CN118459671A - Polymer microsphere, preparation method thereof and lithium ion battery diaphragm - Google Patents
Polymer microsphere, preparation method thereof and lithium ion battery diaphragm Download PDFInfo
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- CN118459671A CN118459671A CN202410478694.3A CN202410478694A CN118459671A CN 118459671 A CN118459671 A CN 118459671A CN 202410478694 A CN202410478694 A CN 202410478694A CN 118459671 A CN118459671 A CN 118459671A
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- 239000004005 microsphere Substances 0.000 title claims abstract description 173
- 229920000642 polymer Polymers 0.000 title claims abstract description 101
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 20
- 238000002360 preparation method Methods 0.000 title abstract description 10
- 238000000034 method Methods 0.000 claims abstract description 36
- 230000009477 glass transition Effects 0.000 claims abstract description 25
- 230000008569 process Effects 0.000 claims abstract description 16
- 238000001035 drying Methods 0.000 claims description 52
- 239000000178 monomer Substances 0.000 claims description 41
- 238000000889 atomisation Methods 0.000 claims description 40
- 239000000839 emulsion Substances 0.000 claims description 28
- 238000006243 chemical reaction Methods 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 claims description 15
- CQEYYJKEWSMYFG-UHFFFAOYSA-N butyl acrylate Chemical compound CCCCOC(=O)C=C CQEYYJKEWSMYFG-UHFFFAOYSA-N 0.000 claims description 13
- 239000003999 initiator Substances 0.000 claims description 13
- 238000010008 shearing Methods 0.000 claims description 10
- 238000003756 stirring Methods 0.000 claims description 10
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 9
- 238000001694 spray drying Methods 0.000 claims description 9
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims description 7
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 7
- 239000012295 chemical reaction liquid Substances 0.000 claims description 7
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 claims description 6
- 239000002994 raw material Substances 0.000 claims description 6
- 239000003431 cross linking reagent Substances 0.000 claims description 5
- DXPPIEDUBFUSEZ-UHFFFAOYSA-N 6-methylheptyl prop-2-enoate Chemical compound CC(C)CCCCCOC(=O)C=C DXPPIEDUBFUSEZ-UHFFFAOYSA-N 0.000 claims description 4
- 238000007720 emulsion polymerization reaction Methods 0.000 claims description 4
- XFTALRAZSCGSKN-UHFFFAOYSA-M sodium;4-ethenylbenzenesulfonate Chemical compound [Na+].[O-]S(=O)(=O)C1=CC=C(C=C)C=C1 XFTALRAZSCGSKN-UHFFFAOYSA-M 0.000 claims description 4
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 claims description 3
- 239000012298 atmosphere Substances 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 3
- 238000007731 hot pressing Methods 0.000 abstract description 31
- 230000000694 effects Effects 0.000 abstract description 21
- 241000238367 Mya arenaria Species 0.000 abstract description 13
- 239000012528 membrane Substances 0.000 abstract description 9
- 238000000498 ball milling Methods 0.000 abstract description 7
- 238000004537 pulping Methods 0.000 abstract description 6
- 230000000630 rising effect Effects 0.000 abstract description 4
- 239000002245 particle Substances 0.000 description 16
- 239000000243 solution Substances 0.000 description 16
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 14
- 239000000843 powder Substances 0.000 description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 10
- 230000002572 peristaltic effect Effects 0.000 description 10
- MYRTYDVEIRVNKP-UHFFFAOYSA-N 1,2-Divinylbenzene Chemical compound C=CC1=CC=CC=C1C=C MYRTYDVEIRVNKP-UHFFFAOYSA-N 0.000 description 9
- 239000007864 aqueous solution Substances 0.000 description 8
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 7
- 239000003792 electrolyte Substances 0.000 description 7
- 230000008961 swelling Effects 0.000 description 7
- 238000004132 cross linking Methods 0.000 description 6
- 238000004090 dissolution Methods 0.000 description 6
- 239000010410 layer Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- SBVKVAIECGDBTC-UHFFFAOYSA-N 4-hydroxy-2-methylidenebutanamide Chemical compound NC(=O)C(=C)CCO SBVKVAIECGDBTC-UHFFFAOYSA-N 0.000 description 5
- 238000007599 discharging Methods 0.000 description 5
- 238000001914 filtration Methods 0.000 description 5
- 239000002002 slurry Substances 0.000 description 5
- 239000000758 substrate Substances 0.000 description 5
- 239000004743 Polypropylene Substances 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 229920001155 polypropylene Polymers 0.000 description 4
- OMIGHNLMNHATMP-UHFFFAOYSA-N 2-hydroxyethyl prop-2-enoate Chemical compound OCCOC(=O)C=C OMIGHNLMNHATMP-UHFFFAOYSA-N 0.000 description 3
- CNCOEDDPFOAUMB-UHFFFAOYSA-N N-Methylolacrylamide Chemical compound OCNC(=O)C=C CNCOEDDPFOAUMB-UHFFFAOYSA-N 0.000 description 3
- 239000011247 coating layer Substances 0.000 description 3
- 229920001577 copolymer Polymers 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- -1 Polyethylene Polymers 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000004721 Polyphenylene oxide Substances 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000001768 carboxy methyl cellulose Substances 0.000 description 2
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 239000007888 film coating Substances 0.000 description 2
- 238000009501 film coating Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000011268 mixed slurry Substances 0.000 description 2
