Abstract:
Disclosed herein is a metal current collector for a solid oxide fuel cell including: a plurality of supports in one direction having a length part extended in one direction; a plurality of supports in another direction having a length part extended in a direction different from that of the support in one direction; and a plurality of pores enclosed by the supports in one direction and the support in another direction that are arranged to intersect with each other, wherein the support is provided with a cutting part so that the length part thereof is not integrally connected.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2012-0087748, filed on Aug. 10, 2012, entitled “Current Collector for Solid Oxide Fuel Cell and Solid Oxide Fuel Cell Having the Same”, which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a current collector for a solid oxide fuel cell and a solid oxide fuel cell having the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a fuel cell is a device directly converting chemical energy of fuel (hydrogen, liquefied natural gas (LNG), liquefied petroleum gas (LPG), or the like) and oxygen (air) into electrical and thermal energy by an electrochemical reaction. The existing power generation technologies should perform processes such as fuel combustion, steam generation, turbine driving, generator driving, or the like, while the fuel cell does not need to perform processes such as fuel combustion, turbine driving, or the like. As a result, the fuel cell is a new power generation technology capable of increasing power generation efficiency without causing environmental problems. The fuel cell minimally discharges air pollutants such as SO X , NO X , or the like, and generates less carbon dioxide, such that chemical-free, low-noise, non-vibration power generation, or the like, may be implemented. 
         [0006]    There are various types of fuel cells such as a phosphoric acid fuel cell (PAFC), an alkaline fuel cell (AFC), a polymer electrolyte membrane fuel cell (PEMFC), a direct methanol fuel cell (DMFC), a solid oxide fuel cell (SOFC), or the like. Among them, the solid oxide fuel cell (SOFC) depends on activation polarization, which lowers over-voltage and irreversible loss to increase power generation efficiency. Further, since the reaction rate in electrodes is rapid, the SOFC does not need expensive precious metals as an electrode catalyst. Therefore, the solid oxide fuel cell is an essential power generation technology in order to enter a hydrogen economy society in the future. 
         [0007]    A method of manufacturing porous metal oxide foam for a cathode current collector of a solid oxide fuel cell stack is disclosed in Patent Document 1, wherein a net (for example, Pt mesh current collector) made of precious metals is arranged between the cathode and a separation plate. 
         [0008]    Generally, in the solid oxide fuel cell according to the prior art, a unit cell may be damaged due to an increase in its own load at the time of assembling a stack. Therefore, a mesh-type current collector suggested in Patent Document 1 is used in the solid oxide fuel cell to serve as a buffering member reducing a load applied to the unit cell by the load at the time of assembling the stack. In addition, the mesh-type current collector may improve electrical contact between the separation plate and the cathode. 
         [0009]    Currently, a mesh-type current collector capable of improving buffering action and current collection has been developed. However, when a metal current collector is exposed at a high temperature for a long period time, generally stress is increased in the metal current collector and contact resistance at a contact portion with the cathode is increased, such that performance of the solid oxide fuel cell may be deteriorated. 
       PRIOR ART DOCUMENT 
     Patent Document 
       [0000]    
       
         (Patent Document 1) Korean Patent Laid-open Publication No. 10-0797048 
       
     
       SUMMARY OF THE INVENTION 
       [0011]    The present invention has been made in an effort to provide a metal current collector having a corrugated mesh structure in which internal stress deformation may be minimized, and a solid oxide fuel cell having the same. 
         [0012]    As described above, an object of the present invention is to provide a metal current collector capable of minimize internal stress deformation, and a solid oxide fuel cell stacked in a stack state using the metal current collector. 
         [0013]    According to a preferred embodiment of the present invention, there is provided a metal current collector for a solid oxide fuel cell including: a plurality of supports in one direction having a length part extended in one direction; a plurality of supports in another direction having a length part extended in a direction different from that of the support in one direction; and a plurality of pores enclosed by the support in one direction and the support in another direction that are arranged to intersect with each other, wherein the support is provided with a cutting part so that the length part is not integrally connected. 
         [0014]    The length part of the support in one direction may be provided with the cutting part at which the length part thereof is not integrally connected but disconnected. 
         [0015]    The length part of the support in another direction may be provided with the cutting part at which the length part thereof is not integrally connected but disconnected. 
         [0016]    The support in one direction may be corrugated in a wave shape in a length direction. 
         [0017]    The support in another direction may be corrugated in a wave shape in a length direction. 
