CN111697190A - Polyaryletherketone for lithium battery diaphragm - Google Patents
Polyaryletherketone for lithium battery diaphragm Download PDFInfo
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- CN111697190A CN111697190A CN202010692018.8A CN202010692018A CN111697190A CN 111697190 A CN111697190 A CN 111697190A CN 202010692018 A CN202010692018 A CN 202010692018A CN 111697190 A CN111697190 A CN 111697190A
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
- C08G65/34—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives
- C08G65/38—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives derived from phenols
- C08G65/40—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives derived from phenols from phenols (I) and other compounds (II), e.g. OH-Ar-OH + X-Ar-X, where X is halogen atom, i.e. leaving group
- C08G65/4012—Other compound (II) containing a ketone group, e.g. X-Ar-C(=O)-Ar-X for polyetherketones
- C08G65/4018—(I) or (II) containing halogens other than as leaving group (X)
- C08G65/4025—(I) or (II) containing fluorine other than as leaving group (X)
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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Abstract
The invention provides polyaryletherketone for a lithium battery diaphragm and a lithium battery diaphragm comprising the same, wherein the polyaryletherketone comprises the following structural units:
the structure of the chain link AR is:
the lithium battery diaphragm provided by the invention is prepared by coating polyaryletherketone on the surface of an ozone modified polyolefin film, scraping the film and carrying out phase conversion, has excellent thermal stability and electrochemical performance, and adopts the lithiumThe lithium ion battery obtained by the battery diaphragm has excellent comprehensive performance, and the discharge specific capacity, the coulombic efficiency and the cycling stability of the lithium ion battery are obviously improved.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to polyaryletherketone for a lithium battery diaphragm.
Background
The lithium ion battery has the advantages of high working voltage, wide working temperature range, high energy density, long cycle life, small pollution, no memory effect and the like, is the most promising and competitive secondary battery at present, and is widely applied to a plurality of high-technology fields of automobiles, mobile communication, aerospace, mechanical equipment and the like. With the reduction of manufacturing cost and the further improvement of performances such as battery life and reliability, the lithium ion battery has been completely exposed in the application fields such as electric vehicles and energy storage.
The lithium ion battery mainly comprises a positive electrode, a negative electrode, a diaphragm, electrolyte, a battery shell and the like. The diaphragm is used as an important component of the lithium ion battery, and mainly has the main functions of avoiding the direct contact between a positive electrode and a negative electrode and preventing internal short circuit; while maintaining good ion permeability and providing a channel for the transfer of lithium ions. Therefore, an ideal separator should be resistant to chemical and electrochemical interactions from the electrodes and electrolyte, and have high dimensional thermal stability to prevent safety issues mainly caused by overcharging, shorting, thermal runaway, and even explosions.
At present, commercial lithium battery separators are mainly polyolefin films, but the melting point of polyolefin materials is low, when a battery is out of control, the temperature of the inside of the battery is rapidly increased, so that the separators are greatly thermally contracted, the thermal stability is not high, a large-area short circuit is generated inside the battery, and the safety problem of the battery is caused.
Polyaryletherketone (PAEK) is an important high-performance polymer material and has the characteristics of good heat resistance, excellent electrical property and good mechanical property. The structure of the lithium ion battery diaphragm contains ether bonds (AR-O-AR), carbonyl (-CO-) and other polar groups, so that the lithium ion battery diaphragm has good wettability to electrolyte, and is an ideal reinforcing material for improving the performance of the lithium ion battery diaphragm.
The inventor's former patent document CN109942808A discloses a polyaryletherketone and application thereof in a lithium battery diaphragm, wherein the diaphragm comprises a polyolefin substrate film and a heat-resistant layer adhered thereon, the heat-resistant layer is prepared by adding a mixed solution of methanesulfonic acid and sulfuric acid into polyaryletherketone to prepare a casting solution, coating the casting solution on the polyolefin substrate film, impregnating in a coagulation bath through a phase inversion method to form a porous film, and then soaking, washing and drying to obtain the lithium battery diaphragm. The existence of the polyaryletherketone improves the heat resistance and the mechanical property of the battery diaphragm, but the polyaryletherketone has poor adhesion with the polyolefin diaphragm, and the interface layer has adverse effect on the efficiency of the battery, so that the battery diaphragm is not suitable for commercial popularization.
It is important to note that the polyolefin film also has hydrophobicity, has poor wetting property to the electrolyte, is not beneficial to the migration of lithium ions in the charging and discharging process, and the unilateral improvement of the performance of the polyaryletherketone can not make the performance of the lithium battery diaphragm reach the best, and the wetting property of the polyolefin film to the electrolyte and the adhesion to the PAEK need to be improved.
