Electrode layer and battery

Abstract

To provide an electrode layer with little increase in resistance due to charge and discharge.SOLUTION: An electrode layer comprising: an electrode active material; and a solid electrolyte containing a halogen element, wherein a liberation rate of the halogen element in the solid electrolyte is less than 12.6%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electrode layer and a battery. [Background technology]

[0002] Various technologies have been proposed for batteries such as those disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-098419 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a negative electrode composite containing a Si-based active material, a solid electrolyte, and an organic solvent, but the electrode layer containing the solid electrolyte deteriorates during repeated charge and discharge, which tends to increase the resistance of the battery.

[0005] The present disclosure has been made in view of the above circumstances, and has as its main object to provide an electrode layer in which the increase in resistance due to charging and discharging is small. [Means for solving the problem]

[0006] That is, the present disclosure includes the following aspects. <1> An electrode layer, the electrode layer includes an electrode active material and a solid electrolyte containing a halogen element, An electrode layer, wherein the liberation rate of the halogen element in the solid electrolyte is less than 12.6%.

[0007] <2> The electrode active material is a Si-based active material. <1> The electrode layer according to claim 1.

[0008] <3> The free halogen element rate in the solid electrolyte is 6.2% or more and 8.4% or less. <1> or <2> The electrode layer according to claim 1.

[0009] <4> A battery comprising, in this order, a positive electrode layer, an electrolyte layer, and a negative electrode layer, The negative electrode layer is <1> ~ <3> A battery, wherein the electrode layer is the electrode layer described in any one of the above items.

[0010] <5> <4> wherein the electrolyte layer contains a solid electrolyte. [Effects of the Invention]

[0011] The present disclosure has an effect of making it possible to obtain an electrode layer in which the increase in resistance due to charging and discharging is small. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of the electrode layer that do not characterize the present disclosure) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field. In the present disclosure, unless otherwise specified, the average particle size of particles is the median diameter (D50) value, which is the particle size at 50% of the cumulative value in the volume-based particle size distribution measured by laser diffraction / scattering particle size distribution measurement.

[0014] A. Electrode layer In the present disclosure, an electrode layer comprising: the electrode layer includes an electrode active material and a solid electrolyte containing a halogen element, The electrode layer has a rate of liberation of the halogen element in the solid electrolyte of less than 12.6%.

[0015] When an electrode layer contains a solid electrolyte containing halogen elements, halogen elements such as iodine in the solid electrolyte are gradually released during repeated charge and discharge, causing the solid electrolyte to deteriorate and its ionic conductivity to decrease. As a countermeasure, it was found that by controlling the rate of halogen element release in the solid electrolyte, the release of halogen elements can be suppressed, and as a result, the increase in battery resistance due to repeated charge and discharge can be suppressed.

[0016] 1. Electrode active material The electrode active material in the present disclosure is a negative electrode active material when the electrode layer is a negative electrode layer, and is a positive electrode active material when the electrode layer is a positive electrode layer.

[0017] Examples of negative electrode active materials in the present disclosure include Si-based active materials, carbon-based active materials, oxide-based active materials, and Li-based active materials. Examples of Si-based active materials include simple Si, Si alloys, Si oxides, and Si carbides. Si alloys are alloys containing Si as the main component. Examples of metals other than Si in Si alloys include Na, W, Mo, Cr, V, Nb, Fe, Ti, Zr, and Hf. Si alloys may contain only one or more metals other than Si. Examples of Si oxides include SiO. Examples of Si carbides include SiC. Examples of carbon-based active materials include graphite, hard carbon, and soft carbon. An example of the oxide-based active material is lithium titanate. Examples of Li-based active materials include elemental Li and Li alloys, etc. Examples of metal elements other than lithium contained in Li alloys include Mg, Ag, In, Sn, Si, Ga, Au, and Pt.

[0018] The positive electrode active material in the present disclosure may be, for example, an oxide active material. Examples of the oxide active material include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. A coating layer containing a Li-ion conductive compound may be formed on the surface of the positive electrode active material. This is because it can suppress the reaction between the positive electrode active material and the solid electrolyte (particularly a sulfide solid electrolyte). Examples of Li-ion conductive compounds include B2O3, Li2B4O7, LiBPO4, Li3PO4, LiPO3, and LiNbO3. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less. The coverage of the Li-ion conductive compound that coats the positive electrode active material is, for example, 70% or more, or may be 90% or more, or even 100%. The method for coating the Li-ion conductive compound is not particularly limited, and any conventionally known method can be used as appropriate.

