KR102154549B1 - Polyimide xerogel separator with amino-fuctionalized hollow mesoporous silica particels and manufacturing method of the same - Google Patents

Abstract

The present invention relates to a method for manufacturing a polyimide xerogel separation membrane including hollow mesoporous silica particles with a surface modified by an amine group, which has a small shrinkage and maintains porosity. According to the present invention, the method comprises the following steps of: manufacturing hollow mesoporous silica particles; using alkoxysilane to modify a surface of the hollow mesoporous silica particles with an amine group; reacting dianhydride and aromatic diamine in a polar organic solvent to compose a polyamic acid precursor; introducing the hollow mesoporous silica particles with the surface modified with the amine group to the polyamic acid precursor to manufacture a hybrid precursor; performing an imidization reaction for the hybrid precursor to manufacture polyimide gel including the hollow mesoporous silica particles with the surface modified with the amine group; replacing the polar solvent with a nonpolar solvent; and freeze-drying the polyimide gel to manufacture a xerogel separation membrane.

Description

Polyimide zero gel separation membrane containing hollow mesoporous silica particles whose surface is modified with amine groups, and its manufacturing method {POLYIMIDE XEROGEL SEPARATOR WITH AMINO-FUCTIONALIZED HOLLOW MESOPOROUS SILICA PARTICELS AND MANUFACTURING METHOD OF THE SAME}

The present invention relates to a polyimide zero gel separator and a method of manufacturing the same, and more particularly, a polyimide zero gel separator that exhibits less shrinkage and maintains porosity by using silica particles whose surface is modified with an amine group in the freeze-drying process. It relates to a manufacturing method.

Xerogel is a material having a large surface area, low density, thermal conductivity, and dielectric constant as a 3D network type material having micropores. Zerogel, which is a porous material, can be usefully used as a dielectric material, catalyst, aerospace industry, refrigerator, especially a separator due to its properties such as thermal insulation and sound absorption.

Like silica gel, which is the most common form, it can be classified as zero gel made of inorganic substances and zero gel applied with organic substances, carbon, and organic-inorganic hybrid substances. Among them, silica gel has a limitation in being used for industrial and daily use due to its weak mechanical properties. Although studies using polymer materials such as epoxy and isocyanate are being conducted, various studies on organic zerogels have been attempted due to a significant increase in thermal conductivity.

Although research on organic zerogels using polyimide is in progress, there is a limitation in that shrinkage occurs a lot and pore characteristics decrease in the drying process. In order to reduce the shrinkage that occurs during the drying process of the polyimide gel, it is required to develop a crosslinking agent capable of creating a three-dimensional structure.

In order to solve the above problems, the present invention introduces silica particles whose surface has been modified with an amine group in the freeze-drying process of a polyimide zerogel separator, thereby reducing shrinkage and maintaining porosity. It aims to provide.

In order to achieve the above object, the present invention comprises the steps of preparing hollow mesoporous silica particles; Modifying the surface of the hollow mesoporous silica particles with an amine group using alkoxysilane; Synthesizing a polyamic acid precursor by reacting an aromatic dianhydride and an aromatic diamine with an organic polar solvent; Preparing a hybrid precursor by introducing hollow mesoporous silica particles whose surface is modified with an amine group into the polyamic acid precursor; Producing an imidation reaction on the hybrid precursor to prepare a polyimide gel containing hollow mesoporous silica particles whose surface is modified with an amine group; Replacing the polar solvent with a non-polar solvent; And freeze-drying the polyimide gel to prepare a zero gel separator. It provides a method for producing a polyimide zero gel separator including hollow mesoporous silica particles whose surface is modified with an amine group.

At this time, the alkoxy silane is preferably one selected from the group consisting of 3-amidopropyltrimethoxysilane (APTMS) and 3-aminopropyltriethoxysilane (APTES).

The aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), Pyromellitic dianhydride (PMDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), 4,4'-oxydiphthalic dianhydride (ODPA) and 3,3',4 It is preferably one selected from the group consisting of, 4'-diphenylsulfone tetracarboxylic dianhydride (DSDA).

In addition, the aromatic diamine is 4,4'-oxydianiline (4,4'-ODA), 2,2'-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane (AHHFP), 3,4'-oxydianiline (3,4'-ODA), 4,4'-sulfonyldianiline (4,4'-DDS), 1,4-phenylene diamine (1,4-PDA), It is preferably one selected from the group consisting of diaminophenylmethane (MDA) and 2,2'-dimethylbenzidine (DMBZ).

