JP6481989B1 - Lithium sulfur solid battery - Google Patents

Abstract

A novel lithium-sulfur solid state battery is provided.
SOLUTION: A sulfur positive electrode 11, a lithium negative electrode 12, and a solid electrolyte 13 are provided. The solid electrolyte 13 is disposed between the sulfur positive electrode 11 and the lithium negative electrode 12. The void portion opens to the outside of the conductive sheet, the sulfur positive electrode 11 contains sulfur in the void portion, and the sulfur positive electrode 11 contains sulfur. The lithium sulfur solid battery 1 whose quantity is 6 mg / cm < ² > or more.
[Selection] Figure 1

Description

  The present invention relates to a lithium sulfur solid battery.

In recent years, electronic devices and communication devices are rapidly becoming portable and cordless. Secondary batteries with high energy density and excellent load characteristics are demanded as power sources for these electronic and communication devices, and the use of lithium secondary batteries with high voltage, high energy density, and excellent cycle characteristics is expanding. doing.
On the other hand, batteries with a higher energy density are required for the popularization of electric vehicles and the promotion of the use of natural energy. Therefore, development of a new lithium secondary battery that replaces a lithium ion secondary battery that uses a lithium composite oxide such as LiCoO ₂ as a constituent material of the positive electrode is desired.

  Sulfur has a very high theoretical capacity density of 1672 mAh / g, and a lithium-sulfur battery using sulfur as a constituent material of the positive electrode has the possibility of achieving the highest energy density theoretically among the batteries. ing. Therefore, research and development of lithium-sulfur batteries have been actively conducted.

When an organic electrolyte is used as the electrolyte of a lithium-sulfur battery, sulfur molecules and reaction intermediates (for example, lithium polysulfide) are dissolved and diffused in the organic electrolyte during charging and discharging. Thus, there is a problem that the self-discharge and the deterioration of the negative electrode are caused and the battery performance is lowered.
Therefore, in order to solve such problems, a method of modifying the electrolytic solution by adding an acid such as hydrochloric acid or nitric acid to the electrolytic solution (see Patent Document 1), as a constituent material of the positive electrode, Ketjen Black A method using a composite encapsulating sulfur nanoparticles (see Patent Document 2) has been proposed.

JP2013-114920A JP 2012-204332 A

However, in the methods disclosed in Patent Documents 1 and 2, since the electrolyte itself is in a liquid state, it is not possible to completely suppress dissolution of sulfur molecules and reaction intermediates in the electrolytic solution, and a sufficient effect can be obtained. There was no problem.
As a method for solving the problems when such an electrolytic solution is used, there is a method using a solid electrolyte. However, a lithium-sulfur solid battery equipped with a solid electrolyte has not yet been sufficiently technically studied, and there is room for significant improvement.

  This invention is made | formed in view of the said situation, and makes it a subject to provide a novel lithium sulfur solid battery.

In order to solve the above problems, the present invention employs the following configuration.
[1]. The lithium sulfur solid battery, wherein the sulfur content of the sulfur positive electrode is 6 mg / cm ² or more.
[2]. The lithium sulfur solid battery according to [1], wherein the sulfur positive electrode further contains an ionic liquid in the gap portion of the conductive sheet.

[3]. The lithium-sulfur solid battery according to [2], wherein the ionic liquid is a solvated ionic liquid comprising a glyme-lithium salt complex.
[4]. The lithium-sulfur solid battery according to any one of [1] to [3], wherein the constituent material of the solid electrolyte is an oxide-based material.
[5]. The lithium sulfur solid battery according to any one of [1] to [4], wherein an operating temperature of the lithium sulfur solid battery is 110 to 160 ° C.

  According to the present invention, a novel lithium-sulfur solid state battery is provided.

It is sectional drawing which shows typically an example of the principal part of the lithium sulfur solid battery of this embodiment. It is sectional drawing which shows typically an example of the principal part of the other lithium sulfur solid battery of this embodiment. It is the imaging data acquired about the sulfur positive electrode obtained in Example 1 using the scanning electron microscope. It is the imaging data acquired about the carbon cloth used in Example 1 using the scanning electron microscope. It is the discharge curve obtained when the constant current charging / discharging test was done about the battery cell obtained in Example 1. FIG. It is the discharge curve obtained when the constant current charging / discharging test was done about the battery cell obtained by the reference example 1. FIG.

<< Lithium sulfur solid battery >>
A lithium-sulfur solid battery according to an embodiment of the present invention includes a sulfur positive electrode, a lithium negative electrode, and a solid electrolyte, and the solid electrolyte is disposed between the sulfur positive electrode and the lithium negative electrode, The sulfur positive electrode has a conductive sheet having a large number of voids, the voids open to the outside of the conductive sheet, the sulfur positive electrode contains sulfur in the voids, The sulfur positive electrode has a sulfur content of 6 mg / cm ² or more.
In the sulfur positive electrode of the lithium-sulfur solid battery of the present embodiment, normally used conductive assistants and binders are unnecessary. Therefore, the energy density of the lithium-sulfur solid battery of this embodiment is high.

In the present specification, “the sulfur content (mg / cm ² )” of the sulfur positive electrode is a surface area of 1 cm ² of the sulfur positive electrode when viewed from above with the sulfur positive electrode viewed from directly above, unless otherwise specified. This means the sulfur content (mg) of the sulfur positive electrode.

  A preferable operating temperature of the lithium sulfur solid battery is 110 to 160 ° C. That is, it is preferable that sulfur is melted during the operation of the lithium sulfur solid battery. By operating the lithium-sulfur solid battery in this manner, the utilization efficiency of sulfur is high and the battery characteristics are excellent.

First, the structure of the lithium-sulfur solid battery of the present embodiment will be described with reference to the drawings.
In addition, in order to make the features of the present invention easy to understand, the drawings used in the following description may show the main parts in an enlarged manner for convenience, and the dimensional ratios of the respective components are the same as the actual ones. Not necessarily.

FIG. 1 is a cross-sectional view schematically showing an example of a main part of the lithium-sulfur solid battery of the present embodiment.
The lithium sulfur solid battery 1 shown here includes a sulfur positive electrode 11, a lithium negative electrode 12, and a solid electrolyte 13.
In the lithium sulfur solid battery 1, the solid electrolyte 13 is disposed between the sulfur positive electrode 11 and the lithium negative electrode 12. That is, in the lithium-sulfur solid battery 1, the sulfur positive electrode 11, the solid electrolyte 13, and the lithium negative electrode 12 are laminated in this order in the thickness direction.

The sulfur positive electrode 11 has a conductive sheet having a large number of voids. The gap portion of the conductive sheet is open to the outside of the conductive sheet at least before the production of the sulfur positive electrode 11 (step where the void portion does not contain sulfur). And the sulfur positive electrode 11 contains sulfur in the said space | gap part.
The sulfur content of the sulfur positive electrode 11 is 6 mg / cm ² or more.

In the lithium-sulfur solid battery 1, for example, the sulfur positive electrode 11 and the lithium negative electrode 12 are further provided with terminals for connection to an external circuit, respectively.
In the lithium-sulfur solid battery 1, the entire laminated structure of the sulfur positive electrode 11, the solid electrolyte 13, and the lithium negative electrode 12 is housed in a container as necessary.
The lithium-sulfur solid battery 1 further includes a mechanism (leakage suppression mechanism) that suppresses leakage of sulfur in the molten state in the sulfur positive electrode 11 to the outside of the lithium-sulfur solid battery 1 as necessary. May be. For example, the container may also serve as such a leakage suppression mechanism.
Next, the configuration of each layer of the lithium-sulfur solid battery of the present embodiment will be described in detail.

