JP2012052204A - Aluminum alloy foil for lithium-ion battery electrode material, and electrode material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy for lithium-ion battery electrode material having high electric conductivity, excellent heat-softening resistance, and excellent adhesive strength with an active material.SOLUTION: The aluminum alloy foil for lithium-ion battery electrode material, has the composition composed by mass% of 0.010-0.10% Zr, ≤0.020% the total of Ti and V, ≤0.15% Si, ≤1.6% Fe, ≤0.060% Cu, ≤0.040% Mn, ≤0.030% Mg, ≤0.030% Cr, ≤0.65% Zn and the balance Al with inevitable impurities, and has ≥59% IACS of electric conductivity.

Description

  The present invention relates to an aluminum alloy foil or an aluminum alloy foil used as an electrode material of a lithium ion battery, particularly as a positive electrode material.

  In recent years, lithium ion batteries have been widely used as power sources for mobile devices such as mobile phones and laptop computers because of their advantages such as high energy density and lack of memory effect. In the future, it is also promising as a power source for hybrid vehicles and electric vehicles.

The electrode material of this lithium ion secondary battery includes a positive electrode plate, a separator, and a negative electrode plate. An aluminum alloy foil that has excellent electrical conductivity, does not affect the electrical efficiency of the secondary battery, and generates less heat is used as a support for the positive electrode material, and JIS 1085 and JIS 1N30 aluminum alloys are generally used. . An active material mainly composed of a lithium-containing metal oxide such as LiCoO ₂ is applied to the surface of the aluminum alloy foil. As a manufacturing method, an active material having a thickness of about 100 μm is applied to both sides of an aluminum alloy foil of about 20 μm, and after a drying process for removing the solvent in the active material, the density of the active material is further increased and the adhesiveness is increased. Press for securing. The positive electrode plate manufactured in this manner is laminated with the separator and the negative electrode plate, and then wound and stored in the case.

  Among the manufacturing processes as described above, the drying process may exceed 200 ° C. under severe conditions. In this case, aluminum is softened and easily deforms. In that case, when the packing density of the active material is increased in the subsequent pressing step, the aluminum alloy foil is plastically deformed and a desired density cannot be obtained, or the adhesion between the active material and the aluminum alloy foil is reduced. There is a problem. In order to solve this problem, Patent Document 1 discloses a method of preventing peeling from an active material without increasing plastic strength in the crimping process by increasing the strength of an aluminum alloy foil. Patent Document 2 discloses a method for preventing peeling from the active material without suppressing plastic deformation in the pressure-bonding process as in Patent Document 1 by suppressing softening of the aluminum alloy foil in the drying process.

In any of the above methods, the effect is obtained by adding an alloy element such as Mn, Cu, or Mg. However, in this method, the electrical conductivity of the aluminum alloy foil is lowered, and the aluminum alloy foil is used as a current collector There is a problem that the merit to do decreases.
JP 2008-150651 A Japanese Patent Laid-Open No. 11-67220

  The present invention provides an aluminum alloy foil for an electrode material of a lithium ion battery having high conductivity, excellent heat softening resistance, and excellent adhesion to an active material.

  As a result of intensive studies in order to solve the above problems, an aluminum alloy foil having high heat-softening resistance was found while maintaining high conductivity by adding a small amount of Zr and appropriately suppressing the amount of impurities. The aluminum alloy foil is not softened in the drying process of the active material and is not plastically deformed in the subsequent pressing process of the active material, so that high adhesiveness with the active material is obtained.

That is, according to the first aspect of the present invention, Zr: 0.010 to 0.10 mass% (hereinafter referred to as “%”), the total of Ti and V: 0.020% or less, Si: 0.15% or less Fe: 1.6% or less, Cu: 0.060% or less, Mn: 0.040% or less, Mg: 0.030% or less, Cr: 0.030% or less, Zn: 0.65% or less The balance is an aluminum alloy foil for a lithium ion battery electrode material, wherein the balance is made of Al and inevitable impurities, and the electrical conductivity is 59% IACS or more.
The second invention according to claim 2 is the aluminum alloy foil of the first invention, wherein Si: 0.10% or less, Fe: 1.5% or less, Cu: 0.050% or less, Mn: 0.020% or less, Mg: 0.020% or less, Cr: 0.010% or less, and Zn: 0.50% or less.
Further, a third invention according to claim 3 is an electrode material for a lithium ion battery provided with the aluminum alloy foil of the first or second invention.

  According to the present invention, an aluminum alloy foil having high electrical conductivity and excellent heat resistance softening property is obtained, and in producing a lithium ion battery electrode material, an electrode having low internal resistance and excellent adhesion to an active material. A material is obtained.

