TW202400846A - Electrolytic copper foil, electrode and lithium ion battery comprising the same - Google Patents

Abstract

Provided are an electrolytic copper foil, an electrode and a lithium ion battery comprising the same. The electrolytic copper foil has a first surface and a second surface opposite the first surface, wherein the first surface and the second surface are analyzed by GIXRD, the absolute deviation of the full width at half maximum (FWHM) of the characteristic peaks of crystal face (111) of the first surface and the second surface is less than 0.14, the first surface and the second surface each have a nanoindentation more than or equal to 0.3 GPa and less than or equal to 3.0 GPa, and the yield strength of the electrolytic copper foil is more than 230 MPa. By controlling the absolute deviation of FWHM of the characteristic peaks of crystal face (111) of the two surfaces, the nanoindentation of the two surfaces and the yield strength of the electrolytic copper foil, the level of tolerance of the electrolytic copper foil in multiple charge-discharge cycles is raised, the warpage of the electrolytic copper foil is decreased, and the yield rate and value of the lithium ion battery are increased.

Description

Electrolytic copper foil and electrodes and lithium ion batteries containing the same

The present disclosure relates to an electrolytic copper foil, and in particular, to an electrolytic copper foil that can be used in lithium-ion batteries, an electrode including the same, and a lithium-ion battery.

Copper foil has good electrical conductivity and has the advantage of low cost compared to precious metals such as silver. Therefore, it is not only widely used in basic industries, but also an important raw material for advanced technology industries; for example, copper foil can be used as a lithium ion Battery electrode materials are widely used in portable electronic devices (PED), electric vehicles (EV), energy storage systems (ESS) and other fields.

When copper foil is used as an electrode material for lithium-ion batteries, the active material coated on it will shrink and expand during multiple charging and discharging processes, causing the copper foil to deform. If the mechanical strength of the copper foil is insufficient, the copper foil will be damaged multiple times. During the charging and discharging process, the active material shrinks and expands, causing breakage and even damage to the lithium-ion battery.

On the other hand, the production process of lithium-ion batteries involves the step of coating active materials on copper foil. If the copper foil is uneven and its corners have warped structures, it will degrade the quality of the active materials coated on the copper foil and reduce the subsequent Process yield of electrodes and lithium-ion batteries.

Therefore, there is still a need to improve the copper foil's tolerance to multiple charge and discharge processes and reduce the warpage of the copper foil, in order to improve the process yield of electrodes and lithium-ion batteries.

In view of the shortcomings of the existing technology, one of the objectives of the present disclosure is to improve the conventional copper foil so that when the copper foil is used as an electrode for a lithium-ion battery, it can maintain good tolerance after multiple charge and discharge cycles.

One of the purposes of this disclosure is to improve the conventional copper foil, which has a flat surface and can effectively reduce the degree of warpage.

Another purpose of this disclosure is to improve the conventional copper foil and improve the process yield and value of its subsequent applications as current collectors, electrodes and lithium-ion batteries.

In order to achieve the aforementioned objectives, the present disclosure provides an electrolytic copper foil, which has a first surface and a second surface located on opposite sides. The first surface and the second surface are analyzed by low grazing angle X-ray diffraction (GIXRD). The absolute difference between the characteristic peak half-width of the (111) crystal plane on the first surface and the characteristic peak half-width of the (111) crystal plane on the second surface is less than 0.14, and the first surface and the second surface of the electrolytic copper foil The nanoindentation hardness of the two surfaces is independently 0.3 GPa to 3.0 GPa, and the yield strength of the electrolytic copper foil is greater than 230 MPa.

The present disclosure controls the absolute difference of the characteristic peak half-width of the (111) crystal plane of the first surface and the second surface of the electrolytic copper foil, the nanoindentation hardness of the first and second surfaces, and the yield of the electrolytic copper foil. The strength can specifically improve the endurance of the electrolytic copper foil during multiple charge and discharge processes, and at the same time reduce the warpage of the electrolytic copper foil, so that it can be used as a highly tolerant collector material, thereby improving the manufacturing process of lithium-ion batteries. Yield and product value.

Preferably, the half-height width of the characteristic peak of the (111) crystal plane of the first surface and the second surface of the electrolytic copper foil can be independently 0.10 to 0.38; more preferably, the first surface and the second surface of the electrolytic copper foil The characteristic peak widths at half maximum of the (111) crystal planes on the two surfaces can be independently from 0.13 to 0.38. In one embodiment, the characteristic peak width at half maximum of the (111) crystal plane of the first surface and the second surface of the electrolytic copper foil can be independently 0.13 to 0.27; in another embodiment, the electrolytic copper foil The characteristic peak half-width of the (111) crystal plane on the first surface of the copper foil may be from 0.13 to 0.38, and the characteristic peak half-width of the (111) crystal plane on the second surface of the electrolytic copper foil may be from 0.20 to 0.30.

