CN115224439A - High-performance lithium ion battery diaphragm and preparation method thereof - Google Patents
High-performance lithium ion battery diaphragm and preparation method thereof Download PDFInfo
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- CN115224439A CN115224439A CN202210961464.3A CN202210961464A CN115224439A CN 115224439 A CN115224439 A CN 115224439A CN 202210961464 A CN202210961464 A CN 202210961464A CN 115224439 A CN115224439 A CN 115224439A
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 60
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 60
- 238000002360 preparation method Methods 0.000 title claims abstract description 30
- 238000000576 coating method Methods 0.000 claims abstract description 101
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 25
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 24
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- 238000009835 boiling Methods 0.000 claims description 6
- ZXEKIIBDNHEJCQ-UHFFFAOYSA-N isobutanol Chemical compound CC(C)CO ZXEKIIBDNHEJCQ-UHFFFAOYSA-N 0.000 claims description 6
- RLSSMJSEOOYNOY-UHFFFAOYSA-N m-cresol Chemical compound CC1=CC=CC(O)=C1 RLSSMJSEOOYNOY-UHFFFAOYSA-N 0.000 claims description 6
- 239000004952 Polyamide Substances 0.000 claims description 5
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- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 4
- 229920000604 Polyethylene Glycol 200 Polymers 0.000 claims description 4
- 229920002565 Polyethylene Glycol 400 Polymers 0.000 claims description 4
- 239000002202 Polyethylene glycol Substances 0.000 claims description 4
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- 229920000435 poly(dimethylsiloxane) Polymers 0.000 claims description 4
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- LCZVSXRMYJUNFX-UHFFFAOYSA-N 2-[2-(2-hydroxypropoxy)propoxy]propan-1-ol Chemical compound CC(O)COC(C)COC(C)CO LCZVSXRMYJUNFX-UHFFFAOYSA-N 0.000 claims description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 3
- 239000004696 Poly ether ether ketone Substances 0.000 claims description 3
- 239000004642 Polyimide Substances 0.000 claims description 3
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- 239000004760 aramid Substances 0.000 claims description 3
- 229920003235 aromatic polyamide Polymers 0.000 claims description 3
- QLVWOKQMDLQXNN-UHFFFAOYSA-N dibutyl carbonate Chemical compound CCCCOC(=O)OCCCC QLVWOKQMDLQXNN-UHFFFAOYSA-N 0.000 claims description 3
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims description 3
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 3
- 229920002530 polyetherether ketone Polymers 0.000 claims description 3
- 229920001721 polyimide Polymers 0.000 claims description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 3
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 3
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims 1
- 229940113088 dimethylacetamide Drugs 0.000 claims 1
- KKEYFWRCBNTPAC-UHFFFAOYSA-L terephthalate(2-) Chemical compound [O-]C(=O)C1=CC=C(C([O-])=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-L 0.000 claims 1
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- 206010016654 Fibrosis Diseases 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
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- 229910052744 lithium Inorganic materials 0.000 description 1
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/491—Porosity
-
- 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
Abstract
The invention discloses a high-performance lithium ion battery diaphragm and a preparation method thereof, and belongs to the technical field of lithium ion battery diaphragms. The preparation method of the diaphragm comprises the following steps: s1, pre-coating an anti-blocking hole solution on one or two surfaces of a polyolefin diaphragm substrate to enable the anti-blocking hole solution to quickly permeate into pores of the substrate and remove redundant anti-blocking hole solution on the surface of the substrate; s2, coating a high molecular solution on one surface of the polyolefin diaphragm base material prepared in the step S1 to obtain a coating diaphragm; s3, pre-drying the coating diaphragm to enable a high molecular solution to form a film on the polyolefin diaphragm substrate, and performing wet solidification on the pre-dried coating diaphragm; and S4, washing the solidified and shaped coating diaphragm with water, and drying the coating diaphragm for the second time after washing to obtain the high-performance lithium ion battery diaphragm. The lithium ion battery diaphragm prepared by the preparation method has the advantages of excellent heat resistance, high porosity, high strength, high heat resistance, ultrathin property, lyophilic liquid retention and the like.
Description
Technical Field
The invention relates to the technical field of lithium ion battery diaphragms, in particular to a high-performance lithium ion battery diaphragm and a preparation method thereof.
Background
The diaphragm is one of the essential key materials of the lithium ion battery, is a porous film with electronic insulation and ion conduction performance, and is generally obtained by taking polyolefin as a raw material and continuously processing and forming the polyolefin by equipment through a wet process or a dry process. The physical and chemical properties of the separator greatly affect the overall electrical performance of the battery.
