JP2005222764A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique of a fuel cell which prevents contamination of a refrigerant caused by corrosion of the refrigerant in the fuel cell, and prevents forming of a short circuit caused by the contamination, at a low cost without losing a cooling effect. <P>SOLUTION: An inner face of a communicating hole 16 for supplying the refrigerant which penetrates unit power generation cells 31, 32, and an inner face of a refrigerant introducing portion to a refrigerant path of a separator are insulated, and an insulating coating 21 and an insulating portion 34 are formed. In this structure, liquid resistance per one unit power generation cell of the refrigerant in the communicating hole 16 for supplying the refrigerant is set to be 1.5 to 30kΩ, while liquid resistance resulting from the insulating portion 34 is set to be 0.2 to 15MΩ. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell cooling technique, and more particularly to a technique for preventing refrigerant contamination.

  The polymer electrolyte fuel cell has a structure in which a refrigerant flows in the fuel cell in order to remove heat generated by the cell reaction. In this structure, in a fuel cell in which unit fuel cells (cells) and separators are stacked, through holes having the same shape that penetrate in the stacking direction are formed at the same locations on the stack surfaces of the cells and separators. And this communicating hole is connected to the refrigerant flow path provided in the surface of the separator which isolate | separates a cell, If a refrigerant | coolant is poured through this communicating hole, a refrigerant will flow into the refrigerant flow path of a separator and a separator will be cooled. Thereby, the solid polymer fuel cell is cooled.

  Since the polymer electrolyte fuel cell has a structure in which a large number of cells are stacked to generate a generated voltage, members having different potentials exist through the above-described communication holes. For this reason, electrical insulation is requested | required of a refrigerant | coolant. If the refrigerant has unacceptable electrical conductivity, a short circuit via the refrigerant is formed, and the battery function is impaired.

  Further, the refrigerant is required to have a temperature characteristic that can cope with a wide temperature range (around −30 ° C. to 150 ° C.) in addition to the high insulating properties described above. In a fuel cell for automobiles, it is desirable to use pure water as a refrigerant from the viewpoint of electrical insulation, but from the viewpoint of antifreezing, it is general to use a pure water dilution of ethylene glycol or the like.

  When a metal material is used for the separator, impurity ions leak from the separator into the refrigerant due to corrosion. For this reason, even when a highly insulating substance is used as the refrigerant, after a certain amount of use time, the insulation of the refrigerant deteriorates due to the contamination of the refrigerant. For this reason, the electrical insulation between the members to be cooled via the refrigerant becomes a problem.

  A technique described in Patent Document 1 is known as a technique for ensuring electrical insulation between members to be cooled that exist via a refrigerant. In this technology, a communication hole penetrating the laminated structure and an inner surface of a refrigerant path (a surface in contact with the refrigerant) provided in the separator are coated with an insulating coating by a sol-gel method to ensure electric insulation. It is.

  Further, as an approach different from the technique described in Patent Document 1, the technique described in Patent Document 2 is known. In this technology, a material that absorbs and discharges ions in the cooling water when electricity is applied is placed in the part that comes into contact with the coolant, which is a refrigerant, and the potential of the cooling water is far away from the part in contact with the cooling water. It is a way to prevent it.

Japanese Patent Laid-Open No. 7-230818 JP 2001-297784 A

  However, the method of forming an insulating coating on the refrigerant path described in Patent Document 1 has a problem in that the heat conductivity of the insulating coating is inferior and the heat exchange efficiency using the refrigerant is lowered, leading to a reduction in cooling effect. It was. In addition, the technique described in Patent Document 2 has a problem in that the apparatus is complicated and expensive members must be used, resulting in high costs.

  It is an object of the present invention to provide a technique for realizing the prevention of refrigerant contamination caused by corrosion in a fuel cell and the formation of a short circuit due to the contamination without lowering the cooling effect and at a low cost. To do.

  A fuel cell according to the present invention includes a unit power generation cell having a separator having a refrigerant path formed on a surface thereof, a refrigerant communication hole for refrigerant supply provided through the unit power generation cell and having an inner surface insulated, and a refrigerant discharge Refrigerant communication hole, a refrigerant introduction portion for introducing refrigerant into the refrigerant path from the refrigerant supply refrigerant communication hole, and a refrigerant for discharging refrigerant from the refrigerant path to the refrigerant discharge hole for refrigerant discharge An insulating portion having an inner surface covered with an insulation coating, and a liquid resistance of the refrigerant communication hole for supplying the refrigerant per unit power generation cell is 1.5 to 30 kΩ, and the insulating portion The liquid resistance in is 0.2 to 15 MΩ.

  In the present invention, the liquid resistance of the refrigerant communication hole in the unit power generation cell is an electric resistance indicated by the refrigerant in the refrigerant communication hole whose inner surface per unit power generation cell is covered with insulation. The liquid resistance of the refrigerant communication hole is proportional to the cell thickness and inversely proportional to the refrigerant conductivity and the cross-sectional area of the refrigerant communication hole. Usually, the liquid resistance of the refrigerant communication hole is calculated from the length (cell thickness) of the refrigerant communication hole in the unit cell, the cross-sectional area of the refrigerant communication hole, and the conductivity of the refrigerant. In order to adjust the liquid resistance of the refrigerant communication hole, a combination of the three parameters of the length (cell thickness) of the refrigerant communication hole, the cross-sectional area of the refrigerant communication hole, and the conductivity of the refrigerant may be adjusted.

