JP2013026063A - Positive electrode for secondary battery with current collector made of aluminum alloy, and manufacturing method of positive electrode for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode for a secondary battery having excellent adhesion to a positive electrode active material and good charge and discharge characteristics.SOLUTION: The positive electrode for a secondary battery comprises: a positive electrode current collector 100 composed of an aluminum alloy foil; and a positive electrode active material layer on a surface of the positive electrode current collector 100, which includes a positive electrode active material capable of occluding and releasing lithium. The positive electrode current collector 100 has reentrants and protrusions on the surface thereof. The surface of the positive electrode current collector 100 with the reentrants and protrusions has an average surface roughness Ra of 0.07-4.0 μm. The average distance between local peaks 06 of the reentrants and protrusions is 20-50 μm. The average circle-equivalent diameter of pits 04 forming the reentrants and protrusions is 4.0-600 μm. The density of the pits 04 falls between 300 /mand 5000 /minclusive.

Description

  The present invention relates to a positive electrode for a secondary battery using an aluminum alloy current collector and a method for producing the positive electrode for the secondary battery.

To manufacture a positive electrode material for a lithium ion secondary battery, first, an active material such as LiCoO ₂ , a conductive material such as carbon, and a binder such as PVDF are kneaded to produce a paste. Next, this paste is applied to both sides of an aluminum hard foil or aluminum soft foil (hereinafter simply referred to as “aluminum alloy foil”) of about 10 to 30 μm to a thickness of about 50 to 200 μm and dried. Then, the positive electrode material of a lithium ion secondary battery is manufactured by performing each process of a press, a slit, and a cutting | disconnection sequentially to this aluminum alloy foil.

  In the processing steps from the application to the aluminum alloy foil serving as the electrode base material to the battery assembly described above, it is required to manufacture an electrode material with higher accuracy at a lower cost. Furthermore, in order to increase the life of the battery, there is a strong demand for a positive electrode and an aluminum current collector that have improved adhesion between the aluminum alloy foil serving as the electrode substrate and the above active material.

  Since the aluminum alloy foil constituting the positive electrode current collector is generally manufactured by cold rolling, the surface thereof is relatively smooth, and the adhesion of the positive electrode active material to the positive electrode current collector is Low. In particular, when the amount of the active material contained in the positive electrode active material is increased in order to increase the capacity of the lithium ion secondary battery, the amount of the binder is relatively decreased, so that the adhesion of the positive electrode active material to the positive electrode current collector is further increased. If the adhesion is reduced, the lithium ion secondary battery has a reduced discharge capacity with a small number of charge / discharge cycles.

  For this reason, Patent Document 1 is devised such that the surface of the aluminum alloy foil is roughened by sandblasting to improve the adhesion of the positive electrode active material to the positive electrode current collector.

Further, in Patent Document 2, when a pure Al foil is anodized to form an anodized film on the surface, and then the anodized film is removed with phosphoric acid, the average pit diameter on the surface is 0.05-0. It is described that a pure Al foil in which pits within a range of 10 μm are formed at an average density of 100 to 500 / μm ² is obtained. Further, when a pure Al foil having pits is used as a positive electrode current collector film, a slurry containing a positive electrode active material and a binder is applied to the surface of the positive electrode current collector film and then dried to form a positive electrode active material film. It is described that the adhesion of the positive electrode active material film to the current collector film is improved.

  Furthermore, in Patent Document 3, the surface of the aluminum alloy foil is roughened by spraying alumina particles onto the surface of the aluminum alloy foil through water or a nonflammable organic solvent, and the average roughness is obtained as the roughness of at least one surface. An aluminum alloy foil for a current collector used for a secondary battery or an electric double layer capacitor having Ra of 0.3 μm to 1.5 μm and a maximum height Ry of 0.5 μm to 5.0 μm is disclosed.

  Patent Document 4 describes that a pitch in a wedge shape is manufactured by subjecting an aluminum alloy foil to a surface treatment such as etching.

  Non-Patent Document 1 describes an oil pit generated on the surface of an aluminum alloy foil, although it is a technical field that has nothing to do with the positive electrode material of a lithium ion secondary battery.

Japanese Patent Laid-Open No. 9-22699 JP 2000-113892 A JP 11-162470 A JP 2008-060124 A

Fukuda et al. "Rolling technology of pure titanium sheet" R & D KOBE STEEL ENGINEERING REPORT / Vol. No. 49 3 (Dec. 1999)

However, the prior art described in the above literature has room for improvement in the following points.
First, as in Patent Document 1 and Patent Document 3, when the surface is roughened by sandblasting or alumina particle injection, the adhesion of the positive electrode active material to the positive electrode current collector made of aluminum alloy foil is certain. To improve. However, even in such a case, the adhesion of the positive electrode active material to the positive electrode current collector made of the aluminum alloy foil is not yet sufficient, and further improvement in the adhesion of the positive electrode active material to the positive electrode current collector has been demanded. .

  Secondly, the pit formation by the anodic oxide film of Patent Document 2 is that the thickness of the aluminum alloy foil of the commonly used positive electrode current collector is only 15 to 30 μm, and in order to anodize the material of this thickness Has to be treated for a long time at a low voltage, and if anodizing for a long time, pinholes (holes) are opened in the aluminum alloy foil, and sometimes it melts and breaks the foil. There are things to do. Further, even if the above-mentioned problems are not caused by anodic oxidation, the thickness of the foil is further reduced by the subsequent phosphoric acid treatment, and it is easy to cut on the line, which is a problem in terms of productivity and cost.

  Thirdly, in Patent Document 4, when aluminum alloy foil is subjected to a surface treatment such as etching, it becomes a very expensive product, and it is expected that lower weight and higher functionality will be required in the future. It becomes difficult to satisfy.

  The present invention has been made in view of the above circumstances, and has excellent adhesion between a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium and a positive electrode current collector made of an aluminum alloy foil. It aims at providing the positive electrode for secondary batteries.

  As a result of repeating intensive trial and error in order to solve the above-mentioned problems, the present inventors, as shown in Non-Patent Document 1, have oil pits on the surface of an aluminum alloy foil that has been considered to be a surface defect in the conventional technical common sense. Rather, I came up with the idea of actively using it. Based on this idea, the present inventors have determined the shape and distribution of oil pits that do not adversely affect the surface of the aluminum alloy foil, and have improved adhesion between the positive electrode current collector and the positive electrode active material. Succeeded to improve.

  In the process, the present inventors have further noticed that undulation may occur on the surface of the aluminum alloy foil when performing cold rolling to create oil pits on the surface of the aluminum alloy foil. I noticed the possibility of being rather active. And based on this idea, the present inventors, in addition to the oil pits on the surface of the aluminum alloy foil, provided undulations of appropriate conditions, so that an exquisite shape and a combination of oil pits and undulations having different properties can be obtained. As a result, it was found that the unevenness of the distribution was completed, and as a result, the adhesion between the positive electrode current collector and the positive electrode active material was further improved.