- 238000007719 peel strength test Methods 0.000 description 2
- 229920000570 polyether Polymers 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 2
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 2
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulphite Substances [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 239000000080 wetting agent Substances 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000003995 emulsifying agent Substances 0.000 description 1
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- VOZRXNHHFUQHIL-UHFFFAOYSA-N glycidyl methacrylate Chemical compound CC(=C)C(=O)OCC1CO1 VOZRXNHHFUQHIL-UHFFFAOYSA-N 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
- 239000004926 polymethyl methacrylate Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000000528 statistical test Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
Landscapes
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention provides a polymer microsphere, a preparation method thereof and a lithium ion battery diaphragm, and relates to the technical field of lithium ion battery preparation; the polymer microsphere comprises a core body and a shell coated on the outer side of the core body; wherein the shell has a glass transition temperature that is lower than the glass transition temperature of the core; and the glass transition temperature of the shell ranges from 50 ℃ to 100 ℃. According to the polymer microsphere provided by the invention, through adopting the hard core soft shell structure, the soft shell can be converted into a viscous state along with the rising of temperature in the hot pressing process on the premise of avoiding deformation of the polymer microsphere in the ball milling pulping, hot pressing and other processes and guaranteeing the structural stability, so that the effect of bonding the membrane and the electrode plate can be achieved after the polymer microsphere is applied to the membrane, and the hot pressing effect of the polymer microsphere is improved.
Description
Technical Field
The invention relates to the technical field of lithium ion battery preparation, in particular to a polymer microsphere, a preparation method thereof and a lithium ion battery diaphragm.
Background
The diaphragm is used as a main component unit of the lithium ion battery, plays a role in separating two poles, provides lithium ion and electrolyte channels, has important influences on safety, capacity, charge and discharge power, cycle performance and the like of the lithium ion battery, and commercial products mainly comprise a Polyethylene (PE) diaphragm and a polypropylene (PP) diaphragm, but due to poor heat resistance, the diaphragm is greatly contracted at high temperature, two extremely short circuits are easily caused, the battery is deformed slightly, and the battery burns heavily, so that the personnel property safety is threatened.
At present, a heat-resistant ceramic layer with the thickness of 2-5 mu m is formed on the surface of a diaphragm substrate by coating ceramic slurry, so that the heat resistance of the diaphragm substrate is improved. However, due to the high specific gravity of the ceramic particles, the quality and thickness of the composite membrane can be additionally increased by the existence of the ceramic heat-resistant layer, which is not beneficial to the improvement of the energy density of the lithium ion battery. Based on this problem, it is well documented to introduce polymeric microspheres, such as PMMA microspheres, on a separator substrate to increase battery energy density.
However, the polymer microspheres used in the diaphragm at present have low bonding strength and poor hot-pressing effect, and the electrochemical performance of the lithium ion battery is affected.
Disclosure of Invention
In order to solve the problem of poor hot-pressing effect of polymer microspheres in the prior art, the invention provides the polymer microspheres, and the polymer microspheres are provided with the outer shell layer with low Tg, so that the outer shell layer can play a role of bonding a diaphragm and an electrode plate after hot-pressing, the bonding strength of the outer shell layer is improved, and the problem of poor hot-pressing effect of the polymer microspheres in the prior art is solved.
The technical scheme adopted for solving the technical problems is as follows:
A polymer microsphere, comprising a core body and a shell body coated on the outer side of the core body; wherein the shell has a glass transition temperature that is lower than the glass transition temperature of the core; and the glass transition temperature of the shell ranges from 50 ℃ to 100 ℃.
Optionally, the glass transition temperature of the core body ranges from 90 ℃ to 120 ℃.
Optionally, the polymeric microspheres have an outer diameter of (4.5-5.5) μm.
Another object of the present invention is to provide a method for preparing the polymer microsphere as described above, comprising the steps of:
S1: the mass ratio is 1: the soft monomer and the hard monomer of (20-45) are used as raw materials to generate seed microspheres through soap-free emulsion polymerization;
s2: taking the seed microsphere as a core, wherein the mass ratio is 1: copolymerizing the soft monomer of (3-13) with a hard monomer to form a microsphere emulsion;
S3: the polymer microsphere is prepared by taking the microsphere emulsion as a raw material and adopting a high-temperature atomization drying process.
Optionally, the soft monomers in step S1 and step S2 are each selected from at least one of butyl acrylate and isooctyl acrylate.
