Electrode active material, electrode composite material, electrode layer, battery, and method for producing same

Abstract

The invention relates to an electrode active material, an electrode mixture, an electrode layer, a battery, and methods for manufacturing the same. The main purpose of the present invention is to provide an electrode active material having little change in volume due to charge and discharge. The present disclosure solves the above-mentioned problem by providing an electrode active material having a silicon inclusion compound type II crystal phase, the electrode active material having voids inside primary particles, and the void amount P1 of voids having a pore diameter of 5 nm or less being 0.015 cc / g to 0.05 cc / g (inclusive).

Description

Technical Field

[0001] The present disclosure relates to an electrode active material, an electrode composite material, an electrode layer, a battery, and methods for manufacturing them. 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 for electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), or hybrid vehicles (HEVs) has been continuously advanced. In addition, as an electrode active material for batteries, Si (silicon) is known. For example, Patent Document 1 discloses an electrode active material having a crystal phase of silicon clathrate type II and having voids inside primary particles.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2023-044620 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] Si has a large theoretical capacity and is effective for increasing the energy density of batteries. However, Si has a large volume change during charge and discharge. If the volume change during charge and discharge is large, for example, problems such as the function of the electrode being easily reduced may occur during repeated charge and discharge.

[0008] In view of the above actual situation, the present disclosure is completed, and the main object is to provide an electrode active material with a small volume change caused by charge and discharge.

[0009] Means for Solving the Problems

[0010] [1] An electrode active material is an electrode active material having a crystal phase of silicon clathrate type II, wherein voids are present inside primary particles, and the void volume P1 of voids with a pore diameter of 5 nm or less is 0.015 cc / g or more and 0.05 cc / g or less.

[0011] [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.

[0012] [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.

[0013] [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.

[0014] [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.

[0015] [6] The electrode active material according to any one of [1] to [5], wherein the electrode active material has the crystal phase of the silicon clathrate type II as the main phase.

[0016] [7] An electrode composite material containing the electrode active material according to any one of [1] to [6] and at least one selected from a conductive material and a binder.

[0017] [8] The electrode composite material according to [7], wherein the electrode composite material further contains a solid electrolyte.

[0018] [9] The electrode composite material according to [8], wherein the solid electrolyte contained in the electrode composite material is a sulfide solid electrolyte.

[0019]

[10] An electrode layer for use in a battery, the electrode layer comprising an electrode active material having the crystal phase of the silicon clathrate type II and having voids inside the primary particles, and the void volume Q1 of voids with a pore diameter of 5 nm or less is 0.008 cc / g or more and 0.04 cc / g or less.

[0020]

[11] The electrode layer according to

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

[0021]

[12] The electrode layer according to

[10] or

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

[0022]

[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 with a pore diameter of 100 nm or less is 10% or more.

[0023]

[14] The electrode layer according to any one of

[10] to

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

[0024]

[15] The battery is a battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer or the negative electrode layer is the electrode layer according to any one of

[10] to

[14] .

[0025]

[16] A method for manufacturing an electrode active material, comprising: 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 crystal phase of silicon clathrate type II; and a liquid treatment step of subjecting the precursor active material to liquid treatment with hydrofluoric acid to obtain an electrode active material, 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.

[0026]

[17] The method for manufacturing an electrode active material according to

[16] , wherein in the 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.

[0027]

[18] A method for manufacturing an electrode composite material, comprising: a preparation step of preparing an electrode active material by using the method for manufacturing an electrode active material according to

[16] or

[17] ; and a mixing step of mixing the electrode active material and at least one selected from a conductive material and a binder to obtain an electrode composite material.

[0028]

[19] A method for manufacturing an electrode layer, comprising: a preparation step of preparing an electrode active material by using the method for manufacturing an electrode active material according to

[16] or

[17] ; a mixing step of mixing the electrode active material and at least one selected from a conductive material and a binder to obtain an electrode composite material; and an electrode layer forming step of using the electrode composite material to form an electrode layer.

[0029]

[20] A method for manufacturing a battery, comprising: a preparation step of preparing an electrode active material by using the method for manufacturing an electrode active material according to

[16] or

[17] ; a mixing step of mixing the electrode active material and at least one selected from a conductive material and a binder to obtain an electrode composite material; and an electrode layer forming step of using the electrode composite material to form an electrode layer.

[0030] Effects of the Invention

[0031] The present disclosure achieves the effect of being able to obtain an electrode active material with a small volume change caused by charge and discharge. Description of the Drawings

[0032] Figure 1A schematic three-dimensional view for explaining the crystal phase of Si.

[0033] Figure 2 An exemplary schematic cross-sectional view of the battery of the present disclosure.

[0034] Figure 3 A flowchart exemplifying a method for manufacturing an electrode active material in the present disclosure.

[0035] Figure 4 XRD diagrams of the active material before and after liquid treatment using an HF aqueous solution.

[0036] Explanation of reference numerals

[0037] 1... Positive electrode layer

[0038] 2... Negative electrode layer

[0039] 3... Electrolyte layer

[0040] 4... Positive electrode current collector

[0041] 5... Negative electrode current collector

[0042] 10... Battery Detailed description of the invention

[0043] Hereinafter, the electrode active material, electrode composite material, electrode layer, battery, and their manufacturing methods of the present disclosure will be described in detail.

[0044] A. Electrode active material

[0045] The electrode active material in the present disclosure has a crystal phase of silicon clathrate type II and has voids inside the primary particles. In addition, the void volume P1 of voids with a pore (micropore) diameter of 5 nm or less is large.

[0046] According to the present disclosure, since the void volume P1 is large, the electrode active material has a small volume change caused by charge and discharge. Through previous research, the present inventors have obtained the following understanding: by increasing the void volume of minute voids with a pore diameter of 100 nm or less, the collapse of voids caused by pressing treatment can be suppressed. Furthermore, it has been found that by increasing the void volume of minute voids with a pore diameter of 10 nm or less, while significantly suppressing the collapse of voids caused by pressing treatment, the filling rate of deposited Li in the voids can be increased, and the volume change caused by charge and discharge can be effectively suppressed.

