High-strength polyester film for composite current collectors

Abstract

This invention provides a high-strength polyester film for composite current collectors, relating to the field of polyester film technology. It includes a surface layer and an intermediate layer. The surface layer has two layers, upper and lower, with the intermediate layer located between the two surface layers. The surface layer comprises the following components in the indicated mass ratio: 70-90 parts PET resin masterbatch, 5-15 parts reinforcing fiber, 3-8 parts conductive particles, and 3-8 parts additives. The intermediate layer comprises the following components in the indicated mass ratio: 60-80 parts PET resin masterbatch, 20-30 parts reinforcing fiber, and 3-8 parts additives. This invention combines two surface layers with a single intermediate layer, possessing the characteristics of PET resin. The addition of reinforcing fiber and conductive particles improves the performance and strength of the current collector. It helps maintain the performance of PET while increasing overall strength through co-extrusion and biaxial stretching. Verification shows that the tensile strength exceeds the industry standard for current collectors.

Description

Technical Field

[0001] This invention relates to the field of polyester film technology, and in particular to a high-strength polyester film for composite current collectors. Background Technology

[0002] Composite current collectors are electrochemical materials that use PET or other raw material films as base films and deposit copper / aluminum molecules on both sides of the film through processes such as vacuum coating. Compared with traditional current collectors, composite current collectors adopt a three-layer composite structure of "metal-polymer material-metal". Nanoscale metals are formed on the surface of polymer films through vacuum evaporation, magnetron sputtering and other methods, and then the metal layer is deposited and thickened to more than 1μm through electroplating.

[0003] Polyester film is commonly used as the intermediate base film in composite current collectors. Polyester film is a film made of a polymer material with many advantages, including high stability, excellent physical properties, and strong mechanical and chemical properties. In recent years, the main polymer films used in composite current collectors include PP (polypropylene), PET (polyethylene terephthalate), and PI (polyimide). Among these, PI film is relatively expensive and less commonly used. PET film is the cheapest and has relatively good adhesion to copper, but its chemical stability and electrical insulation are generally poor. PP film is thin and has high chemical stability, which is beneficial for improving battery energy density, but its adhesion is worse than PET. Currently, conventional materials all have their own advantages and disadvantages. Whether in terms of strength or metal adhesion, they are difficult to meet the development and use of composite current collectors. For example, the tensile strength of traditional polyester film in the machine travel direction and the transverse direction is less than 300 MPa, while the current collector industry requires tensile strength greater than 300 MPa in all directions. Especially at a certain deformation, such as 10%, the tensile strength of the film in all directions must be greater than 140 MPa. Therefore, this invention proposes a high-strength polyester film for composite current collectors to solve the problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a high-strength polyester film for composite current collectors. This high-strength polyester film for composite current collectors is composed of two surface layers combined with a single intermediate layer, possessing the characteristics of PET resin, and incorporating reinforcing fibers and conductive particles to improve the performance and strength of the current collector. It is beneficial to maintain the performance of PET while increasing the overall strength through composite co-extrusion and biaxial stretching.

[0005] To achieve the objective of this invention, the invention is implemented through the following technical solution: a high-strength polyester film for composite current collectors, comprising a surface film layer and an intermediate layer, characterized in that: the surface film layer has upper and lower layers, and the intermediate layer is located between the two surface film layers;

[0006] The surface layer comprises the following components in the following mass ratio: 70-90 parts PET resin masterbatch, 5-15 parts reinforcing fiber, 3-8 parts conductive particles and 3-8 parts additives.

[0007] The intermediate layer comprises the following components in the indicated mass ratio: 60-80 parts PET resin masterbatch, 20-30 parts reinforcing fiber, and 3-8 parts additives;

[0008] The polyester film is obtained by co-extruding and biaxially stretching the two outer and middle layers.

[0009] A further improvement is that the surface film layer comprises the following components in the indicated mass ratio: 80 parts PET resin masterbatch, 10 parts reinforcing fiber, 5 parts conductive particles, and 5 parts additives.

[0010] A further improvement is that the intermediate layer comprises the following components in the indicated mass ratio: 70 parts PET resin masterbatch, 25 parts reinforcing fiber, and 5 parts additives.

[0011] A further improvement is that the reinforcing fiber is one of carbon fiber, glass fiber, or a mixture of the two.

