CN116102775A - Porous polyimide film for lithium ion battery and preparation method thereof - Google Patents
Porous polyimide film for lithium ion battery and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a porous polyimide film for a lithium ion battery and a preparation method thereof, and belongs to the technical field of films. The preparation method of the porous polyimide film for the lithium ion battery comprises the following steps: (1) Dissolving dianhydride monomer in a solvent, adding a mixed solution of diamine monomer, mono-amino end-capped degradable polyester and the solvent, mixing, and stirring for reaction under inert atmosphere to obtain a viscous solution; (2) And (3) coating the viscous solution, drying, stretching and fixing, and performing high-temperature treatment to obtain the porous polyimide film. The porous polyimide film prepared by the method has the advantages of high pore diameter uniformity, good repeatability, uniform thickness and good mechanical property.
Description
Technical Field
The invention relates to the technical field of films, in particular to a porous polyimide film for a lithium ion battery and a preparation method thereof.
Background
The polymer separator applied to lithium ion batteries in the domestic market at present is mainly based on polyolefin materials: polyethylene and polypropylene. The polyolefin film has the characteristics of good tensile strength, low cost, easy processing and the like. Meanwhile, the polyolefin film has the defects of low melting point, poor thermal stability, flammability, poor affinity with high-polarity electrolyte and the like due to low polarity. Therefore, a porous Polyimide (PI) film having excellent properties is considered as a high-end film for lithium ion batteries, which replaces the conventional polyolefin film.
The method for preparing the porous PI film mainly comprises a template method, a phase inversion method and an electrostatic spinning method.
The template method needs to prepare a PI composite film containing a pore-forming agent, and then remove the pore-forming agent by means of chemical corrosion, solvent dissolution or calcination to obtain the PI porous film. Common porogens include metal oxides, hydroxides or non-metal oxides, organic blowing agents, low decomposition temperature polymers, and the like. The PI porous membrane prepared by the method has uneven pore diameter and poor mechanical property.
The phase inversion method is to knife coat a polyamic acid (PAA) precursor solution or a soluble PI solution on a support (e.g., glass, etc.), submerge into a precipitation solvent, and phase separate the polymer in its solvent/precipitation solvent mixture. After the solvent is removed, the space occupied by the non-solvent forms a pore canal, and the pore structure of the porous membrane can be simply and effectively regulated and controlled by changing the formula and the process conditions of the casting solution. The PI porous membrane prepared by this method is often disordered.
The nanofiber membrane prepared by the electrostatic spinning technology has a 3D network structure and high porosity, and provides a rich channel for rapid migration of lithium ions therein. Compared with the traditional non-woven fabric, the nanofiber membrane has finer fiber diameter (between a few nanometers and hundreds of nanometers), smaller pore diameter and is beneficial to relieving the self-discharge phenomenon of the battery. However, electrostatic spinning is easy to be interfered by vibration and an electric field, meanwhile, the PI film prepared under the condition of the method has uneven pore diameter, partial pores are larger than 10 mu m, and the strength of the spinning film is generally poor.
Disclosure of Invention
The invention aims to provide a porous polyimide film for a lithium ion battery and a preparation method thereof, which are used for solving the problems in the prior art. The PI film prepared by the invention overcomes the defects of uneven pore size and poor strength of the PI film in the prior art, and has the advantages of uniform and adjustable pore size (the pore size of the finally formed porous polyimide film can be changed by changing the molecular weight of the segmented copolymer formed by the PAA and the degradable polyester), good tensile strength, good thermal stability and the like.
In order to achieve the above object, the present invention provides the following solutions:
one of the technical schemes of the invention is as follows: the preparation method of the porous polyimide film for the lithium ion battery comprises the following steps:
(1) Dissolving dianhydride monomer in a solvent, adding a mixed solution of diamine monomer, mono-amino end-capped degradable polyester and the solvent, mixing, and stirring for reaction under inert atmosphere to obtain a viscous solution;
(2) And (3) coating the viscous solution, drying, stretching and fixing, and performing high-temperature treatment to obtain the porous polyimide film.
