Electrode layer and battery

Abstract

The invention relates to an electrode layer and a battery. The main purpose of the present invention is to provide an electrode layer having low initial resistance. In the present invention, the problem is solved by providing an electrode layer containing an electrode active material containing an element Si and a solid electrolyte containing an element A as a main component of an anion, the degree of overlap (D) between the element Si and the element A is calculated on the basis of an element mapping image obtained by SEM-EDX measurement, and the degree of overlap (D) between the element Si and the element A is calculated on the basis of an element mapping image obtained by SEM-EDX measurement. And D is greater than-0.472 and no greater than 0.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrode layer and a battery. BACKGROUND

[0002] In recent years, development of batteries has been popular. For example, in the automobile industry, development of batteries for electric vehicles (BEV), plug-in hybrid electric vehicles (PHEV), or hybrid electric vehicles (HEV) is being carried out. In addition, as an electrode active material used in a battery, Si (silicon) is known. For example, in Patent Literature 1, an active material is disclosed, which is an active material containing Si, in which a void is present inside a primary particle.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2023-167083 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] An electrode active material containing Si element has a large theoretical capacity, and is effective for high energy density of a battery. On the other hand, in an electrode layer, it is assumed that the higher the dispersion state of an electrode active material and a solid electrolyte is, the lower the initial resistance is, but it was unexpectedly found that if the dispersion state of an electrode active material and a solid electrolyte is too high, the initial resistance becomes high.

[0008] The present application was completed in view of the above-described actual circumstances, and the main object is to provide an electrode layer having low initial resistance.

[0009] METHOD FOR SOLVING THE PROBLEM [1]

[0011] An electrode layer containing an electrode active material containing Si element and a solid electrolyte containing A element as anions as a main component, in which,

[0012] When the degree of overlap D of the above-described Si element and the above-described A element is calculated based on an elemental mapping image obtained by SEM-EDX measurement, the above-described D is greater than -0.472 and is 0 or less. [2]

[0014] The electrode layer according to [1], in which the above-described D is -0.39 or more. [3]

[0016] The electrode layer according to [1] or [2], in which the above-described D is -0.35 or more and -0.10 or less. [4]

[0018] The electrode layer according to any one of [1] to [3], wherein the oxygen content of the electrode active material is 1.0 mass% or more and 10 mass% or less, the electrode layer contains a solvent component, and δp in the Hansen solubility parameter (HSP) of the solvent component is 2.0 MPa 0.5 The following. [5]

[0020] The electrode layer according to any one of [1] to [4], wherein the oxygen content of the electrode active material is 1.0 mass% or more and 10 mass% or less, and δp in the Hansen solubility parameter (HSP) of the solid electrolyte is 10.0 MPa 0.5 and 15.0 MPa 0.5 The following. [6]

[0022] The electrode layer according to any one of [1] to [5], wherein the solid electrolyte is a sulfide solid electrolyte containing sulfur element as the A element. [7]

[0024] The electrode layer according to any one of [1] to [6], wherein the electrode active material is porous. [8]

[0026] The electrode layer according to any one of [1] to [7], wherein the electrode active material has a silicon clathrate type crystal phase. [9]

[0028] The electrode layer according to any one of [1] to [8], wherein the electrode active material is a negative electrode active material.

[10]

[0030] A battery is a battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer or the negative electrode layer is the electrode layer according to any one of [1] to [9].

[11]

[0032] The battery according to

[10] , wherein the electrolyte layer contains a solid electrolyte.

[0033] Effects of the Invention

[0034] In the present invention, an electrode layer having a low initial resistance can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic cross-sectional view illustrating a battery of the present invention.

[0036] Figure 2 is a mapping image of Si.

[0037] Figure 3 is a mapping image of S.

[0038] Figure 4 is an image showing the degree of overlap D of Si and S. DETAILED DESCRIPTION

[0039] Hereinafter, the electrode layer and the battery of the present application are described in detail.

[0040] A. Electrode layer

[0041] The electrode layer of the present application contains an electrode active material containing Si element and a solid electrolyte containing A element as an anion as a main component. In addition, when the degree of overlap D of Si element and A element is calculated based on the element mapping image obtained by SEM-EDX measurement, the above D is in a prescribed range.

[0042] According to the present application, the degree of overlap D is in a prescribed range, and thus the electrode layer becomes low in initial resistance. As described above, Si has a large theoretical capacity, and is effective for high energy density of the battery. On the other hand, in the electrode layer, it is assumed that the higher the dispersion state of the electrode active material and the solid electrolyte, the lower the initial resistance, but it was unexpectedly found that if the dispersion state of the electrode active material and the solid electrolyte is too high, the initial resistance becomes high. In contrast to this, in the present application, by moderately adjusting the dispersion state of the electrode active material and the solid electrolyte, it is possible to reduce the initial resistance of the electrode layer.

[0043] In the present application, the cross section of the electrode layer is subjected to SEM-EDX measurement, and an element mapping image is obtained, and based on the obtained element mapping image, the degree of overlap D of Si element and A element is calculated. The degree of overlap D is an index based on so-called correlation coefficient. Details of the calculation method of the degree of overlap D are described in the Examples described later. The degree of overlap D is usually greater than -0.472, can be -0.42 or more, can be -0.39 or more, or can be -0.35 or more. If the degree of overlap D is too low, the dispersion state of the electrode active material and the solid electrolyte becomes high, but unexpectedly the initial resistance becomes high. The reason is not clear, but it is presumed that because the dispersion state of the electrode active material and the solid electrolyte becomes high, the electron conduction path becomes insufficient. On the other hand, the degree of overlap D is usually 0 or less, can be -0.05 or less, or can be -0.10 or less. If the degree of overlap D is too high, it is likely that the dispersion state of the electrode active material and the solid electrolyte becomes low, and thus the ion conduction path becomes insufficient, and the initial resistance becomes high.