[0012] A further improvement is that the conductive particles are one of carbon black and silver powder, or a mixture of the two.

[0013] A further improvement is that the additive is one of an antioxidant or a plasticizer, or a mixture of both.

[0014] A further improvement is that the preparation of the high-strength polyester film for the composite current collector includes the following steps:

[0015] PET resin masterbatch, reinforcing fibers, conductive particles and additives are added to an auxiliary extruder and heated to a molten state to obtain a surface film melt.

[0016] PET resin masterbatch, reinforcing fibers and additives are added to the main extruder and heated to a molten state to form an intermediate layer melt;

[0017] The surface layer melt and the intermediate layer melt are extruded through a three-layer co-extrusion die. The extruded melt is attached to the chilling roller by electrostatic adsorption. The melt is cooled by the chilling roller at a set temperature and speed to reduce the temperature of the melt and promote its solidification and molding to obtain a casting sheet.

[0018] The casting is placed on a stretching device and stretched longitudinally and laterally, with a lateral stretching rate of 4-5 times and a longitudinal stretching rate of 3-4 times. The thickness of the biaxially stretched polyester film is measured using a thickness measuring instrument to ensure that it meets the thickness standard requirements. Finally, it is subjected to traction, edge trimming, and winding to obtain a semi-finished product.

[0019] The semi-finished product is subjected to quality inspection, slitting, and packaging to obtain a high-strength polyester film for current collectors.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. This invention uses two surface layers combined with a single intermediate layer to form a high-strength polyester film, which has the characteristics of PET resin. Reinforcing fibers and conductive particles are added to improve the performance and strength of the current collector. While maintaining the performance of PET, the overall strength is increased by composite co-extrusion and biaxial stretching. It has been verified that the tensile strength exceeds the standard of the current collector industry. Attached Figure Description

[0022] Figure 1 This is a diagram illustrating the composition of the present invention. Detailed Implementation

[0023] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0024] Example 1

[0025] according to Figure 1 As shown in the figure, this embodiment proposes a high-strength polyester film for composite current collectors, including a surface film layer and an intermediate layer. The surface film layer has two layers, upper and lower, and the intermediate layer is located between the two surface film layers.

[0026] The surface film layer comprises the following components in the indicated mass ratio: 70 parts PET resin masterbatch, 5 parts reinforcing fiber, 3 parts conductive particles, and 3 parts additives. The surface film layer improves the performance and strength of the current collector. When used as a current collector in energy devices such as batteries, it can enhance the device's electron transfer capability. In the event of an abnormal short circuit in the battery, the base film melts and breaks upon heating, preventing combustion caused by continuous short circuits and improving the safety of the energy device.

[0027] The intermediate layer comprises the following components in the indicated mass ratio: 60 parts PET resin masterbatch, 20 parts reinforcing fiber, and 3 parts additives.

[0028] The reinforcing fiber is carbon fiber. The conductive particles are carbon black. The additives are antioxidants.

[0029] The preparation of the high-strength polyester film for the composite current collector includes the following steps:

[0030] PET resin masterbatch, reinforcing fibers, conductive particles and additives are added to an auxiliary extruder and heated to a molten state to obtain a surface film melt.

[0031] PET resin masterbatch, reinforcing fibers and additives are added to the main extruder and heated to a molten state to form an intermediate layer melt;

[0032] The surface layer melt and the intermediate layer melt are extruded through a three-layer co-extrusion die. The extruded melt is attached to the chilling roller by electrostatic adsorption. The melt is cooled by the chilling roller at a set temperature and speed to reduce the temperature of the melt and promote its solidification and molding to obtain a casting sheet.

[0033] The casting is placed on a stretching device and stretched longitudinally and laterally, with a lateral stretching rate of 4-5 times and a longitudinal stretching rate of 3-4 times. The thickness of the biaxially stretched polyester film is measured using a thickness measuring instrument to ensure that it meets the thickness standard requirements. Finally, it is subjected to traction, edge trimming, and winding to obtain a semi-finished product.

[0034] The semi-finished product is subjected to quality inspection, slitting, and packaging to obtain a high-strength polyester film for current collectors.

