Patent Publication Number: US-2011065019-A1

Title: Combined cell module for solid oxide fuel cell

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of U.S. Patent Application No. 61/242,689, filed on Sep. 15, 2009, in the United States Patent and Trademark Office, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present invention relates to a combined cell module in which multiple solid oxide fuel cells are combined in series. 
     2. Description of Related Art 
     Solid oxide fuel cells (SOFCs) can generate power with relatively low pollution, high-efficiency, and the like. The SOFCs can be utilized in stationary power generation systems, small independent sources, and vehicle power sources. An SOFC cell may be manufactured as a tube-type cell, a flat-tube-type cell, or a flat-plate-type cell. The tube-type or flat-tube-type cell may be manufactured to have a structure for a cathode supported cell, a segmented in series cell, an anode supported cell, or the like. 
     Generally, anode supported SOFC cells are used for small SOFC systems in the range of 1 to 10 KW. On the other hand, cathode supported SOFC cells or segmented in series cells are used for large SOFC systems in the range of 100 KW or more. 
     SUMMARY 
     An aspect of an embodiment of the present invention is directed toward a combined cell module for a solid oxide fuel cell (SOFC) with a structure in which a plurality of anode supported SOFC cells are combined in series that is capable of can improving mechanical stability and reliability. 
     Another aspect of an embodiment of the present invention, is directed toward a combined cell module for an SOFC for which a large-size SOFC system using a plurality of anode supported SOFC cells can be effectively designed and manufactured. 
     An embodiment of the present invention provides a combined cell module for a solid oxide fuel cell, including: a first sub-cell; a second sub-cell; a connector between the first and second sub-cells, each of the first and second sub-cells having a hollow portion extending along its length direction, each of the first and second sub-cells including: a first electrode; a second electrode; an electrolyte layer between the first and second electrodes; and a support member extending along the length direction within the hollow portion, the support members of the first and second sub-cells being physically coupled to each other via the connector, and at least one of the first electrode or the second electrode of the first sub-cell being electrically coupled to at least one of the first electrode or the second electrode of the second sub-cell via the connector. 
     The second electrode of the first sub-cell may be electrically coupled in series to the first electrode of the second sub-cell via the connector. 
     The combined cell module may further include an insulating sealing member between the connector and the first sub-cell and configured to electrically insulate the first electrode of the first sub-cell from the first electrode of the second-sub cell. 
     The support members of the first and second sub-cells may be screw coupled to each other via the connector at the central axis of the combined cell module. 
     The connector may include a body having at least one through-hole opening configured to allow a fluid to flow between the first sub-cell and the second sub-cell. 
     The at least one through-hole opening may include a plurality of through-hole openings around the central axis of the combined cell module. 
     The connector may include a body and a coupling portion protruding from the body, the coupling portion being configured to couple the connector to the support member of at least one of the first sub-cell or the second sub-cell. 
     The coupling portion may have a screw thread, and the support member of at least one of the first sub-cell or the second sub-cell may have a corresponding screw thread at an end thereof and be configured to engage with the screw thread of the coupling portion. 
     The screw thread of the support member may be a male screw thread, and the screw thread of the coupling portion may be a female screw thread. 
     The support member may have a screw thread at each end thereof to enable the support member to be connected between the connector and another connector, and the coupling portion of the connector may have a screw thread at each end thereof to enable the connector to be connected between the support members of the first and second sub-cells. 
     The connector may be integrally provided with the support member of the second sub-cell. 
     The support member may have a first screw thread, the connector may have a second screw thread, and the first screw thread of the support member of the first sub-cell may be configured to be screwed into the second screw thread of the connector. 
     The combined cell module may further include a coupling portion configured to couple the support member of the first sub-cell to the connector. 
     The coupling portion may have a double male-ended screw thread configured for insertion into a female screw thread of the connector and a female screw thread of the support member of the first sub-cell. 
     The combined cell module may further include a current collecting layer on the second electrode, on the electrolyte layer and on the connector. 
     The combined cell module may further include a conducting porous member within the hollow portion, wherein the porous member is between the first electrode and the support member, and the current collecting layer of the first sub-cell is in contact with the conducting porous member of the second sub-cell between the first electrode of the second sub-cell and the support member of the second sub-cell. 
     The combined cell module may further include a resilient portion, wherein the connector includes a main body and a support member body, the resilient portion being connected to the main body. 
     The resilient portion may be adapted to expand and contract between the first and second sub-cells so as to reduce the effects of thermal expansion. 
     The combined cell module may further include a current collecting layer on the second electrode and an interconnection coupling the current collecting layer to the connector across the resilient portion, the interconnection being configured to electrically couple the first and second sub-cells to each other. 
     The connector may include a first material, the support member may include a second material, the first and second materials may have different coefficients of thermal expansion, and relative lengths of the coupling portion and the support member may be configured to reduce the effects of thermal expansion. 
     In one embodiment of the present invention, the combined cell includes a buffer portion. The buffer portion is disposed between the support members of the first and second sub-cells. The buffer portion includes a coupling portion having a different thermal expansion coefficient from that of the support member. The length of the coupling portion is determined to reduce a difference of thermal expansion coefficients between the cells and the support members. 
     In one embodiment, the buffer portion includes a resilient portion disposed between the tube-type cell of the first sub-cell and the connector. In one embodiment of the present invention, the length of the coupling member may be configured to reduce the difference between thermal expansion coefficients between the cells and the support members 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention. 
         FIG. 1  is a schematic front view of a combined cell module for a solid oxide fuel cell (hereinafter, referred to as an SOFC combined cell module or a combined cell module) according to a first embodiment of the present invention. 
         FIG. 2  is a schematic cross-sectional view of the SOFC combined cell module according to the first embodiment of the present invention. 
         FIG. 3A  is a schematic cross-sectional view of a sub-cell of the combined cell module of  FIG. 2 . 
         FIG. 3B  is a schematic exploded cross-sectional view of the sub-cell of  FIG. 3A . 
