WO2023146324A1 - Method for enhancing adhesion of aluminum foil - Google Patents

Abstract

The invention of the present application relates to a method for enhancing adhesion to a cathode material by removing rolling oil from the surface of an aluminum foil used as a cathode current collector and corroding the surface of the aluminum foil to adjust the roughness of the surface.

Description

How to improve adhesion of aluminum foil

This application claims the benefit of priority based on Korean Patent Application No. 2022-0012923 dated January 28, 2022 and Republic of Korea Patent Application No. 2022-0013758 dated January 28, 2022, and published in the literature of the Korean patent application All contents are incorporated as part of this specification.

The present invention relates to a method for improving the adhesion of aluminum foil. Specifically, it relates to a method of improving adhesion to a cathode material by removing rolling oil from the surface of an aluminum foil used as an anode current collector and controlling surface roughness by corroding the surface of the aluminum foil.

A secondary battery is formed by accommodating an electrode assembly and an electrolyte solution in a battery case. The electrode assembly is a jelly-roll-type assembly consisting of a long sheet-shaped positive electrode and a negative electrode with a separator interposed therebetween and then rolled up, or a stack-type assembly having a structure in which rectangular positive and negative electrodes are stacked with a separator interposed therebetween, and a unit. A stack-folding assembly in which cells are wound by a long separator film, or a lamination-stack assembly in which battery cells are stacked and attached to each other with a separator interposed therebetween, but is not limited thereto.

As a method of manufacturing an electrode of a secondary battery, a slurry prepared by dispersing an active material, a conductive material, and a binder in a solvent is coated on an electrode current collector and dried.

A metal foil is generally used as an electrode current collector, and in particular, an aluminum foil is mainly used as an anode current collector and a copper foil is mainly used as an anode current collector.

The aluminum foil used as the positive electrode current collector is manufactured by cold rolling to have a thickness of 10 to 20 μm so as to have required properties as the current collector. During rolling, the shape of the rolling roll is transferred to the surface of the foil as it is, and aluminum foil having a generally beautiful surface is produced. In the rolling process, rolling oil is used to reduce frictional heat and improve product surface quality, and rolling oil remains when a specific cleaning process is not performed.

The rolling oil is directly related to the wettability of the aluminum foil, and the more the rolling oil remains on the surface, the lower the wettability. When the wettability of the aluminum foil is low, it becomes difficult to coat the cathode material on the surface of the aluminum foil during the cathode production process. The decrease in adhesion between the positive electrode current collector, aluminum foil, and the positive electrode material is one of the very important causes of defects that greatly affect battery performance.

The adhesion between aluminum foil, which is the positive electrode current collector, and the positive electrode material is affected by residual rolling oil, surface shape, contact area between the positive electrode material and the current collector, and chemical affinity of the surface. Basically, it is necessary to remove the remaining rolling oil, and the most effective way to additionally increase the adhesion is to maximize the adhesion area between the positive electrode material and the current collector. Aluminum is a metal with low hardness and is easy to control the surface shape, through which the bonding area can be increased.

The prior art does not recognize the problem caused by the rolling oil, or when the technology is applied, a problem may occur in the basic physical properties of the cathode current collector.

Patent Document 1 relates to a process for removing rolling oil, and includes a process of heat-treating a coiled foil for 1 hour or more. When heat treatment is performed for a long time as in Patent Document 1, the strength of the thin aluminum foil itself may decrease. When rolled like a jelly-roll assembly, the stress applied to the current collector located inside increases, and when the method according to Patent Document 1 is applied, it may cause a big problem in the performance and safety of the battery itself. In addition, in light of the recent trend of increasing energy density, the method according to Patent Document 1 is difficult to apply to thin materials.

Patent Document 1 also proceeds with heat treatment for the foil in a rolled state, and a difference occurs in the evaporation rate between the inside and outside of the roll, which makes it difficult to obtain uniform physical properties for the entire aluminum foil.

Patent Document 2 relates to a method for manufacturing an aluminum foil for an electrolytic capacitor including a heat treatment step of heating the aluminum foil at a temperature of 200 to 300° C. for 10 seconds to 12 hours in a wound state. Patent Document 2 relates to an electrolytic capacitor, but does not recognize the improvement of wettability by removing the rolling oil of aluminum foil, and when applied to a positive electrode current collector with a high heat treatment temperature, It may affect strength. Patent Document 2 describes a process of immersing in an aqueous alkali solution as an additional process, but then again annealing (heat treatment) at 480 to 620 ° C., resulting in a problem of strength due to high temperature.

