Copper foil, current collector and lithium ion secondary battery

Abstract

To provide a copper foil, a current collector for a lithium ion secondary battery, and a lithium ion secondary battery.SOLUTION: The present disclosure provides a copper foil containing 2 ppm to 21 ppm of silver, 0.5 ppm to 5.5 ppm of titanium, and 2 ppm to 80 ppm of sulfur, the copper foil having an orientation index of (220) plane of 2.05 to 3.08.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to copper foils that have a wide range of applications, particularly for lithium-ion secondary batteries. [Background technology]

[0002] Due to their small size, high energy density, long life, fast charging capability, small memory effect, and low cost, lithium-ion secondary batteries are widely used in various portable electronic devices such as mobile phones, laptops, tablet PCs, and cameras, as well as in electric vehicles and energy storage systems, making them an indispensable part of modern life. In pursuit of higher energy density and achieving the goals of small volume and high energy, technologies to improve the characteristics of lithium-ion secondary batteries are still being developed and innovated.

[0003] In lithium-ion secondary batteries, copper foil is a good conductor of current and can be used as a negative electrode current collector material. However, if the copper foil itself has poor mechanical properties and sags, or if wrinkles occur after coating the copper foil with carbon-based or silicon-based active materials, or if the copper foil cannot adapt to the thermal expansion and contraction phenomena that occur during the charge and discharge process of lithium-ion secondary batteries and cracks occur, this will affect the reliability and lifespan of the battery. Therefore, improvements to copper foil for lithium-ion secondary batteries are needed to meet these needs. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above, the present disclosure provides a copper foil that has good electrical conductivity, is resistant to sagging, and is resistant to wrinkling after application of substances such as active materials. Furthermore, when applied to lithium ion secondary batteries, the copper foil of the present disclosure can adapt to thermal expansion and cold contraction during charge and discharge processes and is resistant to cracking. [Means for solving the problem]

[0005] The copper foil of the present disclosure contains 2 ppm to 21 ppm of silver, 0.5 ppm to 5.5 ppm of titanium, and 2 ppm to 80 ppm of sulfur, and the orientation index of the (220) plane of the copper foil is 2.05 to 3.08.

[0006] In one specific embodiment, the copper foil contains 5 ppm to 20 ppm of silver. In another specific embodiment, the copper foil contains 0.5 ppm to 5 ppm of titanium. In another specific embodiment, the copper foil contains 5 ppm to 70 ppm of sulfur.

[0007] In one specific embodiment, the ratio of the orientation index of the (220) plane to the orientation index of the (111) plane of the copper foil is 2.77 to 5.40. In another specific embodiment, the orientation index of the (111) plane of the copper foil is 0.57 to 0.87.

[0008] In one specific embodiment, the tensile strength of the copper foil is 45 kg / mm 2 ~85kg / mm 2 In another specific embodiment, the tensile strength of the copper foil is 60 kg / mm 2 ~80kg / mm 2 is.

[0009] In one specific embodiment, the conductivity of the copper foil is 80% IACS (International Annealed Copper Standard) or greater.

[0010] In one specific embodiment, the copper foil has a first surface and a second surface opposite to the first surface, and the ten-point average roughness Rz of the first surface and the second surface of the copper foil is 2.5 μm or less.

[0011] In one specific embodiment, the elongation of the copper foil is 1% to 15%.

[0012] In one specific embodiment, the thickness of the copper foil is 3 μm to 35 μm.

[0013] In one specific embodiment, the copper foil comprises a copper layer and a treatment layer.

[0014] In one specific embodiment, a treatment layer of the copper foil is formed on at least one surface of the copper layer, said treatment layer being formed of an organic or inorganic material.

[0015] In one specific embodiment, the inorganic material comprises at least one selected from the group consisting of chromium, nickel, zinc, cobalt, manganese, and tin.

[0016] In one specific embodiment, the organic material comprises at least one selected from the group consisting of carbon, oxygen, nitrogen, sulfur, and silicon.

[0017] In one specific embodiment, the organic material comprises at least one selected from the group consisting of a porphyrin compound, a silane compound, a benzotriazole compound, and a triazine trithiol compound.

[0018] The present disclosure further provides a current collector for a lithium ion secondary battery, comprising the copper foil described herein.

[0019] The present disclosure further provides a lithium ion secondary battery comprising a current collector according to the present disclosure. [Effects of the Invention]

[0020] The present disclosure primarily controls the content of non-copper elements (i.e., elements other than copper) in copper foil, specifically the content of elements such as silver, titanium, and sulfur, and also controls the crystal orientation index of the copper foil, specifically the orientation index of the (220) plane, thereby imparting excellent electrical conductivity and mechanical properties to the copper foil. The present disclosure also further improves the properties of the copper foil by controlling the tensile strength of the copper foil within a specific range. The technical means described in the present disclosure provide copper foil with good electrical conductivity, reduced sagging, and reduced wrinkling after application of substances such as active materials. It has also been discovered that when the copper foil of the present disclosure is applied to lithium-ion secondary batteries, it can adapt to thermal expansion and contraction during charge and discharge and is less susceptible to cracking. DETAILED DESCRIPTION OF THE INVENTION

[0021] The above summary is not intended to represent every particular embodiment or every aspect of the present disclosure, but rather, the above summary merely provides an illustration of novel aspects and features of the present disclosure.

[0022] Hereinafter, the embodiments of the present disclosure will be described by way of specific specific embodiments, and those skilled in the art will easily understand other advantages and effects of the present disclosure from the disclosure of this specification.

