JP2005166572A - Electrochemical device, manufacturing method and driving method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical device capable of taking out a high output from the initial operation of the device, and a manufacturing method and a driving method thereof.
SOLUTION: A fuel having a laminated structure 3 composed of a first electrode 6, a second electrode 8, and an electrolyte layer 1 sandwiched between the electrodes, and configured to be driven in the presence of a liquid. In the electrochemical device 2 such as a battery, the electrochemical layer 1 and the electrolyte in the first electrode 6 and the second electrode 8 are pretreated with the liquid. In the method for manufacturing an electrochemical device, the electrolyte layer 1 and the electrolyte in the first electrode 6 and the second electrode 8 are pretreated with the liquid. In the method for driving an electrochemical device, the driving is started after the electrolyte layer 1 and the electrolyte in the first electrode 6 and the second electrode 8 are pretreated with the liquid. Driving method.
[Selection] Figure 2

Description

  The present invention relates to an electrochemical device suitable for a fuel cell or the like, and a manufacturing method and a driving method thereof.

  Perfluorosulfonic acid resins are currently used in electrochemical devices that have an MEA (Membrane & Electrode Assembly) composed of an anode electrode, a cathode electrode, and an electrolyte layer formed of a solid polymer electrolyte, and use an alcohol aqueous solution as a fuel. A polymer having high ion conductivity such as (PFSI) (Nafion (registered trademark) manufactured by DuPont) is used as the electrolyte layer and the binder in the electrode (for example, Patent Document 1 and Patent Document 2 described later). reference.).

  On the other hand, alcohols such as methanol are mainly used as fuel. In addition, there are research examples of organic substances such as hydrogen gas, dimethyl ether (DME), and diethyl ether (DEE) (see, for example, Patent Document 3 below).

  Among these, a direct methanol fuel cell (DMFC) that directly reacts methanol as a fuel at an anode electrode has high expectation as a next-generation power source for small portable fuel cells and the like because high energy density is realized. .

JP-A-61-67787 (Column 11, line 16 to column 15, line 7) JP-A-61-67788 (column 12, line 9 to column 16, line 2) Japanese Examined Patent Publication No. 3-208260 (page 3, lower right column, lines 1 to 16; FIG. 1)

  In the conventional examples as described above, for example, a method of thermocompression bonding is generally employed when an electrolyte layer made of a perfluorosulfonic acid resin and an electrode having a catalyst layer are joined.

  However, when thermocompression bonding is performed at a temperature higher than the glass transition point (for example, about 120 ° C.) of the material constituting the electrolyte layer, a perfluorosulfonic acid resin having a thermal history higher than the glass transition point once. In the electrolyte layer, the liquid content decreases, and the ionic conductivity decreases accordingly.

  As a result, simply configuring the MEA according to the conventional example as a fuel cell cannot obtain a high output from the initial operation of the apparatus, starts at a low load, and gradually increases with the recovery of the liquid content of the electrolyte resin. The load was increasing. For this reason, it was necessary to perform repeated measurements in order to determine the maximum output when evaluating MEAs as well as actual devices.

  In addition, in an actual apparatus, in most cases, a plurality of MEAs are stacked and used, but since each MEA is exposed to different conditions such as temperature depending on the stacking position, the recovery rate of the liquid content of each MEA is There was variation.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electrochemical device that can extract a high output from the initial operation of the device, and a method for manufacturing and driving the same. It is to provide.

  That is, the present invention includes an electrochemical device configured to have a stacked structure including a first electrode, a second electrode, and an electrolyte layer sandwiched between the electrodes, and to be driven in the presence of a liquid. In the electrochemical device, at least the electrolyte layer is pretreated with the liquid.

  In the method of manufacturing an electrochemical device having a laminated structure including a first electrode, a second electrode, and an electrolyte layer sandwiched between the electrodes, and configured to be driven in the presence of a liquid. In addition, the present invention relates to a method for manufacturing an electrochemical device, wherein at least the electrolyte layer is pretreated with the liquid.

