Production method of ultrathin 4.5 mu m battery aluminum foil and application of ultrathin 4.5 mu m battery aluminum foil to composite current collector

Abstract

The invention belongs to the technical field of non-ferrous metal processing, and relates to a production method of 4.5 [mu] m ultrathin battery aluminum foil, which comprises the following steps: adopting a 1235D alloy blank, and carrying out five-pass rolling (final-pass double rolling + 50% reduction rate) and tempering at 120 DEG C for 15 hours at a 9 [mu] m stage; the rolling oil contains mao19 base oil, 6%-8% of MARK625HB and 1%-3% of MARK625W3; and roller convexity / roughness hierarchical control is carried out. The tensile strength of the prepared aluminum foil is larger than or equal to 180 MPa, pinholes are smaller than or equal to 1000 / m < 2 >, and the wetting tension is larger than or equal to 32 dyn. According to the invention, the prepared 4.5 [mu] m ultrathin battery aluminum foil is compounded with a high polymer material to form a composite current collector with an aluminum foil-high polymer material-aluminum foil structure. According to the method, the rolling limit is broken through, and mass production of the ultra-strong and ultra-thin 4.5-micron battery aluminum foil is achieved through five-pass and double rolling; the performance reaches the standard, annealing-free compounding is achieved, and a surface oil film directly meets the PE / PET thermal compounding requirement; and safety verification: the anti-puncture qualified rate after compounding is 100%. The problems that the ultrathin aluminum foil is broken during rolling, pin holes exceed the standard and annealing is needed before compositing are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of non-ferrous metal processing, and relates to an aluminum foil, in particular to a production method of 4.5 μm ultra-thin battery aluminum foil and application of the same to a composite current collector. BACKGROUND

[0002] With the national new energy strategy layout and development, new energy battery technology has developed unprecedentedly. Although the energy density is improved with the thinning of the aluminum foil thickness, the safety problem of battery anti-penetration short circuit brings serious challenges.

[0003] To solve the safety problem, in the existing technical solutions, there are two solutions. One is to adopt a vacuum aluminum plating process on both sides of the insulating polymer material, which needs to be repeatedly vacuum plated for several times to achieve a 1 μm aluminum thickness layer. The process is complex, the yield is low, and the aluminum layer organization is not dense and easy to peel off, and the welding property with the tab is poor. The other solution is to use 4.5 μm aluminum foil + 2 μm polymer material + 4.5 μm aluminum foil composite. The polymer material in it serves as both an adhesive for the two layers of aluminum foil and an anti-penetration insulating material. This solution basically solves the problems existing in the aluminum plating process, but requires thin and uniform aluminum foil with few pinholes, high strength and elongation, and the ability to be compounded without annealing treatment.

[0004] Battery aluminum foil requires good electrical conductivity, so the raw material is generally pure aluminum (i.e. 1 series) for production. However, aluminum foil with too high purity has low strength, which cannot meet the requirements of the battery aluminum foil slurry coating and compaction process. Therefore, the general production of battery aluminum foil uses 1235, 1060, 1145, 1100 alloys in the 1 series plus some trace elements to adjust the performance, and the strength and elongation are improved through work hardening. The thickness of the commonly used power battery aluminum foil is generally 12 μm-15 μm. Since it is coated with carbon on both sides, it needs to have the same surface activity, so single continuous rolling is generally used to meet the surface quality requirements. However, the production of 4.5 μm ultra-thin aluminum foil has exceeded the rolling thickness limit of single rolling, and two double rolling must be used to achieve such thickness.

[0005] The new energy battery has the demand of high energy density and high safety, the composite current collector takes the polymer material as the base film, and is plated with copper or aluminum on both sides to form a "sandwich" structure, such as "aluminum foil-polymer material-aluminum foil" structure, which becomes the focus of the industry. The traditional vacuum aluminum plating process causes peeling (bonding force ≤1 N / cm) due to weak aluminum layer bonding force, and the welding interface resistance is >10 mΩ, which has the problems of easy peeling of the aluminum layer and poor weldability; and the composite current collector needs to use ultra-hard state rolling, and when the thickness is ultra-thin, such as 4.5 μm, the crystal boundary stress accumulates too much in the double-rolling process, which causes the pinhole to exceed the standard (>5000 / m²) and the elongation to deteriorate (<0.5%). The prior art cannot meet the following requirements at the same time: ultra-strong mechanical properties, tensile strength ≥180 MPa, elongation ≥1%; ultra-thin thickness: 4.5 μm±3%; high surface properties, wetting tension ≥32 dyn, meet the requirements of no annealing treatment before compounding; few defect control, pinhole ≤1000 / m 2 , to avoid battery short circuit.

