WO2005057700A1

WO2005057700A1 - Porous and continuous composite membrane and method of preparing the same

Info

Publication number: WO2005057700A1
Application number: PCT/KR2004/003238
Authority: WO
Inventors: Jae-Do Nam
Original assignee: Sungkyunkwan University
Priority date: 2003-12-10
Filing date: 2004-12-10
Publication date: 2005-06-23
Also published as: KR20050056892A

Abstract

The present invention relates to a porous and continuous composite membrane and a method of manufacturing the same. More specifically, the invention relates to a porous and continuous composite membrane and a method of manufacturing the same, in which fine particles having a size of a few nanometers to a few micrometers are dispersed uniformly to thereby enhance the physical property of the membrane, or solid particles capable of improving the functionality are uniformly dispersed. The invention can easily control the thickness of the membrane, and is suitable for mass production. According to the invention, the porous and continuous composite membrane can be formed in the form of thin film structure. The membrane of the invention can be applied to an electric-electronic component such as a multi layer ceramic capacitor, a coating, a medicinal scaffold, an porous membrane for a filter, a catalyst/electrode/filtering membrane for a fuel cell, and the like, to which the conventional coating and membrane manufacturing method cannot be easily and readily applied.

Description

POROUS AND CONTINUOUS COMPOSITE MEMBRANE AND METHOD OF

PREPARING THE SAME

Technical Field The present invention relates to a porous and continuous

composite membrane and a method of manufacturing the same. More

specifically, the invention relates to a porous and continuous

composite membrane and a method of manufacturing the same, in

which fine particles having a size of a few nanometers to a few

micrometers are dispersed uniformly to thereby enhance the

physical property of the membrane. In particular, the invention

relates to a battery (cell) including a porous and continuous

membrane in which solid particles having a size of a few

nanometers to a few micrometers are dispersed uniformly in a

plurality of polymer nano-fibers of which contacting points are

fusion-bonded, or the dispersed solid particles are dissolved,

the porous and continuous membrane being used as a filtering

membrane, an electrolyte membrane, an electrode layer or a

catalyst layer, when it is applied to batteries.

Background Art A porous and continuous composite membrane, which is

prepared by dispersing an excessive amount of particles in a polymer material, is industrially of importance. A porous

membrane of a few micrometers having an excessive amount of

particles contained therein is reguired in the porous structure

of medicinal scaffold, a catalyst/electrode/filtering membrane

for fuel cells, a biodegradable polymer porous membrane, a

porous membrane for filters, a porous membrane used for

fabrication of condensers, a porous filter of secondary

batteries, or the like. Dispersion of the excessive amount of

particles in a polymer cannot be easily carried out because the

particles are entangled with one another due to the

electrostatic attractive force of the particles, the hydrogen

bond thereof, the Van der Waals' force, or the like. Therefore,

Dispersion of the particles is performed by means of a physical

agitation for a long time, an ultrasonic dispersion, and an

addition of appropriate dispersing agent.

However, even though the particles are dispersed in the

liquid state through the above means, they are cohered again

when the solvent of the solution is dried or the polymer is

solidified from the melted state. Therefore, a membrane with an

excessive amount of particles uniformly dispersed therein cannot

be easily achieved.

In addition, the process for manufacturing a continuous

membrane from a polymer mixture containing the solid particles

can be exemplified by a dip coating, a spin coating, an Inkjet printing, a silkscreen printing, or the like. These processes

can be selected depending on the applications since each process

has advantages or disadvantages according to the area to be

coated, the thickness of membrane, the property of polymer

solution. However, in the case where a large amount of solid

particles must be dispersed in a polymer, in particular in case

of manufacturing a membrane having fine particles of a few

nanometers to a few micrometers, the particles are more severely

entangled so that they cannot be easily dispersed. Each process

has difficulties, such as, in the case where mass production is

desired, a thin membrane of a few nanometers to a few

micrometers must be fabricated, or the thickness of a membrane

must be finely controlled.

In particular, batteries have a wide range of applications

as an energy source for a portable and high-performance design,

and a light, thin, short and compact design of electrical

equipment and devices, which are closely related with the 21-

human century life. For these purposes, a high-performance

battery (cell) is an essential prerequisite. Therefore, a

secondary battery (cell) or a fuel cell including a common

battery (cell) has been widely researched in order to develop a

portable and high-performance design and also a light, thin,

short and compact design.

Among them, the secondary battery (cell) is of significant importance, in terms of the recycling of resources, and the

prevention of environmental contamination. In addition, it has

been of great importance as a battery (cell) for the portable

communication equipment, and also a battery (cell) for the storage of electricity.

The electrochemical reaction in the secondary battery (cell)

depends on the inherent property of the electrode active

material, and, in particular, is significantly affected by the

filtering membrane and the electrolyte during the course of ion-

transportation. Therefore, the core of battery (cell)

development lies in selection of optimum materials and

enhancement of its performance. Most researches are focused on

a filtering membrane for preventing contact of the cathode and

the anode while enabling a free movement of ions. A membrane

made of polyolefine series polymer and fluoric polymer has been

used as a filtering membrane of secondary batteries. Polyamide,

polysulfone, polyolefine polymer, and copolymer can be a

material suitable for a light, thin, short and small design of

secondary batteries since they have a high chemical stability

and a good workability, as compared with the conventional case

of using a liquid.

In case of a conventional lithium polymer secondary

battery (cell) using as the battery (cell) electrolyte a hybrid

polymer electrolyte, which is a fluoric polymer developed by A.S. Gozdz et al . in Bell Communication Research (Bellcore), a

polymer membrane containing plasticizer is manufacture, the

plasticizer is extracted to thereby form pores in the surface and inside of the membrane, and then a liquid electrolyte is

injected into the pores, thereby providing a polymer membrane

having ion-conductivity. In the case of this method, since the

process before the introduction of the liquid electrolyte is not

very sensible to moisture or oxygen, advantageously the operational environment can be relatively easily established.

However, since a plasticizer is used for forming the pores, a

series of complicated and time-consuming processes are required

in order to extract and dry the plasticizer.

In addition, as one example of home research and

development, a hybrid polymer electrolyte having the ion-

conductivity to lithium ion has been manufactured by dissolving

polysulfone polymer in N-methylpyrollidone, casting it and

dipping in a non-solvent such as distilled water to thereby form

a porous membrane, and introducing a liquid electrolyte. In

case of this case, however, the polysulfone used for

manufacturing" the polymer membrane does not have an adequate

capacity to absorb the liquid electrolyte, and thus the polymer

electrolyte fail to exhibit an adequate conductivity and

produces a poor contact with the electrodes, and increases the

interface resistance. In addition, the filtering membrane for the secondary

battery (cell) or a common battery (cell) must have a good

mechanical strength so as not to be destroyed by an external

force from the outside of the battery (cell) and thus create a

contact between the electrodes due to the external force. In order to generate a high power, an adequate amount of

electrolyte must be absorbed inside the filtering membrane to

provide a high ion-conductivity between the electrodes (a low

interface resistance with the electrodes) . Therefore, in order to accomplish the above purposes, there

is a need to improve the material properties of the filtering

membrane, and control the size, the structure, and the content

of the pores. However, a satisfactory manufacturing process has

not been proposed yet. Furthermore, a fuel cell is an electricity generation

device, in which, when hydrogen molecule (H ) and oxygen molecule (0₂) are electrochemically reacted with each other, electricity

and heat is generated while producing water, which can be

considered as a reverse reaction of water electrolysis.

Depending on the type of electrolyte to be used, the fuel cell

is categorized into five types: a phosphoric acid fuel cell

(PAFC), an alkaline fuel cell (AFC), a polymer electrolyte

membrane fuel cell (PEMFC) , a molten carbonate fuel cell (MCFC) ,

a solid oxide fuel cell (SOFC) , and a direct methanol fuel cell ( DMFC ) . The basic structure of the fuel cell includes each

electrode layer such as a fuel electrode (cathode) for receiving

fuel and an air electrode (anode) , and an electrolyte layer for

partitioning the electrodes and transferring a cation. The

operational principle utilizes the mobile electrons generated

when hydrogen and oxygen are reacted in the cathode and the

anode. The hydrogen gas is introduced into the cathode of the

fuel cell to react with a catalyst contained in the electrode

and produce hydrogen ion (H⁺) and electron (e^~) . The produce

hydrogen ion is moved towards the anode via the electrolyte, and

the electron is moved towards the anode via an external circuit

and electrochemically reacts with in-flowing oxygen gas to

thereby generate electric current (direct current) while

producing water. At this time, heat is generated as a by¬

product. This heat is used for steam-generation for the self-

reformer of the fuel cell system (in case of a fuel cell type

having a reformer installed therein) , or used for heating or

cooling, or discharged as an exhausted heat when it is not

particularly to be used. The direct current generated by the

fuel cell may be altered into an alternating current by an

inverter, or directly used for an electric power for DC motors.

