Stacked all-solid-state battery

Abstract

The laminated all-solid battery of the present application has a plurality of positive electrode layers including a positive electrode current collector layer and a positive electrode active material layer, a plurality of negative electrode layers including a negative electrode current collector layer and a negative electrode active material layer, and a plurality of solid electrolyte layers including a solid electrolyte layer, and has a laminate in which the positive electrode layers and the negative electrode layers are alternately laminated via the solid electrolyte layers, wherein the plurality of solid electrolyte layers are composed of a plurality of solid electrolyte layers belonging to a first group and at least one solid electrolyte layer belonging to a second group having a thickness larger than the first group, the first group has a first solid electrolyte layer having the smallest thickness, and the second group is composed of a second solid electrolyte layer having a thickness of 2 times or more the first solid electrolyte layer, when the average thickness of the plurality of solid electrolyte layers belonging to the first group is set as t a , and the average thickness of the solid electrolyte layer belonging to the second group is set as t b , the following (1) formula relationship is satisfied: 2t a ≤ t b … (1).

Description

Technical Field

[0001] This invention relates to a stacked all-solid-state battery.

[0002] This application claims priority based on Japanese Patent Application No. 2020-009570, filed in Japan on January 24, 2020, the contents of which are incorporated herein by reference. Background Technology

[0003] In recent years, significant advancements in electronic technology have enabled the miniaturization, lightweighting, thinning, and multifunctionality of portable electronic devices. Consequently, there is a strong demand for improved miniaturization, lightweighting, thinning, and reliability of batteries, which power these devices. This has led to increased attention on all-solid-state lithium-ion secondary batteries composed of solid electrolytes.

[0004] Currently, widely used lithium-ion secondary batteries have traditionally used electrolytes, such as organic solvents, as the medium for ion movement. However, lithium-ion secondary batteries using electrolytes pose a risk of leakage. Furthermore, the organic solvents used in the electrolyte are flammable substances, thus requiring further improvements in battery safety.

[0005] Therefore, as one of the countermeasures to improve the safety of lithium-ion secondary batteries, it has been proposed to replace the electrolyte with a solid electrolyte. Furthermore, the development of all-solid-state batteries, in which other components are also made of solids, is underway.

[0006] Generally, it is preferred that the solid electrolyte constituting an all-solid-state battery be dense. However, due to the volume expansion and contraction of the electrode layer accompanying the charging and discharging reaction of lithium ions, internal stress acts on the all-solid-state battery, posing a technical problem of crack formation. As a result, the internal resistance increases and the cycle characteristics deteriorate.

[0007] To address this technical problem, Patent Document 1 describes a solid electrolyte layer that has a portion with low porosity formed near the electrode layer and a portion with high porosity formed far from the electrode layer. This solid electrolyte layer can mitigate the internal stress on the solid electrolyte layer caused by volume expansion and contraction, thereby increasing the discharge capacity and improving cycle characteristics.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: International Publication No. 2013 / 175993 Summary of the Invention

[0011] The technical problem that the invention aims to solve

[0012] However, in stacked all-solid-state batteries with a solid electrolyte layer as shown in Patent Document 1, the internal resistance of the solid electrolyte layer actually increases, making it impossible to obtain sufficient cycle characteristics. In addition, the internal stresses accompanying volume expansion and contraction concentrate in the high-porosity solid electrolyte layer, which may easily lead to cracks in the solid electrolyte layer.

[0013] The purpose of this invention is to provide a stacked all-solid-state battery that suppresses crack formation and has excellent cycle characteristics.

[0014] Means for solving technical problems

[0015] In order to solve the aforementioned technical problem, the present invention provides the following means.

[0016] The first embodiment of the stacked all-solid-state battery of the present invention comprises: a plurality of positive electrode layers including a positive electrode current collector layer and a positive electrode active material layer; a plurality of negative electrode layers including a negative electrode current collector layer and a negative electrode active material layer; and a plurality of solid electrolyte layers including a solid electrolyte. The stacked all-solid-state battery has a stack formed by alternately stacking the positive electrode layers and the negative electrode layers via the solid electrolyte layers.

[0017] The plurality of solid electrolyte layers are composed of a plurality of solid electrolyte layers belonging to a first group and at least one solid electrolyte layer belonging to a second group with a thickness greater than that of the first group.

[0018] The first group has a first solid electrolyte layer with the smallest thickness.

[0019] The second group consists of a second solid electrolyte layer with a thickness more than twice that of the first solid electrolyte layer.

[0020] Let the average thickness of the multiple solid electrolyte layers belonging to the first group be t. a Let the average thickness of the solid electrolyte layer belonging to the second group be t. b When, the following relationship (1) is satisfied.

[0021] 2t a ≤t b …(1)

[0022] In the stacked all-solid-state battery of the above embodiments, the first group may also be composed of the first solid electrolyte layer and a third solid electrolyte layer with a thickness less than twice that of the first solid electrolyte layer.

[0023] Furthermore, the t b Relative to t a It can also satisfy the following equation (2).

[0024] 2t a ≤tb ≤10t a …(2)

[0025] Furthermore, the number of solid electrolyte layers in the first group can be more than the number of solid electrolyte layers in the second group.

[0026] In addition, the solid electrolyte layer belonging to the first group and the solid electrolyte layer belonging to the second group may also contain solid electrolytes with the same crystal structure.

[0027] The solid electrolyte layer belonging to the first group and the solid electrolyte layer belonging to the second group may also contain a solid electrolyte with any crystal structure selected from NASICON type, garnet type, perovskite type and LISICON type.

[0028] The effects of the invention

[0029] The stacked all-solid-state battery of the present invention suppresses the generation of cracks and has excellent cycle characteristics. Attached Figure Description

[0030] Figure 1 This is an external view of the stacked all-solid-state battery according to the first embodiment of the present invention.

[0031] Figure 2 This is an external view of the laminated body according to the first embodiment of the present invention.

[0032] Figure 3 This is a cross-sectional view of the stacked all-solid-state battery according to the first embodiment of the present invention.

[0033] Figure 4 This is a cross-sectional view of a tandem all-solid-state battery, a comparative example of this application.

[0034] Figure 5 This is a cross-sectional view of the stacked all-solid-state battery according to the second embodiment of the present invention. Detailed Implementation

[0035] The following is a brief reference to the appendix. Figure 1 The following describes one embodiment of the present invention in detail. The accompanying drawings used in the following description are sometimes simplified for ease of understanding of the features of this embodiment, and the dimensions and ratios of the constituent elements may differ from the actual dimensions. The substances, dimensions, etc., illustrated in the following description are examples, and this embodiment is not limited thereto; it can be implemented with appropriate modifications within the scope of achieving the effects of the present invention. For example, the structures described in different embodiments can be appropriately combined to implement the invention.

[0036] Examples of stacked all-solid-state batteries include all-solid-state lithium-ion secondary batteries, all-solid-state sodium-ion secondary batteries, all-solid-state potassium-ion secondary batteries, and all-solid-state magnesium-ion secondary batteries. The following description uses an all-solid-state lithium-ion secondary battery as an example; however, this invention can generally be applied to any stacked all-solid-state secondary battery.

[0037] (First Embodiment)

[0038] (Stacked solid-state battery)

[0039] use Figures 1-3 The stacked all-solid-state battery of this embodiment will be described. For example... Figure 1 As shown, the stacked all-solid-state battery 0 of the first embodiment has a stack 10, a positive external electrode 60, and a negative external electrode 70. Figure 2 As shown, the laminate 10 is a hexahedron with four side surfaces 21, 22, 23, and 24, a top surface 25, and a bottom surface 26. Furthermore, a positive external electrode 60 and a negative external electrode 70 are formed on any of a pair of opposing side surfaces. Figure 1 The implementation method of the stacked all-solid-state battery is in Figure 2 An embodiment in which a positive external electrode 60 is formed on the side 21 of the laminate 10 and a negative external electrode 70 is formed on the side 22.

[0040] Next, use Figure 3 The cross-sectional view illustrates the stacked all-solid-state battery 100 of this embodiment. In the stacked all-solid-state battery 100, a positive electrode layer 1 having a positive electrode current collector layer 1A, a positive electrode active material layer 1B, and a side edge layer 3, and a negative electrode layer 2 having a negative electrode current collector layer 2A, a negative electrode active material layer 2B, and a side edge layer 3 are alternately stacked via solid electrolyte layers. The solid electrolyte layer preferably includes a stack body 20, which at least includes a storage element that holds the solid electrolyte layer A and a solid electrolyte layer B with a thickness greater than that of the solid electrolyte layer A, and includes an outer layer 4 that holds the storage element. The closest solid electrolyte layers A and B are stacked via either the positive electrode layer 1 or the negative electrode layer 2.