Preferably, the absolute difference between the characteristic peak half-width of the (111) crystal plane on the first surface of the electrolytic copper foil and the characteristic peak half-width of the (111) crystal plane on the second surface can be less than 0.135; More preferably, the absolute difference between the characteristic peak half-width of the (111) crystal plane of the first surface of the electrolytic copper foil and the characteristic peak half-width of the (111) crystal plane of the second surface can be 0.010 to 0.135. . During the research process, the applicant found that the absolute difference between the characteristic peak half-width of the (111) crystal plane on the first surface of the electrolytic copper foil and the characteristic peak half-width of the (111) crystal plane on the second surface is more than 0.14. At this time, the electrolytic copper foil will seriously warp, and at the same time, the endurance of the electrolytic copper foil during multiple charge and discharge processes will be deteriorated.

Preferably, the nanoindentation hardness of the first surface and the second surface of the electrolytic copper foil can be independently 0.4 GPa to 2.5 GPa; more preferably, the nanoindentation hardness of the first surface and the second surface of the electrolytic copper foil can be 0.4 GPa to 2.5 GPa. The indentation hardness can independently range from 0.4 GPa to 2.3 GPa. In one embodiment, the nanoindentation hardness of the first surface of the electrolytic copper foil can be 0.3 GPa to 3.0 GPa, and the nanoindentation hardness of the second surface of the electrolytic copper foil can be 1.0 GPa to 2.0 GPa; in another embodiment, the nanoindentation hardness of the first surface of the electrolytic copper foil can be 0.4 GPa to 2.5 GPa, and the nanoindentation hardness of the second surface of the electrolytic copper foil can be 1.0 GPa. to 2.0 GPa. During the research process, the applicant found that electrolytic copper foil is used as a lithium-ion battery current collector. If the nanoindentation hardness on any side of the electrolytic copper foil is greater than 3.0 GPa, its surface properties are too hard and brittle, and cracks and chips are prone to occur during the charging and discharging process. Causes the active material coated on it to fall off, thereby reducing its tolerance during multiple charge and discharge processes; if the nanoindentation hardness on any side is less than 0.3 GPa, its surface strength is too low, and it will easily The occurrence of cracks and chips will also reduce its resistance to repeated charging and discharging processes.

Preferably, the absolute difference between the nanoindentation hardness of the first surface of the electrolytic copper foil and the nanoindentation hardness of the second surface can be less than 1.0 GPa. More preferably, the first nanoindentation hardness of the electrolytic copper foil The absolute difference between the nanoindentation hardness of the surface and the nanoindentation hardness of the second surface may be 0.1 GPa to 1.0 GPa.

Preferably, the yield strength of the electrolytic copper foil can be more than 240 MPa; more preferably, the yield strength of the electrolytic copper foil can be 240 MPa to 500 MPa.

In one embodiment, the thickness of the electrolytic copper foil can be 4 microns to 20 microns; in another embodiment, the thickness of the electrolytic copper foil can be 6 microns to 20 microns.

The present disclosure further provides an electrode for a lithium-ion battery, which includes the aforementioned electrolytic copper foil.

The present disclosure also provides a lithium-ion battery, which includes the aforementioned electrode.

According to the present disclosure, the electrolytic copper foil can be used as a negative electrode of a lithium-ion battery and can also be used as a positive electrode of a lithium-ion battery. The electrolytic copper foil can be suitable for use as a current collector, and at least one layer of active material is coated on one or both sides of the electrolytic copper foil to form an electrode of a lithium ion battery.

According to the present disclosure, active materials can be divided into positive active materials and negative active materials. The negative active material contains a negative active material, which can be a carbon-containing material, a silicon-containing material, a silicon-carbon composite, a metal, a metal oxide, a metal alloy or a polymer; preferably it is a carbon-containing material or a silicon-containing material, but Not limited to this. Specifically, the carbon-containing substance can be mesophase graphite powder (MGP), non-graphitizing carbon, coke, graphite, glasslike carbon (glasslike) carbon), carbon fiber, activated carbon, carbon black or polymer calcined material, but not limited thereto; wherein, coke includes pitch coke, needle coke or petroleum coke, etc.; the The calcined polymer is obtained by firing high polymers such as phenol-formaldehyde resin or furan resin at appropriate temperatures so that they are carbonated. The silicon-containing material has an excellent ability to form an alloy with lithium ions and an excellent ability to extract lithium ions from the alloy lithium. Moreover, when the silicon-containing material is used in a lithium-ion secondary battery, the advantage of having a large energy density can be achieved; Silicon substances can be combined with cobalt (Co), iron (Fe), tin (Sn), nickel (Ni), copper (Cu), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), chromium (Cr), ruthenium (Ru), molybdenum (Mo) or a combination thereof to form an alloy material. The element of the metal or metal alloy may be selected from the group consisting of: cobalt, iron, tin, nickel, copper, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium, ruthenium and molybdenum , but not limited to this. Examples of the metal oxide are ferric oxide, ferric tetroxide, ruthenium dioxide, molybdenum dioxide and molybdenum trioxide, but are not limited thereto. Examples of the polymer are polyacetylene and polypyrrole, but are not limited thereto.

