Patent Publication Number: US-2011076597-A1

Title: Wire mesh current collector, solid state electrochemical devices including the same, and methods of making the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     This application claims priority to U.S. Provisional Application No. 61/246,702, entitled “Wire Mesh Current Collector,” filed Sep. 29, 2009, the entirety of which is incorporated by reference herein. 
    
    
     GOVERNMENT RIGHTS 
     This invention was made with government support under Contract No. DE-AC05-00OR22725 awarded by the U.S. Department of Energy. The government has certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     This disclosure relates to the field of solid state electrochemical devices, e.g., fuel cells. More particularly, this disclosure relates to current collectors for electrodes for solid state electrochemical devices. 
     BACKGROUND 
     A solid state electrochemical device or cell comprises two electrodes—the anode and the cathode—and a dense electrolyte membrane which separates the anode and the cathode regions of the cell. For example, fuel cells generally have a fuel electrode (anode) and an oxidant electrode (cathode). In a hydrogen/oxygen fuel cell, hydrogen passes over the anode where it dissociates into protons and electrons. The protons are conducted through the membrane to the cathode, while the electrons are forced to travel in an external circuit, wherein electrical power may be generated. Oxygen is provided at the cathode where it reacts with the electrons that traveled through the external circuit and the protons that were conducted through the membrane to form water, which becomes a generally benign waste discharge product. 
     The performance of a solid state electrochemical device such as a fuel cell depends at least in part upon the efficiency of the construction that removes electrons from the cathode and distributes the electrons at the cathode. This efficiency depends at least in part upon the uniformity of electrical conductivity across the surface of each electrode. Sometimes when electrical conduction is not uniform, thermal hot spots may form on the electrodes. Such thermal hotspots may damage the electrode. What are needed therefore are improved electron distribution systems for solid state electrochemical devices and improved methods for fabrication of elements for solid state electrochemical devices that will provide a more efficient and uniform distribution of electrons. 
     SUMMARY OF THE INVENTION 
     In one embodiment, the present disclosure provides a tubular conductive wire mesh that includes a conductive wire forming a knit mesh. The knit mesh has a series of adjacent substantially uniform interconnected generally triangular loops, where each generally triangular loop has a base portion and a tip portion. For each generally triangular loop, the conductive wire extends from the tip portion of a generally triangular first loop through the base portion of a longitudinally adjacent generally triangular second loop to form a junction and then forms the base portions of generally triangular third and fourth loops that are laterally adjacent the first loop. Furthermore, the knit mesh has a cylindrical free-state configuration. The tubular conductive wire mesh may be used as a current collector for electrodes for solid state electrochemical devices, such as solid oxide fuel cells. 
     The present disclosure also provides a non-rigid tubular conductive wire mesh that has a maximum insertion diameter, a minimum envelope diameter, a longitudinal compressive yield strength, and a longitudinal tensile yield strength. Under a longitudinal compressive force that does not exceed the longitudinal compressive strength of the conductive wire mesh, the conductive wire mesh is expandable to an expanded inside diameter that is larger than the maximum insertion diameter, and under a longitudinal tensile force that does not exceed the longitudinal tensile strength of the mesh the conductive wire mesh is contractible to a contracted outside diameter that is less than the minimum envelope diameter. 
     Methods are provided for fabricating an element for a solid state electrochemical device that incorporates a tubular fuel cell body and a tubular conductive wire mesh disposed adjacent an interior portion of the tubular fuel cell body. Methods are provided for fabricating an element for a solid state electrochemical device that incorporates a tubular fuel cell body and a tubular conductive wire mesh disposed adjacent an exterior portion of the tubular fuel cell body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various advantages are apparent by reference to the detailed description in conjunction with the figures, wherein elements are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein: 
         FIG. 1  is a perspective view of a tubular conductive wire mesh for use with an electrode for a solid state electrochemical device. 
         FIG. 2  is a detailed view of an exemplary knit mesh for use with an electrode for a solid state electrochemical device. 
         FIG. 3 . is a detailed view of an exemplary woven mesh for use with an electrode for a solid state electrochemical device. 
         FIG. 4  is a cutaway view of a tubular conductive wire mesh electrically coupled to an inside surface of an electrode for a solid state electrochemical device. 
         FIG. 5  is a view of a tubular conductive wire mesh electrically coupled to an outside surface of an electrode for a solid state electrochemical device. 
         FIG. 6  is a perspective view of a tubular conductive wire mesh positioned for insertion adjacent an inside surface of an electrode for a solid state electrochemical device, by pushing. 
         FIG. 7 . is a perspective view of a tubular conductive wire mesh positioned for insertion adjacent an inside surface of an electrode for a solid state electrochemical device, by pulling. 
         FIG. 8  is a cutaway view of a woven mesh and a coil spring electrically coupled to an inside surface of an electrode for a solid state electrochemical device. 
         FIG. 9  is a cutaway view of a woven mesh and two seating rings electrically coupled to an inside surface of an electrode for a solid state electrochemical device. 
         FIG. 10  is a cutaway view of a woven mesh and a coil spring electrically coupled to an outside surface of an electrode for a solid state electrochemical device. 
