JPS634670B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid electrochemical device and a method for manufacturing the same.

Solid electrochemical devices generally include a working electrode, a counter electrode that faces the working electrode through a solid electrolyte layer made of an ionically conductive solid electrolyte, and, if necessary, a counter electrode that is arranged to accurately detect the potential of the working electrode. It consists of a reference electrode that is separately provided to face the working electrode with a solid electrolyte layer interposed therebetween, and the amount of electricity that passes between the working electrode and the counter electrode changes depending on the amount of electricity that passes between the working electrode and the reference electrode. It has a property that the potential changes almost linearly, and when the current supply is stopped, the current potential is maintained as it is.

When this solid-state electrochemical element is sequentially charged, rested, discharged, and rested, the ideal progression of the potential of the working electrode with respect to the reference electrode is as shown in Figure 1, because each operating point has a break. It is shown as a combination of several straight lines.

That is, when the element is charged with a constant current (current is passed from the working electrode to the opposite electrode), the potential of the working electrode with respect to the reference electrode increases almost linearly with time. Next, the value at the time of energization is continued to be held. Next, when a constant current is discharged (current is applied in the direction from the counter electrode to the active electrode), the potential of the active electrode decreases almost linearly over time. Next, when switching to a state in which the energization is stopped, the operating electrode potential continues to hold the value at the time when the energization was stopped.

The structure of a solid-state electrochemical device having such characteristics has a cross section shown in FIG. 2A or B, as is already well known. Second
Taking as an example the case where the device configurations in Figures A and B use a copper ion conductive solid electrolyte,
In the figure, 1 is a counter electrode, which is formed by press-molding a mixture of Cu2S and a solid electrolyte. Thereon, a solid electrolyte layer 2, a working electrode layer 3 made of a mixture of Cu2S and a solid electrolyte, a solid electrolyte layer 2', and a reference electrode layer 4 made of the same material as the counter electrode are formed by press molding in sequence. Finally, the reference electrode and counter current collector electrodes 6, 6' are press-fitted with a final pressure and then taken out from the mold to form a molded element. The current collecting electrodes 5, 5' of the working electrode are either press-fitted after the device is molded, as shown in FIG. 2A, or inserted between the working electrode 3 and the solid electrolyte layer 2' during molding, as shown in FIG. 2B. After molding the device, a part of the reference electrode 4 and the solid electrolyte layer 2' are cut out, and the current collecting electrode 5' of the working electrode is taken out. Next, connect the lead wires 8, 8', 8'' to each current collecting electrode with solder or conductive adhesive 7, 7', 7'', and cover the device with an exterior cover if necessary to protect the element. Perform step 9 with resin.

In the above-mentioned conventional device, the yield for obtaining the operating characteristics shown in FIG. 1 was poor, and it took a great deal of effort to improve the yield. That is, as shown in FIG. 2A, when the working electrode current collecting electrode 5 is press-fitted after the element molding, the current collecting electrode 5 is inserted into the working electrode 3 in the following manner.
In some cases, it is press-fitted close to the reference electrode 4 (in extreme cases, it is press-fitted into the solid electrolyte layer 2'), and in other cases, it is press-fitted at a position closer to the counter electrode 1 side. In order to obtain the operating characteristics shown in FIG. 1, the working electrode current collecting electrode 5 must be inserted correctly at the interface between the working electrode 3 and the solid electrolyte layer 2' as shown in FIG. 2B. Must be. If the current collecting electrode is not inserted correctly, the operating characteristics of the element will continue to change in the direction in which the potential has changed during energization, even after the energization of the element is stopped, as shown in Figure 3a. (hereinafter referred to as overshoot), or
Or, as shown in Figure 3b, the potential is not maintained well when the current is stopped, and the potential after charging is stopped is
The potential decreases from the potential when charging is stopped, or
The potential after discharging is stopped gradually increases from the potential at the time of discharging, which has the effect that the potential is not stable.

On the other hand, if you try to configure it as shown in Figure 2B,
Although it is necessary to cut out a part of the reference electrode 4 and the solid electrolyte layer 2', this operation weakens the bond between each layer of the element, and as a result, as shown in FIG. Sudden change in potential (△V) when stopping, starting and stopping discharge
begins to occur. Furthermore, even if there is no such sudden change in potential during device fabrication, when a durability test such as a thermal shock test is performed, ΔV increases as shown in b in FIG. 5.

The object of the present invention is to eliminate the above-mentioned drawbacks and to easily and simply manufacture an element having operating characteristics as shown in FIG. 1 with good yield. Another purpose is to further improve the reliability of the element and to produce an element that can withstand long-term use even in harsh environments.

