Method for manufacturing porous silicon clathrate electrode active material and method for manufacturing lithium ion battery

Abstract

To provide a method for manufacturing a porous silicon clathrate electrode active material having a high content of type II silicon clathrate and many pores, and a method for manufacturing a lithium ion battery including producing such a silicon clathrate electrode active material.SOLUTION: A method disclosed herein of manufacturing a porous silicon clathrate electrode active material includes a step (a) of providing a composition including silicon clathrate particles containing a silicon clathrate type I and a silicon clathrate type II, and a step (b) of removing at least a portion of the silicon clathrate type I to form pores in the silicon clathrate particles or increase the pores of the silicon clathrate particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a porous silicon clathrate electrode active material and a method for producing a lithium ion battery. [Background technology]

[0002] In recent years, the development of batteries has been actively pursued. For example, in the automotive industry, development of batteries for use in electric vehicles or hybrid vehicles is progressing. Silicon is known as an electrode active material for batteries, particularly lithium-ion batteries.

[0003] Silicon electrode active materials have a large theoretical capacity and are effective in increasing the energy density of batteries. However, they suffer from the problem of large expansion during charging. It is known that the use of silicon clathrate electrode active materials as silicon electrode active materials can suppress expansion during charging.

[0004] For example, Patent Document 1 discloses a silicon clathrate electrode active material having a silicon clathrate type II crystalline phase, voids inside the primary particles, and a void volume of voids having a pore diameter of 100 nm or less of 0.05 cc / g or more and 0.15 cc / g or less. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-158004 Summary of the Invention [Problem to be solved by the invention]

[0006] There are two types of silicon clathrate crystals: type I silicon clathrate and type II silicon clathrate. In particular, type II silicon clathrate efficiently occludes lithium in the cage structure of the crystal, resulting in small expansion and contraction during battery charging and discharging.

[0007] Furthermore, silicon clathrate particles having pores can absorb expansion caused by charging the battery, thereby reducing the expansion during charging.

[0008] Under these circumstances, there is a need to develop a method for producing silicon clathrate particles that contain a high proportion of type II silicon clathrate and have many pores.

[0009] The present disclosure aims to provide a method for producing a porous silicon clathrate electrode active material that has a high content of type II silicon clathrate and many pores, and a method for producing a lithium ion battery that includes producing such a silicon clathrate electrode active material. [Means for solving the problem]

[0010] The present inventors have found that the above problems can be solved by the following means. <Aspect 1> A method for producing a porous silicon clathrate electrode active material, comprising the steps of: (a) providing a composition comprising silicon clathrate particles containing a type I silicon clathrate and a type II silicon clathrate; and (b) removing at least a portion of the type I silicon clathrate to form pores in the silicon clathrate particles or increase the porosity of the silicon clathrate particles; <Aspect 2> 2. The method of claim 1, wherein the ratio of the mass of the type I silicon clathrate to the total mass of the composition including the silicon clathrate particles is 5.0 mass% or more. <Aspect 3> 2. The method of embodiment 1, wherein in step (b), the silicon clathrate particles are contacted with a hydrogen fluoride solution to remove at least a portion of the type I silicon clathrate. <Aspect 4> Aspect 4. The method of aspect 3, wherein the solvent for the hydrogen fluoride solution is a mixed solvent of water and an organic solvent. <Aspect 5> A method according to any one of Aspects 1 to 4, wherein the silicon clathrate electrode active material is for use as a negative electrode active material in a lithium ion battery. <Aspect 6> Producing a silicon clathrate electrode active material by the method according to any one of aspects 1 to 5; and forming an electrode active material layer containing the silicon clathrate electrode active material; A method for manufacturing a lithium-ion battery, comprising: [Effects of the Invention]

[0011] According to the method of the present invention for producing a porous silicon clathrate electrode active material, it is possible to produce silicon clathrate particles having a high content of type II silicon clathrate and many pores. The present disclosure also provides a method for producing a lithium-ion battery that includes producing such a silicon clathrate electrode active material. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a graph showing the relationship between the content of type I silicon clathrate in a composition containing silicon clathrate particles and the increase in the number of pores of 100 nm or less after removal of the type I silicon clathrate. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present disclosure.

