JP2004265685A - Manufacturing method of lithium ion conductive sulfide glass and glass ceramic and all solid type battery using the glass ceramic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture lithium ion conductive sulfide glass and glass ceramic that have a high electric conductivity at room temperatures by a simple method from a material easily acquired and inexpensive. <P>SOLUTION: In manufacturing the lithium ion conductive sulfide glass, a material containing lithium sulfide with a crystal particle size of 140 nm or less is used as a starting raw material, and this raw material is vitrified by mechanical milling. Then, in the manufacturing method of the lithium ion conductive sulfide glass ceramic, the lithium ion conductive sulfide glass is fired at glass transition temperature or higher. Thereby, the electric conductivity at room temperature is improved to 10<SP>-4</SP>S/cm or more. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a lithium ion conductive sulfide glass and a glass ceramic, and an all-solid-state battery using the glass or the glass ceramic as a solid electrolyte.
[0002]
[Prior art]
It is known that lithium ion conductive sulfide glass and glass ceramics can be used as an electrolyte of an all-solid-state lithium secondary battery. Such a sulfide glass is prepared by mixing glass-forming agents such as SiS ₂ , phosphorus pentasulfide (P ₂ S ₅ ) and B ₂ S ₃ with lithium sulfide (Li ₂ S) as a glass modifier and melting by heating. After that, it is obtained by quenching (for example, see Patent Document 1).
The present inventors also disclose that such a sulfide glass can be obtained by mechanically milling a sulfide crystal at room temperature (see Patent Document 2).
[0003]
[Problems to be solved by the invention]
In these methods, lithium sulfide, which is a glass modifier, is used as one of the starting materials. However, lithium sulfide has low reactivity, does not efficiently react with the above-mentioned glass former, etc., and unreacted lithium sulfide is produced. Since a large amount remains, the target sulfide glass cannot be obtained. Further, when a large amount of unreacted lithium sulfide remains, the performance as an electrolyte is lowered, and there is a problem that it cannot be used as an electrolyte of an all-solid-state lithium battery.
The present inventors have been studying a method for producing a lithium ion conductive sulfide glass starting from a more easily available and inexpensive raw material.
For example, the present inventors have performed mechanical milling using metallic lithium (Li) or lithium sulfide (Li ₂ S), elemental silicon (Si) and elemental sulfur (S) as starting materials, thereby obtaining lithium ion conductive sulfide. It has been disclosed that glass can be obtained (see Patent Document 2).
However, the sulfide glass has a problem that the mechanical milling time is longer and the electric conductivity of the obtained sulfide glass is lower than when lithium sulfide and SiS ₂ are used as raw materials.
The present inventors have continued to study for the purpose of producing a sulfide glass having higher electric conductivity, and have found that a sulfide ceramic mainly containing lithium sulfide and phosphorus pentasulfide exhibits high lithium ion conductivity. (See Patent Document 3).
It has also been found that by subjecting a sulfide obtained by mechanical milling of lithium sulfide and phosphorus pentasulfide to a baking treatment at a temperature equal to or higher than the glass transition temperature, the electrical conductivity at room temperature is improved (see Non-Patent Document 1). ). Further, as a more available raw material, metallic phosphorus is added to vitrified elemental phosphorus (P) and elemental sulfur (S) by mechanical milling, and the resulting mixture is further mechanically milled to have an electric conductivity of 10 at room temperature. It was also found that a sulfide glass on the order of ^-5 S / cm was obtained (see Non-Patent Document 2).
[0004]
[Patent Document 1]
JP-A-9-283156 [Patent Document 2]
JP-A-11-134937 [Patent Document 3]
JP 2001-250580 A [Non-Patent Document 1]
Chemistry Letters 2001
[Non-patent document 2]
Tatsumi Sanda: Abstracts of the Chemical Society of Japan 2001 Spring Meeting Abstracts 2E341
[0005]
[Means for Solving the Problems]
The present inventors further studied a production method using a raw material which is simple and easily available, and using metallic lithium or lithium sulfide, elemental sulfur (S) and elemental phosphorus (P) as starting materials, It has been found that a sulfide glass obtained by milling has the same performance as a lithium ion conductive sulfide glass produced by mechanical milling using lithium sulfide and phosphorus pentasulfide as raw materials (Japanese Patent Application No. 2002-005855). . Furthermore, a simple and efficient manufacturing method was examined, and by using lithium sulfide (Li ₂ S) having a specific particle size as one of the starting materials, a sulfide glass useful as a solid electrolyte could be obtained. And completed the present invention.
