JP2019125502A - Sulfide solid electrolyte - Google Patents

Abstract

To provide, mainly, a sulfide solid electrolyte with good oxidation resistance.SOLUTION: The invention provides a sulfide solid electrolyte with a composition represented by general formula (1) defined by Li{Ge+A}{P+B}S, where A and B are each independently Fe, Ag, Zn, Si, Sb, Pb or Cu, and 1.2≤x≤2.0, 10≤y≤18, 0≤δ≤0.1, 0≤γ≤0.05 and δ+γ>0 are satisfied.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a sulfide solid electrolyte with good oxidation resistance.

  With the rapid spread of information related devices such as personal computers, video cameras and mobile phones and communication devices in recent years, development of batteries used as the power source is regarded as important. Also, in the automobile industry and the like, development of high-power and high-capacity batteries for electric vehicles or hybrid vehicles is in progress. Among various batteries, lithium batteries are currently attracting attention from the viewpoint of high energy density.

  Since lithium batteries currently on the market use an electrolytic solution containing a flammable organic solvent, a structure for attachment of a safety device for preventing temperature rise at the time of short circuit and short circuit prevention is required. On the other hand, since the lithium battery in which the battery is totally solidified by replacing the electrolyte solution with the solid electrolyte layer does not use a flammable organic solvent in the battery, the safety device can be simplified.

A sulfide solid electrolyte is known as a solid electrolyte used for lithium solid state batteries. For example, Patent Document 1, the general _{formula: Li a M b N c P} d S e X f ( In the formula, M is selected Si, Ge, and Sn element, N is the Sb, Bi, B, Al An element selected from Ga, In, Tl, Pb, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Zn and Cu, X is an element selected from F, I, Br, Cl and At A to f represent composition ratios of the respective elements, the ratio of b and d (b: d) is 0 to 0.25: 1, and the ratio of a, c, d, e and f (a: A sulfide solid electrolyte having a composition represented by c: d: e: f) satisfying 1 to 12: 0 to 0.2: 1: 0.1 to 9: 0 to 9) is disclosed. . Patent Document 1 aims to lower the heat treatment temperature for crystallization.

JP, 2017-117635, A

  The sulfide solid electrolyte has the advantage of high Li ion conductivity. On the other hand, in the case of a lithium solid battery containing a sulfide solid electrolyte, the sulfide solid electrolyte may be oxidized and generate heat, for example, when placed in a high temperature state. Therefore, it is desirable that the sulfide solid electrolyte has high oxidation resistance. This indication is an invention made in view of the above-mentioned situation, and makes it a main purpose to provide a sulfide solid electrolyte with good oxidation resistance.

In order to achieve the above object, the present disclosure provides a sulfide solid electrolyte having a composition represented by the following general formula (1).
General formula (1): Li _y {Ge _(1-δ) + A _(δ) } _3-x {P _(1-γ) + B _(γ) } _x S ₁₂
(In the above general formula (1), A and B are each independently Fe, Ag, Zn, Si, Sb, Pb or Cu, 1.2 ≦ x ≦ 2.0, 10 ≦ y ≦ 18, 0 ≦ δ ≦ 0.1, 0 ≦ γ ≦ 0.05, δ + γ> 0 is satisfied

  According to the present disclosure, by having the composition represented by the above general formula (1), a sulfide solid electrolyte having good oxidation resistance can be obtained.

  The sulfide solid electrolyte of the present disclosure has an effect that oxidation resistance is good.

It is a schematic sectional drawing which shows an example of the lithium solid battery of this indication. It is the result of DSC measurement (oxidation tolerance test) of Examples 1-12 and Comparative Examples 1-7. It is the result of the XRD measurement of Examples 1-12 and Comparative Examples 1-7.

Hereinafter, the details of the sulfide solid electrolyte of the present disclosure will be described.
The sulfide solid electrolyte of the present disclosure has a composition represented by the following general formula (1).
General formula (1): Li _y {Ge _(1-δ) + A _(δ) } _3-x {P _(1-γ) + B _(γ) } _x S ₁₂
(In the above general formula (1), A and B are each independently Fe, Ag, Zn, Si, Sb, Pb or Cu, 1.2 ≦ x ≦ 2.0, 10 ≦ y ≦ 18, 0 ≦ δ ≦ 0.1, 0 ≦ γ ≦ 0.05, δ + γ> 0 is satisfied

  According to the present disclosure, by having the composition represented by the above general formula (1), a sulfide solid electrolyte having good oxidation resistance can be obtained.

