JP2014127387A - Method for producing sulfide solid electrolyte material and lithium solid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfide solid electrolyte material having high Li ion conductivity.SOLUTION: There are provided a method for producing a sulfide solid electrolyte material, and a lithium solid battery containing a sulfide solid electrolyte material produced by the method for producing a sulfide solid electrolyte material. The method for producing a sulfide solid electrolyte material comprises: an amorphization step of performing the amorphization of a raw material composition containing LiS, a sulfide of A (A represents at least one of P, Si, Ge, Al and B), and LiX (X represents a halogen) to synthesize sulfide glass; and a heat treatment step of heating the sulfide glass at a temperature of a crystallization temperature or above to synthesize glass ceramic. In the heat treatment step, the rate of temperature increase up to the crystallization temperature is 6°C/min or more.

Description

  The present invention relates to a method for producing a sulfide solid electrolyte material having high Li ion conductivity and a lithium solid state battery containing the sulfide solid electrolyte material.

  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 a high Li ion conductivity, it is useful for increasing the output of the battery, and various studies have been made heretofore. For example, Patent Document 1 discloses a sulfide solid electrolyte material, which is a glass having an ionic conductor having an ortho composition and LiI and having a glass transition point. Patent Document 1 describes that the sulfide solid electrolyte material may be heat-treated at a temperature equal to or higher than the crystallization temperature (paragraph 0068).

JP 2012-48973 A

  There is a demand for a sulfide solid electrolyte material having high Li ion conductivity, and the conventional sulfide solid electrolyte material described in Patent Document 1 has room for further improvement in ion conductivity.

  The present invention has been made in view of the above circumstances, and its main object is to provide a method for producing a sulfide solid electrolyte material having high Li ion conductivity.

As a result of intensive studies, the present inventors have found that glass ceramics synthesized by subjecting a specific sulfide glass doped with LiX to heat treatment have extremely high Li ion conductivity.
As a result of further intensive studies by the present inventors, when the glass is heat-treated into glass ceramics, the glass is slowly heated (for example, at a heating rate of 1 to 5 ° C./min) in order to sufficiently grow crystals. Although it is common technical knowledge, it is surprising that the Li ion conductivity of the resulting glass ceramic is greatly improved by rapidly raising the temperature of the sulfide glass at a rate of temperature increase of 6 ° C./min or more. I found.

That is, the method for producing a 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). An amorphizing step of amorphizing a raw material composition containing (a) and synthesizing a sulfide glass; and a heat treatment step of synthesizing glass ceramics by heating the sulfide glass at a temperature equal to or higher than a crystallization temperature. In the heat treatment step, the rate of temperature rise to the crystallization temperature is 6 ° C./min or more.
According to the production method of the present invention, it is possible to obtain a sulfide solid electrolyte material having high Li ion conductivity.

  In the heat treatment step, the sulfide glass can be put into a system heated in advance to the crystallization temperature or higher. By introducing the sulfide glass into the preheated system, the temperature rise rate of the sulfide glass can be easily controlled to a desired rate of 6 ° C./min or more.

  In the heat treatment step, the sulfide glass is preferably heated at a temperature equal to or higher than the crystallization temperature for 1 to 3 hours.

  Examples of the raw material composition include those containing P sulfide as the A sulfide and LiI as the LiX.

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 electrolyte interposed between the positive electrode active material layer and the negative electrode active material layer. A positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer containing a sulfide solid electrolyte material produced by the production method of the present invention. It is characterized by doing.
Since the lithium solid state battery of the present invention contains the sulfide solid electrolyte material obtained by the production method of the present invention, it has a high Li ion conductivity and can achieve high output.

  According to the present invention, it is possible to provide a sulfide solid electrolyte material and a lithium solid battery having high Li ion conductivity.

It is a flowchart which shows an example of the manufacturing method of the sulfide solid electrolyte material of this invention. It is a schematic sectional drawing which shows an example of the lithium solid battery of this invention. It is a measurement result of Li ion conductivity with respect to the sample obtained in Examples 1-2 and Comparative Examples 1-3.

  Hereinafter, the manufacturing method of the sulfide solid electrolyte material of the present invention and the lithium solid state battery will be described in detail.

A. First, 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). An amorphization step of amorphizing a raw material composition containing sulphide and synthesizing a sulfide glass; and a heat treatment step of synthesizing glass ceramics by heating the sulphide glass at a temperature equal to or higher than a crystallization temperature. And in the heat treatment step, the rate of temperature rise to the crystallization temperature is 6 ° C./min or more.

FIG. 1 is a flowchart showing an example of a method for producing a sulfide solid electrolyte material of the present invention. In FIG. 1, first, a raw material composition containing Li ₂ S, P ₂ S ₅ and LiI is prepared. Next, a sulfide containing an ion conductor (for example, Li ₃ PS ₄ ) having Li, P and S and LiI by performing mechanical milling on the raw material composition as an amorphization step. Synthesize glass. Next, the sulfide glass obtained by the amorphization step is heated at a temperature increase rate of 6 ° C./min or more, and heat treatment is performed at a temperature of the crystallization temperature or more, so that glass ceramics (sulfide solid electrolyte material) )
In the present invention, the sulfide glass means a material synthesized by amorphizing the raw material composition, not only a strict “glass” in which periodicity as a crystal is not observed in X-ray diffraction measurement or the like, It means all materials synthesized by amorphization by mechanical milling described later. 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.
In the present invention, glass ceramics 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 inventors have prepared 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 a halogen). A glass ceramic having high Li ion conductivity has been successfully synthesized by heat-treating a sulfide glass obtained by amorphization at a temperature higher than the crystallization temperature. This is considered to be because a crystalline phase excellent in Li ion conductivity (hereinafter sometimes referred to as a high Li ion conductive crystal phase) is produced by heating the sulfide glass at a temperature higher than the crystallization temperature. .

  In the glass ceramics, the Li ion conductivity of the glass ceramics can be improved by increasing the crystallinity (ratio) of the high Li ion conductive crystal phase as described above. Therefore, the present inventors have intensively studied to increase the crystallinity of the glass ceramics. Surprisingly, when the temperature of the sulfide glass is raised to a temperature higher than the crystallization temperature, the rate of temperature increase is 6. It has been found that the Li ion conductivity of the glass ceramic obtained is significantly improved by setting the temperature to be at least ° C / min.

In general, when glass is heat-treated to generate a crystal phase and synthesize glass ceramics, in order to sufficiently grow the crystal, the temperature is raised slowly (for example, 1 to 5 ° C./min), It is considered effective to heat for a long time. Therefore, glass ceramics obtained by rapidly raising the temperature of a sulfide glass to a temperature equal to or higher than the crystallization temperature at a high temperature rising rate contrary to the technical common sense of 6 ° C./min or higher exhibit high Li ion conductivity. This is an unexpected result.
The reason why the Li ion conductivity of the glass ceramic is improved by heating the sulfide glass at a temperature of 6 ° C./min or higher to a temperature of the crystallization temperature or higher when heat-treating the sulfide glass at a temperature of the crystallization temperature or higher is as follows. So guessed.

  That is, first, if the rate of temperature rise to a temperature equal to or higher than the crystallization temperature is as small as 5 ° C./min or less, S (sulfur) is easily released from the sulfide glass, resulting in a composition shift of the glass ceramic. It is considered that the glass ceramics having a desired composition can be synthesized by suppressing S omission by setting to / min or more.

  In addition, the high Li ion conductive crystalline phase produced by heat-treating sulfide glass at a temperature above the crystallization temperature is a thermodynamically slightly unstable (metastable phase), and the crystallization temperature is It is considered to be close to the crystallization temperature of another crystal phase (stable phase) that is thermochemically stable. For this reason, if the rate of temperature rise is small and the temperature rise time to a temperature above the crystallization temperature is long, another crystal phase (stable phase) that is thermodynamically stable is also generated, and high Li ion conductivity in glass ceramics. It is considered that the crystallinity (ratio) of the crystal phase is lowered. On the other hand, by setting it to 6 degrees C / min or more, it is thought that the phase transition from the said metastable phase to a stable phase can be suppressed, and the ratio of a high Li ion conductive crystalline phase can be made to increase.

On the other hand, since the high Li conductive crystal phase obtained by crystallizing the sulfide glass obtained by amorphizing the raw material composition by heat treatment is close to the nucleation temperature and the crystal growth temperature, the sulfide glass It is considered that nucleation and crystal growth proceed almost simultaneously on the surface of Therefore, even if the temperature is rapidly increased to 6 ° C / min or higher up to a temperature higher than the crystallization temperature, sufficient heat treatment at a temperature higher than the crystallization temperature improves the crystallinity of the high Li ion conductive crystal phase. It is thought that it can be made.
For the reasons as described above, according to the present invention, the crystallinity (ratio) of the high Li ion conductive crystal phase is increased while suppressing the composition shift and the phase transition from the metastable phase to the stable phase. Therefore, it is considered that a sulfide solid electrolyte having high Li ion conductivity can be obtained.

Hereafter, the manufacturing method of the sulfide solid electrolyte material of this invention is demonstrated for every process.
The method for producing a sulfide solid electrolyte material of the present invention has at least an amorphization step and a heat treatment step.
Hereinafter, each process is demonstrated in order.

1. Amorphization process
First, the amorphization process in the present invention will be described. The amorphizing step in the present invention contains 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). This is a step of making the raw material composition amorphous to synthesize sulfide glass.
The raw material composition in this step contains Li ₂ S, sulfides of A (A is at least one of P, Si, Ge, Al and B), and LiX (X is a halogen). is there.

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.
Examples of the sulfide of A contained in the raw material composition include P ₂ S ₃ , P ₂ S ₅ , SiS ₂ , GeS ₂ , Al ₂ S ₃ , B ₂ S _{3 and the} like. Since a glass ceramic with high Li ion conductivity can be obtained, the sulfide of A is preferably P ₂ S ₃ and P ₂ S ₅ in which A is P, and particularly preferably P ₂ S ₅ .

Feedstock composition, if 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%, More preferably, it is in the range of 72 mol% to 78 mol%, and still more preferably in the range of 74 mol% to 76 mol%. The same applies when the raw material composition contains Li ₂ S and Al ₂ S _3, and also when Li ₂ S and B ₂ S ₃ are contained.
On the other hand, the raw material composition, if 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 a range of 62.5mol% ~70.9mol% Preferably, it is in the range of 63 mol% to 70 mol%, more preferably in the range of 64 mol% to 68 mol%. The same applies when the raw material composition contains Li ₂ S and GeS ₂ .

In the raw material composition, X in LiX is halogen, and specific examples include F, Cl, Br, and I. Among them, Cl, Br, and I are preferable, and I is particularly preferable. This is because glass ceramics having high Li ion conductivity can be obtained.
Further, the ratio of LiX in the raw material composition is not particularly limited as long as it is a ratio capable of synthesizing a desired glass ceramic, and is slightly different depending on the synthesis conditions, but in the range of more than 13 mol% and less than 30 mol%. It is preferable to be within.

  In this step, examples of the method for amorphizing the raw material composition include mechanical milling and melt quenching, and mechanical milling is particularly preferable. 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 desired 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. Specifically, the rotation speed of the base plate when performing the planetary ball mill is, for example, preferably in the range of 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 of the container used for the ball mill and the ball for grinding include ZrO ₂ and Al ₂ O _3. The diameter of the ball for grinding is within a range of 1 mm to 20 mm, for example. It is preferably within the range of 10 g to 100 g.

  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.

  The polar aprotic liquid is not particularly limited. 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 tetrahydrofuran; chloroform, chloride Alkyl halides such as methyl and methylene chloride; esters such as ethyl acetate; fluorinated benzene, heptane fluoride, 2,3-dihydroperfluoropentane, 1,1,2,2,3,3,4 Fluorine compounds such as heptafluorocyclopentane can be mentioned.
The amount of the liquid added is not particularly limited.

  When the raw material composition is amorphized by wet mechanical milling, the obtained sulfide glass is preferably dried. This is for removing the liquid used in the mechanical milling remaining in the sulfide glass. The drying temperature is preferably lower than the crystallization temperature of the sulfide glass, and is preferably in the range of 100 ° C to 150 ° C, for example.

2. Next, the heat treatment process in the present invention will be described. The heat treatment step in the present invention is a step of synthesizing glass ceramics by heating the sulfide glass to a crystallization temperature at a heating rate of 6 ° C./min or higher and heating at a temperature higher than the crystallization temperature.

The heat treatment temperature of the sulfide glass is a temperature equal to or higher than the crystallization temperature of the sulfide glass, and the crystallization temperature of the sulfide glass can be determined by differential thermal analysis (DTA). The heat treatment temperature is not particularly limited as long as it is higher than the crystallization temperature. For example, in the X-ray diffraction measurement using CuKα rays, the heat treatment temperature can be determined from the temperature at which glass ceramics having peaks at 2θ = 20.2 ° and 23.6 ° are obtained. This peak is a peak derived from 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 °.
A specific heat treatment temperature is, for example, 160 ° C. or higher, particularly 170 ° C. or higher, and particularly preferably 180 ° C. or higher. On the other hand, the upper limit of the heat treatment temperature is not particularly limited as long as it is a temperature capable of synthesizing a desired glass ceramic, and is slightly different depending on the composition of the sulfide glass. Is preferred.
Although the heat treatment method is not particularly limited, for example, a method using a firing furnace can be mentioned.

As described above, the present invention is characterized in that the speed of raising the temperature of the sulfide glass to the heat treatment temperature (temperature higher than the crystallization temperature) is 6 ° C./min or more. Increasing the crystallinity (ratio) of the high Li ion conductive crystal phase while suppressing the composition shift and phase transition to the stable phase by setting the rate of temperature rise to the heat treatment temperature to 6 ° C./min or more. Can do.
The rate of temperature increase is not particularly limited as long as it is 6 ° C./min or higher, but is preferably 10 ° C./min or higher because a higher effect of improving Li ion conductivity is obtained. On the other hand, from the viewpoint of nucleation rate and temperature control, the rate of temperature rise is preferably 1000 ° C./min or less.
In addition, the temperature increase rate of sulfide glass can be measured and controlled by a general method. For example, when a sulfide glass equipped with a thermocouple is put into a firing furnace and the temperature of the sulfide glass is periodically measured (for example, every second) by the thermocouple, the temperature rise rate of the sulfide glass is increased. Can be calculated.
The method for controlling the rate of temperature rise of the sulfide glass is not particularly limited, and a general method can be adopted. For example, a method for controlling the rate of temperature rise of the firing furnace for performing heat treatment can be mentioned. The temperature in the heat treatment system (temperature in the firing furnace) when the sulfide glass is charged is not particularly limited, and may be room temperature or may be heated. The heat treatment system is preheated, in particular, heated to a temperature equal to or higher than the crystallization temperature of the sulfide glass, and the sulfide glass is put into the heated system (firing furnace) to be 10 ° C./min or more. In particular, it is possible to achieve a high temperature rising rate such as 20 ° C./min or more, and a sulfide solid electrolyte material having higher lithium conductivity can be obtained.

  The heating time of the sulfide glass at a temperature equal to or higher than the crystallization temperature (heat treatment temperature) is appropriately selected depending on the heat treatment temperature described above, and is preferably in the range of 1 minute to 24 hours, for example. , Preferably in the range of 30 minutes to 3 hours. In particular, since the growth of the high Li conductive crystal phase is sufficiently advanced, the S loss and the phase transition to the other crystal phase of the high Li conductive crystal phase can be suppressed. It is preferable to be within the range.

  The heat treatment in this step is preferably performed in an inert gas atmosphere (for example, an Ar gas atmosphere). This is because deterioration (for example, oxidation) of the sulfide glass can be prevented.

3. Other Steps The present invention has at least the above-described amorphization step and heat treatment step, but may have other steps as necessary. Examples of other processes include a atomization process.

  According to the method for producing a sulfide solid electrolyte material of the present invention as described above, Li, A (A is at least one of P, Si, Ge, Al, and B), X (X is a halogen). , S-containing glass ceramics, and a sulfide-based solid electrolyte material having high Li ion conductivity can be obtained.

Examples of the sulfide solid electrolyte material obtained by the present invention include Li, A (A is at least one of P, Si, Ge, Al and B), and S, and LiX (X Is a halogen). At this time, at least a part of LiX is usually present in a state of being taken into the structure of the ionic conductor as a LiX component.
Here, 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.

Here, “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.

It is preferable that the sulfide solid electrolyte material obtained by the present invention 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 using CuKα rays. 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 sulfide solid electrolyte material obtained by this invention does not contain bridge | crosslinking sulfur substantially. This is because the amount of hydrogen sulfide generated is small. “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.

  Further, the ratio of LiX in the sulfide solid electrolyte material obtained by the present invention is not particularly limited as long as it is a glass ceramic having a high Li ion conductive crystal phase. For example, it is more than 13 mol% and more than 30 mol%. A small amount is preferable, and in particular, it is preferable to be within a range of 15 mol% to 25 mol%.

Examples of the shape of the sulfide solid electrolyte material obtained by 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 a 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 obtained by the present invention can be used for any application that requires Li ion conductivity, but can be suitably used as a battery material.

B. Next, a lithium solid state battery 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 is obtained by the above-described production method of the present invention. It is characterized by containing.

  By using the sulfide solid electrolyte material obtained by the manufacturing method of the present invention described above, a lithium solid battery having high Li ion conductivity can be obtained, and the output of the battery can be increased.

FIG. 2 is a schematic cross-sectional view showing an example of the lithium solid state battery of the present invention. A lithium solid battery 10 shown in FIG. 2 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, at least one of the positive electrode active material layer 1, the negative electrode active material layer 2, and the solid electrolyte layer 3 is manufactured by the manufacturing method described in the above section “A. Manufacturing method of sulfide solid electrolyte material”. The main feature is that it contains a sulfide solid electrolyte material.
The lithium solid state battery of the present invention may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as 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.
Hereinafter, the lithium solid state battery of the present invention will be described for each configuration.

1. Solid electrolyte layer First, the solid electrolyte layer in the present invention will be described. The solid electrolyte layer in the present invention is a layer interposed between the positive electrode active material layer and the negative electrode active material layer, and is a layer containing at least 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, and examples thereof include a sulfide solid electrolyte material and an oxide solid electrolyte material. The sulfide solid electrolyte material is preferable in that it has a higher ionic conductivity than the oxide solid electrolyte material, and the oxide solid electrolyte material has higher chemical stability than the sulfide solid electrolyte material. This is preferable.
The solid electrolyte material may be an amorphous material or a crystalline material. The amorphous material can be obtained, for example, by applying a mechanical milling method or a melt quenching method to the raw material composition. The crystalline material can be obtained, for example, by applying a solid phase method to the raw material composition.
Among them, the solid electrolyte material is preferably a sulfide solid electrolyte material produced by the above-described “A. Method for producing sulfide solid electrolyte material”.

In the solid electrolyte layer, the content of the sulfide solid electrolyte material is not particularly limited as long as a desired insulating property is obtained. For example, the content is in the range of 10% by volume to 100% by volume. , Preferably in 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 in addition to the solid electrolyte material. By containing a binder, a flexible solid electrolyte layer can be obtained. Examples of the binder include fluorine-containing binders such as PTFE and PVDF.

  Examples of the method for forming the solid electrolyte layer include a pressing method. In addition, 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.

2. Next, 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.

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. It is preferable to have a potential of 3.0 V (vs. Li) or more. 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 preferably contains a solid electrolyte material in addition to the positive electrode active material. This is because the positive electrode active material is in contact with the solid electrolyte material, and the ionic conductivity of the positive electrode active material layer can be improved. As the solid electrolyte material, the same materials as those described in the section “1. Solid electrolyte layer” can be used, and among them, the solid electrolyte material is manufactured by the above-mentioned “A. Method for manufacturing sulfide solid electrolyte material”. A sulfide solid electrolyte material is preferred.
In the positive electrode active material layer, the content of the sulfide solid electrolyte material is, for example, in the range of 0.1% by volume to 80% by volume with respect to the formed positive electrode active material layer, and in particular, 1% by volume to 60% by volume. %, Particularly in the range of 10% to 50% by volume.

  The positive electrode active material layer 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. As the binder, the same materials as those described in the section “1. Solid electrolyte layer” described above can be used.

As a method for forming the positive electrode active material layer, for example, the above-described material is formed on the solid electrolyte layer or the positive electrode current collector by a press method, a sputtering method, a PVD method, a CVD method, an electrolytic plating method, an electroless plating method, or the like. The method of forming a layer is mentioned.
The thickness of the positive electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

3. 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.

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.
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 negative electrode active material layer preferably contains a solid electrolyte material in addition to the negative electrode active material. This is because the negative electrode active material and the solid electrolyte material are in contact with each other, and the ionic conductivity of the negative electrode active material layer can be improved.
As the solid electrolyte material, the same materials as those described in the section “1. Solid electrolyte layer” can be used, and among them, the solid electrolyte material is manufactured by the above-mentioned “A. Method for manufacturing sulfide solid electrolyte material”. A sulfide solid electrolyte material is preferred.
The content of the sulfide solid electrolyte material 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 in the range of 10% by volume to 50% by volume. It is preferable to be within.

  The negative electrode active material layer may further contain at least one of a conductive material and a binder in addition to the negative electrode active material and the solid electrolyte material. As the conductive material and the binder, the same materials as those described in the section “2. Positive electrode active material layer” can be used.

As a method for forming the negative electrode active material layer, for example, the above-described material is formed on the solid electrolyte layer or the negative electrode current collector by a press method, a sputtering method, a PVD method, a CVD method, an electrolytic plating method, an electroless plating method, or the like. The method of forming a layer is mentioned.
The thickness of the negative electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

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.
As a battery case used in the present invention, a general lithium solid battery case can be used. Examples of the battery case include a SUS battery case.

  The method for producing a 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 a method similar to a general method for producing a lithium solid state battery may be used. it can. 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.

  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 under an Ar atmosphere (dew point -70 ° C.).

[Comparative 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 ratio of LiI to the total of Li ₂ S, P ₂ S ₅ and LiI was 20 mol%. The weighed starting materials are mixed for 5 minutes in an agate mortar, 2 g of the mixture is put into a planetary ball mill container (45 cc, made of ZrO ₂ ), 4 g of dehydrated heptane (water content of 30 ppm or less) is added, and further ZrO ₂ balls (Φ = 5 mm) 53 g was added, and the container was completely sealed. This container was attached to a planetary ball mill (P-7 manufactured by Fritsch), and mechanical milling was performed at a base plate rotation speed of 500 rpm for 40 hours. Then, heptane was removed by drying at 100 ° C. to obtain a sulfide glass.

[Comparative Example 2]
0.5 g of sulfide glass obtained in the same manner as in Comparative Example 1 was placed in a glass tube, and the glass tube was placed in a SUS sealed container. The sealed container was placed in a furnace at room temperature (about 25 ° C.), heated to 180 ° C. at 1 ° C./min, and heat-treated at 180 ° C. for 3 hours to obtain glass ceramics.

[Comparative Example 3]
0.5 g of sulfide glass obtained in the same manner as in Comparative Example 1 was vacuum-sealed in a quartz tube, and the quartz tube was placed in a furnace at room temperature (about 25 ° C.). The temperature was raised in min and heat treatment was performed at 180 ° C. for 3 hours to obtain glass ceramics.

[Example 1]
Glass ceramics were obtained in the same manner as in Comparative Example 3 except that the temperature increase rate was changed to 10 ° C./min.

[Example 2]
Glass ceramics sealed in a vacuum glass with sulfide glass was installed in a furnace previously maintained at 180 ° C., and the glass ceramics was the same as in Comparative Example 3 except that the heating rate was changed to 20 ° C./min. Got.

[Evaluation]
(Li ion conductivity measurement)
For the samples obtained in Examples 1-2 and Comparative Examples 1-3, 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 11.28 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. The measurement temperature was adjusted to 25 ° C. with a thermostatic bath.
The results are shown in Table 1 and FIG.

As shown in Table 1 and FIG. 3, the glass ceramics obtained in Examples 1 and 2 and Comparative Examples 2 to 3 showed higher Li ion conductivity than the sulfide glass of Comparative Example 1. This is presumably because a high Li ion conductive crystal phase (metastable phase) was precipitated by heat treatment of the sulfide glass.
Moreover, as for the glass ceramics of Examples 1-2, all showed high Li ion conductivity compared with the glass ceramics of Comparative Examples 2-3. This is because, when heat-treating the sulfide glass, by increasing the rate of temperature rise to the crystallization temperature of the sulfide glass, a composition shift due to volatilization of S, a phase transition from a metastable phase to a stable phase, etc. This is thought to be because the decrease in lithium ion conductivity caused by the above was suppressed. In addition, the high Li ion conductive crystal phase is considered to proceed almost simultaneously on the surface of the sulfide glass because the nucleation temperature and the crystal growth temperature are close. Therefore, even if the heating rate up to the crystallization temperature is increased, if the heating time at a temperature higher than the crystallization temperature is secured, the generation and growth of the crystal phase having high Li ion conductivity can be sufficiently advanced. It is thought that you can.

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 (5)

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) is made amorphous and sulfided An amorphization step of synthesizing the glass,
A heat treatment step of heating the sulfide glass at a temperature equal to or higher than a crystallization temperature to synthesize glass ceramics;
Have
The method for producing a sulfide solid electrolyte material, wherein, in the heat treatment step, a rate of temperature rise to the crystallization temperature is 6 ° C./min or more.   2. The method for producing a sulfide solid electrolyte material according to claim 1, wherein, in the heat treatment step, the sulfide glass is charged into a system heated in advance to the crystallization temperature or higher.   3. The method for producing a sulfide solid electrolyte material according to claim 1, wherein in the heat treatment step, heating is performed at a temperature not lower than the crystallization temperature for 1 to 3 hours.   4. The method for producing a sulfide solid electrolyte material according to claim 1, wherein the raw material composition contains a sulfide of P as the sulfide of A and LiI as the LiX. 5. 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 interposed between the positive electrode active material layer and the negative electrode active material layer Because
5. The sulfide solid electrolyte material produced by the production method according to claim 1, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains. A lithium solid state battery characterized by that.

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