Further, in the step (1), the dianhydride monomer is pyromellitic dianhydride; the solvent is N, N' -dimethylacetamide; the diamine monomer is selected from any one of 4,4' -diaminodiphenyl ether and p-phenylenediamine; the mono-amino-terminated degradable polyester is selected from any one of amino-terminated poly-L-lactic acid, amino-terminated poly-glycolic acid and amino-terminated poly-epsilon-caprolactone.
Further, the preparation method of the amino-terminated poly-L-lactic acid specifically comprises the following steps:
A. dissolving stannous octoate and N- (4-hydroxymethyl phenyl) carbamic acid tert-butyl ester in a solvent, stirring and reacting under an inert atmosphere, adding levorotatory lactide, stirring uniformly, and then freezing by 3 times of liquid nitrogen, vacuumizing and introducing N 2 A thawing process, finally heating and reacting, and precipitating with methanol to obtain flocculent solid;
the structural formula of the N- (4-hydroxymethyl phenyl) carbamic acid tert-butyl ester is shown as a formula (1):
the structural formula of the flocculent solid is shown as the formula (2):
B. dissolving the flocculent solid in a solvent, adding trifluoroacetic acid, stirring for reaction, steaming under reduced pressure to remove the flocculent solid, dissolving the solid in the solvent again, then washing with sodium bicarbonate aqueous solution and water to be neutral in sequence, adding anhydrous sodium sulfate for stirring for reaction, and steaming under reduced pressure to remove the solvent to obtain the amino-terminated poly-L-lactic acid.
The structural formula of the amino-terminated poly-L-lactic acid is shown as a formula (3):
further, the preparation method of the amino-terminated polyglycolic acid specifically comprises the following steps:
step 1, stannous octoate and N- (4-hydroxymethyl phenyl) carbamic acid tert-butyl ester are dissolved in a solvent, stirred and reacted under inert atmosphere, glycolide is added, stirred uniformly, and then 3 times of liquid nitrogen freezing, vacuumizing and N introducing are carried out 2 A thawing process, finally heating and reacting, and precipitating with methanol to obtain flocculent solid;
the structural formula of the flocculent solid is shown as formula (4):
and 2, dissolving the flocculent solid in a solvent, adding trifluoroacetic acid, stirring for reaction, evaporating under reduced pressure, dissolving the solid in the solvent again, washing with sodium bicarbonate aqueous solution and water to be neutral in sequence, adding anhydrous sodium sulfate for stirring for reaction, and evaporating under reduced pressure to remove the solvent to obtain the amino-terminated polyglycolic acid.
The amino-terminated polyglycolic acid is shown as a formula (5):
further, the preparation method of the amino-terminated poly epsilon-caprolactone specifically comprises the following steps:
dissolving stannous octoate and N- (4-hydroxymethyl phenyl) carbamic acid tert-butyl ester in a solvent, stirring and reacting under an inert atmosphere, adding epsilon-caprolactone, stirring uniformly, and then freezing by 3 times of liquid nitrogen, vacuumizing and introducing N 2 A thawing process, finally heating and reacting, and precipitating with methanol to obtain flocculent solid;
the structural formula of the flocculent solid is shown as formula (6):
and II, dissolving the flocculent solid in a solvent, adding trifluoroacetic acid, stirring for reaction, evaporating under reduced pressure, dissolving the solid in the solvent again, washing with sodium bicarbonate aqueous solution and water to be neutral in sequence, adding anhydrous sodium sulfate for stirring for reaction, and evaporating under reduced pressure to remove the solvent to obtain the amino-terminated poly epsilon-caprolactone.
The structural formula of the amino-terminated poly epsilon-caprolactone is shown as a formula (7):
further, in the step (1), the molar ratio of the dianhydride monomer to the diamine monomer is 1:1; the temperature of the stirring reaction is room temperature and the time is 24 hours.
Further, in the step (2), the thickness of the coating film is 70 to 80 μm; the drying is specifically as follows: drying is carried out at 60℃for 1h and then at 120℃for 1h.
