Composite material and electrochemical device

Abstract

Provided is a substance comprising: a solid electrolyte (150) containing a halogen element and having defects in the crystal structure thereof; and one or more oxides (160) that are in contact with at least a part of the particle surface of the solid electrolyte and have a composition different from that of the solid electrolyte. The oxide is a substance represented by at least one of compositional formulae DVEYOZ and EYOZ. In the formulae, D and E each represent one or more elements; D represents an alkali metal or an alkaline earth element; E represents a transition metal of Groups 3 to 6 or an element of Groups 13 to 16; and V, Y, and Z each represent an arbitrary number.

Description

Composite Material and Electrochemical Device Cross - reference to Related Applications

[0001] This application is based on Japanese Patent Application No. 2025 - 8488 filed on January 21, 2025, the content of which is incorporated herein by reference.

[0002] This disclosure relates to a composite material and an electrochemical device.

[0003] Patent Document 1 discloses an ion - conductive solid electrolyte containing a halogen element and having a defect structure. This solid electrolyte has a crystal structure represented by the composition formula Aa ２－α Ab （１＋α）／３ B ２ O ７－β X γ and has a three - dimensional network of octahedrons composed of BO ６ and forms a tunnel structure in which cations composed of Aa and Ab and a halogen element composed of X are arranged.

[0004] Japanese Patent No. 7334813

[0005] However, the halogen element contained in the solid electrolyte exists as a weak conjugate with Aa / Ab in the tunnel structure, and since the solid electrolyte contains a defect structure and is in an unstable state, the halogen element is likely to desorb. Therefore, when the solid electrolyte described in Patent Document 1 is heat - formed, the halogen element may desorb, and the ionic conductivity of the solid electrolyte may decrease.

[0006] In view of the above, an object of this disclosure is to suppress the desorption of a halogen element from a solid electrolyte containing a halogen element and having a defect structure.

[0007] To achieve the above object, the composite material of this disclosure includes a solid electrolyte containing a halogen element and having defects in the crystal structure, and one or more oxides that are in contact with at least a part of the particle surface of the solid electrolyte and have a composition different from that of the solid electrolyte. The oxide has a composition formula of D Ｖ E Ｙ O Ｚ or E Ｙ O ＺA substance represented by at least one of the following: where D is an alkali metal or alkaline earth element, E is a transition metal of groups 3-6 or an element of groups 13-16, D and E are each one or more types of elements, and V, Y, and Z are any number.

[0008] According to the composite material of this disclosure, the composite material has an oxide in contact with at least a portion of the solid electrolyte, which can suppress the detachment of halogen elements from the solid electrolyte during heating and suppress the decrease in the ionic conductivity of the solid electrolyte.

[0009] This is a cross-sectional view showing the configuration of the secondary battery according to the first embodiment. This is a diagram showing the crystal structure of the pyrochlore-type solid electrolyte. This is a diagram showing the manufacturing process of the pyrochlore-type solid electrolyte. This is a diagram showing the molding process and heating process of the composite material. This is a chart showing the type of solid electrolyte, the type of oxide, and the amount of decomposition products produced in the examples and comparative examples. This is a diagram showing the relative density when the oxide content and sintering temperature of the composite material are changed. This is a diagram showing the ionic conductivity when the oxide content and sintering temperature of the composite material are changed. This is a cross-sectional view showing the configuration of the secondary battery according to the second embodiment. This is a cross-sectional view showing the configuration of the secondary battery according to the third embodiment.

[0010] Several embodiments for implementing this disclosure are described below with reference to the drawings. In each embodiment, parts corresponding to matters described in a preceding embodiment may be denoted by the same reference numerals, and redundant explanations may be omitted. If only a part of the configuration is described in each embodiment, other parts of the configuration can be applied to other embodiments described in advance. Not only are combinations of parts that are explicitly shown to be combinable in each embodiment possible, but embodiments can also be partially combined even if not explicitly shown, as long as there are no particular problems with the combination.

[0011] (First Embodiment) Hereinafter, embodiments of the solid electrolyte for secondary batteries of the present disclosure applied to a lithium-ion battery will be described with reference to the drawings. The secondary battery 10 of this first embodiment is a lithium-ion battery in which charging and discharging are performed by lithium ions moving between the negative electrode layer 12 and the positive electrode layer 14 as conductive ions.

[0012] As shown in Figure 1, the secondary battery 10 comprises a negative electrode current collector 11, a negative electrode layer 12, a positive electrode current collector 13, a positive electrode layer 14, and an electrolyte layer 15. These layers 11 to 15 are arranged in a stacked configuration. The secondary battery 10 corresponds to an electrochemical device, the positive electrode layer 14 corresponds to the first electrode layer, and the negative electrode layer 12 corresponds to the second electrode layer.

[0013] An electrolyte layer 15 is sandwiched between a negative electrode layer 12 and a positive electrode layer 14. The negative electrode layer 12 and the positive electrode layer 14 are in contact with the electrolyte layer 15, and the negative electrode layer 12 and the positive electrode layer 14 are connected via the electrolyte layer 15. The secondary battery 10 of this first embodiment is a lithium-ion battery cell in which charging and discharging are performed by lithium ions moving between the negative electrode layer 12 and the positive electrode layer 14 via the electrolyte layer 15.

[0014] A laminate containing the negative electrode layer 12, the positive electrode layer 14, and the electrolyte layer 15 is provided between the negative electrode current collector 11 and the positive electrode current collector 13. The negative electrode current collector 11 is in contact with the negative electrode layer 12. The positive electrode current collector 13 is in contact with the positive electrode layer 14. The negative electrode current collector 11 and the positive electrode current collector 13 are connected via the laminate.

[0015] The negative electrode current collector 11 and the positive electrode current collector 13 can be made of any material suitable for use as a current collector in a lithium-ion battery. In this first embodiment, Cu is used as the negative electrode current collector 11 and Al is used as the positive electrode current collector 13.

[0016] The negative electrode layer 12 contains a negative electrode active material 120. The negative electrode active material 120 can be any material that can be used as a negative electrode active material for lithium-ion batteries, such as carbon-based negative electrode materials, oxide-based negative electrode materials, or metal-based negative electrode materials. These negative electrode materials may be used individually or in combination.

[0017] As carbon-based anode materials, for example, natural graphite, artificial graphite, and hard carbon can be used. As oxide-based anode materials, for example, Li ４ Ti ５ O １２ , TiO ２ (B), TiNb ２ O ７For example, silicon-based anode materials and lithium metal can be used as metallic anode materials.

