KR101432862B1 - Porous support and method for manufacturing the same - Google Patents

Abstract

The present invention provides a nano-web structure comprising nanofibers, which facilitates preparation of thin films and control of porosity, and inorganic particles having excellent heat resistance are distributed in the nano-web to improve heat resistance, Thereby facilitating the post-processing. Thus, the present invention relates to a porous support that can be used as a separation membrane of a secondary battery or an electrolyte membrane of a fuel cell, and a method of manufacturing the same. The porous support of the present invention comprises nanofibers having an average diameter of 0.005 to 5 탆; And inorganic particles, wherein the inorganic particles are distributed between the nanofibers in the nanofiber, the nanofiber having a nanofiber structure comprising the nanofibers.

Description

[0001] Porous support and method for manufacturing same [0002]

More particularly, the present invention relates to a porous support which can be used as a separation membrane of a secondary battery or an electrolyte membrane of a fuel cell, and a manufacturing method thereof.

The porous support can be used for various purposes because of its wide surface area and excellent porosity. For example, it can be used for a water purification filter, an air purification filter, a composite material, an electrolyte membrane for a fuel cell, or a separation membrane for a secondary battery.

The secondary battery is largely composed of an anode, a separator, a cathode, and an electrolyte. Here, the separator separates the cathode and the anode of the secondary battery and serves to pass the electrolyte. At present, a polyolefin-based separator such as polyethylene or polypropylene is generally used as a separator for a secondary battery. However, since the polyolefin-based separator has poor heat resistance, if the temperature of the battery rises sharply, the separator ruptures and is short-circuited to cause the battery to explode.

A fuel cell is a power generation type battery that combines hydrogen and oxygen to produce electricity. Unlike conventional chemical cells, such as batteries and accumulators, fuel cells can continue to produce electricity as long as hydrogen and oxygen are supplied. They are twice as efficient as internal combustion engines because they have no heat loss. They convert chemical energy directly into electrical energy It has a low emission of pollutants. Since the fuel cell operates at a high temperature to improve the activity of the electrode, the electrolyte membrane for a fuel cell is required to have high heat resistance. However, when the polyolefin-based porous support as described above is used for an electrolyte membrane for a fuel cell, there is a problem that the battery deteriorates due to poor heat resistance.

In order to solve the above-mentioned problems, there has been proposed a technique of coating inorganic particles on a polyolefin-based porous film in the form of a film. However, in this case, since the inorganic particles block the pores formed on the film, the electric conductivity and the like may be lowered, and the roughness is increased as the inorganic particles are coated on the surface, have. In addition, since the film-like separation membrane has a low porosity, the porosity of the separation membrane is low and the production of the membrane is not easy, and the pore diameter, which is the diameter of the pore, can not be easily controlled.

The present invention has been devised to solve the above-described problems, and it is an object of the present invention to provide a separator of a secondary battery or an electrolyte membrane of a fuel cell, which is easy to control the degree of porosity and the heat resistance, And to provide a porous support which can be used and a production method thereof.

According to an aspect of the present invention, there is provided a porous support comprising: a nanofiber having an average diameter of 0.005 to 5 탆; And inorganic particles, wherein the inorganic particles are distributed between the nanofibers in the nanofiber, the nanofiber having a nanofiber structure comprising the nanofibers.

According to another aspect of the present invention, there is provided a method of manufacturing a porous support, comprising: preparing a spinning solution containing an organic polymer; electrospinning the spinning solution to prepare a nanostructure having an average diameter of 0.005 to 5 μm; Fabricating a nanobeb made of fibers; And coating the inorganic particles with the nanoweb.

The present invention according to the above configuration has the following effects.

First, since the porous support according to the present invention is composed of a nanofiber that is an aggregate of nanofibers, it is easy to control the degree of thinning and porosity.

Second, since the porous support according to the present invention has excellent heat resistance, it can be operated safely without explosion at a high temperature for a long time.

Thirdly, since the inorganic particles are distributed among the nanofibers in the nanofiber, the porosity of the nanofiber does not decrease and the post-process is facilitated as the modulus of elasticity increases.

Such a porous support can be used as a separation membrane for a secondary battery or an electrolyte membrane for a fuel cell.

1 is a schematic view of a porous support according to the prior art;
2 is a schematic view of a porous support according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

2 is a schematic view of a porous support according to an embodiment of the present invention. As shown in FIG. 2, the porous support according to the present invention comprises nanofibers made of the nanofibers 10 having an average diameter of 0.005 to 5 μm, and inorganic fibers distributed among the nanofibers 10 in the nanofiber Particles 30 as shown in FIG.

