JP7093078B2 - A solid electrolyte for an all-solid lithium-sulfur battery made of Li2S-P2S5-SeS2-based glass ceramic, a positive electrode material suitable for the solid electrolyte, a method for producing these, and an all-solid lithium-sulfur battery containing these. - Google Patents

Description

The present invention relates to a solid electrolyte for an all-solid lithium-sulfur battery made of Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic, a positive electrode material suitable for the solid electrolyte, a method for producing the same, and an all-solid lithium containing them. Regarding sulfur batteries.

With the demand for larger size, higher performance, and lower cost of lithium-ion batteries, all-solid-state lithium secondary batteries using inorganic solid electrolytes (for example, all-solid-state lithium-sulfur (Li-S) batteries) are safer. It is attracting attention as a next-generation storage battery with excellent reliability.

Non-Patent Document 1 is a paper entitled "Development of All-Solid Battery Using Sulfurized Glass Electrolyte and Future Prospects", in which solid electrolytes made of Li ₂ SP ₂ S ₅ glass ceramic are various solids. It has been reported that the electrolyte has a high ionic conductivity, and that the lithium ionic conductivity differs depending on the composition (mixing ratio) of the material and the degree of structural disorder.

For example, a sulfur powder called polysulfide called polysulfide made of S8 is used for the positive electrode, metallic Li is used for the negative electrode, and a sulfide-based material Li _{2 SP 2} S ₅ system material and lithium iodide (Li I) are mixed for the electrolyte. It is described that the all-solid-state lithium-sulfur (Li—S) battery produced by pressurizing the cell exhibited a large discharge capacity density (FIG. 2 of Non-Patent Document 1 and the like).

Further, in Non-Patent Documents 1 and 2, in order to further increase the conductivity of the solid electrolyte composed of Li ₂ SP ₂ S ₅ series glass ceramic, the element of Li ₂ SP ₂ S ₅ series glass ceramic is described. It is disclosed that the method of substituting or adding an element is effective. For example, it is described that the conductivity was increased by replacing a part of P ₂ S ₅ with P ₂ S ₃ or P ₂ O ₅ , and that the conductivity was increased when LiI or GeS ₂ was added. ing. These increases in conductivity are believed to be due to sulfur deficiency, new crystal formation and improved crystallinity. It should be noted that the replacement with P2 O ₅ is also disclosed in Non-Patent Document ₃ .

"Development and future prospects of all-solid-state batteries using sulfide glass-based electrolytes", Masahiro Tatsumisago, Graduate School of Engineering, Osaka Metropolitan University, 2014, Crushing (57), 3-10, 2014 Structure, ionic conductivity and electrochemical stability of Li2S-P2S5-LiI glass and glass-ceramic electrolytes, Satoshi Ujiie, Akitoshi Hayashi, Masahiro Tatsumisago, Solid State Ionics 211 (2012) 42-45 "Improved chemical stability and cyclability in Li2S-P2S5-P2O5-ZnO composite electrolytes for all-solid-state rechargeable lithium batteries", Akitoshi Hayashi et al., Journal of Alloys and Compounds 591 (2014) 247-250

As mentioned above, among the solid electrolytes, the research and development of the solid electrolyte made of Li ₂ SP ₂ S ₅ system glass ceramic is underway, but the lithium ion conductivity and the maintenance of the battery capacity when charging and discharging are repeated are being promoted. There is still room for improvement in terms of points.

Therefore, the present invention is an improved solid electrolyte of Li 2SP _{2S 5 system} glass ceramic, and all _- solid lithium sulfur with improved lithium ion conductivity and stability of battery capacity when charging and discharging are repeated. It is an object of the present invention to provide a solid electrolyte for a battery and a method for producing the same. It is also an object of the present invention to provide a positive electrode material for use in combination with the solid electrolyte, a method for producing the same, and an all-solid lithium-sulfur battery provided with the solid electrolyte.

As a result of diligent research to achieve the above object, the present inventors have obtained a Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic having a specific composition, which is an improved Li ₂ SP ₂ S ₅ glass ceramic. It has been found that the above object can be achieved when used, and the present invention has been completed.