[0018] The negative electrode layer 12 may contain a conductive additive, a binder, and a polymer. The conductive additive can be, for example, a carbon material such as carbon black. As the binder, an aqueous binder such as a mixture of SBR (styrene-butadiene rubber) and CMC (carboxymethylcellulose) can be used. Furthermore, the negative electrode layer 12 may contain a solid electrolyte.

[0019] The positive electrode layer 14 contains a positive electrode active material 140. The positive electrode active material 140 can be any material that can be used as a positive electrode active material for lithium-ion batteries. The positive electrode layer 14 may also contain a conductive additive and a binder. Furthermore, the positive electrode layer 14 may contain an electrolyte and a polymer. As the binder contained in the positive electrode layer 14, for example, an organic binder can be used. As an organic solvent binder, for example, polyvinylidene fluoride (PVdF), an acrylic binder, a urethane binder, etc. can be used. Furthermore, the positive electrode layer 14 may also contain a solid electrolyte.

[0020] As the positive electrode active material 140, for example, a layered active material, a spinel-type active material, or an olivine-type active material can be used. As a layered active material, for example, LiCoO ２ (LCO), LiNiO ２ (LNO), LiNi ０．８ Co ０．１５ Al ０．０５ O ２ (NCA), LiNi ０．８ Co ０．１ Mn ０．１ O ２ (NCM811), LiNi ０．３３ Mn ０．３３ Co ０．３３ O ２ Such ternary cathode materials can be used. For example, LiMn ２ O ４ LiNi ０．５ Mn １．５ O ４For example, LiMn can be used as an olivine-type active material. ０．８ Fe ０．２ PO ４ (LMFP), LiFePO ４ (LFP) can be used.

[0021] The electrolyte layer 15 is provided in direct contact with the negative electrode layer 12 and the positive electrode layer 14. The electrolyte layer 15 contains an electrolyte material that has lithium ion conductivity. The electrolyte material of the electrolyte layer 15 has ion conductivity and can move lithium ions between the negative electrode layer 12 and the positive electrode layer 14.

[0022] In this first embodiment, the electrolyte material of the electrolyte layer 15 includes a composite material 100. The electrolyte layer 15 may also contain a binder. Furthermore, the electrolyte layer 15 may also contain an electrolyte solution and a polymer. The electrolyte solution can be, for example, ethylene carbonate. The electrolyte solution may also be an ionic liquid. As the polymer, for example, polyethylene oxide can be used.

[0023] The composite material 100 contains a solid electrolyte 150 and an oxide 160. In this first embodiment, the composite material 100 is formed in particulate form, and the oxide 160 is supported on the surface of the solid electrolyte 150.

[0024] The solid electrolyte 150 and the oxide 160 are substances with different chemical compositions. In other words, the composite material 100 is composed of a material containing multiple different materials.

[0025] The solid electrolyte 150 is an oxide-based solid electrolyte containing halogen elements and having defects in its crystal structure. The oxide-based solid electrolyte constituting the solid electrolyte 150 has lithium ion conductivity.

[0026] Examples of oxide-based solid electrolytes that can be used include pyrochlore-type solid electrolytes, perovskite-type solid electrolytes, and fluorite-type solid electrolytes. In this first embodiment, a pyrochlore-type solid electrolyte is used as the solid electrolyte 150. The pyrochlore-type solid electrolyte in this first embodiment has the compositional formula "Aa ２－α Ab（１＋α）／３ B ２ O ７－β X γ This is an oxide-based solid electrolyte having a pyrochlore structure, which will be explained in detail later.

[0027] The oxide 160 is provided to suppress the desorption of halogen elements from the solid electrolyte 150 when the composite material 100 is heated. It is sufficient that at least a portion of the oxide 160 is in contact with the solid electrolyte 150. The larger the contact area of ​​the oxide 160 with the solid electrolyte 150, the greater the effect of suppressing the desorption of halogen elements.

[0028] In this first embodiment, the oxide 160 coats the surface of the solid electrolyte 150. This increases the contact area between the oxide 160 and the solid electrolyte 150, thereby enhancing the effect of suppressing the detachment of halogen elements from the solid electrolyte 150 by the oxide 160. The oxide 160 only needs to coat at least a portion of the solid electrolyte 150, or it may coat the entire surface of the solid electrolyte 150.

[0029] The coverage of the solid electrolyte 150 with oxide 160 is preferably at least 5%, more preferably 10%, and even more preferably 30%. To enhance the effect of suppressing the desorption of halogen elements from the solid electrolyte 150, it is desirable to make the coverage of the solid electrolyte 150 with oxide 160 as high as possible. From this viewpoint, the coverage of the solid electrolyte 150 with oxide 160 is preferably 50% or higher, and more preferably 70% or higher.

[0030] The coverage rate of the solid electrolyte 150 by oxide 160 is the percentage of the surface area of ​​the solid electrolyte 150 that is covered by oxide 160. The coverage rate of the solid electrolyte 150 by oxide 160 can be measured, for example, by cutting the particles of the composite material 100 using ion milling or the like, and using an elemental mapping image of the SEM image of the particle cross-section.

[0031] If the content of oxide 160 in the composite material 100 is too low, material decomposition will occur due to halogen volatilization of the solid electrolyte 150, and the volatilization of oxide 160 itself will also become significant. For this reason, it is desirable that the content of oxide 160 in the composite material 100 be 0.2 wt% or more, and more preferably 0.5 wt% or more. On the other hand, if the content of oxide 160 in the composite material 100 is too high, the ionic conductivity of the composite material 100 will decrease. For this reason, it is desirable that the content of oxide 160 in the composite material 100 be 20 wt% or less, and more preferably 15 wt% or less.

[0032] Furthermore, by setting the content of oxide 160 in the composite material 100 to a specific range, the relative density of the composite material 100 can be improved. From the viewpoint of improving the relative density of the composite material 100, it is desirable that the content of oxide 160 in the composite material 100 be 0.5 to 2 wt%.

[0033] The oxide 160 is a substance containing oxygen atoms and has a different chemical composition from the solid electrolyte 150. One or more types of substances can be used for the oxide 160.

