JP2014089971A - Sulfide solid electrolytic material, lithium solid battery, and manufacturing method of sulfide solid electrolytic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfide solid electrolytic material having a high Li-ion conductivity chiefly.SOLUTION: To solve the problem, a sulfide solid electrolytic material is provided, which is composed of a glass ceramic, and comprises Li, A (A is at least one of P, Si, Ge, Al and B), X (X is halogen), and S. The sulfide solid electrolytic material has peaks at 2θ=20.2° and 23.6° in X-ray diffraction measurement with Cu Kα rays.

Description

  The present invention relates to a sulfide solid electrolyte material having high Li 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. Furthermore, a sulfide solid electrolyte material is known as a solid electrolyte material used for such a solid electrolyte layer.

Since the sulfide solid electrolyte material has high Li ion conductivity, it is useful for increasing the output of the battery, and various studies have been made heretofore. For example, Non-Patent Document 1 discloses a LiI—Li ₂ S—P ₂ S ₅ -based amorphous material obtained by a mechanical milling method. Non-Patent Document 2 discloses a crystalline material represented by Li ₆ PS ₅ X (X = Cl, Br, I).

Naoko Torui and two others, “Synthesis of LiI-Li2S-P2S5 Amorphous Material by Mechanical Milling Method and Its Lithium Ion Conduction Properties”, Abstracts of Solid State Ionics Conference, Vol. 23, p. Issued 26-27, 2003 F. Stader et al., “Crystalline halide substituted Li-argyrodites as solid electrolyte for lithium ion batteries”, 216th ECS (The Electrochemical Society) Meeting with EuroCVD 17 and SOFC XI-11th International Symposium On Solid Oxide Fuel Cells, 2009, http : //www.electrochem.org/meetings/scheduler/abstracts/216/0590.pdf

  Conventionally, a sulfide solid electrolyte material having high Li ion conductivity has been demanded. This invention is made | formed in view of the said situation, and makes it a main objective to provide the sulfide solid electrolyte material with high Li ion conductivity.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, when LiX-doped sulfide glass is subjected to heat treatment to synthesize glass ceramics, there is a limited LiX addition range and heat treatment temperature range. The inventors found that glass ceramics with extremely high Li ion conductivity can be obtained. Furthermore, it has also been found that the reason why the Li ion conductivity is increased is due to a novel crystal phase that has not been known so far. The present invention has been made based on these findings.

  That is, in the present invention, Li, A (A is at least one of P, Si, Ge, Al and B), X (X is halogen), S, glass ceramics, CuKα Provided is a sulfide solid electrolyte material characterized by having peaks at 2θ = 20.2 ° and 23.6 ° in X-ray diffraction measurement using a line.

  According to the present invention, since it has a specific peak in X-ray diffraction measurement, a sulfide solid electrolyte material having high Li ion conductivity can be obtained.

  In the above invention, the sulfide solid electrolyte material is an ion conductor having Li, A (A is at least one of P, Si, Ge, Al and B), and S, and LiX (X is a halogen). It is preferable that it is comprised from these.

  In the said invention, it is preferable that the ratio of the said LiX is more than 14 mol% and less than 30 mol%.

  In the said invention, it is preferable that the said ion conductor has an ortho composition. This is because a sulfide solid electrolyte material having high chemical stability can be obtained.

  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 a solid electrolyte formed between the positive electrode active material layer and the negative electrode active material layer A lithium solid state battery, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains the sulfide solid electrolyte material described above. Provide batteries.

  According to the present invention, a lithium solid battery having high Li ion conductivity can be obtained by using the sulfide solid electrolyte material described above. As a result, the output of the battery can be increased.

In the present invention, a raw material composition containing a sulfide of Li ₂ S, A (A is at least one of P, Si, Ge, Al, and B), and LiX (X is halogen) In the amorphization step of synthesizing the sulfide glass and heating the sulfide glass at a temperature equal to or higher than the crystallization temperature and measuring 2θ = 20.2 in the X-ray diffraction measurement using CuKα rays. And a heat treatment step of synthesizing the glass ceramic having a peak at 23.6 °, and the glass ceramic obtains the proportion of the LiX contained in the raw material composition and the heat treatment temperature in the heat treatment step. And a method for producing a sulfide solid electrolyte material, characterized by being adjusted as described above.

  According to the present invention, a sulfide solid electrolyte material having high Li ion conductivity can be obtained by adjusting the ratio of LiX contained in the raw material composition and the heat treatment temperature in the heat treatment step.

  In the said invention, the ratio of the said LiX contained in the said raw material composition is a ratio which can synthesize | combine the said glass ceramic within the range of 14 mol%-30 mol% or its vicinity, The heat processing temperature in the said heat processing process Is preferably a temperature at which the glass ceramic can be synthesized at around 200 ° C.

  In the said invention, it is preferable that the ratio of the said LiX contained in the said raw material composition is less than 30 mol% more than 14 mol%, and the heat processing temperature in the said heat processing process is less than 200 degreeC.

