WO2004095474A1 - Lithium ion-conductive sulfide glass, process for producing glass ceramic, and wholly solid type cell made with the glass ceramic - Google Patents

Abstract

A process for producing a lithium ion-conductive sulfide glass having high electrical conductivity at room temperature from starting materials comprising lithium sulfide and at least one member selected among phosphorus pentasulfide, elemental phosphorus, and elemental sulfur, which comprises: (I) adding at least 6.5 parts by weight of lithium sulfate and/or at least 2.2 parts by weight of lithium thiosulfate as a glass modifier per 100 parts by weight of the lithium sulfide to the starting materials and vitrifying the materials by mechanical milling; or (II) adding at least 0.9 parts by weight of lithium hydroxide as a glass modifier per 100 parts by weight of the lithium sulfide to the starting materials and vitrifying the materials by mechanical milling. By burning this lithium ion-conductive sulfide glass at a temperature not lower than the glass transition temperature thereof, a lithium ion-conductive sulfide glass ceramic having even higher electrical conductivity at room temperature can be produced.

Description

 Specification

 Method for producing lithium ion conductive sulfide glass and glass ceramics and all-solid-state battery using the glass ceramics

 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. Background 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 composed of glass forming agents such as SiS ₂ , phosphorus pentasulfide (P ₂ S ₅ ) and B ₂ S _3, and a glass modifier lithium sulfide (L i ₂ S). It is obtained by mixing, heating and melting, followed by quenching (for example, see Japanese Patent Application Laid-Open No. 9-283156).

 The present inventors also disclose that such a sulfide glass can be obtained by subjecting a sulfide crystal to mechanical calcination at room temperature (see Japanese Patent Application Laid-Open No. 11349349/1999). ).

 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 react efficiently 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. In addition, if a large amount of unreacted lithium sulfide remains, the performance as an electrolyte decreases, and there is a problem that it cannot be used as an electrolyte of an all-solid-state lithium battery.

The present inventors have proposed a method of starting from a more easily available and less expensive raw material. We have been investigating the production method of palladium ion conductive sulfide glass.

For example, the present inventors have conducted mechanical milling using lithium metal (L i) or lithium sulfide (L i ₂ S), elemental silicon (Si), and elemental sulfur (S) as starting materials. It has been disclosed that a lithium ion conductive sulfide glass can be obtained (see JP-A-11-349337).

However, the sulfide glass as compared to the case where the lithium sulfide and S i S ₂ as a raw material, the longer it takes mechanical milling, there is electrical conductivity problem also that low sulfide glass obtained.

 The present inventors have continued to study for the purpose of producing sulfide glass having higher electric conductivity, and found that sulfide ceramics containing lithium sulfide and phosphorus pentasulfide as main components exhibit high lithium ion conductivity. (See Japanese Patent Application Laid-Open No. 2001-250580).

In addition, it was also found that the sulfide obtained by mechanical milling of lithium sulfide and phosphorus pentasulfide can be baked at a temperature higher than the glass transition temperature to improve the electrical conductivity at room temperature. etters 200 1). Furthermore, as a more available raw material, metallic lithium is added to vitrified elemental phosphorus (P) and elemental sulfur (S) by mechanical milling, and the electrical conductivity at room temperature is increased by mechanical milling. 0_ ⁵ SZ cm order of sulfide glass was also found that obtained (Tatsumi sand, et al: see spring meeting Abstracts 2 E 34 1 the chemical Society of Japan 200 a year). Disclosure of the invention

The present inventors have further studied a production method using a raw material that is simple and easily available, and using metallic lithium or lithium sulfide, elemental sulfur (S) and elemental phosphorus (P) as starting materials. Used, obtained by mechanical milling It has been found that sulfide glass has the same performance as lithium ion conductive sulfide glass manufactured by mechanical milling using lithium sulfide and phosphorus pentasulfide as raw materials (Japanese Patent Application No. 2002-005855). In addition, we examined the simple and efficient production methods, the use of more than one selected as a glass modifier of lithium sulfate (L i ₂ S 0 ₄₎及Pi Chio lithium sulfate _{(L i 2 S 2 0 3} ) As a result, they found that a sulfide glass useful as a solid electrolyte was obtained, and completed the present invention.

