Solid electrode layer and method for manufacturing the same

Abstract

To provide a solid electrode layer that has enabled a constitution In which a solid electrolyte material and a positive electrode active material are evenly and homogeneously dispersed in a positive electrode layer, using, as an invention target material, a layered rock salt-type oxide, which is a positive electrode active material that not only suppresses generation of impurities during sintering with a solid electrolyte layer, but also can be expected to achieve performance as high as applicable to a current all-solid-state lithium-ion secondary battery.SOLUTION: A solid electrode layer includes a lithicone type oxide and a layered rock salt type oxide. Therein: a content of impurities calculated from an X-ray diffraction diagram of the solid electrode layer is 1.0 mol% or less based on 100 mol% of a total amount of the solid electrode layer; an average diameter of shapes obtained by performing Voronoi division on the layered rock salt type oxide is 0.50 to 2.00 μm; and a standard deviation of the average diameter of the shapes obtained by performing Voronoi partitioning on the layered rock salt type oxide is 1.00 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a solid electrode layer and a method for producing the same. [Background technology]

[0002] High-energy-density lithium secondary batteries are currently widely used as power sources for small portable devices, electric vehicles, and other devices. Furthermore, there is a growing demand for rechargeable batteries that can be surface-mounted onto substrates using a reflow process, targeting IoT applications such as backup power sources for real-time clocks and wireless communication modules. For these applications, ensuring high heat resistance and safety of rechargeable batteries is crucial. Among lithium-ion secondary batteries, all-solid-state lithium-ion secondary batteries using oxide solid electrolytes do not use flammable organic electrolytes like conventional lithium-ion secondary batteries. Therefore, they are ideal for substrate-mounted secondary batteries, which require high reliability and heat resistance. They are energy storage devices with extremely high heat resistance and safety. Furthermore, the oxide solid electrolyte used in these all-solid-state lithium-ion secondary batteries is chemically stable in air, making them highly durable among all-solid-state lithium-ion secondary batteries.

[0003] In manufacturing an all-solid-state lithium-ion secondary battery, typically, at least a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are joined by sintering. However, when an oxide solid electrolyte is used, a side reaction occurs between the oxide solid electrolyte and the positive electrode active material during sintering, resulting in the generation of impurities that inhibit the battery reaction.

[0004] In Patent Document 1, in order to suppress this side reaction, it is described that a Nasicon-type phosphate compound is used as the solid electrolyte material, and a spinel-type oxide containing at least one of Ni and Mn is used as the positive electrode active material. Patent Document 1 describes that this combination prevents impurities from being generated during sintering, but in reality, when a Nasicon-type phosphate compound is used as the solid electrolyte material, the firing temperature described in Patent Document 1 is insufficient for sintering to the point where the solid electrolyte material and the positive electrode active material are bonded, and the generation of impurities cannot be suppressed during production at the sintering temperature that leads to bonding, resulting in a deterioration in battery performance.

[0005] Patent Document 1 also describes the use of a Nasicon-type phosphate compound as the solid electrolyte material and a specific oxide (Nb2O5, WO3, MoO3, Ta2O5, etc.) as the positive electrode active material in order to suppress this side reaction. However, when the oxides described therein are used, the energy density of the all-solid-state lithium-ion secondary battery is not sufficient, and they are not used in current all-solid-state lithium-ion secondary batteries, so they are not versatile.

[0006] From the above, in order to achieve high-performance battery characteristics, it is necessary not only to suppress the generation of impurities during sintering with the solid electrolyte layer, but also to disperse the solid electrolyte material and the positive electrode active material evenly and homogeneously in the positive electrode layer, in the case of layered rock salt oxides, which are positive electrode active materials that can be expected to achieve high performance as used in current all-solid-state lithium-ion secondary batteries. However, it is difficult to say that this is achieved in Patent Document 1.

[0007] On the other hand, in Non-Patent Document 1, a positive electrode active material that is a layered rock salt oxide and Li 2.2 C 0.8 B 0.2 It is described that when an O3 solid electrolyte is used, the generation of impurities in the positive electrode layer is suppressed and the all-solid-state lithium ion secondary battery operates normally. 3.5 Ge 0.5 V 0.5It is described that when the O4 solid electrolyte is mixed by hand, the generation of impurities in the positive electrode layer is suppressed, and the all-solid-state lithium-ion secondary battery operates normally. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2012 / 043566 [Non-patent literature]

[0009] [Non-Patent Document 1] Solid State Ionics, 288, 248-252 (2016). [Non-patent document 2] ACS Appl. Energy Mater., 4, 30-34 (2021). Summary of the Invention [Problem to be solved by the invention]

[0010] However, in both of the methods of Non-Patent Documents 1 and 2, the solid electrolyte material and the positive electrode active material are not uniformly and homogeneously dispersed in the positive electrode layer, and there is room for improvement in terms of capacity, cycle characteristics, and rate characteristics.

[0011] From the above viewpoints, the present invention aims to provide a solid electrode layer in which the solid electrolyte material and the positive electrode active material are uniformly and homogeneously dispersed in the positive electrode layer, for a layered rock salt oxide, which is a positive electrode active material that not only suppresses the generation of impurities during sintering with a solid electrolyte layer but is also expected to achieve high performance similar to that used in current all-solid-state lithium ion secondary batteries. [Means for solving the problem]

