JP2015032550A - Sulfide solid electrolyte material, cell and method of producing sulfide solid electrolyte material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfide solid electrolyte material good in ion conductivity.SOLUTION: A sulfide solid electrolyte material contains Li element, Si element, P element and S element and is free of Ge element, Sn element and O element and has a peak at the position of 2θ=29.58°±0.50° in the X-ray diffraction measurement using the CuKα ray but no peak at the position of 2θ=27.33°±0.50° or has a value of I/Iof lower than 0.50, where Iis the diffraction intensity of the peak at 2θ=29.58°±0.50° and Iis the diffraction intensity of the peak at 2θ=27.33°±0.50°.

Description

  The present invention relates to a sulfide solid electrolyte material having good ion conductivity.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, development of batteries that are used as power sources has been 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 being promoted. Currently, lithium batteries are attracting attention among various batteries from the viewpoint of high energy density.

  Since lithium batteries currently on the market use an electrolyte containing a flammable organic solvent, it is possible to install safety devices that suppress the temperature rise during short circuits and to improve the structure and materials to prevent short circuits. Necessary. In contrast, a lithium battery in which the electrolyte is changed to a solid electrolyte layer to make the battery completely solid does not use a flammable organic solvent in the battery, so the safety device can be simplified, and manufacturing costs and productivity can be reduced. It is considered excellent.

A sulfide solid electrolyte material is known as a solid electrolyte material used for an all solid lithium battery. For example, Patent Document 1 discloses a Li ion conductor (sulfide solid electrolyte material) having a composition of Li _(4-x) Ge _(1-x) P _x S ₄ .

International Publication No. 2011/118801

  From the viewpoint of increasing the output of a battery, a solid electrolyte material having good ion conductivity is required. The present invention has been made in view of the above problems, and a main object of the present invention is to provide a sulfide solid electrolyte material having good ion conductivity.

In order to solve the above-mentioned problems, in the present invention, X-ray diffraction measurement using a CuKα ray, which contains Li element, Si element, P element and S element, does not contain Ge element, Sn element and O element. Or 2θ = 29.58 ° ± 0.50 ° at the peak, and X-ray diffraction measurement using CuKα ray does not have a peak at 2θ = 27.33 ° ± 0.50 °, when having peaks at the 2θ = 27.33 ° ± 0.50 °, the diffraction intensity of the peak of the 2θ = 29.58 ° ± 0.50 ° and _{I a,} the 2θ = 27.33 ° ± Provided is a sulfide solid electrolyte material characterized in that the value of I _B / I _A is less than 0.50 when the diffraction intensity of a peak at 0.50 ° is I _B.

  According to the present invention, since the ratio of the crystal phase having a peak near 2θ = 29.58 ° is high, a sulfide solid electrolyte material having good ion conductivity can be obtained.

In the present invention, the octahedron O composed of Li element and S elements, M _a element and the tetrahedron T ₁ composed of S elements, M _b element and tetrahedron T consists S elements _The tetrahedron T ₁ and the octahedron O share a ridge, and the tetrahedron T ₂ and the octahedron O mainly contain a crystal structure sharing a vertex, and the _Ma element and at least one of the M _b element comprises a Si element, at least one of the M _a element and the M _b element comprises a P element, Ge element, sulfide solid which is characterized by not containing Sn element and O elemental An electrolyte material is provided.

According to the present invention, since octahedron O, tetrahedron T ₁ and tetrahedron T ₂ have a predetermined crystal structure (three-dimensional structure), a sulfide solid electrolyte material having good ion conductivity can be obtained. .

  In the said invention, it is preferable that the molar ratio of the said P element with respect to the sum total of the said Si element and the said P element exists in the range of 0.5-0.7.

In the above invention, the sulfide solid electrolyte material is represented by Li _(4-x) Si _(1-x) P _x S ₄ (x satisfies 0.5 ≦ x ≦ 0.7). Is preferred.

  In the present invention, a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and an electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer In which at least one of the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer contains the sulfide solid electrolyte material described above.

  According to the present invention, a high-power battery can be obtained by using the above-described sulfide solid electrolyte material.

  Further, in the present invention, there is provided a method for producing the sulfide solid electrolyte material described above, wherein the ionized by mechanical milling using the raw material composition containing the components of the sulfide solid electrolyte material. Sulfurization comprising: an ion conductive material synthesis step for synthesizing a conductive material; and a heating step for obtaining the sulfide solid electrolyte material by heating the amorphous ion conductive material. A method for producing a solid electrolyte material is provided.

  According to the present invention, a sulfide solid electrolyte having a high proportion of crystal phase having a peak near 2θ = 29.58 ° is obtained by performing amorphization in an ion conductive material synthesis step and then performing a heating step. Material can be obtained. Therefore, a sulfide solid electrolyte material having good ion conductivity can be obtained.