In one embodiment, the active material can be added with auxiliary additives as needed, and the auxiliary additives can be binders and/or weak acid reagents, but are not limited to this. Preferably, the binder can be polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (poly( acrylic acid (PAA), polyacrylonitrile (PAN) or polyacrylate (polyacrylate). The weak acid reagent can be oxalic acid, citric acid, lactic acid, acetic acid or formic acid.

According to the disclosure, depending on the composition of the positive electrode slurry, the lithium-ion battery of the disclosure can be a lithium cobalt battery (LiCoO ₂ battery), a lithium nickel battery (LiNiO ₂ battery), a lithium manganese battery (LiMn ₂ O ₄ battery), _{Lithium cobalt nickel} battery ( _LiCo

According to the present disclosure, the electrolyte may include a solvent, an electrolyte, or optional additives. Solvents in the electrolyte include non-aqueous solvents, such as cyclic carbonates such as ethylene carbonate (EC) or propylene carbonate (PC); dimethyl carbonate (DMC), carbonic acid Chain carbonates such as diethyl carbonate (DEC) or ethyl methyl carbonate (EMC); or sultones (sultones), but are not limited to this; the aforementioned solvents can be used alone It is also possible to use two or more solvents in combination. Electrolytes include: lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(oxalate)borate ) and lithium bis (trifluoromethane sulfonimide), but are not limited to this.

In other embodiments, solid electrolytes (solid electrolytes) can be used in lithium ion batteries to replace the above-mentioned electrolytes; for example, the solid electrolytes can be crystalline electrolytes, glassy electrolytes, glass-ceramic electrolytes, or polymer electrolytes. But it is not limited to this. Specifically, the crystalline electrolyte can be a sulfide solid electrolyte such as lithium superion conductor (LISICON) type or Argyrodite type; or it can be a garnet structure type (Garnet type) or a perovskite structure type. (Peroskite type), NASICON structural type, etc. oxide solid electrolytes, but are not limited to this. The glassy electrolyte may be a glassy solid electrolyte such as oxide or sulfide, but is not limited thereto. The polymer electrolyte can be a pure solid polymer electrolyte such as polyethylene oxide-based (PEO-based), polypropylene oxide-based (PPO-based), etc.; or it can be a polyacrylonitrile-based electrolyte. (polyacrylonitrile-based, PAN series), polymethyl methacrylate-based (poly(methyl methacrylate)-based, PMMA series), polyvinyl chloride-based (poly(vinyl chloride)-based, PVC series), polyvinylidene fluoride Colloidal polymer electrolytes such as ethylene-based (poly(vinylidene fluoride)-based, PVDF-based), but are not limited thereto.

According to the present disclosure, the lithium-ion battery may be a stacked lithium-ion battery including negative electrodes and positive electrodes stacked through a separator film, or it may be a spiral-wound stacked lithium-ion battery including continuous electrodes and separators spirally wound together. , but not limited to this. According to different application products, the lithium-ion battery disclosed in the present disclosure can be used in notebook personal computers, mobile phones, electric vehicles, and energy storage systems, and can be made into, for example, cylindrical secondary batteries, prismatic secondary batteries, pouch-shaped secondary batteries, or button-shaped secondary batteries. Secondary batteries, but not limited to this.

Below, several examples are enumerated to illustrate the implementation of electrolytic copper foil, and several comparative examples are provided as comparisons. Those with ordinary knowledge in the art can easily understand the advantages that can be achieved by the present disclosure through the content of the following examples and comparative examples. and effect. It should be understood that the embodiments listed in this specification are only used to illustrate the implementation of the present disclosure, and are not intended to limit the scope of the present disclosure. Those with ordinary knowledge in the technical field can make decisions based on common knowledge without departing from the present disclosure. Various modifications and changes may be made in order to implement or apply the contents of this disclosure.

As shown in Figure 1, the equipment for producing electrolytic copper foil includes an electrolytic deposition device 10, an anti-rust treatment device 20 and a series of guide rollers. The electrolytic deposition device 10 includes a cathode roller 11 , an insoluble anode plate 12 , a copper electrolyte 13 and a feed tube 14 . The cathode roller 11 is a rotatable titanium cathode roller. The insoluble anode plate 12 is an IrO ₂ coated titanium plate, which is disposed below the cathode roller 11 and substantially surrounds the lower half of the cathode roller 11 . The insoluble anode plate 12 has a surface facing the cathode roller. Anode surface 121 of barrel 11 . The cathode roller 11 and the insoluble anode plate 12 are spaced apart from each other to accommodate the copper electrolyte 13 introduced through the feed pipe 14 . The anti-rust treatment device 20 includes an anti-rust treatment tank 21 and two sets of electrode plates 211a and 211b arranged therein. A series of guide rollers includes a first guide roller 31, a second guide roller 32, a third guide roller 33, a fourth guide roller 34, a fifth guide roller 35 and a sixth guide roller 36, which can transport the electrolytically deposited original material. The foil is sent to the anti-rust treatment device 20 for anti-rust treatment. After the original foil is anti-rust treated, an air knife 40 is used to remove excess anti-rust material on the surface, and finally the electrolytic copper foil 50 is obtained by winding up on the sixth guide roller 36 .