Disclosure of Invention
The invention provides polyaryletherketone with a specific structure as a heat-resistant coating of a polypropylene film, which improves the thermal stability, mechanical strength and electrochemical performance of a diaphragm, and also provides a method for modifying the surface of the polypropylene film by using ozone, which improves the wettability of the polypropylene film on electrolyte and the adhesion of the polypropylene film on the polyaryletherketone coating, thereby preparing a lithium ion battery diaphragm with excellent thermal stability and electrochemical performance.
The first purpose of the invention is to provide polyaryletherketone suitable for a lithium battery diaphragm. Specifically, the invention provides polyaryletherketone for a lithium battery diaphragm, which comprises the following structural units:
the structure of the chain link AR is:
wherein R in unit 11、R2Independently selected from C1-C6 alkyl, C1-C6 haloalkyl, and R1、R2At least one of which is haloalkyl; r in unit 23、R4Independently selected from C1-C6 alkyl, C1-C6 carboxy, and R3、R4At least one is C1-C6 carboxyl; r in unit 35、R6Independently selected from C1-C6 alkyl, C1-C6 haloalkyl; r7、R8Independently selected from C1-C6 alkyl, C2-C6 alkenyl, and R7、R8At least one of which is C2-C6 alkenyl.
Preferably, the C1-C6 alkyl group is selected from methyl, ethyl, propyl, isopropyl, butyl or isobutyl, preferably methyl; the C1-C6 haloalkyl is selected from trifluoromethyl, trichloromethyl or tribromomethyl, preferably trifluoromethyl; the C1-C6 carboxyl is selected from carboxyl, ethylcarboxyl or propylcarboxyl, preferably propylcarboxyl; the C2-C6 alkenyl is selected from vinyl, propenyl, 1-butenyl or 2-butenyl, preferably allyl.
More preferably, in the polyaryletherketone, R is1And R2Is C1-C3 haloalkyl, preferably trifluoromethyl; r3Is C1-C4 alkyl, preferably methyl; r4Is a C1-C4 carboxyl group, preferably a 1-propanoic acid group; r is5And R6Is C1-C3 alkyl, preferably methyl; r is7And R8Alkenyl of C2 to C3, preferably allyl.
The PAEK molecular chain segment with the novel structure provided by the invention contains more aromatic rings, so that the high molecular chain segment has higher rigidity, and the heat resistance is more excellent. The carboxyl on the unit 2 improves the transfer rate of lithium ions through a desolvation effect, inhibits the movement of anions by utilizing a hydrogen bond, and can greatly improve the transference number of the lithium ions under the combined action of the two effects, thereby improving the performance of the lithium ion battery.
Further, the number ratio of the unit 1, the unit 2 and the unit 3 in the polyaryletherketone is 3-5:0.5-2:4-6, preferably 3.5-4.5:0.5-1.5: 4.5-5.5.
Further, the weight average molecular weight of the polyaryletherketone is 5-10 ten thousand g/mol.
The second object of the present invention is to provide a method for preparing the above polyaryletherketone, comprising the following steps:
adding a monomer 1, a monomer 2, a monomer 3, a monomer 4, a Lewis base and a catalyst into an organic solvent according to a certain ratio, and carrying out polycondensation reaction under the conditions of heating and stirring to obtain the product polyaryletherketone, wherein the monomers 1-3 have the following structures:
wherein the radical R1-R8As previously described, monomer 4 is 1, 4-bis (4-fluorobenzoyl) benzene.
The molar ratio of the monomer 1, the monomer 2 and the monomer 3 is 3-5:0.5-2:4-6, preferably 3.5-4.5:0.5-1.5:4.5-5.5, and most preferably 4:1: 5.
The amount of monomer 4 is 1 to 1.2 times the total of monomer 1, monomer 2 and monomer 3.
The organic solvent is a nonpolar aprotic organic solvent, and is specifically selected from at least one of benzene, toluene, dimethylformamide, dimethyl sulfoxide and 1, 3-dimethyl-2-imidazolidinone; the Lewis base is selected from at least one of diphenyl sulfone, sulfolane and N-methyl pyrrolidone; the catalyst is an inorganic alkaline compound, and is specifically selected from at least one of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.
The Lewis base is selected from at least one of diphenyl sulfone, sulfolane and N-methyl pyrrolidone;
the catalyst is an inorganic basic compound, such as sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide and the like.
A third object of the present invention is a lithium battery separator comprising an ozone modified polyolefin separator and a polyaryletherketone as described above.
The lithium battery diaphragm is prepared by carrying out phase conversion on a polyaryletherketone solution dissolved in methyl sulfonate on an ozone oxidation modified polyolefin diaphragm, and the obtained lithium battery diaphragm has excellent electrochemical performance and thermal stability.
The polyolefin is selected from one of a Polyethylene (PE) single-layer film, a polypropylene (PP) single-layer film and a PP/PE/PP three-layer composite film; preferably a polypropylene (PP) monolayer film.
