Surface treated copper foil for lithium-ion secondary batteries

Abstract

A surface treated copper foil comprises a copper foil having a first surface and an opposite second surface and two treatment layers respectively arranged on the first surface and the second surface. Each treatment layer provides a treatment surface, and the treatment surface has a ten-point average roughness Rz in the range of 1.2 μm to 4.6 μm and a roughness of 490,000 to 1,080,000 mm ‑2 In addition, the chromium content in each treatment layer is 25 to 70 μg / dm 2 The surface treated copper foil has excellent electrode active material coating properties, such as good adhesion and uniformity.

Description

Technical Field

[0001] The present invention relates to a surface-treated copper foil which can be used as a current collector in, for example, a lithium-ion secondary battery. The present invention also relates to a surface-treated copper foil having excellent adhesion to an active material layer. Background Art

[0002] Lithium-ion secondary batteries have a combination of high energy and high power density, making them a technology of choice for portable electronic devices, power tools, electric vehicles (EVs), energy storage systems (ESS), mobile phones, tablet computers, aerospace applications, military applications, and railways. Electric vehicles (EVs) include hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and pure battery electric vehicles (BEVs). If electric vehicles (EVs) replace most of the transportation vehicles powered by fossil fuels (e.g., gasoline, diesel, etc.), lithium-ion secondary batteries will significantly reduce greenhouse gas emissions. The high energy efficiency of lithium-ion secondary batteries can also allow them to be used in various grid applications, including improving the quality of energy harvested from wind, solar, geothermal and other renewable sources, thus contributing to their wider use in establishing a sustainable energy economy.

[0003] Therefore, lithium-ion secondary batteries have attracted strong interest in basic research from commercial capital and government and academic laboratories. Although research and development in this field have been extensive in recent years, and lithium-ion secondary batteries are currently in use, there is still a need for batteries with higher capacity, higher current generation, and more charge and discharge cycles to extend their service life. In addition, it is necessary to improve the weight of the battery to improve its application in a variety of environments, such as vehicles, portable electronic devices, and aerospace applications.

[0004] Lithium-ion secondary batteries typically include a collector of a metal foil on which an active material is deposited. Copper is generally used as a collector because it is a good conductor of electric current. As the demand for lower weight batteries becomes more and more urgent, thinner collectors are needed to reduce the size and weight of lithium-ion secondary batteries. In addition, in order to increase the capacity of lithium-ion secondary batteries, materials such as silicon (Si) are mixed or filled into the high-capacity active materials of the battery. In contrast to carbon, silicon-based active materials have higher lithium-ion battery capacity, so they can reach almost ten times the energy capacity per gram (mAh / g). Lithium-ion batteries with silicon-based anodes have greater energy storage capacity and / or smaller battery size, or longer battery cycle life. However, silicon-based anodes have limitations in application because the size of silicon changes by up to 400% when lithium ions are inserted and removed. This phenomenon leads to crushing of active materials and capacity decay. In addition, silicon-based anode materials are easily detached from the collector, resulting in lithium battery failure.

[0005] Additional challenges are associated with processing. For example, processing includes depositing the active material on the copper foil from a slurry, drying the combined copper foil and active material in an oven at high temperature, and a subsequent calendering step. Fragmentation of the copper foil often occurs after the calendering step. Moreover, because the above steps occur in ambient air, the copper foil is exposed to oxygen and may be oxidized, increasing the possibility of damage. Although copper foil typically includes an anti-rust coating such as a chromium coating, in some instances, if the copper foil is not adequately coated, it may not provide adequate protection for the copper foil, and if too much chromium is used, it may increase the resistance of the electrode.

[0006] Therefore, there is still a need for improvement in copper foil used in lithium ion secondary batteries. There is a need for copper foil with improved surface properties, such as adhesion between the copper foil and the active material. In addition, good uniformity and good mechanical strength of the active material on the electrode allow it to withstand damage during processing, which can further meet other requirements. Summary of the invention

[0007] In general, the present invention relates to a copper foil, such as an electrolytic copper foil that can be used as a current collector in a lithium ion secondary battery. The surface treated copper foil is prepared to have high adhesion to an active material.