Patent Document 3 relates to a method for producing a porous aluminum electrolytic foil in which heat treatment is performed at 80 to 550° C. for 2 to 120 minutes on the porous aluminum electrolytic foil. Patent Document 3 cannot be used as an anode current collector because the material is porous, and has the same problems as Patent Document 1 due to the method of heat-treating the foil itself as in Patent Document 1.

In Patent Document 4, aluminum foil used as a current collector is washed with an organic solvent and then subjected to various processes such as drying, ethanol washing, and washing with an anode material. Patent Document 4 Also, the process by which the rolling oil can be removed, but the method by washing as in Patent Document 4 is not only cumbersome with many steps, but also has a fear that the cleaning liquid itself remains.

Patent Document 5 is a process of annealing aluminum foil at 450 to 600 ° C. The temperature is very high and cannot be applied to heat treatment to remove rolling oil.

As described above, the conventional method has many steps and is cumbersome or has a problem of remaining cleaning solution. In addition, the high heat treatment temperature degrades the physical properties of aluminum foil, or proceeds in a rolled state, so that uniform physical properties cannot be expected.

The prior art for controlling the surface shape also has the following problems.

Patent Document 6 relates to an aluminum foil used as a current collector, and has an acid-cleaned or alkali-cleaned surface. In the case of Patent Document 6, residual oil or acid/base components may remain after washing. In order to solve this problem, if the cleaning time is increased, a problem in which productivity is lowered occurs.

Patent Document 7 describes a method for treating the surface of an aluminum current collector including etching an aluminum foil in an aqueous hydrochloric acid solution, post-treatment in a mixed solution of phosphoric acid and ammonium salt, and heat-treating the post-treated aluminum foil. are doing Patent Document 7 also does not proceed with surface treatment only by washing in that a step of heat treatment after acid treatment is added.

In Patent Document 8, heat treatment is performed after acid treatment, and in Patent Document 9, etching and electrical treatment are performed in sodium hydroxide, hydrochloric acid, nitric acid, sulfuric acid, and the like.

As such, in the conventional method, even if the cleaning solution is used, acid/base components remain, or if the cleaning time is increased to remove them, productivity may decrease. there is

Republic of Korea Patent Publication No. 2006-0127031 ('Patent Document 1')

Japanese Patent Registration No. 3852632 ('Patent Document 2')

Republic of Korea Patent Registration No. 1958507 ('Patent Document 3')

Chinese Patent Registration No. 100527300 ('Patent Document 4')

Japanese Unexamined Patent Publication No. 1998-242005 ('Patent Document 5')

Republic of Korea Patent Publication No. 2014-0024466 ('Patent Document 6')

Republic of Korea Patent Publication No. 2018-0034150 ('Patent Document 7')

Republic of Korea Patent Registration No. 1415642 ('Patent Document 8')

Republic of Korea Patent Publication No. 2014-0136220 ('Patent Document 9')

The present invention is to solve the above problems, and an object of the present invention is to provide a method for improving the adhesion between an aluminum foil used as a cathode current collector and a cathode material.

Specifically, the purpose is to improve the wettability of the aluminum foil surface by removing the rolling oil on the surface of the aluminum foil used as the positive electrode current collector. Another object of the present invention is to provide an improved method for removing rolling oil, which has uniform physical properties with respect to the entire aluminum foil and does not lower the strength of the aluminum foil.

Another object of the present invention is to provide a method for adjusting the roughness of the surface of an aluminum foil used as a cathode current collector. Another object of the present invention is to provide an improved method for controlling the roughness of a surface, which does not contain acid/base residual components and does not require a separate high-temperature drying process to remove the residual components.

In order to solve the above problems, the present invention is a method of drying the unrolled aluminum foil with hot air to remove the rolling oil on the surface of the additional aluminum foil and / or etching the unrolled aluminum foil with an acidic solution or a basic solution, and the etched Provides a pretreatment method for an electrode current collector aluminum foil including a method of adjusting the roughness of the surface of the aluminum foil by washing the unrolled aluminum foil and drying the remaining material of the washed unrolled aluminum foil using a physical absorbent. .