         [0018]    According to another preferred embodiment of the present invention, there is provided a solid oxide fuel cell including: a unit cell including an anode, an electrode, and a cathode; separation plates including channels formed at an upper or lower surface thereof so as to supply gas and arranged in parallel with each other by a predetermined interval; and a cathode current collector disposed between the separation plate and the cathode of the unit cell and having a mesh structure. 
         [0019]    Preferably, the cathode current collector may be corrugated in a wave shape in a length direction and include at least one cutting part at which the support is cut. 
         [0020]    Particularly, the cathode current collector may include: a plurality of supports in one direction including a cutting part partially formed at a length part thereof; a plurality of supports in another direction corrugated in a wave shape in a length part; and a plurality of pores enclosed by the support in one direction and the support in another direction that are arranged to intersect with each other. 
         [0021]    In other words, the solid oxide fuel cell described above may include the cathode current collector having a corrugated mesh structure. 
         [0022]    Selectively, the length part of the support in another direction may be provided with a cutting part. 
         [0023]    In addition, the solid oxide fuel cell may further include an anode current collector disposed between the separation plate and the cathode of the unit cell and having a mesh structure. 
         [0024]    Preferably, the anode current collector may include: a plurality of supports in one direction corrugated in a wave shape in a length direction and including a cutting part partially formed at a length part thereof; a plurality of supports in another direction corrugated in a wave shape in a length direction; a plurality of pores enclosed by the support in one direction and the support in another direction that are arranged to intersect with each other. 
         [0025]    In other words, the solid oxide fuel cell may include the anode current collector having a corrugated mesh structure. 
         [0026]    Selectively, the length part of the support in another direction may be provided with a cutting part. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0028]      FIG. 1  is a perspective view showing a metal current collector having a corrugated mesh structure according to a preferred embodiment of the present invention; 
           [0029]      FIG. 2  is a cross-sectional view showing a portion of the metal current collector taken along line A-A of  FIG. 1 ; 
           [0030]      FIG. 3  is a perspective view showing a metal current collector having a corrugated mesh structure according to another preferred embodiment of the present invention; and 
           [0031]      FIG. 4  is an exploded perspective view of a solid oxide fuel cell using the metal current collector according to the preferred embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    The objects, features and advantages of the present invention will be more clearly understood from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted. Further, in the following description, the terms “first”, “second”, “one side”, “the other side” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. Further, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted. 
         [0033]    Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
         [0034]      FIG. 1  is a perspective view showing an example of a metal current collector having a corrugated mesh structure according to a preferred embodiment of the present invention, and  FIG. 2  is a cross-sectional view showing a portion of the metal current collector taken along line A-A of  FIG. 1 . 
         [0035]    Referring to  FIGS. 1 and 2 , the metal current collector  100  for a solid oxide fuel cell according to the preferred embodiment of the present invention is woven in a mesh structure in which at least one support  110  in one direction and at least one support  120  in another direction are arranged to intersect with each other so as to have pores  130  via the supports  110  and  120 . This metal current collector  100  is formed with a plurality of pores  130  enclosed by the supports  110  in one direction and the supports  120  in another direction as described above, wherein these pores  130  may supply uniform gas to a surface of an electrode (for example, cathode) to reduce polarization resistance. 
         [0036]    The metal current collector  100  may be made of a material that is not physically and chemically deformed even in the case in which the material is exposed time at a high temperature of 600° C. or more, under oxidizing atmosphere, and reducing atmosphere for a long period. 
         [0037]    Preferably, the metal current collector  100  according to the preferred embodiment of the present invention has a corrugated mesh structure corrugated three-dimensionally rather than a flat mesh structure. As shown in  FIG. 1 , the support  110  in one direction is corrugated in a wave shape in a length direction, and at the same time, the support  120  in another direction is corrugated in a wave shape in a length direction. 
         [0038]    The metal current collector  100  having the corrugated mesh structure has a predetermined height due to crests and troughs of the support  110  in one direction and the support  120  in another direction, and load to be applied to a unit cell in the solid oxide fuel cell having a stack structure may be buffered by this height. 
         [0039]    Particularly, the metal current collector  100  having the mesh structure includes at least one cutting part  111  and  121 . For example, the current collector  100  according to the present invention include at least one cutting part  111  at the support  110  in one direction and at least one cutting part  121  at the support  120  in another direction. The cutting part of the metal current collector  100  is not limited to having a pattern shown in  FIGS. 1 and 2 , but may have a random arrangement pattern. 
