JP2019121455A - Solid battery - Google Patents

Abstract

To provide a solid battery including an active material layer having good ion conductivity.SOLUTION: A solid battery 10 comprises: a positive electrode active material layer 1; a negative electrode active material layer 2; and a solid electrolyte layer 3 disposed between the positive electrode active material layer 1 and the negative electrode active material layer 2. In the solid battery 10, at least one of the positive electrode active material layer 1 and the negative electrode active material layer 2 contains: an active material; a sulfide solid electrolyte containing Li, P and S elements; and a solvation ionic liquid containing a Li salt and a Lewis base. The mole ratio of the Li salt to the Lewis base is 0.8 or more and 1.5 or less. The percentage of the solvation ionic liquid to the sulfide solid electrolyte is 0.5 vol.% or more and 20 vol.% or less.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to solid state batteries.

  A solid battery is a battery having a solid electrolyte layer between a positive electrode active material layer and a negative electrode active material layer, and the safety device is simplified compared to a liquid battery having an electrolytic solution containing a flammable organic solvent. It has the advantage of being easy.

  For example, Patent Document 1 discloses that two types of solid electrolyte particles having different particle sizes are added to each of a solid electrolyte layer, a positive electrode active material layer, and a negative electrode active material layer. Patent Document 2 discloses a positive electrode material for a lithium-sulfur solid battery, which contains sulfur, a conductive material, a binder, and an ionic liquid or a solvated ionic liquid.

  In addition, Patent Document 3 includes a polymer containing lithium salt or an ionic liquid, and includes an intervening layer interposed between the bonding portion of the positive electrode member and the negative electrode member, and the negative electrode active material contains a specific negative electrode active material. A non-aqueous electrolyte battery is disclosed.

JP, 2013-157084, A JP, 2017-168435, A Japanese Patent Application Publication No. 2012-014892

  The active material layer used in the solid battery often contains a solid electrolyte in addition to the active material in order to secure an ion conduction path. Further, among solid electrolytes, a sulfide solid electrolyte is a relatively soft material, and plastic deformation is easily caused by pressing.

  For example, when only a sulfide solid electrolyte is pressed to form a solid electrolyte layer, the sulfide solid electrolyte is plastically deformed, and a solid electrolyte layer with few voids can be obtained. On the other hand, when the active material and the sulfide solid electrolyte are pressed to form the active material layer, the sulfide solid electrolyte is plastically deformed and disposed so as to surround a hard active material, but, for example, the active material is densely packed There is a tendency for voids to occur in the As a result, the ion conduction path is reduced, and the ion conductivity of the active material layer is reduced.

  This indication is made in view of the above-mentioned situation, and makes it a main purpose to provide a solid battery provided with an active material layer which has good ion conductivity.

  In order to solve the above problems, in the present disclosure, a solid battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. And at least one of the positive electrode active material layer and the negative electrode active material layer is a solvation containing an active material, a sulfide solid electrolyte containing Li element, P element and S element, an Li salt and a Lewis base An ionic liquid, and the molar ratio of the Li salt to the Lewis base is 0.8 or more and 1.5 or less, and the ratio of the solvated ionic liquid to the sulfide solid electrolyte is 0.5 Provided is a solid battery having a volume percent or more and 20 volume percent or less.

  According to the present disclosure, since the active material layer contains a specific amount of a solvated ionic liquid having a specific Li salt concentration, the solid battery can be provided with an active material layer having good ion conductivity.

  The present disclosure has the effect of being able to provide a solid state battery provided with an active material layer having good ion conductivity.

FIG. 1 is a schematic cross-sectional view illustrating a solid state battery of the present disclosure. It is a SEM image of a positive electrode active material layer and a solid electrolyte layer. It is a result of the ion conductivity measurement with respect to the active material layer obtained in Examples 1-5 and Comparative Examples 1-3. It is the result of the ion conductivity measurement with respect to the active material layer obtained in Examples 4 and 6 and Comparative Examples 1 and 4.