  The insulating part is provided between a refrigerant introduction part to the refrigerant path formed in the separator and a refrigerant discharge part from the refrigerant path. An insulating part is comprised by insulatingly coating the part which contact | connects a refrigerant | coolant. The position of the insulating portion is arbitrary, but for example, by providing an insulating coating portion on the refrigerant introduction portion and the refrigerant discharge portion, and adjusting the length of the insulating coating portion (this length is called creepage distance) The structure which ensures liquid resistance can be mentioned. In this case, an insulating part is not formed in the refrigerant path, and an insulating part is formed in the vicinity of both ends of the refrigerant path, whereby a predetermined liquid resistance can be ensured without reducing the cooling efficiency of the refrigerant.

  The liquid resistance indicated by the insulating part is proportional to the length of the insulating part along the refrigerant flow path and the conductivity of the refrigerant, and inversely proportional to the cross-sectional area of the flow path in the insulating part. In order to adjust the liquid resistance in the insulating portion, a combination of these three parameters may be adjusted.

  In the present invention, by providing a portion subjected to insulation coating on the surface in contact with the refrigerant between the communication hole and the refrigerant guide / discharge portion, the corrosion current that flows through the refrigerant due to the resistance of the liquid resistance indicated by these portions. Suppress. That is, the corrosion current is generated by using the voltage generated in the fuel cell as a driving force, but by appropriately securing the liquid resistance exhibited by the refrigerant in the insulating portion, the corrosion current flowing in the non-insulating portion is suppressed. is there. At this time, by actively utilizing the liquid resistance indicated by the insulating portion of the communication hole, it is possible to suppress a decrease in power generation efficiency, which is a problem when securing this liquid resistance only between the refrigerant guide and discharge parts. it can.

  That is, in the present invention, the inner surface of the communication hole, which is a passage through which the stacked cells pass and supply and distribute the refrigerant to each cell, is covered with insulating clothing, and the liquid resistance indicated by that portion is used to suppress the corrosion current. . In other words, by setting the liquid resistance per cell of the communication hole whose inner surface is insulation-coated to a predetermined range, the action of suppressing the corrosion current is also borne by the liquid resistance in the communication hole, and thereby, between the refrigerant guide and discharge parts of the separator. This reduces the burden of inhibiting the corrosion current borne by the insulation. By doing so, it is possible to suppress the corrosion current without increasing the length (creeping distance) of the insulation-coated portion formed between the refrigerant conducting and discharging portions. Therefore, the area of the non-power generation part can be reduced, and both the anticorrosion of the non-insulation part of the separator and the pursuit of power generation efficiency of the fuel cell can be achieved.

  In the present invention, it is preferable that the insulating portion is provided in the refrigerant introduction portion and / or the refrigerant discharge portion. According to this aspect, since the electric insulation coating is formed on the refrigerant introduction portion to the refrigerant path of the separator and the refrigerant discharge portion therefrom, and no electric insulation coating is formed on the refrigerant path, the cooling effect by the refrigerant is reduced. Can be suppressed. Moreover, since the coating for electrical insulation may be a coating of silicone rubber or the like, it can be realized at a low cost.

  In the present invention, the conductivity of the refrigerant is preferably as low as possible, preferably 10 μS / cm or less. If the conductivity of the refrigerant exceeds 10 μS / cm, the influence of the corrosion current flowing through the refrigerant becomes large, and the effect of suppressing the corrosion current by setting the liquid resistance of the present invention becomes small.

  Next, the lower limit of the liquid resistance of the communication hole per cell will be described. When the liquid resistance of the communication hole is about the same as that of a normal conductor, the cells are short-circuited via the refrigerant, so that the liquid resistance of the communication hole per cell needs a value of a certain level or more. The lower limit of the liquid resistance of the communication hole per cell is preferably about 1.5 kΩ as will be described later. If the liquid resistance of the communication hole per cell is less than 1.5 kΩ, the effect of the liquid resistance of the communication hole is reduced, which is not preferable.

  The upper limit of the liquid resistance of the communication hole per cell has the following critical meaning. That is, the higher the liquid resistance of the communication hole per cell, the better from the viewpoint of the insulating properties of the refrigerant. However, when the resistance is increased to a certain level, the effect of suppressing corrosion shows a saturation tendency. Further, in order to increase the liquid resistance of the communication hole per cell, it is only necessary to reduce the cross-sectional area of the communication hole. However, this restricts the flow rate of the refrigerant flowing through each cell. This means that in a structure in which a large number of cells are stacked, it becomes difficult to distribute the refrigerant evenly to each cell. In order to increase the liquid resistance of the communication holes per cell, there is a method of increasing the cell thickness and lengthening the length of the communication holes, but this is not preferable because the fuel cell becomes larger and heavier.

