Solid-state battery and method for manufacturing solid-state battery

Abstract

The invention relates to a solid-state battery and a method for manufacturing the solid-state battery. A solid-state battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order, the positive electrode active material layer and the solid electrolyte layer containing moisture: (i) the moisture content of the positive electrode active material layer is 100-350 ppm and the moisture content of the solid electrolyte layer is 1500-2000 ppm; and / or (ii) the hydroxyl group standard value of the positive electrode active material layer is 0.63-0.71 and the hydroxyl group standard value of the solid electrolyte layer is 0.87-1.04.

Description

Technical Field

[0001] The present invention relates to a solid-state battery and a method for manufacturing the same. Background Art

[0002] A solid-state battery is a secondary battery that includes a solid electrolyte as an electrolyte and has attracted attention because of its high safety compared to a liquid battery that uses an electrolytic solution as an electrolyte. The output power of the solid-state battery is smaller than that of the liquid battery, and various developments have been made to improve this problem. There is known an electrochemical element including a solid electrolyte as follows.

[0003] In International Publication No. 2018 / 026009, there is disclosed an electrochemical element including a laminate having a positive electrode, a negative electrode, and a solid electrolyte sandwiched between the positive electrode and the negative electrode, the laminate containing moisture, and the amount of moisture contained in the laminate being 0.001% by mass or more and less than 0.3% by mass with respect to the laminate. According to the electrochemical element of International Publication No. 2018 / 026009, it is possible to maintain operation when a high voltage is applied. Summary of the Invention

[0004] For example, as disclosed in International Publication No. 2018 / 026009, the performance of a solid-state battery is improved by uniformly adsorbing a predetermined amount of moisture to an electrode laminate including a solid electrolyte. However, a solid-state battery in which an appropriate amount of moisture is adsorbed to a positive electrode active material layer and a solid electrolyte layer, respectively, rather than to the entire electrode laminate, and its performance are not well known.

[0005] Therefore, an object of the present invention is to provide a solid-state battery capable of suppressing an increase in resistance.

[0006] The present invention achieves the above object by the following means.

[0007] <Mode 1>

[0008] A solid-state battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order,

[0009] wherein the positive electrode active material layer and the solid electrolyte layer contain moisture,

[0010] (i) the amount of moisture in the positive electrode active material layer is 100 to 350 ppm and the amount of moisture in the solid electrolyte layer is 1500 to 2000 ppm, and / or

[0011] (ii) the hydroxyl standard value of the positive electrode active material layer is 0.63 to 0.71 and the hydroxyl standard value of the solid electrolyte layer is 0.87 to 1.04.

[0012] <Mode 2>

[0013] The solid-state battery according to Mode 1, wherein the moisture content of the negative electrode active material layer is 300 ppm or less, and / or the hydroxyl standard value of the negative electrode active material layer is 0.37 or less.

[0014] <Mode 3>

[0015] The solid-state battery according to Mode 1 or 2, wherein the solid electrolyte layer contains a sulfide solid electrolyte.

[0016] <Mode 4>

[0017] The solid-state battery according to any one of Modes 1 to 3, wherein

[0018] A part of the moisture contained in the positive electrode active material layer is physically adsorbed water physically adsorbed on the positive electrode active material layer,

[0019] Relative to the moisture content in the positive electrode active material layer, the moisture content of the physically adsorbed water is 0.50 to 0.90.

[0020] <Mode 5>

[0021] A method for manufacturing the solid-state battery according to any one of Modes 1 to 4, comprising the following steps:

[0022] In an environment with a dew point of 0 °C or lower, causing the positive electrode active material layer and the solid electrolyte layer to adsorb moisture respectively; and

[0023] Stacking the moisture-adsorbed positive electrode active material layer, the moisture-adsorbed solid electrolyte layer, and the negative electrode active material layer in sequence to obtain a solid-state battery.

[0024] The solid-state battery according to the present invention can suppress an increase in resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the drawings, wherein the same reference numerals denote the same elements.

[0026] Figure 1 is a schematic diagram for explaining the solid-state battery of the present invention. DETAILED DESCRIPTION

[0027] Hereinafter, the embodiments of the present invention will be described in detail. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention. In addition, in the description of the drawings, the same reference numerals are assigned to the same elements, and repeated descriptions are omitted.

[0028] Regarding the present invention, "composite material" refers to a composition that can form a positive electrode active material layer or the like as it is, or can form a positive electrode active material layer or the like by further containing other components. In addition, regarding the present invention, "composite material slurry" refers to a slurry that contains a dispersion medium in addition to the "composite material" and forms a positive electrode active material layer or the like by coating and drying.

[0029] Regarding the present invention, "solid-state battery" refers to a battery that uses at least a solid electrolyte as an electrolyte. Therefore, a solid-state battery can use a combination of a solid electrolyte and a liquid electrolyte as an electrolyte. In addition, the solid-state battery of the present invention can also be an all-solid-state battery, that is, a battery that uses only a solid electrolyte as an electrolyte.

[0030] "Solid-State Battery"

[0031] The solid-state battery of the present invention sequentially has a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer. The positive electrode active material layer and the solid electrolyte layer contain moisture. (i) The moisture content of the positive electrode active material layer is 100 to 350 ppm and the moisture content of the solid electrolyte layer is 1500 to 2000 ppm, and / or (ii) the hydroxyl standard value of the positive electrode active material layer is 0.63 to 0.71 and the hydroxyl standard value of the solid electrolyte layer is 0.87 to 1.04.

[0032] According to the solid-state battery of the present invention, an increase in resistance can be suppressed.

[0033] Although not limited by theory, it is speculated that a specified amount of moisture adsorbed on the positive electrode active material layer and the solid electrolyte layer penetrates into the interface between the positive electrode active material layer and the solid electrolyte layer, and a reaction layer with an appropriate thickness is formed at this interface. The oxidative decomposition of the solid electrolyte during charging is suppressed by this reaction layer, and thus an increase in resistance can be suppressed.