         FIG. 4A  is a schematic front view of an A-type support member of  FIG. 3B . 
         FIG. 4B  is a schematic right side view of the A-type support member of  FIG. 4A . 
         FIG. 5A  is a schematic front view of an A-type connector of  FIG. 3B . 
         FIG. 5B  is a schematic left side view of the A-type connector of  FIG. 5A . 
         FIG. 5C  is a schematic right side view of the A-type connector of  FIG. 5A . 
         FIG. 6  is a schematic front view of a combined cell module according to a second embodiment of the present invention. 
         FIG. 7  is a schematic cross-sectional view of the combined cell module according to the second embodiment of the present invention. 
         FIG. 8  is a schematic cross-sectional view of a sub-cell of the combined cell module of  FIG. 7 . 
         FIG. 9A  is a schematic front view of a support member integrated with a connector (hereinafter, referred to as a B-type support member), used in the combined cell module of  FIG. 7 . 
         FIG. 9B  is a schematic longitudinal cross-sectional view of the B-type support member of  FIG. 9A . 
         FIG. 9C  is a schematic left side view of the B-type support member of  FIG. 9A . 
         FIG. 9D  is a schematic right side view of the B-type support member of  FIG. 9A . 
         FIG. 10  is a schematic front view of a B-type coupling portion used in the combined cell module of  FIG. 7 . 
         FIG. 11  is a schematic front view of a combined cell module according to a third embodiment of the present invention. 
         FIG. 12  is a cross-sectional view of the combined cell module according to the third embodiment of the present invention. 
         FIG. 13  is a schematic cross-sectional view of a sub-cell of the combined cell module of  FIG. 12 . 
         FIG. 14A  is a schematic front view of a support member integrated with a connector and a resilient portion (hereinafter, referred to as a C-type support member), used in the combined cell module of  FIG. 12 . 
         FIG. 14B  is a schematic longitudinal cross-sectional view of the C-type support member of  FIG. 14A . 
         FIG. 14C  is a schematic left side view of the C-type support member of  FIG. 14A . 
         FIG. 14D  is a schematic right side view of the C-type support member of  FIG. 14A . 
         FIG. 15  is a schematic front view a C-type coupling member applicable to the combined cell module of  FIG. 12 . 
         FIG. 16  is a schematic front view of a combined cell module according to a fourth embodiment of the present invention. 
         FIG. 17  is a schematic cross-sectional view of the combined cell module according to the fourth embodiment of the present invention. 
         FIG. 18  is a schematic cross-sectional view of a sub-cell of the combined cell module of  FIG. 17 . 
         FIG. 19A  is a schematic front view of a support member integrated with a connector and a resilient portion (hereinafter, referred to as a D-type support member), used in the combined cell module of  FIG. 17 . 
         FIG. 19B  is a schematic longitudinal cross-sectional view of the D-type support member of  FIG. 19A . 
         FIG. 19C  is a schematic left side view of the D-type support member of  FIG. 19A . 
         FIG. 19D  is a schematic right side view of the D-type support member of  FIG. 19A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
     In the drawings, the thickness and size of layers may be exaggerated for clarity. 
     The manifold mentioned in the following description refers to a structure provided with a flow path for smoothly supplying, distributing or discharging a fluid. In the description related to the accompanying drawings, a housing or boundary wall forming a manifold is designated by a reference numeral and referred to as the manifold, for convenience of illustration. 
       FIG. 1  is a schematic front view of a combined cell module for a solid oxide fuel cell (hereinafter, referred to as an SOFC combined cell module or a combined cell module) according to a first embodiment of the present invention.  FIG. 2  is a schematic cross-sectional view the SOFC combined cell module according to the first embodiment of the present invention. 
     Referring to  FIGS. 1 and 2 , the combined cell module  100  is manufactured by combining a plurality of SOFC sub-cells  110   a ,  110   b ,  110   c  and  110   d  with the same structure with one another in series in the flow direction of a fuel. Here, each of the SOFC sub-cells becomes a unit cell structure for manufacturing the combined cell module  100 . A connector  130   a ,  130   b ,  130   c  or  130   d  (hereinafter, referred to as an A-type connector) may be provided between adjacent SOFC sub-cells. 
     Each of the sub-cells  110   a ,  110   b ,  110   c  and  110   d  includes a plurality of tube-type SOFC cells and an A-type support member  120   a ,  120   b ,  120   c  or  120   d  inserted into a hollow portion of each of the SOFC cells. Hereinafter, each of the SOFC cells is referred to as a cell. Each of the cells has a structure in which an anode is stacked on a first side of an electrolyte layer and a cathode are stacked on a second side of an electrolyte layer, respectively. Each of the cells becomes a unit in which electricity is generated by an electrochemical reaction of a fuel and an oxidizer. Here, the fuel is supplied to the anode, and the oxidizer is supplied to the cathode. 
     Each of the A-type connectors  130   a ,  130   b ,  130   c  and  130   d  is integrally provided with a buffer portion for reducing an effect of a difference between thermal expansion coefficients of the cell and the support member. 
     In one embodiment of the present invention, both end portions of the combined cell module  100  in its longitudinal direction are connected to first and second manifolds  140   a  and  140   b , respectively. In this case, the first A-type connector  130   a  connects the first SOFC sub-cell  110  to the first manifold  140   a  so that a fluid can flow therethrough. The first A-type connector  130   a  may have a structure in which a first female screw (see  133  of  FIG. 3A ) is omitted or may be configured so that the hole of the first female screw is filled with a material (e.g., a predetermined material). An end connector  130   e  may be provided at one side of the fourth SOFC sub-cell  110   d . The end connector  130   e  is connected to the second manifold  140   b  so that a fluid can flow therethrough. The end connector  130   e  may have a structure in which a portion (see  136  of  FIG. 3B ) of the A-type connector is omitted. 
