Patent Application
20230378527
The present application relates to a complex oxide having a crystal structure with high density and high ion conductivity, a method for producing this complex oxide and an all-solid-state lithium ion secondary battery containing this complex oxide as a solid electrolyte material.
Lithium ion secondary batteries have a high energy density and can be operated at a high potential compared with secondary batteries such as nickel-cadmium batteries and nickel-hydrogen batteries. Therefore, lithium ion secondary batteries are being widely used in small information equipment such as mobile phones or notebook computers. In addition, since size reduction and weight reduction of lithium ion secondary batteries are easy to achieve, the demand therefor as secondary batteries for hybrid vehicles or electric vehicles is increasing.
Furthermore, in consideration of safety, research and development is underway regarding all-solid-state lithium ion secondary batteries where a flammable electrolytic solution is not used. Solid electrolytes that are used in all-solid-state lithium ion secondary batteries are required to have high lithium ion conductivity. As oxide-based materials having high lithium ion conductivity, materials having a cubic garnet-type structure have been reported (Patent Document 1), and research and development of these materials is progressing. Particularly, materials having a chemical composition Li7−xLa3Zr2−xTaxO12 have high ion conductivity when x is near 0.5.
It is known that materials having this cubic garnet-type structure are hard to sinter and production of high-density compacts is difficult. In addition, solid electrolytes having this cubic garnet-type structure have high ion conductivity at room temperature, but the activation energy is near 0.45 ev, and the ion conductivity decreases at low temperatures. In order to realize high ion conductivity, there is a need to reduce grain boundary resistance and interface resistance, and thus solid materials that are high-density compacts, particularly, single crystal materials, are desirable as solid electrolytes. Single crystal materials are not affected by grain boundaries and are thus expected to have a high lithium ion conductive property. In addition, single crystal materials are capable of preventing short circuits between positive and negative electrodes in charging and discharging processes and enable thickness reduction and thus provide the possibility of size reduction of all-solid-state lithium ion secondary batteries in the future.
Based on these problems, there have been reports of growing a single crystal of Li7−xLa3Zr2−xTaxO12 or Li7−xLa3Zr2−xNbxO12 having a garnet-type structure using a melting method (Patent Document 2 and Patent Document 3). In addition, as additional oxide-based materials exhibiting high lithium ion conductivity, a material having a perovskite-type structure (Non-Patent Document 1) or a material having a polyanionic NASION-type structure (Non-Patent Document 2) has been reported. As described above, there have been a number of reported examples regarding cubic garnet-type solid electrolytes, perovskite-type solid electrolytes and NASICON-type solid electrolytes each having high lithium ion conductive property, but only a few examples have been reported regarding a material having a different structure.
The present application has been made in consideration of such circumstances, and an objective thereof is to develop a novel solid electrolyte having high density and high lithium ion conductivity and having low activation energy.
The inventors of the present application found that, when a mixed raw material blended to be Li(4−x)ySr(2−x)zLaxZrO6 (0≤x≤1.0, y=1.2 and z=1.2) is formed into a rod shape, and then this compact is melted and rapidly cooled by an FZ method using infrared condensed heating, it is possible to produce a rod of a high-density complex oxide single crystal represented by Li4−xSr2−xLaxZrO6 (0≤x≤1.0). That is, the growth of a single crystal of a solid electrolyte having a new crystal structure that is different from the cubic garnet-type structure, the perovskite-type structure and the NASICON-type structure and for which analogue crystal structures have never been reported was achieved.
The thickness of a silicon single crystal can be reduced by polishing using a wire saw. A rod of the high-density complex oxide single crystal of the present application also has high strength. Therefore, the high-density complex oxide single crystal of the present application can also be easily cut with a diamond cutter or the like. The inventors of the present application also found that it is possible to produce a thin piece having a thickness of approximately 0.1 mm of a complex oxide single crystal represented by Li4−xSr2−xLaxZrO6 (0≤x≤1.0). It is possible to reduce the thickness of this complex oxide single crystal to approximately 0.03 mm.
The complex oxide of the present application has a chemical composition represented by Li4−xSr2−xLaxZrO6 (0≤x≤1.0) and belongs to a monoclinic space group P21/n.
In a method for producing a complex oxide of the present application, at least a part of a raw material having a chemical composition represented by Li(4−x)ySr(2−x)zLaxZrO6 (0≤x≤1.0, 1<y and 1<z) is melted to form a molten portion and the molten portion is moved at a movement speed of 8 mm/h or faster to produce a complex oxide having a chemical composition represented by Li4−xSr2−xLaxZrO6 (0≤x≤1.0), having a relative density of 99% or more and belonging to a monoclinic space group P21/n.
