CN113193299A - High-temperature-resistant polypropylene diaphragm for lithium battery and preparation method - Google Patents
High-temperature-resistant polypropylene diaphragm for lithium battery and preparation method Download PDFInfo
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Abstract
The invention belongs to the technical field of lithium battery diaphragms, and particularly relates to a high-temperature-resistant polypropylene diaphragm for a lithium battery and a preparation method thereof. The method of the invention comprises the following steps: adding diamine and dianhydride into a solvent for dispersion, reacting for 3-5 h at room temperature, adding lithium salt for dispersion to obtain a viscous liquid, spraying the viscous liquid by using a porous spinneret plate with the aperture of 0.1mm, and washing by using deionized water to obtain microporous crude fibers; cutting the blank into pieces with the length of 3-10 mm; preparing a polypropylene base film by tape casting, then rolling the micropore crude fiber on the surface of the polypropylene base film, and then synchronously compounding a layer of polypropylene base film on the micropore crude fiber surface; rolling at 210-220 ℃; and (3) performing biaxial stretching on the rolled film at the temperature of 145-160 ℃. The diaphragm provided by the invention has the advantages of high temperature resistance, safety and stability, high porosity, excellent aperture distribution uniformity, lower cost and higher efficiency, and can realize integrated continuous industrial production.
Description
Technical Field
The invention belongs to the technical field of lithium battery diaphragms, and particularly relates to a high-temperature-resistant polypropylene diaphragm for a lithium battery and a preparation method thereof.
Background
The rechargeable lithium ion secondary battery has the characteristics of long cycle life, high specific energy and no memory effect, has the advantages of quick charge and discharge, safety, reliability and the like, and becomes the first choice of electric automobiles in recent years. The lithium battery mainly comprises a negative electrode material, a positive electrode material, a diaphragm and electrolyte, wherein the diaphragm is used as a porous material and plays a role of separating the positive electrode and the negative electrode of the battery to prevent the two electrodes from contacting short circuits, and meanwhile, the diaphragm is required to have stable micropores so that lithium ions can freely pass through the micropores.
At present, the mainstream products of the lithium ion battery separator are polypropylene and polyethylene porous membranes. The high-power lithium ion battery has high mechanical property, good chemical corrosion resistance and low production cost, but in the application of a power battery, due to poor wettability and weak liquid absorption capacity, high-rate charge and discharge are difficult to realize, the thermal deformation is increased under the high-temperature circulation condition, the high-temperature melting deformation and the rupture are caused, the short circuit is formed, and serious potential safety hazards exist.
Patent application with application number CN201911306997 proposes a high temperature thermal shrinkage resistant lithium battery diaphragm and a preparation method thereof, wherein the high temperature thermal shrinkage resistant lithium battery diaphragm comprises: a base material with distributed micropores and ceramic slurry coated on the base material; wherein the surface friction coefficient of the base material is 0.01 to 2.5. The base material with a large surface friction coefficient is selected, so that the combination of the base material and the ceramic slurry is facilitated, the adhesion force of the ceramic slurry serving as a coating and the base material is improved, and the shrinkage performance of the lithium battery diaphragm at high temperature is inhibited.
The patent application with the application number of CN202010129221 provides a heat-shrinkage-resistant polyethylene lithium battery diaphragm and a preparation method thereof, wherein metal organic framework powder loading a lithium ion conductor is obtained through in-situ reaction, and is compounded with heat-resistant non-woven fabric containing high-specific-surface-area inorganic porous nano fibers to form a high-temperature-resistant framework with high ion passage rate, and the heat resistance and the mechanical property of the whole diaphragm are improved by the non-woven fabric framework containing inorganic fibers and a metal organic framework material, so that the heat shrinkage rate of the diaphragm is reduced; and further, the diaphragm has good liquid absorption and retention capacity by virtue of a porous structure rich in a metal organic framework, and can form a three-dimensional network structure with a lithium ion conductor, so that the ion passing rate is improved, and the charge and discharge performance of the battery is improved.
