JPH0316921A - Synthesis method of silver ion conductive solid electrolyte - Google Patents

Abstract

PURPOSE:To enable easy synthesis of silver ion conductive solid electrolyte by conducting the reaction of a mixture of silver iodide, silver oxide and tungsten oxide in the molten state with heat. CONSTITUTION:A mixture of silver iodide, silver oxide, and tungsten oxide, or a mixture of silver iodide and silver tungstate are used as a starting substance to synthesize silver ion conductive solid electrolyte. Thus, presynthesis of silver tungstate becomes unnecessary and the synthetic process can be simplified. Further, the solid electrolyte is prepared without use of unnecessary substance for the electrolyte an the costs can be decreased. Further, the mixture of feedstocks is heated in air without use of Pyrex glass tubes for enclosing the mixture and a large amount of product can be produced in no need of oxygen gas or nitrogen gas. Thus, installation costs are reduced.

Description

[Detailed Description of the Invention] Industrial Fields of Application The present invention (all-solid-state secondary batteries)
This invention relates to a method for forming a silver ion conductive solid electrolyte.

Conventional technologyCurrently, electrochemical devices such as batteries use liquid as an electrolyte, which makes it impossible to completely eliminate problems such as electrolyte leakage. In order to make the device thinner, attempts are being made in various fields to use a solid electrolyte instead of a liquid electrolyte and to make the device completely solid.

The main solid electrolytes used here include copper ion conductive materials, silver ion conductive materials, lithium ion conductive materials, etc.In particular, silver ion conductive solid electrolytes made of phosphorous iodide, silver oxyoxide, etc.In the atmosphere It is stable against humidity and oxygen, making it an extremely useful material for constructing highly reliable electrochemical devices.

Among these silver ion conductive solid electrolytes made of silver iodide and silver oxyoxide, the silver ion solid electrolyte made of silver iodide and silver tungstate represented by AgsI4WOm (its glass transition temperature is higher than that of others) Because it exhibits high thermal stability and thermal stability, research is progressing in various fields.

This A. As a method for combining a silver ion solid electrolyte consisting of silver iodide and silver tungstate represented by geI4WOa (Yo Takahashi et al.'s paper (J. Electrochem.
．． Soc. , vol. 120, No.
5,647 (1973), etc., silver tungstate was mixed as a starting material.
A method has been adopted in which the mixture is melt-reacted.

In addition, the melting reaction (according to Takahashi et al. cited above) is carried out in a Pyrex tube sealed under reduced pressure.

Also Y. C. According to Chan et al., a method of melting reaction in an oxygen atmosphere has been adopted (Proceec et al.
ring of NCKU/ASS Inter
National Symposium On
Engineering Science and
Mechanics p. 1381-138
8) According to Wang Shung, a method of melting and reacting in a nitrogen atmosphere is used (Material
s for Solid Sta.
t e B a t t e r
i es, p. 4 67-4.7
3, (1986)).

Problems to be Solved by the Invention However, in order to obtain silver tungstate used in solid electrolytes, there is a method in which an aqueous solution of sodium tungstate is mixed with a nitrate solution, and the precipitate of silver tungstate is filtered from the aqueous solution and washed with water. As a result, there is a problem that not only does the process become complicated, but also that impurities such as sodium and lithium may remain in the obtained silver ion conductive solid electrolyte. The problem is that the cost is high because unnecessary substances such as sodium are used in the solid electrolyte.

Furthermore, when the melting reaction is carried out in a Pyrex tube sealed under reduced pressure, when a large amount of solid electrolyte is combined, the starting material for the combination must be sealed in small amounts at a time. In addition, in order to carry out the melting reaction in an oxygen or nitrogen atmosphere, oxygen gas or nitrogen gas and its supply equipment must be provided. However, there is a problem that the cost becomes high.

