Aluminum alloy foil for positive current collector of lithium ion battery

Abstract

An aluminum alloy foil for a positive electrode current collector of a lithium ion battery can replace a common aluminum alloy foil for a high-strength low-conductivity or low-strength high-conductivity positive electrode current collector, and comprises the following components in percentage by mass: 0.1-0.15 wt.% of Zr, 0.1-0.2 wt.% of Cu and the balance of Al, the tensile strength range at the normal temperature is 171-245MPa, and the tensile strength range at the temperature of 50 DEG C is 173-210MPa. In an Al-xCu-0. 1Zr (x = 0.1 wt.%, 0.15 wt.% or 0.2 wt.%) ternary alloy system, along with the increase of the Cu content, the corrosion potentials of the aluminum-copper-zirconium alloy are respectively-756 mV,-717 mV,-711 mV and-706 mV, the corrosion potentials are continuously and positively shifted, and the corrosion resistance of the alloy foil is continuously enhanced.

Description

Technical Field

[0001] The present invention relates to a technology in the field of aluminum alloy materials, in particular to an aluminum alloy foil for positive electrode current collector of lithium ion batteries with high strength and excellent corrosion resistance. Background Art

[0002] Aluminum alloy foils for positive electrode current collectors of lithium-ion batteries prepared by prior art have problems such as low tensile strength or poor corrosion resistance. At present, aluminum alloy foils with high tensile strength and excellent corrosion resistance are still in demand. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes an aluminum alloy foil for positive electrode current collector of lithium ion battery, which can replace the commonly used high-strength and low-conductivity or low-strength and high-conductivity aluminum alloy foil for positive electrode current collector. The tensile strength of the aluminum alloy foil obtained after heat treatment at 125°C for 5 hours is in the range of 171 to 245MPa at room temperature, and the tensile strength at 50°C is in the range of 173 to 210MPa. In the Al-xCu-0.1Zr (x=0.1wt.%, 0.15wt.%, 0.2wt.%) ternary alloy system, with the increase of Cu content, the corrosion potential of aluminum-copper-zirconium alloy is -756mV, -717mV, -711mV, -706mV respectively, the corrosion potential continues to shift positively, and the corrosion resistance of the alloy foil continues to increase.

[0004] The present invention is achieved through the following technical solutions:

[0005] The invention relates to an aluminum alloy foil for positive electrode current collector of lithium ion battery with low alloying design, the components and mass percentage contents of which are: Zr: 0.1-0.15wt.%, Cu: 0.1-0.2wt.%, and the balance is Al (and inevitable impurities).

[0006] The aluminum alloy foil has a room temperature tensile strength range of 214-245 MPa after heat treatment at 125° C. for 5 hours, and a tensile strength range of 203.43-210 MPa at 50° C. In the Al-xCu-0.1Zr (x=0.1wt.%, 0.15wt.%, 0.2wt.%) ternary alloy system, as the Cu content increases, the corrosion potential of the aluminum-copper-zirconium alloy continues to shift positively, and the corrosion resistance of the alloy foil continues to increase.

[0007] The present invention relates to a method for manufacturing the aluminum alloy foil for positive electrode current collector, which adopts industrial aluminum ingot as raw material, adds Al-50wt.%Cu master alloy and 10wt.%Zr master alloy according to proportion after melting, and then smelts, homogenizes, and obtains the aluminum alloy foil through hot rolling and cold rolling.

[0008] In the whole smelting process, the alloy composition content is controlled to be Zr: 0.1-0.15wt.%, Cu: 0.1-0.2wt.%, and the rest is composed of aluminum and other inevitable impurities.

[0009] The homogenization treatment is carried out at a temperature of 590-600° C. and a heat preservation time of 8-10 hours.

[0010] The hot rolling is controlled to have a thickness of 3 mm.

[0011] The cold rolling is performed to control the thickness to be 0.006-0.08 mm. Technical Effects

[0012] The aluminum foil for positive electrode current collector of the present invention has excellent tensile strength and corrosion resistance compared to the unilateral high strength of other aluminum alloy foils or pure aluminum foils for positive electrode current collectors by adding microalloyed Cu and Zr elements with a total content of less than 0.35wt.%. The present invention is ternary low-alloyed, easy to control, and does not contain multiple elements such as Si, Fe, Zn, Mn, La, etc. In the Al-Cu-Zr alloy, the precipitated second phase Al2Cu can strengthen the alloy, and the microalloying of the Zr element can bring fine grain strengthening to the alloy. At the same time, trace amounts of Cu and Zr elements have obvious effects on improving the mechanical properties and corrosion resistance of the current collector, which has not been tried in previous patents and is innovative. DETAILED DESCRIPTION Example 1