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

It is a schematic sectional drawing which shows an example of the lithium solid battery of this invention. It is a flowchart which shows an example of the manufacturing method of the sulfide solid electrolyte material of this invention. It is a result of the X-ray diffraction measurement with respect to the glass ceramic obtained in Examples 1-5. It is a result of the X-ray diffraction measurement with respect to the glass ceramic obtained by Comparative Examples 2-4. It is a measurement result of Li ion conductivity with respect to the sample obtained in Examples 1-5 and Comparative Examples 1-9. It is a result of the X-ray diffraction measurement with respect to the glass ceramics obtained in Examples 6 to 8 and Comparative Example 11. It is a measurement result of Li ion conductivity with respect to the sample obtained in Examples 6-8 and Comparative Examples 10 and 11.

  Hereinafter, the sulfide solid electrolyte material, the lithium solid battery, and the method for producing the sulfide solid electrolyte material 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 comprises Li, A (A is at least one of P, Si, Ge, Al and B), X (X is a halogen), S, and glass ceramics. In addition, X-ray diffraction measurement using CuKα rays has a peak at 2θ = 20.2 ° and 23.6 °.

  According to the present invention, since it has a specific peak in X-ray diffraction measurement, a sulfide solid electrolyte material having high Li ion conductivity can be obtained. This peak is a peak of a new crystal phase that has not been known so far, and since the Li ion conductivity of the new crystal phase is high, the Li ion conductivity of the sulfide solid electrolyte material is improved.

Further, since the sulfide solid electrolyte material of the present invention is a glass ceramic, it has an advantage of higher heat resistance than sulfide glass. For example, Li ion conductivity can be made higher by doping LiI into Li ₂ S—P ₂ S ₅ based sulfide glass. However, when LiI is doped, the crystallization temperature of sulfide glass may decrease. When a sulfide glass having a low crystallization temperature is used in, for example, a battery, there is a problem that heat is generated due to the crystallization of the sulfide glass when the battery temperature reaches or exceeds the crystallization temperature of the sulfide glass. As a result, there is a problem that each material constituting the battery is deteriorated (deteriorated) or the battery case or the like is damaged. On the other hand, according to the present invention, it is possible to obtain a sulfide solid electrolyte material in which the adverse effect of heat generation due to crystallization is prevented by using glass ceramics crystallized in advance. Further, there is an advantage that the battery cooling mechanism and the safety mechanism can be simplified.

Further, in Non-Patent Document _{1, LiI-Li 2 S-} P 2 S 5 based amorphous material obtained by mechanical milling method is disclosed. However, Non-Patent Document 1 does not describe or suggest that heat treatment is performed on LiI—Li ₂ S—P ₂ S ₅ -based sulfide glass. Further, even if the heat treatment is performed on the _{LiI-Li 2 S-P 2} S 5 based sulfide glass, in order to precipitate the novel crystal phase you may need to adjust the rate and heat treatment temperature of LiI Non-Patent Document 1 does not suggest that point at all. On the other hand, Non-Patent Document 2 discloses a crystalline material represented by Li ₆ PS ₅ X (X = Cl, Br, I). By adding I, Li ions of the crystalline material are disclosed. The results show that the conductivity decreases, and it is suggested that the addition of halogen does not simply improve the Li ion conductivity in crystals (glass ceramics).

  One feature of the sulfide solid electrolyte material of the present invention is that it is a glass ceramic. The glass ceramic in the present invention refers to a material obtained by crystallizing sulfide glass. Whether it is glass ceramics can be confirmed by, for example, an X-ray diffraction method. The sulfide glass is a material synthesized by amorphizing the raw material composition, and not only a strict “glass” in which periodicity as a crystal is not observed in X-ray diffraction measurement or the like, but also mechanical milling described later. It means all materials synthesized by making them amorphous. Therefore, even in the case where, for example, a peak derived from a raw material (LiI or the like) is observed in X-ray diffraction measurement or the like, any material synthesized by amorphization corresponds to sulfide glass.

  One feature of the sulfide solid electrolyte material of the present invention is that it has peaks at 2θ = 20.2 ° and 23.6 ° in X-ray diffraction measurement using CuKα rays. This peak is a peak of a new crystal phase that has not been known so far, and is a peak of a crystal phase having high Li ion conductivity. This crystal phase may be referred to as a high Li ion conductive crystal phase. Here, the peak at 2θ = 20.2 ° means not only a strict peak at 2θ = 20.2 ° but also a peak within a range of 2θ = 20.2 ° ± 0.5 °. Depending on the crystal state, the position of the peak may slightly move back and forth, so it is defined as above. Similarly, the peak at 2θ = 23.6 ° is not only a strict peak at 2θ = 23.6 °, but also a peak within a range of 2θ = 23.6 ° ± 0.5 °. The sulfide solid electrolyte material of the present invention preferably has a high Li ion conductive crystal phase as a main component. Specifically, the ratio of the high Li ion conductive crystal phase in the total crystal phase is 50 mol% or more. Is preferred.

  On the other hand, the sulfide solid electrolyte material of the present invention may have peaks at 2θ = 21.0 ° and 28.0 ° in X-ray diffraction measurement using CuKα rays. This peak has been clarified by the inventors' previous studies, and is a peak of a new crystal phase that has not been known so far, as described above. It is a peak of a crystalline phase with low properties. This crystal phase may be referred to as a low Li ion conductive crystal phase. Here, the peak at 2θ = 21.0 ° means not only a strict peak at 2θ = 21.0 ° but also a peak within a range of 2θ = 21.0 ° ± 0.5 °. Depending on the crystal state, the position of the peak may slightly move back and forth, so it is defined as above. Similarly, the peak at 2θ = 28.0 ° is not only a strict peak at 2θ = 28.0 ° but also a peak within a range of 2θ = 28.0 ° ± 0.5 °. The sulfide solid electrolyte material of the present invention preferably has a low proportion of low Li ion conductive crystal phase.

