Polyimide film and its manufacturing method

Abstract

This invention relates to a polyimide membrane, a method for manufacturing the polyimide membrane, and an energy storage device comprising the polyimide membrane, wherein the polyimide membrane contains a polyimide comprising a dianhydride monomer and a diamine monomer as polymerization units, the diamine monomer comprising 4,4-diaminodiphenylmethane and m-phenylenediamine.

Description

Technical Field

[0001] This invention relates to a polyimide film with excellent tensile properties and cost-effectiveness, and a method for manufacturing the same. Background Technology

[0002] Polyimide (PI) is based on a rigid aromatic backbone and an imide ring with excellent chemical stability. It is a polymer material with the highest level of chemical resistance, electrical insulation, chemical resistance and weather resistance among organic materials.

[0003] In particular, due to its excellent insulating properties, such as its low dielectric constant and other superior electrical properties, polyimide has attracted much attention as a high-functionality polymer material in many fields, including electrical, electronic, and optical fields.

[0004] Based on its excellent heat resistance and insulation properties, polyimide film is used in applications requiring heat-resistant masks, such as backing tape, insulation of lithium-ion secondary battery electrodes, component mounting and reflow soldering processes in various electronic products, and manufacturing processes.

[0005] Recently, with the expansion of the electric vehicle market, the battery market (especially rechargeable batteries) is experiencing rapid growth. To ensure reliability, medium and large batteries for electric vehicles and small batteries for mobile applications require high-purity insulation.

[0006] In particular, with the series of fires involving electric vehicle batteries, the importance of ensuring safety has become increasingly prominent, necessitating the development of polyimide films as battery insulating materials.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Publication No. 2003-192788 Summary of the Invention

[0010] Technical issues

[0011] The purpose of this invention is to provide a polyimide film with both excellent tensile properties and cost-effectiveness, as well as a method for manufacturing the same.

[0012] Therefore, the essential objective of this invention is to provide specific embodiments thereof.

[0013] Technical solution

[0014] An embodiment of the present invention for achieving the above objectives provides a polyimide film containing a polyimide comprising a dianhydride monomer and a diamine monomer as polymerization units, wherein the diamine monomer comprises 4,4-diaminodiphenylmethane (MDA) and m-phenylenediamine (MPD).

[0015] Another embodiment of the present invention provides a method for manufacturing a polyimide film, comprising: (a) polymerizing a dianhydride monomer with a diamine monomer comprising 4,4-diaminodiphenylmethane and m-phenylenediamine in an organic solvent to manufacture polyamic acid; and

[0016] (b) The step of imidizing the polyamic acid.

[0017] Another embodiment of the present invention provides an energy storage device comprising the above-described polyimide membrane.

[0018] The effects of the invention

[0019] The polyimide film according to an embodiment of the present invention can simultaneously possess excellent tensile properties and economy by using a specific dianhydride component and a specific diamine component in a specific molar ratio.

[0020] On the other hand, the present invention may include the polyimide film as described above for effective application in energy storage devices, etc. Detailed Implementation

[0021] Hereinafter, embodiments of the invention will be described in more detail in the order of "polyimide film" and "method for manufacturing polyimide film".

[0022] It should be noted beforehand that the terms or words used in this specification and claims should not be interpreted in their usual or dictionary meanings, but rather should be interpreted as meanings and concepts consistent with the technical ideas of the invention, based on the principle that the inventors may appropriately define the concepts of terms in order to best describe their invention.

[0023] Therefore, the embodiments described in this specification are only one of the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. It should be understood that at the time of this application, there may be many equivalents and modifications that can replace these embodiments.

[0024] In this specification, unless the context clearly indicates otherwise, singular expressions include plural expressions. Terms such as “comprising,” “having,” or “possessing” are intended to specify the presence of a feature, number, step, constituent element, or combination thereof implemented, and should be understood not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, constituent elements, or combinations thereof.

[0025] In this specification, when quantities, concentrations or other values ​​or parameters are given as a range, preferred range or preferred upper and lower limit, they should be understood to specifically disclose all ranges formed by any pair of any upper or preferred range limits and any lower or preferred range limits, regardless of whether the range is disclosed individually.

