Oxide, method for producing same, solid electrolyte, and electricity storage device

Abstract

Provided are: a novel zirconium phosphate-based oxide having high Li conductivity; and a method for producing the zirconium phosphate-based oxide. Also provided are a solid electrolyte and a power storage device using the oxide. The present invention provides an oxide which satisfies the following formula (1). Li1 + x + y-zM1xZr2-xM2yM3zP3-y-zO12 (1) (In formula (1), M1 includes Fe or In, M2 includes Si, and M3 includes W; x > 0, y > = 0, z > = 0, and y + z > 0.

Description

Technical Field

[0001] The present invention relates to an oxide and a method for producing the same, a solid electrolyte and an electricity storage device. Background Art

[0002] As secondary batteries, various power storage devices such as nickel-hydrogen secondary batteries, lithium-ion secondary batteries, and electric double layer capacitors are put into practical use. Among them, demand for lithium-ion batteries (LIBs) is increasing due to their high energy density and battery capacity.

[0003] LIB has a negative electrode, a positive electrode and an electrolyte, and is a secondary battery that charges and discharges by moving lithium ions between the two electrodes via an electrolyte. The electrolyte generally uses an organic electrolyte, which is an organic electrolyte in which electrolyte salts such as LiPF6 are dissolved in a carbonate-based solvent. However, due to the use of flammable organic solvents, there is a problem that the possibility of fire during a short circuit cannot be ruled out. As a method that can solve this problem, a fully solid-state battery using a solid electrolyte with Li ion conductivity is being studied.

[0004] As for solid electrolytes having Li ion conductivity, sulfide-based solid electrolytes, polymer solid electrolytes, oxide-based solid electrolytes, etc. are known. Among them, oxide-based solid electrolytes are more stable in the atmosphere than sulfide-based solid electrolytes, and have better Li ion conductivity than polymer solid electrolytes. However, compared with sulfide-based solid electrolytes, oxide-based solid electrolytes have poor Li ion conductivity, and research on oxide-based solid electrolytes with better Li ion conductivity is underway.

[0005] As one of the oxide-based solid electrolytes, Li 1+x Al x Ti 2-x (PO4)3 (hereinafter also referred to as "LATP"), Li 1+x Al x Ge 2-x NASICON-type structure oxides such as (PO4)3 (hereinafter also referred to as "LAGP"), zirconium phosphate LiZr2(PO4)3 (hereinafter also referred to as "LZP"). It is known that LATP is at 2.45V (vs Li / Li + ) potential reduction. Therefore, when used as an electrolyte, the cell voltage of the battery cannot be increased, and the energy density is limited. In addition, it is known that LAGP is difficult to reduce compared to LATP, and its reduction resistance is not necessarily sufficient.

[0006] On the other hand, as disclosed in Patent Document 1, LZP has higher reduction resistance than LATP and LAGP, and is expected to be a highly stable electrolyte for all-solid batteries. However, LZP has a problem of low Li ion conductivity compared to LATP and LAGP, and improvement is needed. As shown in Patent Documents 2 to 4 listed below, studies have been conducted on improving the ion conductivity of zirconium phosphate.

[0007] Patent document 2 discloses a fully solid-state battery having a solid electrolyte material, wherein the main component of the solid electrolyte material is a lithium-containing zirconium phosphate compound (Patent document 2 [Claim 7]). Patent document 2 discloses a lithium-containing zirconium phosphate compound in which a portion of phosphorus is replaced by silicon (Patent document 2 [Claim 8]), triclinic LiZr2(PO4)3, monoclinic Li 1.3 Zr2(P 0.9 Si 0.1 O4)3 has an activation energy Ea of more than 50 kJ / mol and is therefore more preferred (Patent Document 2

[0063] ).

[0008] Patent Document 3 discloses a solid electrolyte whose main component is a zirconium phosphate compound containing lithium, and which exhibits high Li ion conductivity by substituting a part of zirconium element with indium or chromium element.

[0009] Patent Document 4 discloses a solid electrolyte of a lithium-containing phosphoric acid compound having a cubic crystal structure. In its examples, it is disclosed that zirconium phosphate doped with a specific element exhibits high Li ion conductivity. Prior art literature Patent Literature

[0010] Patent Document 1: International Publication No. 2011 / 065388 Patent Document 2: Japanese Patent Application Publication No. 2015-065021 Patent Document 3: Japanese Patent Application Laid-Open No. 04-160011 Patent Document 4: International Publication No. 2018 / 181674 Summary of the invention Technical problem to be solved by the invention

[0011] The electrolytes disclosed in Patent Documents 2, 3, and 4 are all electrolytes capable of imparting good Li ion conductivity, but the values ​​are insufficient compared to those of current lithium ion batteries and further improvement is required.