         FIG. 11  is a cutaway view of a woven mesh and two seating rings electrically coupled to an outside surface of an electrode for a solid state electrochemical device. 
         FIG. 12  is a perspective view and an end view of an exemplary tubular fuel cell body. 
         FIG. 13  is a perspective view of an exemplary tubular fuel cell body. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of the preferred and other embodiments, reference is made to the accompanying drawings, which form a part hereof, and within which are shown by way of illustration the practice of specific embodiments of elements for solid state electrochemical devices comprising a tubular conductive wire mesh. The following detailed description also presents preferred and other embodiments of methods for fabricating elements for solid state electrochemical devices. It is to be understood that other embodiments may be utilized, and that structural changes may be made and processes may vary in other embodiments. 
     Various embodiments of wire mesh materials that may be used as a current collector in solid state electrochemical devices such as fuel cells are disclosed herein. In some embodiments this mesh material may be inserted into an interior portion of a tubular fuel cell electrode. Various mechanisms may be used, if needed, to expand the mesh material to enhance its electrical contact with an interior surface of the tube. In some embodiments the wire mesh material may be applied to an exterior surface of a tubular fuel cell electrode. In some embodiments, the mesh material may be coupled to the tubular fuel cell electrode by an electrically conductive paste to enhance the electrical contact of the mesh material to the electrode. Wire mesh materials that are installed with individual tubular fuel cell electrodes of a tubular fuel cell array may be interconnected,in either series or parallel configurations. 
       FIG. 1  presents a view of one embodiment of a tubular conductive wire mesh  10  for a fuel cell. The tubular conductive wire mesh  10  has a first end  14 , a second end  18 , a length  22 , and a mesh pattern  26 . For referential purposes, a first arrow  30  represents the longitudinal orientation of the mesh pattern  26  and a second arrow  34  represents the circumferential orientation of the mesh pattern  26 . In accordance with the disclosure herein, generally the circumferential shape of a tubular conductive wire mesh (e.g., conductive wire mesh  10 ) is oval, having an elliptical aspect ratio (i.e., a ratio of width  38  over length  42 ) that may range from 1.0 (substantially circular) to about 1.3. In  FIG. 1  the mesh pattern  26  is generalized.  FIGS. 2 &amp; 3  illustrate specific embodiments (a knit mesh  100  and a woven mesh, respectively) of the generalized mesh pattern  26 . 
     The knit mesh  100  of  FIG. 2  is fabricated from a single conductive wire  104 . The knit mesh  100  has a plurality of substantially uniform interconnected loops  108 . The substantially uniform interconnected loops  108  are disposed adjacent each other in the longitudinal orientation (as indicated by the first arrow  30  of  FIG. 1 ) and the substantially uniform interconnected loops  108  are disposed adjacent each other in the circumferential orientation (as indicated by the second arrow  34  of  FIG. 1 ). The interconnected loops  108  are generally triangular shaped, with each loop  108  having a base portion  112  and a tip portion  116 . Using loops  120 ,  124 ,  128 ,  132  as examples, the conductive wire  104  extends from the tip portion  136  of a generally triangular first loop  120  through the base portion  140  of a longitudinally adjacent generally triangular second loop (loop  124  in this example) to form a junction  144  and then the conductive wire  104  forms the base portions ( 148  and  152 ) of generally triangular third and fourth loops ( 128  and  132 ) that are laterally adjacent the first loop  120 . 
     Generally triangular loops (e.g., loops  108 ) typically have a loop aspect ratio (e.g., a ratio of height  60  to base  64  as depicted in  FIG. 1 ) that ranges from about 1 to about 3, with a loop aspect ratio of 2 being typical. 
     In the example of  FIG. 2 , the generally triangular loops that are circumferentially adjacent (e.g., loops  128  and  120 , loops  120  and  136 ) are triangularly inverted. That is, the third loop  128  has its tip portion pointed toward the second end  18  whereas the circumferentially adjacent first loop  120  has its tip portion pointed toward the first end  14  and the circumferentially adjacent fourth loop  132  has its tip portion pointed toward the second end  18 . When counting loops around the circumference of conductive wire mesh  10 , loops  128  and  120  are counted as two loops. 
     Note that the loops  108  that are disposed at the first end  14  of the conductive wire mesh  10  are “loose loops.” That is, for the generally triangular loops  108  that are disposed at the first end ( 14  in  FIG. 1 ) of the conductive wire mesh  10 , the conductive wire  104  will not extend from the tip portion (e.g.,  136 ) of the generally triangular loops  108  through the base portion (e.g.,  140 ) of a longitudinally adjacent generally triangular loop  108  because at the first end  14  there are no generally triangular loops  108  that extend beyond the tip portions ( 136 ) of the generally triangular loops  108  that are disposed at the first end ( 14  in  FIG. 1 ) of the conductive wire mesh  10 . 
     The junctions  144  form locations on the tubular conductive wire mesh  10  where the conductive wire  104  overlaps itself. These overlaps provide a repetitive pattern of localized bumps. These localized bumps provide slight variations (along the longitudinal direction of the first arrow  30 ) of the inside diameter  68  and the outside diameter  72  of the tubular conductive wire mesh  10 . That is, the outside diameter (e.g., outside diameter  72  of  FIG. 1 ) is typically slightly larger at a junction (e.g., junction  144  of  FIG. 2 ) than the average outside diameter of the overall tubular conductive wire mesh  10 . This pattern of localized bumps also provides a localized inside diameter (e.g., inside diameter  68  of  FIG. 1 ) such that the tubular conductive wire mesh  10  has a minimum inside diameter (e.g., the inside diameter  68 ) that is typically slightly smaller than the average inside diameter of the overall tubular conductive wire mesh  10 . These bumps may form preferred electrical contact points when the knit wire mesh  100  is used as a component in an electrode for a solid state electrochemical device. 
