CN110021729A - A kind of composite diaphragm and preparation method thereof of gradient low temperature closed pore - Google Patents

A kind of composite diaphragm and preparation method thereof of gradient low temperature closed pore Download PDF

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Publication number
CN110021729A
CN110021729A CN201910322963.6A CN201910322963A CN110021729A CN 110021729 A CN110021729 A CN 110021729A CN 201910322963 A CN201910322963 A CN 201910322963A CN 110021729 A CN110021729 A CN 110021729A
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layer
micro
basement membrane
closed pore
nano
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王哲
麻小挺
刘琳
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Shenzhen Zhongxing New Material Technology Ltd By Share Ltd
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Shenzhen Zhongxing New Material Technology Ltd By Share Ltd
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403Manufacturing processes of separators, membranes or diaphragms
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409Separators, membranes or diaphragms characterised by the material
    • H01M50/411Organic material
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409Separators, membranes or diaphragms characterised by the material
    • H01M50/44Fibrous material
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Cell Separators (AREA)
  • Laminated Bodies (AREA)

Abstract

This application discloses a kind of composite diaphragms and preparation method thereof of gradient low temperature closed pore.The composite diaphragm of the application includes basement membrane, the low temperature closed pore layer for being applied to one surface of basement membrane and the high-temperaure coating for being applied to another surface;Low temperature closed pore layer be fusing point lower than 140 DEG C of polymer water dispersion emulsion coating at;High-temperaure coating is coated by ceramics or aramid fiber;Basement membrane is made of upper epidermis, middle layer and layer, and middle layer is the multilayered structure that polypropylene layer and polyethylene layer are formed by micro-nano lamination techniques, and upper layer is polypropylene layer.The composite diaphragm of the application, multilayered structure is prepared using micro-nano lamination techniques, safety is more preferable, while improving the mechanical properties such as diaphragm tensile strength and puncture strength, diaphragm can be accomplished thinner, be able to satisfy demand of the slimming high safety lithium battery diaphragm to mechanical property and safety.High-temperaure coating and low temperature closed pore layer slimming battery diaphragm have better heat-resisting quantity and closed pore safety.

Description

A kind of composite diaphragm and preparation method thereof of gradient low temperature closed pore
Technical field
This application involves lithium ion battery separator fields, a kind of composite diaphragm more particularly to gradient low temperature closed pore and its Preparation method.
Background technique
With the development of electric car and energy storage industry, the requirement to lithium battery is higher and higher, it is desirable that and lithium battery is safer, Energy density is higher.Lithium battery diaphragm is one of the material of most critical inside lithium battery, directly influence lithium battery safety and Energy density, so preparing the microporous barrier that safe and environment-friendly, thickness is thin, inexpensive is the difficult point in lithium battery diaphragm development process. Currently, the manufacturing method of lithium battery diaphragm has wet process and two kinds of dry method.Wherein wet process is needed using a large amount of organic diluents, The device is complicated, at high cost, easily causes environmental pollution.Dry method with respect to wet process for, equipment is simple, and at low cost, non-environmental-pollution is asked Topic.Dry method is broadly divided into dry method simple tension and dry method biaxial tension technology.Dry method biaxial tension technology preparation microporous barrier at Hole is uneven, and mainly due to polypropylene, in beta crystal, the position of pore-forming and the size of pore-forming into alpha-crystal form conversion process are uncontrollable System.So the prevailing technology of dry method diaphragm is that dry method list draws diaphragm now.
Guarantee lithium battery safety, energy density is high, and needing lithium battery diaphragm to reach application on some key performances needs It asks, such as thickness is thin, intensity is high, defect is few, safety is high etc..Realize these crucial performance indicators, lithium battery diaphragm The control of structure design and processes is most important.
At the initial stage of battery short circuit heating, if diaphragm can be breaking in time, further stop or prevent short circuit, it can Greatly improve the safety of lithium battery.Existing wet process diaphragm usually uses ultrahigh molecular weight polyethylene standby, melt flows speed Degree is slow, and pyrocondensation is big in temperature-rise period, cannot timely closed pore.Dry method polypropylene diaphragm closed pore temperature is higher, pyrocondensation in temperature-rise period Greatly, so cannot respond faster and protect cell safety.In dry method polypropylene, polyethylene/polypropylene three-layer membrane, although setting Polyethylene layer is counted as protection, but polyethylene layer is in centre, needs certain heat transfer and time just and can play the role of and is breaking.
Summary of the invention
The purpose of the application is to provide a kind of composite diaphragm and preparation method thereof of improved gradient low temperature closed pore.
To achieve the goals above, the application uses following technical scheme:
The one side of the application discloses a kind of composite diaphragm of gradient low temperature closed pore, including basement membrane, is coated on basement membrane one The low temperature closed pore layer on a surface and high-temperaure coating coated on another surface of basement membrane;Low temperature closed pore layer is that fusing point is lower than 140 DEG C The water dispersion emulsion coating of polymer form;High-temperaure coating is coated with by ceramics or aramid fiber;Basement membrane is by upper epidermis, centre Layer and layer composition, middle layer are the multilayered structure that polypropylene layer and polyethylene layer are formed by micro-nano lamination techniques, upper table Layer and layer are polypropylene layer.
