An aluminum foil for batteries, a preparation method thereof, and a preparation device

Abstract

The present invention provides an aluminum foil for batteries, a preparation method thereof, and a preparation device. The aluminum foil for batteries includes an aluminum foil, an Al4C3 layer, and a carbon coating layer connected in sequence from bottom to top; the thickness of the Al4C3 layer is 10 - 250 nm; the thickness of the carbon coating layer is 0.1 - 5 μm. This aluminum foil for batteries improves the bonding strength between the carbon coating and the aluminum foil and the stability of the current collector, improves the electrical conductivity and thermal conductivity of the carbon coating, reduces the impedance of the electrode sheet. At the same time, since there is no traditional drying process in the preparation process, the manufacturing cost is saved by 30 - 40%, and solvent materials such as NMP that are environmentally polluting are not used in the manufacturing process, which is environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of aluminum foils for batteries, and particularly relates to an aluminum foil for batteries, a preparation method thereof, and a preparation device thereof. Background Art

[0002] Aluminum foils can be used as the positive current collectors of lithium-ion secondary batteries, but there are the following problems: First, there is a contact impedance at the interface between the aluminum foil and the positive active material, resulting in excessive polarization and heavy heat generation during the charge and discharge process; Second, the adhesion between the aluminum foil and the active material and the conductive agent is weak. As the charge and discharge proceed, the volume of the active material continuously collides and contracts, and it is easy to peel off from the aluminum foil, accelerating the attenuation of the battery capacity and life; Finally, the electrolyte reacts with the aluminum foil, further accelerating the attenuation of the battery life.

[0003] To solve the above problems, a large number of modification studies on aluminum foils have been carried out in recent years, such as chemical etching, corona treatment, surface carbon coating, etc. Among them, the aluminum foil with surface carbon coating (abbreviated as carbon-coated aluminum foil) has been widely used because it reduces the contact impedance between the positive current collector and the active material, reduces polarization, and improves the charge and discharge performance and rate performance of the battery to a certain extent.

[0004] The carbon-coated aluminum foil is divided into two types: water-based and oil-based. That is, the dispersed carbon black, carbon nanotubes and other conductive carbon materials are coated on the aluminum foil. Since the dispersion of these conductive carbon materials in the solvent system is poor, it is difficult to evenly and finely coat the coating on the aluminum foil during the preparation of the carbon-coated aluminum foil, reducing the bonding strength between the coating and the aluminum foil and the stability of the current collector. The lithium-ion secondary battery made of such a carbon-coated aluminum foil is extremely prone to the phenomenon of cyclic diving during the cycle. Summary of the Invention

[0005] The present invention provides an aluminum foil for batteries, a preparation method thereof, and a preparation device thereof, which can improve the bonding strength between the carbon coating and the aluminum foil and the stability of the current collector, and at the same time improve the conductivity and thermal conductivity of the coating, and reduce the impedance of the electrode sheet.

[0006] Specifically, the present invention provides the following technical solutions:

[0007] An aluminum foil for batteries, comprising an aluminum foil, an Al 4 C 3 layer and a carbon coating layer connected in sequence from bottom to top;

[0008] The thickness of the Al 4 C 3 layer is 10-250 nm;

[0009] The thickness of the carbon coating layer is 0.1-5 μm.

[0010] During the R & D process of the manufacturing process of aluminum foil for batteries, the inventor found that after the corona treatment of the aluminum foil surface, it has a strong adsorption capacity and can adsorb the carbon formed by the high-temperature cracking of the carbon source to form a carbon coating layer with a uniform coating; then under the action of high-energy laser with a specific power, the aluminum foil reacts with the carbon atoms in the innermost layer of the carbon coating layer to generate a compound with a specific thickness of Al 4 C 3 compound. This layer of compound improves the bonding strength between the carbon coating layer and the aluminum foil. At the same time, under the action of this high-energy laser, part or all of the remaining carbon source atoms are graphitized, further improving the electrical conductivity and heat dissipation performance of the carbon layer.