Optionally, the hard monomers in step S1 and step S2 are each selected from at least one of methyl methacrylate, styrene, acrylonitrile, sodium p-styrenesulfonate, acrylic acid, and methacrylic acid.
Optionally, step S1 includes: mixing soft monomer, hard monomer and water according to the formula amount, stirring and shearing under inert gas atmosphere, heating to 60-80 ℃, dripping initiator, reacting, and obtaining seed microspheres to obtain reaction liquid.
Optionally, step S2 includes: and adding soft monomers, hard monomers and an initiator into the reaction liquid according to the formula amount, reacting, and then dropwise adding a cross-linking agent to continue the reaction to obtain the microsphere emulsion.
Optionally, the atomization drying temperature of the high-temperature atomization drying process in the step S3 is 60-200 ℃.
It is a further object of the present invention to provide a lithium ion battery separator comprising the polymeric microspheres as described above.
The beneficial effects of the invention are as follows:
According to the polymer microsphere provided by the invention, through adopting the hard core soft shell structure, the soft shell can be converted into a viscous state along with the rising of temperature in the hot pressing process on the premise of avoiding deformation of the polymer microsphere in the ball milling pulping, hot pressing and other processes and guaranteeing the structural stability, so that the effect of bonding the membrane and the electrode plate can be achieved after the polymer microsphere is applied to the membrane, and the hot pressing effect of the polymer microsphere is improved.
Drawings
The invention will be further described with reference to the drawings and examples.
FIG. 1 is a photograph of primary polymer microspheres prepared in example 1 of the present invention;
FIG. 2 is a photograph of the secondary polymeric microspheres prepared in example 1 of the present invention;
FIG. 3 is a graph showing statistical tests of the particle size of polymer microspheres in example 1 of the present invention;
FIG. 4 is a graph showing statistical measurement of the particle size of polymer microspheres in example 2 of the present invention.
Detailed Description
The present invention will now be described in further detail. The embodiments described below are exemplary and intended to illustrate the invention and should not be construed as limiting the invention, as all other embodiments, based on which a person of ordinary skill in the art would obtain without inventive faculty, are within the scope of the invention.
In order to solve the problem of poor hot-pressing effect of polymer microspheres in the prior art, the invention provides a polymer microsphere, which comprises a core body and a shell body coated on the outer side of the core body; wherein the glass transition temperature of the shell is lower than the glass transition temperature of the core body, thereby forming a hard core-soft shell structure; in the application process, the hard core can resist structural deformation of the sphere in the ball milling pulping, hot pressing and other processes; the invention further prefers that the glass transition temperature of the shell ranges from 50 ℃ to 100 ℃, so that the soft shell can play a role in bonding the diaphragm and the electrode plate after hot pressing, and the hot pressing effect of the polymer microsphere is improved.
According to the polymer microsphere provided by the invention, through adopting the hard core soft shell structure, the soft shell can be converted into a viscous state along with the rising of temperature in the hot pressing process on the premise of avoiding deformation of the polymer microsphere in the ball milling pulping, hot pressing and other processes and guaranteeing the structural stability, so that the effect of bonding the membrane and the electrode plate can be achieved after the polymer microsphere is applied to the membrane, and the hot pressing effect of the polymer microsphere is improved.
In order to avoid stability of the polymeric microsphere structure, the preferred glass transition temperature of the nucleus of the present invention is in the range of 90-120 ℃.
Furthermore, the polymer microsphere is preferably provided with the outer diameter of (4.5-5.5) mu m, so that the particle size of the polymer microsphere is ensured to be larger than the thickness of a coating layer on the diaphragm after drying, the polymer microsphere is in a naked state on the coating layer, and after hot pressing treatment, the bonding effect is better exerted, and the bonding effect on the diaphragm and an electrode material is improved.
In addition, through the combination of the large particle size of the polymer microsphere and the hard core, the deformation of the polymer microsphere is small in the hot pressing process of the battery core of the lithium ion battery, a certain internal gap can be provided, the lithium ion conduction is promoted, the expansion of the battery core is inhibited, the gap of the diaphragm is not blocked to a large extent, and the improvement of the energy density and the safety performance of the battery is facilitated.
Another object of the present invention is to provide a method for preparing the polymer microsphere as described above, comprising the steps of:
S1: the mass ratio is 1: the soft monomer and the hard monomer of (20-45) are used as raw materials to generate seed microspheres through soap-free emulsion polymerization;
in the step, seed microspheres with higher glass transition temperature are generated by matching soft monomers with hard monomers, and the seed microspheres further serve as nuclei of polymer microspheres; specifically, the glass transition temperature of the core body ranges from 90 ℃ to 120 ℃.