[0041] In this embodiment, an example is described where multiple solid electrolyte layers A have the same thickness, and the thickness of solid electrolyte layer B is more than twice the thickness of solid electrolyte layer A. In this embodiment, the multiple solid electrolyte layers A are first solid electrolyte layers belonging to group 1. Furthermore, in this embodiment, solid electrolyte layer B is a second solid electrolyte layer belonging to group 2. Additionally, the positive electrode layer 1 is electrically bonded to the positive external electrode 60 on side 21, and the negative electrode layer 2 is electrically bonded to the negative external electrode 70 on side 22.

[0042] Furthermore, let the average thickness of the solid electrolyte layer A be t. a Let the average thickness of the solid electrolyte layer B be t. b When the solid-state battery 100 satisfies the following formula (1), in this embodiment, the thickness of the solid electrolyte layer A is the same, and the average thickness of the solid electrolyte layer A refers to the thickness of the solid electrolyte layer A.

[0043] 2t a ≤t b …(1)

[0044] The stacked all-solid-state battery 100 constructed in this way can suppress volume expansion caused by the charge-discharge reaction of lithium ions. The details of this main reason are not yet clear, but it is believed that in the stacked all-solid-state battery 100, by having a solid electrolyte layer B with a thickness at least twice that of the solid electrolyte layer A, the stress load of volume expansion accompanying the charge-discharge reaction is dispersed by the solid electrolyte layer B, which can suppress cracks within the stack, resulting in improved cycle characteristics. On the other hand, in the stacked all-solid-state battery 200 without a solid electrolyte layer B, since the stress load of volume expansion is not dispersed, cracks are sometimes easily generated within the stack, and the internal resistance locally increases. Therefore, the current concentrates in areas with low internal resistance, and the cycle characteristics tend to decrease.

[0045] Furthermore, the t b Relative to t a Preferably, the following equation (2) is satisfied.

[0046] 2t a ≤t b ≤10t a …(2)

[0047] Furthermore, the number of layers in the solid electrolyte layer A can be more than the number of layers in the solid electrolyte layer B.

[0048] When a solid electrolyte layer B has an average thickness that is more than 10 times that of the solid electrolyte layer A, the internal resistance of the stacked all-solid-state battery increases due to the solid electrolyte layer B, and sometimes the capacity decreases.

[0049] Furthermore, solid electrolyte layer A and solid electrolyte layer B preferably have the same crystal structure.

[0050] Furthermore, the solid electrolyte is preferably any one of the crystal structures of NASICON type, garnet type or perovskite type that exhibits high ionic conductivity.

[0051] When solid electrolyte layers A and B have the same crystal structure, their charge-discharge reactions occur uniformly due to their identical ionic conductivity. Consequently, the stress load caused by volume expansion is also uniformly generated, suppressing cracks within the laminate and improving the battery's cycle characteristics. Conversely, when solid electrolyte layers have different crystal structures, their charge-discharge reactions become non-uniform due to their different ionic conductivity, resulting in non-uniform stress loads caused by volume expansion. Therefore, cracks are more likely to form within the laminate.

[0052] Figure 4 This is a cross-sectional view showing a comparative example of a stacked all-solid-state battery 200. The comparative example of the stacked all-solid-state battery 200 is not included in this invention. The stacked all-solid-state battery 200 comprises: a storage element consisting of alternating positive electrode layer 1 and negative electrode layer 2 via multiple solid electrolyte layers A0 of approximately the same thickness; and an outer layer 4 sandwiching the storage element. The positive electrode layer 1 is electrically bonded to a positive external electrode 60 via a side surface 21, and the negative electrode layer 2 is electrically bonded to a negative external electrode 70 via a side surface 22. The stacked all-solid-state battery 200 differs from the all-solid-state battery 100 of the first embodiment in that it does not have a solid electrolyte layer B belonging to the second group.

[0053] It should be noted that, as will be explained in the following instructions, sometimes either or both of the positive electrode active material and the negative electrode active material are collectively referred to as active material, either or both of the positive electrode current collector layer and the negative electrode current collector layer are collectively referred to as current collector layer, either or both of the positive electrode active material layer and the negative electrode active material layer are collectively referred to as active material layer, either or both of the positive electrode and the negative electrode are collectively referred to as electrode, and either or both of the positive electrode external electrode and the negative electrode external electrode are collectively referred to as external electrode.

[0054] (Solid electrolyte layer)

[0055] The solid electrolyte layer A and solid electrolyte layer B of the stacked all-solid-state battery 100 in this embodiment are not particularly limited, and may, for example, contain a solid electrolyte having any one of the crystal structures selected from NASICON type, garnet type, perovskite type, and LISICON type. For example, conventional solid electrolyte materials such as oxide-type lithium-ion conductors having NASICON type, garnet type, perovskite type, and LISICON type crystal structures can be used. Examples include ion conductors (e.g., Li) with a NASICON type crystal structure containing at least Li (lithium), M (M being at least one of Ti (titanium), Zr (zirconium), Ge (germanium), Hf (hafnium), Sn (tin), P (phosphorus), and O (oxygen). 1+x Al x Ti2-x (PO4)3; LATP); and ionic conductors with a garnet-type crystal structure containing at least Li (lithium), Zr (zirconium), La (lanthanum) and O (oxygen) (e.g., Li7La3Zr2O). 12 ; LLZ), or ionic conductors with garnet-like structures; and ionic conductors with perovskite-type structures containing at least Li (lithium), Ti (titanium), La (lanthanum), and O (oxygen) (e.g., Li). 3x La 2 / 3-x TiO3; LLTO); and lithium-ion conductors (e.g., Li) with a LISICON-type crystal structure containing at least Li, Si, P and O. 3.5 Si 0.5 P 0.5 O 3.5 At least one of LSPO. That is, these ionic conductors can be used in combination, or two or more can be used in combination.

[0056] As the solid electrolyte material in this embodiment, a lithium-ion conductor having a NASICON-type crystal structure is preferably used, for example, a material containing LiTi2(PO4)3(LTP), LiZr2(PO4)3(LZP), or Li 1+x Al x Ti 2-x (PO4)3(LATP, 0<x≤0.6), Li 1+x Al x Ge 2-x (PO4)3(LAGP, 0<x≤0.6), Li 1+x Y x Zr 2-x (PO4)3 (LYZP, 0 < x ≤ 0.6) represents a solid electrolyte material.

[0057] (Positive electrode layer and negative electrode layer)

[0058] For example, multiple positive electrode layers 1 and negative electrode layers 2 are respectively provided in the laminate 20, and they are opposite each other via solid electrolyte layers.

[0059] The positive electrode layer 1 has a positive current collector layer 1A, a positive active material layer 1B, and a side edge layer 3. The negative electrode layer 2 has a negative current collector layer 2A and a negative active material layer 2B.

[0060] (Positive electrode active material layer and negative electrode active material layer)

[0061] In this embodiment, the positive electrode active material layer 1B and the negative electrode active material layer 2B at least comprise known materials capable of adsorbing and releasing lithium ions as the positive and negative electrode active materials, respectively. Furthermore, they may also contain conductive additives and ion-conducting additives. Preferably, the positive and negative electrode active materials are capable of effectively inserting into and detaching lithium ions.

[0062] Examples of positive and negative electrode active materials include transition metal oxides and transition metal composite oxides. More specifically, lithium manganese composite oxide (Li₂Mn) is an example of a positive and negative electrode active material. a Ma 1-a O3 (0.8≤a≤1, Ma=Co, Ni), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese spinel (LiMn2O4), general formula: LiNi x Co y Mn z The composite metal oxides represented by O2 (x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1), lithium vanadium compounds (LiV2O5), olivine-type LiMbPO4 (where Mb is one or more elements selected from Co (cobalt), Ni (nickel), Mn (manganese), Fe (iron), Mg (magnesium), Nb (niobium), Ti (titanium), Al (aluminum), Zr (zirconium), lithium vanadium phosphate (Li3V2(PO4)3 or LiVOPO4), Li excess system solid solution cathodes represented by Li2MnO3-LiMcO2 (Mc=Mn, Co, Ni), and lithium titanate (Li4Ti5O) 12 ), titanium dioxide (TiO2), Li s Ni t Co u Al v Composite metal oxides, etc., represented by O2 (0.9 < s < 1.3, 0.9 < t + u + v < 1.1).

[0063] As the positive and negative active materials of this embodiment, it is preferred to contain a phosphate compound as the main component. For example, it is preferred to be any one or more of the following: olivine-type LiMbPO4 (wherein Mb is one or more elements selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr), lithium vanadium phosphate (LiVOPO4, Li3V2(PO4)3, Li4(VO)(PO4)2), lithium vanadium pyrophosphate (Li2VOP2O7, Li2VP2O7) and Li9V3(P2O7)3(PO4)2, and particularly preferred to be one or both of LiVOPO4 and Li3V2(PO4)3.

