CN113948767B - Preparation method of safe lithium battery electrolyte containing microcapsule and lithium battery - Google Patents
Preparation method of safe lithium battery electrolyte containing microcapsule and lithium battery Download PDFInfo
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- CN113948767B CN113948767B CN202111217870.0A CN202111217870A CN113948767B CN 113948767 B CN113948767 B CN 113948767B CN 202111217870 A CN202111217870 A CN 202111217870A CN 113948767 B CN113948767 B CN 113948767B
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- 239000003094 microcapsule Substances 0.000 title claims abstract description 116
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 104
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 103
- 239000003792 electrolyte Substances 0.000 title claims abstract description 88
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 229920001807 Urea-formaldehyde Polymers 0.000 claims abstract description 24
- 238000000034 method Methods 0.000 claims abstract description 13
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 27
- 238000003756 stirring Methods 0.000 claims description 24
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 16
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 16
- GZCGUPFRVQAUEE-SLPGGIOYSA-N aldehydo-D-glucose Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C=O GZCGUPFRVQAUEE-SLPGGIOYSA-N 0.000 claims description 16
- 239000004202 carbamide Substances 0.000 claims description 16
- QQZOPKMRPOGIEB-UHFFFAOYSA-N 2-Oxohexane Chemical class CCCCC(C)=O QQZOPKMRPOGIEB-UHFFFAOYSA-N 0.000 claims description 13
- 229920000877 Melamine resin Polymers 0.000 claims description 13
- 238000001035 drying Methods 0.000 claims description 13
- WVSNNWIIMPNRDB-UHFFFAOYSA-N 1,1,1,3,3,4,4,5,5,6,6,6-dodecafluorohexan-2-one Chemical compound FC(F)(F)C(=O)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F WVSNNWIIMPNRDB-UHFFFAOYSA-N 0.000 claims description 12
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 10
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims description 10
- 239000000243 solution Substances 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 9
- 101150058243 Lipf gene Proteins 0.000 claims description 8
- 239000007864 aqueous solution Substances 0.000 claims description 8
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims description 8
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 claims description 8
- 230000001502 supplementing effect Effects 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 8
- 229910013870 LiPF 6 Inorganic materials 0.000 claims description 7
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 7
- 239000002131 composite material Substances 0.000 claims description 7
- 239000007788 liquid Substances 0.000 claims description 7
- 229910016722 Ni0.5Co0.2Mn0.3 Inorganic materials 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- 239000004698 Polyethylene Substances 0.000 claims description 5
- 229920000573 polyethylene Polymers 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 4
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims description 4
- 238000007865 diluting Methods 0.000 claims description 4
- 239000012153 distilled water Substances 0.000 claims description 4
- 230000001804 emulsifying effect Effects 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 229910001416 lithium ion Inorganic materials 0.000 claims description 4
- 239000006228 supernatant Substances 0.000 claims description 4
- 229910013872 LiPF Inorganic materials 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 239000012528 membrane Substances 0.000 claims 1
- 238000011031 large-scale manufacturing process Methods 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 12
- 239000000463 material Substances 0.000 description 7
- 239000011358 absorbing material Substances 0.000 description 6
- 239000002775 capsule Substances 0.000 description 6
- 238000001816 cooling Methods 0.000 description 6
- 238000006116 polymerization reaction Methods 0.000 description 6
- 238000000354 decomposition reaction Methods 0.000 description 5
- 238000004880 explosion Methods 0.000 description 5
- 239000012782 phase change material Substances 0.000 description 4
- IDBYQQQHBYGLEQ-UHFFFAOYSA-N 1,1,2,2,3,3,4-heptafluorocyclopentane Chemical compound FC1CC(F)(F)C(F)(F)C1(F)F IDBYQQQHBYGLEQ-UHFFFAOYSA-N 0.000 description 3
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 239000011162 core material Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000003063 flame retardant Substances 0.000 description 3
- 125000001153 fluoro group Chemical class F* 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 238000011065 in-situ storage Methods 0.000 description 3
- -1 melamine modified urea formaldehyde resin Chemical class 0.000 description 3
- 239000007784 solid electrolyte Substances 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 229910016739 Ni0.5Co0.2Mn0.3(OH)2 Inorganic materials 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000013068 control sample Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- HANVTCGOAROXMV-UHFFFAOYSA-N formaldehyde;1,3,5-triazine-2,4,6-triamine;urea Chemical compound O=C.NC(N)=O.NC1=NC(N)=NC(N)=N1 HANVTCGOAROXMV-UHFFFAOYSA-N 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002641 lithium Chemical class 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 1
- 238000000879 optical micrograph Methods 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000004094 surface-active agent Substances 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
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
-
- 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
-
- 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)
- Electrochemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Dispersion Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The invention relates to the technical field of lithium batteries, and discloses a preparation method of a safe lithium battery electrolyte containing a microcapsule body and a lithium battery thereof, wherein the preparation method comprises the following steps: s1) preparing a water-soluble urea resin prepolymer; s2) preparing microcapsules containing wrapping films; s3) preparing a microcapsule; s4) preparing the safe lithium battery electrolyte containing the microcapsule; the safe lithium battery electrolyte containing the microcapsule is simple and efficient in process, high in practicability, low in replacement cost and suitable for large-scale production of lithium batteries; the lithium battery prepared by the electrolyte prepared by the preparation method provided by the invention can effectively inhibit potential safety hazards in the lithium battery when the lithium battery contains the microcapsule body and is in thermal runaway.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a preparation method of a safe lithium battery electrolyte containing microcapsule bodies and a lithium battery thereof.
