KR102581018B1 - Electrolytic copper foil with high strength for current collector of lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to an electrolytic copper foil for a lithium secondary battery current collector having high strength, a current collector manufactured using the same, and a lithium secondary battery. More specifically, it relates to a high-strength electrolytic copper foil whose half width at room temperature remains constant even after high-temperature heat treatment. The electrolytic copper foil according to the present invention can maintain high strength characteristics even after heat treatment and has the effect of preventing the occurrence of wrinkles and warping, so it can withstand volume changes and heat generation phenomena of lithium secondary batteries and maintain stable capacity and performance. Electrolytic copper foil can be provided.

Description

Electrolytic copper foil for current collector of lithium secondary battery having high strength and lithium secondary battery comprising the same {Electrolytic copper foil with high strength for current collector of lithium secondary battery and lithium secondary battery comprising the same}

The present invention relates to an electrolytic copper foil for a lithium secondary battery current collector having high strength, a current collector manufactured using the same, and a lithium secondary battery. More specifically, the full width at half maximum (FWHM) at room temperature is constant even after high temperature heat treatment. It is about high-strength electrolytic copper foil that is maintained well.

In order to respond to the rapidly increasing energy consumption and change it to an environmentally friendly consumption form, research is being conducted focusing on alternative energy and alternative power sources, that is, electrochemical energy production methods. In particular, secondary batteries have been developed as a method of storing and converting electrochemical energy. Among secondary batteries, lithium secondary batteries, which have excellent discharge performance and high energy density, are used not only for small IT devices such as mobile phones and notebook PCs, but also for medium and large-sized batteries such as electric vehicles and power storage. Applications are expected.

In a lithium secondary battery, the negative electrode consists of a current collector on which a layer of negative electrode active material is applied, and copper foil is generally used as a material for the negative electrode current collector. The copper foil is mainly used as rolled copper foil, but the manufacturing cost is high and it is difficult to manufacture wide copper foil, and the adhesion to the active material is reduced due to contamination from the lubricant used during rolling processing, which reduces the charge and discharge cycle characteristics of the battery. This is known to decrease. Accordingly, the development of technology using electrolytic copper foil as a current collector to replace rolled copper foil is attracting attention.

The thinner the thickness of the electrolytic copper foil used as the negative electrode current collector for lithium secondary batteries, the more active materials it can contain, increasing the capacity of the secondary battery. However, if the thickness of the copper foil is thin, the strength decreases accordingly, making it difficult to handle. The possibility of rupture increases. Therefore, in the case of ultra-thin material, tensile strength characteristics become more important. In addition, in the case of metal-based and composite-based active materials that have recently been in the spotlight for high-capacity use, severe volume expansion occurs, and high-strength electrolytic copper foil that can cope with this is required (see Non-Patent Document 1).

Lithium secondary batteries are accompanied by volume changes during charging and discharging and heat generation due to overcharging. In addition, the active material on the current collector weakens the adhesion of the active material applied to the surface of the current collector due to physical forces such as deterioration of the lithium secondary battery, swelling, or external shock, and a gap occurs between the adhesive surface of the current collector and the active material. A phenomenon in which current and electrons are concentrated at a specific point occurs (see Patent Document 1). Therefore, in order to respond to the high temperature drying conditions during active material coating and the volume expansion and heat generation phenomenon during repeated charging and discharging of the battery, the tensile strength is maintained even during heat treatment, excellent adhesion to the active material, and wrinkles, curls, etc. are maintained. There is a need for copper foil that does not generate heat.

Under this background, the present inventors have made extensive research efforts to develop an electrolytic copper foil that maintains high strength characteristics even after heat treatment. As a result, the present inventors have manufactured an electrolytic copper foil whose half width at room temperature and tensile strength at room temperature remain constant even after heat treatment, thereby exhibiting high strength characteristics and showing wrinkles and fractures. It was confirmed that it was possible to manufacture an electrolytic copper foil that does not occur, and the present invention was completed.

Republic of Korea Patent Publication No. 10-2014-0078883

Kim TR et al., Carbon letters, 2007, 8(4), 335-339.

The purpose of the present invention is to provide an electrolytic copper foil whose half width at room temperature remains constant even after heat treatment.

Another object of the present invention is to provide a current collector for a lithium secondary battery manufactured using the electrolytic copper foil.

Another object of the present invention is to provide a lithium secondary battery including a current collector manufactured using the electrolytic copper foil.

