Abstract:
A system and associated methods for the fabrication and evaluation of an array of electrode or electrolyte materials for use in a solid oxide fuel cell, the system including a material handling device operable for individually containing a plurality of materials, a mixing device operable for mixing the plurality of materials to form a plurality of combinations of the plurality of materials, and a material delivery device operable for delivering a predetermined one of the plurality of combinations of the plurality of materials to each of a plurality of regions of a substrate, wherein the plurality of regions of the substrate form an array. The system also including a temperature control device operable for heating the array, thereby sintering the array. The system further including one or more sampling mechanisms operable for gathering performance data from each of the plurality of regions of the substrate and a testing device operably coupled to the one or more sampling mechanisms, wherein the testing device is operable for receiving the performance data associated with each of the plurality of regions of the substrate and evaluating the relative performance of each of the plurality of regions of the substrate.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to solid oxide fuel cells and associated large-scale power generation, distributed power, and vehicular applications. More specifically, the present invention relates to systems and methods for the fabrication and evaluation of arrays of electrode and electrolyte materials for use in solid oxide fuel cells.  
         BACKGROUND OF THE INVENTION  
         [0002]    A solid oxide fuel cell (“SOFC”) is an electrochemical device that may be used in, for example, large-scale power generation, distributed power, and vehicular applications. One of the key challenges in developing a SOFC is developing high-performance electrode and electrolyte materials that meet SOFC performance and cost requirements. While there are lists of potential candidate materials for both electrodes and electrolytes, significant efforts are required to optimize material combinations, chemical compositions, processing conditions, and the like. This is especially true as the vast majority of such potential candidate materials are either ternary or quaternary-based.  
           [0003]    For example, yttria-stabilized zirconia (“YSZ”) is commonly used as an electrolyte material in SOFCs. However, electrolyte performance is relatively sensitive to the ratio of Y to Zr, and this component ratio must be carefully optimized. The same is true with respect to other potential candidate materials for electrolytes, including Sr-doped CeO2, CGO, and the like. Electrode material composition is also critical to the performance of a SOFC. For example, the composition of LaxSr1xMnO (3) (“LSM”), a common cathode material, may greatly affect its electrical conductivity and electrochemical activity.  
           [0004]    Typically, a plurality of combinations of elements or components with varying chemical compositions are individually formulated and tested in order to achieve optimal performance for electrode and electrolyte materials, a relatively slow, labor-intensive, and costly process. Thus, what is needed are high-throughput systems and methods that make SOFC-related materials development more efficient.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    The present invention provides systems and methods that use a combinatorial electrochemistry approach to achieve the high-throughput fabrication and evaluation of arrays of electrode and electrolyte materials for use in solid oxide fuel cells (“SOFCs”). Advantageously, the present invention provides systems and methods that allow for the design of arrays of insulated electrodes, the preparation of electrode and electrolyte samples with controlled material compositions, and the multi-channel testing of those samples.  
           [0006]    In one embodiment of the present invention, a system for the fabrication and evaluation of an array of electrode or electrolyte materials for use in a solid oxide fuel cell includes a material handling device operable for individually containing a plurality of materials; a mixing device operable for mixing the plurality of materials to form a plurality of combinations of the plurality of materials; a material delivery device operable for delivering a predetermined one of the plurality of combinations of the plurality of materials to each of a plurality of regions of a substrate, wherein the plurality of regions of the substrate form an array; a temperature control device operable for heating the array, thereby sintering the array; one or more sampling mechanisms operable for gathering performance data from each of the plurality of regions of the substrate; and a testing device operably coupled to the one or more sampling mechanisms, wherein the testing device is operable for receiving the performance data associated with each of the plurality of regions of the substrate and evaluating the relative performance of each of the plurality of regions of the substrate.  