[0019] The electrode active material is usually in the form of particles. The electrode active material may be in the form of primary particles or secondary particles formed by aggregation of primary particles. The electrode active material may also be porous. That is, the electrode active material may have voids inside the primary particles. The proportion of voids in the primary particles (porosity) is, for example, 4% or more, and may be 10% or more. The porosity may be, for example, 40% or less, and may be 20% or less. The porosity can be determined, for example, by the following procedure. First, a cross section of an electrode layer containing an electrode active material is obtained by ion milling. The cross section is then observed with a scanning electron microscope (SEM) to obtain a photograph of the particles. From the obtained photograph, the electrode active material portion and the void portion are clearly distinguished using image analysis software and binarized. The areas of the electrode active material portion and the void portion are determined, and the porosity (%) is calculated using the following formula: Porosity (%) = 100 × (void area) / ((electrode active material area) + (void area))

[0020] The electrode active material may be crystalline or amorphous. When the electrode active material is a Si-based active material and is crystalline, the electrode active material usually has a Si crystalline phase. An example of the Si crystalline phase is a diamond-type crystalline phase. General Si contains the diamond-type crystalline phase as the Si crystalline phase. The electrode active material may contain the diamond-type crystalline phase as the main phase of the Si crystalline phase. Another example of a Si crystalline phase is a silicon clathrate crystalline phase. The silicon clathrate crystalline phase may be a silicon clathrate I crystalline phase or a silicon clathrate II crystalline phase. In a silicon clathrate crystalline phase, a plurality of Si elements form a polyhedron (cage) including a pentagon or hexagon. This polyhedron has a space inside that can encapsulate metal ions such as Li ions. By inserting metal ions into this space, volume change due to charge and discharge can be suppressed. The Si-based active material may contain a silicon clathrate I crystalline phase or a silicon clathrate II crystalline phase as the main phase of the Si crystalline phase. A method for producing a silicon clathrate crystalline phase includes, for example, reacting Na with Si to produce a Na-Si alloy, and then calcining the Na-Si alloy to remove Na from the Na-Si alloy.

[0021] The average particle size (D50) of the electrode active material is not particularly limited, but may be, for example, 0.01 μm or more and 50 μm or less, or 0.5 μm or more and 30 μm or less.

[0022] The BET specific surface area of ​​the electrode active material is not particularly limited, but is, for example, 30 m 2 / g or more, and 40m 2 / g or more, and 2 / g or more, and 2 On the other hand, the BET specific surface area of ​​the electrode active material may be, for example, 150 m2 / g or less.

[0023] The electrode active material may or may not be coated with a coating layer containing a solid electrolyte. The solid electrolyte constituting the coating layer is not particularly limited, but examples include the solid electrolytes described in "2. Solid Electrolytes" below, and in particular, a sulfide solid electrolyte may be used. The coverage of the coating layer with respect to the electrode active material is, for example, 50% or more, or may be 70% or more, or may be 90% or more. The thickness of the coating layer is, for example, 1 nm or more and 100 nm or less, or may be 5 nm or more and 50 nm or less, or may be 10 nm or more and 30 nm or less.

[0024] The proportion of the electrode active material in the electrode layer is, for example, 20% by mass or more, or may be 30% by mass or more, or may be 40% by mass or more. If the proportion of the electrode active material is too low, sufficient energy density may not be obtained. On the other hand, the proportion of the electrode active material in the electrode layer is, for example, 80% by mass or less, or may be 70% by mass or less, or may be 60% by mass or less. If the proportion of the electrode active material is too high, the ionic conductivity and electronic conductivity of the electrode layer may relatively decrease.