In order to achieve the above object, the first aspect of the present invention is an electrolytic copper foil for a lithium secondary battery current collector, and the room temperature half width of the diffraction peak for the (111) crystal plane in the X-ray diffraction spectrum for the electrolytic copper foil (Full Width at Half) Maximum, FWHM) is 0.18 to 0.35°, and the half width after heat treatment at 130°C for 10 minutes is maintained at more than 97% of the half width at room temperature.

In the present invention, the room temperature tensile strength of the electrolytic copper foil is 45 to 70 kgf/mm ² It is characterized in that the tensile strength after heat treatment at 130°C for 10 minutes is more than 90% of the tensile strength at room temperature.

A second aspect of the present invention provides a current collector for a lithium secondary battery manufactured using the electrolytic copper foil.

A third aspect of the present invention provides a lithium secondary battery including a current collector manufactured using the electrolytic copper foil.

The electrolytic copper foil according to the present invention can maintain high strength characteristics even after heat treatment and has the effect of preventing the occurrence of wrinkles and warping, so it can withstand volume changes and heat generation phenomena of lithium secondary batteries and maintain stable capacity and performance. Electrolytic copper foil can be provided.

Figure 1 is a diagram showing the X-ray diffraction spectrum and half width at room temperature of an electrolytic copper foil for a lithium secondary battery current collector according to Example 1 of the present invention.
Figure 2 is a diagram showing the X-ray diffraction spectrum and half width of the electrolytic copper foil for a lithium secondary battery current collector according to Example 1 of the present invention after heat treatment at 130°C for 10 minutes.

The following will be described in detail with reference to examples, but the present invention is not limited or restricted by the examples. In describing the embodiments, detailed descriptions of well-known functions or configurations may be omitted to make the gist of the present invention clear. Like reference numerals refer to like elements throughout the specification.

Throughout the specification of the present application, when a part is said to “include” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

Throughout this specification, the term "combination thereof" included in the Markushi format expression means a mixture or combination of one or more components selected from the group consisting of the components described in the Markushi format expression, It means including one or more selected from the group consisting of.

Hereinafter, an electrolytic copper foil for a lithium secondary battery current collector having high strength according to the present invention, a current collector manufactured using the same, and a lithium secondary battery will be described in detail.

The electrolytic copper foil for a lithium secondary battery current collector of the present invention has a room temperature half width of the diffraction peak for the (111) crystal plane in the The characteristic is that the width is maintained at more than 97% of the half width at room temperature.

The physical properties of electrolytic copper foil can be shown to meet the required conditions by controlling factors such as gloss, tensile strength, elongation, and crystal orientation, and thus electrolytic copper foil of the required quality can be manufactured. The electrolytic copper foil according to the present invention used the half width value as the control factor, and the half width value of the peak for the (111) plane of the electrolytic copper foil was constant in the X-ray diffraction spectrum for the electrolytic copper foil at room temperature and the electrolytic copper foil after high temperature heat treatment. By maintaining the range, it is possible to produce an electrolytic copper foil that exhibits excellent physical properties and high strength characteristics at room temperature and maintains these characteristics even after high temperature treatment.

The half width refers to the difference between two different diffraction angle (2θ) values corresponding to the maximum intensity value shown in the peak curve for the (111) crystal plane of the electrolytic copper foil in the X-ray diffraction spectrum and the intensity value corresponding to half of it. do. During the manufacturing process of the electrolytic copper foil according to an embodiment of the present invention, the half width at room temperature measured with respect to the (111) surface may be 0.18 to 0.35°, and the above range is the half width at which the bending of the copper foil is alleviated without wrinkles occurring in the high-strength copper foil. It is a width range. If the half width of the electrolytic copper foil is less than 0.18°, it corresponds to a case where the copper crystal particles in the copper foil are large. In this case, it is difficult to realize high strength of the electrolytic copper foil and wrinkles may occur in the copper foil. In addition, if the half width of the electrolytic copper foil is greater than 0.35°, it means that the copper crystal particles in the copper foil are small. In this case, it is difficult to control mechanical properties such as elongation and gloss in addition to strength, and bending occurs in the copper foil, making it difficult to manufacture. Problems may arise in handling during the process.