S2: seed microspheres are taken as cores, and the mass ratio is 1: copolymerizing the soft monomer of (3-13) with a hard monomer to form a microsphere emulsion;
In the step, a shell with lower glass transition temperature is generated at the outer side of the seed microsphere through the coordination of the soft monomer and the hard monomer and is marked as a primary polymer microsphere; specifically, the glass transition temperature of the shell ranges from 50 ℃ to 100 ℃.
S3: the polymer microsphere is prepared by taking microsphere emulsion as a raw material and adopting a high-temperature atomization drying process.
In order to increase the particle size of the polymer microspheres to further improve the bonding effect, in step S3, based on the characteristic that the primary polymer microspheres have soft shells, the low glass transition temperature Tg of the outer shell copolymer of the primary polymer microspheres is utilized, and a high-temperature atomization drying method is adopted, so that in the high-temperature atomization drying process, the shells of the primary polymer microspheres are bonded with each other to form secondary polymer microspheres with larger particle sizes, namely the polymer microspheres of the target product.
According to the preparation method of the polymer microsphere, firstly, a seed microsphere with higher Tg is produced by soap-free emulsion polymerization of soft and hard monomers in a certain proportion, and the seed microsphere is taken as a core, and the soft and hard monomers in a certain proportion are copolymerized to form a low Tg outer shell layer, so that the primary polymer microsphere with a hard core-soft shell structure and uniform particle size is prepared; further adopting a high-temperature atomization drying process to prepare the high-particle-diameter secondary polymer microsphere for the battery diaphragm; the polymer microsphere has a hard core and soft shell structure, and can be converted into a viscous state along with the rising of temperature in the hot pressing process on the premise of avoiding deformation of the polymer microsphere in the ball milling pulping, hot pressing and other processes and guaranteeing the structural stability, so that the effect of bonding the membrane and electrode plates can be achieved after the polymer microsphere is applied to the membrane, and the hot pressing effect of the polymer microsphere is improved.
In the invention, the soft monomers in the step S1 and the step S2 are preferably at least one selected from butyl acrylate and isooctyl acrylate; preferably, the hard monomers in the step S1 and the step S2 are at least one selected from methyl methacrylate, styrene, acrylonitrile, sodium p-styrenesulfonate, acrylic acid and methacrylic acid; and further preferably the hard monomer is methyl methacrylate.
Specifically, the preferred step S1 of the present invention is performed as follows: mixing soft monomer, hard monomer and water according to the formula amount, stirring and shearing under inert gas atmosphere, heating to 60-80 ℃, dripping initiator, reacting, and obtaining seed microspheres to obtain reaction liquid.
The initiator is preferably a water-soluble initiator, and further preferably the initiator is at least one selected from potassium persulfate (KPS), ammonium Persulfate (APS), ammonium persulfate-Bruggolite FF, and potassium persulfate-sodium sulfite; preferably, the rotating speed of high-speed shearing is 8000-9000r/min; the reaction time is preferably 1 to 2 hours.
The preferred step S2 of the invention is carried out according to the following method: according to the formula amount, soft monomers, hard monomers and an initiator are added into the reaction liquid to react, and then a cross-linking agent is dripped to continue the reaction to obtain the microsphere emulsion.
The initiator in the step is preferably a water-soluble initiator, and further preferably the initiator is at least one selected from the group consisting of potassium persulfate (KPS), ammonium Persulfate (APS), ammonium persulfate-Bruggolite FF6, and potassium persulfate-sodium sulfite; preferably, the cross-linking agent is at least one selected from the group consisting of methylolacrylamide, glycidyl methacrylate, hydroxyethyl acrylate, hydroxyethyl acrylamide and divinylbenzene; and further preferably the cross-linking agent is a mixture of hydroxyethylacrylamide and divinylbenzene.
In order to ensure the smooth generation of the secondary polymer microspheres, the atomization drying temperature of the high-temperature atomization drying process in the step S3 is preferably 60-200 ℃, and further preferably 100-160 ℃, so as to ensure the mutual adhesion of shells of the primary polymer microspheres in the high-temperature atomization drying process, and realize the manufacturing of the secondary microspheres.
Specifically, step S3 is preferably performed according to the following procedure: the microsphere emulsion is pumped to the upper part of a drying chamber to be atomized into tiny liquid drops under high pressure, and is dried and agglomerated into secondary polymer microspheres by reverse or homodromous gradient hot air in the drying chamber, and the secondary polymer microspheres are blown to a secondary drying port to be further dried, so that the target product polymer microspheres are obtained.
Wherein the temperature of the drying chamber is 60-200 ℃, the drying air quantity is 10-500CFM, the residence time is 1-100s, the atomization air pressure of the emulsion is 0.1-1MPa, the inner diameter of the atomization nozzle is 0.3-2mm, the temperature of the secondary drying nozzle is 30-120 ℃, and the diameter of the nozzle is 0.1-5mm; the preferred process is as follows: the temperature of the drying chamber is 100-160 ℃, the drying air quantity is 70-200CFM, the residence time of the drying chamber is 2-10s, the atomization air pressure of the emulsion is 0.5-0.7MPa, the inner diameter of the atomization nozzle is 0.7mm, the drying temperature of the secondary drying nozzle is 50-90 ℃, and the inner diameter of the nozzle is 0.7-1.0mm.