  Further, in a method for driving an electrochemical device having a laminated structure including a first electrode, a second electrode, and an electrolyte layer sandwiched between the electrodes, and configured to be driven in the presence of a liquid. In addition, the present invention relates to a method for driving an electrochemical device, wherein the driving is started after at least the electrolyte layer is pretreated with the liquid.

According to the present invention, in an electrochemical device such as a fuel cell configured to be driven in the presence of the liquid, at least the electrolyte layer is pretreated with the liquid, so at least the electrolyte layer contains liquid. The rate can be increased and ion conductivity of protons (H ⁺ ) and the like can be improved. In addition, characteristics can be made uniform in the laminated structure by the pretreatment. Therefore, a high output can be taken out from the initial operation of the device. In the present invention, the above “initial operation of the device” means, for example, when about 100 hours have elapsed since the start of actual driving (power generation).

  In the present invention, it is preferable that the pretreatment is performed by bringing the liquid into contact with the electrolyte layer and the electrolyte in the first electrode and the second electrode by dipping or the like.

  In addition, it is preferable that the pretreatment is performed at a concentration higher than the liquid concentration at the time of driving in the electrolyte layer and the electrolyte in the first electrode and the second electrode, and in the pretreatment, It is preferable to control at least the concentration of the liquid and / or the processing temperature.

  As the pretreatment liquid, it is preferable to use water, alcohol such as methanol, ethanol, isopropanol or a mixture thereof.

  In the state of the device structure having the multilayer structure, the pretreatment is performed by supplying the liquid and bringing the liquid into contact with the electrolyte layer and the electrolyte in the first electrode and the second electrode. Preferably it is done. The reason why the pretreatment is performed in the state of the device structure is to effectively prevent the laminated structure from being difficult to handle because of the thin film, and to causing wrinkles in the pretreatment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment FIG. 1 is a flowchart showing an example of a method for producing an electrochemical device according to the present invention in the order of steps.

  As shown in FIG. 1, first, a laminated structure (MEA (Membrane & Electrode Assembly)) composed of a first electrode, a second electrode, and an electrolyte layer sandwiched between the electrodes is manufactured. Each of the first electrode and the second electrode has a catalyst layer. The electrolyte layer is not particularly limited, but can be formed of, for example, perfluorosulfonic acid resin (PFSI).

  Specifically, an ion conductive material contained as a binder in the electrolyte layer, the first electrode, and the second electrode in a state where the electrolyte layer is sandwiched between the first electrode and the second electrode. The first electrode, the second electrode, and the electrolyte layer are joined to each other by raising the temperature to a glass transition point (for example, about 120 ° C. in PFSI) or higher and performing thermocompression bonding. Can be produced.

  At this time, once the liquid content of the electrolyte layer made of perfluorosulfonic acid resin having a thermal history higher than the glass transition point and the electrolyte in the first electrode and the second electrode decreases, Along with this, the ionic conductivity also decreases.

  Next, using the laminated structure produced as described above, an electrochemical device based on the present invention, which is suitable for a fuel cell and the like described later and configured to be driven in the presence of a liquid, is produced. .

  Next, in the state of the device structure having the laminated structure, the electrolyte layer is supplied by supplying the liquid and bringing the liquid into contact with the electrolyte layer and the electrolyte in the first electrode and the second electrode. And the pretreatment of the electrolyte in the first electrode and the second electrode. The reason why the pretreatment is performed in the state of the device structure is to effectively prevent the laminated structure from being difficult to handle because of the thin film, and to causing wrinkles in the pretreatment.

  As the liquid, it is preferable to use water, alcohol or a mixture thereof. Examples of the alcohol include methanol, ethanol, isopropanol and the like.

  Here, it is preferable to perform the pretreatment at a concentration higher than the liquid concentration at the time of driving in the electrolyte layer and the electrolyte in the first electrode and the second electrode, and in the pretreatment, It is preferable to control the concentration of the liquid and / or the processing temperature. By controlling the concentration of the liquid and / or the treatment temperature, the treatment time of the pretreatment can be appropriately selected.