It should be noted that the composite diaphragm of the application, one side basement membrane is designed to multilayered structure, especially middle layer Multilayered structure is made using micro & nano technology, defect existing for single-layer septum is compensated for, avoids security risk;On the other hand pass through Micro-nano lamination techniques solve the problems, such as that film by dry method clear opening is more, and improve the mechanical property such as tensile strength, puncture strength Can, intermediate multilayer is polyethylene layer and polypropylene layer, can be polyethylene layer and polypropylene multi-layer superposition or each layer alternating layer Folded, overlay order can be adjusted according to function, with polythene material addition and control polyethylene layer close to surface layer, can To realize the function of quicking break, guarantee lithium battery safety.High-temperaure coating further improves the tensile strength of composite diaphragm With the mechanical properties such as puncture strength, and make composite diaphragm high temperature resistance with higher.The low temperature closed pore layer of the application, can The closed pore temperature for the polyethylene layer for being different from middle layer, i.e. realization gradient closed pore function is set as needed;So-called gradient The closed pore temperature of closed pore function, that is, low temperature closed pore layer and polyethylene layer increases or submits in gradient, closes for example, low temperature can be designed The closed pore temperature of aperture layer is lower, and the closed pore temperature of polyethylene layer is higher, and at the beginning of battery mid-winter, low temperature closed pore layer first melts It is disconnected, preliminary protective effect is played, as constant temperature increases, second class protection is played the role of in polyethylene layer fusing.The application's Composite diaphragm can satisfy demand of the lithium battery diaphragm of slimming high safety to mechanical property and high security.
Preferably, middle layer is answering for the 4-32 layer stackup that polypropylene layer and polyethylene layer are formed by micro-nano lamination techniques Close structure.
It should be noted that wherein interbed is formed using micro-nano lamination techniques in the basement membrane of the application, preparation process environmental protection Safety, product cost are high;Also, as the number of plies of micro-nano layer stackup increases, the mechanical properties such as puncture resistant, tear-proof are improved, Defects count can also reduce.
Preferably, the polypropylene that basement membrane uses is greater than 96%, poly- third that melt index is 0.3-5g/10min for isotacticity Alkene.
Preferably, the polyethylene that basement membrane uses is the high density polyethylene (HDPE) of melt index 0.05-5g/10min.
It should be noted that the basement membrane of the application, upper epidermis, middle layer and layer can be used same isotacticity and The polypropylene of melt index also can be used and limit the polypropylene of the different isotacticities and melt index in range in the application, It is not specifically limited herein.
Preferably, basement membrane with a thickness of 10-25 microns, wherein upper epidermis with a thickness of 2-4 microns, the thickness of layer It is 2-4 microns.
It should be noted that outermost two surface layers of basement membrane are designed as thicker layer by the application, its purpose is to more Good protects basement membrane not by breakage;It is appreciated that the overall thickness of basement membrane itself is not thick, middle layer uses micro-nano lamination techniques system It is standby, each layer be all it is very thin, if two not thicker surface layers, be easy to cause breakage in subsequent process.
Preferably, the porosity of basement membrane is 20%-60%.
Preferably, low temperature closed pore layer with a thickness of 1-6 microns, high-temperaure coating with a thickness of 1-6 microns.
It should be noted that the low temperature closed pore layer and high-temperaure coating of the application, effect is to further enhance THIN COMPOSITE The performance of film, for example, the effect of low temperature closed pore layer be enable the laminated film of the application lower than 140 DEG C at a temperature of close Hole, in time open circuit, prevents short circuit, improves the safety of battery;The effect of high-temperaure coating further increases laminated film Mechanical property.Therefore, the specific thickness of low temperature closed pore layer and high-temperaure coating can not be made to have herein depending on product demand Body limits.
Preferably, polymer of the fusing point lower than 140 DEG C is polyethylene wax.
Preferably, the partial size of polymer is 50 nanometers -2 microns in water dispersion lotion.
It should be noted that in the low temperature closed pore layer of the application, it is preferred to use the polymer that partial size is 50 nanometers -2 microns Particle is coated with to form coating;Because partial size is smaller, the fusing point for being coated with the coating of formation is lower, on the one hand can block dry method list On the other hand the surface defect of membrane can preferably realize low temperature closed pore function.
In the composite diaphragm of the application, the middle layer of basement membrane is prepared using micro-nano lamination techniques, is actually used A kind of polyolefin micropore membrane preparation device newly developed.Specifically, the device includes extruder, micro-nano layer multiplier, extrusion die Head and cooling traction module;Extruder is used to squeeze out the polyolefine material of melting;A kind of micro-nano layer multiplier generally shunt is divided Layer container, technique accept extruder, if then forming a layer per one for the polyolefine material of melting to be divided into carried interest, Ultimately form the composite multi-layer melt of several layer stackups;Extrusion die technique accepts micro-nano layer multiplier, for squeezing out several layers The composite multi-layer melt of stacking;Cooling traction module technique accepts extrusion die, for by the polyolefin of micro-nano layer multiplication answer The cooling of multilayer melt is closed, is cast and draws to subsequent processing.