That is, the present invention relates to the following solid electrolyte for an all-solid lithium-sulfur battery and a method for producing the same, a positive electrode material for use in combination with the solid electrolyte and a method for producing the same, and an all-solid lithium-sulfur battery provided with the solid electrolyte.
1. 1. In Li ₂ SP ₂ S ₅ series glass ceramics
A part of P ₂ S ₅ is replaced with Se S ₂ , and the content of Se S ₂ is 1 to 6 mol% of the content of P ₂ S ₅ Li ₂ SP ₂ S ₅ -SeS ₂ system. A solid electrolyte for all-solid lithium-sulfur batteries, characterized by being made of glass ceramic.
2. 2. The composition of the Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic is
7Li ₂ S- (3-x) P ₂ S ₅ -xSeS ₂
[However, x indicating the molar ratio of SeS ₂ is 0 <x ≦ 0.1. ]
The solid electrolyte according to Item 1 above.
3. 3. The composition of the Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic is
8Li ₂ S- (2-x) P ₂ S ₅ -xSeS ₂
[However, x indicating the molar ratio of SeS ₂ is 0 <x ≦ 0.1. ]
The solid electrolyte according to Item 1 above.
4. Item 2. The solid electrolyte according to any one of Items 1 to 3 above, further containing at least one element selected from the group consisting of Fe, Mg, Ca, V, Se and Sn.
5. The above-mentioned item, wherein the raw material mixture containing Li ₂ S powder, P ₂ S ₅ powder and Se S ₂ powder is pulverized at room temperature using a ball mill, and then the pulverized product is calcined in an inert gas atmosphere. The method for producing a solid electrolyte according to any one of 1 to 4.
6. A positive electrode material for use in combination with the solid electrolyte according to any one of Items 1 to 4 above in an all-solid-state lithium-sulfur battery, wherein the Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic and sulfur are used. A positive electrode material for an all-solid-state lithium-sulfur battery, which comprises an S-Li ₂ SP ₂ S ₅ -SeS ₂ -C system composite which is a composite of carbon and carbon.
7. The sulfur and carbon materials are pulverized at room temperature using a ball mill, and then a mixture of the pulverized product and the Li ₂ SP ₂ S ₅ -SeS ₂ system glass ceramic is pulverized at room temperature using a ball mill. Item 6. The method for producing a positive electrode material according to Item 6.
8. An all-solid-state lithium-sulfur battery comprising a positive electrode material, a negative electrode material, and the solid electrolyte according to any one of Items 1 to 4 above.

The solid electrolyte for an all-solid-state lithium-sulfur battery of the present invention comprises a Li ₂ SP ₂ S ₅ -SeS ₂ series glass ceramic having a specific composition, and is lithium as compared with the conventional Li ₂ SP ₂ S ₅ series glass ceramic. The ionic conductivity is improved. Further, the all-solid-state lithium-sulfur battery provided with the solid electrolyte has improved the stability of the battery capacity when charging and discharging are repeated. Further, the method for producing a solid electrolyte and a positive electrode material of the present invention is useful as a method for producing a positive electrode material used in combination with the solid electrolyte and the solid electrolyte, respectively.

It is a figure which shows the result of the test example 1 (X-ray diffraction pattern of a glass ceramic). It is a figure which shows the result of the test example 2 (the ionic conductivity of a glass ceramic). It is a figure which shows the result of the test example 3 (impedance plot of a glass ceramic). It is a figure which shows the result of the test example 4 (the DC current curve of a glass ceramic). It is a figure which shows the result of Test Example 5 (charging / discharging characteristic 1 of an all-solid-state lithium-sulfur battery). It is a figure which shows the result of Test Example 6 (charging / discharging characteristic 2 of an all-solid-state lithium-sulfur battery). It is sectional drawing which shows an example of the arrangement of a positive electrode material 1, a solid electrolyte 2, a negative electrode material 3, and a stainless steel disk 4 in an all-solid-state lithium-sulfur battery.

