Electrode active material, electrode mixture, electrode layer, battery, and manufacturing method for those

Abstract

To provide an electrode active material whose volume change due to charging and discharging is small.SOLUTION: The present disclosure provides an electrode active material having a crystal phase of a silicon class rate II type. A gap is included inside a primary particle and the cavity amount P1 of the gap with a pore diameter of 5 nm or less is 0.015 cc / g or more and 0.05 cc / g or less. The problem can be solved by providing such an electrode active material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an electrode active material, an electrode binder, an electrode layer, a battery, and methods for manufacturing these.

Background Art

[0002] In recent years, battery development has been actively carried out. For example, in the automotive industry, the development of batteries used in battery electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), or hybrid electric vehicles (HEVs) has been advanced. Also, Si (silicon) is known as an electrode active material used in batteries. For example, Patent Document 1 discloses an electrode active material having a silicon clathrate II-type crystal phase and having voids inside the primary particles.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Si has a large theoretical capacity and is effective for increasing the energy density of the battery. On the other hand, Si has a large volume change during charge and discharge. When the volume change during charge and discharge is large, for example, there are problems such as the function of the electrode being likely to deteriorate when charge and discharge are repeated.

[0005] The present disclosure has been made in view of the above circumstances, and the main object is to provide an electrode active material with a small volume change due to charge and discharge.

Means for Solving the Problems

[0006] [1] An electrode active material having a silicon clathrate II-type crystal phase, having voids inside the primary particles, The electrode active material has a void volume P1 of voids with a pore diameter of 5 nm or less, which is 0.015 cc / g or more and 0.05 cc / g or less.

[0007] [2] The electrode active material according to [1], wherein the ratio (P1 / P2) of the void volume P1 to the void volume P2 of voids with a pore diameter of 10 nm or less is 50% or more.

[0008] [3] The electrode active material according to [1] or [2], wherein the void volume P2 of voids with a pore diameter of 10 nm or less is 0.03 cc / g or more and 0.08 cc / g or less.

[0009] [4] The electrode active material according to any one of [1] to [3], wherein the ratio (P1 / P3) of the void volume P1 to the void volume P3 of voids with a pore diameter of 100 nm or less is 6.5% or more.

[0010] [5] The electrode active material according to any one of [1] to [4], wherein the void volume P3 of voids with a pore diameter of 100 nm or less is 0.1 cc / g or more and 0.5 cc / g or less.

[0011] [6] The electrode active material according to any one of [1] to [5], wherein the electrode active material has the silicon class rate II type crystal phase as the main phase.

[0012] [7] An electrode mixture containing the electrode active material according to any one of [1] to [6] and at least one of a conductive material and a binder.

[0013] [8] The electrode mixture according to [7], wherein the electrode mixture further contains a solid electrolyte.

[0014] [9] The electrode mixture according to [8], wherein the solid electrolyte contained in the electrode mixture is a sulfide solid electrolyte.

[0015]

[10] An electrode layer used in a battery, wherein the electrode layer has a crystalline phase of silicon class rate type II and contains an electrode active material having voids inside primary particles, An electrode layer in which the void volume Q1 of voids having a pore diameter of 5 nm or less is 0.008 cc / g or more and 0.04 cc / g or less.

[0016]

[11] The electrode layer according to

[10] , wherein the ratio (Q1 / Q2) of the void volume Q1 to the void volume Q2 of voids having a pore diameter of 10 nm or less is 50% or more.

[0017]

[12] The electrode layer according to

[10] or

[11] , wherein the void volume Q2 of voids having a pore diameter of 10 nm or less is 0.01 cc / g or more and 0.05 cc / g or less.

[0018]

[13] The electrode layer according to any one of

[10] to

[12] , wherein the ratio (Q1 / Q3) of the void volume Q1 to the void volume Q3 of voids having a pore diameter of 100 nm or less is 10% or more.

[0019]

[14] The electrode layer according to any one of

[10] to

[13] , wherein the void volume Q3 of voids having a pore diameter of 100 nm or less is 0.07 cc / g or more and 0.2 cc / g or less.

[0020]

[15] 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, The battery, wherein the positive electrode layer or the negative electrode layer is the electrode layer according to any one of

[10] to

[14] .

[0021]

[16] An alloying step of reacting a Na source and a Si source to obtain a Na-Si alloy, Firing the above Na—Si alloy to reduce the amount of Na in the above Na—Si alloy and form a precursor active material having a silicon class rate II crystal phase; A liquid treatment step of subjecting the above precursor active material to a liquid treatment using hydrofluoric acid to obtain an electrode active material; which has the concentration of hydrogen fluoride in the above hydrofluoric acid is 3% by weight or more; A method for producing an electrode active material, wherein the treatment time in the above liquid treatment step is 3 hours or more and less than 24 hours.

[0022]

[17] A method for producing an electrode active material according to

[16] , wherein in the above electrode active material, the void volume P1 of voids having a pore diameter of 5 nm or less is 0.015 cc / g or more and 0.05 cc / g or less.

[0023]

[18] A preparation step of preparing an electrode active material by the method for producing an electrode active material according to

[16] or

[17] ; A mixing step of mixing the above electrode active material with at least one of a conductive material and a binder to obtain an electrode mixture; which has

[0024]

[19] A preparation step of preparing an electrode active material by the method for producing an electrode active material according to

[16] or

[17] ; A mixing step of mixing the above electrode active material with at least one of a conductive material and a binder to obtain an electrode mixture; An electrode layer forming step of forming an electrode layer using the above electrode mixture; which has

[0025]

[20] A preparation step of preparing an electrode active material by the method for producing an electrode active material according to

[16] or

[17] ; A mixing step of mixing the above electrode active material with at least one of a conductive material and a binder to obtain an electrode mixture; An electrode layer forming step of forming an electrode layer using the above electrode mixture; A method for manufacturing a battery having

Advantages of the Invention

[0026] In the present disclosure, there is an effect that an electrode active material with a small volume change due to charge and discharge can be obtained.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0028] Hereinafter, the electrode active material, electrode binder, electrode layer, battery, and their manufacturing methods in the present disclosure will be described in detail.

[0029] A. Electrode active material The electrode active material in the present disclosure has a crystal phase of silicon class rate type II and has voids inside the primary particles. Also, the void volume P1 of voids with a pore diameter of 5 nm or less is large.

