JP2021123517A - Manufacturing method of porous silicon grain, manufacturing method of electrode for electricity storage device, manufacturing method of whole solid lithium ion secondary battery, porous silicon grain, electrode for electricity storage device, and whole solid lithium ion secondary battery - Google Patents

Abstract

To provide an Si-containing material with more suppressed decrease in charge-discharge behavior.SOLUTION: A manufacturing method of a porous silicon grain includes: melting and granulating a silicon alloy involving 50 mass% or over of Al as a first element and 50 mass% or under of Si to give grains; and forming pores by removing the first element in the silicon alloy to obtain porous silicon grain. The porous silicon grain has an average grain diameter of 0.1 μm or over and 100 μm or under, includes a silicon having three-dimensional network backbone including voids, has an average void rate of 50 vol.% or over and 95 vol.% or under, includes Si of 85 mass% or over and Al of 15 mass% or under at an element ratio excluding oxygen.SELECTED DRAWING: None

Description

In the present specification, a method for producing porous silicon particles, a method for producing an electrode for a power storage device, a method for manufacturing an all-solid-state lithium ion secondary battery, a porous silicon particle, an electrode for a power storage device, and an all-solid-state lithium ion secondary battery are described. Disclose.

Conventionally, in a negative electrode material of silicon, 70 parts by mass of massive Si and 30 parts by mass of Al powder are mixed, and then the alloy is atomized under an argon atmosphere by a gas atomization method using helium gas, and then Al is removed with hydrochloric acid. The resulting porous silicon has been proposed (see, for example, Patent Document 1). It is said that this porous silicon can completely suppress pulverization due to expansion and contraction of the volume of the active material during charging and discharging, peeling of the active material from the current collector, and lack of contact with the conductive material. Further, as a method for producing a silicon material, an intermediate alloy element containing Mg, Co, Cr, Cu, Fe, etc. and a Si alloy with Si are mixed with an intermediate alloy element and a molten metal element in a molten metal containing a predetermined molten metal element. It has been proposed to obtain porous silicon particles by separating the second phase and Si fine particles in which the above-mentioned material is substituted and removing the second phase (see, for example, Patent Document 2). It is said that the porous silicon particles can have high capacity and high cycle characteristics.

Japanese Unexamined Patent Publication No. 2004-214504 Japanese Unexamined Patent Publication No. 2012-82125

However, in the above-mentioned production method of Patent Document 1, an alloy having a Si content of 50% by mass or more is used, and it is not yet sufficient for suppressing defects due to expansion and contraction of Si. In the method for producing porous silicon particles of Patent Document 2, a silicon alloy containing an intermediate alloy element is melted and replaced in a molten metal containing a predetermined molten element, that is, a treatment at a high temperature is required, which is a simple manufacturing process. Was required.

The present disclosure has been made in view of such a problem, and is a method for producing porous silicon particles capable of further suppressing a decrease in charge / discharge characteristics, a method for producing an electrode for a power storage device, and an all-solid-state lithium ion secondary. A main object of the present invention is to provide a method for manufacturing a battery, porous silicon particles, an electrode for a power storage device, and an all-solid-state lithium ion secondary battery.

As a result of diligent research to achieve the above-mentioned object, the present inventors prepared a silicon alloy containing Al having a blending ratio close to that of the eutectic composition, and when Al was removed by acid and / or alkali treatment, charging and discharging were performed. It has been found that porous silicon particles capable of further suppressing deterioration of characteristics can be obtained, and the method for producing porous silicon particles of the present disclosure, the method for producing electrodes for power storage devices, and the production of an all-solid-state lithium ion secondary battery have been found. We have completed the method, porous silicon particles, electrodes for power storage devices, and all-solid-state lithium-ion secondary batteries.

That is, the method for producing porous silicon particles of the present disclosure is as follows.
A particle-forming step of melting a silicon alloy containing 50% by mass or more of the first element Al and 50% by mass or less of Si to form particles.
A porosity step of removing the first element in the silicon alloy to obtain porous silicon particles,
Is included.

The method for manufacturing electrodes for power storage devices of the present disclosure is described.
The porous silicon particles obtained by the above-mentioned method for producing porous silicon particles are used as an electrode active material and compressed so that the average porosity of the porous silicon particles is in the range of 5% by volume or more and 50% by volume or less. Pressing process,
Is included.

The method for manufacturing the all-solid-state lithium-ion secondary battery of the present disclosure is as follows.
Using the storage device electrode obtained by the above-described method for manufacturing a power storage device electrode as a negative electrode, a laminate in which a positive electrode, a solid electrolyte that conducts lithium ions, and the negative electrode are laminated is produced, and the prepared laminate is produced. Lamination restraint process of restraining with a restraint member in the stacking direction,
Is included.

The porous silicon particles of the present disclosure are
Elements having an average particle size in the range of 0.1 μm or more and 100 μm or less, containing skeletal silicon having a three-dimensional network structure with voids, an average porosity in the range of 50% by volume or more and 95% by volume or less, and excluding oxygen. Si is contained in the range of 85% by mass or more and Al is contained in the range of 15% by mass or less in the ratio of.

The electrode for a power storage device of the present disclosure contains the above-mentioned porous silicon particles as an electrode active material, and the average void ratio of the porous silicon particles is compressed in the range of 5% by volume or more and 50% by volume or less. ..

The all-solid-state lithium-ion secondary battery of the present disclosure is
Positive electrode A positive electrode containing an active material and a positive electrode
The negative electrode, which is the electrode for the power storage device described above, and the negative electrode
A solid electrolyte that is interposed between the positive electrode and the negative electrode and conducts lithium ions,
It is equipped with.

According to the present disclosure, deterioration of charge / discharge characteristics can be further suppressed in a material containing Si. The reason why such an effect can be obtained is presumed as follows. For example, the silicon negative electrode for a lithium ion secondary battery has a theoretical capacity of 4199 mAh / g, which is about 10 times higher than the theoretical capacity of 372 mAh / g of general graphite, and further increases the capacity and energy density. Is expected. On the other hand, the silicon that occludes lithium ions is Li _4.4 Si, and its volume expands to about four times that of silicon before lithium occlusal. On the other hand, according to the present disclosure, this is selectively removed by using an acid or alkali that dissolves a substance other than silicon, which is mainly Al, contained in the silicon alloy, and the pore size is small and the porosity is large. Porous silicon particles can be easily produced. Porous silicon particles having a small pore size and a large porosity have a large volume expansion and contraction when used in a power storage device such as a lithium ion secondary battery. Therefore, for example, a charge / discharge cycle. Since charge / discharge characteristics such as characteristics are improved, a high-performance power storage device can be easily obtained.

