JP3032309B2 - Method for producing lithium ion conductive solid electrolyte - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a solid electrolyte used in electrochemical devices such as batteries and capacitors.

[0002]

2. Description of the Related Art An all-solid battery using a solid electrolyte has attracted a great deal of attention for realizing a highly reliable battery with no fear of liquid leakage. In particular, a battery using lithium is expected as a battery having a high capacity. Have been. The lithium ion conductive solid electrolyte of the compound represented by the chemical formula shown in Chemical Formula 1 has already been used as a solid electrolyte when constituting a power supply for driving a cardiac pacemaker.

[0003]

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[0004] However, there are few examples in which the lithium ion conductive solid electrolyte is used as a practical element as described above, and this is due to the low ionic conductivity of the lithium ion conductive solid electrolyte. In order to overcome such problems, as a solid electrolyte having a relatively high ionic conductivity, an oxyacid salt-based lithium ion conductive solid electrolyte represented by a compound represented by the following chemical formula (2) has been proposed. I have.

[0005]

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The solid electrolyte is prepared by mixing a predetermined amount of each raw material and sealing the glass in an inert gas atmosphere such as argon.
After heating and melting, solid ionics is a method of allowing natural cooling or rapid cooling in liquid nitrogen (Kodansha 1986
77).

[0007]

In order to solve this problem, a method for producing a lithium ion conductive solid electrolyte according to the present invention comprises a lithium salt of an oxyacid with a transition metal and oxygen,
The valence of the transition metal constituting the oxyacid is a single valence.
And the lithium salt has a stoichiometric composition.
A method for producing a solid electrolyte of titanium ion, comprising:
Melt of said lithium salt by metal transfer and oxygen, or before
The molten raw material that constitutes the lithium salt is placed in an oxygen atmosphere.
Medium, at a rate of 10 ⁵ ° C / sec or more and 10 ⁷ ° C / sec or less
The feature is that electron conductivity is reduced by cooling.
I do.

[0008]

Means for Solving the Problems To solve this problem, the method for producing a solid electrolyte according to the present invention is characterized in that the oxyacid-based lithium ion conductive solid electrolyte has a single valence of the transition metal constituting the oxyacid. It is produced by rapidly cooling in an oxygen atmosphere a valence solid electrolyte and a molten oxylate-based lithium ion conductive solid electrolyte or a raw material constituting the same.

[0009]

In order to solve the above-mentioned problems, the present inventors have found that when the melt of the solid electrolyte is quenched in an oxygen atmosphere, the electron conductivity is remarkably reduced and the ionic conductivity is improved at the same time. This is considered to be based on the following operation.

That is, according to the production method described in the prior art, the lithium ion conductive solid electrolyte represented by the compound of the chemical formula (2) has a slight non-chemical A transition metal such as V having a stoichiometric composition and thus forming an oxyacid has a mixed valence,
It is believed that electrons conduct hopping conduction in the mixed valence portion, which gives rise to electron conductivity of the solid electrolyte. For example, the compound of the chemical formula shown in the above (Chemical Formula 2) is melted in an atmosphere of an inert gas such as argon or in a glass sealed tube,
When allowed to cool naturally or quenched in liquid nitrogen, the valence of V becomes a mixture of tetravalent and pentavalent, and electron conductivity is generated through this mixture. However, when the melt is rapidly cooled in an oxygen atmosphere, the valence of V is unified to pentavalent, the electron conductivity due to the above-mentioned hopping disappears, and a lithium ion conductive solid electrolyte having low electron conductivity is obtained. .

Production of a solid electrolyte according to one embodiment of the present invention
The method will be specifically described with reference to the drawings.

Example 1 In FIG. 1, powder of a compound of the chemical formula shown in Chemical Formula 3 was quantified in a molar ratio of 17: 4: 3, dispersed in normal hexane, and dried in dry air at 600 ° C. for 3 hours. After heating, allow to cool to room temperature.

