Electrode active material, electrode mixture, battery and method for producing the same

Abstract

A main object of the present disclosure is to provide an electrode active material whose volume change due to charge and discharge is small. The present disclosure achieves the object by providing an electrode active material containing Si, wherein a Si-H bond is present on a surface of the electrode active material; and a proportion of an amount of hydrogen (wt%) with respect to a BET specific surface area (m 2 / g) is more than 0.0034.

Description

Technical area

[0001] The present disclosure relates to an electrode active material, an electrode mixture, a battery and a method for producing the same. State of the art

[0002] In recent years, battery development has been actively pursued. For example, the development of batteries for battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), or hybrid electric vehicles (HEVs) in the automotive industry has been advanced. Furthermore, Si (silicon) has become known as an electrode active material for batteries. For example, Patent Literature 1 discloses an electrode active material comprising a silicon clathrate II-type crystal phase and a cavity within a primary particle. Citation listPatent literature

[0003] Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 2023-044620 Revelation OverviewTechnical Problem

[0004] The theoretical capacity of Si is large, and it is advantageous for enabling a battery with high energy density. On the other hand, the volume change of Si during charging and discharging is large. If the volume change during charging and discharging is large, there is a problem that, for example, the function of an electrode tends to be impaired during repeated charging and discharging.

[0005] The present disclosure has been made in consideration of the above circumstances, and a main object thereof is to provide an electrode active material whose volume change due to charge and discharge is small. Solution to the problem [1] An electrode active material containing Si, wherein a Si-H bond is present on a surface of the electrode active material, and a proportion of an amount of hydrogen (wt%) in relation to a specific BET surface area (m 2 / g) is more than 0.0034. [2] The electrode active material according to [1], wherein the proportion is 0.0039 or more. [3] The electrode active material according to [1] or [2], wherein the proportion is 0.05 or less. [4] The electrode active material according to any one of [1] to [3], wherein the BET specific surface area is 50 m 2 / g or more. [5] The electrode active material according to any one of [1] to [4], wherein the amount of hydrogen is 0.20 wt% or more. [6] The electrode active material according to any one of [1] to [5], wherein the proportion is 0.0060 or more and the amount of hydrogen is 0.40 wt% or more. [7] The electrode active material according to any one of [1] to [5], wherein the proportion is more than 0.0034 and less than 0.0046 and the amount of hydrogen is 0.30 wt% or less. [8] The electrode active material according to any one of [1] to [7], wherein the electrode active material comprises a silicon clathrate II type crystal phase as a main phase. [9] The electrode active material according to any one of [1] to [8], wherein the electrode active material comprises a cavity within a primary particle.

[10] The electrode active material according to [9], wherein a proportion of the void is 4% or more and 40% or less.

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

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

[12] The electrode mixture according to

[11] further containing a solid electrolyte.

[13] The electrode mixture according to

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

[14] A battery comprising a cathode layer, an anode layer and an electrolyte layer disposed between the cathode layer and the anode layer, wherein the cathode layer or the anode layer contains the electrode mixture according to one of the items

[11] to

[13] .

[15] The battery according to

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

[16] The battery according to

[14] or

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

[17] The battery according to

[16] , wherein the solid electrolyte contained in the electrolyte layer is a sulfide solid electrolyte, and a thickness of the electrolyte layer is 0.1 µm or more and 100 µm or less.

[18] The battery according to any one of items

[14] to

[17] , wherein the cathode layer contains a rock salt bed type active material.

[19] A method for producing an electrode active material, the method comprising: an alloying step in which a Na-Si alloy is obtained by reacting a Na source and a Si source, a firing step in which the Na-Si alloy is fired to reduce the amount of Na in the Na-Si alloy and to form a precursor active material containing a silicon clathrate II type crystal phase, and a liquid treatment step in which a liquid treatment of the precursor active material is carried out using a hydrofluoric acid, wherein in the liquid treatment step, a liquid treatment condition is set such that a proportion of an amount of hydrogen (wt%) with respect to a specific BET surface area (m2 / g) becomes more than 0.0034.

[20] The method for producing an electrode active material according to

[17] , wherein a concentration of hydrogen fluoride in the hydrofluoric acid is 3 wt% or more, and a treatment time in the liquid treatment step is 3 hours or more.

[21] A method for producing an electrode active material, the method comprising: an alloying step in which a Na-Si alloy is obtained by reacting a Na source and a Si source, a firing step in which the Na-Si alloy is fired to reduce the amount of Na in the Na-Si alloy and to form an electrode active material containing a silicon clathrate II type crystal phase, wherein in the alloying step, a metallic Na particle is used as a Na source.

[22] The method for producing an electrode active material according to

[21] , wherein the average particle size of the metallic Na particle is 10 µm or less.

[23] A method for producing an electrode mixture, the method comprising: a preparation step of preparing an electrode active material by the method for producing an electrode active material according to any one of items

[19] to

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

[24] A method of manufacturing a battery, the method comprising: a preparation step of preparing an electrode active material by the method for producing an electrode active material according to any one of items

[19] to

[22] ; a mixing step of mixing the electrode active material with at least one conductive material and a binder to obtain an electrode mixture, and an electrode layer forming step of forming an electrode layer using the electrode mixture. Beneficial effects of disclosure

[0006] The present disclosure shows such an effect that an electrode active material whose volume change due to charge and discharge is small is obtained. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A and Fig. 1B are schematic perspective views explaining the crystal phase of Si. Fig. 2A and Fig. 2B are explanatory views explaining the hydrogen connector in the present disclosure. Fig.3 is a schematic cross-sectional view illustrating the battery of the present disclosure. Fig. 4 is a flowchart illustrating the method for producing the electrode active material in the present disclosure. Fig. 5 is a flowchart illustrating the method for producing the electrode active material in the present disclosure. Description of the embodiments

[0007] The electrode active material, the electrode mixture, the battery and the method for producing them in the present disclosure are explained in more detail below. A. Electrode active material

[0008] The electrode active material in the present disclosure contains Si. Further, a Si-H bond is present on a surface of the electrode active material. Further, in the electrode active material, a rate of an amount of hydrogen (wt%) with respect to a BET specific surface area (m 2 / g) in the specified range.

[0009] According to the present disclosure, the Si-H bond is present on the surface of the electrode active material, and the proportion of the amount of hydrogen with respect to the BET specific surface area is within the specified range, and thus the volume change of the electrode active material due to charge and discharge is small.

