Electrode active material, electrode mixture, 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 containing Si. On a surface of the electrode active material, a Si-H bond exists and the ratio of the hydrogen quantity (wt%) to the BET specific surface area (m2 / g) is more than 0.0034. 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, a battery, and methods for manufacturing these.

Background Art

[0002] In recent years, the development of batteries 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 batteries. On the other hand, Si has a large volume change during charge and discharge. When the volume change during charge and discharge is large, there are problems such as the function of the electrode being likely to deteriorate when charge and discharge are repeated, for example.

[0005] The present disclosure has been made in view of the above circumstances, and the main object thereof 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 containing Si, wherein Si-H bonds are present on the surface of the electrode active material, The ratio of the hydrogen amount (weight %) to the BET specific surface area (m 2 / g) is greater than 0.0034, the electrode active material.

[0007] [2] The electrode active material according to [1], wherein the ratio is 0.0039 or more.

[0008] [3] The electrode active material according to [1] or [2], wherein the ratio is 0.05 or less.

[0009] [4] The BET specific surface area is 50 m 2 / g or more, the electrode active material according to any one of [1] to [3].

[0010] [5] The electrode active material according to any one of [1] to [4], wherein the hydrogen amount is 0.20 weight % or more.

[0011] [6] The electrode active material according to any one of [1] to [5], wherein the ratio is 0.0060 or more and the hydrogen amount is 0.40 weight % or more.

[0012] [7] The electrode active material according to any one of [1] to [5], wherein the ratio is greater than 0.0034 and less than 0.0046, and the hydrogen amount is 0.30 weight % or less.

[0013] [8] The electrode active material according to any one of [1] to [7], which has a silicon class rate II-type crystal phase as a main phase.

[0014] [9] The electrode active material according to any one of [1] to [8], which has voids inside the primary particles.

[0015]

[10] The electrode active material described in [9], wherein the ratio of the voids is 4% or more and 40% or less.

[0016]

[11] An electrode mixture containing the electrode active material described in any one of [1] to

[10] and at least one of a conductive material and a binder.

[0017]

[12] The electrode mixture described in

[11] , wherein the electrode mixture further contains a solid electrolyte.

[0018]

[13] The electrode mixture described in

[12] , wherein the solid electrolyte contained in the electrode mixture is a sulfide solid electrolyte.

[0019]

[14] 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 contains the electrode mixture described in any one of

[11] to

[13] .

[0020]

[15] The battery described in

[14] , wherein the negative electrode layer contains the electrode mixture.

[0021]

[16] The battery described in

[14] or

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

[0022]

[17] The solid electrolyte contained in the electrolyte layer is a sulfide solid electrolyte, and The battery described in

[16] , wherein the thickness of the electrolyte layer is 0.1 μm or more and 100 μm or less.

[0023]

[18] The battery described in any one of

[14] to

[17] , wherein the positive electrode layer contains a rock salt layer-structured active material.

[0024]

[19] 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 class rate 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, and in the liquid treatment step, the production method of an electrode active material, wherein the liquid treatment conditions are adjusted so that the ratio of the hydrogen amount (weight %) to the BET specific surface area (m 2 / g) is greater than 0.0034.

[0025]

[20] The concentration of hydrogen fluoride in the hydrofluoric acid is 3% by weight or more, and the treatment time in the liquid treatment step is 3 hours or more. The production method of the electrode active material according to

[17] .

[0026]

[21] 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 an electrode active material having a silicon class rate II-type crystal phase, and in the alloying step, the production method of an electrode active material, wherein metal Na particles are used as the Na source.

[0027]

[22] The average particle diameter of the metal Na particles is 10 μm or less. The production method of the electrode active material according to

[21] .

[0028]

[23] A preparation step of preparing an electrode active material by the production method of the electrode active material according to any one of

[19] to

[22] , a mixing step of mixing the electrode active material with at least one of a conductive material and a binder to obtain an electrode composite material, and

[0029]

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

[19] to

[22] , 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, comprising:

Advantages of the Invention

[0030] 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

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0032] Hereinafter, the electrode active material, electrode mixture, battery, and manufacturing methods thereof in the present disclosure will be described in detail.

[0033] A. Electrode Active Material The electrode active material in the present disclosure contains Si. Further, Si-H bonds are present on the surface of the electrode active material. Also, in the electrode active material, the ratio of the hydrogen amount (weight %) to the BET specific surface area (m 2 / g) is within a predetermined range.

[0034] According to the present disclosure, since Si-H bonds exist on the surface of the electrode active material and the ratio of the amount of hydrogen to the BET specific surface area is within a predetermined range, the electrode active material has a small volume change due to charge and discharge.