At present, most diaphragms are mainly Polyethylene (PE), polypropylene (PP) diaphragms or composite membranes of the two materials, and although the PE diaphragms, the PP diaphragms or the PP/PE/PP composite diaphragms are low in cost, easy to process and mature in technology and can meet the requirements of large-scale production and application, the polyolefin material is difficult to meet the increasing requirements of lithium ion batteries on safety application performance due to the inherent defect of insufficient heat resistance of the polyolefin material. Therefore, there is a need for improvement of the separator or selection of a thin film material having more excellent properties. At present, diaphragm products such as PET non-woven fabric diaphragms, cellulose diaphragms, PI diaphragms and electrostatic spinning diaphragms prepared from brand new materials appear in the market, and the novel diaphragms generally have excellent heat resistance, good air permeability, high porosity and good battery application safety performance, but also have the problems of high cost, insufficient product uniformity, poor consistency and the like, so that the novel diaphragms are difficult to replace the current mainstream polyolefin diaphragms.
The general technical improvement method is to carry out secondary processing on the polyolefin diaphragm, and the processing mode is mainly to coat one or more functional coatings on the surface of a polyolefin diaphragm substrate by adopting a micro-gravure coating machine, so that a new function is given to the diaphragm substrate or the physical and chemical properties of the diaphragm are improved. The processing mode has the advantages of easiness in processing, high efficiency, flexible and changeable combination, customization, capability of meeting the requirements of different customers and the like, but the inherent defects of coating processing inevitably cause the coating material to permeate into the pore structure of the diaphragm, and the high molecular binder forms a compact film on the surface of the base material of the diaphragm to cause the occurrence of pore blocking, thereby obviously influencing the application performance of the diaphragm in the battery.
Therefore, it is necessary to develop a high-performance lithium ion battery separator having excellent heat resistance, high porosity, high strength, ultra-thin properties, and lyophilic and liquid retention properties, and a preparation method thereof.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a high-performance lithium ion battery diaphragm,
in order to solve the problems, the technical scheme adopted by the invention is as follows:
a preparation method of a high-performance lithium ion battery diaphragm comprises the following steps:
s1, adding a penetrant into a low-boiling-point solvent to prepare an anti-blocking pore solution; pre-coating the anti-blocking solution on one or two surfaces of the polyolefin diaphragm substrate to enable the anti-blocking solution to quickly permeate into pores of the substrate and remove redundant anti-blocking solution on the surface of the polyolefin substrate;
s2, preparing a high molecular solution; coating a high molecular solution on one surface of the polyolefin diaphragm substrate prepared in the step S1 to obtain a coating diaphragm;
s3, pre-drying the coating diaphragm to enable a high molecular solution to form a film on a polyolefin diaphragm base material, and performing wet solidification on the pre-dried coating diaphragm;
and S4, washing the solidified and shaped coating diaphragm with water, and drying the coating diaphragm for the second time after the washing is finished to obtain the high-performance lithium ion battery diaphragm.
Preferably, the osmotic agent in step S1 is one or a combination of any two or more of ethylene glycol, glycerol, tripropylene glycol, PEG-200, and PEG-400.
Preferably, the low-boiling-point solvent in the step S1 is an amphiphilic solvent with a boiling point less than 100 ℃ and containing polar groups and non-polar groups; wherein the polar group is one of-OH, -O-, -CO-, -Cl and-COO-; the nonpolar group is-CH 3 、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-C 6 H 5 -、-CH 3 CH(CH 3 )-、-CH 2 C(CH 3 ) 2 -one of the above.
Preferably, the low-boiling point solvent is selected from one or a combination of any two of methanol, ethanol, isopropanol, dichloromethane, diethyl ether, acetone, butanone, tetrahydrofuran, ethyl acetate and ethylene glycol dimethyl ether.
Preferably, the amount of the low-boiling-point solvent used in step S1 is 100 parts by mass, and the amount of the penetrating agent used in step S1 is 0.5 to 5 parts by mass.
Preferably, the anti-clogging solution in step S1 is coated on the polyolefin separator substrate by dip coating or roll coating.
Preferably, the polyolefin diaphragm substrate is one of a dry single-layer or multi-layer PP diaphragm, a wet single-layer or multi-layer PE diaphragm or a PE and PP composite diaphragm; the thickness of the polyolefin diaphragm base material is 3-16 mu m.
Preferably, the coating weight m = V P ρ of the pore-blocking-preventing solution in step S1, V being the volume of the polyolefin separator substrate in cm 3 (ii) a P is the porosity of the polyolefin diaphragm base material, and the unit is%; rho is the density of the anti-blocking pore solution, and the unit is g/cm 3 。
Preferably, the solid content of the polymer solution in step S2 is 1-30%, and the viscosity is 100-5000 mpa.s.
Preferably, the polymer solution comprises the following components in parts by mass: 100 parts of good solvent, 5-30 parts of high polymer resin, 1-10 parts of coagulant and 0.1-2 parts of auxiliary agent.
More preferably, the good solvent is one or a combination of two or more selected from dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, m-cresol, dibutyl carbonate, ethyl acetate, and water.
More preferably, the polymer resin is a polar polymer resin having a melting point of > 100 ℃ or a Tg value of > 100 ℃.