[0026] When a range of values ​​is mentioned in this specification, unless otherwise described, the range is intended to include its endpoint and all integers and fractions within that range. It is not intended to limit the scope of the invention to the specific values ​​mentioned when defining the range.

[0027] In this specification, "dianhydride" is intended to include its precursors or derivatives, which, although technically not dianhydrides, will still react with diamines to form polyamic acid, which can then be converted into polyimide.

[0028] In this specification, "diamine" is intended to include its precursors or derivatives, which, although technically not diamines, will still react with dianhydrides to form polyamic acid, which can then be converted into polyimide.

[0029] In this specification, the "to" and "~" in "a to b" and "a~b" which represent numerical ranges are defined as ≥ a and ≤ b.

[0030] The polyimide film of the present invention contains a polyimide comprising a dianhydride monomer and a diamine monomer as polymerization units, wherein the diamine monomer may comprise 4,4-diaminodiphenylmethane (MDA) and m-phenylenediamine (MPD).

[0031] The 4,4-diaminodiphenylmethane is a diaminodiphenyl ether (4,4′-Oxydianiline, ODA) with the oxygen atom replaced by CH2, and has a similar structure to diaminodiphenyl ether. It is a commercially available and inexpensive diamine monomer.

[0032] However, due to the difference in structural flexibility between 4,4-diaminodiphenylmethane and diaminodiphenyl ether, polyimide films made using 4,4-diaminodiphenylmethane tend to have lower tensile properties than polyimide films made using diaminodiphenyl ether.

[0033] On the other hand, m-phenylenediamine is an isomer of p-phenylenediamine (PPD). Unlike p-phenylenediamine, its two amino groups are located in the meta position on the benzene ring.

[0034] When used in combination with 4,4-diaminodiphenylmethane, m-phenylenediamine can improve the reduction in tensile properties caused by the use of 4,4-diaminodiphenylmethane.

[0035] In one implementation, the dianhydride monomer may comprise pyromelliticdianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylicdianhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylicdianhydride (BTDA), or a combination thereof.

[0036] In one implementation example, based on a total content of 100 mol% of the dianhydride monomers, the content of the pyromellitic dianhydride can be 90 mol% or more.

[0037] For example, the content of the pyromellitic dianhydride can be 95 mol% or more, or 100 mol%.

[0038] On the other hand, when biphenyltetracarboxylic dianhydride and / or benzophenone tetracarboxylic dianhydride are included as the dianhydride monomers, based on a total dianhydride monomer content of 100 mol%, the content of biphenyltetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, or a combination thereof can be 0.1 mol% or more and 5 mol% or less. In this case, based on a total dianhydride monomer content of 100 mol%, the content of pyromellitic dianhydride can be 95 mol% or more and 99.9 mol% or less.

[0039] The polyimide chain derived from biphenyltetracarboxylic dianhydride has a structure called charge transfer complex (CTC), which is a regular linear structure in which the electron donor and electron acceptor are close to each other and the intermolecular interaction is enhanced.

[0040] In addition, benzophenone tetracarboxylic dianhydride, which has a carbonyl group, also contributes to the expression of CTC, just like biphenyl tetracarboxylic dianhydride.

[0041] In particular, pyromellitic dianhydride may be included as one of the aforementioned dianhydride components. Pyromellitic dianhydride, as a dianhydride component with a relatively rigid structure, is preferred in that it imparts appropriate elasticity to the polyimide film.

[0042] Furthermore, biphenyl tetracarboxylic dianhydride and benzophenone tetracarboxylic dianhydride contain two benzene rings corresponding to the aromatic moiety, while pyromellitic dianhydride contains one benzene ring corresponding to the aromatic moiety.

[0043] The increase in the content of pyromellitic dianhydride in the dianhydride component can be understood as an increase in the number of imide groups in the molecule when the molecular weight is the same. This can be understood as the proportion of imide groups derived from the pyromellitic dianhydride in the polyimide polymer chain being relatively increased relative to the imide groups derived from biphenyltetracarboxylic dianhydride and benzophenonetetracarboxylic dianhydride.

[0044] If the content of pyromellitic dianhydride is reduced excessively, the components of the relatively rigid structure will decrease, and the mechanical properties of the polyimide film may drop below the desired level.