Moreover, it can be judged from the result of X-ray diffraction measurement that the sulfide solid electrolyte material of the present invention has a specific peak. On the other hand, for example, when the ratio of the high Li ion conductive crystal phase is small and the ratio of the low Li ion conductive crystal phase is large, the peaks at 2θ = 20.2 ° and 23.6 ° appear small, and 2θ = 221. 0 ° and 28.0 ° appear greatly. Here, the peak intensity at 2θ = 20.2 ° with respect to the peak intensity at 2θ = 21.0 ° is I _20.2 / I _21.0, and 2θ = 23.6 with respect to the peak intensity at 2θ = 21.0 °. The peak intensity at ° is I _23.6 / I _21.0 . The sulfide solid electrolyte material of the present invention has peaks at 2θ = 20.2 ° and 23.6 °, indicating that I _20.2 / I _21.0 and I _23.6 / I _21.0 are 0 respectively. .1 or more (preferably 0.2 or more). In the present invention, I _20.2 / I _21.0 is preferably 1 or more. It is because it can be set as the sulfide solid electrolyte material with many ratios of a high Li ion conductive crystal phase.

  The sulfide solid electrolyte material of the present invention has Li, A (A is at least one of P, Si, Ge, Al and B), X (X is halogen), and S. On the other hand, as described above, the sulfide solid electrolyte material of the present invention has a specific peak in the X-ray diffraction measurement. Here, the X-ray diffraction measurement is a technique for identifying the atomic arrangement inside the crystal by analyzing the X-ray diffraction result by the crystal lattice. Therefore, in principle, the peak pattern in the X-ray diffraction measurement depends on the crystal structure, but does not greatly depend on the type of atoms constituting the crystal structure. Therefore, the same pattern can be obtained if the same crystal structure is formed regardless of the types of A and X. That is, regardless of the types of A and X, the same pattern can be obtained if a high Li ion conductive crystal phase is formed. Note that the position of this pattern may slightly move back and forth. From this point, it is preferable to define the peaks at 2θ = 20.2 ° and 23.6 ° within a range of ± 0.5 °. .

  In addition, the sulfide solid electrolyte material of the present invention includes Li, A (A is at least one of P, Si, Ge, Al, and B), and S, LiX (X is halogen). Preferably). At least a part of LiX usually exists in a state of being incorporated into the structure of the ionic conductor as a LiX component.

The ion conductor in the present invention has Li, A (A is at least one of P, Si, Ge, Al and B), and S. The ionic conductor is not particularly limited as long as it has Li, A, and S. Among them, it is preferable to have an ortho composition. This is because a sulfide solid electrolyte material having high chemical stability can be obtained. Here, ortho generally refers to one having the highest degree of hydration among oxo acids obtained by hydrating the same oxide. In the present invention, the crystal composition in which Li ₂ S is added most in the sulfide is called the ortho composition. For example, Li ₃ PS ₄ corresponds to the ortho composition in the Li ₂ S—P ₂ S ₅ system, Li ₃ AlS ₃ corresponds to the ortho composition in the Li ₂ S—Al ₂ S ₃ system, and Li ₂ S—B _2. In the S ₃ system, Li ₃ BS ₃ corresponds to the ortho composition, in the Li ₂ S—SiS ₂ system, Li ₄ SiS ₄ corresponds to the ortho composition, and in the Li ₂ S—GeS ₂ system, Li ₄ GeS _{4 corresponds} to the ortho composition. Applicable.

In the present invention, “having an ortho composition” includes not only a strict ortho composition but also a composition in the vicinity thereof. Specifically, the main component is an anion structure having an ortho composition (PS ₄ ³⁻ structure, SiS ₄ ⁴⁻ structure, GeS ₄ ⁴⁻ structure, AlS ₃ ³⁻ structure, BS ₃ ³⁻ structure). The ratio of the anion structure of the ortho composition is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, based on the total anion structure in the ion conductor, 90 mol % Or more is particularly preferable. The ratio of the anion structure of the ortho composition can be determined by Raman spectroscopy, NMR, XPS, or the like.

Further, the sulfide solid electrolyte material of the present invention includes Li ₂ S, A (A is at least one of P, Si, Ge, Al and B), and LiX (X is halogen). It is preferable that the raw material composition containing the above is made amorphous and further heat-treated.

Li ₂ S contained in the raw material composition preferably has few impurities. This is because side reactions can be suppressed. Examples of the method for synthesizing Li ₂ S include the method described in JP-A-7-330312. Furthermore, Li ₂ S is preferably purified using the method described in WO2005 / 040039. On the other hand, examples of the sulfide A contained in the raw material composition include P ₂ S ₃ , P ₂ S ₅ , SiS ₂ , GeS ₂ , Al ₂ S ₃ , and B ₂ S ₃ .