[0012] The present invention has been made in view of the above-mentioned actual situation, and its object is to provide a novel zirconium phosphate-based oxide showing high Li conductivity and a method for producing the same. Furthermore, its object is to provide a solid electrolyte and a power storage device using the oxide. Technical means to solve technical problems

[0013] The inventors of the present invention conducted intensive research to solve the above-mentioned problems and discovered the following insights, thereby completing the present invention: for zirconium phosphate [LiZr2(PO4)3]-based oxides, excellent Li ion conductivity is exhibited when Fe or In is doped at the Zr site and a specific element is doped at the P site.

[0014] The present invention is as follows. [1] An oxide, wherein the oxide satisfies the following formula (1). Li 1+x+y-z M1 x Zr 2-x M2 y M3 z P 3-y-z O 12 ···(1) (Wherein, in formula (1), M1 includes Fe or In, M2 includes Si, and M3 includes W; x, y, and z satisfy x>0, y≥0, z≥0, and y+z>0) [2] The oxide according to [1], wherein x ≤ 0.3 is satisfied. [3] The oxide according to [1] or [2], wherein y≤0.2 is satisfied. [4] The oxide according to any one of [1] to [3], wherein z ≤ 0.2 is satisfied. [5] The oxide according to any one of [1] to [4], wherein M1 includes Fe. [6] A solid electrolyte comprising the oxide according to any one of [1] to [5]. [7] The solid electrolyte according to [6], wherein the relative density of the solid electrolyte is 80% or more. [8] An electricity storage device comprising the solid electrolyte according to [6] or [7]. [9] A method for producing an oxide, the method being the method for producing an oxide according to any one of [1] to [5], wherein the method comprises: a mixing step of mixing a plurality of supply components in a manner satisfying the formula (1) to obtain a mixture of the supply components, wherein the supply components include one or more elements selected from the group consisting of Li, M1, M2, M3, Zr and P; and The firing step is to fire the mixture to obtain the oxide.

[10] The method for producing an oxide according to [9], wherein layered zirconium phosphate is used as a supply component for P and Zr.

[11] The method for producing an oxide according to [9] or

[10] , wherein the mixing is wet mixing.

[12] The method for producing an oxide according to any one of [9] to

[11] , wherein the calcining step includes a calcining step at 900° C. or higher. Beneficial Effects

[0015] According to the oxide of the present invention, high lithium ion conductivity can be obtained for a zirconium phosphate-based oxide. According to the solid electrolyte of the present invention, high lithium ion conductivity can be obtained for the zirconium phosphate-based oxide. According to the power storage device of the present invention, the zirconium phosphate-based oxide can be used as a solid electrolyte. According to the method for producing an oxide of the present invention, a zirconium phosphate-based oxide having high lithium ion conductivity can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [ Figure 1 ] Schematically shows an example (a) and another example (b) of an all-solid-state battery as a power storage device. DETAILED DESCRIPTION

[0017] Hereinafter, the present invention will be described in detail. In addition, unless otherwise clearly stated, "%" means "mass %", "part" means "mass part", "ppm" means "mass ppm", and "value X to value Y" means "value X or more and value Y or less". Furthermore, each of the embodiments described below may be an embodiment in which two or more of them are combined.

[0018] [1] Oxide The oxide of the present invention is characterized by satisfying the following formula (1). An oxide, wherein the oxide satisfies the following formula (1). Li 1+x+y-z M1 x Zr 2-x M2 y M3 z P 3-y-z O 12 ···(1) (Wherein, in formula (1), M1 includes Fe or In, M2 includes Si, and M3 includes W; x, y, and z satisfy x>0, y≥0, z≥0, and y+z>0)

[0019] In other words, the oxide can be said to be an oxide in which a portion of Zr is replaced by M1 (including Fe or In) and a portion of P is replaced by M2 (including Si) and / or M3 (including W) in an oxide based on LiZr2(PO4)3 (base, parent structure).

[0020] In the formula (1), x, y and z are not particularly limited as long as they satisfy x>0, y≥0, z≥0 and y+z>0. For example, when x>0, y>0 and z=0, formula (1) is expressed as “Li 1+x+y M1 x Zr 2-x M2 y P 3-y O 12 ”. In addition, for example, when x>0, y=0 and z>0, formula (1) is expressed as "Li 1+x-z M1 x Zr 2-x M3 z P 3-z O 12 ”. In addition, for example, when x>0, y>0 and z>0, formula (1) is expressed as "Li 1+x+y-z M1 x Zr 2- x M2 y M3 z P 3-y-z O 12 ”.

[0021] M1 includes Fe or In. In other words, it may include an element that becomes a trivalent cation other than Fe or In. Such an element includes elements that become trivalent cations in Group 13 elements, transition elements (Groups 3 to 11 elements), Sb, Bi, and the like.

[0022] M2 includes Si. In other words, it may include an element other than Si that becomes a tetravalent cation. Examples of such elements include Group 14 elements, elements that become tetravalent cations among transition elements (Group 3 to Group 11 elements), Te, and the like.

[0023] M3 includes W. In other words, an element that becomes a hexavalent cation other than W may be included. Examples of such an element include elements that become a hexavalent cation among transition elements (Group 3 to Group 11 elements) and Group 16 elements.