[0014] <<Method for producing porous silicon clathrate electrode active material>> The disclosed method for producing a porous silicon clathrate electrode active material includes: (a) providing a composition comprising silicon clathrate particles containing a type I silicon clathrate and a type II silicon clathrate; and (b) removing at least a portion of the type I silicon clathrate to form pores in the silicon clathrate particles or increase the porosity of the silicon clathrate particles.

[0015] The present inventors have discovered that there is a difference in solubility between type I silicon clathrate and type II silicon clathrate in certain solutions, particularly hydrogen fluoride (HF) solution, i.e., type I silicon clathrate has higher solubility in HF solution. Therefore, the present inventors have discovered that by using an HF solution or the like to dissolve and remove type I silicon clathrate from silicon clathrate particles containing type I silicon clathrate and type II silicon clathrate, thereby generating pores in the locations where type I silicon clathrate had been present, it is possible to form pores in the silicon clathrate particles or increase the pores in the silicon clathrate particles.

[0016] This makes it possible to obtain a porous silicon clathrate that expands little during charging.

[0017] In the present disclosure, the "electrode active material" can be used as either a "positive electrode active material" or a "negative electrode active material", and is particularly used as a "negative electrode active material".

[0018] <Providing a composition containing silicon clathrate particles> The method of the present disclosure includes providing a composition comprising silicon clathrate particles that include a type I silicon clathrate and a type II silicon clathrate.

[0019] A composition including such silicon clathrate particles can be prepared by preparing a sodium silicon (NaSi) alloy and removing sodium from the NaSi alloy.

[0020] Specifically, a silicon source is first reacted with a sodium source such as sodium hydride to prepare a NaSi alloy. The NaSi alloy thus prepared is then heated to remove sodium from the NaSi alloy and form a clathrate, thereby preparing a composition containing silicon clathrate particles. Alternatively, the NaSi alloy thus prepared is reacted with aluminum fluoride as a sodium trapping agent to remove sodium from the NaSi alloy and form a clathrate, thereby preparing a composition containing silicon clathrate particles.

[0021] In a composition containing silicon clathrate particles that can be used as a raw material in the method of the present disclosure, the ratio of the mass of type I silicon clathrate to the total mass of the composition containing silicon clathrate particles may be 5.0 mass% or more, 6.0 mass% or more, 6.5 mass% or more, 6.8 mass% or more, or 7.0 mass% or more, and may be 12.0 mass% or less, 10.0 mass% or less, 9.0 mass% or less, 8.5 mass% or less, or 8.0 mass% or less.

[0022] The content ratio of type I silicon clathrate and type II silicon clathrate in the silicon clathrate particles can be calculated, for example, from the peak intensity ratio in the results of X-ray diffraction (XRD) measurement.

[0023] <Removal of type I silicon clathrate> The method of the present disclosure includes removing at least a portion of the type I silicon clathrate to form pores in the silicon clathrate particles or to increase the porosity of the silicon clathrate particles.

[0024] The silicon clathrate particles may be contacted with a hydrogen fluoride solution to remove at least a portion of the type I silicon clathrate.

[0025] The solvent for the hydrogen fluoride solution may be water, an organic solvent, or a mixed solvent of water and an organic solvent. When the solvent contains water, that is, water or a mixed solvent of water and an organic solvent, and particularly when the mixed solvent is water and an organic solvent, it is preferable in that the generation of by-products such as sodium silicofluoride (NaSiF) can be suppressed.

[0026] The solvent preferably contains an organic solvent, which can reduce the amount of water remaining in the silicon clathrate electrode active material. The proportion of the organic solvent in the solution may be 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0027] The organic solvent may be any organic solvent capable of dissolving hydrogen fluoride, and when used in combination with water, any organic solvent capable of dissolving hydrogen fluoride and compatible with water may be used. The organic solvent is preferably an alcohol, more preferably a lower alcohol, and even more preferably ethanol.

[0028] In the method of the present disclosure, the ratio of the amount (mol) of hydrogen fluoride to the mass (g) of silicon clathrate (HF [mol] / Si [g]) may be 0.006 mol / g or more, 0.01 mol / g or more, 0.02 mol / g or more, 0.03 mol / g or more, 0.04 mol / g or more, or 0.05 mol / g or more, and may be 0.25 mol / g or less, 0.20 mol / g or less, 0.15 mol / g or less, 0.13 mol / g or less, or 0.11 mol / g or less. When this ratio is within the above range, type I silicon clathrate can be highly selectively removed from the silicon clathrate particles.

