Metal foil with excellent edge breaking elongation and secondary battery including same

Abstract

The present invention provides a metal foil 100 having significantly improved edge breakage resistance by selectively increasing the elongation of both edge portions 60 of the metal foil, as well as a secondary battery electrode and a secondary battery including the metal foil.

Description

[Technical Field]

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

[0002] Electrolytic copper foil is generally used as the base material for printed circuit boards (PCBs) in the electrical and electronics industries. Its physical properties have also been improved, making it widely used as a negative electrode current collector for secondary batteries. As a result, demand for electrolytic copper foil is rapidly increasing, particularly in small products such as slim notebook computers, personal digital assistants (PDAs), e-books, MP3 players, next-generation mobile phones, and ultra-thin flat panel displays.

[0003] Such an electrolytic copper foil is produced by a method in which an aqueous sulfuric acid-copper sulfate solution is used as an electrolyte, a direct current is applied between a positive electrode immersed in the electrolyte and a rotating negative electrode drum to deposit electrodeposited copper on the drum surface, and the deposited electrodeposited copper is peeled off from the surface of the rotating negative electrode drum and continuously wound up.

[0004] On the other hand, electrolytic copper foils are used as current collectors 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 foils are prone to breakage and are difficult to handle, resulting in reduced manufacturing yield and productivity. Therefore, there is a demand for copper foils that do not break during the battery manufacturing process or during battery operation. Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have recognized that in the case of a metal foil having a thickness of about 20 μm or less, fracture mainly starts from the edge.

[0006] Therefore, the technical objective of the present invention is to provide a metal foil with improved edge breakage resistance by selectively increasing the elongation of specified end regions based on a plane parallel to the longitudinal direction of the metal foil.

[0007] Another technical object of the present invention is to provide an electrode for a secondary battery using the above-mentioned metal foil, and a secondary battery including the electrode.

[0008] Other objects and advantages of the present invention will be more clearly set forth in the detailed description of the invention and claims that follow. [Means for solving the problem]

[0009] In order to achieve the above technical objectives, the present invention provides a metal foil having one side and another side, wherein both end edge portions of the side parallel to the longitudinal direction of the metal foil have a first elongation (E1), and the remaining area of ​​the metal foil excluding the edge portions has a second elongation (E2), and the first elongation is 110% or more of the second elongation.

[0010] According to one embodiment of the present invention, the elongation change rate (RE) according to the following formula 2 may be 10% or more. [Formula 2] RE = (E1 - E2 / E2) x 100

[0011] According to one embodiment of the present invention, the difference between the first elongation (E1) and the second elongation (E2) may be in the range of 1 to 20%.

[0012] According to 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%.

[0013] According to one embodiment of the present invention, the breaking strength of both edge portions may be 35 to 55 kpsi, and the breaking strength of the remaining region of the metal foil excluding the edge portions may be 50 to 85 kpsi.

[0014] According to one embodiment of the present invention, the edge portion may be in a range of up to 15 mm from one end in the length direction of the metal foil.

[0015] According to one embodiment of the present invention, the metal foil may be a roll of wound metal foil.

[0016] According to one embodiment of the present invention, both edge portions of the metal foil may be locally heat-treated while being transferred from the first roller to the second roller.

[0017] According to one embodiment of the present invention, the heat treatment may be carried out under inert conditions at a temperature of 150° C. or higher for 0.1 to 60 seconds.

[0018] According to 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.

[0019] According to one embodiment of the present invention, the metal foil may have a thickness of 3 to 20 μm.

[0020] According to one embodiment of the present invention, the roughness (Rz) of each of the two surfaces of the metal foil may be 0.5 to 5.0 μm, and the difference in surface roughness between the one surface and the other surface may be 2.0 μm or less.

[0021] According to one embodiment of the present invention, the metal foil further includes at least one anticorrosion layer formed on the surface thereof, and the at least one anticorrosion layer may include at least one of chromium (Cr), molybdenum (Mo), nickel (Ni), a silane compound, and a nitrogen compound.