As hydrogen gas as the fuel of fuel cells, pure hydrogen

may be used, or hydrogen produced by reforming methane or ethanol through a reformer may be utilized. In case of oxygen

gas, pure oxygen can increase the generating efficiency of the

fuel cell, but the oxygen storage cost and the increased weight

must be considered. Therefore, in many cases, air is directly used although it does not have a good generating efficiency. A

solid polymer fuel cell uses mainly a catalytic electrode

containing platinum in order to enhance its reactivity.

Particularly, in the polymer electrolyte membrane fuel cell (PEMFC) and the direct methanol fuel cell (DMFC), the

electrolyte is a solid polymer electrolyte membrane made of

solid polymer and functions to transfer hydrogen ion (H⁺) form

one electrode to the other. For this purpose, the polymer

electrolyte membrane fuel cell (PEMFC) employs as the solid

electrolyte membrane a cation exchange membrane in which a

functional group assuming a negative electric charge is bonded

to a hydrophobic polymer, thereby passing hydrogen ion (H⁺) . A

typical example therefor may be Nation supplied by Dupont in the

United States.

In this way, the cation exchange membrane used in the

polymer electrolyte membrane fuel cell contains a functional

group having a negative electric charge (typically, sulfonate

group [SO^3-] ) in the fine-pored wall of the membrane, and thus

attracts only the oppositely-charged ion (cation) into the fine

pores of the membrane. The oppositely charged ion (cation) received inside the fine pores is weakly bonded with one negatively charged functional group of the cation exchange

membrane. Thereafter, the cation is detached from the

functional group and bonded again to next another functional

group. This course of actions is repeated continuously such

that the cation passes through the membrane. At this time, the

identically charged ion (anion) or the solvent (water, etc.)

fails to pass through the membrane.

In order to improve the reactivity in these reactions, it

is necessary that the membrane be constituted of a porous

membrane. The electrolyte membrane is preferred to be as thin

as possible, in order to minimize the resistance (ion-transfer

resistance) between two electrodes. Also, the membrane is

preferred to be thin and simultaneously have an adequate

mechanical strength, in order to prevent a mechanical failure (tearing or the like) when assembling the cell. However, a

membrane meeting the above requirements has not been proposed

yet .

In addition, in case of the direct methanol fuel cell,

commonly platinum catalyst is dispersed in the electrolyte

membrane to form a catalyst layer to increase its reactivity.

In the case of currently commercialized fuel cells, the activity

of the platinum catalyst is not adequately reflected on the

reaction, so that a large amount of platinum catalyst must be used. If the amount of platinum catalyst is not enough,

methanol is not decomposed and moved to the opposite electrode.

That is, the methanol crossover phenomenon cannot be prevented to deteriorate its performance significantly. This acts as a

big obstacle to the commercialization of fuel cells.

In the commercialized direct methanol fuel cell, platinum

catalyst is used in such a way that platinum is supported on

carbon or like and dispersed in the electrolyte membrane.

However, this platinum-supported catalyst is not efficiently

dispersed and cohered with, each other, and also the surface of

the catalyst is thickly coated with the polymer used as a binder,

thereby significantly deteriorating its performance. That is, during the manufacturing process of fuel cells, the catalyst is

mixed in the electrolyte solution such as Nation or the like,

and then pressed to form a catalyst layer or an electrode layer.

During this process, the catalyst is aggregated with each other

and the surface of the catalyst is covered with the electrolyte

polymer, so that the efficiency of catalyst is disadvantageously

degraded.

Disclosure of Invention

Technical Problem

The present invention has been made in order to solve the

above problems in the art occurring in the prior art, and it is an object of the invention to provide a porous and continuous

composite membrane, in which solid particles capable of

improving the physical properties of the membrane and enhancing

the functionality of the membrane are uniformly dispersed, in

particular to provide a porous and continuous composite membrane

with solid particles dispersed uniformly therein and having a

thickness on the order of nanometers.

Another object of the invention is to provide a porous and

continuous composite membrane having a good physical property,

while having a thickness on the order of nanometers and a high

content of pores .

A further object of the invention is to provide a porous

and continuous composite membrane, in which solid particles

capable of improving the properties of the membrane and

enhancing the functionality thereof can be uniformly dispersed.

A further object of the invention is to provide a method of

manufacturing a porous and continuous composite membrane with

solid particles uniformly dispersed therein, which can enable

mass production, easily control the thickness of the membrane,

and manufacture the membrane in the form of thin film.

A further object of the invention is to provide a method of

manufacturing a porous and continuous composite membrane having

a thickness on the order of nanometers, a high content of pores,

and a good physical property, which is suitable for mass production and can easily control the thickness of the membrane.

A further object of the invention is to provide a

battery (cell) including a filtering membrane, an electrolyte

membrane, an electrode layer, or a catalyst layer, which has a

mechanical strength to be able to prevent contact between the

electrodes due to an external force and a high ion-conductivity,

and in which a functional particle or a catalyst can be

efficiently dispersed.

A further object of the invention is to provide a secondary

battery (cell) including a filtering membrane, which can obtain

the above functions while having a thickness on the order of

nanometers, thereby enabling a light, thin, short and small

design.

A further object of the invention is to provide a fuel cell

including an electrolyte membrane, an electrode layer, or a

catalyst layer, which has a high reactivity and a low resistance

between the electrodes, and can be easily handled and has a high

efficiency when the fuel cell is fabricated.

Technical Solution

In order to accomplish the above object, according to one

aspect of the invention, there is provided a porous and

continuous composite membrane comprising a) a plurality of

polymer nano-fibers, each of which is a mono-filament, a continuous fiber, or a mixture thereof, the contacting points

between the nano-fibers being fusion-bonded, and b) a plurality

of solid particles evenly dispersed inside the plurality of

polymer nano-fibers. In addition, according to one embodiment of the invention,

the porous and continuous composite membrane is dissolved in a

soluble solvent such that the solid particles are dissolved from

the porous and continuous membrane, thereby forming pores

therein. According another aspect of the invention, there is

provided a method of manufacturing a porous and continuous

composite membrane. The method of the invention comprises steps

of: a) dispersing a solid particle in a polymer solution; b)

electro-spinning the polymer solution with the solid particle

dispersed therein to thereby produce a nano-fiber web; and c)

heating or heating/pressurizing the nano-fiber web, thereby

producing a porous membrane.

In addition, the method of the invention may further

comprises a step of d) forming a pore by dissolving the porous

and continuous membrane in a soluble solvent in such a manner

that the solid particle is dissolved from the porous and

continuous membrane.

According to another aspect of the invention, there is

provided a battery (cell) including a porous and continuous membrane used as a filtering membrane, an electrolyte membrane,

an electrode layer, or a catalyst layer. Here, the porous and

continuous membrane comprises: a) a plurality of polymer nano-

fibers, each of which is a mono-filament, a continuous fiber, or

a mixture thereof, the contacting points between the nano-fibers

being fusion-bonded, and b) a plurality of solid particles

evenly dispersed inside the plurality of polymer nano-fibers.

In addition, according to another aspect of the invention,

there is provided a secondary battery (cell) including the above

porous and continuous membrane as a filtering membrane.

Furthermore, according to another aspect of the invention,

there is provided a fuel cell including the above porous and

continuous membrane as an electrolyte membrane, an electrode

layer, or a catalyst layer.

Advantageous Effects

According to the present invention, in the case where a

large amount of functional particles are contained uniformly in

a polymer desired by a user, a porous and continuous membrane

having a functionality or an improved physical property can be obtained. Since the solid particles are easily dispersed, a

porous and continuous membrane with fine particles dispersed

uniformly therein can be achieved, in which the solid particle

has a size of a few nano-meters to a few micrometers. Also, due to the dispersion of fine particles, the resultant thin film

with the solid particle dispersed therein can be made to be very

thin. In addition, the content, the size and the shape of the

pores in the porous and continuous membrane can be controlled,

variously according to the user's desire.

In addition, the porous and continuous composite membrane

of the invention has a wide range of applications, such as

electric-electronic components such as a condenser, coating

materials, medicinal scaffolds, an organic EL, a PDP, a

biodegradable porous polymer membrane, a porous membrane for

filters, a display, a fuel cell, a secondary battery (cell) , and

the like.

Furthermore, according to the manufacturing method of the

invention, a large amount of solid particles can be efficiently

dispersed. Since the dispersion is easily carried out, fine

solid particles can be dispersed. Therefore, the solid particle

to be dispersed can become smaller, thereby enabling the

manufacturing of a thin film. The content, the shape, and the

size of the pores in the porous and continuous membrane can be

controlled.

Furthermore, the method of manufacturing a porous and

continuous membrane of the invention can easily control the

thickness of the membrane, and is suitable for mass production,

along with the reduced manufacturing cost and fixing cost. In particular, due to the improved mechanical strength

through the dispersion of solid particles, the battery (cell)

containing the porous and continuous membrane as the filtering

membrane can avoid failure of the battery (cell) by an external

force or a short-circuit between the electrodes, in the case where the battery (cell) is fabricated in a light and thin design.

