Solid-state battery

Abstract

Provided is a solid-state battery that comprises a positive electrode part that includes a positive electrode active material, a negative electrode part that includes a negative electrode active material, and a solid electrolyte part. At least one of the positive electrode part and the solid electrolyte part includes a first solid electrolyte. The solid-state battery also comprises an interposing layer that is interposed between the positive electrode active material and the first solid electrolyte and contacts both the positive electrode active material and the first solid electrolyte. The first solid electrolyte includes Li, M, S, and O and has at least a crystal phase that has a tetragonal crystal structure. M is one or more elements that are selected from group 14 and group 15 and include at least Sn. The molar ratio of O to M is 0.1–3.0. The thickness of the interposing layer is less than 500 nm.

Description

solid state battery

[0001] This disclosure relates to solid-state batteries.

[0002] Rechargeable batteries, which can be repeatedly charged and discharged, have long been used in a variety of applications. For example, rechargeable batteries are used as power sources for electronic devices such as smartphones and laptop computers.

[0003] In secondary batteries, a liquid electrolyte is generally used as a medium for ion transfer that contributes to charging and discharging. In other words, so-called electrolyte solutions are used in secondary batteries. However, safety is generally required in such secondary batteries in terms of preventing electrolyte leakage. Furthermore, since organic solvents used in electrolyte solutions are flammable substances, safety is also required in that respect.

[0004] Therefore, research is underway on solid-state batteries that use solid electrolytes instead of liquid electrolytes.

[0005] K. Kanazawa, et al., Inorg. Chem., 2018, 57, 9925-9930

[0006] Japanese Patent Publication No. 2021-136149

[0007] The inventors of this invention recognized that conventional solid-state batteries have problems that need to be overcome and recognized the need to take countermeasures. Specifically, they identified the following problems:

[0008] Non-patent document 1 and patent document 1 use a Li-Sn-S solid electrolyte as a sulfide solid electrolyte with excellent water resistance. By using a Li-Sn-S solid electrolyte, the water resistance of the solid battery can be improved compared to conventionally known sulfide solid electrolytes.

[0009] However, the solid electrolytes described in Non-Patent Document 1 and Patent Document 1 have a narrower potential window and inferior oxidation resistance compared to conventional sulfide solid electrolytes. Therefore, they may become electrochemically unstable in the high potential range, potentially leading to increased charge transfer resistance.

[0010] This disclosure has been made in view of the above issues. Specifically, the primary object of this disclosure is to provide a solid-state battery containing a sulfide solid electrolyte and having better oxidation resistance.

[0011] To achieve the above objective, one embodiment of the present disclosure provides a solid battery comprising a positive electrode portion containing a positive electrode active material, a negative electrode portion containing a negative electrode active material, and a solid electrolyte portion, wherein at least one of the positive electrode portion and the solid electrolyte portion contains a first solid electrolyte, and further comprises an intervening layer interposed between the positive electrode active material and the first solid electrolyte, and in contact with each of the positive electrode active material and the first solid electrolyte, wherein the first solid electrolyte comprises a crystalline phase having a tetragonal crystal structure and contains Li, M, S, and O, where M is one or more elements selected from Group 14 and Group 15 containing at least Sn, the molar ratio of O to M is 0.1 or more and 3.0 or less, and the thickness of the intervening layer is less than 500 nm.

[0012] A solid-state battery according to one embodiment of the present disclosure comprises a sulfide solid electrolyte and has more suitable oxidation resistance.

[0013] Figure 1 is a schematic cross-sectional view showing a solid-state battery according to the first embodiment of this disclosure. Figure 2 is a schematic cross-sectional view showing a modified example of the solid-state battery according to the first embodiment of this disclosure. Figure 3 is a schematic cross-sectional view showing a solid-state battery according to the second embodiment of this disclosure. Figure 4 is an enlarged cross-sectional view showing portion A of the solid-state battery shown in Figure 3. Figure 5 is a schematic cross-sectional view showing a modified example of the solid-state battery according to the second embodiment of this disclosure. Figure 6 is a schematic cross-sectional view showing a solid-state battery according to the third embodiment of this disclosure. Figure 7 is an enlarged cross-sectional view showing portion B of the solid-state battery shown in Figure 6.

[0014] The solid-state battery of this disclosure will be described in detail below. The applicant provides the following description and examples so that those skilled in the art can fully understand this disclosure, and it should be noted that these are not intended to limit the subject matter described in the claims. In other words, this disclosure is not particularly limited to the preferred embodiments etc. described below, and can be modified and implemented as appropriate within the scope of its purpose. For the sake of convenience, in order to explain the main points or to facilitate understanding, embodiments etc. may be shown separately, but partial substitution and / or combination of configurations shown in different embodiments etc. is possible. In the description of such embodiments, redundant explanations of substantially identical matters may be omitted, and only the differences may be explained. In particular, similar effects of similar configurations may not be mentioned sequentially for each embodiment. Also, although the explanation will be given with reference to the drawings as necessary, the contents shown in the drawings are only schematically and illustrative for the purpose of understanding this disclosure, and the appearance and dimensional ratios may differ from the actual product.

[0015] In this specification, "cross-sectional view" refers to the form of a solid-state battery's stacked structure as viewed from a direction approximately perpendicular to the stacking direction (simply put, the form when cut by a plane parallel to the thickness direction of the layers). Furthermore, in this specification, "plan view" or "plan view shape" refers to a sketch of the object as viewed from above or below along the thickness direction of the layers (i.e., the stacking direction mentioned above).

[0016] In this specification, “up and down” and “left and right” as used directly or indirectly correspond to the up and down and left and right directions in the figures, respectively. Unless otherwise specified, the same reference numeral or symbol indicates the same component, part, or has the same meaning.

[0017] In this disclosure, "solid-state battery" broadly refers to a battery whose components are made of solids, and narrowly refers to an all-solid-state battery whose components (particularly preferably all components) are made of solids. In one preferred embodiment, the solid-state battery in this disclosure is a stacked solid-state battery configured such that each layer constituting the battery component unit is stacked on top of the others. "Solid-state battery" includes not only primary batteries but also so-called "secondary batteries" that can be repeatedly charged and discharged. The term "secondary battery" is not overly restrictive and may also include, for example, energy storage devices. Below, we will describe the specific configuration of a solid-state battery using a solid-state battery, which is a secondary battery, as an example.

[0018] The features of this disclosure relate to the positive electrode and solid electrolyte components included in the solid-state battery. Below, in order to understand the overall structure of the solid-state battery, the basic configuration of the solid-state battery of this disclosure will be described. However, the configuration of the solid-state battery described here is merely an example for understanding the invention and does not limit the invention.

[0019] [Basic Configuration of Solid-State Battery] Figure 1 is a schematic cross-sectional view of a solid-state battery according to the first embodiment of the present disclosure. The solid-state battery 1 has at least an electrode portion including a positive electrode portion 20 and a negative electrode portion 30, and a solid electrolyte portion 40. Specifically, as shown in Figure 1, the solid-state battery 1 includes a battery component consisting of a positive electrode portion 20, a negative electrode portion 30, and a solid electrolyte portion 40 interposed between them.

