CN113013547A - Lithium battery composite diaphragm and preparation method thereof - Google Patents
Lithium battery composite diaphragm and preparation method thereof Download PDFInfo
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- CN113013547A CN113013547A CN202110220370.6A CN202110220370A CN113013547A CN 113013547 A CN113013547 A CN 113013547A CN 202110220370 A CN202110220370 A CN 202110220370A CN 113013547 A CN113013547 A CN 113013547A
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 71
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 71
- 239000002131 composite material Substances 0.000 title claims abstract description 52
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 229910052901 montmorillonite Inorganic materials 0.000 claims abstract description 96
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 claims abstract description 94
- 239000007788 liquid Substances 0.000 claims abstract description 35
- 239000011248 coating agent Substances 0.000 claims abstract description 31
- 238000000576 coating method Methods 0.000 claims abstract description 31
- 239000011230 binding agent Substances 0.000 claims abstract description 29
- 239000000843 powder Substances 0.000 claims abstract description 25
- 239000006255 coating slurry Substances 0.000 claims abstract description 21
- 238000001035 drying Methods 0.000 claims abstract description 20
- 239000002135 nanosheet Substances 0.000 claims abstract description 18
- 239000002904 solvent Substances 0.000 claims abstract description 17
- 239000006185 dispersion Substances 0.000 claims abstract description 12
- 239000012670 alkaline solution Substances 0.000 claims abstract description 10
- 238000009210 therapy by ultrasound Methods 0.000 claims abstract description 10
- 239000000839 emulsion Substances 0.000 claims abstract description 7
- 238000000926 separation method Methods 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims abstract description 7
- 238000001764 infiltration Methods 0.000 claims abstract description 6
- 230000008595 infiltration Effects 0.000 claims abstract description 6
- 238000002156 mixing Methods 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 20
- -1 polytetrafluoroethylene Polymers 0.000 claims description 14
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 9
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 9
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 9
- 239000002033 PVDF binder Substances 0.000 claims description 9
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims description 8
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 8
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 8
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 238000005119 centrifugation Methods 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 4
- 239000000243 solution Substances 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 3
- WHQSYGRFZMUQGQ-UHFFFAOYSA-N n,n-dimethylformamide;hydrate Chemical compound O.CN(C)C=O WHQSYGRFZMUQGQ-UHFFFAOYSA-N 0.000 claims description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 17
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 17
- 230000005540 biological transmission Effects 0.000 abstract description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 238000009776 industrial production Methods 0.000 abstract 1
- 239000000463 material Substances 0.000 description 27
- 239000010410 layer Substances 0.000 description 10
- 239000003792 electrolyte Substances 0.000 description 9
- 239000004698 Polyethylene Substances 0.000 description 8
- 239000012528 membrane Substances 0.000 description 8
- 229920000573 polyethylene Polymers 0.000 description 8
- 239000004743 Polypropylene Substances 0.000 description 6
- 239000011229 interlayer Substances 0.000 description 6
- 229920001155 polypropylene Polymers 0.000 description 6
- 238000005524 ceramic coating Methods 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 4
- 229920000098 polyolefin Polymers 0.000 description 4
- 239000010409 thin film Substances 0.000 description 4
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 150000001768 cations Chemical class 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000009736 wetting Methods 0.000 description 3
- 229910018060 Ni-Co-Mn Inorganic materials 0.000 description 2
- 229910018209 Ni—Co—Mn Inorganic materials 0.000 description 2
- FBDMTTNVIIVBKI-UHFFFAOYSA-N [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] Chemical compound [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] FBDMTTNVIIVBKI-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000005342 ion exchange Methods 0.000 description 2
- 238000011031 large-scale manufacturing process Methods 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- 229920001166 Poly(vinylidene fluoride-co-trifluoroethylene) Polymers 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- VNSBYDPZHCQWNB-UHFFFAOYSA-N calcium;aluminum;dioxido(oxo)silane;sodium;hydrate Chemical compound O.[Na].[Al].[Ca+2].[O-][Si]([O-])=O VNSBYDPZHCQWNB-UHFFFAOYSA-N 0.000 description 1
