Patent Publication Number: US-2011070526-A1

Title: Fuel cell

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority of Taiwan Patent Application No. 098131901, filed on Sep. 22, 2009, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a fuel cell, and more particularly to a fuel cell that effectively prevents leakage and mixing of fuel and oxygen therein. 
     2. Description of the Related Art 
     Fuel cells employ fuel, such as methanol or hydrogen, and oxygen to generate electricity. To enable an electrochemical reaction in a fuel cell, fuel and oxygen are respectively transported into the fuel cell via proper passages. Here, the structure of the passages must prevent the fuel and oxygen from leaking and mixing with each other, such that good operational efficiency can be maintained and required operational safety can be ensured. 
     A conventional fuel cell often comprises a plurality of cell units. Each cell unit comprises a membrane electrode assembly (MEA) having a proton exchange membrane, an anode catalyst layer, and a cathode catalyst layer. 
     Proper gas passages are formed in the fuel cell for transporting the fuel and oxygen thereinto, enabling the electrochemical reaction (or a redox reaction). For example, for a fuel cell employing methanol (CH 3 OH) as fuel, the methanol and oxygen are respectively transported to an anode reaction side and a cathode reaction side of each membrane electrode assembly, performing the redox reaction. Here, the redox reaction at the anode reaction side and cathode reaction side is as follows. 
     At the anode reaction side: CH 3 OH+H 2 O CO 2 +6H + +6e −   
     At the cathode reaction side: 3/2O 2 +6H + +6e − 3H 2 O 
     Accordingly, to provide an airtight effect among the gas passages of the fuel cell, a gasket is disposed between two adjacent members, preventing the fuel and oxygen from leaking and mixing with each other. 
     Referring to  FIG. 1 , a conventional fuel cell  1  comprises a first oppressive collector board  11 , a second oppressive collector board  12 , a first mono-sided channel plate  21 , a second mono-sided channel plate  22 , a plurality of double-sided channel plates  30 , a plurality of membrane electrode assemblies  40 , and a plurality of gaskets  50 . The first mono-sided channel plate  21  and second mono-sided channel plate  22  respectively abut the first oppressive collector board  11  and second oppressive collector board  12 . The gaskets  50  are respectively attached between the first mono-sided channel plate  21  and the membrane electrode assembly  40 , between the membrane electrode assembly  40  and the double-sided channel plate  30 , and between the membrane electrode assembly  40  and the second mono-sided channel plate  22  by soft or rigid washers with glue. The first oppressive collector board  11  is opposite the second oppressive collector board  12 . The first mono-sided channel plate  21 , second mono-sided channel plate  22 , double-sided channel plates  30 , membrane electrode assemblies  40 , and gaskets  50  are fixed by the first oppressive collector board  11  and second oppressive collector board  12 . 
     Moreover, the first oppressive collector board  11  comprises an anode inlet  11   a , an anode outlet  11   b , a cathode inlet  11   c , and a cathode outlet  11   d . Here, the methanol (CH 3 OH) enters the fuel cell  1  via the anode inlet  11   a  and flows to the anode reaction sides  41  of the membrane electrode assemblies  40  through the first mono-sided channel plate  21  and double-sided channel plates  30  (as shown in  FIG. 2 ). Here, the flow direction of the methanol is indicated by arrows A shown in  FIG. 2 . The methanol then leaves the fuel cell  1  via the anode outlet  11   b . In another aspect, the oxygen enters the fuel cell  1  via the cathode inlet  11   c  and flows to the cathode reaction sides  42  of the membrane electrode assemblies  40  through the double-sided channel plates  30  and second mono-sided channel plate  22  (as shown in  FIG. 2 ). Here, the flow direction of the oxygen is indicated by arrows B shown in  FIG. 2 . The oxygen then leaves the fuel cell  1  via the cathode outlet  11   d.    