Al-Si dual system phase diagram. Explanatory drawing which shows an example of the structure of a power storage device 10. SEM image of the Al—Si alloy after gas atomization of Experimental Example 1. SEM image and EDAX mapping image of the porous silicon particles of Experimental Example 1. The pore distribution curve of the porous silicon particles of Experimental Example 1. Explanatory drawing of evaluation cell 30. Charge / discharge curves of the evaluation cells of Experimental Examples 1 and 7.

(Manufacturing method of porous silicon particles)
The method for producing porous silicon particles of the present disclosure includes a particleization step and a porosification step. In the particle formation step, a process of melting a silicon alloy containing the first elements Al and Si to form particles is performed. In the porosification step, a process of removing the first element in the silicon alloy to obtain porous silicon particles is performed.

(Particle process)
In the particle formation step, a silicon alloy containing the first element in the range of 50% by mass or more and Si in the range of 50% by mass or less is used. In this step, it is preferable to use a silicon alloy containing the first element in the range of 60% by mass or more, more preferably to use a silicon alloy containing 70% by mass or more, and to use a silicon alloy containing 80% by mass or more. It may be a thing. Further, in this step, it is preferable to use a silicon alloy containing the first element in the range of 92% by mass or less, more preferably to use a silicon alloy containing 90% by mass or less, and in the range of 85% by mass or less. A silicon alloy containing the mixture may be used. A silicon alloy containing the first element in such a range is preferable because it can further increase the porosity and obtain voids having a more suitable shape and size. Further, when the first element is 92% by mass or less, the silicon skeleton can be maintained, and when it is 50% by mass or more, the porosity can be further increased. When the Al content is high, a single phase of Al is largely precipitated when the alloy is melted to form an alloy and then rapidly cooled, so that many voids can be formed. In this step, it is preferable to use a silicon alloy containing the first element within the range of eutectic composition. The eutectic composition is 87.6% by mass for Al and 12.6% by mass for Si, but it may be in the vicinity of the eutectic composition, and a predetermined subeutectic composition or a part of the hypereutectic composition may be used. It may have a width. For example, it may include a range of ± 3% by mass with respect to the eutectic composition. FIG. 1 is an Al—Si dual system equilibrium state diagram.

In this particle formation step, the silicon alloy containing a second element containing one or more of Ca, Cu, Mg, Na, Sr and P in addition to the first element and Si may be used. Of these, as the second element, one or more of Ca, Na and Sr is preferable. The second element is less than the content of the first element, eg, for the entire silicon alloy. It is preferably contained in a silicon alloy in a range of 10% by mass or less, and more preferably in a range of 5% by mass or less.

In this particle-forming step, the molten silicon alloy may be atomized by any one of a gas atomizing method, a water atomizing method, and a roll quenching method. The molten metal of the raw material of the silicon alloy may be cast into a mold, and the obtained ingot may be crushed into particles. Of these, the gas atomizing method is more preferable as the method for atomizing the silicon alloy. In gas atomization, it is preferable to carry out the molten metal in an Ar atmosphere, and it is preferable to carry out the particle formation in an Ar or He atmosphere. In the particle formation step, it is preferable to particle the silicon alloy in the range of the average particle size of 0.1 μm or more and 100 μm or less. For example, the average particle size of these particles is preferably 0.5 μm or more and 10 μm or less, more preferably 1 μm or more and 5 μm or less, and further preferably 1 μm or more and 3 μm or less. The silicon alloy particles may be appropriately selected according to the characteristics required for the power storage device. Here, the average particle size of the particles shall be obtained as an average value obtained by observing the particles with a scanning electron microscope (SEM), totaling the major axis of each particle as the diameter of the particles, and dividing by the number of particles. ..

(Pollification process)
In the porosity step, a process of removing substances other than Si from the particles of the silicon alloy produced above is performed. Examples of the substance other than Si include Al of the first element and its compound, and the second element and its compound. In this step, it is preferable to selectively remove the first element Al and its compound, and the second element and its compound with an acid or an alkali. The acid or alkali used is preferably one that elutes elements and / or compounds other than silicon in the silicon alloy and does not elute silicon, and examples thereof include hydrochloric acid, sulfuric acid, and sodium hydroxide. The acid or alkali is preferably an aqueous solution. The concentration of the acid or alkali is not particularly limited as long as it can remove Al of the first element and its compound, and the second element and its compound, and is, for example, in the range of 1 mol / L or more and 5 mol / L or less. Can be done. This removal treatment may be performed by heating at, for example, 20 ° C. to 60 ° C. Further, in the removal treatment, it is preferable to immerse the silicon alloy particles in an acid or alkaline solution and stir for about 1 to 5 hours. The obtained porous silicon particles are then washed and dried.

In the porosity step, substances other than Si may be removed in the range of 85% by mass or more and 100% by mass or less. For example, the first element, the second element, and other oxygen may remain, but since they are unnecessary components for the porous silicon particles, it is more preferable that they are less. In this step, porous silicon particles having an average porosity in the range of 50% by volume or more and 95% by volume or less may be obtained. This average porosity is a value measured with a mercury porosity meter.

(Porous silicon particles)
The porous silicon particles of the present disclosure are produced by the above-mentioned production method, have an average particle size in the range of 0.1 μm or more and 100 μm or less, and contain skeleton-like silicon having a three-dimensional network structure having voids. The average porosity is in the range of 50% by volume or more and 95% by volume or less, Si is contained in the range of 85% by mass or more and Al is contained in the range of 15% by mass or less in the ratio of elements other than oxygen. In these porous silicon particles, the average porosity is preferably higher, preferably 60% by volume or more, more preferably 70% by volume or more, still more preferably 80% by volume or more. Further, from the necessity of the presence of the silicon skeleton, the average porosity is preferably 95% by volume or less, more preferably 90% by volume or less, and further preferably 86% by volume or less. In the porous silicon particles, the pore diameter of the voids is preferably in the range of 1 nm or more and 1 μm or less, and may be 10 nm or more, 50 nm or more, or 100 nm or more. The pore diameter of the void may be 500 nm or less, 300 nm or less, or 250 nm or less.