All-solid-state lithium-sulfur (Li-S) solid electrolyte for batteries (solid electrolyte)
The solid electrolyte for an all-solid lithium-sulfur battery of the present invention (hereinafter, also referred to as “solid electrolyte of the present invention”) is a Li ₂ SP ₂ S ₅ system glass ceramic in which a part of P ₂ S ₅ is SeS ₂ . It is characterized in that it is composed of a Li ₂ SP ₂ S ₅ -SeS ₂ system glass ceramic having a SeS ₂ content of 1 to 6 mol% of the P ₂ S ₅ content.

The solid electrolyte of the present invention having the above-mentioned characteristics is composed of a Li ₂ SP ₂ S ₅ -SeS ₂ system glass ceramic having a specific composition, and is lithium ion as compared with the conventional Li ₂ SP ₂ S ₅ system glass ceramic. The conductivity is improved. Further, the all-solid-state lithium-sulfur battery provided with the solid electrolyte has improved the stability of the battery capacity when charging and discharging are repeated.

The solid electrolyte of the present invention is a Li ₂ SP ₂ S ₅ -SeS _{2 glass ceramic in which a part of P 2 S 5} is replaced with Se S ₂ in the Li ₂ SP ₂ S ₅ glass ceramic. Therefore, the content of SeS ₂ may be 1 to _{6 mol% of the content of P2 S 5 ,} but 1 to 5.3 mol% is preferable, and 3 to 3.5 mol% is more preferable. ..

Among the above, the solid electrolyte of the present invention has a particularly glass-ceramic composition.
7Li ₂ S- (3-x) P ₂ S ₅ -xSeS ₂
[However, x indicating the molar ratio of SeS ₂ is 0 <x ≦ 0.1. ]
Is preferable. The x indicating the content _{(mol%) of SeS 2 with} respect to the content of P2 S ₅ may be 0 <x≤0.1, but 0.03≤x≤0.1 is preferable, and particularly 0. .08 ≦ x ≦ 0.1 is preferable.

Also, as another aspect, especially the composition of glass-ceramic,
8Li ₂ S- (2-x) P ₂ S ₅ -xSeS ₂
[However, x indicating the molar ratio of SeS ₂ is 0 <x ≦ 0.1. ]
Is preferable. The x indicating the content _{(mol%) of SeS 2 with} respect to the content of P2 S ₅ may be 0 <x≤0.1, but 0.03≤x≤0.1 is preferable, and particularly 0. .08 ≦ x ≦ 0.1 is preferable.

The solid electrolyte of the present invention preferably further contains at least one element selected from the group consisting of Fe, Mg, Ca, V, Se and Sn. By containing these elements, the effect of increasing the conductivity of the solid electrolyte can be easily obtained. Although the content of these elements is not limited, the content ₍ mol%) of these elements with respect to the content of P2 _S5 is preferably 0.03 to 0.3 mol%, preferably 0.08 to 0.08. 0.1 mol% is more preferable. These elements are contained, for example, by substituting a part of P ₂ S ₅ with at least one kind (additive) such as FeCl ₂ , FeCl ₃ , MgS, CaS, V ₂ S ₃ , SeCl ₂ , SnCl ₂ and the like. Can be done.
(Manufacturing method of solid electrolyte)
The method for producing the solid electrolyte of the present invention is not limited, but a raw material mixture containing Li ₂ S powder, P ₂ S ₅ powder and Se S ₂ powder (including the above-mentioned additives if necessary) is used in a ball mill. After pulverizing at room temperature, the pulverized product can be suitably produced by firing in an atmosphere of an inert gas. The content of the powder of each component in the raw material mixture is not limited, and each component may be blended so as to have the composition of the glass ceramic constituting the solid electrolyte of the present invention.

When the raw material mixture is pulverized, it may be pulverized using a ball mill at room temperature, but for example, it is preferably pulverized for 10 to 60 hours using a high-speed planetary ball mill, and more preferably 25 to 35 hours. The pulverized product may be fired in an inert gas atmosphere to obtain a desired glass ceramic, but it is particularly preferable to fire at 230 to 280 ° C. in an argon gas atmosphere, and to fire at 255 to 265 ° C. More preferred. The firing time can be appropriately adjusted depending on the firing temperature, but is preferably 1 to 4 hours, more preferably 2 to 3 hours.