It should be noted that the polyolefin micropore membrane preparation device of the application, fills in existing polyolefin micropore film preparation Set middle introducing micro-nano layer multiplier, prepare the MIcroporous polyolefin film of multilayered structure using micro-nano layer multiplier, remaining module or Component, such as extruder, extrusion die and cooling traction module etc., can refer to existing MIcroporous polyolefin film dry method tension Preparation facilities.The basic principle of micro-nano layer multiplier is, if the polyolefine material of melting is divided into carried interest, independently forms per one One layer, therefore, however, it would be possible to if being divided into carried interest, form several layers, the MIcroporous polyolefin film of such multilayered structure, either machine Tool intensity or porosity are better than the MIcroporous polyolefin film of individually stratification.In the application, technique undertaking refers to according to polyolefin For the module that the movement of material is passed through, the two is in the relationship of front and back station;The module or component that technique is accepted, can be It links together, is also possible to that front and back station connects together using pipeline acquisition traction device.
Preferably, micro-nano layer multiplier include technique accept entrance, shunting section, layering section, interflow section, changeover portion and Outlet section;The outlet of entrance and extruder connects, for receiving the polyolefine material of the melting squeezed out by extruder;Shunting section Including several shunt conduits, if for the polyolefine material of melting to be divided into carried interest;It is layered section and accepts shunting section, for quilt If the fused polyolefin material for being divided into carried interest is pre-chilled, it is allowed to still maintain layering after collaborating again, without merging one It rises;Collaborate section and accept layering section, if for being gradually close together the fused polyolefin material of carried interest;Changeover portion accepts interflow Section, if for carried interest fused polyolefin material gradually to be suppressed layered, and it is final stacked together;Outlet section accepts transition Section obtains the polyolefin composite multi-layer melt of micro-nano layer multiplication if the composite multi-layer melt for exporting a layer stackup;Extrusion die Head is connect with outlet section, for squeezing out the polyolefin composite multi-layer melt of micro-nano layer multiplication.
It should be noted that entrance, shunting section, layering section, interflow section, the specific constructive form of changeover portion and outlet section Only in a kind of implementation of the application device, the micro-nano layer doubler structures that specifically use, however not excluded that it can also be used Its similar structure is not specifically limited herein with realizing shunting, layer functions.
Preferably, the application device further includes co-extrusion module, and co-extrusion module is set to extruder and micro-nano layer multiplier Between entrance, the polyolefine material for squeezing out multiple extruders converges extrusion, is then conveyed to micro-nano layer multiplier again Carry out the multiplication of micro-nano layer.
It should be noted that in the preparation process of MIcroporous polyolefin film, it usually can be by of the same race or different materials polyenes Hydrocarbon coextrusion, to form multilayer complex films, for example, by using identical trade mark polypropylene or polyethylene, different trade mark polypropylene or poly- second Alkene coextrusion or different materials, as polypropylene and two kinds of polyethylene it is polyolefin coextruded;Therefore, it is necessary to use co-extrusion module The polyolefin for the similar and different material that multiple extruders squeeze out is converged into extrusion, then carries out micro-nano layer multiplication.
Preferably, the application device includes that several micro-nano layer multipliers are connected, using crowded between micro-nano layer multiplier Die head transition connects out, the last one micro-nano layer multiplier is accepted after connecting extrusion die with cooling traction module technique.
It should be noted that the number of share of stock that each micro-nano layer multiplier can distribute is limited, therefore, if only with The micro-nano layer that one micro-nano layer multiplier is capable of forming also is limited.In order to obtain the micro-nano layer of more numbers of plies, the application Multiple micro-nano layer multipliers are used in series in preferred scheme, are obtained with more numbers of plies in this way.In principle, it is assumed that polyene Hydrocarbon material is to be expressed into micro-nano layer multiplier by co-extrusion module by converging after two kinds of polyolefin plastifying fusions of A and B, if each micro- Layer multiplier of receiving can distribute 2 strands, and the number of plies that can be obtained if n micro-nano layer multiplier is connected is 2 × 2nLayer;Also It is to say, the number of plies that the series connection of several micro-nano layer multipliers can obtain is x × ynLayer, wherein x is the polyene that co-extrusion module squeezes out Hydrocarbon number, the i.e. quantity of extruder, y are that each micro-nano layer multiplier can distribute number of share of stock, and n is the series connection of micro-nano layer multiplier Number.In general, the quantity of extruder is 1,2 or 3, and therefore, the value of x is usually 1-3, certainly, if do not considered Machine cost or some special producing demands can also use more extruders.Usual each micro-nano layer multiplier can 2 strands or 4 strands are distributed, therefore, the value of y can be 2 or 4, certainly, also be not excluded for other special designs.The multiplication of micro-nano layer The stock that the number of device depends on the number of plies of required MIcroporous polyolefin film and each micro-nano layer multiplier can distribute Number;For example, in the case where distributing 4 strands for two extruders, each micro-nano layer multiplier, 3 micro-nano layer multiplier series connection 128 layers of MIcroporous polyolefin film can have been prepared;Although number of plies increase has increase to the mechanical performance of MIcroporous polyolefin film, But if the number of plies is too many, the tortuosity ratio in hole increases, and will affect ventilative value;Therefore, usual for 4 strands of micro-nano layer multiplier Using 1-3, and for 2 strands of micro-nano layer multiplier using 1-5, certainly, according to different product demands, It can be connected, be not specifically limited herein using more micro-nano layer multipliers.