The invention also provides a preparation method of the lithium battery diaphragm, which comprises the following steps:
1) preparation of polyaryletherketone coating solution: dissolving polyaryletherketone in a methanesulfonic acid solution, and mixing and stirring to obtain a uniformly mixed solution; wherein, the mass fraction of the polyarylether polymer solution is 5-10%, preferably 6-8%;
2) oxidizing and modifying the lithium battery diaphragm: putting the polyolefin diaphragm into an ozone atmosphere for oxidation modification;
3) coating and forming: carrying out film scraping operation on one surface of the polyolefin film subjected to oxidation modification by using the polyaryletherketone mixed solution obtained in the step 1); and placing the lithium battery diaphragm in a coagulating bath, performing pore-forming by adopting a phase inversion method, soaking and washing, and drying to obtain the modified polyaryletherketone coated lithium battery diaphragm.
Preferably, the mass fraction of the polyarylether polymer solution is 5-10%, preferably 6-8%.
In one embodiment of the present invention, the ozone atmosphere means that the polyolefin membrane is placed in an ozone reactor, the concentration of ozone is controlled, the flow rate of gas is controlled by a gas flow meter, and the reaction time is recorded. Preferably, the ozone volume concentration of the ozone oxidation modified polyolefin film in the step 2) is 25-60%, and the oxidation treatment time is 20-50 min; preferably, the volume concentration of the ozone is 40-50%, and the oxidation treatment time is 30-40 min.
The film scraping speed in the step 3) is 1-2cm s-1Setting the thickness of the scraping film to be 20-25 mu m; the coagulating bath is water, alcohol/water mixed solution, or acetone/water mixed solutionWherein the alcohol/water mixed solution is preferably methanol/water, propanol/water, isopropanol/water.
The inventor finds that the polyolefin diaphragm base layer after ozone treatment has good affinity and enhanced adhesiveness to the polyaryletherketone prepared by the invention, so that the mechanical property and the thermal stability of the diaphragm are further improved; meanwhile, the diaphragm after oxidation treatment has advantages in porosity and supporting rate, so that the electrochemical performance of the battery assembled by the diaphragm is excellent, and the specific discharge capacity and the coulombic efficiency are improved simultaneously.
The invention also provides a lithium battery which comprises a positive electrode, a negative electrode and the electrolyte, and the lithium battery diaphragm is as above.
The invention has the beneficial effects that:
1. the invention provides a polyaryletherketone with a specific structure as a heat-resistant coating of a polypropylene film, wherein units 1, 2 and 3 can be prepared by the same method, only different needed groups are needed to be introduced, the preparation is simpler and more convenient, and the weight average molecular weight, the glass transition temperature and the melting temperature of the polyaryletherketone are optimized to a certain degree, so that the polyaryletherketone coating can greatly improve the thermal stability of the polypropylene film on the premise of meeting the mechanical property of a battery film, and the electrochemical property of the film can be improved to a certain degree.
2. The invention also provides a method for preparing the porous membrane by carrying out phase conversion on the PP lithium battery diaphragm subjected to ozone oxidation treatment by using the PAEK solution dissolved in the methyl sulfonate. Ozone (O)3) The oxygen molecule carries an oxygen atom to form the PP film, so that the PP film is only in a temporary storage state, the carried oxygen atom is taken as an oxidant, the rest atoms are combined into oxygen to enter a stable state, secondary pollution is avoided, an oxidation reaction can be carried out at a lower temperature, the damage of the PP film caused by high temperature is avoided, the active groups on the surface of the PP film can be increased, and the wettability of the PP film to electrolyte and the adhesion to PAEK are improved. The porosity and the loading rate of the PP lithium battery diaphragm after ozone oxidation can be regulated and controlled by changing the ozone oxidation condition.
3. The thickness of the film can be coated by the control of the scraper, and the thickness of the prepared diaphragm is about 20 mu m. The diaphragm is thin and low in resistance, and is beneficial to charge transfer and lithium ion conduction. On the premise of ensuring safety, the thinner the diaphragm is, the lower the cost is, the more applicable scenes are, and the convenience is brought to commercial popularization.
4. The PP lithium battery diaphragm after ozone oxidation has higher adhesion to polyaryletherketone; the polyaryletherketone has high heat resistance level, good flame retardance and excellent electrochemical performance, and can effectively improve the heat resistance and the heat shrinkage of the PP film; the PAEK is coated on the surface of the oxidized PP film by a phase inversion method, so that more pore channels and circuitous structures can be formed, the lithium ion conduction efficiency and the electrochemical performance of the diaphragm can be effectively improved, the formation of lithium dendrites can be inhibited, and the performance and the service life of the battery are improved.
Drawings
FIG. 1 shows a reaction apparatus of an oxidation apparatus for ozone oxidation modification of a PP lithium battery separator.
FIG. 2 is a photograph, from left to right, of the separator of the comparative example after treatment at 120 deg.C, 160 deg.C, 180 deg.C, and 200 deg.C, respectively, for 0.5 h.
