JP5553004B2 - Sulfide solid electrolyte material, lithium solid battery, and method for producing sulfide solid electrolyte material - Google Patents

Description

  The present invention relates to a sulfide solid electrolyte material that prevents the adverse effects of heat generation associated with crystallization.

  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 the manufacturing cost and productivity It is considered excellent. Furthermore, sulfide solid electrolyte materials are known as solid electrolyte materials used for such solid electrolyte layers.

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.

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

For example, the sulfide solid electrolyte material of _{LiI-Li 2 S-P 2} S 5 based _amorphous, by doping with LiI in _{Li 2 S-P 2 S 5} , is possible to increase the Li ion conductivity it can. However, by doping LiI, the crystallization temperature of the amorphous sulfide solid electrolyte material is lowered, and the crystallization temperature may be about 90 ° C. depending on the composition.

  When an amorphous sulfide solid electrolyte material having a low crystallization temperature is used in a battery, for example, if the battery temperature reaches or exceeds the crystallization temperature of the amorphous sulfide solid electrolyte material, the battery is in use. There is a problem of unexpected heat generation. 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.

  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 that prevents the adverse effects of heat generated by crystallization.

  In order to solve the above-described problems, the present invention provides a sulfide solid electrolyte material having Li, P, S, and I and being a glass ceramic.

  According to the present invention, it is possible to obtain a sulfide solid electrolyte material in which the adverse effect of heat generated by crystallization is prevented by using glass ceramics crystallized in advance.

  In the said invention, it is preferable that the said sulfide solid electrolyte material has a diffraction peak in 2 (theta) = 21 degrees and 28 degrees in the X-ray-diffraction measurement using a CuK alpha ray. It is because it can be set as the sulfide solid electrolyte material with high Li ion conductivity.

In the above-mentioned invention, the sulfide solid electrolyte _material, Li 2 _S, it is preferable that obtained by using the P 2 _{S 5} and LiI.

  In the said invention, it is preferable that content of the said LiI exists in the range of 1 mol%-60 mol%.

  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 I will provide a.

  According to the present invention, since 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, a lithium solid state battery that prevents the adverse effects of heat generation due to crystallization is prevented. It can be. Thereby, it becomes a lithium solid state battery excellent in durability.

In the present invention, the raw material composition containing Li ₂ S, P ₂ S ₅ and LiI is made amorphous to synthesize an amorphous sulfide solid electrolyte material; And a heat treatment step of obtaining a sulfide solid electrolyte material that is glass ceramic by heat-treating the sulfide solid electrolyte material at a temperature equal to or higher than a crystallization temperature. .

  According to the present invention, an amorphous sulfide solid electrolyte material is synthesized and then subjected to heat treatment, whereby a sulfide solid electrolyte material in which the adverse effects of heat generation due to crystallization can be prevented can be obtained.

  The sulfide solid electrolyte material of the present invention has the effect of preventing the adverse effects of heat generation associated with crystallization.

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 sulfide solid electrolyte material obtained in Example 1 and Comparative Example 1. It is a result of the differential thermal analysis with respect to the sulfide solid electrolyte material obtained in Example 1 and Comparative Example 1. It is a result of Li ion conductivity measurement with respect to the sulfide solid electrolyte material obtained in Example 1 and Comparative Example 1.

  Hereinafter, the sulfide solid electrolyte material, the lithium solid battery, and the 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 has Li, P, S, and I and is a glass ceramic.

  According to the present invention, it is possible to obtain a sulfide solid electrolyte material in which the adverse effect of heat generated by crystallization is prevented by using glass ceramics crystallized in advance. Therefore, for example, when the sulfide solid electrolyte material of the present invention is used for a battery, it is possible to prevent the deterioration (deterioration) of each material constituting the battery or the damage of the battery case or the like. Further, there is an advantage that the battery cooling mechanism and the safety mechanism can be simplified.

