TWI844427B - High thermal-stability separator and method for manufacturing thereof - Google Patents

Abstract

A high thermal-stability separator and method for manufacturing thereof are disclosed. The high thermal-stability separator comprises a porous film and a titanium oxide or/and titanium hydroxide deposition, wherein the porous film comprises a porous substrate and a inorganic layer, wherein the inorganic layer comprises a plurality of inorganic particles and a binder, the inorganic layer is formed on at least one surface of the porous substrate, and the porous substrate and the inorganic layer have a plurality of interconnected porous structures; and the titanium oxide or/and titanium hydroxide deposition is formed on the surface of the inorganic layer and the inner walls of porous structures. The present high thermal-stability separator can provide enhanced compression retention and excellent high temperature melt integrity, and maintain a satisfied air permeability (Gurley) after compression.

Description

High thermal stability isolation film and preparation method thereof

The present invention relates to a high thermal stability isolation film, and in particular to a high thermal stability isolation film comprising a titanium oxide or/and titanium hydroxide film and a method for manufacturing the high thermal stability isolation film.

In the application process of lithium-ion batteries, the separator must meet sufficient mechanical performance requirements to withstand various forces inside and outside the battery, especially pressure. In fact, lithium-ion batteries need to apply stacking pressure to the battery during assembly to maintain close contact between all components, and the external loads and collisions during daily use of the battery will also cause fluctuations in internal pressure. Most importantly, in each charge and discharge cycle of lithium-ion batteries, the embedding and de-embedding of lithium ions is not only an electrochemical process, but also causes the volume expansion of the electrode material. The expanded electrode inevitably squeezes the limited space inside the battery, compressing the separator film, causing the micropores of the separator film to deform, thereby reducing the ionic conductivity along the thickness direction. Therefore, it is an important issue to strengthen the compression resistance of the battery separator film and maintain a certain air permeability after compression.

Furthermore, the melt integrity of the battery separator at high temperatures is a key characteristic to ensure battery safety. If heat accumulates inside the battery due to temperature rise caused by external high temperature, overcharging, internal short circuit or any other abnormal electrochemical reaction, high-temperature melt integrity can provide additional safety. Because the separator film still maintains its integrity at high temperatures, it can prevent the electrodes from contacting each other at high temperatures and causing thermal runaway. The separator film used for lithium-ion batteries uses polyolefin materials as the base material, that is, polyethylene (PE) and/or polypropylene (PP), which have insufficient melt integrity at high temperatures. Therefore, a separator film with high-temperature melt integrity is required.

The present invention discloses a high thermal stability isolation film, which has enhanced compression resistance and high temperature melting integrity, and still maintains a certain air permeability after compression.

The high thermal stability isolation membrane of the present invention comprises a porous membrane and a titanium oxide or/and titanium hydroxide thin film, wherein the porous membrane comprises a porous substrate and an inorganic layer, wherein the inorganic layer comprises a plurality of inorganic particles and a binder, and the inorganic layer is formed on at least one surface of the porous substrate, and the porous substrate and the inorganic layer have a plurality of porous structures that are interconnected; and the titanium oxide or/and titanium hydroxide thin film is formed on the surface of the porous membrane and on the inner walls of the porous structures.

The high heat-stable isolation film disclosed in the present invention has a compression resistance greater than 90% after being compressed for 30 seconds at a load of 88 Kgf/ ^cm2 , and a decrease in air permeability (Gurley) of less than 35% after compression.

The high temperature rupture temperature of the high thermal stability isolation film disclosed in the present invention is greater than 170°C.

In the thermally stable isolation film disclosed in the present invention, the titanium oxide or/and titanium hydroxide thin film is formed by a chemical solution deposition method, which is formed by applying a precursor solution on the porous membrane and then applying a reaction solution to react the precursor solution with the reaction solution. In an embodiment of the thermally stable isolation film disclosed in the present invention, the precursor solution is a 0.25wt% to 3wt% titanium alkoxide solution, the solvent of the titanium alkoxide solution is methanol, ethanol, isopropanol or a combination thereof, wherein the reaction solution is an aqueous solution of 30 to 70 weight percent of alcohol.

In the high thermal stability isolation film disclosed in the present invention, the titanium oxide or/and titanium hydroxide film further comprises an adhesion promoter, a stabilizer or a metal salt.

In the high heat-stable isolation film disclosed in the present invention, the tackifier is poly(meth)acrylate, poly-N-vinyl acetamide, crosslinked (meth)acrylic resin, acrylonitrile-acrylate copolymer, acrylonitrile-acrylamide-acrylate copolymer or a combination thereof.

In the high thermal stability isolation film disclosed in the present invention, the stabilizer is hexamethyldisilazane.

In the high heat stable isolation film disclosed in the present invention, the metal salt is sodium bromide, potassium iodide, magnesium chloride, strontium chloride, calcium chloride, strontium bromide, copper chloride or a combination thereof.

The invention discloses a highly thermally stable isolation membrane, wherein the porous substrate of the porous membrane can be a single-layer or multi-layer porous structure substrate of polyolefin, polyester or polyamide.

In the high thermal stability isolation film disclosed in the present invention, the inorganic layer of the porous film comprises a plurality of inorganic particles and a binder, wherein the inorganic layer forms a porous structure that is interconnected with the porous substrate. In one embodiment of the present invention, the inorganic layer may comprise 1 to 20 weight percent of the binder and 80 to 99 weight percent of the inorganic particles. In a preferred embodiment of the present invention, the porous film may comprise an inorganic layer on one or both surfaces thereof.

In the high thermal stability isolation film disclosed in the present invention, the inorganic particles contained in the inorganic layer of the porous film are selected from Mg(OH) ₂ , BaSO ₄ , BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-x La _x Zr _1-y (Zr,TiyO ₃ ) (PLZT, wherein 0＜x＜1 and 0＜y＜1), Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al(OH) ₃ , Al ₂ O ₃ , boehmite (AlOOH), SiC, TiO ₂ and their combinations.

In the high heat stability isolation film disclosed in the present invention, the binder contained in the inorganic layer of the porous film is ethylene-vinyl acetate copolymer (EVA), poly (meth) acrylate, cross-linked (meth) acrylic resin, fluorine rubber, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), poly-N-vinyl acetamide, polyvinylidene fluoride (PVDF), polyurethane or a combination thereof.

Another aspect of the present invention discloses a method for preparing a high thermal stability isolation membrane, the steps of which include: providing a porous membrane, comprising a porous substrate and an inorganic layer, wherein the inorganic layer comprises a plurality of inorganic particles and a binder, and the inorganic layer is formed on at least one surface of the porous substrate, and the porous substrate and the inorganic layer have a plurality of porous structures that are interconnected; forming a titanium oxide and/or titanium hydroxide film on the surface of the porous membrane and on the inner walls of the porous structures.

The present invention discloses a method for preparing a high thermal stability isolation membrane, wherein the step of forming a titanium oxide or/and titanium hydroxide thin film on the porous membrane surface of the porous membrane and the inner wall of the porous structures comprises: preparing a first chemical deposition solution set, which comprises a first precursor solution containing 0.25 weight percent (wt%) to 3wt% of a titanium alkoxide solution and a first reaction solution containing 30 wt% to 70wt% of an alcohol aqueous solution; applying the first precursor solution and the first reaction solution to the porous membrane in sequence, allowing the first precursor solution to react with the first reaction solution, and forming a titanium oxide or/and titanium hydroxide thin film on the porous membrane surface of the porous membrane and the inner wall of the porous structures.