[0035] Example 2

[0036] according to Figure 1 As shown in the figure, this embodiment proposes a high-strength polyester film for composite current collectors, including a surface film layer and an intermediate layer. The surface film layer has two layers, upper and lower, and the intermediate layer is located between the two surface film layers.

[0037] The surface film layer comprises the following components in the indicated mass ratio: 80 parts PET resin masterbatch, 10 parts reinforcing fiber, 5 parts conductive particles, and 5 parts additives. The surface film layer improves the performance and strength of the current collector. When used as a current collector in energy devices such as batteries, it can enhance the device's electron transfer capability. In the event of an abnormal short circuit in the battery, the base film melts and breaks upon heating, preventing combustion caused by continuous short circuits and improving the safety of the energy device.

[0038] The intermediate layer comprises the following components in the indicated mass ratio: 70 parts PET resin masterbatch, 25 parts reinforcing fiber, and 5 parts additives.

[0039] The reinforcing fiber is carbon fiber. The conductive particles are carbon black. The additives are antioxidants.

[0040] The preparation of the high-strength polyester film for the composite current collector includes the following steps:

[0041] PET resin masterbatch, reinforcing fibers, conductive particles and additives are added to an auxiliary extruder and heated to a molten state to obtain a surface film melt.

[0042] PET resin masterbatch, reinforcing fibers and additives are added to the main extruder and heated to a molten state to form an intermediate layer melt;

[0043] The surface layer melt and the intermediate layer melt are extruded through a three-layer co-extrusion die. The extruded melt is attached to the chilling roller by electrostatic adsorption. The melt is cooled by the chilling roller at a set temperature and speed to reduce the temperature of the melt and promote its solidification and molding to obtain a casting sheet.

[0044] The casting is placed on a stretching device and stretched longitudinally and laterally, with a lateral stretching rate of 4-5 times and a longitudinal stretching rate of 3-4 times. The thickness of the biaxially stretched polyester film is measured using a thickness measuring instrument to ensure that it meets the thickness standard requirements. Finally, it is subjected to traction, edge trimming, and winding to obtain a semi-finished product.

[0045] The semi-finished product is subjected to quality inspection, slitting, and packaging to obtain a high-strength polyester film for current collectors.

[0046] Example 3

[0047] according to Figure 1 As shown in the figure, this embodiment proposes a high-strength polyester film for composite current collectors, including a surface film layer and an intermediate layer. The surface film layer has two layers, upper and lower, and the intermediate layer is located between the two surface film layers.

[0048] The surface film layer comprises the following components in the indicated mass ratio: 90 parts PET resin masterbatch, 15 parts reinforcing fiber, 8 parts conductive particles, and 8 parts additives. The surface film layer improves the performance and strength of the current collector. When used as a current collector in energy devices such as batteries, it can enhance the device's electron transfer capability. In the event of an abnormal short circuit in the battery, the base film melts and breaks upon heating, preventing combustion caused by continuous short circuits and improving the safety of the energy device.

[0049] The intermediate layer comprises the following components in the indicated mass ratio: 80 parts PET resin masterbatch, 30 parts reinforcing fiber, and 8 parts additives.

[0050] The reinforcing fiber is carbon fiber. The conductive particles are carbon black. The additives are antioxidants.

[0051] The preparation of the high-strength polyester film for the composite current collector includes the following steps:

[0052] PET resin masterbatch, reinforcing fibers, conductive particles and additives are added to an auxiliary extruder and heated to a molten state to obtain a surface film melt.

[0053] PET resin masterbatch, reinforcing fibers and additives are added to the main extruder and heated to a molten state to form an intermediate layer melt;

[0054] The surface layer melt and the intermediate layer melt are extruded through a three-layer co-extrusion die. The extruded melt is attached to the chilling roller by electrostatic adsorption. The melt is cooled by the chilling roller at a set temperature and speed to reduce the temperature of the melt and promote its solidification and molding to obtain a casting sheet.

[0055] The casting is placed on a stretching device and stretched longitudinally and laterally, with a lateral stretching rate of 4-5 times and a longitudinal stretching rate of 3-4 times. The thickness of the biaxially stretched polyester film is measured using a thickness measuring instrument to ensure that it meets the thickness standard requirements. Finally, it is subjected to traction, edge trimming, and winding to obtain a semi-finished product.