[0047] The present disclosure has found that, for example, by actively performing liquid treatment using hydrofluoric acid, the void volume P1 of minute voids with a pore diameter of 5 nm or less can be increased. It is presumed that the reason is that, during charging, the precipitated Li preferentially fills the minute voids with a pore diameter of 5 nm or less. It is presumed that by actively performing liquid treatment using hydrofluoric acid, while the surface of the electrode active material is etched, the crystalline phase of the silicon clathrate type I contained in the electrode active material disappears, and the void volume P1 increases. By increasing the void volume P1, the volume change caused by charge and discharge can be effectively suppressed.

[0048] Furthermore, the electrode active material in the present disclosure has a crystalline phase of silicon clathrate type II. As Figure 1 (a) shows, in the crystalline phase of silicon clathrate type II, a polyhedron (cage) containing pentagons or hexagons is formed using a plurality of Si elements. The polyhedron has a space inside that can accommodate metal ions such as Li ions. By inserting metal ions into this space, the volume change caused by charge and discharge can be suppressed. Especially in a solid battery, in order to suppress the volume change caused by charge and discharge, generally, a high constraint pressure needs to be applied. However, by using the electrode active material of the present disclosure, a reduction in the constraint pressure can be achieved. As a result, the enlargement of the constraint jig can be suppressed. On the other hand, as Figure 1 (b) shows, in the crystalline phase of diamond-type silicon, a tetrahedron is formed using a plurality of Si elements. The tetrahedron does not have a space inside that can accommodate metal ions such as Li ions. Therefore, compared with the crystalline phase of silicon clathrate type II, the diamond-type silicon crystalline phase is less likely to suppress the volume change caused by charge and discharge.

[0049] The shape of the active material of the present disclosure is usually particulate. The active material can be primary particles or secondary particles aggregated from primary particles. In either case, there are usually voids inside the primary particles.

[0050] The electrode active material preferably has a large number of 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, can be 0.020 cc / g or more, and can be 0.023 cc / g or more. On the other hand, the void volume P1 is usually 0.05 cc / g or less, can be 0.04 cc / g or less, and can be 0.035 cc / g or less. The void volume in the present disclosure means the cumulative pore volume. For example, it can be obtained by BET measurement, gas adsorption method, mercury porosimetry, 3D-SEM, or 3D-TEM.

[0051] The electrode active material preferably has a large number of 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. In addition, 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.

[0052] The electrode active material preferably has a large number of 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. In addition, 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.

[0053] The electrode active material preferably has voids inside the primary particles. The ratio (void fraction) of the voids in the primary particles is, for example, 4% or more, and may be 10% or more. In addition, the above void fraction is, for example, 40% or less, and may be 20% or less. The void fraction can be obtained, for example, by the following steps. First, for the electrode layer containing the electrode active material, cross-sectioning is performed 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, using image analysis software, the silicon part and the void part are strictly distinguished and binarized. The areas of the silicon part and the void part are obtained, and the void fraction (%) is calculated by the following formula.

[0054] Void fraction (%) = 100 × (void part area) / ((silicon part area) + (void part area))

[0055] There is no particular limitation on the average particle diameter (D 50 ) of the electrode active material. For example, it is 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, by measurement using a scanning electron microscope (SEM). In addition, there is no particular limitation on the BET specific surface area of the electrode active material. For example, it is 30 m 2 / g or more, may be 40 m 2 / g or more, and may be 50 m2 above / g, and can be 60 m 2 above / g. On the other hand, the BET specific surface area of the electrode active material is, for example, 150 m 2 / g or less.

[0056] The electrode active material has a crystal phase of silicon clathrate type II. Among them, the electrode active material preferably has a crystal phase of silicon clathrate type II as the main phase. The so-called "main phase" means that the peak belonging to this crystal phase has the largest diffraction intensity among the peaks observed in the X-ray diffraction measurement. The proportion of the crystal phase of silicon clathrate type II contained in the electrode active material is, for example, 80% by weight or more, can be 85% by weight or more, can be 90% by weight or more, can be 95% by weight or more. In addition, the proportion of the crystal phase of silicon clathrate type II contained in the electrode active material can be 100% by weight, or can be 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).

[0057] The crystal phase of silicon clathrate type II generally belongs to the space group (Fd-3m). In the X-ray diffraction measurement using CuKα rays, the crystal phase of silicon clathrate type II has typical peaks at the positions of 2θ = 20.09°, 21.00°, 26.51°, 31.72°, 36.26°, and 53.01°. Each of these peak positions can move (shift) back and forth within a range of ±0.50°, can move back and forth within a range of ±0.30°, or can also move back and forth within a range of ±0.10°.

[0058] In the crystal phase of silicon clathrate type II, the peak located at 2θ = 20.09° ± 0.50° is designated as peak A, and the peak located at 2θ = 31.72° ± 0.50° is designated as peak B. In addition, the intensity of peak A is designated as I A , and the intensity of peak B is designated as I B . On the other hand, the maximum intensity at 2θ = 22° to 23° is designated as I M . Usually, no peak of the crystal phase related to Si appears in the range of 2θ = 22° to 23°, so it can be used as a reference.

[0059] 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 judged that the crystal phase of silicon clathrate type II is basically not formed. The value of I A / I M is, for example, 1.75 or more, and can be 1.80 or more. On the other hand, I A / IM The value is, for example, 10 or less, and may be 5 or less.

[0060] I B / I M The value is preferably greater than 1. In the case of I B / I M when the value is 1 or less, it can be determined that the crystal phase of silicon clathrate type II is not substantially formed. I B / I M The 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.

