Preparation method of carbon-coated aluminum foil, carbon-coated aluminum foil and lithium ion battery

Abstract

The invention relates to a preparation method of a carbon-coated aluminum foil, and belongs to the technical field of lithium ion battery material preparation. The method comprises the following steps: vertically hanging an aluminum foil coil between an unwinding mechanism and a winding mechanism, and naturally unfolding the aluminum foil coil under the action of gravity; at least one electrostatic spinning liquid supply device is arranged on each of the two sides of the aluminum foil, and the distance between a spinning nozzle and the aluminum foil is 5-30 cm; under the action of positive and negative high-voltage electric fields, a carbon-coated spinning solution containing a conductive agent, a binder and a solvent is sprayed on the two surfaces of the aluminum foil to form a double-surface carbon-coated layer. Wherein the spinning nozzle is connected with a positive high-voltage power supply of 5-50kV, and the winding machine or the unwinding machine is connected with a negative high-voltage power supply of-20-0kV; the flow velocity of the spinning solution is 0.05-5 mL / h, and the winding speed and the unwinding speed are both 0.01-2 m / min; the mass ratio of the conductive agent to the binder is (1-100): 1, and the solid content of the spinning solution is 5-20wt%. The carbon-coated aluminum foil prepared by the invention can be applied to lithium ion batteries, and has the advantages of simple process, uniform coating and high production efficiency.

Description

Technical Field

[0001] The present invention relates to the field of battery material preparation, and specifically to a method for preparing carbon-coated aluminum foil. More specifically, it relates to a method for simultaneously coating conductive carbon layers on both sides of aluminum foil using electrostatic spinning technology, as well as the carbon-coated aluminum foil prepared by the method and its application in lithium-ion batteries. Background Art

[0002] Carbon-coated aluminum foil is widely used as the negative electrode current collector in lithium-ion batteries. The carbon layer attached to its surface helps improve the conductivity of the electrode and the bonding strength between the electrodes. Traditional methods for preparing carbon-coated aluminum foil mainly include roller coating and blade coating. These methods rely on mechanical contact to apply carbon slurry and have achieved a certain degree of scale in actual production. For example, existing patent CN107654321A discloses a carbon coating method based on a roller coating device. By controlling the viscosity of the carbon slurry and the gap between the blade and the blade, a single-sided carbon layer is applied, which has a certain degree of continuity and practicality.

[0003] However, there are still many problems with the above-mentioned roller coating or scraping coating methods. On the one hand, the coating device (such as coating roller, scraper) has high precision requirements, and a slight deviation can easily cause uneven thickness or scratches of the carbon layer on the surface of the aluminum foil; on the other hand, this type of contact operation has hidden dangers such as waste of carbon slurry and unstable adhesion of the carbon layer, and is not suitable for high-consistency process requirements such as flexible adjustment and double-sided simultaneous coating. In order to solve the above problems, some studies have attempted to use electrospinning technology for non-contact carbon coating. For example, patent CN115117365A proposes an electrostatic spinning device, which deposits carbon slurry on the surface of the current collector in a direction through a high-voltage electrostatic nozzle, and has certain non-contact and high uniformity characteristics.

[0004] Although electrospinning has shown excellent potential in carbon material deposition, existing solutions mostly focus on single-sided laying or horizontal arrangement, which still has obvious deficiencies in structural integration, carbon layer consistency and double-sided collaborative spraying. As described in CN115117365A, the structure still relies on a fixed single-sided spinning unit, which cannot achieve efficient double-sided synchronous coating; the spinning distance and electric field polarity layout are not clearly optimized. Therefore, it is urgent to propose a double-sided synchronous electrostatic spraying method that is suitable for vertically unfolded aluminum foil, has a symmetrical structure, and has high spinning stability, so as to improve production efficiency, carbon layer uniformity and carbon layer adhesion performance, and meet the process requirements of the next generation of high-performance battery manufacturing. Summary of the Invention

[0005] In order to solve the technical problems existing in the existing carbon-coated aluminum foil preparation method, such as the roller coating method has high requirements for the coating roller, the scraper easily causes scratches on the aluminum foil, it is impossible to coat both sides of the aluminum foil at the same time, resulting in low production efficiency, the high water content of the conductive slurry requires high-temperature drying, resulting in high energy consumption and large space occupation of the equipment, and the complex and cumbersome process of the existing electrospinning method, the present invention provides a method for preparing carbon-coated aluminum foil.