[0023] It should be noted that all ranges and values ​​herein are inclusive and combinable. When a range of numerical values ​​is provided, each value between the upper and lower limits of the range, including the upper and lower limits of the range, is considered to be disclosed herein. It should be understood that any numerical range cited herein is intended to include all subranges encompassed by the range. For example, a range of "1 to 10" is intended to include all subranges between the stated minimum value of 1 and the stated maximum value of 10, and also to include the stated minimum and maximum values, in other words, to have a minimum value of 1 or more and a maximum value of 10 or less. Because the disclosed numerical ranges are continuous, they include each value between the stated minimum and maximum values.

[0024] As used herein, the terms "comprise," "comprise," "contain," or "have" refer to a specific element, and unless otherwise specified, may further include other elements, components, structures, regions, portions, devices, systems, steps, or connections, and do not exclude these other elements. In other words, when a claimed invention "comprises," "comprises," "contains," or "has" a specific element, other elements not specified are permitted, whether or not they are required.

[0025] The terms "upper" and "lower" used in this specification are merely for the purpose of facilitating the description of specific embodiments of the present invention, and are not intended to limit the scope of the present invention. Any adjustment, replacement, or modification of the relative positions and relationships thereof should be considered within the scope of the present invention, provided that it does not substantially change the technical content of the present invention.

[0026] Unless expressly stated otherwise herein, the singular forms "a," "an," and "said" as used herein include the plural forms, and "or" as used herein can be used interchangeably with "and / or."

[0027] A first aspect of the present disclosure provides a copper foil composed primarily of copper (e.g., containing more than 99.5 wt% copper, preferably more than 99.9 wt% copper) and containing trace amounts of non-copper elements. In some specific embodiments, the copper foil can be produced by electrolysis (i.e., an electrolytic copper foil can be produced). During the electrolysis process, other non-copper elements in the electrolyte may be deposited along with the copper or may be added to the copper foil by adhesion, deposition, or the like, thereby causing the electrolytic copper foil to contain trace amounts of non-copper elements. The present disclosure controls the trace amounts of non-copper elements to contain 2 ppm to 21 ppm of silver, 0.5 ppm to 5.5 ppm of titanium, and 2 ppm to 80 ppm of sulfur in the copper foil. The content of these elements can be measured by conventional methods, such as, but not limited to, inductively coupled plasma spectroscopy (ICP).

[0028] The copper foil of the present disclosure contains 2 ppm to 21 ppm of silver, and more particularly, 5 ppm to 20 ppm of silver, for example, 2 ppm, 2.5 ppm, 3 ppm, 3.5 ppm, 4 ppm, 4.5 ppm, 5 ppm, 5.5 ppm, 6 ppm, 6.5 ppm, 7 ppm, 7.5 ppm, 8 ppm, 8.5 ppm, 9 ppm, 9.5 ppm, 10 ppm, 11 ppm, 12 ppm, 13 ppm, 14 ppm, 15 ppm, 16 ppm, 17 ppm, 18 ppm, 19 ppm, 20 ppm, or 21 ppm of silver. The copper foil of the present disclosure contains 0.5 ppm to 5.5 ppm of titanium, and more specifically, 0.5 ppm to 5 ppm of titanium, for example, 0.5 ppm, 1 ppm, 1.5 ppm, 2 ppm, 2.5 ppm, 3 ppm, 3.5 ppm, 4 ppm, 4.5 ppm, 5 ppm, or 5.5 ppm of titanium. The copper foil of the present disclosure contains 2 ppm to 80 ppm of sulfur, and more particularly, 5 ppm to 70 ppm of sulfur, for example, 2 ppm, 3 ppm, 4 ppm, 5 ppm, 6 ppm, 7 ppm, 8 ppm, 9 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm, 55 ppm, 60 ppm, 65 ppm, 70 ppm, 75 ppm, or 80 ppm of sulfur.

[0029] The crystal orientation of the copper foil of the present disclosure is controlled. Specifically, the orientation index of the (220) plane of the copper foil is controlled. The orientation index of a certain crystal plane refers to the ratio of the following two values: (i) the value obtained by dividing the X-ray diffraction intensity of a certain crystal plane of the test sample by the sum of the X-ray diffraction intensities of all the crystal planes of the test sample, and (ii) the value obtained by dividing the X-ray diffraction intensity of a certain crystal plane of the standard sample by the sum of the X-ray diffraction intensities of all the crystal planes of the standard sample. Therefore, the orientation index M(220) of the (220) plane can be expressed by the following formula.

[0030]

number

[0031] Among these, I(200) represents the X-ray diffraction intensity of the (220) plane of the test copper foil sample. ΣI(hkl) represents the sum of the X-ray diffraction intensity of each crystal plane of the test copper foil sample. IF(220) represents the X-ray diffraction intensity of the (220) plane of the standard sample. ΣIF(hkl) represents the sum of the X-ray diffraction intensity of each crystal plane of the standard sample. Furthermore, the X-ray diffraction intensity of each crystal plane of the standard sample is the diffraction intensity of the (hkl) crystal plane of the J6 standard copper powder specified by the American Society for Testing and Materials (ASTM) (PDF#040836). In some specific embodiments, ΣI(hkl) represents the sum of the X-ray diffraction intensities of the (111), (200), (220), and (311) planes of the test copper foil sample, and ΣIF(hkl) represents the sum of the X-ray diffraction intensities of the (111), (200), (220), and (311) planes of the standard sample.

[0032] In some specific embodiments, the orientation index of each crystal plane of the copper foil can be obtained by measuring one surface of the copper foil. When the copper foil is produced by electrolysis, the surface can be the drum surface or the deposition surface. In some specific embodiments, when the copper foil is produced by electrolysis, the orientation index of each crystal plane of the copper foil can be obtained by measuring the deposition surface of the copper foil.

