Solid-state battery

Abstract

An object of the present disclosure is to provide a solid-state battery capable of reducing the resistance increase rate of the battery due to endurance without significantly increasing the initial direct current resistance.SOLUTION: A solid-state battery in which a positive electrode current collector layer 110, a positive electrode active material layer 120, a solid electrode layer 130, a negative electrode active material layer 140, and a negative electrode current collector layer 150 are stacked in this order, the positive electrode active material layer 120 and the solid electrode layer 130 contain sulfide solid electrolyte particles, and M represented by the following Formula 1 is 1.15 to 3.00: M = M1 / M2 Formula 1M1: M2: The ratio of the number of oxygen atom (s) to the number of atom (s) of a specific type of element constituting the sulfide solid electrolytic particles in the center of the solid electrolytic layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to solid-state batteries. [Background technology]

[0002] Solid-state batteries are secondary batteries that contain a solid electrolyte as an electrolyte, and have attracted attention because they are safer than liquid-based batteries that use an electrolytic solution as an electrolyte. Various developments have been made to improve the output of solid-state batteries, and the following electrochemical elements containing solid electrolytes are known.

[0003] Patent Document 1 discloses 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, the moisture content of the laminate being 0.001% by mass or more and less than 0.3% by mass with respect to the laminate. The electrochemical element in Patent Document 1 is said to be able to maintain operation when a high voltage is applied. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 026009 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a solid-state battery that can reduce the rate of increase in resistance of the battery due to endurance without significantly increasing the initial DC resistance. [Means for solving the problem]

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

[0007] <Aspect 1> 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 stacked in this order; the positive electrode active material layer and the solid electrolyte layer contain sulfide solid electrolyte particles, A solid state battery in which M represented by the following formula 1 is 1.15 to 3.00: M=M1 / M2…Formula 1 M1: the ratio of the number of oxygen atoms to the number of atoms of a specific type of element constituting the sulfide solid electrolyte particles in the vicinity of the positive electrode current collector layer of the positive electrode active material layer, M2: The ratio of the number of oxygen atoms to the number of atoms of a specific type of element that constitutes the sulfide solid electrolyte particle at the center of the solid electrolyte layer. <Aspect 2> The solid state battery according to embodiment 1, wherein M in formula 1 is 1.20 to 2.00. <Aspect 3> A method for producing the solid-state battery according to aspect 1 or 2, comprising the steps of: (a) providing a preliminary electrode laminate in which a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer are laminated in this order; and (b) The preliminary electrode laminate is held in an environment with a dew point of −80° C. or higher and 0° C. or lower for 30 seconds or longer to cause the preliminary electrode laminate to absorb moisture, thereby producing an electrode laminate. <Aspect 4> Between step (a) and step (b) (a-2) pressing the preliminary electrode laminate at a temperature of 100°C or higher and 200°C or lower; 4. The method of embodiment 3, further comprising: <Aspect 5> After step (b), (b-2) forming a spare solid-state battery by disposing a current collector layer on the surface of the electrode laminate; and (b-3) pressing the spare solid-state battery at a temperature of 100°C or higher and 200°C or lower; 5. The method of embodiment 3 or 4, further comprising: [Effects of the Invention]

[0008] According to the solid-state battery of the present disclosure, the rate of increase in the resistance of the battery due to endurance can be reduced without significantly increasing the initial DC resistance. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a solid state battery according to the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view illustrating the method for manufacturing a solid state battery according to the present disclosure. [Figure 3] FIG. 3 is a schematic cross-sectional view for explaining the method for manufacturing a solid state battery according to the present disclosure. [Figure 4] FIG. 4 is a graph showing the relationship between M (=M1 / M2) and the initial DC resistance and the resistance increase rate for the solid state batteries of the Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present disclosure. In addition, in the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions will be omitted.

[0011] In the present disclosure, a "composite" refers to a composition that can constitute an electrode active material layer, etc., either as it is or by further containing other components. Also, in the present disclosure, a "composite slurry" refers to a slurry that contains a dispersion medium in addition to a "composite" and can be applied and dried to form an electrode active material layer, etc.

[0012] In the context of the present disclosure, a "solid-state battery" refers to a battery that uses at least a solid electrolyte as the electrolyte, and therefore a solid-state battery may use a combination of a solid electrolyte and a liquid electrolyte as the electrolyte. Alternatively, the solid-state battery of the present disclosure may be an all-solid-state battery, i.e., a battery that uses only a solid electrolyte as the electrolyte.

[0013] 《Solid-state battery》 The solid-state battery of the present disclosure comprises: 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 stacked in this order; the positive electrode active material layer and the solid electrolyte layer contain sulfide solid electrolyte particles, M represented by the following formula 1 is 1.15 to 3.00: M=M1 / M2…Formula 1 M1: the ratio of the number of oxygen atoms to the number of atoms of a specific type of element constituting the sulfide solid electrolyte particle in the sulfide solid electrolyte particle near the positive electrode current collector layer of the positive electrode active material layer, M2: In the sulfide solid electrolyte particle at the center of the solid electrolyte layer, the ratio of the number of oxygen atoms to the number of atoms of a specific type of element constituting the sulfide solid electrolyte particle.