           [0007]    In another embodiment of the present invention, a method for the fabrication and evaluation of an array of electrode or electrolyte materials for use in a solid oxide fuel cell includes individually containing a plurality of materials; mixing the plurality of materials to form a plurality of combinations of the plurality of materials; delivering a predetermined one of the plurality of combinations of the plurality of materials to each of a plurality of regions of a substrate, wherein the plurality of regions of the substrate form an array; heating the array, thereby sintering the array; gathering performance data from each of the plurality of regions of the substrate; and receiving the performance data associated with each of the plurality of regions of the substrate and evaluating the relative performance of each of the plurality of regions of the substrate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a schematic diagram of one embodiment of a system for the fabrication of an array of electrode or electrolyte materials for use in solid oxide fuel cells (“SOFCs”);  
         [0009]    [0009]FIG. 2 is a schematic diagram of one embodiment of a system for the evaluation of an array of electrode or electrolyte materials for use in SOFCs; and  
         [0010]    [0010]FIG. 3 is a flow chart of one embodiment of a method for the fabrication and evaluation of an array of electrode or electrolyte materials for use in SOFCs. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]    The present invention provides systems and methods that use a combinatorial electrochemistry approach to achieve the high-throughput fabrication and evaluation of arrays of electrode and electrolyte materials for use in solid oxide fuel cells (“SOFCs”). The present invention provides systems and methods that allow for the design of arrays of insulated electrodes, the preparation of electrode and electrolyte samples with controlled material compositions, and the multi-channel testing of those samples.  
         [0012]    Referring to FIG. 1, in one embodiment of the present invention, a system  10  for the fabrication of an array of electrode or electrolyte materials for use in SOFCs includes a plurality of materials  12  (materials A, B, and C are shown) suitable for delivery to the surface of a substrate  14 . The plurality of materials  12  may form a coating  16  on the surface of the substrate  14  or, alternatively, they may infiltrate the substrate  14 , forming an array  18  of electrode or electrolyte materials suitable for evaluation. The plurality of materials  12  may form the array  18  of electrode or electrolyte materials by selectively altering the chemical composition and/or physical microstructure of each of a plurality of regions  20  of the substrate  14 . Thus, the plurality of materials  12  may form, for example, a discrete array of electrode materials separated by electrolyte material, a continuous array of electrode materials, a discrete array of electrolyte materials, a continuous array of electrolyte materials, or any combination thereof. Optionally, the electrode material(s) and the electrolyte material(s) may be integrally formed with the substrate  14 . Each of the plurality of regions  20  of the substrate  14  may be between about 1 mm and about 1 cm in height/width  22 , although other suitable dimensions may be utilized.  
         [0013]    The plurality of materials  12  may include, for example, a plurality of materials suitable for providing predetermined metal ions or combinations of metal ions to the surface of the substrate  14 , such as metal oxides, metal carbonates, and the like (transition metals, rare earths, alkaline metals, alkaline earth metals, oxides, mixtures of oxides, and mixtures of metals). The substrate  14  may be an electrode material, an electrolyte material, or a sacrificial material. The substrate  14  may be porous or dense yttria-stabilized zirconia (“YSZ”), a green ceramic or polymer, or the like. For the evaluation of electrode materials for use in SOFCs, a Fe—Cr alloy or a conductive ceramic or metal, such as LaCrO3 or platinum, may be used for the array electrodes. For the evaluation of electrolyte materials for use in SOFCs, a conductive material or metal, such as a LaxSr1-xMnO (3) (“LSM”)-coated Fe—Cr alloy, LaCrO3, or platinum, may be used for the counter-electrode. Other suitable materials known to those of ordinary skill in the art may also be used for both the array electrodes, the array electrolytes, and the counter-electrodes. The plurality of materials  12  may further include binders and/or carrier materials to enhance the coating and/or infiltrating processes.  
         [0014]    Prior to being delivered to the surface of the substrate  14 , the plurality of materials  12 , or precursor components, are mixed using a mixing device  24 . The mixing device  24  may include a mixing-T, one or more tubes incorporating one or more baffles, a variable-speed rotary mixer, a screw mixer, a sonic mixer, or the like. The plurality of materials  12  are delivered to the surface of the substrate  14  using a delivery device  26  and, optionally, a masking device (not shown). The delivery device  26  may include, for example, a syringe, a pipette, a micro-dispenser, a liquid coating device, a spin coating device, a dip coating device, an elongate coating head, a powder coating device, a vapor coating device, an infiltration device, or any other dispensing or coating device known to those of ordinary skill in the art. Preferably, the delivery device  26  is movable relative to the surface of the substrate  14 , either via movement of the delivery device  26  or via movement of the substrate  14  (such as through the use of a movable stage (not shown) or the like). Thus, predetermined combinations of the plurality of materials  12  may be selectively delivered to predetermined regions  20  of the substrate. These predetermined combinations of the plurality of materials  12  may be formed by selectively controlling the flow rates of each of the plurality of materials  12  to the mixing device  24  and/or the delivery device  26 . Thus, the predetermined combinations of the plurality of materials  12  may vary discretely or continuously as a function of substrate position.  