As described above, the sulfide solid electrolyte has the advantage of high Li ion conductivity. On the other hand, in the case of a lithium solid battery containing a sulfide solid electrolyte, the sulfide solid electrolyte may be oxidized and generate heat, for example, when it is placed in a high temperature state (for example, a high temperature state of about 315 ° C.).
For example, the sulfide solid electrolyte represented by the general formula (2) has an advantage that the lithium ion conductivity is good, but has a problem that the oxidation resistance is relatively low.
General formula (2): Li _y Ge _3-x P _x S ₁₂
(In the above general formula (2), 1.2 ≦ x ≦ 2.0, 10 ≦ y ≦ 18 are satisfied.)
The reason is that Ge and P elements have low bonding with S elements, so when placed at high temperature, for example, Ge elements and P elements are easily detached from S elements and bonded to O elements. It is guessed to be because it

  On the other hand, in the present disclosure, a sulfide solid is obtained by substituting a part of the Ge element or P element in the general formula (2) with a specific element (Fe, Ag, Zn, Si, Sb, Pb or Cu) It has been found that the oxidation resistance of the electrolyte can be improved. The reason is presumed to be that the specific element has high bondability with the S element, and for example, it is difficult to be detached from the S element even when placed in a high temperature state.

  Since the sulfide solid electrolyte of the present disclosure has good oxidation resistance, it can suppress heat generation, for example, when the battery is placed at high temperature. Thus, a sulfide solid electrolyte having good thermal stability can be obtained.

The sulfide solid electrolyte of the present disclosure has a composition represented by the general formula (1).
General formula (1): Li _y {Ge _(1-δ) + A _(δ) } _3-x {P _(1-γ) + B _(γ) } _x S ₁₂
(In the above general formula (1), A and B are each independently Fe, Ag, Zn, Si, Sb, Pb or Cu, 1.2 ≦ x ≦ 2.0, 10 ≦ y ≦ 18, 0 ≦ δ ≦ 0.1, 0 ≦ γ ≦ 0.05, δ + γ> 0 is satisfied
In the general formula (1), the Ge element of δ × 100% (molar ratio) is substituted with the A element, and the P element of γ × 100% (molar ratio) is B It can also be understood as a composition substituted by an element. In the general formula (1), the value of S may vary depending on, for example, the type of the raw material composition (for example, the type of the raw material composition containing the A element or the B element). Therefore, it is preferable that the value of S is strictly a value rounded to 12 and specifically a value of 11.5 or more and 12.4 or less.

In the general formula (1), x may be 1.2 or more, and may be, for example, 1.5 or more, or may be 1.6 or more. Further, x may be 2.0 or less.
In the general formula (1), y may be 10 or more, and may be, for example, 10.02 or more, or may be 10.06 or more. Further, y may be 18 or less, for example, 10.4 or less, or 10.3 or less.

  In the general formula (1), A and B are each independently Fe, Ag, Zn, Si, Sb, Pb or Cu. A and B may be the same element or different elements.

In the general formula (1), δ may be 0 or more, may be larger than 0, and may be 0.02 or more. Further, δ may be 0.1 or less.
In the general formula (1), γ may be 0 or more, may be larger than 0, may be 0.01 or more, and may be 0.02 or more. Further, γ may be 0.05 or less.
In the general formula (1), δ and γ satisfy δ + γ> 0. That is, if δ = 0, then γ> 0, and if γ = 0, then δ> 0. Further, δ + γ is, for example, 0.15 or less.
In the present disclosure, in the general formula (1), δ = 0 or γ = 0 may be satisfied.

  The sulfide solid electrolyte of the present disclosure may be amorphous or crystalline, but is preferably crystalline. It is because Li ion conductivity can be made better.