That is, according to the present invention, there is provided a positive electrode for a secondary battery having a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium on the surface of a positive electrode current collector made of an aluminum alloy foil. The electrical surface has irregularities, the average surface roughness Ra of the irregular surface of the positive electrode current collector is 0.07 to 4.0 μm, the average interval between the local peaks of the irregularities is 20 to 50 μm, The average equivalent circle diameter of the pits constituting the irregularities is 4.0 to 600 μm, the average pit depth is 0.3 to 3.0 μm, and the density of pits is 300 / m ² or more and 5000 / Provided is a positive electrode for a secondary battery that is m ² or less.

  According to this configuration, the shape and distribution of the pits that do not adversely affect the aluminum alloy foil surface as a defect are realized, and the unevenness of the shape and distribution having an exquisite balance is provided including those pits. Thus, a positive electrode for a secondary battery that is remarkably excellent in adhesion between the positive electrode current collector and the positive electrode active material can be obtained.

Further, according to the present invention, there is provided a method for producing a positive electrode for a secondary battery having a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium on a surface of a positive electrode current collector made of an aluminum alloy foil. The kinematic viscosity of the rolling oil is 1.9 to 3.5 × 10 ⁻³ Pa · s, the rolling speed is 400 to 1200 m / min, and the average roll surface roughness Ra is 0.00. There is provided a method for producing a positive electrode for a secondary battery, including a step of cold rolling under conditions of 10 to 5.0 μm and a finish rolling ratio of 20 to 50% to obtain the aluminum alloy foil.

  According to this method, since the oil pit is formed by cold rolling when manufacturing the aluminum alloy foil, the oil pit can be formed without adding a special process to the manufacturing process of the normal aluminum alloy foil. An aluminum alloy foil can be produced. In addition, when cold rolling to create oil pits on the aluminum alloy foil surface, undulations occur on the aluminum alloy foil surface, so the shape has an exquisite balance due to the combination of oil pits and undulations having different properties from each other As a result, the adhesion between the positive electrode current collector and the positive electrode active material is dramatically improved. That is, according to this method, since the unevenness is formed by cold rolling when manufacturing the aluminum alloy foil, there are fewer pinholes than when the unevenness is formed by etching or the like, so cutting even if transported at high speed Thus, a positive electrode for a secondary battery that is remarkably excellent in adhesion between the positive electrode current collector and the positive electrode active material can be obtained by a low-cost manufacturing process.

  The positive electrode for a secondary battery according to the present invention is provided with unevenness of shape and distribution having an exquisite balance as described above on the surface of the aluminum alloy foil, so that the adhesion between the positive electrode current collector and the positive electrode active material is remarkably high. Are better.

  In addition, the method for producing a positive electrode for a secondary battery according to the present invention forms an unevenness on the surface of the aluminum alloy foil by cold rolling at the time of producing the aluminum alloy foil, so that the positive electrode current collector and the positive electrode active material are closely adhered. Thus, a positive electrode for a secondary battery that is remarkably excellent in properties can be produced at low cost.

FIG. 1 is a conceptual diagram of an aluminum alloy foil for explaining the undulations formed by undulation and oil pits on the surface of the aluminum alloy foil used in the positive electrode for a secondary battery according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate. In addition, in this embodiment, when it describes as AB, it means that it is A or more and B or less.

<Positive electrode for secondary battery>
FIG. 1 is a conceptual diagram of an aluminum alloy foil for explaining the undulations formed by undulation and oil pits on the surface of the aluminum alloy foil used in the positive electrode for a secondary battery according to the present embodiment. The positive electrode for a secondary battery according to this embodiment is a positive electrode for a secondary battery having a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium on the surface of a positive electrode current collector 100 made of an aluminum alloy foil. is there.

  In the present embodiment, the “secondary battery” includes a storage battery and a rechargeable battery, and is a concept including a battery that can be used as a battery by storing electricity by charging and can be used repeatedly. . The “positive electrode” is a concept including a cathode and an electrode on the side where positive charges move from the solution toward the electrode (an electrode on which electrons are emitted toward the solution).

  Here, the positive electrode active material contained in the positive electrode for the secondary battery includes a cobalt-based material, an iron phosphate-based material, a spinel manganese-based material, a cobalt-nickel-manganese ternary material, and a cobalt-nickel-aluminum ternary system. In order to improve the performance of the secondary battery, it is preferable to include one or more materials selected from the group consisting of materials.

  In addition, when this positive electrode active material layer is applied to the surface of the positive electrode current collector 100 made of the aluminum alloy foil 02, the positive electrode active material, a conductive material such as carbon, and a binder such as PVDF are combined. It is preferable that the paste is prepared by kneading and then applied to the surface of the positive electrode current collector 100 made of the aluminum alloy foil 02. Further, the surface of the positive electrode current collector 100 made of the aluminum alloy foil 02 may be subjected to a base treatment such as carbon coating before the coating.

  Further, the surface of the positive electrode current collector 100 made of the aluminum alloy foil 02 has irregularities. And since this unevenness | corrugation satisfies the specific conditions mentioned later, the positive electrode electrical power collector 100 which consists of this aluminum alloy foil 02 has the adhesiveness with a positive electrode active material, and is excellent in the cycling characteristics after charging / discharging. It has the characteristics that can contribute to the long life of the secondary battery.

  Specifically, the unevenness of the surface of the positive electrode current collector 100 described above is such that when the aluminum alloy foil 02 constituting the positive electrode current collector 100 is cold-rolled, the positive electrode current collector made of the aluminum alloy foil 02 is formed. In order to improve the adhesion between the positive electrode current collector 100 and the positive electrode active material, it is preferable that the undulations and pits 04 are formed on the surface of the body 100. The pits 04 constituting the irregularities are wedge-shaped oil pits 04 formed when the above-described aluminum alloy foil is cold-rolled, so that the gap between the positive electrode current collector 100 and the positive electrode active material is It is preferable for improving the adhesion.

  Here, the “oil pit” is a concept including a concave portion on the surface formed by lubrication with oil during cold rolling and nonuniform pressure and tension by a roll, and usually exists in a rolled material. The size, distribution density, and the like of the oil pits 04 can be changed by controlling the conditions of each factor of rolling oil kinematic viscosity, rolling speed, roll surface roughness, finish rolling rate, and rolling load. Among these, the rolling load is controlled mainly to obtain a desired thickness of the aluminum alloy foil 100, so that it is difficult to contribute to changing the properties of the oil pit 04. Accordingly, the size, distribution density, and the like of the oil pits 04 are mainly determined by factors such as kinematic viscosity, rolling speed, roll surface roughness, and finish rolling rate of the rolling oil, as will be described later.

