Electrode active material composite particles, their manufacturing methods, electrode mixtures and batteries

Abstract

This invention relates to electrode active material composite particles, methods for manufacturing the same, electrode mixtures, and batteries. The electrode active material composite particles of this disclosure comprise a porous carbon material and spherical silicon particles contained within the porous carbon material. The electrode active material composite particles of this disclosure have pores. A method for manufacturing the electrode active material composite particles according to this disclosure includes producing spherical silicon particles by decomposing a silane halide on a porous carbon material. An electrode mixture of this disclosure comprises the electrode active material composite particles of this disclosure. A battery of this disclosure comprises an electrode active material layer, and the electrode active material layer comprises the electrode mixture of this disclosure.

Description

Technical Field

[0001] This disclosure relates to electrode active material composite particles, methods for manufacturing them, electrode mixtures, and batteries. Background Technology

[0002] Japanese Patent Application Publication No. 2024-073597 (JP 2024-073597 A) discloses a composite comprising a porous carbon framework and silicon, and an electrode comprising such a composite. JP 2024-073597 A further discloses a method for embedding silicon into a porous carbon framework using silane gas via chemical vapor deposition (CVD). Summary of the Invention

[0003] Silicon electrode active materials can expand and contract during battery charging and discharging. Therefore, batteries containing silicon electrode active materials may experience volume changes associated with this expansion and contraction. Even for electrode active material composites containing porous carbon materials and silicon, there is still room for improvement in suppressing this battery volume change.

[0004] The purpose of this disclosure is to provide electrode active material composite particles capable of suppressing battery volume changes, a method for manufacturing the same, an electrode mixture comprising such electrode active material composite particles, and a battery comprising such an electrode mixture.

[0005] The inventors have discovered that the above problems can be solved by the following means.

[0006] First aspect

[0007] An electrode active material composite particle comprises: a porous carbon material; and spherical silicon particles retained within the porous carbon material, wherein the electrode active material composite particle has pores.

[0008] Second aspect

[0009] According to the electrode active material composite particles of the first aspect, the spherical silicon particles have an average particle size of 0.1 μm or more and 1.0 μm or less.

[0010] Third aspect

[0011] An electrode mixture comprising composite particles of electrode active materials according to the first or second aspect.

[0012] Fourth aspect

[0013] A battery comprising an electrode active material layer, wherein the electrode active material layer comprises an electrode mixture according to a third aspect.

[0014] Fifth aspect

[0015] A method for manufacturing electrode active material composite particles according to a first or second aspect, the method comprising producing the spherical silicon particles by decomposing a silane halide on the porous carbon material.

[0016] This disclosure provides electrode active material composite particles capable of suppressing battery volume changes, a method for manufacturing the same, an electrode mixture comprising such electrode active material composite particles, and a battery comprising such an electrode mixture. Attached Figure Description

[0017] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein like symbols denote like elements, and wherein: Figure 1 This is a cross-sectional scanning electron microscope (SEM) image of the electrode active material composite particles in the embodiment; Figure 2 This is a diagram illustrating the cumulative pore size distribution of the electrode active material composite particles and the porous carbon material in the embodiments; Figure 3 This is a diagram illustrating the micropore size distribution of the electrode active material composite particles and the porous carbon material in the embodiments; and Figure 4 This is a cross-sectional SEM image of the electrode active material composite particles of the comparative example. Detailed Implementation

[0018] The embodiments of this disclosure will now be described in detail. This disclosure is not limited to the embodiments described below, and various modifications can be made within the scope of this disclosure.

[0019] Electrode active material composite particles

[0020] The electrode active material composite particles of this disclosure comprise a porous carbon material and spherical silicon particles contained within the porous carbon material. The electrode active material composite particles of this disclosure have pores.

[0021] The inventors have discovered that the electrode active material composite particles of this disclosure can suppress battery volume changes associated with the expansion and contraction of silicon particles during battery charging and discharging.

[0022] While not wishing to be bound by any particular theory, the reasoning is as follows: In porous electrode active material composite particles, the pores are believed to mitigate the effects of silicon particle expansion and contraction during battery charging and discharging. Spherical silicon particles are considered to expand and contract isotropically. Therefore, compared to non-spherical silicon particles, the pores more effectively mitigate the effects of spherical silicon particle expansion and contraction, thereby suppressing battery volume changes.

[0023] "Electrode active material" can be "positive electrode active material" or "negative electrode active material", and can be particularly "negative electrode active material".