[0034] Figure 1 It is a schematic diagram showing one mode of the solid-state battery of the present invention, but it is not limited to this case.

[0035] The solid-state battery 100 sequentially has a positive electrode active material layer 110, a solid electrolyte layer 120, and a negative electrode active material layer 130. A specified amount of moisture is contained in the positive electrode active material layer 110 and the solid electrolyte layer 120. By the specified amount of moisture contained in the positive electrode active material layer 110 and the solid electrolyte layer 120, an increase in the resistance of the solid-state battery can be suppressed.

[0036] <Configuration of Solid-State Battery>

[0037] The solid-state battery of the present invention sequentially has a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer. The solid-state battery of the present invention may optionally have a positive electrode current collector layer and a negative electrode current collector layer, or may sequentially have a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer.

[0038] <Positive electrode current collector layer>

[0039] The material for the positive electrode current collector layer is not particularly limited, and materials commonly used as the positive electrode current collector of a solid-state battery can be appropriately adopted. Examples of the material for the positive electrode current collector layer include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. In addition, the positive electrode current collector layer may have a certain coating on its surface for the purpose of adjusting resistance, etc. Further, the positive electrode current collector layer may be plated or vapor-deposited with the above metals on a metal foil or a substrate.

[0040] The shape of the positive electrode current collector layer is not particularly limited, and examples include foil shape, plate shape, or mesh shape, etc. Among them, a foil shape is preferred.

[0041] The thickness of the positive electrode current collector layer is not particularly limited, and it can be 0.1 μm or more, or 1 μm or more, and can also be 1 mm or less, or 100 μm or less.

[0042] <Positive electrode active material layer>

[0043] The positive electrode active material layer contains at least a positive electrode active material and moisture, and may also optionally contain a solid electrolyte, a conductive additive, a binder, etc. The positive electrode active material layer may contain various other additives in addition to these. The content of each of the positive electrode active material, the conductive additive, the binder, etc. in the positive electrode active material layer can be appropriately determined according to the target battery performance. For example, when the entire positive electrode active material layer (the entire solid component) is set to 100% by mass, the content of the positive electrode active material can be 40% by mass or more, 50% by mass or more, 60% by mass or more, and can also be less than 100% by mass or 90% by mass or less.

[0044] (Moisture content of the positive electrode active material layer)

[0045] In the solid-state battery of the present invention, the moisture content of the positive electrode active material layer is 100 to 350 ppm. From the viewpoint of forming a reaction layer, the moisture content of the positive electrode active material layer can be 100 ppm or more, 150 ppm or more, 200 ppm or more, or 250 ppm or more, and from the viewpoint of suppressing hydrolysis of the solid electrolyte, it can be 350 ppm or less, 340 ppm or less, or 330 ppm or less. The moisture content of the positive electrode active material layer can be measured using a Karl Fischer apparatus (Karl Fischer apparatus CA-310 and moisture vaporization apparatus VA-300 manufactured by Nitto Seiko). Specifically, the positive electrode active material layer can be heated to 200 °C using the moisture vaporization apparatus VA-300, and the moisture generated by heating can be measured using the Karl Fischer apparatus CA-310 to obtain the moisture content.

[0046] (Standard value of hydroxyl groups in the positive electrode active material layer)

[0047] In the solid-state battery of the present invention, the standard value of hydroxyl groups in the positive electrode active material layer is 0.63 to 0.71. From the viewpoint of forming a reaction layer, the standard value of hydroxyl groups in the positive electrode active material layer can be 0.63 or more, 0.64 or more, 0.65 or more, 0.66 or more, 0.67 or more, or 0.68 or more, and from the viewpoint of suppressing hydrolysis of the solid electrolyte, it can be 0.71 or less, 0.70 or less, or 0.69 or less. The standard value of hydroxyl groups in the positive electrode active material layer can be measured by Fourier transform infrared spectroscopy (FT-IR) to measure the absorbance at 3300 cm -1 of the positive electrode active material layer and the absorbance at 1180 cm -1 and calculate the ratio of the absorbance at 3300 cm -1 to the absorbance at 1180 cm -1 as the standard value of hydroxyl groups in the positive electrode active material layer.

[0048] (Moisture content of physically adsorbed water relative to the moisture content contained in the positive electrode active material layer)

[0049] Part of the moisture contained in the positive electrode active material layer is not particularly limited and may be physically adsorbed water physically adsorbed on the positive electrode active material layer. The amount of moisture of the physically adsorbed water is not particularly limited and may be 0.50 to 0.90 relative to the amount of moisture contained in the positive electrode active material layer. The amount of moisture of the physically adsorbed water relative to the amount of moisture contained in the positive electrode active material layer may be 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, or 0.70 or more, and may also be 0.90 or less, 0.85 or less, 0.80 or less, or 0.75 or less. Regarding the amount of moisture of the physically adsorbed water relative to the amount of moisture contained in the positive electrode active material layer, it can be measured by temperature-programmed desorption mass spectrometry (TPD-MS) under the conditions of a measurement temperature of 30 to 500 °C and a heating rate of 10 °C / minute, and calculated based on the resulting production rate curve of water (m / z = 18). Specifically, as the amount of moisture of the physically adsorbed water, the amount of moisture generated when heated to 100 °C is calculated based on the peak area at a measurement temperature of 30 to 100 °C of the water production rate curve. Then, as the amount of moisture contained in the positive electrode active material layer, the amount of moisture generated when heated to 120 °C is calculated based on the peak area at a measurement temperature of 30 to 120 °C of the water production rate curve. Then, based on the separately calculated amounts of moisture, the amount of moisture of the physically adsorbed water relative to the amount of moisture contained in the positive electrode active material layer can be calculated and obtained.

