Metal foil having excellent edge elongation at break and secondary battery comprising same

Abstract

Provided are: a metal foil (100) in which the edge fracture resistance is significantly improved by selectively increasing the elongation of both end edge sections (60) of the metal foil; an electrode for a secondary battery, which includes the metal foil; and a secondary battery.

Description

Technical Field

[0001] The present invention relates to a metal foil having significantly improved edge fracture resistance by selectively increasing the elongation at both ends of the metal foil, and to a secondary battery electrode and a secondary battery including the metal foil. Background Art

[0002] Electrolytic copper foil is commonly used as a base material for printed circuit boards (PCBs) used in the electrical and electronic industries. Furthermore, by improving its physical properties, it is widely used as a negative electrode current collector for secondary batteries. As a result, demand for electrolytic copper foil has increased dramatically, centered around small products such as ultra-thin notebook computers, personal digital assistants (PDAs), e-books, MP3 players, next-generation mobile phones, and ultra-thin flat-panel displays.

[0003] Such electrolytic copper foil can be produced by the following method: using a sulfuric acid-copper sulfate aqueous solution as an electrolyte, applying direct current between a positive electrode immersed in the electrolyte and a rotating negative electrode roller to precipitate copper electrolytically deposited on the roller surface, and removing the precipitated electrolytically deposited copper from the surface of the rotating negative electrode roller and continuously winding it.

[0004] Electrolytic copper foil, on the other hand, is used as a current collector for printed circuit boards and secondary batteries. In particular, thin current collectors are required to increase the capacity of lithium secondary batteries. However, such thin copper foil is prone to breakage, making it difficult to handle, which reduces production yield and productivity. Therefore, there is a need for a copper foil that does not break during battery manufacturing or operation. Summary of the Invention

[0005] Technical issues

[0006] The present invention has recognized that metal foil having a thickness as thin as about 20 μm or less mainly breaks from its edges.

[0007] Therefore, the technical problem of the present invention is to provide a metal foil having improved edge fracture resistance by selectively increasing the elongation of predetermined end regions based on a plane parallel to the longitudinal direction of the metal foil.

[0008] Furthermore, another technical problem of the present invention is to provide a secondary battery electrode using the metal foil and a secondary battery including the same.

[0009] Other objects and advantages of the present invention can be more clearly explained through the following detailed description of the invention and the scope of protection claimed in the invention.

[0010] Technical Solution

[0011] In order to solve the above-mentioned technical problems, the present invention provides a metal foil having one side and another side, wherein the edge portions at both ends of the surface parallel to the longitudinal direction of the metal foil have a first elongation (E1), and the remaining area of the metal foil except the edge portions has a second elongation (E2), and compared with the second elongation, the first elongation is greater than 110%.

[0012] In one embodiment of the present invention, the elongation change rate (RE) according to the following formula 2 may be greater than 10%.

[0013] Formula 2 RE=(E1-E2 / E2)×100

[0014] In one embodiment of the present invention, the difference between the first elongation (E1) and the second elongation (E2) may be in a range of 1% to 20%.

[0015] In one embodiment of the present invention, the first elongation (E1) may be 3% to 30%, and the second elongation (E2) may be 2% to 20%.

[0016] In one embodiment of the present invention, the breaking strength of the edge portions at both ends may be 35 kpsi to 55 kpsi, and the breaking strength of the remaining area of the metal foil excluding the edge portions may be 50 kpsi to 85 kpsi.

[0017] In one embodiment of the present invention, the edge portion may be in a range from one end of the metal foil in the length direction to 15 mm.

[0018] In one embodiment of the present invention, the metal foil may be a rolled metal foil roll.

[0019] In one embodiment of the present invention, during the process of the metal foil being transferred from the first roller to the second roller, the edge portions at both ends may be subjected to local heat treatment.

[0020] In one embodiment of the present invention, the heat treatment can be performed at a temperature above 150° C. for 0.1 second to 60 seconds under an inactive condition.

[0021] In one embodiment of the present invention, the metal foil may be one or more metals selected from the group consisting of Cu, Al, Ni, Fe, Ag, and Au, or alloys thereof.

[0022] In one embodiment of the present invention, the thickness of the metal foil may be 3 μm to 20 μm.