[0008] In a first aspect, the present invention provides a surface-treated copper foil, comprising a copper foil and two treatment layers. The copper foil has a first side and an opposite second side. One of the two treatment layers is disposed on the first side, and the other of the two treatment layers is disposed on the second side. Each treatment layer provides a treatment surface having a ten point average roughness Rz in the range of 1.2 μm to 4.6 μm and a roughness of 490,000 to 1,080,000 mm. -2 The peak density (Spd) ranges from 25 to 70 μg / dm 2 within the range.

[0009] In some options of the first aspect, the treated surface has an Rz of 1.5 μm to 3.4 μm. Optionally, the treated surface has an Rz of 490,000 to 950,000 mm -2 Optionally, the treated surface has an Rz of 1.5 μm to 3.4 μm, and it has a diameter of 490,000 to 950,000 mm -2 Optionally, the treated surface has a Spd of 490,000 to 900,000 mm -2 Spd.

[0010] In some other options of the first aspect, the chromium content in each treatment layer is 25 to 60 μg / dm 2Optionally, each treatment layer comprises a roughened particle layer and an anti-rust layer. Optionally, the copper foil is an electrolytic copper foil.

[0011] Also in the first aspect, the surface treated copper foil optionally also has a 36 kg / mm 2 Up to 60kg / mm 2 The tensile strength (TS) of the present invention is within the range of 1000 % and the tensile strength reduction (TSR) is less than 45%, wherein the TSR is defined as Formula I:

[0012]

[0013] Wherein, TSa is the residual tensile strength of the surface-treated copper foil after annealing at 140° C. for 10 minutes. Optionally, the surface-treated copper foil has a TSR of less than 10%.

[0014] In a second aspect, the present invention provides a lithium ion secondary battery, comprising a surface treated copper foil according to the first aspect and an active material applied to at least a portion of the treated surface. Optionally, the copper foil is an electrolytic copper foil having a roller surface corresponding to the first surface and a deposition surface corresponding to the second surface. Optionally, the active material is only applied to the treated surface close to the deposition surface of the copper foil. In some options, the battery is configured as a laminated battery, and in some other options, the battery is configured as a button battery.

[0015] The surface treated copper foil described herein has excellent surface properties, such as adhesion to active materials. In addition, in some embodiments, the uniformity and mechanical strength of the coating are further improved, so that the surface treated copper foil can withstand damage during processing such as calendering.

[0016] The above summary is not intended to represent every specific embodiment or every aspect of the present invention. Instead, the foregoing summary merely provides examples of novel aspects and features herein. The above features and advantages, together with other features and advantages of the present invention, will be apparent from the following detailed description of representative specific embodiments and modes for implementing the present invention when combined with the appended claims. DETAILED DESCRIPTION

[0017] The surface-treated copper foil of the present invention has two opposite sides. The surface-treated copper foil includes a copper foil as a main body (also referred to as a main body copper foil), and the copper foil as a main body can be a rolled copper foil or an electrolytic copper foil. The copper foil is substantially composed of copper (e.g., >99wt% copper), and the first side and the opposite second side of the copper foil are coated to provide a surface-treated copper foil having a coating on both opposite sides. The coating includes a treatment layer, and the treatment layer includes 25 to 70μg / dm 2Each treatment layer provides a treatment surface, and the treatment surface of each treatment layer has a roughness Rz controlled within a range of 1.2 μm to 4.6 μm and a thickness of 490,000 to 1,080,000 mm -2 Peak density (Spd) within the range.

[0018] In some specific embodiments, the surface-treated copper foil is prepared from an electrolytic copper foil obtained by roller deposition to provide a main copper foil having a roller surface and a deposition surface. As used herein, the "roller surface" of the copper foil is the surface of the copper foil that contacts the roller used during the electrodeposition process; and the "deposition surface" is the opposite side of the roller surface, or the surface of the copper foil that contacts the electrolyte during the electrodeposition process of forming the copper foil. These terms relate to a manufacturing method for manufacturing an electrolytic copper foil, which includes partially immersing a rotating roller assembly in an electrolyte containing copper ions. Therefore, under the action of the electric current, the copper ions are attracted to the roller and reduced, resulting in copper metal plating on the roller surface and forming an electrolytic copper foil on the roller surface. In a continuous process, the copper foil is removed by rotating the roller and rotating out of the electrolyte with the formed copper foil and the roller. For example, in a continuous process, the copper foil can be pulled away from the roller as it is formed and travels on or through the roller. In some specific embodiments, the roller surface corresponds to the first surface, and the deposition surface corresponds to the second surface.

