Solid electrolyte and all-solid-state battery

Abstract

This solid electrolyte is formed from a compound represented by the following general formula (1).　(1): LixM2(PO4)z (In the general formula (1), M represents at least one kind of an element having a valence of 1-4, x represents a number satisfying 0.800 ≤ x ≤ 1.900, and z represents a number satisfying 2.600 ≤ z ≤ 2.800.)

Description

Technical Field

[0001] The present invention relates to a solid electrolyte and an all-solid-state battery. This application claims priority based on Japanese Patent Application No. 2019-227467 filed in Japan on December 17, 2019, and incorporates its content herein by reference.

Background Art

[0002] In recent years, the development of electronics technology has been remarkable, and portable electronic devices have been made smaller, lighter, thinner, and more multifunctional. Along with this, there is a strong demand for batteries that power electronic devices to be smaller, lighter, and more reliable, and all-solid-state batteries using solid electrolytes as electrolytes have attracted attention.

[0003] In order to improve the characteristics such as the cycle characteristics of all-solid-state batteries, it is effective to improve the ionic conductivity of solid electrolytes. Therefore, as a material for solid electrolytes, phosphate compounds having a NASICON-type crystal structure are widely used (Patent Documents 1 to 4). Phosphate compounds having a NASICON-type crystal structure are generally represented by LiM 2 (PO 4 ) 3 . Here, M is a tetravalent metal.

[0004] Further, in order to further improve the ionic conductivity, it has been studied to substitute a part of M with an element having a valence of 1 to 3 (Patent Documents 1 to 4). For example, Patent Document 4 discloses a chemical formula Li 1+X M y (PO 4 ) 3(A part of P may be substituted with at least one selected from the group consisting of Si, B, and V. M contains at least one of the elements that become monovalent to tetravalent cations, and -0.200 ≦ x ≦ 0.900, 2.001 ≦ y ≦ 2.200). A solid electrolyte material represented by this is described. According to this Patent Document 4, when M contains at least one of the elements that become monovalent to tetravalent cations and 2.001 ≦ y ≦ 2.200, it is said that the ionic conductivity of the solid electrolyte can be improved. This is generally LiM 2 (PO 4 ) 3 When compared with a phosphate compound having a NASICON-type crystal structure represented by, the composition ratio of PO 4 is small.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] For improving the cycle characteristics of all-solid-state batteries, further improvement in the ionic conductivity of solid electrolytes is desired. Therefore, an object of the present invention is to provide a novel solid electrolyte with improved ionic conductivity and an all-solid-state battery using the same, which exhibits excellent cycle characteristics.

Means for Solving the Problems

[0007] The inventors of the present invention have the general formula Li x M 2 (PO 4 )z In a solid electrolyte having a NASICON-type crystal structure represented by the formula, M which is a metal element and PO 4 As a result of intensive studies on the composition ratio of, PO 4 By setting the composition ratio of to be in the range of 2.600 or more and 2.800 or less, it was found that the ionic conductivity of the solid electrolyte can be further improved, and the present invention was completed. That is, the present invention provides the following means to solve the above problems.

[0008] [1] The solid electrolyte according to the first aspect is composed of a compound represented by the following general formula (1). Li x M 2 (PO 4 ) z ···(1) (In the general formula (1), M represents at least one element having a valence of 1 to 4, x represents a number satisfying 0.800 ≤ x ≤ 1.900, and z represents a number satisfying 2.600 ≤ z ≤ 2.800.)

[0009] [2] In the general formula (1), M may be a configuration containing at least one element selected from the group consisting of Na, K, Ag, Au, Ba, Cr, Mn, Fe, Co, Ni, Pd, Pt, Sc, Y, V, Nb, Ta, Ru, Rh, Ir, Al, Ga, In, Mo, W, Tc, Re, Os, Ti, Zr, Hf, Ge, Si, Sn.

[0010] [3] In the general formula (1), M may be a configuration containing at least one element having a valence of 4.

[0011] [4] In the solid electrolyte according to the above aspect, the general formula (1) may be a configuration represented by the following general formula (2). Li x M’ y M” 2-y (PO 4 ) z ···(2) (In general formula (2), M'represents at least one element selected from the group consisting of Na, K, Sr, Ba, Sc, Y, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Ni, Pd, Pt, Ag, Au, Cd, Hg, Al, Ga, In, Rh, Ir, and Ti; M" represents at least one element having a tetravalent valence; x represents a number satisfying 0.800 ≦ x ≦ 1.900; y represents a number satisfying 0.001 ≦ y ≦ 1.999; and z represents a number satisfying 2.600 ≦ z ≦ 2.800.)

[0012] [5]In the solid electrolyte according to the above aspect, M" in the general formula (2) may be configured to represent at least one element selected from the group consisting of Ti, Zr, Hf, Ge, Si, and Sn.

[0013] [6]The all-solid-state battery according to the second aspect includes a solid electrolyte layer containing the solid electrolyte according to the above aspect, a positive electrode joined to one surface of the solid electrolyte layer, and a negative electrode joined to the other surface of the solid electrolyte.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a novel solid electrolyte with improved ionic conductivity and an all-solid-state battery using the same.

Brief Description of the Drawings

[0015]

Figure 1

Modes for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in detail with appropriate reference to the drawings. The drawings used in the following description may show, for the sake of convenience, the characteristic parts enlarged in order to make the features of the present invention easier to understand, and the dimensional ratios of the respective components may be different from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and it can be implemented with appropriate changes without changing the gist thereof.

[0017] [All-solid-state battery] FIG. 1 is an enlarged cross-sectional schematic view of the main part of an all-solid-state battery according to the first embodiment. As shown in FIG. 1, the all-solid-state battery 10 has a laminate 4. The laminate 4 has a plurality of positive electrode layers 1, a plurality of negative electrode layers 2, and a solid electrolyte layer 3 located between the positive electrode layer 1 and the negative electrode layer 2. The positive electrode layer 1 is an example of a first electrode layer, and the negative electrode layer 2 is an example of a second electrode layer. Either the first electrode layer or the second electrode layer functions as a positive electrode, and the other functions as a negative electrode. The positive and negative of the electrode layer change depending on which polarity is connected to the external terminal.