[0023] In one embodiment of the present invention, the roughness (Rz) of both sides of the metal foil may be 0.5 μm to 5.0 μm respectively, and the surface roughness difference between the one side and the other side may be less than 2.0 μm.

[0024] In one embodiment of the present invention, the metal foil further includes one or more anti-corrosion layers formed on the surface. The anti-corrosion layers may include at least one of chromium (Cr), molybdenum (Mo), nickel (Ni), a silane compound, and a nitrogen compound.

[0025] In one embodiment of the present invention, the metal foil may be an electrolytic metal foil.

[0026] In one embodiment of the present invention, the metal foil can be used as a negative electrode current collector of a lithium secondary battery.

[0027] Furthermore, the present invention provides an electrode for a secondary battery including the metal foil and a secondary battery including the electrode.

[0028] Effects of the Invention

[0029] According to one embodiment of the present invention, a metal foil having excellent fracture resistance can be provided by selectively increasing the elongation of both end edges in the entire region of the metal foil.

[0030] Therefore, when the metal foil of the present invention is used as a battery current collector, not only can the quality reliability be continuously maintained during the preparation process, processing and use of the secondary battery, but also many performances can be exerted by preventing cracks and tears in the metal foil during battery charging and discharging.

[0031] The effects of the present invention are not limited to the above-mentioned examples, and more effects are included in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 1 is a cross-sectional view showing the structure of a metal foil according to an embodiment of the present invention.

[0033] Figure 2 This is a cross-sectional view showing the structure of a metal foil according to another embodiment of the present invention.

[0034] Figure 3 This is a diagram briefly showing the process of preparing a metal foil according to one embodiment of the present invention.

[0035] Figure 4 FIG. 1 is a diagram briefly illustrating a process for preparing a metal foil according to an embodiment of the present invention.

[0036] Description of Reference Signs 100, 200: Metal foil 10a: One side (drum side) 10b: The other side (electrolyte side) 20: Anti-corrosion layer 50: Metal layer 60: Edge 400: Local heat treatment device. DETAILED DESCRIPTION

[0037] Hereinafter, the present invention will be described in detail.

[0038] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification are used in accordance with the meanings commonly understood by persons of ordinary skill in the art to which this invention belongs. Furthermore, unless otherwise specifically defined, they are not to be interpreted in an ideal or exaggerated manner.

[0039] Furthermore, throughout this specification, when a portion is referred to as "including" a certain structural element, unless otherwise stated, it should be understood as an open-ended term that includes the possibility of also including other structural elements, rather than excluding other structural elements. Furthermore, throughout this specification, "upper" or "upper portion" refers not only to the upper or lower portion of the subject portion, but also to the portion including other portions in between, and does not necessarily indicate the upper side based on the direction of gravity. Furthermore, in this specification, terms such as "first" and "second" do not indicate arbitrary order or importance, but are used to distinguish between structural elements.

[0040] Furthermore, the terms "preferred" or "preferably" as used in this specification refer to embodiments of the present invention that provide a specified advantage under specified circumstances. However, other embodiments may also be preferred under the same or other circumstances. Additionally, the mention of one or more preferred embodiments does not imply that other embodiments are useless, nor does it exclude other embodiments from the scope of the present invention.

[0041] metal foil

[0042] One example of the present invention is a metal foil that can be applied to a current collector of a secondary battery, a copper laminate (CCL), and / or a printed circuit board (PCB), and more specifically, a battery foil.

[0043] The metal foil is characterized in that at least one edge portion of a surface parallel to the longitudinal direction of the metal foil, specifically, both end edges, selectively exhibits a higher elongation than the remaining area. This differs from conventional metal foils, which have substantially the same elongation across the entire area or exhibit varying elongation depending on a specific direction, such as the width or length.

[0044] Reference Figure 1 The structure of the metal foil of the present invention will be described. Figure 1 This is a cross-sectional view showing the structure of the metal foil of the present invention.

[0045] Reference Figure 1 The metal foil 100 of the present invention includes a metal layer having one surface 10a and another surface 10b. The elongation of the edge portions 60 at both ends of the surface parallel to the longitudinal direction of the battery foil 100 can be 110% or greater compared to the elongation of the remaining region 50 of the metal foil excluding the edge portions 60. Specifically, the elongation can be in the range of 110% to 600%, and more specifically, in the range of 110% to 460%.