[0050] (Positive electrode active material)

[0051] The material of the positive electrode active material is not particularly limited as long as it can occlude and release lithium ions. As the positive electrode active material, for example, it can be lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium manganate (LiMn2O4), lithium nickel cobalt manganate (NCM: LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2), lithium nickel cobalt aluminate (LiNi 0.8 (CoAl) 0.2 O2), and a lithium-manganese spinel substituted with a foreign element represented by Li 1+x Mn 2-x-y M y O4 (M is one or more metal elements selected from Al, Mg, Co, Fe, Ni, and Zn), but is not limited to these.

[0052] The positive electrode active material is not particularly limited and may have a coating layer. The coating layer is a layer of a material having a form of a coating layer containing a substance having lithium ion conductivity, low reactivity with the positive electrode active material and the solid electrolyte, and capable of remaining non-flowing even when in contact with the active material and the solid electrolyte. As a specific example of the material constituting the coating layer, in addition to LiNbO3, Li4Ti5O12 , Li3PO4, Li-Ti-Al-F based materials, etc., but not limited to these.

[0053] The shape of the positive electrode active material is not particularly limited as long as it is a shape commonly used as the positive electrode active material of a solid-state battery. The positive electrode active material can be, for example, particulate. The positive electrode active material can be primary particles or secondary particles formed by aggregation of multiple primary particles. The average particle diameter D of the positive electrode active material 50 can be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and can also be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. It should be noted that the average particle diameter D 50 is the particle diameter (median diameter) at the cumulative value of 50% in the volume-based particle size distribution obtained by the laser diffraction / scattering method.

[0054] (Solid electrolyte)

[0055] The material of the solid electrolyte is not particularly limited. For example, it can be a sulfide solid electrolyte, an oxide solid electrolyte, a polymer electrolyte, etc.

[0056] Examples of the sulfide solid electrolyte include sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, thiogermanate-type solid electrolytes, etc., but not limited to these. Examples of specific sulfide solid electrolytes include Li2S-P2S5 systems (Li7P3S 11 , Li3PS4, Li8P2S9, etc.), Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2 (Li 13 GeP3S 16 , Li 10 GeP2S 12 , etc.), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS 6-x Cl x , etc., or combinations thereof, but not limited to these.

[0057] Examples of the oxide solid electrolyte include Li7La3Zr2O 12 , Li 7-x La3Zr 1-x Nb x O 12 , Li 7- 3x La3Zr2Al x O 12 , Li3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4 or Li 3+x PO 4-x N x (LiPON), etc., but not limited to these.

[0058] Sulfide solid electrolytes and oxide solid electrolytes can be glass or devitrified glass (glass ceramics).

[0059] Examples of polymer electrolytes include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof, etc., but not limited to these.

[0060] (Conductive additive)

[0061] There is no particular limitation on the conductive additive. The conductive additive can be, for example, vapor-grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotube (CNT), carbon nanofiber (CNF), conductive material carbon, etc., but not limited to these. The conductive additive can be, for example, particulate or fibrous, and its size is not particularly limited. There is no particular limitation on the conductive additive, and only one kind can be used alone, or two or more kinds can be used in combination.

[0062] (Binder)

[0063] There is no particular limitation on the binder. The binder can be, for example, polyvinylidene fluoride (PVdF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), etc., but not limited to these. There is no particular limitation on the binder, and only one kind can be used alone, or two or more kinds can be used in combination.

[0064] The shape of the positive electrode active material layer is not particularly limited. For example, it can be a positive electrode active material layer in the form of a sheet with a substantially flat surface. The thickness of the positive electrode active material layer is not particularly limited. For example, it can be 0.1 μm or more, 1 μm or more, or 10 μm or more, and can also be 2 mm or less, 1 mm or less, or 500 μm or less.

[0065] The positive electrode active material layer can be manufactured by applying a known method. For example, the positive electrode composite material containing the above various components can be formed by dry or wet forming, etc., to easily form the positive electrode active material layer. The positive electrode active material layer can be formed together with the positive electrode current collector layer or separately from the positive electrode current collector layer.

[0066] <Solid electrolyte layer>

[0067] The solid electrolyte layer contains at least a solid electrolyte and moisture, and may contain a conductive additive, a binder, etc. as required. The solid electrolyte layer is not particularly limited, and preferably contains a sulfide solid electrolyte.

[0068] (Moisture content of the solid electrolyte layer)

[0069] In the solid-state battery of the present invention, the moisture content of the solid electrolyte layer is 1500 to 2000 ppm. From the viewpoint of forming the reaction layer, the moisture content of the solid electrolyte layer can be 1500 ppm or more, 1600 ppm or more, 1700 ppm or more, 1800 ppm or more, or 1900 ppm or more. From the viewpoint of suppressing the hydrolysis of the solid electrolyte, it can be 2000 ppm or less or 1950 ppm or less. Regarding the measurement of the moisture content of the solid electrolyte layer, reference can be made to the description of the above-mentioned "(Moisture content of the positive electrode active material layer)".

[0070] (Hydroxyl standard value of the solid electrolyte layer)

[0071] In the solid-state battery of the present invention, the hydroxyl standard value of the solid electrolyte layer is 0.87 to 1.04. From the viewpoint of forming the reaction layer, the hydroxyl standard value of the solid electrolyte layer can be 0.87 or more, 0.90 or more, 0.95 or more, or 1.00 or more. From the viewpoint of suppressing the hydrolysis of the solid electrolyte, it can be 1.04 or less, 1.03 or less, or 1.02 or less. Regarding the measurement of the hydroxyl standard value of the solid electrolyte layer, reference can be made to the description of the above-mentioned "(Hydroxyl standard value of the positive electrode active material layer)".

[0072] Regarding the solid electrolyte, the conductive additive, and the binder, reference can be made to the description of the above-mentioned "<Positive electrode active material layer>".

[0073] The thickness of the solid electrolyte layer is not particularly limited. For example, it can be 0.1 μm or more, 1 μm or more, or 10 μm or more, and can also be 2 mm or less, 1 mm or less, or 500 μm or less.

[0074] The solid electrolyte layer can be easily formed, for example, by forming a solid electrolyte composite material containing the above-mentioned solid electrolyte and binder, etc. using a dry or wet method.