Based on newly developed polyolefin micropore membrane preparation device, the preparation method of the composite diaphragm of the application, including it is following Step:
(a) preparation of polymer-coated slurry: the polymer by fusing point lower than 140 DEG C is dispersed in water, and water dispersion is made Lotion;
(b) by ceramic particle or aramid fiber powder dispersion liquid solvent, coating the preparation of high-temperaure coating coating slurry: is made Slurry;
(c) micro-nano is laminated: the pp material for preparing middle layer and polyethylene raw material being squeezed out by two extruders, then Converged by co-extrusion module and be expressed into micro-nano layer multiplier, forms the middle layer of the multilayered structure of micro-nano stacking;
(d) preparation of co-extrusion diaphragm: the pp material for preparing upper epidermis and layer is squeezed out by two extruders, so The upper epidermis of extrusion, middle layer and layer are converged into extrusion by co-extrusion die head afterwards, form co-extrusion diaphragm;
(e) it anneals: the co-extrusion diaphragm progress high-temperature heat treatment prepared being formed and improves platelet, that is, is made annealing treatment, high temperature The temperature of heat treatment is 110-135 DEG C;
(f) it stretches: three step process is carried out to the product of annealing, i.e. cold drawing, hot-drawn and thermal finalization, described in acquisition Basement membrane;
(g) it is coated with: the polymer-coated slurry of preparation and high-temperaure coating coating slurry is respectively coated on the two of basement membrane A surface, drying obtain the composite diaphragm of the application.
Preferably, (d) in stretching step, cold drawing multiplying power 1.02-1.4, cold drawing temperature is 40-120 DEG C;Hot-drawn multiplying power 1.3- 3.0,110-135 DEG C;Thermal finalization multiplying power 0.99-0.7, heat setting temperature are 120-135 DEG C.
Due to using the technology described above, the beneficial effects of the present application are as follows:
The composite diaphragm of the application, basement membrane using micro-nano lamination techniques prepare polypropylene layer and polyethylene layer composition it is more The middle layer of layer structure, on the one hand, multilayered structure has better safety;On the other hand, micro-nano lamination techniques form centre Layer, while the tensile strength and the mechanical properties such as puncture strength for improving battery diaphragm, battery diaphragm can be accomplished it is thinner, It can satisfy demand of the lithium battery diaphragm of slimming high safety to mechanical property and safety.By adjusting poly- second in middle layer Distance of the alkene layer away from surface can also realize the adjusting of the function of quicking break of different-effect, to meet different cut-out functions Use demand.On this basis, high-temperaure coating makes laminated film have better high temperature resistance, and low temperature closed pore layer makes Laminated film can realize closed pore function at a lower temperature, improve the safety of laminated film;So that slim electrochemical cell Diaphragm has better heat-resisting quantity and closed pore safety.
Detailed description of the invention
Fig. 1 is the organigram of polyolefin micropore membrane preparation device in the embodiment of the present application;
Fig. 2 is the structural schematic diagram of micro-nano layer multiplier in the embodiment of the present application;
Fig. 3 is the structural schematic diagram of the composite diaphragm of gradient low temperature closed pore in the embodiment of the present application.
Specific embodiment
The preparation of the creative basement membrane that micro-nano lamination techniques are applied to battery diaphragm of the application, specifically, basement membrane by Upper epidermis, middle layer and layer composition, wherein middle layer is that polypropylene layer and polyethylene layer are formed by micro-nano lamination techniques Multilayered structure.
It should be noted that the micro-nano laminar composite that micro-nano lamination techniques are formed is in polymer high performance and function Changing aspect has great potential, can be improved the toughness and intensity of composite material.Micro-nano lamination techniques are applied to high-strength and high ductility at present Material, high-barrier packaging material, sonar stealth material, electromagnetic shielding, micro-nano capacitor high-performance dielectric material, a variety of drugs Integrated controllable sustained-release material etc..Micro-nano laminar composite increases with the number of plies, and the mechanical properties such as puncture resistant, tear-proof mention Height, defects count reduce;The application creatively mutually ties the demand of lithium battery diaphragm with the design of the structure of micro-nano stratified material It closes, the mechanical properties such as integrally stretching intensity, the puncture strength of battery diaphragm can be effectively improved, to prepare slimming, height Safety, high-intensitive, environmental protection lithium battery diaphragm.
The application is described in further detail below by specific embodiments and the drawings.Following embodiment is only to the application It is further described, should not be construed as the limitation to the application.
Embodiment 1
The polyolefin micropore membrane preparation device of this example, wherein be used to prepare the middle layer of the multilayered structure of micro-nano stacking Part, as shown in Figure 1, including two extruders 1, co-extrusion module 5, micro-nano layer multiplier 2, extrusion die 3 and cooling traction mould Block 4;Wherein, two extruders 1 are respectively used to squeeze out the pp material and polyethylene raw material of preparation middle layer;Co-extrusion module 5 It is set to the delivery outlet of two extruders, the polyolefine material for squeezing out two extruders converges extrusion, then conveys again To micro-nano layer multiplier 2;The generally a kind of shunting tiered container of micro-nano layer multiplier 2, the melting for squeezing out co-extrusion module 5 If polyene hydrocarbon material be divided into carried interest, then per one formed a layer, ultimately form the composite multi-layer melt of several layer stackups; 3 technique of extrusion die accepts micro-nano layer multiplier 2, the middle layer melt of the multilayered structure for squeezing out the stacking of several layers micro-nano; After middle layer melt and upper epidermis and the melt of layer converge, the cooling traction module 4 accepted by technique is by the polyene of extrusion Hydrocarbon composite multi-layer melt is cooling, is cast and draws to subsequent processing.