[0034] For example, the oxide 160 is a composite oxide D Ｖ E Ｙ O Ｚ Alternatively, E is a simple oxide. Ｙ O Ｚ At least one of the following can be used. D and E are each one or more types of elements, where D is an alkali metal or alkaline earth element, and E is a transition metal of groups 3-6 or an element of groups 13-16. V, Y, and Z are any number. D and E may be composed of multiple elements.

[0035] Oxide 160 includes Li-containing oxides and Li-free oxides. Examples of Li-containing oxides include Li ３ PO ４ Li ３ BO ３ Li ２ CO ３ Li ２ SO４ Li ２ ZrO ３ Li ２ WO ４ LiNO ３ LiNbo ３ At least one of these can be used. These Li-containing oxides are D Ｖ E Ｙ O Ｚ For example, LaNboO is a Li-free oxide. ４ , B ２ O ３ Al ２ O ３ Ga ２ O ３ , GeO ２ SiO ２ , ZrO ２ , Y ２ O ３ WO ３ At least one of these can be used. These Li-free oxides are E Ｙ O Ｚ That is the case.

[0036] The oxide constituting the oxide 160 is preferably a material that is chemically stable with respect to the solid electrolyte 150 and has low reactivity with the solid electrolyte 150. By using an oxide 160 that is chemically stable with respect to the solid electrolyte 150, halogen desorption from the solid electrolyte 150 can be effectively suppressed.

[0037] The oxide 160 is preferably at a lower melting point than the solid electrolyte 150, and preferably at a lower melting point than the heating temperature of the composite material 100. The heating temperature of the composite material 100 can be, for example, 800 to 1000°C.

[0038] By using a low-melting-point oxide 160, the oxide 160 melts more easily when the composite material 100 is heated, increasing the contact area between the solid electrolyte 150 and the oxide 160, and thus increasing the coating area of ​​the solid electrolyte 150 by the oxide 160. As a result, the effect of suppressing the desorption of halogen elements from the solid electrolyte 150 by the oxide 160 is enhanced.

[0039] Examples of the oxide 160 having a melting point lower than that of the solid electrolyte 150 include Li-containing oxides. For example, Li ３ PO ４ has a melting point of 830 °C, Li ３ BO ３ has a melting point of 700 °C, Li ２ CO ３ has a melting point of 720 °C, Li ２ SO ４ has a melting point of 850 °C, Li ２ ZrO ３ has a melting point of 730 °C, Li ２ WO ４ has a melting point of 742 °C, and LiNO ３ has a melting point of 253 °C.

[0040] The oxide 160 can be used in combination of two or more kinds. By using a combination of a plurality of oxides as the oxide 160, the melting point of the oxide 160 can be lowered by a eutectic reaction. As a combination of the oxides constituting the oxide 160, for example, WO ３ -Al ２ O ３ , LiNO ３ -Al ２ O ３ and the like can be used.

[0041] When a Li-free oxide is used as the oxide 160, Li contained in the solid electrolyte 150 diffuses into the oxide 160 during firing. The oxide 160 reacts with Li to lower its melting point, and it can be expected to melt at a temperature lower than its original melting point.

[0042] It is desirable to use a material that is stable at the positive electrode potential and the negative electrode potential for the oxide 160. The secondary battery 10 of the first embodiment has a potential window of 0 to 5 V (V vs. Li ＋ / Li), and if it is a material that is stable within this potential range, the secondary battery 10 containing the oxide 160 can be used stably. As the oxide 160 that is stable at the positive electrode potential and the negative electrode potential, for example, Li ３ PO ４ , Li ３ BO ３ , Li[[ID=******]] ２ CO ３ can be used.

[0043] It is desirable that the oxide 160 has ionic conductivity. The ionic conductivity of the oxide 160 can be improved, thereby improving the output characteristics of the secondary battery 10. A higher ionic conductivity of the oxide 160 is desirable; specifically, an ionic conductivity of 10 is desirable. －８ It is desirable that the ionic conductivity be 10 / cm or higher. －８ For example, Li ３ PO ４ Li ３ BO ３ Li ２ WO ４ Li ２ CO ３ -Li ３ BO ３ One could list these:

[0044] Furthermore, the oxide 160 functions as an elemental diffusion barrier layer. For example, when the composite material 100 and the positive electrode active material 140 are heated in contact, the oxide 160 can suppress the diffusion of elements contained in the solid electrolyte 150 into the positive electrode active material 140, and can also suppress the diffusion of elements contained in the positive electrode active material 140 into the solid electrolyte 150. This suppresses the generation of by-products associated with elemental diffusion between the positive electrode active material 140 and the solid electrolyte 150.

[0045] Here, we will explain the pyrochlore-type solid electrolyte used as solid electrolyte 150. The pyrochlore-type solid electrolyte has the composition formula "Aa ２－α Ab （１＋α）／３ B ２ O ７－β X γIt has a pyrochlore structure represented by the above compositional formula. In the above compositional formula, O is an oxygen atom, and Aa, Ab, B, and X represent any element or group. Aa, Ab, and B are each different types of cations, O and X are each different types of anions, and X is a halogen element. Aa is an alkali metal cation. Pyrochlore-type solid electrolytes contain multiple cations in their composition, consisting of an alkali metal cation Aa and multiple cations Ab and B other than the alkali metal cation Aa. In other words, pyrochlore-type solid electrolytes contain multiple cations in their composition, including the alkali metal cation Aa.

[0046] As shown in Figure 2, the pyrochlore-type solid electrolyte is BO ６ It has a crystal structure in which a three-dimensional network of octahedrons is formed. ６ In this structure, cation B is at the center, with O at the vertices, and adjacent BO ６ It shares a vertex with BO. ６ In this three-dimensional network, hexagonal tunnel structures are formed in which cations Aa / Ab and halogen X are arranged.

[0047] In the above compositional formula, 0.6 < α < 2.0, 0 < β ≤ 1, and 0 < γ ≤ 1. A change in α alters the compositional ratio of Aa and Ab, and a change in β and γ alters the compositional ratio of O and X.

[0048] Cation Aa is an alkali metal cation. As the alkali metal represented by Aa, any of Li, Na, K, Rb, or Cs can be used. As cation Aa, Mg or H other than alkali metals may also be used. In other words, cation Aa contains at least one selected from Li, Na, K, Rb, Cs, Mg, and H. In this first embodiment, Li is used as Aa. The composition ratio (2-α) of Aa is in the range of 0 < (2-α) < 1.4.