  Hereinafter, the solid battery of the present disclosure will be described in detail.

  FIG. 1 is a schematic cross-sectional view showing an example of the solid state battery of the present disclosure. The solid battery 10 shown in FIG. 1 comprises a positive electrode active material layer 1, a negative electrode active material layer 2, a solid electrolyte layer 3 disposed between the positive electrode active material layer 1 and the negative electrode active material layer 2, and a positive electrode active material layer. A positive electrode current collector 4 for collecting current 1 and a negative electrode current collector 5 for collecting current of the negative electrode active material layer 2 are provided. At least one of the positive electrode active material layer 1 and the negative electrode active material layer 2 includes an active material, a sulfide solid electrolyte containing Li, P and S elements, and a solvated ionic liquid containing a Li salt and a Lewis base. contains. The molar ratio of Li salt to Lewis base and the ratio of solvated ionic liquid to sulfide solid electrolyte are within the specified range.

  According to the present disclosure, since the active material layer contains a specific amount of a solvated ionic liquid having a specific Li salt concentration, the solid battery can be provided with an active material layer having good ion conductivity. As described above, when the active material and the sulfide solid electrolyte are pressed to form the active material layer, the sulfide solid electrolyte is plastically deformed and disposed so as to surround a hard active material, but, for example, the active material is densely packed There is a tendency for voids to occur in the As a result, the ion conduction path is reduced, and the ion conductivity as the active material layer is reduced.

On the other hand, in the present disclosure, the void of the active material layer can be filled with the solvated ionic liquid by using a specific amount of a solvated ionic liquid having a particular Li salt concentration. As a result, an active material layer having good ion conductivity can be obtained. In addition, since general ionic liquids and electrolytes easily react with the sulfide solid electrolyte, ion conduction in the active material layer may be inhibited. On the other hand, the solvated ionic liquid has an advantage that it does not react with the sulfide solid electrolyte and the ion conduction in the active material layer is less likely to be inhibited because the chemical stability is very high.
Hereinafter, the solid battery of the present disclosure will be described for each configuration.

1. Positive Electrode Active Material Layer The positive electrode active material layer is a layer containing at least a positive electrode active material. The positive electrode active material layer preferably contains a positive electrode active material, a sulfide solid electrolyte containing Li element, P element and S element, and a solvated ionic liquid containing Li salt and Lewis base.

(1) Positive Electrode Active Material The positive electrode active material is not particularly limited, but typically an oxide active material can be mentioned. As the oxide active material, for example, a rock salt layered type active material such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ , Li ( Examples include spinel-type active materials such as Ni _0.5 Mn _1.5 ) O ₄ , and olivine-type active materials such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , and LiCuPO ₄ .

The surface of the positive electrode active material may be coated with a coat layer. The coat layer can suppress the reaction between the positive electrode active material and the solid electrolyte (in particular, a sulfide solid electrolyte). The coating layer, for _{example, LiNbO 3, Li 3 PO 4} , Li -containing oxides such as LiPON like. The average thickness of the coat layer is, for example, 1 nm or more. On the other hand, the average thickness of the coating layer is, for example, 20 nm or less, and may be 10 nm or less.

Examples of the shape of the positive electrode active material include particulates. The average particle size (D ₅₀ ) of the positive electrode active material is, for example, 0.1 μm or more and 50 μm or less. In addition, an average particle diameter can be calculated from the measurement by a laser diffraction type particle size distribution analyzer, a scanning electron microscope (SEM), for example.

  The proportion of the positive electrode active material contained in the positive electrode active material layer is, for example, 40% by weight or more, and may be 50% by weight or more, or 60% by weight or more. On the other hand, the proportion of the positive electrode active material contained in the positive electrode active material layer is, for example, 95% by weight or less.