[0046] The elongation is based on the measurement according to IPC-TM-650 2.4.18. The thinner the metal foil, the lower the elongation. Therefore, the thickness of the metal foil is 3 μm to 20 μm. In the following description, the elongation of the edge portions of the metal foil 100 in the longitudinal direction is marked as the first elongation (E1). Furthermore, the elongation of the remaining region of the metal foil excluding the edge portion is represented by a second elongation (E2).

[0047] Thin metal foils are typically prone to tearing (fracture), primarily at their edges. In secondary battery manufacturing, this is particularly common during the winding and active material coating processes, leading to reduced productivity and yield.

[0048] In contrast, the metal foil 100 of the present invention selectively performs local heat treatment only on the edge portions 60 at both ends in the longitudinal direction under specified conditions, thereby increasing the elongation of the edge portion 60 relative to the entire area 50 of the relevant metal foil (excluding the edge portion) to provide the edge portion 60 with elongation edge fracture resistance. When the metal foil 100 with such a high edge elongation is used as a current collector for a secondary battery, it has convenient handling and excellent processability in the battery preparation process, thereby ensuring high productivity and preparation yield. In particular, the edge portion of the metal foil of the present invention has high elongation and excellent fracture resistance not only within the normal thickness range, but also in a thin thickness of less than 20μm, thereby showing high capacity characteristics of the battery by increasing the load of active material applied to the metal foil.

[0049] In a specific example, the metal foil 100 may have a change in elongation (RE) of 10% or more according to the following formula 2. Specifically, it may be 10% to 400%, and more specifically, it may be 10% to 360%.

[0050] Formula 2 RE=(E1-E2 / E2)×100

[0051] According to a specific example, the difference between the first elongation (E1) and the second elongation (E1) can be in the range of 1% to 20%, more specifically, 2% to 18%. For example, the first elongation of the edge portions 60 at both ends can be 3% to 30%, more specifically, 5% to 30%. Furthermore, the second elongation can be 2% to 20%, more specifically, 3% to 20%.

[0052] According to another specific example, the fracture strength of the edge portions 60 of the metal foil 100 along the longitudinal direction may be 35 kpsi to 55 kpsi, and the fracture strength of the remaining region 50 of the metal foil excluding the edge portions 60 may be 50 kpsi to 85 kpsi.

[0053] In this specification, the edge portion 60 may refer to the range from one end of the metal foil 100 to 15 mm, based on a plane parallel to the longitudinal direction of the metal foil 100. Specifically, it may refer to the range from one end of the metal foil 100 to 10 mm. The metal foil 100 of the present invention, which has such a physical property of elongation at both end edges, can also be represented by physical properties such as average grain size.

[0054] The method for preparing the metal foil 100 of the present invention having the above-mentioned elongation characteristics of the edge portion is not particularly limited. For example, it can be prepared by selectively performing a local heat treatment only on the edge portions at both ends under predetermined conditions (see the following). Figure 3-Figure 4 ).

[0055] The specific heat treatment method and conditions are not particularly limited, as long as the metal foil 100 of the present invention can be selectively heat-treated only at the longitudinal end edges 60. For example, various methods known in the art to which the present invention pertains may be employed, such as conventional high-frequency induction heating, infrared (IR), and hot air heating. High-frequency induction heating, which can be adjusted to facilitate selective heating of specific areas, is particularly preferred.

[0056] Furthermore, the heat treatment temperature is not particularly limited. For example, it can be a temperature above the softening point of the metal foil 100, that is, above the softening temperature, for example, above 150°C. In one specific example, the edge portions 60 of the metal foil 100 can be locally heat treated at a temperature of 150°C to 500°C for 0.1 to 60 seconds under inert conditions. In this case, the inert conditions are not particularly limited, and nitrogen gas or inert gas known in the art can be used.

[0057] The shape of the metal foil 100 of the present invention is not particularly limited and can have a common shape known in the art. For example, the metal foil 100 can be a sheet or a roll of metal foil known in the art.

