Secondary battery

Abstract

This secondary battery comprises a positive electrode (14), a negative electrode (12), an electrolyte layer (15), and a shut-off layer (16). The electrolyte layer is formed from an electrolyte material that has lithium-ion conductivity. The shut-off layer contains a lithium-ion-conducting solid material that has lithium-ion conductivity. The electrolyte layer is interposed between the negative electrode and the shut-off layer. The electrolyte material is a solid electrolyte, a liquid electrolyte, a polymer, or a mixture of the foregoing. The shut-off layer is formed from the lithium-ion-conducting solid material alone or from a mixture of the lithium-ion-conducting solid material and at least one of the solid electrolyte, the liquid electrolyte, and the polymer. The lithium-ion-conducting solid material is at least one of a pyrochlore-type solid electrolyte, a NASICON-type solid electrolyte, and a perovskite-type solid electrolyte. The decrease of lithium-ion conductivity of the lithium-ion-conducting solid material upon contact with lithium metal is greater than that of the electrolyte material.

Description

Cross - reference to related applications

[0001] This application is based on Japanese Patent Application No. 2022 - 175676 filed on November 1, 2022, the content of which is incorporated herein by reference.

Technical Field

[0002] The present disclosure relates to a secondary battery that suppresses short - circuiting between electrodes.

Background Art

[0003] As a secondary battery, a lithium - ion battery in which charge and discharge are performed by lithium ions moving between a positive electrode and a negative electrode is known. In a lithium - ion battery, when charge and discharge are repeated, dendrites of lithium metal grow from the negative electrode and reach the positive electrode, which may cause a short - circuit between the electrodes.

[0004] On the other hand, Patent Document 1 discloses providing a shut - off layer containing a lithium - ion conductive liquid that reacts with lithium metal to generate an electron insulator between the electrolyte layer and the positive electrode of a lithium - ion battery. According to the secondary battery of Patent Document 1, when dendrites grown from the negative electrode reach the shut - off layer, an electron insulator is generated and the growth of dendrites is suppressed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] However, in the secondary battery of Patent Document 1, although the lithium-ion conductive liquid in the shut-off layer is held by the porous membrane, since it is still a liquid, it is difficult to continuously hold it completely. Therefore, due to the expansion and contraction stress associated with the charge and discharge of the secondary battery, there is a risk that the lithium-ion conductive liquid will leak out and contact the negative electrode. When the lithium-ion conductive liquid contacts the negative electrode, an insulator is generated near the interface between the negative electrode and the electrolyte, causing a decrease in battery performance due to an increase in resistance.

[0007] In view of the above points, an object of the present disclosure is to provide a secondary battery that can be stably used while suppressing a short circuit between electrodes.

[0008] The secondary battery of the present disclosure includes a positive electrode, a negative electrode, an electrolyte layer, and a shut-off layer. The positive electrode contains a positive electrode active material. The negative electrode contains a negative electrode active material. The electrolyte layer is provided adjacent to the negative electrode and is composed of an electrolyte material having lithium-ion conductivity. The shut-off layer is provided adjacent to the positive electrode and contains a lithium-ion conductive solid material having lithium-ion conductivity. An electrolyte layer is interposed between the negative electrode and the shut-off layer. The electrolyte material is at least one of a solid electrolyte different from the lithium-ion conductive solid material, an electrolyte solution, a polymer, or a mixture thereof.

[0009] The first aspect of the present disclosure is , shi The shut-off layer is composed of only a lithium-ion conductive solid material, or a mixture of a lithium-ion conductive solid material and at least one of a solid electrolyte, an electrolytic solution, and a polymer. The lithium-ion conductive solid material is at least one of a pyrochlore-type solid electrolyte, a NASICON-type solid electrolyte, and a perovskite-type solid electrolyte. The lithium-ion conductive solid material has a greater decrease in lithium-ion conductivity when in contact with lithium metal than the electrolyte material. different from the lithium-ion conductive solid material The lithium-ion conductive solid material is at least one of a pyrochlore-type solid electrolyte, a NASICON-type solid electrolyte, and a perovskite-type solid electrolyte. The lithium-ion conductive solid material has a greater decrease in lithium-ion conductivity when in contact with lithium metal than the electrolyte material. , su The lithium-ion conductive solid material is at least one of a pyrochlore-type solid electrolyte, a NASICON-type solid electrolyte, and a perovskite-type solid electrolyte. The lithium-ion conductive solid material has a greater decrease in lithium-ion conductivity when in contact with lithium metal than the electrolyte material.

[0010] Further, in the second aspect of the present disclosure, the lithium-ion conductive solid material forms a non-conductor of lithium ions when in contact with lithium metal.

[0011] Accordingly, it is possible to provide a secondary battery that can be stably used while suppressing a short circuit between electrodes.

Brief Description of the Drawings

[0012]

Figure 1

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Figure 10

Modes for Carrying Out the Invention

[0013] Hereinafter, a plurality of embodiments for implementing the present disclosure will be described with reference to the drawings. In each embodiment, the same reference numerals may be assigned to portions corresponding to those described in the preceding embodiments, and redundant descriptions may be omitted. When only a part of the configuration is described in each embodiment, other embodiments described previously can be applied to other parts of the configuration. Not only combinations of parts that are clearly indicated as combinable in each embodiment, but also embodiments can be partially combined with each other without particular hindrance to the combination, even if not explicitly stated.

[0014] (First Embodiment) Hereinafter, a first embodiment in which the secondary battery of the present disclosure is applied to a lithium-ion battery will be described with reference to the drawings. The secondary battery 10 of this embodiment is a lithium-ion battery cell in which charge and discharge are performed by lithium ions moving between the negative electrode 12 and the positive electrode 14.

[0015] As shown in FIG. 1, the secondary battery 10 includes a negative electrode current collector 11, a negative electrode 12, a positive electrode current collector 13, a positive electrode 14, an electrolyte layer 15, and a shut layer 16. These layers 11 to 16 are provided in a stacked manner.

[0016] An electrolyte layer 15 and a shut layer 16 are provided between the negative electrode 12 and the positive electrode 14. The electrolyte layer 15 is provided on the negative electrode 12 side, and the negative electrode 12 is in contact with the electrolyte layer 15. The shut layer 16 is provided on the positive electrode 14 side, and the positive electrode 14 is in contact with the shut layer 16. The negative electrode 12 and the positive electrode 14 are connected via the electrolyte layer 15 and the shut layer 16.

[0017] These negative electrode 12, positive electrode 14, electrolyte layer 15, and shut layer 16 are 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 12, and the positive electrode current collector 13 is in contact with the positive electrode 14. The negative electrode current collector 11 and the positive electrode current collector 13 are connected via a laminate including the negative electrode 12, the positive electrode 14, the electrolyte layer 15, and the shut layer 16.

[0018] The negative electrode current collector 11 and the positive electrode current collector 13 can be made of any material that can be used as a current collector for a lithium-ion battery. In this embodiment, Cu is used as the negative electrode current collector 11, and Al is used as the positive electrode current collector 13.

[0019] The negative electrode current collector 11 and the positive electrode current collector 13 can have any shape, and can be, for example, in the form of a foil or a plate. In this embodiment, foil-shaped current collectors 11 and 13 are used. The current collectors 11 and 13 may have a three-dimensional structure, and for example, a structure provided with protrusions or a mesh structure can be adopted.