[0013]

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Thereafter, this is placed in a glassy carbon container 1 and then placed in an infrared image furnace 2 through which an argon gas containing 1% by volume of oxygen has flowed, for about 700 hours.
The conditioning material is melted by heating to ° C. The melt is quenched at a cooling rate of 10 ⁵ ° C./sec by dropping it onto a rotating roller 3 having a sufficient heat capacity and coated with titanium to form a glass container 4.
To be collected. The rotary roller 3 where the melt is quenched and the surrounding atmosphere are kept in an oxygen atmosphere by oxygen introduced from the oxygen inlet 5. Finally, this was pulverized in a dry air atmosphere to obtain a lithium ion conductive solid electrolyte A. As a comparative example, powder of a compound of the chemical formula shown in Chemical Formula 3 was quantified in a molar ratio of 17: 4: 3,
Dispersed in normal hexane, heated in dry air at 600 ° C. for 3 hours, allowed to cool to room temperature, and pulverized to obtain a fine powder, which was then press-molded at a pressure of 3 ton / cm ² and sealed in a quartz glass container. Then, after sintering at 1000 ° C. for 1 hour, the mixture was allowed to cool to room temperature and pulverized in a dry air atmosphere to obtain a lithium ion conductive solid electrolyte B. The atmosphere gases used in the above-described manufacturing process have a purity of 99.99% or more. In this embodiment, the cooling is performed at a cooling rate of 10 ⁵ ° C / sec., But the same effect can be obtained when the cooling rate is 10 ⁵ to 10 ⁷ ° C / sec.

As described above, the electric conductivity and the electron conductivity of the lithium ion conductive solid electrolyte A prepared according to the production method of the present embodiment and the lithium ion conductive solid electrolyte B prepared by the conventionally known production method are compared. Was evaluated. The measurement of electric conductivity is performed in an argon atmosphere.
Powder samples A and B were formed by pressurizing and molding metal lithium electrodes at both ends of the molded product under a pressure of 3 ton / cm ² by a vacuum evaporation method, and the complex impedance was measured. The result is shown in FIG. In FIG. 2, the electric conductivity is the reciprocal of the value of the intercept of the complex impedance with the horizontal axis, as is well known. The electron conductivity was measured by pressing powder samples A and B at a pressure of 3 ton / cm ^{2 at} a pressure of 3 ton / cm ^2. After applying a constant voltage of volts and a sufficient time had passed, the measurement was performed by measuring a current value at which the voltage became a constant value. The above measurement results are shown in FIG. All measurements were performed in a dry argon atmosphere. In FIG. 3, the vertical axis indicates the electron conductivity and the ionic conductivity obtained from the difference between the electric conductivity and the electron conductivity, and the horizontal axis indicates the measurement temperature. As is apparent from the figure, according to the manufacturing method of this example, the ionic conductivity was increased and the electron conductivity was significantly reduced as compared with those manufactured by the conventional manufacturing method.

Further, V constituting the solid electrolytes A and B
Was confirmed by XPS (X-ray light spectroscopy). In sample B, the tetravalent V was present at about 50 atomic% relative to the pentavalent V,
It was confirmed that the detection limit was 1 atomic% or less, which is the detection limit of S, and a result was obtained which proved the factors described in the above operation.

In this embodiment, the melt of the raw material constituting the solid electrolyte was quenched in an oxygen atmosphere. However, even if the solid electrolyte prepared according to the conventional manufacturing method is melted and quenched in the oxygen atmosphere, It goes without saying that a similar effect is produced.

Example 2 In this example, the effect of the method for producing a solid electrolyte of the present example will be described taking a compound of the chemical formula shown in Chemical Formula 4 as an oxyacid salt type lithium ion conductive solid electrolyte as an example. Is described. For the synthesis, the same apparatus as the manufacturing apparatus shown in FIG. 1 of Example 1 was used.

[0019]

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The powder of the compound of the chemical formula shown in Chemical Formula 5 is quantitatively determined at a molar ratio of 9: 3: 1, dispersed in normal hexane, heated in dry air at 600 ° C. for 3 hours, and then cooled to room temperature. Thereafter, this is placed in a glassy carbon container 1 and then heated to about 700 ° C. in an infrared image furnace 2 in which an argon gas containing 1% by volume of oxygen has flowed to melt the conditioning material.

[0021]

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The melt is quenched at a cooling rate of 10 ⁵ ° C / sec by dropping it onto a rotating roller 3 having a sufficient heat capacity and coated with titanium, and is collected in a glass container 4. The rotary roller 3 where the melt is quenched and the surrounding atmosphere are kept in an oxygen atmosphere by oxygen introduced from the oxygen inlet 5. Finally, this was pulverized in a dry air atmosphere to obtain a lithium ion conductive solid electrolyte C. As a comparative example,
The powder of the compound of the chemical formula shown in Chemical Formula 5 was quantified in a molar ratio of 9: 3: 1, dispersed in normal hexane, and dried in dry air.
After heating at 00 ° C. for 3 hours, the mixture was allowed to cool to room temperature, and the fine powder obtained by pulverization was molded under pressure at a pressure of 3 ton / cm ² , sealed in a quartz glass container, and sintered at 800 ° C. for 1 hour. After cooling, the mixture was allowed to cool to room temperature and pulverized in a dry air atmosphere to obtain a lithium ion conductive solid electrolyte D. The atmosphere gases used in the above-described manufacturing process were all 9% pure.
It is not less than 9.99%. Further, in the present embodiment was conducted at 10 ⁵ ° C. / sec as the cooling rate of the melt, 10 ⁵ ~
It produces similar effects at 10 ⁷ ° C. / sec.

