Member for lithium ion battery negative electrode material, manufacturing method for skeleton structure serving as core, lithium ion battery negative electrode material and manufacturing method for same, and lithium ion battery negative electrode containing lithium ion battery negative electrode material

Abstract

Provided are a member for a lithium ion battery negative electrode material, a manufacturing method for a skeleton structure serving as a core, a lithium ion battery negative electrode material and a manufacturing method for the same, and a lithium ion battery negative electrode containing the lithium ion battery negative electrode material, all of which are capable of providing a lithium ion battery having high capacity and high charge and discharge reversibility. This member for the lithium ion battery negative electrode material is a carbon material that forms a skeleton structure serving as a core. The member has pores, which are through-holes or bottomed holes, in the surface of the skeleton of the skeleton structure. The skeleton structure is used as a skeleton disposed inside silicon of the lithium ion battery negative electrode material. This lithium ion battery negative electrode material has a skeleton structure which is a carbon material disposed inside silicon.

Description

Lithium-ion battery negative electrode material member, method for manufacturing core skeletal structure, lithium-ion battery negative electrode material and manufacturing method thereof, and lithium-ion battery negative electrode containing the lithium-ion battery negative electrode material

[0001] The present invention relates to a lithium ion battery negative electrode material member, a method for producing a core skeletal structure, a lithium ion battery negative electrode material and a method for producing the same, and a lithium ion battery negative electrode containing the lithium ion battery negative electrode material.

[0002] Since its birth, lithium-ion batteries have been used in a wide range of applications, including smartphones and electric vehicles (EVs). As a result, the manufacturing of lithium-ion batteries has been subject to cost competition and the market demand for higher performance. 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 a support for a negative electrode active material (lithium) is formed from a silicon single crystal 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] Increasing the capacity of lithium-ion batteries is possible 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 state, 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).

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

[0006] 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.

[0007] 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.

[0008] 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 the volume expansion of the silicon portion, which is one of the reasons why the charge-discharge reversibility of lithium-ion batteries is hindered.

[0009] Specifically, the lithium-silicon combination reaction that occurs during the initial charging stage allows for a relatively smooth volume expansion. However, when lithium is released from the silicon in later stages, the silicon's hardness can prevent it from shrinking. In this case, the contact between the silicon, conductive additive, and current collector involved in charging and discharging is lost, impairing electronic conduction, leaving lithium in the battery during discharge or preventing the next charge. If this process is repeated, coupled with reactions with the electrolyte, resistance increases and the battery becomes inactive. This results in deterioration of the anode and a shortened battery life.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a lithium-ion battery negative electrode material member, a method for producing a core skeletal structure, a lithium-ion battery negative electrode material and a method for producing the same, and a lithium-ion battery negative electrode containing the lithium-ion battery negative electrode material, which enable the provision of a silicon-based lithium-ion battery with high capacity and high charge / discharge reversibility.

[0011] In order to solve the above problems, the lithium ion battery negative electrode material member, the method for manufacturing the core skeletal structure, the lithium ion battery negative electrode material and its manufacturing method, and the negative electrode including the lithium ion battery negative electrode material of the present invention employ the following means.

[0012] A first aspect of the present invention provides a lithium ion battery negative electrode material member for use as a skeleton to be disposed inside silicon of a lithium ion battery negative electrode material, the negative electrode material member being a carbon material that forms a core frame (hereinafter also referred to as "CF"), and having pores that are through holes or bottomed holes on the surface of the skeleton of the skeletal frame.

[0013] In the first aspect, the skeletal structure may be made of at least one of a carbonaceous material, a graphene material, and a thin-layer graphene material.

[0014] In the first aspect, the skeletal structure may have at least one of a plate shape, a curved surface shape, and an irregular surface shape.

[0015] In the first aspect, the skeletal structure may be particles, and the average particle size of the particles may be 1.3 μm or more and 10.5 μm or less.

[0016] In the first embodiment, the skeletal structure may have an effective spatial index, calculated by dividing the pore volume by the oil absorption amount, of 1.5 to 10.5.

[0017] In the first aspect, at least a portion of the skeletal structure may be spherical or approximately spherical particles.

[0018] In the first embodiment, the skeletal structure may be particles, and the particles may have an average aspect ratio of 1 to 5.

[0019] In the first aspect, the skeletal structure may be composed of at least one of a carbon meso sponge and a graphene meso sponge.

[0020] In a second aspect of the present invention, there is provided a method for producing a core skeletal structure made of a carbon material, the method comprising the steps of: arranging ceramic particles to serve as a template; flowing an organic hydrocarbon through the ceramic particles to coat the surfaces of the ceramic particles with a carbon layer or a graphene layer by a chemical vapor deposition (CVD) method; dissolving and eluting the ceramic particles with an acid; forming a skeletal structure precursor having intraparticle spaces by dissolving and eluting the ceramic particles with an acid; and heat-treating the obtained skeletal structure precursor to obtain a skeletal structure. The produced skeletal structure has pores, which are through-holes or bottomed pores, on the surface of its skeleton.

[0021] In the second embodiment, the ceramic particles may contain pores therein.

[0022] The second aspect may include a step of granulating the ceramic particles into a roughly spherical shape before the step of coating with the carbon layer or graphene layer.

[0023] In the second embodiment, the step of heat-treating the resulting skeletal structure precursor may not be carried out.

[0024] In the second embodiment, a pore compression treatment may be carried out after the step of obtaining the skeletal structure.

[0025] A third aspect of the present invention provides a lithium-ion battery negative electrode material comprising silicon and a skeletal structure disposed inside the silicon to form a core, the skeletal structure being made of a carbon material, and having pores, which are through holes or bottomed pores, on the surface of the skeleton of the skeletal structure.

[0026] In the third aspect, at least a part of the skeletal structure may be sandwiched between silicon.

[0027] In the third aspect, the silicon may include silicon oxide, such as SiO, SiO２ , Si and SiO ２ a mixture of Si ３ O ２ The composition of silicon oxide is, for example, Si ｘ O ｙ where x=1 to 3 and y=1 to 2.

[0028] In the third aspect, the silicon may have one or more protective coating layers made of a carbonaceous material, a graphene material, or a thin layer of graphene material on the outside of the surface thereof.

[0029] In the third aspect, a barrier layer void (hereinafter also referred to as "BLV") may be present between the protective coating layer and the outer surface of the silicon.

[0030] A fourth aspect of the present invention provides a method for producing a negative electrode material for a lithium ion battery, the method comprising the steps of: placing a core skeletal structure made of a carbon material in a reaction vessel; and flowing a silicon-containing compound through the reaction vessel at 300°C to 900°C to deposit silicon on the outer surface of the core skeletal structure by a CVD method. The surface of the skeleton of the skeletal structure has pores that are through-holes or bottomed pores. The temperature at which the silicon-containing compound is flowed may be 400°C, 450°C, 500°C, 600°C, 700°C, or 800°C.

[0031] In the fourth aspect, the silicon-containing compound is silane (SiH ４ ) may be included.

[0032] In the fourth aspect, the silicon-containing compound gas may be diluted with an inert gas.

[0033] In the fourth aspect, after the step of placing the skeletal structure, the process includes the steps of evacuating the reaction vessel to create a vacuum 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.

[0034] In the above embodiment, CVD may be carried out while a mixed gas is being circulated.

[0035] In the fourth aspect, one or more protective coating layers made of carbonaceous, graphene, or thin-layer graphene may be formed on the outer surface of the deposited silicon.

[0036] The fourth aspect may further include the steps of: after depositing silicon on the outer surface of the skeletal structure, heating the skeletal structure at 200°C to 500°C in an atmosphere containing at least oxygen to incorporate an oxide into the silicon; replacing the atmosphere in the reaction vessel with an inert gas; and forming a protective coating layer made of any of carbonaceous, graphene, and thin-layer graphene on the outer surface of the oxide-containing silicon under a flow of a gas of a carbon-containing compound.

[0037] The fourth aspect may further include, after the step of depositing silicon on the outer surface of the skeletal structure, the steps of providing an oxide layer on the outer surface of the deposited silicon, forming a protective coating layer made of any of carbonaceous, graphene, and thin-layer graphene on the outer surface of the oxide layer by a CVD method using a hydrocarbon gas, and dissolving and eluting the oxide layer with an acid to form a void layer between the protective coating layer and the outer surface of the deposited silicon.

[0038] A fifth aspect of the present invention provides a negative electrode for a lithium ion battery, comprising the negative electrode material for a lithium ion battery according to the third aspect.

[0039] The negative electrode material of the present invention has a core skeletal structure composed of a carbon material inside silicon. The flexibility of this skeletal structure mitigates the adverse effects of volume expansion and contraction that occur during charge and discharge reactions between lithium and silicon, and its conductivity suppresses side reactions caused by overvoltage during charge and discharge, resulting in a negative electrode material with high capacity and long life. Furthermore, by using a negative electrode containing such a negative electrode material, it is possible to obtain a lithium-ion battery with high capacity and long life.

[0040] 1 is a TEM photograph showing an example of the structure of a lithium ion battery negative electrode material according to one embodiment of the present invention. FIG. 2 is a diagram showing an example of the cross-sectional structure of a lithium ion battery equipped with a negative electrode containing the lithium battery negative electrode material according to one embodiment of the present invention. FIG. 3 is a TEM photograph of a core framework (CF) obtained in Example 1. FIG. 4 is a diagram showing the pore distribution of a magnesium oxide nanopowder serving as a template. FIG. 5 is a diagram showing the pore distribution of an obtained CF. FIG. 6 is a TEM image photograph of a lithium ion battery negative electrode material in which silicon is precipitated on a CF obtained in Example 1. FIG. 7 is a SEM image photograph of a CF obtained in Example 2. FIG. 8 is a high-resolution SEM image photograph of the surface of a CF obtained in Example 2. FIG. 9 is an ultra-high-resolution TEM image photograph of a CF obtained in Example 2. FIG. 10 is a TEM image photograph of a CFSI negative electrode material obtained in Example 1. FIG. 11 is a TEM image photograph of a Si negative electrode material obtained in Comparative Example 1. FIG. 12 is a TEM image photograph of carbon black in Comparative Example 1. FIG. 13 is a TEM image photograph of a CFSI negative electrode material obtained in Example 10. FIG. 14 is a TEM image photograph of a CFSI negative electrode material obtained in Example 11. 1 is a SEM image of CF obtained in Example 14.

[0041] Hereinafter, one embodiment of the lithium ion battery negative electrode material member, the method for manufacturing the core skeletal structure, the lithium ion battery negative electrode material and its manufacturing method, and the lithium ion battery negative electrode including the lithium ion battery negative electrode material of the present invention will be described with reference to the drawings.

[0042] 1. Lithium-ion Battery Negative Electrode Material An example of the structure of the lithium-ion battery negative electrode material of this embodiment is shown in Figure 1. The lithium-ion battery negative electrode material of this embodiment has a structure in which silicon (Si) is precipitated on the surface of a core skeletal structure (CF) within the space of this skeletal structure. Silicon is present not only on the outside of the skeletal structure but also in the spaces present inside the skeletal structure. The skeletal structure of this embodiment functions as a component for a lithium-ion battery negative electrode material. In Figure 1, CF represents the skeletal structure, Si represents silicon, BL represents the protective coating layer, and BLV represents the void layer within the protective coating layer. Each of these components will be described in order below.

[0043] 2. Core Skeleton (CF) In this embodiment, this core skeletal structure is called a core frame (hereinafter also referred to as "CF"). The CF has a nanoscale space inside the skeletal structure. In the lithium ion battery negative electrode material of this embodiment, silicon is fragmented into nanoscale particles and present in this internal space. The reason for fragmenting the silicon is to minimize the impact of structural destruction of the negative electrode material that occurs during charging and discharging when used in a lithium ion battery. This skeletal structure is formed from a carbon material. The three-dimensional connections of the carbon material that form the skeletal structure are formed by at least one of carbon-carbon covalent bonds, hydrogen bonds, and physical contact between the core skeletons. As an example, the skeletal structure is formed by three-dimensionally connecting plate-like carbon pieces.

[0044] Any inorganic compound, such as a metal, can be used for the skeletal structure as long as it meets the requirements, but a carbon material is preferably used in terms of conductivity and light weight. Flexible graphene is preferably used as the carbon material in order to follow the morphological changes caused by the expansion and contraction of the negative electrode material during use of the lithium-ion battery. Thin-layer graphene, which is stacked with a small number of layers, is more preferably used. The skeletal structure is composed of at least one of a plate shape, a curved surface shape, and an irregular surface shape.