[0022] According to one embodiment of the present invention, the metal foil may be an electrolytic metal foil.

[0023] According to one embodiment of the present invention, the metal foil may be used as a negative electrode current collector of a lithium secondary battery.

[0024] The present invention also provides an electrode for a secondary battery including the metal foil described above, and a secondary battery including the electrode. [Effects of the Invention]

[0025] According to one embodiment of the present invention, by selectively increasing the elongation of both edge portions of the entire region of the metal foil, it is possible to provide a metal foil having excellent fracture resistance.

[0026] As a result, when the metal foil according to the present invention is used as a current collector for a battery, not only can the quality reliability of the secondary battery be continuously maintained during the manufacturing process, processing, and use thereof, but also cracks and tears in the metal foil during charging and discharging of the battery can be prevented, thereby enabling the metal foil to exhibit various excellent performances.

[0027] The effects of the present invention are not limited to the above-mentioned examples, and various other effects are included in this specification. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a cross-sectional view showing the structure of a metal foil according to one embodiment of the present invention. [Figure 2] FIG. 4 is a cross-sectional view showing the structure of a metal foil according to another embodiment of the present invention. [Figure 3] 1 is a diagram illustrating a manufacturing process of a metal foil according to an embodiment of the present invention. [Figure 4] 1 is a diagram illustrating a manufacturing process of a metal foil according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be described in detail below. Unless otherwise defined, all terms (including technical and scientific terms) used in this specification can be used in a manner commonly understood by those skilled in the art to which the present invention belongs. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless explicitly defined otherwise.

[0030] Furthermore, throughout this specification, when a part "comprises" a certain element, unless otherwise specified, it should be understood as an open-ended term that does not exclude other elements but includes the possibility of further including other elements. Furthermore, throughout this specification, "on" or "above" means not only being located above or below the part in question, but also including cases where there are other elements therebetween, and does not necessarily mean being located above in the direction of gravity. Furthermore, in this specification, terms such as "first" and "second" do not indicate any order or importance, but are used to distinguish elements from each other.

[0031] Also, as used herein, the terms "preferred" and "preferably" refer to embodiments of the invention that may offer certain benefits, under certain circumstances, although other embodiments may also be preferred, under the same or different circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

[0032] <Metal foil> One embodiment of the present invention is a metal foil applicable to current collectors of secondary batteries, copper clad laminates (CCLs), and / or printed circuit boards (PCBs), and more specifically, a battery foil.

[0033] The metal foil is characterized in that at least one edge portion, specifically both edge portions, of a surface parallel to the length direction of the metal foil has a higher elongation than the remaining region, which differentiates it from conventional metal foils that have substantially the same elongation over the entire region or that have different elongation along a specific direction such as the width direction or length direction.

[0034] The configuration of the metal foil according to the present invention will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing the structure of the metal foil according to the present invention.

[0035] 1, a metal foil 100 according to the present invention includes a metal layer having one surface 10a and another surface 10b, and the elongation of edge portions 60 at both ends of the surfaces parallel to the longitudinal direction of the battery foil 100 may be 110% or more of the elongation of the remaining region 50 of the metal foil excluding the edge portions 60. Specifically, the elongation may be in the range of 110 to 600%, and more specifically, 110 to 460%.

[0036] Here, the elongation is based on a value measured in accordance with the IPC-TM-650 2.4.18 standard. Furthermore, because elongation can decrease as the metal foil thickness decreases, the standard elongation is based on a metal foil thickness of 3 to 20 μm. In the following explanation, the elongation of both edge portions in the length direction of the metal foil 100 is symbolized and represented as a first elongation (E1), and the elongation of the remaining region of the metal foil excluding the edge portions is represented as a second elongation (E2).

[0037] Generally, thin metal foils are prone to tearing (fracture), and this usually starts at the edges of the foil. This is especially true during the winding and active material coating processes in the secondary battery manufacturing process, which can lead to reduced productivity and manufacturing yields.