[0044] 1. Electrode active material

[0045] The electrode active material in the present application contains Si element. As the electrode active material, for example, Si single substance, Si alloy, Si oxide, Si carbide can be listed. The Si alloy is an alloy in which Si is the main component. As the metal other than Si in the Si alloy, for example, Na, W, Mo, Cr, V, Nb, Fe, Ti, Zr, and Hf can be listed. The Si alloy can contain only one metal other than Si, or can contain two or more metals other than Si. As the Si oxide, for example, SiO can be listed. In addition, as the Si carbide, for example, SiC can be listed.

[0046] The oxygen amount of the electrode active material is not particularly limited, and is, for example, 1.0 mass% or more and 10 mass% or less. The oxygen amount of the electrode active material can be 3.0 mass% or more, or 5.0 mass% or more. On the other hand, the oxygen amount of the electrode active material can be 9.0 mass% or less, 8.0 mass% or less, or 7.0 mass% or less. The oxygen amount of the electrode active material is typically the oxygen amount present on the surface of the electrode active material, and is, for example, a value measured by an oxygen-nitrogen-hydrogen (ONH) analysis device. For example, if the electrode active material is cleaned with an aqueous hydrofluoric acid solution, a hydrogen end is generated on the surface of the electrode active material, and the oxygen amount on the surface of the electrode active material decreases.

[0047] The shape of the electrode active material is typically particulate. The electrode active material can be a primary particle, or a secondary particle in which primary particles are aggregated. In addition, the electrode active material is preferably porous (porous Si). That is, the electrode active material preferably has a void inside the primary particle. The proportion of the void in the primary particle (void ratio) is, for example, 4% or more, or 10% or more. In addition, the above void ratio is, for example, 40% or less, or 20% or less. The void ratio can be obtained, for example, by the following procedure. First, for an electrode layer containing the electrode active material, a cross section is exposed by ion milling processing. Then, the cross section is observed by SEM (scanning electron microscope) to obtain a photograph of the particles. Using image analysis software, the silicon portion and the void portion are strictly distinguished from the obtained photograph, and binarization is performed. The areas of the silicon portion and the void portion are obtained, and the void ratio (%) is calculated according to the following formula.

[0048] Void ratio (%) = 100 x (void portion area) / ((silicon portion area) + (void portion area))

[0049] The electrode active material preferably has a large number of voids having a pore diameter of 5 nm or less. The void amount P1 of the voids having a pore diameter of 5 nm or less is, for example, 0.015 cc / g or more, can be 0.020 cc / g or more, or can be 0.023 cc / g or more. On the other hand, the void amount P1 is, for example, 0.05 cc / g or less, can be 0.04 cc / g or less, or can be 0.035 cc / g or less. The void amount in the present application refers to the cumulative pore volume, which can be obtained by, for example, BET measurement, gas adsorption method, mercury porosimetry measurement, 3D-SEM, or 3D-TEM.

[0050] The electrode active material preferably has a large number of voids having a pore diameter of 10 nm or less. The void amount P2 of the voids having a pore diameter of 10 nm or less is, for example, 0.030 cc / g or more, can be 0.035 cc / g or more, or can be 0.040 cc / g or more. On the other hand, the void amount P2 is, for example, 0.08 cc / g or less, can be 0.07 cc / g or less, or can be 0.06 cc / g or less. In addition, the ratio (P1 / P2) of the void amount P1 to the void amount P2 is, for example, 50% or more, can be 55% or more, or can be 57% or more. On the other hand, P1 / P2 is, for example, 80% or less, can be 70% or less, or can be 65% or less.

[0051] The electrode active material preferably has a large number of voids having a pore diameter of 100 nm or less. The void amount P3 of the voids having a pore diameter of 100 nm or less is, for example, 0.10 cc / g or more, can be 0.20 cc / g or more, or can be 0.32 cc / g or more. On the other hand, the void amount P3 is, for example, 0.50 cc / g or less, can be 0.45 cc / g or less, or can be 0.38 cc / g or less. In addition, the ratio (P1 / P3) of the void amount P1 to the void amount P3 is, for example, 6.0% or more, can be 6.5% or more, or can be 6.9% or more. On the other hand, P1 / P3 is, for example, 15% or less, can be 12% or less, or can be 10% or less.

[0052] As an example of a method of producing a porous electrode active material, a method in which an alloy of Li and Si (Li-Si alloy) is produced, and then Li is removed from the Li-Si alloy can be given. The Li-Si alloy can be obtained, for example, by mixing Li and Si. The ratio of Li to Si (Li / Si) is, for example, 1.0 or more, can be 2.0 or more, can be 3.0 or more, or can be 4.0 or more. On the other hand, Li / Si is, for example, 8.0 or less. As a method of removing Li from the Li-Si alloy, a method in which the Li-Si alloy is reacted with a Li extraction material can be given. As the Li extraction material, alcohols such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol; and acids such as acetic acid, formic acid, and propionic acid can be given.