[0012] The inventors of the present invention have conducted extensive research to achieve the above-mentioned object. As a result, in the solid electrode layer containing a silicon-type oxide and a layered rock salt-type oxide, the content of materials other than the silicon-type oxide and the layered rock salt-type oxide calculated from the X-ray diffraction pattern is reduced, and the average diameter of the figure obtained by performing Voronoi division on the layered rock salt-type oxide and the standard deviation of the average diameter are reduced, so that the solid electrolyte material and the positive electrode active material can be evenly and homogeneously dispersed in the positive electrode layer, and it has been found that the above problems can be solved. The present invention has been completed as a result of further research based on such findings. That is, the present invention includes the following configurations. <> Item 1. A solid electrode layer containing a silicon-type oxide and a layered rock salt-type oxide, <> where the content of impurities calculated from the X-ray diffraction pattern of the solid electrode layer is 1.0 mol% or less based on 100 mol% of the total amount of the solid electrode layer, <> the average diameter of the figure obtained by performing Voronoi division on the layered rock salt-type oxide is 0.50 to 2.00 μm, and <> the standard deviation of the average diameter of the figure obtained by performing Voronoi division on the layered rock salt-type oxide is 1.00 μm or less. <> Item 2. The silicon-type oxide is represented by the general formula (1): <> Li<> x1 M<> 1 O<> y1 (1)<> [where x1 represents 3.0 < x1 < 4.0. y1 represents 3.8 < y1 < 4.2. M <> 1 represents at least one selected from the group consisting of Ge, Si, V, Ti, P, and S.]<> The solid electrode layer according to Item 1, which is an oxide represented by the formula. <> Item 3. The solid electrode layer according to Item 2, where the M <> 1 includes Ge and / or Si and at least one selected from the group consisting of V, Ti, P, and S. <> Item 4. The silicon-type oxide is Li <> 3.5 Ge <> 0.5 V<> 0.5 O4、Li <> 3.7 Ge <> 0.7 V <> 0.3 O4、Li3.3 Ge 0.3 V 0.7 O4, Li 3.75 Ge 0.75 P 0.25 O4, Li 3.5 Ge 0.75 S 0.25 O4, or Li 3.5 Si 0.25 Ti 0.25 V 0.5 O4 as described in any one of items 1 to 3 of the solid electrode layer. Item 5. The silicon-type oxide is Li 3.5 Ge 0.5 V 0.5 O4 as described in any one of items 1 to 4 of the solid electrode layer. Item 6. The layered rock salt-type oxide has the general formula (2): LiM 2 O y2 (2) [In the formula, y2 represents 1.5 < y2 < 2.5. M 2 represents at least one selected from the group consisting of Co, Mn, Ni, Al, and Li.] The solid electrode layer as described in any one of items 1 to 5, which is an oxide represented by the formula. Item 7. The layered rock salt-type oxide is LiCoO2, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.5 Mn 0.5 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, or Li 1.20 Ni 0.16 Mn 0.55 Co 0.09 O2 as described in any one of items 1 to 6 of the solid electrode layer. Item 8. The layered rock salt-type oxide is LiCoO2, and the solid electrode layer as described in any one of items 1 to 7. Item 9. The solid electrode layer for an all-solid-state lithium-ion secondary battery as described in any one of items 1 to 8. Item 10. The solid electrode layer according to any one of Items 1 to 9, which is a solid positive electrode layer. Item 11. An all-solid-state lithium ion secondary battery comprising the solid electrode layer according to any one of items 1 to 10. Item 12. A method for producing a solid electrode layer according to any one of items 1 to 10, (1) a step of subjecting a lithiated oxide and a layered rock salt oxide to a low crystallization treatment; (2) A step of heat treating the low-crystallization product obtained in the step (1) at 600 to 1000°C to obtain a solidified molded body. A manufacturing method comprising: Item 13. The manufacturing method according to Item 12, wherein the low crystallization treatment is a mechanical milling treatment and / or a melt quenching treatment. Item 14. A precursor of a solid electrode layer containing a lithiated oxide and a layered rock salt oxide, the content of impurities calculated from the X-ray diffraction pattern of the precursor is 1 mol % or less, with the total amount of the solid electrode layer being 100 mol %, A solid electrode layer precursor that, in an X-ray diffraction pattern using synchrotron X-rays with a wavelength of 0.05 nm in the range of 2θ=4 to 26°, has only peaks of rock-salt oxides assigned to the space group Fm-3m and a halo peak at 2θ=5 to 8°, but does not have a peak with a maximum value at 2θ=6 to 7°, which is characteristic of layered rock-salt oxides. [Effects of the Invention]

[0013] According to the present invention, it is possible to not only suppress the generation of impurities during sintering with a solid electrolyte layer, but also to provide a solid electrode layer in which a solid electrolyte material and a positive electrode active material are uniformly and homogeneously dispersed in the positive electrode layer, for a layered rock salt type oxide, which is a positive electrode active material that can be expected to achieve high performance such as that used in current all-solid-state lithium ion secondary batteries. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a powder X-ray diffraction pattern of the low crystallinity product obtained in Reference Example 1. [Figure 2]1 shows powder X-ray diffraction patterns of the positive electrode powders obtained in Example 1 and Comparative Examples 1 and 2, and the low-crystallization product obtained in Reference Example 1. [Figure 3] This shows experimental and calculated values ​​obtained by Rietveld analysis of the X-ray diffraction pattern of the solid positive electrode layer obtained in Example 1. The inset shows an enlarged view of the range of 2θ = 30 to 40°. The fitting difference between the measured values ​​and the calculated pattern is shown below the X-ray diffraction pattern, and the calculated position of each crystalline phase is also shown below that. [Figure 4] This shows experimental and calculated values ​​obtained by Rietveld analysis of the X-ray diffraction pattern of the solid positive electrode layer obtained in Comparative Example 2. The inset shows an enlarged view of the range of 2θ = 30 to 40°. The fitting difference between the measured values ​​and the calculated pattern is shown below the X-ray diffraction pattern, and the calculated position of each crystalline phase is also shown below that. [Figure 5] 1 is a cross-sectional scanning electron microscope image of the solid positive electrode layer obtained in Example 1. [Figure 6] 1 is a cross-sectional scanning electron microscope image of the solid positive electrode layer obtained in Comparative Example 2. [Figure 7] 2 is a diagram showing a cross-sectional scanning electron microscope image of the solid positive electrode layer obtained in Example 1, which has been subjected to image binarization processing. FIG. [Figure 8] 10 is a diagram showing a cross-sectional scanning electron microscope image of the solid positive electrode layer obtained in Comparative Example 2, which has been subjected to image binarization processing. [Figure 9] 2 is a diagram showing Voronoi division of a cross-sectional scanning electron microscope image of the solid positive electrode layer obtained in Example 1 after image binarization processing. FIG. [Figure 10] 10 is a diagram showing Voronoi division after binarization of a cross-sectional scanning electron microscope image of a solid positive electrode layer obtained in Comparative Example 2. FIG. [Figure 11] 1 is a graph showing the average diameter and standard deviation of the average diameter of Voronoi tessellation patterns for the solid positive electrode layer obtained in Example 1. [Figure 12] 10 is a graph showing the average diameter and standard deviation of the average diameter of the Voronoi tessellation diagram for the solid positive electrode layer obtained in Comparative Example 2. [Figure 13]FIG. 10 is a diagram showing the layer structure of the all-solid-state lithium secondary battery constructed in Test Example 3. [Figure 14] 1 shows charge / discharge curves of the all-solid-state lithium secondary battery of Example 1. [Figure 15] 1 shows charge / discharge curves of the all-solid-state lithium secondary battery of Comparative Example 1. [Figure 16] 1 shows charge / discharge curves of the all-solid-state lithium secondary battery of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0015] In this specification, the term "containing" is a concept that encompasses all of "comprise," "consist essentially of," and "consist only of."

[0016] In addition, in this specification, when a numerical range is expressed as "A to B," it means "not less than A and not more than B."

[0017] Furthermore, in this specification, Voronoi division refers to division in which the boundaries of the two closest particles in a binarized image are connected at equal distances, and the average diameter of the figures obtained by performing Voronoi division refers to the diameter of a circle having the area of ​​each figure.

[0018] 1.Solid electrode layer The solid electrode layer of the present invention is a solid electrode layer containing a lithiated oxide and a layered rock salt oxide, the content of impurities calculated from an X-ray diffraction pattern of the solid electrode layer is 1 mol % or less, with the total amount of the solid electrode layer being 100 mol %, The average diameter of the figure obtained by performing Voronoi division on the layered rock salt type oxide is 0.5 to 2.0 μm, and The standard deviation of the average diameter of the figure obtained by subjecting the layered rock salt type oxide to Voronoi tessellation is 1.0 μm or less.

[0019] (1-1) Lithium-ion oxide The LISICON-type oxide contained in the solid electrode layer of the present invention means an oxide having a crystal structure similar to γ-Li3PO4 (space group: Pnma) or Li4SiO4 (space group: P21 / m), contains many lithium ions in the structure, and has a wide lithium ion conduction path, so it can be used as a solid electrolyte material. That is, the silicon-type oxide can have a γ-Li3PO4-type crystal structure or a Li4SiO4-type crystal structure. Such LISICON-type oxides are not particularly limited. For example, General formula (1): Li x1 M 1 O y1 (1) [where x1 represents 3.0 < x1 < 4.0. y1 represents 3.8 < y1 < 4.2. M 1 represents at least one selected from the group consisting of Ge, Si, V, Ti, P, and S.] The oxide represented by is preferred.

