JP2022176803A - Solid electrolyte material, manufacturing method therefor and battery - Google Patents

Abstract

To provide solid electrolyte material enabling reduction of a value of resistance of a battery.SOLUTION: Solid electrolyte material is provided, including: sulfide that has a composition including lithium, phosphorus, and sulfur and has an argyrodite type crystal structure; lithium phosphate; and sulfate ions. In the solid electrolyte material, a content of sulfate ions is equal to or more than 0.5 mass%. When the solid electrolyte material is measured by a θ-2θ method using CuKα rays having wavelengths of 0.15405nm and 0.15444nm as X-ray sources in an X-ray diffraction pattern, a first peak is observed in a range of a value of a diffraction angle 2θ being equal to or more than 21° and less than 23°and a second peak is observed in a range of the value of the diffraction angle 2θ being equal to or more than 25°and less than 27°, wherein a ratio of intensity of the first peak to that of the second peal is equal to or more than 0.03 and less than 0.15.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present disclosure relates to solid electrolyte materials, methods of manufacturing the same, and batteries.

There is a demand for an all-solid-state lithium-ion secondary battery that uses a solid electrolyte as the electrolyte and is more excellent in safety. Examples of solid electrolytes include oxide solid electrolytes containing lithium, metal elements and oxygen, sulfide solid electrolytes containing lithium, phosphorus and sulfur, and halogen solid electrolytes containing lithium, metal elements and halogen. Among these, sulfides having an aldirodite structure have attracted attention as sulfide-based solid electrolytes because of their high ionic conductivity and low production cost.

For example, Patent Document 1 discloses a solid electrolyte material having a peak corresponding to Li ₇ PS ₆ and a peak corresponding to Li ₃ PO ₄ in X-ray diffraction measurement, which has high Li ion conductivity and is thermally stable. A material with high resistance has been proposed.

JP 2017-33858 A

An object of one aspect of the present disclosure is to provide a solid electrolyte material capable of reducing the resistance value of a battery and a method for producing the same.

A first aspect is to obtain a mixture containing a compound containing lithium, a compound containing phosphorus and sulfur, a metal sulfate and a metal phosphate, and heat-treating the mixture to obtain a heat-treated product containing sulfate ions and lithium phosphate. and a method for producing a solid electrolyte material. The lithium-containing compound in the production method includes at least one selected from the group consisting of lithium sulfide, lithium oxide and lithium carbonate. In addition, the mixture in the production method has a metal phosphate content of less than 15.0% by mass.

A second embodiment is a solid electrolyte material containing lithium, phosphorus and sulfur in its composition and containing a sulfide having an algyrodite crystal structure, lithium phosphate, and sulfate ions. The solid electrolyte material has a sulfate ion content of 0.5% by mass or more. In the X-ray diffraction pattern of the solid electrolyte material, the value of the diffraction angle 2θ is 21° or more and less than 23° when measured by the θ-2θ method using CuKα rays with wavelengths of 0.15405 nm and 0.15444 nm as the X-ray source. A first peak is observed in the range of , and a second peak is observed in a range in which the value of the diffraction angle 2θ is 25° or more and less than 27°, and the ratio of the intensity of the first peak to the intensity of the second peak is 0. 03 or more and less than 0.15.

According to one aspect of the present disclosure, it is possible to provide a solid electrolyte material capable of reducing resistance in a battery and a method for producing the same.

1 is a cross-sectional view showing a schematic configuration of a battery 1000; FIG. FIG. 2 is a cross-sectional view showing a schematic configuration of a measurement cell for evaluating battery characteristics; 1 is an X-ray diffraction (XRD) pattern of solid electrolyte materials according to Example 1 and Comparative Example 1. FIG. 4 shows XRD patterns of solid electrolyte materials according to Examples 2, 3, and 4. FIG. 4 shows XRD patterns of solid electrolyte materials according to Comparative Examples 2, 3 and 4. FIG.

In this specification, the term "process" is not only an independent process, but even if it cannot be clearly distinguished from other processes, it is included in this term as long as the intended purpose of the process is achieved. . In addition, the content of each component in the composition means the total amount of the plurality of substances present in the composition unless otherwise specified when there are multiple substances corresponding to each component in the composition. Furthermore, the upper and lower limits of the numerical ranges described herein can be arbitrarily selected and combined. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below exemplify the solid electrolyte material, the method for producing the same, and the battery for embodying the technical idea of the present invention. It is not limited to manufacturing methods and batteries.

