CN107170942B - High-temperature-resistant aramid fiber lithium ion battery composite diaphragm and preparation method thereof - Google Patents
High-temperature-resistant aramid fiber lithium ion battery composite diaphragm and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/491—Porosity
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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Abstract
The invention discloses a high-temperature-resistant aramid fiber lithium ion battery composite diaphragm and a preparation method thereof, and belongs to the technical field of lithium ion battery materials. The invention comprises a base film and a coating coated on one side or two sides of the base film, wherein the coating is an aramid fiber coating, and the aramid fiber coating is prepared from the following raw materials in percentage by weight: 1-6% of aramid fiber, 5-12% of pore-forming agent, 0.5-5% of inorganic ceramic particles and 77-93.5% of organic solvent; the aramid fiber is taken from aramid fiber polymer, and the content of the aramid fiber in the aramid fiber polymer is 10-30% by weight. The interface adhesive force of the coating and the base film is good, the coating is not easy to fall off under long-time and high-strength use conditions, the air permeability value and the pore diameter are adjustable, the heat resistance, the electrolyte wettability and the puncture strength are effectively improved, and the safety performance of the lithium ion battery diaphragm is improved; the invention adopts the non-solvent phase-induced conversion method to carry out gel film forming, has simple and controllable process and is easy for batch and continuous production.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery materials, and particularly relates to a high-temperature-resistant aramid fiber lithium ion battery composite diaphragm and a preparation method thereof.
Background
Lithium ion batteries have been widely used in mobile electronic devices and power devices due to their advantages of high energy density, long cycle life, etc., however, frequent safety accidents of lithium ion batteries have attracted much attention. The diaphragm is one of the important components of the lithium ion battery, can provide a lithium ion transmission channel, and can prevent the short circuit caused by the contact of the positive electrode and the negative electrode, and has very important influence on the safety of the lithium ion battery, so that the development of the lithium ion battery has higher requirements on the performance of the diaphragm.
The polyolefin diaphragm is the most widely used lithium ion battery diaphragm at present, but the polyolefin diaphragm has the problems of too high thermal shrinkage and insufficient electrolyte wettability. The most widely used polyolefin separators at present are Polyethylene (PE) and polypropylene (PP), which undergo softening deformation above 100 ℃. In order to improve the thermal stability and wettability of the polyolefin separator, the current main solution is to coat a coating on one side or both sides of the polyolefin separator, wherein the coating has high thermal stability, so that the thermal shrinkage performance of the separator and the safety performance of the lithium ion battery can be improved.
Two common coating methods of the current coating are adopted, one is that polyvinylidene fluoride (PVDF) is dissolved in acetone and coated on a polyolefin substrate, and the solvent is volatilized through drying to obtain a heat-resistant polymer coating with a microporous structure; the method can improve the heat resistance of the diaphragm, the wettability of the electrolyte and the adhesion with the electrode; however, the PVDF coating has a large safety risk because of the adoption of low-boiling-point organic solvents such as acetone and the like as pore-forming agents; meanwhile, the method is difficult to accurately control the thickness and the appearance of the microporous layer of the heat-resistant polymer, has strict requirements on the environmental humidity, and is easy to cause the phenomena of hole breaking, hole cracking and the like or form a compact film once the environmental humidity is changed. Alternatively, a heat-resistant inorganic coating is applied to the polyolefin separator, the commonly used coated inorganic particles being alumina (Al)2O3) Zirconium dioxide (ZrO)2) Silicon dioxide (SiO)2) Etc.; the method can effectively improve the high temperature resistance, the affinity and the wettability of the electrolyte, the puncture strength and the fusing temperature of the diaphragm,the risk that the lithium dendrites pierce the diaphragm is reduced, and the overall safety of the diaphragm is improved; however, the ceramic coating has the problems of poor bonding performance with a substrate and easy powder falling, and the increase of the bonding force through a binder causes the air permeability of the diaphragm to be poor; meanwhile, the strong water absorption of the ceramic particles brings troubles to the production of the lithium ion battery, the requirement can be met only by drying the electric core assembled by the polyolefin diaphragm at 80 ℃ before liquid injection, the liquid injection requirement can be met only by drying the electric core assembled by the ceramic diaphragm at the temperature of more than 110 ℃, and the production cost of a lithium ion battery manufacturer is increased.
The aramid fiber has excellent performances of ultrahigh strength, high modulus, high temperature resistance, chemical corrosion resistance and the like, the thermal decomposition temperature can reach 400-430 ℃, and the heat resistance and the safety performance of the lithium ion battery can be greatly improved. Chinese patent (CN101872852A) mainly uses ultra-short aramid fiber, and adds aramid fibrid to make battery diaphragm of aramid fiber; the diaphragm prepared by the papermaking process has the advantages of large thickness, large pore diameter and pore diameter distribution, poor uniformity and large self-discharge effect, and is difficult to be used for 3C lithium ion batteries. Chinese patent (CN104993089A) coats aramid fiber slurry consisting of aramid fiber dissolving liquid, emulsifier solution and polymer adhesive on a base film, and the aramid fiber coated lithium ion battery diaphragm is obtained after soaking and drying. Chinese patent (CN104979515A) mixes aramid polymer with emulsifier and adhesive to form slurry, steam pre-coagulation is carried out in the environment with the humidity more than 90% after coating, and then aramid fiber coating lithium ion battery diaphragm is obtained by washing; in the method, the emulsifier, the adhesive and the solvent are added separately, so that the dissolving process is increased, and meanwhile, the added adhesive can cause the air permeability of the coating layer to be reduced, and the lithium ion migration speed and the cycle performance of the battery are reduced. Chinese patent (CN103531736A) adopts a mixture of two solvents with polarity less than 5 as a pore-forming agent, and after the mixture is dissolved with aramid fiber, the pore-forming agent is pre-formed by volatilization in the air, and the aramid fiber coated lithium ion battery diaphragm is obtained by washing; the method also adopts the aramid fiber to dissolve to prepare the dissolving solution, the dissolving process can cause the decomposition of the aramid fiber, the molecular weight degradation and the loss of the aramid fiber coating performance, and meanwhile, the coating layer prepared by the method has poor binding power and is easy to fall off, and the processing, the manufacturing and the recycling of the diaphragm in the battery are not facilitated. Chinese patent (CN103824988A) adopts electrostatic spinning to prepare an aramid nanofiber membrane, and then a composite nanofiber lithium ion battery diaphragm is prepared; the electrostatic spinning process is complex, multiple in control factors, low in production efficiency, high in equipment cost, poor in product consistency and stability and difficult in industrialization.