1. Aluminum alloy foil for lithium ion battery electrode material The aluminum alloy foil for lithium ion battery electrode material of one embodiment of the present invention is a total of Zr: 0.010 to 0.10 mass% (hereinafter referred to as%), Ti and V. : 0.020% or less, Si: 0.15% or less, Fe: 1.6% or less, Cu: 0.060% or less, Mn: 0.040% or less, Mg: 0.030% or less, Cr: 0 0.030% or less, Zn: 0.65% or less, the balance is made of Al and inevitable impurities, and the conductivity is 59% IACS or more.

  First, the control range of alloy components will be described.

  Zr can obtain high heat-softening resistance even in a small amount. If the addition amount is less than 0.010%, a sufficient effect cannot be obtained, and softening occurs when the active material drying step is at a high temperature. Further, it is plastically deformed in the subsequent pressing step of the active material, and not only the density of the active material is increased, but also the adhesiveness between the active material and the aluminum alloy foil is lowered and peeling occurs. On the other hand, when the addition amount exceeds 0.10%, the electrical conductivity decreases, and the internal resistance as a battery increases.

  The reason why the total content of Ti and V as impurities is 0.020% or less is to keep the conductivity high. If the total content of these elements exceeds 0.020%, it becomes difficult to ensure a conductivity of 59% IACS. As a control method for Ti and V, it may be adjusted as usual by selection of raw materials, blending ratio, etc., but even with a large blend of Ti and V, a boride is formed by B treatment in a melting furnace and settled. It is also possible to control by the removal method.

For impurities other than Ti and V, the content should be as low as possible in order to make the conductivity 59% IACS or higher.
Si is inevitably contained in the metal, but its content is 0.15% or less, preferably 0.10% or less. Fe is inevitably contained in the bullion. Fe hardly dissolves in Al, so there is little influence on the electrical conductivity. Even if it is contained in the alloy, the characteristics are not greatly impaired. The Fe content is 1.6% or less, preferably 1.5% or less.

  Moreover, since Cu, Mn, Mg, Cr, and Zn also lower the electrical conductivity, the content thereof needs to be equal to or less than the reference value determined for each element. The Cu content is 0.060% or less, preferably 0.050% or less. The Mn content is 0.040% or less, and preferably 0.020% or less. The Mg content is 0.030% or less, and preferably 0.020% or less. The Cr content is 0.030% or less, preferably 0.010% or less. The Zn content is 0.65% or less, preferably 0.50% or less.

  If the element specified here is within the content range shown here, the conductivity can be 59% IACS or higher. The lower limit value of the element content specified here is not particularly limited, but is 0.1, 0.01, 0.001, 0.0001, or 0%, for example. In addition, elements that are not specified here are allowed to be included in the alloy as inevitable impurities as long as the electrical conductivity is within a range not lower than 59% IACS.

  The reason why the conductivity is set to 59% IACS or more is to suppress the internal resistance of the battery as much as possible. If it is less than 59% IACS, it is inferior to the conventional pure aluminum (1000 series) foil, and in order to suppress the loss of internal resistance and maintain the same performance, the foil is thickened and the battery is large. Measures such as conversion are necessary.

  As for the production process of the aluminum alloy foil, an alloy ingot having the above composition is produced by ordinary DC casting, and then homogenized, hot-rolled, cold-rolled, and optionally subjected to intermediate annealing according to conventional methods. Is done. The intermediate annealing may be performed after hot rolling or during a plurality of cold rollings after hot rolling. As long as annealing can be maintained at a temperature of 500 ° C. or higher, a batch annealing furnace or a continuous annealing furnace may be used. If the holding temperature is less than 500 ° C., Zr cannot be in a solid solution state, and sufficient heat-resistant softening property cannot be obtained.

  Further, there is no problem even if the holding time is short (it may be 0 seconds), and the temperature raising rate and the cooling rate are not particularly limited. When a continuous annealing furnace is used, Zr is made into a solid solution state by applying rapid heat treatment, holding, and rapid cooling heat treatment (heating and cooling rate of 1 ° C./second or more) to a temperature of 500 ° C. or higher. It becomes possible to improve. Further, this intermediate annealing step is not essential, but when a homogenization treatment at 550 ° C. or lower is adopted, the annealing by the continuous annealing furnace should be inserted into the step. When a homogenization treatment at 550 ° C. or higher is performed, the solid solution state of Zr is good, and a good result can be obtained without necessarily inserting an intermediate annealing step.

  Moreover, you may use the continuous casting rolling equipment by a twin roll method etc. for casting. In this case, the cooling rate at the time of casting is high and a good solid solution state of Zr can be obtained. There is also an advantage that the manufacturing cost is reduced.

2. Lithium ion battery electrode material Drying by applying an active material mainly composed of a lithium-containing metal oxide (for example, LiCoO ₂ ) to the aluminum alloy foil surface (preferably on both sides) of the above embodiment, and removing the solvent in the active material The electrode material (positive electrode material) of a lithium ion battery is obtained by performing press for further increasing the density of the active material and ensuring adhesion through the process. This electrode material has high adhesion between the aluminum alloy foil and the active material. Moreover, since the electrical conductivity of aluminum alloy foil is high, the internal resistance of the battery manufactured using this electrode material becomes low.