The average particle size of the porous silicon particles is preferably 0.1 μm or more, more preferably 1 μm or more, and may be 5 μm or more. The average particle size of the particles is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. The porous silicon particles contain 85% by mass or more of Si in terms of the ratio of elements other than oxygen, and the content of Si is preferably higher, 90% by mass or more, or 94% by mass or more. It may be 96% by mass or more. Further, the Si content may contain 98% by mass or less of Si, 97% by mass or less, or 96% by mass or less in terms of the ratio of elements other than oxygen. Further, the porous silicon particles contain Al in a range of 15% by mass or less, but the Al content is more preferably small, 10% by mass or less, more preferably 6.5% by mass or less, and 5. 2% by mass or less is more preferable. The porous silicon particles may contain 1% by mass or more of Al, 2% by mass or more, or 3% by mass or more. Further, the porous silicon particles may contain one or more of Ca, Cu, Mg, Na, Sr and P as the second element in the range of 15% by mass or less. It is preferable that the amount of elements other than Si is less.

(Electrodes for power storage devices)
The electrode for a power storage device of the present disclosure includes the above-mentioned porous silicon particles as an electrode active material. This electrode is either a positive electrode or a negative electrode based on the potential of the opposite electrode with respect to the potential of the active material, but when lithium is used as a carrier, it is preferably a negative electrode. This electrode can be used, for example, in a lithium ion secondary battery, a hybrid capacitor, an air battery, or the like. The electrode for the power storage device may be one in which the average porosity of the porous silicon particles is compressed in the range of 5% by volume or more and 50% by volume or less. In this electrode, the porosity of the porous silicon particles may be reduced by compressing at the time of fabrication. Compared to those prepared in the range of 5% by volume or more and 50% by volume or less of the porosity of the porous silicon particles, those prepared in the range of 50% by volume or more and 95% by volume and then compressed to obtain the voids are in this range. Shows better charge / discharge characteristics depending on the shape of the. For example, when porous silicon particles are used as the negative electrode active material of a lithium ion secondary battery, the smaller the pores, the more uniformly the lithium ions are alloyed when they are alloyed, so that the stress concentration is reduced and the electrode itself. It is possible to prevent the deterioration of the battery. The average porosity of the compressed porous silicon particles may be appropriately adjusted according to the characteristics required for the electrode for the power storage device, and may be, for example, 10% by volume or more or 20% by volume or more. Further, the average porosity of the compressed porous silicon particles may be, for example, 40% by volume or less or 30% by volume or less.

The electrode for the power storage device may be one in which the above-mentioned porous silicon particles are formed on the current collector and fixed on the current collector. This electrode can be obtained by mixing porous silicon particles with a conductive material or binder and a solvent as needed to form a paste and applying it on a current collector, or by applying porous silicon particles to a conductive material or a conductive material as needed. It can be produced by a step of mixing with a binder and crimping to a current collector. In this electrode, the content of the porous silicon particles is preferably larger, preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 85% by mass or more. The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance. For example, graphite such as natural graphite (scaly graphite, scaly graphite) or artificial graphite, acetylene black, carbon black, or Ketjen. One or a mixture of two or more of black, carbon whisker, needle coke, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) can be used. The binder plays a role of binding the active material particles and the conductive material particles, and is, for example, a fluororesin such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, or polypropylene. Thermoplastic resins such as polyethylene, ethylene propylene diene rubber (EPDM), sulfonated EPDM rubber, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more. Further, an aqueous dispersion of cellulose-based binder or styrene-butadiene rubber (SBR), which is an aqueous binder, can also be used. As the solvent, for example, an organic solvent such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran can be used. .. Further, a dispersant, a thickener or the like may be added to water, and the active material may be slurried with a latex such as SBR. Examples of the coating method include roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater and the like, and any of these can be used to obtain an arbitrary thickness and shape. The current collector may be appropriately selected according to the potential of the active material, and for example, aluminum, titanium, stainless steel, nickel, iron, copper, calcined carbon, conductive polymer, conductive glass, and the like. For the purpose of improving adhesiveness, conductivity and oxidation resistance, a surface of aluminum, copper or the like treated with carbon, nickel, titanium, silver or the like can be used. For these, it is also possible to oxidize the surface. Examples of the shape of the current collector include foil, film, sheet, net, punched or expanded, lath, porous body, foam, and fiber group forming body. As the thickness of the current collector, for example, one having a thickness of 1 to 500 μm is used. The amount of the active material complex formed may be appropriately set according to the desired performance required for the power storage device.

In this electrode, the electrode active material may contain an active material other than the porous silicon particles in addition to the porous silicon particles within a range in which both a low restraining pressure and a capacity retention rate can be compatible. For example, the electrode active material _{may contain a carbonaceous material, Li 4} Ti ₅ O _12, or the like. However, from the viewpoint of further increasing the battery capacity, it is preferable that the entire electrode active material is 100% by mass, for example, the porous silicon particles occupy 50% by mass or more, preferably 90% by mass or more.

(Power storage device)
The power storage device of the present disclosure includes an electrode having the above-mentioned porous silicon particles. This power storage device may include a positive electrode, a negative electrode, and an ionic conduction medium that is interposed between the positive electrode and the negative electrode and conducts carrier ions. Porous silicon particles can be used as the negative electrode active material. The power storage device may be any one of a lithium ion secondary battery, a hybrid capacitor, an air battery, and the like. In the positive electrode, as the positive electrode active material, a sulfide containing a transition metal element, an oxide containing lithium and a transition metal element, or the like can be used. Specifically, _{transition metal sulfides such as TiS 2} , TiS ₃ , MoS ₃ , and FeS _2, and the basic composition formula is Li _(1-x) MnO ₂ (0 <x <1, etc., the same applies hereinafter) and Li _{(1). -x)} Lithium-manganese composite oxide with Mn ₂ O _{4, etc., Lithium cobalt composite oxide with basic composition formula as Li (1-x)} CoO _2, etc., basic composition formula as Li _(1-x) NiO _2, etc. lithium nickel composite oxide and a _{Li (1-x) Ni a} Co b Mn c O 2 (a + b + c = 1) lithium-nickel-cobalt-manganese composite oxide, and the like basic formula, LiV ₂ O ₃ the basic formula A lithium vanadium composite oxide such as, or a transition metal oxide having a basic composition formula of V ₂ O _{5 or the like can be used.} Of these, lithium transition metal composite oxides, such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , Li _(1-x) Ni _1/3 Co _1/3 Mn _1/3 O _{2, and the} like are preferred. The "basic composition formula" means that other elements such as Al and Mg may be contained. Alternatively, the positive electrode active material may be a carbonaceous material used in a capacitor, a lithium ion capacitor, or the like. Examples of the carbonaceous material include activated carbons, cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbon fibers, carbon nanotubes, polyacenes and the like. Of these, activated carbons showing a high specific surface area are preferable. Activated carbon as a carbonaceous material preferably has a specific surface area of 1000 m ² / g or more, and more preferably 1500 m ² / g or more. When the specific surface area is 1000 m ² / g or more, the discharge capacity can be further increased. The specific surface area of this activated carbon ^{is preferably 3000 m 2} / g or less, and ^{more preferably 2000 m 2} / g or less, from the viewpoint of ease of production. As the conductive material, the binder, the solvent, the current collector, and the like used for the positive electrode, those exemplified by the above-mentioned electrodes can be appropriately used.