<Sulfur cathode>
[Conductive sheet]
The conductive sheet can function as a positive electrode current collector.
The conductive sheet has a large number of voids, and the sulfur positive electrode contains sulfur in the voids.
The gap is open to the outside of the conductive sheet. Therefore, for example, a sulfur positive electrode containing sulfur in the voids of the conductive sheet can be produced by impregnating the conductive sheet with molten sulfur or a sulfur solution.

The shape of the gap in the conductive sheet is not particularly limited as long as the above conditions are satisfied.
For example, the gap may be connected to one or more other gaps, or may be independent without being connected to other gaps.
In addition, the connected gap portion and the non-connected gap portion may penetrate from one surface of the conductive sheet to the other surface on the opposite side, or may be conducted without penetrating. It may be a dead end inside the sex sheet.
In addition, both of the connected gap portion and the non-connected gap portion may reach the same surface again from one surface of the conductive sheet via the inside of the conductive sheet.

  As a form of the conductive sheet, for example, a porous material or a fibrous material in which fibrous materials are aggregated to form a layer (in this specification, it is referred to as “fiber assembly”). And the like. For example, the fiber assembly may be configured such that fibrous materials are entangled with each other, or may be configured by stacking the fibrous materials regularly or irregularly.

The constituent material of the conductive sheet may be conductive as long as it does not have reactivity with sulfur.
More specifically, examples of the constituent material of the conductive sheet include carbon, metal (single metal, alloy), and the like.
Especially, as a preferable constituent material of a conductive sheet, the constituent material of a positive electrode electrical power collector is mentioned, More specifically, carbon, copper, aluminum, titanium, nickel, stainless steel etc. are mentioned, for example.

  The constituent material of the conductive sheet may be only one kind, or two or more kinds, and when there are two or more kinds, the combination and ratio thereof can be arbitrarily selected according to the purpose.

  Examples of preferable conductive sheets include carbon felt and carbon cloth.

  The thickness of the conductive sheet is not particularly limited, and may be set as appropriate according to the purpose of the applied battery. Usually, the thickness of the conductive sheet is preferably 50 to 30000 μm, and more preferably 100 to 3000 μm.

  In addition, when the thickness of the conductive sheet clearly varies depending on the portion of the conductive sheet, such as when the degree of unevenness on the surface of the conductive sheet is high, the maximum thickness is the thickness of the conductive sheet. (The thickness of the thickest part of the conductive sheet is the thickness of the conductive sheet). This applies not only to the conductive sheet, but also to the thicknesses of all layers (a sulfur positive electrode, a lithium negative electrode, and a solid electrolyte described later).

[Sulfur, sulfur solution]
As described above, the sulfur positive electrode can be produced by impregnating the conductive sheet with molten sulfur or a sulfur solution.
The sulfur solution can be obtained by dissolving sulfur in a solvent.
The solvent of the sulfur solution is not particularly limited as long as it can dissolve sulfur and does not alter the conductive sheet.
The solvent may be either an inorganic solvent or an organic solvent.
Examples of the inorganic solvent include carbon disulfide.
Examples of the organic solvent include benzene, toluene, n-hexane, and the like.

  As for the solvent in the said sulfur solution, only 1 type may be sufficient and it may be 2 or more types, and when it is 2 or more types, those combinations and ratios can be arbitrarily selected according to the objective.

The concentration of sulfur in the sulfur solution is not particularly limited as long as the void portion of the conductive sheet can be impregnated with the sulfur solution.
The concentration of sulfur in the sulfur solution can be appropriately adjusted according to, for example, the type of solvent.
The concentration of sulfur in the sulfur solution is preferably 0.1 to 35% by mass, for example. When the concentration is equal to or higher than the lower limit, a sulfur positive electrode having a large sulfur content can be obtained more easily. When the concentration is equal to or lower than the upper limit value, the handleability of the sulfur solution at the time of impregnation into the conductive sheet becomes better.

As a method of impregnating the conductive sheet with molten sulfur at the time of producing the sulfur positive electrode, for example, a method of placing solid sulfur on the surface of the conductive sheet and heating and melting the sulfur in this state (In this specification, it may be abbreviated as “impregnation method A”); a method of supplying sulfur in a molten state by heating to the surface of the conductive sheet (in this specification, “impregnation method B”). May be abbreviated as ")".
In the impregnation method A, for example, sulfur on the conductive sheet may be heated together with the conductive sheet.
In the impregnation method B, for example, molten sulfur may be supplied to the surface of the conductive sheet while heating. Moreover, you may supply sulfur, heating a conductive sheet at the temperature equivalent to sulfur.

In particular, in the impregnation method A, the molten sulfur is naturally impregnated into the conductive sheet by gravity simply by heating the sulfur on the conductive sheet, so that it can be impregnated very easily.
Therefore, the method of impregnating the conductive sheet with the molten sulfur is preferably impregnation method A.

  The temperature of sulfur when the conductive sheet is impregnated with molten sulfur is preferably 120 to 160 ° C, more preferably 135 to 160 ° C, and particularly preferably 150 to 160 ° C. When the temperature is in such a range, the melt viscosity of sulfur is sufficiently lowered, and sulfur can be easily introduced into the void portion of the conductive sheet, and the sulfur content in the void portion becomes better. . As a result, in the sulfur positive electrode, normally used conductive assistants and binders are unnecessary, and the energy density of the lithium-sulfur solid battery becomes higher.

  Examples of the method for impregnating the conductive sheet with the sulfur solution during the production of the sulfur positive electrode include a method of supplying the sulfur solution to the surface of the conductive sheet; a method of immersing the conductive sheet in the sulfur solution, and the like. .

  It is preferable to appropriately adjust the temperature of the sulfur solution when the conductive sheet is impregnated with the sulfur solution according to the type of the solvent in the sulfur solution. For example, the temperature of the sulfur solution is preferably equal to or lower than the boiling point of the solvent in the sulfur solution. When the temperature is equal to or lower than the upper limit value, the sulfur solution can be easily introduced into the void portion of the conductive sheet, and the sulfur content in the void portion becomes better. As a result, in the sulfur positive electrode, normally used conductive assistants and binders are unnecessary, and the energy density of the lithium-sulfur solid battery becomes higher.

  The lower limit of the temperature of the sulfur solution when the conductive sheet is impregnated with the sulfur solution is not particularly limited as long as the sulfur solution does not solidify. For example, the temperature is preferably 15 ° C. or higher in terms of easy preparation of a sulfur solution and good handleability of the sulfur solution.

When the conductive sheet is impregnated with the sulfur solution, it is necessary to dry the sulfur solution (remove the solvent in the sulfur solution).
The sulfur solution may be dried by a known method. For example, the sulfur solution may be dried under normal pressure, reduced pressure, or blowing conditions, or may be performed in the air or in an inert gas atmosphere.
The drying temperature (solvent removal temperature) is preferably adjusted as appropriate according to the type of solvent in the sulfur solution. For example, the drying temperature of the sulfur solution is preferably equal to or higher than the boiling point of the solvent in the sulfur solution.