     The combined cell module  100  has a current collecting layer  117  disposed on a second electrode  116  of each of the SOFC sub-cells  110   a ,  110   b ,  110   c  and  110   d . In one embodiment of the present invention, as illustrated in the partially enlarged view of  FIG. 2 , the current collecting layer  117  is extended to cover the second electrode  116  of the first SOFC sub-cell  110   a , to cover an electrolyte layer  114  exposed to one side of the second electrode  116  and to cover a portion of the A-type connector  130   b  in the second SOFC sub-cell  110   b  adjacent to the first SOFC sub-cell  110   a.    
     In this embodiment, two adjacent sub-cells are electrically connected to each other in series by the current collecting layer  117 , the conductive A-type connector  130   b , a conductive porous member  118  in contact with the A-type connector  130   b , an insulative sealing member  150  and the insulative A-type support member  120   b . That is, the current collecting layer  117  in contact with the second electrode  116  of the first SOFC sub-cell  110   a  is connected to the porous member  118  of the second SOFC sub-cell  110   b  adjacent to the first SOFC sub-cell  110   a  through the A-type connector  130   b , so that the combined cell module  100  has not only a physically serial connection structure but also an electrically serial connection structure. 
     An SOFC sub-cell (hereinafter, referred to as a sub-cell) of the combined cell module  100  according to the first embodiment of the present invention will be described in more detail with reference to  FIGS. 3A to 5C . 
       FIG. 3A  is a schematic cross-sectional view of a sub-cell of the combined cell module of  FIG. 2 .  FIG. 3B  is a schematic exploded sectional view of the sub-cell of  FIG. 3A .  FIG. 4A  is a schematic front view of an A-type support member of  FIG. 3B .  FIG. 4B  is a schematic right side view of the A-type support member of  FIG. 4A .  FIG. 5A  is a schematic front view of an A-type connector of  FIG. 3B .  FIG. 5B  is a schematic left side view of the A-type connector of  FIG. 5A .  FIG. 5C  is a schematic right side view of the A-type connector of  FIG. 5A . 
     Referring to  FIGS. 3A and 3B , the sub-cell  110   b  includes a tube-type cell  101   b  and an A-type support member  120   b  inserted into a hollow portion  102  of the tube-type cell  101   b . The sub-cell  110   b  may further include a porous member  118  and a sealing member  150 . 
     The A-type connector  130   b  is between two adjacent tube-type cells. However, it is described in this embodiment that the A-type connector  130   b  is included in the sub-cell  110   b  for convenience of illustration with respect to the combined cell module  100 . 
     The tube-type cell  101   b  is provided with a structure in which a first electrode  112 , an electrolyte layer  114 , and a second electrode  116  are stacked. The electrolyte layer  114  and the second electrode  116  are sequentially stacked on the outer surface of the first electrode  112 . The second electrode  116  may be formed to have a shorter length than that of the electrolyte layer  114  so that the electrolyte layer  114  is exposed at both end portions of the cell  101   b  in its longitudinal direction. Thus, the second electrode  116  is not electrically short-circuited with the first electrode  112 . 
     In one embodiment, the first electrode  112  may be formed as a tube-type anode support having the hollow portion  102 . A porous Ni-YSZ cermet may be used as the material of the first electrode  112 . The electrolyte layer  114  may be formed of an ion conducting oxide for transporting oxygen ions, e.g., yttria stabilized zirconia (YSZ). The second electrode  116  may be formed of a porous mixed conducting oxide. The tube-type cell  101   b  including the first electrode  112 , the electrolyte layer  114 , and the second electrode  116  generates electricity and water by an electrochemical reaction of hydrogen and oxygen supplied to the first and second electrodes  112  and  116 , respectively. 
     The A-type support member  120   b  is inserted into the hollow portion  102  of the tube-type cell  101   b . The A-type support member  120   b  includes a rod-shaped body  122  of which the interior is fully filled. The A-type support member  120   b  further includes combining portions  124   a  and  124   b  respectively disposed at each end portion of the body  122  with stepped portions  123   a  and  123   b  interposed therebetween (see  FIGS. 4A and 4B ). The combining portions  124   a  and  124   b  may have the shape of a male screw having a smaller sectional area than that of the body  122 . Here, the male screw has convex and concave portions spirally formed on its surface. In one embodiment, the A-type support member  120   b  may be formed of alumina (Al 2 O 3 ). The thermal expansion coefficient of the alumina is about 8×10 −6 [K −1 ] from room temperature to about 1000° C. 
     In one embodiment, the A-type connector  130   b  has a structure in which a shaft portion protrudes from a central portion at one side of a wheel-shaped body  132 . That is, the A-type connector  130   b  includes: a first female screw  133  formed inside the central portion of a first surface of the body  132 ; a plurality of openings  134   a ,  134   b ,  134   c , and  134   d , formed around the first female screw  133  to pass through the body  132 ; and a coupling portion  136  protrudes outside from the central portion of a second surface opposite to the first surface of the body  132  (see  FIGS. 5A to 5C ). 
     The coupling portion  136  is integrally provided with the A-type connector  130   b  and has a sectional area and a sectional shape, similar to those of the A-type support member  120   b . A second female screw  137  is provided at a central portion of the coupling portion  136  so that the first and second female screws  133  and  137  face each other. The second female screw  137  of the A-type connector  130   b  is screw-connected to the combining portion  124   a  at one side of the A-type support member  120   b.    
     In one embodiment, the A-type connector  130   b  may be formed of ferrite stainless steel. The thermal expansion coefficient of the ferrite stainless steel is about 13×10 −6 [K −1 ] from room temperature to about 1000° C. 
     The length L 2  (see  FIG. 5A ) of the coupling portion  136  is appropriately controlled depending on a difference between thermal expansion coefficients of the cell  101   b  and the A-type support member  120   b . In one embodiment, the ratio of the length L 2  of the coupling portion to the length L 1  of the A-type support member (see  FIG. 4A ) is configured so that the thermal expansion coefficient of the combined structure of the coupling portion  136  and the A-type support member  120   b  is 95 to 105%. For example, the length L 1  (see  FIG. 4A ) of the A-type support member  120   b  may be about 80% and the length L 2  of the coupling portion  136  may be about 20% with respect to the length obtained by roughly subtracting the length L 3  (see  FIG. 5A ) of the body  132  of the A-type connector  130   b  from the length L 0  (see  FIG. 3A ) of the sub-cell  110   b . In this case, the thermal expansion coefficient of the combined structure of the A-type support member  120   b  and the coupling portion  136  is about 9×10 −6 [K −1 ] from room temperature to about 1000° C. 
