KR101639783B1 - Method for preparing gas diffusion layer for fuel cell, gas diffustion layer prepared by the method, Electrode and Fuel cell comprising the same - Google Patents

Abstract

The present invention relates to a method for producing a carbon slurry, which comprises mixing a carbon powder, a hydrophobic binder and a dispersion medium to prepare a carbon slurry; Coating the carbon slurry on a substrate using a coater; And drying the coated carbon slurry to form a gas diffusion layer, wherein the dispersion medium comprises a fuel comprising 50 to 95% by weight of ethylene glycol, 2 to 40% by weight of water, and 0.05 to 10% by weight of a dispersant A method for manufacturing a gas diffusion layer for a battery is presented.

Fuel cell

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a gas diffusion layer for a fuel cell, a gas diffusion layer manufactured by the method, an electrode employing the same and a fuel cell,

The present invention relates to a method for producing a gas diffusion layer for a fuel cell, a gas diffusion layer produced by the method, an electrode employing the same, and a fuel cell, and more particularly to a carbon slurry having improved dispersibility of carbon A method for manufacturing a diffusion layer for a fuel cell, a gas diffusion layer manufactured by the method, an electrode employing the diffusion layer, and a fuel cell.

Recently, interest in renewable energy is increasing. Among renewable energy sources, fuel cells are attracting attention as automotive power sources, household power sources, and portable power sources because they are environmentally friendly, have high energy density, and have a long life span.

The fuel cell can be classified into a polymer electrolyte membrane fuel cell (PEMFC), a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), a solid oxide And a solid oxide fuel cell (SOFC). The operating temperature of the fuel cell, the material of the component parts, and the like depend on the type of electrolyte used. In addition, the fuel cell is classified into a direct fuel supply type or an internal reforming type according to a manner in which fuel is supplied to the anode, and a direct methanol fuel cell (DMFC) is a typical direct fuel supply type.

PEMFC (Polymer Electrolyte Membrane Fuel Cell) has superior power, lower operating temperature, and faster response characteristics than other fuel cells.

A fuel cell is composed of a power generation unit, a reformer, a fuel tank, and a fuel pump, in which electricity is generated. The power generation portion forms the main body of the fuel cell, and the fuel pump supplies the fuel in the fuel tank to the reformer. Hydrogen gas is generated through the reformer and fuel is supplied to the power generation unit by the pump to generate electric energy by electrochemical reaction. The power generation unit may include a membrane electrode assembly (MEA) composed of an anode, a cathode, and a polymer electrolyte membrane.

The direct methanol fuel cell, which is being studied with a small portable power source, uses methanol as the fuel, so it does not use a hydrogen reformer, etc., and operates at a low temperature, so that the system can be made simple and compact.

The principle of electricity generation in the direct methanol fuel cell is that methanol is supplied to the anode electrode, and methanol is decomposed into hydrogen ions, electrons and carbon dioxide (CO ₂ ) by the oxidation reaction of the electrode catalyst, and hydrogen ions are decomposed into the polymer electrolyte membrane The electrons move to the cathode through the external circuit. In the cathode, water is generated by the reaction of oxygen introduced in the air, electrons moved through the external circuit, and hydrogen ions moved through the membrane.

The electrochemical reaction is represented by the following reaction formula (1).

<Reaction Scheme 1>

_{Anode: CH 3 OH + H 2 O} → CO 2 + 6H + + 6e -

Cathode: 3/2 O ₂ + 6H ⁺ + 6e ^- ? 3H ₂ O

Overall reaction: CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O

Since the electrochemical reaction is completed through oxidation and reduction of the fuel in the membrane / electrode assembly, the performance of the fuel cell is influenced by the membrane / electrode assembly. Generally, an electrode for a polymer electrolyte fuel cell is manufactured by forming a microporous layer called a gas diffusion layer on carbon fiber, which is an electrical conductor, and coating a catalyst slurry composed of a platinum catalyst, a hydrogen ion conductive binder and a solvent on the gas diffusion layer. Therefore, the catalyst layer in which the integrated oxidation-reduction reaction takes place is an important component. However, such an oxidation-reduction reaction also ensures optimal performance when the fuel is supplied smoothly. Therefore, the gas diffusion layer It is important. In addition, there is a demand for a technique capable of mass-producing a diffusion layer serving as a support of an electrode in order to commercially produce a large amount of fuel cells.