  In addition, by reducing the conductivity of the refrigerant, it is possible to ensure liquid resistance. However, a certain increase in the conductivity of the refrigerant due to elution of contaminant components not due to electrolytic corrosion from the constituent materials of the fuel cell is practical. Unavoidable. For this reason, securing liquid resistance by reducing the initial conductivity of the refrigerant unnecessarily is difficult to maintain in the long run and lacks practicality. For these reasons, it is appropriate that the upper limit of the liquid resistance of the communication hole per cell is about 30 kΩ.

  When the liquid resistance between the refrigerant introduction part and the discharge part of the separator part in the unit cell is less than 0.2 MΩ, the conductivity of the refrigerant is significantly increased. This is because the corrosion current flowing due to the low liquid resistance promotes the progress of corrosion of the material constituting the separator, and the concentration of metal ions in the refrigerant increases accordingly.

  The upper limit of the liquid resistance between the refrigerant introduction part and the discharge part of the separator part in the unit cell is preferably about 15 MΩ. This is because when the liquid resistance between the refrigerant introduction part and the discharge part in the separator part becomes higher than 15 MΩ, the suppression effect of the corrosion current tends to saturate, and the power generation efficiency decreases due to the reduction of the power generation area according to the securing of the insulation part It is because it becomes.

  Hereinafter, a decrease in power generation efficiency due to the inability to secure a power generation area will be described. In order to ensure the liquid resistance between the refrigerant introduction part and the discharge part of the separator part, a predetermined length (this length is referred to as creepage distance) for ensuring the liquid resistance between the refrigerant introduction part and the discharge part. It is necessary to provide a secured insulating part. In this insulating part, since the inner surface is covered with insulation, the cooling effect by the refrigerant is reduced. For this reason, the region where the insulating portion is provided must be a non-power generation region. Therefore, in order to ensure the liquid resistance, when the creeping distance is increased, the non-power generation area of the separator must be increased, and the power generation efficiency is reduced.

  As described above, the liquid resistance of the communication hole per cell is suitably 1.5 to 30 kΩ, and the liquid resistance between the refrigerant inlet and outlet of the separator portion of the unit cell is 0.2 to 15 MΩ. Is appropriate.

  Another configuration of the fuel cell according to the present invention includes a unit power generation cell provided with a separator having a refrigerant path formed on a surface thereof, and a refrigerant communication for supplying a refrigerant that is provided through the unit power generation cell and has an inner surface insulated. The refrigerant is discharged from the refrigerant path to the hole and the refrigerant communication hole for discharging the refrigerant, the refrigerant introduction portion for introducing the refrigerant from the refrigerant communication hole for supplying the refrigerant to the refrigerant path, and the refrigerant communication hole for discharging the refrigerant. And a liquid resistance R1 between the two ends of the refrigerant communication hole for supplying the refrigerant and a liquid resistance R2 at the insulating part. , (R1 / R2) = 0.1-3.

  In the other configuration, the liquid resistance R1 between both ends of the refrigerant communication hole is the number of the liquid resistance and the number of unit power generation cells indicated by the communication holes per unit power generation cell in a structure in which a plurality of unit power generation cells are stacked. Is defined as the product of

  According to the other configuration, the inner surface of the refrigerant communication hole is coated with an insulation, and the integrated value R1 of the liquid resistance indicated by the refrigerant communication hole of each cell is approximately the same as the liquid resistance R2 indicated by the insulating portion of the separator of each cell. By doing so, the burden of the voltage drop function which an insulation part bears can be reduced. Thereby, the creepage distance for ensuring an insulating part can be suppressed, the cooling effective area in each separator part can be ensured large, and the fall of the power generation efficiency by providing an insulating part can be suppressed.

  The value of R1 / R2 is suitably set so as to satisfy the relationship of 0.1-3. When the value of R1 / R2 is less than 0.1, the effect of the voltage drop effect borne by the refrigerant communication hole is reduced, thereby increasing the burden on the insulating portion and ensuring a large creepage distance of the insulating portion. Since it disappears, it is not preferable.

  In order to increase the value of R1 / R2, it is necessary to reduce the cross-sectional area of the refrigerant communication hole or reduce the conductivity of the refrigerant in order to ensure the value of R1. However, as described above, reducing the cross-sectional area of the refrigerant communication hole causes a decrease in the supply amount of the refrigerant, and there is a limit to reducing the conductivity of the refrigerant. In order to increase the value of R1 / R2, it is conceivable to decrease R2, but reducing the liquid resistance exhibited by the insulating portion provided between the conducting and discharging portions of the refrigerant path of the separator is corrosive. From the viewpoint of obtaining a current suppressing effect, it is not preferable. Therefore, it is preferable that the value of R1 / R2 is kept within a range not exceeding 3.

  The invention described above is particularly useful when applied to a fuel cell having a structure in which 50 or more unit power generation cells are stacked. As will be described later, the present invention uses an accumulated liquid resistance (integrated value of the liquid resistance per cell) of the refrigerant communication holes penetrating a large number of stacked cells, and is located on the high potential side via the refrigerant. Thus, the corrosion current that becomes prominent in the high potential side cell is suppressed. Therefore, the effect becomes remarkable when a certain number of cells are stacked. As will be described later, the effect of suppressing the corrosion current appears when the number of stacked cells exceeds 50, and the effect becomes particularly remarkable when the number of stacked cells exceeds 100.