[0045] For this reason, the mechanical properties of the polyimide film may decrease depending on the content of the biphenyl tetracarboxylic dianhydride and benzophenone tetracarboxylic dianhydride.

[0046] In one embodiment, the dianhydride monomer may be composed of pyromellitic dianhydride, and the diamine monomer may be composed of 4,4-diaminodiphenylmethane and m-phenylenediamine.

[0047] That is, the polyimide film may be a polyimide film containing a three-component polyimide system composed of pyromellitic dianhydride, 4,4-diaminodiphenylmethane and m-phenylenediamine.

[0048] In one implementation example, based on a total content of 100 mol% of the diamine monomers, the content of 4,4-diaminodiphenylmethane may be 70 mol% or more and 95 mol% or less, and the content of m-phenylenediamine may be 5 mol% or more and 30 mol% or less.

[0049] For example, based on a total content of 100 mol% of the diamine monomers, the content of 4,4-diaminodiphenylmethane can be 75 mol% or more and 90 mol% or less, and the content of m-phenylenediamine can be 10 mol% or more and 25 mol% or less.

[0050] If the content of the above-mentioned 4,4-diaminodiphenylmethane is higher or lower than the range of the present invention, it may lead to a decrease in the elongation of the polyimide film, or a decrease in economic efficiency due to an increase in the cost of purchasing monomers.

[0051] In one implementation example, the elongation of the polyimide film can be 80% or more.

[0052] For example, the elongation of the polyimide film can be 85% or more or 90% or more.

[0053] Furthermore, the elongation of the polyimide film can be 120% or less. For example, the elongation of the polyimide film can be 110% or less.

[0054] In one implementation, the polyimide may be a random copolymer or a block copolymer. When the polyimide is a random copolymer, it can achieve a better elongation than a block copolymer, and is therefore preferred.

[0055] In this invention, a method for manufacturing polyamic acid can be exemplified as follows:

[0056] (1) A method of polymerization in which the diamine component is added in full to the solvent, and then the dianhydride component is added to make it substantially equimolar with the diamine component;

[0057] (2) Add the dianhydride component in full to the solvent, and then add the diamine component to make it substantially equimolar with the dianhydride component, in order to carry out polymerization;

[0058] (3) After adding a portion of the diamine component to the solvent, a portion of the dianhydride component is mixed at a ratio of approximately 95 to 105 mol% relative to the reaction component, and the remaining diamine component is added, followed by the remaining dianhydride component, so that the diamine component and the dianhydride component are substantially equimolar, in order to carry out the polymerization method.

[0059] (4) After adding the dianhydride component to the solvent, a portion of the diamine compound is mixed at a ratio of 95-105 mol% relative to the reaction components, and other dianhydride components are added, and the remaining diamine components are added to make the diamine components and dianhydride components substantially equal in molar, so as to carry out the polymerization method.

[0060] (5) A method in which a portion of the diamine component and a portion of the dianhydride component react in a solvent in such an excess manner to form a first composition, and a portion of the diamine component and a portion of the dianhydride component react in another solvent in such an excess manner to form a second composition, and then the first and second compositions are mixed and polymerization is completed, wherein if the diamine component is in excess when the first composition is formed, the dianhydride component is in excess in the second composition; if the dianhydride component is in excess in the first composition, the diamine component is in excess in the second composition, and the first and second compositions are mixed such that the total diamine component and the dianhydride component used in these reactions are substantially equimolar, and polymerization is carried out.

[0061] However, the polymerization method is not limited to the examples above, and polyamic acid can obviously be produced using any known method.

[0062] In one specific example, the method for manufacturing the polyimide film of the present invention may include:

[0063] (a) the step of polymerizing a dianhydride monomer with a diamine monomer comprising 4,4-diaminodiphenylmethane and m-phenylenediamine in an organic solvent to produce polyamic acid; and (b) the step of imidizing the polyamic acid.

[0064] In one implementation, the dianhydride monomer may comprise pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, or a combination thereof.

[0065] In one implementation example, the elongation of the polyimide film manufactured by the method described above can be 80% or more.

