Support structure for lithium ion battery negative electrode material, method for producing said support structure, lithium ion battery negative electrode material including said support structure, method for producing said lithium ion battery negative electrode material, negative electrode, and lithium ion battery provided with said negative electrode

Abstract

A support structure for a lithium ion battery negative electrode material according to the present invention comprises: a three-dimensional reaction layer formed by three-dimensionally arranging one or a plurality of reaction layers comprising carbon; a plurality of conduction holes formed in the reaction layers; and a pocket, which is a space formed inside the three-dimensional reaction layer. The pocket is divided into a plurality of sections by a defining wall comprising one or a plurality of reaction layers, and serves as a skeleton in which silicon is disposed. The space section index, which is obtained by dividing the specific surface area by the total pore volume, may be 260 or more, the specific surface area being obtained by nitrogen adsorption / desorption.

Description

Support structure for lithium ion battery negative electrode material, method for manufacturing the same, lithium ion battery negative electrode material including the support structure, method for manufacturing the same, negative electrode, and lithium ion battery including the same

[0001] The present invention relates to a support structure for a lithium-ion battery anode material and a method for manufacturing the same, a lithium-ion battery anode material including a support structure for a lithium-ion battery anode material and a method for manufacturing the same, a negative electrode including the lithium-ion battery anode material, and a lithium-ion battery including the negative electrode.

[0002] Since its birth, lithium-ion batteries have been widely used in a wide range of applications, including smartphones and electric vehicles (EVs). As a result, there has been a cost competition in the manufacture of lithium-ion batteries, and the demand for higher performance continues in the market. In order to protect the global environment, carbon dioxide (CO ２ ) In order for low-emission electric vehicles to replace gasoline-powered vehicles, one of the necessary conditions is to increase the driving range of EVs.

[0003] From the viewpoint of the characteristics of lithium ion batteries, there is a demand for higher capacity lithium ion batteries. Patent Document 1 discloses a nonaqueous electrolyte secondary battery in which the support for the negative electrode active material (lithium) is made of single crystal silicon, in order to address the problem that a negative electrode current collector using lead or a lead alloy has a small capacity per weight.

[0004] Lithium-ion batteries can be made to have a high capacity by controlling the amount of lithium ions contained in the positive electrode material incorporated into the battery during manufacturing. To achieve this, it is necessary to develop a high-capacity negative electrode that can receive lithium ions from the positive electrode without causing an overcharge, and to ensure the reversibility of charge and discharge of the positive and negative electrode materials that repeatedly exchange that amount of lithium ions (see, for example, Patent Document 2 and Non-Patent Document 1).

[0005] JP-A-5-74463 JP-A-7-29602

[0006] Journal of the Electrochemical Society, 157(4), A392-A398, 2010

[0007] Regarding negative electrode materials, graphite-based materials composed of carbon are widely used from the viewpoints of stable supply as an industrial product, cost, and quality. However, it is clear that the commonly used graphite-based materials have reached their theoretical limit in terms of the demand for higher capacity mentioned above.

[0008] As an alternative to graphite-based materials, anode materials containing silicon or tin, which utilize electrochemical lithium alloying reactions, have been introduced to the market. Anode materials containing silicon or tin have a particularly high lithium content, are low-toxicity, and are readily available. However, due to manufacturing costs and insufficient performance, their product lifespans have not been long. Silicon-based materials, which are becoming increasingly popular worldwide for various applications such as semiconductor materials and silicone resins, have undergone various improvements as lithium alloy materials, but have not yet reached the level of graphite-based materials in terms of practicality.

[0009] In the lithium alloying reaction, silicon and lithium bond together as electrons are exchanged, and the bonded phase spreads throughout the particles, expanding the crystal lattice and causing volume expansion, which is one of the reasons why the charge-discharge reversibility of lithium-ion batteries is hindered.

[0010] In graphite-based anode materials, when lithium ions are initially stored between the carbon layers, inert reactants formed during electrochemical reactions between electrolyte components and lithium, etc., are deposited on the surface of the carbon layers, preventing potential side reactions during subsequent lithium ion insertion and desorption. Although a similar phenomenon occurs when silicon-based materials are used, repeated volume changes repeatedly expose new reaction interfaces that are not covered by inert reactants. As a result, lithium ions are consumed in repeated side reactions, and the battery capacity decreases with each cycle. Therefore, while lithium-ion batteries using silicon-based materials can be designed to have a higher initial capacity than those using graphite-based materials, their charge / discharge capabilities have not yet reached a practical level.

[0011] To avoid the volume change, which is a major degradation mechanism mentioned above, and the associated adverse effects, nanoparticle silicon and particle surface coating have been reported (Cui, L.F.; Ruffo, R.; Chan, C.K.; Peng, H.L.; Cui, Y., Nano Letters 2009, 9, 491).

[0012] In particular, thick carbon coatings, obtained by heat-treating and carbonizing high-molecular-weight polymers, prevent electrolyte penetration. Furthermore, as the carbon coating becomes thicker, it becomes brittle, leading to increased cracking caused by expansion during charging, leading to rapid deterioration. This prevents the initial charge-discharge reaction from proceeding sufficiently, resulting in a decrease in battery capacity and a deterioration in cycle life.

[0013] The present invention has been made in view of the above circumstances, and aims to provide a silicon-based support structure for a lithium-ion battery anode material having high capacity and high charge / discharge reversibility, a method for manufacturing the same, a lithium-ion battery anode material including a support structure for a lithium-ion battery anode material and a method for manufacturing the same, a negative electrode including the lithium-ion battery anode material, and a lithium-ion battery including the negative electrode.

[0014] In order to solve the above problems, the support structure for a lithium ion battery anode material and its manufacturing method, the lithium ion battery anode material including the support structure for a lithium ion battery anode material and its manufacturing method, the anode including the lithium ion battery anode material, and the lithium ion battery including the anode of the present invention employ the following means.

[0015] A first aspect of the present invention provides a support structure for a lithium-ion battery negative electrode material, which serves as a skeleton on which silicon is arranged, and which comprises a three-dimensional reaction layer formed by three-dimensionally arranging one or more reaction layers made of carbon, a plurality of conductive holes formed in the reaction layer, and a pocket which is a space formed inside the three-dimensional reaction layer, and the pocket is divided into a plurality of compartments by partition walls made of one or more of the reaction layers.

[0016] A second aspect of the present invention provides a support structure for a lithium ion battery negative electrode material, which serves as a skeleton on which silicon is arranged, the support structure comprising a three-dimensional reaction layer formed by three-dimensionally arranging one or more reaction layers made of carbon, a plurality of conductive holes formed in the reaction layer, and pockets which are spaces formed inside the three-dimensional reaction layer, and which has a spatial partition index of 260 or more, obtained by dividing the specific surface area determined by a nitrogen adsorption / desorption method by the total pore volume.

[0017] In the above aspect, a plurality of introducing holes may be arranged to allow gas or liquid to communicate from the outside of the support structure to the inside of the pocket, or from the inside of the pocket to the outside of the support structure.

[0018] In the above aspect, the reaction layer may include a carbon meso-sponge or a graphene meso-sponge.

[0019] In the above aspect, the thickness of the reaction layer may be 0.3 nm or more.

[0020] In the above embodiment, the total pore volume measured by nitrogen adsorption / desorption method may be 0.7 cc / g or more.

[0021] In the above embodiment, the introducing pores may be comprised of micropores, mesopores, and macropores, and the ratio of the volume of mesopores to the total pore volume measured by a nitrogen adsorption / desorption method may be 60% or more, and the ratio of the volume of micropores to the total pore volume may be greater than the ratio of the volume of macropores to the total pore volume.

[0022] In the above-mentioned embodiment, the introducing pores may be comprised of micropores, mesopores, and macropores, and the ratio of the volume of macropores to the ratio of the volume of micropores to the total pore volume (micropore ratio / macropore ratio) may be 0.26 or more and 40 or less in the total pore volume measured by a nitrogen adsorption / desorption method.

[0023] In the above embodiment, the ratio of the total volume of the through-holes having a pore size of 5 nm to 15 nm, as measured by nitrogen adsorption / desorption, to the total pore volume may be 50% or more.

[0024] In the above embodiment, the mode pore diameter measured by nitrogen adsorption / desorption method may be 1 nm to 70 nm.

[0025] In the above embodiment, the specific surface area is 400 m ２ / g or more 2600m ２ / g or less.

[0026] In a third aspect of the present invention, there is provided a method for manufacturing a support structure for a lithium-ion battery anode material, which serves as a skeleton in which silicon is arranged, and which comprises a three-dimensional reaction layer formed by three-dimensionally arranging one or more reaction layers made of carbon, a plurality of conductive holes formed in the reaction layer, and pockets that are spaces formed inside the three-dimensional reaction layer. The method includes the steps of: placing ceramic particles that serve as a template for the reaction layer, the ceramic particles including at least connected-shaped particles, in a reaction vessel; circulating an organic hydrocarbon compound through the reaction vessel and using a chemical vapor deposition (CVD) method to coat the surfaces of the ceramic particles with a thermal decomposition product of the organic hydrocarbon, thereby forming a reaction layer having a plurality of conductive holes; dissolving the ceramic particles having the reaction layer formed on their surfaces with an acid; discharging, washing, and drying the dissolved product of the ceramic particles; forming a support structure precursor having spaces therein; and heat-treating the support structure precursor to obtain the support structure.

[0027] In the above embodiment, the ceramic particles may contain pores therein.

[0028] The above embodiment may include a step of mechanically cohesively shaping the support structure for the negative electrode material.

[0029] In the above-described aspect, the aggregation and shaping step may include a process of reducing the diameter of the introducing holes.

[0030] In the above embodiment, the drying may be performed by heating at a temperature of room temperature or higher and 250°C or lower.

[0031] A fourth aspect of the present invention provides a lithium ion battery negative electrode material comprising: a support structure for a lithium ion battery negative electrode material that serves as a skeleton in which silicon is disposed; the support structure comprising: a three-dimensional reaction layer formed by three-dimensionally arranging one or more reaction layers made of carbon; a plurality of conductive holes formed in the reaction layer; and a pocket that is a space formed inside the three-dimensional reaction layer, the pocket being divided into a plurality of compartments by partition walls made of one or more of the reaction layers; and a particulate silicon compound disposed inside the pocket, wherein voids are provided in at least a portion of the pocket between the particulate silicon compound and the reaction layer, and the lithium ion battery negative electrode material contains the silicon particles in at least one or more of the plurality of compartments in the pocket.

[0032] In the above-described embodiment, when the particulate silicon compound in the pocket undergoes an alloying reaction with lithium ions, of the first reaction in which lithium ions that have been conducted on the surface or inside of the reaction layer reach the silicon particles in the pocket and alloy them, and the second reaction in which lithium ions contained in the electrolyte that has penetrated into the voids in the pocket via the conductive holes reach the particulate silicon compound in the pocket and alloy them, the second reaction may occur first, or the first reaction and the second reaction may occur in parallel.

[0033] In the above aspect, an outer protective layer made of a reactive layer may be provided on at least a portion of the outermost surface of the support structure.

[0034] In the above aspect, silicon may be disposed between the outermost surface of the support structure and the outer protective layer, and a gap layer may be present at least partially between the outer protective layer and the silicon.

[0035] In the above embodiment, the outer protective layer may have one or more through holes.

[0036] In the above embodiment, the pore closure index, which is the reciprocal of the total pore volume determined by the nitrogen adsorption / desorption method and the density determined by the butanol substitution method, may be 0.6 or more.

[0037] In the above embodiment, the pore closure index, which is the reciprocal of the total pore volume determined by the nitrogen adsorption / desorption method and the density determined by the butanol substitution method, may be less than 0.6.

[0038] In the above embodiment, the total volume of the introducing pores having a diameter of 1.0 nm or more may be 50% or more of the total pore volume.

[0039] In the above embodiment, the particulate silicon compound may include any one of silicon monoxide, silicon dioxide, and silicon dioxide trioxide.

[0040] A fifth aspect of the present invention provides a method for producing a lithium ion battery negative electrode material according to the fourth aspect, comprising the steps of: placing the support structure for a lithium ion battery negative electrode material according to the first aspect in a reaction vessel; and flowing a silicon-containing compound through the reaction vessel at 300°C to 900°C to deposit silicon on at least one of the outer surface of the support structure and an internal pocket of the three-dimensional reaction layer by a CVD method, wherein the silicon-containing compound is introduced into the pocket via a conductive hole.

[0041] In the above-described embodiment, after the step of disposing the support structure for a lithium-ion battery negative electrode material, the method further includes the steps of evacuating the inside of the reaction vessel to create a vacuum state and raising the temperature to a temperature at which a CVD reaction is performed, and CVD may be performed after introducing a mixed gas in which gaseous silane is diluted with an inert gas into the reaction vessel that has been placed in a vacuum state.

[0042] In the above aspect, a step of forming an oxide layer by heating and oxidizing the surface of the silicon deposited on at least one of the outer surface of the support structure and the pocket inside the three-dimensional reaction layer using an oxidizing agent may be included.

[0043] In the above aspect, after the step of forming the oxide layer, one or more types of gaseous organic molecules serving as a carbon source may be introduced into the reaction vessel, and the gaseous organic molecules may be thermally decomposed at 400°C or higher. Carbon contained in the thermally decomposed gaseous organic molecules may be deposited on the surface of the deposited silicon-containing anode material, thereby forming an external protective layer made of a reaction layer on at least a part of the outermost surface of the anode material.

[0044] In the above-described aspect, the gaseous organic molecules are molecules produced by volatilization or thermal decomposition at a high temperature of at least one selected from organic substances or polymers that are gaseous, solid, or liquid at room temperature, and the gaseous organic molecules may be one or more selected from hydrocarbons such as methane, ethane, propane, butane, acetylene, ethylene, propylene, and butene, benzene, toluene, naphthalene, biphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride, hexafluoroisopropylidenedianiline or its anhydride, benzophenonetetracarboxylic dianhydride, oxydiphthalic dianhydride, pyromellitic dianhydride, bisphenol A dianihydride, and cyclohexanetetracarboxylic dianhydride.

[0045] In the above aspect, after the external protective layer is formed, a process may be performed in which an oxide layer on the silicon surface deposited on the outer surface of the support structure is dissolved with acid, and the dissolved product of the oxide layer is discharged and washed away, thereby forming an air gap layer at least in a portion between the external protective layer and the silicon deposited on the outer surface of the support structure.

[0046] In a sixth aspect of the present invention, there is provided a method for producing a lithium-ion battery negative electrode material according to the fourth aspect, comprising the steps of: placing silicon particles having an oxide film on their surfaces in a reaction vessel; heating the reaction vessel and introducing a source gas containing carbon into the reaction vessel; disposing a product of thermal decomposition of the source gas at 400°C or higher on the surfaces of the silicon particles by a CVD method to form a three-dimensional reaction layer composed of reaction layers made of carbon and having a plurality of through holes arranged three-dimensionally; removing the oxide film on the surfaces of the silicon particles by an acid treatment; and cleaning the silicon particles from which the oxide film has been removed and the reaction layer, wherein in the step of removing the oxide film, voids are formed in pockets formed inside the three-dimensional reaction layer, at least in part between the silicon particles and the three-dimensional reaction layer.