[0035] Here, when the surface of the electrode active material (Si-based active material) is oxidized, its polarity increases, its affinity with the solid electrolyte increases, and its dispersibility increases. On the other hand, generally, since the conductive material has a low polarity, when the surface of the electrode active material (Si-based active material) is oxidized, the dispersibility between the electrode active material and the conductive material decreases. In the electrode layer, usually, since the content of the conductive material is less than the content of the solid electrolyte, when the dispersibility between the electrode active material and the conductive material decreases, reaction unevenness is likely to occur, and it becomes difficult to suppress the volume change due to charge and discharge. In contrast, in the present disclosure, for example, by hydrogen-terminating the surface of the electrode active material, Si-H bonds are introduced onto the surface of the electrode active material, and the dispersibility between the electrode active material and the conductive material is improved. As a result, the reaction uniformity in the electrode layer is improved, and the volume change due to charge and discharge can be suppressed.

[0036] Furthermore, the electrode active material in the present disclosure has, for example, a crystalline phase of silicon clathrate type II. As shown in FIG. 1(a), in the crystalline phase of silicon clathrate type II, polyhedra (cages) including pentagons or hexagons are formed by a plurality of Si elements. This polyhedron has a space inside that can encapsulate 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 crystalline 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 encapsulate metal ions such as Li ions, the crystalline phase of diamond-type silicon is less likely to suppress volume changes due to charge and discharge compared to the crystalline phase of silicon clathrate type II. On the other hand, an electrode active material having a crystalline phase of diamond-type silicon has the advantage that it is easier to manufacture compared to an electrode active material having a silicon clathrate type II. Further, the electrode active material in the present disclosure may have a crystalline phase of silicon clathrate type I. Note that the crystalline phase of silicon clathrate type I and the crystalline phase of silicon clathrate type II may be collectively referred to as the crystalline phase of silicon clathrate type.

[0037] The electrode active material in the present disclosure has Si-H bonds on its surface. The Si-H bonds are formed, for example, by treating the surface of the electrode active material with hydrofluoric acid. As shown in FIG. 2(a), a natural oxide film exists on the surface of the electrode active material (Si-based active material). When the surface of such an electrode active material is treated with hydrofluoric acid, as shown in FIG. 2(b), the surface of the electrode active material is etched (SiO2 + 6HF(aq) → H2SiF6), and Si and H existing around it are bonded to form Si-H bonds (hydrogen termination).

[0038] The presence of Si-H bonds can be confirmed by infrared spectroscopy (IR method). The peak of the Si-H bond usually appears in the range of 2100 cm -1 ~2300 cm -1 . In the present disclosure, the peak of the Si-H bond may be referred to as peak α. On the other hand, the peak of the Si-OH bond usually appears in the range of 3610 cm -1 ~3670 cm -1 . In the present disclosure, the peak of the Si-OH bond may be referred to as peak β. Let the peak intensities of peak α and peak β be I α and I β , respectively. The ratio of I β to I α (I α / I β ) is not particularly limited. For example, it may be greater than 0.63, may be 0.65 or more, may be 0.70 or more, or may be 0.80 or more.

[0039] In the present disclosure, the ratio of the hydrogen amount (weight %) to the BET specific surface area (m 2 / g) is usually greater than 0.0034. The above ratio may be 0.0039 or more, may be 0.0046 or more, may be 0.0050 or more, or may be 0.0060 or more. If the above ratio is too small, it may be difficult to improve the dispersibility between the electrode active material and the conductive material. On the other hand, the above ratio is, for example, 0.05 or less, may be 0.04 or less, or may be 0.03 or less.

[0040] The BET specific surface area of the electrode active material is not particularly limited. For example, it is 30 m 2 / g or more, may be 40 m 2 / g or more, may be 50 m 2 / g or more, or 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 2It is below / g. Also, the hydrogen content of the electrode active material is, for example, 0.20 wt% or more, may be 0.30 wt% or more, may be 0.40 wt% or more, and may be 0.50 wt% or more. On the other hand, the hydrogen content of the electrode active material is, for example, 3.0 wt% or less.

[0041] In the present disclosure, the ratio of the hydrogen content (wt%) to the BET specific surface area (m 2 / g) is 0.0060 or more, and the hydrogen content of the electrode active material may be 0.40 wt% or more. In this case, the volume change due to charge and discharge can be significantly reduced. Also, the BET specific surface area (m 2 / g), the ratio of the hydrogen content (wt%) is greater than 0.0034 and less than 0.0046, and the hydrogen content of the electrode active material may be 0.30 wt% or less. In this case as well, the volume change due to charge and discharge can be significantly reduced.