  On the other hand, Non-Patent Document 1 states that “the oil pit is a concave surface defect in the material to be rolled because the lubricant is contained in a roll bite (referring to a gap between a pair of upper and lower two rolls). In the past, there has been common technical knowledge that oil pits 04 should be endeavored to be reduced because they are surface defects.

  On the other hand, as shown in Non-Patent Document 1, the present inventors rather positively utilize the oil pit 04 on the surface of the aluminum alloy foil 02 that has been considered to be a surface defect in the conventional technical common sense. I came up with it. Based on this idea, the present inventors have determined the shape and distribution state of oil pits 04 as will be described later, which do not adversely affect the surface of the aluminum alloy foil 02, and the positive electrode current collector 100 and the positive electrode active material We succeeded in improving the adhesion.

  In the process, the inventors further performed the aluminum alloy foil 02 when performing cold rolling to create an oil pit 04 having a shape and a distribution state as described later on the surface of the aluminum alloy foil 02. I noticed that swells may occur on the surface, and I noticed the possibility of using them more actively. Then, based on this idea, the present inventors provide oil pits 04 and undulations having different properties from each other by providing undulations of appropriate conditions as described later on the surface of the aluminum alloy foil 02 in addition to the oil pits 04. It has been found that unevenness of exquisite shape and distribution is formed on the surface of the aluminum alloy foil 02 by the combination, and as a result, the adhesion between the positive electrode current collector 100 and the positive electrode active material is further improved.

  As a result, the positive electrode for the secondary battery of the present embodiment is subject to the expansion and contraction of the active material layer accompanying the long-term lithium ion doping / dedoping in the positive electrode active material, which the positive electrode of the conventional secondary battery has. As a result, the interfacial delamination between the layers occurred, and the problem that the cycle life of the battery tends to be reduced was successfully overcome. That is, in the positive electrode for a secondary battery of this embodiment, in addition to forming oil pits 04 having a shape and a distribution state as described later on the surface of the aluminum alloy foil 02, undulations under appropriate conditions as described later are further provided. By providing, it succeeded in overcoming the decrease in adhesion due to expansion and contraction of the active material layer.

  Specifically, the surface roughness Ra (specified in JIS B0601-1994) of the uneven surface of the positive electrode current collector 100 (affected by the shape and distribution of both the oil pit 04 and the swell described above. ) Is preferably 0.07 to 4.0 μm. An average surface roughness Ra of 0.07 μm or more is preferable because adhesion between the positive electrode current collector 100 and the positive electrode active material is improved. On the other hand, an average surface roughness Ra of 4.0 μm or less is preferable because the surface undulation does not become too large, and it is difficult to cause ground scratches or pinholes. The average surface roughness Ra is 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5, 2 0.0, 2.5, 3.0, 3.5, and 4.0 μm may be within the range of any two numerical values. Conversely, if the average surface roughness Ra is less than 0.07 μm, sufficient adhesion to the active material cannot be obtained, and if the average surface roughness Ra exceeds 4.0 μm, the adhesion is improved. This is not preferable because it tends to cause scratches and pinholes.

  Moreover, it is preferable that the average space | interval (For example, the average value of the space | interval 08 between the mountain peaks of the above-mentioned adjacent wave | undulation) of the unevenness | corrugation local peak 06 of the surface of said positive electrode collector 100 is 20-50 micrometers. It is preferable that the average interval between the local peaks 06 of the irregularities be 20 μm or more because it is less necessary to finely irregularize the rolling roll and the manufacturing cost can be reduced. On the other hand, it is preferable that the average interval between the concave and convex local peaks 06 is 50 μm or less because the adhesion between the positive electrode current collector 100 and the positive electrode active material is improved. The average interval between the local peaks 06 of the unevenness may be within a range of any two numerical values included in 20, 25, 30, 35, 40, 45, and 50 μm. On the other hand, if the average interval between the local peaks 06 of the irregularities on the surface of the positive electrode current collector 100 (for example, the average value of the interval 08 between the peaks of adjacent undulations described above) is less than 20 μm, very fine irregularities are formed on the rolling roll. This is not preferable because it is not only inefficient but also costly. On the other hand, if it exceeds 50 μm, the adhesion with the active material becomes poor, such being undesirable.

  In addition, the oil pit 04 on the surface of the positive electrode current collector 100 is one element constituting the unevenness formed by the cold rolling formed on the surface of the positive electrode current collector 100 as described above. The average equivalent circle diameter of the oil pit 04 is preferably 4.0 to 600 μm in order to improve the adhesion between the positive electrode current collector 100 and the positive electrode active material. The average equivalent circle diameter of the oil pits 04 is preferably 4.0 μm or more, because the adhesion between the positive electrode current collector 100 and the positive electrode active material becomes strong. On the other hand, when the average equivalent circle diameter of the oil pits 04 is 600 μm or less, the depth of the oil pits 04 is not excessively increased, and pinholes are hardly generated. The average equivalent circle diameter of the oil pit 04 is an arbitrary two numerical values included in 4.0, 5.0, 10, 20, 30, 40, 50, 100, 200, 300, 400, 500, 600 μm. It may be within the range. On the other hand, if the average equivalent circle diameter of the oil pit 04 is less than 4.0 μm, sufficient adhesion to the active material cannot be obtained, and if the average equivalent circle diameter exceeds 600 μm, the amount of attached oil becomes too large. This is not preferable because the active material peels off. A particularly preferred range is 50 to 500 μm.

In addition, the average depth of the oil pits 04 on the surface of the positive electrode current collector 100 is 0.3 to 3.0 μm, which improves the adhesion between the positive electrode current collector 100 and the positive electrode active material. It is preferable for this purpose. If the average depth of the oil pits 04 is 0.3 μm or more, the adhesion between the positive electrode current collector 100 and the positive electrode active material is increased, which is preferable. Further, it is preferable that the average depth of the oil pits 04 is 3.0 μm or less because it is difficult to cause pinholes and breakage. The average depth of the oil pit 04 is any two numerical values included in 0.3, 0.4, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 μm. It may be within the range.
On the other hand, if the average depth of the oil pits 04 is less than 0.3 μm, the adhesion force between the positive electrode current collector 100 and the positive electrode active material becomes small, which is not preferable. If it exceeds 0 μm, pinholes are likely to occur in the aluminum foil as the positive electrode current collector, which is not preferable. A particularly preferable range is 0.4 to 2.0 μm.