[0061] The electrode active material in the present disclosure may or may not have the crystal phase of silicon clathrate type I. The so-called "not having... crystal phase" means that the peak of this crystal phase is not confirmed in the X-ray diffraction measurement. The crystal phase of silicon clathrate type I generally belongs to the space group (Pm-3n). In the X-ray diffraction measurement using CuKα rays, the crystal phase of silicon clathrate type I has typical peaks at positions of 2θ = 19.44°, 21.32°, 30.33°, 31.60°, 32.82°, 36.29°, 52.39°, 55.49°. Each of these peak positions can move back and forth within a range of ±0.50°, can move back and forth within a range of ±0.30°, and can move back and forth within a range of ±0.10°.

[0062] The electrode active material in the present disclosure may or may not have the crystal phase of diamond-type silicon. In addition, the crystal phase of diamond-type silicon has typical peaks at positions of 2θ = 28.44°, 47.31°, 56.10°, 69.17°, 76.37° in the X-ray diffraction measurement using CuKα rays. Each of these peak positions can move back and forth within a range of ±0.50°, can move back and forth within a range of ±0.30°, and can move back and forth within a range of ±0.10°.

[0063] As the peak of the crystal phase of diamond-type silicon, when observing the peak C located at 2θ = 28.44° ± 0.50°, the intensity of the peak C is set as I C I A / I C For example, it is greater than 1, and may be 1.5 or more, may be 2 or more, 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

[0064] The composition of the electrode active material of the present disclosure is not particularly limited, and it is preferably composed of Na x Si​136 (0≤x≤24) is represented. x can be 0 and can be greater than 0. On the other hand, x can be 20 or less, can be 10 or less, can 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. Furthermore, 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 O (oxygen). In addition, the electrode active material may contain a trace amount of C (carbon) from the manufacturing process.

[0065] The electrode active material of the present disclosure is generally used in a battery. The electrode active material of the present disclosure can be a negative electrode active material or a positive electrode active material, and the former is preferred. As a manufacturing method of the electrode active material, for example, the manufacturing methods described in "E. Manufacturing method of electrode active material" described later can be cited.

[0066] B. Electrode composite material

[0067] The electrode composite material of the present disclosure contains the above-mentioned electrode active material and at least one selected from a conductive material and a binder.

[0068] According to the present disclosure, by using the above-mentioned electrode active material, an electrode composite material with a small volume change caused by charge and discharge is obtained.

[0069] The electrode composite material contains at least one of a conductive material and a binder, and an electrode active material. Regarding the electrode active material, it is the same as the content described in the above-mentioned "A. Electrode active material". The electrode active material can be a negative electrode active material or a positive electrode active material, and the former is preferred. That is, the electrode composite material can be a negative electrode composite material or a positive electrode composite material, and the former is preferred.

[0070] The proportion of the electrode active material in the electrode composite material is, for example, 20% by weight or more, can be 30% by weight or more, can be 40% by weight or more. If the proportion of the electrode active material is too small, it may not be possible to obtain sufficient energy density. On the other hand, the proportion of the electrode active material is, for example, 80% by weight or less, can be 70% by weight or less, can be 60% by weight or less. If the proportion of the electrode active material is too large, relatively, the ionic conductivity and electronic conductivity in the electrode composite material may decrease.

[0071] The electrode composite material contains at least one of a conductive material and a binder. As the conductive material, for example, carbon materials, metal particles, and conductive polymers can be cited. As the carbon materials, for example, particulate carbon materials such as acetylene black (AB) and Ketjen black (KB); fibrous carbon materials such as carbon fiber, carbon nanotube (CNT), and carbon nanofiber (CNF). In addition, as the binder, for example, rubber-based binders and fluoride-based binders can be cited.

[0072] 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. Examples of the sulfide solid electrolyte include a solid electrolyte containing an Li element, an X element (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and an S element. In addition, the sulfide solid electrolyte may further contain at least one of an O element and a halogen element. Examples of the halogen element include an F element, a Cl element, a Br element, and an I element. The sulfide solid electrolyte may be glass (amorphous) or glass-ceramic. Examples of the sulfide solid electrolyte include Li2S-P2S5, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-SiS2, Li2S-GeS2, and Li2S-P2S5-GeS2. In addition, the electrode composite material may further contain a dispersion medium.

[0073] C. Electrode layer

[0074] The electrode layer of the present disclosure is an electrode layer for a battery, and includes an electrode active material having a crystal phase of silicon clathrate type II and having voids inside primary particles. In addition, the void volume Q1 of voids having a pore diameter of 5 nm or less is large.

[0075] According to the present disclosure, since the void volume Q1 is large, the electrode layer has a small volume change caused by charge and discharge.

[0076] The electrode layer preferably has a large number of 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, and 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.

[0077] The electrode layer preferably has a large number of voids having a pore diameter of 10 nm or less. The void volume Q2 of voids having 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. In addition, 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.

[0078] The electrode layer preferably has a large number of 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. In addition, 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.

[0079] The electrode layer contains an electrode active material and at least one selected from a conductive material and a binder. In addition, the electrode layer may contain an electrolyte. For 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, and 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. In addition, as a manufacturing method of the electrode layer, for example, the manufacturing methods described in the following "F. Manufacturing method of electrode layer" can be cited.

[0080] D. Battery

[0081] Figure 2 is a schematic cross-sectional view showing an example of the battery of the present disclosure. Figure 2 The battery 10 shown in has: a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 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".

[0082] According to the present disclosure, by using the above electrode layer, a battery with a small volume change caused by charge and discharge is obtained. As described above, the electrode layer may be a negative electrode layer or a positive electrode layer, and the former is preferred. Hereinafter, for the case where the electrode layer is a negative electrode layer, the details of the battery will be described.

[0083] 1. Negative electrode layer

[0084] The negative electrode layer is a layer containing at least a negative electrode active material. For the negative electrode layer, since it is the same as that described in the above "C. Electrode layer", the description thereof is omitted here.

