JP6672485B2 - Ion conductor, lithium battery, and method for producing ionic conductor - Google Patents

Description

  The technology disclosed by the present specification relates to an ionic conductor.

  In recent years, with the spread of electronic devices such as personal computers and mobile phones, the spread of electric vehicles, and the expansion of the use of natural energy such as sunlight and wind power, demand for high-performance batteries has increased. Above all, utilization of an all-solid lithium-ion secondary battery in which the battery elements are all solid is expected. An all-solid lithium-ion secondary battery is safer than a conventional lithium-ion secondary battery that uses an organic electrolyte in which a lithium salt is dissolved in an organic solvent because there is no risk of leakage or ignition of the organic electrolyte. In addition, since the exterior can be simplified, the energy density per unit mass or unit volume can be improved.

For example, an oxide-based lithium ion conductor or a sulfide-based lithium ion conductor is used as the solid electrolyte used for the electrolyte layer and the electrode of the all-solid lithium ion secondary battery. The oxide-based lithium ion conductor has a high lithium ion conductivity (for example, 1.0 × 10 ⁻⁵ to 1.0 × 10 ^{5 at} 25 ° C.) in a sintered body that has been heat-treated at a high temperature of about 1000 ° C. ^-3 S / cm), but when the unsintered powder is pressed, the lithium ion conductivity is extremely low (for example, 1.0 × 10 ⁻⁷ S / cm or less at 25 ° C.). ). For this reason, the oxide-based lithium ion conductor requires more energy to obtain high lithium ion conductivity, and the degree of freedom in selecting materials such as electrodes when used as a battery is reduced.

On the other hand, the sulfide-based lithium ion conductor has a higher ion conductivity than the oxide-based lithium ion conductor. This is because the sulfide has a higher polarizability than the oxide. Therefore, the sulfide-based lithium ion conductor has a high lithium ion conductivity in the particles. Furthermore, since the sulfide-based lithium ion conductor is easily plastically deformed, the adhesion between particles is increased only by pressing in a relatively low temperature range (for example, about 25 ° C. to 200 ° C.), and the high lithium ion conductivity ( For example, at 25 ° C., about 1.0 × 10 ^{−4 to} 1.0 × 10 ⁻² S / cm). However, the sulfide-based lithium ion conductor reacts with moisture in the atmosphere to generate hydrogen sulfide gas, and thus may not be preferable in terms of safety.

  In addition, by mixing an oxide-based lithium ion conductor having a high lithium ion conductivity and a sulfide-based lithium ion conductor having a high lithium ion conductivity to prepare a lithium ion conductor, safety is improved and lithium is improved. A technique for achieving both improvement in ionic conductivity is known (for example, see Patent Document 1).

US Patent Application Publication No. 2015/0171463

  The ion conductor obtained by mixing the oxide-based lithium ion conductor and the sulfide-based lithium ion conductor as described above has a reduced content ratio of the sulfide-based lithium ion conductor. Since it contains an ion conductor, there is room for improvement in safety.

  In addition, such a subject is not limited to the ion conductor used for the electrolyte layer and the electrode of the all-solid-state lithium ion secondary battery, but is a problem common to ion conductors having lithium ion conductivity in general.

  This specification discloses a technique capable of solving the above-described problem.

  The technology disclosed in this specification can be realized, for example, as the following modes.

(1) An ion conductor disclosed in the present specification is an ion conductor including a plurality of oxide-based lithium ion conductor particles, wherein a lithium halide is provided between two of the oxide-based lithium ion conductor particles. And at least one of a lithium halide hydrate and a lithium halide hydroxide. According to the present ion conductor, safety is improved because it does not contain a sulfide-based lithium ion conductor, and lithium halide and lithium halide hydrate are interposed between oxide-based lithium ion conductor particles. Since there is a region in which at least one of a substance and a lithium halide hydroxide is present, adhesion between particles is improved, and lithium ion conductivity is improved.

(2) In the ionic conductor, the halogen element of the lithium halide may include iodine (I). According to the present ionic conductor, since there is a region in which at least one of lithium iodide, lithium iodide hydrate and lithium iodide hydroxide exists between the oxide-based lithium ion conductor particles. In addition, adhesion between particles is improved, and lithium ion conductivity is improved.

(3) In the ionic conductor, the halogen element of the lithium halide may include bromine (Br). According to the present ionic conductor, since there is a region in which at least one of lithium bromide, lithium bromide hydrate and lithium bromide hydroxide exists between the oxide-based lithium ion conductor particles. In addition, adhesion between particles is improved, and lithium ion conductivity is improved.

(4) In the ionic conductor, the halogen element of the lithium halide may include chlorine (Cl). According to the present ion conductor, since there is a region in which at least one of lithium chloride, lithium chloride hydrate and lithium chloride hydroxide exists between the oxide-based lithium ion conductor particles, And the lithium ion conductivity is improved.

(5) In the ionic conductor, a fracture surface is used as an index indicating the degree of deviation in the distribution of the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide in the ionic conductor. The standard deviation calculated from the abundance ratio of the oxide-based lithium ion conductor particles and the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide is 0.6. It is good also as composition which is less than. According to the present ionic conductor, the distribution of lithium halide, lithium halide hydrate, or lithium halide hydroxide in the ion conductor has a small bias, and the lithium halide, lithium halide hydrate, or In addition, since the lithium halide hydroxide is evenly distributed, adhesion between particles is greatly improved, and lithium ion conductivity is greatly improved.

(6) In the ionic conductor, a fracture surface is used as an index indicating the degree of deviation in the distribution of the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide in the ionic conductor. In the above, a specific element excluding lithium and oxygen is selected from the elements contained in the oxide-based lithium ion conductor particles, the proportion of the specific element is Xi, the lithium halide, the halogenated Assuming that the proportion of the halogen element contained in the lithium hydrate or the lithium halide hydroxide is Yi, the ratio of Yi to Xi (Yi / Xi) is Ri, and m positions (where m is The standard deviation calculated from the data group (ratio R1 to ratio Rm) composed of m ratios Ri in an integer of 9 or more is less than 0.6. It may be configured that. According to the present ionic conductor, the distribution of lithium halide, lithium halide hydrate, or lithium halide hydroxide in the ion conductor has a small bias, and the lithium halide, lithium halide hydrate, or In addition, since the lithium halide hydroxide is evenly distributed, adhesion between particles is greatly improved, and lithium ion conductivity is greatly improved.

(7) In the ion conductor, the area ratio of a region occupied by the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide in a fracture surface of the ion conductor is defined as Za, Assuming that the area ratio of the region occupied by the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide on the cut surface of the ionic conductor is Zb, a configuration satisfying the relationship of Za> Zb is provided. Is also good. According to the present ion conductor, there are many regions in which lithium halide, lithium halide hydrate, or lithium halide hydroxide exists between two oxide-based lithium ion conductor particles, The adhesion is greatly improved, and the lithium ion conductivity is greatly improved.

(8) In the ion conductor, an area occupied by the oxide-based lithium ion conductor particles and the lithium halide, the lithium halide hydrate, or the at least one cut surface of the ion conductor. When the ratio of the area occupied by the particles containing the lithium halide hydroxide to Xa: (100−Xa), a configuration satisfying 30 ≦ Xa <100 may be adopted. According to the present ionic conductor, when the ratio of the oxide-based lithium ion conductor particles to the particles containing lithium halide, lithium halide hydrate, or lithium halide hydroxide is within the above range, lithium ion The conductivity is greatly improved.