The patent application with the application number of CN2014100619967 provides a composite nanofiber lithium battery diaphragm and a preparation method thereof, the composite nanofiber lithium battery diaphragm is formed by compounding at least one layer of meta-aramid nanofiber membrane containing nanoparticles and at least one layer of low-melting-point polymer nanofiber membrane containing nanoparticles, and nanofibers in the fiber membranes containing the nanoparticles are mutually staggered and bonded and interconnected at the staggered points. The closed pore temperature is 130-170 ℃, the fiber membrane does not shrink after closed pore, the thermal shrinkage rate is less than 2 percent when the fiber membrane is heated for 1 hour at the high temperature of 250 ℃, the tensile strength is 100-1000 MPa, and the fiber membrane has the performances of thermal closed effect, good thermal dimensional stability and high strength.
However, in these synthesis methods, all inorganic nano materials are used, the production process is relatively complex, and the raw material cost is high, which is not economical enough for mass production, so that it has very important practical significance for optimizing the organic heat-resistant modification process of the lithium battery diaphragm.
The patent application with the application number of CN2019105927416 discloses a porous polyimide film and a preparation method and application thereof, which comprises the steps of carrying out low-temperature polycondensation reaction on binary anhydride and diamine in a polar solvent to generate a precursor polyamide acid PAA solution, adding an additive into the precursor polyamide acid PAA solution, stirring to form a casting film solution, defoaming and scraping the casting film solution, coating the casting film solution on a glass plate, immersing the glass plate into a coagulating bath, taking out and naturally airing the glass plate, and carrying out thermal imidization or chemical imidization treatment to obtain the porous polyimide film. The invention does not need high temperature and high pressure, has simple requirements on film making equipment and is beneficial to realizing large-scale industrial application. In addition, the film has adjustable thickness, porosity of more than 40 percent, high liquid absorption rate, good wettability with lithium ion electrolyte and excellent high temperature resistance, and is expected to become one of the next generation lithium ion battery diaphragm materials.
The patent application with the application number of CN2019103836412 discloses a diaphragm for a lithium ion battery and a preparation method, the thickness of the diaphragm is 5-10 mu m, the thermal shrinkage rate at 150 ℃ is lower than 1.2%, the diaphragm comprises a first ceramic layer, a gel polymer layer and a third ceramic layer, the gel polymer layer is positioned on two surfaces of the first ceramic layer, the third ceramic layer is positioned on the outer surface of the gel polymer layer, the first ceramic layer comprises 60-80% of ceramic oxide and 20-40% of adhesive by weight percent, the particle size of the ceramic oxide is 10-30nm, the gel polymer layer is an aqueous solution of polymer particles, the particle size of the polymer particles is 30-50nm, the third ceramic layer comprises 80-90% of ceramic oxide and 10-20% of adhesive by weight percent, the particle size of the ceramic oxide is 30-80nm, the diaphragm is small in thickness, high temperature resistant and low in thermal shrinkage value, is more stable.
Patent application No. CN2016108193143 discloses a high-safety composite lithium battery diaphragm and a preparation method thereof. The composite diaphragm mainly comprises core-shell functional microspheres and a fiber framework, wherein the core-shell functional microspheres can be converted into a molten state at high temperature to endow the diaphragm with a closed-cell characteristic, so that deep thermal runaway of a battery is prevented; the core-shell functional microspheres can be converted into an electronic conducting state under high potential, and a micro short circuit is formed in the battery to prevent the battery from being deeply overcharged; the fiber skeleton imparts sufficient mechanical properties to the composite separator. Firstly, coating an oxidizable and doped electroactive material on the surface of a thermosensitive organic microsphere to form a core-shell functional microsphere; and then compounding the functional microspheres with a fiber framework to form the high-safety composite lithium battery diaphragm. The diaphragm has sensitive thermal runaway response function and voltage runaway response function, the safety of the lithium ion battery is greatly improved, and the obtained diaphragm has the advantages of excellent safety performance, low cost, easiness in large-scale large-size production and the like.
The patent application with the application number of CN201610005811X discloses a preparation method of a special diaphragm for a lithium ion battery, wherein the special diaphragm for the lithium ion battery comprises a substrate layer, the substrate layer is a polyethylene porous membrane or a polypropylene porous membrane, aromatic polyamide or aromatic polyimide is uniformly attached to the surface of the substrate layer, the thickness of the special diaphragm for the lithium ion battery is 0.02-0.045mm, and the porosity of the special diaphragm for the lithium ion battery is 50-60%. Compared with the prior art, the invention has the advantages of excellent thermal aging resistance, high porosity and air permeability, and the prepared diaphragm has low closed pore temperature, small thickness and high diaphragm breaking temperature.