Therefore, there is a demand for a method capable of mass-producing a gas diffusion layer having excellent cell performance by using a carbon slurry which is excellent in dispersibility and can obtain a uniform coating.

According to an aspect of the present invention, there is provided a method of manufacturing a gas diffusion layer for a fuel cell.

Another aspect of the present invention is to provide a gas diffusion layer produced by the above production method.

Another aspect of the present invention is to provide an electrode for a fuel cell comprising a gas diffusion layer produced by the above production method.

Another aspect of the present invention is to provide a fuel cell including a gas diffusion layer manufactured by the above-described manufacturing method.

According to an aspect of the present invention, there is provided a method for producing a carbon slurry, comprising: mixing a carbon powder, a hydrophobic binder and a dispersion medium to prepare a carbon slurry;

Coating the carbon slurry on a substrate using a coater; And

And sintering the coated carbon slurry to form a gas diffusion layer,

Wherein the dispersion medium comprises 50 to 95% by weight of ethylene glycol, 2 to 40% by weight of water, and 0.05 to 10% by weight of a dispersant.

According to another aspect of the present invention, there is provided a gas diffusion layer produced by the above method.

According to another aspect of the present invention, there is provided an electrode for a fuel cell including a gas diffusion layer manufactured by the above method.

According to still another aspect of the present invention, there is provided a fuel cell including a gas diffusion layer manufactured by the above method.

According to one aspect of the present invention, a fuel cell including a gas diffusion layer manufactured by a new method has improved cell performance and is easy to mass-produce.

Hereinafter, a method of manufacturing a gas diffusion layer for a fuel cell, a gas diffusion layer manufactured by the method, an electrode for a fuel cell including the gas diffusion layer, and a fuel cell according to an embodiment of the present invention will be described in detail.

A method of manufacturing a gas diffusion layer for a fuel cell according to an embodiment of the present invention includes: preparing a carbon slurry by mixing carbon powder, a hydrophobic binder, and a dispersion medium; Coating the carbon slurry on a substrate using a coater; And sintering the coated carbon slurry to form a gas diffusion layer, wherein the dispersion medium comprises 50 to 95% by weight of ethylene glycol, 2 to 40% by weight of water, and 0.05 to 10% by weight of a dispersant.

The gas diffusion layer production method improves the dispersibility of the carbon and the hydrophobic binder in the carbon slurry by using the dispersion medium containing the mixed solvent having the predetermined composition and the dispersant. The gas diffusion layer prepared using the carbon slurry with improved dispersibility has low fuel supply to the fuel cell electrode and gas discharge from the electrode. As a result, the performance of the fuel cell can be improved. In addition, in the above manufacturing method, by using a coater, the diffusion layer can be continuously or intermittently printed on the substrate in various patterns. Therefore, the gas diffusion layer production method is suitable for mass production of the gas diffusion layer.

If the composition of the mixed solvent is out of the defined composition range, the dispersibility of the carbon and the binder in the slurry may be deteriorated. Specifically, when the ethylene glycol content in the dispersion medium is less than 50% by weight, the dispersibility of the carbon powder may be significantly reduced. If the content of the ethylene glycol is more than 95% by weight, the amount of the solvent is excessively large, Problems may arise during the application of the slurry using coating equipment. If the content of water in the dispersion medium is less than 2% by weight, dispersion of the binder may be difficult. If it is more than 40% by weight, the viscosity of the slurry may be too low to be coated. If the content of the dispersant in the dispersion medium is less than 0.05% by weight, dispersion of carbon and the binder may be difficult. If the content of the dispersant is more than 10% by weight, the electrical resistance of the microporous layer may increase.

