Solid-state battery

Abstract

The object of the present disclosure is to provide a solid-state battery having a high capacity maintenance rate and a low battery resistance even when a solid electrolyte layer containing a support is used. The solid-state battery is a solid-state battery sequentially having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, characterized in that the solid electrolyte layer has a first solid electrolyte layer and a second solid electrolyte layer, the first solid electrolyte layer is disposed adjacent to the positive electrode layer or the negative electrode layer, the second solid electrolyte layer is disposed adjacent to the first solid electrolyte layer, the first solid electrolyte layer contains a solid electrolyte, and the second solid electrolyte layer is a sheet containing a support having a void and the solid electrolyte layer, the solid electrolyte being disposed on the surface of the support and inside the void.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a solid-state battery. BACKGROUND

[0002] Solid-state batteries are attracting attention in that a solid electrolyte is used instead of an electrolyte containing an organic solvent as an electrolyte interposed between a positive electrode and a negative electrode.

[0003] Patent Literature 1 discloses a solid electrolyte sheet containing a nonwoven fabric and a solid electrolyte inside and on the surface of the nonwoven fabric.

[0004] Patent Literature 2 discloses a separator obtained by supporting crystalline oxide-based inorganic solid electrolyte particles on a substrate in one layer, the solid electrolyte particles being exposed on both surfaces of the separator, the exposure rate of the solid electrolyte particles being 10 to 100% on both surfaces of the separator, and the substrate being a nonwoven fabric.

[0005] Prior Art Documents

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2016-031789

[0007] Patent Literature 2: Japanese Patent Application Publication No. 2020-188026 SUMMARY

[0008] From the viewpoint of improving the capacity retention rate of a solid-state battery, a solid electrolyte layer containing a support is used as a solid electrolyte layer of a solid-state battery.

[0009] In a solid-state battery using a solid electrolyte layer containing a support, the contact resistance of the solid electrolyte layer with a positive electrode and a negative electrode is high. Therefore, a solid-state battery using a solid electrolyte layer containing a support is required to reduce the battery resistance while maintaining a desired capacity retention rate.

[0010] The present disclosure was made in view of the above circumstances, and the main object is to provide a solid-state battery having a high capacity retention rate and a low battery resistance even when a solid electrolyte layer containing a support is used.

[0011] The solid-state battery of the present disclosure is a solid-state battery sequentially having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, characterized by

[0012] the solid electrolyte layer has a first solid electrolyte layer and a second solid electrolyte layer,

[0013] the first solid electrolyte layer is disposed adjacent to the positive electrode layer or the negative electrode layer,

[0014] the second solid electrolyte layer is disposed adjacent to the first solid electrolyte layer,

[0015] The first solid electrolyte layer contains a solid electrolyte,

[0016] The second solid electrolyte layer is a sheet containing a support having pores and the solid electrolyte, the solid electrolyte being disposed on the surface of the support and inside the pores.

[0017] In the solid-state battery of the present disclosure, the solid electrolyte layer can be:

[0018] The solid electrolyte layer further has a third solid electrolyte layer,

[0019] The first solid electrolyte layer is disposed adjacent to the negative electrode layer,

[0020] The third solid electrolyte layer is disposed adjacent to the positive electrode layer,

[0021] The second solid electrolyte layer is disposed between the first solid electrolyte layer and the third solid electrolyte layer,

[0022] The third solid electrolyte layer contains the solid electrolyte.

[0023] In the solid-state battery of the present disclosure, the support can have a porosity of 70% or more and 90% or less.

[0024] In the solid-state battery of the present disclosure, the support can be a nonwoven fabric.

[0025] In the solid-state battery of the present disclosure, the solid electrolyte can be a sulfide-based solid electrolyte.

[0026] In the solid-state battery of the present disclosure, the second solid electrolyte layer can have a thickness of 10 μm or more and 25 μm or less.

[0027] In the solid-state battery of the present disclosure, the first solid electrolyte layer and the third solid electrolyte layer can have a thickness of 3 μm or more and 10 μm or less.

[0028] The present disclosure can provide a solid-state battery having a high capacity retention rate and a low battery resistance even when a solid electrolyte layer containing a support is used. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a cross-sectional schematic view showing an example of the solid-state battery of the present disclosure.

[0030] LEGEND

[0031] 11 negative current collector

[0032] 12 negative electrode layer

[0033] 13 first solid electrolyte layer

[0034] 14 2nd solid electrolyte layer

[0035] 15 3rd solid electrolyte layer

[0036] 16 positive electrode layer

[0037] 17 positive electrode current collector

[0038] 100 solid-state battery DETAILED DESCRIPTION

[0039] The solid-state battery of the present disclosure is a solid-state battery having, in order, a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, characterized in that,

[0040] the solid electrolyte layer has a 1st solid electrolyte layer and a 2nd solid electrolyte layer,

[0041] the 1st solid electrolyte layer is disposed adjacent to the positive electrode layer or the negative electrode layer,

[0042] the 2nd solid electrolyte layer is disposed adjacent to the 1st solid electrolyte layer,

[0043] the 1st solid electrolyte layer contains a solid electrolyte,

[0044] the 2nd solid electrolyte layer is a sheet containing a support having a void and the solid electrolyte, the solid electrolyte being disposed on the surface of the support and inside the void.

[0045] Figure 1 is a cross-sectional schematic view showing an example of the solid-state battery of the present disclosure.