  When the sulfide solid electrolyte of the present disclosure is a crystal, it preferably has a peak at a position of 2θ = 29.58 ° ± 0.50 ° in X-ray diffraction measurement using CuKα. This crystal phase is called crystal phase A. Crystalline phase A further comprises 2θ = 12.35 ° ± 0.50 °, 14.43 ° ± 0.50 °, 17.38 ° ± 0.50 °, 20.18 ° ± 0.50 °, 20 .44 ° ± 0.50 °, 23.56 ° ± 0.50 °, 23.96 ° ± 0.50 °, 24.93 ° ± 0.50 °, 26.96 ° ± 0.50 °, 29 .07 ° ± 0.50 °, 29.58 ° ± 0.50 °, 31.71 ° ± 0.50 °, 32.66 ° ± 0.50 °, 33.39 ° ± 0.50 ° May have a peak. The width of these peak positions may be ± 0.30 ° or ± 0.10 °. The peak in the crystal phase A is a peak derived from the LGPS type crystal phase.

  The sulfide solid electrolyte of the present disclosure preferably contains crystal phase A as a main phase. The ratio of the crystal phase A to all the crystal phases contained in the sulfide solid electrolyte is, for example, 50% by weight or more, and may be 70% by weight or more, or 90% by weight or more. The proportion of the upper crystal phase A can be measured, for example, by synchrotron radiation XRD.

The sulfide solid electrolyte of the present disclosure has Li ion conductivity. The Li ion conductivity at 25 ° C. is, for example, 4.0 × 10 ⁻³ S / cm or more, and preferably 4.5 × 10 ⁻³ S / cm or more. The Li ion conductivity of the sulfide solid electrolyte can be measured, for example, by an alternating current impedance method.

The shape of the sulfide solid electrolyte of the present disclosure is not particularly limited, and examples thereof include particulate. The average particle size (D ₅₀ ) of the sulfide solid electrolyte may be, for example, 0.1 μm or more and 50 μm or less. The average particle size can be determined, for example, from the result of particle size distribution measurement by a laser diffraction scattering method.

As a method for producing a sulfide solid electrolyte according to the present disclosure, for example, an amorphization step of mixing raw material compositions so as to have the composition represented by the above-mentioned general formula (1) and performing amorphization treatment The manufacturing method which it has can be mentioned. The method for producing a sulfide solid electrolyte may further include a heat treatment step of heat treating the obtained sulfide glass to obtain a sulfide solid electrolyte having an LGPS type crystal phase. As a raw material composition, for example, Li ₂ S, P ₂ S ₅ , GeS ₂ , Zn ₂ S ₃ , Fe ₂ S ₃ , Sb ₂ S ₅ , Pb ₂ S ₃ , SiS ₂ , Ag ₂ S, Cu ₂ S Can be mentioned. Moreover, as an amorphization process, a mechanical milling process is mentioned, for example.

The sulfide solid electrolyte of the present disclosure can be used in any application requiring Li ion conductivity. Among them, the sulfide solid electrolyte of the present disclosure is preferably used in a lithium solid battery. FIG. 1 is a schematic cross-sectional view showing an example of the lithium solid state battery of the present disclosure. The lithium solid battery 10 in FIG. 1 is formed between a positive electrode active material layer 1 containing a positive electrode active material, a negative electrode active material layer 2 containing a negative electrode active material, and the positive electrode active material layer 1 and the negative electrode active material layer 2. , The positive electrode current collector 4 for collecting current from the positive electrode active material layer 1, the negative electrode current collector 5 for collecting current from the negative electrode active material layer 2, and a battery case for housing these members. And 6. In the present disclosure, it is preferable that at least one of the positive electrode active material layer 1, the negative electrode active material layer 2, and the solid electrolyte layer 3 contain the above-described sulfide solid electrolyte.
Hereinafter, each structure in a lithium solid battery is demonstrated.

The positive electrode active material layer is a layer containing at least a positive electrode active material, and may contain at least one of a solid electrolyte, a conductive material, and a binder, as necessary. In particular, in the present disclosure, the positive electrode active material layer preferably contains a solid electrolyte, and the solid electrolyte is preferably the above-described sulfide solid electrolyte. The proportion of the sulfide solid electrolyte contained in the positive electrode active material layer is, for example, 0.1% by volume or more, and may be 1% by volume or more, or 10% by volume or more. On the other hand, the ratio of the sulfide solid electrolyte is, for example, 80% by volume or less, may be 60% by volume or less, and may be 50% by volume or less. Moreover, as a positive electrode active material, for example, LiCoO ₂ , LiMnO ₂ , Li ₂ NiMn ₃ O ₈ , LiVO ₂ , LiCrO ₂ , LiFePO ₄ , LiCoPO ₄ , LiNiO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ mag can be mentioned. Since the sulfide solid electrolyte of the present disclosure has good oxidation resistance, when used together with the oxide positive electrode active material, for example, when the battery is placed at high temperature, the sulfide solid electrolyte and the oxide positive electrode active material are It is presumed that the reaction can be effectively suppressed.

