KR20170068686A - Composite materials separator and method of manufacturing the same - Google Patents

Abstract

A composite separator plate capable of ensuring uniform electrical conductivity in all areas and a method of manufacturing the same.
The composite separator according to the present invention comprises a carbon fiber woven structure; And a conductive filler sheet laminated on upper and lower surfaces of the carbon fiber woven structure, respectively.

Description

Technical Field [0001] The present invention relates to a composite material separator,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite separator and a method of manufacturing the same, and more particularly, to a composite separator which can ensure a uniform electrical conductivity in all regions and a method of manufacturing the same.

The separator plate, which is a component of the fuel cell stack, functions as a reaction gas (hydrogen and oxygen) supply and water discharge passage, and electrically connects the inside of the fuel cell stack. For this function, the separator requires excellent electrical conductivity, mechanical properties, corrosion resistance and low hydrogen permeability.

Recently, a redox flow cell, which has received a great deal of attention from large secondary batteries, also includes a separator plate, which is also required to have excellent electrical conductivity, mechanical properties, corrosion resistance, chemical resistance and electrolyte impermeability.

In order to satisfy this, a composite separator plate in which a carbon fiber woven fabric is impregnated with a thermosetting resin has been manufactured. However, the composite separator plate manufactured by this method has a problem that a thick resin layer exists on the carbon fiber woven fabric, .

In recent years, in order to solve this problem, research has been actively conducted on a composite separator plate in which a conductive filler is dispersed in a liquid thermosetting resin and then impregnated with a carbon fiber woven fabric.

However, in the case of the composite separator in which the conductive filler is dispersed, there is a disadvantage in that the processability of uniformly dispersing the conductive filler in the thermosetting resin lowers the processability due to the high viscosity of the thermosetting resin. In addition, when the dispersibility of the dispersion containing the conductive filler added to the thermosetting resin is not excellent, the conductivity of the composite separator varies depending on the area of the composite separator. When the dispersibility of the dispersion is excellent, the thermosetting resin and the conductive filler There is a phenomenon that an excessive amount of the conductive filler exists in only a part of the composite separator plate. Accordingly, there is a problem that the reliability of the large thickness deviation of the composite separator plate is low when applied to a battery.

Also, if the conductive filler is excessively penetrated into the carbon fiber woven fabric, it may interfere with the contact between the strands of the fiber bundle, resulting in a deterioration of electrical conductivity.

A related prior art is Korean Patent Laid-Open Publication No. 10-2014-0046772 (published on April 21, 2014), which discloses a separator for a redox flow cell and a redox flow cell including the separator .

It is an object of the present invention to provide a composite separator which can ensure a uniform electrical conductivity in all regions and a method of manufacturing the composite separator.

According to an aspect of the present invention, there is provided a composite separator comprising: a carbon fiber woven structure; And a conductive filler sheet laminated on upper and lower surfaces of the carbon fiber woven structure, respectively.

According to an aspect of the present invention, there is provided a method of manufacturing a composite separator, comprising: (a) coating a dispersion in which an electrically conductive filler is dispersed in an organic solvent, and then volatilizing the organic solvent to form a conductive filler sheet; (b) impregnating the carbon fiber woven fabric with a thermosetting resin to form a carbon fiber woven structure; (c) laminating conductive filler sheets on the upper and lower surfaces of the carbon fiber woven structure, respectively; And (d) pressing and hardening the carbon fiber woven structure and the conductive filler sheet by a hot press to obtain a composite separator plate.

The composite separator according to the present invention and the method of manufacturing the same can provide an excellent mechanical strength by inserting a carbon fiber woven structure in which a thermosetting resin is impregnated into a carbon fiber woven fabric in the middle, The conductive filler sheet designed to be distributed in a sheet type is distributed on the upper and lower surfaces of the carbon fiber woven structure, respectively, so that it is possible to obtain excellent electrical conductivity in all areas without causing a deviation in conductivity.

In addition, the composite separator according to the present invention and the method for manufacturing the same may be manufactured by adding a conductive filler to an organic solvent having a viscosity lower than that of a thermosetting resin, The control of the distribution of the conductive filler is easy, and the manufacturing process is simple and the process can be simplified.