Further, in the step (2), the high temperature treatment specifically includes: the treatment is carried out according to the temperature ranging from 100 ℃ for 1h to 200 ℃ for 1h to 300 ℃ for 1h to 350 ℃ for 2 h.
The second technical scheme of the invention is as follows: the porous polyimide film prepared by the preparation method.
The third technical scheme of the invention: an application of the porous polyimide film in a lithium ion battery.
The invention discloses the following technical effects:
(1) The porous polyimide film prepared by the method has the advantages of high pore diameter uniformity, good repeatability, uniform thickness and good mechanical property.
(2) The lithium ion battery prepared by the porous polyimide film has good charge-discharge rate performance and safety performance.
(3) The invention takes the mono-amino end capped degradable polyester as a polyamide acid (PAA) molecular weight control agent to form a segmented copolymer of PAA and the degradable polyester, adjusts the molecular weight of the PAA and the degradable polyester and the ratio of the PAA and the degradable polyester (the molecular weight of the PAA can be controlled by changing the initial molar ratio of dianhydride to diamine, the molecular weight of the mono-amino end capped degradable polyester can be adjusted by changing the molar ratio of N- (4-hydroxymethyl phenyl) carbamic acid tert-butyl ester to lactide (glycolide and epsilon-caprolactone), the ratio of dianhydride to diamine to mono-amino end capped degradable polyester (molar ratio) =1:1:x, the ratio of the PAA to the polyester in the segmented copolymer can be changed by changing the numerical value of x), forms an ordered structure through self-assembly of the segmented copolymer, and the degradable polyester component is cracked off while amination is carried out at the same time of high Wen Xianya, thus obtaining the ordered porous PI film (porous polyimide film); in the block polymer stage, the stretching, fixing and forming are adopted, so that the mechanical strength after imidization is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block copolymer of the invention of example 1 step (3) in which a dianhydride, diamine and a mono-amino terminated degradable polyester are reacted to form a polymer in N 2 A graph of thermal weight loss under an atmosphere;
FIG. 2 is an SEM image of a porous polyimide film prepared according to example 1 of the present invention;
FIG. 3 is a block copolymer of the invention of example 2 step (3) in which a dianhydride, diamine and a mono-amino terminated degradable polyester are reacted to form a polymer in N 2 A graph of thermal weight loss under an atmosphere;
FIG. 4 is an SEM image of a porous polyimide film prepared according to example 2 of the present invention;
FIG. 5 is a block copolymer of the invention of example 3 step (3) in which a dianhydride, diamine and a mono-amino terminated degradable polyester are reacted to form a polymer in N 2 A graph of thermal weight loss under an atmosphere;
FIG. 6 is an SEM image of a porous polyimide film prepared according to example 3 of the present invention;
FIG. 7 is an SEM image of a porous polyimide film prepared according to example 4 of the present invention;
FIG. 8 is an SEM image of a porous polyimide film prepared according to example 5 of the present invention;
FIG. 9 is an SEM image of a porous polyimide film prepared according to example 6 of the present invention;
FIG. 10 is an SEM image of a polyimide film prepared according to comparative example 1 of the present invention;
FIG. 11 is an SEM image of a polyimide film prepared according to comparative example 2 of the present invention;
fig. 12 is an SEM image of the polyimide film prepared in comparative example 3 of the present invention.