[0047] A seventh aspect of the present invention is a method for producing a lithium ion battery negative electrode material according to the fourth aspect, comprising the steps of: placing silicon particles having an oxide film on their surfaces in a reaction vessel; heating the reaction vessel and introducing a source gas containing carbon into the reaction vessel; disposing a product of thermal decomposition of the source gas at 400°C or higher on the surface of the silicon particles by a CVD method to form a three-dimensional reaction layer in which reaction layers made of carbon and having a plurality of through holes are arranged three-dimensionally; evacuating the reaction vessel to create a vacuum state and raising the temperature to a temperature at which a CVD reaction is performed; and introducing a mixed gas obtained by diluting gaseous silane with an inert gas into the evacuated reaction vessel. and forming an external protective layer made of a reaction layer on at least a portion of the surface of the silicon by introducing one or more types of gaseous organic molecules that serve as a carbon source into a reaction vessel and thermally decomposing the gaseous organic molecules at 400°C or higher, and depositing carbon contained in the thermally decomposed gaseous organic molecules on the surface of the deposited silicon. The present invention provides a method for producing an anode material for a lithium ion battery, the method comprising the steps of: performing CVD on a silicon substrate; introducing one or more types of gaseous organic molecules that serve as a carbon source into a reaction vessel and thermally decomposing the gaseous organic molecules at 400°C or higher, and depositing carbon contained in the thermally decomposed gaseous organic molecules on the surface of the deposited silicon, thereby forming an external protective layer made of a reaction layer on at least a portion of the surface of the silicon; and dissolving an oxide layer on the surface of the silicon with an acid, wherein the dissolved product of the oxide layer is discharged and washed, and a void layer is formed at least in part between the external protective layer and the silicon deposited on the outermost surface of the three-dimensional layer.

[0048] An eighth aspect of the present invention provides a lithium ion battery negative electrode, comprising a support structure for a lithium ion battery negative electrode material according to the first aspect.

[0049] A ninth aspect of the present invention provides a lithium ion battery negative electrode comprising the lithium ion battery negative electrode material according to the fourth aspect.

[0050] A tenth aspect of the present invention provides a lithium ion battery comprising the lithium ion battery negative electrode according to the eighth aspect.

[0051] The negative electrode material according to the present invention allows lithium ions contained in the electrolyte to efficiently reach the surfaces of silicon particles, thereby providing a negative electrode material for lithium ion batteries with high capacity and high reversibility in charge and discharge.

[0052] FIG. 1B is an image of a unit particle that is a part of the configuration of the negative electrode material according to an embodiment of the present invention. FIG. 1C is an image illustrating a pocket in an example of a negative electrode material according to an embodiment of the present invention. FIG. 1D is an image illustrating a pocket in another example of a negative electrode material according to an embodiment of the present invention. FIG. 1E is an image illustrating an example of a support structure for a negative electrode material according to an embodiment of the present invention, and is a SEM image of the support structure obtained in Example 6. FIG. 1F is an image illustrating an example of a support structure for a negative electrode material according to an embodiment of the present invention, and is a partial enlarged view of FIG. 1D. FIG. 1G is an image illustrating an example of a support structure for a negative electrode material according to an embodiment of the present invention, and is a TEM image of the support structure obtained in Example 6. FIG. 1G is an image illustrating an example of a support structure for a negative electrode material according to an embodiment of the present invention, and is a partial enlarged view of FIG. 1D. FIG. 1H is an image illustrating an example of a support structure for a negative electrode material according to an embodiment of the present invention, and is a TEM image of the support structure obtained in Example 6. FIG. 1 is an image diagram for explaining a part of the manufacturing process of another example of a negative electrode material according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of the deposition form of silicon on the support structure of the present invention. FIG. 3 is a TEM image of a lithium ion battery negative electrode material according to an embodiment of the present invention. FIG. 4 is a diagram showing an outline of the manufacturing process of an example of a support structure according to an embodiment of the present invention. FIG. 5 is a diagram showing an outline of the manufacturing process of another example of a support structure according to an embodiment of the present invention. FIG. 6 is a diagram showing an image of an intermediate stage of the manufacturing process of an example of a lithium ion battery negative electrode material according to an embodiment of the present invention, showing a state in which the exterior of the silicon deposited on the surface has been oxidized. FIG. 7 is a diagram showing an image of an intermediate stage of the manufacturing process of an example of a lithium ion battery negative electrode material according to an embodiment of the present invention, showing a state in which an external protective layer has been formed on the surface of the silicon deposited on the surface.FIG. 1 is an image of an example in which silane CVD is performed on a support structure obtained from a linked mold, and silicon is filled so as to fill the inside of the pockets. FIG. 2 is an image of an example of a manufacturing process of an example of a lithium ion battery negative electrode material according to an embodiment of the present invention, showing a state in which a void layer has been formed by removing the silicon oxide layer inside the outer protective layer. FIG. 3 is a schematic diagram showing only a Gay-lussac pycnometer used in measuring the permeability of an electrolyte according to an embodiment of the present invention. FIG. 4 is a schematic diagram showing a state in which a Gay-lussac pycnometer used in measuring the permeability of an electrolyte according to an embodiment of the present invention is filled with PC. FIG. 5 is a schematic diagram showing a state in which a sample is contained in a Gay-lussac pycnometer used in measuring the permeability of an electrolyte according to an embodiment of the present invention. FIG. 6 is a schematic diagram showing a state in which a Gay-lussac pycnometer used in measuring the permeability of an electrolyte according to an embodiment of the present invention is filled with PC and contains a sample. FIG. 7 is a diagram showing an example of the cross-sectional structure of a lithium ion battery according to an embodiment of the present invention. FIG. 8 is a TEM image of a lithium ion battery negative electrode material according to a comparative example. FIG. 9 is a diagram showing a nitrogen adsorption / desorption curve obtained by measuring the void volume of a lithium ion battery negative electrode material according to an example. FIG. 1 is a diagram showing the distribution of electrolyte conducting pore diameters obtained by measuring the electrolyte conducting pore diameters of a lithium ion battery negative electrode material according to one example. FIG. 2 is a diagram showing the relationship between total void volume and permeability in examples and comparative examples. FIG. 3 is a diagram showing the relationship between permeability and discharge capacity in examples and comparative examples. FIG. 4 is a diagram showing the relationship between specific surface area and total void volume in examples and comparative examples. FIG. 5 is a diagram showing the relationship between specific surface area and permeability in examples and comparative examples. FIG. 6 is a diagram showing the relationship between the ratio of the discharge capacity at the 10th cycle to the discharge capacity at the first cycle and the permeability in examples and comparative examples. FIG. 7 is a diagram showing the relationship between the micropore ratio / macropore ratio and the cycle capacity retention rate in examples and comparative examples. FIG. 8 is a diagram showing the relationship between the spatial compartment index and the cycle capacity retention rate in examples and comparative examples.

[0053] An embodiment of a lithium ion battery negative electrode material (hereinafter also referred to as "negative electrode material") according to the present invention will be described below with reference to the drawings. The lithium ion battery negative electrode material according to this embodiment will be described below. The lithium ion battery negative electrode material is one of the components that make up the negative electrode of a lithium ion battery. FIG. 1A is a diagram schematically showing a portion of a lithium ion battery negative electrode material 1 according to an embodiment of the present invention. FIG. 2 is an SEM image of the lithium ion battery negative electrode material according to one embodiment of the present invention, and FIG. 3 is an enlarged view of a portion of FIG. 2.

[0054] The lithium-ion battery negative electrode material 1 according to this embodiment has a unit structure in which silicon particles 5 are contained inside a shell formed by one or more carbon layers, as shown in FIG. 1A, or a structure in which a plurality of the unit structures of FIG. 1A are aggregated to form an aggregate, as shown in FIG. 2. The unit structure of the negative electrode material 1 shown in FIG. 1A is referred to as a "unit particle" in this specification. The unit particle of the negative electrode material 1 can also be formed as an aggregate structure in which a plurality of unit particles are aggregated or bonded, as shown in FIG. 2, by a manufacturing method described below. The silicon particles 5 function as an active material in the negative electrode material.

[0055] The unit particle shown in FIG. 1A has a three-dimensional shape in which multiple reaction layers 2 made of carbon are stacked to form a three-dimensional reaction layer 3. FIG. 1B shows the state before silicon is placed inside the unit particle. As shown in FIG. 1B, this three-dimensional reaction layer 3 forms a pocket 7 inside the unit particle. As shown in FIG. 1A, silicon (Si) particles 5 are placed inside the pocket 7 of the negative electrode material 1 to form the unit particle. The average particle size of the silicon particles 5 is approximately 10 nm to 100 nm, and preferably 30 nm to 70 nm.

[0056] Before silicon is placed in the pocket, the unit particles may exist singly as shown in Figure 1B, or may form an aggregate structure in which multiple particles are aggregated or bonded together as shown in Figure 1C, which is called a three-dimensional carbon layer structure. The three-dimensional carbon layer structure is also called a support structure for anode material 11 from the viewpoint of a structure that supports the silicon contained therein when used as a cathode material, and has an appearance as shown in Figures 1D to 1F. Hereinafter, the support structure for anode material will also be simply called a support structure.

[0057] The silicon particles 5 are not limited to spherical particles. Other than spherical particles, for example, they may be slightly flat or have an uneven surface, or may be in a shape in which a plurality of spherical particles are connected together like a string of beads. In this specification, the term "granular body" includes these shapes other than spherical particles.

[0058] A conductive hole 4 is provided on the reaction layer 2, connecting the pocket 7 present inside the three-dimensional reaction layer 3 with the outside of the three-dimensional reaction layer 3. Through this conductive hole, an electrolyte solution or gas is introduced into the three-dimensional reaction layer 3 or discharged from the inside of the three-dimensional reaction layer 3 to the outside. When the reaction layer 2 defining the pocket 7 inside the three-dimensional reaction layer 3, i.e., when a plurality of reaction layers 2 are stacked to form the three-dimensional reaction layer 3, and silicon is placed inside the pocket 7, a void 6 is provided between the innermost reaction layer 2 and the silicon particles 5. In this case, the electrolyte solution permeates the void 6 via the conductive hole 4 and reaches the surfaces of the silicon particles 5 placed in the pocket 7 inside the three-dimensional reaction layer 3. The conductive hole 4 through which the electrolyte solution is conducted is also referred to as an electrolyte conductive hole.

[0059] 1B and 1C, the reaction layer 2 may be provided with a plurality of conductive holes 4. Therefore, in the support structure 11 for a negative electrode material in a state before silicon is placed in the pocket, as shown by the dotted arrows in FIGS. 1G and 1H, gas can be introduced into the support structure through the conductive holes 4, and the gas can be discharged from the support structure to the outside through the same or different conductive holes 4. In other words, gas can pass through the inside of the support structure through the conductive holes 4.

[0060] During the production of the negative electrode material, the organic material serving as the carbon source undergoes thermal decomposition, and the resulting thermal decomposition products are deposited on the surfaces of the silicon particles 5, forming a carbon layer and the conductive holes 4. Organic materials that are gaseous at room temperature are easy to use. Among these, organic materials with double or more bonds are prone to thermal decomposition, and the bonds broken during decomposition tend to bond with other thermal decomposition products, making them prone to forming heterogeneous structures. By utilizing such bonding reactions, it is possible to create a carbon layer with structural defects, i.e., a reactive layer 2 with conductive holes 4.

[0061] The conductive holes 4 function effectively when their pore diameters have a distribution range of approximately 1.0 nm to 100 nm. The pore diameter of the conductive holes 4 is measured by the method described below. The pore diameters of less than 60 nm present in the three-dimensional reaction layer 3 containing the silicon particles 5 can be controlled by the method of carbon atom deposition during the formation of the carbon layer on the surface of the silicon particles 5. The pore diameter can be controlled by selecting various production conditions, such as the molecular weight of the organic material used as a raw material, the type of bond (single bond, double bond, or triple bond), the amount of organic material supplied, the pyrolysis temperature, and the heating rate. Furthermore, the deposition of carbon atoms can also be controlled by using a mixture of an organic compound having only single bonds (e.g., methane, ethane, propane, butane, etc.) and an organic compound having double or more bonds (e.g., acetylene, ethylene, propylene, butene, benzene, etc.), thereby enabling the formation of effective electrolyte conductive holes with a desirable pore diameter.

[0062] By providing the conductive holes 4 in the reaction layer 2, lithium ions contained in the electrolyte solution can reach the surfaces of the silicon particles 5 more efficiently than in a negative electrode material in which the conductive holes 4 are not provided in the reaction layer 2. This suppresses the increase in overvoltage during the alloying reaction, allowing the initial charging reaction to proceed smoothly.

[0063] As described above, a plurality of the introduction holes 4 may be provided in the reaction layer 2. The total volume of the introduction holes 4 having a diameter greater than 1.0 nm may account for 50% or more of the total pore volume. By making the diameter of the introduction holes 4 that account for 50% or more of the total pore volume greater than 1.0 nm, the electrolyte can penetrate into the pockets 7 in the negative electrode material and efficiently reach the silicon particles in the pockets 7, allowing the alloying reaction to proceed appropriately. The total volume of the introduction holes 4 having a diameter of 1.0 nm or more may be 60% or more, 70% or more, or 80% or more of the total volume of the introduction holes 4.

[0064] Depending on the manufacturing conditions, the negative electrode material of this embodiment may have a structure in which unit particles are independent, or may have an aggregate structure in which multiple unit particles are bonded together. The aggregate structure includes strong chemical bonds, such as carbon-carbon bonds, and weak bonds, such as electrostatic forces and van der Waals forces. In areas with weak bonds, the three-dimensional reaction layer forms an outer wall, and strictly speaking, the unit particles exist independently. On the other hand, in areas with strong bonds, multiple unit particles are integrated in a connected shape. In this connected structure, multiple three-dimensional reaction layers are adjacent to each other, and therefore pockets within the three-dimensional reaction layer are adjacent to each other via the three-dimensional reaction layer. In other words, when multiple unit particles integrated together are viewed as a single aggregate structure, the three-dimensional reaction layer exists as an inner wall between adjacent pockets. In this specification, these outer and inner walls are also referred to as "three-dimensional layer walls."

[0065] In this embodiment, as will be described later, the permeability is calculated when the electrolyte permeates the entire spatial volume, which includes the space surrounded by the outer walls of the three-dimensional reaction layers of adjacent unit particles and the voids between the three-dimensional reaction layers and the silicon particles. Strictly speaking, the electrolyte also permeates the voids inside each independent particle.

[0066] When determining the permeability of the electrolyte into the negative electrode material, the procedure is complicated due to the problem of moisture absorption, etc., because the electrolyte uses a special solvent. To address this problem, the permeability of the electrolyte can be easily determined by using propylene carbonate (PC) or butanol instead of the electrolyte. The details of the measurement method will be described later.

[0067] The total pore volume (total space volume) and the pore diameter of the introducing hole 4 can be determined by nitrogen adsorption / desorption under the condition of P / P0 = 0 to 0.99. The details of the measurement by nitrogen adsorption / desorption will be described later.