All-solid-state lithium-sulfur (Li-S) battery The solid electrolyte of the present invention is useful as a solid electrolyte for an all-solid-state lithium-sulfur (Li-S) battery, and the solid electrolyte can be combined with a positive electrode material and a negative electrode material. Allows an all-solid-state lithium-sulfur battery to be constructed.

(Positive electrode material)
The positive electrode material is not limited, and a positive electrode material known for all-solid lithium-sulfur batteries (for example, S—Li ₂ SP ₂ S5 _- C composite) can be used, but in the present invention, the solid is said. S-Li ₂ SP ₂ S ₅ -SeS ₂ which is a composite of Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic, sulfur and carbon as a positive electrode material for use in combination with an electrolyte. A positive electrode material made of a C-based composite is preferable.

Such a positive electrode material is an S-Li ₂ SP ₂ S in which a part of the P ₂ S ₅ is replaced with Se S ₂ in the conventional S-Li ₂ SP ₂ S ₅ -C composite. Any composite material represented by ₅ -SeS _{2 -} C may be used, and among them, the content of SeS ₂ is 1 to ₆ mol% of the content of P2 S5, as in the solid electrolyte of the present invention. Of these, 1 to 5.3 mol% is preferable, and 3 to 3.5 mol% is more preferable. In particular,
S-7Li ₂ S- (3-x) P ₂ S ₅ -xSeS ₂ -C
[However, x indicating the molar ratio of SeS ₂ is 0 <x ≦ 0.1. ]
And what is
S-8Li ₂ S- (2-x) P ₂ S ₅ -xSeS ₂ -C
[However, x indicating the molar ratio of SeS ₂ is 0 <x ≦ 0.1. ]
Is preferable. By using such a composite material, the stability of the battery capacity when the all-solid-state lithium-sulfur battery is repeatedly charged and discharged is likely to be improved.

The method for producing the positive electrode material is not limited, but after pulverizing the sulfur and carbon materials at room temperature using a ball mill, a mixture of the pulverized product and Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic is prepared. It can be suitably produced by pulverizing at room temperature using a ball mill. The blending ratio of the sulfur, the carbon material and the Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic can be appropriately set so that the obtained positive electrode material has a desired composition.

Examples of the carbon material include acetylene carbon black (AB), artificial graphite (Super P), graphite, vapor-grown carbon fiber, carbon nanotubes and the like.

When the sulfur and carbon materials are pulverized at room temperature using a ball mill, for example, it is preferably pulverized for 5 to 15 hours using a high energy planetary ball mill, and more preferably 8 to 10 hours. When a mixture of a pulverized product and a Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic is pulverized at room temperature using a ball mill, for example, it is pulverized for 5 to 15 hours using a high energy planetary ball mill. It is preferable to grind it for 8 to 10 hours, and it is more preferable to grind it for 8 to 10 hours.

(Negative electrode material)
The negative electrode material is not limited, and a negative electrode material known for all-solid-state lithium-sulfur batteries can be used. For example, a composite material of lithium and a carbon material such as metallic lithium, a lithium alloy (Li-In, Li-Al, Li-Si, etc.), a lithium-graphite interlayer compound, and the like can be mentioned. These negative electrode materials can usually be used in the form of metal leaf.

(Example of Li-S battery)
FIG. 7 shows a schematic cross-sectional view of an example of the arrangement of the positive electrode material 1, the solid electrolyte 2, the negative electrode material 3, and the stainless steel disk 4 in the all-solid-state lithium-sulfur battery.

Li-S batteries can be assembled, for example, in a dry argon-filled glove box. As an example of the assembling method, first, the positive electrode material powder and the solid electrolyte powder are sequentially filled in a cell having a diameter of 8 to 12 mm, and then pressed at a pressure of 200 to 400 MPa for 1 to 5 minutes. Next, a lithium metal leaf, which is a negative electrode material, is placed on the surface of the solid electrolyte, and the three-layer pellets are sandwiched between two stainless steel discs. Next, the sandwiched pellets are pressurized at room temperature for 1 to 5 minutes at 50 to 200 MPa to obtain a Li-S battery.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples.