[0045] Graphene has a structure in which hexagonal carbon network planes, each formed by bonding benzene rings, grow planarly to form a single sheet-like layer. Graphite is a structure in which many graphenes are stacked. On the other hand, a structure in which hexagonal carbon network planes grow planarly but have a small number of layers, and therefore have elastic deformability, is defined as a thin graphene material in this specification. Graphene is a carbon material with high electronic conductivity due to its highly regular planar structure.

[0046] The CF of this embodiment is formed as a particulate material composed of primary particles and secondary particles three-dimensionally connected. When stress is applied to a CF containing graphene or thin-layer graphene, the three-dimensional shape of the thin-layer graphene portion of the primary particles and secondary particles is mainly deformed and compressed. On the other hand, when the applied stress is released, the deformed portion recovers to a certain extent due to its elastic deformability. The portion that does not recover upon release of the stress is a portion with low elasticity. If the portion made of thin-layer graphene contains many structural defects or many amorphous bonds, the shape will not recover, i.e., it has plastic deformability against stress. Such a structural portion that has plastic deformability against stress exhibits high strength against stress or is easily deformed and cannot be restored thereafter.

[0047] A primary particle (hereinafter also referred to as PP) is a hollow particle having a three-dimensional skeleton and an internal space. A secondary particle is formed by a plurality of primary particles adhering to each other. FIG. 6A is a photograph showing an enlarged portion of an example of a secondary particle. In other words, the entirety of FIG. 6A shows the structure of a secondary particle. The portion surrounded by the dashed line in FIG. 6A corresponds to a primary particle.

[0048] The carbon material of this embodiment may contain graphene as the carbonaceous material. Graphene, which has a single plate-like structure, is a two-dimensional plate-like structure. In contrast, carbon meso sponge (hereinafter also referred to as "CMS") and graphene meso sponge (hereinafter also referred to as "GMS") have a skeletal structure containing three-dimensional nano-sized spaces, and are suitable for the CF of the present invention. The CMS of this embodiment is a structure formed by coating a carbon layer or graphene layer on a ceramic template particle containing micropores using CVD or the like, dissolving and eluting the ceramic template particle with acid, and then washing the resulting structure. GMS is obtained by treating CMS at high temperature.

[0049] When GMS is treated at high temperatures, oxygen functional groups and other components are eliminated, and at the same time, carbon radicals at the ends of the six-membered ring bond together, creating a GMS structure that connects defects. This results in the development of characteristic physical properties such as flexibility due to the graphene structure. On the other hand, in CMS that is not treated at high temperatures, structural defects remain, but the existing oxygen functional groups act as reaction points with silane gas, which, depending on the reaction conditions, can easily penetrate into the CF, resulting in a larger amount of silicon deposition, which can be desirable. Therefore, depending on the desired performance of the silicon-based anode material, CFs that do not undergo high-temperature treatment can also be used.

[0050] As described above, in the negative electrode material member of this embodiment, the graphene or thin-layer graphene portion has elastic deformability, and the portion other than the graphene or thin-layer graphene is amorphous carbon and has plastic deformability. The primary particles of the negative electrode material member of this embodiment deform when stress is applied. Depending on the magnitude of the applied stress, some of the multiple primary particles may recover their shape when the stress is released, while other parts of the multiple primary particles may maintain a permanently deformed state. This mechanical property is caused by the influence of the carbonaceous microstructure. The degree of elastic deformation and the degree of plastic deformation of the negative electrode material member can be measured by the ultra-small load-unload test described below.

[0051] When the thin graphene layer is relatively thick, the thin graphene layer maintains elastic deformation within a certain stress range, but undergoes sudden plastic deformation when a certain threshold is exceeded. General carbon materials may be deformed by a relatively large stress, resulting in particle destruction. In other words, the negative electrode material of this embodiment has the property of returning to its original shape with almost no deformation under weak stress, such as in an extremely small load / unload test, i.e., the property of a large amount of work required for elastic deformation.

[0052] The state of the microcrystalline structure of thin graphene can be analyzed by Raman spectroscopy.

[0053] The characteristics of CMS and GMS are explained below.

[0054] CMS and GMS contain a plurality of primary particles having a three-dimensional skeleton with an internal space. Some of the primary particles are adhered to each other to form secondary particles. The secondary particles have the property of undergoing plastic deformation in an extremely small load / unload test, with some of them not recovering their original shape. In this embodiment, the three-dimensional skeleton is made of a skeletal structure.

[0055] The carbonaceous material constituting the CMS or GMS may contain graphene. The plastic deformation power of the CMS or GMS may be 5% or more and 92% or less.

[0056] The pore volume of the carbon material of this embodiment is not particularly limited, but is preferably 0.1 cc / g or more, or 1 cc / g or more, 1.5 cc / g or more, 2 cc / g or more, or 2.95 cc / g or more, as measured by nitrogen adsorption / desorption analysis. The upper limit is not limited to these values, but is preferably 20 cc / g or less, 15 cc / g or less, 10 cc / g or less, 8 cc / g or less, 7 cc / g or less, 6.1 cc / g or less, or 5.7 cc / g or less. Furthermore, it is preferable that the pore volume of CMS or GMS measured by gas adsorption method be 1 cc / g or more and 4 cc / g or less.

[0057] In addition to pore volume, other indicators that represent the higher-order structure of a skeletal structure with adjusted three-dimensional nano-sized space size and pore diameter include oil absorption, structural complexity, and interparticle void volume.

[0058] Oil absorption refers to the amount of oil absorbed by a powder under certain conditions. Measurement of oil absorption (JIS K6217-4) includes oil absorption, which is one of the basic properties of carbon black for rubber. For example, carbon black is formed from an aggregate structure of primary particles. The fine voids within the aggregate structure and the voids between the aggregate structures have the ability to absorb oil, and the amount of oil absorbed is used as an index of the development of the aggregate structure, known as "oil absorption."

[0059] The CF of this embodiment has an internal space and an external space surrounded by an outer wall, and the total volume of the space can be measured in accordance with the oil absorption capacity (JIS K5101-13-1; Testing methods for pigments - Part 13: Oil absorption - Section 1: Refined linseed oil method).

[0060] The lower limit of the oil absorption capacity of the CF of this embodiment is 400 mL / 100 g or more, preferably 600 mL / 100 g or more, more preferably 800 mL / 100 g or more, even more preferably 1000 mL / 100 g or more, and most preferably 1400 mL / 100 g or more.

[0061] The upper limit of the oil absorption of the CF of this embodiment is not limited to these, but is usually 5000 mL / 100 g or less, preferably 4000 mL / 100 g or less, more preferably 3500 mL / 100 g or less, even more preferably 3000 mL / 100 g or less, and most preferably 2500 mL / 100 g or less.

[0062] When the oil absorption amount is within this range, the CF has a large spatial volume and can be filled with a large amount of silicon generated from silane gas, thereby improving the capacity of the negative electrode material.

[0063] In the gas-to-solid conversion process, such as from silane to silicon, the size of the void space and the affinity (wettability) for the framework structure during the morphological transformation are thought to be important factors for forming the reaction field. More specifically, the organic-like silane gas transforms from an organic-like low-molecular-weight polysilane to a high-molecular-weight polysilane and then to solid silicon as it thermally decomposes. The inventors discovered that the ratio of the pore volume, which is a measure of the amount of gas diffusing in the gas-phase process, to the oil absorption, which is a measure of the permeation space into which the liquid organic material is wetted in the liquid-phase process, reflecting the organic properties, correlates with the performance of the final silicon-containing anode material.

[0064] The index of the substantial silicon growth spatial structure during silane CVD (hereinafter referred to as the effective spatial index) is calculated by multiplying the oil absorption amount (mL / g) by the pore volume (mL / g, condition: P / P ０ = 0.99).

[0065] A CFSI negative electrode material with high capacity and high cycle performance can be realized when the pore volume is in the range of 0.3 to 6.0 mL / g and the effective spatial index is in the range of 1.5 to 10.5. The effective spatial index is preferably in the range of 1.6 to 8.0, more preferably 1.6 to 5.0, and most preferably 1.7 to 3.0.

[0066] The carbon layer stacking index of CMS or GMS, as determined by Raman spectroscopy, is 0.4 or more and 5 or less. The carbon layer stacking index may be 0.5 or more and 4.5 or less, or 1 or more and 4 or less.

[0067] Preferably, the bulk modulus K of CMS or GMS is 2 GPa or less, and the average graphene network plane size L is 50 nm or more. The average number of layers n in CMS or GMS may be 1 to 6, and the pore diameter d may be 1 to 65 nm. The BET specific surface area S of CMS or GMS may be 400 m ２ / g or more 2600m ２ / g or less.

[0068] The BET specific surface area of ​​the carbon material of this embodiment is not particularly limited, but is preferably 100 to 2700 m, calculated from nitrogen adsorption as specified in JIS Z8830. ２ / g, 300-2500m ２ / g, 500-2000m ２ / g, 600-1800m ２ / g, or 800 to 1200 m ２ When the BET specific surface area of ​​the carbon material of this embodiment is in this range, the electrical conductivity and oil absorption are favorably increased.

[0069] Amount of edge sites of CMS or GMS N ｅｄｇｅ The edge site specific surface area S of CMS or GMS is preferably 500 μmol / g or less. ｅｄｇｅ is 30m ２ / g or less. The pore volume V of CMS or GMS ｔｏｔａｌ is 1.9 cm ３ / g or more 5cm ３ / g or less.

[0070] The method for producing CF according to this embodiment includes the steps of arranging ceramic particles to serve as a template, circulating organic hydrocarbon by CVD to coat the surfaces of the ceramic particles with a carbon layer or graphene layer, and dissolving the ceramic particles used as the template with acid to elute them.

[0071] Typical ceramics are manufactured by blending powders of non-ferrous metal materials such as zirconia and alumina according to the desired product, molding them, and then sintering them. Ceramics are dense and hard, and have high heat resistance, corrosion resistance, and insulating properties, and they do not oxidize or rust. In contrast, the ceramic particles used as the mold in this embodiment are composed of, for example, metal nanoparticles that can be dissolved in acid during the separation process.

[0072] When hydrofluoric acid is used in the separation step, a template made of nanoparticles of alumina, zeolite, or the like can be used. To avoid the use of hydrofluoric acid in the separation step, it is preferable to use a template made of metal nanoparticles made of an alkaline earth metal oxide. Specifically, a template made of nanoparticles of magnesium oxide, calcium carbonate, calcium oxide, silicon dioxide, or the like can be used.

[0073] Porous ceramics with nanoscale pores can be used as the template ceramic particles. When the use of hydrofluoric acid is to be avoided in the separation process, the template ceramic particles are preferably composed of an alkaline earth metal oxide, more preferably magnesium oxide, calcium carbonate, or calcium oxide. When hydrofluoric acid is used in the separation process, ceramic particles composed of alumina, zeolite, etc. can be used.

[0074] Porous ceramics have numerous pores (micropores) inside them, and like general ceramics, they have high strength, rigidity, and heat resistance. This creates spaces filled with gas inside, making porous ceramics very light, with a small heat capacity and low thermal conductivity. Porous ceramics can be manufactured by freely controlling the size and shape of the pores, the structure, and the percentage of pores per unit area (porosity), which can give them a variety of functions.

[0075] The framework of this embodiment has nanoscale spaces, which can be produced by using ceramic template particles with nanoscale particle sizes.

[0076] The ceramic particles used in this embodiment may contain pores therein. The ceramic particles may contain micropores with a pore diameter of 100 nm or less. The pore diameter is preferably 100 nm or less, more preferably 1 nm or more and 65 nm or less, and most preferably 2 nm or more and 40 nm or less.

[0077] The carbon fiber of this embodiment may have pores, and the pores may be through-holes or bottomed pores. When silicon is deposited on the carbon fiber during the production of a silicon negative electrode material, silicon enters and deposits not only in the through-holes but also in the bottomed pores. The carbon fiber may include micropores of 100 nm or less. The pore diameter is preferably 100 nm or less, more preferably 1 nm or more and 65 nm or less, and most preferably 2 nm or more and 40 nm or less.

[0078] By using a structure having a CF with an internal space as a skeleton, it is possible to suppress structural destruction caused by electronic conduction and expansion and contraction that accompany charging and discharging during use of a lithium-ion battery.