[0058] Refer to the following Figure 4 After the foil forming process, the metal foil 100 can selectively undergo local heat treatment at both end edges in the longitudinal direction of the metal foil while being transferred from any first roller to the second roller. More specifically, the metal foil 100 can undergo local heat treatment at both end edges 60 in the longitudinal direction of the metal foil while being transferred from any first roller to the second roller. The metal foil can then be re-rolled into a roll shape by the second roller. The metal foil 100 can then be slitting to a desired size or width as needed.

[0059] Due to the high elongation and high fracture resistance of the edge portion 60 of the metal foil processed as described above, it is possible to minimize edge fracture (tearing) that occurs during subsequent processes of the metal foil or in the electrode preparation process of a battery utilizing the metal foil, such as the winding process or the electrode active material coating process. Furthermore, the metal foil retains the inherent properties of the metal foil in the remaining region 50 excluding the edge portion 60, thereby achieving the excellent quality reliability inherent to the metal foil. For example, when the edge portion of a high-strength metal foil is subjected to the localized heat treatment process described above, it can simultaneously exhibit high tensile properties and high fracture resistance at the edge portion.

[0060] On the other hand, the metal foil 100 of the present invention is an electrolytic metal foil produced through a foil-making process using an electroplating method. More specifically, one side of the metal foil 100 has a relatively low roughness, forming a shiny surface ("S-side," drum surface) 10a with high gloss, while the other side has a relatively high roughness, forming a matte surface ("M-side," electrolyte surface) 10b with a so-called mountain structure.

[0061] In this case, the binding force with the active material and the battery yield will vary greatly depending on the surface state of the metal foil 100 used as the current collector. For example, if the surface is excessively uneven due to the unevenness of the metal foil surface, the discharge capacity retention rate of the secondary battery will be reduced. On the contrary, if the surface is too uniform, it will be difficult to ensure the binding force between the current collector and the active material, which will cause internal short circuits and other problems during the operation of the secondary battery due to the separation of the active material from the current collector. In addition, depending on the state of the metal foil, the difference in the amount of active material coating between the two sides will be induced. Such uneven coating amount between the two sides will cause the problem of reduced electrode capacity and / or unstable activity due to the difference in deformation between the two sides of the current collector. Therefore, in the present invention, the surface roughness of both sides of the metal foil 100 is adjusted within a specified range, so that the physical properties required for the copper foil 100 as a current collector, namely, excellent binding force with the active material and high discharge capacity retention rate, can be ensured.

[0062] In one specific example, the metal foil 100 includes a roll surface (e.g., one surface, 10a) and an electrolyte surface (e.g., the other surface, 10b). Based on Rz (ten-point average roughness), the surface roughness of both surfaces can be approximately 0.5 μm to 5.0 μm, specifically, 1.0 μm to 4.0 μm. More specifically, the surface roughness of the roll surface (e.g., S surface, 10a) of the copper foil can be 1.0 μm to 2.5 μm, and the surface roughness of the electrolyte surface (e.g., M surface, 10b) can be 1.0 μm to 2.5 μm.

[0063] In another specific example, the surface roughness difference between the roller surface 10 a and the electrolyte surface 10 b of the metal foil 100 may be less than 1.0 μm, specifically, less than 0.5 μm.

[0064] Furthermore, the thickness of the metal foil 100 can be within a typical thickness range known in the art to which the present invention pertains. For example, it can be 3 μm to 20 μm, but is not limited thereto. If the thickness of the metal foil 100 is less than approximately 3 μm, it will be difficult to handle the metal foil during the battery manufacturing process, reducing operability. If the thickness of the metal foil 100 is greater than approximately 20 μm, it will be difficult to manufacture a high-capacity battery when the metal foil 100 is used as a current collector due to the increased volume of the current collector.

[0065] The metal foil 100 of the present invention is not particularly limited in terms of its components, composition, and / or structure as long as it satisfies the aforementioned elongation characteristics of the edge portions 60 at both ends of the surface parallel to the longitudinal direction of the metal foil.