[0046] As shown in Figure 1 The solid-state battery 100 has, in order, a negative electrode current collector 11, a negative electrode layer 12, a 1st solid electrolyte layer 13, a 2nd solid electrolyte layer 14, a 3rd solid electrolyte layer 15, a positive electrode layer 16, and a positive electrode current collector 17.

[0047] The solid-state battery of the present disclosure has, in order, a positive electrode layer, a solid electrolyte layer, and a negative electrode layer.

[0048] The solid-state battery of the present disclosure can have a positive electrode including a positive electrode layer, a solid electrolyte layer, and a negative electrode including a negative electrode layer.

[0049] [SOLID ELECTROLYTE LAYER]

[0050] The solid electrolyte layer has at least a 1st solid electrolyte layer and a 2nd solid electrolyte layer, and can have a 3rd solid electrolyte layer as needed.

[0051] In the case where the solid electrolyte layer is a 2-layer structure, the first solid electrolyte layer is disposed adjacent to the positive electrode layer or the negative electrode layer.

[0052] In the case where the solid electrolyte layer is a 2-layer structure, the second solid electrolyte layer is disposed adjacent to the first solid electrolyte layer.

[0053] In the case where the solid electrolyte layer is a 3-layer structure, the first solid electrolyte layer is disposed adjacent to the negative electrode layer.

[0054] In the case where the solid electrolyte layer is a 3-layer structure, the third solid electrolyte layer is disposed adjacent to the positive electrode layer.

[0055] In the case where the solid electrolyte layer is a 3-layer structure, the second solid electrolyte layer is disposed between the first solid electrolyte layer and the third solid electrolyte layer.

[0056] The second solid electrolyte layer includes a support having pores and a solid electrolyte.

[0057] The second solid electrolyte layer is a sheet in which a solid electrolyte is disposed on the surface of a support and inside the pores. By disposing a solid electrolyte on the surface of a support and inside the pores, the contact area of the positive electrode and the negative electrode with the solid electrolyte increases, and the battery resistance can be reduced.

[0058] The support is not particularly limited as long as it has pores, and for example, can be a nonwoven fabric. The pore size distribution of a woven fabric is narrow due to the spaces between the fibers, whereas the pore size distribution of a nonwoven fabric is wide, and there are pores with a large pore volume and pores with a small pore volume. If a nonwoven fabric that contains a solid electrolyte on the surface and inside the pores is used, the small pores effectively suppress the detachment of the solid electrolyte, and the support assumes self-supporting properties and flexibility, and the large pores function to form ion channels.

[0059] The fiber material for the nonwoven fabric is not particularly limited, and can be a fiber that has insulation and flexibility without adversely affecting the solid electrolyte. As the fiber material, for example, resins such as polyester-based resins, polyolefin-based resins, and polyamide-based resins can be given. As the polyester-based resins, for example, polyethylene terephthalate (PET) and the like can be given. As the polyolefin-based resins, for example, polyethylene (PE), polypropylene (PP), and the like can be given. As the polyamide-based resins, for example, nylon and aramid and the like can be given. In addition, as the material of the fiber, glass can be used. That is, the nonwoven fabric can be a glass fiber nonwoven fabric. The fiber diameter and the fiber length of the fiber that constitutes the nonwoven fabric are not particularly limited.

[0060] As the type of the nonwoven fabric, for example, chemical bonding nonwoven fabrics, thermal bonding nonwoven fabrics, air-laid nonwoven fabrics, spunlace nonwoven fabrics, spunbond nonwoven fabrics, melt-blown nonwoven fabrics, needle punch nonwoven fabrics, and stitch-bonded nonwoven fabrics, and the like can be given.

[0061] The porosity of the support is not particularly limited; for example, it can be 50% or more, 60% or more, or 70% or more. If the porosity of the support is too small, the internal resistance is likely to increase. On the other hand, the porosity of the support can be, for example, 95% or less, or even 90% or less. If the porosity of the support is too large, it may not be able to function as a support. The porosity of the support can be determined, for example, by observing the cross-section of the nonwoven fabric. Furthermore, the size of the pores is not particularly limited.

[0062] The ratio of the total volume of the solid electrolyte to the total volume of the pores in the support is, for example, 50% or more, 70% or more, or 90% or more.

[0063] The thickness of the support can be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. On the other hand, the thickness of the support can be, for example, 25 μm or less. The thickness of the support can be the same as the thickness of the second solid electrolyte layer.

[0064] The thickness of the second solid electrolyte layer can be greater than 10 μm and less than 25 μm.

[0065] By setting the thickness of the second solid electrolyte layer to 10 μm or more, a solid electrolyte can be contained on the surface of the support and inside the pores, and the solid electrolyte is also distributed inside the pores and extends to the back side of the support. Therefore, the above-mentioned functions can be ensured. In addition, by setting the thickness of the second solid electrolyte layer to 25 μm or less, the increase in impedance of the solid battery can be suppressed, and the reduction in the discharge capacity of the solid battery can be suppressed.

[0066] One method for forming the second solid electrolyte layer is by applying a coating liquid (solid electrolyte layer paste) containing a solid electrolyte to the surface of a support disposed on a substrate and then drying it. In this way, a self-supporting second solid electrolyte layer is formed by peeling the support off the substrate after the coating liquid has dried. The substrate used as the support is not particularly limited as long as it is insoluble in solvents such as xylene used as the solid electrolyte layer paste; examples include metal foil, glass plates, and polyethylene terephthalate films.

[0067] The first and third solid electrolyte layers contain solid electrolytes.