In addition, the present invention also provides a polyimide zerogel separation membrane including hollow mesoporous silica particles having a surface manufactured by the above manufacturing method modified with an amine group.

According to the present invention, when silica particles having a surface modified with an amine group are introduced during the manufacturing process of the polyimide zerogel separator, heat shrinkage occurring during the freeze-drying process is reduced, thereby increasing the yield and maintaining the pore characteristics.

The thus prepared polyimide zerogel separator may have a uniform thickness, pore size, and porosity surface, while improving ionic conductivity, electrochemical stability, interfacial compatibility, and discharge capacity.

1 schematically shows a process of preparing hollow mesoporous silica particles whose surface is modified with an amine group according to an embodiment of the present invention.
FIG. 2 schematically shows a synthesis process of a polyimide including hollow mesoporous silica particles whose surface is modified with an amine group according to an embodiment of the present invention.
FIG. 3 schematically illustrates a process of gelling a polyimide containing hollow mesoporous silica particles having a surface modified with an amine group and a process of manufacturing a zerogel separator according to an embodiment of the present invention.
4 is an image of a scanning electron microscope (Scanning Electron Microscope) and a transmission electron microscope (Transmission Electron Microscope) of the hollow mesoporous silica particles according to Example 1 of the present invention.
5 shows an image of a scanning electron microscope (Scanning Electron Microscope) and an infrared spectroscopy absorption spectrum (FT-IR) result of a hollow mesoporous silica particle having a surface modified with an amine group according to Example 1 of the present invention.
6 and 7 show a cross-section and a scanning electron microscope image of a surface of a polyimide zerogel separator prepared in Example 1 and Comparative Example 1, respectively.
8 shows photographs of polyimide zerogel separators prepared in Example 1 and Comparative Example 1 at 100°C, 200°C, and 250°C, respectively.
9 shows the results of measuring the voltage-current density of a lithium secondary battery including a polyimide zerogel separator prepared in Example 1 and Comparative Example 1, respectively.
FIG. 10 is a graph showing the results of measuring the interface resistance and the interface resistance after 4 days of a lithium secondary battery including a polyimide zerogel separator prepared in Example 1 and Comparative Example 1, respectively.
11 is a lithium secondary battery including a polyimide zerogel separator prepared in Example 1 and Comparative Example 1, respectively, at 0.2, 0.5, 1, 2, 0.2 C-rate, respectively, charging/discharging to measure the discharge capacity One result is shown.
FIG. 12 shows the results of measuring discharge capacity per weight by repeatedly charging/discharging a lithium secondary battery including a polyimide zerogel separator prepared in Example 1 and Comparative Example 1 at 0.5 C-rate for 100 cycles. I did it.

In the present invention, various modifications may be made and various forms may be applied, and specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific form disclosed, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing each drawing, similar reference numerals have been used for similar elements. In the accompanying drawings, the dimensions of the structures are shown to be enlarged than actual for clarity of the present invention. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance the possibility of being added.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

The present invention comprises the steps of preparing hollow mesoporous silica particles; Modifying the surface of the hollow mesoporous silica particles with an amine group using alkoxysilane; Synthesizing a polyamic acid precursor by reacting an aromatic dianhydride and an aromatic diamine with an organic polar solvent; Preparing a hybrid precursor by introducing hollow mesoporous silica particles whose surface is modified with an amine group into the polyamic acid precursor; Producing an imidation reaction on the hybrid precursor to prepare a polyimide gel containing hollow mesoporous silica particles whose surface is modified with an amine group; Replacing the polar solvent with a non-polar solvent; And freeze-drying the polyimide gel to prepare a zero gel separator. It provides a method for producing a polyimide zero gel separator including hollow mesoporous silica particles whose surface is modified with an amine group.

(a) First, hollow mesoporous silica particles are prepared/produced.

The preparation of the hollow mesoporous silica particles is specifically as follows.

The synthesized polystyrene (0.5g), CTAB (0.8g) and distilled water (34ml) were added to the flask, and ammonium hydroxide (1ml) and ethanol (14ml) were added to start the reaction at room temperature. Then, add TEOS (1.5ml) dropwise and react at room temperature for 3 days. The product is placed in a centrifuge and washed twice with ethanol and distilled water, respectively. Thereafter, the final product is freeze-dried to prepare hollow mesoporous silica particles.

(b) The hollow mesoporous silica particles are surface-modified using an alkoxysilane in the presence of an ethanol solvent to prepare hollow mesoporous silica particles whose surface is modified with an amine group.

