Isolating membrane, electrochemical device comprising isolating membrane and electronic device

Abstract

The invention provides an isolating membrane, an electrochemical device comprising the isolating membrane and an electronic device. The isolating membrane comprises a porous base material, an inorganic material layer and a bonding layer, wherein the inorganic material layer is arranged between the porous base material and the bonding layer; the adhesive layer comprises a copolymer, monomers forming the copolymer comprise a first monomer and a second monomer, the first monomer is propylene, and the second monomer comprises at least one of ethylene, vinylidene fluoride, vinyl chloride, butadiene, isoprene, styrene, acrylonitrile, ethylene oxide, propylene oxide, acrylate, vinyl acetate or caprolactone. The isolating membrane can reduce expansion and deformation of the lithium ion battery and improve the performance of the lithium ion battery.

Description

[0001] This application is a divisional application with application number 202011048075.9, application date September 29, 2020, and invention name “An isolation membrane, an electrochemical device and an electronic device comprising the isolation membrane”. Technical Field

[0002] The present application relates to the field of electrochemical technology, and in particular to an isolation membrane, an electrochemical device and an electronic device comprising the isolation membrane. Background Art

[0003] Lithium-ion batteries have the characteristics of high energy, high operating voltage, low self-discharge rate, small size and light weight, and are widely used in various fields such as power storage, portable electronic devices and electric vehicles. The separator in lithium-ion batteries is usually set between the positive electrode and the negative electrode to block the electron channel between the positive and negative electrodes and conduct lithium ions at the same time.

[0004] The prior art usually improves the performance of the isolating membrane by modifying the surface of the isolating membrane or setting a coating, for example, coating an organic adhesive layer on the isolating membrane to improve the adhesion between the isolating membrane and the pole piece. However, the existing organic adhesive layer swells greatly after being immersed in the electrolyte or after being formed, resulting in a rapid decrease in the adhesion between the pole piece and the isolating membrane interface, which in turn causes the adhesion of the isolating membrane to be at a low level after the first charge of the lithium-ion battery, affecting the subsequent performance of the lithium-ion battery.

[0005] Therefore, there is an urgent need for a separator with higher adhesion, especially a separator with high adhesion after being soaked in electrolyte. Summary of the invention

[0006] The purpose of the present application is to provide an isolation membrane, an electrochemical device and an electronic device comprising the isolation membrane, so as to improve the bonding performance between the isolation membrane and the electrode interface. The specific technical solution is as follows:

[0007] The first aspect of the present application provides a separation film, comprising a porous substrate, an inorganic material layer and an adhesive layer,

[0008] Wherein, the inorganic material layer is disposed between the porous substrate and the bonding layer;

[0009] The adhesive layer comprises a copolymer, and the monomers forming the copolymer include a first monomer and a second monomer;

[0010] The first monomer is propylene;

[0011] The second monomer includes at least one of ethylene, vinylidene fluoride, vinyl chloride, butadiene, isoprene, styrene, acrylonitrile, ethylene oxide, propylene oxide, acrylate, vinyl acetate or caprolactone.

[0012] In one embodiment of the present application, the copolymer has at least one of the following characteristics:

[0013] a) the copolymer has a crystallinity of 10% to 40%;

[0014] b) the softening temperature of the copolymer is 70°C to 90°C;

[0015] c) the weight average molecular weight of the copolymer is 500 g / mol to 1,000,000 g / mol;

[0016] d) the Dv50 of the copolymer is 0.1 μm to 10 μm;

[0017] e) the isotacticity of the copolymer is 35% to 80%.

[0018] In one embodiment of the present application, the first monomer accounts for 30 mol % to 95 mol % of the total monomers of the copolymer, and the second monomer accounts for 5 mol % to 70 mol % of the total monomers of the copolymer.

[0019] In one embodiment of the present application, the thickness of the adhesive layer is 1 μm to 10 μm.

[0020] In one embodiment of the present application, the porosity of the porous substrate is 20% to 80%, and the thickness of the porous substrate is 2 μm to 30 μm.

[0021] In one embodiment of the present application, the thickness of the inorganic material layer is 20nm to 1900nm, the total mass percentage of metal elements, oxygen elements and nitrogen elements in the inorganic material layer is more than 96%, and the inorganic material layer does not contain an adhesive.

[0022] In one embodiment of the present application, the thickness of the inorganic material layer is 50 nm to 900 nm, and the total mass percentage of metal elements, oxygen elements and nitrogen elements in the inorganic material layer is greater than 99.01%.

[0023] In one embodiment of the present application, the inorganic material layer includes α-Al 2 O 3 , Si oxide, Si nitride, Ti oxide, Ti nitride, Zn oxide, Zn nitride, Mg oxide, Mg nitride, Zr oxide, Zr nitride, Ca oxide, Ca nitride, Ba oxide or Ba nitride.

[0024] In one embodiment of the present application, the inorganic material layer is a porous structure formed by the accumulation of nanoclusters, pores exist between the nanoclusters, and the average pore diameter of the pores is 0.1 nm to 100 nm.

[0025] In one embodiment of the present application, at least a portion of the inorganic material layer covers the inner wall of the pores of the porous substrate, and the depth of the inorganic material layer embedded in the pores is 1 / 1000 to 1 / 21 of the thickness of the porous substrate.

[0026] In one embodiment of the present application, the porosity of the inorganic material layer is 10% to 60%, and the peeling strength between the inorganic material layer and the porous substrate is not less than 30 N / m.

[0027] In one embodiment of the present application, the bonding layer is directly disposed on one surface of the porous substrate.

[0028] The second aspect of the present application provides an electrochemical device, which includes a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet, and the separator is the separator described in the first aspect above.

[0029] A third aspect of the present application provides an electronic device, which includes the electrochemical device described in the second aspect.

[0030] The present application provides an isolation membrane, an electrochemical device and an electronic device comprising the isolation membrane. By setting an adhesive layer, the adhesion between the isolation membrane and the electrode interface can be improved; by setting an inorganic material layer between the porous substrate and the adhesive layer, the heat shrinkage resistance and needle puncture resistance of the isolation membrane can be further improved, thereby improving the safety of the lithium-ion battery. In addition, the copolymer in the isolation membrane of the present application has excellent resistance to electrolyte swelling. Even after being immersed in the electrolyte for a long time, the isolation membrane has high adhesion, thereby reducing the expansion and deformation of the lithium-ion battery.

[0031] In this application, the term "Dv50" means the particle size that reaches 50% of the volume accumulation from the small particle size side in the volume-based particle size distribution; that is, the volume of particles smaller than this particle size accounts for 50% of the total volume of all particles. The particle size is measured using a laser particle size analyzer.