The room temperature tensile strength of the electrolytic copper foil according to the present invention is 45 to 70 kgf/mm ² It may be, and the tensile strength after heat treatment at 130°C for 10 minutes may be 90% or more of the tensile strength at room temperature. The tensile strength of the electrolytic copper foil is 45 kgf/mm ² If it is less than 70 kgf/mm 2 , wrinkles may occur due to low mechanical strength during roll-to-roll work in the lithium secondary battery manufacturing process, and the tensile strength is 70 kgf/mm ² If it exceeds, the elongation of the electrolytic copper foil may decrease and breakage may occur during the battery manufacturing process.

In addition, if the tensile strength of the electrolytic copper foil after heat treatment is 90% or more of the room temperature tensile strength, the strength can be maintained even after heat treatment, and softening does not occur under high temperature drying conditions during active material coating and during the roll press process, so wrinkles do not occur and handling is easy. It is easy and the yield can be increased.

The elongation of the electrolytic copper foil according to the present invention may be 2 to 20%. If the elongation rate is less than 2%, fracture may occur due to volume changes in the active material layer during charging and discharging, which may cause defects. If it exceeds 20%, it is easily stretched during the negative electrode current collector manufacturing process, making it easy to deform the electrode. It can happen.

The surface roughness Rz of each of the matte side (M side) and shiny side (S side) of the electrolytic copper foil according to the present invention may be 2.0 μm or less.

On one side of the electrolytic copper foil, a shiny surface (S-side) with relatively low illumination is formed, and on the other side, a matte surface (M-side) is formed with the same or higher relative illumination compared to the S-side. If the surface roughness Rz exceeds 2.0 μm, the thickness of the active material layer may become uneven and uniform charging and discharging may not occur, which may deteriorate the lifespan characteristics of the lithium battery.

The thickness of the electrolytic copper foil according to the present invention may be 5 to 20 μm. The thinner the thickness of the electrolytic copper foil, the more the current collector with the active material attached can be included in the secondary battery, which is advantageous for high capacity. However, if the thickness is less than 5 μm, the mechanical strength may decrease and the possibility of fracture may increase, and the thickness of the electrolytic copper foil may increase. If it exceeds 20 μm, the amount that can be included in the secondary battery decreases, making it difficult to achieve high capacity.

Electrolytic copper foil according to an embodiment of the present invention can be manufactured through a conventional electrolytic foil manufacturing device. That is, a drum that functions as a cathode and an anode are installed in a container into which an electrolyte is continuously supplied, and the drum and the anode are spaced apart so that the electrolyte can be interposed, and a current is applied between them. At this time, as the drum rotates, electrolytic copper foil may be electrodeposited on the drum surface and wound through a guide roll. The electrolyte solution may be a copper electrolyte solution containing copper ions, sulfuric acid, chlorine, and an organic additive. The organic additive may be a thiourea-based compound or a cellulose-based compound. The electrolyte solution may contain 70 to 100 g/L of copper ions, 70 to 100 g/L of sulfuric acid, 10 ppm or less of chlorine, and 5 ppm or less of organic additives.

The thiourea-based compounds can improve the manufacturing stability and strength of electrolytic copper foil, and include diethylthiourea, ethylenethiourea, acetylenethiourea, dipropylthiourea, N-trifluoroacetylthiourea, Dibutylthiourea, N-ethylthiourea, N-cyanoacetylthiourea, N-allylthiourea, o-tolylthiourea , N,N'-butylene thiourea, thiazolidinethiol, 4-thiazolinethiol, 4-methyl-2-pyrimidinethiol (4 -methyl-2-pyrimidinethiol), 2-thiouracil, or a combination thereof, but is not necessarily limited to these, and any thiourea-based compound that can be used as an additive in the art is possible.

In addition, the cellulose-based compound can be added as an agent to achieve stable low illumination, and may be hydroxyethyl cellulose (HEC), carboxymethyl cellulose, or a combination thereof, but is not limited thereto. Any additive commonly used as an electrolytic copper foil can be used without limitation. Additionally, sulfide-based compounds and polymer nitrides may be additionally added to the electrolyte solution.

The temperature of the copper electrolyte solution used in the manufacturing process of the electrolytic copper foil according to one embodiment of the present invention may be 40 to 60° C., and the current density used in the manufacturing process may be 30 to 60 A/dm ² .

The manufacturing process of the electrolytic copper foil according to one embodiment of the present invention may additionally perform purification processes such as carbon filtration, diatomaceous earth filtration, and hydrogen peroxide addition to minimize organic impurities in the electrolyte solution.