Disclosure of Invention
Aiming at the problem that the existing lithium battery diaphragm is easy to melt, deform and crack at high temperature, the invention provides a preparation method of a high-temperature-resistant polypropylene diaphragm for a lithium battery.
In order to solve the first technical problem of the present invention, the preparation method of the high temperature resistant polypropylene separator for the lithium battery of the present invention comprises the following steps:
(1) adding diamine and dianhydride into a solvent for dispersion, reacting for 3-5 h at room temperature, adding lithium salt for dispersion to obtain a viscous liquid, spraying the viscous liquid by using a porous spinneret plate with the aperture of 0.1mm, and washing by using deionized water to obtain microporous crude fibers;
(2) drying the microporous coarse fibers obtained in the step (1), and cutting into microporous coarse fibers with the length of 3-10 mm;
(3) preparing a polypropylene base film by tape casting, rolling the microporous coarse fibers prepared in the step (2) on the surface of the polypropylene base film, and synchronously compounding a layer of polypropylene base film on the microporous coarse fiber surface to enable the microporous coarse fiber layer to be sandwiched between two polypropylene base films to form a sandwich structure; then rolling at 210-220 ℃ to ensure that the microporous crude fiber is dehydrated and gradually changed into polyimide fiber which is attached to the polypropylene base film;
(4) and (3) performing biaxial stretching on the rolled film in the step (3) at the temperature of 145-160 ℃ to obtain the high-temperature-resistant polypropylene diaphragm for the lithium battery.
Further preferably, the dianhydride in step (1) is one or more of pyromellitic dianhydride, biphenyl dianhydride, triphenyl diether dianhydride, diphenyl ether dianhydride, thioether dianhydride, benzophenone dianhydride and bisphenol A type diether dianhydride.
Further preferably, the dianhydride in step (1) is one or more of pyromellitic dianhydride, biphenyl dianhydride, triphenyl diether dianhydride and diphenyl ether dianhydride.
Further preferably, the diamine in step (1) is one or more of 4, 4' -diaminodiphenyl ether diamine, p-phenylenediamine, diphenyl diether diamine, and bisphenol a diether diamine.
Further preferably, the diamine in step (1) is one or more of 4, 4' -diaminodiphenyl ether diamine, p-phenylenediamine and diphenyl diether diamine.
Further preferably, the solvent in step (1) is one or more of dimethylacetamide, dimethylformamide, N-dimethylpyrrolidone, dimethyl sulfoxide and tetrahydrofuran.
Further preferably, the solvent in step (1) is one or more of dimethylacetamide, dimethylformamide, N-dimethylpyrrolidone and dimethyl sulfoxide.
More preferably, the lithium salt in step (1) is LiClO4、LiPF6、LiAsF6、LiSO3F、LiCF3SO3One or more of (a).
Further preferably, the diamine, the dianhydride, the solvent and the lithium salt in the step (1) are mixed according to the mass ratio: 3:2:10:0.2-0.3.
Further preferably, the microporous coarse fiber layer in step (3) is sandwiched between two polypropylene-based films to form a sandwich structure, wherein the mass ratio of the polypropylene-based film, the microporous coarse fiber layer and the polypropylene-based film is controlled to be 2: 1: 2.
further preferably, the biaxial stretching in the step (4) is 5 to 8 times of longitudinal stretching ratio and 3 to 5 times of transverse stretching ratio.
The second technical problem to be solved by the invention is to provide a high-temperature-resistant polypropylene diaphragm for a lithium battery.
In order to solve the second technical problem of the present invention, the high temperature resistant polypropylene diaphragm for a lithium battery is prepared by the above preparation method of the high temperature resistant polypropylene diaphragm for a lithium battery.