  The sulfide solid electrolyte material of the present invention is characterized by being a glass ceramic. The glass ceramic in the present invention refers to a material obtained by crystallizing an amorphous sulfide solid electrolyte material. Whether or not the sulfide solid electrolyte material of the present invention is crystallized can be confirmed by, for example, an X-ray diffraction method.

  The above-mentioned amorphous sulfide solid electrolyte material is a material synthesized by amorphizing a raw material composition, and is strictly “amorphous” in which periodicity as a crystal is not observed in X-ray diffraction measurement or the like. ”As well as all materials synthesized by amorphization by mechanical milling described later. Therefore, in the X-ray diffraction measurement etc., for example, even if a peak derived from the raw material (LiI etc.) is observed, the amorphous sulfide solid electrolyte material can be used as long as it is a material synthesized by amorphization. It corresponds to.

  In the present invention, among them, the amorphous sulfide solid electrolyte material is preferably strictly amorphous, and more preferably strictly glass. It is because it can be set as glass ceramics with high Li ion conductivity by making amorphous property higher. Note that the strict glass refers to a strict amorphous material in which a glass transition point is observed. The presence or absence of a glass transition point can be confirmed by differential thermal analysis (DTA). Moreover, exact | strict glass can be obtained, for example by performing wet mechanical milling, as described in the Example mentioned later.

The sulfide solid electrolyte material of the present invention contains Li, P, S, and I, and is preferably formed using Li ₂ S, P ₂ S _5, and LiI. Li ₂ S 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. P ₂ S ₅ and LiI are also preferably low in impurities.

In the present invention, the ratio of Li ₂ S to the total of Li ₂ S and P ₂ S ₅ is not particularly limited, but is preferably in the range of 70 mol% to 80 mol%, for example, 72 mol% to More preferably, it is in the range of 78 mol%, and still more preferably in the range of 74 mol% to 76 mol%. This is because a sulfide solid electrolyte material having an ortho composition or a composition in the vicinity thereof can be obtained, and 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. In the Li ₂ S—P ₂ S ₅ system, Li ₃ PS ₄ corresponds to the ortho composition. 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: 25 on a molar basis. It is.

  On the other hand, the ratio of LiI in the sulfide solid electrolyte material of the present invention is not particularly limited, but is preferably, for example, 1 mol% or more, more preferably 5 mol% or more, and more preferably 10 mol% or more. More preferably. This is because if the content of LiI is too small, it may not contribute to the improvement of Li ion conductivity. On the other hand, the LiI ratio is, for example, preferably 60 mol% or less, more preferably 50 mol% or less, and further preferably 40 mol% or less. This is because if the content of LiI is too large, Li ion conductivity may be lowered.

The sulfide solid electrolyte material of the present invention preferably has diffraction peaks at 2θ = 21 ° and 28 ° in X-ray diffraction measurement using CuKα rays. It is because it can be set as the sulfide solid electrolyte material with high Li ion conductivity. In addition, as described in Examples described later, these diffraction peaks do not correspond to any known diffraction peak including Li, P, S, and I, and Li ₃ PS ₄ and LiI constitute an ordered structure. Therefore, it is presumed to be a new diffraction peak that appears.

Examples of the shape of the sulfide solid electrolyte material of the present invention include particles. The average particle diameter 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. Furthermore, when using the said sulfide solid electrolyte material for a battery, you may use for a positive electrode active material layer (positive electrode body), may be used for a negative electrode active material layer (negative electrode body), and may be used for an electrolyte layer.

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. is there.

  According to the present invention, since 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, a lithium solid state battery that prevents the adverse effects of heat generation due to crystallization is prevented. It can be. Thereby, it becomes a lithium solid state battery excellent in durability.