Also, the sulfide solid electrolyte material is preferably substantially free of Li 2 _S. It is because it can be set as the sulfide solid electrolyte material with little hydrogen sulfide generation amount. Li ₂ S reacts with water to generate hydrogen sulfide. For example, when the proportion of Li ₂ S contained in the raw material composition is large, Li ₂ S tends to remain. “Substantially free of Li ₂ S” can be confirmed by X-ray diffraction. Specifically, when it does not have a Li ₂ S peak (2θ = 27.0 °, 31.2 °, 44.8 °, 53.1 °), it is determined that it does not substantially contain Li ₂ S. can do.

Moreover, it is preferable that the said sulfide solid electrolyte material does not contain bridge | crosslinking sulfur substantially. It is because it can be set as the sulfide solid electrolyte material with little hydrogen sulfide generation amount. “Bridged sulfur” refers to bridged sulfur in a compound obtained by reacting Li ₂ S with the sulfide of A described above. For example, Li ₂ S and _P 2 _{S 5} is bridging sulfur reactions to become _{S 3} PS-PS 3 structure corresponds. Such bridging sulfur easily reacts with water and easily generates hydrogen sulfide. Furthermore, “substantially free of bridging sulfur” can be confirmed by measurement of a Raman spectrum. For example, in the case of a Li ₂ S—P ₂ S ₅ sulfide solid electrolyte material, the peak of the S ₃ P—S—PS ₃ structure usually appears at 402 cm ⁻¹ . Therefore, it is preferable that this peak is not detected. Moreover, the peak of PS ₄ ³⁻ structure usually appears at 417 cm ⁻¹ . In the present invention, the intensity _{I 402} at 402 cm ^-1 is preferably smaller than the intensity _{I 417} at 417 cm ^-1. More specifically, the strength I ₄₀₂ is preferably 70% or less, more preferably 50% or less, and even more preferably 35% or less with respect to the strength I ₄₁₇ . As for the sulfide solid electrolyte material other than Li 2 _{S-P 2} S ₅ based, to identify the unit containing the crosslinking sulfur, by measuring the peak of the unit, are substantially free of bridging sulfur It can be judged that there is no.

In the case of a Li ₂ S—P ₂ S ₅ -based sulfide solid electrolyte material, the ratio of Li ₂ S and P ₂ S ₅ to obtain the ortho composition is Li ₂ S: P ₂ S ₅ = 75 on a molar basis. : 25. The same applies to the Li ₂ S—Al ₂ S ₃ -based sulfide solid electrolyte material and the Li ₂ S—B ₂ S ₃ -based sulfide solid electrolyte material. On the other hand, in the case of a Li ₂ S—SiS ₂ -based sulfide solid electrolyte material, the ratio of Li ₂ S and SiS ₂ to obtain the ortho composition is Li ₂ S: SiS ₂ = 66.7: 33.3 on a molar basis. It is. The same applies to the case of a Li ₂ S—GeS ₂ -based sulfide solid electrolyte material.

The raw material composition is, when containing Li ₂ S and _P 2 _{S 5,} the proportion of Li ₂ S to the total of Li ₂ S and _P 2 _{S 5} is preferably in the range of 70 mol% 80 mol% 72 mol% to 78 mol% is more preferable, and 74 mol% to 76 mol% is more preferable. Incidentally, the raw material composition is, when containing Li ₂ S and _Al 2 _{S 3,} which is the same when containing Li ₂ S and _B 2 _{S 3.} On the other hand, the raw material composition is, when containing Li ₂ S and SiS _2, the ratio of Li ₂ S to the total of Li ₂ S and SiS ₂ is in the range of 62.5mol% ~70.9mol% Is preferable, it is more preferable that it is in the range of 63 mol% to 70 mol%, and it is more preferable that it is in the range of 64 mol% to 68 mol%. The same applies when the raw material composition contains Li ₂ S and GeS ₂ .

  X in LiX is halogen, and specific examples thereof include F, Cl, Br, and I. Among these, Cl, Br, and I are preferable. This is because a sulfide solid electrolyte material having high ion conductivity can be obtained. Further, the ratio of LiX in the sulfide solid electrolyte material of the present invention is not particularly limited as long as it is a ratio capable of synthesizing a desired glass ceramic. % To 25 mol% is more preferable.

Examples of the shape of the sulfide solid electrolyte material of the present invention include particles. The average particle diameter (D ₅₀ ) of the particulate sulfide solid electrolyte material is preferably in the range of 0.1 μm to ₅₀ μm, for example. The sulfide solid electrolyte material preferably has high Li ion conductivity, and the Li ion conductivity at room temperature is preferably 1 × 10 ⁻⁴ S / cm or more, for example, 1 × 10 ⁻³ S. / Cm or more is more preferable.

  The sulfide solid electrolyte material of the present invention can be used for any application that requires Li ion conductivity. Especially, it is preferable that the said sulfide solid electrolyte material is what is used for a battery.

B. Next, the lithium solid state battery of the present invention will be described. The lithium solid state 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, and a solid formed between the positive electrode active material layer and the negative electrode active material layer. A lithium solid state battery having an electrolyte layer, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains the sulfide solid electrolyte material described above It is.