[0006] The technical solution adopted by the present invention to solve the technical problem is: to provide a method for preparing carbon-coated aluminum foil, comprising the following steps:

[0007] a) Place the aluminum foil roll vertically on the unwinder, fix the head end of the aluminum foil on the winder, and place the aluminum foil perpendicular to the ground;

[0008] b) placing at least one electrospinning solution supply device containing a carbon-coated spinning solution on each side of the aluminum foil;

[0009] c) the spinning nozzle of the electrospinning liquid supply device is connected to a positive high-voltage power supply, wherein the voltage of the positive high-voltage power supply is 20-100 kV;

[0010] d) The winder or unwinder is connected to a negative high-voltage power supply, wherein the voltage of the negative high-voltage power supply is -20 to 0 kV;

[0011] e) Under the action of positive and negative high voltage electric fields, carbon spinning solution is sprayed onto both sides of the aluminum foil to form a double-sided carbon coating layer.

[0012] Preferably, the flow rate of the carbon-coated spinning solution is 0.05-5 mL / h.

[0013] Preferably, the winding speed of the winder and the unwinding speed of the unwinder are both 0.01-2 m / min.

[0014] Preferably, the distance between the spinning nozzle of the electrospinning liquid supply device and the aluminum foil is 5-30 cm.

[0015] Preferably, the carbon-coated spinning solution comprises a conductive agent, a binder and a solvent.

[0016] Preferably, the preparation process of the carbon-coated spinning solution comprises: mixing a binder, a solvent and a conductive agent, and stirring to obtain the carbon-coated spinning solution.

[0017] Preferably, the mass ratio of the conductive agent to the binder is (1-100):1.

[0018] Preferably, the solid content of the carbon-coated spinning solution is 5-20 wt%.

[0019] Preferably, the conductive agent includes any one of graphite, carbon black, CNT, hard carbon, VGCF or graphene, or a combination of at least two thereof.

[0020] Preferably, the binder includes any one of PVDF, PTFE, PVA or PAA, or a combination of at least two of them.

[0021] Preferably, the solvent comprises deionized water.

[0022] Preferably, the stirring and mixing time is 0.5-3h.

[0023] The beneficial effects of the present invention are:

[0024] 1) The present invention provides electrospinning liquid supply devices on both sides of the aluminum foil, and in combination with the drive of the winder and unwinder, it can simultaneously prepare a carbon coating layer on both sides of the aluminum foil, thereby achieving simultaneous coating of both sides of the aluminum foil and greatly improving the production efficiency of the carbon-coated aluminum foil;

[0025] 2) The present invention uses electrospinning technology, which allows the solvent to be volatilized during the spinning process, eliminating the need for an additional drying step. This simplifies the preparation process of the carbon-coated aluminum foil and reduces energy consumption. By controlling the speed of the winder and unwinder and the flow rate of the carbon-coated spinning solution, the surface density of the carbon-coated layer can be precisely adjusted, thereby improving the accuracy of the carbon-coated layer density.

[0026] 3) The present invention solves the problems of severe scraper scratches, difficult plate roller cleaning, troublesome plate roller replacement, cumbersome carbon coating layer density control process, low production efficiency and high energy consumption in the existing coating process, thereby achieving the purpose of reducing costs and increasing efficiency; BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the electrospinning process of Example 1 of the present invention;

[0028] Among them, 1-aluminum foil, 2-winding machine, 3-unwinding machine, 4-electrospinning liquid supply device. DETAILED DESCRIPTION

[0029] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings and embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment provides a method for preparing a carbon-coated aluminum foil, which comprises the following steps:

[0032] Step a: The aluminum foil roll is suspended vertically between an unwinding mechanism and a rewinding mechanism, allowing it to unwind naturally under the action of gravity. Specifically, the aluminum foil roll is placed perpendicular to the ground, with its ends resting on the rewinding and unwinding mechanisms, respectively. With the aluminum foil roll suspended vertically, gravity allows it to unwind naturally, resulting in a smooth surface that facilitates uniform carbon coating.