- 239000002734 clay mineral Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000002001 electrolyte material Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000000713 high-energy ball milling Methods 0.000 description 1
- 238000000703 high-speed centrifugation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000010954 inorganic particle Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 229910000273 nontronite Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920001707 polybutylene terephthalate Polymers 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920000139 polyethylene terephthalate Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
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- 238000000527 sonication Methods 0.000 description 1
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- 238000006467 substitution reaction Methods 0.000 description 1
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- 238000012546 transfer Methods 0.000 description 1
- 238000001132 ultrasonic dispersion Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- 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
-
- 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
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- 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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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Nanotechnology (AREA)
- Manufacturing & Machinery (AREA)
- General Chemical & Material Sciences (AREA)
- Electrochemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Composite Materials (AREA)
- Cell Separators (AREA)
- Secondary Cells (AREA)
Abstract
The invention provides a lithium battery composite diaphragm and a preparation method thereof, wherein the preparation method comprises the following steps: s1, dispersing the pretreated montmorillonite in a solvent, and uniformly stirring and dispersing to obtain montmorillonite dispersion liquid; s2, taking the upper layer turbid liquid of the montmorillonite dispersion liquid, placing the upper layer turbid liquid in a centrifugal tube for centrifugal treatment to obtain montmorillonite nanosheets, placing the montmorillonite nanosheets in an alkaline solution for infiltration, then carrying out ice-bath ultrasonic treatment to prepare montmorillonite emulsion, and finally carrying out solid-liquid separation and drying to obtain montmorillonite powder; s3, uniformly mixing the montmorillonite powder and an oil-based binder to form oil-based coating slurry; and S4, coating the oil-based coating slurry on the surface of a lithium battery diaphragm, and drying to obtain the lithium battery composite diaphragm. The lithium battery composite diaphragm provided by the invention is beneficial to the rapid transmission of lithium ions on the diaphragm, improves the cycle performance and the ionic conductivity of the lithium battery composite diaphragm, has the advantages of simple and feasible preparation process, high product purity and low preparation cost, and is suitable for large-scale industrial production.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a lithium battery composite diaphragm and a preparation method thereof.
Background
With the rapid development of lithium ion battery application, a lithium battery diaphragm, which is one of the key materials of a lithium battery structure, gradually becomes a hot spot of research in the field of lithium batteries, and the diaphragm mainly has the functions of isolating, positive and negative electrodes, preventing electrons from freely passing through, and allowing ions in electrolyte/liquid to freely pass between the positive electrode and the negative electrode. The performance of the separator determines the interface structure, internal resistance, etc. of the battery, and directly affects the capacity, cycle and safety of the battery. The conventional commercialized separator materials mainly include polyolefin separator materials such as Polyethylene (PE) and polypropylene (PP), but the mechanical strength and relatively low melting point of the polyolefin separator limit the improvement of the safety performance of the lithium battery.
At present, surface modification of an existing polyolefin membrane becomes an important means for improving safety of a membrane, for example, an inorganic coating composite membrane, also called a ceramic composite membrane, is to coat inorganic particles with a certain thickness and high temperature resistance on the surface of a polyolefin membrane, such as PE or PP, serving as a support membrane to form a ceramic coating. The diaphragm with the ceramic coating has good thermal stability and mechanical performance, but the ceramic coating is too thick and hinders the conduction of lithium ions, and the aperture of the ceramic surface is small, so that the electrolyte is difficult to enter pores, the wetting speed of the diaphragm is slow, and the use efficiency is influenced.
