CN114039165B - Composite diaphragm with high temperature heat-resistant shrinkage and compression elasticity - Google Patents
Composite diaphragm with high temperature heat-resistant shrinkage and compression elasticity Download PDFInfo
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Abstract
The invention provides a high-performance and economical composite diaphragm, which has low heat shrinkage rate at a high temperature of 140 ℃; the novel economic composite diaphragm with compression elasticity and economy and the manufacturing method thereof can self-adapt to volume expansion and contraction of the anode material in a wide temperature range from minus 30 ℃ to high temperature 70 ℃; the total thickness of the composite diaphragm is 14-40 micrometers, and the composite diaphragm mainly comprises two layers (A)/(B), wherein an oil-containing base film with compression elasticity and high strength in a wide temperature range is used as the layer (A), and the thickness of the layer (A) is 8-20 micrometers; the superfine fiber melt-blown microporous layer with low thermal shrinkage rate at the high temperature of 140 ℃ is used as a layer (B), the thickness of the layer (B) is 6-20 micrometers, and the porosity of the layer (B) is 50-77%.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a key diaphragm material used in a power battery and an energy storage battery.
Background
The lithium ion battery has high energy density and no memory effect, is widely applied to the fields of mobile phones, notebook computers, electric automobiles, energy storage and the like, and the power battery serving as a mobile energy source and the battery for energy storage used in a fixed position at present are required to improve the cycle life and the safety.
In order to improve the energy density of the power battery or the energy storage battery produced by partial enterprises, the negative electrode active material of the battery core is doped with nano wires of a silicon material or nano particles of the silicon material, and due to the huge volume expansion of the silicon material during charging, micro short circuit formed by local micro-piercing of a diaphragm often occurs, so that the self-discharge and consistency of the battery are affected, and serious malignant accidents such as short circuit heating, ignition explosion and the like are even caused; the conventional power or energy storage battery uses a wet PE base film plus a ceramic coating composite diaphragm or adopts a dry single-pull PP diaphragm with the thickness of 25-30 micrometers; although the ceramic coating has certain capacity of inhibiting micro-short circuit, the ceramic coating composite diaphragm basically has no compression elasticity in the thickness direction, cannot adapt to the volume expansion of the cathode material during charging, and the internal stress accumulation and fatigue of the battery core often cause the local stripping of the active material of the pole piece, and the consistency and the cycle life of the battery pack are required to be improved. The dry single-pull PP diaphragm has low transverse strength, low needling strength and easy tearing, and when the current battery is used, the micro short circuit resistance and the safety of the battery can be barely accepted by increasing the thickness to more than 25 microns, so that the energy density and the power characteristic of the battery are influenced; the dry single pull PP separator also has no compression elasticity function, and the consistency and cycle life of the battery pack also need to be improved.
In order to adapt to the volume expansion of the anode material during charging and the volume contraction behavior of the anode material during discharging, battery manufacturers on the basis of a conventional wet PE (polyethylene) base film combined single-sided ceramic coating composite diaphragm continue to spray or print a dot matrix coating of PVDF (polyvinylidene fluoride) copolymer on the surface of the diaphragm, and moderate swelling of the PVDF copolymer after electrolyte is absorbed is expected to occur, so that a gel-state elastomer is formed to compensate and adapt to the volume expansion/contraction behavior of the anode; however, the PVDF copolymer lattice by rotary spraying or printing is difficult to realize uniform microscopic distribution, and the battery is also inconsistent in terms of micro short circuit, self discharge and the like, so that the cycle life and the safety of the battery are affected.
The tensile strength, the needling strength, the tearing resistance and the micro-short circuit resistance of the conventional wet PE membrane are superior to those of a dry single-pull PP membrane, paraffin oil is generally adopted as a high-temperature compatilizer of PE during the manufacturing of the wet PE membrane, paraffin oil is subjected to high-temperature mixing and then subjected to thermally induced phase separation, low-temperature casting, then the two-way hot stretching strengthening is carried out, on-line dichloromethane extraction and drying are carried out, secondary transverse pulling and heat setting treatment is carried out continuously, the production flow of the wet PE membrane is long, the equipment investment of a production line is huge, the energy consumption of production operation is high, and in addition, the environmental protection problem of emission and treatment of dichloromethane solvents and waste gas also exists.