Method for Producing Solid Electrolyte Material The method for producing a solid electrolyte material comprises a preparation step of obtaining a mixture containing a compound containing lithium, a compound containing phosphorus and sulfur, a metal sulfate and a metal phosphate, and heat-treating the prepared mixture. and a heat treatment step of obtaining a heat treated product containing sulfate ions and lithium phosphate. The compound containing lithium contained in the mixture contains at least one selected from the group consisting of lithium sulfide, lithium oxide and lithium carbonate. Also, the content of metal phosphate in the mixture is less than 15.0% by mass.

A solid electrolyte material produced by adding a predetermined amount of a metal sulfate in addition to a metal phosphate when producing a solid electrolyte material containing a sulfide having an aldirodite-type crystal structure. The resistance value in the battery is reduced. For example, it can be considered that the presence of predetermined amounts of sulfate ions and lithium phosphate in the solid electrolyte material improves the conductivity of lithium ions.

Preparatory Step In the preliminary step, a mixture containing a compound containing lithium, a compound containing phosphorus and sulfur, a metal sulfate and a metal phosphate is obtained. The mixture may also further contain a chlorine-containing compound. The mixture may be, for example, a raw material composition of a solid electrolyte material.

Lithium-containing compounds include lithium sulfide (e.g., Li ₂ S), lithium oxide (e.g., Li ₂ O), lithium carbonate (e.g., Li ₂ CO ₃ ), and the like, and are selected from the group consisting of these. and preferably at least lithium sulfide.

The content of the compound containing lithium in the mixture may be, for example, 3 mol or more and 7 mol or less, preferably 3.1 mol or more and 5 mol or less, relative to 1 mol of the compound containing phosphorus and sulfur, More preferably, it may be 3.3 mol or more and 4.3 mol or less. Here, the content of compounds containing lithium does not include compounds containing metal sulfates, metal phosphates, and chlorine, which will be described later.

A compound containing phosphorus and sulfur may be, for example, a compound having a phosphorus-sulfur bond. Compounds containing phosphorus and sulfur include diphosphorus trisulfide ₍ e.g., _P2S3 ) _, diphosphorus pentasulfide (e.g., _P2S5 ), etc., and at least It may contain one, preferably at least diphosphorus pentasulfide.

The metal sulphate may be, for example, an alkali metal sulphate. Examples of metal sulfates include lithium sulfate (e.g., Li ₂ SO ₄ ), sodium sulfate (Na ₂ SO ₄ ), and the like, and may preferably contain at least one selected from the group consisting of these. may contain at least lithium sulfate.

The content of metal sulfate in the mixture may be, for example, 1.0% by mass or less, preferably 0.7% by mass or less, 0.6% by mass or less, or 0.55% by mass or less, relative to the mixture. It's okay. In addition, the lower limit of the content of the metal sulfate may be, for example, 0.01% by mass or more, preferably 0.1% by mass or more, 0.2% by mass or more, or 0.4% by mass with respect to the mixture. or more. When the content of the metal sulfate is within the above range, the lithium ion conductivity of the produced solid electrolyte material tends to be further improved, the battery resistance is further reduced, and the battery characteristics are further improved.

A metal phosphate may be, for example, an alkali metal phosphate. Examples of the metal phosphate include lithium phosphate (e.g., Li ₃ PO ₄ ), sodium phosphate (Na ₃ PO ₄ ), and the like, and contain at least one selected from the group consisting of these. Well, preferably, it may contain at least lithium phosphate.

The content of the metal phosphate in the mixture may be, for example, 15.0% by mass or less, preferably 10.0% by mass or less, 7.0% by mass or less, 5.0% by mass or less, based on the mixture. Alternatively, it may be 3.0% by mass or less. Moreover, the lower limit of the content of the metal phosphate may be, for example, 0.1% by mass or more, preferably 0.5% by mass or more, or 1.0% by mass or more with respect to the mixture. When the content of the metal phosphate is within the above range, the battery resistance of the produced solid electrolyte material tends to be further reduced.

The chlorine-containing compound may be, for example, a metal chloride, preferably an alkali metal chloride. Alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and the like. Specific examples of the chlorine-containing compound include lithium chloride (e.g., LiCl), sodium chloride (e.g., NaCl), potassium chloride (e.g., KCl), etc. At least one compound selected from the group consisting of these It may contain seeds, preferably at least lithium chloride.

The content of the compound containing chlorine in the mixture may be, for example, 0 mol or more and 3.9 mol or less, preferably 1 mol or more and 3.7 mol or less, more preferably 1 mol or less of the compound containing phosphorus and sulfur. may be 2.9 mol or more and 3.5 mol or less. When the content of the compound containing chlorine in the mixture is within the above range, the effect of reducing internal resistance, which will be described later, tends to be greater.

