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. The solid-state battery sequentially comprises a positive electrode active material layer, a solid electrolyte layer and a negative electrode active material layer, wherein the positive electrode active material layer contains moisture; and the moisture content of the positive electrode active material layer is 500 ppm to 1200 ppm, the hydroxyl group standard value of the positive electrode active material layer is 0.72 to 0.85, or the moisture content of the positive electrode active material layer is 500 ppm to 1200 ppm and the hydroxyl group standard value of the positive electrode active material layer is 0.72 to 0.85.

Description

Technical Field

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

[0002] A solid-state battery is a secondary battery that includes a solid electrolyte as an electrolyte. Compared with a liquid battery that uses an electrolytic solution as an electrolyte, the solid-state battery has attracted attention due to its higher safety. The output power of the solid-state battery is lower than that of the liquid battery. In order to improve the output power, various developments have been made. The following electrochemical elements containing a solid electrolyte are known.

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

[0004] For example, as described in International Publication No. WO 2018 / 026009, it is known that the performance of a solid-state battery is improved by uniformly adsorbing a predetermined amount of moisture in an electrode laminate including a solid electrolyte. However, how to adsorb an appropriate amount of moisture in the positive electrode active material layer (rather than in the entire electrode laminate) has not been fully understood. In addition, the solid-state battery using the positive electrode active material layer and the performance of the solid-state battery have not been fully understood.

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

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

[0007] Aspect 1

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

[0009] the positive electrode active material layer contains moisture; and

[0010] the amount of moisture in the positive electrode active material layer is 500 ppm to 1200 ppm, and / or the hydroxyl standard value of the positive electrode active material layer is 0.72 to 0.85.

[0011] Aspect 2

[0012] The solid-state battery according to Aspect 1, wherein

[0013] (i) The moisture content of the solid electrolyte layer is 300 ppm or less, and the moisture content of the negative electrode active material layer is 300 ppm or less, and / or

[0014] (ii) The hydroxyl standard value of the solid electrolyte layer is 0.55 or less, and the hydroxyl standard value of the negative electrode active material layer is 0.37 or less.

[0015] Aspect 3

[0016] The solid-state battery according to Aspect 1 or 2, wherein the solid electrolyte layer contains a sulfide solid electrolyte.

[0017] Aspect 4

[0018] The solid-state battery according to any one of Aspects 1 to 3, wherein:

[0019] A part of the moisture contained in the positive electrode active material layer is physically adsorbed water physically adsorbed in the positive electrode active material layer; and

[0020] Relative to the moisture content contained in the positive electrode active material layer, the moisture content of the physically adsorbed water is 0.5 to 0.9.

[0021] Aspect 5

[0022] The method for manufacturing a solid-state battery according to any one of Aspects 1 to 4, the manufacturing method comprising:

[0023] Adsorbing moisture into the positive electrode active material layer in an environment with a dew point of 0 °C or lower; and

[0024] Stacking the positive electrode active material layer adsorbed with moisture, the solid electrolyte layer, and the negative electrode active material layer in this order to obtain the solid-state battery.

[0025] By using the solid-state battery in the present disclosure, an increase in resistance can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described below with reference to the drawings, in which the same reference numerals denote the same elements, wherein:

[0027] Figure 1 is a conceptual diagram for describing the solid-state battery in the present disclosure. DETAILED DESCRIPTION

[0028] Embodiments of the present disclosure will be described in detail below. The present disclosure is not limited to the embodiments described below, and various modifications can be made within the scope of the gist of the present disclosure during implementation. In addition, in the description of the drawings, the same reference numerals denote the same elements, and repeated descriptions are omitted.

[0029] In the present disclosure, a "composite material" refers to a composition that can directly or by further containing other components form a positive electrode active material layer or the like. In addition, in the present disclosure, a "composite material slurry" refers to a slurry that contains a dispersion medium in addition to the "composite material" and can form a positive electrode active material layer or the like by coating and drying.

[0030] In the present disclosure, a "solid-state battery" refers to a battery that uses at least a solid electrolyte as an electrolyte. Therefore, in a solid-state battery, a combination of a solid electrolyte and a liquid electrolyte can be used as the electrolyte. In addition, the solid-state battery in the present disclosure can be an all-solid-state battery, that is, a battery that uses only a solid electrolyte as the electrolyte.

[0031] Solid-state battery

[0032] The solid-state battery in the present disclosure sequentially includes a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, wherein:

[0033] the positive electrode active material layer contains moisture; and

[0034] the moisture content of the positive electrode active material layer is 500 ppm to 1200 ppm, and / or the hydroxyl standard value of the positive electrode active material layer is 0.72 to 0.85.

[0035] By using the solid-state battery in the present disclosure, an increase in resistance can be suppressed.

