CN112952296A - Ionic membrane, preparation method thereof and semi-solid electrolyte battery - Google Patents
Ionic membrane, preparation method thereof and semi-solid electrolyte battery Download PDFInfo
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- CN112952296A CN112952296A CN202110295413.7A CN202110295413A CN112952296A CN 112952296 A CN112952296 A CN 112952296A CN 202110295413 A CN202110295413 A CN 202110295413A CN 112952296 A CN112952296 A CN 112952296A
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- 239000012528 membrane Substances 0.000 title claims abstract description 64
- 239000007784 solid electrolyte Substances 0.000 title claims abstract description 9
- 238000002360 preparation method Methods 0.000 title claims abstract description 8
- 239000000919 ceramic Substances 0.000 claims description 64
- 239000002131 composite material Substances 0.000 claims description 43
- 239000002002 slurry Substances 0.000 claims description 34
- 239000006185 dispersion Substances 0.000 claims description 33
- -1 polypropylene Polymers 0.000 claims description 27
- 239000011248 coating agent Substances 0.000 claims description 25
- 238000000576 coating method Methods 0.000 claims description 25
- 238000002156 mixing Methods 0.000 claims description 25
- 238000005524 ceramic coating Methods 0.000 claims description 22
- 239000004743 Polypropylene Substances 0.000 claims description 21
- 229920001155 polypropylene Polymers 0.000 claims description 21
- 229920000098 polyolefin Polymers 0.000 claims description 20
- 239000004094 surface-active agent Substances 0.000 claims description 20
- 239000002245 particle Substances 0.000 claims description 17
- 239000008367 deionised water Substances 0.000 claims description 16
- 229910021641 deionized water Inorganic materials 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 238000001816 cooling Methods 0.000 claims description 14
- 239000002270 dispersing agent Substances 0.000 claims description 14
- 239000011230 binding agent Substances 0.000 claims description 13
- 238000001035 drying Methods 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 13
- 238000005096 rolling process Methods 0.000 claims description 13
- 239000000155 melt Substances 0.000 claims description 12
- CVJYOKLQNGVTIS-UHFFFAOYSA-K aluminum;lithium;titanium(4+);phosphate Chemical compound [Li+].[Al+3].[Ti+4].[O-]P([O-])([O-])=O CVJYOKLQNGVTIS-UHFFFAOYSA-K 0.000 claims description 10
- 239000004721 Polyphenylene oxide Substances 0.000 claims description 9
- 229920001577 copolymer Polymers 0.000 claims description 9
- 238000001125 extrusion Methods 0.000 claims description 9
- 229920000570 polyether Polymers 0.000 claims description 9
- 238000000137 annealing Methods 0.000 claims description 8
- 229910052710 silicon Inorganic materials 0.000 claims description 8
- 239000010703 silicon Substances 0.000 claims description 8
- 239000002033 PVDF binder Substances 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 229910000664 lithium aluminum titanium phosphates (LATP) Inorganic materials 0.000 claims description 6
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 6
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims description 5
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 5
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 4
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 4
- 238000007873 sieving Methods 0.000 claims description 4
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 claims description 3
- 238000009998 heat setting Methods 0.000 claims description 3
- 239000004576 sand Substances 0.000 claims description 3
- 238000007493 shaping process Methods 0.000 claims description 3
- 229920002125 Sokalan® Polymers 0.000 claims description 2
- 239000004584 polyacrylic acid Substances 0.000 claims description 2
- 238000009776 industrial production Methods 0.000 abstract description 2
- 210000004379 membrane Anatomy 0.000 description 50
- 239000000243 solution Substances 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 239000000843 powder Substances 0.000 description 9
- 150000002500 ions Chemical class 0.000 description 8
- 239000011347 resin Substances 0.000 description 8
- 229920005989 resin Polymers 0.000 description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 239000010410 layer Substances 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 239000011245 gel electrolyte Substances 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 210000001787 dendrite Anatomy 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 239000011244 liquid electrolyte Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- JFBZPFYRPYOZCQ-UHFFFAOYSA-N [Li].[Al] Chemical compound [Li].[Al] JFBZPFYRPYOZCQ-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 210000002469 basement membrane Anatomy 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000010416 ion conductor Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Classifications
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Cell Separators (AREA)
Abstract
The invention discloses an ionic membrane, a preparation method thereof and a semi-solid electrolyte battery. The ionic membrane has good ionic conductivity, low interface impedance and heat resistance by constructing a conductive network, can be applied to industrial production in a mature way, and has application prospect.