[0024] The constituent elements of the electrode active material composite particles of this disclosure will now be described.

[0025] Porous carbon materials

[0026] The electrode active material composite particles of this disclosure comprise porous carbon material. The porous carbon material retains silicon within its pores.

[0027] The porous carbon material is not particularly limited. The porous carbon material can be, for example, activated carbon. The porous carbon material can be a material with interconnected pores. An example of such a material is the commercially available CNovel (registered trademark) MH-00.

[0028] The pore size and pore volume of the porous carbon material are not particularly limited. When measured by gas adsorption, the porous carbon material can have pores smaller than 10 nm, and the pore volume can be greater than or equal to 0.30 cc / g, greater than or equal to 0.40 cc / g, greater than or equal to 0.50 cc / g, greater than or equal to 0.55 cc / g, or greater than or equal to 0.60 cc / g, and less than or equal to 1.00 cc / g, less than or equal to 0.90 cc / g, less than or equal to 0.80 cc / g, less than or equal to 0.75 cc / g, or less than or equal to 0.70 cc / g.

[0029] In the micropore size distribution of porous carbon materials determined by gas adsorption, the maximum peak position can be above 1 nm, above 2 nm, above 3 nm, or above 4 nm, and can be below 10 nm, below 7 nm, below 5 nm, or below 4 nm.

[0030] Gas adsorption methods are not particularly limited and can, for example, involve determining the N2 adsorption isotherm and then obtaining the cumulative pore size distribution and differential pore size distribution using the Barrett-Joyner-Halenda (BJH) method. In this case, the BELSORP MAX X specific surface area and pore size distribution analyzer manufactured by Microtrac can be used. The pore size and pore volume can be determined from the cumulative pore size distribution and differential pore size distribution obtained therefrom. The pore volume of the electrode active material composite particles, described later, can also be determined using the same method.

[0031] Spherical silicon particles

[0032] The electrode active material composite particles disclosed herein contain spherical silicon particles contained within a porous carbon material. This allows the pores to more effectively mitigate the effects of silicon particle expansion and contraction, thereby suppressing battery volume changes.

[0033] Silicon is not particularly restricted and can be silicon produced, for example, by means of halogenated silanes.

[0034] In this disclosure, "spherical" refers to a shape with an aspect ratio of 3 or less. Therefore, the aspect ratio of silicon particles can be 3.0 or less, 2.5 or less, 2.0 or less, 1.5 or less, 1.3 or less, 1.2 or less, or 1.1 or less, or it can be 1.0.

[0035] For example, the aspect ratio can be determined from a cross-sectional SEM image of the electrode active material composite particles obtained by scanning electron microscopy (SEM). Specifically, for multiple particles in the image, the longest dimension between the opposite ends of each particle is divided by its shortest dimension, and the average of these values ​​is taken as the aspect ratio.

[0036] For example, cross-sectional SEM images of electrode active material composite particles can be obtained using the following method: First, the electrode active material composite particles are mixed with zinc powder, and the mixture is shaped into granules using a press. Then, the granules are processed using a cross-section polishing machine to prepare a sample, and a cross-sectional SEM image of the sample is obtained.

[0037] The average particle size of the spherical silicon particles can be greater than 0.1 μm and less than 1.0 μm. The average particle size can be greater than 0.1 μm, greater than 0.2 μm, or greater than 0.3 μm, and can be less than 1.0 μm, less than 0.8 μm, less than 0.6 μm, less than 0.5 μm, less than 0.4 μm, less than 0.3 μm, or less than 0.2 μm. This effectively suppresses cell volume changes.

[0038] The average particle size can be determined by observation using an electron microscope (e.g., SEM). For example, the average particle size can be defined as the average of the maximum Fret diameters of multiple particles. It is preferable to use a large number of samples. The number of samples can be, for example, more than 20, more than 50, or more than 100. The average particle size can be appropriately adjusted by changing the manufacturing conditions of the silicon particles.

[0039] More specifically, the average particle size can be determined as follows. First, the electrode active material composite particles are mixed with zinc powder, and the mixture is shaped into granules using a press. A sample is then prepared by processing the granules using a cross-section polishing machine. The sample thus prepared is observed using SEM. The diameter of each silicon particle can be determined using scale bars at various magnifications. The diameters of multiple silicon particles are measured, and the average of the measured diameters is calculated as the average particle size.