[0064] In this embodiment, the main component refers to the active material of the phosphate compound having a ratio of more than 50 parts by weight when the total amount of the positive electrode active material and the negative electrode active material is set to 100 parts by weight. Preferably, the ratio of the active material of the phosphate compound is more than 80 parts by weight.

[0065] Furthermore, these positive and negative electrode active materials can replace a portion of each element with different elements, or they can change the stoichiometric composition. LiVOPO4 and Li3V2(PO4)3 preferably have lithium defects, and Li is more preferred. x VOPO4 (0.94≤x≤0.98) or Li y V2(PO4)3(2.8≤y≤2.95).

[0066] In addition, as negative electrode active materials, Li metal, Li-Al alloy, Li-In alloy, carbon, silicon (Si), and silicon oxide (SiO) can be used, for example. x Lithium titanate (Li4Ti5O) 12 ), titanium dioxide (TiO2).

[0067] Here, there is no significant difference between the active materials constituting the positive electrode active material layer 1B and the negative electrode active material layer 2B. Comparing the potentials of the compounds in the positive and negative electrode active material layers, the compound exhibiting the higher potential can be used as the positive electrode active material, and the compound exhibiting the lower potential can be used as the negative electrode active material. Furthermore, as long as the compound simultaneously possesses lithium-ion release and lithium-ion adsorption properties, the same material can be used to constitute both the positive electrode active material layer 1B and the negative electrode active material layer 2B.

[0068] Examples of conductive additives include carbon materials such as carbon black, acetylene black, Ketjen black, carbon nanotubes, graphite, graphene, and activated carbon, as well as metal materials such as gold, silver, palladium, platinum, copper, and tin.

[0069] As an ion-conducting aid, it may be a solid electrolyte, for example. Specifically, the solid electrolyte may be made of the same material as the solid electrolyte layer 50.

[0070] When using a solid electrolyte as an ion-conducting agent, the ion-conducting agent and the solid electrolyte used for solid electrolyte layers A and B are preferably made of the same material.

[0071] (Positive current collector and negative current collector)

[0072] The materials used for the positive electrode current collector layer 1A and the negative electrode current collector layer 2A constituting the tandem all-solid-state battery 100 of this embodiment are preferably materials with high conductivity, such as silver, palladium, gold, platinum, aluminum, copper, nickel, etc. Copper is particularly preferred because it is difficult to react with oxide-type lithium-ion conductors, thereby reducing the internal resistance of the tandem all-solid-state battery. The materials used for the positive electrode current collector layer 1A and the negative electrode current collector layer 2A can be the same or different materials.

[0073] Furthermore, the positive electrode current collector layer 1A and the negative electrode current collector layer 2A of the stacked all-solid-state battery 100 of this embodiment preferably contain positive electrode active material and negative electrode active material, respectively.

[0074] By including positive electrode active material in the positive electrode current collector layer 1A and negative electrode active material in the negative electrode current collector layer 2A, the adhesion between the positive electrode current collector layer 1A and the positive electrode active material layer 1B and the negative electrode current collector layer 2A and the negative electrode active material layer 2B is improved, which is therefore preferred.

[0075] In this embodiment, the ratio of positive electrode active material to negative electrode active material in the positive electrode current collector layer 1A and the negative electrode current collector layer 2A is not particularly limited as long as it functions as a current collector. The volume ratio of positive electrode current collector to positive electrode active material, or negative electrode current collector to negative electrode active material, is preferably in the range of 90 / 10 to 70 / 30.

[0076] (Side edge layer)

[0077] In this embodiment, the side edge layer 3 of the stacked all-solid-state battery 100 is preferably provided to eliminate the height difference between the solid electrolyte layer A and the positive electrode layer 1, as well as the height difference between the solid electrolyte layer A and the negative electrode layer 2. Therefore, the side edge layer 3 represents the area other than the positive electrode layer 1. With the presence of such a side edge layer 3, the height difference between the solid electrolyte layer A and the positive electrode layer 1 and the negative electrode layer 2 is eliminated, so the density of the electrode becomes higher, and it is difficult to produce interlayer delamination or warping caused by the firing of the stacked all-solid-state battery 100.

[0078] The material constituting the side edge layer 3 preferably includes the same material as the solid electrolyte layer A. Therefore, it is preferable to include an oxide-type lithium-ion conductor having a NASICON-type, garnet-type, or perovskite-type crystal structure. Examples of lithium-ion conductors having a NASICON-type crystal structure include: ion conductors having a NASICON-type crystal structure containing at least Li, M (M being at least one of Ti (titanium), Zr (zirconium), Ge (germanium), Hf (hafnium), Sn (tin)); ion conductors having a garnet-type crystal structure or a similar structure containing at least Li, Zr, La, and O; and ion conductors having a perovskite-type structure containing at least Li, Ti, La, and O. That is, one type of these ion conductors can be used, or multiple types can be used in combination. The stacked all-solid-state battery 100 according to this embodiment can suppress crack formation and improve cycle characteristics.

[0079] (Outer layer)

[0080] The outer layer 4 is disposed in the stacking direction in any one or both of the regions outside of either the positive electrode layer 1 (positive electrode current collector layer 1A) or the negative electrode layer 2 (negative electrode current collector layer 2A). Figure 3 (The middle layer represents both). The outer layer 4 can also be made of the same material as the solid electrolyte layer A. Furthermore, in this embodiment, the stacking direction is... Figure 3 The z-direction corresponds to it.

[0081] The thickness of the outer layer 4 is not particularly limited, for example, it can be 20 μm or more and 100 μm or less. With a thickness of 20 μm or more, the positive electrode layer 1 or negative electrode layer 2 on the surface closest to the stacked body 20 in the stacking direction is less likely to be oxidized by the atmosphere during the firing process, resulting in a high-capacity stacked all-solid-state battery. Furthermore, if the thickness is set to 100 μm or less, it becomes an all-solid-state secondary battery that ensures sufficient moisture resistance, high reliability, and high volumetric energy density even in high-temperature and high-humidity environments.

[0082] (Second Implementation)

[0083] Figure 5 This is an enlarged cross-sectional view of the main part of the stacked solid-state battery 300 of the second embodiment. In the stacked solid-state battery 300, the same reference numerals are used for structures identical to those in the stacked solid-state battery 100, and sometimes descriptions are omitted. Details will be described later. The thickness of the solid electrolyte layer in the stacked solid-state battery 300 of the second embodiment is different from that in the stacked solid-state battery 100 of the first embodiment.

[0084] The stacked all-solid-state battery 300 has a stack 20A, a positive external electrode 60, and a negative external electrode 70. The stack 20A has a positive electrode layer 1, a negative electrode layer 2, solid electrolyte layers A1-A5, B1, and B2, and an outer layer 4. The outer layer 4 holds the positive electrode layer 1, the negative electrode layer 2, and the solid electrolyte layers A1-A5, B1, and B2 in the stacking direction. In this embodiment, the positive electrode layer 1, the negative electrode layer 2, and the solid electrolyte layers A1-A5, B1, and B2 held by the outer layer 4 are sometimes collectively referred to as energy storage elements.

[0085] Positive electrode layer 1 and negative electrode layer 2 are electrode layers, one of which functions as the positive electrode and the other as the negative electrode. The positive or negative polarity of the electrode layer varies depending on which polarity is connected to the external terminal. In this embodiment, positive electrode layer 1 is connected to the positive external electrode 60, and negative electrode layer 2 is connected to the negative external electrode 70, so positive electrode layer 1 functions as the positive electrode and negative electrode layer 2 functions as the negative electrode.

[0086] The positive electrode layer 1 has a positive current collector layer 1A and a positive active material layer 1B containing positive active material. The negative electrode layer 2 has a negative current collector layer 2A and a negative active material layer 2B containing negative active material.

[0087] The positive electrode current collector layer 1A and the negative electrode current collector layer 2A exhibit excellent conductivity. For example, the positive electrode current collector layer 1A and the negative electrode current collector layer 2A may be made of silver, palladium, gold, platinum, aluminum, copper, or nickel. Copper is difficult to react with the positive electrode active material, the negative electrode active material, and the solid electrolyte. For example, if copper is used for the positive electrode current collector layer 1A and the negative electrode current collector layer 2A, the internal resistance of the stacked all-solid-state battery 300 can be reduced. The materials constituting the positive electrode current collector layer 1A and the negative electrode current collector layer 2A can be the same or different.

[0088] The positive electrode active material layer 1B is formed on one or both sides of the positive electrode current collector layer 1A. The positive electrode active material layer 1B may also be absent on the side of the positive electrode current collector layer 1A where the opposing negative electrode layer 2 is not present. Similarly, the negative electrode active material layer 2B is formed on one or both sides of the negative electrode current collector layer 2A. The negative electrode active material layer 2B may also be absent on the side of the negative electrode current collector layer 2A where the opposing positive electrode layer 1 is not present. For example, the uppermost or lowermost positive electrode layer 1 or negative electrode layer 2 of the laminate 5 may also lack a positive electrode active material layer 1B or a negative electrode active material layer 2B on one side.