[0075] <Negative electrode active material layer>

[0076] The negative electrode active material layer contains at least a negative electrode active material, and may also optionally contain a conductive assistant, a binder, a solid electrolyte, etc. The negative electrode active material layer may further contain various additives in addition to these. The contents of the negative electrode active material, the conductive assistant, the binder, the solid electrolyte, etc. in the negative electrode active material layer can be appropriately determined according to the target battery performance. For example, assuming the whole of the negative electrode active material layer (the whole solid component) is 100% by mass, the content of the negative electrode active material can be 40% by mass or more, 50% by mass or more, or 60% by mass or more, and can also be 100% by mass or less or 90% by mass or less.

[0077] (Moisture content of the negative electrode active material layer)

[0078] The moisture content of the negative electrode active material layer is not particularly limited and can be 300 ppm or less. Additionally, the moisture content of the negative electrode active material layer can be 150 ppm or more, 160 ppm or more, 170 ppm or more, 180 ppm or more, 190 ppm or more, or 200 ppm or more, and can also be 300 ppm or less, 280 ppm or less, 260 ppm or less, 240 ppm or less, or 220 ppm or less. Regarding the measurement of the moisture content of the negative electrode active material layer, reference can be made to the description of the above “(Moisture content of the positive electrode active material layer)”.

[0079] (Hydroxyl standard value of the negative electrode active material layer)

[0080] The hydroxyl standard value of the negative electrode active material layer is not particularly limited and can be 0.37 or less. Additionally, the hydroxyl standard value of the negative electrode active material layer can be 0.01 or more, 0.02 or more, 0.04 or more, 0.06 or more, or 0.08 or more, and can also be 0.37 or less, 0.31 or less, 0.25 or less, 0.19 or less, or 0.13 or less. Regarding the measurement of the hydroxyl standard value of the negative electrode active material layer, reference can be made to the description of the above “(Hydroxyl standard value of the positive electrode active material layer)”.

[0081] (Negative electrode active material)

[0082] As the negative electrode active material, various substances having a potential (charge-discharge potential) for occluding and releasing lithium ions lower than that of the positive electrode active material of the present invention described above can be used. The material of the negative electrode active material is not particularly limited and can be metallic lithium, or a material capable of occluding and releasing metal ions such as lithium ions. As the material capable of occluding and releasing metal ions such as lithium ions, for example, alloy-based negative electrode active materials, carbon materials, or lithium titanate (Li4Ti5O 12 ) etc. can be cited, but are not limited to these.

[0083] There is no particular limitation on the alloy-based negative electrode active material. For example, a Si alloy-based negative electrode active material or a Sn alloy-based negative electrode active material can be cited. The Si alloy-based negative electrode active material includes silicon, silicon oxide, silicon carbide, silicon nitride, or a solid solution thereof. In addition, the Si alloy-based negative electrode active material may contain metal elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, Ti, etc. The Sn alloy-based negative electrode active material includes tin, tin oxide, tin nitride, or a solid solution thereof. In addition, the Sn alloy-based negative electrode active material may contain metal elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, Si, etc.

[0084] There is no particular limitation on the carbon material. For example, hard carbon, soft carbon, graphite, etc. can be cited.

[0085] There is no particular limitation on the shape of the negative electrode active material, as long as it is the shape of a negative electrode active material commonly used in a solid-state battery. The negative electrode active material can be, for example, particulate or flaky.

[0086] The solid electrolyte, conductive assistant, and binder that can be contained in the negative electrode active material layer can be referred to the description of the above “<Positive electrode active material layer>”.

[0087] There is no particular limitation on the shape of the negative electrode active material layer. For example, it can be a flaky negative electrode active material layer having a substantially flat surface. There is no particular limitation on the thickness of the negative electrode active material layer. For example, it can be 0.1 μm or more, 1 μm or more, or 10 μm or more, and can also be 2 mm or less, 1 mm or less, or 500 μm or less.

[0088] The negative electrode active material layer can be manufactured by applying a known method. For example, the negative electrode composite material containing the above various components can be formed by dry or wet forming, etc., and the negative electrode active material layer can be easily formed. The negative electrode active material layer can be formed together with the negative electrode current collector layer or separately from the negative electrode current collector layer.

[0089] <Negative electrode current collector layer>

[0090] There is no particular limitation on the material for the negative electrode current collector layer, and a material commonly used as a negative electrode current collector in a solid-state battery can be appropriately adopted. As the material for the negative electrode current collector layer, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, or a carbon sheet, etc. can be cited, but it is not limited to these cases. The negative electrode current collector layer can have a certain coating on its surface for the purpose of adjusting resistance, etc.

[0091] The shape of the negative electrode current collector layer is not particularly limited, and examples thereof include a foil shape, a plate shape, or a mesh shape. Among them, a foil shape is preferred.

[0092] The thickness of the negative electrode current collector layer is not particularly limited, and it may be 0.1 μm or more or 1 μm or more, and may also be 1 mm or less or 100 μm or less.

[0093] <Shape, etc. of the solid-state battery>

[0094] As the shape of the solid-state battery, for example, a coin type, a laminate type, a cylindrical type, or a square type can be cited, but it is not limited to these cases.

[0095] <Manufacturing method of the solid-state battery>

[0096] The solid-state battery of the present invention can be manufactured by a manufacturing method including the following steps.

[0097] In an environment where the dew point is 0°C or lower, the positive electrode active material layer and the solid electrolyte layer are respectively adsorbed with moisture; and

[0098] The above-mentioned positive electrode active material layer adsorbed with moisture, the above-mentioned solid electrolyte layer adsorbed with moisture, and the negative electrode active material layer are laminated in sequence to obtain a solid-state battery.

[0099] According to the manufacturing method of the solid-state battery of the present invention, a solid-state battery capable of suppressing an increase in resistance can be manufactured.