[0038] In contrast, the metal foil 100 of the present invention is provided with a selective localized heat treatment under specified conditions only at both longitudinal edge portions 60, thereby increasing the elongation of the edge portions 60 compared to the entire region 50 of the metal foil (excluding the edge portions), and thus providing high edge fracture resistance. When the metal foil 100 having such high edge elongation is used as a current collector for a secondary battery, it exhibits ease of handling and excellent processability during the battery manufacturing process, ensuring high productivity and manufacturing yield. In particular, the metal foil of the present invention has high edge elongation and excellent fracture resistance, not only in the normal thickness range but also at a thickness of 20 μm or less, thereby increasing the loading amount of active material applied to the metal foil and demonstrating high-capacity battery characteristics.

[0039] According to one specific example, the metal foil 100 may have an elongation change rate (RE) of 10% or more, as determined by the following formula 2. Specifically, it may be 10 to 400%, and more specifically, 10 to 360%. [Formula 2] RE = (E1 - E2 / E2) x 100

[0040] According to one specific example, the difference between the first elongation (E1) and the second elongation (E2) may be in the range of 1 to 20%, more specifically 2 to 18%. For example, the first elongation of both end edge portions 60 may be 3 to 30%, more specifically 5 to 30%. Also, the second elongation may be 2 to 20%, more specifically 3 to 20%.

[0041] According to another specific example, the breaking strength of both edge portions 60 of the metal foil 100 in the longitudinal direction may be 35 to 55 kpsi, and the breaking strength of the remaining region 50 of the metal foil excluding the edge portions 60 may be 50 to 85 kpsi.

[0042] In this specification, the edge portion 60 may refer to a range of up to 15 mm from one end of the metal foil 100, based on a plane parallel to the longitudinal direction of the metal foil 100. Specifically, it may be a range of up to 10 mm from one end of the metal foil 100. The metal foil 100 according to the present invention, which has such elongation properties at both edge portions, may be expressed in terms of physical properties such as average grain size.

[0043] The method for manufacturing the metal foil 100 of the present invention having the above-mentioned edge elongation characteristics is not particularly limited, and as an example, it can be manufactured by selectively performing local heat treatment on only both end edge portions under specified conditions (see Figures 3 to 4).

[0044] The specific heat treatment method and conditions are not particularly limited as long as only both longitudinal edge portions 60 of the entire region of the metal foil 100 according to the present invention can be selectively heat-treated. For example, various methods known in the art, such as high-frequency induction heating, infrared (IR), and hot air heating, may be applied. In particular, high-frequency induction heating is preferred because it is easy to selectively heat-treat specific regions and is adjustable.

[0045] The heat treatment temperature is not particularly limited, and may be, for example, a temperature above the softening point of the metal foil 100, i.e., the softening proceeding temperature, for example, 150°C or higher. According to one specific example, both edge portions 60 of the metal foil 100 may be locally heat-treated under inert conditions at a temperature of 150 to 500°C for 0.1 to 60 seconds. In this case, the inert conditions are not particularly limited, and nitrogen gas or an inert gas known in the art may be freely used.

[0046] The metal foil 100 according to the present invention is not particularly limited and may have any conventional shape known in the art. For example, the metal foil 100 may be a metal foil roll wound into a sheet or roll as known in the art.

[0047] Referring to FIG. 4, after the metal foil 100 has undergone a foil-making process, both end edge portions in the length direction of the metal foil may be selectively locally heat-treated while the metal foil is being transferred from a first roller to a second roller. More specifically, while the metal foil roll is being pulled out from a first roller and transferred to a second roller, both end edge portions 60 of the metal foil 100 may be locally heat-treated by edge heat treatment devices disposed on both ends of the metal foil in the length direction, and then the metal foil may be rewound into a roll by the second roller. The metal foil 100 may then be slit to a desired size and width as needed.