[0024] In formula (1), as described above, x, y and z satisfy x>0, y≥0, z≥0 and y+z>0. Furthermore, it is preferred to satisfy x≤0.3, and a better Li ion conductivity can be obtained compared with the case of x>0.3. It is believed that this is because the segregation of M1 can be suppressed by satisfying x≤0.3. As the content of M1 increases, it approaches the solid solubility limit to the Zr site, and begins to form an impurity phase containing more M1, which hinders Li ion conduction. In other words, even if the α phase with high Li ion conductivity is the dominant structure, the presence of the impurity phase will hinder Li ion conduction. Therefore, it is preferred that the composition is difficult to form an impurity phase. From this point of view, it is believed that the condition of x≤0.3 contributes. In addition, the presence or absence of M1 segregation can be detected by measuring the distribution of M1 using energy dispersive X-ray spectroscopy. In addition, M1 has a smaller valence than Zr, so the electrostatic repulsion with the univalent cation, i.e., Li ion, is smaller than that of Zr. Therefore, it is believed that by replacing Zr with M1, the diffusion of Li ions near M1 becomes easy to occur. On the other hand, if the amount of M1 substitution increases, the effect of hindering Li ion conduction caused by the capture of Li ions near M1 becomes significant. Therefore, it is believed that if the amount of M1 substitution increases, the ion conductivity deteriorates. From this point of view, it is believed that the condition of x≤0.3 contributes. Here, the upper limit of x preferably satisfies x ≤ 0.25. The lower limit of x preferably satisfies x ≥ 0.01, more preferably satisfies x ≥ 0.05, and even more preferably satisfies x ≥ 0.10.

[0025] Furthermore, it is preferred to satisfy y≤0.2, which can obtain better Li ion conductivity than the case of y>0.2. It is believed that Si is different from M1, and even if y>0.2 (for example, y=0.3), the solid solubility limit of Si will not be reached, and segregation will not occur (the presence or absence of Si segregation can be detected by measuring the distribution of Si using energy dispersive X-ray spectroscopy). On the other hand, compared with the α phase and / or α′ phase being stable phases in the range of 0<y≤0.2, it is observed that as the Si content increases, the β phase and / or β′ phase become stable phases. In other words, among the four phases (α phase, α′ phase, β and β′ phases) that zirconium phosphate-based oxides having a NASICON-type crystal structure are known to have, the α phase has high Li ion conductivity, and it can be said that 0<y≤0.2 is a dominant condition for the formation of the α phase. However, when y≤0.2 and y>0.2 are compared at the same firing temperature, the firing temperature required for the latter to form the α phase becomes higher. Therefore, it is considered that the defect caused by y>0.2 can be eliminated by increasing the firing temperature. However, from the viewpoint of energy cost during production, it is preferable that a high Li ion conductivity can be obtained at a lower firing temperature. In addition, M2 has a smaller valence than P, so the electrostatic repulsion with the univalent cation, i.e., Li ion, is smaller than P. Therefore, it is believed that by replacing P with M2, the diffusion of Li ions near M2 becomes easy to occur. On the other hand, if the amount of M2 substitution increases, the effect of hindering Li ion conduction caused by the capture of Li ions near M2 becomes significant. Therefore, it is believed that if the amount of M2 substitution increases, the ion conductivity deteriorates. From this point of view, it is believed that the condition of x≤0.3 contributes. Here, the upper limit of y preferably satisfies y≤0.15, and further preferably satisfies y≤0.10. In addition, the lower limit of y preferably satisfies y≥0.01, and further preferably satisfies y≥0.03.

[0026] In addition, further, it is preferred to satisfy z≤0.2, and better Li ion conductivity can be obtained compared with the case of z>0.2. It is believed that this is because the segregation of M3 can be suppressed. If the content of M3 increases, it will approach the solid solubility limit to the P site, and an impurity phase containing more M3 will begin to form, and the impurity phase will hinder Li ion conduction. In other words, even if the α phase with high Li ion conductivity is the dominant structure, the presence of the impurity phase will hinder Li ion conduction. Therefore, it is preferred that the composition is difficult to form an impurity phase. From this point of view, it is believed that the condition of z≤0.3 contributes. In addition, the presence or absence of segregation of M3 can be detected by measuring the distribution of M3 using energy dispersive X-ray spectroscopy. Here, the upper limit of z preferably satisfies z≤0.15, and further preferably satisfies z≤0.10. In addition, the lower limit of z preferably satisfies z≥0.01, and further preferably satisfies z≥0.03.

[0027] In the oxide represented by formula (1), the stoichiometric ratio of O is expressed as 12, but in practice, the value may be less than 12 or greater than 12 as long as the charge of the oxide as a whole is kept neutral. For example, when formula (1) is expressed as formula (2) as follows (M1, M2, M3, x, y and z are the same as those in formula (1)): Li 1+x+y-z M1 x Zr 2-x M2 y M3 z P 3-y-z O 12±α ···(2) For example, α can be set to 0≤α≤1.