When the sulfur positive electrode is obtained by impregnating a conductive sheet with molten sulfur or a sulfur solution, sulfur has a specific content in the voids of the conductive sheet. That is, sulfur is agglomerated in the void portion of the conductive sheet, and is held in contact with the surface of the void portion in a state in which generation of a gap is suppressed. In other words, in the void portion of the conductive sheet, the massive sulfur has a large contact area with the surface of the void portion. This is an effect due to the molten sulfur or the sulfur solution being filled in the voids of the conductive sheet by impregnation into the conductive sheet. For example, when the conductive sheet is impregnated with a sulfur dispersion containing undissolved sulfur, the undissolved sulfur is finally in the form of particles or the like in the voids of the conductive sheet. Retained. In such a sulfur positive electrode, the contact area between sulfur and the surface of the gap is reduced.
In the lithium-sulfur solid battery of this embodiment, the sulfur positive electrode contains sulfur in a specific state as described above, so that normally used conductive assistants and binders are unnecessary, and the energy density is increased.

  Furthermore, in the sulfur positive electrode according to the present embodiment, the sulfur content can be increased as compared with the case where sulfur is not contained because the sulfur is in a specific content state. This is because the sulfur content in the voids of the conductive sheet increases. Thus, when it will be in the state which content of sulfur increased, the lithium sulfur solid battery of this embodiment increases the usage-amount of sulfur, and also has the outstanding battery characteristic also in this point.

In this embodiment, the sulfur content of the sulfur positive electrode is 6 mg / cm ² or more, preferably 10 mg / cm ² or more, more preferably 15 mg / cm ² or more, and 20 mg / cm ² or more. It is particularly preferred that

In the present embodiment, the upper limit value of the sulfur content of the sulfur positive electrode is not particularly limited. For example, the sulfur content of the sulfur positive electrode is preferably 300 mg / cm ² or less in terms of easier production of the sulfur positive electrode.

In the present embodiment, the sulfur content of the sulfur positive electrode can be appropriately adjusted so as to be within a range set by arbitrarily combining the above-described preferable lower limit value and upper limit value. For example, the sulfur content of sulfur positive electrode is preferably 6~300mg / cm ^2, more preferably 10-300 mg / cm ^2, more preferably from 15~300mg / cm ^2, 20 It is particularly preferred that it is ˜300 mg / cm ² . However, these are examples of the sulfur content of the sulfur positive electrode.

  As described above, in the sulfur positive electrode in the present embodiment, the components used in the normal positive electrode, such as a conductive auxiliary agent and a binder, are due to the presence of sulfur in the voids of the conductive sheet. Is unnecessary. Thus, the sulfur content in the sulfur positive electrode can be increased by eliminating (not containing) components other than sulfur in the conductive sheet.

[Ionic liquid]
The sulfur positive electrode preferably further contains an ionic liquid in the void portion of the conductive sheet. The ionic liquid is excellent in high-temperature stability and can easily move lithium ions. Therefore, although the sulfur positive electrode contains the ionic liquid, the ionic liquid moves lithium ions between the sulfur positive electrode and the solid electrolyte although the contact area between the sulfur positive electrode and the solid electrolyte is small. Therefore, although the solid battery using such a sulfur positive electrode uses a solid electrolyte, the interface resistance value at the sulfur positive electrode interface is reduced, and the battery characteristics are more excellent.

  The ionic liquid can be appropriately selected from, for example, known ones.

  Examples of the ionic liquid include ionic compounds that are liquid at a temperature of less than 170 ° C., solvated ionic liquids, and the like.

(Ionic compounds that are liquid at temperatures below 170 ° C)
The cation part constituting the ionic compound may be either an organic cation or an inorganic cation, but is preferably an organic cation.
The anion part constituting the ionic compound may be either an organic anion or an inorganic anion.

Among the cation moieties, examples of the organic cation include an imidazolium cation, a pyridinium cation, a pyrrolidinium cation, a phosphonium cation, and an ammonium cation. , Sulfonium cation and the like.
However, the organic cation is not limited to these.

Among the anion moieties, examples of the organic anion include alkyl sulfate anions such as methyl sulfate anion (CH ₃ SO ₄ ⁻ ) and ethyl sulfate anion (C ₂ H ₅ SO ₄ ⁻ );
Tosylate anion (CH ₃ C ₆ H ₄ SO ₃ ⁻ );
Alkanesulfonate anions such as methanesulfonate anion (CH ₃ SO ₃ ⁻ ), ethanesulfonate anion (C ₂ H ₅ SO ₃ ⁻ ), butanesulfonate anion (C ₄ H ₉ SO ₃ ⁻ );
Trifluoromethanesulfonate anion (CF ₃ SO ₃ ⁻ ), pentafluoroethanesulfonate anion (C ₂ F ₅ SO ₃ ⁻ ), heptafluoropropanesulfonate anion (C ₃ H ₇ SO ₃ ⁻ ), nonafluorobutanesulfonate anion (C ₄₎ H ₉ SO ₃ ^-) perfluoroalkane sulfonate anions such as (perfluoroalkanesulfonate anion);
Bis (trifluoromethanesulfonyl) imide anion ((CF ₃ SO ₂ ) N ⁻ ), bis (nonafluorobutanesulfonyl) imide anion ((C ₄ F ₉ SO ₂ ) N ⁻ ), nonafluoro-N-[(trifluoromethane) Sulfonyl] butanesulfonylimide anion ((CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) N ⁻ ), N, N-hexafluoro-1,3-disulfonylimide anion (SO ₂ CF ₂ CF ₂ CF ₂ SO ₂ N ^-) perfluoroalkanesulfonyl anion such as (perfluoroalkanesulfonylimide anion);
Acetate anion (CH ₃ COO ⁻ );
Hydrogen sulfate anion (HSO ₄ ⁻ ); and the like.
However, the organic anion is not limited to these.

Among the anion moieties, examples of inorganic anions include bis (fluorosulfonyl) imide anion (N (SO ₂ F) ₂ ⁻ ); hexafluorophosphate anion (PF ₆ ⁻ ); tetrafluoroborate anion (BF ₄ ⁻ ). Halide ions such as chloride ions (Cl ⁻ ), bromide ions (Br ⁻ ), iodide ions (I ⁻ ), tetrachloroaluminate anions (AlCl ₄ ⁻ ), thiocyanate anions (SCN ⁻ ), etc. Is mentioned.
However, the inorganic anion is not limited to these.

  Examples of the ionic compound include those composed of a combination of any one of the above cation moieties and any one of the above anion moieties.

  Examples of the ionic liquid in which the cation portion is an imidazolium cation include 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide, 1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide, 1 -Methyl-3-propylimidazolium bis (trifluoromethanesulfonyl) imide, 1-hexyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3- Methyl imidazolium chloride, 1-ethyl-3-methylimidazolium methanesulfonate, 1-butyl-3-methylimidazolium methanesulfonate, 1,2,3-trimethylimidazolium methyl sulfate, methyl imi Zorium chloride, methyl imidazolium hydrogen sulfate, 1-ethyl-3-methyl imidazolium hydrogen sulfate, 1-butyl-3-methyl imidazolium hydrogen sulfate, 1-butyl-3-methyl imidazolium hydrogen sulfate, 1-ethyl-3-methylimidazolium tetrachloroaluminate, 1-butyl-3-methylimidazolium tetrachloroaluminate, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-butyl-3-methylimidazolium methyl sulfate, 1-ethyl-3-methylimidazolium thiocyanate, 1-butyl-3-methyl Imidazolium thiocyanate, 1-ethyl-2,3-dimethyl-imidazolium ethylsulfate, and the like.

  Examples of the ionic liquid in which the cation portion is a pyridinium cation include 1-butylpyridinium bis (trifluoromethanesulfonyl) imide, 1-butyl-3-methylpyridinium bis (trifluoromethanesulfonyl) imide, and the like.

  Examples of the ionic liquid in which the cation portion is a pyrrolidinium cation include 1-methyl-1-propylpyrrolidinium bis (trifluoromethanesulfonyl) imide and 1-butyl-1-methylpyrrolidinium bis (trifluoromethanesulfonyl). An imide etc. are mentioned.