[0006] In summary, the prior art cannot meet the key requirements of the 4.5 μm ultra-thin battery aluminum foil for the composite current collector, such as rolling feasibility, excellent mechanical properties, low pinhole defects, high surface wetting tension, and no annealing treatment for compounding, and a production method of the aluminum foil suitable for such high-strength, ultra-thin double-rolling must be researched from the aspects of the blank, rolling process, rolling oil lubrication, and roller parameters. SUMMARY

[0007] In view of the problems of the existing technology, such as the increase of pinholes, the decrease of strength, and the insufficient surface wetting tension of the ultra-thin 4.5 μm aluminum foil in the double-rolling process, and the requirement of no annealing treatment to meet the compounding process, the purpose of the present application is to disclose a production method of an ultra-thin 4.5 μm battery aluminum foil for a composite current collector.

[0008] TECHNICAL SOLUTION

[0009] A production method of an ultra-thin 4.5 μm battery aluminum foil, comprising: alloy selection, five-pass rolling, intermediate annealing, special rolling oil preparation, and roller parameter control, wherein,

[0010] The alloy selection selects a 1235D alloy aluminum foil blank with a thickness of 220 μm;

[0011] The five-pass rolling comprises: first pass, thickness from 220 μm→98 μm, reduction ratio 55.4%; second pass, thickness from 98 μm→42 μm, reduction ratio 57.1%; third pass, thickness from 42 μm→19 μm, reduction ratio 54.7%; fourth pass, thickness from 19 μm→9 μm, reduction ratio 52.6%; and fifth pass double-rolling, the aluminum foil with a thickness of 9 μm is double-rolled to a thickness of 4.5 μm per sheet, and the pass reduction ratio is ≤50% to avoid plate shape distortion;

[0012] The intermediate tempering is carried out at 120 DEG C x 15h after the fourth pass, and the aluminum foil thickness is 9 mu m, so as to eliminate the internal stress in the grain part;

[0013] The special rolling oil is prepared by adding 6-8% of MARK625HB and 1-3% of MARK625W3 in the mao19 special oil as the base oil according to the mass ratio; preferably 7% of MARK625HB and 2% of MARK625W3.

[0014] The roller parameter control is that the support roller has a convexity of 60 mu m and a roughness Ra of 0.6; the rough rolling roller has a convexity of 40 mu m and a roughness Ra of 0.23; the medium rolling roller has a convexity of 60 mu m and a roughness Ra of 0.13; and the finishing rolling roller has a convexity of 60 mu m and a roughness Ra of 0.09.

[0015] In the preferred disclosure of the application, the first-pass rolling process is that the tension is 40-50 N / mm 2 at the inlet and 40-60 N / mm 2 at the outlet; the oil temperature is 35-45 DEG C, the oil pressure is 6-7 Bar; the rolling force is 1700+ / -200 kN, and the plate shape value is 10 N / mm 2 .

[0016] In the preferred disclosure of the application, the second-pass rolling process is that the tension is 40-50 N / mm 2 at the inlet and 40-60 N / mm 2 at the outlet; the oil temperature is 35-45 DEG C, the oil pressure is 6-7 Bar; the rolling force is 1700+ / -200 kN, and the plate shape value is 10 N / mm 2 .

[0017] In the preferred disclosure of the application, the third-pass rolling process is that the tension is 45-55 N / mm 2 at the inlet and 40-50 N / mm 2 at the outlet; the oil temperature is 40-45 DEG C, the oil pressure is 6-7 Bar; the rolling force is 1800+ / -100 kN, and the plate shape value is 10 N / mm 2 .

[0018] In the preferred disclosure of the application, the fourth-pass rolling process is that the tension is 50-70 N / mm 2 at the inlet and 35-45 N / mm 2 at the outlet; the oil temperature is 35-40 DEG C, the oil pressure is 6 Bar; the rolling force is 1800+ / -100 kN, and the plate shape value is 5-7 N / mm 2 .

[0019] In the preferred disclosure of the application, the fifth-pass rolling process is that the final rolling tension is 35-40 N / mm 2 at the inlet and 30-40 N / mm2 ; oil temperature 35-40℃, oil pressure 6Bar; rolling force 1800±100kN, plate shape value 5-7N / mm 2 .

[0020] The ultra-thin 4.5-micron battery aluminum foil prepared by the method has the performance indexes of tensile strength ≥180MPa, elongation rate ≥1%, and pinholes ≤1000 / m 2 , and wetting tension ≥32dyn.

