JP6783731B2 - Sulfide solid electrolyte - Google Patents

Description

The present disclosure relates to a sulfide solid electrolyte in which the generation of hydrogen sulfide is suppressed.

With the rapid spread of information-related devices such as personal computers, video cameras and mobile phones, and communication devices in recent years, the development of batteries used as their power sources has been emphasized. In addition, the automobile industry and the like are also developing high-output and high-capacity batteries for electric vehicles or hybrid vehicles. At present, among various batteries, lithium batteries are attracting attention from the viewpoint of high energy density.

Since the lithium battery currently on the market uses an electrolytic solution containing a flammable organic solvent, it is necessary to attach a safety device that suppresses a temperature rise at the time of a short circuit and a structure for preventing the short circuit. On the other hand, a lithium battery in which the battery is completely solidified by replacing the electrolytic solution with a solid electrolyte layer does not use a flammable organic solvent in the battery, so that the safety device can be simplified.

Since the sulfide solid electrolyte has high lithium ion conductivity, it is useful for increasing the output of the battery, and various studies have been conducted conventionally. For example, Patent Document 1 discloses a sulfide solid electrolyte having a Li ₇ P ₃ S ₁₁ crystal phase. Further, Patent Document 2 discloses a method for producing a sulfide solid electrolyte, which comprises a step of vitrifying a mixture A containing Li ₂ S, P ₂ S ₅ and Li ₃ N.

Patent Document 3 discloses a sulfide solid electrolyte containing an O element and an F element. Patent Document 4 discloses a lithium ion conductive material containing a sulfide solid electrolyte (for example, Li ₃ PS ₄ ) and an inhibitor (for example, CuO) containing a metal having a lower ionization tendency than hydrogen. Patent Document 5 discloses a sulfide solid electrolyte containing crystallized glass represented by 75Li ₂ S · (25-x) P ₂ S ₅ · xP ₂ O ₅ . Further, Non-Patent Document 1 _discloses a sulfide solid electrolyte represented by _{(75-1.5x) Li 2 S · 25P} 2 S 5 · xLi 3 N.

Japanese Unexamined Patent Publication No. 2005-228570 JP 2015-146239 Japanese Unexamined Patent Publication No. 2012-054212 Japanese Unexamined Patent Publication No. 2011-113720 Japanese Unexamined Patent Publication No. 2011-057500

Akihiro Fukushima et al., “Mechanochemical synthesis of high lithium ion conducting solid electrolytes in Li2S-P2S5-Li3N system”, Solid State Ionics 304 (2017) 85-89

The conventional Li ₇ P ₃ S ₁₁ crystal phase has high Li ion conductivity, but hydrogen sulfide is likely to be generated when it comes into contact with water. The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a sulfide solid electrolyte having a small amount of hydrogen sulfide generated while maintaining high Li ion conductivity.

In order to solve the above problems, in the present disclosure, a crystal phase containing Li element, P element, S element and N element and having a Li ₇ P ₃ S ₁₁ structure is provided, and the general formula: xLi ₂ S-30P. ₂ Provided is a sulfide solid electrolyte having a composition represented by S _5- yLi ₃ N (1 ≦ y ≦ 7, 66.5 ≦ x + y ≦ 73.1).

According to the present disclosure, since it has a crystal phase having a Li ₇ P ₃ S ₁₁ structure and has a predetermined composition, it is a sulfide solid electrolyte that generates a small amount of hydrogen sulfide while maintaining high Li ion conductivity. Can be.

The sulfide solid electrolyte of the present disclosure has an effect that the amount of hydrogen sulfide generated is small while maintaining high Li ion conductivity.