[0053] As another example of a method of producing a porous electrode active material, a method in which an alloy of Mg and Si (Mg-Si alloy) is produced, and then Mg is removed from the Mg-Si alloy can be given. The Mg-Si alloy can be obtained, for example, by heating a mixture of Mg and Si. The ratio of Mg to Si (Mg / Si) is, for example, 1.0 or more, can be 1.5 or more, or can be 2.0 or more. On the other hand, Mg / Si is, for example, 6.0 or less. As a method of removing Mg from the Mg-Si alloy, a method in which Mg in the Mg-Si alloy is changed to MgO by heating the Mg-Si alloy in a non-reactive gas atmosphere containing oxygen, and then the MgO is removed using an acid solution can be given. As the acid solution, an aqueous solution containing hydrochloric acid (HCl) and hydrogen fluoride (HF) can be given.

[0054] The electrode active material can be crystalline or amorphous. In the case where the electrode active material is crystalline, the electrode active material generally has a Si crystal phase. As an example of the Si crystal phase, a diamond-type crystal phase can be given. General Si contains a diamond-type crystal phase as the Si crystal phase. The electrode active material can also contain a diamond-type crystal phase as a main phase of the Si crystal phase.

[0055] As other examples of the Si crystal phase, a silicon clathrate type crystal phase can be given. The silicon clathrate type crystal phase can be a silicon clathrate type I crystal phase or a silicon clathrate type II crystal phase. In the silicon clathrate type crystal phase, a plurality of Si elements forms a polyhedron (cage) including pentagons or hexagons. The polyhedron has a space in the inside which can accommodate metal ions such as Li ions. By inserting metal ions in the space, volume change caused by charge and discharge can be suppressed. The electrode active material can contain the silicon clathrate type I crystal phase as a main phase of the Si crystal phase, or can contain the silicon clathrate type II crystal phase as a main phase of the Si crystal phase. As a method of producing the silicon clathrate type crystal phase, for example, a method in which Na is reacted with Si to produce a Na-Si alloy, and then the Na-Si alloy is fired to remove Na from the Na-Si alloy can be given.

[0056] The average particle diameter (D 50 ) of the electrode active material is not particularly limited, and is, for example, 0.1 μm or more and 50 μm or less, or can be 0.5 μm or more and 30 μm or less. The average particle diameter (D 50 ) can be calculated from measurement based on a scanning electron microscope (SEM), for example. In addition, the BET specific surface area of the electrode active material is not particularly limited, and is, for example, 30 m 2 / g or more, can be 40 m 2 / g or more, can be 50 m 2 / g or more, or can be 60 m 2 / g or more. On the other hand, the BET specific surface area of the electrode active material is, for example, 150 m 2 / g or less.

[0057] The electrode active material can be coated with a coating layer containing a solid electrolyte, or can not be coated. The solid electrolyte constituting the coating layer is not particularly limited, and the solid electrolytes described in "2. Solid electrolyte" described later can be given, of which a sulfide solid electrolyte is preferred. The coating rate of the coating layer with respect to the electrode active material is, for example, 50% or more, can be 70% or more, or can be 90% or more. The thickness of the coating layer is, for example, 1 nm or more and 100 nm or less, can be 5 nm or more and 50 nm or less, or can be 10 nm or more and 30 nm or less.

[0058] The proportion of the electrode active material in the electrode layer is, for example, 20 mass% or more, can be 30 mass% or more, or can be 40 mass% or more. If the proportion of the electrode active material is too small, it can be difficult to obtain sufficient energy density. On the other hand, the proportion of the electrode active material in the electrode layer is, for example, 80 mass% or less, can be 70 mass% or less, or can be 60 mass% or less. If the proportion of the electrode active material is too large, it can be relatively difficult to increase the ion conductivity and the electron conductivity in the electrode layer.

[0059] 2. Solid electrolyte

[0060] The electrode layer contains a solid electrolyte containing an A element as an anion as a main component. By adding the solid electrolyte, the ion conductivity of the electrode layer is improved. As the solid electrolyte, for example, inorganic solid electrolytes such as a sulfide solid electrolyte, a halide solid electrolyte, and an oxide solid electrolyte can be listed. Among them, the solid electrolyte is preferably a sulfide solid electrolyte. This is because the ion conductivity is high. The sulfide solid electrolyte is an electrolyte containing an S element as the A element, the halide solid electrolyte is an electrolyte containing an X element (X is, for example, at least one of F, Cl, Br, and I) as the A element, and the oxide solid electrolyte is an electrolyte containing an O element as the A element.

[0061] The sulfide solid electrolyte contains at least a Li element and an S element. The sulfide solid electrolyte preferably further contains a Me element (Me is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In). In addition, the sulfide solid electrolyte can contain halogen elements such as F, Cl, Br, and I.

[0062] The sulfide solid electrolyte can be a glass-based (amorphous-based) sulfide solid electrolyte, a glass-ceramic-based sulfide solid electrolyte, or a crystal-based sulfide solid electrolyte. The sulfide solid electrolyte can have a crystal phase. As the above crystal phase, for example, a Thio-LISICON-type crystal phase, a argyrodite-type crystal phase, and an LGPS-type crystal phase can be listed.

[0063] The composition of the sulfide solid electrolyte is not particularly limited, and 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 listed. In these compositions, x preferably satisfies 0.7≤x≤0.8. In addition, as another example of the composition of the sulfide solid electrolyte, Li 7-x PS 6-x X x X is at least one of F, Cl, Br, and I, and x satisfies 0≤x<2. In addition, as another example of the composition of the sulfide solid electrolyte, Li 4-x Me 1-x P x S4 (0 < x < 1). Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0064] The δp (polar term) in the Hansen solubility parameter (HSP) of the solid electrolyte is, for example, 10.0 MPa 0.5 The above can be 12.0 MPa 0.5 The above can also be 12.5 MPa 0.5 The above. In addition, the δp of the solid electrolyte is, for example, 15.0 MPa 0.5 The above. The δp (polar term) in the Hansen solubility parameter can be calculated based on Hansen Solubility Parameters: A user’s handbook, Second Edition. Boca Raton, Fla: CRC Press. (Hansen, Charles (2007)).