As the ion conducting medium, a non-aqueous electrolyte solution containing a supporting salt, a non-aqueous gel electrolyte solution, or the like can be used. Examples of the solvent for the non-aqueous electrolytic solution include carbonates, esters, ethers, nitriles, furans, sulfolanes, dioxolanes and the like, and these can be used alone or in combination. Specifically, as carbonates, cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl-n-butyl carbonate, and methyl-t. Chain carbonates such as -butyl carbonate, di-i-propyl carbonate, t-butyl-i-propyl carbonate, cyclic esters such as γ-butyl lactone and γ-valerolactone, methyl formate, methyl acetate, ethyl acetate, Chain esters such as methyl butyrate, ethers such as dimethoxyethane, ethoxymethoxyethane, diethoxyethane, nitriles such as acetonitrile and benzonitrile, furans such as tetrahydrofuran and methyl tetrahydrofuran, sulfolane, tetramethylsulfolane and the like. Examples thereof include sulfolanes, dioxolanes such as 1,3-dioxolane and methyldioxolane. Of these, a combination of cyclic carbonates and chain carbonates is preferable. According to this combination, not only the cycle characteristics that express the battery characteristics by repeated charging and discharging are excellent, but also the viscosity of the electrolytic solution, the electric capacity of the obtained battery, the battery output, etc. can be balanced. can. Supporting salts include, for example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiSbF ₆ , LiSiF _{6 , LiAlF 4} , LiSCN, LiClO. ₄ , LiCl, LiF, LiBr, LiI, LiAlCl _{4 and the} like. Of these, from the group consisting _{of inorganic salts such as LiPF 6} , LiBF ₄ , LiAsF ₆ , and LiClO ₄ , and organic salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiC (CF ₃ SO ₂ ) _3. It is preferable to use one selected salt or a combination of two or more salts from the viewpoint of electrical characteristics. The concentration of this supporting salt in the non-aqueous electrolyte solution is preferably 0.1 mol / L or more and 5 mol / L or less, and more preferably 0.5 mol / L or more and 2 mol / L or less. When the concentration at which the supporting salt is dissolved is 0.1 mol / L or more, a sufficient current density can be obtained, and when it is 5 mol / L or less, the electrolytic solution can be made more stable. Further, a flame retardant such as phosphorus or halogen may be added to this non-aqueous electrolytic solution.

Further, instead of the liquid ion conductive medium, a solid ion conductive polymer can be used as the ion conductive medium. As the ionic conductive polymer, for example, a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinylpyrrolidone, vinylidene fluoride and a supporting salt can be used. Further, an ionic conductive polymer and a non-aqueous electrolyte solution can be used in combination. Further, as the ionic conductive medium, in addition to the ionic conductive polymer, an inorganic solid electrolyte, a mixed material of an organic polymer electrolyte and an inorganic solid electrolyte, an inorganic solid powder bound by an organic binder, or the like can be used.

The power storage device may include a separator between the negative electrode and the positive electrode. The separator is not particularly limited as long as it has a composition that can withstand the range of use of the lithium secondary battery. For example, a polymer non-woven fabric such as a polypropylene non-woven fabric or a polyphenylene sulfide non-woven fabric, or a thin fine olefin resin such as polyethylene or polypropylene A porous membrane can be mentioned. These may be used alone or in combination of two or more.

The shape of the power storage device is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Further, it may be applied to a large-sized vehicle used for an electric vehicle or the like. FIG. 2 is an explanatory diagram showing an example of the structure of the power storage device 10. The power storage device 10 has a positive electrode 12, a negative electrode 15, and an ion conductive medium 18. The positive electrode 12 has a positive electrode active material 13 and a current collector 14. The negative electrode 15 has a negative electrode active material 16 and a current collector 17. The negative electrode active material 16 is the above-mentioned porous silicon particles 21 and has voids 23.

(All-solid-state lithium-ion secondary battery)
The power storage device is preferably an all-solid-state lithium-ion secondary battery. An all-solid-state battery is preferable because it can further suppress changes in performance due to the electrolytic solution and further enhance safety. This all-solid-state lithium-ion secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode which is an electrode for a power storage device described above, and a solid electrolyte which is interposed between the positive electrode and the negative electrode and conducts lithium ions. It may be a thing. As the positive electrode, any of the above-mentioned power storage devices can be used. Further, as the negative electrode, the above-mentioned electrode for a power storage device can be used.

The solid electrolyte may be, for example, a garnet-type oxide containing at least Li, La, and Zr. This solid electrolyte may have a basic composition of Li _{7.0 + xy} (La _3-x , A _x ) (Zr _2-y , T _y ) O ₁₂ . However, A is one or more of Sr and Ca, T is one or more of Nb and Ta, and satisfies 0 <x ≦ 1.0 and 0 <y <0.75. Alternatively, the solid electrolyte has a basic composition (Li _{7-3z + xy} M _z ) (La _3-x A _x ) (Zr _2-y T _y ) O ₁₂ or (Li _{7-3z + xy} M _z ) (La). It may be a garnet-type oxide represented by _3-x A _x ) (Y _2-y T _y ) O _12. However, in the formula, the element M is 1 or more of Al and Ga, the element A is 1 or more of Ca and Sr, and T is 1 or more of Nb and Ta, and 0 ≦ z ≦ 0.2 and 0 ≦ x. It may be assumed that ≦ 0.2 and 0 ≦ y ≦ 2. In this basic composition formula, it is more preferable to satisfy 0.05 ≦ z ≦ 0.1. In this basic composition formula, it is more preferable to satisfy 0.05 ≦ x ≦ 0.1. Further, in this basic composition formula, it is more preferable to satisfy 0.1 ≦ y ≦ 0.8. In such a range, the ionic conductivity can be made more suitable.