[0020] In general formula (1), M 1 represents at least one selected from the group consisting of Ge, Si, V, Ti, P, and S. Among them, from the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer, and achieving uniform and homogeneous dispersion of the solid electrolyte material and the positive electrode active material in the positive electrode layer, etc., it is preferable to include Ge and / or Si and at least one selected from the group consisting of V, Ti, P, and S, more preferably to include Ge and at least one selected from the group consisting of V, Ti, P, and S, and even more preferably to include Ge and V.

[0021] In general formula (1), x1 represents 3.0 < x < 4.0. From the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer, and achieving uniform and homogeneous dispersion of the solid electrolyte material and the positive electrode active material in the positive electrode layer, etc., 3.2 < x1 < 3.8 is preferable, and 3.3 < x1 < 3.7 is more preferable.

[0022] In the general formula (1), y1 satisfies 3.8 < y1 < 4.2. From the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer and achieving uniform and homogeneous dispersion of the solid electrolyte material and the cathode active material in the cathode layer, 3.9 < y1 < 4.1 is preferable.

[0023] Examples of such silicon-type oxides that satisfy such conditions include, for example, Li 3.5 Ge 0.5 V 0.5 O4, Li 3.7 Ge 0.7 V 0.3 O4, Li 3.3 Ge 0.3 V 0.7 O4, Li 3.75 Ge 0.75 P 0.25 O4, Li 3.5 Ge 0.75 S 0.25 O4, Li 3.5 Si 0.25 Ti 0.25 V 0.5 O4, etc. Among them, from the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer and achieving uniform and homogeneous dispersion of the solid electrolyte material and the cathode active material in the cathode layer, Li 3.5 Ge 0.5 V 0.5 O4, Li 3.7 Ge 0.7 V 0.3 O4, Li 3.3 Ge 0.3 V 0.7 O4, Li 3.75 Ge 0.75 P 0.25 O4, Li 3.5 Ge 0.75 S 0.25 O4, etc. are preferable, Li 3.5 Ge 0.5 V 0.5 O4, Li 3.7 Ge 0.7 V 0.3 O4, Li 3.3 Ge 0.3 V 0.7 O4, etc. are more preferable, Li 3.5 Ge 0.5 V 0.5 O4, etc. are even more preferable.

[0024] These silicon-based oxides can be used alone or in combination of two or more. Also, known or commercially available products can be used as these silicon-based oxides.

[0025] (1-2) Layered rock salt-type oxide As the layered rock salt-type oxide, it can be used as an electrode active material (especially a cathode active material). Such a layered rock salt-type oxide is not particularly limited, and the general formula (2): LiM 2 O y2 (2) [In the formula, y2 represents 1.5 < y2 < 2.5. M 2 represents at least one selected from the group consisting of Co, Mn, Ni, Al, and Li.] The oxide represented by is preferred.

[0026] In general formula (2), M 2 represents at least one selected from the group consisting of Co, Mn, Ni, Al, and Li. Among them, from the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer, and the uniform and homogeneous dispersion of the solid electrolyte material and the cathode active material in the cathode layer, etc., it is preferably included at least one selected from the group consisting of Co, Mn, Ni, and Li, more preferably included at least one selected from the group consisting of Co, Mn, and Ni, and even more preferably includes Co.

[0027] In general formula (2), y2 represents 1.5 < x1 < 2.5. From the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer, and the uniform and homogeneous dispersion of the solid electrolyte material and the cathode active material in the cathode layer, etc., 1.7 < y2 < 2.3 is preferred, 1.8 < y2 < 2.2 is more preferred, and 1.9 < y2 < 2.1 is even more preferred.

[0028] Examples of the layered rock salt-type oxide that satisfies such conditions include, for example, LiCoO2, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.5 Mn0.5 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, Li 1.20 Ni 0.16 Mn 0.55 Co 0.09 Among them, LiCoO2, LiNiO2, etc. are used from the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer, and uniformly and homogeneously dispersing the solid electrolyte material and the positive electrode active material in the positive electrode layer. 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.5 Mn 0.5 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2, Li 1.20 Ni 0.16 Mn 0.55 Co 0.09 O2, etc. are preferred, LiCoO2, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.5 Mn 0.5 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2 and the like are more preferable, and LiCoO2 and the like are even more preferable.

[0029] These layered rock salt type oxides can be used alone or in combination of two or more types. Furthermore, these layered rock salt type oxides can be publicly known or commercially available products.

[0030] (1-3) Solid electrode layer In the solid electrode layer of the present invention, the content of the above-mentioned lithizone-type oxide is preferably 10.0 mol% or more, based on the total amount of the solid electrode layer being 100% by mass, from the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer, uniformly and homogeneously dispersing the solid electrolyte material and the positive electrode active material in the positive electrode layer, etc., and more preferably 20.0 mol% or more from the viewpoint of ensuring ion conduction paths in the solid electrolyte. The upper limit of the content of the above-mentioned lithizone-type oxide is not particularly limited, and can usually be 66.7 mol% or less.

[0031] In the solid electrode layer of the present invention, the content of the layered rock salt type oxide is preferably 33.3 mol% or more, based on the total amount of the solid electrode layer being 100 mass%, from the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer, uniformly and homogeneously dispersing the solid electrolyte material and the positive electrode active material in the positive electrode layer, etc., and more preferably 40.0 mol% or more from the viewpoint of the energy density of the battery. The upper limit of the content of the layered rock salt type oxide is not particularly limited, and can usually be 90.0 mol% or less.

[0032] In the solid electrode layer of the present invention, the impurity content calculated from the X-ray diffraction pattern of the solid electrode layer is 1.0 mol % or less, preferably 0.1 mol % or less, with the total amount of the solid electrode layer being 100 mol %. If the impurity content exceeds 1.0 mol %, it is not possible to suppress impurity generation during sintering with the solid electrolyte layer, resulting in poor battery performance. There is no particular lower limit for the impurity content, and 0 mol % is most preferable from the viewpoint of battery performance. Furthermore, when the solid electrode layer of the present invention does not intentionally contain any electrode constituent materials other than the above-mentioned lithizone-type oxide and layered rock salt-type oxide, the term "impurities" refers to all materials other than the above-mentioned lithizone-type oxide and layered rock salt-type oxide. Furthermore, when the solid electrode layer of the present invention intentionally contains electrode constituent materials such as a conductive additive and a binder in addition to the above-mentioned lithizone-type oxide and layered rock salt-type oxide, the term "impurities" refers to all materials other than the above-mentioned electrode constituent materials (in other words, the lithizone-type oxide, layered rock salt-type oxide, conductive additive, and binder).

[0033] In addition to the lithizone-type oxide and the layered rock salt-type oxide, the solid electrode layer of the present invention may intentionally contain electrode constituent materials that have conventionally been contained in all-solid-state lithium ion secondary batteries, such as a conductive additive, a binder, a plasticizer, etc. In the solid negative electrode layer, the negative electrode active material may be covered with a conductive additive.

[0034] Examples of the conductive additive that can be used include one or more of graphite; carbon black (acetylene black, ketjen black, etc.); amorphous carbon materials such as carbon materials with amorphous carbon generated on the surface; fibrous carbon (vapor-grown carbon fiber, carbon fiber obtained by spinning pitch and then carbonizing it, etc.); carbon nanotubes (various multi-layer or single-layer carbon nanotubes); conductive metal fine particles (palladium, etc.); and conductive oxide fine particles (ruthenium oxide, etc.).