Disclosure of Invention
The invention provides a high-temperature-resistant aramid fiber lithium ion battery composite diaphragm and a preparation method thereof aiming at the existing problems, the composite diaphragm not only improves the interface bonding performance of a coating and a base material, but also greatly improves the puncture performance, the heat shrinkage performance, the electrolyte wettability and the like of the diaphragm, and improves the safety of the lithium ion battery in long-term use.
The invention relates to a high-temperature-resistant aramid fiber lithium ion battery composite diaphragm which is mainly realized by the following technical scheme: the coating is an aramid fiber coating, and the aramid fiber coating is prepared from the following raw materials in percentage by weight: 1-6% of aramid fiber, 5-12% of pore-forming agent, 0.5-5% of inorganic ceramic particles and 77-93.5% of organic solvent; the aramid fiber is obtained from aramid fiber polymers, and the content of the aramid fiber in the aramid fiber polymers is 10-30% by weight.
The aramid fiber is selected as an organic material, is added in the form of aramid fiber polymer, does not contain processing aids such as adhesives and the like, has small interface stress between the obtained aramid fiber coating and the base film, is in good contact and not easy to fall off, and is not easy to fall off even if being used for a long time and under high strength; the obtained aramid coating has adjustable air permeability value and pore diameter, wide application, low thermal shrinkage and good heat resistance, effectively solves the problem of poor wettability of the base film to electrolyte, improves the puncture strength of the base film and improves the use safety performance of the lithium ion battery diaphragm.
As a preferred embodiment, the aramid fiber is one or two of meta-aramid fiber or para-aramid fiber, and the molecular weight of the aramid fiber is 5000-200000 Da. The invention directly adopts the aramid fiber in the aramid fiber polymer, the aramid fiber performance of the intermediate is excellent, and the phenomena of decomposition of the aramid fiber, molecular weight degradation and loss of the aramid fiber coating performance caused by the dissolving process of the aramid fiber can not occur.
As a preferred embodiment, the pore-forming agent is any one or two of an inorganic pore-forming agent and an organic pore-forming agent, the inorganic pore-forming agent is any one or more of lithium chloride, sodium chloride, magnesium chloride, calcium carbonate or calcium chloride, and the organic pore-forming agent is any one or more of methanol, ethanol, propanol, glycerol, polyethylene glycol, acetone, acetic acid, tetrahydrofuran, polyvinylpyrrolidone, ethyl acetate or petroleum ether. In the present invention, polyethylene glycol with different molecular weight can be selected, for example: PEG, Mw: 200-; the pore-forming agent can be inorganic pore-forming agent or organic pore-forming agent or mixture of inorganic pore-forming agent and organic pore-forming agent, and the pore structure and pore diameter of the coating can be effectively improved by adjusting the addition type and content of the pore-forming agent, and the air permeability and electrochemical performance of the composite diaphragm can be adjusted.
As a preferred embodiment, the inorganic ceramic particles are any one or more of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide and barium oxide, and the average particle size of the inorganic ceramic particles is 10-100 nm. The addition of the inorganic ceramic particles further reduces the heat shrinkage of the aramid coating and improves the heat resistance of the composite diaphragm; in addition, the addition of the nano or micron inorganic ceramic particles does not influence the bonding performance of the aramid fiber and the base material, the phenomenon of powder falling does not occur, an adhesive is not required to be added, the manufacturing process of the diaphragm is not prolonged, and the production cost of a lithium ion battery manufacturer is not increased. The addition of the inorganic ceramic particles improves the lyophilic property, the puncture resistance and the heat shrinkage performance of the diaphragm.
As a preferred embodiment, the organic solvent is one or any more of N, N-dimethylacetamide, N-methylpyrrolidone, N-dimethylformamide, and dimethyl phthalate. N, N-dimethylacetamide is DMAc for short, N-methylpyrrolidone is NMP for short, N, N-dimethylformamide is DMF for short, and dimethyl phthalate is DMP for short, and the organic solvents have good dissolving performance on aramid fibers, can enable aramid fibers, inorganic ceramic particles and pore-forming agents to be well dissolved and dispersed in the organic solvents, and are beneficial to forming uniform composite diaphragms.
As a preferable embodiment, the base membrane is a porous base membrane, the porous base membrane is a polyolefin diaphragm with the thickness of 5-40 μm and the porosity of 30-80%, and the polyolefin diaphragm is any one of a polyethylene lithium ion battery diaphragm, a polypropylene lithium ion battery diaphragm and a polypropylene/polyethylene/polypropylene three-layer or multi-layer co-extrusion composite lithium ion battery diaphragm. The porous base film is matched with the aramid fiber coating, the original air permeability of the porous base film is basically not influenced, and the air permeability value is adjustable and controllable.
As a preferred embodiment, the thickness of the aramid coating is 0.5 to 10 μm. A coating film with the thickness of 0.5-10 mu m is formed on the base film through the aramid fiber coating, so that the heat shrinkage of the base film is improved, the puncture strength of the base film is effectively improved, and the safety performance of the lithium ion battery diaphragm is improved.
The invention relates to a preparation method of a high-temperature-resistant aramid fiber lithium ion battery composite diaphragm, which is mainly realized by the following technical scheme: the method comprises the following steps: (1) preparing an aramid fiber membrane casting solution: mixing aramid fiber, pore-forming agent, inorganic ceramic particles and organic solvent, stirring at 50-80 ℃ to completely dissolve the aramid fiber and the pore-forming agent to obtain casting solution; (2) defoaming: defoaming the casting solution obtained in the step (1) for 5-60min at 50-80 ℃ until no bubbles exist; (3) film formation by non-solvent phase inversion method: taking a basement membrane, coating a layer of defoamed membrane casting solution on the basement membrane, standing for 5-60s, placing the basement membrane in a coagulating bath for coagulation, wherein the coagulating bath is a solvent and non-solvent coagulating bath or a water vapor coagulating bath, taking the basement membrane with aramid fibers after coagulation for 1-10min, placing the basement membrane in water for soaking for 10-60min, and taking out the basement membrane; (4) and (3) drying: and drying at 40-80 ℃ for 10-60min to obtain the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm.