By controlling the structure, the size and the content of the

pores, the amount of electrolyte to be absorbed in the membrane

is maximized, so that a high ion-conductivity and a low

interface resistance can be achieved, thereby enabling

fabrication of a high-efficient battery (cell) . A continuous

membrane having a fine porous structure and an ion-conductivity

for a specific ion can be obtained, thereby enabling to

fabricate a battery (cell) having an electrolyte membrane of high

reaction efficiency. Through dispersion of catalytic particles

or functional particles and efficient control of the dispersion,

a battery (cell) having a high-performance catalyst layer and

electrode layer can be fabricated.

In addition, in the case where the pore is formed by

dissolving the soluble salt, various shapes and contents of the

pore can be achieved through a simple process, relatively to the

conventional manufacturing method of membrane. Therefore, the

manufacturing process can be simplified, along with the easy

control of the process. In particular, in case of the secondary battery (cell) of

the invention, the thickness control can be easily carried out,

through a general mass production method. The thin films can be

fabricated, depending on the application specifications. In

this way, therefore, the entire weight of the battery (cell) can

be reduced.

Furthermore, in case of the fuel cell of the invention, it

includes a porous membrane so that an adequate reactivity can be

achieved. The electrolyte membrane can be formed in the form of

a thin film to reduce the resistance thereof, so that favorable

energy efficiency can be achieved. The reduced strength due to

the reduced thickness can be compensated through the dispersion

of the solid particles.

Brief Description of Drawings

Further objects and advantages of the invention can be more

fully understood from the following detailed description taken

in conjunction with the accompanying drawings, in which.:

FIG. 1 shows a schematic diagram of an electro-spinning

system for use in the present invention;

FIG. 2 is a SEM (scanning electron microscope) photograph

shown the solid particles spun with polylactic acid (PLLA)

according to a method of the invention;

FIG. 3 is a SEM photograph showing a porous and continuous membrane prepared in such a manner that a PLLA and solid

particles are spun together into a nano-fiber web, which is

pressed by a press;

FIG. 4 is a SEM photograph showing a porous and continuous

membrane where the soluble salt particle is removed after

pressing a PLLA fiber layer spun together with the soluble salt

particles;

FIG. 5 is a SEM photograph showing the surface of a porous

film for batteries which is composed of solid nano—particles and

nano-fibers; and

FIG. 6 is a SEM photograph showing the fractured surface of

the porous film for batteries, which is composed of solid nano-

particles and nano-fibers.

* REFERENCE NUMERALS IN DRAWINGS * 10 : Capillary tube

15 : Nano-fiber web

20 : Collector electrode

Best Mode for Carrying Out the Invention The preferred embodiments of the present invention will be

hereafter described in detail.

A porous and continuous composite membrane according to the

invention comprises a plurality of polymer nano-fibers, each of

which is a mono-filament, a continuous fiber, or a mixture thereof and the contacting point between the fibers is fusion-

bonded, and a plurality of solid particles evenly dispersed

inside the plurality of polymer nano-fibers. The porous and

continuous composite membrane of the invention is manufactured

by dispersing solid particles into a polymer solution, and

electro-spinning the solid particle-dispersed solution to

thereby form mono-filaments and continuous fibers. The polymer

nano-fiber web of nano-size, which is the mono-filaments, the

continuous fibers, or their mixture, is heated or

heated/pressurized to thereby produce the porous and continuos

composite membrane of the invention.

In general, in order to form a porous and continuous

membrane, the membrane must contain pores inside thereof, and

the ingredients of the membrane are to be fine in order to

disperse solid particles.

The nano-fiber used in the invention functions to form the

pores and disperse the solid particles. That is, in case of

polymer nano-fibers, in particular, of mono-filaments, generally

they are arranged without orientation or regularity. When they

are laminated, they are disorderly distributed, entangled and

overlapped. In addition, the nano-fibers have a high specific

surface area and are complicatedly overlapped with each other,

and thus numerous contacting points exist between the fibers.

Therefore, the plurality of contacting points between the fibers is fusion-bonded such that the aggregation of nano-fibers is

transformed into a continuous membrane.

The solid particles used in the invention are dispersed in

the fine nano-fibers. Therefore, the dispersion can be more

effectively and uniformly achieved.

The diameter of the solid particle can be selected

variously, depending on the applications of the porous and

continuous membrane. In particular, when the solid particle has

a spherical shape, it is preferred to have a diameter of 2nm to

30μm. When the solid particle is not spherical, its long axis is

preferred to be 2nm to 30μιm. In addition, the material used as the solid particles,

which is dispersed in the porous and continuous composite

membrane, includes a soluble solid particle and a non-soluble

solid particle. In particular, it is constituted of a material

capable of electro-spinning such as an organic material

containing a soluble salt, an inorganic material, a metallic

material, an organic/inorganic solid particle coated with a

metal, a carbon nano-tube, or the mixture thereof. The solid

particle can be selected appropriately, depending on its

application specification. That is, it can be applied in

various forms, depending on its purposes such as improvement in

the mechanical strength, or provision of the functionality.

In particular, in the case where the solid particle is a soluble salt, the salt is dissolved, and the portion where the

salt has existed is replaced with a pore, thereby enabling a

porous membrane. In this case, advantageously the percentage,

size, shape of the pore can be adjusted by controlling the

content, the size, and the shape of the salt.

Specifically, the solid particle may be made of an organic

material such as polymer, carbon, a carbon nano-tube, rubber, or

protein; a functional ceramic inorganic material such as silica

series, alumina series, titanium series, ITO (Indium Tin Oxide)

series, dielectric ceramic, or piezoelectric ceramic; or a

metallic material such as platinum, gold, silver, copper,

ruthenium (Ru) , aluminum, or copper. These materials can be

used individually as a single material or in a mixture of at

least two thereof. In addition, the surface of the solid

particle, which has a size of a few or a few hundreds nanometer,

can be coated with a metallic thin film or a functional material

including a catalyst. Furthermore, since the solid particle is

simply a mixture through dispersion, a common solid particle

used in the art may be employed. The solid particle is dispersed in a continuous membrane

comprised of nano-fibers and its dispersion is relatively easy,

as compared with a general continuous membrane. Therefore, a

wide range of dispersion ratio can be achieved from a small

amount to a larger amount of solid particles. In particular, the solid particle is preferred to be contained in an amount of

2 to 95% by volume. When the solid particle is used in the

above range, the workability such as in the electro-spinning can

be more effectively improved. In case of conventional solid particles, the finer the

solid particle is, the severer they are entangled. Therefore,

it is difficult employing a fine particle as the dispersion

particle. In case of the solid particles used in the invention,

the fine particles can be easily dispersed, and thus a finer

particle can be utilized. Where the size of the solid particle

is within the above range, its mass production and workability

are excellent and thus its economical efficiency is

distinguished.

The thickness of the porous and continuous membrane, which

is constituted of the above constituents, may be controlled

appropriately, depending on its applications and uses. In

particular, the thickness is preferred to be within a range of

2nm to 500μm. This is, in case of the porous and continuous membrane constituted of nano-fiber according to the invention, a

uniform dispersion of fine particles can be achieved. Therefore,

in case of a membrane with solid particles dispersed therein,

the finer the dispersed particle is, the thinner membrane can be

fabricated. With the particles not damaged, a membrane having a

thickness of the particle size or several times of the particle size can be manufactured.

In addition, according to the invention, the above porous

and continuous membrane is dissolved in a soluble solvent such

that the solid particle, i.e., the soluble salt is dissolved from the porous and continuous membrane and thus the place of

the dissolved solid particle (soluble salt) is replaced with

pores, thereby providing a porous and continuous membrane.

Advantageously, the percentage, the size and the shape of the

pores can be controlled by controlling the content, the size,

and the shape of the salt, etc.

In the porous and continuous membrane where the soluble

salt is replaced with pores as described above, the percentage

of the pores (porosity) can be adjusted appropriately by

controlling the content of the salt, depending on the

application and uses thereof. Preferably, the porosity is in an

amount of 2 to 95% by volume based on the entire porous and

continuous membrane. Within the above range of porosity, it has

a good physical property and a good workability for mass

production. The porous and continuous composite membrane according to

the invention has a wide range of applications, such as

electric-electronic components, batteries, medicinal scaffolds,

a porous membrane for filters, coating materials, a fuel cell,

an organic EL, a PDP, a biodegradable porous and continuous polymer membrane, and a display. Specifically, it includes a

partition plate of electrolytic batteries, a

catalyst/electrode/filtering membrane of fuel cells or a

partition plate of secondary batteries (in particular, a

filtering membrane for lithium ion secondary batteries) , a

scaffold for cell culture, a wet permeable membrane and waterproof clothes, a gas permeable membrane, a reverse osmosis

filter, an ultra-filtration membrane, a fine-filtration membrane

(water treatment, etc), or the like. In particular, when a bio-medicinal scaffold employs the

porous and continuous membrane of the invention, where the

soluble salt used as solid particles is replaced for pores, it

is favorable for the cell to be implanted in the surface of the

fiber, and it is advantageous, as compared to the conventional

polymer process or scaffold structure, since the blood and

nerves is supplied to the cell through the empty space of the

nano-fiber web. In addition, the nano-fiber web fabricated by

electro-spinning has a narrow space. Therefore, as the cell

begins to grow, the space for the cell to grow cannot be secured,

in the case where only the electro-spinning is utilized. In the

present invention, a solid salt particle, which has a size for

the cell to grow in a polymer solution, is contained and

dispersed above 90% by volume, and then the membrane is

fabricated by the electro-spinning. Therefore, a space for the cell to grow can be provided.