[0033] In some specific embodiments, the orientation index of the (220) plane of the copper foil is 2.05 to 3.08, for example, 2.05, 2.10, 2.20, 2.25, 2.30, 2.37, 2.40, 2.41, 2.50, 2.60, 2.70, 2.80, 2.90, 3.00, or 3.08. In some specific embodiments, the orientation index of the (111) plane of the copper foil is 0.57 to 0.87, for example, 0.57, 0.58, 0.60, 0.62, 0.69, 0.70, 0.80, or 0.87. In some specific embodiments, the ratio of the orientation index of the (220) plane to the orientation index of the (111) plane of the copper foil is 2.77 to 5.40, for example, 2.77, 2.80, 2.90, 3.00, 3.10, 3.20, 3.26, 3.30, 3.31, 3.40, 3.43, 3.50, 3.60, 3.70, 3.80, 3.90, 4.00, 4.10, 4.20, 4.30, 4.31, 4.40, 4.50, 4.60, 4.70, 4.80, 4.90, 5.00, 5.10, 5.20, 5.30, or 5.40.

[0034] In addition to controlling the content of non-copper elements in the copper foil, the present disclosure also monitors the tensile strength. 2 ~85kg / mm 2 and more specifically, 60 kg / mm 2 ~80kg / mm 2 In some specific embodiments, the tensile strength refers to the tensile strength in the transverse direction (TD). 2 ~85kg / mm 2 The tensile strength of, for example, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84 or 85 kg / mm 2 is.

[0035] In some specific embodiments, the conductivity of the copper foil is measured to be 80% IACS or greater, e.g., 80% IACS, 81% IACS, 82% IACS, 83% IACS, 84% IACS, 85% IACS, 86% IACS, 87% IACS, 88% IACS, 89% IACS, or 90% IACS.

[0036] In some specific embodiments, the copper foil has a first surface and an opposite second surface, and the ten-point average roughness Rz of the first surface and the second surface of the copper foil is 2.5 μm or less, respectively, and more specifically, Rz is 2.0 μm or less, respectively, e.g., 2.5 μm, 2.4 μm, 2.3 μm, 2.2 μm, 2.1 μm, 2.0 μm, 1.9 μm, 1.8 μm, 1.7 μm, 1.6 μm, 1.5 μm, 1.4 μm, 1.3 μm, 1.2 μm, 1.1 μm, or 1.0 μm.

[0037] In some specific embodiments, the thickness of the copper foil may be 3 μm to 35 μm, but considering some specific applications or desired mechanical properties, the thickness of the copper foil may be 3 μm to 10 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or 35 μm.

[0038] The preparation of the copper foil of the present disclosure will be described below by way of example. In some specific embodiments, the copper foil can be produced by electrolysis. Electrodeposited copper foil can be produced by electrolysis (also called "electrodeposition," "electrodeposition," or "electroplating") using a foil-forming machine. The foil-forming machine can include at least a drum as a cathode, a mating insoluble metal anode plate, and an electrolyte supply pipe. The drum is a rotatable metal drum with a mirror-finished surface. The metal anode plate can be detachably fixedly installed in the lower half of the drum so as to surround the lower half. The supply pipe can be fixedly installed directly below the drum and located between the two metal anode plates. The drum surface of the electrolytic copper foil is the surface that contacts the drum used in the electrolysis process, and the deposition surface is the surface opposite the drum surface, or the surface that contacts the electrolyte in the electrolysis process. The method for producing electrolytic copper foil involves partially immersing a rotating drum member in an electrolyte containing copper ions and non-copper elemental ions, followed by the application of an electric current, which attracts the ions to the drum and reduces them, coating the surface of the drum, thereby forming copper foil (i.e., electrolytic copper foil) on the drum surface. In a continuous process, the drum is rotated, the electrolytic copper foil thereon is unwound, and new electrolytic copper foil continues to form on the drum surface not covered with electrolytic copper foil. The unwound foil is separated from the drum, for example, by an external force, and then passes through or passes through downstream rollers. In some specific embodiments, the drum surface corresponds to the first surface, and the deposition surface corresponds to the second surface.

[0039] The electrolyte solution further contains additives in addition to the primary copper ions. In one specific embodiment, the additives may be inorganic and / or organic, such as silver-containing additives, titanium-containing additives, sulfur-containing additives, and other additives. In one specific embodiment, the silver-containing additives include, but are not limited to, silver salts such as silver nitrate, silver sulfate, and silver chloride. The titanium-containing additives include, but are not limited to, titanium salts such as titanium sulfate. The sulfur-containing additives include, but are not limited to, thiourea, ethylenethiourea, 3-S-isothiuronium propyl sulfonate (UPS), bis-(sodium sulfopropyl)-disulfide (SPS), sodium 3-mercapto-1-propanesulfonate (MPS), and the like. In one specific embodiment, other additives include polymers such as gelatin, polyethylene glycol, cellulose-based water-soluble polymers, polyethyleneimine, and polyacrylamide. Decomposition products of the above polymers, such as gelatin decomposition products, may also be added as additives. The decomposition products of the above polymers can be produced by decomposing the polymers using an electrolytic method. For example, in a system including a titanium plate as a positive electrode, a copper plate as a negative electrode, a polymer-containing aqueous solution of 10 g / L to 50 g / L, and an auxiliary agent (e.g., sodium thiosulfate, potassium sulfide, etc.), the decomposition products of the above polymers can be produced at 5 A / dm 2 ~30A / dm 2 The polymer decomposition product can be obtained by electrolysis for 8 to 15 seconds at a current density of 10000. The weight average molecular weight (Mw) of the polymer is 20,000 to 100,000, and the weight average molecular weight (Mw) of the decomposition product of the polymer is 6,000 to 30,000, but can be adjusted as necessary.