  Examples of the ionic liquid in which the cation portion is a phosphonium cation include tetrabutylphosphonium bis (trifluoromethanesulfonyl) imide, tributyldodecylphosphonium bis (trifluoromethanesulfonyl) imide, and the like.

  Examples of the ionic liquid whose cation portion is an ammonium cation include methyltributylammonium methylsulfate, butyltrimethylammonium bis (trifluoromethanesulfonyl) imide, trimethylhexylammonium bis (trifluoromethanesulfonyl) imide, and the like.

(Solvated ionic liquid)
Preferred examples of the solvated ionic liquid include those composed of a glyme-lithium salt complex.

Examples of the lithium salt in the glyme-lithium salt complex include lithium bis (fluorosulfonyl) imide (LiN (SO ₂ F) ₂ , which may be abbreviated as “LiFSI” in this specification), lithium bis ( Trifluoromethanesulfonyl) imide (LiN (SO ₂ CF ₃ ) ₂ , which may be abbreviated as “LiTFSI” in this specification).

Examples of the glyme in the glyme-lithium salt complex include triethylene glycol dimethyl ether (CH ₃ (OCH ₂ CH ₂ ) ₃ OCH ₃ , triglyme), tetraethylene glycol dimethyl ether (CH ₃ (OCH ₂ CH ₂ ) ₄ OCH ₃ , Tetraglyme) and the like.

  Examples of the glyme-lithium salt complex include a complex composed of one molecule of glyme and one molecule of lithium salt, but the glyme-lithium salt complex is not limited thereto.

  The glyme-lithium salt complex is obtained by, for example, mixing lithium salt and glyme so that the molar ratio of lithium salt (mol): glyme (mol) is preferably 10:90 to 90:10. Can be made.

  Preferred examples of the glyme-lithium salt complex include triglyme-LiFSI complex, tetraglyme-LiFSI complex, triglyme-LiTFSI complex, tetraglyme-LiTFSI complex, and the like.

  The ionic liquid which a sulfur positive electrode contains may be only 1 type, 2 or more types, and when it is 2 or more types, those combinations and ratios can be arbitrarily selected according to the objective.

  Among the above, the ionic liquid contained in the sulfur positive electrode is preferably a solvated ionic liquid comprising a glyme-lithium salt complex.

  In the case of using an ionic liquid, in the sulfur positive electrode, the ratio of the content of the ionic liquid to the total content of sulfur and the ionic liquid ([content of the ionic liquid of the sulfur positive electrode (part by mass)] / [sulfur and ions of the sulfur positive electrode The total content of liquid (parts by mass)] × 100) is not particularly limited, but is preferably 5 to 95% by mass, and more preferably 10 to 90% by mass. The electroconductivity of a sulfur positive electrode improves more because the ratio of the said content is more than the said lower limit. When the content ratio is equal to or lower than the upper limit value, the charge / discharge characteristics of the battery are further improved.

[Other ingredients]
The sulfur positive electrode may contain other components that do not correspond to any of the conductive sheet, sulfur, and ionic liquid, regardless of the inside and outside of the void portion of the conductive sheet.
The other components are not particularly limited as long as they do not hinder the function of the sulfur positive electrode.
The other component contained in the sulfur positive electrode may be only one type, two or more types, and in the case of two or more types, the combination and ratio thereof can be arbitrarily selected according to the purpose.
For example, the sulfur positive electrode may contain components used in a normal positive electrode, such as a conductive additive and a binder. When the sulfur positive electrode contains a conductive additive, it may be contained as a composite of sulfur and conductive aid. The composite of sulfur and a conductive additive is obtained by, for example, mixing sulfur and a carbon-containing material (for example, ketjen black) and firing.

Examples of the conductive aid include graphite (graphite); carbon black such as ketjen black and acetylene black; carbon nanotube; graphene; fullerene.
Examples of the binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyacrylic acid (PAA), lithium polyacrylate (PAALi), and styrene butadiene rubber ( SBR), polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyethylene glycol (PEG), carboxymethyl cellulose (CMC), polyacrylonitrile (PAN), polyimide (PI) and the like.

However, in the sulfur positive electrode, as the content of the other components increases, the sulfur content decreases accordingly.
From such a viewpoint, in the sulfur positive electrode, the ratio of the content of the other components to the total content of components other than the conductive sheet ([content of other components in the sulfur positive electrode (part by mass)] / [sulfur The total content (parts by mass) of components other than the conductive sheet in the positive electrode] × 100) is preferably 10% by mass or less, more preferably 5% by mass or less, and 3% by mass or less. Is more preferably 1% by mass or less, and most preferably 0% by mass, that is, the sulfur positive electrode does not contain the other components.
In other words, in the sulfur positive electrode, the ratio of the total content of sulfur and ionic liquid to the total content of components other than the conductive sheet ([total content of sulfur and ionic liquid in the sulfur positive electrode (parts by mass)] / [sulfur The total content (parts by mass) of components other than the conductive sheet in the positive electrode is preferably 90% by mass or more, more preferably 95% by mass or more, and 97% by mass or more. Is more preferably 99% by mass or more, and most preferably 100% by mass.
A lithium-sulfur solid battery satisfying such conditions has more excellent battery characteristics.

  The thickness of the sulfur positive electrode is not particularly limited, and may be set as appropriate according to the purpose of the applied battery. Usually, it is preferable that the thickness of a sulfur positive electrode is 100-30000 micrometers, and it is more preferable that it is 200-3000 micrometers.

<Lithium negative electrode>
The lithium negative electrode in the lithium sulfur solid battery of the present embodiment may be a known one.

  The thickness of the lithium negative electrode is not particularly limited, and may be set as appropriate according to the purpose of the applied battery. Usually, the thickness of the lithium negative electrode is preferably 10 to 2000 μm, and more preferably 100 to 1000 μm.

<Solid electrolyte>
The constituent material of the solid electrolyte in the lithium-sulfur solid battery of the present embodiment is not particularly limited, and may be any of a crystalline material, an amorphous material, and a glass material.
More specifically, as a constituent material of the solid electrolyte, for example, a material containing no sulfide and containing an oxide (sometimes referred to as an “oxide-based material” in this specification), at least a sulfide is used. Known ones are included, including those (sometimes referred to as “sulfide-based materials” in this specification).

Examples of the oxide-based material include Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ), Li _2.9 PO _3.3 N _0.46 (LIPON), and La _0.51 Li _0.34 TiO _2.94. , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , 50Li ₄ SiO ₄ .50Li ₃ BO ₃ , Li _3.6 Si _0.6 P _0.4 O ₄ , Li _1.07 Al _{0 .69} Ti _1.46 (PO ₄ ) ₃ , Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) _{3 and the} like.
Examples of the oxide-based material include a material obtained by adding (doping) an element such as aluminum, tantalum, niobium, or bismuth to a composite oxide such as Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ). It is done. Here, the element to be added may be only one kind, or may be two or more kinds, and when there are two or more kinds, the combination and ratio thereof can be arbitrarily selected according to the purpose.

Examples of the sulfide-based materials, for _{example, Li 10 GeP 2 S 12 (} LGPS), Li 3.25 Ge 0.25 P 0.75 S 4, 30Li 2 S · 26B 2 S 3 · 44LiI, 63Li 2 S · 36SiS ₂ · 1Li ₃ PO ₄ , 57Li ₂ S · 38SiS ₂ · 5Li ₄ SiO ₄ , 70Li ₂ S · 30P ₂ S ₅ (LIISPS), 50Li ₂ S · 50GeS ₂ , Li ₇ P ₃ S ₁₁ , Li _3.25 P _0.95 S ₄ or the like.