[0066] In one implementation example, based on a total content of 100 mol% of the diamine monomers, the content of 4,4-diaminodiphenylmethane may be 70 mol% or more and 95 mol% or less, and the content of m-phenylenediamine may be 5 mol% or more and 30 mol% or less.

[0067] In this invention, the polymerization method of polyamic acid as described above can be defined as random or block polymerization. The polyimide film made from the polyamic acid of this invention produced by the process described above can preferably be used to improve the tensile properties and economy of this invention.

[0068] On the other hand, there are no particular limitations on the solvent used to synthesize polyamic acid. Any solvent that can dissolve polyamic acid can be used, but amide-based solvents are preferred.

[0069] Specifically, the solvent can be an organic polar solvent, more specifically an aprotic polar solvent, for example, one or more selected from the group consisting of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), p-chlorophenol, o-chlorophenol, N-methylpyrrolidone (NMP), γ-butyrolactone (GBL), and diethylene glycol dimethyl ether (Diglyme), but not limited thereto, and can be used alone or in combination as needed.

[0070] In one example, N,N-dimethylformamide and N,N-dimethylacetamide are particularly preferred as the solvents described above.

[0071] Furthermore, in the polyamic acid manufacturing process, fillers other than nano-silica can be added to improve various properties of the film, such as lubricity, thermal conductivity, corona resistance, and Knoop hardness. There are no particular limitations on the added fillers, but preferred examples include titanium dioxide, alumina, silicon nitride, boron nitride, dicalcium phosphate, calcium phosphate, and mica.

[0072] The particle size of the filler is not particularly limited and can be determined based on the characteristics of the membrane to be modified and the type of filler added. Typically, the average particle size is 0.05 to 100 μm, preferably 0.1 to 75 μm, more preferably 0.1 to 50 μm, and especially preferably 0.1 to 25 μm.

[0073] If the particle size is below this range, it is difficult to show a modification effect; if it is above this range, it may seriously damage the surface properties or cause a significant decrease in mechanical properties.

[0074] Furthermore, there is no particular limitation on the amount of filler added; it can be determined based on the characteristics of the membrane to be modified or the particle size of the filler. Typically, the amount of filler added is 0.01 to 100 parts by weight relative to 100 parts by weight of polyimide, preferably 0.01 to 90 parts by weight, and more preferably 0.02 to 80 parts by weight.

[0075] If the filler content is below this range, the modification effect brought about by the filler will be difficult to show; if it is above this range, it may seriously damage the mechanical properties of the membrane. There are no particular limitations on the method of adding the filler, and any known method can be used.

[0076] In the manufacturing method of the present invention, the polyimide film can be manufactured by thermal imidization and chemical imidization.

[0077] In addition, it can also be manufactured by a combined imidization method that combines thermal imidization and chemical imidization.

[0078] The thermal imidization method refers to a method that eliminates chemical catalysts and uses heat sources such as hot air or infrared dryers to induce the imidization reaction.

[0079] Regarding the thermal imidization method, the gel film can be heat-treated at a variable temperature ranging from 100 to 600°C to imidize the amic acid groups present in the gel film; more specifically, the heat treatment can be performed at 200 to 500°C, and more specifically, at 300 to 500°C, to imidize the amic acid groups present in the gel film.

[0080] It should be noted that during the formation of the gel film, a portion of the amic acid (approximately 0.1 mol% to 10 mol%) may also be imidized. For this purpose, the polyamic acid composition can be dried at a variable temperature ranging from 50°C to 200°C, which can also be included in the scope of the above-mentioned thermal imidization method.

[0081] For chemical imidization, polyimide films can be manufactured using dehydrating agents and imidizing agents according to methods known in the art. Here, "dehydrating agent" refers to a substance that promotes the ring-closing reaction by dehydrating polyamic acid. Non-limiting examples include aliphatic anhydrides, aromatic anhydrides, N,N'-dialkylcarbodiimides, halogenated lower aliphatic and halogenated lower fatty acid anhydrides, arylphosphonic acid dihalides, and thionyl halides. Among these, aliphatic anhydrides are preferred from the perspective of availability and cost. Non-limiting examples include acetic anhydride (or acetic anhydride, AA), propionic anhydride, and lactic anhydride, which can be used alone or in combination.