[0065] The proportion of the solid electrolyte in the electrode layer is, for example, 10 mass% or more, can be 20 mass% or more, and can be 30 mass% or more. If the proportion of the solid electrolyte is too small, it can be that the ion conduction path in the electrode layer is insufficient. On the other hand, the proportion of the solid electrolyte in the electrode layer is, for example, 60 mass% or less, and can be 50 mass% or less. If the proportion of the solid electrolyte is too large, it can be that the proportion of the electrode active material relatively decreases and the energy density decreases.

[0066] 3. Binder

[0067] The electrode layer can contain a conductive material. The binder can or can not contain an unsaturated bond. The unsaturated bond is preferably an olefinic unsaturated bond. The binder can have an unsaturated bond in the main chain or can have an unsaturated bond in the side chain. As the binder containing an unsaturated bond, for example, a butadiene rubber-based binder (BR-based binder) such as styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butadiene rubber (BR), a styrene-based block copolymer such as styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and ethylene-propylene-diene copolymer (EPDM) can be exemplified.

[0068] The proportion of the binder in the electrode layer is, for example, 0.5 mass% or more, can be 1.0 mass% or more, and can be 1.5 mass% or more. If the proportion of the binder is too small, it can be that the increase in resistance caused by charge and discharge cannot be sufficiently reduced. On the other hand, the proportion of the binder in the electrode layer is, for example, 5 mass% or less, and can be 3 mass% or less. If the proportion of the binder is too large, it can be that the proportion of the electrode active material relatively decreases and the energy density decreases.

[0069] 4. Conductive material

[0070] The electrode layer can contain a conductive material. By adding a conductive material, the electron conductivity of the electrode layer is improved. As the conductive material, for example, carbon materials, metal particles, conductive polymers can be listed. As the carbon material, for example, particles of carbon materials such as acetylene black (AB), ketjen black (KB), fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), carbon nanofibers (CNF) can be listed.

[0071] The proportion of the conductive material in the electrode layer is, for example, 0.1% by mass or more, can be 0.5% by mass or more, or can be 1.0% by mass or more. If the proportion of the conductive material is too small, it can be possible that the electron conduction path in the electrode layer is insufficient. On the other hand, the proportion of the conductive material in the electrode layer is, for example, 5% by mass or less, or can be 3% by mass or less. If the proportion of the conductive material is too large, it can be possible that the proportion of the electrode active material relatively decreases and the energy density decreases.

[0072] 5. Electrode layer

[0073] The electrode layer can contain a solvent component. The solvent component is, for example, a residual component of a solvent (dispersion medium) used at the time of production of the electrode layer. The solvent component is preferably low in polarity. If the solvent component is high in polarity, for example, the dispersibility of the solid electrolyte is improved, but if the solvent component remains in the electrode layer, it can be possible that the solid electrolyte deteriorates due to the remaining solvent component. On the other hand, if the solvent component is low in polarity, it is possible to suppress deterioration of the solid electrolyte due to the remaining solvent component.

[0074] The δp in the Hansen solubility parameter (HSP) of the solvent component is, for example, 6.0 MPa 0.5 may be 5.5 MPa 0.5 may be 4.0 MPa 0.5 may be 3.5 MPa 0.5 may be 2.0 MPa 0.5 may be 1.5 MPa 0.5 may also be 1.0 MPa 0.5 may be 0 MPa 0.5 may be greater than 0 MPa 0.5 As the solvent component, for example, tetralin, diisobutyl ketone, dodecane, isodecane, butyl butyrate, mesitylene, heptane, dibutyl ether, decane, toluene can be listed.

[0075] The proportion of solvent in the electrode layer can be, for example, 10 ppm or more, 50 ppm or more, or 100 ppm or more. If the proportion of solvent is too low, the load on the electrode layer drying process may increase. On the other hand, the proportion of solvent in the electrode layer can be, for example, 15,000 ppm or less, 5,000 ppm or less, or 500 ppm or less. If the proportion of solvent is too high, the formability of the electrode layer may decrease. The proportion of solvent in the electrode layer can be determined, for example, using gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS).

[0076] As described above, the electrode layer contains at least an electrode active material and a solid electrolyte comprising A as the main anion. In this invention, an organic compound having two or more benzene rings may be present between the electrode active material and the solid electrolyte. This organic compound exhibits high chemical stability, thus suppressing the degradation of the solid electrolyte associated with charging and discharging (e.g., reductive decomposition, oxidative decomposition). Therefore, the increase in resistance caused by charging and discharging can be suppressed. Particularly preferred is the conjugated extension of the inner part of one benzene ring to the outer part (e.g., another benzene ring). Furthermore, the organic compound may be dispersed in the aforementioned binder present between the electrode active material and the solid electrolyte.

[0077] Organic compounds having two or more benzene rings include, for example, compounds represented by the following general formula (1) or general formula (2).

[0078]

[0079] (where R is in the formula) 1 and R 2 Each is an independent organic group, R 3 ~R 10 Each is independently a hydrogen atom or a substituent, n 1 (Integers between 0 and 4.)