     In the example of  FIG. 2  the junctions  144  form a spiral pattern (depicted as spiral pattern  76  in  FIG. 1 ) in the knit mesh  100 . Typically a spiral pattern may proceed from one end (e.g. the second end  18 ) to the other end (e.g. the first end  14 ) of a conductive wire mesh (e.g., conductive wire mesh  10 ) at a pitch angle  80  that may vary from about zero degrees to about thirty degrees for different portions of a circumferential path. Not all conductive wire meshes (particularly not all woven meshes) form a spiral pattern of junctions. 
       FIG. 3  illustrates a second specific example (a woven mesh  200 ) of the generalized mesh pattern  26  of  FIG. 1 . The woven mesh  200  has a plurality of conductive wires  204  that are woven together to form a plurality of cells  208 . The conductive wires  204  also form a plurality of junctions  212  where the conductive wires  204  overlap. These overlaps provide a repetitive pattern of localized bumps where a maximum outside diameter (e.g., diameter  72  of  FIG. 1 ) is typically slightly larger than the average diameter of the overall tubular conductive wire mesh  10  and a minimum inside diameter (e.g., inside diameter  68  of  FIG. 1 ) that is slightly less than the average inside diameter of the overall tubular conductive wire mesh  10 . As with the bumps formed by the junctions  144  of the knit mesh  100  of  FIG. 2 , these bumps formed by the junctions  204  of the woven mesh  200  of  FIG. 3  may form preferred electrical contact points when the woven mesh  200  is used as a component in an electrode for a solid state electrochemical device. 
     The loops  108  of the knit mesh  100  of  FIG. 2  and the cells  208  of the woven mesh  200  of  FIG. 3  are examples of “segments” of a mesh pattern. Other repetitive interlocking patterns may also be used to form a tubular conductive wire mesh (generically-depicted as tubular conductive wire mesh  10  in  FIG. 1 ) that has segments. For example a tubular conductive wire mesh may be formed using a weave similar to that which is used in a chain-link (or “cyclone”) fence. The individual diamond-shaped portions of such a weave pattern are the segments of that tubular conductive wire mesh. 
     The term “free-state,” as used herein, refers to an environment where a conductive wire mesh (either a knit mesh or a woven mesh) is subject to no external force except gravity. In many embodiments a tubular conductive wire mesh (either a knit mesh or a woven mesh) has a “cylindrical free-state configuration.” A knit mesh or a woven mesh that has a cylindrical free-state configuration (as depicted for the tubular conductive wire mesh  10  of  FIG. 1 ) intrinsically has a generally tubular shape without any external shaping mechanism causing it to have a generally tubular shape. A knit mesh or a woven mesh that has a cylindrical free-state configuration is a conductive wire mesh that does not collapse to a flat tube if placed on its side, and does not collapse into a pile if placed on an end. In contrast, a tubular conductive wire mesh formed using the weave pattern of a chain-link fence will collapse to a flat tube if placed on its side, and therefore such a tubular conductive wire mesh does not have a cylindrical free-state configuration. 
     For the tubular conductive wire mesh  10  the outside diameter  72  and the inside diameter  68  are free-state diameters, and the length  22  is a free-state length. A tubular conductive wire mesh may be configured to have a cylindrical free-state configuration even if the loops (e.g., the loops  108  of the knit mesh  100  of  FIG. 2 ) or the cells (e.g., the cells  208  of the woven mesh  200  of  FIG. 3 ) of the tubular conductive wire mesh (e.g.,  10 ) are not rigidly interconnected. A rigid interconnection is an interconnection wherein the interconnected pieces cannot be moved relative to each other without breaking a bond (such as a weld or a crimp) formed between the interconnected pieces. Loops and cells that are not rigidly interconnected are referred to herein as “loose segments.” A conductive wire mesh having a cylindrical free-state configuration may be formed using loose segments by using comparatively stiff, resilient wires to form the knit mesh (e.g.,  100  of  FIG. 2 ) or to form the woven mesh (e.g.,  200  of  FIG. 3 ). 
     Conductive wire meshes have yield strengths. A yield strength is the maximum force that may be applied to a conductive wire mesh without plastically deforming (e.g., bending) any of the wire(s) used in construction of the mesh to the extent that the wire does not return to its original shape when the force is removed. The term “non-rigid” as used herein refers to a characteristic of an element wherein the element flexes visibly (without magnification of the image) under forces that are applied to the element manually without the application of leveraging forces from tools. In non-rigid embodiments of a conductive wire mesh, when the mesh is constrained to its free-state length, there is a maximum diameter rod that may be inserted inside the mesh without exceeding the yield strength of the mesh. This maximum diameter is referred to herein as the “maximum insertion diameter” of the mesh. In non-rigid embodiments of a conductive wire mesh, when the mesh is constrained to its free-state length, there is a minimum diameter cylinder into which the mesh may placed without exceeding the yield strength of the mesh. This minimum diameter is referred to herein as the “minimum envelope diameter.” In non-rigid embodiments of a conductive wire mesh, when the length of the mesh is not constrained, there is a maximum longitudinal compressive force that may be applied to the mesh without exceeding the yield strength of the mesh. This maximum compressive force is referred to herein as the “longitudinal compressive yield strength” of the mesh. In non-rigid embodiments of a conductive wire mesh, when the length of the mesh is not constrained, there is a maximum longitudinal tensile (i.e., stretching) force that may be applied to the mesh without exceeding the yield strength of the mesh. This maximum tensile force is referred to herein as the “longitudinal tensile yield strength” of the mesh. 