[0010] 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 improves. Since a conductive material generally has low polarity, the dispersibility of the electrode active material and the conductive material decreases when the surface of the electrode active material (Si-based active material) is oxidized. In the electrode layer, the content of the conductive material is generally lower than that of the solid electrolyte. Thus, when the dispersibility of the electrode active material and the conductive material decreases, reaction unevenness easily occurs, and it is difficult to suppress the volume change due to charging and discharging.In contrast, in the present disclosure, a Si-H bond is introduced to the surface of the electrode active material, for example, by a hydrogen bond to the surface of the electrode active material to improve the dispersibility of the electrode active material and the conductive material. This improves the reaction uniformity in the electrode layer, and the volume change due to charging and discharging can be suppressed.

[0011] Furthermore, the electrode active material in the present disclosure comprises, for example, a silicon clathrate II type crystal phase. As in Fig.As shown in Figure 1A, in the silicon clathrate II-type crystal phase, a plurality of Si elements are formed into a polyhedron (cage) comprising pentagons and hexagons. This polyhedron has a space inside containing metal ions, such as Li ions. The metal ions are intercalated into this space to prevent volume changes due to charging and discharging. Particularly in an all-solid-state battery, in order to suppress volume changes due to charging and discharging, it is generally necessary to apply a high confinement pressure. However, by using the electrode active material in the present disclosure, a reduction in the confinement pressure can be achieved, and as a result, the increase in the size of the confinement device can be suppressed. As shown in Fig.As shown in Figure 1B, in the diamond-like silicon crystal phase, a plurality of Si elements are formed into a tetrahedron. The tetrahedron has no internal space including metal ions such as Li ions, and thus its volume change due to charge and discharge cannot be easily suppressed by the diamond-like silicon crystal phase, compared with the silicon clathrate II type crystal phase. The electrode active material comprising a diamond-type silicon crystal phase is advantageous in that production is easier compared with the silicon clathrate II type electrode active material. Further, in the present disclosure, the electrode active material may comprise a silicon clathrate I type crystal phase. Incidentally, the silicon clathrate I type crystal phase and the silicon clathrate II type crystal phase may be generally referred to as a silicon clathrate type crystal phase.

[0012] The electrode active material in the present disclosure includes a Si-H bond on its surface. The Si-H bond can be formed, for example, by treating the surface of the electrode active material with a hydrofluoric acid. As described in Fig. As shown in Figure 2A, a natural oxide film is present 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. As shown in Figure 2B, the surface of the electrode active material is etched (SiO2 + 6HF (aq) → H2SiF6), and Si and H are formed around this terminal to form a Si-H bond (hydrogen terminal).

[0013] The presence of the Si-H bond can be confirmed by infrared spectroscopy (IR method). The peak of the Si-H bond usually appears in the region of 2100 cm -1 up to 2300 cm -1In the present disclosure, the peak of the Si-H bond may be referred to as peak α. Meanwhile, the peak of a Si-OH bond normally appears in the region of 3610 cm -1 up to 3670 cm -1 . In the present disclosure, the peak of the Si-OH bond may be referred to as peak β. The intensities of peak α and peak β are expressed as I α or I β The ratio of I α to I β , i.e. I α / I β is not particularly limited, for example, it can be greater than 0.63, 0.65 or more, 0.70 or more, and 0.80 or more.

[0014] In the present disclosure, the proportion of an amount of hydrogen (wt%) with respect to a BET specific surface area (m 2 / g) is usually more than 0.0034. The proportion can be 0.0039 or more, 0.0046 or more, 0.0050 or more, and 0.0060 or more. If the proportion is too small, it may be difficult to improve the dispersibility of the electrode active material and the conductive material. Meanwhile, the proportion is, for example, 0.05 or less, may be 0.04 or less, and may be 0.03 or less.

[0015] The specific BET surface area of the electrode active material is not particularly limited and is, for example, 30 m 2 / g or more, can reach 40 m 2 / g or more, 50 m 2 / g or more and 60 m 2 / g or more. Meanwhile, the BET specific surface area of the electrode active material is, for example, 150 m 2 / g or less. Further, the amount of hydrogen in 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. Meanwhile, the amount of hydrogen in the electrode active material is, for example, 3.0 wt% or less.

[0016] In the present disclosure, a proportion of the amount of hydrogen (wt%) with respect to the BET specific surface area (m 2 / g) may be 0.0060 or more, and the amount of hydrogen of the electrode active material may be 0.40 wt% or more. In this case, the volume change due to charging and discharging can be significantly reduced. Furthermore, the proportion of the amount of hydrogen (wt%) with respect to the BET specific surface area (m 2 / g) may be more than 0.0034 and less than 0.0046, and the amount of hydrogen in the electrode active material may be 0.30 wt% or less. Furthermore, in this case, the volume change due to charging and discharging can be significantly reduced.

[0017] The electrode active material comprises, for example, a silicon clathrate II-type crystal phase. Specifically, the electrode active material preferably comprises the silicon clathrate II-type crystal phase as the main phase. "Main phase" means that the peak corresponding to this crystal phase has the largest diffraction intensity among the peaks observed in an X-ray diffraction measurement. The proportion of the silicon clathrate II-type crystal phase comprising 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. Further, the proportion of the silicon clathrate II-type crystal phase comprising the electrode active material may be 100 wt% and may be less than 100 wt%.The proportion of the crystal phase can be obtained by performing a Rietvelt analysis on the XRD measurement result and using the analysis result and an RIR method (Reference Intensity Ratio method).

[0018] The silicon clathrate II crystal phase typically belongs to the space group Fd-3m. In an X-ray diffraction measurement using a CuKα source, the silicon clathrate II crystal phase exhibits typical peaks at the positions 2θ = 20.09°, 21.00°, 26.51°, 31.72°, 36.26°, and 53.01°. Each of these peaks can shift within the range of ± 0.50°, ± 0.30°, and ± 0.10°.

[0019] In the silicon clathrate II type crystal phase, a peak at 2θ = 20.09°± 0.50° is regarded as peak A and a peak at 2θ = 31.72°± 0.50° is regarded as peak B. Furthermore, the intensity of peak A is referred to as I A and the intensity of peak B as I B The intensity maximum at 2θ = 22° to 23° is called IM Since 2θ = 22° to 23° is the range where the crystal phase peaks related to Si do not normally appear, it can be used as a basis.

[0020] The value of I A / I M is preferably greater than 1. If the value of I A / I M 1 or less, it can be assumed that the silicon clathrate II type crystal phase is essentially not formed. The value of I A / I M is, for example, 1.75 or more and can be 1.80 or more. Meanwhile, the value of I A / I M for example 10 or less and can be 5 or less.

[0021] The value of I B / I M is preferably greater than 1. If the value of I B / I M1 or less, it can be assumed that the silicon clathrate II type crystal phase is essentially not formed. The value of I B / I M is, for example, 1.35 or more and can be 1.40 or more. Meanwhile, the value of I B / I M for example 7 or less and can be 4 or less.

