JP2011165637A - Positive electrode collector, method of manufacturing the same, and positive electrode body for lithium ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode collector excelling in adhesiveness to a positive electrode active material layer when used in a lithium ion battery, a method of manufacturing the same, and a positive electrode body for a lithium ion battery. <P>SOLUTION: The positive electrode collector 11 formed with a positive electrode active material layer on a surface and used as a positive electrode body for a lithium ion battery includes aluminum alloy foil 1, and has a plurality of holes 2 at a front surface side of the aluminum alloy foil 1 formed with the positive electrode active material layer where the average hole diameter of the plurality of holes 2 is ≥1.0 μm, and an average aspect ratio defined by (average hole diameter/average hole depth) is ≤1.0. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a positive electrode current collector used for a lithium ion battery, a method for producing the same, and a positive electrode body for a lithium ion battery.

  Lithium ion batteries mainly include a negative electrode body, a positive electrode body, a separator that insulates these electrode bodies, an electrolyte solution that assists charge transfer between the electrode bodies, and a battery case that houses these. The positive electrode body is obtained by coating the surface of a positive electrode current collector made of an aluminum alloy foil with a positive electrode active material.

In recent years, the demand for the energy density of a battery to be mounted is increasing more and more due to the miniaturization and high performance of portable devices. Among them, a lithium ion battery is starting to be widely used as a power source of the portable device because it shows a higher voltage and a higher energy density (charge / discharge capacity) than a nickel-cadmium battery or a nickel-hydrogen battery. In addition, as environmental awareness increases, there is a demand for a shift from automobiles that currently use fossil fuels to electric cars and hybrid cars that emit less CO ₂ , and lithium ion batteries are expected to be installed in these vehicles. Is growing.

  Therefore, the characteristics required for the positive electrode body constituting the lithium ion battery are that there is no decrease in charge / discharge capacity or increase in internal resistance. Such characteristics are achieved by increasing the charge / discharge cycle durability, and it is important to suppress peeling and dropping of the positive electrode active material layer from the positive electrode current collector when the charge / discharge cycle is repeated. . For the purpose of improving the adhesion between the positive electrode current collector and the positive electrode active material layer, Patent Document 1 discloses a rough surface having a predetermined thickness on the surface side of the positive electrode current collector with which the positive electrode active material layer is integrated. A positive electrode body on which a surface layer is formed is described, and it is described that the rough surface layer has spongy pores having an average pore diameter of 0.05 to 0.5 μm.

JP-A-11-86875

  However, in the positive electrode body described in Patent Document 1, adhesion between the positive electrode current collector and the positive electrode active material layer is enhanced by a roughened layer formed on the surface of the positive electrode current collector. Since the average pore diameter of the pores in the surface layer is as small as 0.05 to 0.5 μm and the pore shape is spongy (see FIG. 3), the positive electrode active material layer is difficult to enter into the pores. As a result, there is a problem that the positive electrode body of a lithium ion battery for automobiles that has been increasing in recent years is insufficient from the viewpoint of adhesion between the positive electrode current collector and the positive electrode active material layer.

  The present invention has been made in view of the above problems, and when used in a lithium ion battery, a positive electrode current collector excellent in adhesion to the positive electrode active material layer, a method for producing the same, and the positive electrode current collector The positive electrode body for lithium ion batteries using this is provided.

  As a means for solving the above-mentioned problems, a positive electrode current collector according to the present invention is a positive electrode current collector having a positive electrode active material layer formed on the surface thereof to be a positive electrode body for a lithium ion battery, wherein an aluminum alloy foil is used. And having a plurality of holes on the surface side of the aluminum alloy foil on which the positive electrode active material layer is formed, the average hole diameter of the plurality of holes being 1.0 μm or more, and (average hole diameter / average hole depth) The average aspect ratio defined by is 1.0 or less.

  According to the above configuration, the aluminum alloy foil is provided, and the aluminum alloy foil has a plurality of holes having a predetermined average pore diameter and an average aspect ratio on the surface side on which the positive electrode active material layer is formed. When the positive electrode active material layer is formed, the positive electrode active material layer enters the plurality of holes, and an anchor effect is generated on the surface of the aluminum alloy foil. As a result, the adhesion between the aluminum alloy foil and the positive electrode active material layer is improved.