  The constituent material of the solid electrolyte may be only one type, or two or more types, and in the case of two or more types, the combination and ratio thereof can be arbitrarily selected according to the purpose.

  The constituent material of the solid electrolyte is preferably the oxide-based material from the viewpoint that a solid electrolyte having high stability in the air and high density can be produced.

  The thickness of the solid electrolyte is not particularly limited, and may be set as appropriate according to the purpose of the applied battery. Usually, the thickness of the solid electrolyte is preferably 10 to 1200 μm. When the thickness of the solid electrolyte is equal to or more than the lower limit, the manufacturing and handling properties are improved. When the thickness of the solid electrolyte is equal to or less than the upper limit value, the resistance value of the lithium sulfur solid battery is further reduced.

  The solid electrolyte can be produced, for example, by selecting a raw material such as a metal oxide, a metal hydroxide, or a metal sulfide according to the intended type and firing the raw material. What is necessary is just to set the usage-amount of a raw material suitably considering the atomic ratio of each metal in a solid electrolyte, etc.

  The lithium-sulfur solid state battery of the present embodiment is not limited to the above-described one, and a part of the configuration described above has been changed, deleted, or added within the scope not departing from the gist of the present invention. It may be.

<Other layers>
For example, the lithium-sulfur solid battery of this embodiment includes one or more other layers that do not correspond to any of a sulfur positive electrode, a solid electrolyte, and a lithium negative electrode, and each layer includes one or more layers. It may be.
The other layers are not particularly limited as long as the effects of the present invention are not impaired, and can be arbitrarily selected according to the purpose.
Examples of the other layers include a gold sputter layer and a lithium ion conductive layer described later.

[Gold sputter layer]
The lithium-sulfur solid battery of this embodiment may include a gold sputter layer disposed between the solid electrolyte and the lithium negative electrode.
For example, in a lithium-sulfur solid battery in which a gold sputter layer is disposed between a lithium negative electrode and a solid electrolyte and these three layers are in direct contact with each other in this order, the gold sputter layer is not disposed. As compared with the case, the interface resistance value at the lithium negative electrode interface is reduced.

  The thickness of the gold sputter layer is preferably 50 nm or more, and more preferably 100 to 200 nm.

[Lithium ion conductive layer]
The lithium-sulfur solid battery according to the present embodiment may include a lithium ion conductive layer disposed between the solid electrolyte and the lithium negative electrode.
The lithium ion conductive layer contains an ionic liquid and conducts lithium ions between the lithium negative electrode and the solid electrolyte.

More specifically, the lithium ion conductive layer is formed from one surface (which may be referred to as “first surface” in this specification) to the other surface (in this specification, “second surface”). It has a large number of voids that may reach up to Therefore, a liquid substance or a fine substance can be moved between the lithium negative electrode and the solid electrolyte via the lithium ion conductive layer.
Further, the lithium ion conductive layer holds the ionic liquid in the voids and the like. Lithium ions can be dissolved in this ionic liquid. Therefore, lithium ions can be easily conducted between the lithium negative electrode and the solid electrolyte (in the thickness direction of the lithium ion conductive layer) via the lithium ion conductive layer.

  A portion of the lithium ion conductive layer that has the void portion, holds the ionic liquid, and maintains the shape of the lithium ion conductive layer is referred to as a “main body portion” in the present specification. That is, the lithium ion conductive layer includes the main body portion and an ionic liquid held by the main body portion.

  In the lithium-sulfur solid battery of the present embodiment, the presence of the lithium ion conductive layer allows the ionic liquid in the lithium ion conductive layer to be used in the lithium ion conductive layer, in other words, between the lithium negative electrode and the solid electrolyte. Precipitation of metallic lithium is suppressed. Here, “precipitation of metallic lithium in the lithium ion conductive layer is suppressed” means that “metal lithium is not precipitated at all in the lithium ion conductive layer or metal lithium is precipitated in the lithium ion conductive layer”. Also means that the amount of precipitation is very small. Therefore, the lithium ion conductive layer smoothly conducts lithium ions between the lithium negative electrode and the solid electrolyte. Further, by suppressing the deposition of metallic lithium in this way, the deposition of metallic lithium is also suppressed in the solid electrolyte. That is, in a lithium-sulfur solid battery, continuous deposition of metallic lithium from the lithium ion conductive layer to the sulfur positive electrode through the solid electrolyte is suppressed. As a result, in a lithium-sulfur solid battery, for example, when charging / discharging is performed, occurrence of a short circuit and cracking of the solid electrolyte can be suppressed.

(Main body)
As a main part of the lithium ion conductive layer, for example, a porous body or a fibrous material in which fibrous materials are aggregated to form a layer (in this specification, referred to as “fiber aggregate”) In some cases).

  It is preferable that the main body does not react with the lithium negative electrode, does not dissolve, and does not deteriorate under the temperature condition during operation of the lithium sulfur solid battery. Here, “deterioration of the main body” means that the composition of the components of the main body changes. The temperature at the time of operation | movement of a lithium sulfur solid battery is 110-160 degreeC as above-mentioned, for example. Therefore, the main body of the lithium ion conductive layer is preferably stable under such temperature conditions.

In such a main body, examples of the constituent material of the porous body or fiber assembly include synthetic resin, glass, paper, and the like, and synthetic resin or glass is preferable.
Especially, it is more preferable that the constituent material of the main body is polyimide or glass. That is, the lithium ion conductive layer more preferably contains polyimide or glass as a constituent material.

  The constituent material of the main body part of the lithium ion conductive layer may be only one type, or two or more types, and in the case of two or more types, the combination and ratio thereof can be arbitrarily selected according to the purpose.

(Ionic liquid)
Examples of the ionic liquid contained in the lithium ion conductive layer include the same ionic liquid as that contained in the above-described sulfur positive electrode (for example, an ionic compound that is liquid at a temperature of less than 170 ° C., a solvated ionic liquid, etc.).

  The ionic liquid contained in the lithium ion conductive layer may be only one kind, or two or more kinds, and when there are two or more kinds, the combination and ratio thereof can be arbitrarily selected according to the purpose.

  The ionic liquid contained in the lithium ion conductive layer may be the same as or different from the ionic liquid contained in the above-described sulfur positive electrode.

  The ionic liquid contained in the lithium ion conductive layer is preferably a solvated ionic liquid comprising a glyme-lithium salt complex. When the lithium ion conductive layer contains such an ionic liquid, the effect of suppressing the precipitation of metallic lithium in the solid electrolyte is further enhanced.

The content of the ionic liquid in the lithium ion conductive layer is not particularly limited.
However, the ratio of the total volume of the ionic liquid held in the lithium ion conductive layer to the total volume of the voids in the main body of the lithium ion conductive layer ([total of ionic liquid held in the lithium ion conductive layer Volume] / [total volume of voids in the main body of the lithium ion conductive layer] × 100) is preferably 80 to 120% by volume at room temperature. The said ratio is more than the said lower limit, and the precipitation inhibitory effect of metallic lithium in a solid electrolyte becomes higher. The excessive use of an ionic liquid is suppressed because the said ratio is below the said upper limit.
The reason why the ratio can be larger than 100% by volume is that an ionic liquid can be present in the lithium ion conductive layer in addition to the voids of the main body.
In the present specification, “normal temperature” means a temperature that is not particularly cooled or heated, that is, a normal temperature, and includes a temperature of 15 to 25 ° C., for example.

