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: The positive electrode active material layer 120, the solid electrolytic layer 130, and the negative electrode active material layer 140 are stacked in this order, the positive electrode active material layer 120, the solid electrolytic layer 130, and the negative electrode active material layer 140 include sulfide solid electrolytes, a surface water amount of the positive electrode stack 100 is 200 to 1500ppm, and a ratio of the surface water amount to a total water amount present in the entire positive electrode stack 100 is 0.5 to 1.0.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> an electrode stack in which a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer are stacked in this order; the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer each contain a sulfide solid electrolyte; The surface moisture content of the electrode laminate is 200 to 1500 ppm, and the ratio of the surface moisture content to the total moisture content present in the entire electrode laminate is 0.50 to 1.00; solid state battery. <Aspect 2> 2. The solid state battery according to aspect 1, wherein the electrode laminate has a surface moisture content of 200 to 600 ppm. <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 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 the 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 the surface moisture content 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: an electrode stack in which a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer are stacked in this order; the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer each contain a sulfide solid electrolyte; The surface moisture content of the electrode laminate is 200 to 1500 ppm, and The ratio of the surface moisture content to the total moisture content present throughout the electrode laminate is 0.50 to 1.00.

[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 an electrode laminate containing a sulfide solid electrolyte, the amount of moisture present on the surface of the electrode laminate, and the initial DC resistance and resistance increase rate exhibit the following relationship: When the amount of moisture on the surface of the electrode laminate 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] Furthermore, the present inventors have found that 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) can be obtained only when the ratio of the surface moisture content to the total moisture content present in the entire electrode stack is high.

[0017] Based on these findings, the present inventors have come up with the idea of ​​a solid-state battery that can achieve 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 the "surface moisture content" of the electrode laminate and the "ratio of the surface moisture content to the total moisture content of the electrode laminate."

[0018] Without being limited by theory, it is speculated that when a predetermined amount of surface moisture is adsorbed onto an electrode laminate in which the positive electrode active material layer, solid electrolyte layer, and negative electrode active material layer contain a sulfide solid electrolyte, the surface moisture adsorbed onto the electrode laminate penetrates to the interface between the positive electrode active material and the solid electrolyte, forming a reaction layer with an appropriate thickness at the interface, and this reaction layer suppresses oxidative decomposition of the sulfide solid electrolyte during charging, thereby making it possible to reduce the rate of resistance increase due to durability without significantly increasing the initial DC resistance.

[0019] 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.

[0020] The solid-state battery 10 includes an electrode stack 100 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. The positive electrode active material layer 120, the solid electrolyte layer 130, and the negative electrode active material layer 140 contain a sulfide solid electrolyte. The electrode stack 100 has a surface moisture content of 200 to 1500 ppm, and the ratio of the surface moisture content to the total moisture content present throughout the electrode stack 100 is 0.50 to 1.00. When the sulfide-containing electrode stack has a surface moisture content within a predetermined range, the rate of increase in resistance due to durability can be reduced without significantly increasing the initial DC resistance.

[0021] <Moisture content of electrode laminate> (Surface moisture content) In the solid state battery of the present disclosure, the surface moisture content of the electrode laminate is 200 to 1500 ppm, and preferably 200 to 600 ppm. The surface moisture content may be, for example, 200 ppm or more, 220 ppm or more, or 240 ppm or more, and may be 1500 ppm or less, 1200 ppm or less, 900 ppm or less, or 600 ppm or less.

[0022] In the present disclosure, the "surface moisture content" can be determined by the following method. First, 20 sheets of the electrode laminate are punched out to a diameter of 9.2 mm and introduced into a Karl Fischer apparatus (Karl Fischer apparatus CA-310 and moisture vaporizer VA-300, manufactured by Nitto Seiko). Next, the punched electrode laminate is placed in the moisture vaporizer VA-300, which has been preheated to 200°C, and the amount of moisture desorbed from the electrode laminate by heating is measured using the Karl Fischer apparatus CA-310, and the obtained moisture content is defined as the surface moisture content. The measurement is terminated when the detected moisture content becomes 0.02 μg / sec or less. The surface moisture content is the moisture content obtained by measuring while maintaining the laminate structure of the electrode laminate, and is considered to be mainly the amount of moisture desorbed from the surface of the electrode laminate.