Furthermore, it has also been found that the sulfide glass obtained by the present invention is improved in electrical conductivity at room temperature to 10 ⁻⁴ S / cm or more by performing a baking treatment once at a glass transition temperature or higher.
[0006]
That is, the present invention
(1) In producing a lithium ion conductive sulfide glass, a raw material containing lithium sulfide having a crystal particle diameter of 140 nm or less is used as a starting material, and the raw material is vitrified by mechanical milling. Method for producing ion-conductive sulfide glass,
(2) The method for producing a lithium ion conductive sulfide glass according to (1), wherein the starting material other than lithium sulfide contains one or more elements selected from sulfur and phosphorus.
(3) Lithium ion conductive sulfide glass ceramics, characterized in that the lithium ion conductive sulfide glass vitrified by mechanical milling described in (1) or (2) above is fired at a glass transition temperature or higher. Manufacturing method,
(4) The method for producing a lithium ion conductive sulfide glass-ceramic according to (3), wherein the firing is performed at 150 ° C. or more;
(5) The method for producing a lithium ion conductive sulfide glass ceramic according to (3) or (4), wherein the calcination is performed in a vacuum or in the presence of an inert gas.
(6) The method for producing a lithium ion conductive sulfide glass according to (1) or (2), wherein the decomposition voltage of the sulfide glass is at least 3 V;
(7) The method for producing a lithium ion conductive sulfide glass ceramic according to any of (3) to (5), wherein the decomposition voltage of the sulfide glass ceramic is at least 3 V;
(8) An all-solid-state battery using a lithium ion conductive sulfide glass produced by the method according to any of (1), (2), and (6) as a solid electrolyte;
(9) Provided is an all-solid-state battery using a lithium-ion conductive sulfide glass ceramics produced by the method according to any of (3) to (5) and (7) as a solid electrolyte. Is what you do.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, a starting material containing lithium sulfide (Li ₂ S) having a crystal particle diameter of 140 nm or less is used. The crystal particle diameter of lithium sulfide (Li ₂ S) is preferably 137 nm or less, more preferably 135 nm or less. When lithium sulfide (Li ₂ S) having a crystal particle diameter of more than 140 nm is used, vitrification does not sufficiently proceed, so that an intended product cannot be obtained.
Lithium sulfide (Li ₂ S) used in the present invention may be produced by any production method, and may be used without particular limitation as long as it is industrially produced and sold. What was manufactured by the manufacturing method described in Unexamined-Japanese-Patent No. 2000-247609 is preferable. The crystal particle diameter of lithium sulfide can be calculated from the crystal peak derived from the plane index (111) by the Scherrer equation based on the result of measurement using an X-ray diffractometer.
[0008]
The starting material other than lithium sulfide (Li ₂ S) is not particularly limited, but examples include a material containing one or more elements selected from sulfur and phosphorus. Specifically, elemental sulfur, elemental phosphorus, SiS ₂ , phosphorus pentasulfide (P ₂ S ₅ ), B ₂ S _{3 and the} like can be mentioned. Elemental sulfur and elemental phosphorus can be used without particular limitation as long as they are industrially produced and sold. Further, as the elemental sulfur, molten sulfur produced in a refinery or the like can be used as it is.
When lithium sulfide (Li ₂ S), elemental sulfur (S) and elemental phosphorus (P) are used as a starting material, the mixing ratio of the elemental sulfur and the elemental phosphorus is not particularly limited. On the other hand, elemental sulfur of 0.5 to 3.5 and elemental phosphorus of 0.2 to 1.5 are preferred. When lithium sulfide (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) are used as starting materials, the molar ratio of phosphorus pentasulfide to phosphorus pentasulfide is preferably 0.05 to 1.0.
[0009]
In the present invention, mechanical milling is used to vitrify a starting material containing lithium sulfide (Li ₂ S). According to mechanical milling, since glass can be synthesized at around room temperature, there is an advantage that thermal decomposition of a starting material does not occur and a glass having a charged composition can be obtained. In addition, mechanical milling has an advantage that the glass can be finely divided at the same time as the synthesis of the glass.
