A wrinkle-resistant separator for soft-shell lithium batteries and its preparation process

Abstract

This invention discloses an anti-wrinkle separator for soft-shell lithium batteries and its preparation process, belonging to the field of soft-shell lithium battery technology. It includes an anti-wrinkle film layer and a base film layer. Both ends of the base film layer are embedded within the anti-wrinkle film layer, and the anti-wrinkle film layer is bonded to the base film layer by a hot melt adhesive. The hot melt adhesive is composed of the following raw materials in parts by weight: 42-68 parts of an ethylene-vinyl acetate copolymer mixture, 5-13 parts of silicone oil, 5-12 parts of a plasticizer, 10-27 parts of a tackifying resin, 0-6 parts of an antioxidant, 3-6 parts of a surface adhesion aid, and 0-2 parts of a UV absorber. This invention solves the problem that existing lithium battery separators are prone to wrinkling and deformation during prolonged use. This invention improves the overall anti-wrinkle performance of the anti-wrinkle separator, avoids wrinkling and deformation, and fully ensures the normal use of the anti-wrinkle separator.

Description

Technical Field

[0001] This invention relates to the field of soft-shell lithium battery technology, specifically to an anti-wrinkle separator for soft-shell lithium batteries and its preparation process. Background Technology

[0002] Lithium-ion batteries are widely used as power sources for various mobile devices due to their high energy density, high operating voltage, lack of memory effect, and long cycle life. They are particularly favored in the electric vehicle sector for their high charge-discharge performance. With the widespread application of lithium-ion batteries in electric vehicles, high capacity, high output, and high safety have become the development direction for power batteries. Correspondingly, lithium battery separators are also continuously developing towards higher heat resistance, higher safety, and higher ion permeability.

[0003] Chinese patent CN108565379B discloses a lithium battery separator and its preparation method. The method includes: 1) dissolving an aromatic polymer and ceramic powder in a solvent to obtain an aromatic polymer slurry; 2) coating the aromatic polymer slurry onto the surface of a lithium battery base film; 3) washing the structure obtained in step 2) in a constant-temperature water bath and then drying it to obtain the lithium battery separator. This method allows the aromatic polymer slurry to crystallize and precipitate a fibrous network morphology at a suitable rate after being coated onto the base film surface, forming a three-dimensional network fiber structure. Using this three-dimensional network fiber structure as a framework ensures that the aromatic polymer coated film has excellent heat resistance. Furthermore, the mesh in the three-dimensional network fiber structure gives the separator high air permeability. However, the above patent has the following drawbacks in practical use:

[0004] Existing lithium battery separators are prone to wrinkling and deformation during prolonged use. Summary of the Invention

[0005] The purpose of this invention is to provide an anti-wrinkle separator for soft-shell lithium batteries and its preparation process, which can improve the overall anti-wrinkle performance of the anti-wrinkle separator, avoid wrinkles and deformation of the anti-wrinkle separator, fully ensure the normal use of the anti-wrinkle separator, and solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An anti-wrinkle separator for a soft-shell lithium battery includes an anti-wrinkle film layer and a base film layer. Both ends of the base film layer are embedded in the anti-wrinkle film layer, and the anti-wrinkle film layer is bonded to the base film layer by a hot melt adhesive. The thickness of the anti-wrinkle film layer is 2μm-7μm, and the thickness of the base film layer is 8μm-16μm. The hot melt adhesive is composed of the following raw materials in parts by weight: 42-68 parts of ethylene-vinyl acetate copolymer mixture, 5-13 parts of silicone oil, 5-12 parts of plasticizer, 10-27 parts of tackifying resin, 0-6 parts of antioxidant, 3-6 parts of surface adhesion aid, and 0-2 parts of ultraviolet absorber.

[0008] Preferably, the anti-wrinkle film layer includes an anti-wrinkle base layer and elastic protrusions. The inner end face of the anti-wrinkle base layer is provided with uniformly distributed elastic protrusions. The anti-wrinkle base layer and the elastic protrusions are integrally formed. The anti-wrinkle base layer is bonded to the base film layer by hot melt adhesive, and the elastic protrusions are inserted into the base film layer.

[0009] Preferably, the anti-wrinkle base layer and the elastic bumps are both composed of the following parts by weight of raw materials: 20-36 parts of nylon fiber and 20-42 parts of polyester fiber.