Background
The lithium battery is a new energy source for energy storage, which is widely popularized at present, has the advantages of high working voltage, large specific energy, high energy utilization rate, long cycle life and the like, and is widely applied to the fields of portable electronic equipment, electric automobiles, energy storage systems and the like.
When the lithium battery is in thermal runaway, the electrolyte can undergo decomposition reaction when the temperature rises continuously, so that a large amount of combustible gas is generated, and combustion explosion is further initiated.
The solution scheme in the prior art is that a solvent with high thermal stability is selected as an electrolyte solvent to be used, and a flame retardant is added into the electrolyte to further improve the flame retardant property of the electrolyte. These solutions belong to passive protection strategies, only the heat resistance of the lithium battery can be improved, but the thermal runaway of the lithium battery cannot be ensured not to be further deteriorated, and the occurrence of combustion explosion is stopped. And the flame retardant additive can affect the electrochemical performance of the lithium battery, and the cost of the electrolyte solvent with high thermal stability is high.
Disclosure of Invention
Based on the prior art defects, the invention provides a preparation method of a safe lithium battery electrolyte containing microcapsule bodies, wherein the microcapsule bodies contained in the electrolyte can inhibit thermal runaway of a lithium battery, so that the internal structure of the battery can be prevented from being damaged, and fire or explosion accidents of a battery system are avoided.
Another object of the present invention is to provide a lithium battery prepared using the electrolyte obtained by the above-mentioned preparation method, the prepared lithium battery having a function of suppressing deterioration of thermal runaway.
To achieve the purpose, the invention adopts the following technical scheme:
the preparation method of the safe lithium battery electrolyte containing the microcapsule comprises the following steps:
s1) adding formaldehyde into urea, stirring until urea particles are completely dissolved, adjusting the pH value of a system, adding melamine, and reacting for 1h at 60-70 ℃ under the stirring condition of 400rpm to prepare a water-soluble urea-formaldehyde resin prepolymer;
s2) adding the water-soluble urea-formaldehyde resin prepolymer into a sodium dodecyl benzene sulfonate aqueous solution, diluting and stirring, then adding a perfluorinated hexanone liquid, stirring and emulsifying for 30min, then stirring at 45-55 ℃ and dropwise adding a sulfuric acid solution with the concentration of 1%, acidifying and adjusting the pH value of a system, heating to 55-65 ℃, adding a small amount of distilled water, solidifying for 2h, washing, standing, and removing supernatant to obtain microcapsules containing wrapping films;
s3) supplementing the water-soluble urea resin prepolymer to the microcapsule containing the wrapping film, repeating the steps for 2-3 times according to the step S2) to obtain a microcapsule containing a multi-layer wrapping film, washing the microcapsule containing the multi-layer wrapping film with acetone, filtering, and drying to obtain a microcapsule body;
s4) LiPF commercially available 6 Concentration is 1mol/l, volume concentration ratio of EC and DMC is l: liPF of l 6 Adding the microcapsule into EC+DMC commercial electrolyte, and supplementing LiPF 6 The safe lithium battery electrolyte containing the microcapsule is prepared by keeping the concentration of lithium ions in the electrolyte at a constant value of 1 mol/l.