[0020] The negative electrode 12 contains a negative electrode active material. As the negative electrode active material, any material that can be used as a negative electrode active material for a lithium-ion battery can be used, and for example, lithium metal, graphite, Si, or a mixture thereof can be used. In this embodiment, lithium metal is used as the negative electrode active material.

[0021] The positive electrode 14 contains a positive electrode active material. As the positive electrode active material, any material that can be used as a positive electrode active material for a lithium-ion battery can be used.

[0022] As the positive electrode active material, for example, a layered active material, a spinel-type active material, or an olivine-type active material can be used. As the layered active material, for example, ternary cathode materials such as LiCoO2 (LCO), LiNiO2 (LNO), LiNi 0.8 Co 0.15 Al 0.05 O2 (NCA), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) can be used. As the spinel-type active material, for example, LiMn2O4, LiNi 0.5 Mn 1.5 O4 can be used. As the olivine-type active material, for example, LiMn 0.8 Fe 0.2 PO4 (LMFP), LiFePO4 (LFP) can be used.

[0023] Among the above-described positive electrode active materials, generally, the olivine-type active material has the lowest ion conductivity. Therefore, when an olivine-type active material is used as the positive electrode active material of the secondary battery 10, dendrites are likely to be generated from the negative electrode 12 during charging.

[0024] The positive electrode 14 may contain at least one of an electrolyte solution and a polymer in addition to the positive electrode active material. As the electrolyte solution, for example, ethylene carbonate or the like can be used. The electrolyte solution may be an ionic liquid. As the polymer, for example, polyethylene oxide can be used.

[0025] The electrolyte layer 15 is provided so as to be in direct contact with the negative electrode 12. The electrolyte layer 15 is composed of an electrolyte material having lithium ion conductivity. The electrolyte layer 15 has a function of conducting lithium ions between the negative electrode 12 and the positive electrode 14 and ensuring insulation between the negative electrode 12 and the positive electrode 14.

[0026] In principle, the electrolyte material used for the electrolyte layer 15 does not have a decrease in lithium ion conductivity even when it comes into contact with lithium metal. However, when the electrolyte material comes into contact with lithium metal, it does not exclude the possibility that the lithium ion conductivity of the electrolyte material changes slightly due to factors such as the presence of surface impurities and the compatibility of the interface. Even if the electrolyte material comes into contact with lithium metal and the lithium ion conductivity decreases the most, it only decreases to up to one fraction of several minutes before coming into contact with lithium metal, and the resistance only increases several times or less.

[0027] As the electrolyte material of the electrolyte layer 15, a solid electrolyte, an electrolyte solution, a polymer, or a mixture thereof can be used. Among these electrolyte materials, generally, the electrolyte solution has the highest lithium ion conductivity, followed by the polymer and the solid electrolyte in that order. The usable temperature range is generally the highest for the solid electrolyte, followed by the polymer and the electrolyte solution in that order.

[0028] When a short circuit occurs in the secondary battery 10, the safety is generally highest for solid electrolytes, followed by polymers and electrolytes in that order. On the other hand, since the short circuit in the secondary battery 10 occurs due to non-uniform reaction caused by uneven current density, the worse the contact between the negative electrode active material and the electrolyte material, the easier it is for a short circuit to occur. For this reason, generally, a solid electrolyte is most likely to have a short circuit, and the likelihood of a short circuit decreases in the order of polymers and electrolytes.

[0029] In this embodiment, a solid electrolyte is used as the electrolyte material of the electrolyte layer 15. As the solid electrolyte, for example, an oxide-based solid electrolyte or a sulfide-based solid electrolyte can be used. In this embodiment, LLZO (Li7La3Zr2O 12 ) which is an oxide-based solid electrolyte is used as the electrolyte layer 15. The electrolyte layer 15 may contain at least one of an electrolyte solution and a polymer in addition to the solid electrolyte. As the electrolyte solution, for example, ethylene carbonate or the like can be used. The electrolyte solution may be an ionic liquid. As the polymer, for example, polyethylene oxide can be used.

[0030] The shut layer 16 and the negative electrode 12 are provided so as not to be in direct contact with each other, and the electrolyte layer 15 is interposed between the shut layer 16 and the negative electrode 12. The shut layer 16 contains a lithium ion conductive solid material whose lithium ion conductivity decreases when it comes into contact with lithium metal. The lithium ion conductive solid material is an ion conductor having lithium ion conductivity. The lithium ion conductive solid material of the shut layer 16 can be provided by coating the surface of the positive electrode 14 or the electrolyte layer 15 formed in a sheet shape, or can be provided by coating the surface of the particulate negative electrode active material.

[0031] The lithium-ion conductive solid material has a greater decrease in lithium-ion conductivity when in contact with lithium metal than the electrolyte material used for the electrolyte layer 15. As described above, the electrolyte material of the electrolyte layer 15 hardly decreases in lithium-ion conductivity even when in contact with lithium metal. In contrast, when the lithium-ion conductive solid material comes into contact with lithium metal, the lithium-ion conductivity decreases to at least 1 / 100 or less and the resistance increases by 100 times or more compared to before contacting the lithium metal.

[0032] That is, when the lithium-ion conductive solid material comes into contact with lithium metal, the ion conductivity decreases by two digits or more and the resistance increases by two digits or more. Thus, when the lithium-ion conductive solid material contacts lithium metal, the lithium-ion conductivity decreases by two digits or more and the resistance increases by two digits or more, the current value that can be energized becomes 1 / 100 or less, and it becomes difficult to function as a battery. Note that an electrolyte layer 15 is interposed between the shut-off layer 16 and the negative electrode 12, and normally lithium metal does not contact the shut-off layer 16, and the lithium-ion conductivity of the lithium-ion conductive solid material does not decrease.

[0033] The shut-off layer 16 may contain at least one of an electrolytic solution and a polymer in addition to the lithium-ion conductive solid material. As the electrolytic solution, for example, ethylene carbonate or the like can be used. The electrolytic solution may be an ionic liquid. As the polymer, for example, polyethylene oxide can be used.

[0034] From the viewpoint of reducing the cell resistance, it is desirable that the thickness of the shut-off layer 16 be as thin as possible. In the present embodiment, the thickness of the shut-off layer 16 is set to 10 μm or less. On the other hand, if the thickness of the shut-off layer 16 is too thin, it becomes difficult to form the shut-off layer 16 uniformly, and there is a possibility that a region where the shut-off layer 16 does not exist may be formed. Therefore, the thickness of the shut-off layer 16 is desirably 2 to 3 μm or more.

[0035] When Li metal precipitates non-uniformly on the negative electrode 12, dendrites are likely to grow from the negative electrode 12. When dendrites reach the shut-off layer 16 from the negative electrode 12 through the electrolyte layer 15, the lithium ion conductivity of the lithium ion conductive solid material decreases at the site in contact with the lithium metal in the shut-off layer 16, the resistance increases, and it becomes insulated. That is, when the lithium ion conductive solid material comes into contact with lithium metal, the ion conductivity greatly decreases to form a non-conductor of lithium ions. The "non-conductor of lithium ions" means a state in which the lithium ion conductive solid material comes into contact with lithium metal and the ion conductivity decreases to 1 / 100 or less.

