Stacked all-solid-state battery

Abstract

This stacked all-solid-state battery is provided with: a plurality of positive electrode layers, each of which comprises a positive electrode collector layer and a positive electrode active material layer; a plurality of negative electrode layers, each of which comprises a negative electrode collector layer and a negative electrode active material layer; and a plurality of solid electrolyte layers, each of which comprises a solid electrolyte layer. This stacked all-solid-state battery has a multilayer body wherein the positive electrode layers and the negative electrode layers are alternately stacked upon each other, with the solid electrolyte layers being interposed therebetween. With respect to this stacked all-solid-state battery, the plurality of solid electrolyte layers are composed of a plurality of solid electrolyte layers that belong to a first group and at least one solid electrolyte layer that belongs to a second group and has a thicker thickness than those in the first group; the first group includes a first solid electrolyte layer which has the minimum thickness; the second group includes a second solid electrolyte layer which has a thickness that is not less than twice the thickness of the first solid electrolyte layer; and if ta is the average thickness of the plurality of solid electrolyte layers that belong to the first group and tb is the average thickness of the solid electrolyte layers that belong to the second group, formula (1) is satisfied. Formula (1): 2ta ≤ tb

Description

[Technical Field]

[0001] The present invention relates to a stacked all-solid-state battery. This application claims priority based on Japanese Patent Application No. 2020-009570, filed on January 24, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] In recent years, electronics technology has made remarkable progress, with efforts being made to make portable electronic devices smaller, lighter, thinner, and more multifunctional. Accordingly, there is a strong demand for batteries that serve as the power source for these electronic devices to be smaller, lighter, thinner, and more reliable. All-solid-state lithium-ion secondary batteries, which use solid electrolytes, have attracted attention.

[0003] Currently, commonly used lithium-ion secondary batteries have traditionally used electrolytes (electrolytic solutions) such as organic solvents as a medium for ion migration. However, lithium-ion secondary batteries using electrolytic solutions have the risk of electrolyte leakage. In addition, because organic solvents and other materials used in electrolytic solutions are flammable, there is a need to further improve the safety of batteries.

[0004] Therefore, as one of the measures to improve the safety of lithium-ion secondary batteries, it has been proposed to replace the electrolyte solution with a solid electrolyte. Furthermore, development of all-solid-state batteries, in which other components are also made of solids, is underway.

[0005] It is generally considered desirable for the solid electrolyte in an all-solid-state battery to be dense, but the volume expansion and contraction of the electrode layer accompanying the charge and discharge reaction of lithium ions causes internal stress in the all-solid-state battery, which can lead to cracks. As a result, it was found that the internal resistance increases and the cycle characteristics deteriorate.

[0006] In response to these issues, Patent Document 1 discloses that by providing a solid electrolyte layer in which a portion with low porosity is formed in a region close to the electrode layer and a solid electrolyte layer in which a portion with high porosity is formed in a region away from the electrode layer, it is possible to alleviate the internal stress applied to the solid electrolyte layer due to volume expansion and contraction, thereby increasing the discharge capacity and improving the cycle characteristics. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2013 / 175993 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in a stacked-type all-solid-state battery provided with a solid electrolyte layer as in Patent Document 1, the internal resistance of the solid electrolyte layer increases, and sufficient cycle characteristics cannot be obtained. Also, there is a concern that the internal stress caused by volume expansion and contraction is concentrated in the solid electrolyte layer with a high porosity, making the solid electrolyte layer more susceptible to cracking.

[0009] An object of the present invention is to provide a stacked all-solid-state battery that suppresses the occurrence of cracks and has excellent cycle characteristics. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides the following means.

[0011] A stacked all-solid-state battery according to a first aspect of the present invention is a stacked all-solid-state battery including: a plurality of positive electrode layers each including a positive electrode current collector layer and a positive electrode active material layer; a plurality of negative electrode layers each including a negative electrode current collector layer and a negative electrode active material layer; and a plurality of solid electrolyte layers each including a solid electrolyte, wherein the positive electrode layers and the negative electrode layers are alternately stacked with the solid electrolyte layers interposed therebetween; the plurality of solid electrolyte layers include 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 greater than that of the first group, the first group has a first solid electrolyte layer with a smallest thickness; the second group is composed of a second solid electrolyte layer having a thickness at least twice that of the first solid electrolyte layer, The average thickness of the plurality of solid electrolyte layers belonging to the first group is t a and the average thickness t b When this is the case, the relationship of the following equation (1) is satisfied. 2t a ≦t b ···(1)

[0012] In the stacked all-solid-state battery according to the above aspect, the first group may include the first solid electrolyte layer and a third solid electrolyte layer having a thickness less than twice that of the first solid electrolyte layer.

[0013] Furthermore, the above t a for the above t b may satisfy the following formula (2). 2t a ≦t b ≦10t a ···(2)

[0014] Furthermore, the number of layers in the first group of solid electrolyte layers may be greater than the number of layers in the second group of solid electrolyte layers.

[0015] Furthermore, the solid electrolyte layers belonging to the first group and the solid electrolyte layers belonging to the second group may contain solid electrolytes having the same crystal structure.

[0016] The solid electrolyte layer belonging to the first group and the solid electrolyte layer belonging to the second group may contain a solid electrolyte having any one crystal structure selected from the group consisting of a Nasicon type, a garnet type, a perovskite type, and a lysiccon type. [Effects of the Invention]

[0017] The stacked all-solid-state battery according to the present invention suppresses the occurrence of cracks and has excellent cycle characteristics. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an external view of a stacked all-solid-state battery according to a first embodiment of the present invention. FIG. [Figure 2] 1 is an external view of a laminate according to a first embodiment of the present invention. [Figure 3] 1 is a cross-sectional view of a stacked all-solid-state battery according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a cross-sectional view of a stacked all-solid-state battery according to a comparative example in the present application. [Figure 5] FIG. 3 is a cross-sectional view of a stacked all-solid-state battery according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The drawings used in the following description may be simplified for the sake of convenience in order to clearly illustrate the features of the present embodiment, and the dimensional ratios of the components may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present embodiment is not limited thereto. Appropriate modifications can be made within the scope of the effects of the present invention. For example, the configurations described in different embodiments can be appropriately combined.

[0020] 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, all-solid-state magnesium ion secondary batteries, etc. Although the following description will be given using an all-solid-state lithium ion secondary battery as an example, the present invention is generally applicable to stacked all-solid-state secondary batteries.

[0021] "First embodiment" (Stacked all-solid-state battery) The stacked all-solid-state battery of this embodiment will be described with reference to FIGS. 1 to 3. As shown in FIG. 1, the stacked all-solid-state battery 0 of the first embodiment has a stacked body 10, a positive external electrode 60, and a negative external electrode 70. As shown in FIG. 2, the stacked body 10 is a hexahedron having four side surfaces 21, 22, 23, and 24, an upper surface 25, and a lower surface 26. Furthermore, the positive external electrode 60 and the negative external electrode 70 are formed on either of a pair of opposing side surfaces. Note that the embodiment of the stacked all-solid-state battery 0 of FIG. 1 is one in which the positive external electrode 60 is formed on the side surface 21 of the stacked body 10 of FIG. 2, and the negative external electrode 70 is formed on the side surface 22.

[0022] Next, a stacked all-solid-state battery 100 of this embodiment will be described using the cross-sectional view of Fig. 3. The stacked all-solid-state battery 100 is formed by alternately stacking a positive electrode layer 1 having a positive electrode current collector layer 1A, a positive electrode active material layer 1B, and a side margin 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 margin layer 3, with a solid electrolyte layer interposed therebetween. The solid electrolyte layer preferably includes at least a storage element sandwiching a solid electrolyte layer A and a solid electrolyte layer B having a thickness greater than that of the solid electrolyte layer A, and a stack 20 including an outer layer 4 sandwiching the storage element. The nearest solid electrolyte layer A and solid electrolyte layer B are stacked with the positive electrode layer 1 or the negative electrode layer 2 interposed therebetween. In this embodiment, an example will be described in which the thicknesses of the multiple solid electrolyte layers A are the same, and the thickness of the solid electrolyte layer B is at least twice the thickness of the solid electrolyte layer A. In this embodiment, the multiple solid electrolyte layers A are first solid electrolyte layers belonging to a first group. In addition, in this embodiment, the solid electrolyte layer B is a second solid electrolyte layer belonging to a second group. The positive electrode layer 1 is electrically joined to the positive external electrode 60 at a side surface 21, and the negative electrode layer 2 is electrically joined to the negative external electrode 70 at a side surface 22.