[0022] The electrode active material in the present disclosure may or may not include a silicon clathrate I-type crystal phase. "Not including or including a crystal phase" generally means that the peaks of this crystal phase are not confirmed by X-ray diffraction measurement. Meanwhile, the electrode active material in the present disclosure may include a silicon clathrate I-type crystal phase as the main phase. The silicon clathrate I-type crystal phase typically belongs to the Pm-3n space group. The silicon clathrate I-type crystal phase has typical peaks at positions 2θ = 19.44°, 21.32°, 30.33°, 31.60°, 32.82°, 36.29°, 52.39°, and 55.49° in X-ray diffraction measurement using a CuKα beam. Each of these peaks can shift within the range of ± 0.50°, within the range of ± 0.30° and within the range of ± 0.10°.

[0023] The electrode active material in the present disclosure may or may not include a diamond-like silicon crystal phase. Meanwhile, the electrode active material in the present disclosure may include a diamond-like silicon crystal phase as the main phase. Further, in an X-ray diffraction measurement using a CuKα beam, the diamond-like silicon crystal phase exhibits typical peaks at the positions 2θ = 28.44°, 47.31°, 56.10°, 69.17°, and 76.37°. Each of these peaks may shift within the range of ±0.50°, within the range of ±0.30°, and within the range of ±0.10°.

[0024] If a peak C at 2θ = 28.44° ± 0.50° is observed as the peak of the diamond-like silicon crystal phase, the intensity of the peak C is expressed as I C considered. I A / I C For example, is greater than 1, can be 1.5 or more, can be 2 or more, and can be 3 or more. The preferred range of I B / I Cis the same as the preferred range of I A / I C .

[0025] The composition of the electrode active material in the present disclosure is not particularly limited, but is preferably Na x Si 136 (0 ≤ x ≤ 24). The "x" can be 0 and can be greater than 0. Meanwhile, the "x" can be 20 or less, 10 or less, and 5 or less. The composition of the electrode active material can be obtained by, for example, EDX, XRD, XRF, ICP, and atomic absorption method. Incidentally, an unavoidable oxidation film generally forms on the surface of the electrode active material. For this reason, the electrode active material may contain a small amount of O (oxygen). Furthermore, the electrode active material may contain a small amount of C (carbon) derived from the production steps.

[0026] The electrode active material in the present disclosure may be a primary particle and a secondary particle that is an aggregation of the primary particles. The average particle size (D 50 ) of the electrode active material is not particularly limited and is, for example, 0.1 µm or more and 50 µm or less, and may be 0.5 µm or more and 30 µm or less. The average particle size (D 50 ) can be calculated, for example, from a measurement with a scanning electron microscope (SEM).

[0027] The electrode active material preferably includes a void inside the primary particle. The void ratio in the primary particle is, for example, 4% or more, and may be 10% or more. Further, the void ratio is, for example, 40% or less, and may be 20% or less. The void ratio can be obtained, for example, by the following methods. First, the electrode layer comprising the electrode active material is subjected to ion milling to take out the cross section. Then, the cross section is observed with an SEM (Scanning Electron Microscope) to obtain an image of the particles. From the obtained image, a silicon portion and the void portion are distinguished and binarized using image analysis software. The area of the silicon portion and the void portion is obtained, and the void ratio (%) is calculated using the following equation. Void fraction (%) = 100 * (area of the empty section) / ((area of the silicone section) + (area of the empty section))

[0028] Preferably, the electrode active material includes a plurality of pores having a pore diameter of 5 nm or less. The amount P1 of a void having a pore diameter of 5 nm or less is, 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. The pore amount P1 is, 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 amount of void in the present disclosure means an integrating hole volume and can be obtained by, for example, a BET measurement, a gas absorption method, a mercury porosimeter measurement, 3D-SEM, and 3D-TEM.

[0029] Preferably, the electrode active material includes a plurality of pores having a pore diameter of 10 nm or less. The amount P2 of a void having 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. The pore amount 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. Further, the proportion of the pore amount P1 with respect to the pore amount P2, ie, P1 / P2, is, for example, 50% or more, may be 55% or more, and may be 57% or more. Meanwhile, P1 / P2 is, for example, 80% or less, may be 70% or less, and may be 65% or less.

[0030] Preferably, the electrode active material comprises a plurality of pores having a pore diameter of 100 nm or less. The pore amount P3 of a pore having 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. The pore amount 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 proportion of the pore amount P1 with respect to the pore amount P3, ie, P1 / P3, is, for example, 6.0% or more, may be 6.5% or more, and may be 6.9% or more. Meanwhile, P1 / P3 is, for example, 15% or less, may be 12% or less, and may be 10% or less.

[0031] The electrode active material in the present disclosure is typically used for a battery. The electrode active material in the present disclosure may be either an anode active material or a cathode active material, with the former being preferred. Examples of methods for producing the electrode active material may include, for example, the methods described later in "D. Method for Producing Electrode Active Material." B. Electrode mixture

[0032] The electrode mixture in the present disclosure contains the above-described electrode active material and at least one of a conductive material and a binder.

[0033] According to the present disclosure, the use of the above-described electrode active material enables a smaller volume change of the electrode mixture due to charging and discharging.

[0034] The electrode mixture contains the electrode active material and at least one of a conductive material and a binder. The electrode active material has the same content as that described above under "A. Electrode Active Material." The electrode active material can be an anode active material or a cathode active material, with the former being preferable. In other words, the electrode mixture can be an anode mixture or a cathode mixture, with the former being preferable.

[0035] The proportion of the electrode active material in the electrode mixture is, for example, 20 wt% or more, may be 30 wt% or more, and may be 40 wt% or more. If the proportion of the electrode active material is too small, there is a possibility that sufficient energy density will not be obtained. For example, the proportion of the electrode active material is 80 wt% or less, may be 70 wt% or less, and may be 60 wt% or less. If the proportion of the electrode active material is too high, there is a possibility that the ionic conductivity and electronic conductivity in the electrode mixture will be relatively deteriorated.

[0036] The electrode mixture contains at least one of a conductive material and a binder. Examples of the conductive material may include a carbon material, a metal particle, and a conductive polymer. Examples of the carbon material may include a particulate carbon material such as acetylene black (AB) and Ketjen black (KB), and a fibrous carbon material such as carbon fiber, carbon nanotube (CNT), and carbon nanofiber (CNF). Other examples of binders may include rubber-based binders and fluoride-based binders.