(2) Sulfide Solid Electrolyte The positive electrode active material layer preferably contains a sulfide solid electrolyte. The sulfide solid electrolyte preferably contains Li element, P element and S element. The sulfide solid electrolyte may further contain at least one of Cl element, Br element and I element. The sulfide solid electrolyte may further contain at least one of Ge element, Si element and Sn element. The sulfide solid electrolyte may further contain an O element.

The sulfide solid electrolyte may contain an ion conductor containing Li element, P element and S element. The ion conductor preferably contains PS ₄ ^3- as a main component of the anion structure. The phrase "having PS ₄ ^3- as the main component of the anion structure" means that the proportion of PS ₄ ^3- is the largest among all the anion structures in the ion conductor. The proportion of PS ₄ ^3- in the total anion structure is, for example, 60 mol% or more, and may be 70 mol% or more, 80 mol% or more, or 90 mol% or more. The proportion of PS ₄ ^3- can be determined by, for example, Raman spectroscopy, NMR, or XPS. In addition, a part of the S element of the ion conductor may be replaced by the O element.

When the sulfide solid electrolyte contains the above ion conductor, it may further contain LiX. Examples of LiX include LiCl, LiBr and LiI. Further, at least a part of LiX is preferably present in a state of being incorporated into the structure of the ion conductor as a LiX component. The proportion of LiX in the sulfide solid electrolyte is, for example, 1 mol% or more, and may be 10 mol% or more. On the other hand, the ratio of LiX is, for example, 50 mol% or less, and may be 35 mol% or less. The sulfide solid electrolyte has a composition represented by xLiX · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ) (x satisfies 0 ≦ x ≦ 50) Good.

The sulfide solid electrolyte may have PS ₄ ³⁻ and at least one of GeS ₄ ⁴⁻ , SiS ₄ ⁴⁻ , and SnS ₄ ⁴⁻ as an anion structure.

  The sulfide solid electrolyte may be amorphous or crystalline. An example of the former is a sulfide glass, and an example of the latter is a crystallized sulfide glass (glass ceramic). The sulfide solid electrolyte may also have a so-called LGPS type crystal phase.

The shape of the sulfide solid electrolyte may, for example, be in the form of particles. The average particle size (D ₅₀ ) of the sulfide solid electrolyte is, for example, 5 μm or more, and may be 10 μm or more. On the other hand, the average particle diameter (D ₅₀ ) of the sulfide solid electrolyte is, for example, 200 μm or less, and may be 100 μm or less. The average particle size can be calculated, for example, by measurement with a laser diffraction particle size distribution analyzer. The sulfide solid electrolyte preferably has high ion conductivity, and the ion conductivity at 25 ° C. is, for example, 1 × 10 ⁻⁴ S / cm or more, and 1 × 10 ⁻³ S / cm or more. It is also good.

  The proportion of the sulfide solid electrolyte contained in the positive electrode active material layer is, for example, 10% by weight or more, and may be 20% by weight or more, or 40% by weight or more. On the other hand, the proportion of the sulfide solid electrolyte contained in the positive electrode active material layer is, for example, 60% by weight or less. Moreover, the ratio of the sum total of the positive electrode active material and the sulfide solid electrolyte contained in the positive electrode active material layer is, for example, 80% by weight or more, and may be 90% by weight or more.

(3) Solvated ionic liquid The positive electrode active material layer preferably contains a solvated ionic liquid containing a Li salt and a Lewis base. In a solvated ionic liquid containing a Li salt and a Lewis base, the Lewis base coordinates (solvates) with the Li ion of the Li salt to form a complex cation, and the anion of the Li salt becomes an anion of the solvated ionic liquid. The melting point of the solvated ionic liquid may be 80 ° C. or less, or 60 ° C. or less. On the other hand, the melting point of the solvated ionic liquid is, for example, 0 ° C. or more. In particular, the solvated ionic liquid is preferably liquid at 25 ° C. The complex cation preferably has Li ions and a Lewis base, for example, in a molar ratio of Li ion: Lewis base = 1: 1.

