JP2004235169A - Solid polymer fuel cell, its manufacturing process and electrolyte film therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high strength and high power efficiency electrolyte film and a solid polymer fuel cell using the same. <P>SOLUTION: The electrolyte film 10 is a film for a solid polymer electrolyte fuel cell, and comprises an electrode forming region 12 to which an anode 20 and a cathode 22 is formed, and a peripheral region 14 to which no electrode is formed. The electrode forming region 12 is formed thinner than that of the peripheral region 14. The solid polymer electrolyte fuel cell 60 is formed by stacking a plurality of cell units 26 having a fuel chamber 30 formed in the anode side and an oxidizing agent chamber 34 formed in the cathode side, to a cell 24 that has the anode 20 formed in an electrode forming region 12 of the above electrolyte film 10 and the cathode 22 formed in another electrode forming region 12. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an electrolyte membrane for a polymer electrolyte fuel cell having excellent power generation efficiency and durability, and a polymer electrolyte fuel cell using the same.

  As shown in FIG. 8, the polymer electrolyte fuel cell 60 has a cell 24 having an anode 20 on one side of an electrolyte membrane 10 and a cathode 22 on the other side, and a fuel chamber 30 formed on one side. And a plurality of cell units 26 sandwiched by an oxidant plate 36 having an oxidant chamber 34 formed on one side. Note that only one cell unit is shown in the figure.

  The fuel chamber 30 is supplied with a fuel gas such as pure hydrogen gas or hydrogen-rich gas reformed by a reformer. The oxidizing agent chamber 34 is supplied with an oxidizing gas containing an oxygen gas sent from a fan or the like.

When the fuel gas and the oxidizing gas are supplied, on the anode side, the hydrogen gas in the fuel gas generates protons and electrons by a reaction of H ₂ → 2H ⁺ + 2e ⁻ . Protons pass through the solid polymer electrolyte membrane to the cathode, and electrons flow through an external circuit (not shown). At the cathode, oxygen gas in the oxidant, protons that have moved through the solid polymer electrolyte membrane, and electrons that have flowed through the external circuit are reacted by a reaction of 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O. It generates water and generates electromotive force.

  As shown in FIG. 8, the electrolyte membrane 10 is formed so that the film thickness C is substantially uniform over the entire surface, and the anode 20 and the cathode 22 are connected to the fuel chamber 30 and the oxidation chamber 30 as shown in FIG. It is formed in a region (hereinafter, referred to as an “electrode formation region”) facing the agent chamber 34.

  As shown in FIG. 9, a seal member 40 for preventing the leakage of the reaction gas is provided between the outer peripheral region 14 of the electrolyte membrane 10 where the electrodes are not formed and the outer peripheral portions of the fuel plate 32 and the oxidant plate 36. , And the fuel chamber 30 and the oxidant chamber 34 are mounted around the outer circumference of the fuel chamber 30, respectively.

  The electrolyte membrane 10 is desirably formed to be thin in order to reduce electric resistance, activate water movement in the membrane, and easily maintain a wet state. However, when the thickness of the electrolyte membrane 10 is reduced, the strength at the outer peripheral seal portion is reduced, and the electrolyte membrane 10 may be damaged. If the electrolyte membrane 10 is damaged at the seal portion, the reaction gas leaks, so that the utilization rates of the fuel gas and the oxidizing gas are reduced, and the power generation efficiency is reduced.

  An object of the present invention is to provide an electrolyte membrane having increased strength without lowering the power generation efficiency, and a polymer electrolyte fuel cell using the same.

  In order to solve the above problem, the polymer electrolyte membrane for a polymer electrolyte fuel cell 10 of the present invention has an electrode forming region 12 in which both electrodes of an anode 20 and a cathode 22 are formed, and an outer peripheral region 14 in which no electrodes are formed. An electrolyte membrane for a polymer electrolyte fuel cell, wherein the thickness of the electrode formation region 12 is formed to be smaller than the thickness of the outer peripheral region 14.

  Further, the polymer electrolyte fuel cell 60 of the present invention has a fuel chamber on the anode side with respect to the cell 24 in which the anode 20 is formed in one electrode forming region 12 and the cathode 22 is formed in the other electrode forming region 12 of the electrolyte membrane 10. 30, in a polymer electrolyte fuel cell in which a plurality of cell units 26 each having an oxidant chamber 34 formed on the cathode side are stacked, the thickness of the electrode forming region 12 as the electrolyte membrane 10 is set to be smaller than the thickness of the outer peripheral region 14. Also, an electrolyte membrane formed so as to be thin is used.

  In the electrolyte membrane 10 of the present invention, the electrode formation region 12 in which both the anode 20 and the cathode 22 are formed is formed to be thin, so that the electric resistance is small and water movement in the electrolyte membrane is reduced. The electrolyte membrane can be activated and the wet state of the electrolyte membrane can be easily maintained.