[0033] Step b: Install at least one electrospinning liquid supply device on each side of the aluminum foil. Each device includes a spinning nozzle and a liquid supply unit, with the nozzle and the aluminum foil spaced 20 cm apart. Specifically, one electrospinning liquid supply device is placed on each side of the aluminum foil, each device including a spinning nozzle and a liquid supply unit. The minimum distance between the spinning nozzle and the aluminum foil is set to 20 cm. This distance ensures sufficient fiber stretching and proper solvent volatilization during the electrospinning process, thereby forming a uniform carbon coating.

[0034] Step c: Under the action of positive and negative high-voltage electric fields, the carbon-coated spinning liquid is sprayed onto both sides of the aluminum foil to form a double-sided carbon-coated layer. Specifically, the spinning nozzle of the electrospinning liquid supply device is connected to a positive high-voltage power supply with a voltage of 50kV, and the winding mechanism is connected to a negative high-voltage power supply with a voltage of -10kV. Under the action of positive and negative high-voltage electric fields, the carbon-coated spinning liquid is ejected from the spinning nozzle, stretched into fibers under the action of the electric field force, and deposited on the surface of the aluminum foil to form a uniform carbon-coated layer. The electrospinning liquid supply device controls the liquid supply rate through an injection pump, and adopts a single needle structure to evenly distribute the carbon-coated liquid. The flow rate of the carbon-coated spinning liquid is 2mL / h.

[0035] In this embodiment, the spinning solution includes a conductive agent, a binder, and a solvent. Specifically, the carbon-coated spinning solution includes graphite as the conductive agent, PVDF as the binder, and deionized water as the solvent. The carbon-coated spinning solution preparation process includes: stirring and mixing PVDF and deionized water for 120 minutes to obtain a mixed solution with a solid content of 15wt%, then adding graphite to the mixed solution at a mass ratio of 50:1 to PVDF, and stirring and mixing for 2 hours to obtain the carbon-coated spinning solution.

[0036] In this embodiment, the winding speed of the winding mechanism and the unwinding speed of the unwinding mechanism are both 1 m / min. This speed setting can ensure that the aluminum foil maintains appropriate tension and flatness during the electrospinning process, which is conducive to the uniform formation of the carbon coating layer.

[0037] Through the above steps, an aluminum foil uniformly coated with carbon on both sides can be obtained. The carbon-coated aluminum foil has good electrical conductivity and mechanical strength and is suitable for current collector materials of lithium-ion batteries.

[0038] Example 2

[0039] This embodiment provides a method for preparing a carbon-coated aluminum foil, which comprises the following steps:

[0040] Step a: Suspend the aluminum foil roll vertically between the unwinding and rewinding mechanisms, allowing it to unwind naturally under the action of gravity. Specifically, the aluminum foil roll is placed perpendicular to the ground, with its ends resting on the rewinding and unwinding mechanisms, respectively. With the roll suspended vertically, gravity allows the foil to unwind naturally, forming a smooth surface.

[0041] Step b: Place at least one electrospinning liquid supply device on each side of the aluminum foil. The liquid supply device includes a spinning nozzle and a liquid supply unit, and the distance between the nozzle and the aluminum foil is 5 cm. Specifically, one electrospinning liquid supply device is placed on each side of the aluminum foil, and each electrospinning liquid supply device includes a spinning nozzle and a liquid supply unit.

[0042] Step c: Under the action of positive and negative high-voltage electric fields, the carbon-coated spinning solution is sprayed onto both sides of the aluminum foil to form a double-sided carbon-coated layer. Specifically, the spinning nozzle of the electrospinning liquid supply device is connected to a positive high-voltage power supply with a voltage of 20kV, and the unwinding mechanism is connected to a negative high-voltage power supply with a voltage of -20kV. Under the action of the positive and negative high-voltage electric fields, the carbon-coated spinning solution is ejected from the spinning nozzle, stretched into fibers under the action of the electric field force, and deposited on the surface of the aluminum foil to form a uniform carbon-coated layer. The electrospinning liquid supply device controls the liquid supply rate by a push pump, and the flow rate of the carbon-coated spinning solution is 0.05mL / h.

[0043] In this embodiment, the spinning solution includes a conductive agent, a binder, and a solvent. Specifically, the carbon-coated spinning solution includes carbon black as the conductive agent, PVA as the binder, and deionized water as the solvent. The carbon-coated spinning solution preparation process includes: stirring and mixing PVA and deionized water for 60 minutes to obtain a mixed solution with a solid content of 5wt%, then adding carbon black to the mixed solution in a mass ratio of 1:1, and stirring and mixing for 3 hours to obtain the carbon-coated spinning solution.