[0036] Although not limited by theory, it is speculated that a predetermined amount of moisture adsorbed 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 the interface. The reaction layer inhibits the oxidative decomposition of the solid electrolyte during charging, thereby suppressing an increase in resistance.

[0037] Figure 1 It is a conceptual diagram showing one aspect of the solid-state battery in the present disclosure. The solid-state battery in the present disclosure is not limited to this aspect.

[0038] The solid-state battery 100 sequentially includes a positive electrode active material layer 110, a solid electrolyte layer 120, and a negative electrode active material layer 130. The positive electrode active material layer 110 contains a predetermined amount of moisture. Since the positive electrode active material layer 110 contains a predetermined amount of moisture, an increase in the resistance of the solid-state battery can be suppressed.

[0039] Constitution of a solid-state battery

[0040] The solid-state battery in the present disclosure sequentially includes a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer. The solid-state battery in the present disclosure may optionally include a positive electrode current collector layer and a negative electrode current collector layer, and may sequentially include 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.

[0041] Positive electrode current collector layer

[0042] The material used in the positive electrode current collector layer is not particularly limited. Generally used materials for the positive electrode current collector of a solid-state battery can be appropriately adopted. Examples of the material used in the positive electrode current collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel, but are not limited thereto. In addition, the positive electrode current collector layer may include a certain coating on its surface, for example, for adjusting resistance. In addition, the positive electrode current collector layer may be a layer obtained by plating or depositing one of the above metals on a metal foil or substrate.

[0043] The shape of the positive electrode current collector layer is not particularly limited, and may include, for example, foil-like, plate-like, and mesh-like. Among them, foil-like is preferred.

[0044] The thickness of the positive electrode current collector layer is not particularly limited. The thickness of the positive electrode current collector layer may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

[0045] Positive electrode active material layer

[0046] 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. In addition, the positive electrode active material layer may contain various additives. The respective contents 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 expected battery performance. For example, when the whole (the whole solid component) of the positive electrode active material layer is 100% by mass, the content of the positive electrode active material may be 40% by mass or more, 50% by mass or more, or 60% by mass or more, and may be less than 100% by mass or 90% by mass or less.

[0047] Moisture content of the positive electrode active material layer

[0048] In the solid-state battery of the present disclosure, the moisture content of the positive electrode active material layer is from 500 ppm to 1200 ppm. From the viewpoint of forming the reaction layer, the moisture content of the positive electrode active material layer may be 500 ppm or more, 700 ppm or more, 900 ppm or more, or 1100 ppm or more; from the viewpoint of suppressing hydrolysis of the solid electrolyte, the moisture content of the positive electrode active material layer may be 1200 ppm or less or 1150 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 evaporation apparatus VA-300 manufactured by Nitto Seiko Co., Ltd.). Specifically, the positive electrode active material layer is heated to 200 °C by the moisture evaporation apparatus VA-300, and the moisture generated by heating is measured by the Karl Fischer apparatus CA-310, whereby the moisture content can be evaluated.

[0049] Hydroxyl standard value of the positive electrode active material layer

[0050] In the solid-state battery of the present disclosure, the hydroxyl standard value of the positive electrode active material layer is from 0.72 to 0.85. From the viewpoint of forming the reaction layer, the hydroxyl standard value of the positive electrode active material layer may be 0.72 or more, 0.76 or more, 0.80 or more, or 0.83 or more; from the viewpoint of suppressing hydrolysis of the solid electrolyte, the hydroxyl standard value of the positive electrode active material layer may be 0.85 or less or 0.84 or less. 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 by 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.

[0051] Moisture content of physically adsorbed water relative to the moisture content contained in the positive electrode active material layer

[0052] Although there is no particular limitation, a part of the moisture contained in the positive electrode active material layer may be physically adsorbed water physically adsorbed in the positive electrode active material layer. The amount of moisture of the physically adsorbed water is not particularly limited, and relative to the amount of moisture contained in the positive electrode active material layer, the amount of moisture of the physically adsorbed water 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 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 be 0.90 or less, 0.85 or less, 0.80 or less, or 0.75 or less. 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 measured by temperature-programmed desorption mass spectrometry (TPD-MS) at a measurement temperature of 30°C to 500°C and a heating rate of 10°C / min, and evaluated from the obtained production rate curve of water (m / z = 18). Specifically, from the peak area at the measurement temperature of 30°C to 100°C of the production rate curve of water, the amount of moisture generated when heated to 100°C is calculated as the amount of physically adsorbed water. Next, from the peak area at the measurement temperature of 30°C to 120°C of the production rate curve of water, the amount of moisture generated when heated to 120°C is calculated as the amount of moisture contained in the positive electrode active material layer. Then, from the calculated amounts of moisture, the amount of physically adsorbed water relative to the amount of moisture contained in the positive electrode active material layer can be calculated and evaluated.