  Further, since the film thickness of the outer peripheral region 14 where both electrodes are not formed is large, the strength is high, and even if the seal member 40 is strongly pressed, there is no breakage. Therefore, leakage of the reaction gas is prevented, and a predetermined utilization rate of the fuel gas and the oxidizing gas can be secured.

  The polymer electrolyte fuel cell 60 using the electrolyte membrane 10 of the present invention has high cell performance and can achieve long life.

  The electrolyte membrane 10 can be formed from a polymer material such as perfluorocarbon sulfonic acid.

  In order to reduce the film thickness of the electrode forming region 12, the electrolyte membrane 10 is formed into a film mold 52 in which a portion corresponding to the electrode forming region 12 protrudes in a convex shape as shown in FIG. It can be prepared by pouring a solution (for example, Nafion solution: manufactured by Aldrich Chemical Co., Ltd.) and evaporating the solvent. FIG. 1A shows an electrolyte membrane 10 manufactured using the membrane mold 52. Alternatively, the prepared concave electrolyte membranes may be bonded together, or two convex membrane dies 52 may be prepared and pressed from both sides to prepare an electrolyte membrane having concave sides.

  As shown in FIG. 2, an electrolyte material 11a having a portion corresponding to an electrode formation region is disposed on one or both sides of an electrolyte material 11 having a substantially uniform film thickness, and these electrolyte materials are hot-pressed or the like. The electrolyte membrane 10 can also be manufactured by joining 11 and 11a.

  As shown in FIG. 3, the cell 24 is formed by joining an anode 20 and a cathode 22 made of platinum-supporting carbon to the electrode forming region 12 of the electrolyte membrane 10 by hot pressing.

  The plates 32 and 36 sandwiching the cell 24 are made of a porous carbon material. As shown in FIG. 9, a fuel chamber 30 is formed in the fuel plate 32 on the anode side of the two plates so as to face the anode. An oxidant chamber 34 is formed in the oxidant plate 36 on the cathode side so as to face the cathode. Although the fuel plate 32 and the oxidant plate 36 are formed of different members in the drawing, they may be formed of a so-called bipolar plate (not shown) having an oxidant chamber formed on the back surface of the fuel chamber.

  As shown in FIG. 9, the cell unit 26 is provided with seal members 40 on both surfaces of the outer peripheral region of the cell 24, and the two plates are arranged so that the anode and the fuel chamber 30 and the cathode and the oxidant chamber 34 face each other. It is produced by sandwiching a cell.

  FIG. 3 is a sectional view of the cell unit 26 of the present invention. As shown in the figure, in the electrolyte membrane 10 of the present invention, the film thickness B in the outer peripheral region is larger than the film thickness A in the electrode forming region, and therefore, as shown in FIG. The strength of the outer peripheral region can be increased as compared with the case where the conventional electrolyte membrane 10 which is almost the same is used.

  A polymer electrolyte fuel cell 60 is manufactured by stacking a large number of the cell units 26 having the above-described configuration. The fuel cell 30 of the manufactured polymer electrolyte fuel cell 60 has a fuel gas, and an oxidant gas has an oxidant gas 34). , Power can be generated.

  Electrolyte films 10 were prepared by changing the thickness B (average value) of the outer peripheral region 14 with respect to the film thickness A (minimum value) of the electrode formation region 12 (see Table 1), and electrodes were formed on these electrolyte films 10. A polymer electrolyte fuel cell 60 using cells 1 to 4 was assembled, and the cell performance was compared. Table 1 also shows the film thickness ratio A / B.

アノード２０及びカソード２２の両電極は、カーボンペーパーからなる電極基材に、白金担持カーボン６０重量％、Ｎａｆｉｏｎ溶液２０重量％、ＰＴＦＥ２０重量％からなる触媒層をスクリーン印刷することによって作製した。

Both electrodes of the anode 20 and the cathode 22 were prepared by screen-printing a catalyst layer composed of 60% by weight of platinum-supported carbon, 20% by weight of Nafion solution, and 20% by weight of PTFE on an electrode substrate made of carbon paper.

Both of the obtained electrodes were hot-pressed in the electrode forming region 12 of the electrolyte membrane at 150 ° C. and 50 kg / cm ² for 60 seconds, thereby producing Cell 1 and Cell 4.

The cell unit 26 was assembled using the produced cells, and cell voltages were measured immediately after the start of operation and after 500 hours of operation. The operating conditions were a current density of 0.5 A / cm ² , a cell temperature of 80 ° C., a fuel gas utilization of 70%, and an oxidizing gas (air) utilization of 20%.