Has the advantages that: the lithium salt is dispersed in the polycondensate synthesized by the binary anhydride and the diamine to form fibers, the lithium salt is eluted to form crude fibers, the crude fibers are sandwiched in a polypropylene film to form a sandwich, in the heat treatment and stretching processes, the microporous crude fibers are gradually stretched and dehydrated to form rings to be converted into polyimide fibers, and the polyimide fibers and the polypropylene microporous film form a composite film. The lithium battery diaphragm prepared by the method has high porosity, excellent aperture distribution uniformity, lower cost and higher efficiency, and can realize integrated continuous industrial production.
Drawings
FIG. 1: example 1 variation before and after the heat-shrink test of the membrane, wherein, above: before treatment, the following steps are carried out: after treatment;
FIG. 2: comparative example 1 change before and after the heat-shrinking test of the membrane, wherein, above: before treatment, the following steps are carried out: after treatment;
FIG. 3: the invention relates to a process flow chart for preparing a high-temperature-resistant polypropylene diaphragm.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
Example 1
A preparation method of a high-temperature-resistant polypropylene diaphragm for a lithium battery comprises the following steps:
(1) dispersing 4, 4' -diaminodiphenyl ether diamine and biphenyl dianhydride in dimethyl formamide solvent, reacting at room temperature for 4 hr, and adding LiClO4Dispersing lithium salt to obtain viscous liquid, spraying the viscous liquid by using a porous spinneret plate with the aperture of 0.1mm, and washing by using deionized water to obtain microporous crude fiber; diamine, dianhydride, solvent and lithium salt according to the mass ratio: 3:2:10: 0.2;
(2) drying the microporous coarse fibers obtained in the step (1), and cutting into microporous coarse fibers with the length of 10 mm;
(3) preparing a polypropylene base film by tape casting, rolling the microporous coarse fibers prepared in the step (2) on the surface of the polypropylene base film, and synchronously compounding a layer of polypropylene base film on the microporous coarse fiber surface to enable the microporous coarse fiber layer to be sandwiched between two polypropylene base films to form a sandwich structure; then rolling at 210 ℃ to ensure that the microporous crude fiber is dehydrated and gradually changed into polyimide fiber which is attached to the polypropylene base film;
(4) and (3) biaxially stretching the rolled film in the step (3) at 145 ℃, wherein the longitudinal stretching ratio is 5 times, and the transverse stretching ratio is 3 times, so as to obtain the high-temperature-resistant polypropylene diaphragm for the lithium battery.
Example 2
A preparation method of a high-temperature-resistant polypropylene diaphragm for a lithium battery comprises the following steps:
(1) dispersing 4, 4' -diaminodiphenyl ether diamine and triphendiether dianhydride in dimethyl formamide solvent, reacting at room temperature for 3 hr, and adding LiClO4Dispersing lithium salt to obtain viscous liquid, spraying the viscous liquid by using a porous spinneret plate with the aperture of 0.1mm, and washing by using deionized water to obtain microporous crude fiber; diamine, dianhydride, solvent and lithium salt according to the mass ratio: 3:2:10: 0.2;
(2) drying the microporous coarse fibers obtained in the step (1), and cutting into microporous coarse fibers with the length of 5 mm;
(3) preparing a polypropylene base film by tape casting, rolling the microporous coarse fibers prepared in the step (2) on the surface of the polypropylene base film, and synchronously compounding a layer of polypropylene base film on the microporous coarse fiber surface to enable the microporous coarse fiber layer to be sandwiched between two polypropylene base films to form a sandwich structure; then rolling at 210 ℃ to ensure that the microporous crude fiber is dehydrated and gradually changed into polyimide fiber which is attached to the polypropylene base film; wherein the mass ratio of the polypropylene basal membrane, the micropore crude fiber layer and the polypropylene basal membrane is controlled to be 2: 1: 2;
(4) and (3) biaxially stretching the rolled film in the step (3) at 150 ℃, wherein the longitudinal stretching ratio is 6 times, and the transverse stretching ratio is 5 times, so as to obtain the high-temperature-resistant polypropylene diaphragm for the lithium battery.