[0010] Preferably, the anti-wrinkle base layer is made of nylon fiber and polyester fiber as raw materials, which are extruded by a twin-screw extruder, biaxially stretched, cooled and shaped to obtain the anti-wrinkle base layer. The anti-wrinkle base layer is then processed and slit to form elastic protrusions on the inner end face of the anti-wrinkle base layer to obtain an anti-wrinkle film layer.

[0011] Preferably, both ends of the base film layer are provided with positioning grooves for the elastic protrusions to be engaged, and the elastic protrusions match the positioning grooves.

[0012] Preferably, the base film layer is composed of the following raw materials in parts by weight: 20-36 parts of polyethylene resin and 18-32 parts of polypropylene resin.

[0013] Preferably, the base film layer is made from polyethylene resin and polypropylene resin as raw materials, and is obtained by extrusion, biaxial stretching, cooling and shaping using a twin-screw extruder.

[0014] According to another aspect of the present invention, a process for preparing an anti-wrinkle separator for a soft-shell lithium battery is provided, comprising the following steps:

[0015] S1. Preparation of the anti-wrinkle film layer:

[0016] Nylon fibers and polyester fibers are added to a twin-screw extruder, and after extrusion, biaxial stretching, cooling and shaping, an anti-wrinkle base layer is obtained. The anti-wrinkle base layer is then processed and slit to form elastic protrusions on the inner end face of the anti-wrinkle base layer, thus obtaining an anti-wrinkle film layer.

[0017] S2. Preparation of the base film layer:

[0018] Polyethylene resin and polypropylene resin are added to a twin-screw extruder, and the mixture is extruded, biaxially stretched, cooled and shaped to obtain a base film layer.

[0019] S3. Preparation of anti-wrinkle diaphragm:

[0020] A hot melt adhesive is placed in the gap between the anti-wrinkle film layer and the base film layer to laminate the anti-wrinkle film layer and the base film layer, thereby obtaining an anti-wrinkle diaphragm.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The anti-wrinkle separator for soft-shell lithium batteries of the present invention and its preparation process involve adding anti-wrinkle film layers to both sides of the base film layer, using nylon fiber and polyester fiber as raw materials, and extruding, biaxially stretching, cooling and shaping through a twin-screw extruder to obtain an anti-wrinkle base layer. The anti-wrinkle base layer is then processed and slit to form elastic protrusions on the inner end face of the anti-wrinkle base layer, thus obtaining an anti-wrinkle film layer. The anti-wrinkle base layer is then bonded to the base film layer with hot melt adhesive, and the elastic protrusions are inserted into the base film layer, which can improve the overall anti-wrinkle performance of the anti-wrinkle separator, avoid wrinkles and deformation of the anti-wrinkle separator, and fully ensure the normal use of the anti-wrinkle separator. Attached Figure Description

[0023] Figure 1 This is a front view schematic diagram of the anti-wrinkle separator of the soft-shell lithium battery of the present invention;

[0024] Figure 2 This is a cross-sectional view of the anti-wrinkle separator of the soft-shell lithium battery of the present invention.

[0025] Figure 3 This is a front exploded view of the anti-wrinkle separator of the soft-shell lithium battery of the present invention.

[0026] Figure 4 A frontal schematic diagram showing the positioning grooves formed on the base film layer of the present invention;

[0027] Figure 5 This is a frontal schematic diagram of the anti-wrinkle base layer of the present invention with elastic protrusions.

[0028] In the diagram: 1. Anti-wrinkle film layer; 11. Anti-wrinkle base layer; 12. Elastic protrusions; 2. Base film layer; 21. Positioning groove. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] To address the issue of existing lithium-ion battery separators easily wrinkling and deforming during prolonged use, please refer to [link to relevant documentation]. Figures 1-5 This embodiment provides the following technical solution:

[0031] Example 1

[0032] An anti-wrinkle separator for a soft-shell lithium battery includes an anti-wrinkle film layer 1 and a base film layer 2.

[0033] It should be noted that the thickness of the anti-wrinkle film layer 1 is 2μm-7μm, and the thickness of the base film layer 2 is 8μm-16μm.

[0034] Specifically, by setting anti-wrinkle membrane layers 1 on both sides of the base membrane layer 2, the overall anti-wrinkle performance of the anti-wrinkle diaphragm can be improved, preventing wrinkles and deformation of the anti-wrinkle diaphragm and ensuring its normal use.