An all-solid-state lithium ion secondary battery of the present application has a positive electrode, a negative electrode and a solid electrolyte, and the solid electrolyte is composed of the complex oxide of the present application.
According to the present application, a complex oxide Li4−xSr2−xLaxZrO6 (0≤x≤1.0) having high density and high ion conductivity and having low activation energy and an all-solid-state lithium ion secondary battery in which this complex oxide is used as a solid electrolyte material are obtained.
The inventors of the present application intensively studied a method for melting and cooling a mixed raw material containing an excess of lithium and strontium compared with the composition proportions of a target complex oxide. As a result, the inventors of the present application found that a complex oxide single crystal of Li4−xSr2−xLaxZrO6 (0≤x≤1.0) that belongs to the monoclinic system can be produced by this method. In addition, the inventors of the present application confirmed that a thin piece of this single crystal can be mechanically produced and completed inventions to be disclosed in the present application. A complex oxide of an embodiment of the present application has a chemical composition represented by Li4−xSr2−xLaxZrO6 (0≤x≤1.0), being monoclinic and belongs to a space group P21/n.
The high-density single crystal of the present embodiment belonging to the monoclinic system and having a crystal structure for which no analogue crystal structures have been thus far reported cannot be produced by a normal FZ method in which a sample rod is rotated at slower than 20 rpm and a molten portion of the sample rod is lowered at a movement speed of approximately 2 mm/h. This is because cavities enter Li4−xSr2−xLaxZrO6 (0≤x≤1.0). When a molten portion of a mixed raw material having a rod shape is lowered at a movement speed of 8 mm/h or faster while rotating the mixed raw material at a rotation speed of 20 rpm or faster and this molten portion is cooled at a high speed, a crystal with no cavities can be produced.
A rod of the obtained high-density complex oxide Li4−xSr2−xLaxZrO6 (0≤x≤1.0) can be cut to an arbitrary thickness with a diamond cutter or the like. In addition, the complex oxide raw crystal of the present embodiment can be produced by melting a mixed raw material in which the amounts of lithium and strontium are increased with respect to the stoichiometric proportion of each metal in the chemical composition Li4−xSr2−xLaxZrO6 (0≤x≤1.0) in consideration of the fact that lithium and strontium volatilize at high temperatures.
The relative density of the complex oxide of the present embodiment is preferably 99% or more and particularly preferably 100%. The relative density is calculated by measuring the outline of a produced thin piece, calculating the apparent volume and dividing the apparent density calculated from a measured mass by a true density that is obtained from a single crystal X-ray structural analysis result. The complex oxide of the present embodiment has high density and thus can be easily cut to an arbitrary thickness with a diamond cutter or the like.
In addition, the complex oxide of the present embodiment can be used as a solid electrolyte material having high ion conductivity (for example, 6.0×10−4 S/cm or more) and low activation energy (for example, 0.20 eV or more and 0.30 eV or less). Specifically, Li3.957Sr1.957La0.043ZrO6 can be used as a solid electrolyte material having lithium ion conductivity of 6.0×10−4 S/cm or more and an activation energy of 0.24 eV.
The complex oxide of the present embodiment is produced by melting at least a part of a raw material having a chemical composition represented by Li(4−x)ySr(2−x)zLaxZrO6 (0≤x≤1.0, 1<y and 1<z) to form a molten portion and moving the molten portion at a movement speed of 8 mm/h or faster. Specifically, the complex oxide single crystal of the present embodiment is grown by an FZ method, a Czochralski (Cz) method, a Bridgman method, a pedestal method or the like. An appropriate production method may be selected from these depending on the desired size, shape and the like of the crystal of the complex oxide to be produced.
A crystal of a complex oxide Li4−xSr2−xLaxZrO6 (0≤x≤1.0) having a relative density of 100%, that is, a single crystal of the original complex oxide Li4−xSr2−xLaxZrO6 (0≤x≤1.0), can be produced by the FZ method or the Cz method. The single crystal of the complex oxide Li4−xSr2−xLaxZrO6 (0≤x≤1.0) having a relative density of 100% has characteristics of a high lithium ion conductive property and low activation energy. In the case of producing the complex oxide of the present embodiment by the FZ method, a crystal is grown by melting a rod-shaped raw material while rotating the raw material on a surface perpendicular to the longitudinal direction of the raw material at a rotation speed of 20 rpm or faster and moving a molten portion in the longitudinal direction.