[0040] In the electrode active material composite particles of this disclosure, the mass ratio of spherical silicon particles to porous carbon material can be 0.1 or more and 10.0 or less. This mass ratio can be 0.1 or more, 0.3 or more, 0.5 or more, 0.7 or more, 0.9 or more, or 1.0 or more, and can be 10.0 or less, 7.0 or less, 5.0 or less, 3.0 or less, 2.0 or less, or 1.0 or less. That is, the mass ratio of silicon particles to porous carbon material can be 1:1.

[0041] hole

[0042] The electrode active material composite particles disclosed herein have pores.

[0043] The pore volume is not particularly limited. For example, in the method for manufacturing electrode active material composite particles described later, when three alumina boats are used, the electrode active material composite particles obtained from the alumina boats located upstream, midstream, and downstream relative to the Ar flow containing halosilane vapor can have the same or different pore volumes.

[0044] For the electrode active material composite particles obtained from the upstream alumina boat, the pore volume can be above 500cc / g, above 600cc / g, above 700cc / g, or above 750cc / g, and can be below 900cc / g, below 850cc / g, or below 800cc / g.

[0045] For the composite particles of electrode active materials obtained from upstream and downstream alumina boats, the pore volume can be above 300cc / g, above 400cc / g, or above 500cc / g, and can be below 700cc / g, below 600cc / g, or below 5500cc / g.

[0046] In the micropore size distribution obtained by gas adsorption, the maximum peak position of the electrode active material composite particles can be above 1 nm, above 2 nm, above 3 nm, or above 4 nm, and can be below 10 nm, below 7 nm, below 5 nm, or below 4 nm.

[0047] Method for manufacturing composite particles of electrode active materials

[0048] The method for manufacturing electrode active material composite particles according to this disclosure includes producing spherical silicon particles by decomposing halogenated silanes on a porous carbon material.

[0049] The method for decomposing silane halides on porous carbon materials is not particularly limited and can be, for example, chemical vapor deposition (CVD). A specific example is as follows: First, an alumina boat containing porous carbon material is placed in a tube furnace. The tube furnace is purged with argon (Ar) and heated. At this time, the Ar flow rate can be appropriately adjusted, and in particular, the Ar flow rate can be reduced. Then, the Ar line is switched from the tube furnace to a container containing silane halides, and Ar is bubbled through the silane halides. The resulting Ar containing silane halides vapor is introduced into the tube furnace. Simultaneously, hydrogen is introduced into the tube furnace. By maintaining this state, the silane halides can be decomposed on the porous carbon material. As a result, spherical silicon particles are produced.

[0050] The silane halide is not particularly limited, and examples include tetrachlorosilane, trichlorosilane, dichlorosilane, and monochlorosilane. In particular, tetrachlorosilane (TCS) can be used. Therefore, it is possible to efficiently manufacture electrode active material composite particles containing spherical silicon particles.

[0051] The heating temperature is not particularly limited and can be, for example, above 300°C, above 500°C, above 600°C, or above 700°C, and can be below 1000°C, below 900°C, below 800°C, or below 700°C.

[0052] There are no particular restrictions on the time for introducing Ar and hydrogen containing halogenated silane vapors into the tubular furnace, and it can be, for example, more than 3 hours, more than 5 hours, more than 6 hours, or more than 7 hours, or less than 30 hours, less than 20 hours, less than 15 hours, less than 10 hours, less than 8 hours, or less than 7 hours.

[0053] Electrode mixture

[0054] The electrode mixture of this disclosure comprises the electrode active material composite particles of this disclosure. Optionally, the electrode mixture may further comprise a solid electrolyte, conductive additives, binders, etc.

[0055] In this disclosure, "electrode mixture" refers to a composition that can constitute an electrode active material layer, either alone or together with other components. "Electrode mixture slurry" refers to a slurry containing an "electrode mixture" and a dispersion medium that can be applied and dried to form an electrode active material layer.

[0056] In this disclosure, "electrode mixture" can be "positive electrode mixture" or "negative electrode mixture", and can be particularly "negative electrode mixture".

[0057] The constituent elements of the electrode mixture of this disclosure will now be described.

[0058] Electrode active material composite particles

[0059] For information on composite particles of electrode active materials, please refer to the above description.

[0060] The content of composite particles of electrode active materials in the electrode mixture is not particularly limited and can be appropriately set considering the desired battery capacity, etc.

[0061] solid electrolyte

[0062] Examples of solid electrolytes include inorganic solid electrolytes, such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, or halide solid electrolytes, as well as organic polymer electrolytes, such as polymer electrolytes. Solid electrolytes can be, in particular, sulfide solid electrolytes.