[0032] The term "isotacticity" refers to the percentage of isotactic copolymers in the total amount of copolymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the present application and the prior art, the following briefly introduces the drawings required for use in the embodiments and the prior art. Obviously, the drawings described below are only some embodiments of the present application.

[0034] Figure 1 A schematic diagram of an isolation membrane according to an embodiment of the present application;

[0035] Figure 2 A schematic diagram of an isolation membrane according to another embodiment of the present application;

[0036] Figure 3 A schematic diagram of an isolation membrane according to another embodiment of the present application;

[0037] Figure 4 This is a schematic diagram of an isolation membrane according to a fourth embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0039] It should be noted that in the specific embodiments of the present application, a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to a lithium-ion battery.

[0040] The present application provides an isolation film, such as Figure 1 or Figure 2 As shown, it includes a porous substrate 1, an inorganic material layer 2 and an adhesive layer 3, wherein the inorganic material layer is arranged between the porous substrate and the adhesive layer;

[0041] The adhesive layer comprises a copolymer, and monomers forming the copolymer include a first monomer and a second monomer;

[0042] The first monomer is propylene;

[0043] The second monomer includes at least one of ethylene, vinylidene fluoride, vinyl chloride, butadiene, isoprene, styrene, acrylonitrile, ethylene oxide, propylene oxide, acrylate, vinyl acetate or caprolactone.

[0044] The inorganic material layer of the present application may be disposed between the porous substrate and the adhesive layer.

[0045] In one embodiment, reference Figure 1 The inorganic material layer can be arranged on both surfaces of the porous substrate, and in this case, an adhesive layer can be arranged on the side of the inorganic material layer that is not in contact with the porous substrate.

[0046] In one embodiment, reference Figure 2, one of the surfaces of the porous substrate is also directly provided with an adhesive layer, the other surface of the porous substrate may be provided with an inorganic material layer, and the side of the inorganic material layer that is not in contact with the porous substrate may also be provided with an adhesive layer. The inorganic material layer of the present application may partially cover the surface of the porous substrate, or may completely cover the surface of the porous substrate. The adhesive layer of the present application may partially cover the surface of the porous substrate or the inorganic material layer, or may completely cover the surface of the porous substrate or the inorganic material layer.

[0047] The isolation membrane of the present application, wherein the inorganic material layer can improve the heat shrinkage resistance of the porous substrate, and the bonding layer can improve the bonding strength between the porous substrate of the present application and the pole piece, and between the inorganic material layer and the pole piece, thereby reducing the expansion and deformation of the lithium-ion battery.

[0048] Furthermore, the adhesive layer of the present application includes a copolymer, and the monomers forming the copolymer include at least two monomers, wherein the first monomer is propylene, and the first monomer accounts for 30 mol% to 95 mol% of the total monomer amount of the copolymer. By controlling the first monomer within the above ratio, the adhesive of the present application can have good bonding performance, electrolyte swelling property and good electrolyte stability. Preferably, the first monomer accounts for 50 mol% to 90 mol% of the total monomer amount of the copolymer, and more preferably, 60 mol% to 80 mol%.

[0049] The second monomer includes at least one of ethylene, vinylidene fluoride, vinyl chloride, butadiene, isoprene, styrene, acrylonitrile, ethylene oxide, propylene oxide, (meth) acrylate, vinyl acetate or caprolactone, and the second monomer accounts for 5mol% to 70mol% of the total monomer amount of the copolymer, preferably 10mol% to 50mol%, and more preferably 20mol% to 40mol%. The second monomer can be selected from a combination of one or more monomers of the above monomers. When a combination of multiple monomers is selected to provide the second monomer, the ratio between the monomers is not specifically limited and can be any ratio as long as the requirements of this application are met.

[0050] In one embodiment of the present application, the crystallinity of the copolymer is 10% to 40%. When the crystallinity of the copolymer is within the above range, an adhesive having a suitable softening temperature and good adhesion can be obtained.

[0051] In one embodiment of the present application, the softening temperature of the copolymer is 70°C to 90°C. By controlling the softening temperature of the copolymer of the present application, the copolymer of the present application can have better adhesion. In particular, when the above copolymer is included in the separator of the present application, the adhesion between the porous substrate and the positive and negative pole pieces of the lithium-ion battery, and between the inorganic material layer and the pole piece can be improved, and the expansion and deformation of the lithium-ion battery can be reduced.

[0052] In one embodiment of the present application, the weight average molecular weight of the copolymer is 500 g / mol to 1,000,000 g / mol, preferably 1,000 g / mol to 100,000 g / mol, and more preferably 5,000 g / mol to 50,000 g / mol. When the weight average molecular weight is within the above range, a copolymer with good adhesion can be obtained.

[0053] In one embodiment of the present application, the copolymer is in the form of particles, and its particle Dv50 is 0.1 μm to 10 μm, preferably 0.5 μm to 5 μm, and more preferably 1 μm to 3.5 μm. The particle size of the copolymer of the present application is within the above range, such as Figure 3 As shown, particle bumps can be formed in the bonding layer 3, and a certain gap is formed when the separator contacts the pole piece. The gap plays a role in buffering the expansion and deformation of the lithium-ion battery, especially the gap at the corner of the lithium-ion battery, which can alleviate the expansion and deformation of the lithium-ion battery during later use. However, the particle size should not be too small or too large. If the particle size is too small, a gap cannot be formed between the pole piece and the separator. If the particle size is too large, the bonding effect is affected and the energy density of the lithium-ion battery is reduced.

[0054] In one embodiment of the present application, the isotacticity of the copolymer is 35% to 80%, preferably 40% to 60%. When the isotacticity of the copolymer is within the above range, an adhesive with appropriate softening temperature and good adhesion can be obtained.

[0055] In one embodiment of the present application, the thickness of the adhesive layer is 1 μm to 10 μm. The thickness of the adhesive layer of the present application is within the above range, which can increase the content of electrode active materials in the lithium ion battery, thereby increasing the energy density of the lithium ion battery.

[0056] In one embodiment of the present application, the porosity of the porous substrate is 20% to 80%, and the thickness of the porous substrate is 2 μm to 30 μm. The porosity of the porous substrate is within the above range, which can improve the air permeability of the separator and thus improve the ion transmission performance, but the porosity should not be too high, otherwise it will affect the puncture resistance of the separator. The thickness of the porous substrate is within the above range, which can make the separator have good mechanical properties, and the thinner thickness can increase the content of electrode active materials in the lithium-ion battery, thereby improving the energy density of the lithium-ion battery.