Example 3
A preparation method of a high-temperature-resistant polypropylene diaphragm for a lithium battery comprises the following steps:
(1) adding diphenyl diether diamine and biphenyl dianhydride into a dimethylformamide solvent for dispersion, reacting for 4 hours at room temperature, and adding LiPF6Dispersing lithium salt to obtain viscous liquid, spraying the viscous liquid by using a porous spinneret plate with the aperture of 0.1mm, and washing by using deionized water to obtain microporous crude fiber; diamine, dianhydride, solvent and lithium salt according to the mass ratio: 3:2:10: 0.3;
(2) drying the microporous coarse fibers obtained in the step (1), and cutting into microporous coarse fibers with the length of 6 mm;
(3) preparing a polypropylene base film by tape casting, rolling the microporous coarse fibers prepared in the step (2) on the surface of the polypropylene base film, and synchronously compounding a layer of polypropylene base film on the microporous coarse fiber surface to enable the microporous coarse fiber layer to be sandwiched between two polypropylene base films to form a sandwich structure; then rolling at 210 ℃ to ensure that the microporous crude fiber is dehydrated and gradually changed into polyimide fiber which is attached to the polypropylene base film; wherein the mass ratio of the polypropylene basal membrane, the micropore crude fiber layer and the polypropylene basal membrane is controlled to be 2: 1: 2;
(4) and (3) biaxially stretching the rolled film in the step (3) at 160 ℃, wherein the longitudinal stretching ratio is 5 times, and the transverse stretching ratio is 5 times, so as to obtain the high-temperature-resistant polypropylene diaphragm for the lithium battery.
Example 4
A preparation method of a high-temperature-resistant polypropylene diaphragm for a lithium battery comprises the following steps:
(1) adding p-phenylenediamine and biphenyl dianhydride into a dimethylformamide solvent for dispersion, reacting for 5 hours at room temperature, and adding LiClO4Dispersing lithium salt to obtain viscous liquid, spraying the viscous liquid by using a porous spinneret plate with the aperture of 0.1mm, and washing by using deionized water to obtain microporous crude fiber; diamine, dianhydride, solvent and lithium salt according to the mass ratio: 3:2:10: 0.2;
(2) drying the microporous coarse fibers obtained in the step (1), and cutting into microporous coarse fibers with the length of 7 mm;
(3) preparing a polypropylene base film by tape casting, rolling the microporous coarse fibers prepared in the step (2) on the surface of the polypropylene base film, and synchronously compounding a layer of polypropylene base film on the microporous coarse fiber surface to enable the microporous coarse fiber layer to be sandwiched between two polypropylene base films to form a sandwich structure; then rolling at 210 ℃ to ensure that the microporous crude fiber is dehydrated and gradually changed into polyimide fiber which is attached to the polypropylene base film; wherein the mass ratio of the polypropylene basal membrane, the micropore crude fiber layer and the polypropylene basal membrane is controlled to be 2: 1: 2;
(4) and (3) biaxially stretching the rolled film in the step (3) to a longitudinal stretching ratio of 8 times and a transverse stretching ratio of 3 times at the temperature of 150 ℃ to obtain the high-temperature-resistant polypropylene diaphragm for the lithium battery.
Comparative example 1
(1) Preparing a polypropylene-based film by tape casting, then rolling the polypropylene-based film at 210 ℃ between two polypropylene-based films, and stretching the polypropylene-based film at 145 ℃ in two directions, wherein the longitudinal stretching ratio is 5 times and the transverse stretching ratio is 3 times, thus obtaining the diaphragm for the lithium battery.
Comparative example 1 does not use polyimide fibers, the heat resistance of the separator is significantly reduced, and the separator is very likely to shrink at high temperatures. But also the porosity is reduced.
Comparative example 2
(1) Adding 4, 4' -diaminodiphenyl ether diamine and biphenyl dianhydride into a dimethylformamide solvent for dispersion, reacting for 4 hours at room temperature, and then spraying the viscous liquid by using a porous spinneret plate with the aperture of 0.1mm to obtain microporous crude fibers; diamine, dianhydride and solvent according to the mass ratio: 3:2: 10;
(2) drying the microporous coarse fibers obtained in the step (1), and cutting into microporous coarse fibers with the length of 10 mm;
(3) preparing a polypropylene base film by tape casting, rolling the microporous coarse fibers prepared in the step (2) on the surface of the polypropylene base film, and synchronously compounding a layer of polypropylene base film on the microporous coarse fiber surface to enable the microporous coarse fiber layer to be sandwiched between two polypropylene base films to form a sandwich structure; then rolling at 210 ℃ to ensure that the microporous crude fiber is dehydrated and gradually changed into polyimide fiber which is attached to the polypropylene base film;
(4) and (3) biaxially stretching the rolled film in the step (3) at 145 ℃, wherein the longitudinal stretching ratio is 5 times, and the transverse stretching ratio is 3 times, so as to obtain the high-temperature-resistant polypropylene diaphragm for the lithium battery.
