Method for manufacturing interconnector for solid oxide fuel cell with improved step coverage

Abstract

The present invention relates to a method for manufacturing an interconnector for a solid oxide fuel cell with improved step coverage, the method comprising the steps of: preparing a substrate composed of a ferrite-based stainless steel containing chromium; dipping the substrate in a first plating solution containing cobalt ions to form a strike plating layer on the surface of the substrate; and dipping the substrate with the strike plating layer formed on the surface thereof in a second plating solution containing cobalt ions and organic additives including saccharin and thiourea to form a cobalt plating layer on the surface of the strike plating layer, thereby manufacturing an interconnector for a solid oxide fuel cell.

Description

Method for manufacturing a separator for a solid oxide fuel cell with improved step coverage

[0001] The present invention relates to a method for manufacturing a separator for a solid oxide fuel cell with improved step coverage.

[0002] Solid oxide fuel cells are composed of stacked unit cells that include interconnectors, an anode, an electrolyte, and a cathode. In solid oxide fuel cells, interconnectors are placed between the unit cells and electrically connect the anode of one cell to the cathode of the adjacent cell. It is important for these interconnectors to maintain high conductivity at high temperatures for long periods of time.

[0003] Ferritic stainless steel containing chromium is generally used as the substrate for separators for solid oxide fuel cells. When using a separator containing the aforementioned substrate, chromium is known to volatilize from the substrate in the operating environment of the solid oxide fuel cell, and the volatilized chromium reacts with the electrode to deposit chromium oxide on the electrode. As a result, the deposited chromium oxide interferes with the electrochemical reaction of the electrode, thereby degrading the performance of the solid oxide fuel cell.

[0004] To prevent this, research and development are underway on methods for forming a coating layer on the surface of the separator using CVD or PVD deposition, forming a plating layer using electroplating, or modifying the surface of the separator. However, methods for forming a coating layer on the surface of the separator using CVD or PVD deposition have the disadvantage of requiring a long time to form the coating layer, resulting in high process costs.

[0005] When forming a coating layer using an electroplating method, there is an advantage of saving time and cost compared to forming a coating layer using CVD deposition or PVD deposition, but there was a problem of poor step coverage because it was difficult to form a uniform coating layer due to the shape of the separator for a solid oxide fuel cell in which irregularities and grooves are alternately formed.

[0006] The purpose of the present invention is to solve the above-mentioned problem, and to provide a method for manufacturing a separator for a solid oxide fuel cell with improved step coverage, which uses a plating solution containing an organic additive when forming a coating layer using electroplating so that the coating layer is formed more uniformly when forming a plating layer on the surface of a substrate using electroplating, thereby improving the step coverage.

[0007] The purpose of the present invention is not limited to the purposes mentioned above, and other purposes not mentioned can be clearly understood from the description below.

[0008] In order to achieve the above-described object, a method for manufacturing a separator for a solid oxide fuel cell with improved step coverage according to an embodiment of the present invention comprises the steps of: preparing a substrate made of ferritic stainless steel containing chromium, and having a pattern formed on one surface thereof with irregularities and grooves alternately formed along the longitudinal direction; immersing the substrate in a first plating solution containing cobalt ions, and generating a current density of 200 to 400 mA / cm, which is calculated according to the reaction area between the substrate and the first plating solution. 2 This includes a step of applying a current to the first plating solution to form a strike plating layer on the surface of the substrate; and a step of immersing the substrate, on the surface of which the strike plating layer is formed, in a second plating solution containing an organic additive including saccharin and thiourea and cobalt ions, and applying a current to the second plating solution to form a cobalt plating layer on the surface of the strike plating layer, thereby manufacturing a separator for a solid oxide fuel cell.

[0009] The method for manufacturing a separator for a solid oxide fuel cell using multilayer plating to achieve the above-described purpose according to embodiments of the present invention by the above-described configuration has the following effects.

[0010] By using a plating solution containing an organic additive when forming a coating layer on the surface of a substrate using electroplating, a coating layer can be formed more uniformly in areas where unevenness is formed and areas where grooves are formed, thereby providing a separator for a solid oxide fuel cell with improved step coverage.

[0011] FIG. 1 is a flowchart illustrating a method for manufacturing a separator for a solid oxide fuel cell with improved step coverage according to one embodiment of the present invention.

[0012] FIG. 2 is a cross-sectional view illustrating a separator for a solid oxide fuel cell manufactured according to one embodiment of the present invention.

[0013] Figure 3 is a drawing for explaining the analysis results according to Test Example 1.

[0014] Figure 4 is an image obtained by analyzing a separator for a solid oxide fuel cell manufactured according to Example 1 using a scanning electron microscope according to Test Example 1.

[0015] Figure 5 is an image obtained by analyzing a separator for a solid oxide fuel cell manufactured according to Comparative Example 1 using a scanning electron microscope according to Test Example 1.