  The Li salt preferably contains one Li ion in one molecule. Further, as the anion of Li salt, for example, imide anions represented by bis (fluoromethanesulfonyl) imide (FSI) anion, bis (trifluoromethanesulfonyl) imide (TFSI) anion, etc., hexafluorophosphate anion, tris (pentapentamer) Examples include phosphate anions represented by fluoroethyl) trifluorophosphate anion and the like, tetrafluoroborate (TFB) anion and triflate anion.

  The Lewis base includes, for example, glyme. As glyme, for example, diethylene glycol diethyl ether (G2, diglyme), triethylene glycol dimethyl ether (G3, triglyme), tetraethylene glycol dimethyl ether (G4, tetraglyme), diethylene glycol dibutyl ether, diethylene glycol methyl ethyl ether, triethylene glycol methyl ethyl Ether, triethylene glycol butyl methyl ether may be mentioned.

  The molar ratio of Li salt to Lewis base is, for example, 0.8 or more, and may be 1 or more. On the other hand, the molar ratio of Li salt to Lewis base is, for example, 1.5 or less, and may be 1.25 or less.

  The ratio of the solvated ionic liquid to the sulfide solid electrolyte is, for example, 0.5% by volume or more, and may be 1% by volume or more, or 5% by volume or more. On the other hand, the ratio of the solvated ionic liquid to the sulfide solid electrolyte is, for example, 20% by volume or less, and may be 15% by volume or less, or 10% by volume or less.

  The proportion of the solvated ionic liquid contained in the positive electrode active material layer is, for example, less than 10% by weight, and may be 9% by weight or less, 8% by weight or less, or 6% by weight or less It is also good.

(4) Positive Electrode Active Material The positive electrode active material layer may further contain a conductive material. The addition of the conductive material can improve the electron conductivity of the positive electrode active material layer. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. The positive electrode active material layer may further contain a binder. Examples of the binder include fluorine-containing binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), rubber binders such as butadiene rubber, and acrylic binders.

  The thickness of the positive electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less. Examples of the method of forming the positive electrode active material layer include a method of coating and drying a slurry containing at least a positive electrode active material, a sulfide solid electrolyte, a solvated ionic liquid, and a dispersion medium.

2. Anode Active Material Layer The anode active material layer is a layer containing at least an anode active material. The negative electrode active material layer preferably contains a negative electrode active material, a sulfide solid electrolyte containing Li element, P element and S element, and a solvated ionic liquid containing Li salt and Lewis base.

Although a negative electrode active material is not specifically limited, For example, a carbon active material, a metal active material, and an oxide active material are mentioned. Examples of the carbon active material include graphite, hard carbon and soft carbon. On the other hand, examples of the metal active material include simple substances such as Li, In, Al, Si, and Sn, and alloys containing at least one of these elements. As oxide active material, for _example, Li 4 TiO _5.

Examples of the shape of the negative electrode active material include particles. The average particle size (D ₅₀ ) of the negative electrode active material is, for example, 0.1 μm or more and 50 μm or less. In addition, an average particle diameter can be calculated from the measurement by a laser diffraction type particle size distribution analyzer, a scanning electron microscope (SEM), for example. The proportion of the negative electrode active material contained in the negative electrode active material layer is, for example, 40% by weight or more, and may be 50% by weight or more, or 60% by weight or more. On the other hand, the proportion of the negative electrode active material contained in the negative electrode active material layer is, for example, 95% by weight or less.

  The matters relating to the sulfide solid electrolyte and the solvated ionic liquid are the same as the contents described in the above “1. Positive electrode active material layer”, and thus the description thereof is omitted here. In addition, the ratio of the sulfide solid electrolyte contained in the negative electrode active material layer, the ratio of the solvated ionic liquid contained in the negative electrode active material layer, the ratio of the total of the negative electrode active material contained in the negative electrode active material layer and the sulfide solid electrolyte, etc. The preferable range relating to is the same as the preferable range in the positive electrode active material layer described above, and thus the description thereof is omitted here. Furthermore, although the negative electrode active material layer may contain at least one of a conductive material and a binder, the matters regarding these are also the same as the contents described above.

