Ultra-high strength separator and method for manufacturing the same

Abstract

Ultra-high strength separator and method for manufacturing the same. The method includes: (1) mixing and heating a composition containing a polyolefin resin, an antioxidant, and a pore-forming agent to form a molten mixture, extruding the mixture through a die, and cooling it to form a cast piece; (2) sequentially performing a first longitudinal stretching and a first transverse stretching on the cast piece to obtain a stretched film; (3) performing a second longitudinal stretching on the stretched film; (4) performing a second transverse stretching; and (5) sequentially performing extraction, a third transverse stretching, and heat curing to obtain an ultra-high strength separator. The separator manufactured by the method of the present disclosure has a significantly improved tensile strength in the longitudinal and transverse stretching directions, and its puncture strength can also be much higher than that of other separators of the same thickness. When the separator disclosed herein is used in a lithium-ion battery, it can provide better isolation and protection for the positive and negative electrodes of the battery when the battery is subjected to an external impact. As a result, the risk of short circuit caused by separator breakage can be avoided, and the safety performance of the lithium-ion battery can be improved.

Description

Technical Field

[0001] The present disclosure relates to the field of lithium-ion battery separators, and more particularly, to ultra-high strength separators and methods for manufacturing the same.

Background Art

[0002] Lithium-ion batteries have been widely used in the fields of electronic devices, new energy vehicles, and wind energy storage in recent years; lithium-ion battery separators are important components of lithium-ion batteries; separators play the role of separating the positive and negative electrodes to prevent short circuits and allowing the electrolyte solution to pass through to generate current; the main characteristics of separators include porosity, air permeability, tensile strength, puncture strength, shutdown temperature, etc. The performance of the separator directly affects the capacity, cycle performance, and safety performance of the battery. Therefore, improving the performance of the separator is very important for the performance of lithium-ion batteries.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Currently, the main process of the most common wet method for manufacturing separators is: extruder → die → cast → machine direction (MD) → first transverse direction stretching (TD1) → extraction → second transverse direction stretching (TD2) → heat curing. This method is mature, controllable, and a common method for manufacturing conventional base films. However, due to the footprint of the equipment and the limitations of the method, the stretching ratios in the machine direction (abbreviated as "MD" hereinafter in this specification, which is the casting direction) and the transverse direction (abbreviated as "TD" hereinafter in this specification, which is perpendicular to the casting direction) of this traditional method are usually less than 15 times, and are subject to certain limitations, which limit the tensile strength and puncture strength of the separator. In recent years, concerns about safety have become common regarding lithium-ion batteries, and research on the safety of lithium-ion batteries has received even more attention. For some separators, the requirements for tensile strength and puncture strength are becoming increasingly high. Sometimes, it is required to minimize the thickness of the separator while increasing the puncture strength of the separator.

[0004] Therefore, it is desirable to develop an ultra-thin separator with ultra-high strength and puncture strength that breaks through the limitations of the mechanical properties of traditional separators.

Means for Solving the Problem

[0005] Content of the present disclosure Due to the limitations of the device and the one-step MD+TD stretching method, the current mainstream separator stretching technology cannot achieve an ultra-high stretching ratio. Therefore, the present disclosure hereby proposes to manufacture an ultra-high-strength polyethylene separator that overcomes the disadvantages of the low stretching ratio in the traditional method and can be rapidly mass-produced.

[0006] To achieve the above object, the technical solution of the present disclosure is implemented as follows.

[0007] In one aspect, the present disclosure provides a separator with a thickness in the range of 4 μm to 8 μm, a transverse tensile strength of more than 4000 kgf / cm 2 sup, and a machine direction tensile strength of 4000 kgf / cm2 To provide an ultra-high strength separator with a puncture strength per unit thickness of 100 gf / μm or more.

[0008] Furthermore, in some embodiments, the transverse tensile strength of the ultra-high strength separator is 4500 kgf / cm 2 ~7000 kgf / cm 2 and the longitudinal tensile strength of the ultra-high strength separator is 4500 kgf / cm 2 ~7000 kgf / cm 2 and the puncture strength per unit thickness of the ultra-high strength separator is in the range of 100 gf / μm to 200 gf / μm.

[0009] Furthermore, in some embodiments, the porosity of the ultra-high strength separator is in the range of 30% to 50%, and the air permeability of the ultra-high strength separator is in the range of 50 seconds / 100 ml to 300 seconds / 100 ml.

[0010] In another aspect, the present disclosure is a method for manufacturing an ultra-high strength separator, comprising: (1) mixing and heating a composition containing a polyolefin resin, an antioxidant, and a pore-forming agent to form a molten mixture, extruding the mixture through a die, and cooling it to form a cast sheet; (2) sequentially performing a first longitudinal stretching and a first transverse stretching on the cast sheet to obtain a stretched film; (3) performing a second longitudinal stretching on the stretched film; (4) performing a second transverse stretching; (5) sequentially performing extraction, a third transverse stretching, and heat curing to obtain an ultra-high strength separator. A method is provided.

[0011] In some embodiments, the polyolefin resin in step (1) is high molecular weight polyethylene, and its molecular weight is in the range of 600,000 to 2,000,000.

[0012] In some embodiments, the antioxidant in step (1) is one or more selected from amines, sulfur-containing compounds, nitrogen-containing compounds, phosphorus-containing compounds, and organometallic salts.

[0013] In some embodiments, the pore former in step (1) is one or more selected from white oil, paraffin oil, and polyethylene glycol.