  In this invention, there exists an effect that the sulfide solid electrolyte material with favorable ion conductivity can be obtained.

It is a perspective view explaining an example of the crystal structure of the sulfide solid electrolyte material of this invention. It is a schematic sectional drawing which shows an example of the battery of this invention. It is explanatory drawing which shows an example of the manufacturing method of the sulfide solid electrolyte material of this invention. It is an X-ray diffraction spectrum of the sulfide solid electrolyte material obtained in Examples 1-3. 4 is an X-ray diffraction spectrum of the sulfide solid electrolyte material obtained in Examples 4 and 5. FIG. It is an X-ray diffraction spectrum of the sulfide solid electrolyte material obtained in Comparative Examples 1-3. It is a measurement result of Li ion conductivity of the sulfide solid electrolyte material obtained in Examples 1-5 and Comparative Examples 1-3.

  Hereinafter, the sulfide solid electrolyte material, battery, and method for producing the sulfide solid electrolyte material of the present invention will be described in detail.

A. First, the sulfide solid electrolyte material of the present invention will be described. The sulfide solid electrolyte material of the present invention can be roughly divided into two embodiments. Therefore, the sulfide solid electrolyte material of the present invention will be described separately for the first embodiment and the second embodiment.

1. First Embodiment The sulfide solid electrolyte material of the first embodiment contains Li element, Si element, P element and S element, does not contain Ge element, Sn element and O element, and uses CuKα rays. It has a peak at the position of 2θ = 29.58 ° ± 0.50 ° in the line diffraction measurement, and has a peak at the position of 2θ = 27.33 ° ± 0.50 ° in the X-ray diffraction measurement using the CuKα ray. If the peak has a peak at the position of 2θ = 27.33 ° ± 0.50 °, the diffraction intensity of the peak at 2θ = 29.58 ° ± 0.50 ° is I _A , and the above 2θ = 27. the diffraction intensity of the peak of 33 ° ± 0.50 ° upon the _{I B,} in which the value of I B / _{I a} is equal to or less than 0.50.

According to the first embodiment, since the ratio of the crystal phase having a peak near 2θ = 29.58 ° is high, a sulfide solid electrolyte material having good ion conductivity can be obtained. Furthermore, since Si is contained, a sulfide solid electrolyte material having a low reduction potential can be obtained. Since Si has a small ionic radius and forms a strong bond with S, it is considered that Si has a property that is difficult to be reduced and decomposed, and as a result, it is presumed that the reduction potential is lowered. Moreover, since the sulfide solid electrolyte material of the first embodiment does not contain Ge element and Sn element, it can be a sulfide solid electrolyte material that is not easily reduced and decomposed. Incidentally, when comparing the alloying potential between Li, Si whereas a near ^{0.35V (Li / Li +),} Ge is around ^{0.4V (Li / Li +),} Sn 0. It is around 6 V (Li / Li ⁺ ). Moreover, the sulfide solid electrolyte material of the first embodiment can reduce the cost by using a Si element that is cheaper than the Ge element and the Sn element. Moreover, since the sulfide solid electrolyte material of the first embodiment does not contain an O element, it can be a sulfide solid electrolyte material having high ion conductivity. For example, when a raw material containing oxygen is used, there is a possibility that a sulfide solid electrolyte material in which O element is unevenly distributed in the crystal is obtained. In the LiSiPS system, the unevenly distributed O element may inhibit ionic conduction.

  Here, the LiGePS-based sulfide solid electrolyte material described in Patent Document 1 has a peak in the vicinity of 29.58 °. The crystal phase having this peak is referred to as crystal phase A. Crystal phase A is a crystal phase with high ion conductivity. The crystal phase A is usually 2θ = 17.38 °, 20.18 °, 20.44 °, 23.56 °, 23.96 °, 24.93 °, 26.96 °, 29.07 °. , 29.58 °, 31.71 °, 32.66 °, and 33.39 °. Note that these peak positions may vary around ± 0.50 ° with the crystal lattice slightly changing depending on the material composition and the like. The sulfide solid electrolyte material of the first embodiment is considered to have a crystal phase similar to the crystal phase A.

  The LiGePS sulfide solid electrolyte material described in Patent Document 1 has a peak in the vicinity of 2θ = 27.33 °. The crystal phase having this peak is referred to as crystal phase B. The crystal phase B is a crystal phase having lower ion conductivity than the crystal phase A described above. The crystal phase B usually has 2θ = 17.46 °, 18.12 °, 19.99 °, 22.73 °, 25.72 °, 27.33 °, 29.16 °, 29.78 °. It is thought that it has a peak. Note that these peak positions may also fluctuate within a range of ± 0.50 °.