[0035] Both ends of the basement membrane layer 2 are embedded in the anti-wrinkle membrane layer 1, and the anti-wrinkle membrane layer 1 is bonded to the basement membrane layer 2 by hot melt adhesive.

[0036] It should be noted that the hot melt adhesive is composed of the following raw materials in parts by weight: 42-68 parts of ethylene-vinyl acetate copolymer mixture, 5-13 parts of silicone oil, 5-12 parts of plasticizer, 10-27 parts of tackifying resin, 0-6 parts of antioxidant, 3-6 parts of surface tackifier, and 0-2 parts of ultraviolet absorber.

[0037] The anti-wrinkle film layer 1 includes an anti-wrinkle base layer 11 and elastic bumps 12.

[0038] It should be noted that the inner end face of the anti-wrinkle base layer 11 is provided with uniformly distributed elastic protrusions 12. The anti-wrinkle base layer 11 and the elastic protrusions 12 are integrally formed. The anti-wrinkle base layer 11 is bonded to the base film layer 2 by hot melt adhesive, and the elastic protrusions 12 are inserted into the base film layer 2.

[0039] Specifically, the anti-wrinkle base layer 11 and the elastic bumps 12 are both composed of the following parts by weight of raw materials: 20 parts of nylon fiber and 20 parts of polyester fiber.

[0040] It should be noted that nylon fiber has excellent abrasion resistance, tensile strength, elongation at break, elastic recovery rate, and fatigue resistance; polyester fiber has excellent wrinkle resistance and shape retention, with high strength and elastic recovery ability, making it durable, wrinkle-resistant, and requires no ironing. By using nylon fiber and polyester fiber as raw materials, extruding, biaxially stretching, cooling, and shaping through a twin-screw extruder, an anti-wrinkle base layer 11 is obtained. After processing and slitting, elastic protrusions 12 are formed on the inner end face of the anti-wrinkle base layer 11 to obtain an anti-wrinkle membrane layer 1, which can improve the overall anti-wrinkle performance of the anti-wrinkle diaphragm, prevent wrinkles and deformation of the anti-wrinkle diaphragm, and fully ensure the normal use of the anti-wrinkle diaphragm.

[0041] It should be noted that the anti-wrinkle base layer 11 is made from nylon fiber and polyester fiber as raw materials. It is produced by extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder. The anti-wrinkle base layer 11 is then processed and slit to form elastic protrusions 12 on the inner end face of the anti-wrinkle base layer 11, thus producing the anti-wrinkle film layer 1.

[0042] Both ends of the basement membrane layer 2 are provided with positioning grooves 21 for the elastic protrusions 12 to be inserted into, and the elastic protrusions 12 match the positioning grooves 21.

[0043] Specifically, the base film layer 2 is composed of the following parts by weight of raw materials: 20-36 parts of polyethylene resin and 18-32 parts of polypropylene resin.

[0044] The base film layer 2 is made from polyethylene resin and polypropylene resin through extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder.

[0045] To better demonstrate the preparation process of the anti-wrinkle separator for a soft-shell lithium battery, this embodiment proposes a preparation process for an anti-wrinkle separator for a soft-shell lithium battery according to the above-mentioned method, including the following steps:

[0046] S1. Preparation of anti-wrinkle film layer 1:

[0047] Nylon fibers and polyester fibers are added to a twin-screw extruder, and after extrusion, biaxial stretching, cooling and shaping, an anti-wrinkle base layer 11 is obtained. The anti-wrinkle base layer 11 is processed and slit to form elastic protrusions 12 on the inner end face of the anti-wrinkle base layer 11, thus obtaining an anti-wrinkle film layer 1.

[0048] S2, Preparation of basement membrane layer 2:

[0049] Polyethylene resin and polypropylene resin are added to a twin-screw extruder, and the mixture is extruded, biaxially stretched, cooled and shaped to obtain the base film layer 2.

[0050] S3. Preparation of anti-wrinkle diaphragm:

[0051] A hot melt adhesive is placed in the gap between the anti-wrinkle film layer 1 and the base film layer 2 to laminate the anti-wrinkle film layer 1 and the base film layer 2, thereby obtaining an anti-wrinkle diaphragm.