[0044] In this embodiment, the winding speed of the winding mechanism and the unwinding speed of the unwinding mechanism are both 2 m / min. This speed setting can ensure that the aluminum foil maintains appropriate tension and flatness during the electrospinning process, which is conducive to the uniform formation of the carbon coating layer.

[0045] Through the above steps, an aluminum foil uniformly coated with carbon on both sides can be obtained. The carbon-coated aluminum foil has good electrical conductivity and mechanical strength.

[0046] Example 3

[0047] This embodiment provides a method for preparing a carbon-coated aluminum foil, which comprises the following steps:

[0048] Step a: Suspend the aluminum foil roll vertically between the unwinding and rewinding mechanisms, allowing it to unwind naturally under the action of gravity. Specifically, the aluminum foil roll is placed perpendicular to the ground, with its ends resting on the rewinding and unwinding mechanisms, respectively. With the roll suspended vertically, gravity allows the foil to unwind naturally, forming a smooth surface.

[0049] Step b: Install at least one electrospinning liquid supply device on each side of the aluminum foil. The liquid supply device includes a spinning nozzle and a liquid supply unit. The distance between the nozzle and the aluminum foil is 30 cm. Specifically, one electrospinning liquid supply device is placed on each side of the aluminum foil. Each electrospinning liquid supply device includes a spinning nozzle and a liquid supply unit.

[0050] Step c: Under the action of positive and negative high-voltage electric fields, the carbon-coated spinning solution is sprayed onto both sides of the aluminum foil to form a double-sided carbon-coated layer. Specifically, the spinning nozzle of the electrospinning liquid supply device is connected to a positive high-voltage power supply with a voltage of 100kV, and the winding mechanism is connected to a negative high-voltage power supply with a voltage of -1kV. Under the action of the positive and negative high-voltage electric fields, the carbon-coated spinning solution is ejected from the spinning nozzle, stretched into fibers under the action of the electric field force, and deposited on the surface of the aluminum foil to form a uniform carbon-coated layer. The electrospinning liquid supply device controls the liquid supply rate by a push pump, and the flow rate of the carbon-coated spinning solution is 5mL / h.

[0051] In this embodiment, the spinning solution includes a conductive agent, a binder, and a solvent. Specifically, the carbon-coated spinning solution includes CNTs as the conductive agent, PAA as the binder, and deionized water as the solvent. The carbon-coated spinning solution preparation process includes: stirring and mixing PAA and deionized water for 180 minutes to obtain a mixed solution with a solid content of 20 wt%. CNTs are then added to the mixed solution at a mass ratio of CNT to PAA of 100:1. The mixture is stirred and mixed for 1 hour to obtain the carbon-coated spinning solution.

[0052] In this embodiment, the winding speed of the winding mechanism and the unwinding speed of the unwinding mechanism are both 0.01 m / min. This speed setting can ensure that the aluminum foil maintains appropriate tension and flatness during the electrospinning process, which is conducive to the uniform formation of the carbon coating layer.

[0053] Through the above steps, an aluminum foil uniformly coated with carbon on both sides can be obtained. The carbon-coated aluminum foil has good electrical conductivity and mechanical strength.

[0054] Example 4

[0055] This embodiment provides a method for preparing a carbon-coated aluminum foil, which comprises the following steps:

[0056] Step a: Suspend the aluminum foil roll vertically between the unwinding and rewinding mechanisms, allowing it to unwind naturally under the action of gravity. Specifically, the aluminum foil roll is placed perpendicular to the ground, with its ends resting on the rewinding and unwinding mechanisms, respectively. With the roll suspended vertically, gravity allows the foil to unwind naturally, forming a smooth surface.

[0057] Step b: Install at least one electrospinning liquid supply device on each side of the aluminum foil. Each device includes a spinning nozzle and a liquid supply unit, with the nozzle and the aluminum foil spaced 15 cm apart. Specifically, three electrospinning liquid supply devices, each including a spinning nozzle and a liquid supply unit, are placed on each side of the aluminum foil. These three electrospinning liquid supply devices are arranged on the same horizontal line, ensuring a more uniform carbon coating on the aluminum foil surface.