The sulfide solid electrolyte material of the first embodiment may have a crystal phase similar to the crystal phase B. In a first embodiment, 2 [Theta] = 29.58 diffraction intensity of the peak in the vicinity ° and _{I A,} if the diffraction intensity of the peak near 2 [Theta] = 27.33 ° was _{I B,} the value of I B / _{I A} Is, for example, less than 0.50, preferably 0.45 or less, more preferably 0.25 or less, further preferably 0.15 or less, and 0.07 or less. Particularly preferred. Further, the value of I _B / I _A is preferably 0. In other words, the sulfide solid electrolyte material of the first embodiment preferably has no peak around 2θ = 27.33 °.

  In addition, the sulfide solid electrolyte material of the first embodiment contains at least a Li element, a Si element, a P element, and a S element. The sulfide solid electrolyte material of the first embodiment may contain only Li element, Si element, P element and S element, or may further contain other elements. A part of the Li element may be substituted with a monovalent or divalent metal element, or may not be substituted. When a part of the Li element is replaced with another element, ion conductivity may be improved. Examples of the metal element include at least one of Na, K, Mg, Ca, and Zn.

  Further, a part of the Si element or P element may be substituted by a trivalent, tetravalent or pentavalent element, or may not be substituted. Examples of these elements include at least one of Sb, B, Al, Ga, In, Ti, Zr, V, and Nb. The substitution amount of the metal element can be determined, for example, by XRD Rietveld analysis and ICP emission spectroscopy.

  In the first embodiment, the molar ratio of P element to the sum of Si element and P element (number of moles of P element / (total number of moles of Si element and P element)) is, for example, 0.5 or more. It is preferable that it is 0.6 or more. On the other hand, the molar ratio is, for example, preferably 0.7 or less, and more preferably 0.65 or less. This is because the ratio of the Si element and the P element in the crystal phase A is optimized, the bottleneck in the ion conduction path is eliminated, and the ion conductivity is improved.

  Moreover, the sulfide solid electrolyte material of the first embodiment does not contain Ge element and Sn element. “No Ge element” means that the molar ratio of Ge element to the sum of Si element, P element and Ge element (number of moles of Ge element / (total number of moles of Si element, P element and Ge element)) , 0.1 or less. The same applies to the definition of “not containing Sn element”. Especially, it is preferable that each said molar ratio is 0.07 or less, and it is more preferable that it is 0.05 or less. This is because the reduction resistance can be improved. The molar ratio may be zero. The molar ratio can be confirmed by ICP emission spectroscopy. By obtaining the mass distribution by ICP emission spectroscopy and dividing by the atomic weight, the number of moles (molar fraction) of each element can be obtained.

  Moreover, the sulfide solid electrolyte material of the first embodiment does not contain an O element. “O element does not contain” means that the molar ratio of the O element to the sum of the S element and the O element (the number of moles of the O element / (the total number of moles of the S element and the O element)) is 0.2 or less. That means. Among these, the molar ratio is preferably 0.1 or less, and more preferably 0.07 or less. This is because the ion conductivity can be improved. The molar ratio may be zero. The molar ratio can be confirmed, for example, by XRD Rietveld analysis and neutron diffraction Rietveld analysis.

The composition of the sulfide solid electrolyte material of the first embodiment, but is not particularly limited as long as the composition can be obtained the value of a given I _{B /} I _A, for example, Li _(4-x) It is preferably represented by Si _(1-x) P _x S ₄ (x satisfies 0.5 ≦ x ≦ 0.7). This is because a sulfide solid electrolyte material having high ion conductivity can be obtained. The composition of Li _(4-x) Si _(1-x) P _x S ₄ corresponds to the composition of the solid solution of Li ₃ PS ₄ and Li ₄ SiS ₄ . That is, this composition corresponds to the composition on the tie line of Li ₃ PS ₄ and Li ₄ SiS ₄ . Li ₃ PS ₄ and Li ₄ SiS ₄ both correspond to the ortho composition and have an advantage of high chemical stability.

_Also, x in _{Li (4-x) Si (} 1-x) P x S 4 is not particularly limited as long as the value can be obtained the value of a given _I B / _{I A,} among others 0.55 ≦ x is preferable, and 0.6 ≦ x is more preferable. On the other hand, x preferably satisfies x ≦ 0.7, and more preferably satisfies x ≦ 0.65. This is because a sulfide solid electrolyte material having good ion conductivity can be obtained.

In addition, the reduction potential of the sulfide solid electrolyte material of the first embodiment is preferably 0.3 V (vs Li / Li ⁺ ) or less, for example, and preferably 0.25 V (vs Li / Li ⁺ ) or less. More preferred.