[0089] The positive electrode active material layer 1B and the negative electrode active material layer 2B contain positive and negative electrode active materials that accept and accept electrons. They may also contain conductive additives, ion-conducting additives, etc. Preferably, the positive and negative electrode active materials are capable of effectively inserting and removing lithium ions.

[0090] Furthermore, the positive current collector layer 1A and the negative current collector layer 2A may also contain positive and negative active materials, respectively. The content ratio of active materials in each current collector is not particularly limited as long as it functions as a current collector. For example, the volume ratio of positive current collector / positive active material, or negative current collector / negative active material, is preferably in the range of 90 / 10 to 70 / 30.

[0091] Solid electrolyte layers A1–A5, B1, and B2 are located between the positive electrode active material layer 1B and the negative electrode active material layer 2B in the stacking direction. Solid electrolyte layers A1–A5, B1, and B2 contain a solid electrolyte. A solid electrolyte is a substance (e.g., particles) capable of ion movement by an externally applied electric field. For example, lithium ions move within the solid electrolyte by an externally applied electric field. Furthermore, a solid electrolyte is an insulator that impedes the movement of electrons.

[0092] The solid electrolyte layers A1 to A5, B1, and B2 of the stacked all-solid-state battery 300 in this embodiment are not particularly limited, and may, for example, contain a solid electrolyte having any one of the crystal structures selected from NASICON type, garnet type, perovskite type, and LISICON type. Examples include: an ion conductor (e.g., Li) having a NASICON type crystal structure containing at least Li (lithium), M (M being at least one of Ti (titanium), Zr (zirconium), Ge (germanium), Hf (hafnium), Sn (tin), P (phosphorus), and O (oxygen). 1+x Al x Ti 2-x (PO4)3; LATP); and ionic conductors with a garnet-type crystal structure containing at least Li (lithium), Zr (zirconium), La (lanthanum) and O (oxygen) (e.g., Li7La3Zr2O). 12 ;LLZ), or ionic conductors with garnet-like structures; and ionic conductors with perovskite-type structures containing at least Li (lithium), Ti (titanium), La (lanthanum), and O (oxygen) (e.g., Li). 3x La 2 / 3- x TiO3; LLTO); and lithium-ion conductors (e.g., Li) with a LISICON-type crystal structure containing at least Li, Si, P and O. 3.5 Si 0.5 P 0.5 O 3.5 At least one of LSPO. That is, these ionic conductors can be used in combination, or two or more can be used in combination.

[0093] The thicknesses of the solid electrolyte layers A1 to A5, B1, and B2 are, for example, in the range of 0.5 μm or more and 20.0 μm or less. By setting the thickness of the solid electrolyte layers A1 to A5 to 0.5 μm or more, short circuits between the positive electrode layer 1 and the negative electrode layer 2 can be reliably prevented. Furthermore, by setting the thickness to 20.0 μm or less, the migration distance of lithium ions is shortened, thereby reducing the internal resistance of the stacked all-solid-state battery.

[0094] Solid electrolyte layers A1 to A5 belong to Group 1. Solid electrolyte layer A1 is the thinnest solid electrolyte layer among solid electrolyte layers A1 to A5, B1, and B2. The thickness of each of solid electrolyte layers A2 to A5 is more than 1 times but less than 2 times the thickness of solid electrolyte layer A1.

[0095] Solid electrolyte layers B1 and B2 belong to group 2. The thickness of solid electrolyte layers B1 and B2 is more than twice the thickness of solid electrolyte layer A1. The number of solid electrolyte layers belonging to group 2 is any number, with at least one.

[0096] The configuration of the solid electrolyte layer belonging to Group 2 can be arbitrarily selected. For example, when there is only one solid electrolyte layer belonging to Group 2, it can be configured such that the number of solid electrolyte layers belonging to Group 1 sandwiched between the outer layer 4 on the upper side of the stacking direction and the solid electrolyte layer of Group 2 closest to the outer layer 4 on the upper side of the stacking direction, and the number of solid electrolyte layers belonging to Group 1 sandwiched between the outer layer 4 on the lower side of the stacking direction and the solid electrolyte layer of Group 2 closest to the outer layer 4 on the lower side of the stacking direction, are equal. That is, it can also be configured such that the number of solid electrolyte layers belonging to Group 1 that are further on the upper side of the stacking direction than the solid electrolyte layers belonging to Group 2, and the number of solid electrolyte layers belonging to Group 1 that are further on the lower side of the stacking direction than the solid electrolyte layers belonging to Group 2, are equal. In addition, when there are two or more solid electrolyte layers belonging to the second group, the number of solid electrolyte layers belonging to the first group sandwiched by the outer layer 4 on the upper side of the stacking direction and the solid electrolyte layer of the second group closest to the outer layer 4 on the upper side of the stacking direction, the number of solid electrolyte layers belonging to the first group sandwiched by the outer layer 4 on the lower side of the stacking direction and the solid electrolyte layer of the second group closest to the outer layer 4 on the lower side of the stacking direction, and the number of solid electrolyte layers belonging to the first group sandwiched by adjacent solid electrolyte layers belonging to the second group are equal.

[0097] The average thickness t of the solid electrolyte layers A1 to A5 in Group 1 a The average thickness t of solid electrolyte layers B1 and B2 belonging to group 2 b It satisfies the following equation (1).

[0098] 2t a ≤tb …(1)

[0099] In addition, the average thickness t of the solid electrolyte layers A1 to A5 belonging to Group 1 a The average thickness t of solid electrolyte layers B1 and B2 belonging to group 2 b It can also satisfy the following equation (2).

[0100] 2t a ≤t b ≤10t a …(2)

[0101] In this embodiment, the solid electrolyte layer with the smallest thickness among all solid electrolyte layers, such as solid electrolyte layer A1, is sometimes referred to as the first solid electrolyte layer. Additionally, in this embodiment, solid electrolyte layers with a thickness more than twice the thickness of the first solid electrolyte layer, such as solid electrolyte layers B1 and B2, are sometimes referred to as the second solid electrolyte layer. Furthermore, in this embodiment, solid electrolyte layers with a thickness greater than the first solid electrolyte layer but less than twice that of the first solid electrolyte layer, such as solid electrolyte layers A2 to A5, are sometimes referred to as the third solid electrolyte layer.

[0102] Even the stacked solid-state battery 300 of this embodiment can achieve the same effect as the stacked solid-state battery 100 of the first embodiment.

[0103] Furthermore, in this embodiment, an example is shown where the thicknesses of each layer of solid electrolyte layers A1 to A5 belonging to Group 1 and the thicknesses of each layer of solid electrolyte layers B1 and B2 belonging to Group 2 are different, but they can also be the same.

[0104] Furthermore, in this embodiment, the case of having 5 solid electrolyte layers A1 to A5 as the solid electrolyte layer belonging to Group 1 is exemplified, but the number of solid electrolyte layers belonging to Group 1 is any number of at least 2. Additionally, in this embodiment, the case of having 2 solid electrolyte layers B1 and B2 as the solid electrolyte layer belonging to Group 2 is exemplified, but the number of solid electrolyte layers belonging to Group 2 is any number of at least 1.

[0105] Furthermore, in this embodiment, a case where there is only one first solid electrolyte layer is illustrated. However, it is also possible for at least one of the solid electrolyte layers A2 to A5 to be the same as the solid electrolyte layer A1, and for a structure in which there are multiple first solid electrolyte layers.

[0106] (Manufacturing method of stacked all-solid-state battery)

[0107] The stacked all-solid-state battery 100 of this embodiment can be manufactured according to the following steps. The materials of the positive electrode current collector layer 1A, the positive electrode active material layer 1B, the solid electrolyte layer A, the solid electrolyte layer B, the negative electrode current collector layer 2A, the negative electrode active material layer 2B, and the side edge layer 3 are pasted. The paste-forming method is not particularly limited; for example, powders of the above materials can be mixed in a carrier to obtain a paste. Here, the carrier is a general term for the medium in the liquid phase, including solvents, binders, etc. The binder contained in the paste used to form the green sheet or printing layer is not particularly limited; polyvinyl acetal resin, cellulose resin, acrylic resin, polyurethane resin, vinyl acetate resin, polyvinyl alcohol resin, etc., can be used, and the slurry can contain at least one of these resins.

[0108] In addition, the paste may also contain plasticizers. There are no particular restrictions on the types of plasticizers; phthalates such as dioctyl phthalate and diisononyl phthalate can be used.

[0109] This method can be used to prepare pastes for positive electrode current collector layers, positive electrode active material layers, solid electrolyte layers, negative electrode active material layers, negative electrode current collector layers, and side edge layers.