The lithium ion conductive layer may be composed of one layer (single layer), or may be composed of two or more layers. When the lithium ion conductive layer is composed of a plurality of layers, the plurality of layers may be the same as or different from each other, and the combination of these layers is not particularly limited.
In the present specification, not only the lithium ion conductive layer, but “a plurality of layers may be the same or different from each other” means “all layers may be the same or all layers. May be different, or only a part of the layers may be the same, ”and“ a plurality of layers are different from each other ”means that“ at least one of the constituent material and thickness of each layer is the same. Means different.

The thickness of the lithium ion conductive layer is not particularly limited.
The thickness of the lithium ion conductive layer composed of a plurality of layers means the total thickness of all the layers constituting the lithium ion conductive layer.

  However, the thickness of the lithium ion conductive layer is preferably 10 μm or more in that the effect of suppressing the deposition of metallic lithium in the solid electrolyte becomes higher. If the thickness of the lithium ion conductive layer is equal to or more than the lower limit, no metal lithium is precipitated in the lithium ion conductive layer, or even if a small amount of metal lithium is precipitated in the lithium ion conductive layer, The effect does not reach the solid electrolyte. As a result, in the lithium-sulfur solid battery, continuous deposition of metallic lithium between the lithium ion conductive layer and the sulfur positive electrode through the solid electrolyte is suppressed.

On the other hand, the lithium ion conductive layer preferably has a thickness of 100 μm or less from the viewpoint that the thickness of the lithium ion conductive layer does not become excessive (more appropriate).
Usually, as the lithium ion conductive layer becomes thinner, the resistance value in the lithium ion conductive layer decreases, and the energy density of the lithium sulfur solid battery increases.

FIG. 2 is a cross-sectional view schematically showing an example of a main part of another lithium-sulfur solid battery of the present embodiment.
The lithium sulfur solid battery 2 shown here includes a sulfur positive electrode 11, a lithium negative electrode 12, a solid electrolyte 13, and another layer 14. In the lithium-sulfur solid battery 2, the sulfur positive electrode 11, the solid electrolyte 13, the other layer 14, and the lithium negative electrode 12 are laminated in this thickness direction in this order.
In FIG. 2, reference numeral 14 a indicates the first surface of the other layer 14, reference numeral 14 b indicates the second surface of the other layer 14, and reference numeral T ₁₄ indicates the thickness of the other layer 14.
The lithium-sulfur solid battery 2 is the same as the lithium-sulfur solid battery 1 shown in FIG. 1 except that another layer 14 is provided between the solid electrolyte 13 and the lithium anode 12.

The lithium-sulfur solid battery of this embodiment can be distinguished from other lithium-sulfur solid batteries, for example, by observing the cross section of the sulfur positive electrode.
As a sulfur positive electrode, for example, a conductive additive is observed in a cross section of a conductive sheet containing sulfur, a conductive additive, a binder, and, if necessary, an ionic liquid in a void portion of the conductive sheet. Since a carbon-based material is usually used as the conductive assistant as described above, a black component is observed in a wide region in the cross section of the sulfur positive electrode containing the conductive assistant. On the other hand, in the cross section of the sulfur positive electrode of the lithium-sulfur solid battery of the present embodiment, usually no conductive additive is observed.
Moreover, the sulfur positive electrode containing sulfur, a conductive additive, a binder and the like as described above is a dispersion containing these components (the same as the “sulfur dispersion containing undissolved sulfur” described above). It produces using the positive electrode material which is. In that case, as described above, in the cross section of the sulfur positive electrode, it is observed that undissolved sulfur is retained in the voids of the conductive sheet in the form of particles or the like as it is. On the other hand, in the cross section of the sulfur positive electrode of the lithium-sulfur solid battery of the present embodiment, as described above, massive sulfur suppressed the generation of gaps with respect to the surface of the conductive sheet gap. It is observed that it is held in contact with the state.

  The lithium-sulfur solid battery of this embodiment has excellent battery characteristics as described above, and has high safety. The lithium-sulfur solid state battery is suitable for use as, for example, a household power source; an emergency power source;

<< Production Method of Lithium Sulfur Solid Battery >>
The lithium-sulfur solid battery of the present embodiment includes, for example, a step of producing the sulfur positive electrode by impregnating the conductive sheet with molten sulfur or a sulfur solution, and the sulfur positive electrode, solid electrolyte, and lithium negative electrode. In order, it can manufacture by the manufacturing method which has the process of laminating | stacking in these thickness directions.
For example, the lithium-sulfur solid battery of this embodiment can be manufactured by the same method as that of a known lithium-sulfur solid battery, except that the above-described specific process is performed as a process for producing a sulfur positive electrode.

<Step of producing a sulfur positive electrode>
In the step of producing the sulfur positive electrode, as described above, the sulfur positive electrode is produced by impregnating the conductive sheet with molten sulfur or a sulfur solution.
In this step, the method for impregnating the conductive sheet with molten sulfur or a sulfur solution is as described above.

In the case of producing a sulfur positive electrode containing an ionic liquid in the void portion of the conductive sheet, for example, a sulfur positive electrode containing sulfur in the void portion of the conductive sheet (conducting conductive material containing sulfur) by the above-described method. After producing the conductive sheet, the void portion of the conductive sheet in the sulfur positive electrode may be further impregnated with an ionic liquid.
As a sulfur positive electrode, in the case where a conductive sheet containing a component other than sulfur or an ionic liquid is prepared in a void portion of the conductive sheet, at a suitable timing according to the type of the other component, What is necessary is just to further impregnate the space | gap part of an electroconductive sheet with another component.

  After performing the step of producing the sulfur positive electrode, for example, if necessary, any step such as cooling the conductive sheet or processing the obtained product into a desired size or shape is suitable. A sulfur positive electrode is obtained by carrying out at different timings.

<Process for producing other layers>
In the case of manufacturing the lithium-sulfur solid state battery including the other layer according to the present embodiment, the other layer may be manufactured at a timing and method suitable for the type in the manufacturing method described above. .

[Step of producing a gold sputter layer]
The gold sputter layer can be produced by sputtering gold at a target location (usually, the surface on the negative electrode side of the solid electrolyte) by a known method.

[Process for producing lithium ion conductive layer]
The lithium ion conductive layer is prepared, for example, by preparing a first raw material composition containing the constituent material of the main body, an ionic liquid, and a solvent as necessary. It can be formed by applying the first raw material composition and drying it as necessary. This method is a method in which the main body and the lithium ion conductive layer are formed simultaneously. When no solvent is used, it is not necessary to dry the coated first raw material composition.

At the time of preparing the first raw material composition, the temperature and time during the addition and mixing of each raw material are not particularly limited as long as each raw material does not deteriorate.
For example, although the temperature at the time of mixing may be 15-50 degreeC, this is an example.
The method of mixing each raw material is not particularly limited, and is a known method such as a method of mixing by rotating a stirring bar, a stirring bar or a stirring blade; a method of mixing using a mixer; a method of mixing by applying ultrasonic waves, and the like. What is necessary is just to select suitably from the method.

The first raw material composition can be applied to the surface on which the lithium ion conductive layer is to be formed by a known method.
The temperature of the 1st raw material composition to apply is not specifically limited unless the formation object surface of a lithium ion conductive layer, the constituent material of a main-body part, an ionic liquid, a solvent, etc. deteriorate. For example, although the temperature of the 1st raw material composition at this time may be 15-50 degreeC, this is an example.

  When the first raw material composition is dried, the drying can be performed by a known method under normal pressure or reduced pressure. The drying temperature of a 1st raw material composition is not specifically limited, For example, although 20-100 degreeC may be sufficient, this is an example.