It is explanatory drawing which shows an example of the manufacturing method of the sulfide solid electrolyte of this disclosure. It is the schematic sectional drawing which shows an example of the lithium solid-state battery of this disclosure. It is the time lapse of the amount of hydrogen sulfide generated with respect to the sulfide solid electrolyte obtained in Example 2 and Comparative Example 1. It is the result of the Li ion conductivity measurement with respect to the sulfide solid electrolyte obtained in Examples 1 and 2 and Comparative Examples 1 and 3. It is the result of the Li ion conductivity measurement with respect to the sulfide solid electrolyte obtained in Examples 3 and 4 and Comparative Examples 1, 4 and 5. It is the result of the XRD measurement with respect to the sulfide solid electrolyte obtained in Examples 1 and 2 and Comparative Examples 1 and 3. It is an enlarged view which enlarged a part of FIG. It is the result of the XRD measurement with respect to the sulfide solid electrolyte obtained in Examples 3 and 4 and Comparative Examples 1, 4 and 5. It is an enlarged view which enlarged a part of FIG. It is the result of Raman spectroscopic measurement for the sulfide solid electrolyte obtained in Examples 1 and 2 and Comparative Examples 1 and 3. It is the result of Raman spectroscopic measurement for the sulfide solid electrolyte obtained in Examples 3 and 4 and Comparative Examples 1, 4 and 5.

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

The sulfide solid electrolyte of the present disclosure contains a Li element, a P element, an S element and an N element, has a crystal phase having a Li ₇ P ₃ S ₁₁ structure, and has a general formula: xLi ₂ S-30P ₂ S ₅ −. It has a composition represented by yLi ₃ N (1 ≦ y ≦ 7, 66.5 ≦ x + y ≦ 73.1).

According to the present disclosure, since it has a crystal phase having a Li ₇ P ₃ S ₁₁ structure and has a predetermined composition, it is a sulfide solid electrolyte that generates a small amount of hydrogen sulfide while maintaining high Li ion conductivity. Can be. As described above, the conventional Li ₇ P ₃ S ₁₁ crystal phase has high Li ion conductivity, but hydrogen sulfide is likely to be generated when it comes into contact with water. Conventional _Li 7 _P 3 _{S 11} crystal phase, as an anion unit has a _PS ^{4 3-} units and _P 2 _S ^{7 4-} _units, P ₂ ^{S 7 4-} _units, S ₃ PS-PS 3 It has a cross-linked sulfur structure. Since crosslinked sulfur (-S-) is less stable to water, it is presumed that hydrogen sulfide is generated.

On the other hand, in the present disclosure, a crystal phase having a Li ₇ P ₃ S ₁₁ structure is provided. From the results of Examples described later, it is presumed that this crystal phase is a crystal phase in which N element is dissolved in a Li ₇ P ₃ S ₁₁ crystal phase. By N elements in solid solution, P ₂ S ₇ ^4- proportion of units is reduced, the result can be a hydrogen sulfide generation amount is small sulfide solid electrolyte. Further, since the sulfide solid electrolyte of the present disclosure has a structure similar to that of the conventional Li ₇ P ₃ S ₁₁ crystal phase (Li ₇ P ₃ S ₁₁ structure), high Li ion conductivity can be maintained. Further, since the sulfide solid electrolyte of the present disclosure has a predetermined composition, the proportion of the crystal phase having the Li ₇ P ₃ S ₁₁ structure can be sufficiently increased.

The sulfide solid electrolyte of the present disclosure contains Li element, P element, S element and N element. The composition of the sulfide solid electrolyte can be confirmed, for example, by radiofrequency inductively coupled plasma (ICP) emission spectroscopy.

The sulfide solid electrolyte of the present disclosure comprises a crystal phase (crystal phase A) having a Li ₇ P ₃ S ₁₁ structure. It is presumed that the crystal phase A is a crystal phase in which the N element is dissolved in the Li ₇ P ₃ S ₁₁ crystal phase. The crystal phase A has a peak at a position similar to that of the Li ₇ P ₃ S ₁₁ crystal phase in the X-ray diffraction measurement using CuKα ray. Typical peaks of the Li ₇ P ₃ S ₁₁ crystal phase are 2θ = 17.8 °, 18.2 °, 19.8 °, 21.8 °, 23.8 °, 25.9 °, 29.5 °. Appears at the °, 30.0 ° position. The crystal phase A also preferably has a peak at a position of ± 0.5 ° (preferably a position of ± 0.3 °) at each of the above positions.