  According to the present invention, it is possible to reduce the voltage applied to the portion of the separator that is not covered with insulation through the refrigerant, thereby suppressing the corrosion current and suppressing the progress of corrosion. Thereby, contamination of the refrigerant can be prevented, and further, formation of a short circuit due to the contamination of the refrigerant can be prevented. Moreover, the said effect can be acquired at low cost, without reducing the cooling effect by a refrigerant | coolant.

  Moreover, since corrosion of a separator can be suppressed, the reduction | decrease in the board thickness of a separator and the fall of the intensity | strength of a separator can be suppressed. In particular, since the corrosion current can be suppressed, the elution of metal ions from the separator when a metal separator is used can be suppressed, the conductivity of the refrigerant is significantly increased by the influence of the metal ions, and the electrolysis by the influence of the metal ions is performed. It is possible to suppress a decrease in power generation capacity according to a decrease in the ion exchange amount of the membrane.

  In addition, by optimizing the combination of the range of the liquid resistance indicated by the refrigerant communication hole per unit power generation cell and the range of the liquid resistance indicated between the refrigerant guide and discharge parts to the refrigerant path formed in the separator, The anticorrosion effect can be obtained without increasing the area of the power generation unit. That is, a decrease in power generation efficiency of the fuel cell can be minimized while preventing the separator from corroding.

  Further, in a fuel cell having a structure in which a plurality of cells are stacked, an inner surface of a communication hole penetrating the plurality of cells is insulated and a liquid resistance R1 between both ends of the communication hole is formed in a flow path connected to a refrigerant path of the separator. By using the same resistance as the liquid resistance R2 indicated by the insulating portion (specifically, (R1 / R2) = about 0.1 to 3), the corrosion current in the cell located on the high potential side can be reduced. Thus, corrosion of the cell constituent material can be suppressed.

1. Configuration of Embodiment First, a schematic structure of the embodiment will be described. FIG. 1 is a cross-sectional view showing a cross-sectional structure of a unit power generation cell constituting the fuel cell of the embodiment. FIG. 2 is a plan view showing the structure of the separator. The unit power generation cell 31 has a structure in which an MEA (Membrane Electrode Assembly) 1 is sandwiched between an anode side separator (negative electrode side separator) 2 and a cathode side separator (positive electrode side separator) 3.

  The MEA 1 has a structure in which electrodes are bonded to both surfaces of an electrolyte membrane, and is also called a membrane electrode assembly. FIG. 1 also shows a cathode-side separator 3 of an adjacent unit power generation cell stacked with the unit power generation cell 31. In the fuel cell, a necessary voltage is secured by repeatedly laminating the unit structures shown in FIG. Reference numeral 30 denotes a gasket for preventing gas leakage.

  A groove 11 for flowing a fuel gas for supplying hydrogen is formed on the power generation surface (surface on the MEA side) of the anode separator 2, and a groove for flowing refrigerant on the refrigerant surface (surface opposite to the MEA side). 19 is formed. Further, a groove 18 for flowing a gas serving as an oxidant is formed on the power generation surface of the cathode-side separator 3, and a groove 20 for flowing a refrigerant is formed on the refrigerant surface.

  The groove 19 formed in the anode side separator 2 of the unit power generation cell 31 and the groove 20 formed in the cathode side separator 3 of the adjacent unit power generation cell are combined to form the refrigerant path 4. The anode side separator 2 of the unit power generation cell 31 and the cathode side separator 3 of the adjacent unit power generation cell are cooled by the refrigerant flowing through the refrigerant path 4.

  In the anode side separator 2 and the cathode side separator 3, communication holes 12 to 15 are formed. These holes serve as communication holes that penetrate each cell in a structure in which unit power generation cells are stacked.

  That is, reference numeral 12 shown in FIG. 2 is a fuel gas supply communication hole for supplying fuel gas to the groove 11 of the anode-side separator 2 of each unit power generation cell in a structure in which unit power generation cells 31 are stacked in multiple layers. . Reference numeral 13 denotes a fuel for collecting unreacted fuel gas discharged from the groove 11 of the anode-side separator 2 of each unit power generation cell and discharging it outside the fuel cell in a structure in which the unit power generation cells 31 are stacked in multiple layers. It is a communication hole for gas discharge. Reference numeral 14 denotes an oxidant gas supply communication hole for supplying an oxidant gas to the groove 18 of the cathode-side separator 3 of each unit power generation cell in a structure in which the unit power generation cells 31 are stacked in multiple layers. Reference numeral 15 denotes a structure in which the unit power generation cells 31 are stacked in multiple layers to collect unreacted oxidant gas discharged from the groove 18 of the cathode side separator 3 of each unit power generation cell and discharge it outside the fuel cell. This is a communication hole for discharging the oxidant gas.