  According to the present invention, a lithium solid battery having high Li ion conductivity can be obtained by using the sulfide solid electrolyte material described above. As a result, the output of the battery can be increased.

FIG. 1 is a schematic cross-sectional view showing an example of a lithium solid state battery of the present invention. A lithium solid battery 10 shown in FIG. 1 includes 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 between the positive electrode active material layer 1 and the negative electrode active material layer 2. A positive electrode current collector 4 that collects current from the positive electrode active material layer 1, and a negative electrode current collector 5 that collects current from the negative electrode active material layer 2. In the present invention, it is significant 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 sulfide solid electrolyte material described in "A. Sulfide solid electrolyte material". Features.
Hereinafter, the lithium solid state battery of the present invention will be described for each configuration.

1. First, the positive electrode active material layer in the present invention will be described. The positive electrode active material layer in the present invention is a layer containing at least a positive electrode active material, and may further contain at least one of a solid electrolyte material, a conductive material and a binder as necessary.

  In the present invention, the solid electrolyte material contained in the positive electrode active material layer is preferably the sulfide solid electrolyte material described in the above “A. Sulfide solid electrolyte material”. The content of the sulfide solid electrolyte material in the positive electrode active material layer is, for example, in the range of 0.1% by volume to 80% by volume, especially in the range of 1% by volume to 60% by volume, in particular, 10% by volume to It is preferably within the range of 50% by volume.

As the positive electrode active material, is not particularly limited, for _{example, LiCoO 2, LiMnO 2, LiNiO} 2, LiVO 2, LiNi 1/3 Co 1/3 Mn 1/3 rock salt layered type active material such as _{O 2} And spinel type active materials such as LiMn ₂ O ₄ and Li (Ni _0.5 Mn _1.5 ) O ₄ , and olivine type active materials such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , and LiCuPO ₄ . Si-containing oxides such as Li ₂ FeSiO ₄ and Li ₂ MnSiO ₄ may be used as the positive electrode active material.

  In particular, when the above-described sulfide solid electrolyte material has an ionic conductor having an ortho composition and uses LiI, the positive electrode active material has a potential of 2.8 V (vs Li) or higher. Preferably, it has a potential of 3.0 V (vs Li) or higher. It is because the oxidative decomposition of LiI can be effectively suppressed. Conventionally, since LiI was considered to decompose near 2.8 V, a sulfide solid electrolyte material having LiI has not been used for the positive electrode active material layer. On the other hand, since the above-described sulfide solid electrolyte material has an ionic conductor having an ortho composition, it is considered that LiI is stabilized by interaction with the ionic conductor and oxidative decomposition of LiI can be suppressed.

  Examples of the shape of the positive electrode active material include a particle shape, and among them, a spherical shape or an elliptical shape is preferable. Moreover, when a positive electrode active material is a particle shape, it is preferable that the average particle diameter exists in the range of 0.1 micrometer-50 micrometers, for example. Further, the content of the positive electrode active material in the positive electrode active material layer is, for example, preferably in the range of 10% by volume to 99% by volume, and more preferably in the range of 20% by volume to 99% by volume.

  The positive electrode active material layer in the present invention may further contain at least one of a conductive material and a binder in addition to the positive electrode active material and the solid electrolyte material. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. Examples of the binder include fluorine-containing binders such as PTFE and PVDF. The thickness of the positive electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

2. Next, the negative electrode active material layer in the present invention will be described. The negative electrode active material layer in the present invention is a layer containing at least a negative electrode active material, and may further contain at least one of a solid electrolyte material, a conductive material, and a binder as necessary.

  In the present invention, the solid electrolyte material contained in the negative electrode active material layer is preferably the sulfide solid electrolyte material described in the above “A. Sulfide solid electrolyte material”. The content of the sulfide solid electrolyte material in the negative electrode active material layer is, for example, in the range of 0.1% by volume to 80% by volume, especially in the range of 1% by volume to 60% by volume, in particular, 10% by volume to It is preferably within the range of 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. Further, the content of the negative electrode active material in the negative electrode active material layer is, for example, preferably in the range of 10% by volume to 99% by volume, and more preferably in the range of 20% by volume to 99% by volume. The conductive material and the binder are the same as those used for the positive electrode active material layer described above. The thickness of the negative electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

3. Next, the solid electrolyte layer in the present invention will be described. The solid electrolyte layer in the present invention is a layer formed between the positive electrode active material layer and the negative electrode active material layer, and is a layer composed of a solid electrolyte material. The solid electrolyte material contained in the solid electrolyte layer is not particularly limited as long as it has Li ion conductivity.

  In the present invention, the solid electrolyte material contained in the solid electrolyte layer is preferably the sulfide solid electrolyte material described in the above “A. Sulfide solid electrolyte material”. The content of the sulfide solid electrolyte material in the solid electrolyte layer is not particularly limited as long as a desired insulating property can be obtained. For example, within the range of 10% by volume to 100% by volume, It is preferably within the range of 50% to 100% by volume. In particular, in the present invention, it is preferable that the solid electrolyte layer is composed only of the sulfide solid electrolyte material.

  The solid electrolyte layer may contain a binder. This is because a solid electrolyte layer having flexibility can be obtained by containing a binder. Examples of the binder include fluorine-containing binders such as PTFE and PVDF. 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.