[0019] One feature of the surface treated copper foil according to some specific embodiments is surface roughness. As used herein, "roughness" refers to the deviation of the surface from an ideal, perfectly smooth surface in a direction orthogonal to the actual surface. Various methods of quantifying roughness are known in the art. For example, the ten-point average roughness Rz is the surface roughness based on a profile analysis of the surface over a sampling length (L). The average value of the sum of the five highest vertices and the five lowest vertices is calculated, which is represented by Formula II:

[0020]

[0021] In Formula II: Rp1, Rp2, Rp3, Rp4 and Rp5 are the heights from the highest vertex to the fifth highest vertex in L; and Rv1, Rv2, Rv3, Rv4 and Rv5 are the heights from the lowest point to the fifth lowest point in L.

[0022] In some embodiments, it has been found that Rz can adjust the adhesion of copper foil to active materials. Without being limited to any particular theory, copper foil with very low Rz cannot provide sufficient anchoring force for active materials, while copper foil with too high Rz cannot form a uniform coating. Adhesion can be tested by, for example, the peel strength test described below. In some specific embodiments, the Rz on the treated side of the surface treated copper foil is greater than or equal to 1.2 μm and less than or equal to 4.6 μm, for example, about 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5 or 4.6 μm, and any values ​​between the above listed values.

[0023] Another feature of the surface treated copper foil according to some specific embodiments is the peak density (Spd). As used herein, "peak density", "Spd" and "density of peaks" are the same terms and represent the number of peaks in a given surface area. The peak density (Spd) is based on ISO 25178-2:2012 definition.

[0024] In some embodiments, the Spd can have a strong influence on the adhesion of the surface. Without being limited to any particular theory, if the Spd is too small, the contact between the active material and the surface of the surface treated copper foil is insufficient, resulting in low peel strength. Conversely, if the Spd is too large, the active material slurry such as the anode slurry may not be able to fully penetrate into the recesses between the peaks on the surface. Once the slurry has been dried on the surface, poor contact due to poor permeability of the slurry can lead to poor peel strength. In some embodiments, the treated surface has a thickness of 490,000 mm. -2 The minimum value is as low as 1,080,000mm -2 In some embodiments, the Spd is less than or equal to 1,000,000, 950,000, 900,000, 800,000, 700,000, 600,000 or 500,000 mm. -2 In some embodiments, Spd is greater than or equal to 500,000, 600,000, 700,000, 800,000, 900,000 or 1,000,000 mm. -2 It should be understood that some specific embodiments may include any value between the above high values ​​and low values.

[0025] In some embodiments, the surface treated copper foil includes a roughening particle layer as part of the treatment layer. In some embodiments, the roughening particle layer may include metal roughening particles such as copper roughening particles. For example, the roughening particles may be formed by electroplating a metal on the copper foil. In some embodiments, the copper roughening particles may be made of copper or a copper alloy. In some embodiments, the treatment layer includes a metal capping layer on the metal roughening particles, such as a copper deposition on the copper roughening particles. For example, the metal capping layer helps prevent the metal roughening particles from peeling off.

[0026] In some specific embodiments, the surface treated copper foil includes an anti-rust layer as part of the treatment layer, which can protect the surface treated copper foil from degradation such as corrosion. The anti-rust layer can be prepared by any known method, including immersing or passing the copper foil or the copper foil covered with roughening particles through a solution containing an anti-rust forming additive, or plating (e.g., electroplating) a metal or alloy film on the copper foil or the copper foil covered with roughening particles. For example, the electroplating bath includes any one or more of zinc, chromium, nickel, cobalt, molybdenum, vanadium, and combinations thereof, or an organic compound that forms an anti-rust layer. The process can be continuous and part of an overall process for preparing the surface treated copper foil.