[0110] The prepared solid electrolyte layer paste is applied to a substrate such as polyethylene terephthalate (PET) to the desired thickness and dried as needed to produce a raw sheet for solid electrolyte (solid electrolyte layer A). Similarly, a raw sheet for solid electrolyte (solid electrolyte layer B) is produced using the same steps for a solid electrolyte layer B that has a greater thickness than solid electrolyte layer A.

[0111] There are no particular limitations on the manufacturing method of the above-mentioned solid electrolyte green sheets, and known methods such as doctor blade coating, die coating machine, comma coating machine, and gravure coating machine can be used.

[0112] Next, the positive electrode active material layer 1B, the positive electrode current collector layer 1A, and the positive electrode active material layer 1B are sequentially screen-printed onto the green sheet (solid electrolyte layer A) to form the positive electrode layer 1. Furthermore, to fill the height difference between the green sheet (solid electrolyte layer A) and the positive electrode layer 1, a side edge layer 3 is formed in the area outside the positive electrode layer 1 by screen printing, thus fabricating a positive electrode unit (a unit on which the positive electrode layer 1 and the side edge layer 3 are formed in the solid electrolyte layer A).

[0113] The negative electrode unit can also be made using the same method as the positive electrode unit.

[0114] Then, the positive electrode unit and the negative electrode unit are alternately biased and stacked with one end of the positive electrode not aligned with the other end of the negative electrode. After stacking to a predetermined number of layers, a solid electrolyte layer B with a thickness greater than that of the solid electrolyte layer A is stacked. Next, the positive electrode unit and the negative electrode unit are stacked to the predetermined number of layers again, thereby fabricating a stacked substrate composed of elements of a stacked all-solid-state battery. In addition, in the stacked substrate, outer layers can be provided on two main surfaces of the stack as needed. The outer layers can use the same material as the solid electrolyte layer, for example, a green sheet for solid electrolytes can be used. In addition, the solid electrolyte layer B can be a single layer or multiple layers (multiple locations). It is preferable that the solid electrolyte layer B is provided in a manner that divides the number of stacked elements equally or approximately equally. For example, in the case of a 31-layer stack with one solid electrolyte layer B, it is sufficient to provide one solid electrolyte layer B at the 16th layer. In this case, the aforementioned stacked body, via the solid electrolyte layer B, becomes a stacked all-solid-state battery with a configuration of 15 layers / 15 layers. Similarly, when there are two (two) solid electrolyte layers B, it is sufficient to have one solid electrolyte layer B in each of the 11th and 21st layers. In this case, the stacked body, via the solid electrolyte layer B, becomes a stacked all-solid-state battery with a configuration of 10 layers / 9 layers / 10 layers.

[0115] Furthermore, regarding the stacking positions where the aforementioned solid electrolyte layer B is located, it is not necessary to divide the stacking layers equally or approximately equally; it is sufficient to have a thick solid electrolyte layer B at least at any stacking position. By including the aforementioned solid electrolyte layer B, the volume expansion of the stacked all-solid-state battery can be dispersed.

[0116] The above manufacturing method is a method for manufacturing a parallel-type stacked solid-state battery 100. The manufacturing method for a series-type stacked solid-state battery is simply to stack the positive electrode and the negative electrode in the same way, that is, without bias.

[0117] Furthermore, by applying pressure to the fabricated laminated substrates using molding, warm isostatic pressing (WIP), cold isostatic pressing (CIP), or isostatic pressing, the adhesion can be improved. Pressurization is preferably performed while heating is in progress, for example, at temperatures between 40 and 95°C.

[0118] The fabricated laminated substrate can be cut into unburned laminated solid-state batteries 10 using a cutting device.

[0119] The stacked solid-state battery 10 is sintered by debinding and firing. The debinding and firing can be carried out at a temperature of 600°C to 1000°C under a nitrogen atmosphere. The holding time for debinding and firing is, for example, 0.1 to 6 hours.

[0120] Tumble grinding is performed to prevent chipping by chamfering the corners of the laminate and to expose the current collector layer at the end faces. It can be performed on the laminate 10 of an unfired all-solid-state battery or on the laminate 10 after firing. Tumble grinding can be performed as dry tumble grinding without water or wet tumble grinding with water. In the case of wet tumble grinding, an aqueous solution such as water is added to the tumble grinding machine.

[0121] There are no particular limitations on the conditions for roller processing; they can be adjusted appropriately, as long as they are carried out within the range that does not produce defects such as cracks or gaps in the laminate.

[0122] Furthermore, in order to efficiently extract current from the stack 10 of the tandem all-solid-state battery, external electrodes (positive external electrode 60 and negative external electrode 70) can be provided. The external electrodes are formed on either side of a pair of opposite sides of the stack 10. Examples of methods for forming the external electrodes include sputtering, screen printing, and dip coating. In screen printing and dip coating, a paste containing metal powder, resin, and solvent is prepared and formed as the external electrode. Then, a soldering process to remove the solvent and a plating process to form terminal electrodes on the surface of the external electrode are performed. On the other hand, in sputtering, the external electrode and terminal electrode can be formed directly, so the soldering and plating processes are unnecessary.

[0123] To improve moisture resistance and impact resistance, the laminate 10 of the aforementioned stacked all-solid-state battery can, for example, be sealed inside a button cell. The sealing method is not particularly limited; for example, the laminate after firing can be sealed with resin. Alternatively, an insulating paste with insulating properties, such as Al2O3, can be applied or impregnated around the laminate, and then sealed by heat treatment of the insulating paste.

[0124] Furthermore, while the above embodiment illustrates a method for manufacturing a stacked all-solid-state battery that includes a step of forming a side edge layer using a paste for the side edge layer, the method for manufacturing a stacked all-solid-state battery in this embodiment is not limited to this example. For instance, the step of forming the side edge layer using a paste for the side edge layer may be omitted. The side edge layer may also be formed, for example, by deforming a paste for the solid electrolyte layer during the manufacturing process of the stacked all-solid-state battery.

[0125] The embodiments of the present invention have been described in detail above, but are not limited to the embodiments described above, and various modifications can be made.

[0126] Example

[0127] Hereinafter, based on the above-described embodiments, the present invention will be further described in more detail using examples and comparative examples, but the present invention is not limited to these examples. Unless otherwise specified, the "parts" of the amount of materials added in the preparation of the paste refer to "parts by mass".

[0128] (Example 1)

[0129] (Preparation of positive and negative electrode active materials)

[0130] The positive and negative electrode active materials were prepared according to the following steps: Li₂CO₃, V₂O₅, and NH₄H₂PO₄ were used as starting materials and wet-mixed in a ball mill for 16 hours to dehydrate and dry the mixture. The resulting powder was calcined at 850°C in a nitrogen-hydrogen mixed gas for 2 hours. After calcination, it was wet-milled again in a ball mill for 16 hours, and finally dehydrated and dried to obtain the powders of the positive and negative electrode active materials.

[0131] The obtained active material was subjected to X-ray diffraction (XRD) and inductively coupled plasma (ICP) luminescence spectrophotometry, and the results confirmed it to be lithium vanadium phosphate Li3V2(PO4)3. Furthermore, the identification of the X-ray diffraction pattern was based on JCPDS card 74-3236: Li3V2(PO4)3.

[0132] (Preparation of positive electrode active material paste and negative electrode active material paste)

[0133] Both the positive electrode active material paste and the negative electrode active material paste are prepared by adding 15 parts of ethyl cellulose as a binder and 65 parts of dihydroterpene alcohol as a solvent to 100 parts of the obtained positive electrode active material and negative electrode active material powder, and then mixing and dispersing them.

[0134] (Preparation of solid electrolyte paste)

[0135] The solid electrolyte was prepared according to the following steps. Li₂CO₃ (lithium carbonate), TiO₂ (titanium oxide), Al₂O₃ (aluminum oxide), and NH₄H₂PO₄ (ammonium dihydrogen phosphate) were used as starting materials, and the materials were weighed in a molar ratio of Li, Al, Ti, and PO₄ of 1.3:0.3:1.7:3.0 (=Li:Al:Ti:PO₄). The materials were wet-mixed in a ball mill for 16 hours, and then dehydrated and dried. The resulting powder was calcined at 800°C in atmospheric conditions for 2 hours, followed by wet pulverization in a ball mill for another 16 hours. Finally, the powder was dehydrated and dried to obtain the solid electrolyte powder.

[0136] The obtained solid electrolyte powder was analyzed using XRD and ICP-based spectroscopy, and the results confirmed it to be Li with a NASICON-type crystal structure. 1.3 Al 0.3 Ti 1.7 (PO4)3 (lithium aluminum titanium phosphate). Additionally, the identification of the X-ray diffraction pattern was based on JCPDS card 35-0754: LiTi2(PO4)3.