[0035] When a conductive additive is intentionally contained in the solid electrode layer of the present invention, the content of the conductive additive is preferably 0.01 to 20.0 mass %, and more preferably 0.1 to 5.0 mass %, based on 100 mass % of the total amount of the solid electrode layer of the present invention, from the viewpoint of battery performance and the like.

[0036] As the binder, for example, an acrylic resin or the like can be used, and as the plasticizer, for example, a phthalate ester or the like can be used.

[0037] When a binder is intentionally contained in the solid electrode layer of the present invention, the content of the binder is preferably 0.01 to 10.0 mass %, and more preferably 0.1 to 5.0 mass %, based on 100 mass % of the total amount of the solid electrode layer of the present invention, from the viewpoint of battery performance and the like.

[0038] In the solid electrode layer of the present invention, the average diameter of the figure obtained by Voronoi tessellation of the layered rock salt oxide is 0.50 to 2.00 μm, preferably 0.55 to 1.50 μm. It is difficult to produce a solid electrode layer in which the average diameter of the figure obtained by Voronoi tessellation is 0.50 μm or less. On the other hand, if the average diameter of the figure obtained by Voronoi tessellation exceeds 2.00 μm, the solid electrode layer will be destroyed due to the expansion and contraction of the positive electrode active material in the positive electrode layer during battery operation, resulting in poor capacity, cycle characteristics, and rate characteristics, especially cycle characteristics.

[0039] In the solid electrode layer of the present invention, the standard deviation of the average diameter of the figure obtained by Voronoi tessellation of the layered rock salt oxide is 1.00 μm or less, preferably 0.01 to 0.80 μm. By setting the standard deviation of the average diameter of the figure obtained by Voronoi tessellation to 1.00 μm or less, it is possible to evenly and homogeneously disperse the solid electrolyte material and the positive electrode active material in the positive electrode layer. On the other hand, if the standard deviation of the average diameter of the figure obtained by Voronoi tessellation exceeds 1.00 μm, it is not possible to evenly and homogeneously disperse the solid electrolyte material and the positive electrode active material in the positive electrode layer, resulting in poor capacity, cycle characteristics, and rate characteristics.

[0040] The thickness of the solid electrode layer of the present invention is not particularly limited, and is preferably 5 μm or more from the viewpoint of ease of molding into an all-solid-state lithium ion secondary battery, and is preferably 5 to 200 μm from the viewpoint of ease of ensuring energy density by making the battery more compact, and is more preferably 5 to 50 μm from the viewpoint of ease of exhibiting battery performance, particularly appropriate rate characteristics.

[0041] The solid electrode layer of the present invention that satisfies the above conditions not only suppresses the generation of impurities during sintering with the solid electrolyte layer, but also is a solid electrode layer (particularly a solid cathode layer) in which the solid electrolyte material and the cathode active material are dispersed evenly and homogeneously in the cathode layer for layered rock salt oxides, which are cathode active materials that are expected to achieve high performance such as those used in current all-solid-state lithium-ion secondary batteries. Therefore, when an all-solid-state lithium-ion secondary battery is formed using this solid electrode layer, it exhibits excellent battery properties such as capacity, cycle characteristics, and rate characteristics, and is useful as a solid electrode layer for an all-solid-state lithium-ion secondary battery (particularly a solid cathode layer for an all-solid-state lithium-ion secondary battery).

[0042] 2. All-solid-state lithium-ion secondary battery The all-solid-state lithium ion secondary battery of the present invention is not particularly limited as long as it includes the above-described solid electrode layer of the present invention, and other configurations can be the same as those of a conventional all-solid-state lithium ion secondary battery.

[0043] Such an all-solid-state lithium ion secondary battery of the present invention can usually be an all-solid-state lithium secondary battery including (laminates) a positive electrode current collector foil, a solid positive electrode layer, a solid electrolyte layer, a solid negative electrode layer, and a negative electrode current collector foil in this order.

[0044] Furthermore, as described above, the all-solid-state lithium-ion secondary battery of the present invention not only suppresses the generation of impurities during sintering with the solid electrolyte layer, but also suppresses the generation of impurities even when sintering each layer, since the solid electrolyte material and the positive electrode active material are uniformly and homogeneously dispersed in the positive electrode layer, targeting layered rock salt oxides, which are positive electrode active materials that are expected to achieve high performance as used in current all-solid-state lithium-ion secondary batteries. For this reason, it is preferable that the layers of the all-solid-state lithium-ion secondary battery of the present invention are joined together.

[0045] In the present invention, the term "all-solid-state lithium ion secondary battery" is a concept that also encompasses all-solid-state lithium secondary batteries that use lithium metal as the negative electrode layer.

[0046] Although the solid electrode layer of the present invention is not excluded from being used as a solid negative electrode layer, it is a solid electrode layer in which a solid electrolyte material and a positive electrode active material are evenly and homogeneously dispersed in the positive electrode layer, targeting a layered rock salt-type oxide which is a positive electrode active material capable of achieving high performance as used in current all-solid-state lithium-ion secondary batteries. Therefore, it is preferably used as a solid positive electrode layer.

[0047] There is no particular limitation on the positive electrode current collector foil, and various metals, alloys, carbon materials, etc. can be used. For example, gold, aluminum, copper, stainless steel, nickel, titanium, or their alloys, carbon materials, etc. can be mentioned.

[0048] The thickness of the positive electrode current collector foil is not particularly limited, and from the viewpoint of ensuring the energy density by making it more compact within the range that can be formed into an all-solid-state battery, 5 to 50 μm is preferable.

[0049] Examples of the solid electrolyte constituting the solid electrolyte layer include, in addition to the above-mentioned silicon-type oxide, oxides having a perovskite-type structure containing lithium ((Li,La)TiO3, etc.), NASICON-type oxides (Li 1+n+m M n E 2-n Si m P 3-m O 12 ; 0 ≦ n ≦ 0.4, 0 < m ≦ 0.6, M represents Al and / or Ga. E represents at least one selected from the group consisting of Ti, Ge, and Zr.), garnet-type oxides (Li7La3Zr2O 12 etc.), etc. can also be mentioned. From the viewpoints of suppressing the generation of impurities during sintering with the solid electrolyte layer, and the uniform and homogeneous dispersion of the solid electrolyte material and the positive electrode active material in the positive electrode layer, etc., the above-mentioned silicon-type oxide is preferable. In particular, using the same material as the solid electrolyte contained in the solid positive electrode layer is preferable from the viewpoints of the ease of bonding between the solid electrolyte layer and the solid positive electrode layer, ionic conductivity, etc.

[0050] As the negative electrode active material constituting the solid negative electrode layer, lithium metal, a lithium storage carbon material, a lithium alloy (such as Li-Al alloy, Li-In alloy, Li-Sn alloy), lithium titanate or lithium storage titanate (Li4Ti5O 12 , anatase TiO2, etc.), silicon, a silicon-containing compound (such as SiO, SiC), a NASICON-type oxide (Li 1+n+m M n E 2-n Si m P 3-m O 12 ; 0 ≦ n ≦ 0.4, 0 < m ≦ 0.6, M represents Al and / or Ga. E represents at least one selected from the group consisting of Ti, Ge, and Zr.). etc. can be mentioned. From the viewpoint of the energy density of the entire all-solid-state lithium-ion secondary battery, lithium metal or a lithium storage carbon material is preferable, and from the viewpoint of the safety of the entire all-solid-state lithium-ion secondary battery, lithium titanate or lithium storage titanate is preferable.

[0051] When the electron conductivity of the solid negative electrode layer is low, a conductive aid or the like may be included in the solid positive electrode layer and the solid negative electrode layer. Also, in the solid negative electrode layer, the negative electrode active material may be covered with a conductive aid.