[0013] In this embodiment, the aluminum alloy foil for the positive electrode current collector is prepared, specifically comprising:

[0014] 1) using a vacuum induction melting method to melt and cast a refined aluminum ingot, an aluminum-zirconium alloy with a zirconium mass fraction of 10 wt.%, and a copper-aluminum alloy with a copper mass fraction of 50 wt.% into an alloy ingot with a thickness of 20 mm, and performing a homogenization treatment at 590° C. for 8 hours;

[0015] 2) hot rolling the homogenized alloy to 3 mm and then cold rolling it to an aluminum alloy foil with a thickness of 0.07 mm;

[0016] 3) heat treating the aluminum alloy foil at 125° C. for 5 hours to obtain the aluminum alloy foil for the positive electrode current collector;

[0017] The mass fraction of copper element in the aluminum alloy foil used for the positive electrode current collector is 0.1wt.%, the mass fraction of zirconium is 0.1wt.%, and the balance is aluminum. Example 2

[0018] The difference between this embodiment and embodiment 1 is that the mass fraction of copper in the current collector is 0.15 wt.%, the mass fraction of zirconium is 0.1 wt.%, and the other conditions and parameters are exactly the same as those in embodiment 1. Example 3

[0019] The present embodiment differs from the first embodiment in that the mass fraction of copper in the current collector is 0.2 wt.%, the mass fraction of zirconium is 0.1 wt.%, and the other conditions and parameters are exactly the same as those in the first embodiment. Example 4

[0020] The only difference between this embodiment and embodiment 1 is that the mass fraction of copper in the current collector is 0.15 wt.%, the mass fraction of zirconium is 0.15 wt.%, and the other conditions and parameters are exactly the same as those in embodiment 1. Comparative Example 1

[0021] The comparative aluminum alloy foil prepared in this embodiment specifically includes:

[0022] 1) Refined aluminum ingots, pure silver ingots and copper-aluminum alloy with a copper mass fraction of 50% were melted and cast into alloy ingots by vacuum induction melting method. The ingot thickness was 20 mm and the ingots were homogenized at 590° C. for 8 h;

[0023] 2) hot rolling the homogenized alloy to 3 mm and then cold rolling it to an aluminum alloy foil with a thickness of 0.07 mm;

[0024] 3) heat treating the aluminum alloy foil at 125° C. for 5 h to obtain the aluminum alloy foil for the positive electrode current collector;

[0025] The aluminum alloy foil for positive electrode current collector contains 0.15% silver by mass, 0.1% copper by mass, 0.2% silicon by mass, 0.25% iron by mass, and the remainder is aluminum. Comparative Example 2

[0026] The only difference between this comparative example and Example 1 is that copper is not added, and other conditions and parameters are exactly the same as those in Example 1. Comparative Example 3

[0027] This comparative example directly uses 3003 aluminum alloy as the aluminum alloy foil for the positive electrode current collector, which contains 0.6wt.% silicon, 0.15wt.% copper, 0.7wt.% iron, 0.1wt.% zinc, and 1.5wt.% manganese. Performance Testing

[0028] The performance test conditions of the aluminum alloy samples with different compositions in the above embodiments are as follows:

[0029] 1) Room temperature tensile test: A standard tensile specimen was made according to the national standard GB / T228-2002, and stretched on a Zwick Z20 universal tensile testing machine. The tensile speed was set to 1 mm / min, and the extensometer length was 40 mm. The tensile strength and elongation were measured. The tensile specimen for the test was cut from the aluminum alloy foil along the rolling direction, and the tensile strength and elongation were measured under the above test conditions.

[0030] 2) High temperature tensile test: The high temperature tensile test instrument used is a CMT 5105 microcomputer-controlled universal material testing machine with a tensile rate of 1 mm / min. Some mechanical properties of the sample are measured to characterize the mechanical properties of the alloy foil at high temperature and compared with the parameters at room temperature.

[0031] 3) Tafel polarization curve test: The electrochemical workstation uses CHI 660, the electrochemical test environment is 3.5wt.% NaCl solution, the voltage scanning range is -1~0V, and the scanning speed is 1mV / s. Before starting to test the polarization curve, the assembled three-electrode system needs to be left to stand for a sufficient time to ensure the stability of the system and to ensure that the fluctuation of the open circuit voltage is within the range of 0.01V. After the test, the tangent of the anode and cathode curves can be drawn by extrapolation. The horizontal coordinate corresponding to the intersection is the corrosion potential, and the vertical coordinate is the corrosion current density.