[0014] Furthermore, in some embodiments, for both the first longitudinal stretching and the first transverse stretching in step (2), the stretching temperature ranges from 60 °C to 150 °C, and the stretching ratio ranges from 3 to 15 times.

[0015] Furthermore, in some embodiments, for the second longitudinal stretching in step (3), the stretching temperature ranges from 60 °C to 140 °C, and the stretching ratio ranges from 2 to 10 times.

[0016] Furthermore, in some embodiments, for the second transverse stretching in step (4), the stretching temperature ranges from 90 °C to 140 °C, and the stretching ratio ranges from 2 to 10 times.

[0017] Furthermore, in some embodiments, for the third transverse stretching in step 5, the stretching temperature ranges from 100 °C to 150 °C, and the stretching ratio ranges from 1.1 to 2 times.

[0018] Furthermore, in some embodiments, the temperature of the heat curing in step (5) ranges from 110 °C to 150 °C.

[0019] In another aspect, the present disclosure is a method for manufacturing an ultra-high-strength separator, (1) mixing and heating a composition containing a polyolefin resin, an antioxidant, and a pore former to form a molten mixture, extruding the mixture through a die, and cooling it to form a cast sheet; (2) sequentially performing a first longitudinal stretching and a first transverse stretching on the cast sheet to obtain a stretched film; (3) performing a second longitudinal stretching on the stretched film; (4) A step of performing simultaneous biaxial stretching; (5) A step of sequentially performing extraction, third transverse stretching, and heat curing to obtain an ultra-high-strength separator; provided is a method including these steps.

[0020] In some embodiments, the polyolefin resin in step (1) is high molecular weight polyethylene, and its molecular weight ranges from 600,000 to 2,000,000.

[0021] In some embodiments, the antioxidant in step (1) is one or more selected from nitrogen-containing compounds such as amines, sulfur-containing compounds, phosphorus-containing compounds, and organic metal salts. In some embodiments, examples of the nitrogen-containing compound include, but are not limited to, diaryl secondary amines, p-phenylenediamine derivatives, and aldehyde amines; examples of the sulfur-containing compound include, but are not limited to, didodecyl thiodipropionate and molybdenum dialkyldithiocarbamate; examples of the phosphorus-containing compound include, but are not limited to, zinc dialkyldithiophosphate, etc.; examples of the organic metal salt include, but are not limited to, molybdate, etc.

[0022] In some embodiments, the pore former in step (1) is one or more selected from white oil, paraffin oil, and polyethylene glycol.

[0023] Further, in some embodiments, for both the first longitudinal stretching and the first transverse stretching in step (2), the stretching temperature ranges from 60 °C to 150 °C, and the stretching ratio ranges from 3 to 15 times.

[0024] Further, in some embodiments, for the second longitudinal stretching in step (3), the stretching temperature ranges from 60 °C to 140 °C, and the stretching ratio ranges from 2 to 10 times.

[0025] Furthermore, in some embodiments, for the simultaneous biaxial stretching in step (4), the stretching temperature ranges from 90°C to 140°C, and the stretching ratio ranges from 1.5×1.5 to 12×12 times.

[0026] Furthermore, in some embodiments, for the third transverse stretching in step (5), the stretching temperature ranges from 100°C to 150°C, and the stretching ratio ranges from 1.1 to 2 times.

[0027] Furthermore, in some embodiments, the temperature for heat curing in step (5) ranges from 110°C to 150°C.

[0028] As disclosed in this specification, the present disclosure provides a method for manufacturing a separator, including a second longitudinal stretching or simultaneous biaxial stretching together with a second transverse stretching for increasing the stretching ratios of the longitudinal stretching and the transverse stretching by cascade stretching before the extraction operation. Also, by the method disclosed in this specification including a second longitudinal stretching or simultaneous biaxial stretching before the second transverse stretching, the width of the film is significantly reduced, thereby eliminating the process of separator slitting and improving the manufacturing efficiency and equipment utilization rate. The separator manufactured by the method of the present disclosure has significantly improved tensile strengths in the longitudinal and transverse stretching directions, and its puncture strength can also be much higher than that of other separators of the same thickness. When the separator disclosed in this specification is used in a lithium-ion battery, it can provide better isolation and protection for the positive and negative electrodes of the battery when the battery is subjected to an external impact. As a result, the risk of short circuit caused by separator breakage is avoided, and the safety performance of the lithium-ion battery is improved.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

[0030] Legend of the figures: S1 - Extrusion; S2 - Cooling and sheet forming; S3 - MD1; S4 - TD1; S5 - MD2; S6 - TD2; S7 - SBS (i.e., simultaneous biaxial stretching); S8 - Extraction; S9 - TD3; S10 - Heat curing.

[0031] **Specific Embodiments** Specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are used only for exemplifying and explaining the present disclosure and do not limit the present disclosure. The endpoints and any values of the ranges disclosed herein are not limited to the exact ranges or values, but should be understood to include values close to those ranges or values. A range of values, the values of the endpoints of each range, the values of the endpoints of each range and the values of individual points, as well as the values of individual points, can be combined with each other to generate one or more new ranges of values, which will be considered as specifically disclosed herein.

[0032] As shown in FIG. 1, the main flow of the wet method for separator manufacturing in the prior art is: S1 Extrusion → S2 Cooling and sheet forming → S3 MD1 → S4 TD1 → S8 Extraction → S6 TD2 → S10 Heat curing.