[0023] (ratio of surface moisture to total moisture) In the solid-state battery of the present disclosure, the ratio of the surface moisture content to the total moisture content present throughout the electrode laminate is 0.50 to 1.00. This ratio may be, for example, 0.50 or more, 0.70 or more, or 0.90 or more, or 1.00 or less, 0.99 or less, or 0.98 or less. The ratio of the surface moisture content to the total moisture content can be calculated from the total moisture content described below and the surface moisture content.

[0024] In the present disclosure, the "total moisture content" can be determined by the following method. First, the electrode laminate is pulverized in a mortar, and the powder obtained by pulverization is introduced into a Karl Fischer apparatus (Karl Fischer apparatus CA-310 and moisture vaporizer VA-300, manufactured by Nitto Seiko). Next, the powder is placed in the moisture vaporizer VA-300, which has been preheated to 200°C, and the amount of moisture desorbed from the powder by heating is measured using the Karl Fischer apparatus CA-310. The obtained moisture content is defined as the total moisture content. The measurement is terminated when the detected moisture content becomes 0.02 μg / sec or less. The total moisture content is the moisture content obtained by pulverizing the electrode laminate and measuring the powder, and is considered to be the amount of moisture desorbed including from the interior of the electrode laminate.

[0025] <Configuration of electrode laminate> In the solid-state battery of the present disclosure, the electrode laminate has a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer stacked in this order. The electrode laminate may have, for example, a positive electrode current collector layer and a negative electrode current collector layer. The electrode laminate is not particularly limited, but preferably has 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 in this order, and more 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 in this order.

[0026] <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.

[0027] 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.

[0028] <Cathode active material layer> The positive electrode active material layer contains at least a positive electrode active material and a sulfide solid electrolyte, and may further contain, optionally, a conductive additive, a binder, etc. The contents of each of the positive electrode active material, the sulfide solid electrolyte, the conductive additive, the binder, etc. in the positive electrode active material layer may be appropriately determined depending on the desired battery performance.

[0029] (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 Mn z O2), lithium nickel-cobalt-aluminate (LiNi 0.8 (CoAl) 0.2 O2), etc., but are not limited to these.

[0030] 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.

[0031] 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.

[0032] (Sulfide solid electrolyte) Examples of sulfide solid electrolytes include, but are not limited to, sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, and argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes 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 PS 6-x Cl x or a combination thereof. The sulfide solid electrolyte is not particularly limited, but may be glass or crystallized glass (glass ceramics).

[0033] (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.

[0034] (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.

[0035] 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.

[0036] 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.

[0037] <Solid electrolyte layer> The solid electrolyte layer contains at least a sulfide solid electrolyte, and may contain, as necessary, a conductive additive, a binder, etc. For the sulfide solid electrolyte, the conductive additive, and the binder, please refer to the description above in "<<Positive Electrode Active Material Layer>>".

[0038] 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.

[0039] 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.

[0040] <Negative electrode active material layer> The negative electrode active material layer contains at least a negative electrode active material and a sulfide solid electrolyte, and may further contain, optionally, a conductive additive, a binder, and the like. The sulfide solid electrolyte, conductive additive, and binder that may be contained in the negative electrode active material layer can be found in the above description of "<Positive Electrode Active Material Layer>". The respective contents of the negative electrode active material, sulfide solid electrolyte, conductive additive, binder, and the like in the negative electrode active material layer may be appropriately determined depending on the desired battery performance.

[0041] (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.

[0042] The negative electrode active material may be in the form of, for example, particles or a sheet.

[0043] 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.

[0044] 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.

[0045] <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.

[0046] 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.

[0047] <Structure of solid-state battery> The solid-state battery is not particularly limited, but may further include a positive electrode current collector layer and a negative electrode current collector layer as necessary. For the positive electrode current collector layer and the negative electrode current collector layer, see the above "<Configuration of electrode laminate>".

[0048] The solid-state battery may be enclosed in a laminate film, although it is not particularly limited thereto, and may be confined under a confining pressure of, for example, 5 MPa, although it is not particularly limited thereto.

[0049] <<Shape of solid-state batteries>> Examples of the shape of the solid-state battery include, but are not limited to, a coin type, a laminate type, a cylindrical type, and a square type.

[0050] <<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.

[0051] <<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 the electrode laminate.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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 case.

[0059] 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).

[0060] <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.

[0061] 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.

[0062] 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.

[0063] <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.

[0064] 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.

[0065] 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.

[0066] <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.

[0067] 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.

[0068] 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.

[0069] 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]

[0070] 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.