[0137] 100 parts of ethanol and 200 parts of toluene, used as solvents, were added to 100 parts of the solid electrolyte powder and wet-mixed using a ball mill. Then, 16 parts of polyvinyl butyral binder and 4.8 parts of benzyl butyl phthalate were added and wet-mixed using a ball mill to prepare a solid electrolyte paste.

[0138] (Fabrication of solid electrolyte sheets)

[0139] Using a doctor blade sheet forming machine, the aforementioned solid electrolyte paste is applied onto a PET film, thereby producing a sheet of solid electrolyte layer A. In addition, multiple sheets of solid electrolyte layer B, consisting of a thickness 1 to 15 times that of solid electrolyte layer A, are also produced following the same steps.

[0140] (Preparation of positive and negative current collector pastes)

[0141] As positive and negative current collectors, Cu powder is mixed with the prepared positive and negative active material powders at a volume ratio of 80 / 20. Then, 100 parts of the mixture, 10 parts of ethyl cellulose as a binder, and 50 parts of dihydroterpineol as a solvent are added to mix and disperse the mixture to prepare positive and negative current collector layer pastes.

[0142] (Preparation of external electrode paste)

[0143] Cu powder, epoxy resin and solvent are mixed and dispersed using a ball mill to prepare a thermosetting external electrode paste.

[0144] Using the sheet of solid electrolyte layer A, the sheet of solid electrolyte layer B, the positive electrode current collector paste, the negative electrode current collector paste, and the external electrode paste, a stacked all-solid-state battery is fabricated according to the following steps.

[0145] (Fabrication of the positive electrode unit)

[0146] On a portion of the main surface of the aforementioned solid electrolyte layer A, a positive electrode active material layer is formed using a screen printing machine and dried at 80°C for 10 minutes. A positive electrode current collector layer is then formed on this positive electrode active material layer and dried at 80°C for 10 minutes. Next, another positive electrode active material layer is formed on the aforementioned positive electrode current collector layer and dried at 80°C for 10 minutes, thereby forming a positive electrode layer on a portion of the main surface of the solid electrolyte layer A, where the positive electrode current collector layer is sandwiched between the positive electrode active material layer and the positive electrode active material layer. Next, on the main surface of the solid electrolyte layer A where the aforementioned positive electrode layer has not been formed, a solid electrolyte layer of approximately the same height as the aforementioned positive electrode layer is formed and dried at 80°C for 10 minutes. Finally, by peeling off the PET film, a positive electrode unit with the positive electrode layer and solid electrolyte layer formed on the main surface of the solid electrolyte layer A is fabricated.

[0147] (Fabrication of the negative electrode unit)

[0148] The negative electrode unit is manufactured using the same steps as the positive electrode unit described above.

[0149] (Fabrication of a stacked solid-state battery)

[0150] The positive electrode unit and the negative electrode unit are stacked while offsetting one end of the positive electrode layer and the negative electrode layer. At this time, the positive electrode unit and the negative electrode unit are stacked alternately in the order of positive electrode unit and negative electrode unit. The solid electrolyte layer sandwiched between the positive electrode layer and the negative electrode layer is regarded as layer 1, and it is stacked up to 15 layers. In addition, when stacking 15 layers, the negative electrode layer is stacked on the topmost layer. Next, a solid electrolyte layer B with a thickness of twice that of the solid electrolyte layer A is stacked on the negative electrode layer as the 16th solid electrolyte layer. Next, the positive electrode unit is flipped up and down and stacked in such a way that the positive electrode layer is stacked on the solid electrolyte layer B. Next, the negative electrode unit is also flipped up and down and stacked, and 15 layers are stacked while offsetting one end of the positive electrode layer and the negative electrode layer in the same way as before, thereby creating a laminated substrate consisting of a total of 31 layers in the stacking direction, namely solid electrolyte layer A (15 layers), solid electrolyte layer B (1 layer), and solid electrolyte layer A (15 layers).

[0151] A plurality of solid electrolyte layers A are stacked on the upper and lower surfaces of the aforementioned laminated substrate, and an outer layer composed of solid electrolyte layers is respectively provided. The outer layers provided on the upper and lower surfaces are formed to have the same thickness.

[0152] For the aforementioned multilayer substrate, to improve the adhesion at the interfaces of each layer, a multilayer chip is fabricated by hot pressing after molding and then cutting. Next, the multilayer chip is placed in a ceramic holder and held at 600°C for 2 hours in a nitrogen atmosphere to remove the adhesive. Then, it is held at 750°C for 2 hours in a nitrogen atmosphere to fire the multilayer chip, which is then removed after natural cooling.

[0153] (External electrode formation process)

[0154] Cu external electrode paste was applied to the end face of the sintered stacked chip and kept at 150°C for 30 minutes to perform thermal curing, thereby forming an external electrode and fabricating the stacked all-solid-state battery of Example 1.

[0155] (Evaluation of the thickness of the solid electrolyte layer)

[0156] The average thickness t of the solid electrolyte layer A in the stacked all-solid-state battery of Example 1 a And the thickness t of the solid electrolyte layer B b The thickness of the solid electrolyte layer is calculated through image analysis after obtaining a cross-sectional photograph of the all-solid-state battery using a field emission scanning electron microscope (FE-SEM). A straight line perpendicular to the positive electrode active material layer 1B or negative electrode active material layer 2B located at the end of the stacking direction is drawn. The length between adjacent positive electrode active material layers 1B and negative electrode active material layers 2B on this line is defined as the thickness of the solid electrolyte layer sandwiched between the adjacent positive electrode active material layers 1B and negative electrode active material layers 2B. In this embodiment, the thickness of the solid electrolyte layer refers to the thickness of the solid electrolyte layer at the center of the width direction of the stack 20. Here, the width direction of the stack refers to the direction in which the stack 20 is sandwiched between the positive electrode external electrode 60 and the negative electrode external electrode 70. Figure 3 In the x-direction. Measure the thickness of the entire solid electrolyte layer A, calculate the average thickness of solid electrolyte layer A, and the result t. a The thickness is 5 μm. Similarly, the average thickness of the solid electrolyte layer B is calculated, and the result is t. b It is 10 μm. Average thickness ratio t b / t a The result is 2. The results are shown in Table 1.

[0157] (Comparative Example 1)

[0158] The stacked all-solid-state battery of Comparative Example 1 differs from Example 1 only in that the 16th solid electrolyte layer B has the same configuration as the solid electrolyte layer A. That is, the 16th solid electrolyte layer of the stacked all-solid-state battery of Comparative Example 1 is a sheet with a thickness equal to that of solid electrolyte layer A. In the stacked all-solid-state battery of Comparative Example 1, the multiple solid electrolyte layers consist only of solid electrolyte layers belonging to Group 1, and there are no solid electrolyte layers belonging to Group 2.

[0159] (Compare Examples 2 and 3)

[0160] The stacked all-solid-state batteries of Comparative Examples 2 and 3 differ from Example 1 only in that the 16th solid electrolyte layer B is replaced with a solid electrolyte B′. In each of Comparative Examples 2 and 3, as the solid electrolyte B′, sheets with a thickness of 1.2 times and 1.6 times that of the solid electrolyte layer A of Example 1 are stacked, respectively. Therefore, in the stacked all-solid-state batteries of Comparative Examples 2 and 3, the multiple solid electrolyte layers are composed only of solid electrolyte layers belonging to Group 1, and there are no solid electrolyte layers belonging to Group 2. Hereinafter, for ease of explanation, in Comparative Examples 2 and 3, the solid electrolyte layer stacked instead of the 16th solid electrolyte layer B of Example 1 will be referred to as solid electrolyte layer B′, and the other solid electrolyte layers will be referred to as solid electrolyte layer A′. In addition, the average thickness of solid electrolyte layer A′ and the thickness (average thickness) of solid electrolyte layer B′ will be referred to as t. a ′、t b Other conditions were followed in the same manner as in Example 1 to fabricate a stacked all-solid-state battery. a ′、t b ′ and t b ′ / t a The measurements were also performed following the same steps as in Example 1.

[0161] (Examples 2, 3, 4, and 5)

[0162] In the stacked all-solid-state batteries of Examples 2, 3, 4, and 5, the 16th solid electrolyte layer B was formed by stacking sheets of solid electrolyte layer B with a thickness of 3, 6, 10, and 15 times that of the aforementioned solid electrolyte layer A, respectively. Otherwise, the stacked all-solid-state batteries were fabricated following the same steps as in Example 1. For t a t b and t b / t a The measurements were also performed following the same steps as in Example 1.