[0028] In addition, the phase structure in the oxide of the present invention is not limited, and as a result, an oxide with high Li ion conductivity is preferred. Among them, it is preferably NASICON (Na Super Ionic Conductor) type. This is because the NASICON type has advantages in terms of utilization as a solid electrolyte. In other words, unlike a layered structure, the mobile space of the Li ions of the NASICON type is extended to three dimensions, and zirconium is also stable at high voltage, so it is useful as a solid electrolyte with a high operating voltage. In addition, whether or not the oxide of the present invention is of NASICON type can be determined based on the diffraction pattern obtained by powder X-ray diffraction measurement.

[0029] Furthermore, although the phase structure of the oxide of the present invention is not limited, it is preferred that the proportion of the α phase is high. This is because although the zirconium phosphate oxide can have four phases, namely, the α phase, the α′ phase, the β phase, and the β′ phase, the α phase has an isotropic crystal structure, so the Li ion conductivity becomes the highest. In addition, what phase the oxide of the present invention is in can be confirmed by X-ray diffraction measurement. Specifically, it can be confirmed by measurement in the examples described later.

[0030] From the viewpoint of obtaining more excellent Li ion conductivity, the relative density of the oxide of the present invention is preferably 80% or more, more preferably 85% or more, further preferably 90% or more, and further preferably 95% or more. Here, the relative density can be obtained by measuring the diameter, thickness and mass of the solid electrolyte, calculating the measured density from the measured values ​​of volume and mass, and then calculating the ratio (%) of the measured density to the theoretical density.

[0031] The use of the oxide of the present invention is not particularly limited, and it can be used, for example, as a material for a power storage device (material for an all-solid-state battery, various secondary battery materials, etc.), a CO2 sensor, etc. Specifically, there can be mentioned a solid electrolyte (solid electrolyte material) of an all-solid battery, an electrode (electrode material) of an all-solid battery, a separator, and the like.

[0032] [2] Method for producing oxide The oxide may be produced by any method, such as a solid phase method or a liquid phase method. In the present invention, the oxide may be produced by a solid phase method. More specifically, the oxide may be produced by a mixing step and a firing step.

[0033] In the above, the mixing step is a step of mixing a plurality of supply components in a manner satisfying the formula (1) to obtain a mixture of supply components, wherein the supply components include one or more elements selected from the group consisting of Li, M1, M2, M3, Zr and P. In the above, the firing step is a step of firing the mixture to obtain an oxide.

[0034] In the present method, the supply components of each element supplying Li, M1, M2, M3, Zr and P may be an inorganic compound or an organic compound. Among them, as the Li supply component, M1 supply component (Fe supply component or In supply component), M2 supply component (Si supply component), M3 supply component (W supply component), and Zr supply component, for example, carbonates, bicarbonates, sulfates, sulfites, nitrates, nitrites, phosphates, acetates, citrates, ammonium salts, oxides, hydroxides, chlorides, sulfides, etc. of these metal elements can be used. In addition, these supply components can be compounds in which one supply component contains two or more elements among Li, M1, M2, M3, and Zr.

[0035] On the other hand, as the P supply component, for example, a compound that does not contain one or more elements among Li, M1, M2, M3 and Zr, such as ammonium phosphate and ammonium hydrogen phosphate, can be used, but in the present invention, it is preferred to use a compound containing one or more elements among Li, M1, M2, M3 and Zr. Among them, in this method, it is preferred to use a zirconium phosphate compound as a supply component (a supply component of P and Zr).

[0036] Zirconium phosphate compounds include zirconium hydrogen phosphates such as Zr(HPO4)2 and Zr(HPO4)2·nH2O, zirconium phosphates such as Zr3(PO4)4, zirconium hydrogen phosphates such as Zr(PO4)(H2PO4) and Zr(PO4)(H2PO4)2·nH2O, and HZr2(PO4)3, ZrP2O7, (ZrO)2P2O7, etc. In addition, the above n is usually 0≤n≤2 (for example, n=1, n=1.5, n=2). In particular, Zr(HPO4)2·nH2O, which is called layered zirconium phosphate, is preferably used in the present invention. By using Zr(HPO4)2·nH2O, the burned product (also the pre-burned product) can be easily recovered after burning (also after pre-burning). That is, for example, ZrO2 and NH4H2PO4 can be used instead of Zr(HPO4)2·nH2O to obtain the oxide of the present invention, but if these supply components are used to manufacture the oxide of the present invention, the shape of the burned product (also the pre-burned product) changes during the burning process and adheres to the container, making it difficult to recover the burned product (also the pre-burned product), so the operability is poor. In contrast, if Zr(HPO4)2·nH2O is used as a supply component, the shape of the burned product (also the pre-burned product) hardly changes and does not adhere to the container, so the operability is excellent.