The micro-nano layer multiplier 2 of this example, as shown in Fig. 2, including entrance 21, shunting section 22, layering section that technique is accepted 23, collaborate section 24, changeover portion 25 and outlet section 26;Entrance 21 is connect with the outlet of co-extrusion module 5, for receiving by coextruding die The polyolefine material for the melting that block squeezes out;Shunting section 22 includes several shunt conduits, the polyolefine material point for that will melt If may be generally divided into two strands or four strands at carried interest, Fig. 2, which is shown, is divided into four strands of micro-nano layer multiplier, and still, this example considers The number of plies to MIcroporous polyolefin film easily causes ventilative value too much and is significantly increased, and this example is specifically using can be divided into two strands Micro-nano layer multiplier, i.e. shunting section 22 include two shunt conduits, and the polyolefine material of melting is divided into two strands;Layering section 23 is held Shunting section 22 is connect, for the fused polyolefin material for being divided into two strands to be pre-chilled, is allowed to still maintain after collaborating again point Layer, without being fused together;Collaborate section 24 and accept layering section 23, for two strands of fused polyolefin materials to be gradually close in one It rises;Changeover portion 25 accepts interflow section 24, for two strands of fused polyolefin materials gradually to be suppressed layered, and is finally layered in one It rises, forms the structure of 2 × 2 total four layer stackups;Outlet section 26 accepts changeover portion 25, for exporting the composite multi-layer of four layer stackups The middle layer melt of the multilayered structure of melt, i.e. micro-nano stacking.
It is appreciated that above is only illustratively to illustrate that the polyolefin of this example is micro- using two strands of micro-nano layer multipliers Hole membrane preparation device can be connected, specifically, micro-nano if it is desired to obtaining the structure with multilayer using multiple micro-nano layer multipliers It is connected between layer multiplier using extrusion die transition, the last one micro-nano layer multiplier is drawn after connecting extrusion die with cooling Module process is accepted.For example, 2 × 2 can be obtained if connected using n micro-nano layer multipliernThe micro-nano of layer is laminated more The middle layer melt of layer structure.Depending on production requirement, it is not specifically limited herein.
Polyolefin micropore membrane preparation device based on this example, the preparation method of the composite diaphragm of the gradient low temperature closed pore of this example The following steps are included:
(a) preparation of polymer-coated slurry: the polymer by fusing point lower than 140 DEG C is dispersed in water, and water dispersion is made Lotion;This example specifically prepares water dispersion lotion using polyethylene wax, and the partial size of polyethylene wax is 500 nanometers, water dispersion cream The solid content of liquid is 35%;Polymer by fusing point lower than 140 DEG C is dispersed in water, and water dispersion lotion is made;Add binder Obtain polymer-coated slurry;This example specifically using polyethylene wax water dispersion lotion, receive for 500 by the partial size of polyethylene wax Rice, fusing point are 117 degree, and the solid content of water dispersion lotion is 35%;Binder uses polyacrylate emulsion, according to solid content ratio Example is binder: polyethylene wax=1:19.Polyethylene water dispersion lotion and polyacrylate emulsion are mixed using high-speed dispersion equipment It closes dispersion and obtains poly polymer coating slurry
(b) by ceramic particle or aramid fiber powder dispersion liquid solvent, coating the preparation of high-temperaure coating coating slurry: is made Slurry;Specific steps are as follows: prepared by 1. ceramic slurries: ceramic particle uses α phase high purity aluminium oxide, purity 99.93%, grain Spending D50 is 500 nanometers, and by ceramics and water, ammonium polyacrylate class dispersing agent, polyacrylate emulsion binder is according to solid content ratio The ratio that example is 40:57.88:0.12:2 mixes, and high speed dispersion obtains ceramic slurry.2. prepared by aramid fiber slurry: selecting Mw molecule The meta-aramid powder of amount 430000, using N, N dimethyl acetamide is solvent, by aramid fiber powder and N, N dimethyl acetamide Proportionally aramid fiber slurry is obtained for the ratio mixed at high speed of 1:9.
(c) micro-nano is laminated: the pp material for preparing middle layer and polyethylene raw material being squeezed out by two extruders, then Converged by co-extrusion module and be expressed into micro-nano layer multiplier, forms the middle layer of the multilayered structure of micro-nano stacking;
(d) preparation of co-extrusion diaphragm: the pp material for preparing upper epidermis and layer is squeezed out by two extruders, so The upper epidermis of extrusion, middle layer and layer are converged into extrusion by co-extrusion die head afterwards, form co-extrusion diaphragm;
(e) it anneals: the co-extrusion diaphragm progress high-temperature heat treatment prepared being formed and improves platelet, that is, is made annealing treatment, high temperature The temperature of heat treatment is 110-135 DEG C;
(f) it stretches: three step process is carried out to the product of annealing, i.e. cold drawing, hot-drawn and thermal finalization, described in acquisition Basement membrane;
(g) it is coated with: the polymer-coated slurry of preparation and high-temperaure coating coating slurry is respectively coated on the two of basement membrane A surface, drying obtain the composite diaphragm of this example.