1 is a cross-sectional view of a composite separator according to an embodiment of the present invention;
2 is a process flow diagram illustrating a method of manufacturing a composite separator according to an embodiment of the present invention.
3 is a SEM photograph of a composite separator produced according to Example 1. Fig.
4 is a SEM photograph of a carbon fiber separator manufactured according to Comparative Example 2. FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a composite separator according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a composite separator according to an embodiment of the present invention.

1, a composite separator plate 100 according to an embodiment of the present invention includes a carbon fiber woven structure 120 and conductive filler sheets 140 (not shown) stacked on upper and lower surfaces of the carbon fiber woven structure 120, respectively. ). The carbon fiber woven fabric structure 120 and the conductive filler sheet 140 are pressed together by a hot press method and have a structure in which they are bonded together.

The carbon fiber woven structure 120 is disposed in the middle of the composite separator plate 100 to improve the mechanical strength of the composite separator plate 100. The carbon fiber woven structure 120 preferably has a thickness of 200 to 400 mu m. If the thickness of the carbon fiber woven structure 120 is less than 200 탆, the thickness of the carbon fiber woven structure 120 may be too small to secure mechanical strength. On the contrary, when the thickness of the carbon fiber woven structure 120 exceeds 400 탆, the thickness and the volume of the carbon fiber woven fabric structure 120 increase only without increasing the effect, which may result in weight reduction and thinning.

Such a carbon fiber woven structure 120 includes at least one vertically stacked carbon fiber woven fabric 122 and a resin layer 124 impregnated with the carbon fiber woven fabric 122. 1 illustrates a structure in which a resin layer 124 is impregnated into one piece of carbon fiber woven fabric 122.

The carbon fiber woven fabric 122 can be produced by weaving 1,000 to 70,000 strands of fiber bundles into weft and warp yarns, respectively. At this time, the fiber bundles of the carbon fiber woven fabric 122 have a circular or elliptical cross-sectional structure. The fiber bundles of the carbon fiber woven fabric 122 may have an average spacing of 1.5 to 2.0 mm.

The resin layer 124 is impregnated in the inside of the carbon fiber woven fabric 122 to improve the mechanical strength. The resin layer 124 is formed of any one material selected from among a phenol resin, an epoxy resin, an amino resin, a urea resin, a melamine resin, an unsaturated polyester resin, a polyurethane resin, and a thermosetting resin including a polyimide resin.

The conductive filler sheet 140 is laminated on the top and bottom surfaces of the carbon fiber woven structure 120, respectively. The conductive filler sheet 140 may be prepared by coating a dispersion in which the conductive filler is dispersed in an organic solvent, and then volatilizing the organic solvent.

Therefore, it is preferable to use an organic solvent having excellent volatility. Specific examples thereof include ethanol, butanol, ethyl acetate, octanol, ethoxy ethanol pentanol, methoxy ethanol, ethylene glycol, acetone, tetrahydrofuran, dimethylformamide , Dimethylamine, dichloromethane, and diethylether may be used.

Particularly, since the viscosity of the organic solvent is much lower than the viscosity of the thermosetting resin, when the conductive filler sheet 140 is formed by volatilizing the organic solvent after coating a dispersion in which the conductive filler is dispersed in the organic solvent, The conductive filler can be dispersed uniformly over the entire region of the conductive film 140. [ As a result, it becomes possible to ensure a uniform electrical conductivity in the entire region.

Since the conductive filler sheet 140 is prepared not by adding the conductive filler to the thermosetting resin but by dispersing the conductive filler in an organic solvent having a viscosity lower than that of the thermosetting resin, And the manufacturing process is simple, so that the process can be simplified.

As the conductive filler, at least one selected from carbon nanotube, graphite powder, chopped carbon fiber, carbon black and carbon powder may be used. have.

The conductive filler sheet 140 preferably has a thickness of 5 to 100 mu m. When the thickness of the conductive filler sheet 140 is less than 5 占 퐉, the thickness is too thin, which makes handling difficult and deteriorates electrical conductivity. On the contrary, when the thickness of the conductive filler sheet 140 exceeds 100 mu m, it may be a factor that raises only the manufacturing cost without increasing any further effect, which is not economical.

In the composite separator according to the present invention, a carbon fiber woven structure in which a thermosetting resin is impregnated into a carbon fiber woven fabric is interposed in the middle to ensure excellent mechanical strength, and the conductive filler is uniform The conductive filler sheet designed to be dispersed so as to be distributed on the upper and lower surfaces of the carbon fiber woven structure can be provided with excellent electrical conductivity in all regions without causing a deviation in conductivity.