[0048] The metal foil of the present invention processed as described above has high elongation and high breakage resistance at the edge portion 60, which minimizes breakage (tear) at the edge portion during subsequent manufacturing processes of the metal foil or during processes for manufacturing battery electrodes using the metal foil, such as the winding process and the electrode active material coating process. Furthermore, the metal foil retains the inherent physical properties of the remaining region 50, excluding the edge portion 60, thereby achieving excellent quality and reliability attributable to the metal foil. For example, when the edge portion of a high-strength metal foil is locally heat-treated as described above, it can exhibit high elongation properties and high breakage resistance at the edge portion.

[0049] The metal foil 100 according to the present invention is an electrolytic metal foil manufactured by a foil manufacturing process using electroplating. More specifically, one side of the metal foil 100 has a shiny surface (S surface, drum surface) 10a with relatively low roughness and high gloss, and the other side has a matte surface (M surface, electrolyte surface) 10b with relatively high roughness and low gloss due to a so-called mountain structure.

[0050] In this case, the bonding strength with the active material and battery yield can vary significantly depending on the surface condition of the metal foil 100 used as a current collector. For example, excessively uneven surface roughness of the metal foil can result in a decrease in the discharge capacity retention rate of the secondary battery. Conversely, an excessively uniform surface can make it difficult to ensure the bonding strength between the current collector and the active material, leading to problems such as the active material detaching from the current collector during operation of the secondary battery, resulting in an internal short circuit. Furthermore, the coating amount of the active material on both sides can vary depending on the condition of the metal foil. Such uneven coating amount can lead to differential deformation between the two sides of the current collector, resulting in a decrease in electrode capacity and / or unstable behavior. Therefore, in the present invention, by adjusting the surface roughness of both sides of the metal foil 100 within a predetermined range, the required physical properties of the copper foil 100 used as a current collector, i.e., excellent bonding strength with the active material and high discharge capacity retention rate, can be achieved.

[0051] According to one specific example, the metal foil 100 includes a drum surface (e.g., one surface 10a) and an electrolyte surface (e.g., other surface 10b), and the surface roughness of both surfaces may be about 0.5 to 5.0 μm, specifically 1.0 to 4.0 μm, based on Rz (ten-point average roughness). More specifically, the surface roughness of the drum surface (e.g., S-side 10a) of the copper foil may be 1.0 to 2.5 μm, and the surface roughness of the electrolyte surface (e.g., M-side 10b) may be 1.0 to 2.5 μm.

[0052] According to another specific example, the difference in surface roughness between the drum surface 10a and the electrolyte surface 10b of the metal foil 100 may be 1.0 μm or less, specifically 0.5 μm or less.

[0053] The thickness of the metal foil 100 may be within a range of normal thicknesses known in the art. For example, it may be 3 μm to 20 μm, but is not particularly limited to this range. If the thickness of the metal foil 100 is excessively thin, less than about 3 μm, handling of the metal foil in the battery manufacturing process becomes difficult, reducing workability. If the thickness of the metal foil 100 exceeds about 20 μm, when the metal foil 100 is used as a current collector, the increase in volume due to the thickness of the current collector makes it difficult to manufacture a high-capacity battery.

[0054] The metal foil 100 according to the present invention is not particularly limited in terms of the components, composition, and / or structure constituting the metal foil, as long as it satisfies the elongation characteristics of both end edge portions 60 of the surfaces parallel to the longitudinal direction of the metal foil described above.

[0055] The metal foil 100 may be made of a conventional conductive metal known in the art. For example, the metal foil 100 may be made of one or more metals selected from the group consisting of Cu, Al, Ni, Fe, Ag, and Au, or an alloy thereof. Preferably, the metal foil 100 may be made of a metal consisting of Cu, Ni, and Al, or an alloy thereof. In this case, the metal components contained in the alloy are not particularly limited, and conventional metals known in the art may be used. Specifically, the metal foil 100 may be a copper foil made of copper or a copper alloy. For example, the copper foil may be any conventional copper foil known in the art, without limitation. Examples of the copper foil include standard metal foil, highly elongated copper foil, high-strength copper foil, and copper foil for electric vehicle batteries. However, the present invention is not limited thereto. The metal foil 100 may be in the form of a foil, specifically, a flat copper foil.