[0020] The solid-state battery 1 according to this disclosure typically comprises at least one battery component unit along the stacking direction Z, each unit consisting of a positive electrode portion 20, a negative electrode portion 30, and a solid electrolyte portion 40 interposed between them. The positive electrode portion 20 and the negative electrode portion 30 are stacked alternately via the solid electrolyte portion 40. Although Figure 1 illustrates a configuration in which one layer of positive electrode portion 20, one layer of negative electrode portion 30, and a solid electrolyte portion 40 located between the positive electrode portion 20 and the negative electrode portion 30 are stacked, the number of layers is not limited to this example. For example, multiple layers (e.g., tens to hundreds of layers) of positive electrode portions 20 and negative electrode portions 30 may be stacked via the solid electrolyte portion 40.

[0021] (Positive electrode part 20 / Negative electrode part 30) The positive electrode part 20 includes a positive electrode active material layer 22 containing a positive electrode active material. In one embodiment, the positive electrode part 20 may further contain a solid electrolyte. On the other hand, the negative electrode part 30 includes a negative electrode active material layer 32 containing a negative electrode active material. In one embodiment, the negative electrode part 30 may further contain a solid electrolyte. The positive electrode part 20 and the negative electrode part 30 having such a configuration can also be referred to as a "composite positive electrode body" and a "composite negative electrode body", respectively.

[0022] The positive electrode active material and the negative electrode active material are substances that participate in the transfer of electrons in the solid-state battery 1. Ions move (conduct) between the positive electrode part 20 and the negative electrode part 30 through the solid electrolyte, and charge and discharge are performed by the transfer of electrons. The electrode active materials contained in the positive electrode part 20 and the negative electrode part 30 are preferably capable of occluding and releasing ions that contribute to charge and discharge, such as lithium ions or sodium ions. That is, the solid-state battery is preferably an all-solid-state secondary battery in which ions that contribute to charge and discharge, such as lithium ions or sodium ions, move between the positive electrode part 20 and the negative electrode part 30 through the solid electrolyte to perform charge and discharge of the battery.

[0023] (Positive electrode active material) Examples of the positive electrode active material contained in the positive electrode part 20 include at least one selected from the group consisting of a lithium-containing phosphate compound having a NASICON-type structure, a lithium-containing phosphate compound having an olivine-type structure, a lithium-containing layered oxide, and a lithium-containing oxide having a spinel-type structure.

[0024] An example of the lithium-containing phosphate compound having a NASICON-type structure is Li ３ [[ID=ll]]V ２ (PO ４ ) ３ etc. Examples of the lithium-containing phosphate compound having an olivine-type structure include Li ３ Fe ２ (PO ４ ) ３ LiFePO ４ and / or LiMnPO ４ etc. Examples of the lithium-containing layered oxide include LiCoO ２, and / or LiCo １／３ Ni １／３ Mn １／３ O ２ Examples include LiMn. ２ O ４ , and / or LiNi ０．５ Mn １．５ O ４ Examples include the following. The type of lithium compound is not particularly limited, but may be, for example, lithium transition metal composite oxides and lithium transition metal phosphate compounds. Lithium transition metal composite oxides are a general term for oxides that contain lithium and one or more transition metal elements as constituent elements. Lithium transition metal phosphate compounds are a general term for phosphate compounds that contain lithium and one or more transition metal elements as constituent elements. The type of transition metal element is not particularly limited, but may be, for example, cobalt (Co), nickel (Ni), manganese (Mn), and iron (Fe).

[0025] In addition, the positive electrode active material may be, for example, an oxide, disulfide, chalcogenide, or conductive polymer. Oxides may be, for example, titanium oxide, vanadium oxide, or manganese dioxide. Disulfides may be, for example, titanium disulfide or molybdenum sulfide. Chalcogenides may be, for example, niobium selenide. Conductive polymers may be, for example, disulfide, polypyrrole, polyaniline, polythiophene, polyparastyrene, polyacetylene, or polyacene.

[0026] (Negative electrode active material) Examples of negative electrode active materials include oxides containing at least one element selected from the group consisting of titanium (Ti), silicon (Si), tin (Sn), chromium (Cr), iron (Fe), niobium (Nb), and molybdenum (Mo), carbon materials such as graphite, graphite-lithium compounds, lithium alloys, lithium-containing phosphate compounds having a NASCICON-type structure, lithium-containing phosphate compounds having an olivine-type structure, and lithium-containing oxides having a spinel-type structure. An example of a lithium alloy is Li-Al. An example of a lithium-containing phosphate compound having a NASCICON-type structure is Li ３ V ２ (PO ４ ) ３ , and / or LiTi ２ (PO ４ ) ３ Examples include Li ３ Fe ２ (PO ４ ) ３ , and / or LiCuPO ４ Examples include Li ４ Ti ５ O １２ These are some examples.

[0027] In addition, in the solid-state battery 1, the positive electrode portion 20 and the negative electrode portion 30 may be made of the same material, or they may be made of different materials.

[0028] The thickness of the positive electrode portion 20 and the negative electrode portion 30 is not particularly limited, but for example, they may be 2 μm or more and 50 μm or less, and more particularly 5 μm or more and 30 μm or less, respectively.

[0029] (Positive electrode current collector layer / Negative electrode current collector layer) Although not essential, the positive electrode portion 20 and the negative electrode portion 30 may each be provided with a positive electrode current collector 21 and a negative electrode current collector 31. The positive electrode current collector 21 and the negative electrode current collector 31 may each be in the form of foil. Parts of the positive electrode current collector 21 and the negative electrode current collector 31 may each be exposed to the outside of the solid battery 1. For example, the positive electrode current collector 21 and the negative electrode current collector 31 may each have an electrical connection part for electrically connecting to the outside. In one embodiment, the solid battery 1 may further be provided with end face electrodes (not shown) on the end face of the laminate of the positive electrode portion 20, the negative electrode portion 30 and the solid electrolyte portion 40, and electrically connected to the positive electrode current collector 21 and the negative electrode current collector 31, respectively.

[0030] As described above, the positive electrode current collector 21 and the negative electrode current collector 31 are not essential in a solid-state battery, and solid-state batteries without such positive electrode current collectors 21 and negative electrode current collectors 31 are also conceivable. In other words, the solid-state battery of this disclosure may be a so-called current collector-less solid-state battery.

[0031] (Solid Electrolyte Section) The solid electrolyte section 40 includes a solid electrolyte that can conduct ions that contribute to charging and discharging, such as lithium ions or sodium ions. In particular, the solid electrolyte section 40 that forms a battery component unit in the solid battery 1 may form a layer between the positive electrode section 20 and the negative electrode section 30 that can conduct ions that contribute to charging and discharging, such as lithium ions or sodium ions. The solid electrolyte section 40 only needs to be provided between the positive electrode section 20 and the negative electrode section 30. In other words, the solid electrolyte section 40 may exist around the positive electrode section 20 and / or the negative electrode section 30 so as to protrude from between the positive electrode section 20 and the negative electrode section 30.

[0032] The thickness of the solid electrolyte portion 40 is not particularly limited. The thickness of the solid electrolyte portion 40 located between the positive electrode portion 20 and the negative electrode portion 30 may be, for example, 1 μm or more and 15 μm or less, and particularly 1 μm or more and 5 μm or less.