[0032] Table 1 Alloy foil performance test results

[0033] As shown in Table 1, the alloy foils of Examples 1 to 4 have relatively good comprehensive properties. The room temperature tensile strength of the aluminum alloy foil for positive electrode current collector of the present invention is greater than 214.61 MPa, and can reach up to 245.28 MPa. The room temperature elongation can reach more than 1.15%, and can reach up to 2.15%. The high temperature tensile strength is greater than 203.43 MPa, and can reach up to 210.95 MPa. The high temperature elongation can reach more than 3.1%, and can reach up to 4.36%. The corrosion potential is ≥717.26 mV, and the corrosion current is ≤7.73×10 -6 A / cm 2 It has excellent comprehensive tensile strength and elongation, and can fully meet the comprehensive requirements of strength and corrosion resistance of aluminum alloy foil used in lithium-ion batteries.

[0034] Comparison between Example 1 and Comparative Example 1 shows that in Example 1, 0.1 wt.% Cu element is microalloyed in Al-0.1Zr alloy, and the corrosion potential is positively shifted from -756.37 mV to -717.26 mV, and the corrosion current is positively shifted from 41.30×10 -6 A / cm 2 Reduced to 7.73×10 -6 A / cm2 It can be found that the addition of trace Cu element significantly improves the corrosion resistance of the alloy.

[0035] In the Al-xCu-0.1Zr (x=0, 0.1, 0.15, 0.2) alloy system, by comparing Comparative Example 1 with Examples 1-3, the room temperature tensile strength is up to 232.52MPa, the elongation is up to 2.15%, the high temperature tensile strength is up to 210.95MPa, and the high temperature elongation is up to 4.47%. Under the premise of meeting the tensile strength and conductivity, the corrosion potential of Example 2 is -711mV, and the corrosion current is 1.43×10 -6 A / cm 2 , in Examples 1 to 3, the samples have excellent corrosion resistance and tensile strength.

[0036] Compared with Examples 2 and 4, in Example 5, the Cu element content is increased from 0.1wt.% to 0.15wt.%, and the room temperature tensile strength is increased to 245.28MPa. At the same time, the corrosion potential is shifted positively to a large extent, from -711.52mV to -705.43mV. It can be seen that all aspects of the performance of the alloy are significantly improved.

[0037] Comparing Example 4 with Comparative Example 2, after microalloying the Zr element, Example 4 has a room temperature tensile strength of 245.28 MPa, which is much greater than 201.10 MPa of Comparative Example 2, and the tensile strength is greatly improved. The high temperature tensile strength of Example 4 is also much greater than that of Comparative Example 2, and the corrosion resistance of Example 4 is also better. Under the same ternary microalloying conditions, the comprehensive performance of Example 4 is better.

[0038] Comparing Example 4 with Comparative Example 3, on the one hand, although the tensile strength of Example 4 is higher, Comparative Example 3 is a common commercial aluminum alloy, which is a typical high alloy with complex elements. On the other hand, the corrosion resistance of Example 4 is much better than that of Comparative Example 3. The corrosion potential of the system of the present invention is about -700mV, and the tensile strength is greater than 200MPa, which is significantly better than the prior art.

[0039] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. An aluminum alloy foil for a positive electrode current collector of a lithium ion battery, characterized in that: Its components and mass percentage contents are: Zr: 0.1-0.15wt.%, Cu: 0.1-0.2wt.%, and the balance is Al; The aluminum alloy foil has a room temperature tensile strength range of 214 to 245 MPa after heat treatment at 125°C for 5 hours, and a tensile strength range of 203.43 to 210 MPa at 50°C; in the ternary alloy system of Al-xCu-0.1Zr, x=0.1wt.%, 0.15wt.%, 0.2wt.%, as the Cu content increases, the corrosion potential of the aluminum-copper-zirconium alloy continues to shift positively, and the corrosion resistance of the alloy foil continues to increase.

2. The method for producing an aluminum alloy foil for a positive electrode current collector according to claim 1, wherein: Industrial aluminum ingots are used as raw materials, Al-50wt.% Cu master alloy and 10wt.% Zr master alloy are added according to the proportion after melting, and then smelted, homogenized, hot-rolled and cold-rolled to obtain the product.

3. The method according to claim 2, characterized in that: In the smelting, the alloy composition content is controlled to be Zr: 0.1-0.15wt.%, Cu: 0.1-0.2wt.%.

4. The method according to claim 2, characterized in that: The homogenization treatment is carried out at a temperature of 590-600° C. and a heat preservation time of 8-10 hours.

5. The method according to claim 2, characterized in that: The hot rolling is controlled to have a thickness of 3 mm.

6. The method according to claim 2, characterized in that: The cold rolling is performed to control the thickness to be 0.006-0.08 mm.

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