[0053] Positive electrode active material

[0054] There is no particular limitation on the material of the positive electrode active material as long as it can store and release lithium ions. Examples of the positive electrode active material include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), lithium nickel cobalt manganese oxide (NCM: LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2), lithium nickel cobalt aluminum oxide (LiNi 0.8 (CoAl) 0.2 O2), and Li-Mn spinel in which a foreign element substitution 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 thereto.

[0055] Although not particularly limited, the positive electrode active material may include a coating layer. The coating layer is a layer containing a substance having lithium ion conductivity, low reactivity with the positive electrode active material or the solid electrolyte, and not flowing even when the substance comes into contact with the active material or the solid electrolyte and capable of maintaining the shape of the coating layer. Specific examples of the material constituting the coating layer include LiNbO3, Li4Ti5O 12 , Li3PO4, and Li-Ti-Al-F materials, but are not limited thereto.

[0056] The shape of the positive electrode active material is not particularly limited as long as it is a general shape of the positive electrode active material of a solid-state battery. For example, the positive electrode active material may have a particulate shape. The positive electrode active material may have primary particles or may have secondary particles in which a plurality of primary particles are aggregated. For example, the average particle diameter D 50 may be 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. The average particle diameter D 50 is the particle diameter (median particle diameter) at which the cumulative value is 50% in the volume-based particle size distribution evaluated by the laser diffraction / scattering method.

[0057] Solid electrolyte

[0058] The material of the solid electrolyte is not particularly limited. For example, it may be a sulfide solid electrolyte, an oxide solid electrolyte, a polymer electrolyte, or the like.

[0059] Examples of the sulfide solid electrolyte include sulfide amorphous solid electrolytes, sulfide crystalline solid electrolytes, and thiargillite solid electrolytes, but are not limited thereto. Specific examples of the sulfide solid electrolyte include Li2S-P2S5 (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 and combinations thereof, but are not limited thereto.

[0060] Examples of the oxide solid electrolyte include Li7La3Zr2O12 , Li 7−x La3Zr 1−x Nb x O 12 , Li 7− 3x La3Zr2Al x O 12 , Li 3x 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 and Li 3+x PO 4− x N x (LiPON), but not limited thereto.

[0061] The sulfide solid electrolyte and the oxide solid electrolyte may be glass, or may be crystalline glass (glass ceramic).

[0062] Examples of the polymer electrolyte include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers of polyethylene oxide and polypropylene oxide, but are not limited thereto.

[0063] Conductive additive

[0064] The conductive additive is not particularly limited. Examples of the conductive additive include vapor-grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotube (CNT), carbon nanofiber (CNF), and conductive carbon, but are not limited thereto. The conductive additive may have, for example, a particulate or fibrous form, and the size of the particles or fibers is not particularly limited. Although not particularly limited, as the conductive additive, only one kind may be used, or two or more kinds may be used in combination.

[0065] Binder

[0066] The binder is not particularly limited. The binder may be composed of, for example, materials such as polyvinylidene fluoride (PVdF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), and styrene-butadiene rubber (SBR), but is not limited thereto. Although not particularly limited, as the binder, only one kind may be used, or two or more kinds may be used in combination.

[0067] The shape of the positive electrode active material layer is not particularly limited. For example, a sheet-shaped positive electrode active material layer having a substantially flat surface can be used. The thickness of the positive electrode active material layer is not particularly limited. For example, the thickness of the positive electrode active material layer can be 0.1 μm or more, 1 μm or more, or 10 μm or more, and can be 2 mm or less, 1 mm or less, or 500 μm or less.

[0068] The positive electrode active material layer can be manufactured by known methods. The positive electrode active material layer can be easily formed, for example, by dry or wet forming of a positive electrode composite material containing the above various components. The positive electrode active material layer can be formed together with the positive electrode current collector layer, or can be formed separately from the positive electrode current collector layer.

[0069] Solid electrolyte layer

[0070] The solid electrolyte layer contains at least a solid electrolyte, and may contain a conductive additive, a binder, etc. as needed. The solid electrolyte layer is not particularly limited, and preferably should contain a sulfide solid electrolyte.

[0071] Moisture content of the solid electrolyte layer

[0072] The moisture content of the solid electrolyte layer is not particularly limited, and can be 300 ppm or less. In addition, the moisture content of the solid electrolyte layer can be 0 ppm or more, 1 ppm or more, 10 ppm or more, 50 ppm or more, or 100 ppm or more, and can be 300 ppm or less, 280 ppm or less, 260 ppm or less, or 240 ppm or less. Regarding the measurement of the moisture content of the solid electrolyte layer, reference can be made to the description in "Moisture content of the positive electrode active material layer" above.