FIG. 3 shows, from left to right, photographs of the separator of example 4 after treatment at 120 ℃, 160 ℃, 180 ℃ and 200 ℃ for 0.5h, respectively.
FIG. 4 shows, from left to right, photographs of the separator of example 5 after treatment at 120 ℃, 160 ℃, 180 ℃ and 200 ℃ for 0.5h, respectively.
FIG. 5 shows, from left to right, photographs of the separator of example 6 after treatment at 120 ℃, 160 ℃, 180 ℃ and 200 ℃ for 0.5h, respectively.
FIG. 6 is a photograph, from left to right, of the separator of example 7 after treatment at 120 ℃, 160 ℃, 180 ℃ and 200 ℃ for 0.5h, respectively.
Fig. 7 is a graph showing the battery performance at 25 c of the separators in comparative example 1, example 4, example 5, example 6, and example 7.
Detailed Description
The polyaryletherketones provided by the present invention and the lithium battery separators made therefrom are further described in detail below with reference to specific examples for the purpose of making the present application more clearly understood and appreciated by those skilled in the art. The following specific examples should not be construed or interpreted as limiting the scope of the claims of the present application in any way. For example, the disclosed values or specific materials in the examples should not be limited to the values or specific materials, but rather other ranges of values or materials that perform the same function are reasonably contemplated by one skilled in the art.
The reagents used in the present invention are all conventional commercially available reagents unless otherwise specified.
Preparation of polyaryletherketones
The polyaryletherketone of the invention is prepared by taking four monomers as an example, wherein the monomer 1 is selected from hexafluorobisphenol A, the monomer 2 is selected from 4, 4-bis (4-hydroxyphenyl) pentanoic acid, and the monomer 3 is selected from 2, 2' -diallyl bisphenol A, and the synthesis route is as follows:
the method comprises the following specific steps: hexafluorobisphenol A (0.32mol), 4-bis (4-hydroxyphenyl) pentanoic acid (0.08mol)5, 2' -diallyl bisphenol A (0.4mol), 1, 4-bis (4-fluorobenzoyl) benzene (0.88mol), anhydrous potassium carbonate (0.84mol), sulfolane (TMS)750mL and toluene 350mL are sequentially added into a three-neck flask provided with a mechanical stirrer, a nitrogen inlet pipe, a thermometer and a water separator, the temperature is raised to 140 ℃ under stirring for reaction for 3 hours, water generated by the reaction is thoroughly taken out, the temperature is continuously raised to release the toluene, and then the temperature is raised to 220 ℃ for reaction for 6 hours to obtain a viscous reaction solution. Discharging the viscous reaction liquid in distilled water, cooling, crushing the product, washing with deionized water and ethanol for 5 times respectively, and vacuum drying at 100 ℃ for 24 hours to obtain the product polyaryletherketone. The ratio of the three types of units in the repeating units on the polymer is calculated according to the charging molar ratio of the monomers, namely, the unit 1: the unit 2: the unit 3 is 4:1: 5. In the polymer structure, subscripts 4, 1, 5 are only the ratio of the number of each unit, not the number of repeating units, and the number of repeating units can be calculated from the molecular weight.
The polyaryletherketone product prepared by the preparation example is characterized, and the weight average molecular weight, the glass transition temperature and the melting temperature are tested. The weight average molecular weight is 7.6 ten thousand g/mol, the glass transition temperature is 158 ℃, and the melting temperature is 364 ℃.
The weight average molecular weight is measured by a static light scattering method and is measured by an Autosizer4700 of British Markov company.
The glass transition temperature (Tg) and the melting temperature (Tm) are obtained by DSC thermal analysis, the instrument is an Shimadzu DSC-60 type automatic differential scanning calorimeter, the test conditions are that the heating rate is 10K/min, N2An atmosphere.
Preparation of polyaryletherketone coating solutions
2ml of concentrated sulfuric acid solution is added into 25ml of methane sulfonate solution, and the mixture is fully stirred to prepare uniform mixed solution. Weighing 2.8g of Polyaryletherketone (PAEK), adding into the solution, stirring thoroughly, dissolving for 24h, and making into polyaryletherketone coating solution with mass fraction of 7%.
Oxidation modified PP lithium battery diaphragm
Cutting a PP lithium battery diaphragm into a 3 x 5cm thin film, placing the thin film on a glass plate, paving the thin film, placing the thin film into an ozone reactor, opening the ozone generator, introducing ozone, controlling the concentration of the ozone through the ozone generator, controlling the flow rate of the ozone to be 300L/h through a gas flowmeter, recording the reaction time, closing the ozone generator after the reaction is finished, and directly taking out the PP film subjected to oxidation modification from the reactor.