Further, the density of the oil pits 04 on the surface of the positive electrode current collector 100 is not less than 300 / m ^{2 and not} more than 5000 / m ² , thereby improving the adhesion between the positive electrode current collector 100 and the positive electrode active material. It is preferable for improvement. It is preferable that the density of the oil pits 04 is 300 pieces / m ² or more because the adhesion between the positive electrode current collector 100 and the positive electrode active material is increased. Further, if the density of the oil pits 04 is 5000 pieces / m ² or less, the surface roughness does not become too large, and it is preferable that the inner winding part is less likely to be broken and cut off after being incorporated in the battery. . The density of this oil pit 04 is any two included in 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000 pieces / m ² . It may be within a numerical range. If the density of the oil pits 04 is less than 300 / m ² , the adhesion with the positive electrode active material cannot be improved. On the other hand, if the density of the oil pits exceeds 5000 / m ² , the surface roughness becomes too large. Since it is easy to bend and cut at a portion where the curvature of the inner winding portion is small after being incorporated in the battery, it is not preferable.

  The size and distribution density of the oil pits 04 on the surface of the positive electrode current collector 100 are measured as follows. Specifically, the surface of the aluminum alloy foil is photographed with a microscope, the obtained image is binarized, the image corresponding to the roll eyes is removed, and then the size and distribution density are obtained by an image analyzer.

  Further, the interval 08 between the local peaks of the irregularities on the surface of the positive electrode current collector 100 is measured as follows. Specifically, the average interval (Sr, Sf) between local peaks can be measured by the method defined in JIS B0601 (1994).

  In addition, the thickness of the aluminum alloy foil 02 constituting the positive electrode current collector 100 is preferably 6.0 to 30 μm, and more preferably 10 to 20 μm from the viewpoint of improving the quality of the secondary battery. If the thickness of the aluminum alloy foil 02 is 6.0 μm or more or 10 μm or more, the number of pinholes in the aluminum alloy foil 02 is reduced, and the aluminum alloy foil 02 is cut or wrinkled during the manufacturing process of the positive electrode material of the lithium ion secondary battery. It becomes difficult for trouble to occur. On the other hand, if the thickness is 30 μm or less or 20 μm or less, the thickness of the paste layer containing the active material to be coated on the aluminum alloy foil 02 can be increased as the positive electrode material incorporated into the lithium ion secondary battery container having a certain volume. As a result, the output density of the battery is improved. The thickness of the aluminum alloy foil 02 may be within the range of any two numerical values included in 6.0, 7.0, 8.0, 9.0, 10, 15, 20, 25, and 30 μm. Good. If the thickness of the aluminum alloy foil 02 is less than 6.0 μm or less than 10 μm, it is difficult to prevent an increase in pinholes no matter how the manufacturing conditions are controlled. Since the thickness of the electric body becomes too thick, the volume of the battery itself becomes large, and it becomes difficult to fit the battery in the limited volume.

  The positive electrode for a secondary battery according to the present embodiment may have a configuration in which the unevenness is provided on one surface of the positive electrode current collector 100 and the positive electrode active material layer is provided on the one surface. In addition, the positive electrode for a secondary battery according to the present embodiment may have a configuration in which the above-described unevenness is provided on both surfaces of the positive electrode current collector 100 and the above-described positive electrode active material layer is provided on both surfaces thereof. In any configuration, there is an advantage that the adhesion between the positive electrode current collector 100 and the positive electrode active material is increased.

<Method for producing positive electrode for secondary battery>
The method for producing a positive electrode for a secondary battery according to the present embodiment has a positive electrode active material layer containing a positive electrode active material capable of inserting and extracting lithium on the surface of the positive electrode current collector 100 made of the aluminum alloy foil 02. This is a method for producing a positive electrode for a secondary battery. This production method includes a step of cold rolling an aluminum alloy sheet under the conditions described later to obtain an aluminum alloy foil 02.

  In this production method, the oil pits 04 are formed by cold rolling (specifically, cold rolling for foil rolling described later) when manufacturing the aluminum alloy foil 02, so that ordinary aluminum The aluminum alloy foil 02 having the oil pits 04 can be produced without adding a special process to the manufacturing process of the alloy foil 02. Further, when cold rolling is performed to form the oil pits 04 on the surface of the aluminum alloy foil 02, undulations are generated on the surface of the aluminum alloy foil 02. Therefore, an exquisite combination of oil pits 04 and undulations having different properties from each other. As a result, unevenness with a balanced shape and distribution is completed, and as a result, the adhesion between the positive electrode current collector 100 and the positive electrode active material is further improved dramatically. That is, according to this method, since the unevenness is formed by cold rolling when manufacturing the aluminum alloy foil 02, since there are fewer pinholes than when forming the unevenness by etching or the like, even if transported at high speed Without being cut, a positive electrode for a secondary battery that is remarkably excellent in adhesion between the positive electrode current collector 100 and the positive electrode active material can be obtained by a low-cost manufacturing process.

  In this production method, during cold rolling for foil rolling described later, the size, distribution density, waviness width and height of the oil pits 04 are determined according to the kinematic viscosity of the rolling oil, the rolling speed, the roll surface roughness, and the like. It can be changed by controlling the conditions of each factor of the finish rolling rate and rolling load. Among these, the rolling load is mainly controlled to obtain the desired thickness of the aluminum alloy foil 02, and therefore it is difficult to contribute to changing the properties of the oil pit 04 and the swell. Therefore, the size, distribution density, waviness width and height of the oil pits 04 are, as will be described later, the kinematic viscosity of the rolling oil, the rolling speed, the roll during cold rolling for foil rolling described later. It is determined mainly by factors of surface roughness and finish rolling rate.

  Specifically, in order to increase the number of oil pits (n), the oil film thickness of the aluminum alloy foil 02 that is the entry side material is increased during cold rolling for foil rolling described later. In order to increase the oil film thickness, the kinematic viscosity (v) of the rolling oil is high, the rolling speed (s) is fast, the roll surface roughness (f) is rough, and the finish rolling rate (r) is small. What is necessary is just to make small the biting angle of the material at the side of rolling.

By the way, if we show these relations in equation (1),
n = k · v · s · f / r · p (1)
It becomes the relationship. (P is the rolling load, k is a constant and changes from time to time depending on the material and equipment)

Moreover, what is necessary is just to make kinematic viscosity (v) of rolling oil high in order to generate many waviness. The present inventor has found that it is difficult to increase only the oil pit or only the swell. That is, in a normal manufacturing method, both change with the same tendency.
A preferable range of these conditions is as described later.

That is, in the cold rolling for foil rolling described later, the kinematic viscosity of the rolling oil is 1.9 to 3.5 × 10 ⁻³ Pa · It is preferable to use s. When the kinematic viscosity of the rolling oil is 1.9 × 10 ⁻³ Pa · s or more, there is an advantage that the oil film thickness is increased and the foil can be rolled thinly. Also, if the kinematic viscosity of this rolling oil is 3.5 × 10 ⁻³ Pa · s or less, the kinematic viscosity and the distillation point are in a correlation, so that the rolling oil remaining on the foil surface is reduced, and more There is an advantage that the positive electrode active material is easily adhered. The rolling oil has a kinematic viscosity of 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 × 10 ⁻³ Pa · s.