In the method of the present invention, it is not necessary to pulverize or cut again when pulverizing the ion-conductive sulfide glass. Such a pulverized glass can be used as a solid electrolyte by, for example, directly or pressure-molding a pellet into a solid state battery.
ADVANTAGE OF THE INVENTION According to the method of this invention, the manufacturing process of the ion conductive sulfide glass as a solid electrolyte for batteries can be simplified, and the cost can be reduced. Further, according to the mechanical milling, an ion conductive sulfide glass having a fine powder and a uniform particle size can be produced.
If such a glass ceramic is used as a solid electrolyte, the contact interface between the positive electrode and the negative electrode can be increased and the adhesion can be improved.
[0010]
The reaction by mechanical milling is performed in an inert gas (nitrogen gas, argon gas, etc.) atmosphere. Although various types of mechanical milling can be used, it is particularly preferable to use a planetary ball mill. In a planetary ball mill, the base plate revolves while the pot rotates, and very high impact energy can be efficiently generated.
The rotation speed and rotation time of the mechanical milling are not particularly limited, but the higher the rotation speed, the higher the production speed of the sulfide glass, and the longer the rotation time, the higher the conversion of the starting material to the sulfide glass.
By baking the sulfide glass obtained by mechanical milling at a glass transition temperature (150 ° C.) or higher, preferably 200 to 500 ° C., the sulfide glass ceramics having improved electrical conductivity at room temperature (25 ° C.) is obtained. can get. The shape of the sulfide glass to be subjected to the firing treatment is not particularly limited, but it may be in the form of a powder or may be formed into a pellet by pressure.
The firing treatment is preferably performed in the presence of an inert gas (such as a nitrogen gas or an argon gas) or in a vacuum. The heating rate, the cooling rate, and the firing time during the firing process are not particularly limited.
The sulfide glass ceramics thus obtained is suitable as a solid electrolyte.
[0011]
【Example】
Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1
As starting materials, lithium sulfide crystals (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) having a crystal particle diameter of 120 nm were used. Here, as a lithium sulfide crystal having a crystal particle diameter of 120 nm, lithium sulfide manufactured by Furuuchi Chemical Industry Co., Ltd. was used.
These powders were weighed in a dry box under an atmosphere of argon at a molar ratio of 8/2 (Li ₂ S / P ₂ S ₅ ), charged into an alumina pot, and completely sealed. This pot was attached to a planetary ball mill, and initially milled at low speed (rotational speed: 85 rpm) for several minutes in order to sufficiently mix the starting materials. Thereafter, the rotational speed was gradually increased, and mechanical milling was performed at 370 rpm for 20 hours. The crystal particle diameter of lithium sulfide was calculated from the crystal peak derived from the plane index (111) by the Scherrer equation based on the result of measurement using an X-ray diffractometer (XD-D1, manufactured by Shimadzu Corporation).
As a result of X-ray diffraction of the obtained powdered glass, the peak of lithium sulfide (Li ₂ S) disappeared, and it was confirmed that vitrification had progressed.
This powder sample was formed into a pellet under an inert gas (nitrogen) atmosphere under a pressure of 370 MPa (3700 kg / cm ² ), and then a carbon paste was applied as an electrode, and the electric conductivity was measured by an AC two-terminal method. As a result, the electrical conductivity at room temperature (25 ° C.) was 1.7 × 10 ⁻⁴ S / cm.
[0012]
Example 2
Powdered glass was obtained and pelletized in the same manner as in Example 1 except that lithium sulfide (Li ₂ S) having a crystal particle diameter of 130 nm was used instead of lithium sulfide (Li ₂ S) having a crystal particle diameter of 120 nm. It was molded under pressure. When the electric conductivity was measured in the same manner as in Example 1, the electric conductivity at room temperature (25 ° C.) was 8.0 × 10 ⁻⁵ S / cm. Here, as the lithium sulfide crystal having a crystal particle diameter of 130 nm, lithium sulfide manufactured by Aldrich was used.