A portion of the chlorine-containing compound may be replaced with a bromine-containing compound. The bromine-containing compound may be, for example, a metal bromide, preferably an alkali metal bromide. Alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and the like. Specific examples of the bromine-containing compound include lithium bromide (e.g., LiBr), sodium bromide (e.g., NaBr), potassium bromide (e.g., KBr), and the like. and preferably at least lithium bromide. When part of the chlorine-containing compound is replaced with a bromine-containing compound, the content of the bromine-containing compound may be greater than 0 mol and less than 1 mol with respect to 1 mol of the chlorine-containing compound, It may be preferably 0.5 mol or less, more preferably 0.1 mol or less. The lower limit of the content of the bromine-containing compound relative to the chlorine-containing compound may be, for example, 0.001 mol or more. Further, when part of the chlorine-containing compound is replaced with a bromine-containing compound, the total amount of the chlorine-containing compound and the bromine-containing compound is 0 mol or more per 1 mol of the compound containing phosphorus and sulfur. It may be 9 mol or less, preferably 1 mol or more and 3.7 mol or less, more preferably 2.9 mol or more and 3.5 mol or less.

In the mixture, part of the chlorine-containing compound may be substituted with a compound containing halogen atoms other than chlorine and bromine. Halogen atoms contained in compounds containing halogen atoms other than chlorine and bromine include fluorine and iodine, and at least one of these may be contained. Compounds containing halogen atoms other than chlorine and bromine may, for example, contain metal halides, preferably alkali metal halides, and at least lithium halides.

When the mixture contains a compound containing a halogen atom other than chlorine and bromine, the content of the compound containing a halogen atom other than chlorine and bromine in the mixture is, for example, greater than 0 mol and 0.5 mol per 1 mol of the compound containing chlorine. It may be 1 mol or less, preferably more than 0 mol and 0.05 mol or less.

The mixture is obtained by weighing and mixing a compound containing lithium, a compound containing phosphorus and sulfur, a metal sulfate, a metal phosphate and, if necessary, a compound containing chlorine so that each has a desired content. can be prepared. For example, the total molar content ratio of the compound containing lithium and the compound containing chlorine to the compound containing phosphorus and sulfur in the mixture may be, for example, 3 or more and 8 or less, preferably 5 or more and 7.8 or less, more preferably may be 6 or more and 7.5 or less.

Examples of mixing methods for mixing raw materials include high-speed shear mixers, ball mills, bead mills, vibration mills, planetary ball mills, and other mixing methods that can apply mechanical stress.

Heat Treatment Step In the heat treatment step, the prepared mixture is heat treated to obtain a heat treated product containing sulfate ions and lithium phosphate. The heat-treated product contains lithium, phosphorus and sulfur in its composition and may contain a sulfide having an algyrodite-type crystal structure, and the sulfide having an algyrodite-type crystal structure may contain a crystal phase. When the sulfide contains a crystalline phase, it may contain a crystalline phase having a _composition represented by _Li7PS6 .

The heat treatment temperature of the mixture may be, for example, 400° C. or higher, preferably 450° C. or higher, or 500° C. or higher. The upper limit of the heat treatment temperature may be, for example, 1000° C. or lower, preferably 800° C. or lower, or 600° C. or lower. The heat treatment time may be, for example, 1 hour or more and 20 hours or less, preferably 5 hours or more and 15 hours or less. The heat treatment atmosphere may be, for example, an inert gas atmosphere such as nitrogen gas or rare gas, or the heat treatment may be performed under reduced pressure.

Solid Electrolyte Material The solid electrolyte material contains lithium, phosphorus and sulfur in its composition, and contains a sulfide having an aldirodite crystal structure, lithium phosphate, and sulfate ions. In the X-ray diffraction pattern of the solid electrolyte material, the value of the diffraction angle 2θ is 21° or more and less than 23° when measured by the θ-2θ method using CuKα rays with wavelengths of 0.15405 nm and 0.15444 nm as the X-ray source. A first peak is observed in the range of , and a second peak is observed in a range in which the value of the diffraction angle 2θ is 25° or more and less than 27°. Furthermore, the ratio of the intensity of the first peak to the intensity of the second peak may be, for example, 0.03 or more and less than 0.15. The content of sulfate ions contained in the solid electrolyte material may be, for example, 0.5% by mass or more with respect to the solid electrolyte material.