In comparative example 2, no lithium salt was used, and the resulting fiber had no micropores, which affected the porosity of the separator and thus ion transport.
Comparative example 3
(1) Dispersing 4, 4' -diaminodiphenyl ether diamine and biphenyl dianhydride in dimethyl formamide solvent, reacting at room temperature for 4 hr, and adding LiClO4Dispersing lithium salt to obtain viscous liquid, spraying the viscous liquid by using a porous spinneret plate with the aperture of 0.1mm, and washing by using deionized water to obtain microporous crude fiber; diamine, dianhydride, solvent and lithium salt according to the mass ratio: 3:2:10: 0.2;
(2) drying the microporous coarse fibers obtained in the step (1), and cutting into microporous coarse fibers with the length of 10 mm;
(3) preparing a polypropylene base film by tape casting, rolling the microporous coarse fibers prepared in the step (2) on the surface of the polypropylene base film, and synchronously compounding a layer of polypropylene base film on the microporous coarse fiber surface to enable the microporous coarse fiber layer to be sandwiched between two polypropylene base films to form a sandwich structure; then rolling at 250 ℃ to ensure that the microporous crude fiber is dehydrated and gradually changed into polyimide fiber which is attached to the polypropylene base film;
(4) and (3) biaxially stretching the rolled film in the step (3) at 145 ℃, wherein the longitudinal stretching ratio is 5 times, and the transverse stretching ratio is 3 times, so as to obtain the high-temperature-resistant polypropylene diaphragm for the lithium battery.
Comparative example 3 when the composite polypropylene film and the fiber were rolled, the polypropylene film was easily and rapidly melted by using a high rolling temperature, so that the micropores of the composite fiber were blocked, and the porosity of the micropores was affected, thereby affecting the ion transport property.
And (3) performance detection:
with reference to ISO 14616-1997 determination of shrinkage stress of heat-shrinkable films of polyethylene, ethylene copolymers and mixtures thereof, a Labthink Jinan Languang FST-02 film heat-shrinkable performance tester is adopted to cut the test sample into strip test samples of 15 mm x 130 mm, one end of each test sample is fixed on a clamp, and the other end of each test sample is fixed on a shrinkage displacement sensor to ensure that the samples are flat. Setting the experiment temperature to be 120 ℃, starting heating the equipment, when the temperature in the test chamber reaches the set temperature, sending the sample into the test chamber, carrying out heat treatment for 1h, and recording the shrinkage rate of the diaphragm.
The tensile strength of the separator was tested with reference to the standard GB/T1040.3-2006.
And testing the puncture strength of the diaphragm according to the specification of the reference standard GB/T36363-2018 polyolefin diaphragm for the lithium ion battery.
And testing the porosity of the diaphragm by referring to the specification of GB/T36363-2018 polyolefin diaphragm for the lithium ion battery.
The test results are shown in table 1.
TABLE 1 test results of examples and comparative examples
| Tensile strength (MPa) | Puncture strength (N/um) | Porosity (%) | Thermal shrinkage (%) | |
| Example 1 | 53.7 | 2.07 | 39.8 | 6.7 |
| Example 2 | 52.1 | 2.01 | 38.5 | 7.3 |
| Example 3 | 50.8 | 2.03 | 38.1 | 7.8 |
| Example 4 | 53.3 | 2.09 | 39.7 | 6.9 |
| Comparative example 1 | 21.8 | 1.93 | 24.3 | 18.3 |
| Comparative example 2 | 54.1 | 2.09 | 33.2 | 6.4 |
| Comparative example 3 | 54.5 | 2.11 | 27.1 | 6.8 |
Through tests, the temperature resistance performance of the invention is better, the shrinkage rate of the diaphragm prepared in example 1 is only 6.7% under heat treatment at 120 ℃ for 1h, which is much lower than 18.3% of that of comparative example 1, because the polyimide fiber is used as a framework in example 1, the polyimide fiber does not melt and soften at high temperature, the shrinkage of the diaphragm is effectively inhibited, and as shown in fig. 1, the diaphragm basically has no obvious change before and after heat treatment; whereas the membrane of comparative example 1 showed a significant overall shrinkage, as shown in figure 2.