     In non-rigid examples of a conductive wire mesh, when the knit mesh  100  of  FIG. 2  or the woven mesh  200  of  FIG. 3  is used to form the tubular conductive wire mesh  10  of  FIG. 1 , the tubular conductive wire mesh may be configured such that a longitudinal compressive force causes the distance between the segments of the mesh pattern to decrease slightly, and causes the free-state length  22  of the tubular conductive wire mesh  10  to decrease, and causes the outside diameter  72  and the inside diameter  68  of the tubular conductive wire mesh  10  to both increase slightly to expanded inside and outside diameters. The longitudinal compressive force may be applied by combination of (a) a first longitudinal force applied at first end  14  vectored toward the second end  18  and (b) a second longitudinal force applied at the second end  18  vectored toward the first end  14 . Such a compressive force may be used to expand the inside diameter of a tubular conductive wire mesh to fit the conductive wire mesh over the outside surface of a tubular fuel cell electrode having an outside diameter that is greater than the maximum insertion diameter of the mesh. If such a conductive wire mesh is positioned inside a tubular fuel cell electrode having an inside diameter that is greater than the minimum envelope diameter of the mesh, such a longitudinal compressive force may be used to press the conductive wire mesh against an inside surface of the tubular fuel cell electrode. 
     Furthermore, in such non-rigid examples, when the knit mesh  100  of  FIG. 2  or the woven mesh  200  of  FIG. 3  is used to form the tubular conductive wire mesh  10  of  FIG. 1 , the tubular conductive wire mesh may be configured such that a longitudinal stretching force causes the distance between the segments of the mesh pattern to increase slightly, and causes the free-state length  22  of the tubular conductive wire mesh  10  to increase, and causes the outside diameter  72  and the inside diameter  68  of the tubular conductive wire mesh  10  to both decrease slightly to constricted (smaller) inside and outside diameters. The longitudinal stretching force may be applied by a combination of (a) a first longitudinal force applied at first end  14  vectored away from the second end  18  and (b) a second longitudinal force applied at the second end  18  vectored away from the first end  14 . Such a stretching force may be used to contract the inside diameter of a tubular conductive wire mesh to fit the conductive wire mesh inside a tubular fuel cell electrode having an inside diameter that is less than the minimum envelope diameter of the mesh. Similarly, if such a conductive wire mesh is positioned on the outside of a tubular fuel cell electrode having an outside diameter less than the insertion diameter of the mesh, such a longitudinal tensile force may be used to press the conductive wire mesh against the outside surface of the tubular fuel cell electrode. 
     In a typical example, when applying a longitudinal compressive force that does not cause the longitudinal compressive strength of the tubular conductive wire mesh to be exceeded, the tubular conductive wire mesh is (a) expandable to an expanded inside diameter that is at least one percent larger than the free-state inside diameter and (b) expandable to an expanded outside diameter that is at least one percent larger than the free-state outside diameter. 
       FIG. 4  illustrates an element for a solid state electrochemical device  250 . The element  250  has a tubular fuel cell body  254  that has an interior portion  258  with an inside surface  262  and an inside diameter  266 . A portion of the tubular fuel cell body  254  has been cut away to illustrate that the tubular conductive wire mesh  10  of  FIG. 1  is disposed in the interior portion  258  of the tubular fuel cell body  254 , adjacent the inside surface  262 . The tubular conductive wire mesh  10  can be in electrical contact with tubular fuel cell body  254 , an electrode that is part of the tubular fuel cell body, or both. 
       FIG. 4  is generalized to show only a single layer for the tubular fuel cell body  254 , of the solid state electrochemical device  250 . However, it should be understood that the tubular fuel cell body  254  can include multiple layers, including, but not limited to, porous support members, electrodes, i.e., anodes and cathodes, and dense electrolytes. Furthermore, it should be understood, that the inside surface  262  of the tubular fuel cell body  254  can be the innermost layer of the tubular fuel cell body  254 , e.g., a porous support member or an electrode, such as a porous anode or porous cathode. 
     As used herein, “tubular fuel cell body” is used to refer to the core elements of a tubular fuel cell, such as an anode, a cathode, a dense solid electrolyte disposed between the anode and the cathode, and any porous support tubes, porous metallic layers, or buffer layers. Exemplary fuel cell bodies include, but are not limited to, those shown in  FIGS. 12 &amp; 13 , as well as, the fuel cell bodies shown in U.S. Pat. No. 7,785,747, issued Sep. 31, 2010; U.S. Patent Application Publication No. 2007-0141424 published Jun. 21, 2007; U.S. Pat. No. 7,758,993 issued Jul. 20, 2010; U.S. Patent Application Publication No. 2007-0237998 published Oct. 11, 2007; and U.S. Patent Application Publication No. 2008-0254335 published Oct. 16, 2008, the entireties of which are hereby incorporated by reference. 
     The tubular porous metallic materials, such as support tubes and porous metallic layers, described herein can comprise any porous, sinterable material selected from the group consisting of a non-noble transition metal, metal alloy, and a cermet incorporating one or more of a non-noble transition metal and a non-noble transition metal alloy, preferably a stainless steel, and more preferably a ferritic and/or austenitic stainless steel. Exemplary sinterable materials include Series 300 and 400 stainless steel, including 434L stainless steel powder having a particle size of 25-53 μm. Exemplary support tubes can be of any diameter or length with a wall thickness no greater than about 4 mm, or no greater than 1 mm. In addition, porous support tubes and/or porous metallic layers can have an average pore size in the range of 1 to 30 μm, or 1.5 to 20 μm, or 2 to 15 μm. Moreover, the porous support tubes and/or porous metallic layers should have an average pore volume in the range of 20 to 50 volume percent and should be electrically conductive at all fuel cell operating temperatures. 
     The anode material can be any anode material including a cermet composition. Examples of suitable cermet compositions include, but are not limited to Ni—YSZ, Ni—GdCeO 2 , Ni—SmCeO 2 , and Ag—SmCeO 2 . The anode thickness can be in a range of 5-70 μm, or 5-60 μm, or 5-50 μm, or 5-40 μm. The anode can have an average pore size of 1-20 μm and pore volume of 25-40 volume percent. 