(9) In the ion conductor, an area occupied by the oxide-based lithium ion conductor particles and the lithium halide, the lithium halide hydrate, or the at least one cut surface of the ion conductor. When the ratio of the area occupied by the particles containing the lithium halide hydroxide to Xa: (100−Xa), a configuration satisfying 38 ≦ Xa ≦ 97 may be adopted. According to the present ionic conductor, when the ratio of the oxide-based lithium ion conductor particles to the particles containing lithium halide, lithium halide hydrate, or lithium halide hydroxide is within the above range, lithium ion The conductivity is significantly improved.

(10) In the above ionic conductor, the lithium ion conductivity at 25 ° C. may be 1.0 × 10 ⁻⁵ S / cm or more. According to the present ion conductor, high lithium ion conductivity can be secured at room temperature.

(11) In the above ion conductor, the oxide-based lithium ion conductor is an ion conductor having a garnet-type structure or a garnet-like structure containing at least Li, Zr, La, and O; and Li and M (M is at least one of Ti, Zr and Ge), an ion conductor having a NASICON-type structure containing at least P and O, and a perovskite-type structure containing at least Li, Ti, La and O It is good also as a structure which is at least 1 type among the ion conductor which has. According to the present ionic conductor, adhesion between particles is improved, and lithium ion conductivity is improved.

  Note that the technology disclosed in the present specification can be realized in various forms, for example, an ion conductor, a lithium battery including the ion conductor, a method for manufacturing the same, and the like. It is possible.

FIG. 2 is an explanatory diagram schematically showing a cross-sectional configuration of an all-solid lithium-ion secondary battery 102 according to the embodiment. It is explanatory drawing (SEM image of a fractured surface) which shows the structure of the lithium ion conductor LIC of this embodiment. It is explanatory drawing (SEM-EDS image of a fractured surface) which shows the structure of the lithium ion conductor LIC of this embodiment. 5 is a flowchart illustrating a method for manufacturing the lithium ion conductor LIC of the embodiment. FIG. 7 is an explanatory diagram showing an example of an experimental result for examining whether or not a crystal phase has changed. FIG. 4 is an explanatory diagram showing a configuration of each sample and a performance evaluation result in a first performance evaluation. FIG. 4 is an explanatory diagram showing a configuration of each sample and a performance evaluation result in a first performance evaluation. It is a graph which shows the measurement result of lithium ion conductivity Ci of each sample in the 1st performance evaluation. It is explanatory drawing (SEM image of a fractured surface) which shows the structure of the lithium ion conductor LIC in which heat processing is not performed. It is explanatory drawing (SEM-EDS image of a torn surface) which shows the structure of the lithium ion conductor LIC in which heat processing is not performed. It is explanatory drawing (SEM image of a cut surface) which shows the structure of the lithium ion conductor LIC of this embodiment. It is explanatory drawing (SEM-EDS image of the cut surface) which shows the structure of the lithium ion conductor LIC of this embodiment. FIG. 9 is an explanatory diagram illustrating a configuration of each sample and a performance evaluation result in a second performance evaluation. It is an explanatory view showing composition of each sample in the 3rd performance evaluation, and a performance evaluation result.

A. Embodiment:
A-1. Configuration of all solid state battery 102:
FIG. 1 is an explanatory diagram schematically illustrating a cross-sectional configuration of an all-solid-state lithium-ion secondary battery (hereinafter, referred to as “all-solid-state battery”) 102 in the present embodiment. FIG. 1 shows mutually orthogonal XYZ axes for specifying a direction. In the present specification, for convenience, the positive direction of the Z axis is referred to as an upward direction, and the negative direction of the Z axis is referred to as a downward direction.

  The all-solid-state battery 102 includes a battery main body 110, a first current collecting member 154 disposed on one side (upper side) of the battery main body 110, and a second current collector member 154 disposed on the other side (lower side) of the battery main body 110. And a current collecting member 156. The first current collecting member 154 and the second current collecting member 156 are substantially plate-shaped members having conductivity, for example, stainless steel, Ni (nickel), Ti (titanium), Fe (iron), Cu ( It is formed of a conductive metal material, a carbon material, or the like selected from copper), Al (aluminum), and an alloy thereof.

  The battery body 110 is a secondary battery in which the battery elements are all solid, and includes an electrolyte layer 112, a positive electrode layer 114 arranged on one side (upper side) of the electrolyte layer 112, and the other side ( (A lower side).

The electrolyte layer 112 has a substantially flat plate shape, and is formed of a lithium ion conductor LIC which is a solid electrolyte. The positive electrode layer 114 has a substantially flat plate shape and includes a positive electrode active material PAM and a lithium ion conductor LIC having the same configuration as the lithium ion conductor LIC included in the electrolyte layer 112. As the positive electrode active material PAM, for example, S (sulfur), TiS ₂ , LiCoO ₂ , LiMn ₂ O ₄ , LiFePO ₄ or the like is used. The negative electrode layer 116 has a substantially flat plate shape, and includes a negative electrode active material NAM and a lithium ion conductor LIC having the same configuration as the lithium ion conductor LIC included in the electrolyte layer 112. As the negative electrode active material NAM, for example, Li metal, Li-Al alloy, Li ₄ Ti ₅ O ₁₂ , carbon, Si (silicon), SiO or the like is used. The positive electrode layer 114 and the negative electrode layer 116 may further contain a conductive additive (for example, conductive carbon, Ni, Pt (platinum), Ag (silver)).

A-2. Configuration and manufacturing method of lithium ion conductor LIC:
The all-solid-state battery 102 of the present embodiment is characterized by a lithium ion conductor LIC that is a solid electrolyte used for the electrolyte layer 112, the positive electrode layer 114, and the negative electrode layer 116. Hereinafter, the configuration and the manufacturing method of the lithium ion conductor LIC will be described. FIG. 2 and FIG. 3 are explanatory diagrams illustrating the configuration of the lithium ion conductor LIC of the present embodiment. FIG. 2 shows an SEM image (× 1000) of the fracture surface of the lithium ion conductor LIC, and FIG. 3 shows an SEM-EDS image (× 1000) of the fracture surface of the lithium ion conductor LIC corresponding to FIG. Elemental mapping image) (1000 times). The lithium ion conductor LIC shown in FIGS. 2 and 3 is a sample 12 (see FIG. 6) in performance evaluation described later.

  As shown in FIGS. 2 and 3, the lithium ion conductor LIC of the present embodiment includes oxide-based lithium ion conductor particles 52, lithium halide hydrate-containing particles 54, and lithium halide hydroxide-containing particles 56. And More specifically, the lithium ion conductor LIC has a region in which the lithium halide hydrate-containing particles 54 and / or the lithium halide hydroxide-containing particles 56 exist between the oxide-based lithium ion conductor particles 52. (The regions shown in FIGS. 2 and 3). That is, in the lithium ion conductor LIC of the present embodiment, the voids between the oxide-based lithium ion conductor particles 52 are formed by the lithium halide hydrate-containing particles 54 and / or the lithium halide hydroxide-containing particles 56. It is in a buried state. In FIG. 2, for convenience, the positions of the lithium halide hydrate-containing particles 54 and the lithium halide hydroxide-containing particles 56 are illustrated by arrows. This is the position where the lithium halide hydrate-containing particles 54 or the lithium halide hydroxide-containing particles 56 are present. The same applies to FIG. 3 and subsequent figures.