[0079] The size of the three-dimensional nano-sized spaces and the diameter of the pores within the framework structure can be adjusted by appropriately selecting the size of the template ceramic particles and the internal pore structure, or by using oxidative etching or impact destruction.

[0080] By narrowing the space within the framework through the physical stress treatment described above, the thickness of the deposited silicon can be reduced, thereby suppressing the expansion of the silicon during charging and discharging. Any pressure method can be used to apply physical stress, but the particle strength will vary depending on factors such as the number of graphene layers that make up the framework.

[0081] When pressing powder particles, it is possible to select the conditions under which the appropriate pressure is applied by selecting the appropriate pressing device, holding container, pressing element, etc. Other methods that can be used include uniaxial powder pressing and roll pressing. Hydraulic pressure and hydrostatic pressure can also be used as pressure sources.

[0082] The pore size can be changed by compressing the pores under pressure. For example, by compressing CF with a peak diameter of 50 nm in the pore size distribution, the pore size can be reduced to approximately 10 nm or less.

[0083] If the pore size is small while the reduction in total void volume is small, the reduction in negative electrode capacity is also small. A small pore size allows the deposited silicon to have a smaller thickness, resulting in favorable cycle reversibility. Similar to the pore size, the preferred thickness is 0.9 to 20 nm, more preferably 0.9 to 15 nm, and most preferably 1.0 to 10 nm.

[0084] The CF may be in a particulate form, and the particle size, particle size distribution (particle size distribution) and shape may affect the expansion during charge and discharge.

[0085] Powdered carbon fiber has a particle size distribution. When producing an electrode using a negative electrode material in which silicon is deposited on carbon fiber, the carbon fiber must be adjusted to a certain particle size in order to form a slurry together with a binder and apply it. In this case, the average particle size of the carbon fiber is preferably 1.3 μm to 50 μm, more preferably 1.5 μm to 30 μm, and most preferably 2 μm to 15 μm.

[0086] The aspect ratio is one index of shape. In general negative electrode materials, the smaller the aspect ratio, the more fluid the powder, which improves ease of handling in the manufacturing process and electrode packing. CF consists of particles of various sizes and shapes, so the average aspect ratio is used. In an SEM observation image of CF particles, the major and minor axes of 100 particles are measured, and the value obtained by dividing the major axis by the minor axis is taken as the aspect ratio. The average of all measurements is defined as the average aspect ratio. The average aspect ratio of CF particles is preferably 1 to 10, more preferably 1 to 7, and most preferably 1 to 5.

[0087] The average aspect ratio of CF indicates the three-dimensional anisotropy of the particles, and in CFSI, where silicon is deposited on CF, this is a factor that leads to anisotropy when silicon alloys with Li and expands. The aspect ratio is the ratio of the long axis to the short axis of the particle. When the aspect ratio of CF is small, the expansion of CFSI particles with silicon deposited in the electrode occurs more evenly in three dimensions, and the higher the anisotropy, the greater the expansion distance in the long axis direction. There is an optimal aspect ratio depending on the electrode design, such as the amount of CFSI added to the electrode and the electrode thickness. In general, the smaller the aspect ratio of CF, the more isotropic the expansion of CFSI particles with silicon deposited on CF in the electrode, and the smaller the impact of expansion on the electrode, resulting in better characteristics.

[0088] To obtain CF with a small aspect ratio, it can be separated by pulverization and classification. To efficiently produce CF with a small aspect ratio industrially, ceramic particles with a primary particle size of nm are granulated to 100 μm or less by a granulation operation, and then subjected to a CF treatment. The granulation operation can be suitably performed using commercially available dedicated equipment, and methods such as using a media-type rotary granulator using hard beads, or methods such as adding a liquid to form a slurry and then spray-drying it into spherical powder can also be used.

[0089] Granulated ceramic particles are most preferably spherical with an aspect ratio of 1.0, but because ceramic particles vary in powder size and shape, they may also be roughly spherical. By including even a small amount of these small aspect ratio particle powders in CF, a more suitable silicon-based negative electrode material can be obtained.

[0090] The smaller the ratio of the core skeletal structure to silicon, the greater the negative electrode capacity, but the greater the impact of structural destruction due to expansion and contraction during charge and discharge. This leads to a decline in the performance of lithium-ion batteries. Maintaining an appropriate ratio of the core skeletal structure to silicon improves the reversibility of charge and discharge. Therefore, the ratio of CF to silicon can be appropriately selected depending on the purpose.

[0091] 3. Protective Barrier Layer (BL) Next, the protective barrier layer (hereinafter also referred to as "BL") will be described. A silicon negative electrode material having CF inside (hereinafter also referred to as "CFSI negative electrode material") may have a protective barrier layer. The protective barrier layer is provided to suppress structural destruction due to the formation of a reaction film with the electrolyte and expansion and contraction. The protective barrier layer is provided on the outermost layer of CFSI when the amount of silicon deposition is increased to increase the capacity of the CFSI negative electrode material. For this reason, the BL is required to have a certain degree of strength and flexibility. Carbonaceous materials, graphene materials, and thin-layer graphene materials are preferably used as the BL material.

[0092] The BL of the present invention can be produced by applying the technology of chemical vapor deposition (hereinafter also referred to as "CVD"). In this embodiment, among CVD methods, template chemical vapor deposition (hereinafter referred to as "T-CVD") is preferred. This is a technique in which an organic gas is passed through a material to be coated that has CVD activity and is heated in an inert gas atmosphere, and carbon atoms of the organic matter in the gas are condensed to form a carbonaceous film.

[0093] To give the silicon surface CVD activity, catalytic active sites necessary for carbonaceous material generation are formed on the silicon surface by treating it with an oxide layer coating or a silane coupling agent.

[0094] 4. Barrier Layer Void (BLV) in Protective Coating Layer In this embodiment, before providing the BL by CVD or the like as described above, an oxide layer is formed on the silicon surface, and then after the BL is formed, the oxide layer is removed with a reagent, thereby providing a void layer between the BL and the silicon surface layer. In this specification, this is referred to as a barrier layer void in the protective coating layer (hereinafter also referred to as "BLV"). By providing such a void layer, structural damage caused by charge and discharge can be alleviated.

[0095] The amount of silicon in the CFSI anode material determines the anode capacity and expansion / contraction amount, but by changing the amount of oxide layer accordingly, the thickness (or volume) of the void layer can be adjusted, which alleviates structural destruction and improves charge / discharge reversibility.

[0096] Acids and alkalis can be used as reagents for removing contained oxides. In this embodiment, it is preferable to use an acid, and more preferably hydrofluoric acid.

[0097] The amount of the oxide layer is adjusted to adjust the spatial volume of the BLV, but leaving the oxide layer is preferable because the strength of the oxide layer prevents deterioration of the CSI negative electrode material during rapid charging and discharging.

[0098] When the contained oxide is layered, the thickness of the layer is preferably 1000 nm or less. The lower limit of the layer thickness is preferably 10 nm or more, more preferably 30 nm or more, and even more preferably 50 nm or more. The upper limit of the layer thickness is preferably 800 nm or less, and even more preferably 500 nm or less.

[0099] 5. Manufacturing Method of CFSI Negative Electrode Material Next, a manufacturing method of the CFSI negative electrode material will be described. In this embodiment, a CFSI negative electrode material containing CF is manufactured by contacting a compound containing silicon element with CF at high temperature and depositing silicon on the CF by a vapor phase deposition reaction (CVD method).

[0100] The CF to be used can be previously subjected to pulverization and classification to adjust the particle size to suit the intended use. The average particle size is preferably 1 to 70 μm, more preferably 2 to 30 μm.

[0101] Furthermore, after the final process is completed, the particle size can be adjusted by further pulverization or classification depending on the intended use. The average particle size is preferably 1 to 70 μm, more preferably 2 to 30 μm.

[0102] Silane (SiH) is a compound containing silicon. ４ ) and diluting gaseous silane with an inert gas to form a mixed gas for CVD.

[0103] In this embodiment, a CFSI negative electrode material containing CF is produced by depositing silicon on CF by a CVD method in which a compound containing silicon is brought into contact with CF placed in a reaction vessel at high temperature. Silane (SiH ４ ) and CVD may be performed using a mixed gas in which gaseous silane is diluted with an inert gas.

[0104] First, CF is placed in a reaction vessel. Next, a silicon-containing compound is circulated at high temperature, and silicon is deposited on the surface of the CF by CVD. At this time, silicon is also deposited in the spaces formed inside the three-dimensional structure of the CF.

[0105] Gaseous silane can be mixed with other inert gases, such as nitrogen gas. The treatment temperature and time can be varied, and the treatment temperature can be, for example, 300°C to 400°C, 400°C to 500°C, 500°C to 600°C, 600°C to 700°C, 700°C to 800°C, or 800°C to 900°C. A temperature of 410 to 600°C is preferred to produce industrially stable materials. The gas mixture can be 0.1% to 1% by volume silane gas, with the remainder being an inert gas. Alternatively, the gas mixture can be 1% to 10% by volume silane and the remainder being an inert gas, 10% to 20% by volume silane and the remainder being an inert gas, or 20% to 50% by volume silane and the remainder being an inert gas. Alternatively, the gas mixture can be 50% or more by volume silane and the remainder being an inert gas. In order to produce an industrially stable CFSI negative electrode material that can stably exhibit negative electrode material properties such as capacity and number of cycles, the concentration of silane gas in the CVD process is preferably 0.5 to 20% by volume.

[0106] The reactor in which the CVD process is carried out can be a fluidized bed reactor, a static bed reactor, an elevator kiln, a rotary kiln, a box kiln, or any other suitable reactor type, according to various designs known in the art. In a preferred embodiment, CF is treated in a reactor in which the gas is fluidized or a reactor in which the gas is stirred, so that the CF is treated under conditions that allow the CF to come into uniform contact with the raw material gas.

[0107] Alternatively, after placing the CF, a mixed gas in which silane is diluted with an inert gas may be introduced into a reaction vessel evacuated to a vacuum, followed by CVD. An appropriate amount of the mixed gas may be introduced in pulses at short intervals. In this case, the silane is reliably filled into the nanostructure of the CF, followed by thermal decomposition, allowing silicon to be deposited and filled in a close-packed manner. This process may be repeated depending on the purpose to obtain high capacity and high reversibility.

[0108] Furthermore, the method for producing a lithium-ion battery negative electrode material of this embodiment may include, after the step of depositing silicon on the outer surface of CF, the steps of providing an oxide layer on the outer surface of the deposited silicon, forming a protective coating layer made of any of carbonaceous, graphene, and thin-layer graphene on the outer surface of the oxide layer by a CVD method using a hydrocarbon gas, and dissolving and eluting the oxide layer with an acid to form a void layer between the protective coating layer and the outer surface of the deposited silicon.

[0109] By adjusting the amount of oxide layer on the silicon outer surface, the spatial volume of the BLV can be adjusted. By leaving the oxide layer, the strength of the oxide layer prevents the CFSI anode material from being damaged during rapid charging and discharging, thereby reducing degradation. Furthermore, the dissolution process can be omitted, reducing manufacturing costs.

[0110] As described above, the negative electrode material according to this embodiment includes a process of forming a protective coating layer by placing the product of thermal decomposition of a carbon-containing source gas on the surface of deposited silicon, followed by removing the oxide layer present between the deposited silicon and the protective coating layer by acid treatment. Therefore, the protective coating layer having a three-dimensional structure and composed of either carbonaceous, graphene, or thin-layer graphene obtained in the above process is thin but flexible, and thus has some resistance to expansion during lithium-silicon alloy formation. In the negative electrode material according to this embodiment, a BLV is provided between the silicon and the BL. This makes it possible to appropriately prevent the collapse and scattering of silicon particles, which can occur when silicon expands and contracts due to the alloying and dealloying reactions, causing repeated volume increases and decreases.

[0111] 6. Preparation of Protective Coating Layer and Void Layer in Protective Coating Layer The lithium-ion battery negative electrode material of this embodiment may have a protective coating layer (BL) on the deposited silicon. The predetermined temperature in the step of forming the protective coating layer is in the range of 400°C to 1200°C. If the temperature is below 400°C, carbon is less likely to deposit on the surface. If the temperature exceeds 1200°C, silicon and carbon react to form Si-C bonds, which is undesirable because it prevents the formation of the intended protective coating layer.