Disclosure of Invention
In view of the above, the invention aims to provide a lithium ion battery diaphragm and a preparation method thereof, so as to solve the problems of poor wettability and poor performance of the existing ceramic coating diaphragm.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a preparation method of a lithium battery composite diaphragm comprises the following steps:
s1, dispersing the pretreated montmorillonite in a solvent, and uniformly stirring and dispersing to obtain montmorillonite dispersion liquid;
s2, taking the upper layer turbid liquid of the montmorillonite dispersion liquid, placing the upper layer turbid liquid in a centrifugal tube for centrifugal treatment to obtain montmorillonite nanosheets, placing the montmorillonite nanosheets in an alkaline solution for infiltration, then carrying out ice-bath ultrasonic treatment to prepare montmorillonite emulsion, and finally carrying out solid-liquid separation and drying to obtain montmorillonite powder;
s3, uniformly mixing the montmorillonite powder and an oil-based binder to form oil-based coating slurry;
and S4, coating the oil-based coating slurry on the surface of a lithium battery diaphragm, and drying to obtain the lithium battery composite diaphragm.
Optionally, the particle size of the pretreated montmorillonite is 600-1000 meshes.
Optionally, the solvent comprises one of N-methylpyrrolidone, isopropanol, water, ethanol, methanol, and N, N-dimethylformamide.
Optionally, in S2, the centrifugation conditions include a centrifuge rotation speed of 2000-12000rpm, a centrifugation time of 1-15min, the soaking time of 5-12h, and the sonication time of 1-3 h.
Optionally, the oil-based binder is a viscous solution of a binder dissolved in N-methyl pyrrolidone, the binder including one of polyvinylidene fluoride, polytetrafluoroethylene, and poly (vinylidene fluoride-co-hexafluoropropylene).
Optionally, in the oil-based coating slurry, the mass ratio of the montmorillonite powder to the binder is 10: (0.1-2).
Optionally, in S4, applying the oil-based coating slurry to the surface of the lithium battery separator includes: and coating the oil-based coating slurry on the surface of the lithium battery diaphragm at room temperature by using a coating machine, wherein the coating thickness is 1-5 mu m.
Optionally, in S4, the drying condition is a drying temperature of 25 ℃ to 60 ℃ and a drying time of 2 to 30 min.
Compared with the prior art, the preparation method of the lithium battery composite diaphragm provided by the invention has the following advantages:
(1) according to the invention, the structural performance and the coating mechanism of montmorillonite are utilized to effectively improve the transferability of lithium ions on the diaphragm, so that the prepared lithium battery composite diaphragm not only has good thermal stability, but also has excellent wetting performance and ultrahigh electrolyte liquid absorption rate and retention rate, thereby obviously improving the rate capability, the cycle stability under high rate and the coulombic efficiency of the lithium battery.
(2) The method provided by the invention has the advantages of simple process, environmental protection, low cost, easiness for large-scale production and certain commercial prospect.
The invention also aims to provide a lithium battery composite diaphragm to solve the problem of poor wettability of the existing ceramic coating diaphragm.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a lithium battery composite diaphragm is prepared by the preparation method of the lithium battery composite diaphragm.
Compared with the prior art, the lithium battery composite diaphragm and the preparation method of the lithium battery composite diaphragm have the same advantages, and are not repeated herein.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief description will be given below to the drawings required for the description of the embodiments or the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.
Fig. 1 is an SEM image of a lithium battery composite separator according to an embodiment of the present invention;
fig. 2 is a specific capacity-voltage curve of a 811 nickel cobalt manganese oxide lithium battery assembled by coating a Celgard 2400 thin-film material with the lithium battery composite diaphragm obtained in example 1, within a voltage range of 2.7-4.3V and under a 1C rate, for 1 turn, 5 turns, 10 turns and 20 turns respectively;
FIG. 3 is a curve of specific charge-discharge capacity and coulombic efficiency of a 811 Ni-Co-Mn acid lithium battery assembled by Celgard 2400 thin-film material coated with the composite diaphragm of the lithium battery obtained in example 1, circulating 20 times at 1C rate within a voltage range of 2.7-4.3V;
fig. 4 is a flowchart of a method for manufacturing a lithium battery composite separator according to an embodiment of the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with specific embodiments, the examples given are intended to illustrate the invention and are not intended to limit the scope of the invention. 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.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The terms "comprising," "including," "containing," and "having" are intended to be inclusive, i.e., that additional steps and other ingredients may be added without affecting the result.