The sulfide solid electrolyte material of the first embodiment is usually a sulfide solid electrolyte material having crystallinity. The sulfide solid electrolyte material of the first embodiment preferably has high ionic conductivity, and the ionic conductivity of the sulfide solid electrolyte material at 25 ° C. is 1.0 × 10 ⁻³ S / cm or more. It is preferable. Moreover, the shape of the sulfide solid electrolyte material of the first embodiment is not particularly limited, and examples thereof include powder. Furthermore, the average particle diameter of the powdered sulfide solid electrolyte material is preferably in the range of 0.1 μm to 50 μm, for example.

  Since the sulfide solid electrolyte material of the first embodiment has high ionic conductivity, it can be used for any application that requires ionic conductivity. Especially, it is preferable that the sulfide solid electrolyte material of a 1st embodiment is what is used for a battery. This is because it can greatly contribute to the high output of the battery. The method for producing the sulfide solid electrolyte material of the first embodiment will be described in detail in “C. Method for producing sulfide solid electrolyte material” described later. Further, the sulfide solid electrolyte material of the first embodiment may have the characteristics of the second embodiment described later.

2. Second Embodiment Next, a second embodiment of the sulfide solid electrolyte material of the present invention will be described. Sulfide solid electrolyte material of the second embodiment, the octahedron O composed of Li element and S elements, a tetrahedron T ₁ composed of M _a element and S elements, composed of M _b elements and S elemental and a tetrahedron T ₂ that is, the tetrahedron T ₁ and the octahedron O share a crest above tetrahedron T ₂ and the octahedron O contains mainly a crystalline structure that share vertices, at least one of the M _a element and the M _b element comprises a Si element, characterized in that said at least one of M _a element and the M _b element which comprises a P element, not containing Ge elements, Sn element and O elemental It is what.

According to the second embodiment, since the octahedron O, the tetrahedron T ₁ and the tetrahedron T ₂ have a predetermined crystal structure (three-dimensional structure), a sulfide solid electrolyte material having good ion conductivity is obtained. Can do. Furthermore, since Si is contained, a sulfide solid electrolyte material having a low reduction potential can be obtained.

FIG. 1 is a perspective view for explaining an example of the crystal structure of the sulfide solid electrolyte material of the second embodiment. In the crystal structure shown in FIG. 1, the octahedron O is typically a LiS ₆ octahedron having Li as a central element and six S at the apex of the octahedron. The tetrahedron T ₁ has Ma as _a central element, has four S at the apex of the tetrahedron, and is typically a SiS ₄ tetrahedron and a PS ₄ tetrahedron. Tetrahedron T ₂ are, have a M _b as the central element, it has four S to the apex of the tetrahedron, typically PS ₄ tetrahedron. Furthermore, the tetrahedron T ₁ and the octahedron O share a ridge, and the tetrahedron T ₂ and the octahedron O share a vertex.

At least one of the M _a element and _{M b} element, typically includes a Si element. That may be M _a element or M _b element contains a Si element, both M _a element and M _b element may contain a Si element. At least one of the _{M a} element and _{M b} element, typically includes a P element. That, M _a element or M _b element may include a P element, both M _a element and M _b element may include a P element.

  The sulfide solid electrolyte material of the second embodiment is characterized mainly by containing the crystal structure as a main component. The ratio of the crystal structure in the entire crystal structure of the sulfide solid electrolyte material is not particularly limited, but is preferably higher. This is because a sulfide solid electrolyte material having high ion conductivity can be obtained. Specifically, the ratio of the crystal structure is preferably 70 wt% or more, and more preferably 90 wt% or more. In addition, the ratio of the said crystal structure can be measured by synchrotron radiation XRD, for example. In particular, the sulfide solid electrolyte material of the second embodiment is preferably a single-phase material having the above crystal structure. This is because the ion conductivity can be made extremely high.

Incidentally, M _a element in the second embodiment, the M _b elements and other matters are the same as in the first embodiment described above, the description thereof is omitted here.

B. Battery Next, the battery of the present invention will be described. The battery of the present invention includes a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, an electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer, In which at least one of the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer contains the sulfide solid electrolyte material described above.

  According to the present invention, a high-power battery can be obtained by using the above-described sulfide solid electrolyte material.

FIG. 2 is a schematic cross-sectional view showing an example of the battery of the present invention. The battery 10 in FIG. 2 was formed between the positive electrode active material layer 1 containing the positive electrode active material, the negative electrode active material layer 2 containing the negative electrode active material, and the positive electrode active material layer 1 and the negative electrode active material layer 2. An electrolyte layer 3, a positive electrode current collector 4 for collecting current of the positive electrode active material layer 1, a negative electrode current collector 5 for collecting current of the negative electrode active material layer 2, and a battery case 6 for housing these members. It is what you have. In the present invention, at least one of the positive electrode active material layer 1, the negative electrode active material layer 2, and the electrolyte layer 3 contains the sulfide solid electrolyte material described in the above-mentioned “A. Sulfide solid electrolyte material”. And In particular, in the present invention, the sulfide solid electrolyte material contained in the negative electrode active material layer 2 or the electrolyte layer 3 is preferably in contact with the negative electrode active material. The above-mentioned sulfide solid electrolyte material has a low reduction potential, and has an advantage that the range of selection of usable negative electrode active materials is wider than when a sulfide solid electrolyte material not containing Si is used, and a negative electrode active material having a low operating potential This is because there is an advantage that the battery voltage increases by using.
Hereinafter, the battery of this invention is demonstrated for every structure.