4). Other Configurations The lithium solid state battery of the present invention has at least the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte 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. Among them, SUS is preferable. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, and carbon. Among them, SUS is preferable. 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 lithium solid state battery. Moreover, the battery case of a general lithium solid battery can be used for the battery case used for this invention. Examples of the battery case include a SUS battery case.

5. Lithium solid battery The lithium solid battery of the present invention may be a primary battery or a secondary battery, and among these, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as a vehicle-mounted battery. Examples of the shape of the lithium solid state 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 lithium solid state battery of the present invention is not particularly limited as long as it is a method capable of obtaining the above-described lithium solid state battery, and the same method as a general lithium solid state battery manufacturing method is used. be able to. As an example of a method for producing a lithium solid state battery, a power generation element is manufactured by sequentially pressing 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, A method of storing the power generation element in the battery case and caulking the battery case can be exemplified.

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 includes a sulfide of Li ₂ S, A (A is at least one of P, Si, Ge, Al and B), and LiX (X is a halogen). In an amorphization step of amorphizing a raw material composition containing sulphide and synthesizing a sulfide glass, and heating the sulfide glass at a temperature equal to or higher than a crystallization temperature, and measuring X-ray diffraction using CuKα rays A heat treatment step of synthesizing a glass ceramic having a peak at 2θ = 20.2 ° and 23.6 °, and a ratio of the LiX contained in the raw material composition and a heat treatment temperature in the heat treatment step. The glass ceramics are adjusted so as to obtain the above-mentioned glass ceramics.

FIG. 2 is a flowchart showing an example of a method for producing a sulfide solid electrolyte material of the present invention. In FIG. 2, first, a raw material composition containing LiI, Li ₂ S and P ₂ S ₅ is prepared. Next, by performing mechanical milling on the raw material composition, an ion conductor (for example, Li ₃ PS ₄ ) having Li, P, and S and a sulfide glass having LiI are synthesized. Next, the sulfide glass is heat-treated at a temperature equal to or higher than the crystallization temperature, and glass ceramics (sulfide solids) having peaks at 2θ = 20.2 ° and 23.6 ° in X-ray diffraction measurement using CuKα rays. An electrolyte material is obtained.

According to the present invention, a sulfide solid electrolyte material having high Li ion conductivity can be obtained by adjusting the ratio of LiX contained in the raw material composition and the heat treatment temperature in the heat treatment step.
Hereafter, the manufacturing method of the sulfide solid electrolyte material of this invention is demonstrated for every process.

1. Amorphization process The amorphization process in the present invention includes a sulfide of Li ₂ S, A (A is at least one of P, Si, Ge, Al, and B), and LiX (X is a halogen). A raw material composition containing (a) is made amorphous to synthesize a sulfide glass.

Regarding the sulfide of Li ₂ S, A (A is at least one of P, Si, Ge, Al and B) and LiX (X is halogen) in the raw material composition, the above-mentioned “A. sulfide” Since it is the same as the content described in "Solid electrolyte material", description here is abbreviate | omitted. The proportion of LiX in the raw material composition is not particularly limited as long as a desired glass ceramic can be synthesized, and is slightly different depending on the synthesis conditions. The ratio of LiX in the raw material composition is preferably such a ratio that the glass ceramic can be synthesized within the range of 14 mol% to 30 mol% or in the vicinity thereof. Note that, in the conditions of Examples described later, a desired glass ceramic was obtained when the LiX ratio was more than 14 mol% and less than 30 mol%.

  Examples of the method for amorphizing the raw material composition include mechanical milling and melt quenching, and mechanical milling is preferable among them. This is because processing at room temperature is possible, and the manufacturing process can be simplified. In addition, although the melt quench method has limitations on the reaction atmosphere and reaction vessel, mechanical milling has an advantage that a sulfide glass having a desired composition can be easily synthesized. The mechanical milling may be dry mechanical milling or wet mechanical milling, but the latter is preferred. This is because the raw material composition can be prevented from adhering to the wall surface of a container or the like, and a more amorphous sulfide glass can be obtained.

  Mechanical milling is not particularly limited as long as the raw material composition is mixed while applying mechanical energy, and examples thereof include a ball mill, a vibration mill, a turbo mill, a mechanofusion, and a disk mill. Among these, a ball mill is preferable, and a planetary ball mill is particularly preferable. This is because the desired sulfide glass can be obtained efficiently.

Various conditions of mechanical milling are set so that a desired sulfide glass can be obtained. For example, when a planetary ball mill is used, the raw material composition and grinding balls are added to the container, and the treatment is performed at a predetermined rotation speed and time. In general, the larger the number of revolutions, the faster the generation rate of sulfide glass, and the longer the treatment time, the higher the conversion rate from the raw material composition to sulfide glass. 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 1 hour to 100 hours, and more preferably in the range of 1 hour to 50 hours. Examples of the material for the container and ball for grinding used in the ball mill include ZrO ₂ and Al ₂ O ₃ . Moreover, the diameter of the ball for grinding | pulverization exists in the range of 1 mm-20 mm, for example.