The electrolytic copper foil disclosed in the present disclosure can adjust the electrolytic deposition parameters in the process according to needs. In one embodiment, the copper electrolyte formula in the electrolytic deposition step may include copper sulfate, sulfuric acid, chloride ions, sodium 3-mercapto-1-propanesulfonate (MPS) , collagen and sodium ions, but not limited to this; in the described aspect, the copper sulfate concentration can be 200 grams/liter (g/L) to 400 g/L, and the sulfuric acid concentration can be 80 g/L to 80 g/L. 150 g/L, the chloride ion concentration can be 20 ppm to 60 ppm, the sodium 3-mercapto-1-propanesulfonate concentration can be 20 ppm to 30 ppm, the collagen concentration can be 10 ppm to 40 ppm, and the collagen molecular weight can be is 1000 Dalton (Da) to 10000 Da, the sodium ion concentration can be 10 ppm to 30 ppm; the temperature of the copper electrolyte in the electrolytic deposition step can be 40°C to 50°C, and the current density can be 40 amps/ Square decimeter (A/dm ² ) to 50 A/dm ² ; the roughness (Rz) of the anode surface can be less than 15 microns.

The electrolytic copper foil disclosed in the present disclosure can be electroplated and rust-proofed according to requirements. The anti-rust liquid used can be an organic anti-rust liquid containing azole compounds (azole), or an anti-rust liquid such as chromium, nickel, or zinc. Rust liquid, tin anti-rust liquid and other inorganic anti-rust liquids. In one implementation, the anti-rust liquid may be a chromium anti-rust liquid, the chromic acid concentration may be 1.5 g/L to 5.0 g/L, the current density may be 0.5 A/dm ² to 6.0 A/dm ² , and the chromium The liquid temperature of the anti-rust liquid can be 20°C to 40°C, and the anti-rust treatment time can be 2 seconds to 4 seconds, but is not limited to this.

According to the present disclosure, the physical properties of the electrolytic copper foil can adjust the copper electrolyte formula and related process parameters in the electrolytic deposition step according to needs. For example, the amount of collagen added, the amount of sodium ions added, and the anode surface roughness of the anode plate are adjusted to control the nanoindentation hardness of the electrolytic copper foil, the half-height width of the characteristic peak of the (111) crystal plane, and the yield strength. etc., but not limited to this.

"Electrolytic Copper Foil"

Example 1 to 10

In Examples 1 to 10, the production equipment shown in Figure 1 was used, and electrolytic copper foil was produced through substantially the same electrolytic deposition steps and anti-rust treatment steps in sequence. The methods of manufacturing the electrolytic copper foil 50 of Examples 1 to 10 are collectively described below.

First, the copper electrolyte 13 for the electrolytic deposition step is prepared. During the electrolytic deposition step, the cathode roller 11 rotates at a fixed axis at a constant speed, and current is applied to the cathode roller 11 and the insoluble anode plate 12 so that the copper electrolyte The copper ions in 13 are deposited on the surface of the cathode roller 11 to form an original foil, and then the original foil is peeled off from the cathode roller 11 and guided to the first guide roller 31 .

Here, the formula of copper electrolyte 13 and the process conditions of electrolytic deposition are as follows: I. The formula of copper electrolyte 13: copper sulfate (CuSO ₄ ‧5H ₂ O): about 280 g/L; sulfuric acid: about 90 g/L ; Chloride ion (Cl ^- ): about 20 ppm; sodium 3-mercapto-1-propanesulfonate (MPS, purchased from HOPAX): about 20 ppm; collagen: molecular weight about 2500, The content is shown in Table 1 below; and sodium ion (Na ⁺ ): the content is shown in Table 1 below. II. Electrolytic deposition process conditions: temperature of copper electrolyte 13: about 50°C; anode surface roughness (Rz): as shown in Table 1 below; and current density: about 50 A/dm ² .

Among them, the roughness of the anode surface refers to the maximum height measured according to the JIS B 0601-1994 standard method. Here, the instruments and conditions selected to measure Rz on the anode surface are as follows: I. Measuring instruments: Portable surface roughness measuring instrument (contact type): SJ-410, purchased from Mitutoyo. II. Measurement conditions: Tip radius: 2 microns; Needle tip angle: 60°; Cut off length (λc): 0.8 mm; and Evaluation length: 4 mm.

Subsequently, the original foil is transported to the anti-rust treatment device 20 through the first guide roller 31 and the second guide roller 32 for anti-rust treatment. The original foil is immersed in the anti-rust treatment tank 21 filled with chromium anti-rust liquid, and then passes through the third During the transportation of the guide roller 33, two sets of electrode plates 211a and 211b are used to perform anti-rust treatment on the opposite surfaces of the original foil, and a first anti-rust layer and a second anti-rust layer are electrolytically deposited on the opposite surfaces of the original foil. .

Here, the formula of chromium anti-rust liquid and the process conditions of anti-rust treatment are as follows: I. The formula of chromium anti-rust liquid: Chromic acid (CrO ₃ ): about 1.5 g/L. II. Process conditions for anti-rust treatment: Liquid temperature: 25°C; Current density: about 0.5 A/dm ² ; and treatment time: about 2 seconds.