In the preparation method of the high thermal stability isolation film disclosed in the present invention, the titanium alkoxide of the first precursor solution is titanium methanol, titanium ethanol, titanium isopropoxide and titanium tert-butoxide or a combination thereof, and preferably titanium isopropoxide, and the solvent of the titanium alkoxide solution is methanol, ethanol or isopropanol or a combination thereof. In a preferred embodiment of the present invention, the first precursor solution is a solution containing 0.25 weight percent (wt%) to 2.5wt% of titanium alkoxide.

In the preparation method of the high thermal stability isolation film disclosed in the present invention, the alcohol of the first reaction solution is methanol, ethanol, isopropanol, ethoxyethanol, allyl alcohol, ethylene glycol or a combination thereof. In a preferred embodiment of the present invention, the first reaction solution is preferably an aqueous solution of 40 to 60 wt % of alcohol. In a preferred embodiment of the present invention, the first reaction solution is an aqueous solution of methanol, ethanol or isopropanol or a combination thereof.

In the method for preparing the high thermal stability isolation film disclosed in the present invention, the first precursor solution further comprises a stabilizer, wherein the amount of the stabilizer in the first precursor solution is 0.5wt% to 7wt%.

In the preparation method of the high thermal stability isolation film disclosed in the present invention, the first reaction solution further comprises a viscosity enhancer, wherein the usage amount of the viscosity enhancer in the reaction solution is 0.05wt% to 5wt%.

In the preparation method of the high thermal stability isolation membrane disclosed in the present invention, after preparing the first chemical deposition solution set, it further includes the step of preparing a second chemical deposition solution set, which includes a second precursor solution containing 0.25wt% to 3wt% titanium alkoxide solution and a second reaction solution of 30 to 70wt% alcohol aqueous solution, and after the first precursor solution and the first reaction solution are sequentially applied to the porous membrane, the second precursor solution and the second reaction solution are sequentially applied to the porous membrane.

In the preparation method of the high thermal stability isolation film disclosed in the present invention, the type or concentration of phthalate used in the second precursor solution can be the same as or different from the titanium alkoxide solution of the first precursor solution; the titanium alkoxide of the second precursor solution is titanium methoxide, titanium ethoxide, titanium isopropoxide and titanium tert-butoxide or a combination thereof, and the solvent used is methanol, ethanol or isopropanol or a combination thereof. In a preferred embodiment of the present invention, the second precursor solution is a solution containing 0.25 weight percent (wt%) to 2.5wt% of titanium alkoxide.

In the preparation method of the high thermal stability isolation film disclosed in the present invention, the alcohol type or concentration used in the second reaction solution can be the same as or different from that in the first reaction solution, wherein the alcohol in the second reaction solution is methanol, ethanol, isopropanol, ethoxyethanol, allyl alcohol, ethylene glycol or a combination thereof. In a preferred embodiment of the present invention, the second reaction solution is preferably an aqueous solution of 40 to 60 weight percent of alcohol. In a preferred embodiment of the present invention, the second reaction solution is an aqueous solution of methanol, ethanol or isopropanol or a combination thereof.

In the method for preparing the high thermal stability isolation film disclosed in the present invention, the second precursor solution further comprises a stabilizer, and the amount of the stabilizer used in the second precursor solution is 0.5wt% to 7wt%.

In the preparation method of the high thermal stability isolation film disclosed in the present invention, the second reaction solution further comprises a viscosity enhancer, wherein the usage amount of the viscosity enhancer in the reaction solution is 0.05wt% to 5wt%.

The present invention discloses a method for preparing a high thermal stability isolation film, wherein the second reaction solution further comprises a metal salt, wherein the amount of the metal salt in the reaction solution is 5wt% to 20wt%.

Another aspect of the present invention is a high thermal stability isolation membrane, which includes a porous membrane having a plurality of porous structures, and a titanium oxide or/and titanium hydroxide-silicon oxide film is provided on the surface of the porous membrane and the inner wall of the porous structures.

Another aspect of the preparation method of the high thermal stability isolation membrane disclosed in the present invention includes the following steps: providing a porous membrane having a plurality of porous structures, and a first titanium oxide or/and titanium hydroxide thin film is formed on the surface of the porous membrane and the inner walls of the porous structures; preparing a third chemical deposition solution set, which includes a 1 wt% to 10 wt% alkoxysilane solution and a third reaction solution of a 90 wt% to 99.5 wt% alcohol aqueous solution; applying the alkoxysilane solution and the third reaction solution to the porous membrane in sequence, allowing the alkoxysilane solution to react with the third reaction solution to form a second titanium oxide or/and titanium hydroxide-silicon oxide thin film on the surface of the porous membrane and the inner walls of the porous structures.

In another aspect of the method for preparing a high thermal stability isolation film of the present invention, the alkoxysilane solution is a tetraethoxysilane solution, and the solvent in the alkoxysilane solution is methanol, ethanol, or isopropanol or a combination thereof.

In another aspect of the method for preparing a high thermal stability isolation film of the present invention, the alkoxysilane solution further comprises a catalyst, preferably ammonia water. In a preferred embodiment, the amount of the catalyst used is 5 to 15 parts by weight per 100 parts by weight of the solvent.

In another aspect of the method for preparing a high thermal stability isolation film disclosed in the present invention, the third reaction solution is an aqueous solution of alcohol, wherein the alcohol is methanol, ethanol, isopropanol, ethoxyethanol, allyl alcohol, ethylene glycol or a combination thereof.

The above invention contents are intended to provide a simplified summary of the present disclosure so that readers can have a basic understanding of the present disclosure. The invention contents here are not a complete overview of the present disclosure, and are not intended to point out the important/key elements of the embodiments of the present invention or to define the scope of the present invention. After reading the following implementation methods, those with ordinary knowledge in the technical field to which the present invention belongs can easily understand the basic spirit of the present invention and the technical means and implementation modes adopted by the present invention.

In order to make the disclosure of the present invention more detailed and complete, the following provides an illustrative description of the implementation and specific embodiments of the present invention; however, this is not the only form of implementing or using the specific embodiments of the present invention. The embodiments disclosed below can be combined or replaced with each other under beneficial circumstances, and other embodiments can be added to one embodiment without further recording or description.

The advantages, features and technical methods achieved by the present invention will be described in more detail with reference to exemplary embodiments so as to be easier to understand, and the present invention may be implemented in different forms, so it should not be understood to be limited to the embodiments described herein. On the contrary, for those with ordinary knowledge in the relevant technical field, the provided embodiments will make the present invention more thorough and comprehensive and fully convey the scope of the present invention, and the present invention will only be defined by the scope of the attached patent application.

Unless otherwise defined, all terms (including technical and scientific terms) and technical nouns used in the following text are essentially the same as the meanings generally understood by technical personnel in the field to which the present invention belongs. For example, those terms defined in commonly used dictionaries should be understood to have meanings consistent with the content of the relevant field, and unless clearly defined in the following text, they will not be understood in an overly idealized or overly formal sense.

Furthermore, as used herein, "(meth)acrylate" refers to methacrylate and acrylate.

The present invention discloses a high thermal stability isolation membrane, which comprises a porous membrane, a porous substrate and an inorganic layer, wherein the inorganic layer comprises a plurality of inorganic particles and a binder, and the inorganic layer is formed on at least one surface of the porous substrate, and the porous substrate and the inorganic layer have a plurality of porous structures that are interconnected; and a titanium oxide or/and titanium hydroxide film formed on the surface of the porous membrane and on the inner walls of the porous structures.

The high heat-stable isolation film of the present invention has a compression resistance greater than 90% after being subjected to a load of 88 Kgf/ ^cm2 for 30 seconds, providing enhanced compression resistance to suppress the deformation of the isolation film holes due to the corresponding force and maintain the ionic conductivity in the thickness direction.