The wet PE diaphragm can not be used independently in the fields of power batteries and energy storage batteries which need longer service lives of more than 5 years at present, because the PE diaphragm has the ageing problem that the high-voltage oxidation gradually strength is reduced, the PE is generally isolated from the positive pole piece by adopting a ceramic coating, so that the cost of the wet ceramic coating composite diaphragm is far higher than that of a dry PP, and the market competitiveness is poor.
When the power and energy storage battery is normally used, the battery can possibly experience a low-temperature environment of minus 30 ℃, when the battery is operated outdoors in summer, the temperature of an electric core in the battery pack can be close to 70 ℃, the battery pole pack is initially tighter, after the battery pole pack is subjected to high temperature, if plastic deformation occurs on the diaphragm, the compression stress in the thickness direction between the pole packs can be partially released, the sealing contact between the battery pole packs and the diaphragm is not facilitated, and the consistency of the battery can be affected. When a power battery or an energy storage battery for an electric automobile is used in winter in certain areas, the battery can be placed in an environment close to minus 30 ℃ in the charging process or after being fully charged, so that the diaphragm is expected to keep toughness and moderate compression elasticity keeping capability even at minus 30 ℃, and the diaphragm does not have the problems of local brittle fracture and the like under the action of longitudinal tensile stress; even at low temperatures of-30 ℃, it is desirable that the separator still maintain moderate compressive elasticity; internal stress of the active material coating of the pole piece is reduced through elastic deformation of the diaphragm, and local stripping of the active material coating of the pole piece caused by local stress concentration is prevented; in summary, it is desirable that the separator has compression elasticity and high strength in a wide temperature range from minus 30 ℃ to 70 ℃ at low temperature.
The traditional wet PE base film and the ceramic coating composite diaphragm or the dry single-pull PP diaphragm have larger heat shrinkage rate at the high temperature of 140 ℃; the safety of the battery is not sufficient.
The present invention has been made in order to overcome the above limitations of the prior art.
Disclosure of Invention
The invention provides a high-performance and economical composite diaphragm, which can self-adapt to volume expansion/contraction of a negative electrode material, has compression elasticity in a wide temperature range from minus 30 ℃ to high temperature 70 ℃, has low thermal shrinkage rate at high temperature of 140 ℃, and is economical.
The composite diaphragm with high temperature heat shrinkage resistance and compression elasticity is characterized in that the total thickness of the composite diaphragm is 14-40 micrometers, and mainly comprises two layers (A)/(B), wherein an oil-containing base film with compression elasticity and high strength in a wide temperature range from minus 30 ℃ to high temperature 70 ℃ is used as the layer (A), and the thickness of the layer (A) is 8-20 micrometers; a micro porous layer of superfine fiber melt-blown cloth with low thermal shrinkage rate at 140 ℃ is used as a layer (B), the thickness of the layer (B) is 6-20 micrometers, and the porosity of the layer (B) is 50-77%; clamping the composite diaphragm between the positive pole piece and the negative pole piece, applying pressure of 0.15MPa in the thickness direction, and keeping the composite diaphragm at a high temperature of 140 ℃ for 2 hours, wherein the thermal shrinkage rate of the composite diaphragm in the MD and TD directions is less than 3%; Uniformly applying 0.30MPa pressure to the composite diaphragm in the thickness direction in a wide temperature range from minus 30 ℃ to high temperature 70 ℃ and maintaining the pressure for 2 hours, then releasing the pressure, taking the thickness of the composite diaphragm tested after the 3 rd compression/release as an initial value (T 0), and elastically recovering the total thickness of the composite diaphragm to not lower than 85% of the initial value (T 0) after 5000 times of compression/release cycles; The oil-based film (A) layer is characterized in that the main raw material composition comprises: (A1) A high-density polyethylene HDPE or a combination of HDPE of different molecular weights having a weight average molecular weight of from 40 to 150 and a content (W1) of from 20 to 36 parts by weight; (A2) A high flash point ester high temperature compatibilizer having an open flash point greater than 205 ℃ of dioctyl sebacate DOS and/or dioctyl terephthalate DOTP or a combination of both, the content (W2) being between 36 and 90 parts by weight; (A3) Thermoplastic elastomer OBC having compression elasticity in a wide temperature range, the content (W3) being between 0.20 (W1) and 0.80 (W1) parts by weight; The