode for electrochemical testing. Electrochemical data is obtained by changing the scan rate, and the electrochemical area is calculated according to the Randles-Sevcik equation.

[0044] (1) Electron backscatter diffraction (EBSD) test: A C-Swift EBSD detector manufactured by Oxford Instruments in the UK is used to observe and characterize the crystal structures of the samples of each example and comparative example. In order to clearly observe the grain boundary profile of the sample, the cross-section is polished in advance using an ion milling machine for 20 minutes, the observation magnification is 3000 times, and the twin region and twin ratio are analyzed through the image processing software: Aztec Crystal.

[0045] (2) Tensile strength and elongation test: According to the test method GB / T29847-2013, a HY-0230 universal material testing machine manufactured by Shanghai Hengyi Precision Instrument Co., Ltd. is 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 is a strip specimen, and the distance between the clamps is 50 mm. The sample is measured ten times and the average value is taken as the final tensile strength and elongation of the sample. Specifically, both the measured tensile strength and elongation are the average values of the transverse and longitudinal directions. Five copper foil strips with a size of 15*100 mm in both the transverse and longitudinal directions are cut, and the tensile strength and elongation of the sample are 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 is taken as the final tensile strength and elongation value of the sample.

[0046] (3) Cell disassembly: The battery is disassembled in a constant-temperature and dry environment (temperature 25°C, humidity (RH) ≤ 30%). First, tape is attached to the two tab ends of the battery to avoid short-circuiting due to metal contact; then a deep scratch is made around the battery at a distance of 0.5 cm from the top with a blade, but the battery case is not completely cut through; starting from the battery corner, an oblique cutting pliers is used to gradually peel off the 0.5 cm aluminum shell of the cover and the case, and then the remaining electrolyte inside the battery is poured into a waste liquid bucket; after complete peeling, the cover can be lifted to take out the wound core from the aluminum shell, and attention should be paid not to cut the wound core at the edge of the aluminum shell; the insulating film outside the wound core is removed, and the two tabs together with the cover are cut off (the cutting position is as close as possible to the electrode end to avoid short-circuiting during subsequent disassembly); the tapes on the upper and lower sides are torn off, the outermost termination tape is found, and after removing the tape, the separator, negative electrode plate, separator, and positive electrode plate are unfolded in sequence. The unfolded electrode plates should be separated to avoid contact between the positive and negative electrode plates. Finally, the condition of the negative electrode plate is observed, such as whether there is wrinkling, breakage, and shedding of active substances, etc.

[0047] Example 1

[0048] Copper raw materials such as copper wire and copper plate with a purity of ≥99.5% or above are added to the copper melting tank in a ratio of 1:1 or 1:2, and high-temperature air is blown by a screw blower to dissolve them in a sulfuric acid solution to prepare the main electrolyte; after the main electrolyte is filtered through a diatomite filter, a security filter, and a precision filter in three stages, it is mixed with an organic composite additive to form a copper sulfate electrolyte. After the copper sulfate electrolyte is heated to 55°C by a plate heat exchanger, it is injected into the electrolytic cell. A closed electrolytic system is composed of a cathode roller with a cathode on the roller surface of a titanium ring immersed half a circle and an anode plate made of an insoluble material. A current of 30000 A is applied and the cathode roller cylinder runs at a constant speed. The copper sulfate electrolyte contains 92 g / L of Cu 2+ , 110 g / L of sulfuric acid, 30 ppm of chloride ions, and an organic composite electrolyte additive. Among them, component A is composed of 50 ppm of SPS and 80 ppm of MPS, component B is composed of 10 ppm of PEG and 50 ppm of PVP, and the molecular weight of PEG is 6000. Component C is composed of 5 ppm of collagen and 30 ppm of PEI, and is added to the copper sulfate electrolyte after dilution. It is supplied to the electrolytic system through a pipeline at the bottom of the electrolytic cell at a flow rate of 40 m 3 / h. After the copper foil is transferred out of the liquid with the roller, it is continuously peeled off from the cathode roller, subjected to anti-oxidation treatment with a passivation solution, dried, wound into the original foil, annealed, and slit to be used as a lithium-ion copper foil.

[0049] Three rolls of 9000 m copper foil are produced in batches. Three samples of the original foil with the full width are taken, baked at 150°C for 10 min, and then the tensile strength and elongation of the copper foil are tested. The test results are shown in Table 1.