Furthermore, after the high thermal stability isolation film of the present invention is compressed at a load of 88 Kgf/ ^cm2 for 30 seconds, the pores of the isolation film do not produce excessive deformation due to stress, and a certain air permeability can still be maintained, that is, the air permeability (Gurley) decreases by less than 35%, which can avoid the stress during use causing the internal resistance or internal pressure of the battery to increase.

In this article, the so-called "reduction in air permeability after compression (Gurley, sec/100c.c.)" refers to the decrease in air permeability caused by the destruction of the physical structure of the separator film after it is compressed at a load of 88 Kgf/ ^cm2 for 30 seconds. The calculation method is that the air permeability before compression is G1, and the air permeability after compression is G2, then the air permeability reduction after compression (%) = (1 - G1/G2) × 100%.

In a preferred embodiment of the high thermal stability barrier film of the present invention, the air permeability (Gurley) decreases by less than 30%.

The high-thermal stability isolation film disclosed in the present invention has a high-temperature rupture temperature greater than 170°C. Its melting integrity at high temperatures can prevent electrodes from contacting each other, thereby increasing the safety of the battery.

In the thermally stable isolation film disclosed in the present invention, the titanium oxide or/and titanium hydroxide thin film is formed by a chemical solution deposition method, which is formed by applying a precursor solution on the porous membrane and then applying a reaction solution to react the precursor solution with the reaction solution. In an embodiment of the thermally stable isolation film disclosed in the present invention, the precursor solution is a 0.25wt% to 3wt% titanium alkoxide solution, the solvent of the titanium alkoxide solution is methanol, ethanol, isopropanol or a combination thereof, wherein the reaction solution is an aqueous solution of 30 to 70 weight percent of alcohol.

The high thermal stability isolation film disclosed in the present invention, wherein the titanium oxide or/and titanium hydroxide film further comprises an adhesion promoter, a stabilizer or a metal salt.

In a preferred embodiment of the high thermal stability isolation film of the present invention, the titanium oxide or/and titanium hydroxide film may further include a viscosity enhancer to enhance the adhesion of the titanium oxide or/and titanium hydroxide to the surface of the porous film and the inner wall of the porous structure. Suitable viscosity enhancers may be, for example but not limited to, poly(meth)acrylate resins, crosslinked (meth)acrylate resins, poly-N-vinyl acetamide, acrylonitrile-acrylate copolymers, acrylonitrile-acrylamide-acrylate copolymers or combinations thereof.

In the high thermal stability isolation film of the present invention, the viscosity enhancer suitable for titanium oxide or/and titanium hydroxide film can be selected from commercially available products, such as BM-950B manufactured by Japan Zeon Co., Ltd., PNVA GE191 series (such as GE191-103, GE191-104, GE191-107 or GE191-108) manufactured by Japan Showa Denko Co., Ltd., "Soteras ^TM CCS-V Binder" manufactured by Ashland Co., Ltd., USA, "CYJ-01" manufactured by Zhuhai Chenyu New Material Technology Co., Ltd., China, etc.

In a preferred embodiment of the high thermal stability isolation film of the present invention, the titanium oxide or/and titanium hydroxide film may further include a stabilizer to stabilize the titanium oxide or/and titanium hydroxide. The suitable stabilizer may be hexamethyldisilazane.

In a preferred embodiment of the high thermal stability isolation film of the present invention, the titanium oxide or/and titanium hydroxide film may further include a metal salt to reduce the water content of the titanium oxide or/and titanium hydroxide film. The applicable metal salt may be sodium bromide, potassium iodide, magnesium chloride, strontium chloride, calcium chloride, strontium bromide, copper chloride or a combination thereof.

The high thermal stability isolation film disclosed in the present invention, wherein the titanium oxide or/and titanium hydroxide film may further contain additives such as flame retardants, antioxidants, surface modifiers or antistatic agents as required.

Another aspect of the present invention is a high thermal stability isolation membrane, which comprises a porous membrane, which comprises a porous substrate and an inorganic layer, wherein the porous substrate and the inorganic layer have a plurality of porous structures that are interconnected, and the surface of the inorganic layer and the porous structures have a titanium oxide or/and titanium hydroxide-silicon oxide film.

The present invention discloses a high thermal stability isolation membrane, wherein the porous substrate of the porous membrane can be a single-layer or multi-layer porous structure substrate of polyolefin, polyester or polyamide, without special restrictions. In one embodiment of the present invention, the porous substrate can be, for example, a single-layer polyethylene, a single-layer polypropylene, a double-layer polyethylene/polypropylene, a three-layer polypropylene/polyethylene/polypropylene, polyester or polyamide, but is not limited thereto. In one embodiment of the present invention, the thickness of the porous substrate can be between about 5 micrometers (µm) and 30µm, preferably between 7µm and 25µm, and its porosity is between about 30% and 50%.

In the high thermal stability isolation film of the present invention, the porous substrate comprises an inorganic layer on one or both surfaces thereof, the inorganic layer comprising a plurality of inorganic particles and a binder, wherein the inorganic layer forms a plurality of porous structures interconnected with the porous substrate. In one embodiment of the present invention, the inorganic layer may comprise 80 to 99 weight percent of inorganic particles and 1 to 20 weight percent of binder.

In the high thermal stability insulating film of the present invention, the inorganic particles suitable for the inorganic layer of the porous film are selected from the group consisting of Mg(OH) ₂ , BaSO ₄ , BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-x La _x Zr _1-y (Zr,TiyO ₃ ) (PLZT, wherein 0＜x＜1 and 0＜y＜1), Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , boehmite (AlOOH), SiC, TiO ₂ and combinations thereof. In the high thermal stability separator of the present invention, the binder applicable to the inorganic layer of the porous membrane is not particularly limited, and those known to be applicable to the separator field can be used, such as a binder having high electrochemical stability, good wettability to electrolyte and chemical resistance. In one embodiment of the present invention, the binder that can be used can be ethylene-vinyl acetate copolymer, poly (meth) acrylate, cross-linked (meth) acrylic resin, fluorine rubber, styrene-butadiene rubber, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, poly-N-vinyl acetamide, polyvinylidene fluoride, polyurethane or a combination thereof, but is not limited thereto. In the high thermal stability isolation film of the present invention, the inorganic layer of the porous film can be coated by methods known in the art without particular limitation, such as roller coating, doctor blade coating, dip coating, wheel coating, rotary coating, slit coating, and other coating methods commonly used in the art.

In another embodiment of the present invention, a method for preparing a high thermal stability isolation membrane is disclosed, the steps of which include: providing a porous membrane, comprising a porous substrate and an inorganic layer, wherein the inorganic layer comprises a plurality of inorganic particles and a binder, and the inorganic layer is formed on at least one surface of the porous substrate, and the porous substrate and the inorganic layer have a plurality of porous structures that are interconnected; forming a titanium oxide and/or titanium hydroxide film on the surface of the porous membrane and on the inner walls of the porous structures of the porous membrane. The titanium oxide or/and titanium hydroxide thin film of the high thermal stability isolation membrane of the present invention can be formed on the surface of the porous membrane and the inner wall of the porous structure of the porous membrane by, for example but not limited to, chemical solution deposition. Other methods of forming thin films, such as but not limited to chemical vapor deposition, atomic layer deposition, etc., can also be applied to the present invention.