The sulfide solid electrolyte of the present disclosure preferably has a crystal phase A as a main phase. The ratio of the crystal phase A in all the crystal phases contained in the sulfide solid electrolyte is, for example, 50% by weight or more, 70% by weight or more, or 90% by weight or more. The ratio of the crystal phase A can be obtained from, for example, the result of synchrotron radiation XRD.

Sulfide solid electrolyte of the present disclosure provides an X-ray diffraction measurement using a CuKα line, Li ₃ N peaks (e.g. α-type Li ₃ N peak, 2θ = 21.6 ° ± 0.5 ° , 27.9 It is preferable not to have ° ± 0.5 °). Also, the sulfide solid electrolyte of the present disclosure provides an X-ray diffraction measurement using a CuKα ray, the peak of _{Li 2 S (2θ = 27.0 °} ± 0.5 °, 31.2 ° ± 0.5 °, It is preferable not to have 44.8 ° ± 0.5 °, 53.1 ° ± 0.5 °). In particular, the sulfide solid electrolyte of the present disclosure is preferably a single-phase material of crystal phase A.

The sulfide solid electrolyte of the present disclosure has a composition represented by the general formula: xLi ₂ S-30P ₂ S _5- yLi ₃ N (1 ≦ y ≦ 7, 66.5 ≦ x + y ≦ 73.1). This general formula is referred to as general formula (1). For example, x in the general formula (1) is 59.5 or more, and may be 61.5 or more. On the other hand, x in the general formula (1) is, for example, 72.1 or less, and may be 70.0 or less. Further, y in the general formula (1) is, for example, 1 or more, and may be 3.1 or more. On the other hand, y in the general formula (1) is, for example, 7 or less, and may be 5 or less. Further, x + y in the general formula (1) is, for example, 66.5 or more, and may be 67.5 or more. On the other hand, x + y in the general formula (1) is, for example, 73.1 or less, and may be 71 or less.

In addition, the general formula (1) exemplifies the ratio of Li element, P element, S element and N element using Li ₂ S, P ₂ S ₅ , and Li ₃ N, and is an example of a sulfide solid electrolyte. It does not specify that the raw material composition is Li ₂ S, P ₂ S ₅ , Li ₃ N. The sulfide solid electrolyte of the present disclosure also includes, for example, a sulfide solid electrolyte produced by using a simple substance S, a simple substance P, or the like as a raw material. Formula (1) has the general formula _{(2): Li (2x +} 3y) P 60 S (x + 150) can also be expressed as _{N y.}

Further, in the general formula (1), x and y may have a relationship of x = 70-1.5y. In that case, the general formula (1) can be expressed as the general formula (3): (70-1.5y) Li ₂ S · 30P ₂ S ₅ · yLi ₃ N. The general formula (3) is based on the molar composition represented by Li ₂ S: P ₂ S ₅ = 70:30, and even if the ratio of Li ₃ N is changed, Li of the entire sulfide solid electrolyte is used. Corresponds to the Li fixed value type composition in which the ratio of The preferred range of y in the general formula (3) is the same as that described above.

Further, in the general formula (1), the ratio of Li ₂ S and P ₂ S ₅ may be fixed at a molar ratio of 70:30. In that case, the general formula (1) can be expressed as the general formula (4): 70Li ₂ S-30P ₂ S _5- yLi ₃ N. The general formula (4) corresponds to a Li excess type composition having an excess of Li, based on the molar composition represented by Li ₂ S: P ₂ S ₅ = 70:30. The preferred range of y in the general formula (4) is the same as that described above. The general formula (4) can also be expressed as the general formula (4'): (100-Y) (0.7Li ₂ S · 0.3P ₂ S ₅ ) · YLi ₃ N. In this case, y = 100Y / (100-Y). Further, also in the general formulas (3), (4) and (4'), as in the general formula (1), the raw materials of the sulfide solid electrolyte are Li ₂ S, P ₂ S ₅ and Li ₃ N. It is not specific.