  The positive electrode active material layer may further contain a conductive material. The conductivity of the positive electrode active material layer can be improved by the addition of the conductive material. Examples of the conductive material include acetylene black, ketjen black, carbon fiber and the like. In addition, the positive electrode active material layer may contain a binder. As a kind of binder, fluorine-containing binders, such as polyvinylidene fluoride (PVDF), etc. can be mentioned, for example. The thickness of the positive electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

  The negative electrode active material layer is a layer containing at least a negative electrode active material, and may contain at least one of a solid electrolyte, a conductive material, and a binder, as necessary. In particular, in the present disclosure, it is preferable that the negative electrode active material layer contain a solid electrolyte, and the solid electrolyte be the above-mentioned sulfide solid electrolyte. The proportion of the sulfide solid electrolyte contained in the negative electrode active material layer is, for example, 0.1% by volume or more, and may be 1% by volume or more, or 10% by volume or more. On the other hand, the ratio of the sulfide solid electrolyte is, for example, 80% by volume or less, may be 60% by volume or less, and may be 50% by volume or less. Moreover, as a negative electrode active material, a metal active material and a carbon active material can be mentioned, for example. As a metal active material, In, Al, Si, Sn etc. can be mentioned, for example. On the other hand, examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, soft carbon and the like.

  The conductive material and the binder used in the negative electrode active material layer are the same as those in the above-described positive electrode active material layer. The thickness of the negative electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

  The solid electrolyte layer is a layer formed between the positive electrode active material layer and the negative electrode active material layer. The solid electrolyte layer usually contains a solid electrolyte. In the present disclosure, the solid electrolyte layer preferably contains the above-mentioned sulfide solid electrolyte. The proportion of the sulfide solid electrolyte contained in the solid electrolyte layer is, for example, 10% by volume or more, and may be 50% by volume or more. On the other hand, the proportion of the sulfide solid electrolyte is, for example, 100% by volume or less. The thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less. Moreover, as a method of forming a solid electrolyte layer, for example, a method of compression-molding a solid electrolyte can be mentioned.

The lithium solid battery at least includes the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material 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.
The lithium solid battery 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.

  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.

  The present disclosure will be described more specifically.

Comparative Example 1
Li ₂ S, GeS ₂ and P ₂ S ₅ were used as starting materials. Each material was weighed and mixed at a composition ratio of Li ₁₀ GeP ₂ S ₁₂ to obtain a mixture. Li ₁₀ Ge ₁ P ₂ S ₁₂ has a composition in which x = 1, y = 10, δ = 0, and γ = 0 in general formula (1) (x = 1, y = 10 in general formula (2) Composition). 2 g of the obtained mixture was put into a zirconia ball pot container (volume 45 ml) and sealed together with 53 g of zirconia balls (φ 5 mm). The container was attached to a planetary ball mill (PULVERISETTE 7 manufactured by Fritche), and powder was obtained by mechanical milling at a rotational speed of 500 rpm for 40 hours. The obtained powder was formed into pellets of about 10 mm in diameter. The obtained pellet was placed in a tubular furnace into which 0.5 L / min of H ₂ S gas and 0.5 L / min of Ar gas were introduced, and heat treatment was performed at 550 ° C. for 8 hours. A sulfide solid electrolyte was obtained by the above procedure.

Example 1
In Example 1 and Comparative Example 2, 2% (molar ratio) of the composition represented by the general formula (2): Li _y Ge _3-x P _x S ₁₂ (x = 1, y = 10) A sulfide solid electrolyte in which the Ge element was replaced with another element was synthesized.

In Example 1, Li ₂ S, GeS ₂ , Pb ₂ S ₃ and P ₂ S ₅ are used as starting materials, and each material has a composition ratio of Li ₁₀ Ge _0.98 Pb _0.02 P ₂ S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except that it was weighed and mixed. Li ₁₀ Ge _0.98 Pb _0.02 P ₂ S ₁₂ corresponds to a composition in which x = 1, y = 10, δ = 0.02, γ = 0 and A is Pb in the general formula (1) Do.