[0040] In some specific embodiments, when copper foil is produced by electrolysis, the composition and properties of the copper foil can be controlled by controlling the composition of the electrolyte (e.g., the concentrations of copper ions, non-copper element ions, and other substances) and various operation parameters (e.g., current density, electrolyte temperature, processing time, etc.) during the electrolysis process. In one specific embodiment, controlling the composition of the electrolyte is an example of a means for controlling the content of non-copper elements in the electrodeposited copper foil. Based on this embodiment, each component of the electrolyte can be controlled. For example, when the composition of the electrolyte contains copper sulfate, sulfuric acid, chloride ions, and additives, the content of non-copper elements in the electrodeposited copper foil can be controlled by controlling the concentrations of these components. In another specific embodiment, the concentration of copper sulfate (CuSO4·5H2O) can be controlled to 200 g / L to 400 g / L, the concentration of sulfuric acid to 80 g / L to 150 g / L, the concentration of chloride ions to 20 ppm to 100 ppm, and the concentration of additives to 10 ppm to 300 ppm. In another specific embodiment, an example of a means for further controlling the content of non-copper elements in the electrolytic copper foil is to control the concentration of additives.

[0041] In this disclosure, we have discovered that controlling the content of non-copper elements in copper foil can improve its properties. For example, controlling the silver content to 2 ppm or more and the sulfur content to 2 ppm or more can reduce wrinkles that occur during processing, while the opposite can increase wrinkles. These wrinkles can cause the copper foil to become uneven, which is unfavorable for application. Especially when a coating material is present on the surface of the copper foil, these wrinkles can cause insufficient contact between the copper foil and the coating material, increasing the risk of detachment. Furthermore, we have discovered that controlling the titanium content to 0.5 ppm or more can prevent copper foil sagging, while the opposite cannot. Furthermore, in this disclosure, we have discovered that when applied to lithium-ion secondary batteries, controlling the silver content to 2 to 21 ppm, the titanium content to 0.5 to 5.5 ppm, and the sulfur content to 2 to 80 ppm can significantly reduce the occurrence of cracks after charge and discharge. According to the present disclosure, if the silver content and sulfur content are less than 2 ppm, the surface condition or mechanical properties of the copper foil may be poor, making it more susceptible to wrinkling during processing. It is also believed that if the titanium content is less than 0.5 ppm, the mechanical properties of the copper foil may also be poor. Furthermore, non-copper elements such as silver, titanium, and sulfur are present at the grain boundaries of the copper foil. Therefore, based on this, it is believed that if the silver, titanium, and sulfur content at these grain boundaries is too high, the crystal strength will be weakened and the copper foil will become brittle. Furthermore, if the silver content or titanium content is too high, the electrical conductivity will decrease.

[0042] The present disclosure also discovered that the performance of copper foil can be improved by controlling the orientation index of the (220) plane of the copper foil. If the orientation index of the (220) plane (i.e., M(220)) or the ratio of the orientation index of the (220) plane to the orientation index of the (111) plane (i.e., M(220) / M(111)) is too low, for example, wrinkles are likely to occur after a substance such as an active material is applied to the copper foil.

[0043] In some specific embodiments, the copper foil may have a multilayer structure, for example, the copper foil includes a copper layer and a treatment layer. In some specific embodiments, the treatment layer is a layer formed on the surface of the copper layer by further treating the copper layer. In some specific embodiments, the treatment layer is formed on at least one surface of the copper layer. When the copper foil is produced by electrolysis, the surface may be a drum surface or a deposition surface. The treatment layer protects the copper layer from the influence of external factors, thereby preventing deterioration of the copper foil due to oxidation, corrosion, etc. In some specific embodiments, the treatment layer is, for example, an anti-corrosion treatment layer. The treatment layer can be prepared by any known method, and the method may include a step of immersing or passing the copper layer through a solution containing the material to be the treatment layer, or a step of plating the material to be the treatment layer onto the copper layer (e.g., using an electroplating bath). This process may be continuous and may be part of the overall process for preparing a surface-treated copper foil. The thickness of the treatment layer may be 0.2 nm to 100 nm.

[0044] In some specific embodiments, the treatment layer is made of organic or inorganic materials.In some specific embodiments, the inorganic material comprises at least one selected from the group consisting of chromium, nickel, zinc, cobalt, manganese and tin.In some specific embodiments, the organic material comprises at least one selected from the group consisting of carbon, oxygen, nitrogen, sulfur and silicon.In some specific embodiments, the organic material comprises at least one selected from the group consisting of porphyrin compounds, silane compounds, benzotriazole compounds and triazinetrithiol compounds.

[0045] In some specific embodiments, the anti-rust solution may be a chromium anti-rust treatment solution, the main component of which is chromium trioxide (CrO), the concentration of chromium trioxide may be 1.5 g / L to 5.0 g / L, the temperature of the anti-rust treatment solution may be 20°C to 40°C, and the current density of the anti-rust treatment may be 0.5 A / dm 2 ~6.0A / dm 2The rust prevention treatment time may be, but is not limited to, 2 to 4 seconds.

[0046] A second aspect of the present disclosure provides a current collector for a lithium ion secondary battery, comprising the copper foil of the present disclosure.