According to the invention, a method of preparing a porous

and continuous composite membrane. In the method of the

invention, solid particles are dispersed in a polymer solution, the solution with the solid particles dispersed therein is

electro-spun to thereby create a nano-fiber web, and then the

nano-fiber web is heated or heated/pressurized.

The polymer used in the invention is a compound as a raw

material for the nano-fiber, and a material capable of being

dissolved by a solvent.

The polymer may include all kinds of polymers, depending on

the application of the porous and continuous membrane, as long

as they are capable of electro-spinning. For example, in the

case where the porous and continuous composite membrane is

utilized for industrial purposes, it is preferable in terms of

its economical efficiency that polyethylene, polypropylene,

cellulose or the like is utilized. When it is applied to a

human body, it is preferred to use a polymer such as polyglycol

acid, polylactic acid, polylactic acid-glycolic acid copolymer,

polycaprolactone, polyamino acid, polyanhydride, polyorthoester,

or the like.

Although the above polymer is not particularly limited as

long as it has a molecular weight to the extent to be electro-

spun, it is in particular preferred to have a molecular weight of above 10,000. If the polymer has a molecular weight of at

least 10,000, a fiber form can be easily obtained when electro-

spinning and the resultant porous and continuous composite

membrane comes to have a good physical property. The higher the

molecular weight of the polymer becomes, the thinner the

diameter of the electro-spun nano-fiber becomes, and thus the

more contacting points are created advantageously. Furthermore,

in terms of the workability for mass production and the physical

property of the resultant porous and continuous composite

membrane, the polymer process can be carried out from the

molecular weight of at least 2,000. In case of ultra high

molecular weight polyethylene, a polymer having a molecular

weight of up to 1,000,000 to 5,000,000 is processable.

The content of solvent in the polymer solution used in the

invention is acceptable if it is appropriate to dissolve the

polymer and disperse solid particles. Therefore, those skilled

in the art can select according to the type of the polymer and

the solid particle. In particular, the polymer solution is

preferred to have a viscosity of 0.1 cp (10^~3 Pa.s) to 10³ Pa.s.

When the viscosity of the polymer solution is within the above

range, the electro-spinning and the morphology of the nano-fiber

web can be easily controlled.

The diameter of the solid particle can be selected

variously, depending on the applications of the porous and continuous membrane. In particular, when the solid particle has

a spherical shape, it is preferred to have a diameter of 2nm to

30μm. When the solid particle is not spherical, its long axis is

preferred to be 2nm to 30μm. In addition, the material used as the solid particles,

which is dispersed in the porous and continuous composite

membrane, includes a soluble solid particle and a non-soluble

solid particle. In particular, it is constituted of a material

capable of electro-spinning such as an organic material

containing a soluble salt, an inorganic material, a metallic

material, an organic/inorganic solid particle coated with a

metal, a carbon nano-tube, or the mixture thereof. The solid

particle can be selected appropriately, depending on its

application specification. That is, it can be applied in

various forms, depending on its purposes such as improvement in

the mechanical strength, or provision of the functionality.

In particular, in the case where the solid particle is a

soluble salt, the salt is dissolved, and the portion where the

salt has existed is replaced with a pore, thereby enabling a

porous membrane. In this case, advantageously the percentage,

size, shape of the pore can be adjusted by controlling the

content of the content, the size, and the shape of the salt.

Specifically, the solid particle may be made of an organic

material such as polymer, carbon, a carbon nano-tube, rubber, or protein; a functional ceramic inorganic material such as silica

series, alumina series, titanium series, ITO (Indium Tin Oxide)

series, dielectric ceramic, or piezoelectric ceramic; or a

metallic material such as platinum, gold, silver, copper,

ruthenium (Ru) , aluminum, or copper. These materials can be

used individually as a single material or in a mixture of at least two thereof. In addition, the surface of the solid

particle, which has a size of a few or a few hundreds nanometer,

can be coated with a metallic thin film or a functional material

including a catalyst. Furthermore, since the solid particle is

simply a mixture through dispersion, a common solid particle

used in the art may be employed.

The solid particle is dispersed in a continuous membrane

comprised of nano-fibers and its dispersion is relatively easy,

as compared with a general continuous membrane. Therefore, a

wide range of dispersion ratio can be achieved from a small

amount to a larger amount of solid particles. In particular,

the solid particle is preferred to be contained in an amount of

2 to 95% by volume. When the solid particle is used in the

above range, the workability such as in the electro-spinning can

be more effectively improved.

Furthermore, according to the invention, in order to

disperse solid particles in a polymer solution, all the

agitating methods commonly used in mixing solid particles homogeneously into a polymer solution may be employed. Also, an

appropriate dispersing agent can be mixed. In particular, in

case of dispersing solid particles of a nano-size, an ultrasonic

dispersion method is preferable for uniform dispersion. The polymer solution with the solid particles dispersed

therein is electro-spun in order to create mono-filaments,

continuous fibers, or a mixture thereof, which forms a nano-web

having a nano-size. Of course, in case of the mono-filament, it

can be fabricated so as to have a length having a nano- or

micro-size.

FIG. 1 shows a schematic diagram of an electro-spinning

system for use in the present invention. As illustrated in FIG.

1, a strong electric field is applied to a polymer solution or a

melted material inside a capillary tube 10. Then, when the

surface tension of liquid and the electrical force are in

balance, a liquid drop formed at the tip of the capillary tube

is transformed into a pointed conical shape and simultaneously

the liquid is spun. The fiber spun as described above is

accelerated and becomes thinner and thinner by the electrical

field, and becomes unstable to be collected in a non-continuous

form in the surface of the grounded metal, which is a collector

electrode 20. That is, in the case where the material dissolved

in the solution has a lower molecular weight, generally it

exhibits the form of small particles, and thus called as an electro-spraying. As in the present invention, when a material

having a higher molecular weight is electro-spun, generally a

fiber having a very small diameter of about lOOnm is obtained in

the form of a fiber, which does not have any directionality or

regularity. Therefore, the process for manufacturing a fiber

from a polymer having a high molecular weight is called an

electro-spinning, dissimilar to the electro-spraying.

The present invention employs the electro-spinning process.

That is, an excessive amount of solid particles is dispersed in

various conventional polymer solutions through a solid particle

dispersion method, and then electro-spun to produce a nano-fiber

web 15, which is an overlapped and entangled state of fine

fibers of a few nanometers.

The nano-fiber web formed by electro-spinning the polymer

solution is a nano-fiber with solid particles completely

dispersed and loaded thereon. While the solvent is evaporated,

this nano-fiber web is solidified in a short period of time.

Therefore, a state that the solid particles are uniformly

dispersed in the nano-fiber is obtained. The above-formed nano-fiber web is simply heated, or heated

and simultaneously pressed to melt the polymer, in such a manner

that a fusion-boding is formed at the contacting points between

the fibers, thereby providing the porous and continuous

composite membrane. At this time, the heating may be applied to the whole web,

or may be locally applied. A simple heating can be carried out,

or a pressuring (pressing) is performed along with the heating.

That is, plural nano-fibers forms contacts between the fibers,

which has various contacting angles, contacting positions, and

contacting areas. When the temperature is increased above the

melting temperature of the polymer by heating, or

heating/pressing, the fiber becomes a melt state and the melt is

accumulated in the contacted area. This accumulated melt

generates a contact angle with the surface of the fiber, and the

contact angle produces an attraction force, by which the fibers

are drawn to each other. The nano-fibers are fusion-boned until

the contact angle is vanished.

The nano-fiber, in particular, the mono-filament has a very

small size and a light weight, and thus the surface tension is

high, relatively to the gravity. Therefore, the fusion-bonding

between the fibers can be efficiently effected. In particular,

when the pressing is carried out simultaneously, the nano-fiber

web can be transformed into a desired shape, and at the same

time the porosity thereof can be controlled through the pressing.

Particularly, in the case where the heating and the

pressing are carried out simultaneously, preferably, they are

performed such that the resultant porous and continuous membrane

has a thickness of 2nm to 500μm. As previously described, the thickness of the porous and continuous membrane has a

relationship with the size of dispersed particles and the extent

of dispersion thereof. Therefore, when fine particles are

dispersed, a thinner porous and continuous membrane can be

formed.

The heating and pressing can be carried out through a roll

pressing, a press pressing, an autoclave pressing, or the like.

According to the application of the above heating and pressing,

a membrane of uniform thickness can be obtained, the thickness

of the membrane can be easily controlled, and a mass production

can be achieved.

Specifically, in the above roll pressing process, the

melted nano-fiber web is passed and pressed through a nip roll,

which is composed of at least 2 rolls and heated to above the

dissociation-transition temperature of the polymer. After the

press roll, while passing a cooling roll, it is adjusted below

the dissociation-transition temperature of the polymer, thereby

fixing the thickness of the film, together with cooling.