[0014] According to the solid-state battery of the present disclosure, the rate of increase in the resistance of the battery due to endurance can be reduced without significantly increasing the initial DC resistance.

[0015] The present inventors have found that for a solid-state battery containing sulfide solid electrolyte particles, the oxygen atoms present on the surface of the positive electrode active material layer (near the positive electrode current collector layer in the positive electrode active material layer) of the solid-state battery have the following relationship with the initial DC resistance and the resistance increase rate: As M, expressed by the above formula 1, of the solid-state battery increases, the resistance increase rate of the solid-state battery due to durability decreases (i.e., the DC resistance of the solid-state battery is more likely to decrease due to durability), while the initial DC resistance increases.

[0016] Based on this finding, the present inventors have conceived of a solid-state battery that can obtain the effect of reducing the rate of increase in resistance of a solid-state battery due to durability (i.e., the effect of making it easier for the DC resistance of a solid-state battery to decrease due to durability) without significantly increasing the initial DC resistance, by appropriately controlling "M represented by the above formula 1" of the solid-state battery.

[0017] Without being limited by theory, it is speculated that when a predetermined amount of surface moisture is adsorbed onto an electrode laminate including sulfide solid electrolyte particles in a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, the surface moisture adsorbed onto the electrode laminate reacts with the sulfide solid electrolyte particles on the surface of the positive electrode active material layer to form a reaction layer, and this reaction layer suppresses oxidative decomposition of the sulfide solid electrolyte particles during charging, thereby preventing a significant increase in initial DC resistance and reducing the rate of resistance increase due to durability.

[0018] FIG. 1 is a cross-sectional schematic diagram showing one embodiment of the solid-state battery of the present disclosure, but the present disclosure is not limited to this embodiment.

[0019] The solid-state battery 10 includes a positive electrode current collector layer 110, a positive electrode active material layer 120, a solid electrolyte layer 130, a negative electrode active material layer 140, and a negative electrode current collector layer 150 stacked in this order. The positive electrode active material layer 120 and the solid electrolyte layer 130 contain sulfide solid electrolyte particles. When the value of M in the above formula 1 is 1.15 to 3.00, the initial DC resistance does not increase significantly, and the rate of increase in resistance due to durability can be reduced.

[0020] <M (=M1 / M2) of solid-state batteries> In the solid state battery of the present disclosure, M represented by the following formula 1 is 1.15 to 3.00, and preferably 1.20 to 2.00. M may be, for example, 1.15 or more, 1.20 or more, 1.22 or more, or 1.24 or more, or may be 3.00 or less, 2.80 or less, 2.60 or less, 2.40 or less, 2.20 or less, 2.00 or less, 1.80 or less, or 1.60 or less. M=M1 / M2…Formula 1 M1: the ratio of the number of oxygen atoms to the number of atoms of a specific type of element constituting the sulfide solid electrolyte particle in the sulfide solid electrolyte particle near the positive electrode current collector layer of the positive electrode active material layer, M2: In the sulfide solid electrolyte particle at the center of the solid electrolyte layer, the ratio of the number of oxygen atoms to the number of atoms of a specific type of element constituting the sulfide solid electrolyte particle.

[0021] (About M1) The sulfide solid electrolyte particles in the vicinity of the positive electrode current collector layer of the positive electrode active material layer may be sulfide solid electrolyte particles in the vicinity of the positive electrode current collector layer of the positive electrode active material layer, for example, at a position within 5 μm from the surface of the positive electrode active material layer on the positive electrode current collector layer side.

[0022] The specific type of element constituting the sulfide solid electrolyte particles is not particularly limited, but may include phosphorus contained in the sulfide solid electrolyte particles.

[0023] In the present disclosure, "M1" can be calculated by the following method. The cut surface of the electrode laminate included in the solid-state battery is cross-sectionally processed using an ion milling device (ArBlade5000 manufactured by Hitachi High-Technologies) to prepare an ion-milled cross section. Next, the ion-milled cross section is analyzed using a scanning electron microscope (SU8230 manufactured by Hitachi High-Technologies) and an Ultim Exteme windowless EDS / EDX detector. 、 The atomic concentration of a specific type of element and the atomic concentration of oxygen are measured for sulfide solid electrolyte particles present near the positive current collector layer of the positive electrode active material layer, for example, at a position within 5 μm from the surface of the positive current collector layer side of the positive electrode active material layer. The atomic concentration of the specific type of element and the atomic concentration of oxygen are measured for 10 sulfide solid electrolyte particles, the respective average values ​​are calculated, and the ratio of the average atomic concentration of oxygen to the average atomic concentration of the specific type of element is calculated. This calculated ratio can be used as the ratio of the number of oxygen atoms to the number of atoms of the specific type of element constituting the sulfide solid electrolyte particles, i.e., M1, in the sulfide solid electrolyte particles near the positive current collector layer of the positive electrode active material layer.