According to the invention, aramid fiber, a pore-forming agent, inorganic ceramic particles and an organic solvent are mixed, dissolved and defoamed, and then a film is formed by adopting a non-solvent phase-induced conversion method and is obtained by drying, the obtained aramid fiber coating has good binding force with a base film, the accurate control of the aperture and porosity of an aramid fiber microporous layer can be realized, meanwhile, the performance of the composite diaphragm for adsorbing electrolyte is improved, and the lyophilic and liquid retention capability of the composite diaphragm is greatly improved; the non-solvent induced phase transformation method has the advantages of short process flow, controllable conditions (such as easy adjustment of the composition of casting solution and effective combination of film making process), mild reaction, high production efficiency, easy batch and continuous production and the like, and has great practical value.
In a preferred embodiment, in the solvent and non-solvent coagulation bath, the non-solvent is water, the solvent is any one or more of N, N-dimethylacetamide, N-methylpyrrolidone, N-dimethylformamide, dimethyl phthalate or ethanol, and the volume percentage concentration of the solvent in the solvent and non-solvent coagulation bath is 10-90%; the ambient temperature of the water vapor coagulation bath is 40-60 ℃, and the relative humidity is 60-90%. The membrane is formed by adopting a non-solvent phase-induced conversion method, and a membrane surface layer and an internal membrane microporous structure are formed under the effective cooperation effect of a solvent and a non-solvent, so that the membrane surface layer and the internal membrane microporous structure formed under the environment have the advantages of better pore diameter uniformity, stable structure, controllable conditions and good use effect.
In a preferred embodiment, in the step (2), the viscosity of the defoamed casting solution is 20 to 1000 cP. The viscosity of the defoamed casting solution can be effectively controlled, so that the casting solution can be better adhered to a base film, the adhesive force between the casting solution and the base film is increased, and meanwhile, the fluidity of the casting solution can be improved by controlling the viscosity, so that various coating modes can be selected.
Compared with the prior art, the invention has the beneficial effects that: the invention selects aramid fiber as organic material, the aramid fiber is added in the form of aramid fiber polymer, processing aids such as adhesive and the like are not contained, and the obtained aramid fiber coating and matrixThe interface stress between films is small, the contact is good, the films are not easy to fall off, and the films are not easy to fall off even if the films are used for a long time and under high strength; the air permeability value of the obtained aramid fiber coating is 300-1000s/in2The membrane has the advantages of being adjustable and controllable in the range of ∙ 100cc ∙ 1.22Kpa, wide in application, low in thermal shrinkage and good in heat resistance, effectively solving the problem of poor wettability of the base membrane to electrolyte, improving the puncture strength of the base membrane and improving the use safety performance of the lithium ion battery membrane. Meanwhile, the preparation method of the composite diaphragm has the advantages of short process flow, mild conditions, high production efficiency, easiness in batch and continuous production and the like, and is suitable for expanded production.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical effects in the prior art, the following will be briefly described with reference to the drawings used in the description of the embodiments or the prior art, and it is obvious that the drawings in the following description are only part of the drawings of some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a graph showing the results of measuring the contact angle between a PE-based film and an electrolyte according to the present invention;
FIG. 2 is a graph showing the results of measuring the contact angle between the composite separator and the electrolyte according to the first embodiment of the present invention;
FIG. 3 shows the results of cycle performance tests of different separators in lithium ion batteries;
FIG. 4 is a scanning electron microscope image of the surface of the composite separator of the present invention;
in FIG. 3, ■ -PE-based membranes and ● -composite separators are shown.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention relates to a high-temperature-resistant aramid fiber lithium ion battery composite diaphragm which comprises a base film and coatings coated on one side or two sides of the base film, wherein the coatings are aramid fiber coatings, and the aramid fiber coatings are prepared from the following raw materials in percentage by weight: 1-6% of aramid fiber, 5-12% of pore-forming agent, 0.5-5% of inorganic ceramic particles and 77-93.5% of organic solvent; the aramid fiber is obtained from aramid fiber polymers, and the content of the aramid fiber in the aramid fiber polymers is 10-30% by weight.
Further, the aramid fiber is one or two of meta-aramid fiber or para-aramid fiber, and the molecular weight of the aramid fiber is 5000-.
Preferably, the pore-forming agent is any one or two of an inorganic pore-forming agent and an organic pore-forming agent, the inorganic pore-forming agent is any one or more of lithium chloride, sodium chloride, magnesium chloride, calcium carbonate or calcium chloride, and the organic pore-forming agent is any one or more of methanol, ethanol, propanol, glycerol, polyethylene glycol, acetone, acetic acid, tetrahydrofuran, polyvinylpyrrolidone, ethyl acetate or petroleum ether.
Preferably, the inorganic ceramic particles are any one or more of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide and barium oxide, and the average particle size of the inorganic ceramic particles is 10-100 nm.
Preferably, the organic solvent is any one or more of N, N-dimethylacetamide, N-methylpyrrolidone, N-dimethylformamide and dimethyl phthalate.
Specifically, the base membrane is a porous base membrane, the porous base membrane is a polyolefin diaphragm with the thickness of 5-40 μm and the porosity of 30-80%, and the polyolefin diaphragm is any one of a polyethylene lithium ion battery diaphragm, a polypropylene lithium ion battery diaphragm and a polypropylene/polyethylene/polypropylene three-layer or multi-layer co-extrusion composite lithium ion battery diaphragm. More preferably, the thickness of the porous base film is 10 to 25 μm, and the porosity of the porous base film is 50 to 70%.
Further, the thickness of the aramid coating is 0.5-10 μm.