Example 1 (Preparation of glass ceramic)
A mixture of powders of Li ₂ S, P ₂ S ₅ and Se S ₂ having a molar ratio of 7: 2.9: 0.1 is an argon-filled agate pot with 10 agate balls (diameter 10 mm) (capacity 45 cm ³ ). The mixture was mechanically pulverized and mixed at room temperature for 30 hours at a rotation speed of 510 rpm using a planetary ball mill device. Next, the obtained powder was heated at 260 ° C. for ₂ hours in an argon atmosphere to obtain 70Li 2S _{-29P 2S 5-1SeS 2 glass ceramic} .

Example 2 (Preparation of glass ceramic)
A mixture of powders of Li ₂ S, P ₂ S ₅ and Se S ₂ having a molar ratio of 7: 2.95: 0.05 is an argon-filled agate pot with 10 agate balls (diameter 10 mm) (capacity 45 cm ³ ). The mixture was mechanically pulverized and mixed at room temperature for 30 hours at a rotation speed of 510 rpm using a planetary ball mill device. Next, the obtained powder was heated at 260 ° C. for ₂ hours in an argon atmosphere to obtain _70Li 2S _{- 29.5P2S5-0.5SeS2} glass ceramic.

Example 3 (Preparation of glass ceramic)
A mixture of powders of Li ₂ S, P ₂ S ₅ and Se S ₂ having a molar ratio of 7: 2.97: 0.03 is an argon-filled agate pot with 10 agate balls (diameter 10 mm) (capacity 45 cm ³ ). The mixture was mechanically pulverized and mixed at room temperature for 30 hours at a rotation speed of 510 rpm using a planetary ball mill device. Next, the obtained powder was heated at 260 ° C. for _{2 hours in an argon atmosphere to obtain 70Li 2S-29.7P 2S 5-0.3SeS 2 glass ceramic .}

Comparative Example 1 (Preparation of glass ceramic)
A mixture of powders of Li ₂ S and P ₂ S ₅ having a molar ratio of 7: 3 was placed in an argon-filled agate pot (capacity 45 cm ³ ) having 10 agate balls (diameter 10 mm) and used with a planetary ball mill device. Then, the mixture was mechanically pulverized and mixed at a rotation speed of 510 rpm at room temperature for 30 hours. Next, the obtained powder was heated at 260 ° C. for 2 hours in an argon atmosphere to obtain a _70Li 2S _{- 30P2S5} glass ceramic.

Comparative Example 2 (Preparation of glass ceramic)
A mixture of powders of Li ₂ S, P ₂ S ₅ and Se S ₂ having a molar ratio of 7: 2.7: 0.3 is an argon-filled agate pot with 10 agate balls (diameter 10 mm) (capacity 45 cm ³ ). The mixture was mechanically pulverized and mixed at room temperature for 30 hours at a rotation speed of 510 rpm using a planetary ball mill device. Next, the obtained powder was heated at 260 ° C. for ₂ hours in an argon atmosphere to obtain 70Li 2S _{-27P 2S 5-3SeS 2 glass ceramic} .

Comparative Example 3 (Preparation of glass ceramic)
A mixture of powders of Li ₂ S, P ₂ S ₅ and Se S ₂ having a molar ratio of 7: 2.5: 0.5 is an argon-filled agate pot with 10 agate balls (diameter 10 mm) (capacity 45 cm ³ ). The mixture was mechanically pulverized and mixed at room temperature for 30 hours at a rotation speed of 510 rpm using a planetary ball mill device. Next, the obtained powder was heated at 260 ° C. for ₂ hours in an argon atmosphere to obtain 70Li 2S _{-25P 2S 5-5SeS 2 glass ceramic} .

Example 4 (Manufacturing of all-solid-state Li-S battery)
S-70Li ₂ S-29P ₂ S _{5-1SeS 2} -C In order to obtain a composite positive electrode, first, sulfur (S) and carbon black powder (C) are mixed in a ratio of 3: 1 (% by weight) in a menu pot. And mechanically pulverized and mixed at 370 rpm for 8 hours at room temperature using a planetary ball mill device.

Next, the SC composite material and 70Li ₂ S-29P ₂ S _5-1 SeS ₂ glass ceramic were mixed at a ratio of 2: 3 (wt%), mechanically ground at 370 rpm for 8 hours, and then S-70Li ₂ . A powder material for S-29P ₂ S _{5-1SeS 2} -C composite positive electrode was obtained.