In the press pressing, the nano-fiber web is pre-heated

using an oven, and then pressed in a press adjusted below the

melting temperature of the polymer and cooled, thereby finally

controlling the thickness of the film.

Finally, in the autoclave pressing, the spun nano-fiber web

is hand-laid up inside the vacuum film such as nylon, polyimide, polypropylene, or the like, and made vacuum. Then, a pressure

of 2 to 100 atm is exerted to the nano-fiber web while heating

the nano-fiber web to above the melting temperature of the polymer, to thereby reduce the number of pores present inside

the nano-fiber web and form a flat surface thereof by means of

the uniform pressure of the gas. Thereafter, after the film is

completely formed, the nano-fiber web is cooled to below the

melting point of the polymer while maintaining the pressure,

thereby obtaining a final film. In addition, according to the invention the manufacturing

method of the porous and continuous composite membrane further

comprises a step of dissolving the above-prepared porous and

continuous composite membrane into a soluble solvent in such a

manner that the solid particle is dissolved from the porous and

continuous membrane to therefore form pores inside thereof.

The percentage, size, shape of the pores can be adjusted by

controlling the content, the size, and the shape of the soluble

salt .

In the porous and continuous membrane where the soluble

salt is replaced with pores as described above, the percentage

of the pores (porosity) can be adjusted appropriately by

controlling the content of the salt, depending on the

application and uses thereof. Preferably, the porosity is in an

amount of 2 to 95% by volume based on the entire porous and continuous membrane. Within the above range of porosity,

advantageously, it has a good physical property and a good

workability for mass production.

The manufacturing method of the porous and continuous

composite membrane according to the invention employs an

electro-spinning process and thus can coat a three-dimensional

shape efficiently, even in the case where the whole product can

be dipped into the coating solution, or the portion to be coated

is formed of a complicated three-dimensional shape and thus

cannot use a silk-screen printing, or the like. That is, only

the portion to be coated can be heated and pressed, and then

coated. In addition, advantageously a large amount of solid

particles can be dispersed efficiently.

In addition, according to the present invention, a

battery (cell) containing a porous and continuous membrane is

provided. The battery (cell) of the invention comprises a porous

and continuous membrane used as a filtering membrane, an

electrolyte membrane, an electrode layer or a catalyst layer.

The porous and continuous membrane comprises a) a plurality of

polymer nano-fibers, each of which is a mono-filament, a

continuous fiber, or a mixture thereof and the contacting points

between the fibers are fusion-bonded, and b) a plurality of

solid particles evenly dispersed inside the plurality of polymer

nano-fibers . In general, a battery (cell) includes two electrodes and an

electrolyte electrically connecting the two electrodes. For the

purpose of a compact construction of battery (cell) , the two

electrodes are spatially very close to each other, and thus

embraces a danger of a short-circuit due to contact between the

electrodes. Therefore, in order to maintain the conductivity

between the electrodes while avoiding the direct contact of the

electrodes, a porous filtering membrane is included between the two electrodes so as to be capable of containing a large amount

of electrolyte and thus minimize resistance. In addition, a

certain type battery (cell) includes a porous electrolyte

membrane capable of exchanging a specific ion, preventing short-

circuit of the electrodes, and promoting the ion exchange. The

fuel cell also includes an electrode layer having a porous

structure where ionization of fuel and oxidation of the ionized

fuel are performed, and which has conductivity for providing an

electron passage and facilitates this reaction. Furthermore,

the fuel cell includes a catalyst layer, which contains a

catalytic material for promoting the ionization of hydrogen at

the electrode layer and has a porous structure for obtaining

reactivity.

In addition, according to the invention, a battery (cell)

including as a filtering membrane, an electrolyte membrane, an

electrode layer, or a catalyst layer thereof a porous and continuous membrane. The porous and continuous membrane used in

the battery (cell) of the invention is manufactured by a method

according to the invention. According to the method of the

invention, solid particles are dispersed in a polymer solution.

Then, the solution with the solid particles dispersed therein is electro-spun to thereby form a nano-fiber web, which is composed

of a nano-fiber in the form of a mono-filament, a nano-fiber in

the form of a continuous fiber, or a mixture thereof.

Thereafter, the nano-fiber web is heated, or heated/pressurized

to obtain a porous and continuous membrane.

The polymer used in the present invention includes a

compound, which can be used as a raw material of the fiber, and

includes a polymer material capable of dissolving by a solvent,

or electro-spinning in a melted form. The polymer may include all kinds of polymers, depending on

the battery (cell) using the porous and continuous membrane, as

long as they are capable of electro-spinning. For example, a

polymer stable against electrolyte can be used so that the

porous and continuous membrane can act adequately as a filtering

membrane. A polymer containing polyethylene, polypropylene,

polyamide, polyimide, polysulfone, polyolefine, Nation,

polymergel, fluoric polymer, fluorene, polystyrene, a

combination thereof, or the like may be used. In particular,

with respect to the selection of polymer materials, a polymer having conductivity to electrons or ions can be selected in

order to form an electrode layer, a polymer material containing

a functional group for transferring specific ions can be

selected in order to form an electrolyte membrane, and a polymer

material having a high mechanical strength and ion-conductivity

can be selected in order to form a filtering membrane.

The range of molecular weight of the polymer, the solvent

in the polymer solution, the viscosity, the size and shape of

the solid particle, the mixing method, whether or not the

additive is applied and the type of the additives may be applied

in the same manner as described previously, in conjunction with

the composite material. The material used as the solid

particles dispersed in the porous and continuous membrane may

utilize the same specifications as that of the solid particle

used in the composite material. In particular, in order to

provide a catalytic function, the particles used for a

battery (cell) may include a catalyst particle where a catalytic

material such as platinum, ruthenium, or the like is supported

on carbon. In addition, it may include a nano-sized inorganic

particle coated with a catalytic material such as platinum,

ruthenium, or the like. The inorganic particle can be made of

mica, or montmorillonite, which can be formed into a nano-sized

particle. The function materials are coated preferably with a

thickness of 0.2nm to 30μm, in order to provide an adequate functionality and optimize the use of the functional material.

Furthermore, in order to increase the dielectric coefficient

thereof, a dielectric particle may be contained, and in order to

increase the conductivity thereof, a conductive particle may be

included.

In addition, a method of supporting/coating a functional

material such as platinum on the surface of the nano-sized

organic or inorganic particle may employ an electroless plating,

an elecro-plating, a sputtering process, a vapor deposition, a

chemical vapor deposition (CVD) , or a plasma coating process.

When required, a sintering process may be added to thereby

improve the bonding force between the particle and the coating

material. The coated nano-particles made of such as mica or

montmorillonite has a plate-like shape having a very large

surface area, and thus in the case where a functional material

is coated, its effect can be maximized.

As described above, in the case where the solid particles

with a catalytic material contained therein are dispersed, the

resultant continuous membrane can be used as a catalytic layer

of batteries. If a conductive particle is dispersed, an

electrode layer of batteries can be formed. When the solid

particles containing the catalytic material are dispersed in the

continuous membrane containing a functional group capable of

forming an electrolyte membrane, it can provide a catalyst and electrode layer, which can serve as an electrode layer and a

catalytic layer simultaneously.

Furthermore, particularly in the case where a carbon nano-

tube is used as the solid particle, the porous and continuous

membrane with the carbon nano-tube dispersed therein can be used

in a battery (cell) including a secondary battery (cell) or a fuel

cell, thereby taking advantage of the unique electrical and

mechanical characteristics thereof. That is, according to the

present invention, the carbon nano-tube is dispersed in a

polymer solution, and thus the strand of the carbon nano-tube

can be loosened without entangling.

As described above, the solid particle is dispersed in a

continuous membrane comprised of fibers and its dispersion of

solid particles is relatively easy, as compared with a general

continuous membrane. Therefore, a wide range of dispersion

ratio can be achieved from a small amount to a larger amount of

solid particles. In particular, the content of solid particles

dispersed in the polymer solution can be controlled

appropriately so as to optimize the dispersion thereof, the

easiness of electro-spinning, the functionality of the

continuous membrane, or the like. Therefore, in the porous and

continuous composite membrane, the content of the solid

particles dispersed in the porous and continuous composite

membrane can be adjusted variously, and its content can be controlled within the range of 2 to 95% in terms of volume ratio, The polymer solution with solid particles dispersed therein is electro-spun to form a nano-web, using the electro-spinning

process illustrated in FIG. 1. According to the invention, an

excessive amount of solid particles is dispersed in various

conventional polymer solutions through a solid particle

dispersion method, and then electro-spun to produce a nano-fiber web 15, which is an overlapped and entangled state of fine

fibers having a size of a few to a few thousands nanometers. In

the above elecro-spinning process, by controlling the conditions

of electro-spinning, the web can be formed such that it is

constituted of a nano-fiber in the form of a mono-filament, a

nano-fiber in the form of a continuous fiber, or a mixture of

the mono-filament and the continuous fiber. The nano-fiber web

is spun in a state that the solid particles are completely

dispersed and loaded in the fibers. As the solvent is

evaporated from the web, this fiber web is solidified in a short

period of time. Therefore, a state that the solid particles are

uniformly dispersed in the fiber is achieved. The fiber web prepared as described above is fabricated

into a porous and continuous membrane, using the method

described previously in connection with the composite material,

which a simple heating is carried out, or heating and pressing

(pressurizing) are performed simultaneously. In addition, as described previously, in case of the porous

and continuos membrane as prepared above, similarly, soluble

salt is dispersed and the solid particle is dissolved in a

soluble solvent such that the particles are dissolved therefrom

to form pores, thereby providing a porous and continuous membrane for batteries.