Additionally, surface treatment may be additionally selectively performed on the electrolytic copper foil. In one embodiment of the present invention, the electrolytic copper foil may be subjected to chromate treatment on the surface of the electrolytic copper foil through an immersion process using a rust preventive liquid containing chromic acid as a main ingredient, thereby further improving moisture resistance and heat resistance.

Another aspect of the present invention provides a current collector for a lithium secondary battery manufactured using an electrolytic copper foil whose half width after heat treatment is maintained at 97% or more of the half width at room temperature. Since the current collector is made of the electrolytic copper foil described above, not only can it provide high mechanical strength even after heat treatment, but it can also easily accommodate changes in the volume of the electrode active material.

Another aspect of the present invention provides a lithium secondary battery including a current collector manufactured using an electrolytic copper foil whose half width after heat treatment is maintained at 97% or more of the half width at room temperature. The lithium secondary battery according to the present invention can provide improved lifespan characteristics and stable high efficiency characteristics by employing a negative electrode including a current collector made of the above-described electrolytic copper foil, and can especially exhibit excellent lifespan characteristics even at high temperatures.

The lithium secondary battery includes a negative electrode; anode; and an electrolyte disposed between the anode and the cathode.

The negative electrode includes the aforementioned current collector; and a negative electrode active material layer disposed on at least one surface of the current collector, wherein the negative electrode active material layer may include a negative electrode active material, a binder, and a conductive material.

The negative electrode active material may be a non-carbon-based material. For example, the negative electrode active material is one or more selected from the group consisting of a metal alloyable with lithium, an alloy of a metal alloyable with lithium and another metal, an oxide of a metal alloyable with lithium, a transition metal oxide, and a non-transition metal oxide. may include.

The metal alloyable with lithium is Si, Sn, Al, Ge, Pb, Bi, Si-Y alloy (Y is an alkali metal, alkaline earth metal, group 13-16 element, transition metal, rare earth element, or a combination thereof. , but not Si), a Sn-Y alloy (where Y is an alkali metal, an alkaline earth metal, a group 13 to 16 element, a transition metal, a rare earth element, or a combination thereof, but not Sn), etc. The element Y includes Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Ge, P, As, Sb, Bi, S, Se, Te, It may be Po, or a combination thereof.

The transition metal oxide may be lithium titanium oxide, vanadium oxide, or lithium vanadium oxide, and the non-transition metal oxide may be SnO ₂ or SiO _x (0<x<2), but is not limited thereto. Specifically, the negative electrode active material is Si, Sn, Pb, Ge, Al, SiO _x (0<x≤2), SnO _y (0<y≤2), Li ₄ Ti ₅ O ₁₂ , TiO ₂ , LiTiO ₃ , It may be one or more selected from the group consisting of Li ₂ Ti ₃ O ₇ , but is not necessarily limited to these, and any non-carbon-based negative electrode active material that is used in the art is possible.

Additionally, a composite of the non-carbon-based negative electrode active material and a carbon-based material may also be used, and a carbon-based negative electrode active material may be additionally included in addition to the non-carbon-based material. The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as natural graphite or artificial graphite in the form of non-shaped, plate-shaped, flake, spherical or fibrous shapes, and the amorphous carbon may be soft carbon (low-temperature calcined carbon). , hard carbon, mesophase pitch carbide, or calcined coke, but is not limited thereto.

As the conductive material, metal powders such as acetylene black, Ketjen black, natural graphite, artificial graphite, carbon black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, etc. can be used, and polyphenylene derivatives, etc. One type or a mixture of one or more types of conductive materials may be used, but are not limited to these, and any conductive material that can be used as a conductive material in the relevant technical field may be used. Additionally, the above-described crystalline carbon-based material may be added as a conductive material.

The binder includes vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, or styrene butadiene rubber-based polymer. It can be used, but is not limited to these, and any binder that can be used in the art can be used.

The cathode can be manufactured by the following method. First, a negative electrode active material composition containing a mixture of a negative electrode active material, a conductive material, a binder, and a solvent is prepared, and the negative electrode active material composition is directly coated on a metal current collector to produce a negative electrode plate. Alternatively, the negative electrode active material composition may be cast on a separate support, and then the film peeled from the support may be laminated on a metal current collector to produce a negative electrode plate. The cathode is not limited to the forms listed above and may have forms other than those listed above.