At this time, surface modification is performed using one selected from the group consisting of 3-aminopropyltrimethoxysilane (APTMS) and 3-aminopropyltriethoxysilane (APTES) as the alkoxy silane. Preferably, the amount of the alkoxy silane used is 0.01 to 1 ml, more preferably 0.1 ml.

FIG. 1 schematically illustrates a process of preparing hollow mesoporous silica particles whose surface is modified with an amine group.

(c) An organic polar solvent is reacted with an aromatic dianhydride and an aromatic diamine to synthesize a polyamic acid precursor represented by Scheme 1. In this step, the molar ratio of the aromatic dianhydride and the aromatic diamine is m+1:m so that the dianhydride group is disposed at the end.

The organic polar solvent may be one selected from the group consisting of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), and dimethylformamide (DMF).

The aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), Pyromellitic dianhydride (PMDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), 4,4'-oxydiphthalic dianhydride (ODPA) and 3,3',4 , 4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA) is preferably one selected from the group consisting of, but is not limited thereto.

The aromatic diamine is 4,4'-oxydianiline (4,4'-ODA), 2,2'-bis (3-amino-4-hydroxyphenyl)-hexafluoropropane (AHHFP), 3, 4'-oxydianiline (3,4'-ODA), 4,4'-sulfonyldianiline (4,4'-DDS), 1,4-phenylene diamine (1,4-PDA), diamino It is preferable that it is one selected from the group consisting of phenylmethane (MDA) and 2,2'-dimethylbenzidine (DMBZ), but is not limited thereto.

In this step, a polyamic acid precursor in a solution state is formed by reacting the anhydride group of dianhydride and the amine group of diamine as specified in Scheme 1 below. Subsequently, as described later (see Reaction Scheme 2 below), an imidation reaction is performed using a catalyst to form a polyimide polymer through a dehydration condensation reaction.

[Scheme 1]

[Scheme 2]

Ar is one or more aromatics selected from the following structural formulas 1 to 6, and Ar' is one or more aromatics selected from the following structural formulas 7 to 13. However, it is not limited thereto.

In the above Schemes 1 and 2, n is preferably an integer of 15 to 30. Here, if n is less than 15, the length of the polymer chain is insufficient, so that a gel is not formed well. If n is out of 30, the biggest characteristic of the zero gel is porosity, and the polymer chain is longer than a certain There is a problem in that the porosity of the zerogel is insufficient due to the increase of the organic matter on the ground.

(d) The hollow mesoporous silica particles having the surface modified with an amine group are added to the polyamic acid precursor solution to prepare a hybrid precursor.

(e) 1 to 2 ml of pyridine may be used as a catalyst for allowing the hybrid precursor to undergo a chemical imidization reaction, and in addition, 1,4-diazabicycle octane may be used as an imidization catalyst. It is also preferable to apply heat at 150 to 200°C instead of using a catalyst for the imidation reaction. As described above, 2 to 3 ml of a dehydrating agent is used for imidization using an imidation catalyst and removing water generated by the condensation reaction. As the dehydrating agent, an aliphatic acid anhydride such as acetic anhydride or an aromatic acid anhydride may be used, and as a catalyst, aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethyl aniline, pyridine, isoquinoline, β-pi Heterocyclic tertiary amines such as choline, Y-picoline, and 3,5-lutidine may be used, and among them, acetic anhydranhydr is preferably used. Through the above reaction, a polyimide gel (gelled polyimide polymer) is prepared within 30 minutes to 1 hour. Through the above-described imidation reaction, the polyamic acid precursor is imidized into polyamide, and gelation occurs in shape. The polyimide gel contains hollow mesoporous silica particles whose surface is modified with an amine group.

FIG. 2 schematically illustrates the synthesis process of a polyimide including hollow mesoporous silica particles whose surface is modified with an amine group.

(f) To perform lyophilization, the polar solvent is substituted with a non-polar solvent. The non-polar solvent is preferably one selected from the group consisting of ethanol, t-butanol, acetone, and hexane, but is not limited thereto.

(g) The polyimide gel is freeze-dried to prepare a zero-gel separator.

3 schematically illustrates a process of gelling a polyimide including hollow mesoporous silica particles having a surface modified with an amine group and a process of manufacturing a zerogel separator.