     If the length L 2  of the coupling portion  136  is controlled, i.e., if the ratio of the lengths L 1  and L 2  of the A-type support member  120   b  and the coupling portion  136  is controlled, it is possible to reduce or prevent undesired thermal stress from being generated from the combined cell module  100  due to the difference of thermal expansion coefficients between the cells and the support members. 
     Referring back to  FIGS. 3A and 3B , the porous member  118  may be provided between the first electrode  112  and the A-type support member  120   b  in the sub-cell  110   b . The porous member  118  may be formed in the shape of a pipe having a hollow portion  119  by appropriately pressurizing a flexible member. The material of the porous member  118  may include a metal felt such as a nickel felt and a metal mesh having a similar shape to the metal felt. The porous member  118  may have a conducting property (e.g., be formed of an electrically conducting material, such as metal). 
     The sealing member  150  is provided at a boundary portion between the cell  101   b  and the A-type connector  130   b . The sealing member  150  may be provided at both end portions of the sub-cell  110   b  in its longitudinal direction. In one embodiment, the sealing member  150  is formed of a material having a high sealing performance when pressure stress is generated in the A-type support member  120   b  and the cell  101   b  in operation of the combined cell module  100 . The material of the sealing member  150  may include a Mica-based material and/or Thermiculite (product name). If the sealing member  150  is used, a manufacturing process can be simplified as compared with a sealing process using a brazing technique, and impurity mixture can be reduced as compared with a glass-type sealing process. 
     Hereinafter, the process of manufacturing the combined cell module  100  of the first embodiment will be described in more detail. 
     First, an yttria-stabilized zirconia (YSZ) powder mixed with 40 vol % nickel (Ni), available for an anode electrode material, is kneaded by adding activated carbon, organic binder and water to the YSZ powder, and the kneaded slurry is extrusion-molded. After drying the extrusion-molded slurry, an anode support tube is prepared by sintering the dried slurry at about 1300° C. 
     Subsequently, the YSZ powder that is an electrolyte material is prepared as an electrolyte slurry, and the electrolyte slurry is then dip-coated on the anode support tube using a slurry coating technique. The electrolyte slurry coated on the anode support tube is dried at a room temperature and then sintered at about 1400° C. 
     Subsequently, a (La,Sr)MnO3 (LSM) powder available for a cathode material is prepared as a cathode slurry, and the cathode slurry is then dip-coated on the electrolyte layer of the anode support tube. The cathode slurry coated on the electrolyte layer of the anode support tube is dried and then sintered at about 1200° C. 
     The manufactured SOFC cell has an outer diameter of about 20 mm, an inner diameter of about 16 mm and a length of about 300 mm. 
     Subsequently, a nickel felt is inserted into the manufactured SOFC cell. Then, the A-type support member formed of alumina and the A-type connector formed of stainless steed are prepared, and the combining portion  124   a  at one side of the A-type support member is screw-connected to a second female screw  137  of the A-type connector. 
     Subsequently, the A-type support member having the A-type connector combined at one side thereof is inserted in a hollow portion of the cell into which the nickel felt is inserted from the other side opposite to the one side of the A-type support member. In another embodiment of the present invention, the A-type support member having the A-type connector combined at one side thereof may be inserted together with the nickel felt into the hollow portion of the cell while having been previously inserted into a hollow portion of the nickel felt. 
     Subsequently, a plurality of sub-cells are prepared in which the nickel felt and the A-type support member are inserted, and the A-type connector is connected to one side of the A-type support member. The prepared sub-cells are screw-connected to one another in a longitudinal direction thereof. 
     Subsequently, boundary portions between the cells and the A-type support members are sealed with a sealing member  150 . Thermiculite #866 (product name) may be used as the sealing member  150 . 
     Subsequently, the current collecting layer  117  is formed by coating a La 0.9 Sr 0.1 CoO 3  powder available for a cathode current collecting material on the second electrode  116  of each of the sub-cells using a plasma spray technique. The current collecting layer  117  is formed to cover the second electrode  116  of the first sub-cell (e.g.,  110   a ), the electrolyte layer  114  exposed to one side of the second electrode  116 , and a portion of the A-type connector (e.g.,  130   b ) between the first sub-cell and the second sub-cell (e.g.,  110   b ) adjacent to the first sub-cell. 
     Hereinafter, the operation of the combined cell module  100  of the first embodiment will be described in more detail. 
     In  FIG. 2 , a black arrow  141  indicate the flow direction of a fuel, and a white arrow  143  indicate the flow direction of an oxide. The fuel may include methane, propane, butane and/or the like. The oxidizer may include air, oxygen, gas, and/or the like. 
     The fuel flows from the first manifold  140   a  to the hollow portion at one side of the combined cell module  100  flows along the outer surfaces of the A-type support members  120   a  to  120   d . At this time, the fuel passes through the A-type connectors  130   a  to  130   d , openings at the end connector  130   e , and the porous member  118  between the openings. Most of the fuel that flows into the combined cell module  100  is converted into a reformate gas containing abundant hydrogen under a high-temperature atmosphere. The hydrogen is supplied to the first electrode of each of the sub-cells while moving along the flow direction of the fuel. 
     The combined cell module  100  generates electric energy and water by an electrochemical reaction of oxygen in the air and hydrogen. Here, the oxygen is supplied to the second electrode  116 , and the hydrogen is supplied to the first electrode  112 . The electric energy is supplied to an external circuit or load connected to the combined cell module  100 . A reaction byproduct, such as water, and an unreacted fuel are moved along the flow direction of the fuel on the outer surface of the rod-shaped A-type support member and then discharged to the second manifold  140   b  connected to the other side of the combined cell module  100 . 