[0029] The contact method is exemplified by a mixing operation such as stirring, but is not limited thereto.

[0030] The contact time may be 0.5 hours or more, 1 hour or more, or 2 hours or more, and may be 6 hours or less, 5 hours or less, or 4 hours or less.

[0031] In the silicon clathrate electrode active material produced by the method of the present disclosure, the ratio of the mass of the type II silicon clathrate to the total mass of the type I silicon clathrate and the type II silicon clathrate may be 93.5 mass% or more, 94.0 mass% or more, 95.0 mass% or more, 96.0 mass% or more, 97.0 mass% or more, 98.0 mass% or more, or 99.0 mass% or more.

[0032] The silicon clathrate particles may contain pores with a diameter of 100 nm or less.

[0033] In the method of the present disclosure, the step (b) can increase the number of pores contained in the silicon clathrate particles, particularly pores with a diameter of 100 nm or less. The increase in the number of pores can be calculated as the difference between the number of pores after the step (b) and the number of pores before the step (b).

[0034] The increase in pores with a diameter of 100 nm or less may be 0.01 cc / g or more, 0.03 cc / g or more, 0.04 cc / g or more, 0.05 cc / g or more, or 0.06 cc / g or more, and may be 0.50 cc / g or less, 0.40 cc / g or less, 0.30 cc / g or less, 0.25 cc / g or less, 0.20 cc / g or less, 0.17 cc / g or less, or 0.15 cc / g or less.

[0035] <Application> The silicon clathrate electrode active material in the method of the present disclosure can be used as the negative electrode active material in a lithium ion battery.

[0036] <<Lithium-ion battery manufacturing method>> The disclosed method of making a lithium ion battery includes making a silicon clathrate electrode active material by the disclosed method and forming an electrode active material layer containing the silicon clathrate electrode active material.

[0037] For the method for producing the silicon clathrate electrode active material, reference can be made to the above description regarding the method for producing the silicon clathrate electrode active material of the present disclosure.

[0038] The method for forming the electrode active material layer is not particularly limited, and any known method can be used. For example, when the negative electrode active material layer contains the silicon clathrate electrode active material of the present disclosure, a slurry containing the silicon clathrate electrode active material can be applied to a negative electrode current collector and dried to obtain an electrode active material layer formed on the negative electrode current collector layer, i.e., a negative electrode active material layer.

[0039] The method for forming the battery is not particularly limited, and any known method can be used. Hereinafter, a method for manufacturing a battery in which the negative electrode active material layer contains the silicon clathrate electrode active material of the present disclosure will be described.

[0040] The method for manufacturing a battery according to the present disclosure may include, in addition to manufacturing a silicon clathrate electrode active material and forming a negative electrode active material layer containing the silicon clathrate electrode active material, arranging a negative electrode current collector layer, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order.

[0041] <Negative electrode current collector layer> The material used for the negative electrode current collector layer is not particularly limited, and any material that can be used as a negative electrode current collector for a battery can be appropriately adopted. For example, copper, a copper alloy, and copper plated or vapor-deposited with nickel, chromium, carbon, or the like may be used, but is not limited to these.

[0042] The shape of the negative electrode current collector layer is not particularly limited, and examples thereof include foil, plate, mesh, etc. Among these, foil is preferred.

[0043] <Negative electrode active material layer> The negative electrode active material layer of the present disclosure is a layer containing a negative electrode active material, and optionally an electrolyte, a conductive additive, and a binder.

[0044] (Negative electrode active material) The negative electrode active material comprises a silicon clathrate electrode active material of the present disclosure.

[0045] (electrolyte) The material of the solid electrolyte is not particularly limited, and any material that can be used as a solid electrolyte for a lithium ion battery can be used. For example, the solid electrolyte may be a sulfide solid electrolyte.

