Anode and cathode composite current collector of lithium battery

Abstract

An anode and cathode composite current collector of a lithium battery is provided with an insulating film, metal material layers are attached to the two surfaces of the insulating film, and the anode composite current collector is formed when the metal material layers are made of aluminum; the metal material layer is a negative electrode composite current collector when being copper; the thickness of the insulating film is 4-10 mu, the thickness of the metal material layer is 1-2 mu, and the thickness of the insulating film is not less than 50% of the total thickness. The insulating film is made of maleic anhydride modified polyethylene or maleic anhydride modified polypropylene. The metal material layer is attached to the surface of the insulating film in a vacuum plating or magnetron sputtering mode. Or soft metal compounding is adopted. And the fire risk in the puncturing process of the lithium battery can be greatly reduced. Meanwhile, the thickness of the insulating layer exceeds 50%, and the density of the insulating layer is only 1 / 3-1 / 2 of that of aluminum, so that the weight of the current collector can be greatly reduced, and the energy density of the battery can be greatly improved. The thickness is reduced, the weight is reduced, and meanwhile, the requirements of a battery coating and rolling process can be well met.

Description

Technical Field

[0001] The invention relates to the technical field of lithium batteries, in particular to a positive and negative composite current collector for lithium batteries and a hot-polishing method. Background Art

[0002] The current collector of traditional lithium batteries is made of aluminum foil or copper foil. Its disadvantages are that it is easy to catch fire during the puncture process, which poses a high risk. In addition, lithium batteries are now pursuing energy density. The higher the energy density, the lighter and smaller the battery can be. However, when the thickness of the aluminum foil of the positive electrode current collector is less than 9 microns, it is very easy to break during the battery coating and rolling process, making it impossible to achieve the best of both worlds. Summary of the invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies in the prior art and propose a composite current collector for positive and negative electrodes of a lithium battery that can greatly increase the energy density and reduce the risk of puncture and fire.

[0004] The technical problem to be solved by the present invention is achieved through the following technical solution: a composite current collector for positive and negative electrodes of a lithium battery, which is characterized by: An insulating film is provided, and metal material layers are attached to two surfaces of the insulating film. When the metal material layer is aluminum, it is a positive electrode composite current collector; when the metal material layer is copper, it is a negative electrode composite current collector; The thickness of the insulating film is 4-10 μm, and the thickness of the metal material layer is 1-2 μm, wherein the thickness of the insulating film is not less than 50% of the total thickness.

[0005] The technical problem to be solved by the present invention can be further achieved by the following technical solution: the insulating film is a single-layer film composed of maleic anhydride-modified polyethylene or maleic anhydride-modified polypropylene.

[0006] The technical problem to be solved by the present invention can be further achieved by the following technical solution: the insulating film is a three-layer structure film with PET in the middle and maleic anhydride-modified polyethylene and / or maleic anhydride-modified polypropylene on both sides.

[0007] The technical problem to be solved by the present invention can be further achieved by the following technical solution: the metal material layer is attached to the surface of the insulating film by vacuum plating or magnetron sputtering.

[0008] The technical problem to be solved by the present invention can be further achieved by the following technical solution: the metal material layer is made of soft metal.

[0009] The technical problem to be solved by the present invention can be further achieved by the following technical scheme: after two layers of 4~6μ soft metal are composited and solidified with an insulating film through a high-strength adhesive, they are rolled to the required thickness using precision rolling equipment, and then the rolled metal surface is cleaned and micro-corroded.

[0010] The technical problem to be solved by the present invention can be further achieved by the following technical solution, wherein the high-strength adhesive is a polyurethane adhesive.

[0011] The technical problem to be solved by the present invention can be further achieved by the following technical solution: two layers of 4-6μ soft metal, high-strength adhesive and insulating film are dry-compounded or extruded and then cured.

[0012] Compared with the existing technology, the positive and negative current collectors in lithium batteries are made from the original aluminum foil and copper foil into composite aluminum foil and copper foil with intermediate insulation, which can greatly reduce the risk of fire during the puncture of lithium batteries. At the same time, since the thickness of the insulating layer exceeds 50%, and its density is only 1 / 3 to 1 / 2 of aluminum, the weight of the current collector can be greatly reduced, which can greatly improve the energy density of the battery. While reducing the thickness and weight, it can also meet the requirements of the battery coating rolling process. DETAILED DESCRIPTION

[0013] The specific technical scheme of the present invention is further described below. In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer and to facilitate those skilled in the art to further understand the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments, and do not constitute a limitation on the rights thereof. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0014] A lithium battery positive and negative electrode composite current collector, An insulating film is provided, and metal material layers are attached to two surfaces of the insulating film. When the metal material layer is aluminum, it is a positive electrode composite current collector; when the metal material layer is copper, it is a negative electrode composite current collector; The thickness of the insulating film is 4-10 μm, and the thickness of the metal material layer is 1-2 μm, wherein the thickness of the insulating film is not less than 50% of the total thickness.