     Accordingly, by separation of the gaskets  50  attached between the first mono-sided channel plate  21  and the membrane electrode assembly  40 , between the membrane electrode assembly  40  and the double-sided channel plate  30 , and between the membrane electrode assembly  40  and the second mono-sided channel plate  22 , the methanol supposed to flow to the anode reaction sides  41  of the membrane electrode assemblies  40  does not leak to the cathode reaction sides  42  of the membrane electrode assemblies  40  while the oxygen supposed to flow to the cathode reaction sides  42  of the membrane electrode assemblies  40  does not leak to the anode reaction sides  41  of the membrane electrode assemblies  40 , thereby preventing mixing of the methanol and oxygen. 
     Nevertheless, when the fuel cell  1  is subjected to a non-uniform fastening force during assembly thereof or is subjected to external impact, deflection or deformation often occurs to the soft gaskets  50 , as shown in  FIG. 3 . At this point, the deflected or deformed gaskets  50  can no longer provide proper separation between the first mono-sided channel plate  21  and the membrane electrode assembly  40 , between the membrane electrode assembly  40  and the double-sided channel plate  30 , and between the membrane electrode assembly  40  and the second mono-sided channel plate  22 . Accordingly, when the methanol and oxygen enter the fuel cell  1  respectively via the anode inlet  11   a  and cathode inlet  11   c , the methanol, flowing to the anode reaction sides  41 , leaks to the cathode reaction sides  42  (as indicated by arrows A′) and the oxygen, flowing to the cathode reaction sides  42 , leaks to the anode reaction sides  41  (as indicated by arrows B′), causing mixing of the methanol and oxygen. Thus, the operational efficiency and safety of the fuel cell  1  are adversely affected. 
     Hence, there is a need for a fuel cell with rigid hydrophilic gaskets that can provide airtight functions without application by using glue, preventing leakage and mixing of fuel and oxygen therein. 
     BRIEF SUMMARY OF THE INVENTION 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     An exemplary embodiment of the invention provides a fuel cell comprising a first mono-sided channel plate, at least one double-sided channel plate, a second mono-sided channel plate, a plurality of membrane electrode assemblies, and a plurality of rigid hydrophilic gaskets. The double-sided channel plate comprises a first side channel and a second side channel opposite and separated from the first side channel. The membrane electrode assemblies are respectively disposed between the first mono-sided channel plate and the double-sided channel plate and between the double-sided channel plate and the second mono-sided channel plate. The membrane electrode assemblies comprise a plurality of anode reaction sides and a plurality of cathode reaction sides. The anode reaction sides respectively connect to a channel of the first mono-sided channel plate and the second side channel of the double-sided channel plate. The cathode reaction sides respectively connect to the first side channel of the double-sided channel plate and a channel of the second mono-sided channel plate. The rigid hydrophilic gaskets are respectively abutted between the first mono-sided channel plate and the anode reaction side of one of the membrane electrode assemblies, between the cathode reaction side of one of the membrane electrode assemblies and the first side channel of the double-sided channel plate, between the second side channel of the double-sided channel plate and the anode reaction side of one of the membrane electrode assemblies, and between the cathode reaction side of one of the membrane electrode assemblies and the second mono-sided channel plate. 
     The rigid hydrophilic gaskets are subjected to a plasma treatment to provide a plurality of polar groups. The rigid hydrophilic gaskets are attached to the first mono-sided channel plate, the anode reaction sides of the membrane electrode assemblies, the cathode reaction sides of the membrane electrode assemblies, the double-sided channel plate, and the second mono-sided channel plate by the polar groups and water. 
     The rigid hydrophilic gaskets are subjected to a corona treatment to provide a plurality of polar groups. The rigid hydrophilic gaskets are attached to the first mono-sided channel plate, the anode reaction sides of the membrane electrode assemblies, the cathode reaction sides of the membrane electrode assemblies, the double-sided channel plate, and the second mono-sided channel plate by the polar groups and water. 
     The hardness value of the rigid hydrophilic gaskets exceeds Rockwell hardness 50. 
     The fuel cell further comprises a first oppressive collector board and a second oppressive collector board. The first oppressive collector board opposes the second oppressive collector board and comprises an anode inlet and a cathode inlet. The anode inlet connects to the channel of the first mono-sided channel plate and the second side channel of the double-sided channel plate. The cathode inlet connects to the first side channel of the double-sided channel plate and the channel of the second mono-sided channel plate. 