[0046] Examples of sulfide solid electrolytes include, but are not limited to, amorphous sulfide solid electrolytes, crystalline sulfide solid electrolytes, and argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes include Li2S-P2S5-based (Li7P3S 11 , Li3PS4, Li8P2S9, etc.), Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2 (Li 13 GeP3S 16 , Li 10 GeP2S 12 ), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS 6-x Cl x etc.; or combinations thereof, but are not limited to these.

[0047] The sulfide solid electrolyte may be glass or crystallized glass (glass ceramic).

[0048] When the negative electrode active material layer contains a solid electrolyte, the mass ratio of the silicon clathrate electrode active material to the solid electrolyte in the negative electrode active material layer (mass of silicon clathrate electrode active material: mass of solid electrolyte) is preferably 85:15 to 30:70, and more preferably 80:20 to 40:60.

[0049] The electrolyte preferably contains a supporting salt and a solvent.

[0050] Examples of supporting salts (lithium salts) for the electrolyte solution having lithium ion conductivity include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3.

[0051] Examples of solvents used in the electrolytic solution include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).The electrolytic solution preferably contains two or more solvents.

[0052] (Conductive additive) The conductive additive is not particularly limited, and may be, for example, VGCF (Vapor Grown Carbon Fiber), acetylene black (AB), Ketjen black (KB), carbon nanotubes (CNT), carbon nanofibers (CNF), or the like, but is not limited thereto.

[0053] (binder) The binder is not particularly limited, and may be, for example, but not limited to, a material such as polyvinylidene fluoride (PVdF), butadiene rubber (BR), or styrene butadiene rubber (SBR), or a combination thereof.

[0054] The thickness of the negative electrode active material layer may be, for example, 0.1 to 1000 μm.

[0055] <Electrolyte layer> The electrolyte layer contains at least an electrolyte. In addition to the electrolyte, the electrolyte layer may contain a binder, etc., as necessary. For the electrolyte and the binder, reference can be made to the above description of the negative electrode active material layer of the present disclosure.

[0056] The thickness of the electrolyte layer is, for example, 0.1 to 300 μm, and preferably 0.1 to 100 μm.

[0057] <Cathode active material layer> The positive electrode active material layer is a layer containing a positive electrode active material, and optionally an electrolyte, a conductive additive, a binder, and the like.

[0058] The material of the positive electrode active material is not particularly limited. For example, the positive electrode active material may be lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), lithium manganese oxide (LiMnO), LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, Li 1+x Mn 2-x-y Heteroelement-substituted Li-Mn spinel with a composition represented by MyO4 (M is one or more metal elements selected from Al, Mg, Co, Fe, Ni, and Zn), lithium titanate (Li x TiO y ), lithium metal phosphate (LiMPO4, M is one or more metals selected from Fe, Mn, Co, and Ni), etc., but are not limited to these.

[0059] The positive electrode active material may have a coating layer. The coating layer is a layer containing a substance that has lithium ion conductivity, low reactivity with the positive electrode active material and solid electrolyte, and can maintain the shape of the coating layer without flowing even when in contact with the active material and solid electrolyte. Specific examples of materials that constitute the coating layer include LiNbO3 and Li4Ti5O 12 , Li3PO4, etc., but are not limited to these.

[0060] The positive electrode active material may be, for example, particulate. The average particle size (D50) of the positive electrode active material is not particularly limited, but may be, for example, 10 nm or more, or 100 nm or more. On the other hand, the average particle size (D50) of the positive electrode active material is, for example, 50 μm or less, or may be 20 μm or less. The average particle size (D50) can be calculated, for example, from measurements using a laser diffraction particle size distribution analyzer or a scanning electron microscope (SEM).

[0061] For the electrolyte, the conductive additive, and the binder, reference can be made to the above descriptions regarding the negative electrode active material layer of the present disclosure.

[0062] When the positive electrode active material layer contains a solid electrolyte, the mass ratio of the positive electrode active material to the solid electrolyte in the positive electrode active material layer (mass of the positive electrode active material: mass of the solid electrolyte) is preferably 85:15 to 30:70, and more preferably 80:20 to 50:50.

[0063] The thickness of the positive electrode active material layer is, for example, 0.1 μm to 1000 μm, preferably 1 μm to 100 μm, and more preferably 30 μm to 100 μm.