[0068] The thickness of the first and third solid electrolyte layers can be greater than 3 μm and less than 10 μm. The thickness of the first and third solid electrolyte layers can be the same or different.

[0069] As a method of forming the first solid electrolyte layer and the third solid electrolyte layer, a method of performing press forming on a solid electrolyte material powder containing a solid electrolyte, and the like can be given. In the case of performing press forming on the solid electrolyte material powder, a press pressure of 1 MPa or higher and around 2000 MPa or lower is generally applied.

[0070] As the press method, the press method exemplified at the time of forming the positive electrode layer can be given.

[0071] As the solid electrolyte contained in the solid electrolyte layer, a publicly known solid electrolyte that can be used for a solid-state battery can be appropriately used, and inorganic solid electrolytes such as a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a hydride-based solid electrolyte, a halide-based solid electrolyte, and a nitride-based solid electrolyte can be given. The sulfide-based solid electrolyte can contain sulfur (S) as a main component of an anion element. The oxide-based solid electrolyte can contain oxygen (O) as a main component of an anion element. The hydride-based solid electrolyte can contain hydrogen (H) as a main component of an anion element. The halide-based solid electrolyte can contain halogen (X) as a main component of an anion element. The nitride-based solid electrolyte can contain nitrogen (N) as a main component of an anion element.

[0072] As the sulfide-based solid electrolyte, for example, Li2S-P2S5, Li2S-SiS2, LiX-Li2S-SiS2, LiX-Li2S-P2S5, LiX-Li2O-Li2S-P2S5, LiX-Li2S-P2O5, LiX-Li3PO4-P2S5, and Li3PS4, and the like can be given. Further, the above description of "Li2S-P2S5" means a material obtained using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions. In addition, "X" in the above LiX represents a halogen element. One or two or more kinds of LiX can be contained in the raw material composition containing the above LiX. In the case of containing two or more kinds of LiX, the mixing ratio of two or more kinds is not particularly limited.

[0073] The molar ratio of each element in the sulfide-based solid electrolyte can be controlled by adjusting the content of each element in the raw material. In addition, the molar ratio and the composition of each element in the sulfide-based solid electrolyte can be measured by, for example, an ICP emission spectroscopy.

[0074] The sulfide-based solid electrolyte can be a sulfide glass, can be a crystallized sulfide glass (glass ceramic), or can be a crystalline material obtained by a solid phase reaction treatment of a raw material composition.

[0075] The crystalline state of the sulfide-based solid electrolyte can be confirmed by, for example, performing powder X-ray diffraction measurement on the sulfide-based solid electrolyte using CuKα rays.

[0076] The sulfide glass can be obtained by subjecting a raw material composition (e.g., a mixture of Li2S and P2S5) to amorphous processing. As the amorphous processing, for example, mechanical grinding can be cited.

[0077] The glass ceramic can be obtained, for example, by subjecting the sulfide glass to heat treatment.

[0078] The heat treatment temperature can be a temperature higher than a crystallization temperature (Tc) observed by thermal analysis of the sulfide glass, and is usually 195°C or higher. On the other hand, the upper limit of the heat treatment temperature is not particularly limited.

[0079] The crystallization temperature (Tc) of the sulfide glass can be measured by differential thermal analysis (DTA).

[0080] The heat treatment time is not particularly limited as long as a desired crystallinity of the glass ceramic can be obtained, and is, for example, in the range of 1 minute to 24 hours, of which the range of 1 minute to 10 hours can be cited.

[0081] The method of the heat treatment is not particularly limited, and a method using a firing furnace can be cited, for example.

[0082] As the oxide-based solid electrolyte, for example, a solid electrolyte containing a Li element, a Y element (Y is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and an O element can be cited. As specific examples of the oxide-based solid electrolyte, garnet-type solid electrolytes such as Li7La3Zr2O 12 , Li 7-x La3(Zr 2-x Nb x )O 12 (0≤x≤2), Li5La3Nb2O 12 , (Li, La)TiO3, (Li, La)NbO3, (Li, Sr)(Ta, Zr)O3, and the like; sodium superionic conductor-type solid electrolytes such as Li(Al, Ti)(PO4)3 and Li(Al, Ga)(PO4)3; Li-P-O-based solid electrolytes such as Li3PO4 and LIPON (a compound in which part of O of Li3PO4 is substituted with N); and Li-B-O-based solid electrolytes such as Li3BO3 and a compound in which part of O of Li3BO3 is substituted with C. In the present disclosure, the symbol "(A, B, C)" in the chemical formula means "at least one selected from A, B, and C".

[0083] The hydride-based solid electrolyte has, for example, a Li and a complex anion containing hydrogen. As the complex anion, for example, (BH4) - , (NH2) -, (AlH4) - , and (AlH6) 3- , etc.

[0084] As the halide-based solid electrolyte, for example, Li 6-3z Y z X6(X is at least one of Cl and Br, and z satisfies 0 < z < 2), etc.

[0085] As the nitride-based solid electrolyte, for example, Li3N, etc. can be given.

[0086] From the viewpoint of good handleability, the shape of the solid electrolyte can be granular.

[0087] The average particle diameter of the solid electrolyte particle is not particularly limited, and for example, can be 10 nm or more, or can be 100 nm or more. On the other hand, the average particle diameter of the solid electrolyte particle is for example 25 μm or less, or can be 10 μm or less. The average particle diameter of the solid electrolyte particle can be smaller than the thickness of the support, or can be smaller than the pore diameter of the pores of the support.