[0052] Example 2

[0053] An anti-wrinkle separator for a soft-shell lithium battery includes an anti-wrinkle film layer 1 and a base film layer 2.

[0054] It should be noted that the thickness of the anti-wrinkle film layer 1 is 2μm-7μm, and the thickness of the base film layer 2 is 8μm-16μm.

[0055] Specifically, by setting anti-wrinkle membrane layers 1 on both sides of the base membrane layer 2, the overall anti-wrinkle performance of the anti-wrinkle diaphragm can be improved, preventing wrinkles and deformation of the anti-wrinkle diaphragm and ensuring its normal use.

[0056] Both ends of the basement membrane layer 2 are embedded in the anti-wrinkle membrane layer 1, and the anti-wrinkle membrane layer 1 is bonded to the basement membrane layer 2 by hot melt adhesive.

[0057] It should be noted that the hot melt adhesive is composed of the following raw materials in parts by weight: 42-68 parts of ethylene-vinyl acetate copolymer mixture, 5-13 parts of silicone oil, 5-12 parts of plasticizer, 10-27 parts of tackifying resin, 0-6 parts of antioxidant, 3-6 parts of surface tackifier, and 0-2 parts of ultraviolet absorber.

[0058] The anti-wrinkle film layer 1 includes an anti-wrinkle base layer 11 and elastic bumps 12.

[0059] It should be noted that the inner end face of the anti-wrinkle base layer 11 is provided with uniformly distributed elastic protrusions 12. The anti-wrinkle base layer 11 and the elastic protrusions 12 are integrally formed. The anti-wrinkle base layer 11 is bonded to the base film layer 2 by hot melt adhesive, and the elastic protrusions 12 are inserted into the base film layer 2.

[0060] Specifically, the anti-wrinkle base layer 11 and the elastic bumps 12 are both composed of the following parts by weight of raw materials: 20 parts of nylon fiber and 42 parts of polyester fiber.

[0061] It should be noted that nylon fiber has excellent abrasion resistance, tensile strength, elongation at break, elastic recovery rate, and fatigue resistance; polyester fiber has excellent wrinkle resistance and shape retention, with high strength and elastic recovery ability, making it durable, wrinkle-resistant, and requires no ironing. By using nylon fiber and polyester fiber as raw materials, extruding, biaxially stretching, cooling, and shaping through a twin-screw extruder, an anti-wrinkle base layer 11 is obtained. After processing and slitting, elastic protrusions 12 are formed on the inner end face of the anti-wrinkle base layer 11 to obtain an anti-wrinkle membrane layer 1, which can improve the overall anti-wrinkle performance of the anti-wrinkle diaphragm, prevent wrinkles and deformation of the anti-wrinkle diaphragm, and fully ensure the normal use of the anti-wrinkle diaphragm.

[0062] It should be noted that the anti-wrinkle base layer 11 is made from nylon fiber and polyester fiber as raw materials. It is produced by extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder. The anti-wrinkle base layer 11 is then processed and slit to form elastic protrusions 12 on the inner end face of the anti-wrinkle base layer 11, thus producing the anti-wrinkle film layer 1.

[0063] Both ends of the basement membrane layer 2 are provided with positioning grooves 21 for the elastic protrusions 12 to be inserted into, and the elastic protrusions 12 match the positioning grooves 21.

[0064] Specifically, the base film layer 2 is composed of the following parts by weight of raw materials: 20-36 parts of polyethylene resin and 18-32 parts of polypropylene resin.

[0065] The base film layer 2 is made from polyethylene resin and polypropylene resin through extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder.

[0066] The anti-wrinkle diaphragm was prepared using the same preparation process as in Example 1. The difference from Example 1 is that the mass fraction of polyester fiber is increased in Example 2.

[0067] Example 3

[0068] An anti-wrinkle separator for a soft-shell lithium battery includes an anti-wrinkle film layer 1 and a base film layer 2.

[0069] It should be noted that the thickness of the anti-wrinkle film layer 1 is 2μm-7μm, and the thickness of the base film layer 2 is 8μm-16μm.

[0070] Specifically, by setting anti-wrinkle membrane layers 1 on both sides of the base membrane layer 2, the overall anti-wrinkle performance of the anti-wrinkle diaphragm can be improved, preventing wrinkles and deformation of the anti-wrinkle diaphragm and ensuring its normal use.