In addition, the composite separator according to the embodiment of the present invention is not made by adding a conductive filler to a thermosetting resin, but by preparing a conductive filler sheet in such a manner that a conductive filler is added and dispersed in an organic solvent having a much lower viscosity than a thermosetting resin Therefore, the control of the distribution of the conductive filler is easy, and the manufacturing process is simple, so that the process can be simplified.

Hereinafter, a method of manufacturing a composite separator according to an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a process flow diagram illustrating a method of manufacturing a composite separator according to an embodiment of the present invention.

2, the composite separator manufacturing method according to an embodiment of the present invention includes a conductive filler sheet forming step S210, a carbon fiber woven fabric structure forming step S220, a laminating step S230, and a hot pressing step S240).

Conductive filler sheet formation

In the conductive filler sheet forming step (S210), a dispersion in which the conductive filler is dispersed in an organic solvent is coated, and then the organic solvent is volatilized to form a conductive filler sheet.

At this time, as the conductive filler, at least one selected from a carbon nanotube, a graphite powder, a chopped carbon fiber, a carbon black and a carbon powder is used .

As the organic solvent, it is preferable to use one having excellent volatility. Specific examples thereof include ethanol, butanol, ethyl acetate, octanol, ethoxyethanol pentanol, methoxyethanol, ethylene glycol, acetone, tetrahydrofuran, dimethylformamide , Dimethylamine, dichloromethane, and diethylether may be used.

In this step, since the viscosity of the organic solvent is much lower than the viscosity of the thermosetting resin, dispersion can be easily performed. When the dispersion liquid in which the conductive filler is dispersed in the organic solvent is coated and cured as described above, the conductive filler in the dispersion can be uniformly distributed over the entire area. As a result, the conductive filler is uniformly distributed over the entire area of the conductive filler sheet So that it becomes possible to ensure uniform and excellent electrical conductivity in the entire region.

At this time, at least one of knife coating, spray coating, dip coating and bar coating may be used, and in this case, spray time, dip coating time The thickness of the conductive filler sheet can be adjusted by adjusting the knife height, the height of the bar, and the like.

Here, the dispersion in which the conductive filler is dispersed in an organic solvent can be produced by coating and curing the release film to produce a conductive filler sheet, and then peeling the conductive filler sheet from the release film.

Carbon Fiber Woven Structure Formation

In the step of forming the carbon fiber woven structure (S220), the carbon fiber woven fabric is impregnated with a thermosetting resin to form a carbon fiber woven structure.

At this time, the thermosetting resin may be any one selected from among a phenol resin, an epoxy resin, an amino resin, a urea resin, a melamine resin, an unsaturated polyester resin, a polyurethane resin and a thermosetting resin including a polyimide resin.

In order to homogeneously impregnate the thermosetting resin, a liquid thermosetting resin composition is prepared by using at least one of knife coating, spray coating, dip coating and bar coating methods. Lt; / RTI > After such application, the thermosetting resin is cured.

Accordingly, the carbon fiber woven structure may include a carbon fiber woven fabric in which at least one is vertically stacked, and a resin layer impregnated in the carbon fiber woven fabric. At this time, the carbon fiber woven fabric may be one sheet, or a plurality of sheets of two or more sheets may be laminated vertically.

At this time, the carbon fiber woven fabric may be one produced by weaving fiber bundles each having 1,000 to 70,000 strands in weft and weft, respectively. The fiber bundles of such carbon fiber woven fabrics have a circular or elliptical cross-sectional structure. And, the fiber bundles of the carbon fiber woven fabric may have an average spacing of 1.5-2.0 mm.

Lamination

In the laminating step S230, conductive filler sheets are laminated on the upper and lower surfaces of the carbon fiber woven structure, respectively. Thereby, the carbon fiber woven structure is interposed between the two conductive filler sheets to have a sandwich structure.

Hot press

In the hot press step S140, the carbon fiber woven structure and the conductive filler sheet are squeezed and cured by hot pressing to obtain a composite separator plate.