The solvent may be N-methylpyrrolidone, acetone, or water, but is not limited to these and any solvent that can be used in the art can be used. The contents of the negative electrode active material, conductive material, binder, and solvent are at levels commonly used in lithium batteries, and one or more of the conductive material, binder, and solvent may be omitted depending on the use and configuration of the lithium secondary battery.

The anode can be manufactured by the following method. First, a positive electrode active material composition containing a mixture of a positive electrode active material, a conductive material, a binder, and a solvent is prepared, and the positive electrode active material composition is directly coated and dried on a metal current collector to manufacture a positive electrode plate. Alternatively, the positive electrode active material composition may be cast on a separate support, and then the film peeled from the support may be laminated on a metal current collector to produce a positive electrode plate.

The positive electrode active material may include one or more selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide, but is not necessarily limited to these and is within the technical field. Any available cathode active material can be used. For example, LiNiO ₂ , LiCoO ₂ , LiMn _x O _x (x=1, 2), LiNi _{1 -x Mn x} O ₂ (0<x<1), LiNi _{1 -x- y} Co _x Mn _y O ₂ (0≤x≤0.5, 0≤y≤0.5), LiFeO ₂ , V ₂ O ₅ , TiS, MoS, etc. may be used. In the positive electrode active material composition, the conductive material, binder, and solvent may be the same as those in the negative electrode active material composition. Meanwhile, it is also possible to form pores inside the electrode plate by further adding a plasticizer to the positive electrode active material composition and/or the negative electrode active material composition.

A separator may be inserted between the anode and the cathode. Any separator commonly used in lithium batteries can be used. An electrolyte that has low resistance to ion movement and has excellent electrolyte moisturizing ability can be used. For example, it may be selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, and may be in the form of non-woven or woven fabric. As a non-limiting example, a rollable separator such as polyethylene or polypropylene may be used in the lithium ion battery.

The separator can be manufactured according to the following method. A separator composition is prepared by mixing a polymer resin, a filler, and a solvent, and the separator composition can be directly coated and dried on the top of the electrode to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled from the support is laminated on the electrode to form a separator.

The polymer resin used to manufacture the separator is not particularly limited, and any materials used in the binder of the electrode plate can be used. For example, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, or mixtures thereof can be used.

The electrolyte disposed between the anode and the cathode may be an organic electrolyte solution. Additionally, the electrolyte may be solid. The solid electrolyte may be boron oxide or lithium oxynitride, but is not limited to these, and any solid electrolyte that can be used in the art can be used. The solid electrolyte may be formed on the cathode by a method such as sputtering.

The organic electrolyte solution can be prepared by dissolving lithium salt in an organic solvent. The organic solvent may be any organic solvent that can be used in the art. Non-limiting examples of the organic solvent include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, Propyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethyl Acetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

The lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _{2x + 1} SO ₂ )(C _y F _{2y + 1} SO ₂ ) (where x, y are natural numbers), LiCl, LiI, or a mixture thereof, but is not limited thereto and is used as a lithium salt in the art. Anything that can be used can be used.

Hereinafter, the present invention will be described in detail through examples. However, these examples are for illustrating the present invention in more detail, and the scope of the present invention is not limited to these examples.

Example : Electrolyzed copper foil manufacturing

Example One

To manufacture electrolytic copper foil by electrolysis, a making machine was used with an insoluble anode (DSE; Dimensionally Stable Electrode) and a titanium cathode drum facing each other, and the temperature of the copper electrolyte solution was maintained at 55°C. Plating was performed at a current density of 40 A/dm ² , and a copper electrolyte containing 70 g/L of copper ions and 85 g/L of sulfuric acid as a basic composition was used. The copper electrolyte solution was purified through a carbon filter. Chlorine and organic additives were additionally added to the copper electrolyte solution, and the composition of the added chlorine and organic additives is shown in Table 1 below. The electrolytic copper foil prepared above was subjected to chromate treatment on the surface by immersing it in a separate anti-rust tank containing 5 g/L of chromic acid solution for 2 seconds.

Example 2 to 4 and Comparative example 1 to 4

Electrolytic copper foil was manufactured in the same manner as Example 1, except that the composition of the copper electrolyte solution was changed as shown in Table 1 below.

In Table 1, the abbreviations refer to the following compounds.