[0030] According to the present disclosure, since the void volume P1 is large, an electrode active material with a small volume change due to charge and discharge is obtained. The present inventors have obtained the finding that by increasing the void volume of minute voids with a pore diameter of 100 nm or less, the collapse of voids due to pressing treatment is suppressed in previous research. Furthermore, by increasing the void volume of minute voids with a pore diameter of 10 nm or less, the collapse of voids due to pressing treatment can be significantly suppressed, and at the same time, the filling rate of deposited Li in the voids can be increased, and it has been found that the volume change due to charge and discharge can be effectively suppressed.

[0031] In contrast, in the present disclosure, for example, it has been found that by actively performing liquid treatment with hydrofluoric acid, it is possible to increase the void volume P1 of minute voids having a pore diameter of 5 nm or less. It is presumed that this is because during charging, the minute voids having a pore diameter of 5 nm or less are preferentially filled with deposited Li. By actively performing liquid treatment with hydrofluoric acid, it is presumed that while the surface of the electrode active material is etched, the silicon class rate I-type crystal phase contained in the electrode active material disappears and the void volume P1 increases. By increasing the void volume P1, volume changes due to charge and discharge can be effectively suppressed.

[0032] Furthermore, the electrode active material in the present disclosure has a silicon class rate II-type crystal phase. As shown in Fig. 1(a), in the silicon class rate II-type crystal phase, a polyhedron (cage) containing a pentagon or a hexagon is formed by a plurality of Si elements. This polyhedron has a space inside that can enclose metal ions such as Li ions. By inserting metal ions into this space, volume changes due to charge and discharge can be suppressed. Particularly in a solid battery, in order to suppress volume changes due to charge and discharge, generally, it is necessary to apply a high restraint pressure. However, by using the electrode active material in the present disclosure, reduction of the restraint pressure can be achieved, and as a result, enlargement of the restraint jig can be suppressed. On the other hand, as shown in Fig. 1(b), in the crystal phase of diamond-type silicon, tetrahedrons are formed by a plurality of Si elements. Since the tetrahedron does not have a space inside that can enclose metal ions such as Li ions, the crystal phase of diamond-type silicon is less likely to suppress volume changes due to charge and discharge compared to the silicon class rate II-type crystal phase.

[0033] The shape of the active material in the present disclosure is usually particulate. The active material may be primary particles or secondary particles formed by aggregation of primary particles. In any case, usually, voids are present inside the primary particles.

[0034] The electrode active material preferably has many voids with a pore diameter of 5 nm or less. The void volume P1 of the voids with a pore diameter of 5 nm or less is usually 0.015 cc / g or more, may be 0.020 cc / g or more, and may be 0.023 cc / g or more. On the other hand, the void volume P1 is usually 0.05 cc / g or less, may be 0.04 cc / g or less, and may be 0.035 cc / g or less. The void volume in the present disclosure means the cumulative pore volume and can be determined by, for example, BET measurement, gas adsorption method, mercury porosimeter measurement, 3D-SEM, and 3D-TEM.

[0035] The electrode active material preferably has many voids with a pore diameter of 10 nm or less. The void volume P2 of the voids with a pore diameter of 10 nm or less is, for example, 0.03 cc / g or more, may be 0.035 cc / g or more, and may be 0.04 cc / g or more. On the other hand, the void volume P2 is, for example, 0.08 cc / g or less, may be 0.07 cc / g or less, and may be 0.06 cc / g or less. Also, the ratio (P1 / P2) of the void volume P1 to the void volume P2 is, for example, 50% or more, may be 55% or more, and may be 57% or more. On the other hand, P1 / P2 is, for example, 80% or less, may be 70% or less, and may be 65% or less.

[0036] The electrode active material preferably has many voids with a pore diameter of 100 nm or less. The void volume P3 of the voids with a pore diameter of 100 nm or less is, for example, 0.1 cc / g or more, may be 0.2 cc / g or more, and may be 0.32 cc / g or more. On the other hand, the void volume P3 is, for example, 0.5 cc / g or less, may be 0.45 cc / g or less, and may be 0.38 cc / g or less. Also, the ratio (P1 / P3) of the void volume P1 to the void volume P3 is, for example, 6.0% or more, may be 6.5% or more, and may be 6.9% or more. On the other hand, P1 / P3 is, for example, 15% or less, may be 12% or less, and may be 10% or less.

[0037] The electrode active material preferably has voids inside the primary particles. The ratio of voids (void fraction) in the primary particles is, for example, 4% or more, and may be 10% or more. Further, the void fraction may be, for example, 40% or less, and may be 20% or less. The void fraction can be determined, for example, by the following procedure. First, cross-sectioning is performed on the electrode layer containing the electrode active material by ion milling. Then, the cross-section is observed with an SEM (scanning electron microscope) to obtain a photograph of the particles. From the obtained photograph, the silicon part and the void part are distinguished using image analysis software and binarized. The areas of the silicon part and the void part are determined, and the void fraction (%) is calculated from the following formula. Void fraction (%) = 100 × (void area) / ((silicon area) + (void area))

[0038] The average particle diameter (D 50 ) of the electrode active material is not particularly limited, but is, for example, 0.1 μm or more and 50 μm or less, and may be 0.5 μm or more and 30 μm or less. The average particle diameter (D 50 ) can be calculated, for example, from measurements by a scanning electron microscope (SEM). Further, 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 may be 40 m 2 / g or more, and may be 50 m 2 / g or more, and may 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.

[0039] The electrode active material has a silicon clathrate type II crystal phase. Among them, it is preferable that the electrode active material has the silicon clathrate type II crystal phase as the main phase. The "main phase" means that the peak belonging to the crystal phase has the largest diffraction intensity among the peaks observed by X-ray diffraction measurement. The proportion of the silicon clathrate type II crystal phase contained in the electrode active material is, for example, 80% by weight or more, and may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. Also, the proportion of the silicon clathrate type II crystal phase contained in the electrode active material may be 100% by weight or less than 100% by weight. The proportion of the crystal phase can be obtained by performing Rietveld analysis on the XRD measurement results and using the analysis results and the RIR method (Reference Intensity Ratio method).

[0040] The silicon clathrate type II crystal phase usually belongs to the space group (Fd-3m). The silicon clathrate type II crystal phase has typical peaks at positions of 2θ = 20.09°, 21.00°, 26.51°, 31.72°, 36.26°, and 53.01° in X-ray diffraction measurement using CuKα radiation. These peak positions may shift before and after within a range of ±0.50°, may shift before and after within a range of ±0.30°, or may shift before and after within a range of ±0.10°.

[0041] In the silicon clathrate type II crystal phase, the peak located at 2θ = 20.09° ± 0.50° is defined as peak A, and the peak located at 2θ = 31.72° ± 0.50° is defined as peak B. Also, let the intensity of peak A be I A and the intensity of peak B be I B . On the other hand, let the maximum intensity at 2θ = 22° to 23° be I M . Since no peak of the crystal phase related to Si usually appears in the range of 2θ = 22° to 23°, it can be used as a reference.