[0056] According to one specific example, the metal foil 100 may be a copper foil formed by electroplating in an electrolytic solution by applying a current between a spaced electrode plate and a rotating drum. The electrolytic solution may have a composition including, but is not limited to, 50 to 150 g / L of copper ions, 50 to 150 g / L of sulfuric acid, 1 to 100 ppm of halogen, 3 to 1500 ppb of brightener, 3 to 4000 ppb of low-molecular-weight gelatin, 3 to 3000 ppb of HEC, and 1 to 20 ppb of leveler.

[0057] Unless otherwise specified, the above-described physical properties may be based on a metal foil thickness of 3 to 20 μm, but the thickness is not limited to the above-described range and can be appropriately adjusted within a normal thickness range known in the art.

[0058] Meanwhile, referring to FIG. 2, a metal foil 200 according to an embodiment of the present invention may have at least one anticorrosive layer 20 formed on its surfaces 10a and 10b.

[0059] The anticorrosion layer 20 is selectively formed on the surfaces 10a, 10b of the metal foil 100 to prevent corrosion of the metal foil 100. The anticorrosion layer 20 may contain a conventional inorganic anticorrosion material, an organic anticorrosion material, or a mixture thereof known in the art, and may contain at least one of chromium (Cr), molybdenum (Mo), nickel (Ni), a silane compound, and a nitrogen compound, for example.

[0060] Here, the nitrogen compound may include at least one of conventional triazole compounds and amine compounds known in the art. Usable triazole compounds may be selected from benzotriazole, tolyltriazole, carboxybenzotriazole, chlorobenzotriazole, ethylbenzotriazole, and naphthotriazole. Usable amine compounds may be selected from amides, acrylamides, acetamides, auramine, dodecyltrimethyl ammonium bromide (DTAB), and diethylenetriamine (DETA).

[0061] The anticorrosion layer 20 not only provides the above-mentioned anticorrosion properties to the metal foil 100, but also serves to provide heat resistance and / or properties that increase the bonding strength with the active material.

[0062] The metal foil 100 according to the present invention may be produced using a conventional electrolytic foil production apparatus, and is not particularly limited thereto. For example, a drum functioning as a negative electrode and an anode are provided in a container to which an electrolyte is continuously supplied, and a current is applied between the drum and the anode while they are spaced apart so that the electrolyte is interposed between them. During this process, as the drum rotates, electrolytic copper foil is electrodeposited on the drum surface, and then the foil is wound around a guide roll.

[0063] Here, the electrolyte may be any conventional electroplating electrolyte known in the art without any restrictions. For example, the electrolyte may contain copper sulfate, sulfuric acid, and a trace amount of chlorine as the main components, and may further contain at least one conventional plating additive.

[0064] The additives may be any additives commonly used in the electroplating field without limitation, and examples thereof include accelerators, brighteners, levelers, suppressors, and mixtures thereof.

[0065] The accelerator / brightener is added to impart gloss to the plating surface and obtain a fine plating layer. Examples of such additives include organic compounds containing disulfide bonds (-SS-) or mercapto groups (-SH), and sulfonate-based additives containing sulfides. Specific examples include at least one of MPS (3-mercaptopropyl sulfonate), SPS (bis-(3-sulfopropyl)-disulfide), DPS (3-N,N-dimethlyamonodithiocarbamoy-1-propanesulfonic acid), and PTA (polymethyldithiocarbonic amine-sulfopropylsulfonate).