 The present inventors have also found that sulfide glass useful as a solid electrolyte can be obtained by using lithium hydroxide (LiOH) as a glass modifier, and have completed the present invention. .

Furthermore, sulfide glass obtained in the present invention, by performing once baked conversion treatment at a temperature above the glass transition temperature was also found that the electrical conductivity at room temperature is above toward the least 1 0- ⁴ SZcm.

 That is, the present invention

 (1) In producing a lithium ion conductive sulfide glass, a raw material containing lithium sulfide and at least one selected from phosphorus pentasulfide, elemental phosphorus, and elemental io is used as a starting material, and the raw material is glass-modified. As an agent, 6.5 parts by mass or more of lithium sulfate and Z or 22 parts by mass or more of lithium thiosulfate are added to 100 parts by mass of lithium sulfide, and the raw material is vitrified by mechanical milling. A method for producing a lithium ion conductive sulfide glass (I),

 (2) The method for producing lithium ion conductive sulfide glass ceramics described in (1) above, wherein the lithium ion conductive sulfide glass vitrified by mechanical milling is fired at a glass transition temperature or higher.

(3) The method for producing a lithium ion conductive sulfide glass-ceramic as described in (1) above, wherein the firing is performed at 150 ° C or more. (4) The method for producing a lithium ion conductive sulfide glass ceramic as described in (1) or (3) above, wherein the calcination is performed in a vacuum or in the presence of an inert gas.

 方法 The method for producing a lithium ion conductive sulfide glass according to す る, wherein the decomposition voltage of the sulfide glass is at least 3 V.

方法 The method for producing lithium ion-conductive sulfide glass ceramics according to any one of the above items ④ to ④, wherein a decomposition voltage of the sulfide glass ceramic is at least 3 V.

 全 All-solid-state battery, characterized by using a lithium ion conductive sulfide glass produced by the method according to the above ① or と し て as a solid electrolyte,

全 An all-solid-state battery using a lithium ion conductive sulfide glass ceramics produced by the method according to any one of the above-mentioned items 1 to 3 as a solid electrolyte.

Is provided.

 In addition, the present invention

 製造 In producing a lithium ion conductive sulfide glass, a raw material containing lithium sulfide and at least one selected from phosphorus pentasulfide, elemental phosphorus and elementary metal is used as a starting material. As a modifier, lithium ion conduction is characterized by adding 0.9 parts by mass or more of lithium hydroxide to 100 parts by mass of lithium sulfide and vitrifying the raw material by mechanical milling. Production method of crystalline sulfide glass (II),

 方法 A method for producing a lithium ion conductive sulfide glass-ceramic, according to the above ⑨, characterized in that the lithium ion conductive sulfide glass vitrified by mechanical milling is fired at a glass transition temperature or higher.

方法 A method for producing a lithium ion conductive sulfide glass ceramics according to the above ⑩, characterized by firing at 150 ° C. or higher, 方法 The method for producing a lithium ion conductive sulfide glass ceramic according to the above ⑩ or と す る, wherein the calcination is performed in a vacuum or in the presence of an inert gas;

 方法 The method for producing a lithium ion conductive sulfide glass as described in 、 above, wherein the decomposition voltage of the sulfide glass is at least 3 V.⑭ The decomposition voltage of the sulfide glass ceramics is at least 3 V. V. The method for producing a lithium ion-conductive sulfide glass ceramics according to any one of the above items 1 to 4,

 全 All-solid-state battery, characterized by using a lithium ion conductive sulfide glass produced by the method according to the above ⑨ or と し て as a solid electrolyte,

 全 An all-solid-state battery using a lithium ion conductive sulfide glass ceramics produced by the method according to any one of the above-mentioned ⑩ to ⑫ and ⑭ as a solid electrolyte.