The present invention solves the complexity of the conditions such as vacuum sealed tubes and atmosphere during the melting reaction of silver tungstate, and makes it possible to form a silver ion conductive solid electrolyte in an easy manner. Along with this, it is possible to reduce the cost of gathering commandments.

Means for Solving the Problems The present invention achieves the above objects by melting and reacting a mixture of silver iodide, silver oxide and tungsten oxide to form a silver ion conductive solid electrolyte. It is characterized by

Also, a mixture of silver iodide, silver oxide, and tungsten oxide
Alternatively, a silver ion conductive solid electrolyte can be formed by heating and melting a mixture of silver iodide and silver tungstate in the atmosphere.

151 According to the present invention, by synthesizing a silver ion conductive solid electrolyte using a mixture of silver iodide, silver oxide, and tungsten oxide, or a mixture of silver iodide and silver tungstate as a starting material, tungsten There is no need to synthesize acid silver in advance, and the abrasive synthesis process can be simplified. Furthermore, since synthesis is performed without using components unnecessary for the solid electrolyte, costs can be reduced.

In addition, by heating the starting material mixture in the atmosphere, there is no need to seal the starting material mixture in a Pyrex tube, making it easy to synthesize in large quantities, and synthesis can be performed without using oxygen or nitrogen gas. This eliminates the need for these gases and their supply equipment, reducing costs.

Example (First Example) First, silver iodide (AgI), a special grade reagent, was used as a starting material.
, silver oxide (Ag20), tungsten oxide (WO
a) in a molar ratio of 4: 1: 1 (W00 was weighed out in a molar ratio of 4: 1: 1 and mixed in an alumina mortar. This mixture was pressurized and pelletized. The reaction product was then sealed in a Pyrex tube under reduced pressure and melted and reacted at 400°C for 18 hours.
As a comparative example, a silver ion conductive solid electrolyte A represented by s I aW O a was obtained using silver iodide and silver tungstate as starting materials.A silver ion conductive solid electrolyte B was obtained by the following method. First, silver nitrate (AgNOs) and sodium tungstate (NapWOJ・2'H*○) were weighed out at a molar ratio of 1:1.These were dissolved and mixed in pure water.The precipitate was filtered from this solution. After washing seven times with pure water, it was dried at 120°C for 3 hours in a nitrogen atmosphere.
Silver tungstate represented by 4 was obtained by the same method as above, except that a mixture of the thus obtained A g sw O a and the AgI used above was used in a molar ratio of 4=1. A silver ion conductive solid electrolyte B represented by AgeI4W○4 was obtained, and the obtained solid electrolyte A was
Characteristics of , B were evaluated by measuring ionic conductivity and electronic insulation properties. First, the ionic conductivity was evaluated by weighing 200 mg of powder of solid electrolytes A and B obtained in the above manner, and placing a platinum plate of 10 mm diameter on both sides. Plates L, 4ton/
am'' to a diameter of 10 mm to construct an electrical conductivity measurement cell.The temperature change in electrical conductivity was evaluated using the alternating current impedance measurement method.The results are shown in Figure 1. However, in Figure 1, the vertical axis shows electrical conductivity logarithmically, and the horizontal axis shows the reciprocal of absolute temperature.

No major difference was observed between solid electrolytes A and B, and AgI, A g * O, W O * of this example
Regarding solid electrolyte A using AgI as a starting material, it was found that the comparison example showed the same ionic conductivity as solid electrolyte B using AgI and Ag-WO4 as a starting material.Next, regarding the electronic insulation property, Like?
Weighed 200 mg of solid electrolyte A and B powder, placed a platinum plate on one side as an ion blocking electrode with a diameter of 10 mm, and a silver plate with a diameter of 10 mm on the other.
A cell for measuring electronic conductivity was constructed by pressurizing the cell to a diameter of 10 mm at a temperature of 20° C., and was evaluated by measuring the steady current flowing when a constant voltage was applied at 20° C.1. The results are shown in Figure 2, with the horizontal axis representing the voltage of the platinum plate relative to the silver plate, and the vertical axis representing the steady current value.