[0068] As will be described in detail later, the voids within the unit particles are formed by dissolving and removing the oxide layer formed on the surface of the silicon particles with acid. The ratio of the voids to the total volume of the unit particles is preferably 0.01 or more. When a portion of the silicon particle from which the oxide layer has been removed comes into contact with the electrolyte, a reaction begins at the contact point. Because a solid-state reaction occurs inside the silicon particles, the electrolyte can penetrate even the smallest voids, thereby increasing the reactivity of the battery.

[0069] When coating with an oxide layer is actively performed, an oxidizing agent is used and heated at a high temperature to obtain a suitable oxide layer on the surface of the silicon particles. Examples of the oxidizing agent include air, oxygen, ozone, nitric acid, sulfuric acid, hydrogen peroxide, peroxide, permanganates such as potassium permanganate, potassium nitrate, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, cerium ammonium nitrate, chromic acid, dichromate, CO, CO ２ , water vapor, NO ２ , S.O. ２ , PxOy, hydrobromic acid, hydroiodic acid, organic soluble strong acids such as p-toluenesulfonic acid, liquid organic strong acids such as methanesulfonic acid, and other organic strong acids can be suitably used.

[0070] Although the silicon oxide layer does not contribute to the anode reaction, even a small portion of the silicon particle surface that is not covered with the oxide layer can act as a starting point for the anode reaction. The unreacted oxide layer may remain in a solid state and serve to reinforce the silicon active material. In this case, the conditions for removing the oxide layer can be controlled to maintain a state in which maximum effect can be obtained. The conditions for removing the oxide layer can be controlled by the type of acid, concentration, temperature, time, etc.

[0071] The shape and form of the aggregate structure when it is formed reflect the shape and form of the silicon particles or silicon granules used. When independent silicon particles are used, independent unit particles are formed, and in this case, they take an independent form with at least an outer wall. When multiple silicon particles or silicon granules are used that are connected together, an aggregate structure is formed in which multiple unit particles are connected together. In this case, the size of the pockets inside the aggregate structure is larger than the size of the pockets per independent unit particle.

[0072] The reaction layer 2 is made of carbon. The reaction layer 2 may be a graphene sheet or a graphene meso sponge. The reaction layer 2 is formed during the production stage of the negative electrode material via the generation of a pyrolysis product of a carbon-containing raw material gas, which will be described later. When the graphene sheet, graphene meso sponge, or carbon meso sponge formed by the production method of this embodiment is formed to a small thickness, the formed reaction layer has appropriate flexibility.

[0073] The thickness of the reaction layer 2 is 0.3 nm to 9 nm, preferably 0.5 nm to 4 nm. Multiple reaction layers 2 may be arranged on one silicon particle 5. As an example, in the anode material 1 shown in FIG. 4, multiple reaction layers 2 are overlapped, with the thickness of the overlapping portions being 3 nm. If the reaction layer 2 is thicker than 9 nm, it becomes difficult for the electrolyte to penetrate. Even if the reaction layer 2 is formed, the thickness reduces the flexibility of the three-dimensional structure of the three-dimensional reaction layer. As a result, the anode material 1 becomes brittle and prone to cracking, which, when applied to a lithium-ion battery, results in a decrease in battery capacity and deterioration of cycle life.

[0074] When adjacent unit particles form an aggregate structure, the total spatial volume, which is the sum of the volume of the space surrounded by the outer walls of the three-dimensional reaction layers 3 of the adjacent unit particles and the volume of the voids 6 inside the unit particles, is preferably 0.43 mL / g or more and 0.80 mL / g or less per negative electrode material. By setting the total spatial volume to a value within this range, the permeation rate into the total spatial volume, including the spaces, voids 6, and conductive holes, can be 70% or more. A permeation rate of 70% or more allows lithium ions contained in the electrolyte to efficiently reach the surfaces of the silicon particles 5, allowing the initial charging reaction to proceed smoothly. This allows a good coating that suppresses side reactions to be uniformly formed on the surfaces of the silicon particles 5 at the beginning of the alloying reaction, thereby suppressing a decrease in charge / discharge efficiency. As a result, a discharge capacity of 2600 mAh / g or more can be ensured after 10 cycles. Strictly speaking, the total spatial volume also includes the volume of the gaps present between the multiple reaction layers 2.

[0075] In the negative electrode material according to this embodiment, it is also possible to measure the volume of the voids in the unit particles.

[0076] [Battery Reaction] In the anode reaction using the anode material according to this embodiment, electrons transferred from an external circuit reach the surface of silicon particles 12, where they combine with lithium ions to form a Li-Si reaction phase, producing an alloyed composition (Si-Lix). The Li-Si reaction phase then spreads within the particles, and the formation of the Li-Si reaction phase progresses up to the limit of chemical combination, i.e., before the lithium metal deposition potential. The Li-Si alloying reaction expands the crystal lattice, causing the volume of the silicon particles to expand, thereby charging the battery. Conversely, after the lithium ions are released, the volume of the silicon particles shrinks, causing the battery to discharge.

[0077] An illustration of the battery reaction is shown in Figure 5. When charged, the silicon 12 in the pocket becomes a Si-Li compound, and the crystallites expand, increasing its volume. The three-dimensional reaction layer may be destroyed during the battery reaction depending on the strength of its structure. On the other hand, if the three-dimensional reaction layer is highly flexible and resistant to destruction, the expansion will not resemble the shape before charging, and if there is space, the microcrystals will expand as units. When discharging, the silicon returns to Si from areas that are easy to discharge, but the expanded and expanded shape remains almost unchanged.

[0078] In the initial stage of the formation of the Li-Si reaction phase in the alloying reaction, inert reactants consisting of electrolyte components and lithium, etc., are deposited on the surfaces of the silicon particles, forming a film. As the volume of the silicon particles changes due to repeated charging and discharging, the surface condition of the silicon particles changes, and new reaction interfaces that are not covered by inert reactants are repeatedly exposed.

[0079] On the exposed reaction interface, new inactive reactants (e.g., side reaction product 16 in FIG. 5) are deposited by the side reactions, and lithium ions are consumed in the side reactions, so the reversible lithium capacity in the battery system decreases. This decrease leads to a decrease in the battery capacity.

[0080] During the battery reaction, inactive reactants produced by the electrochemical reaction between lithium in the electrolyte and silicon particles 5 are deposited on the surfaces of the silicon particles 5, forming a coating on the surfaces of the silicon particles 5. The negative electrode material according to this embodiment is configured to have an electrolyte permeability of 70% or more. This allows lithium ions contained in the electrolyte to efficiently reach the surfaces of the silicon particles 5, allowing the initial charging reaction to proceed smoothly. This allows a good coating that suppresses side reactions to be uniformly formed on the silicon surface at the beginning of the alloying reaction, thereby preventing a decrease in charge / discharge efficiency. The presence of this good coating shortens the initial charging time during operation as a battery, improving productivity and contributing to reduced manufacturing costs.

[0081] On the other hand, depending on the charging rate, the film formed by the side reaction may become relatively thick, increasing the reaction resistance and thereby deteriorating the rate characteristics.

[0082] In contrast, the above problem can be solved by reducing the total volume of space through which the electrolyte permeates and lowering the electrolyte permeation rate. In this case, the initial charging time of the battery is extended and manufacturing productivity is reduced, but the film formed by side reactions becomes thinner. This improves rate characteristics and makes the battery suitable for applications requiring high performance.

[0083] The electrolyte permeability depends on the proportion of pore spaces (closed pores) within the negative electrode material that cannot be penetrated by the electrolyte. The proportion of closed pores can be calculated by replacing it with the proportion of spaces that cannot be penetrated by organic solvents such as butanol, and this can be conveniently expressed as the reciprocal of the butanol density measured by liquid displacement. This value is defined as the closed pore index. In other words, the larger the proportion of closed pores, the more difficult it is for the electrolyte to penetrate; therefore, it is synonymous with an index of the ease of electrolyte penetration into all pores. For example, the desired closed pore index can be achieved by applying a protective coating (external protective layer) composed mainly of carbonaceous materials to the outermost surface of the negative electrode material after silicon placement, adjusting the coating ratio, etc.

[0084] When the pore closure index of the negative electrode material is less than 0.6, the charge rate index increases and charging productivity improves. Furthermore, when the pore closure index exceeds 0.6, cycle life improves. When aiming for improved productivity, the pore closure index is preferably 0.44 or more but less than 0.6, and when aiming for long life, the pore closure index is preferably 0.6 or more but less than 0.99.

[0085] The negative electrode material of this embodiment is configured such that, when silicon particles 5 arranged in pockets within the three-dimensional reaction layer 3 undergo an alloying reaction with lithium ions, a first reaction occurs in which lithium ions are conducted on the surface of the reaction layer 2, or within the reaction layer 2, or, if multiple reaction layers 2 are stacked to form the three-dimensional reaction layer 3, between the multiple stacked reaction layers, and reach the silicon particles 5 arranged in the pockets within the three-dimensional reaction layer 3 to form an alloy; and a second reaction occurs in which lithium ions contained in the electrolyte that has permeated into voids within the three-dimensional reaction layer 3 via the electrolyte introduction holes (Introduction holes) reach the silicon particles 5 within the three-dimensional reaction layer 3 to form an alloy. Either the second reaction occurs first, or the first and second reactions occur in parallel.

[0086] In the first reaction, lithium ions dissolved in the electrolyte solution travel along the surface of the reaction layer 2 or between multiple layers of the reaction layer 2, react with carbon, and then reach the silicon particles 5 disposed in the pockets 7 to form Li-Si alloys. The first reaction between the lithium ions and carbon is a lithium insertion reaction between carbon (or graphene) layers in the carbon material (which may be crystalline graphite or non-crystalline amorphous carbon) used as the negative electrode material for non-silicon-based lithium-ion batteries. This reaction also proceeds in the carbon layer even when the reaction layer made of carbon does not have electrolyte conduction holes. This is because some lithium ions can penetrate the pockets 7 through solid-state conduction within the carbon layer and reach the silicon particles 5. The lack of conduction holes reduces the efficiency with which lithium ions enter the pockets 7, and therefore the reaction proceeds more slowly than the second reaction.

[0087] In the second reaction, the electrolyte penetrates into the voids in the three-dimensional reaction layer through the electrolyte introduction holes, and the lithium ions dissolved in the electrolyte reach the silicon particles arranged in the pockets in the three-dimensional reaction layer and form Li-Si alloys. The electrolyte introduction holes in the reaction layer make it easier for the lithium ions in the electrolyte to reach the silicon particles in the pockets. Therefore, the second reaction starts faster than the first reaction.

[0088] To efficiently promote the alloying reaction, the anode must be designed to prioritize the second reaction described above. Therefore, the electrolyte is infiltrated through the electrolyte conduction holes to transport lithium ions in the electrolyte into the voids present in the three-dimensional reaction layer. However, the spaces are larger than the voids, allowing the electrolyte to penetrate more easily. As a result, the carbon layer is more likely to come into contact with the electrolyte, allowing the second reaction to proceed preferentially, but this reaction alone is not sufficient to achieve high capacity. The lithium ions reach the silicon particles through both conduction in the carbon layer and penetration of the electrolyte, maximizing reactivity.

[0089] In this specification, the first and second reactions are initiated by a reaction between carbon and lithium ions and a reaction between silicon and lithium ions, respectively. Before the reaction, carbon and silicon have different natural potentials in the electrolyte. Electrons flowing from the external circuit combine with lithium ions to react first with carbon in the first reaction and directly with silicon in the second reaction, producing compounds. Immediately after the reaction, both carbon and silicon exhibit potentials different from their natural potentials, with silicon exhibiting a generally higher potential than carbon.

[0090] In other words, by measuring the potential after the start of this reaction, it is possible to determine which reaction is proceeding first, the first or the second. In addition, this can sometimes be determined by the difference in the diffusion coefficient obtained by electrochemical measurement. The potential can be measured on the surface of the anode material in the anode. For example, the electrode is immersed in the electrolyte, and the potential between it and metallic lithium is measured with a voltmeter (or electrochemical device).

[0091] Furthermore, the first reaction and the second reaction may be distinguished by analyzing the state of combination with lithium in the compound produced by the reaction, i.e., the state of existence of each element. The state of existence of each element can be detected by instrumental analysis such as high-resolution X-ray photoelectron spectroscopy (binding energy of elements such as Li, C, Si, F, and O) and MAS solid-state NMR (nuclei such as Li, Si, C, F, and O).

[0092] [Gaps between Silicon Particles and Three-Dimensional Reaction Layer] In the negative electrode material 1 according to this embodiment, gaps 6 are provided between the silicon particles 5 and the three-dimensional reaction layer 3 in the pockets 7 inside the three-dimensional reaction layer 3. In a configuration in which the three-dimensional reaction layer 3 is formed by stacking a plurality of reaction layers 2, the gaps 6 are formed between the silicon particles 5 and the reaction layer 2 that is closest to the pocket 7 among the plurality of reaction layers 2.

[0093] The silicon particles 5 expand and contract due to alloying and dealloying reactions with lithium ions, repeatedly increasing and decreasing in volume. In the negative electrode material according to this embodiment, voids are provided between the silicon particles 5 and the three-dimensional reaction layer 3, which makes it possible to absorb the volume fluctuations caused by the expansion and contraction of the silicon particles 5. This makes it possible to suppress the collapse and scattering of silicon particles that occurs in negative electrode materials in which no voids are provided between the three-dimensional reaction layer 3 and the silicon particles 5. As a result, the negative electrode material 1 according to this embodiment can maintain stable cycles over long periods of charge and discharge, and can also increase charge and discharge capacity.

[0094] 6 and 7 are conceptual diagrams illustrating the process of generating particles of the negative electrode material according to this embodiment. The three-dimensional reaction layer 3 has an important function of absorbing volume fluctuations due to the expansion / contraction of silicon particles 5. By utilizing this function and synthesizing and placing highly controlled silicon active material compounds 9 in the pockets 7 by suitably selecting the shape, morphology, crystallinity, and other compound elements of silicon, a higher performance negative electrode material can be obtained.

[0095] To achieve this, a three-dimensional carbon layer structure having a pocket 7 is prepared in advance, and then a gaseous or liquid raw material is introduced into the pocket, and the production reaction is carried out by adjusting the atmosphere, for example, an inert atmosphere, and adjusting reaction conditions such as temperature by heating, etc. In this way, the silicon active material compound 9 can be suitably produced and placed at a predetermined position within the pocket 7.

[0096] The three-dimensional carbon layer structure can be fabricated by the method exemplified in this embodiment. For example, SiO ２ On the other hand, after coating with carbon by CVD, SiO ２ Then, as shown by the dotted lines in Figures 6 and 7(b), a silicon-containing gas 8, such as silane gas, is passed through the introducing holes 4 at high temperatures to produce silicon active material compounds 9 (Figure 6) and silicon 12 (Figure 7(c)) in the pockets 7 and on the outer shell of the three-dimensional carbon layer structure. Hereinafter, this manufacturing method will be referred to as the flow method.

[0097] In addition, as Si-containing gaseous compounds, organic compounds, inorganic compounds, and compounds evaporated into atomic form or ionized gases can also be circulated through the three-dimensional carbon layer structure instead of silane gas.

[0098] The silicon active material compound 9 can be highly controlled in its form and shape by selecting various conditions for the formation of the above-described formation mechanism. For example, the silicon active material compound 9 can be formed into a plurality of particles or a plate-like form, or a non-particulate form such as a coating layer along the inner surface of the pocket 7 as shown in FIG. 6 , and can be formed and installed inside the pocket 7 or on the outer shell of the three-dimensional carbon layer structure.