1. Negative electrode active material layer The negative electrode active material layer in the present invention is a layer containing at least a negative electrode active material, and may contain at least one of a solid electrolyte material, a conductive material and a binder, if necessary. good. In particular, in the present invention, the negative electrode active material layer preferably contains a solid electrolyte material, and the solid electrolyte material is the sulfide solid electrolyte material described above. This is because the sulfide solid electrolyte material has a low reduction potential, and the range of selection of usable negative electrode active materials is wider than when a sulfide solid electrolyte material containing no Si is used. The ratio of the sulfide solid electrolyte material contained in the negative electrode active material layer varies depending on the type of the battery. For example, it is in the range of 0.1% by volume to 80% by volume, and in particular, 1% by volume to 60% by volume. It is preferable to be within the range, particularly within the range of 10% by volume to 50% by volume. 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, and soft carbon. In particular, in the present invention, the negative electrode active material layer contains the sulfide solid electrolyte material, and the operating potential of the negative electrode active material (potential at which Li ion insertion reaction occurs) is less than the reduction potential of the sulfide solid electrolyte material. Is preferably high.

  The negative electrode active material layer may further contain a conductive material. By adding a conductive material, the conductivity of the negative electrode active material layer can be improved. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. The negative electrode active material layer may contain a binder. Examples of the type of binder include fluorine-containing binders such as polyvinylidene fluoride (PVDF). Moreover, it is preferable that the thickness of a negative electrode active material layer exists in the range of 0.1 micrometer-1000 micrometers, for example.

2. Electrolyte layer The electrolyte layer in this invention is a layer formed between a positive electrode active material layer and a negative electrode active material layer. The electrolyte layer is not particularly limited as long as it is a layer capable of conducting ions, but is preferably a solid electrolyte layer made of a solid electrolyte material. This is because a battery with higher safety can be obtained as compared with a battery using an electrolytic solution. Furthermore, in this invention, it is preferable that a solid electrolyte layer contains the sulfide solid electrolyte material mentioned above. The ratio of the sulfide solid electrolyte material contained in the solid electrolyte layer is, for example, preferably in the range of 10% to 100% by volume, and more preferably in the range of 50% to 100% by volume. The thickness of the solid electrolyte layer is, for example, preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm. Moreover, as a formation method of a solid electrolyte layer, the method of compression-molding a solid electrolyte material etc. can be mentioned, for example.

Further, the electrolyte layer in the present invention may be a layer composed of an electrolytic solution. When the electrolytic solution is used, it is necessary to further consider safety compared to the case where the solid electrolyte layer is used, but a battery with higher output can be obtained. In this case, usually, at least one of the positive electrode active material layer and the negative electrode active material layer contains the above-described sulfide solid electrolyte material. The electrolytic solution usually contains a lithium salt and an organic solvent (nonaqueous solvent). Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , and LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC An organic lithium salt such as (CF ₃ SO ₂ ) ₃ can be used. Examples of the organic solvent include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), butylene carbonate (BC), and the like.

3. Positive electrode active material layer The positive electrode active material layer in the present invention is a layer containing at least a positive electrode active material, and may contain at least one of a solid electrolyte material, a conductive material and a binder, if necessary. good. In particular, in the present invention, the positive electrode active material layer preferably contains a solid electrolyte material, and the solid electrolyte material is preferably the sulfide solid electrolyte material described above. The ratio of the sulfide solid electrolyte material contained in the positive electrode active material layer varies depending on the type of the battery. For example, it is in the range of 0.1% by volume to 80% by volume, and in particular, 1% by volume to 60% by volume. It is preferable to be within the range, particularly within the range of 10% by volume to 50% by volume. As the 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 etc. can be mentioned. Note that the conductive material and the binder used in the positive electrode active material layer are the same as those in the negative electrode active material layer described above. Moreover, it is preferable that the thickness of a positive electrode active material layer exists in the range of 0.1 micrometer-1000 micrometers, for example.

4). Other Configurations The battery of the present invention has at least the negative electrode active material layer, the electrolyte layer, and the positive electrode active material layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material layer and a negative electrode current collector for collecting current of the negative electrode active material layer. Examples of the material for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, and carbon. In addition, the thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably appropriately selected according to the use of the battery. Moreover, the battery case of a general battery can be used for the battery case used for this invention. Examples of the battery case include a SUS battery case.