[0088] In the present disclosure, unless otherwise specified, the average particle diameter of the particle is the value of the median diameter (D50) based on volume obtained by laser diffraction / scattering particle size distribution measurement. In addition, in the present disclosure, the median diameter (D50) is the diameter (volume average diameter) at which the cumulative volume of the particles reaches half (50%) of the total volume when the particles are arranged in order from the particles having a small particle diameter.

[0089] The solid electrolyte can be used alone, or two or more kinds can be used. In addition, in the case where two or more kinds of solid electrolytes are used, two or more kinds of solid electrolytes can be mixed, or a multilayer structure can be obtained by forming two or more layers of each of the solid electrolyte layers.

[0090] The proportion of the solid electrolyte in the solid electrolyte layer is not particularly limited, and for example, can be 50% by mass or more, can be in the range of 60% by mass or more and 100% by mass or less, can be in the range of 70% by mass or more and 100% by mass or less, or can be 100% by mass.

[0091] From the viewpoint of exhibiting plasticity, etc., the solid electrolyte layer can contain a binder. As such a binder, materials exemplified as the binder for the positive electrode layer, etc. can be exemplified. However, in order to easily achieve high output, from the viewpoint of preventing excessive aggregation of the solid electrolyte and enabling formation of a solid electrolyte layer in which the solid electrolyte is uniformly dispersed, etc., the binder contained in the solid electrolyte layer can be 5% by mass or less.

[0092] [Positive Electrode]

[0093] The positive electrode includes a positive electrode layer, and as needed, a positive electrode current collector.

[0094] [Positive electrode layer]

[0095] The positive electrode layer includes a positive electrode active material, and can also include a solid electrolyte, a conductive material, and a binder, etc. as optional components.

[0096] The kind of the positive electrode active material is not particularly limited, and any material capable of being used as an active material for a solid battery can be used. The positive electrode active material can be exemplified by, for example, metal lithium (Li), lithium alloy, LiCoO2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi x Co 1-x O2 (0 < x < 1), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, Li-Mn spinel with hetero-element substitution, lithium titanate, lithium metal phosphate, LiCoN, Li2SiO3, and Li4SiO4, transition metal oxide, TiS2, Si, SiO2, Si alloy, and lithium-storing intermetallic compound, etc. The Li-Mn spinel with hetero-element substitution is, for example, LiMn 1.5 Ni 0.5 O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4, and LiMn 1.5 Zn 0.5 O4, etc. The lithium titanate is, for example, Li4Ti5O 12 , etc. The lithium metal phosphate is, for example, LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4, etc. The transition metal oxide is, for example, V2O5and MoO3, etc. The lithium-storing intermetallic compound is, for example, Mg2Sn, Mg2Ge, Mg2Sb, and Cu3Sb, etc.

[0097] Examples of lithium alloys include Li-Au, Li-Mg, Li-Sn, Li-Si, Li-Al, Li-B, Li-C, Li-Ca, Li-Ga, Li-Ge, Li-As, Li-Se, Li-Ru, Li-Rh, Li-Pd, Li-Ag, Li-Cd, Li-In, Li-Sb, Li-Ir, Li-Pt, Li-Hg, Li-Pb, Li-Bi, Li-Zn, Li-Tl, Li-Te, and Li-At. Examples of Si alloys include alloys with metals such as Li, and also alloys with at least one metal selected from Sn, Ge, and Al.

[0098] The shape of the positive electrode active material is not particularly limited; it can be granular. When the positive electrode active material is granular, it can be either primary particles or secondary particles.

[0099] A coating layer containing Li-ion-conducting oxides can be formed on the surface of the positive electrode active material. This is because it can suppress the reaction between the positive electrode active material and the solid electrolyte.

[0100] Examples of Li-ion-conducting oxides include LiNbO3 and Li4Ti5O. 12 And Li3PO4, etc. The thickness of the coating layer is, for example, 0.1 nm or more, or 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, or 20 nm or less. The coverage of the coating layer on the surface of the positive electrode active material is, for example, 70% or more, or 90% or more.

[0101] As a solid electrolyte, the same solid electrolyte as that illustrated in the solid electrolyte layer can be exemplified.

[0102] There is no particular limitation on the content of solid electrolyte in the positive electrode layer. When the total mass of the positive electrode layer is set to 100% by mass, it can be in the range of 1 to 80% by mass.

[0103] As a conductive material, known materials can be used, such as carbon materials and metal particles. Examples of carbon materials include at least one selected from acetylene black, furnace black, VGCF, carbon nanotubes, and carbon nanofibers. From the viewpoint of electronic conductivity, at least one of VGCF, carbon nanotubes, and carbon nanofibers can be selected. Examples of metal particles include particles of Ni, Cu, Fe, and SUS.

[0104] There is no particular limit to the amount of conductive material in the positive electrode layer.

[0105] As the binder (adhesive), acrylonitrile-butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), styrene-butadiene rubber (SBR), and the like can be exemplified. The content of the binder in the positive electrode layer is not particularly limited.

[0106] The thickness of the positive electrode layer is not particularly limited.

[0107] The positive electrode layer can be formed by a publicly known method.

[0108] For example, the positive electrode active material and other components as necessary are put into a solvent and stirred, thereby preparing a slurry for the positive electrode layer, and the slurry for the positive electrode layer is coated on one side of a substrate such as a positive electrode current collector and dried, thereby obtaining the positive electrode layer.

[0109] The solvent can be, for example, butyl acetate, butyl butyrate, mesitylene, tetralin, heptane, N-methyl-2-pyrrolidone (NMP), and the like.