     The dense solid electrolyte can be a non-porous and/or essentially fully dense O 2 -permeable or H 2 -permeable electrolyte composition. Examples of suitable electrolyte compositions include but are not limited to YSZ, GdCeO 2 , SmCeO 2 , LaSrGaMgO 3 , BaCeYO 3 , and La 2 Mo 2 O 9 . The electrolyte can have a thickness in a range of 2-80 μm, or 2-70 μm, or 2-60 μm, or 2-50 μm. The electrolyte should be dense and gas tight to prevent the air and fuel from mixing. 
     The cathode can include an alkaline earth substituted lanthanum manganite, alkaline earth substituted lanthanum ferrite, lanthanum strontium iron cobaltite, or a mixed ionic-electronic conductor. Exemplary cathode materials include doped and undoped oxides or mixtures of oxides in the pervoskite family such as LaMnO 3 , LaNiO 3 , LaCoO 3 , LaCrO 3  and other electronically conducting mixed oxides generally composed of rare earth oxides mixed with oxides of cobalt, nickel, copper, iron, chromium, manganese, and combinations of such oxides. A strontium doped lanthanum manganite material may be used as the cathode material with the preferred cathode material being La 8 Sr 2 MnO 3 . The cathode thickness can be in a range of 5-70 μm, or 5-60 μm, or 5-50 μm, or 5-40 μm. The cathode can have an average pore size of 1-15 μm and pore volume of 25-40 volume percent. 
       FIG. 5  illustrates an element for a solid state electrochemical device  280 . The element  280  has a tubular fuel cell body  284  that has an outside surface  288  and an outside diameter  292 . The tubular conductive wire mesh  10  of  FIG. 1  is disposed adjacent the outside surface  288  of the tubular fuel cell body  284 . 
       FIG. 5  is generalized to show only a single layer for the tubular fuel cell body  284 , of the solid state electrochemical device  280 . However, it should be understood that the tubular fuel cell body  284  can include multiple layers, including, but not limited to, porous support members, electrodes, i.e., anodes and cathodes, and dense electrolytes. Furthermore, it should be understood, that the outside surface  288  of the tubular fuel cell body  284  can be the outsidemost layer of the tubular fuel cell body, e.g., a porous support member or an electrode, such as a porous anode or porous cathode. Exemplary fuel cell bodies include, but are not limited to, those shown in  FIGS. 12 &amp; 13 , as well as, the fuel cell bodies shown in U.S. Pat. No. 7,785,747, issued Sep. 31, 2010; U.S. Patent Application Publication No. 2007-0141424 published Jun. 21, 2007; U.S. Pat. No. 7,758,993 issued Jul. 20, 2010; U.S. Patent Application Publication No. 2007-0237998 published Oct. 11, 2007; and U.S. Patent Application Publication No. 2008-0254335 published Oct. 16, 2008, the entireties of which are hereby incorporated by reference. 
     In fabricating an element for a solid state electrochemical device, the tubular conductive wire mesh typically has a free-state outside diameter that is not more than about five percent larger than a tubular electrode&#39;s inside diameter into which it is inserted and a tubular conductive wire mesh typically has a free-state outside diameter that is not less than about ninety five percent of the outside diameter of a tubular electrode over which it is drawn. 
       FIG. 6  illustrates an assembly operation for fabricating an element for a solid state electrochemical device that includes a tubular fuel cell body  300  having an interior portion  304  with an inside surface  308  and an inside diameter  312 . An inside surface  308  of an exemplary fuel cell body  300  can be a porous support tube, an electrode, such as a porous anode or porous cathode, or any other component of a tubular fuel cell body  300 . A tubular conductive wire mesh  316  having the following characteristics has been selected for this application. The tubular conductive wire mesh  316  has a longitudinal tensile yield strength and a plurality of junctions (such as junctions  144  in  FIG. 2  or junctions  212  in  FIG. 3 ). Preferably the tubular conductive wire mesh  316  is formed with loose segments and has a cylindrical free-state configuration. In the embodiment of  FIG. 6  the tubular conductive wire mesh  316  has been selected to be constrictable to a constricted diameter  320  that is substantially no more than the inside diameter  312  of the tubular fuel cell body  300  by applying to the tubular conductive wire mesh  316  a longitudinal stretching force that is less than the longitudinal tensile yield strength. The longitudinal stretching force may be applied by a first stretcher bar  324  and a second stretcher bar  328  that may be moved apart from each other along a push rod  322  to create the longitudinal stretching force. In some embodiments the constricted diameter  320  may be the free-state diameter of the tubular conductive wire mesh  316 , and in such embodiments the longitudinal stretching force may be substantially zero. A longitudinal stretching force is helpful for inserting the tubular conductive wire mesh  316  into the interior portion  304  of the tubular fuel cell body  300  if the free-state diameter of the tubular conductive wire mesh  316  is greater than or equal to the inside diameter  312  of the tubular fuel cell body  300 . A longitudinal stretching force is generally needed for inserting the tubular conductive wire mesh  316  into the interior portion  304  of the tubular fuel cell body  300  if the maximum envelope diameter of the tubular conductive wire mesh is greater than the inside diameter of the tubular fuel cell body  300  in order to provide a constricted outside diameter  320  of the tubular conductive wire mesh  316  that is constricted to be less than the inside diameter  312  of the tubular fuel cell body  300 . 
     A further useful criterion for selection of a tubular conductive wire mesh  316  is that the conductive wire mesh is expandable to an expanded diameter that is substantially equal to the inside diameter of the tubular fuel cell body  300  by applying a seating force. If the tubular conductive wire mesh  316  has a cylindrical free-state configuration and if the free state diameter of the tubular conductive wire mesh  316  is greater than the inside diameter  312  of the tubular fuel cell body  300  (such that a longitudinal stretching force has been applied to stretch the tubular wire mesh  316  to provide a constricted outside diameter  320  that is less than the inside diameter  312  of the tubular fuel cell body  300 ), then the seating force may be applied by a natural resilience of the tubular conductive wire mesh to return to its free state diameter when the stretching force is removed. 