After the anti-rust treatment is completed under the above conditions, the anti-rust treated copper foil is guided to the fourth guide roller 34, and the air knife 40 is used to remove excess anti-rust material on the surface and dry it, and then through the fifth guide roller 34. The roller 35 transfers it to the sixth guide roller 36, and winds it up on the sixth guide roller 36 to obtain the electrolytic copper foil 50.

According to the above manufacturing method, the electrolytic copper foils of Examples 1 to 8 with a thickness of about 8 microns, Example 9 with a thickness of about 6 microns, and Example 10 with a thickness of about 20 microns can be produced respectively. The differences between Examples 1 to 10 mainly lie in the thickness of the obtained electrolytic copper foil, the collagen content, the sodium ion content in the copper electrolyte, and the roughness of the anode surface in the electrolytic deposition step. As shown in Figure 2, the electrolytic copper foil 50 of each embodiment includes a copper layer 51 (equivalent to the original foil without the aforementioned anti-rust treatment step), a first anti-rust layer 52 and a second anti-rust layer 53. The copper layer 51 It includes a deposited side (deposited side) 511 and a drum side (drum side) 512 located on the opposite side. During the electrolytic deposition process, the deposited side 511 is the surface of the original foil facing the insoluble anode plate, and the drum side 512 is the original foil and the cathode. The surface in contact with the roller; the first anti-rust layer 52 is formed on the deposition surface 511 of the copper layer 51. The first anti-rust layer 52 has a first surface 521 located on the outermost side, and the second anti-rust layer 53 is formed on the copper layer. 51 on the roller surface 512, and the second anti-rust layer 53 has a second surface 531 located on the outermost side. The first surface 521 and the second surface 531 are the two outermost surfaces of the electrolytic copper foil 50 located on the opposite sides. .

Comparative example 1 to 6

Comparative Examples 1 to 6 are used as controls for Examples 1 to 10, which generally adopt the same preparation method as Examples 1 to 10, except that the collagen content, sodium ion content and anode surface of the copper electrolyte used in each comparative example Each Rz is different, and the above parameters are listed in Table 1. In addition, the structures of the electrolytic copper foils of Comparative Examples 1 to 6 are also shown in Figure 2, and their thicknesses are all 8 microns. Table 1: The thickness of the electrolytic copper foils of Examples 1 to 10 (E1 to E10) and Comparative Examples 1 to 6 (C1 to C6), the collagen content in the copper electrolyte used in the process, the sodium ion content and the anode surface Rz Thickness (micron) Collagen content (ppm) Sodium ion content (ppm) Anode surface Rz (micron) E1 8 10 10 2 E2 8 20 10 2 E3 8 30 10 2 E4 8 40 10 2 E5 8 20 20 2 E6 8 20 30 2 E7 8 20 10 8 E8 8 20 10 15 E9 6 20 10 2 E10 20 20 10 2 C1 8 5 10 2 C2 8 20 40 2 C3 8 20 5 2 C4 8 20 10 18 C5 8 20 10 20 C6 8 20 10 1

Test example 1 : Low grazing angle X Light diffraction analysis (grazing incidence X-ray diffraction , GIXRD)

In this test example, the electrolytic copper foils of the aforementioned Examples 1 to 10 and Comparative Examples 1 to 6 are used as samples to be tested. An X-ray diffraction analyzer is used to conduct a low grazing angle X-ray diffraction experiment, and the TOPAS software is used to calculate the respective values. The half-maximum width of the characteristic peak of the (111) crystal plane of the first surface and the second surface of the sample was measured to obtain the surface structure of the first surface and the second surface. The results are shown in Table 2.

Here, the instruments and parameters selected for low grazing angle X-ray diffraction analysis are as follows: I. Measuring instruments: X-ray diffraction analyzer: Bruker D8 ADVANCE Eco. II. Measurement conditions: Incident light angle: 0.8°.

Test example 2 : Nanoindentation hardness

In this test example, the electrolytic copper foils of the above-mentioned Examples 1 to 10 and Comparative Examples 1 to 6 are used as the samples to be tested, and the nanoindentation system is used to conduct the test to obtain the nanometer values of the first surface and the second surface of the samples to be tested. Indentation hardness, the results are shown in Table 2.

Here, the instruments and measurement conditions selected to measure the nanoindentation hardness of electrolytic copper foil are as follows: I. Measuring instruments: Nano indentation system: MTS nano indenter XPW system, model: XPW291; and Probe: Berkovich indenter with a radius of curvature less than or equal to 50 nanometers. II. Measurement conditions: Pressing speed: 0.04 mm/second; and Indentation depth: 300 nm.

Test example 3 : Yield strength

In this test example, the electrolytic copper foils of the aforementioned Examples 1 to 10 and Comparative Examples 1 to 6 are used as samples to be tested. Each sample to be tested is analyzed according to the IPC-TM-650 2.4.4.18 standard method to obtain an X-axis strain (Ɛ ), the Y-axis is the stress-strain curve of stress (σ), draw a straight line parallel to the Y-axis when the strain is 0.5%, the intersection point of the measured curve of the sample to be tested and the straight line is is the yield strength, and the results are shown in Table 2.