[0047] A current collector and an electrode for a lithium-ion secondary battery are manufactured by coating at least one layer of active material on at least one side of the copper foil of the present disclosure. The current collector may be a positive electrode current collector and / or a negative electrode current collector, and the electrode may be a positive electrode and / or a negative electrode. The active materials can be divided into positive electrode active materials and negative electrode active materials. The negative electrode active material contains a negative electrode active material, which may be a carbon-containing material, a silicon-containing material, a silicon carbide composite, a metal, a metal oxide, a metal alloy, or a polymer, and is more preferably a carbon-containing material or a silicon-containing material, but is not limited to these. Specifically, the carbon-containing material may be, but is not limited to, mesophase graphite powder (MGP), non-graphitizing carbon, coke, graphite, glassy carbon, carbon fiber, activated carbon, carbon black, or a polymer calcined product. Among these, the coke may include pitch coke, needle coke, or petroleum coke. The polymer calcined product can be obtained by calcining a polymer, such as a phenolic resin or a furan resin, at an appropriate temperature to facilitate carbonation. The silicon-containing material has excellent abilities to form alloys with lithium ions and extract lithium ions from lithium alloys. When used in lithium-ion secondary batteries, the silicon-containing material can achieve the advantage of high energy density. The silicon-containing material can be combined with cobalt, iron, tin, nickel, copper, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium, ruthenium, molybdenum, or a combination thereof to form an alloy material. The metal or metal alloy element can be selected from, but not limited to, the group consisting of cobalt, iron, tin, nickel, copper, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium, ruthenium, and molybdenum. Examples of such metal oxides include, but are not limited to, iron trioxide, iron trioxide, ruthenium dioxide, molybdenum dioxide, and molybdenum trioxide. Examples of such polymers include, but are not limited to, polyacetylene and polypyrrole.

[0048] The active material may optionally contain auxiliary additives, which may be, but are not limited to, a binder and / or a weak acidic agent. For example, the binder may be polyvinylidene fluoride, styrene butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, or polyacrylic acid ester, and the weak acidic agent may be oxalic acid, citric acid, lactic acid, acetic acid, or formic acid.

[0049] A third aspect of the present disclosure provides a lithium ion secondary battery including the current collector of the present disclosure.

[0050] According to the present disclosure, based on the compositional components of different positive electrode pastes, the lithium ion secondary battery of the present disclosure can be classified into a lithium cobalt battery (LiCoO2 battery), a lithium nickel battery (LiNiO2 battery), a lithium manganese battery (LiMn2O4 battery), a lithium cobalt nickel battery (LiCo X The battery may be, but is not limited to, a Ni1-XO2 battery or a LiFePO4 battery.

[0051] According to the present disclosure, a lithium-ion secondary battery includes an electrolyte solution, which may include a solvent, an electrolyte, or additives as needed. The solvent in the electrolyte solution includes a non-aqueous solvent, such as, but not limited to, cyclic carbonates such as ethylene carbonate and propylene carbonate, linear carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, or sultones. The solvents may be used individually or in combination of two or more solvents. The electrolyte may include, but is not limited to, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(oxalate)borate, and lithium bis(trifluoromethanesulfonyl)imide.

[0052] In one specific embodiment, the lithium ion secondary battery may employ a solid electrolyte instead of the above-mentioned electrolyte solution. For example, the solid electrolyte may be, but is not limited to, a crystalline electrolyte, a glass electrolyte, a glass ceramic electrolyte, or a polymer electrolyte. Specifically, the crystalline electrolyte may be, but is not limited to, a sulfide solid electrolyte such as a lithium superionic conductor (LISICON) type or an argyrodite type, or an oxide solid electrolyte such as a garnet type, a perovskite type, or a NASICON type. The glass electrolyte may be, but is not limited to, a glass solid electrolyte such as an oxide or a sulfide. The polymer electrolyte may be, but is not limited to, a pure solid polymer electrolyte such as a polyethylene oxide-based (PEO-based) or polypropylene oxide-based (PPO-based) or a colloidal polymer electrolyte such as a polyacrylonitrile-based (PAN-based), poly(methyl methacrylate)-based (PMMA-based), poly(vinyl chloride)-based (PVC-based), or poly(vinylidene fluoride)-based (PVDF-based).

[0053] According to the present disclosure, the lithium ion secondary battery may be, but is not limited to, a stacked lithium ion secondary battery including a negative electrode and a positive electrode stacked with a separator interposed therebetween, or a spirally wound stacked lithium ion secondary battery including continuous electrodes and a separator spirally wound together.Depending on various application products, the lithium ion secondary battery of the present disclosure may be applied to laptops, mobile phones, electric vehicles, and energy storage systems, and may be manufactured as, for example, but not limited to, a cylindrical secondary battery, a prismatic secondary battery, a pouch-type secondary battery, or a button-type secondary battery.

[0054] Further, the following examples will provide more specific details. However, the interpretation of the present disclosure should not be limited by the following examples. It should be understood that within the scope of the present disclosure, the technical features (e.g., examples) mentioned above and below can be freely combined with each other to form new or more preferred technical solutions, but are omitted for the sake of brevity.

[0055] (Example)

[0056] A copper electrolyte solution was prepared using the following materials, and the cathode titanium drum was rotated at a constant speed around a fixed axis to contact the copper electrolyte solution. A current was applied to the cathode titanium drum and the insoluble anode plate (i.e., under the following electrolysis conditions), and the copper electrolyte solution was deposited on the surface of the cathode titanium drum to form an electrolytic copper foil. The electrolytic copper foil was then peeled off and guided to the guide roller of the set. [Copper electrolyte formulation] Copper sulfate (CuSO4·5H2O): 320g / L Sulfuric acid: 85g / L Chloride ions: 77 ppm [Electrolysis conditions] Temperature: 48℃ Current density: 44A / dm 2 Electrolytic copper foil thickness: 4 to 10 μm

[0057] The electrodeposited copper foil was then transported to a rust prevention treatment device by the guide rollers of the set, and subjected to rust prevention treatment. The electrodeposited copper foil was immersed in a rust prevention treatment tank filled with a rust prevention treatment solution, and a rust prevention layer was formed on the surface of the electrodeposited copper foil by the electrode plates of the two sets. [Rust prevention treatment liquid formulation] Chromium trioxide (CrO3): 1.5g / L [Rust prevention treatment conditions] Temperature: 25℃ Current density: 0.5A / dm 2 Electroplating time: 2 seconds

[0058] After the rust-proofing treatment was completed, the rust-proofed electrodeposited copper foil was continuously guided between the guide rollers of the set, and excess rust-proofing solution and other substances on the surface were removed with an air knife, followed by drying and winding to obtain an electrodeposited copper foil.