[0018] Each positive electrode layer 1 is connected to a positive electrode external terminal 5, and each negative electrode layer 2 is connected to a negative electrode external terminal 6. The positive electrode external terminal 5 and the negative electrode external terminal 6 are electrical contacts with the outside.

[0019] (Laminate) The laminate 4 has a plurality of positive electrode layers 1, a plurality of negative electrode layers 2, a plurality of solid electrolyte layers 3, and a plurality of side margin layers 7. A solid electrolyte layer 3 is located between each positive electrode layer 1 and the negative electrode layer 2. In addition, a side margin layer 7 having substantially the same thickness as the positive electrode layer 1 is formed at one end of the positive electrode layer 1 not connected to the positive electrode external terminal 5. Similarly, a side margin layer 7 having substantially the same thickness as the negative electrode layer 2 is also formed at one end of the negative electrode layer 2 not connected to the negative electrode external terminal 6. Charge and discharge of the all-solid-state battery 10 are performed by the transfer of lithium ions between the positive electrode layer 1 and the negative electrode layer 2 through the solid electrolyte layer 3.

[0020] "Solid electrolyte layer" The solid electrolyte layer 3 contains a solid electrolyte. The solid electrolyte consists of a compound represented by the following general formula (1). The solid electrolyte may contain anion vacancies.

[0021] Li x M 2 (PO 4 ) z ···(1) In the general formula (1), x represents a number satisfying 0.800 ≤ x ≤ 1.900. z represents a number satisfying 2.600 ≤ z ≤ 2.800. It is preferable that z is a number satisfying 2.650 ≤ z ≤ 2.800. Note that the x and the z are calculated with the composition ratio of M being 2.

[0022] In the general formula (1), M represents at least one element having a valence of 1 to 4. M preferably contains at least one element selected from the group consisting of Na (sodium), K (potassium), Ag (silver), Au (gold), Ba (barium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), Pd (palladium), Pt (platinum), Sc (scandium), Y (yttrium), V (vanadium), Nb (niobium), Ta (tantalum), Ru (ruthenium), Rh (rhodium), Ir (iridium), Al (aluminum), Ga (gallium), In (indium), Mo (molybdenum), W (tungsten), Tc (technetium), Re (rhenium), Os (osmium), Ti (titanium), Zr (zirconium), Hf (hafnium), Ge (germanium), Si (silicon), Sn (tin). It is more preferable that M contains only elements having a valence of 4 or contains elements having a valence of 1 to 3 and elements having a valence of 4.

[0023] As the element having a valence of 4, Ti, Zr, Hf, Ge, Si, Sn can be used. These elements may be used alone or in combination of two. When M contains only elements having a valence of 4, M is preferably Ti alone or contains at least one of Zr, Hf, Ge, Si, Sn and Ti.

[0024] When M contains an element having a valence of monovalent to trivalent and an element having a valence of tetravalent, it is preferably a compound represented by the following general formula (2).

[0025] Li x M’ y M” 2-y (PO 4 ) z ···(2) In the general formula (2), x and z are the same as in the case of the general formula (1) above. y represents a number satisfying 0.001 ≦ y ≦ 1.999. It is preferable that y is a number satisfying 0.100 ≦ y ≦ 0.300. Note that the above x and z are calculated with the sum of the composition ratios of M' and M'' being 2.

[0026] In the general formula (2), M’ represents at least one element selected from the group consisting of Na, K, Sr, Ba, Sc, Y, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Ni, Pd, Pt, Ag, Au, Cd, Hg, Al, Ga, In, Rh, Ir, Ti. It is preferable that M’ is at least one element selected from the group consisting of Sr, Ba, Sc, Y, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Ni, Pd, Pt, Ag, Au, Cd, Hg, Al, Ga, In, Rh, Ir, Ti.

[0027] In the general formula (2), M” represents at least one element having a tetravalent valence. It is preferable that M” is at least one element selected from the group consisting of Ti, Zr, Hf, Ge, Si, Sn.

[0028] The solid electrolyte preferably has a NASICON-type crystal structure. A phosphate compound having a NASICON-type crystal structure is generally represented by LiM 2 (PO 4 ) 3 . In contrast, as is clear from the general formula (1) above, the solid electrolyte of the present invention is PO 4The composition ratio is preferably 2.600 or more and 2.800 or less. The reason for the improvement in the ionic conductivity of the solid electrolyte is not necessarily clear, but it is considered that the amount of the composition ratio of the anion PO 4 is less than the stoichiometric composition, and due to the generation of lattice defects, cations (especially Li ions) can move more easily within the crystal. Note that in the solid electrolyte, part of the P of PO 4 may be substituted with an element that forms a tetrahedral structure together with oxygen such as Si (silicon), B (boron), Mo (molybdenum), S (sulfur), W (tungsten), V (vanadium).

[0029] The shape of the solid electrolyte is not particularly limited. The shape of the solid electrolyte is, for example, spherical, ellipsoidal, needle-shaped, plate-shaped, scaly, tube-shaped, wire-shaped, rod-shaped, or amorphous. The average particle diameter (D50) of the solid electrolyte is, for example, 0.1 μm or more and 10 μm or less, and may also be 0.3 μm or more and 9 μm or less. D50 is the diameter of the particle at which the integrated value in the distribution curve obtained by particle size distribution measurement is 50%. The particle size distribution of the particles is measured, for example, by a particle size distribution measuring device using the laser diffraction / scattering method (Microtrac method).

[0030] The solid electrolyte can be produced, for example, by preparing a powder of a carbonate-containing phosphate (solid electrolyte precursor) containing Li and an element represented by M represented by the following formula (3), and then heating the powder of the solid electrolyte precursor to remove carbonate ions.

[0031] Li x M 2 (PO 4 ) z (CO 3 ) 4.5-1.5z ···(3) In the general formula (3), M, x, and z are the same as in the case of the general formula (1) above. That is, in the general formula (3), x represents a number satisfying 0.800 ≤ x ≤ 1.900. z represents a number satisfying 2.600 ≤ z ≤ 2.800. It is preferable that z is a number satisfying 2.650 ≤ z ≤ 2.800. Note that the x and the z are calculated with the composition ratio of M being 2.