Here, the instruments and measurement conditions selected to measure the yield strength of electrolytic copper foil are as follows: I. Measuring instruments: AG-I universal tensile machine was purchased from Shimadzu Corp. II. Measurement conditions: Sample size: length approximately 100 mm, width approximately 12.7 mm; Chuck distance: 50 mm; and Crosshead speed: 50mm/min.

Test example 4 : Electrolytic copper foil warping

Pull out a sample of about 50 cm in length from the electrolytic copper foils of Examples 1 to 10 and Comparative Examples 1 to 6 obtained by the aforementioned winding on the sampling table, and take a 50 cm × 50 cm sample with the pulled end as one side. Each test piece is placed on the sampling platform with its warped side facing up. Use a ruler to measure the height difference between the two corners of the pull-out end relative to the plane of the sampling platform as the warpage value. Then, compare each example and comparative example. The higher warpage value measured at the two corners of the pull-out end of the test piece is the maximum warpage value. The results are shown in Table 2.

"Electrode"

Example 1A to 10A , comparative example 1A to 6A

The first surface and the second surface of the electrolytic copper foils of the aforementioned Examples 1 to 10 and Comparative Examples 1 to 6 can be respectively coated with negative electrode slurries containing negative electrode active materials to form negative electrodes for lithium ion batteries. Specifically, the negative electrode can be generally produced through the steps described below.

First, prepare the negative electrode slurry, whose composition is as follows: Mesophase graphitic carbon microspheres (MGP): 93.9 parts by weight, as the negative electrode active material; Conductive carbon black (Super P): 1 part by weight, as the conductive additive; Polypropylene Vinyl difluoride (PVDF 6020): 5 parts by weight, as solvent binder; oxalic acid: 0.1 parts by weight; and N -methylpyrrolidone (NMP): 60 parts by weight.

Next, the aforementioned negative electrode slurry is coated on the first surface and the second surface of the electrolytic copper foil respectively. The coating thickness of the negative electrode slurry is about 200 microns each, and heated in an oven at 100°C for 15 minutes to initially remove the slurry. water; then use a rolling machine to roll it to obtain a rolled electrolytic copper foil (density reaches 1.5 grams/cubic centimeter (g/ ^cm3 )); then heat the aforementioned rolled electrolytic copper foil at 120°C The water was completely removed for 10 hours to obtain the negative electrodes of Examples 1A to 10A and Comparative Examples 1A and 6A.

Here, the coating conditions and rolling conditions set when making the negative electrode are as follows: I. Coating conditions: Coating rate: 5 m/min; Coating thickness: approximately 200 μm on each side. II. Rolling conditions: Rolling speed: 1 m/min; Rolling pressure: 3000 pounds per square inch (psi); Roller size of rolling machine: 250 mm (outer diameter, φ) × 250 mm (width); Roller hardness: 62 to 65HRC; and Roller material: high carbon chromium bearing steel (SUJ2).

"Lithium-ion Battery"

Examples 1A to 10A and Comparative Examples 1A to 6A were matched with the same type of positive electrode to prepare lithium ion batteries of Examples 1B to 10B and Comparative Examples 1B to 6B. For the convenience of explanation, the manufacturing process of lithium-ion batteries using the aforementioned negative electrode is described below.

First, prepare a cathode slurry with the following composition: Lithium cobalt oxide (LiCoO ₂ ): 89 parts by weight, as the cathode active material; Flake graphite (KS6): 5 parts by weight, as a conductive additive; Conductive carbon black ( Super P): 1 part by weight as a conductive additive; polyvinylidene fluoride (PVDF 1300): 5 parts by weight as a solvent binder; and N -methylpyrrolidone (NMP): 195 parts by weight.

Next, the positive electrode slurry is coated on both surfaces of the aluminum foil. After the solvent evaporates, the aforementioned positive electrode and the negative electrodes of each embodiment and each comparative example are cut to specific sizes, and then the positive electrode and the negative electrode are sandwiched Microporous isolation membranes (model: Celgard 2400, manufactured by Celgard Company) are alternately pushed and placed in a pressing mold (model: LBC322-01H, purchased from Xinzhoubang Technology Co., Ltd.) filled with electrolyte, and the seal is obtained Laminated lithium-ion battery (dimensions: 250 mm × 154 mm × 12 mm).

Test example 5 :Tolerance

After the lithium ion batteries of Examples 1B to 10B and Comparative Examples 1B to 6B were subjected to 400 charge and discharge cycles under the following conditions, the lithium ion batteries were disassembled, the electrolytic copper foil of the negative electrode was taken out, and the negative electrode slurry on it was removed to obtain The electrolytic copper foil with the negative electrode slurry was then cleaned and cut into test pieces with a size of 150 mm × 12.7 mm. The test piece was used as a sample to be tested for the MIT folding endurance test (MIT folding test), the tolerance measured in this test example is evaluated by the number of times the test piece can withstand folding before rupture, and the results are shown in Table 2.