[0016] Figure 6 is a drawing showing the results of analyzing the step coverage according to Test Example 1 for the separator for a solid oxide fuel cell manufactured according to Example 1 and Comparative Examples 1 to 3, respectively.

[0017] Figure 7 is a drawing showing the results of analyzing the step coverage according to Test Example 1 for the separator for a solid oxide fuel cell manufactured according to each of Comparative Examples 4 to 7.

[0018] Figure 8 is a diagram showing the results of an overvoltage change analysis according to a reference example.

[0019] In order to achieve the above-described object, a method for manufacturing a separator for a solid oxide fuel cell with improved step coverage according to an embodiment of the present invention comprises the steps of: preparing a substrate made of ferritic stainless steel containing chromium, and having a pattern formed on one surface thereof with irregularities and grooves alternately formed along the longitudinal direction; immersing the substrate in a first plating solution containing cobalt ions, and generating a current density of 200 to 400 mA / cm, which is calculated according to the reaction area between the substrate and the first plating solution. 2 This includes a step of applying a current to the first plating solution to form a strike plating layer on the surface of the substrate; and a step of immersing the substrate, on the surface of which the strike plating layer is formed, in a second plating solution containing an organic additive including saccharin and thiourea and cobalt ions, and applying a current to the second plating solution to form a cobalt plating layer on the surface of the strike plating layer, thereby manufacturing a separator for a solid oxide fuel cell.

[0020] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. Meanwhile, the terminology used in this specification is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular includes the plural unless specifically stated otherwise.

[0021] Hereinafter, with reference to the attached drawings, a separator for a solid oxide fuel cell using multilayer plating according to embodiments of the present invention and a method for manufacturing the same will be described in detail.

[0022] A method for manufacturing a separator for a solid oxide fuel cell with improved step coverage according to an embodiment of the present invention is for manufacturing a separator (10) for a solid oxide fuel cell in which a coating layer (200) including a strike plating layer and a cobalt plating layer is formed on the surface of a substrate (100) using electroplating. The method for manufacturing a separator for a solid oxide fuel cell with improved step coverage according to an embodiment of the present invention includes a substrate preparation step (S100), a strike plating layer forming step (S200), and a cobalt plating layer forming step (S300).

[0023]

[0024] A substrate (100) composed of ferritic stainless steel containing chromium is prepared (S100).

[0025] The substrate (100) prepared in the substrate preparation step (S100) may have a pattern formed in which irregularities (110) and grooves (120) are alternately formed along the length direction on one side.

[0026] The groove (120) formed in the substrate (100) prepared in the substrate preparation step (S100) can act as a passage for supplying reaction gas (hydrogen, oxygen, or air) and discharging water when applying the separator (10) manufactured according to one embodiment of the present invention to a solid oxide fuel cell.

[0027] The width and depth of the groove (120) formed in the substrate (100) prepared in the substrate preparation step (S100) are not limited as long as the groove (120) can act as a path for the movement of reaction gas and water, and for example, the width may be 1 to 2 mm.

[0028] If the width of the groove (120) formed in the substrate (100) is less than 1 mm, in the strike plating layer forming step (S200) and the cobalt plating layer forming step (S300), when forming the strike plating layer and the cobalt plating layer, respectively, the strike plating layer and the cobalt plating layer formed in the area where the unevenness (110) of the substrate (100) is formed may be formed too thickly than the strike plating layer and the cobalt plating layer formed in the area where the groove (120) is formed.

[0029] The unevenness (110) of the substrate (100) prepared in the substrate preparation step (S100) may be formed as the grooves (120) are formed, and accordingly, a plurality of grooves (120) may be formed on one surface of the substrate (100) at intervals corresponding to the width of the unevenness (110).

[0030]

[0031] In the substrate preparation step (S100), the prepared substrate (100) is electroplated to form a strike plating layer on the surface of the substrate (100) (S200).

[0032] The strike plating layer forming step (S200) may be a step of immersing the substrate (100) prepared in the substrate preparation step (S100) in a first plating solution containing transition metal ions and applying current to the first plating solution to form a strike plating layer on the surface of the substrate (100).

[0033] The strike plating layer forming step (S200) may be a step of forming a strike plating layer including cobalt on the surface of the substrate (100).

[0034] The strike plating layer formation step (S200) may include a first plating solution preparation step (S210) and a first plating step (S220).

[0035] The first plating solution preparation step (S210) may be a step of preparing a first plating solution containing cobalt ions to form a strike plating layer in the first plating step (S220).

[0036] The first plating solution preparation step (S210) may be a step of preparing a first plating solution having a pH of more than 3 and less than 3.5 by mixing a cobalt ion precursor, an acid solution, and water.

[0037] In the first plating solution preparation step (S210), the acid solution mixed in the preparation of the first plating solution is intended to ensure that the pH of the first plating solution is greater than 3 and less than 3.5. Any acid solution generally used in the preparation of the plating solution is not limited, and for example, hydrochloric acid (HCl) can be used.