[0099] 8A and 8B are diagrams showing examples of the morphology of silicon deposited on the surface of the support structure of this embodiment during the silane CVD process using the flow method. In the support structure of this embodiment, at the initial stage of silane CVD, both particulate silicon inside the pocket and a coating layer along the inner surface of the pocket may be present, as shown in FIG. 8A, or silicon may grow to fill the space within the pocket, as shown in FIG. 8B. Furthermore, by continuing silane CVD further, silicon may fill not only the space within the pocket but also the through holes in the reaction layer, so that silicon is produced on the outside of the support structure, as shown in FIG. 8C.

[0100] By selecting the composition of the raw material compound, SiO ｘ , Si ｘ N ｙ, Si ｘ S ｙ It is possible to obtain a silicon active material compound 9 in which the above-mentioned compounds are partially produced. This makes it possible to realize a negative electrode material having practical properties such as high capacity and high charge / discharge reversibility.

[0101] In addition, SiO for forming a three-dimensional carbon layer structure ２ The inorganic compound can be replaced by an inorganic compound that can maintain its shape and form at high temperatures. As the inorganic compound, so-called oxide ceramics and inorganic carbonates can also be used. For example, Al ２ O ３ , MgO, ZrO ２ and inorganic carbonates such as ammonium carbonate, sodium carbonate, potassium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, iron carbonate, etc. Preferred inorganic carbonates are sodium carbonate, potassium carbonate, calcium carbonate, etc., and particularly preferred is calcium carbonate.

[0102] The three-dimensional carbon layer structure before silicon is placed in the pockets is also referred to as a support structure for a negative electrode material or a support structure from the viewpoint of a structure that supports the silicon contained therein when used as a negative electrode material. The total pore volume of the support structure determined by a nitrogen adsorption / desorption method is preferably 0.7 cc / g or more and 4 cc / g or less, more preferably 0.8 cc / g or more and 3 cc / g or less, and even more preferably 0.9 cc / g or more and 2.7 cc / g or less. The larger the pore volume, the higher the theoretical Si content and the higher the capacity obtained. However, if the pore volume is too large, the structural strength decreases, and the function of the support structure deteriorates.

[0103] The through-pores may be micropores, mesopores, or macropores. The total pore volume measured by nitrogen adsorption / desorption may be such that the total volume of micropores is 9% to 85%, the total volume of mesopores is 10% to 80%, and the total volume of macropores is 2% to 30%. Alternatively, the ratio of the volume of mesopores to the total pore volume may be 60% or more, and the ratio of the volume of micropores to the total pore volume may be greater than the ratio of the volume of macropores to the total pore volume.

[0104] Furthermore, the ratio of micropore volume to macropore volume (micro ratio / macro ratio; hereinafter also referred to as micro-macro ratio) is preferably 0.26 to 40, more preferably 0.5 to 33, and even more preferably 0.70 to 25. A large micro-macro ratio means that the pockets in the support structure are in a small compartmentalized state. When the support structure of this embodiment has an appropriately large micro-macro ratio, it is possible to highly mitigate the expansion of silicon.

[0105] The support structure and negative electrode material of this embodiment preferably have pores of various sizes. The International Union of Pure and Applied Chemistry (IUPAC) defines pores with a diameter of less than 2 nm as micropores, pores with a diameter of 2 to 50 nm as mesopores, and pores with a diameter of more than 50 nm as macropores. The characteristics of the pore size distribution can be appropriately defined by calculating the proportion of pores with pore diameters within the above ranges in the total space volume (total pore volume).

[0106] The ratio of the total volume of the through pores having a pore size of 5 to 15 nm, as measured by nitrogen adsorption / desorption, to the total pore volume is preferably 50% or more, more preferably 75% or more, and even more preferably 80% or more.

[0107] The mode pore diameter measured by nitrogen gas adsorption / desorption method is preferably 1 nm or more and 70 nm or less, more preferably 1 nm or more and 60 nm or less, and even more preferably 1 nm or more and 50 nm or less. The mode pore diameter in the pore distribution of the support structure means the peak top value in the pore distribution curve.

[0108] The specific surface area of ​​the support structure is 400 m ２ / g or more 2600m ２ / g or less is preferable, and 500m ２ / g or more 2300m ２ / g or less is more preferable, and 600m ２ / g or more 2000m ２ / g or less is more preferable.

[0109] In the support structure of this embodiment, it is desirable to divide the pockets as finely as possible to suitably mitigate the expansion of silicon due to charging. That is, the extent to which the space represented by the pore volume determined by nitrogen adsorption / desorption measurement is divided by compartment walls consisting of reaction layer surfaces is an important indicator. This is defined as the spatial compartment index, and the value obtained by dividing the specific surface area determined by the nitrogen adsorption / desorption method by the total pore volume is used. The spatial compartment index is preferably 260 to 3000, more preferably 300 to 2200, and even more preferably 500 to 1500. A large spatial compartment index means that the pockets in the support structure have small compartments. A moderately large spatial index can highly mitigate the expansion of silicon.

[0110] The pocket inside the support structure is divided into multiple compartments by partition walls made of one or more reaction layers. Here, "divided into compartments" in this specification does not necessarily mean that the space is completely closed by the partition walls. For example, even if there is a hole connecting to an adjacent compartment, as shown in Figure 1C or Figure 7(c), it can be said to be divided into two compartments.

[0111] [Method for Manufacturing Negative Electrode Material] In the method for manufacturing a negative electrode material according to this embodiment, nano-sized silicon particles with oxidized surfaces are heated, and a product of thermal decomposition of a carbon-containing raw material gas is placed on the surface of the silicon particles 5 to form a carbon layer. This is followed by a step of removing the oxide film present on the silicon particle surface by acid treatment. In this embodiment, the carbon layer is used as the reaction layer 2. After the oxide film is removed, gaps formed between the reaction layer 2 and the silicon particles 5 become voids 6.

[0112] The specific steps will be explained in order. (1) Carbon Layer Formation Process: An oxide film formed by oxidizing silicon is formed on the surface of silicon particles having nano-sized particles, specifically particles with a particle size of approximately 10 nm to 100 nm. The silicon particles having the oxide film on their surface are placed in a reaction vessel, and a source gas containing carbon is flowed while the vessel is maintained at a predetermined temperature. This forms a carbon layer (reaction layer) on the surface of the oxide film. The formed reaction layer has a three-dimensional structure. The carbon layer may be a graphene layer, a multilayered graphene layer, a porous carbon meso-sponge, or an amorphous structure.

[0113] In this process, when forming a carbon layer on the surface of the oxide film of the silicon particles, a plurality of independent unit structures may be formed, or adjacent silicon particles having an oxide film on their surfaces may be joined together via the carbon layer to form an aggregate structure, in which at least two adjacent unit structures have silicon particles adjacent to each other with the carbon layer interposed therebetween.

[0114] Instead of silicon particles having an oxide film on their surface, a support structure can be suitably produced by forming an aggregate structure of unit particles having a particle diameter of 1 to 50 nm, such as the above-mentioned oxide ceramics or inorganic carbonate, and forming a carbon layer on the surface. Schematic diagrams of the production of a support structure using oxide ceramics, inorganic carbonate, or the like as a mold are shown in Figures 10 and 11.

[0115] The predetermined temperature in the carbon layer formation step is in the range of 400°C to 1200°C. If the temperature is below 400°C, carbon is unlikely to deposit on the surface. If the temperature exceeds 1200°C, silicon and carbon react to form Si-C bonds, which is undesirable as it prevents the formation of the desired carbon layer.

[0116] In order to control the number of layers to be formed to one or more, it is preferable to use a dry method, chemical vapor deposition (CVD), for the carbon layer in this step.

[0117] A vacuum pulse CVD method can also be used, in which silicon particles are placed in a reaction vessel, a vacuum is applied, and a gas is passed through the vessel for a specific period of time one or more times, thereby depositing a carbon layer on the surface of the silicon particles having an oxide film on the surface.

[0118] Furthermore, in order to promote the reaction for forming the carbon layer by the CVD method, a radical reaction mechanism consisting of organic compounds, hydrogen, water, metal elements, etc. may be utilized.

[0119] When the carbon layer formation step is performed by the CVD method, the pressure can be, for example, 1 kPa to 200 kPa. The temperature increase rate in the carbon layer formation step is, for example, 1°C to 50°C / min. When the product of thermal decomposition of the source gas is placed on the oxide film on the surface of the silicon particles, by gradually increasing the temperature at a rate of 1°C to 50°C / min, crystallization proceeds at a moderate rate compared to when heating is performed suddenly with a larger temperature gradient, and a homogeneous carbon layer can be formed.

[0120] On the other hand, when an organic substance having double or more bonds is used as a carbon source in forming a carbon layer, it is susceptible to thermal decomposition, and the bonds broken during decomposition are likely to bond with other pyrolysis products, resulting in the formation of a structure with a disordered six-membered carbon ring structure. By utilizing such a bonding reaction, a carbon layer (reaction layer) having structural defects, i.e., introduction holes 4, is formed.

[0121] In the carbon layer formation process, gaseous organic molecules are used as a carbon source for the carbon atoms that constitute the carbon layer. The gaseous organic molecules are one or more selected from hydrocarbons such as methane, ethane, propane, butane, acetylene, ethylene, propylene, or butene, cyclohexanetetracarboxylic dianhydride (CPDA), or aromatic compounds such as benzene, toluene, naphthalene, biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), hexafluoroisopropylidenedianiline anhydride (6FDA), pyromellitic dianhydride (PMDA), benzophenonetetracarboxylic dianhydride (BTDA), and bisphenol A dianihydride (PADA). Preferably, the gaseous organic molecules are methane, acetylene, ethylene, or propylene.

[0122] In the carbon layer forming step, in addition to the above-mentioned source gas, for example, an inert gas may be used as a carrier gas. Furthermore, in addition to the inert gas, a gas containing oxygen gas, hydrogen gas, or the like may also be used as the carrier gas. In the carbon layer forming step, from the viewpoint of forming one or two carbon layers, the flow rate of the carrier gas is preferably controlled to 0.05 m / min to 1.00 m / min, and the amount of the source gas relative to the total amount of the source gas and the carrier gas is preferably controlled to 1 vol % to 60 vol %.

[0123] (2) Oxide Film Removal Step In this step, the silicon oxide film between the silicon particles and the carbon layer is removed by dissolution. Here, because the carbon layer has many tiny pores, the solvent used to dissolve the oxide film penetrates the carbon layer. Hydrofluoric acid (HF) is used to remove the silicon oxide film. Because carbon is a material that is resistant to hydrofluoric acid, a strong acid, the structure of the carbon layer formed earlier is maintained during this step. After the HF removal reaction, the HF is removed from the carbon layer and the surface of the silicon particles by washing using a known method.

[0124] As described above, the negative electrode material according to this embodiment is produced by placing the product of thermal decomposition of a carbon-containing source gas on an oxide film on the surface of silicon particles to form a carbon layer, and then removing the oxide layer between the silicon particles and the carbon layer by acid treatment. Therefore, the three-dimensional reaction layer made of carbon and having a three-dimensional structure obtained in the above-described process is thin but flexible, and has some resistance to expansion during lithium-silicon alloy formation. In the negative electrode material according to this embodiment, voids are provided between the silicon particles and the carbon layer. This effectively prevents the collapse and scattering of silicon particles, which can occur when the silicon particles expand and contract due to the alloying and dealloying reactions, causing repeated volume increases and decreases.

[0125] After the carbon layer formation process and the oxide film removal process, numerous pores are formed in the carbon layer formed in the carbon layer formation process. These numerous pores are generated when a portion of the carbon layer becomes unevenly structured when pyrolysis products are deposited on the surface of the silicon particles during the carbon layer formation process. When used as a negative electrode material in a negative electrode, these pores function as electrolyte introduction holes through which an electrolyte passes. The carbon layer with these pores forms the negative electrode material as a reaction layer. Gaps formed by randomly overlapping multiple layers also function as introduction holes. In the negative electrode material produced by the production method according to this embodiment, the diameter of the formed electrolyte introduction holes is mostly greater than 1.0 nm. The total volume of introduction holes with a diameter of 1.0 nm or greater may be 50% or more of the total pore volume, and may be 60% or more, 70% or more, or 80% or more. Specific methods for measuring the diameter of the introduction holes are described below. FIG. 9 shows a TEM image of a unit particle containing silicon particles in pockets inside the three-dimensional reaction layer. Introduction holes are formed in the reaction layer.

[0126] When the silicon active material compound 9 is generated and placed in the pockets 7 in the three-dimensional reaction layer by the above-mentioned flow method, suitable introduction holes are required to allow the Si-containing gas 8, such as silane gas, to flow at high temperatures. That is, the physical properties of the support structure to be manufactured, such as the specific surface area, pore volume, pore diameter, and pore diameter distribution, can be highly adjusted depending on the presence of the introduction holes. Methods for adjusting the presence of the introduction holes are described below.

[0127] Schematic diagrams of the manufacturing of the support structure are shown in Figures 10 and 11. The support structure used in the flow method is 30 to 500 m ２ This can be suitably obtained by using an oxide ceramic or inorganic carbonate having a specific surface area of ​​1 / g and a primary particle size of 1 to 60 nm, forming a carbon layer on the surface (step a in FIGS. 10 and 11 ), and then dissolving and removing the oxide or carbonate inside the carbon layer with an inorganic solvent such as an acid or alkali (step b in FIGS. 10 and 11 ). In other words, as shown in FIGS. 10 and 11 , a reaction layer 2 is formed using a ceramic or inorganic carbonate as a template 10, and then the template material is dissolved and removed to obtain a support structure 11.

[0128] The ceramics may be composed of particles existing independently, particles connected by sintering during a subsequent heat treatment, or particles that are connected from the beginning during the production process. Figure 10 shows an example of using particles existing independently, and Figure 11 shows an example of using connected particles.

[0129] After forming the carbon layer, the solvent is washed away to remove unnecessary materials, and the layer is then dried. Drying is preferably performed at a temperature of room temperature or higher and 250°C or lower. If necessary, the layer is further heat-treated in an inert atmosphere at a temperature of room temperature or higher and up to 1800°C or lower, or 1600°C or lower, 1200°C or lower, or 900°C or lower, to obtain a support structure. This heat treatment connects crystal structure defects in the carbon reaction layer, and the mechanical strength properties, such as flexibility, of the entire support structure are suitably adjusted.

[0130] The shape and physical properties of the secondary agglomerated particles of the support structure can also be adjusted by mechanical or physical post-treatment. For example, if the support structure is in an agglomerated state, the size and shape can be adjusted by mechanical crushing, or if it is in an excessively crushed state, by cutting and polishing, ball mill stirring, collision granulation, pressure treatment, or the like to achieve an agglomerated shape. Furthermore, to obtain a suitable through-hole diameter, the support structure can be pressurized using a plate- or roll-type pressure device to reduce the through-hole diameter. These mechanical or physical post-treatments can suitably adjust physical properties such as particle size, specific surface area, bulk density, pore diameter, and pore volume.