[0110] The method of coating the slurry for the positive electrode layer on one side of a substrate such as a positive electrode current collector is not particularly limited, and a doctor blade method, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a gravure coating method, a screen printing method, and the like can be exemplified.

[0111] As the substrate, for example, a metal foil of Cu, Al, and the like, or the like can be used.

[0112] In addition, as another method of forming the positive electrode layer, a positive electrode mixture powder containing the positive electrode active material and other components as necessary can be press-formed to form the positive electrode layer. In the case where the positive electrode mixture powder is press-formed, a press pressure of 1 MPa or higher and 2,000 MPa or lower is generally applied.

[0113] The press method is not particularly limited, and a method of applying pressure using a flat press and a roll press, or the like can be exemplified.

[0114] [Positive electrode current collector]

[0115] As the positive electrode current collector, a publicly known metal that can be used as a current collector for a solid-state battery can be used. As such a metal, a metal material containing one or two or more elements selected from Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In can be exemplified. As the positive electrode current collector, SUS, aluminum, nickel, iron, titanium, carbon, and the like can be exemplified.

[0116] The form of the positive electrode current collector is not particularly limited, and can be various forms such as a foil and a mesh. The thickness of the positive electrode current collector varies depending on the form, and can be, for example, in the range of 1 μm to 50 μm, or in the range of 5 μm to 20 μm.

[0117] [Negative electrode]

[0118] The negative electrode includes a negative electrode layer, and includes a negative electrode current collector as necessary.

[0119] [Negative electrode layer]

[0120] The negative electrode layer contains at least a negative electrode active material, and contains a solid electrolyte, a conductive material, a binder, and the like as necessary.

[0121] As the negative electrode active material, graphite, mesocarbon microbeads (MCMB), highly oriented pyrolytic graphite (HOPG), hard carbon, soft carbon, lithium simple substance, lithium alloy, Si simple substance, Si alloy, and Li4Ti5O12, and the like can be given. As the lithium alloy and the Si alloy, the same alloys as those exemplified as the positive electrode active material can be used. 12

[0122] The shape of the negative electrode active material is not particularly limited, and for example, particle shape and plate shape, and the like can be given. In the case where the negative electrode active material is in particle shape, the negative electrode active material can be a primary particle, or can be a secondary particle.

[0123] The conductive material and the binder used for the negative electrode layer can use the same materials as those exemplified in the positive electrode layer. The solid electrolyte used for the negative electrode layer can exemplify the same solid electrolytes as those exemplified in the solid electrolyte layer.

[0124] The thickness of the negative electrode layer is not particularly limited, and for example, can be 10 to 100 μm.

[0125] The content of the negative electrode active material in the negative electrode layer is not particularly limited, and for example, can be 20 to 90 mass%.

[0126] [Negative electrode current collector]

[0127] The material of the negative electrode current collector can be a material that is not alloyed with Li, and for example, SUS, copper, nickel, and the like can be given. As the form of the negative electrode current collector, for example, foil shape and plate shape, and the like can be given. The planar shape of the negative electrode current collector is not particularly limited, and for example, circular shape, elliptical shape, rectangular shape, and an arbitrary polygonal shape, and the like can be given. In addition, the thickness of the negative electrode current collector differs depending on the shape, and for example, can be in the range of 1 μm to 50 μm, or can be in the range of 5 μm to 20 μm.

[0128] The solid-state battery has an exterior body and a restraining member, and the like as necessary, the exterior body houses a laminate, and the laminate has, in order, a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector.

[0129] The material of the exterior body is not particularly limited as long as it is stable to the electrolyte, and for example, resins such as polypropylene, polyethylene, and acrylic resin, and the like can be given. ​

[0130] The constraint member can be any known constraint member that can be used as a constraint member for a solid-state battery as long as it can apply a constraint pressure in the stacking direction to the stacked body. For example, a constraint member in which a plate-shaped portion sandwiching both surfaces of the stacked body, a rod-shaped portion connecting the two plate-shaped portions, and an adjustment portion connected to the rod-shaped portion and adjusting the constraint pressure by a threaded structure or the like can be mentioned. The desired constraint pressure can be applied to the stacked body by the adjustment portion.

[0131] The constraint pressure is not particularly limited and can be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. This is because the contact between the layers is easily made good by increasing the constraint pressure. On the other hand, the constraint pressure can be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less. This is because if the constraint pressure is too large, the constraint member is required to have high rigidity, and the constraint member can be large-sized.

[0132] The solid-state battery can have only one of the above-described stacked bodies, or can be obtained by stacking a plurality of stacked bodies.

[0133] The solid-state battery can be a primary battery or a secondary battery, and can be particularly a secondary battery. The secondary battery can be repeatedly charged and discharged. The secondary battery is useful, for example, as an on-vehicle battery. In addition, the solid-state battery can be a solid-state lithium secondary battery or a solid-state lithium ion secondary battery.

[0134] As the shape of the solid-state battery, for example, a coin type, a laminate type, a cylindrical type, and a square type can be mentioned.

[0135] In the present disclosure, the solid-state battery can be an all-solid-state battery in which a solid electrolyte is used instead of an electrolyte solution containing an organic solvent as an electrolyte layer interposed between a positive electrode and a negative electrode, and the positive electrode, the negative electrode, and the electrolyte layer are all composed of solid materials.