[0038] If the pH of the first plating solution is greater than 3 and less than 3.5 in the first plating solution preparation step (S210), a strike plating layer can be smoothly formed on the surface of the substrate (100) in the first plating step (S220).

[0039] If the pH of the first plating solution prepared in the first plating solution preparation step (S210) is less than 3, it may be difficult to form a strike plating layer, and if it exceeds 3.5, the pH may be too high, resulting in the formation of a strike plating layer with a cloudy surface, and the mechanical properties of the formed strike plating layer may deteriorate.

[0040] In the first plating solution preparation step (S210), the cobalt ion precursor mixed in the preparation of the first plating solution is mixed to ensure that the first plating solution contains cobalt ions, and may be at least one of cobalt (II) chloride hexahydrate (CoCl2·6H2O) and cobalt (II) sulfate heptahydrate (CoSO4·7H2O), but is not limited thereto, and a cobalt ion precursor generally used to form a strike plating layer in the electroplating field may be used.

[0041] The first plating solution preparation step (S210) may be a step of preparing a first plating solution having a concentration of a cobalt ion precursor of 90 to 110 g / L.

[0042] If the concentration of the cobalt ion precursor of the first plating solution manufactured in the first plating solution preparation step (S210) is less than 90 g / L, when current is applied in the first plating step (S220), the number of ions reduced to metal is small, so the plating efficiency is low, and the formation of the strike plating layer may not be effectively achieved.

[0043] If the concentration of the cobalt ion precursor of the first plating solution manufactured in the first plating solution preparation step (S210) exceeds 110 g / L, the formation of a strike plating layer can be achieved in the first plating step (S220), but the cobalt ion precursor may be excessively used to form the strike plating layer, resulting in excessive process costs.

[0044] In the first plating solution preparation step (S210), when preparing the first plating solution by mixing a cobalt ion precursor, hydrochloric acid is mixed so that the concentration of hydrochloric acid becomes 80 to 90 ml / L, thereby preparing the first plating solution having a pH of more than 3 and less than 3.5.

[0045]

[0046] In the first plating solution preparation step (S210), the substrate (100) prepared in the substrate preparation step (S100) and the electrode are immersed in the first plating solution prepared in the first plating solution preparation step, and a current is applied to the first plating solution to form a strike plating layer on the surface of the substrate (100) (S220).

[0047] The first plating step (S220) may be a step of forming a strike plating layer including cobalt on the surface of the substrate (100) prepared in the substrate preparation step (S100).

[0048] When a strike plating layer is formed in the first plating step (S220), the cobalt plating layer can be formed more smoothly than when the cobalt plating layer is formed directly on the surface of the substrate (100) in the cobalt plating layer forming step (S300).

[0049] In addition, when a strike plating layer is formed in the first plating step (S220), the cobalt plating layer can be effectively adhered to the substrate (100).

[0050] The first plating solution preparation step (S210) is a current density calculated according to the reaction area between the first plating solution prepared in the first plating solution preparation step (S210) and the substrate (100) of 200 to 400 mA / cm 2 This may be a step of forming a strike plating layer on the surface of the substrate (100) by applying current to the first plating solution in which the substrate (100) is immersed.

[0051] In the first plating step (S220), the current density calculated according to the reaction area between the first plating solution and the substrate (100) is 200 mA / cm 2 If current is applied to the first plating solution so that it is less than 0.01, the strength of the current applied to the first plating solution may be weak, and the strike plating layer may not be formed smoothly.

[0052] In the first plating step (S220), the current density calculated according to the reaction area between the first plating solution and the substrate (100) is 400 mA / cm 2 If a current is applied to the first plating solution exceeding , excessive hydrogen may be generated during the formation of the strike plating layer, which may cause the formation of bubbles in the strike plating layer.

[0053] Preferably, the first plating step (S220) has a current density of 250 to 350 mA / cm calculated according to the reaction area between the first plating solution and the substrate (100). 2 This may be a step of forming a strike plating layer including cobalt by applying current to the first plating solution in which the substrate (100) is immersed.

[0054] The first plating step (S220) may be a step of forming a strike plating layer by applying current to the first plating solution prepared in the first plating solution preparation step (S210) while stirring at a stirring speed of 150 to 250 rpm.

[0055] When the first plating solution is stirred during the formation of the strike plating layer in the first plating step (S220), the strike plating layer can be formed smoothly as ions are uniformly dispersed and not locally present within the first plating solution.

[0056] If the speed of stirring the first plating solution in the first plating step (S220) is less than 150 rpm, the stirring speed may be slow and the ions in the first plating solution may not be uniformly distributed throughout.

[0057] If the speed of stirring the first plating solution in the first plating step (S220) exceeds 250 rpm, the ions in the first plating solution can be uniformly distributed throughout, but further increase in speed may be meaningless.