[0131] As described above, the flow-through method can generate silicon 12 not only in the pocket but also on the outer shell of the support structure, as shown in Figure 8(c). Silicon comes into direct contact with the electrolyte, and volume changes due to expansion during charging and discharging can immediately cause structural destruction and rapid degradation. Therefore, by forming a carbon reaction layer as an external protective layer to protect the surface of the silicon compound generated on the outer shell, degradation of the silicon can be effectively suppressed.

[0132] 12 is a diagram showing an image of an intermediate stage in the manufacturing process of an example of a lithium-ion battery negative electrode material according to an embodiment of the present invention, illustrating the state in which the exterior of the silicon deposited on the surface has been oxidized. In the state in which silicon has filled the spaces within the pockets and the conductive holes in the reaction layer with silicon, and silicon has been generated even on the exterior of the support structure (as illustrated in FIG. 8(c)), heating the exterior silicon produces silicon oxide (silicon oxide) 13 on the surface of the silicon (FIG. 12).

[0133] FIG. 13 illustrates a state in which an outer protective layer 14 is formed on the outside of the silicon oxide 13 formed on the surface as shown in FIG.

[0134] The outer protective layer can be produced from the same raw materials as the carbon layer described above. That is, gaseous organic molecules are used as the carbon source for the carbon atoms that make up the outer protective layer. The gaseous organic molecules are selected from one or more of the following: hydrocarbons such as methane, ethane, propane, butane, acetylene, ethylene, propylene, or butene; cyclohexanetetracarboxylic dianhydride (CPDA); or aromatic compounds such as benzene, toluene, naphthalene, biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), pyromellitic dianhydride (PMDA), hexafluoroisopropylidenedianiline anhydride (6FDA), benzophenonetetracarboxylic dianhydride (BTDA), and bisphenol A dianihydride (PADA). Preferably, the gaseous organic molecules are methane, acetylene, ethylene, or propylene.

[0135] 14 is an illustration of an example in which silane CVD is performed on a support structure 1' obtained from a linked template, and silicon is filled to fill the interior of the pockets. In this way, in the negative electrode material of this embodiment, when multiple three-dimensional reaction layers are linked and the interior thereof becomes conductive, the filled silicon may exist across multiple unit particles. While FIG. 14 illustrates a shape in which two unit particles are linked, the number of links in the support structure of this embodiment is not limited to two, and three or more may be linked.

[0136] [Measurement of space volume and electrolyte introduction hole (introduction hole) diameter] Nitrogen adsorption / desorption measurement of the support structure can be performed using a specific surface area / pore distribution measurement device (BELSORP MAX, manufactured by BEL Japan). In this embodiment, the measurement was performed under conditions of -196°C. Before the measurement, a degassing treatment was performed by vacuum drying at 150°C for 6 hours. The equilibrium judgment condition when measuring the pressure inside the sample tube was 300 seconds.

[0137] As an example, a nitrogen adsorption / desorption isotherm obtained using the sample of Example 1, which will be described later, is shown in Figure 19. The vertical axis of Figure 19 represents the adsorption amount, and the horizontal axis represents the relative pressure. Based on the obtained nitrogen adsorption / desorption isotherm, the total volume of the space was calculated by converting the nitrogen adsorption amount at -196°C and a relative pressure P / P0 = 0.99 into a volume at the density of liquid nitrogen.

[0138] Adsorption isotherms were measured, and the obtained data were analyzed using the software Autosorb 1 (manufactured by Anton Paar Japan). In the case of type I adsorption isotherms, the distribution of the diameter of the introduction pores was analyzed with reference to a kernel calculated by density functional theory (DFT method) assuming slit-type pores. For samples showing type IV adsorption isotherms, the pore size distribution was analyzed by applying the Barrett-Joyner-Halenda method (BJH method) to each adsorption isotherm. The diameter d of the introduction pores was calculated by fitting with a Gaussian function. The resulting distribution diagram of the void volume and the diameter of the electrolyte introduction pores is shown in FIG. 20.

[0139] Nitrogen adsorption and desorption measurements were performed on the obtained support structure using the above-mentioned device. Prior to measurement, the sample was dried under reduced pressure at 150°C for 6 hours using a BEL pre. From the obtained adsorption isotherm, the specific surface area (also referred to as BET specific surface area) was determined using the BET method. The applicable range of the BET method was P / P0 = 0.05 to 0.3. Furthermore, based on the obtained adsorption and desorption isotherm, the total pore volume was measured by converting the amount of nitrogen adsorbed at -196°C and a relative pressure P / P0 = 0.99 into a volume at the density of liquid nitrogen. The results are shown in Table 1. The pore size distribution was determined using the BJH method.

[0140] During use as a battery, the entire support structure may be destroyed, exposing the silicon and causing excessive contact with the electrolyte. Such contact increases side reactions, resulting in significant capacity degradation with increased cycles. To mitigate this type of destruction, the negative electrode material of this embodiment provides voids within the pockets of the negative electrode material and a void layer (second void) 15 between the external protective layer and the silicon ( FIG. 15 ). The void phase 15 is formed by dissolving and removing the silicon oxide 13 present inside the external protective layer 14 after the external protective layer 14 is formed.

[0141] Such a void layer can provide space to absorb volume changes in silicon due to expansion and contraction of silicon during charging and discharging. This can mitigate the structural impact on the support structure caused by expansion and contraction of silicon during battery operation. The optimal size of the voids depends on the dimensions and shape of the silicon produced, and in this embodiment, this can be suitably adjusted by adjusting the manufacturing conditions. However, a certain degree of contact between the silicon active material and the reaction layer is necessary to supply electrons necessary for the charge and discharge reactions.

[0142] [Measurement of Electrolyte Permeability] When determining the permeability of the electrolyte into the negative electrode material, PC or n-butanol can be used instead of the electrolyte to measure the filling rate of the total space volume (total pore volume), which is the sum of the voids in the three-dimensional reaction layer in which the silicon particles are arranged in the pockets, the space surrounded by the outer wall of the three-dimensional reaction layer, and the space in the conductive holes.

[0143] First, the measurement method using a PC will be described. First, the density of carbon particles was determined by a gas substitution method using helium gas as a probe. In this embodiment, an Accupyc II 1345-10CC manufactured by Shimadzu Corporation was used as the measurement device, and measurements were performed using a known method. The obtained density was referred to as the He density ρ Ｈｅ Let's say.

[0144] The PC density measurement was carried out using a Gay-Lussac type pycnometer, as shown in Figures 16A to 16D. Figure 16A shows the pycnometer alone, Figure 16B shows the pycnometer filled with PC, Figure 16C shows the pycnometer containing the sample (negative electrode material), and Figure 16D shows an image of the pycnometer filled with PC and containing the sample. The PC density ρPC at standard temperature (20°C) can be calculated as follows. The mass of the pycnometer itself (Figure 16A) is W ０ (g), when the pycnometer is filled with PC (Fig. 16B), its mass is W １ (g), when the sample is placed in the pycnometer (Fig. 16C), the mass is W ２ (g), and when PC is added to fill the pycnometer (Fig. 16D), the mass is W ３ The apparent density of the sample is given by "mass of the sample" ÷ "(volume occupied by the sample) + (volume of pores that PC cannot enter)". Therefore, the density of PC is ρ Ｐ Then, it can be calculated by the following formula (1).

[0145]

[0146] W ３ In order to impregnate the pores with PC, the sample was placed in a pycnometer, filled with a solvent, and then vacuum impregnation was carried out under reduced pressure for 1 hour, and the measurement was carried out after another day had passed. ＰＣ Furthermore, the total space volume V calculated from the nitrogen adsorption / desorption measurement ｔｏｔａｌ The apparent density inside the carbon particle can be calculated from the density of He using the following equation (2): ０ Let's say.

[0147]

[0148] When PC does not penetrate into the carbon particles at all, that is, when the pore filling rate of PC is 0%, the ρ calculated from the density measurement using a pycnometer is ＰＣ is ρ ０ Conversely, when PC penetrates into all pores, that is, when the pore filling rate is 100%, ρ ＰＣ is ρ Ｈｅ The space volume permeability of PC was defined as follows:

[0149]

[0150] The permeability of the electrolyte to the total space volume, which includes the space surrounded by the outer walls of multiple adjacent three-dimensional reaction layers 3 and the voids 6 between the three-dimensional reaction layers 3 and the silicon particles 5, when the electrolyte permeates to the vicinity of the silicon particles before the alloying reaction was measured by the above-mentioned method for Examples 1 to 5 and Comparative Examples 1 and 2. The measurement results are shown in Table 1.

[0151] Next, we will explain the density (Db) measurement method using the butanol substitution method using n-butanol. A low butanol density indicates that there are many spaces that butanol cannot penetrate and that the electrolyte does not easily penetrate. A high butanol density indicates that there are many spaces that butanol can penetrate and that the electrolyte can easily penetrate. In this way, butanol density can be suitably used as information on the pore space within the negative electrode material.

[0152] The n-butanol density (Db) of the negative electrode material was measured by the liquid phase displacement method (pycnometer method; apparatus AUTO TRUE DENSER MAT-7000, manufactured by Seishin Enterprises) in the following steps.

[0153] (1) The weight of the thoroughly dried pycnometer is measured and designated as Wa.

[0154] (2) After drying the sample, place it in the pycnometer measured in (1) and weigh it; the weight is designated as Wb.

[0155] (3) Add n-butanol (special grade) to the pycnometer measured in (2) up to the marked line, and let the resulting weight be Wc.

[0156] (4) Fill the pycnometer from (1) with butanol only up to the mark on the pycnometer, and let the weight be Wd.

[0157] The test temperature was measured, and the density of butanol at that temperature was ρ Ｂ Then, Db can be calculated by the following equation (4) using Wa, Wb, Wc, and Wd obtained in (1) to (4): Db = [(Wb - Wa) / (Wb - Wa - Wc + Wd)] × ρ Ｂ ...(4)

[0158] [Example of practical use of negative electrode material] When used alone, the negative electrode material according to this embodiment can be used in a battery at the maximum capacity per weight of the negative electrode material. However, expansion and contraction during charging and discharging may shorten the lifespan depending on the application. In the case of current electronic devices and electric vehicles, more practical lifespan characteristics can be obtained by mainly using a carbonaceous material for current lithium-ion battery negative electrodes and adding the negative electrode material according to this embodiment as part of the negative electrode. In this case, the negative electrode material according to this embodiment is added to the carbonaceous material so that the amount of Si is 3% or more and 30% or less, preferably 5% or more and 20% or less, by weight.

[0159] The carbonaceous material can be low-crystalline carbon, high-crystalline carbon, or the like. Typical examples of low-crystalline carbon include softened carbon and hardened carbon. High-crystalline carbon can be used in amorphous, plate-like, flaky, spherical, or fibrous shapes. Examples of high-crystalline carbon include natural graphite, artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microspheres, mesophase pitch, and high-temperature-calcined carbon such as petroleum and coal-based coke.

[0160] The physical properties of anode materials are determined by the device design and manufacturing process requirements that stem from constraints such as the use of lithium-ion batteries. In manufacturing anode materials, the physical properties required to achieve the desired properties are selected, and the manufacturing process is designed accordingly. These physical properties include powder particle size and distribution, specific surface area, and density.

[0161] As an example, the powder particle size is appropriately selected in consideration of other constituent requirements of the lithium ion battery, but from the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, an average particle size of 1 to 70 μm is usually preferred, and 3 to 30 μm is more preferred.

[0162] [Negative electrode conductive additive] When applying a negative electrode material to a negative electrode, in order to achieve higher practical characteristics, another type of carbon material intended to assist conductivity can be suitably used as a conductive additive for the negative electrode in order to ensure conductivity and electrode structure retention even after long-term cycling.

[0163] The other types of carbon materials are not particularly limited as long as they are conventional materials used as electrode materials, and examples thereof include acetylene black, ketjen black, lamp black, furnace black, carbon black, graphite, carbon fiber, graphite fiber, nanofiber, nanotube, coke, hard carbon, amorphous carbon, and graphene meso sponge.

[0164] These carbon materials can be used alone or in combination of two or more. The amounts used are selected depending on the intended use, and the weight ratio of [one type of carbon material]:[another type of carbon material] is usually in the range of 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0165] Next, a lithium ion battery including an electrode containing the lithium ion battery negative electrode material of this embodiment will be described.

[0166] 17 shows the cross-sectional structure of an example of a lithium-ion battery 200 according to this embodiment. This lithium-ion battery 200 is a coin-type battery in which a disc-shaped positive electrode 212 housed in a metal exterior part 211 and a disc-shaped negative electrode 214 housed in a metal exterior part 213 are stacked with a separator 215 interposed therebetween. A metal spring 218 and a spacer 219 are disposed between the exterior part 213 and the negative electrode 214. The interiors of the exterior parts 211 and 213 are filled with a liquid electrolyte, and the peripheral edges of the exterior parts 211 and 213 are sealed by being crimped with a seal gasket 217 interposed therebetween.

[0167] The positive electrode 212 is generally obtained by applying a slurry made by mixing a metal oxide material, a conductive additive that aids in electronic conductivity, a binder, and a solvent onto a current-collecting metal foil such as rolled aluminum foil to form a coating film, heating and drying to remove the solvent, and then forming the coating into a predetermined size and density.

[0168] A metal oxide material that can be used as a positive electrode active material is one that can release electrons to the external circuit of the battery and simultaneously release Li ions to the electrolyte. The amount of Li ions contained varies depending on the chemical composition, crystalline structure, etc., but a material that can reversibly absorb and release many Li ions is preferred.

[0169] The negative electrode 214 is obtained by coating a current collecting metal foil such as rolled copper foil with a slurry of a negative electrode material, a binder, and a solvent, and then heating and drying the coating to remove the solvent, followed by forming the negative electrode into a predetermined size and density. The negative electrode material according to this embodiment can be used as the negative electrode material.

[0170] Depending on the application of the lithium-ion battery, multiple negative electrode materials can be mixed in a predetermined ratio to obtain a desired discharge profile. When the negative electrode material has a smooth surface that results in insufficient particle-to-particle contact, it is also preferable to use a conductive additive to enhance electronic conductivity. Carbon-based materials, metal-based materials, and other highly electronically conductive materials can be used as the conductive additive.

[0171] The negative electrode material and the conductive additive are often in powder form. Therefore, it is preferable to mix them with a small amount of a binder to fix them to each other and to the current collecting metal foil. The binder must be chemically and electrochemically inert and have some elasticity and affinity, and a plastic resin material is preferably used.

[0172] Examples of the lithium ion battery negative electrode material according to this embodiment will be described below.

[0173] Example 1 Metallic silicon particles with an average particle size of 50 nm and an oxide film were packed into a heat treatment vessel and then loaded into a tube furnace. The interior was purged with argon, and the temperature was then raised to 880°C. While maintaining the temperature constant, a mixed gas of 25% methane by volume and 75% argon by volume was passed through for 30 minutes to form a carbon layer on the silicon particles. After cooling, the particles were removed and subjected to HF treatment to obtain carbon-layered silicon particles from which the oxide film had been removed. The resulting particles were pulverized in a pot-type ceramic ball mill for 30 minutes and then classified to obtain the negative electrode material of Example 1 with an average particle size of 3 μm. An SEM image of the lithium-ion battery negative electrode material obtained in Example 1 is shown in Figure 2. A transmission electron microscope (TEM) image (Figure 4) of the lithium-ion battery negative electrode material obtained in Example 1 confirmed the formation of a layered graphite structure.