[0025] 2.Solid electrolyte The electrode layer contains a solid electrolyte. Addition of the solid electrolyte improves the ionic conductivity of the electrode layer. The solid electrolyte may be an inorganic solid electrolyte such as a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, or a complex hydride solid electrolyte, or an organic solid electrolyte such as a gel electrolyte. Among these, the solid electrolyte may be a sulfide solid electrolyte, because it has high ionic conductivity. A sulfide solid electrolyte is an electrolyte containing S element as the main anion component. The solid electrolyte contained in the electrode layer may be any solid electrolyte containing a halogen element. The free halogen element ratio in the solid electrolyte may be less than 12.6%, and may be 6.2% or more and 8.4% or less. The rate of liberation of halogen elements in a solid electrolyte can be calculated by comparing a map of sulfur element S obtained by SEM-EDX or STEM-EDX with a map of halogen element X, and calculating the ratio of the area of ​​the region where only halogen element X is detected to the total area of ​​the region where both sulfur element S and halogen element X are detected (the area where S and X overlap) and the region where only halogen element X is detected (the area where only halogen element X is detected). Freedom rate (%) = 100 × (area of ​​X only) / ((area where S and X overlap) + (area of ​​X only)) The liberation rate of halogen elements in the solid electrolyte may be controlled by changing the drying temperature, drying time, and drying atmosphere conditions of the slurry for producing the electrode layer. The drying temperature of the slurry for producing the electrode layer may be 150°C to 250°C. The drying time of the slurry for producing the electrode layer may be 30 minutes to 3 hours, or may be 1 to 2 hours. The drying atmosphere of the slurry for producing the electrode layer may be a nitrogen atmosphere, an Ar atmosphere, a vacuum atmosphere, or the like.

[0026] The sulfide solid electrolyte typically contains at least Li and S. The sulfide solid electrolyte may further contain Me (Me is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In). The sulfide solid electrolyte may also contain a halogen element such as F, Cl, Br, or I.

[0027] The sulfide solid electrolyte may be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide solid electrolyte may have a crystalline phase. Examples of the crystalline phase include a Thio-LISICON-type crystalline phase, an Argyrodite-type crystalline phase, and an LGPS-type crystalline phase.

[0028] The composition of the sulfide solid electrolyte is not particularly limited. For example, xLi2S·(1 - x)P2S5 (0.5 ≦ x < 1), yLiI·zLiBr·(100 - y - z)(xLi2S·(1 - x)P2S5) (0.5 ≦ x < 1, 0 ≦ y ≦ 30, 0 ≦ z ≦ 30) can be mentioned. In these compositions, x may satisfy 0.7 ≦ x ≦ 0.8. Also, as another example of the composition of the sulfide solid electrolyte, Li 7-x PS 6-x X x can be mentioned. X is at least one of F, Cl, Br, and I, and x satisfies 0 ≦ x < 2. Also, as another example of the composition of the sulfide solid electrolyte, Li 4-x Me 1-x P x S4 (0 < x < 1) can be mentioned. Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi. Examples of the sulfide solid electrolyte include LiI - LiBr - Li2S - P2S5, LiI - Li2S - P2S5, LiI - Li2S - P2O5, and LiI - Li3PO4 - P2S5, etc.

[0029] From the viewpoint of good handleability, the shape of the solid electrolyte may be particulate. Also, the average particle diameter (D50) of the particles of the solid electrolyte is not particularly limited and may be 1 nm to 100 μm.

[0030] The proportion of the solid electrolyte in the electrode layer may be, for example, 10% by mass or more. If the proportion of the solid electrolyte is too small, there may be a shortage of ion conduction paths in the electrode layer. On the other hand, the proportion of the solid electrolyte in the electrode layer may be, for example, 60% by mass or less. If the proportion of the solid electrolyte is too large, relatively, the proportion of the electrode active material will be reduced, and the energy density may be lowered.

[0031] 3. Conductive material The electrode layer may contain a conductive material. Addition of the conductive material improves the electronic conductivity of the electrode layer. Examples of the conductive material include carbon materials, metal particles, and conductive polymers. Examples of the carbon material include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as vapor grown carbon fiber (VGCF), carbon nanotubes (CNT), and carbon nanofibers (CNF).

[0032] The proportion of the conductive material in the electrode layer may be, for example, 0.1% by mass or more. If the proportion of the conductive material is too low, the electron conduction path in the electrode layer may be insufficient. On the other hand, the proportion of the conductive material in the electrode layer may be, for example, 5% by mass or less. If the proportion of the conductive material is too high, the proportion of the electrode active material may be relatively low, which may result in a low energy density.