The invention discloses a preparation method of a high-temperature-resistant aramid fiber lithium ion battery composite diaphragm, which comprises the following steps of: (1) preparing an aramid fiber membrane casting solution: mixing aramid fiber, pore-forming agent, inorganic ceramic particles and organic solvent, stirring at 50-80 ℃ to completely dissolve the aramid fiber and the pore-forming agent to obtain casting solution; (2) defoaming: defoaming the casting solution obtained in the step (1) for 5-60min at 50-80 ℃ until no bubbles exist; (3) film formation by non-solvent phase inversion method: taking a basement membrane, coating a layer of defoamed membrane casting solution on the basement membrane, standing for 5-60s, placing the basement membrane in a coagulating bath for coagulation, wherein the coagulating bath is a solvent and non-solvent coagulating bath or a water vapor coagulating bath, taking the basement membrane with aramid fibers after coagulation for 1-10min, placing the basement membrane in water for soaking or running water for overflowing for 10-60min, and taking out; (4) and (3) drying: and drying at 40-80 ℃ for 10-60min to obtain the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm.
Preferably, in the solvent and non-solvent coagulation bath, the non-solvent is water, the solvent is one or more of N, N-dimethylacetamide, N-methylpyrrolidone, N-dimethylformamide, dimethyl phthalate or ethanol, and the volume percentage concentration of the solvent in the solvent and non-solvent coagulation bath is 10-90%; the ambient temperature of the water vapor coagulation bath is 40-60 ℃, and the relative humidity is 60-90%.
Further, in the step (2), the viscosity of the deaerated casting solution is 20 to 1000 cP. Preferably 50-800 cP. More preferably, the step (1) is stirred at 60-80 ℃, the step (2) is defoamed at 60-80 ℃, the defoamed casting solution is coated on the base film by any one of dipping, pulling, rotating, dip coating, spray coating, scraping, coating wire rod or micro-concave roller coating, and the step (3) is kept in the air for 10-30s, solidified for 1-5min and soaked in water for 10-30 min.
Example one
Mixing 5g of aramid fiber, 1.25g of glycerol, 1.25g of polyvinylpyrrolidone, 0.25g of alumina particles (with the average particle size of 10nm) and 42.25g of DMAc, wherein the aramid fiber is taken from aramid fiber polymer, the solid content of the aramid fiber in the aramid fiber polymer is 10%, and mechanically stirring in an oil bath at 50 ℃ until the aramid fiber and a pore-forming agent are completely dissolved to obtain a casting solution of the aramid fiber; after stirring is stopped, defoaming for 5min in an oil bath at 50 ℃; paving a 20 mu mPE base film on a clean glass plate flatly, wherein the porosity of the PE base film is 30%, pouring a proper amount of defoamed film casting solution on the PE base film, scraping the film by using a wire rod, staying in the air for 5s, slowly immersing into a coagulating bath of DMAc and water at a constant speed at room temperature to form a film, removing the PE film with aramid fibers after 1min, immersing in water for 10min, and taking out; drying in an oven at 40 deg.C for 60min, and taking out.
The composite diaphragm of the lithium ion battery in the embodiment is prepared from 1% of aramid fiber, 5% of pore-forming agent, 0.5% of inorganic ceramic particles and 93.5% of organic solvent.
Example two
Mixing 4.54g of aramid fiber, 1g of acetone, 1.5g of polyvinylpyrrolidone, 0.5g of silicon dioxide particles (with the average particle size of 30nm) and 42.46g of DMF (dimethyl formamide), wherein the aramid fiber is taken from an aramid fiber polymer, the solid content of the aramid fiber in the aramid fiber polymer is 22 percent, the aramid fiber is para-aramid fiber, and the molecular weight of the aramid fiber is 5000-10000Da, and mechanically stirring in an oil bath at the temperature of 60 ℃ until the aramid fiber and a pore-forming agent are completely dissolved to obtain a casting solution of the aramid fiber; after stirring is stopped, defoaming for 10min in an oil bath at 60 ℃; spreading a 20-micron PE base film on a clean glass plate flatly, wherein the porosity of the PE base film is 30%, coating the PE base film in a dip-coating mode, staying in the air for 15s, slowly and uniformly soaking the PE base film in a coagulation bath of DMF (dimethyl formamide) and water at room temperature to form a film, removing the PE film with aramid fibers after 3min, soaking the PE film in water for 20min, and taking out the PE film; drying in an oven at 60 deg.C for 45min, and taking out.
The composite diaphragm of the lithium ion battery in the embodiment is prepared from 2% of aramid fiber, 5% of pore-forming agent, 1% of inorganic ceramic particles and 92% of organic solvent.
EXAMPLE III
Mixing 9.08g of aramid fiber, 2.5g of magnesium chloride, 2.5g of polyvinylpyrrolidone, 1g of silica particles (with an average particle size of 50nm) and 34.92g of NMP, wherein the aramid fiber is taken from an aramid fiber polymer, the solid content of the aramid fiber in the aramid fiber polymer is 22%, and mechanically stirring in an oil bath at 80 ℃ until the aramid fiber and a pore-forming agent are completely dissolved to obtain a casting solution of the aramid fiber; after stirring is stopped, defoaming for 20min in an oil bath at the temperature of 80 ℃; laying a 20-micron PE (polyethylene) base film on a clean glass plate flatly, wherein the porosity of the PE base film is 30%, pouring a proper amount of defoamed film casting solution on the PE base film, scraping the film by using a scraper, staying in the air for 30s, slowly immersing in a coagulating bath of NMP (N-methyl pyrrolidone) and water at room temperature at a constant speed to form a film, removing the PE film with aramid fibers after 5min, immersing in water for 30min, and taking out; drying in an oven at 80 deg.C for 10min, and taking out.
The composite diaphragm of the lithium ion battery in the embodiment is prepared from 4% of aramid fiber, 10% of pore-forming agent, 2% of inorganic ceramic particles and 84% of organic solvent.