Referring to fig. 1, a reaction device of an oxidation device for modifying a PP lithium battery diaphragm by ozone oxidation comprises an ozone generator 1, two connecting pipes 2 and 3, a gas flowmeter 4 and a reactor 5; wherein, one end of the connecting pipe 2 is connected with the ozone generator 1, and the other end is connected with the gas input end of the gas flowmeter 4; one end of the other connecting pipe 3 is connected with the gas output end of the gas flowmeter 4, and the other end is connected with an interface at the bottom of the reactor 5; the bottom of the reactor 5 is provided with polyester fabric 6, and a PP lithium battery diaphragm is arranged inside the reactor.
Coating and forming
Coating an oxidation modified PP film by using the Polyaryletherketone (PAEK) mixed solution obtained in the example 1, placing the polyaryletherketone mixed solution at one end of a composite film, and carrying out film scraping operation in a certain direction by using a scraper to control the film scraping speed and the film thickness;
placing the obtained membrane in a coagulating bath, and performing pore-forming by adopting a phase inversion method, wherein the coagulating bath can be a mixed solution of water, methanol and water and a mixed solution of acetone and water, so as to obtain a PAEK coated PP lithium battery diaphragm; and soaking, washing and drying to obtain the PAEK coated PP lithium battery diaphragm.
Battery performance test of lithium battery diaphragm
The PAEK coating PP lithium battery diaphragm prepared by the invention is assembled into a CR2025 button half-cell according to the following steps: 1) 80 wt% of LiFePO410 wt% of Super P and 10 wt% of polyvinylidene fluoride are mixed in N-methyl pyrrolidone, coated on an aluminum foil, dried and sliced to prepare a positive electrode; 2) cutting the lithium battery diaphragm prepared by the invention into a shape suitable for a CR2025 battery case for later use; 3) the electrolyte adopts 1M LiPF6The solvent is EC/EMC with the volume ratio of 1:1, and the negative electrode is lithium foil; 4) after the components are assembled in a glove box in the order of a positive electrode shell, a diaphragm, an electrolyte, a lithium foil, a steel sheet and a negative electrode shell, the CR2025 type battery is manufactured on a packaging machine in a sealing mode. After the cell was assembled, the button cell was placed in a multichannel cell tester (novyi, blue) for testing at 25 ℃ at a charge-discharge rate of 0.2C.
Example 1
Is prepared by the steps as followsOxidation modified PP lithium battery diaphragmIn the step, the ozone concentration of the ozone generator is set to be 25%, and the treatment time is 25 min. Taking out the PP membrane after the treatment is finished, placing the PP membrane on a glass plate, and paving the PP membrane; in thatCoating of Shaping ofIn the procedure, 2ml of the above-prepared coating solution was sucked onto a film, and the thickness of the scraped film with a doctor blade was set to 15 μm at 1 cm. multidot.s-1The speed of (3) to perform film scraping. The prepared PAEK coated PP lithium battery diaphragm is placed in a coagulating bath (mixed solution of methanol and water in a volume ratio of 1: 4) by taking methanol water as the coagulating bath, phase conversion is carried out at 25 ℃, and the solution is kept stand for 10min after being uniformly mixed until the solution is stable. Taking out the PAEK coated PP lithium battery diaphragm which is subjected to phase inversion, soaking the diaphragm in pure water to remove salt solution, and drying the diaphragm in vacuum to prepare the PAEK coated PP lithiumA battery separator.
Example 2
Otherwise, the operation was the same as in example 1 except thatOxidation modified PP lithium battery diaphragmIn the step, the ozone concentration of the ozone generator is set to be 30%, and the treatment time is 30 min.
Example 3
Otherwise, the operation was the same as in example 1 except thatOxidation modified PP lithium battery diaphragmIn the step, the ozone concentration of the ozone generator is set to be 40%, and the treatment time is 30 min.
Example 4
Otherwise, the operation was the same as in example 1 except thatOxidation modified PP lithium battery diaphragmIn the step, the ozone concentration of the ozone generator is set to be 50%, and the treatment time is 30 min.
Example 5
Otherwise, the operation was the same as in example 1 except thatOxidation modified PP lithium battery diaphragmIn the step, the ozone concentration of the ozone generator is set to be 50%, and the treatment time is 40 min.
Example 6
Otherwise, the operation was the same as in example 1 except thatOxidation modified PP lithium battery diaphragmIn the step, the ozone concentration of the ozone generator is set to be 50%, and the treatment time is 50 min.
Example 7
Otherwise, the operation was the same as in example 1 except thatOxidation modified PP lithium battery diaphragmIn the step, the ozone concentration of the ozone generator is set to be 60%, and the treatment time is 50 min.
Example 8
The other operations are the same as those of example 4 except thatPreparation of polyaryletherketonesIn the step, the molar ratio of 1 unit to 2 unit to 3 unit of hexafluorobisphenol A (0.3mol), 4-bis (4-hydroxyphenyl) pentanoic acid (0.12mol)5 and 2, 2' -diallyl bisphenol A (0.37mol) is about 5:2:6, and the weight average molecular weight of the prepared polyaryletherketone is 7.2 kg/mol.