[0100] (Method of adsorbing moisture)

[0101] As a method of adsorbing moisture to the positive electrode active material layer, for example, the positive electrode active material layer can be left standing for a predetermined time in a glove box or the like whose humidity is adjusted to a dew point of -60°C to adsorb moisture, but it is not limited to this case. The method of adsorbing moisture to the solid electrolyte layer is the same as that of the positive electrode active material layer.

[0102] As the dew point of the environment in which moisture adheres to the positive electrode active material layer and the solid electrolyte layer, from the viewpoint of suppressing the structural change of the solid electrolyte, it can be 0°C or lower, -10°C or lower, -30°C or lower, or -50°C or lower, and can also be -80°C or higher, -75°C or higher, -70°C or higher, or -65°C or higher.

[0103] As the time when moisture adheres to the positive electrode active material layer and the solid electrolyte layer, there is no particular limitation, and it can be 1 second or more, 10 seconds or more, 30 seconds or more, 1 minute or more, 10 minutes or more, 30 minutes or more, or 1 hour or more, and can also be 5 hours or less, 3 hours or less, 1 hour or less, or 30 minutes or less.

[0104] (Laminating method)

[0105] As a method for laminating a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, specifically, for example, a solid electrolyte layer formed on a substrate may be respectively overlapped on the surfaces of the negative electrode active material layers formed on both sides of the negative electrode current collector and pressed, the solid electrolyte layer may be transferred onto the surfaces of the negative electrode active material layers, the substrate in contact with the solid electrolyte layer may be peeled off, the solid electrolyte layer may be laminated on the negative electrode active material layer, and then, a positive electrode active material layer formed on a substrate may be respectively overlapped on the surfaces of the solid electrolyte layers laminated on both sides of the negative electrode active material layer and pressed, the positive electrode active material layer may be transferred onto the surfaces of the solid electrolyte layers, the substrate in contact with the positive electrode active material layer may be peeled off, and the positive electrode active material layer may be laminated on the solid electrolyte layer, but it is not limited to this case.

[0106] The above laminate may be made into a solid-state battery, or a positive electrode current collector layer and / or a negative electrode current collector layer may be provided on a laminate formed by laminating a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer as needed, and the solid-state battery may be made by encapsulating it with a laminate film. The solid-state battery is not particularly limited, and for example, it may be constrained at a constraint pressure of 5 MPa.

[0107] The present invention will be described in more detail with reference to the embodiments shown below, but the scope of the present invention is not limited to these embodiments.

[0108] <Moisture content of positive electrode active material layer, solid electrolyte layer, negative electrode active material layer, and densified laminate>

[0109] The moisture content of each of the above layers and the above laminate is measured using a Karl Fischer apparatus (Karl Fischer apparatus CA-310 and moisture vaporization apparatus VA-300 manufactured by Nitto Seiko). Specifically, the measurement sample is heated to 200 °C using the moisture vaporization apparatus VA-300, and the moisture generated by heating is measured using the Karl Fischer apparatus CA-310 to obtain the moisture content.

[0110] <Hydroxyl standard value of positive electrode active material layer and solid electrolyte layer>

[0111] Regarding the hydroxyl standard value of the positive electrode active material layer, the absorbance at 3300 cm -1 and the absorbance at 1180 cm -1 of the positive electrode active material layer are measured using Fourier transform infrared spectroscopy (FT-IR), and the ratio of the absorbance at 3300 cm -1 to the absorbance at 1180 cm -1 is calculated as the hydroxyl standard value of the positive electrode active material layer. Regarding the hydroxyl standard value of the solid electrolyte layer, it is also obtained by the same method as the hydroxyl standard value of the positive electrode active material layer.

[0112] 《Example 1》

[0113] <Fabrication of the positive electrode active material layer A1>

[0114] Mix LiNi 0.8 (CoAl) 0.2 O2 coated with an Li-Ti-Al-F-based material as the positive electrode active material, a Li2S-P2S5-based glass-ceramic as the solid electrolyte, conductive carbon as the conductive additive, a binder, a dispersant, and an appropriate amount of solvent, and perform a dispersion treatment using an ultrasonic homogenizer to prepare a positive electrode composite material slurry. Then, coat the obtained positive electrode composite material slurry onto an aluminum foil by die coating and dry it to form a positive electrode active material layer on one side of the aluminum foil. Leave the obtained positive electrode active material layer to stand for a specified time in a humidity-controlled glove box with a dew point set at -60°C to obtain the positive electrode active material layer A1 adsorbed with moisture. The moisture content of the positive electrode active material layer A1 is 101 ppm, and the hydroxyl standard value is 0.65.

[0115] <Fabrication of the solid electrolyte layer B1>

[0116] Mix an LiI-LiBr-Li2S-P2S5-based glass-ceramic (average particle size 2.5 μm) as the solid electrolyte, conductive carbon as the conductive additive, a binder, a dispersant, and an appropriate amount of solvent, and perform a dispersion treatment using an ultrasonic homogenizer to prepare a solid electrolyte composite material slurry. Then, coat the obtained solid electrolyte composite material slurry onto an aluminum foil by die coating and dry it to form a solid electrolyte layer on one side of the aluminum foil. Leave the obtained solid electrolyte layer to stand for a specified time in a humidity-controlled glove box with a dew point set at -60°C to obtain the solid electrolyte layer B1 adsorbed with moisture. The moisture content of the solid electrolyte layer B1 is 1515 ppm, and the hydroxyl standard value is 0.89.