[0049] The cation Ab contains at least one lanthanide. At least one of La, Ce, Nd, and Sm can be used as the lanthanide represented by Ab. In this first embodiment, La is used as Ab. The composition ratio of Ab (1+α) / 3 is in the range of 0.53 < (1+α) / 3 < 1.

[0050] The basic structure of cation Ab consists of lanthanides, and some of the lanthanides constituting Ab may be substituted with alkaline earth metals (Ca, Mg, Sr, etc.). In this first embodiment, the pyrochlore-type solid electrolyte is thought to have improved ionic conductivity because the inclusion of lanthanides in the pyrochlore structure, where 0.6 < α < 2.0 and 0 < β ≤ 1 in the above composition formula, creates defects in the crystal structure. In this first embodiment, La is used as Ab.

[0051] The pyrochlore-type solid electrolyte of this first embodiment has a composition formula "A" which is a common pyrochlore structure. ２ B ２ O ７ In this mixture, cation A is a composite cation using lithium metal and a lanthanide. This is thought to contribute to the improvement of the ionic conductivity of the pyrochlore-type solid electrolyte.

[0052] Cation B is a metallic cation distinct from Aa and Ab, and is a transition metal or a metal selected from Group 13 to Group 15 elements. In the crystal, B forms an octahedron surrounded by six oxygen atoms. As the transition metal represented by B, Group 4 or Group 5 transition metals can be used, and more specifically, at least one of Nb, Ta, Ti, Zr, Hf, or V can be used. As Group 13 elements represented by B, Al, Ga, and In can be used; as Group 14 elements, Ge and Sn can be used; and as Group 15 elements, Sb and Bi can be used.

[0053] As described above, the oxide-based ion conductor 14b of this first embodiment exhibits electronic conductivity when lithium ions, which are conduction ions, are inserted into its crystal structure. When the electrode potential of the oxide-based ion conductor 14b is reduced, the lithium ion insertion and deinsertion reaction of the oxide-based ion conductor 14b is promoted. In pyrochlore-type solid electrolytes, the electrode potential at which the lithium ion insertion and deinsertion reaction occurs changes depending on the type of cation B. In pyrochlore-type solid electrolytes, the effect of exhibiting electronic conductivity can be greatly enhanced when Nb is used as the cation metal represented by B in the composition formula.

[0054] Halogen X is substitutable for the oxygen atoms that make up the pyrochlore structure. X has different electronegativity and polarizability from oxygen atoms. At least one of F, Cl, Br, or I can be used as the halogen element represented by X. X may also be a group of halogen elements. The composition ratio γ of X is in the range of 0 < γ ≤ 1, and at least some of the oxygen atoms that make up the pyrochlore structure are substituted with X.

[0055] The pyrochlore-type solid electrolyte of this first embodiment has a defect structure in which lattice defects are included in the crystal, by substituting some of the oxygen atoms constituting the pyrochlore structure with halogens that have different electronegativity and polarizability from the oxygen atoms. It is believed that the ionic conductivity of the pyrochlore-type solid electrolyte of this first embodiment is improved because the pyrochlore structure contains defect structures.

[0056] The pyrochlore-type solid electrolyte of this first embodiment is a halogen-containing oxide containing halogen X. The pyrochlore-type solid electrolyte containing halogen X facilitates the insertion and removal of Li due to defects in the crystal structure, making it easier to exhibit the electronic conductivity of the pyrochlore-type solid electrolyte. It is particularly desirable to use F as halogen X.

[0057] In pyrochlore-type solid electrolytes, halogen X exists as a weak bond with cations Aa and Ab within the tunnel structure, and is also in an unstable state due to the presence of defect structures, making it easy for halogen elements to detach from the crystal structure. Therefore, when pyrochlore-type solid electrolytes are sintered and molded by heating, halogen elements tend to volatilize and detach. The larger the atomic weight of halogen X, the higher its volatility and the easier it is for it to detach from pyrochlore-type solid electrolytes.

[0058] In the pyrochlore-type solid electrolyte of this first embodiment, a portion of Aa and Ab is missing as a defect structure. The compositional formula of a typical pyrochlore structure is "A ２ B ２ O ７ In this case, the composition ratio of cation A is 2. In contrast, in the pyrochlore-type solid electrolyte of this first embodiment, the composition ratios of Aa and Ab are "2-α" and "(1+α) / 3", respectively, and since 0.6 < α < 2.0, the sum of the composition ratios of Aa and Ab is less than 2. In other words, in the crystal structure of the pyrochlore-type solid electrolyte of this first embodiment, at least a portion of either Aa or Ab is missing. The composition ratio corresponding to the missing portions of Aa and Ab is (2α-1) / 3.

[0059] In addition to deviations in composition ratios, defect structures can also be formed by making the sum of the valencies of the cations consisting of Aa, Ab, and B and the anions consisting of O and X in the above composition formula negative.

[0060] Furthermore, the pyrochlore-type solid electrolyte of this first embodiment is a complex anion compound in which multiple anions such as O and X are included in the pyrochlore structure, and BO ６ Because there is a halogen element represented by X in the coordination octahedron structure, the alkali metal Aa is BO ６ Without relying on the coordination octahedron, BO ６ It can be positioned in the center of the space with the coordination octahedron. Therefore, it is thought that the pyrochlore-type solid electrolyte of this first embodiment exhibited high ionic conductivity when used with an electric field applied, such as in a battery.

[0061] Furthermore, since α, β, and γ in the above compositional formula affect lattice defects and ionic conductivity, it is desirable to use them within an appropriate range. Larger values ​​of α, β, and γ increase the defect concentration in the crystal lattice, but beyond a certain amount, the concentration of alkali metal represented by Aa decreases, and the ionic conductivity declines. For this reason, it is desirable to control α within the range of 0.6 < α < 2.0, β within the range of 0 < β ≤ 1, and γ within the range of 0 < γ ≤ 1.

[0062] As a pyrochlore-type solid electrolyte, Li １．２５ La ０．５８ Nb ２ O ６ F, Li １．２５ La ０．５８ Nb ２ O ６ F ０．８ Cl ０．２ Li １．２５ La ０．５８ Nb ２ O ６ F ０．８ Br ０．２ Examples include the following.

[0063] Li, which is a pyrochlore-type solid electrolyte in this first embodiment １．２５ La ０．５８ Nb ２ O ６ F (LLNOF) is 1 x 10 －３ Ionic conductivity of S / cm or higher has been obtained. The pyrochlore-type solid electrolyte of this first embodiment exhibits significantly higher ionic conductivity than other oxide-type solid electrolytes such as garnet-type oxides.