When the solid electrolyte material contains lithium phosphate and sulfate ions in addition to the sulfide having the aldirodite crystal structure, the conductivity of lithium ions is improved. In addition, when forming a battery, the internal resistance is reduced, and excellent battery characteristics can be exhibited. This can be considered, for example, as follows. When a sulfide having an algyrodite-type crystal structure is used as a solid electrolyte, the presence of lithium phosphate, which has a higher lithium concentration than that of the sulfide having an algyrodite-type crystal structure, on the surface of the solid electrolyte particles improves the diffusion of lithium ions. It is thought that the battery resistance is improved. The aldirodite-type crystal structure has a structure of Li ₂ S—Li ₃ PS ₄ —Li ₂ S, but when lithium sulfate is present in the vicinity, part of it is replaced with Li ₃ PS ₄ to form a solid solution. it is conceivable that. As a result, lithium vacancies occur in the solid electrolyte, creating vacant lithium sites. When the solid electrolyte material contains lithium chloride, it is thought that part of the lithium chloride is replaced with Li ₂ S to form a solid solution, resulting in lithium deficiency and forming vacant lithium sites. It is considered that the replacement of the respective units of Li ₂ S and Li ₃ PS ₄ in this manner synergistically improves the lithium ion conductivity.

The solid electrolyte material contains lithium, phosphorus and sulfur in its composition and contains a sulfide having an aldirodite crystal structure. The sulfide constituting the solid electrolyte material may contain a crystal phase having a _composition represented by _Li7PS6 , for example. The presence of a crystal phase having a composition represented by Li ₇ PS ₆ in the sulfide can be confirmed, for example, by X-ray diffraction (XRD) measurement. Specifically, when the solid electrolyte material is subjected to XRD measurement by the θ-2θ method using CuKα rays with wavelengths of 0.15405 nm and 0.15444 nm as the X-ray source, the crystal phase having the composition represented by Li ₇ PS ₆ Corresponding peaks usually appear at 2θ=25.7°, 30.2°, 31.6°, 45.3°, 48.2°, 52.7°.

The content of lithium in the sulfide composition may be, for example, 4 mol or more and 7 mol or less, preferably 5 mol or more and 6 mol or less, per 1 mol of phosphorus. The content of sulfur in the sulfide composition may be, for example, 3 mol or more and 6 mol or less, preferably 4 mol or more and 5 mol or less, per 1 mol of phosphorus.

The sulfide having an aldirodite-type crystal structure may contain halogen in its composition. Containing a halogen tends to further improve the lithium ion conductivity. Halogen includes chlorine, bromine, iodine, etc., may contain at least one selected from the group consisting of these, may contain one of chlorine and bromine, and may contain at least chlorine. The inclusion of chlorine tends to result in a sulfide solid electrolyte with higher chemical stability.

When the sulfide having an aldirodite-type crystal structure contains halogen in the composition, the content of halogen in the composition of the sulfide may be, for example, greater than 0 mol and not more than 2 mol per 1 mol of phosphorus, preferably 1 It may be mol or more and 2 mol or less, more preferably 1.4 mol or more and 1.8 mol or less. When the halogen contained in the composition of the sulfide having the aldirodite-type crystal structure is within the above range, the lithium ion conductivity of the sulfide tends to be more easily improved.

The solid electrolyte material contains lithium phosphate in addition to sulfide having an aldirodite crystal structure. The presence of lithium phosphate in solid electrolyte materials can be evaluated using X-ray diffraction patterns. Specifically, when the solid electrolyte material is subjected to XRD measurement by the θ-2θ method using CuKα rays with wavelengths of 0.15405 _nm and 0.15444 nm as X-ray sources, lithium phosphate (for example, Li ₃ PO ) corresponds to Peaks usually appear at 2θ=22.3°, 23.2°, 24.8°, 33.9° and 36.6°.

A solid electrolyte material containing lithium phosphate in addition to a sulfide having an aldirodite-type crystal structure corresponds to lithium phosphate (e.g., _{Li PO} ) in an X-ray diffraction pattern using CuKα rays as an X-ray source. It may have a first peak and _a second peak corresponding to a crystal phase having a composition represented by _Li7PS6 . The first peak may have, for example, a diffraction angle 2θ value of 21° or more and less than 23°, and may be about 22.3°. The second peak may have a diffraction angle 2θ of, for example, 25° or more and less than 27°, and may be about 25.7°.

The content of lithium phosphate contained in the solid electrolyte material can be evaluated using, for example, an X-ray diffraction pattern. Specifically, it can be evaluated by the ratio of the intensity of the first peak to the intensity of the second peak (hereinafter also simply referred to as "peak intensity ratio"). In the solid electrolyte material, the ratio of the intensity of the first peak to the intensity of the second peak may be, for example, 0.03 or more and less than 0.15, preferably 0.04 or more, or 0.045 or more. , and preferably less than or equal to 0.10, or less than or equal to 0.06. When the peak intensity ratio corresponding to the content of lithium phosphate is within the above range, the battery resistance tends to be further reduced.