When the movement speed of the molten portion is set to be as fast as 8 mm/h or faster, decomposition of the raw material caused by lithium volatilization can be avoided. The movement speed of this molten portion is preferably 8 mm/h or faster and 19 mm/h or slower. In addition, in the molten portion, volatilization of lithium generates bubbles, but the bubbles can be removed by setting the rotation speed of the rod-shaped raw material to be as fast as 20 rpm or faster. The rotation speed of the raw material is preferably 20 rpm or faster and 60 rpm or slower. In addition, the melting of the raw material and the movement of the molten portion are preferably performed in a dry air atmosphere. A crystal of Li4−xSr2−xLaxZrO6 (0≤x≤1.0) having a relative density of 99% or more can be produced as described above.
A method for producing the complex oxide of the present embodiment will be described more specifically using the growth of a crystal of Li4−xSr2−xLaxZrO6 (0≤x≤1.0) having a relative density of 99% or more and belonging to the monoclinic system, for which no analogue crystal structures have been thus far reported, as an example. First, a rod-shaped raw material is produced as described below. In the beginning, in consideration of the fact that lithium salts and strontium salts volatilize at high temperatures, a lithium compound, a strontium compound, a lanthanum compound and a zirconium compound are weighed so that Li:Sr:La:Zr becomes the stoichiometric proportions (so-called mole proportions) of (4−x)y:(2−x)z:x:1 (0≤x≤1.0, 1<y and 1<z). y and z are preferably 1.1 or more and more preferably 1.15 or more and 1.25 or less.
The lithium compound is not particularly limited as long as lithium is contained, and examples thereof include oxides such as Li2O, carbonates such as Li2CO3 and the like. The strontium compound is not particularly limited as long as strontium is contained, and examples thereof include oxides such as SrO, carbonates such as SrCO3 and chlorides such as SrCl2. The lanthanum compound is not particularly limited as long as lanthanum is contained, and examples thereof include oxides such as La2O3, hydroxides such as La(OH)3 and the like. The zirconium compound is not particularly limited as long as zirconium is contained, and examples thereof include oxides such as ZrO2, chlorides such as ZrCl4 and the like.
In addition, compounds composed of two or more elements selected from lithium, strontium, lanthanum and zirconium may be used and weighed so that Li:Sr:La:Zr becomes the mole proportions of (4−x)y:(2−x)z:x:1 (0≤x≤1.0, 1<y and 1<z). Examples of such compounds composed of two or more elements include lithium zirconium oxides such as LiZrO3, strontium zirconium oxides such as SrZrO4 and the like.
Next, the weighed individual compounds are mixed together. The mixing method is not particularly limited as long as these individual compounds can be uniformly mixed, and the compounds may be mixed using, for example, a mixing machine such as a mixer by a wet method or a dry method. In addition, the obtained mixture is loaded into a crucible with a lid, then, preliminarily baked at 600° C. to 900° C., preferably at 650° C., loaded into a rubber tube or the like to be made into a rod shape and then formed by isostatic pressing, whereby a powder that serves as a raw material is obtained. It is more preferable to repeatedly crush, mix and bake the raw material that has been once preliminarily baked one more time.
Next, the obtained raw material powder is crushed to decrease particle sizes in order to make forming easy. The crushing method is not particularly limited as long as the powder can be made fine, and the raw material powder may be crushed using, for example, a crushing device such as a planetary ball mill, a hot mill or a bead mill by a wet method or a dry method. In addition, the obtained crushed object is loaded into a rubber tube and then formed into a rod shape by isostatic pressing. Next, the obtained rod-shaped compact is baked at approximately 600° C. to 850° C., preferably 700° C. to 850° C., for approximately four hours, whereby a rod-shaped raw material is obtained. At this point in time, the chemical composition of the raw material is Li(4−x)ySr(2−x)zLaxZrO6 (0≤x≤1.0, 1<y and 1<z).
In addition, this rod-shaped raw material is melted in an infrared condensed heating furnace and then rapidly cooled, whereby Li4−xSr2−xLaxZrO6 (0≤x≤1.0) having a relative density of 99% or more and belonging to the monoclinic system, for which no analogue crystal structures are known, is produced. A single crystal of Li4−xSr2−xLaxZrO6 (0≤x≤1.0) having a length of 2 cm or longer is obtained by this production method. Therefore, thin pieces having the same qualities can be easily produced by cutting.