In the positive electrode current collector according to the present invention, the hole is preferably a pit-shaped hole.
According to the said structure, when a hole shape is a pit shape, a positive electrode active material layer becomes easy to penetrate | penetrate inside a hole, and the anchor effect on the aluminum alloy foil surface further increases. As a result, the adhesion between the aluminum alloy foil and the positive electrode active material layer is further improved.

  In the positive electrode current collector according to the present invention, the aluminum alloy foil having a plurality of holes preferably includes an organic phosphonic acid layer containing organic phosphonic acid on the surface side on which the positive electrode active material layer is formed.

  According to the above configuration, when the aluminum alloy foil having a plurality of holes includes the organic phosphonic acid layer on the surface side on which the positive electrode active material layer is formed, the positive electrode active material layer is formed on the aluminum alloy foil. The positive electrode active material layer enters inside the plurality of holes, an anchor effect is generated on the surface of the aluminum alloy foil, and a chemical bond is generated between the organic phosphonic acid layer and the positive electrode active material layer. As a result, the aluminum alloy foil and the positive electrode are formed by an additive effect of a physical bond due to the anchor effect of entering the positive electrode active material layer into the hole and a chemical bond between the organic phosphonic acid layer and the positive electrode active material layer. Adhesiveness with the active material layer is further improved.

  In the positive electrode current collector according to the present invention, the organic phosphonic acid is preferably at least one selected from methylphosphonic acid, ethylphosphonic acid, and vinylphosphonic acid.

  According to the above configuration, when the organic phosphonic acid is one or more selected from methylphosphonic acid, ethylphosphonic acid, and vinylphosphonic acid, chemical bonding between the organic phosphonic acid layer and the positive electrode active material layer is achieved. It becomes stronger and the adhesion between the aluminum alloy foil and the positive electrode active material layer is further improved.

The method for producing a positive electrode current collector according to the present invention is characterized in that the surface of an aluminum alloy foil is subjected to direct current electrolytic etching.
According to the above procedure, a number of holes having a predetermined average hole diameter and average aspect ratio are formed on the surface of the aluminum alloy foil by direct current electrolytic etching of the surface of the aluminum alloy foil.

  In the method for producing a positive electrode current collector according to the present invention, the surface of the aluminum alloy foil subjected to direct current electrolytic etching is preferably treated with an organic phosphonic acid aqueous solution.

  According to the above procedure, the surface of the aluminum alloy foil subjected to direct current electrolytic etching is treated with an organic phosphonic acid aqueous solution, so that the uneven shape of the hole formed by direct current electrolytic etching is not crushed and along the uneven shape of the hole. Thus, the organic phosphonic acid layer can be formed uniformly.

The positive electrode body for a lithium ion battery according to the present invention includes the positive electrode current collector and a positive electrode active material layer made of a positive electrode active material formed on a surface side having a plurality of holes of the positive electrode current collector. Features.
According to the configuration, the positive electrode current collector and the positive electrode active material layer are provided, and the positive electrode active material layer is formed on the surface side having the plurality of holes of the positive electrode current collector, whereby the positive electrode current collector and the positive electrode Adhesion with the active material layer is improved.

According to the positive electrode current collector and the positive electrode body for a lithium ion battery of the present invention, when used in a lithium ion battery, the adhesiveness with the positive electrode active material layer is excellent. And the charge / discharge cycle durability excellent in the lithium ion battery can be added.
According to the method for producing a positive electrode current collector of the present invention, a positive electrode current collector excellent in adhesion with the positive electrode active material layer can be obtained.

(A), (b) is sectional drawing which shows typically the structure of the positive electrode electrical power collector which concerns on this invention. It is sectional drawing which shows typically the structure of the positive electrode body for lithium ion batteries which concerns on this invention. It is sectional drawing which shows the structure of the conventional positive electrode electrical power collector typically.