Comparative Example 2
Except that Li ₂ S, GeS ₂ , WS ₂ and P ₂ S ₅ were used as starting materials, and each material was weighed and mixed at a composition ratio of Li ₁₀ Ge _0.98 W _0.02 P ₂ S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1. Li ₁₀ Ge _0.98 W _0.02 P ₂ S ₁₂ corresponds to a composition in which x = 1, y = 10, δ = 0.02, γ = 0 and A is W in the general formula (1) Do.

Example 2
In Examples 2 and 3 and Comparative Examples 3 and 4, they are represented by the general formula (2): Li _y Ge _3-x P _x S ₁₂ (x = 1, y = 10, 10.06, or 10.02) The sulfide solid electrolyte was synthesized in which 1% (molar ratio) of P element was substituted by another element with respect to the composition.

In Example 2, Li ₂ S, GeS ₂ , Sb ₂ S ₅ , and P ₂ S ₅ are used as starting materials, and each material has a composition ratio of Li ₁₀ Ge ₁ P _1.98 Sb _0.02 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except that the mixture was measured and mixed to obtain a mixture. Li ₁₀ Ge ₁ P _1.98 Sb _0.02 S ₁₂ corresponds to a composition in which x = 1, y = 10, δ = 0, γ = 0.01 and B is Sb in the general formula (1) .

[Example 3]
Using Li ₂ S, GeS ₂ , Pb ₂ S ₃ and P ₂ S ₅ as starting materials, each material is weighed and mixed at a composition ratio of Li _10.06 Ge ₁ P _1.98 Pb _0.02 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the above point. Li _10.06 Ge ₁ P _1.98 Pb _0.02 S ₁₂ in the general formula (1) is x = 1, y = 10.06, δ = 0, γ = 0.01 and B is Pb It corresponds to the composition.

Comparative Example 3
Using Li ₂ S, GeS ₂ , SnS ₂ and P ₂ S ₅ as starting materials, each material was weighed and mixed at a composition ratio of Li _10.02 Ge ₁ P _1.98 Sn _0.02 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the following. Li _10.02 Ge ₁ P _1.98 Sn _0.02 S ₁₂ is x = 1, y = 10.02, δ = 0, γ = 0.01 in the general formula (1), and B is Sn It corresponds to the composition.

Comparative Example 4
Using Li ₂ S, GeS ₂ , WS ₂ and P ₂ S ₅ as starting materials, each material was weighed and mixed at a composition ratio of Li _10.02 Ge ₁ P _1.98 W _0.02 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the following. Li _10.02 Ge ₁ P _1.98 W _0.02 S ₁₂ is x = 1, y = 10.02, δ = 0, γ = 0.01 and B is W in the general formula (1) It corresponds to the composition.

Example 4
In Examples 4 to 8 and Comparative Example 5, the composition represented by the general formula (2): Li _y Ge _3-x P _x S ₁₂ (x = 1, y = 10, 10.2, or 10.3) On the other hand, a sulfide solid electrolyte was synthesized in which 10% (molar ratio) of the Ge element was replaced with another element.

In Example 4, using Li ₂ S, GeS ₂ , Zn ₂ S ₃ , and P ₂ S ₅ as starting materials, each material has a composition of Li _10.2 Ge _0.9 Zn _0.1 P ₂ S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except that the ratio was measured and mixed. Li _10.2 Ge _0.9 Zn _0.1 P ₂ S ₁₂ has x = 1, y = 10.2, δ = 0.1, γ = 0 in the general formula (1), and A is Zn It corresponds to the composition.

[Example 5]
Using Li ₂ S, GeS ₂ , Fe ₂ S ₃ and P ₂ S ₅ as starting materials, each material is weighed and mixed at a composition ratio of Li _10.2 Ge _0.9 Fe _0.1 P ₂ S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the above point. Li _10.2 Ge _0.9 Fe _0.1 P ₂ S ₁₂ has x = 1, y = 10.2, δ = 0.1, γ = 0 in the general formula (1), and A is Fe It corresponds to the composition.