[0024] In the above-described solid-state battery 10 of FIG. 1, the sulfide solid electrolyte particles in the vicinity of the positive electrode current collector layer of the positive electrode active material layer may be sulfide solid electrolyte particles that are present at a position within 5 μm from the surface of the positive electrode active material layer 120 on the positive electrode current collector layer 110 side, and M1 can be calculated by measuring, for example, the phosphorus atom number concentration and the oxygen atom number concentration of these sulfide solid electrolyte particles.

[0025] (About M2) The sulfide solid electrolyte particle at the center of the solid electrolyte layer is a sulfide solid electrolyte particle at the center in the thickness direction of the solid electrolyte layer.

[0026] The specific type of element constituting the sulfide solid electrolyte particles is not particularly limited, but may include phosphorus contained in the sulfide solid electrolyte particles.

[0027] In the present disclosure, "M2" can be calculated by the following method. A cut surface of an electrode laminate included in a solid-state battery is cross-sectionally processed using an ion milling device (ArBlade5000, manufactured by Hitachi High-Technologies) to prepare an ion-milled cross section. Next, a scanning electron microscope (SU8230, manufactured by Hitachi High-Technologies) and an Ultim Exteme windowless EDS / EDX detector are used to measure the atomic concentration of a specific type of element and the atomic concentration of oxygen for a sulfide solid electrolyte particle located at the center of the thickness direction of the solid electrolyte layer. The atomic concentration of a specific type of element and the atomic concentration of oxygen for 10 sulfide solid electrolyte particles are measured, the respective average values ​​are calculated, and the ratio of the average atomic concentration of oxygen to the average atomic concentration of the specific type of element is calculated. This calculated ratio can be used as the ratio of the number of oxygen atoms to the number of atoms of a specific type of element constituting the sulfide solid electrolyte particle at the center of the solid electrolyte layer, i.e., M2.

[0028] In the solid state battery 10 of FIG. 1 described above, the sulfide solid electrolyte particles at the center of the solid electrolyte layer 130 are sulfide solid electrolyte particles at the center in the thickness direction of the solid electrolyte layer 130, and sulfide solid electrolyte particles at an intermediate position between the surface of the solid electrolyte layer 130 on the positive electrode active material layer 120 side and the surface of the solid electrolyte layer 130 on the negative electrode active material layer 140 side. For these sulfide solid electrolyte particles, for example, the phosphorus atom number concentration and the oxygen atom number concentration can be measured to calculate M2.

[0029] <Structure of solid-state battery> The solid-state battery of the present disclosure has 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 stacked in this order. The solid-state battery is not particularly limited, but preferably has a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer stacked in this order.

[0030] <Positive electrode current collector layer> Examples of materials used for the positive electrode current collector layer include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. The positive electrode current collector layer may have a coating layer on its surface for the purpose of adjusting resistance, etc. The positive electrode current collector layer may also be a metal foil or a substrate on which the above metals are plated or vapor-deposited.

[0031] The shape of the positive electrode current collector layer is not particularly limited, but examples thereof include foil, plate, and mesh. Among these, foil is preferred. The thickness of the positive electrode current collector layer is not particularly limited, but may be 0.1 μm or more, or 1 μm or more, or 1 mm or less, or 100 μm or less.

[0032] <Cathode active material layer> The positive electrode active material layer contains at least a positive electrode active material and sulfide solid electrolyte particles, and may further contain, optionally, a conductive additive, a binder, etc. The contents of each of the positive electrode active material, sulfide solid electrolyte particles, conductive additive, binder, etc. in the positive electrode active material layer may be appropriately determined depending on the desired battery performance.

[0033] (Cathode active material) The material of the positive electrode active material is not particularly limited as long as it can absorb and release lithium ions. Examples of the positive electrode active material include lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), lithium manganese oxide (LiMnO), and nickel-cobalt-manganese oxide (NCM:LiCO x Ni y Mnz O2), lithium nickel-cobalt-aluminate (LiNi 0.8 (CoAl) 0.2 O2), etc., but are not limited to these.

[0034] The positive electrode active material may have a coating layer, although it is not particularly limited. The coating layer is a layer containing a substance that has lithium ion conductivity, low reactivity with the positive electrode active material and the solid electrolyte, and can maintain the shape of the coating layer without flowing even when in contact with the active material and the solid electrolyte. Specific examples of materials that constitute the coating layer include LiNbO3 and Li4Ti5O 12 , Li3PO4, Li-Ti-Al-F based materials, etc., but are not limited to these.