[0037] In addition, in the above-mentioned mixing process, several supply components are weighed in a manner that satisfies the formula (1) (i.e., in a manner that satisfies the stoichiometric ratio of the composition shown in formula (1)) and then the weighed objects are mixed, wherein the supply components contain one or more elements selected from Li, M1, M2, M3, Zr and P. Mixing can be performed by dry mixing, but it is preferred to use a liquid for wet mixing. Compared with the case of dry mixing, wet mixing can increase the density of the sintered body after firing, and can also relatively improve the Li ion conductivity. As the liquid used for wet mixing, water, various organic solvents, and mixtures thereof can be appropriately used.

[0038] In the firing step, the mixture obtained in the mixing step may be fired without being formed, or may be fired after being formed. The firing temperature is not limited, and can be, for example, 900° C. or higher, preferably 1000° C. or higher, more preferably 1100° C. or higher, further preferably 1150° C. or higher, further preferably 1200° C. or higher, and further further preferably 1250° C. or higher. Also, for example, it can be 1600° C. or lower, preferably 1500° C. or lower, more preferably 1400° C. or lower, further preferably 1350° C. or lower, and further preferably 1300° C. or lower.

[0039] Furthermore, firing can be performed in one stage or in multiple stages through pre-firing. That is, the temperature can be increased stepwise from a low temperature compared to the firing temperature, and finally the temperature required for firing can be applied. In addition, for each pre-firing, a pulverizing step of pulverizing the obtained pre-fired product can be performed. In the case of firing in multiple stages, for example, firing can be divided into 2 stages (first pre-firing at a temperature above 1000°C and below 1150°C, and formal firing at above 1150°C), firing can be divided into 3 stages (first pre-firing in a temperature range above 400°C and below 800°C, second pre-firing in a temperature range above 800°C and below 1200°C, and formal firing in a temperature range above 1200°C), or firing can be divided into 4 or more stages. In addition, the firing time is not limited. For example, the preliminary firing can be performed for 1 hour to 40 hours, and the main firing can be performed for 1 hour to 40 hours.

[0040] [3] Solid electrolyte The solid electrolyte of the present invention is characterized by containing the above-mentioned oxide. The amount of the oxide contained in the solid electrolyte is not limited. For example, if the content of the oxide is set to X mass%, it can be set to 0<X (mass%)≤100, wherein the content of the oxide is the content of the oxide when the solid electrolyte as a whole is set to 100 mass%. In addition, for example, it can be set to 50≤X (mass%)≤100, and can be set to 75≤X (mass%)≤100.

[0041] Although the solid electrolyte of the present invention has Li ion conductivity, it may include other oxides not represented by formula (1). As other solid electrolytes, for example, oxides with Li ion conductivity satisfying the following formula (3), oxides with Li ion conductivity satisfying the following formula (4), oxides with Li ion conductivity satisfying the following formula (5), oxides with Li ion conductivity satisfying the following formula (6), oxides with Li ion conductivity satisfying the following formula (7), etc. can be cited. They can be used only one kind, or two or more kinds can be used in combination.

[0042] Li 1+2x+y M1 x M2 y Zr 2-x-y P3O 12 ···(3) (Wherein, in formula (3), M1 is a divalent metal, M2 is a trivalent metal, and x and y satisfy x≥0, y≥0, and x+y>0) Li 1+z Zr2Si z P 3-z O 12 ···(4) (Wherein, in formula (4), z>0 is satisfied) Li 1+2x+y+z M1 xM2 y Zr 2-x-y M3 z P 3-z O 12 ···(5) (Wherein, in formula (5), M1 is a divalent metal, M2 is a trivalent metal, M3 is a tetravalent element, and x, y and z satisfy x≥0, y≥0, z>0 and x+y>0) Li 1+x+z M2 x M4 y Zr 2-x-y M3 z P 3-z O 12 ···(6) (Wherein, in formula (6), M2 is a trivalent metal, M3 is a tetravalent element, M4 is a tetravalent element other than Si, and x, y and z satisfy x≥0, y≥0, z>0 and x+y>0) Li 1+x-y+z M2 x M5 y Zr 2-x-y M3 z P 3-z O 12 ···(7) (Wherein, in formula (7), M2 is a trivalent metal, M3 is a tetravalent element, M5 is a pentavalent element, and x, y and z satisfy x≥0, y≥0, z>0 and x+y>0) In addition, M1 in the above formula (3) and formula (5) can be applied to divalent non-metallic elements and divalent metal elements. In addition, M2 in the above formula (3) and formula (5) to formula (7) can be applied to trivalent non-metallic elements and trivalent metal elements. In addition, M3 in the above formula (5) to formula (7) can be applied to tetravalent non-metallic elements and tetravalent metal elements. In addition, M4 in the above formula (6) can be applied to tetravalent non-metallic elements and tetravalent metal elements other than Si. In addition, M5 in the above formula (7) can be applied to pentavalent non-metallic elements and pentavalent metal elements.