[0033] 4. Binder The electrode layer may contain a binder, such as styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butadiene rubber (BR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-isoprene-styrene block copolymer (SIS), or ethylene-propylene-diene copolymer (EPDM).

[0034] The proportion of the binder in the electrode layer may be, for example, 0.5% by mass or more. If the proportion of the binder is too low, it may be difficult to sufficiently reduce the increase in resistance due to charging and discharging. On the other hand, the proportion of the binder in the electrode layer may be, for example, 5% by mass or less. If the proportion of the binder is too high, the proportion of the electrode active material may be relatively low, which may result in a low energy density.

[0035] The electrode layer in the present disclosure is typically used in batteries. The electrode layer may be a negative electrode layer or a positive electrode layer. The thickness of the electrode layer is, for example, 0.1 μm or more and 1000 μm or less, or 1 μm or more and 500 μm or less, or 30 μm or more and 100 μm or less.

[0036] The method for producing the electrode layer is not particularly limited, and examples thereof include a production method having the following steps: a preparation step of preparing the electrode active material, a mixing step of mixing the electrode active material, the solid electrolyte, and a solvent to obtain an electrode slurry, and an electrode layer formation step of forming an electrode layer using the electrode slurry. The present disclosure can also provide such a production method for the electrode layer.

[0037] The preparing step is a step of preparing the electrode active material. The electrode active material is the same as that described above in "1. Electrode Active Material." The mixing step is a step of mixing the electrode active material, the solid electrolyte, and a solvent to obtain an electrode slurry. In the present disclosure, an electrode slurry containing the electrode active material, the solid electrolyte, and the solvent can also be provided.

[0038] Examples of the solvent (dispersion medium) include tetralin, diisobutyl ketone, butyl butyrate, mesitylene, heptane, dibutyl ether, decane, and toluene, and the solvent may contain two or more of these.

[0039] The electrode layer forming step is a step of forming an electrode layer using the electrode slurry. The method for forming the electrode layer is not particularly limited, and known methods can be used. For example, the method for forming the electrode layer includes a method in which the electrode slurry is applied to an electrode current collector and then dried. When forming the electrode layer, a pressing process may be performed to press the electrode layer in the thickness direction. Examples of the pressing process include a roller press and a flat plate press.

[0040] B.Battery Fig. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. The battery 10 shown in Fig. 1 includes a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, and a negative electrode current collector 5 that collects current from the negative electrode layer 2. In the present disclosure, the positive electrode layer 1 or the negative electrode layer 2 is the electrode layer described above in "A. Electrode Layer."

[0041] According to the present disclosure, by using the above-described electrode layer, a battery with a small increase in resistance due to charging and discharging can be obtained. As described above, the electrode layer may be a negative electrode layer, a positive electrode layer, or a negative electrode layer.

[0042] 1. Negative electrode layer The negative electrode layer is a layer containing at least a negative electrode active material. The negative electrode layer may also contain at least one of a solid electrolyte, a solvent component, a conductive material, and a binder, as needed. Furthermore, when the negative electrode layer is an electrode layer according to the present disclosure, the negative electrode layer contains at least a negative electrode active material and a solid electrolyte containing a halogen element. The negative electrode active material, solid electrolyte, solvent component, conductive material, and binder used in the negative electrode layer are the same as those described above in "A. Electrode Layer," and therefore will not be described here. The mass ratio of the negative electrode active material to the solid electrolyte may be 85:15 to 30:70, or 80:20 to 40:60.

[0043] 2. Positive electrode layer The positive electrode layer is a layer containing at least a positive electrode active material. The positive electrode layer may also contain at least one of a solid electrolyte, a solvent component, a conductive material, and a binder, as needed. Furthermore, when the positive electrode layer is an electrode layer according to the present disclosure, the positive electrode layer contains at least a positive electrode active material and a solid electrolyte containing a halogen element. The positive electrode active material, solid electrolyte, solvent component, conductive material, and binder used in the positive electrode layer are the same as those described above in "A. Electrode layer," and therefore will not be described here. The mass ratio of the positive electrode active material to the solid electrolyte may be 85:15 to 30:70, or may be 80:20 to 50:50.

[0044] 3. Electrolyte layer The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least an electrolyte. The electrolyte may be a solid electrolyte or a liquid electrolyte (electrolytic solution).