[0037] The electrode mixture may further contain a solid electrolyte. Examples of the solid electrolyte may include an inorganic solid electrolyte such as a sulfide solid electrolyte, an oxide solid electrolyte, a nitride solid electrolyte, and a halide solid electrolyte; and an organic polymer electrolyte such as a polymer electrolyte. Examples of the sulfide-based solid electrolyte may include a solid electrolyte containing a 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. Further, the sulfide solid electrolyte may contain at least one O element and a halogen element. Examples of the halogen element may include an F element, a Cl element, a Br element, and an I element. The sulfide solid electrolyte may be made of (amorphous) glass and a glass-ceramic.Examples of the sulfide-based solid electrolyte may include Li2S-P2S5, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-SiS2, Li2S-GeS2, and Li2S-P2S5-GeS2. Furthermore, the electrode mixture may also contain a dispersion medium. C. Battery

[0038] Fig. 3 is a schematic sectional view illustrating the battery in the present disclosure. The Fig. 3 comprises the cathode layer 1, the anode layer 2, the electrolyte layer 3 arranged between the cathode layer 1 and the anode layer 2, the cathode current collector 4 for collecting current from the cathode layer 1, and the anode current collector 5 for collecting current from the anode layer 2. In the present disclosure, the cathode layer 1 or the anode layer 2 contains the electrode mixture described under “B. Electrode Mixture” above.

[0039] According to the present disclosure, the use of the above-described electrode mixture enables a battery to experience less volume change during charging and discharging. As described above, the electrode mixture may be an anode mixture or a cathode mixture, with the former being preferred. Details of the battery when the electrode mixture is the anode mixture will be explained below. 1. Anode layer

[0040] The anode layer in the present disclosure contains the electrode mixture (anode mixture) described above. The electrode mixture has the same content as that described in "B Electrode Mixture" above; thus, the descriptions are omitted here. Further, the anode layer may contain an electrolyte as needed. The electrolyte has the same content as that described in "3. Electrolyte Layer." The thickness of the anode 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. Further, examples of the method for forming the anode layer may include a method in which the electrode mixture is applied to the anode current collector. 2. Cathode layer

[0041] The cathode layer is a layer containing at least one cathode active material. Furthermore, the cathode layer may contain at least one electrolyte, a conductive material, and a binder, as needed.

[0042] Examples of the cathode active material may include an oxide active material. Examples of the oxide active material may include a rock salt bed type active material, for example, LiCoO2, LiMnO2, LiNiO2, LiVO2 and LiNi 1 / 3 CO 1 / 3 Mn 1 / 3 O2, a spinel-type active material such as LiMn2O4, Li4Ti5O 12 and Li (Ni 0.5 Mn 1.5 ) O4, and an olivine type active material such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0043] A coating containing a conductive Li-ion oxide can be formed on the surface of the oxide active material. This is done to inhibit the reaction between the oxide active material and the solid electrolyte (especially a sulfide-based solid electrolyte). Examples of the conductive Li-ion oxide can include LiNbO3. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less. Furthermore, Li2S, for example, can be used as the cathode active material.

[0044] Examples of the shape of the active cathode material may include a granular form. The average particle size (D 50 ) of the cathode active material is not particularly limited and is, for example, 10 nm or more and may be 100 nm or more. Meanwhile, the average particle size (D 50) of the active cathode material is, for example, 50 µm or less and may be 20 µm or less.

[0045] The electrolyte used for the cathode layer has the same content as that described in "3. Electrolyte Layer." Furthermore, the conductive material and binder to be used for the cathode layer are identical in content to those described in "B. Electrode Mixture" above; therefore, their descriptions are omitted here. The thickness of the cathode 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. 3. Electrolyte layer

[0046] The electrolyte layer is a layer formed between the cathode layer and the anode layer and contains at least one electrolyte. The electrolyte can be a solid electrolyte or an electrolyte solution (liquid electrolyte).

[0047] The solid electrolyte has the same contents as that described above under "B Electrode Layer"; thus, the descriptions are omitted here. The liquid electrolyte preferably contains a supporting electrolyte and a solvent. Examples of the supporting electrolyte (lithium salt) of the electrolyte that exhibits lithium ion conductivity may include an inorganic lithium salt such as LiPF6, LiBF4, LiClO4, and LiAsF6; and an organic lithium salt such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. The solvent used for the electrolyte may include, for example, a cyclic ester (cyclic carbonate) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and a chain ester (chain carbonate) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). Preferably, the liquid electrolyte contains two or more types of solvents.

[0048] For example, the thickness of the electrolyte layer is 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. 4. Other constitutions

[0049] The battery in the present disclosure preferably includes a cathode current collector for collecting current from the cathode layer and an anode current collector for collecting current from the anode layer. Examples of the material for the cathode current collector may include SUS, aluminum, nickel, iron, titanium, and carbon. Examples of the material for the anode current collector may include SUS, copper, nickel, and carbon.

[0050] The battery in the present disclosure may further include a clamping device that applies clamping pressure along the thickness direction of the cathode layer, the electrolyte layer, and the anode layer. Particularly, when the electrolyte layer is a solid electrolyte layer, it is preferable to apply clamping pressure to form an excellent ion conduction path and electron conduction path. The clamping pressure is, for example, 0.1 MPa or more, may be 1 MPa or more, and may be 5 MPa or more. Meanwhile, the clamping pressure is, for example, 100 MPa or less, may be 50 MPa or less, and may be 20 MPa or less. 5. Battery

[0051] 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 a liquid electrolyte, and may be an all-solid-state battery in which the electrolyte layer contains a solid electrolyte. The all-solid-state battery may be a semi-solid-state battery or a solid-state battery. In the present disclosure, the semi-solid-state battery is a battery in which the electrolyte layer includes an inorganic solid electrolyte and a liquid component (for example, an ionic solution). In the present disclosure, the all-solid-state battery is a battery in which the electrolyte layer includes only the inorganic solid electrolyte as the electrolyte.Furthermore, in the present disclosure, the battery may be a primary battery or a secondary battery, but preferably a secondary battery among the batteries. This is because it can be repeatedly charged and discharged and is useful, for example, as a car-mounted battery.

[0052] The battery may, for example, comprise a power source for vehicles, such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, it is preferably used as a power source for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs). Furthermore, the battery may be used as a power source for means of transportation other than vehicles (e.g., rail vehicles, ships, and aircraft) and as a power source for electronic products such as information processing devices. D. Process for producing electrode active material

[0053] The methods for producing the electrode active material in the present disclosure can be roughly divided into two aspects. 1. First aspect

[0054] Fig.4 is a flowchart illustrating the method for producing the electrode active material according to the first aspect. In the Fig. In the manufacturing method shown in Figure 4, a Na-Si alloy is first obtained by reacting a Na source and a Si source (an alloying step). The Na-Si alloy is then fired to reduce the amount of Na in the Na-Si alloy and form a precursor active material comprising a silicon clathrate II type crystal phase (a firing step). Subsequently, a liquid treatment of the precursor active material is carried out with a hydrofluoric acid to obtain an electrode active material (a liquid treatment step). In the liquid treatment step, a liquid treatment condition is set such that a proportion of an amount of hydrogen (wt%) with respect to a BET specific surface area (m 2 / g) becomes greater than 0.0034.