[0057] In one embodiment of the present application, the thickness of the inorganic material layer is 20nm to 1900nm, the total mass percentage of metal elements, oxygen elements and nitrogen elements in the inorganic material layer is more than 96%, and the inorganic material layer does not contain an adhesive, which can make the inorganic material layer thinner. At the same time, the inorganic material layer can have better mechanical strength at a thinner thickness, thereby improving the puncture resistance of the isolation membrane.

[0058] Preferably, the thickness of the inorganic material layer is 50nm to 900nm, more preferably 200nm to 450nm. If the inorganic material layer is too thin, the protective effect on the isolation membrane is weak. If the inorganic material layer is too thick, the air permeability of the porous substrate is affected and the energy density of the lithium-ion battery is affected. The total mass percentage of metal elements, oxygen elements and nitrogen elements in the inorganic material layer is more than 99.01%, so that the inorganic material layer has better mechanical strength. The metal element in the inorganic material layer of the present application may include at least one of Al, Ti, Zn, Mg, Zr, Ca or Ba.

[0059] In one embodiment of the present application, the inorganic material layer includes α-Al 2 O 3 , Si oxide, Si nitride, Ti oxide, Ti nitride, Zn oxide, Zn nitride, Mg oxide, Mg nitride, Zr oxide, Zr nitride, Ca oxide, Ca nitride, Ba oxide or Ba nitride, at least one of them has high wear resistance, high melting point, high chemical stability and good mechanical properties.

[0060] In one embodiment of the present application, the inorganic material layer is a porous structure formed by the accumulation of nanoclusters, and there are pores between the nanoclusters, and the average pore size of the pores is 0.1nm to 100nm. The nanoclusters may include the above-mentioned metal oxides or non-metallic oxides. The average pore size of the gaps between the nanoclusters is within the above range, which can further improve the air permeability of the isolation membrane, thereby improving the ion transmission performance, and ultimately improving the electrochemical performance of the lithium ion battery.

[0061] In one embodiment of the present application, at least a portion of the inorganic material layer covers the inner wall of the pores of the porous substrate, and the depth of the inorganic material layer embedded in the pores is 1 / 1000 to 1 / 21 of the thickness of the porous substrate, so that the inorganic material layer is in close contact with the porous substrate, further improving the puncture resistance and heat shrinkage resistance of the isolation membrane of the present application.

[0062] In one embodiment of the present application, the porosity of the inorganic material layer is 10% to 60%. The porosity of the inorganic material layer within the above range can further improve the air permeability of the separator, thereby improving the ion transmission performance. The interfacial peeling strength between the inorganic material layer and the porous substrate is not less than 30N / m. After the separator is placed at 90°C for 1 hour, the longitudinal thermal shrinkage rate and the transverse thermal shrinkage rate are both less than 3%, so that the inorganic material layer is not easy to fall off in the case of long-term circulation of the lithium-ion battery, thereby improving the safety performance of the lithium-ion battery.

[0063] In one embodiment of the present application, the adhesion strength of the isolation membrane before immersion in the electrolyte is 40N / m to 110N / m, the adhesion strength after immersion in the electrolyte for not less than 10 hours is 15N / m to 35N / m, the puncture strength is 3N to 8N, and the air permeability is 100s / 100mL to 280s / 100mL, and it has excellent adhesion, electrolyte resistance, puncture resistance and air permeability.

[0064] In lithium-ion batteries, the degree of swelling of the copolymer in the adhesive layer in the electrolyte used in the lithium-ion battery will affect the performance of the lithium-ion battery. The degree of swelling of the copolymer in the electrolyte used in the lithium-ion battery refers to the performance of the copolymer swelling after absorbing the electrolyte or the solvent in the electrolyte after drying. If the copolymer swells too much, the isolation membrane will separate from the pole piece, causing the lithium-ion battery to swell or deform, thereby affecting the safety of the lithium-ion battery. In one embodiment of the present application, the electrolyte swelling degree of the copolymer of the present application is 10% to 30%.

[0065] The preparation method of the copolymer of the present application is not particularly limited, and can be prepared by methods known to those skilled in the art, and can be selected according to the type of monomers used, such as a solution method, a slurry method, a gas phase method, and the like.

[0066] For example, when the second monomer is selected from ethylene, the following method can be used:

[0067] The main catalyst and the co-catalyst are respectively dissolved in hexane to obtain a hexane solution of the main catalyst and a hexane solution of the co-catalyst, and then the hexane is added into the reactor. Then, the hexane solution of the main catalyst and the hexane solution of the co-catalyst are added into the reactor under the protection of nitrogen, and then propylene and ethylene are introduced. The temperature is raised to 50°C to 60°C. During the reaction, the pressure in the reactor is maintained at 0.3MPa to 0.5MPa. After reacting for 0.5h to 2h, the reaction is terminated with acidified ethanol. The product is washed with anhydrous ethanol for 3 to 5 times, filtered, and dried in a vacuum drying oven at 50°C to 70°C for 3h to 5h.

[0068] The present application has no particular restrictions on the main catalyst and the co-catalyst, as long as the purpose of the present invention can be achieved. For example, a metallocene catalytic system is used, wherein the main catalyst includes a metallocene complex (such as ferrocene or its derivatives), and the co-catalyst includes methylaluminoxane; and the present application has no particular restrictions on the amount of the main catalyst and the co-catalyst added, as long as the purpose of the present invention can be achieved. In addition, the reactor can be vacuum evacuated before the reaction, and then the reactor can be replaced with nitrogen 3 to 5 times to make the reactor clean.

[0069] When the second monomer is selected from butadiene, the preparation method of the propylene-ethylene copolymer is the same as the preparation method of the propylene-ethylene copolymer except that the ethylene in the preparation method of the propylene-ethylene copolymer is replaced by butadiene.

[0070] When the second monomer is selected from acrylic ester, the difference from the above-mentioned method for preparing propylene-ethylene copolymer is that the ethylene in the method for preparing propylene-ethylene copolymer is replaced by acrylic ester, and under the protection of nitrogen, hexane, a hexane solution of the main catalyst, and a hexane solution of the co-catalyst are added to the reactor, and then acrylic ester is added, and then propylene is introduced, and the rest is the same as the above-mentioned method for preparing propylene-ethylene copolymer.

[0071] The acrylate monomer may be selected from any one of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, isooctyl acrylate or hydroxyethyl acrylate.

[0072] The copolymerization of other monomers is not listed one by one in this application, and the preparation methods known in the art can be adopted.

[0073] Furthermore, the present application has no particular limitation on the material of the porous substrate, as long as the purpose of the present application can be achieved. For example, the porous substrate includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester or natural fiber.