[0064] <Positive electrode current collector layer> The material used for the positive electrode current collector layer is not particularly limited, and any material that can be used as a positive electrode current collector for a battery can be appropriately adopted. Examples of the material include, but are not limited to, SUS, nickel, chromium, gold, platinum, aluminum, iron, titanium, zinc, and the like, as well as these metals plated or vapor-deposited with nickel, chromium, carbon, and the like.

[0065] The shape of the positive electrode current collector layer is not particularly limited, and examples thereof include foil, plate, mesh, etc. Among these, foil is preferred.

[0066] The lithium ion battery produced by the method of the present disclosure may be a liquid-based battery containing an electrolytic solution as the electrolyte layer, or may be a solid-state battery having a solid electrolyte layer as the electrolyte layer. In the context of the present disclosure, the term "solid-state battery" refers to a battery that uses at least a solid electrolyte as the electrolyte, and therefore a solid-state battery may use a combination of a solid electrolyte and a liquid electrolyte as the electrolyte. The solid-state battery of the present disclosure may also be an all-solid-state battery, i.e., a battery that uses only a solid electrolyte as the electrolyte.

[0067] The lithium ion battery produced by the method of the present disclosure may be a primary battery or a secondary battery.

[0068] Examples of the shape of the lithium ion battery include coin type, laminate type, cylindrical type, and square type. [Example]

[0069] 《Synthesis of porous silicon clathrate electrode active material》 <Alloying> (Synthesis Example 1) Si powder (Kojundo Kagaku, SIEPB32) was prepared as a silicon (Si) source. This Si powder and metallic lithium (Li) were weighed out at a molar ratio of Li / Si = 4.0, and the weighed Si powder and Li were mixed in a mortar in an argon atmosphere to obtain a lithium silicon (LiSi) alloy. The obtained LiSi alloy was reacted with ethanol in an argon atmosphere and treated with hydrogen fluoride (HF) to obtain Si powder with voids inside the primary particles, i.e., Si powder with a porous structure.

[0070] A sodium-silicon (NaSi) alloy was produced using porous Si powder and sodium hydride (NaH) as a sodium (Na) source. The NaH used was previously washed with hexane. NaH and porous Si powder were weighed out in a molar ratio of 1.05:1, and the weighed NaH and porous Si powder were mixed using a cutter mill. The resulting mixture was heated in a heating furnace under an argon atmosphere at 500°C for 40 hours to obtain a powdered NaSi alloy.

[0071] <Clathrate> (Synthesis Example 1) The resulting NaSi alloy and aluminum fluoride (AlF3) were weighed out to a molar ratio of 1:0.34, and the weighed NaSi alloy and AlF3 were mixed using a cutter mill to obtain a reaction raw material. The resulting powdered reaction raw material was placed in a stainless steel reaction vessel and heated in a heating furnace under an argon atmosphere at 340°C for 60 hours to obtain a reaction product containing silicon clathrate particles. The resulting reaction product was acid-washed using a mixed solvent of HNO3 and HO in a volume ratio of 10:90 to remove by-products from the reaction product. After washing, the mixture was filtered, and the filtered solid was dried at 120°C for 3 hours or more to obtain a composition containing silicon clathrate particles of Synthesis Example 1, which contained type I silicon clathrate and type II silicon clathrate.

[0072] (Synthesis Examples 2 to 4) In the same manner as in Synthesis Example 1, compositions containing silicon clathrate particles of Synthesis Examples 2 to 4 were obtained.

[0073] <Removal of type I silicon clathrate> Example 1 2.2 g of the composition containing the silicon clathrate particles of Synthesis Example 1 was added to 100 ml of ethanol and 3.71 ml of a 46 wt % HF aqueous solution and stirred. This solution was stirred for 3 hours to allow a reaction, and the I-type silicon clathrate was removed. The resulting reaction solution was filtered, and the filtered solid was washed eight times with 20 ml of ethanol. After washing, the solid was dried overnight at 60°C to obtain the silicon clathrate electrode active material of Example 1.

[0074] Examples 2 and 3 Silicon clathrate electrode active materials of Examples 2 and 3 were obtained in the same manner as in Example 1, except that compositions containing the silicon clathrate particles of Synthesis Examples 2 and 3 were used. Note that in each Example, the Example number and Synthesis Example number correspond to each other.