[0058] The thickness of the strike plating layer formed in the first plating step (S220) may be 0.1 to 0.3 ㎛ so that the cobalt plating layer can be smoothly adhered in the second plating step (320).

[0059] If the thickness of the strike plating layer formed in the first plating step (S220) exceeds 0.3 ㎛, excessive hydrogen may be generated during the formation of the strike plating layer, and the strike plating layer may not have sufficient adhesive strength.

[0060]

[0061] In the strike plating layer forming step (S200), the substrate (100) having the strike plating layer formed on the surface is immersed in a second plating solution, and current is applied to the second plating solution to form a cobalt plating layer on the surface of the strike plating layer (S300).

[0062] That is, the method for manufacturing a separator for a solid oxide fuel cell with improved step coverage according to one embodiment of the present invention may be to manufacture a separator for a solid oxide fuel cell having a structure in which a coating layer (200) including a strike plating layer and a cobalt plating layer is formed on the surface of a substrate (100).

[0063] The cobalt plating layer forming step (S300) may be a step of preparing a second plating solution containing an organic additive including saccharin and thiourea and cobalt ions, immersing a substrate (100) having a strike plating layer formed thereon in the prepared plating solution, and applying current to the second plating solution in which the substrate (100) is immersed to form a cobalt plating layer on the surface of the strike plating layer, thereby completing a separator (10) for a solid oxide fuel cell.

[0064] The cobalt plating layer forming step (S300) may be a step of forming a cobalt plating layer on a substrate (100) on which a strike plating layer is formed on the surface.

[0065] The cobalt plating layer formation step (S300) may include a second plating solution preparation step (S310) and a second plating step (S320).

[0066] The second plating solution preparation step (S310) may be a step of preparing a second plating solution containing cobalt ions.

[0067] The second plating solution preparation step (S310) may be a step of preparing the second plating solution by mixing a cobalt ion precursor, an acid solution, saccharin, and thiourea.

[0068] In the second plating solution preparation step (S310), the cobalt ion precursor mixed in the preparation of the second plating solution is mixed to ensure that the second plating solution contains cobalt ions, and may be at least one of cobalt (II) chloride hexahydrate (CoCl2·6H2O) and cobalt (II) sulfate heptahydrate (CoSO4·7H2O).

[0069] The second plating solution preparation step (S310) may be a step of preparing a second plating solution having a concentration of cobalt ion precursor of 90 to 110 g / L.

[0070] If the concentration of the cobalt ion precursor of the second plating solution manufactured in the second plating solution preparation step (S310) is less than 90 g / L, when current is applied in the second plating step (S320), the number of ions reduced to metal is small, so the plating efficiency is lowered, and the formation of the cobalt plating layer may not be effectively achieved.

[0071] If the concentration of the cobalt ion precursor of the second plating solution manufactured in the second plating solution preparation step (S310) exceeds 110 g / L, a cobalt plating layer can be formed in the second plating step (S320), but the cobalt ion precursor may be excessively used to form the cobalt plating layer, resulting in excessive process costs.

[0072] In the second plating solution preparation step (S310), the acid solution mixed in the preparation of the second plating solution is intended to make the pH of the second plating solution 4 to 4.5, and is not limited to any acid solution generally used in the preparation of the plating solution, and may include, for example, at least one of boric acid (H3BO3) and sulfuric acid, and preferably, boric acid.

[0073] If the pH of the second plating solution is 4 to 4.5 in the second plating solution preparation step (S310), a cobalt plating layer can be smoothly formed on the surface of the strike plating layer formed on the surface of the substrate (100) in the second plating step (S320).

[0074] If the pH of the second plating solution prepared in the second plating solution preparation step (S310) is less than 4, the formation of the cobalt plating layer (300) may not occur smoothly, and if the pH of the second plating solution prepared in the second plating solution preparation step (S310) exceeds 4.5, a cobalt plating layer with a cloudy surface may be formed in the second plating step (S320), and the mechanical properties of the formed cobalt plating layer may deteriorate.

[0075] In the second plating solution preparation step (S310), when preparing the second plating solution, boric acid is mixed so that the concentration of boric acid becomes 30 to 40 g / L, thereby preparing the second plating solution having a pH of 4 to 4.5.

[0076] In the second plating solution preparation step (S310), the saccharin mixed in the preparation of the second plating solution may act as a plating accelerator that promotes plating when forming a cobalt plating layer, and the thiourea may act as a plating suppressor that prevents the formation of a cobalt plating layer.

[0077] The molecular weight of saccharin is known to be 183.18 g / mol, and the molecular weight of thiourea is known to be 76.12 g / mol. Accordingly, when electroplating is performed in the second plating step (S320) using the second plating solution prepared in the second plating solution preparation step (S310), thiourea can diffuse at a relatively faster rate than saccharin within the second plating solution.