[0023] Furthermore, the average thickness of the solid electrolyte layer A is t a , the average thickness of the solid electrolyte layer B is t bWhen this is set, the all-solid-state battery 100 satisfies the following formula (1): In this embodiment, the thickness of the solid electrolyte layer A is uniform, and the average thickness of the solid electrolyte layer A means the thickness of the solid electrolyte layer A. 2t a ≦t b ···(1)

[0024] The stacked all-solid-state battery 100 having such a configuration can suppress volume expansion caused by the charge / discharge reaction of lithium ions. Although the details of the reason for this are not clear, it is believed that by providing the stacked all-solid-state battery 100 with at least a solid electrolyte layer B that is at least twice as thick as the solid electrolyte layer A, the stress load caused by volume expansion associated with the charge / discharge reaction is dispersed by the solid electrolyte layer B, making it possible to suppress cracking within the stack, resulting in improved cycle characteristics. On the other hand, in the stacked all-solid-state battery 200 that does not include the solid electrolyte layer B, the stress load caused by volume expansion is not dispersed, which may easily cause cracking within the stack and result in localized increases in internal resistance. As a result, current tends to concentrate in areas with low internal resistance, making the cycle characteristics more likely to deteriorate.

[0025] Furthermore, the above t a for the above t b It is preferable that satisfies the following formula (2). 2t a ≦t b ≦10t a ···(2)

[0026] Furthermore, the number of layers of the solid electrolyte layer A may be greater than the number of layers of the solid electrolyte layer B.

[0027] When a solid electrolyte layer B having an average thickness 10 times or more the average thickness of the solid electrolyte layer A is provided, the internal resistance of the stacked all-solid-state battery may increase due to the solid electrolyte layer B, resulting in a decrease in capacity.

[0028] Furthermore, it is preferable that the solid electrolyte layer A and the solid electrolyte layer B have a solid electrolyte with the same crystal structure.

[0029] Furthermore, the solid electrolyte preferably has one of the crystal structures of Nasicon type, garnet type, or perovskite type, which exhibit high ionic conductivity.

[0030] When solid electrolyte layer A and solid electrolyte layer B have solid electrolytes with the same crystal structure, the ionic conductivity is the same, so charge and discharge reactions occur uniformly in both layers. Therefore, the stress load due to volume expansion also occurs uniformly in both layers, which suppresses cracking within the laminate and improves the cycle characteristics of the battery. On the other hand, when solid electrolytes with different crystal structures are used, the ionic conductivity is different, so the charge and discharge reactions in both layers become uneven, and therefore the stress load due to volume expansion in both layers also becomes uneven. Therefore, cracks are more likely to occur within the laminate.

[0031] 4 shows a cross-sectional view of a stacked all-solid-state battery 200 according to a comparative example. The stacked all-solid-state battery 200 according to the comparative example is not included in the present invention. The stacked all-solid-state battery 200 is a stack 30 including a storage element in which positive electrode layers 1 and negative electrode layers 2 are alternately arranged with solid electrolyte layers A0 of approximately the same thickness interposed therebetween, and outer layers 4 that sandwich the storage element, in which the positive electrode layer 1 is electrically joined to a positive external electrode 60 via a side surface 21, and the negative electrode layer 2 is electrically joined 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 according to the first embodiment in that it does not have a solid electrolyte layer B belonging to the second group.

[0032] In the following explanation in the specification, either or both of the positive electrode active material and the negative electrode active material may be collectively referred to as the active material, either or both of the positive electrode current collector layer and the negative electrode current collector layer may be collectively referred to as the current collector layer, either or both of the positive electrode active material layer and the negative electrode active material layer may be collectively referred to as the active material layer, either or both of the positive electrode and the negative electrode may be collectively referred to as the electrode, and either or both of the positive electrode external electrode and the negative electrode external electrode may be collectively referred to as the external electrode.

[0033] (Solid electrolyte layer) The solid electrolyte layer A and the solid electrolyte layer B of the stacked all-solid-state battery 100 of this embodiment are not particularly limited, and may include a solid electrolyte having any one of the crystal structures selected from the group consisting of Nasicon-type, garnet-type, perovskite-type, and lysiccon-type crystal structures. For example, a general solid electrolyte material such as an oxide-based lithium ion conductor having a Nasicon-type, garnet-type, perovskite-type, or lysiccon-type crystal structure can be used. An ion conductor having a Nasicon-type crystal structure containing at least Li (lithium), M (M is at least one of Ti (titanium), Zr (zirconium), Ge (germanium), Hf (hafnium), and Sn (tin)), P (phosphorus), and O (oxygen) (e.g., Li 1+x Al x Ti 2-x (PO4)3; LATP), and ionic conductors having a garnet-type crystal structure containing at least Li (lithium), Zr (zirconium), La (lanthanum), and O (oxygen) (e.g., Li7La3Zr2O 12 ;LLZ), or ion conductors having a garnet-like structure, and ion conductors having a perovskite-type structure containing at least Li (lithium), Ti (titanium), La (lanthanum), and O (oxygen) (for example, Li 3x La 2 / 3-x TiO3; LLTO), and lithium ion conductors having a lithicon-type crystal structure containing at least Li, Si, P, and O (e.g., Li 3.5 Si 0.5 P 0.5 O 3.5 In other words, these ion conductors may be used alone or in combination of two or more.

[0034] As the solid electrolyte material of this embodiment, it is preferable to use a lithium ion conductor having a Nasicon-type crystal structure, such as LiTi2(PO4)3(LTP), LiZr2(PO4)3(LZP), Li 1+x Al x Ti 2-x (PO4)3(LATP, 0 <x≦0.6))、Li1+x Al x Ge 2-x (PO4)3 (LAGP, 0 < x ≤ 0.6), Li 1+x Y x Zr 2-x Preferably includes a solid electrolyte material represented by (PO4)3 (LYZP, 0 < x ≤ 0.6).

[0035] (Positive electrode layer and negative electrode layer) The positive electrode layer 1 and the negative electrode layer 2 are each provided with a plurality in the laminate 20, for example, and face each other through the solid electrolyte layer.

[0036] The positive electrode layer 1 has a positive electrode current collector layer 1A, a positive electrode active material layer 1B, and a side margin layer 3. The negative electrode layer 2 has a negative electrode current collector layer 2A and a negative electrode active material layer 2B.

[0037] (Positive electrode active material layer and negative electrode active material layer) The positive electrode active material layer 1B and the negative electrode active material layer 2B according to the present embodiment contain known materials capable of at least occluding and releasing lithium ions as the positive electrode active material and the negative electrode active material. In addition, a conductive aid and an ion-conducting aid may be included. It is preferable that the positive electrode active material and the negative electrode active material can efficiently insert and desorb lithium ions.

[0038] Examples of the positive electrode active material and the negative electrode active material include transition metal oxides and transition metal composite oxides. Specifically, for example, lithium manganese composite oxide Li2Mn a Ma 1-a O3 (0.8 ≤ a ≤ 1, Ma = Co, Ni), lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium manganese spinel (LiMn2O4), general formula: LiNi x Co y Mn zComposite 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 solid solution cathodes represented by Li2MnO3 - LiMcO2 (Mc = Mn, Co, Ni), lithium titanate (Li4Ti5O 12 ), titanium oxide (TiO2), Li s Ni t Co u Al v Composite metal oxides represented by O2(0.9 < s < 1.3, 0.9 < t + u + v < 1.1), etc.

[0039] As the cathode active material and the anode active material of this embodiment, it is preferable to contain a phosphate compound as a main component. For example, olivine-type LiMbPO4 (where 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 any one or more of Li9V3(P2O7)3(PO4)2 are preferable. In particular, one or both of LiVOPO4 and Li3V2(PO4)3 are preferable.

[0040] The main component in this embodiment means that when the total amount of the cathode active material and the anode active material is 100 parts by mass, the ratio of the active material of the phosphate compound is greater than 50 parts by mass, and it is preferable that the ratio of the active material of the phosphate compound is 80 parts by weight or more.