  Moreover, in order to form the unevenness | corrugation of the above-mentioned preferable shape and distribution in the case of the cold rolling for foil rolling mentioned later, it is preferable that a rolling speed shall be 400-1200 m / min. If this rolling speed is 400 m / min or more, there is an advantage that the heat generation of the material during rolling increases, and it is easy to roll into a thin foil by self-healing. Moreover, if this rolling speed is 1200 m / min or less, there is an advantage that the rolling oil remaining on the foil surface does not increase and the adhesion with the positive electrode active material does not decrease. The kinematic viscosity of the rolling oil may be within a range of any two numerical values included in 400, 500, 600, 700, 800, 900, 1000, 1100, and 1200 m / min.

  Moreover, in order to form the unevenness | corrugation of the above-mentioned preferable shape and distribution in the case of the cold rolling for the foil rolling mentioned later, roll surface roughness (Ra) shall be 0.10-5.0 micrometers. preferable. If the roll surface roughness (Ra) is 0.10 μm or more, there is an advantage that the oil film at the time of rolling becomes thick, oil pits can easily be increased, and the foil rolling speed can be easily increased. As described above, more oil pits can be formed as the rolling speed increases. Moreover, if this roll surface roughness (Ra) is 5.0 micrometers or less, there exists an advantage that the rolling oil which remains on the surface after rolling does not increase, and adhesive force with a positive electrode active material does not fall. The roll surface roughness (Ra) is 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, It may be within the range of any two numerical values included in 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 μm.

  Moreover, in order to form the unevenness | corrugation of the above-mentioned preferable shape and distribution in the case of the cold rolling for foil rolling mentioned later, it is preferable that a finish rolling rate shall be 20 to 50%. If this finish rolling rate is 20% or more, there is an advantage that the number of foil rolling operations is not increased, and manufacturing can be performed while maintaining low cost. Further, if the finish rolling rate is 50% or less, the biting angle into the rolling roll does not increase, the rolling oil remaining on the foil surface does not increase, and the adhesion strength with the positive electrode active material does not decrease. There is. This finish rolling ratio may be within a range of any two numerical values included in 20, 25, 30, 35, 40, 45, and 50%.

  In the method for producing a positive electrode for a secondary battery according to the present embodiment, the aluminum alloy foil 02 can be manufactured as follows, for example. Specifically, the aluminum alloy foil 02 can be obtained by sequentially performing homogenization, hot rolling, cold rolling and foil rolling on an aluminum ingot obtained by semi-continuous casting. Moreover, it may replace with hot rolling of the aluminum ingot by semi-continuous casting, and a continuous cast board may be thrown into the process after cold rolling. In addition, as needed, immediately after hot rolling or in the middle of cold rolling, a rolled sheet is heated at 250 to 450 ° C. for 1 to 10 hours in a batch annealing furnace, or at 380 to 580 ° C. for 1 second to 3 minutes in a continuous annealing furnace. Intermediate annealing may be performed by any of the methods described above, and final annealing may be performed on the foil-rolled aluminum alloy foil 02.

  In the homogenization treatment of the aluminum ingot, the aluminum ingot is homogeneously heated in order to minimize segregation of elemental components contained in the aluminum ingot. Specifically, after smoothing the rolled surface of the aluminum ingot by chamfering, homogenization is performed at 480 to 620 ° C. for 1 to 20 hours.

  Next, the aluminum ingot is subjected to homogenization and then hot rolled. In this hot rolling, hot rough rolling and hot finish rolling are sequentially performed. Hot rough rolling is a process of rolling a high-temperature aluminum ingot after homogenization to an aluminum alloy sheet having a thickness of about 20 to 40 mm.

  Next, hot rolling is performed on the rolled sheet obtained by hot rolling the aluminum ingot to produce a hot rolled sheet. Hot finish rolling is a rolling process in which a rolled plate after hot rough rolling is further thinly rolled and an aluminum alloy plate is finally wound in a coil shape at about 250 to 350 ° C. Hot finish rolling is generally a method in which a pair of rolls is made into one set, a plurality of sets of rolls are arranged in parallel, and a rolled plate is supplied between the rolls to continuously reduce the thickness of the rolled plate. Is adopted.

  Subsequently, the obtained hot-rolled sheet is subjected to cold rolling and foil rolling in this order. This cold rolling is performed in the same manner as when manufacturing a normal aluminum alloy foil 02. Specifically, a hot rolled sheet is supplied between a pair of rolls maintained at 40 to 60 ° C. A cold rolled sheet is manufactured by reducing the thickness of the rolled sheet. This cold rolling is repeated a plurality of times to produce a cold rolled sheet having a thickness of 0.3 to 0.5 mm. In addition, lubricating oil is normally supplied between a pair of rolls.

  Next, the cold rolled sheet is rolled. This foil rolling is also performed in the same manner as when producing a normal aluminum alloy foil 02, and a cold rolling plate is supplied to a general-purpose cold rolling mill and rolled, and the thickness is 0.2 mm or less, preferably An aluminum alloy foil 02 having a thickness of 6.0 to 30 μm is manufactured.

  As described above, the aluminum alloy foil 02 thus obtained is subjected to control of the kinematic viscosity of the rolling oil, the rolling speed, the roll surface roughness, and the finish rolling rate when the cold-rolled sheet is rolled. Therefore, on the surface of the obtained aluminum alloy foil 02, preferable size, distribution density, waviness width and height of the oil pits 04 are realized.

  As mentioned above, although embodiment of this invention was described, these are illustrations of this invention and various structures other than the above are also employable.

  For example, in the above embodiment, a positive electrode for a secondary battery including a positive electrode current collector made of an aluminum alloy foil has been described. However, the above aluminum alloy foil can also be used for a negative electrode current collector. Also in this case, since the above-mentioned aluminum alloy foil has irregularities that satisfy specific conditions on the surface, a negative electrode active material is attached to the surface of the negative electrode current collector made of the aluminum alloy foil to form a negative electrode for a secondary battery. In the case of forming, the adhesion is improved.

EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these. The present invention relates to a positive electrode for a secondary battery including a positive electrode current collector made of an aluminum alloy foil, but can be used for both a negative electrode and a positive electrode (for example, an active material of Li ₄ Ti ₅ O ₁₂ (Also, aluminum foil can be used for the negative electrode). The following examples show examples applied to the present aluminum alloy foil in the positive electrode.

(Examples 1-13, Comparative Examples 1-2)
No. shown in Table 1. An aluminum ingot containing the chemical component A was produced by semi-continuous casting at a solidification rate of 50 mm / min. Each aluminum ingot contained 0.05% by weight or less of inevitable impurity components not shown in Table 1.

  Next, after smoothing the rolling surface of the aluminum ingot by chamfering, the aluminum ingot was homogenized at 520 ° C. for 6 hours, and then hot rough rolling was applied to the aluminum ingot at a rolling rate. The hot-rolled sheet having a thickness of 3 mm was manufactured by subjecting the obtained aluminum alloy sheet to hot finish rolling. The temperature of the aluminum alloy sheet immediately after completion of hot finish rolling was 360 ° C.