Example four
Mixing 26.4g of aramid fiber, 7.2g of calcium chloride, 6g of polyvinylpyrrolidone, 5.5g of alumina particles (average particle size of 10nm), 34.9g of DMAc and 30g of DMF (dimethyl formamide), wherein the aramid fiber is obtained from aramid fiber polymer, the solid content of the aramid fiber in the aramid fiber polymer is 25 percent, the aramid fiber is meta-aramid fiber, the molecular weight of the aramid fiber is 10000-100000Da, and mechanically stirring in an oil bath at 80 ℃ until the aramid fiber and a pore-forming agent are completely dissolved to obtain a casting solution of the aramid fiber; after stirring is stopped, defoaming for 30min in an oil bath at the temperature of 80 ℃; laying a 20-micron PE (polyethylene) base film on a clean glass plate flatly, wherein the porosity of the PE base film is 30%, pouring a proper amount of defoamed film casting solution on the PE base film, scraping the film by using a wire rod, staying in the air for 60s, slowly immersing into a solidification bath of DMAc (dimethyl formamide), DMF (dimethyl formamide) and water at a constant speed to form a film, removing the PE film with aramid fibers after 10min, immersing in water for 45min, and taking out; drying in an oven at 80 deg.C for 30min, and taking out.
The composite diaphragm of the lithium ion battery in the embodiment is prepared from 6% of aramid fiber, 12% of pore-forming agent, 5% of inorganic ceramic particles and 77% of organic solvent.
EXAMPLE five
Mixing 22g of aramid fiber, 3g of PEG2000, 2.5g of polyvinylpyrrolidone, 1.3g of titanium dioxide particles (average particle size of 10nm), 2g of alumina particles (average particle size of 10nm) and 79.2g of DMAc, wherein the aramid fiber is taken from aramid fiber polymer, the solid content of the aramid fiber in the aramid fiber polymer is 30%, and mechanically stirring in an oil bath at 80 ℃ until the aramid fiber and a pore-forming agent are completely dissolved to obtain a casting solution of the aramid fiber; after stirring is stopped, defoaming in an oil bath at 80 ℃ for 60 min; laying a 20-micron PE (polyethylene) base film on a clean glass plate flatly, wherein the porosity of the PE base film is 30%, pouring a proper amount of defoamed film casting solution on the PE base film, scraping the film by using a scraper, staying in the air for 60s, slowly immersing into a coagulating bath of ethanol and water at room temperature at a constant speed to form a film, removing the PE film with aramid fibers after 3min, putting into water, immersing for 60min, and taking out; drying in an oven at 60 deg.C for 60min, and taking out.
The composite diaphragm of the lithium ion battery in the embodiment is prepared from 6% of aramid fiber, 5% of pore-forming agent, 3% of inorganic ceramic particles and 86% of organic solvent.
EXAMPLE six
Mixing 4.54g of aramid fiber, 2.5g of acetic acid, 2.5g of polyvinylpyrrolidone, 0.25g of alumina particles (average particle size of 10nm) and 40.21g of DMAc, wherein the aramid fiber is taken from aramid fiber polymer, the solid content of the aramid fiber in the aramid fiber polymer is 22 percent, the aramid fiber is meta-aramid fiber, the molecular weight of the aramid fiber is 100000-200000Da, and mechanically stirring in an oil bath at 80 ℃ until the aramid fiber and a pore-forming agent are completely dissolved to obtain a casting solution of the aramid fiber; after stirring is stopped, defoaming for 30min in an oil bath at the temperature of 80 ℃; laying a 16-micron PE (polyethylene) base film on a clean glass plate flatly, wherein the porosity of the PE base film is 50%, pouring a proper amount of defoamed film casting solution on the PE base film, scraping the film by using a scraper, staying in the air for 20s, slowly immersing in a solidification bath of DMP (dimethyl formamide) and water at a constant speed at room temperature to form a film, removing the PE film with aramid fibers after 3min, immersing in water for 60min, and taking out; drying in an oven at 60 deg.C for 60min, and taking out.
The composite diaphragm of the lithium ion battery in the embodiment is prepared from 2% of aramid fiber, 10% of pore-forming agent, 0.5% of inorganic ceramic particles and 92.5% of organic solvent.
EXAMPLE seven
Mixing 4.54g of aramid fiber, 2.5g of PEG2000, 2.5g of polyvinylpyrrolidone, 0.25g of titanium dioxide particles (average particle size of 100nm) and 40.21g of DMAc, wherein the aramid fiber is obtained from aramid fiber polymer, the solid content of the aramid fiber in the aramid fiber polymer is 22 percent, the aramid fiber is para-aramid fiber, the molecular weight of the aramid fiber is 10000-100000Da, and mechanically stirring the aramid fiber and the pore-forming agent in an oil bath at 80 ℃ until the aramid fiber and the pore-forming agent are completely dissolved to obtain a casting solution of the aramid fiber; after stirring is stopped, defoaming for 30min in an oil bath at the temperature of 80 ℃; spreading a 16-micron PE (polyethylene) base film on a clean glass plate flatly, wherein the porosity of the PE base film is 50%, pouring a proper amount of defoamed film casting liquid on the PE base film, scraping the film by using a scraper, staying in the air for 20s, slowly immersing in a coagulating bath of DMAc and water at a constant speed at room temperature to form a film, removing the PE film with aramid fibers after 3min, putting the PE film in the water for soaking for 60min, taking out, drying in a 60-DEG C oven for 60min, and taking out.
The composite diaphragm of the lithium ion battery in the embodiment is prepared from 2% of aramid fiber, 10% of pore-forming agent, 0.5% of inorganic ceramic particles and 87.5% of organic solvent.
Example eight
Mixing 4.54g of aramid fiber, 2.5g of calcium carbonate, 2.5g of polyvinylpyrrolidone, 0.25g of silica particles (with the average particle size of 30nm) and 40.21g of DMAc, wherein the aramid fiber is taken from aramid fiber polymer, the solid content of the aramid fiber in the aramid fiber polymer is 22%, and mechanically stirring in an oil bath at the temperature of 80 ℃ until the aramid fiber and a pore-forming agent are completely dissolved to obtain a casting solution of the aramid fiber; after stirring is stopped, defoaming for 30min in an oil bath at the temperature of 80 ℃; laying a 16-micron PE (polyethylene) base film on a clean glass plate flatly, wherein the porosity of the PE base film is 50%, pouring a proper amount of defoamed film casting solution on the PE base film, scraping the film by using a wire rod, staying in the air for 10s, slowly immersing into a coagulating bath of DMAc and water at a constant speed at room temperature to form a film, removing the PE film with aramid fibers after 3min, putting the PE film in the water, immersing for 60min, and taking out; drying in an oven at 60 deg.C for 60min, and taking out.