Is provided. BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, as a starting material, a material containing at least one selected from lithium sulfide (L i ₂ S), phosphorus pentasulfide (P ₂ S ₅ ), elemental phosphorus (P), and elemental zeolite (S) is used. . The lithium sulfide (L i 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. The one manufactured by the manufacturing method described in Japanese Patent Application Laid-Open No. 2000-24076 is preferred.

Phosphorus pentasulfide, 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 (L i ₂ S), elemental sulfur (S) and elemental phosphorus (P) are used as starting materials, the mixing ratio of the elemental sulfur and the elemental phosphorus is a molar ratio of 1 to lithium sulfide. Preferably, the elemental sulfur is 0.5 to 3.5, and the elemental phosphorus is 0.2 to 1.5. When lithium sulfide (L i ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) are used as starting materials, the molar ratio of lithium pentasulfide to phosphorus pentasulfide is 0.05 to 1.0. preferable. In addition,

(S i), metallic germanium (G e), metallic aluminum (A 1), metallic iron (F e), metallic zinc (Zn) and elemental boron (B) are also amorphous by elemental sulfur and mechanical milling. Produces crystalline or crystalline sulfides (Tatsumi Sanda et al.

: The Chemical Society of Japan 2001 Spring Meeting Abstracts 2 E 34 1) Therefore, some of the starting materials for the lithium ion conductive sulfide glass described above can be replaced with these.

In the method of manufacturing the lithium ion conductive sulfide glass of the present invention (I), as a glass modifier, selected from lithium sulfate (L i ₂ S0 ₄₎ and Chio sulfate lithium © beam _{(L i 2 S 2 0 3} ) Use more than one type. The addition amount of lithium sulfate needs to be 6.5 parts by mass or more based on 100 parts by mass of lithium sulfide, and is preferably 7 to 20 parts by mass. The addition amount of lithium thiosulfate is required to be 2.2 parts by mass or more with respect to 100 parts by mass of lithium sulfide, and is preferably 2.7 to 15 parts by mass. When used in combination with lithium sulfate (L i ₂ S 0 ₄₎ and Chio lithium sulfate _{(L i 2 S 2 0 3} ), its use proportion is L i ₂ SO ₄ in a weight ratio: L i ₂ S ₂ O ₃ = l: 0.135 to ₂ is preferable, and Li ₂ SO ₄ : Li ₂ S ₂ O ₃ = l: 0.15 to 1.8 is more preferable.

In the method (II) for producing a lithium ion conductive sulfide glass of the present invention, lithium hydroxide (L i OH) is used as a glass modifier. The addition amount of lithium hydroxide needs to be 0.9 part by mass or more with respect to 100 parts by mass of lithium sulfide, and is preferably 1.2 to 20 parts by mass. In the present invention, the vitrification of a starting material containing lithium sulfide (L i ₂ S) and one or more selected from phosphorus pentasulfide (P ₂ S ₅ ), simple phosphorus (P) and simple element (S). In addition, mechanical milling is used. According to mechanical milling, since glass can be synthesized at around room temperature, there is an advantage that the starting material is not thermally decomposed and a glass having a charged composition can be obtained. In addition, mechanical milling has the advantage that the glass can be pulverized simultaneously with the synthesis of the glass.

 In the method of the present invention, it is not necessary to newly grind or cut the ion conductive sulfide glass when pulverizing it. Such finely ground 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 with the positive electrode and the negative electrode can be increased and the adhesion can be improved.

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 revolves while the pot rotates, and can efficiently generate extremely high impact energy.