[0042] The electrode active material has, for example, a silicon clathrate II-type crystal phase. Among them, it is preferable that the electrode active material has a silicon clathrate II-type crystal phase as the main phase. The "main phase" means that the peak belonging to that crystal phase has the largest diffraction intensity among the peaks observed by X-ray diffraction measurement. The ratio of the silicon clathrate II-type crystal phase contained in the electrode active material is, for example, 80 wt% or more, may be 85 wt% or more, may be 90 wt% or more, and may be 95 wt% or more. Also, the ratio of the silicon clathrate II-type crystal phase contained in the electrode active material may be 100 wt% or less than 100 wt%. The ratio 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).

[0043] The crystal phase of silicon class rate II typically belongs to the space group (Fd-3m). In the X-ray diffraction measurement using CuKα rays, the crystal phase of silicon class rate II has typical peaks at positions of 2θ = 20.09°, 21.00°, 26.51°, 31.72°, 36.26°, and 53.01°. 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°.

[0044] In the crystal phase of silicon class rate II, 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, the intensity of peak A is denoted as I A and the intensity of peak B is denoted as I B . On the other hand, the maximum intensity at 2θ = 22° - 23° is denoted as I M . Since there is usually no peak of the crystal phase related to Si in the range of 2θ = 22° - 23°, it can be used as a reference.

[0045] I A / I M The value of is preferably greater than 1. When the value of I A / I M is 1 or less, it can be determined that the crystal phase of silicon class rate II is not substantially formed. The value of I A / I M is, for example, 1.75 or more, and may be 1.80 or more. On the other hand, the value of I A / I M is, for example, 10 or less, and may be 5 or less.

[0046] I B / I M The value of is preferably greater than 1. When the value of I B / I M is 1 or less, it can be determined that the crystal phase of silicon class rate II is not substantially formed. I B / I MThe value is, for example, 1.35 or more, and may be 1.40 or more. On the other hand, I B / I M The value is, for example, 7 or less, and may be 4 or less.

[0047] The electrode active material in the present disclosure may or may not have a silicon class rate I-type crystal phase. "Not having a crystal phase" means that no peak of the crystal phase is confirmed in X-ray diffraction measurement. On the other hand, the electrode active material in the present disclosure may have a silicon class rate I-type crystal phase as a main phase. The silicon class rate I-type crystal phase usually belongs to the space group (Pm-3n). The silicon class rate I-type 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°.

[0048] The electrode active material in the present disclosure may or may not have a diamond-type silicon crystal phase. On the other hand, the electrode active material in the present disclosure may have a diamond-type silicon crystal phase as a main phase. Also, the diamond-type silicon crystal phase has typical peaks at positions of 2θ = 28.44°, 47.31°, 56.10°, 69.17°, 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°.

[0049] 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 I C is defined as. I A / I Cis, for example, greater than 1, may be 1.5 or more, may be 2 or more, and may be 3 or more. I B / I C The preferred range of I A / I C is the same as the preferred range of.

[0050] The composition of the electrode active material in the present disclosure is not particularly limited, but Na x Si 136 (0 ≦ x ≦ 24) is preferably represented. 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, and 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. Note that an inevitable oxide film is generally 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.

[0051] The electrode active material in the present disclosure may be primary particles or secondary particles in which the primary particles are aggregated. The average particle diameter (D 50 ) 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).

[0052] The electrode active material preferably has voids inside the primary particles. The ratio of voids (void fraction) in the primary particles may be, 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 part area) / ((silicon part area)+(void part area))

[0053] 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 may be, for example, 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 may be, for example, 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 integrated pore volume and can be determined, for example, by BET measurement, gas adsorption method, mercury porosimeter measurement, 3D-SEM, 3D-TEM.

[0054] 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 may be, 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 may be, 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. Further, the ratio (P1 / P2) of the void volume P1 to the void volume P2 may be, for example, 50% or more, may be 55% or more, and may be 57% or more. On the other hand, P1 / P2 may be, for example, 80% or less, may be 70% or less, and may be 65% or less.

[0055] 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. Further, 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.

[0056] 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 "D. Method for Manufacturing Electrode Active Material" described later.

[0057] B. Electrode composite material The electrode composite material in the present disclosure contains the above-described electrode active material and at least one of a conductive material and a binder.

[0058] 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.

[0059] The electrode composite material contains the electrode active material and at least one of a conductive material and a binder. The electrode active material is the same as the content described in "A. Electrode Active Material" above. 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.

[0060] 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, it may not be possible to obtain a sufficient energy density. 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.

[0061] 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), and 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.