Alternatively, as solid electrolytes, for example, general Li ₃ N, Li ₁₄ Zn (GeO ₄ ) ₄ called LISION, Li sulfide Li _3.25 Ge _0.25 P _0.75 S ₄ , perovskite type La _0.5 Li _0.5 TiO ₃ , (La _2/3 Li _3x □ _{1 / 3-2x} ) TiO ₃ (□: atomic pores), garnet type Li ₇ La ₃ Zr ₂ O ₁₂ , NASICON type _{Li Ti 2} (PO ₄ ) ₃ , Li _1.3 M _0.3 Ti _1.7 (PO ₃ ) ₄ (M = Sc, Al) and the like. _{In addition, Li 7} P ₃ S ₁₁ obtained from glass having a composition of 80 Li ₂ S / 20 P ₂ S ₅ (mol%), which is a glass ceramic, and _{Li 10} Ge ₂ PS, which is a sulfide-based substance having high conductivity. ₂ etc. can also be mentioned. For glass-based inorganic solid electrolytes, Li ₂ S-SiS ₂ , Li ₂ S-SiS _2- LiI, Li ₂ S-SiS _{2 -Li 3} PO ₄ , Li ₂ S-SiS _{2 -Li 4} SiO ₄ , Li ₂ S- P ₂ S ₅ , Li ₃ PO _{4- Li 4} SiO ₄ , Li ₃ BO _{4- Li 4} SiO ₄ , and _{Li 2} O with _{SiO 2} , GeO ₂ , B ₂ O ₃ , P ₂ O ₅ as glass-based substances Examples thereof include those used as network modifiers. _{In addition, Li 2} S-GeS ₂ system, Li ₂ S-GeS _2- ZnS system, Li ₂ S-Ga ₂ S ₂ system, Li ₂ S-GeS _{2 -Ga 2} S ₃ system, Li ₂ S as thioricicon solid electrolytes. -GeS ₂ -P ₂ S ₅ series, Li ₂ S-GeS _2- SbS ₅ series, Li ₂ S-GeS _2- Al ₂ S ₃ series, Li ₂ S-SiS ₂ series, Li ₂ S-P ₂ S ₅ Examples include the Li ₂ S-Al ₂ S ₃ system, the LiS-SiS _2- Al ₂ S ₃ system, and the Li ₂ S-SiS _2- P ₂ S ₅ system. These solid electrolytes may be formed in a plate shape and arranged between the positive electrode and the negative electrode.

Further, the all-solid-state lithium ion secondary battery may include a restraining member that restrains the laminated body in which the positive electrode, the solid electrolyte, and the negative electrode are laminated with respect to the stacking direction. This restraint member is, for example, formed by a pair of plate-shaped portions sandwiching the laminate from both ends in the stacking direction of the laminate, a rod-shaped portion connecting the pair of plate-shaped portions, and a screw structure connected to the rod-shaped portion. It may be provided with an adjusting portion for adjusting the distance between the pair of plate-shaped portions.

(Manufacturing method of electrodes for power storage devices)
In the method for producing an electrode for a power storage device of the present disclosure, the porous silicon particles obtained by the above-mentioned method for producing porous silicon particles are used as an electrode active material, and the average porosity of the porous silicon particles is 5% by volume or more and 50. It includes a pressing step of compressing so as to be in the range of% by volume or less. According to this pressing step, the porosity can be lowered and the energy density can be further increased while maintaining a suitable pore shape. In this step, the porous silicon particles may be compressed so that the average porosity is in the range of 10% by volume or more, 20% by volume or more, and 40% by volume or less or 30% by volume or less. The average porosity of the compressed porous silicon particles may be appropriately adjusted according to the characteristics required for the electrode for the power storage device. In this pressing step, for example, the electrodes may be pressed in the range of 2 MPa or more and 20 MPa or less. In the pressing process, the porous silicon particles are mixed with a conductive material or a binder and a solvent as needed to form a paste and applied onto the current collector, or the porous silicon particles are conductive as needed. It may be mixed with a material or a binder and crimped to a current collector. As the blending amount of the porous silicon particles and the like, the contents described in the electrode for the power storage device can be appropriately used.

(Manufacturing method of power storage device)
In the method for manufacturing a power storage device of the present disclosure, the electrode for a power storage device obtained by the method for manufacturing an electrode for a power storage device described above is used as a negative electrode, the positive electrode and the negative electrode are opposed to each other, and lithium ions are inserted between the positive electrode and the negative electrode. An ionic conduction medium that conducts may be interposed. A separator may be interposed between the positive electrode and the negative electrode. As the positive electrode, the negative electrode, the ion conducting medium and the separator, any of those mentioned in the above-mentioned power storage device can be appropriately used.

(Manufacturing method of all-solid-state lithium-ion secondary battery)
In the method for manufacturing an all-solid-state lithium ion secondary battery of the present disclosure, the electrode for a power storage device obtained by the method for manufacturing an electrode for a power storage device described above is used as a negative electrode, and a positive electrode, a solid electrolyte that conducts lithium ions, and a negative electrode are used. Includes a laminate manufacturing step of producing a laminated laminate. As the positive electrode, the negative electrode, and the solid electrolyte used in this production method, any of the above-mentioned all-solid-state lithium ion secondary batteries can be appropriately used. Further, the thickness and size of the positive electrode, the negative electrode, and the solid electrolyte used in this production method can be appropriately selected according to the desired battery characteristics. Further, in this manufacturing method, the pressing step in the manufacturing method of the electrode for the power storage device may be performed in the laminate manufacturing step. That is, when pressing the laminate in which the positive electrode, the solid electrolyte, and the negative electrode are laminated, the negative electrode may be pressed at the same time.

The method for manufacturing the all-solid-state lithium-ion secondary battery may further include a stacking restraint step of restraining the manufactured laminate with a restraining member in the stacking direction. The restraining pressure of the laminated body is preferably in the range of 2 MPa or more and 20 MPa or less, for example.

As described in detail above, the present disclosure can further suppress a decrease in charge / discharge characteristics in a material containing Si. The reason why such an effect can be obtained is presumed as follows. For example, the silicon negative electrode for a lithium ion secondary battery has a theoretical capacity of 4199 mAh / g, which is about 10 times higher than the theoretical capacity of 372 mAh / g of general graphite, and further increases the capacity and energy density. Is expected. On the other hand, the silicon that occludes lithium ions is Li _4.4 Si, and its volume expands to about four times that of silicon before lithium occlusal. On the other hand, according to the present disclosure, this is selectively removed by using an acid or alkali that dissolves a substance other than silicon, which is mainly Al, contained in the silicon alloy, and the pore size is small and the porosity is large. Porous silicon particles can be easily produced. Porous silicon particles having a small pore size and a large porosity have a large volume expansion and contraction when used in a power storage device such as a lithium ion secondary battery. Therefore, for example, a charge / discharge cycle. Since charge / discharge characteristics such as characteristics are improved, a high-performance power storage device can be easily obtained.

It goes without saying that the present disclosure is not limited to the above-described embodiment, and can be implemented in various embodiments as long as it belongs to the technical scope of the present disclosure.