[0080] As a compound represented by general formula (1), for example, 9,9-bis(4-glycidoxyphenyl)fluorene, represented by the following chemical formula (1), can be listed.

[0081]

[0082] As another example of an organic compound having two or more benzene rings, compounds represented by the following general formula (3) can be listed.

[0083]

[0084] (In the formula, S is a single bond or an organic group, R) 11 ~R 20each independently is a hydrogen atom or a substituent.

[0085] As the compound represented by General Formula (3), for example, 1,3-diphenyl-2,3-epoxy-1-propanone represented by Chemical Formula (2) below can be cited.

[0086]

[0087] The electrode layer in the present application is generally used for a battery. The electrode layer can be either a negative electrode layer or a positive electrode layer, but is preferably the former. The thickness of the electrode layer is, for example, 0.1 μm or more and 1000 μm or less, can be 0.1 μm or more and 500 μm or less, or can be 0.1 μm or more and 100 μm or less.

[0088] The manufacturing method of the electrode layer is not particularly limited, and for example, a manufacturing method having the following steps can be cited: a preparation step of preparing the above-described electrode active material; a mixing step of mixing the above-described electrode active material, the above-described binder, and a solvent to obtain an electrode slurry; and an electrode layer formation step of forming an electrode layer using the above-described electrode slurry. In the present application, a manufacturing method of the electrode layer can also be provided.

[0089] The above-described preparation step is a step of preparing the above-described electrode active material. As for the above-described electrode active material, the same content as described in the above "1. Electrode active material" applies. In addition, the mixing step is a step of mixing the above-described electrode active material, the above-described binder, and a solvent to obtain an electrode slurry. As for the above-described solvent (dispersion medium), the same content as described above applies. In the present application, an electrode slurry containing the above-described electrode active material, the above-described binder, and the above-described solvent can also be provided.

[0090] The above-described electrode layer formation step is a step of forming an electrode layer using the above-described electrode slurry. The method of forming the electrode layer is not particularly limited, and a publicly known method can be employed. As the method of forming the electrode layer, for example, a method of applying the electrode slurry to an electrode current collector and drying it can be cited. At the time of forming the electrode layer, a pressing treatment of pressing the electrode layer in the thickness direction can be performed. As the pressing treatment, for example, roll pressing or flat plate pressing can be cited.

[0091] B. Battery

[0092] Figure 1 is a schematic cross-sectional view illustrating a battery of the present application. Figure 1 The battery 10 illustrated has 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 performs current collection of the positive electrode layer 1, and a negative electrode current collector 5 that performs current collection of the negative electrode layer 2. In the present application, the positive electrode layer 1 or the negative electrode layer 2 is the electrode layer described in the above "A. Electrode layer".

[0093] According to the present application, by using the above electrode layer, a battery having a low initial resistance is obtained. As described above, the electrode layer can be a negative electrode layer or a positive electrode layer, but is preferably the former. Hereinafter, the battery will be described in detail with respect to the case where the electrode layer is a negative electrode layer.

[0094] 1. Negative electrode layer

[0095] The negative electrode layer is a layer containing at least a negative electrode active material. With respect to the negative electrode layer, the same applies as described in the above "A. Electrode layer", and thus the description here is omitted.

[0096] 2. Positive electrode layer

[0097] The positive electrode layer is a layer containing at least a positive electrode active material. In addition, the positive electrode layer can contain at least one of an electrolyte, a conductive material, and a binder, as necessary.

[0098] As the positive electrode active material, for example, an oxide active material can be cited. As the oxide active material, for example, LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, and the like rock-salt layered active materials; LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, and the like spinel active materials; LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, and the like olivine active materials can be cited.

[0099] A coating layer containing a Li-ion conductive oxide can also be formed on the surface of the oxide active material. This is because the reaction of the oxide active material with the solid electrolyte (particularly, the sulfide solid electrolyte) can be suppressed. As the Li-ion conductive oxide, for example, LiNbO3 can be cited. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less. In addition, as the positive electrode active material, for example, Li2S can also be used.

[0100] As the shape of the positive electrode active material, for example, a particle shape can be cited. The average particle diameter (D 50 ) of the positive electrode active material is not particularly limited, and is, for example, 10 nm or more, and can also be 100 nm or more. On the other hand, the average particle diameter (D 50 ) of the positive electrode active material is, for example, 50 μm or less, and can also be 20 μm or less.

[0101] The electrolyte used in the positive electrode layer is the same as that described in "3. Electrolyte layer". Also, the conductive material and the binder used in the positive electrode layer are the same as those described in the above "A. Electrode layer", and thus the description thereof is omitted here. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less, can be 0.1 μm or more and 500 μm or less, or can be 0.1 μm or more and 100 μm or less.

[0102] 3. Electrolyte layer

[0103] 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 can be a solid electrolyte or a liquid electrolyte (electrolytic solution).

[0104] The solid electrolyte is the same as that described in the above "A. Electrode layer", and thus the description thereof is omitted here. On the other hand, the electrolytic solution preferably contains a supporting salt and a solvent. As the supporting salt (lithium salt) of the electrolytic solution having lithium ion conductivity, for example, 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 can be listed. As the solvent used in the electrolytic solution, for example, 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 ethylmethyl carbonate (EMC) can be listed. The electrolytic solution preferably contains two or more kinds of solvents.

[0105] The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less, can be 0.1 μm or more and 500 μm or less, or can be 0.1 μm or more and 100 μm or less.