  The thickness of the negative electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less. Examples of the method of forming the negative electrode active material layer include a method of coating and drying a slurry containing at least a negative electrode active material, a sulfide solid electrolyte, a solvated ionic liquid, and a dispersion medium.

3. Solid Electrolyte Layer The solid electrolyte layer is a layer disposed between the positive electrode active material layer and the negative electrode active material layer. The solid electrolyte layer contains at least a solid electrolyte and may optionally contain a binder. The solid electrolyte layer preferably contains a sulfide solid electrolyte. The sulfide solid electrolyte and the binder are the same as the contents described in the above “1. Positive electrode active material layer”, and thus the description thereof is omitted here.

  The thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less. As a method of forming a solid electrolyte layer, for example, a method of compression molding a solid electrolyte may be mentioned.

4. Other Components The solid battery of the present disclosure at least includes the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer described above. Furthermore, usually, it has a positive electrode current collector for collecting current in the positive electrode active material layer, and a negative electrode current collector for collecting current in the negative electrode active material layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium and carbon. On the other hand, examples of the material of the negative electrode current collector include SUS, copper, nickel and carbon. The thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably selected appropriately in accordance with the application of the battery. Moreover, the battery case of a general battery can be used for the battery case used for this indication, for example, the battery case made from SUS is mentioned.

5. Solid-State Battery The solid-state battery of the present disclosure is usually a lithium battery. In addition, the solid battery of the present disclosure may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because the battery can be repeatedly charged and discharged, and it is useful as, for example, an on-vehicle battery. Further, the solid battery of the present disclosure may be a single layer battery or a laminated battery. The laminated battery may be a monopolar laminated battery (parallel connected laminated battery) or a bipolar laminated battery (series connected laminated battery). Examples of the shape of the solid battery include coin type, laminate type, cylindrical type and square type.

  The present disclosure is not limited to the above embodiment. The above-described embodiment is an exemplification, which has substantially the same configuration as the technical idea described in the claims of the present disclosure, and exhibits the same operation and effect as the present invention. It is included in the technical scope of the disclosure.

  Hereinafter, the present disclosure will be more specifically described.

Example 1
(Synthesis of sulfide solid electrolyte)
Li ₂ S (Furuuchi Chemical Co., Ltd.), P ₂ S ₅ (Aldrich Co.) and LiI (Nichiho Chemical Co., Ltd.) have a molar ratio of 30 LiI · 70 (0.75 Li ₂ S · 0.25 P ₂ S ₅ ) And mixed for 5 minutes in an agate mortar. Dehydrated heptane (manufactured by Kanto Chemical Industry Co., Ltd.) was added to the obtained mixture, and mechanical milling was performed for 40 hours using a planetary ball mill. Thereafter, heptane was removed by drying to obtain a sulfide solid electrolyte.

(Preparation of ionic liquid)
An Li liquid (lithium bis (trifluoromethanesulfonyl) imide, LiTFSI) was mixed in a proportion of 1.5 mol with 1 mol of tetraglyme (manufactured by Kishda Chemical Co., Ltd.) to obtain an ionic liquid (solvated ionic liquid).

(Preparation of negative electrode slurry)
It contains 1.0 g of negative electrode active material (silicon, high purity chemical), 0.04 g of conductive material (VGCF, manufactured by Showa Denko), a sulfide solid electrolyte and an ionic liquid (solvated ionic liquid), and is used for the sulfide solid electrolyte 0.776 g of a composition (referred to as composition A) in which the ionic liquid (solvated ionic liquid) is 10% by volume, 0.02 g of a binder (PVDF, manufactured by Kreha), and a dispersion medium (butyl butyrate, manufactured by Nacalai Tesque) 2. 4 g was weighed and treated with an ultrasonic homogenizer (UH-50 manufactured by SMT) to obtain a negative electrode slurry.