[0050] By weight, 90 parts of silicon-carbon active material, 7 parts of conductive carbon black, 2.0 parts of styrene-butadiene rubber (SBR), 1.0 part of carboxymethyl cellulose (CMC) and 210 parts of deionized water are mixed into a slurry, which is coated on two opposite surfaces of the lithium-ion copper foil of this embodiment using a doctor blade, rolled after gradient drying, cut into a negative electrode sheet. A positive electrode sheet, which is also made by coating the active material on aluminum foil, followed by gradient drying, rolling and cutting processes, and a separator are wound into a core in the order of negative electrode sheet, separator, and positive electrode sheet and then hot-pressed, assembled in pairs into a square aluminum shell and welded airtight, leaving only the liquid injection port, and then placed in an oven and baked for 24 h to ensure that the water content of the negative electrode sheet < 300 ppm. After passing the moisture detection, commercially available electrolyte is injected for the first time, and after high-temperature activation, formation, secondary liquid addition, sealing, normal-temperature aging, and grading, a square battery with a capacity of 110 Ah is obtained. Finally, 20 PCS of square batteries are charged at a charging voltage of 4.2 V and discharged at a discharging voltage of 3.2 V, with a charge-discharge rate of 1C at room temperature. After 5000 charge-discharge cycles, 10 PCS of square batteries are disassembled when fully charged to observe the shedding of the active material on the negative electrode sheet and the wrinkling and cracking of the electrode sheet. 10 PCS of square batteries are disassembled when empty, and after the active material on the detached electrode sheet is dissolved in pure water, the negative electrode current collector after cyclic charge and discharge is obtained. After baking at 105 °C for 10 min, a sample is taken to measure its elongation rate, and the test results are shown in Table 1.

[0051] Example 2

[0052] Compared with Example 1, the difference is that Component A consists of 50 ppm of SPS and 70 ppm of MPS, Component B is 32 ppm of PEG with a molecular weight of 6000, and Component C consists of 10 ppm of collagen and 30 ppm of PEI.

[0053] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0054] Example 3

[0055] Compared with Example 1, the difference is that Component A consists of 40 ppm of SPS and 75 ppm of MPS, Component B consists of 15 ppm of PEG and 60 ppm of PVP with a molecular weight of 6000, and Component C is 17 ppm of collagen.

[0056] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0057] Example 4

[0058] Compared with Example 1, the difference is that the A component consists of 40 ppm of SPS and 85 ppm of MPS, the B component consists of 15 ppm of PEG and 55 ppm of PVP, and the molecular weight of PEG is 6000, and the C component is 22 ppm of gelatin.

[0059] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0060] Example 5

[0061] Compared with Example 1, the difference is that the A component consists of 55 ppm of SPS and 75 ppm of HP, the B component consists of 15 ppm of PPG and 45 ppm of PVP, and the C component consists of 10 ppm of gelatin and 30 ppm of PEI.

[0062] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0063] Example 6

[0064] Compared with Example 1, the difference is that the A component consists of 55 ppm of SPS and 60 ppm of HP, the B component consists of 24 ppm of PPG and 77 ppm of PVP, and the C component consists of 12 ppm of collagen and 25 ppm of PEI.

[0065] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0066] Example 7

[0067] Compared with Example 1, the difference is that the A component consists of 55 ppm of SPS and 88 ppm of HP, the B component consists of 15 ppm of PEG and 63 ppm of PVP, and the molecular weight of PEG is 6000, and the C component consists of 12 ppm of collagen and 25 ppm of PEI.

[0068] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0069] Example 8

[0070] Compared with Example 1, the difference is that the A component consists of 55 ppm of SPS and 75 ppm of HP, the B component consists of 15 ppm of PPG and 55 ppm of PVP, and the molecular weight of PEG is 6000, and the C component consists of 10 ppm of gelatin and 30 ppm of thiazolidinethione.

[0071] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0072] Example 9

[0073] Compared with Example 1, the difference is that Component A consists of 65 ppm of SPS and 75 ppm of HP, Component B consists of 30 ppm of PPG and 35 ppm of PVP, and Component C consists of 8 ppm of gelatin and 42 ppm of thiazolidinethione.

[0074] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0075] Example 10

[0076] Compared with Example 1, the difference is that Component A consists of 65 ppm of SPS and 55 ppm of HP, Component B consists of 30 ppm of PPG and 30 ppm of PVP, and Component C consists of 12 ppm of collagen and 20 ppm of thiazolidinethione.

[0077] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0078] Example 11

[0079] Compared with Example 1, the difference is that Component A consists of 50 ppm of SPS and 80 ppm of MPS, Component B consists of 15 ppm of PEG and 55 ppm of PVP, and Component C is 17 ppm of collagen.

[0080] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0081] Example 12

[0082] Compared with Example 1, the difference is that Component A consists of 55 ppm of SPS and 60 ppm of HP, Component B consists of 15 ppm of PEG and 55 ppm of PVP, and Component C consists of 10 ppm of collagen and 30 ppm of PEI.

[0083] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0084] Comparative Example 1

[0085] Compared with Example 1, the difference is that the copper sulfate electrolyte contains 92 g / L of Cu 2+ , 110 g / L of sulfuric acid, 22 ppm of chloride ions and an organic composite electrolyte additive. Among them, Component A consists of 30 ppm of SPS and 45 ppm of MPS, Component B consists of 15 ppm of PPG and 10 ppm of PVP, and Component C consists of 8 ppm of collagen and 5 ppm of PEI.

[0086] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0087] Comparative Example 2

[0088] Compared with Example 1, the difference is that the copper sulfate electrolyte contains 92 g / L of Cu 2+ , 110 g / L of sulfuric acid, 22 ppm of chloride ions and an organic composite electrolyte additive. Among them, Component A consists of 45 ppm of SPS and 45 ppm of MPS, Component B consists of 15 ppm of PEG and 10 ppm of PVP, and the molecular weight of PEG is 6000, and Component C is 15 ppm of collagen.