In the case of producing a high-density single crystal of Li4−xSr2−xLaxZrO6 (0≤x≤1.0) by the CZ method, the single crystal is produced by the following procedure. First, a raw material is put into a crucible and heated to be melted. Next, a seed crystal is dipped in the melt of the raw material and lifted while being rotated. It is considered that, when the movement speed of a molten portion, that is, the lifting speed of the seed crystal is set to be as fast as 8 mm/h or faster, the volatilization of lithium and strontium is suppressed and a high-density Li4−xSr2−xLaxZrO6 (0≤x≤1.0) crystal can be obtained.
In addition, the high-density complex oxide Li4−xSr2−xLaxZrO6 (0≤x≤1.0) of the present embodiment has an excellent lithium ion conductive property and thus can be used as a solid electrolyte for all-solid-state lithium ion secondary batteries. That is, an all-solid-state lithium ion secondary battery of the embodiment of the present application has a positive electrode, a negative electrode and a solid electrolyte, and the solid electrolyte is composed of the complex oxide of the present embodiment. Hereinafter, the inventions disclosed in the present application will be described more specifically using examples. The inventions disclosed in the present application are not limited to these examples by any means.
(Production of Powdery Mixed Raw Material of Li4.7484Sr2.3484La0.043ZrO6)
13.4461 g of lithium carbonate Li2CO3 (manufactured by Rare Metallic Co., Ltd., purity: 99.99% (the same below)), 26.5725 g of strontium carbonate SrCO3 (manufactured by Rare Metallic Co., Ltd., purity: 99.99% (the same below)), 0.5369 g of lanthanum oxide La2O3 (manufactured by Rare Metallic Co., Ltd., purity: 99.99% (the same below)) and 9.4445 g of zirconium oxide ZrO2 (manufactured by Rare Metallic Co., Ltd., purity: 99.99% (the same below)) were put into an agate mortar and uniformly mixed together by a wet method in which ethanol was used. The lanthanum oxide had been preliminarily baked at 900° C. in advance before use.
Regarding the mole proportions Li:Sr:La:Zr of metals in this mixture, there were an excess of lithium (20 mol %) and an excess of strontium (20 mol %) with respect to the mole proportions of a target object Li3.957Sr1.957La0.043ZrO6 (Li4−xSr(2−x)LaxZrO6 where x=0.043)). That is, the chemical composition of this mixture corresponds to Li4.7484Sr2.3484La0.043ZrO6 (Li(4−x)ySr(2−x)zLaxZrO6 where x=0.043, y=1.2 and z=1.2).
50.000 g of this mixture was loaded into an alumina crucible with a lid (manufactured by Nikkato Corporation, C3 type). This was put into a box-type electric furnace (manufactured by Yamato Scientific Co., Ltd., FP100 type) and preliminarily baked at 650° C. for six hours, thereby obtaining a powder. 50 g of the obtained powder, 300 g of zirconia balls having a diameter of 5 mm and 100 g of isopropanol were loaded into a zirconia crushing container having a capacity of 250 mL and rotated using a planetary ball mill (manufactured by Fritsch GmbH, Model P-6) at a revolution speed of 200 rpm for a total of 300 minutes, thereby crushing this powder. The crushed powder was dried at 100° C. for 24 hours and classified using a sieve having a mesh size of 250 μm, thereby obtaining a powdery mixed raw material.
A rod-shaped raw material was produced using the powdery mixed raw material obtained above by the following procedure. 15.127 g of this powdery mixed raw material was loaded into a rubber die and degassed. This die was put into water in a sealed state and maintained at 40 MPa for five minutes. After the pressure of the water was decreased, a compact was removed from the die. The compact had a cylindrical shape that was 1.1 cm in diameter and 8.0 cm in height. This cylindrical compact was baked using a box-type electric furnace (manufactured by Denken Co., Ltd., Model No. KDF009) at 850° C. for four hours. The removed compact, that is, a rod-shaped raw material had a cylindrical shape that was 1.0 cm in diameter and 7.7 cm in height.