[0106] 4. Other configurations

[0107] The battery of the present application preferably has a positive electrode current collector that collects the positive electrode layer and a negative electrode current collector that collects the negative electrode layer. As the material of the positive electrode current collector, for example, SUS, aluminum, nickel, iron, titanium, and carbon can be listed. On the other hand, as the material of the negative electrode current collector, for example, SUS, copper, nickel, and carbon can be listed.

[0108] The battery of the present application can further have a constraint jig that imparts a constraint pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer in the thickness direction. Particularly in the case where the electrolyte layer is a solid electrolyte layer, in order to form a good ion conduction path and an electron conduction path, it is preferable to impart a constraint pressure. The constraint pressure is, for example, 0.1 MPa or more, can be 1 MPa or more, or can be 5 MPa or more. On the other hand, the constraint pressure is, for example, 100 MPa or less, can be 50 MPa or less, or can be 20 MPa or less.

[0109] 5. Battery

[0110] The kind of the battery of the present application is not particularly limited, and is typically a lithium ion battery. In addition, the battery of the present application can be a liquid battery in which the electrolyte layer contains an electrolytic solution, or can be a solid battery in which the electrolyte layer contains a solid electrolyte. The solid battery can be a semi-solid battery or a full solid battery. In the present application, the semi-solid battery is a battery in which the electrolyte layer has an inorganic solid electrolyte and a liquid component (for example, an ionic liquid). In the present application, the full solid battery is a battery in which the electrolyte layer contains only an inorganic solid electrolyte as an electrolyte. In addition, the battery of the present application can be a primary battery or a secondary battery, and is preferably a secondary battery. This is because it is useful as, for example, a battery for a vehicle, which is repeatedly charged and discharged.

[0111] As the use of the battery, for example, a power source for a vehicle such as a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), an electric vehicle (BEV), a gasoline vehicle, a diesel vehicle, and the like can be exemplified. It is particularly preferable to be used as a power source for driving a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), or an electric vehicle (BEV). In addition, the battery can also be used as a power source for a moving body other than a vehicle (for example, a train, a ship, an airplane), and can also be used as a power source for an electric product such as an information processing device.

[0112] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are examples, and any technical solution having substantially the same configuration and exerting the same effects as those recited in the claims of the present application is included in the technical scope of the present application.

[0113] Example

[0114] [Example 1]

[0115] (Production of electrode active material)

[0116] Li and Si powder were weighed in a molar ratio of 4:1, mixed with a mortar under an Ar atmosphere at room temperature for 0.5 hours, and thereby caused to react. Thus, Li4Si was obtained. The obtained Li4Si was caused to react with ethanol under an Ar atmosphere. It was considered that the obtained reaction product contained Si and CH3CH2OLi. The reaction product was filtered, and the filtered solid component was dried at 120°C for 3 hours or more, thereby obtaining porous Si in powder form.

[0117] Using the obtained porous Si, a Na-Si alloy was produced using NaH as a Na source. Note that as NaH, NaH that had been previously washed with hexane was used. NaH and the porous Si were weighed in a molar ratio of 1.05:1, and mixed using a chopper. The mixture of NaH and the porous Si was heated using a heating furnace under an Ar atmosphere at 475°C for 40 hours, and thereby a Na-Si alloy in powder form was obtained.

[0118] Using the obtained Na-Si alloy, a silicon clathrate was produced by a solid phase method further using AlF3 as a Na trapping agent. Na-Si alloy and AlF3 were weighed in a molar ratio of 1:0.35, mixed using a chopper, and thereby a reaction raw material was obtained. The obtained reaction raw material in powder form was put into a stainless steel reaction vessel, and was caused to react by heating using a heating furnace under an Ar atmosphere at 310°C for 60 hours, and thereby a precursor active material was obtained.

[0119] It was considered that the obtained precursor active material contained NaF and Al as by-products. Therefore, the precursor active material was washed using a mixed solvent in which HNO3 and H2O were mixed at a volume ratio of 10:90. Thus, the by-products in the reaction product were removed. After the washing, the precursor active material was filtered, and the filtered solid component was dried at 120°C for 3 hours or more, and thereby an electrode active material was obtained.

[0120] (Production of a negative electrode)

[0121] The obtained electrode active material, sulfide solid electrolyte (Li2S-P2S5 glass ceramic), conductive material (VGCF), tetrahydronaphthalene solution containing binder (BR type binder) at a mass ratio of 5% were added to a polypropylene container, and the mixture was stirred for 30 seconds using an ultrasonic dispersion device (UH-50 manufactured by SMT). Next, the container was vibrated for 30 minutes using an oscillator (TTM-1 manufactured by Shibata Scientific Co., Ltd.) to obtain a negative electrode slurry. The mass ratio of electrode active material, sulfide solid electrolyte, conductive material, and binder was electrode active material: sulfide solid electrolyte: conductive material: binder = 51.27: 42.7: 0.77: 2.89. The obtained negative electrode slurry was coated onto a negative electrode current collector (Cu foil, manufactured by UACJ) using a scraper method with a coater, and dried on a hot plate at 100°C for 30 minutes. This yielded a negative electrode having a negative electrode current collector and a negative electrode layer.