[0066] The metal foil 100 can be made of a common conductive metal known in the technical field to which the present invention belongs. For example, the metal foil 100 can be made of one or more metals selected from the group consisting of Cu, Al, Ni, Fe, Ag and Au, or their alloys. Preferably, it can be a metal consisting of Cu, Ni and Al, or their alloys. In this case, the technical components contained in the alloy are not particularly limited, and common metals known in the technical field to which the present invention belongs can be used. Specifically, the metal foil 100 can be a copper foil consisting of copper or a copper alloy. For example, the copper foil can use common copper foils known in the technical field to which the present invention belongs without restriction, for example, it can be standard metal foil, high tensile copper foil, high strength copper foil or copper foil for electric vehicle batteries. However, it is not limited thereto. Moreover, the metal foil 100 can be in the shape of a foil, specifically, it can be a flat copper foil.

[0067] In one specific example, the metal foil 100 may be a copper foil formed by electroplating between an electrode plate and a rotating drum separated by an electrolyte solution. The electrolyte solution may include 50 g / l to 150 g / l of copper ions, 50 g / l to 150 g / l of sulfuric acid, 1 ppm to 100 ppm of halogen, 3 ppb to 1500 ppb of a brightener, 3 ppb to 4000 ppb of low molecular weight gelatin, 3 ppb to 3000 ppb of HEC, and 1 ppb to 20 ppb of a leveling agent, but is not limited thereto and may have a conventional electrolyte composition known in the art.

[0068] Furthermore, unless otherwise specified, the aforementioned physical properties are based on a metal foil thickness of 3 μm to 20 μm, but are not limited to the aforementioned thickness range and can be appropriately adjusted within the thickness range known in the art to which the present invention pertains.

[0069] On the other hand, refer to Figure 2 The metal foil 200 according to one embodiment of the present invention may include one or more anti-corrosion layers 20 formed on its surfaces 10 a and 10 b.

[0070] The anti-corrosion layer 20 is selectively formed on the surfaces 10a and 10b of the metal foil 100 to prevent corrosion. The anti-corrosion layer 20 may comprise a conventional inorganic anti-corrosion material, an organic anti-corrosion material, or a mixture thereof, as known in the art. For example, the anti-corrosion layer 20 may contain one or more of chromium, molybdenum, nickel, a silane compound, and a nitrogen compound.

[0071] The nitrogen compound may include one or more triazole compounds and amine compounds known in the art. The triazole compound may be selected from benzotriazole, methylbenzotriazole, carboxybenzotriazole, chlorobenzotriazole, ethylbenzotriazole, and naphthotriazole. Furthermore, the amine compound may be selected from amide, acrylamide, acetamide, auramine, dodecyltrimethylammonium bromide (DTAB), and diethylenetriamine (DETA).

[0072] In addition to the aforementioned anti-corrosion properties for the metal foil 100 , the anti-corrosion layer 20 may also enhance heat resistance and / or bonding strength with active materials.

[0073] The metal foil 100 of the present invention can be produced using conventional electrolytic foil-making equipment, without particular limitation. For example, a drum (acting as a negative electrode) and an anode (acting as an anode) are placed in a container continuously supplied with electrolyte, and current is applied with the electrolyte interposed between the drum and the anode. In this case, as the drum rotates, electrolytic copper foil is deposited on the drum surface and then rolled by guide rollers.

[0074] The electrolyte may be any conventional electroplating electrolyte composition known in the technical field to which the present invention belongs, with copper sulfate, sulfuric acid and a trace amount of chlorine as main components, and may contain one or more conventional electroplating additives.

[0075] The additives may be additives commonly used in the electroplating field without limitation, for example, accelerators, brighteners, levelers, inhibitors or mixtures thereof.

[0076] Accelerators / brighteners are added to impart gloss to the surface of the plated layer and achieve a finer coating. For example, organic compounds containing disulfide bonds (-SS-) or mercapto groups (-SH) or sulfonate-containing sulfides can be used. Specific examples include at least one of 3-mercaptopropanesulfonic acid (MPS), bis(3-sulfopropyl)disulfide (SPS), 3-(N,N-dimethylaminodithiocarbamoy-1-propanesulfonic acid (DPS), and polymethyldithiocarbonic amine-sulfopropylsulfonate (PTA).