 The rotation speed and rotation time of the mechanical milling are not particularly limited, but the higher the rotation speed, the faster the sulfide glass generation rate.The longer the rotation time, the higher the conversion rate of the starting material to the sulfide glass. Get higher.

The glass transition temperature of the sulfide glass obtained by mechanical milling (1 By firing at 50 ° C or more, preferably at 200 to 500 ° C, a sulfide glass-ceramic having improved electrical conductivity at room temperature (25 ° C) can be obtained. The shape of the sulfide glass to be subjected to the baking treatment is not particularly limited, but may be in a powder form or may be a pressure-formed pellet.

 The firing treatment is preferably performed in the presence of an inert gas (such as nitrogen gas or argon gas) or under vacuum. The heating rate, cooling rate, and firing time during the firing process are not particularly limited.

 The sulfide glass ceramics thus obtained is suitable as a solid electrolyte. 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 a starting material, a lithium crystals sulfide (L i ₂ S) and phosphorus pentasulfide (P ₂ S _5), as a glass modifier, lithium sulfate (L i ₂ S0 ₄₎ and Chi O lithium sulfate (L i ₂ S ₂ 0 ₃₎ was used.

In a dry box under argon atmosphere, lithium sulfide crystals and phosphorus pentasulfide were weighed at a molar ratio of 6.9 / ₂ (L i ₂ S / P ₂ S ₅ ), and lithium sulfide crystals (L against i ₂ S) 1 00 parts by weight were weighed in a ratio of ₂ S0 ₄₎ 1 1. ₄ parts by mass Chio lithium sulfate _{(L i 2 S 2 0 3} ) 3. 6 parts by weight of lithium sulphate (L i These powders were put into an alumina pot and completely sealed. The pot was mounted on a planetary ball mill, and initially milled at a low speed (rotational speed: 85 rpm) for several minutes to thoroughly mix the starting materials. Then, the rotational speed was gradually increased, and mechanical milling was performed at 370 rpm for 20 hours. As a result of X-ray diffraction of the obtained powdered glass, the peak of lithium sulfide (L i ₂ S) disappeared, and it was confirmed that vitrification had progressed.

This powder sample was formed into a pellet under the pressure of ² OMPa (200 kg / cm ² ) in an inert gas (nitrogen) atmosphere, and a carbon paste was applied as an electrode. Room temperature

Electrical conductivity at (25.C) was ^{1. 7 X 1 0_ 4 S /} cm.

Example 2

The pellet obtained in Example 1 was calcined at 250 ° C. in the presence of an inert gas (nitrogen) to obtain a sulfide glass ceramic. After cooling, the measured electrical conductivity in the same manner as in Example 1, the electric conductivity at room temperature (25 ° C) a ^{7. 2 X 1 0- 4 S /} cm, the electric conductivity by firing Has improved.

Comparative Example 1

Against lithium sulfide crystal (L i ₂ S) 1 0◦ part by weight, lithium sulfate (L i ₂ S_〇 ₄₎ 6.3 parts by及Pi Chio lithium sulfate (L i ₂ S ₂ 〇 ₃₎ 1.93 A glass powder was obtained in the same manner as in Example 1, except that the powder was weighed out in parts by mass and used. As a result of X-ray diffraction of the obtained powdered glass, a large peak of unreacted lithium sulfate (Li ₂ S) was detected.

This 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 in the same manner as in Example 1. The room temperature (25 ° C electrical conductivity at) was very low and ^{1. 0 X 1 0_ 5 SZ cm} .

Comparative Example 2

Against lithium sulfide crystal (L i ₂ S) 1 00 parts by weight, lithium sulfate _{(L i 2 S0 4) 5.} 6 parts by mass及Pi Chio lithium sulfate _{(L i 2 S 2 0 3} ) 2. 0 parts by weight , Weighed in the same manner as in Example 1 except that it was used. Powder was obtained. As a result of X-ray diffraction of the obtained powdered glass, a large peak of unreacted lithium sulfide (L i ₂ S) was detected.