The solid electrolyte material contains sulfate ions. The content of sulfate ions contained in the solid electrolyte material may be, for example, 0.5% by mass or more, preferably 0.54% by mass or more, relative to the solid electrolyte material. Moreover, the upper limit of the content of sulfate ions may be, for example, 1.0% by mass or less, preferably 0.8% by mass or less, relative to the solid electrolyte material. When the content of sulfate ions is within the above range, the lithium ion conductivity tends to be further improved, the battery resistance is further reduced, and the battery characteristics are further improved.

The content of sulfate ions contained in the solid electrolyte material is measured by high frequency inductively coupled plasma emission spectrometry (ICP emission spectrometry).

In the composition of the solid electrolyte material, the composition ratio of lithium atoms may be, for example, 4 mol or more and 7 mol or less, preferably 5 mol or more and 6 mol or less, per 1 mol of phosphorus. Also, the composition ratio of sulfur atoms may be, for example, 3 mol or more and 6 mol or less, preferably 4 mol or more and 5 mol or less, per 1 mol of phosphorus. Also, the composition ratio of oxygen atoms may be, for example, 0 mol or more and 4 mol or less, preferably 0.1 mol or more and 2.0 mol or less, per 1 mol of phosphorus. Also, the composition ratio of halogen atoms may be, for example, 0 mol or more and less than 2 mol, preferably 1.4 mol or more and 1.8 mol or less, per 1 mol of phosphorus.

The solid electrolyte material may have, for example, a composition represented by formula (I) below.
Li _r PS _s O _t X _u (I)
In formula (I), r, s, t and u are respectively 4≦r≦7, 3≦s≦6, 0≦t≦4 and 0≦u<2, and X is F, Cl, Br, It may be at least one selected from the group consisting of I. Preferably, 5≦r≦6, 4≦s≦5, 0.1≦t≦2 and 1.4≦u≦1.8, and X may be at least one of Br and Cl.

Battery A battery comprises an electrolyte containing the above solid electrolyte material, a positive electrode, and a negative electrode. The electrolyte may form an electrolyte layer disposed between the positive and negative electrodes. Here, a configuration example of the battery will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of a battery 1000. FIG. Battery 1000 comprises a positive electrode 201 and a negative electrode 203 and an electrolyte layer 202 disposed between the positive electrode 201 and the negative electrode 203 . The positive electrode 201 comprises a positive electrode active material layer containing a positive electrode active material 204 . In addition to the positive electrode active material 204, the positive electrode active material layer forming the positive electrode 201 may contain a conductive aid, the solid electrolyte material 100, and the like. Also, the positive electrode 201 may include a current collector and a lead connected to the current collector. The negative electrode 203 includes a negative electrode active material layer containing a negative electrode active material 205 . In addition to the negative electrode active material 205, the negative electrode active material layer forming the negative electrode 203 may contain a conductive aid, the solid electrolyte material 100, and the like. Also, the negative electrode 203 may have a current collector and a lead connected to the current collector. Electrolyte layer 202 includes a solid electrolyte material. An example of the battery is a lithium ion battery, and may be an all-solid secondary battery.

The lithium-ion battery in this specification includes a lithium-ion secondary battery using a lithium-transition metal composite oxide for the positive electrode and a lithium-sulfur battery using a material that absorbs and releases lithium for the negative electrode. For specific examples of the lithium transition metal composite oxide, see, for example, International Publication No. 2017/141735, paragraph 0066 (U.S. Publication No. 2018/0309167, paragraphs 0152 to 0156), etc. You can refer to it. In addition, reference can be made to, for example, paragraph 0058 of International Publication No. 2015/056564 (paragraph 0070 of US Patent Publication No. 2016/0254529) for materials that occlude and release lithium.

For the positive electrode active material 204, for example, a lithium-transition metal composite oxide is used, and a transition metal oxide having a layered rock salt structure, a transition metal oxide having a spinel structure, or the like described in the above publications can be applied. can. In addition, the positive electrode active material 204 includes a lithium-containing transition metal phosphate compound, a lithium-containing transition metal halogenated phosphate compound, a lithium-containing transition metal silicate compound, a transition metal fluoride, a transition metal sulfide, and a transition metal oxyfluoride. metal oxides, transition metal oxysulfides, transition metal oxynitrides and the like are also used. In the case of a lithium-sulfur battery, elemental sulfur or the like can be used as the positive electrode active material.

The average particle size of the positive electrode active material 204 may be, for example, 0.1 μm or more and 30 μm or less. When the average particle diameter of the positive electrode active material 204 is 30 μm or less, diffusion of lithium in the positive electrode active material 204 does not become too slow, and the battery may operate more easily at high output. The thickness of the positive electrode active material layer may be, for example, 10 μm or more and 500 μm or less. If the positive electrode active material layer has a thickness of 10 μm or more, it may become easier to secure a sufficient energy density of the battery. Moreover, if the thickness of the positive electrode active material layer is 500 μm or less, high-power operation may be facilitated.