     The electrochemical reaction respectively generated at the first and second electrodes (anode and cathode) of each of the sub-cells are represented by the following reaction formula 1. 
     
       
         
           
             
               
                 
                   
                     
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       FIG. 6  is a schematic front view of a combined cell module according to a second embodiment of the present invention.  FIG. 7  is a schematic cross-sectional view of the combined cell module according to the second embodiment.  FIG. 8  is a schematic cross-sectional view of a sub-cell of the combined cell module of  FIG. 7 .  FIG. 9A  is a schematic front view of a support member integrated with a connector (hereinafter, referred to as a B-type support member), used in the combined cell module of  FIG. 7 .  FIG. 9B  is a schematic longitudinal cross-sectional view of the B-type support member of  FIG. 9A .  FIG. 9C  is a schematic left side view of the B-type support member of  FIG. 9A .  FIG. 9D  is a schematic right side view of the B-type support member of  FIG. 9A .  FIG. 10  is a schematic front view of a coupling portion (hereinafter, referred to as a B-type coupling portion) used in the combined cell module of  FIG. 7 . 
     Referring to  FIGS. 6 to 8 , the combined cell module  200  includes a plurality of sub-cells  210   a ,  210   b ,  210   c  and  210   d . Each of the sub-cells includes a plurality of cells and B-type support members  220   a ,  220   b ,  220   c  and  220   d  each having a portion inserted into a hollow portion of each of the cells in its longitudinal direction. Connectors  230   a ,  230   b ,  230   c  and  230   d  are integrally provided at one side of the respective B-type support members. The combined cell module  200  further includes B-type coupling portions  250   a ,  250   b ,  250   c  and  250   d  between two adjacent sub-cells and between a sub-cell positioned at one end of the combined cell module  200  and an end connector  230   e . The end connector  230   e  is provided between one end of the combined cell module  200  and a manifold  140   b.    
     Each of the sub-cells  210   a ,  210   b ,  210   c  and  210   d  includes a first electrode  112  for forming a tube-type support, and an electrolyte layer  114  and a second electrode  116 , sequentially stacked on the outer surface of the first electrode  112 . 
     The B-type support members  220   a ,  220   b ,  220   c  and  220   d  are physically connected while being electrically isolated from one another. The B-type support members  220   a ,  220   b ,  220   c  and  220   d  are serially located from one end to the other end of the combined cell module  200 . In one embodiment, as illustrated in  FIGS. 9A to 9D , each of the B-type support members has a structure in which a long handle is attached to a central portion of one side of a wheel-shaped body  232 . That is, each of the B-type support members includes a first female screw  233  formed in an interior of the central portion at one side of the body  232 , a plurality of openings  234   a ,  234   b ,  234   c  and  234   d  passing through the body  232  in one direction (e.g., a longitudinal direction) around the first female screw  233 , and a support portion  222  extending in a longitudinal direction to the exterior from the central portion of the other side of the body  232  while facing the first female screw  233 . A second female screw  237  is formed at the end of the support portion  222 , extending to the exterior. Flanges  238   a  and  238   b  are respectively formed at first and second ends of the body  232  to slightly protrude in the longitudinal direction. 
     The B-type coupling portions  250   a ,  250   b ,  250   c  and  250   d  have a thermal expansion coefficient different from that of the B-type support members, and are between the B-type support members. In one embodiment, each of the B-type coupling portions  250   a ,  250   b ,  250   c  and  250   d  has the shape of a double male screw as illustrated in  FIG. 10 . That is, each of the B-type coupling portions includes a short cylindrical body  242 , and first and second male screws  244   a  and  244   b  respectively extending by a length (e.g., a predetermined length) to the exterior from both end portions of the body  242  with stepped portions interposed therebetween. Here, the sectional area of each of the first and second male screws  244   a  and  244   b  is smaller than that of the body  242 . 
     In this embodiment, the B-type support member may be formed of ferrite stainless steel, and the B-type coupling portion may be formed of alumina (Al 2 O 3 ). In this case, the length of the B-type coupling portion and the length of the support portion of the B-type support member are controlled by considering the thermal expansion coefficient of the tube-type cell constituting the sub-cell, thereby reducing the effect of the difference between thermal expansion coefficients of components of the combined cell module  200 . For example, it is assumed that the length L 5  (see  FIG. 9A ) of the support portion  222  of the B-type support member is about 80% and the length L 7  (see  FIG. 10 ) of the body  242  of the B-type coupling portion is about 20%, based on the length of the sub-cell or tube-type cell. Then, the thermal expansion coefficient of the combined structure of two components becomes about 12×10 −6 [K −1 ] from room temperature to about 1000° C. 
     Referring back to  FIGS. 7 and 8 , in one embodiment, a porous member  118  is between the first electrode  112  and the support portion  222  of each of the B-type support members  220   a ,  220   b ,  220   c  and  220   d  in the SOFC combined cell module  200 . The porous member  118  is flexible and is filled in the space between the first electrode  112  and the support portion  222  in the sub-cell. The porous member  118  (e.g., formed of a metal) has a conductive property, and connects the first electrode  112  and the support portion  222  in the sub-cell. 
     In one embodiment, an insulating member  252  is provided between adjacent sub-cells. That is, the insulating member  252  allows the first electrode  112  of the first sub-cell  210   a  to be electrically insulated from the connector  230   b  of the second sub-cell  210 . One side of the insulating member  252  may be supported by a flange portion of the connector  230   b.    
     In one embodiment, boundary portions between the sub-cells  210   a ,  210   b ,  210   c  and  210   d  and between the cell of each of the sub-cells and the connector may be sealed with a sealing member  260 . The sealing member  260  may be formed by melting BNi-2 (Cr 7%, B 3%, Si 4.5%, Fe 3%, C 0.05%, Ni Bal.) available for a Ni-based brazing material using an induction brazing technique. 