         [0015]    The system  10  for the fabrication of an array of electrode or electrolyte materials for use in SOFCs may also include a temperature control device  28  for heating the array  18  of electrode or electrolyte materials, thereby sintering the array  18  of electrode or electrolyte materials to remove any binders and/or carrier materials prior to SOFC assembly and evaluation.  
         [0016]    The system  10  for the fabrication of an array of electrode or electrolyte materials for use in SOFCs may further include a counter-electrode  30  disposed adjacent to the substrate  14  (i.e., the electrolyte or array of electrolytes) and the electrode or array of electrodes, allowing for the combinatorial evaluation of an array of SOFCs. For example, the counter-electrode  30  may consist of an anode disposed adjacent to the electrolyte, the electrolyte disposed between the anode and an array of electrodes consisting of an array of cathodes.  
         [0017]    Referring to FIG. 2, in another embodiment of the present invention, a system  40  for the evaluation of an array of electrode or electrolyte materials for use in SOFCs includes the substrate  14 , the coating  16  or infiltration layer (not shown), and the counter-electrode  30  described above, the substrate  14  and the coating  16  or infiltration layer forming the array  18  of electrode or electrolyte materials (or the array  18  of SOFCs in combination with the counter-electrode  30 ).  
         [0018]    Preferably, the system  40  for the evaluation of an array of electrode or electrolyte materials for use in SOFCs also includes a testing device  42  operably coupled to each of the plurality of regions  20  of the substrate  14  (i.e., members of the array  18 ) via one or more leads, probes, sensors, or the like, referred to herein as one or more sampling mechanisms  44 . The testing device  42  gathers data from the one or more sampling mechanisms  42  and, optionally, in combination with a computer  46 , evaluates and compares the relative performance of each member of the array  18 . The testing device  42  and the computer  46  may comprise a multi-channel electrochemical workstation capable of sampling each member of the array  18  in series or in parallel. For the evaluation of electrode materials for use in SOFCs, electrical resistance, potential, current or the like may be measured, evaluated, and compared. For example, potential may be measured using a current approach. Current may be measured using a constant-voltage approach. For the evaluation of electrolyte materials for use in SOFCs, ionic resistance, open circuit voltage, or the like may be measured, evaluated, and compared using an alternating-current (“AC”) impedance analyzer, a potentiastat, or the like. Preferably, with respect to the measurement of ionic resistance, it is measured using electrochemical impedance spectroscopy at a single frequency. Other measurement, evaluation, and comparison tools and techniques related to the performance of electrodes, electrolytes, and SOFCs are known to those of ordinary skill in the art and may be implemented in conjunction with the systems and methods of the present invention. Such tools and techniques may also be implemented in conjunction with an environmental control device  48  operable for isolating the array  18  of electrodes, electrolytes, or SOFCs from the surrounding environment.  
         [0019]    Referring to FIG. 3, in a further embodiment of the present invention, a method  50  for the fabrication and evaluation of an array of electrode or electrolyte materials for use in SOFCs includes providing a plurality of materials suitable for delivery to the surface of a substrate. (Block  52 ). As described above, the plurality of materials may form a coating on the surface of the substrate or, alternatively, they may infiltrate the substrate, forming an array of electrode or electrolyte materials suitable for evaluation. (See Blocks  62  and  64 ). The plurality of materials may form the array of electrode or electrolyte materials by selectively altering the chemical composition and/or physical microstructure of each of a plurality of regions of the substrate. Thus, the plurality of materials may form, for example, a discrete array of electrode materials separated by electrolyte material, a continuous array of electrode materials, a discrete array of electrolyte materials, a continuous array of electrolyte materials, or any combination thereof. The method  50  may also include providing a plurality of binders and/or carrier materials to enhance the coating and/or infiltrating processes. (Block  54 ).  