The rolling rate was calculated based on the following equation, where t _{0 is} the thickness of the aluminum ingot before hot rough rolling and t ₁ is the thickness of the rolled plate at the end of hot rough rolling. Value.
Rolling ratio (%) = 100 × (t ₀ −t ₁ ) / t ₀

  After the hot-rolled aluminum alloy sheet is cooled to room temperature, the hot-rolled sheet is cold-rolled to a thickness of 0.65 mm, and then the aluminum alloy sheet is heated at 300 ° C. for 4 hours. Intermediate annealing.

  Subsequently, these aluminum alloy plates were cold-rolled using a normal rolling oil to form 0.3 mm aluminum alloy plates, and then the surface roughness and the average distance (Sr) between local peaks shown in Table 2 were measured. Using the work roll and rolling oil having the viscosity shown in Table 2, foil rolling was performed at the rolling speed and finish rolling rate shown in Table 2 to obtain an aluminum alloy foil for lithium ion secondary batteries having a thickness of 15 μm.

  The surface roughness of the work roll and the average distance (Sr) between the local peaks can be obtained by polishing under desired conditions using a desired grindstone and grinding fluid.

  About the obtained aluminum alloy foil for lithium ion secondary batteries, the surface roughness of the aluminum alloy foil surface, the average space | interval (Sf) of a local summit, oil pit average size, and oil pit average depth were calculated | required.

[Surface roughness of work roll and aluminum alloy foil surface, average distance between local peaks (Sr, Sf)]
The surface roughness Ra and the average distance (Sr, Sf) between the local peaks were measured by the method defined in JIS B0601 (1994).

[Oil pit average depth]
Ten oil pits observed with a Keyence laser microscope (main body: VK-8500, microscope: VK-8510, analysis software: VK-HIW), depth of focus: 0.01 μm, objective lens × 10 times Depth was determined and averaged.

A slurry containing a positive electrode active material was applied to each obtained aluminum alloy foil by the following method and dried at 150 ° C. That is, first, lithium carbonate (Li ₂ CO ₃ ) and manganese dioxide (MnO ₂ ) are mixed so that the molar ratio of Li and Mn is 1: 2, and this mixture is heated at a temperature of 800 ° C. for 24 hours. Thus, a particulate lithium manganese composite oxide having a composition formula represented by LiMnO ₄ was prepared. Subsequently, 11% by weight of a vinylidene fluoride-hexafluoropropylene (VDF-HFP) copolymer (HFP) copolymerization ratio (12% by weight) was dissolved in acetone to prepare an acetone solution. The lithium manganese composite oxide and acetylene black were added and mixed so that the solid content of the copolymer was 10 wt%, the lithium manganese composite oxide was 81 wt%, and the acetylene black was 9 wt%. . This suspension was formed into a film by casting and allowed to stand at room temperature and air-dry to produce a sheet-like positive electrode layer having a thickness of 100 μm.

  A vinylidene fluoride-hexafluoropropylene (VDF-HFP) copolymer (copolymerization ratio of HFP: 12% by weight) was dissolved in 11% by weight in acetone to prepare an acetone solution. Carbon fiber (trade name, Melbronn Mild, manufactured by Petka Co., Ltd.) was added and mixed so that the solid content of the copolymer was 20% by weight and the pitch-based carbon fiber was 80% by weight. The suspension was formed into a film by casting, and allowed to stand at room temperature and air-dry, thereby producing a sheet-like negative electrode layer having a thickness of 100 μm.

  Further, 11% by weight of a vinylidene fluoride-hexafluoropropylene (VDF-HFP) copolymer (HFP copolymerization ratio: 12% by weight) was dissolved in acetone to prepare an acetone solution, and this acetone solution was formed by casting. A film-like solid polymer electrolyte layer having a thickness of 30 μm was prepared by leaving the film at room temperature and drying it naturally.

Next, the sheet-like positive electrode layer and the aluminum alloy foil (positive electrode current collector) having a roughened surface are laminated using a double roll laminator to form a sheet-like positive electrode, and simultaneously the sheet-like negative electrode layer. And a copper foil (negative electrode current collector) are laminated using a double roll laminator to form a sheet-like negative electrode, and the sheet-like solid polymer electrolyte layer is interposed between these positive and negative electrodes, and a double roll laminator is used. Laminated. The 5-layer laminate was dissolved in an electrolytic solution in which 1 mol / L of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solvent of ethylene carbonate (EC) -dimethyl carbonate (DMC) (mixing ratio 2: 1). A polymer electrolyte secondary battery was manufactured by immersing the sheet-like material for 10 minutes and impregnating the sheet-like positive electrode layer, the sheet-like negative electrode layer, and the sheet-like solid polymer electrolyte layer with the electrolytic solution.

(Example 14)
A polymer electrolyte secondary battery was produced in the same manner as in Example 13 except that the positive electrode active material was changed to lithium cobalt oxide (LiCoO ₂ ).

(Example 15)
A polymer electrolyte secondary battery was produced in the same manner as in Example 13, except that the positive electrode active material was changed to a lithium composite oxide containing cobalt-nickel-manganese ternary material.

(90 ° peel test)
The surface of the positive electrode obtained in Examples and Comparative Examples having a width of 20 mm and a length of 100 mm, to which the positive electrode slurry was applied, was attached to a peeling test jig with a double-sided tape (535A manufactured by Nitto Denko), and the positive electrode was attached. The electrode was pulled vertically by pinching one end in the length direction perpendicular to the surface, and the strength when the positive electrode active material layer was peeled was measured. The results are shown in Tables 2 and 3.

(Electrochemical property test)
-Production of test cell As working electrode, the size of the disk-shaped positive electrode obtained in Examples and Comparative Examples was adjusted so that the cell capacity was 5 Ah, lithium metal was used as the counter electrode, and 1 mol of LiPF was used as the electrolyte. A beaker cell using a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (mixed volume 1: 1) in which ₆ was dissolved was prepared.

-Electrochemical property test The test for evaluating the charge / discharge performance of the positive electrode was performed using the test cell.
The process of scanning the potential of the working electrode in the base direction (reduction side) is referred to as charging, and the process of scanning the noble direction (oxidation side) of the working electrode is referred to as discharge.

  First, the initial charge / discharge was CC (constant current) at 0.2 CA, then switched to CV (constant voltage), and charging was performed over 8 hours up to 4.2V. Discharge was performed up to 2.7 V at 0.2 CA. Charging / discharging was repeated 50 cycles. The evaluation temperature was 25 ° C.