The composite diaphragm of the lithium ion battery in the embodiment is prepared from 2% of aramid fiber, 10% of pore-forming agent, 0.5% of inorganic ceramic particles and 87.5% of organic solvent.
Example nine
Mixing 4.54g of aramid fiber, 2.5g of lithium chloride, 2.5g of polyvinylpyrrolidone, 0.25g of silicon dioxide particles (with the average particle size of 50nm) and 40.21g of DMAc, wherein the aramid fiber is obtained from aramid fiber polymer, the solid content of the aramid fiber in the aramid fiber polymer is 22 percent, the aramid fiber is meta-aramid fiber, the molecular weight of the aramid fiber is 100000-200000Da, and mechanically stirring in an oil bath at 80 ℃ until the aramid fiber and a pore-forming agent are completely dissolved to obtain a casting solution of the aramid fiber; after stirring is stopped, defoaming for 60min in an oil bath at 80 ℃; laying a 16-micron PE (polyethylene) base film on a clean glass plate flatly, wherein the porosity of the PE base film is 50%, pouring a proper amount of defoamed film casting solution on the PE base film, scraping the film by using a scraper, staying in a vapor bath for 2min, immersing in a room-temperature water bath at a constant speed to form a film, immersing in water for 60min, and taking out; drying in an oven at 60 deg.C for 60min, and taking out.
The composite diaphragm of the lithium ion battery in the embodiment is prepared from 2% of aramid fiber, 10% of pore-forming agent, 0.5% of inorganic ceramic particles and 87.5% of organic solvent.
Comparative example 1
Weighing 2.3g of DMF, adding 0.05g of polyethylene glycol, stirring until the mixture is completely dissolved, adding 6g of meta-aramid polymer, 20% of aramid active ingredient and 0.5-2.0 ten thousand of aramid molecular weight into the dissolved solution, stirring uniformly, then sequentially adding 1.5g of dichloromethane and 0.15g of vinyl pyrrolidone and vinyl acetate (PVP-VA) copolymer adhesive while stirring, and dispersing uniformly to obtain aramid pulp; selecting a polyethylene base film with the thickness of 20 microns, wherein the porosity is 30%, and coating aramid fiber slurry on two sides of the base film in a slit coating mode at the coating speed of 30 m/min. Pre-solidifying for 3s in an environment with 95% humidity, washing for 15s, and drying by using a three-stage oven, wherein the temperature of each stage of oven is 60 ℃, 60 ℃ and 55 ℃, and drying to obtain the aramid polymer coated lithium ion battery diaphragm to obtain a first control sample.
Comparative example No. two
Weighing 2g of DMAc, adding 0.1g of sodium polyacrylate, stirring until the DMAc is completely dissolved, adding 4.4g of meta-aramid polymer into the dissolved solution, wherein the aramid content is 10%, the aramid molecular weight is 8-10 ten thousand, stirring uniformly, then sequentially adding 3.35g of isopropanol and 0.05g of vinyl pyrrolidone and vinyl acetate (PVP-VA) copolymer adhesive while stirring, and uniformly dispersing to obtain aramid pulp; selecting a 16-micron-thickness polyethylene base film, wherein the porosity is 50%, and coating aramid fiber slurry on one side of the base film in a gravure coating mode at a coating speed of 15 m/min; pre-solidifying for 10s in an environment with the humidity of 90%, washing for 10s, and drying by using a three-stage oven, wherein the temperature of each stage of oven is 55 ℃, 60 ℃ and 70 ℃, and drying to obtain the aramid polymer coated lithium ion battery diaphragm to obtain a second control sample.
Nine lithium ion battery composite separators obtained in examples one to nine of the present invention, a control sample one and a control sample two were subjected to thickness, strength, air permeability and heat shrinkability tests, respectively, and polyethylene base films having the same thickness and porosity were subjected to thickness, strength, air permeability and heat shrinkability tests according to the same method, wherein the base film used in examples one to five was a 20 μm polyethylene base film, the base film selected in the control sample one was also a 20 μm polyethylene base film, and a 20 μm polyethylene base film was used as a control sample three, the base film used in examples six to nine was a 16 μm polyethylene base film, the control sample two was also a 16 μm polyethylene base film, and a 16 μm polyethylene base film was used as a control sample four, and the test results are listed in tables 1 and 2, respectively, and in tables 1 and 2, the thickness was tested according to the method specified in GB/667T 2-2001,
tensile strength was measured according to the method specified in GB/13022-91, puncture strength was measured according to the method specified in GB/T21302-2007, air permeability was measured according to the method specified in GB/1038, and heat shrinkage was measured according to the method specified in GB/T12027-2004.
Table 1 comparison of the performance test results of the aramid coating of the present invention on a 20 μm polyethylene based film
As can be seen from table 1, the high temperature resistant aramid lithium obtained in the first to fifth embodiments of the present inventionThe thickness of the composite diaphragm of the ion battery is 21.9-28.9 μm, which is basically increased by 0.8-7.9 μm compared with the corresponding polyethylene base film (namely, a comparison sample III), and is basically consistent with the thickness of the lithium ion battery diaphragm (namely, a comparison sample I) with the aramid fiber coating prepared by the existing method; the tensile strength MD of the high-temperature-resistant aramid fiber lithium ion battery composite membrane prepared in the first to fifth embodiments of the invention is basically consistent with that of a lithium ion battery membrane with an aramid fiber coating prepared by the existing method (namely, a comparison sample I); however, the puncture strength of the high-temperature-resistant aramid fiber lithium ion battery composite membrane obtained in the first to fifth embodiments of the invention is 635.9-682.2g, which is obviously higher than that of a polyethylene-based membrane (i.e., a third control sample) and also obviously higher than that of a lithium ion battery membrane with an aramid fiber coating prepared by the existing method (i.e., a first control sample); in addition, the high-temperature resistant aramid fiber lithium ion battery composite membrane obtained in the first embodiment to the fifth embodiment of the invention has the air permeability value of 360.5-453.2s/in2∙ 100cc ∙ 1.22 Kpa; after the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm obtained in the first to fifth embodiments of the invention is placed in a 90 ℃ oven for 1 hour, the transverse and longitudinal thermal shrinkage values are 0, and after the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm is placed in a 105 ℃ oven for 1 hour, the transverse and longitudinal thermal shrinkage values are<0.5%, after being placed in an oven at 120 ℃ for 1 hour, the transverse and longitudinal heat shrinkage values thereof<5 percent; this is significantly better than the corresponding polyethylene-based film (i.e., control three) and the aramid-coated lithium ion battery separator prepared by the prior art method (i.e., control one).