[0112] The oxide layer on the silicon surface suppresses the degradation of the CSI anode material due to its strength during rapid charging and discharging. Therefore, a moderately high-strength layer such as an oxide layer is preferable from the viewpoint of the effect of suppressing the degradation of the anode material. On the other hand, the presence of an oxide layer on the silicon surface reduces the amount of silicon available for reaction. It can be used to the extent that the decrease in anode capacity does not substantially affect the battery capacity. These high-strength layers should be kept as small as possible. The amount is preferably 50% by volume or less, more preferably 30% or less, and even more preferably 20% or less, of the total volume of the CSFI.

[0113] In order to control the number of layers to be formed to one or more layers, it is preferable to use a dry method, chemical vapor deposition (CVD), for forming the protective coating layer in this step.

[0114] A vacuum pulse CVD process can also be used in which a reaction vessel containing oxide-coated silicon is evacuated and gas is allowed to flow for a specific period of time one or more times, thereby depositing a protective coating over the oxide layer covering the silicon surface.

[0115] In addition, in order to promote the reaction for forming the protective coating layer by the CVD method, a radical reaction mechanism consisting of organic compounds, hydrogen, water, metal elements, etc. may be utilized.

[0116] When the protective coating layer forming step is performed by the CVD method, the pressure can be, for example, 1 to 200 kPa. The temperature increase rate in the protective coating layer forming step is, for example, 1 to 50°C / min. When the product of thermal decomposition of the source gas is placed on the oxide layer on the silicon surface, by gradually increasing the temperature at a rate of 1 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.

[0117] On the other hand, when an organic substance with double or more bonds is used as a carbon source in forming a protective coating layer, it is prone to thermal decomposition, and the bonds broken during decomposition tend to bond with other pyrolysis products, resulting in the formation of a disordered six-membered carbon ring structure. By utilizing such bonding reactions, a protective coating layer with structural defects, i.e., conductive holes, can be formed.

[0118] In the protective coating layer forming step, gaseous organic molecules are used as a carbon source for the carbon atoms that constitute the protective coating layer. The gaseous organic molecules are one or more 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. Preferably, the gaseous organic molecules are methane, acetylene, ethylene, or propylene.

[0119] In the protective coating layer forming step, in addition to the above-mentioned raw material 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 protective coating layer forming step, from the viewpoint of disposing one or two protective coating layers, the flow rate of the carrier gas is preferably controlled to 0.05 to 1.00 m / min, and the amount of the raw material gas relative to the total amount of the raw material gas and the carrier gas is preferably controlled to 1 to 60% by volume.

[0120] The lithium-ion battery negative electrode material of this embodiment may have a protective coating layer void (BLV) between the deposited silicon and the protective coating layer. The BLV is generated by removing the oxide layer between the silicon surface and the protective coating layer by dissolving it with acid. Here, since the protective coating layer has many micropores, the solvent for dissolving the oxide layer penetrates the protective coating layer. Hydrofluoric acid (HF) is preferably used to remove the oxide layer. Even during this process, the structure of the previously formed protective coating layer is maintained because carbon is a material that is resistant to hydrofluoric acid, which is a strong acid. After the removal reaction with HF, the material is washed using a known method to remove the dissolved oxide layer-derived material and HF from the protective coating layer and the silicon surface.

[0121] 7. Negative Electrode and Battery Comprising CFSI Negative Electrode Material Next, a lithium ion secondary battery equipped with an electrode containing the lithium ion battery negative electrode material of this embodiment will be described.

[0122] 2 shows an example of the cross-sectional structure of a coin-type lithium-ion battery 200. This lithium-ion battery 200 is formed by stacking a disk-shaped positive electrode 212 housed in a metal exterior part 211 and a disk-shaped negative electrode 214 housed in a metal exterior part 113 with a separator 215 interposed between them. 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 peripheries of the exterior parts 211 and 213 are sealed by being crimped with a seal gasket 217.

[0123] Next, the negative electrode 214 will be described. The negative electrode 214 can be obtained by coating a current collecting metal foil such as rolled copper foil with a slurry made by mixing a carbonaceous material as a main active material, a binder, and a solvent, and then heating and drying the resulting mixture to remove the solvent, followed by forming the resulting mixture into a predetermined size and density.

[0124] The negative electrode material of this embodiment is preferably used by mixing the main active material. When the carbon-based material is in powder form, it can be easily mixed with a binder and a solvent.

[0125] As a carbonaceous material that can be used for the negative electrode, it is preferable that the material has many stabilizing sites inside, and can bond and stabilize Li ions with electrons flowing from an external circuit.

[0126] For example, any material of organic origin, whether high or low in crystallinity, can be used, and graphite, coke, amorphous carbon, hard carbon, polymer carbon, etc. can be suitably used. In this case, the principle is that Li ions are sandwiched between graphene layers, etc., and bond with electrons to stabilize them.

[0127] As another stabilization mechanism, a method of electrochemically forming an intermetallic compound can also be used, and silicon, tin, zinc, bismuth, antimony, cadmium, lead, germanium, etc. can be suitably used.

[0128] In addition, other materials that exhibit low electrochemical reaction potentials and are used for the negative electrode of lithium-ion batteries can also be used, such as compounds of metals with oxygen, sulfur, halogens, nitrogen, phosphorus, etc.

[0129] Depending on the application of the lithium ion battery, a plurality of the above negative electrode materials can be mixed in a predetermined ratio and used to obtain a desired discharge profile.

[0130] The physical properties of anode materials are determined by the requirements of the device (e.g., storage battery) design and manufacturing process, which are based on constraints such as the usage of lithium-ion batteries. The manufacturing process is designed to achieve the desired physical properties. Physical properties of commonly used anode materials include the powder particle size and distribution, specific surface area, and density.

[0131] As an example, the powder particle size of a commonly used negative electrode material is appropriately selected in consideration of other constituent requirements of the lithium-ion battery. From the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, the powder particle size of a general negative electrode material is preferably 1 to 70 μm on average, more preferably 2 to 30 μm. The CFSI negative electrode material of this embodiment is also a powder particle, and the average particle size (average particle size) is preferably 2 μm to 20 μm, more preferably 3 μm to 18 μm, and even more preferably 4 μm to 10 μm.

[0132] The above-mentioned negative electrode materials generally have high electronic conductivity, but some materials have smooth surfaces and insufficient contact between particles, so it is preferable to add a conductive additive to improve electronic conductivity. Carbon-based materials, metal-based materials, and other materials with high electronic conductivity can also be used as materials, with carbon-based materials being preferred. The skeletal structure of this embodiment described above may also be used as a conductive additive.

[0133] The amount of conductive additive used should be kept to a minimum, and the content of the negative electrode material, which determines the capacity of the lithium-ion battery, should be maximized.

[0134] Examples of conventional carbon-based materials include soot, acetylene black, ketjen black, lamp black, furnace black, carbon black, graphite, carbon fiber, graphite fiber, nanofiber, nanotube, coke, hard carbon, and amorphous carbon.

[0135] In comparison, CMS and GMS, which function as skeletal structures, have significant features not found in conventional materials, and can be combined with conventional materials as needed to achieve even greater efficacy. For example, flake graphite and highly linear carbon nanotubes have high electronic conductivity but low ion storage capacity. Therefore, by combining them with the anode material of the present invention, it is possible to construct an excellent battery reaction assistance system that combines electronic conductivity with ion storage capacity.

[0136] Carbon blacks, such as acetylene black, are composed of interconnected structural particles with diameters of several tens of nanometers. However, the crystallinity of carbon is not particularly high, the structural length is short, and they are prone to collapse, making them difficult to transport electrons over long distances. Despite these properties, by combining them with the auxiliary material of the present invention, it is possible to realize a system that maintains electronic conductivity and also has ion supply ability, even when the three-dimensional structure is maintained or when the three-dimensional structure is crushed and flattened like flake graphite.

[0137] The suitable ratio of the skeletal structure to be contained in the negative electrode varies depending on the type of positive electrode material, the type and amount of binder, the battery capacity design, etc. In this embodiment, as described above, the ratio of the skeletal structure to be added to the positive electrode is preferably 0.1 wt % or more and 5 wt % or less per electrode mixture. By adding the skeletal structure in this range, good characteristics can be obtained.

[0138] The current collecting metal foil is preferably made of a material that is inexpensive and durable for industrial use, and is preferably a material that does not electrochemically react with the potential developed by the negative electrode. For example, copper foil, nickel foil, titanium foil, and stainless steel foil are preferred as the current collecting metal foil, and electrolytic copper foil and rolled copper foil, which are generally readily available, are more preferred.

[0139] The method for forming the coating film of the above-mentioned slurry can be a commonly used printing technique. When the thickness is small, gravure printing or the like is preferably used, and when the thickness is large, printing techniques such as doctor blade printing or die printing are preferably used.

[0140] Thereafter, the coating film is dried by heating. Any drying method can be used, and a method that can achieve the desired binding strength by the binder is preferably used.

[0141] Thereafter, when forming the negative electrode into a predetermined size, an industrially available cutting blade and the like and the method thereof are preferably used. In addition, to achieve a predetermined density, an industrially available pressing device and the like and the method thereof are preferably used as needed.

[0142] The negative electrode material and conductive additive are often in powder form, and in order to fix them together and on the current collecting metal foil, it is preferable to mix them with a small amount of binder. The binder is required to be chemically and electrochemically inert and to have some degree of elastic deformability and affinity, and a plastic resin material is preferably used.

[0143] Another application of the framework structure is to use it in the form of a paint in which the powder is dispersed in a liquid solvent at a certain ratio. In this case, the solvent can be an organic or inorganic compound applicable to the production of lithium-ion batteries. To maintain a good dispersion state of the powder in the solvent, an organic or inorganic dispersant (e.g., a monomolecular or plastic resin material) can be suitably used.

[0144] Examples of the plastic resin material include fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol; halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride; conductive polymers such as polyaniline; alkane-based polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; ring-containing polymers such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone; acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide; carboxymethyl cellulose; and styrene-butadiene rubber. The resin materials may also be mixtures, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, or block copolymers. The weight average molecular weight of these resins is usually 10,000 to 3,000,000, and preferably 100,000 to 1,000,000. If the molecular weight is too small, the strength of the coating film decreases, and if it is too large, the viscosity increases, making it difficult to form an electrode.

[0145] In order to distribute the binder sufficiently uniformly and to form a coating film of the slurry with the predetermined dimensions, an appropriate slurry solvent can be used that dissolves only the binder resin and does not dissolve other materials. For example, when polyvinylidene fluoride is used, dimethylformamide is preferably used as the solvent. Alternatively, N-methylpyrrolidone can be used as the solvent, and the solvent can be selected appropriately depending on the conditions of the manufacturing process.

[0146] The positive electrode 212 is generally obtained by applying a slurry, which is a mixture of a metal oxide material, a conductive additive that aids electronic conductivity, a binder, and a solvent, onto a current collecting metal foil such as rolled aluminum foil to form a coating film, which is then heated and dried to remove the solvent, and then formed into a predetermined size and density.

[0147] A metal compound 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.

[0148] Examples of such materials include transition metal oxides, composite oxides of lithium and transition metals, and transition metal sulfides. Examples of transition metals that can be used include Fe, Co, Ni, and Mn. Specific examples include MnO, V, and the like. ２ O ５ , V ６ O １３ , TiO ２ transition metal oxides such as LiNiO ２ , LiCoO ２ , LiMn ２ O ４ etc., TiS ２ , FeS, MoS ２ In order to improve the properties of these inorganic compounds, specific elements may be partially substituted with other elements.

[0149] In addition to the inorganic compounds listed above, there are also positive electrode materials made of organic compounds, such as polyaniline, polypyrrole, polyacene, disulfide-based compounds, polysulfide-based compounds, and N-fluoropyridinium salts. The positive electrode material may also be a mixture of the inorganic and organic compounds listed above.

[0150] The physical properties of cathode materials are determined by the requirements of the battery design and manufacturing process, which are based on constraints such as the type of use of lithium-ion batteries. In manufacturing cathode materials, the process is designed to achieve the desired physical properties. Physical properties include powder particle size and distribution, specific surface area, and density.

[0151] 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 30 μm is usually preferred, and an average particle size of 1 to 10 μm is more preferred.