The sulfide solid electrolyte of the present disclosure preferably has high Li ion conductivity. The Li ion conductivity at 25 ° C. is, for example, 1 × 10 ^-3 S / cm or more. The shape of the sulfide solid electrolyte is not particularly limited, and examples thereof include particulate matter. The average particle size (D ₅₀ ) of the sulfide solid electrolyte is, for example, 0.1 μm or more and 50 μm or less.

The method for producing the sulfide solid electrolyte of the present disclosure is not particularly limited. FIG. 1 is an explanatory diagram showing an example of the method for producing a sulfide solid electrolyte of the present disclosure. In FIG. 1, first, the raw material composition (for example, Li ₂ S, P ₂ S ₅ , Li ₃ N) is amorphized to obtain sulfide glass (amorphization step). Next, the sulfide glass is heat-treated to obtain a crystalline material (heat treatment step). By performing the above steps, the above-mentioned sulfide solid electrolyte can be obtained.

The raw material composition is usually obtained by mixing raw materials containing Li element, P element, S element and N element. Examples of the raw material containing the Li element include Li sulfide and Li nitride. Specifically, Li ₂ S and Li ₃ N can be mentioned. Examples of the raw material containing the P element include simple substance P and sulfide of P. The P sulfides, for _example, a P 2 _{S 5} or the like. Examples of the raw material containing the S element include a simple substance of S, the above-mentioned Li sulfide, and P sulfide. Examples of the raw material containing the N element include the above-mentioned Li nitride as described above.

Examples of the method for amorphizing the raw material composition include a mechanical milling method such as a ball mill and a vibration mill, and a melt quenching method. The mechanical milling method may be a dry method or a wet method, but the latter is preferable from the viewpoint of uniform treatment. The type of dispersion medium used in the wet mechanical milling method is not particularly limited. The various conditions of the mechanical milling method are set so that a desired sulfide glass can be obtained.

The sulfide glass obtained by amorphization preferably does not have a crystal-derived peak in the XRD measurement.

The heat treatment temperature in the heat treatment step is, for example, 240 ° C. or higher, 250 ° C. or higher, or 260 ° C. or higher. On the other hand, the heat treatment temperature may be, for example, 320 ° C. or lower, 310 ° C. or lower, or 300 ° C. or lower. The heating time is, for example, 0.5 hours or more, and may be 1 hour or more. On the other hand, the heating time is, for example, 10 hours or less, and may be 5 hours or less.

The heat treatment is preferably performed under closed conditions, for example. This is because the N element can be easily incorporated into the sulfide solid electrolyte by performing the operation under the closed condition. This is also because it is possible to suppress the discharge of the N element as N _{2 from} the reaction system. Examples of the atmosphere during the heat treatment include a vacuum and an inert gas atmosphere.

The sulfide solid electrolyte of the present disclosure can be used in any application requiring ionic conductivity. Above all, the sulfide solid electrolyte of the present disclosure is preferably used for a lithium solid state battery. That is, in the present disclosure, it is also possible to provide a lithium solid-state battery using the above-mentioned sulfide solid electrolyte. FIG. 2 is a schematic cross-sectional view showing an example of the lithium solid-state battery of the present disclosure. The lithium solid cell 10 in FIG. 2 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 a positive electrode active material layer 1 and a negative electrode active material layer 2. A battery case for accommodating the solid electrolyte layer 3, the positive electrode current collector 4 for collecting the positive electrode active material layer 1, the negative electrode current collector 5 for collecting the negative electrode active material layer 2, and these members. 6 and. 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 contains the above-mentioned sulfide solid electrolyte.
Hereinafter, each configuration of the lithium solid-state battery of the present disclosure will be described.