[0032] The solid electrolyte precursor can be synthesized by a liquid phase method. Specifically, it can be manufactured as follows. First, an Li source, an M source, a PO 4 source, and a CO 3 source are weighed so as to have the target composition. Next, the M source is dissolved in an organic solvent, and the Li source, the PO 4 source, and the CO 3 source are added thereto, and a sol of the solid electrolyte precursor is prepared by stirring and mixing. The obtained sol is dried to obtain a gel. The obtained gel is dried and, if necessary, pulverized to obtain a powder of the solid electrolyte precursor.

[0033] The materials used as the Li source, the M source, the PO 4 source, and the CO 3 source are not particularly limited. As the Li source and the M source, carbonates, nitrates, oxides, hydroxides, chlorides, phosphates, etc. can be used. The carbonate also acts as the CO 3 source, and the phosphate also acts as the PO 4 source. As the PO 4 source, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, etc. can be used. As the CO 3 source, ethylene carbonate, lithium carbonate, ammonium bicarbonate, etc. can be used.

[0034] When removing carbonate ions from the powder of the solid electrolyte precursor, the heating temperature is not particularly limited as long as it is 300°C or higher, but it is preferably a temperature below the sintering temperature of the solid electrolyte precursor powder, particularly a temperature below 600°C. The atmosphere during heating is not particularly limited, and it can be an air atmosphere, a nitrogen atmosphere, an argon atmosphere, or an oxygen atmosphere.

[0035] After removing carbonate ions, the solid electrolyte precursor is preferably fired at a temperature of 600°C or higher and 1500°C or lower in order to improve crystallinity. The atmosphere during firing is not particularly limited as long as it is other than a carbon dioxide gas atmosphere, and it can be an air atmosphere, a nitrogen atmosphere, an argon atmosphere, or an oxygen atmosphere. Incidentally, anion vacancies are generated in the solid electrolyte precursor from which carbonate ions have been removed.

[0036] "Positive electrode layer and negative electrode layer" For example, there are a plurality of positive electrode layers 1 and negative electrode layers 2 in the laminate 4. The positive electrode layer 1 is joined to one main surface of the solid electrolyte layer 3, and the negative electrode layer 2 is joined to the other surface of the solid electrolyte layer 3.

[0037] The positive electrode layer 1 has a positive electrode current collector layer 1A and a positive electrode active material layer 1B. The negative electrode layer 2 has a negative electrode current collector layer 2A and a negative electrode active material layer 2B.

[0038] The positive electrode current collector layer 1A and the negative electrode current collector layer 2A contain a conductive material. The positive electrode current collector layer 1A and the negative electrode current collector layer 2A preferably contain 50% or more of the conductive material. Examples of the conductive material include, for example, silver, palladium, gold, platinum, aluminum, copper, nickel, carbon, and the like. In particular, copper hardly reacts with the positive electrode active material, the negative electrode active material, and the solid electrolyte. For example, when copper is used for the positive electrode current collector layer 1A and the negative electrode current collector layer 2A, the internal resistance of the all-solid-state battery 10 can be reduced. The conductive material is not limited to this as long as it does not decompose within the operating voltage range of the battery. Furthermore, the materials constituting the positive electrode current collector layer 1A and the negative electrode current collector layer 2A may be the same or different.

[0039] The positive electrode current collector layer 1A may contain a positive electrode active material described later. The negative electrode current collector layer 2A may contain a negative electrode active material described later. The content ratio of the active material contained in each current collector layer is not particularly limited as long as it functions as a current collector. The volume ratio of the conductive material to the positive electrode active material in the positive electrode current collector layer 1A is, for example, in the range of 90:10 to 70:30. Similarly, the volume ratio of the conductive material to the negative electrode active material in the negative electrode current collector layer 2A is, for example, in the range of 90:10 to 70:30. When the positive electrode current collector layer 1A and the negative electrode current collector layer 2A contain a positive electrode active material and a negative electrode active material, respectively, the adhesion between the positive electrode current collector layer 1A and the positive electrode active material layer 1B and the adhesion between the negative electrode current collector layer 2A and the negative electrode active material layer 2B are improved.

[0040] The positive electrode active material layer 1B is formed on one or both sides of the positive electrode current collector layer 1A. The positive electrode active material layer 1B may not be provided on the surface of the positive electrode current collector layer 1A on the side where the opposing negative electrode layer 2 does not exist. The negative electrode active material layer 2B is formed on one or both sides of the negative electrode current collector layer 2A. The negative electrode active material layer 2B may not be provided on the surface of the negative electrode current collector layer 2A on the side where the opposing positive electrode layer 1 does not exist. For example, the positive electrode layer 1 or the negative electrode layer 2 located in the uppermost layer or the lowermost layer of the laminate 4 may not have the positive electrode active material layer 1B or the negative electrode active material layer 2B on one side.

[0041] The positive electrode active material layer 1B and the negative electrode active material layer 2B contain, as the positive electrode active material and the negative electrode active material, at least a compound capable of occluding and releasing lithium ions. The positive electrode active material layer 1B and the negative electrode active material layer 2B may contain, in addition to the active material, a conductive assistant, an ion-conducting assistant, a binder, and the like. It is preferable that the positive electrode active material and the negative electrode active material can efficiently insert and desorb lithium ions.

[0042] The positive electrode active material and the negative electrode active material are, for example, transition metal oxides and transition metal composite oxides. Specifically, the positive electrode active material and the negative electrode active material are, for example, lithium manganese composite oxide Li 2 Mn a Ma 1-a O 3 (0.8 ≦ a ≦ 1, Ma = Co, Ni), lithium cobalt oxide (LiCoO 2) Lithium nickelate (LiNiO 2 ) Lithium manganese spinel (LiMn 2 O 4 ) General formula: LiNi x Co y Mn z O 2 (x + y + z = 1, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1) Composite metal oxide represented by, lithium vanadium compound (LiV 2 O 5 ), Olivine type LiMbPO 4 (However, Mb is one or more elements selected from Co (cobalt), Ni (nickel), Mn (manganese), Fe (iron), Mg (magnesium), Nb (niobium), Ti (titanium), Al (aluminum), Zr (zirconium)), lithium vanadium phosphate (Li 3 V 2 (PO 4 ) 3 Or LiVOPO 4 ), Li 2 MnO 3 -LiMcO 2 (Mc = Mn, Co, Ni) Li-excess solid solution cathode represented by, lithium titanate (Li 4 Ti 5 O 12 ), Titanium oxide (TiO 2 ), Li s Ni t Co u Al v O 2 (0.9 < s < 1.3, 0.9 < t + u + v < 1.1) Composite metal oxide and the like.