More preferably, the polymer resin is selected from one or a combination of any two or more of polyacrylonitrile, polyethylene terephthalate, polyarylether, polyarylate, polyamide, polyimide, aromatic polyamide, polyetheretherketone, and polyvinyl alcohol.
Further preferably, the coagulant is selected from one or a combination of any two or more of methanol, ethanol, isopropanol, isobutanol, ethylene glycol, glycerol, and water.
Further preferably, the adjuvant is an amphiphilic material containing both a hydrophilic group and a lipophilic group.
Further preferably, the auxiliary agent is one or a combination of more than two of fatty alcohol-polyoxyethylene ether, multi-branched alcohol-modified polyoxyethylene ether, alkyne diol-modified polyoxyethylene ether, polydimethylsiloxane and polyethylene glycol 200-400.
Further preferably, the polymer solution is prepared according to the following method: adding the macromolecular resin into a good solvent with the formula amount, heating to 40-80 ℃, stirring for 0.5-2.0 h, cooling to room temperature after the macromolecular resin is dissolved until the solution becomes clear and transparent, adding a coagulant and an auxiliary agent with the formula amount, and stirring for 0.1-1.0 h to obtain the macromolecular solution.
Preferably, the polymer solution is coated on one surface of the polyolefin separator substrate in step S2 by spot coating or spray coating.
Preferably, the thickness of the polymer solution coating liquid drop is 10 to 50 μm, the diameter is 0.1 to 1mm, and the coating speed is 20 to 100m/min.
Preferably, the pre-drying manner in step S3 is microwave drying.
More preferably, the power of the microwave drying is 500-900 w, the temperature is 20-60 ℃, and the drying time is 1-5 min.
Preferably, the solidification solution used in the wet solidification in step S3 is a mixed solution in which the good solvent and water are mixed in a mass ratio of 1.
Preferably, the treatment temperature of the wet solidification in the step S3 is 30-50 ℃, and the treatment time is 1-10 min.
Preferably, the treatment temperature of the water washing in the step S4 is 20 to 40 ℃ and the water washing time is 1 to 10min.
Preferably, in step S4, secondary drying is performed by means of roller contact drying and/or hot air drying.
More preferably, the drying temperature of the secondary drying is 40 to 100 ℃ and the drying time is 0.5 to 5min.
Preferably, the high-performance lithium ion battery diaphragm has the thickness of 5-20 mu m, the tensile strength MD/TD of more than or equal to 150MPa, the temperature of 130 ℃ of 1.0h, the thermal shrinkage rate MD/TD of less than or equal to 3/2, the porosity of 45-50 percent and the liquid retention rate of more than or equal to 100 percent.
Compared with the prior art, the invention has the beneficial effects that:
the preparation method of the lithium ion battery diaphragm provided by the invention combines the original anti-blocking hole solution and the high molecular solution coating formula with the unique preparation process, so that the prepared lithium ion battery diaphragm has excellent heat resistance while ensuring the physical and chemical indexes such as high strength and the like of the polyolefin diaphragm substrate, the high porosity and the liquid retention rate of the ultrathin diaphragm are obviously improved, the comprehensive performance is good, and the problems of insufficient heat resistance and other performances of the current mainstream polyolefin diaphragm and easy hole blocking caused by secondary processing of the coated diaphragm are effectively solved.
Drawings
Fig. 1 is a scanning electron microscope SEM image of the high-performance lithium ion battery separator prepared in example 1 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
A preparation method of a high-performance lithium ion battery diaphragm sequentially comprises the steps of coating an anti-blocking solution on a diaphragm substrate, coating a high polymer solution on the diaphragm substrate, pre-drying, wet-process solidification, water washing and secondary drying, and specifically comprises the following steps:
s1, adding a penetrant into a low-boiling-point solvent to prepare an anti-blocking pore solution; the anti-blocking pore solution is pre-coated on one or two surfaces of the polyolefin membrane substrate in a dip coating or roll coating mode through a first coating device of a coating machine, so that the anti-blocking pore solution quickly permeates into pores of the substrate, is filled in empty pores of the polyolefin membrane substrate and keeps a saturated state, and redundant anti-blocking pore solution on the surface of the polyolefin substrate is removed in a self-leveling or equipment scraping mode and the like.