[0066] In addition, a decelerator / inhibitor (suppressor, carrier) adsorbs to the surface, hindering the approach of copper ions and slowing down the electroplating process. It is a component added to achieve stable, low roughness. Examples include HEC (hydroxyethyl cellulose), PEG (polyethylene glycols), PPG (polypropylene glycols), polyvinyl alcohol, low-molecular-weight gelatin (molecular weight: approximately 1,000 to 100,000), cellulose-based additives, and polymeric organic compounds such as collagen, or mixtures thereof. Other examples include polyether-based polymers, organic compounds with nitrogen-containing functional groups, sulfosuccinate-based surfactants, and / or ethanediamine oxirane-based surfactants.

[0067] The leveling agent is a component added to remove surface irregularities and obtain a flat copper foil with low roughness. For example, low molecular weight nitrides (e.g., thiourea, amides, benzimidazole, benzthiazole, dimethylaniline, etc.) may be used. Specifically, compounds such as thiourea, JGB (Janus Green B), PEI, and 3-(benzothiazolyl-2-mercapto)propylsulfonic acid may be used.

[0068] According to one specific example, the electrolyte contains 50 to 150 g / L of copper ions, 50 to 150 g / L of sulfuric acid, and 1 to 100 ppm of halogen. At least one additive acting as a brightener may be contained at 3 to 1500 ppb, and at least one additive acting as a carrier and leveler may be added at a controlled amount of 1 to 4000 ppb.

[0069] The specific composition of the additives added to the electrolyte may include 3 to 1500 ppb of a brightener, 3 to 4000 ppb of low molecular weight gelatin, 3 to 3000 ppb of HEC, and 1 to 20 ppb of a leveler.

[0070] The electroplating conditions applied during electrodeposition of the electrolytic copper foil can be appropriately adjusted within the range known in the art. For example, the current density is 30 ASD to 100 ASD (A / dm 2 ), specifically, 30ASD to 80ASD (A / dm 2 ) The temperature of the electrolytic solution may be, for example, 35 to 75°C, specifically 40 to 60°C. The flow rate of the electrolytic solution supplied may be, for example, 30 to 120 m / s. 3 / hr, specifically 50-100m 3 / hr, but is not specifically limited to the above range.

[0071] By adjusting the composition of the electrolyte, current density, temperature, type and / or content of additives, factors such as the difference in surface roughness between the M side (e.g., 10a) and S side (e.g., 10b) of the copper foil can be adjusted.

[0072] The electrolytic metal foil electrodeposited as described above is peeled from the drum surface and then wound around a guide roll to form a wide and long film-like metal foil roll. This metal foil roll is then transported through at least one optional roller, and both end edge portions 60 are locally heat-treated, thereby completing the production of the metal foil 100 according to the present invention. The metal foil may then be wound into a roll again. Alternatively, the metal foil may be wound into a roll again and slit into smaller width unit metal foils as needed.

[0073] If necessary, the metal foil may be further subjected to electrolytic or electroless plating of metals such as Ni, Cr, Mo, and Ag to impart properties to the foil. Furthermore, the metal foil may be further subjected to organic coatings known in the art, such as silane, BTA, and conductive polymers, to enhance adhesion, prevent rust, and reduce contact resistance. Additionally, at least one of the usual nodule treatments, heat-resistant treatments, chemical-resistant treatments, and rust-prevention treatments known in the art may be further performed.

[0074] <Electrode> Another embodiment of the present invention is an electrode for a secondary battery that includes the above-described metal foil as a current collector.

[0075] In lithium secondary batteries, a foil made of aluminum (Al) is generally used as a positive electrode current collector that is bonded to a positive electrode active material, and a foil made of copper (Cu) is generally used as a negative electrode current collector that is bonded to a negative electrode active material. Therefore, in the present invention, a case where the copper foil 100 is used as a negative electrode current collector will be described.

[0076] According to one embodiment, the negative electrode includes the above-described metal foil; and a negative electrode active material layer disposed on the metal foil.

[0077] Such a negative electrode active material layer contains a negative electrode active material, and may further contain a conventional binder and / or conductive material known in the art.