A positive electrode current collector according to the present invention will be described with reference to the drawings.
As shown in FIG. 1A, the positive electrode current collector 11 is made of an aluminum alloy foil 1 and has a plurality of (many) holes 2 on the surface thereof. Moreover, although the thickness of the aluminum alloy foil 1 changes with uses of the positive electrode body for lithium ion batteries in which a positive electrode current collector is used, it is generally 10 to 100 μm. Here, as shown in FIG. 2, the surface is a surface on the side where the positive electrode active material layer 12 is formed when used for a positive electrode body for a lithium ion battery (hereinafter sometimes referred to as a positive electrode body) 10. It is.

  The aluminum alloy foil 1 is preferably a 3000 series alloy foil made of a JIS-defined 3000 series alloy, particularly a 3003 alloy. The reason is that 3000 series alloy foil is excellent in the intensity | strength of foil itself. The aluminum alloy foil 1 is inferior in strength to the 3000 series alloy foil, but may be a 1000 series alloy foil made of a 1000 series alloy (pure aluminum).

  The holes 2 have an average hole diameter of 1.0 μm or more and an average aspect ratio defined by (average hole diameter / average hole depth) of 1.0 or less. And since the hole 2 has such an average hole diameter and average aspect ratio, when used for the positive electrode body 10, the anchor effect of the positive electrode current collector 11 (aluminum alloy foil 1) is improved, and the positive electrode current collector 11 and the positive electrode active material layer 12 are improved in adhesion. When the average hole diameter of the holes 2 is less than 1.0 μm, the average hole diameter is small, so that when used in the positive electrode body 10, the positive electrode active material layer 12 is difficult to enter inside the holes, and the anchor effect of the aluminum alloy foil 1 is reduced. . Further, when the average aspect ratio exceeds 1.0, the average hole depth is not sufficient, and therefore, when used in the positive electrode body 10, the positive electrode active material layer 12 entering the inside of the hole is reduced, and the anchor effect of the aluminum alloy foil 1 is reduced. Decrease. The upper limit of the average pore diameter is not particularly limited, but can be, for example, 5 μm or less. Further, the lower limit of the average aspect ratio is not particularly limited, but may be 0.5 or more, for example.

  Moreover, it is preferable that the positive electrode current collector 11 has a pit shape (cylindrical shape) in the shape of the holes 2 on the surface thereof. When the hole 2 has a pit shape, the positive electrode active material layer 12 can easily enter the hole when used in the positive electrode body 10, and the anchor effect of the positive electrode current collector 11 (aluminum alloy foil 1) is improved. The adhesion between the current collector 11 and the positive electrode active material layer 12 is improved. And as shown in FIG. 3, when the hole shape is spongy like the hole 22 of the roughening layer 21a formed in the surface of the conventional positive electrode collector 20 (aluminum alloy foil 21), a positive electrode body When used, the positive electrode active material layer is less likely to enter the hole, the anchor effect of the positive electrode current collector 20 is reduced, and the adhesion between the positive electrode current collector 20 and the positive electrode active material layer is reduced. Moreover, formation of such a pit-shaped hole is achieved by roughening the surface of the aluminum alloy foil 1 by direct current electrolytic etching in the method of manufacturing the positive electrode current collector 11 as described later.

  As shown in FIG. 1B, the positive electrode current collector 11 has an aluminum alloy foil 1 having a plurality of (many) holes 2 formed on the surface side where the positive electrode active material layer 12 (see FIG. 2) is formed. It is preferable to provide an organic phosphonic acid layer 1a containing phosphonic acid. In the positive electrode current collector 11, the organic phosphonic acid layer 1 a is uniformly formed along the uneven surfaces of the numerous holes 2 formed on the surface of the aluminum alloy foil 1. And the hole 2 of the surface of the aluminum alloy foil 1 in which the organic phosphonic acid layer 1a was formed has an average pore diameter of 1.0 μm or more and an average aspect ratio of 1.0 or less. The hole 2 is preferably a pit-shaped hole. The details of the hole 2 are as described above.

Organic phosphonic acids are methylphosphonic acid (CH ₃ P (O) (OH) ₂ ), ethylphosphonic acid (C ₂ H ₅ P (O) (OH), from the viewpoint of ease of handling and superiority in adhesion improvement effect. ₂ ) or vinylphosphonic acid (C ₂ H ₃ P (O) (OH) ₂ ).