[0045] The electrolyte may contain a supporting salt and a solvent. Examples of supporting salts (lithium salts) for the lithium ion conductive electrolyte include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. Examples of solvents used in the electrolyte include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). It is preferable that the electrolyte contain two or more solvents.

[0046] The solid electrolyte is the same as that described above in "A. Electrode Layer," and therefore will not be described here. The solid electrolyte used in the electrolyte layer may or may not contain a halogen element. The solid electrolyte may be used alone or in combination of two or more. When two or more solid electrolytes are used, the two or more solid electrolytes may be mixed, or two or more solid electrolyte layers may be formed to form a multilayer structure. The proportion of the solid electrolyte in the electrolyte layer is not particularly limited, but is, for example, 50% by mass or more, and may be in the range of 60% by mass to 100% by mass, 70% by mass to 100% by mass, or even 100% by mass. The solid electrolyte may contain less than 10% by mass of electrolytic solution relative to the total amount of electrolyte. The solid electrolyte may also be a composite solid electrolyte containing an inorganic solid electrolyte and a polymer electrolyte. When the electrolyte layer is a solid electrolyte layer, the solid electrolyte layer contains a solid electrolyte and, if necessary, a binder and the like. Examples of the binder include the binders that can be contained in the electrode layer described above. When the solid electrolyte layer contains a binder, the content of the binder may be 0% by mass to 10% by mass with respect to the total amount of the solid electrolyte layer.

[0047] The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less, or may be 0.1 μm or more and 500 μm or less, or may be 0.1 μm or more and 100 μm or less.

[0048] 4. Other configurations The battery according to the present disclosure may have a positive electrode current collector that collects current from the positive electrode layer, and a negative electrode current collector that collects current from the negative electrode layer.

[0049] Examples of materials for the positive electrode current collector include SUS, Cr, Au, Pt, Zn, aluminum, copper, nickel, iron, titanium, and carbon. The thickness of the positive electrode current collector is, for example, 0.1 μm or more and 100 μm or less. The positive electrode current collector may be in the form of a foil or a plate. The positive electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on its surface.

[0050] Examples of materials for the negative electrode current collector include SUS, aluminum, copper, nickel, iron, titanium, and carbon. Examples of the shape of the negative electrode current collector include foil and plate. The shape of the negative electrode current collector in plan view is not particularly limited, but examples include circular, elliptical, rectangular, and any polygonal shape. The thickness of the negative electrode current collector varies depending on the shape, but may be, for example, within a range of 1 μm to 50 μm. The negative electrode current collector may have a buffer layer, an elastic layer, or a PTC thermistor layer disposed on its surface.

[0051] The battery of the present disclosure may further include a restraining jig that applies a restraining pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer in the thickness direction. In particular, when the electrolyte layer is a solid electrolyte layer, the restraining pressure may be applied to form good ion conduction paths and electron conduction paths. The restraining pressure may be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. Meanwhile, the restraining pressure may be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0052] 5.Battery The type of battery in the present disclosure is not particularly limited, but is typically a lithium-ion battery. Furthermore, the battery in the present disclosure may be a liquid battery whose electrolyte layer contains an electrolytic solution, or a solid battery whose electrolyte layer contains a solid electrolyte. The solid battery may be a semi-solid battery or an all-solid-state battery. In the present disclosure, a semi-solid battery is a battery whose electrolyte layer contains an inorganic solid electrolyte and a liquid component (e.g., an ionic liquid). In the present disclosure, an all-solid-state battery is a battery whose electrolyte layer contains only an inorganic solid electrolyte. Furthermore, the battery in the present disclosure may be a primary battery or a secondary battery, but a secondary battery is particularly preferred. This is because it can be repeatedly charged and discharged and is useful, for example, as an on-board battery. The shape of the battery is not particularly limited, and may be, for example, a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, or a laminate type.

[0053] Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, the battery may be used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for mobile objects other than vehicles (for example, trains, ships, and aircraft), and as a power source for electrical appliances such as information processing devices.

[0054] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0055] [Example 1] (Preparation of electrode active material) Metallic Li and Si powder were weighed out in a molar ratio of 4:1 and mixed in a mortar under an Ar atmosphere at room temperature for 0.5 hours to react. This produced Li4Si. The resulting Li4Si was then reacted with ethanol under an Ar atmosphere. The resulting reaction product is believed to contain Si and CH3CHOLi. The reaction product was filtered, and the filtered solid was dried at 120°C for at least 3 hours to produce powdered porous Si.