[0064] Next, a method for producing the pyrochlore-type solid electrolyte used as the solid electrolyte 150 in this first embodiment will be described. Figure 3 shows a method for producing LLNOF as a pyrochlore-type solid electrolyte. In the method for producing the pyrochlore-type solid electrolyte, the first mixing step S10, the first calcination step S11, the second mixing step S12, and the second calcination step S13 are carried out in order.

[0065] (First Mixing Step) First, a lanthanum source, a lithium source, and a niobium source are prepared as raw materials for a pyrochlore-type solid electrolyte, and a first mixing step S10 is performed to mix them. As the lanthanum source, lithium source, and niobium source, metal oxides and metal carbon oxides can be used. In this first embodiment, La is used as the lanthanum source. ２ O ３ Li as a lithium source ２ CO ３ , Nb as a niobium source ２ O ５ It uses. In the first mixing step, La ２ O ３ Li ２ CO ３ Nb ２ O ５ Mix them in the specified ratio.

[0066] (First firing process) Next, La ２ O ３ Li ２ CO ３ Nb ２ O ５ A first calcination step S11 is performed to calcine the mixture. In the first calcination step S11, two stages of calcination are performed. As the first stage, the mixture is calcined in air at 500°C for 6 hours. Calcination removes moisture and other substances from the mixture, thereby increasing its reactivity. Following calcination, the mixture is calcined in air at 1200°C for 4 hours. This process generates Li, a precursor of the target product. ０．５ La ０．５ Nb ２ O ６ You can obtain this.

[0067] (Second mixing step) Next, a fluorine source is prepared as a raw material, and this is used as a precursor Li ０．５ La ０．５ Nb ２ O ６ A second mixing step S12 is performed, in which the mixture is added. Metal fluorides can be used as the fluorine source. In this first embodiment, LiF and LaF are used as the fluorine source. ３ It uses LiF, which is both a fluorine source and a lithium source, and LaF ３ It is a fluorine source and a lanthanum source. In the second mixing step, LiF and LaF３ Li in a predetermined ratio ０．５ La ０．５ Nb ２ O ６ Mix with it.

[0068] (Second firing process) Next, Li ０．５ La ０．５ Nb ２ O ６ And LiF and LaF ３ A second firing step S50 is performed in which the mixture of is fired. In the second firing step S50, Li is fired in a nitrogen atmosphere. ０．５ La ０．５ Nb ２ O ６ And LiF and LaF ３ The mixture is baked by heating it at 1000°C for 6 hours.

[0069] Through the above process, the composition formula "Li １．２５ La ０．５８ Nb ２ O ６ A solid electrolyte 150 consisting of a pyrochlore-type solid electrolyte represented by "F" can be obtained.

[0070] Furthermore, in the above manufacturing process, La ２ O ３ Li ２ CO ３ Nb ２ O ５ The mixing ratio of LiF and LaF ３ By changing the mixing ratio, the composition formula "Li ２－α La （１＋α）／３ Nb ２ O ７－β F γ A pyrochlore-type solid electrolyte represented by " can be obtained. In this composition formula, α is La ２ O ３ Li ２ CO ３ Nb ２ O ５ This can be adjusted by changing the mixing ratio of β and γ. β and γ are LiF and LaF ３This can be adjusted by changing the mixing ratio. Also, some of the material sublimes during firing. Therefore, α, β, and γ can also be adjusted by changing the firing conditions, furnace atmosphere, and furnace size in the first and second firing processes.

[0071] The oxide 160 coating on the surface of the solid electrolyte 150 can be performed by grinding using a ball mill, or by liquid-phase or gas-phase methods. In the liquid-phase method, for example, the oxide 160 can be dissolved in water or an organic solvent, the solid electrolyte 150 can be immersed in the solvent, and the solvent can be dried to coat it with the oxide 160. In the gas-phase method, for example, the oxide 160 can be coated on the surface of the solid electrolyte 150 by PVD (sputtering), CVD (chemical vapor deposition), or ALD (atomic layer deposition).

[0072] The particulate composite material 100 can be used as the electrolyte layer 15, for example, in the form of a compacted powder or a molded body formed by firing. As a molded body formed by firing, it can be a block-shaped sintered body or a sheet-like member such as a ceramic sheet.

[0073] Next, the molding method for the composite material 100 will be explained using Figure 4. The molding method for the composite material 100 includes a preparation step S100, a molding step S110, and a heating step S120.

[0074] First, a preparation step S100 is performed to prepare particulate composite material 100. Next, a molding step S110 is performed to press-molde the particulate composite material 100 at a predetermined pressure (for example, 100 MPa). A compacted composite material 100 can be obtained by the molding step S110.

[0075] Next, a heating step S120 is performed in which the compacted composite material 100 is heated at a predetermined temperature (for example, 1000°C for 6 hours). A sintered body of the composite material 100 can be obtained by the heating step S120. It is desirable that the heating temperature for producing the sintered body be set to be above the melting point of the oxide 160 and below the melting point of the solid electrolyte 150. The sintered body of the composite material 100 obtained in the heating step S120 can be used as the electrolyte layer 15.

[0076] By heating the sintered composite material 100 above the melting point of the oxide 160, the oxide 160 melts, improving the coverage of the solid electrolyte 150 by the oxide 160. This enhances the effect of the oxide 160 in suppressing halogen desorption from the solid electrolyte 150.

[0077] Furthermore, by heating the oxide 160 above its melting point, the oxide 160 melts, and the oxide 160 of the adjacent composite material 100 becomes integrated. As a result, the relative density of the composite material 100 increases, and the contact area with the adjacent composite material 100 expands. Consequently, the interfacial resistance of the adjacent composite material 100 can be reduced, and the ionic conductivity of the composite material 100 can be improved.

[0078] Figure 4 shows a step in which the composite material 100 constituting the electrolyte layer 15 is molded and then heated. However, the composite material 100 constituting the electrolyte layer 15 and the other components of the secondary battery 10 may be molded and heated simultaneously. For example, the composite material 100 constituting the electrolyte layer 15 and the positive electrode active material 140 constituting the positive electrode layer 14 can be molded and heated simultaneously.

[0079] Here, examples and comparative examples of the composite material 100 of the first embodiment will be described with reference to Figure 5. Examples 1 to 10 differ in the type of solid electrolyte 150 or oxide 160. Comparative examples 1 to 3 differ in the type of solid electrolyte 150 and do not contain oxide 160.