Description
Technical Field
The invention belongs to the technical field of battery diaphragms, and particularly relates to an ionic membrane and a preparation method thereof, and a semi-solid electrolyte battery containing the ionic membrane.
Background
In the lithium ion battery, the diaphragm is used as one of four key materials of the lithium ion battery, and the performance of the diaphragm can influence the electrical performance and the safety performance of the battery to a certain extent. At present, the material of the lithium ion battery diaphragm is usually polyolefin material, the heat resistance is poor, the temperature is rapidly increased to reach the melting temperature of the diaphragm quickly when thermal runaway is caused by internal short circuit in the battery, and the battery is likely to be ignited and exploded. The main direction of improvement at present is to compound a polyolefin diaphragm with other film materials or coat a functional coating on the surface of the polyolefin diaphragm so as to obtain a multilayer composite diaphragm or a functional coating diaphragm with higher safety, but the diaphragms cannot completely meet the requirements of power batteries on the safety of the diaphragms.
Among lithium ion batteries, a solid-state battery is a battery using a solid electrode and a solid electrolyte, and has higher safety performance and energy density, but the current solid-state electrolyte has some problems of large interface resistance and the like, and the solid-state battery has no industrialization trend of mature application.
Disclosure of Invention
In view of the above, the present invention is directed to an ion membrane and a method for manufacturing the same, wherein the ion membrane is constructed with a conductive network, has a good ionic conductivity, a low interfacial resistance and a low heat resistance, and can be applied to industrial production.
In order to achieve the purpose, the invention adopts the following technical scheme:
the present invention first provides an ionic membrane, which comprises:
a composite base film made by mixing polyolefin and a first conductive ceramic;
and the conductive ceramic coating is formed by drying conductive ceramic slurry on the surface of the composite base film, and the conductive ceramic slurry is prepared by mixing second conductive ceramic, a dispersing agent, a binder, a surfactant and deionized water.
Furthermore, the conductive ceramic coating is arranged on two opposite surfaces of the composite base film, and the thickness of a single surface of the conductive ceramic coating is 1-4 microns.
Further, in the composite base film, the weight parts of the components are as follows: 80-100 parts of polyolefin and 10-20 parts of first conductive ceramic, wherein the polyolefin is selected from polypropylene, and the first conductive ceramic is selected from titanium aluminum lithium phosphate.
Preferably, the melt index of the polypropylene at 230 ℃ and under the condition of 2.16kg is less than 3g/10min, the particle size D50 of the lithium aluminum titanium phosphate is less than 50nm, and Dmax is less than 100 nm.
Further, the conductive ceramic slurry comprises the following components in parts by weight: 30-45 parts of second conductive ceramic, 0.2-1 part of dispersant, 5-15 parts of binder, 0.3-1 part of surfactant and 60-90 parts of deionized water.
Further, the second conductive ceramic is selected from titanium aluminum lithium phosphate, the particle size D50 of the second conductive ceramic is less than 500nm, and Dmax of the second conductive ceramic is less than 1000 nm;
the dispersing agent is selected from at least one of polyacrylic acid ammonium salt copolymer solution and polyvinyl alcohol solution;
the binder is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and polytetrafluoroethylene;
the surfactant is at least one selected from polyether modified organic silicon and nonionic fluorocarbon.
The invention also provides a preparation method of the ionic membrane, which comprises the following steps:
uniformly mixing polyolefin and first conductive ceramic according to a ratio, adding into an extrusion device, blending, extruding, cooling and forming a film, longitudinally stretching, annealing, heat setting and rolling to obtain a composite base film;
mixing and dispersing the second conductive ceramic, the dispersing agent and the deionized water according to the proportion to obtain a dispersion liquid; adding a binder and a surfactant into the dispersion liquid, dispersing at a low speed for 1-3 h, and sieving with a 200-mesh sieve to obtain conductive ceramic slurry;
and uniformly coating the conductive ceramic slurry on the surface of the composite base film, and drying to obtain the ionic membrane.