  Specifically, the concentration of the liquid used to drive the electrochemical device, for example, the liquid such as a methanol aqueous solution having a concentration higher than 0.4 to 3 mol / l, for example, 2 to 6 mol / l, for example, The pretreatment can be performed by immersing in the state of the device structure having the laminated structure at a treatment temperature of room temperature to 80 ° C., for example, for 1 to 24 hours.

  Further, the liquid used for driving the electrochemical device, for example, a liquid such as a methanol aqueous solution having the same concentration as 0.4 to 3 mol / l or a lower concentration, for example 0 to 2 mol / l. For example, the pretreatment may be performed by immersing in a device structure having the laminated structure at a treatment temperature of room temperature to 80 ° C. for a long time, for example, 1 to 100 hours.

  Furthermore, the concentration of the liquid used for driving the electrochemical device, for example, a liquid such as a methanol aqueous solution having a concentration equal to or lower than 0.4 to 3 mol / l, for example, 0 to 2 mol / l. The pretreatment may be performed by immersing in a state of a device structure having the laminated structure at a high temperature, for example, at a processing temperature of 60 to 100 ° C., for example for 1 to 24 hours.

  Thereby, the liquid content of the electrolyte layer and the electrolyte in the first electrode and the second electrode in the electrochemical device according to the present invention is 27 immediately after the production of the laminated structure, for example, at a methanol concentration of 1 mol / l. It can be improved, for example, to 32 to 35% by weight, compared to ˜29% by weight.

  After the pretreatment, driving of the electrochemical device according to the present invention is started.

According to the present embodiment, since the electrolyte layer and the electrolyte in the first electrode and the second electrode are pretreated with the liquid in the state of the device structure having the laminated structure, the electrolyte By increasing the liquid content of the layer and the electrolyte in the first electrode and the second electrode, it is possible to improve the ion conductivity of protons (H ⁺ ) and the like. In addition, characteristics can be made uniform in the laminated structure by the pretreatment. Therefore, a high output can be taken out from the initial operation of the device.

Second Embodiment Next, an example in which the electrochemical device according to the present invention is applied to a fuel cell in which fuel is supplied to the first electrode and oxygen is supplied to the second electrode will be described.

  FIG. 2 is a schematic cross-sectional view of an example of an electrochemical device according to the present invention configured as a fuel cell.

  This fuel cell 2 has a laminated structure comprising a negative electrode (fuel electrode) 6 with a terminal 5, a positive electrode (oxygen electrode) 8 with a terminal 7, and an electrolyte layer 1 sandwiched between the two electrodes. It has a body (MEA) 3. Further, each of the negative electrode 6 and the positive electrode 8 has a catalyst layer 9.

  The electrolyte layer 1 and the electrolyte in the negative electrode 6 and the positive electrode 8 are pretreated with the liquid in the same manner as in the first embodiment.

In the mechanism of the fuel cell 2, the methanol aqueous solution is passed through the methanol aqueous solution flow path 12 on the negative electrode 6 side during use. While the fuel (methanol) passes through the flow path 12, hydrogen ions are generated at the negative electrode 6, and the hydrogen ions pass through the electrolyte layer 1 and move to the positive electrode 8 side. On the other hand, electrons released when ionizing pass through the external circuit and move to the positive electrode 8 side. In the positive electrode 8, hydrogen ions and electrons react with oxygen (air) passing through the O ₂ flow path 13, thereby taking out a desired electromotive force.

  Here, a plurality of laminated structures (MEA) 3 composed of the negative electrode 6 with the catalyst layer 9, the electrolyte layer 1, and the positive electrode 8 with the catalyst layer 9 may be laminated to form an integral structure. There is an effect that a higher electromotive force can be easily obtained. Moreover, although the example using methanol aqueous solution was demonstrated as a fuel, of course, it is also possible to use another fuel.

In the fuel cell 2, the electrolyte layer 1, the negative electrode 6, and the electrolyte in the positive electrode 8 are pretreated with the liquid, and therefore the liquid content of the electrolyte layer 1, the negative electrode 6, and the electrolyte in the positive electrode 8. And ion conductivity of protons (H ⁺ ) and the like can be improved. Therefore, a high output can be taken out from the initial operation of the device.