[0174] In a dry state, 68 parts by weight of negative electrode material, 10 parts by weight of conductive additive (manufactured by Denki Kagaku Kogyo, trade name: Denka Black), 12 parts by weight of carboxymethyl cellulose (CMC), and 10 parts by weight of styrene butadiene rubber (SBR; manufactured by JSR) were dissolved in water and mixed, and further water was added to prepare a slurry. This was applied to a 20 μm thick Cu current collector and dried at 110 ° C., then punched out to Φ15 mm and pressed at 30 kN to form a negative electrode. After vacuum drying the negative electrode at 120 ° C., in a glove box with an argon gas atmosphere, 1M LiPF was added to the electrolyte. ６ Using a solution (a 1:1 mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC)) and a polypropylene separator, a 2032-type negative electrode test battery with a metallic Li counter electrode was fabricated.

[0175] The test battery was charged to 0 V (vs Li / Li) at 0.2 A / g per negative electrode material. ＋ ) and then charged to a current of 0.01 A / g. Then, at 0.2 A / g, the battery was charged to 1.5 V (vs. Li / Li ＋ ) and then discharge was completed. The above charge and discharge cycle was repeated 10 times. The initial charge and discharge capacity and efficiency, and cycle test retention rate (based on one cycle) of the obtained test battery were measured.

[0176] [Example 2] A negative electrode material was obtained in the same manner as in Example 1, except that when the metal silicon particles having an oxide film were heat-treated, the temperature was raised to 880°C at a rate of 5°C / min and held at that temperature, and from the point when the temperature reached 780°C, a mixed gas of 15% by volume of methane and 85% by volume of argon was flowed for a total of 50 minutes to form a carbon layer on the silicon particles. Thereafter, a negative electrode test battery was fabricated in the same manner as in Example 1, and a similar charge-discharge cycle test was performed.

[0177] [Example 3] A negative electrode material was obtained in the same manner as in Example 1, except that a mixed gas of 15% by volume of methane, 10% by volume of acetylene, and 75% by volume of argon was used when heat-treating the metal silicon particles having an oxide film. Thereafter, a negative electrode test battery was fabricated in the same manner as in Example 1, and a similar charge-discharge cycle test was performed.

[0178] [Example 4] A negative electrode material was obtained in the same manner as in Example 1, except that the carbon layer-forming silicon particles, which had been subjected to HF treatment and had had their oxide film removed, were classified without being pulverized to obtain a negative electrode material with an average particle size of 3 μm. Thereafter, a negative electrode test battery was fabricated in the same manner as in Example 1, and a similar charge-discharge cycle test was performed.

[0179] [Example 5] The negative electrode material obtained in Example 1 was further heat-treated in an air stream at 300°C for 3 hours, and then the atmosphere was changed to argon, and the temperature was raised to 800°C, and heat-treated for 2 hours to obtain a negative electrode material. Thereafter, a negative electrode test battery was fabricated in the same manner as in Example 1, and a similar charge-discharge cycle test was performed.

[0180] Comparative Example 1: Concentrated ammonium hydroxide was added to a vigorously stirred ethanol / water (3:1) dispersion of silicon particles (average particle size approximately 100 nm), and tetraethoxysilane (TEOS) was added dropwise. The mixture was stirred for 24 hours, washed, and then dried to obtain surface-oxidized silicon particles. These particles were mixed with a DMF solution of polyacrylonitrile, and the resulting suspension was added and dispersed in an excess amount of a 2% polyvinylpyrrolidone (PVP) solution of pure water. The resulting suspension was then washed and dried to obtain polyacrylonitrile-coated silicon particles. These particles were oxidized at 230°C under an air flow, then heated to 850°C at a rate of 5°C / min under a nitrogen flow, and heated for 2 hours to obtain carbon-coated silicon particles. The particles were dispersed and stirred in a 3% HF solution to dissolve the oxide layer, then washed with water, dried, and crushed and classified to obtain a negative electrode material with an average particle size of 3 μm (carbon coating approximately 30 nm). A negative electrode test battery was then fabricated in the same manner as in Example 1, and the same charge / discharge cycle test was performed.

[0181] A TEM image of the lithium-ion battery negative electrode material obtained in Comparative Example 1 is shown in Figure 18. It can be seen from Figure 18 that the carbon layer of the negative electrode material of the Comparative Example shown in Figure 18 is thicker than the reaction layer according to this embodiment shown in Figure 4. It can also be seen that no electrolyte conducting holes are formed in the carbon layer of the negative electrode material of the Comparative Example.

[0182] [Comparative Example 2] A negative electrode material having an average particle size of 3 μm (carbon coating: approximately 10 nm) was obtained in the same manner as in Comparative Example 1, except that the concentration of polyacrylonitrile in the DMF solution was reduced to one-third. Thereafter, a negative electrode test battery was produced in the same manner as in Example 1, and the same charge-discharge cycle test was performed.

[0183] [Measurement of space volume and electrolyte pore diameter] Nitrogen adsorption / desorption measurements of the negative electrode materials obtained in the examples and comparative examples were carried out at -196°C using a specific surface area / pore size distribution measuring device (BELSORP MAX, manufactured by BEL Japan). Prior to the measurement, a degassing treatment was carried out by vacuum drying at 150°C for 6 hours. The equilibrium judgment condition for measuring the pressure inside the sample tube was 300 seconds.

[0184] As an example, a nitrogen adsorption / desorption isotherm obtained using the sample of Example 1 is shown in Figure 19. The vertical axis of Figure 19 represents the adsorption amount, and the horizontal axis represents the relative pressure. Based on the obtained nitrogen adsorption / desorption isotherm, the total volume of the space was calculated by converting the nitrogen adsorption amount at -196°C and a relative pressure P / P0 = 0.96 into a volume at the density of liquid nitrogen.

[0185] Adsorption isotherms were measured, and the obtained data was analyzed using the software Autosorb 1 (manufactured by Anton Paar Japan). In the case of a type I adsorption isotherm, the distribution of the diameter of the electrolyte introduction pores was analyzed with reference to a kernel calculated using density functional theory (DFT method) assuming slit-type pores. For samples showing a type IV adsorption isotherm, the pore size distribution was analyzed by applying the Barrett-Joyner-Halenda method (BJH method) to each adsorption isotherm. The diameter d of the electrolyte introduction pores was calculated by fitting with a Gaussian function. A distribution diagram with the obtained space volume and the diameter of the electrolyte introduction pores on the vertical and horizontal axes, respectively, is shown in FIG. 20.

[0186] [Evaluation of Physical Properties of Negative Electrode Material] Various physical properties of the negative electrode test batteries obtained in each Example and Comparative Example are summarized in Table 1. Table 1 shows the propylene carbonate impregnation rate, specific surface area (SSA), total void volume, helium density, average particle size, and the charge capacity at the first cycle, discharge capacity at the first cycle, and the ratio of discharge capacity to charge capacity at the first cycle (1 ｓｔ CE), the retention rate of discharge capacity relative to charge capacity in the second cycle (2 ｎｄ Retention), the retention rate of discharge capacity relative to charge capacity at the 10th cycle (10 ｓｔ The results of the study were summarized.

[0187]

[0188] Fig. 21 is a graph showing the relationship between total void volume and permeability in Examples and Comparative Examples, with the vertical axis showing permeability and the horizontal axis showing total void volume. Fig. 22 is a graph showing the relationship between permeability and discharge capacity in Examples and Comparative Examples, with the vertical axis showing discharge capacity and the horizontal axis showing permeability. Fig. 23 is a graph showing the relationship between specific surface area and total void volume in Examples and Comparative Examples, with the vertical axis showing total void volume and the horizontal axis showing specific surface area. Fig. 24 is a graph showing the relationship between specific surface area and permeability in Examples and Comparative Examples, with the vertical axis showing permeability and the horizontal axis showing specific surface area. Fig. 25 is a graph showing the relationship between the retention rate of discharge capacity at the 10th cycle relative to the discharge capacity at the first cycle (vertical axis) and the permeability (horizontal axis) in Examples and Comparative Examples.

[0189] The results shown in Figures 21 to 25 will be considered in conjunction with the results shown in Table 1. The permeability of the negative electrode materials used in the negative electrode test batteries of Examples 1 to 5 was 84% ​​or higher, while the permeability of the negative electrode material used in the comparative negative electrode test battery did not reach 70%. Figure 21 also indicates that the high permeability of the negative electrode material of this example is proportional to the total void volume. The total void volume of the negative electrode material of this example was the smallest at 0.562 mL / g in Test Example 4, while the maximum volume of the negative electrode test battery using the comparative negative electrode material was 0.42 mL / g. It was confirmed that the negative electrode materials used in the negative electrode test batteries of Examples 1 to 5 all exhibited higher total void volumes and higher permeability than the negative electrode material used in the comparative negative electrode test battery.

[0190] Regarding discharge capacity, the negative electrode test batteries of Examples 1 to 5 had a discharge capacity of 2680 mAh / g or more in the first cycle, while the discharge capacity of the negative electrode test battery of the comparative example did not reach 2600 mAh / g. From FIG. 22 , it can be seen that in the negative electrode test batteries using the negative electrode material of this example, the high permeability of the negative electrode material is proportional to the magnitude of the discharge capacity. All of the negative electrode materials used in the negative electrode test batteries of Examples 1 to 5 have a higher permeability than the negative electrode material used in the negative electrode test battery of the comparative example. Furthermore, it was found that the negative electrode test batteries of the examples not only exhibited a high first-cycle discharge capacity but also maintained cycle stability over long-term charge / discharge cycles compared to the battery of the comparative example.

[0191] Regarding the specific surface area, the specific surface area of ​​the negative electrode material of the negative electrode test batteries of Examples 1 to 5 was 190 m ２ / g or more, the specific surface area of ​​the negative electrode material of the comparative negative electrode test battery is at most 150 m ２ / g. From FIG. 23, it can be seen that the high specific surface area of ​​the negative electrode test battery using the negative electrode material according to this example corresponds to a large total void volume. Similarly, from FIG. 24, it can be seen that the high specific surface area of ​​the negative electrode test battery using the negative electrode material according to this example corresponds to a high permeability. It was confirmed that the negative electrode materials of the negative electrode test batteries of Examples 1 to 5 all had a large specific surface area, a large total void volume, and a high permeability compared to the negative electrode materials of the negative electrode test batteries of the comparative examples.

[0192] Regarding the relationship between the permeability of the negative electrode material and the ratio of the discharge capacity at the 10th cycle to the discharge capacity at the first cycle of the negative electrode test battery, the comparison of the permeability of the negative electrode material of Examples 1 to 5 and the comparative example has been described above. The ratio of the discharge capacity at the 10th cycle to the discharge capacity at the first cycle of the negative electrode test battery using the negative electrode material according to this example was very high, ranging from 92% to 96%, while the ratio was as high as 91% for the negative electrode test battery using the comparative example negative electrode material. From FIG. 25 , it can be seen that the high permeability of the negative electrode test battery using the negative electrode material according to this example corresponds to the high ratio of the discharge capacity at the 10th cycle to the discharge capacity at the first cycle. It was confirmed that the negative electrode materials of the negative electrode test batteries of Examples 1 to 5 all exhibited high permeability and high retention rates compared to the negative electrode material of the comparative example negative electrode test battery.

[0193] In the negative electrode material according to this embodiment, the rate of the second reaction described above is increased by adopting a configuration that can increase the permeability of the electrolyte. As shown in the results of the examples and comparative examples, it was confirmed that by manufacturing using the manufacturing method according to this embodiment, the permeability of the electrolyte can be increased compared to the comparative examples.

[0194] The method for producing an anode material according to this embodiment involves a step of placing the product of thermal decomposition of a carbon-containing source gas at 400°C or higher on the surface of heated silicon particles. This step causes the organic substance serving as the carbon source to thermally decompose, and the pyrolysis product is deposited on the surface of the silicon particles, forming a reaction layer and electrolyte introduction holes. The presence of electrolyte introduction holes in the reaction layer increases the rate of the second reaction described above.

[0195] The negative electrode material in the comparative example was carbonized by heat treatment of a high molecular weight polymer. As a result, a relatively thick carbon coating (carbon layer) was formed on the silicon particles, preventing the electrolyte from penetrating into the negative electrode material. This prevented the initial charge / discharge reaction from proceeding sufficiently. Furthermore, the lithium alloying / dealloying reaction caused the silicon particles to expand / contract, increasing / decreasing their volume. Such volume fluctuations caused the hard carbon layer to crack easily, resulting in a decrease in battery capacity and deterioration of cycle life.

[0196] In the comparative negative electrode material, the carbon layer, which corresponds to the reaction layer in this embodiment, does not have electrolyte conduction holes. Therefore, lithium ions in the electrolyte first react with the carbon layer and then migrate through the interior of the carbon layer. The lithium ions then reach the surface of the silicon particles and only then react with silicon. That is, the supply rate of lithium ions to the silicon particles is slow. Therefore, lithium ions are likely to precipitate as metallic lithium on the carbon layer, which accelerates the deterioration of the negative electrode material. As the metallic lithium precipitation reaction progresses, the amount (thickness) of metallic lithium produced increases, resulting in increased resistance and a further increase in overvoltage. At a certain point, the alloying reaction progresses rapidly, making the silicon particles more susceptible to cracking. This cracking increases the surface area of ​​the silicon particles, which rapidly reacts with the electrolyte. Such a rapid reaction forms a low-quality film, which increases the resistance of the metallic reaction and adversely affects the reversibility of charge and discharge.

[0197] The negative electrode material according to this example was manufactured by placing the product of thermal decomposition of a carbon-containing source gas on the surface of silicon particles, forming a carbon layer, and then removing the oxide layer on the silicon particle surface by acid treatment. Removal of the oxide layer in the oxide film removal process creates voids between the carbon layer and the silicon particles. Therefore, the three-dimensional reaction layer formed by the above process, which is made of carbon and has a three-dimensional structure, is thin yet flexible and somewhat resistant to expansion during lithium-silicon alloy formation. Furthermore, the voids between the silicon particles and the carbon layer adequately prevent particle collapse and scattering, which occurs when silicon particles expand and contract due to alloying and dealloying reactions, resulting in repeated volume increases and decreases. This allows for stable cycling over long periods of charge and discharge, while maintaining high charge and discharge capacity.

[0198] The specific surface area of ​​the negative electrode material of the negative electrode test battery according to this example is larger than that of the negative electrode material of the negative electrode test battery of the comparative example. This indicates that the carbon layer formed by the manufacturing method according to this example has electrolyte conduction holes, which indicates that the structural uniformity of the carbon layer is disrupted. The larger specific surface area increases the space through which the electrolyte can penetrate ( FIG. 19 ) and increases the electrolyte penetration rate into the negative electrode material ( FIG. 20 ).