[0059] Example 1

[0060] The copper electrolyte contains the copper sulfate, sulfuric acid, and chloride ions, as well as the following additives: 20 ppm gelatin (Mw 40,000-60,000, purchased from Koei Kasei Co., Ltd.), 10 ppm gelatin decomposition product (Mw 12,000-16,000), 2 ppm thiourea, 35 ppm silver nitrate, and 10 ppm titanium sulfate. The gelatin decomposition product is prepared by first adding gelatin and sodium thiosulfate to water and mixing them to form an aqueous solution containing 20 g / L of gelatin and 20 g / L of sodium thiosulfate. Electrolysis is then performed, using a titanium plate as the positive electrode and a copper plate as the negative electrode, with a current density of 20 A / dm. 2 This was performed for 10 seconds at 100°C to produce an aqueous solution containing small molecular gelatin decomposition products. The content of the gelatin decomposition products was based on the total copper electrolyte solution, and an appropriate amount of the aqueous solution was added to the copper electrolyte solution. An electrolytic copper foil was formed on the drum surface using the copper electrolyte solution under the above electrolysis conditions, forming a copper layer. After this, an anti-rust treatment was performed to form anti-rust layers on both sides of the electrolytic copper foil. Excess anti-rust treatment solution and other substances were removed, and the foil was dried to finally obtain an electrolytic copper foil with a thickness of 6 μm.

[0061] Example 2

[0062] A copper electrolyte solution was prepared according to Example 1, except that the gelatin content was adjusted to 24 ppm and the gelatin decomposition product content was adjusted to 6 ppm. Using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 6 μm and having an anticorrosive layer on both sides was prepared.

[0063] Example 3

[0064] A copper electrolyte solution was prepared according to Example 1, except that the gelatin, gelatin decomposition product, thiourea, silver nitrate, and titanium sulfate were adjusted to 24 ppm, 6 ppm, 4 ppm, 45 ppm, and 15 ppm, respectively. Further, using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 6 μm and having anticorrosive layers on both sides was prepared.

[0065] Example 4

[0066] A copper electrolyte solution was prepared according to Example 1, but the thiourea content was adjusted to 1 ppm. Further, using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 6 μm and having an anticorrosive layer on both sides was prepared.

[0067] Example 5

[0068] A copper electrolyte solution was prepared according to Example 1, except that the gelatin content was adjusted to 24 ppm and the gelatin decomposition product content was adjusted to 6 ppm. Using the copper electrolyte solution according to Example 1, a 4 μm-thick electrolytic copper foil having anticorrosive layers on both sides was prepared.

[0069] Example 6

[0070] A copper electrolyte solution was prepared according to Example 1, except that the gelatin content was adjusted to 24 ppm and the gelatin decomposition product content was adjusted to 6 ppm. Using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 10 μm and having anticorrosive layers on both sides was prepared.

[0071] Comparative Example 1

[0072] A copper electrolyte solution was prepared according to Example 1, but without adding silver nitrate and titanium sulfate. Further, using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 6 μm and having an anticorrosive layer on both sides was prepared.

[0073] Comparative Example 2

[0074] A copper electrolyte solution was prepared according to Example 1, except that the gelatin content was adjusted to 24 ppm and the gelatin decomposition product content was adjusted to 6 ppm, and silver nitrate and titanium sulfate were not added. Further, using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 6 μm and having an anticorrosive layer on both sides was prepared.

[0075] Comparative Example 3

[0076] A copper electrolyte solution was prepared according to Example 1, but without adding titanium sulfate. Further, using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 6 μm and having an anticorrosive layer on both sides was prepared.

[0077] Comparative Example 4

[0078] A copper electrolyte solution was prepared according to Example 1, but without adding silver nitrate. Further, using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 6 μm and having an anticorrosive layer on both sides was prepared.

[0079] Comparative Example 5

[0080] A copper electrolyte solution was prepared according to Example 1, except that the gelatin, silver nitrate, and titanium sulfate were adjusted to 30 ppm, 5 ppm, and 1 ppm, respectively, and no gelatin decomposition product was added. Using the copper electrolyte solution according to Example 1, a 6 μm-thick electrolytic copper foil having anticorrosive layers on both sides was prepared.

[0081] Comparative Example 6

[0082] A copper electrolyte solution was prepared according to Example 1, except that the gelatin, gelatin decomposition product, silver nitrate, and titanium sulfate were adjusted to 24 ppm, 6 ppm, 50 ppm, and 20 ppm, respectively. Using the copper electrolyte solution according to Example 1, a 6 μm-thick electrolytic copper foil having anticorrosive layers on both sides was prepared.

[0083] Comparative Example 7

[0084] A copper electrolyte solution was prepared according to Example 1, except that the gelatin, gelatin decomposition product, silver nitrate, and titanium sulfate were adjusted to 24 ppm, 6 ppm, 100 ppm, and 40 ppm, respectively. Using the copper electrolyte solution according to Example 1, a 6 μm-thick electrolytic copper foil having anticorrosive layers on both sides was prepared.