  Examples according to the present invention will be described below.

Example 1
The laminated structure is formed by thermocompression bonding of an electrolyte layer made of perfluorosulfonic acid resin (PFSI) and a catalyst layer made of platinum-supporting carbon and PFSI under conditions of 120 ° C. or higher, 20 kg / cm ² or higher, and 5 to 30 minutes. A body (MEA) was prepared. And the electrochemical device as shown in FIG. 2 was produced using obtained MEA. Here, when the liquid content (methanol concentration) of the electrolyte layer in the electrochemical device was measured, it was 27% by weight. In addition, said "weight%" was computed by the following formula | equation (1) (hereinafter the same).

    % By weight = weight of aqueous solution / dry weight of resin × 100 (1)

  The characteristics of the electrochemical device produced as described above were evaluated. The measurement is performed by supplying 1 mol / l aqueous methanol solution to the anode side and supplying air to the cathode side at 80 ° C. The relationship between the current density and the internal resistance, the relationship between the current density and the voltage, and The relationship between current density and power density was measured. The results are shown in FIG.

  Next, in the state of the device structure having the above laminated structure, it was immersed in a 0.6 mol / l aqueous methanol solution at room temperature for 100 hours. At the time of immersion, power was not generated in the state of the device structure having the above laminated structure, and only liquid circulation was performed. By dipping in the state of the device structure, it is possible to prevent the sealing performance from being lowered due to wrinkles generated by the increase in the moisture content of the electrolyte layer. Thereafter, the liquid content (methanol concentration) of the electrolyte layer was measured and found to be 32% by weight. The electrochemical device was measured in the same manner as described above. The results are also shown in FIG.

  As is clear from FIG. 3, the electrochemical device before being immersed in the 0.6 mol / l aqueous methanol solution had a low liquid content of 27% by weight in the electrolyte layer. During the repeated measurement period, the internal resistance was high, and the voltage and maximum output were low. In contrast, an electrochemical device in which the electrolyte layer and the electrolyte in the first electrode and the second electrode are pretreated by immersing in a 0.6 mol / l aqueous methanol solution for 100 hours is an electrolyte. Since the liquid content of the layer increased to 32% by weight, the voltage and maximum output were greatly improved and the internal resistance was reduced from the beginning of 3 minutes after starting to drive the device. In addition, the pretreatment made it possible to align the characteristics in the laminated structure in advance before use, and the time for peaking was about the same.

Example 2
An electrochemical device as shown in FIG. 2 was prepared, and a 6 mol / l methanol aqueous solution was circulated in the flow channels 12 and 13 at 80 ° C. for 3 hours, in the same manner as in Example 1, before the treatment and The device characteristics after the treatment were measured. The results are also shown in FIG. When the liquid content of the electrolyte layer was measured, it was 28% by weight before the treatment with the 1 mol / l aqueous methanol solution, but increased to 33% by weight after the treatment.

  As is clear from FIG. 4, the electrochemical device before treatment with the 6 mol / l methanol aqueous solution had a low liquid content of 28% by weight of the electrolyte layer. Therefore, repeated measurement over 180 minutes after starting to drive the device. During this period, the internal resistance was large, and the voltage and maximum output were low. On the other hand, in the electrochemical device after the 6 mol / l methanol aqueous solution was treated at 80 ° C. for 3 hours, the liquid content of the electrolyte layer was increased to 33% by weight. From the beginning of the minute, the voltage and maximum output improved significantly, and the internal resistance also decreased. In addition, the pretreatment made it possible to align the characteristics in the laminated structure in advance before use, and the time for peaking was about the same.

As is clear from the above, according to the present invention, in the electrochemical device configured to be driven in the presence of the liquid such as an aqueous methanol solution, the electrolyte layer, the first electrode, and the second electrode Since the electrolyte is pretreated with the liquid, the liquid content of the electrolyte layer and the electrolyte in the first electrode and the second electrode is increased, and ion conductivity such as proton (H ⁺ ) is increased. Was able to improve. Therefore, a high output could be extracted from the initial operation of the device.