The oxide-based lithium ion conductor particles 52 contained in the lithium ion conductor LIC are, for example, ion conductors having a garnet type structure or a garnet type similar structure containing at least Li, Zr, La, and O (for example, Li ₇ La ₃ Zr ₂ O ₁₂ (hereinafter referred to as “LLZ”) or particles obtained by subjecting LLZ to elemental substitution of Mg (magnesium) and Sr (strontium) (hereinafter referred to as “LLZ-MgSr”) , Li and M (M is at least one of Ti, Zr, Ge (germanium)), P (phosphorus) and O, and an ion conductor having a NASICON type structure (for example, Li _1.5 Al _{0.5 Ge 1.5 (PO 4) 3} ( hereinafter, referred to as "LAGP") particles), Li, Ti, La and O at least containing One kind of particles of the ion conductor having a perovskite structure, or a particle obtained by mixing at least two kinds of these.

The lithium halide hydrate-containing particles 54 contained in the lithium ion conductor LIC are, for example, particles of LiI (lithium iodide) hydrate (LiI.H ₂ O) or LiBr (lithium bromide). Hydrate (LiBr.H ₂ O) particles, LiCl (lithium chloride) hydrate (LiCl.H ₂ O) particles, and particles mainly composed of these lithium halide hydrates (for example, iodine) Amorphous body containing lithium chloride). In addition, a main component means the component whose content rate is 50 w% or more. The lithium halide hydroxide-containing particles 56 contained in the lithium ion conductor LIC include, for example, particles of LiI hydroxide (Li ₂ I (OH) or Li ₄ (OH) ₃ I) or LiBr Hydroxide (Li ₂ Br (OH) or Li ₄ (OH) ₃ Br) particles, LiCl hydroxide (Li ₂ Cl (OH) or Li ₄ (OH) ₃ Cl) particles, lithium halide (For example, an amorphous body containing lithium iodide hydroxide). That is, in the present embodiment, the halogen element of the lithium halide contains at least one of iodine (I), bromine (Br), and chlorine (Cl).

In the examples shown in FIGS. 2 and 3, LLZ-MgSr particles are used as oxide-based lithium ion conductor particles 52, and LiI.H ₂ O particles are used as lithium halide hydrate-containing particles 54. This is an example in which particles of Li ₂ I (OH) or Li ₄ (OH) ₃ I are used as the lithium halide hydroxide-containing particles 56.

  FIG. 4 is a flowchart illustrating a method for manufacturing the lithium ion conductor LIC of the present embodiment. First, an oxide-based lithium ion conductor powder and a lithium halide powder are prepared (S110), and the prepared powders are mixed at a predetermined ratio (S120). After molding the obtained mixed powder, a heat treatment (for example, 80 ° C., 17 hours) is performed on the mixed powder (S130). The treatment temperature may be 25 ° C or higher, and the heat treatment temperature is preferably 60 ° C or higher and 452 ° C or lower, more preferably 70 ° C or higher and 300 ° C or lower, and is preferably 80 ° C or higher and 200 ° C or lower. More preferred. Further, the heat treatment may be performed in a pressurized state. The load in this case is preferably at least 0.1 kN, more preferably at least 0.5 kN, even more preferably at least 1 kN. By applying pressure, the adhesion between the lithium ion conductor particles and lithium halide hydrate or lithium halide hydroxide is improved, and the ionic conductivity is increased, so that the performance of the lithium ion conductor LIC is improved. improves.

  Here, since lithium halide has hygroscopicity and deliquescent, in the process of manufacturing the above-mentioned lithium ion conductor LIC, the raw material lithium halide is converted into lithium halide hydrate or lithium halide hydroxide. Change phase. FIG. 5 is an explanatory diagram showing an example of an experimental result for examining the presence or absence of a change in the crystal phase. In this experiment, using LiI as a lithium halide raw material, XRD measurements were performed on samples at each stage when a lithium ion conductor LIC was manufactured according to the method shown in FIG. We checked whether things were included.

As shown in FIG. 5, the raw material of LiI contained a small amount of a hydrate of LiI (LiI.H ₂ O) in addition to LiI, which occupies the majority. From this result, it is considered that the LiI raw material reacted with water in the air and changed into a hydrate. In addition, the sample after mixing the LiI raw material with the LLZ powder contains a small amount of LiI hydrate (LiI.H ₂ O) in addition to LLZ and LiI, and further contains LiI hydroxide (LiI). ₂ I (OH)). From this result, it is considered that the reaction promoted the reaction between the LiI raw material and water by the mixing, and the phase change from LiI to a hydrate and a hydroxide proceeded. Further, in the sample after the heat treatment (no pressurization) was performed on the mixed powder, the content of LiI was small, and the hydrate of LiI (LiI.3H ₂ O) accounted for the majority, hydroxides of LiI _(Li 2 I _(OH) and _Li 4 _(OH) 3 _I) was also included. From this result, it is considered that the reaction between the LiI raw material and water was further promoted by the heat treatment, and most of the LiI raw material changed into a hydrate and a hydroxide. Incidentally, similarly for samples after performing the heat treatment (with pressure) with respect to the mixed powder, the content of LiI becomes slightly hydrate (LiI · 3H 2 _O) the majority of LiI accounting, hydroxides _(Li 2 I _(OH) and _Li 4 _(OH) 3 _I) of LiI were also included. The magnitude relationship between the contents shown in FIG. 5 is a comparison from the viewpoint of the volume ratio.

  From the above, when the lithium ion conductor LIC is manufactured according to the above-described manufacturing method, the lithium ion conductor LIC having the above-described configuration, that is, the oxide-based lithium ion conductor particles 52 and the lithium halide hydrate-containing particles 54 And a lithium ion hydroxide-containing particle 56 can be produced.

  In the above-described production method, a lithium halide hydrate and / or a lithium halide hydroxide powder is used as a raw material instead of or in addition to the lithium halide powder. You may. Even in this manner, a lithium ion conductor LIC including the oxide-based lithium ion conductor particles 52, lithium halide hydrate-containing particles 54, and lithium halide hydroxide-containing particles 56 can be manufactured. In the present specification, particles containing at least one of lithium halide, lithium halide hydrate and lithium halide hydroxide are referred to as lithium halide-based particles.

As described above, the lithium ion conductor LIC used in the all-solid-state battery 102 of the present embodiment includes the lithium halide hydrate-containing particles 54 and / or the halogen between the oxide-based lithium ion conductor particles 52. Since there is a region in which the lithium hydroxide-containing particles 56 are present, the oxide-based lithium ion conductor particles 52 are fused by the lithium halide hydrate-containing particles 54 and / or the lithium halide hydroxide-containing particles 56. By attaching, the particles have high adhesion between the particles and have a high lithium ion conductivity (for example, 1.0 × 10 ⁻⁵ S / cm or more at 25 ° C.). Further, the lithium ion conductor LIC of the present embodiment has a high lithium ion conductivity only by performing a heat treatment at a lower temperature without forming a sintered body by a heat treatment at a relatively high temperature (for example, about 1000 ° C.). Therefore, energy required for manufacturing can be reduced, and a thermal load is not applied to the positive electrode layer 114 and the negative electrode layer 116, so that the degree of freedom in material selection of the positive electrode layer 114 and the negative electrode layer 116 can be improved. Can be. Further, the lithium ion conductor LIC of the present embodiment has high safety because it does not contain a sulfide-based lithium ion conductor that generates hydrogen sulfide by reacting with moisture in the atmosphere.

In general, the lithium ion conductivity (25 ° C.) of lithium halide or its hydrate / hydroxide is extremely low at about 1.0 × 10 ⁻⁷ S / cm. The inventor of the present application has reported that lithium ion conductivity is greatly improved by adding and mixing lithium halide or a hydrate or hydroxide thereof having an extremely low lithium ion conductivity to an oxide-based lithium ion conductor. It has been found that effects that are difficult to predict can be obtained. In this regard, the present invention can be said to be an invention that is extremely difficult for those skilled in the art to come up with.