Further, in the step of obtaining the composite base film, the working temperature of the extrusion equipment is 100-200 ℃, the temperature of the die head is 160-260 ℃, the temperature of the cooling roller is 40-100 ℃, the stretching ratio is less than 3 times, the stretching speed is 10-50 m/min, and the shaping temperature after stretching is 100-130 ℃.
Further, in the step of obtaining the conductive ceramic slurry, the mixing and dispersing are carried out in a sand mill with the rotating speed of 400-600 rpm;
the low-speed dispersion is carried out by adopting a dispersion machine with the power of 600-800W and the temperature of 25-40 ℃.
The invention further provides a semi-solid electrolyte battery, which comprises a diaphragm, wherein the diaphragm is the ionic membrane.
Compared with the prior art, the invention has the following excellent effects:
the ionic membrane is a composite base membrane obtained by mixing polyolefin and conductive ceramic, and the surface of the composite base membrane is coated with the conductive ceramic coating, so that the conductive ceramic coating and the conductive ceramic in the composite base membrane are matched to construct a conductive network, the ionic conductivity of the ionic membrane is improved, and the ionic membrane has lower interface impedance.
The ionic membrane has certain strength, meets the requirement of the diaphragm, and has better heat-resistant stability.
The preparation of the ionic membrane, wherein the composite base membrane is prepared by extrusion, has simple process; the conductive ceramic slurry mixing process is simple and quick, has low cost, and has good coatability and strong processability, so that the preparation process of the ionic membrane is mature and is easy to industrialize.
Compared with a lithium ion battery, the semisolid battery assembled by the ionic membrane and the gel electrolyte eliminates the potential safety hazards of corrosion and leakage of the liquid electrolyte, has higher thermal stability, higher energy density and better safety performance when the weight is reduced. The solid conductive ceramic is selected, the valence reduction of Ti and lithium in the ionic membrane at the negative electrode side is mainly carried out, a film layer which can be integrated with an SEI film can be formed between the ionic membrane and the negative electrode plate, the side reaction is further reduced, and the formation of lithium dendrite is prevented.
Detailed Description
In order that the invention may be more fully understood, reference will now be made to the specific embodiments illustrated. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The invention discloses in a first aspect an ionic membrane comprising:
a composite base film made by mixing polyolefin and a first conductive ceramic;
and the conductive ceramic coating is formed by drying conductive ceramic slurry on the surface of the composite base film, and the conductive ceramic slurry is prepared by mixing second conductive ceramic, a dispersing agent, a binder, a surfactant and deionized water.
The ionic membrane is matched with the conductive ceramic coating in the composite base membrane to construct a conductive network, so that the ionic conductivity of the diaphragm is improved, the interface impedance is reduced, and the ionic membrane has excellent heat-resistant stability because the conductive ceramic has lower heat conductivity coefficient and larger specific heat capacity compared with common ceramic. In addition, it is understood that the conductive ceramic coating may be double-coated or single-coated on the surface of the composite base film, and may be adjusted as needed, and when single-coated, the conductive ceramic coating side is used for the negative electrode side.
Further, the thickness of the conductive ceramic coating in the invention is not particularly limited, and can be adjusted according to industry internal coating thickness, preferably, in some specific embodiments of the invention, the conductive ceramic coating is double-sided coated, and in order to optimize the performance of the ionic membrane, the single-sided thickness of the conductive ceramic coating is 1-4 μm.
Further, in the composite base film, the weight parts of the components are as follows: 80-100 parts of polyolefin and 10-20 parts of first conductive ceramic, wherein the polyolefin is selected from polypropylene, the first conductive ceramic is selected from titanium aluminum lithium phosphate (LATP), and the polyolefin is not particularly limited, and the polyolefin can be selected from polyolefin components which are conventionally adopted in the field, besides the polypropylene, polyethylene and the like, and the polyolefin is not specifically illustrated.