[0033] The outer surface of the solid-state battery 1 may be covered with a protective layer 10. The protective layer 10 is a layer provided to physically and chemically protect the solid-state battery 1. The protective layer 10 may be provided so as to overlap the laminate of the positive electrode portion 20, the negative electrode portion 30, and the solid electrolyte portion 40 in a plan view. That is, as shown in Figure 1, the protective layer 10 may be provided on both sides of the solid-state battery 1 in the stacking direction Z of the electrode portion and the solid electrolyte portion. The material of the protective layer 10 is not particularly limited as long as it is an insulator, and may be, for example, resin, glass, ceramics, etc.

[0034] The solid-state battery 1 may further include reinforcing portions 60 provided on opposing sides in a direction intersecting the stacking direction Z. The reinforcing portions 60 may contribute to preventing short circuits in the solid-state battery 1. The reinforcing portions 60 are not particularly limited as long as they are insulators, and may be made of, for example, resin, glass, ceramics, etc.

[0035] [Features of the Solid-State Battery of This Disclosure] As a result of diligent research, the inventors have newly discovered that a solid-state battery with better oxidation resistance can be provided by having a structure in which a positive electrode active material, an intervening layer containing an element that contributes to charging and discharging, such as Li or Na, and a sulfide solid electrolyte having a predetermined composition are adjacent in this order. The embodiments of the solid-state battery of this disclosure having a structure in which a positive electrode active material, an intervening layer, and a sulfide solid electrolyte having a predetermined composition are adjacent in this order will be described below.

[0036] (First Embodiment) The solid battery 1 of the present disclosure includes a solid electrolyte portion 40 which contains a first solid electrolyte that is a sulfide solid electrolyte having a predetermined composition. The solid battery 1 further includes an intervening layer 50 which is interposed between the positive electrode active material layer 22 and the solid electrolyte portion 40 and is arranged to be in contact with both the positive electrode active material layer 22 and the solid electrolyte portion 40. That is, the solid battery 1 of the present disclosure has a structure in which the positive electrode active material layer 22, the intervening layer 50 containing an element that contributes to charging and discharging, such as Li or Na, and the solid electrolyte portion 40 containing the first solid electrolyte are in contact in this order. In other words, the positive electrode active material layer 22 is in contact with the intervening layer 50, and the solid electrolyte portion 40 may be in contact with the intervening layer 50 on the side opposite to the positive electrode active material layer 22. In short, the positive electrode active material layer 22 and the solid electrolyte portion 40 may be arranged so as to sandwich the intervening layer 50 in the stacking direction Z.

[0037] In this embodiment, the intervening layer 50 may be located between the positive electrode portion 20 and the solid electrolyte portion 40. That is, in the solid-state battery 1, the solid electrolyte portion 40, the intervening layer 50, and the positive electrode portion 20 may be stacked in this order along the stacking direction Z. More specifically, in the positive electrode portion 20, the positive electrode active material layer 22 may be formed in a layer adjacent to the intervening layer 50. Therefore, the solid electrolyte portion 40, the intervening layer 50, and the positive electrode active material layer 22 of the positive electrode portion 20 may be stacked in this order along the direction Z.

[0038] The first solid electrolyte includes at least a crystalline phase having a tetragonal crystal structure. For example, the first solid electrolyte may include at least a crystalline phase having a tetragonal crystal structure belonging to the P4 / mmm space group.

[0039] For example, the first solid electrolyte may have a crystalline phase having a tetragonal crystal structure as a single phase. Alternatively, the first solid electrolyte may further include an amorphous phase and / or a crystalline phase having a hexagonal crystal structure in addition to the crystalline phase having a tetragonal crystal structure. The hexagonal crystalline phase may be, for example, P6 ３ It may have a crystal structure belonging to the space group / mmc.

[0040] The crystal structure of the first solid electrolyte can be measured by X-ray diffraction (XRD). Specifically, a test piece obtained by taking a portion of the solid electrolyte part 40 containing the first solid electrolyte can be measured using an XRD diffractometer (e.g., Bruker D8 ADVANCE) within a predetermined measurement angle range (e.g., 2θ = 10 to 50 degrees), and the crystal structure of the first solid electrolyte can be determined from the obtained diffraction pattern. Alternatively, the crystal structure of the first solid electrolyte can be measured by electron diffraction using a transmission electron microscope (TEM). Specifically, a sample piece obtained by cutting a portion of the solid electrolyte part 40 containing the first solid electrolyte can be measured using a TEM (e.g., JEOL JEM-F200), and the crystal structure of the first solid electrolyte can be determined from the obtained diffraction pattern.

[0041] The first solid electrolyte comprises Li, M, sulfur (S), and oxygen (O). That is, in the solid battery 1 of this disclosure, an oxygen-doped sulfide solid electrolyte is used as the first solid electrolyte, which is arranged adjacent to the positive electrode active material layer 22 via an intervening layer 50. Here, M is one or more elements selected from Groups 14 and 15, which include at least Sn. By including such M, the reactivity of the sulfide solid electrolyte with water is reduced, and the water resistance of the solid battery can be improved. In other words, the first solid electrolyte comprises at least Li, Sn, S, and O, and optionally further comprises at least one element M' selected from Groups 14 and 15, excluding Sn. For example, M' may be at least one element selected from the group consisting of carbon (C), silicon (Si), germanium (Ge), lead (Pb), nitrogen (N), phosphorus (P), antimony (Sb), and bismuth (Bi). From the standpoint of excellent water resistance and electrochemical stability, the first solid electrolyte is particularly preferably composed of Si and / or Sb.

[0042] In the first solid electrolyte, the molar ratio of O to M (hereinafter also referred to as the "O / M ratio") is 0.1 or more and 3.0 or less. In other words, in the solid battery of this disclosure, the first solid electrolyte, which is arranged adjacent to the positive electrode active material via the intervening layer 50, is a sulfide solid electrolyte doped with oxygen at an O / M ratio of 0.1 or more and 3.0 or less. If the first solid electrolyte contains multiple elements as M (for example, containing Sn and at least one element selected from groups 14 and 15 excluding Sn), the O / M ratio is calculated as the molar ratio of O to the total of the elements contained as M.

[0043] The oxidation resistance of a sulfide solid electrolyte can be improved by doping it with a predetermined amount of oxygen. When prioritizing the sulfide solid electrolyte's suitable oxidation resistance, the O / M ratio in the sulfide solid electrolyte is preferably greater than 0.1 and less than 3.0.

[0044] The intervening layer 50 located between the positive electrode active material layer 22 and the solid electrolyte portion 40 may be made of a material that contains at least an element that contributes to charging and discharging, such as Li or Na, and is capable of conducting ions that contribute to charging and discharging, such as lithium ions or sodium ions. In cross-sectional view, the thickness of the intervening layer is less than 500 nm. Such an intervening layer 50 can contribute to improving ionic conductivity by making the interface between the positive electrode active material layer 22 and the solid electrolyte layer 41 containing the first solid electrolyte (hereinafter also referred to as the "first solid electrolyte layer"). In other words, the intervening layer 50 can contribute to improving ionic conductivity between the positive electrode active material and the solid electrolyte. Based on this structure and function, the intervening layer 50 can also be referred to as, for example, an intermediate layer, a buffer layer, or an ionic conductor layer.