Wherein, cold drawing multiplying power 1.02-1.4, cold drawing temperature are 40-120 DEG C;Hot-drawn multiplying power 1.3-3.0,110-135 DEG C;Heat Be formed multiplying power 0.99-0.7, and heat setting temperature is 120-135 DEG C.
Polyolefin micropore membrane preparation device and preparation method based on this example, this example are prepared for the compound of gradient low temperature closed pore Diaphragm, structure as shown in figure 3, include basement membrane 31, the low temperature closed pore layer 32 coated on one surface of basement membrane and be coated on basement membrane it is another The high-temperaure coating 33 on one surface;Wherein, basement membrane 31 is made of upper epidermis 311, middle layer 312 and layer 313.Wherein, on Surface layer 311 uses isotacticity 98%, melt index to be made of the polypropylene of 2g/10min, the use of layer 313 isotacticity 98%, Melt index is made of the polypropylene of 2g/10min, and middle layer 312 is that 4 layer polypropylene layers and 4 strata pvdf layers pass through micro-nano layer The middle layer of the composite layered structure for the 8 cross layered layer stackups that folded technology is formed, 8 layer stackups of preparation specifically uses two Concatenated micro-nano layer multiplier.Wherein, the polypropylene that the polypropylene layer with upper epidermis 311 of middle layer 312 uses is identical, polyethylene Layer is made of the high density polyethylene (HDPE) of melt index 0.5g/10min.The basement membrane overall thickness of this example is 16 microns, upper epidermis thickness It is 2 microns, layer is 12 microns with a thickness of 2 microns of intermediate layer thickness, each polypropylene layer and each polyethylene layer in middle layer Thickness is equal.
The low temperature closed pore layer of this example is that polymer-coated slurry is coated with the structure sheaf to be formed, polyethylene wax in water dispersion lotion Partial size be 500 nanometers, fusing point is 117 degree, and the solid content of water dispersion lotion is 35%, and polyethylene wax aqueous dispersions pass through intaglio plate The mode of roller coating is coated on a surface of basement membrane, and coating layer thickness is 2 microns.
The high-temperaure coating of this example is that ceramic slurry is coated with the structure sheaf to be formed, and the ceramic coating of this example specifically uses D50 For 500 nanometers of alumina ceramic grain, ceramic coating with a thickness of 2 microns, coating slurry is applied by way of intaglio plate roller coating It is distributed in another surface of basement membrane.
In the preparation method of this example, (c) in annealing steps, the temperature of annealing is 125 DEG C;(d) cold in stretching step Multiplying power 1.1 is drawn, cold drawing temperature is 80 DEG C, hot-drawn multiplying power 2.1,122 DEG C of hot-drawn temperature, thermal finalization multiplying power 0.8, heat setting temperature 130℃。
Embodiment 2
This example prepares the composite diaphragm of gradient low temperature closed pore using the identical device and method of embodiment 1, the difference is that The upper epidermis of this example uses isotacticity 98%, melt index to be made of the polypropylene of 1.2g/10min, and layer uses isotacticity 99%, melt index is made of the polypropylene of 1.5g/10min, and it is micro- that middle layer is that 8 layer polypropylene layers and 8 strata pvdf layers pass through The middle layer of the composite construction for the 16 cross layered layer stackups that lamination techniques of receiving are formed, 16 layer stackups of preparation specifically uses three A concatenated micro-nano layer multiplier.Wherein, the polypropylene that the polypropylene layer with upper epidermis of middle layer use is identical, polyethylene layer by The high density polyethylene (HDPE) of melt index 0.7g/10min is made.The basement membrane overall thickness of this example is 16 microns, and upper epidermis is micro- with a thickness of 1 Rice, layer are 14 microns with a thickness of 1 micron of intermediate layer thickness, the thickness phase of each polypropylene layer and each polyethylene layer in middle layer Deng.Remaining, including low temperature closed pore layer and high-temperaure coating it is all same as Example 1.
In the preparation method of this example, (c) in annealing steps, the temperature of annealing is 128 DEG C;(d) cold in stretching step Multiplying power 1.1 is drawn, cold drawing temperature is 60 DEG C, hot-drawn multiplying power 2.3,125 DEG C of hot-drawn temperature, thermal finalization multiplying power 0.9, heat setting temperature 128℃。
The low temperature closed pore layer of this example is that polymer-coated slurry is coated with the structure sheaf to be formed, polyethylene wax in water dispersion lotion Partial size be 400 nanometers, fusing point is 105 degree, and the solid content of water dispersion lotion is 42%, and polyethylene wax aqueous dispersions pass through intaglio plate The mode of roller coating is coated on a surface of basement membrane, and coating layer thickness is 2 microns.