[0027] In some specific embodiments, the surface treated copper foil includes two treatment layers, for example, two treatment layers located on a first side and an opposite second side, and the chromium content in the treatment layers is controlled within a range between a low value and a high value. Not attributable to a specific mechanism, if the chromium content is too low, the surface area coverage of chromium is small after the roughening treatment, and the peel strength is reduced. Conversely, if the chromium content is too high, the chromium coverage is too high or too thick, resulting in high resistance, for example, when the copper foil is used as an electrode for a lithium ion battery. In some specific embodiments, the chromium content is greater than or equal to 25, 30, 35, 40, 45, 50, 55, 60 or 65 μg / dm 2 In some embodiments, the chromium content is less than or equal to 70, 65, 60, 55, 50, 45, 40, 35 or 30 μg / dm 2 It should be understood that different specific embodiments may include any chromium content value between the above-mentioned high value and low value.

[0028] In some specific embodiments, the surface treated copper foil is characterized by tensile strength (TS). As used herein, "tensile strength" is the maximum tensile stress that a material can withstand before a mechanical break or rupture, such as breaking into two parts. The tensile strength (TS) is controlled to provide a surface treated copper foil that can withstand tearing caused by processing (such as pulling and calendering between rollers). The tensile strength (TS) is related to the grain size of the copper in the copper foil, because an increase in grain boundaries increases the force required to deform the copper foil. When the tensile strength (TS) is too low, the surface treated copper foil may be more easily bent and torn, and when the tensile strength (TS) is too high, the surface treated copper foil is difficult to bend and may be detrimental to further processing.

[0029] In some embodiments, the tensile strength (TS) is controlled within a range between a low value and a high value. In some embodiments, the low value of the tensile strength (TS) is greater than or equal to 36, 40, 45, 50, or 55 kg / mm 2 In some embodiments, the high value of tensile strength (TS) is less than or equal to 60, 55, 50, 45 or 40 kg / mm 2 It should be understood that for the surface treated copper foil of different specific embodiments, any tensile strength (TS) value between the above-mentioned high value and low value is included.

[0030] In some specific embodiments, the surface treated copper foil is characterized by the residual tensile strength (TSa) after heating to an elevated temperature and cooling to room temperature. The above heat treatment can simulate the thermal history experienced by the copper foil during the drying process of the active material slurry. After oven baking, the tensile strength of the surface treated copper foil will be reduced, which may cause the copper foil to break during further processing such as calendering. As used herein, "tensile strength reduction" or "TSR" is the percentage of the residual tensile strength (TSa) compared to the original tensile strength (TS) after the sample is subjected to an annealing step at 140°C for 10 minutes, which is defined by the aforementioned formula I. Without being limited to any particular theory, a high TSR indicates that the surface treated copper foil is prone to recrystallization and is thermally unstable. In some specific embodiments, the TSR contained herein is controlled to have a value less than or equal to 45%. In some specific embodiments, the TSR is less than or equal to 40%, 30% or 10%.

[0031] In some specific embodiments, the surface treated copper foil is at least partially coated with an active material. For example, the active material may be an active anode material, such as an active anode material comprising carbon, silicon, germanium, and a combination or mixture thereof. In some specific embodiments, the active anode material comprises silicon. In some specific embodiments, only one side of the treated surface is coated with an active material. In some specific embodiments, the surface treated copper foil is an electrolytic copper foil having a roller surface corresponding to the first surface and a deposition surface corresponding to the second surface, and the active material is at least partially coated on the treated surface close to the deposition surface (i.e., the first surface) of the copper foil.

[0032] In some specific embodiments, the surface treated copper foil can be used as a current collector in a battery such as a lithium ion secondary battery. In some specific embodiments, the battery is configured as a laminated battery, for example, including a copper negative electrode current collector, a negative electrode active material, a separator, a positive electrode active material, and a positive electrode current collector. In some other specific embodiments, the battery is configured as a button cell.