[0080] In Examples 1-7, 9, and 10, the content of oxide 160 in the composite material 100 was 10 wt%. In Example 8, the content of oxide 160 in the composite material 100 was 5 wt%. In Examples 1-10, the solid electrolyte 150 and oxide 160 were mixed by grinding using a ball mill.

[0081] Examples 1-10 and Comparative Examples 1-3 use a pyrochlore-type solid electrolyte as the solid electrolyte 150. Examples 1-8 and Comparative Example 1 use Li as the solid electrolyte 150. １．２５ La ０．５８ Nb ２ O ６ F is used. In Example 9 and Comparative Example 2, Li is used as the solid electrolyte 150.１．２５ La ０．５８ Nb ２ O ６ F ０．８ Cl ０．２ In Example 10 and Comparative Example 3, Li was used as the solid electrolyte 150. １．２５ La ０．５８ Nb ２ O ６ F ０．８ Br ０．２ It uses this.

[0082] Example 1 uses Li as oxide 160. ３ BO ３ Example 2 uses LaNbO as oxide 160. ４ Example 3 uses Li as oxide 160. ３ PO ４ Example 4 uses Li as oxide 160. ２ CO ３ Example 5 uses WO as oxide 160. ３ Examples 6, 9, and 10 use Al as oxide 160. ２ O ３ Example 7 uses WO as oxide 160. ３ and Al ２ O ３ A mixture of the following is used. Example 8 uses B as oxide 160. ２ O ３ This is used. As mentioned above, comparative examples 1 to 3 do not contain oxide 160.

[0083] In Examples 1 to 7, the composite material 100 was heated to 1000°C. In Examples 8 to 10, the composite material 100 was heated to 800°C. In Comparative Examples 1 to 3, the solid electrolyte 150 was heated to 1000°C.

[0084] Next, the amount of decomposition products produced from the solid electrolyte 150 after heating in Examples 1 to 10 and Comparative Examples 1 to 3 will be described. Decomposition products are substances produced by the elimination of halogen elements from the solid electrolyte 150. The decomposition products of the pyrochlore-type solid electrolytes used in Examples 1 to 10 and Comparative Examples 1 to 3 are, for example, LiNbO ３ These are some examples. The amount of decomposition products was measured using an X-ray diffractometer (XRD).

[0085] In Examples 1 to 10, no decomposition products were detected. In other words, in Examples 1 to 10, which used a composite material 100 containing a solid electrolyte 150 and an oxide 160, no decomposition products of the solid electrolyte 150 were generated after heating.

[0086] On the other hand, in Comparative Examples 1 to 3, where the oxide 160 was not provided and only the solid electrolyte 150 was used, decomposition products were detected. In Comparative Example 1, the amount of decomposition products was 8 wt%, in Comparative Example 2, it was 15 wt%, and in Comparative Example 3, it was 18 wt%.

[0087] Comparative Example 1 contains only F as the halogen element in the solid electrolyte 150, Comparative Example 2 contains F and Cl as halogen elements in the solid electrolyte 150, and Comparative Example 3 contains F and Br as halogen elements in the solid electrolyte 150. The amount of decomposition products produced increased in the order of Comparative Example 1, Comparative Example 2, and Comparative Example 3, indicating that halogen elements in the solid electrolyte 150 are more volatile and easier to desorb the larger their atomic weight.

[0088] Next, we will explain the relative density and ionic conductivity of the composite material 100 when the content of oxide 160 in the composite material 100 and the sintering temperature of the composite material 100 are changed. Figure 6 shows the relative density of the composite material 100, and Figure 7 shows the ionic conductivity of the composite material 100. In the composite material 100 in Figures 6 and 7, oxide 160 is B ２ O ３ Using Li as the solid electrolyte 150 １．２５ La ０．５８ Nb ２ O ６ F (LLNOF) was used. In the examples shown in Figures 6 and 7, B is used as oxide 160. ２ O ３ The composite material 100 is sintered at a temperature in the range of 500 to 900°C, which is above the melting point (480°C) of the material.

[0089] As shown in Figure 6, the relative density of the composite material 100 is high when the sintering temperature is 700 to 800°C. In particular, the relative density of the composite material 100 is high when the oxide 160 content in the composite material 100 is in the range of 0.5 to 2 wt%. At sintering temperatures of 800°C or lower, the relative density of the composite material 100 is highest when the oxide 160 content is 0.5 wt%.

[0090] As shown in Figure 7, when the oxide 160 content is 0.2 wt%, 0.5 wt%, and 1 wt%, the ionic conductivity of the composite material 100 is high when the sintering temperature is in the range of 700 to 800°C. When the oxide 160 content is 2 wt% and 5 wt%, the ionic conductivity of the composite material 100 is high when the sintering temperature is in the range of 700 to 900°C. In particular, the ionic conductivity of the composite material 100 is high when the oxide 160 content in the composite material 100 is in the range of 0.5 to 2 wt%. At a sintering temperature of 700 to 800°C, the ionic conductivity of the composite material 100 is highest when the oxide 160 content is 0.5 wt%.

[0091] Furthermore, when the sintering temperature is 800°C or higher, B is used as oxide 160. ２ O ３ Due to the increased volatilization, relative density and ionic conductivity could not be measured when the oxide 160 content was 0.2 wt%, 0.5 wt%, or 1 wt%.

[0092] In the secondary battery 10 of the first embodiment described above, the electrolyte material of the electrolyte layer 15 is a composite material 100 having a solid electrolyte 150 containing a halogen element and having a defect structure, and one or more oxides 160 having a different composition from the solid electrolyte 150 and in contact with at least a part of the particle surface of the solid electrolyte 150.

[0093] In this first embodiment, the composite material 100 has an oxide 160 in contact with at least a portion of the solid electrolyte 150, which suppresses the detachment of halogen elements from the solid electrolyte 150 during heating and prevents a decrease in the ionic conductivity of the solid electrolyte 150. Furthermore, according to this first embodiment, even when the secondary battery 10 becomes hot due to charging or discharging, the detachment of halogen elements from the solid electrolyte 150 can be suppressed and a decrease in the ionic conductivity of the solid electrolyte 150 can be prevented. As a result, a decrease in the output characteristics of the secondary battery 10 using the composite material 100 can be prevented.