[0077] Furthermore, the retarders / inhibitors are components added to achieve stable low roughness by adsorbing on the surface to hinder the approach of copper ions, thereby prolonging the electroplating process. For example, hydroxyethyl cellulose (HEC), polyethylene glycols (PEG), polypropylene glycols (PPG), polyvinyl alcohols, low molecular weight gelatin (molecular weight: about 1000 to 100000), cellulose additives, polymer organic compounds such as collagen, or mixtures thereof can be used. In addition, polyether-based polymers and organic substances having functional groups containing nitrogen atoms, sulfosuccinate-based surfactants, and / or ethandiamineoxirane-based surfactants can be used.

[0078] Furthermore, a leveler is a component added to eliminate surface height differences and achieve a flat, low-roughness copper foil. For example, low-molecular-weight nitrides (e.g., thioureas, amides, benzimidazoles, benthiazols, dimethylaniline, etc.) can be used. Specifically, compounds such as thiourea, Janus Green B (JGB), polyethyleneimine (PEI), and 3-(2-benzothiazolylmercapto)-propyl-sulfonic acid can be used.

[0079] In a specific example, the electrolyte may include 50 g / l to 150 g / l of copper ions, 50 g / l to 150 g / l of sulfuric acid, 1 ppm to 100 ppm of halogen, 3 ppb to 1500 ppb of at least one additive that acts as a glossing agent, and 1 ppb to 4000 ppb of at least one additive that acts as a carrier and a leveling agent.

[0080] The specific composition of the additives added to the electrolyte may include 3 ppb to 1500 ppb of a glossing agent, 3 ppb to 4000 ppb of low molecular weight gelatin, 3 ppb to 3000 ppb of HEC, and 1 ppb to 20 ppb of a leveling agent.

[0081] Furthermore, the electroplating conditions used in the electrolytic deposition of the electrolytic copper foil can be appropriately adjusted within the range known in the art to which the present invention pertains. For example, the current density can be 30ASD to 100ASD (A / dm 2 ), specifically, it can be in the range of 30ASD to 80ASD (A / dm 2 ). Also, for example, the temperature of the electrolyte may be 35° C. to 75° C., specifically, 40° C. to 60° C. Also, for example, the flow rate of the supplied electrolyte may be 30 m 3 / hr to 120m 3 / hr, specifically, it can be 50m 3 / hr to 100m 3 / hr. However, it is not specifically limited to the aforementioned range.

[0082] The surface roughness difference between the M side (eg, 10a) and the S side (eg, 10b) of the copper foil can be adjusted by adjusting the composition, current density, temperature, type and / or content of the electrolyte.

[0083] As described above, after the electrolytically deposited electrolytic metal foil is peeled from the drum surface, it is then rolled by guide rollers to form a wide, long, film-like metal foil roll. While this metal foil roll is being conveyed by at least one arbitrary roller, the end edges 60 are locally heat-treated to complete the metal foil 100 of the present invention. The roll can then be rewound into a roll. Furthermore, the rewound metal foil can be cut into smaller pieces of metal foil as needed.

[0084] If necessary, additional electrolytic or electroless plating of metals such as Ni, Cr, Mo, and Ag may be applied to the metal foil to impart specific properties. Furthermore, coatings of organic materials known in the art to the present invention, such as silane, BTA, and conductive polymers, may be applied to enhance adhesion to the metal foil, provide corrosion protection, and reduce contact resistance. Furthermore, one or more conventional treatments known in the art to the present invention, such as agglomeration treatment, heat resistance treatment, chemical resistance treatment, and corrosion resistance treatment, may also be applied.

[0085] electrode

[0086] Yet another embodiment of the present invention is an electrode for a secondary battery including the metal foil as a current collector.

[0087] Typically, in lithium secondary batteries, the negative electrode current collector bonded to the negative electrode active material uses a foil formed of aluminum (Al), while the negative electrode current collector bonded to the negative electrode active material uses a foil formed of copper (Cu). Therefore, the present invention will be described using the copper foil 100 as the negative electrode current collector.

[0088] In one specific example, the negative electrode includes the metal foil and a negative electrode active material layer disposed on the metal foil.

[0089] The negative electrode active material layer contains a negative electrode active material and may further contain a common binder and / or a conductive material known in the technical field to which the present invention pertains.

[0090] The negative electrode active material can be any compound that can achieve ion intercalation and deintercalation. Non-limiting examples of the negative electrode active material that can be used include carbon-based and silicon-based negative electrode active materials. In addition, lithium metal or its alloys, other materials that can absorb and release lithium and have a potential to lithium of less than 2V, such as TiO2, SnO2, and Li4Ti5O 12 and other metal oxides.