Hereinafter, an example in which the porous silicon and the power storage device of the present disclosure are specifically manufactured will be described as an experimental example. Experimental Examples 1 to 5 are examples of the present disclosure, and Experimental Examples 6 and 7 are comparative examples.

[Manufacturing of negative electrode active material]
(Experimental Example 1)
87% by mass of 10 mm square lumpy Al and 13% by mass of lumpy Si were weighed and mixed, and melted by a high-frequency heating method in an Ar-inert atmosphere to obtain an alloy molten metal. An AlSi alloy powder having an average particle size of 8 μm was obtained from this molten alloy by a gas atomization method using an Ar inert gas (particulation step). This alloy powder had an Al—Si eutectic composition (see FIG. 1), and was an AlSi alloy powder composed of a eutectic Si phase and an Al phase. When the obtained powder was subjected to X-ray diffraction, the presence of Al phase and Si phase as crystalline phases was confirmed. Next, the obtained alloy powder was placed in 3 mol / L hydrochloric acid diluted in pure water, stirred at room temperature of 25 ° C. for 1 hour, filtered while thoroughly washing, and dried in a vacuum drying oven at 30 ° C. for 2 hours. (Pollation step). In this way, the negative electrode active material of Example 1 was produced.

(Experimental Example 2)
The negative electrode active material of Experimental Example 2 was produced in the same manner as in Experimental Example 1 except that 82% by mass of Al and 18% by mass of Si were used. The alloy powder at this time had an Al—Si hypereutectic composition and was an AlSi alloy powder composed of primary crystal Si, eutectic Si phase and Al phase. The acid treatment was carried out under the same conditions as in Experimental Example 1 to obtain the negative electrode active material of Experimental Example 2.

(Experimental Example 3)
The negative electrode active material of Experimental Example 3 was produced in the same manner as in Experimental Example 1 except that 73% by mass of Al and 27% by mass of Si were used. The alloy powder at this time had an Al—Si hypereutectic composition and was an AlSi alloy powder composed of primary crystal Si, eutectic Si phase and Al phase. The acid treatment was carried out under the same conditions as in Experimental Example 1 to obtain the negative electrode active material of Experimental Example 3.

(Experimental Example 4)
The negative electrode active material of Experimental Example 4 was produced in the same manner as in Experimental Example 1 except that 90% by mass of Al and 10% by mass of Si were used. The alloy powder at this time had an Al—Si subeutectic composition and was an AlSi alloy powder composed of primary Al, eutectic Si phase and Al phase. The acid treatment was carried out under the same conditions as in Experimental Example 1 to obtain the negative electrode active material of Experimental Example 4.

(Experimental Example 5)
The negative electrode active material of Experimental Example 5 was produced in the same manner as in Experimental Example 1 except that 87% by mass of Al, 10% by mass of Si, and 3% by mass of Cu were used. The alloy powder at this time was an AlSiCu alloy powder composed of a primary crystal Al, a eutectic Si phase, and an Al ₂ Cu phase. The acid treatment was carried out under the same conditions as in Experimental Example 1 to obtain the negative electrode active material of Experimental Example 5.

(Experimental Example 6)
The negative electrode active material of Experimental Example 6 was produced in the same manner as in Experimental Example 1 except that 43% by mass of Al and 57% by mass of Si were used. The alloy powder at this time had an Al—Si hypereutectic composition and was an AlSi alloy powder composed of primary crystal Si, eutectic Si phase and Al phase. The acid treatment was carried out under the same conditions as in Experimental Example 1 to obtain the negative electrode active material of Experimental Example 6.

(Experimental Example 7)
A Si powder having an average particle size of 5 μm was used as the negative electrode active material of Experimental Example 7.

(Measurement of physical properties of porous silicon particles)
The acid-treated porous silicon powder was _{dissolved in HF and HNO 3,} and the amount of Al in porous silicon was measured by ICP emission spectroscopy (ICP-OES, PS3520U VDDII II manufactured by Hitachi High-Tech Science). In addition, observation and elemental analysis were performed with a scanning electron microscope (SEM, Hitachi S-4300) and energy dispersive X-ray analysis (EDAX, Hitachi S-4300). In addition, the pore distribution was measured with a mercury porosimeter (POWERMASTER 60GT manufactured by Kantachrome).

(Physical property measurement results and consideration)
FIG. 3 is an SEM image of the Al—Si alloy after gas atomization of Experimental Example 1. As shown in FIG. 3, a structure in which eutectic Si exists between large primary crystals Al was confirmed. 4A and 4B are an SEM image and an EDAX mapping image of the porous silicon particles of Experimental Example 1, FIG. 4A is an overall image, FIGS. 4B and C are enlarged images, and FIG. 4D is an EDAX image. In Experimental Example 1, Si is 13% by mass as the composition of the raw material, but as shown in FIG. 4B, it contains skeletal silicon having a three-dimensional network structure that maintains the shape of the particles and has voids inside the particles. It was confirmed that it was a structure. In addition, although a very small amount of Al and O were detected in the EDAX image, it was found that the structure was composed of Si. It was also confirmed that most of the primary crystal Al was removed by the porosity step, which is an acid treatment at room temperature. The Al concentration after the porosification treatment determined by ICP-OES was 4.2% by mass, and from this result, it is considered that most of the aluminum was eluted to form porous silicon from the composition of the raw material powder. rice field. FIG. 5 is a pore distribution curve of the porous silicon particles of Experimental Example 1. In the water porosimeter, since the measurement results may include pores between the particles, the alloy particles before the porosification treatment and the porous silicon particles after the porosification treatment are measured, and the difference value is calculated. The pore volume was used. In FIG. 5, the difference is shown in shading. As shown in FIG. 5, the pore diameter was 1 μm or less, which was consistent with the size of the voids confirmed by the SEM image. As a result of measurement with a mercury porosimeter, the pore distribution of the porous silicon particles of Experimental Example 1 was 50 to 500 nm, the pore diameter was the largest at around 200 nm, and the porosity was 76% by volume.

Table 1 summarizes the raw material composition ratios (% by mass), the amount of residual Al after acid treatment (mass%), and the porosity (volume%) of Experimental Examples 1 to 7. The amount of Al is a measurement result by ICP-OES, and the porosity is a value excluding interparticle vacancies. As shown in Table 1, the amount of residual Al after the acid treatment in Experimental Examples 1 to 7 was 3.2 to 6.2% by mass, and most of the Al was eluted by the porosification treatment which is the acid treatment. all right. The porosity of Experimental Examples 1 to 5 was 62 to 86% by volume, whereas the porosity of Experimental Example 6 was 33% by volume, and the porosity was low.