Detailed Description
Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
The following examples and comparative examples of the present invention use tert-butyl N- (4-hydroxymethylphenyl) carbamate prepared as follows:
2.46g of p-aminobenzyl alcohol (0.02 mol) and 4.8g of di-tert-butyl dicarbonate (0.022 mol) were each introduced into a 250mL three-necked flask equipped with a magnetic rotor at room temperature, 50mL of tetrahydrofuran was added thereto, and N was introduced 2 Stirring to dissolve, cooling to 0deg.C, slowly adding 22mL 1mol/L tetrahydrofuran solution of hexamethyldisilazide, gradually heating to room temperature, and N 2 Stirring for 24h under protection, pouring into 100mL of deionized water, extracting with dichloromethane for 2 times (2X 50 mL), washing the dichloromethane phase with deionized water twice (2X 50 mL), adding anhydrous sodium sulfate into the dichloromethane phase, stirring at room temperature for 12h, filtering, decompressing to remove dichloromethane, recrystallizing the obtained solid in petroleum ether (40-60 ℃) to obtain 3.35g of acicular solid, namely the tert-butyl N- (4-hydroxymethyl phenyl) carbamate, wherein the structural formula is as follows:
example 1
A preparation method of a porous polyimide film for a lithium ion battery comprises the following steps:
(1) 0.04g of stannous octoate and 0.223g N- (4-hydroxymethylphenyl) carbamic acid tert-butyl ester (0.001 mol) were dissolved in 100mL of anhydrous toluene and added to a 250mL polymerization flask with a magnetic rotor and dried at room temperature by N 2 Stirring for 12h, adding 14.4g (0.1 mol) of L-lactide, stirring uniformly, freezing with 3 times of liquid nitrogen, vacuumizing, and introducing N 2 The reaction was carried out at 110℃for 12h, the product was precipitated with methanol and dried in vacuo to give 13.1g of a flocculent solid of the formula:
(2) Dissolving the flocculent solid prepared in the step (1) in 130mL of dichloromethane, adding 25mL of trifluoroacetic acid, stirring at room temperature for 45min, steaming under reduced pressure to remove dichloromethane and excess trifluoroacetic acid, redissolving the remaining solid in 130mL of dichloromethane, washing a dichloromethane phase with 100mL of saturated aqueous sodium bicarbonate solution, washing an aqueous phase with dichloromethane for 2 times (2X 20 mL), merging dichloromethane phases, washing the dichloromethane phase with deionized water to be neutral, adding anhydrous sodium sulfate, stirring and drying overnight, filtering, removing dichloromethane under reduced pressure to obtain 12.4g of amino-terminated poly-L-lactic acid (with a number average molecular weight of 14200 and a molecular weight distribution index of 1.12), wherein the molecular weight distribution index is represented by the following structural formula:
(3) 5.45g (0.025 mol) of pyromellitic dianhydride was dissolved in 45g of N, N' -dimethylacetamide and added to a 250mL three-necked flask with a magnetic rotor; 5g of 4,4 '-diaminodiphenyl ether (0.025 mol) and 5.25g of the amino-terminated poly-L-lactic acid prepared in the step (2) are dissolved in 90g of N, N' -dimethylacetamide, and then added into a three-necked flask, and N is introduced 2 Stirring at room temperature for 24h to obtain a viscous solution; the viscous solution was manually coated on a clean and dry glass plate with a wire rod film coater to a thickness of 70 μm, then placed in a forced air drying oven, dried at 60℃for 1 hour and dried at 120℃for 1 hour, the film was peeled off from the glass plate (corresponding thermal weight loss curve at this time is shown in FIG. 1), cut into a fixed shape, stretched (stretched flat) and clamped with a special clamp, placed in a muffle furnace, and treated at 100℃for 1 hour to 200℃for 1 hour to 300℃for 1 hour to 350℃for 2 hours to obtain 9.38g of a porous polyimide film, and a scanning electron microscope was used to take a SEM image of the film section (see FIG. 2).