The anti-blocking pore solution prepared in the step S1 has strong pore permeability and is based on a polyolefin diaphragmThe material has excellent affinity and is easy to volatilize, and is suitable for dip coating, roll coating or spray coating. Specifically, the anti-blocking pore solution consists of a solvent and a penetrating agent, wherein the main body of the anti-blocking pore solution is the solvent, and the penetrating agent plays an auxiliary role and specifically comprises 100 parts by mass of the solvent and 0.5-5 parts by mass of the penetrating agent. The solvent contains an amphiphilic structure, namely contains polar groups and nonpolar groups, and the polar groups can be one of-OH, -O-, -CO-, -Cl and-COO-; the nonpolar group may be-CH 3 、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-C 6 H 5 -、-CH 3 CH(CH 3 )-、-CH 2 C(CH 3 ) 2 -one of the above. The solvent can be methanol with boiling point less than 100 deg.C, ethanol, isopropanol, dichloromethane, diethyl ether, acetone, butanone, tetrahydrofuran, ethyl acetate, or ethylene glycol dimethyl ether. The penetrating agent can reduce the surface tension of the solvent, assists the solvent to quickly penetrate into the pore structure of the polyolefin membrane substrate, and can be generally a small-molecule nonionic surfactant, specifically one or any combination of ethylene glycol, glycerol, tripropylene glycol, PEG-200 and PEG-400.
The polyolefin diaphragm base material used by the invention can be one of a dry single-layer or multi-layer PP diaphragm, a wet single-layer or multi-layer PE diaphragm or a PE and PP composite diaphragm, and the thickness of the polyolefin diaphragm base material is 3-16 mu m. The coating weight of the anti-blocking pore solution is related to the diaphragm base material, and the specific coating weight is m = V.P.rho, V is the volume of the polyolefin diaphragm base material and is expressed in cm 3 (ii) a P is the porosity of the polyolefin diaphragm base material, and the unit is%; rho is the density of the anti-blocking pore solution, and the unit is g/cm 3 . The appropriate number of coating rolls is selected according to the characteristics of the substrate so as to determine the coating amount.
S2, preparing a high molecular solution; and (2) coating the high polymer solution on one surface of the polyolefin diaphragm substrate prepared in the step (S1) in a spot coating or spraying manner through a second coating device (a spot carving coating roller or a rotary spraying machine) of the coating machine, wherein the size of coating or spraying liquid drops is as follows: the thickness is 10-50 μm, the diameter is 0.1-1 mm, the coating speed is 20-100 m/min, and the coating diaphragm is obtained after coating.
In the step S2, since the pore structure in the polyolefin diaphragm substrate is filled with the anti-blocking solution, the polymer material hardly penetrates into the pore structure of the substrate when the polymer solution is coated. The polymer solution has high solid content and moderate viscosity and is suitable for roller coating or spraying, specifically, the solid content of the polymer solution is more than 1 percent, specifically 1 to 30 percent, preferably 5 to 30 percent; the viscosity is 100-5000 mPa.s. The polymer solution comprises a ternary system composed of a good solvent, polymer resin, a coagulant, an auxiliary agent and the like, and specifically comprises the following components in parts by mass: 100 parts of good solvent, 5-30 parts of high polymer resin, 1-10 parts of coagulant and 0.1-2 parts of auxiliary agent.
In the polymer solution, the good solvent as a good solvent of the polymer resin may be one or a combination of two or more of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, m-cresol, dibutyl carbonate, ethyl acetate, and water.
The polymer resin is used as main functional resin for modifying the surface of an interface between high-performance lithium ion battery diaphragm materials, and can show the heat resistance, lyophilic liquid retention performance and porosity of the diaphragm materials, so that the application electrical property and safety performance of the diaphragm battery are improved. The polymer resin is a polar polymer material with a melting point of more than 100 ℃ or a Tg value of more than 100 ℃, and specifically can be one or a combination of more than two of polyacrylonitrile, polyethylene terephthalate, polyarylether, polyarylate, polyamide, polyimide, aromatic polyamide, polyetheretherketone or polyvinyl alcohol.
The coagulant is a poor solvent insoluble in the polymer resin, and specifically may be one or a combination of two or more of methanol, ethanol, isopropanol, isobutanol, ethylene glycol, glycerol, and water. The interaction between the poor solvent as a coagulant and the polymer resin chain unit is small, resulting in contraction of the polymer resin chain coil, and the terminal distance is small, so that the polymer tends to be insoluble, coagulated, precipitated and fiberized.
The auxiliary agent is an amphiphilic material simultaneously containing a hydrophilic group and a lipophilic group, and specifically can be one or the combination of more than two of fatty alcohol-polyoxyethylene ether, multi-branched alcohol-modified polyoxyethylene ether, alkynediol-modified polyoxyethylene ether, polydimethylsiloxane and polyethylene glycol 200-400. The auxiliary agent is used for promoting a ternary system consisting of the solvent, the high-molecular resin and the coagulant to form a homogeneous solution and stabilize.
The polymer solution is prepared by the following method: adding the macromolecular resin into a good solvent with the formula amount, heating to 40-80 ℃, stirring for 0.5-2.0 h, cooling to room temperature after the macromolecular resin is dissolved until the solution becomes clear and transparent, adding a coagulant and an auxiliary agent with the formula amount, and stirring for 0.1-1.0 h to obtain the macromolecular solution.