In one aspect of the method for preparing the high thermal stability isolation membrane of the present invention, the titanium oxide or/and titanium hydroxide film is formed on the surface of the porous membrane and on the inner walls of the porous structures of the porous membrane, and the steps include: preparing a first chemical deposition solution set, which includes a first precursor solution containing 0.25wt% to 3wt% of a titanium alkoxide solution and a first reaction solution of 30wt% to 70wt% of an alcohol aqueous solution; applying the first precursor solution and the first reaction solution to the porous membrane in sequence, allowing the first precursor solution to react with the first reaction solution, and forming a titanium oxide or/and titanium hydroxide film on the surface of the porous membrane and on the inner walls of the porous structures of the porous membrane.

In the preparation method disclosed in the present invention, the titanium alkoxide of the first precursor solution is titanium methanol, titanium ethanol, titanium isopropoxide and titanium tert-butoxide or a combination thereof, and preferably titanium isopropoxide, and the solvent of the titanium alkoxide solution is methanol, ethanol or isopropanol or a combination thereof. In a preferred embodiment of the present invention, the first precursor solution is a solution containing 0.25 weight percent (wt%) to 2.5wt% of titanium alkoxide.

In the preparation method disclosed in the present invention, the first reaction solution is an aqueous solution of alcohol, and the applicable alcohol can be methanol, ethanol, isopropanol, ethoxyethanol, allyl alcohol, ethylene glycol or a combination thereof. In a preferred embodiment of the present invention, the first reaction solution is preferably an aqueous solution of 40 to 60 wt % alcohol. In a preferred embodiment of the present invention, the first reaction solution is an aqueous solution of methanol, ethanol or isopropanol or a combination thereof.

In the preparation method of the high thermal stability isolation film disclosed in the present invention, the first precursor solution further comprises a stabilizer to stabilize titanium oxide and/or titanium hydroxide, wherein the amount of the stabilizer in the first precursor solution is 0.5wt% to 7wt%, preferably between 1wt% and 5wt%. The applicable stabilizer may be hexamethyldisilazane.

In the preparation method of the high thermal stability isolation film disclosed in the present invention, the first reaction solution further comprises a thickener to enhance the adhesion between the titanium oxide and/or titanium hydroxide and the surface of the porous membrane and the inner wall of the porous structure, wherein the amount of the thickener solution used in the first reaction is between 0.05wt% and 5wt%, preferably between 0.05wt% and 3wt%. Applicable thickeners may be, for example but not limited to, poly(meth)acrylate resins, crosslinked (meth)acrylate resins, poly-N-vinyl acetamide, acrylonitrile-acrylate copolymers, acrylonitrile-acrylamide-acrylate copolymers or combinations thereof.

In the preparation method disclosed in the present invention, the first chemical deposition solution set can be applied to the porous membrane by a solution bath method or a spraying method.

In another embodiment of the preparation method disclosed in the present invention, after preparing the first chemical deposition solution set, a second chemical deposition solution set is further prepared, which includes a second precursor solution containing 0.25wt% to 3wt% titanium alkoxide solution and a second reaction solution of 30 to 70wt% alcohol aqueous solution, and after the first precursor solution and the first reaction solution are applied to the porous membrane, the second precursor solution and the second reaction solution are applied in sequence.

In the preparation method disclosed in the present invention, the second precursor solution is a titanium alkoxide solution, and the type or concentration of the titanium alkoxide used can be the same as or different from the titanium alkoxide solution of the first precursor solution; the titanium alkoxide of the second precursor solution is titanium methanol, titanium ethanol, titanium isopropoxide and titanium tert-butoxide or a combination thereof, and the solvent used is methanol, ethanol or isopropanol or a combination thereof. In a preferred embodiment of the present invention, the second precursor solution is a titanium alkoxide solution containing 0.25 weight percent (wt%) to 2.5wt%.

In another preferred embodiment of the preparation method disclosed in the present invention, the alcohol type or concentration used in the second reaction solution can be the same as or different from that of the first reaction solution, wherein the alcohol is methanol, ethanol, isopropanol, ethoxyethanol, allyl alcohol, ethylene glycol or a combination thereof. In a preferred embodiment of the present invention, the second reaction solution is preferably an aqueous solution of 40 to 60 wt % of alcohol. In a preferred embodiment of the present invention, the second reaction solution is an aqueous solution of methanol, ethanol or isopropanol or a combination thereof.

In another preferred embodiment of the method for preparing a thermally stable isolation film disclosed in the present invention, the second precursor solution may further include a stabilizer. The stabilizer used in the present invention is hexamethyldisilazane, wherein the amount of the stabilizer used in the first precursor solution and the second precursor solution may be the same or different, preferably between 0.5wt% and 7wt%, and particularly preferably between 1wt% and 5wt%.

In another preferred embodiment of the preparation method of the high thermal stability isolation film disclosed in the present invention, the second reaction solution may further contain a thickener. The thickener applicable in the present invention is poly (meth) acrylate, cross-linked (meth) acrylic resin, poly-N-vinyl acetamide, acrylonitrile-acrylate copolymer, acrylonitrile-acrylamide-acrylate copolymer or a combination thereof. In a preferred embodiment of the preparation method of the present invention, the amount of the thickener used in the first or second reaction solution may be the same or different. In a preferred embodiment of the preparation method of the present invention, the amount of the thickener used in the second reaction solution is between 0.05wt% and 5wt%, preferably between 0.05% and 3wt%.

In another preferred embodiment of the preparation method of the high thermal stability isolation film disclosed in the present invention, the second reaction solution may further contain a metal salt. Applicable metal salts may be sodium bromide, potassium iodide, magnesium chloride, strontium chloride, calcium chloride, strontium bromide, copper chloride or a combination thereof. In a preferred embodiment of the preparation method disclosed in the present invention, the metal salt is used in an amount of 5wt% to 20wt% in the second reaction solution.

In the preparation method disclosed in the present invention, the first or second reaction solution may further contain additives such as antistatic agents, flame retardants, antioxidants, or surface modifiers as required.

In the preparation method disclosed in the present invention, the second chemical deposition solution set can be applied to the porous membrane by a solution bath method or a spraying method.

Another aspect of the present invention is a method for preparing a high thermal stability isolation membrane, the steps of which include: providing a porous membrane having a plurality of porous structures, and a titanium oxide or/and titanium hydroxide film on the surface of the porous membrane and the porous structures; forming a titanium oxide or/and titanium hydroxide-silicon oxide film on the surface of the porous membrane and on the inner walls of the porous structures of the porous membrane.

The present invention discloses a method for preparing a high thermal stability isolation film, wherein the titanium oxide and/or titanium hydroxide-silicon oxide thin film can be formed on the surface of the porous membrane and the inner wall of the porous structure of the porous membrane by, for example but not limited to, chemical solution deposition. Other methods for forming thin films, such as but not limited to chemical vapor deposition, atomic layer deposition, etc., can also be applied to the present invention.

In another embodiment of the present invention, the titanium oxide or/and titanium hydroxide-silicon oxide thin film is formed on the surface of the porous membrane and the inner wall of the porous structure of the porous membrane by chemical solution deposition, and the steps include: providing a porous membrane having a plurality of porous structures and having a first titanium oxide or/and titanium hydroxide thin film on the surface of the porous membrane and the porous structures of the porous membrane; preparing a third chemical deposition solution set, which includes a 1wt% A third reaction solution of an alkoxysilane solution with a weight percent of 1 to 10 wt % and an aqueous solution of an alcohol with a weight percent of 90 wt % to 99.5 wt % is prepared; after applying the alkoxysilane solution to the porous membrane, the third reaction solution is applied to the porous membrane to allow the alkoxysilane solution to react with the third reaction solution to form a second titanium oxide or/and titanium hydroxide-silicon oxide thin film on the surface of the porous membrane and on the inner walls of the porous structures of the porous membrane.