[0011] Preferably, in the above-mentioned aluminum foil for batteries, the thickness of the aluminum foil is 3 - 30 μm.

[0012] Preferably, in the above-mentioned aluminum foil for batteries, the thickness of the carbon coating layer is 0.5 - 2.5 μm.

[0013] Preferably, in the above-mentioned aluminum foil for batteries, the carbon coating layer is a pyrolytic carbon material.

[0014] Preferably, in the above-mentioned aluminum foil for batteries, the graphitization degree of the pyrolytic carbon is 30 - 100%, more preferably 80 - 100%.

[0015] The present invention also provides a method for preparing the above-mentioned aluminum foil for batteries, including the following steps:

[0016] Provide an aluminum foil;

[0017] Perform high-voltage corona treatment on at least part of the surface of the aluminum foil;

[0018] Form a carbon coating layer on the surface of the aluminum foil after the high-voltage corona treatment;

[0019] Provide a laser light source and irradiate it on the carbon coating layer so that it penetrates the carbon coating layer to the contact surface between the carbon coating layer and the aluminum foil to form an Al 4 C 3 layer.

[0020] Preferably, in the above-mentioned preparation method, the thickness of the aluminum foil is 3 - 30 μm;

[0021] and / or, the thickness of the carbon coating layer is 0.1 - 5 μm, further preferably 0.5 - 2.5 μm;

[0022] and / or, the thickness of the Al 4 C 3 layer is 10 - 250 nm.

[0023] Preferably, in the above preparation method, the power of the high-voltage corona treatment is 20-30 KW, the voltage is 10-15 KV, the frequency is 15-20 KHZ, and the surface dyne value of the aluminum foil after the high-voltage corona treatment is 36-38 dyn.

[0024] Preferably, in the above preparation method, the material of the carbon coating layer is pyrolytic carbon, and the pyrolytic carbon is a carbon material obtained by pyrolyzing a carbon source;

[0025] More preferably, the carbon source is paraffin wax, and the pyrolysis temperature is 800-1000 °C;

[0026] Even more preferably, the grade of the paraffin wax is 52#, 54#, 56# or 60#.

[0027] Preferably, in the above preparation method, the power of the laser light source is 10-30 KW, and the wavelength is 375-1650 nm.

[0028] Preferably, after the laser light source irradiates, the graphitization degree of the carbon coating layer is 30-100%, and more preferably 80-100%.

[0029] Preferably, in the above preparation method, the aluminum foil irradiated by the laser light source is heat-treated. Preferably, the heat treatment is carried out at 100-150 °C for 1-10 minutes. Under such conditions, the heat treatment can effectively eliminate the stress generated during the irradiation of the laser light source.

[0030] The present invention also provides the application of the above aluminum foil for batteries or the aluminum foil for batteries prepared by the above preparation method on the positive current collector of a lithium-ion battery.

[0031] The present invention also provides a preparation device for the above aluminum foil for batteries, including an aluminum foil unwinder, a corona treatment unit, a carbon coating unit, a carbon curing unit and an aluminum foil winder arranged in sequence;

[0032] Among them, the corona treatment unit is used to perform high-voltage corona treatment on one side surface of the aluminum foil;

[0033] The carbon coating unit is used to form a carbon coating layer on the surface of the aluminum foil after the high-voltage corona treatment;

[0034] The carbon curing unit includes a laser generator, and the laser generator is used to provide a laser light source, which irradiates on the carbon coating layer so as to penetrate through the carbon coating layer to the contact surface between the carbon coating layer and the aluminum foil to form an Al 4 C 3 layer.

[0035] Preferably, in the above preparation device, the power of the laser generator is 10 - 30 KW, and the wavelength is 375 - 1650 nm.

[0036] Preferably, in the above preparation device, the carbon coating unit includes a paraffin cracking device, and the paraffin cracking device is used to provide paraffin cracking carbon for forming the carbon coating layer.