At this time, the hot press is preferably performed for 30 to 60 minutes under the conditions of 120 to 180 DEG C and 20 to 30 tons. If the hot press temperature is less than 120 占 폚 or the hot press time is less than 30 minutes, there is a great possibility that sufficient curing is not achieved. On the contrary, when the hot press temperature exceeds 180 DEG C or the hot press time exceeds 60 minutes, it may be a factor for raising the manufacturing cost without further increase in the effect, which is not economical.

In addition, when the hot press pressure is less than 20 ton, the adhesion force between the carbon fiber woven structure and the conductive filler sheet is insufficient, and peeling may occur. Conversely, if the hot press pressure exceeds 30 tones, excessive pressure may cause damage to the carbon fiber woven structure and the conductive filler sheet, such as cracks.

The thickness is decreased by the pressing by the hot pressing step (S140). After performing this hot pressing step (S140), the carbon fiber woven structure has a thickness of 200 to 400 mu m, and each of the conductive filler sheets may have a thickness of 5 to 100 mu m.

In the composite separator plate produced by the above-described processes (S210 to S240), a carbon fiber woven structure in which a thermosetting resin is impregnated into a carbon fiber woven fabric is interposed in the middle to secure an excellent mechanical strength, The conductive filler sheet designed to be a dispersed sheet type so that the fillers are uniformly distributed is laminated on the upper and lower surfaces of the carbon fiber woven structure, respectively, so that it is possible to obtain excellent electrical conductivity in all regions without causing a deviation in conductivity.

In addition, instead of adding the conductive filler to the thermosetting resin, the composite separator produced by the method according to the embodiment of the present invention may be produced by dispersing a conductive filler in an organic solvent having a viscosity lower than that of a thermosetting resin, Since the sheet is manufactured, the distribution of the conductive filler can be easily controlled, and the manufacturing process can be simplified, so that the process can be simplified.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

1. Composite separator manufacturing

Example 1

A dispersion in which 100 g of carbon nanotubes were dispersed in 1 L of ethanol was coated on the release PET to a thickness of 80 탆 and ethanol was volatilized at 40 캜 to prepare a carbon nanotube sheet.

Then, one carbon fiber woven fabric was impregnated with an epoxy resin to prepare a 400 탆 thick carbon fiber woven structure.

Next, two carbon nanotube sheets were laminated on the upper and lower surfaces of one carbon fiber woven structure, respectively, and pressed and cured by hot pressing for 40 minutes under the conditions of 150 캜 and 25 ton to prepare composite separator plates. At this time, the final thickness of the carbon fiber woven structure by the hot press was 250 占 퐉, and the final thickness of the carbon nanotube sheet was 33 占 퐉.

Example 2

The composite separator was prepared in the same manner as in Example 1, except that the mixture was pressed and cured by hot pressing at 130 占 폚 and 25 ton for 50 minutes.

Example 3

Except that a dispersion liquid in which 200 g of graphite powder was dispersed in 3 liters of ethanol was coated on the releasing PET to a thickness of 80 탆 and then ethanol was volatilized at 40 캜 to prepare a graphite powder sheet. .

Comparative Example 1

The carbon fiber woven fabric was impregnated with an epoxy resin to prepare a carbon fiber separator having a thickness of 400 탆.

Comparative Example 2

The carbon fiber woven fabric was impregnated with a composite resin having a composition ratio of 1 wt% of carbon nanotubes and 99 wt% of an epoxy resin to prepare a carbon fiber separator having a thickness of 400 탆.

Comparative Example 3

The carbon fiber woven fabric was impregnated with a composite resin having a composition ratio of 3 wt% of carbon nanotubes and 97 wt% of an epoxy resin to prepare a carbon fiber separator having a thickness of 400 탆.

2. Microstructure Observation

FIG. 3 is a SEM photograph of a composite separator manufactured according to Example 1, and FIG. 4 is a SEM photograph of a carbon fiber separator manufactured according to Comparative Example 2. FIG.

As shown in FIG. 3, a composite separator manufactured according to Example 1 is prepared by coating a dispersion in which carbon nanotubes are dispersed in ethanol, and then volatilizing ethanol to produce a carbon nanotube sheet. Can be confirmed to be uniformly distributed over the entire area.

On the other hand, as shown in FIG. 4, the carbon fiber separator manufactured according to Comparative Example 2 can not uniformly disperse the carbon nanotubes in the entire region, and thus it is confirmed that the epoxy resin in some regions is exposed to the outside .