[0043] [4] All-solid-state batteries The all-solid-state battery 1 of the power storage device of the present invention is an all-solid-state battery characterized by comprising the above-mentioned solid electrolyte 23 (solid electrolyte layer) (refer to Figure 1 ). Generally, the all-solid-state battery 1 includes a positive electrode 22 (positive electrode layer) and a negative electrode 24 (negative electrode layer) in addition to the solid electrolyte 23. The all-solid-state battery may be a block type (see Figure 1 (a)), or a thin film type (refer to Figure 1 (b)).

[0044] The all-solid-state battery 1 is a block type (refer to Figure 1 (a)), the positive electrode 22 and the negative electrode 24 can be arranged opposite to each other with the solid electrolyte 23 interposed therebetween. In addition, the positive electrode 22 and the negative electrode 24 are each arranged in contact with the solid electrolyte 23. For example, the all-solid-state battery 1 can include the solid electrolyte 23, the positive electrode 22 and the negative electrode 24 as an integral sintered body. More specifically, in the case where the solid electrolyte 23 (solid electrolyte layer) has the properties and state of having two main surfaces (i.e., in the case of a plate-like body, a film-like body, a sheet or a film, etc.), it can be a structure in which the positive electrode 22 is provided on one main surface and the negative electrode 24 is provided on the other main surface with the solid electrolyte 23 interposed therebetween.

[0045] The positive electrode generally contains a positive electrode active material, and may also contain, for example, one or more of a conductive material, a solid electrolyte, a binder, and the like. Similarly, the negative electrode also generally contains a negative electrode active material, and may also contain, for example, one or more of a conductive material, a solid electrolyte, a binder, and the like. In addition, each electrode may include a current collector. That is, the positive electrode 22 may include a positive electrode current collector 21 on the surface not in contact with the solid electrolyte 23. Similarly, the negative electrode 24 may include a negative electrode current collector 25 on the surface not in contact with the solid electrolyte 23.

[0046] In the all-solid-state battery 1, a thin-film type (refer to Figure 1 In the case of (b)), the positive electrode 22 and the negative electrode 24 may be separately arranged so that a portion of each is in contact with the solid electrolyte 23. For example, the all-solid-state battery 1 may include a single sintered body in which the layers are stacked in the order of the negative electrode 24, the solid electrolyte 23, and the positive electrode 22. When the all-solid-state battery 1 is a thin film type, similarly to the block type, the positive electrode generally contains a positive electrode active material, and may also contain one or more of, for example, a conductive material, a solid electrolyte, a binder, etc., and the negative electrode generally contains a negative electrode active material, and may also contain one or more of, for example, a conductive material, a solid electrolyte, a binder, etc. In addition, each electrode may have a current collector. Example

[0047] 《Manufacturing of Oxides》 (1) Embodiment 1 As supply components, 4.684 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 0.801 g of zirconium hydroxide, 0.413 g of lithium carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 0.032 g of silicon dioxide, and 0.008 g of iron (III) oxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) were weighed respectively in a manner to obtain a molar ratio shown in Example 1 of Table 1 (Li:Fe:Zr:P:Si=1.06:0.01:1.99:2.95:0.05), and each sample was put into a mortar, and 25 g of pure water was added for wet mixing to obtain a mixture. The obtained mixture was dried at 100°C for 2 hours, transferred to an alumina crucible (capacity 30 mL), heated to 1100°C over 5.5 hours, and maintained for 5 hours for first pre-firing. Thereafter, it was left to cool to room temperature to obtain a first pre-firing product. The first pre-fired product obtained is crushed in a mortar, and 0.3 g of the crushed product of the first pre-fired product is placed in a mold with a diameter of 1.2 cm, and a load of 1 t is applied by a hydraulic press to form a coin. The molded product is placed on a platinum plate, and the temperature is raised to 800°C in 30 minutes, and then further raised to 1300°C in 2 hours, and maintained for 6 hours for formal firing. After that, it is allowed to cool to room temperature to obtain the oxide of Example 1. In addition, in the examples of this specification, the value of n in Zr(HPO4)2·nH2O is set to n=1.0. The same applies below.

[0048] (2) Example 2 to Example 15 As in the case of Example 1, the samples were weighed so as to have the molar ratios shown in Examples 2 to 15 in Table 1, and each sample was put into a mortar, and 25 g of pure water was added for wet mixing to obtain a mixture. The obtained mixture was pre-fired and fired under the same conditions as in Example 1 to obtain oxides of Examples 2 to 15. In addition, for Example 2, Example 3 and Example 5, the first pre-fired product was molded into a coin shape in the same manner as Example 1, and the obtained molded product was placed on a platinum plate, and the temperature was raised to 800°C in 30 minutes, and then the temperature was raised to 1170°C, 1200°C, and 1350°C in 2 hours and maintained for 6 hours, respectively, for main firing. Thereafter, the product was left to cool to room temperature, and the oxides of Example 2, Example 3 and Example 5 were obtained. In Examples 10 to 12, indium (III) oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as a raw material of indium. In Example 15, tungsten (VI) oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as a raw material of tungsten.