[0043] As the positive electrode active material and the negative electrode active material of the present embodiment, it is preferable to contain a phosphate compound as a main component. For example, lithium vanadium phosphate (LiVOPO 4 , Li 3 V 2 (PO 4 ) 3 , Li 4 (VO)(PO 4 ) 2 ), Lithium vanadium pyrophosphate (Li 2 VOP2 O 7 , Li 2 VP 2 O 7 ), and Li 9 V 3 (P 2 O 7 ) 3 (PO 4 ) 2 is preferably any one or more of them. In particular, LiVOPO 4 and Li 3 V 2 (PO 4 ) 3 is preferably one or both of them.

[0044] The main component in this embodiment refers to the case where, when the total amount of the positive electrode active material and the negative electrode active material in the positive electrode active material layer and the negative electrode active material layer is 100 parts by mass, the proportion occupied by the phosphate compound is greater than 50 parts by mass. The proportion occupied by the phosphate compound is preferably 80 parts by weight or more.

[0045] Also, these positive electrode active materials and negative electrode active materials may have a part of each element substituted with a different element or may vary from the stoichiometric composition. LiVOPO 4 and Li 3 V 2 (PO 4 ) 3 preferably has a lithium deficiency, and Li x VOPO 4 (0.94 ≦ x ≦ 0.98) or Li x V 2 (PO 4 ) 3 (2.8 ≦ x ≦ 2.95) is more preferable.

[0046] Also, as the negative electrode active material, for example, Li metal, Li-Al alloy, Li-In alloy, carbon, silicon (Si), silicon oxide (SiO x ), lithium titanate (Li 4 Ti 5 O 12 ), titanium oxide (TiO 2 ) can be used.

[0047] Here, there is no clear distinction between the active materials constituting the positive electrode active material layer 1B or the negative electrode active material layer 2B. By comparing the potentials of the two types of compounds, namely the compound in the positive electrode active material layer and the compound in the negative electrode active material layer, the compound showing a more noble potential can be used as the positive electrode active material, and the compound showing a more base potential can be used as the negative electrode active material. Also, as long as it is a compound having both a lithium ion release function and a lithium ion occlusion function, the active materials constituting the positive electrode active material layer 1B and the negative electrode active material layer 2B may use the same material. By making the active materials constituting the positive electrode active material layer 1B and the negative electrode active material layer 2B the same material, a non-polar all-solid-state battery is obtained, so there is no need to specify the direction even when attaching to a circuit board, and the mountability can be facilitated.

[0048] Examples of the conductive assistant include carbon materials such as carbon black, acetylene black, ketjen black, carbon nanotubes, graphite, graphene, activated carbon, and metal materials such as gold, silver, palladium, platinum, copper, and tin.

[0049] As the ion-conducting assistant, for example, a solid electrolyte can be used. Specifically, as the solid electrolyte, the same material as the solid electrolyte contained in the solid electrolyte layer 3 can be used.

[0050] As the binder, for example, an organic binder or an inorganic binder can be used. Examples of the organic binder include polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), polyacrylate (PAA), polyimide (PI), polyamideimide (PAI), and the like. Examples of the inorganic binder include lithium halide, silicate-based compounds, phosphate-based compounds, low melting point glass, and the like.

[0051] (External terminal) The positive electrode external terminal 5 and the negative electrode external terminal 6 are made of, for example, a material with excellent conductivity. The positive electrode external terminal 5 and the negative electrode external terminal 6 are, for example, any of silver, gold, platinum, aluminum, copper, tin, and nickel. The positive electrode external terminal 5 and the negative electrode external terminal 6 may be a single layer or multiple layers.

[0052] (Protective layer) The all-solid-state battery 10 may have a protective layer on its outer periphery that electrically, physically, and chemically protects the laminate 4 and the terminals. The protective layer is preferably made of a material that is excellent in insulation, durability, moisture resistance, and environmentally safe. The protective layer is, for example, glass, ceramics, a thermosetting resin, or a photocurable resin. The material of the protective layer may be only one type or a plurality may be used in combination. The protective layer may be a single layer or multiple layers. The protective layer is preferably an organic-inorganic hybrid in which a thermosetting resin and ceramic powder are mixed.

[0053] Next, a method for manufacturing the all-solid-state battery according to the present embodiment will be described. The all-solid-state battery 10 may be manufactured by a simultaneous firing method or a sequential firing method. The simultaneous firing method is a method of laminating the materials for forming each layer and then firing them all at once. The sequential firing method is a method of firing each layer every time it is laminated. The simultaneous firing method has a simpler working process than the sequential firing method. Also, the laminate 4 manufactured by the simultaneous firing method is denser than the laminate 4 manufactured by the sequential firing method. Hereinafter, the case of using the simultaneous firing method will be described as an example.

[0054] First, pastes for each layer constituting the laminate 4 are prepared. The materials for the positive electrode current collector layer 1A, the positive electrode active material layer 1B, the solid electrolyte layer 3, the negative electrode active material layer 2B, the negative electrode current collector layer 2A, and the side margin layer 7 are each made into a paste. The method of making the paste is not particularly limited. For example, a paste can be obtained by mixing the powder of each material in a vehicle. A vehicle is a general term for a medium in a liquid phase. The vehicle contains a solvent and a binder.

[0055] The laminate is preferably prepared by preparing a positive electrode active material layer unit and a negative electrode active material layer unit described below, and using this positive electrode active material layer unit and negative electrode active material layer unit for production.

[0056] The positive electrode active material layer unit can be produced by the following procedure. First, a paste for a solid electrolyte layer is formed into a sheet shape on a PET film by the doctor blade method and dried to form a solid electrolyte green sheet. Next, a paste for a positive electrode active material layer is screen-printed on a part of the obtained solid electrolyte green sheet and dried to form a positive electrode active material layer.