[0037] Preferably, in the above preparation device, the carbon curing unit further includes a cooling device, and the cooling device is used to closely adhere to one side surface of the aluminum foil that is not irradiated by the laser light source.

[0038] Beneficial effects achieved by the present invention:

[0039] The aluminum foil for batteries, its preparation method and preparation device provided by the present invention improve the bonding strength between the carbon coating and the aluminum foil and the stability of the current collector, improve the electrical conductivity and thermal conductivity of the carbon coating, reduce the impedance of the electrode sheet. At the same time, since there is no traditional drying process in the preparation process, the manufacturing cost is saved by 30 - 40%, and solvent materials such as NMP that are environmentally polluting are not used in the manufacturing process, which is environmentally friendly. Description of the Drawings

[0040] Figure 1 It is a schematic structural diagram of the preparation device for the aluminum foil for batteries of the present invention. Among them, 1 - unwinding reel, 2 - transfer shaft, 3 - corona treatment unit, 4 - corona device, 5 - carbon coating unit, 6 - air inlet, 7 - paraffin cracking device, 8 - air outlet, 9 - carbon curing unit, 10 - cooling device, 11 - laser generator, 12 - heat treatment device, 13 - winding reel. Detailed Embodiments

[0041] The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications.

[0042] In the following embodiments, for those instruments and the like whose manufacturers are not specified, they are all conventional products that can be obtained through regular channels. The methods are all conventional methods unless otherwise specified, and the raw materials used can all be obtained from public commercial channels unless otherwise specified.

[0043] Embodiment 1

[0044] Embodiment 1 provides a device for preparing aluminum foil for batteries (partially referring to Figure 1 ), including an unwinding reel 1, a transfer shaft 2, a corona treatment unit 3, a carbon coating unit 5, a carbon curing unit 9, a heat treatment device 12, and a winding reel 13 arranged in sequence;

[0045] The corona treatment unit 3 includes a corona device 4;

[0046] The carbon coating unit 5 includes a paraffin cracking device 7, an air inlet 6, and an air outlet 8;

[0047] The carbon curing unit 9 includes a laser generator 11 and a cooling device 10.

[0048] Example 2

[0049] A method for preparing aluminum foil for batteries using the device described in Example 1 specifically includes the following steps:

[0050] (1) Unwinding: Unwind the 12-μm-thick aluminum foil through the unwinding shaft 1, and then transfer it to the corona treatment unit 3 by the transfer shaft 2, with a tape running speed of 100 m / s;

[0051] (2) Corona treatment: Perform high-voltage corona treatment on the lower surface of the aluminum foil through the corona device 4. The power of the corona device 4 is 25 KW, the voltage is 12 KV, and the frequency is 20 KHZ. After the high-voltage corona treatment, the surface dyne value of the aluminum foil reaches 38 dyn;

[0052] (3) Carbon coating: Transfer the corona-treated aluminum foil to the carbon coating unit 5, pass it through the paraffin cracking device 7, and adsorb a 1-μm-thick pyrolytic carbon layer on the lower surface of the aluminum foil to form a carbon coating layer; in the carbon coating unit 5, the flow rate of the protective gas is controlled at 2 m 3 / min, enter through the air inlet 6, and discharge through the air outlet 8; the paraffin grade used in the paraffin cracking device 7 is 52#, and the cracking temperature is controlled at 920 °C;

[0053] (4) Carbon curing: Transfer the carbon-coated aluminum foil to the carbon curing unit 9, pass it through the laser generator 11, and irradiate the lower surface of the aluminum foil with a laser light source with a power of 15 KW and a wavelength of 375 nm so that it penetrates the carbon coating layer to the contact surface between the carbon coating layer and the aluminum foil to form a 60-90-nm-thick Al 4 C 3 layer to increase the bonding force between the carbon layer and the aluminum foil; during the irradiation of the laser light source, the upper surface of the aluminum foil is closely attached to the cooling device 10, and the temperature of the cooling water in the cooling device 10 is controlled at 0-7 °C to prevent deformation and other damages caused by overheating during the irradiation of the laser light source; after the irradiation of the laser light source, the graphitization degree of the pyrolytic carbon in the carbon coating layer is 83%;

[0054] (5) Heat treatment: Transfer the carbon-cured aluminum foil to the heat treatment device 12 and perform heat treatment at 120 °C for 6 min to eliminate the stress generated during the above processing;

[0055] (6) Rewinding: Rewind on the rewinding shaft 13 to obtain the finished aluminum foil for batteries.