[0073] Hydroxyl standard value of the solid electrolyte layer

[0074] The hydroxyl standard value of the solid electrolyte layer is not particularly limited, and can be 0.55 or less. In addition, the hydroxyl standard value of the solid electrolyte layer can be 0.460 or more, 0.461 or more, 0.470 or more, 0.480 or more, or 0.500 or more, and can be 0.550 or less, 0.543 or less, 0.537 or less, or 0.530 or less. Regarding the measurement of the hydroxyl standard value of the solid electrolyte layer, reference can be made to the description in "Hydroxyl standard value of the positive electrode active material layer" above.

[0075] Regarding the solid electrolyte, conductive additive, and binder, reference can be made to the description in "Positive electrode active material layer" above.

[0076] The thickness of the solid electrolyte layer is not particularly limited. For example, the thickness of the solid electrolyte layer may be 0.1 μm or more, 1 μm or more, or 10 μm or more, and may be 2 mm or less, 1 mm or less, or 500 μm or less.

[0077] The solid electrolyte layer can be easily formed, for example, by dry or wet forming of a solid electrolyte composite material containing the above solid electrolyte, binder, etc.

[0078] Negative electrode active material layer

[0079] 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. In addition, the negative electrode active material layer may contain various additives. The respective contents of the negative electrode active material, conductive assistant, binder, solid electrolyte, etc. in the negative electrode active material layer can be appropriately determined according to the expected battery performance. For example, when the whole (total solid content) of the negative electrode active material layer is 100% by mass, the content of the negative electrode active material may be 40% by mass or more, 50% by mass or more, or 60% by mass or more, and may be 100% by mass or less or 90% by mass or less.

[0080] Moisture content of the negative electrode active material layer

[0081] The moisture content of the negative electrode active material layer is not particularly limited, and may be 300 ppm or less. In addition, the moisture content of the negative electrode active material layer may 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 may 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 in "Moisture content of the positive electrode active material layer" above.

[0082] Hydroxyl standard value of the negative electrode active material layer

[0083] The hydroxyl standard value of the negative electrode active material layer is not particularly limited, and may be 0.37 or less. In addition, the hydroxyl standard value of the negative electrode active material layer may be 0.01 or more, 0.02 or more, 0.04 or more, 0.06 or more, or 0.08 or more, and may 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 in "Hydroxyl standard value of the positive electrode active material layer" above.

[0084] Negative electrode active material

[0085] As the negative electrode active material, various substances can be used in which the potential for storing and releasing lithium ions (charge-discharge potential) is lower than that of the above-described positive electrode active material in the present disclosure. The material of the negative electrode active material is not particularly limited, and it may be metallic lithium, or it may be a material capable of storing and releasing metal ions (such as lithium ions). Examples of materials capable of storing and releasing metal ions (such as lithium ions) include alloy-based negative electrode active materials, carbon materials, and lithium titanate (Li4Ti5O 12 ), but are not limited thereto.

[0086] The alloy-based negative electrode active material is not particularly limited, and examples of the alloy-based negative electrode active material include Si alloy-based negative electrode active materials and Sn alloy-based negative electrode active materials. Examples of the Si alloy-based negative electrode active material include silicon, silicon oxide, silicon carbide, silicon nitride, and solid solutions thereof. In addition, the Si alloy-based negative electrode active material may contain metal elements other than silicon, for example, it may contain Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, Ti, etc. Examples of the Sn alloy-based negative electrode active material include tin, tin oxide, tin nitride, and solid solutions thereof. In addition, the Sn alloy-based negative electrode active material may contain metal elements other than tin, for example, it may contain Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, Si, etc.

[0087] The carbon material is not particularly limited, and examples of the carbon material include hard carbon, soft carbon, and graphite.

[0088] The shape of the negative electrode active material is not particularly limited, and the general shape of the negative electrode active material of the solid-state battery can be adopted. For example, the negative electrode active material may have a particulate shape, or may have a flaky shape.

[0089] Regarding the solid electrolyte, conductive additive, and binder that may be contained in the negative electrode active material layer, reference may be made to the description in "positive electrode active material layer" above.

[0090] The shape of the negative electrode active material layer is not particularly limited. For example, a flaky negative electrode active material layer having a substantially flat surface can be adopted. The thickness of the negative electrode active material layer is not particularly limited. For example, the thickness of the negative electrode active material layer may be 0.1 μm or more, 1 μm or more, or 10 μm or more, and may be 2 mm or less, 1 mm or less, or 500 μm or less.

[0091] The negative electrode active material layer can be manufactured using known methods. The negative electrode active material layer can be easily formed, for example, by dry or wet forming of a negative electrode composite material containing the above components. The negative electrode active material layer can be formed together with the negative electrode current collector layer, or can be formed separately from the negative electrode current collector layer.

[0092] Negative electrode current collector layer

[0093] There is no particular limitation on the material used in the negative electrode current collector layer. Generally used materials for the negative electrode current collector of a solid-state battery can be appropriately employed. Examples of materials used in the negative electrode current collector layer include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and carbon sheets, but are not limited thereto. The negative electrode current collector layer can include a coating on its surface, for example, for adjusting resistance.