[0035] The shape of the positive electrode active material is not particularly limited, but may be particulate. 50 The average particle size D may be, for example, 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. 50 is the particle size (median size) at 50% cumulative value in the volume-based particle size distribution determined by laser diffraction / scattering method.

[0036] (Sulfide solid electrolyte particles) Examples of sulfide solid electrolyte particles include, but are not limited to, sulfide-based amorphous solid electrolyte particles, sulfide-based crystalline solid electrolyte particles, and argyrodite-type solid electrolyte particles. Specific examples of sulfide solid electrolyte particles include Li2S-P2S5-based (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 ), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS6-x Cl x or a combination thereof. The sulfide solid electrolyte particles are not particularly limited, but may be glass or crystallized glass (glass ceramics).

[0037] (Optional ingredient - conductive additive) The conductive additive may be, for example, vapor grown carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotube (CNT), carbon nanofiber (CNF), conductive carbon, etc., but is not limited to these. The conductive additive may be, for example, particulate or fibrous, and its size is not particularly limited. The conductive additive is not particularly limited, but one type may be used alone, or two or more types may be used in combination.

[0038] (Optional ingredient - binder) The binder may be, for example, but is not limited to, polyvinylidene fluoride (PVdF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), etc. The binder is not particularly limited, and one type may be used alone, or two or more types may be used in combination.

[0039] The thickness of the positive electrode active material layer is not particularly limited, and may be, for example, 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.

[0040] The positive electrode active material layer can be easily formed, for example, by dry or wet forming a positive electrode mixture containing the above-mentioned various components. The positive electrode active material layer may be formed together with the positive electrode current collector layer or may be formed separately from the positive electrode current collector layer.

[0041] <Solid electrolyte layer> The solid electrolyte layer contains at least sulfide solid electrolyte particles, and may contain, as necessary, a conductive additive, a binder, etc. For the sulfide solid electrolyte particles, the conductive additive, and the binder, please refer to the description above in "<<Positive Electrode Active Material Layer>>".

[0042] The thickness of the solid electrolyte layer is not particularly limited, but may be, for example, 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.

[0043] The solid electrolyte layer can be easily formed, for example, by dry or wet molding a solid electrolyte mixture containing the above-mentioned solid electrolyte and a binder.

[0044] <Negative electrode active material layer> The negative electrode active material layer contains at least a negative electrode active material, and may further contain, optionally, sulfide solid electrolyte particles, a conductive additive, a binder, and the like. The above description of "<Positive Electrode Active Material Layer>" can be referenced for the sulfide solid electrolyte particles, conductive additive, and binder that may be contained in the negative electrode active material layer. The respective contents of the negative electrode active material, sulfide solid electrolyte particles, conductive additive, binder, and the like in the negative electrode active material layer may be appropriately determined depending on the desired battery performance.

[0045] (Negative electrode active material) As the negative electrode active material, various materials can be used that have a potential (charge / discharge potential) at which lithium ions are absorbed and released that is lower than that of the positive electrode active material. The material for the negative electrode active material is not particularly limited, and may be metallic lithium, or a material capable of absorbing and releasing metal ions such as lithium ions. The material capable of absorbing and releasing metal ions such as lithium ions is not particularly limited, but may be an alloy-based negative electrode active material, a carbon material, or lithium titanate (Li4Ti5O 12 Examples of alloy-based negative electrode active materials include, but are not limited to, Si alloy-based negative electrode active materials and Sn alloy-based negative electrode active materials. Examples of carbon materials include, but are not limited to, hard carbon, soft carbon, graphite, and the like.

[0046] The negative electrode active material may be in the form of, for example, particles or a sheet.

[0047] The thickness of the negative electrode active material layer is not particularly limited, but may be, for example, 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.

[0048] The negative electrode active material layer can be easily formed, for example, by dry or wet forming a negative electrode mixture containing the above-mentioned various components. The negative electrode active material layer may be formed together with the negative electrode current collector layer or may be formed separately from the negative electrode current collector layer.

[0049] <Negative electrode current collector layer> Examples of materials used for the negative electrode current collector layer include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and a carbon sheet. The negative electrode current collector layer may have a coating layer on its surface for the purpose of adjusting the resistance, etc.

[0050] The shape of the negative electrode current collector layer is not particularly limited, but examples thereof include foil, plate, and mesh. Of these, foil is preferred. The thickness of the negative electrode current collector layer is not particularly limited, but may be 0.1 μm or more, or 1 μm or more, or 1 mm or less, or 100 μm or less.

[0051] <<Shape of solid-state batteries, etc.>> The shape of the solid-state battery may be, for example, a coin type, a laminate type, a cylindrical type, or a square type, but is not limited thereto. The solid-state battery may be encapsulated in a laminate film, but is not particularly limited thereto. The solid-state battery may also be confined under a confining pressure of, for example, 5 MPa.