Preferably, in step S1), the mixing mass ratio of urea and formaldehyde is 1:2, and the mass ratio of melamine added to urea is 0.05:1.
Preferably, in step S1), the solvent used for adjusting the pH is triethanolamine, and the pH of the solution is 7-8.
Preferably, in step S2), the stirring speed is 600r/min and the pH value is 2-3.
Preferably, in the step S2), the mass concentration of the perfluoro-hexanone in the aqueous solution is 0.8-1g/ml, the mass concentration of the sodium dodecyl benzene sulfonate is 0.4-0.5wt%, and the mass concentration of the water-soluble urea resin prepolymer is 2-2.5g/ml.
Preferably, in the step S3), the mass concentration of the additionally added water-soluble urea resin prepolymer is 1-1.5g/ml.
Preferably, in step S3), the drying temperature is 60℃and the drying time is 12 hours.
Preferably, in step S4), the mass of the microcapsule added is LiPF 6 15-40% of the mass of the EC+DMC commercial electrolyte.
Furthermore, the invention also provides a lithium battery using the safe lithium battery electrolyte prepared by the preparation method of the safe lithium battery electrolyte containing the microcapsule, which comprises a Ni0.5Co0.2Mn0.3 positive electrode and an artificial graphite negative electrode, wherein the electrolyte is the safe lithium battery electrolyte containing the microcapsule, the Ni0.5Co0.2Mn0.3 positive electrode and the artificial graphite negative electrode are separated by a polypropylene-polyethylene composite diaphragm, the rupture temperature of a film layer of the microcapsule is 120+/-5 ℃, and the particle size of the microcapsule is 5-10 mu m.
The technical scheme of the invention has the beneficial effects that: the preparation method of the safe lithium battery electrolyte containing the microcapsule body adopts an in-situ polymerization method, takes low-melting-point liquid perfluorinated hexanone as a capsule core material, takes melamine modified urea formaldehyde resin as a capsule wall material and sulfuric acid as a catalyst, prepares perfluorinated hexanone/MUF microcapsules, and forms the microcapsule body through multiple packages; the microcapsule is coated with heat absorbing phase change material (fluorine derivative, such as perfluoro-hexanone or heptafluorocyclopentane), and in the initial stage of thermal runaway of lithium battery, the electrolyte is decomposed when the temperature rises above 150 ℃ due to the decomposition of SEI solid electrolyte interface film, and then the diaphragm in the electrolyte is melted.
Furthermore, the invention provides the lithium battery using the safe lithium battery electrolyte containing the microcapsule, when the prepared lithium battery is in thermal runaway, the composite diaphragm contained in the lithium battery can be broken at 120+/-5 ℃ and release the heat absorbing material, the lithium battery has a good active cooling protection function, potential safety hazards in the lithium battery can be effectively restrained, the process is simple and efficient, the practicability is strong, the replacement cost of the electrolyte is low, and the lithium battery is suitable for mass production of the lithium battery.
Drawings
FIG. 1 is an optical micrograph of a microcapsule body of an embodiment of the present invention;
FIG. 2 is a scanning electron micrograph of the microcapsule body of FIG. 1;
fig. 3 is a schematic view showing the structure of a lithium battery containing a safe lithium battery electrolyte using a microcapsule containing body according to an embodiment of the present invention;
FIG. 4 is a photograph of a sample of a flexible package lithium battery using a safe lithium battery electrolyte containing microcapsules;
fig. 5 is a thermal runaway test chart of a flexible package lithium battery using a safe lithium battery electrolyte containing microcapsules and a lithium battery using a commercially available commercial electrolyte according to an embodiment of the present invention.
Detailed Description
In the description herein, reference to the term "embodiment," "example," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
The technical scheme of the invention is further described below with reference to the specific embodiments.