[0122] (The production of the positive electrode)

[0123] Add positive electrode active material (LiNi) to the polypropylene container 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (average particle size 6 μm), sulfide solid electrolyte (Li2S-P2S5 glass-ceramic), conductive material (VGCF), butyl butyrate solution containing PVDF binder at a ratio of 5% by mass, and butyl butyrate were stirred for 30 seconds using an ultrasonic dispersion device (UH-50 manufactured by SMT). Next, the container was vibrated for 3 minutes using an oscillator (TTM-1 manufactured by Shibata Scientific Co., Ltd.), then stirred for 30 seconds using the ultrasonic dispersion device, and vibrated for 3 minutes using the oscillator to obtain a positive electrode slurry. The obtained positive electrode slurry was coated onto a positive current collector (Al foil, manufactured by Showa Denko) using a scraper method with a coater, and dried on a hot plate at 100°C for 30 minutes. This yielded a positive electrode having a positive current collector and a positive electrode layer. It should be noted that the area of ​​the positive electrode is smaller than that of the negative electrode.

[0124] (Fabrication of the solid electrolyte layer)

[0125] A sulfide solid electrolyte (Li2S-P2S5-based glass ceramic), a heptane solution containing BR-type binder at a ratio of 5% by mass, and heptane were added to a polypropylene container and stirred for 30 seconds using an ultrasonic dispersion device (UH-50 manufactured by SMT). Next, the container was vibrated for 30 minutes using an oscillator (TTM-1 manufactured by Shibata Scientific Co., Ltd.) to obtain a slurry. The obtained slurry was applied to a release sheet (Al foil) using a doctor blade method with a spreader and dried on a hot plate at 100°C for 30 minutes. This yielded a transfer component having a release sheet and a solid electrolyte layer.

[0126] (Manufacture of all-solid-state battery)

[0127] The solid electrolyte layer for bonding was disposed on the positive electrode layer of the positive electrode, and the resulting product was disposed on a roll press, and pressing was performed under conditions of 100 kN / cm and 165°C. Thus, a first layered product was obtained. Next, the negative electrode was disposed on the roll press, and pressing was performed under conditions of 60 kN / cm and 25°C. Thus, a pressed negative electrode was obtained. Then, the solid electrolyte layer for bonding and the transfer member were disposed in this order from the negative electrode layer side. At this time, the solid electrolyte layer for bonding was disposed so as to face the solid electrolyte layer of the transfer member. The resulting layered product was disposed on a flat uniaxial press, and pre-pressing was performed under conditions of 100 MPa and 25°C for 10 seconds. Then, the release sheet was peeled off from the solid electrolyte layer. Thus, a second layered product was obtained. Next, the solid electrolyte layer for bonding of the first layered product was disposed so as to face the solid electrolyte layer of the second layered product, and the resulting product was disposed on the flat uniaxial press, and pressing was performed under conditions of 200 MPa and 120°C for 1 minute. Thus, an all-solid-state battery was obtained.

[0128] [Example 2]

[0129] After drying at 120°C for 3 hours or more, liquid treatment was performed using an aqueous HF solution for 1 hour, and the resulting product was filtered, and the filtered solid component was dried at 120°C for 3 hours or more. Other than this, the same operations as in Example 1 were performed, and an electrode active material (negative electrode active material) was obtained. When the negative electrode slurry was prepared, the obtained electrode active material (negative electrode active material) was used, and other than this, the same operations as in Example 1 were performed, and an all-solid-state battery was obtained.

[0130] [Example 3]

[0131] After drying at 120°C for 3 hours or more, liquid treatment was performed using an aqueous HF solution for 1 hour, and the resulting product was filtered, and the filtered solid component was dried at 120°C for 3 hours or more. Other than this, the same operations as in Example 1 were performed, and an electrode active material (negative electrode active material) was obtained. When the negative electrode slurry was prepared, the obtained electrode active material (negative electrode active material) was used, and the amount of the binder used was changed to 0.86 times, and other than this, the same operations as in Example 1 were performed, and an all-solid-state battery was obtained.

[0132] [Comparative Example 1]

[0133] A sulfide solid electrolyte (Li2S-P2S5-based glass ceramic) was immersed in a tetrahydronaphthalene solution containing a binder (BR-based binder) at a proportion of 5% by mass for 1 hour, and was dried. Thus, a sulfide solid electrolyte having a coating layer on the surface was obtained. When the negative electrode slurry was prepared, the obtained sulfide solid electrolyte was used, and the amount of the binder used was changed to 1.14 times, and other than this, the same operations as in Example 1 were performed, and an all-solid-state battery was obtained.

[0134] [evaluation]

[0135] (SEM observation)

[0136] The electrode active material obtained in Examples 1 and 2 was observed using a scanning electron microscope (SEM). As a result, it was confirmed that the electrode active material was porous and had voids inside primary particles.

[0137] (XRD measurement)

[0138] X-ray diffraction (XRD) measurement using Cu Kα rays was performed on the electrode active material obtained in Examples 1 and 2. As a result, it was confirmed that the electrode active material had a silicon clathrate type II crystal phase as a main phase.

[0139] (Overlap of Si element and S element)

[0140] The negative electrode layer in the all-solid-state battery obtained in Examples 1 to 3 and Comparative Example 1 was subjected to cross-section processing, and SEM-EDX measurement was performed on the cross-section of the negative electrode layer, and mapping images of Si and S were obtained, respectively. The measurement conditions were that the EDX magnification was set to 1000 times, the acceleration voltage was set to 5 kV, and the measurement time was set to 60 seconds. The mapping images were taken as objects in a region of 50 μm x 50 μm or more.

[0141] The obtained mapping images were digitized using OpenCV, and noise was removed using a Gaussian filter. Figure 2 is a mapping image of Si, and noise was removed from the mapping image, and then a binary image was obtained. In addition, Figure 3 is a mapping image of S, and noise was removed from the mapping image, and then a binary image was obtained. Next, the binary image of Si and the binary image of S were overlapped, and thereby a composite image for evaluating the overlap of Si and S was obtained.