[0052] <<Applications of solid-state batteries>> The solid-state battery in the present disclosure may be, for example, a lithium-ion secondary battery. The solid-state battery in the present disclosure may also be, for example, an in-vehicle battery, or may be used as a power source for a moving body other than a vehicle (for example, a train, a ship, or an aircraft), or may be used as a power source for an electrical appliance such as an information processing device.

[0053] <<Solid-state battery manufacturing method>> The solid-state battery of the present disclosure can be manufactured by a method comprising the following steps: (a) providing a preliminary electrode laminate in which the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer are laminated in this order; and (b) The preliminary electrode laminate is held in an environment with a dew point of −80° C. or higher and 0° C. or lower for 30 seconds or longer to cause the preliminary electrode laminate to absorb moisture, thereby producing an electrode laminate.

[0054] According to the manufacturing method of the solid-state battery of the present disclosure, it is possible to manufacture a battery that does not significantly increase the initial DC resistance and that can reduce the rate of increase in the resistance of the battery due to durability.

[0055] FIG. 2 is a cross-sectional schematic view showing one embodiment of the method for producing a solid-state battery according to the present disclosure, but the present invention is not limited to this embodiment.

[0056] First, as shown in FIG. 2A , a preliminary electrode laminate 101 is provided, in which a positive electrode active material layer 120, a solid electrolyte layer 130, and a negative electrode active material layer 140 are stacked in this order. For example, a method for providing the preliminary electrode laminate 101 involves superposing a solid electrolyte layer on each surface of a negative electrode active material layer formed on both sides of a negative electrode current collector layer and pressing the solid electrolyte layer to transfer the solid electrolyte layer to the surface of the negative electrode active material layer, thereby stacking the solid electrolyte layer on the negative electrode active material layer. Next, a positive electrode active material layer is superposed on each surface of the solid electrolyte layer stacked on both sides of the negative electrode active material layer and pressing the positive electrode active material layer to transfer the positive electrode active material layer to the surface of the solid electrolyte layer, thereby stacking the positive electrode active material layer on the solid electrolyte layer, thereby providing a preliminary electrode laminate in which a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, and a positive electrode active material layer are stacked in this order. 2C , the preliminary electrode laminate 101 is held in an environment with a dew point of −80° C. or higher and 0° C. or lower for 30 seconds or longer to cause the preliminary electrode laminate 101 to adsorb moisture 200, thereby producing an electrode laminate 100. Then, a solid-state battery 10 can be manufactured using this electrode laminate 100.

[0057] The method for producing a solid-state battery according to the present disclosure is not particularly limited, but may include the following step between step (a) and step (b): (a-2) pressing the preliminary electrode laminate at a temperature of 100°C or higher and 200°C or lower; It may further include.

[0058] In the above-described FIG. 2, first, as shown in FIG. 2A, a preliminary electrode laminate 101 is provided. Next, as shown in FIG. 2B, the preliminary electrode laminate 101 is pressed at a temperature of 100°C or higher and 200°C or lower. By pressing the preliminary electrode laminate 101, the preliminary electrode laminate 101 can be densified. Then, as shown in FIG. 2C, moisture is adsorbed into the preliminary electrode laminate 101 to produce an electrode laminate 100, and this electrode laminate 100 can be used to manufacture a solid-state battery 10.

[0059] The method for producing a solid-state battery according to the present disclosure is not particularly limited, but may include the steps of: (b-2) forming a spare solid-state battery by disposing a current collector layer on the surface of the electrode laminate; and (b-3) pressing the spare solid-state battery at a temperature of 100°C or higher and 200°C or lower; It may further include.

[0060] FIG. 3 is a cross-sectional schematic view showing one embodiment of the method for producing a solid state battery according to the present disclosure, but the present invention is not limited to this embodiment.

[0061] 3A, for example, a cathode active material layer 120, a solid electrolyte layer 130, an anode active material layer 140, an anode current collector layer 150, an anode active material layer 140, a solid electrolyte layer 130, and a cathode active material layer 120 are stacked in an electrode laminate 100. A cathode current collector layer 110 is disposed on the surface of the cathode active material layer 120 to form a spare solid state battery 11. Next, as shown in FIG. 3B, the spare solid state battery 11 is pressed at a temperature of 100°C or higher and 200°C or lower. A current collector layer can be provided on the surface of the electrode laminate 100 by steps (b-2) and (b-3).

[0062] <Water absorption method> As a method for adsorbing moisture into the preliminary electrode laminate, for example, the preliminary electrode laminate can be left standing in a glove box or the like whose humidity is controlled to a dew point of −50°C for a predetermined period of time to adsorb moisture, but the method is not limited to this.