Before drying the unrolled aluminum foil with hot air, the unrolled aluminum foil may be immersed in a solvent, and the solvent may have a boiling point of 150° C. or less. The solvent may include one or more of the group including H ₂ O, C ₃ H ₆ O, CH ₃ OH, C ₂ H ₅ OH, CHCl ₃ , CH ₂ Cl ₂ , and C ₆ H ₁₄ .

Drying with the hot air may be carried out at 80 ° C or higher, preferably 80 ° C or higher and 150 ° C or lower, for 10 seconds or longer and 10 minutes or lower.

Drying the remaining material using a physical absorbent may include placing a sheet of fibrous component between the unrolled aluminum foil and the roll so that the remaining material is absorbed by the sheet of fibrous component when the unrolled aluminum foil moves. there is. At this time, when the unrolled aluminum foil moves, the sheet of the fibrous component may also move at the same speed.

The sheet of the fibrous component may be an artificial fabric containing one or more from the group consisting of nylon, rayon, acrylic, and polyester.

Meanwhile, a separate drying process may be added after the method of adjusting the roughness of the surface.

The acidic solution may be at least one selected from the group consisting of HNO ₃ , H ₂ SO ₄ , H ₃ PO ₄ , and HCl, and the basic solution may be at least one selected from the group consisting of Na ₃ PO ₄ and NaOH. .

The etching may be performed for 1 to 60 seconds, and the washing may use water.

The thickness of the aluminum foil may be 10 to 20 μm, preferably 10 to 15 μm.

Only a method of removing the pressing oil or a method of adjusting the roughness of the surface may be performed.

Applying the method of adjusting the roughness of the surface to the aluminum foil that has undergone the method of removing the rolling oil by another method, or removing the rolling oil to the aluminum foil that has undergone the method of adjusting the roughness of the surface method can be applied.

After the method of removing the rolling oil and/or the method of adjusting the surface roughness, the aluminum foil may be rolled again, or the aluminum foil may be coated with a positive electrode and dried, and then rolled again.

The present invention also provides an aluminum foil electrode current collector obtained by the pretreatment method of the electrode current collector aluminum foil and an electrode assembly including the aluminum foil electrode current collector as a positive electrode current collector.

The present invention can also be provided by combining the means for solving the above problems.

As such, the present invention can improve the adhesion between the aluminum foil used as the positive electrode current collector and the positive electrode material.

Specifically, by removing the rolling oil on the surface of the aluminum foil used as the positive electrode current collector to improve the wettability of the surface of the aluminum foil, adhesion to the positive electrode material can be improved.

In the present invention, in removing the rolling oil, the entire aluminum foil has uniform physical properties, and the strength of the aluminum foil is not lowered.

In the present invention, even when the thickness of the aluminum foil is 10 to 20 μm, preferably 10 to 15 μm, more preferably 10 to 12 μm, the entire aluminum foil has uniform physical properties and the strength of the aluminum foil is not reduced. There is an excellent effect that does not.

In the present invention, adhesion to the cathode material may be improved by adjusting the roughness of the surface of the aluminum foil used as the cathode current collector.

The present invention can also provide an improved method for controlling the roughness of a surface, which does not contain residual acid/base components and does not require a separate high-temperature drying process to remove the residual components.

1 is a schematic diagram of a cathode active material coating process according to the prior art.

2 is a schematic diagram of a cathode active material coating process using a cathode current collector according to a first embodiment of the present invention.

3 is an example of a Dyne Test according to the present invention.

4 is a schematic diagram of a cathode active material coating process using a cathode current collector according to a second embodiment of the present invention.

5 is a schematic diagram of an etching process according to a second embodiment of the present invention.

6 is a schematic diagram showing a difference in contact area with a cathode material according to the surface shape of an aluminum foil.

7 is a scanning electron microscope (SEM) photograph of the surface of an aluminum foil before surface treatment according to the present invention.

8 is a scanning electron microscope (SEM) photograph of the surface of an aluminum foil after surface treatment according to the present invention.

Hereinafter, embodiments in which a person skilled in the art can easily practice the present invention will be described in detail with reference to the accompanying drawings. However, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention in describing the operating principle of the preferred embodiment of the present invention in detail, the detailed description will be omitted.