[0045] The intervening layer 50 can contribute to improving the ionic conductivity of the solid-state battery 1, and further, to suppressing side reactions at the interface between the positive electrode active material layer 22 and the solid electrolyte portion 40. On the other hand, if the thickness of the intervening layer 50 is excessively large, the conduction distance of ions that contribute to charging and discharging, such as lithium ions or sodium ions, will increase, which may actually increase the charge transfer resistance of the solid-state battery 1. The thickness of the intervening layer 50 may be in the range of greater than 0 nm and less than 500 nm. If the reduction of charge transfer resistance of the solid-state battery is important, the thickness of the intervening layer 50 is preferably 5 nm or more and 230 nm or less, and more preferably 5 nm or more and 12 nm or less.

[0046] The solid-state battery of this disclosure uses a solid electrolyte portion 40 containing a first solid electrolyte having the above-described composition and crystal structure, and the solid electrolyte portion 40 is arranged adjacent to the positive electrode active material layer 22 via an intervening layer 50 having the above-described thickness. The above-described first solid electrolyte contains one or more elements selected from Groups 14 and 15, including at least Sn, and has excellent water resistance. Furthermore, according to this disclosure, it has been newly discovered that the oxidation resistance of the first solid electrolyte can be improved by doping the sulfide solid electrolyte with oxygen in a predetermined molar ratio and by having an intervening layer 50 of a predetermined thickness between it and the positive electrode active material layer 22. Specifically, the solid-state battery of this disclosure exhibits a higher initial discharge capacity and lower charge transfer resistance because side reactions between the positive electrode active material and the first solid electrolyte in the high-potential range are suitably suppressed. Therefore, according to this disclosure, a solid-state battery that is more suitable in terms of oxidation resistance as well as water resistance can be obtained.

[0047] The structure in which the positive electrode active material layer 22, the intervening layer 50, and the solid electrolyte portion 40 containing the first solid electrolyte are adjacent in this order can be observed by measuring a cross-section of the solid-state battery 1 along the stacking direction Z. Specifically, the solid-state battery 1 is cut along the stacking direction Z, the obtained cross-section is polished with a polishing device (e.g., Hitachi High-Tech Corporation, IM-4000), and ion milling is performed with an ion milling device. Subsequently, the positive electrode active material layer 22, the intervening layer 50, and the solid electrolyte portion 40 containing the first solid electrolyte can be identified from images obtained using a scanning electron microscope (SEM) (e.g., Hitachi High-Tech Corporation, S-4800) or a transmission electron microscope (TEM).

[0048] Furthermore, the composition of the positive electrode active material layer 22, the intervening layer 50, and the solid electrolyte portion 40 can also be determined by performing compositional analysis using an energy-dispersive X-ray fluorescence spectrometer (EDX) (for example, HORIBA's x-max). Alternatively, compositional analysis can also be performed using a secondary ion mass spectrometer (SIMS) or an electron probe microanalyzer (EPMA).

[0049] The O / M ratio in the first solid electrolyte may also be determined by the compositional analysis described above. For example, compositional analysis may be performed using an EDX analyzer in point analysis mode with an acceleration voltage of 15 kV and a discharge current of 10 μA, and the mole fraction of each element detected may be determined to calculate the O / M ratio. The measurement may be performed at any 10 locations, and the average value may be taken as the O / M ratio of the first solid electrolyte.

[0050] Furthermore, by analyzing elemental mapping images acquired by SEM / EDX or TEM / EDX using image analysis software, the thickness of the intervening layer 50 located between the positive electrode active material 22 and the solid electrolyte portion 40 can be measured. Specifically, the thickness can be measured at any five locations in the intervening layer 50, and the average value of these measurements can be used as the thickness of the intervening layer 50.

[0051] The intervening layer 50 may be made of a material capable of conducting ions that contribute to charging and discharging, such as lithium ions or sodium ions. For example, the intervening layer 50 may be a metal oxide containing Li. In one preferred embodiment, the intervening layer 50 is represented as Li-A-X, where A is at least one element selected from the group consisting of Ti (titanium), Nb (niobium), P (phosphorus), Zr (zirconium), Ta (tantalum), Al (aluminum), and Si (silicon), and X is at least one element selected from the group consisting of B (boron), N (nitrogen), O (oxygen), F (fluorine), Cl (chlorine), Br (bromine), and I (iodine). By positioning the intervening layer 50 having the above composition between the positive electrode active material and the first solid electrolyte, a solid-state battery exhibiting low charge transfer resistance and being more favorable in terms of oxidation resistance can be obtained. With regard to achieving lower charge transfer resistance and improving oxidation resistance and water resistance, it is more preferable that the intervening layer 50 contains at least O as X.

[0052] Figure 2 is a schematic cross-sectional view showing a modified example of a solid-state battery according to the first embodiment of the present disclosure. As shown, the solid electrolyte portion 40 may include a solid electrolyte layer 41 containing a first solid electrolyte and a solid electrolyte layer containing a solid electrolyte different from the first solid electrolyte. In other words, the solid electrolyte portion 40 may have a laminated structure including a plurality of solid electrolyte layers. For example, the solid electrolyte portion 40 may have a structure in which a first solid electrolyte layer 41 located on the positive electrode portion 20 side and a second solid electrolyte layer 42 located on the negative electrode portion 30 side of the first solid electrolyte layer 41 are laminated along direction Z. The first solid electrolyte may be included in at least the first solid electrolyte layer 41 located on the positive electrode portion 20 side. The second solid electrolyte layer 42 may contain a second solid electrolyte which is a solid electrolyte different from the first solid electrolyte. In such a structure, the intervening layer 50 is located between the positive electrode portion 20 and the first solid electrolyte layer 41.

[0053] Examples of the second solid electrolyte include crystalline solid electrolytes, glass-based solid electrolytes, and glass-ceramic solid electrolytes. The second solid electrolyte layer 42 may contain one or more of the above-mentioned solid electrolytes.

[0054] Crystalline solid electrolytes include, for example, oxide-based crystalline materials and sulfide-based crystalline materials. Examples of oxide-based crystalline materials include lithium-containing phosphate compounds having a nasicone structure, oxides having a perovskite structure, oxides having a garnet-type or garnet-type similar structure, and oxide glass-ceramic lithium-ion conductors.

[0055] Lithium-containing phosphate compounds having a nasicone structure include Li ｘ M ｙ (PO ４ ) ３ (In the formula, 1 ≤ x ≤ 2, 1 ≤ y ≤ 2, and M is at least one selected from the group consisting of titanium (Ti), germanium (Ge), aluminum (Al), gallium (Ga), and zirconium (Zr)). An example of a lithium-containing phosphate compound having a nasicone structure is, for example, Li １．２ Al ０．２ Ti １．８ (PO４ ) ３ Examples include the following. An example of an oxide having a perovskite structure is La ０．５５ Li ０．３５ TiO ３ Examples include Li ７ La ３ Zr ２ O １２ Examples include the above. In addition, examples of sulfide-based crystalline materials include argyrodite-type and thio-LISICON. Examples of argyrodite-type sulfide-based crystalline materials include Li ７－ｘ PS ６－ｘ A ｘ (In the formula, A is one or more elements selected from the group consisting of Cl, Br, and I, and 0.5 ≤ x ≤ 1.8) For example, Li ３ PS ４ Li ４ SnS ４ Li ７ P ３ S １１ And so on. As for thio-LISICON, for example Li ３．２５ Ge ０．２５ P ０．７５ S ４ and Li １０ GeP ２ S １２ These are some examples. The crystalline solid electrolyte may also contain polymer materials (for example, polyethylene oxide (PEO)).