[0049] (3) Comparative Example 1 As the supply components, 4.762 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 0.778 g of zirconium oxide, and 0.389 g of lithium carbonate were weighed respectively in a molar ratio (Li:Zr:P=1.00:2.00:3.00) as shown in Comparative Example 1 of Table 1, and each sample was put into a mortar, and 25 g of pure water was added for wet mixing to obtain a mixture. The obtained mixture was subjected to the same treatment as in Example 1 to obtain the oxide of Comparative Example 1.

[0050] (4) Comparative Example 2 4.777 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 0.702 g of zirconium oxide, 0.410 g of lithium carbonate, and 0.042 g of iron (III) oxide were weighed respectively so as to obtain a molar ratio (Li:Fe:Zr:P=1.05:0.05:1.95:3.00) as shown in Comparative Example 2 of Table 1, and each sample was put into a mortar, and 25 g of pure water was added for wet mixing to obtain a mixture. The obtained mixture was subjected to the same treatment as in Example 1 to obtain the oxide of Comparative Example 2.

[0051] (5) Comparative Example 3 4.747 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 0.698 g of zirconium oxide, 0.408 g of lithium carbonate, and 0.073 g of indium (III) oxide were weighed respectively so as to obtain a molar ratio (Li:In:Zr:P=1.05:0.05:1.95:3.00) as shown in Comparative Example 3 of Table 1, and each sample was put into a mortar, and 25 g of pure water was added for wet mixing to obtain a mixture. The obtained mixture was subjected to the same treatment as in Example 1 to obtain the oxide of Comparative Example 3.

[0052] (6) Comparative Example 4 4.681 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 0.816 g of zirconium oxide, 0.409 g of lithium carbonate, and 0.032 g of silicon dioxide were weighed respectively so as to obtain a molar ratio (Li:Zr:Si:P=1.05:2.00:0.05:2.95) shown in Comparative Example 4 of Table 1, and each sample was put into a mortar, and 25 g of pure water was added for wet mixing to obtain a mixture. The obtained mixture was subjected to the same treatment as in Example 1 to obtain the oxide of Comparative Example 4.

[0053] (7) Comparative Example 5 4.612 g of layered zirconium phosphate (Zr(HPO4)2·nH2O), 0.804 g of zirconium oxide, 0.364 g of lithium carbonate, and 0.120 g of tungsten (VI) oxide were weighed respectively so as to obtain a molar ratio (Li:Zr:W:P=0.95:2.00:0.05:2.95) shown in Comparative Example 5 of Table 1, and each sample was put into a mortar, and 25 g of pure water was added for wet mixing to obtain a mixture. The obtained mixture was subjected to the same treatment as in Example 1 to obtain the oxide of Comparative Example 5.

[0054] 《Explanation of Evaluation Methodology》 (1) Determination of relative density The relative density of each oxide of Examples 1 to 15 and Comparative Examples 1 to 5 was calculated, and the results are shown in Table 1. The calculation method is as follows. The diameter, thickness and mass of the oxide produced above were measured, and the measured density was calculated from the measured values ​​of volume and mass. Then, the relative density was calculated by calculating the ratio (%) of the measured density to the theoretical density.

[0055] (2) Confirmation of crystal phase The main crystal phase of each oxide of Examples 1 to 15 and Comparative Examples 1 to 5 was confirmed by X-ray diffraction (XRD) measurement, and the results are shown in Table 1. The XRD measurement conditions are as follows. X-ray diffraction measuring apparatus: D8ADVANCE manufactured by Bruker AXS Characteristic X-ray: CuKα Test voltage: 40kV Measuring current: 40mA Measurement method: Continuous Measuring range: 10°≤2θ≤80° Step size: 0.01° Scanning speed: 2.5° / min

[0056] Then, the crystal phase data of LiZr2(PO4)3 included in the Inorganic Crystal Structure Database (ICSD) (i.e., ICSD: 201935 (α phase); ICSD: 89456 (α′ phase); ICSD: 91113 (β phase); ICSD: 91112 (β′ phase)) and analysis software (manufactured by BRUKER, trade name "DIFFRAC.TOPAS") were used to confirm the crystal phases generated by the various oxides of Examples 1 to 15 and Comparative Examples 1 to 5, and the results are recorded in Table 1. In Table 1, the notation "α" indicates that the main crystal phase is the α phase, and the notation "β'" indicates that the main crystal phase is the β' phase.

[0057] (3) Evaluation of ionic conductivity (3-1) Formation of current collector layer By masking with a polyimide tape, a circular exposed surface with a diameter of 6 mm is formed at the center of both sides of each oxide (coin-shaped sintered particles) obtained in the above-mentioned Examples 1 to 15 and Comparative Examples 1 to 5. Thereafter, a collector layer is formed on the above-mentioned exposed surface by sputtering. The collector layer is formed into a gold (Au) layer with a thickness of about 50 nm. A gold vapor deposition device (manufactured by EIKO Corporation, ion plating machine IB-2 / IB-3) was used for sputtering.