The average particle size of the positive electrode active material 204 may be larger than the average particle size of the solid electrolyte material 100 . As a result, the positive electrode active material 204 and the solid electrolyte material can form a good dispersion state in the positive electrode active material layer.

The volume ratio of the positive electrode active material 204 to the total volume of the positive electrode active material 204 and the solid electrolyte material 100 contained in the positive electrode active material layer may be, for example, 30% or more and 95% or less. When the volume ratio is 30% or more, the energy density of the battery can be sufficiently ensured. Further, when the volume ratio is 95% or less, there is a possibility that the operation at high output becomes easier.

The electrolyte layer 202 may be a solid electrolyte layer containing the solid electrolyte materials described above. The thickness of the solid electrolyte layer may be, for example, 1 μm or more and 100 μm or less. If the thickness of the solid electrolyte layer is 1 μm or more, short circuit between the positive electrode 201 and the negative electrode 203 can be suppressed. Further, if the thickness of the solid electrolyte layer is 100 μm or less, there is a possibility that the operation at high output becomes easier.

The negative electrode active material 205 includes a material that can absorb and release metal ions such as lithium ions. Specifically, a metal material, a carbon material, or the like is used as the negative electrode active material 205 . The metallic material may be a single metal or an alloy. Examples of metallic materials include lithium metal, lithium alloys, and the like. Examples of carbon materials include natural graphite, coke, ungraphitized carbon, carbon fiber, spherical carbon, artificial graphite, and amorphous carbon.

The average particle size of the negative electrode active material 205 may be, for example, 0.1 μm or more and 100 μm or less. When the average particle size of the negative electrode active material 205 is 0.1 μm or more, the negative electrode active material 205 and the solid electrolyte material 100 may form a good dispersion state in the negative electrode active material layer. Thereby, it is possible to suppress deterioration of the charge/discharge characteristics of the battery. Further, when the average particle size of the negative electrode active material 205 is 100 μm or less, diffusion of lithium in the negative electrode active material 205 does not become too slow, and the battery may operate more easily at high output.

The average particle size of the negative electrode active material 205 may be larger than the average particle size of the solid electrolyte material 100 . As a result, the negative electrode active material 205 and the solid electrolyte material can form a good dispersion state in the negative electrode active material layer.

The volume ratio of the negative electrode active material 205 to the total volume of the negative electrode active material 205 and the solid electrolyte material 100 contained in the negative electrode active material layer may be, for example, 30% or more and 95% or less. When the volume ratio is 30% or more, the energy density of the battery can be sufficiently ensured. Further, when the volume ratio is 95% or less, there is a possibility that the operation at high output becomes easier.

At least one of the positive electrode 201 and the negative electrode 203 may contain a conductive aid as necessary. A conductive aid is used to reduce the electrical resistance of the battery. Examples of conductive aids include graphites such as natural graphite and artificial graphite, and carbons such as acetylene black and ketjen black.

EXAMPLES The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples.

Example 1
Raw materials Li ₂ S, P ₂ S ₅ , LiCl, Li ₂ SO ₄ and Li ₃ PO ₄ were mixed in a dry atmosphere with a dew point of −50° C. or lower, and the molar ratio was Li ₂ S:P ₂ S ₅ :LiCl:Li _{2 .} SO ₄ :Li ₃ PO ₄ =3.74:1:3.28:0.03:0.05. These were pulverized and mixed by an absolute mill to obtain a mixture. The obtained mixture was filled in a crucible and placed in a sealed container made of quartz. A carbon packing was placed in the sealed container and tightened with a torque of 3.4 Nm. The sealed container was heat-treated at 500° C. for 8 hours in a nitrogen atmosphere to obtain a solid electrolyte material powder of Example 1. The solid electrolyte material of Example 1 had a composition represented by Li _5.5 PS _4.2 O _0.1 Cl _1.7 . Table 1 also shows the Li ₂ SO ₄ content (% by mass) in the mixture.

Example 2
Weigh so that the molar ratio of the raw materials in the mixture is Li ₂ S:P ₂ S ₅ :LiCl:Li ₂ SO ₄ :Li ₃ PO ₄ =3.76:1:3.43:0.03:0.14 A powder of the solid electrolyte material of Example 2 was obtained in the same manner as in Example 1 except for the above. The solid electrolyte material of Example 2 had a composition represented by Li _5.5 PS _4.0 O _0.5 Cl _1.6 .