[0056] Examples of glass-based solid electrolytes include oxide-based glass materials and sulfide-based glass materials. For example, an oxide-based glass material is 50Li ４ SiO ４ ・50Li ３ BO ３ These are some examples. Also, as sulfide-based glass materials, for example, 30Li ２ S-26B ２ S ３ ・44LiI, 63Li ２ S-36SiS ２ ・1Li ３ PO ４ , 57Li ２S・38SiS ２ ・5Li ４ SiO ４ 、70Li ２ S・30P ２ S ５ および50Li ２ S・50GeS ２ などがある。

[0057] As the glass-ceramic solid electrolyte, for example, oxide-based glass-ceramic materials and sulfide-based glass-ceramic materials can be mentioned. As the oxide-based glass-ceramic materials, for example, phosphate compounds (LATP) containing lithium, aluminum and titanium as constituent elements, and phosphate compounds (LAGP) containing lithium, aluminum and germanium as constituent elements can be mentioned. As LATP, for example, Li １．０７ Al ０．６９ Ti １．４６ (PO ４ ) ３ etc. can be used. Also, as LAGP, for example, Li １．５ Al ０．５ Ge １．５ (PO ４ ) etc. can be used. Further, as the sulfide-based glass-ceramic materials, for example, Li ７ P ３ S １１ and Li ３．２５ P ０．９５ S ４ etc. can be mentioned.

[0058] (Second Embodiment) Fig. 3 is a schematic cross-sectional view of the solid battery 1B according to the second embodiment. Also, Fig. 4 is an enlarged view of part A of the solid battery shown in Fig. 3. As shown in Figs. 3 and 4, the solid battery 1B according to the second embodiment is different from the solid battery according to the first embodiment in that the positive electrode active material layer 22 includes positive electrode active material particles 22a, an intervening layer 50 covering the positive electrode active material particles 22a, and a first solid electrolyte.

[0059] Specifically, the positive electrode active material layer 22 may contain positive electrode active material particles 22a having a particulate shape. In this specification, "particulate shape" is not limited to a specific regular shape, but refers to a state in which minute individual units exhibit a shape that is generally spherical, elliptical, irregular, or angular. In other words, "particulate" refers to a state that can be recognized as powder or fine particles, and is distinguished from continuous forms such as continuous film or layer. The positive electrode active material particles 22a do not necessarily have a uniform particle size. The shape of the positive electrode active material particles 22a is not particularly limited and may be various shapes such as substantially spherical, flattened, or irregular. In such embodiments, the positive electrode active material layer 22 is not composed of a positive electrode active material having a continuous film or layer shape, but may have a layered structure macroscopically due to the arrangement of multiple particles.

[0060] The outer surface of the positive electrode active material particles 22a may be covered by the intervening layer 50. Therefore, the intervening layer 50 may cover the outer surface of each of the multiple positive electrode active material particles 22a in the positive electrode active material layer 22. The intervening layer 50 does not necessarily have to completely cover the entire outer surface of each positive electrode active material particle 22a. For example, there may be areas on the outer surface of the positive electrode active material particles 22a that are not covered by the intervening layer 50.

[0061] The thickness of the intervening layer 50 covering the positive electrode active material particles 22a may be greater than 0 nm and less than 500 nm. If reducing the charge transfer resistance of the solid-state battery is important, the thickness of the intervening layer 50 is preferably 5 nm or more and 230 nm or less, and more preferably 5 nm or more and 12 nm or less.

[0062] The positive electrode active material layer 22 further includes a solid electrolyte 24 that fills the spaces between a plurality of positive electrode active material particles 22a coated by an intervening layer 50. The solid electrolyte 24 can also be understood as a solid electrolyte phase that exists between the plurality of positive electrode active material particles 22a coated by the intervening layer 50. The solid electrolyte 24 includes a first solid electrolyte. In other words, in the positive electrode active material layer 22, the spaces between the plurality of positive electrode active material particles 22a coated by the intervening layer 50 may be filled with a first solid electrolyte. This can also be understood as a structure in which the positive electrode active material layer 22 comprises a plurality of positive electrode active material particles 22a dispersed in a solid electrolyte phase 24 containing a first solid electrolyte, and each of the positive electrode active material particles 22a is coated by an intervening layer 50.

[0063] In this way, a solid-state battery 1B may be constructed having a structure in which the positive electrode active material, the intervening layer 50, and the first solid electrolyte are adjacent in this order. This makes it possible to obtain a solid-state battery that includes the first solid electrolyte and is more suitable in terms of oxidation resistance. Furthermore, as described above, the first solid electrolyte also has excellent water resistance. Therefore, with this configuration, the spaces between the positive electrode active material particles 22a can be filled with a solid electrolyte 24 containing the first solid electrolyte which has excellent water resistance and oxidation resistance. This makes it possible to improve the water resistance and oxidation resistance of the solid-state battery.

[0064] Furthermore, the first solid electrolyte may also be included in the solid electrolyte section 40. That is, the first solid electrolyte may be included in both the positive electrode active material layer 22 and the solid electrolyte section 40. Alternatively, as shown in the solid battery 1C in Figure 5, the solid electrolyte section 40 may contain a solid electrolyte different from the first solid electrolyte. In other words, the positive electrode section 20 may contain the first solid electrolyte, while the solid electrolyte section 40 may not contain it.

[0065] (Third Embodiment) Figure 6 is a schematic cross-sectional view of a solid-state battery 1D according to the third embodiment. Figure 7 is a schematic enlarged view of portion B of the solid-state battery 1D shown in Figure 6. As shown, the solid-state battery 1D according to the third embodiment differs from the solid-state battery according to the first embodiment in that, in the positive electrode active material layer 22, the positive electrode active material particles 22a are covered by an intervening layer 50 and a solid electrolyte coating layer 26 containing a first solid electrolyte.

[0066] As shown in Figures 6 and 7, the solid-state battery 1D includes a plurality of positive electrode active material particles 22a in the positive electrode active material layer 22, and each of the positive electrode active material particles 22a is multilayer-coated by an intervening layer 50 and a solid electrolyte coating layer 26 containing a first solid electrolyte. In other words, the positive electrode active material layer 22 may contain a plurality of positive electrode active material particles 22a that are double-coated by an intervening layer 50 and a solid electrolyte coating layer 26. Specifically, an intervening layer 50 may be formed on the outer surface of the positive electrode active material particles 22a, and a solid electrolyte coating layer 26 may be further formed on the intervening layer 50. Because the solid electrolyte coating layer 26 contains the first solid electrolyte as described above, the positive electrode active material particles 22a, the intervening layer 50, and the solid electrolyte coating layer 26 containing the first solid electrolyte are adjacent in this order. With such a configuration, a solid-state battery more suitable in terms of water resistance and oxidation resistance can be obtained.