[0085] 2. Positive electrode layer

[0086] The positive electrode layer is a layer containing at least a positive electrode active material. Additionally, the positive electrode layer may contain at least one of an electrolyte, a conductive material, and a binder as needed.

[0087] As the positive electrode active material, for example, oxide active materials can be cited. As the oxide active materials, for example, rock salt layer-structured active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.; spinel-type active materials such as LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, etc.; olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4.

[0088] A coating containing a Li-ion conductive oxide can be formed on the surface of the oxide active material. This is because it can inhibit the reaction between the oxide active material and the solid electrolyte (especially sulfide solid electrolyte). As the Li-ion conductive oxide, for example, LiNbO3 can be cited. The thickness of the coating is, for example, 1 nm or more and 30 nm or less. Additionally, as the positive electrode active material, for example, Li2S can also be used.

[0089] As the shape of the positive electrode active material, for example, particulate shape can be cited. There is no particular limitation on the average particle size (D 50 ) of the positive electrode active material. For example, it is 10 nm or more and can be 100 nm or more. On the other hand, the average particle size (D 50 ) of the positive electrode active material is, for example, 50 μm or less and can be 20 μm or less.

[0090] Regarding the electrolyte used for the positive electrode layer, it is the same as the content described in "3. Electrolyte layer". Additionally, regarding the conductive material and binder used for the positive electrode layer, they are the same as the content described in the above "B. Electrode composite material", so 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, can be 0.1 μm or more and 500 μm or less, and can be 0.1 μm or more and 100 μm or less.

[0091] 3. Electrolyte layer

[0092] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer and contains at least an electrolyte. The electrolyte can be a solid electrolyte or a liquid electrolyte (electrolyte solution).

[0093] For the solid electrolyte, it is the same as the content described in the above "B. Electrode Composite Material", so the description here is omitted. On the other hand, the electrolyte preferably contains a supporting salt and a solvent. As the supporting salt (lithium salt) of the electrolyte having lithium ion conductivity, for example, inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAsF6, etc. can be cited; organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, LiC(CF3SO2)3, etc. can be cited. As the solvent for the electrolyte, for example, cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be cited; chain-like esters (chain-like carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc. can be cited. The electrolyte preferably contains two or more solvents.

[0094] The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less, can be 0.1 μm or more and 500 μm or less, and can be 0.1 μm or more and 100 μm or less.

[0095] 4. Other Components

[0096] The battery of 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. As the material of the positive electrode current collector, for example, SUS, aluminum, nickel, iron, titanium, and carbon can be cited. On the other hand, as the material of the negative electrode current collector, for example, SUS, copper, nickel, and carbon can be cited.

[0097] The battery of the present disclosure may further have 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, in order to form good ion conduction paths and electron conduction paths, it is preferable to apply a restraining pressure. The restraining pressure is, for example, 0.1 MPa or more, can be 1 MPa or more, and can be 5 MPa or more. On the other hand, the restraining pressure is, for example, 100 MPa or less, can be 50 MPa or less, and can be 20 MPa or less.

[0098] 5. Battery

[0099] There is no particular limitation on the type of the battery of the present disclosure. Typically, it is a lithium-ion battery. Additionally, the battery of 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 (such as 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 the electrolyte. Additionally, the battery of the present disclosure may be a primary battery or a secondary battery, and preferably a secondary battery. This is because it can be repeatedly charged and discharged, and can be used as, for example, a vehicle-mounted battery.

[0100] As uses of the battery, for example, power sources for vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), battery electric vehicles (BEV), gasoline vehicles, and diesel vehicles can be cited. It is particularly preferably used as a driving power source for a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a battery electric vehicle (BEV). Additionally, the battery can be used as a power source for moving bodies other than vehicles (such as railways, ships, and aircraft), and can also be used as a power source for electrical products such as information processing devices.

[0101] E. Method for manufacturing electrode active material

[0102] Figure 3 is a flowchart exemplifying the method for manufacturing the electrode active material of the present disclosure. In Figure 3 the manufacturing method shown, first, a Na source and a Si source are reacted to obtain a Na-Si alloy (alloy chemical process). Next, the Na-Si alloy is fired to reduce the amount of Na in the Na-Si alloy, and a precursor active material having a crystal phase of silicon clathrate type II is formed (firing process). Next, the precursor active material is subjected to liquid treatment using hydrofluoric acid to obtain the electrode active material (liquid treatment process). In the present disclosure, the concentration of hydrofluoric acid is 3 wt% or more, and the treatment time in the liquid treatment process is 3 hours or more and less than 24 hours.

[0103] According to the present disclosure, by performing the liquid treatment process, an electrode active material with a small volume change caused by charge and discharge can be obtained.

[0104] 1. Alloy chemical process

[0105] The alloy chemical process in the present disclosure is a process in which a Na source and a Si source are reacted to obtain a Na-Si alloy.

[0106] The Si source is particles containing at least Si. The Si source can be elemental Si or an alloy of Si and other metals. When the Si source is an alloy, it preferably contains Si as the main component. The proportion of Si in the alloy is, for example, 50 atomic % or more, can be 70 atomic % or more, or can be 90 atomic % or more.

[0107] The Si source is preferably porous Si having a large number of voids inside the primary particles. As a method for manufacturing the Si source (porous Si), for example, a method of manufacturing an alloy of Li and Si (Li-Si alloy) and then removing Li from the Li-Si alloy can be cited. The Li-Si alloy is obtained, for example, by mixing Li and Si. The proportion of Li relative to Si (Li / Si) is, for example, 1.0 or more, can be 2.0 or more, can be 3.0 or more, or can be 4.0 or more. On the other hand, Li / Si is, for example, 8.0 or less. As a method 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 cited. As the Li extraction material, for example, alcohols such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol; acids such as acetic acid, formic acid, propionic acid, and oxalic acid can be cited.