These organic phosphonic acids have two OH groups, and these OH groups inevitably exist on the surface of the aluminum alloy material due to the covalent bond with Al or O of the oxide film (Al ₂ O ₃ ). Bond firmly. On the other hand, as shown in FIG. 2, when used in the positive electrode body 10, a positive electrode active material layer 12 is formed on the positive electrode current collector 11. The organic phosphonic acid has high affinity with the positive electrode active material layer 12 and is chemically bonded. In particular, the organic phosphonic acid has a high affinity with a fluorine-based binder such as polyvinylidene fluoride or polytetrafluoroethylene contained as a binder in the positive electrode active material layer 12 and is chemically bonded. As a result, when the positive electrode active material layer 12 is formed on the positive electrode current collector 11, physical bonding due to the anchor effect of the penetration of the positive electrode active material layer 12 into the pores of the aluminum alloy foil 1, and organic phosphonic acid Due to the additive effect of the chemical bond between the layer 1a and the positive electrode active material layer 12, the adhesion between the positive electrode current collector 11 (aluminum alloy foil 1) and the positive electrode active material layer 12 is further improved.

Next, a method for manufacturing the positive electrode current collector according to the present invention will be described.
The method for producing the positive electrode current collector is characterized in that the surface of the aluminum alloy foil is subjected to direct current electrolytic etching under a predetermined condition. Then, by such direct current electrolytic etching (roughening treatment), a number of pit-shaped holes having the above average hole diameter and average aspect ratio are formed on the surface of the aluminum alloy foil.

  Examples of the method for roughening the aluminum alloy foil include AC electrolytic etching, DC electrolytic etching, and chemical etching. In each etching method, the form of roughening can be changed by appropriately selecting the composition, temperature, time, frequency, current density, multistage etching method, and the like of the etching solution. However, for example, in AC electrolytic etching, as shown in FIG. 3, a spongy hole having a small average pore diameter (average pore diameter: less than 1.0 μm) is formed, and a large average pore diameter (average pore diameter: 1.0 μm or more) is formed. It is not easy to form a pit-shaped hole. In addition, in chemical etching, when the pit-shaped holes as shown in FIGS. 1A and 1B are formed, the entire surface of the aluminum alloy foil is chemically dissolved. It is not easy to form. Further, even when searching for chemical etching conditions for forming deep holes, various adjustments such as the treatment liquid composition, the treatment liquid temperature, and the additive are necessary, and the setting thereof is not easy. Therefore, in the method for producing a positive electrode current collector according to the present invention, DC electrolytic etching is used as a method for roughening the aluminum alloy foil.

The treatment conditions for the direct current electrolytic etching are not particularly limited as long as the holes having the above-described conditions are formed. For example, the current density is 400 mA / cm ² or less (preferably ²⁰ to 400 mA / cm ² ), and the electrolysis time is 1 Seconds or more (preferably 1 to 60 seconds, more preferably 1 to 30 seconds). By setting the current density to 400 mA / cm ² or less, the average pore diameter and surface density of the pores can be sufficiently secured, and by ensuring the electrolysis time of 1 second or more, a sufficient average pore depth is secured. Can do.

  The electrolytic etching solution used for direct current electrolytic etching is not particularly limited as long as it is generally used in electrolytic etching, and various acid solutions or a mixed solution thereof can be used, for example. The mixing ratio of various acid solutions when using the mixed solution is appropriately set according to the average pore diameter, average aspect ratio, and surface density of the holes formed on the surface of the aluminum alloy foil.

  Moreover, it is preferable that the manufacturing method of the positive electrode electrical power collector which concerns on this invention processes the surface of the aluminum alloy foil which carried out the direct current electrolytic etching with organic phosphonic acid aqueous solution. Then, by treating with such an organic phosphonic acid aqueous solution, an organic phosphonic acid layer is formed on the surface of the aluminum alloy foil, and the organic phosphonic acid layer is formed on the uneven surface of many holes formed by direct current electrolytic etching. It is formed uniformly along.