[0082] Furthermore, "imide agent" refers to a substance that promotes the ring-closing reaction of polyamic acid, such as aliphatic tertiary amines, aromatic tertiary amines, heterocyclic tertiary amines, and other amine-based components. Among these, heterocyclic tertiary amines are preferred from the perspective of their reactivity as catalysts. Non-limiting examples of heterocyclic tertiary amines include quinoline, isoquinoline, β-methylpyridine (BP), and pyridine, which can be used alone or in combination of two or more.

[0083] The amount of dehydrating agent added is preferably in the range of 0.5 to 5 moles, and particularly preferably in the range of 1.0 to 4 moles, relative to 1 mole of amyl acid groups in polyamic acid. Furthermore, the amount of imidizing agent added is preferably in the range of 0.05 to 2 moles, and particularly preferably in the range of 0.2 to 1 mole, relative to 1 mole of amyl acid groups in polyamic acid.

[0084] If the amounts of the dehydrating agent and imidizing agent added are below the ranges mentioned above, the chemical imidization will be insufficient, and the resulting polyimide film may develop cracks and its mechanical strength may decrease. Furthermore, if these amounts are above the ranges mentioned above, the imidization process may proceed too quickly; in this case, it may be difficult to cast into a film shape, or the resulting polyimide film may exhibit brittle properties, which is therefore undesirable.

[0085] As an example of the composite imidization method, a polyimide film can be manufactured by adding a dehydrating agent and an imidizing agent to a polyamic acid solution, heating it at 80 to 200°C, preferably 100 to 180°C, to partially cure and dry it, and then heating it at 200 to 400°C for 5 to 400 seconds.

[0086] The present invention provides an energy storage device comprising the above-mentioned polyimide membrane.

[0087] In one implementation example, the energy storage device may be a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor.

[0088] In particular, the aforementioned polyimide film can be used in the form of insulating tape for energy storage devices.

[0089] Implementation of the invention

[0090] The effects and functions of the invention are further described in detail below through specific embodiments. However, such embodiments are presented merely as examples of the invention, and the scope of the invention is not defined by them.

[0091] <Manufacturing Example>

[0092] While injecting nitrogen into a 500 ml reactor equipped with a stirrer and nitrogen injection / exhaust pipe, DMF was added. After setting the reactor temperature to 30°C, 4,4-diaminodiphenylmethane (MDA), m-phenylenediamine (MPD), and pyromellitic dianhydride (PMDA), which are diamine components, were added, and it was confirmed that they were completely dissolved.

[0093] Then, while heating the reactor to 40°C under a nitrogen atmosphere, stirring was continued for 120 minutes to produce polyamic acid.

[0094] The polyamic acid produced in this way is mixed with a catalyst and a dehydrating agent, and after removing air bubbles by high-speed rotation at speeds of 1,500 rpm or higher, it is coated onto a glass substrate using a spin coater.

[0095] The above-mentioned polyimide film precursor composition was cast onto an SUS plate using a scraper and dried at 110°C for 4 minutes, thereby producing a gel film.

[0096] After separating the gel membrane from the SUS plate, it is heat-treated at 250~400°C for 8 minutes to produce a polyimide membrane with a thickness of 25μm.

[0097] The thickness of the obtained polyimide film was 25 μm. The thickness of the obtained polyimide film was measured using an Electric Film Thickness Tester from Anritsu.

[0098] <Examples 1 to 4 and Comparative Examples 1 to 5>

[0099] The manufacturing process was carried out according to the manufacturing example described above, and the contents of the diamine monomer and dianhydride monomer were adjusted as shown in Table 1.

[0100] [Table 1]

[0101]

[0102] <Experimental Example> Evaluation of Elongation

[0103] The elongation of the polyimide films manufactured in Examples 1 to 4 and Comparative Examples 1 to 5, as shown in Table 1 above, was measured and is presented in Table 2.

[0104] (1) Elongation

[0105] Elongation was measured using an Instron 3365SER instrument according to ASTM D 882 measurement method.

[0106] [Table 2]

[0107]

[0108] The monomer price per 1 kg of membrane in Table 2 above is calculated based on the monomer price in September 2023.