     The first mono-sided channel plate, double-sided channel plate, and second mono-sided channel plate comprise graphite, metal, plastic, epoxy resin, macromolecular polymer, glass epoxy-group resin, or glass-reinforced macromolecular material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a schematic perspective view of a conventional fuel cell; 
         FIG. 2  is a schematic partial cross section of the conventional fuel cell in a normal operational status; 
         FIG. 3  is a schematic partial cross section of the conventional fuel cell in an abnormal operational status; 
         FIG. 4  is a schematic perspective view of a fuel cell of the invention; 
         FIG. 5  is a schematic partial cross section of the fuel cell of the invention; and 
         FIG. 6  is a schematic plane view of a partial structure of the fuel cell of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
     Referring to  FIG. 4 , a fuel cell  100  comprises a first oppressive collector board  111 , a second oppressive collector board  112 , a first mono-sided channel plate  121 , a second mono-sided channel plate  122 , a plurality of double-sided channel plates  130 , a plurality of membrane electrode assemblies  140 , and a plurality of rigid hydrophilic gaskets  150 . 
     The first oppressive collector board  111  opposes the second oppressive collector board  112  and comprises an anode inlet  111   a , an anode outlet  111   b , a cathode inlet  111   c , and a cathode outlet  111   d.    
     As shown in  FIG. 4  and  FIG. 5 , the first mono-sided channel plate  121  and second mono-sided channel plate  122  abut the first oppressive collector board  111  and second oppressive collector board  112 , respectively. Here, the first mono-sided channel plate  121  and second mono-sided channel plate  122  are respectively formed with a (curved) channel  121   a  and a (curved) channel  122   a.    
     Each double-sided channel plate  130  comprises a first side (curved) channel  131  and a second side (curved) channel  132  opposite and separated from the first side channel  131 , as shown in  FIG. 5 . Moreover, the first mono-sided channel plate  121 , double-sided channel plates  130 , and second mono-sided channel plate  122  may be composed of graphite, metal, plastic, epoxy resin, macromolecular polymer, glass epoxy-group resin, or glass-reinforced macromolecular material. 
     The membrane electrode assemblies  140  are respectively disposed between the first mono-sided channel plate  121  and the double-sided channel plate  130 , between the double-sided channel plates  130 , and between the double-sided channel plate  130  and the second mono-sided channel plate  122 . Moreover, each membrane electrode assembly  140  comprises an anode reaction side  141  and a cathode reaction side  142 . Here, as shown in  FIG. 5 , the anode reaction sides  141  respectively connect to the channel  121   a  of the first mono-sided channel plate  121  and the second side channels  132  of the double-sided channel plates  130 , and the cathode reaction sides  142  respectively connect to the first side channels  131  of the double-sided channel plates  130  and the channel  122   a  of the second mono-sided channel plate  122 . 
     The rigid hydrophilic gaskets  150  are respectively abutted between the first mono-sided channel plate  121  and the anode reaction side  141  of one of the membrane electrode assemblies  140 , between the cathode reaction side  142  of one of the membrane electrode assemblies  140  and the first side channel  131  of the double-sided channel plate  130 , between the second side channel  132  of the double-sided channel plate  130  and the anode reaction side  141  of one of the membrane electrode assemblies  140 , and between the cathode reaction side  142  of one of the membrane electrode assemblies  140  and the second mono-sided channel plate  122 . Here, the rigid hydrophilic gaskets  150  may be subjected to a plasma or corona treatment to provide a plurality of polar groups, such as hydroxyl groups (OH). Specifically, the rigid hydrophilic gaskets  150  are attached to the first mono-sided channel plate  121  composed of graphite, the anode reaction sides  141  and cathode reaction sides  142  of the membrane electrode assemblies  140 , the double-sided channel plate  130  composed of graphite, and the second mono-sided channel plate  122  composed of graphite by the polar groups and water. More specifically, the rigid hydrophilic gaskets  150  are not attached to the first mono-sided channel plate  121 , the anode reaction sides  141  and cathode reaction sides  142  of the membrane electrode assemblies  140 , the double-sided channel plate  130 , and the second mono-sided channel plate  122  by glue. Moreover, in this embodiment, the hardness value of the rigid hydrophilic gaskets  150  exceeds Rockwell hardness 50. Thus, deflection or deformation can hardly occur on (bridges D, as shown in FIG.  6 ,) the rigid hydrophilic gaskets  150 . 