[0056] The semi-finished product is subjected to quality inspection, slitting, and packaging to obtain a high-strength polyester film for current collectors.

[0057] Based on Examples 1, 2, and 3, it can be concluded that the surface layer prepared by the present invention using the following mass ratio of 70-90 parts PET resin masterbatch, 5-15 parts reinforcing fiber, 3-8 parts conductive particles, and 3-8 parts additives, and the intermediate layer prepared using the following mass ratio of 60-80 parts PET resin masterbatch, 20-30 parts reinforcing fiber, and 3-8 parts additives, improves the performance and strength of the current collector.

[0058] Verification example:

[0059]

[0060] This high-strength polyester film for composite current collectors is composed of two surface layers combined with a single intermediate layer. It possesses the characteristics of PET resin, and incorporates reinforcing fibers and conductive particles to improve the current collector's performance and strength. While maintaining the properties of PET, the overall strength is increased through co-extrusion and biaxial stretching. Verification has shown that its tensile strength exceeds industry standards for current collectors. When used as a current collector in energy devices such as batteries, it enhances the device's electron transfer capability. In the event of an abnormal short circuit in the battery, the base film melts and breaks upon heating, preventing combustion caused by continuous short circuits and improving the safety of the energy device. Furthermore, the surface and intermediate layers are prepared using longitudinal and transverse stretching processes, with the longitudinal and transverse stretching ratios controlled between 4-5 times and 3-4 times, respectively, further improving the strength and stability of the polyester film and meeting the demands of modern energy devices for high-performance current collectors.

[0061] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-strength polyester film for a composite current collector comprising a surface film layer and an intermediate layer, characterized in that: The surface film layer has two layers, upper and lower, and the middle layer is located between the two surface film layers; the composite current collector uses a high-strength polyester film as the battery current collector, which melts and breaks when the battery experiences an abnormal short circuit, so as to avoid combustion caused by continuous short circuit and improve battery safety. The surface film layer comprises the following components in the indicated mass ratio: 70-90 parts PET resin masterbatch, 5-15 parts reinforcing fiber, 3-8 parts conductive particles, and 3-8 parts additives. The surface film layer improves the performance and strength of the current collector, maintaining the performance of PET while increasing the overall strength. The intermediate layer comprises the following components in the indicated mass ratio: 60-80 parts PET resin masterbatch, 20-30 parts reinforcing fiber, and 3-8 parts additives; The additive is one of antioxidants and plasticizers, or a mixture of the two; the reinforcing fiber is one of carbon fiber and glass fiber, or a mixture of the two; the conductive particles are one of carbon black and silver powder, or a mixture of the two. The two outer film layers and the middle layer are composite co-extruded and biaxially stretched to obtain the polyester film; The preparation of the high-strength polyester film for the composite current collector includes the following steps: PET resin masterbatch, reinforcing fibers, conductive particles and additives are added to an auxiliary extruder and heated to a molten state to obtain a surface film melt. PET resin masterbatch, reinforcing fibers and additives are added to the main extruder and heated to a molten state to form an intermediate layer melt; The surface layer melt and the intermediate layer melt are extruded through a three-layer co-extrusion die. The extruded melt is attached to the chilling roller by electrostatic adsorption. The melt is cooled by the chilling roller at a set temperature and speed to reduce the temperature of the melt and promote its solidification and molding to obtain a casting sheet. The casting is placed on a stretching device and stretched longitudinally and laterally, with a lateral stretching rate of 4-5 times and a longitudinal stretching rate of 3-4 times. The thickness of the biaxially stretched polyester film is measured using a thickness measuring instrument to ensure that it meets the thickness standard requirements. Finally, it is subjected to traction, edge trimming, and winding to obtain a semi-finished product. The semi-finished product is subjected to quality inspection, slitting, and packaging to obtain a high-strength polyester film for current collectors.

2. The high-strength polyester film for composite current collectors according to claim 1, characterized in that: The surface layer comprises the following components in the indicated mass ratio: 80 parts PET resin masterbatch, 10 parts reinforcing fiber, 5 parts conductive particles, and 5 parts additives.

3. The high-strength polyester film for composite current collectors according to claim 1, characterized in that: The intermediate layer comprises the following components in the indicated mass ratio: 70 parts PET resin masterbatch, 25 parts reinforcing fiber, and 5 parts additives.

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