[0062] 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. 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. The electrode composite material may further contain a dispersion medium.

[0063] C. Battery FIG. 3 is a schematic cross-sectional view illustrating a battery in the present disclosure. The battery 10 shown in FIG. 3 includes a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, and a negative electrode current collector 5 that collects current from the negative electrode layer 2. In the present disclosure, the positive electrode layer 1 or the negative electrode layer 2 contains the electrode composite material described in the above “B. Electrode Composite Material”.

[0064] According to the present disclosure, by using the above-described electrode composite material, a battery with a small volume change due to charge and discharge can be obtained. As described above, the electrode composite material may be a negative electrode composite material or a positive electrode composite material, but the former is preferred. Hereinafter, when the electrode composite material is a negative electrode composite material, the details of the battery will be described.

[0065] 1. Negative Electrode Layer The negative electrode layer in the present disclosure contains the above-described electrode composite material (negative electrode composite material). Since the electrode composite material is the same as that described in the above “B. Electrode Composite Material”, the description here is omitted. Further, the negative electrode layer may contain an electrolyte as necessary. The electrolyte is the same as that described in “3. Electrolyte Layer”. The thickness of the negative electrode 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. Further, as a method for forming the negative electrode layer, for example, a method of coating the electrode composite material (negative electrode composite material) on the negative electrode current collector can be mentioned.

[0066] 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 as necessary.

[0067] Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include rock salt layer-structured active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, and spinel-type active materials such as LiMn2O4, Li4Ti5O 12, Li(Ni 0.5 Mn 1.5 )O4 and other spinel-type active materials, olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4 can be mentioned.

[0068] 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 the 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. Also, for example, Li2S can be used as the positive electrode active material.

[0069] Examples of the shape of the positive electrode active material include particulate. The average particle size (D 50 ) is not particularly limited, but for example, it is 10 nm or more, and it may be 100 nm or more. On the other hand, the average particle size (D 50 ) is, for example, 50 μm or less, and it may be 20 μm or less.

[0070] Regarding the electrolyte used in the positive electrode layer, it is the same as the content described in "3. Electrolyte layer". Also, 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, and it may be 0.1 μm or more and 500 μm or less, or it may be 0.1 μm or more and 100 μm or less.

[0071] 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).

[0072] Regarding the solid electrolyte, since it is the same as the content described in the above "B. Electrode composite material", the description here is omitted. On the other hand, the electrolytic solution preferably contains a supporting salt and a solvent. Examples of the supporting salt (lithium salt) of the electrolytic solution 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 electrolytic solution 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 electrolytic solution preferably contains two or more solvents.

[0073] 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.

[0074] 4. Other configurations The battery in the present disclosure preferably has a positive electrode current collector for collecting current of the positive electrode layer and a negative electrode current collector for collecting current of 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.

[0075] 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 in order to form a good ion conduction path and electron conduction path. The restraining pressure is, for example, 0.1 MPa or more, may be 1 MPa or more, and may be 5 MPa or more. On the other hand, the restraining pressure is, for example, 100 MPa or less, may be 50 MPa or less, and may be 20 MPa or less.

[0076] 5. Battery The type of battery in the present disclosure is not particularly limited, but is typically a lithium ion battery. Further, 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. Further, the battery in the present disclosure may be a primary battery or a secondary battery, but is preferably a secondary battery among them. This is because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery.

[0077] Examples of the uses of the battery include power sources for vehicles such as hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), battery electric vehicles (BEV), 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). Further, the battery may be used as a power source for moving bodies other than vehicles (for example, railways, ships, and airplanes), or may be used as a power source for electric products such as information processing devices.

[0078] D. Method for manufacturing electrode active material The method for manufacturing an electrode active material in the present disclosure can be roughly classified into two embodiments.

[0079] 1. First Embodiment FIG. 4 is a flowchart illustrating a method for manufacturing an electrode active material according to the first embodiment. In the manufacturing method shown in FIG. 4, 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 liquid treatment step, the liquid treatment conditions are adjusted so that the ratio of the hydrogen amount (weight %) to the BET specific surface area (m 2 / g) becomes larger than 0.0034.

[0080] According to the first embodiment, by performing the liquid treatment step, an electrode active material with a small volume change due to charge and discharge can be obtained.

[0081] (1) Alloying step The alloying step in the first embodiment is a step of reacting a Na source and a Si source to obtain a Na—Si alloy.

[0082] 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.