[0036] In the shut-off layer 16, the lithium precipitation reaction stops near the contact site with the lithium metal, and the growth of dendrites stops. That is, the shut-off layer 16 has a shut-down function that restricts the movement of lithium ions between the negative electrode 12 and the positive electrode 14 to stop the function of the secondary battery 10 and suppresses the short circuit between the negative electrode 12 and the positive electrode 14.

[0037] As the lithium ion conductive solid material whose lithium ion conductivity decreases upon contact with lithium metal, at least one of a pyrochlore-type oxide solid electrolyte, a NASICON-type oxide solid electrolyte, and a perovskite-type oxide solid electrolyte can be used. As the pyrochlore-type oxide solid electrolyte, for example, Li 1.25 La 0.58 Nb2O6F can be used. As the NASICON-type oxide solid electrolyte, for example, Li 1.4 Al 0.4 Ti 1.6 (PO4)3 (LATP) can be used. As the perovskite-type oxide solid electrolyte, for example, La 0.57 Li 0.29 TiO3 (LLTO) can be used.

[0038] Figure 4 shows Li 1.25 La 0.58 Nb2O6F, Li 1.4 Al 0.4 Ti 1.6(PO4)3 and La 0.57 Li 0.29 It shows the change over time of the resistance value (Ω) when lithium metal is brought into contact with Li

[0039] As shown in Figure 4, the resistance value before contact with lithium metal is about 80 to 200 Ω, and Li 1.25 La 0.58 Nb2O6F is the lowest, followed by La 0.57 Li 0.29 TiO3 is low, and Li 1.4 Al 0.4 Ti 1.6 (PO4)3 is the highest.

[0040] And when lithium metal is brought into contact, Li 1.25 La 0.58 Nb2O6F, Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and La 0.57 Li 0.29 TiO3 gradually increases in resistance value, and after reaching about 100,000 Ω, the resistance value becomes constant. Li 1.25 La 0.58 Nb2O6F, Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and La 0.57 Li 0.29 The resistance value after contact with lithium metal of Li 1.25 La 0.58 Nb2O6F is the fastest, followed by Li 1.4 Al 0.4 Ti 1.6 (PO4)3 is fast, and La 0.57 Li 0.29 TiO3 is the slowest.

[0041] Figure 5 shows Li 1.25 La 0.58 Nb2O6F, Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and La 0.57 Li0.29 It shows the change over time of the resistance increase rate when lithium metal is brought into contact with TiO3.

[0042] As shown in FIG. 5, the resistance increase rate when lithium metal is brought into contact is the largest for Li 1.25 La 0.58 Nb2O6F, followed by Li 1.4 Al 0.4 Ti 1.6 (PO4)3 is large, and La 0.57 Li 0.29 TiO3 is the smallest.

[0043] That is, among the above-mentioned lithium-ion conductive solid materials, the pyrochlore-type solid electrolyte has the fastest resistance increase rate and the largest resistance increase rate when in contact with lithium metal. Therefore, when a pyrochlore-type solid electrolyte is used as the lithium-ion conductive solid material contained in the shut-off layer 16, the time until shutdown is the shortest and the safety is improved.

[0044] Also, the pyrochlore-type solid electrolyte has the lowest resistance value before contact with lithium metal (i.e., during normal times). For this reason, among the above-mentioned lithium-ion conductive solid materials, the pyrochlore-type solid electrolyte has the highest ionic conductivity during normal times, and the input / output characteristics of the secondary battery 10 are excellent.

[0045] The pyrochlore-type solid electrolyte is excellent in safety and has a higher ionic conductivity compared to other oxide-based solid electrolytes. Furthermore, the pyrochlore-type solid electrolyte has the property of increasing resistance and decreasing ionic conductivity when in contact with lithium metal when it contains a specific type of cation.

[0046] The lithium-ion conductive solid material of the present embodiment has a composition formula of "Aa 2-α Ab (1+α) / 3 B2O 7-β X βIt is an oxide solid electrolyte having a pyrochlore structure represented by 」. In the above composition formula, O is an oxygen atom, and Aa, Ab, B, and X represent arbitrary elements or groups. Aa, Ab, and B are different types of cations, respectively, and O and X are different types of anions, respectively. In the above composition formula, 0.6 < α < 2.0 and 0 < β ≤ 1. By changing α, the composition ratio of Aa and Ab changes, and by changing β, the composition ratio of O and X changes.

[0047] Aa is an alkali metal. As the alkali metal represented by Aa, any one of Li, Na, and K can be used. In this embodiment, Li is used as Aa. The composition ratio (2 - α) of Aa is within the range of 0 < (2 - α) < 1.4.

[0048] Ab contains at least a lanthanoid. As the lanthanoid represented by Ab, at least any one of La, Ce, Nd, and Sm can be used. In this embodiment, La is used as Ab. The composition ratio (1 + α) / 3 of Ab is within the range of 0.53 < (1 + α) / 3 < 1.

[0049] The basic structure of Ab consists of a lanthanoid, and a part of the lanthanoid constituting Ab may be substituted with an alkaline earth metal (such as Ca, Mg, Sr). In the above composition formula, the pyrochlore structure of the shut layer 16 of this embodiment has 0.6 < α < 2.0 and 0 < β ≤ 1, and it is considered that defects occur in the crystal structure due to the inclusion of a lanthanoid, improving the ionic conductivity.

[0050] In the pyrochlore-type solid electrolyte of this embodiment, the A cation in the general pyrochlore-type composition formula "A2B2O7" is a composite cation using a lithium metal and a lanthanoid. This is considered to contribute to the improvement of the ionic conductivity of the pyrochlore-type solid electrolyte.

[0051] B is a cationic metal different from Aa and Ab, and is a metal selected from Group 4 elements, Group 5 elements, or Group 15 elements. B forms an octahedron surrounded by six O atoms in the crystal. As the Group 4 element, Group 5 element, or Group 15 element represented by B, at least any one of Nb, V, Sb, Bi, Ta, Zr, Ti, and Hf can be used. For the pyrochlore-type solid electrolyte using at least any one of Nb, V, Sb, Bi, Ta, Zr, Ti, and Hf as the B cation, the lithium ion conductivity decreases due to contact with metallic lithium. This point will be described in detail later.

[0052] X is an anion that can replace the O atoms constituting the pyrochlore structure. X has different electronegativity and polarizability from O atoms. As the anion represented by X, at least any one of F, S, Cl, and OH can be used. The composition ratio β of X is within the range of 0 < β ≤ 1, and at least a part of the O atoms constituting the pyrochlore structure is replaced by X. In this embodiment, F is used as X.

[0053] The pyrochlore-type solid electrolyte of this embodiment has a defective structure containing lattice defects in the crystal because a part of the O atoms constituting the pyrochlore structure is replaced by an anion having different electronegativity and polarizability from the O atoms. It is considered that the ion conductivity of the pyrochlore-type solid electrolyte of this embodiment is improved because the defective structure is included in the pyrochlore structure.

[0054] In the pyrochlore-type solid electrolyte of this embodiment, a part of Aa and Ab is in a defective state as a defect structure. The composition formula of a general pyrochlore structure is "A2B2O7", and the composition ratio of the A cation is 2. In contrast, in the pyrochlore-type solid electrolyte of this 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. That is, in the crystal structure of the pyrochlore-type solid electrolyte of this embodiment, at least a part of either Aa or Ab is defective. Note that the composition ratio corresponding to the defective parts of Aa and Ab is (2α-1) / 3.