[0152] Since the above-mentioned positive electrode materials generally have low electronic conductivity, it is preferable to have a battery reaction auxiliary material that assists electronic conductivity coexist in the positive electrode. Commonly used conductive auxiliary materials include carbon-based materials and metal-based materials, and other materials with high electronic conductivity can also be used, with carbon-based materials being preferred. The skeletal structure of this embodiment may be used as a battery reaction auxiliary material.

[0153] The amount of coexisting battery reaction auxiliary materials should be kept to a minimum, and the content of the positive electrode material, which determines the capacity of the lithium-ion battery, should be maximized.

[0154] Examples of conventional carbon-based materials include soot, acetylene black, ketjen black, lamp black, furnace black, carbon black, graphite, carbon fiber, graphite fiber, nanofiber, nanotube, coke, hard carbon, and amorphous carbon.

[0155] In contrast, when the skeletal structure of the present embodiment is used as a battery reaction assisting material, it has significant features not found in conventional materials. Because the skeletal structure of the present embodiment includes a graphene portion with a relatively large area in its structure, it has few defects other than carbon-carbon bonds, such as oxygen-containing functional groups at the ends of carbon bonds in a six-membered ring. As a result, it is less likely to deteriorate and decompose in the electrochemical oxidative environment to which it is exposed inside a battery.

[0156] Furthermore, if necessary, further benefits can be obtained by combining the above-mentioned conventional materials. For example, flake graphite and highly linear carbon nanotubes have high electronic conductivity but low ion storage capacity. By combining these properties with the skeletal structure of this embodiment, it is possible to construct an excellent battery reaction assistance system that combines electronic conductivity with ion storage capacity.

[0157] Carbon blacks, such as acetylene black, are composed of interconnected structural particles with diameters of several tens of nanometers. However, carbon does not have high crystallinity, its structural length is short, and it easily collapses, making it difficult to transport electrons over long distances. By combining this with the above-mentioned skeletal structure, it is possible to realize a system that maintains electronic conductivity and also has ion supply capabilities, even when the three-dimensional structure is maintained or when the three-dimensional structure is crushed and flattened like flake graphite.

[0158] The preferred ratio of the carbonaceous framework in the positive electrode varies depending on the type of positive electrode material, the type and amount of binder, the battery capacity design, etc. In this embodiment, as described above, the addition ratio of the battery reaction auxiliary material to the positive electrode is preferably 0.1 wt % or more and 5 wt % or less per electrode mixture. By adding the material in this range, good characteristics can be obtained.

[0159] The positive electrode material and the skeletal structure are often in powder form, and in order to fix them together and on the current collecting metal foil, it is preferable to mix them with a small amount of a binder. The binder is required to be chemically and electrochemically inert and to have some elastic deformability and affinity, and a plastic resin material is preferably used.

[0160] Another application of the battery reaction assisting material is in the form of a coating material in which the powder is dispersed in a liquid solvent at a certain ratio. In this case, the solvent can be an organic or inorganic compound applicable to the production of lithium-ion batteries. To maintain a good dispersion state of the powder in the solvent, an organic or inorganic dispersant (e.g., a monomolecular or plastic resin material) can be suitably used.

[0161] Examples of the plastic resin material include fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene, CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide, polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol, halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride, conductive polymers such as polyaniline, alkane-based polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene, unsaturated polymers such as polybutadiene and polyisoprene, ring-containing polymers such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone, and acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide. The resin materials may also be mixtures, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, or block copolymers. The weight average molecular weight of these resins is usually 10,000 to 3,000,000, and preferably 100,000 to 1,000,000. If the molecular weight is too small, the strength of the coating film decreases, and if it is too large, the viscosity increases, making it difficult to form an electrode.

[0162] In order to distribute the binder sufficiently uniformly and to form a coating film of the slurry with the predetermined dimensions, an appropriate slurry solvent can be used that dissolves only the binder resin and does not dissolve other materials. For example, when polyvinylidene fluoride is used, dimethylformamide is preferably used as the solvent. Alternatively, N-methylpyrrolidone can be used as the solvent, and the solvent can be selected appropriately depending on the conditions of the manufacturing process.

[0163] The current collecting metal foil is preferably made of a material that is inexpensive and durable for industrial use, and is preferably made of a material that has electrochemical resistance to the potential developed by the positive electrode. Examples of the current collecting metal foil include aluminum foil, nickel foil, titanium foil, and stainless steel foil, and more preferably rolled aluminum foil, which is commonly available.

[0164] A commonly used printing technique can be used to form a coating film of the slurry on the current collecting metal foil. When the coating thickness is small, gravure printing or the like is preferably used, and when the coating thickness is large, doctor blade printing, die printing or the like is preferably used.

[0165] Thereafter, the coating film is dried by heating. Any drying method can be used, and a method that can achieve the desired binding strength by the binder is preferably used.

[0166] Thereafter, when forming the cathode into a predetermined size, an industrially available cutting blade and the like and the method thereof are preferably used. In addition, to achieve a predetermined density, an industrially available pressing device and the like and the method thereof are preferably used as needed.

[0167] A battery electrolyte that is applied to a lithium ion battery will now be described.

[0168] An electrolyte is a solute dissolved in an organic solvent, and is usually the main component.

[0169] One of the components of the electrolyte is a solute that is the source of ions, that is, a Li salt.

[0170] The type of solute is not particularly limited, and any solute known to be used in this lithium ion battery can be used. Specific examples include the following:

[0171] An example of the solute is LiPF ６ and LiBF ４ inorganic salts such as LiCF ３ SO ３ , LiN(CF ３ SO ２ ) ２ , LiN(C ２ F ５ SO ２ ) ２ , Li cyclic 1,2-perfluoroethane disulfonylimide, Li cyclic 1,3-perfluoropropane disulfonylimide, LiN(CF ３ SO ２ ) (C ４ F ９ SO ２), LiC(CF ３ SO ２ ) ３ , LiPF ４ (CF ３ ) ２ , LiPF ４ (C ２ F ５ ) ２ , LiPF ４ (CF ３ SO ２ ) ２ , LiPF ４ (C ２ F ５ SO ２ ) ２ , LiBF ２ (CF ３ ) ２ , LiBF ２ (C ２ F ５ ) ２ , LiBF ２ (CF ３ SO ２ ) ２ , LiBF ２ (C ２ F ５ SO ２ ) ２ and Li bis(oxalate)borate.

[0172] Of these, LiPF ６ , LiBF ４ , LiN(CF ３ SO ２ ) ２ and LiN(C ２ F ５ SO ２ ) ２ is preferred in terms of exhibiting battery performance, and LiPF ６ and LiBF ４ is preferred.

[0173] These Li salts may be used alone or in combination of two or more.

[0174] The content of the Li salt in the electrolyte varies depending on the type of solvent in which the Li salt is dissolved and the mixed composition, but the content of the Li salt in the electrolyte is preferably 7 to 190 wt %, more preferably 10 to 180 wt %, and even more preferably 13 to 150 wt %.

[0175] Next, the organic solvent used in the electrolyte will be described.

[0176] The type of solvent is not particularly limited, and can be appropriately selected from those conventionally known as solvents, such as cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, cyclic carboxylic acid esters, chain carboxylic acid esters, phosphorus-containing organic solvents, and the like, which have no unsaturated bond.

[0177] In addition to viscosity, factors that affect the migration of Li ions include the viscosity and solvating power of the organic solvent. Solvating power is the force that dissociates dissolved ions, and if it is too strong, it will inhibit the migration of ions, so there is an optimum value.

[0178] Furthermore, practical lithium-ion batteries can be used under a wide range of environmental conditions, and physical properties such as the melting and boiling points of organic solvents must also be kept within certain ranges.

[0179] A practical solution to the above requirements is to use a mixture of multiple organic solvents. The mixture composition is determined by taking into consideration practical properties, such as the combination of organic solvents with high and low melting points, or organic solvents with high and low solvating power.

[0180] In the electrolyte, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate, neither of which has a carbon-carbon unsaturated bond.

[0181] Examples of cyclic carbonates include alkylene carbonates having an alkylene group having 2 to 4 carbon atoms, such as ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are preferred from the viewpoint of improving battery characteristics, and ethylene carbonate is particularly preferred.

[0182] As the chain carbonates, dialkyl carbonates are preferred, and the number of carbon atoms in the constituent alkyl groups is preferably 1 to 5, and particularly preferably 1 to 4. Specific examples include dialkyl carbonates such as symmetric chain alkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; and asymmetric chain alkyl carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate. Among these, dimethyl carbonate is the most preferred in terms of viscosity because it has the lowest viscosity.

[0183] However, because dimethyl carbonate has a slightly low boiling point, more suitable properties can be obtained by further mixing it with a chain carbonate having a higher boiling point. Diethyl carbonate is the preferred chain carbonate to be mixed, but other chain carbonates can also be used without any problems.

[0184] The mixing ratio also varies depending on the desired practical properties. There is an optimum ratio of the chain carbonate to the cyclic carbonate, taking into account the ratio of the Li salt.

[0185] The content of the cyclic carbonate in the electrolyte is preferably 1 to 35% by weight, more preferably 3 to 30% by weight, and even more preferably 4 to 25% by weight. A mixture of multiple cyclic carbonates can be used.

[0186] On the other hand, the content of the chain carbonate in the electrolyte is preferably 40 to 70% by weight, more preferably 43 to 68% by weight. A plurality of chain carbonates can be used in combination.

[0187] The following combinations are suitable as overall compositions. Among combinations of ethylene carbonate and dialkyl carbonates, ethylene carbonate and dimethyl carbonate are preferred, and a symmetric chain dialkyl carbonate and / or an asymmetric chain dialkyl carbonate may also be included. For example, combinations containing ethylene carbonate, a symmetric chain dialkyl carbonate, and an asymmetric chain dialkyl carbonate, such as ethylene carbonate, dimethyl carbonate, and diethyl carbonate; ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate; or ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, are preferred because they provide a good balance between cycle characteristics and high-power discharge characteristics. Among these, ethyl methyl carbonate is preferred as the asymmetric chain dialkyl carbonate, and the alkyl group of the alkyl carbonate preferably has 1 to 2 carbon atoms.

[0188] Furthermore, as a solvent that aids in the dissociation and migration of ions, cyclic ethers, chain ethers, cyclic carboxylic acid esters, chain carboxylic acid esters, etc. may be added in addition to the above-mentioned main organic solvents.

[0189] Examples of cyclic ethers include tetrahydrofuran and 2-methyltetrahydrofuran, and examples of chain ethers include dimethoxyethane and dimethoxymethane.

[0190] Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone, and examples of chain carboxylic acid esters include methyl acetate, methyl propionate, ethyl propionate, and methyl butyrate.

[0191] Among these, chain carboxylic acid esters are particularly preferred.

[0192] Furthermore, it is also preferable to add a fluorine-containing cyclic carbonate having two or more fluorine atoms to the electrolyte.

[0193] The number of fluorine atoms in a fluorinated cyclic carbonate having two or more fluorine atoms is not particularly limited, but in the case of fluorinated ethylene carbonate, the lower limit is usually two or more and the upper limit is usually four or less, preferably three or less.

[0194] In the case of fluorinated propylene carbonate, the lower limit is usually 2 or more, and the upper limit is usually 6 or less, preferably 5 or less. In particular, those in which two or more fluorine atoms are bonded to carbons forming a ring structure are preferred from the viewpoint of improving cycle characteristics and storage characteristics.

[0195] Among these, fluorinated ethylene carbonates having two or more fluorine atoms are preferred from the viewpoint of improving battery characteristics, and among these, cis-4,5-difluoro-1,3-dioxolane-2-one, trans-4,5-difluoro-1,3-dioxolane-2-one, and 4,4-difluoro-1,3-dioxolane-2-one are particularly preferred.

[0196] The fluorine-containing cyclic carbonate having two or more fluorine atoms may be used alone or in combination of two or more. The proportion of the fluorine-containing cyclic carbonate compound having two or more fluorine atoms in the nonaqueous electrolyte solution is not particularly limited in order to exhibit the effects of this embodiment, but is usually 0.001 wt% or more, preferably 0.01 wt% or more, more preferably 0.1 wt% or more, particularly preferably 0.2 wt% or more, and most preferably 0.25 wt% or more. At a concentration lower than this, the effects of this embodiment may be difficult to exhibit. Conversely, if the concentration is too high, the internal pressure of the battery may increase during high-temperature storage, so the upper limit is usually 10 wt% or less, preferably 4 wt% or less, more preferably 2 wt% or less, particularly preferably 1 wt% or less, and most preferably 0.5 wt% or less.