(Manufacturing a lithium secondary battery using a non-aqueous electrolyte solution)
82% by mass of each of the negative electrode active materials of Experimental Examples 1 to 7, 6% by mass of acetylene black having an average particle size of 2 μm as a conductive material, and 12% by mass of polyimide as a binder were weighed and mixed, and N-methyl was mixed. After adding pyrrolidone, the mixture was stirred to prepare a negative electrode mixture slurry. Next, this slurry was applied onto a copper foil having a thickness of 12 μm, dried, and rolled to prepare a negative electrode having a thickness of 50 μm. It was estimated that by this rolling, the porosity of the porous silicon particles was reduced to about 50% by volume while maintaining the three-dimensional network structure. The prepared negative electrode electrode was punched into a circle having a diameter of 16 mm, and a porous poroethylene separator was sandwiched between the negative electrode electrode, and metallic lithium was laminated as a counter electrode to form a laminated body. _{Subsequently, an electrolytic solution in which LiPF 6} was added at a concentration of 1 mol / L to a mixed solvent in which ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl carbonate (EMC) was mixed at a volume ratio of 3: 4: 3 was added. By injecting liquid into the above-mentioned laminate, a lithium secondary battery, which is a tom cell type small battery cell, was manufactured. The obtained lithium secondary battery was repeatedly charged and discharged for 10 cycles with a current density of 0.2 C in a battery voltage range of 0 V to 1.5 V.

(Characteristics of lithium secondary battery using non-aqueous electrolyte solution)
Table 2 shows the initial discharge capacity (mAh / g) of Experimental Examples 1 to 7, the discharge capacity (mAh / g) after 10 cycles, and the capacity retention rate (%). Capacity retention, the discharge capacity to Q ₁ 1 cycle, using the discharge capacity Q ₁₀ at the 10th cycle was determined from the equation: Q ₁₀ / Q ₁ × 100. As shown in Table 2, it was as low as 26% in Experimental Example 7, and it was presumed that the silicon particles having no voids could not absorb the volume change and the electrode had a problem. Further, even in Experimental Example 6 in which the porosity was as low as 33% by volume, the capacity retention rate was less than 70%, which was found to be insufficient. On the other hand, in the lithium secondary batteries of Experimental Examples 1 to 5, the capacity retention rate showed a good value of 84 to 93%, and it was found that the electrodes were stable. As described above, as shown in Experimental Examples 1 to 5, when the porous silicon particles having a porosity of 60% by volume or more are compressed and the porosity is in the range of 5% by volume or more and 50% by volume or less, the capacity retention rate is particularly increased. I found that I could do it.

(Manufacture of lithium all-solid-state secondary battery using solid electrolyte)
(Preparation of positive electrode)
In a polypropylene container, butyl butyrate, a 5% by mass butyl butyrate solution which is a PVdF-based binder, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ particles having an average particle size of 6 μm as a positive electrode active material, and a solid electrolyte. A glass ceramic containing Li ₂ SP ₂ S ₅ and a vapor-grown carbon fiber (VGCF) as a conductive material were added, and the mixture was stirred with an ultrasonic disperser (UH-50 manufactured by SMT) for 30 seconds. The mass ratio of the positive electrode active material, the solid electrolyte, the conductive material, and the binder (solid component) was 70:10:10:10. Next, the container was shaken with a shaker (TTM-1 manufactured by Shibata Scientific Technology Co., Ltd.) for 3 minutes, and further stirred with an ultrasonic disperser for 30 seconds. Then, the slurry was further shaken with a shaker for 3 minutes to obtain a slurry. The slurry was applied onto an aluminum foil (manufactured by Showa Denko Co., Ltd.) having a thickness of 10 μm by a blade method using an applicator. Then, it was dried on a hot plate at 100 ° C. for 30 minutes to obtain a positive electrode having a positive electrode mixture layer (thickness 50 μm) on an aluminum foil.

(Preparation of negative electrode)
The particle size of Si particles (including porous silicon particles) as the negative electrode active material was measured by a particle size distribution measuring device (Sirocco2000 manufactured by Malvern) based on a laser diffraction / light scattering method. The average particle size (D50) of the silicon material contained in the negative electrode was 5 to 15 μm, D10 was 1 to 2 μm, and D90 was 10 to 20 μm. In the measured volume-based particle size distribution, the particle size corresponding to the cumulative 10% by volume from the fine particle side is D10, the particle size corresponding to the cumulative 50% by volume is D50, and the particle size corresponding to the cumulative 90% by volume is D90. And said. A glass ceramic containing butyl butyrate, a 5% by mass butyl butyrate solution of a PVdF-based binder, Si particles of Experimental Examples 1 to 7 as a negative electrode active material, and Li ₂ SP ₂ S _{5 as a solid electrolyte in a polypropylene container.} Was added, and the mixture was stirred with an ultrasonic disperser (UH-50 manufactured by SMT) for 30 seconds. Next, the container was shaken with a shaker (TTM-1 manufactured by Shibata Scientific Technology Co., Ltd.) for 30 seconds to obtain a slurry. The slurry was applied onto a copper foil having a thickness of 10 μm by a blade method using an applicator. Then, it was dried on a hot plate at 100 ° C. for 30 minutes to obtain a negative electrode having a negative electrode mixture layer (thickness 30 μm) on a copper foil.

(Preparation of solid electrolyte layer)
To a polypropylene container, heptane, a 5% by mass heptane solution of a BR-based binder, _{and a glass ceramic containing LiI-LiBr-Li 2 SP 2} S ₅ as a solid electrolyte are added, and an ultrasonic disperser (manufactured by SMT) is added. It was stirred with UH-50) for 30 seconds. Next, the container was shaken with a shaker (TTM-1 manufactured by Shibata Scientific Technology Co., Ltd.) for 30 seconds to obtain a slurry. The slurry was coated on a base material (aluminum foil) by a blade method using an applicator. Then, the solid electrolyte layer (thickness 15 μm) was formed on the base material by drying on a hot plate at 100 ° C. for 30 minutes.

(Manufacturing of all-solid-state lithium-ion battery)
The solid electrolyte layer and the positive electrode were laminated and pressed at 1 ^{ton / cm 2} so that the solid electrolyte layer was in contact with the positive electrode mixture layer. Then, the base material was peeled off to form a two-layer body consisting of a solid electrolyte layer and a positive electrode. Next, the two layers and the negative electrode are laminated so that the solid electrolyte layer of the two layers and the negative electrode mixture layer come into contact with each other, ^{and pressed at 6 ton / cm 2} between the positive electrode and the negative electrode. A laminate having a solid electrolyte was obtained. The obtained laminate (cell) was restrained at a predetermined restraining pressure using a screw tightening type restraining member 35 as shown in FIG. 6 to obtain an evaluation cell which is an all-solid-state lithium ion battery. FIG. 6 is an explanatory diagram of the evaluation cell 30. The evaluation cell 30 is an all-solid-state lithium secondary battery, and includes a restraint member 31, a positive electrode 32, a negative electrode 35, a solid electrolyte 38, and a battery case 39. The positive electrode 32, the negative electrode 35, and the solid electrolyte 38 constitute the laminate 37. The battery case 39 houses the laminated body 37. The restraining member 37 restrains the battery case 39 from all sides in a direction in which the laminated body 37 does not peel off.