A-3. Performance evaluation:
(First performance evaluation)
A plurality of samples of the lithium ion conductor LIC were prepared, and the lithium ion conductivity Ci and the like of each sample were measured as performance evaluation. 6 and 7 are explanatory diagrams showing the configuration of each sample and the results of the first performance evaluation in the first performance evaluation. FIG. 8 shows the lithium ion conductivity of samples 1 to 19 in the first performance evaluation. It is a graph which shows the measurement result of Ci. Each plot number (P1 to P19) in FIG. 8 corresponds to each sample number (1 to 19) in FIG. Some of the samples (samples 4 and 12) shown in FIG. 6 are also shown in FIG.

  FIG. 6 and FIG. 7 show the materials used for producing each sample. In the first performance evaluation, LLZ-MgSr was used as the oxide-based lithium ion conductor, and LiI was used as the lithium halide. FIGS. 6 and 7 show, for each sample, particles containing oxide-based lithium ion conductor particles (specifically, LLZ-MgSr particles) and lithium halide hydrate (or hydroxide) at the cut surface. (Specifically, the ratio of the oxide-based lithium ion conductor particles to the total amount of the particles and the hydrate (or hydroxide) -containing particles of LiI (hereinafter referred to as “oxide-based ratio X”) is shown. ing. In addition, the ratio of the oxide-based lithium ion conductor particles refers to the area of the oxide-based lithium ion conductor particles and the lithium halide hydrate (or hydroxide) in an image analysis using a cross-sectional image described later. It can be indicated by the area ratio determined from the area of the contained particles. Here, the ratio between the oxide-based lithium ion conductor particles and the lithium halide hydrate (or hydroxide) -containing particles is expressed as X: (100−X) using the oxide-based ratio X. You. Further, the oxide-based ratio X in the raw material stage is maintained at substantially the same value in the lithium ion conductor LIC manufactured through the mixing process and the heat treatment of the raw material. Samples (samples 1 and 9) in which the value of the oxide-based proportion X is 0 (zero)% are lithium halide hydrate (or hydroxide) -containing particles (LiI hydrate (or hydroxide)). The samples (samples 8, 16, and 19), which are composed only of the oxide-based lithium ion conductor particles (LLZ-MgSr particles), are composed only of the oxide-based lithium ion-conductive particles (samples 8, 16, and 19). Have been.

  FIG. 6 shows a method of the mixing process (S120 in FIG. 4). As the mixing process, a mixing process using a mortar or a mixing process using a planetary ball mill was performed. It should be noted that the mixing process is not performed on the sample in which the value of the oxide-based ratio X is 0 (zero)% or 100%. Further, in all the samples shown in FIG. 7, the mixing process using the mortar was performed, and thus the item of “mixing process” is omitted in FIG. FIGS. 6 and 7 show the temperature and time of the heat treatment (S130 in FIG. 4). As the heat treatment, heat treatment at 80 ° C. for 17 hours or heat treatment at 1100 ° C. for 4 hours was performed. Note that heat treatment was not performed on Samples 1 to 8, 17, 20, and 21.

  As shown in FIGS. 6 and 7, Samples 1 to 8, 20, and 21 were produced without heat treatment, and were powders. Samples 1 to 8, 20, and 21 differ from each other in the value of the oxide-based ratio X. On the other hand, Samples 9 to 16, 22, and 23 are heated products produced by performing a heat treatment at 80 ° C. for 17 hours on powder having the same configuration as Samples 1 to 8, 20, and 21, respectively. Among the samples 1 to 16, 20 to 23, in the sample containing both LLZ-MgSr and LiI (samples 2 to 7, 10 to 15, and 20 to 23), the mixing process using a mortar is performed. .

  Sample 17 is a sample obtained by replacing the mixing method in Sample 4 with a method using a planetary ball mill. Similarly, Sample 18 is a sample 12 in which the mixing method is replaced by a planetary ball mill. It was replaced by the method that was used. In general, when the mixing process using a planetary ball mill is performed, the average particle size of the particles constituting the lithium ion conductor LIC is smaller than when the mixing process using a mortar is performed, and the particle size varies. Becomes smaller.

  Sample 19 is a sintered body produced by performing a heat treatment at 1100 ° C. for 4 hours on LLZ-MgSr powder. Hereinafter, a method for producing each sample will be described in detail.

First, Li ₂ CO ₃ , MgO, La (OH) ₃ , SrCO ₃ , and ZrO ₂ were added so that the composition became Li _6.95 Mg _0.15 La _2.75 Sr _0.25 Zr _2.0 O _12. Weighed. At that time, in consideration of the volatilization of Li at the time of firing, Li ₂ CO ₃ was further added so as to be about 15 mol% excess in terms of element. This raw material was put into a nylon pot together with zirconia balls, and pulverized and mixed in a ball mill for 15 hours in an organic solvent. After mixing, the slurry was dried and calcined at 1100 ° C. for 10 hours on an MgO plate. The composition of the powder after calcination may be slightly different from the above composition. The calcined powder was pulverized with a ball mill to obtain LLZ-MgSr powder.

  For Samples 2 to 7, 20, and 21, the prepared LLZ-MgSr powder and lithium iodide powder (manufactured by Kojundo Chemical Laboratory, purity: 99.9%) were used in accordance with the oxide ratio X of each sample. The mixture was mixed at the mixing ratio described above, and crushed and mixed in a mortar for 15 minutes to obtain a mixed powder. Note that for the samples 1 and 8, a single powder is used, so that no mixing process is performed. For samples 1 to 8, 20, and 21, the mixed powder (or single powder) was put into a cylindrical insulating container having a diameter of 10 mm, and pressed together with a stainless steel current collector at 360 MPa by a press to obtain a green compact. For each of the obtained green compacts (samples 1 to 8, 20, and 21), the lithium ion conductivity Ci at 25 ° C. was measured by an AC impedance method (using 1470E and 1255B manufactured by Solartron).

  For samples 9 to 16, 22, and 23, after preparing green compacts in the same manner as samples 1 to 8, 20, and 21, the green compacts were fixed again at 50 MPa and sealed in an Ar (argon) atmosphere. It was put in a glass container, and heat-treated at 80 ° C. for 17 hours in a high-temperature bath (PU-1KPH manufactured by ESPEC) in the atmosphere to obtain a heated product. Each of the obtained heated products (samples 9 to 16, 22, and 23) was cooled to 25 ° C., and the lithium ion conductivity Ci was measured in the same manner as in samples 1 to 8, 20, and 21.

  For sample 17, the prepared LLZ-MgSr powder and lithium iodide powder (purity 99.9%, manufactured by Kojundo Chemical Laboratory) were blended at a blending ratio according to the oxide-based ratio X, Using a planetary ball mill, a 45 cc zirconia pot and 40 g of Φ4 mm balls were crushed and mixed at 200 rpm for 3 hours to obtain a mixed powder. Thereafter, similarly to the samples 1 to 8, 20, and 21, a green compact was obtained from the mixed powder, and the lithium ion conductivity Ci was measured for the obtained green compact (sample 17). For sample 18, after obtaining a green compact in the same manner as sample 17, heat treatment was performed in the same manner as in samples 9 to 16, 22, and 23 to obtain a heated product, and the obtained heated product (sample 18) , The lithium ion conductivity Ci was measured.