[0067] The positive electrode active material layer 22 may further contain a solid electrolyte 24A that fills the spaces between a plurality of positive electrode active material particles 22a coated by the intervening layer 50 and the solid electrolyte coating layer 26. The solid electrolyte 24A can also be understood as a solid electrolyte phase that fills the spaces between a plurality of positive electrode active material particles 22a coated by the intervening layer 50 and the solid electrolyte coating layer 26. The solid electrolyte 24A may contain a second solid electrolyte, which is a solid electrolyte different from the first solid electrolyte. In other words, in the positive electrode active material layer 22, a second solid electrolyte different from the first solid electrolyte may be filled between a plurality of positive electrode active material particles 22a coated by the intervening layer 50 and the solid electrolyte coating layer 26. To put it another way, a plurality of positive electrode active material particles 22a coated by the intervening layer 50 and the solid electrolyte coating layer 26 containing the first solid electrolyte may be dispersed in the solid electrolyte 24A containing the second solid electrolyte in the positive electrode active material layer 22.

[0068] According to the above configuration, by using the above-described first solid electrolyte, which is an oxygen-doped sulfide solid electrolyte, as the solid electrolyte coating layer 26 that coats the positive electrode active material particles 22a via the intervening layer 50, the water resistance and oxidation resistance of the solid battery can be improved. Furthermore, the contact between the coated positive electrode active material particles 22a and the second solid electrolyte present in the solid electrolyte portion 40 with the positive electrode active material particles 22a is reduced compared to the first solid electrolyte. Therefore, as the second solid electrolyte, for example, a solid electrolyte that prioritizes ionic conductivity over oxidation resistance can be used. This can improve the ionic conductivity of the solid battery. Thus, the above configuration may be particularly useful when both oxidation resistance and ionic conductivity of the solid battery are important.

[0069] The solid electrolyte coating layer 26 does not necessarily have to completely cover the entire outer surface of each positive electrode active material particle 22a. For example, there may be areas on the outer surface of the positive electrode active material particle 22a where the solid electrolyte coating layer 26 is not present on the intervening layer 50. The thickness of the solid electrolyte coating layer 26 formed on the intervening layer 50 is, for example, greater than 0 nm and 500 nm or less, and may be, for example, 5 nm to 230 nm, and preferably 5 nm to 12 nm.

[0070] The embodiments of this disclosure have been described above, but these are merely typical examples. Therefore, those skilled in the art will easily understand that this disclosure is not limited thereto, and various embodiments are conceivable without altering the essence of this disclosure.

[0071] Furthermore, the above-described embodiment of the present disclosure encompasses the following preferred embodiments. First embodiment: A solid battery comprising a positive electrode portion containing a positive electrode active material, a negative electrode portion containing a negative electrode active material, and a solid electrolyte portion, wherein at least one of the positive electrode portion and the solid electrolyte portion contains a first solid electrolyte, and further comprises an intervening layer interposed between the positive electrode active material and the first solid electrolyte, and in contact with each of the positive electrode active material and the first solid electrolyte, wherein the first solid electrolyte comprises a crystalline phase having a tetragonal crystal structure and contains Li, M, S, and O, where M is one or more elements selected from Group 14 and Group 15 containing at least Sn, the molar ratio of O to M is 0.1 or more and 3.0 or less, and the thickness of the intervening layer is less than 500 nm. Second embodiment: The solid battery according to the first embodiment, wherein the solid electrolyte portion contains the first solid electrolyte, and the intervening layer is located between the positive electrode portion and the solid electrolyte portion. Third aspect: The solid battery according to the second aspect, wherein the solid electrolyte portion comprises a first solid electrolyte layer located on the positive electrode side and a second solid electrolyte layer located on the negative electrode side of the first solid electrolyte layer, and at least the first solid electrolyte layer contains the first solid electrolyte. Fourth aspect: The solid battery according to the first aspect, wherein the positive electrode portion comprises a positive electrode active material layer containing particulate positive electrode active material, and the positive electrode active material layer comprises an intervening layer covering the particulate positive electrode active material and a first solid electrolyte adjacent to the intervening layer. Fifth aspect: The solid battery according to the fourth aspect, wherein the first solid electrolyte is filled in the positive electrode active material layer between the particulate positive electrode active material covered by the intervening layer. Sixth aspect: The solid battery according to the fourth aspect, wherein both the positive electrode active material layer and the solid electrolyte portion contain the first solid electrolyte. Seventh aspect: A solid-state battery according to the fourth aspect, wherein the particulate positive electrode active material is covered by an intervening layer that covers the positive electrode active material and a solid electrolyte coating layer that covers the intervening layer, and the solid electrolyte coating layer contains the first solid electrolyte. Eighth aspect: A solid-state battery according to any one of the first to seventh aspects, wherein the molar ratio of O to M is 0.5 or more and 2.3 or less. Ninth aspect: A solid-state battery according to any one of the first to eighth aspects, wherein the thickness of the intervening layer is 5 nm or more and 230 nm or less.10th aspect: A solid-state battery according to any of the 1st to 8th aspects, wherein the thickness of the intervening layer is 5 nm or more and 12 nm or less. 11th aspect: A solid-state battery according to any of the 1st to 10th aspects, wherein the intervening layer contains an oxide represented by Li-A-X, where A is one or more elements selected from the group consisting of Ti, Nb, P, Zr, Ta, Al, and Si, and X is one or more elements selected from the group consisting of B, N, O, F, Cl, Br, and I. 12th aspect: A solid-state battery according to the 11th aspect, wherein X contains at least O.

[0072] In accordance with this disclosure, a demonstration test was conducted. The structure shown in Figure 3 was adopted as the solid-state battery structure.

[0073] <Example 1> (Preparation of positive electrode active material particles coated in an intervening layer) Commercially available LiCoO ２ Using powder (Nippon Chemical Industries, Cellseed C-5H) as the base material, a 5% by mass Li-Nb ethoxide-ethanol solution was used as a precursor solution and coated using a rolling fluidized powder coating apparatus (Powrec, MP-01). LiCoO coated with the precursor ２ The powder is heat-treated at 350°C for 2 hours under a pure oxygen atmosphere to remove alkoxides and produce LiNbO ３ LiCoO coated with ２ Obtained LiNboO ３ The amount of coverage is LiCoO ２ The amount was set to 1.0 mass%. After heat treatment, the coated LiCoO ２ The powder was observed using a transmission electron microscope (JEOL Ltd., JEM-F200) to determine LiCoO ２ LiNbO coating the powder ３ The thickness of the sample was confirmed to be approximately 10 nm. The precursor solution was prepared by dissolving commercially available ethoxylithium (High Purity Chemicals) and Nb ethoxide (High Purity Chemicals) in an inert gas solution of dehydrated ethanol (Fujifilm Wako).