  Reference numeral 16 shown in FIG. 2 denotes a refrigerant supply communication hole for supplying a refrigerant to the groove 19 of the anode-side separator 2 of each unit power generation cell in a structure in which the unit power generation cells 31 are laminated in multiple layers. Reference numeral 17 denotes a refrigerant discharge communication hole for collecting and discharging the refrigerant discharged from the groove 19 of the anode separator 2 of each unit power generation cell in a structure in which the unit power generation cells 31 are stacked in multiple layers. It is. The refrigerant supply communication hole 16 supplies the refrigerant to the groove 20 also on the refrigerant surface of the cathode separator 3, and the refrigerant discharge communication hole 17 has a structure for collecting the refrigerant from the groove 20.

  An insulating coating 21 is formed on the entire inner surface of the refrigerant supply communication hole 16. An insulating coating 22 is also formed on the entire inner surface of the refrigerant discharge communication hole 17.

  Further, on the refrigerant surface of the anode separator 2, in the refrigerant introduction portion from the refrigerant supply communication hole 16 to the groove 19 constituting the refrigerant path and the refrigerant discharge portion from the groove 19 to the refrigerant discharge communication hole 17, Insulating coatings 23 and 24 are formed on the inner surface. Also on the refrigerant surface of the cathode-side separator 3, grooves are introduced into the refrigerant introduction part from the refrigerant supply communication hole 16 to the groove 20 constituting the refrigerant path and the refrigerant discharge part from the groove 20 to the refrigerant discharge communication hole 17. Insulating coatings 25, 26 are formed on the inner surface of 20. By these insulating coatings, an insulating portion having a predetermined creepage distance can be obtained.

  This structure will be described in more detail. FIG. 3 is a diagram showing a cross section of a structure in which two unit power generation cells are stacked. Unlike FIG. 1, FIG. 3 shows a cross-sectional structure of the refrigerant supply communication hole 16 portion.

  FIG. 3 shows unit power generation cells 31 and 32 having the same structure. As shown in FIG. 3, the cathode side separator 3 of the unit power generation cell 31 and the anode side separator 2 of the unit power generation cell 32 are overlapped. And the groove | channel 20 formed in the refrigerant | coolant surface of the cathode side separator 3 of the unit power generation cell 31 and the groove | channel 19 formed in the refrigerant | coolant surface of the anode side separator 2 of the unit power generation cell 32 match, and the refrigerant | coolant path | route 33 is formed. It is formed. An insulating coating 21 is formed on the inner surface of the refrigerant supply communication hole 16, and the insulating coating 23 and the inner surface of the refrigerant introduction portion 35 (bridge portion) that connects the refrigerant path 33 and the refrigerant supply communication hole 16 are also formed. 25 is formed, and the insulating part 34 is configured. By forming the insulation coatings 23 and 25, the refrigerant introduction part 35 is configured as an insulation part 34 that electrically insulates the separator material from the refrigerant. In addition, the code | symbol 37 is a gasket for ensuring airtightness.

  In the present embodiment, the entire refrigerant introduction portion 35 is the insulating portion 34, but the insulating portion 34 may be formed in a part of the refrigerant introduction portion 35. Further, the insulating portion may be further divided and arranged.

2. Manufacturing Example of Embodiment Next, a procedure and materials for manufacturing the embodiment will be described with specific examples.

(Production procedure of MEA1)
First, carbon powder carrying a platinum catalyst on the surface was prepared, and this carbon powder was dispersed in an alcohol solution of a polymer electrolyte to obtain a polymer electrolyte slurry. On the other hand, a carbon paper having a thickness of 200 μm serving as a gas diffusion electrode was immersed in an aqueous dispersion of polytetrafluoroethylene (PTFE), which was dried and heat-treated to obtain a water-repellent porous electrode substrate.

  And the gas diffusion electrode which has the electrode reaction layer by a polymer electrolyte on one side was obtained by apply | coating the above-mentioned polymer electrolyte slurry to one side of the above-mentioned porous electrode base material, and also making it dry. Two gas diffusion electrodes were prepared, the electrode reaction layers were inside, the electrolyte layer was sandwiched therebetween, and hot pressing was performed at 110 ° C. for 30 seconds to obtain an MEA.

  As a member constituting the gas diffusion electrode, in addition to carbon paper, carbon cloth woven with flexible carbon fiber, carbon felt formed by mixing carbon fiber and carbon powder, adding an organic binder, and the like are used. be able to.

(Manufacturing procedure of separator)
Next, the manufacturing procedure of the anode side separator 2 and the cathode side separator 3 will be described. Here, the case where the anode side separator 2 and the cathode side separator 3 are manufactured with the same material will be described. Here, a 0.2 mm-thick stainless steel plate having the composition shown in Table 1 below was pressed to obtain an anode-side separator 2 and a cathode-side separator 3 having the shapes shown in FIG.

  Then, a coating of 0.5 mm thick silicone rubber was formed inside the refrigerant supply communication hole 16 and the refrigerant discharge communication hole 17 (part in contact with the refrigerant), and further inside the groove of the refrigerant introduction part and the refrigerant discharge part. . This coating ensures electrical insulation between the separator material and the refrigerant. By the covering with the silicone rubber, the refrigerant introduction portion 35 shown in FIG. 3 is configured as an insulating portion. Moreover, although not shown in figure, a refrigerant | coolant discharge part is comprised as an insulation part by the same structure.