Here, the conditions for the charge and discharge cycle test are as follows: Charging mode: constant current-constant voltage (CCCV); Discharge mode: constant current (CC); Charging voltage: 4.2 volts (V); Charging current: 5C; Discharge voltage: 2.8 V: Discharge current: 5C; and Measuring temperature: approximately 55°C.

Here, the conditions for the MIT folding endurance test are as follows: MIT folding endurance testing machine: HT-8636A, purchased from HUNGTA; Bending angle: 135°; Bending speed: 175 times/min (CPM); Curvature radius: 0.38 mm; load: 0.5 kg; and clamp distance: 92 mm. Table 2: Characteristic peak half-maximum width of the (111) crystal plane of the first surface and the (111) crystal plane of the second surface of Examples 1 to 10 (E1 to E10) and Comparative Examples 1 to 6 (C1 to C6) The half-height width of the characteristic peak, the absolute difference of the half-height width of the characteristic peak of the (111) crystal plane of the first surface and the second surface, the nanoindentation hardness of the first surface, the nanoindentation hardness of the second surface , the absolute difference in nanoindentation hardness of the first surface and the second surface, yield strength, maximum warpage value and folding endurance after 400 times of charge and discharge. (111)Characteristic peak half-maximum width of crystal plane Nanoindentation hardness (GPa) Yield strength (MPa) Maximum warpage value (mm) The number of folding endurance after charging and discharging first surface second surface absolute difference first surface second surface absolute difference E1 0.137 0.245 0.108 0.49 1.48 0.99 240 2 55 E2 0.139 0.251 0.112 0.51 1.46 0.95 295 3 94 E3 0.142 0.254 0.112 0.52 1.52 1 374 3 135 E4 0.131 0.252 0.121 0.51 1.48 0.97 456 4 201 E5 0.141 0.255 0.114 1.39 1.50 0.11 290 3 90 E6 0.138 0.247 0.109 2.28 1.46 0.82 296 2 77 E7 0.264 0.246 0.018 1.13 1.48 0.35 297 1 92 E8 0.378 0.246 0.132 1.82 1.51 0.31 292 4 79 E9 0.141 0.253 0.112 0.61 1.46 0.85 301 3 111 E10 0.143 0.254 0.111 0.64 1.47 0.83 287 3 106 C1 0.135 0.251 0.116 0.48 1.47 0.99 156 3 twenty three C2 0.140 0.252 0.112 3.56 1.45 2.11 297 3 36 C3 0.141 0.257 0.116 0.26 1.46 1.2 296 3 38 C4 0.394 0.251 0.143 2.33 1.48 0.85 295 6 19 C5 0.421 0.253 0.168 3.04 1.47 1.57 294 9 12 C6 0.072 0.258 0.186 0.44 1.47 1.03 294 12 8

As shown in Table 2 above, the electrolytic copper foils of Examples 1 to 10 can have both (1) the first surface and the second surface having appropriate characteristic peak half-width absolute differences (less than 0.14) of the (111) crystal plane; (2) The first surface and the second surface of the electrolytic copper foil have the characteristics of appropriate nanoindentation hardness (0.3 GPa to 3.0 GPa) and (3) yield strength greater than 230 MPa, so the warpage of the electrolytic copper foil The degree can be effectively suppressed, which can improve the quality of active materials coated in subsequent processes. Specifically, the maximum warpage value of the electrolytic copper foils in Examples 1 to 10 can be controlled to less than 5 mm; using this electrolytic copper The lithium ion battery made of the electrolytic copper foil in Examples 1 to 10 still has good tolerance after 400 charge and discharge cycles. Finally, its folding resistance is at least 50 times.

In contrast, the electrolytic copper foils of Comparative Examples 1 to 6 are because the electrolytic copper foils cannot simultaneously have (1) the absolute difference in half-height width of the characteristic peak of the (111) crystal plane of the first surface and the second surface is within an appropriate range, ( 2) The nanoindentation hardness of the first surface and the second surface is within an appropriate range and (3) the yield strength is greater than 230 MPa. Therefore, the lithium ion batteries made of the electrolytic copper foils of Comparative Examples 1 to 6 perform better during charge and discharge. After 400 cycles, it cannot have good mechanical strength. The lithium-ion battery made of the electrolytic copper foil has a folding endurance of less than 40 times after 400 charge and discharge cycles. Even the electrolytic copper of Comparative Examples 1 to 3 The maximum warpage value of the foil can be controlled to less than 5 mm. However, after 400 charge and discharge cycles of the lithium-ion battery produced, the electrolytic copper foil broke after being bent less than 40 times, indicating that it was broken for many times. The tolerance of secondary charge and discharge processes is poor, which is not conducive to application to lithium-ion batteries.