(1) Positive Electrode Active Material Layer 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, if necessary. .. In particular, in the present disclosure, it is preferable that the positive electrode active material layer contains a solid electrolyte, and the solid electrolyte is the sulfide solid electrolyte described above. The proportion of the sulfide solid electrolyte contained in the positive electrode active material layer is, for example, 0.1% by volume or more, may be 1% by volume or more, or may be 10% by volume or more. On the other hand, the ratio of the sulfide solid electrolyte is, for example, 80% by volume or less, 60% by volume or less, or 50% by volume or less. Examples of the positive electrode active material include 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. _Second grade can be mentioned.

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

(2) Negative electrode active material layer 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, if necessary. .. In particular, in the present disclosure, it is preferable that the negative electrode active material layer contains a solid electrolyte, and the solid electrolyte is the sulfide solid electrolyte described above. The proportion of the sulfide solid electrolyte contained in the negative electrode active material layer is, for example, 0.1% by volume or more, may be 1% by volume or more, or may be 10% by volume or more. On the other hand, the ratio of the sulfide solid electrolyte is, for example, 80% by volume or less, 60% by volume or less, or 50% by volume or less. Further, examples of the negative electrode active material include a metal active material and a carbon active material. Examples of the metal active material include In, Al, Si and Sn. 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 for the negative electrode active material layer are the same as those for the positive electrode active material layer described above. The thickness of the negative electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

(3) Solid Electrolyte Layer 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, it is preferable that the solid electrolyte layer 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 and the like can be mentioned.

(4) Other Structure The lithium solid-state battery has at least the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer described above. Further, it usually has a positive electrode current collector that collects electricity from the positive electrode active material layer and a negative electrode current collector that collects electricity from 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. Further, it is preferable to appropriately select the thickness and shape of the positive electrode current collector and the negative electrode current collector according to the application of the battery and the like. Further, as the battery case used in the present disclosure, a battery case of a general battery can be used, and examples thereof include a battery case made of SUS.

(5) Lithium solid-state battery The lithium solid-state battery may be a primary battery or a secondary battery, but a secondary battery is preferable. This is because it can be repeatedly charged and discharged, and is useful as an in-vehicle battery, for example. Examples of the shape of the lithium solid-state battery include a coin type, a laminated type, a cylindrical type, and a square type. Further, the method for manufacturing the lithium solid-state battery is not particularly limited as long as the above-mentioned battery can be obtained, and the same method as the general method for manufacturing the lithium solid-state battery can be used. As an example of the manufacturing method, a power generation element is produced by sequentially pressing a material constituting a positive electrode active material layer, a material constituting a solid electrolyte layer, and a material constituting a negative electrode active material layer, and this power generation element is produced. Can be mentioned as a method of storing the battery inside the battery case and crimping the battery case.

The present disclosure is not limited to the above embodiment. The above embodiment is an example, and any object having substantially the same structure as the technical idea described in the claims of the present disclosure and exhibiting the same effect and effect is the present invention. Included in the technical scope of the disclosure.

Hereinafter, the present disclosure will be described in more detail.

[Comparative Example 1]
As a raw material, lithium sulfide _(Li 2 S, Mizuno manufactured sum Chemical Industry), diphosphorus pentasulfide _(P 2 _{S 5,} Aldrich), using lithium nitride _(Li 3 N, Aldrich). Each of the raw _material, in the composition of _{(70-1.5y) Li 2 S · 30P} 2 S 5 · yLi 3 N, was weighed so that y = 0. 1 g of the weighed mixture was put into a pot (45 cc, manufactured by ZrO ₂ ) of a planetary ball mill together with 500 ZrO ₂ balls having a diameter of 4 mm and sealed. This container was attached to a planetary ball mill machine (manufactured by Fritsch, P-7), and mechanical milling was performed at a base rotation speed of 510 rpm for 45 hours to obtain sulfide glass.

The obtained sulfide glass was placed in a quartz tube and vacuum-sealed at 30 Pa or less. Then, a sulfide solid electrolyte was obtained by heat treatment at a temperature (200 ° C. to 350 ° C.) higher than the crystallization temperature (Tc) observed by differential thermal analysis (DTA). Instead of the vacuum, an inert atmosphere (e.g., Ar atmosphere, N ₂ atmosphere) may be subjected to heat treatment at.