[0041] In addition, these positive electrode active materials and negative electrode active materials may have some of the elements substituted with different elements, and may have a different stoichiometric composition. LiVOPO4 and Li3V2(PO4)3 are preferably lithium deficient, and Li x VOPO4(0.94≦x≦0.98) and Li y It is more preferable if V2(PO4)3 (2.8≦y≦2.95).

[0042] Examples of the negative electrode active material include Li metal, Li-Al alloy, Li-In alloy, carbon, silicon (Si), and silicon oxide (SiO x ), lithium titanate (Li4Ti5O 12 ), titanium oxide (TiO2) can be used.

[0043] Here, there is no clear distinction between the active materials constituting the positive electrode active material layer 1B and the negative electrode active material layer 2B, and by comparing the potentials of two types of compounds, the compound in the positive electrode active material layer and the compound in the negative electrode active material layer, the compound showing a more noble potential can be used as the positive electrode active material, and the compound showing a more base potential can be used as the negative electrode active material. Furthermore, the same material may be used to constitute the positive electrode active material layer 1B and the negative electrode active material layer 2B, as long as the compound has the ability to simultaneously release and store lithium ions.

[0044] Examples of the conductive aid include carbon materials such as carbon black, acetylene black, ketjen black, carbon nanotubes, graphite, graphene, and activated carbon, and metal materials such as gold, silver, palladium, platinum, copper, and tin.

[0045] The ion-conducting aid is, for example, a solid electrolyte. Specifically, the solid electrolyte may be the same material as that used for the solid electrolyte layer 50.

[0046] When a solid electrolyte is used as the ion-conducting aid, it is preferable that the ion-conducting aid and the solid electrolyte used in the solid electrolyte layers A and B are made of the same material.

[0047] (Positive electrode current collector and negative electrode current collector) The materials constituting 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 are preferably materials with high electrical conductivity, such as silver, palladium, gold, platinum, aluminum, copper, or nickel. Copper is particularly preferred because it is less likely to react with oxide-based lithium ion conductors and has the effect of reducing the internal resistance of the stacked all-solid-state battery. The materials constituting the positive electrode current collector layer 1A and the negative electrode current collector layer 2A may be the same or different.

[0048] 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 a positive electrode active material and a negative electrode active material, respectively.

[0049] It is desirable that the positive electrode current collector layer 1A and the negative electrode current collector layer 2A contain a positive electrode active material and a negative electrode active material, respectively, because this improves the adhesion between the positive electrode current collector layer 1A and the positive electrode active material layer 1B, and between the negative electrode current collector layer 2A and the negative electrode active material layer 2B.

[0050] The ratio of the positive electrode active material to the negative electrode active material in the positive electrode current collector layer 1A and the negative electrode current collector layer 2A of this embodiment is not particularly limited as long as they function as current collectors. However, it is preferable that the volume ratio of the positive electrode current collector to the positive electrode active material, or the volume ratio of the negative electrode current collector to the negative electrode active material, is in the range of 90 / 10 to 70 / 30.

[0051] (Side margin layer) The side margin layer 3 of the stacked all-solid-state battery 100 of this embodiment is preferably provided to eliminate the step between the solid electrolyte layer A and the positive electrode layer 1, and the step between the solid electrolyte layer A and the negative electrode layer 2. Therefore, the side margin layer 3 refers to the region other than the positive electrode layer 1. The presence of such a side margin layer 3 eliminates the step between the solid electrolyte layer A and the positive electrode layer 1 and the negative electrode layer 2, thereby increasing the density of the electrodes and making it less likely for delamination or warpage to occur during firing of the stacked all-solid-state battery 100.

[0052] The material constituting the side margin layer 3 preferably includes, for example, the same material as that of the solid electrolyte layer A. Therefore, it is preferable to include an oxide-based 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 (where M is at least one of Ti (titanium), Zr (zirconium), Ge (germanium), Hf (hafnium), and Sn (tin)), P, and O; ion conductors having a garnet-type crystal structure or a garnet-like 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. In other words, these ion conductors may be used alone or in combination. The stacked all-solid-state battery 100 according to this embodiment can suppress cracking and improve cycle characteristics.

[0053] (outer layer) The outer layer 4 is disposed in one or both (both in FIG. 3 ) of the regions outer than either the positive electrode layer 1 (positive electrode current collector layer 1A) or the negative electrode layer 2 (negative electrode current collector layer 2A) in the stacking direction. The outer layer 4 may be made of the same material as the solid electrolyte layer A. In this embodiment, the stacking direction corresponds to the z direction in FIG. 3 .

[0054] The thickness of the outer layer 4 is not particularly limited, but is, for example, 20 μm or more and 100 μm or less. When the thickness is 20 μm or more, the positive electrode layer 1 or the negative electrode layer 2 closest to the surface in the stacking direction of the laminate 20 is less likely to be oxidized by the influence of the atmosphere in the firing process, resulting in a high-capacity laminated all-solid-state battery. Furthermore, when the thickness is 100 μm or less, sufficient moisture resistance is ensured even in high-temperature and high-humidity environments, resulting in an all-solid-state secondary battery that is highly reliable and has a high volumetric energy density.

[0055] "Second embodiment" 5 is an enlarged schematic cross-sectional view of a main portion of the stacked all-solid-state battery 300 according to the second embodiment. In the stacked all-solid-state battery 300, the same components as those in the stacked all-solid-state battery 100 are denoted by the same reference numerals, and the description thereof may be omitted. As will be described in detail later, the stacked all-solid-state battery 300 according to the second embodiment differs from the stacked all-solid-state battery 100 according to the first embodiment in the thickness of the solid electrolyte layer.

[0056] The stacked all-solid-state battery 300 has a stacked body 20A, a positive electrode external electrode 60, and a negative electrode external electrode 70. The stacked body 20A has a positive electrode layer 1, a negative electrode layer 2, solid electrolyte layers A1 to A5, B1, and B2, and an outer layer 4. The outer layer 4 sandwiches the positive electrode layer 1, the negative electrode 2, and the solid electrolyte layers A1 to 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 to A5, B1, and B2 sandwiched between the outer layers 4 may be collectively referred to as an electricity storage element.

[0057] The positive electrode layer 1 and the negative electrode layer 2 are electrode layers, one of which functions as a positive electrode and the other as a negative electrode. The positive and negative polarities of the electrode layers depend on the polarity of the external terminals connected to them. In this embodiment, the positive electrode layer 1 is connected to the positive external electrode 60, and the negative electrode layer 2 is connected to the negative external electrode 70, so that the positive electrode layer 1 functions as a positive electrode and the negative electrode layer 2 functions as a negative electrode.

[0058] The positive electrode layer 1 has a positive electrode current collector layer 1A and a positive electrode active material layer 1B containing a positive electrode active material. The negative electrode layer 2 has a negative electrode current collector layer 2A and a negative electrode active material layer 2B containing a negative electrode active material.

[0059] The positive electrode current collector layer 1A and the negative electrode current collector layer 2A have excellent electrical conductivity. The positive electrode current collector layer 1A and the negative electrode current collector layer 2A are made of, for example, silver, palladium, gold, platinum, aluminum, copper, or nickel. Copper does not easily react with the positive electrode active material, the negative electrode active material, or the solid electrolyte. For example, using copper for the positive electrode current collector layer 1A and the negative electrode current collector layer 2A can reduce the internal resistance of the stacked all-solid-state battery 300. The materials constituting the positive electrode current collector layer 1A and the negative electrode current collector layer 2A may be the same or different.

[0060] 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 not be present on the side of the positive electrode current collector layer 1A on which the opposing negative electrode layer 2 is not present. 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 not be present on the side of the negative electrode current collector layer 2A on which the opposing positive electrode layer 1 is not present. For example, the positive electrode layer 1 or the negative electrode layer 2 located in the uppermost or lowermost layer of the laminate 5 may not have the positive electrode active material layer 1B or the negative electrode active material layer 2B on one side.

[0061] The positive electrode active material layer 1B and the negative electrode active material layer 2B contain a positive electrode active material and a negative electrode active material that donate and accept electrons. They may also contain a conductive additive, an ion-conducting additive, etc. The positive electrode active material and the negative electrode active material are preferably capable of efficiently inserting and extracting lithium ions.