  The processing conditions for the DC electrolytic etching of the aluminum alloy foil are the same as described above. The treatment method with an organic phosphonic acid aqueous solution is not particularly limited as long as an organic phosphonic acid layer can be formed. For example, a method of applying an organic phosphonic acid aqueous solution to the surface of an aluminum alloy foil after direct current electrolytic etching, or direct current electrolytic etching. A method of immersing the later aluminum alloy foil in an organic phosphonic acid aqueous solution may be mentioned. The treatment method is preferably the latter method from the viewpoint of the uniformity of the formation of the organic phosphonic acid layer.

  The immersion conditions in the organic phosphonic acid aqueous solution are preferably that the organic phosphonic acid concentration in the aqueous solution is 0.01 to 100 g / L, the temperature of the aqueous solution is 30 to 90 ° C., and the immersion time is 10 to 120 seconds. When the organic phosphonic acid concentration in the aqueous solution is lower than 0.01 g / L, the temperature of the aqueous solution is lower than 30 ° C., and the immersion time is shorter than 10 seconds, an organic phosphonic acid layer is formed in the surface. The region tends to be non-uniform, and it is difficult to obtain the effect of improving the adhesion by forming the organic phosphonic acid layer. On the other hand, even when the concentration of the organic phosphonic acid in the aqueous solution is higher than 100 g / L, the temperature of the aqueous solution is higher than 90 ° C., and the immersion time is longer than 120 seconds, the thickness of the organic phosphonic acid layer becomes uneven. It is easy to obtain the effect of improving the adhesion by forming the organic phosphonic acid layer.

  The thickness of the organic phosphonic acid layer is not particularly limited, but is preferably several to several tens of mm. Since the organic phosphonic acid layer has such a thickness, the organic phosphonic acid layer can be uniformly formed along the uneven surface of the hole without crushing the uneven shape of the pit-shaped hole formed by direct current electrolytic etching. It becomes easy to form. In addition, since the organic phosphonic acid layer is a very thin film, it is difficult to inhibit the transfer of electrons between the positive electrode active material layer and the aluminum alloy foil.

  Moreover, the manufacturing method of the positive electrode electrical power collector which concerns on this invention will not be specifically limited if the above-mentioned direct current | flow electrolysis etching is included, Other processes may be included. As another treatment, for example, a washing treatment using water or alkali that cleans the surface of the aluminum alloy foil before and after the direct current electrolytic etching may be performed.

Next, the positive electrode body for a lithium ion battery according to the present invention will be described.
As shown in FIG. 2, the positive electrode body 10 for a lithium ion battery includes the above-described positive electrode current collector 11 and a positive electrode active material layer 12 formed on the surface side having a large number of holes of the positive electrode current collector 11. It is characterized by that. Thus, the positive electrode active material layer 12 is formed on the surface side of the positive electrode current collector 11 having a large number of holes, whereby the adhesion between the positive electrode current collector 11 and the positive electrode active material layer 12 is improved. Moreover, although the thickness of the positive electrode current collector 11 and the positive electrode active material layer 12 varies depending on the use of the lithium ion battery used, the thickness: 10 to 100 μm of the positive electrode current collector 11, the thickness: 10 A positive electrode active material layer 12 of ˜150 μm is preferable. Since the positive electrode current collector 11 is as described above, the description thereof is omitted.

  The positive electrode active material layer 12 is made of a positive electrode active material, and the positive electrode active material is not particularly limited as long as it is a material capable of occluding and releasing lithium ions, and examples thereof include lithium-containing compounds, among lithium-containing compounds. A composite oxide of lithium and manganese, a composite oxide of lithium and cobalt, and a composite oxide of lithium and nickel are preferable. Further, in order to stabilize the slurry used later when the positive electrode active material layer 12 is formed on the surface of the positive electrode current collector 11 and to provide the positive electrode active material layer 12 with sufficient strength, an average of the positive electrode active material is used. The particle size is preferably 30 μm or less.