[0071] Both ends of the basement membrane layer 2 are embedded in the anti-wrinkle membrane layer 1, and the anti-wrinkle membrane layer 1 is bonded to the basement membrane layer 2 by hot melt adhesive.

[0072] It should be noted that the hot melt adhesive is composed of the following raw materials in parts by weight: 42-68 parts of ethylene-vinyl acetate copolymer mixture, 5-13 parts of silicone oil, 5-12 parts of plasticizer, 10-27 parts of tackifying resin, 0-6 parts of antioxidant, 3-6 parts of surface tackifier, and 0-2 parts of ultraviolet absorber.

[0073] The anti-wrinkle film layer 1 includes an anti-wrinkle base layer 11 and elastic bumps 12.

[0074] It should be noted that the inner end face of the anti-wrinkle base layer 11 is provided with uniformly distributed elastic protrusions 12. The anti-wrinkle base layer 11 and the elastic protrusions 12 are integrally formed. The anti-wrinkle base layer 11 is bonded to the base film layer 2 by hot melt adhesive, and the elastic protrusions 12 are inserted into the base film layer 2.

[0075] Specifically, the anti-wrinkle base layer 11 and the elastic bumps 12 are both composed of the following parts by weight of raw materials: 36 parts of nylon fiber and 20 parts of polyester fiber.

[0076] It should be noted that nylon fiber has excellent abrasion resistance, tensile strength, elongation at break, elastic recovery rate, and fatigue resistance; polyester fiber has excellent wrinkle resistance and shape retention, with high strength and elastic recovery ability, making it durable, wrinkle-resistant, and requires no ironing. By using nylon fiber and polyester fiber as raw materials, extruding, biaxially stretching, cooling, and shaping through a twin-screw extruder, an anti-wrinkle base layer 11 is obtained. After processing and slitting, elastic protrusions 12 are formed on the inner end face of the anti-wrinkle base layer 11 to obtain an anti-wrinkle membrane layer 1, which can improve the overall anti-wrinkle performance of the anti-wrinkle diaphragm, prevent wrinkles and deformation of the anti-wrinkle diaphragm, and fully ensure the normal use of the anti-wrinkle diaphragm.

[0077] It should be noted that the anti-wrinkle base layer 11 is made from nylon fiber and polyester fiber as raw materials. It is produced by extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder. The anti-wrinkle base layer 11 is then processed and slit to form elastic protrusions 12 on the inner end face of the anti-wrinkle base layer 11, thus producing the anti-wrinkle film layer 1.

[0078] Both ends of the basement membrane layer 2 are provided with positioning grooves 21 for the elastic protrusions 12 to be inserted into, and the elastic protrusions 12 match the positioning grooves 21.

[0079] Specifically, the base film layer 2 is composed of the following parts by weight of raw materials: 20-36 parts of polyethylene resin and 18-32 parts of polypropylene resin.

[0080] The base film layer 2 is made from polyethylene resin and polypropylene resin through extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder.

[0081] The anti-wrinkle diaphragm was prepared using the same preparation process as in Example 1. The difference from Example 1 is that the mass fraction of nylon fiber in Example 3 is increased.

[0082] Example 4

[0083] An anti-wrinkle separator for a soft-shell lithium battery includes an anti-wrinkle film layer 1 and a base film layer 2.

[0084] It should be noted that the thickness of the anti-wrinkle film layer 1 is 2μm-7μm, and the thickness of the base film layer 2 is 8μm-16μm.

[0085] Specifically, by setting anti-wrinkle membrane layers 1 on both sides of the base membrane layer 2, the overall anti-wrinkle performance of the anti-wrinkle diaphragm can be improved, preventing wrinkles and deformation of the anti-wrinkle diaphragm and ensuring its normal use.

[0086] Both ends of the basement membrane layer 2 are embedded in the anti-wrinkle membrane layer 1, and the anti-wrinkle membrane layer 1 is bonded to the basement membrane layer 2 by hot melt adhesive.

[0087] It should be noted that the hot melt adhesive is composed of the following raw materials in parts by weight: 42-68 parts of ethylene-vinyl acetate copolymer mixture, 5-13 parts of silicone oil, 5-12 parts of plasticizer, 10-27 parts of tackifying resin, 0-6 parts of antioxidant, 3-6 parts of surface tackifier, and 0-2 parts of ultraviolet absorber.