Table 2 comparison of the performance test results of the aramid coating of the present invention on a 16 μm polyethylene based film
As can be seen from table 2, the thickness of the high-temperature-resistant aramid lithium ion battery composite separator obtained in the sixth to ninth embodiments of the present invention is between 17.21 and 17.94 μm, which is substantially increased by 0.78 to 1.51 μm compared with a corresponding polyethylene-based film (i.e., a control sample four), and is substantially the same as the thickness of a lithium ion battery separator with an aramid coating (i.e., a control sample two) prepared by the existing method; sixth to ninth embodiments of the present inventionThe tensile strength MD of the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm is basically consistent with that of a lithium ion battery diaphragm (namely a control sample II) with an aramid fiber coating prepared by the conventional method; however, the puncture strength of the high-temperature-resistant aramid fiber lithium ion battery composite membrane obtained in the sixth to ninth embodiments of the invention is 634.1-655.7g, which is obviously higher than that of a polyethylene-based membrane (i.e., a control sample four) and also obviously higher than that of a lithium ion battery membrane with an aramid fiber coating prepared by the existing method (i.e., a control sample two); in addition, the high-temperature resistant aramid fiber lithium ion battery composite membrane obtained in the sixth embodiment to the ninth embodiment has the air permeability value of 314.4-379.5s/in2∙ 100cc ∙ 1.22Kpa is adjustable, which is obviously superior to the lithium ion battery diaphragm with aramid fiber coating prepared by the existing method (namely the control sample II); after the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm obtained in the sixth to ninth embodiments is placed in a 90 ℃ oven for 1 hour, the transverse and longitudinal thermal shrinkage values are 0, and after the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm is placed in a 105 ℃ oven for 1 hour, the transverse and longitudinal thermal shrinkage values are<0.5%, after being placed in an oven at 120 ℃ for 1 hour, the transverse and longitudinal heat shrinkage values thereof<4 percent; this is significantly better than its corresponding polyethylene-based film (i.e., control four) and the aramid-coated lithium ion battery separator prepared by the prior art method (i.e., control two).
Respectively placing the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm prepared in the first to ninth embodiments of the invention and the corresponding polyethylene-based membrane in electrolyte, and measuring a contact angle on a DSA25 optical contact angle measuring instrument produced by Klussian scientific instruments (Shanghai); as a result of experiments, the contact angle of the PE diaphragm serving as the base film and the electrolyte is 30-36.5 degrees, while the contact angle of the composite diaphragm of the invention and the electrolyte is 10-25 degrees. And the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm prepared in the first to ninth embodiments of the invention and the polyethylene base film corresponding thereto are respectively placed in an electrolyte, and then the liquid absorption rate before and after soaking is measured, and finally, the diaphragm is loaded into a lithium ion battery for capacity maintenance and cycle performance test.
TABLE 3 liquid absorption rate of the composite separator of the present invention and its base film in electrolyte
Fig. 1 and 2 respectively show the measurement results of the contact angle between the high-temperature resistant aramid lithium ion battery composite diaphragm prepared in the first embodiment of the present invention and the corresponding polyethylene base film and the electrolyte, the test temperature of the contact angle in fig. 1 and 2 is 20 ℃, the liquid is water, and as can be seen from fig. 1 and 2, the contact angle between the 20 μm PE diaphragm serving as the base film and the electrolyte is 36.4 °, and the contact angle between the composite diaphragm of the present invention and the electrolyte is 20.9 °. Table 3 lists the liquid absorption rates of the high-temperature resistant aramid fiber lithium ion battery composite membrane prepared in the first embodiment of the present invention and the polyethylene base membrane and the electrolyte solution corresponding thereto before and after soaking, and as can be seen from table 3, the liquid absorption rate of the PE base membrane is only 76.35%, and the liquid absorption rate of the reference sample is 94.95%, while the liquid absorption rate of the high-temperature resistant aramid fiber lithium ion battery composite membrane prepared by the method of the present invention reaches 122.27%, so that the aramid fiber composite membrane prepared by the present invention has better affinity with the electrolyte solution, high liquid absorption rate, and better lyophilic liquid retention property in the use of the lithium ion battery, thereby improving the discharge capacity and cycle performance of the battery. Fig. 3 shows the capacity retention and cycle performance tests of the high-temperature resistant aramid fiber lithium ion battery composite diaphragm prepared in the first embodiment of the invention and the corresponding polyethylene base film after the lithium ion battery is loaded in the diaphragm, as can be seen from fig. 3, after 40 times of battery charge and discharge cycles, the specific discharge capacity of the polyethylene base film is reduced from 76.54mAh/g to 62.85mAh/g, and the capacity retention rate is 82%, while the specific discharge capacity of the high-temperature resistant aramid fiber lithium ion battery composite diaphragm is only reduced from 78.21mAh/g to 73.74mAh/g, and the capacity retention rate is 94.28%, so that the high-temperature resistant aramid fiber lithium ion battery composite diaphragm has better capacity retention rate and cycle performance, and the service life of the battery is effectively prolonged.
Therefore, the wettability of the composite diaphragm on the electrolyte is greatly improved, the problem of poor wettability of the polyolefin on the electrolyte can be effectively solved by coating the aramid fiber on the surface of the polyolefin base film, the liquid absorption rate of the electrolyte is greatly improved, and the capacity maintenance and the cycle life of the lithium ion battery are improved.