[0062] The positive electrode current collector layer 1A and the negative electrode current collector layer 2A may contain a positive electrode active material and a negative electrode active material, respectively. The content ratio of the active materials contained in each current collector is not particularly limited as long as they function as current collectors. For example, the volume ratio of the positive electrode current collector / positive electrode active material or the negative electrode current collector / negative electrode active material is preferably in the range of 90 / 10 to 70 / 30.

[0063] The solid electrolyte layers A1 to 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. The solid electrolyte layers A1 to A5, B1, and B2 contain a solid electrolyte. The solid electrolyte is a substance (e.g., particles) that can move ions when an externally applied electric field is applied. For example, lithium ions move within the solid electrolyte when an externally applied electric field is applied. The solid electrolyte is also an insulator that inhibits the movement of electrons.

[0064] The solid electrolyte layers A1 to A5, B1, and B2 of the stacked all-solid-state battery 300 of this embodiment are not particularly limited, and may include, for example, a solid electrolyte having any one of the crystal structures selected from the group consisting of Nasicon-type, garnet-type, perovskite-type, and lithicon-type crystal structures. The solid electrolyte may include an ion conductor (e.g., Li) having a Nasicon-type crystal structure containing at least Li (lithium), M (M is at least one of Ti (titanium), Zr (zirconium), Ge (germanium), Hf (hafnium), and Sn (tin)), P (phosphorus), and O (oxygen). 1+x Al x Ti 2-x (PO4)3; LATP), and ionic conductors having a garnet-type crystal structure containing at least Li (lithium), Zr (zirconium), La (lanthanum), and O (oxygen) (e.g., Li7La3Zr2O 12 ;LLZ), or ion conductors having a garnet-like structure, and ion conductors having a perovskite-type structure containing at least Li (lithium), Ti (titanium), La (lanthanum), and O (oxygen) (for example, Li 3x La 2 / 3-x TiO3; LLTO), and lithium ion conductors having a lithicon-type crystal structure containing at least Li, Si, P, and O (e.g., Li 3.5 Si 0.5 P 0.5 O 3.5 In other words, these ion conductors may be used alone or in combination of two or more.

[0065] The thickness of the solid electrolyte layers A1 to A5, B1, and B2 is, for example, in the range of 0.5 μm to 20.0 μm. By making the thickness of the solid electrolyte layers A1 to A5 0.5 μm or more, it is possible to reliably prevent a short circuit between the positive electrode layer 1 and the negative electrode layer 2, and by making the thickness 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.

[0066] The solid electrolyte layers A1 to A5 belong to Group 1. The solid electrolyte layer A1 is the solid electrolyte layer with the smallest thickness among the solid electrolyte layers A1 to A5, B1, and B2. The thickness of each of the solid electrolyte layers A2 to A5 is equal to or greater than one time and less than two times the thickness of the solid electrolyte layer A1.

[0067] The solid electrolyte layers B1 and B2 belong to the second group. The thickness of the solid electrolyte layers B1 and B2 is at least twice the thickness of the solid electrolyte layer A1. The number of solid electrolyte layers belonging to the second group is an arbitrary number of at least one.

[0068] The arrangement of the solid electrolyte layers belonging to the second group may be selected arbitrarily. For example, when the number of solid electrolyte layers belonging to the second group is one, the number of solid electrolyte layers belonging to the first group sandwiched between the outer layer 4 on the upper side in the stacking direction and the solid electrolyte layer belonging to the second group closest to the outer layer 4 on the upper side in the stacking direction may be equal to the number of solid electrolyte layers belonging to the first group sandwiched between the outer layer 4 on the lower side in the stacking direction and the solid electrolyte layer belonging to the second group closest to the outer layer 4 on the lower side in the stacking direction. In other words, the number of solid electrolyte layers belonging to the first group above the solid electrolyte layers belonging to the second group in the stacking direction may be equal to the number of solid electrolyte layers belonging to the first group below the solid electrolyte layers belonging to the second group. Furthermore, when the number of solid electrolyte layers belonging to the second group is two or more, they may be arranged so that the number of solid electrolyte layers belonging to the first group sandwiched between the upper outer layer 4 in the stacking direction and the solid electrolyte layer belonging to the second group closest to the upper outer layer 4 in the stacking direction, the number of solid electrolyte layers belonging to the first group sandwiched between the lower outer layer 4 in the stacking direction and the solid electrolyte layer belonging to the second group closest to the lower outer layer 4 in the stacking direction, and the number of solid electrolyte layers belonging to the first group sandwiched between adjacent solid electrolyte layers belonging to the second group are equal.

[0069] The average thickness t of the solid electrolyte layers A1 to A5 belonging to the first group a and the average thickness t of the solid electrolyte layers B1 and B2 belonging to the second group b This satisfies the following formula (1). 2t a ≦t b ···(1)

[0070] The average thickness t of the solid electrolyte layers A1 to A5 belonging to the first group a and the average thickness t of the solid electrolyte layers B1 and B2 belonging to the second group b The following formula (2) may be satisfied. 2t a ≦t b ≦10t a ···(2)

[0071] In this embodiment, a solid electrolyte layer having the smallest thickness among all solid electrolyte layers, such as solid electrolyte layer A1, may be referred to as a first solid electrolyte layer. Also in this embodiment, a solid electrolyte layer having a thickness at least twice that of the first solid electrolyte layer, such as solid electrolyte layers B1 and B2, may be referred to as a second solid electrolyte layer. Also in this embodiment, a solid electrolyte layer having a thickness greater than or equal to twice that of the first solid electrolyte layer, such as solid electrolyte layers A2 to A5, may be referred to as a second solid electrolyte layer. less than This solid electrolyte layer is sometimes called the third solid electrolyte layer.

[0072] The stacked all-solid-state battery 300 according to this embodiment also provides the same effects as the stacked all-solid-state battery 100 according to the first embodiment.

[0073] In this embodiment, the thicknesses of the solid electrolyte layers A1 to A5 belonging to the first group and the thicknesses of the solid electrolyte layers B1 and B2 belonging to the second group are different from each other, but they may be the same.

[0074] Although the present embodiment exemplifies a case in which the solid electrolyte layers belonging to the first group include five layers, solid electrolyte layers A1 to A5, the number of solid electrolyte layers belonging to the first group may be any number of at least 2. Furthermore, the present embodiment exemplifies a case in which the solid electrolyte layers belonging to the second group include two layers, solid electrolyte layers B1 and B2, the number of solid electrolyte layers belonging to the second group may be any number of at least 1.

[0075] Although the present embodiment illustrates the case where there is one first solid electrolyte layer, at least one of the solid electrolyte layers A2 to A5 may be the same as the solid electrolyte layer A1, and there may be a plurality of first solid electrolyte layers.

[0076] (Method of manufacturing stacked all-solid-state batteries) The stacked all-solid-state battery 100 of this embodiment can be manufactured by the following procedure. The materials for 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 margin layer 3 are formed into a paste. The method for forming the paste is not particularly limited, but for example, a paste can be obtained by mixing powders of the materials in a vehicle. Here, the term "vehicle" refers to a liquid medium, including solvents, binders, etc. The binder contained in the paste for forming the green sheet or printed layer is not particularly limited, but examples thereof include polyvinyl acetal resin, cellulose resin, acrylic resin, urethane resin, vinyl acetate resin, and polyvinyl alcohol resin. The slurry can contain at least one of these resins.

[0077] The paste may also contain a plasticizer. The type of plasticizer is not particularly limited, but phthalate esters such as dioctyl phthalate and diisononyl phthalate may be used.

[0078] By this method, a paste for a positive electrode current collector layer, a paste for a positive electrode active material layer, a paste for a solid electrolyte layer, a paste for a negative electrode active material layer, a paste for a negative electrode current collector layer, and a paste for a side margin layer are prepared.

[0079] The prepared paste for the solid electrolyte layer is applied to a substrate such as polyethylene terephthalate (PET) in a desired thickness and dried as necessary to prepare a green sheet for the solid electrolyte (solid electrolyte layer A). Also, for the solid electrolyte layer B, which is thicker than the solid electrolyte layer A, a green sheet for the solid electrolyte (solid electrolyte layer B) is prepared in the same manner.