The powdered glass was formed into a pellet under pressure in the same manner as in Example 1, a carbon paste was applied as an electrode, and the electrical conductivity was measured in the same manner as in Example 1. electrical conductivity at C) was very low and ^{5. 0 X 1 0- 6 S /} cm.

Example 3

 An all-solid-state lithium secondary battery was manufactured using the pellet-shaped sulfide glass ceramics obtained in Example 2 as a solid electrolyte.

Lithium copartate showing a potential exceeding 4 V was used for the positive electrode, and indium metal was used for the negative electrode. At a current density of 50 μ AZc m ^2, it was subjected to constant current discharge measurement was possible charging and discharging. In addition, the charge / discharge efficiency was 100%, which proved that excellent cycle characteristics were exhibited.

Example 4

Lithium sulfide crystals (L ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) were used as starting materials, and lithium hydroxide (L i OH) was used as a glass modifier.

In a dry box under argon atmosphere, lithium sulfide crystals and phosphorus pentasulfide were weighed at a molar ratio of 6.9 / ₂ (L i ₂ S / P ₂ S ₅ ), and lithium sulfide crystals (L i ₂ S) 100 parts by mass of lithium hydroxide

(L i OH) 2. The powder was weighed at a ratio of 1 part by mass, and these powders were charged into an alumina pot and completely sealed. This pot was mounted on a planetary pole mill, and initially milled at a low speed (rotational speed: 85 rpm) for several minutes in order to mix the starting materials sufficiently. Thereafter, the rotational speed was gradually increased, and mechanical milling was performed at 370 rpm for 20 hours.

As a result of X-ray diffraction of the obtained powdered glass, lithium sulfide (Li ₂ The peak in s) disappeared, confirming that vitrification had progressed.

This powder sample was formed into a pellet under the pressure of 2 OMPa (200 kg / cm ² ) in an inert gas (nitrogen) atmosphere, and then carbon paste was applied as an electrode, and electric conduction was performed by an AC two-terminal method. Room temperature

Electrical conductivity at (25 ° C) is 8. was 1 X 10- ⁵ SZcm.

Example 5

The pellets obtained in Example 4 were calcined at 250 ° C. in the presence of an inert gas (nitrogen) to obtain sulfide glass ceramics. After cooling, the measured electrical conductivity in the same manner as in Example 1, the electrical conductivity at room temperature (25 ° C) is 3. 0 X 10- ⁴ SZcm, electrical conductivity is improved by firing Was.

Comparative Example 3

Glass powder was prepared in the same manner as in Example 4 except that 0.53 parts by mass of lithium hydroxide (L i OH) was weighed with respect to 100 parts by mass of lithium sulfide crystal (L i ₂ S). Obtained. As a result of X-ray diffraction of the obtained powdered glass, a large peak of unreacted lithium sulfide (L i ₂ S) was detected.

The powdered glass was pressed into a pellet in the same manner as in Example 4, a carbon paste was applied as an electrode, and the electrical conductivity was measured in the same manner as in Example 4. The room temperature (25 ° C ) Had a very low electric conductivity of 1.0 × 10 ⁵ SZ cm.

Comparative Example 4

A glass powder was obtained in the same manner as in Example 4, except that 0.74 parts by mass of lithium hydroxide (L i OH) was weighed with respect to 100 parts by mass of lithium sulfide crystal (L i ₂ S). Was. As a result of X-ray diffraction of the obtained powdered glass, a large peak of unreacted lithium sulfide (L i ₂ S) was detected.

The powdered glass was pressed into a pellet in the same manner as in Example 4, The carbon paste was applied as was subjected to measurement of electrical conductivity in the same manner as in Example 1, the electrical conductivity at room temperature (25 ° C) is extremely and ^{5. 0 X 1 0- 6 S /} cm Was low.