In the method for preparing the high thermal stability isolation film of the present invention, the alkoxysilane solution is tetraethoxysilane, and the solvent in the alkoxysilane solution is methanol, ethanol, isopropanol or a combination thereof.

In the preparation method of the high thermal stability isolation film of the present invention, the alkoxysilane solution further comprises a catalyst, preferably ammonia water. In a preferred embodiment, the catalyst is used in an amount of 5 to 15 parts by weight per 100 parts by weight of the solvent.

In the preparation method disclosed in the present invention, the method for applying the third chemical deposition solution set to the porous membrane can be a solution bath method or a spraying method.

The following embodiments are used to further illustrate the present invention, but the content of the present invention is not limited thereto.

Embodiment

Preparation Example: Preparation of Inorganic Particle Coating

38 g of aluminum oxide (CQ-030EN, purchased from Shandong Guoci Functional Materials Co., Ltd., China), 0.68 g of dispersant (BYK-154, purchased from BYK, Germany) and 52.9 g of deionized water were mixed and stirred uniformly. Then 3.4 g of polyacrylate and 0.13 g of polyether-modified siloxane surfactant (BYK-349, purchased from BYK, Germany) were added and mixed and stirred uniformly to obtain an inorganic particle coating solution.

The inorganic particle coating liquid is coated on a 9 µm thick polyethylene porous substrate (porosity 48%) and dried. An inorganic layer with a thickness of 2 µm is formed on one side of the porous substrate, and the total thickness of the single-layer porous membrane is 11 µm; or an inorganic layer with a thickness of 2 µm is formed on both sides of the porous substrate, and the total thickness of the double-layer porous membrane is 13 µm.

Example 1: Preparation of Isolation Film

4 g of titanium isopropoxide (TTIP) was added to 196 g of 99.5% anhydrous ethanol, and the mixture was stirred at room temperature to obtain a first precursor solution. 100 g of deionized water and 100 g of 95% ethanol were uniformly mixed and stirred to obtain a first reaction solution.

2 g of titanium isopropoxide was added to 198 g of 99.5% anhydrous ethanol, and stirred at room temperature to obtain a second precursor solution. 100 g of deionized water and 95% ethanol were uniformly mixed, and stirred at room temperature to obtain a second reaction solution.

The double-coated porous membrane obtained in the preparation example is immersed in the first precursor solution, and the excess liquid on the surface is removed after being taken out. Then, it is immersed in the first reaction solution, and the excess liquid on the surface is removed after being taken out, and it is dried at 80°C for 5 minutes. Then, it is immersed in the second precursor solution, and the excess liquid on the surface is removed after being taken out, and then immersed in the second reaction solution, and the excess liquid on the surface is removed after being taken out, and it is dried at 80°C for 5 minutes to form a titanium oxide or/and titanium hydroxide film on the surface of the porous membrane and the inner wall of the porous structure to obtain a high thermal stability isolation membrane.

The obtained high thermal stability isolation film was tested by the test method described below. The test results are listed in Table 1.

Thickness test: According to GB/T6672-2001 test standard, use a film thickness meter (VL-50-B, purchased from Mitutoyo, Japan) to test. Use a flat probe with a diameter of 3mm and a downward probe load of 0.01N for testing.

Air permeability (Gurley) test: According to ASTM D-726, the test film is cut into 1 square inch size, and the air permeability is obtained by measuring the time required for 100 c.c. of air to pass through the test film using a Gurley permeability meter.

Thermal shrinkage test: Cut a 10×10cm sample and mark the initial lengths M0 and T0 in the longitudinal direction (MD) and transverse direction (TD) at the center of the sample before testing. After marking, place the sample between two A4 papers and heat it in an oven at 150℃ for 1 hour. After heating, place the sample in the same environment as the measuring instrument for 30 minutes, and then measure the longitudinal length M1 and transverse length T1 of the sample center. Longitudinal (MD) thermal shrinkage rate (SMD) = (M0-M1)/M0x100% Transverse (TD) thermal shrinkage rate (STD) = (T0-T1)/T0x100%

Mechanical strength test: According to ASTM D882-09, the tested isolation film was cut into pieces with a width of 10 mm and a length of ≥ 150 mm in the longitudinal direction (MD) and transverse direction (TD). The pieces were stretched at a rate of 500 mm/min using a universal tensile testing machine. The maximum load value at the time of fracture was obtained and then divided by the cross-sectional area of the isolation film (specimen width × substrate thickness). The tensile strength of the isolation film in the longitudinal direction (MD) and transverse direction (TD) was calculated.

Puncture resistance (gf): The puncture strength was measured using a tensile tester (MSG-5, purchased from Kato Tech, Japan). A round-headed stainless steel needle with a needle diameter of 1 mm and an R angle of 0.5 mm was used to puncture the sample at a test speed of 100±10 mm/min. The maximum force (gf) required to puncture the isolation film was recorded.

Liquid absorption rate test: Cut the tested isolation film into a size of 80 mm × 10 mm, suspend the sample vertically in a wetting solvent (propylene carbonate (PC) and diethyl carbonate (DEC) mixed in a weight ratio of 1:1) in a closed space, and mark the initial liquid level on the sample. After 1 minute, record the height (mm) of the isolation film capillary absorption starting from the initial liquid level.

Contact angle measurement: The contact angle was measured using a contact angle meter (Phoenix 150, purchased from Jingzhi Technology, Taiwan). A 2mm diameter syringe was used to absorb propylene carbonate (PC, purity 99%) and mounted on the meter. The isolation film sample to be tested was fixed on the sample carrier. A volume of liquid was squeezed from the syringe and dropped onto the sample to be tested. The optical system CCD was used to measure and the computer software further calculated the contact angle.

Crack test: Cut 3 cm x 20 cm separator film samples and place them in a 200℃ oven for 1 hour. Take them out and visually inspect them for cracks. 'X' means there are cracks; '∆' means it cannot be determined due to membrane shrinkage; '¡' means there are no cracks.

Melt integrity: Cut a 8mm long and 4.5m wide isolation film sample and place it in the sample tank of a thermomechanical analyzer (TMA 450, purchased from TA Instruments, USA). The temperature was raised to 200°C at a rate of 5°C/min under a load of 0.01N. The film rupture temperature was recorded after the test. Under a fixed load of 0.01N, the isolation film reached the thermal limit with the increase of temperature. When the deformation reached the maximum value, it was judged to be broken. The fracture temperature point was defined as the film rupture temperature.

Compression resistance: Cut 50 pieces of 4 cm x 4 cm isolation film and stack them into samples. Measure the initial thickness (T1) as mentioned above, then place them in the fixture, apply a load of 88 Kgf/ ^cm2 and hold the pressure for 30 seconds before stopping. After the measurement, measure the compressed thickness of the sample (T2). Sample compression rate (%) = (T1- T2) / T1×100; Compression resistance = 100% - sample compression rate%

Air permeability after compression: Measure the air permeability (G1) according to the aforementioned air permeability test method; then compress the sample using the aforementioned compression resistance test method, and measure the air permeability (G2) according to the aforementioned air permeability test method; G2 is the air permeability after compression. Air permeability reduction rate after compression (%) = (1-G1/G2) × 100%.

Example 2: Preparation of Isolation Film

1.6 g of titanium isopropoxide was added to 198.4 g of 99.5% anhydrous ethanol, and the mixture was stirred at room temperature to obtain a first precursor solution. 98.4 g of deionized water and 98.4 g of 95% ethanol were uniformly mixed, and 3 g of poly-N-vinyl acetamide (PNVA GE191-107, purchased from Showa Denko K.K., Japan) was added, and the mixture was stirred at room temperature to obtain a first reaction solution. 0.13 g of acrylonitrile-acrylamide-acrylate copolymer (BM-950B, purchased from Zeon Co., Ltd., Japan) was added, and the mixture was stirred at room temperature to obtain a first reaction solution.