The porous support comprises a plurality of uniformly distributed pores 20 as it is composed of a collection of nanofibers 10 that are irregularly and discontinuously connected three-dimensionally. The porous support composed of a plurality of uniformly distributed pores 20 has excellent gas or ionic conductivity. The pore diameter of the pores 20 formed in the porous support may be in the range of 0.05 to 30 탆. If the pore size is less than 0.05 탆, the conductivity of the separation membrane may drop sharply, Mu m, the mechanical strength of the separator may be lowered. The porosity of the porous support, which indicates the degree of formation of the pores 20 of the porous support, may be within a range of 50 to 80%. If the porosity of the porous support is less than 50%, the conductivity of the separation membrane may be lowered. If the porosity of the porous support exceeds 80%, the mechanical strength and shape stability of the separation membrane may be deteriorated.

Wherein the nanofibers 10 are selected from the group consisting of nylon, polyimide, polybenzoxazole, polyethylene terephthalate, polyethylene, polypropylene, polytetrafluoroethylene, polyarylene ether sulfone, polyetheretherketone, But is not limited thereto.

In order to provide a high porosity and a thin film as described above, it is preferable that the average diameter of the nanofibers 10 is within the range of 0.005 to 5 mu m. When the average diameter of the nanofibers 10 constituting the nano-web is less than 0.005 m, the mechanical strength of the porous support may deteriorate and the average diameter of the nanofibers 10 constituting the nano- The porosity and the thickness of the porous support may not be easily adjusted.

The porous support has a nano-web structure composed of nanofibers (10), and the inorganic particles (30) are evenly distributed among the nanofibers (10) inside the nanofibers. The inorganic particles 30 greatly improve the heat resistance of the porous support, and thus prevent the membrane from rupturing at a high temperature when used as a separation membrane for a secondary battery or an electrolyte membrane for a fuel cell.

As shown in FIG. 2, the inorganic particles 30 are distributed between the nanofibers 10, so that the conductivity of the porous support does not decrease significantly. As shown in FIG. 1, in the conventional separation membrane, the inorganic particles 30 are coated on the porous membrane 100 to block the pores 200 of the porous membrane, thereby decreasing the porosity and increasing the conductivity Fall off. In addition, since the conventional separation membrane is coated with the inorganic particles 30 on the surface of the porous membrane 100, the roughness increases and post-processing is not easy. That is, the adhesion of the inorganic particles 30 to other materials decreases, have.

In addition, since the inorganic particles 30 are distributed between the nanofibers 10, they can increase the elastic modulus of the porous support. The porous support having a high porosity is low in modulus of elasticity and easily deformed by an external force, so that the processability may be deteriorated in a post-process. However, in the porous support of the present invention, since the inorganic particles 30 are distributed between the nanofibers 10, the inorganic particles 30 have a high elastic modulus by acting as a reinforcing agent.

The inorganic particles 30 may be at least one selected from the group consisting of TiO ₂ , BaTiO ₃ , Li ₂ O, LiF, LiOH, Li ₃ N, BaO, Na ₂ O, Li ₂ CO ₃ , CaCO ₃ , LiAlO ₂ , SiO ₂ , Al ₂ O ₃ , SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiC, or a mixture thereof.

The inorganic particles 30 do not limit the size of the particles but preferably have an average diameter of 0.01 to 10 mu m. If the average diameter is less than 0.01 mu m, the dispersibility may deteriorate and the physical properties may not be uniform. On the other hand, when the average diameter exceeds 10 탆, the inorganic particles 30 are not uniformly distributed in the nanoweb, and as the thickness increases, the separation membrane produced therefrom may have deteriorated mechanical properties.

The porous support may comprise a polymeric binder. Such a polymeric binder serves to interconnect and fix the nanoparticles and the inorganic particles 30, thereby preventing the inorganic particles 30 from easily falling off from the nanofibers. The kind of the polymeric binder is not particularly limited, and it may be a conventional polymeric binder.

Since the porous support having such a structure has an elastic modulus of 80 to 150 MPa, the porous support is excellent in shape stability and can be easily post-processed.

In addition, since the porous support contains inorganic particles having excellent heat resistance, it can be used as a separation membrane for a secondary battery or an electrolyte membrane of a fuel cell, which has a thermal decomposition temperature of 580 to 600 ° C and thus requires excellent thermal stability at a high temperature .

Hereinafter, a method for manufacturing a porous support according to an embodiment of the present invention will be described.

The method for producing a porous support according to the present invention comprises the steps of preparing a spinning solution containing an organic polymer and electrospunning the spinning solution to prepare a nanoweb comprising nanofibers 10 having an average diameter of 0.005 to 5 μm , And coating the inorganic particles (30) on the nanoweb.

The step of preparing the nano-web comprises: preparing a spinning liquid by dissolving the organic polymer in a solvent, supplying the spinning solution to a spinneret nozzle to which voltage is applied, and discharging the spinning solution through the spinning nozzle to form nanofibers 10 And collecting the nanofibers 10 in a current collector.

The electrospinning has an advantage that fibers having a diameter of nano unit can be easily produced, and these nanofibers 10 are tangled together to form a nanoweb. Such electrospinning can produce a nanoweb that can easily control the thickness and porosity. Therefore, when such a nanoweb is applied to a separation membrane of a secondary battery, the secondary battery has excellent electric conductivity and low electric resistance, and thus can have excellent performance.