[0033] As shown in FIG. 2, a method for manufacturing an ultra-high-strength separator, (1) A step of pre-mixing a dry powder of high molecular weight polyethylene and an antioxidant, then adding the pre-mixed mixture together with an organic pore former to a twin-screw extruder, extruding the mixture through a die in S1, and then cooling it through a chill roll in S2 to form a cast sheet; (2) A step of sequentially performing S3 MD1 and S4 TD1 on the cast sheet to obtain a stretched film; (3) A step of performing S5 MD2 on the stretched film; (4) The step of performing S6 TD2, (5) By using an extraction solvent in S8, extracting the organic pore former in the separator, and then performing S9 TD3 stretching and S10 heat curing to obtain an ultra-high-strength separator, A method is provided that includes this.

[0034] Furthermore, in some embodiments, the extrusion speed in die extrusion ranges from 60 kg / h to 350 kg / h, and the extrusion temperature ranges from 150 °C to 250 °C.

[0035] If the extrusion speed and / or extrusion temperature are too high or too low, this can easily lead to melt fracture or excessive casting defects; the morphology of the cast sheet plays an important role in maintaining a high draw ratio, and thus, if the cast sheet contains many defects, this can easily lead to the breakage of the separator during the stretching process.

[0036] Furthermore, in some embodiments, the molecular weight of the high-molecular-weight polyethylene in step (1) ranges from 600,000 to 2,000,000; in step (1), the concentration of the antioxidant is expressed in "parts by mass". For example, the amount of high-molecular-weight polyethylene is 100 parts by mass, the amount of the antioxidant ranges from, for example, 0.1 to 1 part by mass, and the amount of the organic pore former ranges from, for example, 233 to 400 parts by mass. In some embodiments, the amount of high-molecular-weight polyethylene is 100 parts by mass, the amount of the antioxidant ranges from 0.1 to 1 part by mass, and the amount of the organic pore former ranges from 233 to 360 parts by mass. In some embodiments, the amount of high-molecular-weight polyethylene is 100 parts by mass, the amount of the antioxidant ranges from 0.2 to 0.5 parts by mass, and the amount of the organic pore former ranges from 250 to 360 parts by mass.

[0037] Furthermore, in some embodiments, the antioxidant in step (1) is one or more selected from amines, sulfur-containing compounds, nitrogen-containing compounds, phosphorus-containing compounds, and organic metal salts.

[0038] Furthermore, in some embodiments, the pore-forming agent in step (1) is one or more selected from white oil, paraffin oil, and polyethylene glycol.

[0039] Furthermore, in some embodiments, for both S3 MD1 and S4 TD1 in step 2, the stretching temperature ranges from 60°C to 150°C, preferably from 60°C to 125°C, for example, in the range of 60°C to 120°C; the stretching ratio ranges from 3 to 15 times, preferably from 8 to 15 times, for example, in the range of 8 to 10 times.

[0040] Furthermore, in some embodiments, for S5 MD2 in step (3), the stretching temperature ranges from 60°C to 140°C, preferably from 60°C to 130°C, and the stretching ratio ranges from 2 to 10 times, preferably from 2.5 to 10 times.

[0041] After the S4 TD1 stretching, the resulting film may become much wider. Therefore, the width of the film is then significantly reduced by the S5 MD2 stretching, thereby eliminating the process of separator slitting, improving the production efficiency and equipment utilization rate, increasing the stretching ratio of the film, and promoting subsequent stretching.

[0042] Furthermore, in some embodiments, for S6 TD2 in step (4), the stretching temperature ranges from 90°C to 140°C, preferably from 90°C to 130°C, and the stretching ratio ranges from 2 to 10 times, preferably from 3 to 10 times.

[0043] Here, since the S6 TD2 stretching is performed on the film with reduced width, the stretching ratio of the film further increases.

[0044] Furthermore, let the draw ratio in the MD direction of S3 be "a", the draw ratio in the TD direction of S4 be "b", the draw ratio in the MD direction of S5 be "c", and the draw ratio in the TD direction of S6 be "d". Define the product of "a" and "c" as "e", that is, a×c = e. Similarly, define the product of "b" and "d" as "f", that is, b×d = f. The values of "e" and "f" disclosed in this specification are, in some embodiments, independently in the range of 15 to 150, preferably 25 to 150, for example 30 to 150, and more specifically 100 to 150.

[0045] As disclosed in this specification, the S5 MD2 operation, together with the S6 TD2 operation, is applied before the S8 extraction, and the draw ratios in the MD and TD directions are increased by cascade drawing. As a result, the total draw ratios "e" and "f" in the MD and TD directions can reach values in the range of 15 to 150 times, and thus the plane draw ratio can reach values in the range of 225 to 22500 times. The separator manufactured by the method of the present disclosure has significantly improved tensile strengths in the MD and TD directions, and its puncture strength can also be much higher than the puncture strength of other separators of the same thickness.

[0046] Furthermore, in some embodiments, for S9 TD3 in step (5), the drawing temperature is in the range of 100°C to 150°C, preferably 100°C to 130°C, and the draw ratio is in the range of 1.1 to 2 times, preferably 1.2 to 2 times.

[0047] Furthermore, in some embodiments, the temperature of the S10 heat curing in step (5) is in the range of 110°C to 150°C, preferably 110°C to 135°C.