[0056] The obtained porous Si was used to produce a Na-Si alloy using NaH as a Na source. The NaH used was previously washed with hexane. NaH and porous Si were weighed out to a molar ratio of 1.05:1 and mixed using a cutter mill. The mixture of NaH and porous Si was heated in a heating furnace under an Ar atmosphere at 475°C for 40 hours to obtain a powdered Na-Si alloy.

[0057] Using the obtained Na-Si alloy and AlF3 as a Na trapping agent, silicon clathrate was produced by solid-phase method. The Na-Si alloy and AlF3 were weighed out to a molar ratio of 1:0.35 and mixed using a cutter mill to obtain a reaction material. The obtained powdered reaction material was placed in a stainless steel reaction vessel and heated in a heating furnace under an Ar atmosphere at 310°C for 60 hours to react, obtaining a precursor active material.

[0058] The obtained precursor active material is thought to contain NaF and Al as by-products. Therefore, the precursor active material was washed with a mixed solvent of HNO3 and HO in a volume ratio of 10:90. This removed the by-products from the reaction product. After washing, the mixture was filtered, and the filtered solid was dried at 120°C for more than 3 hours to obtain porous clathrate Si as the electrode active material. The obtained electrode active material was subjected to X-ray diffraction (XRD) measurement using CuKα radiation, and the results confirmed that the electrode active material had a silicon clathrate type II crystalline phase as the main phase.

[0059] (Preparation of negative electrode) The resulting electrode active material, a sulfide solid electrolyte (LiI-Li2S-P2S5-based glass ceramic), a conductive material (VGCF), and a diisobutyl ketone solution containing 5% by mass of a binder (PVDF-based binder), and diisobutyl ketone as a solvent for preparing the negative electrode slurry, were placed in a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50, manufactured by SMT). The container was then shaken for 30 minutes using a shaker (TTM-1, manufactured by Shibata Scientific Co., Ltd.) to obtain the negative electrode slurry. The resulting negative electrode slurry was applied to a negative electrode current collector (Cu foil, manufactured by UACJ) using an applicator by the blade method and dried for 1 hour on a hot plate at 185 °C under an Ar atmosphere. This resulted in a negative electrode comprising a negative electrode current collector and a negative electrode layer.

[0060] (Preparation of positive electrode) The positive electrode active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3A butyl butyrate solution containing 5% by mass of 02 (average particle size 6 μm), a sulfide solid electrolyte (LiI-Li2S-P2S5-based glass ceramic), a conductive material (VGCF), and a PVDF-based binder was added, and the mixture was stirred for 30 seconds using an ultrasonic disperser (UH-50, manufactured by SMT). The container was then shaken for 3 minutes using a shaker (TTM-1, manufactured by Shibata Scientific Co., Ltd.), followed by another 30 seconds of stirring using the ultrasonic disperser and another 3 minutes of shaking using the shaker to obtain a positive electrode slurry. The resulting positive electrode slurry was applied to a positive electrode current collector (Al foil, manufactured by Showa Denko KK) using an applicator by the blade method and dried for 30 minutes on a hot plate at 100 °C under an Ar atmosphere. This resulted in a positive electrode comprising a positive electrode current collector and a positive electrode layer. The area of ​​the positive electrode layer was smaller than that of the negative electrode layer.

[0061] (Fabrication of solid electrolyte layer) A sulfide solid electrolyte (LiI-Li2S-P2S5-based glass ceramic), a heptane solution containing 5% by mass of a BR binder, and heptane were added to a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50, manufactured by SMT). The container was then shaken for 30 minutes using a shaker (TTM-1, manufactured by Shibata Scientific Co., Ltd.) to obtain a slurry. The resulting slurry was applied to a release sheet (Al foil) using an applicator by the blade method and dried on a hot plate at 100°C for 30 minutes. This resulted in a transfer member having a release sheet and a solid electrolyte layer.