         [0020]    Prior to being delivered to the surface of the substrate, the plurality of materials, or precursor components, are mixed using a mixing device. (Block  56 ). As described above, the mixing device may include a mixing-T, one or more tubes incorporating one or more baffles, a variable-speed rotary mixer, a screw mixer, a sonic mixer, or the like. The plurality of materials are then delivered to the surface of the substrate using a delivery device and, optionally, a masking device. (Block  58 ). As described above, the delivery device may include, for example, a syringe, a pipette, a micro-dispenser, a liquid coating device, a spin coating device, a dip coating device, an elongate coating head, a powder coating device, a vapor coating device, an infiltration device, or any other dispensing or coating device known to those of ordinary skill in the art. Preferably, the delivery device is movable relative to the surface of the substrate, either via movement of the delivery device or via movement of the substrate (such as through the use of a movable stage or the like). (Block  60 ). Thus, predetermined combinations of the plurality of materials may be selectively delivered to predetermined regions of the substrate. These predetermined combinations of the plurality of materials may be formed by selectively controlling the flow rates of each of the plurality of materials to the mixing device and/or the delivery device. Thus, the predetermined combinations of the plurality of materials may vary discretely or continuously as a function of substrate position.  
         [0021]    As described above, the system for the fabrication of an array of electrode or electrolyte materials for use in SOFCs may also include a temperature control device for heating the array of electrode or electrolyte materials, thereby sintering the array of electrode or electrolyte materials to remove any binders and/or carrier materials prior to SOFC assembly and evaluation. (Blocks  65  and  67 ).  
         [0022]    The method  50  for the fabrication and evaluation of an array of electrode or electrolyte materials for use in SOFCs may further include attaching a counter-electrode to the substrate (i.e., the electrolyte or array of electrolytes) and the electrode or array of electrodes, allowing for the combinatorial evaluation of an array of SOFCs. (Block  66 ). As described above, the counter-electrode may consist of an anode disposed adjacent to the electrolyte, the electrolyte disposed between the anode and an array of electrodes consisting of an array of cathodes.  
         [0023]    In another embodiment of the present invention, the method  50  for the fabrication and evaluation of an array of electrode or electrolyte materials for use in SOFCs includes operably coupling a testing device to each of the plurality of regions of the substrate (i.e., members of the array) via one or more leads, probes, sensors, or the like, referred to herein as one or more sampling mechanisms. The testing device gathers data from the one or more sampling mechanisms and, optionally, in combination with a computer, evaluates and compares the relative performance of each member of the array. (Block  68 ) As described above, the testing device and the computer may comprise a multi-channel electrochemical workstation capable of sampling each member of the array in series or in parallel. For the evaluation of electrode materials for use in SOFCs, electrical resistance, ionic resistance, potential, current, or the like may be measured, evaluated, and compared. For example, potential may be measured using a constant-current approach. Current may be measured using a constant-voltage approach. For the evaluation of electrolyte materials for use in SOFCs, ionic resistance, open circuit voltage, or the like may be measured, evaluated, and compared using an AC impedance analyzer, a potentiastat, or the like. Preferably, with respect to the measurement of ionic resistance, it is measured using electrochemical impedance spectroscopy at a single frequency or multiple frequencies. Other measurement, evaluation, and comparison tools and techniques related to the performance of electrodes, electrolytes, and SOFCs are known to those of ordinary skill in the art and may be implemented in conjunction with the systems and methods of the present invention. Such tools and techniques may also be implemented in conjunction with an environmental control device operable for isolating the array of electrodes, electrolytes, or SOFCs from the surrounding environment.  
         [0024]    It is apparent that there have been provided, in accordance with the systems and methods of the present invention, high-throughput techniques for the fabrication and evaluation of arrays of electrode and electrolyte materials for use in solid oxide fuel cells. Although the systems and methods of the present invention have been described with reference to preferred embodiments and examples thereof, other embodiments and examples may perform similar functions and/or achieve similar results. All such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the following claims.