[0094] The shape of the negative electrode current collector layer is not particularly limited, and can include, for example, foil shape, plate shape, and mesh shape. Among them, foil shape is preferred.

[0095] The thickness of the negative electrode current collector layer is not particularly limited. The thickness of the negative electrode current collector layer can be 0.1 μm or more or 1 μm or more, and can be 1 mm or less or 100 μm or less.

[0096] The shape, etc. of the solid-state battery

[0097] Examples of the shape of the solid-state battery include coin type, laminated type, cylindrical type, and square type, but are not limited thereto.

[0098] Manufacturing method of the solid-state battery

[0099] The solid-state battery in the present disclosure can be manufactured by a manufacturing method including the following steps:

[0100] In an environment with a dew point of 0 °C or lower, adsorb moisture into the positive electrode active material layer; and

[0101] Stack the positive electrode active material layer in which moisture has been adsorbed, the solid electrolyte layer, and the negative electrode active material layer in sequence, thereby obtaining the solid-state battery.

[0102] Using the manufacturing method of the solid-state battery in the present disclosure, a solid-state battery capable of suppressing an increase in resistance can be manufactured.

[0103] Method for adsorbing moisture

[0104] As a method for adsorbing moisture into the positive electrode active material layer, for example, the positive electrode active material layer can be placed in a glove box or the like in which the humidity is adjusted to a dew point of -60 °C for a predetermined time to adsorb moisture, but the method for adsorbing moisture into the positive electrode active material layer is not limited thereto.

[0105] From the viewpoint of suppressing the structural change of the solid electrolyte, in an environment where moisture adheres to the positive electrode active material layer, the dew point can be 0°C or lower, -10°C or lower, -30°C or lower, or -50°C or lower, and can be -80°C or higher, -75°C or higher, -70°C or higher, or -65°C or higher.

[0106] The time for moisture to adhere to the positive electrode active material layer is not particularly limited. The time for moisture to adhere to the positive electrode active material layer can be 1 second or longer, 10 seconds or longer, 30 seconds or longer, 1 minute or longer, 10 minutes or longer, 30 minutes or longer, or 1 hour or longer, and can be 5 hours or shorter, 3 hours or shorter, 1 hour or shorter, or 30 minutes or shorter.

[0107] Lamination method

[0108] As a method for laminating the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer, specifically, for example, on each surface of the negative electrode active material layer formed on two surfaces of the negative electrode current collector, the solid electrolyte layer formed on a substrate is overlapped and pressed, the solid electrolyte layer is transferred onto the surface of the negative electrode active material layer, and the substrate in contact with the solid electrolyte layer is removed, thereby laminating the solid electrolyte layer on the negative electrode active material layer. Next, on each surface of the solid electrolyte layer laminated on two surfaces of the negative electrode active material layer, the positive electrode active material layer formed on a substrate is overlapped and pressed, the positive electrode active material layer is transferred onto the surface of the solid electrolyte layer, and the substrate in contact with the positive electrode active material layer is removed, thereby laminating the positive electrode active material layer on the solid electrolyte layer. However, the method for laminating the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is not limited thereto.

[0109] The above laminate can be used as a solid-state battery. Alternatively, a positive electrode current collector layer and / or a negative electrode current collector layer can be provided as needed on the laminate in which the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer are laminated, and it can be encapsulated with a laminated film and used as a solid-state battery. Although not particularly limited, the solid-state battery can be constrained, for example, at a constraint pressure of 5 MPa.

[0110] The present disclosure will be described in more detail with reference to the following examples. The scope of the present disclosure is not limited to the examples.

[0111] Moisture content of positive electrode active material layer, solid electrolyte layer, negative electrode active material layer, and densified laminate

[0112] The moisture content of each of the above layers and the above laminate was measured using a Karl Fischer apparatus (Karl Fischer apparatus CA-310 and moisture evaporation apparatus VA-300 manufactured by Nitto Seiko Co., Ltd.). Specifically, the measurement sample was heated to 200 °C by the moisture evaporation apparatus VA-300, and the moisture generated by heating was measured by the Karl Fischer apparatus CA-310, thereby evaluating the moisture content.

[0113] Hydroxyl standard value of the positive electrode active material layer

[0114] 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 were measured by Fourier transform infrared spectroscopy (FT-IR), and the ratio of the absorbance at 3300 cm -1 to the absorbance at 1180 cm -1 was calculated as the hydroxyl standard value of the positive electrode active material layer.