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. The solid electrolyte layer 3 formed on the cathode, the positive electrode current collector 4 for collecting current of the positive electrode active material layer 1, the negative electrode current collector 5 for collecting current of the negative electrode active material layer 2, and these members are housed. A battery case 6 is provided. 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 sulfide solid electrolyte material described above has an ortho composition or a composition in the vicinity thereof, the positive electrode active material preferably has a potential of 2.8 V (vs Li) or higher, and 3.0 V (vs Li) or higher. It is more preferable to have a potential of 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, when the sulfide solid electrolyte material has an ortho composition or a composition in the vicinity thereof, 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 according to the present invention comprises a synthesis step of amorphizing a raw material composition containing Li ₂ S, P ₂ S ₅ and LiI to synthesize an amorphous sulfide solid electrolyte material, And heat-treating the amorphous sulfide solid electrolyte material at a temperature equal to or higher than the crystallization temperature to obtain a sulfide solid electrolyte material that is 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 amorphous sulfide solid electrolyte material having an ion conductor (for example, Li ₃ PS ₄ ) having Li, P, and S and LiI Is synthesized. Next, the amorphous sulfide solid electrolyte material is heat-treated at a temperature equal to or higher than the crystallization temperature to obtain a sulfide solid electrolyte material that is a glass ceramic.

According to the present invention, an amorphous sulfide solid electrolyte material is synthesized and then subjected to heat treatment, whereby a sulfide solid electrolyte material in which the adverse effects of heat generation due to crystallization can be prevented can be obtained.
Hereafter, the manufacturing method of the sulfide solid electrolyte material of this invention is demonstrated for every process.

1. Synthetic Step The synthetic step in the present invention is a step in which a raw material composition containing Li ₂ S, P ₂ S ₅ and LiI is made amorphous to synthesize an amorphous sulfide solid electrolyte material.

Li 2 _S in the raw material _composition, the ratio of P ₂ S ₅ and LiI are the same as described in the above "A. sulfide solid electrolyte material", it is omitted description herein. Examples of the method for amorphizing the raw material composition include mechanical milling and melt quenching, and mechanical milling is preferable. This is because processing at room temperature is possible, and the manufacturing process can be simplified. 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 sulfide solid electrolyte material with higher amorphousness 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 a desired sulfide solid electrolyte material can be obtained efficiently.

  Various conditions of mechanical milling are set so that a desired sulfide solid electrolyte material can be obtained. For example, when a planetary ball mill is used, a raw material composition and grinding balls are added, and the treatment is performed at a predetermined number of revolutions and time. In general, the higher the number of rotations, the faster the production rate of the sulfide solid electrolyte material, and the longer the treatment time, the higher the conversion rate from the raw material composition to the sulfide solid electrolyte 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 1 hour to 100 hours, and more preferably in the range of 1 hour to 50 hours.

  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 a raw material composition or a sulfide solid electrolyte material. 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.

  As the amorphous sulfide solid electrolyte material obtained by this step has a lower crystallization temperature, the lower the crystallization temperature, the lower the temperature. For this reason, the lower the crystallization temperature of the amorphous sulfide solid electrolyte material, the more effective the effect of the present invention is. For example, considering the temperature during battery use, the crystallization temperature of the amorphous sulfide solid electrolyte material is preferably 200 ° C. or lower, and more preferably 150 ° C. or lower.

The amorphous sulfide solid electrolyte material obtained by this step usually has an ion conductor having Li, P, and S (Li ₂ S—P ₂ S ₅ system ion conductor) and LiI. is there. The ionic conductor preferably has an ortho composition. The above “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 (PS ₄ ^3- structure) having an ortho composition. 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 ionic conductor, It is particularly preferably 90 mol% or more. The ratio of the anion structure of the ortho composition can be determined by Raman spectroscopy, NMR, XPS, or the like.

It is preferable that the amorphous sulfide solid electrolyte material obtained by this step does not substantially contain 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.

It is preferable that the amorphous sulfide solid electrolyte material obtained by this step does not substantially contain bridging sulfur. 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 formed by reaction of Li ₂ S and P ₂ S ₅ . 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 based amorphous 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 .