[0048] As shown in Figure 3, a method for manufacturing an ultra-high-strength separator, (1) Pre-mix a dry powder of high molecular weight polyethylene and an antioxidant, then add the pre-mixed mixture together with an organic pore former to a twin-screw extruder, extrude the mixture through a die in S1, and then, in S2, cool it through a chill roll to form a cast sheet; (2) Sequentially performing S3 MD1 and S4 TD1 on the cast film to obtain a stretched film; (3) Performing S5 MD2 on the stretched film; (4) Performing S7 SBS; (5) By using an extraction solvent in S8, extracting the organic pore former in the separator, and then performing S9 TD3 stretching and S10 heat curing to obtain an ultra-high-strength separator; A method is provided that includes the above steps.

[0049] In some embodiments, the extrusion speed in die extrusion ranges from 60 kg / h to 350 kg / h, and the extrusion temperature ranges from 150 °C to 250 °C.

[0050] If the extrusion speed and / or extrusion temperature are too high or too low, this can easily lead to melt fracture or excessive casting defects; the morphology of the cast film plays an important role in maintaining a high draw ratio, and thus, if the cast film contains many defects, this can easily lead to the breakage of the separator during the stretching process.

[0051] Furthermore, in some embodiments, the molecular weight of the high molecular weight polyethylene in step (1) ranges from 600,000 to 2,000,000; the concentration of the components is expressed in "parts by mass". For example, the amount of high molecular weight polyethylene is 100 parts by mass, the amount of the antioxidant ranges from 0.1 to 1 part by mass, and the amount of the organic pore former ranges from 233 to 400 parts by mass. In some embodiments, the amount of high molecular weight polyethylene is 100 parts by mass, the amount of the antioxidant ranges from 0.1 to 1 part by mass, and the amount of the organic pore former ranges from 233 to 360 parts by mass. In some embodiments, the amount of high molecular weight polyethylene is 100 parts by mass, the amount of the antioxidant ranges from 0.2 to 0.5 part by mass, and the amount of the organic pore former ranges from 250 to 360 parts by mass.

[0052] Furthermore, in some embodiments, the antioxidant in step (1) is one or more selected from amines, sulfur-containing compounds, nitrogen-containing compounds, phosphorus-containing compounds, and organometallic salts.

[0053] Furthermore, in some embodiments, the pore former in step (1) is one or more selected from white oil, paraffin oil, and polyethylene glycol.

[0054] Furthermore, in some embodiments, for both S3 MD1 and S4 TD1 in step (2), the stretching temperature ranges from 60°C to 150°C, preferably from 60°C to 125°C, for example, in the range of 60°C to 120°C, and the stretching ratio ranges from 3 to 15 times, preferably from 8 to 15 times, for example, in the range of 8 to 10 times.

[0055] Furthermore, in some embodiments, for S5 MD2 in step (3), the stretching temperature ranges from 60°C to 140°C, preferably from 60°C to 130°C, and the stretching ratio ranges from 2 to 10 times, preferably from 2.5 to 10 times.

[0056] After the S4 TD1 stretching, the film may become much wider. Therefore, the width of the film is then significantly reduced by the S5 MD2 stretching, thereby eliminating the separator slitting process, improving the production efficiency and equipment utilization rate, increasing the stretching ratio of the film, and facilitating subsequent stretching.

[0057] Furthermore, in some embodiments, for S7 SBS in step (4), the stretching temperature ranges from 90°C to 140°C, and the stretching ratio ranges from 1.5×1.5 to 12×12 times, preferably from 3×3 to 12×12 times, for example, in the range of 5×5 to 12×12 times, or 8×8 to 12×12 times.

[0058] Since the S7 SBS stretching is performed on the film with reduced width, the stretching ratio of the film further increases.

[0059] Furthermore, let the draw ratio of S3 MD1 be "a", the draw ratio of S4 TD1 be "b", the draw ratio of S5 MD2 be "c", the draw ratio of S7 SBS be "g", and define the product of "a", "c", and "g" as "h", that is, a×c×g = h. Similarly, define the product of "b" and "g" as "k", that is, b×g = k. The values of "h" and "k" are, independently, preferably in the range of 15 to 150, more preferably 30 to 150, for example, 50 to 150, 64 to 150, 75 to 150, 100 to 150, or 125 to 150, or 128 to 150.

[0060] As disclosed herein, the S5 MD2 operation, together with the S7 SBS operation, is applied before S8 extraction, and the draw ratios in the MD and TD directions are increased by cascade drawing. As a result, the total draw ratios "h" and "k" in the MD and TD directions can reach values in the range of, for example, 15 to 150 times. Therefore, the planar draw ratio can reach values in the range of, for example, 225 to 22500 times. The separator manufactured by the method of the present disclosure has significantly improved tensile strengths in the MD and TD directions, and its puncture strength can also be much higher than the puncture strength of other separators of the same thickness.

[0061] Furthermore, in some embodiments, for S9 TD3 in step (5), the drawing temperature is in the range of 100°C to 150°C, preferably 100°C to 130°C, and the draw ratio is in the range of 1.1 to 2 times, preferably 1.2 to 2 times.

[0062] Furthermore, in some embodiments, for the S10 heat curing in step (5), the temperature is in the range of 110°C to 150°C, preferably 110°C to 135°C.