(Fuel cell manufacturing procedure)
First, the MEA manufactured by the above-described procedure was cut so that the electrode area was 200 cm ² . Next, the MEA processed to a predetermined size is disposed with an anode separator (FIG. 1) in a state in which a silicone rubber gasket (corresponding to reference numeral 30 in FIG. 1 or FIG. 3) serving as a gas seal material is disposed around the MEA. 2) and a cathode separator (corresponding to reference numeral 3 in FIG. 1) to obtain a unit power generation cell, and a laminate in which 100 cells were further laminated was obtained. Then, a copper current collector plate is arranged at both ends of the laminate, and a pair of stainless steel plates are arranged outside through an insulating material, and the two stainless steel plates are tightened with bolts at a pressure of 15 kg / cm ^2. A fuel cell was obtained.

3. About the test of the prototype fuel cell In the fuel cell manufactured by the above-described procedure, the cross-sectional area of the refrigerant communication hole for supply and discharge, the length of the refrigerant introduction part and the refrigerant discharge part (creeping distance) in each cell, and the refrigerant Conductivity was prepared in various combinations as shown in Table 2 below, and a 1000-hour endurance operation test was conducted.

The durability operation test was performed using high-purity hydrogen gas as the fuel gas and air as the oxidant gas. The supply pressure of hydrogen gas was 0.1 kgf / cm ² , the exhaust side was open to the atmosphere, the supply pressure of air was 0.05 kgf / cm ² , and the exhaust side was also open to the atmosphere. The gas utilization was 70% on the hydrogen side and 40% on the air side. As the refrigerant, a 30% ethylene glycol aqueous solution having a conductivity shown in Table 2 was circulated in a total amount of 20 liters. The refrigerant was cooled by a heat exchanger, and the battery temperature during operation was maintained at 75 ° C. by adjusting the cooling efficiency and circulation speed.

The gas utilization rate is an index indicating the ratio of gas utilized for the electrode reaction when the current density of the generated electric power is 0.3 A / cm ² .

  In Table 2, the conversion resistance in the refrigerant communication hole is a liquid resistance in the length per cell of one communication hole (two communication holes are arranged for supply and discharge). The liquid resistance per cell is the electric resistance indicated by the refrigerant existing in the communication hole in the dimension in the thickness direction of the unit power generation cells 31 and 32 in FIG. The conversion resistance in the refrigerant communication hole is calculated from the initial conductivity of the refrigerant, the cross-sectional area of the communication hole, and the cell thickness.

  Moreover, the conversion resistance in the refrigerant introduction / discharge section is the total value of the liquid resistance indicated by the refrigerant in the refrigerant introduction section (part 35 in FIG. 3) and the refrigerant discharge section. The conversion resistance in the refrigerant introduction / discharge section is calculated from the initial conductivity of the refrigerant, the cross-sectional areas of the refrigerant introduction section and the refrigerant discharge section, and the length (creeping distance) of the refrigerant introduction section and the refrigerant discharge section. In addition, although the refrigerant | coolant discharge part of the same structure as a refrigerant | coolant introduction part is provided in the other end of the refrigerant path of a separator, this refrigerant | coolant discharge part was set as the same structure and the same dimension setting as a refrigerant | coolant introduction part. Table 3 shows the electrical conductivity before and after the endurance test conducted under the above conditions.

  As is apparent from Tables 2 and 3, when the insulating part is not provided on the separator, that is, when the insulating-introduced refrigerant introducing part and the refrigerant discharging part are not provided, the conductivity of the refrigerant after the endurance operation test is remarkably increased. This is because the effect of suppressing the corrosion current due to the presence of the insulating portion cannot be obtained. The increase rate of the refrigerant conductivity was calculated by ((B / A) -1) × 100, where A is the conductivity before the durability test of the refrigerant and B is the conductivity after the durability test.

  On the other hand, it can be seen that if the liquid resistance of the refrigerant introduction / discharge section is about 0.2 MΩ, the increase in the conductivity of the refrigerant can be suppressed considerably. From this, the effect of providing the refrigerant introduction part and the refrigerant discharge part in which the insulating coating is formed is confirmed.

  Further, it can be seen that the increase in the conductivity of the refrigerant before and after the endurance operation test becomes smaller when the liquid resistance of the refrigerant introduction / discharge section is increased. The reason why the increase rate of the refrigerant conductivity in Example A9 is slightly large is that the initial conductivity is small, and therefore the effect of the increase in conductivity due to factors other than the corrosion of the separator material appears strongly.

  Also, from Tables 2 and 3, it is possible to confirm the effect of adjusting the cross-sectional area of the refrigerant communication holes and using the liquid resistance of the refrigerant communication holes per cell. For example, when Example A2 and Comparative Example B1 are compared, the liquid resistance of both refrigerant guide / discharge parts is the same, but the rate of increase in the conductivity of the refrigerant is four times or more that of Comparative Example B1. large. In Example A2, since the initial refrigerant conductivity is low, the effect of the increase in conductivity due to factors other than corrosion is large, which is a disadvantageous condition compared to Comparative Example B1, but the rate of increase in the conductivity of the refrigerant is a comparative example. Compared to B1, it is 1/4 or less. This is because the liquid resistance per cell of the refrigerant communication hole in Example A2 is set to be 30 times larger than that in Comparative Example B1.