[Example 6]
Using Li ₂ S, GeS ₂ , Pb ₂ S ₃ and P ₂ S ₅ as starting materials, each material is weighed and mixed at a composition ratio of Li _10.2 Ge _0.9 Pb _0.1 P ₂ S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the above point. Li _10.2 Ge _0.9 Pb _0.1 P ₂ S ₁₂ has a composition in which x = 1, y = 10, δ = 0.1, γ = 0 in the general formula (1), and A is Pb Applicable

[Example 7]
Li ₂ S, GeS ₂ , Ag ₂ S, P ₂ S ₅ were used as starting materials, and each material was weighed and mixed in a composition ratio of Li _10.3 Ge _0.9 Ag _0.1 P ₂ S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the point. Li _10.3 Ge _0.9 Ag _0.1 P ₂ S ₁₂ has x = 1, y = 10.2, δ = 0.1, γ = 0 in the general formula (1), and A is Ag It corresponds to the composition.

[Example 8]
Li ₂ S, GeS ₂ , Cu ₂ S, P ₂ S ₅ were used as starting materials, and each material was weighed and mixed at a composition ratio of Li _10.3 Ge _0.9 Cu _0.1 P ₂ S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the point. Li _10.3 Ge _0.9 Cu _0.1 P ₂ S ₁₂ has x = 1, y = 10.3, δ = 0.1, γ = 0 in the general formula (1), and A is Cu It corresponds to the composition.

Comparative Example 5
Except that Li ₂ S, GeS ₂ , WS ₂ and P ₂ S ₅ were used as starting materials, and each material was weighed and mixed at a composition ratio of Li ₁₀ Ge _0.9 W _0.1 P ₂ S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1. Li ₁₀ Ge _0.9 W _0.1 P ₂ S ₁₂ corresponds to a composition in which y = 10, x = 1, δ = 0.1, γ = 0 and A is W in the general formula (1) .

[Example 9]
In Examples 9 to 12 and Comparative Examples 6 and 7, general formula (2): Li _y Ge _3-x P _x S ₁₂ (x = 1, y = 10, 10.1, 10.3 or 10.4) A sulfide solid electrolyte was synthesized in which 5% (molar ratio) of P element was substituted by another element with respect to the composition represented by

In Example 9, Li ₂ S, GeS ₂ , SiS ₂ and P ₂ S ₅ are used as starting materials, and each material has a composition ratio of Li _10.1 Ge ₁ P _1.9 Si _0.1 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except that it was weighed and mixed. Li _10.1 Ge ₁ P _1.9 Si _0.1 S ₁₂ is x = 1, y = 10.1, δ = 0, γ = 0.05 in the general formula (1), and B is Si It corresponds to the composition.

[Example 10]
Using Li ₂ S, GeS ₂ , PbS ₂ and P ₂ S ₅ as starting materials, each material was weighed and mixed at a composition ratio of Li _10.3 Ge ₁ P _1.9 Pb _0.1 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the following. Li _10.3 Ge ₁ P _1.9 Pb _0.1 S ₁₂ is x = 1, y = 10.3, δ = 0, γ = 0.05 in the general formula (1), and B is Pb It corresponds to the composition.

[Example 11]
Using Li ₂ S, GeS ₂ , Ag ₂ S, P ₂ S ₅ as starting materials, each material was weighed and mixed at a composition ratio of Li _10.4 Ge ₁ P _1.9 Ag _0.1 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the point. Li _10.4 Ge ₁ P _1.9 Ag _0.1 S ₁₂ has x = 1, y = 10.4, δ = 0, γ = 0.05 in the general formula (1), and B is Ag It corresponds to the composition.

[Example 12]
Using Li ₂ S, GeS ₂ , Cu ₂ S, and P ₂ S ₅ as starting materials, each material was weighed and mixed at a composition ratio of Li _10.4 Ge ₁ P _1.9 Cu _0.1 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the point. Li _10.4 Ge ₁ P _1.9 Cu _0.1 S ₁₂ is x = 1, y = 10.4, δ = 0, γ = 0.05 in the general formula (1), and B is Cu It corresponds to the composition.

Comparative Example 6
Using Li ₂ S, GeS ₂ , SnS ₂ and P ₂ S ₅ as starting materials, each material was weighed and mixed at a composition ratio of Li _10.1 Ge ₁ P _1.9 Sn _0.1 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except for the following. Li _10.1 Ge ₁ P _1.9 Sn _0.1 S ₁₂ is x = 1, y = 10.1, δ = 0, γ = 0.05 in the general formula (1), and B is Sn It corresponds to the composition.