  Moreover, the positive electrode active material layer 12 may contain a conductive material and a binder as necessary in addition to the positive electrode active material. The conductive material is a substance that improves the conductivity of the positive electrode active material layer 12, and examples thereof include carbon, carbon black such as acetylene black and ketjen black, and the like. The binder is a substance that immobilizes the positive electrode active material in the positive electrode active material layer 12 and includes a fluorine-based binder. Among the fluorine-based binders, polyvinylidene fluoride (PVDF, polyvinylidene fluoride), polytetra Fluoroethylene (PTFE) is preferred.

  The method for producing the positive electrode body 10 for a lithium ion battery is not particularly limited as long as the positive electrode active material layer 12 can be formed (integrated) on the surface of the positive electrode current collector 11. For example, the positive electrode active material, conductive material, and A method in which a slurry in which a binder is added to a solvent and mixed is applied onto the positive electrode current collector 11 made of an aluminum alloy foil by a bar coater or a doctor blade and dried is preferable. Here, as a solvent, tetrahydrofuran (THF) which is a volatile organic solvent having a boiling point of 100 ° C. or less, acetone, and the like are preferable from the viewpoint of workability. The contents of the positive electrode active material, the conductive material and the binder in the slurry vary depending on the use of the lithium ion battery in which the positive electrode body 10 is used, but generally the positive electrode active material is 70 to 100% by mass, preferably 90%. It is preferable that -98 mass%, a conductive material is 1-50 mass%, preferably 2-30 mass%, and a binder is 1-50 mass%, preferably 5-15 mass%.

Next, examples of the positive electrode current collector according to the present invention will be specifically described in comparison with comparative examples that do not satisfy the requirements of the present invention.
As the aluminum alloy foil, a 3003 alloy foil having a film thickness of 15 μm was used. The aluminum alloy foil was cut into 50 × 50 mm and used as a sample. As shown in Table 1, a mixed solution of perchloric acid: acetic acid = 4: 1 (mass% ratio) was used as the electrolytic etching solution, and the electrolytic etching solution was kept at 10 ± 1 ° C. using a cooler and was slightly stirred. The surface of the sample was subjected to direct current electrolytic etching treatment in an electrolytic etching solution to which was added. The current density was appropriately set between ^{20 and} 450 mA / cm ² . Moreover, the electrolysis time was appropriately set between 1 to 30 seconds in which the thickness of the aluminum alloy foil was not significantly reduced from the viewpoint of the strength of the positive electrode current collector. Then, the positive electrode current collector (sample No. 1-5 of an Example, sample No. 6-7 of a comparative example) which has many holes in the aluminum alloy foil surface by fully washing with pure water and drying. )

In addition, an untreated aluminum alloy foil that was not subjected to etching treatment was used as a positive electrode current collector (sample No. 8 in the comparative example). Further, as shown in Table 1, a 1000 series alloy foil having a film thickness of 15 μm was cut into 50 × 50 mm to obtain a sample, and hydrochloric acid: phosphoric acid: nitric acid: sulfuric acid = 10: 1: 4: 0.1 as an electrolytic etching solution. Using a mixed solution of (mass% ratio), in an electrolytic etching solution (25 ± 1 ° C.) with slight stirring, AC electrolytic etching was performed on the surface of the sample with a current density of 300 mA / cm ² and an electrolysis time of 10 seconds. It processed, washed with water, and dried and obtained the positive electrode electrical power collector (sample No. 9 of a comparative example).

  About the obtained positive electrode collector (sample No. 1-5 of an Example, sample No. 6-9 of a comparative example), observation magnification 500 times in the aluminum foil surface with a laser microscope (Keyence Corporation VK-9510) And the average pore diameter and average pore depth were measured. The results are shown in Table 1. In addition, the hole shape was also observed, and the positive electrode current collector (Comparative Sample No. 9) showed spongy holes, and the other positive electrode current collectors (Example Sample Nos. 1 to 5, Comparative Example) In sample Nos. 6 to 8) of the example, pit-like holes were observed.