[0074] There are no special restrictions on the positive electrode plate in this application, as long as the purpose of this application can be achieved. For example, the positive electrode plate generally includes a positive current collector and a positive active material layer. Among them, the positive current collector is not particularly limited, and can be any positive current collector known in the art, such as aluminum foil, aluminum alloy foil or composite current collector. The positive active material layer includes a positive active material, and the positive active material is not particularly limited. Any positive active material known in the art can be used, for example, it can include lithium nickel cobalt manganese oxide (811, 622, 523, 111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. At least one.

[0075] There is no particular limitation on the negative electrode plate in the present application, as long as the purpose of the present application can be achieved. For example, the negative electrode plate generally comprises a negative electrode current collector and a negative electrode active material layer. Among them, the negative electrode current collector is not particularly limited, and any negative electrode current collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collector. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material is not particularly limited, and any negative electrode active material known in the art can be used. For example, it can include at least one of artificial graphite, natural graphite, mesophase carbon microbeads, soft carbon, hard carbon, silicon, silicon carbon, lithium titanate, etc.

[0076] The lithium-ion battery of the present application further comprises an electrolyte, which may be one or more of a gel electrolyte, a solid electrolyte and an electrolyte, wherein the electrolyte comprises a lithium salt and a non-aqueous solvent.

[0077] In some embodiments of the present application, the lithium salt is selected from LiPF 6 , LiBF 4 、LiAsF 6 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 、LiSiF 6 , LiBOB and lithium difluoroborate. For example, the lithium salt can be selected from LiPF 6 because it can give high ionic conductivity and improve the cycle characteristics.

[0078] The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents or a combination thereof.

[0079] The carbonate compound may be a linear carbonate compound, a cyclic carbonate compound, a fluorinated carbonate compound or a combination thereof.

[0080] Examples of the above-mentioned chain carbonate compounds are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC) and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC) and combinations thereof. Examples of fluorinated carbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate and combinations thereof.

[0081] Examples of the above carboxylic acid ester compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerolactone, mevalonolactone, caprolactone and combinations thereof.

[0082] Examples of the above ether compound are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0083] Examples of the above other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphoric acid esters and combinations thereof.

[0084] The present application also provides an electrochemical device, including a positive electrode sheet, a negative electrode sheet and a separator. The separator is located between the positive electrode sheet and the negative electrode sheet and has good safety performance.

[0085] The present application also provides an electronic device, comprising the electrochemical device described in the embodiments of the present application, which has good safety performance.

[0086] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0087] The preparation process of the electrochemical device is well known to those skilled in the art and is not particularly limited in this application. For example, a lithium-ion battery can be manufactured by overlapping the positive electrode and the negative electrode via a separator, and placing them in a housing after winding, folding, etc. as required, injecting an electrolyte into the housing and sealing it, wherein the separator used is the above-mentioned separator provided in this application. In addition, an overcurrent protection element, a guide plate, etc. can also be placed in the housing as required to prevent the pressure inside the lithium-ion battery from rising and overcharging and discharging.

[0088] The present application has no particular restrictions on the preparation method of the isolation membrane, and for example, the isolation membrane can be prepared by the following method:

[0089] Using plasma-assisted thermal evaporation deposition method, an inorganic material layer is formed on the surface of the porous substrate, and the thickness of the inorganic material layer is 20nm to 1900nm;

[0090] The copolymer, N-dodecyldimethylamine and polydimethylsiloxane are mixed in a mass ratio of 88-92:2-5:5-9 to obtain a mixture, and then the mixture is dissolved in a solvent to obtain an adhesive slurry with a solid content of 30% to 50%;

[0091] The adhesive slurry is uniformly coated on at least one surface of the porous substrate and the inorganic material layer to form an adhesive layer, and the thickness of the single adhesive layer is 1 μm to 10 μm.

[0092] Among them, the heating source of the plasma-assisted thermal evaporation deposition method is an electron beam, and the heating target material is an aluminum-magnesium alloy (Al content is 90wt% to 95wt%). Under vacuum conditions, oxygen is used as the reaction gas to control the temperature of the porous substrate to be less than 100°C. By adjusting the heating evaporation current to 40A to 60A, the process chamber vacuum degree to 0.3Pa to 0.5Pa, the oxygen flow rate to 400sccm to 600sccm, the plasma power to 400W to 600W, and the evaporation time to 2min to 180min, the deposition rate of the inorganic material layer on the surface of the porous substrate is controlled, thereby controlling the thickness and porosity of the inorganic material layer. In addition, the inorganic material layer can be formed on one surface of the porous substrate or on both surfaces of the porous substrate.

[0093] The solvent for dissolving the mixture is selected from at least one of acetone and butanone.

[0094] Example

[0095] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are by mass.

[0096] Test methods and equipment:

[0097] Calculation of the total mass content of metal elements, oxygen elements and nitrogen elements in the inorganic material layer:

[0098] Samples were taken from the inorganic material layer, and an energy dispersive spectrometer (EDS, Zeiss SIGMA+X-max EDS(ND)) was used to test the samples to calculate the total mass content of metal elements, oxygen elements, and nitrogen elements in the inorganic material layer.

[0099] Test of bonding strength between porous substrate and inorganic material layer:

[0100] Under the conditions of 25±0.5℃ and atmospheric pressure, use 3M double-sided tape to evenly stick it on the steel plate, then evenly stick the surface of the inorganic material layer on the porous substrate of the isolation membrane test sample on the double-sided tape with a width of 2cm. Use a high-speed rail tensile testing machine to peel off the porous substrate and the inorganic material layer. The speed of the high-speed rail tensile testing machine is 0.1 m / min. The steel plate is fixed on the slide rail for lateral movement, keeping the steel plate at 90° with the isolation membrane. According to the data graph of tension and displacement, read the maximum tension F (N).

[0101] Acupuncture strength test:

[0102] Prepare a sheet sample of isolation membrane (1cm×1cm), fix it under the test fixture, use a high-speed rail tensile tester and a puncture fixture, use a puncture needle with a diameter of 1mm on the puncture tester (model CCY-02), puncture at a speed of 50mm / min, and measure the puncture force F after the data stabilizes, in N.

[0103] Thermal shrinkage test:

[0104] The isolation film was cut into square samples (100mm×100mm) and marked in the longitudinal (MD) and transverse (TD) directions. The lengths in the longitudinal (MD) and transverse (TD) directions were then tested with a projection tester and recorded as L1 and L2. The isolation film was then placed in a 90°C blast oven and taken out after 1 hour. The lengths in the MD and TD directions were tested again with a projection tester and recorded as L3 and L4.