In addition, the same reference numerals are used for parts having similar functions and actions throughout the drawings. Throughout the specification, when a part is said to be connected to another part, this includes not only the case where it is directly connected, but also the case where it is indirectly connected with another element interposed therebetween. In addition, including a certain component does not exclude other components unless otherwise stated, but means that other components may be further included.

(Example 1) Hereinafter, a method of improving the wettability of an aluminum foil by removing rolling oil from the surface of the aluminum foil among the pretreatment methods of the aluminum foil of the current collector according to the present invention will be described.

1 is a schematic diagram of a cathode active material coating process according to the prior art. In the case of the prior art, the aluminum foil is unrolled, coated with a positive electrode and dried, and then rolled again.

A method for improving the wettability of aluminum foil according to the present invention includes a method of unrolling an aluminum foil in a roll state and drying the unrolled aluminum foil with hot air. A step of rolling the aluminum foil again after drying with hot air may be added, or a step of coating the positive electrode on the aluminum foil, drying it, and then rolling it again may be added.

After additionally applying the method for controlling surface roughness according to the present invention, a step of rolling the aluminum foil again is added, or a step of coating the aluminum foil with a positive electrode and drying it and then rolling it again is added. It can be.

Figure 2 is a schematic diagram of a positive electrode active material coating process using a positive electrode current collector according to a first embodiment of the present invention. What has been added is shown.

2 also shows a step of immersing the unrolled aluminum foil in a solvent before drying the unrolled aluminum foil with hot air. The solvent has a boiling point of 150 ° C or less, and specifically, the solvent includes H ₂ O, C ₃ H ₆ O, CH ₃ OH, C ₂ H ₅ OH, CHCl ₃ , CH ₂ Cl ₂ , C ₆ H ₁₄ One or more of the groups may be included.

The drying with hot air is performed at 80° C. or more, preferably at 80° C. to 150° C. for a predetermined time, and the predetermined time is 10 seconds or more and 10 minutes or less. In general, rolling oil used for aluminum foil is volatile and may vary depending on the components of the product, but is usually volatilized below 200 ° C. In the case of aluminum foil having a thickness of 20 μm or less that can be used as a current collector, the strength was not lowered when drying was performed at 150 ° C or less for 10 seconds or more and 10 minutes or less.

If the drying temperature is less than 80 ° C, drying is not performed properly, and if it exceeds 150 ° C, the strength of the aluminum foil may be weakened. If the drying time is less than 5 seconds, heat energy transfer by hot products is not sufficient, and if the drying time exceeds 10 minutes, productivity is excessively reduced.

The aluminum foil has a thickness of 10 to 20 μm, preferably 10 to 15 μm, and more preferably 10 to 12 μm.

The present invention also relates to an electrode current collector aluminum foil obtained by the method for improving the wettability of an aluminum foil, an electrode assembly including the electrode current collector aluminum foil as a positive electrode current collector, a battery including the electrode assembly, and a battery including the battery A module and a battery pack including the battery are provided.

<Manufacture of positive electrode>

A positive electrode including an aluminum foil, which is a positive electrode current collector according to the present invention, is coated with a positive electrode active material on the upper and lower surfaces of the aluminum foil, and dried by applying heat at a predetermined temperature for a predetermined time, for example, at 80 ° C. for 20 minutes A drying process may be performed, and a positive electrode may be formed by applying a roll press to the additionally dried positive electrode current collector and positive electrode active material to pressurize them.

Examples of the cathode active material include layered compounds such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ) or compounds substituted with more transition metals; lithium manganese oxides such as Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3; Formula LiMn _2-x M _x O ₂ (Where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (Where M = Fe, Co, Ni , Cu or Zn); LiMn ₂ O ₄ in which Li part of the formula is substituted with an alkaline earth metal ion; disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , LiNi _x Mn _2-x O ₄ (0.01 ≤ x ≤ 0.6), and the like can be used.

The cathode active material may include a binder and a conductive material, and may further include two other components such as a viscosity modifier, a filler, a crosslinking accelerator, a coupling agent, and an adhesion promoter.

The binder is a component that assists in the bonding of the positive electrode active material and the conductive material and the bonding to the current collector, and is typically added in an amount of 1 to 50% by weight based on the total weight of the positive electrode active material. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, and tetrafluorocarbons. roethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluororubber, various copolymers thereof, and the like.