4). Analysis by an equivalent circuit The corrosion current flowing through the refrigerant of the fuel cell having the basic structure shown in FIGS. 1 to 3 can be analyzed by an equivalent circuit described below. FIG. 4 is an equivalent circuit focusing on the refrigerant of the fuel cell configured using the embodiment. The example shown in FIG. 4 shows an example of a fuel cell in which 220 unit power generation cells that generate a voltage of 1 V are stacked in series.

In the equivalent circuit shown in FIG. 4, _RA is the total value of the liquid resistance of the refrigerant introduction part and the refrigerant discharge part formed at both ends of the refrigerant path in the separator of each cell. R _B is a liquid resistance of the refrigerant supply passage in per cell.

FIG. 5 shows the relationship between the position of the cell and the corrosion current flowing through the separator refrigerant path when the insulating coating on the inner surface of the refrigerant communication hole is not formed, that is, in the equivalent circuit of FIG. 4 when R _B = 0. It is a data plot figure.

  As shown in FIG. 5, in a structure in which a large number of cells are stacked, in a cell on the low potential side (cell 1 or a cell close to cell 1), an anticorrosion current flows in the refrigerant path, and the high potential side (cell 220 or In the side cell close to the cell 220), a corrosion current flows in the refrigerant path.

  FIG. 6 is a diagram showing the relationship between the number of stacked cells and the corrosion current flowing in the fuel cell. In FIG. 6, data (1) indicates the insulation coating in the refrigerant communication holes (the refrigerant supply communication holes and the refrigerant discharge communication holes) in the fuel cell using the unit power generation cell configured under the conditions shown in Example A7 of Table 2. 5 is simulation data obtained on the basis of the equivalent circuit model shown in FIG. 4, assuming that the formation of is not performed, and the relationship between the number of stacked cells and the corrosion current flowing between the positive electrode and the negative electrode of the fuel cell.

  Data (2) is actually measured data for determining the relationship between the number of cell stacks in a fuel cell using unit power generation cells configured under the conditions shown in Example A7 of Table 2 and the total amount of corrosion current flowing in the fuel cell. is there.

  Data (3) shows the relationship between the number of cell stacks in the fuel cell using the unit power generation cell configured under the conditions shown in Example A7 of Table 2 and the total amount of corrosion current flowing in the fuel cell, as shown in FIG. It is the simulation data calculated | required based on the equivalent circuit model.

  As can be seen from FIG. 6, the corrosion current flowing in the fuel cell can be greatly suppressed by forming the insulating coating in the refrigerant communication hole. In particular, it can be seen that the effect is remarkable when the number of cells to be stacked exceeds 50, and that the effect of suppressing the corrosion current is extremely large when the number of cells to be stacked is more than 100. Moreover, the validity of the equivalent circuit of FIG. 4 is understood from the coincidence between the measured data (2) and the simulation data (3) with good accuracy.

The effect of electrically insulating the inner surface of the refrigerant communication hole penetrating each cell from the refrigerant can be described using the equivalent seaway of FIG. That is, the corrosion current (in the case of the 4 models, 220V at maximum) integrating the potential difference between the voltage of 1V applied to each cell stacked although to generate a driving-force, only no R _B R _A in some cases, only R _a is a load of the potential difference, as compared with the case where R _B is present, resulting in more corrosion current flows. In contrast, when the R _B are present at a certain value, because it becomes a load R _B, pressurized voltage applied by the liquid resistance is divided, the potential is reduced applied to the separator portion not insulated. Thereby, the corrosion current which flows into the separator part which is not insulated can be suppressed.

Especially when the number of stacked cells is large, even with a small value of R _B, in the cell of the high potential side, the value of the product of the number of laminated R _B and the cell comes into play, as shown in FIG. 5 In particular, the effect of suppressing the generation of corrosion current, which is a problem in the high potential side cell, is increased. This is as shown in FIG. 6, when the number of stacked cells is more than a certain degree, it appears also that the effect of providing the R _B is obtained remarkably.

Hereinafter, added more detailed description about the function and effect of the provision of the R _B. First, when the data shown in Table 2 and Table 3 are arranged, the following Table 4 is obtained.

In Table 4, the converted liquid resistance R1 between both ends is the resistance value indicated by the refrigerant communication holes per cell in the structure of the refrigerant communication holes penetrating a large number of stacked cells (in this case, 100 cells). This is an integrated value for the entire fuel cell. For example, liquid resistance indicated by the refrigerant communicating hole in one per cell is _{R B,} when the number of stacked cells is 220, and R1 = 220 × _{R B.}

  As is apparent from Table 4, even if the liquid resistance of the refrigerant communication holes per cell is small, the accumulated liquid resistance of the communication holes is the separator portion when viewed in units of fuel cells in which a large number of cells are stacked. The value is comparable to the liquid resistance of the insulating part.

  Table 4 shows that when the liquid resistance between both ends of the communication hole in the fuel cell is comparable to the liquid resistance of the insulating portion of the separator part, the effect of insulating the communication hole and providing liquid resistance is remarkably obtained. It can be said that it is shown.