Example 3
Weigh so that the molar ratio of the raw materials in the mixture is Li ₂ S:P ₂ S ₅ :LiCl:Li ₂ SO ₄ :Li ₃ PO ₄ =3.90:1:3.68:0.025:0.25 A powder of the solid electrolyte material of Example 3 was obtained in the same manner as in Example 1 except for the above. The solid electrolyte material of Example 3 had a composition represented by Li _5.4 PS _3.6 O _0.9 Cl _1.6 .

Example 4
Weigh so that _{the molar ratio of the raw materials in the mixture is Li2S:P2S5:LiCl:Li2SO4:Li3PO4 = 3.65 : 1 : 3.43} :0.04:0.14 A powder of the solid electrolyte material of Example 4 was obtained in the same manner as in Example 1 except for the above. The solid electrolyte material of Example 4 had a composition represented by Li _5.2 PS _3.9 O _0.6 Cl _1.6 .

Comparative example 1
A solid electrolyte of Comparative Example 1 was prepared in the same manner as in Example 1 except that the molar ratio of the raw materials in the mixture was Li ₂ S:P ₂ S ₅ :LiCl=3.8:1:3.2. A powder of material was obtained. The solid electrolyte material of Comparative Example 1 had a composition represented by Li _5.4 PS _4.4 Cl _1.6 .

Comparative example 2
Same as _Example 1 except that the molar ratio of raw materials in the mixture _{was Li2S} : _P2S5 :LiCl: _Li2SO4 = 3.84:1:3.22:0.03. Then, powder of the solid electrolyte material of Comparative Example 2 was obtained. The solid electrolyte material of Comparative Example 2 had a composition represented by Li _5.3 PS _4.35 O _0.05 Cl _1.6 .

Comparative example 3
Same as _{Example 1 except that the molar ratio of the raw materials in the mixture was Li2S:P2S5:LiCl:Li3PO4 = 3.92 : 1} :3.23:0.30. Then, powder of the solid electrolyte material of Comparative Example 3 was obtained. The solid electrolyte material of Comparative Example 3 had a composition represented by Li _5.2 PS _3.9 O _0.5 Cl _1.4 .

Comparative example 4
Weigh so that the molar ratio _{of the raw materials in the mixture is Li2S:P2S5:LiCl:Li2SO4:Li3PO4 = 3.85 : 1 :} 3.99:0.03:0.5 Powder of the solid electrolyte material of Comparative Example 4 was obtained in the same manner as in Example 1 except that the above was performed. The solid electrolyte material of Comparative Example 4 had a composition represented by Li _5.0 PS _3.1 O _1.4 Cl _1.4 .

Evaluation crystal structure analysis The crystal structure of the solid electrolyte material is analyzed by measuring the X-ray diffraction pattern of a sample packed in a closed cell at a dew point of -50 ° C. using an X-ray diffraction device (manufactured by RIGAKU, SmartLab). rice field. CuKα rays with wavelengths of 0.15405 nm and 0.15444 nm were used as the X-ray source.

In the obtained X-ray diffraction pattern, a peak at 2θ = 22.3° as a first peak corresponding to Li ₃ PO ₄ and a peak at 2θ = 25.7° as a second peak corresponding to Li ₇ PS ₆ was selected, and the ratio of the intensity of the first peak to the intensity of the second peak (peak intensity ratio) was calculated. Table 1 shows the results.

XRD patterns of the solid electrolyte materials obtained in Example 1 and Comparative Example 1 are shown in FIG. As shown in FIG. 3, the solid electrolyte materials of Example 1 and Comparative Example 1 had peaks corresponding to Li ₇ PS ₆ (2θ=, 25.7°, 30.2°, 31.6°, 45. 3°, 48.2°, 52.7°) were confirmed. In the solid electrolyte material of Example 1, peaks corresponding to Li ₃ PO ₄ (2θ = 22.3°, 23.2°, 24.8°, 33.9°, 36.6°) were confirmed. rice field.

XRD patterns of the solid electrolyte materials obtained in Examples 2, 3 and 4 are shown in FIG. As shown in FIG. 4, the solid electrolyte materials of Examples 2, 3 and 4 had peaks corresponding to Li ₇ PS ₆ (2θ=, 25.7°, 30.2°, 31.6° °, _45.3 °, 48.2°, 52.7°) and peaks corresponding to _Li3PO4 (2θ = 22.3°, 23.2°, 24.8°, 33.9°, 36.6°) was confirmed.