[0013]
Example 3
The pellets obtained in Example 1 were calcined at 250 ° C. in the presence of an inert gas (nitrogen) to obtain sulfide glass ceramics. After cooling, the electric conductivity was measured in the same manner as in Example 1. The electric conductivity at room temperature (25 ° C.) was 7.2 × 10 ⁻⁴ S / cm, and the electric conductivity was improved by firing. did.
[0014]
Example 4
The pellets obtained in Example 2 were calcined at 250 ° C. in the presence of an inert gas (nitrogen) to obtain sulfide glass ceramics. After cooling, the electric conductivity was measured in the same manner as in Example 1. The electric conductivity at room temperature (25 ° C.) was 3.0 × 10 ⁻⁴ S / cm, and the electric conductivity was improved by firing. did.
[0015]
Comparative Example 1
A powdered glass was obtained in the same manner as in Example 1, except that lithium sulfide (Li ₂ S) having a crystal particle size of 275 nm was used instead of lithium sulfide (Li ₂ S) having a crystal particle size of 120 nm. As a result of X-ray diffraction of the obtained powder glass, a large peak of unreacted lithium sulfide (Li ₂ S) was detected.
The powdered glass was pressed into a pellet in the same manner as in Example 1, a carbon paste was applied as an electrode, and the electrical conductivity was measured by the same method as in Example 1. As a result, at room temperature (25 ° C.) ^{Had a} very low electric conductivity of 1.0 × 10 ⁻⁵ S / cm.
[0016]
Comparative Example 2
Powdered glass was obtained in the same manner as in Example 1 except that lithium sulfide (Li ₂ S) having a crystal particle diameter of 586 nm was used instead of lithium sulfide (Li ₂ S) having a crystal particle diameter of 120 nm. As a result of X-ray diffraction of the obtained powder glass, a large peak of unreacted lithium sulfide (Li ₂ S) was detected.
The powdered glass was pressed into a pellet in the same manner as in Example 1, a carbon paste was applied as an electrode, and the electrical conductivity was measured by the same method as in Example 1. As a result, at room temperature (25 ° C.) ^{Had a} very low electric conductivity of 5.0 × 10 ⁻⁶ S / cm.
[0017]
Example 4
An all-solid-state lithium secondary battery was manufactured using the pellet-shaped sulfide glass ceramics obtained in Example 3 as a solid electrolyte.
Lithium cobalt oxide showing a potential exceeding 4 V was used as a positive electrode, and indium metal was used as a negative electrode. When constant current discharge measurement was performed at a current density of 50 μA / cm ² , charge and discharge were possible. In addition, the charge and discharge efficiency was 100%, and it was found that the battery exhibited excellent cycle characteristics.
[0018]
【The invention's effect】
According to the present invention, a lithium ion conductive sulfide glass and a ceramic having high electrical conductivity at room temperature can be produced by a simple method using easily available and inexpensive raw materials as starting materials.

Claims (9)

In producing a lithium ion conductive sulfide glass, a raw material containing lithium sulfide having a crystal particle diameter of 140 nm or less is used as a starting material, and the raw material is vitrified by mechanical milling. Manufacturing method of sulfide glass. The method for producing a lithium ion conductive sulfide glass according to claim 1, wherein the starting material other than lithium sulfide contains one or more elements selected from sulfur and phosphorus. A method for producing a lithium ion conductive sulfide glass ceramic, comprising firing the lithium ion conductive sulfide glass vitrified by mechanical milling according to claim 1 or 2 at a glass transition temperature or higher. The method for producing a lithium ion conductive sulfide glass ceramic according to claim 3, wherein the firing is performed at 150 ° C or higher. 5. The method for producing a lithium ion conductive sulfide glass ceramic according to claim 3, wherein the calcination is performed in a vacuum or in the presence of an inert gas. The method for producing a lithium ion conductive sulfide glass according to claim 1 or 2, wherein the decomposition voltage of the sulfide glass is at least 3V. The method for producing a lithium ion conductive sulfide glass ceramic according to any one of claims 3 to 5, wherein a decomposition voltage of the sulfide glass ceramic is at least 3V. An all-solid-state battery using a lithium-ion conductive sulfide glass produced by the method according to claim 1 as a solid electrolyte. An all-solid-state battery using a lithium-ion conductive sulfide glass-ceramic produced by the method according to any one of claims 3 to 5 and 7 as a solid electrolyte.