[0088] The anti-wrinkle film layer 1 includes an anti-wrinkle base layer 11 and elastic bumps 12.

[0089] It should be noted that the inner end face of the anti-wrinkle base layer 11 is provided with uniformly distributed elastic protrusions 12. The anti-wrinkle base layer 11 and the elastic protrusions 12 are integrally formed. The anti-wrinkle base layer 11 is bonded to the base film layer 2 by hot melt adhesive, and the elastic protrusions 12 are inserted into the base film layer 2.

[0090] Specifically, the anti-wrinkle base layer 11 and the elastic bumps 12 are both composed of the following parts by weight of raw materials: 36 parts of nylon fiber and 42 parts of polyester fiber.

[0091] It should be noted that nylon fiber has excellent abrasion resistance, tensile strength, elongation at break, elastic recovery rate, and fatigue resistance; polyester fiber has excellent wrinkle resistance and shape retention, with high strength and elastic recovery ability, making it durable, wrinkle-resistant, and requires no ironing. By using nylon fiber and polyester fiber as raw materials, extruding, biaxially stretching, cooling, and shaping through a twin-screw extruder, an anti-wrinkle base layer 11 is obtained. After processing and slitting, elastic protrusions 12 are formed on the inner end face of the anti-wrinkle base layer 11 to obtain an anti-wrinkle membrane layer 1, which can improve the overall anti-wrinkle performance of the anti-wrinkle diaphragm, prevent wrinkles and deformation of the anti-wrinkle diaphragm, and fully ensure the normal use of the anti-wrinkle diaphragm.

[0092] It should be noted that the anti-wrinkle base layer 11 is made from nylon fiber and polyester fiber as raw materials. It is produced by extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder. The anti-wrinkle base layer 11 is then processed and slit to form elastic protrusions 12 on the inner end face of the anti-wrinkle base layer 11, thus producing the anti-wrinkle film layer 1.

[0093] Both ends of the basement membrane layer 2 are provided with positioning grooves 21 for the elastic protrusions 12 to be inserted into, and the elastic protrusions 12 match the positioning grooves 21.

[0094] Specifically, the base film layer 2 is composed of the following parts by weight of raw materials: 20-36 parts of polyethylene resin and 18-32 parts of polypropylene resin.

[0095] The base film layer 2 is made from polyethylene resin and polypropylene resin through extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder.

[0096] The anti-wrinkle diaphragm was prepared using the same preparation process as in Example 1. The difference from Example 1 is that the mass fractions of nylon fiber and polyester fiber in Example 4 are both increased.

[0097] Comparative Example 1

[0098] An anti-wrinkle separator for a soft-shell lithium battery includes an anti-wrinkle film layer 1 and a base film layer 2.

[0099] It should be noted that the thickness of the anti-wrinkle film layer 1 is 2μm-7μm, and the thickness of the base film layer 2 is 8μm-16μm.

[0100] Specifically, by setting anti-wrinkle membrane layers 1 on both sides of the base membrane layer 2, the overall anti-wrinkle performance of the anti-wrinkle diaphragm can be improved, preventing wrinkles and deformation of the anti-wrinkle diaphragm and ensuring its normal use.

[0101] Both ends of the basement membrane layer 2 are embedded in the anti-wrinkle membrane layer 1, and the anti-wrinkle membrane layer 1 is bonded to the basement membrane layer 2 by hot melt adhesive.

[0102] It should be noted that the hot melt adhesive is composed of the following raw materials in parts by weight: 42-68 parts of ethylene-vinyl acetate copolymer mixture, 5-13 parts of silicone oil, 5-12 parts of plasticizer, 10-27 parts of tackifying resin, 0-6 parts of antioxidant, 3-6 parts of surface tackifier, and 0-2 parts of ultraviolet absorber.

[0103] The anti-wrinkle film layer 1 includes an anti-wrinkle base layer 11.

[0104] It should be noted that the anti-wrinkle base layer 11 is bonded to the base film layer 2 by hot melt adhesive.

[0105] Specifically, the anti-wrinkle base layer 11 is composed of the following parts by weight of raw materials: 20 parts of nylon fiber and 20 parts of polyester fiber.