[0199] The higher the penetration rate of the electrolyte into the negative electrode material, the faster the rate of the second reaction described above, allowing the lithium ions contained in the electrolyte to efficiently reach the surface of the silicon particles and suppressing the increase in overvoltage during the alloying reaction. This allows the initial charging reaction to proceed smoothly. As a result, a good coating that suppresses side reactions can be uniformly formed on the surface of the silicon particles at the beginning of the alloying reaction, suppressing the decrease in charge / discharge efficiency. The better the coating formed at the beginning, the less likely it is to deteriorate due to repeated cycles.

[0200] From the results of the above-mentioned test examples, the negative electrode material according to this example exhibited a higher permeability than the negative electrode material according to the comparative example. This indicates that in the negative electrode material according to this example, lithium ions contained in the electrolyte efficiently reached the surfaces of the silicon particles via the electrolyte conducting pores, and the initial charging reaction proceeded smoothly, resulting in a lithium ion battery negative electrode material with high capacity and high charge / discharge reversibility.

[0201] [Example 6] Aluminum oxide nanoparticles (SBa-200, primary particle size 8 nm; manufactured by Sasol Chemicals) were used as micropore-containing template particles for the support structure, and were filled into a heat treatment container and then loaded into a tube furnace. The inside was replaced with Ar gas, and then the temperature was raised to 910°C. If necessary, a preliminary heat treatment was performed for the purpose of dehydration, etc. Then, CH ４ The gas was mixed with Ar gas to a concentration of 20 vol %, and the mixed gas was allowed to flow for 120 minutes to form a carbonaceous film containing a graphene structure on the surface of the template particles. After cooling, the particles were removed and subjected to crushing and classification.

[0202] Next, the template was dissolved from this treated product with hydrofluoric acid, washed while maintaining the intraparticle space, and dried at 250°C or less to obtain a support structure precursor, which was then heat-treated at 1650°C in an inert atmosphere to stabilize the carbon structure, thereby obtaining a support structure for the negative electrode material of Example 1.

[0203] The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area of ​​the obtained support structure were determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0204] Next, the support structure was loaded into a tubular reaction vessel, the inside of which was replaced with nitrogen gas, and then the temperature was raised to 450° C. Then, 4 mol % of silane (SiH ４ A gas mixture of these materials was flowed at 800 cc / min under atmospheric pressure for 90 minutes to deposit silicon on the support structure. After cooling, the product was removed and crushed and classified to obtain a carbon-Si negative electrode material. Chemical analysis revealed that the silicon content (Si content) per gram of the material was 70%.

[0205] In a dry state, 68 parts by weight of the negative electrode material, 10 parts by weight of a conductive additive (manufactured by Denki Kagaku Kogyo, trade name: Denka Black), 12 parts by weight of carboxymethyl cellulose (CMC), and 10 parts by weight of styrene-butadiene rubber (SBR; manufactured by JSR) were dissolved in water and mixed, and further water was added to prepare a slurry. This was applied to a 20 μm thick Cu current collector, dried at 110 ° C, and then punched to a diameter of 14 mm and pressed at 30 kN to form a negative electrode. The negative electrode was dried under vacuum at 120°C, and then in a glove box under an argon gas atmosphere, a 2032-type negative electrode test battery with a metallic Li counter electrode was fabricated using a 1 M LiPF solution (a 1:1 mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC) to which 10 parts by weight of fluoroethylene carbonate (FEC) was added) as the electrolyte and a polypropylene separator.

[0206] The test battery was charged at 0.2 A / g per negative electrode material up to 0.005 V (vs. Li / Li+) and then charged until the current reached 0.01 A / g. The battery was then discharged at 0.2 A / g down to 2.0 V (vs. Li / Li+) to complete the initial charge / discharge cycle. Next, the charge / discharge current was set to 1.0 A / g, and the other conditions were the same as above, and the charge / discharge cycle was repeated 20 times. The resulting test battery was measured for the initial cycle charge / discharge efficiency, initial charge / discharge capacity, and cycle capacity retention ratio at the 20th cycle relative to the first cycle. The results are shown in Table 2.

[0207] Example 7 A support structure was obtained in the same manner as in Example 6, except that magnesium oxide nanoparticles (primary particle size 0.6 μm; manufactured by Guangzhou Hongwu Materials Technology Co., Ltd.) were used as the micropore-containing template particles for the support structure, and the template was eluted with hydrochloric acid. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0208] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0209] [Example 8] Silicon oxide nanoparticles (primary particle size 15 nm; manufactured by Nippon Aerosil) were used as the micropore-containing template particles of the support structure, and CH ４ A support structure was obtained in the same manner as in Example 6, except that a mixed gas of Ar gas and Ar gas was flowed for 30 minutes to form a carbonaceous film on the surface of the template particles. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0210] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0211] [Example 9] Silicon oxide nanoparticles (primary particle size 30 nm; manufactured by Nippon Aerosil) were used as the micropore-containing template particles of the support structure, and CH ４ A support structure was obtained in the same manner as in Example 6, except that a mixed gas of Ar gas and Ar gas was flowed for 90 minutes to form a carbonaceous film on the surface of the template particles. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0212] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0213] [Example 10] Silicon oxide nanoparticles (primary particle size 30 nm; manufactured by Nippon Aerosil) were used as the micropore-containing template particles of the support structure, and CH ４ A support structure was obtained in the same manner as in Example 6, except that a mixed gas of Ar gas and Ar gas was flowed for 40 minutes to form a carbonaceous film on the surface of the template particles. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0214] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0215] [Example 11] Silicon oxide nanoparticles (primary particle size 30 nm; manufactured by Nippon Aerosil) were used as the micropore-containing template particles of the support structure, and CH ４ A support structure was obtained in the same manner as in Example 6, except that a mixed gas of Ar gas and Ar gas was flowed for 30 minutes to form a carbonaceous film on the surface of the template particles. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0216] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0217] [Example 12] The support structure of Example 6 was sandwiched between copper plates and pressed with a roll press (maximum pressure 20 tons) to reduce the number of through-holes, thereby obtaining a support structure. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0218] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0219] [Example 13] The support structure of Example 8 was sandwiched between copper plates and pressed with a roll press (maximum pressure 20 tons) to reduce the number of through-holes, thereby obtaining a support structure. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0220] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0221] [Example 14] The support structure of Example 13 was subjected to an aggregation and shaping treatment using a Hybridizer (NHS-0; manufactured by Nara Machinery Works, Ltd.) to obtain a support structure. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption and desorption. The results are shown in Table 2.

[0222] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0223] [Example 15] In Example 6, the template was dissolved with hydrofluoric acid, washed while maintaining the intraparticle space, and then vacuum dried at 200°C to obtain a support structure without stabilization treatment. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0224] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0225] Comparative Example 3 Silicon oxide nanoparticles (primary particle size 70 nm; manufactured by Nippon Aerosil) were used as the micropore-containing template particles of the support structure. ４ A support structure was obtained in the same manner as in Example 6, except that a mixed gas of Ar gas and Ar gas was flowed for 120 minutes to form a carbonaceous film on the surface of the template particles. The total pore volume, micropore volume, mesopore volume, macropore volume, and BET specific surface area were then determined by nitrogen adsorption / desorption. The results are shown in Table 2.

[0226] Silicon was then deposited on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 1, and battery evaluation was performed.

[0227] [Comparative Example 4] Carbon black (primary particle size 30 nm; manufactured by Denka) was used as a support structure, and silicon was then precipitated on the support structure under the same conditions as in Example 6. After cooling, the product was removed and crushed and classified to obtain a negative electrode material. Chemical analysis revealed that the Si content per gram of material was 70%. A negative electrode test battery was then fabricated under the same conditions as in Example 6, and battery evaluation was performed.

[0228]

[0229] The evaluation results of the batteries obtained in Examples 6 to 15 and Comparative Examples 3 and 4 are shown in Table 2, Figures 26 and 27. Table 2 reveals that the larger the micro-macro ratio and spatial compartmentalization index, the better the cycle characteristics, such as the first cycle charge / discharge efficiency and cycle capacity retention. This is thought to be because the pockets in the support structure were in a suitable small compartment state, which allowed for a significant reduction in silicon expansion. Figure 26 shows the cycle capacity retention on the vertical axis and the micropore ratio / macropore ratio on the horizontal axis.

[0230] A small compartment index means that the proportion of the partition walls in the spatial volume of the pocket is small, making it difficult to achieve the effect of mitigating silicon expansion. A large compartment index also means that there are many partition walls, which increases the edge of the reaction layer that constitutes the support structure. Figure 27 shows the compartment index on the horizontal axis and the cycle capacity retention rate on the vertical axis. As shown in Figure 27, a large compartment index increases the amount of inactive reactants that react with the electrolyte components, increasing resistance and accelerating cycle deterioration, resulting in a decrease in the cycle capacity retention rate. To achieve favorable cycle characteristics, it is necessary to achieve a high level of balance between the spatial volume of the pocket, the amount of silicon therein, and the partition walls.

[0231] [Example 16] The negative electrode material of Example 6 was filled into a heat treatment container and placed in a tube furnace. The tube furnace was heated to 900°C, and a mixed gas containing methane and Ar gas was introduced so that the concentration was 20 vol%. This formed a carbonaceous film containing a graphene structure on the surface of the negative electrode material. After cooling, the material was removed and subjected to crushing and classification. Based on the weight change of the negative electrode material, it was confirmed that a protective layer consisting of 10 wt% pyrolytic carbon had formed on the surface of the negative electrode material.

[0232] The density of the obtained carbonaceous film-formed negative electrode material was measured by a liquid phase displacement method using butanol. The pore closure index was calculated from the reciprocal of the obtained density and was found to be 0.65 cc / g. The results are shown in Table 3.

[0233] A negative electrode test battery was then fabricated under the same conditions as in Example 6. The charge rate index was calculated by dividing the capacity of the constant current portion of the initial charge by the total charge capacity as follows. The test battery was charged at 1.0 A / g of negative electrode material until the current reached 0.005 V (vs. Li / Li+) and then continued charging until the current reached 0.01 A / g. The capacity (CC capacity) when the charge voltage reached 0.005 V (vs. Li / Li+) was divided by the charge capacity (CC-CV capacity) when the current reached 0.01 A / g, giving the charge rate index as an index of productivity in the charging process. After charging, the battery was discharged in the same manner as in Example 6 to determine the initial discharge capacity and charge / discharge efficiency. A charge / discharge cycle test was then performed 20 times to determine the discharge capacity retention. The results are shown in Table 3.

[0234] [Example 17] The negative electrode material of Example 6 was filled into a heat treatment container and placed in a tube furnace. The tube furnace was heated to 280 °C while nitrogen gas was flowing through it. A certain amount of PMDA (pyromellitic dianhydride; special grade reagent) gas, previously sublimed at 280 °C, was mixed into the nitrogen gas, and the temperature inside the tube furnace was raised to 600 °C and maintained for 180 minutes. The gas was then switched to nitrogen gas only, and the material was cooled to room temperature. The weight change of the negative electrode material confirmed that a protective layer consisting of 10 wt. % pyrolytic carbon was formed on the surface of the negative electrode material.

[0235] The density of the obtained carbonaceous film-forming negative electrode material was measured by a liquid phase displacement method using butanol. The pore closure index was calculated from the reciprocal of the obtained density and was found to be 0.67 cc / g. The results are shown in Table 3.

[0236] Thereafter, a negative electrode test battery was fabricated under the same conditions as in Example 6, and the battery was evaluated. The results are shown in Table 3.

[0237] [Example 18] The negative electrode material of Example 6 was filled into a heat treatment container and placed in a tube furnace. The tube furnace was heated to 280 °C while nitrogen gas was flowing through it. A certain amount of gaseous CPDA (cyclohexanetetracarboxylic dianhydride; special grade reagent) previously sublimed at 280 °C was mixed into the nitrogen gas, and the temperature inside the tube furnace was raised to 600 °C and maintained for 180 minutes. The gas was then switched to nitrogen gas only, and the material was cooled to room temperature. From the weight change of the negative electrode material, it was confirmed that a protective layer consisting of 10 wt% pyrolytic carbon was formed on the surface of the negative electrode material.

[0238] The density of the obtained carbonaceous film-forming negative electrode material was measured by a liquid phase displacement method using butanol. The pore closure index was calculated from the reciprocal of the obtained density and was found to be 0.67 cc / g. The results are shown in Table 3.

[0239] Thereafter, a negative electrode test battery was fabricated under the same conditions as in Example 6, and the battery was evaluated. The results are shown in Table 3.

[0240] [Example 19] The negative electrode material of Example 6 was filled into a heat treatment container and placed in a tube furnace. The tube furnace was heated to 280 °C while nitrogen gas was flowing through it. A certain amount of gaseous CPDA (cyclohexanetetracarboxylic dianhydride; special grade reagent) previously sublimed at 280 °C was mixed into the nitrogen gas, and the temperature inside the tube furnace was raised to 600 °C and maintained for 55 minutes. The gas was then switched to nitrogen gas only, and the material was cooled to room temperature. From the weight change of the negative electrode material, it was confirmed that a protective layer consisting of 3 wt% pyrolytic carbon was formed on the surface of the negative electrode material.

[0241] The density of the obtained carbonaceous film-forming negative electrode material was measured by a liquid phase displacement method using butanol. The pore closure index was calculated from the reciprocal of the obtained density and was found to be 0.56 cc / g. The results are shown in Table 3.

[0242] Thereafter, a negative electrode test battery was fabricated under the same conditions as in Example 6, and the battery was evaluated. The results are shown in Table 3.

[0243] [Example 20] The negative electrode material of Example 6 was filled into a heat treatment container and placed in a tube furnace. The tube furnace was heated to 280 °C while nitrogen gas was flowing through it. A certain amount of gaseous CPDA (cyclohexanetetracarboxylic dianhydride; special grade reagent) previously sublimed at 280 °C was mixed into the nitrogen gas, and the temperature inside the tube furnace was raised to 600 °C and maintained for 90 minutes. The gas was then switched to nitrogen gas only, and the material was cooled to room temperature. From the weight change of the negative electrode material, it was confirmed that a protective layer consisting of 5 wt% pyrolytic carbon was formed on the surface of the negative electrode material.

[0244] The density of the obtained carbonaceous film-forming negative electrode material was measured by a liquid phase displacement method using butanol. The pore closure index was calculated from the reciprocal of the obtained density and was found to be 0.60 cc / g. The results are shown in Table 3.

[0245] Thereafter, a negative electrode test battery was fabricated under the same conditions as in Example 6, and the battery was evaluated. The results are shown in Table 3.

[0246] [Example 21] The negative electrode material of Example 6 was filled into a heat treatment container and placed in a tube furnace. The tube furnace was heated to 280 °C while nitrogen gas was flowing through it. A certain amount of gaseous CPDA (cyclohexanetetracarboxylic dianhydride; special grade reagent) previously sublimed at 280 °C was mixed into the nitrogen gas, and the temperature inside the tube furnace was raised to 600 °C and maintained for 216 minutes. The gas was then switched to nitrogen gas only, and the material was cooled to room temperature. From the weight change of the negative electrode material, it was confirmed that a protective layer consisting of 12 wt% pyrolytic carbon was formed on the surface of the negative electrode material.

[0247] The density of the obtained carbonaceous film-forming negative electrode material was measured by a liquid phase displacement method using butanol. The pore closure index was calculated from the reciprocal of the obtained density and was found to be 0.68 cc / g. The results are shown in Table 3.