The XRD patterns of the solid electrolyte materials obtained in Comparative Examples 2, 3 and 4 are shown in FIG. As shown in FIG. 5, the solid electrolyte materials of Comparative Examples 2, 3 and 4 had peaks corresponding to Li ₇ PS ₆ (2θ =, 25.7°, 30.2°, 31.6 °, 45.3 °, 48.2 °, 52.7 °) were confirmed, and the XRD patterns of the solid electrolyte materials obtained in Comparative Examples 3 and 4 further included a peak corresponding to Li ₃ PO ₄ (2θ=22.3°, 23.2°, 24.8°, 33.9°, 36.6°) were confirmed.

Sulfate ion content The solid electrolyte material powders obtained in Examples and Comparative Examples were treated with zinc acetate to remove sulfur as zinc sulfide, and then subjected to high frequency inductively coupled plasma emission spectroscopy (ICP emission spectroscopy). The content of sulfate ions (SO ₄ ²⁻ ) was measured using the analytical method). Table 1 shows the results.

Evaluation of Battery Characteristics Charge-Discharge Characteristics Under a dry atmosphere with a dew point of −50° C. or less, a pressure of 310 MPa was applied using the jig shown in FIG. 2 to compact the solid electrolyte materials obtained in Examples and Comparative Examples. After that, the upper part of the punch 303 was pulled out, and a mixture obtained by mixing the positive electrode material, the solid electrolyte material, and the conductive aid was filled and pressurized at 310 MPa. After that, the punch lower part 302 was pulled out, and the Li negative electrode was stuffed and pressurized at 310 MPa to fabricate a battery. The produced battery was connected to a potentiostat to measure charge capacity and discharge capacity. Efficiency (%) was calculated by dividing the discharge capacity by the measured charge capacity. Table 1 shows the results.

Battery Resistance The battery resistance (Ω) of the battery prepared above was measured at frequencies in the range of 20 Hz to 120 MHz using an impedance measuring device (impedance analyzer E4990A manufactured by Keysight). Table 1 shows the results.

As shown in Table 1, in the batteries fabricated using the solid electrolyte materials of Examples 1 to 4, the battery resistance was reduced.

1000 Battery 100 Solid electrolyte material 201 Positive electrode 202 Electrolyte layer 203 Negative electrode 204 Positive electrode active material 205 Negative electrode active material 300 Pressure molding die 301 Frame mold 302 Punch lower part 303 Punch upper part

Claims (12)

obtaining a mixture comprising a compound containing lithium, a compound containing phosphorus and sulfur, a metal sulfate and a metal phosphate;
heat-treating the mixture to obtain a heat-treated product containing sulfate ions and lithium phosphate;
The compound containing lithium includes at least one selected from the group consisting of lithium sulfide, lithium oxide and lithium carbonate,
The method for producing a solid electrolyte material, wherein the mixture contains less than 15.0% by mass of the metal phosphate. 2. The manufacturing method according to claim 1, wherein the mixture further contains a chlorine-containing compound. 3. The method according to claim 1, wherein the compound containing phosphorus and sulfur contains at least one of phosphorus trisulfide and phosphorus pentasulfide. The compound containing lithium contains lithium sulfide, the compound containing phosphorus and sulfur contains diphosphorus pentasulfide, the compound containing chlorine contains lithium chloride, the metal sulfate contains lithium sulfate, and the metal phosphorus 3. The method of claim 2, wherein the acid salt comprises lithium phosphate. 5. The production method according to any one of claims 1 to 4, wherein the mixture has a content of the metal sulfate of 1.0% by mass or less. The production method according to any one of claims 1 to 5, wherein the mixture has a content of the metal sulfate of 0.7% by mass or less. The production method according to any one of claims 1 to 6, wherein the mixture has a content of the metal phosphate of 10.0% by mass or less. 8. A method according to any one of claims 1 to 7, wherein the heat treatment of said mixture is carried out at a temperature of 400[deg.]C or higher. The composition contains lithium, phosphorus and sulfur, and contains a sulfide having an algyrodite-type crystal structure, lithium phosphate, and sulfate ions,
The content of the sulfate ion is 0.5% by mass or more,
In the X-ray diffraction pattern, when CuKα rays with wavelengths of 0.15405 nm and 0.15444 nm are used as the X-ray source and measured by the θ-2θ method, the value of the diffraction angle 2θ is in the range of 21 ° or more and less than 23 °. A peak is observed, and a second peak is observed in a range where the value of the diffraction angle 2θ is 25 ° or more and less than 27 °, and the ratio of the intensity of the first peak to the intensity of the second peak is 0.03 or more. A solid electrolyte material that is less than .15. 10. The solid electrolyte material according to claim 9, wherein the content of said sulfate ions is 1.0% by mass or less. 11. The solid electrolyte material according to claim 9, wherein said sulfide further contains chlorine. A battery comprising a solid electrolyte containing the solid electrolyte material according to any one of claims 9 to 11, a positive electrode, and a negative electrode.

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