HEC: Hydroxyethyl Cellulose

TU: thiourea

Experiment example One : Electrolyzed copper foil Physical property evaluation

1-1. X-ray diffraction analysis ( XRD ; X-ray diffraction)

X-ray diffraction analysis of the electrolytic copper foil prepared in Examples 1 to 4 and Comparative Examples 1 to 4 was theta-2 theta in the range of diffraction angle 2θ=30-100° using Bruker D8 DISCOVER. The sample was scanned at a speed of 2°/min using (Theta-2-Theta) as the scan axis, and the scan was performed at a wavelength of 1.5406 A at 40 kV and 40 mA using Cu Kα radiation. In addition, X-ray diffraction analysis was performed on the electrolytic copper foil after heat treatment at 130°C for 10 minutes in the same manner as above, and the half width of the peak appearing for the (111) crystal plane of the electrolytic copper foil in the X-ray diffraction spectrum was calculated. did. The results are shown in Table 1 above. In addition, the X-ray diffraction spectra of the electrolytic copper foil prepared in Example 1 at room temperature and after heat treatment (130° C., 10 minutes) are shown in Figures 1 and 2, respectively.

1-2. Tensile strength measurement

Tensile tests of the electrolytic copper foils prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were conducted according to the IPC-TM-650 standard. The maximum load of the tensile strength measured at room temperature is called the room temperature tensile strength, and the tensile strength was measured in the same manner as above using electrolytic copper foil after heat treatment at 130°C for 10 minutes and recorded as the high temperature tensile strength (Table 1).

1-3. surface roughness ( Rz ) and elongation measurement

The surface roughness Rz of the electrolytic copper foil prepared in Examples 1 to 4 and Comparative Examples 1 to 4 was measured according to the JISB0601-1994 standard, and the elongation of the electrolytic copper foil was measured according to the IPC-TM-650 standard, and the results are as follows. It is shown in Table 2.

division Surface roughness (μm) Elongation (%) Example 1 1.6 8.1 Example 2 1.6 7.5 Example 3 1.2 5.1 Example 4 1.9 10.5 Comparative Example 1 2.7 3.4 Comparative Example 2 2.4 8.2 Comparative Example 3 2.6 4.2 Comparative Example 4 1.7 7.9

As a result of evaluating the physical properties of the electrolytic copper foil manufactured in the above example, as shown in Table 1, the half width and tensile strength after heat treatment were maintained at more than 97% and more than 90% of the half width at room temperature and tensile strength at room temperature, respectively. , through this, it was confirmed that it was possible to manufacture electrolytic copper foil that can maintain high strength characteristics even after high-temperature treatment. In addition, it was confirmed that it was possible to manufacture an electrolytic copper foil in which no rupture occurred due to heat treatment or volume change due to heat treatment, as wrinkles were not created on the electrolytic copper foil and warping was alleviated. That is, from the above results, the electrolytic copper foil can withstand the volume change and heat generation phenomenon of the lithium secondary battery and maintain stable capacity and performance, and improves the efficiency and lifespan characteristics of the battery including a current collector made of the electrolytic copper foil. You can see that you can contribute.

So far, the present invention has been examined focusing on its preferred embodiments. A person skilled in the art to which the present invention pertains will understand that the present invention may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative rather than a restrictive perspective. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the equivalent scope should be construed as being included in the present invention.

Claims (7)

As an electrolytic copper foil for a lithium secondary battery current collector,
In the X-ray diffraction spectrum for the electrolytic copper foil, the full width at half maximum (FWHM) of the diffraction peak for the (111) crystal plane is 0.18 to 0.35°, and the half width after heat treatment at 130°C for 10 minutes is Electrolytic copper foil characterized in that it is maintained at more than 97% of the half width at room temperature. The method of claim 1, wherein the room temperature tensile strength of the electrolytic copper foil is 45 to 70 kgf/mm ² An electrolytic copper foil characterized in that the tensile strength after heat treatment at 130°C for 10 minutes is more than 90% of the tensile strength at room temperature. The electrolytic copper foil according to claim 1, wherein the electrolytic copper foil has an elongation of 2 to 20%. The electrolytic copper foil according to claim 1, wherein the surface roughness Rz of each of the matte side (M side) and the shiny side (S side) of the electrolytic copper foil is 2.0 μm or less. The electrolytic copper foil according to claim 1, wherein the electrolytic copper foil has a thickness of 5 to 20 μm. A current collector for a lithium secondary battery manufactured using the electrolytic copper foil for a lithium secondary battery current collector according to claim 1. A lithium secondary battery comprising a current collector manufactured using the electrolytic copper foil for a lithium secondary battery current collector according to claim 1.