[0063] The ultra-high-strength separator obtained by any one of the above-described manufacturing methods of the present disclosure can have a thickness in the range of, for example, 3.7 μm to 8 μm, preferably 4 μm to 6 μm. In some embodiments, the transverse tensile strength of the separator disclosed herein is 4000 kgf / cm 2 super, preferably, 4500 kgf / cm 2 ~7000 kgf / cm 2, for example, 5000 kgf / cm 2 ~7000 kgf / cm 2 , 5500 kgf / cm 2 ~7000 kgf / cm 2 , 5800 kgf / cm 2 ~7000 kgf / cm 2 , 6100 kgf / cm 2 ~7000 kgf / cm 2 , or 6500 kgf / cm 2 ~7000 kgf / cm 2 within the range. In some embodiments, the longitudinal tensile strength of the separator disclosed herein is greater than 4000 kgf / cm 2 , preferably, 5000 kgf / cm 2 ~7000 kgf / cm 2 , for example, 5600 kgf / cm 2 ~7000 kgf / cm 2 , 6200 kgf / cm 2 ~7000 kgf / cm 2 , 6500 kgf / cm 2 ~7000 kgf / cm 2 , or 6800 kgf / cm 2 ~7000 kgf / cm 2 within the range. In some embodiments, the puncture strength per thickness of the separator disclosed herein is 100 gf / μm or more, preferably, in the range of 100 gf / μm to 200 gf / μm, for example, 120 gf / μm to 200 gf / μm, 130 gf / μm to 200 gf / μm, 100 gf / μm to 190 gf / μm, 120 gf / μm to 190 gf / μm, or 130 gf / μm to 190 gf / μm. In some embodiments, the porosity of the separator disclosed herein is in the range of 30% to 50%, and the air permeability of the separator disclosed herein is in the range of 50 seconds / 100 ml to 300 seconds / 100 ml.

[0064] To further understand the present disclosure, the technical solutions provided by the present disclosure will be described in detail below with reference to examples.

[0065] In the following Examples and Comparative Examples, the film performance or parameter tests are carried out according to the following methods.

[0066] 1. Thickness The thickness is measured according to the GB / T6672-2001 standard and tested as follows using a C1216 thickness gauge: Sample the outer periphery of the manufactured base film, cut out 40 mm × 60 mm samples, and test them at room temperature.

[0067] 2. Puncture strength The puncture strength is measured according to the ASTM D3736 standard and tested as follows using a KES-G5 manual compression tester: Cut out 40 mm × 60 mm sample pieces, test them at room temperature, with a test speed of 0.2 cm / second and a stroke of 20 mm.

[0068] 3. MD Tensile strength The MD tensile strength is measured according to the GB / T6672-2001 standard and tested as follows using a tensile tester (AGS-X10KN) manufactured by Shimadzu Corporation: Cut out 15 mm × 15 mm sample pieces, test them at room temperature, with a test speed of 50 mm / minute and a test gauge length of 10 mm.

[0069] 4. TD Tensile strength The TD tensile strength is measured according to the GB / T6672-2001 standard and tested as follows using a tensile tester (AGS-X10KN) manufactured by Shimadzu Corporation: Cut out 15 mm × 15 mm sample pieces, test them at room temperature, with a test speed of 50 mm / minute and a test gauge length of 10 mm.

[0070] [Example 1] 100 parts of high molecular weight polyethylene (average molecular weight 600,000) and 0.1 part of antioxidant were blended and stirred in a mixture; then, the mixture was poured into the feed bin of an extruder, and 360 parts of white oil was added simultaneously; the screw and extrusion speed were adjusted to completely mix and plasticize the high molecular weight polyethylene and white oil; S1 extrusion was carried out through a die; S2 cooling and sheet formation were carried out with a chill roll.

[0071] For the cast sheet, S3 MD1 stretching and S4 TD1 stretching were sequentially carried out. At this time, the stretching ratio was 10 times in both cases, the stretching temperature of S3 MD1 was 120 °C, and the stretching temperature of S4 TD1 was 125 °C.

[0072] For the stretched separator, S5 MD2 stretching was carried out at a stretching ratio of 2.5 times and a stretching temperature of 130 °C; then, S6 TD2 stretching was carried out at a stretching ratio of 3 times and a stretching temperature of 130 °C.

[0073] In S8, dichloromethane was used as an extraction solvent, and the white oil was extracted step by step with an extraction time of 30 minutes. For the separator after extraction, S9 TD3 stretching was carried out at a stretching ratio of 1.2 times and a stretching temperature of 130 °C.

[0074] For the separator stretched in S9 TD3, an S10 heating test was carried out at a heating and curing temperature of 135 °C to obtain an ultra-high strength polyethylene separator.

[0075] (Comparative Example 1) The blending of the same raw materials and S1 extrusion were carried out in the same process as in Example 1; after forming the S2 sheet, only S3 MD1 and S4 TD1 stretching were carried out at the same temperature and stretching ratio; then, S8 extraction was carried out under the same conditions; after extraction, S6 TD2 stretching was carried out at the same temperature and stretching ratio as that of S9 TD3 in Example 1; then, S10 heat curing was carried out at the same temperature and time as that of Example 1 to obtain a comparative sample.

[0076] The test results of the separator products manufactured in Example 1 and Comparative Example 1 are as follows.

[0077] [Table 1]

[0078] [Example 2] 100 parts of high molecular weight polyethylene (average molecular weight 600,000) and 0.5 part of antioxidant were blended and stirred in a mixture; then, the mixture was poured into the feed bin of an extruder, and 360 parts of white oil were added simultaneously; the screw and extrusion speed were adjusted to completely mix and plasticize the high molecular weight polyethylene and white oil; S1 extrusion was carried out through a die; S2 cooling and sheet forming were carried out with a chill roll.