(Preparation of ion conductivity measurement cell)
0.065 g of a sulfide solid electrolyte was added to a 1 cm ² ceramic mold and pressed at 1 ton / cm ² to form a first solid electrolyte layer. On the obtained first solid electrolyte layer, 0.020 g of negative electrode slurry was applied and dried at 100 ° C. for 30 minutes. Then, it pressed by 1 ton / cm < ² > and formed the negative electrode active material layer. On the obtained negative electrode active material layer, 0.065 g of a sulfide solid electrolyte was added, and pressed at 1 ton / cm ² to form a second solid electrolyte layer. Thereby, the ion conductivity measurement cell which has a 1st solid electrolyte layer, a negative electrode active material layer, and a 2nd solid electrolyte layer in this order was obtained.

In addition, a blank cell was produced. 0.065 g of a sulfide solid electrolyte was added to a 1 cm ² ceramic mold and pressed at 1 ton / cm ² to form a first solid electrolyte layer. On the obtained first solid electrolyte layer, 0.065 g of a sulfide solid electrolyte was added, and pressed at 1 ton / cm ² to form a second solid electrolyte layer. Thus, a blank cell having no negative electrode active material layer was obtained.

[Examples 2 to 5]
An ion conductivity measurement cell was obtained in the same manner as in Example 1 except that LiTFSI was mixed at a ratio of 1.25 mol, 1.15 mol, 1 mol, and 0.8 mol with 1 mol of tetraglyme, respectively.

[Examples 6 to 9]
The same as Example 4 except that the proportion of the ionic liquid contained in the composition A was changed to 0.5% by volume, 1% by volume, 5% by volume and 20% by volume, respectively, with respect to the sulfide solid electrolyte. The ion conductivity measuring cell was obtained.

[Example 10]
An ion conductivity measuring cell was obtained in the same manner as in Example 4 except that triglyme was used instead of tetraglyme.

Comparative Example 1
An ion conductivity measuring cell was obtained in the same manner as in Example 1 except that the proportion of the ionic liquid contained in the composition A was changed to 0.

[Comparative Examples 2 and 3]
An ion conductivity measurement cell was obtained in the same manner as in Example 1 except that LiTFSI was mixed at a ratio of 2 mol and 0.6 mol to 1 mol of tetraglyme, respectively.

Comparative Example 4
An ion conductivity measuring cell was obtained in the same manner as in Example 4 except that the proportion of the ionic liquid contained in the composition A was changed to 33% by volume relative to the sulfide solid electrolyte.

Comparative Example 5
Example 1 using 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (EMITFSI) instead of tetraglyme, and mixing LiTFSI at a ratio of 0.2 mol to 1 mol of EMITFSI, Example 1 An ion conductivity measuring cell was obtained in the same manner as in.

Comparative Example 6
An ion conductivity measurement cell was obtained in the same manner as in Example 1 except that dimethyl carbonate (DMC) was used instead of tetraglyme, and LiTFSI was mixed at a ratio of 0.1 mol to 1 mol of DMC.

[Example 11]
A positive electrode active material (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , manufactured by Nichia Corporation) was prepared, and a coat layer (LiNbO ₃ layer) was formed on the surface. 1.5 g of a positive electrode active material having a coating layer, 0.023 g of a conductive material (VGCF, manufactured by Showa Denko), a sulfide solid electrolyte and an ionic liquid (solvated ionic liquid), and an ionic liquid to a sulfide solid electrolyte (solvent 0.239 g of a composition (referred to as composition B) in which the mixed ionic liquid is 10% by volume, 0.011 g of a binder (PVDF, made by Kureha), and 0.8 g of a dispersion medium (butyl butyrate, made by Nacalai Tesque) are weighed The mixture was treated with an ultrasonic homogenizer (UH-50 manufactured by SMT) to obtain a positive electrode slurry. An ion conductivity measurement cell was obtained in the same manner as in Example 4 except that the obtained positive electrode slurry was used instead of the negative electrode slurry.