[0055] According to the first aspect, by performing the liquid treatment step, an electrode active material whose volume change upon charging and discharging is small can be obtained. (1) Alloying step

[0056] The alloying step in the first aspect is a step of obtaining a Na-Si alloy by reacting a Na source and a Si source.

[0057] The Si source is a particle containing at least Si. The Si source can be a simple substance made of Si or an alloy of Si and other metals. If the Si source is an alloy, the alloy preferably contains Si as the main component. The Si content in the alloy is, for example, 50 atomic% or more, may be 70 atomic% or more, and may be 90 atomic% or more.

[0058] The Si source is preferably porous Si that includes many voids inside the primary particle. Examples of methods for producing the Si source (porous Si) may include a method of preparing an alloy of Li with Si (Li-Si alloy), and then removing Li from the Li-Si alloy. The Li-Si alloy can be obtained, for example, by mixing Li and Si. The ratio of Li to Si, i.e., Li / Si, is, for example, 1.0 or more, may be 2.0 or more, 3.0 or more, and 4.0 or more. Meanwhile, Li / Si is, for example, 8.0 or less. Examples of the method for removing Li from the Li-Si alloy may include a method of reacting the Li-Si alloy with a Li extractant.Examples of the Li extractant may include alcohol such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol; and acid such as acetic acid, formic acid, propionic acid, and oxalic acid.

[0059] Further, examples of methods for producing the Si source (porous Si) may include a method in which an alloy of Mg with Si (Mg-Si alloy) is prepared and then Mg is removed from the Mg-Si alloy. The Mg-Si alloy can be obtained, for example, by heating a mixture of Mg and Si. The ratio of Mg to Si, i.e., Mg / Si, is, for example, 1.0 or more, may be 1.5 or more, and may be 2.0 or more. Meanwhile, Mg / Si is, for example, 6.0 or less. Examples of the method for removing Mg from the Mg-Si alloy may include a method in which Mg in the Mg-Si alloy is converted to MgO by heating the Mg-Si alloy in an oxygen-containing inert gas atmosphere, and then MgO is removed by an acid solution. The acidic solution may include, for example, an aqueous solution containing hydrochloric acid (HCl) and hydrogen fluoride (HF).

[0060] Further, examples of the method for producing the Si source (porous Si) may include a method in which an alloy of Mg with Si (Mg-Si alloy) is prepared and then Mg is removed from the Mg-Si alloy, and thereafter an alloy of Li with Si obtained by removing Mg (Li-Si alloy) is prepared and then Li is removed from the Li-Si alloy.

[0061] Meanwhile, the Na source contains at least Na. Examples of the Na source may include a metal Na, NaH, and a metal Na dispersion in which metallic Na particles are dispersed in an oil.

[0062] Examples of methods for obtaining the Na-Si alloy by combining the Na source and the Si source may include a method in which a mixture containing the Na source and the Si source is heated. The heating temperature is, for example, 300°C or more, may be 310°C or more, 320°C or more, and 340°C or more. Meanwhile, the heating temperature is, for example, 800°C or less, may be 600°C or less, and may be 450°C or less. Furthermore, the alloying step is preferably carried out under an inert atmosphere, for example, an Ar atmosphere.

[0063] The Na-Si alloy preferably includes a Zintl phase. The Zintl phase includes typical peaks at positions 2θ = 16.10°, 16.56°, 17.64°, 20.16°, 27.96°, 33.60°, 35.68°, 40.22°, and 41.14° in an X-ray diffraction measurement using a CuKα beam. Each of these peaks can shift within a range of ±0.50°, and it can shift within a range of ±0.30°. The Na-Si alloy preferably includes the Zintl phase as the main phase.

[0064] The composition of the Na-Si alloy is not particularly limited, but is preferably determined by the composition of Na z Si 136 (121 ≤ z ≤ 151). The "z" can be 126 or more, and it can be 131 or more. Meanwhile, the "z" can be 141 or less. In the Na-Si alloy, other elements besides Na and Si can be included. Examples of the additional element can include Li, K, Rb, Cs, Ba, Ga, and Ge. (2) Burning stage

[0065] The firing step in the first aspect is a step of firing the Na-Si alloy to reduce the amount of Na in the Na-Si alloy and form a precursor active material comprising a silicon clathrate II type crystal phase.

[0066] The firing conditions of the Na-Si alloy are adjusted to obtain the desired precursor active material. The firing temperature is, for example, 300°C or more and 400°C or less. The firing time is, for example, 5 hours or more and 120 hours or less. The firing step can be performed in a reduced-pressure atmosphere or in a normal-pressure atmosphere.

[0067] In the firing step, a trapping agent that traps Na in the Na-Si alloy is preferably used. Examples of the trapping agent may include a Na getter agent that reacts with Na vapor generated from the Na-Si alloy. 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 may include SiO, MoO3, FeO, and Fe3O4. When using the Na getter agent, the firing step is preferably carried out under reduced pressure.

[0068] Other examples of the trapping agent may include a Na trapping agent that directly reacts with the Na-Si alloy and captures Na. For example, the Na trapping agent is disposed in a state where it is in contact with the Na-Si alloy. Examples of the Na trapping agent may include CaCl2, AlF3, CaBr2, CaI2, Fe3O4, FeO, MgCl2, ZnO, ZnCl2, and MnCl2. When using the Na trapping agent, the firing step can be performed in a reduced-pressure atmosphere and a normal-pressure atmosphere. (3) Liquid treatment step

[0069] The liquid treatment step in the first aspect is a step of performing a liquid treatment of the precursor active material using a hydrofluoric acid. The hydrofluoric acid is an aqueous solution in which hydrogen fluoride (HF) is dissolved in water. Further, in the liquid treatment step, a liquid treatment condition is set such that a proportion of an amount of hydrogen (wt %) with respect to a BET specific surface area (m 2 / g) becomes greater than 0.0034.

[0070] The concentration of hydrogen fluoride in the hydrofluoric acid is, for example, 1 wt%, may be 2 wt% or more, may be 3 wt% or more, may be 4 wt% or more, and may be 5 wt% or more. The concentration of hydrogen fluoride in the hydrofluoric acid is, for example, 10 wt% or less. Further, the treatment time of the liquid treatment is, for example, 1 hour or more, may be 2 hours or more, 3 hours or more, 4 hours or more, and 5 hours or more. Meanwhile, the treatment time of the liquid treatment is, for example, less than 24 hours, may be 15 hours or less, and may be 10 hours or less. The temperature of the liquid treatment is not particularly limited, it is, for example, a normal temperature.