The preparation method of the safe lithium battery electrolyte containing the microcapsule comprises the following steps:
s1) adding formaldehyde into urea, stirring until urea particles are completely dissolved, adjusting the pH value of a system, adding melamine, and reacting for 1h at 60-70 ℃ under the stirring condition of 400rpm to prepare a water-soluble urea-formaldehyde resin prepolymer;
s2) adding the water-soluble urea-formaldehyde resin prepolymer into a sodium dodecyl benzene sulfonate aqueous solution, diluting and stirring, then adding a perfluorinated hexanone liquid, stirring and emulsifying for 30min, then stirring at 45-55 ℃ and dropwise adding a sulfuric acid solution with the concentration of 1%, acidifying and adjusting the pH value of a system, heating to 55-65 ℃, adding a small amount of distilled water, solidifying for 2h, washing, standing, and removing supernatant to obtain microcapsules containing wrapping films;
s3) supplementing the water-soluble urea resin prepolymer to the microcapsule containing the wrapping film, repeating the steps for 2-3 times according to the step S2) to obtain a microcapsule containing a multi-layer wrapping film, washing the microcapsule containing the multi-layer wrapping film with acetone, filtering, and drying to obtain a microcapsule body;
s4) LiPF commercially available 6 Concentration is 1mol/l, volume concentration ratio of EC and DMC is l: liPF of l 6 Adding the microcapsule into EC+DMC commercial electrolyte, and supplementing LiPF 6 The safe lithium battery electrolyte containing the microcapsule is prepared by keeping the concentration of lithium ions in the electrolyte at a constant value of 1 mol/l.
The preparation method of the safe lithium battery electrolyte containing the microcapsule body adopts an in-situ polymerization method, takes low-melting-point liquid perfluorinated hexanone as a capsule core material, takes melamine modified urea formaldehyde resin as a capsule wall material and sulfuric acid as a catalyst, prepares perfluorinated hexanone/MUF microcapsules, and forms the microcapsule body through multiple wrapping; the microcapsule is coated with heat absorbing phase change material (fluorine derivative, such as perfluoro-hexanone or heptafluorocyclopentane), and in the initial stage of thermal runaway of lithium battery, the electrolyte is decomposed when the temperature rises above 150 ℃ due to the decomposition of SEI solid electrolyte interface film, and then the diaphragm in the electrolyte is melted. Therefore, when the lithium battery using the microcapsule-containing safe lithium battery electrolyte is in thermal runaway, the microcapsule contained therein can crack and release the heat absorbing material, has a good active cooling protection function, can effectively inhibit potential safety hazards in the lithium battery, prevents open fire or explosion during the thermal runaway of the lithium battery, and provides a new solution for safe application of the lithium battery and replacement of the electrolyte.
Preferably, in step S1), the mixing mass ratio of urea and formaldehyde is 1:2, and the mass ratio of melamine added to urea is 0.05:1.
Urea, melamine and formaldehyde are polymerized to form urea formaldehyde resin, and the melamine contained in the modified urea formaldehyde resin can effectively reduce the content of free formaldehyde, so that the electrolyte has better use safety.
Preferably, in step S1), the solvent used for adjusting the pH is triethanolamine, and the pH of the solution is 7-8.
In alkaline environment, the polymerization efficiency of urea, melamine and formaldehyde is higher.
Preferably, in step S2), the stirring speed is 600r/min and the pH value is 2-3.
The microcapsule coating is required to be completed in an acidic environment, the pH value is proper to be 2-3, the pH value is too high or too low, and the coating layer of the microcapsule cannot be formed.
Stirring at a medium speed of 600r/min in an acidic environment, and adding sulfuric acid for catalysis can improve the efficiency of film formation of the prepolymer and coating of the perfluorinated hexanone.
Preferably, in the step S2), the mass concentration of the perfluoro-hexanone in the aqueous solution is 0.8-1g/ml, the mass concentration of the sodium dodecyl benzene sulfonate is 0.4-0.5wt%, and the mass concentration of the water-soluble urea resin prepolymer is 2-2.5g/ml.
The sodium dodecyl benzene sulfonate is used as a surfactant, so that the perfluoro-hexanone in the aqueous solution can be dispersed more uniformly, the concentration of the perfluoro-hexanone wrapped by each microcapsule formed by the urea-formaldehyde resin film is close, and further, the relatively consistent temperature resistance is formed, and the perfluoro-hexanone released after the microcapsule is broken has the same cooling effect.
Preferably, in the step S3), the mass concentration of the additionally added water-soluble urea resin prepolymer is 1-1.5g/ml.
During the repeated wrapping and film forming of step S3), the water-soluble urea-formaldehyde resin prepolymer is replenished about half the total amount of the water-soluble urea-formaldehyde resin prepolymer added for the first time so as to maintain a higher concentration of the urea-formaldehyde resin prepolymer contained.