[0197] Furthermore, cyclic carbonates having unsaturated bonds or aromatic compounds having a total carbon number of 7 or more and 18 or less may be mixed into the electrolyte.

[0198] Among cyclic carbonates having an unsaturated bond, vinylene carbonate, vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate, and 4,5-divinylethylene carbonate are preferred from the viewpoint of improving cycle characteristics, and among these, vinylene carbonate and vinylethylene carbonate are more preferred. These may be used alone or in combination of two or more kinds.

[0199] Preferred aromatic compounds having a total carbon number of 7 or more and 18 or less include biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, and the like.

[0200] It is believed that by suppressing the side reaction between the aromatic compound having a total carbon number of 7 to 18 and the negative and positive electrodes in this way, a significant decrease in discharge characteristics after high-temperature storage can be suppressed.

[0201] In order to achieve the effects of this embodiment, the proportion of aromatic compounds having a total carbon number of 7 to 18 in the electrolyte is usually 0.001 wt% or more, preferably 0.1 wt% or more, particularly preferably 0.3 wt% or more, and most preferably 0.5 wt% or more, with the upper limit being usually 5 wt% or less, preferably 3 wt% or less, and particularly preferably 2 wt% or less. At a concentration lower than this lower limit, the effect of improving safety during overcharge may be difficult to achieve. Conversely, if the concentration is too high, battery characteristics such as high-temperature storage characteristics may be deteriorated.

[0202] The separator 215 separates the positive electrode 212 and the negative electrode 214, prevents short circuits of current due to contact between the two electrodes, and allows lithium ions to pass through. A porous resin film is preferably used for the separator 215.

[0203] Suitable membrane forms include stretched membranes in which pores are formed by stretching bulk resin, and nonwoven fabrics in which a large number of fibrous resin fibers are laminated to form a porous structure like a porous membrane.

[0204] Examples of resin materials include polyolefins, with polyethylene being particularly suitable. Polyethylene has a relatively low melting temperature, and when the battery temperature rises for some reason (e.g., an unsafe condition such as a short circuit), the pores in the membrane are blocked by thermal melting, preventing the movement of driving ions, thereby stopping the reaction and ensuring safety.

[0205] Porous membranes formed by the stretching method are usually prepared by adding a plasticizer to polyolefin, and the plasticizer is removed before and after stretching, resulting in a relatively uniform microporous structure with the areas where the plasticizer was present as the starting points.

[0206] In producing a stretched membrane, stretching is usually carried out in both the longitudinal and transverse directions. A suitable stretched membrane can be obtained by appropriately combining any atmospheric medium, temperature, speed, stress, number of process repetitions, etc., together with the removal of the plasticizer, etc.

[0207] Although the above manufacturing process produces high-quality stretched membranes, it is a multi-step process, which makes it difficult to reduce manufacturing costs, such as process costs, and may be a negative factor in the widespread use of lithium-ion batteries.

[0208] On the other hand, by simplifying the process so that stretching is performed only in the longitudinal direction without using plasticizers, etc., it is possible to obtain a porous membrane that can be produced on an industrial level and whose production cost can be reduced. In this case, the applicable resin is polyolefin, and polypropylene is preferably used.

[0209] The separator interposed between the positive electrode and the negative electrode may be formed from an electrically insulating porous material. Examples of the separator include films made of polymers such as polyolefins (e.g., polyethylene and polypropylene), polyesters, polyethylene terephthalate, and polyimides, or fibrous nonwoven fabrics. The separator may be made of one material alone or multiple materials. The separator may be a single layer or a multilayer (composite film). The separator may contain inorganic nanoparticles such as ceramic. The separator may also be coated on both sides with a polymer compound (e.g., polyvinylidene fluoride).

[0210] In a nonaqueous electrolyte battery, a gelled electrolyte containing a polymer compound that swells in an organic solvent to serve as a support for the nonaqueous electrolyte may be used. This is because the inclusion of a polymer compound that swells in an organic solvent can provide high ionic conductivity, leading to excellent charge / discharge efficiency and preventing leakage of the battery. When the nonaqueous electrolyte contains a polymer compound, the content of the polymer compound is preferably within a range of 0.1% by mass to 10% by mass of the nonaqueous electrolyte.

[0211] When a polymer compound such as polyvinylidene fluoride is applied to both sides of the separator, the mass ratio of the non-aqueous electrolyte to the polymer compound is preferably within a range of 50:1 to 10:1. By setting the mass ratio within this range, higher charge / discharge efficiency can be obtained.

[0212] Examples of the polymer compound include ether-based polymer compounds such as polyvinyl formal, polyethylene oxide, and crosslinked polyethylene oxide-containing polymer compounds, ester-based polymer compounds such as polymethacrylate, acrylate-based polymer compounds, and vinylidene fluoride polymers such as polyvinylidene fluoride and copolymers of vinylidene fluoride and hexafluoropropylene. One type of polymer compound may be used alone, or multiple types may be used in combination. In particular, from the viewpoint of the effect of preventing swelling during high-temperature storage, it is desirable to use a fluorine-based polymer compound such as polyvinylidene fluoride.

[0213] A lithium-ion battery having the above-described configuration operates as follows: When the lithium-ion battery is charged, Li ions contained in the positive electrode 212 pass through the separator 215 and are inserted between the layers of the layered structure of graphite contained in the negative electrode 214. When the battery is subsequently discharged, Li ions are released from between the layers of the layered structure contained in the negative electrode 214 and return to the positive electrode 212 through the separator 215. This series of actions causes the battery reaction to proceed.

[0214] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0215] In the above embodiment, a coin-type lithium ion battery has been described as an example of the lithium ion battery, but the lithium ion battery of this embodiment can be similarly applied to batteries of other shapes such as a button type, a paper type, a square type, or a cylindrical type having a spiral structure. Furthermore, the lithium ion battery of this embodiment can be made into various sizes such as a thin type or a large type.

[0216] Furthermore, although the above description describes an embodiment in which a lithium ion battery according to the present embodiment has a liquid electrolyte, any other electrolytes can be used. For example, gel electrolytes and solid electrolytes can also be suitably used.

[0217] 8. Battery Reaction In the anode reaction at the anode using the anode material according to this embodiment, electrons transferred from an external circuit reach the surface of silicon particles, and Li ions and electrons combine to form a Li-Si reaction phase, producing an alloyed composition. The Li-Si reaction phase then spreads within the particles, and production of the Li-Si reaction phase progresses up to the limit of chemical combination, i.e., before the deposition potential of Li metal. As the Li-Si alloying reaction progresses, the crystal lattice expands, causing the volume of the silicon particles to expand, and the battery is charged. Conversely, after Li is released, the volume of the silicon particles contracts, and the battery is discharged.

[0218] In the initial stage of the formation of the Li-Si reaction phase in the alloying reaction, inert reactants consisting of electrolyte components and Li, 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.

[0219] The side reactions cause the deposition of new inactive reactants on the exposed reaction interface, and the side reactions consume Li ions, reducing the reversible Li capacity within the battery system. This reduction leads to a decrease in the battery capacity.

[0220] [Experiment 1: Production of Different Types of Skeleton Structures] <Example 1> Magnesium oxide nanopowder (primary particle size: 0.5 μm, specific surface area (SSA): 120 m) was used as a template ceramic particle having micropores. ２ The heat treatment vessel was filled with argon gas, and the heat treatment vessel was then placed in a tubular reaction vessel. The inside of the vessel was replaced with argon gas, and the temperature was then raised to 910°C. If necessary, a preliminary heat treatment was carried out for the purpose of dehydration, etc. Then, the argon gas and CH ４ Gas mixture (CH ４ A gas concentration of 20% by volume was flowed for 120 minutes, and a carbonaceous film containing a graphene structure was formed on the template by the T-CVD method. After cooling, the template ceramic particles with the carbonaceous film formed were removed and subjected to a crushing and classification process.

[0221] The pulverized and classified product was then treated with hydrochloric acid to dissolve the template, followed by washing and drying while maintaining the intraparticle space, to obtain a CF precursor (skeleton structure precursor). This was then heat-treated at 1600°C in an inert atmosphere to optimize the carbon structure, yielding the CF of Example 1.

[0222] The particle size distribution of the obtained CF was measured using a laser diffraction particle size distribution analyzer (MT3300EXII-SDC, manufactured by Microtrac-Bell Co., Ltd.) Specifically, each auxiliary material was added to water, and ethanol was further mixed therein before measurement. After ultrasonic treatment for 5 minutes using a triple-frequency ultrasonic cleaner (VS-100III, manufactured by AS ONE Corporation), the particle size distribution was measured using the above-mentioned analyzer.

[0223] The obtained CF was subjected to nitrogen adsorption / desorption measurement using a specific surface area / pore distribution measuring device (BELSORP MAX, manufactured by Microtrac-Bell Corporation) at -196°C under the condition of relative pressure P / P0 = 0.96. The measurement sample was subjected to a degassing treatment by vacuum drying at 150°C for 6 hours before the measurement. The equilibrium judgment condition when measuring the pressure inside the sample tube was 300 seconds. From the obtained nitrogen adsorption / desorption isotherm, the BET specific surface area S (m ２ / g) was calculated.

[0224] Based on the obtained adsorption / desorption isotherms, analysis was performed using software Autosorb 1 (manufactured by Anton Paar Japan). In the case of type I adsorption / desorption isotherms, the pore size distribution was analyzed with reference to a kernel calculated by density functional theory (DFT method) assuming slit-type pores, and the total pore volume was determined. In the case of type IV adsorption / desorption isotherms, the pore size distribution was analyzed by applying the Barrett-Joyner-Halenda method (BJH method) to each adsorption / desorption isotherm, and the total pore volume V (cc / g) was determined.

[0225] As a result of the measurement, the average particle size of the obtained CF was 2.4 μm and the specific surface area was 997 m ２ The pore size distribution of the magnesium oxide nanopowder used as the template ceramic particles is shown in Figure 4A (peak pore size 7 nm), and the pore size distribution curve of the obtained CF is shown in Figure 4B. The pore size distribution was fitted with a Gaussian function to calculate the pore size.

[0226] Next, CF 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 CFSI and CF3 was flowed at 200 cc / min under atmospheric pressure for 130 minutes to deposit silicon on the CF3. After cooling, the product was removed and crushed and classified to obtain a CFSI anode material. Chemical analysis revealed that the silicon content (Si content) per gram of the material was 71.2%. A TEM image of the resulting CFSI anode material is shown in Figure 5.

[0227] In a dry state, 68 parts by weight of CFSI 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 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 under an argon gas atmosphere, 1M LiPF was added to the electrolyte. ６ A 2032-type negative electrode test battery with a metallic Li counter electrode was fabricated using a solution (a 1:1 mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC)) and a polypropylene separator.

[0228] The test cells were charged to 0.005 V (vs Li / Li) at 0.2 A / g per negative electrode material. ＋ ) and charged until the current reached 0.01 A / g. Then, at 0.5 A / g, the battery was charged to 2.0 V (vs. Li / Li ＋ ) and then discharge was completed. Next, the same charging and subsequent discharging cycle was repeated 10 times. The charge-discharge efficiency of the obtained test battery in the first cycle (1 ｓｔ CE), initial discharge capacity, charge-discharge efficiency at the 10th cycle (10 ｔｈ CE) was measured.

[0229] Example 2: Aluminum oxide nanopowder (primary particle size 8 nm, SSA 194 m) was used as the microporous ceramic particles serving as the template. ２ A carbonaceous film containing a graphene structure was formed on the template by T-CVD using a Sigma-Aldrich (Sigma-Aldrich 10000 / g) at a heat treatment temperature of 900°C for 120 minutes. After cooling, the film was removed and subjected to a crushing and classification treatment.

[0230] Next, the pulverized and classified product was treated with hydrofluoric acid to dissolve the template, and then washed and dried while maintaining the intraparticle space, yielding a CF precursor. This was then heat-treated at 1600°C in an inert atmosphere to optimize the carbon structure, yielding the CF of Example 2. The measured physical properties of the resulting CF are shown in Table 1, and an SEM image of the resulting CF is shown in Figure 6A. Figure 6B is a high-resolution SEM image of the surface of the CF obtained in Example 2. Figure 6C is an ultra-high-resolution TEM image of the CF obtained in Example 2.