S3, placing the coating diaphragm in a first microwave drying pretreatment oven for pre-drying, drying the anti-blocking solution, forming a film on the polyolefin diaphragm substrate by using the high molecular solution, and placing the pre-dried coating diaphragm in a first solidification bath tank for wet solidification;
s3, firstly, the anti-blocking pore solution can be rapidly heated to volatilize through simple microwave drying, so that the original pore structure of the polyolefin diaphragm substrate is reduced, and on the other hand, the polymer solution is primarily dried through microwave rapid drying to enable the polymer to be solidified and fiberized to form a continuous phase and form a film on the surface of the substrate, so that the problem of pore blocking of the substrate is avoided, the problem of pore blocking caused by secondary processing such as coating of the diaphragm substrate is greatly improved, and the battery application electrical property of the coated diaphragm is improved. The coating diaphragm pre-dried by microwave is subjected to wet solidification, so that the coating is finally solidified, shaped and porous, the coagulant in the high polymer solution assists the coating to be solidified, and the good solvent is exchanged, so that a porous structure is left.
In the step S3, the output power of the microwave drying is 500-900W, the drying temperature is 20-60 ℃, the drying time is 1-5 min, under the process condition, the anti-blocking hole solution is basically completely volatilized, and meanwhile, the volatilization rate of the good solvent in the high polymer solution coating is 10-30%. If the volatilization rate of the good solvent is less than 10%, the drying degree of the coating is low, the solidification degree of the high polymer is low, the fibrosis cannot be formed, a continuous phase cannot be formed, a film is formed on an interface, and the high polymer solution penetrates into a pore structure of the base material along with the rapid volatilization of the anti-blocking agent, so that the occurrence of hole blocking is caused finally; if the volatilization rate of the good solvent is more than 30 percent, the solidification degree of the surface of the coating is high, a compact cortical structure is formed, the solution in the coating is sealed, the pore-forming process in the subsequent medium-wet solidification treatment process can be obviously influenced, and finally, the coating has fewer pores and is obviously blocked. The treatment temperature of the wet solidification is 30-50 ℃, and the treatment time is 1-10 min; the coagulating liquid used in the coagulating bath is prepared by mixing a good solvent used in a polymer solution and water in a mass ratio of 1.
And S4, placing the solidified and shaped coating diaphragm into a water washing tank for water washing, wherein the water washing temperature is 20-40 ℃, the water washing time is 1-10 min, and after the water washing is finished, performing secondary drying on the coating diaphragm through a second drying box and a hot press roller in a mode of combining direct roller contact drying and hot air drying, wherein the drying temperature is 40-100 ℃, and the drying time is 0.5-5 min, so as to obtain the high-performance lithium ion battery diaphragm.
And S4, washing the residual solvent in the coating by water, further perfecting and shaping the pore structure, and forming the final pore structure by the coating. The secondary drying can remove the residual water in the coating, so that the polymer fiber in the coating is oriented, crystallized, shrunk and shaped.
The high-performance lithium ion battery diaphragm prepared by the preparation method has the thickness of 5-20 mu m, the tensile strength of MD/TD more than or equal to 150MPa, the thermal shrinkage rate of MD/TD at 130 ℃ for 1.0h less than or equal to 3/2, the porosity of 45-50 percent and the liquid retention rate of more than or equal to 100 percent, and is a high-performance lithium ion battery diaphragm integrating high strength, high heat resistance, ultrathin property, high porosity and excellent lyophilic liquid retention performance.
Example 1
A high-performance lithium ion battery diaphragm comprises a diaphragm base material and a high-molecular functional coating coated on the diaphragm base material. The preparation method of the high-performance lithium ion battery diaphragm comprises the following steps:
s1, preparing an anti-blocking solution: adding 1 part of PEG-200 penetrating agent into a low boiling point solvent containing 100 parts of isopropanol, and fully and uniformly stirring to obtain an anti-blocking solution;
s2, preparing a polymer solution: adding 10 parts of polyarylate polymer resin into 100 parts of a good solvent of dimethylacetamide, heating to 60 ℃, stirring for 1.0h, cooling to room temperature after the polyarylate polymer resin is dissolved and the solution becomes clear and transparent, adding 5 parts of isopropanol coagulant and 1 part of polydimethylsiloxane assistant, and stirring for 0.5h to obtain a polymer solution.
S3, coating and pretreatment: coating the anti-blocking solution on one surface of a PE (polyethylene) diaphragm substrate through a micro gravure roll coater, coating the polymer solution on the other surface of the PE diaphragm substrate, and performing microwave pre-drying on the coated diaphragm, wherein the microwave drying power is 600w, the temperature is 40 ℃, and the drying time is 3min; and (3) performing wet solidification on the pre-dried coating diaphragm, wherein the treatment temperature of the wet solidification is 40 ℃, and the treatment time is 3min. Wherein the thickness of the PE diaphragm substrate pair is 9 μm, and the coating speed is 60m/min.