[0033] The surface treated copper foil in the specific embodiments described herein can be used in devices, such as any item or component that requires power for its operation. For example, independent, separate and mobile components and devices require small and light batteries. These devices may include, but are not limited to, vehicles (e.g., cars, trams, buses, trucks, ships, submarines, airplanes), computers (e.g., microcontrollers, laptops, tablets), phones (e.g., smart phones, wireless phones), personal health monitoring and maintenance equipment (e.g., blood glucose monitors, pacemakers), tools (e.g., electric drills, electric saws), lighting devices (e.g., flashlights, emergency lighting, signs), handheld measuring devices (e.g., pH meters, air monitoring devices) and living units (e.g., in spacecraft, trailers, houses, airplanes, submarines).

[0034] It should be understood that within the scope of the present invention, the technical features mentioned above and below (such as embodiments) can be freely combined with each other to form new or preferred technical solutions, which are omitted for the sake of brevity.

[0035] Examples and Comparative Examples

[0036] I. Preparation of surface treated copper foil

[0037] The electrolyte was prepared by dissolving copper wire in a 50 wt % sulfuric acid aqueous solution, thereby obtaining a copper sulfate electrolyte containing 260 to 320 g / L of copper sulfate (CuSO4·5H2O) and 60 to 100 g / L of sulfuric acid. To each liter of the copper sulfate electrolyte were added: 0 to 3.5 mg of gelatin (DV: Nippi); 0 to 3 mg of hydroxyethyl cellulose (LC-400: DAICEL); 0 to 2.4 mg of sodium 3-mercapto-1-propane sulfonate (MPS; HOPAX); 0 to 7 mg of thiourea (manufactured by Panreac Quimica Sau); and 2 to 20 mg of chloride ions. Sixteen solutions were prepared according to the above contents, and the specific concentrations of Examples 1 to 12 and Comparative Examples 13 to 16 are listed in Table 1, respectively.

[0038] The main copper foil (raw copper foil) is prepared by electrodeposition on a rotating roll which is partially immersed in the electrolyte described above and listed in Table 1. The roll acts as a cathode opposite to the anode electrode, causing the copper ions in the electrolyte to be deposited on the roll in a continuous manner. 25 to 70 A / dm 2 The current density is 2000 μm and the temperature of the electrolyte is controlled to be about 40 to 70° C. to prepare a copper foil having a thickness of about at least 7 μm, for example, 8 to 20 μm. The preparation conditions are listed in Table 1.

[0039] Table 1: Preparation conditions of electrolytic copper foil

[0040]

[0041] After the electrolytic copper foil is manufactured, both sides of the main copper foil are treated by roughening treatment. The roughening treatment is performed at a temperature of 25 to 30°C using 30 to 60A / dm 2 The electrodeposition is performed at a current density of 10000 g / L and a residence time in the electrolyte of 3.5 to 7 seconds. The electrolyte includes 120 to 180 g / L of copper sulfate (CuSO4.5H2O), 80 to 120 g / L of sulfuric acid (H2SO4), 3.5 to 5.5 g / L of chloride ions, and 0 to 480 g / L of chromium sulfate (Cr2(SO4)3). Table 2 lists the roughening treatment conditions of 16 embodiments and comparative examples.

[0042] Table 2: Bare copper foil roughening conditions

[0043]

[0044] After the roughening treatment, the copper foil was rinsed with water, and both sides of the roughened copper foil were chromium plated. The chromium plating bath contained 1.5 g / L CrO3. The electroplating was carried out at 5 A / dm 2 This was performed for 5 seconds while the chromium plating bath was maintained at 30°C.

[0045] Table 3 lists several surface treated copper foils prepared as above. The nominal thickness is measured to characterize the surface treated copper foil. Surface roughness (Rz), chromium content and peak density (Spd) can also characterize the characteristics of both sides of the surface treated copper foil. At the same time, the tensile strength (TS) and tensile strength reduction (TSR) are measured, and the elongation is also measured. The properties used to evaluate the performance of the surface treated copper foil, such as the performance for lithium ion batteries, are measured. The peel strength test is used to evaluate the adhesion, such as the test method described below, applying the anode material to one side of the surface treated copper foil. In addition, the test method described below is used to evaluate the uniformity of the active material coating.