[0080] The method for producing the solid electrolyte green sheet is not particularly limited, and known methods such as a doctor blade method, a die coater, a comma coater, or a gravure coater can be used.

[0081] Next, a cathode active material layer 1B, a cathode current collector layer 1A, and a cathode active material layer 1B are printed and laminated in this order on the green sheet for solid electrolyte (solid electrolyte layer A) by screen printing to form the cathode layer 1. Furthermore, in order to fill the step between the green sheet for solid electrolyte (solid electrolyte layer A) and the cathode layer 1, a side margin layer 3 is formed by screen printing in the area other than the cathode layer 1, to produce a cathode unit (solid electrolyte layer A with the cathode layer 1 and side margin layer 3 formed on it).

[0082] The negative electrode unit can be fabricated in the same manner as the positive electrode unit.

[0083] The positive electrode unit and the negative electrode unit are then stacked alternately, offsetting each other so that one end of the positive electrode and one end of the negative electrode do not coincide. After stacking a predetermined number of layers, a solid electrolyte layer B thicker than the solid electrolyte layer A is stacked. Next, the positive electrode unit and the negative electrode unit are stacked again in the same manner until the predetermined number of layers is reached, thereby producing a laminated substrate composed of elements for a laminated all-solid-state battery. If necessary, outer layers may be provided on both main surfaces of the laminated substrate. The outer layers may be made of the same material as the solid electrolyte layer, for example, a green sheet for a solid electrolyte. The solid electrolyte layer B may be provided in a single layer or in multiple layers (in multiple locations). It is preferable to provide the solid electrolyte layer B so that the number of layers of the element is equally or approximately equally divided. For example, if a 31-layer laminate includes one solid electrolyte layer B, the 16th layer may include one solid electrolyte layer B. In this case, a laminated all-solid-state battery having a 15-layer / 15-layer structure is obtained via the solid electrolyte layer B. Similarly, when two solid electrolyte layers B are provided (at two locations), one solid electrolyte layer B may be provided in each of the 11th and 21st layers. In this case, a stacked all-solid-state battery having a 10-layer / 9-layer / 10-layer structure with the solid electrolyte layers B interposed therebetween is obtained.

[0084] Furthermore, the number of stacked layers does not need to be equally or approximately equally divided as to the stacking positions at which the solid electrolyte layers B are provided, and it is sufficient that at least a thick solid electrolyte layer B is provided at any stacking position. By providing the solid electrolyte layers B, it is possible to distribute the volume expansion of the stacked all-solid-state battery.

[0085] The above-described manufacturing method is for producing a parallel-type stacked all-solid-state battery 100, but a manufacturing method for a series-type stacked all-solid-state battery can be achieved by stacking the positive and negative electrodes so that one end of the positive electrode and one end of the negative electrode coincide with each other, that is, without offset.

[0086] Furthermore, the produced laminated substrate can be pressed collectively using a mold press, hot isostatic press (WIP), cold isostatic press (CIP), isostatic press, etc. Pressurization is preferably performed while heating, and can be performed at, for example, 40 to 95°C.

[0087] The produced laminated substrate can be cut into laminates 10 of unfired stacked-type all-solid-state batteries using a dicing device.

[0088] The laminate 10 of the stacked-type all-solid-state battery is de-bindered and fired to sinter the laminate 10. The de-bindering and firing can be performed in a nitrogen atmosphere at a temperature of 600° C. to 1000° C. The retention time for de-bindering and firing is, for example, 0.1 to 6 hours.

[0089] Barrel polishing is performed to chamfer the corners of the laminate to prevent chipping and to expose the current collector layer at the end surface. It may be performed on the unsintered all-solid-state battery laminate 10, or on the laminate 10 after sintering. Barrel polishing methods include dry barrel polishing, which does not use water, and wet barrel polishing, which uses water. When wet barrel polishing is performed, an aqueous solution such as water is separately introduced into the barrel polishing machine.

[0090] The barrel treatment conditions are not particularly limited and can be adjusted as appropriate, provided that the treatment is carried out within a range that does not cause defects such as cracks or chips in the laminate.

[0091] Furthermore, external electrodes (positive external electrode 60 and negative external electrode 70) can be provided to efficiently extract current from the laminate 10 of the stacked all-solid-state battery. The positive external electrode 60 and negative external electrode 70 are formed on either of a pair of opposing side surfaces of the laminate 10. Methods for forming the external electrodes include sputtering, screen printing, and dip coating. In the screen printing and dip coating methods, an external electrode paste containing metal powder, resin, and solvent is prepared and used to form the external electrodes. Next, a baking process is performed to remove the solvent, and a plating process is performed to form terminal electrodes on the surfaces of the external electrodes. On the other hand, the sputtering method makes it possible to directly form the external electrodes and terminal electrodes, eliminating the need for the baking and plating processes.

[0092] The laminate 10 of the stacked-type all-solid-state battery may be sealed, for example, in a coin cell to improve moisture resistance and impact resistance. The sealing method is not particularly limited, and for example, the fired laminate may be sealed with a resin. Alternatively, the laminate may be sealed by applying or dip-coating an insulating paste such as Al2O3 around the periphery of the laminate and then heat-treating the insulating paste.

[0093] In the above embodiment, a method for manufacturing a laminated all-solid-state battery including a step of forming a side margin layer using a paste for the side margin layer has been exemplified, but the method for manufacturing a laminated all-solid-state battery according to this embodiment is not limited to this example. For example, the step of forming a side margin layer using a paste for the side margin layer may be omitted. The side margin layer may be formed, for example, by deformation of the paste for the solid electrolyte layer during the manufacturing process of the laminated all-solid-state battery.

[0094] Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment and can be modified in various ways. [Example]

[0095] The present invention will be described in more detail below based on the above-described embodiment using examples and comparative examples, but the present invention is not limited to these examples. Note that the "parts" used for the amounts of materials used in preparing a paste mean "parts by mass" unless otherwise specified.

[0096] Example 1 (Preparation of Positive Electrode Active Material and Negative Electrode Active Material) The positive and negative electrode active materials were prepared using the following procedure. Li2CO3, V2O5, and NH4H2PO4 were used as starting materials. They were wet-mixed in a ball mill for 16 hours and then dehydrated and dried. The resulting powder was calcined at 850°C for 2 hours in a nitrogen-hydrogen mixed gas. After calcination, the mixture was wet-pulverized again in a ball mill for 16 hours and finally dehydrated and dried to obtain the positive and negative electrode active material powders.

[0097] The active material was confirmed to be lithium vanadium phosphate Li3V2(PO4)3 by X-ray diffraction (XRD) and inductively coupled plasma (ICP) emission spectroscopy. The X-ray diffraction pattern was identified using JCPDS Card 74-3236: Li3V2(PO4)3.

[0098] (Preparation of Positive Electrode Active Material Paste and Negative Electrode Active Material Paste) The positive electrode active material paste and the negative electrode active material paste were prepared by adding 15 parts of ethyl cellulose as a binder and 65 parts of dihydroterpineol as a solvent to 100 parts of the obtained positive electrode active material and negative electrode active material powders, and mixing and dispersing the mixture.

[0099] (Preparation of solid electrolyte paste) The solid electrolyte was prepared using the following procedure. Starting materials were Li2CO3 (lithium carbonate), TiO2 (titanium oxide), Al2O3 (aluminum oxide), and NH4H2PO4 (ammonium dihydrogen phosphate). Each material was weighed so that the molar ratio of Li, Al, Ti, and PO4 was 1.3:0.3:1.7:3.0 (=Li:Al:Ti:PO4). These materials were wet-mixed in a ball mill for 16 hours, then dehydrated and dried. The resulting powder was calcined in air at 800°C for 2 hours, and after calcination, wet-pulverized again in a ball mill for 16 hours. Finally, the solid electrolyte powder was dehydrated and dried.

[0100] The obtained solid electrolyte powder was analyzed using an XRD device and an ICP emission spectrometer, and it was found to be Li with a Nasicon-type crystal structure. 1.3 Al 0.3 Ti 1.7 It was confirmed that the compound was (PO4)3 (lithium aluminum titanium phosphate). The X-ray diffraction pattern was identified using JCPDS Card 35-0754: LiTi2(PO4)3.