[0074] (Synthesis of solid electrolytes) In an atmosphere where the dew point temperature is below -60°C, commercially available Li ２ S and SnS ２The two components were weighed out in a 2:1 molar ratio, mixed in an agate mortar, and then placed in a zirconia pot along with zirconia balls. Under complete sealing, mechanical milling was performed using a planetary ball mill (Fritsch, P-7). Subsequently, the mixture was heat-treated at 260°C for 2 hours under an argon gas atmosphere to extract Li ４ SnS ４ The obtained Li was mixed with dehydrated methanol (Kanto Chemical) and deionized water in a volume ratio of 50:50. ４ SnS ４ The material was dissolved to a concentration of 10% by mass and vacuum-dried at 120°C. Subsequently, it was heat-treated in an inert gas at 200°C for 3 hours to obtain oxygen-doped sulfide solid electrolyte powder (first solid electrolyte powder).

[0075] <Evaluation of Solid Electrolytes> (Composition Analysis) 60 mg of solid electrolyte powder is placed in a 10 mm diameter SUS cylinder and measured at 1 tf / cm². ２ min), and 3 tf / (cm ２ Solid electrolyte pellets were prepared by gradually compacting the material at a rate of min(0). The solid electrolyte pellets were fixed with an aluminum jig and observed using a scanning electron microscope (Hitachi High-Tech, S4800). In addition, compositional analysis was performed using energy-dispersive X-ray spectroscopy in point analysis mode with an acceleration voltage of 15 kV and a discharge current of 10 μA. The proportion of the molar concentration of each element in the total molar concentrations of Sn, S, and O was determined, and the O / Sn ratio was calculated from the molar concentration ratio of O and Sn. The same measurement was performed at 10 arbitrary locations on the solid electrolyte pellet, and the average value was taken as the O / Sn ratio of the first solid electrolyte.

[0076] (Structural Analysis) The crystal structure was analyzed using an X-ray diffractometer (Brker D8 ADVANCE). Specifically, the solid electrolyte pellet was sealed in an atmosphere-shielded holder inside an Ar glove box, and the crystal structure was determined by measuring within the angular range of 2θ = 10° to 50°.

[0077] (Preparation of solid-state battery for evaluation) The positive electrode active material coated with an intervening layer and the solid electrolyte powder obtained according to the method described above were mixed in a mortar in a volume ratio of 75:25 to obtain a positive electrode composite material. Li was added to a 10 mm diameter zirconia cylinder as a second solid electrolyte different from the solid electrolyte powder obtained according to the method described above. ６ PS ５ Add 100 mg of Cl powder (NEIcorp.) and fill to 1 tf / cm². ２ It was then compacted into pellets at min) and 10 mg of cathode composite material was added, resulting in a mixture of 1 tf / cm². ２ min), and 3 tf / (cm ２ - The mixture was compacted in stages (min) to obtain a two-layer pellet. Of the two-layer pellets prepared, the second solid electrolyte Li ６ PS ５ On the Cl side, a 10 mm diameter In metal foil (thickness 0.25 mm) and an 8 mm diameter Li metal foil (thickness 0.20 mm) are layered in order, and 0.5 tf / cm ２ The solid cells were confined in a sealed container and used as evaluation solid batteries.

[0078] (Example 2) A solid battery was prepared in the same manner as in Example 1, except that the volume ratio of methanol to deionized water in the synthesis of the solid electrolyte was set to 75:25.

[0079] (Example 3) A solid battery was prepared in the same manner as in Example 1, except that the volume ratio of methanol to deionized water in the synthesis of the solid electrolyte was set to 25:75.

[0080] (Example 4) A solid-state battery was prepared in the same manner as in Example 1, except that ethoxylithium and Ti ethoxide (Fujifilm Wako) were used as precursor solutions in the preparation of positive electrode active material particles coated with an intervening layer.

[0081] (Example 5) A solid-state battery was prepared in the same manner as in Example 1, except that lithium nitrate (High Purity Chemicals) and phosphoric acid (Fujifilm Wako) were used as precursor solutions in the preparation of positive electrode active material particles coated with an intervening layer.

[0082] (Example 6) A solid-state battery was prepared in the same manner as in Example 1, except that the preparation of the positive electrode active material particles coated with an intervening layer was carried out as follows: LiNbO３ The amount of coating is LiCoO ２ The precursor is separated to a concentration of 5% by mass relative to the given amount, dissolved in a sufficient amount of ethanol, and then converted to LiCoO ２ The mixture was added and stirred at 400 rpm on an 80°C hot plate until the ethanol evaporated. The resulting powder was heat-treated at 350°C for 2 hours in a pure oxygen atmosphere, and LiNbO2 was added. ３ LiCoO coated with ２ I obtained it.

[0083] (Example 7) A solid battery was prepared in the same manner as in Example 1, except that the volume ratio of methanol to deionized water in the synthesis of the solid electrolyte was set to 100:0.

[0084] (Example 8) A solid battery was prepared in the same manner as in Example 1, except that the volume ratio of methanol to deionized water in the synthesis of the solid electrolyte was set to 5:95.

[0085] (Comparative Example 1) In the synthesis of solid electrolytes, Li ４ SnS ４ A solid-state battery was prepared in the same manner as in Example 1, except that the substance was used directly without being dissolved in a methanol-deionized water mixed solvent.

[0086] (Comparative Example 2) LiCoO2 without an intervening layer coating was prepared, and a solid-state battery was manufactured in the same manner as in Example 1.

[0087] (Comparative Example 3) A solid-state battery was prepared in the same manner as in Example 1, except that the preparation of the positive electrode active material particles coated with an intervening layer was carried out as follows: LiNbO ３ The amount of coating is LiCoO ２ The precursor is separated to a concentration of 10% by mass relative to the given amount, dissolved in a sufficient amount of ethanol, and then converted to LiCoO ２ The mixture was added and stirred at 400 rpm on an 80°C hot plate until the ethanol evaporated. The resulting powder was heat-treated at 350°C for 2 hours in a pure oxygen atmosphere, and LiNbO2 was added. ３ LiCoO coated with ２ I obtained it.

[0088] (Comparative Example 4) A solid battery was prepared in the same manner as in Example 1, except that vacuum drying was performed at room temperature during the synthesis of the solid electrolyte.

[0089] (Evaluation of Discharge Capacity) The obtained solid-state batteries were placed in a charge / discharge test machine (Toyo Systems, TOSCAT3100), and the first charge / discharge was performed under the following conditions: charging voltage 3.83V (vs. Li-In), 0.05C (cutoff: 0.01C), and discharging voltage 2.38V (vs. Li-In), 0.05C (cutoff: 0.01C). The total discharge capacity at the end of CC-CV discharge was defined as the discharge capacity.

[0090] When the discharge capacity of the solid batteries of Comparative Example 1 and Example 1 was evaluated as described above, the discharge capacity of the solid battery of Comparative Example 1, which contained an oxygen-doped sulfide solid electrolyte, was 146 mAh / g, while the discharge capacity of the solid battery of Example 1, which contained an oxygen-doped sulfide solid electrolyte, was 151 mAh / g. Therefore, it was found that the solid battery of the present disclosure, which contains an oxygen-doped sulfide solid electrolyte, exhibits a higher discharge capacity compared to the solid battery of Comparative Example 1. This is presumed to be because, in the solid battery of Example 1, the oxidation resistance of the sulfide solid electrolyte was improved, thereby suppressing the decomposition of the sulfide solid electrolyte in the high potential range.