     Additionally, as shown in  FIG. 6 , regarding abutment between the first mono-sided channel plate  121  and the rigid hydrophilic gasket  150 , the rigid hydrophilic gasket  150  covers at least a part of the channel  121   a  connecting to the anode inlet  111   a  and cathode inlet  111   c.    
     Accordingly, when the fuel cell  100  is assembled, the first mono-sided channel plate  121 , second mono-sided channel plate  122 , double-sided channel plates  130 , membrane electrode assemblies  140 , and rigid hydrophilic gaskets  150  are fixed by the first oppressive collector board  111  and second oppressive collector board  112 . Here, as shown in  FIG. 5 , the anode inlet  111   a  of the first oppressive collector board  111  connects to the channel  121   a  of the first mono-sided channel plate  121  and the second side channels  132  of the double-sided channel plates  130 , while the cathode inlet  111   c  of the first oppressive collector board  111  connects to the first side channels  131  of the double-sided channel plates  130  and the channel  122   a  of the second mono-sided channel plate  122 . 
     When the fuel cell  100  is in operation, the fuel, such as methanol, enters the fuel cell  100  via the anode inlet  111   a  of the first oppressive collector board  111  and flows to the anode reaction sides  141  of the membrane electrode assemblies  140  through the channel  121   a  of the first mono-sided channel plate  121  and the second side channels  132  of the double-sided channel plates  130 . Here, the flow direction of the methanol is indicated by arrows A shown in  FIG. 5 . The methanol then leaves the fuel cell  100  via the anode outlet  111   b . In another aspect, the oxygen enters the fuel cell  100  via the cathode inlet  111   c  of the first oppressive collector board  111  and flows to the cathode reaction sides  142  of the membrane electrode assemblies  140  through the first side channels  131  of the double-sided channel plates  130  and the channel  122   a  of the second mono-sided channel plate  122 . Here, the flow direction of the oxygen is indicated by arrows B shown in  FIG. 5 . The oxygen then leaves the fuel cell  100  via the cathode outlet  111   d.    
     Accordingly, by separation of the rigid hydrophilic gaskets  150  abutted between the first mono-sided channel plate  121  and the membrane electrode assembly  140 , between the membrane electrode assembly  140  and the double-sided channel plate  130 , and between the membrane electrode assembly  140  and the second mono-sided channel plate  122 , the methanol flowing to the anode reaction sides  141  of the membrane electrode assemblies  140  does not leak to the cathode reaction sides  142  of the membrane electrode assemblies  140  and the oxygen flowing to the cathode reaction sides  142  of the membrane electrode assemblies  140  does not leak to the anode reaction sides  141  of the membrane electrode assemblies  140 . 
     Specifically, providing the high hardness, the rigid hydrophilic gaskets  150  do not deflect or deform even though the fuel cell  100  is subjected to a non-uniform fastening force during assembly thereof or is subjected to an external impact, securing the separation between the first mono-sided channel plate  121  and the membrane electrode assembly  140 , between the membrane electrode assembly  140  and the double-sided channel plate  130 , and between the membrane electrode assembly  140  and the second mono-sided channel plate  122 , and further preventing leakage and mixing of the methanol and oxygen. Thus, the operational efficiency and safety of the fuel cell  100  is significantly enhanced. Moreover, as the rigid hydrophilic gaskets  150  are attached to the first mono-sided channel plate  121 , the anode reaction sides  141  and cathode reaction sides  142  of the membrane electrode assemblies  140 , the double-sided channel plates  130 , and the second mono-sided channel plate  122  by the polar groups and water, an adhesion process employing glue can be omitted, effectively enhancing convenience for assembly of the fuel cell  100 . 
     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.