The conductive material is a component for further improving the conductivity of the positive electrode active material, and may be added in an amount of 1 to 20% by weight based on the total weight of the positive electrode mixture. The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

Hereinafter, a preferred embodiment 1 is presented to aid understanding of the present invention. However, Example 1 below is only provided to more easily understand the present invention, and the content of the present invention is not limited thereby.

Examples 1-1 to 1-7

An aluminum roll having a thickness of 12 μm was prepared, unrolled, and then dried according to the temperature and time shown in Table 1 below.

Example 1-8, 1-9

An aluminum roll having a thickness of 12 μm was prepared, unrolled, immersed in a 99% acetone solution for 15 seconds, and then dried according to the temperature and time shown in Table 1 below.

Comparative Example 1-1

An aluminum roll having a thickness of 12 μm was prepared and unrolled. It was dried for 10 minutes at room temperature (25°C).

Comparative Examples 1-2 to 1-4

An aluminum roll having a thickness of 12 μm was prepared, unrolled, and then dried according to the temperature and time shown in Table 1 below.

<dyne test>

In order to confirm whether or not the wettability of the aluminum foil is improved, a dyne test was performed. The dyne test is a method according to ISO 8296, and is a method of measuring the surface energy of a material using a dyne solution.

In the present invention, 30 to 50 Dyne test pens containing ethylene glycol monomethyl ether and dye were prepared. The dyne solution in the dyne test pen is a mixture of 2-ethoxyethanol and formamide, and the preceding number represents the surface energy value. For example, 30 dynes represents 30 dynes/cm.

If the liquid film of the dyne solution is broken within 10 seconds after applying the dyne test pen to the surface of the aluminum foil having a width of 10 mm and a length of 10 cm or more according to Examples or Comparative Examples, it was determined that the dyne value was not met. If the liquid film maintained its original shape for 10 seconds or more, it was determined to have the corresponding dyne value. After measuring three times, the average value was described in the dyne test (dynes/cm) in Table 1.

3 is an example of a Dyne Test according to the present invention. The upper picture of FIG. 3 is a picture immediately after the 30 dyne solution is applied to the aluminum foil, and the lower picture of FIG. 3 is a picture of the state in which the liquid film of the 30 dyne solution is broken. In FIG. 3, the horizontal line in the center is the result of the dyne test, and the bright part in the center is the reflected light by the camera.

<Tensile strength>

After the drying process was completed, the aluminum foil was punched into a size of 12.7 mm in width, 12.7 mm in length, and 150 mm, and then the tensile strength was measured using a Universal Testing Machine (UTM). The gauge length is 50 mm, the measurement speed is 20 mm/min, and the measurement direction is MD (Machine Direction). Tensile strength was also measured three times, and the average value was shown in Table 1.

Table 1 below shows the drying temperature and time, dyne test, and tensile strength results of Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-7.

Looking at Table 1, there is no improvement even if dried for 10 minutes or more at less than 80 ° C., but wettability is improved even if dried for 2 minutes or more at 80 ° C. or 10 seconds or more at 150 ° C. Bar, The improvement effect by the method according to the present invention can be clearly seen. In addition, it can be seen that the effect of improving wettability increases when a pretreatment process of immersion in an organic solvent is added.

In Table 1, it can be seen that the higher the value of dynes/cm, the better the wettability, and the wettability can be greatly improved through the method according to the present invention. The higher the dyne test value, the cleaner the surface and the higher the wettability, which is advantageous for coating the slurry on the current collector during the battery production process.

When the tensile strength is low, disconnection may occur due to breakage of the aluminum foil used as the current collector in the process of producing an electrode using the current collector. In addition, the current collector is more likely to be torn or cracked due to deformation due to swelling during charging and discharging of the completed battery cell. If the tensile strength after drying is weakened by 5% or more, and if it falls below 27 kfg / mm2 in the case of Table 1, the probability of disconnection during the electrode roll press process greatly increases. When the drying temperature exceeds 150 ° C., the tensile strength of the aluminum foil is weakened.

(Example 2) Hereinafter, a method of improving the adhesiveness of the aluminum foil through a method of adjusting the roughness of the surface of the aluminum foil among the pretreatment methods of the aluminum foil of the current collector according to the present invention will be described.