For sample 19, a binder was added to the prepared LLZ-MgSr powder, and the mixture was pulverized and mixed in an organic solvent for 15 hours using a ball mill. Thereafter, the slurry was dried to obtain an LLZ-MgSr powder containing a binder. This powder is pressed into a mold having a diameter of 12 mm so as to have a thickness of about 1.5 mm, and a hydrostatic pressure of 1.5 t / cm ² is applied using a cold isostatic press (CIP). Thus, a molded body was obtained. The obtained molded body was covered with a calcined powder having the same composition as the molded body, and heat-treated at 1100 ° C. for 4 hours in a nitrogen atmosphere to obtain a sintered body. When this sintered body was pulverized and the main crystal phase was identified by XRD, the crystal structure of this sintered body was LLZ cubic with high ionic conductivity Ci. A sample for measurement was obtained by polishing both surfaces of the sintered body and performing gold deposition. For the obtained measurement sample (sample 19), the lithium ion conductivity Ci was measured in the same manner as in samples 1 to 8.

  For samples 4, 12, 20 to 23 shown in FIG. 7, oxide-based ionic conductor particles having a fractured surface as an index indicating the magnitude of deviation of the distribution of lithium halide in the lithium-ion conductor LIC. The standard deviation σ was calculated from the existence ratio with the lithium halide hydrate (or hydroxide). In this specification, a fractured surface refers to a cross-section that is formed when an external force is applied to a sample and breaks it, and is a cross-section that is not a cut surface that is processed by polishing, an ion beam, or the like. In addition, the standard deviation σ calculated from the existing ratio of the oxide ion conductor particles having a fractured surface and lithium halide hydrate (or hydroxide) as the index can be obtained by the following method. First, the fracture surface of the sample was subjected to elemental analysis by SEM-EDS measurement, and among the elements constituting the oxide-based lithium ion conductor, the element contained in the lithium halide hydrate (or hydroxide) and the oxygen element were analyzed. The representative element X is selected from the removed elements, and the halogen element Y of the lithium halide hydrate (or hydroxide) is selected. In the sample shown in FIG. 7, La (lanthanum) is selected as a representative element X (hereinafter simply referred to as “element X”) constituting the oxide-based lithium ion conductor, and lithium halide hydrate (or water) is used. I (iodine) was selected as the halogen element Y of the oxide) (hereinafter simply referred to as “element Y”). Next, the ratio Ri (= Yi / Xi) of the element Y to the element X in the fracture surface is calculated. Here, the ratio Ri (= Yi / Xi) is calculated at m points of the sample (where m is an integer of 9 or more). Note that the selection of m locations may be random. Further, an average value is calculated for the calculated ratios Ri (R1 to Rm) at m locations. The ratio Ri (R1 to Rm) calculated at m points is divided by the average value, and a standard deviation σ of the divided value (point m) with respect to the average value is calculated.

  When the deviation of the distribution of lithium halide hydrate (or hydroxide) in the lithium ion conductor LIC is sufficiently small, the standard deviation σ is less than 0.6. In addition, when the deviation of the distribution of lithium halide hydrate (or hydroxide) in the lithium ion conductor LIC is extremely small, the standard deviation σ is less than 0.4. For this reason, it is preferable that the standard deviation σ is less than 0.6, because the deviation of the distribution of lithium halide hydrate (or hydroxide) is sufficiently small, and the lithium ion conductivity Ci is greatly improved. If the standard deviation σ is less than 0.4, the distribution of lithium halide hydrate (or hydroxide) is less biased, and the lithium ion conductivity Ci is significantly improved.

  Further, for samples 4, 12, 20 to 23 shown in FIG. 7, the halogen, which is the area ratio of lithium halide hydrate (or hydroxide) in the cross section (broken surface and cut surface) of lithium ion conductor LIC, is used. The lithium oxide area ratio (%) was calculated. The area ratio of the lithium halide in the fracture surface of the lithium ion conductor LIC is represented by Za, and the area ratio of the lithium halide in the cut surface of the lithium ion conductor LIC is represented by Zb. Here, the fracture surface is synonymous with the fracture surface described above. Further, in this specification, a cut surface refers to a cross section processed by polishing, ion beam, or the like, and is a cross section different from the above-described fractured surface. The cut surface can be obtained by, for example, a cross section polisher method (CP method) or the like. Further, the lithium halide area ratio Za on the fractured surface and the lithium halide area ratio Zb on the cut surface can be determined by element mapping using SEM-EDS.

  When the lithium ion conductor LIC satisfies the relation (Za> Zb) that the lithium halide area ratio Za in the fracture surface is larger than the lithium halide area ratio Zb in the cut surface, the lithium ion conductivity Ci is greatly improved. preferable. Further, when the relationship of the ratio of the area ratio of the lithium halide in the fractured surface to the area ratio of the lithium halide in the cut surface is larger than 1.3 ((Za / Zb)> 1.3), the lithium ion conductivity It is more preferable because Ci is further improved. The fact that the lithium ion conductor LIC satisfies the relationship of Za> Zb means that a region where lithium halide hydrate (or hydroxide) -containing particles exist between oxide-based lithium ion conductor particles. Indicates that there are many. In other words, it can be said that there are many regions where the oxide-based lithium ion conductor particles are covered with lithium halide hydrate (or hydroxide) -containing particles. The reason that can be said in this manner is that the fracture surface is a cross-section obtained by destruction by an external force, so that the fracture occurs between the oxide-based lithium ion conductor particles. In other words, in a form in which there are many regions where lithium halide hydrate (or hydroxide) -containing particles exist between oxide-based lithium ion conductor particles, lithium halide hydrate (or hydroxide) -containing particles Will be expressed more. On the other hand, since the cut surface is a polished surface or a cross section processed by an ion beam or the like, the oxide-based lithium ion conductor particles are also cut, and the internal structure of the oxide-based lithium ion conductor particles is exposed. Become. As a result, the exposed ratio of the oxide-based lithium ion conductor particles is larger at the cut surface than at the fractured surface. However, when there is no region in which the lithium halide hydrate (or hydroxide) -containing particles are present between the oxide-based lithium ion conductor particles, the lithium halide area ratio Za in the fracture surface and the cut surface , The difference hardly appears (that is, Za ≒ Zb (Za and Zb are substantially equal)). Therefore, when the area ratio of the lithium halide in the fracture surface is defined as Za and the area ratio of the lithium halide in the cut surface is defined as Zb, the relationship of Za> Zb is satisfied. It can be said that there are many regions where lithium hydrate (or hydroxide) -containing particles are present.

(Measurement result)
As shown in FIGS. 6 and 8, Samples 10 to 15 exhibited a higher lithium ion conductivity Ci than Samples 2 to 7. Therefore, when the mixed powder of LLZ-MgSr and LiI is heat-treated at about 80 ° C., it can be said that the lithium ion conductivity Ci increases. This is because the LiI hydrate (or hydroxide) is fused by the heat treatment, and the gap between the LLZ-MgSr particles is filled with the LiI hydrate (or hydroxide). It is considered that this is because the adhesion becomes higher.