[0115] Example 1

[0116] Manufacture of the positive electrode active material layer A1

[0117] LiNi coated with Li-Ti-Al-F material as the positive electrode active material 0.8 (CoAl) 0.2 O2, Li2S-P2S5 glass ceramic as the solid electrolyte, conductive carbon as the conductive additive, binder, dispersant, and an appropriate amount of solvent were mixed, and a dispersion process was performed using an ultrasonic homogenizer to prepare a positive electrode composite slurry. Next, the obtained positive electrode composite slurry was coated on an aluminum foil by die coating and dried, thereby forming a positive electrode active material layer on one surface of the aluminum foil. The obtained positive electrode active material layer was placed in a humidity-controlled glove box with a dew point set to -60 °C for a predetermined time to obtain a positive electrode active material layer A1 adsorbed with moisture. The moisture content of the positive electrode active material layer A1 was 576 ppm, and the hydroxyl standard value was 0.73.

[0118] Manufacture of the solid electrolyte layer B1

[0119] Mix the LiI-LiBr-Li2S-P2S5 glass ceramic (average particle size: 2.5 μm) serving as a solid electrolyte, conductive carbon serving as a conductive additive, a binder, a dispersant, and an appropriate amount of solvent, and perform a dispersion process using an ultrasonic homogenizer to prepare a solid electrolyte composite slurry. Next, coat the obtained solid electrolyte composite slurry on an aluminum foil by die coating and dry it to form a solid electrolyte layer B1 on one side of the aluminum foil. Do not place the solid electrolyte layer B1 in a humidity-controlled glove box with a dew point set to -60°C, and do not perform intentional moisture adsorption. The moisture content of the solid electrolyte layer B1 is 235 ppm, and the hydroxyl standard value is 0.53.

[0120] Manufacture of the negative electrode active material layer C1

[0121] Mix Li4Ti5O 12 particles serving as a negative electrode active material, the Li2S-P2S5 glass ceramic serving as a solid electrolyte, conductive carbon serving as a conductive additive, a binder, a dispersant, and an appropriate amount of solvent, and perform a dispersion process using an ultrasonic homogenizer to prepare a negative electrode composite slurry. Next, coat the obtained negative electrode composite slurry on an aluminum foil serving as a negative electrode current collector by die coating and dry it to form a negative electrode active material layer on one surface of the aluminum foil. Thereafter, coat the negative electrode composite slurry on the surface of the aluminum foil where the negative electrode active material layer is not formed by die coating and dry it to form a negative electrode active material layer C1 on both surfaces of the aluminum foil. Do not place the negative electrode active material layer C1 in a humidity-controlled glove box with a dew point set to -60°C, and do not perform intentional moisture adsorption. The moisture content of the negative electrode active material layer C1 is 205 ppm, and the hydroxyl standard value is 0.10. Adjust the basis weight of the negative electrode active material layer such that when the charge specific capacity of the positive electrode active material layer is 200 mAh / g, the charge specific capacity of the negative electrode active material layer is 1 times that of the positive electrode active material layer.

[0122] Manufacture of the densified laminate D1

[0123] The solid electrolyte layer B1 is overlapped and pressed on the respective surfaces of the negative electrode active material layer C1 formed on the two surfaces of the aluminum foil serving as the negative electrode current collector, the solid electrolyte layer B1 is transferred onto the surface of the negative electrode active material layer C1, and the aluminum foil in contact with the solid electrolyte layer B1 is removed, thereby laminating the solid electrolyte layer B1 on the negative electrode active material layer C1. Next, the positive electrode active material layer A1 is overlapped and pressed on the respective surfaces of the solid electrolyte layer B1 laminated on the two surfaces of the negative electrode active material layer C1, the positive electrode active material layer A1 is transferred onto the surface of the solid electrolyte layer B1, and the aluminum foil in contact with the positive electrode active material layer A1 is removed, thereby laminating the positive electrode active material layer A1 on the solid electrolyte layer B1. The produced laminate is roll-pressed at 175 °C and 5 tons / cm, thereby producing a densified laminate D1.

[0124] Manufacture of solid-state battery E1

[0125] The carbon-coated aluminum foil serving as the positive electrode current collector is disposed on the respective surfaces of the positive electrode active material layer A1 of the densified laminate D1 and pressed at 140 °C and 5 MPa for 5 minutes, thereby obtaining a power generation element. In the power generation element, the positive electrode current collector layer, the positive electrode active material layer A1, the solid electrolyte layer B1, the negative electrode active material layer C1, the negative electrode current collector layer, the negative electrode active material layer C1, the solid electrolyte layer B1, the positive electrode active material layer A1, and the positive electrode current collector layer are laminated in sequence. The obtained power generation element is encapsulated with a laminated film and constrained at 5 MPa, thereby manufacturing the solid-state battery E1.