Conventionally, in this type of device, it has been thought that in order to obtain the operating characteristics shown in FIG. 1, it is necessary to improve the bonding state between each layer in the configuration shown in FIG. 2. It's here. To this end, as described above, methods have been taken in which each layer is stacked and press-molded in a mold. This is based on the general idea that it is undesirable to mix other materials into solid electrolytes and electrode materials because it reduces their functionality, and also to improve the cohesion of each layer when the powder is molded. In order to do so, the above-mentioned means have been chosen. However, the inventors have found that, contrary to the above, incorporation of a suitable type and amount of binder yields rather favorable results.

The present invention has been made in view of this point,
The solid electrolyte layer is characterized by containing a thermosetting resin that reacts and hardens when the temperature exceeds a certain temperature.

Hereinafter, the structure of the device and the manufacturing method thereof according to the present invention will be explained with reference to FIGS. 6A and 6B. 6th
FIG. 6A is an exploded perspective view for explaining the manufacturing method of the present invention, and FIG. 6B is a perspective view showing the appearance of the element body obtained by this method. The solid electrolyte layers 12, 12' containing a thermosetting resin, the counter electrode 11, the working electrode 13, and the reference electrode 14 are each separately molded into a tablet. Among these, each of the counter electrode 11, the working electrode 13, and the reference electrode 14 has a current collecting electrode 15 corresponding to 5', 6, 6' in FIG. , 16, 16'(16' is hidden and cannot be seen) are buried in advance. These layers are assembled together in a mold, heated to a temperature higher than the curing temperature of the resin, and then joined by press working to form an element body as shown in Figure 6B. do. After taking out the device from the mold, a part of the reference electrode 14 and the solid electrolyte layer 12' is cut out to take out the active collector electrode 15, and leads are attached to each collector electrode with solder or conductive adhesive. Then, if necessary, apply a resin exterior to complete the process. In this way, an element having substantially the same structure as that shown in cross-section in FIG. 2B is obtained.

As the thermosetting resin used in the present invention, a solvent-free type or a powder type is suitable.
Examples of this type of resin include epoxy resin and polyester resin. If the amount of this resin added is more than 10 parts by weight per 100 parts by weight of the material in the solid electrolyte layer 12 on the counter electrode side, the resistance value of the solid electrolyte layer 2 will increase and the ionic conductivity will be significantly impaired. However, even if the amount of resin added to the solid electrolyte layer 12' on the reference electrode 14 side is increased to 25 parts by weight, the function as an element will not change; layer 1
Due to the high resistance value of 2', it no longer functions as a reference pole. Moreover, when the amount of resin added is less than 1 part by weight, sufficient binding of each layer cannot be obtained.

Hereinafter, specific embodiments of the present invention will be described with reference to FIG. First, as a copper ion conductive solid electrolyte, 1/5 of the Cu ions in CuCl are converted into Rb ⁺ , K ⁺ , NR ₄ ⁺
(R is H or an alkyl group), and 1/4 to 7/20 of the Cl ^- ion.
is substituted with I ^- ion (this is SE
), a mixture of this SE and epoxy powder thermosetting resin at a ratio of 30:1, weighing 0.6 g in diameter.
Mold into a 15φ tablet at room temperature. The counter electrode and reference electrode materials include 9 parts of cuprous sulfide and the above.
Mix 1 part of SE and mold it into a tablet weighing 0.6g and having a diameter of 15φ. As the working electrode, a mixture of equal amounts of cuprous sulfide and the above SE was used, weighing 0.6 g.
Form into a tablet with a diameter of 15φ. In each electrode, a metal is embedded at a preferable position to serve as a current collecting electrode and to which lead wires can be easily soldered. In addition, the tablet that becomes the solid electrolyte layer 12' on the reference electrode side is made by molding a mixture of the above SE and an epoxy powder thermosetting resin in a ratio of 9:1 to a weight of 0.6g and a diameter of 15φ at room temperature. put. As shown in Figure 6A, these tablets are stacked one on top of the other so that they function as devices, placed in a mold that allows the stack to fit smoothly, and heated at 200°C under a pressure of 4 tons/ ^cm2 . A molded element is obtained by pressure molding. Reference electrode 14 and solid electrolyte layer 1 of this molded element
After cutting out a part of 2' and taking out the active collector electrode 15, lead wires are soldered to each collector electrode and covered with resin to obtain an element having the structure shown in FIG. 2B. .

In the above embodiment, cuprous sulfide was used as an example of the electrode material, but copper chalcogenides such as cuprous selenide and cuprous telluride may also be used.

As in the above example, by mixing an appropriate amount of powdered thermosetting resin into the solid electrolyte layer and hardening the resin during heating and pressure, the bond between each layer is strengthened. Instead of stacking each layer one after another in one mold, we improved the manufacturing process by molding each layer into separate tablets and then stacking them together.This not only made it possible to manufacture devices extremely efficiently, but also A significant improvement can also be seen in the reliability of the device.