Comparative Example 7
Except that Li ₂ S, GeS ₂ , WS ₂ and P ₂ S ₅ were used as starting materials, and each material was weighed and mixed at a composition ratio of Li _10.1 Ge ₁ P _1.9 W _0.1 S ₁₂ A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1. Li _10.1 Ge ₁ P _1.9 W _0.1 S ₁₂ is x = 1, y = 10.1, δ = 0, γ = 0.05 and B is W in the general formula (1) It corresponds to the composition.

[Evaluation]
(Oxidation tolerance test (DSC))
15 mg of each sulfide solid electrolyte and 15 mg of Li _0.3 Ni _1/3 Co _1/3 Mn _1/3 O ₂ powder in an inert atmosphere adjusted to a dew point of −80 ° C. or less and an oxygen concentration of 10 ppm or less And mixed for 5 minutes using a mortar. The mixed powder was charged into a φ5 mm pellet molding machine, molded at a pressure of 10 kN / cm ² and then sealed with a SUS pan to obtain a measurement sample. Use an empty SUS pan as a reference, place the measurement sample and reference in the sample chamber, introduce liquid nitrogen and Ae gas at a flow rate of 100 mL / min, and raise the temperature to 50 ° C to 500 ° C at a heating rate of 10 ° C / min. The operation was performed until the heat generation behavior was observed. The results are shown in Tables 1 to 4 and FIG.

  In Examples 1 to 12, it was confirmed that the DSC peak was shifted to a sufficiently high temperature side of 315 ° C. or higher as compared with Comparative Example 1. From this, it was confirmed that Examples 1 to 12 have good oxidation resistance. On the other hand, in Comparative Example 5, it was confirmed that the peak of DSC shifted to the low temperature side as compared with Comparative Example 1. From this, it was confirmed that Comparative Example 5 had reduced oxidation resistance. Moreover, compared with Comparative Example 1, it was confirmed that the peak of DSC shifts to the high temperature side slightly compared with Comparative Example 2 ~ 4. From this, it was confirmed that Comparative Examples 2 to 4 and 6 to 7 can not have sufficient oxidation resistance.

(X-ray diffraction measurement (XRD))
In a glove box (in an inert atmosphere), a sulfide solid electrolyte is enclosed in a quartz capillary of φ5 mm, and an X-ray having a wavelength of 0.8267 Å is used to install BL- installed in the high energy accelerator research mechanism photon factory. The measurement was performed with an 8B X-ray diffractometer. The measurement range was dspacing: 1 Å to 10 Å.
From the obtained values, the peak was converted to a peak of 2θ in X-ray diffraction measurement using a CuKα ray, using a conversion formula of 2d sin θ = λ. The results are shown in FIG.

  In the examples and the comparative examples, each position is 2θ = 12.35 °, 14.43 °, 17.38 °, 20.18 °, 23.96 °, 26.96 °, 29.58 °. Peak was confirmed. This peak is a peak unique to the LGPS crystal phase.

Formula _{(2): Li} relative composition represented by _{x Ge 3-y P y S} 12, in the sulfide solid electrolyte obtained by substituting Ge element by another element, Ge site in LGPS type crystal phase other It is estimated that the element is substituted. In general formula _(2): For the composition represented by _{Li y Ge 3-x P x} S 12, in the sulfide solid electrolyte obtained by substituting P element by another element, the P site in the LGPS type crystal phase It is estimated that it is substituted by another element.

1 ... positive electrode active material layer 2 ... negative electrode active material layer 3 ... electrolyte layer 4 ... positive electrode current collector 5 ... negative electrode current collector 6 ... battery case 10 ... lithium solid battery

Claims (1)

The sulfide solid electrolyte which has a composition represented by following General formula (1).
General formula (1): Li _y {Ge _(1-δ) + A _(δ) } _3-x {P _(1-γ) + B _(γ) } _x S ₁₂
(In the general formula (1), A and B are each independently Fe, Ag, Zn, Si, Sb, Pb or Cu, 1.2 ≦ x ≦ 2.0, 10 ≦ y ≦ 18, 0 ≦ δ ≦ 0.1, 0 ≦ γ ≦ 0.05, δ + γ> 0 is satisfied