  Further, 92% by mass of a positive electrode active material (lithium cobaltate, average particle size of about 3 μm), 3% by mass of a conductive material (carbon), and 5% by mass of a binder (polyvinylidene fluoride) were added to the surface of the obtained positive electrode current collector. A positive electrode body for a lithium ion battery in which slurry mixed in addition to a solvent is applied by a bar coater, and then dried and pressed to form a positive electrode active material layer having a thickness of 80 μm on the surface of the positive electrode current collector (implementation) Sample No. 1-5 of an example and sample No. 6-9 of a comparative example were obtained. And about the obtained positive electrode body for lithium ion batteries, the adhesive evaluation test of a positive electrode active material layer and a positive electrode electrical power collector (aluminum alloy foil) was done.

  As an adhesion evaluation test, a horizontal force (kN / per unit blade width) was determined by a SAICAS test (evaluation of peel strength of thin film by SAICAS method, surface technology, Vol. 58 (2007), No. 5, p. 300). m) was calculated. Specifically, cutting was performed along the interface between the aluminum alloy foil and the positive electrode active material layer using a SAICAS-DN20 type. Initially, two blade directions, that is, a horizontal direction and a vertical direction were moved simultaneously, and the blade was cut into the positive electrode active material layer. When the blade cut into the positive electrode active material layer reaches the vicinity of the interface between the aluminum alloy foil and the positive electrode active material layer, a large change is observed in the force applied to the blade. At this point, the positive electrode active material layer can be separated along the interface with the aluminum alloy foil by stopping the vertical movement and switching the movement of the blade to only one axial direction (horizontal direction) parallel to the interface. it can. The horizontal force during the uniaxial movement corresponds to the adhesion force between the positive electrode active material layer and the aluminum alloy foil.

  By comparing the horizontal force, the adhesion of various positive electrode bodies for lithium ion batteries was evaluated. Specifically, the horizontal force compared to the horizontal force of the positive electrode body for a lithium ion battery (sample No. 8 in the comparative example) using an untreated aluminum alloy foil that has not been subjected to etching treatment as the positive electrode current collector. Is markedly improved (◯), and those having the same horizontal force are considered poor (x). The results are shown in Table 1.

  From the results of Table 1, sample No. In the positive electrode body for lithium ion batteries of 1 to 5, a large number of pores having an average pore diameter of 1.0 μm or more and an average aspect ratio (average pore diameter / average pore depth) of 1.0 or less are formed on the surface of the aluminum alloy foil. Therefore, sample No. of the comparative example. A remarkable improvement in the horizontal force was observed compared to 8, and the adhesion was good (◯).

  In contrast, Sample No. In the positive electrode body for a lithium ion battery of No. 6, many holes formed on the surface of the aluminum alloy foil have an average hole diameter of 1.0 μm or more, but the average hole depth is not sufficient, and the average aspect ratio is 1.0. Therefore, the sample No. of the comparative example. Compared to 8, no significant improvement in horizontal force was observed, and the adhesion was poor (x).

  Sample No. of Comparative Example In the positive electrode body for lithium ion batteries 7 and 9, since many holes formed on the surface of the aluminum alloy foil have an average pore diameter of less than 1.0 μm, the average pore diameter is small and the positive electrode active material is difficult to enter inside the holes. Sample No. of the comparative example. Compared to 8, no significant improvement in horizontal force was observed, and the adhesion was poor (x).

Moreover, the Example of the positive electrode electrical power collector provided with the organic phosphonic acid layer is demonstrated concretely.
As the aluminum alloy foil, a 3003 alloy foil having a film thickness of 15 μm was used. The aluminum alloy foil was cut into 50 × 50 mm and used as a sample. In an electrolytic etching solution using a mixed solution of perchloric acid: acetic acid = 4: 1 (mass% ratio) as an electrolytic etching solution, keeping the electrolytic etching solution at 10 ± 1 ° C. using a cooler, and adding a little stirring. Then, the surface of the sample was subjected to direct current electrolytic etching. The current density was appropriately set between 25 and 400 mA / cm ² . Moreover, the electrolysis time was appropriately set between 1 to 30 seconds in which the thickness of the aluminum alloy foil was not significantly reduced from the viewpoint of the strength of the positive electrode current collector.