[0083] The Si source is preferably porous Si having many voids inside the primary particles. As a method for producing the Si source (porous Si), for example, a method of producing an alloy of Li and Si (Li-Si alloy) and then removing Li from the Li-Si alloy can be mentioned. 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, may be 3.0 or more, or may be 4.0 or more. On the other hand, Li / Si is, for example, 8.0 or less. As a method for removing Li from the Li-Si alloy, for example, a method of reacting the Li-Si alloy with a Li extraction material can be mentioned. Examples of the Li extraction material 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.

[0084] In addition, as a method for producing the Si source (porous Si), for example, a method of producing an alloy of Mg and Si (Mg-Si alloy) and then removing Mg from the Mg-Si alloy can be mentioned. 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 may be 2.0 or more. On the other hand, Mg / Si is, for example, 6.0 or less. As a method for removing Mg from the Mg-Si alloy, for example, a method of heating the Mg-Si alloy in an inert gas atmosphere containing oxygen to change Mg in the Mg-Si alloy to MgO and then removing MgO with an acid solution can be mentioned. Examples of the acid solution include an aqueous solution containing hydrochloric acid (HCl) and hydrogen fluoride (HF).

[0085] In addition, as a method for producing the Si source (porous Si), for example, 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 can be mentioned.

[0086] 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.

[0087] 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, may be 310° C. or higher, may be 320° C. or higher, or may be 340° C. or higher. On the other hand, the heating temperature is, for example, 800° C. or lower, may be 600° C. or lower, or may be 450° C. or lower. Further, the alloying step is preferably carried out under an inert atmosphere such as an Ar atmosphere.

[0088] 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 rays. 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.

[0089] The composition of the Na—Si alloy is not particularly limited, but the composition of Na z Si 136 is preferably represented by (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 the other elements include Li, K, Rb, Cs, Ba, Ga, and Ge.

[0090] (2) Firing step The firing step in the first embodiment 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 having a silicon class rate II type crystal phase.

[0091] 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.

[0092] 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 vapor of Na 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.

[0093] As another example of the scavenger, a Na trap agent that directly reacts with the Na-Si alloy to receive Na can be mentioned. 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.

[0094] (3) Liquid treatment process The liquid treatment process in the first embodiment 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. Also, in the liquid treatment process, the liquid treatment conditions are adjusted so that the ratio of the hydrogen amount (weight %) to the BET specific surface area (m 2 / g) becomes larger than 0.0034.

[0095] The concentration of hydrogen fluoride in hydrofluoric acid is, for example, 1% by weight, and may be 2% by weight or more, 3% by weight or more, 4% by weight or more, or 5% by weight or more. On the other hand, the concentration of hydrogen fluoride in hydrofluoric acid is, for example, 10% by weight or less. Also, the treatment time of the liquid treatment is, for example, 1 hour or more, and may be 2 hours or more, 3 hours or more, 4 hours or more, or 5 hours or more. On the other hand, the treatment time of the liquid treatment is, for example, less than 24 hours, and may be 15 hours or less, or 10 hours or less. The temperature of the liquid treatment is not particularly limited, but is, for example, room temperature.

[0096] Examples of the method for liquid-treating the precursor with hydrofluoric acid include a method of immersing the precursor in hydrofluoric acid and a method of applying hydrofluoric acid to the precursor.

[0097] (4) Electrode active material The electrode active material obtained by the above-described respective steps has, for example, a crystal phase of silicon clathrate type II. Also, by changing the firing conditions, an electrode active material having a crystal phase of silicon clathrate type I can be obtained. Further, in the present disclosure, the above-described liquid treatment step may be performed on a precursor having a diamond-type crystal phase. Also, the electrode active material has an Si—H bond on its surface. Preferred embodiments of the electrode active material are the same as those described in the above “A. Electrode active material”.

[0098] 2. Second Embodiment FIG. 5 is a flowchart illustrating a method for manufacturing an electrode active material according to the second embodiment. In the manufacturing method shown in FIG. 5, first, a Na source and an 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 an electrode active material having a crystal phase of silicon clathrate type II (firing step). In the alloying step, metal Na particles are used as the Na source.

[0099] According to the second embodiment, by using metallic Na particles as the Na source, an electrode active material with small volume change due to charge and discharge can be obtained.

[0100] (1) Alloying step The alloying step in the second embodiment is a step of reacting a Na source and a Si source to obtain a Na—Si alloy. Further, metallic Na particles are used as the Na source. The average particle diameter (D 50 ) is not particularly limited, but for example, it may be 10 μm or less, may be 5 μm or less, may be 3 μm or less, or may be 500 nm or less. Regarding the alloying step in the second embodiment, except for using metallic Na particles as the Na source, it is the same as the content described in the first embodiment above.

[0101] (2) Firing step The firing step in the second embodiment is a step of firing the above Na—Si alloy to reduce the amount of Na in the above Na—Si alloy and form an electrode active material having a silicon class rate II type crystal phase. The firing step is the same as the content described in the first embodiment above.