(Performance evaluation of all-solid-state lithium-ion battery)
The evaluation cell of the obtained all-solid-state lithium-ion secondary battery was repeatedly charged and discharged for 5 cycles with a current density of 0.2 C in a battery voltage range of 3.0 V to 4.5 V. Capacity retention, the discharge capacity to Q ₁ 1 cycle, using the discharge capacity Q ₅ at the fifth cycle was calculated from the equation Q ₅ / Q ₁ × 100. In addition, a pressure sensor (load cell manufactured by Kyowa Electric Co., Ltd.) was inserted into the battery case in the restrained state, and the fluctuation of the restraint pressure during charging and discharging was measured.

(Characteristics of all-solid-state lithium-ion battery)
FIG. 7 is a charge / discharge curve of the evaluation cells of Experimental Examples 1 and 7. Further, the void ratio (volume%) of the silicon particles in the electrodes of Experimental Examples 1 to 7, the initial restraint pressure fluctuation value, the second cycle restraint pressure fluctuation value, the initial discharge capacity (mAh / g), and the fifth cycle discharge capacity. (MAh / g) and capacity retention rate (%) are summarized in Table 3. Table 3 shows the relative values of the restraint pressure fluctuation values standardized with Experimental Example 7 as 100. As shown in FIGS. 7 and 3, the initial discharge capacities of Experimental Examples 1 and 7 are not much different from 147 mAh / g and 141 mAh / g, respectively, whereas the fluctuations in the restraining pressure in the first and second cycles of Experimental Example 1 are the same. As relative values to Experimental Example 7, they decreased significantly to 65.0% and 72.7%, respectively. In addition, the capacity retention rate of Experimental Example 1 was 98.6% as compared with 97.2% of Experimental Example 7, and Experimental Example 1 was preferable. It was expected that when the number of cycles was increased, the decrease in Experimental Example 7 became more remarkable, and the difference in capacity retention rate further widened. Similarly, the restraint pressure fluctuations in the first and second cycles of Experimental Examples 2 to 5 were 61.3 to 68.8% and 65.9 to 75.0% as relative values to Experimental Example 7, and the experiment was conducted. It was found that the restraining pressure was further reduced as compared with Examples 6 and 7. The capacity retention rate of Experimental Examples 2 to 5 was also 98.6 to 98.7%, and it was found that the capacity retention rate was also improved.

It goes without saying that the present invention is not limited to the above-mentioned experimental examples, and can be carried out in various embodiments as long as it belongs to the technical scope of the present invention.

The present disclosure is available in the technical field of secondary batteries.

10 power storage device, 12 positive electrode, 13 positive electrode active material, 14 current collector, 15 negative electrode, 16 negative electrode active material, 17 current collector, 18 ion conductive medium, 21 porous silicon particles, 23 voids, 30 evaluation cells, 31 restraints. Members, 32 positive electrodes, 35 negative electrodes, 37 laminates, 38 solid electrolytes, 39 battery cases.

Claims (14)

A particle-forming step of melting a silicon alloy containing 50% by mass or more of the first element Al and 50% by mass or less of Si to form particles.
A porosity step of removing the first element in the silicon alloy to obtain porous silicon particles,
A method for producing porous silicon particles including. The first element according to claim 1, wherein in the particle formation step, the silicon alloy containing a second element containing one or more of Ca, Cu, Mg, Na, Sr and P in addition to the first element and the Si is used. A method for producing porous silicon particles. The method for producing porous silicon particles according to claim 1 or 2, wherein in the porosity step, the first element is selectively removed by an acid or an alkali. The method for producing porous silicon particles according to any one of claims 1 to 3, wherein in the porosity step, substances other than Si are removed in a range of 85% by mass or more and 100% by mass or less. The method for producing porous silicon particles according to any one of claims 1 to 4, wherein in the porosity step, the porous silicon particles having an average porosity in the range of 50% by volume or more and 95% by volume or less are obtained. The porous silicon particles according to any one of claims 1 to 5, wherein in the particle formation step, the molten metal of the silicon alloy is atomized by any one of a gas atomization method, a water atomization method and a roll quenching method. Manufacturing method. The method for producing porous silicon particles according to any one of claims 1 to 6, wherein in the particle formation step, the silicon alloy is particleized in a range where the average particle size is 0.1 μm or more and 100 μm or less. The porous silicon particles obtained by the method for producing porous silicon particles according to any one of claims 1 to 7 are used as an electrode active material, and the average porosity of the porous silicon particles is 5% by volume or more. Pressing process that compresses to a range of 50% by volume or less,
A method for manufacturing an electrode for a power storage device including. Using the storage device electrode obtained by the method for manufacturing a power storage device electrode according to claim 8 as a negative electrode, a laminate in which a positive electrode, a solid electrolyte conducting lithium ions, and the negative electrode are laminated is produced. Lamination restraint step of restraining the produced laminate with a restraint member in the stacking direction,
A method for manufacturing an all-solid-state lithium-ion secondary battery including. Elements having an average particle size in the range of 0.1 μm or more and 100 μm or less, containing skeletal silicon having a three-dimensional network structure with voids, an average porosity in the range of 50% by volume or more and 95% by volume or less, and excluding oxygen. Si is contained in the range of 85% by mass or more and Al is contained in the range of 15% by mass or less.
Porous silicon particles. The porous silicon particles according to claim 10, wherein the average porosity is 60% by volume or more. The porous silicon particles according to claim 10 or 11, which contain one or more of Ca, Cu, Mg, Na, Sr and P in the range of 15% by mass or less. The porous silicon particles according to any one of claims 10 to 12 are contained as an electrode active material, and the average porosity of the porous silicon particles is compressed in the range of 5% by volume or more and 50% by volume or less. Electrodes for power storage devices. Positive electrode A positive electrode containing an active material and a positive electrode
The negative electrode, which is the electrode for the power storage device according to claim 13,
A solid electrolyte that is interposed between the positive electrode and the negative electrode and conducts lithium ions,
All-solid-state lithium-ion secondary battery with.

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