Example 2
A preparation method of a porous polyimide film for a lithium ion battery comprises the following steps:
(1) 0.03g of stannous octoate and 0.149. 0.149g N- (4-hydroxymethylphenyl) carbamic acid tert-butyl ester (0.00067 mol) were dissolved in 100mL of anhydrous toluene and added to a 250mL polymerization flask with a magnetic rotor and dried at room temperature by N 2 Stirring for 12h, adding 11.6g (0.1 mol) glycolide, stirring, freezing with 3 times liquid nitrogen, vacuumizing, and introducing N 2 The reaction was carried out at 110℃for 12h, the product was precipitated with methanol and dried in vacuo to give 10.7g of a flocculent solid of the formula:
(2) Dissolving the flocculent solid prepared in the step (1) in 120mL of dichloromethane, adding 20mL of trifluoroacetic acid, stirring at room temperature for 45min, steaming under reduced pressure to remove dichloromethane and excess trifluoroacetic acid, redissolving the remaining solid in 120mL of dichloromethane, washing the dichloromethane phase with 100mL of saturated aqueous sodium bicarbonate solution, washing the water phase with dichloromethane 2 times (2X 20 mL), merging the dichloromethane phases, washing the dichloromethane phase with deionized water to be neutral, adding anhydrous sodium sulfate, stirring and drying overnight, filtering, removing dichloromethane under reduced pressure to obtain 10.1g of amino-terminated polyglycolic acid (number average molecular weight is 17230, molecular weight distribution index is 1.20), and the structural formula is as follows:
(3) 5.45g (0.025 mol) of pyromellitic dianhydride was dissolved in 45g of N, N '-dimethylacetamide, and the mixture was put into a 250mL three-necked flask equipped with a magnetic rotor, 2.7g of p-phenylenediamine (0.025 mol) and 4.61g of the terminal amino-polyglycolic acid prepared in the step (2) were dissolved in 90g of N, N' -dimethylacetamide, and then the mixture was put into a three-necked flask, and N was introduced into the flask 2 Stirring at room temperature for 24h to obtain a viscous solution; manually coating the viscous solution on a clean and dry glass plate with a thickness of 80 μm by using a bar coater, and placing in a blast drying oven at 60 DEG CDrying for 1h, drying at 120deg.C for 1h (corresponding thermal weight loss curve is shown in figure 3), removing the film from the glass plate, cutting into fixed shape, stretching (stretching and straightening) with special clamp, clamping, placing in a muffle furnace, treating at 100deg.C for 1 h-200deg.C for 1 h-300deg.C for 2h to obtain 6.88g porous polyimide film, and Scanning Electron Microscope (SEM) for film section (see figure 4).
Example 3
A preparation method of a porous polyimide film for a lithium ion battery comprises the following steps:
(1) 0.05g of stannous octoate and 0.335 t-butyl g N- (4-hydroxymethylphenyl) carbamate (0.0015 mol) were dissolved in 100mL of anhydrous toluene and added to a 250mL polymerization flask with a magnetic rotor and dried at room temperature by N 2 Stirring for 12h, adding 11.4g (0.1 mol) of epsilon-caprolactone, stirring uniformly, freezing with 3 times of liquid nitrogen, vacuumizing and introducing N 2 The thawing process is carried out for 12 hours at 110 ℃, and the product methanol is precipitated and then dried in vacuum to obtain 10.7g flocculent solid, wherein the flocculent solid has the following structural formula:
(2) Dissolving the flocculent solid prepared in the step (1) in 120mL of dichloromethane, adding 20mL of trifluoroacetic acid, stirring at room temperature for 45min, steaming under reduced pressure to remove dichloromethane and excess trifluoroacetic acid, redissolving the remaining solid in 120mL of dichloromethane, washing a dichloromethane phase with 100mL of saturated aqueous sodium bicarbonate solution, washing an aqueous phase with dichloromethane for 2 times (2X 20 mL), merging the dichloromethane phases, washing the dichloromethane phase with deionized water to be neutral, adding anhydrous sodium sulfate, stirring and drying overnight, filtering, and removing dichloromethane under reduced pressure to obtain 10.1g of amino-terminated poly epsilon-caprolactone (number average molecular weight is 7510, molecular weight distribution index is 1.24), wherein the molecular weight is represented by the following structural formula:
(3) 5.45g (0.025 mol) of pyromellitic dianhydride was dissolved in 45g of N, N' -bisMethylacetamide was added to a 250mL three-necked flask equipped with a magnetic rotor, 2.7g of p-phenylenediamine (0.025 mol) and 4.71g of (2) medium-end amino poly- ε -caprolactone were dissolved in 90g of N, N' -dimethylacetamide, and then added to the three-necked flask, followed by N-feeding 2 Stirring at room temperature for 24h to obtain a viscous solution; the viscous solution was manually coated on a clean and dry glass plate with a wire rod film coater to a thickness of 80 μm, and then placed in a forced air drying oven to be dried at 60℃for 1 hour and then at 120℃for 1 hour (corresponding thermal weight loss curve at this time is shown in FIG. 5), the film was peeled off from the glass plate, cut into a fixed shape, stretched (stretched flat) and clamped by a special clamp, placed in a muffle furnace to be treated at 100℃for 1 hour to 200℃for 1 hour to 300℃for 1 hour to 350℃for 4 hours, and 6.79g of a porous polyimide film was obtained, and a scanning electron microscope was used to photograph a film section SEM (see FIG. 6).