[0102] (3) Others The method for manufacturing the electrode active material in the second embodiment may have a liquid treatment step of subjecting the electrode active material to liquid treatment using hydrofluoric acid after the alloying step. The liquid treatment step is the same as the content described in the first embodiment above. Also, regarding the preferred embodiment of the electrode active material obtained by the method for manufacturing the electrode active material in the second embodiment, it is the same as the content described in the above “A. Electrode active material”.

[0103] E. Method for manufacturing electrode composite In the present disclosure, there is provided a method for manufacturing an electrode composite, which includes a preparation step of preparing an electrode active material by the method for manufacturing the electrode active material described above, 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 composite.

[0104] 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. The preparation process is the same as the content described in the above "D. Method for Manufacturing Electrode Active Material".

[0105] 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 the content 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 a known method can be adopted. Also, the preferred embodiments of the obtained electrode composite material are the same as the content described in the above "B. Electrode Composite Material".

[0106] F. Method for Manufacturing Battery In the present disclosure, there is provided a method for manufacturing a battery, which includes a preparation process of preparing an electrode active material by the above-described method for manufacturing an electrode active material, a mixing process of mixing the above 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 process of forming an electrode layer using the above electrode composite material.

[0107] 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 process and the mixing process are the same as the content described in the above "D. Method for Manufacturing Electrode Active Material" and the above "E. Method for Manufacturing Electrode Composite Material".

[0108] The electrode layer formation step is a step of forming an electrode layer using the above electrode composite material. The method of forming the electrode layer is not particularly limited, and a known method can be adopted. Examples of the method of forming the electrode layer include a method of applying the electrode composite material to an electrode current collector. When forming the electrode layer, a pressing process of pressing the electrode layer in the thickness direction may be performed. Examples of the pressing process include roller pressing and flat plate pressing. Further, when the electrode composite material is a slurry containing a dispersion medium, it is preferable to dry it after applying it to the electrode current collector.

[0109] The electrode layer formation step may be a positive electrode layer formation step of forming a positive electrode layer, or may be a negative electrode layer formation step of forming a negative electrode layer. The method for manufacturing a battery in the present disclosure may further include other steps such as an electrolyte layer formation step of forming an electrolyte layer. Also, regarding the preferred embodiments of the obtained battery, they are the same as the contents described in the above "C. Battery".

[0110] Note that the present disclosure is not limited to the above embodiments. The above 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.

Examples

[0111] [Example 1] Metallic Li and Si powder were weighed so that the molar ratio was 4:1, and they were reacted by mixing them in a mortar under the conditions of an Ar atmosphere, room temperature, and 0.5 hours. As a result, Li4Si was obtained. The obtained Li4Si was reacted with ethanol under 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.

[0112] Using the obtained porous Si, a Na-Si alloy was produced using NaH (average particle size 20 μm) 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 to obtain a powdery Na-Si alloy.

[0113] Using the obtained Na-Si alloy, further, using AlF3 as the Na trap agent, silicon clathrate formation by the solid-phase method was carried out. The Na-Si alloy and AlF3 were weighed so as to have a molar ratio of 1:0.35, and 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.

[0114] 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 performed, and the separated solid content 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 performed for 1 hour using an HF aqueous solution with a concentration of 3 wt%. After the liquid treatment, filtration was performed, and the separated solid content was dried at 120°C for 3 hours or more to obtain an electrode active material.

[0115] [Example 2] When producing powdery porous Si, using metallic Li and Si powder at a molar ratio of 4.75:1, when producing the powdery Na-Si alloy, except for heating in a heating furnace under an Ar atmosphere at 400°C for 40 hours, in the same manner as in Example 1, an electrode active material was obtained.

[0116] [Example 3] When producing powdered porous Si, metal Li and Si powder were used in a molar ratio of 4.75:1. 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 Example 1.

[0117] [Example 4] When producing powdered porous Si, metal Li and Si powder were used in a molar ratio of 4.75:1. 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 Example 1.

[0118] [Example 5] 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 Example 1.

[0119] [Comparative Example 1] Except that an ingot of metallic Na cut to 5 cm was used instead of NaH, the electrode active material was obtained in the same manner as in Example 1.

[0120] [Example 6] Metallic Na was pulverized for 30 seconds using a cutter mill to produce Na particles with an average particle size of 3 μm. Except that the obtained Na particles were used instead of NaH, the electrode active material was obtained in the same manner as in Example 1.