In order to assemble the all-solid-state battery shown in FIG. 7, a composite positive electrode and a solid electrolyte powder were filled in a battery cell having a diameter of 12 mm, and then pressed at a pressure of 380 MPa for 3 minutes. A Li foil was placed on the opposite side of the solid electrolyte as a counter electrode, and a pressure of 120 MPa was applied to obtain a solid battery.

Comparative Example 4 (Manufacturing of all-solid-state Li-S battery)
To obtain the S-70Li ₂ S-30P ₂ S ₅ -C composite positive electrode, first, sulfur (S) and carbon black powder (C) were placed in a menow pot at a ratio of 3: 1 (% by weight). Using a planetary ball mill device, the mixture was mechanically ground and mixed at room temperature for 8 hours at 370 rpm.

Next, the SC composite material and Li ₂ SP ₂ S ₅ glass ceramic were mixed at a ratio of 2: 3 (wt%), mechanically pulverized at 370 rpm for 8 hours, and S-70 Li ₂ S-30P. A powder material for a 2S _{5 -} C composite positive electrode was obtained.

In order to assemble the all-solid-state battery shown in FIG. 7, a composite positive electrode and a solid electrolyte powder were filled in a battery cell having a diameter of 12 mm, and then pressed at a pressure of 380 MPa for 3 minutes. A Li foil was placed on the opposite side of the solid electrolyte as a counter electrode, and a pressure of 120 MPa was applied to obtain a solid battery.

Test Example 1
The X-ray diffraction patterns of the glass ceramics prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were examined. The X-ray diffraction spectrum measurement result is shown in FIG.

According to the results of FIG. 1, the X-ray diffraction patterns of the glass ceramics of Examples 1 to 3 and Comparative Example 2 were almost the same as the X-ray diffraction patterns of Comparative Example 1 (standard). However, it was found that the X-ray diffraction pattern of the glass ceramic of Comparative Example 3 changed from the X-ray diffraction pattern of Comparative Example 1 (standard), and the crystal structure of the glass ceramic changed.

Test Example 2
The ionic conductivity of the glass ceramics prepared in Examples 1 to 5 was measured. The measurement results are shown in FIG.

According to the results of FIG. ₂ , 7Li 2S- (3-x) P 2S ₅ - _{xSeS 2}
[However, x indicating the molar ratio of SeS ₂ is 0 <x ≦ 0.1. ]
In the solid electrolyte of the present invention represented by, it was found that the effect of improving the ionic conductivity was greatest when x = 0.1.

Test Example 3
The impedance plots of the glass ceramics prepared in Example 1 and Comparative Example 1 were examined. The measurement results are shown in FIG.

According to the results of FIG. 3, it was found that the bulk resistance (R ₁ ) of the glass ceramic of Example 1 was smaller than the bulk resistance (R ₂ ) of the glass ceramic of Comparative Example 1. The glass ceramics of Example 1 were found to have faster reaction kinetics, lower bulk and interfacial resistance, and higher ionic conductivity (5.28 × 10 ^-3 S · cm ^-1 ).

Test Example 4
The DC current curves of the glass ceramics prepared in Example 1 and Comparative Example 1 were examined. The applied voltage at the time of measurement was 1.0 V, the sample size was 12φ, and the sample thickness was 0.51 mm. The measurement results are shown in FIG.

According to the results of FIG. 4, the glass ceramic of Comparative Example 1 has an ionic conductivity of 2.4 × 10 ^-3 S · cm ^-1 , whereas the glass ceramic of Example 1 has an ionic conductivity of about 5. It was .7 × 10 ^-3 S · cm ^-1 . With the addition of SeS ₂ , the ionic conductivity of the glass ceramic increased more than twice. Moreover, the long-term compatibility of the glass ceramic of Example 1 with the lithium metal is better than that of the glass ceramic of Comparative Example 1.

Test Example 5
The charge / discharge characteristics of the solid-state batteries of Example 4 and Comparative Example 4 were compared. The charge / discharge rate is 0.05C. The measurement results are shown in FIG.