[0091] (Evaluation of Charge Transfer Resistance) The charge transfer resistance of the obtained solid-state batteries was evaluated by measuring the electrochemical impedance using the AC impedance method. A potentiostat (Solartron Analytical, 1260A) was used as the measuring device. Measurements were performed with an AC amplitude of 10 mV in the frequency range of 0.01 Hz to 1 MHz. A charge transfer resistance of 75 Ω or more was evaluated as unacceptable (C), less than 75 Ω as acceptable (B), and 70 Ω or less as good (A). Those rated good (A) and acceptable (B) were deemed to pass, and those rated unacceptable (C) were deemed to fail.

[0092] Table 1 shows the evaluation results of the solid-state batteries for Examples 1 to 8 and Comparative Examples 1 to 4.

[0093]

[0094] The above results show that the solid batteries of Examples 1 to 8 exhibit reduced charge transfer resistance, while the solid batteries of Comparative Examples 1 to 4 exhibit high charge transfer resistance. Therefore, according to this disclosure, a solid battery exhibiting higher discharge capacity and lower charge transfer resistance can be provided. Although not bound by any particular theory, this is presumed to be due to the use of a sulfide solid electrolyte containing one or more elements M selected from Groups 14 and 15, including at least Sn, and being oxygen-doped at an O / M ratio of 0.1 to 3.0, and the provision of an intervening layer with a thickness of less than 500 nm between the positive electrode active material and the sulfide solid electrolyte, which improves the oxidation resistance of the sulfide solid electrolyte and suppresses side reactions at the positive electrode active material / sulfide solid electrolyte interface. Therefore, according to this disclosure, a more suitable solid battery containing a sulfide solid electrolyte and having excellent oxidation resistance can be provided.

[0095] Furthermore, the solid-state batteries of Examples 1 to 8, which include sulfide solid electrolytes having a tetragonal and / or hexagonal crystal structure, exhibit reduced charge transfer resistance compared to the solid-state battery of Comparative Example 4, in which the sulfide solid electrolyte is amorphous. This is presumed to be due to the fact that sulfide solid electrolytes having a crystalline phase are superior to amorphous sulfide solid electrolytes in terms of charge transfer resistance, and that the inclusion of a tetragonal or hexagonal crystal structure improves oxidation resistance and suppresses side reactions at the positive electrode active material / sulfide solid electrolyte interface.

[0096] Furthermore, as shown in the results in Table 1, the solid-state batteries of Examples 1 to 6, in which the O / M ratio was greater than 0.1 and less than 3.0, had a charge transfer resistance of 70 Ω or less, indicating that a more suitable solid-state battery in terms of oxidation resistance was provided. In addition, the solid-state batteries of Examples 1 to 5, in which the thickness of the intervening layer was 5 nm to 230 nm, and furthermore 5 nm to 12 nm, showed an even greater reduction in the value of the charge transfer resistance.

[0097] The solid-state battery of this disclosure can be used in a variety of fields where energy storage is envisioned. While these are merely examples, the solid-state battery of this disclosure can be used in the electrical, information, and communication fields where mobile devices are used (e.g., the electrical and electronic equipment field or mobile device field, including small electronic devices such as mobile phones, smartphones, laptops and digital cameras, activity trackers, ARM computers, electronic paper, RFID tags, card-type electronic money, and smartwatches), household and small industrial applications (e.g., power tools, golf carts, household, caregiving, and industrial robots), large industrial applications (e.g., forklifts, elevators, and port cranes), transportation systems (e.g., hybrid vehicles, electric vehicles, buses, trains, electric-assist bicycles, electric motorcycles, etc.), power grid applications (e.g., various power generation, road conditioners, smart grids, and general household energy storage systems), medical applications (medical equipment such as earphones and hearing aids), pharmaceutical applications (medication management systems, etc.), as well as IoT, space, and deep-sea applications (e.g., space probes, submersible research vessels, etc.).

[0098] 1, 1A to 1D Battery 10 Protective layer 20 Positive electrode part 21 Positive electrode current collector 22 Positive electrode active material layer 22a Positive electrode active material particles 24, 24A Solid electrolyte 26 Solid electrolyte coating layer 30 Negative electrode part 31 Negative electrode current collector 32 Negative electrode active material layer 40 Solid electrolyte part 41 First solid electrolyte layer 42 Second solid electrolyte layer 50 Intervening layer 60 Reinforcement part

Claims

1. A solid-state battery comprising a positive electrode portion containing a positive electrode active material, a negative electrode portion containing a negative electrode active material, and a solid electrolyte portion, wherein at least one of the positive electrode portion and the solid electrolyte portion contains a first solid electrolyte, and further comprises an intervening layer interposed between the positive electrode active material and the first solid electrolyte, and in contact with each of the positive electrode active material and the first solid electrolyte, wherein the first solid electrolyte contains a crystalline phase having a tetragonal crystal structure and contains Li, M, S, and O, where M is one or more elements selected from Group 14 and Group 15 containing at least Sn, the molar ratio of O to M is 0.1 or more and 3.0 or less, and the thickness of the intervening layer is less than 500 nm.

2. The solid battery according to claim 1, wherein the solid electrolyte portion includes the first solid electrolyte, and the intervening layer is located between the positive electrode portion and the solid electrolyte portion.

3. The solid-state battery according to claim 2, wherein the solid electrolyte portion comprises a first solid electrolyte layer located on the positive electrode side and a second solid electrolyte layer located on the negative electrode side of the first solid electrolyte layer, and at least the first solid electrolyte layer contains the first solid electrolyte.

4. The solid-state battery according to claim 1, wherein the positive electrode portion comprises a positive electrode active material layer containing particulate positive electrode active material, and the positive electrode active material layer comprises an intervening layer covering the particulate positive electrode active material and a first solid electrolyte adjacent to the intervening layer.

5. The solid battery according to claim 4, wherein the first solid electrolyte is filled in the positive electrode active material layer between the particulate positive electrode active material covered by the intervening layer.

6. The solid-state battery according to claim 4, wherein both the positive electrode active material layer and the solid electrolyte portion include the first solid electrolyte.

7. The solid battery according to claim 4, wherein the particulate positive electrode active material is covered by an intervening layer that covers the positive electrode active material and a solid electrolyte coating layer that covers the intervening layer, and the solid electrolyte coating layer contains the first solid electrolyte.

8. The solid battery according to any one of claims 1 to 7, wherein the molar ratio of O to M is 0.5 or more and 2.3 or less.

9. The solid battery according to any one of claims 1 to 8, wherein the thickness of the intervening layer is 5 nm or more and 230 nm or less.

10. The solid battery according to any one of claims 1 to 8, wherein the thickness of the intervening layer is 5 nm or more and 12 nm or less.

11. The solid-state battery according to any one of claims 1 to 10, wherein the intervening layer comprises an oxide represented as Li-A-X, where A is one or more elements selected from the group consisting of Ti, Nb, P, Zr, Ta, Al, and Si, and X is one or more elements selected from the group consisting of B, N, O, F, Cl, Br, and I.

12. The solid battery according to claim 11, wherein X comprises at least O.

Images