Example 9
The other operations are the same as those of example 4 except thatPreparation of polyaryletherketonesIn the step (A)The monomer 2 is 4-bis (4-hydroxyphenyl) hexanoic acid, the monomer 3 is 2, 2' -divinyl bisphenol A, and the prepared polyaryletherketone has the weight average molecular weight of 7.4 ten thousand g/mol.
Example 10
The other operations are the same as those of example 4 except thatPreparation of polyaryletherketonesIn the step, the monomer 2 is 4-bis (4-hydroxyphenyl) butyric acid, and the prepared polyaryletherketone has the weight average molecular weight of 7.5 ten thousand g/mol.
Comparative example
The battery is assembled by adopting a commercial PP lithium battery diaphragm.
Comparative example
The PAEK polymer solution is adopted to prepare a membrane on a PP lithium battery diaphragm with a surface which is not modified by ozone oxidation by a phase inversion method, and the PAEK coated PP lithium battery diaphragm is prepared.
Examples of effects
And (3) porosity testing:
cutting the diaphragm to a size of 20mm × 20mm, drying in a vacuum oven at 80 ℃ for 12h, and recording the original mass as W1And measuring the film thickness of at least three positions by using a micrometer screw, taking an average value, and calculating the volume V of the sample. Soaking the sample in 20mL of n-butanol solution for 2h, and then wiping off the excessive liquid on the surface of the sample membrane to obtain a sample with the mass W2The formula for calculating the porosity (P) of the diaphragm is as follows: p ═ W2-W1)/ρV×100％
Wherein W1(g) And W2(g) Respectively representing the mass of the diaphragm before and after absorbing the n-butanol solution; rho (g/cm)3) N-butanol density; v (cm)3) Is the septum sample volume.
And (3) testing the loading rate:
the diaphragm was cut to a size of 20mm × 20mm, dried in a vacuum oven at 80 ℃ for 12h and the original mass recorded as W1Soaking the sample in 20mL of electrolyte for 2h, weighing the excess electrolyte on the surface of the sample film, and recording the mass as W2The loading ratio (EU) of the separator is obtained by the following formula: EU ═ W2-W1)/W1×100％
Wherein W1(g) And W2(g) Respectively show the mass of the diaphragm before and after absorbing the electrolyte。
And (3) testing the battery performance of the PAEK coated PP lithium battery diaphragm:
the results of the above tests are shown in table 1:
TABLE 1
Referring to table 1, it can be seen that the porosity and loading of the ozone oxidized and PAEK coated separator is significantly improved over PP and unoxidized PP separators. Since PAEK coating layers were coated on the PP film after ozone modification under the same conditions, the difference in porosity and loading rate of the respective examples was mainly due to the PP matrix film. The ozone oxidation is proved to modify the PP membrane, the surface of the PP membrane is influenced, the ozone can break the chain of the PP membrane, the surface form and the structure of the PP membrane are changed, the surface of the PP membrane is activated, and the PAEK coating layer is added, so that the porosity and the carrying rate of the prepared membrane are obviously improved compared with those of a comparative example and a comparative example. The PP film of the comparative example is not modified by ozone, has poor adhesion to PAEK and obviously reduced cycling stability.
In addition, the oxidation process of ozone also has an effect on the pore channels of the PP membrane, and along with the deepening of the oxidation degree, partial surface pores of the diaphragm are combined with each other due to the oxidative fracture of molecular chains, so that the number of the pores is gradually reduced, the pore diameter is increased, the total volume of the pores of the diaphragm is increased, the phenomena of increasing the porosity and the loading rate are caused, and the electrochemical performance is further improved. However, the degree of oxidation of the ozonation process is not likely to be too high, or there is a tendency for coulombic efficiency to decrease as the cell is operated for a certain number of cycles.
The ozonization process can generate-OH, C ═ C and-COOH groups on the surface of the PP film, which is also the key point of the ozonization process, on one hand, the wettability of the film surface to electrolyte and the adhesion to PAEK can be effectively improved, on the other hand, the generated carboxyl groups can improve the transference number of lithium ions and improve the performance of the battery as described above.
Referring to Table 1, the specific discharge capacity of the separator of the PP lithium battery in the comparative example was about 145.2mAh g-1And the coulomb efficiency is about 98.5 percent, the cell performance has obvious decline after about 80 cycles, and the comparative example can be cycled for about 70 cycles. The discharge specific capacity and the coulombic efficiency of each embodiment are slowly reduced under the same test condition, and the battery stability is good; in the lithium battery assembled by the PAEK coated PP lithium battery diaphragm in the embodiment 4, the specific discharge capacity is 160.9mAh g-1The coulomb efficiency is 99.9 percent, and the capacity retention rate is 95.2 percent after running for 500 circles; referring to the attached figure 7 in the specification, under the charge and discharge rate of 0.2C, the capacity retention rate of 500 cycles of the battery operated at normal temperature is more than 80%, and the lithium battery with the PAEK coated ozone oxidized PP lithium battery diaphragm provided by the invention has very high cycle stability.