Further, in the present invention, the polypropylene and the lithium aluminum titanium phosphate are not particularly limited, but in order to form a composite base film better and more uniformly, it is preferable that the melt index of the polypropylene at 230 ℃ under 2.16kg is less than 3g/10min, the particle size of the lithium aluminum titanium phosphate is D50 less than 50nm, Dmax is less than 100nm, the molecular weight of the polymer is ensured by selecting the melt index of the polypropylene, and the composite base film can be formed more uniformly by extrusion with the preferred lithium aluminum titanium phosphate, and can be formed better.
Further, the conductive ceramic slurry comprises the following components in parts by weight: 30-45 parts of second conductive ceramic, 0.2-1 part of dispersant, 5-15 parts of binder, 0.3-1 part of surfactant and 60-90 parts of deionized water.
Preferably, the second conductive ceramic is selected from Lithium Aluminium Titanium Phosphate (LATP), the grain size D50 is less than 500nm, Dmax is less than 1000 nm;
the dispersant, the binder and the surfactant in the present invention may be conventionally selected in the art, and the dispersant may be at least one selected from a polyammonium salt copolymer solution and a polyvinyl alcohol solution, and it should be noted that, unless otherwise specified, the dispersant solution herein refers to an aqueous solution, and the mass fraction thereof may be adjusted as needed, and is not specifically limited herein;
the binder can be at least one selected from polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and polytetrafluoroethylene;
the surfactant may be at least one selected from polyether modified silicones and nonionic fluorocarbons. It is understood that the above selections are only examples made in some embodiments of the present invention, and other similar aids in the field can be used in the technical scheme of the present invention.
In a second aspect, the present invention provides a method for preparing an ionic membrane according to the first aspect, comprising the steps of:
uniformly mixing polyolefin and first conductive ceramic according to a ratio, adding into an extrusion device, blending, extruding, cooling and forming a film, longitudinally stretching, annealing, heat setting and rolling to obtain a composite base film;
mixing and dispersing the second conductive ceramic, the dispersing agent and the deionized water according to the proportion to obtain a dispersion liquid; adding a binder and a surfactant into the dispersion liquid, dispersing at a low speed for 1-3 h, and sieving with a 200-mesh sieve to obtain conductive ceramic slurry;
and uniformly coating the conductive ceramic slurry on the surface of the composite base film, and drying to obtain the ionic membrane.
The ionic membrane and the composite base membrane thereof are extruded into a membrane by an extrusion device, and the membrane is obtained by coating conductive ceramic slurry on the surface of the composite base membrane.
Preferably, in some specific embodiments of the present invention, in the step of obtaining the composite base film, the working temperature of the extrusion equipment is 100 to 200 ℃, the die head temperature is 160 to 260 ℃, the cooling roll temperature is 40 to 100 ℃, the stretching ratio is less than 3 times, the stretching rate is 10 to 50m/min, and the shaping temperature after stretching is 100 to 130 ℃.
In the step of obtaining the conductive ceramic slurry, the mixing and dispersing are carried out by a sand mill with the rotating speed of 400-600 rpm;
the low-speed dispersion is carried out by adopting a dispersion machine with the power of 600-800W and the temperature of 25-40 ℃.
In a third aspect, the present invention provides a semi-solid electrolyte battery comprising a separator which is an ionic membrane according to the first aspect of the present invention. In the semi-solid electrolyte battery, the selection of the positive electrode, the negative electrode and the electrolyte is not particularly limited, and can be a conventional selection in the field, and the assembly manner can be realized by a conventional means in the field, so that the detailed description is not provided herein.
The technical scheme of the invention is more clearly and completely illustrated by combining specific examples and comparative examples. In the following examples and comparative examples, "part(s)" and "part(s)" mean part(s) by weight unless otherwise specified.
Example 1
Uniformly mixing 80 parts of polypropylene resin with the melt index of 2.2g/10min and 10 parts of LATP powder with the particle size D50 of 40nm, extruding at 120 ℃, extruding at a die head of 180 ℃, cooling at 60 ℃ to form a sheet film, carrying out annealing treatment by using a stretching ratio of 1 time, longitudinally stretching at 110 ℃ at a longitudinal stretching speed of 10m/min, longitudinally stretching again at 120 ℃ by using a stretching ratio of 1.5 times, and rolling by an adjusting process to obtain the 16-micron composite base film.