[0105] Thermal shrinkage of the isolation film in the MD direction = (L1-L3) / L1×100%;

[0106] The heat shrinkage rate of the separator in the TD direction = (L2-L4) / L2×100%.

[0107] Air permeability test:

[0108] In an environment with a temperature of 15°C to 28°C and a humidity of less than 80%, the test sample is made into a 4cm×4cm size and measured using an air permeability tester (Air-permeability-tester) through the Gurley test (100mL) method to directly obtain the air permeability value. The air permeability unit is s, which represents the time required for 100 mL of air to pass through the 4cm×4cm area isolation membrane.

[0109] Porosity test:

[0110] Dry the isolation film sample in a vacuum drying oven at 105℃ for 2h, take it out and place it in a dryer to cool before testing. Wrap the isolation film flat with A4 paper, lay it flat on the die, and punch it with a punching machine to prepare the sample for testing. First use a micrometer to measure the thickness of the sample, calculate the apparent volume V1 of the sample based on the surface area and thickness of the sample, and then use a true density meter (model AccuPycⅡ) to measure the true volume V2 of the sample, and you can get the porosity = (V1-V2) / V1×100%.

[0111] Test of the adhesion of the isolation film:

[0112] Cut the separator that is not soaked in electrolyte into long strips (1cm×2cm) and fix one side of the sample on an aluminum plate with 3M double-sided tape. Paste one end of the sample on the 3M tape and then use a universal tensile machine to slowly tear off the 3M tape from the sample surface at an angle of 180° to separate the adhesive layer from the inorganic material layer. Record the stable tensile force at the interface separation and calculate the adhesion of the separator that is not soaked in electrolyte based on this, in N / m. To ensure the accuracy of the test results, each sample can be tested multiple times, for example, 3 times, and then the average value is calculated.

[0113] Adhesive strength test after the adhesive is soaked in electrolyte:

[0114] Cut the separator after soaking in electrolyte for 10 hours into long strips (1cm×2cm) and fix one side of the sample on the aluminum plate with 3M double-sided tape, stick one end of the sample on the 3M tape, and then use a universal tensile machine to slowly tear off the 3M tape from the sample surface at an angle of 180°, so that the adhesive layer is separated from the inorganic material layer, record the stable tension at the interface separation, and calculate the adhesion of the separator without electrolyte soaking based on this, in N / m. To ensure the accuracy of the test results, each sample can be tested multiple times, for example 3 times, and then the average value is calculated.

[0115] Capacity test of lithium-ion battery:

[0116] In a constant temperature box at 25±0.5℃, charge at a constant current rate of 1C to a voltage of 4.4V, then charge at a constant voltage of 4.4V to a current of 0.05C, and then discharge at a constant current rate of 1C to a voltage of 3V. The discharge capacity obtained is the battery capacity of the lithium-ion battery.

[0117] Room temperature cycle performance test of lithium-ion batteries:

[0118] At 25°C, charge at a constant current rate of 0.7C to a voltage of 4.4V, then charge at a constant voltage of 4.4V to a current of 0.05C, and then discharge at a constant current rate of 1C to a voltage of 3V, record the discharge capacity of the first cycle, and then repeat the above steps for 100 charge and discharge cycles, and record the discharge capacity of the 100th cycle.

[0119] Cycle capacity retention rate = (discharge capacity at the 100th cycle / discharge capacity at the first cycle) × 100%.

[0120] Internal short circuit defect rate test (Hi-pot test):

[0121] The electrode assembly that has completed winding and welding is hot pressed at 90°C and 0.5MPa for 150s. After hot pressing, a Hioki internal resistance meter is used to apply a 200V voltage between the positive and negative pole ears of the electrode assembly and test its resistance. If the resistance is less than 10MΩ, it is considered an internal short-circuit defective product. Otherwise, it passes the internal short-circuit test. The proportion of defective products is the Hi-pot defective rate.

[0122] Lithium-ion battery thickness expansion test:

[0123] The thickness of the lithium-ion battery is tested using a 600g flat plate thickness gauge and is recorded as PPG thickness.

[0124] Thickness expansion rate of lithium-ion battery = full charge thickness after cycle / first full charge thickness × 100%.

[0125] Lithium-ion battery deformation test:

[0126] Take three points at the position of the positive pole ear of the lithium-ion battery, measure its thickness with a micrometer, take the average value, and record it as the MMC thickness. The deformation degree of the lithium-ion battery = (MMC thickness-PPG thickness) / MMC thickness×100%.

[0127] Example 1

[0128] <1-1. Preparation of copolymer>

[0129] In a 1L stainless steel reactor, 77 parts (volume fraction) of hexane solvent, 19 parts (volume fraction) of the main catalyst ferrocene hexane solution (ferrocene content 70 mg / L), 4 parts (volume fraction) of the co-catalyst methylaluminoxane hexane solution (methylaluminoxane content 10 mg / L) were added under nitrogen protection, and then vinylidene fluoride (PVDF) was added, and then propylene was introduced, and the temperature was raised to 50°C, and the pressure of the reactor was controlled to 0.4MPa. The molar ratio between the first and second monomers was adjusted to 60:40 by adjusting the amount of propylene / vinylidene fluoride added. After reacting for 1 hour, the reaction was terminated with acidified ethanol to obtain propylene-vinylidene fluoride copolymer. The obtained product was washed with anhydrous ethanol 3 times, filtered, and dried in a vacuum drying oven at 60°C for 4 hours. The obtained copolymer has a crystallinity of 30%, a weight average molecular weight of 100000 g / mol, a Dv50 of 4μm, and an isotacticity of 60%.

[0130] <1-2. Preparation of positive electrode sheet>

[0131] The positive electrode active material lithium cobalt oxide, acetylene black, and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 94:3:3, and then N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75%, and stirred evenly. The slurry is evenly coated on one surface of an aluminum foil with a thickness of 12µm, dried at 90°C, and cold pressed to obtain a positive electrode sheet with a positive electrode active material layer thickness of 100μm, and then the above steps are repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. The positive electrode sheet is cut into a specification of 74mm×867mm and welded to the pole ear for standby use.

[0132] <1-3. Preparation of negative electrode sheet>

[0133] The negative electrode active material artificial graphite, acetylene black, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.5:1.5, and then deionized water is added as a solvent to prepare a slurry with a solid content of 70%, and stirred evenly. The slurry is evenly coated on one surface of a copper foil with a thickness of 8µm, dried at 110°C, and cold pressed to obtain a negative electrode sheet with a single-sided negative electrode active material layer coated with a negative electrode active material layer with a thickness of 150μm, and then the above coating steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided negative electrode active material layer coated. The negative electrode sheet is cut into a specification of 74mm×867mm and welded to the pole ear for standby use.