[0075] Example 4 2.2 g of the composition containing the silicon clathrate particles of Synthesis Example 4 was added to 20 ml of water, 75 ml of ethanol, and 4.5 ml of a 46 wt % HF aqueous solution and stirred. This solution was stirred for 3 hours to allow a reaction, and the I-type silicon clathrate was removed. The resulting reaction solution was filtered, and the filtered solid was washed three times with 50 ml of water and once with 20 ml of ethanol. After washing, the mixture was dried overnight at 120°C to obtain the silicon clathrate electrode active material of Example 4.

[0076] (Comparative Example 1) The composition containing the silicon clathrate particles of Synthesis Example 1 was used as the silicon clathrate electrode active material of Comparative Example 1 without removing the I-type silicon clathrate.

[0077] Evaluation Results The content ratio of each component in the composition containing silicon clathrate particles, and the ratio of the mass of the II-type silicon clathrate to the total mass of the I-type silicon clathrate and the II-type silicon clathrate are shown in Table 1 ("Before removal of I-type silicon clathrate" in the table). The proportions of the contained components were calculated from the peak intensity ratio in the XRD measurement results. In Table 1, "II-type" indicates the II-type silicon clathrate, and "I-type" indicates the I-type silicon clathrate.

[0078] The content ratio of each component in the silicon clathrate electrode active material and the ratio of the mass of type II silicon clathrate to the total mass of type I silicon clathrate and type II silicon clathrate are shown in Table 1 ("After type I removal" in the table).

[0079] The increase in the amount of pores of 100 nm or less after removing the I-type silicon clathrate was calculated as the difference in the amount of pores before and after the I-type silicon clathrate removal step. The value of this increase in pores in Example 1 was 0.0661 cc / g (pores of 100 nm or less). The results of this increase in pores in Examples 1 to 4 are shown in Table 1. The values ​​of the increase in pores in Examples 2 to 4 are shown as relative values ​​when the value in Example 1 is set to 100.

[0080] [Table 1]

[0081] As shown in Table 1, the silicon clathrate electrode active material obtained by the method of the present disclosure had an increased content of type II silicon clathrate and an increased amount of pores of 100 nm or less.

[0082] Furthermore, Figure 1 shows a graph illustrating the relationship between the content of type I silicon clathrate in a composition containing silicon clathrate particles and the increase in the number of pores of 100 nm or less after removal of the type I silicon clathrate. As shown in Figure 1, when this content was within the range of the present disclosure, the increase in the number of pores of 100 nm or less after removal of the type I silicon clathrate was large. In Figure 1, "type I" refers to type I silicon clathrate.

Claims

1. A method for producing a porous silicon clathrate electrode active material, comprising the steps of: (a) providing a composition comprising porous silicon clathrate particles containing type I silicon clathrate and type II silicon clathrate; and (b) removing at least a portion of the type I silicon clathrate to form pores in the porous silicon clathrate particles or increase the pores of the porous silicon clathrate particles, wherein the increase in pores with diameters of 100 nm or less after step (b) is 0.06 cc / g or more.

2. The method described in claim 1, wherein the increase in pores with a diameter of 100 nm or less after step (b) is 0.06 cc / g or more and 0.15 cc / g or less.

3. The method described in claim 1, wherein in step (a), the ratio of the mass of the type I silicon clathrate to the total mass of the composition including the porous silicon clathrate particles is 5.0 mass% or more.

4. The method described in claim 2, wherein in step (a), the ratio of the mass of the type I silicon clathrate to the total mass of the composition including the porous silicon clathrate particles is 7.0 mass% or more and 8.0 mass% or less.

5. 2. The method of claim 1, wherein in step (b), the porous silicon clathrate particles are contacted with a hydrogen fluoride solution to remove at least a portion of the type I silicon clathrate.

6. The method according to claim 5, wherein the solvent of the hydrogen fluoride solution is a mixed solvent of water and an organic solvent.

7. 10. The method of claim 1, wherein the porous silicon clathrate electrode active material is for use as an anode active material in a lithium ion battery.

8. Producing a porous silicon clathrate electrode active material by the method according to any one of claims 1 to 7; and forming an electrode active material layer containing the porous silicon clathrate electrode active material; A method for manufacturing a lithium-ion battery, comprising:

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