(Growth of Crystal of Li3.957Sr1.957La0.043ZrO6)
The rod-shaped raw material obtained above was installed in a four-ellipse type infrared condensed heating furnace equipped with a 1 kW halogen lamp (FZ furnace) (manufactured by Crystal Systems Corporation, FZ-T-10000H type), and a dry air atmosphere was formed. The rod-shaped raw material was heated at an output of 21.3% while being rotated on a surface perpendicular to the longitudinal direction at 40 rpm. After a short time, a part of this rod-shaped raw material, which was a polycrystalline sample, was melted to form a molten portion. The installation table of this rod-shaped raw material was lowered at a movement speed of 10 mm/h, thereby growing a high-density complex oxide Li3.957Sr1.957La0.043ZrO6 (hereinafter, referred to as “sample 1” in some cases). The chemical composition of the sample 1 was analyzed by single crystal X-ray crystal structural analysis. The external appearance of the sample 1 is shown in
(Evaluation of Crystal of Li3.957Sr1.957La0.043ZrO6)
The structure of the sample 1 was investigated using a single crystal X-ray diffractometer having a two-dimensional IP detector (manufactured by Rigaku Corporation, R-AXIS RAPID-II). The X-ray diffraction pattern of the sample 1 is shown in
As a result of collecting the diffraction intensity data of sample 1, building a model of the initial crystal structure with a program SUPERFLIP including a charge-flipping method and investigating the crystal structure with a crystal structural analysis program Jana2006, it was found that the sample 1 belonged to the monoclinic system. The sample 1 was cut with a diamond cutter to produce four thin pieces each having a thickness of 0.1 mm, and the relative densities thereof were calculated by the above-described method. As a result, these relative densities were each 99.5%, 99.8%, 99.9% or 100%. As described above, a complex oxide having a relative density of 99.5% or more was obtained.
Energy dispersive X-ray spectroscopic measurement of the sample 1 was performed with an energy dispersive X-ray spectroscopy device (manufactured by JEOL Ltd., JCM-6000) attached to a scanning electron microscope. As a result, it was possible to acquire spectral data as shown in
In addition, the arrangement of lithium ions in the crystal structure of this complex oxide has a three-dimensional lithium path, and, particularly, in a one-dimensional direction, the distance between the lithium ions is close and lithium ion sites are appropriately missing. Therefore, it is considered that the sample 1 has a high lithium ion conductive property and can be applied as a solid electrolyte material. The sample 1 was cut to produce a thin piece that was approximately 0.50 cm in diameter and approximately 0.10 cm in thickness. Gold having a cylindrical shape having a thickness of 40 nm was sputtered in a round shape having a 0.40 cm×0.40 cm bottom surface on the front side and rear side of this thin piece to form electrodes.
As a result of measuring the lithium ion conductivity of this sample by an alternating current impedance method (measuring instrument: Solarton, 1260) at 25° C. in a nitrogen atmosphere, a Nyquist plot shown in
(Production of all-Solid-State Lithium Ion Secondary Battery)
0.0105 mol of lithium acetate dihydrate (manufactured by Sigma-Aldrich Co. LLC) and 0.01 mol of cobalt acetate tetrahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in 100 g of ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.). 10 g of polyvinyl pyrrolidone K-30 (manufactured by Wako Pure Chemical Industries, Ltd.) was added thereto and dissolved therein, thereby preparing 0.1 mol/kg of a lithium cobaltate precursor solution. The reason for setting the amount of lithium acetate to be 5% larger than the amount of cobalt acetate in terms of mole proportion is to compensate for the amount of lithium to be volatilized during baking.
The sample 1 was cut to produce a thin piece that was approximately 0.6 cm in diameter and approximately 0.10 cm in thickness. 10 μL of the precursor solution was added dropwise onto a single surface of this thin piece and preliminarily baked at 400° C. for 20 minutes. After that, the precursor solution was baked at 850° C. for 10 minutes, thereby producing a sample having a lithium cobaltate positive electrode formed on a single surface of the sample 1 (hereinafter, referred to as “sample 2” in some cases). Sample 2 and a metallic lithium plate blanked to a diameter of 4 mm were put into a commercially available HS cell for battery evaluation (manufactured by Hosen Corporation) in a glove box, and an all-solid-state lithium ion secondary battery as shown in
(Production of Powdery Mixed Raw Material of Li4Sr2ZrO6)
A powdery mixed raw material was obtained in the same manner as in Example 1 except that 14.1793 g of lithium carbonate Li2CO3, 25.9684 g of strontium carbonate SrCO3 and 9.8524 g of zirconium oxide ZrO2 were used. Regarding the mole proportions Li:Sr:Zr of metals in this powdery mixed raw material, there were an excess of lithium (20 mol %) and an excess of strontium (20 mol %) with respect to the mole proportions of a target object Li4Sr2ZrO6. That is, the chemical composition of this powdery mixed raw material corresponds to Li4.4Sr2.2ZrO6 (Li(4−x)ySr(2−x)zLaxZrO6 where x=0, y=1.2 and z=1.2).