The present invention will be specifically described below with reference to examples.
The alloy components shown in Table 1 were melted and cast by a conventional method to obtain a slab (plate ingot) having a thickness of 500 mm. Next, this slab was chamfered and then subjected to homogenization, hot rough rolling, and hot finish rolling to obtain a hot-rolled sheet having a thickness of 2.5 mm. Subsequently, cold rolling was performed by a conventional method, and in some cases, intermediate annealing was performed in the middle of a cold rolling pass to obtain a cold rolled sheet having a thickness of 0.25 mm. This was further rolled with a foil mill to a thickness of 15 μm. Table 2 summarizes the homogenization conditions and the presence or absence of intermediate annealing. The heating rate of the continuous annealing furnace was about 120 ° C./min, and the cooling rate was about 180 ° C./min. 520 ° C. × 0 sec of Example 5 in Table 2 is a heat treatment that immediately cools without holding after reaching 520 ° C., and 520 ° C. × 10 sec of Example 7 after reaching 520 ° C. It means a heat treatment in which cooling is started after holding for 10 seconds.

  The aluminum alloy foil thus obtained was measured for a tensile test and conductivity. The electrical conductivity was calculated by the gravimetric method by measuring the electrical resistance using a double bridge based on JIS H 0505.

Next, the positive electrode material of the lithium ion secondary battery was manufactured in each aluminum alloy foil. PVDF (polyvinylidene fluoride) serving as a binder was added to an active material mainly composed of LiCoO ₂ to form a positive electrode slurry. The positive electrode slurry was applied to both sides of an aluminum alloy foil having a width of 30 mm at a thickness of 100 μm, dried at 200 ° C. for 30 minutes, and then rolled by a roller press to give about 20% processing. Thereafter, the adhesion of the active material to the aluminum alloy foil was observed with a microscope. The results are summarized in Table 3.

As apparent from Table 3, No. Those within the scope of the present invention of 1 to 7 have high electrical conductivity and can sufficiently suppress the internal resistance of the battery. Furthermore, the adhesiveness with an active material was also favorable.
No. 8 is a material corresponding to JIS 1085 to which Zr is not added, but has been softened due to severe drying process. Therefore, plastic deformation occurred in the subsequent pressing process, and adhesion with the active material was poor.
No. No. 9 is a material corresponding to JIS1N30 without addition of Zr. Similar to 8, the adhesion to the active material was poor.
No. No. 10 had a Zr content higher than 0.10%, so the conductivity was lower than 59% IACS.
No. No. 11 had a total content of Ti and V higher than 0.020%, so the conductivity was lower than 59% IACS.
No. In No. 12, the Si content was higher than 0.15% and the Fe content was higher than 1.6%, so the conductivity was lower than 59% IACS.
No. In No. 13, the Cu content was higher than 0.060% and the Mg content was higher than 0.030%, so the conductivity was lower than 59% IACS.
No. 14 had a Mn content greater than 0.040%, a Cr content greater than 0.030%, and a Zn content greater than 0.65%, so the conductivity was 59% IACS. Lower than.
No. 10-No. As can be seen from FIG. 14, when the content of impurities that lower the conductivity of the alloy exceeds the reference value determined for each impurity, it is found that the conductivity is lower than 59% IACS, and the Zr content is reduced to 0. It was found that the conductivity was 59% IACS or more by setting the content of each element shown in Table 1 to be equal to or less than the reference value. If the electrical conductivity is high, the internal resistance of the battery is low. Therefore, if the electrode material is produced using the aluminum alloy foil of the present invention, the internal resistance of the battery can be reduced.

  It is possible to provide an aluminum alloy foil for a lithium ion secondary battery electrode material having a low internal resistance and an electrode material using the same while preventing separation from the active material without deformation in the pressing step of the active material coating process. .

Claims (3)

  Zr: 0.010 to 0.10 mass% (hereinafter referred to as “%”), Ti and V: 0.020% or less, Si: 0.15% or less, Fe: 1.6% or less, Cu: 0.0. 060% or less, Mn: 0.040% or less, Mg: 0.030% or less, Cr: 0.030% or less, Zn: 0.65% or less, with the balance being Al and inevitable impurities, An aluminum alloy foil for a lithium ion battery electrode material, wherein the rate is 59% IACS or more.   Si: 0.10% or less, Fe: 1.5% or less, Cu: 0.050% or less, Mn: 0.020% or less, Mg: 0.020% or less, Cr: 0.010% or less, Zn: The aluminum alloy foil according to claim 1, which is 0.50% or less.   The electrode material for lithium ion batteries provided with the aluminum alloy foil of Claim 1 or 2.