Referring to fig. 4, an embodiment of the present invention provides a method for preparing a lithium battery composite separator, including the steps of:
s1, dispersing the pretreated montmorillonite in a solvent, and uniformly stirring and dispersing to obtain montmorillonite dispersion liquid;
s2, taking the upper turbid liquid of the montmorillonite dispersion liquid, placing the upper turbid liquid in a centrifugal tube for centrifugal treatment to obtain montmorillonite nanosheets, placing the montmorillonite nanosheets in an alkaline solution for infiltration, then carrying out ice-bath ultrasonic treatment to obtain montmorillonite emulsion, and finally carrying out solid-liquid separation and drying to obtain montmorillonite powder;
s3, uniformly mixing montmorillonite powder and an oil-based binder to form oil-based coating slurry;
and S4, coating the oil coating slurry on the surface of the lithium battery diaphragm, and drying to obtain the lithium battery composite diaphragm.
Montmorillonite material with molecular formula of Al2(Si2O5)(OH)4Is a clay mineral with a three-layer sheet structure consisting of tetrahedrons, in the crystal structureThe interlayer contains water and exchange cation, and has excellent stability and excellent lithium ion transmission performance. In the embodiment of the invention, the montmorillonite is a montmorillonite mineral and at least comprises one of montmorillonite, nontronite and beidellite.
Compared with the existing ceramic composite membrane, the nano-scale layered montmorillonite is loaded on the lithium ion battery diaphragm, so that direct contact between electrolyte materials and other harmful substances and the diaphragm can be avoided, the thickness of the diaphragm coating can be reduced, the conductivity of lithium ions can be improved, and exchange cations contained in the interlayer structure of the montmorillonite enable the prepared lithium battery composite diaphragm to have higher ion exchange capacity, the wettability of the diaphragm to electrolyte can be effectively improved, and the electrical performance of the lithium battery can be improved.
Specifically, step S1 includes: dispersing the pretreated montmorillonite in a solvent, stirring at the rotation speed of 100-1000rpm at room temperature for 5-8min, and performing ultrasonic dispersion to obtain montmorillonite dispersion liquid.
The solvent comprises one of N-methyl pyrrolidone, isopropanol, water, ethanol, methanol and N, N-dimethylformamide.
The preparation method of the pretreated montmorillonite comprises the following steps: the montmorillonite powder is primarily screened to obtain primarily refined montmorillonite powder with the particle size of 50-400 meshes, and then the primarily refined montmorillonite powder is subjected to high-energy ball milling refinement and screening to obtain the pretreated montmorillonite with the size of 600 meshes and 1000 meshes.
Step S2 specifically includes: placing the upper layer turbid liquid of the montmorillonite dispersion liquid in a centrifugal tube, carrying out centrifugal treatment for 1-15min at the rotating speed of 12000rpm of 2000-plus materials to obtain montmorillonite nanosheets, placing the montmorillonite nanosheets in 300g/L alkaline solution with the concentration of 100-plus materials for soaking for 5-12h, then carrying out ultrasonic treatment for 1-3h at the ultrasonic power of 450-plus materials of 1500KW and the ultrasonic frequency of 28-120kHZ, wherein the temperature of an ultrasonic groove is set at 0 ℃ to prepare montmorillonite emulsion, placing the montmorillonite emulsion in a centrifugal machine, carrying out centrifugal treatment for 1-15min at the rotating speed of 12000rpm of 2000-plus materials for carrying out solid-liquid separation, and finally drying the obtained solid to obtain montmorillonite powder.
The method comprises the steps of screening montmorillonite materials with proper particle sizes, treating with alkaline solution, carrying out ultrasonic grading treatment to obtain uniform micron-level layered montmorillonite materials, dispersing the micron-level layered montmorillonite materials in a solvent, taking upper-layer turbid emulsion, and carrying out high-speed centrifugation to obtain the nanoscale layered montmorillonite. When the micron-sized montmorillonite material is loaded on the diaphragm only by a coater, the coating is rough and uneven due to larger particle size, so that the heating is uneven in the drying process, and the coating material is pulverized and falls off. Compared with the micron-sized montmorillonite material, the nano-sized montmorillonite has more ordered and uniform interlayer stacking on the microstructure, is beneficial to rapid infiltration of electrolyte, and can obtain a uniform and stable coating when a coater is loaded on the diaphragm. By controlling the size of the montmorillonite loaded on the lithium ion battery diaphragm, the thickness of the coating is reduced, and the liquid absorption rate of the diaphragm to electrolyte can be enhanced.