[0055] In addition to the deviation in the composition ratio, in the above composition formula, a defect structure can also be formed by making the total valence of the cations composed of Aa, Ab, and B and the anions composed of O and X negative.

[0056] Moreover, the pyrochlore-type solid electrolyte of this embodiment is a composite anion compound in which a pyrochlore structure contains a plurality of anions such as O and X. Since there is an anion represented by X in the BO6 coordination octahedron structure, the alkali metal of Aa can be located at the central part of the space with the BO6 coordination octahedron without approaching the BO6 coordination octahedron. Therefore, it is considered that the pyrochlore-type solid electrolyte of this embodiment has high ion conductivity when used under an electric field such as a battery.

[0057] In addition, since α and β in the above composition formula affect the lattice defect and the ion conductivity, it is desirable to use them within an appropriate range. When the values of α and β are large, the defect concentration in the crystal lattice increases, but if it exceeds a certain amount, the concentration of the alkali metal represented by Aa decreases and the ion conductivity decreases. Therefore, it is desirable to control α within the range of 0.6 < α < 2.0 and β within the range of 0 < β ≤ 1.

[0058] Here, the decrease in lithium ion conductivity of the pyrochlore-type solid electrolyte of the present embodiment will be described. As described above, a pyrochlore-type solid electrolyte using at least one of Nb, V, Sb, Bi, Ta, Zr, Ti, and Hf as the B cation has the property that its lithium ion conductivity decreases upon contact with metallic lithium.

[0059] In the pyrochlore-type solid electrolyte using Nb as the B cation, when it comes into contact with lithium metal, Nb is reduced, resulting in increased resistance and a decrease in ion conductivity. When a pyrochlore-type solid electrolyte with Nb as the B cation is brought into contact with lithium metal for about several tens of minutes, the bulk conductivity decreases from 3.3×10 -3 S / cm to 6.3×10 -4 S / cm, and the grain boundary conductivity decreases from 2.0×10 -3 S / cm to 6.4×10 -5 S / cm.

[0060] Also, in the pyrochlore-type solid electrolytes using Ta or Zr as the B cation, it has been confirmed that when they come into contact with lithium metal, Ta or Zr is reduced, resulting in increased resistance and a decrease in ion conductivity.

[0061] The band gap Eg of the pyrochlore-type solid electrolyte can be used as an index for the difficulty of reduction of the B cation when in contact with lithium metal, in other words, the difficulty of decrease in ion conductivity. The smaller the band gap Eg, the easier it is for the B cation to be reduced, and the easier it is for the ion conductivity to decrease. The B cation contained in a pyrochlore-type solid electrolyte with a smaller band gap than the pyrochlore-type solid electrolyte containing at least Nb, Ta, and Zr is considered to be reduced when in contact with lithium metal. That is, a pyrochlore-type solid electrolyte with a smaller band gap than the pyrochlore-type solid electrolyte containing Nb, Ta, and Zr as the B cation is considered to have its ion conductivity decreased upon contact with lithium metal.

[0062] The band gaps Eg of pyrochlore-type solid electrolytes calculated by first-principles calculations are 3.293 eV for Li2Nb2O6F, 4.163 eV for Li2Ta2O6F, 3.401 eV for Li2Zr2O6F, 3.429 eV for Li2Ti2O6F, 4.082 eV for Li2Hf2O6F, 1.415 eV for Li2V2O6F, 1.469 eV for Li2Sb2O6F, and 0.789 eV for Li2Bi2O6F.

[0063] Li2Nb2O6F, Li2Ta2O6F, and Li2Zr2O6F are pyrochlore-type solid electrolytes containing Nb, Ta, and Zr as B cations, respectively. Li2Ti2O6F, Li2Hf2O6F, Li2V2O6F, Li2Sb2O6F, and Li2Bi2O6F are pyrochlore-type solid electrolytes with smaller band gaps than the pyrochlore-type solid electrolytes containing Nb, Ta, and Zr as B cations. That is, pyrochlore-type solid electrolytes using at least any one of Nb, V, Sb, Bi, Ta, Zr, Ti, and Hf as the B cation have a reduced lithium ion conductivity when in contact with metallic lithium.

[0064] Next, the pyrochlore-type solid electrolyte of the present embodiment will be described with reference to FIG. 2. In the manufacturing method of the pyrochlore-type solid electrolyte, a first mixing step S10, a first firing step S20, a second mixing step S30, a forming step S40, and a second firing step S50 are performed in order.

[0065] (First mixing step) First, a first mixing step S10 is performed in which a lanthanum source, a lithium source, and a niobium source are prepared as raw materials and mixed. As the lanthanum source, lithium source, and niobium source, metal oxides, metal carbonates, etc. can be used. In the present embodiment, La2O3 is used as the lanthanum source, Li2CO3 is used as the lithium source, and Nb2O5 is used as the niobium source. In the first mixing step, La2O3, Li2CO3, and Nb2O5 are mixed at a predetermined ratio.

[0066] (First firing step) Next, a first firing step S20 of firing a mixture of La2O3, Li2CO3, and Nb2O5 is performed. In the first firing step S20, firing in two stages is performed. As the first stage, a preliminary firing is performed in which the mixture is heated at 500 °C for 6 hours in air. By the preliminary firing, moisture and the like are removed from the mixture, and the reactivity can be enhanced. Following the preliminary firing, a main firing is performed in which the mixture is heated at 1200 °C for 4 hours in air. As a result, Li 0.5 La 0.5 Nb2O6 is obtained.

[0067] (Second mixing step) Next, a fluorine source is prepared as a raw material, and a second mixing step S30 of mixing this with the precursor Li 0.5 La 0.5 Nb2O6 is performed. As the fluorine source, metal fluoride can be used. In the present embodiment, LiF and LaF3 are used as the fluorine source. LiF is a fluorine source and a lithium source, and LaF3 is a fluorine source and a lanthanum source. In the second mixing step, LiF and LaF3 are mixed with Li 0.5 La 0.5 Nb2O6 at a predetermined ratio.

[0068] (Forming step) Next, a forming step S40 of processing the mixed powder of Li 0.5 La 0.5 Nb2O6, LiF, and LaF3 into a pellet shape and pressurizing it at 100 MPa is performed. As a result, a mixture of Li 0.5 La 0.5 Nb2O6, LiF, and LaF3 is formed into a pellet shape.

[0069] (Second firing step) Next, a second firing step S50 of firing a mixture of Li 0.5 La 0.5 Nb2O6, LiF, and LaF3 is performed. In the second firing step S50, the mixture of Li 0.5 La 0.5 Nb2O6, LiF, and LaF3 is heated at 1000 °C for 6 hours in a nitrogen atmosphere for firing.

[0070] Through the above steps, a crystal with a pyrochlore structure represented by the composition formula "Li 1.25 La 0.58 Nb2O6F" can be obtained. This time, the crystal obtained in the second firing step S50 is in the form of pellets. The relative density of the pellet-shaped solid electrolyte sintered body was 78%.