According to the invention, the seed microsphere with higher Tg is prepared by a soap-free emulsion technology, the primary polymer microsphere (with the particle size of 200-600 nm) with a hard core and soft shell structure and uniform particle size is further synthesized, no emulsifying agent is added in the reaction process (dissolution is small), and a crosslinking system is introduced in the reaction process, so that the crosslinking degree of the microsphere is improved, and the dissolution and swelling in electrolyte are reduced. The low glass transition temperature Tg of the microsphere outer shell copolymer is utilized, a high-temperature atomization drying method is adopted to process the microsphere outer shell copolymer into secondary polymer microspheres with the particle size of a few microns, and the particle size and distribution, the glass transition temperature Tg, swelling, dissolution and hot-press bonding stripping performance of the microspheres are adjusted through regulating the synthesis processes such as soft and hard monomer proportion, crosslinking monomer, feeding and the like. And (3) obtaining the polymer microspheres with large size and different surface morphology by adjusting a high-temperature atomization drying process.
In the prepared polymer microsphere, the hard core can resist structural deformation of the sphere in the processes of ball milling pulping, hot pressing and the like, the soft shell is convenient for the primary microsphere to be mutually bonded into the secondary microsphere, and meanwhile, the soft shell plays a role in bonding the diaphragm and the electrode plate after hot pressing.
It is a further object of the present invention to provide a lithium ion battery separator comprising the polymeric microspheres as described above.
The lithium ion battery diaphragm can be prepared according to the following method:
According to the formula amount, polymer microsphere powder, a binder, sodium carboxymethyl cellulose, polyether siloxane wetting agent, dispersing agent and a proper amount of water are prepared into mixture slurry by a ball mill (the rotating speed is 580r/min, and the ball mill is carried out for 1 h). And coating the mixed slurry on a PP diaphragm substrate to form a wet film coating with the thickness of 6-9 mu m, and fully drying at 60 ℃ to obtain the single-sided mixed-coated lithium ion battery diaphragm.
The lithium ion battery diaphragm provided by the invention is used for a lithium ion battery, and has the advantages of high bonding strength, small swelling in electrolyte and good hot pressing effect.
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
Example 1
The embodiment provides a preparation method of polymer microspheres, which is carried out according to the following method:
S1: mixing 20g of methyl methacrylate, 1g of butyl acrylate, 1g of methacrylic acid and 100g of water, introducing nitrogen, stirring and shearing at a high speed of 8000r/min, starting water bath heating (the set temperature is 70 ℃), dropwise adding 20g of aqueous solution containing 0.1gAPS at the temperature of 70 ℃, and reacting for 1h to generate seed microspheres to obtain a reaction solution;
S2: 120g of methyl methacrylate, 20g of butyl acrylate, 4g of acrylic acid and 80g of KPS solution with mass fraction of 0.5% are added into the reaction solution to react for 30 minutes, 10g of hydroxyethyl acrylamide and 2g of DVB are added dropwise, and the temperature is kept at 70 ℃ for 10 hours. Filtering and discharging by a 300-mesh filter screen to obtain milky emulsion, namely microsphere emulsion;
S3: and (3) conveying the microsphere emulsion to a spray drying chamber by utilizing an intermittent peristaltic pump for high-pressure atomization (the volume of a funnel-type drying chamber is 4L), setting the gradient temperature of the spray chamber to 130 ℃, setting the atomization air pressure to be 0.5MPa, arranging a plurality of atomization nozzles on an atomization disc, setting the inner diameter of the nozzles to be 0.5mm, feeding the peristaltic pump to be 1L/h, setting the air quantity to be 72CFM, staying the materials for 3s, primarily drying to form powder, carrying out secondary drying through a discharge hole nozzle, setting the secondary drying temperature to be 65 ℃, setting the inner diameter of the nozzles to be 2.0mm, and settling the powder in a collecting bottle to obtain the secondary polymer microsphere, namely the polymer microsphere.
Calculating the glass transition temperature Tg of the core body and the shell in the polymer microsphere, namely the primary polymer microsphere, according to the FOX formula; the Tg of the nucleus was calculated to be 110℃and the shell Tg was about 75-80℃irrespective of the crosslinking at 72.2 ℃.
Wherein the photo of the primary polymer microsphere obtained in the step S2 is shown in figure 1; the photograph of the secondary polymer microsphere prepared in the step S3 is shown in FIG. 2.