A method for improving adhesion of aluminum foil according to the present invention unrolls aluminum foil in a roll state, etching the unrolled aluminum foil with an acidic solution or a basic solution, and washing the etched unrolled aluminum foil, and drying the remaining material of the washed unrolled aluminum foil using a physical absorbent.

4 is a schematic diagram of a cathode active material coating process using a cathode current collector according to a second embodiment of the present invention. 4 shows that the step of coating the positive electrode on the aluminum foil whose surface roughness is adjusted, drying it, and then rolling it again is shown.

5 is a schematic diagram of an etching process according to a second embodiment of the present invention. Referring to FIG. 5, drying the remaining material using a physical absorbent places a sheet of fibrous component between the unrolled aluminum foil and the roll, and when the unrolled aluminum foil moves, the remaining material is placed on the sheet of fibrous component. material is absorbed. The sheet of the fibrous component may be an artificial fabric containing one or more from the group consisting of nylon, rayon, acrylic, and polyester. In Figure 5, a sheet of fibrous component is indicated by a dotted line, and the remaining material is removed by combining it with a roll. In FIG. 5, when the unrolled aluminum foil moves, the sheet of the fibrous component also moves at the same speed.

Meanwhile, a separate drying process may be added after the method of adjusting the roughness of the surface.

The acidic solution may be at least one selected from the group consisting of HNO ₃ , H ₂ SO ₄ , H ₃ PO ₄ , and HCl, and the basic solution may be at least one selected from the group consisting of Na ₃ PO ₄ and NaOH. .

The etching may be performed for 1 to 60 seconds, and the washing may use water.

A step of re-rolling the aluminum foil after adjusting the surface roughness may be added, or a step of coating the anode material on the aluminum foil, drying it, and then rolling it again may be added.

After additionally applying the method for improving wettability according to the present invention, a step of rolling the aluminum foil again may be added, or a step of coating the positive electrode on the aluminum foil, drying it, and then rolling it again may be added.

The aluminum foil has a thickness of 10 to 20 μm, preferably 10 to 15 μm, and more preferably 10 to 12 μm.

The present invention also includes an aluminum foil obtained by the method for improving the adhesion of the aluminum foil, an electrode assembly including the aluminum foil as a cathode current collector, a battery including the electrode assembly, a battery module including the battery, and the battery A battery pack is provided.

<Manufacture of positive electrode>

Preparation of the positive electrode according to Example 2 is the same as that of the positive electrode according to Example 1.

Hereinafter, a preferred embodiment 2 is presented to aid understanding of the present invention. However, Example 2 below is only provided to more easily understand the present invention, and the content of the present invention is not limited thereby.

Example 2-1

An aluminum roll having a thickness of 12 μm was prepared, unrolled, and immersed in a 10 wt% H ₂ SO ₄ solution for 15 seconds. After washing in water for 15 seconds, the remaining material was absorbed using artificial fabric containing nylon.

Comparative Example 2-1

After preparing an aluminum roll having a thickness of 12 μm, it was unrolled.

Comparative Example 2-2

It is the same as Example 2-1 except that only etching was performed using the same sulfuric acid as Example 2-1.

Comparative Example 2-3

It is the same as Example 2-1 except that only etching and water washing were performed using the same sulfuric acid as Example 2-1.

<Surface shape>

6 is a schematic diagram showing a difference in contact area with a cathode material according to the surface shape of an aluminum foil. The left side of FIG. 6 shows a comparative example, and the right side shows a model of the surface shape according to the present invention. 7 is a scanning electron microscope (SEM) photograph of the surface of an aluminum foil before surface treatment according to the present invention, and FIG. 8 is a scanning electron microscope (SEM) photograph of the surface of an aluminum foil after surface treatment according to the present invention.

Comparing FIG. 7 and FIG. 8 , it can be seen that the surface of the aluminum foil is roughened by Example 2 according to the present invention.

<Surface Roughness>

For surface roughness, the R _a value was measured using a contact roughness meter. The arithmetic average roughness (R _a ) was measured in accordance with the ISO 4287 measurement standard using a contact roughness meter that satisfies the equipment standard ISO 3274. After measuring a total of 10 times, the average value was derived.

<Tensile Strength>

After cutting the aluminum foil to a width of 15 mm, it was stretched at a rate of 20 mm/min, and the maximum tensile strength (N) was measured at this time, which is shown in Table 2 below. Through this, it can be seen that there is no change in the strength of the aluminum foil even when dried under the conditions according to the present invention.