  FIG. 9 and FIG. 10 are explanatory diagrams illustrating the configuration of the lithium ion conductor LIC in which the heat treatment has not been performed. FIG. 9 shows an SEM image (1000 times) of the fracture surface of Sample 4 and FIG. 10 shows a SEM-EDS image (element mapping image) of the fracture surface of Sample 4 corresponding to FIG. Times). As shown in FIGS. 9 and 10, in the lithium ion conductor LIC (sample 4) in which the heat treatment is not performed, the particles 52 of the oxide-based lithium ion conductor (specifically, LLZ-MgSr) are located between the particles 52. Although there are portions where lithium halide hydrate (specifically, LiI) -containing particles 54 or lithium halide hydroxide-containing particles 56 exist, the degree of dispersion of LiI hydrate (or hydroxide) is small. Therefore, adhesion between particles is relatively low. Therefore, in Sample 4, the lithium ion conductivity Ci is relatively low. On the other hand, as shown in FIGS. 2 and 3 described above, in the lithium ion conductor LIC (sample 12) subjected to the heat treatment, the degree of dispersion of LiI hydrate (or hydroxide) is high, and Since the adhesion between them is high, the lithium ion conductivity Ci is relatively high.

FIG. 8 shows a part of a third-order approximate curve AC derived from plots (P9 to P16) of samples 9 to 16. Based on this approximate curve AC, if the oxide-based ratio X is 30% or more and less than 100% (30 ≦ X <100), the lithium ion conductivity Ci is approximately 1.0 × 10 ⁻⁵ S / cm or more. Can be said to be preferable. Further, when the oxide-based ratio X is 38% or more and 97% or less (38 ≦ X ≦ 97), it is about 1.0 × 10 ⁻³ which is equal to or more than the sample 19 which is a sintered body of LLZ-MgSr. Since a lithium ion conductivity Ci of S / cm or more can be obtained, it is more preferable.

  Further, Sample 18 showed a higher lithium ion conductivity Ci than Sample 12. Therefore, it can be said that when the mixing process using the planetary ball mill is performed, the lithium ion conductivity Ci is higher than when the mixing process using the mortar is performed. When the mixing process using a planetary ball mill is performed, the average particle size of the particles constituting the lithium ion conductor LIC is smaller than the case where the mixing process is performed using a mortar, and the variation in the particle size is small. Therefore, it is considered that at least one of them causes the lithium ion conductivity Ci to increase. The average particle size of the oxide-based lithium ion conductor particles of Sample 12 was 14.8 μm, and the average particle size of the oxide-based lithium ion conductor particles of Sample 18 was 3.1 μm.

  Further, as shown in FIG. 7, in the samples 4, 20, and 21 in which the heat treatment was not performed, the standard deviation σ was 0.6 or more. That is, in these samples, it can be said that the distribution of lithium halide hydrate (or hydroxide) has a relatively large bias. Therefore, in these samples, the lithium ion conductivity Ci showed a relatively low value. On the other hand, in the samples 12, 22, and 23 subjected to the heat treatment, the above-described standard deviation σ was less than 0.6. That is, in these samples, it can be said that the distribution bias of the lithium halide hydrate (or hydroxide) is relatively small. Therefore, in these samples, the lithium ion conductivity Ci showed a relatively high value. From this result, it can be said that the value of the standard deviation σ is preferably less than 0.6.

  Further, as shown in FIG. 7, in Sample 4 in which the heat treatment was not performed, the lithium halide area ratio Za on the fractured surface was the same value as the lithium halide area ratio Zb on the cut surface (Za = Zb). That is, in this sample, it can be said that there is little or no region where lithium halide hydrate (or hydroxide) -containing particles exist between the oxide-based lithium ion conductor particles. Therefore, in this sample, the lithium ion conductivity Ci showed a relatively low value. On the other hand, in the samples 12, 22, and 23 that were subjected to the heat treatment, the lithium halide area ratio Za in the fractured surface was a value larger than the lithium halide area ratio Zb in the cut surface (Za> Zb). That is, in these samples, it can be said that there are many regions where lithium halide hydrate (or hydroxide) -containing particles exist between the oxide-based lithium ion conductor particles. Therefore, in these samples, the lithium ion conductivity Ci showed a relatively high value. From these results, it can be said that it is preferable to satisfy the relationship of Za> Zb.

  FIG. 11 and FIG. 12 are explanatory diagrams illustrating the configuration of the lithium ion conductor LIC of the present embodiment. FIG. 11 shows an SEM image (1000 times) of a cut surface of the sample 12, and FIG. 12 shows a SEM-EDS image (element mapping image) (1000 times) of the cut surface of the sample 12 corresponding to FIG. Times). As shown in FIGS. 11 and 12, the lithium halide conductor LIC has a smaller lithium halide area ratio (Zb) in the cut surface of the lithium ion conductor LIC as compared with the fracture surface of the lithium ion conductor LIC shown in FIGS. 2 and 3. Has become.

Note that a sample (hereinafter, referred to as “LLZ-Al”) in which LLZ was subjected to elemental substitution of Al as an oxide-based lithium ion conductor (oxide-based ratio X = 50%), and The sample using LAGP as the oxide-based lithium ion conductor (oxide-based ratio X = 50%) was similarly measured for the lithium-ion conductivity Ci. In these samples, the conditions other than the materials used (the oxide-based ratio X, the mixing method, and the heat treatment conditions) are the same as those of the sample 12. As a result of the measurement, even in samples using LLZ-Al or LAGP as these oxide-based lithium ion conductors, high values of about 4.4 × 10 ⁻⁴ S / cm and 1.2 × 10 ⁻⁴ S / cm were obtained. It was confirmed that the lithium ion conductivity Ci was exhibited.

  The oxide-based ratio X in the lithium ion conductor LIC can be measured by the following method. When the lithium ion conductor LIC is a particle, the particle is embedded in a resin or the like and fixed, and then a cut surface of the particle is obtained by polishing, a cross section polisher method (CP method), or the like. The area ratio of the oxide-based lithium ion conductor is calculated by performing SEM-EDS analysis on the cut surface and obtaining the ratio of the above “element X”. Next, assuming that the whole is 100%, a value obtained by subtracting the area ratio of the oxide-based lithium ion conductor from 100% is defined as the area ratio of the lithium halide hydrate (or hydroxide). When the lithium ion conductor LIC is a bulk body, a cut surface of the bulk body is obtained by polishing or a cross-section polisher method (CP method) on the bulk body. The area ratio of the oxide-based lithium ion conductor is calculated by performing SEM-EDS analysis on the cut surface and obtaining the ratio of the above “element X”. Next, assuming that the whole is 100%, a value obtained by subtracting the area ratio of the oxide-based lithium ion conductor from 100% is defined as the area ratio of the lithium halide hydrate (or hydroxide). In the case where the lithium ion conductor LIC is a bulk material that is used as a mixture with another material (for example, when the lithium ion conductor LIC is used as an electrode material), the mixed materials are identified by crystal structure analysis using XRD. Next, a cut surface of the bulk body is obtained by polishing or a cross section polisher method (CP method) on the bulk body. An SEM-EDS analysis is performed on the cut surface to separate the lithium ion conductor LIC from other materials in accordance with the result of XRD. Then, for the portion of the lithium ion conductor LIC, the ratio of the above “element X” is calculated from the result of elemental analysis by SEM-EDS, and is set as the area ratio of the oxide-based lithium ion conductor. Next, assuming that the entire portion of the lithium ion conductor LIC is 100%, the value obtained by subtracting the area ratio of the oxide-based lithium ion conductor from 100% is calculated as lithium halide hydrate (or hydroxide). Area ratio. That is, in such a case, the ratio occupied by other materials (for example, an electrode active material, a conductive auxiliary agent, and the like) is excluded.