[0134] <1-4. Preparation of isolation film>

[0135] An inorganic material layer was formed on one surface of a 9μm polyethylene (PE) porous substrate (porosity 36%) by plasma-assisted thermal evaporation deposition. The heating source was an electron beam, the heating target was an aluminum-magnesium alloy (Al content 92wt%), and under vacuum conditions, oxygen was used as the reaction gas. The temperature of the porous substrate was controlled to be less than 100°C. The heating evaporation current was adjusted to 50A, the process chamber vacuum was 0.4Pa, the oxygen flow rate was 500sccm, the plasma power was 500W, and the evaporation time was 2min, so that the thickness of the inorganic material layer was 50nm.

[0136] The prepared propylene-vinylidene fluoride copolymer, N-dodecyldimethylamine, and polydimethylsiloxane are mixed in a mass ratio of 90:3:7 to obtain a mixture, and then the mixture is dissolved in acetone to obtain an adhesive slurry with a solid content of 40%;

[0137] The adhesive slurry is evenly coated on both surfaces of the laminate consisting of the porous substrate and the inorganic material layer to form an adhesive layer, so that the thickness of the single adhesive layer is 2 μm. Figure 2 shown.

[0138] <1-5. Preparation of electrolyte>

[0139] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents of ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) were mixed in a mass ratio of 20:30:20:28:2, and then lithium hexafluorophosphate (LiPF6) was added to the non-aqueous organic solvent. 6 ) are dissolved and mixed evenly to obtain an electrolyte, in which LiPF 6 The mass ratio of the aqueous phase to the non-aqueous organic solvent is 8:92.

[0140] <1-6. Preparation of lithium-ion batteries>

[0141] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to play a role of isolation, and then wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, and the moisture is removed at 80°C, and the prepared electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0142] Example 2

[0143] (1-4) Preparation of a separator was carried out in the same manner as in Example 1 except that the deposition time was adjusted to 12 minutes so that the thickness of the inorganic material layer was 300 nm.

[0144] Example 3

[0145] (1-4) Preparation of a separator The same operation as in Example 1 was carried out except that the vapor deposition time was adjusted to 24 minutes so that the thickness of the inorganic material layer was 600 nm.

[0146] Example 4

[0147] (1-4) Preparation of a separator was carried out in the same manner as in Example 1 except that the vapor deposition time was adjusted to 40 min so that the thickness of the inorganic material layer was 1000 nm.

[0148] Example 5

[0149] (1-4) Preparation of a separator The same procedure as in Example 1 was carried out except that the deposition time was adjusted to 80 min so that the thickness of the inorganic material layer was 1900 nm.

[0150] Example 6

[0151] (1-4) Preparation of the isolation film was carried out in the same manner as in Example 1 except that the heating evaporation current was adjusted to 10 A, the evaporation time was adjusted to 180 min, the thickness of the inorganic material layer was adjusted to 450 nm, and the porosity of the inorganic material layer was adjusted to 10%.

[0152] Example 7

[0153] (1-4) In the preparation of the isolation film, the same operation as in Example 1 was carried out except that the heating evaporation current was adjusted to 100 A, the evaporation time was adjusted to 4 min, and the porosity of the inorganic material layer was adjusted to 60%.

[0154] Example 8

[0155] (1-4) Preparation of a separator was carried out in the same manner as in Example 1 except that the vapor deposition time was adjusted to 18 minutes.

[0156] Example 9

[0157] The same operation as in Example 1 was carried out except that the crystallinity of the copolymer was adjusted to 10% in the preparation of the copolymer (1-1) and the deposition time was adjusted to 18 min in the preparation of the separator (1-4). The isotacticity of the obtained copolymer was 40%.

[0158] Example 10

[0159] The same operation as in Example 1 was performed except that the crystallinity of the copolymer was adjusted to 35% in the preparation of the copolymer (1-1) and the deposition time was adjusted to 18 min in the preparation of the separator (1-4). The isotacticity of the obtained copolymer was 50%.

[0160] Embodiment 11

[0161] The same operation as in Example 1 was carried out except that the crystallinity of the copolymer was adjusted to 40% in the preparation of the copolymer (1-1) and the deposition time was adjusted to 18 min in the preparation of the separator (1-4). The isotacticity of the obtained copolymer was 50%.

[0162] Example 12

[0163] The same procedures as in Example 1 were followed except that in (1-1) Preparation of the Copolymer, the weight average molecular weight of the copolymer was adjusted to 1000 g / mol, and in (1-4) Preparation of the Separator, the deposition time was adjusted to 18 min.

[0164] Embodiment 13

[0165] The same procedures as in Example 1 were followed except that in (1-1) Preparation of the copolymer, the weight average molecular weight of the copolymer was adjusted to 10,000 g / mol, and in (1-4) Preparation of the separator, the deposition time was adjusted to 18 min.

[0166] Embodiment 14

[0167] The same procedures as in Example 1 were followed except that in (1-1) Preparation of the Copolymer, the weight average molecular weight of the copolymer was adjusted to 800,000 g / mol, and in (1-4) Preparation of the Separator, the deposition time was adjusted to 18 min.

[0168] Embodiment 15

[0169] The same procedures as in Example 1 were carried out except that (1-1) the Dv50 of the copolymer was adjusted to 1 μm, and (1-4) the deposition time was adjusted to 18 min in the preparation of the separator.

[0170] Example 16

[0171] The same procedures as in Example 1 were carried out except that (1-1) the Dv50 of the copolymer was adjusted to 2 μm, and (1-4) the deposition time was adjusted to 18 min in the preparation of the separator.

[0172] Embodiment 17

[0173] The same procedures as in Example 1 were carried out except that (1-1) the Dv50 of the copolymer was adjusted to 5 μm, and (1-4) the deposition time was adjusted to 18 min in the preparation of the separator.

[0174] Embodiment 18

[0175] The same procedures as in Example 1 were carried out except that (1-1) the Dv50 of the copolymer was adjusted to 10 μm, and (1-4) the deposition time was adjusted to 18 min in the preparation of the separator.

[0176] Embodiment 19

[0177] In the preparation of (1-4) the isolating membrane, the evaporation time of the single inorganic material layer was adjusted to 18 min, except that the inorganic material layer was formed on both surfaces of the PE porous substrate in the isolating membrane. The same operation as in Example 1 was performed. Figure 1 shown.