In the method of manufacturing a gas diffusion layer for a fuel cell according to another embodiment of the present invention, for example, the carbon slurry may include 0.1 to 40 parts by weight of a hydrophobic binder and 50 to 3000 parts by weight of a dispersing medium relative to 100 parts by weight of carbon powder have. If the content of the hydrophobic binder is less than 0.1 part by weight, there is a problem of surface cracking and hydrophobic treatment in the production of the diffusion layer. If the binder content is more than 40 parts by weight, the resistance may increase. If the content of the dispersing medium is less than 50 parts by weight, the viscosity of the slurry becomes too high, which may make it difficult to produce a highly dispersed slurry and apply it to slurry coating equipment. If the content of the dispersing medium exceeds 3,000 parts by weight, The amount of carbon that can be created and carried can be limited.

In the method of manufacturing a gas diffusion layer for a fuel cell according to another embodiment of the present invention, the average particle diameter of the carbon slurry may be 30 to 100 탆. If the average particle diameter is less than 30 m, the size of the pores formed in the diffusion layer may be small and fuel supply and gas discharge may be difficult, and the viscosity of the slurry may be low, which may be difficult to apply to slurry coating equipment. If the average particle diameter is more than 100 mu m, the nozzle of the coater, which is a gap ejection method, may be clogged.

In the method of manufacturing a gas diffusion layer for a fuel cell according to another embodiment of the present invention, the viscosity of the carbon slurry may be 500 to 10,000 cps. If the viscosity is less than 500 cps, it may be difficult to control the amount of the components constituting the diffusion layer when applied to coating equipment. If the viscosity exceeds 10,000 cps, the slurry may block the nozzle of the coater.

In the method of manufacturing a gas diffusion layer for a fuel cell according to another embodiment of the present invention, the hydrophobic binder may be a perfluoropolymer, a benzimidazole-based polymer, a polyimide-derived polymer, a polyetherimide-based polymer, a polyphenylene sulfide- Based polymer, polyether-etherketone-based polymer, polyetherquinoxaline-based polymer, or a mixture thereof, but is not limited thereto, and it is possible to use the polymer in the technical field All of the possible hydrophobic polymers are included.

In the method for manufacturing a gas diffusion layer for a fuel cell according to another embodiment of the present invention, the thickness of the gas diffusion layer may be 5 to 100 탆. If the thickness is less than 5 mu m, fuel supply and gas discharge, which are the main roles of the gas diffusion layer, may not be desired. If the thickness is more than 100 mu m, the resistance of the gas diffusion layer may increase and the electrode performance may deteriorate.

In the method of manufacturing a gas diffusion layer for a fuel cell according to another embodiment of the present invention, the amount of carbon supported on the gas diffusion layer may be 0.5 to 10 mg / cm 2. If the amount of carbon supported is less than 0.5 mg / cm &lt; 2 &gt;, the thickness of the gas diffusion layer may be less than 5 mu m and the diffusion of fuel or gas may be difficult. The resistance of the gas diffusion layer increases, and the cell performance may be deteriorated.

In the method of manufacturing a gas diffusion layer for a fuel cell according to another embodiment of the present invention, the coater may be a slot die coater, a comma coater, a blade coater, a gravure coater, a bar coater, or a lip coater. The kind of the coater is not particularly limited and is not particularly limited as long as it can be formed continuously or intermittently by repeatedly forming electrodes of a certain pattern for describing it as a coater used in the related art. The use of such a coater can enable the mass production of the diffusion layer.

In the method of manufacturing a gas diffusion layer for a fuel cell according to another embodiment of the present invention, it may further include defoaming the carbon slurry before the coating step. The carbon slurry can be uniformly coated on the substrate by the defoaming step.

In the method of manufacturing a gas diffusion layer for a fuel cell according to another embodiment of the present invention, the dispersant may be Surfynol (R) 440, 420, 61 or Triton (R) BYK-024 (BYK Chemie), BYKETOL-PC (BYK Chemie), and mixtures thereof.

A gas diffusion layer according to another embodiment of the present invention is manufactured by the above manufacturing method. Hereinafter, the gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer for a fuel cell will be described in detail with reference to an embodiment.