[0108] In addition, as a method for manufacturing the Si source (porous Si), for example, a method of manufacturing an alloy of Mg and Si (Mg-Si alloy) and then removing Mg from the Mg-Si alloy can be cited. The Mg-Si alloy is obtained, for example, by heating a mixture of Mg and Si. The proportion of Mg relative to Si (Mg / Si) is, for example, 1.0 or more, can be 1.5 or more, or can be 2.0 or more. On the other hand, Mg / Si is, for example, 6.0 or less. As a method 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 cited. As the acid solution, for example, an aqueous solution containing hydrochloric acid (HCl) and hydrogen fluoride (HF) can be cited.

[0109] In addition, as a method for manufacturing the Si source (porous Si), for example, a method of manufacturing an alloy of Mg and Si (Mg-Si alloy), then removing Mg from the Mg-Si alloy, then manufacturing 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 cited.

[0110] On the other hand, the Na source contains at least Na. As the Na source, for example, metallic Na, NaH, and a metallic Na dispersion in which particles of metallic Na are dispersed in oil can be cited.

[0111] As a method for reacting a Na source and a Si source to obtain a Na-Si alloy, for example, a method of heating a mixture containing a Na source and a Si source can be cited. The heating temperature is, for example, 300 °C or higher, can be 310 °C or higher, can be 320 °C or higher, and can be 340 °C or higher. On the other hand, the heating temperature is, for example, 800 °C or lower, can be 600 °C or lower, and can also be 450 °C or lower. In addition, the alloying process is preferably carried out in an inert atmosphere such as an Ar atmosphere.

[0112] 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. Each of these peak positions can move back and forth within a range of ±0.50°, and can also move back and forth within a range of ±0.30°. The Na-Si alloy preferably has a Zintl phase as the main phase.

[0113] The composition of the Na-Si alloy is not particularly limited, and it is preferably represented by the composition of Na z Si 136 (121 ≤ z ≤ 151). z can be 126 or higher, and can also be 131 or higher. On the other hand, z can be 141 or lower. In the Na-Si alloy, other elements other than Na and Si may be present. As other elements, for example, Li, K, Rb, Cs, Ba, Ga, and Ge can be cited.

[0114] 2. Firing process

[0115] The firing process of the present disclosure is a process of firing the above Na-Si alloy to reduce the amount of Na in the above Na-Si alloy and form a precursor active substance having a silicon clathrate type II crystal phase.

[0116] The firing conditions of the Na-Si alloy are appropriately adjusted to obtain a desired precursor active substance. 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 can be carried out in a reduced-pressure atmosphere or in an atmospheric pressure atmosphere.

[0117] In the firing process, it is preferable to use a trapping agent that traps Na in the Na-Si alloy. As an example of the trapping agent, a Na trapping agent that reacts with the vapor of Na generated from the Na-Si alloy can be cited. For example, the Na trapping agent is arranged in a state where it does not come into contact with the Na-Si alloy. As the Na trapping agent, for example, SiO, MoO3, FeO, and Fe3O4 can be cited. When using a Na trapping agent, the firing process is preferably carried out in a reduced-pressure atmosphere.

[0118] As other examples of the scavenger, a Na scavenger that directly reacts with the Na—Si alloy to accept Na can be cited. For example, the Na scavenger is arranged in a state of being in contact with the Na—Si alloy. As the Na scavenger, for example, CaCl2, AlF3, CaBr2, CaI2, Fe3O4, FeO, MgCl2, ZnO, ZnCl2, and MnCl2 can be cited. When using the Na scavenger, the firing step can be carried out in a reduced-pressure atmosphere or in an atmospheric-pressure atmosphere.

[0119] 3. Liquid treatment step

[0120] The liquid treatment step of the present disclosure is a step of subjecting the above-mentioned precursor active material to liquid treatment with hydrofluoric acid to obtain an electrode active material. Hydrofluoric acid is an aqueous solution obtained by dissolving hydrogen fluoride (HF) in water.

[0121] The concentration of hydrogen fluoride in hydrofluoric acid is usually 3% by weight or more, can be 4% by weight or more, and can be 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. In addition, the treatment time of the liquid treatment is usually 3 hours or more, can be 4 hours or more, and can be 5 hours or more. On the other hand, the treatment time of the liquid treatment is usually less than 24 hours, can be 15 hours or less, and can be 10 hours or less. There is no particular limitation on the temperature of the liquid treatment, and it is, for example, room temperature.

[0122] As a method of subjecting the precursor active material to liquid treatment with hydrofluoric acid, for example, a method of immersing the precursor active material in hydrofluoric acid and a method of coating hydrofluoric acid on the precursor active material can be cited.

[0123] 4. Electrode active material

[0124] The electrode active material obtained by the above-mentioned respective steps has a crystal phase of silicon clathrate type II. In addition, it is preferable that the amount of voids 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. The preferred embodiment of the electrode active material is the same as that described in the above-mentioned "A. Electrode active material".

[0125] F. Method for manufacturing electrode composite

[0126] The present disclosure provides a method for manufacturing an electrode composite, which includes: a preparation step of preparing an electrode active material by using the above-mentioned method for manufacturing an electrode active material; and a mixing step of mixing the above-mentioned electrode active material and at least one selected from a conductive material and a binder to obtain an electrode composite.

[0127] According to the present disclosure, by using the above-described electrode active material, an electrode composite material with a small volume change caused by charge and discharge can be obtained. For the preparation process, it is the same as that described in the above "E. Method for manufacturing electrode active material".

[0128] The electrode composite material generally contains an electrode active material and at least one selected from a conductive material and a binder. For the conductive material and the binder, it is the same as that described in the above "B. Electrode composite material". The electrode composite material may further have a dispersion medium or may not have it. In addition, the electrode composite material is usually obtained by mixing an electrode active material and at least one selected from a conductive material and a binder. There is no particular limitation on the mixing method, and a known method can be adopted. In addition, for the preferred embodiment of the obtained electrode composite material, it is the same as that described in the above "B. Electrode composite material".