[0094] Furthermore, in this first embodiment, the oxide 160 coats the surface of the solid electrolyte 150. This increases the contact area between the oxide 160 and the solid electrolyte 150, thereby enhancing the effect of suppressing the detachment of halogen elements from the solid electrolyte 150 by the oxide 160.

[0095] Furthermore, according to this first embodiment, a pyrochlore-type solid electrolyte is used as the solid electrolyte 150. The pyrochlore-type solid electrolyte has high ionic conductivity, which can improve the output of the secondary battery 10.

[0096] Furthermore, in the composite material 100 of this first embodiment, an oxide 160 with a lower melting point than the solid electrolyte 150 is used. By using such a low-melting-point oxide 160, the oxide 160 melts more easily when the composite material 100 is heated, increasing the contact area between the solid electrolyte 150 and the oxide 160, and increasing the coating area of ​​the solid electrolyte 150 by the oxide 160. This enhances the effect of the oxide 160 in suppressing the detachment of halogen elements from the solid electrolyte 150.

[0097] (Second Embodiment) Next, a second embodiment of the present disclosure will be described. Hereinafter, only the parts that differ from the first embodiment will be described.

[0098] As shown in Figure 8, in this second embodiment, the solid electrolyte 150 of the composite material 100 is provided in the electrolyte layer 15, and the oxide 160 of the composite material 100 is provided in the positive electrode layer 14.

[0099] The oxide 160 can be supported on the positive electrode active material 140 of the positive electrode layer 14. In the example shown in Figure 8, the oxide 160 covers the surface of the positive electrode active material 140. The oxide 160 only needs to cover at least a portion of the positive electrode active material 140, and may cover the entire surface of the positive electrode active material 140. The oxide 160 of the positive electrode layer 14 does not necessarily need to cover the surface of the positive electrode active material 140, and particulate positive electrode active material 140 and particulate oxide 160 may be randomly mixed.

[0100] The oxide 160 of the positive electrode layer 14 is in contact with at least a portion of the solid electrolyte 150 of the electrolyte layer 15. In this second embodiment, the composite material 100 is composed of the oxide 160 of the positive electrode layer 14 and the solid electrolyte 150 of the electrolyte layer 15.

[0101] The same effects as those of the first embodiment can be obtained by the embodiments of this second embodiment described above.

[0102] (Third Embodiment) Next, a third embodiment of the present disclosure will be described. Below, only the parts that differ from the above embodiments will be described.

[0103] As shown in Figure 9, in this third embodiment, the electrolyte layer 15 is provided with a solid electrolyte 150, an oxide 160, and a separator 170. The electrolyte layer 15 contains an electrolyte solution.

[0104] The separator 170 has a porous structure and has the function of separating the negative electrode layer 12 and the positive electrode layer 14 while allowing ions to pass through. For example, a porous material can be used as the separator 170. Any material can be used for the separator 170, but it is desirable to use a material with high heat resistance. The electrolyte contains a lithium salt and a solvent. As the lithium salt, a common lithium salt used in lithium-ion batteries (e.g., LiPF4) can be used. ６ ) can be used. As solvents, organic electrolytes, ionic liquids, gel polymers, etc., can be used. These solvents may be used alone or in combination.

[0105] In this third embodiment, the oxide 160 is supported on the surface of the separator 170. The oxide 160 is provided on the surface of the separator 170 facing the positive electrode layer 14. The oxide 160 can be provided by coating the surface of the separator 170. The solid electrolyte 150 is provided in a layer between the separator 170 and the positive electrode layer 14.

[0106] The same effects as those of the first embodiment can be obtained by the embodiments of this third embodiment described above.

[0107] This disclosure is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit of this disclosure. Furthermore, the means disclosed in each of the embodiments may be combined as appropriate to the extent that they are feasible.

[0108] For example, in the above embodiment, an example was described in which the composite material 100 of the present disclosure is applied to a lithium-ion battery in which the conductive ions are lithium ions, but it may also be applied to secondary batteries with different conductive ions. Specifically, the composite material 100 of the present disclosure can be applied to potassium-ion batteries in which potassium ions conduct, sodium-ion batteries in which sodium ions conduct, and the like.

[0109] Furthermore, although the first embodiment described above included an example in which the composite material 100 was provided in the electrolyte layer 15, and the second embodiment described an example in which the composite material 100 was provided in both the positive electrode layer 14 and the electrolyte layer 15, the composite material 100 only needs to be provided in at least one of the positive electrode layer 14, the negative electrode layer 12, and the electrolyte layer 15. If the composite material 100 is provided in at least one of the positive electrode layer 14 and the negative electrode layer 12, the composite material 100 does not necessarily need to be provided in the electrolyte layer 15, and a material other than the composite material 100, such as a polymer, may be used as the electrolyte layer 15.

[0110] Furthermore, the shape of the secondary battery 10 is not limited to the forms described in each of the embodiments above, and can be used in various forms such as cylindrical, rectangular, or pouch-type (laminated).

[0111] Furthermore, the secondary battery 10 described in each of the above embodiments may be configured as a bipolar battery. A bipolar battery has a structure in which multiple battery cells are stacked and connected in series, and adjacent battery cells share a current collector. In other words, the current collector that contacts the positive electrode of one adjacent battery cell contacts the negative electrode of the other adjacent battery cell.

[0112] Furthermore, the secondary battery 10 described in each of the above embodiments may be configured as an anode-free battery. In an anode-free battery, the negative electrode layer 12 is not formed on the negative electrode current collector 11 in the initial state. During charging, lithium ions move from the positive electrode layer 14, causing lithium metal to deposit on the negative electrode current collector 11 and forming the negative electrode layer 12. The lithium metal constituting the negative electrode layer 12 then moves to the positive electrode layer 14 as lithium ions during discharge.

[0113] Furthermore, in a secondary battery 10 using the composite material 100, the negative electrode layer 12, positive electrode layer 14, and electrolyte layer 15 may be individually fired and then assembled, or the negative electrode layer 12, positive electrode layer 14, and electrolyte layer 15 may be integrally molded and then these components may be sintered simultaneously to produce the secondary battery 10. In either configuration, the detachment of halogen elements from the solid electrolyte 150 during sintering can be suppressed, and a decrease in the ionic conductivity of the solid electrolyte 150 can be suppressed.

[0114] Furthermore, the composite material 100 may be combined with a polymer or sulfide material to produce a secondary battery 10 without sintering. Even in such a configuration, when the secondary battery 10 becomes hot due to charging or discharging, the detachment of halogen elements from the solid electrolyte 150 can be suppressed, and the decrease in the ionic conductivity of the solid electrolyte 150 can be suppressed.