First, a carbon slurry is prepared by mixing carbon powder, the above-mentioned hydrophobic binder, and the above-mentioned dispersion medium. The carbon powder may be any one of carbon black, ketjen black, acetylene black, activated carbon powder, carbon molecular sieve, activated carbon having micropores, mesoporous carbon, carbon nanotubes or a mixture thereof.

The carbon slurry may be selectively defoamed using a defoaming device prior to coating onto the carbon support.

The carbon slurry is then coated on a substrate using a coater. The substrate may be a specific film or a substrate made of carbon. If the base material is a specific film, a transfer film in which a carbon slurry is coated on the film to transfer the gas diffusion layer can be obtained. If the base material is a carbon material, the slurry may be coated on the carbon material to form a gas diffusion layer. As the carbon base material, carbon cloth, carbon paper, or the like can be used. The gas diffusion layer substrate may be coated with a hydrophobic substance such as polytetrafluoroethylene (PTFE) on its surface to smooth the fluid flow.

Next, the carbon slurry coated on the substrate is dried and sintered to form a diffusion layer. The drying can be carried out under the general conditions used in the art. For example, the carbon slurry is primarily dried at a temperature of 70 to 100 ° C. for 0.5 to 5 hours, and after the primary drying, the carbon slurry is further sintered at 200 to 400 ^° C., It can be sintered and dried. As a result, a gas diffusion layer whose surface is treated with hydrophobicity and in which fine pores are formed can be formed.

The de-packaging value used in the defoaming step is as shown in FIG. The de-packaging means comprises an upper lid and a main body, and a plurality of holes are formed in the lid. One of the holes is connected to a vacuum pump to remove bubbles from the deaerator and an impeller is installed in another hole to rotate the catalyst slurry in the deaerator. The upper lid and the body of the de-wrapping tooth are sealed with an O-ring and fixed with a fixing clip. The catalyst slurry is stirred by the impeller in the defoaming device, and the bubbles in the slurry are removed by the vacuum pump.

A slot die coater as an embodiment of the coater used in the coating step is shown in Fig. The slot die coater can be continuously or intermittently coated on the substrate with the carbon slurry moving on the substrate 1. In FIG. 2, the funnel-type slurry tank 2 containing the carbon slurry does not remain in the tank due to the inclination. It is also desirable to minimize the distance from the nozzle valve to the slurry tank by directly connecting the slurry tank to the nozzle (3) valve of the coater.

The electrode for a fuel cell according to another embodiment of the present invention includes a gas diffusion layer manufactured by the above manufacturing method. Hereinafter, an electrode for a fuel cell including a gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer for a fuel cell will be described in detail with reference to an embodiment.

The cathode catalyst slurry and the anode catalyst slurry are coated on the gas diffusion layer prepared above, and then the catalyst layer is dried at a temperature of 120 ° C or lower to form a cathode or an anode electrode.

The catalyst layer may include a metal catalyst that promotes oxidation of hydrogen and reduction of oxygen. The catalyst layer is made of platinum, ruthenium, osmium, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, Co, Ni, And &lt; / RTI &gt; In particular, it may include platinum, ruthenium, osmium, platinum-ruthenium alloys, platinum-osmium alloys, platinum-palladium alloys, platinum-cobalt alloys, platinum-nickel alloys or mixtures thereof.

The metal catalyst is generally used while being supported on a carrier. The carrier may be a carbon-based material such as acetylene black or black salt; Or inorganic fine particles such as alumina and silica can be used.

A fuel cell according to another embodiment of the present invention includes a gas diffusion layer manufactured by the manufacturing method. Hereinafter, a fuel cell including a gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer for a fuel cell will be described in detail with reference to an embodiment.