Testing of thermal stability:
and (3) testing conditions are as follows: thermogravimetric analysis (TGA): the membrane was subjected to TGA testing and first dried under vacuum at 60 ℃ for 12 h. The test atmosphere is nitrogen atmosphere, the sample is firstly stabilized in a TGA furnace at 100 ℃ for 30min, the moisture in the film is removed, and then the temperature is raised to 800 ℃ at the temperature raising rate of 10 ℃/min.
Wherein T is5And T10Respectively representing the thermal weight loss temperature of 5 percent and 10 percent of the mass loss of the diaphragm, and adopting a thermal weight loss analyzer to test, wherein the test conditions are 25-800 ℃ and the heating rate of 10 ℃/min.
Test of thermal shrinkage:
the membrane was cut to a size of 20mm × 20mm and the original membrane area A was recorded1Respectively placing in a vacuum drying oven at 120 deg.C, 160 deg.C, 180 deg.C and 200 deg.C for 0.5h, and calculating membrane area A2And recording the dimensional change of the diaphragm by using a photo, wherein the formula of the thermal shrinkage rate of the diaphragm is as follows: (A)1-A2)/A1×100％
Wherein A is1(cm2) And A2(cm2) The areas of the separator before and after the heat treatment are shown.
The thermal stability and shrinkage of the separator obtained according to the present invention were measured, and the results are shown in table 2:
TABLE 2
As can be seen from the data of table 2, the separator of the comparative example was melted at 200 ℃, and the thermal shrinkage could not be measured. The separator of the comparative example, after being treated at 200 c for 0.5h, had a heat shrinkage of 11.2%, which although significantly better than the commercial separator, could not fully satisfy the requirements in some cases. The attached figures 2-6 in the specification show that the PAEK coated PP lithium battery diaphragm in the comparative example, the example 4, the example 5, the example 6 and the example 7 respectively shows excellent heat shrinkage resistance, and it can be seen that the diaphragm subjected to ozone oxidation treatment of the invention almost has no shrinkage phenomenon after being treated at 200 ℃ for 0.5h, and shows ultra-high thermal stability, which indicates that the PP film subjected to ozone oxidation has good adhesion to PAEK due to the activity of the surface thereof, and the high thermal stability of PAEK can be effectively utilized.
Testing of battery performance at high temperature:
in order to test the excellent heat resistance of the separator for lithium batteries provided by the present invention, the separator for lithium batteries was fabricated as described aboveElectricity for lithium battery diaphragm Cell performance testingThe method is the same with other conditions, and the test temperature is set to 55 ℃ to test the performance of the battery. The results are shown in table 3 below:
TABLE 3
It can be seen that the PAEK coated ozone oxidized PP lithium battery separator of the present invention has excellent heat resistance stability and extremely low thermal shrinkage at high temperature (160 ℃), so that the lithium battery assembled with the separator provided by the present invention still maintains good cycle stability at higher temperature.
Claims (10)
1. A polyaryletherketone for a lithium battery separator comprises the following structural units:
the structure of the chain link AR is:
wherein R in unit 11、R2Independently selected from C1-C6 alkyl, C1-C6 haloalkyl, and R1、R2At least one of which is haloalkyl; r in unit 23、R4Independently selected from C1-C6 alkyl, C1-C6 carboxy, and R3、R4At least one is C1-C6 carboxyl; r in unit 35、R6Independently selected from C1-C6 alkyl, C1-C6 haloalkyl; r7、R8Independently selected from C1-C6 alkyl, C2-C6 alkenyl, and R7、R8At least one of which is C2-C6 alkenyl.
2. Polyaryletherketone according to claim 1, wherein said C1-C6 alkyl is selected from methyl, ethyl, propyl, isopropyl, butyl or isobutyl, preferably methyl; the C1-C6 haloalkyl is selected from trifluoromethyl, trichloromethyl or tribromomethyl, preferably trifluoromethyl; the C1-C6 carboxyl is selected from carboxyl, ethylcarboxyl or propylcarboxyl, preferably propylcarboxyl; the C2-C6 alkenyl is selected from vinyl, propenyl, 1-butenyl or 2-butenyl, preferably allyl.
3. The polyaryletherketone of claim 1, wherein R is R1And R2Is C1-C3 haloalkyl, preferably trifluoromethyl; r3Is C1-C4 alkyl, preferably methyl; r4Is a C1-C4 carboxyl group, preferably a 1-propanoic acid group; r is5And R6Is C1-C3 alkyl, preferably methyl; r is7And R8Alkenyl of C2 to C3, preferably allyl.
4. Polyaryletherketone according to claim 1, wherein the ratio of the number of units 1, 2 and 3 is from 3 to 5:0.5 to 2:4 to 6, preferably from 3.5 to 4.5:0.5 to 1.5:4.5 to 5.5; further, the weight average molecular weight of the polyaryletherketone is 5-10 ten thousand g/mol.