The double-coated porous membrane prepared in the preparation example is immersed in the first precursor solution, and the excess liquid on the surface is removed after being taken out. Then, it is immersed in the first reaction solution, and the excess liquid on the surface is removed after being taken out, and dried at 80° C. for 5 minutes to form a titanium oxide or/and titanium hydroxide film on the surface of the porous membrane and the inner wall of the porous structure, so as to prepare a high thermal stability isolation membrane.

The prepared high thermal stability isolation film was tested using the test method described in Example 1. The test results are listed in Table 1.

Example 3: Preparation of Isolation Film

The first precursor solution, the first reaction solution and the second precursor solution were prepared according to Example 1. The second reaction solution was prepared by uniformly mixing 98.4 g of deionized water, 98.4 g of 95% ethanol, 3 g of poly-N-vinyl acetamide (PNVA GE191-107) and 0.13 g of acrylonitrile-acrylamide-acrylate copolymer (BM-950B), and stirring at room temperature to obtain a second reaction solution.

The double-coated porous membrane prepared in the preparation example is sequentially immersed in the first precursor solution, the first reaction solution, the second precursor solution, and the second reaction solution of Example 3 to form a titanium oxide and/or titanium hydroxide film on the surface of the porous membrane and the inner wall of the porous structure to obtain a high thermal stability isolation membrane.

The prepared high thermal stability isolation film was tested using the test method described in Example 1. The test results are listed in Table 1.

Example 4: Preparation of Isolation Film

The first precursor solution, the first reaction solution and the second precursor solution were prepared according to Example 1. The second reaction solution was prepared by uniformly mixing 98.3 g of deionized water, 98.3 g of 95% ethanol and 3 g of poly-N-vinyl acetamide (PNVA GE191-103, purchased from Showa Denko K.K., Japan), adding 0.417 g of polyacrylic acid (PAA) (CYJ-01 Binder A, solid content 48%, purchased from Zhuhai Chenyu New Materials Co., Ltd., China) and stirring at room temperature, and then adding 0.042 g of epoxy resin (CYJ-01 Binder B, solid content 100%, purchased from Zhuhai Chenyu New Materials Co., Ltd., China) and stirring at room temperature to obtain a second reaction solution.

The double-coated porous membrane prepared in the preparation example is sequentially immersed in the first precursor solution, the first reaction solution, the second precursor solution, and the second reaction solution of Example 4 to form a titanium oxide and/or titanium hydroxide film on the surface of the porous membrane and the inner wall of the porous structure to obtain a high thermal stability isolation membrane.

The prepared high thermal stability isolation film was tested using the test method described in Example 1. The test results are listed in Table 1.

Example 5: Preparation of Isolation Film

1.6 g of titanium isopropoxide and 2 g of hexamethyldisilazane were added to 196.4 g of 99.5% anhydrous ethanol and mixed uniformly, and stirred at room temperature to obtain a first precursor reaction solution. 98.4 g of deionized water and 98.4 g of 95% ethanol were mixed uniformly and 3 g of poly-N-vinyl acetamide (PNVA GE191-107) was added, and stirred uniformly at room temperature; 0.13 g of acrylonitrile-acrylamide-acrylate copolymer (BM-950B) was added, and stirred at room temperature to obtain a first reaction solution.

The double-coated porous membrane prepared in the preparation example is sequentially immersed in the first precursor solution and the first reaction solution of Example 5 to form a titanium oxide and/or titanium hydroxide film on the surface of the porous membrane and on the inner wall of the porous structure of the porous membrane to obtain a high thermal stability isolation membrane.

The prepared high thermal stability isolation film was tested using the test method described in Example 1. The test results are listed in Table 1.

Example 6: Preparation of Isolation Film

4 g of titanium isopropoxide and 2 g of hexamethyldisilazane were added to 194 g of 99.5% anhydrous ethanol, mixed evenly, and stirred at room temperature to obtain a first precursor reaction solution. 100 g of deionized water and 100 g of 95% ethanol were evenly mixed and stirred to obtain a first reaction solution.

2 g of titanium isopropoxide and 2 g of hexamethyldisilazane were added to 196 g of 99.5% anhydrous ethanol and mixed uniformly, and stirred at room temperature to obtain a second precursor reaction solution. 98.4 g of deionized water and 98.4 g of 95% ethanol were mixed uniformly and 3 g of poly-N-vinyl acetamide (PNVA GE191-107) was added, and stirred uniformly at room temperature; 0.13 g of acrylonitrile-acrylamide-acrylate copolymer (BM-950B) was added, and stirred at room temperature to obtain a second reaction solution.

The double-coated porous membrane prepared in the preparation example is sequentially immersed in the first precursor solution, the first reaction solution, the second precursor solution, and the second reaction solution of Example 6 to form a titanium oxide and/or titanium hydroxide film on the surface of the porous membrane and on the inner wall of the porous structure of the porous membrane to obtain a high thermal stability isolation membrane.

The prepared high thermal stability isolation film was tested using the test method described in Example 1. The test results are listed in Table 1.

Example 7: Preparation of Isolation Film

1 g of titanium isopropoxide and 10 g of hexamethyldisilazane were added to 189 g of 99.5% anhydrous ethanol, mixed evenly, and stirred at room temperature to obtain a first precursor reaction solution. 100 g of deionized water and 100 g of 95% ethanol were evenly mixed and stirred to obtain a first reaction solution.

1g of titanium isopropoxide and 10g of hexamethyldisilazane were added to 189g of 99.5% anhydrous ethanol and mixed evenly, and stirred at room temperature to obtain a second precursor reaction solution. 98.4g of deionized water and 98.4g of 95% ethanol were mixed evenly and 3g of poly-N-vinyl acetamide (PNVA GE191-107) was added, and stirred evenly at room temperature; 0.13g of acrylonitrile-acrylamide-acrylate copolymer (BM-950B) was added, and stirred at room temperature to obtain a second reaction solution.

The double-coated porous membrane prepared in the preparation example is sequentially immersed in the first precursor solution, the first reaction solution, the second precursor solution, and the second reaction solution of Example 7 to form a titanium oxide and/or titanium hydroxide film on the surface of the porous membrane and on the inner wall of the porous structure of the porous membrane to obtain a high thermal stability isolation membrane.

The prepared high thermal stability isolation film was tested using the test method described in Example 1. The test results are listed in Table 1.

Example 8: Preparation of Isolation Film

The first precursor solution, the first reaction solution and the second precursor solution were prepared according to Example 1. The second reaction solution was prepared by stirring 90 g of deionized water, 90 g of 95% ethanol and 20 g of strontium chloride (SrCl ₂ ∙6H ₂ O, purchased from Thermo Scientific Co. LLC, USA) at room temperature to obtain a second reaction solution.

The double-coated porous membrane prepared in the preparation example is sequentially immersed in the first precursor solution, the first reaction solution, the second precursor solution, and the second reaction solution of Example 8 to form a titanium oxide and/or titanium hydroxide film on the surface of the porous membrane and on the inner wall of the porous structure of the porous membrane to obtain a high thermal stability isolation membrane.

The prepared high thermal stability isolation film was tested using the test method described in Example 1. The test results are listed in Table 1.

Example 9: Preparation of Isolation Film

According to Example 3, a first precursor solution, a first reaction solution, a second precursor solution and a second reaction solution were prepared.