[0231] Silicon was then deposited on the CF under the same conditions as in Example 1. After cooling, the product was removed and crushed and classified to obtain a CFSI anode material. Chemical analysis revealed that the Si content per gram of material was 71.0%. A TEM image of the resulting CFSI anode material is shown in Figure 7. Figure 7 shows that silicon adheres to and sandwiches the CF. Anode test batteries were then fabricated under the same conditions as in Example 1, and battery evaluation was performed.

[0232] Example 3: Magnesium oxide nanopowder (primary particle size: 0.8 μm, specific surface area (SSA): 90 m) was used as a template having micropores. ２ CF was produced under the same conditions as in Example 1, except that a CF containing 10 ...

[0233] Example 4 Silicon dioxide powder (primary particle diameter 40 nm, specific surface area 75 m) was used as a carbonaceous film template. ２ CF was produced under the same conditions as in Example 1, except that a carbon fiber (carbon content: 0 to 1.5%, manufactured by Nippon Aerosil Co., Ltd.) was used. The measured physical properties of the obtained CF are shown in Table 1.

[0234] Thereafter, a CFSI negative electrode material was produced under the same conditions as in Example 1. As a result of chemical analysis, the Si content per gram of the material was 70.6%. Thereafter, a negative electrode test battery was produced under the same conditions as in Example 1, and the battery was evaluated.

[0235] Example 5: Silicon dioxide powder (primary particle diameter 60 nm, specific surface area 55 m) was used as a template. ２ CF was produced under the same conditions as in Example 1, except that a carbon fiber (carbon content: 0 to 1.5%, manufactured by Nippon Aerosil Co., Ltd.) was used. The measured physical properties of the obtained CF are shown in Table 1.

[0236] Thereafter, a CFSI negative electrode material was produced under the same conditions as in Example 1. As a result of chemical analysis, the Si content per gram of the material was 71.1%. Thereafter, a negative electrode test battery was produced under the same conditions as in Example 1, and battery evaluation was performed.

[0237] Example 6: A template of synthetic calcium carbonate NEOLIGHT SA-300 (primary particle diameter 40 nm, manufactured by Takehara Chemical Industry Co., Ltd.) was placed in a quartz boat with approximately 8 g spread over it, and set in the center of a quartz reaction tube of a tubular reaction vessel. While flowing argon gas at a flow rate of 400 mL / min inside the reaction tube, it was heated to 550 ° C. at a temperature increase rate of 10 ° C. / min, and then argon gas was flowed at a flow rate of 320 mL / min and acetylene gas at a flow rate of 80 mL / min, i.e., a raw material gas concentration of 20%, and the temperature was maintained at 550 ° C. for 150 minutes, and CVD processing was performed. Then, while flowing argon gas at a flow rate of 400 mL / min, it was held at 900 ° C. for 120 minutes, and then cooled to room temperature, and the product, the molded carbonaceous laminate, was removed.

[0238] The template was then removed from the resulting molded carbonaceous laminate by the following procedure, yielding CFs. (1) Approximately 8 g of the molded carbonaceous laminate was placed in a 500 mL glass beaker, and approximately 40 mL of ultrapure water was added and stirred with a stirrer. (2) Approximately 40 mL of 8% (2.3 M) hydrochloric acid was added, and the mixture was stirred with a stirrer for 2 hours. (3) The stirred mixture was suction filtered using a PTFE membrane filter (90 mm diameter, 1 μm pore size). (4) The sample remaining in the beaker was rinsed with a small amount of ultrapure water and suction filtered. (5) The sample on the filter was returned to the original glass beaker, and steps (2) to (4) were repeated. (6) Ultrapure water was added to the filter, and the mixture was left to stand for 5 minutes, followed by suction filtration. (7) Step (6) was repeated until the filtrate was neutral, as confirmed by pH test paper. (8) The sample remaining on the filter paper was collected in a beaker and dried overnight in a dryer at 200°C to obtain CF.

[0239] Thereafter, a CFSI negative electrode material was obtained under the same conditions as in Example 1. As a result of chemical analysis, the Si content per gram of the material was 70.2%. A negative electrode test battery was produced under the same conditions as in Example 1, and battery evaluation was performed.

[0240] Example 7 A CF was produced under the same conditions as in Example 6, except that synthetic calcium carbonate (NEOLIGHT SA-200; primary particle size 40 nm, manufactured by Takehara Chemical Industry Co., Ltd.) was used as the template.

[0241] Silicon was then precipitated on the CF under the same conditions as in Example 1. After cooling, the product was removed and crushed and classified to obtain a CFSI negative electrode material. Chemical analysis revealed that the Si content per gram of material was 71.0%. A negative electrode test battery was then fabricated in the same manner as in Example 1, and battery evaluation was performed.

[0242] Comparative Example 1: Instead of CF in Example 1, acetylene black (Denka Black Li100, average particle size 24 μm, specific surface area 68 m) was used. ２ / g, total pore volume 0.26 cc / g. A Si negative electrode material was produced under the same conditions as in Example 1, except that the granulated and pulverized material shown in Figure 9 (TEM image) was used. Chemical analysis showed that the Si content per gram of the obtained Si negative electrode material was 69.7%. A TEM image of the obtained negative electrode material is shown in Figure 8. Thereafter, a negative electrode test battery was produced under the same conditions as in Example 1, and battery evaluation was performed.

[0243] [Experiment 2: Investigation of a Manufacturing Method for CFSI Negative Electrode Material] Example 8 The CF from Example 1 was loaded into a tubular reaction vessel, and the inside of the reaction vessel was evacuated and then heated to 450°C. A gas mixture of nitrogen gas and 4 mol% silane was then introduced, and the pressure was returned to atmospheric pressure. The silane mixed gas was then flowed at 400 cc / min under atmospheric pressure for 180 minutes, depositing silicon on the CF. After cooling, the product was removed and subjected to a crushing and classification process to obtain a CFSI negative electrode material. Chemical analysis revealed that the Si content per gram of material was 71.7%. A negative electrode test battery was then fabricated under the same conditions as in Example 1, and battery evaluation was performed. The results of the battery evaluation are shown in Table 2.

[0244] Example 9 The CF of Example 1 was loaded into a tubular reactor and heated to 450°C. Subsequently, a gas mixture of nitrogen gas and 4 mol% silane was introduced, and the silane mixed gas was flowed at 400 cc / min for 180 minutes under atmospheric pressure, depositing silicon on the CF. Subsequently, argon gas was flowed into the reactor at a flow rate of 400 mL / min, while heating to 600°C. Subsequently, argon gas was flowed at 360 mL / min and acetylene gas at 90 mL / min, i.e., a mixed gas with a raw material gas concentration of 20% by volume, was flowed for 45 minutes while maintaining the temperature at 600°C. A protective coating layer (BL), a carbonaceous film containing a graphene structure, was formed on the silicon by T-CVD, yielding a CFSI anode material. After cooling to room temperature, the product was removed. Chemical analysis revealed that the Si content per gram of the resulting Si anode material was 70.4%. Thereafter, a negative electrode test battery was produced and evaluated under the same conditions as in Example 1. The results of the battery evaluation are shown in Table 2.

[0245] Example 10: The CFSI anode material prepared under the conditions of Example 1 was pulverized and classified, then heat-treated in an air stream at 300°C for 5 hours. The atmosphere was then replaced with argon, and the temperature was raised to 600°C and maintained therein while the argon was flowing. Subsequently, a mixed gas of argon gas and acetylene gas (raw material concentration: 20% by volume) was flowed for 45 minutes, after which the protective coating layer (BL), a carbonaceous film containing a graphene structure, was oxidized by T-CVD to obtain a CFSI anode material formed on silicon with an oxide layer on its surface. Chemical analysis revealed a Si content of 70.1% per gram of the CFSI anode material. TEM images are shown in Figure 10. Furthermore, SEM-EDX analysis confirmed an oxygen content of 1.3%. This confirmed the formation of silicon oxide. Subsequently, anode test batteries were fabricated under the same conditions as in Example 1, and battery evaluation was performed. The battery evaluation results are shown in Table 2.

[0246] Example 11: The CFSI anode material prepared under the conditions of Example 1 was subjected to a pulverization and classification process, followed by heat treatment in an air stream at 300°C for 5 hours. The atmosphere was then replaced with argon, and the temperature was raised to and maintained at 600°C while the argon was flowing. Subsequently, a mixed gas of argon gas and acetylene gas (raw material concentration: 20% by volume) was flowed for 45 minutes, after which the protective coating layer (BL), a carbonaceous film containing a graphene structure, was oxidized by T-CVD to obtain a CFSI anode material formed on silicon with an oxide layer on its surface. After cooling, the resulting product was removed and pulverized and classified.

[0247] The crushed and classified material was then treated with hydrofluoric acid to dissolve the oxide layer, followed by washing and drying to obtain a CFSI anode material having a protective coating layer void layer (BLV) between the BL and the silicon surface. A TEM image of the resulting CFSI anode material is shown in Figure 11. Chemical analysis revealed that the Si content per gram of material was 69.7%. Anode test batteries were then fabricated under the same conditions as in Example 1, and battery evaluation was performed. The results of the battery evaluation are shown in Table 2.

[0248] Example 12 Silicon was deposited on CF under the same conditions as in Example 1, except that the CF precursor was used as CF without being heat-treated at 1600°C in an inert atmosphere. After cooling, the product was removed and crushed and classified to obtain a CFSI negative electrode material. Chemical analysis revealed that the Si content per gram of material was 71.9%. A negative electrode test battery was then fabricated under the same conditions as in Example 1, and battery evaluation was performed. The results of the battery evaluation are shown in Table 2.

[0249] Example 13 The CF (pore peak diameter: 47 nm) obtained in Example 5 was subjected to hydrostatic pressing to obtain a pore-compressed CF (pore peak diameter: 8 nm). Except for using this as the CF, silicon was deposited on the CF under the same conditions as in Example 1. After cooling, the product was removed and subjected to a pulverization and classification process to obtain a CFSI negative electrode material. Chemical analysis revealed that the Si content per gram of the CFSI negative electrode material was 71.3%. Subsequently, a negative electrode test battery was fabricated under the same conditions as in Example 1, and battery evaluation was performed. The results of the battery evaluation are shown in Table 2.

[0250] [Experiment 3: Investigation of the aspect ratio of CF particles] Example 14 Micropore-containing template ceramic particles, which were the same template as used in Example 2, were granulated into an approximately spherical shape using a rotary granulator to obtain approximately spherical granulated particles. CFs were produced under the same conditions as in Example 2 except for the above. An SEM image of the obtained CFs is shown in Figure 12. The image revealed that the particles exhibited approximately spherical shapes with various particle sizes. The granulated particles were crushed and classified, and the average aspect ratio was measured and found to be 1.1. The average aspect ratio of the CFs in Example 2 was 3.1.

[0251] Silicon was then deposited on the CF under the same conditions as in Example 1. After cooling, the product was removed and crushed and classified to obtain a CFSI negative electrode material. Chemical analysis revealed that the average particle size of the resulting CFSI negative electrode material was 6.5 μm and the Si content per gram of material was 71.8%. A negative electrode test battery was then fabricated under the same conditions as in Example 1, and battery evaluation was performed. The results of the battery evaluation are shown in Table 3.

[0252] Example 15 The granulated particles obtained under the conditions of Example 14 were crushed and classified under different conditions to obtain CFs with an average aspect ratio of 1.5. Silicon was then deposited on the CFs under the same conditions as in Example 1. After cooling, the product was removed and crushed and classified to obtain a CFSI negative electrode material. Chemical analysis revealed that the Si content per gram of the obtained CFSI negative electrode material was 71.6%. A negative electrode test battery was then fabricated under the same conditions as in Example 1, and the battery was evaluated. The results of the battery evaluation are shown in Table 3.

[0253] Example 16 The granulated particles obtained under the conditions of Example 14 were crushed and classified under different conditions to obtain CFs with an average aspect ratio of 2.1. Silicon was then deposited on the CFs under the same conditions as in Example 1. After cooling, the product was removed and crushed and classified to obtain a CFSI negative electrode material. Chemical analysis revealed that the Si content per gram of the obtained CFSI negative electrode material was 71.4%. A negative electrode test battery was then fabricated under the same conditions as in Example 1, and the battery was evaluated. The results of the battery evaluation are shown in Table 3.