[0052] As the conductive aid, for example, graphite; carbon black (such as acetylene black, ketjen black); an amorphous carbon material such as a carbon material having amorphous carbon formed on its surface; fibrous carbon (such as vapor-grown carbon fiber, carbon fiber obtained by carbonizing pitch after spinning); carbon nanotube (various multi-layer or single-layer carbon nanotubes); conductive metal fine particles (such as palladium); conductive oxide fine particles (such as ruthenium oxide), etc. can be used alone or in combination of two or more. When the conductive aid is included in the negative electrode layer, the content of the conductive aid is preferably 0.01 to 20.0 parts by mass, and more preferably 0.1 to 5.0 parts by mass, based on 100 parts by mass of the total weight of the negative electrode active material and the solid electrolyte, from the viewpoint of the energy density of the entire all-solid-state lithium-ion secondary battery.

[0053] In addition to the above components, the solid negative electrode layer may also contain various additives such as a binder (acrylic resin, etc.), a plasticizer (phthalate ester, etc.), etc. In this case, the content of the additive is preferably within a range that does not impair the effects of the present invention, and specifically, is preferably 0.01 to 10.0 parts by mass, more preferably 0.1 to 5.0 parts by mass, per 100 parts by mass of the total weight of the negative electrode active material and the solid electrolyte.

[0054] The thickness of the solid negative electrode layer is not particularly limited, and is preferably 10 to 1000 μm, more preferably 10 to 50 μm, from the viewpoint of ensuring energy density by making it more compact within the range that can be molded into an all-solid-state lithium ion secondary battery.

[0055] The negative electrode current collector foil is not particularly limited, and various metals, alloys, carbon materials, etc. are usable. From the viewpoint of being able to sufficiently bond to the negative electrode layer under conditions of low temperature and high pressure, such a negative electrode current collector foil is preferably made of a material having a melting point of 660 to 1727°C, particularly 660 to 1445°C. Examples of materials having such a melting point include gold, aluminum, copper, stainless steel, nickel, titanium, or alloys thereof, and carbon materials.

[0056] As described above, in the all-solid-state lithium-ion secondary battery of the present invention, it is preferable that the layers are bonded together. In particular, the solid electrode layer of the present invention can suppress the generation of impurities when bonding the solid electrode layer and the solid electrolyte layer, so it is preferable that at least the solid electrode layer (particularly the solid cathode layer) and the solid electrolyte layer are bonded together.

[0057] The all-solid-state lithium-ion secondary battery of the present invention preferably comprises (is laminated with) a positive electrode current collector foil, a solid positive electrode layer, a solid electrolyte layer, a solid negative electrode layer, and a negative electrode current collector foil in this order, but a laminate consisting of a solid positive electrode layer, a solid electrolyte layer, and a negative solid electrode layer may be connected in series or parallel between the positive electrode current collector foil and the solid positive electrode layer, or between the solid negative electrode layer and the negative electrode current collector foil. In this case, an insulating layer, a solid electrolyte layer, etc. may be disposed between each laminate (between the solid positive electrode layer and the solid negative electrode layer) as needed. In this case, too, it is preferable that all components are bonded together.

[0058] 3. Manufacturing method of the solid electrode layer The method for producing the solid electrode layer of the present invention is not particularly limited. For example, (1) a step of subjecting a lithiated oxide and a layered rock salt oxide to a low crystallization treatment; (2) A step of heat treating the low-crystallization product obtained in the step (1) at 600 to 1000°C to obtain a solidified molded body. The manufacturing method can be obtained by the following steps.

[0059] (3-1) Process (1) The lithizone-type oxide and layered rock salt-type oxide can be those described above. By using the lithizone-type oxide and layered rock salt-type oxide described above, the proportion of impurities in the resulting solid electrode layer can be reduced.

[0060] The low-crystallization treatment is not particularly limited as long as it can reduce the crystallinity when mixing the lithizone-type oxide and the layered rock salt-type oxide, and for example, mechanical milling treatment and / or melt-quenching treatment can be adopted.

[0061] Mechanical milling, also known as mechanochemical processing, is a method of grinding and mixing raw materials while applying mechanical energy. According to this method, the raw materials are subjected to mechanical impact and friction to grind and mix them, causing the lithicon-type oxide and layered rock salt-type oxide to come into vigorous contact with each other and be finely divided, resulting in a reaction of the raw materials. In other words, mixing, grinding, and reaction occur simultaneously. This makes it possible to more reliably react the raw materials and reduce their crystallinity without heating them to high temperatures. Mechanical milling can sometimes produce a metastable crystal structure that cannot be obtained by ordinary heat treatment.

[0062] Specifically, the mechanical milling treatment can be carried out by mixing and pulverizing using a mechanical pulverizing device such as a ball mill, a bead mill, a rod mill, a vibration mill, a disk mill, a hammer mill, or a jet mill.

[0063] The mixing ratio of these raw materials can be adjusted so as to be the same as the content in the target solid electrode layer.

[0064] For example, assuming the total amount of raw materials to be 100% by mass, 10.0 to 66.7 mol %, preferably 20.0 to 66.7 mol %, of the lysicone-type oxide can be used, and 33.3 to 90.0 mol %, preferably 40.0 to 90.0 mol % of the layered rock salt-type oxide can be used.

[0065] The time for the mechanical milling treatment is not particularly limited, and the mechanical milling treatment can be carried out for any time until the desired low-crystallization product is precipitated.

[0066] For example, mechanical milling can be carried out for a processing time of about 0.1 to 200 hours with an energy amount of about 0.1 to 100 kWh / kg of raw material. This mechanical milling can also be carried out in multiple steps with breaks in between as needed.

[0067] In step (1), the low-crystallization product can also be obtained by melting the lithizone-type oxide and layered rock salt-type oxide by heating and then rapidly cooling them.

[0068] The heating temperature in the melt-quenching treatment is not particularly limited, but is preferably 1000°C or higher, more preferably 1000 to 1200°C, in view of the melting points of the lithiated oxide and the layered rock salt oxide.

[0069] The heating time in the melt-quenching treatment is not particularly limited, but is preferably 0 to 48 hours, more preferably 0 to 12 hours, from the viewpoint of easily obtaining a low-crystallization product in step (1). Note that the heating time can be set to 0 hours, i.e., cooling can be performed immediately after the maximum temperature is reached.

[0070] The heating atmosphere in the melt-quenching treatment is not particularly limited, but it is preferable to perform the treatment in an inert gas atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, or in a vacuum, in order to easily prevent side reactions.

[0071] The molten raw material can then be rapidly cooled.

[0072] In the quenching method, a refrigerant can usually be brought into contact with the raw materials in a molten state. "Contact" includes cases where the refrigerant comes into direct contact with the raw materials in a molten state, and cases where the refrigerant comes into indirect contact with the raw materials in a molten state via a reaction vessel or the like. The temperature of the refrigerant is not particularly limited, but is, for example, -200 to 30°C, or may be -10 to 30°C, or may be -10 to 20°C. The refrigerant may be a liquid, a solid, or a gas. Specific examples of the refrigerant include water, ice, metal, air, and liquid nitrogen. Examples of the quenching method include a water-cooling method, an air-cooling method, and a single-roll method.

[0073] From the viewpoint of low crystallization efficiency, the cooling rate in the rapid cooling is, for example, preferably 1 K / sec or more, more preferably 100 K / sec or more, and even more preferably 1000 K / sec or more. Furthermore, the rapid cooling in the present invention is preferably a process of cooling the raw material until its temperature reaches 20°C or less, and more preferably 0°C or less.