[0121] [Example 7] The operation of pulverizing metallic Na for 30 seconds using a cutter mill was performed 3 times to produce Na particles with an average particle size of 200 nm. Except that the obtained Na particles were used instead of NaH, the electrode active material was obtained in the same manner as in Example 1.

[0122] [Evaluation] (XRD measurement) X-ray diffraction (XRD) measurements using CuKα radiation were performed on the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1. As a result, it was confirmed that all of the electrode active materials had a silicon class rate II-type crystal phase as the main phase. In addition, the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1 all had a slightly diamond-type silicon crystal phase. The proportion of the diamond-type silicon crystal phase (crystalline Si amount) was determined using the RIR method (Reference Intensity Ratio method). The results are shown in Table 1.

[0123] The intensity of peak A located near 2θ = 20.09° in the silicon class rate II-type crystal phase was designated as I A and the intensity of peak B located near 2θ = 31.72° was designated as I B . Also, the maximum intensity at 2θ = 22° to 23° was designated as I M and I A / I M and I B / I M were determined. As a result, in all of the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1, I A / I M was greater than 1 and I B / I M was also greater than 1.

[0124] (Specific surface area measurement) The BET specific surface area was determined for the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1 using a specific surface area measuring device. The results are shown in Table 1.

[0125] (Hydrogen amount measurement) The hydrogen amount was determined for the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1 using an oxygen, nitrogen, hydrogen (ONH) analyzer (EMGA-930, manufactured by Horiba, Ltd.). The results are shown in Table 1.

[0126] (Measurement of volume expansion rate) Using the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1 as the negative electrode active material, all-solid-state batteries were fabricated respectively. The fabrication method is as follows.

[0127] (1) Fabrication of the negative electrode In a polypropylene container, the obtained electrode active material, sulfide solid electrolyte (Li2S-P2S5-based glass ceramic), 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 with an ultrasonic disperser (UH-50 manufactured by SMT). Next, the container was shaken for 30 minutes with a shaker (TTM-1 manufactured by Shibata Scientific Co., Ltd.). Using an applicator, it was coated on a negative electrode current collector (Cu foil, manufactured by UACJ) by the blade method 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.

[0128] (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), sulfide solid electrolyte (Li2S-P2S5-based glass ceramic), 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 with an ultrasonic disperser (UH-50 manufactured by SMT). Next, the container was shaken for 3 minutes with a shaker (TTM-1 manufactured by Shibata Scientific Co., Ltd.), further stirred for 30 seconds with an ultrasonic disperser, and shaken for 3 minutes with a shaker. Using an applicator, it was coated on a positive electrode current collector (Al foil, manufactured by Showa Denko) by the blade method 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. Note that the area of the positive electrode was made smaller than the area of the negative electrode.

[0129] (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 with an ultrasonic disperser (UH-50 manufactured by SMT). Next, the container was shaken for 30 minutes with 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.

[0130] (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.

[0131] 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. Then, the solid electrolyte layer for bonding and the transfer member were arranged in order from the negative electrode layer side. At this time, the solid electrolyte layer for bonding and the solid electrolyte layer in the transfer member were arranged so as to face 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. Then, the release sheet was peeled off from the solid electrolyte layer. Thereby, a second laminate was obtained.

[0132] 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.

[0133] (5) Measurement of volume expansion rate The obtained all-solid-state battery was charged, and the volume expansion rate was measured. The test conditions were a constraint pressure (fixed dimension) of 5 MPa, a charging rate of 0.1C, and a cut-off voltage of 4.55V. The constraint pressure at 4.55V was measured, the increase in constraint pressure from the state before charging was determined, and the volume expansion rate was determined. The results are shown in Table 1. The volume expansion rate results in Table 1 are relative values with the result of Comparative Example 1 set to 100.

[0134] (6) Measurement of resistance increase rate The obtained all-solid-state battery was charged, and the resistance increase rate was measured. First, CCCV charging was performed at 0.1C up to 4.55V, and discharging was performed at 1C down to 3.0V. Next, after charging up to 3.9V, discharging was performed at 0.1C down to 3.7V, and discharging was performed at 14.7 mA for 5 seconds. The initial resistance was determined from the value of the voltage drop. Next, CCCV charging was performed at 1 / 3C up to 4.35V, and CCCV discharging at 1 / 3C down to 3.0V was repeated 100 times. Thereafter, in the same manner as above, the resistance after charge and discharge was determined. The difference between the resistance after charge and discharge and the initial resistance was determined as the resistance increase amount, and the resistance increase rate was determined. The results are shown in Table 1. The resistance increase rate results in Table 1 are relative values with the result of Comparative Example 1 set to 100.