thermoplastic elastomer OBC adopts an ethylene-alpha olefin block copolymer as a raw material, and is mainly technically characterized in that: the melting peak melting point Tm is between 113 and 126 ℃, the latent heat of fusion is between 30 and 120J/g, the density is between 0.86 and 0.92g/cm 3, the crystallization temperature T c is between 90 and 110 ℃, the glass transition temperature Tg is lower than-40 ℃, A weight average molecular weight of from 7 to 40 ten thousand, of formula (HS) n, n being an integer greater than 5, wherein "H" represents a crystalline hard block of predominantly crystallizable ethylene-alpha olefin or pure ethylene having a low comonomer content and a high melting temperature, and "S" represents a soft block of predominantly amorphous ethylene-alpha olefin having a relatively high comonomer content, H and S being joined end-to-end in a linear fashion; The raw material composition of the layer (A) compatible at the high temperature of 195-205 ℃ is mixed into uniform thermodynamic solution at high temperature, high-temperature melt is extruded by a flat die head and then subjected to high Wen Zhu sheets, the internal flow passage of a casting sheet roller is circularly cooled by adopting 70-95 ℃ cooling liquid, so that the roller surface oil-free precipitation type high Wen Zhu sheets are achieved, the sheets are continuously preheated to (T c +3 ℃) to (T m -3 ℃), Adopting synchronous double-pulling or asynchronous double-pulling to carry out hot stretching bidirectional strengthening, then carrying out heat setting treatment, cooling to obtain an oil-containing base film (A) with high strength and compression elasticity comprehensive performance in a wide temperature range, wherein the longitudinal and transverse tensile strength of the oil-containing base film (A) is more than 130MPa, the elongation at break is more than 200%, the needling strength coefficient is more than 40N/micron, uniformly applying 0.30MPa pressure to the oil-containing base film in the thickness direction, maintaining the pressure for 2 hours, then releasing the pressure, taking the thickness of the oil-containing base film tested after the 3rd compression/release as an initial value (T 0), after 5000 times of compression/release cycles, the thickness of the oil-containing base film can be elastically restored to not less than 90% of the initial value (T 0); The superfine fiber melt-blown microporous layer (B) adopts polypropylene and thermoplastic elastomer compatible with the polypropylene at high temperature as main raw materials, and the raw materials mainly comprise the following compositions (B1): 100 parts by weight of a plastic component, a homo-polypropylene having a melt index MFR of 200-2100 or a PP composition of different melt index; (B2): a thermoplastic elastomer component having a weight average molecular weight of 5 to 25 ten thousand SEBS or SEPS or propylene-ethylene copolymer or propylene-octene copolymer or a combination thereof, 5 to 25 parts by weight; (B3): a thermoplastic conditioning material having a weight average molecular weight of less than 15 ten thousand, a propylene-ethylene copolymer or a propylene-octene copolymer having a melting point of 95-115 ℃,2-15 parts by weight; Mixing the main raw materials at high temperature to form uniform thermodynamic solution, forming superfine fiber melt-blown cloth on the surface of a microporous process carrier by adopting a superfine melt-blown process, wherein the diameter of superfine fiber is between 0.20 and 2 microns, the gram weight of each square meter is between 3 and 10 grams, precisely hot-pressing the superfine fiber melt-blown cloth after stripping from the microporous process carrier, and adjusting the porosity to 50 to 77 percent to form a superfine fiber melt-blown cloth microporous layer (B); the oil-based film (A) and the superfine fiber melt-blown microporous layer (B) are compounded together in an unextracted state to form the composite membrane with high-temperature heat-resistant shrinkage and compression elasticity. In the production process, the oil-containing base film (A) is prepared in advance and is compounded with the superfine fiber melt-blown cloth microporous layer (B) in an unextracted state, and the ultrasonic lattice intermittent welding is adopted only within the range of about 3 mm at the width edge during compounding, so that the composite diaphragm with high-temperature heat-resistant shrinkage and compression elasticity is formed. The diameter of the spinneret hole adopted by the superfine melt-blowing process is 0.10-0.25 mm, the length-diameter ratio of the spinneret hole is 30-100, the initial speed V 0 of the melt at the outlet of the spinneret hole is less than or equal to 0.25m/s, and the speed of the hot air outlets at the two sides of the spinneret hole is 100-330m/s. When the composite diaphragm is used for manufacturing the lithium ion battery, one side of a layer (B) of the composite diaphragm is contacted with a positive pole piece of the battery, and one side of an oil-containing base film (A) is contacted with a negative pole piece.