Solid-state batteries show a single plateau at 1.8 V corresponding to the conversion of sulfur to Li _2S . In the charging process, both solid-state batteries show a clear potential plateau near about 2.4 V due to the oxidation reaction of Li _2S to sulfur. Although there was no significant difference in the charge / discharge potential, the decrease in discharge capacity after repeating 5 cycles of charge / discharge was smaller in the solid-state battery of Example 4.

Test Example 6
The charge / discharge characteristics of the solid-state batteries of Example 4 and Comparative Example 4 were compared. The charge / discharge rate is 0.05 C, the charge potential is 1.0 to 3.0 V, and the discharge potential is 3.0 to 1.0 V. The measurement results are shown in FIG.

The solid-state batteries of Example 4 and Comparative Example 4 showed discharge capacities of 950 mAh · g ^-1 and 1187 mAh · g ^-1 , respectively, in the voltage range of 1.0 to 3.0 V. In both cases, the capacity decreased due to repeated charging and discharging, but the solid-state battery of Example 4 showed less decrease in capacity.

The Coulomb efficiency of the solid-state battery of Comparative Example 4 was about 91% in the initial cycle, whereas the Coulomb efficiency of the solid-state battery of Example 4 was about 92%. After 10 cycles, both showed an efficiency of about 98.5%. It can be seen that the solid-state battery of Example 4 is superior in stability to the solid-state battery of Comparative Example 4.

From the results of the above test examples, the solid electrolyte for an all _- solid lithium _- sulfur battery of the present invention has improved lithium ion conductivity as compared with the conventional solid electrolyte made of Li 2SP 2S ₅ series glass ceramic. Further, it can be seen that the all-solid-state lithium-sulfur battery provided with the solid electrolyte of the present invention has improved stability of the battery capacity when charging and discharging are repeated.

1. 1. Positive electrode material 2. Solid electrolyte 3. Negative electrode material 4. Stainless steel disc

Claims (8)

In Li ₂ SP ₂ S ₅ series glass ceramics
A part of P ₂ S ₅ is replaced with Se S ₂ , and the content of Se S ₂ is 1 to 6 mol% of the content of P ₂ S ₅ Li ₂ SP ₂ S ₅ -SeS ₂ system. A solid electrolyte for all-solid lithium-sulfur batteries, characterized by being made of glass ceramic. The composition of the Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic is
7Li ₂ S- (3-x) P ₂ S ₅ -xSeS ₂
[However, x indicating the molar ratio of SeS ₂ is 0 <x ≦ 0.1. ]
The solid electrolyte according to claim 1. The composition of the Li ₂ SP ₂ S ₅ -SeS ₂ glass ceramic is
8Li ₂ S- (2-x) P ₂ S ₅ -xSeS ₂
[However, x indicating the molar ratio of SeS ₂ is 0 <x ≦ 0.1. ]
The solid electrolyte according to claim 1. The solid electrolyte according to any one of claims 1 to 3, further containing at least one element selected from the group consisting of Fe, Mg, Ca, V, Se and Sn. Claimed, wherein a raw material mixture containing Li ₂ S powder, P ₂ S ₅ powder and Se S ₂ powder is pulverized at room temperature using a ball mill, and then the pulverized product is calcined in an inert gas atmosphere. The method for producing a solid electrolyte according to any one of 1 to 4. A positive electrode material for use in combination with the solid electrolyte according to any one of claims 1 to 4 in an all-solid-state lithium-sulfur battery, wherein the Li ₂ SP ₂ S ₅ -SeS ₂ system glass ceramic and sulfur are used. A positive electrode material for an all-solid-state lithium-sulfur battery, which comprises an S-Li ₂ SP ₂ S ₅ -SeS ₂ -C system composite which is a composite of carbon and carbon. The sulfur and carbon materials are pulverized at room temperature using a ball mill, and then a mixture of the pulverized product and the Li ₂ SP ₂ S ₅ -SeS ₂ system glass ceramic is pulverized at room temperature using a ball mill. The method for producing a positive electrode material according to claim 6. An all-solid-state lithium-sulfur battery comprising the positive electrode material, the negative electrode material, and the solid electrolyte according to any one of claims 1 to 4.

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