[0117] <Fabrication of the negative electrode active material layer C1>

[0118] Mix Li4Ti5O 12Particles, Li2S-P2S5-based glass ceramics as a solid electrolyte, carbon as a conductive additive, a binder, a dispersant, and an appropriate amount of solvent are mixed, and dispersed by an ultrasonic homogenizer to prepare a negative electrode composite material slurry. Then, the obtained negative electrode composite material slurry is coated on an aluminum foil as a negative electrode current collector by doctor coating and dried to form a negative electrode active material layer on one side of the aluminum foil. Then, the negative electrode composite material slurry is coated on the surface of the aluminum foil where the negative electrode active material layer is not formed and dried. Thus, a negative electrode active material layer C1 is formed on both sides of the aluminum foil. It should be noted that for the negative electrode active material layer C1, it is not left standing in a humidity-controlled glove box with a dew point set at -60°C, and no intentional adsorption of moisture is carried out. The moisture content of the negative electrode active material layer C1 is 205 ppm, and the hydroxyl standard value is 0.09. Here, regarding the weight per unit area of the negative electrode active material layer, the weight per unit area of the negative electrode active material layer is adjusted so that the charge specific capacity of the negative electrode active material layer becomes 1 times when the charge specific capacity of the positive electrode active material layer is set to 200 mAh / g.

[0119] <Fabrication of the densified laminate D1>

[0120] On the surfaces of the negative electrode active material layers C1 formed on both sides of an aluminum foil as a negative electrode current collector, a solid electrolyte layer B1 is overlapped and pressed respectively, the solid electrolyte layer B1 is transferred onto the surface of the negative electrode active material layer C1, the aluminum foil in contact with the solid electrolyte layer B1 is peeled off, and the solid electrolyte layer B1 is laminated on the negative electrode active material layer C1. Then, on the surfaces of the solid electrolyte layers B1 laminated on both sides of the negative electrode active material layer C1, a positive electrode active material layer A1 is overlapped and pressed respectively, the positive electrode active material layer A1 is transferred onto the surface of the solid electrolyte layer B1, the aluminum foil in contact with the positive electrode active material layer A1 is peeled off, and the positive electrode active material layer A1 is laminated on the solid electrolyte layer B1. The fabricated laminate is roll-pressed at 175°C with 5 tons / cm to fabricate the densified laminate D1.

[0121] <Fabrication of the solid-state battery E1>

[0122] On the surfaces of the positive electrode active material layers A1 of the densified laminate D1, a carbon-coated aluminum foil as a positive electrode current collector is disposed, and pressed at 140°C with 5 MPa for 5 minutes to obtain a power generation element. Here, in the power generation element, a positive electrode current collector layer, a positive electrode active material layer A1, a solid electrolyte layer B1, a negative electrode active material layer C1, a negative electrode current collector layer, a negative electrode active material layer C1, a solid electrolyte layer B1, a positive electrode active material layer A1, and a positive electrode current collector layer are laminated in sequence. The obtained power generation element is sealed with a laminating film and constrained with 5 MPa to fabricate the solid-state battery E1.

[0123] <Resistance increase rate of solid-state battery E1>

[0124] For solid-state battery E1, constant current charging is carried out at 0.3C until the voltage equivalent to 40% of the charging depth is reached, and then constant voltage charging is carried out until the current reaches 0.01C. Then, solid-state battery E1 is placed in a thermostatic bath set at 60°C and stored for 2 weeks. The DC resistance is measured before and after storage in the thermostatic bath. The difference between the DC resistance value after storage and the DC resistance value before storage is divided by the DC resistance value before storage and multiplied by 100 to calculate the resistance increase rate (%) before and after storage (resistance increase rate (%) = (DC resistance after storage (Ω) - DC resistance before storage (Ω)) / DC resistance before storage (Ω) × 100). The resistance increase rate of solid-state battery E1 is -2.51%. It should be noted that the DC resistance value is calculated as follows: For solid-state battery E1 that has been charged with constant current at 0.3C until the voltage equivalent to 40% of the charging depth is reached and then charged with constant voltage until the current reaches 0.01C, constant current discharge is carried out at 72C, and the difference between the voltage before discharge and the voltage after 0.1 second of discharge is divided by the current equivalent to 72C to calculate (DC resistance (Ω) = (voltage before discharge (V) - voltage after 0.1 second of discharge (V)) / current equivalent to 72C (A)).

[0125] <<Example 2>>

[0126] <Fabrication of solid electrolyte layer B2>

[0127] The solid electrolyte layer is formed by the same method as in Example 1, and the obtained solid electrolyte layer is left standing in a humidity-controlled glove box with a dew point set at -60°C for a specified time to obtain a solid electrolyte layer B2 adsorbed with moisture. The moisture content and hydroxyl standard value of solid electrolyte layer B2 are shown in Table 1.

[0128] <Fabrication of solid-state battery E2 and resistance increase rate of solid-state battery E2>

[0129] Except for using solid electrolyte layer B2 instead of solid electrolyte layer B1, solid-state battery E2 is fabricated by the same method as in Example 1. In addition, the resistance increase rate of solid-state battery E2 is obtained by the same method as in Example 1. The resistance increase rate of solid-state battery E2 is shown in Table 1.

[0130] <<Example 3>>

[0131] <Fabrication of positive electrode active material layer A2>

[0132] The positive electrode active material layer was formed by the same method as in Example 1, and the obtained positive electrode active material layer was left standing for a specified time in a humidity-controlled glove box with a dew point set at -60°C to obtain a positive electrode active material layer A2 adsorbed with moisture. The moisture content and hydroxyl standard value of the positive electrode active material layer A2 are shown in Table 1.

[0133] <Fabrication of Solid-State Battery E3 and Rate of Increase in Resistance of Solid-State Battery E3>

[0134] A solid-state battery E3 was fabricated by the same method as in Example 1, except that the positive electrode active material layer A2 was used instead of the positive electrode active material layer A1. In addition, the rate of increase in resistance of the solid-state battery E3 was determined by the same method as in Example 1. The rate of increase in resistance of the solid-state battery E3 is shown in Table 1.

[0135] 《Example 4》

[0136] <Fabrication of Solid-State Battery E4 and Rate of Increase in Resistance of Solid-State Battery E4>

[0137] A solid-state battery E4 was fabricated by the same method as in Example 1, except that the positive electrode active material layer A2 was used instead of the positive electrode active material layer A1 and the solid electrolyte layer B2 was used instead of the solid electrolyte layer B1. In addition, the rate of increase in resistance of the solid-state battery E4 was determined by the same method as in Example 1. The rate of increase in resistance of the solid-state battery E4 is shown in Table 1.