[0046] Table 3: Surface treated copper foil

[0047]

[0048] 1 Calendering test; "O" indicates no break; "X" indicates the surface treated copper foil is broken.

[0049] 2 The uniformity is to evaluate the flatness of the anode active material coated on the surface treated copper foil: "O" indicates good flatness; "△" indicates acceptable flatness; and "X" indicates poor flatness.

[0050] The above results show that the surface treated copper foils in Examples 1 to 12 and Comparative Examples 13 to 15 have a controlled roughness (Rz) ranging from 1.2 μm to 4.6 μm. The surface treated copper foils in Examples 1 to 12 and Comparative Examples 15 and 16 have a controlled roughness (Rz) ranging from 490,000 to 1,080,000 mm -2 The surface treated copper foils of Examples 1 to 12 and Comparative Examples 13, 14 and 16 have a peak density (Spd) of 25 to 70 μg / dm 2 The chromium content in the range of . As can be seen from the above, Examples 1 to 12 all meet the roughness, peak density and chromium content in the aforementioned range. According to the peel strength test, the surface treated copper foils of Examples 1 to 12 all have good adhesion, which shows a peel strength value greater than 0.3kg / cm. Examples 1 to 12 also have at least acceptable active material uniformity. In addition, Rz is controlled in the range of 1.5μm to 3.4μm and the peak density is controlled in the range of 490,000 to 950,000mm -2 The uniformity can be further improved within the range, such as Examples 1 to 5, 8 and 10.

[0051] It can also be seen from the data in Table 3 that in addition to maintaining the roughness, peak density and chromium content within the above range, if the tensile strength (TS) is too high, higher than about 60 kg / mm 2(Example 12), or the TSR is too high, above about 45% (Example 11), and the performance in the calendering test is poor.

[0052] II. Test Methods

[0053] Calendering (pressing) test

[0054] The active material is prepared using 90wt% of a silicon alloy-like active material in powder form (average particle size of 0.1 to 10μm) and 10wt% of a polyimide-based adhesive. The active material is dispersed in an N-methylpyrrolidone (NMP) solvent to form a slurry. The slurry has a liquid-to-solid ratio of 60wt% (60g of NMP: 100g of active material). The slurry is applied to a portion of the surface of the surface-treated copper foil, and the slurry is applied to a thickness of 200μm at a speed of 5 meters per minute. Thereafter, the slurry is dried in an oven set at 140°C for 10 minutes to dry the slurry on the copper foil. A boundary can be defined between the copper foil coated with the active material and the copper foil not coated with the active material. The anode (copper foil + active material) is pressed using a press. The roller of the press has a size of φ250mm×250mm, a hardness of 62 to 65°HRC, and the material of the roller is high carbon chromium bearing steel (SUJ2). Use 1m / min pressing (calendering) speed and 3000psi pressure for pressing. The surface treated copper foil is conveyed so that the boundary between the coated / uncoated copper foil is roughly perpendicular to the conveying direction and roughly parallel to the pressing roller axis. Therefore, the calendering test evaluates whether the surface treated copper foil can withstand the above-mentioned calendering treatment. As the roller rolls over the boundary, if there is no break at the boundary of the surface treated copper foil, it is recorded as a pass or "O". On the contrary, if the surface treated copper foil breaks, it is recorded as a failure or "X".

[0055] Peel strength test

[0056] An anode having active material and rolled as described above was prepared. After rolling, the anode was cut to obtain a sample with a size of 200 mm x 20 mm (length x width). MAGIC TM The adhesive tape (3M Co.) was attached to the surface of the sample, and then the peel strength was measured using a DS2-20N push-pull force gauge from IMADA.

[0057] Tensile strength and elongation percentage

[0058] The tensile strength (TS) and elongation percentage were determined using the standard test method IPC-TM-650. The surface treated copper foil without annealing or rolling was cut to obtain a specimen with a size of 100 mm × 12.7 mm (length × width). The tensile strength (TS) and elongation percentage of the specimen were measured at room temperature (about 25°C) using an AG-I type testing machine (Shimadzu Corporation) with a chuck distance of 50 mm and a crosshead speed of 50 mm / min.