[0163] (Examples 6, 7, and 8)

[0164] Examples 6, 7, and 8 are stacked all-solid-state batteries, except that the solid electrolyte material in the 16th solid electrolyte layer B is changed to a NASICON-type crystal structure, i.e., LTP, LAGP, or LYZP. They are fabricated following the same steps as in Example 2. For t a t b and t b / t a The measurements were performed following the same steps as in Example 1. The solid electrolytes LTP, LAGP, and LYZP were prepared using the following synthesis method.

[0165] LTP was prepared using Li₂CO₃ (lithium carbonate), TiO₂ (titanium oxide), and NH₄H₂PO₄ (ammonium dihydrogen phosphate) as starting materials. The materials were weighed in a Li:Ti:PO₄ molar ratio of 1.0:2.0:3.0 (=Li:Ti:PO₄) and synthesized using the same method as in Example 1. XRD and ICP analysis confirmed that the obtained solid electrolyte was LiTi₂(PO₄)₃.

[0166] LAGP was prepared using the same synthesis method as in Example 1, except that GeO2 was used instead of TiO2 as the starting material, and the Li, Al, Ge, and PO4 were weighed in a molar ratio of 1.3:0.3:1.7:3.0 (=Li:Al:Ge:PO4). XRD and ICP analyses confirmed that the obtained solid electrolyte was Li. 1.3 Al 0.3 Ge 1.7 (PO4)3.

[0167] LYZP was prepared using Li₂CO₃ (lithium carbonate), Y(NO₃)₃ (yttrium nitrate), ZrO(NO₃)₂·2H₂O (zirconium oxynitrate), and NH₄H₂PO₄ (ammonium dihydrogen phosphate) as starting materials. The materials were weighed in a molar ratio of Li, Y, Zr, and PO₄ of 1.1:0.1:1.9:3.0 (=Li:Y:Zr:PO₄) and synthesized using the same method as in Example 1. XRD and ICP analysis confirmed that the obtained solid electrolyte was Li₂CO₃. 1.3 Y 0.3 Zr 1.7 (PO4)3.

[0168] (Examples 9-10)

[0169] Examples 9 and 10 are stacked all-solid-state batteries, except that the solid electrolyte material in solid electrolyte layer A and solid electrolyte layer B is changed to Li7La3Zr2O with a garnet-type crystal structure. 12 (LLZ), Li as a perovskite-type crystal structure 0.3 La 0.55 Apart from TiO3 (LLTO), a stacked all-solid-state battery was fabricated following the same steps as in Example 2. For t a t b and t b / t a The measurements were performed following the same steps as in Example 1. The solid electrolytes of LLZ and LLTO were prepared by the following synthesis method.

[0170] LLZ was prepared using Li₂CO₃ (lithium carbonate), La₂O₃ (lanthanum oxide), and ZrO₂ (zirconia) as starting materials, weighed in a Li:La:Zr molar ratio of 7:3:2 (=Li:La:Zr), and synthesized using the same method as in Example 1. XRD and ICP analyses confirmed that the obtained solid electrolyte was Li₇La₃Zr₂O₃. 12 .

[0171] LLTO was prepared using Li₂CO₃ (lithium carbonate), La₂O₃ (lanthanum oxide), and TiO₂ (titanium oxide) as starting materials, weighed in a Li:La:Ti molar ratio of 0.3:0.55:1.0 (=Li:La:Ti), and synthesized using the same method as in Example 1. XRD and ICP analyses confirmed that the obtained solid electrolyte was Li₂CO₃. 0.3 La 0.55 TiO3.

[0172] (Example 11)

[0173] In the stacked all-solid-state battery of Example 11, the solid electrolyte material in the 16th solid electrolyte layer B was changed to a material made by mixing LATP and LAGP in a weight ratio of 50:50. Otherwise, the stacked all-solid-state battery was fabricated following the same steps as in Example 2. For t a t b and t b / t a The measurements were performed following the same steps as in Example 1.

[0174] (Example 12)

[0175] The stacked all-solid-state battery in Example 12 differs from the one in that the solid electrolyte material in solid electrolyte layer B is changed to Li7La3Zr2O, which has a garnet-type crystal structure. 12 Except for (LLZ), a stacked all-solid-state battery was fabricated following the same steps as in Example 2, for t a t b and t b / t a The measurements were performed following the same steps as in Example 1.

[0176] (Example 13)

[0177] Example 13, a stacked all-solid-state battery, is fabricated following the same steps as Example 2, except that the solid electrolyte layer B sheets from Example 2 are stacked on the 11th and 21st layers respectively. For t a t b and t b / ta The measurements were performed following the same steps as in Example 1.

[0178] (Example 14)

[0179] Example 14, a stacked all-solid-state battery, was fabricated following the same steps as in Example 2, except that the 14th layer was the solid electrolyte layer B from Example 2. For t a t b and t b / t a The measurements were performed following the same steps as in Example 1.

[0180] (Example 15)

[0181] In the stacked all-solid-state battery of Example 15, the solid electrolyte material in solid electrolyte layer A and solid electrolyte layer B is changed to Li. 3.5 Si 0.5 P 0.5 O4(LSPO), except for this, a stacked all-solid-state battery was fabricated following the same steps as in Example 2, for t a t b and t b / t a The measurements were performed following the same steps as in Example 1. The solid electrolyte of LSPO was prepared by the following synthesis method.

[0182] LSPO was prepared using Li₂CO₃, SiO₂, and commercially available Li₃PO₄ as starting materials. These materials were weighed in a molar ratio of 2:1:1 and wet-mixed in a ball mill for 16 hours using water as the dispersion medium. The mixture was then dehydrated and dried. The resulting powder was calcined at 950°C in atmospheric pressure for 2 hours, followed by wet pulverization in a ball mill for another 16 hours. Finally, it was dehydrated and dried to obtain a solid electrolyte powder. XRD and ICP analyses confirmed that the powder was Li₂CO₃. 3.5 Si 0.5 P 0.5 O4(LSPO)

[0183] (Examples 16 and 17)

[0184] In the stacked all-solid-state battery of Example 16, the solid electrolyte layers B (B1, B2) serving as the 11th and 21st layers are respectively stacked with sheets of solid electrolyte layers B1 and B2 having a thickness of 2 times and 6 times that of solid electrolyte layer A. Otherwise, the stacked all-solid-state battery was fabricated following the same steps as in Example 1. For t a t b and t b / t aThe measurements were also performed following the same steps as in Example 1.

[0185] In the stacked all-solid-state battery of Example 17, the solid electrolyte layers B (B1, B2) serving as the 11th and 21st layers are respectively stacked with sheets of solid electrolyte layers B1 and B2 having a thickness of 2 times and 10 times that of solid electrolyte layer A. Otherwise, the stacked all-solid-state battery was fabricated following the same steps as in Example 1. For t a t b and t b / t a The measurements were also performed following the same steps as in Example 1.

[0186] (Example 18)

[0187] In the stacked all-solid-state battery of Example 18, sheets of solid electrolyte layers of different thicknesses are stacked as solid electrolyte layers A (layers 1-10), solid electrolyte layers A (layers 12-20), and solid electrolyte layers A (layers 22-31). Furthermore, the layers are arranged in ascending order of thickness, forming solid electrolyte layers 1-10, 12-20, and 22-31. Additionally, sheets of solid electrolyte layers B1 and B2, each twice the average thickness of solid electrolyte layer A, are stacked as solid electrolyte layers B1 and B2, respectively. Regarding other conditions, the stacked all-solid-state battery is manufactured under the same conditions as in Example 1, and regarding t... a t b and t b / t a The measurements were performed following the same steps as in Example 1.

[0188] (Comparative Example 4)

[0189] In the stacked all-solid-state battery of Comparative Example 4, sheets of solid electrolyte layers of different thicknesses were stacked as solid electrolyte layers A (layers 1-10), solid electrolyte layers A (layers 12-20), and solid electrolyte layers A (layers 22-31). Furthermore, the layers were arranged in ascending order of thickness, becoming solid electrolyte layers 1-10, 12-20, and 22-31. In Comparative Example 4, sheets of solid electrolyte layers B1′ and B2′, each 1.5 times the average thickness of solid electrolyte layer A, were stacked as solid electrolyte layers B′ (B1′, B2′) as solid electrolyte layers B′ and B2′, respectively. Regarding other conditions, the stacked all-solid-state battery was manufactured under the same conditions as in Example 1, and for t... a ′、t b ′ and tb ′ / t a The measurements were also performed following the same steps as in Example 1.

[0190] (Battery Review)

[0191] The stacked all-solid-state batteries fabricated in this embodiment and comparative example can be used to evaluate the following battery characteristics.

[0192] [Charge-discharge cycle test]

[0193] The negative and positive external terminals of the stacked all-solid-state battery fabricated in this embodiment and the comparative example are held with a measuring probe and repeatedly charged and discharged, for example, according to the charge and discharge conditions shown below.