(Second performance evaluation)
FIG. 13 is an explanatory diagram showing a configuration of each sample and a second performance evaluation result in the second performance evaluation. In the second performance evaluation, LLZ-MgSr was used as the oxide-based lithium ion conductor, LiBr was used as the lithium halide, or LiBr and LiI were used together (in this case, the molar ratio between LiBr and LiI was used). Is 1: 1). When LiBr and LiI were used together as lithium halide, the oxide-based ratio X and the like were calculated using the total amount of LiBr and LiI. Samples 31, 32, 35, and 36 were composed only of lithium halide hydrate (or hydroxide) -containing particles because the value of oxide-based ratio X was 0%.

  As shown in FIG. 13, the samples 31, 33, 35, and 37 were produced without performing the heat treatment, and were powder. On the other hand, Samples 32, 34, 36, and 38 are heated products manufactured by performing a heat treatment at 80 ° C. for 17 hours on powder having the same configuration as Samples 31, 33, 35, and 37, respectively. Further, among the samples 31 to 38, in the samples containing both the oxide-based lithium ion conductor and the lithium halide hydrate (or hydroxide) -containing particles (samples 33, 34, 37, and 38), A mixing process using a mortar was performed.

  The method for producing each sample in the second performance evaluation is the same as the method for producing each sample in the first performance evaluation described above, except that the lithium halide used is different. Further, the method of measuring the lithium ion conductivity Ci in the second performance evaluation, and the standard deviation σ calculated from the abundance ratio of the oxide ion conductor particles and the lithium halide hydrate (or hydroxide) in the fracture surface And the method of calculating the lithium halide area ratio are the same as those in the first performance evaluation described above.

  As shown in FIG. 13, the sample 34 subjected to the heat treatment showed a higher lithium ion conductivity Ci than the sample 33 not subjected to the heat treatment. Further, the sample 38 subjected to the heat treatment showed a higher lithium ion conductivity Ci than the sample 37 not subjected to the heat treatment. Therefore, it can be said that when the mixed powder of LLZ-MgSr and LiBr or LiBr + LiI is heat-treated at about 80 ° C., the lithium ion conductivity Ci increases. This is because the hydrate (or hydroxide) of LiBr (and LiI) is fused by the heat treatment, and the gap between the LLZ-MgSr particles is formed by the hydrate (or hydroxide) of LiBr (and LiI). Is buried, which is considered to be due to an increase in adhesion between particles. With respect to the samples (Samples 31, 32, 35, and 36) in which the value of the oxide-based ratio X is 0%, the samples (Samples 31 and 35) that were not subjected to the heat treatment (Samples 31 and 35) were also subjected to the heat treatment (Sample 32). , 36) also had a low lithium ion conductivity Ci.

  As shown in FIG. 13, among the samples (samples 33, 34, 37, 38) containing both the oxide-based lithium ion conductor and the lithium halide hydrate (or hydroxide) -containing particles, In the samples 33 and 37 in which the heat treatment was not performed, the standard deviation σ was 0.6 or more. That is, in these samples, it can be said that the distribution of lithium halide hydrate (or hydroxide) has a relatively large bias. Therefore, in these samples, the lithium ion conductivity Ci showed a relatively low value. On the other hand, in the samples 34 and 38 subjected to the heat treatment, the above-described standard deviation σ was less than 0.6. That is, in these samples, it can be said that the distribution bias of the lithium halide hydrate (or hydroxide) is relatively small. Therefore, in these samples, the lithium ion conductivity Ci showed a relatively high value. From this result, it can be said that the value of the standard deviation σ is preferably less than 0.6.

  As shown in FIG. 13, among the samples (samples 33, 34, 37, 38) containing both the oxide-based lithium ion conductor and the lithium halide hydrate (or hydroxide) -containing particles, In the samples 33 and 37 where the heat treatment was not performed, the lithium halide area ratio Za in the fractured surface was almost the same value as the lithium halide area ratio Zb in the cut surface (Za ≒ Zb). That is, in these samples, it can be said that there is little or no region in which the lithium halide hydrate (or hydroxide) -containing particles exist between the oxide-based lithium ion conductor particles. Therefore, in these samples, the lithium ion conductivity Ci showed a relatively low value. On the other hand, in Samples 34 and 38 subjected to the heat treatment, the lithium halide area ratio Za in the fractured surface was a value larger than the lithium halide area ratio Zb in the cut surface (Za> Zb). That is, in these samples, it can be said that there are many regions where lithium halide hydrate (or hydroxide) -containing particles exist between the oxide-based lithium ion conductor particles. Therefore, in these samples, the lithium ion conductivity Ci showed a relatively high value. From these results, it can be said that it is preferable to satisfy the relationship of Za> Zb.

(Third performance evaluation)
FIG. 14 is an explanatory diagram illustrating the configuration of each sample and the third performance evaluation result in the third performance evaluation. In the third performance evaluation, LLZ-MgSr was used as the oxide-based lithium ion conductor, and LiCl was used as the lithium halide.

  As shown in FIG. 14, each of the samples (Samples 41 and 42) contains both an oxide-based lithium ion conductor and particles containing lithium halide hydrate (or hydroxide). In these samples, a mixing process using a mortar was performed. The sample 41 was produced without performing post-mixing processing, and is a powder. On the other hand, the sample 42 is a formed product produced by performing post-mixing treatment at 25 ° C. for 12 hours (dew point temperature 5 to 7 ° C.) on powder having the same configuration as the sample 41.

  The method of manufacturing each sample in the third performance evaluation is the same as the method of manufacturing each sample in the first performance evaluation described above, except that a different lithium halide is used. Further, the method of measuring the lithium ion conductivity Ci in the third performance evaluation, the standard deviation σ calculated from the existing ratio of the oxide ion conductor particles and the lithium halide hydrate (or hydroxide) in the fractured surface. And the method of calculating the lithium halide area ratio are the same as those in the first performance evaluation described above.

  As shown in FIG. 14, the sample 42 that has performed the post-mixing process has a higher lithium ion conductivity Ci than the sample 41 that has not performed the post-mixing process. Therefore, it can be said that when the mixed powder of LLZ-MgSr and LiCl is subjected to post-mixing treatment at about 25 ° C., the lithium ion conductivity Ci increases. This is because the hydrate (or hydroxide) of LiCl is fused by post-mixing treatment at about 25 ° C., and the void between the LLZ-MgSr particles is filled with the hydrate (or hydroxide) of LiCl. It is considered that this is because the adhesion between the particles is increased.

  Further, as shown in FIG. 14, in the sample 41 in which the post-mixing process was not performed, the above-described standard deviation σ was 0.6 or more. That is, in this sample, it can be said that the bias of the distribution of the lithium halide hydrate (or hydroxide) is relatively large. Therefore, in this sample, the lithium ion conductivity Ci showed a relatively low value. On the other hand, in the sample 42 on which the post-mixing processing was performed, the above-described standard deviation σ was less than 0.6. That is, in this sample, it can be said that the bias of the distribution of the lithium halide hydrate (or hydroxide) is relatively small. Therefore, in this sample, the lithium ion conductivity Ci showed a relatively high value. From this result, it can be said that the value of the standard deviation σ is preferably less than 0.6.

  Further, as shown in FIG. 14, in sample 41 in which the post-mixing treatment was not performed, the lithium halide area ratio Za on the fractured surface was almost the same value as the lithium halide area ratio Zb on the cut surface (Za ≒). Zb). That is, in this sample, it can be said that there is little or no region where lithium halide hydrate (or hydroxide) -containing particles exist between the oxide-based lithium ion conductor particles. Therefore, in this sample, the lithium ion conductivity Ci showed a relatively low value. On the other hand, in the sample 42 on which the post-mixing treatment was performed, the lithium halide area ratio Za in the fracture surface was a value larger than the lithium halide area ratio Zb in the cut surface (Za> Zb). That is, in this sample, it can be said that there are many regions where lithium halide hydrate (or hydroxide) -containing particles exist between the oxide-based lithium ion conductor particles. Therefore, in this sample, the lithium ion conductivity Ci showed a relatively high value. From these results, it can be said that it is preferable to satisfy the relationship of Za> Zb.