[0142] Then, using the obtained composite image, the overlap D was calculated. Specifically, the correlation coefficient of Si and S was calculated for each pixel (1280 x 960), and the correlation coefficient of the entire image (overlap D) was calculated. The calculation of the correlation coefficient was performed by a publicly known image processing software. For reference, as shown in Figure 4 (a) to (c), Si is represented by a mesh pattern, and S is represented by a dot pattern. As shown in Figure 4 (a), in the case where Si and S are completely identical, the correlation coefficient is 1. Note that, as shown on the right side of Figure 4 (a), a region in which neither Si nor S exists is not counted. On the other hand, as shown in Figure 4 (b), in the case where Si and S are completely different, the correlation coefficient is -1. In addition, as shown in Figure 4(c) In the case where Si and S are consistent in half of the entire region and only Si or only S exists in the remaining half as shown, the correlation coefficient is 0.

[0143] (Oxygen content measurement)

[0144] The oxygen content was measured using an oxygen-nitrogen-hydrogen (ONH) analyzer (EMGA-930, HORIBA, Ltd.) for the electrode active material produced in Examples 1 and 2. The results are shown in Table 1.

[0145] (Measurement of initial resistance)

[0146] The full solid batteries obtained in Examples 1 to 3 and Comparative Example 1 were subjected to charge-discharge tests. Specifically, first, CCCV charging was performed at 0.1 C to 4.55 V, and discharging was performed at 1 C to 3.0 V. Next, after charging to 3.9 V, charging was performed at 0.1 C to 3.7 V, and discharging was performed at 14.7 mA for 5 seconds, and the initial resistance was calculated from the value of the voltage drop. The results are shown in Table 1. Note that the value of the initial resistance in Table 1 is a relative value when the result of Comparative Example 1 is taken as 100.

[0147]

[0148] As shown in Table 1, it was confirmed that Examples 1 to 3 had a large degree of overlap D of the Si element and the S element and a low initial resistance compared to Comparative Example 1. In particular, Example 2 had a significantly lower initial resistance than Examples 1 and 3. It was also confirmed that the higher the dispersion state of the electrode active material and the solid electrolyte, the smaller the degree of overlap D, but if the dispersion state of the electrode active material and the solid electrolyte is too high as in Comparative Example 1, the initial resistance increases. It was also suggested that the degree of overlap D can be controlled by the polarity (oxygen content) of the surface of the electrode active material (Si), the polarity of the solvent (dispersion medium) used in the slurry, the polarity of the solid electrolyte, and the amount of the binder.

[0149] In the present application, a combination in which the oxygen content of the electrode active material is around 9 mass% (7 mass% to 11 mass%), the δp of the solvent component is around 0.2 MPa 0.5 (0 MPa 0.5 to 1.0 MPa 0.5 , in particular, 0 MPa 0.5 to 0.5 MPa 0.5 , and the δp of the solid electrolyte is around 13.5 MPa 0.5 (12.5 MPa 0.5 to 15.0 MPa 0.5 ) can be adopted as in Example 1.

[0150] Further, in the present application, the combination can be adopted in which the oxygen amount of the electrode active material is around 5 mass% (3 mass% to 7 mass%), δp of the solvent component is around 0.2 MPa (0.1 MPa to 0.3 MPa) as in Embodiments 2 and 3, and δp of the solid electrolyte is around 13.5 MPa (12.5 MPa to 15.0 MPa). 0.5 0.5 0.5 , particularly 0 MPa 0.5 0.5 0.5 0.5 0.5 .

[0151] Explanation of symbols

[0152] 1 … positive electrode layer

[0153] 2 … negative electrode layer

[0154] 3 … electrolyte layer

[0155] 4 … positive electrode current collector

[0156] 5 … negative electrode current collector

[0157] 10 … battery​​​​​​

Claims

1. An electrode layer, which is an electrode layer containing an electrode active material containing a Si element and a solid electrolyte containing a A element as an anion as a main component, wherein when an overlapping degree D of the Si element and the A element is calculated based on an element mapping image obtained by SEM-EDX measurement, the D is greater than -0.472 and is 0 or less.

2. The electrode layer of claim 1, wherein, the D is -0.39 or more.

3. The electrode layer of claim 1, wherein, the D is -0.35 or more and -0.10 or less.

4. The electrode layer according to claim 1, wherein an oxygen amount of the electrode active material is 1.0 mass% or more and 10 mass% or less, the electrode layer contains a solvent component, The δp in the Hansen Solubility Parameters HSP of the solvent component is 2.0 MPa 0.5 The following.

5. The electrode layer according to claim 1, wherein an oxygen amount of the electrode active material is 1.0 mass% or more and 10 mass% or less, The δp in the Hansen solubility parameter HSP of the solid electrolyte is 10.0 MPa 0.5 Above and 15.0 MPa 0.5 Below.

6. The electrode layer of claim 1, wherein, the solid electrolyte is a sulfide solid electrolyte containing a sulfur element as the A element.

7. The electrode layer of claim 1, wherein, the electrode active material is porous.

8. The electrode layer of claim 1, wherein, the electrode active material has a silicon clathrate type crystal phase.

9. The electrode layer of claim 1, wherein, the electrode active material is a negative electrode active material.

10. A battery, which is a battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer or the negative electrode layer is the electrode layer according to any one of claims 1 to 9.

11. The battery of claim 10, wherein, the electrolyte layer contains a solid electrolyte.

Images