Adding 30 parts of LATP with the particle size D50 of 400nm, 0.2 part of polyacrylic ammonium salt copolymer solution (with the mass concentration of 50%) and 60 parts of deionized water into a sanding dispersion machine, controlling the temperature to be 25 ℃ and the rotating speed to be 400rpm, dispersing for 2 hours, then transferring to the dispersion machine, adding 10 parts of polyvinylidene fluoride and 0.3 part of polyether modified organic silicon surfactant, keeping the temperature of the dispersion machine to be 25 ℃ and the power to be 600W, and dispersing for 2 hours through a 200-mesh screen to obtain the conductive ceramic slurry.
And (3) uniformly coating the conductive ceramic slurry on the surface of the 16-micron composite base film on both sides by using a coating machine, and drying to obtain the ionic film, wherein the thickness of the single-side conductive ceramic coating is 3 microns.
Example 2
100 parts of polypropylene resin with the melt index of 2.8g/10min and 20 parts of LATP powder with the grain diameter D50 of 30nm are uniformly mixed and then extruded at 160 ℃, then extruded at 220 ℃ of a die head and rolled into a sheet film through a cooling roller at 70 ℃, then the sheet film is annealed, the drawing ratio of 1.5 times is used, the longitudinal drawing speed of 15m/min is used for longitudinal drawing at 120 ℃, then the longitudinal drawing ratio of 1.8 times is used, the longitudinal drawing is carried out again at 130 ℃ and 20m/min, and the composite base film with the thickness of 14 mu m is obtained by adjusting and rolling.
Adding 40 parts of LATP with the particle size D50 of 300nm, 0.8 part of polyvinyl alcohol solution (with the mass concentration of 50%) and 80 parts of deionized water into a sanding dispersion machine, controlling the temperature to be 30 ℃ and the rotating speed to be 500rpm, dispersing for 1.5h, then transferring to the dispersion machine, adding 15 parts of polytetrafluoroethylene and 0.8 part of poly-nonionic fluorocarbon surfactant, keeping the temperature of the dispersion machine to be 30 ℃ and the power to be 800W, and dispersing for 1h through a 200-mesh screen to obtain the conductive ceramic slurry.
And (3) uniformly coating the slurry on the surface of the 14-micron composite base film on two sides by using a coating machine, and drying to obtain the ionic membrane, wherein the thickness of the single side of the conductive ceramic coating is 4 microns.
Example 3
Uniformly mixing 85 parts of polypropylene resin with the melt index of 2.4g/10min and 15 parts of LATP powder with the particle size D50 of 25nm, extruding at 180 ℃, extruding at a die head of 200 ℃, cooling at 80 ℃ to form a sheet film, then carrying out annealing treatment by using a stretching ratio of 1.8 times, longitudinally stretching at 100 ℃ at a longitudinal stretching speed of 20m/min, then longitudinally stretching again at 120 ℃ by using a stretching ratio of 2.2 times, and rolling by an adjusting process to obtain the composite base film with the thickness of 12 mu m.
Adding 35 parts of LATP with the particle size D50 of 250nm, 0.5 part of polyacrylic ammonium salt copolymer solution (the mass concentration is 50%) and 70 parts of deionized water into a sanding dispersion machine, controlling the temperature to be 28 ℃ and the rotating speed to be 600rpm, dispersing for 1h, then transferring into the dispersion machine, adding 12 parts of polyvinylidene fluoride-hexafluoropropylene and 0.3 part of polyether modified organic silicon surface active agent, keeping the temperature of the dispersion machine to be 28 ℃ and the power to be 700W, and dispersing for 2h through a 200-mesh screen to obtain the conductive ceramic slurry.
And (3) uniformly coating the surfaces of the composite base membrane with the thickness of 12 mu m on both sides of the conductive ceramic slurry by using a coating machine, and drying to prepare the ionic membrane, wherein the thickness of one side of the conductive ceramic coating is 2 mu m.