[0063] The dew point of the environment in which moisture is allowed to adhere to the preliminary electrode laminate may be 0°C or lower, -10°C or lower, -30°C or lower, or -50°C or lower, or may be -80°C or higher, -75°C or higher, -70°C or higher, or -65°C or higher, from the viewpoint of suppressing structural changes in the solid electrolyte.

[0064] The time for adhering moisture to the preliminary electrode laminate is not particularly limited, but may be 30 seconds or more, 1 minute or more, 10 minutes or more, 30 minutes or more, or 1 hour or more, or may be 5 hours or less, 3 hours or less, 1 hour or less, or 30 minutes or less.

[0065] <Method of pressing preliminary electrode laminate> The method for pressing the preliminary electrode laminate is not particularly limited, but it can be pressed by a roll press.

[0066] The linear pressure used to press the preliminary electrode laminate may be, for example, 1 ton / cm or more, 3 ton / cm or more, or 5 ton / cm or more, or 10 ton / cm or less, 8 ton / cm or less, or 6 ton / cm or less.

[0067] The temperature at which the preliminary electrode laminate is pressed may be, for example, 100°C or higher, 130°C or higher, or 160°C or higher, and may be 200°C or lower, or 180°C or lower.

[0068] <Method for pressing spare solid-state batteries> The method for pressing the spare solid state battery is not particularly limited, but the spare solid state battery can be pressed by applying pressure from the top and bottom surfaces in the stacking direction.

[0069] The pressure used to press the spare solid-state battery may be, for example, 1 MPa or more, 3 MPa or more, or 5 MPa or more, and may be 100 MPa or less, 80 MPa or less, or 50 MPa or less.

[0070] The temperature at which the preliminary solid-state battery is pressed may be, for example, 100°C or higher, 120°C or higher, or 140°C or higher, and may be 200°C or lower, 180°C or lower, or 160°C or lower.

[0071] The time for pressing the spare solid state battery is not particularly limited, but may be 10 seconds or more, 1 minute or more, or 5 minutes or more, or may be 1 hour or less, 30 minutes or less, or 10 minutes or less. [Example]

[0072] The present disclosure will be described in more detail with reference to the following examples, but the scope of the present disclosure is not limited to these examples.

[0073] Example 1 <Preparation of Positive Electrode Active Material Layer A1> LiNi coated with Li-Ti-Al-F material as a positive electrode active material 0.8 (CoAl) 0.2 O2, LiI-LiBr-Li2S-P2S5-based glass ceramics as a solid electrolyte, conductive carbon as a conductive additive, a binder, a dispersant, and an appropriate amount of solvent were mixed and dispersed using an ultrasonic homogenizer to prepare a positive electrode composite slurry. The resulting positive electrode composite slurry was then die-coated onto aluminum foil and dried to form a positive electrode active material layer A1 on one side of the aluminum foil.

[0074] <Preparation of solid electrolyte layer B1> A LiI-LiBr-Li2S-P2S5-based glass ceramic (average particle size 2.5 μm) as a solid electrolyte, conductive carbon as a conductive additive, a binder, a dispersant, and an appropriate amount of solvent were mixed and dispersed using an ultrasonic homogenizer to prepare a solid electrolyte composite slurry. The resulting solid electrolyte composite slurry was then die-coated onto an aluminum foil and dried to form a solid electrolyte layer B1 on one side of the aluminum foil.

[0075] <Preparation of Negative Electrode Active Material Layer C1> Li4Ti5O as a negative electrode active material 12 The particles, LiI-LiBr-Li2S-P2S5-based glass ceramics as a solid electrolyte, conductive carbon as a conductive additive, binder, dispersant, and an appropriate amount of solvent were mixed and dispersed using an ultrasonic homogenizer to prepare a negative electrode composite slurry. The resulting negative electrode composite slurry was then die-coated onto both sides of aluminum foil as a negative electrode current collector and dried to form negative electrode active material layers C1 on both sides of the aluminum foil. The basis weight of the negative electrode active material layer was adjusted so that the charge specific capacity of the positive electrode active material layer was 200 mAh / g, and the charge specific capacity of the negative electrode active material layer was 1x that of the positive electrode active material layer.

[0076] <Preparation of Electrode Stack D1> A solid electrolyte layer B1 was placed on each surface of a negative electrode active material layer C1 formed on both sides of an aluminum foil serving as a negative electrode current collector, and pressed to transfer the solid electrolyte layer B1 to the surface of the negative electrode active material layer C1. The aluminum foil in contact with the solid electrolyte layer B1 was peeled off, and the solid electrolyte layer B1 was laminated on the negative electrode active material layer C1. Next, a positive electrode active material layer A1 was placed on each surface of the solid electrolyte layer B1 laminated on both sides of the negative electrode active material layer C1, and pressed to transfer the positive electrode active material layer A1 to the surface of the solid electrolyte layer B1. The aluminum foil in contact with the positive electrode active material layer A1 was peeled off, and the positive electrode active material layer A1 was laminated on the solid electrolyte layer B1. The prepared electrode laminate was roll-pressed at 175°C and 5 ton / cm to obtain a densified electrode laminate. The obtained densified electrode laminate was left to stand for 17 minutes in a humidity-controlled glove box set at a dew point of -50°C, and moisture was adsorbed to obtain a densified electrode laminate D1.