It is preferable that the amount of silica particles introduced in step (d) is 1 to 20% by weight of the polyimide gel. When the amount of silica particles is less than 1% by weight, the effect of the present invention is not sufficiently exhibited because the pore characteristics are not maintained due to a large amount of shrinkage, and when the amount of silica particles is more than 20% by weight, the silica particles have a certain degree of pores of the polyimide zerogel separator. The effect of the invention does not appear when the secondary battery is applied afterwards due to the agglomeration of the silica particles at the same time as blocking with

It is preferable that the concentration of the solid content of the polyamic acid precursor synthesized in step (c) is 5 to 20% by weight based on the total solution. When the concentration of the solid content of the polyamic acid precursor is less than 5% by weight of the total solution, the polyimide concentration may be low, making it difficult to form a gel, and when it exceeds 20% by weight, the amount of organic matter increases and the porosity of the gel or separator is insufficient Can be set. The polyimide zerogel separator may have a specific surface area of 180 to 300 m ² /g and a porosity of 80 to 90%, but is not limited thereto.

Hereinafter, the present invention will be described in detail through examples, but the following examples and experimental examples are only illustrative of one embodiment of the present invention, and the scope of the present invention is not limited by the following examples and experimental examples. .

[Example 1]

The synthesized polystyrene (0.5g), CTAB (0.8g), and distilled water (34ml) were put into a flask, ammonium hydroxide (1ml) and ethanol (14ml) were added to start the reaction at room temperature. Then, TEOS (1.5ml) was added dropwise and reacted at room temperature for 3 days. The product was placed in a centrifuge and washed twice with ethanol and distilled water, respectively. Thereafter, the final product was freeze-dried to prepare hollow mesoporous silica particles. At this time, images of a scanning electron microscope and a transmission electron microscope of the hollow mesoporous silica particles are shown in FIG. 4.

0.1 g of the prepared hollow mesoporous silica particles were modified with an amine group by adding 0.1 ml of ammonium hydroxide and 0.1 ml of APTMS to a mixed solvent of 1 ml of water/30 ml of ethanol for 48 hours. The ammonium hydroxide serves to induce a hydroxy group on the silica surface to react with APTMS by forming a basic condition. At this time, the image of the scanning electron microscope (Scanning Electron Microscope) and infrared spectroscopy absorption spectrum (FT-IR) results of the hollow mesoporous silica particles modified with an amine group are shown in FIG. 5.

Then, 0.50 g (2.42 mmol) of 4,4'-oxydianiline (ODA) was added to a round bottom flask, and 13.3 ml of a polar solvent DMF was added thereto, followed by stirring until dissolved. Next, 0.76 g (2.50 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), which is 0.08 mmol more than ODA, was added, and stirred for 24 hours under nitrogen conditions to The polyamic acid precursor was synthesized.

A hybrid precursor was prepared by dispersing 0.02 g of silica particles whose surface was modified with an amine group in 13.3 ml of DMF and introducing it into the prepared polyamic acid precursor solution. 1.99 ml of acetic anhydride and 1.61 ml of pyridine were added to the prepared hybrid precursor, and coated with a desired thickness using doctor blading, and then imidization and gelation were performed on a glass substrate to prepare a polyimide gel.

Next, in order to lyophilize, the polar solvent DMF was sequentially substituted with the non-polar solvent ethanol. Specifically, 100% of the polar solvent, DMF, was added to the polyimide gel, and DMF 75%/t-butanol 25%, the next day 25%/75%, and t-butanol 100% were sequentially substituted in this order. I did.

Thereafter, the polyimide gel was lyophilized using a freeze dryer at -50° C. and vacuum to prepare a polyimide zero gel separator.

[Comparative Example 1]

A polyimide zerogel separator was prepared in the same manner as in Example 1, except that silica particles were not added.

[Experimental Example]

1. Cross-sectional and surface photographs of separators: Cross-section and surface scanning electron microscope images of the polyimide zerogel separators prepared in Example 1 and Comparative Example 1, respectively, are shown in FIGS. 6 and 7, respectively. 6 and 7, it can be seen that the separator according to Example 1 exhibits a uniform thickness, pore size, and porosity surface.

2. Thermal stability: In order to check the thermal stability of the polyimide zerogel separators prepared in Example 1 and Comparative Example 1, respectively, pictures of the separators at 100°C, 200°C, and 250°C are shown in FIG. 8. It can be seen from FIG. 8 that heat shrinkage did not occur in both the separators according to Example 1 and Comparative Example 1 even at a high temperature of 250°C.

3. Wetability evaluation and ionic conductivity: The amount of absorbed lithium ion battery electrolyte and ionic conductivity were measured, and the results are shown in Table 1 below. At this time, the electrolyte absorption amount (Eu) was calculated by the following equation as the PVDF electrolyte absorption amount.

In the above formula, W ₀ is the weight of the separator before impregnation with the electrolyte, and W ₁ is the weight of the separator after impregnation with the electrolyte.