[0115] Furthermore, while the above embodiments described examples of applying an electrochemical device using the composite material 100 of this disclosure to a secondary battery 10, the electrochemical device using the composite material 100 can also be applied to applications other than secondary batteries. Examples of applications other than secondary batteries for the electrochemical device using the composite material 100 include an electrochemical device for lithium separation used in direct lithium extraction (DLE) using an ion conductor.

[0116] The electrochemical device for lithium separation used in direct lithium extraction (DLE) comprises a lithium separation membrane made of an ion conductor, an anode connected to the positive electrode of an external power supply, and an anode connected to the negative electrode of an external power supply. A solid electrolyte 150 made of composite material 100 can be used as the ion conductor. By applying a voltage between the anode and cathode from an external power supply, only lithium can be selectively recovered from the lithium-containing solution on the anode side into a recovery solution on the cathode side. The lithium-containing solution is, for example, the electrolyte of a used lithium-ion battery, and the recovery solution is, for example, pure water. The Li separation membrane corresponds to the electrolyte layer, the anode corresponds to the first electrode, and the cathode corresponds to the second electrode.

[0117] The characteristics of the composite material and secondary battery disclosed herein are as follows: (Item 1) A solid electrolyte (150) containing a halogen element and having defects in its crystalline structure, and one or more oxides (160) having a different composition from the solid electrolyte and in contact with at least a portion of the particle surface of the solid electrolyte, wherein the oxide has compositional formula D Ｖ E Ｙ O Ｚ Or E Ｙ O Ｚ A composite material that is a substance represented by at least one of the following.

[0118] However, D and E are each one or more types of elements, D is an alkali metal or alkaline earth element, E is a transition metal of groups 3 to 6 or an element of groups 13 to 16, D and E are each one or more types of elements, and V, Y, and Z are any number. (Item 2) The above D Ｖ E Ｙ O Ｚ Li ３ PO ４ Li ３ BO ３ Li ２ CO ３ Li ２ SO ４ Li ２ ZrO ３ Li ２ WO４ LiNO ３ , LaNbO ４ and LiNbo ３ The composite material described in item 1, which is at least one of the following. (Item 3) The E Ｙ O Ｚ B ２ O ３ Al ２ O ３ Ga ２ O ３ , GeO ２ SiO ２ , ZrO ２ , Y ２ O ３ WO ３ and LaNboO ４ A composite material according to item 1 or 2, wherein at least one of the following conditions is met. (Item 4) The oxide is a composite material according to any one of items 1 to 3, wherein the oxide has a melting point lower than that of the solid electrolyte. (Item 5) The solid electrolyte has a composition formula Aa ２－α Ab （１＋α）／３ B ２ O ７－β X γ (Item 6) A composite material according to any one of items 1 to 4, having a pyrochlore structure represented by Aa, where Aa is an alkali metal, Ab contains at least a lanthanide, B is a cation different from Aa and Ab, and X is the halogen element that can be substituted for the O atom of the pyrochlore structure, and in the composition formula, α is in the range of 0.6 < α < 2.0, β is in the range of 0 < β ≤ 1, and γ is in the range of 0 < γ ≤ 1. (Item 6) An electrochemical device comprising a first electrode layer (14), a second electrode layer (12), and an electrolyte layer (15) sandwiched between the first electrode layer and the second electrode layer, wherein the composite material (100) according to any one of items 1 to 5 is provided in at least one of the first electrode layer, the second electrode layer, and the electrolyte layer. (Item 7) The electrochemical device according to item 6, wherein the composite material is provided in the electrolyte layer. (Item 8) The electrochemical device according to Item 6, wherein the first electrode layer is provided with a positive electrode active material (140), the solid electrolyte is provided in the electrolyte layer, and the oxide is provided in the first electrode layer.

[0119] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, while various combinations and forms are shown in this disclosure, other combinations and forms that include one, more, or fewer of those elements also fall within the scope and concept of this disclosure.

Claims

1. A solid electrolyte (150) containing a halogen element and having defects in its crystalline structure, and one or more oxides (160) having a different composition from the solid electrolyte and in contact with at least a portion of the particle surface of the solid electrolyte, wherein the oxide has compositional formula D Ｖ E Ｙ O Ｚ Or E Ｙ O Ｚ A composite material that is represented by at least one of the following: where D and E are each one or more types of elements, D is an alkali metal or alkaline earth element, E is a transition metal of groups 3 to 6 or an element of groups 13 to 16, D and E are each one or more types of elements, and V, Y, and Z are any number.

2. The D Ｖ E Ｙ O Ｚ is at least one of Li ３ PO ４ , Li ３ BO ３ , Li ２ CO ３ , Li ２ SO ４ , Li ２ ZrO ３ , Li ２ WO ４ , LiNO ３ and LiNbO ３ The composite material according to claim 1.

3. E Ｙ O Ｚ B ２ O ３ Al ２ O ３ Ga ２ O ３ , GeO ２ SiO ２ , ZrO ２ , Y ２ O ３ WO ３ and LaNboO ４ The composite material according to claim 1, which is at least one of the following.

4. The composite material according to claim 1, wherein the oxide has a melting point lower than that of the solid electrolyte.

5. The solid electrolyte has the composition formula Aa ２－α Ab （１＋α）／３ B ２ O ７－β X γ The composite material according to claim 1, having a pyrochlore structure represented by , wherein Aa is an alkali metal, Ab contains at least a lanthanide, B is a cation different from Aa and Ab, X is the halogen element that can be substituted for the O atom of the pyrochlore structure, and in the composition formula, α is in the range of 0.6 < α < 2.0, β is in the range of 0 < β ≤ 1, and γ is in the range of 0 < γ ≤ 1.

6. An electrochemical device comprising a first electrode layer (14), a second electrode layer (12), and an electrolyte layer (15) sandwiched between the first electrode layer and the second electrode layer, wherein the composite material (100) according to any one of claims 1 to 5 is provided in at least one of the first electrode layer, the second electrode layer, and the electrolyte layer.

7. The electrochemical device according to claim 6, wherein the composite material is provided in the electrolyte layer.

8. The electrochemical device according to claim 6, wherein the first electrode layer is provided with a positive electrode active material (140), the solid electrolyte is provided in the electrolyte layer, and the oxide is provided in the first electrode layer.

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