Step S3 specifically includes: preparing an oil-based binder, and then uniformly mixing montmorillonite powder and the oil-based binder to form oil-based coating slurry; wherein the oil-based binder is a viscous solution obtained by dissolving the binder in N-methyl pyrrolidone, and the binder comprises one of polyvinylidene fluoride, polytetrafluoroethylene and poly (vinylidene fluoride-co-hexafluoropropylene). In the oil coating slurry, the mass ratio of the montmorillonite powder to the binder is 10: (0.1-2).
Step S4 specifically includes: and (4) uniformly coating the stable oil coating slurry prepared in the step (S3) on a lithium ion battery diaphragm by using a coating machine to obtain a wet layer diaphragm loaded with the nano-scale montmorillonite, and drying in vacuum for 2-30min at the temperature of 25-60 ℃ to obtain the lithium battery composite diaphragm. Wherein the coating thickness of the montmorillonite layer is 1-5 μm.
The lithium ion battery diaphragm comprises one of a Polyethylene (PE) diaphragm, a polypropylene (PP) diaphragm, a PP/PE composite diaphragm, a polyvinylidene fluoride diaphragm, a polyethylene terephthalate diaphragm, a polybutylene terephthalate diaphragm, a poly (vinylidene fluoride-co-hexafluoropropylene) diaphragm, a poly (vinylidene fluoride-co-trifluoroethylene) diaphragm, a polyester diaphragm, a polyimide diaphragm and a polyamide diaphragm.
Preferably, the lithium ion battery separator used in the embodiment of the present invention includes a polyethylene separator Celgard 2400 having a thickness of 25 to 28 μm.
The method comprises the steps of taking montmorillonite as a raw material, primarily sieving to obtain a primarily refined montmorillonite powder material, dispersing the montmorillonite powder material in a solvent, carrying out ultrasonic treatment, taking turbid liquid on the montmorillonite powder material, carrying out centrifugal treatment, further refining to obtain a montmorillonite nanosheet material, placing a centrifugal product in an alkaline solution, soaking a weak alkaline solution, fully embedding the montmorillonite powder material into montmorillonite interlayers, carrying out ice bath ultrasonic treatment, carrying out solid-liquid separation, drying, weighing a binder material according to a certain mass ratio, dissolving the binder material in an oil solvent, adding the dried montmorillonite nanosheet into a prepared binder, stirring, dispersing and coating the dried montmorillonite nanosheet on a polyethylene diaphragm, and carrying out vacuum drying to obtain the montmorillonite optimized lithium battery composite diaphragm nanosheet. The montmorillonite is used as a lithium battery diaphragm coating to coat the surface of the diaphragm, so that the side reaction of the diaphragm material and electrolyte can be prevented, and the circulation stability of the coating material is improved. In addition, the process provided by the invention is simple in process, green and environment-friendly, low in cost and easy for large-scale production, provides an effective and easy-to-industrialize approach for developing high-performance lithium batteries, and has a certain commercial prospect.
It can be understood that there are many different classification methods for the types of the binder, wherein the classification method is divided into oil-based binder and water-based binder according to the solvent used in preparing the membrane coating, the PVDF provided by the present invention is dissolved in an organic solvent, usually N-methyl pyrrolidone (NMP) is used as a solvent, and the binder prepared by the method is an oil-based binder, which has good pulping effect, strong binding property, and large peel strength of the active material.
The invention further provides a lithium battery composite diaphragm which is prepared by the preparation method of the lithium battery composite diaphragm.