[0042] I A / I M The value of is preferably greater than 1. IA / I M If the value of / I is 1 or less, it can be determined that the silicon class rate type II crystal phase is not substantially formed. I A / I M The value of / I is, for example, 1.75 or more, and may be 1.80 or more. On the other hand, I A / I M The value of / I is, for example, 10 or less, and may be 5 or less.

[0043] I B / I M The value of / I is preferably greater than 1. I B / I M If the value of / I is 1 or less, it can be determined that the silicon class rate type II crystal phase is not substantially formed. I B / I M The value of / I is, for example, 1.35 or more, and may be 1.40 or more. On the other hand, I B / I M The value of / I is, for example, 7 or less, and may be 4 or less.

[0044] The electrode active material in the present disclosure may or may not have a silicon class rate type I crystal phase. "Not having a crystal phase" means that no peak of the crystal phase is confirmed in X-ray diffraction measurement. The silicon class rate type I crystal phase usually belongs to the space group (Pm-3n). The silicon class rate type I crystal phase has typical peaks at positions of 2θ = 19.44°, 21.32°, 30.33°, 31.60°, 32.82°, 36.29°, 52.39°, 55.49° in X-ray diffraction measurement using CuKα rays. These peak positions may shift back and forth within a range of ±0.50°, may shift back and forth within a range of ±0.30°, or may shift back and forth within a range of ±0.10°.

[0045] The electrode active material in the present disclosure may or may not have a diamond-type silicon crystal phase. Further, the diamond-type silicon crystal phase has typical peaks at positions of 2θ = 28.44°, 47.31°, 56.10°, 69.17°, and 76.37° in X-ray diffraction measurement using CuKα rays. These peak positions may shift back and forth within a range of ±0.50°, may shift back and forth within a range of ±0.30°, or may shift back and forth within a range of ±0.10°.

[0046] When peak C located at 2θ = 28.44° ± 0.50° is observed as a peak of the diamond-type silicon crystal phase, the intensity of peak C is denoted as I C Let it be. I A / I C is, for example, greater than 1, may be 1.5 or more, may be 2 or more, or may be 3 or more. I B / I C The preferred range of is the same as the preferred range of I A / I C

[0047] The composition of the electrode active material in the present disclosure is not particularly limited, but is preferably represented by Na x Si 136 (0 ≦ x ≦ 24). x may be 0 or may be greater than 0. On the other hand, x may be 20 or less, may be 10 or less, or may be 5 or less. The composition of the electrode active material can be determined, for example, by EDX, XRD, XRF, ICP, or atomic absorption spectrometry. In general, an inevitable oxide film is formed on the surface of the electrode active material. Therefore, the electrode active material may contain a trace amount of О (oxygen). Further, the electrode active material may contain a trace amount of C (carbon) derived from the manufacturing process.

[0048] The electrode active material in the present disclosure is usually used in a battery. The electrode active material in the present disclosure may be a negative electrode active material or a positive electrode active material, but the former is preferred. Examples of the method for manufacturing the electrode active material include the manufacturing methods described in "E. Method for Manufacturing Electrode Active Material" described later.​

[0049] B. Electrode composite material The electrode composite material in the present disclosure contains at least one of the above-described electrode active material, a conductive material, and a binder.

[0050] According to the present disclosure, by using the above-described electrode active material, an electrode composite material with a small volume change due to charge and discharge can be obtained.

[0051] The electrode composite material contains at least one of an electrode active material, a conductive material, and a binder. The electrode active material is the same as that described in the above “A. Electrode active material”. The electrode active material may be a negative electrode active material or a positive electrode active material, but the former is preferred. That is, the electrode composite material may be a negative electrode composite material or a positive electrode composite material, but the former is preferred.

[0052] The proportion of the electrode active material in the electrode composite material is, for example, 20% by weight or more, and may be 30% by weight or more, or may be 40% by weight or more. If the proportion of the electrode active material is too small, sufficient energy density may not be obtained. On the other hand, the proportion of the electrode active material is, for example, 80% by weight or less, and may be 70% by weight or less, or may be 60% by weight or less. If the proportion of the electrode active material is too large, the ionic conductivity and electronic conductivity in the electrode composite material may relatively decrease.

[0053] The electrode composite material contains at least one of a conductive material and a binder. 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), fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF). Examples of the binder include rubber-based binders and fluoride-based binders.

[0054] The electrode composite material may further contain a solid electrolyte. Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes, and organic polymer electrolytes such as polymer electrolytes. Examples of the sulfide solid electrolyte include solid electrolytes containing Li element, X element (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S element. Further, the sulfide solid electrolyte may further contain at least one of O element and halogen element. Examples of the halogen element include F element, Cl element, Br element, and I element. The sulfide solid electrolyte may be glass (amorphous) or glass ceramics. Examples of the sulfide solid electrolyte include Li2S-P2S5, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-SiS2, Li2S-GeS2, and Li2S-P2S5-GeS2. Further, the electrode composite material may further contain a dispersion medium.

[0055] C. Electrode layer The electrode layer in the present disclosure is an electrode layer used in a battery, and includes an electrode active material having a silicon clathrate type II crystal phase and having voids inside the primary particles. Also, the void volume Q1 of voids having a pore diameter of 5 nm or less is large.

[0056] According to the present disclosure, since the void volume Q1 is large, the electrode layer has a small volume change due to charge and discharge.

[0057] The electrode layer preferably has many voids having a pore diameter of 5 nm or less. The void volume Q1 of voids having a pore diameter of 5 nm or less is usually 0.008 cc / g or more, may be 0.010 cc / g or more, or may be 0.013 cc / g or more. On the other hand, the void volume Q1 is usually 0.04 cc / g or less, and may be 0.03 cc / g or less.

[0058] The electrode layer preferably has many voids with a pore diameter of 10 nm or less. The void volume Q2 of the voids with a pore diameter of 10 nm or less is, for example, 0.01 cc / g or more, may be 0.015 cc / g or more, and may be 0.021 cc / g or more. On the other hand, the void volume Q2 is, for example, 0.05 cc / g or less, and may be 0.04 cc / g or less. Also, the ratio (Q1 / Q2) of the void volume Q1 to the void volume Q2 is, for example, 50% or more, and may be 56.9% or more. On the other hand, Q1 / Q2 is, for example, 90% or less, and may be 80% or less.