[0058] Step c: Under the action of positive and negative high-voltage electric fields, the carbon-coated spinning solution is sprayed onto both sides of the aluminum foil to form a double-sided carbon-coated layer. Specifically, the spinning nozzle of the electrospinning liquid supply device is connected to a positive high-voltage power supply with a voltage of 40kV, and the winding mechanism is connected to a negative high-voltage power supply with a voltage of -5kV. Under the action of the positive and negative high-voltage electric fields, the carbon-coated spinning solution is ejected from the spinning nozzle, stretched into fibers under the action of the electric field force, and deposited on the surface of the aluminum foil to form a uniform carbon-coated layer. The electrospinning liquid supply device controls the liquid supply rate by a push pump, and the flow rate of the carbon-coated spinning solution is 1mL / h.

[0059] In this embodiment, the spinning solution includes a conductive agent, a binder, and a solvent. Specifically, the carbon-coated spinning solution includes graphene as the conductive agent, PTFE as the binder, and deionized water as the solvent. The preparation process of the carbon-coated spinning solution includes: stirring and mixing PTFE and deionized water for 90 minutes to obtain a mixed solution with a solid content of 10wt%, then adding graphene to the mixed solution at a mass ratio of 10:1, and stirring and mixing for 1.5 hours to obtain the carbon-coated spinning solution.

[0060] In this embodiment, the winding speed of the winding mechanism and the unwinding speed of the unwinding mechanism are both 0.5 m / min. This speed setting can ensure that the aluminum foil maintains appropriate tension and flatness during the electrospinning process, which is conducive to the uniform formation of the carbon coating layer.

[0061] Through the above steps, a double-sided uniformly carbon-coated aluminum foil can be obtained. The carbon-coated aluminum foil has good electrical conductivity and mechanical strength. Due to the use of multiple electrospinning liquid supply devices, the carbon-coated aluminum foil prepared in this embodiment has better performance in coating uniformity and production efficiency.

[0062] Example 5

[0063] This embodiment provides a method for preparing a carbon-coated aluminum foil, which comprises the following steps:

[0064] Step a: Suspend the aluminum foil roll vertically between the unwinding and rewinding mechanisms, allowing it to unwind naturally under the action of gravity. Specifically, the aluminum foil roll is placed perpendicular to the ground, with its ends resting on the rewinding and unwinding mechanisms, respectively. With the roll suspended vertically, gravity allows the foil to unwind naturally, forming a smooth surface.

[0065] Step b: Install at least one electrospinning liquid supply device on each side of the aluminum foil. Each device includes a spinning nozzle and a liquid supply unit, with the nozzle and the aluminum foil spaced 10 cm apart. Specifically, three electrospinning liquid supply devices, each including a spinning nozzle and a liquid supply unit, are placed on each side of the aluminum foil. These three electrospinning liquid supply devices are arranged in a vertical line, with the nozzles spaced no further than the total width of the aluminum foil, ensuring a more uniform carbon coating on the aluminum foil surface.

[0066] Step c: Under the action of positive and negative high-voltage electric fields, the carbon-coated spinning solution is sprayed onto both sides of the aluminum foil to form a double-sided carbon-coated layer. Specifically, the spinning nozzle of the electrospinning liquid supply device is connected to a positive high-voltage power supply with a voltage of 80kV, and the unwinding mechanism is connected to a negative high-voltage power supply with a voltage of -15kV. Under the action of the positive and negative high-voltage electric fields, the carbon-coated spinning solution is ejected from the spinning nozzle, stretched into fibers under the action of the electric field force, and deposited on the surface of the aluminum foil to form a uniform carbon-coated layer. The electrospinning liquid supply device controls the liquid supply rate by a push pump, and the flow rate of the carbon-coated spinning solution is 3mL / h.

[0067] In this embodiment, the spinning solution includes a conductive agent, a binder, and a solvent. Specifically, the carbon-coated spinning solution includes a mixture of hard carbon and VGCF as the conductive agent, a mixture of PVDF and PVA as the binder, and deionized water as the solvent. The preparation process of the carbon-coated spinning solution includes: stirring and mixing PVDF, PVA, and deionized water for 150 minutes to obtain a mixed solution with a solid content of 12wt%, then adding a mixture of hard carbon and VGCF to the mixed solution, wherein the mass ratio of the hard carbon and VGCF mixture to the binder is 30:1, and stirring and mixing for 2.5 hours to obtain the carbon-coated spinning solution.