3. Conductivity evaluation

Table 1 shows the results of the conductivity evaluation for the samples prepared according to Examples 1 to 3 and Comparative Examples 1 to 3.

1) Contact resistance measurement

Measurement method: A copper electrode / GDL / separator / GDL / copper electrode was laminated in this order, and a voltage drop between the copper electrodes was measured while applying a current of 5 A to both copper electrodes. The resistance was measured by dividing the value of the current applied to the voltage and the area of the separator used for the measurement was multiplied. At this time, the separation plate was 5 cm in width and 5 cm in length.

In order to reduce the contact resistance between the copper electrode and the GDL, the copper electrode / GDL / copper electrode was laminated in this order and then the resistance was measured. The contact resistance of the separating plate was calculated by subtracting the above value.

[Table 1]

As shown in Table 1, it can be seen that the contact resistance values of the composite separator plates prepared according to Examples 1 to 3 were lower than the contact resistance values of the carbon fiber separator plates prepared according to Comparative Examples 1 to 3 . As a result, it can be seen that Examples 1 to 3 have excellent conductivity as compared with Comparative Examples 1 to 3.

It can be seen that the conductivity of Comparative Example 3 is lower than that of Comparative Example 2 because the conductive filler is not well dispersed even though the content of the conductive filler is increased.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. These changes and modifications may be made without departing from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

100: composite separator plate
120: carbon fiber woven structure
122: Carbon fiber weave
124: resin layer
140: Conductive filler sheet
S210: Conductive filler sheet forming step
S220: Carbon fiber woven structure formation step
S230: Stacking step
S240: Hot press step

Claims (13)

Carbon fiber woven structures; And
A conductive filler sheet laminated on the upper and lower surfaces of the carbon fiber woven structure;
And a composite separator plate.
The method according to claim 1,
The carbon fiber woven structure
Composite separator having a thickness of 200 to 400 탆.
The method according to claim 1,
The carbon fiber woven structure
A carbon fiber woven fabric in which at least one is vertically stacked,
And a resin layer impregnated in the carbon fiber woven fabric.
The method of claim 3,
The resin layer
And a thermosetting resin including a phenol resin, an epoxy resin, an amino resin, a urea resin, a melamine resin, an unsaturated polyester resin, a polyurethane resin and a polyimide resin.
The method according to claim 1,
The conductive filler sheet
A composite separator plate having a thickness of 5 to 100 탆.
The method according to claim 1,
The conductive filler sheet
A composite separator formed by coating a dispersion in which an electrically conductive filler is dispersed in an organic solvent, and volatilizing the organic solvent.
The method according to claim 6,
The conductive filler
A composite separator comprising at least one selected from the group consisting of carbon nanotubes, graphite powder, chopped carbon fiber, carbon black and carbon powder.
(a) coating a dispersion in which an electrically conductive filler is dispersed in an organic solvent, and then volatilizing the organic solvent to form a conductive filler sheet;
(b) impregnating the carbon fiber woven fabric with a thermosetting resin to form a carbon fiber woven structure;
(c) laminating conductive filler sheets on the upper and lower surfaces of the carbon fiber woven structure, respectively; And
(d) pressing and hardening the carbon fiber woven structure and the conductive filler sheet by a hot press to obtain a composite separator plate;
≪ / RTI >
9. The method of claim 8,
The conductive filler
A method for manufacturing a composite separator comprising at least one selected from carbon nanotube, graphite powder, chopped carbon fiber, carbon black and carbon powder .
9. The method of claim 8,
In the step (a)
The organic solvent
And at least one of ethanol, butanol, ethyl acetate, octanol, ethoxy ethanol pentanol, methoxy ethanol, ethylene glycol, acetone, tetrahydrofuran, dimethyl formamide, dimethyl amine, dichloromethane and diethyl ether Wherein the composite separator is formed of a composite material.
9. The method of claim 8,
The carbon fiber weave
At least one of which is vertically laminated.
9. The method of claim 8,
The resin layer
A method for producing a composite separator using any one material selected from a thermosetting resin including a phenol resin, an epoxy resin, an amino resin, a urea resin, a melamine resin, an unsaturated polyester resin, a polyurethane resin and a polyimide resin.
9. The method of claim 8,
In the step (d)
The hot press
Wherein the composite separator is manufactured at a temperature of 120 to 180 DEG C and 20 to 30 tons for 30 to 60 minutes.

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