  After the electrolytic etching treatment, it was sufficiently washed with pure water, dried, and then an organic phosphonic acid layer was formed. Three types of organic phosphonic acids were used: methylphosphonic acid, ethylphosphonic acid, and vinylphosphonic acid. Each organic phosphonic acid was diluted with pure water to prepare a 10 g / L aqueous solution as a treatment solution. The treatment liquid is heated to 60 ° C., the aluminum alloy foil after the electrolytic etching treatment is immersed for 60 seconds, then washed with pure water, dried at room temperature, and provided with an organic phosphonic acid layer A current collector (Sample Nos. 10 to 14 in Examples) was obtained.

  With respect to the obtained positive electrode current collector (Sample Nos. 10 to 14 in Examples), the average hole diameter and average hole depth of the holes formed on the surface of the aluminum alloy foil were measured by the same apparatus and method as in Example 1. did. The results are shown in Table 2. The hole shape was also observed, and pit-shaped holes were observed. Further, it was confirmed by FT-IR analysis that an organic phosphonic acid layer was formed.

  Moreover, the positive electrode active material layer similar to Example 1 was formed in the surface of the obtained positive electrode electrical power collector, and the positive electrode body for lithium ion batteries (sample No. 10-14 of an Example) was obtained. And about the obtained positive electrode body for lithium ion batteries, the adhesive evaluation by a SAICAS test was performed similarly to Example 1. FIG. The results are shown in Table 2.

  From the results in Table 2, sample No. In the positive electrode body for a lithium ion battery of Nos. 10 to 14, a large number of holes having an average pore diameter of 1.0 μm or more and an average aspect ratio of 1.0 or less were formed on the surface of the aluminum alloy foil. A remarkable improvement in the horizontal force was observed compared to 8, and the adhesion was good (◯).

  In addition, Sample No. 10 and no. No. 11 is the same as the sample No. of Example in which the electrolytic etching treatment was performed under the same conditions. 2 (see Table 1), it can be seen that the organic phosphonic acid layer does not affect the average pore diameter and the average pore depth. On the other hand, the horizontal force increased due to the formation of the organic phosphonic acid layer, and improved adhesion was observed. Furthermore, sample No. of an Example. 12 and the sample No. of Example. 3 (see Table 1), Sample No. 13 and no. 14 and the sample No. of Example. 5 (see Table 1), it was found that the organic phosphonic acid layer did not affect the average pore diameter and average pore depth, and improved adhesion due to the formation of the organic phosphonic acid layer was observed. .

DESCRIPTION OF SYMBOLS 1 Aluminum alloy foil 1a Organic phosphonic acid layer 2 Hole 10 Positive electrode body for lithium ion batteries (positive electrode body)
11 Positive Current Collector 12 Positive Electrode Active Material Layer

Claims (7)

  A positive electrode current collector having a positive electrode active material layer formed on a surface thereof to be a positive electrode for a lithium ion battery, comprising an aluminum alloy foil, and a plurality of the aluminum alloy foil on the surface side where the positive electrode active material layer is formed Wherein the plurality of holes have an average hole diameter of 1.0 μm or more and an average aspect ratio defined by (average hole diameter / average hole depth) is 1.0 or less. Current collector.   The positive electrode current collector according to claim 1, wherein the hole is a pit-shaped hole.   3. The positive electrode according to claim 1, wherein the aluminum alloy foil having a plurality of holes includes an organic phosphonic acid layer containing organic phosphonic acid on a surface side on which the positive electrode active material layer is formed. Current collector.   The positive electrode current collector according to claim 3, wherein the organic phosphonic acid is one or more selected from methylphosphonic acid, ethylphosphonic acid, and vinylphosphonic acid.   The method for producing a positive electrode current collector according to claim 1 or 2, wherein the surface of the aluminum alloy foil is subjected to direct current electrolytic etching.   6. The method for producing a positive electrode current collector according to claim 5, wherein the surface of the aluminum alloy foil subjected to direct current electrolytic etching is treated with an organic phosphonic acid aqueous solution.   5. A positive electrode current collector according to claim 1, and a positive electrode active material layer made of a positive electrode active material formed on a surface side having a plurality of holes of the positive electrode current collector. The positive electrode body for lithium ion batteries characterized by the above-mentioned.

Images