2. Next, the heat treatment process in the present invention will be described. The heat treatment step in the present invention is a step in which the amorphous sulfide solid electrolyte material is heat treated at a temperature equal to or higher than the crystallization temperature to obtain a sulfide solid electrolyte material that is glass ceramic.

  The temperature of the heat treatment is not particularly limited as long as it is higher than the crystallization temperature. This is because if the temperature is equal to or higher than the crystallization temperature, adverse effects due to heat generated by crystallization can be prevented. The crystallization temperature of the amorphous sulfide solid electrolyte material can be determined by differential thermal analysis (DTA). Although the upper limit of the temperature of heat processing is not specifically limited, It is preferable that it is crystallization temperature +100 degreeC, and it is more preferable that it is crystallization temperature +50 degreeC. This is because if the temperature of the heat treatment is too high, the Li ion conductivity may decrease. Moreover, specifically, the temperature of the heat treatment is preferably within a range of 90 ° C to 300 ° C, and more preferably within a range of 100 ° C to 200 ° C.

The time for the heat treatment 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). This is because deterioration (for example, oxidation) of the sulfide solid electrolyte material can be prevented. The method for the heat treatment is not particularly limited, and examples thereof include a method using a firing furnace. Also, the sulfide solid electrolyte material of the glass ceramics obtained by the present process is typically, Li, P, ion conductor having S and _{(Li 2 S-P 2 S} 5 based ion conductor), having a LiI It is.

  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), diphosphorus pentasulfide (P ₂ S ₅ ) and lithium iodide (LiI) were used. Next, in a glove box under an Ar atmosphere (dew point −70 ° C.), Li ₂ S and P ₂ S ₅ have a molar ratio of 75Li ₂ S · 25P ₂ S ₅ (Li ₃ PS ₄ , ortho composition). Weighed as follows. Next, LiI was weighed so that LiI was 30 mol%. 2 g of this mixture is charged into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (moisture content of 30 ppm or less, 4 g) is charged, and ZrO ₂ balls (φ = 5 mm, 53 g) are charged. The container was completely sealed (Ar atmosphere). This container was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling was performed 40 times with a base plate rotation speed of 500 rpm and a one-hour treatment and a 15-minute pause. Thereafter, the obtained sample was dried on a hot plate so as to remove heptane to obtain a sulfide solid electrolyte material which is glass. Thereafter, the sulfide solid electrolyte material that is glass was heat-treated in an Ar atmosphere at 180 ° C. (temperature equal to or higher than the crystallization temperature) for 1 hour to obtain a sulfide solid electrolyte material that was glass ceramic. The composition of the obtained sulfide solid electrolyte material was 30LiI · 70 (0.75Li ₂ S · 0.25P ₂ S ₅ ).

[Comparative Example 1]
The sulfide solid electrolyte material that is glass obtained in Example 1 was used as a comparative sample. The composition of the sulfide solid electrolyte material which is glass was 30LiI · 70 (0.75Li ₂ S · 0.25P ₂ S ₅ ).

[Evaluation]
(X-ray diffraction measurement)
X-ray diffraction (XRD) measurement using CuKα rays was performed on the sulfide solid electrolyte materials obtained in Example 1 and Comparative Example 1. For XRD measurement, RINT Ultimate III manufactured by Rigaku was used. The result is shown in FIG. As shown in FIG. 3, in Example 1, the diffraction peak of the crystal was detected and confirmed to be glass ceramics. On the other hand, in Comparative Example 1, the diffraction peak of the crystal was not detected, and it was confirmed to be amorphous. Further, in Example 1, in addition to some LiI crystal diffraction peaks, an unknown diffraction peak was confirmed at 2θ = 21 ° and 28 °. The unknown diffraction peak does not correspond to any known diffraction peak including Li, P, S, and I, and is presumed to be a new diffraction peak that appears because Li ₃ PS ₄ and LiI constitute an ordered structure. Is done.