[0068] In this embodiment, the winding speed of the winding mechanism and the unwinding speed of the unwinding mechanism are both 1.5 m / min. This speed setting can ensure that the aluminum foil maintains appropriate tension and flatness during the electrospinning process, which is conducive to the uniform formation of the carbon coating layer.

[0069] Through the above steps, a double-sided, uniformly carbon-coated aluminum foil is obtained, exhibiting excellent electrical conductivity and mechanical strength. Due to the use of multiple electrospinning liquid supply devices, which are vertically distributed, the carbon-coated aluminum foil prepared in this example exhibits improved coating uniformity and production efficiency.

[0070] Example 6

[0071] This embodiment provides a carbon-coated aluminum foil, which is obtained using the preparation method described in Example 1. Specifically, the carbon-coated aluminum foil is obtained by vertically suspending an aluminum foil roll between an unwinding mechanism and a rewinding mechanism, installing electrostatic spinning liquid supply devices on both sides of the aluminum foil, and spraying a carbon-coated spinning liquid onto both sides of the aluminum foil under the action of positive and negative high-voltage electric fields, thereby forming a double-sided carbon coating.

[0072] The carbon-coated aluminum foil has the following characteristics:

[0073] 1. The carbon coating layer is evenly distributed on both sides of the aluminum foil with consistent thickness;

[0074] 2. The carbon coating layer is firmly bonded to the aluminum foil substrate and is not easy to fall off;

[0075] 3. The carbon coating has good electrical conductivity and low resistivity;

[0076] 4. The surface of the carbon coating is smooth, without obvious defects and cracks;

[0077] 5. The thickness of the carbon coating layer is controllable. By adjusting the electrospinning parameters, carbon coating layers of different thicknesses can be obtained.

[0078] The carbon-coated aluminum foil can be used as a current collector material for lithium-ion batteries, has good electrical conductivity and mechanical strength, and can effectively improve the performance and life of lithium-ion batteries.

[0079] Example 7

[0080] This embodiment provides a lithium-ion battery, which includes the carbon-coated aluminum foil described in Example 6. Specifically, the lithium-ion battery uses the carbon-coated aluminum foil described in Example 6 as a positive electrode current collector, which is combined with a positive electrode active material, an electrolyte, a separator, and a negative electrode to form a complete lithium-ion battery.

[0081] The lithium-ion battery has the following features:

[0082] 1. Due to the use of carbon-coated aluminum foil as the positive electrode current collector, the internal resistance of the battery is reduced and the charge and discharge efficiency is improved;

[0083] 2. The carbon coating layer can improve the bonding force between the current collector and the active material, reduce the shedding of the active material, and improve the cycle life of the battery;

[0084] 3. The carbon coating can improve the conductivity of the current collector, reduce the energy loss of the battery, and increase the energy density of the battery;

[0085] 4. The carbon coating can improve the corrosion resistance of the current collector and extend the service life of the battery;

[0086] 5. The carbon coating can increase the surface area of ​​the current collector, increase the contact area with the active material, and improve the power density of the battery.

[0087] By adopting the carbon-coated aluminum foil of the present invention as the current collector material of the lithium-ion battery, the comprehensive performance of the lithium-ion battery can be significantly improved, including energy density, power density, cycle life and safety performance.

[0088] Example 8

[0089] This embodiment provides a method for preparing a carbon-coated aluminum foil, which comprises the following steps:

[0090] Step a: Suspend the aluminum foil roll vertically between the unwinding and rewinding mechanisms, allowing it to unwind naturally under the action of gravity. Specifically, the aluminum foil roll is placed perpendicular to the ground, with its ends resting on the rewinding and unwinding mechanisms, respectively. With the roll suspended vertically, gravity allows the foil to unwind naturally, forming a smooth surface.

[0091] Step b: Install at least one electrospinning liquid supply device on each side of the aluminum foil. The device includes a spinning nozzle and a liquid supply unit, with the nozzle and the aluminum foil spaced 25 cm apart. Specifically, two electrospinning liquid supply devices, each including a spinning nozzle and a liquid supply unit, are placed on either side of the aluminum foil. These two electrospinning liquid supply devices, located above and below the aluminum foil, ensure a more uniform carbon coating on the surface.