[0063] For example, when the battery is a lithium-ion rechargeable battery, the solid electrolyte can conduct lithium ions.

[0064] Examples of sulfide solid electrolytes capable of conducting lithium ions include solid electrolytes containing Li, element X (X being at least one selected from P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. Sulfide solid electrolytes may also contain O and any or both of a halogen. Examples of halogens include F, Cl, Br, and I.

[0065] Examples of sulfide solid electrolytes include Li₂S-P₂S₅, Li₂S-P₂S₅-LiI, Li₂S-P₂S₅-GeS₂, Li₂S-P₂S₅-Li₂O, Li₂S-P₂S₅-Li₂O-LiI, Li₂S-P₂S₅-LiBr, Li₂S-SiS₂, Li₂S-SiS₂-LiI, Li₂S-SiS₂-LiBr, Li₂S-SiS₂-LiCl, Li₂S-SiS₂-B₂S₃-LiI, Li₂S-SiS₂-P₂S₅-LiI, Li₂S-B₂S₃, and Li₂S-P₂S₅-Z. m S n (where m and n are positive numbers, and Z is any element selected from Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is any element selected from P, Si, Ge, B, Al, Ga, and In).

[0066] Examples of oxide solid electrolytes capable of conducting lithium ions include solid electrolytes containing Li, element Y (Y being at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and O. Specific examples include garnet solid electrolytes, such as Li7La3Zr2O. 12 Li 7–x La3(Zr 2–x Nb x )O 12 (0≤x≤2) and Li5La3Nb2O 12 Perovskite solid electrolytes, such as (Li,La)TiO3, (Li,La)NbO3 and (Li,Sr)(Ta,Zr)O3; NASICON solid electrolytes Li(Al,Ti)(PO4)3 and Li(Al,Ga)(PO4)3; Li-PO solid electrolytes, such as Li3PO4 and LIPON (compounds in which a portion of the O in Li3PO4 is replaced by N); and Li-BO solid electrolytes, such as Li3BO3 and compounds in which a portion of the O in Li3BO3 is replaced by C.

[0067] The content of solid electrolyte in the electrode mixture is not particularly limited and can be appropriately set considering desired ionic conductivity, etc.

[0068] Conductive additives

[0069] Conductive additives can be, for example, carbon materials, metal particles, or combinations thereof. Examples of carbon materials include non-fibrous carbon, such as acetylene black (AB) and Ketjen black (KB); fibrous carbon, such as vapor-grown carbon fibers (VGCF), carbon nanotubes (CNT), and carbon nanofibers (CNF); and combinations thereof. Examples of metal particles include nickel, copper, iron, stainless steel, and combinations thereof.

[0070] The content of conductive additives in the electrode mixture is not particularly limited and can be appropriately set considering desired conductivity properties, etc.

[0071] adhesives

[0072] The adhesive may be, for example, a rubber-based adhesive, such as butadiene rubber, hydrogenated butadiene rubber, styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, acrylate butadiene rubber (ABR), or ethylene propylene rubber; a fluoride-based adhesive, such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, or fluororubber; a polyolefin-based thermoplastic resin, such as polyethylene, polypropylene, or polystyrene; an imide-based resin, such as polyimide or polyamide-imide; an amide-based resin, such as polyamide; an acrylic resin, such as polymethyl acrylate or polyethyl acrylate; a methacrylic resin, such as polymethyl methacrylate or polyethyl methacrylate; or a combination thereof.

[0073] The amount of binder in the electrode mixture is not particularly limited and can be appropriately set considering desired adhesion, etc.

[0074] Other ingredients

[0075] The electrode mixture may further include or exclude components other than those mentioned above.

[0076] Battery

[0077] The battery disclosed herein includes an electrode active material layer, and the electrode active material layer includes the electrode mixture of the present disclosure. The battery disclosed herein may sequentially include 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 case, the electrode active material layer containing the electrode mixture of the present disclosure may be a negative electrode active material layer or a positive electrode active material layer, and may particularly be a negative electrode active material layer.

[0078] The battery disclosed herein can be a liquid battery or a solid-state battery, and particularly a solid-state battery. In this disclosure, a "solid-state battery" means a battery that contains at least a solid electrolyte as an electrolyte. Therefore, a solid-state battery can use a combination of solid and liquid electrolytes as electrolytes. The battery can also be an all-solid-state battery that contains only a solid electrolyte as an electrolyte.

[0079] The battery disclosed herein can be a primary battery or a secondary battery, and in particular a lithium-ion secondary battery.