Referring to fig. 3, the particle size of the polymer microspheres was measured, and the results are shown in table 1:
TABLE 1
Avgerage of Arithmetic Mean of all Measurements:0.311+/-0.0001μm
Example 2
The embodiment provides a preparation method of polymer microspheres, which is carried out according to the following method:
S1: mixing 20g of methyl methacrylate, 0.5g of butyl acrylate, 0.5g of methacrylic acid and 100g of water, introducing nitrogen, stirring and shearing at a high speed of 9000r/min, starting water bath heating (set temperature is 65 ℃), dropwise adding 20g of aqueous solution containing 0.1gAPS at 65 ℃, and reacting for 1.5 hours to generate seed microspheres to obtain a reaction solution;
s2: to a solution of 120g of methyl methacrylate, 10g of isooctyl acrylate, 6g of methacrylic acid and 50g of APS with a mass fraction of 1% was added dropwise 5g of methylolacrylamide, 2g of hydroxyethyl acrylate and 1g of DVB for 20 minutes, and the mixture was incubated at 64.8℃for 10 hours. Simultaneously, 10g of aqueous solution containing 0.25g of FF6 and 10g of aqueous solution containing 0.2g of APS are added dropwise, and the temperature is kept for 2 hours after the dripping (because of lower temperature, an oxidation-reduction system initiator is added, the reaction of monomers is further promoted, and the conversion rate is improved). Filtering and discharging by a 400-mesh filter screen to obtain milky emulsion, namely microsphere emulsion;
S3: and (3) conveying the microsphere emulsion to a spray drying chamber by utilizing an intermittent peristaltic pump for high-pressure atomization (the volume of a funnel-type drying chamber is 4L), setting the temperature of the spray drying chamber to be 150 ℃, setting the atomization air pressure to be 0.6MPa, arranging a plurality of atomization nozzles on an atomization disc, enabling the inner diameter of the nozzles to be 0.7mm, enabling the feeding amount of the peristaltic pump to be 0.8L/h, enabling the air quantity to be 96CFM, enabling materials to stay for 2s, enabling the materials to be primarily dried to form powder, performing secondary drying through a nozzle at a discharge hole, enabling the secondary drying temperature to be 66 ℃, enabling the inner diameter of the nozzle to be 2.0mm, and settling the powder in a collecting bottle to obtain the secondary polymer microsphere, namely the polymer microsphere.
Calculating the glass transition temperature Tg of the core body and the shell in the polymer microsphere, namely the primary polymer microsphere, according to the FOX formula; the Tg of the nucleus was calculated to be 99℃and the shell Tg was about 85-90℃irrespective of the cross-linking at 84.3 ℃.
Referring to fig. 4, the particle size of the polymer microspheres was measured, and the results are shown in table 2:
TABLE 2
Avgerage of Arithmetic Mean of all Measurements：0.254+/-0.1168
Example 3
The embodiment provides a preparation method of polymer microspheres, which is carried out according to the following method:
s1: mixing 20g of methyl methacrylate, 1g of butyl acrylate, 0.2g of sodium p-styrenesulfonate and 100g of water, introducing nitrogen, stirring and shearing at a high speed of 9000r/min, starting water bath heating (the set temperature is 70 ℃), and dripping 20g of aqueous solution containing 0.22gAPS when the temperature is 70 ℃, and generating seed microspheres when the reaction appears bluish, so as to obtain a reaction solution;
S2: the stirring speed was adjusted to 200r/min, 100g of methyl methacrylate, 30g of butyl acrylate, 3g of acrylic acid and 50g of APS solution with mass fraction of 1.2% were added to the reaction solution to react for 20 minutes, 5g of methylolacrylamide, 2g of hydroxyethyl acrylate and 2g of DVB were added dropwise, and the reaction solution was kept at 70℃for 10 hours. Filtering and discharging by a 300-mesh filter screen to obtain milky emulsion, namely microsphere emulsion;
s3: and (3) conveying the microsphere emulsion to a spray drying chamber by utilizing an intermittent peristaltic pump for high-pressure atomization (the volume of a funnel-type drying chamber is 4L), setting the temperature of the spray drying chamber to 120 ℃, setting the atomization air pressure to be 0.7MPa, arranging a plurality of atomization nozzles on an atomization disc, enabling the inner diameter of the nozzles to be 0.7mm, feeding the peristaltic pump to be 1L/h, enabling the air quantity to be 96CFM, enabling materials to stay for 3s, primarily drying to obtain powder, performing secondary drying through a discharge hole nozzle, enabling the secondary drying temperature to be 60 ℃, enabling the inner diameter of the nozzles to be 2.0mm, and settling the powder in a collecting bottle to obtain the secondary polymer microsphere, namely the polymer microsphere.
Calculating the glass transition temperature Tg of the core body and the shell in the polymer microsphere, namely the primary polymer microsphere, according to the FOX formula; the Tg of the nucleus was calculated to be 90℃and the shell Tg was about 55-60℃irrespective of the cross-linking at 54.0 ℃.