Further detailed study of the test results of the electrolytic copper foils of Comparative Examples 1 to 6 shows that the yield strength of the electrolytic copper foil of Comparative Example 1 is below 230 MPa. The lithium ion battery prepared by the electrolytic copper foil after 400 charge and discharge cycles , the number of times of folding resistance is only 23, which shows that its tolerance to multiple charge and discharge processes is poor; the nanoindentation hardness of the first surface of the electrolytic copper foil of Comparative Examples 2 and 3 does not fall between 0.3 GPa and 3.0 GPa, the lithium-ion battery made of the electrolytic copper foil has a folding endurance of 36 and 38 times after 400 charge and discharge cycles, indicating that its tolerance to multiple charge and discharge processes is poor; Comparative Example The absolute difference in the half-height width of the characteristic peak of the (111) crystal plane of the first surface and the second surface of the electrolytic copper foils in 4 and 6 is more than 0.14. Not only the maximum warpage value of the electrolytic copper foil is greater than 5 mm, but it is also easy to The quality of the coated active material is reduced. After 400 charge-discharge cycles, the lithium-ion battery made of the electrolytic copper foil has a folding endurance of 19 times and 8 times respectively. It can be clearly seen that the two have been used for many times. The tolerance of the charge and discharge process is not good; the absolute difference in the characteristic peak half-height width of the (111) crystal plane of the first surface and the second surface of the electrolytic copper foil of Comparative Example 5 is more than 0.14, and the first surface The nanoindentation hardness does not fall between 0.3 GPa and 3.0 GPa. Not only does the maximum warpage value of the electrolytic copper foil exceed 5 mm, it is easy to degrade the quality of the coated active material. The lithium produced by the electrolytic copper foil After 400 charge and discharge cycles, the ion battery has a folding resistance of 12 times. It is obvious that its endurance during multiple charge and discharge processes is not good.

In summary, the present disclosure achieves this by controlling the absolute difference of the characteristic peak half-width of the (111) crystal plane on the first and second surfaces of the electrolytic copper foil, the nanoindentation hardness of the first and second surfaces, and the electrolytic The yield strength of the copper foil can specifically improve the endurance of the electrolytic copper foil during multiple charge and discharge processes, while reducing the warpage of the electrolytic copper foil, thereby increasing the process yield and value of lithium-ion batteries for subsequent applications.

10:Electrolytic deposition device 11:Cathode roller 12:Insoluble anode plate 121: Anode surface 13: Copper electrolyte 14:Feeding pipe 20: Anti-rust treatment device 21: Anti-rust treatment tank 211a, 211b: Plate 31:First guide roller 32:Second guide roller 33:Third guide roller 34:Fourth guide roller 35:Fifth guide roller 36:Sixth guide roller 40:Air knife 50:Electrolytic copper foil 51: Copper layer 511: Deposition surface 512:Roller surface 52: First anti-rust layer 521: First surface 53: Second anti-rust layer 531: Second surface

Figure 1 is a schematic diagram of the production flow of electrolytic copper foils of Examples 1 to 10 and Comparative Examples 1 to 6. 2 is a side view of the electrolytic copper foils of Examples 1 to 10 and Comparative Examples 1 to 6.

without

50:Electrolytic copper foil

51: Copper layer

511: Deposition surface

512:Roller surface

52: First anti-rust layer

521: First surface

53: Second anti-rust layer

531: Second surface

Claims (10)

An electrolytic copper foil, which has a first surface and a second surface located on opposite sides. The first surface and the second surface are analyzed by low grazing angle X-ray diffraction (GIXRD). The (111) crystal of the first surface is The absolute difference between the half-height width of the characteristic peak of the surface and the half-height width of the characteristic peak of the (111) crystal plane of the second surface is less than 0.14, and the nanoindentation hardness of the first surface and the second surface of the electrolytic copper foil Each independently ranges from 0.3 GPa to 3.0 GPa, and the yield strength of the electrolytic copper foil is greater than 230 MPa. The electrolytic copper foil according to claim 1, wherein the characteristic peak half-width of the (111) crystal plane on the first surface and the characteristic peak half-maximum width of the (111) crystal plane on the second surface are each independently from 0.10 to 0.38. The electrolytic copper foil according to claim 1, wherein the characteristic peak half-width of the (111) crystal plane on the first surface and the characteristic peak half-maximum width of the (111) crystal plane on the second surface are each independently from 0.13 to 0.13. 0.38. The electrolytic copper foil according to claim 1, wherein the absolute difference between the nanoindentation hardness of the first surface of the electrolytic copper foil and the nanoindentation hardness of the second surface is less than 1.0 GPa. The electrolytic copper foil according to claim 1, wherein the absolute difference between the characteristic peak half-width of the (111) crystal plane on the first surface and the characteristic peak half-width of the (111) crystal plane on the second surface is Below 0.135. The electrolytic copper foil according to claim 5, wherein the absolute difference between the characteristic peak half-width of the (111) crystal plane on the first surface and the characteristic peak half-width of the (111) crystal plane on the second surface is 0.010 to 0.135. The electrolytic copper foil as claimed in claim 1, wherein the yield strength of the electrolytic copper foil is above 240 MPa. The electrolytic copper foil as claimed in claim 7, wherein the yield strength of the electrolytic copper foil is 240 MPa to 500 MPa. An electrode for a lithium-ion battery, which includes the electrolytic copper foil according to any one of claims 1 to 8. A lithium-ion battery comprising the electrode described in claim 9.

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