[0057] Next, a paste for a positive electrode current collector layer is screen-printed on the obtained positive electrode active material layer and dried to form a positive electrode current collector layer. Then, a paste for a positive electrode active material layer is screen-printed again on the obtained positive electrode current collector layer and dried to form a positive electrode active material layer. In this way, a positive electrode layer is formed on a part of the solid electrolyte layer. Next, a paste for a side margin layer is screen-printed on the solid electrolyte layer where the positive electrode layer is not formed and dried to form a side margin layer. Then, the PET film is peeled off to produce a positive electrode unit. The positive electrode unit has a positive electrode layer 1 (positive electrode active material layer 1B / positive electrode current collector layer 1A / positive electrode active material layer 1B) and a side margin layer 7 formed on the solid electrolyte layer 3.

[0058] Note that the side margin layer 7 eliminates the step between the solid electrolyte layer 3 and the positive electrode layer 1 and the step between the solid electrolyte layer 3 and the negative electrode layer 2 at the end faces where the positive electrode layer 1 and the negative electrode layer 2 do not extend. As the side margin layer 7, it is necessary to use a material with low electronic conductivity, for example, a solid electrolyte is used. The side margin layer 7 may be formed separately as described above. Also, without forming it separately, what is caused by the deformation of the solid electrolyte layer 3 during lamination may be provided as the side margin layer 7 in the positive electrode layer 1 and the negative electrode layer 2.

[0059] The negative electrode unit is fabricated by the same procedure. The negative electrode unit has a negative electrode layer 2 (negative electrode active material layer 2B / negative electrode current collector layer 2A / negative electrode active material layer 2B) and a side margin layer 7 formed on the solid electrolyte layer 3.

[0060] Next, the positive electrode unit and the negative electrode unit are laminated. An offset is made so that one end of each of the positive electrode layer and the negative electrode layer does not face each other, and they are laminated so that the positive electrode layer and the negative electrode layer are each in a comb shape with the solid electrolyte layer in between. Thereby, a laminated substrate including a plurality of positive electrode layers 1, a plurality of negative electrode layers 2, and the solid electrolyte layer 3 positioned between the positive electrode layer 1 and the negative electrode layer 2 is fabricated. Note that, if necessary, outer layers can be provided on both main surfaces of the uppermost layer and the lowermost layer of the laminated substrate. The outer layer can be made of the same material as the solid electrolyte and can be formed by laminating a solid electrolyte green sheet.

[0061] The above-described method of laminating the positive electrode unit and the negative electrode unit is useful when manufacturing a parallel-type all-solid-state battery 10 in which a plurality of positive electrode layers 1 connected to the positive electrode external terminal 5 and a plurality of negative electrode layers 2 connected to the negative electrode external terminal 6 are connected in parallel. When manufacturing a series-type all-solid-state battery in which the positive electrode layer and the negative electrode layer are connected in series, they may be laminated without making an offset so that one end of each of the positive electrode layer and the negative electrode layer faces each other.

[0062] Next, the fabricated laminated substrate is crimped all at once. The crimping is performed while heating at a low temperature. The heating temperature is, for example, 40 to 95°C.

[0063] The fabricated laminate is cut into chips using a dicing device, and then, after performing a debinding process if necessary, it is fired to manufacture a laminate of the all-solid-state battery.

[0064] The laminate of the obtained unfired chips is sintered to obtain the laminate 4 of the all-solid-state battery of the present embodiment. The sintering is performed, for example, by heating in a nitrogen atmosphere in a temperature range of 600°C or higher and 1500°C or lower. The firing time is, for example, 0.1 to 3 hours.

[0065] As described above, before the firing process, a debinding process may be performed as a process separate from the firing process. By thermally decomposing the binder component contained in the laminate 5 before firing, rapid decomposition of the binder component in the firing process can be suppressed. The debinding process is performed, for example, at a temperature in the range of 300°C to 800°C for 0.1 to 10 hours in a nitrogen atmosphere. If it is a reducing atmosphere, firing may be performed, for example, in an argon atmosphere or a nitrogen-hydrogen mixed atmosphere instead of the nitrogen atmosphere.

[0066] The laminate 4 may be placed in a cylindrical container together with an abrasive such as alumina and barrel-polished. The corners of the laminate 4 are chamfered by polishing. The polishing may be performed by sandblasting or the like.

[0067] Finally, the positive electrode external terminal 5 and the negative electrode external terminal 6 are attached to the laminate 4. The positive electrode external terminal 5 and the negative electrode external terminal 6 are each formed so as to be in electrical contact with the positive electrode current collector layer 1A or the negative electrode current collector layer 2A. For example, the positive electrode external terminal 5 is connected to the positive electrode current collector layer 1A exposed from the side surface of the laminate 4, and the negative electrode external terminal 6 is connected to the negative electrode current collector layer 2A exposed from the side surface of the laminate 4. The positive electrode external terminal 5 and the negative electrode external terminal 6 can be manufactured by, for example, a sputtering method, a dipping method, a spray coating method, or the like.

[0068] The solid electrolyte contained in the solid electrolyte layer 3 of the all-solid-state battery 10 according to the present embodiment is composed of the compound represented by the general formula (1) described above, and due to the large ratio of the PO 4 sites with respect to M, the ionic conductivity is improved. Since the all-solid-state battery 10 according to the present embodiment has improved ionic conductivity of the solid electrolyte layer 3, it has excellent electrical characteristics such as cycle characteristics.

[0069] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, each configuration and their combinations in each embodiment are examples, and additions, omissions, substitutions, and other changes of the configuration are possible without departing from the spirit of the present invention.