First, a base material or a transfer film on which the gas diffusion layer and the catalyst layer are formed is bonded to the electrolyte membrane by a transfer process or a hot-pressing process to produce a membrane / electrode assembly. A separator plate is added to the membrane / electrode assembly to obtain a power generating portion. The separator plate is attached to both sides of the membrane / electrode assembly, the separator plate attached to the anode is a separator plate for the anode, and the separator plate attached to the cathode is the separator plate for the cathode. The anode separation plate has a flow path for supplying fuel to the anode, and serves as an electron conductor for transferring electrons generated in the anode to an external circuit or an adjacent unit cell. The cathode separation plate has a flow path for supplying an oxidant to the cathode, and serves as an electron conductor for transferring electrons supplied from the pushing circuit or the adjacent unit cell to the cathode. Methanol aqueous solution is mainly used as the fuel supplied to the anode in the direct methanol fuel cell, and air is mainly used as the oxidizing agent supplied to the cathode.

Examples of the electrolyte membrane include polyimide, polyimidazole, polybenzimidazole, polyetherbenzimidazole, polyarylene ether ketone, ferrier ether ketone, polyether ketone, polyether ketone ketone, polystyrene, napion, , Asiflex, or a mixture thereof, but not limited thereto, and it is not particularly limited as long as it can be used as an electrolyte membrane in the related art. Since the electrolyte membrane absorbs a proper amount of water, it can have excellent ionic conductivity.

The electrolyte membrane may have a number average molecular weight of 1,000 to 1,000,000 and a weight average molecular weight of 10,000 to 1,000,000. The thickness of the polymer electrolyte membrane may be 10 to 300 mu m.

The conditions used in the hot pressing method may be a pressure of 500 to 2,000 psi, a temperature of 50 to 300 DEG C, and a pressing time of 1 to 60 minutes.

Next, the fuel cell is completed by adding at least one reformer, a fuel tank, a fuel pump, and the like to the power generation section.

Hereinafter, the present invention will be described in further detail with reference to preferred examples, but the present invention is not limited thereto.

(Gas diffusion layer production)

Example 1

Preparation of carbon slurry

10 g of carbon black (Vulcan, Cabot) and 0.88 g of a hydrophobic binder solution (PTFE, polytetrafluoroethylene, 60% by weight, Aldrich) were added to 115 g of a dispersing medium and ultrasonic waves were applied for 30 minutes in an ultrasonic mixer (Branson) . The carbon slurry was introduced into a mixed deaerator (FIG. 1, self-produced) and defoamed. The viscosity of the defoamed carbon slurry was 2,500 cps. The dispersion medium is composed of 87.2% by weight of ethylene glycol, 7.3% by weight of deionized water, and 5.5% by weight of a dispersant (Surfynol 占 440).

Formation of gas diffusion layer

The carbon slurry was coated on a 24AA (SGL Co., Germany) using a slot die coater (Narayanano Tech, Korea). The coated carbon slurry was subjected to a primary drying at 80 ° C for 1 hour, then transferred to a furnace oven capable of high temperature drying, and further dried at 225 ° C for 1 hour and at 350 ° C for 30 minutes to disperse the PTFE on the carbon surface uniformly So that the gas diffusion layer was sintered so as to be hydrophobic. The thickness of the coated gas diffusion layer was 20 μm and the amount of carbon supported was 1.5 mg / cm 2. A schematic view of the gas diffusion layer is shown in Fig.

Example 2

10 g of carbon black (Vulcan, Cabot) and 0.88 g of a hydrophobic binder solution (PTFE, polytetrafluoroethylene, 60% by weight, Aldrich) were added to 115 g of a dispersing medium and ultrasonic waves were applied for 30 minutes in an ultrasonic mixer (Branson) . The carbon slurry was introduced into a mixed deaerator (FIG. 1, self-produced) and defoamed. The viscosity of the defoamed carbon slurry was 2,500 cps. The dispersion medium is composed of 50% by weight of ethylene glycol, 40% by weight of deionized water, and 10% by weight of a dispersant (Surfynol 占 440). The formation of the gas diffusion layer is the same as that of the first embodiment.