Example 4
Uniformly mixing 80 parts of polypropylene resin with the melt index of 2.0g/10min and 20 parts of LATP powder with the particle size D50 of 30nm, extruding at 100 ℃, extruding at 160 ℃ of a die head, rolling into a sheet film through a cooling roller at 40 ℃, then carrying out annealing treatment by using a stretching ratio of 1.5 times, longitudinally stretching at 100 ℃ at a longitudinal stretching speed of 10m/min, then longitudinally stretching again at 110 ℃ by using a stretching ratio of 2.0 times, and rolling by an adjusting process to obtain the composite base film with the thickness of 10 mu m.
Adding 45 parts of LATP with the particle size D50 of 400nm, 1 part of polyacrylic ammonium salt copolymer solution (with the mass concentration of 50%) and 90 parts of deionized water into a sanding dispersion machine, controlling the temperature to be 40 ℃ and the rotating speed to be 600rpm, dispersing for 1h, then transferring to the dispersion machine, adding 15 parts of polyvinylidene fluoride-hexafluoropropylene and 1 part of polyether modified organic silicon surface active agent, keeping the temperature of the dispersion machine to be 40 ℃ and the power to be 800W, and dispersing for 2h through a 200-mesh screen to obtain the conductive ceramic slurry.
And (3) uniformly coating the surfaces of the composite base membrane with the thickness of 10 mu m on both sides of the conductive ceramic slurry by using a coating machine, and drying to obtain the ionic membrane, wherein the thickness of one side of the conductive ceramic coating is 3 mu m.
Example 5
Uniformly mixing 85 parts of polypropylene resin with the melt index of 2.5g/10min and 20 parts of LATP powder with the particle size D50 of 30nm, extruding at 200 ℃, extruding at a die head of 260 ℃, rolling into a sheet film through a cooling roller at 100 ℃, then carrying out annealing treatment by using the stretching ratio of 1.8 times, longitudinally stretching at the longitudinal stretching speed of 50m/min at 130 ℃, then longitudinally stretching again at the longitudinal stretching speed of 50m/min at 130 ℃ by using the stretching ratio of 2.8 times, and rolling by an adjusting process to obtain the composite base film with the thickness of 14 mu m.
Adding 30 parts of LATP with the particle size D50 of 300nm, 0.2 part of polyacrylic ammonium salt copolymer solution (the mass concentration is 50%) and 60 parts of deionized water into a sanding dispersion machine, controlling the temperature to be 25 ℃ and the rotating speed to be 400rpm, dispersing for 1h, then transferring to the dispersion machine, adding 5 parts of polytetrafluoroethylene and 0.5 part of polyether modified organic silicon surfactant, keeping the temperature of the dispersion machine to be 25 ℃ and the power to be 600W, and dispersing for 2h through a 200-mesh screen to obtain the conductive ceramic slurry.
And (3) uniformly coating the surfaces of the composite base membrane with the thickness of 14 mu m on both sides of the conductive ceramic slurry by using a coating machine, and drying to prepare the ionic membrane, wherein the thickness of one side of the conductive ceramic coating is 1 mu m.
Comparative example 1
80 parts of polypropylene resin with the melt index of 2.2g/10min and 10 parts of alumina powder with the grain diameter D50 of 40nm are extruded at 120 ℃, then extruded at 180 ℃ of a die head and rolled into a sheet film by a cooling roller at 60 ℃, then the sheet film is annealed by using the stretching ratio of 1 time, the longitudinal stretching speed of 10m/min is longitudinally stretched at 110 ℃, then the longitudinal stretching ratio of 1.5 times is used, the longitudinal stretching is carried out again at 120 ℃ by 15m/min, and the 16 mu m polypropylene base film is obtained by adjusting the process and rolling.
Adding 30 parts of alumina ceramic powder with the particle size D50 of 400nm, 0.2 part of polyacrylic ammonium salt copolymer solution (with the mass concentration of 50%) and 60 parts of deionized water into a sanding dispersion machine, controlling the temperature to be 25 ℃ and the rotating speed to be 400rpm, dispersing for 2 hours, then transferring to the dispersion machine, adding 10 parts of polyvinylidene fluoride and 0.3 part of polyether modified organic silicon surfactant, keeping the temperature of the dispersion machine to be 25 ℃ and the power to be 600W, dispersing for 2 hours, and sieving through a 200-mesh sieve to obtain ceramic slurry.