  The capacity retention rate was determined from the discharge capacity of the first charge / discharge cycle and the discharge capacity of the 50th cycle. The definition of the capacity maintenance rate was as follows. Capacity maintenance rate (%) = (discharge capacity at the 50th cycle / discharge capacity at the first cycle) × 100. The results are shown in Table 2. In addition, the capacity | capacitance maintenance factor shown in Table 2 is the capacity | capacitance computed per weight of the positive electrode active material.

  After 50 cycles, the test cell was disassembled, the positive electrode was taken out, and the state of the positive electrode active material layer was observed. “○” indicates that the positive electrode active material layer is completely left on the positive electrode current collector, “△” indicates that a part of the positive electrode active material layer has been peeled off but remains more than half, and “×” indicates that the positive electrode active material layer has been peeled off more than half. It was. The results are shown in Table 2 and Table 3.

(Example 16, comparative example 3)
No. shown in Table 1. An aluminum ingot containing the chemical component B was produced by semi-continuous casting at a solidification rate of 50 mm / min. Each aluminum ingot contained 0.05% by weight or less of inevitable impurity components not shown in Table 1.

  Next, after smoothing the rolled surface of the aluminum ingot by chamfering, the aluminum ingot was homogenized at 520 ° C. for 1 hour, and then hot rough rolling was applied to the aluminum ingot at a rolling rate. The aluminum alloy sheet thus obtained was subjected to hot finish rolling to produce a hot rolled sheet having a thickness of 2 mm. The temperature of the aluminum alloy sheet immediately after completion of hot finish rolling was 250 ° C.

  After the hot-rolled aluminum alloy sheet is cooled to room temperature, the hot-rolled sheet is cold-rolled to a thickness of 0.75 mm, and then the aluminum alloy sheet is heated at 300 ° C. for 4 hours. Intermediate annealing.

  Subsequently, these aluminum alloy plates were cold-rolled using a normal rolling oil to form 0.3 mm aluminum alloy plates, and then the surface roughness and the average distance (Sr) between local peaks shown in Table 2 were measured. Using the work roll and rolling oil having the viscosity shown in Table 2, foil rolling was performed at the rolling speed and finish rolling rate shown in Table 2 to obtain an aluminum alloy foil for lithium ion secondary batteries having a thickness of 15 μm.

  Table 2 and Table 3 show the characteristics of the aluminum alloy foils thus obtained, which were measured by the same method as described above.

(Example 17, comparative example 4)
No. shown in Table 1. An aluminum ingot containing the chemical component of C was produced by semi-continuous casting at a solidification rate of 50 mm / min. Each aluminum ingot contained 0.05% by weight or less of inevitable impurity components not shown in Table 1.

  Next, after smoothing the rolling surface of the aluminum ingot by chamfering, the aluminum ingot was homogenized at 600 ° C. for 6 hours, and then hot rough rolling was applied to the aluminum ingot at a rolling rate. The hot-rolled sheet having a thickness of 3 mm was manufactured by subjecting the obtained aluminum alloy sheet to hot finish rolling. The temperature of the aluminum alloy plate immediately after the hot finish rolling was 350 ° C.

  After the hot-rolled aluminum alloy sheet is cooled to room temperature, the hot-rolled sheet is cold-rolled to a thickness of 0.65 mm, and then the aluminum alloy sheet is heated at 420 ° C. for 4 hours. Intermediate annealing.

  Subsequently, these aluminum alloy plates were cold-rolled using a normal rolling oil to form 0.3 mm aluminum alloy plates, and then the surface roughness and the average distance (Sr) between local peaks shown in Table 2 were measured. Using the work roll and rolling oil having the viscosity shown in Table 2, foil rolling was performed at the rolling speed and finish rolling rate shown in Table 2 to obtain an aluminum alloy foil for lithium ion secondary batteries having a thickness of 15 μm.

  Table 2 and Table 3 show the characteristics of the aluminum alloy foils thus obtained, which were measured by the same method as described above.

(Example 18, Comparative Example 5)
No. shown in Table 1. An aluminum ingot containing the chemical component of D was produced by semi-continuous casting at a solidification rate of 50 mm / min. Each aluminum ingot contained 0.05% by weight or less of inevitable impurity components not shown in Table 1.

  Next, after smoothing the rolling surface of the aluminum ingot by chamfering, the aluminum ingot was homogenized at 520 ° C. for 3 hours, and then hot rough rolling was applied to the aluminum ingot at a rolling rate. The aluminum alloy sheet thus obtained was hot finish rolled to produce a hot rolled sheet having a thickness of 2.4 mm. The temperature of the aluminum alloy plate immediately after the hot finish rolling was 300 ° C.

  After the hot-rolled aluminum alloy sheet is cooled to room temperature, the hot-rolled sheet is cold-rolled to a thickness of 0.54 mm, and then the aluminum alloy sheet is heated at 385 ° C. for 4 hours. Intermediate annealing.

  Subsequently, these aluminum alloy plates were cold-rolled using a normal rolling oil to form 0.3 mm aluminum alloy plates, and then the surface roughness and the average distance (Sr) between local peaks shown in Table 2 were measured. Using the work roll and rolling oil having the viscosity shown in Table 2, foil rolling was performed at the rolling speed and finish rolling rate shown in Table 2 to obtain an aluminum alloy foil for lithium ion secondary batteries having a thickness of 15 μm.

  Table 2 and Table 3 show the characteristics of the aluminum alloy foils thus obtained, which were measured by the same method as described above.

(Example 19, comparative example 6)
No. shown in Table 1. An aluminum ingot containing the chemical component E was produced by semi-continuous casting at a solidification rate of 50 mm / min. Each aluminum ingot contained 0.05% by weight or less of inevitable impurity components not shown in Table 1.

  Next, after smoothing the rolling surface of the aluminum ingot by chamfering, the aluminum ingot was homogenized at 600 ° C. for 3 hours, and then hot rough rolling was applied to the aluminum ingot at a rolling rate. The aluminum alloy sheet thus obtained was hot finish rolled to produce a hot rolled sheet having a thickness of 4 mm. The temperature of the aluminum alloy plate immediately after the hot finish rolling was 300 ° C.

  After the hot-rolled aluminum alloy sheet is cooled to room temperature, the hot-rolled sheet is cold-rolled to a thickness of 0.50 mm, and then the aluminum alloy sheet is heated at 360 ° C. for 2 hours. Intermediate annealing.

  Subsequently, these aluminum alloy plates were cold-rolled using a normal rolling oil to form 0.3 mm aluminum alloy plates, and then the surface roughness and the average distance (Sr) between local peaks shown in Table 2 were measured. Using the work roll and rolling oil having the viscosity shown in Table 2, foil rolling was performed at the rolling speed and finish rolling rate shown in Table 2 to obtain an aluminum alloy foil for lithium ion secondary batteries having a thickness of 15 μm.

  Table 2 and Table 3 show the characteristics of the aluminum alloy foils thus obtained, which were measured by the same method as described above.