The high-temperaure coating of this example is that aramid fiber slurry is coated with the structure sheaf to be formed, the aramid fiber coating of this example it is micro- with a thickness of 2 Rice, coating slurry are coated on another surface of basement membrane by way of intaglio plate roller coating.
Embodiment 3
This example prepares the composite diaphragm of gradient low temperature closed pore using the identical device and method of embodiment 1, the difference is that The upper epidermis of this example uses isotacticity 99%, melt index to be made of the polypropylene of 1.5g/10min, and layer uses isotacticity 99%, melt index is made of the polypropylene of 2g/10min, and it is micro- that middle layer is that 16 layer polypropylene layers and 16 strata pvdf layers pass through Lamination techniques of receiving formed 32 layer stackups composite construction, preparation 32 layer stackups middle layer specifically use four it is concatenated micro- Receive a layer multiplier.Wherein, the polypropylene that the polypropylene layer with upper epidermis of middle layer use is identical, and polyethylene layer is by melt index The high density polyethylene (HDPE) of 0.3g/10min is made.The basement membrane overall thickness of this example is 16 microns, and upper epidermis is with a thickness of 2 microns, following table Layer is 12 microns with a thickness of 2 microns of intermediate layer thickness, and the thickness of each polypropylene layer and each polyethylene layer is equal in middle layer.Its It is remaining, including low temperature closed pore layer and high-temperaure coating it is all same as Example 1.
In the preparation method of this example, (c) in annealing steps, the temperature of annealing is 128 DEG C;(d) cold in stretching step Multiplying power 1.22 is drawn, cold drawing temperature is 45 DEG C, hot-drawn multiplying power 2.1,128 DEG C of hot-drawn temperature, thermal finalization multiplying power 0.85, heat setting temperature 130℃。
The low temperature closed pore layer of this example is the structure sheaf that the water dispersion emulsion coating of polyethylene wax is formed, and is gathered in water dispersion lotion The partial size of ethylene waxes is 300 nanometers, and fusing point is 97 degree, and the solid content of water dispersion lotion is 40%, and polyethylene wax aqueous dispersions are logical The mode for crossing intaglio plate roller coating is coated on a surface of basement membrane, and coating layer thickness is 2 microns.
The high-temperaure coating of this example is that aramid fiber is coated with the structure sheaf to be formed, the aramid fiber coating of this example with a thickness of 2 microns, apply Cover another surface that slurry is coated on basement membrane by way of intaglio plate roller coating.
Following parameter attribute test is carried out to the composite diaphragm and its basement membrane of the gradient low temperature closed pore of the preparation of embodiment 1 to 3:
(1) thickness is tested
It carries out, is measured using hand-held calibrator, the direction TD along film takes 5 every 5cm with reference to GB/T 6672-2001 Point measurement, the average value of measurement are its thickness, and thickness unit is μm.
(2) tensile strength is tested
It is carried out with reference to GB/T 1040.3-2006, the sample that specification is 100mm × 20mm is taken to measure in electronic tensile machine.
(3) puncture strength is tested
It is carried out with reference to GB/T 21302-2007, takes specimen holder of the diameter greater than 60mm in the puncture fixture of electronic tensile machine In, sample is pierced through downwards with 100mm/s speed with the tack needle that diameter is 1mm and is measured.
(4) ionic conductivity is tested
1 layer of diaphragm is cut into and is matched size with 40mm*60mm metal plate, soft-package battery is assembled into, injects electrolyte, is surveyed AC impedance is tried, is then sequentially placed into 1~4 layer number diaphragm, test resistance value, using the diaphragm number of plies as abscissa, membrane electrical resistance Make curve for ordinate, finding out slope of a curve is ionic conductivity, can characterize lithium ion transfer ability in diaphragm.
(5) closed pore temperature is tested
Using the stretch mode of thermomechanical analyzer (abbreviation TMA), with 3 DEG C/min heating rate, 20mN load measurement sample Product length situation of change, closed pore temperature are that temperature, unit are DEG C at deformation quantity inflection point near fusing point.
(6) broken film temperature is tested
Using the stretch mode of thermomechanical analyzer (TMA), with 3 DEG C/min heating rate, 20mN load measurement sample is long Situation of change is spent, broken film temperature is temperature when sample film ruptures, and unit is DEG C.
(7) pore size is tested
It is tested using capillary flow assay instrument, capillary flow assay instrument is to use indifferent gas by Vesicular protein Body breaks through the diaphragm soaked, and aperture parameters are obtained by calculation in the pressure value of measurement gas outflow, with reference to CB/T2165 into Row.
(8) percent thermal shrinkage is tested
The sample of diaphragm sample 10cm × 10cm ruler is tested into MD, then the direction TD length MD1, TD1 are put sample Enter to have been adjusted in the accurate baking oven of test temperature, place certain time, takes out test MD, the direction TD length MD2, TD2, meter Calculation obtains MD shrinking percentage=(MD1-MD2)/MD1, TD shrinking percentage=(TD1-TD2)/TD1.
At the same time, using 16 microns of microporous polypropylene membrane of the single layer structure conventionally prepared (i.e. PP every Film) as control, it is same to carry out above every test.Embodiment 1 to 3 and every test result of conventional polypropylene microporous barrier are such as Shown in table 1.