         [0040]    Preferably, the cutting parts  111  and  121  of the metal current collector  100  according to the present invention may be formed at the crests and troughs of the support  110  in one direction and/or the support  120  in another direction, and more preferably, at intersection points between the support  110  in one direction and the support  120  in another direction. The cutting parts  111  and  121  arranged as described above may not hinder a flow of gas penetrating through the pore  130  of the metal current collector  100  but allow the gas to flow together with laminar flow. 
         [0041]    In addition, the cutting parts  111  and  121  are formed at an internal portion of the metal current collector  100  except for an edge thereof. 
         [0042]    Generally, the current collector is deformed by thermal stress during a process of generating current at a high temperature environment to generate a crack therein, such that resistance loss may be increased due to this crack. However, the cutting parts  111  and  121  of the metal current collector  100  according to the present invention disperse thermal stress generated in the current collector  100  to prevent a crack of the metal current collector  100  in advance, such that durability of the current collector may be improved. Therefore, durability of the metal current collector  100  according to the present invention may be improved to increase current collection efficiency. In addition, the cutting part  111  and  121  as well as the pore  130  may be used as a passage of gas, for example, air, to improve a flow of air. The metal current collector  100  supports the electrode, for example, the cathode while contacting the cathode at the crests and troughs of the support in one direction and/or the support in another direction except for the pore  130  and the cutting parts  111  and  121 . 
         [0043]      FIG. 3  is a perspective view showing a metal current collector having a corrugated mesh structure according to another preferred embodiment of the present invention. 
         [0044]    The metal current collector  100 ′ according to another preferred embodiment of the present invention is woven by arranging supports  110  in one direction and supports  120 ′ in another direction to intersect with each other. 
         [0045]    The support  110  in one direction is corrugated in a wave shape in a length direction, but the support  120 ′ in another direction is formed in a straight line shape. 
         [0046]    In addition, the support  110  in one direction and the support  120 ′ in another direction include at least one cutting part  111 , similarly to the metal current collector shown in  FIG. 1 . 
         [0047]    In the metal current collector  100 ′ according to the present invention, a length part of the support  120 ′ in another direction may be provided with a cutting part (not shown), as needed. 
         [0048]      FIG. 4  is an exploded perspective view of a solid oxide fuel cell using the metal current collector according to the preferred embodiment of the present invention. The solid oxide fuel cell  1  shown in  FIG. 4 , which is a flat plate type solid oxide fuel cell, is configured of a unit cell (no reference numeral) in which a cathode  10 , an electrolyte  20 , and an anode  30  that are formed in a flat plate shape are sequentially stacked. 
         [0049]    More specifically, the solid oxide fuel cell  1  according to the present invention is configured to include at least one unit cell, a cathode current collector  100 , and a separation plate  400 . Particularly, the separation plate  400  includes channels in order to supply air to the unit cell. 
         [0050]    The separation plate  400  is a constituent member capable of electrically connecting an anode of a unit cell to a cathode of another unit cell arranged to be adjacent to each other but to physically blocking air supplied to the cathode from fuel gas supplied to the anode. 
         [0051]    The unit cell serves to generate electric energy and is formed by stacking the cathode  10 , the electrolyte  20 , and the anode  30  therein as described above. Generally, in the solid oxide fuel cell  1  (SOFC), when fuel gas is hydrogen (H2) or carbon monoxide (CO), the following electrode reaction is performed in the cathode  10  and the anode  30 . 
         [0000]      Cathode: O 2 +4 e   − →2O 2− 
 
         [0000]      Anode: CO+H 2 O→H 2 +CO 2  
 
         [0000]      2H 2 +2O 2− →4 e   − +2H 2 O
 
         [0000]      Entire reaction: H 2 +CO+O 2 →CO 2 +H 2 O
 
         [0052]    That is, oxygen ions (O 2− ) generated in the cathode  10  are transferred to the anode  30  through the electrolyte  20 , and at the same time electrons (e − ) generated in the anode  30  are transferred to the cathode  10  through an external circuit (not shown). In the anode  30 , hydrogen is bonded to oxygen ions to generate electrons and water. As a result, reviewing the entire reaction of the solid oxide fuel cell, hydrogen (H 2 ) or carbon monoxide (CO) are supplied to the anode  30  and oxygen is supplied to the cathode  10 , such that carbon dioxide (CO 2 ) and water (H 2 O) are finally generated. 