The lithium ion conductive solid electrolyte C prepared according to the production method of this embodiment and the D prepared according to a conventionally known production method were subjected to comparative evaluation of electric conductivity and electron conductivity. In the measurement of electric conductivity, powdery samples C and D were pressed and molded at a pressure of 3 ton / cm ^{2 in} an argon atmosphere. This was done by measuring the impedance. The result is shown in FIG. In FIG. 4, the electric conductivity is the reciprocal of the intercept of the complex impedance with the horizontal axis, as is well known. The electron conductivity was measured by pressing powder samples A and B at a pressure of 3 ton / cm ^{2 at} a pressure of 3 ton / cm ^2. After applying a constant voltage of volts and a sufficient time had passed, the measurement was performed by measuring a current value at which the voltage became a constant value. The above measurement results are shown in FIG. All measurements were performed in a dry argon atmosphere. In FIG. 5, the vertical axis indicates the electron conductivity and the ion conductivity obtained from the difference between the electric conductivity and the electron conductivity, and the horizontal axis indicates the measurement temperature. As is clear from the figure, according to this example, a solid electrolyte having high ionic conductivity and low electron conductivity was obtained.

Furthermore was confirmed valence of V constituting the solid electrolyte C and D by XPS (X-ray beam spectroscopy), the sample D, the tetravalent to pentavalent V V
Was present in sample C compared to about 50 atomic%.
It was confirmed that the detection limit was 1 atomic% or less.
The result proves the factors described in the above operation.

In this embodiment, the melt of the raw material constituting the solid electrolyte was quenched in an oxygen atmosphere. However, even if the solid electrolyte prepared according to the conventional manufacturing method is melted and quenched in the oxygen atmosphere, It goes without saying that a similar effect is produced.

In the above examples, the compound of the chemical formula shown in the chemical formula (6) and the compound of the chemical formula shown in the chemical formula (4) are taken as examples of the oxyacid salt-based lithium ion conductive solid electrolyte, and the production method of the present invention is described. Although the effect has been described, it is not particularly necessary to limit the material to this material, and it is needless to say that the material is also effective for producing a known oxylate-based lithium ion conductive solid electrolyte.

[0027]

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[0028]

As is clear from the above description of the embodiment,
According to the method for producing a solid electrolyte of the present invention, a lithium ion conductive solid electrolyte having low electron conductivity can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the concept of an apparatus for producing an oxylate-based lithium ion conductive solid electrolyte according to one embodiment of the present invention.

FIG. 2 Oxygenate-based lithium ion conductive solid electrolyte A
A graph showing the complex impedance of B and B

FIG. 3 is an oxygenate-based lithium ion conductive solid electrolyte A
And graphs showing the characteristics of B

FIG. 4 Oxygenate-based lithium ion conductive solid electrolyte C
Showing the complex impedance of D and D

FIG. 5: Oxylate-based lithium ion conductive solid electrolyte C
Graphs showing characteristics of D and D

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glassy carbon container 2 Infrared image furnace 3 Rotating roller 4 Glass container 5 Oxygen inlet

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kenichi Takeyama 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-2-87415 (JP, A) JP-A-2- 304805 (JP, A) JP-A-60-1003038 (JP, A) JP-B-63-17722 (JP, B2)

Claims (1)

(57) [Claims] 1. A lithium salt of an oxyacid with a transition metal and oxygen, wherein the valence of the transition metal constituting the oxyacid is a single valence, and the lithium salt has a stoichiometric composition. A method for producing an ion-conductive solid electrolyte, comprising a melt of the lithium salt with a transition metal and oxygen,
Or melt of the raw materials constituting the lithium salt, in an oxygen atmosphere, 10 ⁵ ° C. / sec or more and less 10 ⁷ ° C. / sec
A method for producing a lithium ion conductive solid electrolyte , wherein electron conductivity is reduced by quenching at a rapid rate .