Example 4
(1) The amount of the added levorotatory lactide in the step (1) of the example 1 was changed to 28.8g (0.2 mol), the other conditions were unchanged, and after the drying was completed, 26.2g of flocculent solid was obtained;
(2) The preparation process of the amino-terminated poly-L-lactic acid is the same as that of the step (2) of the example 1;
(3) In the process of preparing the porous polyimide film, 5.25g of amino-terminated poly-L-lactic acid in the step (3) of the example 1 is changed to 5.65g, and finally 9.41g of porous polyimide film is obtained, and a Scanning Electron Microscope (SEM) image of a film section is taken (see FIG. 7).
The block copolymer formed by PAA and degradable polyester (mono-amino end-capped degradable polyester) is based on taking mono-amino end-capped degradable polyester as a macromolecular end-capping agent, controlling the molecular weight of the PAA, and changing the value of x can change the molecular weight of the PAA by changing the value of x, wherein the molecular weight of the PAA is controlled by the molecular weight of the PAA. The molecular weight of the mono-amino terminated degradable polyester is controlled by the molar ratio of its monomers to the initiator t-butyl N- (4-hydroxymethylphenyl) carbamate. The theoretical basis is "equimolar monomers aAa and bBb (corresponding to dianhydride and diamine in examples) in polycondensation molecular weight control within the context of" polymer chemistry ", and small amounts of monofunctional monomers (corresponding to the monoamino-terminated degradable polyesters in examples) are additionally added.
Example 5
(1) The amount of glycolide added in step (1) of example 2 was changed to 23.2g (0.2 mol), the other conditions were unchanged, and 21.2g of flocculent solid was obtained after drying was completed;
(2) The process for preparing the amino-terminated polyglycolic acid is the same as that of the step (2) of the example 2;
(3) In the process of preparing the porous polyimide film, 4.61g of the amino-terminated polyglycolic acid in the step (3) of example 2 is changed to 4.62g, and finally 6.90g of the porous polyimide film is obtained, and a Scanning Electron Microscope (SEM) image of a film cross section is taken (see FIG. 8).
Example 6
(1) The amount of epsilon-caprolactone added in the step (1) of the example 3 was changed to 17.1g (0.15 mol), the other conditions were unchanged, and 15.9g of flocculent solid was obtained after drying;
(2) The preparation process of the amino-terminated poly epsilon-caprolactone is the same as that of the step (2) of the example 3;
(3) In the process of preparing the porous polyimide film, 4.71g of amino-terminated poly epsilon-caprolactone in the step (3) of the example 3 is changed to 4.61g, and finally 6.92g of porous polyimide film is obtained, and a Scanning Electron Microscope (SEM) image of a film section is taken (see FIG. 9).
Polyimide film prepared by the reaction of simple dianhydride and diamine has no holes. By changing the mono-amino-terminated degradable polyesters (examples 4 to 6 above, controlling the molecular weight of the polyamic acid) porous polyimide films of different pore sizes can be obtained. The addition of the mono-amino terminated degradable polyester and the polyamide acid form a block copolymer to form the polyimide film with an ordered porous structure. Comparative examples 1 to 3 are polyimide films formed by a method not using a block copolymer.