And (3) uniformly coating the ceramic slurry on the surface of a 16-micron polypropylene base film on both sides by using a coating machine, and drying to obtain a coating film, wherein the thickness of one side of the ceramic coating is 3 microns.
Comparative example 2
80 parts of polypropylene resin with the melt index of 2.2g/10min is extruded at 120 ℃, then extruded at a die head of 180 ℃, and then is rolled into a sheet film through a cooling roller at 60 ℃, then the sheet film is annealed, the stretching ratio of 1 time is used, the longitudinal stretching speed of 10m/min is used for longitudinal stretching at 110 ℃, then the longitudinal stretching ratio of 1.5 times is used, the longitudinal stretching is carried out again at 120 ℃ and 15m/min, and the 16 mu m polypropylene base film is obtained by rolling through an adjusting process.
Adding 40 parts of LATP with D50 of 40nm, 0.2 part of polyacrylic ammonium salt copolymer solution (with the mass concentration of 50%) and 60 parts of deionized water into a sanding dispersion machine, controlling the temperature to be 25 ℃ and the rotating speed to be 400rpm, dispersing for 2 hours, then transferring to the dispersion machine, adding 10 parts of polyvinylidene fluoride and 0.3 part of polyether modified organic silicon surfactant, keeping the temperature of the dispersion machine to be 25 ℃ and the power to be 600W, and dispersing for 2 hours through a 200-mesh screen to obtain the conductive ceramic slurry.
And (3) uniformly coating the conductive ceramic slurry on the surface of a 16-micron polypropylene base film on two sides by using a coating machine, and drying to obtain the ionic film, wherein the thickness of the single-side conductive ceramic coating is 3 microns.
Comparative example 3
Uniformly mixing 80 parts of polypropylene resin with the melt index of 2.2g/10min and 40 parts of LATP powder with the particle size D50 of 40nm, extruding at 120 ℃, extruding at a die head of 180 ℃, cooling at 60 ℃ to form a sheet film, carrying out annealing treatment by using a stretching ratio of 1 time, longitudinally stretching at 110 ℃ at a longitudinal stretching speed of 10m/min, longitudinally stretching again at 120 ℃ by using a stretching ratio of 1.5 times, and rolling by an adjusting process to obtain the 22 mu m composite base film.
Test example
The ionic membranes prepared in examples 1 to 3 and comparative examples 1 to 3 were subjected to 180 deg.c/0.5 h Machine Direction (MD) and Transverse Direction (TD) heat shrinkage and ionic conductivity tests, respectively, and the test results are shown in table 1 below.
TABLE 1 results of ion membrane performance test of examples 1-3 and comparative examples 1-3
Note: table 1 the thermal shrinkage was measured using a high precision oven (DHG-9053A) and a quadratic projector (JIVMS-1510), and the ionic conductivity was measured using a teflon tool with symmetrical electrodes and an electrochemical workstation (1287A/1255B), both according to the national standard.
From the test results in table 1, it can be seen that, compared with the coating films of comparative examples 1-3, the ionic film prepared in example 1 has higher ionic conductivity because the ionic film coated with LATP in example 1 can form a denser heat-resistant layer, the heat-resistant layer has smaller deformation at high temperature and better heat resistance to the coating film by smaller acting force, and meanwhile, the LATP in the coating layer and the LATP particles in the composite base film can form point contact to construct a conductive network. In contrast, in comparative example 1, the conventional alumina ceramic was used, and the difference in high-temperature heat resistance was small, but the conductivity was low. In comparative example 2, the LATP separator coated only on the surface had a slightly low high-temperature heat resistance, and the ion conductor having no point contact was formed between the coating layer and the base film, and the ion conductivity was much lowered. In the comparative example 3, the heat resistance of the whole diaphragm is poor at high temperature because the LATP powder has certain dispersibility. The ion membrane prepared in the embodiments 1, 2 and 3 has good ionic conductivity and high thermal stability, can be used as a high-performance ion membrane applied to a semisolid gel electrolyte battery in a mature and industrialized mode, not only has certain strength and can reduce foreign matters and the like in the battery core manufacturing process to influence the short circuit of the battery, but also has partial pores to allow the gel electrolyte to be soaked, meanwhile, the LATP in the basement membrane and the LATP on the double-sided coating can form a good ion conduction network, the impedance is reduced, the potential safety hazard that the liquid electrolyte can be corroded and leaked is eliminated, the valence reduction can be carried out on Ti and lithium in the LATP ion membrane on the negative electrode side, a membrane layer which can be integrated with the SEI membrane can be formed between the LATP membrane and the negative electrode plate, and the occurrence of side reactions and the formation of lithium dendrites can be further reduced.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. An ionic membrane, comprising:
a composite base film made by mixing polyolefin and a first conductive ceramic;
and the conductive ceramic coating is formed by drying conductive ceramic slurry on the surface of the composite base film, and the conductive ceramic slurry is prepared by mixing second conductive ceramic, a dispersing agent, a binder, a surfactant and deionized water.