[0078] The negative electrode active material is not particularly limited as long as it is a compound capable of intercalation and deintercalation. Non-limiting examples of usable negative electrode active materials include carbon-based and silicon-based negative electrode active materials, as well as lithium metal or its alloys, and other materials capable of absorbing and desorbing lithium and having a potential relative to lithium of less than 2 V, such as TiO2, SnO2, and Li4Ti5O. 12 Metal oxides such as the following may also be used.

[0079] The method for manufacturing an electrode for a secondary battery using the above-described metal foil is obvious to those skilled in the art to which the present invention pertains, and therefore a detailed description thereof will be omitted.

[0080] <Secondary battery> A secondary battery according to another embodiment of the present invention includes a negative electrode provided with the above-described metal foil.

[0081] The secondary battery may be a lithium secondary battery, and specifically may include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0082] According to one embodiment, the lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte supported between the positive electrode and the negative electrode. The battery may further include a separator.

[0083] The lithium secondary battery of the present invention may be manufactured by a conventional method known in the art. For example, the lithium secondary battery may be manufactured by interposing a separator between a positive electrode and a negative electrode, and then introducing an electrolyte containing the electrolyte additive.

[0084] The electrolyte may also be comprised of a conventional lithium salt known in the art; and an electrolyte solvent.

[0085] The separator may be a porous separator, such as a polypropylene-based, polyethylene-based, or polyolefin-based porous separator, or an organic / inorganic composite separator containing an inorganic material.

[0086] The present invention will be described in more detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0087] [Reference example] In the examples of the present invention, copper foils A, B, and C manufactured by a normal foil manufacturing process were used. The manufacturing process for these foils is as follows.

[0088] To prepare the electrolyte, the temperature was adjusted to 60°C, with a copper ion concentration of 80 g / L, a sulfuric acid concentration of 100 g / L, and a chlorine concentration of 30 ppm. Additives added to the electrolyte included low molecular weight gelatin (molecular weight 3,000), HEC (Hydroxyethyl Cellulose), MPS (3-mercaptopropyl sulfonate) as a glossing agent, and thiourea as a leveler.

[0089] Copper foil A was produced using an electrolyte containing 10 ppb of brightener, 10 ppb of low molecular weight gelatin, and 10 ppb of HEC. The temperature of the electrolyte was 55°C, and the flow rate of the electrolyte was 80 m / s. 3 / hr, and the current density is 60 ASD (A / dm 2 ) was decided.

[0090] For copper foil B, an electrolyte solution containing 2,000 ppb of low molecular weight gelatin and 2,000 ppb of HEC was used, and the electrolyte conditions were the same as those for copper foil A.

[0091] Copper foil C was produced using an electrolyte containing 800 ppb of brightener, 2000 ppb of low molecular weight gelatin, 2000 ppb of HEC, and 10 ppb of leveller, under the same electrolyte conditions as those for copper foil A.

[0092] [Example 1] The three copper foils A, B, and C manufactured as described above were each wound at a slitting speed of 1 m / min, with the temperature of the edge heaters located at both ends along the length of the foil adjusted to 250°C. The number of times the copper foil broke was counted after slitting for approximately 100 km. The edge heating section was set to a 1 m section, the heat treatment temperature was set to 250°C, and an inert gas was purged. This was the same as if both edges along the length of the copper foil were heat-treated at 250°C for approximately 1 minute.

[0093] The physical properties of the three copper foil samples that had been locally heat-treated at both edge portions were evaluated by the following methods, and the results are shown in Table 1 below.

[0094] <Physical property evaluation method> (1) Thickness measurement The thickness was measured by the unit weighing method, which is the usual method for measuring the thickness of copper foil (IPC-TM-650 2.2.12).

[0095] (2) Measurement of elongation The elongation (%) was measured using a UTM (Instron, model name: 5942) in accordance with the IPC-TM-650 2.4.18 standard.

[0096] (3) Measurement of tensile strength The tensile strength (kpsi) was measured using a UTM (Instron, model name: 5942) in accordance with the IPC-TM-650 2.4.18 standard.