     A current collecting layer  117   a  is provided on the second electrode  116  of each of the sub-cells. In one embodiment, the current collecting layer  117   a  may be consecutively formed on the second electrode  116 , the electrolyte layer  114  exposed to one side of the second electrode  116 , and a portion of the connector of the B-type support member adjacent to the electrolyte layer  114 . 
     In the combined cell module  200 , the current collecting layer  117   a  connected to the second electrode  116  of the first sub-cell (e.g.,  210   a ) is connected to the first electrode  112  of the second sub-cell (e.g.,  210   b ) through the B-type support member  220   b  of the second sub-cell  210   b . Thus, the electrical serial connection structure of the sub-cells can be stably formed, in addition to the mechanical serial connection structure of the sub-cells. 
       FIG. 11  is a schematic front view of a combined cell module according to a third embodiment of the present invention.  FIG. 12  is a schematic cross-sectional view of the combined cell module according to the third embodiment of the present invention.  FIG. 13  is a schematic cross-sectional view of a sub-cell of the combined cell module of  FIG. 12 .  FIG. 14A  is a schematic front view of a support member integrated with a connector and a resilient portion (hereinafter, referred to as a C-type support member), used in the combined cell module of  FIG. 12 .  FIG. 14B  is a schematic longitudinal cross-sectional view of the C-type support member of  FIG. 14A .  FIG. 14C  is a schematic left side view of the C-type support member of  FIG. 14A .  FIG. 14D  is a schematic right side view of the C-type support member of  FIG. 14A .  FIG. 15  is a schematic front view a coupling member (hereinafter, referred to as a C-type coupling member) applicable to the combined cell module of  FIG. 12 . 
     Referring to  FIGS. 11 to 13 , the combined cell module  300  includes a plurality of sub-cells  310   a ,  310   b ,  310   c  and  310   d . Each of the sub-cells includes a plurality of cells and C-type support members  320   a ,  320   b ,  320   c  and  320   d  each having a portion inserted into a hollow portion of each of the cells in its longitudinal direction. Connectors  330   a ,  330   b ,  330   c  and  330   d  are integrally provided at one side of the respective C-type support members. The combined cell module  300  further includes C-type coupling portions  350   a ,  350   b ,  350   c  and  350   d  disposed between two adjacent C-type support members and between a sub-cell positioned at one end of the combined cell module  300  and an end connector  330   e . The end connector  330   e  connects the one end of the combined cells module  300  to a manifold  140   b  so that a fluid can flow therethrough. 
     Each of the sub-cells  310   a ,  310   b ,  310   c  and  310   d  includes a first electrode  112  for forming a tube-type support, and an electrolyte layer  114  and a second electrode  116 , sequentially sacked on the outer surface of the first electrode  112 . 
     The C-type support members  320   a ,  320   b ,  320   c  and  320   d  are physically connected together with the C-type coupling members  350   a ,  350   b ,  350   c  and  350   d  while being electrically isolated from one another by the C-type coupling members. The C-type support members  320   a ,  320   b ,  320   c  and  320   d  are serially located from one end to the other end of the combined cell module  300 . Here, it can be seen that each of the C-type coupling members serves as a kind of insulating member. 
     In one embodiment, as illustrated in  FIGS. 14A to 14D , each of the C-type support members  320   a ,  320   b ,  320   c  and  320   d  has a structure in which a support portion with a long hand shape is attached to a central portion of one side of a wheel-shaped body  332 , and a resilient portion  342  is integrally formed at an edge of the other side of the body  332 . Here, the body corresponds to each of the connectors  330   a ,  330   b ,  330   c  and  330   d.    
     Each of the C-type support members includes a first female screw  333  formed in an interior of the central portion at one side of the body  332 , a plurality of openings  334   a ,  334   b ,  334   c  and  334   d  passing through the body  332  in one direction (e.g., a longitudinal direction) around the first female screw  333 , and a support portion  322  extending longitudinally to the exterior from the central portion of the other side of the body  332  while facing the first female screw  333 . A second female screw  337  is formed at an end of the support portion  322  to face the first female screw  333 . 
     The resilient portion  342  has an expanding and contracting structure and is integrally connected to an edge of one side surface of the body  332  of the C-type support member at which the first female screw  333  is positioned. The resilient portion  342  is resiliently contracted or expanded slightly between the sub-cells when pressure stress is generated between the sub-cells and the C-type support members. 
     The C-type coupling portions  350   a ,  350   b ,  350   c  and  350   d  have an insulating property. Each of the C-type coupling portions  350   a ,  350   b ,  350   c  and  350   d  has a sectional area and a sectional shape, similar (or identical) to that of the support portion  322  of the C-type support member. The C-type coupling portions  350   a ,  350   b ,  350   c  and  350   d  are between the C-type support members. Each of the C-type coupling portions  350   a ,  350   b ,  350   c  and  350   d  has the shape of a double male screw as illustrated in  FIG. 15 . That is, each of the C-type coupling portions includes a flat cylindrical body  342 , and first and second male screws  344   a  and  344   b  respectively extending by a length (e.g., a predetermined length) to the exterior from central portions at first and second sides of the body  342  with stepped portions  343   a ,  343   b  interposed therebetween. Here, the sectional area of each of the first and second male screws  344   a  and  344   b  is smaller than that of the body  342 . The length of the C-type coupling portion may be shorter than that of the B-type coupling portion of  FIG. 10 . 
     In this embodiment, the C-type support member may be formed of ferrite stainless steel, and the C-type coupling portion may be formed of alumina (Al 2 O 3 ). In this case, the length L 12  (see  FIG. 15 ) of the C-type coupling portion may be appropriately controlled considering the thermal expansion coefficient of the tube-type cell constituting the sub-cell. That is, the ratio of the length L 11  (see  FIG. 14A ) of the support portion of the C-type support member to the length L 12  of the C-type coupling portion is controlled, thereby reducing or preventing undesired thermal stress from being generated due to the difference of thermal expansion coefficients between components of the combined cell module  300 . 