[0091] The method of manufacturing the aforementioned secondary battery electrode using the metal foil is self-evident to those skilled in the art, and a detailed description thereof is omitted here.

[0092] secondary batteries

[0093] A secondary battery according to another embodiment of the present invention includes a negative electrode including the metal foil.

[0094] The secondary battery may be a lithium secondary battery, specifically, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0095] In one specific example, the lithium secondary battery includes: a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; and an electrolyte disposed between the positive electrode and the negative electrode. Furthermore, the battery may include a separator.

[0096] The lithium secondary battery of the present invention can be manufactured by a common method known in the technical field of the present invention. For example, a separator can be placed between the positive electrode and the negative electrode, and then an electrolyte containing the electrolyte additive can be placed therein.

[0097] Furthermore, the electrolyte may include common lithium salts and electrolyte solvents known in the technical field to which the present invention pertains.

[0098] Furthermore, the separator may be a porous separator, for example, a polypropylene-based, polyethylene-based, or polyolefin-based porous separator, or an organic / inorganic composite separator containing an inorganic substance.

[0099] The present invention will be described in detail below by way of examples. However, the following examples are only for the purpose of illustrating the present invention, and the present invention is not limited to the following examples.

[0100] Reference example

[0101] In the examples of the present invention, copper foil A, copper foil B, and copper foil C manufactured by a common foil manufacturing process were used. The manufacturing process of these foils is as follows.

[0102] In order to prepare the electrolyte, the copper ion concentration was adjusted to 80 g / l, the sulfuric acid concentration was adjusted to 100 g / l, and the chlorine concentration was adjusted to 30 ppm at a temperature of 60°C. The additives added to the electrolyte included low-molecular gelatin (molecular weight 3000), HEC (Hydroxyethyl Cellulose), MPS (3-mercaptopropyl sulfonate) as a gloss agent, and thiourea as a leveling agent.

[0103] Copper foil A was produced using an electrolyte solution containing 10 ppb of brightener, 10 ppb of low molecular weight gelatin, and 10 ppb of HEC. In this case, the electrolyte temperature was 55°C and the electrolyte flow rate was 80 m / s. 3 / hr, current density 60ASD (A / dm 2 ).

[0104] Copper foil B used an electrolyte solution containing 2000 ppb of low molecular weight gelatin and 2000 ppb of HEC. The electrolyte solution conditions were the same as those for the production of copper foil A.

[0105] Copper foil C uses an electrolyte containing 800 ppb of brightener, 2000 ppb of low molecular weight gelatin, 2000 ppb of HEC, and 10 ppb of leveling agent. The electrolyte conditions are the same as those for the production of copper foil A.

[0106] Example 1

[0107] The three types of copper foil (A, B, and C) produced as described above were each cut at a speed of 1 m / min while being wound with edge heaters (edge heaters) set at both ends of the foil along its length adjusted to 250°C. Approximately 100 km of cutting was performed, and the number of times the foil was torn was measured. In this case, the edge heating section was a 1-meter section, the heat treatment temperature was set at 250°C, and an inert gas was introduced. This is equivalent to heat-treating the longitudinal edges of the copper foil at 250°C for approximately one minute.

[0108] The physical properties of the three types of copper foil samples having the localized heat treatment at both end edges were evaluated by the following methods. The results are shown in Table 1 below.

[0109] Physical property evaluation methods

[0110] (1) Measuring thickness

[0111] The thickness of copper foil is measured by the unit area weight method, which is a common method for measuring the thickness of copper foil (IPC-TM-650 2.2.12).

[0112] (2) Measure elongation

[0113] The elongation (%) was measured using UTM (Instron Corporation, Model: 5942) according to IPC-TM-650 2.4.18 standard.

[0114] (3) Measurement of breaking strength

[0115] The breaking strength (kpsi) was measured using a UTM (Instron Corporation, Model: 5942) according to IPC-TM-650 2.4.18.

[0116] (4) First elongation increase rate and elongation change rate

[0117] The first elongation increase rate and the elongation change rate were calculated according to the following formulas 1 and 2, respectively.