5. Battery The battery of the present invention may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery. Examples of the shape of the battery of the present invention include a coin type, a laminate type, a cylindrical type, and a square type. Moreover, the manufacturing method of the battery of this invention will not be specifically limited if it is a method which can obtain the battery mentioned above, The method similar to the manufacturing method of a general battery can be used. For example, when the battery of the present invention is an all-solid battery, as an example of the manufacturing method thereof, a material constituting the positive electrode active material layer, a material constituting the solid electrolyte layer, and a material constituting the negative electrode active material layer are sequentially provided. Examples of the method include producing a power generation element by pressing, housing the power generation element inside the battery case, and caulking the battery case.

C. Next, a method for producing a sulfide solid electrolyte material of the present invention will be described. The method for producing a sulfide solid electrolyte material of the present invention is a method for producing the sulfide solid electrolyte material described above, using a raw material composition containing the components of the sulfide solid electrolyte material, by mechanical milling, An ion conductive material synthesis step of synthesizing the amorphous ion conductive material, and a heating step of obtaining the sulfide solid electrolyte material by heating the amorphous ion conductive material. It is characterized by this.

  According to the present invention, a sulfide solid electrolyte having a high proportion of crystal phase having a peak near 2θ = 29.58 ° is obtained by performing amorphization in an ion conductive material synthesis step and then performing a heating step. Material can be obtained. Therefore, a sulfide solid electrolyte material having good ion conductivity can be obtained. Furthermore, since Si is contained, a sulfide solid electrolyte material having a low reduction potential can be obtained.

FIG. 3 is an explanatory view showing an example of a method for producing a sulfide solid electrolyte material of the present invention. In the method for producing a sulfide solid electrolyte material in FIG. 3, first, a raw material composition is prepared by mixing Li ₂ S, P ₂ S ₅ and SiS ₂ . At this time, in order to prevent the raw material composition from being deteriorated by moisture in the air, it is preferable to prepare the raw material composition in an inert gas atmosphere. Next, the raw material composition is ball milled to obtain an amorphous ion conductive material. Next, the amorphous ion conductive material is heated to improve the crystallinity, thereby obtaining a sulfide solid electrolyte material.

In the present invention, a sulfide solid electrolyte material having a high proportion of crystal phase having a peak around 2θ = 29.58 ° can be obtained. The reason will be described below. In the present invention, unlike the conventional solid phase method, which is a conventional synthesis method, an amorphous ion conductive material is synthesized once. As a result, the crystal phase A with high ion conductivity (crystal phase having a peak near 2θ = 29.58 °) is likely to precipitate, and the crystal phase A is positively precipitated by the subsequent heating step. It is considered that the value of I _B / I _A can be made less than 0.50, which was impossible in the past. The reason why the crystalline phase A is likely to precipitate due to the amorphization is not completely clear, but the solid solution region in the ion conductive material changes due to mechanical milling and the crystalline phase A is difficult to precipitate. There is a possibility that the environment has changed to an easy depositing environment.
Hereafter, the manufacturing method of the sulfide solid electrolyte material of this invention is demonstrated for every process.

1. Ion Conductive Material Synthesis Step First, the ion conductive material synthesis step in the present invention will be described. The ion conductive material synthesizing step in the present invention is a step of synthesizing an amorphous ion conductive material by mechanical milling using a raw material composition containing the components of the sulfide solid electrolyte material.

The raw material composition in the present invention contains at least Li element, Si element, P element and S element. Moreover, the raw material composition may contain the other element mentioned above. Examples of the compound containing Li element include a sulfide of Li. Specific examples of the sulfide of Li include Li ₂ S.

Examples of the compound containing Si element include Si simple substance, Si sulfide and the like. Specific examples of the sulfide of Si include SiS _{2 and the} like. Examples of the compound containing the P element include a simple substance of P and a sulfide of P. Specific examples of P sulfide include P ₂ S ₅ . Moreover, a simple substance and sulfide can be used also about the other element used for a raw material composition.

  Mechanical milling is a method of crushing a sample while applying mechanical energy. In the present invention, an amorphous ion conductive material is synthesized by applying mechanical energy to the raw material composition. Examples of such mechanical milling include a vibration mill, a ball mill, a turbo mill, a mechanofusion, a disk mill, and the like, and among them, a vibration mill and a ball mill are preferable.