[0071] Examples of methods for performing the liquid treatment of the precursor active material with the hydrofluoric acid may include a method in which the precursor active material is impregnated with the hydrofluoric acid and a method in which the hydrofluoric acid is applied to the precursor active material. (4) Electrode active material

[0072] The electrode active material obtained through the above-described steps comprises, for example, the silicon clathrate II-type crystal phase. Further, by changing the firing conditions, an electrode active material comprising a silicon clathrate I-type crystal phase can be obtained. Furthermore, in the present disclosure, the above-described liquid treatment step can be performed for a precursor active material comprising a diamond-type crystal phase. Furthermore, the electrode active material comprises an Si-H bond on its surface. Preferred aspects of the electrode active material are the same in content as those described above under "A. Electrode Active Material." 2. Second aspect

[0073] Fig. 5 is a flowchart illustrating the method for producing the electrode active material according to the second aspect. In the Fig.In the manufacturing process shown in Figure 5, a Na-Si alloy is first obtained by reacting a Na source and a Si source (an alloying step). The Na-Si alloy is then fired to reduce the amount of Na in the Na-Si alloy and form an electrode active material comprising a silicon clathrate II-type crystal phase (a firing step). In the alloying step, a metallic Na particle is used as the Na source.

[0074] According to the second aspect, by using the metallic Na particle as a Na source, an electrode active material whose volume change upon charging and discharging is small can be obtained. (1) Alloying step

[0075] The alloying step in the second aspect consists in obtaining a Na-Si alloy by reacting a Na source and a Si source. Furthermore, a metallic Na particle is used as the Na source. The average particle size (D 50 The diameter of the metallic Na particle is not particularly limited; for example, it may be 10 µm or less, 5 µm or less, 3 µm or less, and 500 nm or less. The alloying step in the second aspect is the same in content as that described in the first aspect above, except that the metallic Na article is used as the Na source. (2) Burning stage

[0076] The firing step in the second aspect is a step of firing the Na-Si alloy to reduce the amount of Na in the Na-Si alloy and form an electrode active material comprising a silicon clathrate II type crystal phase. The firing step is identical in content to that described above in the first aspect. (3) Other

[0077] The method for producing an electrode active material in the second aspect may include a liquid treatment step for performing a liquid treatment on an electrode active material using hydrofluoric acid after the alloying step. The liquid treatment step is the same in content as that described in the first aspect above. Furthermore, the preferred aspects of the electrode active material obtained by the method for producing an electrode active material in the second aspect are the same in content as those described above in "A. Electrode Active Material." E. Process for producing an electrode mixture

[0078] The present disclosure includes a method for producing an electrode mixture, the method comprising: a preparation step of preparing an electrode active material by the above-described method for producing an electrode active material; and a mixing step of mixing the electrode active material and at least one conductive material and a binder to obtain an electrode mixture.

[0079] According to the present disclosure, by using the above-described electrode active material, an electrode mixture whose volume change upon charging and discharging is small can be obtained. The preparation step is the same in content as described in "D. Method for Producing Electrode Active Material" above.

[0080] The electrode mixture typically contains the electrode active material and at least one of a conductive material and a binder. The conductive material and the binder have the same contents as those described under "B. Electrode Mixture" above. The electrode mixture may also include a dispersion medium. Furthermore, the electrode mixture is typically obtained by mixing the electrode active material and at least one of the conductive material and the binder. There are no particular restrictions on the mixing methods, and known methods can be used. Furthermore, preferred aspects of the electrode mixture to be obtained are the same as those described above under "B. Electrode Mixture." F. Method for producing a battery

[0081] The present disclosure provides a method for manufacturing a battery, the method comprising: a preparation step of preparing an electrode active material by the above-described method for manufacturing an electrode active material; a mixing step of mixing the electrode active material and at least one of a conductive material and a binder to obtain an electrode mixture; and an electrode layer forming step of forming an electrode layer using the electrode mixture.

[0082] According to the present disclosure, by using the above-described electrode active material, a battery with a small volume change due to charging and discharging can be obtained. The preparation step and the mixing step have the same contents as those described above in "D. Method for producing electrode active material" and "E. Method for producing electrode mixture."

[0083] The electrode layer forming step is a step of forming an electrode layer using the electrode mixture. There are no particular restrictions on the method for forming the electrode layer, and known methods can be used. Examples of methods for forming the electrode layer may include a method of applying the electrode mixture to the electrode current collector. In forming the electrode layer, a pressing treatment of pressing the electrode layer in a thickness direction may be performed. Examples of the pressing may include roll pressing and flat plate pressing. Further, when the electrode mixture is a slurry containing a dispersion medium, drying is preferably performed after applying the electrode mixture to the electrode current collector.

[0084] The electrode layer forming step may be a cathode layer forming step, and it may be an anode layer forming step that forms an anode layer. The method for manufacturing a battery in the present disclosure may further include an additional step, such as an electrolyte layer forming step that forms an electrolyte layer. Furthermore, the preferred aspects of the battery to be obtained are the same in content as those described in "C. Battery" above.

[0085] Incidentally, the present disclosure is not limited to the embodiments. The embodiments are exemplary, and all other variants are intended to be included within the technical scope of the present disclosure if they have substantially the same nature as the technical idea described in the claims of the present disclosure and have similar operation and effect. Examples[Example 1]

[0086] The Li metal and Si powder were weighed in a molar ratio of 4:1 and reacted by mixing with a mortar under an Ar atmosphere at room temperature for 0.5 hours. Thus, Li4Si was obtained. The obtained Li4Si was reacted with ethanol under an Ar atmosphere. The resulting reaction product was expected to include Si and CH3CH2OLi. This reaction product was filtered, and the filtered solid contents were dried at 120°C for 3 hours or more to obtain powdered porous Si.

[0087] Using the obtained porous Si, a Na-Si alloy was prepared using NaH (average particle size: 20 µm) as the Na source. Incidentally, the NaH washed with hexane in advance was used as the NaH. The NaH and porous Si were weighed in a molar ratio of 1.05:1 and mixed with a cutting mill. The mixture of NaH and porous Si was heated in a heating furnace at 475°C for 40 hours under an Ar atmosphere to obtain a powdered Na-Si alloy. A silicon clathrate was formed by a

[0088] A solid-phase process was used to produce a precursor active material using the obtained Na-Si alloy and further using AlF3 as a Na trapping agent. The Na-Si alloy and AlF3 were weighed in a molar ratio of 1:0.35 and mixed with a cutting mill to obtain a reaction raw material. The obtained powdered reaction raw material was placed in a stainless steel reaction vessel and reacted by heating in an Ar atmosphere at 310°C for 60 hours in a heating furnace to obtain a precursor active material.