[0097] (4) First Elongation Increase Rate and Elongation Change Rate The first elongation increase rate and the elongation change rate were calculated by the following formulas 1 and 2, respectively. [Formula 1] First elongation increase rate (%) = E1 / E2 x 100 [Formula 2] Elongation change rate (RE, %) = (E1-E2 / E2) x 100 [Table 1]

[0098] In this case, copper foil B has high tensile strength, low elongation, and is prone to tearing, so it broke in copper foils with a thickness of 10 μm or less. However, when the edge portions were not heat-treated, the number of tears was significantly higher.

[0099] [Example 2] The same procedure as in Example 1 was carried out, except that the slitting speed was changed from 1 m / min to 60 m / min and the heat treatment temperature of the edge portion was changed to 350°C. Example 2 was similar to Example 1, except that both end edge portions in the longitudinal direction of the copper foil were heat treated at 350°C for about 1 second. Thereafter, the physical properties of the three copper foil samples were evaluated in the same manner as in Example 1, and the results are shown in Table 2 below. [Table 2]

[0100] [Comparative Example 1] The three copper foils A, B, and C produced above were used, but the same procedure as in Example 1 was carried out, except that no edge heater was used during slitting and no heat treatment was performed.

[0101] Thereafter, the physical properties of each copper foil sample were evaluated in the same manner as in Example 1, and the results are shown in Table 3 below. [Table 3]

[0102] As shown in Table 3, in the case of Comparative Example 1 in which no heat treatment was performed, the elongation and tensile strength of the copper foil edge portion were the same, and it was found that the thinner the thickness, the more likely breakage occurred during the manufacturing process.

[0103] In contrast, in Examples 1 and 2, it was found that the elongation of both edge portions of the metal foil was selectively increased, and as a result, it was found that the breakage phenomenon occurring during the manufacturing process was significantly reduced not only for thick copper foils but also for thin copper foils with a thickness of 20 μm or less. As a result, it was found that when the metal foil according to the present invention is used as a battery current collector, it is possible to significantly improve the handling property and quality reliability during the manufacturing process, processing, and use of secondary batteries. [Explanation of symbols]

[0104] 100, 200 Metal foil 10a...One side (drum side) 10b...Other side (electrolyte side) 20 Rust prevention layer 50...metal layer 60 Edge 400 Local heat treatment device

Claims

1. A metal foil having one side and another side, Both end edge portions of the surface parallel to the longitudinal direction of the metal foil have a first elongation (E1), The remaining area of ​​the metal foil excluding the edge portion has a second elongation (E2), The metal foil, wherein the first elongation is 110% or more of 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 first elongation is 3 to 30%, The metal foil of claim 1, wherein the second elongation is 2 to 20%.

4. The breaking strength of both edge portions is 35 to 55 kpsi, 2. The metal foil of claim 1, wherein the remaining area of ​​the foil excluding the edges has a breaking strength of 50 to 85 kpsi.

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

6. The metal foil of claim 1 , wherein the metal foil is a wound metal foil roll.

7. 2. The metal foil according to claim 1, wherein both edge portions of the metal foil are locally heat-treated while being transferred from the first roller to the second roller.

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

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

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

11. The roughness (Rz) of each of the two surfaces of the metal foil is 0.5 to 5.0 μm, 2. The metal foil according to claim 1, wherein the difference in surface roughness between said one surface and said other surface is 2.0 μm or less.

12. The metal foil further includes at least one anti-corrosion layer formed on the surface thereof, The metal foil according to claim 1 , wherein the anticorrosive layer contains at least one of chromium (Cr), molybdenum (Mo), nickel (Ni), 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, which is used as a negative electrode current collector of a lithium secondary battery.

15. The metal foil according to any one of claims 1 to 14; and an active material layer disposed on the metal foil; An electrode for a secondary battery comprising:

16. A secondary battery comprising the electrode according to claim 15.

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