[0136] The use of the solid-state battery is not particularly limited, and for example, a power source for a vehicle such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an electric vehicle (BEV), a gasoline vehicle, a diesel vehicle, or the like can be mentioned. In particular, it can be used as a driving power source for a hybrid electric vehicle, a plug-in hybrid electric vehicle, or an electric vehicle. In addition, the solid-state battery in the present disclosure can be used as a power source for a moving body other than a vehicle (for example, a railway, a ship, an aircraft), and can be used as a power source for an electronic product such as an information processing device.

[0137] The manufacturing method of the solid-state battery of the present disclosure, for example, first, a solid electrolyte layer having three layers of a first solid electrolyte layer, a second solid electrolyte layer, and a third solid electrolyte layer is prepared. Then, a positive electrode layer is obtained by pressure forming a positive electrode material powder containing a positive electrode active material on one side of the solid electrolyte layer. Then, a negative electrode layer is obtained by pressure forming a negative electrode material powder on one side of a negative electrode current collector. The negative electrode current collector-negative electrode layer laminate is installed on the side of the solid electrolyte layer opposite to the side on which the positive electrode layer is formed, with the negative electrode layer in contact with the solid electrolyte layer. Then, a positive electrode current collector is installed on the side of the positive electrode layer opposite to the solid electrolyte layer. Thus, the solid-state battery of the present disclosure can be obtained.

[0138] [Example]

[0139] (Example 1)

[0140] <Manufacture of positive electrode>

[0141] As the positive electrode active material, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2 powder having an average particle diameter (D50) of 5 μm measured based on the laser diffraction / scattering method was used. Then, LiNbO3 was coated on the surface of the positive electrode active material using a sol-gel method.

[0142] As the sulfide-based solid electrolyte, 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) glass ceramic having an average particle diameter (D50) of 2.5 μm measured based on the laser diffraction / scattering method was used.

[0143] The above was weighed in such a manner that the weight ratio of the positive electrode active material and the sulfide-based solid electrolyte was active material:solid electrolyte = 75:25, and further, 3% by weight of a SBR (styrene-butadiene rubber)-based binder and 10% by weight of a conductive material (CNF) were weighed with respect to 100 parts by weight of the positive electrode active material, and they were blended with butyl butyrate so that the solid content reached 60% by weight, and ultrasonic dispersion treatment was performed for 1 minute using an ultrasonic dispersion device, whereby a positive electrode layer-forming composition (positive electrode layer paste) was obtained.

[0144] Next, the obtained positive electrode layer paste was uniformly applied to an aluminum foil positive electrode current collector having a thickness of 15 μm in such a manner that the coating amount became 15 mg / cm 2 using a doctor blade coater of a commercially available applicator.

[0145] Then, the obtained coating film was subjected to drying treatment at 100°C for 60 minutes, and a positive electrode in which a positive electrode layer was formed on an aluminum foil positive electrode current collector was obtained.

[0146] <Manufacture of negative electrode>

[0147] As the negative electrode active material, Si powder having an average particle diameter (D50) of 5 μm measured by a laser diffraction / scattering method was used.

[0148] As the solid electrolyte, the same sulfide-based solid electrolyte as that used in the manufacture of the positive electrode was used.

[0149] The above-mentioned negative electrode active material and sulfide solid electrolyte were weighed in such a manner that the weight ratio of the negative electrode active material to the solid electrolyte became negative electrode active material : solid electrolyte = 50 : 50, and further, 3% by weight of SBR-based binder and 10% by weight of conductive material (CNF) were weighed with respect to 100 parts of the negative electrode active material, and they were mixed with butyl butyrate to make the solid content 40% by weight, and ultrasonic dispersion treatment was performed for 1 minute using an ultrasonic dispersion device, whereby a composition for forming a negative electrode layer (paste for negative electrode layer) was obtained.

[0150] Next, the obtained paste for negative electrode layer was uniformly applied to the surface-roughened copper foil negative current collector having a thickness of 25 μm in such a manner that the coating amount became 3 mg / cm 2 .

[0151] Then, the obtained coating film was subjected to drying treatment at 100°C for 60 minutes, whereby a negative electrode having a battery negative electrode layer formed on the surface-roughened copper foil negative current collector was obtained.

[0152] <Manufacture of solid electrolyte layer not containing support>

[0153] A solid electrolyte layer not containing support was manufactured using the above-mentioned sulfide-based solid electrolyte used in the manufacture of the positive electrode. Specifically, 99% by weight of the sulfide-based solid electrolyte and 1% by weight of SBR-based binder were weighed, and they were mixed with butyl butyrate to make the solid content 50% by weight, and ultrasonic dispersion treatment was performed for 1 minute using an ultrasonic dispersion device in the same manner as in the manufacture of the positive electrode, whereby a composition for forming a solid electrolyte (paste for solid electrolyte layer) was obtained.

[0154] Next, the obtained paste for solid electrolyte layer was uniformly applied to the aluminum foil having a thickness of 15 μm in such a manner that the coating amount became 0.6 mg / cm 2 (thickness 3 μm) in the same manner as in the manufacture of the above-mentioned positive electrode. Then, the obtained coating film was subjected to drying treatment at 100°C for 60 minutes, whereby a solid electrolyte layer not containing support was manufactured on the aluminum foil. In the same manner, a total of 2 layers (1st solid electrolyte layer and 3rd solid electrolyte layer) of the solid electrolyte layer not containing support were manufactured.