[0118] Formula 1 First elongation increase rate (%) = E1 / E2×100

[0119] Formula 2 Elongation change rate (RE, %) = (E1-E2 / E2) × 100

[0120] Table 1

[0121] In this case, copper foil B has high breaking strength but low elongation, which corresponds to a copper foil that is easily torn. Tearing occurs in thin copper foils with a thickness of 10 μm or less. However, when the edge portion is not heat treated, the number of tears is significantly high.

[0122] Example 2

[0123] The same procedures as in Example 1 were followed, except that the cutting speed was changed from 1 m / min to 60 m / min and the edge heat treatment temperature was changed to 350°C. Example 2 was similar to Example 1, except that the longitudinal edges of the copper foil were heat treated at 350°C for 1 second. The physical properties of the three copper foil samples were evaluated using the same methods as in Example 1. The results are shown in Table 2 below.

[0124] Table 2

[0125] Comparative Example 1

[0126] The three types of copper foils A, B, and C prepared above were used and the same method as in Example 1 was used except that no heat treatment was performed without using an edge heater during cutting.

[0127] The physical properties of each copper foil sample were evaluated in the same manner as in Example 1. The results are shown in Table 3 below.

[0128] Table 3

[0129] As shown in Table 3, in the case of Comparative Example 1 without heat treatment, the copper foil edge portion showed similar elongation and breaking strength, but had a problem that the thinner the foil, the more likely it was to break during the manufacturing process.

[0130] In comparison, the metal foils of Examples 1 and 2 exhibit selectively increased elongation at both end edges. This significantly reduces breakage during the manufacturing process, not only for thick copper foils but also for thin copper foils with a thickness of 20 μm or less. Consequently, the use of the metal foils of the present invention as battery current collectors significantly improves handling and quality reliability during the manufacturing, processing, and use of secondary batteries.

Claims

1. A metal foil having one side and another side, characterized in that The metal foil has a first elongation E1 at both end edges of a surface parallel to the longitudinal direction. The remaining area of the metal foil except the edge portion has a second elongation E2, The first elongation is 110% or more compared to the second elongation.

2. The metal foil according to claim 1, wherein The elongation change rate RE according to the following formula 2 is 10% or more, Formula 1: RE=(E1-E2 / E2)×100.

3. The metal foil according to claim 1, wherein The first elongation is 3% to 30%, and the second elongation is 2% to 20%.

4. The metal foil according to claim 1, wherein The breaking strength of the two end edges is 35kpsi to 55kpsi. The metal foil has a breaking strength of 50 kpsi to 85 kpsi in the remaining area except the edge portion.

5. The metal foil according to claim 1, wherein The edge portion is a range of 15 mm from one end in the longitudinal direction of the metal foil.

6. The metal foil according to claim 1, wherein The metal foil is a rolled metal foil roll.

7. The metal foil according to claim 1, wherein The end edges are locally heat-treated while the metal foil is being transferred from the first roller to the second roller.

8. The metal foil according to claim 1, wherein The heat treatment is performed under inert conditions at a temperature of 150° C. or higher for 0.1 to 60 seconds.

9. The metal foil according to claim 1, wherein The metal foil is one or more metals selected from the group consisting of Cu, Al, Ni, Fe, Ag, and Au, or alloys thereof.

10. The metal foil according to claim 1, wherein The thickness of the metal foil is 3 μm to 20 μm.

11. The metal foil according to claim 1, wherein The roughness Rz of both sides of the metal foil is 0.5 μm to 5.0 μm respectively. The difference in surface roughness between the one surface and the other surface is 2.0 μm or less.

12. The metal foil according to claim 1, wherein The metal foil further comprises one or more anti-corrosion layers formed on the surface. The anti-corrosion layer includes at least one of chromium, molybdenum, nickel, a silane compound, and a nitrogen compound.

13. The metal foil according to claim 1, wherein The metal foil is an electrolytic metal foil.

14. The metal foil according to claim 1, wherein Suitable for use as negative electrode current collector for lithium secondary batteries.

15. An electrode for a secondary battery, characterized in that: Include: The metal foil according to any one of claims 1 to 14; and An active material layer is provided on the metal foil.

16. A secondary battery, characterized in that: Comprising the electrode according to claim 15.

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