[0059] The electrode layer preferably has many voids with a pore diameter of 100 nm or less. The void volume Q3 of the voids with a pore diameter of 100 nm or less is, for example, 0.07 cc / g or more, may be 0.08 cc / g or more, and may be 0.09 cc / g or more. On the other hand, the void volume Q3 is, for example, 0.2 cc / g or less, may be 0.15 cc / g or less, and may be 0.12 cc / g or less. Also, the ratio (Q1 / Q3) of the void volume Q1 to the void volume Q3 is, for example, 10% or more, may be 12% or more, and may be 13% or more. On the other hand, Q1 / Q3 is, for example, 25% or less, may be 23% or less, and may be 20% or less.

[0060] The electrode layer contains at least one of an electrode active material, a conductive material, and a binder. Further, the electrode layer may contain an electrolyte. Regarding these materials, compositions, and other matters, they are the same as those described in the above "A. Electrode Active Material" and the above "B. Electrode Composite Material". The electrode layer may be a negative electrode layer or a positive electrode layer, but the former is preferred. The thickness of the electrode layer is, for example, 0.1 μm or more and 1000 μm or less, may be 0.1 μm or more and 500 μm or less, and may be 0.1 μm or more and 100 μm or less. Also, as a method for manufacturing the electrode layer, for example, the manufacturing methods described in "F. Method for Manufacturing Electrode Layer" to be described later can be mentioned.

[0061] D. Battery Figure 2 is a schematic cross-sectional view illustrating the battery in the present disclosure. The battery 10 shown in Figure 2 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 for collecting current from the positive electrode layer 1, and a negative electrode current collector 5 for collecting 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 in the above "C. Electrode layer".

[0062] According to the present disclosure, by using the above-described electrode layer, a battery with a small volume change due to charge and discharge can be obtained. As described above, the electrode layer may be a negative electrode layer or a positive electrode layer, but the former is preferred. Hereinafter, when the electrode layer is a negative electrode layer, the details of the battery will be described.

[0063] 1. Negative electrode layer The negative electrode layer is a layer containing at least a negative electrode active material. Since the negative electrode layer is the same as that described in the above "C. Electrode layer", the description here is omitted.

[0064] 2. Positive electrode layer The positive electrode layer is a layer containing at least a positive electrode active material. Further, the positive electrode layer may contain at least one of an electrolyte, a conductive material, and a binder, if necessary.

[0065] Examples of the positive electrode active material include oxide active materials. Examples of the oxide active materials include rock salt layer-type active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, spinel-type active materials such as LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, and olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0066] A coating layer containing a Li-ion conductive oxide may be formed on the surface of the oxide active material. This is because it can suppress the reaction between the oxide active material and the solid electrolyte (especially a sulfide solid electrolyte). Examples of the Li-ion conductive oxide include LiNbO3. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less. Further, for example, Li2S can also be used as the positive electrode active material.

[0067] Examples of the shape of the positive electrode active material include particulate. The average particle diameter (D 50 ) is not particularly limited, but is, for example, 10 nm or more, and may be 100 nm or more. On the other hand, the average particle diameter (D 50 ) is, for example, 50 μm or less, and may be 20 μm or less.

[0068] Regarding the electrolyte used in the positive electrode layer, it is the same as the content described in "3. Electrolyte layer". Further, regarding the conductive material and the binder used in the positive electrode layer, since they are the same as the content described in the above "B. Electrode composite material", the description here is omitted. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less, may be 0.1 μm or more and 500 μm or less, and may be 0.1 μm or more and 100 μm or less.

[0069] 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 (electrolyte solution).

[0070] Regarding the solid electrolyte, since it is the same as the content described in the above "B. Electrode binder", the description here is omitted. On the other hand, the electrolyte preferably contains a supporting salt and a solvent. Examples of the supporting salt (lithium salt) of the electrolyte having lithium ion conductivity include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAsF6, etc., and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, LiC(CF3SO2)3. Examples of the solvent used in the electrolyte include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The electrolyte preferably contains two or more solvents.

[0071] The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less, and 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.

[0072] 4. Other Configurations The battery in the present disclosure preferably has a positive electrode current collector for collecting current from the positive electrode layer and a negative electrode current collector for collecting current from the negative electrode layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of the material of the negative electrode current collector include SUS, copper, nickel, and carbon.

[0073] The battery in the present disclosure may further include a restraining jig that applies a restraining pressure along the thickness direction to the positive electrode layer, the electrolyte layer, and the negative electrode layer. In particular, when the electrolyte layer is a solid electrolyte layer, it is preferable to apply a restraining pressure to form good ion conduction paths and electron conduction paths. The restraining pressure is, for example, 0.1 MPa or more, and may be 1 MPa or more, or may be 5 MPa or more. On the other hand, the restraining pressure is, for example, 100 MPa or less, and may be 50 MPa or less, or may be 20 MPa or less.

[0074] 5. Battery The type of the battery in the present disclosure is not particularly limited, but is typically a lithium ion battery. Also, the battery in the present disclosure may be a liquid battery in which the electrolyte layer contains an electrolytic solution, or may be a solid battery in which the electrolyte layer contains a solid electrolyte. The solid battery may be a semi-solid battery or a all-solid battery. In the present disclosure, a 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 disclosure, an all-solid battery is a battery in which the electrolyte layer has only an inorganic solid electrolyte as an electrolyte. Also, the battery in the present disclosure may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as a vehicle-mounted battery.

[0075] Examples of the uses of the battery include power sources for vehicles such as hybrid vehicles (HEVs), plug-in hybrid vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. In particular, it is preferably used as a driving power source for a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), or a battery electric vehicle (BEV). Also, the battery may be used as a power source for moving bodies other than vehicles (for example, railways, ships, and aircraft), or may be used as a power source for electrical products such as information processing devices.

[0076] E. Method for manufacturing electrode active material Figure 3 is a flowchart illustrating a method for manufacturing an electrode active material in the present disclosure. In the manufacturing method shown in Figure 3, first, a Na source and a Si source are reacted to obtain a Na-Si alloy (alloying step). Next, the Na-Si alloy is fired to reduce the amount of Na in the Na-Si alloy and form a precursor active material having a silicon class rate II-type crystal phase (firing step). Next, the precursor active material is subjected to liquid treatment using hydrofluoric acid to obtain an electrode active material (liquid treatment step). In the present disclosure, the concentration of hydrofluoric acid is 3% by weight or more, and the treatment time in the liquid treatment step is 3 hours or more and less than 24 hours.

[0077] According to the present disclosure, by performing the liquid treatment step, an electrode active material with a small volume change due to charge and discharge can be obtained.