[0178] Embodiment 20

[0179] The same operation as in Example 1 was performed except that the adhesive layer in the isolation film was formed on one surface of the laminate of the porous substrate and the inorganic material layer so that the adhesive layer was in contact with the inorganic material layer. In the preparation of the isolation film (1-4), the evaporation time was adjusted to 18 min. The isolation film structure was as follows: Figure 4 shown.

[0180] Embodiment 21

[0181] The preparation of the copolymer was different from that in Example 1. In the preparation of the separator (1-4), the evaporation time was adjusted to 18 minutes. The same operation as in Example 1 was performed except that the preparation of the copolymer was different from that in Example 1.

[0182] <2-1. Preparation of copolymer>

[0183] In a 1L stainless steel reactor, 77 parts (volume fraction) of hexane solvent, 19 parts (volume fraction) of a hexane solution of the main catalyst ferrocene (ferrocene content 70 mg / L), and 4 parts (volume fraction) of a hexane solution of the co-catalyst methylaluminoxane (methylaluminoxane content 10 mg / L) were added under nitrogen protection, and then a propylene / ethylene mixed gas was introduced, the temperature was raised to 50°C, and the pressure of the reactor was controlled at 0.4MPa. The molar ratio between the first and second monomers was adjusted to 30:70 by adjusting the amount of propylene / ethylene added. After reacting for 1 hour, the reaction was terminated with acidified ethanol to obtain a propylene-ethylene copolymer. The obtained product was washed 3 times with anhydrous ethanol, filtered, and dried in a vacuum drying oven at 60°C for 4 hours.

[0184] Embodiment 22

[0185] The preparation of the copolymer was different from that in Example 1. In the preparation of the separator (1-4), the evaporation time was adjusted to 18 minutes. The same operation as in Example 1 was performed except that the preparation of the copolymer was different from that in Example 1.

[0186] <3-1. Preparation of copolymer>

[0187] In a 1L stainless steel reactor, 77 parts (volume fraction) of hexane solvent, 19 parts (volume fraction) of hexane solution of main catalyst ferrocene (ferrocene content 70 mg / L), and 4 parts (volume fraction) of hexane solution of co-catalyst methylaluminoxane (methylaluminoxane content 10 mg / L) were added under nitrogen protection, and then propylene / butadiene mixed gas was introduced, the temperature was raised to 50°C, and the pressure of the reactor was controlled to 0.4MPa. The molar ratio between the first and second monomers was adjusted to 30:70 by adjusting the amount of propylene / butadiene added. After reacting for 1 hour, the reaction was terminated with acidified ethanol to obtain a propylene-butadiene copolymer. The obtained product was washed 3 times with anhydrous ethanol, filtered, and dried in a vacuum drying oven at 60°C for 4 hours. The weight average molecular weight of the obtained copolymer was 500g / mol.

[0188] Embodiment 23

[0189] The preparation of the copolymer was different from that in Example 1. In the preparation of the separator (1-4), the evaporation time was adjusted to 18 minutes. The same operation as in Example 1 was performed except that the preparation of the copolymer was different from that in Example 1.

[0190] <4-1. Preparation of copolymer>

[0191] In a 1L stainless steel reactor, 77 parts (volume fraction) of hexane solvent, 19 parts (volume fraction) of a hexane solution of the main catalyst ferrocene (ferrocene content 70 mg / L), and 4 parts (volume fraction) of a hexane solution of the co-catalyst methylaluminoxane (methylaluminoxane content 10 mg / L) were added under nitrogen protection, and then ethyl acrylate was added, and then propylene was introduced. The temperature was raised to 50°C, and the pressure of the reactor was controlled to be 0.4MPa. The molar ratio between the first and second monomers was adjusted to 30:70 by adjusting the amount of propylene / ethyl acrylate added. After reacting for 1 hour, the reaction was terminated with acidified ethanol to obtain a propylene-ethyl acrylate copolymer. The obtained product was washed 3 times with anhydrous ethanol, filtered, and dried in a vacuum drying oven at 60°C for 4 hours.

[0192] Embodiment 24

[0193] The preparation of the copolymer was different from that in Example 1. In the preparation of the separator (1-4), the evaporation time was adjusted to 18 minutes. The same operation as in Example 1 was performed except that the preparation of the copolymer was different from that in Example 1.

[0194] <5-1. Preparation of copolymer>

[0195] In a 1L stainless steel reactor, 77 parts (volume fraction) of hexane solvent, 19 parts (volume fraction) of a hexane solution of a main catalyst ferrocene (ferrocene content 70 mg / L), and 4 parts (volume fraction) of a hexane solution of a co-catalyst methylaluminoxane (methylaluminoxane content 10 mg / L) were added under nitrogen protection, and then ethyl acrylate was added, and then propylene and ethylene were introduced. The temperature was raised to 50°C, and the pressure of the reactor was controlled to be 0.4 MPa. The molar ratio of the first and second monomers was adjusted to 30:70 (wherein the molar ratio of ethylene monomer and ethyl acrylate monomer was equal) by adjusting the added amount of propylene / ethylene / ethyl acrylate. After reacting for 1 hour, the reaction was terminated with acidified ethanol to obtain a propylene-ethylene-ethyl acrylate copolymer. The obtained product was washed 3 times with anhydrous ethanol, filtered, and dried in a vacuum drying oven at 60°C for 4 hours.

[0196] Embodiment 25

[0197] (1-4) Preparation of the isolation film The same operation as in Example 1 was carried out except that the vapor deposition time was adjusted to 1 min so that the thickness of the inorganic material layer was 20 nm.

[0198] Embodiment 26

[0199] (1-1) Preparation of a copolymer The same procedure as in Example 1 was carried out except that the Dv50 of the copolymer was adjusted to 0.1 μm and the weight average molecular weight of the copolymer was adjusted to 500 g / mol.

[0200] Embodiment 27

[0201] The same procedures as in Example 1 were carried out except that in the preparation of the copolymer (1-1), the softening temperature of the copolymer was adjusted to 73° C., and in the preparation of the separator (1-4), the deposition time was adjusted to 18 min.

[0202] Embodiment 28

[0203] The same procedures as in Example 1 were carried out except that in the preparation of the copolymer (1-1), the softening temperature of the copolymer was adjusted to 82° C., and in the preparation of the separator (1-4), the deposition time was adjusted to 18 min.

[0204] Embodiment 29

[0205] The same procedures as in Example 1 were carried out except that in (1-1) Preparation of the copolymer, the softening temperature of the copolymer was adjusted to 88° C., and in (1-4) Preparation of the separator, the deposition time was adjusted to 18 min.

[0206] Comparative Example 1

[0207] Except that the isolation film does not contain an inorganic material layer, the rest is the same as that of Example 1.