5. A process for the preparation of a polyaryletherketone according to any one of claims 1 to 4, comprising the steps of:
adding a monomer 1, a monomer 2, a monomer 3, a monomer 4, Lewis base and a catalyst into an organic solvent, and carrying out polycondensation reaction under the conditions of heating and stirring to obtain the product polyaryletherketone, wherein the structure of the monomer 1-3 is as follows:
the monomer 4 is 1, 4-bis (4-fluorobenzoyl) benzene; the amount of the monomer 4 is 1 to 1.2 times the total of the monomer 1, the monomer 2 and the monomer 3, and the amount ratio of the monomer 1, the monomer 2 and the monomer 3 is 3 to 5:0.5 to 2:4 to 6, preferably 3.5 to 4.5:0.5 to 1.5:4.5 to 5.5.
6. A lithium battery separator comprising an ozone-modified polyolefin separator and the polyaryletherketone of any of claims 1-4.
7. The lithium battery separator as claimed in claim 6, wherein the polyolefin is selected from one of a Polyethylene (PE) single layer film, a polypropylene (PP) single layer film, and a PP/PE/PP three-layer composite film; preferably a polypropylene (PP) monolayer film.
8. The lithium battery separator as claimed in claim 6, wherein the ozone modification is carried out by subjecting the polyolefin separator to an oxidation treatment for 20 to 50min under an ozone atmosphere with a volume concentration of 25 to 60%; preferably, the volume concentration of the ozone is 40-50%, and the oxidation treatment time is 30-40 min.
9. A method for preparing a lithium battery separator as claimed in any one of claims 6 to 8, comprising the steps of:
1) preparation of polyaryletherketone coating solution: dissolving polyaryletherketone in a methanesulfonic acid solution, and fully stirring to obtain a uniformly mixed solution;
2) oxidizing and modifying the lithium battery diaphragm: putting the polyolefin diaphragm into an ozone atmosphere for oxidation modification;
3) coating and forming: carrying out film scraping operation on one surface of the polyolefin film subjected to oxidation modification by using the polyaryletherketone mixed solution obtained in the step 1); placing the lithium battery diaphragm in a coagulating bath, performing pore-forming by adopting a phase inversion method, soaking and washing, and drying to obtain a modified polyaryletherketone coated lithium battery diaphragm;
the mass fraction of the polyaryletherketone in the step 1) is 5-10%, preferably 6-8%.
10. A lithium battery comprising a positive electrode, a negative electrode, an electrolyte, and a lithium battery separator as claimed in any one of claims 6 to 8, or a lithium battery separator obtained by the method of claim 8 or 9.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114976473A (en) * | 2022-06-08 | 2022-08-30 | 派恩(中山)科技有限公司 | Modified cellulose membrane used for high-temperature lithium ion battery diaphragm |
| CN115863906A (en) * | 2022-12-20 | 2023-03-28 | 蜂巢能源科技(无锡)有限公司 | Composite diaphragm and preparation method and application thereof |
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| CN108400379A (en) * | 2018-01-17 | 2018-08-14 | 北京大学 | A kind of preparation of the preparation method and full battery of high security lithium ion battery diaphragm |
| KR20190072919A (en) * | 2017-12-18 | 2019-06-26 | 성균관대학교산학협력단 | Polyaryletherketone and method for manufacturing the same |
| CN109942808A (en) * | 2019-03-07 | 2019-06-28 | 东北师范大学 | A kind of poly(aryl ether ketone) and preparation method thereof and the application in lithium battery diaphragm |
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| CN105585732A (en) * | 2015-12-30 | 2016-05-18 | 吉林省聚科高新材料有限公司 | Ultraviolet crosslinking polyaryletherketone porous membrane, preparation method and application of ultraviolet crosslinking polyaryletherketone porous membrane |
| KR20190072919A (en) * | 2017-12-18 | 2019-06-26 | 성균관대학교산학협력단 | Polyaryletherketone and method for manufacturing the same |
| CN108400379A (en) * | 2018-01-17 | 2018-08-14 | 北京大学 | A kind of preparation of the preparation method and full battery of high security lithium ion battery diaphragm |
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| CN114976473A (en) * | 2022-06-08 | 2022-08-30 | 派恩(中山)科技有限公司 | Modified cellulose membrane used for high-temperature lithium ion battery diaphragm |
| CN114976473B (en) * | 2022-06-08 | 2024-05-07 | 派恩(中山)科技有限公司 | Modified cellulose membrane for high-temperature lithium ion battery separator |
| CN115863906A (en) * | 2022-12-20 | 2023-03-28 | 蜂巢能源科技(无锡)有限公司 | Composite diaphragm and preparation method and application thereof |
| CN115863906B (en) * | 2022-12-20 | 2024-02-23 | 蜂巢能源科技(无锡)有限公司 | Composite diaphragm and preparation method and application thereof |
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