[0058] (3-2) AC impedance measurement In the above (3-1), the AC impedance of each oxide of Examples 1 to 15 and Comparative Examples 1 to 5 forming the current collector layer was measured, and complex impedance curves were prepared. Using an impedance analyzer (Keysight, model "E4990A") or a Multi-Potentiostat / Galvanostat equipped with FRA (Frequency Response Analyzer) (Biologic, model "VMP3"), the measurements were performed at a frequency of 20 Hz to 120 MHz, a voltage of 10 mV, and a temperature of 25°C or a frequency of 1 Hz to 1 MHz, a voltage of 10 mV, and a temperature of 25°C for Examples 1 to 15 and Comparative Examples 1 to 5.

[0059] (3-3) Calculation of ionic conductivity The terminal value at the right end of the arc in the complex impedance curve obtained by (3-2) above was taken as the resistance R of each oxide (the sum of the intracrystalline and grain boundary resistances), and the ion conductivity σ (Li ion conductivity) was calculated using the following formula. The results are shown in Table 1. σ=(t / A)×(1 / R) σ: ionic conductivity t: sample thickness A: Electrode area R: Oxide resistance

[0060] (3-4) Calculation of intracrystalline ionic conductivity In the complex impedance curves of Examples 1 to 15 and Comparative Examples 1 to 5 obtained by (3-2) above, for the example of a waveform with two arcs confirmed, the diameter of the first arc is taken as the intracrystalline resistance (Rb), and the intracrystalline ion conductivity σb (intracrystalline Li ion conductivity) is calculated using the following formula. The results are shown below and are also recorded in Table 1. σb=(t / A)×(1 / Rb) σb: ionic conductivity t: sample thickness A: Electrode area Rb: Intracrystalline resistance

[0061] [Table 1]

[0062] 《Evaluation Results》 From the results of Examples 1 to 15, it is understood that the oxide of the present invention is an oxide having excellent Li ion conductivity. Among them, attention was paid to the doping element for Zr. The result showed that when Fe was doped (Example 1, Example 4, Example 6 to Example 9), the Li ion conductivity was more excellent as the substitution ratio x approached 0.15. In addition, when In is doped (Example 10, Example 11), the Li ion conductivity becomes maximum when the substitution ratio x is 0.20. Furthermore, focusing on the main firing temperature (Example 2 to Example 5), the ion conductivity was the most excellent when fired at 1300°C.

[0063] In contrast, the Li ion conductivity of each oxide without doping (Comparative Example 1), only doping with Zr (Comparative Example 2, Comparative Example 3), and only doping with P (Comparative Example 4, Comparative Example 5) is lower than that of Examples 1 to 15, resulting in poor practicality. From the above results, it is understood that by doping both Zr and P with the specific element of the present invention, higher Li ion conductivity is exhibited. Explanation of symbols

[0064] 1: All-solid-state battery 21: Current collector (positive electrode current collector) 22: Positive electrode 23: Solid Electrolyte 24: Negative electrode 25: Current collector (negative electrode current collector) 26: Substrate

Claims

1. An oxide, wherein The oxide satisfies the following formula (1): <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 1+x+y-z <h2 style=";text-align:left;direction:ltr"> M1<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> Zr<h2 style=";text-align:left;direction:ltr"> 2-x <h2 style=";text-align:left;direction:ltr"> M2<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> M3<h2 style=";text-align:left;direction:ltr"> z <h2 style=";text-align:left;direction:ltr"> P<h2 style=";text-align:left;direction:ltr"> 3-y-z <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 12 <h2 style=";text-align:left;direction:ltr"> ···(1) Wherein, in formula (1), M1 includes Fe or In, M2 includes Si, and M3 includes W; and x>0, y≥0, z≥0 and y+z>0 are satisfied.

2. The oxide according to claim 1, wherein Satisfies x≤0.

3.

3. The oxide according to claim 1, wherein Satisfies y≤0.

2.

4. The oxide according to claim 1, wherein Satisfies z≤0.

2.

5. The oxide according to claim 2, wherein The M1 includes Fe.

6. A solid electrolyte, wherein: The solid electrolyte includes the oxide according to any one of claims 1 to 5.

7. The solid electrolyte according to claim 6, wherein The relative density of the solid electrolyte is above 80%.

8. An electric storage device, wherein: The power storage device comprises the solid electrolyte according to claim 7.

9. A method for producing an oxide, the method being the method for producing an oxide according to claim 1, wherein: The manufacturing method comprises: a mixing step of mixing a plurality of supply components in a manner satisfying the formula (1) to obtain a mixture of the supply components, wherein the supply components include one or more elements selected from the group consisting of Li, M1, M2, M3, Zr and P; and The firing step is to fire the mixture to obtain the oxide.

10. The method for producing an oxide according to claim 9, wherein: As a supply component of P and Zr, layered zirconium phosphate is used.

11. The method for producing an oxide according to claim 9, wherein: The mixing is wet mixing.

12. The method for producing an oxide according to any one of claims 9 to 11, wherein The firing step includes a step of firing at 900° C. or higher.

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