[0079] S3 MD1 stretching and S4 TD1 stretching were sequentially carried out on the cast sheet. At this time, the stretching ratio was 10 times in both cases, the stretching temperature of S3 MD1 was 120 °C, and the stretching temperature of S4 TD1 was 125 °C.

[0080] For the stretched separator, S5 MD2 stretching was carried out at a stretching ratio of 2.5 times and a stretching temperature of 130 °C, and then S7 SBS stretching was carried out at a stretching ratio of 3×3 times and a stretching temperature of 130 °C.

[0081] Using dichloromethane as an extraction solvent, the white oil was extracted in step S8 with an extraction time of 30 minutes. For the separator after extraction, S9 TD3 stretching was carried out at a stretching ratio of 1.2 times and a stretching temperature of 130 °C.

[0082] For the separator stretched by S9 TD3, an S10 heating test was carried out at a heating and curing temperature of 135 °C to obtain an ultra-high strength polyethylene separator.

[0083] [Comparative Example 2] The blending of the same raw materials and the S1 extrusion were completed in the same process as in Example 2; after forming the S2 sheet, only the S3 MD1 and S4 TD1 stretching were carried out at the same temperature and draw ratio; then, the S8 extraction was carried out under the same conditions; after extraction, the S6 TD2 stretching was carried out at the same temperature and draw ratio as that of S9 TD3 in Example 2; then, the S10 heat curing was carried out at the same temperature and time as that of Example 2 to obtain a comparative sample.

[0084] The test results of the separator products manufactured in Example 2 and Comparative Example 2 are as follows.

[0085]

Table 2

[0086] [Example 3] 100 parts of high molecular weight polyethylene (average molecular weight 600,000) and 0.5 part of antioxidant were blended and stirred in a mixture; then, the mixture was poured into the feed bin of an extruder, 300 parts of white oil was added simultaneously, and the screw and extrusion speed were adjusted to completely mix and plasticize the high molecular weight polyethylene and the white oil; the S1 extrusion was carried out through a die; the S2 cooling and sheet forming were carried out with a chill roll.

[0087] The S3 MD1 stretching and S4 TD1 stretching were sequentially carried out on the cast sheet. At this time, the draw ratios were both 10 times, the stretching temperature of S3 MD1 was 120 °C, and the stretching temperature of S4 TD was 125 °C.

[0088] For the stretched separator, the S5 MD2 stretching was carried out at a draw ratio of 2.5 times and a stretching temperature of 130 °C, and then the S7 SBS stretching was carried out at a draw ratio of 5×5 times and a stretching temperature of 130 °C.

[0089] Using dichloromethane as an extraction solvent, the white oil was extracted in the S8 stage with an extraction time of 30 minutes. For the separator after extraction, the S9 TD3 stretching was carried out at a draw ratio of 1.2 times and a stretching temperature of 130 °C.

[0090] For the separator stretched with S9 TD3, an S10 heating test was carried out at a heat curing temperature of 135°C to obtain an ultra-high-strength polyethylene separator.

[0091] (Comparative Example 3) The blending of the same raw materials and S1 extrusion were completed by the same process as in Example 3; after forming S2 pieces, only S3 MD1 and S4 TD1 stretching were carried out at the same temperature and stretching ratio; then, S8 extraction was carried out under the same conditions; after extraction, S6 TD2 stretching was carried out at the same temperature and stretching ratio as that of S9 TD3 in Example 3; then, S10 heat curing was carried out at the same temperature and time as that in Example 3 to obtain a comparative sample.

[0092] The test results of the separator products manufactured in Example 3 and Comparative Example 3 are as follows.

[0093]

Table 3

[0094] [Example 4] 100 parts of high molecular weight polyethylene (average molecular weight 600,000) and 0.5 part of antioxidant were blended and stirred in a mixture; then, the mixture was poured into the feed bin of an extruder, and 300 parts of white oil were added simultaneously; the screw and extrusion speed were adjusted to completely mix and plasticize the high molecular weight polyethylene and white oil; S1 extrusion was carried out through a die; S2 cooling and piece forming were carried out with a chill roll.

[0095] S3 MD1 stretching and S4 TD1 stretching were sequentially carried out on the cast piece. At this time, the stretching ratio was 8 times in both cases, the stretching temperature of S3 MD1 was 120°C, and the stretching temperature of S4 TD1 was 125°C.

[0096] For the stretched separator, S5 MD2 stretching was carried out at a stretching ratio of 2 times and a stretching temperature of 130°C, and then S7 SBS stretching was carried out at a stretching ratio of 8×8 times and a stretching temperature of 130°C.

[0097] In S8, dichloromethane was used as the extraction solvent, and white oil was extracted step by step with an extraction time of 30 minutes. For the separator after extraction, S9 TD3 stretching was carried out at a stretching ratio of 1.2 times and a stretching temperature of 130 °C.

[0098] For the separator stretched by S9 TD3, an S10 heating test was carried out at a heating and curing temperature of 135 °C to obtain an ultra-high-strength polyethylene separator.

[0099] (Comparative Example 4) The blend of the same raw materials and S1 extrusion by the same process were carried out as in Example 4; after forming S2 pieces, only S3 MD1 and S4 TD1 stretching were carried out at the same temperature and stretching ratio; then, S8 extraction was carried out under the same conditions; after extraction, S6 TD2 stretching was carried out at the same temperature and stretching ratio as that of S9 TD3 in Example 4; then, S10 heating and curing was carried out at the same temperature and time as that of Example 4 to obtain a comparative sample.