Example 3

10 g of carbon black (Vulcan, Cabot) and 0.88 g of a hydrophobic binder solution (PTFE, polytetrafluoroethylene, 60% by weight, Aldrich) were added to 115 g of a dispersing medium and ultrasonic waves were applied for 30 minutes in an ultrasonic mixer (Branson) . The carbon slurry was introduced into a mixed deaerator (FIG. 1, self-produced) and defoamed. The viscosity of the defoamed carbon slurry was 2,500 cps. The dispersion medium is composed of 95% by weight of ethylene glycol, 4.95% by weight of deionized water, and 0.05% by weight of a dispersant (Surfynol 占 440). The formation of the gas diffusion layer is the same as that of the first embodiment.

Comparative Example 1

A gas diffusion layer was prepared in the same manner as in Example 1, except that a mixed solvent containing 30 wt% of ethylene glycol, 52.2 wt% of deionized water and 18.8 wt% of a dispersing agent (Surfynol 占 440) was used as a dispersion medium.

Comparative Example 2

Except that 1 part by weight of defoamer (BYK-024, BYK Chemie) and 5 parts by weight of an anti-drying agent (BYKETOL-PC, BYK Chemie) were added to 100 parts by weight of the dispersion medium. .

Comparative Example 3

The same procedure as in Example 1 was carried out except that a mixed solvent containing 60% by weight of isopropyl alcohol and 35% by weight of deionized water was used as a dispersion medium and 5% by weight of Surfynol (trade name Surfynol 占 440) To prepare a gas diffusion layer.

Comparative Example 4

Except that a mixed solvent containing 85% by weight of NMP (N-methylpyrrolidone) and 10% by weight of deionized water was used as a dispersion medium and 5% by weight of Surfynol (trade name Surfynol 占 440) A gas diffusion layer was prepared in the same manner as in Example 1.

Comparative Example 5

A gas diffusion layer was prepared in the same manner as in Example 1, except that a mixed solvent containing 45% by weight of ethylene glycol, 35% by weight of deionized water and 20% by weight of a dispersant (Surfynol-440) was used as a dispersion medium.

Comparative Example 6

A gas diffusion layer was prepared in the same manner as in Example 1, except that a mixed solvent containing 35% by weight of ethylene glycol, 60% by weight of deionized water and 5% by weight of a dispersant (Surfynol-440) was used as a dispersion medium.

Comparative Example 7

A gas diffusion layer was prepared in the same manner as in Example 1, except that a mixed solvent containing 60% by weight of ethylene glycol, 5% by weight of deionized water and 35% by weight of a dispersant (Surfynol-440) was used as a dispersion medium.

Reference Example 1

A gas diffusion layer was prepared in the same manner as in Example 1, except that the gas diffusion layer was produced by spray casting instead of the coater in Example 1.

(Preparation of electrode for fuel cell and fuel cell)

Example 4

The anode was prepared by coating an anode catalyst slurry on the gas diffusion layer prepared in Example 1 using a spray casting method, and drying the anode catalyst slurry at 80 ° C for 1 hour to form a catalyst layer carrying 3 mg / cm ^{2 of} an anode catalyst.

1 g of a 60 PtRu / C catalyst (Dongjin Semichem, JA1) and 1.76 g of a binder (10% by weight Nafion solution, Dupont, 15 parts by weight based on 100 parts by weight of the catalyst) were mixed in a 1: 1 volume ratio of isopropyl alcohol and deionized water To 20 g of mixed solvent.

The cathode was prepared and coated with a cathode catalyst slurry on SGL 24BC's base using a spray-casting method, followed by drying at 80 to this ℃ for 1 hour to form a cathode catalyst is 4mg / cm ² supported catalyst.

The cathode catalyst slurry was prepared by mixing 1 g of a 70PtCo / C catalyst (Dongjin Semichem, JC1) and 1.76 g of a binder (10 wt% Nafion solution, Dupont, 15 parts by weight based on 100 parts by weight of the catalyst) in a 1: 1 volume ratio of isopropyl alcohol and deionized water To 20 g of mixed solvent.

A membrane / electrode assembly was prepared by a hot press method with an electrolyte membrane (Dupont, Nafion 112) between the cathode and the anode prepared above.