[0078] In the second plating step (S320), as the electroplating is performed, thiourea diffuses more quickly than saccharin into the portion where the grooves (120) of the substrate (100) are formed, so that thiourea acts mainly in the portion where the grooves (120) of the substrate (100) are formed, where electroplating is relatively difficult to perform, thereby promoting the formation of a cobalt plating layer, and saccharin acts mainly in the portion where the unevenness (110) is formed, where electroplating is relatively easy to perform, thereby hindering the formation of a cobalt plating layer, thereby reducing the difference in thickness of the coating layer (200) between the portion where the unevenness (110) is formed and the portion where the grooves (120) are formed.

[0079] That is, if both saccharin and thiourea are included in the second plating solution manufactured in the second plating solution preparation step (S310), a separator (10) for a solid oxide fuel cell with improved step coating properties can be manufactured.

[0080]

[0081] The second plating solution preparation step (S310) may be a step of preparing a second plating solution having a saccharin concentration of 1 to 20 mM.

[0082] If the concentration of saccharin in the second plating solution manufactured in the second plating solution preparation step (S310) is less than 1 mM, the amount of saccharin may be insufficient, and thus the formation of a cobalt plating layer may not be prevented in the portion where the unevenness (110) of the substrate (100) is formed.

[0083] If the concentration of saccharin in the second plating solution manufactured in the second plating solution preparation step (S310) exceeds 20 mM, the saccharin acts excessively even in the portion where the groove (120) of the substrate (100) is formed, thereby preventing the formation of a cobalt plating layer, and thus the step coverage of the separator (10) for a solid oxide fuel cell may not be improved.

[0084] The second plating solution preparation step (S310) may be a step of preparing a second plating solution having a thiourea concentration of 20 to 50 ppm.

[0085] If the concentration of thiourea in the second plating solution prepared in the second plating solution preparation step (S310) is less than 20 ppm, thiourea may not sufficiently promote the formation of a cobalt plating layer in the portion where the groove (120) of the substrate (100) is formed.

[0086] If the concentration of thiourea in the second plating solution prepared in the second plating solution preparation step (S310) exceeds 50 ppm, the concentration of thiourea is too high compared to the concentration of saccharin, and as thiourea acts excessively even in the portion where the unevenness (110) of the substrate (100) is formed, the step covering property of the separator (10) for a solid oxide fuel cell may not be improved.

[0087]

[0088] In the second plating step (S320), the substrate (100) on which the strike plating layer is formed on the surface in the strike plating layer forming step (S200) is immersed in the second plating solution prepared in the second plating solution preparation step (S310), and current is applied to the second plating solution to form a cobalt plating layer on the surface of the strike plating layer.

[0089] The second plating step (S320) is a current density calculated according to the reaction area between the substrate (100) on which a strike plating layer is formed on the surface and the second plating solution prepared in the second plating solution preparation step (S310) of more than 10 to 30 mA / cm 2 It may be a step of forming a cobalt plating layer by applying current to the second plating solution in which the substrate (100) is immersed so as to be as follows.

[0090] In the second plating step (S320), the current density calculated according to the reaction area between the second plating solution and the substrate (100) is 10 mA / cm 2 If current is applied to the second plating solution so that it becomes as follows, the strength of the current applied to the second plating solution is weak, so not only does the cobalt plating layer not form smoothly, but the formation of the cobalt plating layer is also slowed down, which may lower the productivity of the separator (10) for a solid oxide fuel cell.

[0091] In the second plating step (S320), the current density calculated according to the reaction area between the second plating solution and the substrate (100) is 30 mA / cm 2 If a current is applied to the second plating solution exceeding , excessive hydrogen may be generated during the formation of the cobalt plating layer, which may cause the formation of bubbles in the cobalt plating layer.

[0092]

[0093] <Example 1>

[0094] A substrate (100) was prepared in which protrusions (110) and grooves (120) were alternately and repeatedly formed along the length direction. At this time, the substrate (100) was prepared to be composed of SUS 430 material and formed with a plurality of grooves (120) having a width and depth of 2 mm and 1 mm, respectively.

[0095] A first plating solution was prepared by mixing cobalt(II) chloride hexahydrate (CoCl2·6H2O), hydrochloric acid, and water, in which the concentrations of cobalt(II) chloride hexahydrate (CoCl2·6H2O) and hydrochloric acid were 100 g / L and 85 ml / L, respectively, and a substrate (100) was immersed in the prepared first plating solution and then electroplated to form a strike plating layer on the surface of the substrate (100).

[0096] When forming a strike plating layer on the surface of the substrate (100), a platinum mesh (Pt mesh) was used as the anode, and the substrate (100) was used as the cathode. The current density calculated according to the reaction area between the first plating solution and the substrate (100) was 300 mA / cm. 2 To achieve this, current was applied to the first plating solution for 80 seconds. In addition, the temperature of the first plating solution was 25°C, and the first plating solution was stirred at 200 rpm.