Comparative example 1
The comparative example provides a method for preparing polymer microspheres, which is carried out according to the following method:
S1: mixing 20g of methyl methacrylate, 1g of butyl acrylate, 1g of methacrylic acid and 100g of water, introducing nitrogen, stirring and shearing at a high speed of 8000r/min, starting water bath heating (the set temperature is 70 ℃), dropwise adding 20g of aqueous solution containing 0.1gAPS at the temperature of 70 ℃, and reacting for 1h to generate seed microspheres to obtain a reaction solution;
S2: 120g of methyl methacrylate, 20g of butyl acrylate, 4g of acrylic acid and 80g of KPS solution with mass fraction of 0.5% are added into the reaction solution to react for 30 minutes, 10g of hydroxyethyl acrylamide and 2g of DVB are added dropwise, and the temperature is kept at 70 ℃ for 10 hours. Filtering and discharging by a 300-mesh filter screen to obtain milky emulsion, namely microsphere emulsion;
s3: and (3) drying the microsphere emulsion in a vacuum drying oven at 60 ℃ and 19kPa to obtain the polymer microsphere.
Comparative example 2
The comparative example provides a method for preparing polymer microspheres, which is carried out according to the following method:
S1: mixing 120g of methyl methacrylate, 20g of butyl acrylate, 4g of acrylic acid and 100g of water, introducing nitrogen, stirring and shearing at a high speed of 8000r/min, starting water bath heating (the set temperature is 70 ℃), dropwise adding 20g of aqueous solution containing 0.1gAPS at the temperature of 70 ℃, and reacting for 1h to generate seed microspheres to obtain a reaction solution;
S2: to the reaction solution, 20g of methyl methacrylate, 1g of butyl acrylate, 1g of methacrylic acid and 80g of KPS solution with mass fraction of 0.5% were added to react for 30 minutes, 10g of hydroxyethylacrylamide and 2g of DVB were added dropwise, and the reaction was kept at 70℃for 10 hours. Filtering and discharging by a 300-mesh filter screen to obtain milky emulsion, namely microsphere emulsion;
S3: and (3) conveying the microsphere emulsion to a spray drying chamber by utilizing an intermittent peristaltic pump for high-pressure atomization (the volume of a funnel-type drying chamber is 4L), setting the gradient temperature of the spray chamber to 130 ℃, setting the atomization air pressure to be 0.5MPa, arranging a plurality of atomization nozzles on an atomization disc, setting the inner diameter of the nozzles to be 0.5mm, feeding the peristaltic pump to be 1L/h, setting the air quantity to be 72CFM, staying the materials for 3s, primarily drying to form powder, carrying out secondary drying through a discharge hole nozzle, setting the secondary drying temperature to be 65 ℃, setting the inner diameter of the nozzles to be 2.0mm, and settling the powder in a collecting bottle to obtain the secondary polymer microsphere, namely the polymer microsphere.
Comparative example 3
The comparative example provides a method for preparing polymer microspheres, which is carried out according to the following method:
S1: mixing 20g of methyl methacrylate, 1g of butyl acrylate, 1g of methacrylic acid and 100g of water, introducing nitrogen, stirring and shearing at a high speed of 8000r/min, starting water bath heating (the set temperature is 70 ℃), dropwise adding 20g of aqueous solution containing 0.1gAPS at the temperature of 70 ℃, and reacting for 1h to generate seed microspheres to obtain a reaction solution;
S2: and (3) feeding the obtained reaction liquid to a spray drying chamber by utilizing an intermittent peristaltic pump to perform high-pressure atomization (the volume of a funnel-shaped drying chamber is 4L), setting the gradient temperature of the spray chamber to 130 ℃, setting the atomization air pressure to 0.5MPa, arranging a plurality of atomization nozzles on an atomization disc, setting the inner diameter of the nozzles to 0.5mm, feeding the peristaltic pump to 1L/h, setting the air quantity to 72CFM, staying the materials for 3s, performing primary drying to obtain powder, performing secondary drying through a discharge hole nozzle, setting the secondary drying temperature to 65 ℃, setting the inner diameter of the nozzles to 2.0mm, and settling the powder in a collecting bottle to obtain the secondary polymer microsphere, namely the polymer microsphere.
The properties of the polymer microspheres prepared in the above examples and comparative examples were tested as follows:
1. Dissolution swelling test: dispersing polymer microsphere powder in water to prepare slurry, placing the slurry in a tetrafluoroethylene mold, drying at 120 ℃ to form a film, cutting part of the film, weighing the mass m 0, soaking the film in a mixed electrolyte solvent (ethylene carbonate (EC): diethyl carbonate (DEC): dimethyl carbonate (DMC) in a volume ratio of 1:1:1), soaking the film at 90 ℃ for 1h, taking out the film, slightly wiping off surface liquid, and weighing the mass m 1. The film was dried in an oven at 120℃and the final mass m 2 was weighed, and the dissolution and swelling were calculated according to the following formula.