[0080] The battery disclosed herein can be constrained from both sides of the stacking direction of the aforementioned layers by constraint members such as end plates. Examples of constraint methods include, but are not limited to, using the clamping torque of bolts.

[0081] The components of the battery disclosed herein will now be described. The following description illustrates a case where the electrode active material layer of the electrode mixture comprising this disclosure is a negative electrode active material layer.

[0082] Negative current collector layer

[0083] The negative electrode current collector layer can be in the form of foil, plate, mesh, stamped metal, or foam. Specifically, it can be metal foil, metal mesh, or carbon sheet, and particularly metal foil. The negative electrode current collector layer can be formed from multiple foils or sheets.

[0084] The metal forming the negative electrode current collector layer is not particularly limited and can be, for example, copper, nickel, chromium, gold, platinum, silver, aluminum, iron, titanium, zinc, cobalt, or stainless steel. In particular, the negative electrode current collector layer may contain at least one selected from copper, nickel, and stainless steel.

[0085] For purposes such as resistance adjustment, a coating may be formed on the surface of the negative electrode current collector layer. The negative electrode current collector layer may be a metal foil or substrate plated or vapor-deposited with any of the aforementioned metals. When the negative electrode current collector layer is formed of multiple metal foils, a layer may be further included between these metal foils.

[0086] The thickness of the negative electrode current collector layer is not particularly limited, and can be, for example, 0.1 μm or more, or 1 μm or more, or less than 1 mm, or less than 100 μm.

[0087] Negative electrode active material layer

[0088] The negative electrode active material layer comprises the electrode mixture of this disclosure. Reference can be made to the above description regarding the electrode mixture of this disclosure. The negative electrode active material layer can be formed by molding the electrode mixture of this disclosure itself into a layer.

[0089] The thickness of the negative electrode active material layer is not particularly limited, and can be, for example, greater than 0.1 μm and less than 1000 μm.

[0090] solid electrolyte layer

[0091] The solid electrolyte layer contains at least solid electrolyte particles and may optionally further contain adhesives, etc.

[0092] For information on solid electrolyte particles and binders, please refer to the above description.

[0093] The thickness of the solid electrolyte layer is not particularly limited and can be, for example, greater than 0.1 μm and less than 1000 μm.

[0094] Positive electrode active material layer

[0095] The positive electrode active material layer contains at least a positive electrode active material, and may optionally further contain a solid electrolyte, conductive additives, binders, etc.

[0096] The positive electrode active material is not particularly limited and can be, for example, an oxide active material. Oxide active materials used in lithium-ion batteries can be, for example, LiCoO2, LiMnO2, Li2NiMn3O8, LiVO2, LiCrO2, LiFePO4, LiCoPO4, LiNiO2, or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2. A coating containing Li ion-conducting oxides (such as LiNbO3) can be formed on the surface of these active materials.

[0097] The content of the positive electrode active material in the positive electrode active material layer is not particularly limited.

[0098] For information on solid electrolytes, conductive additives, and binders, please refer to the descriptions above.

[0099] The thickness of the positive electrode active material layer is not particularly limited, and can be, for example, greater than 0.1 μm and less than 1000 μm.

[0100] Positive current collector layer

[0101] The positive electrode current collector layer can be in the form of foil, plate, mesh, stamped metal, or foam. The positive electrode current collector layer can be a metal foil or a metal mesh, and particularly a metal foil. The positive electrode current collector layer can be formed from multiple foils.

[0102] The metal forming the positive current collector layer is not particularly limited and can be, for example, copper, nickel, chromium, gold, platinum, silver, aluminum, iron, titanium, zinc, cobalt, or stainless steel. In particular, the positive current collector layer may contain aluminum.

[0103] For purposes such as resistance adjustment, a coating may be formed on the surface of the positive current collector layer. The positive current collector layer may be a metal foil or substrate plated or vapor-deposited with any of the aforementioned metals. When the positive current collector layer is formed of multiple metal foils, a layer may be further included between these metal foils.

[0104] The thickness of the positive electrode current collector layer is not particularly limited, and can be, for example, greater than 0.1 μm or greater than 1 μm, or less than 1 mm or less than 100 μm.

[0105] Other components

[0106] The aforementioned components of the battery can be housed in a casing. The casing can be any conventionally known battery casing. Multiple batteries can be electrically connected and / or stacked as needed to form a battery pack. In this case, the battery pack can be housed within a known battery casing. The battery may also contain other obvious components, such as necessary terminals. The battery can be, for example, coin-shaped, laminated (bag-shaped), cylindrical, or square.