[0138] 《Comparative Example 1》

[0139] <Fabrication of Positive Electrode Active Material Layer A3>

[0140] The positive electrode active material layer was formed by the same method as in Example 1, and the obtained positive electrode active material layer was left standing for 15 minutes in a humidity-controlled glove box with a dew point set at -60°C to obtain a positive electrode active material layer A3 adsorbed with moisture. The moisture content and hydroxyl standard value of the positive electrode active material layer A3 are shown in Table 2.

[0141] <Fabrication of Solid Electrolyte Layer B3>

[0142] The solid electrolyte layer was formed by the same method as in Example 1, and the obtained solid electrolyte layer was left standing for 15 minutes in a humidity-controlled glove box with a dew point set at -60°C to obtain a solid electrolyte layer B3 adsorbed with moisture. The moisture content and hydroxyl standard value of the solid electrolyte layer B3 are shown in Table 2.

[0143] <Fabrication of Negative Electrode Active Material Layer C2>

[0144] The negative electrode active material layer was formed by the same method as in Example 1, and the obtained negative electrode active material layer was left standing for 15 minutes in a humidity-controlled glove box with a dew point set at -60°C to obtain a negative electrode active material layer C2 adsorbed with moisture. The moisture content and hydroxyl standard value of the negative electrode active material layer C2 are shown in Table 2.

[0145] <Manufacture of Solid-State Battery e1 and Rate of Increase in Resistance of Solid-State Battery e1>

[0146] The solid-state battery e1 was manufactured by the same method as in Example 1, except that the positive electrode active material layer A3 was used instead of the positive electrode active material layer A1, the solid electrolyte layer B3 was used instead of the solid electrolyte layer B1, and the negative electrode active material layer C2 was used instead of the negative electrode active material layer C1. In addition, the rate of increase in resistance of the solid-state battery e1 was determined by the same method as in Example 1. The rate of increase in resistance of the solid-state battery e1 is shown in Table 2.

[0147] <<Comparative Example 2>>

[0148] <Manufacture of Positive Electrode Active Material Layer A4>

[0149] The positive electrode active material layer adsorbed with moisture, A4, was manufactured by the same method as in Comparative Example 1, except that the obtained positive electrode active material layer was left standing for 30 minutes in a humidity-controlled glove box with a dew point set at -60°C. The moisture content and hydroxyl standard value of the positive electrode active material layer A4 are shown in Table 2.

[0150] <Manufacture of Solid Electrolyte Layer B4>

[0151] The solid electrolyte layer adsorbed with moisture, B4, was manufactured by the same method as in Comparative Example 1, except that the obtained solid electrolyte layer was left standing for 30 minutes in a humidity-controlled glove box with a dew point set at -60°C. The moisture content and hydroxyl standard value of the solid electrolyte layer B4 are shown in Table 2.

[0152] <Manufacture of Negative Electrode Active Material Layer C3>

[0153] The negative electrode active material layer adsorbed with moisture, C3, was manufactured by the same method as in Comparative Example 1, except that the obtained negative electrode active material layer was left standing for 30 minutes in a humidity-controlled glove box with a dew point set at -60°C. The moisture content and hydroxyl standard value of the negative electrode active material layer C3 are shown in Table 2.

[0154] <Manufacture of Solid-State Battery e2 and Rate of Increase in Resistance of Solid-State Battery e2>

[0155] The solid-state battery e2 was fabricated by the same method as in Example 1, except that the positive electrode active material layer A4 was used instead of the positive electrode active material layer A1, the solid electrolyte layer B4 was used instead of the solid electrolyte layer B1, and the negative electrode active material layer C3 was used instead of the negative electrode active material layer C1. Additionally, the rate of increase in resistance of the solid-state battery e2 was determined by the same method as in Example 1. The rate of increase in resistance of the solid-state battery e2 is shown in Table 2.

[0156] <<Comparative Example 3>>

[0157] <<Fabrication of the positive electrode active material layer A5>>

[0158] The positive electrode active material layer A5 was formed on the surface of the aluminum foil by the same method as in Example 1. It should be noted that the positive electrode active material layer A5 was not left standing in a humidity-controlled glove box with a dew point set at -60°C, and no intentional water adsorption was performed.

[0159] <<Fabrication of the solid electrolyte layer B5>>

[0160] The solid electrolyte layer B5 was formed on the surface of the aluminum foil by the same method as in Example 1. It should be noted that the solid electrolyte layer B5 was not left standing in a humidity-controlled glove box with a dew point set at -60°C, and no intentional water adsorption was performed.

[0161] <<Fabrication of the densified laminate d3>>

[0162] The densified laminate was fabricated by the same method as in Example 1, except that the positive electrode active material layer A5 was used instead of the positive electrode active material layer A1 and the solid electrolyte layer B5 was used instead of the solid electrolyte layer B1. The resulting densified laminate was left standing in a humidity-controlled glove box with a dew point set at -60°C for 15 minutes to obtain the densified laminate d3 adsorbed with moisture. The moisture content of the densified laminate d3 is shown in Table 2.

[0163] <<Fabrication of the solid-state battery e3 and the rate of increase in resistance of the solid-state battery e3>>

[0164] The solid-state battery e3 was fabricated by the same method as in Example 1, except that the densified laminate d3 was used instead of the densified laminate D1. Additionally, the rate of increase in resistance of the solid-state battery e3 was determined by the same method as in Example 1. The rate of increase in resistance of the solid-state battery e3 is shown in Table 2.

[0165] <<Comparative Example 4>>

[0166] <<Fabrication of the densified laminate d4>>

[0167] Except for allowing the obtained densified laminate to stand for 30 minutes in a humidity conditioning glove box with a dew point set at -60°C, a densified laminate d4 adsorbed with moisture was produced by the same method as in Comparative Example 3. The moisture content of the densified laminate d4 is shown in Table 2.