[0097] A second plating solution containing cobalt ions was prepared. More specifically, cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, saccharin, thiourea, and water were mixed to prepare a second plating solution having concentrations of cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, saccharin, and thiourea of ​​100 g / L, 35 g / L, 1 mM, and 20 ppm, respectively.

[0098] A substrate (100) having a strike plating layer formed on the surface was immersed in a second plating solution and electroplated to form a cobalt plating layer on the surface of the substrate (100).

[0099] When forming a cobalt plating layer, a platinum mesh (Pt mesh) was used as an anode, and a substrate (100) having a strike plating layer formed on the surface was used as a cathode. The temperature of the second plating solution was 25°C, and the second plating solution was stirred at 200 rpm. In addition, the current density calculated according to the reaction area between the second plating solution and the substrate (100) was 30 mA / cm. 2 A separator for a solid oxide fuel cell was manufactured by applying current to the second plating solution for 8000 seconds.

[0100]

[0101] <Comparative Example 1>

[0102] A separator for a solid oxide fuel cell was manufactured in the same manner as in Example 1, except that instead of mixing cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, saccharin, thiourea, and water when manufacturing the second plating solution, cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, and water were mixed to manufacture the second plating solution, where the concentrations of cobalt(II) chloride hexahydrate (CoCl2·6H2O) and boric acid were 100 g / L and 35 g / L, respectively.

[0103]

[0104] <Comparative Example 2>

[0105] A separator (10) for a solid oxide fuel cell was manufactured in the same manner as in Example 1, except that instead of mixing cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, saccharin, thiourea, and water when manufacturing the second plating solution, cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, thiourea, and water were mixed to manufacture the second plating solution in which the concentrations of cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, and thiourea were 100 g / L, 35 g / L, and 20 ppm, respectively.

[0106]

[0107] <Comparative Example 3>

[0108] A separator for a solid oxide fuel cell was manufactured in the same manner as in Example 1, except that instead of mixing cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, saccharin, thiourea, and water when manufacturing the second plating solution, cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, saccharin, and water were mixed to manufacture the second plating solution, wherein the concentrations of cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, and saccharin were 100 g / L, 35 g / L, and 1 mM, respectively.

[0109]

[0110] <Comparative Example 4>

[0111] The current density calculated according to the reaction area between the second plating solution and the substrate (100) when forming the cobalt plating layer is 30 mA / cm 2 Instead of applying current to the second plating solution, the current density calculated according to the reaction area between the second plating solution and the substrate (100) is 10 mA / cm 2 A separator (10) for a solid oxide fuel cell was manufactured in the same manner as Example 1, except that current was applied to the second plating solution.

[0112]

[0113] Comparative Example 5

[0114] The current density calculated according to the reaction area between the second plating solution and the substrate (100) when forming the cobalt plating layer is 30 mA / cm 2 Instead of applying current to the second plating solution, the current density calculated according to the reaction area between the second plating solution and the substrate (100) is 10 mA / cm 2 A separator (10) for a solid oxide fuel cell was manufactured in the same manner as in Comparative Example 1, except that current was applied to the second plating solution.

[0115]

[0116] <Comparative Example 6>

[0117] The current density calculated according to the reaction area between the second plating solution and the substrate (100) when forming the cobalt plating layer is 30 mA / cm 2 Instead of applying current to the second plating solution, the current density calculated according to the reaction area between the second plating solution and the substrate (100) is 10 mA / cm 2 A separator (10) for a solid oxide fuel cell was manufactured in the same manner as in Comparative Example 2, except that current was applied to the second plating solution.

[0118]

[0119] Comparative Example 7

[0120] The current density calculated according to the reaction area between the second plating solution and the substrate (100) when forming the cobalt plating layer is 30 mA / cm 2 Instead of applying current to the second plating solution, the current density calculated according to the reaction area between the second plating solution and the substrate (100) is 10 mA / cm 2 A separator (10) for a solid oxide fuel cell was manufactured in the same manner as Example 3, except that current was applied to the second plating solution.

[0121]

[0122] <Example 1>

[0123] Test Example 1 is a test to confirm the step coverage of a separator (10) for a solid oxide fuel cell manufactured according to Example 1 and Comparative Examples 1 to 7.

[0124] To this end, in Test Example 1, a pair of protrusions (110) of a separator (10) for a solid oxide fuel cell manufactured according to Example 1 and Comparative Examples 1 to 3 and a groove (120) formed therebetween were photographed using a scanning electron microscope. Thereafter, the step coverage was measured using the image obtained using the scanning electron microscope.

[0125] In more detail, referring to FIG. 3, the thickness of the coating layer (200) including the strike plating layer and the cobalt plating layer was measured at a total of nine points (1, 2, 3, 4, 5, 6, 7, 8, 9) from the first point (1) corresponding to the upper surface of one unevenness (110) to the ninth point (9) corresponding to the upper surface of the adjacent unevenness (110), and then the step coverage was analyzed by calculating the ratio of the measured thickness and the thickness measured at the first point (1).