[0254] Example 17 The granulated particles obtained under the conditions of Example 14 were crushed and classified under different conditions to obtain CFs with an average aspect ratio of 4.5. Silicon was then deposited on the CFs under the same conditions as in Example 1. After cooling, the product was removed and crushed and classified to obtain a CFSI negative electrode material. Chemical analysis revealed that the Si content per gram of the obtained CFSI negative electrode material was 71.3%. A negative electrode test battery was then fabricated under the same conditions as in Example 1, and the battery was evaluated. The results of the battery evaluation are shown in Table 3.

[0255] Example 18 The granulated particles obtained under the conditions of Example 14 were crushed and classified under different conditions to obtain CFs with an average aspect ratio of 5.3. Silicon was then deposited on the CFs under the same conditions as in Example 1. After cooling, the product was removed and crushed and classified to obtain a CFSI negative electrode material. Chemical analysis revealed that the Si content per gram of the obtained CFSI negative electrode material was 71.2%. A negative electrode test battery was then fabricated under the same conditions as in Example 1, and the battery was evaluated. The results of the battery evaluation are shown in Table 3.

[0256] <Results and Discussion> Table 1 shows the battery evaluations performed on the negative electrode test batteries (lithium ion batteries) obtained in Examples 1 to 7 and Comparative Example 1.

[0257]

[0258] Table 2 shows the battery evaluation results of the negative electrode test batteries obtained in Examples 8 to 13.

[0259]

[0260] The battery evaluations performed on the negative electrode test batteries obtained in Examples 14 to 18 are shown in Table 3.

[0261]

[0262] As is clear from Table 1, the battery characteristics of the lithium-ion battery negative electrode material of this embodiment are higher than those of the comparative example. The reason for this is due to differences in the internal structure of the negative electrode material and a physical property called the effective spatial index, which is an index of the substantial silicon growth spatial structure during silane CVD.

[0263] The skeletal structure of the negative electrode material contained in the negative electrode test batteries of Examples 1 to 7 all had CF arranged inside silicon, which gave it high electronic conductivity and high flexibility, and it is thought that this made it easy to follow the morphological changes caused by the expansion and contraction of silicon, resulting in high charge / discharge capacity and high cycle retention.

[0264] In particular, in the conversion of silane to silicon, that is, the process of conversion from gas to solid, the size of the space and the affinity (wettability) for the skeletal structure during the morphological change are thought to be important for forming a reaction field.

[0265] During the silane CVD process, organic-like silane gas undergoes thermal decomposition, transforming from organic low-molecular-weight polysilane to high-molecular-weight polysilane and then to solid silicon. During this transformation process, the effective void ratio, which is the ratio of the pore volume (gas-phase measurement of gas diffusion pore volume) to the oil absorption (liquid-phase measurement of the wetted and infiltrated space of liquid organic matter) reflecting the organic properties, is controlled within an appropriate range. This influences the adhesion of silicon to the skeletal structure and the control of silicon crystal nucleation, resulting in a silicon-based anode material that exhibits good cycle and initial capacity characteristics.

[0266] In contrast, when granulated and pulverized carbon black without a hollow structure, as in Comparative Example 1, is used as the skeletal structure disposed inside the silicon, it is unable to keep up with the morphological changes caused by the expansion and contraction of the silicon during charge and discharge, and structural destruction occurs from the first cycle. This is thought to impair electronic conductivity, preventing lithium ions from being released from the charged Li—Si, resulting in a decrease in initial capacity. Furthermore, the carbon black used in the battery of Comparative Example 1 has lower electronic conductivity and is less flexible than the CF of this embodiment. Therefore, it is thought that the electrode resistance tends to increase with each repeated charge and discharge of the battery, resulting in a significant decrease in cycle characteristics in the battery of Comparative Example 1.

[0267] Table 2 shows the results of investigating the manufacturing method of CFSI anode material in Examples 8 to 13. In Example 8, which employed a method of introducing silane gas deep inside the CF, the anode capacity was improved. In Example 9, by covering the silicon surface with a protective coating layer, the adverse effects of silicon particle scattering after structural changes due to charge and discharge were suppressed, improving cycle characteristics.

[0268] In Example 10, the cycle characteristics were further improved by introducing hard silicon oxide by oxidizing part of the silicon and then covering it with a protective coating layer. In Example 11, the silicon oxide was removed from the CFSI of Example 10, creating a void layer within the protective coating layer, which alleviated the effect of the volume increase caused by silicon expansion and improved the cycle characteristics.

[0269] By selecting the manufacturing method according to the battery's application, conditions of use, and required characteristics, it is possible to provide highly optimized anode materials.

[0270] Table 3 shows the results of improving the average aspect ratio, which is a particle property of CF, a component of silicon-based negative electrode material, for application to a practical electrode.

[0271] The average aspect ratio, which indicates steric anisotropy, is a factor that leads to anisotropy when silicon alloys with Li and expands. The smaller the average aspect ratio of CF, the more isotropic the expansion of CFSI particles becomes, and the smaller the impact of expansion. This is thought to result in improved cycle characteristics.

[0272] The skeletal structure of the present invention may have pores, which are through-holes or bottomed pores, on the surface of the skeleton, and may have one or more of the following configurations (1) to (7): (1) a configuration consisting of at least one of carbonaceous, graphene, and thin-layer graphene; (2) a configuration having an outer shell consisting of at least one of plate-like, curved, and irregular surface shapes; (3) a configuration in which the average particle size of the skeletal structure particles is 1.3 μm or more and 10.5 μm or less; (4) a configuration in which the effective spatial index obtained by dividing the pore volume of the skeletal structure by the oil absorption amount is 1.5 to 10.5; (5) a configuration in which at least a portion of the skeletal structure is spherical or approximately spherical particles; (6) a configuration in which the skeletal structure is particles, and the particles have an average aspect ratio of 1 to 5; and (7) a configuration in which the skeletal structure is composed of at least one of carbon meso-sponge and graphene meso-sponge.

[0273] The lithium ion battery negative electrode material of the present invention comprises a skeletal structure made of silicon and a carbon material, and has pores that are through holes or bottomed pores on the surface of the skeleton of the skeletal structure. The negative electrode material may also have one or more of the following structures (8) to (11): (8) a structure in which at least a portion of the skeletal structure is sandwiched between silicon, (9) a structure in which the silicon contains silicon oxide, (10) a structure in which one or more protective coating layers made of carbonaceous material, graphene material, or thin-layer graphene material are provided on the outside of the surface of the silicon, or (11) a structure in which a void layer is provided between the protective coating layer and the outer surface of the silicon.

[0274] The lithium ion battery negative electrode of the present invention contains a lithium ion battery negative electrode material that includes a skeletal structure made of silicon and a carbon material, and the skeletal structure has pores that are through holes or bottomed pores on the surface of the skeleton, and the lithium ion battery negative electrode material may have one or more of the structures (8) to (11) above.

[0275] 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.

[0276] CF: plate-shaped core-skeleton structure BL: protective coating layer BLV: void layer in protective coating layer (void layer) Si: silicon 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 lithium ion battery negative electrode material member for use as a skeleton to be placed inside silicon of a lithium ion battery negative electrode material, the negative electrode material member being a carbon material forming a core skeletal structure, the skeletal structure having pores, which are through holes or bottomed holes, on the surface of the skeleton.

2. The lithium ion battery negative electrode material member according to claim 1, wherein the framework structure is made of at least one of carbonaceous, graphene-based, and thin-layer graphene-based materials.

3. The lithium ion battery negative electrode material member according to claim 1, wherein the skeletal structure has an outer shell having at least one of a plate shape, a curved surface shape, and an irregular surface shape.

4. The lithium ion battery negative electrode material member according to claim 1, wherein the framework structure is in the form of particles, and the average particle size of the particles is 1.3 μm or more and 10.5 μm or less.

5. The lithium ion battery negative electrode material member according to claim 1, wherein the framework structure has an effective space index, calculated by dividing the pore volume by the amount of oil absorbed, of 1.5 to 10.

5.

6. The lithium ion battery negative electrode material member according to claim 1, wherein at least a portion of the skeletal structure is a spherical or approximately spherical particle.

7. The lithium ion battery negative electrode material member according to claim 1, wherein the framework structure is particles, and the particles have an average aspect ratio of 1 to 5.

8. The lithium ion battery negative electrode material member according to claim 1, wherein the framework structure is composed of at least one of a carbon meso sponge and a graphene meso sponge.

9. A method for producing a core skeletal structure made of a carbon material, comprising the steps of: arranging ceramic particles to serve as a template; circulating an organic hydrocarbon to coat the surfaces of the ceramic particles with a carbon layer or a graphene layer by a chemical vapor deposition (CVD) method; dissolving and eluting the ceramic particles with an acid to form a skeletal structure precursor having intraparticle spaces; and heat-treating the obtained skeletal structure precursor to obtain a skeletal structure, wherein the skeletal structure has pores, which are through holes or bottomed holes, on the surface of the skeleton of the skeletal structure.

10. The method for producing a skeletal structure according to claim 9, wherein the ceramic particles contain pores therein.

11. A method for producing a skeletal structure according to claim 9, comprising a step of granulating the ceramic particles into an approximately spherical shape prior to the step of coating with the carbon layer or graphene layer.

12. The method for producing a skeletal structure according to claim 9, wherein the step of heat-treating the obtained skeletal structure precursor is not carried out.

13. The method for producing a skeletal structure according to claim 9, further comprising carrying out a pore compression treatment after the step of obtaining the skeletal structure.

14. A lithium ion battery negative electrode material comprising: silicon; and a skeletal structure disposed inside the silicon to form a core, the skeletal structure being made of a carbon material, and the skeletal structure has pores, which are through holes or bottomed holes, on a surface of the skeleton of the skeletal structure.

15. The lithium ion battery negative electrode material according to claim 14, wherein at least a portion of the framework is sandwiched with silicon.

16. The lithium ion battery negative electrode material of claim 14, wherein the silicon comprises silicon oxide.

17. The lithium ion battery anode material of claim 14, further comprising one or more protective coating layers on an outer surface of the silicon, the protective coating layers being either carbonaceous, graphene or thin-layer graphene.

18. The lithium ion battery anode material of claim 17, further comprising a void layer between the protective coating layer and the outer surface of the silicon.

19. A method for producing a negative electrode material for a lithium ion battery, comprising the steps of: placing a core skeletal structure made of a carbon material in a reaction vessel; and circulating a silicon-containing compound through the reaction vessel at 300°C to 900°C to deposit silicon on the outer surface of the skeletal structure by a CVD method, wherein the skeletal structure has pores, which are through holes or bottomed holes, on the surface of its skeleton.

20. The silicon-containing compound is silane (SiH ４ 20. The method of claim 19, comprising:

21. The method for producing a lithium ion battery negative electrode material according to claim 19, wherein the silicon-containing compound gas is diluted with an inert gas.

22. A method for producing a lithium ion battery negative electrode material as described in claim 19, further comprising the steps of evacuating the reaction vessel to create a vacuum state after the step of arranging the skeletal structure, and raising the temperature to a temperature at which a CVD reaction is performed, and in which a mixed gas of gaseous silane diluted with an inert gas is introduced into the reaction vessel that has been placed in a vacuum state, and then CVD is performed.

23. The method for producing a lithium ion battery negative electrode material according to claim 22, wherein the CVD is carried out while flowing the mixed gas.

24. The method of claim 19, further comprising forming a protective coating layer of either carbonaceous, graphene or thin-layer graphene on the outer surface of the deposited silicon.

25. A method for producing a lithium ion battery negative electrode material as described in claim 19, further comprising the steps of: after depositing silicon on the outer surface of the skeletal structure, heating the skeletal structure in an atmosphere containing at least oxygen at 200°C to 500°C to incorporate an oxide into the silicon; replacing the atmosphere in the reaction vessel with an inert gas; and forming a protective coating layer made of any of carbonaceous, graphene, and thin-layer graphene under a flow of a gas of a compound containing carbon.

26. A method for producing a lithium ion battery negative electrode material as described in claim 19, further comprising the steps of: providing an oxide layer on the outer surface of the precipitated silicon after the step of precipitating silicon on the outer surface of the skeletal structure; forming a protective coating layer made of any one of carbonaceous, graphene, or thin-layer graphene on the outer surface of the oxide layer by a CVD method using a hydrocarbon gas; and dissolving and eluting the oxide layer with an acid to form a void layer between the protective coating layer and the outer surface of the precipitated silicon.

27. A lithium ion battery negative electrode comprising the lithium ion battery negative electrode material of claim 14.

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