[0021] A second object of the application is to apply the prepared ultra-thin 4.5-micron battery aluminum foil to a composite current collector of a power battery.

[0022] In a preferred embodiment of the application, the composite current collector is formed by compounding the ultra-thin 4.5-micron battery aluminum foil with a polymer material to form an "aluminum foil-polymer material-aluminum foil" structure.

[0023] According to the experimental data in Table 1, considering the need to roll the ultra-hard material to the limit thickness of 4.5 microns, the commonly used 1235D alloy with slightly lower performance is selected, the tensile strength is 200MPa@9microns, the trace element enhances the rolling ductility, which is better than the limit processing performance of 1060D / 1145D / 1100D alloy.

[0024] Table 1. Performance table of various battery foil alloys at 9-micron thickness

[0025]

[0026] In order to reduce the internal stress of the grains in the 9-micron-thick state, the 1235D alloy with a slightly lower tensile strength of 200MPa is selected, the thickness is 9 microns, and the internal stress of the grains is eliminated by tempering at 120℃×15h. After tempering, the tensile strength of the aluminum foil is reduced from about 200MPa to about 180MPa, and the elongation rate is maintained at about 3.0%, which ensures that the subsequent double-rolling process does not break and is rolled again. After testing, the internal stress of the grains is reduced by 40% (determined by XRD), and the tensile strength is reduced from 200MPa to 180MPa, which still meets the requirement of ≥180MPa.

[0027] MARK625HB and MARK625W3 are mixed and added, and the addition ratio is 7% and 2% respectively according to the mass percentage, and after being prepared with mao19 special oil, the various indexes of the oil product are as shown in Table 2.

[0028] Table 2. Oil product preparation technical index table

[0029]

[0030] Base oil is mao19 special oil (heat resistance, flowability is good); additives: MARK625HB (7%): enhance oil film strength; MARK625W3 (2%): improve surface wetting tension; effect: oil film strength ≥ 40, wetting tension reaches 33 dyn (> 32 dyn is required).

[0031] Beneficial effects

[0032] The present application breaks the rolling limit: 4.5 μm mass production is realized by five passes + double rolling; performance meets the standard: tensile strength 192.3 MPa, elongation 1.3%; pinhole ≤ 1000 / m 2 , wetting tension 33 dyn; annealing-free compounding: the surface oil film directly meets the PE / PET thermal compounding requirements; safety verification: the qualified rate of puncture test after compounding is 100%. The prepared battery foil can be directly compounded with high molecular materials. The present application solves the problems of rolling fracture, pinhole exceeding the standard and the need for annealing before compounding of ultra-thin aluminum foil. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 . Temperature-time curve diagram of tempering process (horizontal axis is time / h, vertical axis is temperature / ℃), showing the process of keeping 120℃ constant for 15h. DETAILED DESCRIPTION

[0034] The present application will be described in detail below in combination with examples, so that those skilled in the art can better understand the present application, but the present application is not limited to the following examples.

[0035] Example 1

[0036] Blank: 1235D alloy, thickness 220 μm;

[0037] Rolling: rolled to 9 μm according to five pass parameters → tempering (120℃×15h) → double rolling to 4.5 μm;

[0038] Oil: mao19 special base oil + 7% MARK625HB + 2% MARK625W3.

[0039] The detection results are as follows:

[0040] Tensile strength: 192.3 MPa, elongation: 1.3%;

[0041] Pinhole: 850 / m 2 , wetting tension: 33 dyn;

[0042] Compounding test: the puncture test pass rate after thermal compounding with PET is 100%.

[0043] The mao19 special oil, MARK625HB and MARK625W3 are all purchased from Shijiazhuang Xintai Special Oil Co., Ltd.

[0044] The alloy 1235D battery foil with a thickness of 4.5 μm is successfully produced by rolling with the above-mentioned oil, additive, roller and rolling process parameters, and the tensile strength is 192.3 MPa, the elongation is 1.3%, the surface dyne value is 33 dyn, and the pinhole is 850 / m 2 , and all indexes fully meet the expected requirements. The sample is sent to the laboratory, and after oil removal treatment, the hot composite test with insulating polymer material is carried out, the anti-puncture effect reaches 100%, and the safety requirement of new energy power battery is met.

[0045] Example 2

[0046] The process is the same as that in Example 1, wherein the rolling speed is adjusted: the fifth pass speed is reduced to 450 m / min.

[0047] The detection result is that the pinhole is reduced to 700 / m2, and the elongation is 1.1%

[0048] Compared with Example 1, the pinhole density is reduced, and the elongation is slightly reduced.