     For example, it is assumed that the length L 11  of the support portion  322  of the C-type support member is about 95% and the length L 12  of the body  342  of the C-type coupling portion is about 5%, based on the length of the sub-cell. Then, the thermal expansion coefficient of the combined structure of two components becomes about 10×10 −6 [K −1 ] from room temperature to about 1000° C. That is, if the ratio of the lengths L 11  and L 12  of the two combined components is controlled, the thermal expansion coefficient of the combined structures of the C-type support members and the C-type coupling portions is substantially identical to or slightly smaller than that of the tube-type cells, thereby reducing thermal stress from being generated due to the difference of thermal expansion coefficients. 
     Referring back to  FIGS. 12 and 13 , the first C-type support member  320   a  positioned at one end portion of the combined cell module  300  may be provided with a structure in which a resilient portion is omitted, which is slightly different from the second C-type support member  320   b . The connector  330   a  of the first C-type support member  320   a  connects one end of the combined cell module  300  to the first manifold  140   a  so that a fluid can flow therethrough. The end connector  330   e  may have a similar shape to that of the body  332  of the C-type support member. The end connector  330   e  allows the other end of the combined cell module  300  to be fixedly connected to the second manifold  140   b  with the fourth C-type coupling member  350   d  interposed therebetween. 
     In one embodiment of the present invention, a porous member  118  is provided between the first electrode  112  and the support portion  322  of each of the C-type support members  320   a ,  320   b ,  320   c  and  320   d  in the combined cell module  300 . 
     In one embodiment of the present invention, an insulating member  362  is provided between adjacent sub-cells, i.e., a specific sub-cell (e.g.,  310   a ) and another sub-cell (e.g.,  310   b ) adjacent to the specific sub-cell. The insulating member  362  electrically insulates the first electrode  112  in the first sub-cell  310   a  from the resilient portion  342  of the C-type support member  320   b  in the second sub-cell  310   b.    
     In one embodiment of the present invention, boundary portions between the sub-cells  310   a ,  310   b ,  310   c  and  310   d  and between the tube-type cell and the connector in each of the sub-cells may be sealed with a sealing member  370 . The sealing member  370  may be formed to cover the insulating member  362  between two adjacent sub-cells. The sealing member  370  may be formed of a sealing material including glass based, crystallized glass based, MICA, MICA-glass composite, glass-filler composite and the like. 
     A current collecting layer  117   b  is provided on the second electrode  116  of each of the sub-cells  310   a ,  310   b ,  310   c  and  310   d . The current collecting layer  117   b  may be formed of stainless steel, Ni-based thermal resistance alloy containing silver (Ag). In this embodiment, the current collecting layer  117   b  is formed using a conductive mesh. In another embodiment of the present invention, the current collecting layer  117   b  may be formed by winding a conductive wire on the second electrode  116 . In this case, the current collecting layer  117   b  may be welded to the conductive body  332  of the C-type support member using a spot-welding technique. In still another embodiment of the present invention, the current collecting layer  117   b  may be formed by coating a conductive oxide such as LaCoO 3 . 
     In the combined cell module  300 , the current collecting layer  117   b  connected to the second electrode  116  of the first sub-cell (e.g.,  310   a ) is connected to the first electrode  112  of the second sub-cell (e.g.,  310   b ) through the C-type support member  320   b  of the second sub-cell. In the enlarged view of  FIG. 12 , the current collecting layer  117   b  is connected to the connector  330   b  of the C-type support member  230   b  by a wire or interconnection  117   c.    
     According to the aforementioned embodiment, the electrical serial connection structure of the sub-cells can be stably formed as well as the physical serial connection structure of the sub-cells. That is, two or more anode supported cells are physically and electrically connected in series, so that a combined cell module having excellent durability can be easily manufactured. 
       FIG. 16  is a schematic front view of a combined cell module according to a fourth embodiment of the present invention.  FIG. 17  is a schematic cross-sectional view of the combined cell module according to the fourth embodiment of the present invention.  FIG. 18  is a schematic cross-sectional view of a sub-cell of the combined cell module of  FIG. 17 .  FIG. 19A  is a schematic front view of a support member integrated with a connector and a resilient portion (hereinafter, referred to as a D-type support member), used in the combined cell module of  FIG. 17 .  FIG. 19B  is a schematic longitudinal cross-sectional view of the D-type support member of  FIG. 19A .  FIG. 19C  is a schematic left side view of the D-type support member of  FIG. 19A .  FIG. 19D  is a schematic right side view of the D-type support member of  FIG. 19A . 
     Referring to  FIGS. 16 to 18 , the combined cell module includes a plurality of sub-cells  410   a ,  410   b ,  410   c  and  410   d . Each of the sub-cells includes a plurality of cells and D-type support members  420   a ,  420   b ,  420   c  and  420   d  each having a portion inserted into a hollow portion of each of the cells in its longitudinal direction. Connectors  430   a ,  430   b ,  430   c  and  430   d  are integrally provided at one side of the respective D-type support members. The combined cell module  400  further includes insulating members  450  each being between two adjacent D-type support members or between a sub-cell positioned at one end of the combined cell module  400  and an end connector  430   e . The end connector  430   e  connects the one end of the combined cells module  400  to a manifold  140   b  so that a fluid can flow therethrough. 
     Each of the sub-cells  410   a ,  410   b ,  410   c  and  410   d  includes a first electrode  112  for forming a tube-type support, and an electrolyte layer  114  and a second electrode  116 , sequentially sacked on the outer surface of the first electrode  112 . 
     The D-type support members  420   a ,  420   b ,  420   c  and  420   d  are physically connected to one another while being electrically isolated from one another by the insulating members  450 . The B-type support members  420   a ,  420   b ,  420   c  and  420   d  are serially located from one end to the other end of the combined cell module  400 . 