[0107] The method of manufacturing the battery disclosed herein is not particularly limited and may include, for example, forming an electrode active material layer comprising an electrode mixture of the present disclosure.

[0108] For example, the electrode active material layer containing the electrode mixture can be formed by mixing constituent materials such as electrode active material composite particles to obtain the electrode mixture, and then forming the obtained electrode mixture into a layer by dry or wet forming.

[0109] The battery manufacturing method disclosed herein may further include sequentially stacking a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer to form an electrode stack.

[0110] Other components, such as terminals, can be attached to the electrode stack as needed. The battery is obtained by housing the electrode stack within a battery case and sealing it.

[0111] Example

[0112] Synthesis of composite particles for electrode active materials

[0113] Three alumina boats containing porous carbon material were placed in a tube furnace. The amount of porous carbon material was 0.2 g / boat. The tube furnace was purged with argon (Ar) at room temperature at a flow rate of 1 L / min. The Ar flow rate was then reduced to 100 mL / min, and the temperature inside the tube furnace was raised to 700 °C. Subsequently, the Ar line was switched from the tube furnace to a container containing tetrachlorosilane (TCS), and Ar was bubbled through the TCS, with the resulting Ar containing TCS vapor introduced into the tube furnace. Simultaneously, hydrogen was introduced into the tube furnace at a flow rate of 10 mL / min. After 1 hour, the introduction of Ar containing TCS and hydrogen was stopped. As a result, TCS decomposed on the porous carbon material, producing spherical silicon particles. Thus, electrode active material composite particles containing porous carbon material and spherical silicon particles retained within the porous carbon material were obtained. Subsequently, only Ar was introduced into the tube furnace, which was then cooled to room temperature, and the obtained electrode active material composite particles were collected.

[0114] Cross-sectional observation of spherical silicon particles

[0115] Electrode active material composite particles were mixed with zinc powder, and the mixture was shaped into granules using a press. Samples were then prepared by processing the granules using a cross-section polishing machine, and cross-sectional SEM images of the samples were obtained.

[0116] The obtained cross-sectional SEM images are shown in Figure 1 In the middle. For example Figure 1As shown, the silicon particles in the electrode active material composite particles of the embodiment are spherical. This is the same for the electrode active material composite particles obtained from each of the three alumina boats.

[0117] These spherical silicon particles expand and contract isotropically. This indicates that, compared to non-spherical silicon particles, the pores more effectively mitigate the effects of the expansion and contraction of spherical silicon particles, thereby suppressing changes in battery volume.

[0118] Obtain hole size distribution

[0119] For the electrode active material composite particles of the embodiment and the porous carbon material as a reference, N2 adsorption isotherms were measured, and the cumulative pore size distribution and differential pore size distribution were obtained by the Barrett-Joyner-Halenda (BJH) method. In the BJH method measurements, a BELSORP MAX X specific surface area and pore size distribution analyzer manufactured by Microtrac was used. The obtained cumulative pore size distribution and differential pore size distribution are shown in [data missing]. Figure 2 and 3 The pore volume was determined from the obtained pore size distribution. The results are shown in Table 1. Figure 2 and 3 In Table 1, “upstream,” “midstream,” and “downstream” refer to the positions of the three alumina boats relative to the Ar flow containing TCS vapor.

[0120] Table 1

[0121] Comparative example

[0122] The comparative example electrode active material composite particles were obtained in the same manner as in the examples, except that monosilane gas was introduced into the tube furnace instead of Ar containing TCS vapor. Cross-sectional SEM images were then obtained.

[0123] The obtained cross-sectional SEM images are shown in Figure 4 In the middle. For example Figure 4 As shown, in the comparative example of electrode active material composite particles, the silicon particles are so fine that their shape cannot be observed and their average particle size cannot be determined.

Claims

1. A composite particle of electrode active material, comprising: Porous carbon materials; and Spherical silicon particles retained within the porous carbon material. The electrode active material composite particles described therein have pores.

2. The electrode active material composite particles according to claim 1, wherein the spherical silicon particles have an average particle size of 0.1 μm or more and 1.0 μm or less.

3. An electrode mixture comprising the electrode active material composite particles according to claim 1 or 2.

4. A battery comprising an electrode active material layer, wherein the electrode active material layer comprises the electrode mixture according to claim 3.

5. A method for manufacturing electrode active material composite particles according to claim 1 or 2, the method comprising producing the spherical silicon particles by decomposing a silane halide on the porous carbon material.

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