[0078] 1. Alloying step The alloying step in the present disclosure is a step of reacting a Na source and a Si source to obtain a Na-Si alloy.

[0079] The Si source is particles containing at least Si. The Si source may be elemental Si or an alloy of Si and another metal. When the Si source is an alloy, it preferably contains Si as a main component. The ratio of Si in the alloy is, for example, 50 at% or more, may be 70 at% or more, or may be 90 at% or more.

[0080] The Si source is preferably porous Si having many voids inside the primary particles. Examples of the method for producing the Si source (porous Si) include a method of producing an alloy of Li and Si (Li-Si alloy) and then removing Li from the Li-Si alloy. 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, and may be 2.0 or more, 3.0 or more, or 4.0 or more. On the other hand, Li / Si is, for example, 8.0 or less. Examples of the method for removing Li from the Li-Si alloy include a method of reacting the Li-Si alloy with a Li extractant. Examples of the Li extractant include alcohols such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol; and acids such as acetic acid, formic acid, propionic acid, and oxalic acid.

[0081] In addition, examples of the method for producing the Si source (porous Si) include a method of producing an alloy of Mg and Si (Mg-Si alloy) and then removing Mg from the Mg-Si alloy. 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, and may be 1.5 or more, or 2.0 or more. On the other hand, Mg / Si is, for example, 6.0 or less. Examples of the method for removing Mg from the Mg-Si alloy include a method of heating the Mg-Si alloy in an inert gas atmosphere containing oxygen to convert Mg in the Mg-Si alloy to MgO, and then removing MgO with an acid solution. Examples of the acid solution include an aqueous solution containing hydrochloric acid (HCl) and hydrogen fluoride (HF).

[0082] In addition, examples of the method for producing the Si source (porous Si) include a method of producing an alloy of Mg and Si (Mg-Si alloy), then removing Mg from the Mg-Si alloy, then producing an alloy of Si from which Mg has been removed and Li (Li-Si alloy), and then removing Li from the Li-Si alloy.

[0083] On the one hand, the Na source contains at least Na. Examples of the Na source include metallic Na, NaH, and a metallic Na dispersion in which particles of metallic Na are dispersed in oil.

[0084] As a method for reacting the Na source and the Si source to obtain a Na-Si alloy, for example, a method of heating a mixture containing the Na source and the Si source can be mentioned. The heating temperature is, for example, 300 °C or higher, and may be 310 °C or higher, 320 °C or higher, or 340 °C or higher. On the other hand, the heating temperature is, for example, 800 °C or lower, and may be 600 °C or lower, or 450 °C or lower. Further, the alloying step is preferably carried out under an inert atmosphere such as an Ar atmosphere.

[0085] The Na-Si alloy preferably has a Zintl phase. The Zintl phase has typical peaks at positions of 2θ = 16.10°, 16.56°, 17.64°, 20.16°, 27.96°, 33.60°, 35.68°, 40.22°, and 41.14° in X-ray diffraction measurement using CuKα radiation. These peak positions may shift back and forth within a range of ±0.50°, or may shift back and forth within a range of ±0.30°. The Na-Si alloy preferably has the Zintl phase as the main phase.

[0086] The composition of the Na-Si alloy is not particularly limited, but Na z Si 136 is preferably represented by the composition (121 ≤ z ≤ 151). z may be 126 or more, or may be 131 or more. On the other hand, z may be 141 or less. Other elements other than Na and Si may be present in the Na-Si alloy. Examples of other elements include Li, K, Rb, Cs, Ba, Ga, and Ge.

[0087] 2. Firing step The firing step in the present disclosure is a step of firing the above Na-Si alloy to reduce the amount of Na in the above Na-Si alloy and form a precursor material having a silicon-class rate II-type crystal phase.

[0088] The firing conditions of the Na-Si alloy are appropriately adjusted so that a desired precursor active material can be obtained. The firing temperature is, for example, 300°C or higher and 400°C or lower. On the other hand, the firing time is, for example, 5 hours or longer and 120 hours or shorter. The firing process may be carried out in a reduced-pressure atmosphere or in a normal-pressure atmosphere.

[0089] In the firing process, it is preferable to use a scavenger that captures Na in the Na-Si alloy. As an example of the scavenger, a Na getter agent that reacts with the Na vapor generated from the Na-Si alloy can be mentioned. The Na getter agent is arranged, for example, in a state where it is not in contact with the Na-Si alloy. Examples of the Na getter agent include SiO, MoO3, FeO, and Fe3O4. When using a Na getter agent, the firing process is preferably carried out in a reduced-pressure atmosphere.

[0090] Another example of the scavenger includes a Na trap agent that directly reacts with the Na-Si alloy to receive Na. The Na trap agent is arranged, for example, in a state where it is in contact with the Na-Si alloy. Examples of the Na trap agent include CaCl2, AlF3, CaBr2, CaI2, Fe3O4, FeO, MgCl2, ZnO, ZnCl2, and MnCl2. When using a Na trap agent, the firing process may be carried out in a reduced-pressure atmosphere or in a normal-pressure atmosphere.

[0091] 3. Liquid treatment process The liquid treatment process in the present disclosure is a process of subjecting the above-mentioned precursor active material to liquid treatment using hydrofluoric acid to obtain an electrode active material. Hydrofluoric acid is an aqueous solution in which hydrogen fluoride (HF) is dissolved in water.

[0092] The concentration of hydrogen fluoride in hydrofluoric acid is usually 3 wt% or more, may be 4 wt% or more, and may be 5 wt% or more. On the other hand, the concentration of hydrogen fluoride in hydrofluoric acid is, for example, 10 wt% or less. Also, the treatment time of the liquid treatment is usually 3 hours or more, may be 4 hours or more, and may be 5 hours or more. On the other hand, the treatment time of the liquid treatment is usually less than 24 hours, may be 15 hours or less, and may be 10 hours or less. The temperature of the liquid treatment is not particularly limited, but is, for example, room temperature.

[0093] Examples of the method of subjecting the precursor material to liquid treatment with hydrofluoric acid include a method of immersing the precursor material in hydrofluoric acid and a method of applying hydrofluoric acid to the precursor material.

[0094] 4. Electrode active material The electrode active material obtained by the above-described respective steps has a silicon class II type crystal phase. Further, it is preferable that the pore volume P1 of voids having a pore diameter of 5 nm or less in the electrode active material is 0.015 cc / g or more and 0.05 cc / g or less. Preferred embodiments of the electrode active material are the same as those described in the above "A. Electrode active material".