[0106] It should be noted that nylon fiber has excellent abrasion resistance, tensile strength, tensile elongation, elastic recovery rate, and fatigue resistance; polyester fiber has excellent wrinkle resistance and shape retention, with high strength and elastic recovery ability, making it durable, wrinkle-resistant, and requires no ironing. By using nylon fiber and polyester fiber as raw materials, through extrusion, biaxial stretching, cooling, and shaping using a twin-screw extruder, an anti-wrinkle base layer 11 is obtained, which can improve the overall anti-wrinkle performance of the anti-wrinkle diaphragm, prevent wrinkles and deformation of the anti-wrinkle diaphragm, and fully ensure the normal use of the anti-wrinkle diaphragm.

[0107] It should be noted that the anti-wrinkle base layer 11 is made from nylon fiber and polyester fiber as raw materials, and is produced by extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder.

[0108] Specifically, the base film layer 2 is composed of the following parts by weight of raw materials: 20-36 parts of polyethylene resin and 18-32 parts of polypropylene resin.

[0109] The base film layer 2 is made from polyethylene resin and polypropylene resin through extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder.

[0110] Compared with Example 1, the elastic bump 12 structure was omitted in Comparative Example 1. The anti-wrinkle diaphragm was prepared using the preparation process of Example 1, and the preparation step of the elastic bump 12 was omitted accordingly.

[0111] Comparative Example 2

[0112] A wrinkle-resistant separator for a soft-shell lithium battery includes a base film layer 2.

[0113] It should be noted that the thickness of the basement membrane layer 2 is 8μm-16μm.

[0114] Specifically, the base film layer 2 is composed of the following parts by weight of raw materials: 20-36 parts of polyethylene resin and 18-32 parts of polypropylene resin.

[0115] The base film layer 2 is made from polyethylene resin and polypropylene resin through extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder.

[0116] Compared with Example 1, the anti-wrinkle film layer 1 structure was omitted in Comparative Example 1. The anti-wrinkle diaphragm was prepared using the preparation process of Example 1, and the preparation step of the anti-wrinkle film layer 1 was omitted accordingly.

[0117] Anti-wrinkle separators for soft-shell lithium batteries were produced according to the preparation processes provided in Examples 1-4 and Comparative Examples 1-2, and the anti-wrinkle separators of the prepared soft-shell lithium batteries were tested. The test results of their anti-wrinkle performance are shown in Table 1.

[0118] Table 1: Test Table of Anti-wrinkle Performance of Anti-wrinkle Separator for Soft-shell Lithium-ion Batteries

[0119]

[0120] As can be seen from the table above, the anti-wrinkle diaphragms prepared in Examples 1 to 4 all have good anti-wrinkle properties.

[0121] Among them, the anti-wrinkle performance of Example 2 is improved compared with Example 1, indicating that increasing the mass fraction of polyester fiber can improve the anti-wrinkle performance of the anti-wrinkle diaphragm.

[0122] Among them, the wrinkle resistance of Example 3 is improved compared with Example 1, indicating that increasing the mass fraction of nylon fiber can improve the wrinkle resistance of the anti-wrinkle membrane.

[0123] Among them, the wrinkle resistance of Example 4 is improved compared with Example 1, indicating that increasing the mass fraction of polyester fiber and nylon fiber can improve the wrinkle resistance of the anti-wrinkle diaphragm.

[0124] Compared with Example 1, Comparative Example 1 showed reduced anti-wrinkle performance. Since the elastic bumps 12 were not added in Comparative Example 1, the anti-wrinkle performance of the anti-wrinkle diaphragm was reduced, indicating that the elastic bumps 12 can improve the anti-wrinkle performance of the anti-wrinkle diaphragm.

[0125] Compared with Example 1, Comparative Example 2 showed a decrease in anti-wrinkle performance. Since no anti-wrinkle film layer 1 was added in Comparative Example 2, the anti-wrinkle performance of the anti-wrinkle diaphragm was reduced, indicating that anti-wrinkle film layer 1 can improve the anti-wrinkle performance of the anti-wrinkle diaphragm.