[0071] <Measurement of surface moisture content> The surface moisture content of the electrode laminate was measured by punching out 20 sheets of the electrode laminate to a diameter of 9.2 mm and introducing them into a Karl Fischer apparatus (Karl Fischer apparatus CA-310 and moisture vaporizer VA-300, manufactured by Nitto Seiko). Specifically, the punched electrode laminate was placed in a moisture vaporizer VA-300 that had been preheated to 200°C, and the moisture desorbed by heating was measured using the Karl Fischer apparatus CA-310 to determine the surface moisture content. The measurement was terminated when the detected moisture content was 0.02 μg / sec or less.

[0072] <Measurement of total moisture content> The total moisture content of the electrode laminate was measured by processing the electrode laminate into powder in a mortar and introducing the powder into a Karl Fischer apparatus (Karl Fischer apparatus CA-310 and moisture vaporizer VA-300, manufactured by Nitto Seiko). Specifically, the powder was placed in a moisture vaporizer VA-300 preheated to 200°C, and the moisture desorbed by heating was measured using the Karl Fischer apparatus CA-310 to determine the total moisture content. The measurement was terminated when the detected moisture content was 0.02 μg / sec or less.

[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 laminate was roll-pressed at 175°C and 5 ton / cm to obtain a densified electrode laminate. The 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. For the densified electrode laminate D1, the surface moisture content was 251.7 ppm, the total moisture content was 259.3 ppm, and the ratio of the surface moisture content to the total moisture content was 0.97.

[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] <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.

[0079] <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.

[0080] Examples 2 to 4 <Preparation of Electrode Stacks D2 to D4> Electrode stacks D2 to D4 were produced in the same manner as in Example 1, except that instead of leaving the densified electrode stack for 17 minutes in a humidity-controlled glove box set at a dew point of -50°C, the electrode stack was left for a predetermined time in a glove box set at a dew point shown in Table 1. The surface moisture content, total moisture content, and ratio of the surface moisture content to the total moisture content of electrode stacks D2 to D4 were as shown in Table 1 and FIG.

[0081] <Fabrication of Solid-State Batteries E2 to E4, and DC Resistance and Resistance Increase Rate of Solid-State Batteries E2 to E4> Except for using electrode laminates D2 to D4 instead of electrode laminate D1, solid batteries E2 to E4 were produced in the same manner as in Example 1. The initial DC resistance and resistance increase rate of solid batteries E2 to E4 were determined in the same manner as in Example 1. The respective results were as shown in Table 1 and FIG.

[0082] Comparative Example 1 <Preparation of electrode laminate d1> An 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 at −50° C. and no intentional moisture adsorption was performed. The surface moisture content, total moisture content, and ratio of the surface moisture content to the total moisture content of the electrode laminate d1 were as shown in Table 1.

[0083] <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. 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.

[0084] [Table 1]

[0085] In Examples 1 to 4, solid-state batteries E1 to E4 having electrode laminates containing a predetermined amount of surface moisture did not significantly increase their initial DC resistance, and were able to reduce the rate of resistance increase of the batteries 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 resistance increase. On the other hand, solid-state battery e1 in Comparative Example 1, in which surface moisture was not intentionally adsorbed, had a low ratio of surface moisture to total moisture, and therefore had a low initial DC resistance but was less effective in reducing the rate of resistance increase, i.e., the effect of making the battery's DC resistance more likely to decrease due to durability. Figure 4 shows the relationship between the surface moisture content of the solid-state batteries in Examples and Comparative Examples and the initial DC resistance and the rate of resistance increase.

[0086] Although the details are not clear, it is presumed that when a predetermined amount of moisture is adsorbed to an electrode laminate in which the positive electrode active material layer, solid electrolyte layer, and negative electrode active material layer contain a sulfide solid electrolyte, the moisture adsorbed to the electrode laminate penetrates to the interface between the positive electrode active material layer and the solid electrolyte layer, forming a reaction layer with an appropriate thickness at the interface, which suppresses oxidative decomposition of the sulfide solid electrolyte during charging, and thereby making it possible to reduce the rate of increase in resistance due to durability without significantly increasing the initial DC resistance.

[0087] 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]

[0088] 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. an electrode stack in which a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer are stacked in this order; the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer each contain a sulfide solid electrolyte; The surface moisture content of the electrode laminate is 200 to 1500 ppm, and a ratio of the surface moisture content to the total moisture content present in the entire electrode laminate is 0.50 to 1.00; solid state battery.

2. 2. The solid state battery according to claim 1, wherein the surface moisture content of the electrode laminate is 200 to 600 ppm.

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 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 the 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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