The oil in the oil-containing base film (A) layer of the invention refers to a high-flash-point ester high-temperature compatilizer, dioctyl sebacate DOS and/or dioctyl terephthalate DOTP or a combination of the dioctyl sebacate DOS and the dioctyl terephthalate DOTP with the open flash point of more than 205 ℃ can form thermodynamic solution with HDPE at the high temperature of 195-205 ℃.
When the composite membrane is actually produced, the high-strength oil-containing base membrane (A) is prepared in advance, and the conventional dichloromethane extraction and drying procedures for producing the PE membrane by a conventional wet method are not needed, so that the fixed asset amortization cost and the energy consumption cost of a production line of the high-strength oil-containing base membrane (A) are greatly reduced, and the environment-friendly load problem of dichloromethane is avoided; the invention adopts the high-flash-point ester high-temperature compatilizer as the high-temperature compatilizer of the HDPE and the thermoplastic elastomer thereof, the high-flash-point ester high-temperature compatilizer is used as an 'oil' phase to be directly dispersed and retained in a three-dimensional entangled fiber skeleton of the high-strength oil-based film after production, and the high-flash-point ester high-temperature compatilizer can be mutually dissolved with a small molecular ester organic solvent in the electrolyte after the battery is injected into the electrolyte, so that the performance of the battery is basically not adversely affected.
Compared with a wet PE (polyethylene) biaxially oriented thermal tensile membrane, the superfine fiber melt-blown microporous layer has better high-voltage oxidation resistance and low thermal shrinkage rate and compression elasticity, and when the composite membrane is used for manufacturing a lithium ion battery, one side of the superfine fiber melt-blown microporous layer (B) of the composite membrane is contacted with a positive pole piece of the lithium ion battery, and one side of the oil-containing base membrane (A) is contacted with a negative pole piece.
The superfine fiber melt-blown microporous layer (B) with compression elasticity adopts hydrogenated styrene-butadiene block copolymer SEBS raw material as linear triblock copolymer taking polystyrene as a terminal and taking ethylene-butene copolymer obtained by hydrogenation of polybutadiene as an intermediate elastic block, has good thermoplasticity and high elasticity, and can be used for elastic application without vulcanization. The hydrogenated styrene-isoprene segmented copolymer SEPS has a similar structure to SEBS, is a linear triblock copolymer which takes polystyrene as a terminal and takes an ethylene-propylene alternating structure copolymer obtained by hydrogenating polyisoprene as a middle elastic block, and also has excellent thermoplasticity and high elasticity, and can be used without vulcanization. The thermoplastic elastomer and PP plastic and low molecular weight thermoplastic temperature regulator are mixed at 210-250 deg.c to form homogeneous thermodynamic solution, i.e. homogeneous high temperature melt, and the melt viscosity may be regulated to 2 microns below and even below 1.5 microns, so that the novel elastic fiber may be controlled to be finer than that of conventional melt blown PP fiber.
The superfine fiber melt-blown cloth micro-porous layer (B) is formed by adopting a novel elastic fiber structure with compression elasticity and good electrolyte compatibility, wherein an elastomer material and a porous fiber structure can provide compression elasticity, the crystallinity of a PP plastic part is higher, chemical stability of an ester organic solvent in electrolyte is provided for the novel elastic fiber, the PP crystalline part can ensure that even though a microscopic rubber phase SEBS distributed in the novel elastic fiber or a polystyrene crystalline section in SEPS does not generate obvious compression plastic deformation after imbibition swelling, the compression elasticity of the superfine fiber melt-blown cloth at a high temperature of 70 ℃ can be improved, the porosity of a composite membrane is not reduced sharply and increased in resistance after the expansion and compression of a negative electrode, the charge/discharge power characteristic of a battery is influenced, the high-strength oil-containing base membrane (A) with wide temperature range compression elasticity has the mechanical characteristic of preventing the battery from generating micro short circuit, and the composite membrane can promote the consistency, the safety and the service life of the lithium ion battery.