[0059] The test method of residual tensile strength (TSa) is the same as the above test method except for the sample. The surface treated copper foil is cut into 100 mm × 12.7 mm (length × width) as a sample for testing residual tensile strength, and then placed in an oven at 140°C for 10 minutes. After the sample is removed from the oven, it is cooled at room temperature (about 25°C) for at least 5 minutes.

[0060] The tensile strength reduction TSR is defined as formula I:

[0061]

[0062] Chromium content

[0063] First, the surface treated copper foil was cut into a size of 150 mm × 150 mm as a sample to determine the chromium content. A protective coating was applied to one side of the surface treated copper foil to prevent the surface from dissolving. After drying the protective coating, the sample was further cut into a size of 100 mm × 100 mm (area = 1 dm 2 ) size. The sample was then placed in a pan and dissolved in 20 mL of 18% HCl solution at room temperature (about 25°C) for ten minutes. The solution was then poured from the pan into a 50 mL volumetric flask. The pan was rinsed with water and the rinse was added to the volumetric flask to provide a total volume of 50 mL. The chromium content of the solution was measured using ICP-AES.

[0064] Roughness (Rz)

[0065] The profile of the surface-treated copper foil was examined using a surface roughness measuring device (Kosaka Laboratory Co., Ltd.; SE 1700 series). Rz was obtained using the standard test method JIS B 0601-1994.

[0066] Peak density (Spd)

[0067] The peak density (Spd) of the surface-treated copper foil was measured using surface texture analysis using a laser microscope (manufactured by Olympus, LEXT OLS5000-SAF) in accordance with ISO 25178-2: 2012. The following conditions were used.

[0068] Light source: wavelength is 405nm.

[0069] Objective lens: 50X (MPLAPON-100xLEXT).

[0070] Optical zoom:1.0x.

[0071] Area: 129μm×129μm.

[0072] Resolution: 595 pixels × 595 pixels.

[0073] Condition: Automatically remove tilt.

[0074] Filter: S filter = 1 μm, L filter = 100 μm.

[0075] Air temperature: 24±3℃

[0076] Relative humidity: 63 ± 3%.

[0077] Uniformity

[0078] Uniformity evaluates the flatness of the active material coated on the surface treated copper foil. An anode having the active material and the surface treated copper foil was prepared as described in the calendering (pressing) test. After the calendering process, anode strips with a size of 25×5 cm were cut from the coated area of ​​the anode, and five sample pieces were further cut from the anode strip, and each sample piece had a size of 5×5 cm. Afterwards, the weight deviation was determined by formula III:

[0079]

[0080] The distribution of uniformity levels is shown in Table 4.

[0081] Table 4: Uniformity Grades

[0082] Weight deviation Uniformity <3％ O(Good) 3% to 5% Δ(Acceptable) >5％ X(difference)

[0083] As used herein, the terms "comprising" or "including" refer to compositions, methods and their respective components that are essential to the claimed invention, but allow for the inclusion of unspecified elements, whether or not such elements are essential.

[0084] As used herein, the term "consisting essentially of" refers to elements essential to a particular embodiment. The term permits the presence of elements that do not materially affect the basic and novel or functional characteristics of the claimed embodiments of the invention.

[0085] The term "consisting of" refers to the compositions, methods, and respective components described herein, which do not include any elements not recited in the description of that particular embodiment.

[0086] As used in this specification and claims, the singular forms "a", "an", and "the" include the plural forms unless the context clearly dictates otherwise. Thus, for example, description of "the method" includes one or more methods, and / or steps of the type described herein and / or that will be apparent to one of ordinary skill in the art after reading this disclosure and the like. Likewise, the word "or" is intended to include "and" unless the context clearly dictates otherwise.

[0087] Except for the operating examples or otherwise described, in all cases, the numbers used herein to express the quantities of ingredients and reaction conditions should be understood to be modified by the term "about". The term "about" means ± 5% (e.g., ± 4%, ± 3%, ± 2%, ± 1%) of the stated value.