The high-temperature-resistant aramid fiber lithium ion battery composite membranes prepared in the first to ninth embodiments of the invention are respectively scanned on an EVO/MA10 scanning electron microscope produced by Zeiss of Germany, and impedance tests are carried out on the high-temperature-resistant aramid fiber lithium ion battery composite membranes prepared in the first to ninth embodiments of the invention at CHI660E electrochemical workstation produced by Chenghua instruments, the test method is to prepare the composite membranes into half cells, namely, stainless steel sheets, the composite membranes and stainless steel sheets are sequentially put into button battery cases, a proper amount of electrolyte is injected, an alternating current impedance spectrogram is obtained through the electrochemical workstation, the intersection point of a curve on the impedance spectrogram and a real axis is membrane impedance, and the ion conductivity is obtained by calculation of a formula.
Fig. 4 shows an electron microscope scanning image of the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm prepared in the first embodiment of the invention, and as can be seen from fig. 4, the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm has a stable microporous structure, uniform and consistent pore size and good permeability. The impedance test experiment result shows that the diaphragm impedance of the lithium particle battery composite diaphragm is less than 5 ohms, and the ionic conductivity is 0.2-1.0mS ∙ cm-1To (c) to (d); therefore, the composite separator of the present invention has a small impedance and a large ionic conductivity, which indicates that ions in an electrolyte more easily pass through the composite separator of the present invention, thereby allowing the composite separator of the present invention to have more excellent battery performance.
Therefore, compared with the prior art, the invention has the beneficial effects that: the aramid fiber is selected as an organic material, is added in the form of aramid fiber polymer, does not contain processing aids such as adhesives and the like, has small interface stress between the obtained aramid fiber coating and the base film, is in good contact and not easy to fall off, and is not easy to fall off even if being used for a long time and under high strength; the air permeability value of the obtained aramid fiber coating is 300-1000s/in2∙ 100cc ∙ 1.22Kpa, wide application, low thermal shrinkage, good heat resistance, effectively improving the problem of poor wettability of the base film to electrolyte and improving the base filmThe puncture strength of the membrane improves the use safety performance of the lithium ion battery diaphragm. Meanwhile, the preparation method of the composite diaphragm has the advantages of short process flow, mild conditions, high efficiency, easiness in batch and continuous production and the like, and is suitable for expanded production.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (4)
1. The preparation method of the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm comprises a base film and a coating coated on one side or two sides of the base film, wherein the coating is an aramid fiber coating and is characterized in that:
the aramid fiber coating is prepared from the following raw materials in percentage by weight: 1-6% of aramid fiber, 5-12% of pore-forming agent, 0.5-5% of inorganic ceramic particles and 77-93.5% of organic solvent;
the aramid fiber is taken from aramid fiber polymer, the content of the aramid fiber in the aramid fiber polymer is 10-30% by weight, the aramid fiber is one or two of meta-aramid fiber or para-aramid fiber, and the molecular weight of the aramid fiber is 5000-200000 Da;
the pore-forming agent is any one or two of an inorganic pore-forming agent and an organic pore-forming agent, the inorganic pore-forming agent is any one or more of lithium chloride, sodium chloride, magnesium chloride, calcium carbonate or calcium chloride, and the organic pore-forming agent is any one or more of methanol, ethanol, propanol, glycerol, polyethylene glycol, acetone, acetic acid, tetrahydrofuran, polyvinylpyrrolidone, ethyl acetate or petroleum ether;
the inorganic ceramic particles are any one or more of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide or barium oxide, and the average particle size of the inorganic ceramic particles is 10-100 nm;
the organic solvent is any one or more of N, N-dimethylacetamide, N-methylpyrrolidone, N-dimethylformamide or dimethyl phthalate;
the preparation method of the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm comprises the following steps:
(1) preparing an aramid fiber membrane casting solution: mixing aramid fiber, pore-forming agent, inorganic ceramic particles and organic solvent, stirring at 50-80 ℃ to completely dissolve the aramid fiber and the pore-forming agent to obtain casting solution;
(2) defoaming: defoaming the casting solution obtained in the step (1) for 5-60min at 50-80 ℃ until no bubbles exist;
(3) film formation by non-solvent phase inversion method: taking a basement membrane, coating a layer of defoamed membrane casting solution on the basement membrane, standing for 5-60s, placing the basement membrane in a coagulating bath for coagulation, wherein the coagulating bath is a solvent and non-solvent coagulating bath, taking the basement membrane with aramid fibers after coagulating for 1-10min, soaking the basement membrane in water for 10-60min, and taking out the basement membrane;
in the solvent and non-solvent coagulating bath, the non-solvent is water, the solvent is any one or more of N, N-dimethylacetamide, N-methylpyrrolidone, N-dimethylformamide, dimethyl phthalate or ethanol, and the volume percentage concentration of the solvent in the solvent and non-solvent coagulating bath is 10-90%;
(4) and (3) drying: and drying at 40-80 ℃ for 10-60min to obtain the high-temperature-resistant aramid fiber lithium ion battery composite diaphragm.
2. The preparation method of the high-temperature-resistant aramid fiber lithium ion battery composite membrane according to claim 1, characterized by comprising the following steps:
the porous base membrane is a polyolefin diaphragm with the thickness of 5-40 mu m and the porosity of 30-80%, and the polyolefin diaphragm is any one of a polyethylene lithium ion battery diaphragm, a polypropylene lithium ion battery diaphragm and a polypropylene/polyethylene/polypropylene three-layer or multi-layer co-extrusion composite lithium ion battery diaphragm.
3. The preparation method of the high-temperature-resistant aramid fiber lithium ion battery composite membrane according to claim 1, characterized by comprising the following steps:
the thickness of the aramid fiber coating is 0.5-10 mu m.
4. The preparation method of the high-temperature-resistant aramid fiber lithium ion battery composite membrane according to any one of claims 1 to 3, characterized by comprising the following steps:
in the step (2), the viscosity of the defoamed casting solution is 20-1000 cP.
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| PCT/CN2018/074761 WO2018218984A1 (en) | 2017-06-01 | 2018-01-31 | High temperature-resistant aramid lithium-ion battery composite separator and manufacturing method therefor |
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| WO2018218984A1 (en) | 2018-12-06 |
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