[0168] <Fabrication of Solid-State Battery e4 and Rate of Increase in Resistance of Solid-State Battery e4>

[0169] Except for using the densified laminate d4 in place of the densified laminate D1, a solid-state battery e4 was produced by the same method as in Example 1. In addition, the rate of increase in resistance of the solid-state battery e4 was determined by the same method as in Example 1. The rate of increase in resistance of the solid-state battery e4 is shown in Table 2.

[0170] The moisture content, hydroxyl standard value, and rate of increase in resistance of each layer of the solid-state battery are shown in Tables 1 and 2.

[0171]

[0172]

[0173] <<Example 5>>

[0174] <Fabrication of Positive Electrode Active Material Layer A6>

[0175] Except for being placed in a humidity conditioning glove box with a dew point set at -60°C and allowed to stand for 60 minutes, the positive electrode active material layer A6 was produced by the same method as in Example 1.

[0176] <Ratio of Physically Adsorbed Water to Moisture Contained in Positive Electrode Active Material Layer A6>

[0177] For the positive electrode active material layer A6, by temperature-programmed desorption mass spectrometry (TPD-MS), measurement was carried out under the conditions of a measurement temperature of 30 to 500°C and a heating rate of 10°C / minute, and the production rate curve of water (m / z = 18) was determined. Then, as the moisture content of physically adsorbed water, the amount of moisture generated when heated to 100°C was calculated based on the peak area at a measurement temperature of 30 to 100°C of the water production rate curve. Similarly, as the moisture content contained in the positive electrode active material layer, the amount of moisture generated when heated to 120°C was calculated based on the peak area at a measurement temperature of 30 to 120°C of the water production rate curve. The ratio of the moisture content of physically adsorbed water to the moisture content contained in the positive electrode active material layer A6 is 0.70.

[0178] <<Example 6>>

[0179] <Fabrication of Positive Electrode Active Material Layer A7 and Ratio of Physically Adsorbed Water to Moisture Contained in Positive Electrode Active Material Layer A7>

[0180] The positive electrode active material layer produced by the same method as in Example 1 was placed in a humidity-controlled glove box with a dew point set at -50°C and left standing for 60 minutes to obtain a positive electrode active material layer A7 adsorbed with moisture. The ratio of physically adsorbed water to the moisture contained in the positive electrode active material layer A7 was determined by the same method as in Example 5, and the measurement results are shown in Table 3.

[0181]

[0182] In Examples 1 to 4, the positive electrode active material layer and the solid electrolyte layer were respectively adsorbed with a specified amount of moisture, and solid-state batteries were fabricated using them to evaluate the rate of increase in resistance. On the other hand, in Comparative Examples 1 and 2, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer were uniformly adsorbed with moisture under the same conditions, and solid-state batteries were fabricated using them to evaluate the rate of increase in resistance. In addition, in Comparative Examples 3 and 4, the densified laminate was uniformly adsorbed with moisture, and a solid-state battery was fabricated using the densified laminate adsorbed with moisture to evaluate the rate of increase in resistance. It was confirmed that, compared with uniformly adsorbing moisture in all layers or laminates under the same conditions, by separately adsorbing a specified amount of moisture in the positive electrode active material layer and the solid electrolyte layer, an increase in the resistance of the obtained solid-state battery can be suppressed.

[0183] In Examples 5 and 6, the moisture adsorbed on the positive electrode active material layer was analyzed. When the positive electrode active material layer adsorbed moisture in a low dew point environment (dew points of -60°C and -50°C), in the positive electrode active material layer, the amount of physically adsorbed water relative to the amount of moisture contained in the positive electrode active material layer was 0.5 to 0.9, that is, it was confirmed that a large amount of physically adsorbed water was contained in the positive electrode active material layer.

[0184] Although the details are not yet clear, it is speculated that a specified amount of moisture adsorbed on the positive electrode active material layer and the solid electrolyte layer, particularly the large amount of physically adsorbed water contained in the positive electrode active material layer, penetrates to the interface between the positive electrode active material layer and the solid electrolyte layer, and a reaction layer with an appropriate thickness is formed at this interface. By using this reaction layer to suppress the oxidative decomposition of the solid electrolyte during charging, an increase in resistance can be suppressed.

[0185] Preferred embodiments of the solid-state battery and the method for manufacturing the solid-state battery of the present invention are described, but those skilled in the art understand that changes can be made without departing from the claims.

Claims

1. A solid-state battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order, wherein the positive electrode active material layer and the solid electrolyte layer contain moisture, (i) the moisture content of the positive electrode active material layer is 100 to 350 ppm and the moisture content of the solid electrolyte layer is 1500 to 2000 ppm, and / or (ii) the hydroxyl standard value of the positive electrode active material layer is 0.63 to 0.71 and the hydroxyl standard value of the solid electrolyte layer is 0.87 to 1.

04.

2. The solid-state battery according to claim 1, wherein the moisture content of the negative electrode active material layer is 300 ppm or less, and / or the hydroxyl standard value of the negative electrode active material layer is 0.37 or less.

3. The solid-state battery according to claim 1, wherein, The solid electrolyte layer contains a sulfide solid electrolyte.

4. The solid-state battery according to claim 1, wherein a part of the moisture contained in the positive electrode active material layer is physically adsorbed water physically adsorbed on the positive electrode active material layer, and the moisture content of the physically adsorbed water is 0.50 to 0.90 relative to the moisture content contained in the positive electrode active material layer.

5. A method for manufacturing the solid-state battery according to any one of claims 1 to 4, comprising the following steps: in an environment with a dew point of 0°C or lower, causing the positive electrode active material layer and the solid electrolyte layer to adsorb moisture respectively; and stacking the positive electrode active material layer adsorbed with moisture, the solid electrolyte layer adsorbed with moisture, and the negative electrode active material layer in this order to obtain a solid-state battery.

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