  The liquid used for wet mechanical milling preferably has a property of not generating hydrogen sulfide by the reaction with the raw material composition. Hydrogen sulfide is generated when protons dissociated from liquid molecules react with the raw material composition or sulfide glass. Therefore, it is preferable that the liquid has an aprotic property that does not generate hydrogen sulfide. In addition, aprotic liquids can be broadly classified into polar aprotic liquids and nonpolar aprotic liquids.

  Although it does not specifically limit as a polar aprotic liquid, For example, Ketones, such as acetone; Nitriles, such as acetonitrile; Amides, such as N, N- dimethylformamide (DMF); Dimethyl sulfoxide (DMSO) And the like.

  An example of a nonpolar aprotic liquid is alkane that is liquid at room temperature (25 ° C.). The alkane may be a chain alkane or a cyclic alkane. The chain alkane preferably has, for example, 5 or more carbon atoms. On the other hand, the upper limit of the carbon number of the chain alkane is not particularly limited as long as it is liquid at room temperature. Specific examples of the chain alkane include pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, and paraffin. The chain alkane may have a branch. On the other hand, specific examples of the cyclic alkane include cyclopentane, cyclohexane, cycloheptane, cyclooctane, and cycloparaffin.

  Other examples of nonpolar aprotic liquids include aromatic hydrocarbons such as benzene, toluene and xylene; chain ethers such as diethyl ether and dimethyl ether; cyclic ethers such as tetrohydrofuran; chloroform Alkyl halides such as methyl chloride and methylene chloride; esters such as ethyl acetate; fluorinated benzene, heptane fluoride, 2,3-dihydroperfluoropentane, 1,1,2,2,3,3 Fluorine compounds such as 4-heptafluorocyclopentane can be exemplified. In addition, the addition amount of the said liquid is not specifically limited, What is necessary is just a quantity which can obtain a desired sulfide solid electrolyte material.

2. Next, the heat treatment process in the present invention will be described. In the heat treatment step of the present invention, the above-mentioned sulfide glass is heated at a temperature higher than the crystallization temperature, and glass ceramics having peaks at 2θ = 20.2 ° and 23.6 ° in X-ray diffraction measurement using CuKα rays. Is a step of synthesizing.

  The heat treatment temperature is usually higher than the crystallization temperature of sulfide glass. In addition, the crystallization temperature of sulfide glass can be determined by differential thermal analysis (DTA). The heat treatment temperature is not particularly limited as long as the temperature is equal to or higher than the crystallization temperature, but is preferably 160 ° C. or higher, for example. On the other hand, the upper limit of the heat treatment temperature is not particularly limited as long as it is a temperature at which a desired glass ceramic can be synthesized, and is slightly different depending on the composition of the sulfide glass. The upper limit of the heat treatment temperature is usually a temperature at which the glass ceramic can be synthesized at around 200 ° C. Note that, under the conditions of the examples described later, a desired glass ceramic was obtained when the heat treatment temperature was less than 200 ° C.

  The heat treatment time is not particularly limited as long as the desired glass ceramic can be obtained. For example, the heat treatment time is preferably in the range of 1 minute to 24 hours. The heat treatment is preferably performed in an inert gas atmosphere (for example, an Ar gas atmosphere). It is because deterioration (for example, oxidation) of glass ceramics can be prevented. The method for the heat treatment is not particularly limited, and examples thereof include a method using a firing furnace.

  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. Unless otherwise specified, each operation such as weighing, synthesis, and drying was performed in an Ar atmosphere.

[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) and lithium iodide (LiI, manufactured by Aldrich) were used. Next, Li ₂ S and P ₂ S ₅ were weighed so as to have a molar ratio of 75Li ₂ S · 25P ₂ S ₅ (Li ₃ PS ₄ , ortho composition). Next, LiI was weighed so that the LiI ratio was 14 mol%. The weighed starting materials were mixed in an agate mortar for 5 minutes, 2 g of the mixture was put into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (moisture content of 30 ppm or less, 4 g) was added, and ZrO _{2 was} further added. A ball (φ = 5 mm, 53 g) was charged, and the container was completely sealed. This container was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling was performed for 40 hours at a base plate rotation speed of 500 rpm. Then, heptane was removed by drying at 100 ° C. to obtain a sulfide glass.

0.5 g of the obtained sulfide glass was placed in a glass tube, and the glass tube was placed in a SUS sealed container. The sealed container was heat-treated at 190 ° C. for 10 hours to obtain glass ceramics. The molar composition of the obtained glass ceramic corresponds to x = 14 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ).

[Examples 2 to 5]
The ratio of LiI was changed to x = 15, ₂₀ , 24, 25 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ), respectively, and the heat treatment temperature was changed to A glass ceramic was obtained in the same manner as in Example 1 except that the temperature was changed to the temperature described in 1.

[Comparative Examples 1-4]
The ratio of LiI was changed to x = 0, 10, 13, and 30 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ), respectively, and the heat treatment temperature was expressed in each case. A glass ceramic was obtained in the same manner as in Example 1 except that the temperature was changed to the temperature described in 1.

[Comparative Examples 5 to 9]
Example except that the ratio of LiI was changed to x = 0, 10, 20, 30, 40 in xLiI. (100-x) (0.75Li ₂ S.0.25P ₂ S ₅ ), respectively. 1 to obtain sulfide glass. Then, without performing heat treatment, sulfide glass was used as a comparative sample.