Example 6

 An all-solid-state lithium secondary battery was manufactured using the pellet-shaped sulfide glass ceramics obtained in Example 5 as a solid electrolyte.

Lithium cobalt oxide showing a potential exceeding 4 V was used for the positive electrode, and indium metal was used for the negative electrode. When a constant current discharge measurement was performed at a current density of 50 A / cm ² , charging and discharging were possible. In addition, the charge / discharge efficiency was 100%, which proved that excellent cycle characteristics were exhibited. Industrial applicability

 According to the present invention, a lithium ion conductive sulfide glass and a ceramic having high electrical conductivity at room temperature can be provided by a simple method using easily available and inexpensive raw materials as starting materials.

Claims

The scope of the claims 1. In producing a lithium ion conductive sulfide glass, a raw material containing lithium sulfide and at least one selected from phosphorus pentasulfide, elemental phosphorus, and elementary metal is used as a starting material, and glass is used as the raw material. As a modifier, 6.5 parts by mass or more of lithium sulfate and / or 2.2 parts by mass or more of lithium thiosulfate are added to 100 parts by mass of lithium sulfide, and the raw material is vitrified by mechanical milling. A method for producing a lithium-ion conductive sulfide glass. 2. Lithium ion conductive sulfide glass ceramics, characterized in that the lithium ion conductive sulfide glass vitrified by mechanical milling described in claim 1 is fired at a glass transition temperature or higher. Production method. 3. The method for producing a lithium ion conductive sulfide glass ceramics according to claim 2, wherein the firing is performed at a temperature of 3.150 ° C. or higher. 4. The method for producing a lithium ion conductive sulfide glass ceramic according to claim 2, wherein the calcination is performed in a vacuum or in the presence of an inert gas. 5. The method for producing a lithium ion conductive sulfide glass according to claim 1, wherein the decomposition voltage of the sulfide glass is at least 3 V. 6. The method for producing a lithium ion conductive sulfide glass ceramic according to any one of claims 2 to 4, wherein a decomposition voltage of the sulfide glass ceramic is at least 3 V. 7. An all-solid-state battery using a lithium ion conductive sulfide glass produced by the method according to claim 1 or 5 as a solid electrolyte. 8. An all-solid-state battery using a lithium-ion-conductive sulfide glass-ceramic produced by the method according to any one of claims 2 to 4 as a solid electrolyte. 9. In producing the lithium ion conductive sulfide glass, a raw material containing lithium sulfide and at least one selected from phosphorus pentasulfide, elemental phosphorus and elementary metal is used as a starting material, and glass is used as the raw material. As a modifier, at least 0.9 parts by mass of lithium hydroxide is added to 100 parts by mass of lithium sulfide, and the raw material is vitrified by mechanical milling. Method for producing crystalline sulfide glass. 10. Lithium ion conductive sulfide glass ceramics, characterized in that the lithium ion conductive sulfide glass vitrified by mechanical milling according to claim 9 is fired at a glass transition temperature or higher. Manufacturing method. 11. The method for producing a lithium ion conductive sulfide glass ceramics according to claim 10, wherein the firing is performed at a temperature of at least 11.150 ° C. 12. The method for producing a lithium ion conductive sulfide glass ceramic according to claim 10, wherein the calcination is performed in a vacuum or in the presence of an inert gas. 13. The method for producing a lithium ion conductive sulfide glass according to claim 9, wherein a decomposition voltage of the sulfide glass is at least 3 V. 14. The lithium ion conductive sulfide glass-ceramic according to any one of claims 10 to 12, wherein the decomposition voltage of the sulfide glass-ceramic is at least 3 V. Manufacturing method. 15. An all-solid-state battery using the lithium ion conductive sulfide glass produced by the method according to claim 9 or 13 as a solid electrolyte. 16. An all-solid-state battery using a lithium ion conductive sulfide glass ceramics produced by the method according to any one of claims 10 to 12 as a solid electrolyte.