[0092] Step c: Under the action of positive and negative high-voltage electric fields, the carbon-coated spinning solution is sprayed onto both sides of the aluminum foil to form a double-sided carbon-coated layer. Specifically, the spinning nozzle of the electrospinning liquid supply device is connected to a positive high-voltage power supply with a voltage of 60kV, and the winding mechanism is connected to a negative high-voltage power supply with a voltage of -8kV. Under the action of the positive and negative high-voltage electric fields, the carbon-coated spinning solution is ejected from the spinning nozzle, stretched into fibers under the action of the electric field force, and deposited on the surface of the aluminum foil to form a uniform carbon-coated layer. The electrospinning liquid supply device controls the liquid supply rate by an injection pump, and the flow rate of the carbon-coated spinning solution is 1.5mL / h.

[0093] In this embodiment, the spinning solution includes a conductive agent, a binder, and a solvent. Specifically, the carbon-coated spinning solution includes a mixture of graphite and carbon black as the conductive agent, PVDF as the binder, and deionized water as the solvent. The preparation process of the carbon-coated spinning solution includes: stirring and mixing PVDF and deionized water for 135 minutes to obtain a mixed solution with a solid content of 18wt%, then adding a mixture of graphite and carbon black to the mixed solution, wherein the mass ratio of the graphite and carbon black mixture to PVDF is 75:1, and stirring and mixing for 2.2 hours to obtain the carbon-coated spinning solution.

[0094] In this embodiment, the winding speed of the winding mechanism and the unwinding speed of the unwinding mechanism are both 0.8 m / min. This speed setting can ensure that the aluminum foil maintains appropriate tension and flatness during the electrospinning process, which is conducive to the uniform formation of the carbon coating layer.

[0095] Through the above steps, a double-sided, evenly carbon-coated aluminum foil is obtained, exhibiting excellent electrical conductivity and mechanical strength. Due to the use of multiple electrospinning liquid supply devices, positioned above and below the foil, the carbon-coated aluminum foil produced in this example exhibits improved coating uniformity and production efficiency.

[0096] It should be noted that Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, and Example 8 are all methods for preparing carbon-coated aluminum foil.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a carbon-coated aluminum foil, characterized in that: The preparation method comprises the following steps: a) Hang the aluminum foil roll vertically between the unwinding mechanism and the rewinding mechanism, and unfold it naturally under the action of gravity; b) providing at least one electrospinning liquid supply device on both sides of the aluminum foil, wherein the liquid supply device comprises a spinning nozzle and a liquid supply unit, and the distance between the nozzle and the aluminum foil is 5 to 30 cm; c) spraying carbon spinning solution onto both sides of the aluminum foil under the action of positive and negative high voltage electric fields to form a double-sided carbon coating layer; The spinning solution includes a conductive agent, a binder and a solvent.

2. The preparation method according to claim 1, characterized in that The spinning nozzle of the electrospinning liquid supply device is connected to a positive high-voltage power supply, the voltage of which is 5-50kV; the winder or unwinder is connected to a negative high-voltage power supply, the voltage of which is -20-0kV.

3. The preparation method according to claim 1 or 2, characterized in that The flow rate of the carbon-coated spinning solution is 0.05-5 mL / h; Preferably, the winding speed of the winder and the unwinding speed of the unwinder are both 0.01-2 m / min.

4. The preparation method according to any one of claim 3, characterized in that The carbon-coated spinning solution comprises a conductive agent, a binder and a solvent.

5. The preparation method according to claim 4, characterized in that The preparation process of the carbon-coated spinning solution comprises: mixing a binder, a solvent and a conductive agent, and stirring to obtain the carbon-coated spinning solution; Preferably, the mass ratio of the conductive agent to the binder is (1-100):1; Preferably, the solid content of the carbon-coated spinning solution is 5-20 wt%.

6. The preparation method according to claim 5, characterized in that The conductive agent includes any one or a combination of at least two of graphite, carbon black, CNT, hard carbon, VGCF or graphene; Preferably, the binder comprises any one of PVDF, PTFE, PVA or PAA, or a combination of at least two thereof; Preferably, the solvent comprises deionized water; Preferably, the stirring and mixing time is 0.5-3h.

7. A carbon-coated aluminum foil, characterized in that: The carbon-coated aluminum foil is obtained by the preparation method according to any one of claims 1 to 6.

8. A lithium ion battery, characterized in that: The lithium-ion battery comprises the carbon-coated aluminum foil according to claim 7.

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