[0071] Note that by changing the mixing ratios of La2O3, Li2CO3, and Nb2O5 and the mixing ratio of LiF and LaF3 in the above manufacturing process, a crystal with a pyrochlore structure represented by the composition formula "Li 2-α La (1+α) / 3 Nb2O 7-β F β " can be obtained.

[0072] α described in this composition formula can be adjusted by changing the mixing ratios of La2O3, Li2CO3, and Nb2O5. β can be adjusted by changing the mixing ratio of LiF and LaF3. Also, when firing, a part of the material sublimes. Therefore, α and β can also be adjusted by changing the firing conditions, the firing furnace atmosphere, and the firing furnace size in the first firing step and the second firing step.

[0073] Next, the crystal structure of the pyrochlore-type solid electrolyte will be described with reference to FIG. 3. FIG. 3 shows the crystal structure obtained by synchrotron radiation analysis of the pyrochlore-type solid electrolyte. In synchrotron radiation analysis, the crystal structure was obtained by performing Rietveld analysis using the measurement data by X-ray diffraction (XRD).

[0074] As shown in FIG. 3, the pyrochlore-type solid electrolyte has a crystal structure in which a three-dimensional network of octahedrons composed of NbO6 is formed. In NbO6, O is arranged at the vertices with Nb as the center, and adjacent NbO6 share vertices. In the three-dimensional network composed of NbO6, a hexagonal tunnel structure in which cations composed of La / Li and anions composed of F are arranged is formed.

[0075] The secondary battery 10 of the present embodiment described above is provided with a shut-off layer 16 containing a lithium-ion conductive solid material whose lithium-ion conductivity decreases upon contact with lithium metal. As a result, even if dendrites grow from the negative electrode 12, the lithium-ion conductivity decreases in the shut-off layer 16, the resistance increases and insulation occurs, forming a non-conductor of lithium ions. As a result, in the shut-off layer 16, the growth of dendrites can be stopped, and the short circuit between the negative electrode 12 and the positive electrode 14 can be suppressed.

[0076] Further, the lithium-ion conductive solid material is solid and is stably held inside the secondary battery 10. For example, even if the secondary battery 10 expands and contracts during charge and discharge, the lithium-ion conductive solid material of the shut-off layer 16 does not come into direct contact with the negative electrode 12. Therefore, as long as dendrites do not grow from the negative electrode 12 and reach the shut-off layer 16, the lithium-ion conductivity of the lithium-ion conductive solid material does not decrease, and the secondary battery 10 can be used stably.

[0077] Also, by using a pyrochlore-type solid electrolyte as the lithium-ion conductive solid material, the secondary battery 10 can be shut down in a short time due to contact with lithium metal. Therefore, the safety of the secondary battery 10 can be improved.

[0078] In addition, the pyrochlore-type solid electrolyte of the present embodiment is a material with higher ion conductivity than the oxide-based solid electrolyte conventionally known as a solid electrolyte for secondary batteries. Therefore, in the configuration in which the secondary battery 10 is provided with the shut-off layer 16, it is possible to avoid a decrease in ion conductivity while suppressing a short circuit of the secondary battery 10.

[0079] Also, when lithium metal is used as the negative electrode active material of the negative electrode 12, a short circuit of the secondary battery 10 is likely to occur. In the secondary battery 10 using lithium metal as such a negative electrode active material, the short circuit of the secondary battery 10 can be effectively suppressed by providing the shut-off layer 16.

[0080] In addition, when an olivine-type active material is used as the positive electrode active material of the positive electrode 14, the secondary battery 10 is likely to short-circuit. In the secondary battery 10 using such an olivine-type active material as the positive electrode active material, the short circuit of the secondary battery 10 can be effectively suppressed by providing the shut-off layer 16.

[0081] In addition, in the present embodiment, a solid electrolyte is used for the electrolyte layer 15. The solid electrolyte is an electrolyte material that is highly safe while being likely to short-circuit. In the secondary battery 10 using such a solid electrolyte, the short circuit of the secondary battery 10 can be effectively suppressed by providing the shut-off layer 16.

[0082] (Second Embodiment) Next, a second embodiment of the present disclosure will be described. Hereinafter, only the parts different from the first embodiment will be described.

[0083] The positive electrode 14 of the second embodiment contains the same lithium-ion conductive solid material as that used in the shut-off layer 16 in addition to the positive electrode active material. In the secondary battery 10 of the second embodiment having such a configuration, the same effects as those of the first embodiment can be achieved. In addition, by providing the lithium-ion conductive solid material on the positive electrode 14, the ion conductivity of the positive electrode 14 can be improved.

[0084] (Third Embodiment) Next, a third embodiment of the present disclosure will be described. Hereinafter, only the parts different from the above embodiments will be described.

[0085] The shut-off layer 16 of the third embodiment contains the same solid electrolyte (for example, LLZO) as that used in the electrolyte layer 15 in addition to the lithium-ion conductive solid material. In the secondary battery 10 of the third embodiment having such a configuration, the same effects as those of the first embodiment can be achieved.

[0086] (Fourth Embodiment) Next, a fourth embodiment of the present disclosure will be described. Hereinafter, only the parts different from the above embodiments will be described.

[0087] In the positive electrode 14 of the fourth embodiment, in addition to the positive electrode active material, the same lithium ion conductive solid material as that used in the shut-off layer 16 is included. Further, in the shut-off layer 16 of the fourth embodiment, in addition to the lithium ion conductive solid material, the same solid electrolyte (for example, LLZO) as the solid electrolyte used in the electrolyte layer 15 is included. Also in the secondary battery 10 of the fourth embodiment having such a configuration, the same effects as those of the first embodiment can be achieved.

[0088] (Fifth Embodiment) Next, a fifth embodiment of the present disclosure will be described. Hereinafter, only the parts different from the above embodiments will be described.

[0089] In the electrolyte layer 15 of the fifth embodiment, instead of the solid electrolyte, an electrolytic solution and a separator are provided. The separator has a porous structure and functions to separate the negative electrode 12 and the positive electrode 14 and allow ions to pass through. As the separator, for example, a porous body can be used. As the electrolytic solution, for example, ethylene carbonate or the like can be used. The lithium ion conductive solid material of the shut-off layer 16 can be provided by coating the surface of the sheet-shaped positive electrode 14 or the separator, or the surface of the particulate positive electrode active material.

[0090] Also in the secondary battery 10 of the fifth embodiment having such a configuration, the same effects as those of the first embodiment can be achieved. Further, by using an electrolytic solution in the electrolyte layer 15, the occurrence of a short circuit can be suppressed as compared with the case where a solid electrolyte is used.

[0091] (Sixth Embodiment) Next, a sixth embodiment of the present disclosure will be described. Hereinafter, only the parts different from the above embodiments will be described.

[0092] As shown in Fig. 6, the secondary battery 10 in the initial state of the sixth embodiment is provided with a negative electrode current collector 11, an electrolyte layer 15, a shut layer 16, a positive electrode 14, and a positive electrode current collector 13. That is, the secondary battery 10 of the sixth embodiment is configured as an anode-free battery in which the negative electrode 12 is not formed between the negative electrode current collector 11 and the electrolyte layer 15 in the initial state. The initial state is a state in which each component of the secondary battery 10 is assembled and the secondary battery 10 is not charged.