  From Table 4, when the relationship between the liquid resistance R1 between both ends of the refrigerant communication hole for supplying the refrigerant and the liquid resistance R2 in the insulating portion is in the range of (R1 / R2) = 0.1-3, It is concluded that the conductivity can be suppressed.

  In Comparative Examples B1 and B2, the range of (R1 / R2) = 0.1 to 3 is satisfied. However, Comparative Example B1 has a liquid resistance of the refrigerant communication hole that is too small as 0.5 kΩ, so that As shown in FIG. 3, the increase in the conductivity of the refrigerant before and after the durability test is large, which is not preferable. Further, in Comparative Example B1, by increasing the initial refrigerant conductivity to 30 μS / cm, the liquid resistance of the refrigerant communication hole and the refrigerant guide / discharge part is lowered, and the insulation of the refrigerant is greatly sacrificed. It is not preferable in terms.

  Further, Comparative Example B3 is not preferable because the liquid resistance of the refrigerant guide / discharge section is too small, and in order to realize this liquid resistance, the initial conductivity of the refrigerant is increased to an unacceptable level.

  INDUSTRIAL APPLICABILITY The present invention can be used for a fuel cell that suppresses performance degradation caused by separator corrosion. Moreover, it can utilize for the fuel cell which suppressed the contamination of the refrigerant | coolant in operation | movement. A fuel cell using the present invention is small, lightweight, low cost, highly efficient, has little performance degradation, and is suitable for use as an energy source for motor-driven automobiles. Of course, the present invention can be used as a source of various electric energy.

It is sectional drawing which shows the cross-section of the unit power generation cell of embodiment. It is a top view which shows the structure of a separator. It is sectional drawing which shows the cross-sectional structure of the refrigerant | coolant communicating hole vicinity in the structure which laminated | stacked the unit power generation cell. It is an equivalent circuit diagram which shows the electric current path | route which used the refrigerant | coolant as a medium. It is a data plot figure which shows the relationship between the position of the laminated | stacked cell, and the corrosion current. It is a diagram which shows the relationship between the number of lamination | stacking of a cell, and the corrosion current which flows through a fuel cell.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... MEA (Membrane Electrode Assembly), 2 ... Anode side separator, 3 ... Cathode side separator, 4 ... Refrigerant path, 11 ... Groove for flowing fuel gas, 12 ... Communication hole for fuel gas supply, 13 ... Fuel gas discharge Communication holes, 14 ... oxidant gas supply communication holes, 15 ... oxidant gas discharge communication holes, 16 ... refrigerant supply communication holes, 17 ... refrigerant discharge communication holes, 18 ... for flowing a gas to be an oxidant. , 19 ... groove for flowing refrigerant, 20 ... groove for flowing refrigerant, 21 ... insulating coating, 22 ... insulating coating, 23 ... insulating coating, 24 ... insulating coating, 25 ... insulating coating, 26 ... insulating coating , 30 ... gasket, 31 ... unit power generation cell, 32 ... unit power generation cell, 33 ... refrigerant path, 34 ... insulating part, 35 ... refrigerant introduction part, 37 ... gasket

Claims (5)

A unit power generation cell including a separator having a refrigerant path formed on the surface;
A refrigerant communication hole for supplying a refrigerant and a refrigerant communication hole for discharging a refrigerant that are provided through the unit power generation cell and have an inner surface covered with an insulation coating,
Provided between the refrigerant introduction part for introducing the refrigerant into the refrigerant path from the refrigerant communication hole for supplying the refrigerant and the refrigerant discharge part for discharging the refrigerant from the refrigerant path to the refrigerant communication hole for discharging the refrigerant. And an insulating part whose inner surface is insulated and coated,
The liquid resistance of the refrigerant communication hole for supplying the refrigerant per unit power generation cell is 1.5 to 30 kΩ,
A fuel cell having a liquid resistance of 0.2 to 15 MΩ in the insulating portion. A unit power generation cell including a separator having a refrigerant path formed on the surface;
A refrigerant communication hole for supplying a refrigerant and a refrigerant communication hole for discharging a refrigerant that are provided through the unit power generation cell and have an inner surface covered with an insulation coating,
Provided between the refrigerant introduction part for introducing the refrigerant into the refrigerant path from the refrigerant communication hole for supplying the refrigerant and the refrigerant discharge part for discharging the refrigerant from the refrigerant path to the refrigerant communication hole for discharging the refrigerant. And an insulating part whose inner surface is insulated and coated,
The fuel cell, wherein a liquid resistance R1 between both ends of the refrigerant supply hole for supplying the refrigerant and a liquid resistance R2 in the insulating portion satisfy a relationship of (R1 / R2) = 0.1-3.   The fuel cell according to claim 1, wherein the insulating portion is provided in the refrigerant introduction portion and / or the refrigerant discharge portion.   The fuel cell according to claim 1, wherein the electric conductivity of the refrigerant is 10 μS / cm or less.   The fuel cell according to any one of claims 1 to 4, wherein 50 or more unit power generation cells are stacked.

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