S4, washing and drying: washing the solidified and shaped coating diaphragm with water at the treatment temperature of 30 ℃ for 5min; the drying temperature of the secondary drying is 80 ℃, and the drying time is 3min, thus obtaining the high-performance lithium ion battery diaphragm with the coating thickness of 3 mu m and the total thickness of 12 mu m.
Fig. 1 is a SEM image of the high-performance lithium ion battery separator prepared in this example. Fig. 1 shows that the high-performance lithium ion battery separator prepared in the embodiment has few plugged holes, a high pore structure, a large and rich pore structure, and uniform and consistent pore distribution.
Example 2
A high-performance lithium ion battery diaphragm comprises a diaphragm base material and a high-molecular functional coating coated on the diaphragm base material. The preparation method of the high-performance lithium ion battery diaphragm comprises the following steps:
s1, preparing an anti-blocking hole solution: adding 5 parts of PEG-400 penetrating agent into a low boiling point solvent containing 100 parts of ethanol, and fully and uniformly stirring to obtain an anti-blocking solution;
s2, preparing a polymer solution: adding 30 parts of polyarylether polymer resin into 100 parts of dimethylformamide good solvent, heating to 80 ℃, stirring for 1.0h, cooling to room temperature after the polyarylether polymer resin is dissolved and the solution becomes clear and transparent, adding 10 parts of ethanol coagulant and 2 parts of fatty alcohol-polyoxyethylene ether auxiliary agent, and stirring for 1.0h to obtain the polymer solution.
S3, coating and pretreatment: coating the anti-blocking solution on one surface of a PE (polyethylene) diaphragm base material through a micro gravure roll coater, coating the high polymer solution on the other surface of the PE diaphragm base material, and performing microwave pre-drying on the coated diaphragm, wherein the microwave drying power is 900w, the temperature is 60 ℃, and the drying time is 5min; and (3) performing wet solidification on the pre-dried coating diaphragm, wherein the treatment temperature of the wet solidification is 50 ℃, and the treatment time is 8min. Wherein the thickness of the PE diaphragm substrate pair is 9 μm, and the coating speed is 60m/min.
S4, washing and drying: washing the solidified and shaped coating diaphragm with water, wherein the treatment temperature of the washing is 40 ℃, and the washing time is 8min; and drying for 5min at the drying temperature of 90 ℃ to obtain the high-performance lithium ion battery separator with the coating thickness of 3 mu m and the total thickness of 12 mu m.
Example 3
A high-performance lithium ion battery diaphragm comprises a diaphragm base material and a high-molecular functional coating coated on the diaphragm base material. The preparation method of the high-performance lithium ion battery diaphragm comprises the following steps:
s1, preparing an anti-blocking hole solution: adding 0.5 part of glycol penetrant into a low-boiling-point solvent containing 100 parts of methanol, and fully and uniformly stirring to obtain an anti-blocking solution;
s2, preparing a polymer solution: adding 5 parts of polyamide high-molecular resin into 100 parts of a good solvent of di-N-methylpyrrolidone, heating to 80 ℃, stirring for 0.5h, cooling to room temperature after the polyamide high-molecular resin is dissolved and the solution becomes clear and transparent, adding 1 part of methanol coagulant and 0.1 part of multi-branched alcohol modified polyoxyethylene ether assistant, and stirring for 0.1h to obtain a high-molecular solution.
S3, coating and pretreatment: coating the anti-blocking solution on one surface of a PE (polyethylene) diaphragm base material through a micro gravure roll coater, coating the high polymer solution on the other surface of the PE diaphragm base material, and performing microwave pre-drying on the coated diaphragm, wherein the microwave drying power is 500w, the temperature is 30 ℃, and the drying time is 1min; and (3) carrying out wet solidification on the pre-dried coating diaphragm, wherein the treatment temperature of the wet solidification is 30 ℃, and the treatment time is 1min. Wherein the thickness of the PE diaphragm substrate pair is 9 μm, and the coating speed is 60m/min.
S4, washing and drying: washing the solidified and shaped coating diaphragm for 1min at the treatment temperature of 20 ℃; the drying temperature of the secondary drying is 50 ℃, and the drying time is 1min, thus obtaining the high-performance lithium ion battery diaphragm with the coating thickness of 3 mu m and the total thickness of 12 mu m.
Example 4
The present embodiment is different from embodiment 1 in that: in step S3, the polymer solution was coated on both sides of the PE separator substrate by a gravure roll coater, the thickness of the PE separator substrate was 9 μm, the thickness of the single-side coating was 3 μm, the total thickness of the double-side coating was 6 μm, and the remaining components and the preparation method were the same as in example 1.
Comparative example 1
This comparative example differs from example 1 in that: step S1 was omitted, the anti-blocking pore solution was not prepared, the process of coating the anti-blocking pore solution was omitted in S3, and the remaining components and the preparation method were the same as in example 1.
Comparative example 2
This comparative example differs from example 1 in that: in step S1, no penetrant was added, and the remaining components and preparation method were the same as in example 1.