[0126] In summary, the anti-wrinkle separator for soft-shell lithium batteries of the present invention and its preparation process involve adding anti-wrinkle film layers 1 to both sides of the base film layer 2, using nylon fiber and polyester fiber as raw materials, and extruding, biaxially stretching, cooling and shaping through a twin-screw extruder to obtain an anti-wrinkle base layer 11. The anti-wrinkle base layer 11 is then processed and slit to form elastic protrusions 12 on the inner end face of the anti-wrinkle base layer 11, thus obtaining the anti-wrinkle film layer 1. The anti-wrinkle base layer 11 is then bonded to the base film layer 2 with hot melt adhesive, and the elastic protrusions 12 are inserted into the base film layer 2. This improves the overall anti-wrinkle performance of the anti-wrinkle separator, avoids wrinkles and deformation of the anti-wrinkle separator, and fully ensures the normal use of the anti-wrinkle separator.

[0127] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0128] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an anti-wrinkle separator for a soft-shell lithium battery, the method being used to prepare an anti-wrinkle separator for a soft-shell lithium battery, the anti-wrinkle separator comprising an anti-wrinkle film layer (1) and a base film layer (2), characterized in that: Both ends of the base film layer (2) are embedded in the anti-wrinkle film layer (1), and the anti-wrinkle film layer (1) is bonded to the base film layer (2) by hot melt adhesive. The thickness of the anti-wrinkle film layer (1) is 2μm-7μm, and the thickness of the base film layer (2) is 8μm-16μm. The hot melt adhesive is composed of the following raw materials in parts by weight: 42-68 parts of ethylene-vinyl acetate copolymer mixture, 5-13 parts of silicone oil, 5-12 parts of plasticizer, 10-27 parts of tackifying resin, 0-6 parts of antioxidant, 3-6 parts of surface tackifier, and 0-2 parts of ultraviolet absorber. The anti-wrinkle film layer (1) includes an anti-wrinkle base layer (11) and elastic protrusions (12). The inner end face of the anti-wrinkle base layer (11) is provided with uniformly distributed elastic protrusions (12). The anti-wrinkle base layer (11) and the elastic protrusions (12) are integrally formed. The anti-wrinkle base layer (11) is bonded to the base film layer (2) by hot melt adhesive, and the elastic protrusions (12) are inserted into the base film layer (2). The anti-wrinkle base layer (11) and the elastic protrusions (12) are both composed of the following raw materials in parts by weight: 20-36 parts of nylon fiber and 20-42 parts of polyester fiber. The anti-wrinkle base layer (11) is made from nylon fiber and polyester fiber as raw materials, and is extruded by a twin-screw extruder, biaxially stretched, cooled and shaped to obtain the anti-wrinkle base layer (11). The anti-wrinkle base layer (11) is processed and cut to form elastic protrusions (12) on the inner end face of the anti-wrinkle base layer (11) to obtain the anti-wrinkle film layer (1). The preparation process of the anti-wrinkle separator for soft-shell lithium batteries includes the following steps: S1. Preparation of anti-wrinkle film layer (1): Nylon fibers and polyester fibers are added to a twin-screw extruder, and after extrusion, biaxial stretching, cooling and shaping, an anti-wrinkle base layer (11) is obtained. The anti-wrinkle base layer (11) is processed and slit to form elastic protrusions (12) on the inner end face of the anti-wrinkle base layer (11) to obtain an anti-wrinkle film layer (1). S2, Preparation of the basement membrane (2): Polyethylene resin and polypropylene resin are added to a twin-screw extruder, and the mixture is extruded, biaxially stretched, cooled and shaped to obtain a base film layer (2). S3. Preparation of anti-wrinkle diaphragm: A hot melt adhesive is placed in the gap between the anti-wrinkle film layer (1) and the base film layer (2) to laminate the anti-wrinkle film layer (1) and the base film layer (2) to obtain an anti-wrinkle diaphragm.

2. The preparation process of an anti-wrinkle separator for a soft-shell lithium battery according to claim 1, characterized in that: Both ends of the base film layer (2) are provided with positioning grooves (21) for the elastic protrusions (12) to be inserted into, and the elastic protrusions (12) are matched with the positioning grooves (21).

3. The preparation process of an anti-wrinkle separator for a soft-shell lithium battery according to claim 2, characterized in that: The base film layer (2) is composed of the following parts by weight of raw materials: 20-36 parts of polyethylene resin and 18-32 parts of polypropylene resin.

4. The preparation process of an anti-wrinkle separator for a soft-shell lithium battery according to claim 3, characterized in that: The base film layer (2) is made from polyethylene resin and polypropylene resin as raw materials, and is obtained by extrusion, biaxial stretching, cooling and shaping by a twin-screw extruder.

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