[0100] The test results of the separator products manufactured in Example 4 and Comparative Example 4 are as follows.

[0101]

Table 4

[0102] [Example 5] 100 parts of high molecular weight polyethylene (average molecular weight 600,000) and 0.5 part of antioxidant were blended and stirred in a mixture; then, the mixture was poured into the feed bin of an extruder, and 300 parts of white oil was added simultaneously; the screw and extrusion speed were adjusted to completely mix and plasticize the high molecular weight polyethylene and white oil; S1 extrusion was carried out through a die; S2 cooling and piece formation were carried out with a chill roll.

[0103] Sequential S3 MD1 stretching and S4 TD1 stretching were performed on the cast piece. At this time, the stretching ratio was 10 times for both. The stretching temperature of S3 MD1 was 120 °C, and the stretching temperature of S4 TD1 was 125 °C.

[0104] For the stretching separator, S5 MD2 stretching was performed at a stretching ratio of 10 times and a stretching temperature of 130 °C, and then S6 TD2 stretching was performed at a stretching ratio of 10 times and a stretching temperature of 130 °C.

[0105] In S8, dichloromethane was used as the extraction solvent, and white oil was extracted step by step with an extraction time of 30 minutes. For the separator after extraction, S9 TD3 stretching was performed at a stretching ratio of 1.2 times and a stretching temperature of 130 °C.

[0106] For the separator stretched in S9 TD3, an S10 heating test was carried out at a heat curing temperature of 135 °C to obtain an ultra-high-strength polyethylene separator.

[0107] (Comparative Example 5) Blending of the same raw materials and S1 extrusion were completed as in Example 5 by the same process; after forming the S2 piece, only S3 MD1 and S4 TD1 stretching were performed at the same temperature and stretching ratio; then, S8 extraction was carried out under the same conditions; after extraction, S6 TD2 stretching was performed at the same temperature and stretching ratio as that of S9 TD3 in Example 5; then, S10 heat curing was carried out at the same temperature and time as that of Example 5 to obtain a comparative sample.

[0108] The test results of the separator products manufactured in Example 5 and Comparative Example 5 are as follows.

[0109]

Table 5

[0110] [Example 6] 100 parts of high molecular weight polyethylene (average molecular weight 600,000) and 0.5 part of antioxidant were blended and stirred in a mixture; then, the mixture was poured into the feed bin of an extruder, and 300 parts of white oil were added simultaneously; the screw and extrusion speed were adjusted to completely mix and plasticize the high molecular weight polyethylene and the white oil; S1 extrusion was carried out through a die; S2 cooling and sheet forming were carried out with a chill roll.

[0111] S3 MD1 stretching and S4 TD1 stretching were sequentially carried out on the cast sheet. At this time, the stretching ratio of MD1 was 7.5 times, the stretching ratio of TD1 was 15 times, the stretching temperature of S3 MD1 was 120 °C, and the stretching temperature of S4 TD1 was 125 °C.

[0112] For the stretched separator, S5 MD2 stretching was carried out at a stretching ratio of 2 times and a stretching temperature of 130 °C, and then S7 SBS stretching was carried out at a stretching ratio of 10×10 times and a stretching temperature of 130 °C.

[0113] In S8, dichloromethane was used as an extraction solvent, and the white oil was extracted step by step with an extraction time of 30 minutes. For the separator after extraction, S9 TD3 stretching was carried out at a stretching ratio of 1.2 times and a stretching temperature of 130 °C.

[0114] For the separator stretched by S9 TD3, an S10 heating test was carried out at a heating curing temperature of 135 °C to obtain an ultra-high strength polyethylene separator.

[0115] (Comparative Example 6) Blending of the same raw materials and S1 extrusion were carried out according to the same process as in Example 6; after forming the S2 sheet, only S3 MD1 and S4 TD1 stretching were carried out at the same temperature and stretching ratio; then, S8 extraction was carried out under the same conditions; after extraction, S6 TD2 stretching was carried out at the same temperature and stretching ratio as that of S9 TD3 in Example 6; then, S10 heat curing was carried out at the same temperature and time as that in Example 6 to obtain a comparative sample.

[0116] The test results of the separator products manufactured in Example 6 and Comparative Example 6 are as follows.

[0117]

Table 6

[0118] [Example 7] 100 parts of high molecular weight polyethylene (average molecular weight 1,500,000) and 0.5 part of antioxidant were blended and stirred in a mixture; then, the mixture was poured into the feed bin of an extruder, and 300 parts of white oil were added simultaneously; the screw and extrusion speed were adjusted to completely mix and plasticize the high molecular weight polyethylene and white oil; S1 extrusion was carried out through a die; S2 cooling and sheet forming were carried out with a chill roll.

[0119] For the cast sheet, S3 MD1 stretching and S4 TD1 stretching were sequentially carried out. At this time, the stretching ratio was 15 times for both, the stretching temperature of S3 MD1 was 120 °C, and the stretching temperature of S4 TD1 was 125 °C.

[0120] For the stretched separator, S5 MD2 stretching was carried out at a stretching ratio of 10 times and a stretching temperature of 130 °C, and then S6 TD2 stretching was carried out at a stretching ratio of 10 times and a stretching temperature of 130 °C.

[0121] In S8, dichloromethane was used as the extraction solvent, and the white oil was extracted step by step with an extraction time of 30 minutes. For the separator after extraction, S9 TD3 stretching was carried out at a stretching ratio of 1.2 times and a stretching temperature of 130 °C.