[0077] <Fabrication of solid-state battery E1> Carbon-coated aluminum foil was placed on each surface of the positive electrode active material layer A1 of the densified electrode laminate D1 as a positive electrode current collector, and the resulting mixture was pressed at 140°C and 5 MPa for 5 minutes to obtain a power generating element. The power generating element consisted of 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, stacked in this order. The resulting power generating element was laminated and constrained at 5 MPa to produce a solid-state battery E1.

[0078] <Calculation of M for solid-state battery E1> (Calculation method for M1 of solid-state battery E1) The power generating element of the solid-state battery E1 was cut into small pieces, and the cut surfaces were cross-sectionally processed using an ion milling device (ArBlade5000, manufactured by Hitachi High-Technologies) to prepare ion-milled cross sections. Next, a scanning electron microscope (SU8230, manufactured by Hitachi High-Technologies) and an Ultim Exteme windowless EDS / EDX detector were used to measure the phosphorus atom number concentration and oxygen atom number concentration of sulfide solid electrolyte particles present in the vicinity of the positive electrode current collector layer of the positive electrode active material layer, specifically within 5 μm from the surface of the positive electrode current collector layer side of the positive electrode active material layer. The phosphorus atom number concentration and oxygen atom number concentration were measured for 10 sulfide solid electrolyte particles, and the respective average values ​​were calculated to obtain the average phosphorus atom number concentration (P pe ) versus the average oxygen atom concentration (O pe The calculated ratio was defined as the ratio (M1) of the number of oxygen atoms to the number of atoms of a specific type of element constituting the sulfide solid electrolyte particles in the vicinity of the positive electrode current collector layer of the positive electrode active material layer. M1 for the solid battery E1 was 0.199.

[0079] (Calculation method for M2 of solid-state battery E1) An ion-milled cross section was prepared using the same method as in the above "(Method for calculating M1 of solid-state battery E1)". Next, a scanning electron microscope (SU8230 manufactured by Hitachi High-Tech) and an Ultim Exteme windowless EDS / EDX detector were used to measure the phosphorus atom number concentration and oxygen atom number concentration of sulfide solid electrolyte particles present at the center of the thickness direction of the solid electrolyte layer, specifically at a position midway between the surface of the solid electrolyte layer facing the positive electrode active material layer and the surface of the solid electrolyte layer facing the negative electrode active material layer. The phosphorus atom number concentration and oxygen atom number concentration were measured for 10 sulfide solid electrolyte particles, and the respective average values ​​were calculated to obtain the average phosphorus atom number concentration (P se ) versus the average oxygen atom concentration (O se The ratio of oxygen atoms to atoms of a specific type of element constituting the sulfide solid electrolyte particle at the center of the solid electrolyte layer (M2) was calculated. The M2 of the solid battery E1 was 0.161.

[0080] Using M1 and M2 calculated by the above method, M1 was divided by M2 to calculate M. M of the solid state battery E1 was 1.11.

[0081] <Initial DC resistance of solid-state battery E1> The obtained solid state battery E1 was charged at a constant current of 0.3 C until it reached a voltage corresponding to a charge depth of 40%, and then it was charged at a constant voltage of 0.01 C until it reached a current of 0.01 C. The solid state battery E1 was then discharged at a constant current of 72 C, and the difference between the voltage before discharge and the voltage after 0.1 seconds of discharge was divided by the current amount corresponding to 72 C to calculate the initial DC resistance (Ω) of the solid state battery E1. Table 1 and FIG. 4 show the initial DC resistance of the solid state battery E1. The initial DC resistance values ​​in Table 1 are relative values ​​when the initial DC resistance of the solid state battery e1 of Comparative Example 1 is set to 1.00.

[0082] <Resistance increase rate of solid-state battery E1> The solid-state battery E1 was charged at a constant current of 0.3 C until it reached a voltage equivalent to 40% charge, and then at a constant voltage of 0.01 C until it reached a current of 0.01 C. The solid-state battery E1 was then placed in a thermostatic chamber set at 60°C and stored for two weeks. The DC resistance of the solid-state battery E1 was measured before and after storage in the thermostatic chamber, and 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 multiplied by 100 to calculate the resistance increase rate (%) of the solid-state battery E1 due to durability. The resistance increase rate of the solid-state battery E1 was as shown in Table 1 and FIG. 4.