When the formation target surface of the lithium ion conductive layer is an arrangement surface of the lithium ion conductive layer in the lithium-sulfur solid battery (for example, the surface on the lithium negative electrode side of the solid electrolyte, the surface on the solid electrolyte side of the lithium negative electrode, etc.) In this case, the formed lithium ion conductive layer does not need to be moved to another location, and may be arranged as it is.
On the other hand, when the formation target surface of the lithium ion conductive layer is not the arrangement surface of the lithium ion conductive layer in the lithium sulfur solid battery, the formed lithium ion conductive layer is peeled off from this surface, and the lithium sulfur solid battery What is necessary is just to move by sticking to the target arrangement surface in the inside.

In addition, the lithium ion conductive layer is, for example, impregnated with ionic liquid in the main body, or prepared a mixed liquid containing an ionic liquid and a solvent, and impregnated with the mixed liquid in the main body. It can be formed by drying the main body after impregnation if necessary. This method uses a pre-formed main body. When no solvent is used, it is not necessary to dry the main body after impregnation.
In this case, the main body portion is not arranged on the arrangement surface of the lithium ion conductive layer in the lithium-sulfur solid battery, but is handled independently, and after the lithium ion conductive layer is formed, the obtained lithium ion It is preferable that the conductive layer is further bonded to a target arrangement surface in the lithium-sulfur solid battery.

The main body can be produced by a known method, for example, by preparing a second raw material composition containing the constituent material of the main body and molding the second raw material composition.
Moreover, a commercial item may be sufficient as the said main-body part.

  As a method for impregnating the main body with the ionic liquid or mixed liquid, for example, a method of coating the main body with the ionic liquid or mixed liquid, or immersing the main body in the ionic liquid or mixed liquid Methods and the like.

The ionic liquid or mixed liquid can be applied to the main body by a known method.
The temperature of the ionic liquid or mixed liquid impregnated in the main body is not particularly limited as long as the raw materials such as the main body, ionic liquid, and solvent are not deteriorated. For example, the temperature of the ionic liquid or mixed liquid at the time of impregnation may be 15 to 50 ° C., but this is an example.

  Drying of the main body after impregnation with the mixed liquid can be performed by a known method under normal pressure or reduced pressure. The drying temperature at this time is not specifically limited, For example, 20-100 degreeC may be sufficient, but this is an example.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples.

[Example 1]
<Manufacture of lithium-sulfur solid battery>
(Manufacture of sulfur positive electrode)
Powdered sulfur was placed on one surface of a carbon cloth (circular shape having a mass of 7 mg, a diameter of 10 mm, and a thickness of 1000 μm), and the sulfur in this state was heated together with the carbon cloth. The temperature of sulfur at this time was finally set to 120 ° C. or higher. At this time, sulfur gradually impregnated into the conductive sheet as the temperature increased, and became invisible on the carbon cloth when the heating temperature was 120 ° C. The heating temperature was finally 150 ° C. or higher.

Next, the sulfur-impregnated carbon cloth was cooled to solidify the sulfur.
In the carbon cloth after the impregnation and cooling, the sulfur content was 21.7 mg / cm ² .

  Using the scanning electron microscope (SEM), the obtained carbon cloth after impregnation and cooling was observed at a magnification of 300 times. The imaging data acquired at this time is shown in FIG. Further, the carbon cloth before impregnation with sulfur used at this time was similarly observed using SEM. The imaging data acquired at this time is shown in FIG.

As shown in FIG. 4, in the imaging data of the carbon cloth, the fibers constituting the carbon cloth were clearly observed one by one, and it was clearly confirmed that no contained component was present in the voids of the carbon cloth.
On the other hand, as shown in FIG. 3, in the imaging data of the carbon cloth after the impregnation and cooling, fibers constituting the carbon cloth could not be observed except for a partial region on the SEM side. Thus, in the carbon cloth after the impregnation and cooling, sulfur was filled in the gaps of the carbon cloth with almost no gap. In other words, sulfur is agglomerated in the voids of the carbon cloth, and is held in contact with the surface of the voids in a state where the generation of gaps is suppressed.

Next, the carbon cloth after the impregnation and cooling was further impregnated with a tetraglyme-LiTFSI complex (150 mg).
Thus, a sulfur positive electrode was obtained.
In the obtained sulfur positive electrode, the ratio of the content of the ionic liquid to the total content of sulfur and the ionic liquid was 90% by mass.
Moreover, the sulfur content of the obtained sulfur positive electrode was 21.7 mg / cm ^{2 as} described above.

(Manufacture of solid electrolyte)
Lanthanum hydroxide (purity 99.99%, manufactured by High Purity Chemical Laboratory) (40.38 g), lithium hydroxide (purity 98.0%, manufactured by Kanto Chemical Co.) (20.44 g) and zirconium oxide (Tosoh Corporation) (17.47 g) were weighed and mixed while being pulverized with a ball mill for 2 hours. The obtained powder (73.10 g) was weighed, transferred to a firing ceramic container, fired at 900 ° C. for 15 hours using an electric furnace, cooled at a temperature drop rate of 5 ° C./min, and finally at room temperature. To obtain a lithium-lanthanum-zirconium composite oxide.
The obtained composite oxide (54.67 g) and aluminum oxide (γ-alumina, purity 99.99%, manufactured by Kojundo Chemical Laboratory Co., Ltd.) (0.90 g) were weighed and pulverized with a ball mill for 2 hours. While mixing. The resulting mixture was molded using a biaxial press to produce disk-shaped pellets having a diameter of 18 mm and a thickness of 1.5 mm.
Transfer the pellets (0.5 g) obtained above to a firing ceramic container with mother powder (mixed powder of lanthanum hydroxide, lithium hydroxide, zirconium oxide and aluminum oxide), and cover the pellets with mother powder. And firing using an electric furnace. The firing conditions are as follows. That is, the temperature was raised from room temperature to 1200 ° C. at a temperature rising rate of 5 ° C./min, maintained at 1200 ° C. for 24 hours as it was, cooled from here at a temperature lowering rate of 5 ° C./min, and finally cooled to room temperature. Next, the mother powder adhered to the pellets was removed by polishing.
As described above, as a solid electrolyte, a pellet-shaped aluminum-doped lithium-lanthanum-zirconium composite oxide (Al-doped LLZ) compact (Li _6.25 Al _0.25 La ₃ Zr ₂ O ₁₂ , diameter 15 mm, A thickness of 1.0 mm) was obtained.

(Gold sputter layer formation)
A circular polyimide tape (thickness: 0.09 mm, diameter: 18 mm) was concentrically cut into a circle having a diameter of 10 mm to form a ring-shaped masking tape.
Subsequently, this masking tape was affixed on the surface used as the negative electrode side of the Al dope LLZ molded object obtained above.
Next, a gold sputter layer was formed by sputtering gold on the exposed surface on the negative electrode side (the region on the negative electrode side that was not masked with the masking tape). After forming the gold sputter layer, the masking tape was peeled off from the Al-doped LLZ compact.

(Manufacture of lithium-sulfur solid state batteries)
Using a stainless steel electrochemical test battery cell container, the sulfur positive electrode obtained above was placed in this container, and an Al-doped LLZ compact was placed on the sulfur positive electrode on the positive electrode surface. Was placed facing the sulfur positive electrode side.
Next, a lithium foil (diameter 10 mm, thickness 600 μm) as a negative electrode was placed on and adhered to the gold sputter layer provided on the Al-doped LLZ molded body.
Next, a stainless steel foil (diameter: 15 mm, thickness: 500 μm) was placed on the negative electrode as a negative electrode current collector.
Next, a stainless steel washer was placed on the negative electrode current collector, and finally the upper lid was closed.
Thus, a battery cell (lithium sulfur solid battery) having a configuration in which the negative electrode, the gold sputter layer, the solid electrolyte, and the sulfur positive electrode were laminated in this order was obtained.