A compact was obtained in the same manner as in Example 1 except that 14.111 g of the powdery mixed raw material obtained above was used. This compact had a cylindrical shape that was 1.2 cm in diameter and 6.0 cm in height. After that, the compact was baked under the same conditions as in Example 1 to obtain a rod-shaped raw material. The obtained rod-shaped raw material had a cylindrical shape that was 1.1 cm in diameter and 5.3 cm in height.
(Growth of Crystal of Li4Sr2ZrO6)
A high-density complex oxide Li4Sr2ZrO6 (hereinafter, referred to as “sample 3” in some cases) was grown in the same manner as in Example 1 except that the rod-shaped raw material was heated at an output of 19.8%, and the chemical composition was analyzed. The external appearance of the sample 3 is shown in
(Evaluation of Crystal of Li4Sr2ZrO6)
The structure of the sample 3 was investigated in the same manner as in Example 1. The X-ray diffraction pattern of the sample 3 is shown in
As a result of investigating the crystal structure of the sample 3 in the same manner as in Example 1, it was found that the sample 3 belonged to the monoclinic system. Furthermore, in the same manner as in Example 1, four thin pieces of the sample 3 each having a thickness of 0.1 mm were produced, and the relative densities were calculated. As a result, these relative densities were each 99.8%, 99.7%, 99.9% or 100%. As described above, a complex oxide having a relative density of 99.5% or more was obtained.
The sample 3 had a crystal structure shown in
(Production of Powdery Mixed Raw Material of Li3SrLaZrO6)
A powdery mixed raw material was obtained in the same manner as in Example 1 except that 11.1527 g of lithium carbonate Li2CO3, 14.8549 g of strontium carbonate SrCO3, 13.6599 g of lanthanum oxide La2O3 and 10.3325 g of zirconium oxide ZrO2 were used. Regarding the mole proportions Li:Sr:La:Zr of metals in this powdery mixed raw material, there were an excess of lithium (20 mol %) and an excess of strontium (20 mol %) with respect to the mole proportions of a target object Li3SrLaZrO6. That is, the chemical composition of this powdery mixed raw material corresponds to Li4.4Sr2.2ZrO6 (Li(4−x)ySr(2−x)zLaxZrO6 where x=1, y=1.2 and z=1.2).
A compact was obtained in the same manner as in Example 1 except that 18.427 g of the powdery mixed raw material obtained above was used. This compact had a cylindrical shape that was 1.1 cm in diameter and 8.0 cm in height. After that, the compact was baked under the same conditions as in Example 1 to obtain a rod-shaped raw material. The obtained rod-shaped raw material had a cylindrical shape that was 1.0 cm in diameter and 8.0 cm in height.
(Growth of Crystal of Li3SrLaZrO6)
A high-density complex oxide Li3SrLaZrO6 (hereinafter, referred to as “sample 4” in some cases) was grown in the same manner as in Example 1, and the chemical composition was analyzed. The external appearance of the sample 4 is shown in
(Evaluation of Crystal of Li3SrLaZrO6)
The structure of the sample 4 was investigated in the same manner as in Example 1. The X-ray diffraction pattern of the sample 4 is shown in
As a result of investigating the crystal structure of the sample 4 in the same manner as in Example 1, it was found that the sample 4 belonged to the monoclinic system. Furthermore, in the same manner as in Example 1, four thin pieces of the sample 4 each having a thickness of 0.1 mm were produced, and the relative densities were calculated. As a result, these relative densities were each 99.9%, 99.9%, 100% or 99.7%. As described above, a complex oxide having a relative density of 99.5% or more was obtained.
The sample 4 had a crystal structure shown in
Combination of the results of Example 1 to Example 3 show that the lattice constants of Li4−xSr2−xLaxZrO6 (0≤x≤1.0) were a of 0.57 nm±0.02 nm, b of 0.62 nm 0.02 nm, c of 0.84 nm±0.02 nm and a β angle of 97.0°±0.2°.
The complex oxide of the present application having high density and represented by Li4−xSr2−xLaxZrO6 (0≤x≤1.0) can be used as a solid electrolyte material or the like for all-solid-state lithium ion secondary batteries.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-171286 | Oct 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/031700 | 8/30/2021 | WO |