     A longitudinal assembly pushing force  336  may be applied to the tubular conductive wire mesh to insert the tubular conductive wire mesh  316  into the interior portion  304  of the tubular fuel cell body  300 . After the tubular wire mesh  316  is inserted into the interior portion  304  of the tubular fuel cell body  300 , the longitudinal stretching force may be removed from the tubular conductive wire mesh (if the longitudinal stretching force was applied) and the longitudinal assembly force  336  may be removed from the tubular conductive wire mesh. 
       FIG. 7  illustrates an assembly operation where a pulling assembly force  350  may be used to pull the tubular conductive wire mesh  316  into the interior portion  304  of the tubular fuel cell body  300 . An inside surface  308  of an exemplary fuel cell body  300  can be a porous support tube, an electrode, such as a porous anode or porous cathode, or any other component of a tubular fuel cell body  300 . 
     In embodiments where a tubular conductive wire mesh is installed inside a tubular fuel cell body, e.g., in direct and/or electrical contact with a tubular electrode layer, a seating force may be applied to press the tubular conductive wire mesh against the interior surface of the tubular fuel cell body. The seating force may be applied by a separate seating element or, as previously indicated, the seating force may be applied by a resilience of the tubular conductive wire mesh. The purpose of the seating force is to establish that a substantial portion of the junctions of the tubular conductive wire mesh are disposed in contact with the inside surface of the tubular fuel cell body. After seating, the tubular conductive wire mesh may be bonded to the inside surface of the tubular fuel cell body. Exemplary bonding materials include, but are not limited to, perfluorinated resins, such as those sold by E. I. Du Pont De Nemours and Company (“DuPont”) under the TEFLON mark, and perfluorinated sulfonic acid resins, such as those sold by DuPont under the NAFION mark, those sold by Dow Chemical under the DOW mark, those sold by Asahi Glass under the FLEMION mark, those sold by Asahi Chemical under the ACIPLEX mark, and any suitable perfluorinated sulfonic acid resin substitute. 
       FIG. 8  depicts an element for a solid state electrochemical device  360  and illustrates an example of how a separate seating element, spring  364 , may be used to apply a seating force to a tubular conductive wire mesh  368  that is installed inside a tubular fuel cell body  300 . In practice the spring  364  is a continuous spiral spring and the tubular fuel cell body  300  and the tubular conductive wire mesh  368  are full cylindrical shapes. However, in  FIG. 8  portions of the spring  364  and the tubular fuel cell body  300  and the tubular conductive wire mesh  368  are cut-away to simplify the illustration. The tubular conductive wire mesh  368  is formed with loose segments and has a plurality of junctions  372 . The spring  364  presses the majority or nearly all (e.g., &gt;80%, &gt;90%, &gt;95% or even &gt;99%) of the junctions  372  into contact with the inside surface  308  of the tubular fuel cell body  300 . The inside surface  308  of an exemplary fuel cell body  300  can be a porous support tube, an electrode, such as a porous anode or porous cathode, or any other component of a tubular fuel cell body  300 . 
       FIG. 8  also illustrates an electrical lead wire  376  that is electrically connected to the tubular conductive wire mesh  368  via a first spot weld  380 . In the embodiment of  FIG. 8  the spring  364  is electrically conductive and the spring  364  is in electrical contact with the tubular conductive wire mesh  368 . Furthermore, the electrical lead wire  376  is electrically connected to the spring  364  by a second spot weld  384 . In some embodiments only one of the first spot weld  380  and the second spot weld  384  may be employed. In some embodiments the first spot weld  380  and/or the second spot weld  384  may be replaced with a soldered connection, a brazed connection, or a mechanical connection. The electrical lead wire  376  conducts electrical current to or from the element  360 , depending upon the configuration of the solid state electrochemical device  360 . 
       FIG. 9  depicts an element for a solid state electrochemical device  400  and illustrates how a different seating element (a first plug  404  and a second plug  408 ) may be used to apply a seating force to a tubular conductive wire mesh  368  that is installed inside a tubular fuel cell body  300 . In practice the tubular fuel cell body  300  and the tubular conductive wire mesh  368  are full cylindrical shapes, but in  FIG. 9  portions of the tubular fuel cell  300  and the tubular conductive wire mesh  368  are cut-away to simplify the illustration. The plugs  404  and  408  are sized to be pushed into the tubular fuel cell  300  and engage the tubular conductive wire mesh  368  (which is mesh formed with loose segments and has a plurality of junctions  372 ) with a longitudinal compressive force that expands the diameter of the tubular conductive wire mesh  368  and presses the majority or nearly all (e.g., &gt;80%, &gt;90%, &gt;95% or even &gt;99%) of the junctions  372  of the tubular conductive wire mesh  368  into contact with the inside surface  308  of the tubular fuel cell body  300 .  FIG. 9  also illustrates an electrical lead wire  412  that is electrically connected to the tubular conductive wire mesh  368  via a first spot weld  416 . In the embodiment of  FIG. 9  the first plug  404  is electrically conductive and the first plug  404  is in electrical contact with the tubular conductive wire mesh  368 . Furthermore, the electrical lead wire  412  is electrically connected to the first plug  404  by a second spot weld  420 . In some embodiments only one of the first spot weld  416  and the second spot weld  420  may be employed. In some embodiments the first spot weld  416  and/or the second spot weld  420  may be replaced with a soldered connection, a brazed connection, or a mechanical connection. The electrical lead wire  408  conducts electrical current to or from the solid state electrochemical device  400 , depending upon the configuration of the solid state electrochemical device  400 . 