Comparative Example 7
An ion conductivity measuring cell was obtained in the same manner as in Example 11 except that the proportion of the ionic liquid contained in the composition B was changed to 0.

[Evaluation]
(SEM observation)
With respect to the positive electrode active material layer (after pressing) obtained in Comparative Example 7, cross-sectional observation was performed using a scanning electron microscope (SEM). The results are shown in FIG. 2 (a). As shown in FIG. 2A, when the active material and the sulfide solid electrolyte were pressed to form an active material layer, it was confirmed that a void is generated. As shown in FIG. 2 (b), when only the sulfide solid electrolyte was pressed, almost no voids were generated.

(Ion conductivity measurement)
With respect to the ion conductivity measuring cells obtained in Examples 1 to 11 and Comparative Examples 1 to 7, ion conductivity was measured by an alternating current impedance method. For measurement, impedance measurement was performed using Solartron (manufactured by Toyo, Inc.) under conditions of an applied voltage of 10 mV, a measurement frequency range of 0.1 to 1 MHz, and 25 ° C. The resistance value of the active material layer was determined using the obtained resistance value and the resistance value of the blank cell. Furthermore, the ion conductivity of the active material layer was calculated based on the resistance value of the active material layer and the thickness of the active material layer. The results are shown in Table 1, FIG. 3 and FIG.

  As shown in Table 1 and FIG. 3, in Examples 1 to 5, the ion conductivity was higher than in Comparative Examples 1 to 3. The reason why the ion conductivity of Comparative Examples 2 and 3 is lower than that of Comparative Example 1 is presumed to be due to the low ion conductivity of the ionic liquid itself. Thus, it was confirmed that the molar ratio of Li salt to Lewis base of 0.8 or more and 1.5 or less contributes to the improvement of the ion conductivity of the active material layer.

  Moreover, as shown in Table 1 and FIG. 4, the ion conductivity of Examples 4 and 6 to 9 was higher than that of Comparative Examples 1 and 4. When the ratio of the ionic liquid to the sulfide solid electrolyte is too large, the ionic liquid is excessive, and it is presumed that the ion conductivity of the active material layer is lowered by the relative decrease of the ratio of the sulfide solid electrolyte. Thus, it has been confirmed that the ratio of the solvated ionic liquid to the sulfide solid electrolyte is 0.5 volume% or more and 20 volume% or less, which contributes to the improvement of the ion conductivity of the active material layer.

  Moreover, the result of the ion conductivity measurement with respect to the ion conductivity measurement cell similarly produced except having not included an active material in FIG. 4 was described. When the active material was not contained, the ion conductivity of the layer decreased as the proportion of the ionic liquid increased, because the ion conductivity of the ionic liquid was lower than the ion conductivity of the sulfide solid electrolyte. On the other hand, when the active material is contained, the ionic liquid is disposed so as to fill the voids of the active material layer, whereby the ion conductivity of the active material layer is improved.

  In addition, as shown in Table 1, Comparative Examples 5 and 6 had significantly low ion conductivity. The reason is presumed to be that EMITFSI and DMC have reacted with the sulfide solid electrolyte. Moreover, it was confirmed that the ion conductivity in Example 11 is higher than that in Comparative Example 7, and the same effect can be obtained in the positive electrode active material layer.

1 ... positive electrode active material layer 2 ... negative electrode active material layer 3 ... solid electrolyte layer 4 ... positive electrode current collector 5 ... negative electrode current collector 10 ... solid battery

Claims (1)

A solid battery comprising a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer,
At least one of the positive electrode active material layer and the negative electrode active material layer comprises an active material, a sulfide solid electrolyte containing Li, P and S elements, and a solvated ionic liquid containing a Li salt and a Lewis base. Contains
The molar ratio of the Li salt to the Lewis base is 0.8 or more and 1.5 or less.
The solid battery, wherein the ratio of the solvated ionic liquid to the sulfide solid electrolyte is 0.5% by volume or more and 20% by volume or less.