The superfine fiber melt-blown microporous layer (B) has high porosity of 50-77% and submicron-level pore diameter after hot-pressing compounding, and when the composite membrane is applied to a battery, compared with a traditional nano-level microporous wet PE membrane or a traditional dry single-pull PP membrane, the composite membrane is also beneficial to the vacuum drying of a polar group and the rapid permeation during electrolyte injection, and is not easy to generate local bubbles and local barren solution.
In order to better illustrate the invention, the following are some examples.
Examples
Example 1:
The material formulation and the organization structure of the present invention may be variously combined, for example, the following formulation combinations may be adopted, under the understanding of the spirit of the present invention: the composite membrane with high temperature heat shrinkage resistance and compression elasticity has the total thickness of 22-24 microns and mainly comprises two layers (A)/(B), wherein an oil-containing base membrane with compression elasticity and high strength in a wide temperature range from minus 30 ℃ to high temperature 70 ℃ is used as the layer (A), and the thickness of the layer (A) is 11-12 microns; a micro porous layer of superfine fiber melt-blown cloth with low thermal shrinkage rate at 140 ℃ is used as a layer (B), the thickness of the layer (B) is 11-12 micrometers, and the porosity of the layer (B) is 60-70%; Clamping the composite diaphragm between the positive pole piece and the negative pole piece, applying pressure of 0.15MPa in the thickness direction, and keeping the composite diaphragm at a high temperature of 140 ℃ for 2 hours, wherein the thermal shrinkage rate of the composite diaphragm in the MD and TD directions is less than 1%; Uniformly applying 0.30MPa pressure to the composite diaphragm in the thickness direction in a wide temperature range from minus 30 ℃ to high temperature 70 ℃ and maintaining the pressure for 2 hours, then releasing the pressure, taking the thickness of the composite diaphragm tested after the 3 rd compression/release as an initial value (T 0), and elastically recovering the total thickness of the composite diaphragm to 88% or more of the initial value (T 0) after 5000 times of compression/release cycles; The main raw material composition of the oil-based film (A) containing layer comprises: (A1) A high-density polyethylene HDPE having a weight average molecular weight of 60 ten thousand, the content (W1) being 28 parts by weight; (A2) A high-flash ester high-temperature compatilizer, dioctyl sebacate DOS with an opening flash point of more than 210 ℃ and the content (W2) of 55 parts by weight; (A3) Thermoplastic elastomer OBC having compression elasticity in a wide temperature range, the content (W3) being 7 parts by weight; the thermoplastic elastomer OBC raw material adopts an ethylene-alpha olefin block copolymer, INFUSE 9530 produced by Dow chemical; The raw material composition of the (A) layer compatible at the high temperature of 195-205 ℃ is mixed into uniform thermodynamic solution at the high temperature of 198 ℃, high-temperature melt is extruded by a flat die head and then subjected to high Wen Zhu sheets, the internal runner of a casting sheet roller is circularly cooled by cooling water at 90-95 ℃ to achieve the oil-free precipitation type high Wen Zhu sheets on the roller surface, the sheets are continuously preheated to 113 ℃, then subjected to hot stretching bidirectional reinforcement by adopting 1.6 times of small longitudinal pulling and combining the subsequent 5*8 times of synchronous double pulling, then subjected to heat setting treatment at 116 ℃, cooled to obtain the oil-containing base film (A) with high strength and compression elasticity comprehensive performance in a wide temperature range, the range of 30 ℃ below zero to 70 ℃, The longitudinal and transverse tensile strength of the oil-based film (A) is more than 175MPa, the elongation at break is more than 260%, and the needling strength coefficient is more than 46N/micron; The raw materials of the superfine fiber melt-blown microporous layer (B) mainly comprise the following compositions (B1): 100 parts by weight of a plastic component, a homo-polypropylene with a melt index MFR of 1200; (B2): thermoplastic elastomer component, 15 parts by weight of SEBS with 15 ten thousand weight average molecular weight; (B3): thermoplastic regulating material, propylene-octene copolymer with weight average molecular weight less than 15 ten thousand and melting point 98 deg.c in 5 weight portions; the main raw materials are mixed at high temperature to form uniform thermodynamic solution, then superfine fiber melt-blown cloth is formed on the surface of a micro-porous process carrier by adopting a superfine melt-blown process, the diameter of superfine fiber is between 0.50 and 1.6 microns, the gram weight of each square meter is between 5 and 5.5 grams, the superfine fiber melt-blown cloth is firstly subjected to precise hot pressing at 128 ℃ after being peeled off from the micro-porous process carrier, and the porosity is adjusted to 60 to 70 percent, so that a micro-porous layer (B) of the superfine fiber melt-blown cloth is formed; The oil-based film (A) and the superfine fiber melt-blown microporous layer (B) are compounded together in an unextracted state to form the composite membrane with high-temperature heat-resistant shrinkage and compression elasticity.