Swelling= (m 1-m0)/m0 x 100% dissolution= (m 2-m0)/m0 x 100%)
2. Hot press peel strength test: 10 parts of microsphere powder, 7 parts of polyacrylate type binder (De-ratio DA-9250), 1.5 parts of sodium carboxymethylcellulose, 0.3 part of polyether siloxane wetting agent, 0.6 part of dispersing agent and a proper amount of water are prepared into mixture slurry by a ball mill (rotating speed 580r/min, ball milling for 1 h). And coating the mixed slurry on a PP diaphragm substrate to form a wet film coating with the thickness of 6-9um, and fully drying at 60 ℃ to obtain the single-sided mixed coating functional diaphragm. And then the coating layer and the positive pole piece are attached to be subjected to hot pressing qualitative (hot pressing temperature is 80+/-1 ℃, pressure is 0.25MPa, time is 20 s), and 180-degree peel strength test is carried out on a tensile machine.
The test results are shown in Table 3:
TABLE 3 Table 3
From the data in the table above, the polymer microspheres prepared in each embodiment of the invention have the advantages of high bonding strength, small swelling in electrolyte and good hot pressing effect after being used for a diaphragm.
The difference between comparative example 1 and example 1 is that the primary polymer microspheres are not subjected to high-temperature atomization drying, and the prepared polymer microspheres have only small-particle-size microspheres and random aggregates formed by agglomeration and adhesion among part of microspheres in the drying process, and no secondary large-particle-size microspheres are generated, so that the bonding strength is low and the hot pressing effect is poor.
The difference between comparative example 2 and example 1 is that the monomer in step S1 and step S2 is exchanged, and the prepared polymer microsphere has only small particle size microspheres, and the primary microsphere shell Tg is large, so that effective agglomeration bonding cannot be formed in the high-temperature atomization drying process, no secondary large particle size microspheres are generated, and the electrolyte is swelled and has poor hot pressing effect.
The difference between comparative example 3 and example 1 is that no soft shell structure is introduced to the outer side of the seed microsphere, and the prepared polymer microsphere only has small-particle-size microsphere with D50 of 0.2 μm, and the primary microsphere has higher Tg, so that the secondary large-particle-size microsphere cannot be formed by bonding in the high-temperature atomization drying process, no secondary large-particle-size microsphere is generated, and the electrolyte is swelled and has poor hot pressing effect.
With the above-described preferred embodiments according to the present invention as an illustration, the above-described descriptions can be used by persons skilled in the relevant art to make various changes and modifications without departing from the scope of the technical idea of the present invention. The technical scope of the present invention is not limited to the description, but must be determined according to the scope of claims.
Claims (10)
1. A polymer microsphere, comprising a core body and a shell body coated on the outer side of the core body; wherein the shell has a glass transition temperature that is lower than the glass transition temperature of the core; and the glass transition temperature of the shell ranges from 50 ℃ to 100 ℃.
2. The polymeric microsphere of claim 1, wherein the core has a glass transition temperature in the range of from 90 ℃ to 120 ℃.
3. The polymeric microsphere of claim 1, wherein the polymeric microsphere has an outer diameter of (4.5 to 5.5 μm).
4. A method of preparing the polymeric microspheres of any one of claims 1-3, comprising the steps of:
S1: the mass ratio is 1: the soft monomer and the hard monomer of (20-45) are used as raw materials to generate seed microspheres through soap-free emulsion polymerization;
s2: taking the seed microsphere as a core, wherein the mass ratio is 1: copolymerizing the soft monomer of (3-13) with a hard monomer to form a microsphere emulsion;
S3: the polymer microsphere is prepared by taking the microsphere emulsion as a raw material and adopting a high-temperature atomization drying process.
5. The method of claim 4, wherein the soft monomers in step S1 and step S2 are at least one selected from butyl acrylate and isooctyl acrylate.
6. The method of claim 4, wherein the hard monomers in step S1 and step S2 are at least one selected from the group consisting of methyl methacrylate, styrene, acrylonitrile, sodium p-styrenesulfonate, acrylic acid, and methacrylic acid.
7. The method of preparing polymer microspheres according to claim 4, wherein step S1 comprises: mixing soft monomer, hard monomer and water according to the formula amount, stirring and shearing under inert gas atmosphere, heating to 60-80 ℃, dripping initiator, reacting, and obtaining seed microspheres to obtain reaction liquid.
8. The method of preparing polymer microspheres according to claim 7, wherein step S2 comprises: and adding soft monomers, hard monomers and an initiator into the reaction liquid according to the formula amount, reacting, and then dropwise adding a cross-linking agent to continue the reaction to obtain the microsphere emulsion.
9. The method of claim 8, wherein the high temperature spray drying process in step S3 has a spray drying temperature of 60 ℃ to 200 ℃.
10. A lithium ion battery separator comprising the polymeric microspheres of any one of claims 1-3.
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