  The conditions of the vibration mill are not particularly limited as long as an amorphous ion conductive material can be obtained. The vibration amplitude of the vibration mill is, for example, preferably in the range of 5 mm to 15 mm, and more preferably in the range of 6 mm to 10 mm. The vibration frequency of the vibration mill is, for example, preferably in the range of 500 rpm to 2000 rpm, and more preferably in the range of 1000 rpm to 1800 rpm. The filling rate of the sample of the vibration mill is, for example, preferably in the range of 1% by volume to 80% by volume, more preferably in the range of 5% by volume to 60% by volume, and particularly preferably in the range of 10% by volume to 50% by volume. Moreover, it is preferable to use a vibrator (for example, an alumina vibrator) for the vibration mill.

  The conditions of the ball mill are not particularly limited as long as an amorphous ion conductive material can be obtained. In general, the higher the number of rotations, the faster the production rate of the ion conductive material, and the longer the treatment time, the higher the conversion rate from the raw material composition to the ion conductive material. The rotation speed of the base plate when performing the planetary ball mill is preferably in the range of, for example, 200 rpm to 500 rpm, and more preferably in the range of 250 rpm to 400 rpm. Further, the treatment time when performing the planetary ball mill is preferably in the range of, for example, 1 hour to 100 hours, and more preferably in the range of 1 hour to 70 hours.

  In the present invention, it is preferable to synthesize an amorphous ion conductive material so that a crystal phase having a peak near 2θ = 29.58 ° is easily deposited.

2. Heating Step The heating step in the present invention is a step of obtaining the sulfide solid electrolyte material by heating the amorphous ion conductive material.

In the present invention, crystallinity is improved by heating the amorphous ion conductive material. By performing this heating, the crystal phase A having high ion conductivity (a crystal phase having a peak around 2θ = 29.58 °) can be positively precipitated, and the value of I _B / I _A is It could be less than 0.50, which was impossible.

  The heating temperature in the present invention is not particularly limited as long as it is a temperature at which a desired sulfide solid electrolyte material can be obtained. Crystal phase A (crystalline phase having a peak around 2θ = 29.58 °) It is preferable that the temperature is equal to or higher than the crystallization temperature. Specifically, the heating temperature is preferably 300 ° C. or higher, more preferably 350 ° C. or higher, further preferably 400 ° C. or higher, and particularly preferably 450 ° C. or higher. On the other hand, the heating temperature is preferably 1000 ° C. or less, more preferably 700 ° C. or less, further preferably 650 ° C. or less, and particularly preferably 600 ° C. or less. Moreover, it is preferable to adjust a heating time suitably so that a desired sulfide solid electrolyte material may be obtained. Moreover, it is preferable to perform the heating in this invention in inert gas atmosphere or a vacuum from a viewpoint of preventing oxidation. In addition, the sulfide solid electrolyte material obtained by the present invention is the same as the contents described in the above-mentioned “A. Sulfide solid electrolyte material”, and therefore description thereof is omitted here.

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

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1]
As starting materials, lithium sulfide (Li ₂ S, manufactured by Nippon Chemical Industry Co., Ltd.), diphosphorus pentasulfide (P ₂ S ₅ , manufactured by Aldrich Corporation), and silicon sulfide (SiS ₂ , manufactured by High Purity Chemical Co., Ltd.) were used. . These powders were mixed at a ratio shown in Table 1 below in a glove box under an argon atmosphere to obtain a raw material composition. Next, 1 g of the raw material composition was placed in a zirconia pot (45 ml) together with zirconia balls (10 mmφ, 10 pieces), and the pot was completely sealed (argon atmosphere). This pot was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling was performed at a base plate rotation speed of 370 rpm for 40 hours. Thereby, an amorphous ion conductive material was obtained.

Next, the obtained ion conductive material powder was placed in a carbon-coated quartz tube and vacuum-sealed. The pressure of the vacuum sealed quartz tube was about 80 Pa. Next, the quartz tube was placed in a firing furnace, heated from room temperature to 550 ° C. over 6 hours, maintained at 550 ° C. for 8 hours, and then gradually cooled to room temperature. Thereby, a sulfide solid electrolyte material having a composition of Li _3.5 Si _0.5 P _0.5 S ₄ was obtained. The above composition corresponds _to the composition of x = 0.5 in _{Li (4-x) Si (} 1-x) P x S 4.

[Examples 2 to 5, Comparative Examples 1 to 3]
A sulfide solid electrolyte material was obtained in the same manner as in Example 1 except that the ratio of the raw material composition was changed to the ratio shown in Table 1 below.

[Evaluation]
(X-ray diffraction measurement)
X-ray diffraction (XRD) measurement was performed using the sulfide solid electrolyte materials obtained in Examples 1 to 5 and Comparative Examples 1 to 3. XRD measurement was performed on the powder sample under an inert atmosphere and using CuKα rays. The results are shown in FIGS. As shown in FIG. 4A, in Example 1, the above-described peak of the crystal phase A appeared. On the other hand, in Example 1, the peak of 2θ = 27.33 ° ± 0.50 ° which is the peak of the crystal phase B having low ion conductivity was not confirmed (I _B / I _A = 0).