[0135]

Table 1

[0136] As shown in Table 1, it was confirmed that in Examples 1 to 7, the volume expansion rate could be reduced compared to Comparative Example 1. In particular, in Examples 3 to 7, the volume expansion rate could be significantly reduced compared to Comparative Example 1. Furthermore, in Examples 1 to 7, the resistance increase rate could also be reduced compared to Comparative Example 1. Also, it was confirmed that when the amount of crystalline Si was small, the volume expansion rate tended to decrease. In the present disclosure, the proportion of the amount of crystalline Si may be less than 3.6% by weight, may be 2.5% by weight or less, may be 2.0% by weight or less, may be 1.5% by weight or less, or may be 1.2% by weight or less.

[0137] (IR measurement) For the electrode active materials obtained in Examples 1, 3, and 4, infrared spectroscopic measurement (IR measurement, ATR method) was performed using a Fourier transform infrared spectrometer (FTIR, Nicolet iS50, manufactured by Thermo Fisher). The results are shown in Table 2. Peak α appears in the range of 2100 cm -1 ~2300 cm -1 and corresponds to the peak of the Si-H bond. On the other hand, peak β appears in the range of 3610 cm -1 ~3670 cm -1 and corresponds to the peak of the Si-OH bond. Also, let the peak intensities of peak α and peak β be I α and I β respectively.

[0138]

Table 2

[0139] As shown in Table 2, it was confirmed that the longer the treatment time with the HF aqueous solution, the larger α / β becomes, that is, the more hydrogen terminations of Si are generated.

Explanation of Symbols

[0140] 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 containing Si, wherein an Si—H bond exists on the surface of the electrode active material, The electrode active material in which the ratio of the hydrogen amount (wt%) to the BET specific surface area (m ２ / g) is greater than 0.0034.

2. The electrode active material according to claim 1, wherein the ratio is 0.0039 or more.

3. The electrode active material according to claim 1, wherein the ratio is 0.05 or less.

4. The BET specific surface area is 50 m ２ / g or more, the electrode active material according to claim 1.

5. The electrode active material according to claim 1, wherein the hydrogen content is 0.20% by weight or more.

6. The electrode active material according to claim 1, wherein the ratio is 0.0060 or more and the hydrogen content is 0.40% by weight or more.

7. The electrode active material according to claim 1, wherein the ratio is greater than 0.0034 and less than 0.0046, and the hydrogen content is 0.30% by weight or less.

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

9. The electrode active material according to claim 1, wherein the electrode active material has voids inside the primary particles.

10. The electrode active material according to claim 9, wherein the ratio of the voids is 4% or more and 40% or less.

11. An electrode composite material containing the electrode active material according to any one of claims 1 to 10 and at least one of a conductive material and a binder.

12. The electrode composite material according to claim 11, wherein the electrode composite material further contains a solid electrolyte.

13. The electrode composite material according to claim 12, wherein the solid electrolyte contained in the electrode composite material is a sulfide solid electrolyte.

14. 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 contains the electrode composite material according to claim 11.

15. The battery according to claim 14, wherein the negative electrode layer contains the electrode composite material.

16. The battery according to claim 14, wherein the electrolyte layer contains a solid electrolyte.

17. The solid electrolyte contained in the electrolyte layer is a sulfide solid electrolyte, and the thickness of the electrolyte layer is 0.1 μm or more and 100 μm or less. The battery according to claim 16.

18. The battery according to claim 17, wherein the positive electrode layer contains a rock salt layer-type active material.

19. An alloying step of reacting a Na source and an 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 class rate 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; It has, In the liquid treatment step, the liquid treatment conditions are adjusted so that the ratio of the hydrogen amount (wt%) to the BET specific surface area (m ２ / g) becomes larger than 0.0034. A method for producing an electrode active material.

20. The concentration of hydrogen fluoride in the hydrofluoric acid is 3% by weight or more, The production method of the electrode active material according to claim 19, wherein the treatment time in the liquid treatment step is 3 hours or more.

21. 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 an electrode active material having a silicon class rate II-type crystal phase; It has, The production method of the electrode active material, wherein in the alloying step, metal Na particles are used as the Na source.

22. The production method of the electrode active material according to claim 21, wherein the average particle diameter of the metal Na particles is 10 μm or less.

23. A preparation step of preparing an electrode active material by the production method of the electrode active material according to any one of claims 19 to 22; A mixing step of mixing the electrode active material with at least one of a conductive material and a binder to obtain an electrode composite material; The production method of the electrode composite material having.

24. A preparation step of preparing an electrode active material by the production method of the electrode active material according to any one of claims 19 to 22; A mixing step of mixing the electrode active material with 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; The production method of a battery having.

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