[0109] As confirmed by Table 2 above, the elongation of the polyimide film manufactured according to the embodiments of the present invention is measured to be 90% or more.

[0110] Furthermore, as the content of MDA decreases and the content of MPD increases, the elongation tends to increase, and the monomer price per 1 kg of membrane also tends to increase.

[0111] On the other hand, the elongation of the polyimide film using only ODA as the diamine monomer (Comparative Example 1) and the polyimide film using both PPD and ODA as the diamine monomer (Comparative Example 2) was measured to be 90% and 80%, respectively.

[0112] Therefore, it can be confirmed that the polyimide films of Examples 1 to 4, which use MDA and MPD of the present invention as diamine monomers, have the same or better elongation as polyimide films that use only ODA as diamine monomers, even without using ODA as diamine monomers, and the monomer price per 1 kg of film is lower, thus exhibiting excellent economic efficiency.

[0113] Furthermore, it can be confirmed that the polyimide films of Examples 1 to 4 using MDA and MPD of the present invention as diamine monomers have superior elongation compared to polyimide films using PPD and ODA as diamine monomers, and the monomer price per 1 kg of film can be lower.

[0114] On the other hand, it can be confirmed that the polyimide film of Comparative Example 3, which uses MDA and PPD as diamine monomers, has a slightly lower monomer price per kg of film compared to the polyimide film of Example 1, which uses the same amount of MDA but uses MPD instead of PPD, but the elongation is significantly reduced.

[0115] Furthermore, it can be confirmed that the polyimide film of Comparative Example 4, which uses MDA and ODA as diamine monomers, has a significantly lower elongation and a significantly higher price compared to the polyimide film of Example 3, which uses the same amount of MDA but uses MPD instead of ODA.

[0116] It can be confirmed that, compared with the polyimide films of Examples 1 to 4 that use both MDA and MPD, the polyimide film using only MDA as a diamine monomer, i.e., Comparative Example 5, has a lower price but a significantly lower elongation rate of 55%.

[0117] It can be seen that such improvements in elongation and economy are achieved by the specific components and composition ratios in this application, and the content of each component plays a decisive role.

[0118] The above description refers to embodiments of the present invention, but those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above content.

[0119] Industrial availability

[0120] The polyimide film according to an embodiment of the present invention can simultaneously possess excellent tensile properties and economy by using a specific dianhydride component and a specific diamine component in a specific molar ratio.

[0121] On the other hand, the present invention may include the polyimide film as described above for effective application in energy storage devices, etc.

Claims

1. A polyimide film comprising a polyimide containing dianhydride monomers and diamine monomers as polymerization units. The diamine monomers include 4,4-diaminodiphenylmethane, i.e., MDA, and m-phenylenediamine, i.e., MPD.

2. The polyimide film according to claim 1, wherein, The dianhydride monomers include pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), benzophenone tetracarboxylic dianhydride (BTDA), or combinations thereof.

3. The polyimide film according to claim 1, wherein, The dianhydride monomer is composed of pyromellitic dianhydride. The diamine monomer is composed of 4,4-diaminodiphenylmethane and m-phenylenediamine.

4. The polyimide film according to claim 1, wherein, Based on a total content of 100 mol% of the diamine monomers, the content of 4,4-diaminodiphenylmethane is 70 mol% or more and 95 mol% or less, and the content of m-phenylenediamine is 5 mol% or more and 30 mol% or less.

5. The polyimide film according to claim 1, wherein, The elongation of the polyimide film is over 80%.

6. The polyimide film according to claim 1, wherein, The polyimide is a random copolymer or a block copolymer.

7. A method for manufacturing a polyimide film, comprising: (a) The step of polymerizing a dianhydride monomer with a diamine monomer comprising 4,4-diaminodiphenylmethane and m-phenylenediamine in an organic solvent to produce polyamic acid; as well as (b) The step of imidizing the polyamic acid.

8. The method for manufacturing the polyimide film according to claim 7, wherein, The dianhydride monomer comprises pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, or a combination thereof.

9. An energy storage device comprising the polyimide membrane according to any one of claims 1 to 6.

10. The energy storage device according to claim 9, wherein, The energy storage device is a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor.

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