[0095] F. Method for manufacturing electrode mixture In the present disclosure, there is provided a method for manufacturing an electrode mixture, which includes a preparation step of preparing an electrode active material by the above-described method for manufacturing an electrode active material, and a mixing step of mixing the electrode active material with at least one of a conductive material and a binder to obtain an electrode mixture.

[0096] According to the present disclosure, by using the above-described electrode active material, an electrode mixture with a small volume change due to charge and discharge can be obtained. The preparation step is the same as the content described in the above "E. Method for manufacturing electrode active material".

[0097] The electrode composite material usually contains an electrode active material and at least one of a conductive material and a binder. The conductive material and the binder are the same as those described in the above "B. Electrode Composite Material". The electrode composite material may or may not further have a dispersion medium. Also, the electrode composite material is usually obtained by mixing an electrode active material and at least one of a conductive material and a binder. The mixing method is not particularly limited, and known methods can be adopted. Also, the preferred embodiments of the obtained electrode composite material are the same as those described in the above "B. Electrode Composite Material".

[0098] G. Method for Manufacturing Electrode Layer In the present disclosure, there is provided a method for manufacturing an electrode layer, which includes a preparation step of preparing an electrode active material by the above-described method for manufacturing an electrode active material, a mixing step of mixing the electrode active material and at least one of a conductive material and a binder to obtain an electrode composite material, and an electrode layer forming step of forming an electrode layer using the electrode composite material.

[0099] According to the present disclosure, by using the above-described electrode active material, an electrode layer with a small volume change due to charge and discharge can be obtained. The preparation step and the mixing step are the same as those described in the above "E. Method for Manufacturing Electrode Active Material" and the above "F. Method for Manufacturing Electrode Composite Material".

[0100] The electrode layer forming step is a step of forming an electrode layer using the above electrode composite material. The method for forming the electrode layer is not particularly limited, and known methods can be adopted. Examples of the method for forming the electrode layer include a method of coating the electrode composite material on an electrode current collector. When forming the electrode layer, a pressing process for pressing the electrode layer in the thickness direction may be performed. Examples of the pressing process include roller pressing and flat pressing. Also, when the electrode composite material is a slurry containing a dispersion medium, it is preferably dried after coating the electrode current collector.

[0101] The electrode layer forming step may be a positive electrode layer forming step for forming a positive electrode layer or a negative electrode layer forming step for forming a negative electrode layer.

[0102] H. Method for manufacturing a battery In the present disclosure, a preparation step of preparing an electrode active material by the above-described method for manufacturing an electrode active material, a mixing step of mixing the electrode active material with at least one of a conductive material and a binder to obtain an electrode mixture, and an electrode layer forming step of forming an electrode layer using the electrode mixture are provided as a method for manufacturing a battery.

[0103] According to the present disclosure, by using the above-described electrode active material, a battery with a small volume change due to charge and discharge can be obtained. The preparation step, the mixing step, and the electrode layer forming step are the same as those described in the above "E. Method for manufacturing an electrode active material", the above "F. Method for manufacturing an electrode mixture", and the above "G. Method for manufacturing an electrode layer". The method for manufacturing a battery in the present disclosure may further include other steps such as an electrolyte layer forming step of forming an electrolyte layer. Also, preferred embodiments of the obtained battery are the same as those described in the above "D. Battery".

[0104] Note that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits the same operational effects is included in the technical scope of the present disclosure.

Example

[0105] [Comparative Example 1] Metallic Li and Si powder were weighed so that the molar ratio was 4:1, and they were reacted by mixing in a mortar under the conditions of room temperature and 0.5 hours in an Ar atmosphere. As a result, Li4Si was obtained. The obtained Li4Si was reacted with ethanol in an Ar atmosphere. The obtained reaction product is considered to contain Si and CH3CH2OLi. This reaction product was filtered, and the separated solid content was dried at 120°C for 3 hours or more to obtain powdery porous Si.

[0106] Using the obtained porous Si, a Na-Si alloy was produced using NaH as the Na source. Note that as NaH, that which had been washed with hexane in advance was used. NaH and porous Si were weighed so as to have a molar ratio of 1.05:1, and these were 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, whereby a powdery Na-Si alloy was obtained.

[0107] Using the obtained Na-Si alloy, silicon clathrate formation by the solid-phase method was further carried out using AlF3 as the Na trap agent. The Na-Si alloy and AlF3 were weighed so as to have a molar ratio of 1:0.35, and these were mixed using a cutter mill to obtain reaction raw materials. The obtained powdery reaction raw materials were placed in a reaction vessel made of stainless steel and heated and reacted in a heating furnace under an Ar atmosphere at 310 °C for 60 hours to obtain a precursor.

[0108] The obtained precursor is considered to contain NaF and Al as by-products. Therefore, the precursor was washed using a mixed solvent in which HNO3 and H2O were mixed at a volume ratio of 10:90. Thereby, the by-products in the reaction product were removed. After washing, filtration was carried out, and the solid content separated by filtration was dried at 120 °C for 3 hours or more to obtain a powder. Further, 5 g of the obtained powder was measured, and liquid treatment was carried out for 1 hour using an HF aqueous solution having a concentration of 3% by weight. After the liquid treatment, filtration was carried out, and the solid content separated by filtration was dried at 120 °C for 3 hours or more to obtain an electrode active material.

[0109] [Comparative Example 2] When producing powdery porous Si, an electrode active material was obtained in the same manner as in Comparative Example 1, except that metallic Li and Si powder were used at a molar ratio of 4.75:1, and when producing the powdery Na-Si alloy, heating was carried out in a heating furnace under an Ar atmosphere at 400 °C for 40 hours.

[0110] [Example 1] When producing powdered porous Si, metal Li and Si powder were used in a molar ratio of 4.75:1, and except that the treatment time was changed to 3 hours during the liquid treatment with an HF aqueous solution, the electrode active material was obtained in the same manner as in Comparative Example 1.

[0111] [Example 2] When producing powdered porous Si, metal Li and Si powder were used in a molar ratio of 4.75:1, and except that the treatment time was changed to 5 hours during the liquid treatment with an HF aqueous solution, the electrode active material was obtained in the same manner as in Comparative Example 1.

[0112] [Example 3] Except that the treatment time was changed to 5 hours during the liquid treatment with an HF aqueous solution, the electrode active material was obtained in the same manner as in Comparative Example 1.

[0113] [Comparative Example 3] When producing powdered porous Si, metal Li and Si powder were used in a molar ratio of 4.75:1, and except that the concentration was changed to 1 wt% and the treatment time was changed to 5 hours during the liquid treatment with an HF aqueous solution, the electrode active material was obtained in the same manner as in Comparative Example 1.