[0056] The aluminum foil for batteries prepared in this example includes, from bottom to top, an aluminum foil, Al 4C 3 layer and carbon coating layer;

[0057] Among them, the thickness of the aluminum foil is 12 μm; the Al 4 C 3 layer has a thickness of 60 - 90 nm; the carbon coating layer has a thickness of 1 μm, the carbon coating layer is a pyrolytic carbon material, and the graphitization degree of the pyrolytic carbon is 83%.

[0058] Example 3

[0059] A method for preparing aluminum foil for batteries using the device described in Example 1 specifically includes the following steps:

[0060] (1) Unwinding: Unwind the 12-μm-thick aluminum foil through the unwind shaft 1, and then transfer it to the corona treatment unit 3 by the transfer shaft 2, with a tape running speed of 90 m / s;

[0061] (2) Corona treatment: Perform high-voltage corona treatment on the lower surface of the aluminum foil through the corona device 4. The power of the corona device 4 is 25 KW, the voltage is 12 KV, the frequency is 20 KHZ, and the surface dyne value of the aluminum foil reaches 38 dyn after the high-voltage corona treatment;

[0062] (3) Carbon coating: Transfer the corona-treated aluminum foil to the carbon coating unit 5. After passing through the paraffin cracking device 7, a 1-μm-thick layer of pyrolytic carbon is adsorbed on the lower surface of the aluminum foil to form a carbon coating layer; in the carbon coating unit 5, the flow rate of the protective gas is controlled at 1.75 m 3 / min, entering from the inlet 6 and discharging from the outlet 8; the paraffin grade used in the paraffin cracking device 7 is 52#, and the cracking temperature is controlled at 920 °C;

[0063] (4) Carbon curing: Transfer the carbon-coated aluminum foil to the carbon curing unit 9. The laser light source with a power of 20 KW and a wavelength of 450 nm irradiates the lower surface of the aluminum foil through the carbon coating layer to the contact surface between the carbon coating layer and the aluminum foil to form a 50 - 80-nm-thick Al 4 C 3 layer to increase the bonding force between the carbon layer and the aluminum foil; during the irradiation of the laser light source, the upper surface of the aluminum foil is closely attached to the cooling device 10, and the temperature of the cooling water in the cooling device 10 is controlled at 0 - 7 °C to prevent deformation and other damages caused by overheating during the irradiation of the laser light source; after the irradiation of the laser light source, the graphitization degree of the pyrolytic carbon in the carbon coating layer is 95%;

[0064] (5) Heat treatment: Transfer the carbon-cured aluminum foil to the heat treatment device 12 and perform heat treatment at 120 °C for 6 min to eliminate the stress generated during the above processing;

[0065] (6) Rewinding: Rewind at the rewinding shaft 13 to obtain the finished aluminum foil for batteries.

[0066] The aluminum foil for battery prepared in this embodiment includes an aluminum foil, an Al 4 C 3 layer and a carbon coating layer, which are connected in sequence from bottom to top;

[0067] Among them, the thickness of the aluminum foil is 12 μm; the thickness of the Al 4 C 3 layer is 50 - 80 nm; the thickness of the carbon coating layer is 1 μm, the carbon coating layer is a pyrolytic carbon material, and the graphitization degree of the pyrolytic carbon is 95%.