[0126] Rate of increase in resistance of solid-state battery E1

[0127] The solid-state battery E1 was charged at a constant current of about 0.3C until the voltage reached the voltage corresponding to a charge level of 40%, and then charged at a constant voltage until the current reached a current of 0.01C. Thereafter, the solid-state battery E1 was placed in a thermostatic bath with the temperature set at 60°C and stored for two weeks. The DC resistance before and after storage in the thermostatic bath was measured. The difference between the DC resistance value after storage and the DC resistance value before storage was divided by the DC resistance value before storage, and then 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 the solid-state battery E1 was -1.26%. The DC resistance value was calculated as follows. For the solid-state battery E1 after constant current charging at about 0.3C until the voltage reached the voltage corresponding to a charge depth of 40%, followed by constant voltage charging until the current reached 0.01C, it was discharged at a constant current of about 72C, and the difference between the voltage before discharge and the voltage 0.1 seconds after discharge was divided by the current equivalent to 72C (DC resistance (Ω) = (voltage before discharge (V) - voltage 0.1 seconds after discharge (V)) / current equivalent to 72C (A)).

[0128] Example 2

[0129] Manufacture of the positive electrode active material layer A2

[0130] 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 placed in a humidity-controlled glove box with a dew point set at -60°C for a predetermined time to obtain the 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.

[0131] Manufacture of the solid-state battery E2 and the resistance increase rate of the solid-state battery E2

[0132] The solid-state battery E2 was manufactured 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 resistance increase rate of the solid-state battery E2 was evaluated by the same method as in Example 1. The resistance increase rate of the solid-state battery E2 is shown in Table 1.

[0133] Example 3

[0134] Manufacture of the positive electrode active material layer A3

[0135] 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 placed in a humidity-controlled glove box with a dew point set to -60°C for a predetermined time 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 1.

[0136] Manufacture of solid-state battery E3 and rate of increase in resistance of solid-state battery E3

[0137] A solid-state battery E3 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. In addition, the rate of increase in resistance of the solid-state battery E3 was evaluated 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.

[0138] Comparative Example 1

[0139] Manufacture of positive electrode active material layer A4

[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 placed in a humidity-controlled glove box with a dew point set to -60°C for a predetermined time to obtain a positive electrode active material layer A4 adsorbed with moisture. The moisture content and hydroxyl standard value of the positive electrode active material layer A4 are shown in Table 1.

[0141] Manufacture of solid-state battery e1 and rate of increase in resistance of solid-state battery e1

[0142] A solid-state battery e1 was manufactured 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. In addition, the rate of increase in resistance of the solid-state battery e1 was evaluated by the same method as in Example 1. The rate of increase in resistance of the solid-state battery e1 is shown in Table 1.

[0143] Comparative Example 2

[0144] Manufacture of positive electrode active material layer A5

[0145] 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 placed in a humidity-controlled glove box with a dew point set to -60°C for 15 minutes to obtain a positive electrode active material layer A5 adsorbed with moisture. The moisture content and hydroxyl standard value of the positive electrode active material layer A5 are shown in Table 1.

[0146] Manufacture of solid electrolyte layer B2

[0147] The solid electrolyte layer was formed by the same method as in Example 1, and the obtained solid electrolyte layer was placed in a humidity-controlled glove box with a dew point set to -60°C for 15 minutes, thereby obtaining a solid electrolyte layer B2 adsorbed with moisture. The moisture content and hydroxyl standard value of the solid electrolyte layer B2 are shown in Table 1.

[0148] Manufacture of the negative electrode active material layer C2

[0149] 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 placed in a humidity-controlled glove box with a dew point set to -60°C for 15 minutes, thereby obtaining 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 1.

[0150] Manufacture of the solid-state battery e2 and the resistance increase rate of the solid-state battery e2

[0151] The solid-state battery e2 was manufactured 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, the solid electrolyte layer B2 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 resistance increase rate of the solid-state battery e2 was evaluated by the same method as in Example 1. The resistance increase rate of the solid-state battery e2 is shown in Table 1.

[0152] Comparative Example 3

[0153] Manufacture of the positive electrode active material layer A6

[0154] The positive electrode active material layer A6 was formed on the surface of the aluminum foil by the same method as in Example 1. The positive electrode active material layer A6 was not placed in a humidity-controlled glove box with a dew point set to -60°C, and no intentional moisture adsorption was performed.

[0155] Manufacture of the densified laminate d3

[0156] The densified laminate was manufactured by the same method as in Example 1, except that the positive electrode active material layer A6 was used instead of the positive electrode active material layer A1. The obtained densified laminate was placed in a humidity-controlled glove box with a dew point set to -60°C for 15 minutes, thereby obtaining a densified laminate d3 adsorbed with moisture. The moisture content of the densified laminate d3 is shown in Table 1.

[0157] Manufacture of the solid-state battery e3 and the resistance increase rate of the solid-state battery e3

[0158] A 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 evaluated 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.

[0159]

[0160] Example 4

[0161] Fabrication of the positive electrode active material layer A7

[0162] The positive electrode active material layer A7 was fabricated by the same method as in Example 1, except that the positive electrode active material layer A7 was placed in a humidity-controlled glove box with a dew point set at -60 °C and left for 60 minutes.