In the repeated wrapping and film forming processes, a second film layer and a third film layer are formed, and the heat absorbing phase change material perfluorinated hexanone is wrapped between the second film layer and the third film layer, so that the cooling performance of the microcapsule is further improved.
Preferably, in step S3), the drying temperature is 60℃and the drying time is 12 hours.
The microcapsule body is cleaned by acetone, so that the microcapsule body obtained by drying does not contain acidic substances or other impurities, and the microcapsule body is prevented from generating chemical reaction with other substances in electrolyte to damage the performance of the lithium battery when the microcapsule body is used for the lithium battery.
Drying at 60deg.C for 12 hr can completely remove water on the surface of microcapsule, such as microcapsule deformation caused by temperature higher than 65deg.C, and incomplete removal due to low drying efficiency.
Preferably, in step S4), the mass of the microcapsule added is LiPF 6 15-40% of the mass of the EC+DMC commercial electrolyte.
When the content of the added microcapsule is less than 15wt%, the total amount of the heat absorbing material perfluoro-hexanone released by the microcapsule is less, and the cooling effect is insufficient, so that the thermal runaway temperature of the lithium battery still continues to rise; when the amount of the microcapsule exceeds 40wt%, the fluidity and workability of the electrolyte are affected by an excessively high proportion of the microcapsule.
Furthermore, the invention also provides a lithium battery using the safe lithium battery electrolyte prepared by the preparation method of the safe lithium battery electrolyte containing the microcapsule, which comprises a Ni0.5Co0.2Mn0.3 positive electrode and an artificial graphite negative electrode, wherein the electrolyte is the safe lithium battery electrolyte containing the microcapsule, the Ni0.5Co0.2Mn0.3 positive electrode and the artificial graphite negative electrode are separated by a polypropylene-polyethylene composite diaphragm, the rupture temperature of a film layer of the microcapsule is 120+/-5 ℃, and the particle size of the microcapsule is 5-10 mu m.
Lithium battery using the above-described safe lithium battery electrolyte containing microcapsules, liPF 6 When the temperature of the electrolyte rises to 120+/-5 ℃, the urea-melamine-formaldehyde polymerization film layer in the microcapsule body breaks, the heat absorbing material perfluoro hexanone wrapped by the polymerization film layer is released into the electrolyte, and the temperature of the electrolyte is rapidly reduced, so that the lithium battery of the safety lithium battery electrolyte containing the microcapsule body is prevented from firing or even exploding due to overheating.
In the embodiment of the present invention shown in the electron microscope scanning plan view of fig. 2, the microcapsule bodies are contained with a particle size of 5-10 μm.
Examples
1. The preparation of the microcapsule of this example and the assembly of the lithium battery were performed according to the following steps:
s1) adding 2000g of formaldehyde into 1000g of urea, stirring until urea particles are completely dissolved, regulating the pH value of a system to 7.6 by using triethanolamine, adding 50g of melamine, and stirring at 400rpm for reaction for 1h at 70 ℃ to obtain a water-soluble urea-formaldehyde resin prepolymer.
S2) adding 110g of the water-soluble urea formaldehyde resin prepolymer into 500ml of sodium dodecyl benzene sulfonate aqueous solution with the mass concentration of 0.5%, diluting and stirring, then adding 50g of perfluorinated hexanone liquid, stirring and emulsifying for 30min, then stirring at 45 ℃ at 600rpm, dropwise adding sulfuric acid solution with the concentration of 1%, acidifying and adjusting the pH value of the system to 2.8, then heating to 55 ℃, adding a small amount of distilled water, solidifying for 2h, washing, standing, pouring out supernatant fluid, and obtaining the microcapsule containing the wrapping film.
S3) supplementing 55g of the water-soluble urea-formaldehyde resin prepolymer to the microcapsule containing the wrapping film, repeating the step S2) for 2-3 times to prepare the microcapsule containing the multilayer wrapping film, washing the microcapsule with acetone, filtering, and drying at 60 ℃ for 12 hours to prepare a microcapsule body.
S4) at a commercially available LiPF6 concentration of 1mol/l, the volume concentration ratio of EC to DMC of l: liPF of l 6 Adding the microcapsule with the mass accounting for 30 percent of the mass of the commercial electrolyte into the EC+DMC commercial electrolyte, and supplementing and adding LiPF 6 The safe lithium battery electrolyte containing the microcapsule is prepared by keeping the concentration of lithium ions in the electrolyte at a constant value of 1 mol/l.