  FIG. 4 shows the results. Referring to FIG. 4, the cell voltage immediately after the start of the battery operation was substantially the same regardless of the thickness B of the outer peripheral region 14. This is because the outer peripheral region 14 of the electrolyte membrane 10 has not deteriorated immediately after the start of the operation. On the other hand, after the operation for 500 hours, the cell voltage is higher as the film thickness B of the outer peripheral region 14 is larger. It can be seen that the smaller the cell voltage, the greater the decrease in cell voltage. This is because the thinner the film thickness B of the outer peripheral region 14 is, the lower the strength of the outer peripheral seal portion of the electrolyte membrane 10 is. That's because Conversely, a cell having a large film thickness B in the outer peripheral region 14, that is, a cell having a small film thickness ratio A / B, has a high strength in the outer peripheral sealed portion, and therefore, even after a long operation, gas leakage from the sealed portion does not occur. There is almost no occurrence, and a high cell voltage is maintained.

  From these results, it is desirable that the film thickness ratio A / B be 0.7 or less.

  On the other hand, it is difficult to make the film thickness ratio A / B smaller than 0.1 (the film thickness B in the outer peripheral region is larger than 10 times the film thickness A in the electrode forming region) in production. Further, as can be seen from FIG. 4, even if the film thickness ratio A / B is smaller than 0.1, further improvement in performance cannot be expected. Further, if the thickness of the outer peripheral region that does not directly contribute to power generation is made unnecessarily large, there is a disadvantage that the material cost of the electrolyte membrane increases.

  Therefore, it is desirable that the film thickness ratio A / B be 0.1 or more.

  Next, an electrolyte membrane 10 was prepared in which the film thickness A and the film thickness B were changed as shown in Table 2 while keeping the ratio A / B of the film thickness A of the electrode forming region 12 and the film thickness B of the outer peripheral region 14 constant. Then, a polymer electrolyte fuel cell 60 using the cell 5 and the cell 10 having the electrodes formed on the electrolyte membrane 10 was assembled, and the cell voltage immediately after the start of the operation was measured. Except for the difference in the thickness of the electrolyte membrane 10, the manufacturing conditions, experimental conditions, and the like are the same as those in the first embodiment.

  FIG. 5 shows experimental results showing the relationship between the film thickness A of the electrode formation region 12 and the cell voltage.

表２及び図５を参照すると、電極形成領域１２の膜厚Ａが５μｍよりも薄いと、セル性能が低下している。これは、電極形成領域１２の膜厚Ａが薄くなりすぎて、電極どうしの短絡が生じているためと考えられる。また、膜厚Ａが２００μｍよりも大きい場合も、セル電圧が低下している。これは、電極形成領域１２の膜厚Ａが厚くなりすぎると、電解質膜自体の電気抵抗が大きくなるのと共に、電池運転時の膜中の水の移動が阻害されて、膜が乾燥し、電気抵抗が大きくなってしまうためであると考えられる。

Referring to Table 2 and FIG. 5, when the film thickness A of the electrode formation region 12 is smaller than 5 μm, the cell performance is deteriorated. It is considered that this is because the film thickness A of the electrode formation region 12 was too thin, and a short circuit occurred between the electrodes. Also, when the film thickness A is larger than 200 μm, the cell voltage decreases. This is because if the film thickness A of the electrode formation region 12 is too large, the electric resistance of the electrolyte film itself increases, and the movement of water in the film during battery operation is hindered. It is considered that the resistance was increased.

  Therefore, it is desirable that the film thickness A of the electrode formation region 12 be 5 μm or more and 200 μm or less.

  Next, in order to examine the influence of the thickness B of the outer peripheral region 14 on the durability of the electrolyte membrane 10, a cycle test in which the electrolyte membrane 10 was repeatedly wetted and dried was performed, and the amount of gas leak after the test was examined. In the cycle test, as shown in FIG. 6, a cell unit 26 using the electrolyte membrane 10 in which the film thickness A of the electrode forming region 12 was the same as the film thickness B of the outer peripheral region 14 was used. In the present embodiment, the reason why the film thickness A and the film thickness B are set to be the same is that the cycle test in the present embodiment is for the purpose of measuring the gas leak in the outer peripheral region 14, and no gas leak occurs. This is because the film thickness of the electrode forming region 12 does not directly relate to gas leak from the outer peripheral region 14.

  In the experiment, the sealing members 40 were disposed on both outer peripheral surfaces of the electrolyte membrane 10 (made of perfluorocarbon sulfonic acid) having a thickness of 10 cm square and the outer peripheral region 14 having a thickness shown in Table 3 under the same conditions as in Example 1. The cell unit 26 was produced.