     In one embodiment, each of the D-type support members  420   a ,  420   b ,  420   c  and  420   d  has a hammer shape as illustrated in  FIGS. 19A to 19D . That is, each of the D-type support members includes a body  432  corresponding to a head portion, a support portion  422  extending longitudinally in a rod shape from a central portion of one side of the body  432 , and a resilient portion  442  at an end of the other side of the body  432 , which are integrally combined with one another. Each of the D-type support members further includes a first female screw  433  formed inside a central portion of one side of the body  432 , a plurality of openings  434   a ,  434   b ,  434   c  and  434   d  passing through the body  432  in one direction (e.g., a longitudinal direction) around the first female screw  433 , and a male screw  437  formed from an end portion of the support member  422  to the exterior of the support member  422  while facing the first female screw  433 . 
     The resilient member  442  has an expanding and contracting structure and is integrally connected to an edge of one side surface of the body  432  of the C-type support member, at which the first female screw  433  is positioned. The resilient portion  442  is resiliently contracted or expanded between the sub-cells when pressure stress is generated between the sub-cells and the C-type support members. 
     The resilient member  442  of this embodiment is formed to have a higher elastic modulus than that of the resilient portion  342  of  FIG. 13 . Therefore, in the combined cell module  400  of this embodiment, the C-type coupling portions  350   a ,  350   b ,  350   c  and  350   d  of  FIG. 12  may be substantially omitted. However, an insulating member  450  is provided between the D-type support members for the purpose of electrical isolation between the D-type support members. The insulating member  450  may be formed as an insulating coating layer. 
     In this embodiment, the D-type support member may be formed of ferrite stainless steel. In this case, the elastic force of the resilient portion may be appropriately controlled considering the difference of thermal expansion coefficients between the tube-type cell constituting the sub-cell and the D-type support member. That is, the elastic force of the resilient portion  442  is appropriately controlled, thereby reducing thermal stress generated due to the difference of thermal expansion coefficients between components of the combined cell module  400 . 
     Referring back to  FIGS. 17 and 18 , the first D-type support member  420   a  positioned at one end portion of the combined cell module  400  may have a structure in which a resilient portion is omitted, which is slightly different from the second D-type support member  420   b . The connector  430   a  of the first D-type support member  420   a  connects one end of the combined cell module  400  to a manifold  140   a  so that a fluid can flow therethrough. The end connector  430   e  may have a similar shape to that of the body  432  of the D-type support member integrally provided with the resilient portion. The end connector  430   e  connects the other end of the combined cell module  400  to another manifold  140   b  so that a fluid can flow therethrough. 
     In one embodiment of the present invention, a porous member  118  may be provided between the first electrode  112  and the support portion  422  of each of the D-type support members  420   a ,  420   b ,  420   c  and  420   d  in each of the sub-cells constituting the combined cell module  400 . 
     In one embodiment of the present invention, another insulating member  462  (hereinafter, referred to as a second insulating member) may be provided between adjacent sub-cells, i.e., between a specific sub-cell (e.g.,  410   a ) and another sub-cell (e.g.,  410   b ) adjacent to the specific sub-cell. The second insulating member  462  insulates the first electrode  112  of the first sub-cell  410   a  from the resilient portion  442  of the D-type support member  420   b  in the second sub-cell  410   b.    
     In one embodiment of the present invention, boundary portions between the sub-cells  410   a ,  410   b ,  410   c  and  410   d  and between the tube-type cell and the connector in each of the sub-cells may be sealed with a sealing member  470 . The sealing member  470  may be formed to cover the second insulating member  462  between two adjacent sub-cells. The sealing member  470  may be formed of a sealing material including glass based, crystallized glass based, MICA, MICA-glass composite, glass-filler composite and the like. 
     A current collecting layer  117   b  is provided on the second electrode  116  of each of the sub-cells  410   a ,  410   b ,  410   c  and  410   d . The current collecting layer  117   b  may be formed of stainless steel, Ni-based thermal resistance alloy containing silver (Ag). In this embodiment, the current collecting layer  117   b  is formed using a conductive mesh. The current collecting layer  117   b  is connected to the conductive body  432  of the D-type support member through a conducting wire  117   c . The conducting wire  117   c  may be welded to the conductive body  432  using a spot-welding technique. 
     In the combined cell module  400 , the current collecting layer  117   b  connected to the second electrode  116  of the first sub-cell (e.g.,  410   a ) is connected to the first electrode  112  of the second sub-cell (e.g.,  410   b ) through the D-type support member  420   b  of the second sub-cell adjacent to the first sub-cell. Thus, the electrical serial connection structure of the sub-cells can be stably formed as well as the mechanical serial connection structure of the sub-cells. 
     In the aforementioned embodiment, the plurality of sub-cells are configured as anode supported cells. However, it will be apparent through the aforementioned disclosure that the sub-cells of these embodiments can be configured using anode supported cells, cathode supported cells, segmented in series cells or combination thereof. 
     According to the aforementioned embodiments, a plurality of tube-type anode supported SOFC cells are connected to one another in their longitudinal direction using a solid support member, thereby easily manufacturing a combined cell module for a solid oxide fuel cell having a desired length, e.g., at least about 1200 mm. 
     Further, in a serial connection structure of tube-type anode supported SOFC cells, the serial connection structure of SOFC cells can be mechanically and stably supported using support members, and by using a buffer portion, it is possible to prevent a device from being damaged (or reduce the likelihood of the device being damaged) due to the thermal stress generated by the difference of thermal expansion coefficients between components. 
     Further, since the connection between a combined cell module and a manifold is reinforced by the support members, it is possible to prevent a device from being broken (or reduce the likelihood of the device being broken) due to the mechanical stress generated in the combined cell module for a solid oxide fuel cell and a connecting portion of the manifold. 
     Further, in a single combined cell module provided with a plurality of anode supported SOFC cells, the electrical serial connection structure between the SOFC cells and the current collecting structure can be easily formed. 
     Further, a large-size SOFC system can be effectively designed and manufactured using a combined cell module provided with a plurality of anode supported SOFC cells. 
     While aspects of the present invention have been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.