[Example 1]
_(70-1.5y) in the composition of _{Li 2 S · 30P 2 S 5} · yLi 3 N, such that y = 5, except that materials were weighed, sulfide solid electrolyte in the same manner as in Comparative Example 1 Got

[Example 2]
_(70-1.5y) in the composition of _{Li 2 S · 30P 2 S 5} · yLi 3 N, such that y = 7, except that materials were weighed, sulfide solid electrolyte in the same manner as in Comparative Example 1 Got

[Comparative Example 2]
_(70-1.5y) in the composition of _{Li 2 S · 30P 2 S 5} · yLi 3 N, such that y = 10, except that materials were weighed, sulfide solid electrolyte in the same manner as in Comparative Example 1 Got

[Comparative Example 3]
_(70-1.5y) in the composition of _{Li 2 S · 30P 2 S 5} · yLi 3 N, such that y = 20, except that materials were weighed, sulfide solid electrolyte in the same manner as in Comparative Example 1 Got

[Example 3]
The composition was changed to _{70Li 2 S · 30P 2 S 5} · yLi 3 N, in its composition, such that y = 1, except that materials were weighed, the sulfide solid electrolyte in the same manner as in Comparative Example 1 Obtained. Strictly speaking, the above composition is Y = 1 in (100-Y) (0.7Li ₂ S · 0.3P ₂ S ₅ ) · YLi ₃ N.

[Example 4]
In 70Li composition _{2 S · 30P 2 S 5 ·} yLi 3 N, such that y = 3.1, except that materials were weighed to give a sulfide solid electrolyte in the same manner as in Example 3. Strictly speaking, the above composition is Y = 3 at (100-Y) (0.7Li ₂ S · 0.3P ₂ S ₅ ) · YLi ₃ N.

[Comparative Example 4]
In 70Li composition _{2 S · 30P 2 S 5 ·} yLi 3 N, such that y = 11.1, except that materials were weighed to give a sulfide solid electrolyte in the same manner as in Example 3. Strictly speaking, the composition is Y = 10 at (100-Y) (0.7Li ₂ S · 0.3P ₂ S ₅ ) · YLi ₃ N.

[Comparative Example 5]
In 70Li composition _{2 S · 30P 2 S 5 ·} yLi 3 N, such that y = 25, except that materials were weighed to give a sulfide solid electrolyte in the same manner as in Example 3. Strictly speaking, the composition is Y = 20 at (100-Y) (0.7Li ₂ S · 0.3P ₂ S ₅ ) · YLi ₃ N.

[Evaluation]
(Measurement of hydrogen sulfide generation)
The amount of hydrogen sulfide generated by the sulfide solid electrolytes obtained in Examples 1 to 4 and Comparative Examples 1 to 5 was measured. 50 mg of the sulfide solid electrolyte was placed in a glass desiccator having a volume of 2000 cm ³ and exposed to the atmosphere at a humidity of 70%. The hydrogen sulfide concentration in the desiccator was measured by a hydrogen sulfide sensor (GBL-HS, manufactured by Ichinenjiko Co., Ltd.). The amount of hydrogen sulfide generated 5 minutes after the start of exposure was measured. The results are shown in Table 1. Further, as an example of the measurement result, FIG. 3 shows the time passage of the amount of hydrogen sulfide generated with respect to the sulfide solid electrolyte obtained in Example 2 and Comparative Example 1.

(Measurement of Li ion conductivity)
The Li ion conductivity was measured by the AC impedance method for the sulfide solid electrolytes obtained in Examples 1 to 4 and Comparative Examples 1 to 5. By cold-pressing the sulfide solid electrolyte at a pressure of 6 ton / cm ² , pellets having a diameter of 11.28 mm and a thickness of about 500 μm were prepared. The obtained pellets were subjected to AC impedance measurement by FRA (frequency response analyzer, Solartron, SI1260, manufactured by Toyo Corporation) in an Ar atmosphere. The measurement was carried out in a constant temperature bath adjusted to 25 ° C. The results are shown in Table 1, FIG. 4, and FIG.