A separator plate for supplying fuel to the anode side of the membrane / electrode assembly and a separator plate for supplying the oxidant to the cathode side were respectively installed to constitute a unit cell system, and the fuel supply of the anode was supplied from the fuel tank And the cathode was uniformly supplied with fuel by using an air pump to produce a fuel cell.

Examples 5 to 6

A fuel cell was fabricated in the same manner as in Example 4, except that the gas diffusion layers of Examples 2 to 3 were used instead of the gas diffusion layer prepared in Example 1.

Comparative Examples 8 to 14

A fuel cell was manufactured in the same manner as in Example 4, except that the gas diffusion layers prepared in Comparative Examples 1 to 7 were used instead of the gas diffusion layer prepared in Example 1 above.

Reference Example 2

A fuel cell was fabricated in the same manner as in Example 4, except that the gas diffusion layer prepared in Reference Example 1 was used in place of the gas diffusion layer prepared in Example 1 above.

Evaluation Example 1: Evaluation of dispersibility of carbon slurry

The carbon slurry obtained in the gas diffusion layer manufacturing processes of Examples 1 to 3 and Comparative Examples 1 to 7 was put into a beaker and after 3 hours passed, the state of precipitation of the slurry at the bottom of the beaker was visually observed to evaluate the dispersibility, Respectively. The evaluation criteria of dispersibility are as follows.

◎: The slurry deposited on the bottom of the beaker is hardly visible

○: The bottom of the beaker is covered with a partially precipitated slurry

△: Most of the bottom of the beaker is covered with the precipitated slurry

X: The beaker bottom was covered with a completely precipitated slurry

<Table 1>

evaluation Example 1 ◎ Example 2 ○ Example 3 ○ Comparative Example 1 × Comparative Example 2 △ Comparative Example 3 △ Comparative Example 4 × Comparative Example 5 △ Comparative Example 6 × Comparative Example 7 △

As shown in Table 1, the carbon slurries obtained in Examples 1 to 3 using the dispersion medium corresponding to the predetermined composition range of the present invention were less than the dispersion mediums of Comparative Example 1 to 7, The acidity was excellent.

Evaluation Example 2: Evaluation of coating uniformity of carbon slurry

The thicknesses of the gas diffusion layers obtained in Examples 1 to 3 and Comparative Examples 1 to 7 were measured using the LK-GD500 model of KEYENCE. The thicknesses of one end (the extreme end), the other end (end), and the middle point (middle portion) of the gas diffusion layer were measured. The thickness of each point was measured and the deviation was calculated according to the following equation (1). The coating quality of each spot was evaluated according to the following criteria.

A plurality of thickness values {x ₁ , x ₂ , ... , x _n } is m, the standard deviation of thickness σ is given by the following equation (1). n is the number of measured thickness values

&Quot; (1) &quot;

.

&Lt; Evaluation criteria of coating quality &

Good: no uncoated areas, more than 50% of the multiple thickness values measured at each point within ± 10 μm of the average thickness value

Defective: more than 50% of the multiple thickness values measured at more than one uncoated site, at each point exceed ± 10um above the mean thickness value

<Table 2>

The first end Middle part End portion Thickness standard deviation Example 1 Good Good Good 2.32 Example 2 Good Good Good 3.12 Example 3 Good Good Good 2.78 Comparative Example 1 Bad Good Bad 7.07 Comparative Example 2 Good Good Good 2.33 Comparative Example 3 Bad Bad Bad 6.78 Comparative Example 4 Bad Bad Bad 5.38 Comparative Example 5 Good Good Bad 3.52 Comparative Example 6 Bad Bad Bad 6.43 Comparative Example 7 Good Good Bad 3.32

As shown in Table 2, Example 1 according to an embodiment of the present invention showed a lower standard deviation of thickness compared with Comparative Examples and showed good coating quality without coatings. Comparative Example 2 showed a uniform coating thickness and coating quality as compared to Example 1 by further including a defoamer and an anti-drying agent.

Evaluation Example 3: Performance evaluation of fuel cell

4 vol% methanol aqueous solution as fuel was supplied to the anode and air was supplied to the cathode as an oxidant at a rate of 200 cc / min to the fuel cell produced in Examples 4 to 6, Comparative Examples 8 to 14 and Reference Example 2, The performance of the battery system was measured by measuring the current-voltage curve at a temperature of 70 ^° C.