[0101] 100 parts of this solid electrolyte powder was mixed with 100 parts of ethanol and 200 parts of toluene as solvents in a ball mill, followed by wet mixing in a ball mill. Then, 16 parts of a polyvinyl butyral binder and 4.8 parts of benzyl butyl phthalate were added and wet mixed in a ball mill to prepare a solid electrolyte paste.

[0102] (Production of solid electrolyte layer sheet) The solid electrolyte paste was applied to a PET film using a doctor blade type sheet molding machine to produce a sheet of solid electrolyte layer A. A plurality of sheets of solid electrolyte layer B having a thickness 1 to 15 times that of the solid electrolyte layer A were also produced using the same procedure.

[0103] (Preparation of Positive Electrode Current Collector Paste and Negative Electrode Current Collector Paste) To prepare the positive electrode current collector and the negative electrode current collector, Cu powder and the prepared positive electrode active material and negative electrode active material powder were mixed at a volume ratio of 80 / 20, and then 100 parts of the mixture, 10 parts of ethyl cellulose as a binder, and 50 parts of dihydroterpineol as a solvent were added, mixed, and dispersed to prepare a positive electrode current collector layer paste and a negative electrode current collector layer paste.

[0104] (Preparation of external electrode paste) A thermosetting external electrode paste was prepared by mixing and dispersing Cu powder, epoxy resin, and a solvent in a ball mill.

[0105] A stacked all-solid-state battery was fabricated using the solid electrolyte layer A sheet, the solid electrolyte layer B sheet, the positive electrode current collector paste, the negative electrode current collector paste, and the external electrode paste according to the following procedure.

[0106] (Production of positive electrode unit) A positive electrode active material layer was printed on a portion of the main surface of the sheet of the solid electrolyte layer A using a screen printer and dried at 80°C for 10 minutes. A positive electrode current collector layer was printed on this positive electrode active material layer and dried at 80°C for 10 minutes. Furthermore, a positive electrode active material layer was printed on the positive electrode current collector layer and dried at 80°C for 10 minutes, thereby forming a positive electrode layer in which the positive electrode current collector layer was sandwiched between positive electrode active material layers on a portion of the main surface of the sheet of the solid electrolyte layer A. Next, a solid electrolyte layer was printed on the main surface of the sheet of the solid electrolyte layer A on which the positive electrode layer was not printed, to have approximately the same height as the positive electrode layer, and dried at 80°C for 10 minutes. Next, the PET film was peeled off to produce a positive electrode unit in which a positive electrode layer and a solid electrolyte layer were printed on the main surface of the sheet of the solid electrolyte layer A.

[0107] (Production of negative electrode unit) The negative electrode unit was fabricated in the same manner as the positive electrode unit.

[0108] (Fabrication of stacked all-solid-state batteries) The positive electrode unit and the negative electrode unit were stacked while one end of the positive electrode layer and one end of the negative electrode layer were offset. The positive electrode unit and the negative electrode unit were alternately stacked. Each solid electrolyte layer sandwiched between the positive electrode layer and the negative electrode layer was counted as one layer, and these were stacked until 15 layers were reached. When 15 layers were stacked, the negative electrode layer was stacked on top of the other. Next, a sheet of solid electrolyte layer B, twice as thick as the solid electrolyte layer A, was stacked on top of the negative electrode layer as the 16th solid electrolyte layer. The positive electrode unit was then inverted and stacked so that the positive electrode layer was stacked on top of the solid electrolyte layer B. The negative electrode unit was then also inverted and stacked, and 15 layers were stacked while one end of the positive electrode layer and one end of the negative electrode layer were offset in the same manner as above. This produced a laminated substrate consisting of a total of 31 layers, consisting of solid electrolyte layer A (15 layers), solid electrolyte layer B (1 layer), and solid electrolyte layer A (15 layers), in that order in the stacking direction.

[0109] A plurality of sheets of the solid electrolyte layer A were laminated on the upper and lower surfaces of the laminated substrate, and outer layers made of solid electrolyte layers were provided on each surface. The outer layers on the upper and lower surfaces were formed to have the same thickness.

[0110] The laminated substrate was thermocompressed using a die press to enhance adhesion at the interfaces of the layers, and then cut to produce laminated chips. The laminated chips were then placed on a ceramic setter and held at 600°C for 2 hours in a nitrogen atmosphere to remove the binder. The laminated chips were then fired by holding them at 750°C for 2 hours in a nitrogen atmosphere, and then removed after natural cooling.

[0111] (External electrode formation process) A Cu external electrode paste was applied to the end faces of the fired laminated chip and held at 150°C for 30 minutes for thermal curing to form external electrodes, thereby producing a laminated all-solid-state battery according to Example 1.

[0112] (Solid electrolyte layer thickness evaluation) The average thickness t of the solid electrolyte layer A of the stacked all-solid-state battery according to Example 1 a and the thickness t of the solid electrolyte layer B bwas calculated by image analysis after obtaining a cross-sectional photograph of the stacked structure of the all-solid-state battery using a field emission scanning electron microscope (FE-SEM). A line perpendicular to the positive electrode active material layer 1B or the negative electrode active material layer 2B located at the end in the stacking direction was drawn, and the length between the adjacent positive electrode active material layer 1B and the negative electrode active material layer 2B on that line was taken as the thickness of the solid electrolyte layer sandwiched between the adjacent positive electrode active material layer 1B and the negative electrode active material layer 2B. In this embodiment, the thickness of the solid electrolyte layer refers to the thickness of the solid electrolyte layer at the center in the width direction of the laminate 20. Here, the width direction of the laminate is the direction in which the laminate 20 is sandwiched between the positive electrode external electrode 60 and the negative electrode external electrode 70, which refers to the x direction in FIG. 3. The thicknesses of all the solid electrolyte layers A were measured, and the average thickness of the solid electrolyte layers A was calculated, resulting in t a Similarly, the average thickness of the solid electrolyte layer B was calculated to be t b The average thickness ratio t b / t a The result was 2. The results are shown in Table 1.

[0113] (Comparative Example 1) The stacked all-solid-state battery according to Comparative Example 1 differs from Example 1 only in that the 16th solid electrolyte layer B has the same structure as the solid electrolyte layer A. That is, a sheet having a thickness equal to that of the solid electrolyte layer A was stacked as the 16th solid electrolyte layer of the stacked all-solid-state battery according to Comparative Example 1. In the stacked all-solid-state battery according to Comparative Example 1, the multiple solid electrolyte layers consist only of solid electrolyte layers belonging to the first group, and do not have any solid electrolyte layers belonging to the second group.

[0114] (Comparative Examples 2 and 3) The stacked all-solid-state batteries according to Comparative Examples 2 and 3 differ from Example 1 only in that the 16th solid electrolyte layer B was replaced with a solid electrolyte B'. In Comparative Examples 2 and 3, sheets having thicknesses 1.2 and 1.6 times that of the solid electrolyte layer A in Example 1 were stacked as the solid electrolyte B', respectively. Therefore, in the stacked all-solid-state batteries according to Comparative Examples 2 and 3, the multiple solid electrolyte layers consist only of solid electrolyte layers belonging to the first group, and do not include solid electrolyte layers belonging to the second group. Hereinafter, for convenience of explanation, in Comparative Examples 2 and 3, the solid electrolyte layer stacked in place of the 16th solid electrolyte layer B in 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'. The average thickness of the solid electrolyte layer A' and the thickness (average thickness) of the solid electrolyte layer B' will be referred to as t a ´,t b The other conditions were the same as in Example 1, and a stacked all-solid-state battery was fabricated. a ´,t b ´, and t b ´ / t a The measurement was also carried out in the same manner as in Example 1.

[0115] (Examples 2, 3, 4, and 5) The stacked all-solid-state batteries according to Examples 2, 3, 4, and 5 were fabricated in the same manner as in Example 1, except that the 16th solid electrolyte layer B was a sheet of solid electrolyte layer B having a thickness 3 times, 6 times, 10 times, or 15 times that of the solid electrolyte layer A. a , t b , and t b / t a The same procedure as in Example 1 was used to measure the temperature.

[0116] (Examples 6, 7, and 8) The stacked all-solid-state batteries according to Examples 6, 7, and 8 were fabricated in the same manner as in Example 2, except that the solid electrolyte material in the 16th solid electrolyte layer B was changed to LTP, LAGP, or LYZP, which has a Nasicon-type crystal structure. a , t b , and t b / t aThe measurement was carried out in the same manner as in Example 1. The solid electrolytes of LTP, LAGP, and LYZP were prepared by the following synthesis method.