[0093] In the secondary battery 10 of the sixth embodiment, a solid electrolyte (for example, LLZO) is used as the electrolyte layer 15. In the initial state, the negative electrode current collector 11 and the electrolyte layer 15 are arranged adjacent to each other.

[0094] As shown in Fig. 7, when the secondary battery 10 is charged, the negative electrode 12 is formed in the secondary battery 10. When the secondary battery 10 is charged, lithium ions move from the positive electrode 14 to the negative electrode current collector 11 side, and lithium metal is deposited on the negative electrode current collector 11 by a dissolution precipitation reaction, and the negative electrode 12 is formed by this lithium metal. The lithium metal formed on the negative electrode current collector 11 becomes the negative electrode active material.

[0095] The negative electrode 12 is formed between the negative electrode current collector 11 and the shut layer 16. In the sixth embodiment, the negative electrode 12 is formed between the negative electrode current collector 11 and the electrolyte layer 15 and is formed at the interface between the negative electrode current collector 11 and the electrolyte layer 15. The negative electrode 12 is formed so as to be in contact with the negative electrode current collector 11, and electron transfer is possible between the negative electrode 12 and the negative electrode current collector 11. The lithium metal constituting the negative electrode 12 becomes lithium ions during discharge and moves to the positive electrode 14.

[0096] Even in the secondary battery 10 of the sixth embodiment having the above configuration, the same effects as those of the first embodiment can be obtained.

[0097] In addition, in the secondary battery 10 of the sixth embodiment, a coating layer that promotes the dissolution and deposition reaction of lithium metal may be provided on the surface of the negative electrode current collector 11 on the electrolyte layer 15 side. The coating layer can make the dissolution and deposition reaction of lithium metal uniform and promote the deposition of lithium metal. As such a coating layer, an alloy-based material or a carbon-based material can be used.

[0098] (Seventh Embodiment) Next, a seventh embodiment of the present disclosure will be described. Hereinafter, only the parts different from the above embodiments will be described.

[0099] The secondary battery 10 of the seventh embodiment is configured as an anode-free battery, similar to the sixth embodiment. In the secondary battery 10 of the seventh embodiment, a solid electrolyte (for example, LLZO) is used as the electrolyte layer 15.

[0100] As shown in FIG. 8, in the secondary battery 10 of the seventh embodiment, the electrolyte layer 15 includes a dense layer 15a and a porous layer 15b. The dense layer 15a is provided on the positive electrode current collector 13 side and is in contact with the shut-off layer 16. The porous layer 15b is provided on the negative electrode current collector 11 side and is in contact with the negative electrode current collector 11.

[0101] The dense layer 15a and the porous layer 15b are made of the same solid electrolyte and have different densities. The dense layer 15a has a dense structure without pores. The dense layer 15a can ensure the insulation between the negative electrode 12 and the positive electrode 14. The porous layer 15b has a porous structure with a large number of pores and has a lower density than the dense layer 15a.

[0102] The porous layer 15b can have an arbitrary shape, for example, a porous structure in which a large number of pores are regularly formed or a porous structure in which a large number of pores are irregularly formed. The porous layer 15b having a regular porous structure can be created using, for example, a 3D printer or the like. The porous layer 15b having an irregular porous structure can be created, for example, by heating and removing a pore-forming agent mixed in the solid electrolyte.

[0103] When the secondary battery 10 is charged, lithium ions move from the positive electrode 14 to the negative electrode current collector 11 side, and lithium metal is deposited on the negative electrode current collector 11 by a dissolution and precipitation reaction, forming the negative electrode 12.

[0104] The negative electrode 12 is formed between the negative electrode current collector 11 and the shut-off layer 16. In the present seventh embodiment, the negative electrode 12 is formed inside the pores of the porous layer 15b in contact with the negative electrode current collector 11. Therefore, the negative electrode 12 is formed between the negative electrode current collector 11 and the dense layer 15a of the electrolyte layer 15. The negative electrode 12 formed in the porous layer 15b is in contact with the negative electrode current collector 11, enabling the transfer of electrons between the negative electrode 12 and the negative electrode current collector 11.

[0105] Also in the secondary battery 10 of the present seventh embodiment having the above configuration, the same effects as those of the first embodiment can be achieved.

[0106] When the negative electrode 12 is formed at the interface between the negative electrode current collector 11 and the electrolyte layer 15, during charging, the thickness of the secondary battery 10 increases by the amount of increase in the thickness of the negative electrode 12, and during discharging, the thickness of the secondary battery 10 decreases by the amount of decrease in the thickness of the negative electrode 12. In contrast, in the secondary battery 10 of the present seventh embodiment, lithium metal is deposited inside the pores of the porous layer 15b of the electrolyte layer 15 to form the negative electrode 12. Therefore, during charging, the distance between the negative electrode current collector 11 and the electrolyte layer 15 does not increase, and during discharging, the distance between the negative electrode current collector 11 and the electrolyte layer 15 does not decrease, suppressing fluctuations in the thickness of the secondary battery 10 during charge and discharge.

[0107] In the secondary battery 10 of the present seventh embodiment, a coating layer that promotes the dissolution and precipitation reaction of lithium metal may be provided on the surface of the pores of the porous layer 15b. The coating layer can homogenize the dissolution and precipitation reaction of lithium metal. As such a coating layer, an alloy-based material or a carbon-based material can be used.

[0108] (Eighth Embodiment) Next, the eighth embodiment of the present disclosure will be described. Hereinafter, only the parts different from the above embodiments will be described.

[0109] As shown in FIG. 9, the secondary battery 10 of the eighth embodiment has a bipolar structure. The secondary battery 10 of the eighth embodiment is provided with a plurality of battery cells 100 and 101. The plurality of battery cells 100 and 101 are stacked and arranged and connected in series. The number of the battery cells 100 and 101 constituting the secondary battery 10 can be arbitrarily set, and FIG. 9 shows an example in which two battery cells 100 and 101 are stacked and provided.

[0110] The first battery cell 100 and the second battery cell 100 each include a negative electrode 12, an electrolyte layer 15, a shut-off layer 16, and a positive electrode 14. A common current collector 17 is provided between the adjacent first battery cell 100 and the second battery cell 101. The first battery cell 100 and the second battery cell 101 share the common current collector 17.

[0111] The common current collector 17 is sandwiched between the positive electrode 14 of one adjacent first battery cell 100 and the negative electrode 12 of the other adjacent second battery cell 101. The first battery cell 100 and the second battery cell are connected in series via the common current collector 17. Therefore, the positive electrode 14 of the first battery cell 100, the common current collector 17, and the negative electrode 12 of the second battery cell 101 form a bipolar structure.

[0112] In the bipolar secondary battery 10 adopted in the eighth embodiment, current unevenness is likely to occur and lithium metal dendrites are likely to occur due to its structure. In such a bipolar secondary battery 10, by providing the shut-off layer 16, the short circuit of the secondary battery 10 can be effectively suppressed.

Examples

[0113] Next, examples of the present disclosure will be described. In Examples 1 to 4, at least one of the lithium ion conductive solid material of the shut-off layer 16 and the positive electrode active material of the positive electrode 14 is made different. Further, a secondary battery 10 not provided with the shut-off layer 16 is used as a comparative example. Examples 1 to 4 and the comparative example use the configuration of the secondary battery 10 of the second embodiment.