[0248] Thereafter, a negative electrode test battery was fabricated under the same conditions as in Example 6, and the battery was evaluated. The results are shown in Table 3.

[0249] [Example 22] The negative electrode material of Example 6 was filled into a heat treatment container and placed in a tube furnace. The tube furnace was heated to 280 °C while nitrogen gas was flowing through it. A certain amount of gaseous CPDA (cyclohexanetetracarboxylic dianhydride; special grade reagent) previously sublimed at 280 °C was mixed into the nitrogen gas, and the temperature inside the tube furnace was raised to 600 °C and maintained for 270 minutes. The gas was then switched to nitrogen gas only, and the material was cooled to room temperature. From the weight change of the negative electrode material, it was confirmed that a protective layer consisting of 15 wt% pyrolytic carbon was formed on the surface of the negative electrode material.

[0250] The density of the obtained carbonaceous film-forming negative electrode material was measured by a liquid phase displacement method using butanol. The pore closure index was calculated from the reciprocal of the obtained density and was found to be 0.70 cc / g. The results are shown in Table 3.

[0251] Thereafter, a negative electrode test battery was fabricated under the same conditions as in Example 6, and the battery was evaluated. The results are shown in Table 3.

[0252]

[0253] In Examples 16 to 22, a protective layer made of carbon was provided on the surface of the negative electrode material. The amount of the protective layer produced can be highly controlled by adjusting the manufacturing method. This allows the ease of penetration of the electrolyte into the negative electrode material to be adjusted. By making appropriate adjustments, the initial charge time and cycle characteristics can be freely controlled, making it possible to provide batteries that meet the desired manufacturing productivity and quality.

[0254] From Table 3, it was confirmed that when the pore closure index of the negative electrode material is less than 0.6, the charge rate index is 0.8 or more. This improves rapid charging performance and productivity. Furthermore, when the pore closure index of the negative electrode material is more than 0.6, the cycle life is improved, making it possible to provide batteries that are required to have a long life, such as for EVs.

[0255] [Example 23] Silicon was deposited on the support structure of Example 6 at 450°C for 96 minutes under the same conditions as in Example 6. Chemical analysis of the resulting carbon-Si negative electrode material showed that the silicon content (Si content) per gram of material was 75%.

[0256] The negative electrode material was filled into a heat treatment container and placed in a tube furnace. It was then heat-treated in an air stream at 320°C for 4 hours to form an oxide layer on the surface. Chemical analysis revealed that the oxygen content per gram of material was 5% and the silicon content (Si content) was 70%.

[0257] Thereafter, a negative electrode test battery was fabricated under the same conditions as in Example 6, and the battery was evaluated. The results are shown in Table 4.

[0258] [Example 24] Using the negative electrode material of Example 23, a protective layer made of pyrolytic carbon was formed on the surface of the negative electrode material in the same manner as in Example 18. From the change in weight of the negative electrode material, it was confirmed that a 10 wt % protective layer had been formed.

[0259] Next, the negative electrode material was treated with hydrofluoric acid to dissolve the oxide layer, and then washed and dried. As a result of chemical analysis, the silicon content (Si content) per gram of the material was found to be 70%.

[0260] Thereafter, a negative electrode test battery was fabricated under the same conditions as in Example 6, and the battery was evaluated. The results are shown in Table 4.

[0261]

[0262] In the negative electrode material obtained in Example 23, a portion of the silicon was oxidized to introduce hard silicon oxide, thereby reinforcing the negative electrode material, which reduced the adverse effect of silicon expansion and favorably improved the cycle characteristics.

[0263] In the negative electrode material obtained in Example 24, the surface of the oxide layer of the negative electrode material obtained in Example 23 was covered with a protective layer, and the oxide layer was then dissolved and removed with acid. This provided a second void (void layer) between the protective layer and the silicon, which could suitably mitigate the effect of volume increase when the silicon expanded.

[0264] <Additional Notes> The lithium ion battery negative electrode material, the negative electrode including the same, and the lithium ion battery including the negative electrode described in the above-described embodiments can also be understood as follows.

[0265] A lithium-ion battery negative electrode material according to one embodiment of the present invention comprises a three-dimensional reaction layer formed by three-dimensionally arranging reaction layers made of carbon, electrolyte conducting holes formed in the reaction layer, and silicon particles arranged in pockets within the three-dimensional reaction layer, wherein voids are provided between the silicon particles and the three-dimensional reaction layer within the pockets of the three-dimensional reaction layer, and the lithium-ion battery negative electrode material includes a plurality of unit particles each containing the silicon particle within the pockets of the three-dimensional reaction layer, and when an electrolyte permeates to the vicinity of the silicon particle within the pockets before an alloying reaction, a total space volume which is the sum of the volume of the space surrounded by outer walls of the three-dimensional reaction layers of the plurality of adjacent unit particles and the volume of the voids between the three-dimensional reaction layer and the silicon particle is 0.43 mL / g or more.

[0266] In the above aspect, the permeability of the electrolyte to the total space volume may be 70% or more.

[0267] In the above aspect, 50% or more of the electrolyte introducing holes may have a diameter greater than 1.0 nm.

[0268] Another aspect of the present invention provides a lithium-ion battery negative electrode material comprising: a three-dimensional reaction layer formed by three-dimensionally arranging reaction layers made of carbon; electrolyte conducting holes formed in the reaction layer; and silicon grains arranged in pockets inside the three-dimensional reaction layer, wherein the lithium-ion battery negative electrode material has an aggregate structure in which a plurality of unit particles containing the silicon grains are bonded together in the pockets of the three-dimensional reaction layer, and in the aggregate structure, the silicon grains in each pocket of at least two adjacent unit particles are adjacent to each other with the three-dimensional reaction layer acting as a wall between them.

[0269] Yet another aspect of the present invention provides a lithium-ion battery anode material comprising: a three-dimensional reaction layer formed by three-dimensionally arranging reaction layers made of carbon; electrolyte conducting holes formed in the reaction layer; and silicon particles arranged in pockets within the three-dimensional reaction layer, wherein voids are provided between the silicon particles and the three-dimensional reaction layer within the pockets of the three-dimensional reaction layer; and when the silicon particles in the pockets of the three-dimensional reaction layer undergo an alloying reaction with lithium ions, a first reaction occurs in which lithium ions conducted on the surface of or inside the reaction layer reach the silicon particles in the pockets of the three-dimensional reaction layer and alloy them; and a second reaction occurs in which lithium ions contained in an electrolyte that has permeated the voids in the three-dimensional reaction layer via the electrolyte conducting holes reach the silicon particles in the pockets of the three-dimensional reaction layer and alloy them. The lithium-ion battery anode material provides a lithium-ion battery anode material comprising: a first reaction that occurs first;

[0270] In the negative electrode material according to the above embodiment, the reaction layer has electrolyte introduction holes that connect the pockets of the three-dimensional reaction layer formed from the reaction layer to the outside of the three-dimensional reaction layer. The electrolyte penetrates the gaps between the three-dimensional reaction layer and the silicon particles via these electrolyte introduction holes, and reaches the surfaces of the silicon particles arranged in the pockets inside the three-dimensional reaction layer. This allows lithium ions contained in the electrolyte to efficiently reach the surfaces of the silicon particles. This suppresses the increase in overvoltage during the alloying reaction, allowing the initial charging reaction to proceed smoothly.

[0271] In the negative electrode material according to the above embodiment, voids are provided between the silicon particles and the three-dimensional reaction layer within the pockets of the three-dimensional reaction layer. The silicon particles expand and contract due to alloying and dealloying reactions, repeatedly increasing and decreasing in volume. In the negative electrode material according to the present invention, the voids provided between the silicon particles and the three-dimensional reaction layer can absorb the volume fluctuations caused by the expansion and contraction of the silicon particles. This makes it possible to suppress the collapse and scattering of silicon particles that occurs when there are no voids. Therefore, even when charging and discharging for a long period of time, cycle stability can be maintained and a high charge / discharge capacity can be maintained.

[0272] In the above aspect, the negative electrode material may include a plurality of the three-dimensional reaction layers, and a total space volume, which is a sum of a volume of the space surrounded by outer walls of the three-dimensional reaction layers of the plurality of adjacent unit particles and a volume of the void between the three-dimensional reaction layer and the silicon particle when the electrolyte solution penetrates to the vicinity of the silicon particle before the alloying reaction, may be 0.43 mL / g or more.

[0273] In any of the above embodiments, by setting the total void volume to 0.43 mL / g or more, a sufficient amount of lithium ions contained in the electrolyte solution can reach the surface of the silicon particles. This suppresses an increase in overvoltage during the alloying reaction, allowing the initial charging reaction to proceed smoothly. Therefore, a good coating that suppresses side reactions can be uniformly formed on the silicon surface at the initial stage of the alloying reaction, and a decrease in charge / discharge efficiency can be suppressed. The total void volume may be 0.50 mL / g or more, or may be 0.56 mL / g or more.

[0274] In the above aspect, the permeability of the electrolyte to the total space volume may be 70% or more.

[0275] In the above aspect, 50% or more of the electrolyte introducing holes may have a diameter greater than 1.0 nm.

[0276] In the above aspect, a gap may be provided between the silicon grains and the three-dimensional reaction layer within the pocket of the three-dimensional reaction layer, and 50% or more of the electrolyte conducting holes may have a diameter greater than 1.0 nm.

[0277] In any of the above aspects, the reaction layer may be formed by forming pyrolysis products on the surface of the silicon particles at 400°C or higher of one or more gaseous organic molecules that serve as a carbon source.

[0278] In the above aspect, the one or more gaseous organic molecules may be selected from hydrocarbons such as methane, ethane, propane, butane, acetylene, ethylene, propylene, or butene, and aromatic compounds such as benzene, toluene, naphthalene, or pyromellitic dianhydride.

[0279] Yet another aspect of the present invention provides a negative electrode comprising a lithium-ion battery negative electrode material according to any of the above aspects.

[0280] Yet another aspect of the present invention provides a lithium ion battery comprising the negative electrode of the above aspect.

[0281] and removing the oxide film on the surfaces of the silicon particles by an acid treatment. The present invention also provides a method for producing a lithium-ion battery negative electrode material according to any one of the above aspects, the method comprising the steps of: placing silicon particles having an oxide film on their surfaces in a reaction vessel; heating the reaction vessel and introducing a source gas containing carbon into the reaction vessel; thermally decomposing the source gas at 400°C or higher and depositing the product on the surfaces of the silicon particles by a chemical vapor deposition (CVD) method to form the reaction layer; removing the oxide film on the surfaces of the silicon particles by an acid treatment; and cleaning the silicon particles from which the oxide film has been removed and the reaction layer, wherein in the oxide film removing step, voids are formed between the silicon particles and the three-dimensional reaction layer within the pockets of the three-dimensional reaction layer; and by performing the step of forming the reaction layer and the step of removing the oxide film, electrolyte conducting holes are formed in the reaction layer.

[0282] The present invention is not limited to the above-described embodiments and examples, and various design modifications within the scope of the present invention are included in the present invention.

[0283] REFERENCE SIGNS LIST 1, 1' Lithium ion battery negative electrode material (negative electrode material) 2 Reaction layer 3 Three-dimensional reaction layer 4 Electrolyte conducting hole (conduction hole) 5 Silicon particle (silicon granular body) 6 Void 7 Pocket 8 Si-containing gas 9 Silicon active material compound 10 Mold 11 Support structure for lithium ion battery negative electrode material (support structure) 12 Silicon 13 Silicon oxide (silicon oxide) 14 Protective layer 15 Void layer (second void) 16 By-reaction product 200 Lithium ion battery 211 Exterior part 212 Positive electrode 213 Exterior part 214 Negative electrode 215 Separator 217 Seal gasket 218 Spring 219 Spacer

Claims

1. A support structure for lithium-ion battery negative electrode material, which forms the framework on which silicon is arranged, A three-dimensional reaction layer formed by arranging one or more reaction layers made of carbon in a three-dimensional manner, Multiple conductive holes formed in the reaction layer, A pocket, which is a space formed inside the three-dimensional reaction layer, Equipped with, A support structure for lithium-ion battery negative electrode material, wherein the pocket is divided into multiple compartments by defining walls consisting of one or more reaction layers.

2. A support structure for lithium-ion battery negative electrode material, which forms the framework on which silicon is arranged, A three-dimensional reaction layer formed by arranging one or more reaction layers made of carbon in a three-dimensional manner, Multiple conductive holes formed in the reaction layer, A pocket, which is a space formed inside the three-dimensional reaction layer, Equipped with, A support structure for lithium-ion battery negative electrode material, wherein the spatial compartment index, obtained by dividing the specific surface area determined by nitrogen adsorption / desorption by the total pore volume, is 260 or higher.

3. The support structure for lithium-ion battery negative electrode material according to claim 1 or 2, wherein the plurality of conductive holes are arranged to allow gas or liquid to communicate from outside the support structure into the pockets, or from inside the pockets to outside the support structure.

4. The support structure for lithium-ion battery anode material according to claim 1 or 2, wherein the reaction layer comprises a carbon mesoponge or a graphene mesoponge.

5. A support structure for lithium-ion battery negative electrode material, which serves as a framework for silicon, comprises a three-dimensional reaction layer formed by arranging one or more reaction layers made of carbon in a three-dimensional manner, a plurality of conductive holes formed in the reaction layer, and a pocket which is a space formed inside the three-dimensional reaction layer, wherein the pocket is divided into a plurality of compartments by defining walls made of one or more of the reaction layers, A particulate silicon compound arranged inside the pocket, A lithium-ion battery anode material comprising, Within the pocket, a void is provided in at least a portion of the space between the particulate silicon compound and the reaction layer. A lithium-ion battery anode material wherein the lithium-ion battery anode material contains the particulate silicon compound in at least one of the plurality of compartments within the pocket.

6. When the particulate silicon compound in the pocket undergoes an alloying reaction with lithium ions, A first reaction in which lithium ions conducted on or inside the surface of the reaction layer reach the particulate silicon compound in the pocket and form an alloy, A second reaction occurs in which lithium ions contained in the electrolyte that have penetrated into the void within the pocket via the conductive holes reach the particulate silicon compound within the pocket and form an alloy. The lithium-ion battery negative electrode material according to claim 5, wherein the second reaction occurs first, or the first and second reactions occur in parallel.

7. At least a portion of the outermost surface of the support structure is provided with an external protective layer made of a reaction layer, Silicon is placed between the outermost surface of the support structure and the external protective layer. The lithium-ion battery negative electrode material according to claim 5, further comprising a void layer in at least a portion between the external protective layer and the silicon.

8. A method for manufacturing a lithium-ion battery anode material according to claim 5, A step of placing the lithium-ion battery anode material support structure described in claim 1 inside a reaction vessel, A step of flowing a silicon-containing compound through a reaction vessel at 300°C to 900°C and depositing silicon on at least one of the outer surface of the support structure and the pockets inside the three-dimensional reaction layer using the CVD method, Includes, A method for manufacturing a lithium-ion battery anode material, wherein the silicon-containing compound is introduced into the pocket through a conductive hole.

9. A lithium-ion battery anode comprising the lithium-ion battery anode material described in claim 5.

10. A lithium-ion battery comprising a lithium-ion battery anode including the lithium-ion battery anode material support structure described in Claim 1.