(Example 20, Comparative Example 7)
No. shown in Table 1. An aluminum ingot containing the chemical component F was produced by semi-continuous casting at a solidification rate of 50 mm / min. Each aluminum ingot contained 0.05% by weight or less of inevitable impurity components not shown in Table 1.

  Next, after smoothing the rolling surface of the aluminum ingot by chamfering, the aluminum ingot was subjected to homogenization treatment at 600 ° C. for 7 hours, and then hot rough rolling was applied to the aluminum ingot. The hot-rolled sheet having a thickness of 3 mm was manufactured by subjecting the obtained aluminum alloy sheet to hot finish rolling. The temperature of the aluminum alloy sheet immediately after completion of hot finish rolling was 250 ° C.

  After cooling the hot-finished aluminum alloy sheet to room temperature, without performing intermediate annealing, the hot-rolled sheet was cold-rolled using normal rolling oil to obtain a 0.3 mm aluminum alloy sheet. Later, foil rolling was performed at the rolling speed and the finish rolling rate shown in Table 2, using the work roll having the surface roughness shown in Table 2 and the average interval (Sr) of the local peaks (Sr) and the rolling oil having the viscosity shown in Table 2. Thus, an aluminum alloy foil for lithium ion secondary batteries having a thickness of 15 μm was obtained.

  Table 2 and Table 3 show the characteristics of the aluminum alloy foils thus obtained, which were measured by the same method as described above.

(Example 21, Comparative Example 8)
No. shown in Table 1. An aluminum ingot containing the chemical component of G was produced by semi-continuous casting at a solidification rate of 50 mm / min. Each aluminum ingot contained 0.05% by weight or less of inevitable impurity components not shown in Table 1.

  Next, after smoothing the rolling surface of the aluminum ingot by chamfering, the aluminum ingot was subjected to homogenization treatment at 600 ° C. for 7 hours, and then hot rough rolling was applied to the aluminum ingot. The hot-rolled sheet having a thickness of 3 mm was manufactured by subjecting the obtained aluminum alloy sheet to hot finish rolling. The temperature of the aluminum alloy sheet immediately after completion of hot finish rolling was 250 ° C.

  After cooling the hot-finished aluminum alloy sheet to room temperature, without performing intermediate annealing, the hot-rolled sheet was cold-rolled using normal rolling oil to obtain a 0.3 mm aluminum alloy sheet. Later, foil rolling was performed at the rolling speed and the finish rolling rate shown in Table 2, using the work roll having the surface roughness shown in Table 2 and the average interval (Sr) of the local peaks (Sr) and the rolling oil having the viscosity shown in Table 2. Thus, an aluminum alloy foil for lithium ion secondary batteries having a thickness of 15 μm was obtained.

  Table 2 and Table 3 show the characteristics of the aluminum alloy foils thus obtained, which were measured by the same method as described above.

<Consideration of results>
As shown in Table 2 and Table 3, Examples 1 to 19 have sufficient peel strength as a positive electrode current collector of a lithium ion secondary battery. Moreover, since the positive electrode active material is not peeled after 50 cycles of charge and discharge, it can be seen that the adhesion with the positive electrode active material is good. Furthermore, the capacity retention rate is also high, and it is possible to provide a high quality that can sufficiently withstand use as a positive electrode of a lithium ion secondary battery.

  In Comparative Examples 1 to 8, sufficient peel strength could not be secured, and the capacity retention rate was low.

  From these results, in addition to controlling the shape and distribution of the oil pits on the surface of the aluminum alloy foil so as to meet specific conditions, the oil pits and swells having different properties can be obtained by providing swells with appropriate conditions. It is apparent that the combination creates unevenness with an exquisite shape and distribution, and as a result, the adhesion between the positive electrode current collector and the positive electrode active material is dramatically improved.

  In the above, this invention was demonstrated based on the Example. It is to be understood by those skilled in the art that this embodiment is merely an example, and that various modifications are possible and that such modifications are within the scope of the present invention.

For example, in the above embodiment, LiMn ₂ O ₄ is used as the positive electrode active material capable of inserting and extracting lithium, but other positive electrode active materials may be used. For _{example, LiCoO 2, LiNiO 2, LiFePO} 4, LiCo 1/3 Ni 1/3 Mn 1/3 O 2 , etc. can be suitably used as the absorbing and releasing active material capable of lithium. Also in this case, if an aluminum alloy foil having irregularities on the surface satisfying the above conditions is used, it is known that those skilled in the art have good adhesion between the positive electrode current collector and the positive electrode active material. Easy to understand from the examples.

100 Positive electrode current collector 02 Aluminum alloy foil 04 Pit (oil pit)
06 Local peak of uneven surface 08 Spacing between adjacent peak of undulation (interval of local peak of uneven surface)

Claims (7)

A positive electrode for a secondary battery having a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium on the surface of a positive electrode current collector made of an aluminum alloy foil,
The positive electrode current collector surface has irregularities,
The average surface roughness Ra of the uneven surface of the positive electrode current collector is 0.07 to 4.0 μm,
The average interval between the local peaks of the irregularities is 20 to 50 μm,
The average equivalent circle diameter of the pits constituting the irregularities is 4.0 to 600 μm,
The average depth of the pits is 0.3 to 3.0 μm,
The density of the pits is 300 pieces / m ² or more and 5000 pieces / m ² or less,
Secondary battery positive electrode.   The positive electrode for a secondary battery according to claim 1, wherein the pit is a wedge-shaped oil pit formed during cold rolling.   3. The positive electrode for a secondary battery according to claim 1, wherein the irregularities are constituted by undulations on the surface of the positive electrode current collector formed during cold rolling and the pits.   The positive electrode for secondary batteries in any one of Claims 1-3 whose thickness of the positive electrode electrical power collector which consists of the said aluminum alloy foil is 6.0-30 micrometers. Having the irregularities on both surfaces of the positive electrode current collector,
Having the positive electrode active material layer on both surfaces;
The positive electrode for secondary batteries in any one of Claims 1-4.   The positive electrode active material is one or more materials selected from the group consisting of cobalt-based materials, iron phosphate-based materials, spinel manganese-based materials, cobalt-nickel-manganese ternary materials, and cobalt-nickel-aluminum ternary materials. The positive electrode for secondary batteries in any one of Claims 1-5 containing. A method for producing a positive electrode for a secondary battery having a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium on the surface of a positive electrode current collector made of an aluminum alloy foil,
Aluminum alloy plate,
The kinematic viscosity of the rolling oil is 1.9 to 3.5 × 10 ⁻³ Pa · s,
The rolling speed is 400 to 1200 m / min,
The average roll surface roughness Ra is 0.10 to 5.0 μm,
The finish rolling rate is 20-50%,
Including the step of cold rolling under conditions to obtain the aluminum alloy foil,
Production method of positive electrode for secondary battery.