  Further, when Example 1 and Example 2 are compared with each other, the concentration of the aqueous methanol solution used for the pretreatment is higher and the treatment temperature is higher, but the treatment time is shorter, but better characteristics are obtained. I found out that

  While the present invention has been described with reference to the embodiments and examples, the above examples can be variously modified based on the technical idea of the present invention.

  For example, in an electrochemical device based on the present invention suitable for a fuel cell or the like, the shape, configuration, material, and the like can be appropriately selected without departing from the present invention.

It is a flowchart which shows an example of the manufacturing method of the electrochemical device based on this invention in embodiment of this invention in process order. It is a schematic sectional drawing of the electrochemical device based on this invention comprised as a fuel cell equally. It is a graph which compares and shows the characteristic of the device produced by the manufacturing method based on this invention in the Example of this invention. 2 is a graph showing a comparison of the characteristics of devices manufactured by the manufacturing method according to the present invention.

Explanation of symbols

1 ... electrolyte layer, 2 ... fuel cell, 3 ... multilayer structure (MEA), 5, 7 ... terminal, 6 ... anode, 8 ... positive electrode, 9 ... catalyst layer, 12 ... methanol passage, 13 ... O ₂ passage

Claims (17)

  In an electrochemical device having a laminated structure including a first electrode, a second electrode, and an electrolyte layer sandwiched between the electrodes, and configured to be driven in the presence of a liquid, at least the electrolyte layer An electrochemical device characterized in that is pretreated with the liquid.   The electrochemical device according to claim 1, wherein the pretreatment is performed by bringing the liquid into contact with the electrolyte layer and the electrolyte in the first electrode and the second electrode.   The electrochemical device according to claim 2, wherein the pretreatment is performed at a concentration higher than a liquid concentration at the time of driving in the electrolyte layer and the electrolyte in the first electrode and the second electrode.   The electrochemical device according to claim 1, wherein the pretreatment liquid is water, alcohol, or a mixture thereof.   The electrochemical device according to claim 1 configured as a fuel cell.   In the method for manufacturing an electrochemical device having a laminated structure including a first electrode, a second electrode, and an electrolyte layer sandwiched between the electrodes, and configured to be driven in the presence of a liquid, A method for producing an electrochemical device, wherein the electrolyte layer is pretreated with the liquid.   The pretreatment is performed by supplying the liquid and bringing the liquid into contact with the electrolyte layer and the electrolyte in the first electrode and the second electrode in the state of the device structure having the laminated structure. The method for producing an electrochemical device according to claim 6.   The method for manufacturing an electrochemical device according to claim 7, wherein the pretreatment is performed at a concentration higher than the liquid concentration at the time of driving in the electrolyte layer and the electrolyte in the first electrode and the second electrode.   The method for producing an electrochemical device according to claim 8, wherein in the pretreatment, at least a concentration of the liquid and / or a treatment temperature is controlled.   The method for producing an electrochemical device according to claim 6, wherein water, alcohol, or a mixture thereof is used as the pretreatment liquid.   The method for producing an electrochemical device according to claim 6, wherein a fuel cell is produced.   In the method of driving an electrochemical device having a laminated structure composed of a first electrode, a second electrode, and an electrolyte layer sandwiched between the electrodes, and configured to be driven in the presence of a liquid, at least A driving method of an electrochemical device, wherein driving is started after the electrolyte layer is pretreated with the liquid.   The pretreatment is performed by supplying the liquid and bringing the liquid into contact with the electrolyte layer and the electrolyte in the first electrode and the second electrode in the state of the device structure having the laminated structure. The method for driving an electrochemical device according to claim 12.   The method for driving an electrochemical device according to claim 13, wherein the pretreatment is performed at a concentration higher than the liquid concentration at the time of driving in the electrolyte layer and the electrolyte in the first electrode and the second electrode.   The method for driving an electrochemical device according to claim 14, wherein at least the concentration of the liquid and / or the processing temperature is controlled in the pretreatment.   The method for driving an electrochemical device according to claim 12, wherein water, alcohol or a mixture thereof is used as the pretreatment liquid.   The method for driving an electrochemical device according to claim 12, wherein the fuel cell is driven.

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