B. Modification:
The technology disclosed in the present specification is not limited to the above-described embodiment, and can be modified into various forms without departing from the gist thereof. For example, the following modifications are also possible.

  In the above-described embodiment, the lithium ion conductor LIC having the above-described configuration is included in all of the electrolyte layer 112, the positive electrode layer 114, and the negative electrode layer 116. However, the lithium ion conductor LIC having the above-described configuration includes the electrolyte layer 112. It is only necessary that at least one of the positive electrode layer 114 and the negative electrode layer 116 is included. Any one of the electrolyte layer 112, the positive electrode layer 114, and the negative electrode layer 116 may have a lithium ion conductor LIC (for example, sulfide) having another configuration. (A lithium ion conductor or an oxide lithium ion conductor). Further, an intermediate layer is provided between the electrolyte layer 112 and the positive electrode layer 114, or between the electrolyte layer 112 and the negative electrode layer 116, or both, and the lithium ion conductor LIC having the above-described configuration is provided only on the intermediate layer. May be included. Further, the lithium ion conductor LIC having the above-described configuration may be included in all of the intermediate layer, the electrolyte layer 112, the positive electrode layer 114, and the negative electrode layer 116.

  Further, the material forming each member in the above embodiment is merely an example, and each member may be formed of another material.

  Further, in the above embodiment, the lithium ion conductor LIC used for the all solid state battery 102 has been described as an example. However, the present invention is not limited to using a lithium ion conductive solid electrolyte such as a lithium air battery and a lithium flow battery. The present invention can be applied to a lithium ion conductor LIC used for a lithium battery and a lithium ion conductor LIC used for other than a lithium battery.

  Further, in the above embodiment, the lithium ion conductor LIC includes both the lithium halide hydrate-containing particles 54 and the lithium halide hydroxide-containing particles 56. Only one of the lithium halide hydrate-containing particles 54 and the lithium halide hydroxide-containing particles 56 may be included. That is, the lithium ion conductor LIC may include at least one of the lithium halide hydrate-containing particles 54 and the lithium halide hydroxide-containing particles 56. Further, the lithium ion conductor LIC may include particles containing lithium halide in addition to at least one of the particles 54 containing lithium halide hydrate and the particles 56 containing lithium hydroxide. Alternatively, the lithium ion conductor LIC may include particles containing lithium halide, but not particles 54 containing lithium hydrate and particles 56 containing lithium hydroxide. That is, the lithium ion conductor LIC may include at least one of particles containing lithium halide, particles 54 containing lithium hydrate, and particles 56 containing lithium hydroxide.

52: Oxide-based lithium ion conductor particles 54: Lithium halide hydrate-containing particles 56: Lithium halide hydroxide-containing particles 102: All-solid lithium ion secondary battery 110: Battery body 112: Electrolyte layer 114: Positive electrode Layer 116: negative electrode layer 154: current collecting member 156: current collecting member

Claims (13)

In an ion conductor comprising a plurality of oxide-based lithium ion conductor particles,
Between two of the oxide-based lithium ion conductor particles, and have a region of at least one of the presence of the lithium halide and lithium halide hydrate and lithium halide hydroxides,
The ionic conductor, wherein the halogen element of the lithium halide is at least one of iodine (I), bromine (Br), and chlorine (Cl) . The ionic conductor according to claim 1,
An ionic conductor, wherein the halogen element of the lithium halide contains iodine (I). In the ionic conductor according to claim 1 or claim 2,
An ionic conductor, wherein the halogen element of the lithium halide includes bromine (Br). The ionic conductor according to any one of claims 1 to 3,
An ion conductor, wherein the halogen element of the lithium halide includes chlorine (Cl). In the ionic conductor according to any one of claims 1 to 4,
As the index indicating the magnitude of the uneven distribution of the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide in the ion conductor, the oxide-based lithium ion conductor in the fracture surface Particles, the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide, and the value of the standard deviation calculated from the abundance ratio is less than 0.6, Ion conductor. In the ionic conductor according to any one of claims 1 to 4,
As an index indicating the magnitude of the deviation of the distribution of the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide in the ion conductor, the oxide-based lithium ion conduction A specific element excluding lithium and oxygen is selected from the elements contained in the body particles, and the existence ratio of the specific element is defined as Xi, and the lithium halide, the lithium halide hydrate, or the halogen is used. Assuming that the ratio of the halogen element contained in the lithium hydroxide is Yi, the ratio of Yi to Xi (Yi / Xi) is Ri, and m number of m (where m is an integer of 9 or more) m An ionic conductor, wherein a value of a standard deviation calculated from a data group including the ratio Ri (the ratios R1 to Rm) is less than 0.6. The ionic conductor according to any one of claims 1 to 6,
The area ratio of a region occupied by the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide in the fracture surface of the ion conductor is defined as Za, and the halogen in the cut surface of the ion conductor is defined as Za. An ion conductor satisfying a relationship of Za> Zb, where Zb is an area ratio of a region occupied by lithium halide, the lithium halide hydrate, or the lithium halide hydroxide. The ionic conductor according to any one of claims 1 to 7,
Particles containing the area occupied by the oxide-based lithium ion conductor particles and the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide in at least one cut surface of the ion conductor An ion conductor characterized by satisfying 30 ≦ Xa <100, where Xa is the ratio of the area occupied by Xa to (100−Xa). The ionic conductor according to claim 8,
Particles containing the area occupied by the oxide-based lithium ion conductor particles and the lithium halide, the lithium halide hydrate, or the lithium halide hydroxide in at least one cut surface of the ion conductor Satisfies 38 ≦ Xa ≦ 97, where Xa is the ratio of the area occupied by Xa to (100−Xa). The ionic conductor according to any one of claims 1 to 9,
An ionic conductor having a lithium ion conductivity at 25 ° C. of 1.0 × 10 ⁻⁵ S / cm or more. In the ionic conductor according to any one of claims 1 to 10,
The oxide-based lithium ion conductor is an ion conductor having a garnet-type structure or a garnet-like structure containing at least Li, Zr, La, and O; and Li and M (M is Ti, Zr, Ge). At least one of the above), an ion conductor having a NASICON-type structure containing at least P and O, and at least one of an ion conductor having a perovskite-type structure containing at least Li, Ti, La and O An ionic conductor, which is of one type. In a lithium battery including a solid electrolyte layer, a positive electrode, and a negative electrode,
A lithium battery, wherein at least one of the solid electrolyte layer, the positive electrode, and the negative electrode includes the ionic conductor according to any one of claims 1 to 11. In a method for producing an ionic conductor,
An oxide-based lithium ion conductive particle, and a lithium halide-based particle that is a particle containing at least one of lithium halide, lithium halide hydrate, and lithium halide hydroxide, Preparing a mixture by mixing at a volume ratio satisfying 30 ≦ Xb <100 when the volume ratio of the ionic conductor particles and the lithium halide-based particles is Xb: (100−Xb);
Heating the mixture;
Equipped with a,
Halogen element of said lithium halide is characterized by at least 1 Tsudea Rukoto of iodine (I) and bromine (Br) and chlorine (Cl), the production method of the ionic conductor.

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