S5) lithium battery assembly: ni0.5Co0.2Mn0.3 (OH) 2 And taking artificial graphite as a negative electrode, adding the safe lithium battery electrolyte containing the microcapsule, and separating the positive electrode from the negative electrode by using a polypropylene-polyethylene composite diaphragm to assemble the aluminum foil film flexible package sealed lithium battery.
2. The microcapsule body obtained in the step S3) is observed by an optical microscope, a physical photo in the microscope is shown in figure 1, and the microcapsule body obtained by the optical microscope has a relatively standard spherical structure, and the particle size of the microcapsule body is measured to be 5-10 mu m.
3. And (3) observing the microcapsule body prepared in the step (S3) by adopting a scanning electron microscope, wherein a picture of the scanning electron microscope is shown in fig. 2, the microcapsule body is relatively distributed according to the picture, and the defect that the performance of a diaphragm is influenced by an interface gap and the like is avoided.
4. The lithium battery physical photo sealed by the aluminum foil film flexible package prepared in the step S5) is shown in a figure 4, the internal structure is shown in a schematic diagram of figure 3, the electrode on the left side in the figure is a positive electrode, the electrode on the right side in the figure is a graphite electrode, a diaphragm is arranged in the middle of the electrode, electrolyte is filled between the two sides of the diaphragm and the electrode, and the microcapsule prepared in the step S3) is distributed in the electrolyte.
5. Taking the aluminum foil film flexible package lithium battery assembled in the step S5) as a detection sample, and taking the same packaged flexible package lithium battery using the commercial electrolyte without the microcapsule body as a control sample, performing a thermal runaway test to verify the reliability of the lithium battery, wherein the result is shown in fig. 5. The solid line in the figure represents the temperature-time change curve of the flexible package lithium battery of the commercial electrolyte without the microcapsule, the dotted line represents the temperature-time change curve of the flexible package lithium battery of the safe lithium battery electrolyte with the microcapsule prepared by the invention, and the solid line and the dotted line in the figure show that when the temperature of the battery reaches 85 ℃, the polypropylene-polyethylene composite diaphragm is melted and decomposed, the anode and the cathode in the battery are short-circuited, a large amount of heat is instantaneously generated, so that the temperature in the battery is rapidly increased, the battery is exploded by fire, and the temperature is rapidly increased to 700 ℃, as shown by the crest curve of the surrounding area II in the figure. When the temperature of the battery reaches 120 ℃, the microcapsule body can be automatically broken to release the perfluorinated hexanone, so that the heat in the battery is instantaneously absorbed, and the battery is cooled down, therefore, the temperature curve is not increased, but is rapidly reduced, and the battery is rapidly cooled to room temperature to form a horizontal straight line, no fire occurs in the battery, and no explosion occurs. The safe lithium battery electrolyte containing the microcapsule body is provided with the heat absorbing material of perfluoro hexanone which is broken and released at 120-130 ℃, so that a large amount of heat in the electrolyte can be rapidly absorbed, further deterioration of thermal runaway is prevented, decomposition of the electrolyte and melting of a diaphragm can be avoided, the effect is obvious, and the reliability is high.
In summary, the preparation method of the safe lithium battery electrolyte containing the microcapsule body adopts an in-situ polymerization method, takes low-melting-point liquid perfluorinated hexanone as a capsule core material, takes melamine modified urea formaldehyde resin as a capsule wall material and sulfuric acid as a catalyst, prepares perfluorinated hexanone/MUF microcapsules, and forms the microcapsule body through multiple wrapping; the microcapsule is coated with heat absorbing phase change material (fluorine derivative, such as perfluoro-hexanone or heptafluorocyclopentane), and in the initial stage of thermal runaway of lithium battery, the electrolyte is decomposed when the temperature rises above 150 ℃ due to the decomposition of SEI solid electrolyte interface film, and then the diaphragm in the electrolyte is melted.
Furthermore, the invention provides the lithium battery using the safe lithium battery electrolyte containing the microcapsule, when the prepared lithium battery is in thermal runaway, the composite diaphragm contained in the lithium battery can be broken at 120+/-5 ℃ and release the heat absorbing material, the lithium battery has a good active cooling protection function, potential safety hazards in the lithium battery can be effectively restrained, the process is simple and efficient, the practicability is strong, the replacement cost of the electrolyte is low, and the lithium battery is suitable for mass production of the lithium battery.