作製されたセルユニット２６について、セル温度が８０℃となるように維持しつつ、燃料室３０及び酸化剤室３４に、燃料ガス及び酸化剤ガスに代えて、８０℃の飽和状態にあるＮ₂ガスを３０分間供給し、その後、乾燥状態のＮ₂ガスを３０分間供給するサイクルを１００回繰り返し行なった。

While maintaining the cell temperature of the produced cell unit 26 at 80 ° C., the fuel chamber 30 and the oxidant chamber 34 are filled with N ₂ in a saturated state of 80 ° C. instead of the fuel gas and the oxidant gas. A cycle of supplying gas for 30 minutes and then supplying dry N ₂ gas for 30 minutes was repeated 100 times.

  By performing the above cycle, the electrolyte membrane 10 repeats expansion and contraction, and wet and dry. As a result, the deterioration of the low-strength electrolyte membrane 10 is accelerated in the outer peripheral sealing portion. Therefore, the durability of the electrolyte membrane 10 can be determined in a short time by this cycle test.

After the completion of 100 cycles, N ₂ gas was introduced into the cell unit so as to generate a pressure difference of 1 atm from the outside, and the cell unit was allowed to stand in a sealed state for 5 minutes. FIG. 7 shows the results.

  Referring to FIG. 7, when the film thickness B of the outer peripheral region 14 becomes thinner than 10 μm, it can be seen that the internal pressure sharply decreases and the gas leak amount increases. When the gas leak increases, the utilization rates of the fuel gas and the oxidizing gas decrease, and the power generation efficiency decreases. For this reason, it is desirable that the thickness B of the outer peripheral region 14 be 10 μm or more.

  Summarizing the results of Examples 1 to 3 above, the film thickness A of the electrode forming region 12 and the film thickness B of the outer peripheral region 14 are at least such that the film thickness A is smaller than the film thickness B. Under the following conditions, the electrolyte membrane satisfies at least one of the three conditions of a film thickness ratio A / B of 0.1 to 0.7, a film thickness A of 5 μm to 200 μm, and a film thickness B of 10 μm. It is desirable to fabricate 10, and it is more desirable to satisfy two of these conditions, and it is most desirable to satisfy all of these conditions.

  The description of the above embodiments is intended to explain the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof. Further, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims.

(a) is a cross-sectional view illustrating an example of a different electrolyte membrane of the present invention, and (b) is a cross-sectional view illustrating a method of manufacturing a membrane type for manufacturing the electrolyte membrane of (a). It is a perspective view which shows the different manufacturing methods of the electrolyte membrane of this invention. FIG. 2 is a cross-sectional view showing one cell unit of a polymer electrolyte fuel cell to which the electrolyte membrane of the present invention is applied. 4 is a graph showing the results of Example 1. 9 is a graph showing the results of Example 2. FIG. 14 is a sectional view of a cell unit used in Example 3. 9 is a graph showing the results of Example 3. It is sectional drawing which shows 1 cell unit of the conventional polymer electrolyte fuel cell. FIG. 2 is an assembly view showing one cell unit of the polymer electrolyte fuel cell.

Explanation of reference numerals

Reference Signs List 10 electrolyte membrane 12 electrode formation region 14 outer peripheral region 26 cell unit 60 polymer electrolyte fuel cell

Claims (5)

An electrolyte membrane used for a polymer electrolyte fuel cell,
An electrolyte membrane for a polymer electrolyte fuel cell, characterized in that the electrolyte membrane has at least one surface with a recess in which an electrode fits. A method for producing an electrolyte membrane used in a polymer electrolyte fuel cell,
By introducing the solution of the electrolyte membrane into a membrane having a convex portion, a solution introduction step in which a recess for fitting an electrode is formed on at least one surface of the electrolyte membrane,
A solvent removing step of removing a solvent component from the solution of the electrolyte membrane,
A method for producing an electrolyte membrane for a polymer electrolyte fuel cell, comprising: A method for producing an electrolyte membrane used in a polymer electrolyte fuel cell,
Pressing the member against the electrolyte membrane to form a recess in which an electrode is fitted on at least one surface of the electrolyte membrane. An electrolyte membrane for a polymer electrolyte fuel cell, comprising: Manufacturing method. A method for producing an electrolyte membrane used in a polymer electrolyte fuel cell,
An electrolyte material joining step of forming a recess for fitting an electrode on at least one surface of the electrolyte membrane by joining the first electrolyte material and the second electrolyte material. A method for producing an electrolyte membrane for a molecular fuel cell. In a polymer electrolyte fuel cell comprising: an electrolyte membrane; a first electrode formed on one surface of the electrolyte membrane; and a second electrode formed on the other surface of the electrolyte membrane.
The polymer electrolyte fuel cell according to claim 1, wherein the electrolyte membrane has a concave portion on at least one surface where the electrode fits.

Images