No major difference was observed between solid electrolytes A and B, and solid electrolyte A using AgI, AggO, and WO3 of this example as a starting material was compared with L of solid electrolyte A of this example, and AgI and A of comparative example.
It can be seen that it exhibits electronic insulation properties equivalent to solid electrolyte B using g2W○4 as a starting material.

As described above, this example shows that a silver ion conductive solid electrolyte can be easily obtained without impairing the properties of the solid electrolyte such as ionic conductivity and electronic insulation.

(Second Example) A g L A g*0, WOs in molar ratio 4:
1: Pressurize the mixture mixed in 1 to make it into pellets, then put it in a Pyresis crucible and heat it in the air for 40 minutes.
A silver ion conductive solid electrolyte C represented by AgeIaWOa was obtained by the same method as in the first example except that the reaction was carried out at 0°C for 18 hours. Ion conductivity and electronic insulation were evaluated using the same method as in Example 1. The results are shown in Figure 3 (ion conductivity) and Figure 4 (electronic insulation).
Shown below.

Characteristics of solid electrolyte C (i.e., ionic conductivity, electronic insulation, and
I understand that it is possible to easily obtain a silver ion conductive solid electrolyte without impairing the properties of the solid electrolyte such as electronic insulation (third practical example) AgL AgeW○4 was mixed in a molar ratio of 4=1. A -10- silver ion conductive solid electrolyte D represented by A g e I a WO 4 was obtained by the same method as in the second example except that A g e I a W O was used as the starting material. 1,'Y. Ionic conductivity and electronic insulation were evaluated using the same method as in Example 1. The results are shown in FIG. 5 (ion conductivity) and FIG. 6 (electronic insulation).

Characteristics of solid electrolyte D (ion conductivity, electronic insulation, etc.) No major differences were observed from solid electrolyte B in the first example. According to this example, the characteristics of solid electrolyte such as ionic conductivity, electronic insulation, and It can be seen that a silver ion conductive solid electrolyte can be obtained by a simple method without damaging the silver ion conductive solid electrolyte.

In the first and second embodiments, the mixture of tungsten oxide, iodide, mirror oxide, and tungsten oxide was combined in a vacuum sealed tube or in the atmosphere. It goes without saying that the results of Other considerations: pAgI-qAg201r W
Regarding the silver ion conductive solid electrolyte represented by the general formula O a or xAg I'jAg2WOa, L
The only difference is that the structure exhibits ionic conductivity and electronic insulation properties, and it goes without saying that similar effects can be obtained. There is no need to combine acid silver in advance, and a silver ion conductive solid electrolyte can be easily obtained from a mixture of only the solid electrolyte components, and the cost of combining can be reduced accordingly. .

[Brief explanation of the drawing]

The IT diagram shows the ionic conductivity of the solid electrolyte in the first embodiment of the present invention and the comparative example. Figure 2 shows the electronic insulation properties of the solid electrolyte. Characteristics showing the ionic conductivity of the solid electrolyte in Example ＠ Figure 4 shows the characteristics showing the electronic insulation property of the solid electrolyte Figure 5 shows the ionic conductivity of the solid electrolyte in the third example of the present invention Figure 6 shows the same solid electrolyte 1.
FIG. 1 is a characteristic diagram showing the electronic insulation properties of 1 12− .

Claims (3)

[Claims] (1) A method for synthesizing a silver ion conductive solid electrolyte, which is characterized by heating and melting a mixture of silver iodide, silver oxide, and tungsten oxide. (2) The method for synthesizing a silver ion conductive solid electrolyte according to claim 1, characterized in that the heating and melting reaction of a mixture of silver iodide, silver oxide, and tungsten oxide is carried out in the atmosphere. (3) A method for synthesizing a silver ion conductive solid electrolyte, which is characterized by heating and melting a mixture of silver iodide and silver tungstate in the atmosphere.