[0074] The low-crystallization material obtained in step (1) is a solid electrode layer precursor containing a lithiated oxide and a rock-salt oxide, and in an X-ray diffraction pattern in the range of 2θ=4 to 26° using synchrotron X-rays with a wavelength of 0.5 Å, the solid electrode layer precursor has only a peak of a rock-salt oxide belonging to the space group Fm-3m and a halo peak near 2θ=5 to 8°, but does not have a peak with a maximum value at 2θ=6 to 7°, which is characteristic of layered rock-salt oxides (such as space groups R-3m).

[0075] The low crystallization treatment turns the layered rock salt type oxide into a rock salt type oxide, where the rock salt type oxide means an oxide having a rock salt type structure that does not have a layered structure.

[0076] (3-2) Process (2) In step (2), the low-crystallization material that has been once low-crystallized in step (1) can be re-crystallized by heat-treating it to obtain a solidified molded body, thereby obtaining the solid electrode layer of the present invention.

[0077] The heating temperature during the heat treatment is not particularly limited, but from the viewpoint of facilitating the production of the solid electrode layer of the present invention, it is preferably 600 to 1000° C., more preferably 700 to 980° C. The time for maintaining the heating temperature within the above-mentioned range is preferably 1 to 12 hours, from the viewpoint of facilitating the suppression of defects due to volatilization of the low-crystallization material once low-crystallized in step (1), facilitating sufficient crystallization, and facilitating the production of the solid electrode layer of the present invention.

[0078] As a method for such heat treatment, for example, electric furnace sintering can be adopted. However, in the case of the electric current sintering (SPS) method, the heating temperature and heating time tend to be insufficient, resulting in insufficient crystallization, and therefore the solid electrode layer of the present invention cannot be obtained.

[0079] In the electric furnace sintering, the low-crystallization material that has been once low-crystallized in step (1) can be placed in an electric furnace and then heated.

[0080] The above-mentioned step (2) can be carried out immediately after the step (1), or, if necessary, the step (2) can be carried out after a powder compaction treatment.

[0081] 4. Manufacturing method of all-solid-state lithium-ion secondary battery The method for producing the all-solid-state lithium secondary battery of the present invention is not particularly limited. For example, (3) By using a method including a method of heating a sample including the positive electrode current collecting foil, the solid positive electrode layer (the solid electrode layer of the present invention), the solid electrolyte layer, the solid negative electrode layer, and the negative electrode current collecting foil in this order, by using an electric furnace sintering method, the members to be joined can be firmly joined together, and the all-solid-state lithium ion secondary battery of the present invention can be produced.

[0082] Examples of the positive electrode current collector foil, solid positive electrode layer (solid electrode layer of the present invention), solid electrolyte layer, solid negative electrode layer, and negative electrode current collector foil include those described above. Regarding the solid positive electrode layer (solid electrode layer of the present invention), the solidified molded body obtained in the above-mentioned step (2) can be used as is as the solid positive electrode layer (solid electrode layer of the present invention). Alternatively, the solidified molded body obtained in the above-mentioned step (2) can be crushed into powder and then shaped into the shape of the solid positive electrode layer (solid electrode layer of the present invention) by a heating step such as electric furnace sintering or electric current sintering, thereby producing the all-solid-state lithium secondary battery of the present invention. The positive electrode current collector foil, solid positive electrode layer (solid electrode layer of the present invention), solid electrolyte layer, solid negative electrode layer, and negative electrode current collector foil before the heating step can also be prepared by a green sheet production method in which each is coated and dried as a slurry prepared with a solvent, binder, etc., to produce the all-solid-state lithium ion secondary battery of the present invention.

[0083] Specifically, electric current sintering involves filling each layer into a conductive mold (conductive container) and passing a current, preferably a direct current pulse, through the conductive mold (conductive container) (a method known as spark plasma sintering, pulse current sintering, plasma activated sintering, etc.), which heats the conductive mold (conductive container) due to Joule heat, thereby heating and bonding each layer inside the conductive mold (conductive container). The atmosphere during this electric current sintering process is preferably a non-oxidizing atmosphere. While the electric current sintering process may be performed under normal pressure, it is preferable to perform the electric current sintering process under pressure.

[0084] A specific method is to fill each layer into a conductive mold (conductive container), and preferably in a non-oxidizing atmosphere, to pass a pulsed (ON-OFF switching) direct current while applying pressure.

[0085] The material of the conductive mold (conductive container) is not particularly limited as long as it is conductive. For example, materials formed from carbon, iron, iron oxide, aluminum, tungsten carbide, etc., as well as materials formed from a mixture of carbon and / or iron oxide with silicon nitride, etc., can also be suitably used.

[0086] To further suppress side reactions, the electric sintering treatment is preferably carried out in a non-oxidizing atmosphere, for example, an inert gas atmosphere such as argon or nitrogen, or a reducing atmosphere such as hydrogen, etc. Alternatively, the treatment may be carried out under reduced pressure with a sufficiently low oxygen concentration, for example, a reduced pressure of 20 Pa or less (particularly 1 to 20 Pa) of oxygen partial pressure.

[0087] Specifically, when a container that can ensure a sufficiently sealed state is used as the conductive mold (conductive container), the container can be kept in a non-oxidizing atmosphere. Furthermore, the conductive mold (conductive container) does not need to be completely sealed. When an incompletely sealed container is used, the container can be placed in a reaction chamber, and the reaction chamber can be kept in a non-oxidizing atmosphere. This allows each layer to be sintered in a non-oxidizing atmosphere. In this case, the reaction chamber is preferably kept in an inert gas atmosphere or a reducing gas atmosphere of 0.01 MPa or more (particularly 0.05 to 0.2 MPa).

[0088] By applying a DC pulse current to a conductive mold (conductive container) filled with each layer, the conductive container is heated by Joule heat, and the layers are heated and bonded to form an all-solid-state lithium-ion secondary battery. This method allows the production of the intended all-solid-state lithium-ion secondary battery of the present invention in a short time of 30 minutes or less.

[0089] The pressure to be applied to each layer is preferably 5 to 60 MPa, more preferably 10 to 50 MPa, from the viewpoint of easily achieving sufficient bonding.

[0090] The device for electric current sintering is not particularly limited as long as it is capable of heating, cooling, pressurizing, etc. each layer and applying the current required for discharge. For example, a commercially available electric current sintering device (spark plasma sintering device) can be used. Such an electric current sintering device and its principle are disclosed, for example, in JP-A-10-251070. [Example]

[0091] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0092] In the following Examples and Comparative Examples, unless otherwise specified, operations were carried out in a glove box under an argon atmosphere.

[0093] Reference example 1 As a solid electrolyte material, a lithiated oxide (Li 3.5 Ge 0.5 V 0.5 The powder was mixed with commercially available layered rock salt oxide (LiCoO2) as a positive electrode active material in a molar ratio of 1:2.

[0094] The obtained mixture was subjected to low crystallization treatment by mechanical milling at room temperature for 45 hours at 350 rpm using a Fritsch planetary ball mill Pulverisette 7, in a 45 ml zirconia container containing 90 g of 4 mm zirconia balls.

[0095] Comparative example 1 As a solid electrolyte material, a lithiated oxide (Li 3.5 Ge 0.5 V 0.5 The powder was mixed with commercially available layered rock salt oxide (LiCoO2) as a positive electrode active material in a molar ratio of 1:2.