[0089] The obtained precursor active material was assumed to contain NaF and Al as by-products. Subsequently, the precursor active material was washed with a mixed solvent in which HNO3 and H2O were mixed in a volume ratio of 10:90, thereby eliminating the by-products in the reaction product. After washing, the filtered and separated solid was dried at 120°C for 3 hours or more to obtain powder. Further, 5 g of the obtained powder was weighed and taken out, and liquid treatment was carried out with an aqueous HF solution having a concentration of 3 wt% for 1 hour. After the liquid treatment, the filtered and separated solid content was dried at 120°C for 3 hours or more to obtain an electrode active material. [Example 2]

[0090] An electrode active material was obtained in the same manner as in Example 1, except that metal Li and Si powder were used in a molar ratio of 4.75:1 in the preparation of porous Si powder, and heating was carried out under Ar atmosphere at 400°C for 40 hours in a heating furnace in the preparation of Na-Si alloy powder. [Example 3]

[0091] An electrode active material was obtained in the same manner as in Example 1, except that the metal Li and Si powder were used in the preparation of the powdered porous Si in the molar ratio of 4.75:1 and the treatment time in the liquid treatment with the aqueous HF solution was changed to 3 hours. [Example 4]

[0092] An electrode active material was obtained in the same manner as in Example 1, except that the metal Li and Si powder were used in the preparation of the powdered porous Si in the molar ratio of 4.75:1 and the treatment time in the liquid treatment with the aqueous HF solution was changed to 5 hours. [Example 5]

[0093] An electrode active material was obtained in the same manner as in Example 1, except that the treatment time at the time of the liquid treatment with the aqueous HF solution was changed to 5 hours. [Comparison example 1]

[0094] An electrode active material was obtained in the same manner as in Example 1, except that a 5 cm cut metal ingot of Na was used instead of NaH. [Example 6]

[0095] Na particles with an average particle size of 3 µm were prepared by grinding a metal Na with a cutting mill for 30 seconds. An electrode active material was obtained in the same manner as in Example 1, except that the obtained Na particles were used instead of NaH. [Example 7]

[0096] Na particles with an average particle size of 200 nm were prepared by repeating a grinding process of a metal Na with a cutting mill for 30 seconds three times. An electrode active material was obtained in the same manner as in Example 1, except that the obtained Na particles were used instead of NaH. [Evaluation] <xrd-messung>

[0097] X-ray diffraction (XRD) measurements using CuKa radiation were performed on each of 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 the silicon clathrate II-type crystal phase as the main phase. Furthermore, all of the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1 contained a small amount of the silicon clathrate II-type crystal phase. The proportion of the diamond-like silicon crystal phase (crystal Si amount) was obtained using an RIR (Reference Intensity Ratio) method. The results are shown in Table 1.

[0098] In the silicon clathrate II type crystal phase, an intensity of peak A near 2θ = 20.09° was observed as I A and an intensity of peak B near 2θ = 31.72° as I B Furthermore, the intensity maximum at 2θ = 22° to 23° was considered as I M considered, and one obtained I A / I M and I B / I M . As a result, I A / I M greater than 1 and I B / I M was further greater than 1 in all the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1. <Spezifische Oberflächenmessung>

[0099] The BET specific surface areas of the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1 were each measured using a specific surface area meter. The results are shown in Table 1. <Messung der Menge an Wasserstoff>

[0100] The amount of hydrogen in the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1 was determined using an oxygen / nitrogen / hydrogen (ONH) analyzer (EMGA-930 from HORIBA, Ltd.). The results are shown in Table 1. <Messung der Volumenausdehnungsrate>

[0101] An all-solid-state battery was fabricated using the electrode active materials obtained in Examples 1 to 7 and Comparative Example 1 as the anode active material. The fabrication method was as follows. (1) Production of anodes

[0102] The obtained electrode active material, a sulfide solid electrolyte (Li2S-P2S5-based glass-ceramic), a conductive material (VGCF), a butyl butyrate solution containing a PVDF-based binder in a ratio of 5 wt%, and butyl butyrate were placed in a polypropylene container and shaken for 30 seconds using an ultrasonic disperser (UH-50 from SMT Corporation). The container was then shaken for 30 minutes using a shaker (TTM-1 from SIBATA SCIENTIFIC TECHNOLOGY LTD.). The product was applied to an anode current collector (Cu foil from UACJ) using a blade method and an applicator, and dried on a hot plate at 100°C for 30 minutes. Thus, an anode comprising an anode current collector and an anode layer was obtained. (2) Manufacturing the cathode

[0103] A cathode active material (LiNi 1 / 3 CO 1 / 3 Mn 1 / 3 O2, average particle diameter 6 µm), a sulfide solid electrolyte (Li2S-P2S5-based glass-ceramic), a conductive material (VGCF), a butyl butyrate solution containing a PVDF-based binder in a ratio of 5 wt% and butyl butyrate were placed in a polypropylene container and shaken for 30 seconds with an ultrasonic disperser (UH-50 from SMT Corporation). Subsequently, the container was shaken for 3 minutes with a shaker (TTM-1 from SIBATA SCIENTIFIC TECHNOLOGY LTD.), further stirred for 30 seconds with the ultrasonic disperser, and then shaken for 3 minutes with the shaker. The product was applied to a cathode current collector (Al foil from SHOWA DENKO KK) by a blade method using an applicator and dried on a hot plate at 100°C for 30 minutes. Thus, a cathode comprising a cathode current collector and a cathode layer was obtained.By the way, the area of the cathode was made smaller than the area of the anode. (3) Preparation of a solid electrolyte layer

[0104] A sulfide-based solid electrolyte (Li2S-P2S5-based glass-ceramic), a heptane solution containing a butylene rubber-based binder in a ratio of 5 wt%, and heptane were placed in a polypropylene container and shaken for 30 seconds using an ultrasonic disperser (UH-50 from SMT Corporation). The container was then shaken for 30 minutes using a shaker (TTM-1 from SIBATA SCIENTIFIC TECHNOLOGY LTD.). The product was applied to a skived film (Al foil) using a blade method and dried on a hot plate at 100°C for 30 minutes. Thus, a transfer element comprising the skived film and the solid electrolyte layer was obtained. (4) Production of all solid-state batteries

[0105] A solid electrolyte bonding layer was placed on the cathode layer in the cathode and installed in a roller press, then pressed at 100 kN / cm and 165°C. Thus, a first laminated body was obtained.

[0106] The anode was then installed in a roller press and pressed at 60 kN / cm and 25°C. A pressed anode was obtained. Next, the solid electrolyte layer for the interconnection and the transmission element were stacked in order from the anode layer side. The solid electrolyte layer for the interconnection and the solid electrolyte layer in the transmission element were arranged so that they faced each other. The resulting stacked body was installed in a flat uniaxial press and provisionally pressed for 10 seconds at 100 MPa and 25°C.

[0107] The peelable film was then peeled off the solid electrolyte layer, thus creating a second laminated body.