Claims (4)
1. The composite diaphragm with high temperature heat shrinkage resistance and compression elasticity is characterized in that the total thickness of the composite diaphragm is 14-40 micrometers, the composite diaphragm comprises (A)/(B) two layers, an oil-containing base film with compression elasticity and high strength in a wide temperature range from minus 30 ℃ to high temperature 70 ℃ is used as the (A) layer, and the thickness of the (A) layer is 8-20 micrometers; a micro porous layer of superfine fiber melt-blown cloth with low thermal shrinkage rate at 140 ℃ is used as a layer (B), the thickness of the layer (B) is 6-20 micrometers, and the porosity of the layer (B) is 50-77%; clamping the composite diaphragm between the positive pole piece and the negative pole piece, applying pressure of 0.15MPa in the thickness direction, and keeping the composite diaphragm at a high temperature of 140 ℃ for 2 hours, wherein the thermal shrinkage rate of the composite diaphragm in the MD and TD directions is less than 3%; Uniformly applying 0.30MPa pressure to the composite diaphragm in the thickness direction in a wide temperature range from minus 30 ℃ to high temperature 70 ℃ and maintaining the pressure for 2 hours, then releasing the pressure, taking the thickness of the composite diaphragm tested after the 3 rd compression/release as an initial value (T 0), and elastically recovering the total thickness of the composite diaphragm to not lower than 85% of the initial value (T 0) after 5000 times of compression/release cycles; the oil-based film (A) layer is characterized in that the raw materials comprise: (A1) A high density polyethylene HDPE or a combination of HDPE of different molecular weights having a weight average molecular weight of between 40 and 150 ten thousand, in an amount (W1) of between 20 and 36 parts by weight; (A2) A high flash point ester high temperature compatibilizer having an open flash point greater than 205 ℃ of dioctyl sebacate DOS and/or dioctyl terephthalate DOTP or a combination of both, the content (W2) being between 36 and 90 parts by weight; (A3) Thermoplastic elastomer OBC having compression elasticity in a wide temperature range, the content (W3) being between 0.20 (W1) and 0.80 (W1) parts by weight; The thermoplastic elastomer OBC adopts an ethylene-alpha olefin block copolymer as a raw material, and is technically characterized by comprising the following steps: the melting peak melting point T m is between 113 and 126 ℃, the latent heat of fusion is between 30 and 120J/g, the density is between 0.86 and 0.92g/cm 3, the crystallization temperature T c is between 90 and 110 ℃, A glass transition temperature Tg of less than-40 ℃, a weight average molecular weight of from 7 to 40 ten thousand, a formula (HS) n, n being an integer greater than 5, wherein "H" represents a crystalline hard block of crystallizable ethylene-alpha olefin predominately or pure ethylene having a low comonomer content and a high melting temperature, "S" represents a soft block of amorphous ethylene-alpha olefin predominately having a relatively high comonomer content, H and S being joined end-to-end in a linear fashion; The raw material composition of the layer (A) compatible at the high temperature of 195-205 ℃ is mixed into uniform thermodynamic solution at high temperature, high-temperature melt is extruded by a flat die head and then subjected to high Wen Zhu sheets, the internal flow passage of a casting sheet roller is circularly cooled by adopting 70-95 ℃ cooling liquid, so as to achieve the roller surface oil-free precipitation type high Wen Zhu sheets, the sheets are continuously preheated to (T c +3 ℃) to (T m -3 ℃), Adopting synchronous double-pulling or asynchronous double-pulling to carry out hot stretching bidirectional strengthening, then carrying out heat setting treatment, cooling to obtain an oil-containing base film (A) with high strength and compression elasticity comprehensive performance in a wide temperature range, wherein the longitudinal and transverse tensile strength of the oil-containing base film (A) is more than 130MPa, the elongation at break is more than 200%, the needling strength coefficient is more than 40N/micron, uniformly applying 0.30MPa pressure to the oil-containing base film in the thickness direction, maintaining the pressure for 2 hours, then releasing the pressure, taking the