[0085] Comparative Example 8

[0086] A copper electrolyte solution was prepared according to Example 1, but the thiourea content was adjusted to 5 ppm. Further, using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 6 μm and having an anticorrosive layer on both sides was prepared.

[0087] Comparative Example 9

[0088] A copper electrolyte solution was prepared according to Example 1, but without adding thiourea. Further, using the copper electrolyte solution according to Example 1, an electrolytic copper foil having a thickness of 6 μm and having an anticorrosive layer on both sides was prepared.

[0089] Exams and Assessment Methods

[0090] (I) Analysis of metal element content

[0091] 70% nitric acid was diluted with deionized water to prepare 50 mL of 30% nitric acid. The 30% nitric acid was placed in a 250 mL PFA bottle, and 5.4 g of electrolytic copper foil sample was added to the bottle. After dissolution, 85 mL of deionized water was added to obtain a total volume of 135 mL of sample solution. The concentration of non-copper metal elements (silver and titanium in the example below) in the sample solution was analyzed using an inductively coupled plasma optical emission spectrometer (model: Thermo Scientific iCAP 7400 ICP-OES). The unit of measurement obtained is "mg metal / 1 L of sample solution." Since 135 mL of sample solution actually contains 5.4 g of electrolytic copper foil sample, 1 L of sample solution contains 40 g of electrolytic copper foil sample. In other words, the unit of measurement obtained, "mg metal / 1 L of sample solution," is equivalent to "mg metal / 40 g of electrolytic copper foil sample," which can be further converted to "mg metal * 25 / 1 kg of electrolytic copper foil sample," or ppm.

[0092] (II) Analysis of sulfur element content

[0093] First, the ceramic crucible was fired at 1350°C for 15 minutes, and then 1g of electrolytic copper foil sample and 1g of fluxing aid (Copper Metal Accelerator, CAS No. 7440-50-8, manufactured by LECO Corporation) were placed in the ceramic crucible. The ceramic crucible was then clamped and sampled and analyzed using the autosampler of a sulfur analyzer (model number: LECO S744). The measured values ​​are in %, and multiplying these values ​​by 10,000 gives the sulfur content in ppm.

[0094] (III) Orientation index Method: X-light diffraction method Equipment:Bruker D8 ADVANCE ECO Measurement conditions: Measurements were carried out on the deposition surface of the electrolytic copper foil sample. Target material: Co-Kα (1.79026Å) Voltage: 40kV Current: 25mA Scanning range: 2θ=40~120° Scanning rate: 0.39° / sec After obtaining the X-ray diffraction intensities of the (111), (200), (220), and (311) planes, the orientation index of each crystal plane was obtained by dividing the X-ray diffraction intensity of each crystal plane by the sum of the X-ray diffraction intensities of all crystal planes.

[0095] (IV) Tensile strength Standard: IPC-TM-650 Measuring instrument: Shimadzu AG-I type tensile testing machine Test piece dimensions: length 100 mm x width 12.7 mm Test temperature: 25℃ Grip distance: 50mm Pulling speed: 50 mm / min (pulling along the TD)

[0096] (V) Degree of sagging

[0097] A 1,380 mm wide electrodeposited copper foil sample was fed between two horizontal fixed guide rollers 700 mm apart in a slitter, and then the guide rollers were rotated to apply different tensions to the electrodeposited copper foil sample. The appearance of the electrodeposited copper foil sample was then visually inspected and evaluated for sagging and the level of sagging based on Table 1 below. The appearance of the electrodeposited copper foil sample was visually inspected without tension. If there was no sagging, the sagging level was recorded as "0." If there was sagging, further tension was applied and the sample was re-inspected to see if there was any sagging. If an additional 5 kg of tension resulted in no sagging, the sagging level was recorded as "1," i.e., slight sagging. Conversely, if the sagging remained, it was necessary to apply an additional 10 kg of tension. If applying a further tension of up to 10 kg results in no visible sagging, the sagging level is rated as "2," i.e., moderate sagging; conversely, if the sagging remains visible, the sagging level is rated as "3," i.e., severe sagging.

[0098] [Table 1]

[0099] (VI) Wrinkle degree

[0100] A negative electrode paste was prepared using water as the solvent and the negative electrode material listed in Table 2 below at a solid-liquid ratio of 73 wt% (100 g negative electrode material: 73 g water). A 130 μm thick negative electrode paste was applied to the surface of an electrolytic copper foil sample at a speed of 5 m / min, then dried in an oven at 160 °C. The sample was then rolled at a speed of 1 m / min and a pressure of 3000 psi using a roller press (the roller was made of high-carbon chromium bearing steel (SUJ2)). The copper foil was then visually inspected for wrinkles. If no wrinkles were observed at the interface between the negative electrode paste and the electrolytic copper foil sample, the wrinkle level was recorded as "A" and the sample was evaluated as good. If the width of the wrinkled area was greater than 0% but less than 10% of the total width of the copper foil, the wrinkle level was recorded as "B" and the sample was evaluated as having only slight wrinkles. If the width of the wrinkled area exceeds 10% of the total width of the copper foil, the wrinkle level is designated as "C" and the rating is severe wrinkles.

[0101] [Table 2]

[0102] (VII) Electrical conductivity

[0103] Conductivity was measured using an instrument with model number YOKOGAWA 2752 Double Bridge according to ASTM B193-16 standard.