As shown in Table 1 and FIG. 3, Examples 1-4, as compared with Comparative Example 1 containing no Li 3 _N, and reduced hydrogen sulfide emissions. Further, as shown in FIG. 4, it was confirmed that Examples 1 and 2 had an ionic conductivity of 10 ^-3 S / cm or more as in Comparative Example 1. In particular, Example 1 had a remarkable effect of having a higher ionic conductivity than Comparative Example 1. On the other hand, in Comparative Examples 2 and 3, the ionic conductivity was significantly lowered as compared with Examples 1 and 2. Further, as shown in FIG. 5, Examples 3 and 4 had a remarkable effect of having an ionic conductivity equal to or higher than that of Comparative Example 1. On the other hand, in Comparative Examples 4 and 5, the ionic conductivity was significantly lowered as compared with Examples 3 and 4.

(X-ray diffraction measurement)
X-ray diffraction (XRD) measurements were performed on the sulfide solid electrolytes obtained in Examples 1 to 4 and Comparative Examples 1 to 5. Measurements were performed with CuKα rays (1.41 Å) in the range of 2θ = 10 ° to 40 ° using an X-ray diffractometer (SmartLab, manufactured by Rigaku). The results are shown in FIGS. 6 to 9. Note that FIG. 7 is an enlarged view of a part of FIG. 6, and FIG. 9 is an enlarged view of a part of FIG. 8.

As shown in FIG. 6, in Examples 1 and 2 and Comparative Example 1, it was confirmed that the crystal phase having the Li ₇ P ₃ S ₁₁ structure was precipitated in a substantially single phase. On the other hand, in Comparative Examples 2 and 3, in addition to the crystal phase having the Li ₇ P ₃ S ₁₁ structure, other crystal phases such as β-Li ₃ PS ₄ were also precipitated. The results of Examples 1 and 2 and Comparative Example 1 were examined in more detail, as shown in FIG. 7, the addition of Li 3 _N, the peak in the vicinity of 2 [Theta] = 23.8 ° is shifted to a higher angle side It was confirmed that It is presumed that this shift was caused by the solid solution of the N element in the Li ₇ P ₃ S ₁₁ crystal phase.

As shown in FIG. 8, in Examples 3 and 4 and Comparative Example 1, it was confirmed that the crystal phase having the Li ₇ P ₃ S ₁₁ structure was precipitated in a substantially single phase. On the other hand, in Comparative Examples 4 and 5, in addition to the crystal phase having the Li ₇ P ₃ S ₁₁ structure, other crystal phases were also precipitated. The results of Examples 3 and 4 and Comparative Example 1 were examined in more detail, as shown in FIG. 9, the addition of Li 3 _N, the peak in the vicinity of 2 [Theta] = 23.8 ° is shifted to a higher angle side It was confirmed that

(Raman spectroscopy)
Raman spectroscopy was performed on the sulfide solid electrolytes obtained in Examples 1 to 4 and Comparative Examples 1 to 5. A Raman spectrometer (Lab-Ram HR-800, manufactured by Horiba Jobin Yvon) was used. The results are shown in FIGS. 10 and 11. As shown in FIGS. 10 and 11, by the addition of Li _{3 N,} it was confirmed that the ratio of P ₂ ^{S 7 4-} units (unstable bridging sulfur structure) is reduced. As a result, it is presumed that the amount of hydrogen sulfide generated has decreased.

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 6 ... Battery case

Claims (1)

Contains Li element, P element, S element and N element,
It has a crystalline phase with a Li ₇ P ₃ S ₁₁ structure and
General formula: A sulfide solid electrolyte having a composition represented by xLi ₂ S-30P ₂ S _5- yLi ₃ N (1 ≦ y ≦ 7, 66.5 ≦ x + y ≦ 73.1).