[0049] Example 3

[0050] The process is the same as that in Example 1, wherein the additive ratio is adjusted: 6.5% MARK625HB + 2.5% MARK625W3.

[0051] The detection result is that the wetting tension is 34 dyn, and the tensile strength is 195 MPa.

[0052] Compared with Example 1, the wetting tension is improved, and the tensile strength is slightly improved.

[0053] The above-mentioned examples are only specific embodiments of the present application, and do not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for producing an ultra-thin 4.5 μm battery aluminum foil, comprising: Alloy selection, five-pass rolling, intermediate tempering, special rolling oil preparation and roll parameter control, characterized by: The alloy selection is to use 1235D alloy aluminum foil blank with a thickness of 220 μm; The five-pass rolling process includes: a first pass, a thickness reduction from 220 μm to 98 μm, and a reduction rate of 55.4%; a second pass, a thickness reduction from 98 μm to 42 μm, and a reduction rate of 57.1%; a third pass, a thickness reduction from 42 μm to 19 μm, and a reduction rate of 54.7%; a fourth pass, a thickness reduction from 19 μm to 9 μm, and a reduction rate of 52.6%; and a fifth pass, a double-rolling process, in which the aluminum foil having a thickness of 9 μm is double-rolled to a thickness of 4.5 μm per sheet, with a pass reduction rate of ≤50%, to avoid plate shape distortion; The intermediate tempering, after the fourth pass, when the thickness of the aluminum foil is 9 μm, is performed at 120° C. for 15 h to eliminate some of the stress within the grains; The special rolling oil is prepared with the base oil being mao19 special oil, and 6-8% of MARK625HB and 1-3% of MARK625W3 are added according to the mass ratio; The roller parameters are controlled as follows: the support roller has a convexity of 60 μm and a roughness of Ra0.6; the roughing roller has a convexity of 40 μm and a roughness of Ra0.23; the intermediate roller has a convexity of 60 μm and a roughness of Ra0.13; and the finishing roller has a convexity of 60 μm and a roughness of Ra0.

09.

2. The method for producing an ultra-thin 4.5 μm battery aluminum foil according to claim 1, characterized in that: The special rolling oil is prepared by using mao19 special oil as base oil, and adding 7% of MARK625HB and 2% of MARK625W3 according to the mass ratio.

3. The method for producing an ultra-thin 4.5 μm battery aluminum foil according to claim 1, characterized in that: The first rolling process is: tension, entrance 40-50N / mm 2 , outlet 40-60N / mm 2 Oil temperature 35-45℃, oil pressure 6-7Bar; rolling force 1700±200kN, flatness value 10N / mm 2 .

4. The method for producing an ultra-thin 4.5 μm battery aluminum foil according to claim 1, characterized in that: The second rolling process is: tension, entrance 40-50N / mm 2 , outlet 40-60N / mm 2 Oil temperature 35-45℃, oil pressure 6-7Bar; rolling force 1700±200kN, flatness value 10N / mm 2 .

5. The method for producing an ultra-thin 4.5 μm battery aluminum foil according to claim 1, characterized in that: The third rolling process is: tension, entrance 45-55N / mm 2 , outlet 40-50N / mm 2 Oil temperature 40-45°C, oil pressure 6-7 Bar; rolling force 1800±100kN, flatness value 10N / mm 2 .

6. The method for producing an ultra-thin 4.5 μm battery aluminum foil according to claim 1, characterized in that: The fourth rolling process is: tension, entrance 50-70N / mm 2 , outlet 35-45N / mm 2 Oil temperature 35-40℃, oil pressure 6Bar; rolling force 1800±100kN, flatness value 5-7N / mm 2 .

7. The method for producing an ultra-thin 4.5 μm battery aluminum foil according to claim 1, characterized in that: The fifth rolling process is: final rolling tension, entrance 35-40N / mm 2 , outlet 30-40N / mm 2 Oil temperature 35-40℃, oil pressure 6Bar; rolling force 1800±100kN, flatness value 5-7N / mm 2 .

8. An ultra-thin 4.5 μm battery aluminum foil produced according to the method of any one of claims 1 to 7.

9. The ultra-thin 4.5 μm battery aluminum foil according to claim 8, characterized in that: Its performance indicators are tensile strength ≥180MPa, elongation ≥1%, pinholes ≤1000 / m 2 , wetting tension ≥32dyn.

10. A composite current collector, characterized in that: The ultra-thin 4.5 μm battery aluminum foil as claimed in claim 8 or 9 is compounded with a polymer material to form an "aluminum foil-polymer material-aluminum foil" structure.

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