[0104] (VIII) Degree of cracking after charge / discharge test

[0105] Furthermore, this disclosure applies electrolytic copper foil to lithium-ion secondary batteries. The lithium-ion secondary battery preparation method is as follows: A positive electrode paste was prepared using N-methylpyrrolidone (NMP) as a solvent and the positive electrode material listed in Table 3 below at a solid-liquid ratio of 195 wt% (100 g of positive electrode material: 195 g of NMP). A negative electrode paste was prepared using water as a solvent and the negative electrode material listed in Table 2 above at a solid-liquid ratio of 73 wt% (100 g of negative electrode material: 73 g of water).

[0106] [Table 3]

[0107] The positive electrode paste was applied to aluminum foil, and the negative electrode paste was applied to an electrolytic copper foil sample. The sample was then dried in an oven at 160°C to evaporate the solvent. The sample was then rolled at a speed of 1 m / min and a pressure of 3,000 psi using a roller press (the roller was made of high-carbon chromium bearing steel (SUJ2)). The sample was then cut to size to produce positive and negative electrode sheets. Prior to assembly into lithium-ion secondary batteries, the negative electrode sheet was baked in an oven at 140°C for 5 hours to remove moisture. The positive electrode sheet, separator (Celgard®), and negative electrode sheet were rolled together, placed in a container, and the following electrolyte was poured into the container and sealed (the specifications are for a standard cylindrical 18650 battery). The fabricated lithium-ion secondary batteries were subjected to 300 charge / discharge cycles under the following conditions. The lithium-ion secondary batteries were then disassembled and the degree of cracking in the electrolytic copper foil was visually inspected. The results are shown in Table 4. Electrolyte: 1M lithium hexafluorophosphate (LiPF6) and 2 wt% vinylene carbonate (VC) were added to a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:2. Charge / discharge conditions: Room temperature (25℃) Constant current constant voltage (CCCV) mode charging, charging voltage 4.2V, charging current 1C Constant current (CC) mode discharge, discharge voltage 2.8V, discharge current 1C

[0108] The silver content, titanium content, sulfur content, M(111), M(220), M(220) / M(111), tensile strength, degree of sagging, presence or absence of wrinkles and conductivity of each electrodeposited copper foil obtained by the above test methods are shown in Table 4 below.

[0109] [Table 4]

[0110] From the above results, it was found that the electrodeposited copper foil of the present disclosure exhibits excellent effects, such as high conductivity, no sagging, and less wrinkling after application of an active material, by controlling the contents of silver, titanium, and sulfur and the orientation index of the (220) plane. Furthermore, when applied to lithium-ion secondary batteries, the electrodeposited copper foil is less likely to crack even after repeated charging and discharging. In contrast, Comparative Examples 1, 2, 4, and 5 had too low a silver content, which resulted in wrinkles after application of an active material. Comparative Examples 6 and 7 had too high a silver content, which resulted in cracks after repeated charging and discharging. Comparative Examples 1, 2, 3, and 5 had too low a titanium content, which resulted in sagging. Comparative Examples 6 and 7 had too low a titanium content, which resulted in cracks after repeated charging and discharging. Comparative Example 9 had too low a sulfur content, which resulted in wrinkles after application of an active material. In Comparative Example 8, the sulfur content was too high, causing cracks in the copper foil after repeated charge / discharge cycles. In Comparative Examples 2, 5, and 9, the M(220) and M(220) / M(111) ratios were too low, causing wrinkles in the copper foil after application of the active material. In Comparative Example 7, the total silver and titanium content was too high, resulting in a copper foil conductivity lower than 80% IACS.

Claims

1. Contains 2 ppm to 21 ppm of silver, 0.5 ppm to 5.5 ppm of titanium, and 2 ppm to 80 ppm of sulfur; A copper foil having an orientation index of the (220) plane of 2.05 to 3.

08.

2. The copper foil of claim 1 containing 5 ppm to 20 ppm of silver.

3. The copper foil of claim 1 containing 0.5 ppm to 5 ppm of titanium.

4. The copper foil of claim 1 containing 5 ppm to 70 ppm sulfur.

5. 2. The copper foil according to claim 1, wherein the ratio of the orientation index of the (220) plane to the orientation index of the (111) plane is 2.77 to 5.

40.

6. The copper foil according to claim 5, wherein the orientation index of the (111) plane is 0.57 to 0.

87.

7. Tensile strength is 45 kg / mm ２ ~85 kg / mm ２ The copper foil of claim 1 ,

8. Tensile strength is 60 kg / mm ２ ~80 kg / mm ２ The copper foil according to claim 7, wherein

9. 10. The copper foil of claim 1, having a conductivity of 80% IACS or greater.

10. having a first surface and an opposing second surface; The copper foil according to claim 1, wherein the ten-point average roughness Rz of the first surface and the second surface is 2.5 μm or less.

11. The copper foil according to claim 1, having an elongation of 1% to 15%.

12. The copper foil of claim 1, having a thickness of 3 μm to 35 μm.

13. The copper foil of claim 1 comprising a copper layer and a treatment layer.

14. the treatment layer is formed on at least one surface of the copper layer; The copper foil of claim 13, wherein the treatment layer is formed from an organic or inorganic material.

15. 15. The copper foil of claim 14, wherein said inorganic material comprises at least one selected from the group consisting of chromium, nickel, zinc, cobalt, manganese, and tin.

16. 15. The copper foil of claim 14, wherein said organic material comprises at least one selected from the group consisting of carbon, oxygen, nitrogen, sulfur, and silicon.

17. 15. The copper foil of claim 14, wherein the organic material comprises at least one selected from the group consisting of a porphyrin compound, a silane compound, a benzotriazole compound, and a triazinetrithiol compound.

18. A current collector for a lithium ion secondary battery, comprising the copper foil according to any one of claims 1 to 17.

19. A lithium ion secondary battery comprising the current collector according to claim 18.

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