[0126] The analysis results are shown in Figures 4 to 7.

[0127] Fig. 4 is an image obtained by photographing a separator (10) for a solid oxide fuel cell manufactured according to Example 1 using a scanning electron microscope, and Fig. 5 is an image obtained by photographing a separator (10) for a solid oxide fuel cell manufactured according to Comparative Example 1 using a scanning electron microscope. Figs. 4 and 5 show images obtained by photographing at points 1 to 9 (1, 2, 3, 4, 5, 6, 7, 8, 9) of the separator (10) for a solid oxide fuel cell manufactured according to Example 1 and Comparative Example 1, respectively.

[0128] FIG. 6 shows the results of measuring the step coverage according to Test Example 1 of a separator (10) for a solid oxide fuel cell manufactured according to Example 1 and Comparative Examples 1 to 3, and FIG. 7 shows the results of measuring the step coverage according to Test Example 1 of a separator (10) for a solid oxide fuel cell manufactured according to Comparative Examples 4 to 7.

[0129] Referring to FIGS. 4 and 5, it can be confirmed that the coating layer (200) is formed more uniformly at points 1 to 9 (1, 2, 3, 4, 5, 6, 7, 8, 9) in the separator (10) for a solid oxide fuel cell manufactured according to Example 1 than in the separator (10) for a solid oxide fuel cell manufactured according to Comparative Example 1. This is a result confirming that the step coverage is improved when saccharin and thiourea are included as organic additives in the second plating solution during the manufacture of the separator (10) for a solid oxide fuel cell.

[0130] Referring to FIG. 6, it can be confirmed that the step-coverage of the separator (10) for a solid oxide fuel cell manufactured according to Example 1 is improved compared to the step-coverage of the separator (10) for a solid oxide fuel cell manufactured according to Comparative Examples 1 to 3, and this is also a result confirming that the step-coverage is improved when saccharin and thiourea are included in the second plating solution during the manufacture of the separator (10) for a solid oxide fuel cell.

[0131] In more detail, when saccharin and thiourea are included in the second plating solution during the manufacture of a separator (10) for a solid oxide fuel cell, it can be confirmed that the step covering property is improved as saccharin acts predominantly in the upper surface direction of the unevenness (110) and thiourea acts predominantly toward the inside of the groove (120).

[0132] Meanwhile, referring to Figure 7, when forming a cobalt plating layer, the current density is 10 mA / cm 2 When current is applied to the second plating solution, it can be confirmed that the step coverage is similar except in the case where only thiourea is mixed as an organic additive in the second plating solution.

[0133]

[0134] <Reference example>

[0135] A reference example is a test to confirm the change in overvoltage when saccharin, thiourea, hydroxyethyl cellulose, and gelatin are mixed as organic additives in a plating solution prepared by mixing cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, and water, and having concentrations of cobalt(II) chloride hexahydrate (CoCl2·6H2O) and boric acid of 100 g / L and 35 g / L, respectively.

[0136]

[0137] 1 Experimental method

[0138] A plating solution was prepared by mixing cobalt(II) chloride hexahydrate (CoCl2·6H2O), boric acid, and water, with concentrations of cobalt(II) chloride hexahydrate (CoCl2·6H2O) and boric acid of 100 g / L and 35 g / L, respectively.

[0139] A working electrode, a counter electrode, and a reference electrode were immersed in the prepared plating solution. A Cu rotating disk electrode, a Pt counter electrode, and an Ag / AgCl reference electrode were used as the working electrode, counter electrode, and reference electrode, respectively.

[0140] The plating solution immersed with the working electrode, counter electrode, and reference electrode was stirred at 300 rpm for 200 seconds, and the current density calculated according to the reaction area between the plating solution and the working electrode was 30 mA / cm. 2 The plating solution was stabilized by applying current to the plating solution.

[0141] Afterwards, the overvoltage was measured while applying current to the plating solution for 1800 seconds.

[0142] When applying current to the plating solution, the temperature of the plating solution was set to 25 ℃, and the current density calculated according to the reaction area between the plating solution and the working electrode was 30 mA / cm 2This was done by stirring the plating solution at a speed of 300 rpm while applying current to the plating solution.

[0143] In addition, in the reference example, saccharin was added to the plating solution so that the saccharin concentration of the plating solution became 0.1 mM at the time points from 0 to 400 seconds while applying current to the plating solution for 1800 seconds. In addition, saccharin was additionally added at the time points from 0 to 600 seconds, 800 seconds, 1000 seconds, 1200 seconds, 1400 seconds, and 1600 seconds, so that the saccharin concentrations in the plating solution became 1, 2, 5, 10, 15, and 20 μM, respectively.