The lithium battery composite diaphragm provided by the invention comprises a lithium ion battery diaphragm and nanoscale layered montmorillonite loaded on the diaphragm, and the interlayer structure of the montmorillonite is rich in exchange cations and has higher ion exchange capacity, so that the transferability of lithium ions on the diaphragm can be effectively improved; and secondly, the montmorillonite has the adsorbability, and is adhered to the lithium ion battery diaphragm by using an oil-based binder, so that the load stability is better, the liquid absorption rate of the diaphragm to electrolyte is increased, and the electrochemical performance of the lithium ion battery is finally improved.
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are examples of experimental procedures not specified under specific conditions, generally according to the conditions recommended by the manufacturer. Unless otherwise indicated, percentages and parts are by mass.
Example 1
The embodiment provides a preparation method of a lithium battery composite diaphragm, which comprises the following specific steps:
(1) placing 5.00g of ball-milled 800-mesh montmorillonite powder in 100ml (102.60g) of NMP (purity is more than 99.9%) solvent, stirring for 5min in a constant-temperature stirrer with the rotating speed of 2000rpm and the temperature of 25 ℃, and performing ultrasonic treatment to obtain montmorillonite dispersion liquid;
(2) taking the supernatant of the montmorillonite dispersion liquid, carrying out centrifugal treatment to obtain montmorillonite nanosheets with uniform sizes, putting the montmorillonite nanosheets into an alkaline solution for infiltration, fully embedding the montmorillonite nanosheets into montmorillonite interlayers after the montmorillonite nanosheets are infiltrated by a weak alkaline solution, carrying out ice-bath ultrasonic treatment, carrying out solid-liquid separation, and drying to obtain montmorillonite powder;
(3) dissolving 2.00g of polyvinylidene fluoride (PVDF) in 100ml of NMP solvent to prepare 20.00mg/ml of PVDF binder; 5ml of PVDF binder is taken by a liquid-moving gun, is dripped into 1.00g of montmorillonite powder and is uniformly mixed to form oil coating slurry;
(4) and (3) sucking 1ml of oil-based coating slurry by using a liquid transfer gun, dropping the oil-based coating slurry on the Celgard 2400 diaphragm, uniformly coating by using a 30-micron coating machine, placing the diaphragm in a vacuum drying oven at the temperature of 30 ℃, and drying for 0.5h at constant temperature to obtain the lithium battery composite diaphragm.
Fig. 1 is an SEM image of the lithium battery composite separator prepared in example 1, and it can be seen from fig. 1 that the lithium battery composite separator prepared in example 1 is stacked flat and uniformly dispersed layer by layer, each layer has a thickness of 30 to 50nm, and the total thickness of the surface coating is 1 to 5 μm. The invention has the advantages that the prepared lithium battery composite diaphragm is thinner than the existing coating, the thickness of the lithium battery diaphragm can be reduced, and the transmission speed of lithium ions is improved.
In order to test the performance of the montmorillonite modified lithium battery diaphragm prepared in the embodiment 1 of the invention on a lithium battery, the montmorillonite modified lithium battery diaphragm is assembled into a 811 nickel cobalt lithium manganate battery, and a performance test is carried out.
Fig. 2 is a specific capacity-voltage curve of a 811 nickel cobalt manganese oxide lithium battery assembled by coating a Celgard 2400 thin-film material with the lithium battery composite diaphragm obtained in example 1, within a voltage range of 2.7-4.3V and under a 1C rate, at 1 turn, 5 turns, 10 turns and 20 turns respectively. As can be seen from FIG. 2, the voltage platform is stable during charging and discharging of the lithium battery, and after 20 cycles, the capacity retention ratio is 87%.
FIG. 3 is a curve of specific charge-discharge capacity and coulombic efficiency of a 811 Ni-Co-Mn acid lithium battery assembled by Celgard 2400 thin-film material coated with the composite diaphragm of the lithium battery obtained in example 1, circulating 20 times at 1C rate within a voltage range of 2.7-4.3V; it can be seen that the first coulombic efficiency is 87% at the 1C rate, the first specific discharge capacity is 143.82mAh/g, the charge-discharge specific capacity is stabilized at 130mAh/g from the 2 nd cycle, and the coulombic efficiency is stabilized at more than 99%.