In this way, the mechanical strength of the porous and

continuous membrane can be adjusted by controlling the type, the

size, and the dispersed content of the solid particles, and the

size, the structure, and the content of the pores. Depending on

the size, the structure, and the content of the pore, the

content of electrolyte inside the membrane can be controlled.

Therefore, a membrane having a required ion-conductivity and a

low interface resistance can be obtained. Generally, in order to form a porous and continuous

membrane, it must have a structure of having pores thereinside.

It is beneficial that the constituents of the membrane are fine

in order for the solid particles to be dispersed. In addition,

when intended to be used as an electrolyte layer, the prepared

porous membrane can be heated and pressed at a higher

temperature and with a higher pressure to thereby remove the

pores. The continuous membrane as manufactured above has an

excellent particle dispersion characteristic, as compared with

the conventional membrane fabricated by coating. The thickness of the porous and continuous membrane having

the above-described constitution may be controlled appropriately,

depending on the specifications of a battery (cell) to which the

continuous membrane is applied. In particular, the thickness is

preferred to be in the range of 2nm to 500μm. This is, in case of the porous and continuous membrane constituted of the fibers

according to the invention, a uniform dispersion of fine

particles can be achieved. Therefore, in case of a membrane

with solid particles dispersed therein, the finer the dispersed

particle is, the thinner membrane can be fabricated. In this

way, the resistance of the continuous membrane can be minimized.

With the particles not damaged, a membrane having a thickness of

the particle size or a few or a few hundreds times of the

particle size can be manufactured. In addition, the

manufactured membrane is overlapped in several layers and

pressed, to thereby fabricate a thicker membrane. The electro-

spinning can be repeated several times to the same place, and

then the resultant product can be heated and pressurized to

manufacture a thicker membrane. In addition, when a carbon nano-tube is used as the solid

particle to be dispersed, it can be necessary that the carbon

nano-tube is oriented in a certain direction, when required. In

this case, if the carbon nano-tube and the polymer are spun

together through the electro-spinning, it is spun in such a way that the carbon nano-tube is adsorbed around the nano-fiber or

in the surface thereof. Therefore, the carbon nano-tube can be

dispersed, and at the same time, oriented in a certain direction.

Also, if the electrode, to which the fiber web is received, is

formed of a wheel and the electrode wheel is rotated with a high

speed while electro-spinning the nano-fiber, the orientation of

the carbon nano-tube can be promoted. In case of the above

oriented film, the membrane is anisotropic electrically and

mechanically, and thus can be applied to the field of a

battery (cell) , a second battery (cell) , a fuel cell, an electron-

emitting element, or the like.

In addition, according to the invention, the above porous

and continuous membrane is dissolved in a soluble solvent such

that the solid particle, i.e., the soluble salt is dissolved

from the porous and continuous membrane and thus the place of

the dissolved solid particle (soluble salt) is replaced with

pores, thereby providing a porous and continuous membrane.

Advantageously, the percentage (content) , the size and the shape

of the pores can be controlled by controlling the content, the

size, and the shape of the soluble salt, etc. In this case, an

insoluble salt and a soluble salt can be dispersed together and

only the soluble salt can be dissolved to thereby be replaced

with pores. Therefore, the porosity can be controlled by the

dispersion of the soluble salt and the extent of fusion-bonding in the fibers, and its mechanical strength can be controlled by

the dispersion of the insoluble salt.

In the porous and continuous membrane where the soluble

salt is replaced with pores as described above, the percentage of the pores (porosity) can be adjusted appropriately by

controlling the content of the salt, depending on the

specifications of a battery (cell) to which the membrane is

applied. Preferably, the porosity is in an amount of 2 to 95% by

volume based on the entire porous and continuous membrane.

Within the above range of porosity, it has a good physical

property (mechanical property, ion-conductivity, etc.) and a

good workability for mass production. In this way, the

structure, the content, and the size of the pore can be

controlled so as to be able to absorb as much electrolyte as

possible per unit volume.

The battery (cell) may include all of a general primary

battery (cell) , a secondary battery (cell) , and a fuel cell. The

primary and secondary batteries may include a zinc-manganese

battery (cell) , an alkaline battery (cell) , a lithium-ion

battery (cell) , a lead battery (cell) , a nickel-cadmium

battery (cell) , a lithium ion battery (cell) , or the like.

Preferably, the present invention can be applied to the lithium-

ion battery (cell) . The fuel cell may include a phosphoric acid

fuel cell (PAFC) , a alkaline fuel cell (AFC) , a polymer electrolyte membrane fuel cell (PEMFC) , a molten carbonate fuel

cell (MCFC) , a solid oxide fuel cell (SOFC) , and a direct

methanol fuel cell (DMFC) . Preferably, the present invention

can be applied to the polymer electrolyte membrane fuel cell and

the direct methanol fuel cell.

The secondary battery (cell) of the invention comprises a

porous and continuous membrane as the filtering membrane thereof,

and the porous and continuous membrane contains a) a plurality

of polymer fibers in which the contacting points between the

nano-fibers are fusion-bonded, and b) a plurality of solid

particles dispersed uniformly in the plurality of polymer nano-

fibers.

The secondary battery (cell) includes various types of

secondary batteries. In particular, a lithium-ion battery (cell)

is preferred. In this case, the polymer material may be

exemplified by polyamide, polysulfone, polyolefine, copolymer, and fluoric polymer, which have a high mechanical strength and a

high ion-conductivity.

Furthermore, the dispersion of the solid particles may

function to improve its mechanical strength when a thin film is

formed.

The porous and continuous membrane applied to the filtering

membrane of the secondary battery (cell) may be manufactured by

dispersing solid particles in a polymer solution, electro spinning the solution dispersed with the solid particles to form

a fiber web, and heating, or heating/pressurizing the formed

fiber web. Alternatively, solid particles made of a soluble

salt are dispersed in a polymer solution, and the solution with the solid particles dispersed therein is electro-spun. Then,

the spun product is dissolved in a solvent capable of dissolving

the solid particle to thereby form a nano-fiber web, which is

heated or heated/pressurized, thereby finally providing the

porous and continuous membrane for batteries. In the manufacturing of the porous and continuous membrane,

in case of a secondary battery (cell ) , the resistance between the

electrodes needs to be reduced in order to constitute a high

efficient battery (cell) , and thus the electrolyte membrane must

have a thin thickness. For this purpose, a heating/pressing

process including the roll pressing, the press pressing, or the

autoclave pressing may be carried out, or a combination thereof

may be applied. In case of the film manufactured according to

the above method, since the porous and continuous membrane has a

thin thickness, in order to reinforce the mechanical strength of

the filtering membrane, the mechanical strength of the membrane

can be improved, using the dispersion of the solid particles.

Furthermore, in case of the electrolyte membrane for the

fuel cell of the invention, the size, the shape, the content,

the type of the solid particles, and the content of the pore (porosity) can be applied, in the same manner as previously described.

A secondary battery (cell) is often used in a portable form,

and thus a simple, small, light and thin design is required.

The porous and continuous membrane of the invention can be

applied efficiently since it can be formed in the form of a thin

film while maintaining the mechanical strength thereof. In case

of a lithium battery (cell) , a synergetic effect can be achieved,

i.e., the reduction in its weight by using lithium, and also the

reduction in its weight by fabricating it in the form of thin

films .

In addition, the fuel cell of the invention comprises a

porous and continuous membrane as the electrolyte membrane, the

electrode layer, and the catalytic layer, and the porous and

continuous membrane contains a) a plurality of polymer fibers in

which the contacting points between the nano-fibers are fusion-

bonded, and b) a plurality of solid particles dispersed

uniformly in the plurality of polymer nano-fibers.

The fuel cell of the invention may include various types of

fuel cells using a porous membrane as the electrolyte membrane.

In particular, a specific type of fuel cells relevant to the

present invention is exemplified by a polymer electrolyte

membrane fuel cell (PEMFC) and a direct methanol fuel cell

(DMFC) . Particularly, in case of the solid polymer electrolyte

membrane type, the mechanical contact between the electrodes is

avoided to thereby prevent a short-circuit. It includes an

electrolyte membrane, which contains a functional group for ion- transportation and is placed contacted between both electrodes

in order to serve simultaneously as an ion-exchange membrane for

selectively performing the ion-transfer between both electrodes,

an electrode layer for facilitating the supply of fuel and

collecting current, a porous catalytic layer for performing

reaction with fuel and generating hydrogen, and a catalyst and

electrode layer containing a catalytic material in the electrode

layer and for performing the functions of both layers.