Claims (9)
1. A preparation method of a high-temperature-resistant polypropylene diaphragm for a lithium battery is characterized by comprising the following steps:
(1) adding diamine and dianhydride into a solvent for dispersion, reacting for 3-5 h at room temperature, adding lithium salt for dispersion to obtain a viscous liquid, spraying the viscous liquid by using a porous spinneret plate with the aperture of 0.1mm, and washing by using deionized water to obtain microporous crude fibers;
(2) drying the microporous coarse fibers obtained in the step (1), and cutting into microporous coarse fibers with the length of 3-10 mm;
(3) preparing a polypropylene base film by tape casting, rolling the microporous coarse fibers prepared in the step (2) on the surface of the polypropylene base film, and synchronously compounding a layer of polypropylene base film on the microporous coarse fiber surface to enable the microporous coarse fiber layer to be sandwiched between two polypropylene base films to form a sandwich structure; then rolling at 210-220 ℃ to ensure that the microporous crude fiber is dehydrated and gradually changed into polyimide fiber which is attached to the polypropylene base film;
(4) and (3) performing biaxial stretching on the rolled film in the step (3) at the temperature of 145-160 ℃ to obtain the high-temperature-resistant polypropylene diaphragm for the lithium battery.
2. The method for preparing the high temperature resistant polypropylene separator for the lithium battery according to claim 1, wherein the dianhydride in the step (1) is one or more of pyromellitic dianhydride, biphenyl dianhydride, triphenyl diether dianhydride, diphenyl ether dianhydride, thioether dianhydride, benzophenone dianhydride, and bisphenol A type diether dianhydride.
3. The method for preparing a high temperature resistant polypropylene separator for a lithium battery as claimed in claim 1, wherein the diamine in step (1) is one or more of 4, 4' -diaminodiphenyl ether diamine, p-phenylenediamine, diphenyl diether diamine, and bisphenol a diether diamine.
4. The method for preparing a high temperature resistant polypropylene separator for a lithium battery as claimed in claim 1, wherein the solvent in step (1) is one or more of dimethylacetamide, dimethylformamide, N-dimethylpyrrolidone, dimethyl sulfoxide, and tetrahydrofuran.
5. The method for preparing a high temperature resistant polypropylene separator for a lithium battery as claimed in claim 1, wherein the lithium salt in the step (1) is LiClO4、LiPF6、LiAsF6、LiSO3F、LiCF3SO3One or more of (a).
6. The preparation method of the high-temperature-resistant polypropylene separator for the lithium battery as claimed in claim 1, wherein the diamine, the dianhydride, the solvent and the lithium salt in the step (1) are mixed according to a mass ratio: 3:2:10:0.2-0.3.
7. The method as claimed in claim 1, wherein the microporous coarse fiber layer is sandwiched between two polypropylene-based films to form a sandwich structure, wherein the mass ratio of the polypropylene-based film, the microporous coarse fiber layer, and the polypropylene-based film is controlled to be 2: 1: 2.
8. the method for preparing the high-temperature-resistant polypropylene separator for the lithium battery as claimed in claim 1, wherein the biaxial stretching in the step (4) is 5 to 8 times of longitudinal stretching ratio and 3 to 5 times of transverse stretching ratio.
9. A high-temperature-resistant polypropylene diaphragm for a lithium battery is characterized by being prepared by the preparation method of the high-temperature-resistant polypropylene diaphragm for the lithium battery as claimed in any one of claims 1 to 8.
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| CN114497882A (en) * | 2021-11-17 | 2022-05-13 | 河北金力新能源科技股份有限公司 | High-strength para-aramid diaphragm and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114497882A (en) * | 2021-11-17 | 2022-05-13 | 河北金力新能源科技股份有限公司 | High-strength para-aramid diaphragm and preparation method thereof |
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Application publication date: 20210730 |