[0163] Ratio of physically adsorbed water to the water contained in the positive electrode active material layer A7

[0164] The positive electrode active material layer A7 was measured by temperature-programmed desorption mass spectrometry (TPD-MS) at a measurement temperature of 30 °C to 500 °C and a heating rate of 10 °C / min to evaluate the production rate curve of water (m / z = 18). Next, the amount of water generated when heated to 100 °C was calculated from the peak area in the measurement temperature range of 30 °C to 100 °C of the water production rate curve as the amount of physically adsorbed water. Similarly, the amount of water generated when heated to 120 °C was calculated from the peak area in the measurement temperature range of 30 °C to 120 °C of the water production rate curve as the amount of water contained in the positive electrode active material layer. The ratio of the amount of physically adsorbed water to the amount of water contained in the positive electrode active material layer A7 was 0.70.

[0165] Example 5

[0166] Fabrication of the positive electrode active material layer A8 and ratio of physically adsorbed water to the water contained in the positive electrode active material layer A8

[0167] The positive electrode active material layer A8 was fabricated by the same method as in Example 1, except that the positive electrode active material layer A8 was placed in a humidity-controlled glove box with a dew point set at -50 °C and left for 60 minutes. The ratio of the amount of physically adsorbed water to the amount of water contained in the positive electrode active material layer A8 was evaluated by the same method as in Example 4. The measurement results are shown in Table 2.

[0168]

[0169] In Examples 1 to 3 and Comparative Example 1, a predetermined amount of moisture was adsorbed in the positive electrode active material layer, a solid-state battery was manufactured using the positive electrode active material layer, and the resistance increase rate was evaluated. On the other hand, in Comparative Example 2, moisture was uniformly adsorbed in the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer under the same conditions, a solid-state battery was manufactured using the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer, and the resistance increase rate was evaluated. Further, in Comparative Example 3, moisture was uniformly adsorbed in the densified laminate, a solid-state battery was manufactured using the densified laminate, and the resistance increase rate was evaluated.

[0170] From Examples 1 to 3 and Comparative Example 1, it was confirmed that in a solid-state battery using a positive electrode active material layer containing a predetermined amount or more of moisture, an increase in resistance could be suppressed. Further, from Examples 1 to 3 and Comparative Examples 2 and 3, it was confirmed that when a predetermined amount of moisture was adsorbed in the positive electrode active material layer, an increase in resistance in the obtained solid-state battery could be suppressed as compared with uniformly adsorbing moisture in all layers or in the laminate under the same conditions. It was confirmed that even when the total moisture content of each layer was shown to be the same value, there were large differences in the resistance increase rates in Examples 1 and 2 and Comparative Example 2.

[0171] In each of Examples 4 and 5, the moisture adsorbed in the positive electrode active material layer was analyzed. It was confirmed that when moisture was adsorbed into the positive electrode active material layer in an environment with a low dew point (dew point of -60°C or -50°C), the amount of physically adsorbed water in the positive electrode active material layer was 0.5 to 0.9 with respect to the amount of moisture contained in the positive electrode active material layer, that is, the positive electrode active material layer contained a large amount of physically adsorbed water.

[0172] Although the details are not clear, it is presumed that a predetermined amount of moisture adsorbed in the positive electrode active material layer, particularly a 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 having an appropriate thickness is formed at the interface, and the reaction layer suppresses the oxidative decomposition of the solid electrolyte during charging, thereby enabling suppression of an increase in resistance.

[0173] Preferred embodiments of the solid-state battery and the method for manufacturing the solid-state battery in the present disclosure have been described. However, those skilled in the art understand that modifications can be made without departing from the scope of the claims.

Claims

1. A solid - state battery, sequentially comprising a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, wherein: the positive electrode active material layer contains moisture; and the moisture content of the positive electrode active material layer is from 500 ppm to 1200 ppm, and / or the hydroxyl standard value of the positive electrode active material layer is from 0.72 to 0.

85.

2. The solid - state battery according to claim 1, wherein (i) the moisture content of the solid electrolyte layer is 300 ppm or less, and the moisture content of the negative electrode active material layer is 300 ppm or less, and / or (ii) the hydroxyl standard value of the solid electrolyte layer is 0.55 or less, and 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 in the positive electrode active material layer; and relative to the moisture content of the positive electrode active material layer, the moisture content of the physically adsorbed water is from 0.50 to 0.

90.

5. A method for manufacturing the solid - state battery according to any one of claims 1 to 4, the manufacturing method comprising: adsorbing moisture into the positive electrode active material layer in an environment with a dew point of 0 °C or lower; and sequentially laminating the positive electrode active material layer adsorbed with moisture, the solid electrolyte layer, and the negative electrode active material layer to obtain the solid - state battery.

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