[0194] At 25°C, the battery was charged at a constant current rate of 0.2C (CC charging) until a battery voltage of 1.6V was reached. Then, it was discharged at a constant current rate of 0.2C (CC discharging) until a battery voltage of 0V was reached. The above charging and discharging was considered as one cycle, and the discharge capacity retention rate after repeating it for 1000 cycles was evaluated as the charge-discharge cycle characteristic. In addition, the charge-discharge cycle characteristic in this embodiment was calculated using the following formula (1).

[0195] Discharge capacity retention rate (%) after 1000 cycles = (Discharge capacity after 1000 cycles ÷ Discharge capacity after 1 cycle) × 100…(1)

[0196] [Volume Expansion Rate]

[0197] In the above charge-discharge cycle test, the thickness of the stacked solid-state battery before charging and the thickness of the stacked solid-state battery after the first charge were measured, and the volume expansion rate was calculated by the following formula (2).

[0198] Volume expansion rate (%) = (thickness of the stacked solid-state battery at the time of initial charging (mm) ÷ thickness of the stacked solid-state battery before charging (mm)) × 100…(2)

[0199] (result)

[0200] Table 1 shows the average thickness t of the solid electrolyte layer A in the stacked all-solid-state batteries of Examples 1-15 and Comparative Example 1, respectively. a The average thickness t of the solid electrolyte layer B b Average thickness ratio t a / t b The results of volume expansion rate and charge-discharge cycle tests are also presented. Additionally, Table 2 shows the average thickness t of the solid electrolyte layer A′ in the stacked all-solid-state batteries of Comparative Examples 2 and 3, respectively. aThe average thickness t of the solid electrolyte layer B b ′, average thickness ratio t a ′ / t b The results of volume expansion rate and charge-discharge cycle tests are shown. Additionally, Table 3 shows the average thickness t of the solid electrolyte layer A in Examples 16-18 and Comparative Example 4, respectively. a The average thickness t of the solid electrolyte layer B b Average thickness ratio t a / t b Volume expansion rate, and the results of charge-discharge cycle tests (comparative Example 4, more precisely, the average thickness t of the solid electrolyte layer A′). a The average thickness t of the solid electrolyte layer B′ b ′, average thickness ratio t a ′ / t b The stacked all-solid-state batteries of Examples 1-5 were obtained by stacking a solid electrolyte layer B, which is 2 to 15 times thicker than the solid electrolyte layer A, on the 16th layer. Compared with the stacked all-solid-state batteries of Comparative Examples 1-3, the volume expansion rate was suppressed, resulting in excellent cycle characteristics. On the other hand, in Example 5, which has a solid electrolyte layer B with a thickness of 15 times that of the solid electrolyte layer A, although volume expansion was further suppressed, the cycle characteristics were slightly reduced. This suggests that the internal resistance increased due to the excessive thickness of the solid electrolyte layer B. Based on the above results, the stacked all-solid-state battery having a solid electrolyte layer B with a thickness of 2 to 10 times that of the solid electrolyte layer A resulted in superior volume expansion rate and cycle characteristics.

[0201] The stacked all-solid-state batteries in Examples 6-8, by changing the solid electrolyte in the solid electrolyte layer B to a solid electrolyte with a NASICON-type crystal structure other than LATP, resulted in superior volume expansion rate and cycle characteristics compared to the comparative examples.

[0202] In Examples 9 and 10, the stacked all-solid-state batteries were modified by changing the solid electrolytes in solid electrolyte layer A and solid electrolyte B to solid electrolytes with garnet-type and perovskite-type crystal structures, resulting in superior volume expansion rate and cycle characteristics compared to the comparative examples.

[0203] The stacked all-solid-state battery of Example 11 is a modified battery in which multiple solid electrolytes, including LATP and LAGP, are included in the solid electrolyte of the solid electrolyte layer B, resulting in superior volume expansion rate and cycle characteristics compared to the comparative example.

[0204] In Example 12, the stacked all-solid-state battery was modified by using different solid electrolytes in solid electrolyte layer A and solid electrolyte layer B, resulting in a slightly better volume expansion rate and cycle characteristics compared to the comparative example.

[0205] The stacked all-solid-state battery of Example 13 is formed by stacking a solid electrolyte layer B in two locations: layers 11 and 21, resulting in superior volume expansion rate and cycle characteristics compared to the comparative example. Furthermore, compared to Example 2, which has only one solid electrolyte layer B, it exhibits even better volume expansion rate and cycle characteristics.

[0206] The stacked all-solid-state battery of Example 14, in which the solid electrolyte layer B is stacked on the 14th layer, exhibits superior volume expansion rate and cycle characteristics compared to the comparative example. Therefore, it has been confirmed that the stacking position of the solid electrolyte layer B, even if it does not divide the number of element layers equally, contributes to improving volume expansion rate and cycle characteristics.

[0207] In Example 15, the stacked all-solid-state battery was modified by replacing the solid electrolytes in solid electrolyte layers A and B with LSPO solid electrolytes, resulting in superior volume expansion rate and cycle characteristics compared to the comparative example.

[0208] The stacked all-solid-state batteries of Examples 16 and 17 are examples with multiple solid electrolyte layers B of different thicknesses, and they are superior to the comparative examples in terms of volume expansion rate and cycle characteristics.

[0209] The stacked all-solid-state battery of Example 18 is an example with multiple solid electrolyte layers A of different thicknesses, and it is a superior result in terms of volume expansion rate and cycle characteristics compared to the comparative example.

[0210] Comparative Example 4 has multiple solid electrolyte layers B′ and multiple solid electrolyte layers A′ with different thicknesses, and the average thickness ratio t a ′ / t b Comparative examples with a value less than 2 do not yield good volume expansion rate and cycle characteristics.

[0211] [Table 1]

[0212]

[0213] [Table 2]

[0214]

[0215] [Table 3]

[0216]

[0217] The present invention has been described in detail above, but the above embodiments and examples are merely illustrative. The invention disclosed herein includes inventions obtained by various modifications and alterations to the above specific examples.

[0218] Explanation of symbols

[0219] 0…Laminated solid-state battery (appearance image)

[0220] 100…Stacked all-solid-state battery (example)

[0221] 200… Stacked solid-state battery (comparative example)

[0222] 10, 20, 20A, 30… laminated bodies

[0223] 1… Positive electrode layer

[0224] 1A…Positive current collector

[0225] 1B…Positive electrode active material layer

[0226] 2… Negative electrode layer

[0227] 2A… Negative electrode current collector layer

[0228] 2B…Negative electrode active material layer

[0229] 3…side edge layer

[0230] 4…Outer layer (raw sheet for solid electrolyte)

[0231] 60… Positive external electrode

[0232] 70…Negative external electrode

[0233] A, A1, A2, A3, A4, A5… belong to the solid electrolyte layer of Group 1.

[0234] B, B1, B2… belong to the solid electrolyte layer of group 2.

Claims

1. A laminated all-solid battery, characterized by comprising: a plurality of positive electrode layers including a positive electrode current collector layer and a positive electrode active material layer, a plurality of negative electrode layers including a negative electrode current collector layer and a negative electrode active material layer, and a plurality of solid electrolyte layers including a solid electrolyte layer, the laminated all-solid battery has a laminate in which the positive electrode layers and the negative electrode layers are alternately laminated via the solid electrolyte layers, the plurality of solid electrolyte layers are composed of a plurality of solid electrolyte layers belonging to a first group and at least one solid electrolyte layer belonging to a second group having a thickness larger than that of the first group, the first group has a first solid electrolyte layer having a smallest thickness, the second group is composed of a second solid electrolyte layer having a thickness of 2 times or more of the first solid electrolyte layer, the solid electrolyte layer belonging to the first group and the solid electrolyte layer belonging to the second group are respectively in contact with the positive electrode layer on one side in the stacking direction and with the negative electrode layer on the other side in the stacking direction. when the average thickness of the solid electrolyte layer belonging to the first group is set as t a and the average thickness of the solid electrolyte layer belonging to the second group is set as t b the following (1) formula is satisfied: 2t a ≤t b …(1) 2. The laminated all-solid battery according to claim 1, characterized in that the first group is composed of the first solid electrolyte layer and a third solid electrolyte layer having a thickness smaller than 2 times of the first solid electrolyte layer.

3. The laminated all-solid battery according to claim 1, characterized in that the following formula (2) is satisfied:

4. The laminated all-solid battery according to claim 1, characterized in that the solid electrolyte layer belonging to the first group and the solid electrolyte layer belonging to the second group include a solid electrolyte having the same crystal structure.

5. The laminated all-solid battery according to claim 1, characterized in that the solid electrolyte layer belonging to the first group and the solid electrolyte layer belonging to the second group include a solid electrolyte having any one of crystal structures selected from the group consisting of NASICON type, garnet type, perovskite type, and LISICON type. ​ 2t a ≤t b ≤10t a …(2). ​ ​ ​ ​

Images