[0122] For the separator stretched in S9 TD3, an S10 heating test was carried out at a heating and curing temperature of 135 °C to obtain an ultra-high-strength polyethylene separator.

[0123] (Comparative Example 7) The blending of the same raw materials and S1 extrusion were completed as in Example 7 by the same process; after forming the S2 sheet, only S3 MD1 and S4 TD1 stretching were carried out at the same temperature and stretching ratio; then, S8 extraction was carried out under the same conditions; after extraction, S6 TD2 stretching was carried out at the same temperature and stretching ratio as that of S9 TD3 in Example 7; then, S10 heat curing was carried out at the same temperature and time as that in Example 7 to obtain a comparative sample.

[0124] The test results of the separator products manufactured in Example 7 and Comparative Example 7 are as follows.

[0125]

Table 7

Explanation of Symbols

[0126] S1 Extrusion S2 Cooling and Sheet Forming S3, S5 Longitudinal Stretching S4, S6, S9 Transverse Stretching S7 Simultaneous Biaxial Stretching S8 Extraction S10 Heat Curing

Claims

1. An ultra-high-strength separator, wherein the thickness of the ultra-high-strength separator is in the range of 3.7 μm to 8 μm, the transverse tensile strength of the ultra-high-strength separator is 4000 kgf / cm ２ super, and the longitudinal tensile strength of the ultra-high-strength separator is 4000 kgf / cm ２ super, and the puncture strength per unit thickness of the ultra-high-strength separator is 100 gf / μm or more, an ultra-high-strength separator.

2. The transverse tensile strength of the ultra-high-strength separator is in the range of 4500 kgf / cm ２ to 7000 kgf / cm ２ and the longitudinal tensile strength of the ultra-high-strength separator is in the range of 4500 kgf / cm ２ to 7000 kgf / cm ２ and / or the puncture strength per thickness of the ultra-high-strength separator is in the range of 100 gf / μm to 200 gf / μm, the ultra-high-strength separator according to claim 1.

3. The ultra-high strength separator according to claim 1, wherein the porosity of the ultra-high strength separator is in the range of 30% to 50%, and / or the air permeability of the ultra-high strength separator is in the range of 50 seconds / 100 ml to 300 seconds / 100 ml.

4. A method for manufacturing an ultra-high strength separator, comprising: (1) mixing and heating a composition containing a polyolefin resin, an antioxidant, and a pore former to form a molten mixture, extruding the mixture through a die, and then cooling it to form a cast sheet; (2) sequentially performing a first longitudinal stretching and a first transverse stretching on the cast sheet to obtain a stretched film; (3) performing a second longitudinal stretching on the stretched film; (4) performing a second transverse stretching; (5) sequentially performing extraction, a third transverse stretching, and heat curing to obtain an ultra-high strength separator. A method comprising the above steps.

5. The method for manufacturing an ultra-high strength separator according to claim 4, wherein when performing the second transverse stretching in step (4), the stretching temperature is in the range of 90°C to 140°C, and the stretching ratio is in the range of 2 to 10 times.

6. A method for manufacturing an ultra-high strength separator, comprising: (1) mixing and heating a composition containing a polyolefin resin, an antioxidant, and a pore former to form a molten mixture, extruding the mixture through a die, and then cooling it to form a cast sheet; (2) sequentially performing a first longitudinal stretching and a first transverse stretching on the cast sheet to obtain a stretched film; (3) performing a second longitudinal stretching on the stretched film; (4) performing simultaneous biaxial stretching; (5) sequentially performing extraction, a third transverse stretching, and heat curing to obtain an ultra-high strength separator. A method comprising the above steps.

7. The method for manufacturing an ultra-high strength separator according to claim 6, wherein when performing the simultaneous biaxial stretching in step (4), the stretching temperature is in the range of 90°C to 140°C, and the stretching ratio is in the range of 1.5×1.5 to 12×12 times.

8. The method for manufacturing an ultra-high strength separator according to claim 4 or 6, wherein for both the first longitudinal stretching and the first transverse stretching in step (2), the stretching temperature is in the range of 60°C to 150°C, and the stretching ratio is in the range of 3 to 15 times.

9. A method for manufacturing an ultra-high-strength separator according to claim 4 or 6, wherein for the second longitudinal extension of step (3), the extension temperature is in the range of 60°C to 140°C and the extension ratio is in the range of 2 to 10 times.

10. A method for manufacturing an ultra-high-strength separator according to claim 4 or 6, wherein for the third transverse extension of step (5), the extension temperature is in the range of 100°C to 150°C and the extension ratio is in the range of 1.1 to 2 times.

11. A method for manufacturing an ultra-high-strength separator according to claim 4 or 6, wherein the temperature of heat curing in step (5) is in the range of 110°C to 150°C.

12. A method for manufacturing an ultra-high-strength separator according to claim 4 or 6, wherein the polyolefin resin in step (1) is high molecular weight polyethylene and the molecular weight of the high molecular weight polyethylene is in the range of 600,000 to 2,000,000.

13. A method for manufacturing an ultra-high-strength separator according to claim 4 or 6, wherein the antioxidant in step (1) is one or more selected from amines, sulfur-containing compounds, nitrogen-containing compounds, phosphorus-containing compounds, and organic metal salts.

14. A method for manufacturing an ultra-high-strength separator according to claim 4 or 6, wherein the pore former in step (1) is one or more selected from white oil, paraffin oil, and polyethylene glycol.

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