[0108] Subsequently, the solid electrolyte layer for the interconnection in the first laminate and the solid electrolyte layer in the second laminate were arranged to face each other, installed in a flat uniaxial press, and pressed for 1 minute at 200 MPa and 120°C. Thus, an all-solid-state battery was obtained. (5) Measurement of volume expansion rate

[0109] All the obtained all-solid-state batteries were charged accordingly, and the volume expansion rate was measured. The test conditions were the retention pressure (constant rate) of 5 MPa, charge at 0.1 C, and the cut-off voltage of 4.55 V. The retention pressure was measured at 4.55 V, the retention pressure increase amount from the state before charge was obtained, and the volume expansion rate was obtained. The results are listed in Table 1. Incidentally, the volume expansion rate results in Table 1 are the relative values when the result of Comparative Example 1 is regarded as 100. (6) Measurement of the increased resistance rate

[0110] The resulting solid-state battery was charged accordingly, and the resistance increase was measured. First, CCCV charging was performed at 0.1 C to 4.55 V, and the battery was discharged at 1 C to 3.0 V.

[0111] After that, the battery was charged to 3.9V, released at 0.1C to 3.7V, and discharged at 14.7mA for 5 seconds, whereby the initial resistance was obtained from the value of this voltage drop. Next, the charging and discharging of CCCV charging at 1 / 3C to 4.35V and the CCCV discharging at 1 / 3C to 3.0V were repeated 100 times. After that, the resistance after charging and discharging was obtained in the same way as above. The difference between the resistance after charging and discharging and the initial resistance was obtained as the amount of resistance increase, thereby obtaining the resistance increase rate. The results are shown in Table 1. Incidentally, the results of the resistance increase rate in Table 1 are the relative values when the result of Comparative Example 1 is regarded as 100. [Table 1] Well source HF treatment time [h] BET(X) [m 2 / g] Amount of hydrogen (Y) [wt%] Y / X Volume expansion rate (relative value) Resistance rise rate (relative value) Amount of crystalline Si [wt%] Comparison example 1 Na (5cm) 1 53 0.18 0.0034 100 100 3.6 Example 1 Close 1 54.6 0.25 0.0046 82.5 67 2.4 Example 2 Close 1 63.0 0.29 0.0046 67.5 60 1.5 Example 3 Close 3 64.7 0.456 0.0070 50 59 22 Example 4 Close 5 80.4 0.527 0.0066 40 46 2.5 Example 5 Close 5 525 0.492 0.0094 42.5 45 18 Example 6 Na (3µm) 1 52 0.23 0.0044 50 55 1.1 Example 7 Na (200nm) 1 56 0.22 0.0039 45 47 0.4

[0112] As shown in Table 1, it was confirmed that the volume expansion rate was reduced in Examples 1 to 7 compared to Comparative Example 1. In particular, the volume expansion rate of Examples 3 to 7 was significantly reduced compared to Comparative Example 1. Furthermore, the resistance increase rate in Examples 1 to 7 was also reduced compared to Comparative Example 1. Furthermore, it was confirmed that the volume expansion rate tends to be reduced when the crystalline Si amount is small. In the present disclosure, the proportion of the crystalline Si amount may be less than 3.6 wt%, 2.5 wt% or less, 2.0 wt% or less, 1.5 wt% or less, and 1.2 wt% or less. <ir-messung>

[0113] Infrared ray spectroscopy (IR measurement, ATR method) was performed on the electrode active materials obtained in Examples 1, 3, and 4 using a Fourier transform infrared ray spectroscopy device (FTIR, Nicolet iS50, from Thermo Fisher). The results are shown in Table 2. Peak α is a peak located in the range of 2100 cm -1 up to 2300 cm -1 which corresponds to the peak of the Si-H bond. Peak β is a peak that occurs in the region of 3610 cm -1 up to 3670 cm -1 which corresponds to the peak of the Si-OH bond. Furthermore, the peak intensity of peak α is expressed as I α and the peak intensity of peak β as I β designated. [Table 2] HF treatment time [h] IR I α I β I α / I β Example 1 1 0.25 0.4 0.63 Example 3 3 0.375 0.45 0.83 Example 4 5 2.67 2.9 0.92

[0114] As shown in Table 2, it was confirmed that the α / β became larger the longer the treatment time with the aqueous HF solution, that is, the more the hydrogen attachment of Si occurred. List of reference symbols 1 cathode layer 2 Anode layer 3 Electrolyte layer 4 cathode current collectors 5 anode current collectors 10 Battery QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-044620

[0003]

Claims

[1] Electrode active material containing Si, characterized by , that a Si-H bond is present on a surface of the electrode active material, and a proportion of an amount of hydrogen (wt%) in relation to a specific BET surface area (m 2 / g) is more than 0.0034. [2] Electrode active material according to claim 1, characterized by that the specific BET surface area is 50 m 2 / g or more. [3] Electrode active material according to claim 1 or 2, characterized by that the amount of hydrogen is 0.20 wt% or more. [4] Electrode active material according to one of claims 1 to 3, characterized by that the proportion is 0.0060 or more and the amount of hydrogen is 0.40 wt% or more. [5] Electrode active material according to one of claims 1 to 3, characterized bythat the proportion is more than 0.0034 and less than 0.0046 and the amount of hydrogen is 0.30 wt% or less. [6] Electrode active material according to one of claims 1 to 4, characterized by that the electrode active material contains a silicon clathrate II type crystal phase as the main phase. [7] Electrode mixture, characterized by that it contains the electrode active material according to any one of claims 1 to 6 and at least one of a conductive material and a binder. [8] Battery comprising a cathode layer, an anode layer and an electrolyte layer disposed between the cathode layer and the anode layer, characterized by that the cathode layer or the anode layer contains the electrode mixture according to claim 7. [9] A method for producing an electrode active material, the method characterized by is that it includes: an alloying step in which a Na-Si alloy is obtained by reacting a Na source and a Si source, a firing step in which the Na-Si alloy is fired to reduce the amount of Na in the Na-Si alloy and to form a precursor active material containing a silicon clathrate II type crystal phase, and a liquid treatment step in which a liquid treatment of the precursor active material is carried out using hydrofluoric acid, wherein in the liquid treatment step, a liquid treatment condition is set so that a proportion of an amount of hydrogen (wt%) with respect to a BET specific surface area (m 2 / g) is more than 0.0034. [10] A method for producing an electrode active material, the method characterized by is that it includes: an alloying step in which a Na-Si alloy is obtained by reacting a Na source and a Si source, and a firing step of firing the Na-Si alloy to reduce the amount of Na in the Na-Si alloy and to form an electrode active material containing a silicon clathrate II type crystal phase, wherein in the alloying step, a metallic Na particle is used as a Na source.

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