The tests show that the lithium battery composite diaphragm prepared by the embodiment of the invention has excellent wetting performance and ultrahigh electrolyte liquid absorption rate, and can remarkably improve the rate capability, the cycle stability under high rate and the coulombic efficiency of the lithium battery.
Example 2
This example provides a method for preparing a lithium battery composite separator, which is different from example 1 in that:
in the step (3), 2.00g of Polytetrafluoroethylene (PTFE) is dissolved in 100ml of NMP solvent to prepare 20.00mg/ml of PTFE adhesive; taking 5ml of PTFE adhesive by using a liquid-transferring gun, dropwise adding the PTFE adhesive into 1.00g of montmorillonite powder, and uniformly mixing to form oil-based coating slurry;
the other steps and parameters were the same as in example 1.
Example 3
This example provides a method for preparing a lithium battery composite separator, which is different from example 1 in that:
in the step (3), 2.00g of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is dissolved in 100ml of NMP solvent to prepare 20.00mg/ml of PVDF-HFP binder; 5ml of PVDF-HFP binder is taken by a liquid-transferring gun and is dripped into 1.00g of montmorillonite powder, and the mixture is uniformly mixed to form oil coating slurry;
the other steps and parameters were the same as in example 1.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (9)
1. A preparation method of a lithium battery composite diaphragm is characterized by comprising the following steps:
s1, dispersing the pretreated montmorillonite in a solvent, and uniformly stirring and dispersing to obtain montmorillonite dispersion liquid;
s2, taking the upper layer turbid liquid of the montmorillonite dispersion liquid, placing the upper layer turbid liquid in a centrifugal tube for centrifugal treatment to obtain montmorillonite nanosheets, placing the montmorillonite nanosheets in an alkaline solution for infiltration, then carrying out ice-bath ultrasonic treatment to prepare montmorillonite emulsion, and finally carrying out solid-liquid separation and drying to obtain montmorillonite powder;
s3, uniformly mixing the montmorillonite powder and an oil-based binder to form oil-based coating slurry;
and S4, coating the oil-based coating slurry on the surface of a lithium battery diaphragm, and drying to obtain the lithium battery composite diaphragm.
2. The method for preparing the composite separator for the lithium battery as claimed in claim 1, wherein the particle size of the pretreated montmorillonite is 600-1000 meshes.
3. The method of claim 2, wherein in S1, the solvent comprises one of N-methylpyrrolidone, isopropanol, water, ethanol, methanol, and N, N-dimethylformamide.
4. The method for preparing the lithium battery composite diaphragm as recited in any one of claims 1 to 3, wherein in S2, the centrifugation treatment conditions are that the rotation speed of a centrifuge is 2000-12000rpm, the centrifugation time is 1-15min, the soaking time is 5-12h, and the ultrasonic treatment time is 1-3 h.
5. The method for manufacturing a composite separator for a lithium battery according to any one of claims 1 to 3, wherein the oil-based binder is a viscous solution obtained by dissolving a binder in N-methylpyrrolidone, and the binder includes one of polyvinylidene fluoride, polytetrafluoroethylene, and poly (vinylidene fluoride-co-hexafluoropropylene).
6. The method for preparing a lithium battery composite separator according to claim 5, wherein the mass ratio of the montmorillonite powder to the binder in the oil-based coating slurry is 10: (0.1-2).
7. The method for preparing a lithium battery composite separator according to claim 1, wherein the step of applying the oil-based coating paste to the surface of the lithium battery separator in S4 includes: and coating the oil-based coating slurry on the surface of the lithium battery diaphragm at room temperature by using a coating machine, wherein the coating thickness is 1-5 mu m.
8. The method for preparing the lithium battery composite separator according to claim 7, wherein the drying condition in S4 is a drying temperature of 25 ℃ to 60 ℃ and a drying time of 2 to 30 min.
9. A lithium battery composite separator characterized by being produced by the method for producing a lithium battery composite separator according to any one of claims 1 to 8.
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