[Evaluation 1]
(X-ray diffraction measurement)
X-ray diffraction (XRD) measurement using CuKα rays was performed on the glass ceramics obtained in Examples 1 to 5 and Comparative Examples 2 to 4. For XRD measurement, RINT Ultimate III manufactured by Rigaku was used. The results are shown in FIGS. As shown in FIG. 3, the glass ceramics obtained in Examples 1 to 5 were confirmed to have high Li ion conductive crystal phase peaks at 2θ = 20.2 ° and 23.6 °. On the other hand, as shown in FIG. 4, in the glass ceramics obtained in Comparative Examples 2 to 4, the peak of the high Li ion conductive crystal phase was not confirmed, and 2θ = 21.0 ° and 28.0 °. Only the peak of the low Li ion conductive crystal phase was confirmed. Further, from the obtained XRD chart, the peak intensity ratio (I _20.2 / I _21.0 ) of 2θ = 20.2 ° with respect to 2θ = 21.0 ° and 2θ = 23 with respect to 2θ = 21.0 ° A peak intensity ratio (I _23.6 / I _21.0 ) of .6 ° was determined. The results are shown in Table 2. In Example 1, since the peaks at 2θ = 21.0 ° and 28.0 ° were not confirmed, the above peak intensity ratio was not obtained.

(Li ion conductivity measurement)
For the samples obtained in Examples 1 to 5 and Comparative Examples 1 to 9, Li ion conductivity (normal temperature) was measured by the AC impedance method. Li ion conductivity was measured as follows. First, the sample powder was cold pressed at a pressure of 4 ton / cm ² to produce a pellet having a diameter of φ11.29 mm and a thickness of about 500 μm. Next, the pellets were placed in an inert atmosphere container filled with Ar gas, and measurement was performed. For the measurement, Solartron (SI1260) manufactured by Toyo Corporation was used. Moreover, the measurement temperature was adjusted to 25 ° C. in a thermostatic bath. The results are shown in Table 3 and FIG.

  As shown in Table 3 and FIG. 5, all the glass ceramics obtained in Examples 1 to 5 showed high Li ion conductivity. This is considered to be because the glass ceramics obtained in Examples 1 to 5 have a high Li ion conductive crystal phase having peaks of 2θ = 20.2 ° and 23.6 °. Further, Comparative Example 1 and Comparative Example 5, Comparative Example 2 and Comparative Example 6, and Comparative Example 4 and Comparative Example 8 each have the same LiI content x. Thus, when the sulfide glass doped with LiI is heat-treated, the Li ion conductivity usually decreases. On the other hand, the glass ceramics obtained in Examples 1 to 5 show a heterogeneous behavior that Li ion conductivity is improved by heat-treating the sulfide glass, and the Li ion conductivity is glass. It was extremely expensive as a ceramic.

[Examples 6 to 8]
The ratio of LiI was changed to x = 15 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ), and the heat treatment temperatures were 170 ° C., 180 ° C., and 190 ° C., respectively. Glass ceramics were obtained in the same manner as in Example 1 except that the temperature was changed to ° C.

[Comparative Example 10]
The ratio of LiI was changed to x = 15 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ), and sulfide glass was obtained in the same manner as in Example 1. Then, without performing heat treatment, sulfide glass was used as a comparative sample.

[Comparative Example 11]
Except that the ratio of LiI was changed to x = 15 in xLiI · (100−x) (0.75Li ₂ S · 0.25P ₂ S ₅ ) and the heat treatment temperature was changed to 200 ° C. Glass ceramics were obtained in the same manner as in Example 1.

[Evaluation 2]
(X-ray diffraction measurement)
X-ray diffraction (XRD) measurement using CuKα rays was performed on the glass ceramics obtained in Examples 6 to 8 and Comparative Example 11. The measurement method is the same as in Evaluation 1 described above. The result is shown in FIG. As shown in FIG. 6, the glass ceramics obtained in Examples 6 to 8 were confirmed to have high Li ion conductive crystal phase peaks at 2θ = 20.2 ° and 23.6 °. On the other hand, in the glass ceramic obtained in Comparative Example 11, the peak of the high Li ion conductive crystal phase was not confirmed, and the low Li ion conductive crystal phase of 2θ = 21.0 ° and 28.0 ° was observed. Only the peak was confirmed.

(Li ion conductivity measurement)
For the samples obtained in Examples 6 to 8 and Comparative Examples 10 and 11, Li ion conductivity (normal temperature) was measured by the AC impedance method. The measurement method is the same as in Evaluation 1 described above. The result is shown in FIG. As shown in FIG. 7, all the glass ceramics obtained in Examples 6 to 8 exhibited higher Li ion conductivity than Comparative Example 10 in which heating was not performed. On the other hand, it is considered that the sample obtained in Comparative Example 11 could not obtain a high Li ion conductive crystal phase as a result of the heat treatment temperature being too high.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 2 ... Negative electrode active material layer 3 ... Solid electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode collector 10 ... Lithium solid battery

Claims (1)

Li, A (A is at least one of P, Si, Ge, Al and B), S,
Glass ceramics,
A sulfide solid electrolyte material characterized by having peaks at 2θ = 20.2 ° and 23.6 ° in X-ray diffraction measurement using CuKα rays.

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