<Electrode adhesion test>

A slurry was prepared by mixing the cathode active material Li(Ni _1/3 Co _1/3 Mn _1/3 )O ₂ , the binder PVDF, and the conductive material carbon black in a weight ratio of 96:2:2. The slurry was applied to aluminum foil at a constant thickness (5 mg/cm 2 ) using a doctor blade, and dried at 130° C. for 10 minutes to obtain an electrode.

After bonding the slurry surface of the electrode to the steel substrate using double-sided tape, the 90 degree peel strength (peel width 20 mm, peel speed 100 mm/min) was measured.

<Surface pH>

In order to measure the pH change due to the acid solution remaining on the surface, the foil was cut into 10 mm X 10 mm, put in 50 ml of distilled water, washed for 600 seconds, and then the pH of the solution was measured.

Table 2 shows the experimental results for Example 2-1 and Comparative Examples 2-1, 2-2, and 2-3.

In the case of the embodiment of the present invention, it can be seen that while the surface roughness is increased, no foreign substances remain on the surface, and the electrode adhesion is greatly improved. In the case of Comparative Example 2-3, it can be seen that residues still remain on the surface when etching with acid and washing only with water. When the acid solution remains on the surface, it reacts with the electrode or the electrolyte, and as a result, the performance of the battery may be deteriorated.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above information.

The present invention relates to a method for improving adhesion to a cathode material by removing rolling oil from the surface of an aluminum foil used as a cathode current collector and corroding the surface of the aluminum foil to control surface roughness, and thus can be used industrially.

Claims (13)

1. a method of drying the unrolled aluminum foil with hot air to remove the rolling oil on the surface of the additive aluminum foil;

   and/or

   The roughness of the surface of the aluminum foil by etching the unrolled aluminum foil with an acidic solution or a basic solution, washing the etched unrolled aluminum foil, and drying the remaining material of the washed unrolled aluminum foil using a physical absorbent. how to regulate;

   A pretreatment method of an electrode current collector aluminum foil comprising a.
2. According to claim 1,

   A pretreatment method of an electrode current collector aluminum foil of immersing the unrolled aluminum foil in a solvent before drying the unrolled aluminum foil with hot air.
3. According to claim 2,

   The solvent is a pretreatment method of an electrode current collector aluminum foil having a boiling point of 150 ° C or less.
4. According to claim 1,

   Drying with the hot air is a pretreatment method of the electrode collector aluminum foil, which proceeds at 80 ° C. or more and 150 ° C. or less, 10 seconds or more and 10 minutes or less.
5. According to claim 1,

   Drying the remaining material using a physical absorbent is to place a sheet of fibrous component between the unrolled aluminum foil and the roll so that the remaining material is absorbed into the sheet of fibrous component when the unrolled aluminum foil moves. Pretreatment method of electrode current collector aluminum foil.
6. According to claim 5,

   The sheet of the fibrous component is an artificial fabric containing at least one from the group consisting of nylon, rayon, acrylic, and polyester. Pretreatment method of the electrode current collector aluminum foil.
7. According to claim 1,

   The acidic solution is at least one selected from the group consisting of HNO ₃ , H ₂ SO ₄ , H ₃ PO ₄ , and HCl, and the basic solution is at least one selected from the group consisting of Na ₃ PO ₄ and NaOH. Pretreatment method of whole aluminum foil.
8. According to claim 1,

   The etching is a pretreatment method of an electrode current collector aluminum foil in progress for 1 to 60 seconds.
9. According to claim 1,

   The washing is a pretreatment method of an electrode current collector aluminum foil using water.
10. According to claim 1,

    The pretreatment method of the electrode current collector aluminum foil having a thickness of 10 to 20 μm.
11. According to claim 1,

    The method of adjusting the roughness of the surface is applied to the aluminum foil that has undergone the method of removing the rolling oil, or the method of removing the rolling oil is applied to the aluminum foil that has undergone the method of adjusting the roughness of the surface. A pretreatment method for an electrode current collector aluminum foil.
12. An aluminum foil electrode current collector obtained by the method according to any one of claims 1 to 11.
13. An electrode assembly comprising the aluminum foil electrode current collector according to claim 12 as a positive electrode current collector.

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