[0117] LTP was produced using Li2CO3 (lithium carbonate), TiO2 (titanium oxide), and NH4H2PO4 (ammonium dihydrogen phosphate) as starting materials, weighing each material so that the molar ratio of Li, Ti, and PO4 was 1.0:2.0:3.0 (=Li:Ti:PO4), using the same synthesis method as in Example 1. XRD measurement and ICP analysis confirmed that the resulting solid electrolyte was LiTi2(PO4)3.

[0118] LAGP was prepared by the same synthesis method as in Example 1, except that the starting material TiO2 was replaced with GeO2, and the molar ratio of Li, Al, Ge, and PO4 was weighed to be 1.3:0.3:1.7:3.0 (=Li:Al:Ge:PO4). The solid electrolyte obtained from XRD measurement and ICP analysis showed that the 1.3 Al 0.3 Ge 1.7 It was confirmed that the result was (PO4)3.

[0119] 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, weighed out so that the molar ratio of Li, Y, Zr, and PO4 was 1.1:0.1:1.9:3.0 (=Li:Y:Zr:PO4), and synthesized in the same manner as in Example 1. XRD measurement and ICP analysis showed that the solid electrolyte contained Li 1.3 Y 0.3 Zr 1.7 It was confirmed that the result was (PO4)3.

[0120] Examples 9 to 10 In the stacked all-solid-state batteries according to Examples 9 and 10, the solid electrolyte material in the solid electrolyte layer A and the solid electrolyte layer B is Li7La3Zr2O 12 (LLZ), a perovskite-type crystal structure, Li 0.3 La0.55 A stacked all-solid-state battery was fabricated in the same manner as in Example 2, except that TiO3 (LLTO) was used. a , t b , and t b / t a The measurement was carried out in the same manner as in Example 1. The LLZ and LLTO solid electrolytes were prepared by the following synthesis method.

[0121] LLZ was prepared using Li2CO3 (lithium carbonate), La2O3 (lanthanum oxide), and ZrO2 (zirconium oxide) as starting materials, weighed out so that the molar ratio of Li, La, and Zr was 7:3:2 (=Li:La:Zr), and synthesized in the same manner as in Example 1. The solid electrolyte obtained from XRD measurement and ICP analysis was Li7La3Zr2O 12 It was confirmed that this is the case.

[0122] LLTO was prepared using Li2CO3 (lithium carbonate), La2O3 (lanthanum oxide), and TiO2 (titanium oxide) as starting materials, weighed out so that the molar ratio of Li, La, and Ti was 0.3:0.55:1.0 (=Li:La:Ti), and synthesized in the same manner as in Example 1. The solid electrolyte obtained from XRD measurement and ICP analysis showed that the 0.3 La 0.55 It was confirmed to be TiO3.

[0123] Example 11 The stacked all-solid-state battery according to Example 11 was fabricated in the same manner as in Example 2, except that the solid electrolyte material in the 16th solid electrolyte layer B was changed to a mixture of LATP and LAGP in a weight ratio of 50:50. a , t b , and t b / t a was measured in the same manner as in Example 1.

[0124] Example 12 In the stacked all-solid-state battery according to Example 12, the solid electrolyte material in the solid electrolyte layer B is Li7La3Zr2O 12A stacked all-solid-state battery was fabricated in the same manner as in Example 2, except that the thickness was changed to (LLZ). a , t b , and t b / t a was measured in the same manner as in Example 1.

[0125] Example 13 The stacked all-solid-state battery according to Example 13 was fabricated in the same manner as in Example 2, except that the sheets of the solid electrolyte layer B in Example 2 were stacked on the 11th and 21st layers, respectively. a , t b , and t b / t a was measured in the same manner as in Example 1.

[0126] Example 14 The stacked all-solid-state battery according to Example 14 was fabricated in the same manner as in Example 2, except that a sheet of the solid electrolyte layer B in Example 2 was stacked as the 14th layer. a , t b , and t b / t a was measured in the same manner as in Example 1.

[0127] Example 15 In the stacked all-solid-state battery according to Example 15, the solid electrolyte material in the solid electrolyte layer A and the solid electrolyte layer B was Li 3.5 Si 0.5 P 0.5 A stacked all-solid-state battery was fabricated in the same manner as in Example 2, except that O4 (LSPO) was used. a , t b , and t b / t a The measurement was carried out in the same manner as in Example 1. The LSPO solid electrolyte was prepared by the following synthesis method.

[0128] LSPO was prepared by weighing out Li2CO3, SiO2, and commercially available Li3PO4 as starting materials in a molar ratio of 2:1:1, wet-mixing them in a ball mill using water as a dispersion medium for 16 hours, and then dehydrating and drying. The resulting powder was calcined in air at 950°C for 2 hours, wet-pulverized again in a ball mill for 16 hours, and finally dehydrating and drying to obtain a solid electrolyte powder. The results of XRD measurement and ICP analysis showed that the powder contained Li 3.5 Si 0.5 P 0.5 It was confirmed to be O4 (LSPO).

[0129] (Examples 16 and 17) The stacked all-solid-state battery according to Example 16 was prepared in the same manner as in Example 1, except that the 11th and 21st solid electrolyte layers B (B1, B2) were made of sheets of solid electrolyte layers B1 and B2 having thicknesses two and six times the thickness of the solid electrolyte layer A, respectively. a , t b , and t b / t a The same procedure as in Example 1 was used to measure the temperature. The stacked all-solid-state battery according to Example 17 was prepared in the same manner as in Example 1, except that the 11th and 21st solid electrolyte layers B (B1, B2) were made of sheets of solid electrolyte layers B1 and B2 having thicknesses twice and ten times the thickness of the solid electrolyte layer A, respectively. a , t b , and t b / t a The same procedure as in Example 1 was used to measure the temperature.

[0130] Example 18 In the stacked all-solid-state battery according to Example 18, solid electrolyte layer sheets with different thicknesses were stacked as the 1st to 10th solid electrolyte layers A, the 12th to 20th solid electrolyte layers A, and the 22nd to 31st solid electrolyte layers A. The thicknesses were adjusted in ascending order from the 1st to 10th solid electrolyte layers, the 12th to 20th solid electrolyte layers, and the 22nd to 31st solid electrolyte layers. In addition, solid electrolyte layer B1 and B2 sheets each having a thickness twice the average thickness of the solid electrolyte layer A were stacked as the 11th and 21st solid electrolyte layers B (B1, B2). A stacked all-solid-state battery was fabricated in the same manner as in Example 1 under the same conditions as in Example 1, and t a , t b , and t b / t a The same procedure as in Example 1 was used to measure the temperature.

[0131] Comparative Example 4 In the stacked all-solid-state battery according to Comparative Example 4, solid electrolyte layer sheets with different thicknesses were stacked as the 1st to 10th solid electrolyte layers A, the 12th to 20th solid electrolyte layers A, and the 22nd to 31st solid electrolyte layers A. The thicknesses were adjusted in ascending order from the 1st to 10th solid electrolyte layers, the 12th to 20th solid electrolyte layers, and the 22nd to 31st solid electrolyte layers. In Comparative Example 4, solid electrolyte layer B1' and B2' sheets each having a thickness 1.5 times the average thickness of the solid electrolyte layer A were stacked as the 11th and 21st solid electrolyte layers B' (B1', B2'). A stacked all-solid-state battery was fabricated in the same manner as in Example 1 under the same other conditions as in Example 1, and t a ´,t b ´, and t b ´ / t a The measurement was also carried out in the same manner as in Example 1.

[0132] (Battery evaluation) The stacked all-solid-state batteries fabricated in the present examples and comparative examples can be evaluated for the following battery characteristics.

[0133] [Charge / discharge cycle test] The negative electrode external terminal and the positive electrode external terminal of the stacked all-solid-state batteries produced in the present examples and comparative examples were sandwiched between measurement probes, and charging and discharging were repeated under the following charging and discharging conditions, for example.