[0083] Examples 2 to 5 <Preparation of Electrode Stacks D2 to D5> Densified electrode stacks D2 to D5 were produced in the same manner as in Example 1, except that instead of leaving the densified electrode stack in a humidity-controlled glove box set to a dew point of -50°C for 17 minutes, the electrode stack was left in a glove box set to the dew point shown in Table 1 for a predetermined time.

[0084] <Fabrication of Solid-State Batteries E2 to E5, and DC Resistance and Resistance Increase Rate of Solid-State Batteries E2 to E5> Solid state batteries E2 to E5 were produced in the same manner as in Example 1, except that electrode laminates D2 to D5 were used instead of electrode laminate D1. For solid state batteries E2 to E5, M1, M2, and M were as shown in Table 1. The initial DC resistance and resistance increase rate of solid state batteries E2 to E5 were determined in the same manner as in Example 1. The respective results were as shown in Table 1 and FIG. 4.

[0085] Comparative Example 1 <Preparation of electrode laminate d1> A densified electrode laminate d1 was produced in the same manner as in Example 1, except that the densified electrode laminate was not placed in a humidity-controlled glove box set to -50°C and no intentional moisture adsorption was performed.

[0086] <Production of solid-state battery e1, and DC resistance and resistance increase rate of solid-state battery e1> A solid state battery e1 was produced in the same manner as in Example 1, except that electrode laminate d1 was used instead of electrode laminate D1. For solid state battery e1, M1, M2, and M were as shown in Table 1. The initial DC resistance and resistance increase rate of solid state battery e1 were determined in the same manner as in Example 1. The respective results were as shown in Table 1.

[0087] [Table 1]

[0088] In Examples 1 to 5, solid state batteries E1 to E5, in which M represented by Formula 1 is within a predetermined range, did not significantly increase in initial DC resistance, and were able to reduce the rate of increase in resistance of the battery due to durability. Furthermore, solid state batteries E1 and E2 in Examples 1 and 2 showed almost no increase in initial DC resistance, and were able to reduce the rate of increase in resistance. On the other hand, solid state battery e1 in Comparative Example 1, in which surface moisture was not intentionally adsorbed, had a small initial DC resistance but showed little effect in reducing the rate of increase in resistance, i.e., the effect of making the battery's DC resistance more likely to decrease due to durability. Figure 4 shows the relationship between M and the initial DC resistance and the rate of increase in resistance of the solid state batteries in the Examples and Comparative Examples.

[0089] Although the details are not clear, it is speculated that when a predetermined amount of surface moisture is adsorbed onto an electrode laminate containing sulfide solid electrolyte particles in a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, the surface moisture adsorbed onto the electrode laminate reacts with the solid electrolyte on the surface of the positive electrode active material layer to form a reaction layer, and this reaction layer suppresses oxidative decomposition of the sulfide solid electrolyte particles during charging, thereby preventing a significant increase in initial DC resistance and reducing the rate of resistance increase due to durability.

[0090] While preferred embodiments of the disclosed solid-state batteries and methods for manufacturing solid-state batteries have been described, those skilled in the art will recognize that modifications are possible without departing from the scope of the claims. [Explanation of symbols]

[0091] 10 solid state battery 11 Spare solid-state battery 100 Electrode laminate 101 Preliminary electrode laminate 110 Positive electrode current collector layer 120 Cathode active material layer 130 Solid electrolyte layer 140 Negative electrode active material layer 150 Negative electrode current collector layer 200 water

Claims

1. 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 stacked in this order; the positive electrode active material layer and the solid electrolyte layer contain sulfide solid electrolyte particles, A solid state battery in which M represented by the following formula 1 is 1.15 to 3.00: M = M １ / M ２ …Formula 1 M １ : the ratio of the number of oxygen atoms to the number of atoms of a specific type of element constituting the sulfide solid electrolyte particles in the vicinity of the positive electrode current collector layer of the positive electrode active material layer, M ２ : The ratio of the number of oxygen atoms to the number of atoms of a specific type of element constituting the sulfide solid electrolyte particle at the center of the solid electrolyte layer.

2. 2. The solid state battery according to claim 1, wherein M represented by formula 1 is 1.20 to 2.

00.

3. A method for producing the solid state battery according to claim 1, comprising the following steps: (a) providing a preliminary electrode laminate in which a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer are laminated in this order; and (b) The preliminary electrode laminate is held in an environment with a dew point of −80° C. or higher and 0° C. or lower for 30 seconds or longer to cause the preliminary electrode laminate to absorb moisture, thereby producing an electrode laminate.

4. Between step (a) and step (b) (a-2) pressing the preliminary electrode laminate at a temperature of 100°C or higher and 200°C or lower; The method of claim 3 further comprising:

5. After step (b), (b-2) disposing a current collector layer on the surface of the electrode laminate to form a spare solid-state battery; and (b-3) pressing the spare solid-state battery at a temperature of 100°C or higher and 200°C or lower; The method of claim 3 or 4, further comprising:

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