[0155] <Manufacture of solid electrolyte layer containing support>

[0156] A solid electrolyte layer containing a support was produced using the above-mentioned sulfide-based solid electrolyte used in the production of the positive electrode. Specifically, 99% by weight of the sulfide-based solid electrolyte and 1% by weight of the SBR-based binder were weighed, and they were blended with butyl butyrate so that the solid content reached 50% by weight, and ultrasonic dispersion treatment was performed for 1 minute using the same ultrasonic dispersion device as that used for the positive electrode, whereby a composition for solid electrolyte formation (a paste for a solid electrolyte layer) was obtained.

[0157] Next, a PET nonwoven fabric having a thickness of 25 μm and a porosity of 80% was laid on an aluminum foil having a thickness of 15 μm, and the obtained paste for a solid electrolyte layer was applied on the aluminum foil in the same manner as in the production of the positive electrode described above so that the coated amount of the solid electrolyte was 4.8 mg / cm 2 in a manner that the thickness of the nonwoven fabric was 25 μm.

[0158] Then, the obtained coated film was subjected to drying treatment at 100°C for 60 minutes, and a solid electrolyte layer containing a support on an aluminum foil (a second solid electrolyte layer) was produced.

[0159] <Production of a solid battery (battery assembly)>

[0160] The solid electrolyte layer not containing a support (a first solid electrolyte layer) was punched out together with the aluminum foil into a square of 1.4 cm x 1.4 cm. Similarly, the negative electrode was punched out into a square of 1.4 cm x 1.4 cm. The negative electrode and the solid electrolyte layer not containing a support (the first solid electrolyte layer) were overlaid in a manner that the negative electrode layer was in contact with the solid electrolyte layer not containing a support (the first solid electrolyte layer), and pressing was performed at a pressing pressure of 1 ton / cm 2 to obtain a negative electrode-first solid electrolyte layer-aluminum foil.

[0161] Next, the aluminum foil attached to the solid electrolyte layer not containing a support (the first solid electrolyte layer) of the negative electrode-first solid electrolyte layer-aluminum foil was peeled off, and a solid electrolyte layer containing a support (a second solid electrolyte layer) punched out into the same shape was overlaid with the solid electrolyte layer not containing a support (the first solid electrolyte layer), and pressing was performed at a pressing pressure of 1 ton / cm 2 to obtain a negative electrode-first solid electrolyte layer-second solid electrolyte layer.

[0162] In addition, the other solid electrolyte layer not containing a support (the 3rd solid electrolyte layer) was punched out into a square of 1 cm x 1 cm together with the aluminum foil. The positive electrode was punched out into a square of 1.4 cm x 1.4 cm as it was. The positive electrode layer and the solid electrolyte layer not containing a support (the 3rd solid electrolyte layer) were overlaid in such a manner that the positive electrode layer was in contact with the solid electrolyte layer not containing a support (the 3rd solid electrolyte layer), and pressing was performed at a pressing pressure of 1 ton / cm 2 to obtain a positive electrode-3rd solid electrolyte layer-aluminum foil.

[0163] Then, the solid electrolyte layer containing a support (the 2nd solid electrolyte layer) laminated on the negative electrode and the solid electrolyte layer not containing a support (the 3rd solid electrolyte layer) laminated on the positive electrode were overlaid, and pressing was performed at a pressing pressure of 3 tons / cm 2 to obtain a negative electrode-1st solid electrolyte layer-2nd solid electrolyte layer-3rd solid electrolyte layer-positive electrode laminate.

[0164] The laminate thus obtained was sealed with an exterior body composed of an aluminum laminate film to which positive and negative electrode terminals were attached in advance, and a test solid-state battery (a solid-state lithium ion secondary battery) of Example 1 was produced.

[0165] [Example 2]

[0166] In the production of the solid electrolyte layer, the coating amount of the solid electrolyte layer not containing a support (the 1st solid electrolyte layer and the 3rd solid electrolyte layer) was set to 1.0 mg / cm 2 (thickness 5 μm), the nonwoven fabric thickness of the solid electrolyte layer containing a support (the 2nd solid electrolyte layer) was set to 20 μm, and the coating amount of the solid electrolyte was set to 3.9 g / cm 2 (including the thickness of the nonwoven fabric 20 μm), and a test solid-state battery (a solid-state lithium ion secondary battery) of Example 2 was produced using the same materials and procedures as in Example 1 except for this.

[0167] [Example 3]

[0168] In the production of the solid electrolyte layer, the coating amount of the solid electrolyte layer not containing a support (the 1st solid electrolyte layer and the 3rd solid electrolyte layer) was set to 2.0 mg / cm 2 (thickness 10 μm), the nonwoven fabric thickness of the solid electrolyte layer containing a support (the 2nd solid electrolyte layer) was set to 10 μm, and the coating amount of the solid electrolyte was set to 1.9 mg / cm 2 (including the thickness of the nonwoven fabric 10 μm), and a test solid-state battery (a solid-state lithium ion secondary battery) of Example 3 was produced using the same materials and procedures as in Example 1 except for this.

[0169] (Example 4)

[0170] The thickness of the solid electrolyte layer not containing a support (the 1st solid electrolyte layer and the 3rd solid electrolyte layer) was set to 10 μm, the thickness of the solid electrolyte layer containing a support (the 2nd solid electrolyte layer) was set to 20 μm, in the production of the solid battery, the solid electrolyte layer not containing a support (the 1st solid electrolyte layer) was not laminated on the negative electrode, a laminate of negative electrode-2nd solid electrolyte layer-3rd solid electrolyte layer-positive electrode was obtained, and otherwise, the same materials and procedures as in Example 1 were used to produce the test solid battery (solid lithium ion secondary battery) of Example 4.