Therefore, the porous and continuous membrane, or the

porous and continuous membrane, in which a soluble salt is

transformed into pores, serves as an electrolyte membrane for

exchanging hydrogen ion, in the case where it is constituted of

a polymer containing a functional group capable of exchanging

ions. Specifically, the material for the electrolyte membrane

can use Nation (supplied by Dupont in U.S. ) . In case of a fuel

cell, a porous electrolyte membrane is required as the

electrolyte membrane. For example, in case of a hydrogen fuel

cell, the ionization of hydrogen from hydrogen gas and the ion-

transportation are carried out at the electrolyte membrane. In

order to fabricate a high efficient hydrogen fuel cell by facilitating this reaction, it is more favorable to have the

wider reactive interface where the hydrogen gas reacts with the

functional group, and it is beneficial that the whole fuel cell

has a compact size. For this purpose, the present invention

provides a porous structure using a fusion-bonding of the

contacting points between the fine nano-fibers, or a porous and

continuous membrane in which a soluble salt is replaced with

pores .

In addition, the porous and continuous membrane, or the

porous and continuous membrane, in which a soluble salt is

transformed into pores, can constitute an electrode layer for

facilitating the supply of fuel and collecting current, in the

case where electron or ion transfer is constituted of a polymer

or the dispersion of conductive solid particle is performed.

When the porous and continuous member is used as an electrode

layer, the electrode can be constituted of the porous and

continuous body of the invention only, or in the form that the

porous and continuous body is combined with a plate-like

metallic electrode using a conductive wire. In addition, the porous and continuous membrane, or the

porous and continuous membrane, in which a soluble salt is

transformed into pores, can constitute a porous catalytic layer

for performing reaction with fuel and facilitating the

generation of hydrogen ion, in the case where solid particle containing a catalytic material is dispersed. In the case where

the continuous membrane is constituted of a polymer capable of

transferring electron or ion and solid particle containing a

catalytic material is dispersed inside the continuous membrane,

it can constitutes a catalytic electrode layer for performing

reaction with fuel to promote the generation of hydrogen ions,

facilitating the supply of fuel, and collecting current.

Furthermore, in case of a direct methanol fuel cell (DMFC),

in order to obtain the same effect while minimizing methanol

crossover and minimizing the amount of catalytic material used,

solid particles having a size of a few nano-meters, which are

made of Nation or other appropriate polymers and coated with a

catalytic material such as platinum or the like, are dispersed

and spun on the surface of the electrolyte membrane, so that a

porous membrane containing the catalytic material as solid

particles is formed on the electrolyte membrane, thereby

obtaining a catalytic electrode layer.

As previously described, the solid particles to be

dispersed is prepared in such a manner that a functional metal

including platinum is coated in the form of a thin film on the

surface of inorganic or organic nano-particles made of such as

mica or montmorillonite, using an electroless plating, an

elecro-plating, a sputtering process, a vapor deposition, a

chemical vapor deposition (CVD) , a plasma coating process, or the like. These nano-particles is contained in nano-fibers and

attached to the electrolyte membrane, and then fi:xed to the

electrolyte membrane using the pressing process or the like,

thereby enabling to control the methanol crossover. Alternatively, a web is prepared separately by containing these

coated particles in the nano-fibers, and then an electrolyte

membrane with no pore can be fabricated through a pressing

process. The fabricated electrolyte membrane can be served as

an electrolyte membrane of fuel cells. In particular, the coated nano-particles made of such as

mica or montmorillonite has a wide plate-like shape having a

very large surface area, and thus in the case where it is

contained in the electrolyte membrane of fuel cells, methanol to

permeate the electrolyte membrane is made to be reacted, so that

the methanol crossover can be maximally prevented.

The electrolyte membrane as prepared above can control the

methanol transfer since the methanol is reacted by platinum

contained the porous membrane and run out, while generating

methanol crossover when methanol passes through the electrolyte

membrane. In addition, the opposite electrode, where hydrogen

ion is reacted to generate water, is formed with a membrane

containing a catalyst using the same method as in the present

invention, thereby efficiently carrying out the water generation.

Furthermore, the dispersion of the solid particles may function to improve its mechanical strength when a thin film is

formed.

The porous and continuous membrane applied to the

electrolyte membrane, an electrode layer, a catalyst layer, or a

catalytic electrode layer of the fuel cell may be manufactured

by dispersing solid particles in a polymer solution, electro-

spinning the solution dispersed with the solid particles to form

a fiber web, and heating, or heating/pressurizing the formed

fiber web. Alternatively, solid particles made of a soluble

salt are dispersed in a polymer solution, and the solution with

the solid particles dispersed therein is electro-spun. Then,

the spun product is dissolved in a solvent capable of dissolving

the solid particle to thereby form a nano-fiber web, which is

heated or heated/pressurized, thereby finally providing the

porous and continuous membrane for fuel cells.

In the manufacturing of the porous and continuous membrane,

in case of a fuel cell, the resistance between the electrodes

needs to be reduced in order to constitute a high efficient

battery (cell) , and thus the electrolyte membrane must have a

thin thickness. For this purpose, a heating/pressing process

including the roll pressing, the press pressing, or the

autoclave pressing may be carried out, or a combination thereof

may be applied. In case of the film manufactured according to

the above method, since the porous and continuous membrane has a thin thickness, a careful handling is required when fabricating

a fuel cell. For reinforcement thereof, the mechanical strength

of the membrane can be improved, using the dispersion of the

solid particles. Furthermore, in case of the electrolyte membrane for the

fuel cell of the invention, the size, the shape, the content,

the type of the solid particles, and the content of the pore (porosity) can be applied, in the same manner as previously

described. The following examples are provided to more fully

illustrate the present invention, which is not limited thereto.

Example 1. A composite film prepared by dispersing

montmorillonite particle in the cellulose polymer

8% by weight of cellulose diacetates was dissolved in a

mixed solution of methylene chloride : ethanol = 9:1. 8 to 60% by

volume of solid particle made of montmorillonite (MMT) and

having a diameter of 3 to lOμm was uniformly dispersed in the above solution. Then, the solution with the solid particles

dispersed therein was electro-spun. Here, when electro-spinning,

a voltage of 10 to 20kV was applied, and the distance between

the electrodes was 15 to 20cm. an aluminum film was employed in

the collector electrode. In addition, the diameter of the

spinning nozzle was 0.1 to 0.3mm, and the electro-spinning was

carried out at room temperature with atmospheric pressure. In this case, it has been found out that, as the content of MMT is

increased, the resiliency of the nano-fibers is increased and

thus the pores are formed in the form of very firm structure.

Example 2. A composite film prepared by dispersing salt

particles in the polylactic acid (PLLA) cellulose polymer

Polylactic acid (Mn = 218,000, Mw/Mn = 1.55) was dissolved

in chloroform. Then, 3 to 10% by volume of montmorillonite

particles were mixed with the above solution, followed by

electro-spinning. In addition, 90% by volume of a mixture

consisting of aluminum bicarbonate particles, sodium chloride

particles, and montmorillonite particles is mixed to form pores

inside of a scaffold. Here, when electro-spinning, a voltage of

15kV was applied to produce the solution speed of 1 ml/hr, and

the distance between the electrodes was 15 to 20cm. An aluminum

film was in the collector electrode. In addition, the diameter

of the spinning nozzle was 0.1 to 0.5mm, and the electro-

spinning was carried out at room temperature with atmospheric

pressure .

FIG. 2 shows the solid particles spun with polylactic acid

(PLLA) and uniformly dispersed without coagulation.

FIG. 3 shows a fiber bundle manufactured by pressing a

nano-fiber web, which was prepared by the electro-spinning. In

this case, it has been found that the fiber bundle maintains the

shape of fiber due to a lower pressing temperature, and the structure of a porous film is maintained since the space between

the fiber bundles is maintained.

FIG. 4 shows a porous and continuous membrane prepared by

spinning together with soluble salt particles and then removing

the soluble salt particle. It shows that the place where the

salt particle is removed is replaced for pores, and it has a

very uniform distribution of pores.

Example 3. A porous polystyrene (PS) film for batteries

30% by weight of polystyrene was dissolved in a solvent of

dimethylformamide (DMF) , and then 0 to 10% by volume of

montmorillonite particles were mixed with the above solution,

followed by electro-spinning. Here, when electro-spinning, a

voltage of lOkV was applied to produce the solution speed of 0.8

ml/hr, and the distance between the electrodes was 15 to 20cm. A

aluminum film was employed in the collector electrode. In

addition, the diameter of the spinning nozzle was 0.1 to 0.5mm,

and the electro-spinning was carried out at room temperature

with atmospheric pressure. The spun nano-fiber was pressed

using a roll pressing machine. The structure of the porous

membrane prepared by the above procedures is shown in FIGS. 5

and 6. It has been found that the above prepared membrane has

nano-sized pores between the nano-fibers and a very rigid

membrane can be formed. The size of pores and the rigidity of

the membrane could be adjusted by controlling the pressure of the roll pressing machine or the press.