(Differential thermal analysis)
Differential thermal analysis (DTA) was performed on the sulfide solid electrolyte material obtained in Example 1 and Comparative Example 1. For DTA, TGA / SDTA851e manufactured by METTLER was used. The result is shown in FIG. As shown in FIG. 4, in Comparative Example 1, a glass transition point was observed at about 70 ° C., and an exothermic peak due to crystallization was observed at about 90 ° C. This heat generation is generated when a more stable crystal is generated from an amorphous state. On the other hand, in Example 1, no exothermic peak as in Comparative Example 1 was observed. From this, when the sulfide solid electrolyte material obtained in Example 1 is used for a battery, it is possible to prevent unexpected heat generation during use of the battery. As a result, it is possible to prevent the deterioration (deterioration) of each material constituting the battery and the damage of the battery case or the like. Further, there is an advantage that the battery cooling mechanism and the safety mechanism can be simplified.

(Li ion conductivity measurement)
For the sulfide solid electrolyte material obtained in Example 1 and Comparative Example 1, Li ion conductivity (normal temperature) was measured by the AC impedance method. Li ion conductivity was measured as follows. 100 mg of the sample added to the support tube (made by Macor) was sandwiched between electrodes made of SKD. Thereafter, the sample was compacted at a pressure of 4.3 ton / cm ² , and impedance measurement was performed while restraining the sample at 6 Ncm. Solartron 1260 was used for measurement, and the measurement conditions were an applied voltage of 5 mV and a measurement frequency range of 0.01 MHz to 1 MHz. The result is shown in FIG. As shown in FIG. 5, Example 1 has higher Li ion conductivity than Comparative Example 1.

Amorphous sulfide solid electrolyte materials are known to have many systems and compositions in which the Li ion conductivity is rapidly reduced by crystallization, and systems and compositions in which the Li ion conductivity is improved by crystallization are rare. . For reference, a sulfide solid electrolyte material was obtained in the same manner as in Example 1 and Comparative Example 1 except that LiI was not used. When the Li ion conductivity was measured for these sulfide solid electrolyte materials in the same manner as described above, 75Li ₂ S · 25P ₂ S ₅ glass was 5 × 10 ⁻⁴ S / cm, and 75Li ₂ S · cm. The 25P ₂ S ₅ glass ceramics was 1 × 10 ⁻⁴ S / cm. From this, in Example 1, it was confirmed that Li ion conductivity was unexpectedly improved by crystallization by introducing LiI into the composition of 75Li ₂ S · 25P ₂ S ₅ .

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 6 ... Battery case 10 ... Lithium solid battery

Claims (5)

A Li, P, S, and I, Ri glass ceramics der containing _Li 3 PS _4,
A sulfide solid electrolyte material having diffraction peaks at 2θ = 21 ° and 28 ° in an X-ray diffraction measurement using CuKα rays . The sulfide solid electrolyte material according to claim 1 , wherein the sulfide solid electrolyte material is made of Li ₂ S, P ₂ S ₅ and LiI. The sulfide solid electrolyte material according to claim 2 , wherein the content of LiI is in the range of 1 mol% to 60 mol%. A lithium solid state battery having 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 layer formed between the positive electrode active material layer and the negative electrode active material layer Because
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 according to any one of claims 1 to 3. Lithium solid state battery. A synthesis step of amorphizing a raw material composition containing Li ₂ S, P ₂ S ₅ and LiI to synthesize an amorphous sulfide solid electrolyte material;
A heat treatment step of heat-treating the amorphous sulfide solid electrolyte material at a temperature equal to or higher than a crystallization temperature to obtain a sulfide solid electrolyte material that is a glass ceramic containing Li ₃ PS ₄ ;
I have a,
The method for producing a sulfide solid electrolyte material, wherein the sulfide solid electrolyte material has diffraction peaks at 2θ = 21 ° and 28 ° in X-ray diffraction measurement using CuKα rays .

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