The fuel cell performance evaluation results of Example 4 and Comparative Examples 8 to 14 are shown in FIG. 5 in the following Table 3, and the fuel cell performance evaluation results of Example 4 and Reference Example 2 are shown in FIG.

<Table 3>

division Measurement conditions: 60 DEG C -0.4 V Current density
(A) Power density
(mW / cm ² ) Example 4 1.73 139 Example 5 1.68 130 Example 6 1.65 129 Comparative Example 8 1.21 92 Comparative Example 9 1.28 102 Comparative Example 10 1.41 116 Comparative Example 11 1.29 104 Comparative Example 12 1.37 113 Comparative Example 13 1.32 109 Comparative Example 14 1.29 104 Reference Example 1 1.71 134

As shown in Table 3, Example 4 showed improved battery performance as compared to Comparative Examples 8-14. In particular, Comparative Example 9 can produce a gas diffusion layer of good quality with little variation in thickness by applying a water repellent agent and an anti-drying agent to a slurry. However, since the added additive acts as an electrode resistance, It looked.

In addition, as shown in FIG. 3, Example 4 showed improved performance as compared to Reference Example 2. This is because, in the case of Reference Example 2, the diffusion layer having a multilayer structure by the spray casting method increases the resistance of the electrode.

1 is a defoaming device used in Example 1 of the present invention.

2 is a slot die coater used in Example 4 of the present invention.

3 shows the performance evaluation results of the unit cells constructed in Example 4 and Reference Example 2 of the present invention.

Claims (13)

Mixing a carbon powder, a hydrophobic binder and a dispersion medium to prepare a carbon slurry; Coating the carbon slurry on a substrate using a coater; And And drying the coated carbon slurry to form a gas diffusion layer, Wherein the dispersion medium comprises 50 to 95% by weight of ethylene glycol, 2 to 40% by weight of water and 0.05 to 10% by weight of a dispersant, Wherein the gas diffusion layer has a carbon loading of 0.5 to 10 mg / cm &lt; 2 &gt;. The method according to claim 1, wherein the carbon slurry comprises 0.1 to 40 parts by weight of the hydrophobic binder and 50 to 3,000 parts by weight of the dispersion medium with respect to 100 parts by weight of the carbon powder. The method for manufacturing a gas diffusion layer for a fuel cell according to claim 1, wherein the average particle size of the carbon slurry is 30 to 100 占 퐉. The method for manufacturing a gas diffusion layer for a fuel cell according to claim 1, wherein the viscosity of the carbon slurry is 500 to 10,000 cps. The method of claim 1, wherein the hydrophobic binder is selected from the group consisting of perfluorinated polymers, benzimidazole polymers, polyimide polymers, polyetherimide polymers, polyphenylene sulfide polymers, polysulfone polymers, and polyether sulfone polymers , A polyether ketone-based polymer, a polyether-ether ketone-based polymer, and a polyether quinoxaline-based polymer. The method for manufacturing a gas diffusion layer for a fuel cell according to claim 1, wherein the thickness of the gas diffusion layer is 5 to 100 占 퐉. delete The method according to claim 1, wherein the coater is any one selected from the group consisting of a slot die coater, a comma coater, a blade coater, a gravure coater, a bar coater and a lip coater. The method of claim 1, further comprising defoaming the carbon slurry prior to the coating step. The method of claim 1, wherein the dispersant is selected from the group consisting of Surfynol 440, 420, 61 or Triton X-100, Twin 20 (BYC Chemie), BYK-024 (BYK Chemie) -PC (BYK Chemie). &Lt; / RTI &gt; A gas diffusion layer produced by the process according to any one of claims 1 to 6 and 8 to 10. An electrode for a fuel cell comprising a gas diffusion layer produced by the method according to any one of claims 1 to 6 and 8 to 10. A fuel cell comprising a gas diffusion layer produced by the process according to any one of claims 1 to 6 and 8 to 10.

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