[0068] Example 4

[0069] A method for preparing aluminum foil for battery using the device described in Example 1 specifically includes the following steps:

[0070] (1) Unwinding: Unwind the 12-μm-thick aluminum foil through the unwinding shaft 1, and then transfer it to the corona treatment unit 3 by the transfer shaft 2, with a tape running speed of 50 m / s;

[0071] (2) Corona treatment: Perform high-voltage corona treatment on the lower surface of the aluminum foil through the corona device 4. The power of the corona device 4 is 25 KW, the voltage is 12 KV, the frequency is 20 KHZ, and the surface dyne value of the aluminum foil reaches 38 dyn after the high-voltage corona treatment;

[0072] (3) Carbon coating: Transfer the aluminum foil after corona treatment to the carbon coating unit 5. Pass through the paraffin cracking device 7, and a 2-μm-thick pyrolytic carbon layer is adsorbed on the lower surface of the aluminum foil to form a carbon coating layer; in the carbon coating unit 5, the flow rate of the protective gas is controlled at 2 m 3 / min, enter from the inlet 6 and discharge from the outlet 8; the paraffin grade used in the paraffin cracking device 7 is 52#, and the cracking temperature is controlled at 920 °C;

[0073] (4) Carbon curing: Transfer the aluminum foil after carbon coating to the carbon curing unit 9. Pass through the laser generator 11, and a laser light source with a power of 15 KW and a wavelength of 532 nm irradiates the lower surface of the aluminum foil so that it penetrates the carbon coating layer to the contact surface between the carbon coating layer and the aluminum foil to form a 40 - 60-nm-thick Al 4 C 3 layer to increase the bonding force between the carbon layer and the aluminum foil; during the irradiation of the laser light source, the upper surface of the aluminum foil is closely attached to the cooling device 10, and the temperature of the cooling water in the cooling device 10 is controlled at 0 - 7 °C to prevent deformation and other damages caused by overheating during the irradiation of the laser light source; after the irradiation of the laser light source, the graphitization degree of the pyrolytic carbon in the carbon coating layer is 83%;

[0074] (5) Heat treatment: Transfer the aluminum foil after carbon curing to the heat treatment device 12, and perform heat treatment at 120 °C for 8 min to eliminate the stress generated during the above processing;

[0075] (6) Rewinding: The finished battery aluminum foil is obtained by rewinding on the rewinding shaft 13.

[0076] The aluminum foil for batteries prepared in this embodiment includes an aluminum foil, an Al 4 C 3 layer and a carbon coating layer, which are connected in sequence from bottom to top;

[0077] Among them, the thickness of the aluminum foil is 12 μm; the thickness of the Al 4 C 3 layer is 40 - 60 nm; the thickness of the carbon coating layer is 2 μm, the carbon coating layer is a pyrolytic carbon material, and the graphitization degree of the pyrolytic carbon is 83%.

[0078] Test Example

[0079] The lithium iron phosphate positive electrode slurry was respectively coated on the aluminum foil for batteries prepared in Examples 2 - 4 and the ordinary carbon-coated aluminum foil purchased on the market (12-micron 1060 carbon-coated aluminum foil from Guangzhou Nano New Material Technology Co., Ltd.), dried at 95°C, and after rolling, the positive electrode sheet was obtained. After further slitting and winding, a 26650 cylindrical lithium-ion secondary battery with a capacity of 4 Ah was obtained. By mass fraction, the ratio of the positive electrode sheet is: 94% lithium iron phosphate, 3% Super P, 3% PVDF; the compaction density is 2.45 g / cm 3 .

[0080] The performance of the above-prepared positive electrode sheet and 26650 cylindrical lithium-ion secondary battery was tested, and the results are shown in Table 1 below.

[0081] Table 1

[0082] Pole piece adhesion force (mN / mm) Pole piece impedance (Ω) Battery internal resistance (mΩ) Example 1 505 3.2 10.8 Example 2 553 2.7 10.2 Example 3 513 3.1 10.6 Ordinary carbon-coated aluminum foil 439 3.9 12.1

[0083] Among them,

[0084] Test method for the adhesion of the electrode sheet: Cut the rolled electrode sheet into a size of 200 * 20 mm, stick a high-temperature adhesive tape of the same size on the surface of the electrode sheet, and use a universal testing machine to peel it at a speed of 1 mm / s. The minimum value during the peeling process is the adhesion of the electrode sheet.