[0129] G. Method for manufacturing electrode layer

[0130] The present disclosure provides a method for manufacturing an electrode layer, which includes: a preparation process of preparing an electrode active material by using the above-described method for manufacturing an electrode active material; a mixing process of mixing the electrode active material and at least one selected from a conductive material and a binder to obtain an electrode composite material; and an electrode layer forming process of using the electrode composite material to form an electrode layer.

[0131] According to the present disclosure, by using the above-described electrode active material, an electrode layer with a small volume change caused by charge and discharge can be obtained. For the preparation process and the mixing process, it is the same as that described in the above "E. Method for manufacturing electrode active material" and the above "F. Method for manufacturing electrode composite material".

[0132] The electrode layer forming process is a process of using the above electrode composite material to form an electrode layer. There is no particular limitation on the method for forming the electrode layer, and a known method can be adopted. As a method for forming the electrode layer, for example, a method of coating the electrode composite material on an electrode current collector can be cited. When forming the electrode layer, a pressing process of pressing the electrode layer in the thickness direction can be performed. As the pressing process, for example, a roll press and a flat press can be cited. In addition, when the electrode composite material is a slurry containing a dispersion medium, it is preferably dried after being coated on the electrode current collector.

[0133] The electrode layer forming process may be a positive electrode layer forming process for forming a positive electrode layer or a negative electrode layer forming process for forming a negative electrode layer.

[0134] H. Method for manufacturing battery

[0135] The present disclosure provides a method for manufacturing a battery, which includes: a preparation step of preparing an electrode active material by using the above-described method for manufacturing an electrode active material; a mixing step of mixing the above-described electrode active material and at least one selected from a conductive material and a binder to obtain an electrode composite; and an electrode layer forming step of forming an electrode layer by using the electrode composite.

[0136] According to the present disclosure, by using the above-described electrode active material, a battery with a small volume change caused by charge and discharge can be obtained. For the preparation step, the mixing step, and the electrode layer forming step, they are the same as the contents described in the above "E. Method for manufacturing an electrode active material", the above "F. Method for manufacturing an electrode composite", and the above "G. Method for manufacturing an electrode layer". The method for manufacturing a battery of the present disclosure may further include other steps such as an electrolyte layer forming step of forming an electrolyte layer. In addition, for the preferred embodiments of the obtained battery, they are the same as the contents described in the above "D. Battery".

[0137] It should be noted that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are examples, and technical solutions having substantially the same constitution as the technical idea described in the claims of the present disclosure and achieving the same effects are all included in the technical scope of the present disclosure.

[0138] Examples

[0139] [Comparative Example 1]

[0140] Metallic Li and Si powder were weighed so that the molar ratio became 4:1, and they were mixed in a mortar under the conditions of an Ar atmosphere, room temperature, and 0.5 hours to cause them to react. Thus, Li4Si was obtained. The obtained Li4Si was reacted with ethanol in an Ar atmosphere. It was considered that the obtained reaction product contained Si and CH3CH2OLi. The reaction product was filtered, and the solid component separated by filtration was dried at 120 °C for 3 hours or more to obtain powdery porous Si.

[0141] Using the obtained porous Si and using NaH as a Na source, a Na-Si alloy was manufactured. It should be noted that as NaH, a product pre-washed with hexane was used. NaH and porous Si were weighed so that the molar ratio became 1.05:1, and they were mixed using a cutter mill. The mixture of NaH and porous Si was heated in a heating furnace under the conditions of an Ar atmosphere, 475 °C, and 40 hours to obtain a powdery Na-Si alloy.

[0142] Using the obtained Na-Si alloy, and further using AlF3 as a Na capturer, the formation of a silicon clathrate was carried out by a solid-phase method. The Na-Si alloy and AlF3 were weighed so that the molar ratio became 1:0.35, and they were mixed using a cutting mill to obtain reaction raw materials. The obtained powdery reaction raw materials were placed in a stainless-steel reaction vessel and heated and reacted in an Ar atmosphere in a heating furnace at 310 °C for 60 hours to obtain a precursor active substance.

[0143] It was considered that the obtained precursor active substance contained NaF and Al as by-products. Therefore, a mixed solvent prepared by mixing HNO3 and H2O in a volume ratio of 10:90 was used to wash the precursor active substance. Thereby, the by-products in the reaction product were removed. After washing, filtration was carried out, and the solid component 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 a liquid treatment was carried out using an HF aqueous solution with a concentration of 3 wt% for 1 hour. After the liquid treatment, filtration was carried out, and the solid component separated by filtration was dried at 120 °C for 3 hours or more to obtain an electrode active substance.

[0144] [Comparative Example 2]

[0145] When producing powdery porous Si, metallic Li and Si powder were used in a molar ratio of 4.75:1. When producing a powdery Na-Si alloy, it was heated in an Ar atmosphere in a heating furnace at 400 °C for 40 hours. Except for this, an electrode active substance was obtained in the same manner as in Comparative Example 1.

[0146] [Example 1]

[0147] When producing powdery porous Si, metallic Li and Si powder were used in a molar ratio of 4.75:1. When carrying out the liquid treatment using an HF aqueous solution, the treatment time was changed to 3 hours. Except for this, an electrode active substance was obtained in the same manner as in Comparative Example 1.

[0148] [Example 2]

[0149] When producing powdery porous Si, metallic Li and Si powder were used in a molar ratio of 4.75:1. When carrying out the liquid treatment using an HF aqueous solution, the treatment time was changed to 5 hours. Except for this, an electrode active substance was obtained in the same manner as in Comparative Example 1.