In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
The technical principle of the present invention is described above in connection with the specific embodiments. These descriptions are meant only to illustrate the principles of the invention; and should not be construed as limiting the scope of the invention in any way. Based on the explanation herein; other embodiments of the present invention will occur to those skilled in the art without the need for inventive effort; all of which fall within the scope of the present invention.
Claims (8)
1. The preparation method of the safe lithium battery electrolyte containing the microcapsule is characterized by comprising the following steps of:
s1) adding formaldehyde into urea, stirring until urea particles are completely dissolved, adjusting the pH value of a system, adding melamine, and reacting for 1h at 60-70 ℃ under the stirring condition of 400rpm to prepare a water-soluble urea-formaldehyde resin prepolymer;
s2) adding the water-soluble urea-formaldehyde resin prepolymer into a sodium dodecyl benzene sulfonate aqueous solution, diluting and stirring, then adding a perfluorinated hexanone liquid, stirring and emulsifying for 30min, then stirring at 45-55 ℃ and dropwise adding a sulfuric acid solution with the concentration of 1%, acidifying and adjusting the pH value of a system, heating to 55-65 ℃, adding a small amount of distilled water, solidifying for 2h, washing, standing, and removing supernatant to obtain microcapsules containing wrapping films;
s3) supplementing the water-soluble urea resin prepolymer to the microcapsule containing the wrapping film, repeating the steps for 2-3 times according to the step S2) to obtain a microcapsule containing a multi-layer wrapping film, washing the microcapsule containing the multi-layer wrapping film with acetone, filtering, and drying to obtain a microcapsule body;
s4) LiPF commercially available 6 Concentration is 1mol/l, volume concentration ratio of EC and DMC is l: liPF of l 6 Adding the microcapsule into EC+DMC commercial electrolyte, and supplementing LiPF 6 The concentration of lithium ions in the electrolyte is kept at a constant value of 1mol/l, so that the safe lithium battery electrolyte containing the microcapsule is prepared;
in the step S1), the mixing mass ratio of urea to formaldehyde is 1:2, and the mass ratio of added melamine to urea is 0.05:1;
the rupture temperature of the film layer of the microcapsule body is 120+/-5 ℃.
2. The method for preparing a safe lithium battery electrolyte containing a microcapsule according to claim 1, wherein in the step S1), the solvent for adjusting pH is triethanolamine, and the pH of the solution is 7-8.
3. The method for preparing a safe lithium battery electrolyte containing a microcapsule according to claim 1, wherein in the step S2), the stirring speed is 600r/min and the pH value is 2-3.
4. The method for preparing a microcapsule-containing safe lithium battery electrolyte according to claim 1, wherein in step S2), the mass concentration of the perfluoro hexanone in the aqueous solution is 0.8-1g/ml, the mass concentration of the sodium dodecyl benzene sulfonate is 0.4-0.5wt%, and the mass concentration of the water-soluble urea resin prepolymer is 2-2.5g/ml.
5. The method for preparing a safe lithium battery electrolyte containing a microcapsule according to claim 1, wherein in the step S3), the mass concentration of the supplementary water-soluble urea-formaldehyde resin prepolymer is 1-1.5g/ml.
6. The method for preparing a safe lithium battery electrolyte containing a microcapsule according to claim 1, wherein in the step S3), the drying temperature is 60 ℃ and the drying time is 12 hours.
7. The method for preparing a safe lithium battery electrolyte containing a microcapsule according to claim 1, wherein in step S4), the mass of the microcapsule added is LiPF 6 15-40% of the mass of the EC+DMC commercial electrolyte.
8. A lithium battery using the safety lithium battery electrolyte prepared by the preparation method of the safety lithium battery electrolyte containing the microcapsule according to any one of claims 1-7, wherein the lithium battery comprises a Ni0.5Co0.2Mn0.3 positive electrode and an artificial graphite negative electrode, the electrolyte is the safety lithium battery electrolyte containing the microcapsule, a polypropylene-polyethylene composite membrane is arranged between the Ni0.5Co0.2Mn0.3 positive electrode and the artificial graphite negative electrode, and the particle size of the microcapsule is 5-10 μm.
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