[0208] The preparation process of the isolation film is as follows:

[0209] The propylene-vinylidene fluoride copolymer, N-dodecyldimethylamine and polydimethylsiloxane prepared in the preparation of the copolymer (1-1) are mixed in a mass ratio of 90:3:7 to obtain a mixture, and then the mixture is dissolved in acetone to obtain an adhesive slurry with a solid content of 40%;

[0210] The adhesive slurry was evenly coated on both surfaces of the porous substrate to form an adhesive layer, so that the thickness of the single adhesive layer was 2 μm.

[0211] Comparative Example 2

[0212] Except that the preparation process of the isolation film is different from that of Example 1 and the evaporation time is 18 minutes, the rest is the same as Example 1.

[0213] The preparation process of the isolation film is as follows:

[0214] An inorganic material layer was formed on one surface of a 9μm PE porous substrate (porosity of 36%) by plasma-assisted thermal evaporation deposition. The heating source was an electron beam, and the heating target was an aluminum-magnesium alloy (Al content of 92wt%). Under vacuum conditions, oxygen was used as the reaction gas, and the temperature of the porous substrate was controlled to be less than 100°C. The heating evaporation current was adjusted to 50A, the process chamber vacuum degree to 0.4Pa, the oxygen flow rate to 500sccm, the plasma power to 500W, and the evaporation time to 18min, so that the thickness of the inorganic material layer was 450nm.

[0215] Comparative Example 3

[0216] Except for adjusting the Al content in the aluminum-magnesium alloy heating target to 80wt% and the evaporation time to 18min, the rest is the same as Example 1.

[0217] The preparation parameters and test results of each embodiment and comparative example are shown in Table 1 below:

[0218] Table 1 Preparation parameters and test results of each embodiment and comparative example

[0219] Table 2 Test results of lithium ion batteries of various embodiments and comparative examples

[0220] It can be seen from Examples 1-29 and Comparative Example 1 that the isolation film having the inorganic material layer of the present application has improved anti-puncture performance and reduced thermal shrinkage.

[0221] It can be seen from Examples 1-29 and Comparative Example 2 that the isolation membrane having the adhesive layer of the present application has significantly improved adhesion both before and after being soaked in electrolyte, and the deformation and expansion of the lithium-ion battery are significantly reduced.

[0222] It can be seen from Examples 1-29 and Comparative Example 3 that the isolation membrane with a total mass content of metal elements, oxygen elements and nitrogen elements in the inorganic material layer within the scope of the present application has improved puncture resistance, reduced thermal shrinkage, and reduced Hi-pot defective rate of lithium-ion batteries.

[0223] It can be seen from Examples 1-29 and Comparative Examples 1-3 that the battery capacity of the lithium-ion battery having the isolation membrane of the present application is improved, and the cycle capacity retention rate is basically not affected.

[0224] The thickness of the inorganic material layer usually affects the mechanical properties of the isolation membrane; the porosity affects the air permeability of the isolation membrane; the crystallinity of the copolymer usually affects the regularity of its molecular structure; the weight-average molecular weight usually affects its adhesion performance and electrolyte resistance; Dv50 usually affects its specific surface area; the softening temperature usually affects its adhesion performance; it can be seen from Examples 1-29 that as long as the above conditions are within the scope of this application, the copolymer has high adhesion, so that the isolation membrane of the present application has high needle puncture strength and low thermal shrinkage, and the lithium-ion battery has low expansion and deformation, the purpose of the invention of the present application can be achieved.

[0225] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A separator comprising a porous substrate, an inorganic material layer and an adhesive layer, It is characterized in that The inorganic material layer is disposed between the porous substrate and the adhesive layer; The thickness of the inorganic material layer is 20 nm to 1900 nm, and the total mass percentage of metal elements, oxygen elements and nitrogen elements in the inorganic material layer is more than 96%; The adhesive layer comprises a copolymer, and the monomers forming the copolymer include a first monomer and a second monomer; The first monomer is propylene.

2. The isolation film according to claim 1, wherein: The second monomer includes at least one of ethylene, vinylidene fluoride, vinyl chloride, butadiene, isoprene, styrene, acrylonitrile, ethylene oxide, propylene oxide, acrylate, vinyl acetate or caprolactone.

3. The isolation film according to claim 1, wherein: The isotacticity of the copolymer is 35% to 80%.

4. The isolation film according to claim 1, wherein: The copolymer has at least one of the following characteristics: a) the copolymer has a crystallinity of 10% to 40%; b) the softening temperature of the copolymer is 70°C to 90°C; c) the weight average molecular weight of the copolymer is 500 g / mol to 1,000,000 g / mol; d) The Dv50 of the copolymer is 0.1 μm to 10 μm.

5. The isolation film according to claim 1, wherein: The first monomer accounts for 30 mol % to 95 mol % of the total monomers of the copolymer, and the second monomer accounts for 5 mol % to 70 mol % of the total monomers of the copolymer.

6. The isolation film according to claim 1, wherein: The thickness of the adhesive layer is 1 μm to 10 μm.

7. The isolation film according to claim 1, wherein: The porosity of the porous substrate is 20% to 80%, and the thickness of the porous substrate is 2 μm to 30 μm.

8. The isolation film according to claim 1, wherein: The thickness of the inorganic material layer is 50 nm to 900 nm, and the total mass percentage of metal elements, oxygen elements and nitrogen elements in the inorganic material layer is greater than 99.01%.

9. The isolation film according to claim 1, wherein: The inorganic material layer includes at least one of α-Al2O3, Si oxide, Si nitride, Ti oxide, Ti nitride, Zn oxide, Zn nitride, Mg oxide, Mg nitride, Zr oxide, Zr nitride, Ca oxide, Ca nitride, Ba oxide or Ba nitride.

10. The isolation film according to claim 1, wherein The inorganic material layer is a porous structure formed by the accumulation of nanoclusters. There are pores between the nanoclusters, and the average pore diameter of the pores is 0.1 nm to 100 nm.

11. The isolation film according to claim 1, wherein: At least a portion of the inorganic material layer covers the inner wall of the pores of the porous substrate, and the depth of the inorganic material layer embedded in the pores is 1 / 1000 to 1 / 21 of the thickness of the porous substrate.

12. The isolation film according to claim 1, wherein The porosity of the inorganic material layer is 10% to 60%, and the peeling strength between the inorganic material layer and the porous substrate is not less than 30 N / m.

13. The isolation film according to claim 1, wherein: The adhesive layer is also directly disposed on one of the surfaces of the porous substrate.

14. An electrochemical device, comprising a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet, and the separator is the separator according to any one of claims 1 to 13.

15. An electronic device comprising the electrochemical device according to claim 14.

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