Comparative example 3
This comparative example differs from example 1 in that: in the step S2, the coagulant and the auxiliary agent were not added to the polymer solution, and the remaining components and the preparation method were the same as in example 1.
Comparative example 4
The wet-process PE substrate of example 1, which was used as comparative example 4 and was not subjected to any coating process, had a thickness of 9 μm and a porosity of 45%.
Comparative example 5
The polymer solution in example 1 was used as a functional slurry, coated on one surface of a PE separator substrate using the same gravure roll coater as in step S3 in example 1, and then directly dried (temperature 60 ℃, drying time 3 min) to obtain a lithium ion battery-coated separator having a substrate thickness of 9 μm and a coating thickness of 3 μm.
Performance comparison experiment
The lithium ion battery separators of examples 1 to 4 and the separators of comparative examples 1 to 5 were measured and compared for thickness, air permeability, porosity, heat resistance and lyophilic liquid retention property.
Nine groups of lithium battery diaphragms prepared in examples 1 to 4 and comparative examples 1 to 5 were made into soft package lithium ion batteries: model 506090, positive NCM523, negative: natural graphite; electrolyte solution: EC/PC/DMC ratio: 2; the cell resistance and rate performance of the cells were measured.
The results are shown in Table 1.
Table 1 separator prepared in examples and comparative examples each test result
As can be seen from table 1, the high-performance lithium ion battery separator manufactured in example 1 has the best physicochemical properties through a better formula combination and process: the air permeability value is low, the porosity is high, the liquid retention rate is high, the puncture strength is high, the heat shrinkage rate is small at 150 ℃ for 1.0h, and the membrane rupture temperature is high; the battery prepared from the high performance lithium ion battery separator manufactured in example 1 had the best battery performance: the battery has small internal resistance, high capacity and good 3C rate performance.
In example 2, with the increase of the proportion of the polymer resin and the related auxiliary agents, the air permeability value of the manufactured high-performance lithium ion battery diaphragm is increased, the porosity is reduced, the liquid retention rate is reduced, the thermal shrinkage rate at 150 ℃ is increased, the film rupture temperature is slightly reduced, the internal resistance of the manufactured battery is increased, the capacity is reduced, and the 3C multiplying power is slightly poor; in example 3, with the decrease of the ratio of the polymer resin to the related additives, the gas permeability of the manufactured high-performance lithium ion battery separator is increased, the porosity is reduced, the liquid retention rate is reduced, the thermal shrinkage rate at 150 ℃ is increased, the film breaking temperature is reduced, the internal resistance of the manufactured battery is increased, the capacity is reduced, and the multiplying power is slightly reduced, which shows the same rule in example 2; example 4 compared with example 1, only from a single side of 3 u coating to double side of 6 u coating, the permeability value is increased, the porosity is reduced, although the 150 ℃ heat shrinkage rate of the product is reduced, the rupture temperature is increased, but the manufactured battery has the problems of increased internal resistance, reduced capacity and poor rate.
Compared with the embodiment 1, the comparative example 1 lacks of anti-pore-blocking solution and the first coating procedure, the air permeability value of the product is obviously increased by 22 percent, the porosity and the liquid absorption rate are reduced, the heat resistance is slightly poor, the internal resistance of the manufactured battery is obviously increased, the capacity is obviously reduced, and the multiplying power is obviously reduced;
compared with the embodiment 1, the comparative example 2 is lack of the penetrating agent, so that the anti-blocking pore solution is not beneficial to fully penetrating into the pore structure of the substrate, and the subsequent coating polymer solution is easy to penetrate into the pores of the substrate, so that the pore blocking is caused. Therefore, similarly, the air permeability value of the prepared high-performance lithium ion battery separator is increased, the porosity is reduced, the liquid retention rate is reduced, the 150 ℃ heat shrinkage rate is increased, the film rupture temperature is slightly reduced, the internal resistance of the prepared battery is increased, the capacity is reduced, and the 3C multiplying power is deteriorated;
compared with the embodiment 1, the comparative example 3 has the advantages that no coagulant or auxiliary agent is added into the high molecular solution, so that the pore forming property of the coating is poor, the air permeability value of the prepared high-performance lithium ion battery diaphragm is increased, the porosity and the liquid retention rate are reduced, the thermal shrinkage rate at 150 ℃ is increased, the diaphragm breaking temperature is slightly reduced, the internal resistance of the prepared battery is increased, the capacity is reduced, and the 3C multiplying power is reduced;
comparative example 4 adopts PE base material of 9 mu wet method directly without any processing, the product has 150 ℃,1.0h thermal shrinkage close to 100 percent, namely almost shrinkage into resin particles, film rupture temperature of 140 ℃, insufficient heat-resistant support property and poor application safety performance;
the comparative example 5 is a lithium ion battery coating diaphragm prepared by coating polymer solution as functional slurry, compared with the example 1, the process is greatly different, a film forming method of direct drying and solvent volatilization is adopted, materials in the coating easily permeate into a base material, hole blocking is easily caused, the porosity of the diaphragm is obviously reduced, the ventilation value is increased violently, and the battery manufactured by using the lithium ion battery coating diaphragm has extremely high internal resistance and poor rate capability.