[0114] [Comparative Example 4] When producing powdered porous Si, metal Li and Si powder were used in a molar ratio of 4.75:1, and except that the treatment time was changed to 24 hours during the liquid treatment with an HF aqueous solution, the electrode active material was obtained in the same manner as in Comparative Example 1.

[0115] [Comparative Example 5] Crystalline Si (SIEPB23, manufactured by Kojundo Chemical Laboratory Co., Ltd.) was prepared and micronized by mechanical milling. Specifically, 1 g of crystalline Si and 53 g of zirconia balls with a diameter of 1 mm were placed in a container and sealed, and mechanical milling was performed using a planetary ball mill (manufactured by Fritsch) under the conditions of 200 rpm for 3 hours. Thereafter, liquid treatment was performed for 5 hours using an HF aqueous solution with a concentration of 3 wt%. After the liquid treatment, filtration was performed, and the solid content separated by filtration was dried at 120 °C for 3 hours or more to obtain an electrode active material. Table 1 shows the liquid treatment conditions of the electrode active materials in Examples 1 to 3 and Comparative Examples 1 to 5.

[0116] [Table 1]

[0117] [Evaluation] (XRD measurement) X-ray diffraction (XRD) measurement using CuKα rays was performed on the electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4. As a result, it was confirmed that all the electrode active materials had a silicon class rate II-type crystal phase as the main phase.

[0118] The intensity of peak A located near 2θ = 20.09° in the silicon class rate II-type crystal phase was defined as I A and the intensity of peak B located near 2θ = 31.72° was defined as I B . Also, the maximum intensity at 2θ = 22° to 23° was defined as I M , and I A / I M and I B / I M were determined. As a result, for the electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4, all of them had I A / I M greater than 1 and I B / I M also greater than 1.

[0119] Also, in Examples 1 to 3 and Comparative Examples 1 to 4, the ratio of the crystal phase of silicon class rate I before the liquid treatment with the HF aqueous solution was determined by the RIR method (Reference Intensity Ratio method). The results are shown in Table 1. As shown in Table 1, it was confirmed that the precursor substance contained the crystal phase of silicon class rate I before the liquid treatment with the HF aqueous solution. Also, as shown in Figure 4, it was confirmed that the crystal phase of silicon class rate I disappeared before and after the liquid treatment with the HF aqueous solution.

[0120] (Measurement of void fraction) The void fractions of the electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were determined. Specifically, using a high-precision gas adsorption measurement device (BELSORP MAXII, manufactured by microtrac bel), the void fraction P1 with a pore diameter of 5 nm or less, the void fraction P2 with a pore diameter of 10 nm or less, and the void fraction P3 with a pore diameter of 100 nm or less were determined. The results are shown in Table 2.

[0121] (Measurement of specific surface area) For the electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 to 5, the BET specific surface area was determined using a specific surface area measurement device. The results are shown in Table 2.

[0122] [Table 2]

[0123] As shown in Table 2, it was confirmed that the electrode active materials obtained in Examples 1 to 3 had a larger void fraction P1 with a pore diameter of 5 nm or less than the electrode active materials obtained in Comparative Examples 1 to 5. Since the crystal phase of silicon class rate I is more likely to dissolve in the HF aqueous solution than the crystal phase of silicon class rate II, it is presumed that the crystal phase of silicon class rate I disappeared due to the liquid treatment with the HF aqueous solution, and the void fraction P1 with a pore diameter of 5 nm or less increased.

[0124] (Fabrication of all-solid-state battery) The electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were used as the negative electrode active material to fabricate all-solid-state batteries, respectively. The fabrication method is as follows.

[0125] (1) Fabrication of the negative electrode In a polypropylene container, the obtained electrode active material, a sulfide solid electrolyte (Li2S-P2S5-based glass ceramic), a conductive material (VGCF), a butyl butyrate solution containing a PVDF-based binder at a ratio of 5% by weight, and butyl butyrate were added and stirred for 30 seconds using an ultrasonic disperser (UH-50 manufactured by SMT). Next, the container was shaken for 30 minutes using a shaker (TTM-1 manufactured by Shibata Scientific Co., Ltd.). It was coated on a negative electrode current collector (Cu foil, manufactured by UACJ) by the blade method using an applicator and dried on a hot plate at 100 °C for 30 minutes. Thereby, a negative electrode having a negative electrode current collector and a negative electrode layer was obtained.

[0126] (2) Fabrication of the positive electrode In a polypropylene container, a positive electrode active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, average particle size 6 μm), a sulfide solid electrolyte (Li2S-P2S5-based glass ceramic), a conductive material (VGCF), a butyl butyrate solution containing a PVDF-based binder at a ratio of 5% by weight, and butyl butyrate were added and stirred for 30 seconds using an ultrasonic disperser (UH-50 manufactured by SMT). Next, the container was shaken for 3 minutes using a shaker (TTM-1 manufactured by Shibata Scientific Co., Ltd.), further stirred for 30 seconds using an ultrasonic disperser, and shaken for 3 minutes using a shaker. It was coated on a positive electrode current collector (Al foil, manufactured by Showa Denko) by the blade method using an applicator and dried on a hot plate at 100 °C for 30 minutes. Thereby, a positive electrode having a positive electrode current collector and a positive electrode layer was obtained. The area of the positive electrode was made smaller than that of the negative electrode.

[0127] (3) Fabrication of the solid electrolyte layer A polypropylene container was filled with a sulfide solid electrolyte (Li2S-P2S5-based glass ceramic), a heptane solution containing a butylene rubber-based binder at a ratio of 5% by weight, and heptane, and stirred for 30 seconds using an ultrasonic disperser (UH-50 manufactured by SMT). Next, the container was shaken for 30 minutes using a shaker (TTM-1 manufactured by Shibata Scientific Co., Ltd.). Using an applicator, it was coated on a release sheet (Al foil) by the blade method and dried on a hot plate at 100 °C for 30 minutes. Thereby, a transfer member having a release sheet and a solid electrolyte layer was obtained.

[0128] (4) Fabrication of all-solid-state battery A solid electrolyte layer for bonding was placed on the positive electrode layer of the positive electrode, set in a roll press machine, and pressed at 100 kN / cm and 165 °C. Thereby, a first laminate was obtained.

[0129] Next, the negative electrode was set in a roll press machine and pressed at 60 kN / cm and 25 °C. Thereby, a pressed negative electrode was obtained. Thereafter, the solid electrolyte layer for bonding and the transfer member were arranged in order from the negative electrode layer side. At this time, they were arranged so that the solid electrolyte layer for bonding and the solid electrolyte layer in the transfer member faced each other. The obtained laminate was set in a uniaxial planar press machine and pre-pressed at 100 MPa and 25 °C for 10 seconds. Thereafter, the release sheet was peeled off from the solid electrolyte layer. Thereby, a second laminate was obtained.