[0088] If a numerical range is provided, each value between the upper and lower limits of the range and including the upper and lower limits of the range is deemed to be disclosed herein. It should be understood that any numerical range cited herein is intended to include all subranges covered by the range. For example, a range of "1 to 10" is intended to include all subranges between the minimum value 1 and the maximum value 10 contained and include the minimum and maximum values; in other words, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10. Because the disclosed numerical range is continuous, it includes every value between the minimum and maximum values. Unless otherwise expressly stated, the various numerical ranges referred to in this specification are approximate values.

[0089] Unless otherwise defined herein, technical terms used in connection with this application shall have the meanings generally understood by those skilled in the art. Furthermore, unless otherwise required by the context, terms in the singular shall include the plural, and terms in the plural shall include the singular.

[0090] It should be understood that the present invention is not limited to the specific methods, protocols and reagents described herein, and thus may vary. The terminology used herein is only for the purpose of describing specific embodiments and is not intended to limit the scope of the present invention, which is defined only by the claims.

[0091] Any patents, patent applications and publications disclosed herein including ASTM and JIS methods are expressly incorporated herein by reference for description and disclosure purposes, for example, the methods described in these publications can be used in conjunction with the present invention. These publications are provided only because they are disclosed before the filing date of this application. Any content in this regard should not be understood as admitting that the inventor has no right to preempt these disclosures by virtue of previous inventions or for any other reason. All narrations about dates or statements about the contents of these documents are based on information available to the applicant and do not constitute an admission of the correctness of these dates or the contents of these documents.

Claims

1. A surface-treated copper foil, comprising: A copper foil having a first side and an opposite second side, and Two processing layers, one of the two processing layers is disposed on the first surface, the other of the two processing layers is disposed on the second surface, and each processing layer provides a processing surface, in, The treated surface has a ten-point average roughness Rz ranging from 1.52 μm to 4.51 μm and a roughness Rz ranging from 498,526 to 1,079,838 mm -2 The peak density Spd in the range, and The chromium content in each treatment layer is 30.2 to 69.7 μg / dm 2 scope.

2. The surface-treated copper foil according to claim 1, characterized in that: The processed surface has a ten-point average roughness Rz ranging from 1.52 μm to 3.4 μm.

3. The surface treated copper foil according to claim 2, characterized in that: The processing surface has a diameter of 498,526 to 950,000 mm -2 The peak density Spd.

4. The surface-treated copper foil according to claim 1, characterized in that: The processing surface has a diameter of 498,526 to 950,000 mm -2 The peak density Spd.

5. The surface-treated copper foil according to claim 1, characterized in that: The processing surface has a diameter of 498,526 to 900,000 mm -2 The peak density Spd.

6. The surface-treated copper foil according to claim 1, characterized in that: The chromium content in each of the treatment layers is 30.2 to 60 μg / dm 2 .

7. The surface treated copper foil according to claim 1, further having a thickness of 36 kg / mm 2 Up to 60kg / mm 2 The tensile strength TS is within the range and the tensile strength reduction TSR is less than 45%, wherein The tensile strength reduction TSR is defined as: Wherein, the TSa is the residual tensile strength of the surface treated copper foil after annealing at 140° C. for 10 minutes.

8. The surface-treated copper foil according to claim 7, characterized in that: The surface treated copper foil has a tensile strength reduction TSR of less than 10%.

9. The surface-treated copper foil according to claim 1, characterized in that: Each treatment layer includes a coarsened particle layer and an anti-rust layer.

10. The surface-treated copper foil according to claim 1, characterized in that: The copper foil is an electrolytic copper foil. 11 . A lithium ion secondary battery comprising the surface-treated copper foil according to claim 1 and an active material coated on at least a portion of the treated surface.

12. The lithium ion secondary battery according to claim 11, characterized in that: The copper foil is an electrolytic copper foil having a roll surface corresponding to the first surface and a deposition surface corresponding to the second surface.

13. The lithium ion secondary battery according to claim 12, characterized in that: The active material is coated only on the treated surface of the deposition surface of the copper foil.

14. The lithium ion secondary battery according to claim 11, which is configured as a stacked battery. 15 . The lithium ion secondary battery according to claim 11 , which is configured as a button-type battery.

Images