[0015] The insulating film is a single-layer film composed of maleic anhydride-modified polyethylene or maleic anhydride-modified polypropylene.

[0016] Alternatively, the insulating film is a three-layer structure film with PET in the middle and maleic anhydride-modified polyethylene and / or maleic anhydride-modified polypropylene on both sides.

[0017] PET is used, and hot melt adhesive of maleic anhydride modified polyethylene and / or maleic anhydride modified polypropylene is dry-coated on both surfaces of PET. Such modified hot melt adhesives have strong adhesion and bonding strength with metals in hot melt state.

[0018] The metal material layer is attached to the surface of the insulating film by vacuum plating or magnetron sputtering, which can be performed 1 to 3 times to meet the thickness requirement.

[0019] The metal material layer may also be made of soft metal, which is achieved through a heat treatment process to facilitate secondary rolling.

[0020] After two layers of 4~6μ soft metal are composited and cured with a high-strength adhesive and an insulating film, At this time, the thickness of the insulating film should be 5~20μ, and the thickness of the high-strength adhesive should be 3~10μ. Then use precision calendering equipment to calender it to the required thickness.

[0021] Finally, the rolled metal surface is cleaned and subjected to acid micro-etching treatment.

[0022] The high-strength adhesive is a polyurethane adhesive. Polyurethane adhesive refers to an adhesive containing a carbamate group (-NHCOO-) or an isocyanate group (-NCO) in the molecular chain. The high-strength adhesive has a higher viscosity and is relatively flexible, which is convenient for the interlayer strength and extended flexibility required for secondary calendering. The surface of the composite current collector after calendering should be cleaned and slightly acid-etched to increase the surface area during the later coating and enhance the interlayer bonding force.

[0023] Two layers of 4~6μ soft metal, high-strength adhesive and insulating film are dry-compounded or extruded and then cured.

[0024] Changing the positive and negative current collectors in lithium batteries from the original aluminum foil and copper foil to composite aluminum foil and copper foil with intermediate insulation can greatly reduce the risk of fire during lithium battery puncture. At the same time, since the thickness of the insulation layer exceeds 50%, and its density is only 1 / 3 to 1 / 2 of aluminum, the weight of the current collector can be greatly reduced, which can greatly improve the energy density of the battery. While reducing the thickness and weight, it can also meet the requirements of the battery coating rolling process.

Claims

1. A composite current collector for positive and negative electrodes of a lithium battery, characterized in that: An insulating film is provided, and metal material layers are attached to two surfaces of the insulating film. When the metal material layer is aluminum, it is a positive electrode composite current collector; when the metal material layer is copper, it is a negative electrode composite current collector; The thickness of the insulating film is 4-10 μm, and the thickness of the metal material layer is 1-2 μm, wherein the thickness of the insulating film is not less than 50% of the total thickness.

2. The positive and negative composite current collector of a lithium battery according to claim 1, characterized in that: The insulating film is a single-layer film composed of maleic anhydride-modified polyethylene or maleic anhydride-modified polypropylene.

3. The positive and negative composite current collector of a lithium battery according to claim 1, characterized in that: The insulating film is a three-layer structure film with PET in the middle and maleic anhydride-modified polyethylene and / or maleic anhydride-modified polypropylene on both sides.

4. The positive and negative composite current collector for a lithium battery according to claim 1, characterized in that: The metal material layer is attached to the surface of the insulating film by vacuum plating or magnetron sputtering.

5. The positive and negative composite current collector for a lithium battery according to claim 1, characterized in that: The metal material layer is made of soft metal.

6. The positive and negative composite current collector for a lithium battery according to claim 5, characterized in that: After two layers of 4~6μ soft metal are composited and solidified with a high-strength adhesive and an insulating film, they are rolled to the required thickness using precision rolling equipment, and the rolled metal surface is then cleaned and micro-etched.

7. The positive and negative composite current collector for a lithium battery according to claim 6, characterized in that: Two layers of 4~6μ soft metal, high-strength adhesive and insulating film are dry-compounded or extruded and then cured.

8. The positive and negative composite current collector for a lithium battery according to claim 5 or 6, characterized in that: The high-strength adhesive is a polyurethane adhesive.