Furthermore, 16.25 g of tetraethoxysilane (TEOS, purchased from Thermo Scientific, USA) was added to 500 g of 95% ethanol and stirred at 50° C., then 55 g of aqueous ammonia was added and stirred at 50° C. for 15 minutes to obtain an alkoxysilane solution, and 200 g of 95% ethanol was used as the third reaction solution.

The double-layered porous membrane prepared in the preparation example is immersed in the first precursor solution, the first reaction solution, the second precursor solution, and the second reaction solution of the present example 9 in sequence according to the steps of example 1 to form a first titanium oxide and/or titanium hydroxide thin film on the surface of the porous membrane and the inner wall of the porous structure of the porous membrane, and then immersed in an alkoxysilane solution and a third reaction solution in sequence to react with the alkoxysilane solution and the third reaction solution to form a second titanium oxide and/or titanium hydroxide-silicon oxide thin film to obtain a high thermal stability isolation membrane.

The prepared high thermal stability isolation film was tested using the test method described in Example 1. The test results are listed in Table 1.

Example 10: Preparation of Isolation Film

According to Example 3, a first precursor solution, a first reaction solution, a second precursor solution and a second reaction solution were prepared.

The single-layer porous membrane prepared in the preparation example is immersed in the first precursor solution, the first reaction solution, the second precursor solution and the second reaction solution of Example 10 in sequence to form a titanium oxide and/or titanium hydroxide film on the surface of the porous membrane and on the inner wall of the porous structure of the porous membrane to obtain a high thermal stability isolation membrane.

The prepared high thermal stability isolation film was tested using the test method described in Example 1. The test results are listed in Table 1.

Comparison Examples 1 and 2

Comparative Examples 1 and 2 are respectively for preparing the double-layered porous membrane and the single-layered porous membrane prepared in the Examples. In the Comparative Examples, the porous membrane used was not treated with the precursor solution and the reaction solution, but was tested according to the detection method described in Example 1. The test results are listed in Table 1. Table 1: Test results of isolation membrane characteristics of Examples 1 to 9 and Comparative Examples 1 to 2 Comparison Example 1 Comparison Example 2 Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Total thickness(μm) 13 11 13 13 13 13 Porous substrate thickness (μm) 9 9 9 9 9 9 Inorganic layer thickness (μm) 4 2 4 4 4 4 Air permeability (sec/100c.c.) 112 99 122 114 138 130 Thermal Shrinkage (150C@1hr) MD 1.5 >50 1.5 1 1.0 0.75 TD 1.0 >50 1.0 0.5 1.0 0 Tensile strength (Kgf/cm ² ) MD 1620 1589 1601 1600 1589 1555 TD 1611 1499 1588 1567 1383 1546 Puncture resistance (gf) 455 430 445 445 463 431 Liquid suction height (mm) 5.5 2.5 7.5 8.5 9.0 9.5 Contact angle(°) 24.7 23.8 23.4 21.6 19.7 21.1 Crack test X ∆ ¡ ¡ ¡ ¡ Membrane rupture temperature (°) 154.1 152.5 175.7 178.8 ＞200 186.2 Compression resistance (%) 89.2 82.8 91.7 90.2 92.1 93.2 Air permeability after compression (sec/100c.c.) 191 191 172 174 168 172 Air permeability reduction rate after compression (%) 41.4 48.2 29.1 34.5 17.9 24.4 Table 1: Measurement results of isolation film characteristics of Examples 1 to 9 and Comparative Examples 1 to 2 (continued) Embodiment 5 Embodiment 6 Embodiment 7 Embodiment 8 Embodiment 9 Embodiment 10 Total thickness(μm) 13 13 13 13 13 11 Porous substrate thickness (μm) 9 9 9 9 9 9 Inorganic layer thickness (μm) 4 4 4 4 4 2 Air permeability (sec/100c.c.) 108.8 135 110 292 188 120 Thermal Shrinkage (150C@1hr) MD 0.75 1.0 0.75 0.75 0.5 4.0 TD 0.5 0 0.5 0 0 4.0 Tensile strength (Kgf/cm ² ) MD 1587 1622 1587 1555 1539 1577 TD 1570 1601 1577 1498 1519 1560 Puncture resistance (gf) 443 459 439 439 433 443 Liquid suction height (mm) 8.8 9.2 9.0 8.5 10.0 4.0 Contact angle(°) 22.4 19.7 21.3 24.0 18.2 20.2 Crack test ¡ ¡ ¡ ¡ ¡ ¡ Membrane rupture temperature (°) 177.8 ＞200 175.2 ＞200 ＞200 188.4 Compression resistance (%) 91.0 94.3 92.0 90.4 94.9 93.5 Air permeability after compression (sec/100c.c.) 159 172 174 361 232 147 Air permeability reduction rate after compression (%) 31.6 18.8 17.9 19.1 19.0 18.4

From the performance characteristics listed in Table 1, it can be seen that compared with the isolation membranes in Comparative Examples 1 to 2 that do not contain titanium oxide or/and titanium hydroxide thin films, the high heat stability isolation membranes of Examples 1 to 9 of the present invention have a compression resistance greater than 90% and a decrease in air permeability of less than 34.5% after compression; and the membrane breaking temperature is greater than 170°C, and the surface does not crack due to high temperature during the crack test, and the thermal shrinkage rate is low, and it has high-temperature melting integrity and enhanced compression resistance. At the same time, it has better wettability to electrolytes, and can also improve the electrical performance in battery applications.

Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined in the attached patent application.

Claims (40)