Next, a thermal shock test was conducted on the device of the present invention obtained in this way and a conventional device that does not contain a thermosetting resin under the following conditions. Value of sudden change in potential (4th
When ΔV) in the figure is illustrated, it becomes as shown in FIG. The conditions for the thermal shock test were -20°C on the low temperature side and +80°C on the high temperature side, and after being kept in a bath at each temperature for 30 minutes, the operation was repeated to plunge into another bath, and this operation was repeated for 5, 20, and 100 cycles. Afterwards, the device was subjected to a charging/discharging operation of 1 mA, and changes in potential at the start and stop of charging/discharging were read. This rapid change in potential has approximately the same magnitude when charging starts and stops, but its direction is opposite. Furthermore, as shown in FIG. 4, the magnitudes of discharge and charge are almost the same, but the directions are opposite. In FIG. 5, a shows the transition of the value of a sudden change in potential in the thermal shock test of the element according to the present invention,
b shows the transition of a rapid change in potential in a conventional thermal shock test of an element.

As shown in FIG. 5, even if the performance appears to be exactly the same at the beginning, with the conventional element, the bond between layers is gradually impaired due to thermal shock, and the performance of the element deteriorates. The device hardly changes even if the number of cycles increases, and it is possible to provide a highly reliable device.

As is clear from the above description, in the present invention, each layer constituting an element is separately molded into a tablet at room temperature, and then layered in a mold and heated.
Since the layers are pressurized and bonded together using the thermosetting resin contained in each layer, the device can be mass-produced using automatic machines, and the device can be provided at low cost. Furthermore, as is clear from the results of the thermal shock test shown in FIG. 5, an excellent element with little variation in characteristics was obtained, and its practical value is great.

[Brief explanation of the drawing]

Fig. 1 is a preferred curve diagram showing the time change of the operating electrode potential with respect to the reference electrode when the solid-state electrochemical device is charged and discharged with a constant current, and Fig. 2 A and B show an example of the structure of the solid-state electrochemical device. A cross-sectional view, Figure 3 is a defective curve diagram showing the time change of the operating potential with respect to the reference electrode when charging and discharging with a constant current in a conventional element, and Figure 4 shows another defect in the conventional element. The curve diagram, FIG. 5, shows the transition of rapid changes in potential at the start and stop of energization during charging and discharging operations in the present invention and the conventional device with the configuration shown in FIG. 2B when a thermal shock test was conducted. The curve diagram and FIGS. 6A and 6B are an exploded perspective view showing the process of the manufacturing method of the present invention and an external view of the element body. 11... Counter electrode, 12, 12'... Solid electrolyte layer,
13... Operating pole, 14... Reference pole, 15, 16,
16'...Collecting electrode.

Claims (1)

[Claims] 1. A counter electrode having a current collecting electrode is provided on one surface of a working electrode having a current collecting electrode via a first solid electrolyte layer made of an ionically conductive solid electrolyte, and A reference electrode having a current collecting electrode is provided on the other surface via a second solid electrolyte layer made of an ion-conductive solid electrolyte, and the potential of the working electrode with respect to the reference electrode is between the working electrode and the counter electrode. In the solid electrochemical device, the first and second solid electrolyte layers contain a thermosetting resin, and a collector provided at the working electrode is provided. A solid electrochemical device, characterized in that a current collecting electrode is arranged near the interface with the second solid electrolyte layer, and a part of the current collecting electrode is exposed. 2. A solid electrochemical device according to claim 1, characterized in that at least one selected from epoxy resins and polyester resins is used as the thermosetting resin. 3. Molding the material forming the counter electrode, the material forming the working electrode, and the material forming the reference electrode, respectively, with at least a part of the current collecting electrode embedded in each electrode exposed on the surface, and 1st and 2nd
A mixed composition of an ion-conductive solid electrolyte and a thermosetting resin forming the solid electrolyte layer is molded at a temperature at which the thermosetting resin does not harden, and these molded products are used as the counter electrode and the first solid electrolyte layer. , working pole,
a second solid electrolyte layer, a reference electrode, and a current collecting electrode embedded in the counter electrode and the reference electrode;
and arranged on the side not in contact with the second solid electrolyte layer,
Laminating the current collecting electrode embedded in the working electrode on the side in contact with the second solid electrolyte layer, and heating the laminated body at a temperature at which the thermosetting resin hardens.
After pressurizing and molding them into one piece, the reference electrode and a part of the second solid electrolyte layer are removed so that a part of the current collecting electrode embedded in the working electrode is exposed, and then the A method for manufacturing a solid-state electrochemical device, characterized by joining a lead wire to each current collecting electrode.