[0085] Test method for the impedance of the electrode sheet: Cut the rolled electrode sheet into a square size of 4 cm * 8 cm, place the cut electrode sheet between the probes of the BER2200 tester, apply a pressure of 5 MPa, and read the value.

[0086] Test method for the internal resistance of the battery: Use an RJ3563 internal resistance tester to test the internal resistance of the battery under the condition of 1000 HZ.

[0087] Although the present invention has been described in detail above by way of general description, specific embodiments and experiments, modifications or improvements can be made thereto based on the present invention, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A preparation method of aluminum foil for batteries, characterized in that, it comprises the following steps: providing an aluminum foil; performing high-voltage corona treatment on at least part of the surface of the aluminum foil; forming a carbon coating layer on the surface of the aluminum foil after the high-voltage corona treatment; A laser light source is provided to irradiate the carbon coating layer so that it penetrates through the carbon coating layer to the contact surface between the carbon coating layer and the aluminum foil, thereby forming an Al 4 C 3 layer; the thickness of the carbon coating layer is 0.1 - 5 μm; The Al 4 C 3 layer has a thickness of 10 to 250 nm; the power of the laser light source is 10 - 30 KW, and the wavelength is 375 - 1650 nm.

2. The preparation method of aluminum foil for batteries according to claim 1, characterized in that, the thickness of the aluminum foil is 3 - 30 μm.

3. The preparation method of aluminum foil for batteries according to claim 1, characterized in that, the thickness of the carbon coating layer is 0.5 - 2.5 μm.

4. The preparation method of aluminum foil for batteries according to any one of claims 1 - 3, characterized in that, the material of the carbon coating layer is pyrolytic carbon, and the pyrolytic carbon is a carbon material obtained by pyrolyzing a carbon source.

5. The preparation method of aluminum foil for batteries according to claim 4, characterized in that, the carbon source is paraffin wax, and the pyrolysis temperature is 800 - 1000 °C.

6. The preparation method of aluminum foil for batteries according to claim 5, characterized in that, performing heat treatment on the aluminum foil irradiated by the laser light source.

7. The preparation method of aluminum foil for batteries according to claim 6, characterized in that, the heat treatment is carried out at 100 - 150 °C for 1 - 10 minutes.

8. The aluminum foil for batteries produced by the preparation method according to any one of claims 1 - 7, characterized in that, including an aluminum foil, an Al 4 C 3 layer and a carbon coating layer connected in sequence from bottom to top; The Al 4 C 3 layer has a thickness of 10 to 250 nm; the thickness of the carbon coating layer is 0.1 - 5 μm.

9. The aluminum foil for batteries according to claim 8, characterized in that, the thickness of the aluminum foil is 3 - 30 μm.

10. The aluminum foil for batteries according to claim 9, characterized in that, the thickness of the carbon coating layer is 0.5 - 2.5 μm.

11. The aluminum foil for batteries according to any one of claims 8 - 10, characterized in that, the carbon coating layer is a pyrolytic carbon material.

12. The aluminum foil for batteries according to claim 11, characterized in that, the graphitization degree of the pyrolytic carbon is 30 - 100%.

13. The aluminum foil for batteries according to claim 12, characterized in that, the graphitization degree of the pyrolytic carbon is 80 - 100%.

14. A preparation device for performing the preparation method according to any one of claims 1 - 7, characterized in that, it comprises an aluminum foil unwinder, a corona treatment unit, a carbon coating unit, a carbon curing unit and an aluminum foil winder arranged in sequence, wherein the carbon curing unit includes a laser generator.

15. The preparation device according to claim 14, characterized in that, the power of the laser generator is 10 - 30 KW, and the wavelength is 375 - 1650 nm.

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