[0134] In an environment of 25°C, the battery was charged at a constant current of 0.2 C rate (CC charging) until the battery voltage reached 1.6 V, and then discharged at a constant current of 0.2 C rate until the battery voltage reached 0 V (CC discharging). This cycle of charging and discharging was counted as one cycle, and after repeating this cycle up to 1000 times, the discharge capacity retention rate was evaluated as the charge-discharge cycle characteristic. The charge-discharge cycle characteristic in this embodiment was calculated using the following calculation formula (1). Discharge capacity retention rate after 1000 cycles (%) = (discharge capacity after 1000 cycles ÷ discharge capacity after 1 cycle) × 100 (1)

[0135] [Volumetric expansion rate] In the charge-discharge cycle test, the thickness of the stacked all-solid-state battery before charging and the thickness of the stacked all-solid-state battery after the first charge were measured, and the volume expansion coefficient was calculated by the following calculation formula (2). Volume expansion rate (%) = (thickness of stacked all-solid-state battery at first charge (mm) ÷ thickness of stacked all-solid-state battery before charge (mm)) × 100 (2)

[0136] (result) Table 1 shows the average thickness t a , the average thickness t of the solid electrolyte layer B b , average thickness ratio t a / t b The results of the volume expansion coefficient and the charge-discharge cycle test are shown in Table 2. Table 2 shows the average thickness ta' of the solid electrolyte layer A', the average thickness tb' of the solid electrolyte layer B, the average thickness ratio ta' / tb', the volume expansion coefficient and the charge-discharge cycle test results of the stacked all-solid-state batteries according to Comparative Examples 2 and 3. Table 3 shows the average thickness t a , the average thickness t of the solid electrolyte layer B b , average thickness ratio ta / t b , volume expansion coefficient, and charge-discharge cycle test results are shown in Table 1 (Comparative Example 4 is actually the average thickness t 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 according to Examples 1 to 5 have a solid electrolyte layer B, 2 to 15 times thicker than the solid electrolyte layer A, stacked as the 16th layer. Compared to the stacked all-solid-state batteries of Comparative Examples 1 to 3, the volume expansion coefficient was suppressed and excellent cycle characteristics were obtained. On the other hand, in Example 5, which had a solid electrolyte layer B 15 times thicker than the solid electrolyte layer A, the volume expansion was further suppressed, but the cycle characteristics were slightly reduced. This suggests that the internal resistance increased because the solid electrolyte layer B was too thick. From the above results, the stacked all-solid-state batteries having a solid electrolyte layer B 2 to 10 times thicker than the solid electrolyte layer A showed better volume expansion coefficients and cycle characteristics.

[0137] In the stacked all-solid-state batteries according to Examples 6 to 8, the solid electrolyte of the solid electrolyte layer B was changed to a solid electrolyte having a Nasicon-type crystal structure other than LATP, and the volume expansion coefficient and cycle characteristics were superior to those of the comparative example.

[0138] In the stacked all-solid-state batteries according to Examples 9 and 10, the solid electrolytes of the solid electrolyte layer A and the solid electrolyte B were changed to solid electrolytes with garnet-type and perovskite-type crystal structures, and the volume expansion coefficient and cycle characteristics were superior to those of the comparative example.

[0139] In the stacked all-solid-state battery according to Example 11, the solid electrolyte of the solid electrolyte layer B was changed to include a plurality of solid electrolytes, LATP and LAGP, and the result was that the volume expansion coefficient and cycling characteristics were superior to those of the comparative example.

[0140] In the stacked all-solid-state battery according to Example 12, the solid electrolytes in the solid electrolyte layer A and the solid electrolyte layer B were changed to different solid electrolytes, and the volume expansion coefficient and cycle characteristics were slightly better than those of the comparative example.

[0141] The stacked all-solid-state battery of Example 13, in which the solid electrolyte layer B is stacked in two locations, at layers 11 and 21, resulted in a volume expansion coefficient and cycle characteristics superior to those of the comparative example, and also resulted in a volume expansion coefficient and cycle characteristics superior to those of Example 2, which included one layer of the solid electrolyte layer B.

[0142] In the stacked all-solid-state battery according to Example 14, the stacking position of the solid electrolyte layer B was the 14th layer, and the result was that the volume expansion coefficient and cycle characteristics were superior to those of the comparative example. Therefore, it was confirmed that the stacking position of the solid electrolyte layer B had an effect on improving the volume expansion coefficient and cycle characteristics even if it was not a position that equally divided the number of stacked elements.

[0143] In the stacked all-solid-state battery according to Example 15, the solid electrolyte of the solid electrolyte layer A and the solid electrolyte layer B was changed to the LSPO solid electrolyte, and the volume expansion coefficient and cycle characteristics were superior to those of the comparative example.

[0144] The stacked all-solid-state batteries according to Examples 16 and 17 were examples having a plurality of solid electrolyte layers B with different thicknesses, and were superior in volume expansion coefficient and cycle characteristics to the comparative examples.

[0145] The stacked all-solid-state battery according to Example 18 is an example having a plurality of solid electrolyte layers A with different thicknesses, and as a result, the volume expansion coefficient and cycle characteristics were superior to those of the comparative example.

[0146] Comparative Example 4 has a plurality of solid electrolyte layers B' and a plurality of solid electrolyte layers A' having different thicknesses, and the average thickness ratio t a ´ / t b This is a comparative example in which the coefficient of volume expansion is less than 2, and good volume expansion coefficient and cycle characteristics were not obtained.

[0147] [Table 1]

[0148] [Table 2]

[0149] [Table 3]

[0150] Although the present invention has been described in detail above, the above-mentioned embodiments and examples are merely illustrative, and the invention disclosed herein includes various modifications and alterations of the above-mentioned specific examples. [Explanation of symbols]

[0151] 0·········Stacked all-solid-state battery (appearance diagram) 100... Stacked all-solid-state battery (Example) 200... Stacked all-solid-state battery (comparison example) 10, 20, 20A, 30 laminate 1. Positive electrode layer 1A......Positive electrode current collector 1B......Cathode active material layer 2. Negative electrode layer 2A...Negative electrode current collector layer 2B...Negative electrode active material layer 3. Side margin layer 4... Outer layer (green sheet for solid electrolyte) 60 Positive external electrode 70 Negative external electrode A, A1, A2, A3, A4, A5...Solid electrolyte layers belonging to the first group B, B1, B2: Solid electrolyte layers belonging to the second group

Claims

1. A stacked-type all-solid-state battery having a laminate in which a positive electrode layer including a positive electrode current collector layer and a positive electrode active material layer, and a negative electrode layer including a negative electrode current collector layer and a negative electrode active material layer are alternately stacked with a solid electrolyte layer interposed therebetween, the solid electrolyte layer is either a solid electrolyte layer belonging to a first group or a solid electrolyte layer belonging to a second group, The first group includes a first solid electrolyte layer having a smallest thickness, the thicknesses of the solid electrolyte layers belonging to the first group are all less than twice the thickness of the first solid electrolyte layer; the thickness of the solid electrolyte layer belonging to the second group is at least twice as thick as that of the first solid electrolyte layer, The average thickness of the solid electrolyte layers belonging to the first group is t ａ and the average thickness t ｂ A laminated all-solid-state battery that satisfies the relationship of the following formula (1) when 2t ａ ≦t ｂ ・・・(1)

2. The stacked all-solid-state battery according to claim 1, which satisfies the following formula (2): 2t ａ ≦t ｂ ≦10 ａ ・・・(2)

3. 3. The stacked all-solid-state battery according to claim 1, wherein the solid electrolyte layers belonging to the first group and the solid electrolyte layers belonging to the second group contain solid electrolytes having the same crystal structure.

4. The stacked all-solid-state battery according to any one of claims 1 to 3, wherein the solid electrolyte layer belonging to the first group and the solid electrolyte layer belonging to the second group contain a solid electrolyte having any one crystal structure selected from the group consisting of a Nasicon type, a garnet type, a perovskite type, and a lysicone type crystal structure.

5. the first group includes the first solid electrolyte layer and a third solid electrolyte layer having a thickness greater than a thickness of the first solid electrolyte layer and less than twice the thickness of the first solid electrolyte layer; the second group is composed of a second solid electrolyte layer having a thickness at least twice that of the first solid electrolyte layer, 5. The stacked all-solid-state battery according to claim 1, comprising a plurality of the second solid electrolyte layers and a plurality of the third solid electrolyte layers.

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