Examples

[0070] [Example 1] (Preparation of Solid Electrolyte) As starting materials, LiNO 3 ·H 2 O (lithium nitrate monohydrate), AlCl 3 (aluminum chloride), TiCl 4 (titanium chloride), H 3 PO 4 (85% phosphoric acid), NH 4 HCO 3 (ammonium bicarbonate) were prepared. The prepared LiNO 3 ·H 2 O, AlCl 3 , TiCl 4 , H 3 PO 4 and NH 4 HCO 3 were weighed so that the composition ratio of Li, Al, Ti, PO 4 , CO 3 was 1.300:0.300:1.700:2.800:0.300 (=Li:Al:Ti:PO 4 :CO 3 ). Next, the weighed AlCl 3 and TiCl 4 were added to a mixed solvent of ethanol and ion-exchanged water and stirred with a magnetic stirrer for 30 minutes. Further, LiNO 3 ·H 2 O, H 3 PO 4 , and NH 4 HCO 3 were added and stirred for another 2 hours. After stirring, the resulting sol solution was transferred to suction filtration to remove the mixed solvent and dried at 30 °C to obtain a gel. The obtained gel was aged at 100 °C for 6 hours to obtain a precursor of the solid electrolyte. The obtained precursor was heated at 300 °C for 3 hours in an air atmosphere to enhance crystallinity and simultaneously remove carbonate ions in the crystal structure. Next, the precursor from which carbonate ions had been removed was calcined at 700 °C for 1 hour in a nitrogen atmosphere to prepare a calcined product of the solid electrolyte. Then, the calcined product was pulverized to obtain a calcined powder.

[0071] 0.2 g of the obtained calcined powder was placed in a circular mold with a diameter of 12 mm and press-molded at a pressure of 2.0 t / cm 2 to produce a circular molded body. This molded body was fired at 850 °C for 2 hours in a nitrogen atmosphere to obtain a solid electrolyte sintered body according to Example 1.

[0072] [Examples 2 to 6, Comparative Examples 1 to 4] LiNO 3 ·H 2 O, AlCl 3 、TiCl 4 、H 3 PO 4 and NH 4 HCO 3 were mixed in the same manner as in Example 1 except that the ratios of Li, Al, Ti, PO 4 and CO 3 were such that the composition ratios shown in Table 1 below were obtained, and a solid electrolyte sintered body was obtained.

[0073]

Table 1

[0074] [Evaluation] (Composition) The solid electrolyte sintered body was dissolved using nitric acid, and the concentrations of Li, Al, Ti, and P in the obtained solution were measured by ICP emission spectrometry. Then, from the concentrations of each element obtained, the composition ratios of Li, Al, Ti, PO 4 were calculated. In calculating the composition ratios, in the general formula (2) Li x M’ y M” 2-y (PO 4 ) z wherein x and z were calculated by converting with the sum of the composition ratios of M' and M'' being 2. The results are shown in Table 2 below.

[0075] (X-ray Diffraction Pattern) The crystal structure of the solid electrolyte sintered body was measured for its X-ray diffraction pattern using CuKα radiation. As a result of analyzing the obtained X-ray diffraction pattern, LiTi of ICDD card 35-07542 (PO 4 ) 3 (Lithium titanium phosphate) showed the same X-ray diffraction pattern as that of the solid electrolyte of the Example and the Comparative Example, it was confirmed that the solid electrolytes had a NASICON-type crystal structure. The results are shown in Table 2 below.

[0076] (Ionic conductivity) Two stainless steel discs with a diameter of 50 mm and a thickness of 5 mm and two PTFE (polytetrafluoroethylene) discs were prepared respectively. The stainless steel discs and the PTFE discs each had four screw holes. The above-mentioned stainless steel discs and PTFE discs were placed on the top and bottom of the solid electrolyte sintered body, and the solid electrolyte sintered body was pressed by passing screws through the four screw holes and tightening the screws. Specifically, a stack in the order of stainless steel disc / PTFE disc / solid electrolyte sintered body / PTFE disc / stainless steel disc was fastened with screws to form a jig for measuring ionic conductivity. There were screw holes for inserting screws on the side surfaces of the upper and lower punches. Screws were inserted into the upper and lower punches to serve as terminals for measuring ionic conductivity.

[0077] Thereafter, the ionic conductivity of each test body accommodated in the set of the jig for measuring ionic conductivity was measured by an electrochemical impedance measurement method using a potentiostat equipped with a frequency response analyzer. The measurement was carried out under the conditions of a frequency range of 7 MHz to 0.1 Hz, an amplitude of 10 mV, and a temperature of 30°C. The results are shown in Table 2 below.

[0078] [Fabrication of All-Solid-State Battery and Charge / Discharge Cycle Test] The all-solid-state battery was fabricated by the following procedure. Pastes containing each material were prepared to form a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a negative electrode current collector layer, and a side margin layer. Next, a sheet for the solid electrolyte layer was prepared, and an electrode layer and a side margin layer were formed on this sheet for the solid electrolyte layer to fabricate an electrode unit. Then, the all-solid-state battery of the present embodiment was fabricated by alternately laminating the electrode units. Hereinafter, taking Example 1 as a representative, the manufacturing method will be described in more detail step by step.

[0079] (Preparation of Positive Electrode Active Material and Negative Electrode Active Material) As the positive electrode active material and the negative electrode active material, Li 3 V 2 (PO 4 ) 3 was used. As the preparation method, Li 2 CO 3 and V 2 O 5 and NH 4 H 2 PO 4 were used as starting materials, wet mixed in a ball mill for 16 hours, dehydrated and dried, and then the obtained powder was calcined in a nitrogen-hydrogen mixed gas at 700°C for 2 hours. After the calcined product was wet pulverized in a ball mill, it was dehydrated and dried to obtain calcined powders of the positive electrode active material and the negative electrode active material. As a result of measuring the composition of the prepared calcined powder with an X-ray diffractometer, it was confirmed that it was Li 3 V 2 (PO 4 ) 3 .

[0080] (Preparation of Paste for Positive Electrode Active Material Layer and Paste for Negative Electrode Active Material Layer) For both the paste for the positive electrode active material layer and the paste for the negative electrode active material layer, 15 parts of ethyl cellulose as a binder and 65 parts of dihydroterpineol as a solvent were added to 100 parts of the calcined powder of Li 3 V 2 (PO 4 ) 3 , and they were mixed and dispersed to prepare the paste for the positive electrode active material layer and the paste for the negative electrode active material layer.

[0081] (Preparation of Paste for Solid Electrolyte Layer) To 100 parts of the calcined powder of the solid electrolyte prepared in Example 1, 100 parts of ethanol and 200 parts of toluene were added as solvents and wet mixed in a ball mill. Then, 16 parts of a polyvinyl butyral-based binder and 4.8 parts of benzyl butyl phthalate were further added and mixed to prepare a paste for the solid electrolyte layer.