     In some embodiments the first plug  404  of the solid state electrochemical device  400  of  FIG. 9  is configured as an electrically conductive sleeve that extends beyond the end of the tubular fuel cell body  300 . In such embodiments the first plug  404  (configured as a sleeve extending beyond the end of the tubular fuel cell body  300 ) is used to conduct electrical current to or from the solid state electrochemical device  400 , depending upon the configuration of the solid state electrochemical device  400  in which the tubular fuel cell body  300  is employed. The electrical wire leads  376  (of  FIG. 8) and 412  (of  FIG. 9 ) and the first plug  404  (of  FIG. 9 ) when configured as an electrically conducive sleeve that extends beyond the end of the tubular fuel cell body  300  are examples of electrical terminals that may be used to establish an electrical connection to the tubular wire mesh  368  to conduct electrical current to or from the solid state electrochemical device  360  ( FIG. 8 ) or  400  ( FIG. 9 ), depending upon the configuration of the solid state electrochemical device in which the solid state electrochemical device ( 360  or  400 ) is employed. In some embodiments a portion of the tubular wire mesh  368  may comprise an electrical terminal connection for establishing an electrical connection to the tubular wire mesh  368  to conduct electrical current to or from the solid state electrochemical device  360  or  400 . In such embodiments the portion of the tubular wire mesh  368  that comprises the electrical terminal connection typically extends beyond an end of the solid state electrochemical device  360  or  400 . 
       FIGS. 6-9  are generalized to show only a single layer for the tubular fuel cell body  300 , of the solid state electrochemical device. However, it should be understood that the tubular fuel cell body  300  can include multiple layers, including, but not limited to, porous support members, electrodes, i.e., anodes and cathodes, and dense electrolytes. Furthermore, it should be understood, that the inner surface  308  of the tubular fuel cell body  300  can be the innermost layer of the tubular fuel cell body, e.g., a porous support member or an electrode, such as a porous anode or porous cathode. Exemplary fuel cell bodies include, but are not limited to, those shown in  FIGS. 12 &amp; 13 , as well as, the fuel cell bodies shown in U.S. Pat. No. 7,785,747, issued Sep. 31, 2010; U.S. Patent Application Publication No. 2007-0141424 published Jun. 21, 2007; U.S. Pat. No. 7,758,993 issued Jul. 20, 2010; U.S. Patent Application Publication No. 2007-0237998 published Oct. 11, 2007; and U.S. Patent Application Publication No. 2008-0254335 published Oct. 16, 2008, the entireties of which are hereby incorporated by reference. 
     Other embodiments include methods for fabricating an element for a solid state electrochemical device  500  that incorporates a tubular fuel cell body  520  having an outside surface  516 . In such methods a tubular conductive wire mesh  512  may be selected where the mesh has a longitudinal compressive yield strength, a maximum insertion diameter, and a plurality of junctions. The mesh may be further selected such that the tubular conductive wire mesh  512  (i) is expandable to an expanded diameter that is greater than the outside diameter of the tubular fuel cell body  520  by applying a longitudinal compressive force to the tubular conductive wire mesh that is less than the longitudinal compressive yield strength and (ii) is contractible to a contracted diameter that is substantially equal to the outside diameter of the tubular fuel cell body  520  by applying a, seating force. Generally in such embodiments, if the maximum insertion diameter of the tubular wire mesh  512  is less than the outside diameter of the tubular fuel cell body  520 , then the longitudinal-compressive force is applied to the tubular conductive wire mesh in order to expand the inside diameter of the tubular wire mesh. The mesh  512  may be assembled over the outside surface  516  of the tubular fuel cell body  520  by applying a longitudinal assembly force to the tubular conductive wire mesh  512 . If the longitudinal compressive force was applied, then a further step is removing the longitudinal compressive force from the tubular conductive wire mesh  512 . Generally the method further includes applying a seating force to the tubular conductive wire mesh  512 , wherein the majority or nearly all (e.g., &gt;80%, &gt;90%, &gt;95% or even &gt;99%) of the junctions  508  of the tubular conductive wire mesh  512  are disposed in contact with the outside surface  516  of the tubular fuel cell body  520 . After seating, the tubular conductive wire mesh  512  may be bonded to the outside surface  516  of the tubular fuel cell body  520 . Exemplary bonding materials include, but are not limited to, perfluorinated resins and perfluorinated sulfonic acid resins. 
     In embodiments where a tubular conductive wire mesh  512  is installed over the outside surface  516  of a tubular fuel cell body  520 , such as depicted with solid state electrochemical device  500  in  FIG. 10  or solid state electrochemical device  540  of  FIG. 11 , a seating force may be applied to press the tubular conductive wire mesh  512  against the outside surface  516  of the tubular fuel cell body  520 . In  FIG. 10  the seating force is applied by a separate seating element, a spring  504 , which compresses a plurality of junctions  508  of a tubular conductive wire mesh  512  against the outside surface  516  of a tubular fuel cell body  520 . An electrical lead wire  524  is electrically connected to the tubular conductive wire mesh  512  and to the spring  504  in a manner analogous to the connection of the electrical wire lead  376  to the tubular conductive mesh  368  and spring  364  of  FIG. 8 . 