Example 4. A porous film for batteries obtained by

dispersing salt particles

Except that 0 to 90% by volume of solid particles prepared

by mixing aluminum bicarbonate particles, sodium chloride

particles and montmorillonite (MMT) particles in a certain

predetermined ratio were mixed, instead of the montmorillonite

particles, the electro-spinning was carried out in the same

manner as in the previous example 1. The above-prepared porous

film was dissolved in a solvent capable of dissolving the

soluble salt in the solid particles, and thus a final porous

film was manufactured. In this case, it has been found out that,

as the content of MMT is increased, the resiliency of the nano-

fibers is increased and thus the pores are formed in the form of

very firm structure.

Industrial Applicability

According to the present invention, in the case where a

large amount of functional particles are contained uniformly in

a polymer desired by a user, a porous and continuous membrane

having a functionality or an improved physical property can be

obtained. Since the solid particles are easily dispersed, a

porous and continuous membrane with fine particles dispersed

uniformly therein can be achieved, in which the solid particle has a size of a few nano-meters to a few micrometers. Also, due

to the dispersion of fine particles, the resultant thin film

with the solid particle dispersed therein can be made to be very

thin. In addition, the content, the size and the shape of the

pores in the porous and continuous membrane can be controlled,

variously according to the user's desire.

In addition, the inventive porous and continuous composite

membrane has a wide range of applications, such as electric-

electronic components such as a condenser, coating materials,

medicinal scaffolds, an organic EL, a PDP, a biodegradable

porous polymer membrane, a porous membrane for filters, a

display, a fuel cell, a secondary battery (cell) , and the like.

Furthermore, according to the manufacturing method of the

invention, a large amount of solid particles can be efficiently

dispersed. Since the dispersion is easily carried out, fine

solid particles can be dispersed. Therefore, the solid particle

to be dispersed can become smaller, thereby enabling the

manufacturing of a thin film. The content, the shape, and the

size of the pores in the porous and continuous membrane can be

controlled.

Furthermore, the inventive method of manufacturing a porous

and continuous membrane can easily control the thickness of the

membrane, and is suitable for mass production, along with the

reduced manufacturing cost and fixing cost. In particular, due to the improved mechanical strength

through the dispersion of solid particles, the battery (cell)

containing the porous and continuous membrane as the filtering

membrane can avoid failure of the battery (cell) by an external force or a short-circuit between the electrodes, in the case

where the battery (cell) is fabricated on a design basis of

lightness and thinness. By controlling the structure, the size

and the content of the pores, the amount of electrolyte to be

absorbed in the membrane is maximized, so that a high ion-

conductivity and a low interface resistance can be achieved,

thereby enabling fabrication of a high-efficient battery (cell) .

A continuous membrane having a fine porous structure and an ion-

conductivity for a specific ion can be obtained, thereby

enabling fabrication of a battery (cell) having an electrolyte

membrane of high reaction efficiency. Through dispersion of

catalytic particles or functional particles and efficient

control of the dispersion, a battery (cell) having a high-

performance catalyst layer and electrode layer can be fabricated. In addition, in the case where the pore is formed by

dissolving the soluble salt, various shapes and contents of the

pore can be achieved through a simple process, relatively to the

conventional manufacturing method of membrane. Therefore, the

manufacturing process can be simplified, along with the easy

the invention, the thickness control can be easily carried out, through a general mass production method. The thin films can be

fabricated, depending on the application specifications. In

this way, therefore, the entire weight of the battery (cell) can be reduced.

Furthermore, in case of the fuel cell of the invention, it

includes a porous membrane so that an adequate reactivity can be

achieved. The electrolyte membrane can be formed in the form of

a thin film to reduce the resistance thereof, so that favorable

energy efficiency can be achieved. The reduced strength due to the reduced thickness can be compensated through the dispersion

of the solid particles.

While the present invention has been described with

reference to the particular illustrative embodiments, it is not

to be restricted by the embodiments but only by the appended

claims. It is to be appreciated that those skilled in the art

can change or modify the embodiments without departing from the

scope and spirit of the present invention.

Claims

What Is Claimed Is :

1. A porous and continuous composite membrane

comprising: a) a plurality of polymer nano-fibers, each of which

is a mono-filament, a continuous fiber, or a mixture thereof,

the contacting points between the nano-fibers being fusion-

bonded, and b) a plurality of solid particles evenly dispersed

inside the plurality of polymer nano-fibers.

2. The composite membrane according to claim 1, wherein

the solid particle has a diameter of 2nm to 30μm when it has a spherical shape, and the solid particle has a long axis of 2nm

to 30μm when it has a non-spherical shape.

3. The composite membrane according to claim 1, wherein

the solid particle includes a particle made of an inorganic

material containing a soluble salt, an organic material, a

metallic material, or a mixture thereof, or the surface of the

solid particle is coated with a functional material in the

thickness of 0.2nm to 30μm.

4. The composite membrane according to claim 1, wherein

the porous and continuous membrane contains the solid particles

in an amount of 2 to 95% by volume.

5. The composite membrane according to claim 1, wherein

the porous and continuous membrane has a thickness of 2nm to

500μm.

6. The composite membrane according to claim 1, wherein

the porous and continuous composite membrane is dissolved in a

soluble solvent such that the solid particles are dissolved from

the porous and continuous membrane, thereby containing pores in

an amount of 2 to 95% by volume based on the porous and

continuous membrane.

7. The composite membrane according to any one of claims

1 to 6, wherein the porous and continuous composite membrane is

used in an electric-electronic component, a secondary

battery (cell) , a catalyst/electrode/filtering membrane of a fuel

cell, a medicinal scaffold, a filter, a coating material, an

organic EL, a PDP, a biodegradable porous and continuous polymer

membrane, or a display.

8. A method of manufacturing a porous and continuous

composite membrane, the method comprising steps of: a) dispersing a solid particle in a polymer solution; b) electro-spinning the polymer solution with the solid particle dispersed therein to thereby produce a nano-fiber web;

and c) heating or heating/pressurizing the nano-fiber web,

thereby producing a porous membrane.

9. The method according to claim 8, wherein the polymer

in the step a) has a molecular weight of at least 2,000.

10. The method according to claim 8, wherein the

viscosity of the polymer solution in the step a) is within a

range of 10^"3 Pa.s to 10³ Pa.s.

11. The method according to claim 8, wherein the step c)

of heating and pressurizing is carried out by at least one

method selected from the group consisting of a roll pressing, a

press pressing, and an autoclave pressing.

12. The method according to claim 8, wherein the step c)

of heating and pressurizing is carried out such that the

resultant porous and continuous membrane has a thickness of 2nm

to 500μm.

13. The method according to claim 8, further comprising a

step of: d) forming a pore by dissolving the porous and continuous membrane in a soluble solvent in such a manner that

the solid particle is dissolved from the porous and continuous

membrane .

14. A battery (cell) including a porous and continuous

membrane, wherein the porous and continuous membrane comprises:

a) a plurality of polymer nano-fibers, each of which is a mono-

filament, a continuous fiber, or a mixture thereof, the

contacting points between the nano-fibers being fusion-bonded,

and b) a plurality of solid particles evenly dispersed inside

the plurality of polymer nano-fibers.

15. The battery (cell) according to claim 14, wherein the

solid particle has a diameter of 2nm to 30μm when it has a spherical shape, and the solid particle has a long axis of 2nm

to 30μm when it has a non-spherical shape.

16. The battery (cell) according to claim 14, wherein the

solid particle includes a particle made of an inorganic material

containing a soluble salt, an organic material, a metallic

material, or a mixture thereof, or the surface of the solid

particle is coated with a functional material in the thickness

of 0.2nm to 30μm.

17. The battery (cell) according to claim 14, wherein the

porous and continuous membrane contains the solid particles in

an amount of 2 to 95% by volume.

18. The battery (cell) according to claim 14, wherein the

porous and continuous membrane has a thickness of 2nm to 500μm.

19. The battery (cell) according to claim 14, wherein the

porous and continuous membrane is manufactured by a method

comprising steps of: a) dispersing a solid particle in a polymer solution; b) electro-spinning the polymer solution with the solid

particle dispersed therein to thereby produce a nano-fiber web;

and c) heating or heating/pressurizing the nano-fiber web,

thereby producing a porous membrane .

20. The battery (cell) according to claim 19, wherein the

porous and continuous membrane is dissolved in a soluble solvent

such that the solid particle is dissolved from the porous and

continuous membrane, thereby containing pores in an amount of 2

to 95% by volume based on the porous and continuous membrane.

21. The battery (cell) according to claim 19, wherein the pores of the porous and continuous membrane are removed by the

step c) of heating/pressurizing.

22. A secondary battery (cell) including as a filtering

membrane a porous and continuous membrane according to any one

of claims 14 to 21.

23. A fuel cell including as an electrolyte membrane, a

catalyst layer, or an electrode layer a porous and continuous

membrane according to any one of claims 14 to 21.