[0082] (Preparation of Paste for Positive Current Collector Layer and Paste for Negative Current Collector Layer) As the positive current collector and the negative current collector, Cu powder and Li 3 V 2 (PO 4 ) 3 After mixing the calcined powders so that the volume ratio becomes 80 / 20, 10 parts of ethyl cellulose as a binder and 50 parts of dihydroterpineol as a solvent were added and mixed and dispersed to prepare a paste for the positive current collector layer and a paste for the negative current collector layer.

[0083] (Preparation of Paste for Side Margin Layer) To 100 parts of the calcined powder of the solid electrolyte prepared in Example 1, 100 parts of ethanol and 100 parts of toluene were added as solvents and wet-mixed by a ball mill. Then, 16 parts of a polyvinyl butyral-based binder and 4.8 parts of benzyl butyl phthalate were further added and mixed to prepare a paste for the side margin layer.

[0084] (Preparation of Paste for External Terminal) Silver powder, an epoxy resin, and a solvent were mixed and dispersed to prepare a thermosetting paste for the external terminal.

[0085] (Preparation of Sheet for Solid Electrolyte Layer) The paste for the solid electrolyte layer was formed into a sheet on a PET film by the doctor blade method to obtain a sheet for the solid electrolyte layer with a thickness of 15 μm.

[0086] (Preparation of Positive Electrode Unit) On the sheet for the solid electrolyte layer, a paste for the positive electrode active material layer was screen-printed to form a positive electrode active material layer with a thickness of 5 μm, and it was dried at 80°C for 10 minutes. Next, on the positive electrode active material layer, a paste for the positive electrode current collector layer was screen-printed to form a positive electrode current collector layer with a thickness of 5 μm, and it was dried at 80°C for 10 minutes. Further, on the positive electrode current collector layer, a paste for the positive electrode active material layer was screen-printed to form a positive electrode active material layer with a thickness of 5 μm again, and it was dried at 80°C for 10 minutes to fabricate a positive electrode layer on the sheet for the solid electrolyte layer. Next, in the region of the sheet for the solid electrolyte layer where the positive electrode layer was not formed, a paste for the side margin layer was screen-printed to form a side margin layer having the same height as the positive electrode layer in substantially the same plane, and it was dried at 80°C for 10 minutes to fabricate a positive electrode unit.

[0087] (Fabrication of the negative electrode unit) Regarding the negative electrode unit, the negative electrode unit was fabricated in the same manner as the positive electrode unit.

[0088] (Fabrication of the laminate) The positive electrode unit and the negative electrode unit were peeled off from the PET film, and they were laminated with an offset so that one end of the positive electrode layer and one end of the negative electrode layer did not coincide. The solid electrolyte layer sandwiched between the positive electrode layer and the negative electrode layer was taken as one layer, and a laminated substrate was fabricated by laminating so that the solid electrolyte layer became 50 layers. Next, a plurality of sheets for the solid electrolyte layer were laminated as outer layers on both main surfaces of the uppermost layer and the lowermost layer of the laminated substrate to provide an outer layer with a thickness of 500 μm. After this was thermocompression-bonded by a mold press, it was cut to fabricate a laminate of the unburned all-solid-state battery. Next, the laminate was degassed and fired to obtain a laminate of the all-solid-state battery. The firing was carried out by raising the temperature at a rate of 200°C / hour in a nitrogen atmosphere to 850°C, holding at that temperature for 2 hours, and taking it out after natural cooling.

[0089] (Fabrication of the external terminals) An external terminal paste was applied to the end face of the laminate of the all-solid-state battery after firing, and heat curing was carried out at 150°C for 30 minutes to form a pair of external terminals.

[0090] (Charge and discharge cycle test) All solid-state batteries fabricated in this example and the comparative examples were evaluated for charge-discharge cycle characteristics under the charge-discharge conditions shown below. The charge-discharge current is hereafter expressed in terms of the C-rate notation. The C-rate is expressed as nC (or current value [A]) (where n is a numerical value) and means the current at which the nominal capacity (μAh) can be charged and discharged in 1 / n (h). For example, 1C is the charge-discharge current at which the nominal capacity can be charged in 1 h, and 2C means the charge-discharge current at which the nominal capacity can be charged in 0.5 h. For example, in the case of an all-solid-state battery with a nominal capacity of 100 μAh, the current at 0.1C is 10 μA (calculation formula: 100 μA × 0.1 = 10 μA). Similarly, the current at 0.2C is 20 μA, and the current at 1C is 100 μA.

[0091] The charge-discharge cycle test conditions were as follows: under an environment of 25°C, constant-current charge (CC charge) was performed at a constant current of 0.2C rate until the battery voltage reached 1.6V, and then discharge was carried out at a constant current of 0.2C rate until the battery voltage reached 0V (CC discharge). One cycle consisted of the above charging and discharging, and after repeating this up to 500 cycles, the discharge capacity retention rate was evaluated as the charge-discharge cycle characteristics. The charge-discharge cycle characteristics in this embodiment were calculated by the following calculation formula. Discharge capacity retention rate after 500 cycles (%) = (Discharge capacity after 500 cycles ÷ Discharge capacity after 1 cycle) × 100

[0092]

Table 2

[0093] From the results in Table 2, for the solid electrolyte sintered bodies of Examples 1 to 6 where the total composition ratio of Al and Ti was 2 and the composition ratio of PO 4 was in the range of 2.600 to 2.800, compared with the solid electrolyte sintered body of Comparative Example 1 (stoichiometric composition) where the composition ratio of PO 4 was 3.000, the ionic conductivity was significantly improved. Also, it can be seen that the cycle characteristics of the all-solid-state battery using this as the solid electrolyte were improved. The reason for the improved ionic conductivity is not clear, but the following considerations are made. The solid electrolyte sintered bodies obtained in Examples 1 to 6 were CO3 Ions desorb from the PO 4 site, resulting in the generation of lattice defects at the PO 4 site. It is considered that this is due to the generation of lattice defects. In contrast, for the solid electrolyte sintered body of Comparative Example 2 with a composition ratio of PO 4 of 2.900 and the solid electrolyte sintered body of Comparative Example 3 with a composition ratio of PO 4 of 2.850, although the ionic conductivity was improved as in the solid electrolyte sintered body of Comparative Example 1, the improvement in ionic conductivity was slight compared to Examples 1 to 6. This is considered to be because the generation of lattice defects was not sufficient. Also, for the solid electrolyte sintered body of Comparative Example 4 with a composition ratio of PO 4 of 2.580, the ionic conductivity decreased compared to Examples 1 to 6. This is considered to be because the generation of lattice defects became excessive. Note that although not shown in Table 2, anion vacancies are generated in the solid electrolyte sintered body and it is electrically neutral.