[0171] (Example 5)

[0172] The thickness of the solid electrolyte layer not containing a support (the 1st solid electrolyte layer and the 3rd solid electrolyte layer) was set to 10 μm, the thickness of the solid electrolyte layer containing a support (the 2nd solid electrolyte layer) was set to 20 μm, in the production of the solid battery, the solid electrolyte layer not containing a support (the 3rd solid electrolyte layer) was not laminated on the positive electrode, a laminate of negative electrode-1st solid electrolyte layer-2nd solid electrolyte layer-positive electrode was obtained, and otherwise, the same materials and procedures as in Example 1 were used to produce the test solid battery (solid lithium ion secondary battery) of Example 5.

[0173] <Comparative Example 1>

[0174] In the production of the solid electrolyte layer, the coating amount of the solid electrolyte layer not containing a support (the 1st solid electrolyte layer and the 3rd solid electrolyte layer) was set to 6.0 mg / cm 2 The thickness of the solid electrolyte layer not containing a support (the 1st solid electrolyte layer and the 3rd solid electrolyte layer) was set to 10 μm, the thickness of the solid electrolyte layer containing a support (the 2nd solid electrolyte layer) was set to 20 μm, in the production of the solid battery, the solid electrolyte layer not containing a support (the 1st solid electrolyte layer) was not laminated on the negative electrode, a laminate of negative electrode-2nd solid electrolyte layer-3rd solid electrolyte layer-positive electrode was obtained, and otherwise, the same materials and procedures as in Example 1 were used to produce the test solid battery (solid lithium ion secondary battery) of Example 4.

[0175] <Comparative Example 2>

[0176] In the production of the solid electrolyte layer, the coating amount of the solid electrolyte layer containing a support (the 2nd solid electrolyte layer) was set to 5.8 g / cm 2(30 μm including nonwoven fabric), in the production of the solid battery, only the solid electrolyte layer (2nd solid electrolyte layer) containing the support was laminated on the negative electrode, and the solid electrolyte layer (3rd solid electrolyte layer) not containing the support was not laminated on the positive electrode, to obtain a laminate of negative electrode-2nd solid electrolyte layer-positive electrode, and otherwise, using the same materials and procedures as in Example 1, the test solid battery (solid lithium ion secondary battery) of Comparative Example 2 was produced.

[0177] <evaluation>

[0178] <test 1: battery resistance measurement>

[0179] Each of the solid batteries of Examples 1 to 5 and Comparative Examples 1 and 2 was subjected to charge and discharge at 4.5 V-CCCV charge, 1 mA current rate, 0.01 mA current cutoff, 4.0 V-CCCV discharge, 1 mA current rate, and 0.01 mA current cutoff, and left to stand for 1 hour.

[0180] Next, each of the solid batteries was subjected to discharge at CC discharge, 10 mA current rate, and 10 seconds cutoff, and the battery resistance was measured in accordance with Ohm's law. The battery resistance is shown in Table 1.

[0181] <test 2: cycle test>

[0182] Each of the solid batteries after completion of Evaluation 1 was subjected to charge and discharge at 4.5 V-CCCV charge, 1 mA current rate, 0.01 mA current cutoff, 3.0 V-CCCV discharge, 1 mA current rate, and 0.01 mA current cutoff, repeatedly 100 times. The ratio of the discharge capacity at the 100th cycle to the discharge capacity at the 1st cycle was compared as the capacity retention rate. The capacity retention rate is shown in Table 1.

[0183] Capacity retention rate (%): (discharge capacity at the 100th cycle / discharge capacity at the 1st cycle) x 100

[0184] [table 1]

[0185]

[0186] <results>

[0187] Each of the solid batteries of Examples 1 to 3 maintained the effect of improvement in capacity retention rate due to the introduction of the support, and the battery resistance was equivalent to that of the solid battery not containing the support. The contact resistance of the electrode to the solid electrolyte layer containing the support was high, but by interposing the solid electrolyte layer not containing the support between the electrode and the solid electrolyte layer containing the support, the increase in resistance was suppressed.

[0188] It was confirmed that the battery resistance reduction was reduced in each of the solid batteries using the solid electrolyte layer of the 2-layer structure of the solid electrolyte layer not containing the support and the solid electrolyte layer containing the support of Examples 4 and 5, as compared with the case of the solid battery of Comparative Example 2 using the solid electrolyte layer of the structure of the one-layer solid electrolyte layer containing the support.

Claims

1. A solid battery which is a solid battery having, in order, a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, characterized by the solid electrolyte layer has a first solid electrolyte layer, a second solid electrolyte layer, and a third solid electrolyte layer, the first solid electrolyte layer is disposed adjacent to the negative electrode layer, the third solid electrolyte layer is disposed adjacent to the positive electrode layer, the second solid electrolyte layer is disposed between the first solid electrolyte layer and the third solid electrolyte layer, the first solid electrolyte layer and the third solid electrolyte layer contain a solid electrolyte which is 15LiBr-10LiI-75(0.75Li2S-0.25P2S5) glass ceramic, the second solid electrolyte layer is a sheet containing a support having pores and the solid electrolyte, the support having the solid electrolyte disposed on a surface thereof and inside the pores, the support has a porosity of 80%, the second solid electrolyte layer has a thickness of 20 μm or more and 25 μm or less, the first solid electrolyte layer and the third solid electrolyte layer have a thickness of 3 μm or more and 5 μm or less.

2. The solid battery according to claim 1, the support is a nonwoven fabric.

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