From the test results of the separators prepared in the above examples and comparative examples, it can be seen that: the selection and proportion of the thermosensitive functional resin and the pressure-sensitive functional resin, the dosage of the photoinitiator, whether the base material is coated, hot-press compounding and UV curing can influence the physical and chemical properties of the multilayer composite lithium ion battery diaphragm and the application performance of the battery.
In conclusion, the multilayer composite lithium ion battery diaphragm is prepared by combining the unique formula with the unique process, the heat resistance of the diaphragm is obviously improved by adding a new functional layer of the diaphragm, the problems of hole blocking of a base material and porosity reduction are effectively avoided, the application pain points of the product are solved, the transmission channel of lithium ions is effectively improved, and the multiplying power charge and discharge performance of the battery is greatly improved.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.
Claims (10)
1. A preparation method of a high-performance lithium ion battery diaphragm is characterized by comprising the following steps: the method comprises the following steps:
s1, adding a penetrant into a low-boiling-point solvent to prepare an anti-blocking pore solution; pre-coating the anti-blocking solution on one or two surfaces of the polyolefin diaphragm substrate to enable the anti-blocking solution to quickly permeate into pores of the substrate and remove redundant anti-blocking solution on the surface of the polyolefin substrate;
s2, preparing a high molecular solution; coating a high molecular solution on one surface of the polyolefin diaphragm substrate prepared in the step S1 to obtain a coating diaphragm;
s3, performing microwave pre-drying on the coating diaphragm to enable a high molecular solution to form a film on a polyolefin diaphragm substrate, and performing wet solidification on the pre-dried coating diaphragm;
and S4, washing the solidified and shaped coating diaphragm with water, and drying the coating diaphragm for the second time after the washing is finished to obtain the high-performance lithium ion battery diaphragm.
2. The preparation method of the high-performance lithium ion battery separator according to claim 1, characterized in that: in the step S1, the penetrant is one or the combination of more than two of ethylene glycol, glycerol, tripropylene glycol, PEG-200 and PEG-400; the low-boiling point solvent is selected from one or the combination of more than two of methanol, ethanol, isopropanol, dichloromethane, diethyl ether, acetone, butanone, tetrahydrofuran, ethyl acetate and ethylene glycol dimethyl ether.
3. The preparation method of the high-performance lithium ion battery separator according to claim 1, characterized in that: the mass part of the low-boiling-point solvent in the step S1 is 100 parts, and the mass part of the penetrating agent is 0.5-5 parts.
4. The preparation method of the high-performance lithium ion battery separator according to claim 1, characterized in that: the polymer solution comprises the following components in parts by mass: 100 parts of good solvent, 5-30 parts of high polymer resin, 1-10 parts of coagulant and 0.1-2 parts of auxiliary agent.
5. The preparation method of the high-performance lithium ion battery separator according to claim 4, characterized in that: the good solvent is one or the combination of more than two of dimethyl formamide, dimethyl acetamide, N-methyl pyrrolidone, dimethyl sulfoxide, m-cresol, dibutyl carbonate, ethyl acetate or water.
6. The preparation method of the high-performance lithium ion battery separator according to claim 4, characterized in that: the polymer resin is selected from one or the combination of more than two of polyacrylonitrile, polyethylene glycol terephthalate, polyarylether, polyarylate, polyamide, polyimide, aromatic polyamide, polyether ether ketone or polyvinyl alcohol.
7. The preparation method of the high-performance lithium ion battery separator according to claim 4, wherein the preparation method comprises the following steps: the coagulant is selected from one or the combination of any two of methanol, ethanol, isopropanol, isobutanol, glycol, glycerol or water; the auxiliary agent is one or the combination of more than two of fatty alcohol-polyoxyethylene ether, multi-branched alcohol modified polyoxyethylene ether, acetylene glycol modified polyoxyethylene ether, polydimethylsiloxane and polyethylene glycol 200-400.
8. The preparation method of the high-performance lithium ion battery separator according to claim 1, characterized in that: in the step S3, the microwave drying power is 500-900 w, the temperature is 20-60 ℃, and the drying time is 1-5 min; the treatment temperature of the wet solidification is 30-50 ℃, and the treatment time is 1-10 min.
9. The preparation method of the high-performance lithium ion battery separator according to claim 1, characterized in that: the processing temperature of the water washing in the step S4 is 20-40 ℃, and the water washing time is 1-10 min; the drying temperature of the secondary drying is 40-100 ℃, and the drying time is 0.5-5 min.
10. A high performance lithium ion battery diaphragm is characterized in that: the lithium ion battery separator is prepared by the preparation method of any one of claims 1 to 9.
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