         [0053]    The cathode  10  receives oxygen or air from an air channel of the separation plate  400  to serve as a cathode through an electrode reaction. Here, the cathode  10  may be formed by sintering lanthanum strontium manganite ((La 0.84 Sr 0.16 ) MnO 3 ) having high electron conductivity, or the like. Meanwhile, in the cathode  10 , oxygen is converted into oxygen ion by a catalytic reaction of lanthanum strontium manganite to thereby be transferred to the anode  30  through the electrolyte  20 . 
         [0054]    The electrolyte  20 , which is a medium transferring oxygen ions generated in the cathode  10  to the anode  30 , may be formed by sintering yttria stabilized zirconia or scandium stabilized zirconia (ScSZ), gadolinia-doped ceria (GDC), La 2 O 3 -Doped CeO 2  (LDC), or the like. For reference, since tetravalent zirconium ions are partially substituted with trivalent yttrium ions in the yttria stabilized zirconia, one oxygen hole per two yttrium ions is generated therein, and oxygen ions move through the hole at a high temperature. In addition, when pores are generated in the electrolyte  20 , since a crossover phenomenon of directly reacting fuel with oxygen (air) may be generated to reduce efficiency, it needs to be noted so that a scratch is not generated. 
         [0055]    The anode  30  receives fuel from a fuel channel of the separation plate  400  to serve as an anode through an electrode reaction. Selectively, the anode  30  is configured of nickel oxide (NiO) and yttria stabilized zirconia (YSZ), wherein nickel oxide (NiO) is reduced to metallic nickel by hydrogen to ensure electron conductivity, and yttria stabilized zirconia (YSZ) ensures ion conductivity as oxide. 
         [0056]    In the solid oxide fuel cell  1 , current is generally collected in a state in which the separation plate does not contact a portion of an area of the electrode, such that current density becomes non-uniform. Therefore, according to the present invention, the solid oxide fuel cell  1  may include cathode current collector  100 . 
         [0057]    The cathode current collector  100  is loaded between the separation plate  400  and the cathode  10  as shown in  FIG. 4 . 
         [0058]    The solid oxide fuel cell  1  according to the present invention includes the cathode current collector  100  formed of the metal current collector having the corrugated mesh structure described above. The cathode current collector  100  has a structure in which supports in one direction ( 110  in  FIG. 1 ) and supports in another direction ( 120  in  FIG. 1 ) are arranged to intersect with each other, wherein the supports in one direction and/or the supports in another direction are formed in a wave shape. 
         [0059]    Particularly, the cathode current collector  100  includes at least one cutting part, and more specifically, may include a cutting part at which a length part of the support in one direction and/or the support in another direction is partially cut. This cutting part (no reference numeral) may disperse stress of the collector at the time of operation at a high temperature, thereby making it possible to improve durability of the solid oxide fuel cell  1 . 
         [0060]    Selectively, the solid oxide fuel cell  1  according to the present invention may further include an anode current collector  300 . This anode current collector  300  has a corrugated mesh structure in which supports in one direction and supports in another direction are arranged to intersect with each other, similarly to the cathode current collector  100 . The supports in one direction and/or the supports in another direction of the anode current collector  300  are formed of a metal support having a wave shape. 
         [0061]    The anode current collector  300  according to the present invention includes at least one cutting part (no reference numeral) formed therein so as to minimize internal stress deformation. This anode current collector  300  is loaded between the separation plate  400  and the anode  30  as shown in  FIG. 4 . 
         [0062]    For reference, the corrugated mesh structure having a wave shape is simply drawn by a straight mesh structure in  FIG. 4  in order to more clearly show the cutting part of the cathode current collector  100  and/or the cutting part of the anode current collector  300 . 
         [0063]    As set forth above, according to the present invention, sheet resistance loss of the solid oxide fuel cell may be minimized and durability thereof may be improved. 
         [0064]    Particularly, according to the present invention, contact resistance loss between the cathode and the cathode current collector corresponding to ⅔ of the entire sheet resistance loss may be minimized. 
         [0065]    Further, with the current collector according to the present invention, current collecting performance and durability may be secured while minimizing contact resistance loss between the electrode and the current collector. 
         [0066]    Although the embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the present invention is not limited thereto, and 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. 
         [0067]    Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.