     In  FIG. 11  a first ring  544  and a second ring  548  apply opposing longitudinal forces to the tubular conductive wire mesh  508  to stretch the tubular conductive wire mesh  508  taut against the outside surface  516  of the tubular fuel cell body  520 . The opposing longitudinal forces provided by the two rings  544  and  548  are generated by longitudinally stretching the tubular conductive wire mesh  512  over the outside surface  516  of the tubular fuel cell body  520  to a length greater than its free-state length and then applying the two rings  544  and  548  over the tubular conductive wire mesh  512  to maintain the tubular wire mesh  512  in the stretched position and prevent the tubular wire mesh  512  from contracting back to its free-state length. Alternately, the seating force for the tubular conductive wire mesh  512  of  FIG. 10  or  FIG. 11  may be applied by a resilience of the tubular conductive wire mesh  512 . The purpose of the seating force is to establish that the majority or nearly all of the junctions  508  of the tubular conductive wire mesh  512  contact the outside surface  516  of the tubular fuel cell body  520 .  FIG. 11  also illustrates an electrical lead wire  560  that is electrically connected to the tubular conductive wire mesh  512  and to the first ring  544  in a manner analogous to the connection of the electrical wire lead  412  to the tubular conductive wire mesh  368  and the first plug  404  of  FIG. 9 . 
     In some embodiments the first ring  544  of the solid state electrochemical device  540  of  FIG. 11  is used to conduct electrical current to or from the element  400 , depending upon the configuration of the solid state electrochemical device in which the element  400  is employed. The electrical wire lead  524  (of  FIG. 10 ) and the first ring  544  (of  FIG. 11 ) are examples of electrical terminals that may be used to conduct electrical current to or from the element  360  ( FIG. 8 ) or  400  ( FIG. 9 ), depending upon the configuration of the solid state electrochemical device in which the element ( 500  or  540 ) is employed. 
       FIGS. 10 &amp; 11  are generalized to show only a single layer for the tubular fuel cell body  520 , of the solid state electrochemical device  500  and  540  for  FIGS. 10 &amp; 11 , respectively. However, it should be understood that the tubular fuel cell body  520  can include multiple layers, including, but not limited to, porous support members, electrodes, i.e., anodes and cathodes, and dense electrolytes. Furthermore, it should be understood, that the outside surface  516  of the tubular fuel cell body  520  can be the outsidemost layer of the tubular fuel cell body, e.g., a porous support member or an electrode, such as a porous anode or porous cathode. Exemplary fuel cell bodies include, but are not limited to, those shown in  FIGS. 12 &amp; 13 , as well as, the fuel cell bodies shown in U.S. Pat. No. 7,785,747, issued Sep. 31, 2010; U.S. Patent Application Publication No. 2007-0141424 published Jun. 21, 2007; U.S. Pat. No. 7,758,993 issued Jul. 20, 2010; U.S. Patent Application Publication No. 2007-0237998 published Oct. 11, 2007; and U.S. Patent Application Publication No. 2008-0254335 published Oct. 16, 2008, the entireties of which are hereby incorporated by reference. 
       FIG. 12  shows details of an exemplary layered structure that may be present in the tubular fuel cell bodies shown in  FIGS. 4-11 . The tubular fuel cell body  1  of  FIG. 12  includes a porous, sintered metallic support tube  2 , a first porous electrode  3  (cathode or anode), a dense electrolyte layer  4 , a second porous electrode  5  (anode or cathode), and a second porous, sintered tubular member  6 . The potential compositions and properties of these layers can be found herein and in U.S. Patent Application Publication No. 2008/0254335 published Oct. 16, 2008. 
       FIG. 13  shows details of another exemplary layered structure that may be present in the tubular fuel cell bodies shown in  FIGS. 4-11 . The tubular fuel cell body  10  of  FIG. 13  includes a porous, sintered metallic support tube  11 , a first porous electrode  12  (cathode or anode), a dense electrolyte layer  13  and a second porous electrode  14  (anode or cathode). The potential compositions and properties of these layers can be found herein and in U.S. Patent Application Publication No. 2007/0237998 published Oct. 11, 2007. 
     EXAMPLE 
     A sample fuel cell conductive wire mesh was fabricated in the knit mesh pattern of  FIG. 2  using a wire knitting device that is available from ACS Industries, Inc., 1 New England Way, Lincoln, R.I. 02865. The knit mesh had the following configuration (with all dimensions in inches). 
     Wire Diameter: 0.010 
     Number of Loops in circumference: 22 
     Maximum pitch angle: 25° 
     Loop aspect ratio: 2 
     Elliptical aspect ratio: 1.2 
     The fuel cell conductive wire mesh had the following properties: 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                   
                   
               
               
                   
                 Free- 
                 Compressed 
                   
                 % 
                 Stretched 
                   
                 % 
               
               
                   
                 state 
                 State 
                 Difference 
                 Change 
                 State 
                 Difference 
                 Change 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Length 
                 1.35 
                 1.01 
                 0.34 
                 25% 
                 1.48 
                 0.13 
                 10% 
               
               
                 Outside 
                 0.37 
                 0.38 
                 0.01 
                 3% 
                 0.37 
                 0 
                 0% 
               
               
                 Diameter at 
               
               
                 Junctions 
               
               
                 Inside 
                 0.35 
                 0.36 
                 0.01 
                 3% 
                 0.35 
                 0 
                 0% 
               
               
                 Diameter at 
               
               
                 Junctions 
               
               
                   
               
            
           
         
       
     
     In summary, embodiments disclosed herein provide various tubular conductive wire mesh configurations and methods for assembling tubular conductive wire meshes with tubular electrodes. The foregoing descriptions of embodiments have been presented for purposes of illustration and exposition. They are not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of principles and practical applications, and to thereby enable one of ordinary skill in the art to utilize the various embodiments as described and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.