[0096] The resulting mixture was mixed by hand in a mortar at room temperature for 15 minutes.

[0097] Example 1 The low-crystallization product obtained in Reference Example 1 was subjected to a powder compaction treatment using a uniaxial press at room temperature under a pressure of 400 MPa for 1 minute.

[0098] Then, the mixture was fired in an electric furnace at 900° C. for 12 hours to obtain the positive electrode layer of Example 1.

[0099] After cooling to room temperature, the mixture was pulverized in a mortar to obtain the positive electrode powder of Example 1.

[0100] Comparative Example 1 The low-crystallization material obtained in Reference Example 1 was packed into a graphite mold with an inner diameter of 10 mm and placed in an electric sintering machine. The tungsten carbide mold and the current-carrying portion including the electrode portion were placed in a vacuum chamber. The chamber was evacuated to a vacuum (approximately 5 Pa or less) and then filled with high-purity argon gas up to atmospheric pressure. A pulse current of approximately 200 A was then applied to the graphite mold. The vicinity of the tungsten carbide mold was heated at a temperature increase rate of approximately 50°C / min, reaching 400°C 12 minutes after the start of pulse current application. Thereafter, the current application and pressure were immediately stopped, and the mixture was allowed to cool naturally, to obtain a positive electrode layer of Comparative Example 1.

[0101] After cooling to room temperature, the reaction product was removed from the tungsten carbide mold and pulverized in a mortar to obtain a positive electrode powder of Comparative Example 1.

[0102] Comparative Example 2 The low-crystallization product obtained in Comparative Reference Example 1 was subjected to a powder compaction treatment using a uniaxial press at room temperature under a pressure of 400 MPa for 1 minute.

[0103] Next, the mixture was fired in an electric furnace at 900° C. for 12 hours to obtain a positive electrode layer of Comparative Example 2.

[0104] After cooling to room temperature, the mixture was pulverized in a mortar to obtain a positive electrode powder of Comparative Example 2.

[0105] Test Example 1: X-ray diffraction measurement The low-crystallization product obtained in Reference Example 1 was subjected to powder X-ray diffraction measurement using synchrotron X-rays with a wavelength of 0.05 nm. The results are shown in Figures 1 and 2. For reference, Figure 1 shows the powder X-ray diffraction pattern of the raw material, lithiated oxide (Li 3.5 Ge 0.5 V 0.5 Peaks of layered rock salt oxide (LiCoO2) and LiCoO4 are also shown.

[0106] As a result, in Reference Example 1, the low crystallization treatment resulted in the formation of a lithiated oxide (Li 3.5 Ge 0.5 V 0.5The peaks of the layered rock-salt oxide (LiCoO4) and the layered rock-salt oxide (LiCoO2) disappeared, and the peak with a maximum at 2θ = 6 to 7°, which is a peak specific to the layered rock-salt oxide, was not observed, and only the peak of the rock-salt oxide belonging to the space group Fm-3m and the halo peak at 2θ = 5 to 8° were observed. From this, it can be understood that in Reference Example 1, low crystallization was achieved and a non-layered rock-salt oxide was produced.

[0107] Next, powder X-ray diffraction measurements using synchrotron X-rays with a wavelength of 0.05 nm were carried out on the pulverized positive electrode powders obtained in Example 1 and Comparative Examples 1 and 2. The results are shown in FIG.

[0108] As a result, in Comparative Example 1, although firing was performed by electric current sintering, the temperature was insufficient, so crystallization did not occur. As in Reference Example 1, no peak with a maximum at 2θ = 6 to 7°, which is a peak specific to layered rock salt-type oxides, was observed, and only the peak of a non-layered rock salt-type oxide and a halo peak at 2θ = 5 to 8° were confirmed.

[0109] In Comparative Example 2, the low crystallization was not achieved at the time of manual mixing as in Comparative Reference Example 1, and the lithiated oxide (Li 3.5 Ge 0.5 V 0.5 Peaks of both the layered rock salt type oxide (LiCoO4) and the layered rock salt type oxide (LiCoO2) were observed.

[0110] On the other hand, in Example 1, the crystallization was initially low due to the ball mill treatment, but since the heat treatment was performed at a sufficient temperature, the crystallization was low. 3.5 Ge 0.5 V 0.5 Peaks of both the layered rock salt type oxide (LiCoO4) and the layered rock salt type oxide (LiCoO2) were observed.

[0111] Next, the impurity phases in the positive electrode layers of the examples and comparative examples were confirmed by X-ray diffraction using synchrotron X-rays with a wavelength of 0.05 nm. For the positive electrode powders obtained in Example 1 and Comparative Example 2, experimental and calculated values ​​obtained by Rietveld analysis of the X-ray diffraction patterns are shown in Figures 3 and 4. In Figures 3 and 4, the fitting difference between the measured values ​​and the calculated pattern is shown below the X-ray diffraction pattern, and the calculated position of each crystalline phase is also shown below that. As a result, the proportion of the impurity phase was 0.0 mol% in both Example 1 and Comparative Example 2.

[0112] Test Example 2: Electron microscope observation The solid cathode layers obtained in Example 1 and Comparative Example 2 were subjected to cross-sectional scanning electron microscope observation in a range where at least 500 figures obtained by the subsequent Voronoi division could be extracted. The results are shown in Figures 5 and 6 (Figure 5: 5000x, Figure 6: 500x). 3.5 Ge 0.5 V 0.5 O4) is shown in dark gray, and the layered rock salt oxide (LiCoO2), which is the positive electrode active material, is shown in light gray.

[0113] The obtained cross-sectional scanning electron microscope images (Figs. 5 and 6) were binarized using Otsu's algorithm, which has been previously reported (IEEE Trans. Syst. Man Cybern., 9 (1) 1979, 62-66.). The results are shown in Figs. 7 and 8. Here, the solid electrolyte material, lysic oxide (Li 3.5 Ge 0.5 V 0.5 O4) is displayed in white, and the layered rock salt oxide (LiCoO2), which is the positive electrode active material, is displayed in black. By making the contrast between the two clear, the subsequent Voronoi tessellation image processing can be performed appropriately.

[0114] Using the images (Figures 7 and 8) obtained by binarizing the cross-sectional scanning electron microscope images, Voronoi tessellation was performed with the layered rock-salt oxide (LiCoO2), the positive electrode active material, at the center. The results are shown in Figures 9 and 10. Here, Voronoi tessellation refers to a division that connects the boundaries of the two closest layered rock-salt oxide (LiCoO2) particles (black) in the binarized image at equal distances.

[0115] The average diameter and standard deviation of the average diameter were measured from the figures obtained by Voronoi tessellation (FIGS. 9 and 10). The results are shown in FIGS. 11 and 12. As a result, for the solid positive electrode layer of Example 1, the average diameter of the figure obtained by Voronoi tessellation centered on the layered rock-salt oxide (LiCoO2) was 0.68 μm, and the standard deviation of the average diameter was 0.28 μm. Furthermore, for the solid positive electrode layer of Comparative Example 2, the average diameter of the figure obtained by Voronoi tessellation centered on the layered rock-salt oxide (LiCoO2) was 7.28 μm, and the standard deviation of the average diameter was 3.13.