1 membrane properties test result of table
In table 1, the unit of MD tensile strength is Kgf/cm2, the unit of ionic conductivity is mS/cm, and basement membrane 1 is embodiment 1 basement membrane, basement membrane 2 are the basement membrane of embodiment 2, and basement membrane 3 is the basement membrane of embodiment 3.Table 1 the results show that pass through micro-nano lamination Lithium battery diaphragm prepared by mode, compared with the microporous polypropylene membrane of single layer, the battery diaphragm of the embodiment of the present application 1 to 3 all has There are higher tensile strength and puncture strength and lower ionic conductivity and lower closed pore temperature, average pore size also to have It is reduced;These features can satisfy demand of the lithium battery diaphragm to slimming high safety.Also, comparative example 1 to 3 and its Corresponding basement membrane 1, basement membrane 2, basement membrane 3 test result as it can be seen that diaphragm has lower closed pore temperature and higher broken film temperature, it is lower MD and TD shrinking percentage, can preferably guarantee the safety of lithium battery diaphragm.
The foregoing is a further detailed description of the present application in conjunction with specific implementation manners, and it cannot be said that this Shen Specific implementation please is only limited to these instructions.For those of ordinary skill in the art to which this application belongs, it is not taking off Under the premise of from the application design, a number of simple deductions or replacements can also be made.

Claims (10)

1. a kind of composite diaphragm of gradient low temperature closed pore, it is characterised in that: including basement membrane, the low temperature coated on one surface of basement membrane Closed pore layer and high-temperaure coating coated on another surface of basement membrane;
The low temperature closed pore layer is that the water dispersion emulsion coating of polymer of the fusing point lower than 140 DEG C forms;
The high-temperaure coating is coated with by ceramics or aramid fiber;
The basement membrane is made of upper epidermis, middle layer and layer, and it is micro- that the middle layer is that polypropylene layer and polyethylene layer pass through The multilayered structure that lamination techniques of receiving are formed, upper epidermis and layer are polypropylene layer.
2. composite diaphragm according to claim 1, it is characterised in that: the middle layer is that polypropylene layer and polyethylene layer are logical Cross the multilayered structure of the 4-32 layer stackup of micro-nano lamination techniques formation.
3. composite diaphragm according to claim 1, it is characterised in that: the polypropylene that the basement membrane uses is greater than for isotacticity 96%, melt index is the polypropylene of 0.3-5g/10min.
4. composite diaphragm according to claim 1, it is characterised in that: the polyethylene that the basement membrane uses is melt index The high density polyethylene (HDPE) of 0.05-5g/10min.
5. composite diaphragm according to claim 1, it is characterised in that: the basement membrane with a thickness of 10-25 microns, wherein Upper epidermis with a thickness of 2-4 microns, layer with a thickness of 2-4 microns.
6. composite diaphragm according to claim 1, it is characterised in that: the porosity of the basement membrane is 20%-60%.
7. composite diaphragm according to claim 1-6, it is characterised in that: the low temperature closed pore layer with a thickness of 1- 6 microns, the high-temperaure coating with a thickness of 1-6 microns.
8. composite diaphragm according to claim 1-6, it is characterised in that: the fusing point is lower than 140 DEG C of polymerization Object is polyethylene wax;
Preferably, the partial size of polymer is 50 nanometers -2 microns in water dispersion lotion.
9. the preparation method of composite diaphragm according to claim 1-8, it is characterised in that: include the following steps,
(a) preparation of polymer-coated slurry: the polymer by fusing point lower than 140 DEG C is dispersed in water, and water dispersion lotion is made;
(b) by ceramic particle or aramid fiber powder dispersion liquid solvent, coating materials the preparation of high-temperaure coating coating slurry: are made Material;
(c) micro-nano is laminated: the pp material for preparing middle layer and polyethylene raw material being squeezed out by two extruders, then by altogether Crowded module, which is converged, to be expressed into micro-nano layer multiplier, and the middle layer of the multilayered structure of micro-nano stacking is formed;
(d) preparation of co-extrusion diaphragm: the pp material for preparing upper epidermis and layer is squeezed out by two extruders, then by The upper epidermis of extrusion, middle layer and layer are converged extrusion by co-extrusion die head, form co-extrusion diaphragm;
(e) it anneals: the co-extrusion diaphragm progress high-temperature heat treatment prepared being formed and improves platelet, that is, is made annealing treatment, at high warm The temperature of reason is 110-135 DEG C;
(f) it stretches: three step process being carried out to the product of annealing, i.e. cold drawing, hot-drawn and thermal finalization obtains the base Film;
(g) it is coated with: the polymer-coated slurry of preparation and high-temperaure coating coating slurry is respectively coated on to two tables of basement membrane Face, drying obtain the composite diaphragm.
10. preparation method according to claim 9, it is characterised in that: in (d) stretching step, cold drawing multiplying power 1.02- 1.4, cold drawing temperature is 40-120 DEG C;Hot-drawn multiplying power 1.3-3.0,110-135 DEG C;Thermal finalization multiplying power 0.99-0.7, thermal finalization temperature Degree is 120-135 DEG C.
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CN113054324A (en) * 2021-04-21 2021-06-29 上海恩捷新材料科技有限公司 High-safety diaphragm and battery
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