A high thermal stability isolation membrane, comprising: A porous membrane, comprising a porous substrate and an inorganic layer, wherein the inorganic layer comprises a plurality of inorganic particles and a binder, and the inorganic layer is formed on at least one surface of the porous substrate, and the porous substrate and the inorganic layer have a plurality of porous structures that are interconnected; and A titanium oxide or/and titanium hydroxide film, formed on the surface of the porous membrane and the inner wall of the porous structures. A high heat-stable isolation film as described in claim 1, wherein the compression resistance of the high heat-stable isolation film after being subjected to a load of 88 Kgf/ ^cm2 for 30 seconds is greater than 90%. A high thermal stability isolation film as described in claim 1, wherein the air permeability (Gurley) of the high thermal stability isolation film decreases by less than 35% after being subjected to a load of 88 Kgf/ ^cm2 for 30 seconds. A high thermal stability isolation film as described in claim 1, wherein the high temperature rupture temperature of the high thermal stability isolation film is greater than 170°C. A high thermal stability isolation film as described in any one of claims 1 to 4, wherein the titanium oxide and/or titanium hydroxide film is formed by a chemical solution deposition method. A high thermal stability isolation membrane as described in claim 5, wherein the titanium oxide and/or titanium hydroxide film is formed by applying a precursor solution to the porous membrane and subsequently applying a reaction solution to allow the precursor solution to react with the reaction solution. A high thermal stability isolation film as described in claim 6, wherein the precursor solution is a 0.25wt% to 3wt% titanium alkoxide solution. The high heat-stable isolation film as described in claim 7, wherein the titanium alkoxide is titanium methanol, titanium ethanol, titanium isopropoxide, titanium tert-butoxide or a combination thereof. The high heat-stable isolation film as described in claim 7, wherein the solvent of the titanium alkoxide solution is methanol, ethanol, isopropanol or a combination thereof. The high thermal stability isolation film as described in claim 6, wherein the reaction solution is an aqueous solution of 30 to 70 weight percent of alcohol. The high thermal stability isolation film as described in claim 1, wherein the titanium oxide and/or titanium hydroxide film further comprises an adhesion promoter, a stabilizer or a metal salt. The high heat-stable isolation film as described in claim 11, wherein the adhesion promoter is poly(meth)acrylate, poly-N-vinylacetamide, cross-linked (meth)acrylic resin, acrylonitrile-acrylate copolymer, acrylonitrile-acrylamide-acrylate copolymer or a combination thereof. A high thermal stability isolation film as described in claim 11, wherein the stabilizer is hexamethyldisilazane. The high thermal stability isolation film as described in claim 11, wherein the metal salt is sodium bromide, potassium iodide, magnesium chloride, strontium chloride, calcium chloride, strontium bromide, copper chloride or a combination thereof. The high heat-stable isolation film as described in claim 1, wherein the porous substrate is a single-layer or multi-layer porous substrate of polyolefin, polyester or polyamide. The high thermal stability isolation film as described in claim 1, wherein the inorganic layer contains 80wt% to 99wt% of inorganic particles and 1wt% to 20wt% of a binder. The stable high-heat insulation film as described in claim 16, wherein the inorganic particles are Mg(OH) ₂ , BaSO ₄ , BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-x La _x Zr _1-y (Zr,TiyO ₃ ) (PLZT, wherein 0＜x＜1 and 0＜y＜1), Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al(OH) ₃ , Al ₂ O ₃ , boehmite (AlOOH), SiC, TiO ₂ or a combination thereof. A high heat-stable isolation film as described in claim 16, wherein the binder is ethylene-vinyl acetate copolymer (EVA), poly (meth)acrylate, cross-linked (meth)acrylate, fluororubber, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), poly-N-vinyl acetamide, polyvinylidene fluoride (PVDF), polyurethane or a combination thereof. A method for preparing a high thermal stability isolation membrane, the steps of which include: Providing a porous membrane, comprising a porous substrate and an inorganic layer, wherein the inorganic layer comprises a plurality of inorganic particles and a binder, and the inorganic layer is formed on at least one surface of the porous substrate, and the porous substrate and the inorganic layer have a plurality of porous structures that are interconnected; and Forming a titanium oxide or/and titanium hydroxide film on the surface of the porous membrane and the inner walls of the porous structures. The preparation method as described in claim 19, wherein the step of forming a titanium oxide or/and titanium hydroxide film on the surface of the porous membrane and the inner wall of the porous structure comprises: Preparing a first chemical deposition solution set, which comprises a first precursor solution containing 0.25wt% to 3wt% titanium alkoxide solution, and a first reaction solution of 30 to 70wt% alcohol aqueous solution; and Applying the first precursor solution and the first reaction solution to the porous membrane in sequence, allowing the first precursor solution to react with the first reaction solution to form a titanium oxide or/and titanium hydroxide film on the surface of the porous membrane and the inner wall of the porous structure of the porous membrane. The preparation method as described in claim 20, wherein the titanium alkoxide of the first precursor solution is titanium methanol, titanium ethanol, titanium isopropoxide and titanium tert-butoxide or a combination thereof, and the solvent used in the first precursor solution is methanol, ethanol, isopropanol or a combination thereof. The preparation method as described in claim 20, wherein the first precursor solution is a titanium alkoxide solution containing 0.25 weight percent (wt%) to 2.5wt%. The preparation method as described in claim 20, wherein the alcohol in the first reaction solution is methanol, ethanol, isopropanol, ethoxyethanol, allyl alcohol, ethylene glycol or a combination thereof. The preparation method as described in claim 20, wherein the first reaction solution is an aqueous solution of 40 to 60 wt % alcohol. A preparation method as described in claim 20, wherein the first precursor solution further comprises a stabilizer, wherein the amount of the stabilizer used in the first precursor solution is 0.5wt% to 7wt%, and wherein the stabilizer is hexamethyldisilazane. The preparation method as described in claim 20, wherein the first reaction solution further comprises a viscosity enhancer, and the amount of the viscosity enhancer used in the reaction solution is 0.05wt% to 5wt%. The preparation method as described in claim 26, wherein the tackifier is a poly(meth)acrylate resin, a crosslinked (meth)acrylate resin, a poly-N-vinylacetamide, an acrylonitrile-acrylate copolymer, an acrylonitrile-acrylamide-acrylate copolymer or a combination thereof. The preparation method as described in claim 20, wherein after the step of preparing the first chemical deposition solution set, it further includes a step of preparing a second chemical deposition solution set, wherein the second chemical deposition solution set comprises a second precursor solution containing 0.25wt% to 3wt% titanium alkoxide solution and a second reaction solution of 30 to 70wt% alcohol aqueous solution, and after the first precursor solution and the first reaction solution are sequentially applied to the porous membrane, the second precursor solution and the second reaction solution are sequentially applied to the porous membrane. A preparation method as described in claim 28, wherein the titanium alkoxide of the second precursor solution is titanium methanol, titanium ethanol, titanium isopropoxide and titanium tert-butoxide or a combination thereof, and the solvent used in the second precursor solution is methanol, ethanol, isopropanol or a combination thereof, and the alcohol in the second reaction solution is methanol, ethanol, isopropanol, ethoxyethanol, allyl alcohol, ethylene glycol or a combination thereof. The preparation method as described in claim 28, wherein the second precursor solution contains 0.25wt% to 2.5wt% of titanium alkoxide solution. The preparation method as described in claim 28, wherein the second precursor solution further comprises a stabilizer, wherein the amount of the stabilizer used in the second precursor solution is 0.5wt% to 7wt%, and wherein the stabilizer is hexamethyldisilazane. The preparation method as described in claim 28, wherein the second reaction solution further comprises a viscosity enhancer, wherein the viscosity enhancer is used in an amount of 0.05 wt % to 5 wt % in the second reaction solution. The preparation method as described in claim 32, wherein the tackifier is a poly(meth)acrylate resin, a crosslinked (meth)acrylate resin, a poly-N-vinyl acetamide, an acrylonitrile-acrylate copolymer, an acrylonitrile-acrylamide-acrylate copolymer or a combination thereof. The preparation method as described in claim 28, wherein the second reaction solution further comprises a metal salt, wherein the metal salt is used in an amount of 5wt% to 20wt% in the second reaction solution. The preparation method as described in claim 34, wherein the metal salt is sodium bromide, potassium iodide, magnesium chloride, strontium chloride, calcium chloride, strontium bromide, copper chloride or a combination thereof. A high thermal stability isolation membrane comprises a porous membrane having a plurality of porous structures, and a titanium oxide or/and titanium hydroxide-silicon oxide film is provided on the surface of the porous membrane and the inner wall of the porous structures. A method for preparing a high thermal stability isolation membrane, the steps of which include: Providing a porous membrane having a plurality of porous structures, and having a first titanium oxide or/and titanium hydroxide thin film on the surface of the porous membrane and the porous structures; Preparing a third chemical deposition solution set, which includes a third reaction solution of a 1 wt% to 10 wt% alkoxysilane solution and a 90 wt% to 99.5 wt% alcohol aqueous solution; and Applying the alkoxysilane solution to the porous membrane, and then applying the third reaction solution to the porous membrane to form a second titanium oxide or/and titanium hydroxide-silicon oxide thin film on the surface of the porous membrane and the inner wall of the porous structure. The preparation method as described in claim 37, wherein the alkoxysilane solution is tetraethoxysilane, and the solvent in the alkoxysilane solution is methanol, ethanol, or isopropanol or a combination thereof. The preparation method as described in claim 37, wherein the alkoxysilane solution further comprises a catalyst, wherein the catalyst is aqueous ammonia, and the amount used is 5 to 15 parts by weight per 100 parts by weight of the solvent. The preparation method described in claim 38, wherein the third reaction solution is an aqueous solution of alcohol, wherein the alcohol is methanol, ethanol, isopropanol, ethoxyethanol, allyl alcohol, ethylene glycol or a combination thereof.