[0094] [Examples 7 to 10, Comparative Examples 5 to 6] LiNO 3 ·H 2 O, AlCl 3 , TiCl 4 , H 3 PO 4 and NH 4 HCO 3 were mixed in the same manner as in Example 1 except that the ratios of Li, Al, Ti, PO 4 and CO 3 were the composition ratios shown in Table 3 below, and a solid electrolyte sintered body was obtained. For the obtained solid electrolyte sintered body, the composition, X-ray diffraction pattern, and ionic conductivity were evaluated in the same manner as in Example 1. The results are shown in Table 4 below together with the results of Example 3.

[0095]

Table 3

[0096]

Table 4

[0097] From the results in Table 4, it can be seen that for the solid electrolyte sintered compacts of Examples 1 and 7 to 10 where the Li content is in the range of 0.800 or more and 1.900 or less in terms of the composition ratio, the ionic conductivity is particularly improved. Although omitted in Table 4, anion vacancies are generated in the solid electrolyte sintered compact and it is electrically neutral.

[0098] [Examples 11 to 14, Comparative Examples 7 to 10] AlCl 3 Instead of, NaCl (sodium chloride), CoCl 2 (cobalt(II) chloride), YCl 3 (yttrium(III) chloride) or ZrCl 4 (zirconium(IV) chloride) was used, and except that these compounds were mixed so as to have the composition ratios shown in Table 5 below as the amounts of Na, Co, Y or Zr, a solid electrolyte sintered compact was obtained in the same manner as in Example 1. For the obtained solid electrolyte sintered compact, the composition, X-ray diffraction pattern, and ionic conductivity were evaluated in the same manner as in Example 1. The results are shown in Table 6 below.

[0099]

Table 5

[0100]

Table 6

[0101] From the results in Table 6, it can also be seen that for the case of combining the elements of Na (monovalent element), Co (divalent element), Y (trivalent element), and Zr (tetravalent), the ionic conductivity of the solid electrolyte sintered compact is improved. Although omitted in Table 6, anion vacancies are generated in the solid electrolyte sintered compact and it is electrically neutral.

[0102] [Examples 15 to 18] TiCl 4 Instead of, ZrCl 4 (zirconium chloride), HfCl 4 (hafnium chloride), GeCl 4(Germanium chloride) or SnCl 4 (Tin(IV) chloride) was used, and these compounds were mixed in the composition ratios shown in Table 7 below as the amounts of Zr, Hf, Ge, or Sn. Otherwise, in the same manner as in Example 1, a solid electrolyte powder and a solid electrolyte sintered body were obtained. For the obtained solid electrolyte sintered body, the composition, X-ray diffraction pattern, and ionic conductivity were evaluated in the same manner as in Example 1. In the analysis of the X-ray diffraction pattern, the solid electrolyte of Example 15 was LiZr 2 (PO 4 ) 3 (Lithium zirconium phosphate) of ICDD card 072-7742, the solid electrolyte of Example 16 was LiHf 2 (PO 4 ) 3 (Lithium hafnium phosphate) of ICDD card 004-0755, the solid electrolyte of Example 17 was LiGe 2 (PO 4 ) 3 (Lithium germanium phosphate) of ICDD card 080-1992, the solid electrolyte of Example 18 was LiSn 2 (PO 4 ) 3 (Lithium tin phosphate), and since they showed the same X-ray diffraction pattern, it was confirmed that they each had a NASICON-type crystal structure. The results are shown in Table 8 below together with the results of Example 1.

[0103]

Table 7

[0104]

Table 8

[0105] From the results in Table 8, it can be seen that for Zr, Hf, Ge, and Sn as well, the ionic conductivity of the solid electrolyte sintered body is improved in the same manner as for Ti. Although omitted in Table 8, anion vacancies are generated in the solid electrolyte sintered body and it is electrically neutral.

Explanation of Symbols

[0106] 1… positive electrode layer, 1A… positive electrode current collector layer, 1B… positive electrode active material layer, 2… negative electrode layer, 2A… negative electrode current collector layer, 2B… negative electrode active material layer, 3… solid electrolyte layer, 4… laminate, 5… positive electrode external terminal, 6… negative electrode external terminal, 7… side margin layer, 10… all-solid-state battery

Claims

1. A solid electrolyte comprising a NASICON-type compound represented by the following general formula (2). LixM'yM"2-y(PO4)z...(2) (In the general formula (2), M' represents at least one element selected from the group consisting of Na, K, Sr, Ba, Sc, Y, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Ni, Pd, Pt, Ag, Au, Cd, Hg, Al, Ga, In, Rh, Ir, Ti; M" represents at least one element having a tetravalent valence; x represents a number satisfying 0.800 ≤ x ≤ 1.900; y represents a number satisfying 0.001 ≤ y ≤ 1.999; z represents a number satisfying 2.600 ≤ z ≤ 2.800.)

2. The solid electrolyte according to Claim 1, wherein in the general formula (2), M" represents at least one element selected from the group consisting of Ti, Zr, Hf, Ge, Si, Sn.

3. A solid electrolyte comprising a compound represented by the following general formula (2). Li ｘ M' ｙ M'' ２－ｙ (PO ４ ) ｚ ...(2) (In the general formula (2), x represents a number satisfying 0.800 ≤ x ≤ 1.900; y represents a number satisfying 0.001 ≤ y ≤ 1.999; z represents a number satisfying 2.600 ≤ z ≤ 2.800, (M', M") is any of the following combinations: (Al, Ti), (Na, Ti), (Co, Ti), (Y, Ti), (Zr, Ti), (Al, Zr), (Al, Hf), (Al, Ge), (Al, Sn))

4. An all-solid-state battery comprising a solid electrolyte layer containing the solid electrolyte according to any one of Claims 1 to 3, a positive electrode joined to one surface of the solid electrolyte layer, and a negative electrode joined to the other surface of the solid electrolyte.

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