[0130] Next, the solid electrolyte layer for bonding in the first laminate and the solid electrolyte layer in the second laminate were arranged so as to face each other, set in a uniaxial planar press machine, and pressed at 200 MPa and 120 °C for 1 minute. Thereby, an all-solid-state battery was obtained.

[0131] (5) Measurement of void fraction and volume expansion rate The void fraction of the pressed negative electrode was determined. Specifically, using a high-precision gas adsorption measurement device (BELSORP MAXII, manufactured by microtrac bel), the void fraction Q1 with a pore diameter of 5 nm or less, the void fraction Q2 with a pore diameter of 10 nm or less, and the void fraction Q3 with a pore diameter of 100 nm or less were determined. The results are shown in Table 3. Also, the obtained all-solid-state battery was charged, and the volume expansion rate was measured. The test conditions were a confinement pressure (fixed dimension) of 5 MPa, a charging rate of 0.1 C, and a cut-off voltage of 4.55 V. The confinement pressure at 4.55 V was measured, the increase in the confinement pressure from the state before charging was determined, and the volume expansion rate was determined. The results are shown in Table 3. Note that the results of the volume expansion rate in Table 3 are relative values when the result of Comparative Example 1 is taken as 100. Also, the change in the void fraction due to pressing is shown in Table 4.

[0132]

Table 3

[0133]

Table 4

[0134] As shown in Table 3, it was confirmed that the electrode active materials obtained in Examples 1 to 3 had a larger void fraction Q1 with a pore diameter of 5 nm or less compared to the electrode active materials obtained in Comparative Examples 1 and 2. Also, as shown in Table 4, it was confirmed that Q1 / P1 was larger than Q2 / P2, and the voids with a pore diameter of 5 nm or less were less likely to be crushed by pressing. Also, as shown in Table 3, it was confirmed that Examples 1 to 3 could reduce the volume expansion rate compared to Comparative Examples 1 and 2. In particular, Examples 2 and 3 could significantly reduce the volume expansion rate compared to Comparative Example 1.

Explanation of Reference Signs

[0135] 1... Positive electrode layer 2... Negative electrode layer 3... Electrolyte layer 4... Positive electrode current collector 5... Negative electrode current collector 10... Battery

Claims

1. An electrode active material having a silicon clathrate II-type crystal phase, having voids inside the primary particles, The void fraction P of voids with a pore diameter of 5 nm or less １ is 0.015 cc / g or more and 0.05 cc / g or less, which is an electrode active material.

2. The void volume P of voids with a pore diameter of 10 nm or less ２ with respect to the void volume P １ ratio (P １ / P ２ ) is 50% or more, the electrode active material according to claim 1.

3. The void volume P of voids with a pore diameter of 10 nm or less ２ is 0.03 cc / g or more and 0.08 cc / g or less. The electrode active material according to claim 1.

4. The void fraction P of voids having a pore diameter of 100 nm or less ３ of the void fraction P １ ratio (P １ / P ３ ) is 6.5% or more. The electrode active material according to claim 1.

5. The void volume P of voids with a pore diameter of 100 nm or less ３ is 0.1 cc / g or more and 0.5 cc / g or less, and the electrode active material according to claim 1.

6. The electrode active material according to claim 1, wherein the electrode active material has the silicon clathrate II-type crystal phase as the main phase.

7. An electrode composite material containing the electrode active material according to any one of claims 1 to 6 and at least one of a conductive material and a binder.

8. The electrode composite material according to claim 7, wherein the electrode composite material further contains a solid electrolyte.

9. The electrode composite material according to claim 8, wherein the solid electrolyte contained in the electrode composite material is a sulfide solid electrolyte.

10. An electrode layer used in a battery, wherein the electrode layer contains an electrode active material having a silicon clathrate II-type crystal phase and having voids inside the primary particles, The void volume Q of voids with a pore diameter of 5 nm or less １ is an electrode layer that is 0.008 cc / g or more and 0.04 cc / g or less.

11. The void volume Q of voids having a pore diameter of 10 nm or less ２ with respect to the void volume Q １ at a ratio of (Q １ / Q ２ ) of 50% or more, the electrode layer according to claim 10

12. The void volume Q of voids with a pore diameter of 10 nm or less ２ is 0.01 cc / g or more and 0.05 cc / g or less, and the electrode layer according to claim 10.

13. The void fraction Q of voids with a pore diameter of 100 nm or less ３ of the void fraction Q １ ratio (Q １ / Q ３ ) is 10% or more. The electrode layer according to claim 10

14. The void volume Q of voids with a pore diameter of 100 nm or less ３ is 0.07 cc / g or more and 0.2 cc / g or less, and the electrode layer according to claim 10.

15. 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 10 to 14.

16. An alloying step of reacting a Na source and a Si source to obtain a Na—Si alloy, a firing step of firing the Na—Si alloy to reduce the amount of Na in the Na—Si alloy and form a precursor active material having a silicon clathrate II-type crystal phase, a liquid treatment step of subjecting the precursor active material to liquid treatment using hydrofluoric acid to obtain an electrode active material, having, wherein the concentration of hydrogen fluoride in the hydrofluoric acid is 3 wt% or more, and the treatment time in the liquid treatment step is 3 hours or more and less than 24 hours, a method for producing an electrode active material.

17. In the electrode active material, the pore volume P of voids having a pore diameter of 5 nm or less １ is 0.015 cc / g or more and 0.05 cc / g or less, and the method for producing an electrode active material according to claim 16.

18. A preparation step of preparing an electrode active material by the method for producing an electrode active material according to claim 16 or claim 17, a mixing step of mixing the electrode active material and at least one of a conductive material and a binder to obtain an electrode composite material, having, a method for producing an electrode composite material.

19. A preparation step of preparing an electrode active material by the method for producing an electrode active material according to claim 16 or claim 17, a mixing step of mixing the electrode active material and at least one of a conductive material and a binder to obtain an electrode composite material, an electrode layer forming step of forming an electrode layer using the electrode composite material. A method for manufacturing an electrode layer having

20. A preparation step of preparing an electrode active material by the method for manufacturing an electrode active material according to claim 16 or claim 17, A mixing step of mixing the electrode active material with at least one of a conductive material and a binder to obtain an electrode mixture, An electrode layer forming step of forming an electrode layer using the electrode mixture, A method for manufacturing a battery having

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