[0150] [Example 3]

[0151] When carrying out the liquid treatment using an HF aqueous solution, the treatment time was changed to 5 hours. Except for this, an electrode active substance was obtained in the same manner as in Comparative Example 1.

[0152] [Comparative Example 3]

[0153] When producing powdery porous Si, metallic Li and Si powder were used in a molar ratio of 4.75:1. When performing liquid treatment using an HF aqueous solution, the concentration was changed to 1 wt% and the treatment time was changed to 5 hours. Other than this, the electrode active material was obtained in the same manner as in Comparative Example 1.

[0154] [Comparative Example 4]

[0155] When producing powdery porous Si, metallic Li and Si powder were used in a molar ratio of 4.75:1. When performing liquid treatment using an HF aqueous solution, the treatment time was changed to 24 hours. Other than this, the electrode active material was obtained in the same manner as in Comparative Example 1.

[0156] [Comparative Example 5]

[0157] Crystalline Si (SIEPB23, manufactured by Kojundo Chemical Laboratory Co., Ltd.) was prepared and micronized by mechanical grinding. Specifically, 1 g of crystalline Si and 53 g of zirconia balls with a diameter of φ1 mm were placed in a container and sealed, and mechanical grinding was performed using a planetary ball mill (manufactured by Fritsch) under the conditions of 200 rpm and 3 hours. Then, liquid treatment was performed using an HF aqueous solution with a concentration of 3 wt% for 5 hours. After the liquid treatment, filtration was performed, and the solid component separated by filtration was dried at 120 °C for 3 hours or more to obtain the electrode active material. The liquid treatment conditions of the electrode active materials in Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1.

[0158]

Table 1

[0159]

[0160] [Evaluation]

[0161] (XRD measurement)

[0162] For the electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4, X-ray diffraction (XRD) measurement using CuKα radiation was performed. As a result, it was confirmed that all the electrode active materials had a silicon clathrate type II crystal phase as the main phase.

[0163] Let the intensity of peak A located near 2θ = 20.09° in the silicon clathrate type II crystal phase be I A , and let the intensity of peak B located near 2θ = 31.72° be I B . In addition, let the maximum intensity at 2θ = 22° to 23° be I M , and I A / I M and I B / I MAs a result, the electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were all I A / I M was greater than 1, and I B / I M was also greater than 1.

[0164] In addition, in Examples 1 to 3 and Comparative Examples 1 to 4, the RIR method (Reference Intensity Ratio method) was used to determine the proportion of the crystal phase of silicon clathrate type I before liquid treatment with HF aqueous solution. The results are shown in Table 1. As shown in Table 1, before liquid treatment with HF aqueous solution, it was confirmed that the precursor active material contained the crystal phase of silicon clathrate type I. In addition, as Figure 4 shown, it was confirmed that the crystal phase of silicon clathrate type I disappeared before and after liquid treatment with HF aqueous solution.

[0165] (Measurement of void volume)

[0166] The void volumes 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 volume P1 with a pore diameter of 5 nm or less, the void volume P2 with a pore diameter of 10 nm or less, and the void volume P3 with a pore diameter of 100 nm or less were determined. The results are shown in Table 2.

[0167] (Measurement of specific surface area)

[0168] 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.

[0169]

Table 2

[0170]

[0171] As shown in Table 2, it was confirmed that the electrode active materials obtained in Examples 1 to 3 had a larger void volume 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 clathrate type I is more easily dissolved in HF aqueous solution than the crystal phase of silicon clathrate type II, it is speculated that by liquid treatment with HF aqueous solution, the crystal phase of silicon clathrate type I disappears and the void volume P1 with a pore diameter of 5 nm or less increases.

[0172] (Fabrication of all-solid-state battery)

[0173] Using the electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 and 2 as the negative electrode active materials, all-solid-state batteries were fabricated respectively. The fabrication method is as described below.

[0174] (1) Fabrication of the negative electrode

[0175] The obtained electrode active material, sulfide solid electrolyte (Li2S-P2S5-based glass-ceramic), conductive material (VGCF), butyl butyrate solution containing a PVDF-based binder at a ratio of 5 wt%, and butyl butyrate were added to a polypropylene container, and stirred for 30 seconds using an ultrasonic dispersion device (UH-50 manufactured by SMT). Next, the container was vibrated for 30 minutes using a vibrator (TTM-1 manufactured by Shibata Scientific Technology Ltd.). Using a coater and the doctor blade method, it was coated on a negative electrode current collector (Cu foil, manufactured by UACJ), and dried on a hot plate at 100 °C for 30 minutes. Thus, a negative electrode having a negative electrode current collector and a negative electrode layer was obtained.

[0176] (2) Fabrication of the positive electrode

[0177] The 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), butyl butyrate solution containing a PVDF-based binder at a ratio of 5 wt%, and butyl butyrate were added to a polypropylene container, and stirred for 30 seconds using an ultrasonic dispersion device (UH-50 manufactured by SMT). Next, the container was vibrated for 3 minutes using a vibrator (TTM-1 manufactured by Shibata Scientific Technology Ltd.), then stirred for 30 seconds using the ultrasonic dispersion device, and vibrated for 3 minutes using the vibrator. Using a coater and the doctor blade method, it was coated on a positive electrode current collector (Al foil, manufactured by Showa Denko), and dried on a hot plate at 100 °C for 30 minutes. Thus, a positive electrode having a positive electrode current collector and a positive electrode layer was obtained. Further, the area of the positive electrode was made smaller than that of the negative electrode.

[0178] (3) Fabrication of the solid electrolyte layer

[0179] The sulfide solid electrolyte (Li2S-P2S5-based glass-ceramic), heptane solution containing a butene rubber-based binder at a ratio of 5 wt%, and heptane were added to a polypropylene container, and stirred for 30 seconds using an ultrasonic dispersion device (UH-50 manufactured by SMT). Next, the container was vibrated for 30 minutes using a vibrator (TTM-1 manufactured by Shibata Scientific Technology Ltd.). Using a coater and the doctor blade method, it was coated on a release sheet (Al foil), and dried on a hot plate at 100 °C for 30 minutes. Thus, a transfer member having a release sheet and a solid electrolyte layer was obtained.