Comparative example 1
The preparation method of the polyimide film comprises the following steps:
5.45g (0.025 mol) of pyromellitic dianhydride was dissolved in 45g of N, N' -dimethylacetamide and added to a 250mL three-necked flask with a magnetic rotor; 5g (0.025 mol) of 4,4 '-diaminodiphenyl ether (0.025 mol) was dissolved in 90g of N, N' -dimethylacetamide, and then introduced into a three-necked flask 2 Stirring at room temperatureFor 24 hours, 1.81g of tetraethoxysilane is dripped into the mixture, and the mixture is stirred for 8 hours at room temperature to obtain a viscous solution; the viscous solution was manually coated on a clean and dry glass plate with a wire rod film coater to a thickness of 70 μm, dried at 60℃for 1 hour and then dried at 120℃for 1 hour in a forced air drying oven, the film was peeled off from the glass plate, cut into a fixed shape, clamped by a special clamp for stretching (stretching straight), placed in a muffle furnace, treated at 100℃for 1 hour to 200℃for 1 hour to 300℃for 1 hour, cooled to room temperature to obtain 9.94g of film, immersed in 200mL of 36.5wt.% aqueous hydrofluoric acid solution, slowly stirred at room temperature for 72 hours by a magnetic rotor, taken out, washed 3 times with distilled water and absolute ethyl alcohol, and dried at 70℃in vacuum for 24 hours to obtain 9.23g of polyimide film, and a scanning electron microscope was used to photograph a film sectional SEM (see FIG. 10).
Comparative example 2
The comparative example 1 was different from the comparative example 1 in that "1.81 g of ethyl orthosilicate was dropped" instead of "0.73 g of hydrophobic nano silica powder (average particle diameter: 15 to 30 nm) was added", and finally 9.24g of a polyimide film was obtained, and a SEM image of the film cross section was taken of the obtained polyimide film by using a scanning electron microscope (see fig. 11).
Comparative example 3
The preparation method of the polyimide film comprises the following steps:
5.45g (0.025 mol) of pyromellitic dianhydride was dissolved in 45g of N, N' -dimethylacetamide and added to a 250mL three-necked flask with a magnetic rotor; 3g (0.015 mol) of 4,4 '-diaminodiphenyl ether (0.015 mol) and 7.5g of aminopropyl-terminated polydimethylsiloxane having a molecular weight of 750 were dissolved in 80g of N, N' -dimethylacetamide and 40g of tetrahydrofuran, and then introduced into a three-necked flask, through which N was introduced 2 Stirring at room temperature for 24h to obtain a viscous solution; manually coating the viscous solution on a clean and dry glass plate with a wire rod film coater, drying at the thickness of 70 mu m in a blast drying oven at 50 ℃ for 12 hours, drying at the temperature of 120 ℃ for 1 hour, removing the film from the glass plate, cutting into a fixed shape, stretching (stretching and straightening) and clamping by a special clamp, placing in a muffle furnace, treating at the temperature of 100 ℃ for 1 hour to 200 ℃ for 1 hour to 300 ℃ for 1 hour, cooling to room temperature to obtain 9.85g of film, immersing in 200mL of 36.5wt.% hydrofluoric acid aqueous solution, adding a magnetic rotor, slowly stirring at the room temperature for 72 hours, taking out the filmThen, the polyimide film was washed 3 times with distilled water and absolute ethyl alcohol, and dried under vacuum at 70℃for 24 hours to obtain 7.48g of a polyimide film, and SEM images of the film cross-section were taken by a scanning electron microscope (see FIG. 12).
The properties of the porous polyimide films prepared in examples and comparative examples are shown in Table 1.
TABLE 1 polyimide film Properties
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (10)
1. The preparation method of the porous polyimide film for the lithium ion battery is characterized by comprising the following steps of:
(1) Dissolving dianhydride monomer in a solvent, adding a mixed solution of diamine monomer, mono-amino end-capped degradable polyester and the solvent, mixing, and stirring for reaction under inert atmosphere to obtain a viscous solution;
(2) And (3) coating the viscous solution, drying, stretching and fixing, and performing high-temperature treatment to obtain the porous polyimide film.