For even Examples 2-5 and Comparative Examples 1-3, similarly to determine the value of _I B / _{I A.} The results are shown in Table 2.

  As shown in Table 2, in Examples 1 to 3, the peak of the crystal phase B having low ion conductivity was not confirmed. In Examples 4 and 5, the peak of the crystal phase B having low ion conductivity was slightly confirmed. On the other hand, in Comparative Example 1, the crystal phase A with high ion conductivity was not confirmed, and in Comparative Example 2, only a few crystal phases A with high ion conductivity were confirmed. Further, in Comparative Example 3, a slight peak of the crystal phase B having low ion conductivity was confirmed.

(X-ray structural analysis)
The crystal structure of the sulfide solid electrolyte material obtained in Example 1 was identified by X-ray structural analysis. Based on the diffraction pattern obtained by XRD, a crystal system and a crystal group were determined by a direct method, and then a crystal structure was identified by a real space method. As a result, it was confirmed that the crystal structure as shown in FIG. That is, tetrahedron T ₁ (SiS ₄ tetrahedron and PS ₄ tetrahedron) and octahedron O (LiS ₆ octahedron) share a ridge, and tetrahedron T ₂ (SiS ₄ tetrahedron) and octahedron O (LiS ₆ octahedron) was a crystal structure sharing a vertex.

(Li ion conductivity measurement)
Li ion conductivity at 25 ° C. was measured using the sulfide solid electrolyte materials obtained in Examples 1 to 5 and Comparative Examples 1 to 3. First, 200 mg of the sulfide solid electrolyte material was weighed, placed in a cylinder made by Macor and pressed at a pressure of 4 ton / cm ² . Both ends of the obtained pellet were sandwiched between SUS pins, and restraint pressure was applied to the pellet by bolting to obtain an evaluation cell. With the evaluation cell kept at 25 ° C., Li ion conductivity was calculated by the AC impedance method. For the measurement, Solartron 1260 was used, and the applied voltage was 5 mV and the measurement frequency range was 0.01 to 1 MHz. The result is shown in FIG. As shown in FIG. 7, in Examples 1-5, Li ion conductivity higher than Comparative Examples 1 and 2 was shown. In Examples 1 to 5, Li ion conductivity equal to or higher than that of Comparative Example 3 was shown.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 2 ... Negative electrode active material layer 3 ... Electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode collector 6 ... Battery case 10 ... Battery

Claims (6)

Containing Li element, Si element, P element and S element,
Does not contain Ge element, Sn element and O element,
It has a peak at a position of 2θ = 29.58 ° ± 0.50 ° in X-ray diffraction measurement using CuKα ray,
Whether or not there is a peak at a position of 2θ = 27.33 ° ± 0.50 ° in X-ray diffraction measurement using CuKα ray,
If having a peak at the 2θ = 27.33 ° ± 0.50 °, the diffraction intensity of the peak of the 2θ = 29.58 ° ± 0.50 ° and _{I A,} the 2θ = 27.33 ° ± _A sulfide solid electrolyte material, wherein the value of I _B / I _A is less than 0.50 when the diffraction intensity of the peak at 0.50 ° is I _B. Has a octahedron O composed of Li element and S elements, a tetrahedron _{T 1} composed of _{M a} element and S elements, a tetrahedron _{T 2} composed of _{M b} element and S elements, wherein The tetrahedron T ₁ and the octahedron O share a ridge, and the tetrahedron T ₂ and the octahedron O mainly contain a crystal structure sharing a vertex,
At least one of the _{M a} element and the _{M b} element comprises a Si element,
At least one of the M _a element and the M _b element comprises a P element,
A sulfide solid electrolyte material characterized by not containing Ge element, Sn element and O element.   3. The sulfide solid electrolyte material according to claim 1, wherein a molar ratio of the P element to a total of the Si element and the P element is in a range of 0.5 to 0.7. . The sulfide solid electrolyte material is represented by Li _(4-x) Si _(1-x) P _x S ₄ (x satisfies 0.5 ≦ x ≦ 0.7). The sulfide solid electrolyte material according to any one of claims 1 to 3. A battery comprising a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and an electrolyte layer formed 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, the negative electrode active material layer, and the electrolyte layer contains the sulfide solid electrolyte material according to any one of claims 1 to 4. battery. A method for producing a sulfide solid electrolyte material according to any one of claims 1 to 4, comprising:
An ion conductive material synthesizing step of synthesizing an amorphous ion conductive material by mechanical milling using a raw material composition containing components of the sulfide solid electrolyte material;
A heating step of obtaining the sulfide solid electrolyte material by heating the amorphous ion conductive material;
A method for producing a sulfide solid electrolyte material, comprising: