JP5552802B2 - Method for producing sulfide solid electrolyte material, sulfide solid electrolyte material, and lithium battery - Google Patents

Description

The present invention relates to a method for producing a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase, and more specifically, a sulfide solid electrolyte material capable of obtaining a sulfide solid electrolyte material having excellent Li ion conductivity. It relates to the manufacturing method.

  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.

One of the sulfide solid electrolyte materials is a sulfide solid electrolyte material that is a Li ₄ P ₂ S ₆ crystal. The Li ₄ P ₂ S ₆ crystal has a layered structure, and there is a problem that the actual Li ion conductivity is extremely low although the layered structure is considered to have a positive influence on Li ion conduction. With respect to such a problem, Patent Document 1 discloses a lithium magnesium thiophosphate compound in which a part of Li at the Li site of the Li ₄ P ₂ S ₆ crystal is replaced with Mg (Patent Document 1). Claim 1). In this technique, Li ion conductivity is improved by replacing Li with Mg. In Patent Document 1, a Li ₄ P ₂ S ₆ crystal is obtained by vacuum-sealing a pellet containing Li ₂ S, MgS, P ₂ S ₃ and P ₂ S ₅ as a raw material in a quartz tube and heating the pellet at a high temperature. Is synthesized. This is a synthesis by a so-called solid phase method.

Further, in Patent Document 2, a Li ₂ S and _P 2 _{S 5} by glass by mechanical milling method, to synthesize a sulfide glass, by performing heat treatment on the sulfide _glass, Li _{4 P} 2 S Synthesis of a sulfide solid electrolyte material having _six crystal phases is disclosed (FIG. 1 of Patent Document 2). From the viewpoint of heating the sulfide glass at a high temperature, the synthesis method of Patent Document 2 can also be considered as a kind of solid phase method. Non-Patent Document 1 discloses a crystal structure of Li ₄ P ₂ S ₆ crystal.

JP 2003-206110 A JP 2002-109955 A

R. Mercier et al., Journal of Solid State Chemistry, 43, 2, (1982) 151-162

As described above, the sulfide solid electrolyte material having the Li ₄ P ₂ S ₆ crystal phase has a problem that the Li ion conductivity is low. The present invention has been made in view of the above problems, and has a Li ₄ P ₂ S ₆ crystal phase and can provide a sulfide solid electrolyte material having excellent Li ion conductivity. The main object is to provide a method for producing an electrolyte material.

In order to improve the Li ion conductivity of the sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase as a result of intensive studies by the present inventors in order to solve the above-mentioned problems, the above-mentioned patent documents and the like However, it is important not to synthesize a highly crystalline sulfide solid electrolyte material by a solid-phase method, but to synthesize an amorphous-like sulfide solid electrolyte material. to obtain a finding that Li ion conductivity (for example ¹⁰⁴ times) significantly the can be improved. The present invention has been made based on such knowledge.

That is, in the present invention, a preparation process for preparing a raw material composition having a composition capable of forming a Li ₄ P ₂ S ₆ crystal phase, and a mechanical milling method or a melt quenching method are performed on the raw material composition to obtain a Li ₄ And a synthesis step of synthesizing a sulfide solid electrolyte material having a P ₂ S ₆ crystal phase. A method for producing a sulfide solid electrolyte material is provided.

According to the present invention, a sulfide solid electrolyte having a Li ₄ P ₂ S ₆ crystal and excellent Li ion conductivity by performing a mechanical milling method or a melt quenching method on the raw material composition having the above composition. Material can be obtained.

In the above invention, the raw material composition is, lithium sulfide _(Li 2 S), and phosphorus (P) and sulfur (S), the _Li 2 S, the ratio of P and S, on a molar basis, Li ₂ It is preferable that S: P: S = 2: 1.6 to 2.4: 3.2 to 4.8. This is because a composition of Li ₄ P ₂ S ₆ or a composition in the vicinity thereof can be obtained.

In the above invention, the raw material composition contains lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ) and diphosphorus trisulfide (P ₂ S ₃ ), and the Li ₂ S, P The ratio of ₂ S ₅ and P ₂ S ₃ is, on a molar basis, Li ₂ S: P ₂ S ₅ : P ₂ S ₃ = 2: 0.4 to 0.6: 0.4 to 0.6. Is preferred. This is because a composition of Li ₄ P ₂ S ₆ or a composition in the vicinity thereof can be obtained.

  In the said invention, it is preferable to perform the said mechanical milling method in the said synthetic | combination process. This is because processing at room temperature is possible, and the manufacturing process can be simplified.

  Moreover, in this invention, the sulfide solid electrolyte material characterized by obtained by the manufacturing method of the sulfide solid electrolyte material mentioned above is provided.

  According to the present invention, a sulfide solid electrolyte material excellent in Li ion conductivity can be obtained by performing the above-described method for producing a sulfide solid electrolyte material.

In the present _invention, Li ₄ a sulfide solid electrolyte material having a P 2 _{S 6} crystal phase, 2 [Theta] = 32.5 ° near to the _Li 4 main _P 2 _{S 6} crystal phase in X-ray diffraction measurement A sulfide solid electrolyte material having a peak and having a half-width of 0.5 ° or more of the main peak is provided.

  According to the present invention, since the half width of the main peak is not less than the above value, a sulfide solid electrolyte material excellent in Li ion conductivity can be obtained.

In the said invention, it is preferable that Li ion conductivity at room temperature is 1.0 * 10 < ^-5 > S / cm or more.

  In the present invention, a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and an electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer A lithium battery characterized in that at least one of the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer contains the above-described sulfide solid electrolyte material. .

  According to the present invention, by using the above-described sulfide solid electrolyte material, a lithium battery having excellent output characteristics can be obtained.

In the present invention, it has a Li ₄ P ₂ S ₆ crystal phase, and an effect that it is possible to obtain an excellent sulfide solid electrolyte material 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 electric power generation element of the lithium battery of this invention. It is a measurement result of the X-ray diffraction of the sulfide solid electrolyte material obtained by the Example and the comparative example. It is a measurement result of the X-ray diffraction of the sulfide solid electrolyte material obtained by the Example and the comparative example. It is an alternating current impedance plot of the sulfide solid electrolyte material obtained in the Example. It is an alternating current impedance plot of the sulfide solid electrolyte material obtained by the comparative example.

  The sulfide solid electrolyte material production method, sulfide solid electrolyte material and lithium battery of the present invention will be described in detail below.

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 preparation step of preparing a raw material composition having a composition capable of forming a Li ₄ P ₂ S ₆ crystal phase, and a mechanical milling method or a melt quenching method for the raw material composition. And a synthesis step of synthesizing a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase.

According to the present invention, a sulfide solid electrolyte having a Li ₄ P ₂ S ₆ crystal and excellent Li ion conductivity by performing a mechanical milling method or a melt quenching method on the raw material composition having the above composition. Material can be obtained. As described above, the Li ₄ P ₂ S ₆ crystal has a problem that the Li ion conductivity is extremely poor. The reason why the Li ion conductivity is extremely poor is considered to be because the grain boundary resistance between crystals is large. On the other hand, in the present invention, an amorphous-like Li ₄ P ₂ S ₆ crystal can be formed by performing a mechanical milling method or a melt quenching method, and the intergranular resistance between the crystals can be reduced. it can. As a result, the Li ion conductivity of the sulfide solid electrolyte material can be remarkably improved. In the present invention, even without heat treatment after the mechanical milling or melt quenching method, it is possible to obtain a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase. Therefore, there is an advantage that the manufacturing process can be simplified.

In Patent Document 2 described above, a raw material composition containing Li 2 _S and P ₂ S _5, is performed a mechanical milling method, in this case, as described in comparative example described later, mechanical milling method Alone, a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase cannot be synthesized.

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, lithium sulfide (Li ₂ S), phosphorus (P), and sulfur (S) are prepared under an inert gas atmosphere, and these are prepared as Li ₂ S: P: S = 2: 2: 4. (Mole basis) to obtain a raw material composition (preparation step). Next, the raw material composition is subjected to a mechanical milling method at a desired base plate rotation speed and time to synthesize a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase (synthesis step).

The sulfide solid electrolyte material obtained by the production method of the present invention has at least a Li ₄ P ₂ S ₆ crystal phase. Whether or not the sulfide solid electrolyte material has a Li ₄ P ₂ S ₆ crystal phase is determined by X-ray line measurement based on a peak around 2θ = 32.5 ° which is the main peak of the Li ₄ P ₂ S ₆ crystal phase. Judgment can be made based on whether or not it is confirmed. Also, the sulfide-based solid electrolyte material, may have a Li ₄ P ₂ S ₆ crystal phase other than the crystalline phase, but it is preferable that a main component Li ₄ P ₂ S ₆ crystal phase. “Mainly comprising the Li ₄ P ₂ S ₆ crystal phase” means that the intensity of the main peak of the Li ₄ P ₂ S ₆ crystal phase is greater than the intensity of the peaks of the other crystal phases. Furthermore, the sulfide solid electrolyte material may have only a Li ₄ P ₂ S ₆ crystal phase and no other crystal phase peak. Moreover, the sulfide solid electrolyte material obtained by the present invention usually becomes amorphous-like. In the present invention, as described in "B. Sulfide solid electrolyte material 2. Second embodiment" described later, the half width of the main peak of the Li ₄ P ₂ S ₆ crystal phase is a predetermined angle or more. It is preferable that

  Hereafter, the manufacturing method of the sulfide solid electrolyte material of this invention is demonstrated for every process. In the present invention, each step described later is usually performed in an inert gas atmosphere (for example, in an Ar gas atmosphere).

1. Preparation Step First, the preparation step in the present invention will be described. The preparation step in the present invention is a step of preparing a raw material composition having a composition capable of forming a Li ₄ P ₂ S ₆ crystal phase. “A composition capable of forming a Li ₄ P ₂ S ₆ crystal phase” means that when an X-ray line measurement is performed on a sulfide solid electrolyte material obtained by the production method of the present invention, Li ₄ P ₂ A composition in which a peak around 2θ = 32.5 ° which is the main peak of the S ₆ crystal phase can be confirmed.

The raw material composition in the present invention contains at least Li element, P element and S element. The composition of the raw material composition is not particularly limited as long as it is a composition capable of forming a Li ₄ P ₂ S ₆ crystal phase. As an example of a raw material composition may include those containing lithium sulfide (Li 2 _S), phosphorus (P) and sulfur (S). In this case, for example, the composition of Li ₄ P ₂ S ₆ can be obtained by mixing at a molar ratio of Li ₂ S: P: S = 2: 2: 4. Further, Li ₂ S is preferably less 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 phosphorus used in the raw material composition include red phosphorus, yellow phosphorus, black phosphorus, and the like, among which red phosphorus is preferable. Examples of sulfur used in the raw material composition include orthorhombic sulfur, rubbery sulfur, monoclinic sulfur and the like. Among them, orthorhombic sulfur is preferable.

When the raw material composition contains Li ₂ S, P and S, these ratios are not particularly limited as long as they are ratios capable of forming a Li ₄ P ₂ S ₆ crystal phase, but Li ₄ P ₂ It is preferable that the ratio is such that the composition of S ₆ or its vicinity can be obtained. Specifically, the ratio of Li ₂ S, P and S is preferably Li ₂ S: P: S = 2: 1.6 to 2.4: 3.2 to 4.8 on a molar basis. 2: 1.8-2.2: 3.6-4.4 is more preferable, and 2: 1.9-2.1: 3.8-4.2 is even more preferable.

Other examples of the raw material composition include those containing lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ) and diphosphorus trisulfide (P ₂ S ₃ ). . In this case, for example, the composition of Li ₄ P ₂ S ₆ can be obtained by mixing at a molar ratio of Li ₂ S: P ₂ S ₅ : P ₂ S ₃ = 2: 0.5: 0.5. When the raw material composition contains Li ₂ S, P ₂ S ₅ and P ₂ S ₃ , these ratios are not particularly limited as long as they can form a Li ₄ P ₂ S ₆ crystal phase. _but it is preferable that a ratio obtained by composition or near the composition of Li ₄ P 2 _{S 6.} Specifically, the ratio of Li ₂ S, P ₂ S ₅ and P ₂ S ₃ is, on a molar basis, Li ₂ S: P ₂ S ₅ : P ₂ S ₃ = 2: 0.4 to 0.6: It is preferably 0.4 to 0.6, more preferably 2: 0.45 to 0.55: 0.45 to 0.55, and 2: 0.48 to 0.52: 0.48. More preferably, it is -0.52.

2. Synthesis Step Next, the synthesis step in the present invention will be described. The synthesis process in the present invention is a process for synthesizing a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase by performing a mechanical milling method or a melt quenching method on the raw material composition.

In the present invention, it is possible to synthesize an amorphous-like sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase, regardless of whether the melt quenching method or the mechanical milling method is used. Of these, the mechanical milling method is preferable. This is because processing at room temperature is possible, and the manufacturing process can be simplified.

  Mechanical milling is not particularly limited as long as the raw material composition is mixed while applying mechanical energy. And a planetary ball mill is particularly preferable. This is because a desired sulfide solid electrolyte material can be obtained efficiently. Further, in the present invention, a sulfide solid electrolyte material having a certain degree of crystallinity (amorphous like) can be obtained only by mechanical milling and without subsequent heat treatment.

The various conditions of mechanical milling are set so that an amorphous-like sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase can be obtained. For example, when a sulfide solid electrolyte material is produced by a planetary ball mill, the raw material composition and grinding balls are added to the pot, and the treatment is performed at a predetermined rotational speed 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 number of rotations 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 10 hours to 500 hours, and more preferably in the range of 20 hours to 100 hours.

3. Sulfide solid electrolyte material The sulfide solid electrolyte material obtained by the production method of the present invention preferably has a high Li ion conductivity. The Li ion conductivity at room temperature is, for example, preferably 10 ⁻⁶ S / cm or more, and more preferably 10 ⁻⁵ S / cm or more. The sulfide solid electrolyte material is usually in a powder form, and the average diameter thereof is, for example, in the range of 0.1 μm to 50 μm. Moreover, as a use of sulfide solid electrolyte material, a lithium battery use can be mentioned, for example.

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

1. First Embodiment First, a first embodiment of the sulfide solid electrolyte material of the present invention will be described. The sulfide solid electrolyte material of the first embodiment is obtained by the above-described method for producing a sulfide solid electrolyte material.

  According to the first embodiment, a sulfide solid electrolyte material excellent in Li ion conductivity can be obtained by performing the above-described method for producing a sulfide solid electrolyte material. Therefore, for example, a sulfide solid electrolyte material useful for lithium battery applications can be obtained.

  In addition, about the manufacturing method of the sulfide solid electrolyte material in 1st embodiment, the characteristic of a sulfide solid electrolyte material, and other matters, it is the same as the content described in the above-mentioned "A. Manufacturing method of sulfide solid electrolyte material". Therefore, the description here is omitted.

2. Second Embodiment Next, a second embodiment of the sulfide solid electrolyte material of the present invention will be described. The sulfide solid electrolyte material according to the second embodiment is a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase, and the Li ₄ P ₂ S is around 2θ = 32.5 ° in X-ray diffraction measurement. _It has a main peak of _six crystal phases, and the half width of the main peak is 0.5 ° or more.

  According to the second embodiment, since the half width of the main peak is not less than the above value, a sulfide solid electrolyte material excellent in Li ion conductivity can be obtained. Therefore, for example, a sulfide solid electrolyte material useful for lithium battery applications can be obtained.

The sulfide solid electrolyte material of the second embodiment has a main peak of Li ₄ P ₂ S ₆ crystal phase in the vicinity of 2θ = 32.5 ° in X-ray diffraction measurement. Here, 2θ = 32.5 ° means a theoretical value of the main peak according to the XRD database. Therefore, depending on the composition and crystallinity of the sulfide solid electrolyte material, the angle may slightly vary from 2θ = 32.5 °. The main peak of the Li ₄ P ₂ S ₆ crystal phase in the second embodiment appears at 2θ = 32.5 ° ± 0.5 °, for example.

The sulfide solid electrolyte material of the second embodiment may have at least the main peak. On the other hand, since the sulfide solid electrolyte material of the second embodiment has a Li ₄ P ₂ S ₆ crystal phase, a characteristic peak appears in addition to the main peak when the crystallinity is high to some extent. Examples of such peaks include peaks at 2θ = 27.1 °, 52.2 °, and 16.9 ° in descending order of peak intensity. These angles also mean theoretical values based on the XRD database, and there are cases where the angles fluctuate in the same manner as the main peak. Further, the sulfide solid electrolyte material of the second embodiment may have only a main peak, or may have a peak with 2 to 4th intensity. Usually, the higher the crystallinity of the sulfide solid electrolyte material, the greater the number of peaks. Therefore, the crystallinity can also be defined by the number of peaks.

  In the second embodiment, the full width at half maximum of the main peak is usually 0.5 ° or more, preferably 0.55 ° or more, and more preferably 0.60 ° or more. This is because the Li ion conductivity is further improved. On the other hand, the upper limit of the half width of the main peak is not particularly limited. If the crystallinity of the sulfide solid electrolyte material is lowered, the half-value width is increased, but at the same time, the peak intensity is decreased, so that it may be difficult to measure the half-value width. In the second embodiment, it is sufficient that the main peak has crystallinity at which the main peak can be confirmed, and the upper limit of the half width of the main peak is not particularly limited.

  The characteristics of the sulfide solid electrolyte material and other matters in the second embodiment are the same as the contents described in the above “A. Method for producing sulfide solid electrolyte material”. Omitted.

C. Next, the lithium battery of the present invention will be described. The lithium 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 an electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer Wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer contains the above-described sulfide solid electrolyte material.

  According to the present invention, by using the above-described sulfide solid electrolyte material, a lithium battery having excellent output characteristics can be obtained.

FIG. 2 is a schematic cross-sectional view showing an example of the power generation element of the lithium battery of the present invention. A power generation element 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 a positive electrode active material layer 1 and a negative electrode active material layer 2. And the formed electrolyte layer 3. Furthermore, the present invention is characterized in that at least one of the positive electrode active material layer 1, the negative electrode active material layer 2, and the electrolyte layer 3 contains the sulfide solid electrolyte material described above.
Hereinafter, the lithium battery of the present invention will be described for each configuration.

1. Electrolyte Layer First, the electrolyte layer in the present invention will be described. The electrolyte layer in the present invention is a layer formed between the positive electrode active material layer and the negative electrode active material layer. The electrolyte layer is not particularly limited as long as it is a layer capable of conducting Li ions, but is preferably a solid electrolyte layer made of a solid electrolyte material. This is because a highly safe lithium battery (all solid battery) can be obtained. Furthermore, in this invention, it is preferable that a solid electrolyte layer contains the sulfide solid electrolyte material mentioned above. The ratio of the sulfide solid electrolyte material contained in the solid electrolyte layer is, for example, preferably in the range of 10% to 100% by volume, and more preferably in the range of 50% to 100% by volume. In particular, in the present invention, it is preferable that the solid electrolyte layer is composed only of the sulfide solid electrolyte material. This is because a lithium battery with less hydrogen sulfide generation can be obtained. The thickness of the solid electrolyte layer is, for example, preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm. Moreover, as a formation method of a solid electrolyte layer, the method etc. which compression-mold a solid electrolyte material can be mentioned, for example.

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

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 contain at least one of a solid electrolyte material, a conductive material and a binder as necessary. In particular, in the present invention, the solid electrolyte material contained in the positive electrode active material layer is preferably the sulfide solid electrolyte material described above. The ratio of the sulfide solid electrolyte material contained in the positive electrode active material layer varies depending on the type of the lithium battery. It is preferable to be within the range, particularly within the range of 10% by volume to 50% by volume. As the positive electrode active material, for example, LiCoO ₂ , LiMnO ₂ , Li ₂ NiMn ₃ O ₈ , LiVO ₂ , LiCrO ₂ , LiFePO ₄ , LiCoPO ₄ , LiNiO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ etc. can be mentioned.

  The positive electrode active material layer in the present invention may further contain a conductive material. By adding a conductive material, the conductivity of the positive electrode active material layer can be improved. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. The positive electrode active material layer may contain a binder. As a kind of binder, a fluorine-containing binder etc. can be mentioned, for example. Moreover, it is preferable that the thickness of a positive electrode active material layer exists in the range of 0.1 micrometer-1000 micrometers, for example.

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 contain at least one of a solid electrolyte material, a conductive material and a binder as necessary. In particular, in the present invention, the solid electrolyte material contained in the negative electrode active material layer is preferably the sulfide solid electrolyte material described above. The ratio of the sulfide solid electrolyte material contained in the negative electrode active material layer varies depending on the type of the lithium battery. It is preferable to be within the range, particularly within the range of 10% by volume to 50% by volume. Examples of the negative electrode active material include a metal active material and a carbon active material. Examples of the metal active material include In, Al, Si, and Sn. On the other hand, examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Note that the conductive material and the binder used in the negative electrode active material layer are the same as those in the positive electrode active material layer described above. The thickness of the negative electrode active material layer is, for example, in the range of 0.1 μm to 1000 μm.

4). Other Configurations The lithium battery of the present invention has at least the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material layer and a negative electrode current collector for collecting current of the negative electrode active material. 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. Of these, 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 battery. Moreover, the battery case of a general lithium battery can be used for the battery case used for this invention. Examples of the battery case include a SUS battery case. When the lithium battery of the present invention is an all-solid battery, the power generation element may be formed inside the insulating ring.

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

  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]
As starting materials, lithium sulfide (Li ₂ S), phosphorus (P), and sulfur (S) were used. These raw materials were weighed and mixed in a glove box under an argon atmosphere so that the molar ratio of Li ₂ S: P: S = 2: 2: 4 was obtained, thereby obtaining 1 g of a raw material composition. Next, 1 g of the obtained raw material composition was put into a 45 ml zirconia pot, and zirconia balls (Φ10 mm, 10 pieces) were put into it, and the pot was completely sealed. This pot was attached to a planetary ball mill and mechanical milling was performed for 100 hours at a base plate rotation speed of 370 rpm to obtain an amorphous-like sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase.

[Comparative example]
As starting materials, lithium sulfide (Li ₂ S) and diphosphorus pentasulfide (P ₂ S ₅ ) were used. These raw materials were weighed in a glove box under an argon atmosphere so as to have a molar ratio of Li ₂ S: P ₂ S ₅ = 67: 33 and mixed to obtain 1 g of a raw material composition. Next, 1 g of the obtained raw material composition was put into a 45 ml zirconia pot, and zirconia balls (Φ10 mm, 10 pieces) were put into it, and the pot was completely sealed. This pot was attached to a planetary ball mill, and mechanical milling was performed at a platen rotation speed of 370 rpm for 40 hours to obtain glass samples (67Li ₂ S-33P ₂ S ₅ glass, Li ₄ P ₂ S ₇ glass).

Next, the obtained glass sample was heat-treated at 450 ° C. for 3 hours to obtain a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase and high crystallinity. This synthesis method is based on the method described in Non-Patent Document 1. Further, from the viewpoint of heating a glass sample at a high temperature, this synthesis method can be considered as a kind of solid phase method.

[Evaluation]
(X-ray diffraction measurement)
X-ray diffraction measurement was performed using the sulfide solid electrolyte materials obtained in Examples and Comparative Examples. The result is shown in FIG. As shown in FIG. 3, in the example (synthesis by mechanical milling method) as well as the comparative example (synthesis by solid phase method), a sulfide solid electrolyte having a Li ₄ P ₂ S ₆ crystal phase in a single phase The material could be obtained. Moreover, it was confirmed that the sulfide solid electrolyte material obtained in the example is amorphous like and low in crystallinity as compared with the sulfide solid electrolyte material obtained in the comparative example. Both of them had a large main peak in the vicinity of 2θ = 32.5 °. FIG. 4 shows a comparison of both main peaks. As shown in FIG. 4, when the half widths of the two were compared, it was 0.62 ° in the example and 0.20 ° in the comparative example.

In addition, the X-ray-diffraction measurement was performed also about the glass sample produced by the comparative example. As a result, a halo pattern was obtained, and it was judged that glass was produced, so that the Li ₄ P ₂ S ₆ crystal phase was not formed.

(Li ion conductivity measurement)
Li ion conductivity measurement was performed using the sulfide solid electrolyte materials obtained in Examples and Comparative Examples. Li ion conductivity was measured as follows. That is, the powder of the sulfide solid electrolyte material was pelletized, and the Li ion conductivity at room temperature was measured by the AC impedance method. The results are shown in FIGS. 5 and 6 and Table 1.

In FIG. 6, in the AC impedance plot of the comparative example, there was a disturbance of the plot on the high frequency side, but this is a disturbance due to low conductivity, which is considered to be a measurement limit. Therefore, the Li ion conductivity of the comparative example in Table 1 was obtained by fitting. Further, as shown in Table 1, Examples are compared with Comparative Example, it is high 10 ⁴ times the Li ion conductivity was confirmed.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 2 ... Negative electrode active material layer 3 ... Electrolyte layer 10 ... Electric power generation element

Claims (8)

A preparation step of preparing a raw material composition having a composition capable of forming a Li ₄ P ₂ S ₆ crystal phase;
The raw material composition, by row Ukoto mechanical milling or melt quenching method, a synthesis step of synthesizing a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase,
I have a,
The raw material composition contains lithium sulfide (Li ₂ S), phosphorus (P) and sulfur (S), lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ) and ditrisulfide trisulfide. A method for producing a sulfide solid electrolyte material comprising phosphorus (P ₂ S ₃ ) . A preparation step of preparing a raw material composition having a composition capable of forming a Li ₄ P ₂ S ₆ crystal phase;
The raw material composition is subjected to a mechanical milling method or a melt quenching method to synthesize a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase;
Have
The raw material composition contains lithium sulfide (Li ₂ S), phosphorus (P) and sulfur (S), and the ratio of Li ₂ S, P and S is Li ₂ S: P: S on a molar basis. = 2: 1.6 to 2.4: manufacturing method of sulfides solid electrolyte material it is a 3.2 to 4.8. A preparation step of preparing a raw material composition having a composition capable of forming a Li ₄ P ₂ S ₆ crystal phase;
The raw material composition is subjected to a mechanical milling method or a melt quenching method to synthesize a sulfide solid electrolyte material having a Li ₄ P ₂ S ₆ crystal phase;
Have
The raw material composition contains lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ) and diphosphorus trisulfide (P ₂ S ₃ ), and the Li ₂ S, P ₂ S ₅ and P ratio of ₂ S ₃ is on a molar _{basis, Li 2 S: P 2 S} 5: P 2 S 3 = 2: 0.4~0.6: you characterized in that 0.4 to 0.6 manufacturing method of sulfides solid electrolyte material.   The method for producing a sulfide solid electrolyte material according to any one of claims 1 to 3, wherein the mechanical milling method is performed in the synthesis step.   A sulfide solid electrolyte material obtained by the method for producing a sulfide solid electrolyte material according to any one of claims 1 to 4. A sulfide solid electrolyte material having only a Li ₄ P ₂ S ₆ crystal phase,
A sulfide characterized by having a main peak of the Li ₄ P ₂ S ₆ crystal phase in the vicinity of 2θ = 32.5 ° in X-ray diffraction measurement, and a half width of the main peak being 0.5 ° or more. Solid electrolyte material. 7. The sulfide solid electrolyte material according to claim 5, wherein Li ion conductivity at room temperature is 1.0 × 10 ⁻⁵ S / cm or more. A lithium 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 an electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer There,
At least one of the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer contains the sulfide solid electrolyte material according to any one of claims 5 to 7. Lithium battery.

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