<Evaluation of lithium-sulfur solid battery>
The battery cell obtained above was subjected to a constant current charge / discharge test under the conditions of a cut-off potential of 1 to 3.5 V, a current value of 200 μA / cm ² , and a temperature of 120 ° C. The discharge curve (measurement result) obtained at this time is shown in FIG.
From FIG. 5, it was confirmed that the battery cell of a present Example has a favorable battery characteristic.

[Reference Example 1]
<Manufacture of lithium-sulfur solid battery>
(Manufacture of solid electrolyte)
Lanthanum hydroxide (purity 99.99%, manufactured by Shin-Etsu Chemical Co., Ltd.) (33.9 g) and zirconium oxide (manufactured by Tosoh Corporation) (14.7 g) were weighed and mixed while being pulverized with a ball mill for 1 hour. The obtained powder (0.26 g) is weighed, put into a mold die, and the resulting mixture is molded using a uniaxial press machine, whereby a disk-shaped pellet having a diameter of 13 mm and a thickness of 1 mm. Was made.
Next, this disk-shaped pellet was transferred to a firing ceramic container, fired at 1500 ° C. for 36 hours using an electric furnace, and then cooled to room temperature by natural cooling to form a lanthanum-zirconium composite oxide. Got the body.
Separately, lithium hydroxide (purity 98.0%, manufactured by Kanto Chemical Co., Inc.) (2.8 g) was dissolved in water (30 mL), the obtained aqueous solution (1 mL) was weighed, and the lanthanum-zirconium obtained above It added to the ceramic container for baking containing the molded object of complex oxide.
Next, the fired ceramic container after the addition is transferred to a microwave firing furnace, irradiated with microwaves and fired at a furnace internal temperature of 400 ° C. for 36 hours, and a lithium-lanthanum-zirconium composite oxide (LLZ) compact ( 12 mm in diameter, 0.51 mm in thickness, and 0.2647 g in mass).

  Using the obtained LLZ compact, gold was sputtered on the surface on the negative electrode side.

(Manufacture of positive electrode material)
Sulfur (1.8 g) and acetylene black (specific surface area ^68m 2 / g, DBP oil absorption 170cm ³ / 100g, manufactured by Denka Co., Ltd.) was weighed in an agate mortar (0.2 g), was mixed and ground 15 minutes while , N-methylpyrrolidone was added little by little and mixed to prepare a positive electrode material as a viscous slurry.

(Manufacture of sulfur positive electrode)
A circular polyimide tape (thickness: 0.09 mm, diameter: 12 mm) was concentrically cut into a circle with a diameter of 8 mm to obtain a masking tape.
Subsequently, this masking tape was affixed on the surface which becomes the positive electrode side of the LLZ compact | molding | casting in which the gold | metal sputter layer was formed.
Next, the positive electrode material obtained above was adhered to the central portion of the exposed surface on the positive electrode side (the region on the positive electrode side that was not masked with the masking tape). Then, by reciprocating the slide glass a few times so that the positive electrode material is scraped off at the end face of the slide glass, the positive electrode material is spread and applied so as to spread evenly over the entire exposed surface. .
Then, using a vacuum dryer, the coated LLZ compact was dried at 80 ° C. overnight to remove all N-methylpyrrolidone, whereby a sulfur positive electrode (thickness of about 0.09 mm) was formed on the LLZ compact. , 8 mm in diameter).
Subsequently, the masking tape was peeled off from the LLZ molded body to obtain a laminate (0.2673 g) in which a sulfur positive electrode, a solid electrolyte, and a gold sputter layer were laminated in this order. From the mass of this laminate, the mass of the sulfur positive electrode formed was 0.0026 g, the mass of sulfur in the sulfur positive electrode was 2.34 mg, and the sulfur content of the sulfur positive electrode was 4.7 mg / cm ^2. It was.

(Manufacture of lithium-sulfur solid state batteries)
Using a commercially available battery cell container for electrochemical test made of stainless steel, a copper foil (diameter 23 mm, thickness 20 μm) is placed as a current collector in this container, and a lithium foil as a negative electrode is placed on the copper foil. (Diameter 8 mm, thickness 600 μm) was placed.
Next, after superposing the gold sputtered layer of the laminate obtained above on this negative electrode, the lithium foil was brought into close contact with the gold sputtered layer by heating at 120 ° C. The solid electrolyte and the sulfur positive electrode were laminated in this order.
Next, a stainless steel foil (diameter 8 mm, thickness 20 μm) was placed on the sulfur positive electrode as a positive electrode current collector, and finally the upper lid was closed to obtain a battery cell (lithium sulfur solid battery).

<Evaluation of lithium-sulfur solid battery>
The battery cell obtained above was stored at 105 ° C. for 12 hours.
Subsequently, the battery cell after storage was subjected to a constant current charge / discharge test at a temperature of 60 ° C. The discharge curve (measurement result) obtained at this time is shown in FIG.

From FIG. 6, it was confirmed that the battery cell of Reference Example 1 has good battery characteristics.
However, when the sulfur positive electrode of Example 1 was compared with the sulfur positive electrode of Reference Example 1, the sulfur positive electrode of Example 1 had a higher sulfur content. As is clear from FIGS. 5 to 6, the sulfur positive electrode of Example 1 showed a higher capacity.

  The present invention can be used in the general field of lithium-sulfur solid state batteries.

  1, 2 ... lithium-sulfur solid battery, 11 ... sulfur positive electrode, 12 ... lithium negative electrode, 13 ... solid electrolyte, 14 ... other layers

Claims (5)

A sulfur positive electrode, a lithium negative electrode, and a solid electrolyte,
The solid electrolyte is disposed between the sulfur positive electrode and the lithium negative electrode,
The sulfur positive electrode has a conductive sheet having a large number of voids, the voids open to the outside of the conductive sheet, the sulfur positive electrode contains sulfur in the voids,
The content of sulfur of the sulfur positive electrode, Ri 6 mg / cm ² or more der,
The sulfur positive electrode further contains an ionic liquid in the gap of the conductive sheet,
In the sulfur positive electrode, the ratio of the content of the ionic liquid to the total content of the sulfur and the ionic liquid ([content of the ionic liquid of the sulfur positive electrode (part by mass)] / [of sulfur and ionic liquid of the sulfur positive electrode Lithium sulfur solid battery whose total content (parts by mass)] × 100) is 5 to 95% by mass . In the sulfur positive electrode, the ratio of the total content of the sulfur and the ionic liquid to the total content of components other than the conductive sheet ([total content of sulfur and ionic liquid in the sulfur positive electrode (parts by mass)] / [ 2. The lithium-sulfur solid state battery according to claim 1, wherein the total content (parts by mass)] × 100) of components other than the conductive sheet in the sulfur positive electrode is 90% by mass or more .   The lithium sulfur solid battery according to claim 2, wherein the ionic liquid is a solvated ionic liquid composed of a glyme-lithium salt complex.   The lithium sulfur solid battery according to any one of claims 1 to 3, wherein the constituent material of the solid electrolyte is an oxide-based material.   The lithium sulfur solid battery according to any one of claims 1 to 4, wherein an operating temperature of the lithium sulfur solid battery is 110 to 160 ° C.