[0180] (4) Fabrication of the all-solid-state battery

[0181] A solid electrolyte layer for bonding is disposed on the positive electrode layer of the positive electrode, and it is set on a roll press and pressed at 100 kN / cm and 165 °C. Thus, the first laminate was obtained.

[0182] Next, the negative electrode was set on a roll press and pressed at 60 kN / cm and 25 °C. Thus, the pressed negative electrode was obtained. Then, the solid electrolyte layer for bonding and the transfer member were sequentially arranged from the negative electrode layer side. At this time, they were arranged such that the solid electrolyte layer in the solid electrolyte layer for bonding faced the solid electrolyte layer in the transfer member. The obtained laminate was set on a planar uniaxial press and pre-pressed at 100 MPa and 25 °C for 10 seconds. Then, the release sheet was peeled off from the solid electrolyte layer. Thus, the second laminate was obtained.

[0183] Next, they were arranged such that the solid electrolyte layer for bonding in the first laminate faced the solid electrolyte layer in the second laminate, and it was set on a planar uniaxial press and pressed at 200 MPa and 120 °C for 1 minute. Thus, the all-solid-state battery was obtained.

[0184] (5) Measurement of void fraction and volume expansion rate

[0185] The void fraction of the pressed negative electrode was determined. Specifically, using a high-precision gas adsorption amount measuring 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. In addition, the obtained all-solid-state battery was charged, and the volume expansion rate was measured. The test conditions were set as a constraint pressure (fixed size) of 5 MPa, a charge of 0.1 C, and a cut-off voltage of 4.55 V. The constraint pressure at 4.55 V was measured, the increase in the constraint pressure compared with the state before charging was determined, and the volume expansion rate was determined. The results are shown in Table 3. Furthermore, the results of the volume expansion rate in Table 3 are relative values when the result of Comparative Example 1 is set to 100. In addition, the change in the void fraction due to pressing is shown in Table 4.

[0186]

Table 3

[0187]

[0188]

Table 4

[0189]

[0190] As shown in Table 3, it was confirmed that the amount Q1 of voids with a pore diameter of 5 nm or less was larger in the electrode active materials obtained in Examples 1 to 3 than in the electrode active materials obtained in Comparative Examples 1 and 2. In addition, as shown in Table 4, it was confirmed that the Q1 / P1 ratio was larger than the Q2 / P2 ratio, and the voids with a pore diameter of 5 nm or less were not easily crushed by pressing. In addition, as shown in Table 3, it was confirmed that the volume expansion rate could be reduced in Examples 1 to 3 compared with Comparative Examples 1 and 2. In particular, Examples 2 and 3 could significantly reduce the volume expansion rate compared with Comparative Example 1.

Claims

1. An electrode active material having a silicon inclusion compound II type crystal phase, wherein: The primary particles have voids inside, and the void amount 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.

2. The electrode active material according to claim 1, wherein The ratio of the void amount P1 to the void amount P2 of voids having a pore diameter of 10 nm or less, that is, P1 / P2, is 50% or more.

3. The electrode active material according to claim 1, wherein The void amount P2 of voids having a pore diameter of 10 nm or less is 0.03 cc / g or more and 0.08 cc / g or less.

4. The electrode active material according to claim 1, wherein The ratio of the void amount P1 to the void amount P3 of voids having a pore diameter of 100 nm or less, that is, P1 / P3, is 6.5% or more.

5. The electrode active material according to claim 1, wherein The void amount P3 of voids having a pore diameter of 100 nm or less is 0.1 cc / g or more and 0.5 cc / g or less.

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

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

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

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

10. An electrode layer for a battery, comprising an electrode active material having a silicon inclusion compound II type crystal phase and voids inside primary particles, wherein the void amount Q1 of the voids having a pore diameter of 5 nm or less is greater than 0.008 cc / g and less than 0.04 cc / g.

11. The electrode layer according to claim 10, wherein The ratio of the void amount Q1 to the void amount Q2 of voids having a pore diameter of 10 nm or less, that is, Q1 / Q2, is 50% or more.

12. The electrode layer according to claim 10, wherein The void amount 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.

13. The electrode layer according to claim 10, wherein The ratio of the void amount Q1 to the void amount Q3 of voids having a pore diameter of 100 nm or less, that is, Q1 / Q3, is 10% or more.

14. The electrode layer according to claim 10, wherein The void amount 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. 15 . A battery comprising 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 claim 10 .

16. A method for producing an electrode active material, comprising: An alloying step of reacting a Na source and a Si source to obtain a Na-Si alloy; The Na-Si alloy is sintered to reduce the amount of Na in the Na-Si alloy and form a precursor active material having a silicon inclusion compound II type crystal phase; a liquid treatment step of treating the precursor active material with hydrofluoric acid to obtain an electrode active material; in, The concentration of hydrogen fluoride in the hydrofluoric acid is 3% by weight or more, The treatment time in the liquid treatment step is 3 hours or more and less than 24 hours.

17. The method for producing an electrode active material according to claim 16, wherein: In the electrode active material, a void amount 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.

18. A method for manufacturing an electrode composite material, comprising: A step of preparing an electrode active material by using the method for producing an electrode active material according to claim 16 or 17; and A mixing step of mixing the electrode active material and at least one selected from a conductive material and a binder to obtain an electrode composite material.

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

20. A method for manufacturing a battery, comprising: A step of preparing an electrode active material by using the method for producing an electrode active material according to claim 16 or 17; A mixing step of mixing the electrode active material and at least one selected from a conductive material and a binder to obtain an electrode composite; and An electrode layer forming step of forming an electrode layer using the electrode composite material.

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