[0089] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0090] Comparative Example 3

[0091] Compared with Example 1, the difference is that the copper sulfate electrolyte contains 92 g / L of Cu 2+ , 110 g / L of sulfuric acid, 22 ppm of chloride ions and an organic composite electrolyte additive. Among them, Component A consists of 45 ppm of SPS and 30 ppm of MPS, Component B consists of 10 ppm of PEG and 20 ppm of PVP, and the molecular weight of PEG is 6000, and Component C consists of 8 ppm of gelatin and 10 ppm of PEI.

[0092] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0093] Comparative Example 4

[0094] Compared with Example 1, the difference is that the copper sulfate electrolyte contains 92 g / L of Cu 2+, sulfuric acid at 110 g / L, chloride ions at 22 ppm, and an organic composite electrolyte additive. Among them, component A consists of 45 ppm of SPS and 40 ppm of MPS, component B consists of 10 ppm of PEG and 20 ppm of PVP, and the molecular weight of PEG is 6000, and component C consists of 8 ppm of gelatin and 5 ppm of PEI.

[0095] The test results of the tensile and elongation tests of the obtained copper foil are shown in Table 1. The test results of the negative electrode current collector prepared from the copper foil are also shown in Table 1.

[0096] Table 1 Performance results of products in each example and comparative example

[0097]

[0098]

[0099] From Figure 1 and Figure 3 by comparison, Figure 1 the grains of the copper foil are finer and more uniform, there are more grain boundaries, and the grain boundaries can effectively hinder the movement of dislocations. At the same time, the surface of the copper foil is smoother and has fewer defects. According to the smooth fine grain theory: a smooth surface can reduce electron scattering, improve electrical conductivity, and improve the contact with the negative electrode material; a fine grain structure can not only improve the mechanical strength of the copper foil, but also improve the heat dissipation performance.

[0100] From Figure 2 and Figure 4 by comparison, Figure 2 the negative electrode sheet shown is smoother, and there are no abnormalities on the surface of the electrode sheet, while Figure 4 the negative electrode sheet shown has defects such as wrinkles and pinholes. Among them, in the wrinkled part during the charge and discharge cycle of the battery, along with the expansion and contraction of the battery volume, this part is more likely to break or short-circuit, thereby causing thermal runaway.

Claims

1. A copper foil with ultra-high tensile strength and high elongation rate, characterized in that: The surface roughness of the copper foil has a correlation X with the electrochemical area, in cm -1 ; the correlation X satisfies: X = B / A, and X is 10 -11 ~10 -5 cm -1 ; where A represents the electrochemical area of the copper foil and B represents the roughness of the copper foil.

2. The ultra-high tensile strength and high elongation copper foil according to claim 1, characterized in that: The copper foil satisfies one or more of the following (1)-(2): (1) In the grain structure, the proportion of twin grains is 15-50%; (2) In the grain structure, the proportion of the twin grain region is 30%-80%.

3. The ultra-high tensile strength and high elongation copper foil according to claim 1, wherein: At room temperature, the copper foil has a tensile strength of 700-900 MPa and an elongation at break ≥ 3%.

4. The ultra-high tensile strength and high elongation copper foil according to claim 1, wherein: The thickness of the copper foil is 3-6 μm.

5. A method for preparing a copper foil with ultra-high tensile strength and high elongation as claimed in claim 1, comprising the following steps: The ultra-high tensile strength and high elongation copper foil is prepared by an electrolysis method; wherein, The copper sulfate electrolyte used in the electrolysis method comprises the components described below: Copper ions 70 g / L - 110 g / L, sulfuric acid 90 g / L - 130 g / L, chloride ions 10-50 ppm, component A 80-240 ppm, component B 30-150 ppm, and component C 15-100 ppm; Component A is an organic divalent sulfur compound; Component B comprises a polyether compound and a nitrogen-containing heterocyclic compound; Component C is a nitrogen-containing compound.

6. The preparation method according to claim 5, wherein: The organic divalent sulfur compound comprises one or more of sodium polydithiopropanesulfonate, sodium 3-mercapto-1-propanesulfonate, and sodium alkanethiolate propane sulfonate.

7. The preparation method according to claim 5, characterized in that: The mass ratio of the polyether compound to the nitrogen-containing heterocyclic compound is 1:(1-10); the polyether compound comprises one or more of polyethylene glycol and polypropylene glycol; the nitrogen-containing heterocyclic compound comprises polyvinylpyrrolidone.

8. The preparation method according to claim 5, characterized in that: The nitrogen-containing compound comprises one or more of gelatin, collagen, polyethyleneimine, and tetrahydrothiazolethione.

9. The preparation method according to claim 5, characterized in that: The temperature of the copper sulfate electrolyte is 40-70 °C; the current applied during electrolysis is 15000 A - 70000 A.

10. An application of a copper foil with ultra-high tensile strength and high elongation as claimed in claim 1 in a current collector, a pole piece, a battery, or an electrical device.

Images