thickness of the oil-containing base film tested after the 3rd compression/release as an initial value (T 0), after 5000 times of compression/release cycles, the thickness of the oil-containing base film can be elastically restored to not less than 90% of the initial value (T 0); The superfine fiber melt-blown microporous layer (B) adopts polypropylene and thermoplastic elastomer compatible with the polypropylene at high temperature as main raw materials, and the raw materials comprise the following composition (B1): 100 parts by weight of a plastic component, a homo-polypropylene or a composition thereof having a melt index MFR of 200-2100; (B2): a thermoplastic elastomer component having a weight average molecular weight of 5 to 25 ten thousand SEBS or SEPS or propylene-ethylene copolymer or propylene-octene copolymer or a combination thereof, 5 to 25 parts by weight; (B3): a thermoplastic conditioning material having a weight average molecular weight of less than 15 ten thousand, a propylene-ethylene copolymer or a propylene-octene copolymer having a melting point of 95-115 ℃,2-15 parts by weight; Mixing the above raw materials at high temperature to form uniform thermodynamic solution, forming superfine fiber melt-blown cloth on the surface of a microporous process carrier by adopting a superfine melt-blown process, wherein the diameter of superfine fiber is between 0.20 and 2 microns, the gram weight of each square meter is between 3 and 10 grams, precisely hot-pressing the superfine fiber melt-blown cloth after stripping from the microporous process carrier, and adjusting the porosity to 50 to 77 percent to form a superfine fiber melt-blown cloth microporous layer (B); the oil-based film (A) and the superfine fiber melt-blown microporous layer (B) are compounded together in an unextracted state to form the composite membrane with high-temperature heat-resistant shrinkage and compression elasticity.
2. The composite membrane with high-temperature heat-resistant shrinkage and compression elasticity according to claim 1, wherein the oil-containing base membrane (a) is prepared in advance, is compounded with the superfine fiber melt-blown microporous layer (B) in an unextracted state, and is welded together only at the width edges by adopting ultrasonic lattice-like gaps during compounding, so that the composite membrane with high-temperature heat-resistant shrinkage and compression elasticity is formed.
3. The composite membrane with high temperature heat shrinkage resistance and compression elasticity according to claim 1, wherein the diameter of the spinneret orifice used in the ultra-fine melt blowing process is 0.10-0.25 mm, the length-diameter ratio of the spinneret orifice is 30-100, the initial velocity V 0 of the melt at the outlet of the spinneret orifice is less than or equal to 0.25m/s, and the velocity of the hot air at the two sides of the spinneret orifice is 100-330m/s.
4. The composite membrane with high-temperature heat-resistant shrinkage and compression elasticity according to claim 1, wherein the lithium ion battery is manufactured by adopting the composite membrane, one side of a layer (B) of the composite membrane is contacted with a positive pole piece of the battery, and one side of an oil-containing base membrane (A) is contacted with a negative pole piece.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111156145.7A CN114039165B (en) | 2021-09-27 | Composite diaphragm with high temperature heat-resistant shrinkage and compression elasticity |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111156145.7A CN114039165B (en) | 2021-09-27 | Composite diaphragm with high temperature heat-resistant shrinkage and compression elasticity |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01157055A (en) * | 1987-12-11 | 1989-06-20 | Toyobo Co Ltd | Nonwoven fabric for battery separator and its manufacture |
| CN112366421A (en) * | 2020-10-15 | 2021-02-12 | 天津宝润科技有限公司 | Composite diaphragm with compression elasticity and manufacturing method thereof |
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01157055A (en) * | 1987-12-11 | 1989-06-20 | Toyobo Co Ltd | Nonwoven fabric for battery separator and its manufacture |
| CN112366421A (en) * | 2020-10-15 | 2021-02-12 | 天津宝润科技有限公司 | Composite diaphragm with compression elasticity and manufacturing method thereof |
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