[0114] In secondary batteries 10 of Examples 1 to 4 and the Comparative Example, the thickness of the negative electrode 12 was 25 μm, the thickness of the electrolyte layer 15 was 100 μm, and the thickness of the positive electrode 14 was 50 μm. In the secondary batteries 10 of Examples 1 to 4, the thickness of the shut-off layer 16 was 10 μm.

[0115] In secondary batteries 10 of Examples 1 to 4 and the Comparative Example, the positive electrode 14 contains 50% of a positive electrode active material and 50% of a lithium ion conductive solid material. In Examples 1 to 3 and the Comparative Example, as the positive electrode active material, layered active material LiNi 0.8 CoMn 0.1 O2 (NCM811) was used. In Example 4, as the positive electrode active material, olivine type active material LiMn 0.8 Fe 0.2 PO4 (LMFP) was used.

[0116] Also, in secondary batteries 10 of Examples 1 to 4 and the Comparative Example, lithium metal was used as the negative electrode active material of the negative electrode 12, and Li7La3Zr2O 12 (LLZO) was used as the electrolyte material of the electrolyte layer 15.

[0117] In Example 1 and Example 4, as the lithium ion conductive solid material of the shut-off layer 16, pyrochlore type solid electrolyte Li 1.25 La 0.58 Nb2O6F was used. In the second embodiment, as the lithium ion conductive solid material of the shut-off layer 16, NASICON type oxide based solid electrolyte Li 1.4 Al 0.4 Ti 1.6 (PO4)3 (LATP) was used. In the third example, as the lithium ion conductive solid material of the shut-off layer 16, perovskite type oxide based solid electrolyte La 0.57 Li 0.29 TiO3 (LLTO) was used. In the Comparative Example, the shut-off layer 16 is not provided.

[0118] Figure 10 shows the results of a cycle test in which the charge and discharge of the secondary battery 10 were repeated. In the cycle test, the presence or absence of a short circuit, the time from when the resistance of the secondary battery 10 rapidly increased until shutdown, the DC resistance before the DC resistance rapidly increased, and the number of cycles until the resistance of the secondary battery 10 rapidly increased were measured. In the cycle test, the battery temperature was 10°C, the voltage was 4.3V - 2.7V, and the C rate was 0.2C. The resistance evaluation of the secondary battery 10 was performed using the AC impedance method, and the resistance was measured at SOC 50%. Note that the rapid increase in the resistance of the secondary battery 10 occurs when dendrites grow from the negative electrode 12 and the lithium-ion conductive solid material contained in the shut-off layer 16 comes into contact with lithium metal and is reduced.

[0119] As shown in Figure 10, in the comparative example where the shut-off layer 16 was not provided, a short circuit occurred in the secondary battery 10 and the voltage became 0V. In contrast, in Examples 1 to 4 where the shut-off layer 16 was provided, the resistance of the secondary battery 10 increased before the voltage reached 0V, and the charge and discharge of the secondary battery 10 stopped while maintaining the voltage.

[0120] The number of cycles until the resistance of the secondary battery 10 rapidly increased was 113 for Example 1, 108 for Example 2, 98 for Example 3, 70 for Example 4, and 110 for the comparative example. Among Examples 1 to 3 using a layered active material as the positive electrode active material, Example 1 had the largest number of cycles until the resistance of the secondary battery 10 rapidly increased. That is, when using a pyrochlore-type solid electrolyte as the lithium-ion conductive solid material, the number of charge and discharge cycles of the secondary battery 10 can be increased.

[0121] Also, comparing Example 1 and Example 4 using a pyrochlore-type solid electrolyte, Example 4 using an olivine-type active material as the positive electrode active material had a significantly smaller number of cycles until the resistance of the secondary battery 10 rapidly increased than Example 1 using a layered active material as the positive electrode active material. That is, when using an olivine-type active material as the positive electrode active material of the secondary battery 10, dendrites are likely to occur.

[0122] The time from when the resistance of the secondary battery 10 rapidly increased until shutdown was 65 hours for Example 1, 90 hours for Example 2, 120 hours for Example 3, and 62 hours for Example 4. The secondary battery 10 of the comparative example did not shut down. Among Examples 1 to 4, Examples 1 and 4 using the pyrochlore-type solid electrolyte had the shortest time from when the resistance of the secondary battery 10 rapidly increased until shutdown. That is, when using the pyrochlore-type solid electrolyte as the lithium-ion conductive solid material, the secondary battery 10 can be shut down in a short time, and the safety of the secondary battery 10 can be made higher.

[0123] Also, when comparing Examples 1 and 4 using the pyrochlore-type solid electrolyte, Example 4 using the olivine-type active material as the positive electrode active material has a shorter time until shutdown than Example 1 using the layered active material as the positive electrode active material. That is, in the secondary battery 10 using the olivine-type active material where dendrites are likely to occur, by providing the shut-off layer 16, the occurrence of a short circuit can be effectively suppressed.

[0124] The DC resistance of the secondary battery 10 before the rapid increase in DC resistance (i.e., during normal operation) was 80 Ω for Example 1, 207 Ω for Example 2, 147 Ω for Example 3, 74 Ω for Example 4, and 220 Ω for the comparative example. The DC resistance of the secondary battery 10 during normal operation was the highest for Example 1. That is, Example 1 using the pyrochlore-type solid electrolyte has the best input / output characteristics of the secondary battery 10.

[0125] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. Also, the means disclosed in the above embodiments may be appropriately combined within the range where implementation is possible.

[0126] Although the present disclosure has been described based on examples, it is understood that the present disclosure is not limited to such examples or structures. The present disclosure also includes various modifications and variations within an equivalent range. In addition, although various combinations and forms are shown in the present disclosure, other combinations and forms that include only one element, more than one element, or less than one element thereof also fall within the scope and spirit of the present disclosure.