As can be seen in Table 1, it can be seen that the separator according to Example 1 has a high ionic conductivity of 1.95 mS/cm compared to Comparative Example 1 with a high absorption of lithium ion battery electrolyte of 460%.

Thickness(㎛) Density (g/cm ³ ) Porosity (%) Electrolyte
Absorption (%) Bulk resistance (Ω) Ion conductivity
(mS/cm) Example 1 31±1 0.38 72 460 0.79 1.95 Comparative Example 1 32±1 0.54 60 400 0.953 1.67

4. Electrochemical stability: A lithium secondary battery including the polyimide zerogel separator prepared in Example 1 and Comparative Example 1, respectively, was prepared under the same conditions, and the voltage-current density of the lithium secondary battery was measured and the results were shown. It is shown graphically in 9. Through this, it was confirmed that both Example 1 and Comparative Example 1 were electrochemically stable separators at a voltage of 4.8V or less.

5. Interface compatibility: The interface resistance and the interface resistance after 4 days of the prepared lithium secondary battery were measured, respectively, and the result is shown in a graph in FIG. 10. Referring to FIG. 10, it can be seen that in the case of Example 1, even after 4 days, the interfacial resistance increased from 226 Ω to 371 Ω as low as compared to Comparative Example 1, which significantly increased from 224 Ω to 1350 Ω, showing higher compatibility between the electrode and the separator. .

6. Various charging/discharging rates: The lithium secondary battery was charged/discharged at 0.2, 0.5, 1, 2, and 0.2 C-rate, respectively, to measure discharge capacity, and the results are shown in FIG. 11. Referring to FIG. 11, it can be seen that at all current rates of 0.2, 0.5, 1, 2, and 0.2 C-rate, Example 1 exhibits a higher discharge capacity per weight compared to Comparative Example 1.

7. Repeated charging/discharging: The lithium secondary battery was repeatedly charged/discharged at 0.5 C-rate for 100 cycles to measure the discharge capacity per weight, and the results are shown in FIG. 12. Referring to FIG. 12, it can be seen that Example 1 exhibits a stable discharge capacity per weight even with repeated charging/discharging at 0.5 C-rate.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art or those of ordinary skill in the art will not depart from the spirit and scope of the present invention described in the claims to be described later. It will be understood that various modifications and changes can be made to the present invention within the scope of the invention.

Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

Claims (5)

Preparing hollow mesoporous silica particles;
Modifying the surface of the hollow mesoporous silica particles with an amine group using alkoxysilane;
Synthesizing a polyamic acid precursor by reacting an aromatic dianhydride and an aromatic diamine with an organic polar solvent;
Preparing a hybrid precursor by introducing hollow mesoporous silica particles whose surface is modified with an amine group into the polyamic acid precursor;
Producing an imidation reaction on the hybrid precursor to prepare a polyimide gel containing hollow mesoporous silica particles whose surface is modified with an amine group;
Replacing the polar solvent with a non-polar solvent; And
A method of manufacturing a polyimide zero gel separation membrane comprising hollow mesoporous silica particles having a surface modified with an amine group, comprising the step of lyophilizing the polyimide gel to prepare a zero gel separation membrane. The method of claim 1,
The alkoxy silane is 3-amidopropyltrimethoxysilane (APTMS) or 3-aminopropyltriethoxysilane (APTES), wherein the surface is polyimide zero including hollow mesoporous silica particles modified with an amine group. Method for producing a gel separator. The method of claim 1,
The aromatic dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), Pyromellitic dianhydride (PMDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), 4,4'-oxydiphthalic dianhydride (ODPA) and 3,3',4 ,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), characterized in that one selected from the group consisting of a method for producing a polyimide zerogel separation membrane comprising hollow mesoporous silica particles whose surface is modified with an amine group. The method of claim 1,
The aromatic diamine is 4,4'-oxydianiline (4,4'-ODA), 2,2'-bis (3-amino-4-hydroxyphenyl)-hexafluoropropane (AHHFP), 3, 4'-oxydianiline (3,4'-ODA), 4,4'-sulfonyldianiline (4,4'-DDS), 1,4-phenylene diamine (1,4-PDA), diamino Method for producing a polyimide zerogel separation membrane including hollow mesoporous silica particles whose surface is modified with amine groups, characterized in that it is one selected from the group consisting of phenylmethane (MDA) and 2,2'-dimethylbenzidine (DMBZ) . A polyimide zerogel separation membrane comprising hollow mesoporous silica particles having a surface modified with an amine group prepared by the method according to any one of claims 1 to 4.

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