[0116] Test Example 3: All-solid-state lithium-ion secondary battery Solid lithiated oxide (Li 3.5 Ge 0.5 V 0.5 10 mg of the positive electrode powder obtained in Example 1 and Comparative Examples 1 and 2 was spread on 50 mg of 04. The resulting solid electrolyte layer was a thin plate of approximately 10 mm in diameter and 250 μm in thickness, and the solid positive electrode layer was a thin plate of approximately 10 mm in diameter and 50 μm in thickness. A gold plate of 10 mm in diameter and 100 μm in thickness was placed on top of the solid electrolyte layer, and the resulting solid electrolyte layer was sandwiched between a tungsten carbide die and punch. Sintering was performed for 5 minutes at a pressure of 400 MPa, an applied current of approximately 200 A, and a heating temperature of 450°C to obtain a sintered body. A 12 mm diameter piece of metallic lithium was bonded to the solid electrolyte layer side of the resulting sintered body via a polymer electrolyte made of polyethylene oxide (PEO) of approximately 15 mm in diameter, to produce the all-solid-state lithium secondary batteries of Example 1 and Comparative Examples 1 and 2. The configuration of the all-solid-state lithium secondary battery is outlined in FIG. 13.

[0117] Using the all-solid-state lithium secondary batteries of Example 1 and Comparative Examples 1 and 2, in a constant temperature bath at 60°C, (1) Constant current 0.51mA / cm 2 (approximately 0.53C) to an operating voltage of 4.2V, then charged at a constant current of 0.51mA / cm 2 (approximately 0.53 C) to an operating voltage of 2.0 V (Example 1 and Comparative Example 2) (2) Constant current 0.26mA / cm 2 (approximately 0.27C) to an operating voltage of 4.2V, then charged at a constant current of 0.26mA / cm 2 (approximately 0.27 C) to an operating voltage of 2.0 V (Example 1 and Comparative Example 2) (3) Constant current 0.13mA / cm 2 (approximately 0.13C) to an operating voltage of 4.2V, then charged at a constant current of 0.13mA / cm 2 (approximately 0.13 C) to an operating voltage of 2.0 V (Example 1 and Comparative Example 2) (4) Constant current 64μA / cm 2 (approx. 0.07C) to an operating voltage of 4.2V, then a constant current of 64μA / cm 2 (approximately 0.07 C) to an operating voltage of 2.0 V (Example 1 and Comparative Examples 1 and 2) Five charge / discharge cycles were performed under the four conditions.

[0118] 14 to 16 show charge / discharge curves of the all-solid-state lithium secondary batteries of Example 1 and Comparative Examples 1 and 2.

[0119] As a result, in Comparative Example 1, as described above, the obtained solid positive electrode layer was not crystallized, and only the peak of the non-layered rock salt-type oxide was confirmed. Therefore, the solid positive electrode layer did not have either the highly conductive lithiated oxide or the layered rock salt-type oxide with a high theoretical charge capacity. As a result, the charge / discharge capacity was extremely small even under low load conditions, and the cycle characteristics were not sufficient.

[0120] Furthermore, in Comparative Example 2, although both the lithizone-type oxide and the layered rock salt-type oxide were present, the average diameter of the Voronoi tessellation diagram centered on the layered rock salt-type oxide and the standard deviation of the average diameter were large, and therefore it can be seen that the capacity, cycle characteristics, and rate characteristics were all insufficient.

[0121] In contrast, Example 1 contained both a lithizone-type oxide and a layered rock-salt-type oxide, had few impurity phases, and had small average diameters of Voronoi tessellation patterns centered on the layered rock-salt-type oxide and small standard deviations of the average diameters, and therefore was able to sufficiently improve all of the capacity, cycle characteristics, and rate characteristics.

Claims

1. A solid electrode layer containing a lysicone-type oxide and a layered rock salt-type oxide, the content of impurities calculated from an X-ray diffraction pattern of the solid electrode layer is 1.0 mol% or less, with the total amount of the solid electrode layer being 100 mol%, The average diameter of a figure obtained by performing Voronoi division on the layered rock salt type oxide is 0.50 to 2.00 μm, and A solid electrode layer in which the standard deviation of the average diameter of a figure obtained by performing Voronoi tessellation on the layered rock salt type oxide is 1.00 μm or less.

2. (I) The lysicone-type oxide is represented by the general formula (1): Li ｘ１ M １ O ｙ１ (1) [Wherein, x1 represents 3.0<x1<4.0, and y1 represents 3.8<y1<4.

2. １ represents at least one element selected from the group consisting of Ge, Si, V, Ti, P, and S. and (II) The layered rock salt type oxide is represented by the general formula (2): LiM ２ O ｙ２ (2) [Wherein, y2 represents 1.5<y2<2.

5. M ２ represents at least one element selected from the group consisting of Co, Mn, Ni, Al, and Li. is an oxide represented by The solid electrode layer according to claim 1 , wherein at least one of the following is satisfied:

3. Said M １ The solid electrode layer according to claim 2 , wherein the metal oxide layer comprises Ge and / or Si and at least one element selected from the group consisting of V, Ti, P, and S.

4. The lithiated oxide is Li ３．５ Ge ０．５ V ０．５ O ４ , Li ３．７ Ge ０．７ V ０．３ O ４ , Li ３．３ Ge ０．３ V ０．７ O ４ , Li ３．７５ Ge ０．７５ P ０．２５ O ４ , Li ３．５ Ge ０．７５ S ０．２５ O ４ , or Li ３．５ Si ０．２５ Ti ０．２５ V ０．５ O ４ 4. The solid electrode layer of claim 3, wherein:

5. The lithiated oxide is Li ３．５ Ge ０．５ V ０．５ O ４ 5. The solid electrode layer of claim 4, wherein:

6. The layered rock salt oxide is LiCoO ２ , LiNi １／３ Mn １／３ Co １／３ O ２ , LiNi ０．５ Mn ０．５ O ２ , LiNi ０．８ Mn ０．１ Co ０．１ O ２ , LiNi ０．８０ Co ０．１５ Al ０．０５ O ２ , or Li １．２０ Ni ０．１６ Mn ０．５５ Co ０．０９ O ２ 3. The solid electrode layer of claim 2, wherein:

7. The layered rock salt oxide is LiCoO ２ 7. The solid electrode layer of claim 6, wherein:

8. The solid electrode layer according to any one of claims 1 to 7, which is a solid electrode layer for an all-solid-state lithium ion secondary battery.

9. The solid electrode layer according to any one of claims 1 to 7, which is a solid positive electrode layer.

10. An all-solid-state lithium ion secondary battery comprising the solid electrode layer according to any one of claims 1 to 7.

11. A method for producing a solid electrode layer according to any one of claims 1 to 7, comprising: (1) a step of subjecting a lithiated oxide and a layered rock salt oxide to a low-crystallization treatment; and (2) A step of heat treating the low-crystallization product obtained in the step (1) at 600 to 1000°C to obtain a solidified molded product. A manufacturing method comprising:

12. The method according to claim 11, wherein the low crystallization treatment is a mechanical milling treatment and / or a melt quenching treatment.

13. A precursor of a solid electrode layer containing a lithiated oxide and a layered rock salt oxide, the content of impurities calculated from an X-ray diffraction pattern of the precursor is 1 mol % or less, with the total amount of the solid electrode layer being 100 mol %, A solid electrode layer precursor, which has only a peak of a rock salt-type oxide belonging to the space group Fm-3m and a halo peak at 2θ = 5 to 8° in an X-ray diffraction pattern in the range of 2θ = 4 to 26° using synchrotron X-rays with a wavelength of 0.05 nm, but does not have a peak having a maximum value at 2θ = 6 to 7° which is characteristic of a layered rock salt-type oxide.

Images