The coating step comprises the steps of preparing a binder solution by dissolving the binder in a solvent, preparing a coating solution by mixing the binder solution with the inorganic particles (30), and applying the coating solution to a nanoweb, followed by drying Step < / RTI >

The solvent may be an organic solvent if the nanofiber 10 does not dissolve in an ordinary organic solvent at room temperature, and an aqueous solvent if the nanofiber 10 is well soluble in a common organic solvent.

The above coating can be carried out by a conventional method such as dip coating, die coating, roll coating, comma coating, spray coating and the like.

Hereinafter, the effects of the present invention will be described in more detail through specific examples and comparative examples. These embodiments are only for the understanding of the present invention and do not limit the scope of the present invention.

Example  One

The polyamic acid / THF spinning solution having a concentration of 12 wt% was electrospun with a voltage of 30 kV applied thereto, and a precursor of the polyamic acid nanoweb was formed. The imidization reaction was carried out by hot pressing at 150 ° C To prepare a polyimide porous support having a thickness of 20 탆.

The sulfonated polyimide was melted in N-methyl-2-pyrrolidone to prepare a binder solution of 10% by weight. Titanium dioxide inorganic particles (30) were mixed with the binder solution to prepare a 10 wt% coating solution.

The porous support was immersed in the coating solution using a dipping process, the content of the inorganic particles (30) was adjusted using a padding roll, and the organic solvent was dried to prepare a porous support.

Example  2

In Example 1 described above, a polyvinylidene fluoride porous nano-web was used in place of the polyimide porous nano-web, and a coating solution in which titanium dioxide was dissolved in water instead of the coating solution containing a binder was used in Example 1 To prepare a porous support.

The polyvinylidene fluoride porous nanoweb was prepared by the following process. Polyvinylidene fluoride (PVdF) was dissolved in a dimethylformamide solvent to prepare a spinning solution having a concentration of 10%. The spinning solution was discharged from a spinning nozzle to which a voltage of 60 kV was applied to produce a nanoweb. At this time, the distance between the spinning nozzle and the current collector was 60 cm and the discharge amount was 0.5 cc / g per hole. The polyvinylidene fluoride porous nano-web was completed through a process of calendering a nano-web prepared as described above by placing it on a roll heated to 120 ° C.

Comparative Example  One

In Example 1 described above, a porous support was prepared in the same manner as in Example 1, except that the step of coating the titanium dioxide inorganic particles 30 on the polyimide porous nano-web was omitted.

Comparative Example  2

In Example 1 described above, a porous support was prepared in the same manner as in Example 1, except that a polyethylene film 100 in the form of a film instead of a polyimide porous nano-web was used. The polyethylene porous membrane 100 is manufactured through solid-state processing, and the porous membrane 100 is completed through a swelling and rolling process by swelling and washing and a drying process .

The physical properties of the porous supports prepared according to Examples and Comparative Examples were measured by the following methods and are shown in Table 1 below.

Porosity (%) Measure

The porosity of the porous support was calculated by the ratio of the volume of air to the total volume of the porous support using the mass, volume, and density of the porous support as shown below.

Porosity (%) = (air volume / total volume) x 100

Pyrolysis temperature (℃) measurement

The temperature at the beginning of the initial pyrolysis was measured using a thermogravimetric analyzer (PERKIN ELMER, Thermogravimetric Analyzer TGA7). Specific measurement conditions were a temperature range of 30 to 900 占 폚, a temperature increase rate of 20 占 폚 / min, a nitrogen gas flow rate, and a nitrogen gas flow rate of 60 ml / min.

Modulus of elasticity (MPa)

The elastic modulus (MPa) of the porous support was measured according to ASTM D882.

division Porosity (%) Pyrolysis temperature (℃) Modulus of elasticity (MPa) Example 1 70 594.25 116.15 Example 2 55 595.01 120.22 Comparative Example 1 95 579.58 36.15 Comparative Example 2 90 200.26 55.16

10: nanofiber 20: porosity
30: inorganic particles

Claims (10)

delete delete delete delete delete delete delete Preparing a nanoweb comprising nanofibers having an average diameter of 0.005 to 5 占 퐉; And
Coating an inorganic particle on the nano-web,
The method of claim 1,
Preparing a spinning solution comprising a polar amic acid;
Forming a polyamic acid nano-web precursor by electrospinning the spinning solution; And
Imidizing the nano-web precursor,
Wherein the inorganic particle coating step is performed such that the inorganic particles are distributed only between the nanofibers in the nanoweb. 9. The method of claim 8,
Wherein the inorganic particle coating step comprises:
Dissolving the binder in a solvent to prepare a binder solution;
Mixing the inorganic particles with the binder solution to prepare a coating solution; And
Applying the coating solution to the nanoweb, and then drying the coated nanoweb. 10. The method of claim 9,
Wherein the solvent used for preparing the binder solution is an organic solvent or an aqueous solvent.

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