2. The ionic membrane as claimed in claim 1, wherein the conductive ceramic coating is arranged on two opposite surfaces of the composite base membrane, and the single-side thickness of the conductive ceramic coating is 1-4 μm.
3. The ionic membrane as claimed in claim 1, wherein the composite base membrane comprises the following components in parts by weight: 80-100 parts of polyolefin and 10-20 parts of first conductive ceramic, wherein the polyolefin is selected from polypropylene, and the first conductive ceramic is selected from titanium aluminum lithium phosphate.
4. The ionic membrane of claim 3, wherein the polypropylene has a melt index of < 3g/10min at 230 ℃ under 2.16kg, and the lithium aluminum titanium phosphate has a particle size D50 of < 50nm and Dmax of < 100 nm.
5. The ionic membrane according to claim 1, wherein the conductive ceramic slurry comprises the following components in parts by weight: 30-45 parts of second conductive ceramic, 0.2-1 part of dispersant, 5-15 parts of binder, 0.3-1 part of surfactant and 60-90 parts of deionized water.
6. The ionic membrane of claim 1, wherein the second conductive ceramic is selected from the group consisting of lithium aluminum titanium phosphate having a particle size D50 < 500nm, Dmax < 1000 nm;
the dispersing agent is selected from at least one of polyacrylic acid ammonium salt copolymer solution and polyvinyl alcohol solution;
the binder is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and polytetrafluoroethylene;
the surfactant is at least one selected from polyether modified organic silicon and nonionic fluorocarbon.
7. A method of preparing an ionic membrane according to any one of claims 1 to 6, comprising the steps of:
uniformly mixing polyolefin and first conductive ceramic according to a ratio, adding into an extrusion device, blending, extruding, cooling and forming a film, longitudinally stretching, annealing, heat setting and rolling to obtain a composite base film;
mixing and dispersing the second conductive ceramic, the dispersing agent and the deionized water according to the proportion to obtain a dispersion liquid; adding a binder and a surfactant into the dispersion liquid, dispersing at a low speed for 1-3 h, and sieving with a 200-mesh sieve to obtain conductive ceramic slurry;
and uniformly coating the conductive ceramic slurry on the surface of the composite base film, and drying to obtain the ionic membrane.
8. The preparation method of claim 7, wherein in the step of obtaining the composite base film, the working temperature of the extrusion equipment is 100-200 ℃, the temperature of the die head is 160-260 ℃, the temperature of the cooling roll is 40-100 ℃, the stretching ratio is less than 3 times, the stretching speed is 10-50 m/min, and the shaping temperature after stretching is 100-130 ℃.
9. The method according to claim 7, wherein in the step of obtaining the conductive ceramic slurry, the mixing and dispersing are performed in a sand mill with a rotation speed of 400-600 rpm;
the low-speed dispersion is carried out by adopting a dispersion machine with the power of 600-800W and the temperature of 25-40 ℃.
10. A semi-solid electrolyte battery comprising a separator, wherein the separator is an ionic membrane according to any one of claims 1 to 6.
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| CN115842213A (en) * | 2022-09-02 | 2023-03-24 | 北京卫蓝新能源科技有限公司 | Embedded solid electrolyte diaphragm, preparation method and application thereof |
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