2. The method according to claim 1, wherein in the step (1), the dianhydride monomer is pyromellitic dianhydride; the solvent is N, N' -dimethylacetamide; the diamine monomer is selected from any one of 4,4' -diaminodiphenyl ether and p-phenylenediamine; the mono-amino-terminated degradable polyester is selected from any one of amino-terminated poly-L-lactic acid, amino-terminated poly-glycolic acid and amino-terminated poly-epsilon-caprolactone.
3. The preparation method of the amino-terminated poly-L-lactic acid according to claim 2, which specifically comprises the following steps:
A. dissolving stannous octoate and N- (4-hydroxymethyl phenyl) carbamic acid tert-butyl ester in a solvent, stirring and reacting under an inert atmosphere, adding levorotatory lactide, stirring uniformly, then freezing by liquid nitrogen, vacuumizing and introducing N 2 A thawing process, finally heating and reacting, and precipitating with methanol to obtain flocculent solid;
B. dissolving the flocculent solid in a solvent, adding trifluoroacetic acid, stirring for reaction, steaming under reduced pressure to remove the flocculent solid, dissolving the solid in the solvent again, then washing with sodium bicarbonate aqueous solution and water to be neutral in sequence, adding anhydrous sodium sulfate for stirring for reaction, and steaming under reduced pressure to remove the solvent to obtain the amino-terminated poly-L-lactic acid.
4. The preparation method according to claim 2, wherein the preparation method of the amino-terminated polyglycolic acid specifically comprises the following steps:
step 1, stannous octoate and N- (4-hydroxymethyl phenyl) carbamic acid tert-butyl ester are dissolved in a solvent, stirred and reacted under inert atmosphere, glycolide is added, stirred uniformly, and then the mixture is frozen by liquid nitrogen, vacuumized and N is led in 2 A thawing process, finally heating and reacting, and precipitating with methanol to obtain flocculent solid;
and 2, dissolving the flocculent solid in a solvent, adding trifluoroacetic acid, stirring for reaction, evaporating under reduced pressure, dissolving the solid in the solvent again, washing with sodium bicarbonate aqueous solution and water to be neutral in sequence, adding anhydrous sodium sulfate for stirring for reaction, and evaporating under reduced pressure to remove the solvent to obtain the amino-terminated polyglycolic acid.
5. The preparation method according to claim 2, wherein the preparation method of the amino-terminated poly epsilon-caprolactone specifically comprises the following steps:
dissolving stannous octoate and N- (4-hydroxymethyl phenyl) carbamic acid tert-butyl ester in a solvent, stirring and reacting in an inert atmosphere, adding epsilon-caprolactone, stirring uniformly, then freezing by liquid nitrogen, vacuumizing and introducing N 2 A thawing process, finally heating the reactionPrecipitating with methanol to obtain flocculent solid;
and II, dissolving the flocculent solid in a solvent, adding trifluoroacetic acid, stirring for reaction, evaporating under reduced pressure, dissolving the solid in the solvent again, washing with sodium bicarbonate aqueous solution and water to be neutral in sequence, adding anhydrous sodium sulfate for stirring for reaction, and evaporating under reduced pressure to remove the solvent to obtain the amino-terminated poly epsilon-caprolactone.
6. The method of claim 1, wherein in step (1), the molar ratio of dianhydride monomer to diamine monomer is 1:1; the temperature of the stirring reaction is room temperature and the time is 24 hours.
7. The method according to claim 1, wherein in the step (2), the thickness of the coating film is 70 to 80 μm; the drying is specifically as follows: drying is carried out at 60℃for 1h and then at 120℃for 1h.
8. The method according to claim 1, wherein in the step (2), the high temperature treatment is specifically: the treatment is carried out according to the temperature ranging from 100 ℃ for 1h to 200 ℃ for 1h to 300 ℃ for 1h to 350 ℃ for 2 h.
9. A porous polyimide film prepared by the method of any one of claims 1 to 8.
10. Use of the porous polyimide film of claim 9 in a lithium ion battery.
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