[0144]

[0145] In addition, the overvoltage change was analyzed for thiourea (TU), gelatin (Gel), and hydroxyethyl cellulose (HEC) instead of saccharin using the same method as described above, and the overvoltage change of the plating solution (VMS) without organic additives was also analyzed to effectively observe the overvoltage change of the organic additives.

[0146] The change in the concentration of organic additives in the plating solution over time is shown in Table 1 below.

[0147] Current application time (sec) 0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 Organic additive (concentration unit) Saccharin (mM) 0 0.1 1 2 5 1 0 1 5 2 0 Thiourea (ppm) 0 0.1 1 2 5 1 0 2 0 5 0 Gelatin (ppm) 0 0.1 1 2 5 1 0 2 0 5 0 Hydroxyethyl cellulose (ppm) 0 0.1 1 2 5 1 0 2 0 5 0 Organic additive input X 0 ...

[0148] The analysis results are shown in Figure 8.

[0149] Referring to Figure 8, it can be confirmed that when gelatin (Gelatin (Gel)) and hydroxyethyl cellulose (HEC) are added as organic additives, the change in overvoltage is significantly less than when saccharin (Sac) and thiourea (TU) are added.

[0150] In addition, in the case of saccharin, it can be confirmed that the overvoltage change occurs rapidly when the concentration in the plating solution is 1 mM, and in the case of thiourea, it can be confirmed that the overvoltage change occurs rapidly when the concentration in the plating solution is 20 ppm. This is a result that can be confirmed that when saccharin and thiourea are added to a plating solution containing 100 g / L and 35 g / L of cobalt(II) chloride hexahydrate (CoCl2·6H2O) and boric acid, respectively, the concentrations in the plating solution must be 1 mM and 20 ppm or more in order to act as a plating inhibitor and a plating promoter, respectively.

[0151]

[0152] Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering its technical spirit or essential characteristics. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims below rather than the detailed description above, and all changes or modifications derived from the claims and their equivalents should be construed as being included within the scope of the present invention.

[0153] The present invention relates to a method for manufacturing a separator for a solid oxide fuel cell with improved step coverage.

Claims

1. A step for preparing a substrate made of ferritic stainless steel containing chromium, and having a pattern formed with irregularities and grooves alternately formed along the length direction on one surface; The substrate is immersed in a first plating solution containing cobalt ions, and the current density calculated according to the reaction area between the substrate and the first plating solution is 200 to 400 mA / cm 2 A step of applying current to the first plating solution to form a strike plating layer on the surface of the substrate; and A step of manufacturing a separator for a solid oxide fuel cell, comprising: immersing the substrate having the strike plating layer formed on the surface in a second plating solution containing an organic additive including saccharin and thiourea and cobalt ions; and applying current to the second plating solution to form a cobalt plating layer on the surface of the strike plating layer; A method for manufacturing a separator for a solid oxide fuel cell with improved step-by-step coating properties.

2. In paragraph 1, The step of forming the above strike plating layer is A step of preparing a first plating solution having a concentration of cobalt ion precursor of 90 to 110 g / L by mixing a cobalt ion precursor and an acid solution; and The above-mentioned substrate is immersed in the above-mentioned first plating solution, and the current density calculated according to the reaction area between the above-mentioned substrate and the above-mentioned first plating solution is 200 to 400 mA / cm 2 A step of forming the strike plating layer including cobalt by applying current to the first plating solution in which the above-mentioned material is immersed; including A method for manufacturing a separator for a solid oxide fuel cell with improved step-by-step coating properties.

3. In the second paragraph, the step of preparing the first plating solution is The first plating solution is prepared by mixing cobalt chloride hexahydrate as the cobalt ion precursor and hydrochloric acid as the acid solution, and the first plating solution is prepared with the hydrochloric acid concentration of 80 to 90 ml / L. A method for manufacturing a separator for a solid oxide fuel cell with improved step-by-step coating properties.

4. In paragraph 1, The step of forming the above cobalt plating layer is A step of preparing a second plating solution by mixing a cobalt ion precursor, an acid solution, and an organic additive including at least one of saccharin and thiourea; and The substrate on which the strike plating layer is formed is immersed in the second plating solution, and the current density calculated according to the reaction area between the substrate and the second plating solution is greater than 10 and 30 mA / cm 2 A step of forming the cobalt plating layer by applying current to the second plating solution in which the above-mentioned material is immersed so as to be as follows; including A method for manufacturing a separator for a solid oxide fuel cell with improved step-by-step coating properties.

5. In paragraph 1, The step of preparing the second plating solution is The second plating solution is prepared by mixing a cobalt ion precursor, an acid solution, saccharin and thiourea, wherein the concentrations of the cobalt ion precursor, the acid solution, the saccharin and the thiourea are 90 to 110 g / L, 30 to 40 g / L, 1 to 20 mM and 20 to 50 ppm, respectively. A method for manufacturing a separator for a solid oxide fuel cell with improved step-by-step coating properties.

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