[0062] (Fabrication of all-solid-state batteries) A solid electrolyte layer for bonding was placed on the positive electrode layer of the positive electrode, set in a roll press, and pressed at 100 kN / cm and 165°C. This resulted in a first laminate. Next, the negative electrode was set in the roll press and pressed at 60 kN / cm and 25°C. This resulted in a pressed negative electrode. Then, a solid electrolyte layer for bonding and a transfer member were placed in order from the negative electrode layer side. At this time, the solid electrolyte layer for bonding and the solid electrolyte layer on the transfer member were placed facing each other. The resulting laminate was set in a flat uniaxial press and temporarily pressed at 100 MPa and 25°C for 10 seconds. Then, the release sheet was peeled off from the solid electrolyte layer. This resulted in a second laminate. Next, the solid electrolyte layer for bonding in the first laminate and the solid electrolyte layer in the second laminate were placed facing each other, set in a flat uniaxial press, and pressed at 200 MPa and 120°C for 1 minute. This resulted in an all-solid-state battery. The fabricated all-solid-state battery was constrained at a predetermined constraining pressure using a constraining jig.

[0063] [Comparative Example 1] An all-solid-state battery was obtained in the same manner as in Example 1, except that in the preparation of the negative electrode, the negative electrode slurry applied to the negative electrode current collector was dried for 1 hour on a hot plate at 170°C in an Ar atmosphere.

[0064] [Example 2] An all-solid-state battery was obtained in the same manner as in Example 1, except that in the preparation of the negative electrode, the negative electrode slurry applied to the negative electrode current collector was dried on a hot plate at 170°C in an Ar atmosphere for 1 hour, and then further dried on a hot plate at 200°C in a vacuum environment for 1 hour.

[0065] (Measurement of resistance increase) A charge-discharge test was carried out on the all-solid-state batteries obtained in Examples 1 and 2 and Comparative Example 1. Specifically, first, CCCV charging was carried out at 0.1C up to 4.15V, and then discharged at 1C down to 2.5V. The battery was then CCCV charged to 4.15V at 1 / 3C and discharged for 5 seconds at 1 / 3C, and the initial resistance was calculated using the DCIR method from the voltage drop. The battery was then CCCV discharged to 2.5V at 1 / 3C. Next, the battery was subjected to CCCV charging at 1 / 3 C to 4.15 V and CCCV discharging at 1 / 3 C to 2.5 V, and this cycle was repeated 50 times. The resistance after charging and discharging was then determined in the same manner as above. The difference between the resistance after charging and discharging and the initial resistance was calculated as the resistance increase. The results are shown in Table 1. The resistance increase in Table 1 is a relative value, with the result of Comparative Example 1 set to 100.

[0066] (Release rate measurement) After the charge-discharge test, the liberation rate of the I element in the solid electrolyte in the negative electrode layer included in the all-solid-state batteries of Examples 1 and 2 and Comparative Example 1 was measured. The rate of liberation of halogen elements in the solid electrolyte was calculated by comparing the maps of sulfur element S and iodine element I obtained by STEM-EDX, and calculating the ratio of the area of ​​the region where only I was detected to the total area of ​​the region where both sulfur element S and iodine element I were detected (area where S and I overlap) and the region where only I was detected (area where only I was detected). The results are shown in Table 1.

[0067] [Table 1]

[0068] As shown in Table 1, it was confirmed that Examples 1 and 2 had a lower liberation rate of iodine element in the solid electrolyte and a smaller increase in resistance than Comparative Example 1. It is presumed that the lower liberation rate of iodine element in the solid electrolyte suppresses degradation of the solid electrolyte. [Explanation of symbols]

[0069] 1...Positive electrode layer 2...Anode layer 3...electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 10...battery

Claims

1. An electrode layer, the electrode layer includes an electrode active material and a solid electrolyte containing a halogen element, The electrode layer, wherein the liberation rate of the halogen element in the solid electrolyte is less than 12.6%.

2. The electrode layer according to claim 1 , wherein the electrode active material is a Si-based active material.

3. 2. The electrode layer according to claim 1, wherein a liberation rate of the halogen element in the solid electrolyte is 6.2% or more and 8.4% or less.

4. A battery comprising, in this order, a positive electrode layer, an electrolyte layer, and a negative electrode layer, A battery, wherein the negative electrode layer is the electrode layer of claim 1.

5. The all-solid-state battery according to claim 4 , wherein the electrolyte layer includes a solid electrolyte.

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