[0127] The features of the secondary battery disclosed in this specification are shown as follows. (Item 1) A positive electrode (14) containing a positive electrode active material, A negative electrode (12) containing a negative electrode active material, An electrolyte layer (15) provided adjacent to the negative electrode and composed of an electrolyte material having lithium ion conductivity, A shut-off layer (16) provided adjacent to the positive electrode and containing a lithium ion conductive solid material having lithium ion conductivity, Comprising The electrolyte layer is interposed between the negative electrode and the shut-off layer, The electrolyte material is different from the lithium-ion conductive solid material A solid electrolyte, an electrolytic solution, a polymer at least any one of Or a mixture thereof, The shut-off layer is composed of only the lithium ion conductive solid material or a mixture of the lithium ion conductive solid material and , different from the lithium-ion conductive solid material At least one of a solid electrolyte, an electrolytic solution, and a polymer, The lithium ion conductive solid material is a pyrochlore type solid electrolyte, a NASICON type solid electrolyte, a perovskite , su At least one of a type solid electrolyte, The lithium ion conductive solid material has a secondary battery in which the decrease in lithium ion conductivity when in contact with lithium metal is greater than that of the electrolyte material. (Item 2) A positive electrode (14) containing a positive electrode active material, A negative electrode (12) containing a negative electrode active material, An electrolyte layer (15) provided adjacent to the negative electrode and containing an electrolyte material having lithium ion conductivity; A shut-off layer (16) provided adjacent to the positive electrode and containing a lithium ion conductive solid material having lithium ion conductivity; Comprising: The electrolyte layer is interposed between the negative electrode and the shut-off layer; The electrolyte material is at least one of a solid electrolyte different from the lithium-ion conductive solid material, an electrolyte solution, a polymer, or a mixture thereof, The lithium ion conductive solid material forms a non-conductor of lithium ions when in contact with lithium metal. A secondary battery. (Item 3) The lithium ion conductive solid material is at least one of a pyrochlore type solid electrolyte, a NASICON type solid electrolyte, and a perovskite type solid electrolyte. The secondary battery according to item 2. , su (Item 4) The lithium ion conductive solid material has a composition formula Aa 2-α Ab (1+α) / 3 B2O 7-β X β (Aa: alkali metal, Ab: lanthanoid, B: cation metal, X: anion replaceable with O) is an oxide-based solid electrolyte having a pyrochlore structure, 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 the sum of the valences of the cations composed of Aa, Ab, and B and the anions composed of O and X is negative, including a defect structure. The B is at least one of a Group 4 element, a Group 5 element, or a Group 15 element. The secondary battery according to any one of items 1 to 3. (Item 5) The B is at least one of Nb, V, Sb, Bi, Ta, Zr, Ti, Hf. The secondary battery according to item 2 or 3. (Item 6) The positive electrode active material contains an olivine type active material. The secondary battery according to any one of items 1 to 5. (Item 7) ​The secondary battery according to any one of Items 1 to 6, wherein the negative electrode active material contains lithium metal. (Item 8) The electrolyte material the The secondary battery according to any one of Items 1 to 7, wherein the electrolyte material contains a solid electrolyte. (Item 9) Comprising a negative electrode current collector (11), The negative electrode is not provided in the initial state where charging is not performed, The secondary battery according to any one of Items 1 to 8, wherein the negative electrode is formed so as to be in contact with the negative electrode current collector when charging is performed. (Item 10) A plurality of battery cells (100, 101) including the positive electrode, the negative electrode, the electrolyte layer, and the shut layer are provided, Comprising a common current collector (17) sandwiched between the positive electrode of one adjacent battery cell and the negative electrode of the other adjacent battery cell, The secondary battery according to any one of Items 1 to 9, wherein one adjacent battery cell and the other adjacent battery cell are connected in series via the common current collector. (Item 11) The thickness of the shut-off layer is 2 μm or more and 10 μm or less. The secondary battery according to any one of Items 1 to 10. (Item 12) The lithium-ion conductive solid material is Li 1.25 La 0.58 Nb 2 O 6 F, Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 , or La 0.57 Li 0.29 TiO 3 The secondary battery according to any one of Items 1 to 11, including at least one selected from the group consisting of. (Item 13) The positive electrode active material is LiNi 0.8 Co 0.1 Mn 0.1 O 2and LiMn 0.8 Fe 0.2 PO 4 The secondary battery according to Item 1, which is at least any one of. (Item 14) The electrolyte material is Li 7 La 3 Zr 2 O 12 The secondary battery according to any one of Items 1 to 13.

Claims

1. a positive electrode (14) containing a positive electrode active material; a negative electrode (12) containing a negative electrode active material; an electrolyte layer (15) provided adjacent to the negative electrode and composed of an electrolyte material having lithium ion conductivity; a shut-off layer (16) provided adjacent to the positive electrode and containing a lithium ion conductive solid material having lithium ion conductivity; comprising the electrolyte layer is interposed between the negative electrode and the shut-off layer; the electrolyte material is at least one of a solid electrolyte, an electrolytic solution, a polymer, or a mixture thereof, which is different from the lithium ion conductive solid material; the shut-off layer is composed of only the lithium ion conductive solid material, or a mixture of the lithium ion conductive solid material and at least one of a solid electrolyte, an electrolytic solution, and a polymer different from the lithium ion conductive solid material; the lithium ion conductive solid material is at least one of a pyrochlore type solid electrolyte, a NASICON type solid electrolyte, and a perovskite type solid electrolyte; a secondary battery in which the decrease in lithium ion conductivity when the lithium ion conductive solid material is in contact with lithium metal is greater than that of the electrolyte material.

2. a positive electrode (14) containing a positive electrode active material; a negative electrode (12) containing a negative electrode active material; an electrolyte layer (15) provided adjacent to the negative electrode and containing an electrolyte material having lithium ion conductivity; a shut-off layer (16) provided adjacent to the positive electrode and containing a lithium ion conductive solid material having lithium ion conductivity; comprising the electrolyte layer is interposed between the negative electrode and the shut-off layer; The electrolyte material is at least one of a solid electrolyte different from the lithium ion conductive solid material, an electrolytic solution, a polymer, or a mixture thereof. The lithium ion conductive solid material forms a non-conductor of lithium ions when in contact with lithium metal. A secondary battery.

3. The secondary battery according to claim 2, wherein the lithium ion conductive solid material is at least one of a pyrochlore type solid electrolyte, a NASICON type solid electrolyte, and a perovskite type solid electrolyte.

4. The lithium ion conductive solid material has a composition formula Aa ２－α Ab （１＋α）／３ B ２ O ７－β X β (Aa: alkali metal, Ab: lanthanoid, B: cation metal, X: anion replaceable with O), and is an oxide-based solid electrolyte having a pyrochlore structure. 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 the sum of the valences of the cations composed of Aa, Ab, and B and the anions composed of O and X is negative, and it contains a defect structure. The secondary battery according to any one of claims 1 to 3, wherein B is at least one of a Group 4 element, a Group 5 element, or a Group 15 element.

5. The secondary battery according to claim 4, wherein B is at least one of Nb, V, Sb, Bi, Ta, Zr, Ti, Hf.

6. The secondary battery according to claim 1, wherein the positive electrode active material contains an olivine type active material.

7. The secondary battery according to claim 1, wherein the negative electrode active material contains lithium metal.

8. The secondary battery according to claim 1, wherein the electrolyte material contains the solid electrolyte.

9. It includes a negative electrode current collector (11). The negative electrode is not provided in the initial state where charging is not performed, The secondary battery according to claim 1, wherein the negative electrode is formed so as to be in contact with the negative electrode current collector when charging is performed.

10. A plurality of battery cells (100, 101) including the positive electrode, the negative electrode, the electrolyte layer, and the shut-off layer are provided, It includes a common current collector (17) sandwiched between the positive electrode of one adjacent battery cell and the negative electrode of the other adjacent battery cell, The secondary battery according to claim 1, wherein one adjacent battery cell and the other adjacent battery cell are connected in series via the common current collector.

11. The thickness of the shut-off layer is 2 μm or more and 10 μm or less in the secondary battery according to claim 1.

12. The lithium ion conductive solid material includes at least one selected from Li 1.25 La 0.58 Nb 2 O 6 F, Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3, or La 0.57 Li 0.29 TiO 3 in the secondary battery according to claim 1 or 3.

13. The positive electrode active material is at least one of LiNi 0.8 Co 0.1 Mn 0.1 O 2 and LiMn 0.8 Fe 0.2 PO 4 in the secondary battery according to claim 1.

14. The electrolyte material is Li 7 La 3 Zr 2 O 12 in the secondary battery according to claim 1 or 2.

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